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Biomedical subjects

R W Gore

Publications and source records attributed to R W Gore.

At least 37 records · Page 2Linked to original sources
PubMed1983

Comparison of functional and total capillary densities in fast and slow muscles of the chicken.

The anterior latissimus dorsi (ALD) and posterior latissimus dorsi (PLD) of the domestic chicken were used to study the possible differences in functional capillary density of slow and fast skeletal muscle. Frozen sections of each muscle were prepared for histochemical determination of fiber homogeneity, capillary/fiber ratios, and capillary densities. The functional capillary bed (percent open capillaries) was determined by comparing the number of ink-filled capillaries, after a systemic injection of india ink (for 90-120 s), with the total number of capillaries/mm2. ALD is a slow-tonic muscle consisting of two fiber types, with an average of 1.34 +/- 0.03 capillaries/fiber, a density of 699 +/- 20 capillaries/mm2, and a functional capillary bed representing 29% (ratio of open to total number of capillaries/mm2 was 0.286 +/- 0.022) of the total bed. PLD is a fast-twitch muscle also having two fiber types, with an average of 1.08 +/- 0.04 capillaries/fiber, a density of 561 +/- 26 capillaries/mm2, and a functional bed representing 11% (ratio of open capillaries to total is 0.111 +/- 0.014) of the total. These findings of increased capillarity (24% more capillaries/fiber and 25% more capillaries/mm2) and higher functional capillary density in an avian pure slow muscle (ALD), corroborate previous findings of increased capillarity around slow fibers in mixed muscles of several mammalian species. The values given represent the means +/- SEM.

Animals↗
PubMed1982

Fluid exchange across single capillaries in rat intestinal muscle.

Previous studies suggest that large differences exist among fluid exchange parameters in the mesenteric, muscle, and mucosal regions of the small intestine. However, few quantitative data from the separate regions, with the exception of the mesentery, are available for comparison. In this study, quantitative measurements of hydraulic conductivities (LP) and occluded effective pressures (P'e) were made on single capillaries in rat intestinal muscle. The microcirculation of longitudinal intestinal muscle was viewed through a microscope using the method of Bohlen and Gore. The single-occlusion method of Lee, Smaje, and Zweifach was used to estimate LP and P'e in single capillaries. Details of the procedures for analyzing the experimental data using the Lee analytical model are included in an APPENDIX. Measurements were made at four different sites in each capillary studied so gradients in LP could be quantitated and variations in P'e could be detected. The average LP at the venous end of the capillaries was nearly seven times greater than LP at the arterial end. The average LP at the arterial end [18.6 +/- 2.3(SE)% of the distance (%L/Lo) from the fifth-order arterioles] was 1.32 +/- 0.4 X 10(-2) micrometers.s-1.cmH2O-1. The average LP at the venous end (%L/Lo = 81.7 +/- 2.2%) was 9.15 +/- 0.34 X 10(-2) micrometers.s-1.cmH2O-1. Values of LP at intermediate capillary locations 39.9 +/- 2.3 and 61.3 +/- 3.2% were 2.17 +/- 0.34 and 4.48 +/- 0.62 X 10(-2) micrometers.s-1.cmH2O-1, respectively. The total mean LP for all the data (132 samples, 33 capillaries, 10 rats) was 4.19 +/- 0.61 X 10(-2) micrometers.s-1.cmH2O-1. Comparison of these data with results from other tissues indicates that LP of intestinal muscle capillaries is 1.7 times greater than LP of omental capillaries and three times greater than LP of mesenteric capillaries. Values of P'e were corrected for the unoccluded state and were used to calculate total transcapillary pressures (delta P). The results suggested that the intestinal muscle layers were well hydrated and that tissue hydrostatic pressures were positive. Transcapillary fluid fluxes (JVo) at different sites on the capillaries were estimated from the relationship, JVo = LP X delta P. The results imply that intestinal muscle capillaries are primarily an absorptive network when systemic arterial pressure and capillary pressures are normal.

Animals↗
PubMed1982

A comparison of capillary hydraulic conductivities in postural and locomotor muscle.

In a comparative skeletal muscle study Folkow and Halicka (Microvasc. Res. 1: 1-14, 1968) reported that the capillary filtration coefficient (CFC) of postural (red) muscle was two times the CFC of locomotor (white) muscle. It was concluded that the twofold difference in CFC was due solely to a difference in the perfused capillary surface areas (Sf) of red vs. white muscle. However, CFC is the product of capillary hydraulic conductivity (LP) and Sf. Hence their conclusion assumed that the average LP of red muscle capillaries is exactly equal to the average LP of white muscle capillaries. The following study was undertaken to test the validity of this assumption. The microocclusion procedures and analytical model described by Lee et al. (Circ. Res. 28: 358-370, 1971) and Gore [Am. J. Physiol. 242 (Heart Circ. Physiol. 11): H268-H287, 1982] were used to determine LP. Independent measurements of LP were recorded from single capillaries in red, anterior latissimus dorsi (ALD) and white, posterior latissimus dorsi (PLD) muscles of chickens anesthetized with L.A. Thesia. We found that the mean capillary hydraulic conductivity in postural muscle [(LP)ALD = 0.20 +/- 0.06 (SE) micrometers . s-1 . cmH2O-1 (n = 11)] was significantly different from the mean capillary hydraulic conductivity in locomotor muscle [(LP)PLD = 0.061 +/- 0.01 micrometers . s-1 . cmH2O-1 (n = 14)] (P less than 0.05). These results provide direct evidence that observed differences in red vs. white muscle CFC's may not be due solely to different perfused capillary surface areas but may also be due to differences in capillary hydraulic conductivity.

