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Biomedical subjects

M Mason

Publications and source records attributed to M Mason.

At least 127 records · Page 7Linked to original sources
PubMed1982

Methicillin-resistant Staphylococcus aureus: experience in a general hospital over four years.

From 1977 to 1981, 317 patients in a large general hospital became infected with methicillin- and gentamicin-resistant Staphylococcus aureus. The epidemic strain was characterized as bacteriophage type D11/83A/85, resistant to methicillin, cephalosporins and aminoglycosides, and contained a 24 megadalton plasmid which mediated gentamicin resistance. Spread within the hospital followed introduction of this organism into the general surgical and burn services and resulted from cross infection between patients. These services remained a reservoir of infection throughout the four-year period. Only 2% of hospital personnel carried methicillin-resistant S. aureus in their anterior nares, and only one of them was shown to be a long-term carrier. During the epidemic, there was no overall increase in serious staphylococcal infections, as reflected in bacteremias. As methicillin-resistant S. aureus increased, there was a reciprocal decrease in methicillin-sensitive S. aureus. Later, as methicillin-resistant S. aureus bacteremias decreased, methicillin-sensitive S. aureus bacteremias increased. Attempts to control the spread of the organism by containing infected patients on an isolation ward, or by placing all such infected patients in strict isolation, decreased the frequency of infections, but did not eliminate the organism. In 1980, the burn service was separated from the surgical service and moved into a new burn unit. Also, the five-bed rooms in the hospital were being converted to two-bed rooms. With only routine isolation precautions, the epidemic resolved over the next year, although the epidemic strain persists in the hospital.

Cross Infection↗
PubMed1982

Serum ornithine carbamyl transferase activities in Reye's syndrome.

Serum levels of ornithine carbamyl transferase (S-OCT), glutamic oxaloacetic transaminase and glutamic pyruvic transaminase were compared for 37 Reye's syndrome patients with regard to variation with clinical stage an serum ammonia levels. In stage I patients, the mean S-OCT activities were greater and the serum ammonia levels lower than found with patients in the more advanced stages. Covariation of these two parameters was found only in the more advanced stages. No significant correlation with stage or serum ammonia levels was found for S-GOT or S-GPT activities. These observations are discussed in terms of their relevance to reports of an early transient decrease of hepatic OCT activity in Reye's syndrome.

Alanine Transaminase↗
PubMed1982

Serum enzyme alterations in arginine-deficient, influenza-infected ferrets: a potential animal model of Reye's syndrome.

Young male ferrets developed hyperammonemia and encephalopathy soon after eating a diet lacking arginine. Because of this characteristic and their known susceptibility to influenza infections, they were further tested as an animal model for Reye's syndrome (RS), a childhood disorder which sometimes develops following influenza and which is characterized in part by encephalopathy, hyperammonemia, and elevated serum transaminase levels. Either the deficiency or infection alone resulted in minor elevations of serum ornithine carbamyl transferase (S-OCT) activities and together resulted in substantial elevations. These and associated alterations are discussed in relationship to the metabolic disorders occurring in RS.

Ammonia↗
PubMed1982

Radiation exposure and thyroid cancer incidence among Hiroshima and Nagasaki residents.

The dependence of thyroid cancer incidence on radiation exposure level is examined with the use of tumor registry follow-up data on a life-span cohort of 98,610 Hiroshima and Nagasaki residents. The sample includes 112 clinically evident thyroid cancer cases: 62 in Hiroshima and 50 in Nagasaki. A clear, predominantly linear, increase in thyroid cancer incidence corresponds to increasing levels of gamma radiation to the thyroid gland, whereas neutron exposure could not be shown to contribute further to thyroid cancer risk. The relative risk associated with gamma ray exposure is particularly high among persons who were less than 30 years old at the time of radiation exposure. Limitations on the incidence and dosimetry data are discussed, as well as the ability of the Cox regression method to accommodate some of these limitations.

Aged↗
PubMed1981

Feedback effect of estradiol on follicle-stimulating hormone and prolactin secretion during the puerperium.

Injections of 3 mg of estradiol benzoate were given to seven lactating women during the second and third weeks postpartum to study its effects on secretion of follicle-stimulating hormone (FSH) and prolactin during the subsequent 4 days. Administration of estradiol during te second week postpartum had no effect on serum levels of FSH and prolactin, however, 1 week later estradiol injection elicited a double effect: FSH levels decreased and prolactin concentrations increased. Early lactation seems to abolish the estrogen induced positive feedback effect on pituitary gonadotropin secretion. The negative effect of estrogen on FSH secretion and the positive effect on prolactin release became evident by the third week postpartum.

Estradiol↗
PubMed1980

Reading ability and the encoding of item and location information.

Two experiments using duration exposures ranging from 20 to 130 msec are reported that link reading skill in adults to the initial encoding of location information. Highly skilled and less skilled readers were equivalent in identifying single letters presented at a central fixation point. When they had to identify the serial position of a letter, however, highly skilled readers performed significantly more accurately than did less skilled readers. A second experiment used displays that consisted of one letter and three dollar signs. Subjects had to identify the letter under two location cuing conditions. When subjects were cued in advance as to which serial position would contain the letter, highly skilled and less skilled readers were equivalent. When the location of the letter had to be resolved prior to identification, highly skilled readers performed significantly more accurately than did less skilled readers. Results are interpreted to suggest that the role of perception in reading has been underestimated because emphasis has been on item perception, and the perception of spatial location has been largely overlooked.

