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R W Gore

Publications and source records attributed to R W Gore.

At least 19 recordsLinked to original sources
PubMed1992

A novel remote-sensing isometric force transducer for micromechanics studies.

We have developed an innovative transducer for measuring force with femtonewton-to-micronewton resolution in biological systems. A magnetic microsphere is attached to the specimen being studied and is positioned between two electromagnets. Video microscopy and edge detection are used to monitor small movements of the microsphere that occur when the specimen generates force. An automatic control system adjusts the current through the electromagnets to keep the microsphere stationary. Measured force is a linear function of this current. This transducer is unique in its combination of sensitivity and isometric properties and its ability to measure force without direct connections to the specimen. That is, the transducer is "remote sensing" and can measure force through intervening membrane or tissue. The transducer is isometric at steady state to the limit at which displacement of the microsphere can be resolved, which can be as low as 19 nm. The completed system is being used to study the mechanics of interstitial connective tissue but may also be used to study molecular generation of force.

Animals↗
PubMed1991

Microvascular pressure distribution in the hamster testis.

Convective transport is a critical element in the regulation of steroidogenesis and spermatogenesis in the testis. Steroid hormones are distributed to their target cells within seminiferous tubules via interstitial fluid. The movement of interstitial fluid and lymph, which transports protein hormones and many of the substrates required for spermatogenesis and steroidogenesis, is driven by capillary filtration. Despite the importance of convective transport in testicular function, however, the mechanisms regulating transvascular exchange in the testis are unknown. As a first step in understanding this process, we measured directly the microvascular hydrostatic pressure distribution in the hamster testis (pentobarbital sodium, 70 mg/kg ip). Using a servo-null transducer, intravascular pressure was measured in all vessel types accessible beneath the surface of the testis of 19 animals. Systemic arterial pressure averaged 89 +/- 2 (SE) mmHg. The most significant observations were that mean capillary pressure was extremely low (10.1 +/- 0.8 mmHg) and remarkably constant (range 8.2-13.3 mmHg), despite a 45 mmHg range in systemic mean arterial pressure among the animals observed. The maintenance of a low hydrostatic pressure in testicular capillaries may serve to sustain fluid filtration at a rate that prevents washout of essential solutes while preserving convective transport. Unfortunately, the anatomical and functional characteristics that determine this unique microvascular environment may also expose the testis to significant pathological risks. For example, the large pre- to postcapillary resistance ratio observed suggests that testicular capillaries must be highly susceptible to increases in venous pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Simultaneous measurement of capillary distensibility and hydraulic conductance.

Capillaries are often assumed to be indistensible. Only recently has the error caused by capillary distensibility in the measurement of hydraulic conductance been considered. An oil-drop method was used to measure simultaneously distensibility and hydraulic conductance (Lp) of mesenteric capillaries of 40 cranially pithed Rana pipiens. All vessels studied were distensible in the range 5-80 mm Hg, with a mean equilibrium time, teq, of 12.4 +/- 0.5 sec (SEM, n = 7). Capillary distensibility decreased with increasing pressure. Mean capillary distensibilities at 10, 30, and 60 mm Hg were 18.9 +/- 4.9 X 10(-4) (mm Hg)-1, 13.5 +/- 1.2 X 10(-4) (mm Hg)-1 (mean +/- SEM, n = 9), and 7.6 +/- 2.7 X 10(-4) (mm Hg)-1 (mean +/- SEM, n = 7), respectively. Mean values of capillary Lp, uncorrected and corrected for distensibility, were 0.0113 +/- 0.0017 microns(sec.mm Hg)-1 and 0.0083 +/- 0.0016 microns(sec.mm Hg)-1 (SEM, n = 8 capillaries), respectively. A paired t test demonstrated that uncorrected and corrected values of Lp were statistically different from one another (P less than 0.005). Both distensibility and Lp varied widely between capillaries indicating the necessity of measuring and correcting for distensibility in each individual capillary when estimating Lp. The finding of a slow component of vessel distensibility demonstrates that previous filtration data taken not only from single vessels, but also from whole organs, should be reinterpreted.

