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Biomedical subjects

S L White

Publications and source records attributed to S L White.

At least 91 records · Page 5Linked to original sources
PubMed1988

Measuring hospital competition.

This paper appraises the use of the Herfindahl market share index as an exogenous competition variable in empirical studies of the hospital sector. An analysis of cross-sectional Florida data shows that this index itself is significantly influenced by the demand and supply factors commonly included in econometric models of hospital performance. The analysis then illustrates that biased inferences about the effects of market competition on the costs of hospital care may result unless the values of the Herfindahl Index are treated endogenously in hospital cost models.

Costs and Cost Analysis↗
PubMed1987

Competition in health care markets and the development of alternative forms of service delivery.

This paper examines whether alternative forms of health care delivery locate in highly competitive health service markets. The analysis uses cross-sectional Florida data on the penetration of HMOs, ambulatory surgery centers, urgent care centers, hospices and home health programs in local markets characterized by varying levels of competitiveness among hospitals and among physicians. The results show generally that the development of these newer forms of service delivery are not systematically linked to inter-hospital competition but are influenced by physician supply and insurance demand. The potential contribution of such development to cost-containment efforts is thus questioned.

Ambulatory Care Facilities↗
PubMed1987

A redescription of the life cycle of Eimeria mitis Tyzzer, 1929.

Ten-day-old broiler chickens were inoculated with oocysts of a characterized strain of Eimeria mitis, and tissues were fixed at 4, 8, or 24-h intervals after inoculation for histopathological examination. Tissue collections were initiated at the time of inoculation and extended up to 168 h postinoculation. The preferred site of development of E. mitis was found to be the ileum although more limited development of the parasite also took in the jejunum, cecal pouches, cloaca, and bursa of Fabricius. No distinctive and consistent intestinal lesions were macroscopically evident even in heavily parasitized chickens. The prepatent period was approximately 92 h postinoculation. The histopathological features of the E. mitis infections were characterized using conventional bright-field microscopy as well as both scanning and transmission electron microscopy. No extra-intestinal development of the parasite was observed.

Animals↗
PubMed1987

Early histopathologic and ultrastructural alterations in femorotibial joints of partial medial meniscectomized guinea pigs.

The articular cartilage from femorotibial joints of partial medial meniscectomized male guinea pigs was evaluated at 24, 48, 72, and 96 hours post-surgery to determine the sequential histopathologic and ultrastructural alterations. At 24 hours post-surgery, histopathologic alterations were in the superficial and middle layers and consisted of degeneration and necrosis of chondrocytes and minimal decreased intensity of toluidine blue matrix staining. Changes in chondrocytes and matrix became progressively more extensive 48 hours after surgery. Ultrastructurally, the changes in the superficial matrix appeared to be the result of loss of the fine granular material interspersed between collagen fibers. At 72 and 96 hours post-surgery, chondrocyte loss was extensive and surface fibrillation was seen. These findings suggested that chondrocyte death was the initial important event which led to progressive severe cartilage degeneration in this model.

Animals↗
PubMed1987

Investigation of the antimetastatic effects of agents that inhibit cell adhesion or protein glycosylation.

In this overview the authors describe their recent attempts to specifically interfere with the metastatic spread of B16-F10 melanoma cells. Using the experimental metastasis model system, inhibitory effects of (1) coinjection of cells with synthetic peptides derived from the glycoprotein fibronectin, which possess the ability to disrupt cell adhesion, and (2) treatment of cells with inhibitors of protein glycosylation and oligosaccharide processing have been examined.

Animals↗
PubMed1986

Travel distance as time price and the demand for mental health services.

The ways in which health and mental health services are rationed is an area of growing concern among policy makers and administrators. More attention is being focused on how publicly supported mental health services are utilized and on how health care services in general are used depending upon how they are organized and reimbursed. Price is the marketplace's principal rationing device; the price and the consumption of a good are inversely related. Mental health services, however, tend to have a low money such that money price may not act as a rationing device for those services. This investigation examines the effect of travel distance, a surrogate for time price, from one's home to a community mental health center on the utilization of the center's services. A random sample of 224 clients was studied to determine the effect of their individual travel distances, ages, fees at the center, incomes, employment, gender, and the presence of substitutes on the length and intensity of utilization. Six log-linear regression models were specified and Ordinary Least Squares was used to determine the effect of each independent variable on the utilization of services. In each model travel distance as a measure of time price was found to be a significant factor in utilization. Time price elasticities of demand from this study are compared with elasticities reported in earlier time price studies in health care. The administrative and policy implications of the findings are discussed.

