Studies on the physiology of capillaries

Krogh, August; Harrop, George A.; Rehberg, P. Brandt

doi:10.1113/jphysiol.1922.sp002000

Cited by 157 publications

(103 citation statements)

References 3 publications

Supporting

Mentioning

100

Contrasting

Order By: Relevance

“…In fact, gradual shape changes have been observed in the transition from vascular smooth muscle cells to pericytes at both the arteriolar and venular end of the microvascular bed (17,19,37), suggesting that there is no clear demarcation between these cell types within the microvasculature. In all the organs examined, the vascular smooth muscle cells of arterioles and muscular venules were well penetrated by antibody and highly reactive for tropomyosin.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the foot processes have densities that appear similar to the attachment plaques and dense bodies of smooth muscle cells (29,32,34). The presence of such structures within circumferentially oriented pericyte processes suggests a poten-tial contractile function that may contribute to the regulation of blood flow in the microvasculature (12,19,24,37).…”

mentioning

confidence: 89%

See 1 more Smart Citation

Contractile proteins in pericytes. I. Immunoperoxidase localization of tropomyosin.

Joyce¹,

Haire²,

Palade³

1985

The Journal of Cell Biology

147

View full text Add to dashboard Cite

In these studies we have compared the relative amounts and isoforms of tropomyosin in capillary and postcapillary venule pericytes, endothelial cells, and vascular smooth muscle cells in four rat microvascular beds: heart, diaphragm, pancreas, and the intestinal mucosa. The results, obtained by in situ immunoperoxidase localization, indicate that (a) tropomyosin is present in capillary and postcapillary venule pericytes in relatively high concentration; (b) the tropomyosin content of pericytes appears to be somewhat lower than in vascular smooth muscle cells but higher than in endothelia and other vessel-associated cells; and (c) pericytes, unlike endothelia and other nonmuscle cells, contain detectable levels of tropomyosin immunologically related to the smooth muscle isoform. These results and our previous findings concerning the presence of a cyclic GMP-dependent protein kinase (Joyce, N., P. DeCamilli, and J. Boyles, 1984, Microvasc. Res. 28:206-219) in pericytes demonstrate that these cells contain significant amounts of at least two proteins important for contraction regulation. Taken together, the evidence suggests that pericytes are contractile elements related to vascular smooth muscle cells, possibly involved, as are the latter, in the regulation of blood flow through the microvasculature.Pericytes are polymorphic cells closely associated with the walls of capillaries and postcapillary venules. They have a cell body which is often highly elongated, and multiple branching foot processes which partially encircle the vessel wall. Pericytes can be distinguished from other perivascular cells, such as adventitial fibroblasts, by their location within the basement membrane of the vessels, and by the close apposition of the tips of their processes to the underlying endothelium. Electron microscopic studies have identified pericytes in a number of tissues and organs (I0, 12, 20, 36). They may, in fact, be common to all microvascular beds, although their relative frequency and distribution appear to vary from one microvascular bed to another (32,33).The function of pericytes is still unclear; however, morphologic evidence suggests that they may be contractile cells related to vascular smooth muscle. Numerous micro filaments form a continuous plate in the adluminal cytoplasm of their cell body and extend from it into the foot processes, where, in the more distal segments, they fill the cytoplasm to the relative exclusion of other subeellular components. In addition, the foot processes have densities that appear similar to the attachment plaques and dense bodies of smooth muscle cells (29,32,34). The presence of such structures within circumferentially oriented pericyte processes suggests a poten-

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 89%

Contractile proteins in pericytes. I. Immunoperoxidase localization of tropomyosin.

Joyce¹,

Haire²,

Palade³

1985

The Journal of Cell Biology

147

View full text Add to dashboard Cite

show abstract

“…In the past there has been little point in drawing a line between capillaries and venules, because the two types of vessels were generally assumed to be very similar, if not identical, in both structure and function (13). There is, of course, a structural similarity between capillaries and the finest venules: in either case the walls consist of endothelium without a muscular coat; the first smooth muscle cells begin to appear when the caliber reaches 45 to 50 micra (24,25), and a continuous muscular media is not found until the caliber reaches about 200 micra (24,25).…”

Section: Figures 15 and 16mentioning

confidence: 99%

“…It seems more likely that the "unaffected capillaries" may have been the finest. It is worth noting at this point that the vascularization of the skin represents a special case, in that the great majority of the small vessels are venules (32,33,13).…”

