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Biomedical subjects

R Valentine

Publications and source records attributed to R Valentine.

51 records · Page 3Linked to original sources
PubMed1982

RDC depressive subtypes: are they valid?

Ninety patients meeting the Research Diagnostic Criteria (RDC) for major depressive disorder were further diagnosed using the RDC depressive subtypes. Patients with specific RDC subtype diagnoses were compared to those who did not meet the subtype criteria on several variables, including family history, illness course, work history, social history, previous treatment, quality of remissions, and symptomatology. Several items significantly differentiated patients diagnosed as primary, psychotic, and situational from those not so diagnosed: this supports the validity of these subtype categories. However, the study did not support the validity of the incapacitated, agitated, and retarded subtypes. No conclusions could be drawn regarding the endogenous, simple, or recurrent unipolar depressive subtypes.

Adult↗
PubMed1981

Pharmacokinetics and behavioral effects of methylphenidate in Thoroughbred horses.

In horses given (rapid IV) methylphenidate (Ritalin, alpha-phenyl-2-piperidinacetic acid methyl ester; 0.70 mg/kg), plasma concentrations of the drug decreased rapidly at first, with an apparent alpha half-life of about 19 minutes, and then more slowly, with an apparent beta half-life of about 2.4 hours. These data were well fitted by a 2-compartment open model. In blood, about 40% of the methylphenidate present was in the plasma fraction, and of this, about 80% was plasma-protein bound. If given by subcutaneous or IM injection, plasma concentrations of methylphenidate peaked in about 1 hour and were no longer detectable (cleared) from plasma by 6 hours. Urinary clearance time, however, was longer, and between 12 and 24 hours should be allowed for a dose of methylphenidate to "clear" from urine. Using a variable-interval responding apparatus, methylphenidate was shown to stimulate the responding rate of horses up to 6 times above base line, making it the most potent central stimulant tested in this responding apparatus to date. Peak central stimulation at 30 minutes after IV dosing was seen in horses given 0.4 to 1.0 mg of methylphenidate/kg.

Animals↗
PubMed1980

Renal infection with Mycobacterium chelonei.

A case of renal infection with Mycobacterium chelonei is described. The infection probably occurred via haematogenous spread from an infected arteriovenous shunt in a uraemic woman. Prolonged treatment with intravenous cefoxitin combined with oral erythromycin and rifampicin eradicated the organism from the urine. Although renal function stabilised for one year, gradual deterioration to end-stage renal failure occurred.

Adult↗
PubMed1979

Reflection coefficients of homopore membranes: effect of molecular size and configuration.

Osmotic water flow through membranes with uniform defined pores was measured for a variety of macromolecular solutes. Water flow increased linearly with applied hydrostatic pressure, allowing the effective osmotic pressure of the solutes to be estimated by extrapolation. Reflection coefficients for each solute-membrane combination were calculated and correlated with the ratio of solute size to pore size. For the same mean molecular size, proteins were found to have larger reflection coefficients than dextrans. Molecular rigidity may play a role in this difference in behavior.

Dextrans↗
PubMed1977

Drug interactions in the horse: effects of chloramphenicol, quinidine, and oxyphenbutazone on phenylbutazone metabolism.

The plasma half-life of phenylbutazone in horses was not increased after pretreatment with chloramphenicol or quinidine, but was increased after oxyphenbutazone. This increased plasma half-life after oxyphenbutazone is consistent with observations in other species and suggests that oxyphenbutazone inhibits the metabolism of phenylbutazone in horses. Lack of inhibition of phenylbutazone metabolism in the horse by chloramphenicol and quinidine is inconsistent with results obtained in other species.

Animals↗
PubMed1975

Purification and characterization of cardiac tropomyosins.

A new procedure was developed to purify tropomyosin. The procedure was an adaptation of that described for purification of myosin. By eliminating troponin before precipitating with (NH4)2 SO4, it was possible to obtain pure tropomyosin from the same preparation from which myosin was purified. When tropomyosin was subjected to isoelectrofocusing two tropomyosins were present, having similar isoelectric points of pH 5.4 and 5.6; two tropomyosin subunits were resolved in the presence of 6 M urea. The two subunits had very similar isoelectric points, pH 4.7 and 5.0. According to Ouchterlony analyses the tropomyosins from canine skeletal and cardiac tissue were immunologically identical when incubated with goat gammaG antitropomyosin (cardiac).

Amino Acids↗
PubMedDate not supplied

Imipramine metabolism in recurrent depressive episodes.

The long-term maintenance of major affective disorders with tricyclic antidepressants is of obvious interest. However, discrete predictors identifying subgroups 'at-risk' for higher recurrence rates have infrequently been cited. The clinical course of 32 major recurrent depressive patients was monitored over 2 years. Analysis of the total tricyclic concentration and the parent: desmethylated ratio revealed that those subjects in a depressive recurrence previously had had a lower imipramine: desipramine ratio (despite matched dosing and nonsignificant total plasma concentrations) than nonrecurrents. Several hypotheses are discussed.

Adult↗