Discrimination Learning↗
PubMed1979

Purification and comparison of several catalytic parameters of the gamma-glutamyltranspeptidase of rat mammary adenocarcinoma (13762) and of normal rat mammary gland.

A method for the purification of a membrane-bound glycoprotein, gamma-glutamyltranspeptidase ((gamma-glutamyl)-peptide:amino-acid gamma-glutamyltransferase, EC 2.3.2.2), from a transplantable rat mammary tumor (13762 MT) is described. The properties of the tumor enzyme were compared with those of gamma-glutamyltranspeptidase similarly isolated from mammary tissue of nonpregnant multiparous rats. Evidence has been presented elsewhere that the mammary and tumor enzymes exist as groups of species differing in isoelectric point and that the tumor enzyme contains more of the those species with lower isoelectric points. In this study the normal and tumor enzyme preparations are found to be identical or very similar in regards to the effect of papain on molecular size, the ratios of the enzymatic activities as measured with various amino acids, the Km for gamma-glutamyl-p-nitroanilide, and the Ki for inhibition by glutathione. Neuraminidase treatment had no effect on these catalytic properties. The properties observed were generally similar to those previously reported for highly purified rat kidney preparations.

Adenocarcinoma↗
PubMed1979

Tumor inhibitory and non-tumor inhibitory L-asparaginases from Pseudomonas geniculata.

Two enzymes that catalyze the hydrolysis of l-asparagine have been isolated from extracts of Pseudomonas geniculata. After initial salt fractionation, the enzymes were separated by chromatography on diethylaminoethyl-Sephadex and purified to homogeneity by gel filtration, ion-exchange chromatography, and preparative polyacrylamide electrophoresis. The enzymes differ markedly in physicochemical properties. One enzyme, termed asparaginase A, has a molecular weight of approximately 96,000 whereas the other, termed asparaginase AG, has a molecular weight of approximately 135,000. Both enzymes are tetrameric. The asparaginase A shows activity only with l-asparagine as substrate, whereas the asparaginase AG hydrolyzes l-asparagine and l-glutamine at approximately equal rates and it is also active with d-asparagine and d-glutamine as substrates. The asparaginase A was found to be devoid of antitumor activity in mice, whereas the asparaginase AG was effective in increasing the mean survival times of both C3H mice carrying the asparagine-requiring Gardner 6C3HED tumor line and Swiss mice bearing the glutamine-requiring Ehrlich ascites tumor line. These differences in antitumor activity were related to differences in the K(m) values for l-asparagine for the two enzymes. The asparaginase A has a K(m) value of 1 x 10(-3) M for this substrate whereas the corresponding value for the AG enzyme is 1.5 x 10(-5) M. Thus the concentration of asparagine necessary for maximal activity of the asparaginase A is very high compared with that of the normal plasma level of asparagine, which is approximately 50 muM.

Animals↗
PubMed1978

The role of spatial redundancy in grapheme recognition: perception or inference?

The question under investigation is whether spatial redundancy operates by restricting the number of valid alternatives at each serial position or whether it serves a perceptual function by keeping visually confusable graphemes from appearing in the same array and/or maximizing the distance between such graphemes when they do occur in the same array. The first experiment used the same-different task to establish a confusion matrix for 12 non-linguistic symbols. The spatial relation between the members of two pairs of confusable symbols was manipulated in a second experiment, which had subjects look for the presence or absence of a predetermined target symbol in single six-symbol linear arrays. Facilitation was found to be dependent upon the perceptual consequences of serial position constraint rather than upon the constraint per se. The constraint was most effective when it served to prevent members of visually confusable pairs from occurring in the same array. Since spatial redundancy may operate at the feature extraction stage by minimizing competition for the same sets of feature detectors and since words are likely to be high in spatial redundancy, the possibility is raised that part of the word superiority effect may be due to visual factors rather than to linguistic context.

Form Perception↗
PubMed1978

Differences in the isoelectric focusing patterns of gamma-glutamyl transpeptidase from normal and cancerous rat mammary tissue.

Highly purified fractions of gamma-glutamyl transpeptidase [gamma-glutamyltrinsferase; (5-glutamyl)-peptide:amino-acid 5-glutamyltransferase, EC 2.3.2.2] from normal and malignant rat mammary tissue were prepared. Analyses by isoelectric focusing indicate the existence of at least 12 enzymatically active species. The gamma-glutamyl transpeptidase from the tumor tissue had a greater proportion of the activity concentrated in the more negative species than the enzyme from normal tissue. Treatment of the two enzyme preparations with neuraminidase (acylneuraminyl hydrolase, EC 3.2.1.18) greatly reduced this difference. When whole tissue homogenates were treated with papain to solubilize the enzyme and then focused, the same relationship held. The neuraminidase activities in the two homogenates were similar, but the sialytransferase activity (CMP-N-acetylneuraminate:D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1) of the tumor homogenate was 13 times that of the normal mammary homogenate. These observations suggest that the gamma-glutamyl transpeptidase of the tumor is more heavily sialylated than that from the normal tissue, possibly reflecting the greater sialyltransferase activity of the tumor.

Adenocarcinoma↗