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Biomedical subjects

S L Miller

Publications and source records attributed to S L Miller.

At least 145 records · Page 8Linked to original sources
PubMed1980

Fluoride content of domestic waters and mortality due to ischemic heart disease.

The benefits attributed to the ingestion of water-borne fluorides reportedly extend beyond a reduction in the incidence and prevalence of dental caries. Among those claimed is that fluorides may prevent atherosclerosis. In this study, a retrospective analysis of mortality data for 1970 in 15 Texas cities with different levels of natural fluorides in their water supplies revealed no significant differences in the number of deaths caused by ischemic heart disease ( a measure of terminal atherosclerosis). Conversely, the presence of "excessive" flourides did not increase the number of deaths related to atherosclerosis.

Adolescent↗
PubMed1980

Breast self-examination in the primary care setting.

Very little is known about breast self-examination (BSE), a health practice that has been found to be associated with better clinical and pathological breast cancer outcomes. Using data obtained from a sample of 260 women frequenting three primary care centers, this study investigates rates of BSE and how such rates are affected by social and medical factors. Results indicate that BSE practices are influenced to some extent by a woman's race and level of education, while they are significantly affected by her religion. In contrast, there was no evidence to suggest that a woman's knowledge of breast cancer risk factors, or her own level of risk for the disease, affect the extent to which she is likely to self-examine. These findings suggest the need to confirm these social influences on BSE practice using a larger, population based sample. Moreover, the values and attitudes affecting differential rates of BSE performance should be further investigated.

Adult↗
PubMed1979

The porous-surfaced electrode: a new concept in pacemaker lead design.

Three major problems which may be encountered with endocardial pacemaker electrodes are a lack of stable position, a chronic increase in stimulation threshold, and a diminishing magnitude of the sensed endocardial signal. These problems are particularly manifest in the atrium. Having previously shown that porous metal surfaces can support stable tissue ingrowth in both bloodstream and soft tissue environments, we set out todetermine the performance of porous-surfaced endocardial pacing electrodes in the atrial position. In two groups of six dogs each, J-shaped atrial leads with Elgiloy electrode tips (2.3 mm. in diameter, 2.3 mm. in length), having either conventional smooth surfaces (control) or porous surfaces (20 to 50 micron particle size) produced by powder metallurgy techniques, were positioned in the right atrial a-pendage. Stimulation thresholds and P-wave amplitude were repeatedly measured until the dogs were put to death 30 w-eks following implantation. The presence or absence of electrode fixation was observed and the atrial tissue reaction was examined grossly and by both light and scanning electron microscopy (SEM). The porous-surfaced electrodes demonstrated superior long-term stimulation thresholds which, at 30 weeks, averaged less then one third of those in the control group. In addition, the porous group showed a small but significant improvement in the amplitude of the sensed P wave. None of the smooth-surfaced electrodes showed fixation, and the tissue reaction consisted of a thick layer of granulation and fibrous tissue on the underlying endocardium, widely separating the electrode from the myocardium. In contrast, all of the porous-surfaced electrodes were fexed to the endocardium by fibrous tissue ingrowth into the surface pores. This tissue fixation of the electrode tip in close proximity to underlying myocytes explains their superior performance.

Animals↗
PubMed1977

Detection of optical asymmetry in amino acids by gas chromatography for extraterrestrial space exploration: results of a new soil processing scheme with breadboard instrumentation.

The life-detection experiments of the Viking spacecraft are of an active biology type that will attempt to elicit metabolic responses from soil samples. Because bioresponses may be difficult to stimulate, it is desirable also to devise a purely chemical life-detection experiment. The unique chemical property of living systems on which such an experiment could be based is the optical activity of the amino acids that compose its protein. We have devised a new soil processing scheme which has been laboratory tested and for which we have built semi-automated breadboard instrumentation. The system involves the operations of heating, filtering, evaporation, conversion of the isolated amino acids to volatile diastereomers, injection onto a gas chromatographic column, and detection using a flame ionization detector. The breadboard form of the soil processing scheme and instrumentation has been successfully end-to-end tested.

Amino Acids↗
PubMed1976

Origin of organic compounds on the primitive earth and in meteorites.

