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Biomedical subjects

J H Davis

Publications and source records attributed to J H Davis.

At least 127 records · Page 7Linked to original sources
PubMed1983

Death and injury caused by methyl bromide, an insecticide fumigant.

Methyl bromide (MeBr) is used as an insecticide fumigant. Four deaths and three recent hospitalizations have resulted from exposures to MeBr in Dade County, FL. Six cases occurred during burglaries of tented houses over a nine-month period. In four lethal exposures, the symptoms of nausea, vomiting, and malaise preceded fulminant respiratory failure. Two of these also had seizures, delirium, and agitation. Serum or plasma bromide ion levels ranged from 40 to 583 mg/L. Pulmonary edema, hyaline membranes, and hemorrhagic alveolitis were present at autopsy along with varying degrees of cerebral edema. The nonlethal exposures resulted in symptoms of conjunctival irritation, headache, or nausea. Plasma bromide concentrations varied between 17.5 and 321 mg/L. Methyl bromide characteristics, use, morbidity, and mortality in Florida during the past 25 years are reviewed. Remedies for illegal entry are proposed.

Adolescent↗
PubMed1983

Carotid body tumors.

A review of seven carotid body tumors less than 5 cm in diameter confirms the thesis of other recent reports that such tumors can be resected with minimal morbidity. In two of our cases, initial exploration and biopsy were performed not suspecting the nature of the neck mass; in one of these, hypoglossal and facial nerve deficits resulted. Angiography was diagnostic in six of our seven cases and should be used to establish the diagnosis preoperatively in any neck mass of doubtful origin where carotid body tumor is a part of the differential diagnosis.

Adolescent↗
PubMed1983

The acetaminophen experience in south Florida.

Toxicology records of the Dade County Medical Examiner Department were reviewed for the years 1972 to 1981. Any case in which acetaminophen was detected, regardless of the cause of death, was included in the study. Of 95 cases where acetaminophen was detected, no trends were observable in age, sex, or race. Acetaminophen deaths have increased in recent years, probably because of increased marketing of products containing this substance. Some two thirds of the cases involved suicides or accidental deaths, with 40 cases being directly attributable to overdose with a variety of drugs. It is suggested that acetaminophen may be a useful indicator of polydrug overdoses.

Acetaminophen↗
PubMed1983

Beneficial effects of verapamil on postischemic renal failure.

The effects of calcium blockade with verapamil on postischemic renal failure were tested in dogs. Two experiments were performed. In experiment 1 (n = 7), one kidney in each dog received an infusion of verapamil and the other received saline for 30 minutes prior to induction of 1 hour of ischemia. Inulin clearance (CIN), urine flow, and renal blood flow (RBF) were measured. Infusion of verapamil increased urine flow from 0.99 to 4.29 ml/min (P less than 0.001). CIN and RBF did not change significantly nor did urine flow in the saline-treated kidney. Three hours after ischemia there was no significant difference in CIN, although it was lower in verapamil-treated kidneys. RBF declined in both treatments. In experiment 2 (n = 6) kidneys were treated with verapamil and saline for 50 minutes beginning immediately after 1 hour of ischemia. Urine flow and CIN were significantly higher in verapamil-treated kidneys during the infusion (3.09 +/- 0.44 versus 0.26 +/- 0.12 ml/min, P less than 0.001; 28.6 +/- 7 .4 versus 6.2 +/- 3.1 ml/min, P less than 0.025, respectively). CIN remained elevated in verapamil-treated kidneys at 3 hours, however RBF was depressed in both verapamil- and saline-treated kidneys. These results suggest that verapamil is a potent diuretic and that verapamil can be given after renal ischemia with significant attenuation of postischemic renal failure.

Acute Kidney Injury↗
PubMed1982

Evidence for protein-associated lipids from deuterium nuclear magnetic resonance studies of rhodopsin-dimyristoylphosphatidylcholine recombinants.

The technique of deuterium magnetic resonance was used to study the orientational order of the perdeuterated acyl chains of dimyristoylphosphatidylcholine (DMPC-d54) reconstituted with rhodopsin between 0 and 23 degrees C. This range includes the gel to liquid crystalline phase transition of DMPC-d54 at 20 degrees C. Molar lipid/protein (L/P) ratios of L/P = infinity, 150, 50, 30, and 12 were investigated. Measurements of orientational order parameters showed that the addition of rhodopsin broadened the range of the gel to liquid crystalline transition for L/P = 150 and 50. No transition was observed for L/P = 30 and 12. Moment analysis and spectral subtraction both showed that the low temperature spectra for L/P greater than 30 had two components. One was a pure phospholipid gel phase spectrum and the other a spectrum attributed to lipids in protein aggregates. The intensity of the second component corresponded to 30 lipids/protein and its shape was the same as the temperature-independent shape observed for L/P = 30 and 12. No such decomposition into two components was possible in the liquid crystalline phase for L/P greater than 30. Extraction of the oriented 2H NMR spectrum from its powder spectrum showed that the presence of proteins does not modify the distribution of quadrupole splittings but does produce both homogeneous and inhomogeneous broadening. The latter may be related to the heterogeneity seen in the spectra of electron paramagnetic resonance spin labels above the gel to liquid crystalline transition.

