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Biomedical subjects

D E Phillips

Publications and source records attributed to D E Phillips.

69 records · Page 4Linked to original sources

An electron microscopic study of alterations in mouse peripheral nerve and skeletal muscle after chlordecone exposure.

Skeletal muscle and peripheral nerve of mice exposed to subacute doses of chlordecone were examined by electron microscopy to characterize the induced pathology. Adult mice were given daily ip doses of chlordecone for 8 days, then sacrificed on days 8, 15, and 35 of the experiment. Sciatic nerve and gluteal muscle were removed and prepared for electron microscopic examination. In peripheral nerve the most common effect was vesiculation of the cytoplasm of Schwann cells associated with unmyelinated fibers. Some unmyelinated axons were swollen and their microtubules and neurofilaments were replaced by flocculent material. In other unmyelinated axons some mitochondria contained paracrystalline inclusions. Myelinated axons, myelin, and associated Schwann cells were generally unaffected by the chlordecone. In skeletal muscle, during more acute phases of exposure, mitochondrial envelopes increased in density, cristae structure was altered, and membranous whorls were formed in or adjacent to the mitochondria. Glycogen and lipid deposits were decreased in acute phases. During the recovery phase glycogen, lipids and mitochondria reassumed normal structure.

Animals↗

Characteristics of mast cells in Chediak-Higashi mice: light and electron microscopic studies of connective tissue and mucosal mast cells.

The beige mouse, a homologue of the Chediak-Higashi syndrome in man, possesses abnormally large granules in many tissue cells. The granules in the mucosal mast cells (MMC) of the small intestine of beige and littermate C57BL/6J mice were examined after infecting the mice with the intestinal parasite, Nippostrongylus brasiliensis. MMC in both beige and littermate mice had irregular granules which contained paracrystalline substructures embedded in an amorphous matrix. Granules were not observed in fusion with the cell membrane. Instead, in late-stage mast cells, the granule membrane broke down, the granule contents were spread throughout the cytoplasm, and the cell organelles disintegrated. Unlike connective tissue mast cells, MMC were poorly demonstrated with formalin fixation and toluidine blue staining.

Animals↗

Ultrastructure of a marine Synechococcus possessing spinae.

Two Chesapeake Bay isolates of unicellular cyanobacteria belonging to the genus Synechococcus are described. Unicellular cyanobacteria are suspected to be important primary producers in estuarine and marine waters. One isolate (P-11-16) fluoresces red and forms green colonies. The other isolate (P-11-17) fluoresces orange and forms red colonies. Their ultrastructure is very similar to other isolates of Synechococcus except that spinae are formed and are attached to an outer wall layer not found in previously described species. The spinae are straight-walled cylinders, not flared at the base, are 44.0-65.0 nm in diameter, and range up to 2.7 micrometer in length. Substructure of the spinae wall consists of either material organized into stacks of rings or a strand of material helically coiled at a low (1-6 degrees) angle. Such material yielded a 6.0-9.2 nm cross-banding periodicity. Substructure of the rings or strand appeared to consist of bar-shaped, repeating units as seen in negatively stained material. Other procaryotic cell types with spinae, which were isolated from unincubated, natural seawater, are described.

Cell Wall↗

Validity of the laser refraction technique for meridional measurement.

This study assessed the validity of the laser refraction technique for determining the refractive status of a given meridian of the eye. A subjective-to-BVA finding was taken on a total of 75 eyes, and the laser technique was then used to refract each of the 2 principal meridians that had been located by the subjective procedure. Correlations between laser and nonlaser findings indicated that the laser technique is a valid method for meridional refraction. Differential findings for against-the-rule astigmatism are also discussed.

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The development of the blood-brain barrier in alcohol-exposed rats.

Circulating horseradish peroxidase (HRP) was used as a tracer to determine if the blood-brain barrier to protein was altered by dietary prenatal alcohol exposure. Animals were prepared for light microscopic visualization of HRP after HRP infusion on gestational days 16, 18, 20, 22 and postnatal day 4. There was no consistent evidence of HRP leakage through the BBB in the alcohol-exposed animals compared to control animals. Capillary endothelial cells and perivascular astrocytic endfeet were morphologically characterized by electron microscopy in rat optic nerve and cerebellum following dietary prenatal and postnatal ethanol exposure. Photomontages of optic nerve capillaries from G20 and P5 animals and cerebellar capillaries from P15 animals were examined for evidences of effects of alcohol on the development of the capillaries and adjacent astroglial endfeet. There was no consistent evidence of any alcohol-induced effect that could indicate a disruption of the vessel, the endothelial tight junctions, the perivascular glial limiting membranes, or the extent of vascular ensheathment by astrocytic endfeet.

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