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Biomedical subjects

A Wright

Publications and source records attributed to A Wright.

At least 343 records · Page 19Linked to original sources
PubMed1983

Cytotoxic effect of asbestos on macrophages in different activation states.

The in vitro effects due to phagocytosis of asbestos by mouse peritoneal macrophages in various stages of activation have been compared. The amphiboles proved relatively inert; chrysotile, however, expressed a greater degree of cytotoxicity toward those populations of macrophages induced in vivo with asbestos, than toward any of the other populations of cells. These results are compared with data concerning the enzyme release from the different populations of macrophages following phagocytosis of asbestos. The results indicate that those macrophages that have been exposed to a prior stimulation of either amphibole or serpentine asbestos in vivo are particularly sensitive to exposure to a second dose of a toxic fiber.

Animals↗
PubMed1983

Some observations on the in vitro cytotoxicity of chrysotile prepared by the wet dispersion process.

Samples of the chrysotile taken during and after treatment by the wet dispersion process have been tested for their cytotoxic effect in vitro and the results compared with both a UICC chrysotile A sample and a dust prepared from a standard chrysotile textile yarn. Results were obtained from three different in vitro assay systems utilizing P388D1, V79-4 and A549 cells. A sample which still contained the wetting agent used in the wet dispersion process failed to show activity in any of these assays. The other samples, however, were all active with those dusts obtained by milling the final product and by sampling the air of the factory consistently proving significantly more cytotoxic than the standard chrysotile controls. Preliminary results from a parallel in vivo study suggest that these samples are also more active in producing mesotheliomas in rats.

Animals↗
PubMed1982

The Pietermaritzburg craniofacial unit.

The Pietermaritzburg Craniofacial Unit was established in 1976, and since its inception 150 patients with major skull and facial deformities have been referred there from centres throughout South Africa. Fifty craniofacial operations have been performed by the surgeons of the Unit, who form only a part of a team of 16 members from many branches of the medical, dental and allied professions. Craniofacial surgery is defined and reasons are presented for limiting the number of such highly specialized units.

Face↗
PubMed1982

Escherichia coli DNA topoisomerase I mutants have compensatory mutations in DNA gyrase genes.

Escherichia coli deletion mutants lacking DNA topoisomerase I have been identified previously and shown to grow at a normal rate. We show that such strains grow normally only because of spontaneously arising mutations that compensate for the topoisomerase I defect. Several of these compensatory mutations have been found to map at or near the genes encoding DNA gyrase, gyrA and gyrB. DNA gyrase assays of crude extracts show that strains carrying the mutations have lower gyrase activity. Thus the mutations are in the gyrase structural genes or in nearby regulatory sequences. These results, in conjunction with DNA supercoiling measurements of others, indicate that in vivo DNA superhelicity is a result of a balance between topoisomerase I and gyrase activities. An excess of negative supercoils due to an absence of topoisomerase I is deleterious to the cell, but a moderate gyrase deficiency is not harmful.

Chromosome Deletion↗
PubMed1982

Patterns of cloacal water and electrolyte excretion in constantly-loaded intact and colostomized ducks (Anas platyrhynchos).

1. The patterns of cloacal water and electrolyte excretion were qualitatively similar in intact and chronically colostomized ducks given oral loads of either distilled water or electrolyte solution. 2. The rates of Na+ and K+ excretion were each selectively increased in birds loaded with solutions containing a relatively higher concentration of each ion. 3. Compared to the intact birds, the colostomized birds showed lower rates of electrolyte excretion following administration of identical electrolyte loads and thus appeared to be retaining electrolyte. 4. At the same time, a significant antidiuresis of similar magnitude occurred in each group of saline-loaded birds. 5. The possible contributions of renal and post-renal mechanisms to the overall conservation of water in intact and colostomized ducks are discussed.

Animals↗
PubMed1982

Giant cilia in the human organ of Corti.

Fusion of cilia, the growth of clumps of fused cilia and giant cilium formation have been studied in the normal human organ of Corti using the scanning electron microscope. These unusual forms are found mainly in the apical portions of the cochlea and appear to precede the loss of normal apical cilia which increases and extends in a basal direction with age. These changes may be due to low frequency noise damage or be a phenomenom of ageing. The mechanism of their formation is discussed in the light of recent experimental work on cell fusion.

