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Biomedical subjects

A Clarke

Publications and source records attributed to A Clarke.

At least 271 records · Page 15Linked to original sources
PubMed1982

Effects of ACTH, benzodiazepines and 5-HT antagonists on escape from periaqueductal grey stimulation in the rat.

1. The effects of drugs has been studied on escape behaviour of rats following electrical stimulation of the periaqueductal grey, in order to assess the feasibility of using the latency to escape as a measure of experimental anxiety. 2. Escape latencies were decreased by methysergide and cyproheptadine, whilst lorazepam and chlordiazepoxide (CDP) increased the latencies. 3. ACTH marginally decreased escape latencies, and did not alter the response to lorazepam. 4. Difficulties associated with using this paradigm to detect anxiolytic or anxiogenic effects of drugs are discussed.

Adrenocorticotropic Hormone↗
PubMed1982

Relationship between Phospholipid Breakdown and Freezing Injury in a Cell Wall-Less Mutant of Chlamydomonas reinhardii.

The effects of freezing and thawing on a cell wall-less mutant (CW15+) of Chlamydomonas reinhardii were investigated by monitoring enzyme release, cell viability, cell ultrastructure, and lipid composition. Cells suspended in Euglena gracilis medium were extremely susceptible to freezing injury, the median lethal temperature in the presence of extracellular ice being -5.3 degrees C. Cell damage was associated with a release of intracellular enzymes and massive breakdown of cellular organization. Changes in phospholipid fatty acid composition consistent with either a peroxidation process or phospholipase A(2) activity were evident, but the time course of these changes showed clearly that alterations in phospholipid fatty acid composition were a secondary, pathological event and not the the primary cause of freeze-thaw injury in Chlamydomonas reinhardii CW15+.

Journal Article↗
PubMed1981

Exploration and motor activity after intraventricular ACTH, morphine and naloxone.

Intraventricular injection of morphine (5 microgram) and ACTH (2.5 microgram) reduced the time spent head-dipping and the number of head-dips made by rats during a 10-min trial in a holeboard. These effects were reversed by naloxone (2.0 mg/kg, i.p.), in spite of the fact that naloxone alone also reduced these measures of exploration. None of the drugs or drug combinations tested significantly reduced locomotor activity. The results are discussed in relation to the action of ACTH on opiate receptors.

Adrenocorticotropic Hormone↗
PubMed1981

Infundibular ACTH can be excluded as a critical mediator in social behaviours.

Kainic acid lesions of the infundibulum resulted in a significant decrease in infundibular ACTH concentrations. However, the lesioned rats did not differ from the vehicle-injected controls in a social interaction test, in their latency to start drinking in a novel environment, or in their aggressive behaviour in home-cage intruder tests. It can therefore be concluded that endogenous infundibular ACTH does not play a significant role in these behaviours. This can be contrasted with the effects of exogenously administered ACTH which has previously been shown to reduce social interaction and increase aggression. Both the lesioned rats and the controls showed decreased social interaction after ACTH administration, and therefore the infundibulum can be excluded as a critical site of action of exogenous ACTH in mediating this behavioural change.

Adrenocorticotropic Hormone↗
PubMed1980

Intraventricular ACTH reduces social interaction in male rats.

Intraventricular ACTH (1.25 microgram), ACTH (1.6 microgram) and ACTH:D-Phe (1.6 microgram) resulted in significant reductions in the time that pairs of male rats spent in active social interaction. This decrease in social behaviour was not accompanied by a decrease in motor activity. The results are similar to those previously found with peripheral administration of ACTH and suggest that these behavioural effects of ACTH are centrally mediated. None of the ACTH fragments had a significant effect on the latency with which thirsty rats started drinking in an unfamiliar environment. The results are discussed in relation to a possible anxiogenic action of ACTH.

Adrenocorticotropic Hormone↗
PubMed1980

Reaction patterns of herpes simplex virus type 1 and type 2 proteins with sera of patients with uterine cervical carcinoma and matched controls.

Serum from 105 individuals with diagnosed uterine cervical cancer and 231 matched controls were examined for their ability to react with a large number of herpes simplex virus type 1 or type 2 (HSV-1, HSV-2) proteins. Radiolabeled HSV-1 or HSV-2 proteins were mixed with test serum and immune complexes were isolated with staphylococcal protein A. Viral proteins in the immune complexes were resolved by polyacrylamide gel electrophoresis and visualized by fluorography. When the frequency of precipitation for cancer and control serum was calculated for each HSV-1 and HSV-2 protein, the results demonstrated that four HSV-1 and 11 HSV-2 proteins were precipitated more frequently by cases than by controls (p less than or equal to 0.05). However, since these results could be influenced by the presence or absence of HSV-2 specific antibodies as well as social, economic, and sexual history, the data were grouped and analyzed according to these parameters. This enabled all significant differences between case and control sera in the precipitation of HSV-1 or HSV-2 proteins to be abolished except for two HSV-2 proteins with molecular weights of 38,000 and 118,000. These two proteins appear to be tumor associated and not merely covariables of past infection or risk factors alone.

Adult↗
PubMed1979

Pollen-stigma interactions: Identification and characterization of surface components with recognition potential.

