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Biomedical subjects

R Gross

Publications and source records attributed to R Gross.

At least 181 records · Page 10Linked to original sources
PubMed1995

[The general practitioner as physician of first contact with health problems].

An aim of this study was to determine the extent to which general practitioners (GPs) are their patients' physicians of first contact (PFCs) for specific health problems. It was also designed to explain the differences between physicians who treat these problems, and those who do not, by the type of problem presented, the characteristics of the physician, and the characteristics of the environment in which the physician works. The study is based on data collected in a nationwide mail survey in 1993 among 677 GPs working in 1 or more of Israel's 4 health insurance funds. They were asked if they were their patients' PFC for 27 health problems. There was great variation in the responses to this question according to the type of health problem presented. Thus for problems such as abdominal pain or chest pain, 85% of the GPs reported being the PFC, compared with only 50% for problems of suicidal thoughts or alcohol dependence. Multivariate analysis revealed that those more likely to report being their patients' PFC for the majority of problems presented were specialists in family medicine (p < 0.001), physicians under the age of 55 (p < 0.01) and rural physicians (p < 0.05). Our findings support the model which proposes that characteristics of the physician, the type of problem presented, and characteristics of the environment influence the likelihood of the GP being the patient's PFC. The findings have implications for GP training programs designed to enable GPs to cope with the wide range of problems encountered in general practice and to provide high quality care at reasonable cost.

Abdominal Pain↗
PubMed1995

The function of Wolinella succinogenes psr genes in electron transport with polysulphide as the terminal electron acceptor.

The membrane-integrated polysulphide reductase (Psr) of Wolinella succinogenes is part of the electron transport chain catalyzing polysulphide reduction by formate or hydrogen. The isolated enzyme catalyzes sulphide oxidation by dimethylnaphthoquinone. The two hydrophilic subunits, PsrA and PsrB of the enzyme, are encoded by genes that form an apparent operon psrABC together with a third gene. Using homologous recombination, three deletion mutants of W. succinogenes were constructed that lack psrC, psrBC or the whole psr operon. The mutants grown with formate and fumarate were fractionated, and the cell fractions were analyzed for the presence of PsrA and enzyme activity. It was concluded that: (a) polysulphide reductase is a constituent of the wild-type chain catalyzing electron transport from formate to polysulphide; (b) the gene psrC encodes a subunit that anchors the enzyme in the membrane and is required for electron transport; (c) PsrA which probably carries the substrate site, is exposed to the bacterial periplasm; (d) PsrA and PsrB are required for the activity of sulphide oxidation with 2,3-dimethyl-1,4-naphthoquinone. Surprisingly, the delta psrABC mutant could grow with formate and polysulphide. The membrane fraction of the mutant grown under these conditions contained an enzyme that replaced polysulphide reductase in electron transport, and catalyzed sulphide oxidation with 2,3-dimethyl-1,4-naphthoquinone.

Electron Transport↗
PubMed1995

In vivo characterization of the unorthodox BvgS two-component sensor protein of Bordetella pertussis.

Two-component sensor proteins are typically composed of an amino-acid sensory and a carboxy-terminal transmitter domain containing a kinase activity which catalyses the autophosphorylation of a histidine residue. In a second step, the phosphate is transferred to aspartic acid residues located in the receiver domain of the second component, the response regulator. A few sensor proteins such as the BvgS protein of Bordetella pertussis have a more complex structure. BvgS possesses additional C-terminal domains, including receiver and output modules usually found only in the response regulators. The function of these BvgS domains was investigated by mutation and complementation analysis in vivo. BvgS derivatives were constructed lacking the C-terminal domains or containing mutations in conserved amino acids. All mutations caused the inactivation of BvgS as measured by the expression of virulence factors at the transcriptional and translational level after integration of the mutated alleles in the B. pertussis chromosome. However, some of these mutants could be complemented to the wild-type phenotype by the separate expression of various C-terminal BvgS domains in trans indicating a direct interaction of the truncated and complete BvgS proteins. Therefore, the dimerization capacity of the cytoplasmic BvgS domains was analysed using a lambda repressor based dimerization probe system. These results indicated that BvgS has two dimerization regions, one in the transmitter and a second in the C-terminal receiver/output domains. Furthermore, several BvgS hybrid proteins were constructed which contained substitutions of the BvgS receiver and output domains with similar domains of two-component response regulators and of the sensor protein EvgS. It was found that the receiver domain does not carry BvgS-specific functions and can be exchanged by a heterologous receiver domain. However, the BvgS output domain could not be substituted with output domains of the related proteins without inactivation of BvgS.

