Search PubMed⌕ Search

Biomedical subjects

K R Holmes

Publications and source records attributed to K R Holmes.

At least 37 records · Page 2Linked to original sources
PubMed1986

A sensitivity analysis of the Thermal Pulse Decay method for measurement of local tissue conductivity and blood perfusion.

The Thermal Pulse Decay (TPD) method for the determination of local tissue thermal conductivity and blood perfusion rate is based on a comparison of measured with theoretically calculated temperatures. A sensitivity analysis of the theoretical model is performed. This analysis supports the establishment of an experimental protocol which reduces the measurement errors: An "optimal" measurement time interval for typical perfusion rates (up to 6 mL/mL/min) was found to be between 3 and 11 s after the heat pulse is turned off. Within this interval, the maximum error in determination of tissue conductivity and blood perfusion caused by experimental measurement errors is expected not to exceed 5 percent. The presently chosen pulse duration of 3 s is in agreement with the analysis as a good compromise between accuracy and excessive tissue heating.

Humans↗
PubMed1986

Thermal pulse decay method for simultaneous measurement of local thermal conductivity and blood perfusion: a theoretical analysis.

Presented here is a theoretical analysis of the recently developed thermal pulse decay (TPD) method for a simultaneous measurement of local tissue conductivity and blood perfusion rate. The paper describes the theoretical model upon which the TPD method is based and details its capabilities and limitations. The theoretical aspects that affected the development of the measurement protocol are also discussed. The performance of the method is demonstrated with an experimental example which compares the measurements of local kidney blood perfusion rates made using the TPD method with the total renal blood flow obtained coincidentally using a blood flowmeter, in an anesthetized dog.

Animals↗
PubMed1986

Adaptive thermal modeling: a concept for measurement of local blood perfusion in heated tissues.

A new Adaptive Thermal Modeling (ATM) method for the measurement of local tissue blood perfusion rate is introduced. The method is based on a two-phase numerical technique. The first phase includes a fast, finite difference scheme for solution of the transient temperature field. The second phase involves iterative corrections of the perfusion until the modeled temperatures coincide with those measured by the temperature sensors. The results obtained from computer generated "data", as well as from laboratory experiments demonstrate the potential capability of the ATM method to continuously measure local perfusion rates in heated tissues. Rigorous analysis of the technique is planned for the near future so that it can be applied to in vivo measurements of local tissue blood perfusions.

Adaptation, Physiological↗
PubMed1985

Proposed methods for the measurement of regional renal blood flow using heat transfer analysis.

The kidney, with its heterogeneous regional perfusion in the two anatomically and functionally distinct vascular beds of the renal cortex and medulla, and with its non-uniform blood vessel geometries, presents a unique challenge for measuring intrarenal blood flow distribution. Determining whole organ perfusion, on the other hand, is comparatively simple for the kidney, but it provides relatively little information about the suspected dependency of renal excretory function on local perfusion rate. Among the variety of methods proposed for gauging regional renal blood flow, some depend on measuring one or more of the tissue's thermal properties. The most straightforward, but least reliable, involve measurements either of focal tissue temperature alone, or of regional tissue thermal gradients. Simply using heat as a diffusible indicator, however, is unreliable as a measure of blood flow, for many of the same reasons that using an inert gas in a dilution technique is unreliable. Recently developed thermal analytical methods, though, hold promise for measuring local tissue blood flow with accuracy and precision. Two of them are reviewed here. One depends on measurement of the effective thermal conductivity of a small mass of tissue by evaluating the steady state ratio between regional unidirectional heat flux across it and the associated temperature gradient in one vector along a segment of it through an imposed spheroidal heat field. The other depends on analyses of tissue temperature decay subsequent to a controlled pulse of heat delivered through a small inserted thermistor bead. Both techniques use bioheat transfer equations to deduce regional blood flow by differentiating between heat dissipation due to local thermal conductivity and that attributable to the effects of regional convection. Although both methods are unavoidably invasive, neither produces debilitating damage in the tissue volume in which perfusion is measured, nor increases local temperature or metabolism enough to affect blood flow itself. Both techniques quantify local blood flow in small volumes of tissue by detailed evaluation of the many properties of tissue and blood which affect heat transfer, and both allow for a virtually unlimited number of nearly continuous sequential measurements at short (nom. 1 min) time intervals.