Section: O N C L U D I N G R E M a R K Smentioning

confidence: 99%

Studies on Inflammation

Majno

Palade

Schoefl

1961

The Journal of Cell Biology

628

109

View full text Add to dashboard Cite

While it is an established fact that histamine and serotonin increase the permeability of blood vessels, the exact portion of the vascular tree which is so affected has not been conclusively demonstrated. The present study was undertaken to clarify this point.Our experiments were based on a method to which we refer as "vascular labeling," and which permits one to identify leaking vessels by means of visible accumulations of foreign particles within their walls. The mechanism of the labeling, elucidated by previous electron microscopic studies, is the following. Histamine and serotonin cause the endothelial cells of certain vessels to separate, and thus to create discrete intercellular gaps. Plasma escapes through these gaps, and filters through the basement membrane. If the plasma has been previously loaded (by intravenous injection) with colloidal particles of a black material such as carbon or mercuric sulfide, these particles--too large to pass through the basement membrane--will be retained and accumulate in visible amounts within the wall of the leaking vessel. This method is used to maximal advantage if the tissue is cleared and examined by transillumination in toto, so that leaking vessels can be accurately identified in their relationship to the vascular tree.As a test tissue we used the rat cremaster, a laminar striated muscle which can be easily excised with its vascular supply virtually intact. The rats were prepared with an intravenous injection of carbon or HgS, and a subcutaneous injection into the scrotum of histamine, serotonin, or NaC1 (as a control). The injected drug diffused into the underlying cremastcr and the vessels became labeled. One hour later, when the carbon had been cleared from the blood stream, the animal was killed. The cremaster was excised, stretched, fixed in formalin, cleared in glycerin, and examined by transillumination under a light microscope.The lesions induced by histamine and serotonin were identical. The leaking vessels, as indicated by the carbon deposits, always belonged to the venous side of the circulation. The heaviest deposits were found in venules 20 to 30 micra in diameter. The deposits decreased towards larger venules up to a maximum diameter of 75 to 80 micra, and towards the finer vessels until the caliber reached approximately 7 micra. Essentially spared by the deposits were the finest vessels, 4 to 7 micra in diameter, and constituting an extensive network oriented along the muscular fibers.By killing animals at varying intervals after the injections, it was found that the carbon particles were slowly removed from the vascular walls by the action of phagocytic cells. After 10 months there was still enough carbon locally to be recognized by the naked eye.

show abstract

“…Many investigators have presented evidence which suggests that the pressor hormone of the posterior pituitary body may be in part responsible for the maintenance of vascular tone (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33). Others have denied that the evidence is convincing (34)(35)(36)(37)(38).…”

Section: Pi~essor Substances From Body Fluidsmentioning

confidence: 99%

Pressor Substances From the Body Fluids of Man in Health and Disease

Page

1935

Journal of Experimental Medicine

View full text Add to dashboard Cite

1. Extracts of human blood plasma, ascitic and cerebrospinal fluids have been shown to contain a substance or substances which have a prolonged and powerful pressor action when injected into test animals. 2. The chemical properties of the substance suggest those of an organic base. It is extracted with alcohol, soluble in water and acetone, extracted from water by chloroform, and probably is but slightly heat-stable. The plasma colloids seem to hold the substance in a bound state since it does not appear in the ultrafiltrate and is liberated on coagulation of the colloids by alcohol. Coagulation alone of the blood does not cause the substance to be formed. 3. Its action suggests that its pressor effect is brought about by mediation of the central nervous system. This inference was drawn from the following observations. (a) The functional intactness of the central nervous system is essential in order that pressor responses be obtained. Unanesthetized animals exhibit greater vascular responses than do anesthetized. (b) Pithing animals completely abolishes the response. Progressive ablation of the brain to the level of the hind brain does not alter the response, but below this level, injury abolishes the activity of the extract. (c) Some substance in the extract sensitizes the mechanism responsible for the carotid sinus reflex. (d) There is no parallelism between the response to peripherally acting drugs and pressor extracts. (e) Removal of the adrenal glands does not affect its character. 4. The rise in blood pressure appears to be due especially to constriction of the arteries in the splanchnic region. 5. Assay of the pressor extracts is made difficult because of the dependence of the vascular response on the functional state of the central nervous system. The carotid sinus reflex and stimulation with carbon dioxide-air mixtures have proved most useful means for the estimation of this functional state. It has been pointed out that the vascular responses to extract, stimulation of the carotid sinus, and inhalation of carbon dioxide-air vary greatly during the course of an experiment on anesthetized animals. This natural history of the vascular responses has been described. 6. No evidence has been produced by the method employed that the amount of this pressor substance is increased in the blood or spinal fluid of patients with hypertension of varied pathogenesis (nephritic hypertension, essential hypertension, malignant hypertension, eclampsia, and pituitary basophilism).

show abstract

Studies on the physiology of capillaries

Cited by 157 publications

References 3 publications

Contractile proteins in pericytes. I. Immunoperoxidase localization of tropomyosin.

Contractile proteins in pericytes. I. Immunoperoxidase localization of tropomyosin.

Studies on Inflammation

Pressor Substances From the Body Fluids of Man in Health and Disease

Contact Info

Product

Resources

About