Amino Acid Sequence↗
PubMed1995

Global regulatory mechanisms affect virulence gene expression in Bordetella pertussis.

The influence was investigated of DNA gyrase-inhibiting drugs on the expression of various genes of Bordetella pertussis. We show that the promoters of the virulence regulatory bvg locus and of several bvg-regulated virulence factors, such as the fha, ptx, cya, fim2 and vrg6 loci are very sensitive to the action of novobiocin and coumermycin A, as reflected by transcriptional differences in gene expression. Inhibition of DNA gyrase by the drugs led to a strong decrease in transcription of these genes. Interestingly, one gene belonging to the bvg virulence regulon behaved differently: the promoter of the prn locus, coding for the outer membrane protein pertactin, involved in bacterial adhesion to eukaryotic cells, was induced after inhibition of DNA gyrase. The expression of other genes not belonging to the bvg regulon, such as those encoding porin (POR) and superoxide dismutase (SodB), were not, or only weakly, affected by the drugs. This demonstrates that with respect to drug-induced changes in DNA supercoiling there exist different types of promoters in B. pertussis. In an attempt to identify additional regulatory mechanisms that may modulate virulence gene expression, we investigated the effect of various environmental stimuli on the stability of the bvg-regulated vrg6 and the bvg-independent sodB transcripts. We found that some signals transduced via by the BvgS sensor protein, such as variations in the growth temperature or the presence of nicotinic acid, exerted a strong effect on the half life of these transcripts, whereas another modulating agent, MgSO4, did not have any influence.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminocoumarins↗
PubMed1995

Evidence for two different imidazoline sites on pancreatic B cells and vascular bed in rat.

The relative potencies of imidazoline compounds to induce insulin secretion and vascular resistance were compared in the isolated perfused rat pancreas. On insulin secretion, only the two imidazolines, antazoline and efaroxan, induced a concentration-dependent response, antazoline being 10 times more potent than efaroxan. In contrast, idazoxan, a blocker of imidazoline I1 sites, at concentrations up to 30 microM, antagonized the insulin response to 10 microM efaroxan (IC50 approximately equal to 14 +/- 2 microM) without affecting that to 3 microM tolbutamide. On pancreatic vessels, not only antazoline and efaroxan but also idazoxan induced a concentration-dependent vasoconstriction; the rank order of agonist potency was antazoline > efaroxan > idazoxan. In addition, cimetidine, an imidazole known to bind imidazoline I1 sites, ineffective per se, partially reversed the insulin stimulatory effect of efaroxan without affecting its vasoconstrictor effect. This study demonstrates that the insulin secretory and vasoconstrictor actions of imidazolines involve different imidazoline sites in rat pancreas. The results provide evidence for an I1 type mediating insulin secretion on B cells and an I2 type mediating vasoconstriction in vessels.

Adrenergic alpha-Antagonists↗
PubMed1995

Effect of n-hexacosanol on insulin secretion in the rat.

n-Hexacosanol, a long-chain saturated fatty alcohol extracted from Hygrophyla erecta Hochr., has been recently shown to exert neurotrophic properties on central neurons and to stimulate phagocytosis in macrophages. The present work was designed to investigate the effects of hexacosanol on stimulated insulin secretion in vivo and in vitro. In anaesthetized rats, hexacosanol (2 mg/kg i.p.) induced a reduction of the insulin response to an intravenous glucose tolerance test (0.3 g/kg) with a consequent increase in hyperglycaemia. In vitro, in the isolated perfused pancreas, hexacosanol at the concentration of 10(-7) M clearly reduced the two phases of glucose-induced insulin secretion. At the higher concentration (10(-5) M), hexacosanol was no longer able to exert an inhibition of glucose-induced insulin release; surprisingly a stimulating effect occurred which was of the same magnitude as in control experiments with Tween alone, at the concentration used to dissolve hexacosanol. In isolated perifused islets, 22 mM glucose-stimulated insulin release was also inhibited by hexacosanol at the concentrations of 10(-9) M and 10(-7) M, but not at 10(-5) M. In contrast, insulin secretion induced by arginine (20 mM) was not affected by the different concentrations of hexacosanol. It is concluded that n-hexacosanol at 10(-9) M and 10(-7) M exerts an inhibitory effect on insulin secretion stimulated by glucose in vivo and in vitro in the rat, suggesting a direct effect on islets of Langerhans.

Analysis of Variance↗
PubMed1995

Identification of mycobacteria to the species level by automated restriction enzyme fragment length polymorphism analysis.