Animals↗
PubMed1989

Length-tension relationship of vascular smooth muscle in single arterioles.

Longitudinal response gradients in the microcirculation may in part be explained in terms of the length-tension relationship of vascular smooth muscle at different points along the vascular tree. To test this hypothesis, four branching orders of arterial vessels (20-80 microns ID) were dissected from the hamster cheek pouch and cannulated with concentric micropipettes. Intraluminal pressure was monitored with a servo-null micropipette, and arteriolar dimensions were measured using a videomicrometer. All arterioles developed spontaneous tone in physiological saline solution. Pressure-diameter curves were recorded for maximally activated vessels and for passive vessels. Maximal active wall tension varied nearly threefold, but maximal active medial wall stress (approximately 4 x 10(6) dyn/cm2) varied only approximately 20% between the different vessel orders. These data support the concept that smooth muscle cells from vessels of different sizes are mechanically similar but do not completely explain the longitudinal response gradients reported in the cheek pouch microcirculation. An analysis of the effect of arteriolar wall buckling suggests that the luminal folds that develop at short vessel radii may broaden the peak of the active stress-length curve and extend the pressure range over which arterioles are most sensitive to physical and chemical stimuli.

Animals↗
PubMed1987

Double-barrel pipette system for microinjection.

A method for constructing double-barrel micropipettes is described. The pipettes are made from theta-tubing, which permits easy beveling of the tips. The two sides of the system operate independently and are suitable for simultaneous microinjection, microperfusion, or servo-null micropressure measurements.

Animals↗
PubMed1986

Vascular anatomy and hydrostatic pressure profile in the hamster cheek pouch.

The purpose of this study was to describe the vascular architecture and blood supply to the hamster cheek pouch and to measure the intravascular pressure distribution in the entire pouch. Previous anatomic descriptions have focused either on the vasculature of the facial region or on the microcirculation of the cheek pouch tip. Micropressures in cheek pouch capillaries, terminal arterioles, and small venules have not previously been measured. Cheek pouches were prepared for examination under an intravital microscope using both everted and noneverted methods. Microvessel diameters were measured through a video system using a video micrometer, and intravascular hydrostatic pressures were measured with a servo null micropressure system. Blood vessels in the face and pouch were traced after injection of Microfil into the external maxillary artery. The results indicate that the pouch is supplied directly or indirectly by six small arteries in the neck and face. Fifty percent of the total pressure drop across the cheek pouch vasculature occurs in the small cheek pouch arteries, suggesting that these vessels are potentially important in controlling cheek pouch blood flow. The measurements of microvascular pressures and diameters in this study help clarify apparent discrepancies in similar measurements from previous studies.

Adenosine↗
PubMed1985

Immunogenicity of synthetic peptides from circumsporozoite protein of Plasmodium falciparum.

In a study of recombinant proteins that might be useful in developing a vaccine against malaria, synthetic peptides from the circumsporozoite (CS) protein of Plasmodium falciparum were found to be immunogenic for mice and rabbits. Antibody to peptides from the repeating region of the CS protein recognized native CS protein and blocked sporozoite invasion of human hepatoma cells in vitro. Antibodies to peptides from regions I and II had no biologic activity, although antibody to region I recognized processed CS protein by Western blot analysis. These data support the feasibility of developing a vaccine against the sporozoite stage of the malaria parasite by using synthetic peptides of the repeating region of the CS protein conjugated to a carrier protein.

Amino Acid Sequence↗
PubMed1985

A new preparation for microcirculatory studies of the hamster cheek pouch.

