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Biomedical subjects

D B Smith

Publications and source records attributed to D B Smith.

At least 253 records · Page 14Linked to original sources
PubMed1980

Auditory averaged evoked potentials and aging: factors of stimulus, task and topography.

The averaged evoked potential to brief tones was compared for 10 young and 10 elderly female subjects. The amplitudes of the sensory components (P1, N1 and P2) were not affected by an infrequent change in pitch of the tones or instructing subjects to count or ignore them; but overall the elderly had a larger P1 and smaller P2 amplitude and a difference in the scalp distribution of P2. Repetition of the tones produced a decrement in these sensory components and a differential one for young and old subjects A slow potential complex consisting of components N2, P3 and SW appeared to changes in tone pitch and became more pronounced when attention was directed to the tones. Overall smaller SPs for oder subjects were interpreted as evidence for a change with age in the cortical representation of the orienting response. Topographical analysis of SPs indicated diminished activity in frontal (Fz) electrodes for elderly persons, suggestive of an enhanced aging process in the frontal cortices.

Adult↗
PubMed1980

Age differences in the contingent negative variation (CNV): reduced frontal activity in the elderly.

The effects of distraction on the contingent negative variation (CNV) were investigated in a group of 11 elderly (mean = 72.2 years) and a group of 12 young (mean = 23.3 years) subjects. Scalp electrical activity was recorded from midline sites at frontal, central, and parietal locations. Three experimental conditions included Recall, No Recall, and Control situations. In the Recall, or distraction condition, spoken consonant-vowel-consonant (CVC) letters were presented concurrently with the CNV signal interval and were recalled by the subjects after each trial. The No Recall condition was similar to the Recall task except that subjects were not required to repeat the CVSs. The Control condition presented a standard S1 - S2 CNV situation without CVCs. Amplitudes of the CNV, reaction times (RTs), and heart rate (HR) served as indices of distraction. The effects of distraction for both age groups indicated reduced CNVs, lengthened RTs, and elevated HRs. However, a significant age by electrode interaction revealed that while CNV amplitudes at central and parietal sites were comparable between age groups, amplitudes at the frontal placement were consistently reduced in the elderly compared to the young in all conditions. The finding of diminished frontal activity, as measured by the CNV, suggests a process of selective cortical aging and possible cellular loss which may be linked to performance deficits.

Adult↗
PubMed1980

Studies on the Wolfgram high molecular weight CNS myelin proteins: relationship to 2',3'-cyclic nucleotide 3'-phosphodiesterase.

Evidence is presented that the major protein components of the high molecular weight CNS myelin proteins designated as the Wolfgram protein doublet (W1 and W2) contain the enzyme 2',3'-cyclic nucleotide 3'-phosphodiesterase (EC 3.1.4.37, CNP). CNP is a basic hydrophobic protein containing about 830 to 840 amino acid residues. When electrophoresed on SDS polyacrylamide gels, CNP appears as a protein doublet, separated by a molecular weight difference of about 2500-3000 in bovine, human, rat, guinea pig, and rabbit. A similar protein doublet has been identified as the Wolfgram proteins W2 and W1 in myelin and in the chloroform-methanol-insoluble pellet obtained from myelin. Moreover, the relative Coomassie blue staining intensity of the CNP2 plus CNP1 protein doublet among the species examined was remarkably similar to that observed for electrophoresed myelin and chloroform-methanol-insoluble pellet derived from myelin. Antisera raised against purified bovine CNP recognized the W1 and W2 proteins isolated from bovine and human brain. The amino acid composition of pure bovine CNP is presented and compared with the compositions of several rat and bovine Wolfgram proteins obtained by other investigators. Our electrophoretic, compositional, and immunological data support the contention that the enzyme CNP is a major component of the Wolfgram protein doublet.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1980

Prolonged succinylcholine-induced apnea caused by atypical cholinesterase: report of case.

A case of prolonged apnea after administration of succinylcholine in a patient homozygous for the dibucain variant cholinesterase (genotype E1aE1a) has been presented. Knowledge of the patient's medical history, preoperative laboratory tests, and the length of apnea enabled the surgical team to eliminate liver disease, carcinoma, and malnutrition from the differential diagnosis. This, in addition to the patient's failure to respond to an anticholinesterase agent, led to the belief that the patient had an atypical cholinesterase response to succinylcholine and not one secondary to a decreased production of cholinesterase enzyme from an impaired liver or prolonged paralysis for the nondepolarizing agent, pancuronium. Treatment consisted of maintaining adequate pulmonary ventilation nitrous oxide sedation to diminish anxiety until the patient regained spontaneous respiration. Anticholinesterase agents were used after the patient had progressed to a phase II depolarization block. After a cholinesterase assay of the family's serum, all members having the atypical allele were instructed to obtain medical alert identification.

Adult↗
PubMed1979

Myoclonus with electrocerebral silence in a patient receiving penicillin.

Multifocal myoclonus is a well-recognized complication of high doses of penicillin. In man, the site of origin of penicillin-induced myoclonus has not been clearly established, but there is evidence from animal studies that it may originate at a cortical, subcoritcal, or spinal level. We report a case of multifocal myoclonus occurring in a patient receiving large doses of penicillin. The myoclonus appeared when there was no clinical or EEG evidence of upper brain stem or cerebral function. The observations reported suggest that penicillin-induced myoclonus may occur in man and may originate at a caudal brain stem or spinal level.

Adult↗
PubMed1979

EEG and autonomic responding to verbal, spatial and emotionally arousing tasks: differences among adults, adolescents and inhalant abusers.

