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Biomedical subjects

H F Clark

Publications and source records attributed to H F Clark.

At least 91 records · Page 5Linked to original sources
PubMed1976

Ocular pathology induced by the suckling mouse cataract agent.

The eye disease caused by SMCA may be best characterized as an endophthalmitis, with early retinitis followed by subsequent posterior uveitis. Pathologic features of lens included: proliferation and abnormal posterior extension of lens epithelium, increased accumulation of lens capsule material, and production of aberrant lens substance. Cataractous change appears to be secondary to intraocular inflammation. In addition to the above pattern, in roughly 20 per cent of all cases, 3 weeks after inoculation, lens capsule is destroyed giving rise to a foreign body granulomatous reaction.

Animals↗
PubMed1975

RNA polymerase associated with virions of pike fry rhabdovirus.

The association of an RNA-dependent RNA polymerase activity with virions of pike fry rhabdovirus has been demonstrated by both in vitro and in vivo studies. The temperature optimum for the in vitro assay is around 20 C, although enzyme activity can be observed at 4 C. Preparations of pike fry virus possess a glycoprotein, a membrane protein, a nucleoprotein, an L protein, and a phosphoprotein, as well as an RNA of about 3.8 times 10-6 mol wt. A protein kinase activity has been found associated with virus preparations. In vitro RNA product analyses indicate that the virus-associated enzyme functions principally as a transcriptase synthesizing viral-complementary, heteropolymeric RNA.

Animals↗
PubMed1975

Cell to cell transmission of virus in the central nervous system. II. Experimental rabies in mouse.

Rabies virus replication in suckling and adult mouse brains inoculated with either fixed or street virus was studied by light and electron microscopy. Chronologic study of fixed virus-infected suckling mice showed that virus budded from the plasma membrane of neuronal cell processes and perikarya prior to the development of intracytoplasmic virus particles. Nucleocapsids and virions were observed exclusively in perikarya and cellular processes of neuronal cells and, on rare exception in an astrocyte indicating high neurotropism of rabies virus regardless of the strain of virus and the age of host animal. Virus transit between contiguous neuronal cell processes and perikarya was observed in suckling and adult mouse brain after both street virus and fixed virus infection. Nucleocapsids and virions were also found in myelinated axons in addition to the unmyelinated neuronal cell processes. The implication of cell to cell spread of virus within the central nervous system in rabies virus infection is discussed.

Animals↗
PubMed1974

Fish rhabdovirus replication in non-piscine cell culture: new system for the study of rhabdovirus-cell interaction in which the virus and cell have different temperature optima.

The replication of three rhabdoviruses associated with diseases of fish has been demonstrated in cells of continuously cultivated non-piscine cell lines. Spring viremia of carp (SVC) virus and the salmonid fish viruses, Egtved and infectious hematopoietic necrosis virus, all replicated in mammalian WI-38 (human diploid cell strain) and BHK/21 cells and in cells of one or more reptilian cell lines at the temperatures commonly used to propagate these viruses in fish cells. The infections were cytopathic: SVC virus plaque assays may be performed in several types of mammalian cell culture. "Autointerference" apparently mediated by abortive "T" particle formation was observed during serial nondiluted passages of SVC virus in BHK/21 and TH1 cells, but not in RTG-2 or WI-38 cells. Optimal temperatures for replication of SVC and Egtved viruses in BHK/21 cells were identical to those determined in poikilothermic vertebrate cell cultures. However, these viruses replicated relatively more efficiently at suboptimal temperatures in "cold-blooded" vertebrate cells than in the hamster cells. Studies of [(3)H]uridine incorporation into uninfected BHK/21 cells incubated at different temperatures revealed that [(3)H]uridine uptake is sharply reduced at temperatures below 24.5 C. Growth curve studies of SVC virus in BHK/21 cells incubated at 23 C revealed that a clear-cut large excess of virus-induced [(3)H]uridine incorporation could be demonstrated in the absence of actinomycin D. Actinomycin D treatment (1 mug/ml) led to efficient inhibition of control cell [(3)H]uridine uptake, but also markedly reduced the total counts per minute of virus-induced [(3)H]uridine uptake, without depressing the yield of released infectious virus. Actinomycin D added to SVC virus-infected BHK/21 cell cultures at concentrations as low as 0.01 mug/ml caused a significant decrease in the level of virus-induced [(3)H]uridine uptake, despite the fact that this concentration is insufficient to efficiently suppress "background" cellular [(3)H]uridine incorporation.

Animals↗
PubMed1974

Electron microscopy of the suckling mouse cataract agent: a noncultivable animal pathogen possibly related to mycoplasma.

The suckling mouse cataract agent (SMCA) is a filtrable (<220 nm), noncultivable agent isolated from ticks in Georgia in 1961. It grows to high titer in the eyes and brains of intracerebrally inoculated mice in which it induces cataract, uveitis, and chronic brain infection. SMCA in high titer may also be recovered from the tissues of embryonated hen eggs in which the infection is lethal within 4 to 9 days. Fine-structural studies of ultrathin sections of pellets obtained by ultracentrifugation of SMCA-infected egg allantoic fluids have revealed pleomorphic structures with morphological characteristics typical of mycoplasma. Similar organisms have been observed in egg allantoic fluids infected with an SMCA-related tick isolate, GT-48, but not in fluids from uninoculated control eggs. Mycoplasma-like entities were also observed in high concentration within retinal tissues of rats and mice studied at the time of maximal retinitis and uveitis after SMCA inoculation. Comparable tissues from normal mouse eyes were free of microorganisms. These fine-structural observations are in agreement with those reported by other investigators and suggest that SMCA-induced pathology is associated with an agent that resembles mycoplasma in size and morphology but differs from typical mycoplasma in its apparent non-cultivability on artificial media and its resistance to inactivation by broad-spectrum antibiotics.

Animals↗
PubMed1974

Detection of homologous RNA sequences among six rhabdovirus genomes.

Complete transcripts of the genome of vesicular stomatitis virus Indiana strain have been used to hybridize to virion RNA to determine if there is RNA sequence homology among these viruses. Cellular RNA from cells infected by each of these viruses has also been used for hybridization with the homologous or heterologous virion RNA. The results indicate that there is little exact sequence homology among these viruses.

Adenosine↗