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Discipline
Biological
Keywords
Lymphatic System
Primo Vascular System
Observation Type
Follow-up
Nature
Continuing the storyline
Submitted
Sep 9th, 2020
Published
Dec 4th, 2020
  • Abstract

    Numerous studies have reported the existence of an additional vascular system in mammals: the primo vascular system, consisting of primo vessels and primo nodes. We investigated lymphatic vessels from rats by staining lymphatic tissue with the dye Alcian Blue to identify whether they contain primo vessels. In one exceptional specimen, we were able to clearly identify a primo vessel inside a lymphatic vessel. Microscopy images of this specimen are shown in this report and analyzed. Our report is intended to document our findings and to motivate others to repeat and extend our study in order to investigate in detail the presence and physiological role of primo vessels in lymphatic vessels.

  • Figure
  • Introduction

    Comprising lymphatic vessels (LVs), lymph nodes (LNs), lymphoid organs (such as the thymus and spleen), and lymphatic fluid, the lymphatic systems serve important physiological functions in organisms including immunological surveillance, fluid homeostasis (interstitial fluid removal from the tissue) as well as absorption and transport of fats and fatty acids. Although the lymphatic system is well studied, novel anatomical and physiological aspects of it are still being discovered, such as the ability of the autonomic nervous system to control lymphatic vessels, the existence of LVs in the meninges, the fundamental role of the lymphatic system for renal physiology and pathology or the ability of LVs to transition into blood vessels in adult microvascular networks during microvascular remodeling.

    For several decades, researchers have claimed to have discovered a vascular system distinct from the blood and lymph vascular system. The initial discovery by the North Korean researcher Bong-Han Kim was rediscovered decades later by the South Korean research group of Kwang-Sup Soh. Since then, the phenomenon has been continuously investigated but is still almost unknown by Western scientists.

    Soh termed the novel anatomical structure “primo vascular system” (PVS) comprising “primo vessels” (PVs) and “primo nodes” (PNs). Based on immunochemistry, histology, and genetic analysis, several studies have demonstrated so far that the PVS is distinct from blood vessels, lymphatic vessels, or nerves. The PVS has been detected in several animals (e.g. dogs, rats, mice) and in human tissue. In terms of morphology, the PVs of the PVS are about 20–150 µm in width, are filled with a liquid, and comprise subvessels and sinuses (i.e. tubular structures inside the PVs and PNs). PVs are difficult to observe in vivo since they are semitransparent. The dyes Trypan Blue and Alcian Blue have been found to help in identifying the PVS in vivo due to the dyes’ strong ability to stain the PVS. Research so far has identified several physiological functions of the PVS, including its role as a niche and possible transport route for stem cells or stem cell-like cells, immune function, tissue regeneration, erythropoiesis as well as in transporting microvesicles and exosomes.

    PVs have been detected in several different anatomical locations in organisms, including on the surface of organs, inside and along blood vessels, and, fascinatingly, inside LVs.

  • Objective

    We have previously reported on the microscopy analysis of the PVS of rats and our discovery of a red threadlike structure inside PVs and PNs taken from the intestine surface (possibly indicating extramedullary hematopoiesis occurring inside the PVS). The aim of the present publication is to document a well-preserved PVS specimen that shows a PV within an LV in a level of detail never before published.

  • Results & Discussion

    From the LVs extracted from the vena cava of a rat, one LV (with a length of about 9.5 mm) was found to clearly contain a PV (Fig. 1). As figure 1(A-D) shows, the PV is clearly visible as a blue thread-like structure due to the Alcian Blue staining. The microscopic images show the ultrastructure of the PV traversing the LV: (i) The PV lies inside the LV, appearing coiled and circular, possibly due to the rupture of the PV (indicated by an asterisk in Fig.1(A)) and a subsequent shrinking of it. (ii) The PV is about one-third the size of the LV (diameter of the LV: about 150 µm, the diameter of the PV: about 50 µm). (iii) At the anterior part of the LV, a part of the PV can be seen in a coiled form, seemingly the result of a rupture of the whole PV. The tissue in vivo is unlikely to be curled or coiled. (iv) The PV seems to be free-floating within the LV and is not attached to the inner lumen of the LV.

