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Biomedical subjects

R Gross

Publications and source records attributed to R Gross.

At least 217 records · Page 12Linked to original sources
PubMed1994

The virulence regulator protein of Listeria ivanovii is highly homologous to PrfA from Listeria monocytogenes and both belong to the Crp-Fnr family of transcription regulators.

The two pathogenic Listeria species, L. ivanovii and L. monocytogenes, can be differentiated biochemically and show different host ranges. Virulence of L. monocytogenes is dependent on the integrity of prfA which positively and co-ordinately regulates transcription of several virulence genes. Until now, a prfA homologue had not been identified in L. ivanovii. We have now cloned a chromosomal region from L. ivanovii comprising two genes with high homology to the plcA and prfA genes from L. monocytogenes. Distal from prfA, an open reading frame highly homologous to a phosphoribosyl pyrophosphate synthetase gene (prs) was newly identified, defining the border of the virulence gene cluster. Transcription of the gene for ivanolysin O and expression of other genes of the virulence gene cluster in L. ivanovii were dependent on PrfA. The pattern of PrfA-dependent proteins (PdPs) expressed in L. ivanovii was similar, but not identical to that of L. monocytogenes. The PrfA proteins, as predicted from nucleotide sequences of both pathogenic Listeria species, are very similar and show significant homology to the Crp-Fnr family of global transcription regulators.

Amino Acid Sequence↗
PubMed1994

Epithelial cell invasion and survival of Bordetella bronchiseptica.

Wild-type Bordetella bronchiseptica and a bvg mutant strain were used for invasion and survival experiments in human Caco-2 and A549 epithelial cells. Both bacterial strains were able to enter and persist within the host cells for at least a week. A significant proportion of the bacteria from both B. bronchiseptica strains but not from Bordetella pertussis were found free in the cytoplasm, suggesting different invasion and survival strategies of the two species in epithelial cells.

Bordetella bronchiseptica↗
PubMed1994

Effect of mutations causing overexpression of RNA polymerase alpha subunit on regulation of virulence factors in Bordetella pertussis.

In Bordetella pertussis, expression of virulence factors is controlled by the Bvg proteins, which comprise a sensor-regulator two-component signal transduction system. Previously, we described a mutant strain of B. pertussis that had reduced transcription of pertussis toxin and adenylate cyclase toxin genes, while other virulence factors were relatively unaffected. We obtained a B. pertussis clone that repaired the defect in both this strain and an independent mutant strain with a similar phenotype when introduced onto the chromosome by allelic exchange. Further analysis revealed that the mutations were just upstream of the translational start site of the rpoA gene encoding the alpha subunit of RNA polymerase. We confirmed that these mutations were responsible for the mutant phenotype by site-directed mutagenesis. Our hypothesis that these mutations cause an overexpression of rpoA was confirmed by Western immunoblotting and translational fusion analysis. Corroboration of this effect was obtained by overexpressing rpoA on a plasmid in wild-type B. pertussis, which caused the same phenotype as the mutants showed. Conclusions in regard to the identity of the transcription activator of the toxin genes are discussed.

Adenylate Cyclase Toxin↗
PubMed1994

Synthesis and secretion of bacterial antigens by attenuated Salmonella via the Escherichia coli hemolysin secretion system.

We describe a plasmid system which allows the secretion of foreign antigens in attenuated Salmonella aroA strains by the secretion apparatus of E. coli hemolysin. The gene (or gene fragment) encoding the antigen is inserted in frame into a residual position of the hlyA gene, encoding the HlyA secretion signal (HlyAs). Generally, the fused gene is efficiently expressed and the synthesized antigen is in part secreted into the culture supernatant and in part exposed on the surface of the producing Salmonella strain. The successful use of this approach is demonstrated with two antigens of Salmonella typhimurium, PagC and SlyA, both of which are potent virulence factors but produced only in small amounts under in vitro culture conditions and two virulence proteins of Listeria monocytogenes, p60 and listeriolysin. Interestingly the listeriolysin fusion protein proved to be cytolytically active and allowed, when expressed in Salmonella, the escape of these bacteria into the cytoplasm of infected macrophages.

Antigens, Bacterial↗
PubMed1994

In vivo and in vitro effects of adenosine-5'-O-(2-thiodiphosphate) on pancreatic hormones in dogs.

Adenosine-5'-O-(2-thiodiphosphate) (ADP beta S), a P2y purinergic agonist, has been shown to be a potent insulin secretagogue on the isolated rat pancreas. In the present work the effects of ADP beta S on insulin somatostatin, and glucagon secretions were investigated in dogs. In vivo, in anesthetized fasted dogs, i.v. ADP beta S (0.1 mg kg-1) induced an immediate increase in insulin and somatostatin-like immunoreactivity (SLI) but not in glucagon pancreaticoduodenal outputs. In conscious fasted dogs, i.v. ADP beta S (0.1 mg kg-1) produced an immediate and transient augmentation in plasma insulin levels but not in plasma SLI and glucagon levels. In vitro, the effects of ADP beta S were investigated on the isolated uncinate process of dog pancreas, from normal and alloxan-diabetic animals. In normal uncinate process, in presence of 8.3 mM glucose, ADP beta S (1 microM) stimulated insulin and SLI releases but not glucagon release. On uncinate process from diabetic animals, ADP beta S (1 microM) retained its stimulating effects but the responses were impaired as compared with normal dogs: Insulin response was drastically diminished and SLI response strongly enhanced. In conclusion, ADP beta S is a potent insulin secretory agent in dog. This P2y purinoceptor agonist, which exerts a direct stimulatory effect on pancreatic SLI, is interestingly devoid of direct glucagonotropic properties.

