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Biomedical subjects

R E Perkins

Publications and source records attributed to R E Perkins.

29 records · Page 2Linked to original sources
PubMed1982

Impact of coal-coking effluent on sediment microbial communities: a multivariate approach.

The functional response to and recovery from coal-coking waste effluent was evaluated for sediment microbial communities. Twenty estimates of microbial population density, biomass, and activity were measured five times during a 15-month period. Significant effects on microbial communities were observed in response to both wastewater contamination and diversion of the wastewater. Multivariate analysis of variance and discriminant analysis indicated that accurate differentiation between uncontaminated and contaminated sediments required a minimum of nine estimates of community response. Total viable population density, ATP, alkaline phosphatase, naphthalene, and phenanthrene mineralization rates were found to be highly weighted variables in site discrimination. Lipid and glucose mineralization, nitrogen fixation, and sediment protein also contributed significantly to explaining variation among sites. Estimates of anaerobic population densities and rates of methane production contributed little to discrimination among sites in the environment examined. In general, total viable population density, ATP, and alkaline phosphatase activity were significantly depressed in contaminated sediments. However, after removal of this contamination, the previously affected sites demonstrated greater temporal variability but a closer approximation of the mean response at the control site. Naphthalene and phenanthrene mineralization did not follow the general trend and were elevated at the contaminated sites throughout the investigation. Results of the investigation supported the hypothesis that multiple functional measures of microbial community response are required to evaluate the effect of and recovery from environmental contamination. In addition, when long-term effects are evaluated, select physiological traits, i.e., polyaromatic hydrocarbon mineralization, may not reflect population and biomass estimates of community response.

Journal Article↗
PubMed1980

Neuronal morphology of the rabbit cochlear nucleus.

The cytoarchitecture of the cochlear nucleus in young adult albino rabbits (Cuniculus oryctolagus) has been examined in Nissl- and Golgi-impregnated material to compare rabbit cochlear nucleus with other mammalian species. Cochlear nucleus was subdivided into anteroventral (AVCN), posteroventral (PVCN), and dorsal (DCN) regions, as in other mammals. AVCN was characterized by bushy cells and stellate cells. The "bushy" dendritic trees of adjacent bushy cells often overlapped. PVCN was characterized by octopus, elongate, and stellate cells. The dendritic trees of adjacent octopus cells extended in a parallel array across the auditory nerve fibers. DCN had molecular, fusiform and polymorphic layers. The fusiform cell layer was especially prominent, with the fusiform cells appearing visually to be the organizing elements in DCN. The large cells in DCN were the fusiform and giant neurons; the medium cells were the stellate and elongate neurons; the small cells were the cartwheel, small stellate, and granule cells. The cochlear nucleus of rabbit is essentially similar in cytoarchitectural organization to other mammalian species which have been studied. The detailed morphology of the various cell types seen in Golgi preparations is quite similar to that of cat (Brawer et al., '74), although some differences do exist.

Animals↗
PubMed1979

Comparative effects of Aroclor 1254 (polychlorinated biphenyls) and phenanthrene on glucose uptake by freshwater microbial populations.

The effects of polychlorinated biphenyl (PCB) and phenanthrene stress on glucose uptake by natural microbial populations were examined by the heterotrophic potential technique. Temporal and spatial distributions in glucose uptake velocities were examined for natural samples as well as PCB- and phenanthrene-stressed samples. Statistical analysis indicated significant variability among the various samples. It was demonstrated that the environmental variables contributed significantly to the variability in uptake kinetics. Although general trends indicated a PCB-induced stimulation in uptake velocities, these trends were in part masked by sample variability. Data analysis indicated no statistically significant PCB or phenanthrene effect on either total glucose uptake velocities or the proportion of 14CO2 evolved, as compared to natural unstressed samples.

Aroclors↗
PubMed1977

Electromyographic analysis of the "baccinator mechanism" in human beings.

Electromyography of the muscles of the "buccinator mechanism" was undertaken, utilizing indwelling fine-wire electrodes. Electromyograms were made of 14 subjects with normal occlusion during various oral activities. Several activities elicited simultaneous contraction of all muscles. Simultaneous activity represents a potential restraining force of this muscular band on the dentition.