    Our result confirming the presence of a PV inside an LV is in agreement with previously published results documenting a PV inside an LV. The first observation that LVs can have PVs inside was made by Kim in the 1960s, but no photographic evidence was provided in that report, nor was there a description of how to detect PVs in lymphatic specimens. It was Lee et al. in 2005 that presented for the first time microscopic images of LVs with a PV inside (stained with Janus Green B) (diameter of the LVs: 786±5, a diameter of the PV: 154±1 µm, ratio: 5:1). 13 samples of LVs with a PV inside were found in this study and analyzed. The tissue was extracted from rabbits. In this study, the authors provided in particular microscopic evidence of a PN passing through the valve of an LV. In a follow-up study, Lee et al. presented 6 additional specimens extracted from rabbit tissue showing a PV inside an LV (diameter of the LVs: 970±3, a diameter of the PV: 53±2 µm, ratio: 18:1). Johng et al. were the first to analyze the tissue of rats and found specimens of LVs with a PV inside (diameter of the LVs: 240±7, a diameter of the PV: 52±3 µm, ratio: 4.5:1). In agreement with the findings of Lee et al., this study also documented an LV with a PN inside that passes through an LV valve. The study used cobalt-ferrite magnetic nanoparticles to stain the PVS tissue. Staining with these nanoparticles was also made in the study by Yoo et al. where also LVs with a PV inside were documented. The study was done with rats. In a study by Lee and Soh, the authors also reported the detection of LVs from rabbits with a PV inside (diameter of the LVs: 519±139, a diameter of the PV: 32±8 µm, ratio: 16:1). In this study, an LV was found that clearly showed a PV inside that was exiting the LV wall at one point (see Fig. 5B in their publication), proving that the PV can permeate (i.e. enter or exit) an LV. The authors also reported that they were able to pull out a PV from inside an LV, showing that the PV is not tightly attached to the LV wall inside. Lee et al. reported the discovery of an LV from mouse tumor tissue with a PV inside. Shin et al. analyzed LVs from rabbits that contain PVs and found statistically significant differences in gene expression from both tissues, proving that the PV tissue is not identical to LV. An innovative method to study PVs inside LVs in vivo in rats was developed by Kim et al.. The authors develop a window chamber system attached to the skin that allows long-term monitoring of PVs inside LVs along the superficial epigastric vessels.

    Given the significance of this finding for our understanding of anatomy, it is important to ask why such a novel secondary vessel from the PVS has not been observed by many more researchers investigating tissue of the lymphatic system. We also question why the existence of the PVS is not already well known by the scientific community and documented in anatomical textbooks. We believe there are two main reasons for this. First, PVs are semitransparent and easily overlooked when investigating tissue in general and LVs in particular. Second, although several papers have been published about the existence of PVS tissue inside lymphatics, these reports are not well known and have so far, unfortunately, not attracted a great amount of attention from the scientific community.

    The authors of the present report would welcome a detailed and objective study of the PVS without any bias. The existence of the PVS in general, and the existence of PVs inside LVs, should be validated and investigated independently and critically by as many research institutions as possible worldwide. A critical step for the successful validation of our findings is first to find PVs in or on the surface of the tissue. There are two protocols published so far that help to guide through the procedure to find PVs. Furthermore, the authors of the present manuscript volunteer also to train interested researchers directly in finding the PVS.

  • Conclusions

    In this report, we presented an exceptionally clear example of an LV with a PV inside. Our finding is in agreement with other published studies reporting the existence of a secondary vessel, different from an LV, that can be found inside an LV. We agree with the conclusion of Yoo et al. that the “mere demonstration of the existence of this novel structure inside lymphatic vessels is a remarkable event in current anatomy and heralds a breakthrough toward establishing a new anatomical system completely different from the blood vascular, the lymphatic, and the neural systems”. Further studies should replicate and extend our observation with a systematic analysis of the LVs of organisms and the possible role of PVs inside. Despite the anatomical analysis, a detailed analysis is required to understand the physiological significance of the PVS as well as the PVs inside LVs in particular.

  • Limitations

    Our study has two main limitations: First, only one specimen showing an LV with a PV inside is presented. The reason for this is mainly that the detection of such a clear and characteristic specimen as shown in this report is difficult and seldom. Second, only optical microscopy has been used in our study. Additional investigation with immunohistochemistry (for example using monoclonal antibodies specific to the PVS, as recently shown), along classical dyes for lymphatic tissue, endothelial cells, stem cells, etc.), electron microscopy, and X-ray microcomputed tomography (as recently shown to be a valuable tool for PVS characterization would have been advantageous and future studies should perform such analysis.

  • Methods

    For this study, one male Sprague-Dawley rat (Orient Bio, Gyeonggi-do, Korea; age: 6 weeks) was used. The rat was housed with other rats in a temperature-controlled room (20–26°C) under a 12 h light/dark cycle with food and water available ad libitum. The rat was not prepared specifically. A young rat was chosen since young rats have less fat attached to the surface of their intestine which simplifies the detection of the PVS tissue.

    Alcian Blue solution (1%) was made by 0.05 g (Sigma, St. Louis, MO, USA) and dissolved in 15 ml phosphate-buffered saline (PBS, pH 7.4), then filtered through a 0.2 mm filter with a 10 ml syringe.

    After the rat was anesthetized by an intramuscular injection of an anesthetic cocktail (alfaxalone, 41.7 mg/kg, intraperitoneally; xylazine. 16 mg/kg, intraperitoneally), it was placed under a stereomicroscope (OSM-1, Dongwon, Seoul, Korea) and the abdomen was opened. The surgical opening of the abdomen was carefully conducted so as not to cut blood vessels and to stop minimal bleedings immediately to avoid the blood entering the abdominal cavity.

    Alcian Blue solution (1%, 0.2–0.3 ml) was injected into the lymphatic node nearby the lumbar (lumbar node) which being explored without any solution leaking from the node. After 3–5 min, the lymphatic vessel was isolated for further analysis. Why the dyes Trypan Blue and Alcian Blue have a strong ability to stain the PVS is currently an empirical finding that is not completely understood. It is known, however, that Alcian blue (a cationic dye) stains hyaluronic acid (an anionic, nonsulfated glycosaminoglycan) by binding to anionic residues of hyaluronic acids; since the PVS contains hyaluronic acid, this aspect is possibly relevant to explain the ability of the dye to stain the PVS. Trypan blue likely stains in particular the pores, sinuses or gaps on the PVS tissue surface, and seems to be washed away from the PVS more slowly compared to other tissue.

