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Biomedical subjects

R L Berry

Publications and source records attributed to R L Berry.

26 records · Page 2Linked to original sources
PubMed1990

A slice preparation preserving the callosal projection to contralateral visual cortex.

Due to the curved path they follow, the visual callosal projections to areas OC1 and OC2 of the rat visual cortex have been inaccessible to studies using brain slices. In this paper we describe a new slice preparation in which a curved cutting blade was used to obtain slices in which callosal fibers projecting to OC1 or OC2 are preserved. Stimulation of the contralateral white matter resulted in EPSPs recorded in layer II/III and V cells of OC2 studied with intracellular recording. Current source density analysis of extracellular field potentials collected in OC1 and OC2 revealed laminar current sink patterns paralleling the laminar distribution of callosal terminations reported by Miller and Vogt (Dev. Brain Res., 14 (1984) 304-309). Exposure of slices to 2 mM kynurenic acid reversibly abolished current sinks in OC1 recorded in response to callosal stimulation indicating that glutamate receptors mediate the response of OC1 to callosal afferent activity. This new slicing technique can be readily adapted to study other systems in the nervous system in which neural processes follow curved trajectories.

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PubMed1989

Induction of LTP in rat primary visual cortex: tetanus parameters.

Long-term potentiation (LTP), intensively studied in the hippocampus as a possible mnemonic device, has begun to be studied in the neocortex. In this study the effects of varying tetanic stimulus parameters on LTP of field potentials recorded from layer II/III induced by white matter stimulation in the in vitro rat visual cortical slice were examined. Low intensity tetanus was more effective in producing LTP than high-intensity tetanus, although single pulses of very high intensity reliably resulted in LTP. LTP consistently occurred following 2 Hz-60 min, or 100 Hz-10 min tetanus; whereas, 10 min of 7 and 25 Hz tetanus usually resulted in long-lasting depression. Although no obvious rule related tetanus frequency and duration to the incidence of LTP, an inverted-U relationship was found between tetanus frequency and LTP magnitude.

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PubMed1986

Aedes canadensis, a vector of La Crosse virus (California serogroup) in Ohio.

Aedes canadensis was shown to be a vector of La Crosse (LAC) virus in Ohio through isolation of LAC virus from field-collected specimens, infection of 54 of 72 (75%) individuals when fed on viremic suckling mice and transmission of LAC virus by 29 (54%) of infected individuals. Frequent identification of Ae. canadensis as a human biting species implicates it as an auxiliary vector of LAC virus to man. A possible regional association in Ohio of Ae. canadensis and Type C LAC virus is discussed.

Aedes↗
PubMed1983

Reservoir of St. Louis encephalitis virus in Ohio bats.

Inoculation of the big brown bat (Eptesicus fuscus) with a small dose of a St. Louis encephalitis (SLE) virus strain isolated in Ohio indicated that the big brown bat was susceptible to infection. The virus was maintained in the bats through hibernation (70 days), and the bats developed a viremia within 4 days of arousal from hibernation (105 days after inoculation). A field survey of 390 big brown bats and little brown bats (Myotis lucifugus) conducted in 5 regions of Ohio during 1979 to 1981 revealed a SLE virus-neutralizing antibody prevalence of 9%. Cohabitation of natural caves and abandoned mineshafts in Ohio by Culex pipiens mosquitoes, big brown bats, and little brown bats was also documented. Demonstration of a 9% prevalence rate of neutralizing antibody to SLE virus in big brown bats and little brown bats in Ohio during a nonepizootic period indicated that the bat may be involved in the maintenance of SLE virus in enzootic foci and could have a role in dissemination of SLE virus to epizootic foci.

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