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Biomedical subjects

J F Gennaro

Publications and source records attributed to J F Gennaro.

5 recordsLinked to original sources
PubMed1979

A morphometric analysis of the glomerular capillary wall of a new strain of genetically hypertensive mice.

An investigation was performed on a new strain of genetically hypertensive mice to study those aspects of the renal glomerulus which have in the past been implicated in the etiology of renal parenchymal hypertension. Morphometric analyses were carried out utilizing a computerized graphic data analysing system on information obtained through transmission electron microscopy. Chronically hypertensive animals exhibited thinner basement membranes with numerous sub-epithelial focal thickenings, which were largely absent from the normotensive controls. No difference was noted in the width of the epithelial slit pores (interpedicelar spaces). The glomerular capillary loops of the hypertensive animals appeared otherwise unremarkable, as did the urinary space and parietal epithelium of Bowman's capsule. No evidence of renal parenchymal pathologies implicated in the etiology of systemic hypertension was observed, therefore, these animals would seem to be suitable models for human essential hypertension.

Animals↗
PubMed1979

The influence of the buffer on maintenance of tissue lipid in specimens for scanning electron microscopy.

Preparations of tissues and cells for scanning electron microscopy (SEM) fixed with glutaraldehyde (G CHO) buffered in either Na-cacodylate or Piperazine-N-N' bis (20-ethanol sulfonic acid) (PIPES) differ in their morphology. The influence of the nature of these buffers in the tissue fixing and washing solutions on appearance in scanning electron microscopy is described. Biochemical determinations of lipid retention were performed on frog and chick embryos fixed for 24 hours with 3% G CHO in either 0.03 and 0.1 M PIPES (ph. 7.3) or 0.1 M Na-cacodylate (ph. 7.3). Embryonic tissue was chosen for its relatively high lipid content and delicacy which may be expected to enhance the sensitivity at which buffer effects become apparent. The comparable small and uniform sizes of the embryos minimize differences in fixation quality due to penetration. Lipid, recovered from homogenized tissue after treatment with chloroform/methanol/water (1:2.1:1, v/v) was considered as retained. The extraction results, which showed a significant reduction of lipid losses when PIPES buffer was used, are taken to account for the morphological differences observed in SEM and transmission electron microscopy (TEM).

Animals↗
PubMed1978

Reversible depletion of synaptic vesicles induced by application of high external potassium to the frog neuromuscular junction.

1. Reversible depletion of synaptic vesicles from frog cutaneous pectoris neuromuscular junctions was studied by application of a Ringer solution containing 115 mM-K propionate.2. During the release of transmitter, the synaptic vesicle membrane is added to the axolemmal membrane. Under the conditions of high K(+)-induced release, the synaptic vesicle membrane accumulates as folds formed in the region of the axolemmal membrane between the active zones. In depleted terminals, large vesicular structures appear and the evidence shows that some of them (possibly all) are formed as axolemmal infoldings. During formation of such infoldings the active zones remain fixed in position with respect to the post-junctional membrane.3. During recovery in normal Ringer solution, which followed 30 min depolarization in high K(+) Ringer solution, spontaneous m.e.p.p.s were detected as early as 9 min after the start of the recovery period and the average time for their reappearance was 17 min.4. At the end of a 20 min recovery period which followed K(+) depolarization, small accumulations of synaptic vesicles were again found within the terminal close to the active zones. At this time coated vesicles and coated pits were seen associated with the prejunctional axolemma and its infoldings. It appears that synaptic vesicles are re-formed directly from these coated vesicles.5. After 60 min recovery from K(+) depolarization, at which time stimulation of the motor nerve induced a muscle twitch, the structure of the terminals closely resembled that of control preparations.6. The entire synaptic vesicle recycling process can take place in the absence of the neurone soma.

Animals↗
PubMed1975

High-resolution scanning electron microscopy of bacteriophages 3C and T4.

An account is presented of the design and operation of a new scanning electron microscopic, and its first application to the study of biological samples. Bacteriophages were chosen because much of their ultrastructure is beyond the resolution of the conventional scanning electron microscope. The new instrument permits examination of bulk samples with a resolution that exceeds, by at least a factor of 2.5, the resolution obtained in the best secondary electron scanning electron microscopes using high brightness guns, and exceeds by an order of magnitude the resolution of standard scanning electron microscopes using tungsten filament guns. It also permits examination of biological samples in scanning transmission mode at resolutions similar to conventional transmission electron microscopes.

Coliphages↗