Dimyristoylphosphatidylcholine↗
PubMed1982

Human erythrocyte membranes are fluid down to -5 degrees C.

This first observation of the deuterium nuclear magnetic resonance (2H-NMR) spectrum of phospholipid molecules incorporated into intact human erythrocyte ghosts shows that the liquid crystalline phase is stable down to a temperature of -5 degrees C. The quality of the 3H-NMR spectra indicate that it is now possible to carry out clinical studies of erythrocyte membranes using the techniques employed in this study.

Erythrocyte Membrane↗
PubMed1981

Dynamical and temperature-dependent effects of lipid-protein interactions. Application of deuterium nuclear magnetic resonance and electron paramagnetic resonance spectroscopy to the same reconstitutions of cytochrome c oxidase.

2H NMR and EPR spectra have been obtained as a function of temperature and protein concentration from the same samples of beef heart cytochrome c oxidase reconstituted into 1-(16,16,16-trideuteriopalmitoyl)-2-palmitoleoyl-sn-glycero-3-phosphocholine. At all temperatures, the EPR spectra show the characteristic "bound" and "free" components, while the 2H NMR spectra show only a narrow distribution of orientational order parameters. At temperatures near the phase transition of the pure lipid, the dependence of the 2H NMR average orientational order on protein concentration fits a two-stage model in which the phospholipid molecular exchange rapidly between two states tentatively identified as sites either on or off the protein surface. From this model, the 2H NMR spectra yield a value of 0.18 mg of phospholipid per mg of protein as necessary to cover the surface of cytochrome c oxidase, which is the same value as derived from the EPR spectra at -20 degrees C. Both the 2H NMR and EPR spectra vary markedly with temperature. At temperatures well above the phase transition of the pure lipid, the average orientational parameters derived from the 2H NMR spectra are independent of protein concentration and are the same as for the lipid alone. Qualitatively, the EPR spectra show large apparent decreases in the average orientational order with increasing temperature. Analysis of 2H NMR relaxation rates indicates an additional motion in the presence of protein with a correlation time of 10(-6)-10(-7) s. If this new motion is associated with exchange between the two states, a minimum value of 10(6)-10(7) s-1 for the exchange rate is obtained, assuming that the lipids on the protein surface are much more motionally restricted than the rest of the lipid. Such an exchange rate is compatible with the observed differences in 2H NMR and EPR spectra. These results are consistent with short-lived, energetically weak interactions between cytochrome c oxidase and the phospholipids used in this study.

Animals↗
PubMed1981

Structure and chemistry of a metal cluster with a four-coordinate carbide carbon atom.

Molecular metal clusters with carbide carbon atoms of low coordination number have been prepared; they are the anionic [HFe(4)C(CO)(12) (-)] and [Fe(4)C(CO)(12) (2-)] clusters. An x-ray crystallographic analysis of a tetraaminozinc salt of the latter has established a butterfly array of iron atoms with the carbide carbon atom centered above the wings of the Fe(4) core. Each iron atom was bonded to three peripheral carbonyl ligands. The distances from the carbide carbon to iron were relatively short, particularly those to the apical iron atoms (1.80 A average). Protonation of the anionic carbide clusters reversibly yielded HFe(4)(CH)(CO)(12), and methylation of the dianion gave {Fe(4)[CC(O)CH(3)](CO)(12) (-)}. Oxidation of [Fe(4)C(CO)(12) (2-)] yielded the coordinately unsaturated Fe(4)C(CO)(12) cluster, which was extremely reactive. Hydrogen addition to this iron cluster was rapid below 0 degrees C, and a C-H bond was formed in this transformation.

Journal Article↗
PubMed1981

Adoption planning for handicapped children. A medical-social work partnership.

Major changes are taking place in the field of adoption. Once concerned primarily with the placement of newborn infants, the field has broadened, with a major emphasis on the adoption of older children, often from foster care and many times with major handicaps or problems. These children require special families who are willing to adopt them. They require the services of skilled social workers to effectively place them, and they require understanding of the physician who may be involved either with their placement examination or with their subsequent management as an adoptee. A new objective approach to the problem is necessary.

