PubMed Health⌕ Search

Biomedical subjects

S Ryder

Publications and source records attributed to S Ryder.

48 records · Page 3Linked to original sources
PubMed1981

Tyrosine hydroxylase activity in Venezuelan equine encephalomyelitis virus infection.

In rats inoculated with the Venezuelan equine encephalomyelitis (VEE) virus, a significant decrease was found in the tyrosine hydroxylase activity of neostriatum, midbrain, and hypothalamus during the acute phase of the infection. In animals that survived the acute infection, we observed no changes in the enzymatic activity in the same regions studied. Our findings suggest a vulnerability of the dopaminergic and noradrenergic pathways to the infection produced by VEE virus.

Animals↗
PubMed1981

Nature of immunoreactive CCK in rat and pig brain.

Two major classes of immunoreactive cholecystokinin peptides (iCCK) have been identified in rat and pig brains: (1) large basic peptides (Big iCCK) resembling pCCK33 in size and charge; (2) small acidic peptides (Small iCCK) resembling the COOH-terminal fragments of CCK. Boiling 0.1 N HCl maximally extracts Big iCCK; boiling 0.1 N NaOH maximally extracts Small iCCK. The differences in hormonal forms removed by these extractions are not likely to be due to enzymatic conversion during the extraction procedures. Fractionation on Sephadex G50 and starch gel electrophoresis combined with radioimmunoassay using 3 antisera of different specificities: (1) directed towards the NH2-terminus of pCCK33; (2) produced by immunization with CCK8; (3) produced by immunization with CCK4; are consistent with the hypothesis that a major fraction of Big iCCK may represent intact CCK with a COOH-terminus extension as has recently been suggested for gastrin, a molecule having a COOH-terminal pentapeptide identical with that of CCK.

Animals↗
PubMed1981

Cholecystokinin and enkephalin levels following ethanol administration in rats.

Using radioimmunoassay, cholecystokinin and enkephalin levels were determined in the brain and gut of rats following ethanol administration. Acute or chronic administration of ethanol did not affect the cholecystokinin or enkephalin content of rat brain cortex, hypothalamus, striatum or proximal small bowel. This contrasts with the reports of altered levels of several classical neurotransmitters following ethanol administration.

Animals↗
PubMed1981

Alkaline extraction and characterization of cholecystokinin-immunoreactivity from rat gut.

Generally some variation of neutral or acid extractants has been used to recover immunoreactive cholecystokinin (CCK) from gut as well as from brain. Recovery of CCK in 0.1 N NaOH extracts from gut mucosa, gut muscle, or whole gut ranged up to threefold higher than in similar water or 0.1 N HCl extracts, although the reverse was the case for the extraction of secretin from the same tissue. CCK-immunoreactive peptides from rat gut were found to resemble a CCK-33-like peptide, sulfated CCK-12 and CCK-8, as well as smaller COOH-terminal fragments, which are larger than the C-terminal tetrapeptide amide. The fraction of immunoreactivity in the form of a CCK-33-like peptide was greater, although the total recovery was less, in acid extractants of whole gut. Proper interpretation of dynamic changes in gut CCK in response to fasting, feeding, and other laboratory manipulations requires efficient extraction of total immunoreactivity.

Animals↗
PubMed1980

GABA metabolism in Venezuelan equine encephalomyelitis virus infection.

Mice infected with the Venezuelan equine encephalomyelitis virus showed a significant decrease in the GABA content of cerebral hemispheres. Activity of the enzyme which synthetizes GABA, glutamate decarboxylase, is also reduced in whole cerebral hemispheres, neostriatum, and frontal cortex of infected animals, as compared to values obtained from the same regions of control mice. No significant difference was demonstrated in the activities of GABA transaminase, glutamate dehydrogenase, lactate dehydrogenase, succinate dehydrogenase and NAD-malate dehydrogenase in any of the regions studied. The results suggest that the viral infection produced an alteration in the mechanism of GABA synthesis.

Animals↗
PubMed1980

Relationship of serum T4 and T3 to TSH in primary hypothyroidism.

The relationship of serum thyroxine (T4) and 3,5,3'-triiodothyronine (T3) to the thyroid-stimulating hormone (TSH) response to protirelin was studied in 34 hypothyroid patients on a stable maintenance dose of oral levo-thyroxine. Release of TSH from the anterior pituitary, as measured by basal TSH and the TSH response to protirelin, correlated better with serum T4 than serum T3. Our study supports the concept that, in treated hypothyroid patients, serum T4 has a greater relative importance in mediating the actions of thyroid hormone on the anterior pituitary than serum T3.

Adult↗
PubMed1978

Comparative pharmacology of the optical isomers of ketamine in mice.

Relative pharmacological potencies of the optical isomers of ketamine have been estimated in ICR mice. The (+)-isomer was 3X more potent than (-)-ketamine as an analgesic using the phenylquinone writhing test, only 1.5X more potent in terms of hypnotic activity and 1.8X more potent in causing locomotor stimulation. At equianalgesic doses (+)-ketamine caused less stimulation of locomotor activity than the (-)-isomer. These potency differences did not appear to be due to differences in biodisposition although stereoselective metabolism was demonstrated in vivo. Analgesia induced by ketamine was reversed by 10 mg/kg of naloxone.

Analgesics↗
PubMed1977

Conservatism, openness to experience and sample bias.

Two experiments were conducted to examine the relationship between conservatism and openness to experiences. In Study I, the responses of 64 males and 60 females to the Conservatism Scale and the Coan (1972) Experience Inventory were correlated. For the total sample, conservatism was significantly related to the total score of the Experience Inventory plus six of seven of the component scales. Study II examined the relationship between conservatism and the expressed willingness to volunteer for certain psychological experiments that were assumed to require more openness. Subjects were 91 males and 114 females from introductory psychology classes. High conservative subjects were less willing to volunteer for the experiments that required more openness as compared to low conservative subjects. These results were discussed in the context of volunteer bias in psychological research.

Attitude↗
PubMedDate not supplied

A study on the efficacy of digital enhancement of on-line portal images.

A novel method for evaluation of observer performance with portal images has been developed, in which the observer is required to identify and localize predefined anatomical landmarks in digital portal images. The method was employed to compare the spatial accuracy and decision time for landmark localization in unenhanced on-line portal images and images enhanced digitally by selective adaptive histogram modification. The results indicate that anatomical landmarks were more readily identified in the enhanced images, leading to significantly higher accuracy in landmark localization.

Evaluation Studies as Topic↗