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Biomedical subjects

H C Powell

Publications and source records attributed to H C Powell.

16 recordsLinked to original sources
PubMed1979

Endoneurial fluid pressure in wallerian degeneration.

Endoneurial fluid pressure (EFP) was recorded by an active, servo-null pressure system after a glass micropipette was inserted into rat sciatic nerve undergoing wallerian degeneration. The lesions were produced by crushing the left sciatic nerve of the anesthetized animal at its point of entry into the thigh. Eighty-four animals were employed in this experiment, in which EFP was recorded from sham-operated rats and other controls as well as from rats with wallerian degeneration. The experiment was designed so that EFP could be recorded from 2 or more experimental animals at daily intervals starting at day 0 and concluding on day 28. Pressure progressively increased during the first week, reaching a peak elevation four to five times normal. The subsequent decline in EFP was more gradual, with values approaching normal during the third week after injury. Linear regression analysis showed the progressive increase in EFP to be statistically significant (p less than or equal to 0.01). To determine the time at which EFP was maximum, we used the Marquardt computer algorithm for lease-squares estimation of nonlinear variables. By this procedure the peak value for EFP occurred at six days. These biophysical observations were correlated with subsequent microscopic examination of 1 mu thick sections of Araldite-embedded sciatic nerve. Microscopy confirmed the presence of wallerian degeneration associated with edema, which was observed in every instance of elevated EFP.

Animals↗
PubMed1978

Expornitic of avian pox in a zoo.

During a 6-week period at the San Diego Zoo, avian pox occurred in 9 pheasants representing 5 species. Lesions were limited to facial skin and consisted of epithelial cell hyperplasia, secondary inflammatory changes, and intracytoplasmic eosinophilic inclusion bodies which, by electron microscopy, were shown to contain pox virus. The disease was self-limiting in 7 pheasants, but 2 pheasants died. Free-ranging Indian red junglefowl were implicated as the source of the infection.

Animals↗
PubMed1978

Toxoplasmosis of the central nervous system in the adult. Electron microscopic observations.

The fine structure and reproductive mechanisms of Toxoplasma gondii are described in a case of toxoplasma encephalitis. Replication was observed in glial cells by an internal budding process: endodyogeny. Distinctive ultrastructural features associated with host cell penetration, and encystation are described. Electron microscopic features previously reported in tissue culture and in experimentally produced infections with T. gondii are confirmed in the human brain tissue.

Brain↗
PubMed1978

Endoneurial pressure in hexachlorophene neuropathy.

Increased endoneurial pressure of up to 17.0 cm H2O was recorded in the peripheral nerves of rats fed hexachlorophene in their laboratory diet. The pressure was measured using a micropressure transducer developed for recording pressure in the microcirculation. The results were correlated with morphologic findings. Teased nerve fibers and araldite-embedded specimens of hexachlorophene damaged sciatic nerve revealed the characteristic severe intramyelinic edema due to splits in the minor dense lines of compact myelin giving rise to wide interlamellar spaces as shown in previous studies. The endoneurial pressure of rats exposed to hexachlorophene for 11 days and subsequently fed a normal diet returned to normal (0.2-3.0 cm H2O) after 12 days, and morphologic examination showed few residual abnormalities. Prolonged exposure to hexachlorophene for up to 4 weeks caused widespread axonal degeneration in addition to intramyelinic edema. Animals treated with hexachlorophene for 21 days followed by a normal diet for 14 days showed degenerated axons, phagocytosis of myelin as well as interstitial edema and elevated endoneurial pressure. It is suggested that axonal degeneration in hexachlorophene neuropathy is caused by increased endoneurial pressure.

Animals↗
PubMed1978

Schwann cell abnormalities in 2,5-hexanedione neuropathy.

Distinctive cytoplasmic alterations of Schwann cells were observed by electron microscopy in rats and mice with peripheral neuropathy induced by chronic exposure to 2,5-hexanedione. Pronounced enlargement of Schwann cells was due to accumulation of 100 angstrom cytoplasmic filaments and endoplasmic reticulum and was most often observed after 12--15 weeks exposure to 2,5-hexanedione. Examination of teased nerve fibres revealed segmental demyelination and remyelination involving axons of normal diameter as well as giant axons. The filament disorder induced by 2,5-hexanedione administration is not limited solely to axoplasmic contents. Possible mechanisms of demyelination are discussed and the changes are compared to those observed in human neuropathy for which 2,5-hexanedione appears to be the closest experimental model.

Animals↗
PubMed1977

Post-irradiation pituitary sarcoma.

A fibrosarcoma developed in the pituitary fossa of a patient who had been irradiated 13 years previously for treatment of pituitary adenoma. The tumor was a large aggressively growing spindle cell neoplasm which eroded adjacent structures, causing increased intracranial pressure, and eventual cerebellar tonsillar herniation. In common with previously described post-irradiation sarcoma of the pituitary, this lesion developed in the path of irradiation after a long latent period, did not metastasize, and contained histologically recognizable benign appearing pituitary adenoma interspersed among the spindle cell tumor. The dose of radiation (5000 rads) also lay within the range associated with sarcomatous transformation.

