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Biomedical subjects

R G Davis

Publications and source records attributed to R G Davis.

At least 37 records · Page 2Linked to original sources
PubMed1990

Rural hospitals under PPS: a five-year study.

This research examines the impact of prospective payment (PPS) on the financial performance of Kansas hospitals, which are predominantly rural. Financial ratios are presented and regressed on bed size and year. The data suggest that bed size has the strongest effect on financial viability. There are indications of a delayed effect of PPS on the rural, smallest hospitals (fewer than 25 beds), suggesting that non-operating sources of revenue (local property tax mill levies) are being used to subsidize them in the short term. Small hospitals appear to be delaying all capital and long-term costs to survive. The research suggests that the effect of PPS may be long term.

Data Collection↗
PubMed1987

The growth hormone (GH)-releasing hormone (GHRH)-GH-somatomedin axis: evidence for rapid inhibition of GHRH-elicited GH release by insulin-like growth factors I and II.

Hypothalamic-pituitary-end-organ axes are frequently controlled by long loop negative feedback homeostatic mechanisms. Insulin-like growth factor I (IGF-I), IGF-II, and insulin receptors have recently been described in normal and neoplastic rat and acromegalic human pituitary cells, a finding which suggests the possibility that somatomedins might exert feedback at the level of the anterior pituitary. To study the kinetics of this feedback response, we used perifused dispersed rat anterior pituitary cells to learn if somatomedins or insulin could inhibit GH-releasing hormone (GHRH)-stimulated GH secretion. Cells were exposed to hourly boluses of 1 nM GHRH with or without varying doses of IGF or insulin. IGF-I inhibited GHRH-elicited GH release with an IC50 of 6.5 nM; maximal inhibition (approximately 67%) was achieved with 10 nM IGF-I. IGF-II was a less potent hormone, with 10 nM inhibiting about 30% of GHRH-stimulated GH release. Slight inhibition of stimulated GH release (less than 15%) was seen when cells were treated with insulin, but only when doses of insulin of 10 nM or more were used. In conclusion, nanomolar concentrations of IGF-I and IGF-II inhibited GHRH-elicited GH release from perifused rat pituitary cells in a dose-dependent manner; and insulin was not an effective inhibitor of stimulated GH release at physiological peptide concentrations. In conjunction with our previous findings that the concentrations of IGF-I and IGF-II receptors greatly exceed that of insulin receptors on normal rat pituitary cells, we hypothesize that the GH-inhibiting action of high dose insulin is mediated through an IGF receptor.

Animals↗
PubMed1987

Glucocorticoid modulation of growth hormone secretion in vitro. Evidence for a biphasic effect on GH-releasing hormone mediated release.

Glucocorticoids have been shown to have both stimulatory and suppressive effects on GH secretion in vitro and in vivo. In order to study the kinetics of glucocorticoid action on the somatotrope, cultured rat pituitary cells were exposed to dexamethasone for varying periods of time. During short-term incubations (less than or equal to 4 h), dexamethasone inhibited GHRH and forskolin-elicited GH secretion, but during longer incubation periods, the glucocorticoid enhanced both basal and GHRH-stimulated GH release. The inhibitory effect of brief dexamethasone exposure was also seen in cells which previously had been exposed to dexamethasone. In addition, growth hormone secretion from cultured rat and human somatotropinoma cells was inhibited by a brief exposure to dexamethasone. Thus, the nature of glucocorticoid action on the isolated cultured somatotrope is biphasic, with brief exposure inhibiting, and more prolonged exposure stimulating GH secretion.

Animals↗
PubMed1985

Congress and the emergence of public health policy.

Significant changes are occurring in the health care system in the United States, but the direction of change is unclear. This article examines public health policy and argues that Congress may revive national health insurance plans to ensure equal access to care, while achieving more control over government expenditures.

Cost Control↗
PubMed1985

Response of the medullary thick ascending limb to hypothyroidism in the rat.