    The sample was analyzed under a phase-contrast microscope (IX 70 inverted microscope; Olympus Optical Co., LTD, Tokyo, Japan) and images were taken. Image analysis was performed with ImageJ 1.52a and figure 1 was created using Adobe Photoshop (CS6) and Adobe Illustrator (CS6). The raw microscopic images of the specimen shown in figure 1 (n = 14) were stitched together. The white balance of the images was corrected and the background removed.

  • Funding statement

    The research project was enabled by the 2018 SNF Scientific Exchange grant (no. 180409) to F.S. and the National Research Foundation of Korea grant (2018R1D1A1B07043448) to P.D.R.

  • Acknowledgements

    The author would like to thank Rachel Scholkmann for proofreading the manuscript.

  • Ethics statement

    The experimental protocols involving animals were approved by the local Ethics Committee.

    The animal experiments performed were in accordance with the guidelines of the Laboratory Animal Care Advisory Committee of Seoul National University and were approved by the Institute of Laboratory Animal Resource of Seoul National University (SNU-140926-2).

  • References
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    Matters Select16.5/20

    A vessel within a vessel: A microscopy analysis of a primo vessel within a lymphatic vessel

    Affiliation listing not available.
    Continuing the storyline of

  • Felix Scholkmann, Yiming Shen, Pan-Dong Ryu
    Microscopic detection of a red thread-like structure inside primo vessels and primo nodes from the intestine surface of rats
    Matters, 2019 chrome_reader_mode
  • Abstractlink

    Numerous studies have reported the existence of an additional vascular system in mammals: the primo vascular system, consisting of primo vessels and primo nodes. We investigated lymphatic vessels from rats by staining lymphatic tissue with the dye Alcian Blue to identify whether they contain primo vessels. In one exceptional specimen, we were able to clearly identify a primo vessel inside a lymphatic vessel. Microscopy images of this specimen are shown in this report and analyzed. Our report is intended to document our findings and to motivate others to repeat and extend our study in order to investigate in detail the presence and physiological role of primo vessels in lymphatic vessels.

    Figurelink

    Figure 1. Microscopic images of a lymphatic vessel (LV) with a primo vessel (PV) inside.

    (A) Whole LV with the PV inside. The PV is clearly visible as a blue thread-like structure due to the Alcian Blue staining. The whole length of the LV is about 9.5 mm. The asterisk marks the position where the PV inside was possibly ruptured. A frayed part of the PV is visible at this position. On the anterior part, the other frayed part of the PV is visible but blurred.

    (B, C, D) Magnified parts of (A). In all three subfigures, the PV is clearly visible as traversing the LV. The diameter of the LV is about 150 µm and that of the PV about 50 µm. The yellow line with the arrowhead in (D) visualizes the course of the PV with a loop, providing aid to see the three-dimensional structure of the PV.

    Introductionlink

    Comprising lymphatic vessels (LVs), lymph nodes (LNs), lymphoid organs (such as the thymus and spleen), and lymphatic fluid, the lymphatic systems serve important physiological functions in organisms including immunological surveillance, fluid homeostasis (interstitial fluid removal from the tissue) as well as absorption and transport of fats and fatty acids[1][2][3]. Although the lymphatic system is well studied, novel anatomical and physiological aspects of it are still being discovered, such as the ability of the autonomic nervous system to control lymphatic vessels[4], the existence of LVs in the meninges[5][6][7], the fundamental role of the lymphatic system for renal physiology and pathology[8] or the ability of LVs to transition into blood vessels in adult microvascular networks during microvascular remodeling[9].

    For several decades, researchers have claimed to have discovered a vascular system distinct from the blood and lymph vascular system. The initial discovery by the North Korean researcher Bong-Han Kim[10][11] was rediscovered decades later by the South Korean research group of Kwang-Sup Soh. Since then, the phenomenon has been continuously investigated but is still almost unknown by Western scientists[12][13].

    Soh termed the novel anatomical structure “primo vascular system” (PVS) comprising “primo vessels” (PVs) and “primo nodes” (PNs)[13]. Based on immunochemistry, histology, and genetic analysis, several studies have demonstrated so far that the PVS is distinct from blood vessels, lymphatic vessels, or nerves[14][15][16][17][18][19][20][21]. The PVS has been detected in several animals (e.g. dogs, rats, mice) and in human tissue[13]. In terms of morphology, the PVs of the PVS are about 20–150 µm in width, are filled with a liquid[22], and comprise subvessels and sinuses (i.e. tubular structures inside the PVs and PNs)[23]. PVs are difficult to observe in vivo since they are semitransparent. The dyes Trypan Blue and Alcian Blue have been found to help in identifying the PVS in vivo due to the dyes’ strong ability to stain the PVS. Research so far has identified several physiological functions of the PVS, including its role as a niche and possible transport route for stem cells or stem cell-like cells[24][25][26][27][28], immune function[29], tissue regeneration[25][26], erythropoiesis[30][31][32] as well as in transporting microvesicles and exosomes[33][34].

