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Biomedical subjects

R Potts

Publications and source records attributed to R Potts.

32 records · Page 2Linked to original sources
PubMed1986

The effects of television form and violent content on boys' attention and social behavior.

An experiment is reported that examined the independent effects of television content (violence) and television formal features (action level) on children's attention to programs and their postviewing social behavior. Pairs of preschool boys participated in two experimental sessions in which they saw animated and live television programs that varied in violent content (high or low) and formal features (high or low action level). They then played with toys that contained cues for either aggressive or prosocial interaction. Rapid character action facilitated visual attention to the programs; violent tv content did not facilitate attention. On measures of social behavior, strong effects of toy cues were found independently of television treatment effects. Aggressive toys produced aggressive behavior, and prosocial toys produced prosocial behavior; these patterns included some nonspecific, generalized influences in addition to direct demands of the play materials. Violent tv content led to changes in subjects' style of interaction and was also associated with increases in some prosocial behaviors. Television action level had no systematic effects on subjects' behavior. Results are discussed within the theoretical frameworks of observational learning and general arousal. Implications for children's television programming are also discussed.

Aggression↗
PubMed1979

Size fractionation of DNA fragments by liquid-liquid chromatography.

A method for the fractionation of double-stranded DNA fragments from 150 to 22000 b.p. in size by liquid-liquid chromatography is described. The procedure makes use of the fact that the partitioning of DNA in a polyethylene glycol-dextran system is size dependent and can be altered by alkali metal cations. Cellulose or celite are used as supports for the stationary, dextran-rich phase. Examples show the fractionation of digests of T7 DNA produced by Dpn II and Hind II restriction endonulceases as well as lambda DNA digests produced by Hind III and Eco RI restriction endonucleases.

Bacteriophage lambda↗
PubMed1977

Stereochemistry of methylene transfer involving 5,10-methylenetetrahydrofolate.

The stereochemistry of the transfer catalyzed by rabbit liver serine transhydroxymethylase (EC 2.1.2.1) of the prochiral hydroxymethyl group from serine to tetrahydrofolate to form 5,10-methylenetetrahydrofolate was studied. Initial kinetic studies on labeled 5,10-methylenetetrahydrofolate showed that nonenzymatic racemization of the prochiral methylene center was buffer dependent and was slow under the conditions employed. Specifically tritiated (3R)- and (3S)-serines were employed to study the transfer reaction. Reactions were carried out under various conditions and the stereochemistry of the methylene carbon of the 5,10-methylenetetrahydrofolate produced was determined. The enzyme was shown to be partially stereospecific for this transfer reaction, proceeding with a loss of about 50% of the stereochemical purity of the transferred carbon center. Possible mechanistic interpretations of this finding are discussed.

Animals↗
PubMed1976

Stereochemistry of the formation of cysteine by O-acetylserine sulfhydrase.

The enzymatic preparation of (2S, 3R)- and (2S, 3S)-[3-3H] serine from the corresponding stereospecifically tritiated 3-P-glycerates is described. Following conversion into T-acetylserine, these substrates were used to establish the steric course of the O-acetylserine sulfhydrase reaction. The two samples of cysteine formed in this reaction were analyzed for their configuration at C-3. The results indicate that the replacement of the acetoxy by a sulfhydryl group in the O-acetylserine sulfhydrase reaction occurs with retention of configuration at carbon atom 3.

Cysteine↗
PubMedDate not supplied

The influence of subtotal thyroidectomy on the thyroglobulin binding capacity of thyrotoxic serum.

It has been shown previously that large amounts of thyroglobulin are released into the circulation by the trauma of thyroid surgery. In order to characterize the response to this challenge in patients with and without autoimmune disease, serial estimations of thyroglobulin binding capacity (AgBC) using a sensitive double antibody technique were made on 105 patients undergoing partial thyroidectomy for thyrotoxicosis (70 patients prepared medically) and nontoxic goiter (35 patients). Samples were measured the day before, the day of, and on eight subsequent occasions during the first 14 days after surgery. Three distinct patterns of change in AgBC were observed in the thyrotoxic patients: i) when elevated before surgery, it fell acutely within 48 h of operation and rose again within the first 7-10 days (8 patients); ii) it rose briskly, though transiently, when low (less than 10%) before surgery (4 patients); iii) when elevated before surgery, it rose or fell gently afterwards without sudden change (7 patients). The AgBC in 51 of the Graves' disease patients never exceeded 10% during the perioperative period, and was immeasurably low in all nontoxic goiter patients. Autoimmune thyroid disease results from a disturbance of normal tolerance to thyroid antigens, and thyroid surgery provides an in vivo model in which the response to an acute antigenic challenge may be studied. Patients with Graves' disease showed varying degrees of intolerance to the challenge, while those with nontoxic goiter and no evidence of autoimmune disease were uniformly unresponsive.

Adult↗