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Biomedical subjects

A Richardson

Publications and source records attributed to A Richardson.

At least 307 records · Page 17Linked to original sources
PubMed1984

Methodological aspects of receptor research: problems in the assessment of specific and non-specific binding of 3H-dihydroalprenolol to bovine lung membranes.

The binding of the radiolabelled beta-antagonist 3H-DHA to membranes prepared from bovine lung was examined. Three methods for determining the NSB of this ligand (200 microM of (-)-isoprenaline, 10 microM of (-)-propranolol and 10 microM of (-)-alprenolol) were investigated. In experiments designed to measure the Kd and Bmax of 3H-DHA to bovine lung membranes these three methods were not equivalent. (-)-Isoprenaline gave lower estimates of the Kd and Bmax than did (-)-propranolol, which in turn gave lower estimates than (-)-alprenolol. Critical examination of the characteristics of the binding of these three compounds using competition experiments showed that, at the concentrations used, an interaction of (-)-propranolol and (-)-alprenolol with both the receptor and the NSB site was responsible for the observed differences. This result was confirmed by a theoretical consideration of the binding reactions involved. Furthermore, these theoretical studies also revealed other potential problems arising from incorrect NSB measurement, which, if not appreciated, can cause serious misinterpretation of the nature of the receptor-ligand interactions.

Alprenolol↗
PubMed1984

Incidence of bite marks in a selected juvenile population: a preliminary report.

A study of the frequency of bite marks among sheltered children was conducted for a period of three months in the juvenile care facilities in Las Vegas, NV. The study demonstrated an incidence of 1 545 bite marks per 100 000 population. Analysis of the age, sex, and location of bite marks is presented. The study demonstrated an incidence comparable to diseases such as gonorrhea.

Adolescent↗
PubMed1983

The effect of phenobarbital on the transcriptional activity of liver.

The effect of phenobarbital on the transcriptional activity of liver was studied by measuring the synthesis of RNA by suspensions of hepatocytes isolated from rats treated with phenobarbital for various time periods. The absolute rates of RNA synthesis by isolated hepatocytes were determined by measuring the incorporation of [3H]orotic acid into RNA as UMP and the specific radioactivity of the UTP pool. The specific radioactivity of the UTP extracted from hepatocytes isolated from phenobarbital-treated rats was consistently lower than that of the UTP pool of hepatocytes from untreated rats. Phenobarbital treatment increased the rate of RNA synthesis 10-fold over that observed for hepatocytes from untreated rats. The maximum rate of RNA synthesis was observed 16-18 h after phenobarbital administration. Phenobarbital treatment also affected the nuclear-cytoplasmic transport of RNA by isolated hepatocytes. Immediately after phenobarbital treatment, the transport of RNA decreased; however, 24 h after phenobarbital administration, the transport of RNA was increased 4-fold. An increase in the synthesis of RNA in vivo by liver was found 18 h after phenobarbital treatment, and the incubation of suspensions of hepatocytes with various concentrations of phenobarbital increased RNA synthesis significantly.

Animals↗
PubMed1983

Mechanism of the age-related decline in lymphocyte proliferation: role of IL-2 production and protein synthesis.

Although an age-related decline in mitogen-induced proliferation in spleen lymphocytes has been reported by numerous investigators, the molecular mechanism responsible is unknown. In this study, we compared the mitogen-induced proliferation, IL-2 production, and protein synthesis in spleen lymphocytes isolated from 4, 12, 20, and 30 month-old male Fischer F344 rats. IL-2 production by Con A-stimulated lymphocytes, as determined by the ability of the culture supernatants to support the growth of cultured T cells, declined over 72% between 4 and 30 months of age. This decline in IL-2 production paralleled a similar decrease in proliferation. Early protein synthesis by Con A-stimulated spleen lymphocytes was determined by measuring the incorporation of [3H]-valine into acid insoluble material, and this dropped 74% between 4 and 30 months of age. There was a strong correlation between the age-related decline in the three parameters tested. Based on these results, we propose that the age-related decline in protein synthesis may be the molecular basis for the similar decrease in IL-2 production and mitogenesis.

Aging↗
PubMed1983

A method for dissecting two site receptor interactions in ligand binding studies.

A general model has been developed describing the relationship between the measured (IC50) and absolute affinities (KI), observed in radioligand binding studies when two ligands, one radioactive, interact with two receptors or binding sites. The model shows the dependence of the IC50's upon the concentration of radioligand for any combinations of the absolute affinities of the radioligand (Kd's) and the displacing ligand (KI's). By constraining the affinities of the two ligands for the sites, five special cases of the general model can be described that model all possible 'selectivities' the ligands may have for the sites. The properties of these five cases can be exploited experimentally to probe the nature of the ligand/site interactions by the simple expedient of constructing a number of displacement curves at different radioligand concentrations. The method has been tested experimentally in three situations where two ligand/two site interactions occur, and is shown to be a useful technique to qualitatively examine the underlying binding reactions.

