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PubMed1996

Osmotic water permeability of capillaries from the isolated spiral ligament: new in-vitro techniques for the study of vascular permeability and diameter.

Perilymph is separated from blood by a barrier called the blood-labyrinth or blood-perilymph barrier in analogy to the blood-brain or blood-cerebrospinal fluid barrier. These barriers consist mainly of vascular endothelial cells. To characterize the blood-labyrinth barrier we developed in vitro techniques for the quantitative determination of the osmotic water permeability and for the determination of changes in the diameter of isolated inner ear capillaries. Both techniques rely on measurement of the velocity of marker red cells trapped in the lumen of capillaries. The velocity of marker red cells is a measure for the capillary permeability when a water flux across the capillary wall is induced by an osmotic gradient or a measure for a change in the capillary diameter. With these techniques the osmotic water permeability coefficient (Pf) and the pH sensitivity of isolated capillaries from the spiral ligament of the inner ear was determined. Pf at 23 degrees C was (1.49 +/- 0.17) 10(-3) cm/s at pH 7.4 and (1.61 +/- 0.23) 10(-3) cm/s at pH 6.8 (n = 12: mean +/- SEM: n = number of tissues). Pf at 37 degrees C was (2.26 +/- 0.23) 10(-3) cm/s at pH 7.4 and (2.35 +/- 0.17) 10(-3) cm/s at pH 6.8 (n = 13). No change in capillary diameter was observed when the pH of the interstitial fluid was lowered from pH 7.4 to 6.8. These data demonstrate that Pf and the capillary diameter of spiral ligament capillaries are pH independent and suggest that water crosses the blood-labyrinth barrier via an aqueous pathway. Further, these data suggest that the relatively low Pf is another characteristic shared by the blood-labyrinth and the blood-brain barrier.

Animals↗
PubMedDate not supplied

Permeability for horseradish peroxidase in strial capillaries in each turn of cochlea.

The capillary permeability of the stria vascularis in each turn of cochlea was examined at intervals of 10 and 30 min and 1 and 2 h after an injection of horseradish peroxidase (HRP), using light and electron microscopic techniques. Ten minutes after HRP was administered, 18% of examined vessels showed HRP leakage. Thereafter, the level of HRP leakage increased with time. One hour after the injection, HRP had leaked from almost all vessels of the upper three turns. Two hours after the injection, the tracer in the vessel lumen became sparse with very thin staining or nonstaining, and a large amount of HRP was observed outside the vessels. It was noted that the capillary permeability to HRP at the basal turn was different from that of the upper three turns. This seems to be the result of the different pinocytic activity in the capillaries of these two regions. When the tracer disappeared from the vessels (2 h after the HRP injection), labelled vesicles in endothelial cells were frequently visible near the outside surface, whereas very few were visible near the inner surface. It is speculated, therefore, that HRP which has leaked can be reabsorbed back into the blood circulation via a similar micropinocytosis down the concentration gradient.

Animals↗
PubMed2001

Maintenance of cAMP in non-heart-beating donor lungs reduces ischemia-reperfusion injury.

Studies suggest that pulmonary vascular ischemia-reperfusion injury (IRI) can be attenuated by increasing intracellular cAMP concentrations. The purpose of this study was to determine the effect of IRI on capillary permeability, assessed by capillary filtration coeficient (Kfc), in lungs retrieved from non-heart-beating donors (NHBDs) and reperfused with the addition of the beta(2)-adrenergic receptor agonist isoproterenol (iso), and rolipram (roli), a phosphodiesterase (type IV) inhibitor. Using an in situ isolated perfused lung model, lungs were retrieved from NHBD rats at varying intervals after death and either ventilated with O(2) or not ventilated. The lungs were reperfused with Earle's solution with or without a combination of iso (10 microM) and roli (2 microM). Kfc, lung viability, and pulmonary hemodynamics were measured. Lung tissue levels of adenine nucleotides and cAMP were measured by HPLC. Combined iso and roli (iso/roli) reperfusion decreased Kfc significantly (p < 0.05) compared with non-iso/roli-reperfused groups after 2 h of postmortem ischemia. Total adenine nucleotide (TAN) levels correlated with Kfc in non-iso/roli-reperfused (r = 0.89) and iso/roli-reperfused (r = 0.97) lungs. cAMP levels correlated with Kfc (r = 0.93) in iso/roli-reperfused lungs. Pharmacologic augmentation of tissue TAN and cAMP levels might ameliorate the increased capillary permeability observed in lungs retrieved from NHBDs.

