Search PubMed⌕ Search

Biomedical subjects

J C Davis

Publications and source records attributed to J C Davis.

At least 127 records · Page 7Linked to original sources
PubMed1981

The effects of thioridazine on electrical and ischemic ventricular fibrillation in the dog heart in situ.

Lethal ventricular arrhythmias have occurred in patients taking thioridazine. Therefore, we studied two canine models to determine if thioridazine alters vulnerability to ventricular fibrillation. In 30 chloralose-anesthetized dogs, the repetitive response threshold was used to assess vulnerability during right ventricular stimulation with transvenous catheter electrodes. Placebo, 10 mg/kg of thioridazine (therapeutic dose) or 30 mg/kg of thioridazine (high dose) was infused i.v. (n = 10 each group). Repetitive response threshold, diastolic excitability, QRS, Q-Tc and plasma thioridazine concentrations were measured before and after drug. Both 10 and 30 mg/kg of thioridazine increased diastolic excitability threshold (P < .05) while only the 30 mg/kg dose widened QRS (P < .05) and prolonged Q-Tc (P < .05). RRT was unchanged. In 45 pentobarbital-anesthetized dogs, one stage ligation of the left anterior descending coronary artery was performed after pretreatment with placebo, 10 or 30 mg/kg of thioridazine (n = 15 each group). Spontaneous ventricular fibrillation occurred in 6 of 15 dogs (40%) after placebo, 8 of 15 dogs (53%) after 10 mg/kg of thioridazine and 14 of 15 dogs (93%) after 30 mg/ kg of thioridazine. Although thioridazine depressed excitability and had no effect on electrical fibrillation threshold, the 30 mg/kg dose increased the likelihood of spontaneous ventricular fibrillation during acute ischemia.

Animals↗
PubMed1980

The human sinus node electrogram: a transvenous catheter technique and a comparison of directly measured and indirectly estimated sinoatrial conduction time in adults.

To improve methods for evaluating human sinus node function (SNF), we developed a transvenous electrode catheter technique for direct recording of sinus node electrograms in adults. Sinus node electrograms (SNE) characterized by low-frequency, anatomically localized pre-P-wave potentials were obtained in 19 of 23 patients. The SNE configuration was similar to that previously found for endocardial SNE recordings in in vitro atrial preparations, in open-chest dogs and during human open heart surgery. In 16 patients with normal SNF, directly recorded sinoatrial conduction times (SACTs) were 46-116 msec. In three patients with sick sinus syndrome, SACT was 110-126 msec. In 15 of the 19 patients, SACT was estimated by the atrial premature stimulus technique and was compared with the directly measured SACT. When atrial premature depolarizations produced no sinus node depression, the mean differences between the direct and estimated SACT was 1.8 +/- 5.6 msec.

Adult↗
PubMed1980

Pain relief and pituitary function following injection of alcohol into the pituitary fossa.

Eleven patients were investigated for pituitary function after the injection of alcohol into the pituitary fossa; all had persistent pain and 8 had carcinoma of the breast. Most of the patients showed varying degrees of reduction of pituitary activity; 8 patients obtained significant pain relief and 3 patients exhibited polyuria. These 3 observations could not be completely correlated; the possible mechanisms which may lead to pain suppression by this method are discussed.

Adult↗
PubMed1980

Correlative light and electron microscopy of dissociated immature rat testicular cells undergoing morphogenesis in vitro.

