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Biomedical subjects

J R Allen

Publications and source records attributed to J R Allen.

At least 181 records · Page 10Linked to original sources
PubMed1980

T4 ribonucleotide reductase. Physical and kinetic linkage to other enzymes of deoxyribonucleotide biosynthesis.

This laboratory has described a multienzyme aggregate from T4 phage-infected Escherichia coli which seems to participate in deoxyribonucleotide biosynthesis and efficient delivery of DNA precursors to the replication apparatus. This paper describes improved methodology for isolation of this aggregate, and we present three lines of evidence supporting a role for ribonucleoside diphosphate reductase in functioning of the presumed complex. 1) Ribonucleoside diphosphates are readily incorporated into DNA as deoxyribonucleotides in an in situ DNA-synthesizing system from T4 phage-infected cells. 2)Ribonucleotide reductase is associated with the complex, as shown by co-sedimentation of reductase activity with other activities in the multienzyme aggregate we have described. 3)Ribonucleotide reductase is kinetically coupled to at least four other enzymes involved in a sequential pathway. The aggregated enzymes catalyze the five-step conversion of uridine diphosphate to deoxythymidine triphosphate with but a brief lag before dTTP production reaches its maximal rate. These studies have also confirmed the existence of dCTPase-dUTPase and dCMP deaminase activities in the putative complex.

DNA, Bacterial↗
PubMed1980

DNA-histone interactions in nucleosomes.

We have utilized micrococcal nuclease digestion and thermal denaturation studies to investigate the binding of DNA to the histone core of the nucleosome. We conclude that a total of approximately 168 base pairs (bp) of DNA can interact with the histone core under appropriate solution conditions, even in the absence of lysine-rich histones. The interactions in this total length of DNA can be divided into three classes: (a) approximately 22 bp at the ends is bound only at moderate ionic strength. It is easily displaced, and its removal yields the 146 bp core particle. (b) approximately 46 bp near the ends of the core DNA are quite weakly bound to the core, and are displaced at quite moderate temperatures. (c) The remaining central 100 bp are strongly bound, and interact with all of the sites on the histones which strongly protect DNA against DNAse I digestion. A theoretical analysis of the cleavage of nucleosomal DNA by DNAse I has been used to develop evidence that the pattern of protection offered by the histone core is very similar in nuclei to that in isolated core particles.

Animals↗
PubMed1980

Nosocomial surgical infections: incidence and cost.

The data reported in this article support the findings of Dr. Altemeier; that is, infections among surgical patients remain a serious problem today. Urinary tract infections account for approximately 40 per cent of nosocomial infections among surgical patients. Surgical wound and skin infections account for one third of the nosocomial infections among surgical patients. Rates for wound infections rise with age, with increased length of hospitalization before surgery, and with increased duration of surgery. They are higher for patients who have an infection at a distant site and for those who have the more hazardous surgical procedures as determined by risk categories. Gram-negative organisms are more prevalent than gram-positive organisms. A nosocomial surgical wound infection lengthens the hospitalization by an average of 7.4 days and raises the cost of hospitalization by more than 800 dollars. Further analysis of the data is necessary in order to identify the risk factors likely to be most helpful in determining which patients are at increased risk of acquiring a nosocomial infection. Only when these factors are identified can the most direct and effective contact and preventive measures be implemented.

Aged↗
PubMed1980

Residual effects of polychlorinated biphenyls on adult nonhuman primates and their offspring.

After 18 mo of consuming a diet containing 2.5 and 5.0 ppm PCB (Aroclor 1248), during which they and their offspring experienced marked alterations in physical status, female rhesus monkeys were placed on a control diet for 1 yr. During this year there was a decided improvement in their general body health and reproductive capabilities. Infants born to these animals were small at birth and during their postnatal life developed signs of PCB intoxication similar to those observed in their siblings born during the period of PCB exposure. These data indicate that the residual effects of low-level ingestion of PCBs by nonhuman primates persist for over 1 yr after discontinuation of exposure. There are also indications that the fetal and neonatal monkeys born to PCB-exposed mothers are more severely affected for a longer period than are the adult female monkeys.

Abnormalities, Drug-Induced↗
PubMed1980

Streptococcus zooepidemicus (group C) pneumonia in a human.

Lancefield group C streptococcal pneumonia appeared in a previously healthy young adult. The patient apparently acquired the infection while caring for her sick horse, and experienced a gradual onset of the illness. There was rapid accumulation of pleural fluid and empyema requiring open drainage. Group C pneumonia cannot be distinguished from classic group A pneumonia on clinical grounds. Beta-hemolytic streptococci isolated from sputum, transtracheal aspirates, pleural fluid, or blood of patients with pneumonia should be grouped by the precipitin method of Lancefield or one of its more rapid modifications.

Adult↗
PubMed1980

Effects of climate-controlled housing on reproductive potential of rhesus monkeys.

The reproductive adaptability of newly acquired female feral rhesus monkeys was evaluated by comparison of their menstrual records and progesterone levels with those of females in captivity for 3 1/2 years. Housing of the animals under conditions that simulated conditions of the breeding season in the wild resulted in a rapid adjustment with minimal periods of amenorrhoea or anovulation. Both groups of monkeys were similar with respect to menstruation and menstrual cycle length and progesterone levels.

Animals↗
PubMed1979

Responses of rats exposed to polychlorinated biphenyls for fifty-two weeks. II. Compositional and enzymatic changes in the liver.

Male Sprague-Dawley rats consumed a diet to which 100 ppm of various polychlorinated biphenyl (PCB) mixtures (Aroclors 1248, 1254, and 1262) were added for one year. Rats were hepatectomized at 13, 26, and 52 weeks during feeding and at 13 weeks following the discontinuation of the PCB diets. The liver homogenates of these rats had an increase in protein and RNA on a DNA basis and an increase in lipid and a decrease in DNA on the liver weight basis. The hepatic microsomes from these livers also had an increase in protein and cytochrome P-450. The RNA/microsomal protein levels were decreased, and no marked alterations were recorded for the phospholipids and cholesterol on a microsomal protein basis. Increased enzymatic activity was recorded for N-demethylase and nitroreductase. However, the specific activity of glucose-6-phosphatase was decreased throughout the treatment period.

Animals↗