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Biomedical subjects

R Ross

Publications and source records attributed to R Ross.

At least 469 records · Page 26Linked to original sources
PubMedDate not supplied

Human reproductive tissues contain thyrotropin releasing hormone (TRH) and TRH-homologous peptides.

Thyrotropin releasing hormone (TRH) immunoreactive peptides occur in high concentration within rat ventral prostate and human semen. To extend these observations to human reproductive organs, tissue fragments from human prostates undergoing benign hypertrophy were obtained by transurethral resection or open surgery. Human prostate, seminal vesicles, testes, and epididymis were also obtained from cadavers within 24 hours postmortem. After tissue extraction, the total TRH immunoreactivity (TRH IR) was measured by TRH radioimmunoassay. The total TRH IR in autopsy seminal vesicles was significantly greater (P less than 0.01) than in all other autopsy reproductive tissues. The mean autopsy TRH IR of prostate was not significantly different from that measured in prostatic tissue obtained at surgery. High pressure liquid chromatography of extracts of autopsy seminal vesicles, prostate, and testis revealed multiple peaks of TRH IR. The two major peaks corresponded to the two TRH-homologous peptides of human semen and one of the minor peaks cochromatographed with synthetic TRH. The distribution of TRH IR in human reproductive tissues appears to be very different from that in the rat, where ventral prostatic TRH IR levels exceed that of any other reproductive tissue by one to two orders of magnitude.

Aged↗
PubMedDate not supplied

Inertial properties of the human trunk of males determined from magnetic resonance imaging.

The purpose of this study was to evaluate the segmental parameters of the human trunk of males in vivo using magnetic resonance imaging (MRI). In addition, the efficacy of volumetric estimation and existing prediction formulas to produce segmental properties similar to those produced by MRI was evaluated. As opposed to finding one representative normal value for these parameters, a range of normal values was defined. For instance, the average trunk mass was 42.2% +/- 3.5% (x +/- SD) of body mass, but values ranged from 35.8% to 48.0%. To account for segment parameters more accurately, specific anthropometric measures need to be considered in addition to overall measures of body height and mass. These specific measures included segment length, circumference, width, and depth. Studies reporting general percentages based on height and/or mass were found to be inadequate predictors of segmental parameters of the trunk compared with MRI estimates. Volume-based estimates, which assume a uniform density distribution within a segment, were found to correspond closely to MRI values except for the thorax. However, the use of density values reflective of the living in vivo state would likely alleviate this disparity, thus indicating that the volumetric technique may be effective for deriving segmental parameters for large segments of the trunk. Future research should adopt noninvasive techniques such as MRI and/or volumetric estimation to enhance the predictability of segmental parameters of the body for specific population groups characterized by gender, developmental age, body type, and fitness level. Further efforts should be made to establish standardized boundary definitions for trunk segments to avoid unnecessary confusion, from which substantial errors may be introduced into biomechanical linked-segment analyses of human movement.

Abdomen↗
PubMedDate not supplied

Cellular proliferation in atherosclerosis and hypertension.

We have tried to compare the proliferative responses seen in two vascular diseases: atherosclerosis and hypertension. Both diseases involve endothelial injury and proliferation, but our knowledge of this phenomenon is just beginning to emerge. In atherosclerosis the best evidence is that denudation does not occur in the normal young animal. Man, however, ages over a much longer time than our usual animal models, and the study of denudation during the chronic progression of atherosclerotic lesions remains to be done. We need to consider the possibility that repetitive, small lesions may occur at sites of endothelial turnover. We also need to know more about the possible role of nondenuding injuries, including death of endothelial cells in situ and the apparent increased stickiness of endothelial cells and monocytes during the early stages of hypercholesterolemia. The role of endothelial injury in hypertension also needs more study. We know that extensive denudation and thrombosis occur in small vessels subjected to high blood pressure. It is highly probable that release of PDGF occurs at these sites, possibly accounting for the characteristic hyperplasia seen in malignant hypertension. Whether this process is related to the more subtle changes in vessel wall mass seen in chronic hypertension remains unknown. Finally, there are remarkable differences in the proliferative behavior of the smooth muscle cells themselves in these two diseases. Hypertensive vascular disease is, in large part, a disease of the media. Atherosclerosis is characterized by intimal hyperplasia. Injury results in migration of smooth muscle cells from the media and cell division in the intima. It is possible to identify chemotactic factors using putative atherosclerosis risk factors or normal components of serum. This has already been done for one component of lesion formation, PDGF, and there is a report of a monocyte chemotactic factor released by smooth muscle cells. Factors released by other components of lesions may be of considerable interest. In contrast, changes in hypertension occur within a more orderly preservation of vessel wall structure. The wall thickens, but this occurs by increased synthesis of cell mass in the media. The cells themselves do not even divide, but they undergo a form of amitotic replication of their DNA.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Characterization of 1,25-dihydroxyvitamin D3 receptors and in vivo targeting of [3H]-1,25(OH)2D3 in the sheep placenta.

