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Biomedical subjects

A Thomas

Publications and source records attributed to A Thomas.

At least 415 records · Page 23Linked to original sources
PubMed1991

Non-radioactively labelled polynucleotide and oligonucleotide DNA probes, for selectively detecting Escherichia coli strains producing Vero cytotoxins VT1, VT2 and VT2 variant.

Vero cytotoxin producing Escherichia coli (VTEC) were detected in faecal specimens and bacterial isolates, using non-radioactively labelled polynucleotide and oligonucleotide DNA probes specific for Vero cytotoxin (VT) genes. VT1 and VT2 structural gene sequences, previously cloned and used for radioactive probes, were labelled with digoxigenin or biotin. Oligonucleotide gene sequences coding for the A subunit of VT1, VT2 and VT2 variant were labelled with digoxigenin. The VT1 and VT2 probes were specific for detecting VT1 and VT2 gene sequences and gave very similar results to those obtained using the radioactive label 35S as a standard. The VT2 variant probe hybridized only with the strains of porcine origin. For the range of isolates tested, there was little significant difference in specificity and sensitivity between the digoxigenin-labelled polynucleotide and oligonucleotide probes. The biotin system gave rise to more non-specific effects, particularly with some non-E. coli strains, and was therefore less reliable. All of the digoxigenin-labelled probes gave satisfactory results after several times re-use, which is of importance when considering cost.

Bacterial Toxins↗
PubMed1991

Characterization of prostate cancer, benign prostatic hyperplasia and normal prostates using transrectal 31phosphorus magnetic resonance spectroscopy: a preliminary report.

We assessed the ability of 31phosphorus (31P) transrectal magnetic resonance spectroscopy to characterize normal human prostates as well as prostates with benign and malignant neoplasms. With a transrectal probe that we devised for surface coil spectroscopy we studied 15 individuals with normal (5), benign hyperplastic (4) and malignant (6) prostates. Digital rectal examination, transrectal ultrasonography and magnetic resonance imaging were used to aid in accurate positioning of the transrectal probe against the region of interest within the prostate. The major findings of the in vivo studies were that normal prostates had phosphocreatine-to-adenosine triphosphate (ATP) ratios of 1.2 +/- 0.2, phosphomonoester-to-beta-ATP ratios of 1.1 +/- 0.1 and phosphomonoester-to-phosphocreatine ratios of 0.9 +/- 0.1. Malignant prostates had phosphocreatine-to-beta-ATP ratios that were lower (0.7 +/- 0.1) than those of normal prostates (p less than 0.02) or prostates with benign hyperplasia (1.1 +/- 0.2, p less than 0.01). Malignant prostates had phosphomonoester-to-beta-ATP ratios (1.8 +/- 0.2) that were higher than that of normal prostates (p less than 0.02). Using the phosphomonoester-to-phosphocreatine ratio, it was possible to differentiate metabolically malignant (2.7 +/- 0.3) from normal prostates (p less than 0.001), with no overlap of individual ratios. The mean phosphomonoester-to-phosphocreatine ratio (1.5 +/- 0.5) of prostates with benign hyperplasia was midway between the normal and malignant ratios, and there was overlap between individual phosphomonoester-to-phosphocreatine ratios of benign prostatic hyperplasia glands with that of normal and malignant glands. To verify the in vivo results, we performed high resolution magnetic resonance spectroscopy on perchloric acid extracts of benign prostatic hyperplasia tissue obtained at operation and on a human prostatic cancer cell line DU145. The extract results confirmed the differences in metabolite ratios observed in vivo. We conclude that transrectal 31P magnetic resonance spectroscopy can characterize metabolic differences between the normal and malignant prostate.

Adult↗
PubMed1991

Examination of retail chickens and sausages in Britain for vero cytotoxin-producing Escherichia coli.

Samples from chickens and pork sausages were examined for the presence of Vero cytotoxin-producing Escherichia coli by using DNA probes for the Vero cytotoxin genes. Hybridization was detected in 25% of the 184 sausage samples, but none of the chickens was positive. No E. coli O157:H7 strains were isolated, and serotyping showed that the Vero cytotoxin-producing E. coli strains belonged to eight different O serogroups and that six strains had an unidentifiable O antigen.