    PVs have been detected in several different anatomical locations in organisms, including on the surface of organs[16][35][23][20][36][37][22], inside and along blood vessels[38][39][40], and, fascinatingly, inside LVs[41][10][42][43][40][44][45][14][46][47].

    Objectivelink

    We have previously reported on the microscopy analysis of the PVS of rats and our discovery of a red threadlike structure inside PVs and PNs taken from the intestine surface (possibly indicating extramedullary hematopoiesis occurring inside the PVS)[32]. The aim of the present publication is to document a well-preserved PVS specimen that shows a PV within an LV in a level of detail never before published.

    Results & Discussionlink

    From the LVs extracted from the vena cava of a rat, one LV (with a length of about 9.5 mm) was found to clearly contain a PV (Fig. 1). As figure 1(A-D) shows, the PV is clearly visible as a blue thread-like structure due to the Alcian Blue staining. The microscopic images show the ultrastructure of the PV traversing the LV: (i) The PV lies inside the LV, appearing coiled and circular, possibly due to the rupture of the PV (indicated by an asterisk in Fig.1(A)) and a subsequent shrinking of it. (ii) The PV is about one-third the size of the LV (diameter of the LV: about 150 µm, the diameter of the PV: about 50 µm). (iii) At the anterior part of the LV, a part of the PV can be seen in a coiled form, seemingly the result of a rupture of the whole PV. The tissue in vivo is unlikely to be curled or coiled. (iv) The PV seems to be free-floating within the LV and is not attached to the inner lumen of the LV.

    Our result confirming the presence of a PV inside an LV is in agreement with previously published results documenting a PV inside an LV[41][10][42][43][40][44][45][14][46][47]. The first observation that LVs can have PVs inside was made by Kim in the 1960s[10], but no photographic evidence was provided in that report, nor was there a description of how to detect PVs in lymphatic specimens. It was Lee et al.[40] in 2005 that presented for the first time microscopic images of LVs with a PV inside (stained with Janus Green B) (diameter of the LVs: 786±5, a diameter of the PV: 154±1 µm, ratio: 5:1). 13 samples of LVs with a PV inside were found in this study and analyzed. The tissue was extracted from rabbits. In this study, the authors provided in particular microscopic evidence of a PN passing through the valve of an LV. In a follow-up study, Lee et al.[44] presented 6 additional specimens extracted from rabbit tissue showing a PV inside an LV (diameter of the LVs: 970±3, a diameter of the PV: 53±2 µm, ratio: 18:1). Johng et al.[41] were the first to analyze the tissue of rats and found specimens of LVs with a PV inside (diameter of the LVs: 240±7, a diameter of the PV: 52±3 µm, ratio: 4.5:1). In agreement with the findings of Lee et al.[40], this study also documented an LV with a PN inside that passes through an LV valve. The study used cobalt-ferrite magnetic nanoparticles to stain the PVS tissue. Staining with these nanoparticles was also made in the study by Yoo et al.[46] where also LVs with a PV inside were documented. The study was done with rats. In a study by Lee and Soh[43], the authors also reported the detection of LVs from rabbits with a PV inside (diameter of the LVs: 519±139, a diameter of the PV: 32±8 µm, ratio: 16:1). In this study, an LV was found that clearly showed a PV inside that was exiting the LV wall at one point (see Fig. 5B in their publication), proving that the PV can permeate (i.e. enter or exit) an LV. The authors also reported that they were able to pull out a PV from inside an LV, showing that the PV is not tightly attached to the LV wall inside. Lee et al.[45] reported the discovery of an LV from mouse tumor tissue with a PV inside. Shin et al.[14] analyzed LVs from rabbits that contain PVs and found statistically significant differences in gene expression from both tissues, proving that the PV tissue is not identical to LV. An innovative method to study PVs inside LVs in vivo in rats was developed by Kim et al.[42]. The authors develop a window chamber system attached to the skin that allows long-term monitoring of PVs inside LVs along the superficial epigastric vessels.

    Given the significance of this finding for our understanding of anatomy, it is important to ask why such a novel secondary vessel from the PVS has not been observed by many more researchers investigating tissue of the lymphatic system. We also question why the existence of the PVS is not already well known by the scientific community and documented in anatomical textbooks. We believe there are two main reasons for this. First, PVs are semitransparent and easily overlooked when investigating tissue in general and LVs in particular. Second, although several papers have been published about the existence of PVS tissue inside lymphatics, these reports are not well known and have so far, unfortunately, not attracted a great amount of attention from the scientific community.

    The authors of the present report would welcome a detailed and objective study of the PVS without any bias. The existence of the PVS in general, and the existence of PVs inside LVs, should be validated and investigated independently and critically by as many research institutions as possible worldwide. A critical step for the successful validation of our findings is first to find PVs in or on the surface of the tissue. There are two protocols published so far[48][49] that help to guide through the procedure to find PVs. Furthermore, the authors of the present manuscript volunteer also to train interested researchers directly in finding the PVS.