An automated method for the restriction fragment length polymorphism (RFLP) analysis for the differentiation of mycobacteria to the species level is described. After polymerase chain reaction (PCR) amplification of a sequence of the gene encoding the 65-kDa surface antigen common to all mycobacteria the product was investigated by RFLP analysis. For accurate determination of fragment sizes the asymmetrically fluorescein-labelled PCR product was partially digested with restriction site enzymes BstEII and HaeIII. The fragments obtained were analysed electrophoretically using an automated laser fluorescence DNA sequencer. Determination of fragment sizes revealed a deviation of +/- 1 base pair (bp; 0.6%) when compared to expected sizes. The validity of this approach was confirmed by analysing mycobacterial DNA obtained from pure cultures of Mycobacterium (M.) tuberculosis and alcohol-fixed smears as well as paraffin-embedded sputa of patients with culture-proven tuberculosis. Additionally a diagnostic algorithm was established by investigation of cultured M. bovis, M. bovis bacille Calmette-Guérin, M. avium, M. intracellulare and M. fortuitum. The method allows the identification of restriction enzyme sites which are only 40 bp apart. Partial restriction enzyme digestion of asymmetrically fluorescence-labelled PCR products will presumably lead to the discovery of new restriction enzyme sites.

Algorithms↗
PubMed1995

Advances in protein-based three-dimensional optical memories.

An oriented bacteriorhodopsin cube is optimized as a potential three-dimensional optical memory medium. Write/read capability is demonstrated by using the photovoltaic signal induced by two-photon absorption. Our results demonstrate that a two-photon induced photovoltage can he detected in a three-dimensional Bacteriorhodopsin (BR) cube as large as 1.6 x 1.6 x 1.6 cm3. The read/write speed, signal to noise ratio, and the laser damage threshold for the protein-based three-dimensional optical memory is examined.

Bacteriorhodopsins↗
PubMed1995

Intraocular pressure elevation associated with inhalation and nasal corticosteroids.

BACKGROUND: The ocular hypertensive response to corticosteroids is well established. Elevated intraocular pressure (IOP) secondary to corticosteroids by nasal spray or inhalation has rarely been reported. RESULTS: Three patients showed a possible ocular hypertensive response to beclomethasone dipropionate by nasal spray or inhalation. In two patients, the IOP returned to pretreatment levels after discontinuing nasal corticosteroid spray. One patient required medication to control IOP with continued inhaled corticosteroid. One patient later demonstrated an ocular hypertensive response to oral steroids. CONCLUSION: Corticosteroids by nasal spray or inhalation may cause ocular hypertension in susceptible patients. The authors recommend surveillance of IOP in patients using these medications.

Administration, Inhalation↗
PubMed1995

Application of heteroduplex analysis for detecting variation within the growth hormone 2 gene in Salmo trutta L. (brown trout).

A new method to detect variation at a single copy nuclear gene in brown trout, Salmo trutta L., is provided. The technique entails (i) selective gene amplification by the polymerase chain reaction (PCR), (ii) digestion of amplification products by restriction endonucleases to obtain fragments of suitable size, (iii) hybridization with heterologous DNA followed by denaturation and reannealing to obtain heteroduplex molecules, and (iv) screening for variation in polyacrylamide gels. Variation was studied within a growth hormone 2 gene 1489 bp segment and polymorphism was detected in two HinfI-digested fragments. Formation of different heteroduplex patterns in experimental mixtures of digested amplification products from brown trout and Atlantic salmon, Salmo salar L., allowed us to determine the genotype of the brown trout. Polymorphism was observed in four out of six studied populations.

Animals↗
PubMed1995

Effect of daily vs twice weekly iron supplementation in Indonesian preschool children with low iron status.

The effect of daily vs twice weekly iron supplementation on iron status was studied in preschool children with low iron status in a randomized double-masked field trial. Subjects (n = 87) were selected on the basis of their hemoglobin concentration being < 111 g/L in finger-prick blood, and were divided into two groups. For 8 wk one group received a daily supplement of 30 mg Fe, while the other group received 30 mg Fe twice per week. A complete data set was obtained from 32 children in the group supplemented daily and from 33 children in the group supplemented twice weekly. Hemoglobin, serum ferritin, and protoporphyrin increased significantly in both groups (P < 0.001). Changes in hemoglobin and protoporphyrin were correlated with initial hemoglobin concentration (P < 0.001). The difference in treatment effect between groups was not significant after correction for the initial hemoglobin concentration. It is concluded that in preschool children with low iron status, twice weekly iron supplementation has an effect on iron status similar to that of daily supplementation.

Anemia, Iron-Deficiency↗