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Biomedical subjects

D Davis

Publications and source records attributed to D Davis.

At least 235 records · Page 13Linked to original sources
PubMed1987

Norepinephrine kinetics during orthostatic stress in congestive heart failure.

To evaluate the determinants of the plasma norepinephrine (NE) response to orthostatic stress, NE kinetics were measured during steady-state infusion of [3H]NE of high-specific activity for two consecutive 90-minute periods; the first was supine, and the second was during 60 degrees head-up tilt. In 6 normal subjects, plasma NE increased from 242 to 570 pg/ml, and NE clearance decreased from 1.43 to 1.00 l/min X M2. In 6 patients with congestive heart failure, there was no significant change in plasma NE during orthostatic stress. This has been interpreted previously to indicate that there was little activation of the baroreflex arc. In fact, NE clearance decreased from 1.08 to 0.79 l/min X M2; however, there was a decrease in NE spillover from 4.04 to 2.88 nmol/min X M2. A reduction of organ blood flow with tilt could be responsible for the reduced NE clearance by both groups, but the mechanism for the reduction in NE spillover with tilt in congestive heart failure is unclear.

Adult↗
PubMed1986

Heterogeneity in distribution and content of p53 in SV40-transformed mouse fibroblasts.

The high level and intranuclear location of the cellular phosphoprotein p53 are usually regarded as invariant features of SV40-transformed fibroblast lines. During the development of improved methods for immunocytochemical detection of p53 using SVA31 E7 mouse fibroblasts, we have observed unexpected and marked variations in its distribution. Cells grown on plastic coverslips were fixed in acetone and the content and distribution of p53 and SV40 large T-antigen analysed by an indirect immunoperoxidase procedure using monoclonal antibodies PAb122 and PAb 248 for p53, and PAb416 for large T. First, we observed in all cultures an apparent reversal of intracellular compartmentalization, with strong cytoplasmic and absent nuclear/chromatin positivity in mitotic cells and young daughter cells. More importantly, for a short period, between 18-24 h after trypsinization and cell passage, we observed a marked overall reduction in detectable nuclear p53 content in all cells with both PAb122 and PAb248 antibodies. The first observation also held for SV40 large T-antigen, the second only for p53. These variations have important practical implications for the immunocytochemical analysis of cellular content and intracellular compartmentalization of p53. The biological implications of our findings are also discussed.

Animals↗
PubMed1986

Menopause research: the Korpilampi workshop.

A workshop on menopause research focused on three topics: (1) problems and issues in the definition of menopausal status: (2) problems and issues in cross-cultural research: (3) the contributions which research in the behavioural sciences can make to clinical research and practice. Among the conclusions reached by the workshop was the recommendation that researchers should adopt a standard definition of menopause based on the cessation on menses. Yet, while standard definitions are essential to scientific comparison, it is also important to determine how women decide on their own status, particularly when working cross-culturally.

Adult↗
PubMed1986

Simplified method for dissolved DNA determination in aquatic environments.

A method was developed for the determination of dissolved DNA in aquatic environments. The method is based upon the concentration of dissolved DNA by ethanol precipitation of 0.2-mum-pore-size filtered water. The DNA in concentrated extracts was quantified by the fluorescence of Hoechst 33258-DNA complexes. Fluorescence not attributable to DNA was corrected for by DNase I digestion of the extracts and averaged 25% of the total fluorescence for all samples. The effectiveness of the procedure for concentrating dissolved DNA was demonstrated by the efficient (>90%) recovery of internal standards. Concentrations of dissolved DNA from a variety of marine and freshwater environments ranged from 0.2 to 44 mug/liter, with the highest values being obtained for estuarine and river environments. The method is simple, specific for DNA, and more sensitive than previously described methods for the determination of extracellular DNA.

Journal Article↗
PubMed1986

Mechanical support of the circulation followed by cardiac transplantation.

Improvements in both mechanical circulatory support devices and immune therapy promise a wider use of sequential mechanical support as a bridge to orthotopic cardiac transplantation. The intra-aortic balloon pump, the left and right ventricular assist pumps, and the pneumatic artificial heart represent the range of devices capable of keeping a patient alive who is awaiting a donor organ. The major difficulty in using circulatory support devices is infection, which is caused by their required percutaneous tubes. We report here our experiences with mechanical circulatory support devices as a bridge to cardiac transplantation. In a series of 31 consecutive transplant procedures, six patients have required preoperative mechanical circulatory support. The intra-aortic balloon pump was used in two patients for 2 and 14 days, respectively, before transplantation. Both patients are well 10 and 11 months after the transplant procedure. Two patients required the left ventricular assist device for 11 and 21 days and are alive 3 weeks and 8 months, respectively, after transplantation. One patient was supported by the pneumatic artificial heart for 10 days before a donor heart became available but died of septic shock 17 days after transplantation. A second patient received a pneumatic artificial heart 7 days after transplantation when the heart transplant failed. He has been in stable condition for 45 days but is recovering from renal failure. Our early experiences indicate that either partial or total mechanical support as a bridge to transplantation is successful if overwhelming sepsis or renal failure can be avoided.

Adult↗
PubMed1985

15N-labeled Escherichia coli tRNAfMet, tRNAGlu, tRNATyr, and tRNAPhe. Double resonance and two-dimensional NMR of N1-labeled pseudouridine.