    Conclusionslink

    In this report, we presented an exceptionally clear example of an LV with a PV inside. Our finding is in agreement with other published studies reporting the existence of a secondary vessel, different from an LV, that can be found inside an LV. We agree with the conclusion of Yoo et al. that the “mere demonstration of the existence of this novel structure inside lymphatic vessels is a remarkable event in current anatomy and heralds a breakthrough toward establishing a new anatomical system completely different from the blood vascular, the lymphatic, and the neural systems”[46]. Further studies should replicate and extend our observation with a systematic analysis of the LVs of organisms and the possible role of PVs inside. Despite the anatomical analysis, a detailed analysis is required to understand the physiological significance of the PVS as well as the PVs inside LVs in particular.

    Limitationslink

    Our study has two main limitations: First, only one specimen showing an LV with a PV inside is presented. The reason for this is mainly that the detection of such a clear and characteristic specimen as shown in this report is difficult and seldom. Second, only optical microscopy has been used in our study. Additional investigation with immunohistochemistry (for example using monoclonal antibodies specific to the PVS, as recently shown[50][51]), along classical dyes for lymphatic tissue, endothelial cells, stem cells, etc.), electron microscopy, and X-ray microcomputed tomography (as recently shown to be a valuable tool for PVS characterization[52] would have been advantageous and future studies should perform such analysis.

    Methodslink

    For this study, one male Sprague-Dawley rat (Orient Bio, Gyeonggi-do, Korea; age: 6 weeks) was used. The rat was housed with other rats in a temperature-controlled room (20–26°C) under a 12 h light/dark cycle with food and water available ad libitum. The rat was not prepared specifically. A young rat was chosen since young rats have less fat attached to the surface of their intestine which simplifies the detection of the PVS tissue.

    Alcian Blue solution (1%) was made by 0.05 g (Sigma, St. Louis, MO, USA) and dissolved in 15 ml phosphate-buffered saline (PBS, pH 7.4), then filtered through a 0.2 mm filter with a 10 ml syringe.

    After the rat was anesthetized by an intramuscular injection of an anesthetic cocktail (alfaxalone, 41.7 mg/kg, intraperitoneally; xylazine. 16 mg/kg, intraperitoneally), it was placed under a stereomicroscope (OSM-1, Dongwon, Seoul, Korea) and the abdomen was opened. The surgical opening of the abdomen was carefully conducted so as not to cut blood vessels and to stop minimal bleedings immediately to avoid the blood entering the abdominal cavity.

    Alcian Blue solution (1%, 0.2–0.3 ml) was injected into the lymphatic node nearby the lumbar (lumbar node) which being explored without any solution leaking from the node. After 3–5 min, the lymphatic vessel was isolated for further analysis. Why the dyes Trypan Blue and Alcian Blue have a strong ability to stain the PVS is currently an empirical finding that is not completely understood. It is known, however, that Alcian blue (a cationic dye) stains hyaluronic acid (an anionic, nonsulfated glycosaminoglycan) by binding to anionic residues of hyaluronic acids; since the PVS contains hyaluronic acid, this aspect is possibly relevant to explain the ability of the dye to stain the PVS[53][54]. Trypan blue likely stains in particular the pores, sinuses or gaps on the PVS tissue surface, and seems to be washed away from the PVS more slowly compared to other tissue[55].

    The sample was analyzed under a phase-contrast microscope (IX 70 inverted microscope; Olympus Optical Co., LTD, Tokyo, Japan) and images were taken. Image analysis was performed with ImageJ 1.52a and figure 1 was created using Adobe Photoshop (CS6) and Adobe Illustrator (CS6). The raw microscopic images of the specimen shown in figure 1 (n = 14) were stitched together. The white balance of the images was corrected and the background removed.

    Funding Statementlink

    The research project was enabled by the 2018 SNF Scientific Exchange grant (no. 180409) to F.S. and the National Research Foundation of Korea grant (2018R1D1A1B07043448) to P.D.R.

    Acknowledgementslink

    The author would like to thank Rachel Scholkmann for proofreading the manuscript.

    Conflict of interestlink

    The authors declare no conflicts of interest.

    Ethics Statementlink

    The experimental protocols involving animals were approved by the local Ethics Committee.

    The animal experiments performed were in accordance with the guidelines of the Laboratory Animal Care Advisory Committee of Seoul National University and were approved by the Institute of Laboratory Animal Resource of Seoul National University (SNU-140926-2).

    No fraudulence is committed in performing these experiments or during processing of the data. We understand that in the case of fraudulence, the study can be retracted by ScienceMatters.