Action Potentials↗
PubMed1976

Comparison of heat shocking and acridine orange treatment in phage typing of nontypable strains of Staphylococcus aureus.

Forty-five percent of 108 nontypable strains of Staphylococcus aureus from clinical and environmental sources were phage typable after heat shock and acridine orange treatment. Although phage patterns were produced by different types of treatment, the same phage groups were present, showing specificity. The newly typable strains appear to be similar in phage group distribution to the primary typable strains typed at the Peter Bent Brigham Hospital during the same time period. Ten of the originally nontypable S. aureus strains that showed lytic patterns after heat shock or acridine orange treatment were subcultured four times from the treated culture and then tested again with bacteriophages. Phage patterns were still present in 8 of the 10 strains without any further treatment. These findings are compatible with the findings of other workers, who have shown that the insensitivity of primary nontypable S. aureus strains to phage is linked to phage-resistant genes in extrachromosomal genetic elements that can be "cured" by both heat shock and acridine treatment.

Acridines↗
PubMed1975

A study of cochlear innervation patterns in cats and rats with the Golgi method and Nomarkski Optics.

Cochlear innervation patterns were studied in infant cats and rats with the rapid Golgi method. Examination of thick serial sections and surface preparations with the differential interference contrast microscope (Nomarski optics) allowed direct visualization of individually impregnated spiral ganglion cells, complete with their peripheral processes and endings in the organ of Corti. Individually impregnated efferent fibers could be recognized as heavily varicose axons that project radially to endings beneath inner and outer hair cells after taking a tangential course in the intraganglionic spiral bundle. It was often possible to visualize unimpregnated hair cells in contact with the impregnated endings of both types of fibers. There are at least two types of spiral ganglion cells in the cochlea of the infant cat and rat. One type innervates only inner hair cells by means of radial fibers. These ganglion cells constitute the overwhelming majority of ganglion cells impregnated in our preparations, and each cell typically innervates two inner hair cells. Hence, these ganglion cells establish nearly "point-to-point" connections between the auditory nerve and the organ of Corti. The other type of ganglion cell innervates outer hair cells by means of long spiral fibers; each cell typically innervates many outer hair cells through the numerous angular enlargements and short end branches of its spiral fiber. In addition, a few of these spiral fibers also send branches to inner hair cells by means of short collaterals; it remains to be seen if such fibers also occur in mature cochleas. Efferent fibers have been traced to inner and outer hair cell regions. The simplest pattern is formed by fine beaded axons with only a few branches ending mainly beneath inner hair cells. More complex patterns are formed by larger axons with many branches ending beneath inner or outer hair cells. Many efferent fibers send branches to both inner and outer hair cells. Electrophysiological studies so far have not demonstrated different populations of units that clearly correspond to the spiral and radial fibers. Therefore, the physilogical differences between inner and outer hair cell innervation remain undefined.

Afferent Pathways↗
PubMed1975

Bacteriology of normal and infected conjunctiva.

The conjunctivas of 273 inflamed eyes were cultured by both aerobic and anaerobic techniques. Isolations were obtained from 267 (97.8%) of the eyes. Aerobic organisms were isolated from 237 (86.8%) of the conjunctivas. Staphylococcus aureus from 63 (23.1%) of the diseased eyes was the aerobic pathogen most often isolated. Anaerobic bacteria were isolated from 172 (63.0%) of the conjunctivas. Propionibacterium acnes was isolated from 126 (46.2%) of the conjunctivas, and Peptostreptococcus species were isolated from 80 (29.3%) of the conjunctivas. Comparison with the bacteriology of 96 normal eyes showed that anaerobes play a much greater role as etiological agents of conjunctivitis than formerly believed. When anaerobic bacteria were isolated, they appeared on the average in 7 days, indicating that they may be missed by ordinary bacteriological culturing.

Aerobiosis↗
PubMed1974

Cinefluorography.

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Cineradiography↗