Adult↗
PubMed1986

Hepatic peroxisomal changes induced by a tetrazole-substituted alkoxyacetophenone in rats and comparison with other species.

Previous work in this laboratory indicated that compound LY171883, a tetrazole-substituted alkoxyacetophenone with leukotriene D4 antagonist activity, caused dose-related hepatomegaly in rodents without other histological evidence of liver toxicity. In the present studies, administration of LY171883 at dietary concentrations of 0.25 or 0.50% to rats for 2 weeks increased peroxisomal beta-oxidation, catalase activity, and peroxisome volume fraction in the liver. The effects were dose-related and corresponded with increases in liver weight. Dietary concentrations of 0.05 and 0.1% LY171883 did not significantly alter peroxisome morphology, enzyme activity, or liver weight. Serum triglycerides were lowered equivalently by all four dietary concentrations of LY171883, indicating that the hypotriglyceridemia was dissociated from induction of peroxisomal beta-oxidation. The hepatic effects in rats reversed within 16 days after discontinuing treatment with LY171883. Liver weight and peroxisomal enzyme activities were increased in mice by LY171883 in a manner comparable to that observed in rats, whereas hamsters were less responsive. In guinea pigs there was a minor increase in beta-oxidation at a toxic dose of LY171883, but no change in catalase or liver weight. Neither hepatomegaly nor induction of peroxisomal enzymes occurred in beagle dogs or rhesus monkeys given LY171883. Since the hepatic effects of LY171883 in rats are not observed in higher species at a significant multiple of the anticipated clinical dose, it is unlikely that such effects will occur in humans.

Acetophenones↗
PubMed1986

A preliminary study of Cu-, Cd- and Zn-binding components in the hepatopancreas of Palaemon elegans (Crustacea: Decapoda).

Three low molecular weight, metal-binding components have been isolated from the hepatopancreas of the shrimp Palaemon elegans. The two larger components P-I (11-15,000) and P-II (4-6000) were associated with large amounts of copper in field-collected and copper-exposed shrimps and with cadmium in shrimps exposed to elevated Cd concentrations. A smaller component, P-III was associated with zinc. The recovery of these components was dependent upon the use of a protease inhibitor and the reducing agent mercaptoethanol (2-M) during the separation procedure. Copper, zinc and cadmium are not evenly distributed between individual tissues of P. elegans, the highest concentrations occurring in the hepatopancreas, gills and eyes.

Animals↗
PubMed1986

Oligosaccharide modification by swainsonine treatment inhibits pulmonary colonization by B16-F10 murine melanoma cells.

Oligosaccharide moieties of cell-surface glycoconjugates are thought to be involved in recognition events associated with tumor metastasis and invasion. Using swainsonine (SW), an inhibitor of Golgi alpha-mannosidase II that results in the formation of hybrid-type oligosaccharides on N-linked glycoproteins, we have tested the hypothesis that specific glycan structures are required for pulmonary colonization by tumor cells. B16-F10 murine melanoma cells were treated with SW in growth medium and then injected intravenously into syngeneic C57BL/6 mice. This treatment resulted in dramatic inhibition of colonization, but it had no effect on B16-F10 viability or on cellular tumorigenicity after subcutaneous implantation. SW-treated radiolabeled B16-F10 cells were cleared from the lungs at a greater rate than control cells, suggesting that one effect of treatment is to alter tumor cell retention in the target organ. Our results implicate specific glycan structures in pulmonary colonization and offer a potential approach for identification of specific macromolecules involved in tumor cell-organ recognition during metastasis.

Alkaloids↗
PubMed1986

Inhibition of experimental metastasis by castanospermine in mice: blockage of two distinct stages of tumor colonization by oligosaccharide processing inhibitors.