    Referenceslink
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      Lymphatic Structure and Function in Health and Disease
      Academic Press, 2020, page 180 chrome_reader_mode
    2. Abhishek K. Goswami, Minhaj S. Khaja, Trevor Downing, Nima Kokabi, Wael E. Saad, Bill S. Majdalany
      Lymphatic Anatomy and Physiology
      Seminars in Interventional Radiology, 37/2020, pages 227-236 chrome_reader_mode
    3. Tatiana V. Petrova, Gou Young Koh
      Biological functions of lymphatic vessels
      Science, 369/2020 chrome_reader_mode
    4. Samia B. Bachmann, Denise Gsponer, Javier A. Montoya-Zegarra,more_horiz, Michael Detmar
      A Distinct Role of the Autonomic Nervous System in Modulating the Function of Lymphatic Vessels under Physiological and Tumor-Draining Conditions
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    5. Aleksanteri Aspelund, Salli Antila, Steven T. Proulx, Tine Veronica Karlsen, Sinem Karaman, Michael Detmar, Helge Wiig, Kari Alitalo
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      Structural and functional features of central nervous system lymphatic vessels
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    7. Felix Scholkmann, Tanja Restin
      Meningeal lymphatic vessels in the human head: Examples of in vivo visualization with high-resolution 3T MRI
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      Beyond a Passive Conduit: Implications of Lymphatic Biology for Kidney Diseases
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    9. Mohammad S. Azimi, Jessica M. Motherwell, Nicholas A. Hodges, Garret R. Rittenhouse, Dima Majbour, Stacey L. Porvasnik, Christine E. Schmidt, Walter L. Murfee
      Lymphatic‐to‐blood vessel transition in adult microvascular networks: A discovery made possible by a top‐down approach to biomimetic model development
      Microcirculation, 27/2020, page e12595 chrome_reader_mode
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      On the Kyungrak system
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      Kyungrak System and Theory of Sanal (English translation of Kim, 1965)
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    14. Jun-Young Shin, Sang-Heon Choi, da-Woon Choi,more_horiz, Sang-Suk Lee
      Differential Gene Expression by RNA-Seq Analysis of the Primo Vessel in the Rabbit Lymph
      Journal of Acupuncture and Meridian Studies, 12/2019, pages 11-19 chrome_reader_mode
    15. Kwang-Sup Soh, Kyung A. Kang, Yeon Hee Ryu
      50 Years of Bong-Han Theory and 10 Years of Primo Vascular System
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    16. Jung Sun Yoo, M. Hossein Ayati, Hong Bae Kim, Wei-Bo Zhang, Kwang-Sup Soh
      Characterization of the Primo-Vascular System in the Abdominal Cavity of Lung Cancer Mouse Model and Its Differences from the Lymphatic System
      PLOS ONE, 5/2010, page e9940 chrome_reader_mode
    17. Zhao-Feng Jia, Byung-Cheon Lee, Ki-Hoon Eom,more_horiz, Kwang-Sup Soh
      Fluorescent Nanoparticles for Observing Primo Vascular System Along Sciatic Nerve
      Journal of Acupuncture and Meridian Studies, 3/2010, pages 150-155 chrome_reader_mode
    18. So Rim Kim, Seul Ki Lee, Soo Hwa Jang,more_horiz, Pan Dong Ryu
      Expression of Keratin 10 in Rat Organ Surface Primo-vascular Tissues
      Journal of Acupuncture and Meridian Studies, 4/2011, pages 102-106 chrome_reader_mode
    19. Byung-Cheon Lee
      Evidence for novel tubular-bundle structures entangled in the fascia of the inner abdominal wall of a rat
      Micron, 123/2019, page 102681 chrome_reader_mode
    20. Chae Jeong Lim, So Yeong Lee, Pan Dong Ryu
      Identification of Primo-Vascular System in Abdominal Subcutaneous Tissue Layer of Rats
      Evidence-Based Complementary and Alternative Medicine, 2015/2015, pages 1-13 chrome_reader_mode
    21. Jun-Young Shin, Jong-Ok Ji, da-Woon Choi,more_horiz, Sang-Suk Lee
      Expression of Genes in Primo Vasculature Floating in Lymphatic Endothelium Under Lipopolysaccharide and Acupuncture Electric Stimulation
      Journal of Acupuncture and Meridian Studies, 12/2019, pages 3-10 chrome_reader_mode
    22. Baeckkyoung Sung, Min Su Kim, Byung-Cheon Lee, Jung Sun Yoo, Sang-Hee Lee, Youn-Joong Kim, Ki-Woo Kim, Kwang-Sup Soh
      Measurement of flow speed in the channels of novelthreadlike structures on the surfaces of mammalian organs
      Naturwissenschaften, 95/2008, pages 117-124 chrome_reader_mode
    23. Byung‐cheon Lee, Jung Sun Yoo, Vyacheslav Ogay, Ki Woo Kim, Harald Dobberstein, Kwang‐sup Soh, Byung‐soo Chang