Male-female recognition in flowering plants is initiated by mutual contact of pollen and stigma surface components. Analysis of the surface macromolecules of both stigma and pollen of Gladiolus gandavensis revealed a complex mixture of proteins, glycoproteins, and glycolipids. The carbohydrate-containing components amounted to 6% in pollen and 23% in stigma and contained the monosaccharides galactose, arabinose, glucose, mannose, and rhamnose. All the mannose of both preparations was associated with a fraction that bound to concanavalin A. The stigma surface contained an arabinogalactan or arabinogalactan protein as a major component. This component has been isolated by affinity chromatography on tridacnin-Sepharose and shown to be similar in composition to a style canal component isolated in the same way. The capacity of the stigma surface preparations to bind nonspecifically to macromolecules from pollen and other sources has been demonstrated in vivo and in vitro. Specific binding of concanavalin A to the stigma surface decreases the adhesive capacity for pollen protein. The arabinogalactan of the stigma surface may act as an adhesive base. The pollen and stigma surfaces apparently complement one another to provide all the components of an ideal adhesive.

Journal Article↗
PubMed1979

Effect of safety packaging on aspirin ingestion by children.

The effectiveness of child-resistant closures, required under the Poison Prevention Packaging Act of 1970, in reducing the incidence of accidental ingestion of aspirin and aspirin-containing products among children less than 5 years of age has been investigated. Data from Poison Control Centers and the National Center for Health Statistics were analyzed to determine the ingestion level before and two to three years after safety closures were required. Baby aspirin and nonbaby aspirin products were analyzed separately. For baby aspirin. It is estimated that safety packaging has reduced the incidence of ingestions 45% to 55%. For nonbaby aspirin products, the reduction has been 40% to 45%.

Aspirin↗
PubMed1978

The cryopreservation of Chlorella. 4. Accumulation of lipid as a protective factor.

Following growth under sub-optimal concentrations of nutrients, cells of Chlorella emersonii accumulated lipid and became more resistant to the damage caused by freezing and thawing. These results suggest that the factor responsible for the cold hardening of some Chlorella spp is not the effect of low temperatures per se but simply that of the reduced metabolic rate. Evidence is given that the post-thaw injury observed following rapid rates of cooling is associated with the vacuole.

Chlorella↗
PubMed1977

Ia antigenic specificities are oligosaccharide in nature: hapten-inhibition studies.

We have previously reported that the Ia specificities, coded for by the I region within the H-2 complex, appear to consist predominantly of carbohydrate. This conclusion was reached by examining low molecular weight Ia-bearing oligosacharides isolated from mouse serum. We now report hapten-inhibition studies which indicate that the binding of both allogeneic and xenogeneic anti-Ia antibodies to the Ia glycoproteins found predominantly on B lymphocytes can be specifically inhibited by certain free sugars. Both inhibition assays revealed that the specificity for the following Ia antigens resides predominantly in the following sugars: (a) Ia.1: N-acetyl-D-mannosamine or related sugars; (b) Ia.3: alpha-D-galactose and related sugars; (c) Ia.7: L-fucose; and (d) Ia.15: N-acetyl-D-glucosamine. It seems likely that these sugars are found at the terminal nonreducing ends of the carbohydrate portion of the Ia-bearing glycoproteins present in the lymphocyte membrane. In contrast, several public and private H-2 antigenic specificities did not appear to be sugar defined. These studies imply that at least some of the Ia genes from both the I-A and I-C subregions of the I region code for glycosyl transferases which modify oligosaccharide structure and impart specificity to the Ia antigens by alteration of their terminal sugar residues.

Animals↗
PubMed1977

Dose-response relationship after immunization of volunteers with a new, surface-antigen-adsorbed influenza virus vaccine.

Volunteers (15 per group) were given inoculations of various doses (5-400 international units [IU]) of surface-antigen-adsorbed influenza virus A/Port Chalmers/73 vaccine; this vaccine was prepared from purified virus hemagglutinin and neuraminidase antigens and adsorbed to alhydrogel. The titers of hemagglutination-inhibiting (HAI) and neuraminidase-inhibiting antibodies in serum after immunization showed a clear dose-response relationship. Thus, for volunteers given 400, 100, 25, or 5.0 IU of vaccine, the titers of HAI antibody in serum increased 174-, 32-, 12-, and eightfold, respectively. A similar dose response was observed for production of local neutralizing antibody. Immunization with A/Port Chalmers/73 virus vaccine also induced serum HAI antibody to influenza viruses A/Scotland/74, A/England/72, and A/Hong Kong/68; the increase in titers of antibody to these viruses corresponded directly to the degree of cross-reactivity between the virus tested and the vaccine virus. Four weeks after immunization, all volunteers were challenged with attenuated WRL-105 influenza virus. Evidence of viral infection was found in one, two, and two volunteers in each group of 15 subjects previously immunized with 400, 100, and 25 IU of vaccine, respectively; in six of the 15 volunteers given 5.0 IU of vaccine; and in 10 of 15 control subjects. The results suggest that equivalent immunity was induced in volunteers given greater than or equal to 25 IU of vaccine.

Adult↗