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Biomedical subjects

K M Johnson

Publications and source records attributed to K M Johnson.

At least 253 records · Page 14Linked to original sources
PubMed1978

The effect of delta9-tetrahydrocannabinol on the conversion of [3H]trypotphan to 5-[3H] hydroxytryptamine in the mouse brain.

The effects of a 30-min pretreatment with varying doses of delta9-tetrahydrocannibinol (delta9-THC) on the synthesis of 5-[3H]hydroxytryptamine (5-[3H]HT) from an intravenous 10-min pulse of L-[3H]tryptophan ([3H]try) were measured in the mouse brain. We also determined the effects of delta9-THC on several parameters believed to influence the synthesis of brain 5-HT, including total and free plasma tryptophan and the high-affinity synaptosomal uptake of tryptophan. Delta9-THC was found to increase the amount of [3H]try accumulated by the brain as well as the amount of 5-[3H]HT synthesized. This effect was greater at intermediate doses than at the highest dose tested. However, delta9-THC was determined to have no effect on the actual rate of conversion of [3H]try into 5-[3H]HT at any dose tested. Delta9-THC had no effect on either plasma tyrosine ot free tryptophan levels. However, delta9-THC decreased total plasma tryptophan at low and intermediate doses, but had no effect at the highest dose tested. Synaptosomal uptake of [3H]try was unaffected by pretreatment with delta9-THC at any dose tested. These data suggest that delta9-THC increases the synthesis of 5-HT, not by altering the actual rate of conversion of tryptophan to 5-HT, but by altering, via an unknown mechanism, the quantity of tryptophan available for conversion to 5-HT.

Animals↗
PubMed1977

Lassa fever: response to an imported case.

In February, 1976, a Peace Corps worker returned to the United States from Sierra Leone with an undiagnosed illness later recognized as Lassa fever. To assess the risk of transmission and to contain a potential outbreak, we identified 552 contacts as having had exposure to the patient before the start of strict isolation procedures, and maintained intensive surveillance on these contacts for 21 days. At the end of the surveillance period, no illness had developed in contacts. One month later, a serologic survey among 29 of the contacts judged to be at high risk gave no evidence of infection. In response to the importation of this communicable and highly fatal disease, procedures for the isolation of the patient, the identification, surveillance and management of contacts and the handling of laboratory specimens were developed and implemented. These procedures could be adapted to future introductions of highly contagious diseases.

Adult↗
PubMed1977

Time course of delta9-tetrahydrocannabinol inhibition of predatory aggression.

Three studies assessed the time course of inhibition of predatory aggression and changes in levels of brain serotonin following administration of delta9-THC. In Study One, six groups of six rats each were administered 1.25 mg/kg delta9-THC IV and frog-killing behavior was measured at six postinjection intervals: 30, 60, 90, 150, 210, and 270 minutes. In Study Two, four groups of six rats each were tested. Group One received a vehicle control injection and was tested immediately, i.e. zero-minutes, postinjection. The remaining groups received 1.25 mg/kg delta9-THC, and behavior was measured at 0, 15, and 30 min postinjection. In Study Three, two groups of six rats were treated with the vehicle or 1.25 mg/kg delta9-THC and sacrificed one minute postinjection. Additional drug groups were sacrificed at 30 and 210 min postinjection. Levels of 5-HT were determined in four brain sections: cortex, midbrain, medulla, and cerebellum. Significant inhibition of predatory aggression was found for groups tested at 0, 15, and 30 min postinjection. Brain levels of 5-HT in the midbrain and/or medulla were significantly increased over the same period.

Aggression↗
PubMed1977

The circular, segmented nucleocapsid of an arenavirus-Tacaribe virus.

The nucleocapsid structures of Tacaribe virus, a member of the Arenaviridae, were purified from detergent-treated virus particles by equilibrium density gradient centrifugation. Negative-contrast electron microscopy indicated that they were coiled, circular filaments. They had a mean diam. of 5 to 10 nm and two predominant length classes of 640 nm and 1300 nm were found.

Arenaviridae↗
PubMed1977

Isolation of an arenavirus closely related to Lassa virus from Mastomys natalensis in south-east Africa.

Five unidentified virus strains were recovered from the multimammate mouse ,Mastomys natalensis, during the course of studies on arbovirus infections in Mozambique. These agents were found to be morphologically and immunologically related to Lassa virus. Four of 19 sera from Mastomys captured in the study area had antibodies to both Lassa virus and one of the unidentified strains. Although not definitive, the differences noted in results of complement fixation and indirect immunofluorescent tests suggest that these viruses from south-east Africa are not identical to West African Lassa virus.

Africa, Northern↗
PubMed1976

Radioimmunoassay for antibody to hepatitis B surface antigen shows transmission of hepatitis B virus among household contacts.

The epidemiology of infections with hepatitis B virus was studied by measurement of serum antibodies to hepatitis B surface antigen (HBS Ag) with the radioimmuno-precipitation test. Prospective studies of household contacts of HBS Ag-positive patients with acute hepatitis demonstrated that four of 41 children and one of 60 adults experienced anicteric seroconversions. Two of the 60 adults also had mild icteric hepatitis and became chronically antigenemic. Neither HBS Ag nor antibody to HBS Ag was detected in follow-up blood samples from 85 seronegative contacts of HBS Ag-negative patients with hepatitis, although seven icteric secondary cases were identified. Household contacts of HBS Ag carriers frequently had serologic evidence of exposure to hepatitis B virus (44% of adults), but the remainder had neither detectable antigen nor antibody.