Immature rat testicular cells undergo morphogenesis in primary culture (Davis, 1978). Depending upon the number of dissociated testicular cells added to the culture dish, spherical or tubular aggregates were formed. Spherical aggregates resulted from movement of cells into centers of aggregation and the detachment of these cells from the substratum; on the other hand, tubular aggregates resulted from detachment and retraction of the cell monolayer at certain points along its outer edge. In this investigation, the different methods of formation of aggregates by immature rat testicular cells in primary culture were examined with the scanning electron microscope (SEM). The cell types involved in such morphogenesis and their associations within completely formed structures were examined by transmission electron microscopy (TEM). In addition, the rates of formation of aggregates were established by time-lapse cinemicroscopy. During formation of spherical aggregates, the rate of recruitment of cells into centers of aggregation (0.4 +/- 0.006 micrometer/min; means +/- S.E.M., n = 78) was much slower than the rate of cell detachment during formation of tubular aggregates (11.7 +/- 1.8 micrometer/sec; means +/- S.E.M., n = 110). Although specific roles for each cell types in formation of aggregates have not been determined, the associations of cells within the two types of reformed aggregates appeared to be similar. Myofibroblast cells were located in outer cell layers and Sertoli cells were observed to underlie the layers of myofibroblasts in both types of aggregates. Germinal cells, however, were found on the outer surface of spherical aggregates, but in tubular aggregates they were located on the inner surface. Since spherical and tubular aggregates are formed by different methods, this observation suggests that rearrangement of cells, within the aggregates takes place and contributes to the internal morphology of newly formed aggregates.

Animals↗
PubMed1979

Hyperbaric oxygen. A new adjunct in the management of radiation necrosis.

Radiation necrosis is a significant complication of surgery for previously irradiated head and neck malignant neoplasms. We used hyperbaric oxygen therapy (HBO) as adjunctive therapy in 52 cases of radiation necrosis. Thirty-nine cases involved the head and neck. Nineteen of 23 cases of osteoradionecrosis of the mandible remain arrested after as much as two years of follow-up. Fifteen of the 16 cases of soft-tissue radionecrosis of the head and neck were successfully managed with HBO therapy as an adjunct to surgery and antibiotics. Fibroblastic proliferation, collagen formation, and capillary budding require at least 20 to 30 mm Hg of wound Po2. This effect can be achieved in wounds that are rendered hypoxic by radiation endarteritis and ischemia with high-dose or hyperbaric oxygenation.

Adult↗
PubMed1979

Testicular endocrine function in paraplegic men.

The responses of FSH and LH to the injection of LHRH were studied in fifteen paraplegic men and ten normal controls. The basal FSH levels in the paraplegic men were elevated in eight cases, basal LH being raised in nine cases. The responses of FSH were exaggerated in fourteen patients, and LH responses were exaggerated in nine patients. Only one patient was normal in respect of both hormones. Subnormal plasma testosterone was found in three patients. This depressed testicular function could not be explained as being due to spread of urinary tract infection and a direct neurological effect is the probable explanation.

Adolescent↗
PubMed1979

Follicle-stimulating hormone-induced, adenosine 3',5'-monophosphate-mediated movement of immature rat sertoli cells in primary culture.

Sertoli cells dissociated from 10-day-old rat testes form colonies in primary culture in response to FSH. FSH and dibutyryl cAMP stimulated the attachment of Sertoli cells to an equal extent; however, FSH-treated cultures contained a small number of large colonies while dibutyryl cAMP-treated cultures contained a large number of small colonies. This relationship was not altered by the addition of a number of other peptide or steroid hormones. Extracellular cAMP levels and colony density were negatively correlated. Colony size at 24 h of culture was diminished in FSH-treated cultures by the addition of a cAMP antibody at 6 or 12 h of incubation. The addition of cAMP at 24 h to FSH-treated cultures caused a dose-dependent stimulation of colony size but not colony density at 48 h of culture. A point source of cAMP (4 x 10(-3) M in agar) inhibited migration of cells toward the agar spot. An agar spot on the dish substratum containing Sepharose-bound FSH exhibited a halo of cells next to the spot, with a zone lacking cells distal to it. Radioautographs of [125I]iodo-FSH-treated cultures exhibited a nonhomogeneous distribution of silver grains; colony size increased faster than the number of labeled cells. Taken together, the results suggest that 1) FSH is stimulating the attachment of Sertoli cells through an increase in intracellular cAMP, 2) FSH is promoting active aggregation of Sertoli cells in culture through a modulation of extracellular cAMP, and 3) cells with a large amount of bound FSH are acting as centers for aggregation.

Animals↗
PubMed1978

Failure to suppress adrenal function in congenital adrenal hyperplasia (21-hydroxylase deficiency). Three case reports.

