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Biomedical subjects

G E Olson

Publications and source records attributed to G E Olson.

At least 73 records · Page 4Linked to original sources
PubMed1980

Changes in intramembranous particle distribution in the plasma membrane of Didelphis virginiana spermatozoa during maturation in the epididymis.

Structural specializations in the plasma membrane of opossum spermatozoa obtained from different levels of the epididymis have been analyzed in thin sections and freeze-fracture replicas. The maturation process was accompanied by a redistribution of intramembranous particles in the flagellar midpiece region. Caput epididymal spermatozoa are immotile, and freeze-fracture replicas of the midpiece plasma membrane reveal a random arrangement of intramembranous particles. As spermatozoa transit the corpus epididymis, the intramembranous particles in the midpiece plasma membrane are redistributed from a random arrangement to an organized packing pattern. This redistribution apparently involves the formation of chains of intramembranous particles which gradually increase in length, orient parallel to the flagellar long axis, and ultimately form numerous parallel rows, each three to five particles wide. In cauda epididymal spermatozoa the intramembranous particles within the rows are packed in an organized manner, and few free intramembranous particles are noted between rows. Analysis of thin sections revealed that the reorganization of intramembranous particles is accompanied by the deposition of a mat of amorphous material at the cytoplasmic face of the membrane. No striking changes in intramembranous particle distribution during epididymal maturation were found in other flagellar segments or in the plasma membrane overlying the sperm head.

Animals↗
PubMed1980

A silver method for staining normal axis cylinders of central nervous system structures.

The fink-Heimer stain for degenerating axons has been modified for demonstration of normal axis cylinders. The technique stains tissue prepared from a variety of fixation protocols. Vibratome prepared sections, coupled with an efficient use of laboratory time makes this procedure a simple, quick, and repeatable general technique. This preparation provides valuable insight into the histological organization of the intact central nervous system.

Animals↗
PubMed1977

Regional variation in the surface morphology of the epithelium of the rat ductuli efferentes, ductus epididymidis and vas deferens.

The luminal surface of epithelial cells lining the ductuli efferentes, ductus epididymidis and first portion of the vas deferens were studied with the scanning electron microscope. In ductuli efferentes obvious ciliated cells are identified and it is shown that on non-ciliated cells the short microvilli adhere to one another to form clumps of microvilli. In the epididymis two cell types are described and can be identified as principal cells and clear cells based on the presence or absence of microvilli. Clear cells vary in number along the duct, being most numerous distally. Their surface morphology is also most variable distally. In the vas deferens, principal cells with surface microfilli are easily identified; but, in addition, a second cell type is seen, the identity of which is not known.

Animals↗
PubMed1976

Morphological changes in the midpiece of wooly opossum spermatozoa during epididymal transit.

Several ultrastructural changes were found to occur in the midpiece region of wooly opossum spermatozoa during epididymal maturation. The changes include alterations in mitochondrial morphology, development of structural specializations of the plasma membrane, and acquisition of a prominent extracellular coating. The lamellar membrane network which is wound about the periphery of the mitochondria becomes more densely packed during sperm development and the reticular network of membranes noted in the center of the mitochondria of immature sperm disappears leaving a homogeneous electron dense central zone. During epididymal transit the plasma membrane over the sperm midpiece region shows extensive structural modification. In cross sections of paired spermatozoa the plasma membrane of the midpiece regions shows a very regular, repetitive scalloping. In longitudinal sections the scalloping is observed as continuous parallel ridges which extend slightly obliquely to the flagellar long axis. Each ridge appears to be greater in density than the interridge areas. In the epididymis a prominent extracellular coating of dense material is deposited over the midpiece surface; this material is similar in appearance to dense material seen in restricted areas of the epididymal lumen. At the proximal and distal ends of the midpiece the plasma membrane comes into intimate contact with underlying structural specializations and it is suggested that these zones of fusion may serve to preserve regional differences in membrane composition.

Animals↗
PubMed1976

Isolation and characterization of the perforatorium of rat spermatozoa.

The perforatorium of rat spermatozoa was isolated and its protein composition determined. SDS-polyacrylamide gel electrophoresis showed that the organelle is composed of a single polypeptide component with a molecular weight of 13,000. The perforatorium becomes more resistant to solubilization during epididymal transit due to an apparent increase in disulphide bond content. Amino acid analysis of the perforatorium polypeptide revealed a content of 6-5% cysteine.

Amino Acids↗
PubMed1975

Effect of various corticosteroids upon the phagocytic bactericidal activity of neutrophils.

Corticosteroid compounds are used broadly in surgical practice, although mechanisms remain unclarified and efficacy in some situations remains unproved. A recognized adverse effect of steroids in all doses is the potentiation of infection. Specific derivatives of the glucocorticoids appear to have varying degrees of effectiveness in the enhancement of bacterial infection. To evaluate such effects objectively, a series of experiments was undertaken to measure the phagocytic-bactericidal activity of polymorphonuclear leukocytes. This study examines the differential effects of clinical dose equivalents of four glucocorticoid derivatives in depressing in vitro neutrophil phagocytic-bactericidal function. Neutrophils separated from normal human plasma were incubated in vitro in the presence of hydrocortisone sodium phosphate, hydrocortisone sodium succinate, dexamethasone sodium phosphate, and methylprednisolone sodium succinate. Hydrocortisone sodium phosphate, hydrocortisone sodium succinate, and dexamethasone sodium phosphate produce variable, short-term inhibitory effects upon the systems within the neutrophil which are responsible for its bactericidal competency. Methylprednisolone sodium succinate appears to be free of these adverse effects. These in vitro experiments indicate that diminished risk of infection should attend the use of methylprednisolone sodium succinate, although the precise mechanism have not been defined.

Adrenal Cortex Hormones↗
PubMed1971

Isolation of circular deoxyribonucleic acid from Salmonella typhosa hybrids obtained from matings with Escherichia coli Hfr donors.

Heterozygous, partial diploid Salmonella typhosa hybrids obtained from matings with Escherichia coli K-12 Hfr strains were observed to contain supercoiled, circular deoxyribonucleic acid (DNA) when examined by the dye-buoyant density method. Examination of one such S. typhosa hybrid after its loss, by segregation, of the inherited E. coli genetic markers revealed a concurrent loss of its supercoiled circular DNA. Subsequent remating of this segregant with various E. coli Hfr strains resulted in the reappearance of the circular DNA. Molecular weight determinations of circular DNA molecules isolated from a number of S. typhosa partial diploid hybrids were made by sucrose density gradient ultracentrifugation and electron microscopy. These studies revealed a range of molecular sizes among the various hybrids examined, but each hybrid exhibited only a single characteristic size for its contained circular DNA. The range of size is consistent with the presence in each hybrid of a different length of E. coli chromosome. It was concluded that the E. coli Hfr genetic segments transferred to these S. typhosa hybrids were conserved, in the diploid state, in the form of supercoiled, circular DNA molecules.

Centrifugation, Density Gradient↗