Animals↗
PubMed1985

Effects of simulated increases in body weight on the growth of limb bones in hypophysectomized rats.

The purpose of this study was to subject groups of hypophysectomized male and female rats each to a simulated specific 10% increase in body weight, to a maximum of a doubling of body weight, in order to study the effects of quantified, increased, intermittent, compressive forces on limb bone growth. Chronic centrifugation was employed. 21-day-old Sprague-Dawley rats were used. After 60 days of centrifugation, the rats were sacrificed. The humerus, radius, ulna, femur and tibia were removed from each animal, cleared of all soft tissues, and the bone lengths measured on Helios calipers with an accuracy of 1/20 mm. The data were corrected for differences due to individual body weight by dividing bone lengths by the cube root of the body weight of the same animal. Tukey's studentized multiple-range test was performed to identify aggregations (sets) of force groups between which there are significant differences. The data suggest that the simulated increases in body weight, within the range used for this study, enhance bone growth in hypophysectomized female and male rats similarly - hypophysectomy being a condition known to inhibit bone growth.

Animals↗
PubMed1985

Bone mineral content of limb bones of male weanling rats subjected to 30 and 60 days of simulated increases in body weight.

The purpose of this study was to subject groups of male rats each to a specific 10% simulated increase in body weight, ranging from 1.1 to 2.0 g. Constant centrifugation was employed. After 30 and 60 days, rats were sacrificed and perfused with 10% BNF. The humerus, radius, ulna, femur, and tibia were removed, cleared of all soft tissues, weighed, decalcified with EDTA, and reweighed. Bone mineral content (BMC) was determined using the formula: [(Wu - Wd) divided by Wu] X 100. Tukey's multiple range test was used. The data suggest that male weanling rats subjected to simulated increases in body weight, within the range used in this study, undergo enhanced BMC, a bimodal curve describing the relationship between BMC and simulated increases in body weight.

Animals↗
PubMed1985

Effects of simulated increases in body weight from birth on the growth of limb bones in rats.

The purpose of this study was to subject groups of newborn male and female Sprague-Dawley rats each to a specific 10% simulated increase in body weight, to a maximum of a doubling of body weight, to study the effects of quantified, increased, intermittent, compressive forces on limb bone growth. Chronic centrifugation was employed. After 90 days of centrifugation the rats were sacrificed. The humerus, radius, ulna, femur, and tibia were removed from each animal, cleared of all soft tissues, measured and weighed. Tukey's Studentized multiple range test was performed to identify aggregations (sets) of force groups between which there are significant differences. The data suggest that newborn male and female rats subjected to simulated increases in body weight, within the range used for this study, undergo enhanced general body growth and limb bone growth.

Animals↗
PubMed1985

The effects of simulated increases in body weight on the developing rat tibia: a histologic study.

Groups of weanling and newborn Sprague-Dawley rats were each subjected to a specific 10% simulated increase in body weight to a maximum of a doubling of body weight, using constant centrifugation, to study the effects of quantified, increased, intermittent, compressive forces on the histomorphology of the proximal tibial epiphysial growth plate. The weanling rats were sacrificed after 30 and 60 days of centrifugation; the newborn rats were sacrificed after 90 days of centrifugation. The results demonstrated no prominent changes in histomorphology, when compared to the controls, in the weanling rats sacrificed at 30 days of centrifugation, or in newborn rats subjected to 90 days of centrifugation; however, a prominent thinning of the growth plates was observed in the weanling rats sacrificed at 60 days of centrifugation.

Animals↗
PubMed1984

The effects of simulated increases in body weight for 30 and 60 days on bone robusticity of limb bones in rats.