Aged↗
PubMed1977

Congenital lobar emphysema.

Congenital lobar emphysema is reported occurring in a 10 day old, low birth weight infant. Following resection, gross examination of the affected lobe revealed collapsed but unobstructed bronchi, suggesting a cartilaginous defect. The specimen was insufflated with formalin and the bronchial tree dissected out. Histological study including comparison with a normal pulmonary lobe, confirms that abnormalities of cartilage may be important in the pathogenesis of congenital lobar emphysema.

Cartilage↗
PubMed1977

Electron-microscopic appearance of the DA virus, a demyelinating murine virus.

The DA virus is a neurotropic murine virus which can induce acute encephalomyelitis in suckling mice and a chronic myelopathy in weanlings. The agent has been attenuated by serial passage in baby hamster kidney (BHK-21) cells. When attenuated virus is inoculated in 8-week-old C3HeJ mice a myelopathy of delayed onset with prominent demyelination of lateral and anterior columns occurs. The DA virus is believed to be related to the Theiler murine encephalomyelitis (TME) viruses because of the similar clinical and pathological conditions which it causes, and because neutralization tests indicate shared antigens between it and GD7, a TME virus. This paper reports electron-microscopic studies of BHK-21 cells infected with DA virus. The cells were prepared 24 and 48 hr after inoculation. Cytopathic effects were observed and infected cells contained plaques consisting of numerous 25 nm virus particles in crystalline array. The virions were exclusively intracytoplasmic and were morphologically indistinguishable from human poliomyelitis virus. These observations appear to establish DA as a picorna virus, related to the TME virus group. The chronic myelopathy caused by DA may prove relevant to chronic demyelinative myelopathies in man, such as multiple sclerosis, and also to amyotrophic lateral sclerosis.

Animals↗
PubMed1976

Foamy changes of placental cells in fetal storage disorders.

Vacuolar cytoplasm in placental cells was observed in four cases. In each instance the baby was either stillborn or died soon after birth. One infant was shown to have Inclusion cell disease (Mucolipidosis II), whereas in the other cases biochemical studies were noncontributory or could not be carried out. The histologic changes of the placenta described in this report were restricted to the fetal elements and also included the X cells, providing further evidence that these cells are of fetal rather than maternal origin.

Adult↗
PubMed1976

Neutrophilic leukocyte inclusions in colchicine intoxication.

Large, darkly staining, intracytoplasmic inclusions were observed in the neutrophils of a young woman after suicidal ingestion of colchicine. The polymorphonuclear neutrophils also contained intracytoplasmic and intranuclear vacuoles. Electron microscopy enabled further characterization of these morphologic changes that, although nonspecific, are consistent with certain known toxic effects of colchicine.

Adolescent↗
PubMed1975

Meningoencephalitis with toroidal virus-like particles.

A previously healthy middle aged man died following a 6 month illness which presented with middle ear symptoms, apparently resolved, and then 2 months later manifested as encephalitis. The illness was characterized initially by depression and intellectual deterioration. No family member or working associate was affected. The clinical diagnosis of viral encephalitis was confirmed by brain biopsy but no virus was isolated in the laboratory. Numerous intracisternal toroidal virus-like particles were demonstrated by electron microscopy in the perikarya and dendrites but not in glia. The particles resemble, but are not identical to, the oncornaviruses associated with spontaneous and induced murine neoplasms. The resemblance of these structures to the intracisternal toroidal type "A" virus of murine leukemia is noted and other possible causes for this atypical meningoencephalitis are discussed.

Dendrites↗
PubMed1975

Oligodendrocytes and their myelin-plasma membrane connections in JHM mouse hepatitis virus encephalomyelitis.

Mice infected with JHM strain of mouse hepatitis virus develop a demyelinating encephalomyelitis. Myelin sheaths are stripped off axons by invading macrophages after degeneration of the infected oligodendrocytes. The derivation of the virus from granular cytoplasmic particles that condense around and bud into endoplasmic reticulum is demonstrated. The infected oligodendrocytes undergo hypertrophic changes prior to degeneration. Hypertrophic cells are characterized by abundant microtubules, filaments, mitochondria, aggregates of electron-dense particles, and numerous, unusual plasma membrane connections to myelin lamellae. Vacular and hydropic changes are prominent in degenerating cells. The significance of finding infected oligodendrocytes with altered myelin-plasma membrane connections is discussed with reference to the pathogenesis of recurrent, postinfectious demyelination known to develop subsequent to acute virus infections.

Animals↗
PubMedDate not supplied

Increased endoneurial fluid pressure in galactose neuropathy.

Edema and increased endoneurial fluid pressure developed in peripheral nerves of rats that received a diet containing 40% galactose during a study of the role of sugar alcohols in producing neuropathy. Fluid pressure was elevated starting in the third month and progressed to a fivefold increase over control values by the fifth month. Microscopic examination confirmed the presence of edema as predicted by the sorbitol theory, which is often invoked to explain the pathogenesis of diabetic neuropathy.

Animals↗