The present study investigated the physiological responses of an adolescent inhalant abuse group, an adolescent non-abuse group, and an adult non-abuse group elicited by three types of tasks: verbal, spatial, and emotionally arousing. Each group consisted of 10 male Mexican-American subjects. Bilateral EEG and electrodermal activity, as well as heart rate, were monitored. While exploring for possible heart rate and hemispheric alpha wave differences in response to predominantly verbal and spatial tasks, an attempt was also made to discover if electrodermal responses could be bilaterally differentiated. Another purpose of the study was to explore possible psychophysiological differences between a younger and older group, and between an inhalant abusing group and a non-abuse group, in response to the three types of tasks. Results indicated that attempts to produce task-related EEG hemispheric asymmetry were largely nonsuccessful. Bilateral electrodermal responses were also not greatly differentiated. It was suggested that stronger task manipulations were needed. Significant group differences were found for initial physiological response levels (adults demonstrated higher levels than the two adolescent groups) and for heart rate response to the emotionally arousing task (non-abusing subjects demonstrated greater heart rate acceleration than inhalant abusing subjects). It was suggested that group differences in initial levels occurred due to the adult groups's greater involvement in the experimental situation. Heart rate differences to the emotionally arousing situation were discussed in terms of Zuckerman's sensation seeking hypothesis.

Adolescent↗
PubMed1979

Stability of microtubule protein over the pH range: 6.9--9.5.

The pH stability range of a microtubule protein preparation has been investigated between 6.9 and 9.5. Microtubule protein was exposed to various pH values in this range and then returned to pH 6.9. The appearance of microtubules as verified by electron microscopy and sedimentation analysis under polymerizing conditions was taken as an indication of a conformationally stable protein. Between pH 6.9 and pH 8.0 the loss in the ability to form microtubules was found to be reversible, at pH 8.2 it was partially reversible, above pH 8.2 it was irreversible. Tubulin and the microtubule-associated protein fraction were separately exposed to high pH. It was observed that tubulin exposed to high pH can still form microtubules in the presence of untreated microtubule-associated protein. On the other hand, microtubule-associated protein exposed to high pH could not initiate microtubule assembly with untreated tubulin. It was concluded from these observations that the loss in the ability of a microtubule protein preparation to assemble at high pH is due to a change in the microtubule-associated protein fraction and that tubulin is conformationally stable even after exposure to pH 9.5.

Animals↗
PubMed1979

Mouthwash and oral cancer: carcinogen or coincidence?

Among 200 patients with squamous cell cancer of the head and neck, 11 persons abstained from all alcoholic beverages and tobacco. All but one of these 11 patients had used mouthwash many times daily for more than 20 years. Most of them used a brand of mouthwash that contained 25% alcohol. This evidence, along with information from other patients, may be used to confirm or refute the theory that mouthwash may be carcinogenic for susceptible persons.

Aged↗
PubMed1979

Evaluation and control of a respiratory exposure to 3-(dimethylamino) propylamine.

In 1974 a study was undertaken to assess the symptoms and pulmonary function of a group of 25 workers who were exposed to an epoxy resin system in the mold room of a ski manufacturing plant. The amine 3-dimethylamino propylamine (3-DMAPA) was the only volatilized substance. Assemblers, the sub-group with the highest breathing zone exposure to 3-DMAPA (0.9 ppm), had the highest prevalence of symptoms and a significant decrease in lung function over the workshift. Extensive improvements in local ventilation reduced the average breathing zone exposure to nearly one-seventh of the 1974 concentration. A 1977 cross-sectional study showed that at this level there was a marked reduction in symptoms and the expiratory function of assemblers no longer decreased over the workshift. Longitudianl comparison of the lung function of workers exposed more than two years showed evidence of a decrease from 1975 to 1977, but none from 1977 to 1978.

Cross-Sectional Studies↗
PubMed1978

Analysis of charcoal tube samples for carbon disulfide using a photoionization detector.

A gas chromatograph equipped with a photoionization detector was used to detect carbon disulfide eluted from charcoal tubes with acetonitrile. Overall sampling and desorption efficiency for carbon disulfide was found to approach 100 percent when compared to a liquid impingement, colorimetric method. A relative standard deviation of 4.78 percent (sampling plus analysis) was observed when the method was applied to a synthetic test atmosphere of 10 parts per million carbon disulfide. Sensitivity of the proposed method will enable concentrations of 0.10 ppm CS2 to be determined in a 10 liter air sample. The photoionization detector offers several advantages over other detectors, namely ease of operation and greater sensitivity.

Acetonitriles↗
PubMed1978

Variance component analysis of allozyme frequency data from eastern populations of Drosophila melanogaster.

Gene frequency variation at eight polymorphic allozyme loci in Drosophila melanogaster populations in North Carollina and the east coast of the United States were analyzed utilizing the variance component estimation procedures suggested by Cockerham (1969, 1973). These variance components were used to estimate correlations of genes within small geographic regions. The average (over loci) correlation between genes in the same individual within subpopulations was estimated to be 0.033. That between genes in the same subpopulation in different individuals was estimated to be very small, although significantly different from zero. The macrogeographic variation measured by the correlation of genes sampled from the same local region was large for some loci and smaller for others. this variation was also analyzed by correlation with latitude and longitude. Several previously recognized clines were identified as were several new clines.--These results were interpreted as indicating either some degree of nonrandom mating and local breeding unit isolation or a low frequency of null alleles. The geographic and temporal variation has no simple interpretation.

Aldehyde Oxidoreductases↗