      Electron microscopic study of novel threadlike structures on the surfaces of mammalian organs
      Microscopy Research and Technique, 70/2007, pages 34-43 chrome_reader_mode
    24. Min Su Kim, Ju-Young Hong, Su Hong, Byung-Cheon Lee, Chang Hoon Nam, Hee-Jong Woo, Dae-In Kang, Kwang-Sup Soh
      Bong-Han Corpuscles as Possible Stem Cell Niches on the Organ-Surfaces
      Journal of Pharmacopuncture, 11/2008, pages 5-12 chrome_reader_mode
    25. Seung J. Lee, Sang H. Park, Yu I. Kim, Sunhee Hwang, Patrick M. Kwon, In S. Han, Byoung S. Kwon
      Adult Stem Cells from the Hyaluronic Acid-Rich Node and Duct System Differentiate into Neuronal Cells and Repair Brain Injury
      Stem Cells and Development, 23/2014, pages 2831-2840 chrome_reader_mode
    26. Vyacheslav Ogay, Kwang-Sup Soh
      Identification and Characterization of Small Stem-Like Cells in the Primo Vascular System of Adult Animals
      The Primo Vascular System, 2012, pages 149-155 chrome_reader_mode
    27. Rajani Rai, Vishal Chandra, Byoung S. Kwon
      A Hyaluronic Acid-Rich Node and Duct System in Which Pluripotent Adult Stem Cells Circulate
      Stem Cells and Development, 24/2015, pages 2243-2258 chrome_reader_mode
    28. Vitaly Vodyanoy, Oleg Pustovyy, Ludmila Globa, Randy J. Kulesza, Jr., Iryna Sorokulova
      Hemmule: A Novel Structure with the Properties of the Stem Cell Niche
      International Journal of Molecular Sciences, 21/2020, page 539 chrome_reader_mode
    29. Beom K. Choi, Sun H. Hwang, Yu I. Kim,more_horiz, Byoung S. Kwon
      The hyaluronic acid-rich node and duct system is a structure organized for innate immunity and mediates the local inflammation
      Cytokine, 113/2019, pages 74-82 chrome_reader_mode
    30. Chae Jeong Lim, Yiming Shen, So Yeong Lee, Pan Dong Ryu
      Potential Erythropoiesis in the Primo-Vascular System in Heart Failure
      Oxygen Transport to Tissue XXXIX. Advances in Experimental Medicine and Biology, 977/2017, pages 409-415 chrome_reader_mode
    31. P. D. Ryu, Y. Shen, C. J. Lim, S. Y. Lee
      Anemia–Induced Erythropoiesis in Organ Surface Primo Vascular System in Rats
      Journal of Acupuncture and Meridian Studies, 11/2018, pages 189-190 chrome_reader_mode
    32. Felix Scholkmann, Yiming Shen, Pan-Dong Ryu
      Microscopic detection of a red thread-like structure inside primo vessels and primo nodes from the intestine surface of rats
      Matters, 2019 chrome_reader_mode
    33. Chiara Ghiron
      The Primo Vascular System as a Possible Exosomal Route Across the Body: Implications for Tumor Proliferation and Metastasis
      Journal of Acupuncture and Meridian Studies, 12/2019, pages 25-28 chrome_reader_mode
    34. Byung-Cheon Lee, Ji Woong Yoon, Sang Hyun Park, Seung Zhoo Yoon
      Toward a Theory of the Primo Vascular System: A Hypothetical Circulatory System at the Subcellular Level
      Evidence-Based Complementary and Alternative Medicine, 2013/2013, pages 1-5 chrome_reader_mode
    35. Byung-Cheon Lee, Baeckkyoung Sung, Ki-Hoon Eom, Eun-Sung Park, Min Su Kim, Se Hoon Kim, Vyacheslav Ogay, Ki Woo Kim, Yeonhee Ryu, Yeo-Sung Yoon, Kwang-Sup Soh
      Novel Threadlike Structures on the Surfaces of Mammalian Abdominal Organs are Loose Bundles of Fibrous Stroma with Microchannels Embedded with Fibroblasts and Inflammatory Cells
      Connective Tissue Research, 54/2013, pages 94-100 chrome_reader_mode
    36. Chae Jeong Lim, Jong-Hyun Yoo, Yongbaek Kim, So Yeong Lee, Pan Dong Ryu
      Gross Morphological Features of the Organ Surface Primo-Vascular System Revealed by Hemacolor Staining
      Evidence-Based Complementary and Alternative Medicine, 2013/2013, pages 1-12 chrome_reader_mode
    37. Hak‐soo Shin, Hyeon‐min Johng, Byung‐cheon Lee, Sung‐il Cho, Kyung‐soon Soh, Ku‐youn Baik, Jung‐sun Yoo, Kwang‐sup Soh
      Feulgen reaction study of novel threadlike structures (Bonghan ducts) on the surfaces of mammalian organs
      The Anatomical Record Part B: The New Anatomist, 284B/2005, pages 35-40 chrome_reader_mode
    38. Xiaowen Jiang, Hee-Kyeong Kim, Hak-Soo Shin, Byong-Chon Lee, Chunho Choi, Kyung-Soon Soh, Byeung-Soo Cheun, Ku-Youn Baik, Kwang-Sup Soh
      Method for Observing Intravascular BongHan Duct
      arXiv:physics/0211086, 2002 chrome_reader_mode
    39. Byung‐cheon Lee, Ku Youn Baik, Hyeon‐min Johng, Tae Jeong Nam, Jawoong Lee, Baeckkyoung Sung, Chunho Choi, Won‐hee Park, Eun‐sung Park, Dae‐hun Park, Yeo‐sung Yoon, Kwang‐sup Soh
      Acridine orange staining method to reveal the characteristic features of an intravascular threadlike structure