Adoption↗
PubMed1981

Adoption: pediatric, legislative and social issues.

Physicians may find themselves involved in many phases of the adoption process, ranging from advising infertile couples who wish to adopt a child to caring for adopted children, adolescents or adults. Recent legislation has been aimed at making it possible for children to be adopted who have been receiving foster care and at providing financial assistance to implement the adoption of children with handicaps and with medical problems. The adoption process is becoming more open. Adoptees are searching for and finding their biological parents and all parties in the "adoption triangle" are developing relationships with one another.

Adoption↗
PubMed1981

Sudden unexpected death from primary pulmonary hypertension.

Five cases of sudden unexpected death from primary pulmonary hypertension (PPH) are reviewed. Right ventricular myocardial hypertrophy and a dilated pulmonary conus may be the only findings at the initial gross examination. Characteristic microscopic changes in the lungs are primarily those of plexiform vascular lesions. The pathophysiology and morphologic alterations of PPH are discussed, and the association of this entity with collagen vascular diseases and mixed connective tissue disease is emphasized. It is concluded that PPH is an unusual cause of sudden unexpected death and its diagnosis may be difficult because prior signs or symptoms may be absent. The increased familial incidence of PPH underscores the necessity of considering this entity in cases of sudden unexpected death of obscure cause.

Adult↗
PubMed1980

The temperature dependence of molecular order and the influence of cholesterol in Acholeplasma laidlawii membranes.

2H nuclear magnetic resonance (NMR) of Acholesplasma laidlawii membranes grown on a medium supplemented with perdeuterated palmitic acid shows that at 42 degrees C or above, the membrane lipids are entirely in a fluid state, exhibiting the characteristic 'plateau' in the variation of deuterium quadrupolar splitting with chain position. Between 42 and 34 degrees C there is a well-defined gel-to-fluid phase transition encompassing the growth temperature of 37 degrees C, and at lower temperatures the membranes are in a highly ordered gel state. The 2H-NMR spectra of the gel phase membranes are similar to those of multilamellar dispersions of chain perdeuterated dipalmitoyl phosphatidylcholine (Davis, J.H. (1979) Biophys. J. 27, 339) as are the temperature dependences of the spectra and their moments. The incorporation of large amounts of cholesterol into the membrane removes the gel to fluid phase transition. Between 20 and 42 degrees C, the position dependence of the orientational order of the hydrocarbon chains of the membranes is similar to that of the fluid phase of the membranes without cholesterol, i.e., they exhibit the plateau in the deuterium quadrupolar splittings. However, the cholesterol-containing membranes have a higher average order, with the increases in order being greater for positions near the carbonyl group of the acyl chains. Below 20 degrees C the 2H spectra of the membranes containing cholesterol change dramatically in a fashion suggestive of complex motional and/or phase behaviour.

Acholeplasma laidlawii↗
PubMed1980

Quantitative study of the fluidity of Escherichia coli membranes using deuterium magnetic resonance.

Specifically deuterated palmitic acid was incorporated into the membrane phospholipids of the L51 strain of Escherichia coli. The cytoplasmic and outer membranes were separated by using standard techniques and studied by deuterium nuclear magnetic resonance between 0 and 40 degrees C. Distinctive liquid-crystalline and gel spectra were observed to coexist over a wide temperature range. The relative intensities of these spectra provided a direct measure of the fraction of the deuterium-labeled phospholipids in the fluid state as a function of temperature. Above 37 degrees C, the amount of immobilized or gel-phase phospholipid is estimated to be less than 3% of the total phospholipid. The gel to liquid-crystalline transition region for the outer membrane was shifted upwards by approximately 7 degrees C relative to that of the cytoplasmic membrane, in agreement with previous studies [Davis, J. H., Nichol, C. P., Weeks, G., & Bloom, M. (1979) Biochemistry 18, 2103]. The orientational order in the fluid phase of both membranes decreased gradually with increasing temperature and was greater in the outer membrane than in the cytoplasmic membrane. The orientational order of the gel-phase component was the same for both membranes, within an experimental uncertainty of 10%, and was independent of temperature from 0 to 30 degrees C for the outer membrane and from 10 to 30 degrees C for the cytoplasmic membrane.

Cell Membrane↗
PubMed1980

The very sudden cardiac death syndrome -- a conceptual model for pathologists.

Sudden unexpected death usually involves one of two mechanisms, fast heart stoppage or slow heart stoppage with respiratory arrest. These physiological derangements arise from diverse causes that are sometimes purely functional without structural correlates. The autopsy is considered to be only an investigative tool to be employed and is interpreted in the light of the terminal event, social and medical history, and environmental circumstances.

Alcoholism↗