Capillaries↗
PubMed1981

Methods for isolation, cannulation, and in vitro study of single microvessels.

A method is described for the isolation and cannulation of microvessels (12-112 micrometers) that permits study, in vitro, of their physiology and pharmacology. Vessels from the hamster cheek pouch, testis, and mesentery and from rat brain have been isolated at 4 degrees C with specially prepared instruments and viewed with an inverted microscope. The vessels were cannulated at one end by equipment developed for renal tubular perfusion. The uncannulated end of the vessel is sealed, and experiments on reactivity and mechanics are carried out at fixed intravascular pressures. The isolated microvessels studied have a modulus of elasticity that is consistent with that observed in large vessels, and they display similar maximal active tension development (approximately 10(6) dyn/cm2). Reactivity to norepinephrine, acetylcholine, and adenosine are in the normal range for microvessels. Spontaneous tone is present, as evidenced by stable tonic contractions as well as phasic contractions in the frequency range of 3-30/min. The vessels display stress activation (myogenic response) consisting of contraction in response to increased intraluminal pressure. Our findings suggest that this preparation will be very useful in elucidating the physiology and pharmacology of the resistance vessels in the terminal vasculature.

Animals↗
PubMed1978

Intestinal muscle and mucosal blood flow during direct sympathetic stimulation.

The effect of direct sympathetic stimulation on intestinal muscle and submucosal-mucosal vasculatures was studied in the anesthetized rat. Blood flow was calculated from direct measurements of vessel diameter and red cell velocity. Stimulation at 4 Hz caused a slight reduction (4%) in muscle flow, but had no measurable effect on submucosal-mucosal flow; stimulation at 8 and 16 Hz caused muscle flow to decrease to 58.3 +/- 8.7% (SE) and 31 +/- 5.1%, respectively, of control flow, and mucosal flow, to 73 +/- 3.4% and 54.1 +/- 1.2%, respectively, of control flow. Calculations of muscle and mucosal vascular resistances from flows and microvascular pressures indicate that muscle resistance increased proportionately more than mucosal resistance at 4 and 8 Hz. However, during stimulation at 16 Hz, the mucosal resistance is only 55% of control, and muscle resistance is not significantly (P less than 0.05) different from control. Therefore, reduction of muscle and mucosal flows during 16-Hz stimulation must be caused by the intestinal arterioles and venules in series with these vasculatures.

Animals↗
PubMed1975

Pressure regulation in the microcirculation.

The results of direct pressure measurements are described which demonstrate that pressures in a certain fraction of mesenteric capillaries remain remarkably constant during large changes in systemic pressure. The results of isogravimetric studies, reported in the literature, are also described which indicate that this phenomenon may also occur in the intestine. The question is raised whether capillary pressures may therefore be regulated. Pressures recorded from mesenteric arterioles and capillaries are shown which indicate that maintenance of a constant capillary pressure is primarily the consequence of the vascular architecture peculiar to this tissue, and is merely a secondary reflection of mechanisms associated with flow regulation. The results of direct pressure measurements recorded in the microcirculation of intestinal muscle are also shown. These data indicate that capillary pressures in innervated, denervated, and xylocaine-treated intestinal muscle change in direct proportion to variations in arterial pressure. It is concluded that capillary pressures in the intestinal muscle layers are therefore not regulated, so that the observation that capillary pressures may be maintained is probably a phenomenon unique to the mesentery. Pressures recorded from capillaries in the mucosal villi are also shown and compared to capillary pressures measured in the microvasculature of mesentery and intestinal muscle. When systemic pressure was normal (107 +/- 10 mm Hg), capillary pressure in the mesentery averaged 30 to 33 mm Hg; capillary pressures in the intestinal muscle averaged 22 to 24 mm Hg; and capillary pressures in the mucosal villi averaged 13 to 15 mm Hg. These data suggest that mesenteric capillaries are primarily a filtering network; intestinal muscle capillaries are normally in fluid balance; whereas at rest mucosal capillaries are primarily absorptive. These pressures, recorded from the three major regions of the rat intestine, were used to calculate a weighted average for the whole organ. The calculated value, based on assumed values for relative capillary densities, was 17 mm Hg. This result compares favorably with data from whole organ, isogravimetric studies, and may clarify some of the apparent discrepancies between previous isogravimetric and servopressure studies.

Animals↗