The role and relative contributions of different forms of energy to the synthesis of amino acids and other organic compounds on the primitive earth, in the parent bodies or carbonaceous chondrites, and in the solar nebula are examined. A single source of energy or a single process would not account for all the organic compounds synthesized in the solar system. Electric discharges appear to produce amino acids more efficiently than other sources of energy and the composition of the synthesized amino acids is qualitatively similar to those found in the Murchison meteorite. Ultraviolet light is also likely to have played a major role in prebiotic synthesis. Although the energy in the sun's spectrum that can be absorbed by the major constituents of the primitive atmosphere is not large, reactive trace components such as H2S and formaldehyde absorb at longer wavelengths where greater amounts of energy are available and produce amino acids by reactions involving hot hydrogen atoms. The thermal reaction of CO + H2 + NH3 on Fischer-Tropsch catalysts generates intermediates that lead to amino acids and other organic compounds that have been found in meteorites. However, this synthesis appears to be less efficient than electric discharges and to require a special set of reaction conditions. It should be emphasized that after the reactive organic intermediates are generated by the above processes, the subsequent reactions which produce the more complete biochemical compounds are low temperature homogenous reactions occurring in an aqueous environment.

Amino Acids↗
PubMed1976

Myelin synthesis during postnatal nutritional deprivation and subsequent rehabilitation.

Newborn Long-Evans rats were undernourished by maternal deprivation so that by 20 days of age their body and brain weights were about 45 and 80%, respectively, of the values obtained for control (well-nourished) values. Proteins from myelin of undernourished and control rats were separated by polyacrylamide gel electrophoresis in buffers containing sodium dodecyl sulfate. At 15 and 20 days of age the proportion of basic and proteolipid protein was reduced in the starved animals relative to controls, indicative of a delay in maturation. However, by 30 days of age the composition of myelin from starved and control animals appeared similar. At all ages the yield of myelin from brains of starved rats was less than 25% of that obtained from control animals. A series of isotope labeling experiments, using a double label design, was carried out to compare relative rates of incorporation of radioactive amino acids into individual proteins of various brain subcellular fractions. In 20-day-old rats the incorporation of [3H] OR [14C] leucine or glycine into myelin proteins, relative to incorporation into proteins of other subcellular fractions, is preferentially depressed (about 60%) in starved animals. Synthesis of all the myelin proteins was depressed, supporting the hypothesis that the high molecular weight proteins isolated with myelin are true myelin constituents. Similar experiments were conducted using [3H]-and [14C] acetate, choline, or glycerol as precursors of lipids. Incorporation of isotope into lipids of myelin, relative to lipids of other subcellular fractions, was also depressed by about 60% in starved animals. In several experiments we studied synthesis during rehabilitation (ad libitum feeding) following 20 days of postnatal starvation. After 6 days of rehabilitation, incorporation of radioactive precursors into myelin, relative to other subcellular fractions, was still depressed. This result was true for both proteins and lipids, and was interpreted as evicence against the initiation of a process leading to a net recovery of myelin (i.e., an irreversible deficit of myelin synthesis is induced by this regime of nutritional deprivation).

Animals↗
PubMed1976

Preparation of large numbers of uniform tracheal organ cultures for long term studies. I. Effects of serum on establishment in culture.

Rat tracheas were each sectioned into fourteen rings of equal size with a slicing device which holds evenly spaced razor blades in register. The razor blades were positioned to minimize shearing of tissues during sectioning so that there was no gross tissue disruption or cell death distant from cut edges. Hundreds of these fragments can be conveniently prepared for studies requiring replicate samples. The cultures can be established in McCoy's 5a (modified) medium with or without calf serum. Cultures grown in the presence of calf serum were compared with those grown in serum-free medium, using vital phase microscopy, transmission and scanning electron microscopy, and light microscopic autoradiography of thymidine incorporation. When there is calf serum in the medium, epithelization of the entire surface of the ring occurs rapidly with the cells flattening and migrating as a sheet of closely apposed cells. Until migration is complete, mitoses are limited to the original mucosa near the cut edge. Without calf serum, migration is slow. The cells do not flatten or become closely apposed. Mitoses appear later but are present on all areas of the surface before migration is complete. In both serum-containing and serum-free media, ciliated cells are included in the migrating population and differentiation into pseudostratified epithelium occurs on newly epithelialized surfaces. The differing pattern of mitotic activity makes culture in serum-containing media more suitable for studies of wound healing and culture in serum-free medium more useful for some cytotoxicity and carcinogenicity studies.

Animals↗