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Biomedical subjects

R F White

Publications and source records attributed to R F White.

At least 109 records · Page 6Linked to original sources
PubMed1977

A computer program to record technical data in leukapheresis and plateletpheresis procedures.

A computer program for the recording of data and calculation of results from leukapheresis and plateletpheresis procedures is described. It provides a printout of cell yields and other results for each procedure, as well as an updated list of donors and phereses. The data are kept on tape, accessible for periodic statistical analysis. While primarily set up for use with Haemonetics (intermittent-flow centrifugation) equipment, the program is adaptable for other systems.

Blood Transfusion↗
PubMed1975

Inhibition of multiplication of tobacco mosaic virus in protoplasts by antibiotics and its prevention by divalent metals.

At concentrations that inhibit bacterial growth, some antibiotics including gentamicin completely inhibited virus multiplication in protoplasts, and other antibiotics partially inhibited virus multiplication. The inhibition caused by each antibiotic was largely prevented by adding a divalent metal; MnC1(2) was more effective than CaC1(2) and other salts of divalent metals when added at 10 mM to the incubation medium. When added immediately after infection, 1 mug/ml of gentamicin halved the final virus concentration and 3 mug/ml completely inhibited virus multiplication, although 10 mug/ml was required to stop bacterial growth. Gentamicin inhibited virus multiplication even when added 24 h after virus inoculation. Also, when protoplasts were exposed to gentamicin for only 1 or 2 h, either immediately after inoculation or 2 h later, the virus concentration was considerably decreased. Gentamicin seemed not to affect virus multiplication in whole plants. Sap from Dianthus barbatus also strongly inhibited virus multiplication in protoplasts but, unlike gentamicin, it acted in the presence of MnC1(2). By contrast, chelating agents such as 1 mM-EDTA or 5 mM-potassium citrate was strong inhibitors of virus multiplication that were inactive in the presence of MnC1(2). It is suggested that gentamicin and other antibiotics may chelate metals from the protoplast membranes, thus disorganizing their function and affecting virus multiplication.

Anti-Bacterial Agents↗
PubMed1975

Randomization and the analysis of variance.

This paper attempts to strengthen faith in randomization, first by defining it in general and second by showing how it is the fundamental means, in many experiments, of generating the probability space. It is defined by the natural structure of the experimental units (E.U.'s) not by a particular experimental design imposed on that structure. Three examples are given, with the same design but different E.U. structures and randomizations, to show that models developed from experimental designs are superficial, but that their randomization is fundamental.

Analysis of Variance↗
PubMed1973

Betaine-homocysteine transmethylase in Pseudomonas denitrificans, a vitamin B 12 overproducer.

A pantothenate-methionine auxotroph (J741) of Pseudomonas denitrificans was isolated whose growth requirement for methionine could not be satisfied by known precursors of the amino acid, including homocysteine. However, some "methyl rich" compounds such as betaine and dimethylacetothetin (DMT) could satisfy the requirement. S-Methyl-methionine and S-adenosylmethionine were ineffective. Extracts were found to contain an enzyme, betaine-homocysteine transmethylase (BHTase), that uses betaine or DMT as a methyl donor and homocysteine as an acceptor to produce methionine. Growth of J741 in methionine leads to a total repression of the BHTase, whereas the use of DMT leads to a three- to sixfold stimulation of enzyme synthesis compared to betaine-grown cells. The pantothenate requirement is unrelated to the methionine auxotrophy, since the growth of other single auxotrophic mutants as well as revertants of J741 still have their methionine requirement satisfied by betaine or DMT. Another methionine auxotroph that could not use betaine for growth was devoid of BHTase activity.

Betaine↗
PubMed1971

Microbial epoxidation of cis-propenylphosphonic to (-)-cis-1,2-epoxypropylphosphonic acid.

Eighteen species of Penicillium, one of Oidium and one of Paecilomyces were found to effect a stereospecific conversion of cis-propenylphosphonate to fosfomycin which was identified by paper chromatography and gas-liquid chromatography (GLC) of the trimethylsilyl esters. Penicillium spinulosum carried out the epoxidation only after the glucose substrate had been utilized. Glucose controlled the epoxidation since its residual concentrations in the broth severely depresses the reaction. At optimum levels of glucose, an epoxidation efficiency approaching 90% of olefin charged (0.2 g/liter) was obtained after 10 days of incubation. The olefin concentration could be increased to 0.5 g/liter when glucose was replaced by glycerol, whereby a 90% conversion to fosfomycin was attainable in 6 days. The high conversion efficiency, a good agreement between the GLC assay and bioactivity, are indicative of the levorotatory nature of the product.

Alkenes↗
PubMed1971

Porphyrin overproduction by Pseudomonas denitrificans: essentiality of betaine and stimulation by ethionine.

Ethionine supplementation of a defined medium for growth of Pseudomonas denitrificans inhibited vitamin B(12) overproduction and led to the elaboration of a red pigment. The pigment was shown to be coproporphyrin III. Inhibition by ethionine of cobalamin synthesis is probably due to interference of methylation of the corrin nucleus by methionine. Accumulation of coproporphyrin III is thought to result from interference by ethionine with the activity of methionine in the coproporphyrinogenase reaction; this would inhibit formation of heme, the feedback inhibitor and corepressor of delta-aminolevulinate synthetase, thus allowing unregulated synthesis of coproporphyrinogen III and its degradation product, coproporphyrin III. Betaine, known to be required for vitamin B12 overproduction, was found to be an essential requirement for porphyrin overproduction in the presence of ethionine. Low-level production of porphyrin, which occurs in the absence of ethionine, also required betaine supplementation. Betaine is thus required for overproduction of both corrins and porphyrins in P. denitrificans.

Absorption↗
PubMedDate not supplied

Concomitant cortical expression of TNF-alpha and IL-1 beta mRNAs follows early response gene expression in transient focal ischemia.

The expression of tumor necrosis factor alpha (TNF-alpha) and interleukin 1 beta (IL-1 beta) mRNAs was significantly increased in the rat ischemic cortex following temporary occlusion of the middle cerebral artery (TMCAO) with reperfusion. Northern blot analysis demonstrated that the induction of TNF-alpha and IL-1 beta mRNAs occurred as early as 1 h after reperfusion, exhibiting a 4.6-fold increase (p < 0.05, n = 4) and 6.8-fold increase (p < 0.05, n = 4) in the ischemic cortex over control, respectively. TNF-alpha mRNA reached its peak at 3 h (8.0-fold, p < 0.05), whereas IL-1 beta mRNA reached its peak at 6 h (29.5-fold, p < 0.05). Both cytokine mRNA levels remained elevated for up to 2 d after reperfusion. In contrast to the time course of these cytokine mRNAs, c-fos and zif268 mRNAs, two early response genes, displayed a greater and earlier time-response profile. The early induction of c-fos and zif268 mRNAs in temporary brain ischemia with reperfusion suggests their roles in transcriptional regulation. The later concomitant expression of TNF-alpha and IL-1 beta suggests that these cytokines play an important role in the inflammatory response associated with focal ischemia.

Animals↗
PubMedDate not supplied

Criteria for progressive modification of neurobehavioral batteries.

Six specific issues affecting the progressive modification of neurobehavioral test batteries used in field studies of populations exposed to neurotoxicants are discussed and test review recommendations are provided addressing each issue. The issues include: (a) general test review standards, (b) comprehensive assessment, (c) tailored batteries, (d) incorporation of new tests and techniques, (e) personnel and mechanisms for review, and (f) development of a battery assessing peripheral nervous system function.

Behavior↗