Adult↗
PubMed1981

Scanning electron microscopy of the human cochlea--the organ of Corti.

The surface of the organ of Corti from normally hearing adult humans has been examined with the scanning electron microscope. It is possible to construct cytocochleograms and to derive a regression line with confidence limits to represent the distribution of the sensory hair cells. Examining individual hair cells more closely, the number of cilia on each hair cell, decreased linearly with distance, from the base of the cochlea. However, the length of the longest cilia on each outer hair cell increased linearly with distance.

Adult↗
PubMed1981

Scanning electron microscopy of the normal human cochlea.

Preservation of the fine structures of the human cochlea has been achieved by perfusing the cochlea with fixative shortly after death. Following the dissection of the temporal bone the surface of the organ of Corti and stria vascularis has been examined in the scanning electron microscope. The surfaces of the inner and outer hair cells can be seen and the stereocilia projecting from their surfaces closely examined. The number and length of the stereocilia of the outer hair cells changes linearly with distance along the cochlear duct. The surface of the stria vascularis is similar to that seen in other animals.

Adult↗
PubMed1981

Does tracheostomy in children retard the growth of trachea or larynx?

Tracheostomy in children has been reported to cause tracheal stenosis, laryngeal stenosis and subsequent difficulties in decannulation. No long term follow-up studies appear to be in the literature describing the events following decannulation. This study compared the radiological size of the cricoid and tracheal lumens with that of normals. Except in special cases tracheostomy did not affect the subsequent growth of the trachea or cricoid. It is suggested that traumatic tracheal narrowing in children should be managed conservatively.

Child↗
PubMed1981

Isolation and characterization of amber mutations in gene dnaA of escherichia coli K-12.

Amber mutants with defects in the dnaA gene of Escherichia coli K-12 were isolated after localized mutagenesis of the tna-dnaA region of the chromosome. We isolated 36 mutants defective in the initiation of deoxyribonucleic acid replication as determined by their dependence upon integrative suppression by a P2 sig5 prophage. Three of the 36 mutants were shown to contain amber mutations through the use of a temperature-sensitive amber suppressor. These mutations, which mapped between gyrB and tna, were characterized genetically and biochemically as amber mutations in dnaA.

Bacterial Proteins↗
PubMed1981

Cloning and restriction mapping of the alkaline phosphatase structural gene (phoA) of Escherichia coli and generation of deletion mutants in vitro.

The structural gene for alkaline phosphatase (phoA) of Escherichia coli was cloned into the PstI site of pBR322, from a transducing bacteriophage, lambda p(phoA-proC). The restriction map of the plasmid was established. Based upon this information, several phoA deletion plasmids as well as a smaller phoA+ plasmid were constructed. The genetic map and restriction map were correlated by recombination analysis. Cells carrying one of the phoA+ plasmids overproduce alkaline phosphatase 10-fold upon phosphate limitation. However, both regulation and processing of the enzyme were found to be normal.

Alkaline Phosphatase↗
PubMed1980

Scanning electron microscopy of the human cochlea - the stria vascularis.

The endolymphatic surface of the stria vascularis from normally hearing human ears has been studied with the scanning electron microscope. The cells in contact with the endolymph usually have a hexagonal-shaped surface and possess many microvilli, whilst depressions or pits are rarely seen. There is marked heterogeneity of these cells with variations in the size of the cells and the number of microvilli present on each cell. A transitional zone occurs between the stria vascularis and the spiral prominence. The surface of the cells of the transitional zone are larger and elongated whilst the cells of the spiral prominence have a smaller and more regular appearance.

Adult↗
PubMed1980

Scanning electron microscopy of the human cochlea--postmortem autolysis artefacts.

Changes in the ultrastructure of the cochlea due to postmortem autolysis make the assessment of the normal or damaged anatomy difficult. Three methods of preserving the human cochlea were compared on the basis of the state of preservation of the sensory cell hairs of the organ of Corti as seen in the scanning electron microscope. Perfusion of the perilymphatic space with a glutaraldehyde-formaldehyde fixative within 40 min of death gave preservation as good as that seen in animal studies. Injecting formalin into the middle ear within 40 min of death allowed artefacts to develop when compared with the control ear which had been perfused with fixative. Refrigeration and early removal of the temporal bone gave poor preservation of surface structures.

Autolysis↗