Three patients, aged 14, 16, and 32 years respectively, with congenital adrenal hyperplasia (21-hydroxylase deficiency) are described. Excessive adrenal activity and ACTH secretion could not be suppressed with doses of corticosteroids sufficient to cause iatrogenic Cushing's syndrome, even though part of the steroid dosage was administered in the late evening. The resistance to feed-back suppression was of the same order as that seen in Cushing's syndrome. Adrenalectomy was performed in the 16-year-old girl, and was followed by a menarche. Adrenalectomy was considered inadvisable in the other two patients.

Adolescent↗
PubMed1978

Morphogenesis by dissociated immature rat testicular cells in primary culture.

Dissociated cells from immature (15-day) rat testes maintained in primary culture were shown to undergo morphogenesis. Dissociated cells (1-4 X 10(6)) were cultured in 2 ml medium NCTC-135 containing 10% rat serum at 32.5 degrees C under an air; CO2 atmosphere (95%:5%). During the initial culture period (1-3 days) the dissociated cells attached to the culture dish and formed a monolayer. After 4-5 days of culture, aggregates of cells formed at discrete foci within the monolayer; these structures averaged 50 micrometer in diameter and numbered 3-4 X 10(3)/dish. Within 5-6 days of culture some of these aggregates (2-3 X 10(2)) released their contact with the substratum. Histological examination of released aggregates indicated a more regular, tissue-like organization with increasing time in culture. Aggregates at earlier time periods (4-5 days) exhibited concentric rings of cell while by day 6 some aggregates exhibited a vesicular appearance with a single layer of columnar epithelium surrounding a fluid-filled lumen. The type of structure formed varied with plating density; at densities less than 2 X 10(6)/dish the structures were spheroid while at greater densities tubes were formed. Time-lapse observations indicated that spheres formed by movements of cells into an aggregating center while tubes formed by a rolling from the edge of the monolayer. The cells comprising the vesicle epithelium appeared to be predominantly one cell type as determined by light microscopy. These results therefore indicate that dissociated testicular cells have the ability to reform tissue-like associations in culture.

Animals↗
PubMed1977

Feto-maternal bidirectional mixed lymphocyte reaction and survival of fetal allograft.

Maternal and fetal lymphocytes were tolerant of each other in the bidirectional mixed lymphocyte reaction. This seems to be the principal reason why the mother does not reject the fetal allograft. Tolerance between maternal and fetal cells must be largely due to a genetic mechanism, because the bidirectional mixed lymphocyte reaction between parents and older children was much reduced compared with that between randomly selected pairs of controls. This weak reaction disappeared when immunosuppressive agents were given to one member of the parent/child pair, whereas the mixed lymphocyte reaction between unrelated individuals was not abolished by similar immunosuppression. It is suggested that this genetic mechanism is distinct from the HLA system. Tolerance between maternal and fetal cells was not demonstrated in the unidirectional mixed lymphocyte reaction, suggesting that this tolerance requires the viability of the two cell populations.

Female↗
PubMed1977

Altitude decompression sickness: hyperbaric therapy results in 145 cases.

Most cases of decompression sickness that occur at altitude resolve upon descent to lower altitudes. Before the use of hyperbaric therapy, cases that did not resolve accounted for some of the most difficult medical management problems in military aerospace medicine. On 27 March, 1941, the U.S. Navy Diving School successfully used hyperbaric therapy for a case of altitude-induced decompression sickness that did not resolve on return to ground level. Since then, over 145 such cases have been treated by hyperbaric therapy. At first, treatments involved using compressed air, with varying success. Current medical management of altitude-induced decompression sickness requires immediate compression to 2.8 ATA, equivalent to 60 ft of sea water (FSW) pressure, and a series of intermittent oxygen and air breathing periods during the subsequent slow decompression to surface. This report confirms the treatment recommendations set forth by Behnke and Downey, and crystallized by Goodman in 1964. Conclusions are based on treatment experience in the management of 120 cases in U.S. Air Force hyperbaric chambers, and a survey of hyperbaric facilities which have treated 25 other cases.

Adult↗