The extent of maturation of the oligosaccharide subunits of tumor cell glycoproteins appears to correlate with malignant potential, suggesting that modification of oligosaccharide structures may alter metastatic capacity. Castanospermine, a recently discovered inhibitor of glucosidase I, was tested for its effect on experimental metastasis of B16-F10 murine melanoma cells and was compared to treatment with swainsonine and tunicamycin. All three drugs block different steps in the pathway of glycoprotein processing yet each was a potent inhibitor of pulmonary colonization after i.v. injection of treated cells into C57BL/6 mice (greater than or equal to 80% inhibition). This result indicates a generality of inhibition of experimental metastasis by blockage of protein glycosylation or oligosaccharide processing and strongly implicates carbohydrate residues in at least one critical step of the metastatic cascade. Cytotoxic side effects could not account for the inhibitory activity. In order to identify a possible mechanism of inhibition of colonization, the adhesive behavior and pulmonary retention properties of B16-F10 cells treated with the above inhibitors were examined. Tunicamycin-treated B16-F10 cells exhibited poor adhesion to substrate-adsorbed fibronectin and laminin, whereas both castanospermine- and swainsonine-treated cells possessed near normal adhesive capacity; furthermore, the initial rate of loss of tunicamycin-treated cells from the lungs of mice was substantially greater than either control, castanospermine- or swainsonine-treated cells. These data suggest that these processing inhibitors can block experimental metastasis by at least two different mechanisms. The antimetastatic effect of tunicamycin may be related to interference in tumor cell-extracellular matrix interactions, whereas treatment with castanospermine or swainsonine appears to block at a stage distal to initial tumor cell arrest.

Alkaloids↗
PubMed1986

Canine atrioventricular node: scanning electron microscopy and enzyme histochemistry.

Morphologic features of the canine atrioventricular (AV) node were evaluated, using histochemical cholinesterase reactions and scanning electron microscopy. Three distinct regions of the AV node were observed: the transitional zone, superficial AV node, and deep AV node. The transitional zone lacked distinct cellular arrangement, and the cells were large and round with extensive branching on the ends. Superficial AV nodal cells were elongated, tightly packed, and smaller than were transitional cells. The superficial AV node was the densest zone of the AV node. Cell-to-cell contact was end-to-end. Deep AV nodal cells were long, formed laminated fascicles, were larger than the superficial AV nodal cells, and were continuous with the AV bundle.

Acetylcholinesterase↗
PubMed1985

Middle management and the clinician.

It is my position that good clinicians are potentially the best managers for mental health programs. Nonetheless, clinicians who aspire to be managers must prepare themselves for the unsettling changes in self-image and ine one's interpersonal relationships. Also, one must assume a new place in an often chaotic maze that is supposed to be a rational hierarchy. Most important, clinical managers must seriously tackle a new set of theories and techniques to prepare themselves for middle and top level management responsibilities. The 1980s and 1990s are likely to offer great challenges and, one hopes, great rewards to those clinicians who are willing to dedicate their talents, skills, sensitivity, and courage to management.

Administrative Personnel↗
PubMed1985

Scanning electron microscopy of the canine atrioventricular bundle and moderator band.

The atrioventricular (AV) bundle and the moderator band in the canine heart were examined by scanning electron microscopy. The AV bundle and the moderator band both were comprised of large, cylindrically shaped cells. These cells were highly organized into bundles, with minimal lateral communication between bundles. There was extensive cell-to-cell communication between cells within a bundle. The end branching of individual cells was prominent, with some interbundle communication. These results are discussed in relationship to the electrophysiologic properties of the AV bundle and the conduction velocity.

Animals↗
PubMed1984

Radiographic, macroscopic, and microscopic changes in growth plates of calves raised on hard flooring.

The effect of flooring on the development of physeal and metaphyseal lesions of the limbs was studied in 1- to 5-month-old dairy calves. Calves were allotted to 2 groups. Group I was housed on a clay floor throughout the study and group II was housed on metal slats until weaned and then on concrete. Radiographs of the right thoracic limb of the animals were made 7 times during the experimental period and of the right thoracic and pelvic limbs at necropsy. Selected sections of the physeal regions of the distal part of the radius, metacarpus, metatarsus, and rib were examined microscopically. The physes of the limbs in the 2 groups had eosinophilic streaks and patches which originated in the germinal zone and were associated with blood vessels. These foci varied from small streaks parallel to the chondrocyte columns to multiple horizontal branching patches in which cleft formation and necrosis interrupted the physis, resulting in osseous bridging. Remnants of necrotic cartilage or cartilage containing hypertrophied chondrocytes were located in the metaphysis adjacent to the areas of physeal disruption. Multiple undulations of the physes with variations in thickness and orientation of the chondrocyte columns occurred in the physes of all limbs examined. These areas did not interrupt the physis and were not associated with metaphyseal lesions. The ribs in both groups had focal areas of failure of endochondral ossification characterized by elongation of the hypertrophied zone, accumulation of fibrin and hemorrhage in the zone of provisional calcification, and retention of cartilage within the metaphysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