Hypothyroidism in the rat is associated with a decrease in kidney size and weight. We have shown previously that this decrease involves all nephron segments in the cortex and outer medulla and is especially pronounced in the medullary thick ascending limb (mTAL). Therefore, the present study was undertaken for examination of the effect of hypothyroidism on the ultrastructure of the rat mTAL. Hypothyroidism was induced by feeding aminotriazole (ATZ), 0.5 g/kg of food, for 4 weeks. A second group of animals received ATZ plus a daily injection of L-thyroxine (T4). A third group was fed a normal diet only and served as control animals. The kidneys were preserved by in vivo perfusion with 3% glutaraldehyde, and tissue from the inner and outer stripe of the outer medulla was processed for electron microscopy. Morphometric analysis revealed a significant decrease in the cross-sectional area of the mTAL in both the inner and outer stripe of the outer medulla in hypothyroid animals. No changes were observed in the surface density of either the apical or basolateral plasma membranes following ATZ treatment. However, when calculated per millimeter tubule, there was a significant decrease in the surface area (SL) of both the apical and basolateral plasma membranes of the mTAL of hypothyroid animals in comparison with control animals. Simultaneous treatment with T4 prevented the ATZ-induced reduction in both tubule cross-sectional area and in the SL of the plasma membrane. These findings suggest that the observed changes in SL of the plasma membrane of the mTAL are due to a regulatory role of thyroid hormone in membrane proliferation as well as in cell growth in general.

Amitrole↗
PubMed1984

Cryosurgical removal of a large oral hemangioma.

Hemangiomas can present difficult management problems to the oral and maxillofacial surgeon when their removal is indicated. This article outlines total resolution of a large hemangioma with cryosurgery. The technique is simple to use, requiring a single treatment with minimal morbidity and patient discomfort.

Cryosurgery↗
PubMed1983

Marked azotemia and increase in serum creatinine: case report of an unusual feature of acute ureteral obstruction in a renal allograft recipient.

A patient is described who presented with late ureteral necrosis following renal transplantation, a complication that usually is seen in the early perioperative period. The patient was anuric with azotemia and a high serum creatinine. Response to surgical correction of ureteral obstruction was excellent and renal function returned to normal within 6 days postoperatively.

Adult↗
PubMed1983

Kidney structure in hypothyroidism.

Hypothyroidism is associated with changes in renal function and a decrease in kidney weight. The present study was carried out for examination of the effect of the antithyroid drug aminotriazole (ATZ) on kidney structure and especially for determination of whether hypothyroidism affects the whole nephron or only a specific segment of it. Female Sprague-Dawley rats received ATZ in their diet, 0.5 g/kg food for 4 weeks. Control rats received a normal diet. Additional groups of animals receiving ATZ in the diet were given daily injections of L-thyroxine (T4) for determination of whether ATZ-induced changes could be prevented by thyroid hormone. After collection of physiologic data the kidneys were fixed by in vivo perfusion with 3% glutaraldehyde in preparation for light-microscopic morphometry. Following ATZ treatment there was a significant decrease in serum triiodothyronine (T3) and in GFR. Kidney weights were decreased, mainly because of a reduction of cortical tissue. Morphometry showed no changes in the relative volumes of the various compartments of the kidney, indicating that the decrease in weight involved all segments of the nephron. Direct measurements of tubular diameters revealed a decrease in the peritubular diameters in both proximal tubules and the thick ascending limb and a decreased cell height in the thick ascending limb. All the ATZ-induced changes could be prevented by simultaneous treatment with T4, suggesting that the changes were caused by the antithyroid effect of ATZ and were not a nonspecific toxic effect.

Amitrole↗
PubMed1977

Acquisition and retention of verbal associations to olfactory and abstract visual stimuli of varying similarity.

The similarity among a set of stimuli used in a paired-associate (PA) task was controlled by psychological scaling. Three lists of odorants and two lists of abstract figures (forms) with six stimuli in each list were constructed to have varying degrees of intralist similarity. Independent groups learned to associate digit responses with one stimulus list in a PA training session. Recognition of training stimuli presented among 12 distractor stimuli and recall of the associations was tested after 7 days. Within each modality, increased intralist similarity impaired PA acquisition. Between modalities, acquisition was inferior with the odor stimuli. During recognition testing, the olfactory modality supported inferior performance. In recall testing, equivalently learned responses in the two modalities were equally well retained. There appears to be a perceptual limitation in olfaction relative to vision that influences stimulus encoding and stimulus retrieval processes but that does not affect retrieval of associated responses.

Association↗
PubMed1975

Acquisition of verbal associations to olfactory stimuli of varying familiarity and to abstract visual stimuli.

Two paired-associate (PA) learning studies observed the acquisition performance of 85 college students with either odors or abstract figures as stimuli and numbers as responses. In both studies visual PA acquisition was reliably superior to olfactory learning. Since the second study was designed to maximize the learning of associations to the odors and minimize the learning of associations to the figures, it appears that the sense of smell is not as well suited to the PA task as vision when essentially naive subjects are involved. In a third experiment, the familiarity of odors and figures was judged and reported as a graphic magnitude estimation response. These judged stimulus familiarities were used to select stimuli for the PA task. Subsequently, PA acquisition was facilitated by the use of highly familiar odors.

Adolescent↗