Animals↗
PubMed1982

Current concepts: I. The relationship between age-related changes in gene expression, protein turnover, and the responsiveness of an organism to stimuli.

A general decline in gene expression, translation and transcription, has been observed to occur with increasing age in a wide variety of organisms and tissues. Because the level of most enzymes and proteins remains relatively constant with increasing age, one would predict that the decline in gene expression would result in an age-related decline in protein turnover. Recent studies show that protein turnover in mouse liver and nematodes declines with increasing age. The decline in protein turnover could lead to an age-related decrease in the response of inducible enzymes to stimuli. This could explain the molecular basis for the decline in aging organisms to respond to a variety of environmental factors.

Aging↗
PubMed1982

A comparison of the cell-free protein synthetic activities of testicular tissue obtained from rats and mice of various ages.

1. The cell-free protein synthetic activity of the post-mitochondrial supernatant from the testes of 6-, 14-, and 30-month-old Sprague-Dawley rats and C57 B1/6J mice was determined. 2. An age-related decrease in cell-free protein synthesis was observed in both groups of rodents and was similar to the decrease previously reported for Fischer F344 rats. 3. The decrease in cell-free protein synthesis by testicular tissue from rodents occurs primarily after 14 months of age.

Aging↗
PubMed1982

Metabolic activation of chemical carcinogens by kidney from rats and mice of various ages.

1. The ability of homogenates from kidney tissue of 4- to 26-month-old male Fischer F344 rats, 6- to 30-month-old male Sprague-Dawley rats, and 5- to 30-month-old male C57 BL/6J mice to metabolically activate the chemical procarcinogens 2-aminofluorene and aflatoxin B1 to mutagens was measured using the Ames Salmonella/microsome test. 2. The conversion of 2-aminofluorene to mutagenic compounds by kidney homogenates from Fischer F344 and Sprague-Dawley rats and C57 BL/6J mice decreased 35-50% with increasing age. 3. An age-related decrease (50-65%) in the ability of kidney homogenates from Fischer F344 rats and C57 BL/6J mice to convert aflatoxin B1 to mutagenic compounds was also observed.

Aging↗
PubMed1982

Age-related changes in the corneal endothelium of the rat.

The endothelial cells of the rat cornea show a progressive decline in numbers and an increase in pleomorphism from age 6 months to 30 months. These age-related changes correspond closely to those reported in the human cornea from approximately age 20 to age 70 years. The corneal endothelium may be found useful as an index of physiological aging in these and other mammals.

Aging↗
PubMed1982

The transcription of various types of ribonucleic acid by hepatocytes isolated from rats of various ages.

The synthesis of various types of ribonucleic acid (RNA) isolated from 6- to 3-month-old female Fischer F344 rats was compared. The rate of RNA synthesis by freshly prepared hepatocytes was determined by dividing the amount of [3H]orotic acid incorporated into RNA as uridine-5'-monophosphate by the specific activity of the uridine-5'-triphosphate pool. The rate of total RNA synthesis by hepatocytes from 19-month-old rats was 40% less than the rate for hepatocytes from 12-month-old rats. No significant difference in the rate of total RNA synthesis was observed between 19 and 30 months of age. The percentage of [3H]orotic acid incorporated into poly(A) + RNA by 30-month-old rats was approximately 50% less than that observed for hepatocytes isolated from 6-month-old rats. The percentage of [3H]orotic acid incorporated into poly(A)-RNA as ribosomal RNA (38S, 18S, and 5S RNAs) or transfer RNA was similar for 12- and 30-month-old rats. The rate of poly(A) + RNA synthesis by hepatocytes isolated from 30-month-old rats was 65% less than that observed for hepatocytes from 6-month-old rats. In contrast to total RNA synthesis, the rate of poly(A) + RNA synthesis for the 30-month-old rats was significantly less than the rate for 19-month-old rats.

Age Factors↗
PubMed1982

Vividness of memory imagery and self-induced mood change.

Previous research has shown that people who can voluntarily form vivid images are able to exert more control over some of their cognitive and affective functions than people who can voluntarily form only weak images. This study was designed to extend this line of research to the control of mood states. From a sample of first-year psychology students four groups were formed: vivid imagery/elated, vivid imagery/depressed, weak imagery/elated, weak imagery/depressed. Mood change induction procedures were employed in an attempt to produce reversals in the initial mood states. It was found that greater changes occurred for the vivid imagers than for the weak imagers. These results were discussed in relation to the differential effectiveness of the mood induction procedures, the problem of measuring mood and the importance of taking into account individual differences in imagery abilities when planning imagery based treatment.

Adult↗