Animals↗
PubMed1991

Involvement of mono-oxygenases as a major mechanism of deltamethrin-resistance in larvae of three species of mosquitoes.

Role of mono-oxygenases as a mechanism of resistance to the synthetic pyrethroid, deltamethrin in the larvae of Culex quinquefasciatus Say, Aedes aegypti L. and Anopheles stephensi Liston developed by laboratory selections with deltamethrin, DDT or deltamethrin and the synergist, piperonyl butoxide (PBO) in the ratio of 1:5, was investigated. There was a significant correlation with mono-oxygenase activity and larval LC50 to deltamethrin in various strains of all the three species. In addition, the activity of glucose-6-phosphate dehydrogenase (G6PD), the main NADPH generating enzyme for mono-oxygenases, also showed enhanced activity in deltamethrin and DDT-selected strains. The present data, therefore, clearly suggest that deltamethrin resistance in the larvae of Cx. quinquefasciatus, Ae. aegypti and An. stephensi is mainly due to the detoxification of deltamethrin by microsomal mono-oxygenases. High activity of G6PD observed in DDT-selected strains seems to be related to its role as a rate-limiting enzyme in GSH-dependent dehydrochlorination of DDT.

Aedes↗
PubMed1991

Dieulafoy's disease: cause of massive upper gastrointestinal haemorrhage in two Asian women.

Dieulafoy's disease is a submucous arterial malformation of the stomach, and is a known cause of massive upper gastrointestinal bleeding. To date, 125 cases have been reported in the literature. Fatality is high if the condition remains undiagnosed. Endoscopy is difficult but important in the diagnosis of Dieulafoy's disease. Dieulafoy's disease in two Asian women are reported here. Both required large amount of blood transfusions as the diagnosis was not recognised early. Greater awareness of the condition will enable earlier diagnosis and reduced mortality from this condition.

Adult↗
PubMed1990

An initiation signal in the 5' untranslated leader sequence of encephalomyocarditis virus RNA.

A 593 nucleotide fragment of the 5' leader of encephalomyocarditis virus RNA (EMCV-RNA) was linked to the SP6 promoter and inserted upstream of the reporter gene chloramphenicol acetyltransferase (CAT). The presence of the 5'-UTR of EMCV-RNA in the RNA transcripts, made in vitro with the SP6 polymerase, resulted in a strong translational enhancement when tested in the micrococcal nuclease-treated reticulocyte lysate. The transcripts were equally active with or without a 5' methylated capstructure as expected, since EMCV-RNA is one of the mRNAs capable of internal initiation. We searched for a signal in the 5' leader that allows the 43S preinitiation complex to bind internally and localized a hairpin containing a unique nucleotide sequence, CUUUA, present in a domain conserved among cardio- and aphtoviral RNAs. Replacing this sequence into AGCU resulted in a 50% loss of translational activity. A second mutation involving a U-G change in the stem of that hairpin resulted in an almost complete loss of initiation.

Animals↗
PubMed1990

A chloride- and calcium-dependent glutamate-binding protein from rat brain. Identification as a ubiquitous constituent of the inner mitochondrial membrane.

We have recently solubilized and enriched a chloride- and calcium-dependent glutamate-binding protein from rat brain (Brose, N., Halpain, S., Suchanek, C., and Jahn, R. (1989) J. Biol. Chem. 264, 9619-9625). The partially purified protein fraction, containing two major protein components of 51,000 Da and 105,000 Da, was used to generate a rabbit antiserum. This serum quantitatively precipitated the binding activity from membrane extracts. Small amounts of the antiserum inhibited glutamate binding when chloride was absent from the incubation medium. Three protein bands were labeled by the serum on immunoblots. From the affinity purified antibody fractions contained in the serum, only the antibodies directed against a 51,000-Da protein were able to immunoprecipitate the binding activity, indicating that this protein is an essential component of the binding site. A survey of a variety of rat tissues by immunoblot analysis revealed a ubiquitous distribution of the protein. After subcellular fractionation of liver and brain, the 51,000-Da protein copurified with mitochondrial markers. Furthermore, exclusive labeling of mitochondria was observed by light and electron microscopy immunocytochemistry. Subfractionation of purified liver mitochondria resulted in a selective association of the protein with inner mitochondrial membranes. Pharmacological characterization of glutamate binding to liver mitochondrial membranes revealed a pattern almost identical to that of the chloride- and calcium-dependent glutamate-binding site in rat brain.