      The Anatomical Record Part B: The New Anatomist, 278B/2004, pages 27-30 chrome_reader_mode
    40. Byung‐cheon Lee, Jung Sun Yoo, Ku Youn Baik, Ki Woo Kim, Kwang‐sup Soh
      Novel threadlike structures (Bonghan ducts) inside lymphatic vessels of rabbits visualized with a Janus Green B staining method
      The Anatomical Record Part B: The New Anatomist, 286B/2005, pages 1-7 chrome_reader_mode
    41. Hyeon-Min Johng, Jung Sun Yoo, Tae-Jong Yoon, Hak-Soo Shin, Byung-Cheon Lee, Changhoon Lee, Jin-Kyu Lee, Kwang-Sup Soh
      Use of Magnetic Nanoparticles to Visualize Threadlike Structures inside Lymphatic Vessels of Rats
      Evidence-Based Complementary and Alternative Medicine, 4/2007, pages 77-82 chrome_reader_mode
    42. Jungdae Kim, Dong-Hyun Kim, Sharon Jiyoon Jung, Hyun-Ji Gil, Seung Zhoo Yoon, Young-Il Kim, Kwang-Sup Soh
      Monitoring the primo vascular system in lymphatic vessels by using window chambers
      Biomedical Optics Express, 7/2016, pages 1251-1259 chrome_reader_mode
    43. B-C Lee, K-S Soh
      Contrast-enhancing optical method to observe a Bonghan duct floating inside a lymph vessel of a rabbit
      Lymphology, 41/2008, pages 178-185 chrome_reader_mode
    44. Changhoon Lee, Seung–kwon Seol, Byung–cheon Lee, Young–kwon Hong, Jung–ho Je, Kwang–sup Soh
      Alcian Blue Staining Method to Visualize Bonghan Threads Inside Large Caliber Lymphatic Vessels And X-Ray Microtomography to Reveal Their Microchannels
      Lymphatic Research and Biology, 4/2006, pages 181-190 chrome_reader_mode
    45. Sungwoo Lee, Yeonhee Ryu, Jinmyung Cha,more_horiz, Jaekwan Lim
      Primo Vessel Inside a Lymph Vessel Emerging From a Cancer Tissue
      Journal of Acupuncture and Meridian Studies, 5/2012, pages 206-209 chrome_reader_mode
    46. Jung Sun Yoo, Hyeon-Min Johng, Tae-Jong Yoon,more_horiz, Kwang-Sup Soh
      In vivo fluorescence imaging of threadlike tissues (Bonghan ducts) inside lymphatic vessels with nanoparticles
      Current Applied Physics, 7/2007, pages 342-348 chrome_reader_mode
    47. Linlin Zhang, Sang Wook Oh
      Production and Characterization of Monoclonal Antibodies Against Primo Vascular System of Rat
      Journal of Acupuncture and Meridian Studies, 13/2020, pages 110-115 chrome_reader_mode
    48. Su Youn Park, Sharon Jiyoon Jung, Kyoung-Hee Bae, Kwang-Sup Soh
      Protocol for Detecting the Primo Vascular System in the Lymph Ducts of Mice
      Journal of Acupuncture and Meridian Studies, 8/2015, pages 321-328 DOI: 10.1016/j.jams.2015.03.008chrome_reader_mode
    49. Sharon Jiyoon Jung, Sang Yeon Cho, Kyoung-Hee Bae,more_horiz, Kwang-Sup Soh
      Protocol for the Observation of the Primo Vascular System in the Lymph Vessels of Rabbits
      Journal of Acupuncture and Meridian Studies, 5/2012, pages 234-240 DOI: 10.1016/j.jams.2012.07.007chrome_reader_mode
    50. Linlin Zhang, Sang Wook Oh
      Production and Characterization of Monoclonal Antibodies Against Primo Vascular System of Rat
      Journal of Acupuncture and Meridian Studies, 13/2020, pages 110-115 DOI: 10.1016/j.jams.2020.05.001chrome_reader_mode
    51. Chae Jeong Lim, Yeo Sung Yoon, Pan Dong Ryu
      Mesothelial Cells Covering the Surface of Primo Vascular System Tissue
      Journal of Acupuncture and Meridian Studies, 13/2020, pages 33-38 DOI: 10.1016/j.jams.2019.11.002chrome_reader_mode
    52. Chae Jeong Lim, Yiming Shen, Min Cheol Choi, Pan Dong Ryu
      Primo Bundles Identified by Microcomputed Tomography in Primo Vascular Tissue on the Surface of Rat Abdominal Organs
      Journal of Acupuncture and Meridian Studies, 13/2020, pages 136-145 DOI: 10.1016/j.jams.2020.07.002chrome_reader_mode
    53. E. Reale, L. Luciano, M. Spitznas
      Histochemical demonstration of hyaluronic acid molecules by Alcian Blue
      The Histochemical Journal, 18/1986, pages 306-316 DOI: 10.1007/bf01675208chrome_reader_mode
    54. Changhoon Lee, Seung–kwon Seol, Byung–cheon Lee, Young–kwon Hong, Jung–ho Je, Kwang–sup Soh
      Alcian Blue Staining Method to Visualize Bonghan Threads Inside Large Caliber Lymphatic Vessels And X-Ray Microtomography to Reveal Their Microchannels
      Lymphatic Research and Biology, 4/2006, pages 181-190 DOI: 10.1089/lrb.2006.4402chrome_reader_mode
    55. Tae Hee Han, Chae Jeong Lim, Jae-Hong Choi,more_horiz, Pan Dong Ryu
      Viability Assessment of Primo-node Slices From Organ Surface Primo-vascular Tissues in Rats
      Journal of Acupuncture and Meridian Studies, 3/2010, pages 241-248 DOI: 10.1016/s2005-2901(10)60043-xchrome_reader_mode
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