We sought to detect the presence of receptors for 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] in placental tissues of five late gestational pregnant sheep and to quantitate their biochemical properties and abundance. Cytosol prepared from cotyledonary tissue was found to contain two [3H]-1,25(OH)2D3 binding macromolecules that sedimented at 3.2 S and 4.1 S, respectively, on linear (4-20 per cent) hypertonic sucrose gradients. The 4.1 S component cosedimented with serum that had been prelabelled with [3H]-25-hydroxyvitamin D3 (25-OHD3) and was present in cytosols despite extensive washing of the tissue prior to homogenization. Concurrent incubation of the cytosol with [3H]-1,25(OH)2D3 and a tenfold molar excess of radioinert 25-OHD3 resulted in complete resolution of the 3.2 S macromolecule and disappearance of the 4.1 S binding component. The binding of [3H]-1,25(OH)2D3 to the 3.2 S component was completely abolished by coincubation with a 100-fold molar excess of radioinert 1,25(OH)2D3 and was replaced by a well resolved peak in the 4.1 S region. Scatchard analysis of cytosol binding to [3H]-1,25(OH)2D3 in the presence of a tenfold molar excess of radioinert 25OHD3 revealed a single class of non-interacting saturable binding site in the cotyledon and the endometrium of high affinity and low capacity. The mean +/- s.e. of the dissociation constant of the cotyledonary receptor of 0.21 +/- 0.06 nM was not different from that of 0.16 +/- 0.03 nM for the endometrial receptor. However, the abundance of the cotyledonary receptor was fourfold higher than that in the endometrium (110 +/- 20 versus 28 +/- 7 fmol/mg protein). Since it is not possible to completely separate endometrial tissue from cotyledonary tissue, the low abundance of receptor in endometrial cytosols may merely represent contamination of endometrial tissue with cotyledonary tissue. Further analysis of the [3H]-1,25(OH)2D3 occupied receptor in cotyledonary cytosols showed that it bound to DNA cellulose and was eluted with 0.16 M KCl. This in vitro binding of [3H]-1,25(OH)2D3 to DNA was confirmed in vivo by the finding of preferential nuclear targetting of [3H]-1,25(OH)2D3 (56 per cent of total cellular activity), 4 h after fetal intravenous administration of [3H]-1,25(OH)2D3 to five chronically catheterized fetal sheep. Total placental uptake of [3H]-1,25(OH)2D3 at this time amounted to 3.7 +/- 0.9 per cent of the injected dose. Preliminary analysis of ovine placental cytosols revealed a calcium binding protein of similar molecular weight to that found in the ovine intestine and in the intestine and placenta of rodents.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Outcome of domiciliary care after inpatient alcoholism treatment in male veterans.

Current literature is ambiguous as to the impact of extended treatment services following hospitalization on outcomes such as abstinence. This study compares the outcomes of care for 276 veterans who completed inpatient treatment for alcoholism, 77 of whom (28%) were transferred to a domiciliary and the remainder of whom were discharged directly into the community. The domiciliary group of alcoholics differed at baseline from alcoholics discharged to the community with significantly higher psychiatric comorbidity and lower social support, both negative predictors of treatment outcome. A multiple logistic regression model was used to assess the impact of domiciliary placement on: (a) 3-month abstinence comparing the time after discharge from either the domiciliary or the inpatient treatment unit and (b) 12-month abstinence after discharge from the inpatient treatment unit, including patients placed in the domiciliary. Controlling for baseline differences, domiciliary placement was found to be a significant predictor of abstinence (odds ratios of 2.3 for 3-month and 2.5 for 12-month abstinence, p < or = 0.01). In a survival analysis, domiciliary placement was also a significant predictor of time to readmission after treatment discharge with a risk ratio of 0.2 (p < 0.01). Our results demonstrate a protective effect of domiciliary after-care for high risk alcoholics after inpatient treatment.

Adult↗
PubMedDate not supplied

An inter-regional comparison: fatal crashes in the southeastern and non-southeastern United States: preliminary findings.