Existing methods of preparing the hamster cheek pouch for observation under an intravital microscope have several disadvantages. The everted method, described by Duling (Microvasc. Res. 5: 423-429, 1973), appears to restrict blood flow by placing unnatural tension on the retractor muscle and by requiring an incision in the tip of the pouch. The method of Yamaki et al. (Microvasc. Res. 21: 299-301, 1981) requires an incision in the tip of the pouch and complete disconnection of the retractor muscle. The chamber method of Greenblatt et al. (Microvasc. Res. 1: 420-432, 1969) has a limited optical resolution because the tissue cannot easily be transilluminated with properly condensed light. We have devised a less traumatic method of preparing the pouch, which eliminates these disadvantages. The hamster is anesthetized, and a thin, glass support plate is inserted into the left cheek pouch. The plate is constructed and positioned so that it does not restrict flow to any part of the pouch. The free end of the plate is secured to the animal stage. An incision is made in the skin to expose the cheek pouch, and the loose, avascular connective tissue investing the pouch and the retractor muscle is removed. The pouch is positioned at an angle of 20 degrees from the hamster's body in a temperature-controlled chamber over a standard microscope condensor system. Throughout both surgical and experimental procedures, the pouch is superfused with Ringer-bicarbonate solution at 37.5 degrees C. This preparation minimizes surgical trauma and allows the entire vascular supply to the cheek pouch to be studied.

Animals↗
PubMed1985

Capillary pressures in rat intestinal muscle and mucosal villi during venous pressure elevation.

Whole-organ experiments designed to estimate the capillary filtration coefficient require information about the numerical relationship between capillary pressure and venous pressure. Indirect estimates using isogravimetric and isovolumetric methods indicate that 62-85% of a step change in venous pressure reaches the intestinal capillaries, taken as a whole. We have made direct measurements of capillary pressure with a servo-null micropressure system in the microcirculation of both the intestinal muscle and the mucosal villi of rats during local elevation of venous pressure. Consistent regional differences in the relationship between capillary pressure and venous pressure were observed. During increased venous pressure, submucosal arterioles constricted, while muscularis arterioles dilated. The diameter changes of the small arterioles were consistent with blood flow redistribution from mucosa to muscle during venous pressure elevation, but inconsistent with a pure myogenic response. These data raise questions about the exact role for the expression of the myogenic response during venous pressure elevation in the intestine and about previous interpretations of whole-organ experiments concerned with intestinal blood flow and fluid exchange.

Animals↗
PubMed1984

Mechanics of smooth muscle in isolated single microvessels.

In vivo studies on frog mesenteric arterioles (4) indicate that segmental differences in the response of microvessels to physical and chemical stimuli can be explained simply in terms of the length-tension characteristics of vascular smooth muscle at different points along the vascular tree. Studies on single, isolated arterioles in vitro were initiated to examine more closely the validity of this explanation for regional response differences. This paper reports some of the results. First-, second-, and third-order arterioles (18-60 micron i.d.) were dissected from hamster cheek pouches. The vessels were cannulated with a modified Burg microperfusion system, and their mechanical properties studied using the methods described by Duling and Gore. Vessels were activated in four stages with K+ and norepinephrine. During activation, transmural pressures were adjusted to minimize vascular smooth-muscle shortening. Active pressure-diameter curves were recorded while adjusting transmural pressure through the range 5 to 400 cm H20 in 5-25 cm steps. Vessel dimensions were measured with a videomicrometer. Passive curves were obtained after equilibration overnight in Ca2+-free medium. The vessels were then fixed and prepared for histologic sectioning, and measurements of vessel-wall composition were made. The Laplace relationship was used to construct length-tension diagrams, and the histologic data were used to normalize the dimensional data to smooth-muscle lengths. Maximum active tension of second-order arterioles (1,170 dynes/cm) was two times previous values reported by Gore et al. This was due presumably to refinements in techniques and dissection procedures. Maximum active stress averaged 3.9 X 10(+6) dynes/cm2 for second-order arterioles. This number is identical to data obtained from hog carotid strips by Dillon et al.

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↗