The purpose of this study was to subject groups of weanling male rats each to a specific 10% simulated increase in body weight, ranging from 1.1G-2.0G, using constant centrifugation. (In this paper, "G" is the acceleration due to gravity.) After 30 and 60 days, rats were killed and perfused with 10% buffered neutral formalin (B.N.F.). The humerus, radius, ulna, femur, and tibia were removed, cleared of all soft tissues, weighed, and the total length measured. Bone robusticity was calculated using the ponderal index: bone length/3 square root bone weight. Tukey's Multiple Range Test was used. The data suggest that the specific limb bone, G, and duration of centrifugation are each factors in the response of limb bones to simulated increases in body weight.

Animals↗
PubMed1984

The effects of simulated increases in body weight for 60 days on robusticity and mineral content of limb bones of hypophysectomized rats.

The purpose of this investigation was to subject separate male and female groups of weanling hypophysectomized rats each to a specific 10% simulated increase in body weight using constant centrifugation, ranging from 1.1G to 2.0G, to study changes in bone robusticity and bone mineral content. (In this paper, "G" is the acceleration due to gravity.) After 60 days of centrifugation at 24 rpm, the rats were killed and the humerus, radius, ulna, femur, and tibia were removed, cleared of soft tissues, weighed, measured, decalcified with EDTA, and reweighed. Bone robusticity was determined using the ponderal index: P.I. = bone length divided by 3 square root bone weight; and bone mineral content (BMC) was determined using the formula: BMC = [(Wu - Wd) divided by Wu] X 100. Tukey's Studentized Multiple Range T Test was used. The data suggest that, for both male and female hypophysectomized rats, bone robusticity is decreased with simulated increases in body weight; also, for males, a bimodal curve describing the relationship between BMC and simulated increases in body weight is suggested.

Animals↗
PubMed1984

The effects of simulated increases in body weight from birth on bone robusticity of limb bones of rats.

Groups of newborn rats were each subjected to a specific 10% simulated increase in body weight, ranging from 1.1G to 2.0G, to study changes in bone robusticity. (In this paper, "G" is the acceleration due to gravity.) Constant centrifugation was used. At 90 days of age, the rats were killed and the humerus, radius, ulna, femur, and tibia were removed, weighed, and measured. Bone robusticity was calculated using the ponderal index: bone length/3 square root bone weight. Tukey's Multiple Range Test was used. The data suggest that, for both males and females, bone robusticity is increased with simulated increases in body weight.

Animals↗
PubMed1984

The effects of quantified amounts of increased intermittent compressive forces for 30 and 60 days on the growth of limb bones in the rat.

The purpose of this study was to subject groups of rats each to a specific 10% increase in body weight, to a maximum of a doubling of body weight, to study the effects of quantified, increased, intermittent, compressive forces on limb bone growth. Chronic centrifugation was employed. 21-day-old male Sprague-Dawley rats were used. After 30 and 60 days of centrifugation, the rats were killed. The humerus, radius, ulna, femur, and tibia were removed from each animal, cleared of all soft tissues, measured and weighed. The data were corrected for differences due to individual body weight by dividing bone lengths by the cube root of the body weight of the same animal. Tukey's 'Studentized' Multiple Range Test was performed to identify aggregations (sets) of force groups between which there are significant differences. The data suggest that the value of g, together with the amount of time spent at centrifugation, are both significant factors in the effects of increased intermittent, compressive forces, produced by simulated increases in body weight, on limb bone growth.

Animals↗
PubMed1984

Ruminal bypass of drinking water in lactating cows.