Animals↗
PubMed1990

Knowledge, attitudes, treatment practices, and health behaviors of nurses regarding blood cholesterol and cardiovascular disease.

Knowledge, attitudes, and practice patterns concerning cholesterol and heart disease were evaluated in a stratified, random sample of 206 registered nurses at a major academic medical center in New York City. Virtually all nurses were convinced of the importance of diet in reducing heart disease risk, and most (78%) agreed that nutrition counseling should be their responsibility. Although only 19% reported that they were currently counseling, many more felt prepared to counsel about diet or drug therapy (43%). Nurses who were likely to counsel were those working in general medicine, those who were certified nurse practitioners, those who knew their own blood cholesterol level, and those with higher knowledge scores. Level of overall knowledge was associated with the practice of counseling, an attitude that counseling should be a nurse's responsibility, and personal health behavior (knew own level), regardless of age or occupational or degree status. Despite their enthusiasm for heart disease prevention through diet modification, many nurses had substantial knowledge gaps, suggesting that nurses are currently not adequately prepared to counsel about diet and/or drug treatment for high blood cholesterol. Educational strategies and considerations in integrating an expanded role for nurses with those of physicians and dietitians are discussed.

Academic Medical Centers↗
PubMed1990

Symmetry and crystallography: new facilities in the graphic software MANOSK.

The new routine SYMCRY of the graphics program MANOSK is described in this paper. It is designed to analyze interactions between molecular structures related by crystalline symmetry. The symetric objects can be described in the same referential, to be manipulated as an entity, or in a referential of their own, to undergo correlative real-time movements (via the dials), given the symmetry constraints. Crystal packing can be observed, and any command of the main software MANOSK is available for the symmetric objects, including storage of the coordinates of symmetrics in the final orientation.

Computer Graphics↗
PubMed1990

Plasmid-encoded production of coli surface-associated antigen 1 (CS1) in a strain of Escherichia coli serotype O139.H28.

Production of coli surface-associated antigen 1 (CS1) by Escherichia coli strain E24377 of serotype O139.H28 was controlled by a plasmid that also encoded heat stable and heat labile enterotoxins and CS3. The presence of a regulatory sequence was detected on this plasmid by hybridization with the cfaD gene that regulates expression of colonization factor antigen I fimbriae and is at least 96% homologous with the rns sequence controlling production of CS1 or CS2 fimbriae by strains of serotype O6.H16 of appropriate biotype. A separate plasmid, pDEP20, carrying the structural genes for CS1 synthesis was identified and transformed into E. coli strain HB101 or a derivative of strain E24377 without large plasmids. Transformants carrying pDEP20 did not produce CS1 fimbrial antigen, but antigen expression was obtained when a cloned cfaD gene or a wild-type plasmid carrying the rns sequence was introduced. Transposon mutagenesis with Tn1000 identified a 3.7 kbp region of pDEP20 essential for production of CS1 fimbriae. Genes encoding production of CS1 fimbriae were cloned on a 9.9 kbp BamHI fragment and were expressed in the presence of the cfaD sequence. A strain producing both CS1 and CS2 antigens was constructed by introduction of the cloned cfaD gene into a strain of serotype O6.H16 biotype C carrying plasmid pDEP20.

Antigens, Bacterial↗
PubMed1990

Electrochemical characteristics of five quinolone drugs and their effect on DNA damage and repair in Escherichia coli.