The southeastern United States, particularly those states representing the National Highway Traffic Safety Administration's and Federal Highway Administration's Region IV, have consistently had among the highest number of fatal crashes and fatal crash rates compared to the other five regions in the US. These states--Alabama, Florida, Georgia, Kentucky, Mississippi, North Carolina, South Carolina, and Tennessee, are suspected of sharing traits in common that lead to their systematically poor crash record. Inter-regional and intra-regional comparisons, such as the comparison between southeastern and non-southeastern states, raises interesting and challenging research questions that are applicable to similar comparisons. First, is there a sound practical and theoretical justification supporting an inter-regional comparison framework? Second, is there a way to construct a meaningful statistical hypothesis and test to determine whether one region, which is comprised of numerous entities, suffers from a characteristically better or worse crash record? This paper addresses each of these questions. After providing a brief summary of the Southeast's safety record, we discuss the issues pro and con surrounding inter-regional comparisons, illustrating the statistical strategy for such an analysis approach. Then, a simple generalizable statistical procedure is used for testing the hypothesis that southeastern states have a poorer crash record than non-southeastern states. Finally, we explore possible relationships between safety belt use, roadway functional class, vehicle miles of travel, and driver age on fatal crash occurrence. The data used in the analyses are from the Fatal Analysis Reporting System (FARS), primarily data compiled for 1995. The analysis suggests that regional differences in fatal crashes may indeed exist, that these differences are related in part to seat-belt use, VMT by functional classification, and speed limit differences, and that more detailed studies are needed to quantify the effect of these and other factors. The approach developed here lends insight as to where future in-depth studies may reveal causal factors of fatal crashes, and illustrates the relative safety performance records of US regions.

Accidents, Traffic↗
PubMedDate not supplied

The transfer of calcium during perfusion of the placenta and intact and thyroparathyroidectomized sheep.

Placental perfusions were carried out in six ewes during the last two weeks of gestation. Perfusions were carried out using autologous fetal blood and the flow rates adjusted to give a perfusion pressure of 50--70 mmHg. Perfusion plasma calcium concentrations rose steadily throughout the perfusions achieving a mean increase of 1.65 mmol/1 above initial concentration within 100 minutes. A further three ewes in the last two weeks of gestation were thyroparathyroidectomized and normal plasma calcium concentration maintained by an intravenous infusion of calcium borogluconate. After three days, placental perfusions were carried out as before. The mean perfusion plasma calcium concentration achieved by those three ewes in a period of 100 minutes showed an increase of 1.25 mmol/1. It is concluded that the presence of the fetus is not necessary for the continued active transfer of calcium across the placenta from mother to fetus. The reduced rate of accumulation of calcium in the perfusate in TXPTX ewes is attributed to a decline in 1,25-DHCC concentrations in both maternal and fetal circulations. The implications of these results in relation to fetal calcium homeostasis and the placental transfer of calcium are discussed.

Animals↗
PubMedDate not supplied

Lean R value for DXA two-component soft-tissue model: influence of age and tissue or organ type.

Dual-energy X-ray absorptiometry (DXA) is an important new body composition method that is based on tissue attenuation of two main photon energies. When the two photon energies pass through tissue, attenuation at the lower energy compared with that at the higher energy can expressed as a ratio (R), which is used for tissue component identification. We tested whether: (1) the R value of lean tissue is related to age, and (2) the R value of lean tissue differs between soft tissue locations. Elemental content of various tissues from the literature was used. Results show that lean R values for 40 keV and 70 keV are independent of age and tissue type.

Absorptiometry, Photon↗
PubMedDate not supplied

Increased urea kinetic modeling volume. Possible mechanisms and its significance.

The presence of access recirculation reduces delivered urea clearance and produces an increased volume/weight (V/M) ratio in three-point kinetic modeling. We measured R in 20 patients receiving conventional hemodialysis and correlated results with normalized intra-access venous pressure (PIA) and with angiographic or color-flow Doppler studies. Twenty patients were equally divided into those with and without persistently elevated modeled V/W ratios (0.64 vs 0.53), and subdivided into those with native and synthetic bridge graft accesses. Kinetic modeling parameters (Kt/V) and P1A did not differ between the two V/W groups. Modeled volume was quite accurately predicted by the equations in the normal group but deviated by 7.3 +/- 2.1 L in the high V/W ratio group. Three of 10 native and 4 of 10 graft accesses had trivial and hemodynamically insignificant abnormalities by color-flow Doppler or angiography. Recirculation was independent of V/W group and when measured by the slow flow/clamp technique was negligible (< 2.0%). Access flow always exceeded prescribed dialyzer blood flow by more than 300 ml/ min. Therefore, access recirculation was unlikely. In many of the high V/W patients, alternative explanations for falsely high modeled volume were found on follow-up modeling. Only one patient appeared to have a true high volume. The authors conclude that high urea volumes during kinetic modeling are unlikely to occur from access recirculation, but arise from other factors affecting the delivered urea clearance.