Adenine Nucleotides↗
PubMed1998

The capillary filtration coefficient for evaluation of capillary fluid permeability in cat calf muscles.

Measuring the capillary filtration coefficient (CFC) from the transvascular fluid filtration following a fixed increase in transcapillary hydrostatic pressure is a common method to estimate capillary hydraulic permeability (conductivity) in an organ. Constant flow pump perfusion with an artificial perfusate and a maximally dilated vascular bed are often used in CFC studies to avoid influence on CFC of variations in vascular tone, blood flow and perfusion pressure. The present study evaluates if capillary hydraulic conductivity can be estimated by the CFC method, when analyzed on a denervated cat skeletal muscle with quite well-preserved local vascular control and perfused with autologous blood. CFC was estimated by increasing venous pressure and by decreasing tissue pressure, and both during autoperfusion and pressure controlled pump perfusion. A constant filtration rate was achieved 3-4 min after the transcapillary pressure elevation, giving a CFC around 0.0090 mL min-1 mmHg-1 100 g. The CFC did not change with arterial pressure or with reduced vascular tone using the tissue pressure method, but decreased slightly with increased arterial pressure and reduced vascular tone using the venous pressure method. CFC variations with arterial pressure were larger during pump perfusion in which myogenic reactivity is depressed, indicating that influence of myogenic tone on CFC is small. We conclude that CFC can be used to evaluate capillary hydraulic conductivity, and also when arterial pressure, vascular tone and blood flow are altered within reasonable physiological limits during the experiment, and the tissue pressure method and autoperfusion is to be preferred.

Animals↗
PubMed1993

Purification of a capillary permeability-increasing enzyme-2 from the venom of Agkistrodon caliginosus (Kankoku-Mamushi).

A capillary permeability-increasing enzyme-2 was purified from the venom of A. caliginosus by ion-exchange chromatography and gel filtration on Sephadex G-100. By this procedure, 3.1 mg of purified enzyme was obtained from 4 g of the venom. The mol. wt of the purified enzyme was estimated to be approximately 44,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme hydrolyzed N-alpha-tosyl-L-arginine methylester with a specific activity of 56.5 units/mg of protein, and did not show any caseinolytic, clotting or bradykinin-releasing activity. When 13.9 micrograms of the enzyme was injected into the depilated skin on the back of a rabbit, capillary permeability was increased.

Agkistrodon↗
PubMed1983

Vascular recruitment in forearm muscles during exercise.

Blood flow and filtration of water across the vascular bed in human forearm muscles were studied at rest and during graded exercise with a hand ergometer. Blood flow was measured by dye dilution and water filtration was determined after injection of hyperoncotic albumin solution (23%) in the brachial artery creating a tissue to blood ultrafiltration measureable as a dilution in the effluent blood. The filtration constants were expressed as a filtration coefficient Fc (ml water/ml plasma mmHg increase in oncotic pressure), and, multiplying by the plasma flow, as a filtration capacity Kf (ml water/100 ml tissue min mmHg increase in oncotic pressure). During the increase in plasma flow induced by exercise, Fc remained constant at about 0.0007, but Kf increased in parallel with the hyperaemia from 0.0031 to 0.038 when plasma flow increased from 4 to 48 ml (100 ml min)-1. The data suggest a more massive recruitment of exchange area during exercise (a factor 12) than suspected on the basis of ultrafiltration in animals made with the prolonged venous stasis technique (showing a factor 2-5). The estimated variability in exchange surface area indicates, that animal studies of muscle circulation, whether pertaining to capillary permeability or capillary filtration should gain by an independent estimate of the number of capillaries that are flowing during the particular experimental situation.