The N1 imino units in Escherichia coli tRNAfMet, tRNAGlu, tRNAPhe, and tRNATyr were studied by 1H-15N NMR using three different techniques to suppress signals of protons not attached to 15N. Two of the procedures, Fourier internuclear difference spectroscopy and two-dimensional forbidden echo spectroscopy permitted 1H and 15N chemical shifts to be measured simultaneously at 1H sensitivity. The tRNAs were labeled by fermentation of the uracil auxotroph S phi 187 on a minimal medium containing [1-15N]uracil. 1H and 15N resonances were detected for all of the N1 psi imino units except psi 13 at the end of the dihydrouridine stem in tRNAGlu. Chemical shifts for imino units in the tRNAs were compared with "intrinsic" values in model systems. The comparisons show that the A X psi pairs at the base of the anticodon stem in E. coli tRNAPhe and tRNATyr have psi in an anti conformation. The N1 protons of psi in other locations, including psi 32 in the anticodon loop of tRNAPhe, form internal hydrogen bonds to bridging water molecules or 2'-hydroxyl groups in nearby ribose units. These interactions permit psi to stabilize the tertiary structure of a tRNA beyond what is provided by the U it replaces.

Escherichia coli↗
PubMed1985

Anomalous left coronary artery from the pulmonary artery: significance of associated intracardiac defects.

Two patients with anomalous origin of the left main coronary artery from the pulmonary artery had an associated defect (one, critical pulmonary stenosis; the other, ventricular septal defect). They presented with signs and symptoms of the associated defect and the coronary anomaly was unrecognized. Both cases at autopsy lacked the usual large right coronary artery seen with this anomaly. The pathophysiologic features of the combined defects are described, their differences from the isolated anomaly are noted and their relation to surgery is discussed.

Abnormalities, Multiple↗
PubMed1985

The pulmonary hypertension of sclerosing agents is prevented by cyclooxygenase inhibitors.

Sodium morrhuate and sodium tetradecylsulfate are injected during endoscopic sclerotherapy to control variceal bleeding. When administered to sheep they cause transient pulmonary hypertension and increase protein poor lung lymph flow. To determine the etiology of these alterations, we studied three groups of sheep after establishing acute lung lymph fistulas. In Group 1, indomethacin or ibuprofen was infused. In Group 2, 2.5 cc of sodium morrhuate was injected alone (2A) or after indomethacin or ibuprofen pretreatment (2B). In Group 3, 2.5 cc of sodium tetradecylsulfate was given intravenously either alone (3A) or after indomethacin or ibuprofen (3B). When sclerosing agents were given alone (Group 2A and 3A) pulmonary artery pressures increased three-fold at 30 seconds postinjection to 37 +/- 4.4 and 39 +/- 5.7 mmHg respectively with a slow return to baseline over two hours. Lymph flow increased significantly from 1.3 +/- 1.5 to 2.7 +/- 1.5 cc/30 minutes after sodium morrhuate and from 1.2 +/- .62 to 2.7 +/- 1.7 cc/30 mins at 30 minutes after sodium tetradecylsulfate and the lymph/plasma albumin ratio fell. Increased lymph flow persisted through 120 minutes. In those animals receiving a sclerosing agent after indomethacin or ibuprofen (2B and 3B) there was no change in pulmonary artery pressure, lymph flow, lymph plasma albumin ratio, or lung wet weight to dry weight ratios. We conclude that the pulmonary hypertension and increased protein poor lymph flow are mediated by prostaglandins.

Animals↗
PubMed1985

The effects of age and smoking on the plasma protein binding of lignocaine and diazepam.

In 63 healthy ambulant subjects 18 to 88 years of age, the plasma protein binding of diazepam (principally bound to albumin) decreased with age. Diazepam binding in plasma correlated positively with plasma albumin concentration which also decreased with age. In contrast, the plasma protein binding of the basic drug, lignocaine (predominantly bound to alpha 1-acid glycoprotein [AAG]), tended to increase slightly with age. Lignocaine binding in plasma correlated positively with plasma AAG concentration which also increased slightly with age. Smoking did not affect the plasma protein binding of diazepam or lignocaine or the plasma concentrations of albumin, AAG or nonesterified fatty acids. These results suggest that age-related changes in plasma protein binding of lignocaine and diazepam are determined in part by age-related changes in the concentrations of the binding proteins in plasma. The ageing process alone causes only small changes in the plasma protein binding of these drugs compared with the effect of disease states, however.

Adolescent↗
PubMed1985

The longitudinal course of recurrent affective illness: life chart data from research patients at the NIMH.

Using data gathered in a naturalistic study of 95 research patients at the NIMH, a retrospective method of documenting the life course of recurrent affective illness is presented, along with a partial prospective validation of this method. In these patients, the severity, frequency, and duration of manic and depressive episodes, as well as their pattern and distribution, are characterized. These variables are examined in different patients subgrouped according to gender and age of onset, polarity, and rapidity of cycling of illness. The findings are compared with data on the life course of affective illness found in studies from the pre-pharmacologic era.

Adult↗
PubMed1985

Localization of acyl carrier protein in Escherichia coli.

Acyl carrier protein was localized by immunoelectron microscopy in the cytoplasm of Escherichia coli. These data are inconsistent with the previous report of an association between acyl carrier protein and the inner membrane (H. Van den Bosch, J.R. Williamson, and P.R. Vagelos, Nature [London] 228:338-341, 1970). Moreover, bacterial membranes did not bind a significant amount of acyl carrier protein or its thioesters in vitro. A thioesterase activity specific for long-chain acyl-acyl carrier protein was associated with the inner membrane.

Acyl Carrier Protein↗