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Biomedical subjects

R Young

Publications and source records attributed to R Young.

At least 343 records · Page 19Linked to original sources
PubMed1977

Role of ribosomal protein S12 in peptide chain elongation: analysis of pleiotropic, streptomycin-resistant mutants of Escherichia coli.

Some of the spontaneous streptomycin-resistant mutants of Escherichia coli strain C600 exhibit pleiotropic effects in addition to the antibiotic resistance. These effects include decreased growth rates, reduced levels of certain enzymes, and poor support of bacteriophage growth. One of these mutants, strain SM3, was studied further. We have examined the question of whether the reduced growth rate of the mutant SM3 is related to the reduction in relative amounts of ribosomes or to the reduction in the efficiency of ribosomes in protein synthesis. Measurements of alpha, the differential synthesis rate of ribosomal protein, revealed that the protein synthesis effeciency of ribosomes from the mutant strain SM3 was reduced about twofold relative to that of the parent strain C600. Measurements of the induction lag for beta-galactosidase and of the synthesis time of several different molecular-weight classes of proteins indicated that the mutation resulted in a marked reduction in the peptide chain growth rate. This reduction in the chain growth rate probably accounted for most of the observed reduction in the growth rate of the mutant strain. These experimental results show that the strA gene product, the S12 protein of the 30S subunit, is involved in some aspect of protein chain elongation. Presumably this involvement occurs during the messenger ribonucleic acid-directed binding of transfer ribonucleic acid to the ribosome.

Bacterial Proteins↗
PubMed1977

Initiation and termination of deoxyribonucleic acid replication in bacteria after a stepwise increase in the velocity of replication.

The theoretical relations between replication, initiation, termination, and deoxyribonucleic acid (DNA) accumulation were derived for experiments in which the length of the time required for the replication of the bacterial chromosome (C period) can be varied. This theory enables one to determine absolute values of the C period from kinetics of DNA accumulation after a "stepup" with thymine-requiring bacteria that are subjected to a sudden increase in the exogenous thymine concentration. Application of this method of data evaluation to an observed step-up experiment with a thy-derivative of Escherichia coli B/r (ATCC 12407) indicated that the theory describes the observed post-step accumulation of DNA accurately within experimental errors. It is also concluded that changes in the replication velocity (C) do not measurably affect the timing of initiation events in a culture.

DNA Replication↗
PubMed1976

Polypeptide-chain-elongation rate in Escherichia coli B/r as a function of growth rate.

By evaluating the kinetics of radioactive labelling of nascent and finished polypeptides, the peptide-chain elongation rate for Escherichia coli B/r at three different growth rates (mu) was determined to be 17 amino acids/s for the fast-growing cells (mu equals 1.3 and 2.0 doublings/h) and 12 amino acids/s for slow-growing cells (mu equals 0.67 doublings/h). The results agree with the growth-rate-dependence of the rate of peptide-chain elongation found for the translation of newly induced beta-galactosidase messenger in this strain and under these conditions of growth [Dalbow & Young (1975) Biochem. J. 150, 13-20]. Together with the previously observed ribosome efficiency at these growth rates [Dennis & Bremer (1974) J. Mol. Biol. 84, 407-422] the results indicate that the fraction of ribosomes engaged in protein synthesis is about 0.8 at all three growth rates.

Bacterial Proteins↗
PubMed1975

Effect of progesterone on estrogen receptors in the rabbit uterus.

The macromolecular binding of estradiol was investigated in the rabbit uterus under various hormonal states in a search for evidence of progesterone antagonism of the estrogen-receptor complex interaction. Progesterone did not alter the sucrose gradient sedimentation characteristics of the estrogen-receptor complex in estrus or castrate animals. Progesterone treatment of castrated animals did not alter the absolute number of EBS (estrogen-binding sites) per cell, but did result in decreased relative concentration of EBS by increasing the soluble protein content of the cells over that seen in untreated castrates. Castration did not alter the absolute number of EBS per cell but did increase the relative concentration of estrogen binding in the cytosol.

Animals↗
PubMed1975

Treatment of thyrotoxicosis during pregnancy with propranolol.

The treatment of two pregnant thyrotoxic patients with propranolol alone is discussed. One patient had a spontaneous remission during pregnancy wile taking propranolol. In the other patient treatment with propranolol allowed postponement of definitive therapy until after delivery, when the fetus was no longer at risk. There were no complications of therapy in either patient and both infants were normal. The use of propranolol in thyrotoxicosis is discussed and the pertinent literature is reviewed. Regional anesthesia is preferred over general anesthsia in patients taking propranolol. Patients taking propranolol who require general anesthesia for delivery should have continuous monitoring of electrocardiogram and central venous pressure. To this date no method of therapy has been free of fetal side effects. Surgical treatment is associated with occasional abortion or premature labor; antithyroid medication occasionally results in fetal goiter or cretinism.