Adolescent↗
PubMed1976

In vitro alteration of the subcellular distribution of 3H-reserpine in the rat forebrain by delta 9-tetrahydrocannabinol.

delta 9-Tetrahydrocannabinol (delta 9-THC) has been reported to attenuate both reserpine-induced serotonin depletion and reserpine-induced hypothermia. We have observed that delta 9-THC preincubation led to a dose-responsive increase in the amount of 3H-reserpine bound to a crude mitochondrial fraction of rat forebrain. The experiments reported here further characterize this phenomenon. Preincubation with delta 9-THC produced a shift in the localization of 3H-reserpine from the incubation medium and the microsomal supernatant (decrease of 66%) to the crude mitochondrial (CM) pellet (increase of 154%). The CM pellet was subfractionated both by differential centrifugation after osmotic shock and by layering on a five-step discontinuous sucrose gradient and centrifuging at 80,000 x g. Osmotic shock with 0.032 M sucrose and centrifugation revealed that the delta 9-THC-induced increase in 3H-reserpine was contained in both the synaptic vesicle fraction (247%) and the fraction containing myelin, ruptured synaptosomes and mitochondria (324%). Separating the CM fraction into five component parts showed that delta 9-THC increased the 3H-reserpine bound by about 275% in the three fractions containing myelin, membrane fragments or mitochondria. Even more dramatic increases (greater than 1000%) were observed in the two fractions containing cholinergic and non-cholinergic nerve endings. In addition, we have determined that many other drugs which are believed to have membrane mediated mechanisms have no effect on the amount of 3H-reserpine bound to the crude mitochondrial fraction. Although other possibilities exist, these data support the hypothesis that delta 9-THC retards the action of reserpine by altering the normal distribution of reserpine in various membrane components of the rat brain.

Animals↗
PubMed1975

Antigenic relationships among phlebotomus fever group arboviruses and their implication for the epidemiology of sandfly fever.

The antigenic relationships of 21 known or presumed Phlebotomus fever group serotypes and of 2 ungrouped, solvent sensitive, sandfly-associated arboviruses (Pacui and Charleville) were studied by complement fixation, plaque neutralization, and hemagglutination-inhibition methods. Results of complement fixation and neutralization tests were specific, allowing clear separation of the various serotypes, while those of the hemagglutination-inhibition test showed broader crossing and lack of specificity. Pacui virus was shown to be a member of the Phlebotomus fever serogroup. Six new Phlebotomus fever group serotypes are also described, increasing the known members of the group to 22. The implications of these and other recent data about the epidemiology of sandfly fever are discussed.

Animals↗
PubMed1975

The arenaviruses: some priorities for future research.

In this paper Lassa virus is used as a model in pinpointing priorities for future research on the arenaviruses. Suggestions for specific investigations and public health measures cover the detection of Lassa virus infection, the pathology and therapy of the disease, and its prevention and control.

Animals↗
PubMed1975

Performance analysis of tubular membrane oxygenator with turbulent blood flow.

This analysis of turbulent oxygenation predicts a substantial gain in the oxygen-transfer rate relative to current laminar flow membrane systems. As a consequence, major reductions in residence time, membrane area and priming volume would be possible. This straightforward application of the phenomenolgical theory of experiment. The potential gains sre sufficiently impressive to encourage such experimentation.

Blood Flow Velocity↗
PubMed1975

Infection of wild and laboratory animals with Machupo and Latino viruses.

Natural infection with Machupo and Latino viruses occurs only in the cricetine rodent Calomys callosus. Machupo virus induces fatal infection in suckling mice and hamsters, and in adult guinea-pigs, marmosets, and rhesus monkeys. Latino virus kills only suckling hamsters; it produces chronic but non-viraemic infection in Calomys rodents.Machupo virus, in contrast, induces a viraemic immunotolerant infection in suckling Calomys, and a split response in animals more than 9 days of age. Tolerant infection is associated with haemolytic anaemia and splenomegaly, lesions not observed in animals able to clear viraemia and produce circulating neutralizing antibodies. Experimental increase in the fraction of tolerant response was obtained by decreasing the virus dose or by phenotypic inbreeding of rodents. Long-term effects of tolerant infection included mild runting, decreased survival time, and almost total sterility among females, largely caused by fatal virus infection of embryos.

Age Factors↗
PubMed1975

Status of arenavirus vaccines and their application.

A limited but definite need exists for vaccines against Lassa, Junin, and Machupo viruses. Medical and laboratory personnel, as well as defined high-risk population groups, require protection from these highly virulent agents. To date little work has been done on inactivated vaccines for these viruses. A live attenuated Junin vaccine has been tested successfully in more than 600 persons, and a high-passage Machupo virus strain has protected rhesus monkeys against lethal infection produced by a homologous field strain.Work has been initiated on possible heterologous protection induced by infection or antigenic stimulation with arenaviruses not pathogenic for man. Crucial for the eventual development of effective vaccines are the construction of more maximum security laboratories and the further elucidation of the experimental and natural biology of the agents in lower animals and man.

Adolescent↗
PubMed1974

Arenaviruses.

Explore the source record for details and available documents.

Antigens, Viral↗