Adult↗
PubMedDate not supplied

Atherogenesis during low level hypercholesterolemia in the nonhuman primate. I. Fatty streak formation.

Although a large body of data is available concerning atherogenesis in animals maintained at high levels of hypercholesterolemia, little data are available for animals maintained at lower levels of hypercholesterolemia for longer periods of time, closer to those observed in humans. The chronologic sequence of cellular events and interactions that occur during the formation of the lesions of atherosclerosis was investigated during relatively low level hypercholesterolemia (200 to 400 mg/dl) in a series of nonhuman primates (Macaca nemestrina). The arterial tree of each animal was examined by light microscopy and scanning and transmission electron microscopy. Immunohistochemical staining with monoclonal antibodies specific for smooth muscle cells, monocyte-macrophages, and T-lymphocytes was performed to analyze the cellular composition of the lesions. After 6 months of low level hypercholesterolemia, the surface of the aorta contained large numbers of adherent leukocytes, many of which were in the process of entering the artery. This resulted in irregularly shaped nodular elevations, or fatty streaks, preferentially located at branch sites and bifurcations. The fatty streaks consisted of intimal accumulations of numerous lipid-laden macrophages together with relatively small numbers of T-lymphocytes. With lesion progression, the thickness of the fatty streaks increased, and their surfaces became irregular and frequently showed disruptions of covering endothelial cells resulting in exposure of subendothelial macrophages. Platelet microthrombi were observed over some of the exposed macrophages at some branches or bifurcations in every animal studied. These observations made during the early phases of atherosclerosis lesion formation are virtually identical to those described in our previous reports in high level hypercholesterolemic nonhuman primates (600 to 1000 mg/dl) with the exception that the changes occurred more slowly in the lower levels of hypercholesterolemia.

Animals↗
PubMedDate not supplied

Atherogenesis during low level hypercholesterolemia in the nonhuman primate. II. Fatty streak conversion to fibrous plaque.

This study focuses on the formation of lesions of atherosclerosis in the aortas and iliac arteries of nonhuman primates (Macaca nemestrina) maintained on a low level hypercholesterolemic diet (plasma cholesterol 200 to 400 mg/dl) for 2, 3, or 3.5 years. Advanced lesions, or fibrous plaques, were found in all of the animals. The extent and severity of the lesions were closely related to the level and duration of hypercholesterolemia. The presence of monocyte-macrophages, T-lymphocytes, and smooth muscle cells, and the interactions of those cells that precede fibrous plaque formation in these long-term, relatively low level hypercholesterolemic monkeys were similar to those observed in previously published studies of high level hypercholesterolemia in nonhuman primates, with one principal difference: the fibrous plaques in the longer-term, low level hypercholesterolemic animals contained increased amounts of fibrous connective tissue, more smooth muscle cells, and fewer macrophages. As in the studies with high levels of hypercholesterolemia, fibrous plaques were more frequently observed in the abdominal aorta and iliac arteries than in the thoracic aorta and aortic arch. Fibrous plaques were preferentially located at the branches and bifurcations of the arteries. These anatomic sites were consistent with those that contained fatty streaks and fibrofatty lesions in the animals fed the diet for shorter periods of time. These data are compatible with the proposal that many of the fatty streaks are converted to fibrofatty lesions, some of which ultimately become converted to fibrous plaques.

Animals↗
PubMedDate not supplied

Macrophage and smooth muscle cell proliferation in atherosclerotic lesions of WHHL and comparably hypercholesterolemic fat-fed rabbits.

Lesions of atherosclerosis were analyzed at varying stages of development in Watanabe heritable hyperlipidemic (WHHL) and comparably hypercholesterolemic fat-fed (FF) rabbits for the capacity to incorporate thymidine into proliferating cells within both the intima and the underlying media. An identical inverse relationship between the intimal/medial ratio (which reflects both lesion size and severity) and the labeling index was observed for both the WHHL and FF rabbits. Analysis of the spatial distribution of the labeled cells within each lesion revealed the highest rates of thymidine incorporation in cells situated within the superficial areas and lateral margins of the lesions. Up to 12% of the labeled cells were foam cells, which were predominantly located immediately beneath the endothelium and within the lateral margins. Some labeled macrophages were also observed within the necrotic core of advanced lesions. There were no differences in the labeling indexes at differing sites in the aorta, providing lesions of comparable size were compared. Simultaneous thymidine autoradiography and immunostaining with cell type-specific monoclonal antibodies revealed that approximately 30% of the labeled cells were macrophages and 45% were smooth muscle cells in advanced lesions from both WHHL and FF rabbits.

Animals↗