Adolescent↗
PubMed1975

Deanol and methylphenidate in minimal brain dysfunction.

Deanol, a putative acetylcholine precursor, has been used as a treatment for childhood hyperactivity for years. Efficacy has not been satisfactorily established, however. Seventy-four children referred for problems with learning, including many with hyperactivity, were screened for neurological or psychiatric illness, then given deanol, methylphenidate, or placebo in a double-blind fashion for 3 months. Maintenance dose for methylphenidate was 40 mg daily; for deanol, 500 mg. Behavior rating forms, reaction time, and a series of standard psychometric tests were given before and after treatment. Both drugs showed significant improvement on a number of tests; the pattern and degree of change differed slightly for the two. In this paradigm, deanol thus appeared to improve performance in children with learning and behavior disorders. The mechanism of action remains speculative; proof that deanol increases acetylcholine is scanty, and there is a theoretical basis for actually assuming an anticholinergic effect. Further clinical studies on deanol are indicated.

Analysis of Variance↗
PubMed1975

Synthesis time of beta-galactosidase in Escherichia coli B/r as a function of growth rate.

By analysing the kinetics of beta-galactosidase accumulation after induction, the synthesis time of beta-galactosidase in Escherichia coli B/r was found to be 75s in rapidly growing cells (1.36 and 2.1 doublings/h), and 90s in slowly growing cells (0.63 doubling/h). These values correspond to peptide-chain-elongation rates of 16 and 13 amino acids/s respectively, in agreement with previous findings, indicating that the peptide-chain growth rate is constant (presumably maximal) in fast-growing bacteria, but decreased in slowly growing bacteria [Forchhammer & Lindahl (1971) J. Mol. Biol. 55, 563-568].

Amino Acids↗
PubMed1975

Analysis of enzyme induction in bacteria.

The theoretical relations between the induced initiation and accumulation of lac mRNA and its translation are derived, taking the kinetics of repressor-operator dissociation and enzyme maturation into account. These relations are used to evaluate observed data on lac induction and to estimate a number of parameters that characterize the transcription and translation of the beta-galactosidase gene in the bacterium Escherichia coli B/r growing at three different rates (0.7-2.1 doublings/h).

Enzyme Induction↗
PubMed1975

Epidemic Venezuelan equine encephalitis in North America in 1971: vector studies.

A major epidemic of Venezuelan equine encephalitis occurred in south Texas in the summer of 1971. More than 1500 equines died of VEE in Texas, and 110 human cases with no deaths were reported. Vector studies in south Texas and northern Tamaulipas revealed that the overall mosquito infection rates during the peak of the epidemic were about 1:100, one of the highest rates observed for a major epidemic. Mosquito infection rates of this magnitude could easily explain the intensity of VEE outbreaks in both equines and man. A total of 943 VEE virus isolations were made from mosquitoes. Eight of the 12 mosquito species found infected were implicated in the epidemic cycle of VEE for the first time. Sufficient laboratory and field evidence is available to prove that Psorophora confinnis was one of the primary vectors of VEE. The lack of laboratory evidence necessitates the use of the term "probable" primary vectors for other species apparently equally as involved on the basis of field infections; these include Aedes sollicitans, Aedes thelcter and Psorophora discolor. Eight other species from which less than 10 VEE virus isolations were made were considered auxiliary vectors. Mosquitoes of some species were tested individually; such tests showed 2-4% of the probable primary vectors to be infected. The first isolation of VEE virus of the epidemic was made from P. confinnis on June 28, 1971. Highest mosquito infection rates occurred during the week of July 5. Mosquito infection rates declined precipitously in the last 3 weeks of July 1971, signaling the end of the epidemic in the study area. One explanation for the decline was that equines, the principal epidemic hosts, were eliminated as a source of virus by death or by acquisition of natural or induced immunity. Mosquito control appeared to be effective in reducing the infected mosquito population while the immunization of equines with TC 83 VEE vaccine was accomplished. Quarantines appeared to be effective in restricting the VEE virus activity to south Texas. Undoubtedly all of the control measures contributed to stopping the epidemic. Continued VEE surveillance by various government and other agencies failed to reveal any further epidemic VEE activity in the US in 1972. Other arboviruses isolated during the VEE studies in south Texas included St. Louis encephalitis virus, and San Angelo subtype of the California Group. A virus of the Bunyamwera Group was also isolated from Palo Blanco, Tamaulipas.

Animals↗
PubMed1975

Balanced production of 30S and 50S ribosomal proteins after a nutritional shift-up.

The synthesis of bulk ribosomal protein (r-protein) after a nutritional shift-up in Escherichia coli B/r was examined. It was found that the molar ratio of the net synthesis rates of 30S and 50S r-protein remains constant during the transition period after the shift-up and equal to the preshift ratio. The implications for the control of ribosome synthesis are discussed.

Amino Acids↗