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Biomedical subjects

J B Gavin

Publications and source records attributed to J B Gavin.

At least 109 records · Page 6Linked to original sources
PubMed1976

Experimental autoimmune glomerulonephritis in the rat. II. A histopathological and fine structural study.

Human glomerular basement membrane (GBM) emulsified in Freund's complete adjuvant was injected into 16 Holtzman rats. Eleven (69%) of them subsequently developed glomerulonephritis. This disease was characterized by glomerular changes which included focal lobular hypercellularity due to localized hyperplasia of intracapillary (mesangial or endothelial) cells which often obstructed glomerular capillaries. Later, affected lobules showed necrosis of intracapillary cells, and capillary lumina were filled with homogeneous eosinophilic material. An immunoperoxidase technique revealed autologous anti-GBM antibody in all 3 layers of the GBM and in some regions it was present in greater amount in the lamina rara interna and externa than in the lamina densa. Experimental auto-immune glomerulonephritis in the rat is thus characterized morphologically by a focal proliferative glomerulonephritis which proceeds to focal glumerulosclerosis.

Animals↗
PubMed1976

Morphologic and biochemical changes in autolysing dog heart muscle.

The progressive changes in pH, lactate content, and light and electron microscopic appearances were studied in dog myocardium undergoing a 6-hour period of autolysis in vitro at 37 degrees C. and at room temperature. At 37 degrees C. there was a rapid cumulative fall in pH during the 1st hour after excision of the heart and a corresponding increase in lactate content, but little additional change in either subsequently. The nature and sequence of the morphologic alterations at this temperature were generally similar to those which occur in ischemic myocardium in vivo. At room temperature, a much slower cumulative decrease in pH and increase in lactate content took place throughout the whole period of investigation and was paralleled by a slower rate of development of morphologic change.

Animals↗
PubMed1975

The ultrastructure of Candida krusei.

Various methods of chemical fixation and freeze-drying of Candida krusei were compared to determine the most appropriate method for the ultrastructural investigation of the thick walled organisms of this genus. Freeze-drying without chemical fixation was of little value because of insufficient variation in electron density. Potassium permanganate was able to penetrate the intact cell but failed to show cytoplasmic glycogen and lipid and some details of the cell wall. While normal glutaraldehyde, formaldehyde and osmium tetroxide treatment failed to permeate and preserve intracellular structures, several cycles of rapid freezing (- 155 degrees C) and thawing followed by glutaraldehyde fixation and osmium tetroxide post-fixation demonstrated the intracellular details of the majority of cells so treated.

Candida↗
PubMed1975

The ultrastructure of Prototheca wickerhamii.

Two clinical isolates from Prototheca wickerhamii were freeze-dried, fixed and studied by electron microscopy and were also examined growing in culture medium by phase contrast light microscopy. Resting spores placed on fresh medium developed cytoplasmic extensions which sequestrated before proliferation occurred. In the presence of adequate nutrients vegetative spores grew and subdivided to form up to 12 endospores within large sporangia which ruptured to release free spores every 5--6 hours. These proliferating or vegetative spores contained much more endoplasmic reticulum and mitochondria than the resting spores which contained more lipid, and often starch granules as well, but relatively few membranous organelles.

Cell Membrane↗
PubMed1975

The morphology of colony variants of three species of Candida.

The colonies of 12 isolates of 3 Candida spp. with variant colony forms were studied by scanning and transmission electron microscopy. Small colonies were formed by 4 isolates each of C. albicans and C. parapsilosis and by 1 of C. tropicalis. These had an abnormally high proportion of degenerate yeast cells with an associated increase in granular cytoplasmic material intercellularly. The increased matrix in these small colonies formed a thick superficial coat over the organisms. Rough colonies were formed by 1 isolate each of C. albicans, C. tropicalis and C. parapsilosis. The convoluted regions of these colonies contained many pseudohyphal cells but few degenerate cells and little granular or fibrillar material in their intercellular matrices. The shape of colonies of Candida spp. may be altered by variations in the viability or the morphology of the organisms.

Candida↗
PubMed1975

Intercellular matrix in colonies of Candida.

The histochemistry and fine structure of typical colonies of six species of Candida were studied, using a total of 31 clinical isolates. The colonies consisted of viable and degenerate cells which lay in an intercellular matrix. This matrix was made up of amorphous, granular, and fibrillar components, the relative proportions and total amount of which varied from species to species. The cells of all species were surrounded by a zone of homogeneous amorphus material, which may be a highly cross-linked carbohydrate. This separated intact cells from irregularly distributed granular debris derived from the cytoplasm of degenerate cells. Focal cellular degeneration and associated granular debris were present within the colonies of all species and were most common in the surface layers of cells of colonies of C. albicans and C. tropicalis. The large amounts of intercellular matrix in this region formed a surface coat on colonies of these two species. Intercellular strands of cell wall material, and to a lesser extent other membranous elements from degenerate cells, formed a prominent fibrillar meshwork in the colonies of C. albicans and C. tropicalis, but were less common in those of C. pseudotropicalis and C. guilliermondii and seldom seen in those of C. parapsilosis and C. krusei.

