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Biomedical subjects

A Richardson

Publications and source records attributed to A Richardson.

At least 325 records · Page 18Linked to original sources
PubMed1981

Cell-free protein synthesis by kidney from the aging female Fischer F344 rat.

This is the first report to describe and characterize a cell-free protein synthesis system derived from kidney tissue. The optimum conditions for [3H]-valine incorporation into protein by the post-mitochondrial supernatant from whole kidneys were found to be: pH 6.9, 7.5 mM MgCl2, 150 mM KCl, 10 mM ATP, and 2 mM GTP. The cell-free protein-synthetising activities of kidneys isolated from 4.5-, 7.5-, 22-, and 31-month-old female Fischer F344 rats were measured using the post-mitochondrial supernatant. A 73-87% decrease in cell-free protein synthesis was observed between 4.5 and 31 months of age. Both the cell sap and microsomal fractions of the kidney post-mitochondrial supernatant from old rats were less active in protein synthesis than these fractions from the kidneys of young rats. No age-related change in the activity of RNAase in the kidney post-mitochondrial supernatant was observed. Kidney ribosomes stripped of endogenous mRNA were found to be active in poly(uridylic acid)-directed polyphenylalanine synthesis. The effect of aging on the fidelity of translation was determined by measuring poly(uridylic acid)-directed [14C]-phenylalanine and [3H]leucine incorporation by kidney ribosomes isolated from rats of various ages. No age-related change in the fidelity of poly(uridylic acid) translation by kidney ribosomes was observed.

Aging↗
PubMed1981

Age-related changes in isolated rat hepatocytes. Comparison of size, morphology, binucleation, and protein content.

Hepatocytes isolated from 6-, 12-, 18-, and 30-month-old female Fischer F344 rats were examined by scanning electron microscopy. No significant change in cell size with age was observed. However, the surface morphology of the cells isolated from the older animals exhibited a significant increase in surface folds. This feature did not exceed 10% of the cell population until 12 months of age and continued to increase to 31% of the cells in 30-month-old rats. From 6 to 12 months of age, there was a significant increase in protein content of the hepatocytes. No further increase in protein content occurred during senescence. An increase in percentage of binuclear cells occurred after 24 months of age. Because ploidy and binucleation increase with increasing age, it appears that the nuclear/cytoplasmic ratio changes as a function of age.

Aging↗
PubMed1981

Metabolic activation of aflatoxin B1 by liver tissue from male fischer F344 rats of various ages.

The effect of aging on the ability of the liver to activate chemical procarcinogens was studied using 12-, 18-, and 27-month-old male Fischer F344 rats. The cytochrome P-450 content of the S9 and microsomal fractions of the liver decreased approximately 30% between 12 and 18 months of age. The structural conformation of cytochrome P-450 in microsomes from 12-, 18-, and 27-month-old rats was studied using electron-spin resonance spectroscopy. An age-related decrease in the amount of cytochrome P-450 ferric iron in the liver microsomes was observed. The conversion of the chemical procarcinogen aflatoxin B1 to mutagenic compounds by the S9 and microsomal fractions of liver was measured using the Salmonella typhimurium bioassay. A 40-50% decrease in the metabolic activation of aflatoxin B1 was observed between 12 and 18 months of age. However, the activation of aflatoxin B1 did not change after 18 months of age. The age-related decrease in the activation of aflatoxin B1 by liver appears to be due to a decrease in the metabolic activity of the mixed-function oxidase system.

Aflatoxin B1↗
PubMed1981

Prosthodontic treatment of pendulous maxillary tuberosities.

Reduction of the maxillary tuberosities is not always possible when indicated, and it is sometimes necessary to solve the problem by modifying the construction procedures for the complete denture. Because of inadequate space between the maxillary tuberosity and the retromolar pad, acrylic bases of adequate thickness could not be used. Instead, gold shims 1-min thick were cast over the tuberosities. They had loops around the periphery and V-shaped recesses to allow for even finishing of the wax-up of the record base to the gold shims. Jaw relation records were made and the teeth were set in bilateral crossbite because of the discrepancy in arch size. The acrylic resin was then processed, the dentures finished and polished, and normal laboratory and clinical remount procedures observed. Because there was some space available, this technique worked well. Both tuberosities and retromolar pad areas may also be cast in gold to allow for even thinner base in this area; however, when surgical reduction is possible, it is still the preferable treatment.

Aged↗
PubMed1981

The value of profileometry in complete immediate denture service. A preliminary report.

Twelve patients requiring total extractions and provision of immediate complete dentures were randomly selected for analysis. Pre-extraction records including full face and lateral profile photographs were taken under standard distance and lighting conditions. Maxillary and mandibular intraoral views were also exposed. Lateral cephalograms were taken pre-operatively, in both occlusal tooth contact position and the resting jaw relationship. Pre-extraction facial measurements were recorded and included occlusal face height and resting face height as well as the value, in degrees of the columellaphiltral angle, determined with the dentofacial profileometer. Teeth were removed under endotracheal general anaesthesia in hospital, and dentures constructed from pre-extraction records were fitted and adjusted before termination of the anaesthetic. Post-extraction surveillance was conducted in all cases and measurements, cephalograms, and photographs such as were previously taken, were repeated postoperatively for assessment and comparison. Statistical analysis confirmed our clinical and profileometric measurements. The advantage of profileometric pre-extraction records, prefabricated appliances and precision surgery in an immediate complete denture service is established.

Cephalometry↗
PubMed1980

The predisposition to hallucinate.

It is argued that people who are predisposed to mistake a vivid imagination image for a genuine percept (i.e. hallucinators) should show an impaired ability to make clear perceptual-conceptual distinctions (i.e. boundary confusion) and should lack familiarity with internal sources of information. A test of these hypotheses was undertaken by comparing a group of "alcoholic" hallucinators with a group of "alcoholic" non-hallucinators. Some support is claimed for the "boundary confusion" hypothesis but not for the "lack of familiarity" hypothesis. Specifically, it was found that hallucinators performed significantly worse than non-hallucinators on the Embedded Figures Test (a measure of perceptual boundary confusion) and on the Intersensory Time Judgement Test (a measure of conceptual boundary confusion). These results are discussed in relation to other aspects of the predisposition to hallucinate. Some specific research needs are described.

Adult↗
PubMed1980

The prediction of facial growth.

In the two contrasting malocclusions, the open bite and the deep overbite, statistically significant differences are shown in the anterior, middle and posterior endocranial regions. In open bite there is an association between the lower face height and the size of the anterior, middle and posterior cranial regions, but in deep overbite the associations between face height and the endocranial size are less strong. These and other associations if brougth together in a multiple regression analysis may prove useful in prognosticating the final face height in the growing child, particularly in the open-bite case.

Adolescent↗
PubMed1980

Changes in brain protein synthesis during the life span of male Fischer rats.

The cell-free protein synthetic activity of the postmitochondrial supernatant isolated from whole brain of 6- to 32-month-old male Fischer F344 rats was compared. Protein synthesis decreased 56% from 6 to 32 months of age. The decrease in cell-free protein synthesis was not due to an age-related increase in RNase activity. Although monomeric ribosomes (ribosomes stripped of mRNA) isolated from the brains of older rats were less active in polyuridylic acid directed polyphenylalanine synthesis, the fidelity of polyuridylic acid translation by monomeric ribosomes did not decrease with increasing age.

Aging↗