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Biomedical subjects

J C Vaughn

Publications and source records attributed to J C Vaughn.

36 records · Page 2Linked to original sources
PubMed1981

Instrumentation needs of research universities.

This article assesses the status of scientific instruments in major research universities and identifies factors that facilitate or impede their development, acquisition, use, and maintenance. Sixteen universities, six national and government laboratories, and nine commercial laboratories were visited; over 700 individuals were interviewed. Data on instrument acquisition and age were collected. Instrumentation was examined in physics, chemistry, biological sciences, earth sciences, and electrical engineering. The study found that the quality of university instrumentation has seriously deteriorated, due principally to a relative decrease in instrumentation funding, inflexibility within the project grant system, and insufficient support for maintenance.

Costs and Cost Analysis↗
PubMed1976

Conservation of repeated DNA base sequences in Crustacea: a molecular approach to decapod phylogeny.

Analysis of data obtained from molecular hybridization of 3H-labeled repetitious DNA has been utilized to reconstruct the broad outlines of phylogenetic relationships among decapod Crustacea. This molecular reconstruction agrees reasonably well with the paleontological record, and with other schemes obtained by comparative morphological and serological approaches. Preliminary evidence is in line with the hypothesis that continuous addition of new repeated sequence families to the genome over long periods of time may in part account for the correlation observed between percent repetitious DNA hybridized and divergence time. It is tentatively concluded that a core of DNA base sequence homology has been highly conserved throughout the evolution of the Crustacea. Demonstration of inter-species sequence homology has important implications to models which relegate a genetic regulatory function to repeated DNAs.

Animals↗
PubMed1975

DNA reassociation kinetics and chromosome structure in the crabs Cancer borealis and Libinia emarginata.

DNA reassociation kinetics have been partly elucidated for the higher crabs C. borealis and L. emarginata, using calf thymus DNA as a standard. These crabs contain no detectable repeated DNA in the approximate multiplicity frequency range 2-100 copies, which is unusual for invertebrate DNAs. Each species contains a component renaturing at an intermediate rate, and also a very rapidly renaturing fraction. The very rapidly renaturing fraction is considerably larger than the cesium chloride-resolvable satellites of each species. The fraction reassociating at an intermediate rate includes sequences with a reiteration frequency of up to 9.0 X 10(4) copies. This is unusually high for invertebrate DNAs. The nearly exact correlation between kinetic complexity and independently determined haploid genome size leads to the conclusion that the most slowly renaturing sequences of both crab species are present only once per haploid genome. Therefore the chromatids of these species are uninemic structures, and there has been no detectable occurrence of polyploid speciation in the recent evolutionary history of either species.

Animals↗
PubMed1972

A kinetic study of DNA and basic protein metabolism during spermatogenesis in the sand crab, Emerita analoga.

Cytochemical and radioautographic techniques define and confirm a staging scheme for developing spermatids of the decapod crab, Emerita analoga. Quantitative photometric data demonstrate that developing spermatids lose a significant proportion of their nuclear proteins, as evidenced by diminishing binding of fluorodinitrobenzene. Photometric results also show that much (but not all) of the spermatid nuclear protein loss is in somatic-type histone, as evidenced by a dramatic fall in the histone/DNA ratio of these cells during a period in which nuclear DNA content remains constant. By the end of spermiogenesis, the sperm nuclear histone and protamine content is approximately zero, whereas some nonbasic protein persists. Loss of spermatid nuclear somatic-type histone is not accompanied by synthesis of gamete-type histone (e.g. protamine or arginine-rich histone), showing that the processes of displacement and synthesis of nuclear basic proteins during histone transition are not subject to obligatory coupling. Labeling studies suggest that nonbasic acrosomal proteins (presumably partly enzymes) are synthesized in the cytoplasm, after which they move into the acrosome. Stainable basic proteins accumulate in the acrosome during precisely the period of nuclear somatic histone loss, suggesting nuclear-cytoplasmic transfer.

Animals↗