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Biomedical subjects

D G Davis

Publications and source records attributed to D G Davis.

104 records · Page 6Linked to original sources
PubMed1969

Nuclear magnetic resonance studies of hemoglobins. 3. Evidence for the nonequivalence of alpha- and beta-hains in azide derivativeof methemoglobins.

Nuclear magnetic resonance spectroscopy (100-MHz proton) was used to study the low-spin (S = 1/2) azide derivatives of human adult (alpha(2)beta(2)), human fetal (alpha(2)gamma(2)), Zürich (alpha(2)beta(2) (63 His --> Arg)), and horse (alpha(2)'beta(2)') methemoglobins, as well as whale metmyoglobin in 0.1 M deuterated phosphate at pD 7 and at 31 degrees C. The experimental results indicate that the azide-bound heme groups of the alpha- and beta-chains in human adult methemoglobin and of the alpha- and gamma-chains in fetal methemoglobin are not equivalent. The affinity of the beta- or gamma-chain for azide ion appears larger than that of the alpha-chain. The nuclar magnetic resonance spectrum of hemoglobin Zürich shows that the environment of the azide-heme complex in the abnormal beta-chain is altered by the substitution of arginine for histidine in the beta-63 position, while the alpha-heme environment remains unaffected.

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PubMedDate not supplied

Midlife blood pressure and neuritic plaques, neurofibrillary tangles, and brain weight at death: the HAAS. Honolulu-Asia aging Study.

Midlife hypertension is associated with later development of cognitive impairment, vascular dementia (VsD), and possibly Alzheimer's disease (AD). Neuropathic cerebrovascular lesions and brain atrophy have been associated with elevated blood pressure (BP), however, to our knowledge there have been no prospective investigations of an association of blood pressure levels measured in midlife with the microscopic lesions of AD. We investigated the relationship of BP level in midlife to development of neurofibrillary tangles (NFT), neuritic plaques (NP), and low brain weight at autopsy among Japanese-American men who were members of the Honolulu Heart Program/Honolulu-Asia aging Study (HHP/HAAS) cohort. The HHP/HAAS is a population-based, longitudinal study of cognitive function and dementia with 36 years of follow-up. Neocortical and hippocampal NFT and NP were counted per mm(2), and fixed brain weight was measured for 243 decedents. Elevated systolic BP, (> or =160 mm Hg) in midlife was associated with low brain weight and greater numbers of NP in both neocortex and hippocampus. Diastolic BP elevation, (> or =95 mm Hg) was associated with greater numbers of NFT in hippocampus. Results indicate that in addition to the accepted association of high BP with neuropathic cerebrovascular lesions, there is a direct relationship with brain atrophy, NP and NFT.

Aged↗
PubMedDate not supplied

Comparison of neuropathologic criteria for the diagnosis of Alzheimer's disease.

The National Institute on Aging and Reagan Institute (NIA-RI) criteria, and other neuropathologic criteria for Alzheimer's disease (AD), were compared with the clinical diagnosis of dementia in a well defined population of Catholic sisters. The 47-participant subset examined in this study were college educated and lacked complicating conditions such as brain infarcts or diffuse Lewy body disease. Sixteen participants had a clinical diagnosis of dementia. The NIA-RI criteria imply a perfect correlation between neuritic plaque (NP) density and neurofibrillary tangle distribution. However, NP density often did not coincide with tangle distribution. As a result, it was not possible to categorize many of the participants using the NIA-RI guidelines. The 'high likelihood' category of the NIA-RI criteria for AD research settings (neocortical Braak stage and frequent neocortical NP) had relatively high specificity (90% of nondemented participants did not meet this criteria). However, only half of the demented participants were in this category. Neuropathologic criteria requiring the presence of neocortical tangles (rather than neocortical Braak stage) had relatively high sensitivity, accounting for 87-94% of participants with dementia, but also included 32-35% of nondemented participants. Criteria based on neocortical NP or senile plaques had 100% sensitivity, but a majority of nondemented participants also met these criteria. The results support consideration of both tangles and NP for the neuropathologic diagnosis of AD, but indicate that refinement of the NIA-RI criteria is necessary. A possible refinement is suggested for further consideration.

Aged↗
PubMedDate not supplied

Metabolic interactions between glucose, glycerol, alanine and acetate in Leishmania braziliensis panamensis promastigotes.

13C-nuclear magnetic resonance (NMR) spectroscopy was used to investigate the products of glycerol and acetate metabolism released by Leishmania braziliensis panamensis promastigotes and also to examine the interaction of each of these substrates with glucose or alanine. The NMR data were supplemented by measurements of the rates of oxygen consumption and substrate utilization, and of 14CO2 production from 14C-labeled substrate. Cells incubated with [2-13C]glycerol released acetate, succinate and D-lactate in addition to CO2. Cells incubated with acetate released only CO2. More succinate C-2/C-3 than C-1/C-4 was released from both [2-13C]glycerol and [2-13C]glucose, indicating that succinate was formed predominantly by CO2 fixation followed by reverse flux through part of the Krebs cycle. Some redistribution of the position of labeling was also seen in alanine and pyruvate, suggesting cycling through pyruvate/oxaloacetate/phosphoenolpyruvate. Cells incubated with combinations of 2 substrates consumed oxygen at the same rate as cells incubated with 1 or no substrate, even though the total substrate utilization had increased. When promastigotes were incubated with both glycerol and glucose, the rate of glucose consumption was unchanged but glycerol consumption decreased about 50%, and the rate of 14CO2 production from [1,(3)-14C]glycerol decreased about 60%. Alanine did not affect the rates of consumption of glucose or glycerol, but decreased 14CO2 production from these substrates by increasing flow of label into alanine. Although glucose decreased alanine consumption by 70%, it increased the rate of 14CO2 production from [U-14C]- and [l-14C]alanine by about 20%.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