Drinking water that does not equilibrate with ruminal fluid, i.e., bypasses the rumen, was studied qualitatively and quantitatively in eight rumen-fistulated lactating Holstein cows. Decreased temperatures in the sulcus omasi and abomasum shortly after initiation of drinking indicated that water had bypassed the rumen. Recovery of a water-soluble marker, included in drinking water offered after water was withheld for 4.5 or 9 h following feeding, was used to estimate ruminal bypass. For respective treatments, 18 and 5% of drinking water was calculated to have bypassed the rumen. Ruminal bypass in lactating cows drinking relatively large amounts of water could affect comparisons of water intake with total ruminal fluid outflow as measured by dilution of a water-soluble marker. Drinking water should not be assumed to equilibrate with ruminal fluid.

Abomasum↗
PubMed1983

Freud, evolution, and the tragedy of man.

It is argued that Freud was not, as Sulloway (1979) contends, a "crypto-biologist" of the mind, but rather a cultural anthropologist of the mind. Freud's genetic conception of the psychic apparatus was neither exclusively nor critically derived from biology. Rather, it was based on an anthropogenetic approach to the archaic heritage of mind inspired in part by the moral philosophy of Nietzsche. The idea of tragedy was the unifying theme of Freud's cultural interpretation of evolutionary psychology. The historical search for the primal origins of neurosis led Freud to the unavoidable conclusion that neurosis was in the beginning a prehistoric moral dilemma which, over the course of mental evolution, eventually evolved into guilt, discontent, and neurosis as modern-day phylogenetically endowed facts of life. Freud (1930) made it clear that the source of man's biological and cultural evolutionary progress--self-denial--was also responsible for the tragedy of the human condition, namely, repression, eternal psychic ambivalence, and chronic mental illness. He believed that neurosis began, as Nietzsche (1887) exclaimed, with the "reduction of the beast of prey 'man' to a tame and civilized animal..." (p. 42). For both Freud and Nietzsche, the cause of the human tragedy was not merely the fall from Nature, but the inexorable knowledge that Man's denial of his biological heritage was the very basis for being human.

Anthropology, Cultural↗
PubMed1981

Pulse-decay method for measuring the thermal conductivity of living tissues.

The present communication presents a single microprobe technique for measuring tissue thermal properties based on the dissipation of a measured amount of energy and the observation of the resulting temperature rise a given time later. An advantage of this method is that the effective sampling volume can be varied by varying the measurement time. Using a measurement time of a few seconds, the sampling volume was estimated to be several orders of magnitude greater than the probe volume. Hence artifacts due to probe-induced trauma or stress would be insignificant. Additional advantages of the technique are: the results were independent of the probe shape, size and properties, and hence represents absolute measurements without the need for calibration; the required electronics and computations are simple; the determination of thermal conductivity requires only a single measurement; and comparison of data at different measurement times yields a clear and unequivocal indication of nonconductive contributions of heat transfer, if present.

Biomechanical Phenomena↗
PubMed1981

Thermal balance in ketamine-anesthetized rhesus monkey Macaca mulatta.

A partitional calorimetry study compared thermoregulatory responses of unanesthetized adult rhesus monkeys (4 female, 1 male) to those anesthetized with ketamine HCl and exposed to ambient temperature (Ta) of 18, 29, 38 degrees C. Steady-state metabolic heat production (M), mean skin temperature (Tsk), rectal temperature (Tre), respiratory evaporative heat loss (Eres), and total evaporative heat loss (Etot) were measured at each Ta. Average Tre of anesthetized animals was reduced by approximately 1 degree C at Ta 18 degrees C, but thermal balance in anesthetized and control animals was maintained by reflexly decreased tissue conductance and shivering. For anesthetized animals, the average M increased 1.8 times over the lowest value of 40.13 W/m2 at Ta 29 degrees C, compared to a 1.5-fold increase for controls. Responses for both groups were not different at Ta 29 degrees C, both groups regulated body temperatures by vasodilation and increased sweating, but with ketamine sweating was reduced (35%). Effective tissue thermal conductance (K) was lowest at Ta 18 (10.8 W/m2 . degrees C) and increased to 39.4 W/m2 . degrees C at Ta 38 degrees C. No significant difference in K was found between ketamine and control groups at other Ta's.

Animals↗