The object of this study was to determine whether 4-quinolone antimicrobials were reduced under biologically attainable redox conditions and whether they had any effect on DNA in the absence of the DNA gyrase enzyme. Electrochemical characteristics of the drugs were investigated using d c polarography, differential pulse polarography and cyclic voltammetry. The ability of the drugs to interact with, and cause damage to, naked DNA was investigated by a phi X174 DNA double transfection assay. Induction of DNA SOS repair was assessed using a stain of Escherichia coli in which the synthesis of beta-galactosidase was under the control of the su1A gene. Growth studies were performed using a conductimetric method in a Malthus system. All five 4-quinolones examined had redox potentials lower (more negative) than -1.2 V and thus were incapable of being reduced in biological systems, even under strict anaerobiosis. Exposure of all drugs to single-stranded phi X174 DNA for up to 50 h engendered no detectable damage. However, all the drugs induced DNA SOS repair, in the order ciprofloxacin greater than fleroxacin = pefloxacin greater than norfloxacin greater than nalidixic acid. This rank order corresponds approximately with antibacterial efficiency. The growth studies indicated that redoxyendonuclease III and excision repair enzymes may be involved in the fixation of quinolone-induced damage.

4-Quinolones↗
PubMed1990

Q fever in Sokoto, Nigeria.

There is very little information available about the prevalence of Coxiella burnetii in Africa. We obtained blood from 75 Nigerians hospitalized in Sokoto for a variety of acute medical conditions. Their age range was 7 months to 50 years; there were 39 males and 36 females. Antibody titers were determined to phase I and phase II C. burnetii antigens using a microimmunofluorescence test. Thirty-three (44%) had an antibody titer of greater than or equal to 1:8 to phase II C. burnetii. We conclude on the basis of this limited survey that Q fever is common in Nigeria.

Adolescent↗
PubMed1990

Effect of N-acetylcysteine on diaphragm fatigue.

It has recently been postulated that diaphragm fatigue may be due, at least in part, to a form of low-grade injury to subcellular organelles. Moreover, several studies have shown that thiol-containing compounds can protect cardiac and striated skeletal muscle organelles from the deleterious effects of a number of physiological stresses. The purpose of the present study was to determine whether pretreatment with N-acetylcysteine (NAC), a thiol-containing compound, would attenuate the rate of development of diaphragmatic fatigue. Studies were performed with the use of an in situ rabbit diaphragm strip preparation that permitted direct and continuous measurement of diaphragm tension development. Diaphragm fatigue was induced by rhythmically stimulating strips to contract at 30/min (20-Hz trains) for 20 min. The diaphragm force-frequency relationship (10-, 20-, 50-, and 100-Hz stimuli) was assessed immediately before and after fatigue trials and then again 20 min into the period of recovery. Half the animals were treated with intravenous NAC before fatigue, whereas the remaining animals were given intravenous saline. The rate of development of fatigue was markedly greater in saline-treated control than in NAC-treated animals, with reductions in tension of 55 +/- 3 and 34 +/- 3%, respectively, in these two groups of animals over 20 min (P less than 0.001). Although rhythmic stimulation resulted in a downward shift in the force-frequency relationship in both NAC- and saline-treated animals, the magnitude of this shift was substantially greater in saline-treated animals (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcysteine↗
PubMed1990

The New York Longitudinal Study (NYLS): the young adult periods.

This paper focuses on the findings and analyses, both qualitative and quantitative, of the young adult periods; early adult life (EAL) or ages 18 to 24, and young adult life (YAL) or ages 25 to 30. A summary is given of the sample and methods used in the study. Complexities of the life paths of the 133 subjects are traced, and the adolescent findings are discussed. In this middle class sample, the YAL period was found qualitatively to demand greater resolution of goals, life patterns and self-sufficiency than earlier periods.

Adolescent↗
PubMed1990

Serial adrenal ultrasonography in normal neonates.

Six serial ultrasound scans were performed on each of 12 healthy term babies on days 1, 3, 5, 11, 21, and 42 of extrauterine life in order to determine normal neonatal values for various adrenal parameters. Measurements were made of transverse and anteroposterior diameters, of circumference and area in the transverse plane, and of longitudinal length of the adrenals and kidneys. There was a significant decrease in all adrenal parameters of 22%, 25%, 25%, 44%, and 34%, respectively, between days 1 and 5 (p less than .002) and of 46%, 39%, 46%, 67%, and 55%, respectively, between days 1 and 42 (p less than .00005), whereas the kidneys increased in size over the same period.

Adrenal Glands↗