Adult↗
PubMed1985

Lymph flow, lymph protein concentration, and protein output from rat small intestine.

Lymph flow (JL), lymph protein concentration (CL), and protein output (JP) from the main intestinal lymph duct were determined. The basal JL from the mesenteric pedicle alone was the same as that from the mesenteric pedicle attached with a segment of the nonabsorbing intestine, indicating that the basal JL does not originate from the intestine but is totally from the region of the mesenteric pedicle. The basal CL was 3.5-3.8 g/100 ml. When the intestine was absorbing water, JL increased and CL decreased, but JP increased above the basal JP in the initial 20 min of water absorption and then decreased progressively with time. Furthermore, it was estimated that CL in the "excess lymph" (formed during water absorption) was 1.4 +/- 0.2 g/100 ml in the initial 10 min of water absorption and was zero or nearly so in the later periods. From this and other evidence, it is concluded that under various conditions without net water absorption rat small intestine does not produce lymph and that during water absorption there is no significant increase in capillary permeability or capillary filtration. Therefore, the excess lymph could be mostly derived from the fluid absorbed from the lumen of the intestine.

Animals↗
PubMed2004

Fibered confocal fluorescence microscopy (Cell-viZio) facilitates extended imaging in the field of microcirculation. A comparison with intravital microscopy.

This study investigated the capability of fibered confocal fluorescence microscopy (FCFM) to provide in vivo microvascular observations. FCFM is specifically designed for in vivo in situ observation thanks to a probe composed of a fiber bundle and micro-optics having a diameter as small as 650 microm. In the first part of the study, we compared the main characteristics of FCFM with those of intravital fluorescence microscopy (IFM). A mouse cremaster preparation was used as a common basis to allow for imaging with both modalities. We discussed the feasibility of obtaining quantitative measurements usually provided by IFM in the context of FCFM: morphometry, capillary permeability, functional capillary density, vasoconstriction and dilation effects. In addition, the possibility to visualize fluorescent red blood cells or leukocytes was also evaluated. Phototoxicity issues and limitations of FCFM were also discussed. We showed that FCFM allows observations and measurements usually provided by IFM and that the real-time capability of the system, as well as the flexibility and small diameter of the optical probe enable micro-invasiveness and can extend imaging capabilities for in vivo in situ observations when compared to IFM.

Animals↗
PubMed2000

[Morphology of peripheral nerves, their sheaths, and their vascularization].

This review aims to update our understanding of peripheral nerves, including the nature and function of their sheaths and, finally, their vascularization. The peripheral nervous system is made up of nerves whose function is to gather stimuli from the periphery as well as to transport the motor, secretory or vegetative responses that are triggered to the periphery. The connective tissue surrounding peripheral nerves all along their extension is made up of endoneurial, perineurial and epineurial. The endoneurium surrounds individual axons, which are grouped in fasciculi, each of which is surrounded by the perineurium and finally, the group of fasciculi that comprise all the axons present in this nerve are surrounded by the epineurium. Axons form an intraneural plexus such that they occupy positions in the various fasciculi along the trajectory of the plexus. The number and size of fasciculi vary along the trajectory of a nerve as a result of the plexus positioning of the axons. Peripheral nerves are richly vascularized throughout their length, with multiple anastomoses forming the intraneural vascular network, which is made up mainly of arterioles, capillaries, postcapillary venules and venules. Regarding the blood-nerve barrier and the existence of capillary permeability: endoneural capillaries have junctions that are stronger than those of the endothelial cells of vessels in the epineurium and perineurium. Two distinct lymph channels networks are present in the peripheral nerve stems and are separated by the perineural barrier. The nervi-nervorum are special nerves of a sympathetic and sensory nature that arise from the nerve itself and the perivascular plexuses.

Axons↗