Candida↗
PubMed1975

The morphological identification of pathogenic yeasts using carbohydrate media.

Eight isolates of C. albicans were used to determine the frequency with which germ tube formation occurred: on rice extract -Tween 80 agar, on its components, and on 1% bactopeptone agar after three hr at 37 degrees C; in 0.5% aqueous solution of various carbohydrates; in various concentrations of glucose; on 0.5 and 0.1% glucose agar and on various types of agar alone. Subsequently 250 isolates of yeast of the genera Candida, Torulopsis, Trichosporon, Cryptococcus, and Saccharomyces, which were obtained from a clinical laboratory, were spread on rice extract -Tween 80 agar and on 0.1% glucose agar and covered with coverslips. Direct microscopic examination after incubation for three hours at 37 degrees C demonstrated germ tube formation by all 140 isolates of C. albicans, but by none of the other yeasts. The characteristic features of the pseudomycelia of isolates of Candida and Trichosporon were evident on reexamination after a further 45 to 69 hours at room temperature (22 degrees C). These morphological observations suggested the identity of the isolates of Torulopsis, Cryptococcus, and Saccharomyces but identified virtually all (98.2%) of those of the genera which formed pseudomycelia. Of the latter group only four isolates required fermentation and assimilation tests to determine whether they were C. parapsilosis (1) or C. guilliermondii (3).

Agar↗
PubMed1975

Freeze-drying from tertiary butanol in the preparation of endocardium for scanning electron microscopy.

The scanning electron microscope appearances and shrinkage of blocks of canine endocardium prepared by freeze-drying directly, by freeze-drying after replacing tissue water with tertiary butanol (2-methyl propan-2-ol) and by critical point drying were compared. All three methods demonstrated endothelial cells which showed nuclear prominences, microvilli and intercellular boundaries. The microvilli varied in size and number from dog to dog but were generally less well defined in specimens freeze-dried from water. Shrinkage due to t-butanol dehydration was significantly less than that which occurred in ethanol in the critical point drying method. Overall the reduction in surface area was significantly less in specimens freeze-dried directly at -65 C (6.8%) than in those dried from t-butanol at -20 C (15.4%) and those prepared bly critical point drying (22.1%). However the amount of shrinkage observed in t-butanol treated tissue was not significantly different from that which was critical point dried. It was not possible to distinguish between comparable samples prepared by these two methods on the basis of their scanning electron microscopic appearances. Thus the relative simplicity and convenience of the t-butanol method, together with its saving of time, its use of standard freeze-drying equipment and the avoidance of ice-crystal artefact justify its consideration as an alternative method of preparing wet biological tissue for scanning electron microscopy.

Animals↗
PubMed1975

Changes in the microvasculature of ischemic and infarcted myocardium.

The fine structure of the small vessels in experimental myocardial infarcts of 10- to 360-minute duration was studied in 32 dogs and compared with the appearance of the small vessels in the corresponding normal myocardium. Following 10 to 60 minutes of coronary artery occlusion, increasing numbers of endothelial cells showed a marked swelling which was consistent with the presence of an intracellular edema and frequently resulted in various degrees of obstruction of the vessel lumen. After 120 minutes of ischemia, not all endothelial cells were obviously swollen, but all showed signs of degeneration, including changes in organelles similar to those in surrounding muscle cells. A progressive intensification of degenerative changes, particularly with respect to the continuity of the endothelial lining and the integrity of the membrane systems of individual endothelial cells, was observed at 3, 4, 5, and 6 hours after coronary artery ligation, and cell debris could be seen in the lumina of most small vessels.

Animals↗
PubMed1975

Mitochondrial changes in dog myocardium induced by lowered pH in vitro.

The effects of increased acidity and of lactate at acid pH values on the ultrastruct of normal dog myocardium were investigated using a simple in vitro system. Thin tissue slices incubated in isotonic, phosphate-buffered sodium chloride at pH 6.5, 6.8, or 7.0 developed within 10 minutes electron-dense mitochondrial inclusions resembling those seen in dog heart muscle after 40 or more minutes of ischemia. Mitochondria of tissue incubated in a comparable medium incorporating 3000 mu g. of lactate per ml. showed similar electron-dense inclusions, together with marked swelling. These results indicate that lowered tissue pH alone is not responsible for the mitochondrial changes typical of ischemic heart muscle. Since an earlier study has shown that marked mitochondrial swelling without dense granule formation can be produced by incubation of tissue in lactate at physiologic pH, it seems likely that the swelling of mitochondria in ischemic myocardium is due to the accumulation of lactate anions, whereas the development of the mitochondrial inclusions is associated with decreased pH.

Animals↗