Adenosine Diphosphate↗
PubMed1994

New England College of Optometry's impact on Boston neighborhoods.

BACKGROUND: In the 1960s, the city of Boston developed and implemented an innovative plan creating an urban primary health care system. This bold undertaking was predicated on the maximal utilization of a growing network of multidisciplinary neighborhood health centers. Almost concurrently, the New England College of Optometry (NEWENCO) began a total restructuring of its clinical curriculum. The objectives of this NEWENCO initiative were compatible with those of the city's health care restructuring plan. METHODS: The background, planning, structure, implementation and benefits of this collaborative effort are addressed. RESULTS: The two formed a unique partnership that elevated the quality of care for the residents of Boston's neighborhoods and dramatically improved the training experience for NEWENCO students. CONCLUSIONS: The NEWENCO-City of Boston partnership has improved the quality of health care in the urban neighborhoods and enhanced the clinical training of optometric externs.

Boston↗
PubMed1993

Glutamate stimulates glucagon secretion via an excitatory amino acid receptor of the AMPA subtype in rat pancreas.

The effect of L-glutamate was studied on glucagon secretion from rat isolated pancreas perfused with 2.8 mM glucose. L-Glutamate (3.10(-5)-10(-4)M) induced an immediate, transient and concentration-dependent glucagon release. The three non-N-methyl-D-aspartate (NMDA) receptor agonists, kainate (3.10(-5)-3.10(-3)M), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) (3.10(-5)-10(-4)M) and quisqualate (3.10(-6)-10(-5)M), all elicited a peak-shaped glucagon response. Compared to glutamate, AMPA and quisqualate exhibited a similar efficacy, whereas kainate caused a 4-fold higher maximal glucagon response. In contrast, NMDA (10(-3)M) was ineffective. The selective antagonist of non-NMDA receptors, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 5.10(-5)M), totally prevented the glucagon response to 10(-4) M glutamate (IC50 congruent to 0.8 +/- 0.3 10(-6)M) and 3.10(-4)M kainate. Furthermore, quisqualate at a maximal effective concentration (3.10(-4)M) inhibited the response to kainate (10(-3)M). This study showed that L-glutamate stimulates glucagon release in rat pancreas by activating a receptor of the AMPA subtype.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1993

Different mechanisms are involved in neuropeptide Y-induced pancreatic vasoconstriction and inhibition of insulin secretion.

We have studied the mechanisms whereby neuropeptide Y (NPY) inhibits insulin secretion and induces vasoconstriction in the isolated perfused rat pancreas. Neither prazosin (alpha 1-adrenoceptor antagonist; 6 microM) nor yohimbine (alpha 2-adrenoceptor antagonist; 0.6 microM) affected the effects of neuropeptide Y (1 nM). Also the Ca2+ channel antagonist, verapamil (5 microM), which itself decreased insulin output by 55%, could not affect the neuropeptide Y-induced inhibition of insulin secretion. However, verapamil impaired the neuropeptide Y-induced decrease in pancreatic outflow rate. Finally, neuropeptide Y (1 and 10 nM) suppressed the insulin secretion induced by dibutyryl cAMP (100 microM) and the cyclic nucleotide suppressed the neuropeptide Y-induced vasoconstriction. We conclude that the secretory and vascular effects of neuropeptide Y are mediated by different processes in the perfused rat pancreas: inhibition of insulin secretion seems mediated by a mechanism distal to and/or different from cAMP generation, whereas vasoconstriction seems to involve uptake of extracellular Ca2+ and to be sensitive to dibutyryl cAMP. Both effects occur independently of adrenoceptor receptors.

Adrenergic alpha-Antagonists↗
PubMed1993

Differential regulation of Bordetella pertussis virulence factors.

Bordetella pertussis, the causative agent of whooping cough, regulates its virulence factors coordinately according to environmental parameters such as temperature and certain chemicals. A regulatory locus has been characterized which is essential for this regulation. This bvg locus codes for a two-component regulatory system composed of the sensor protein BvgS and the transcriptional activator protein BvgA. It has been shown that the BvgA and BvgS proteins are sufficient for the transcriptional regulation of some virulence factors such as the filamentous haemagglutinin (FHA) involved in adhesion. The recent identification of new regulatory mutants demonstrates that the regulation of some virulence factors such as the pertussis toxin (PTX) and the adenylate cyclase toxin (CYA) is more complex and involves additional regulatory factor(s). This finding suggests that the regulation of the various virulence factors is coordinated at the highest level of regulation, but there may be differences in the fine regulation of some of the factors such as the adhesins and the toxins.

Bacterial Proteins↗
PubMed1993

Low compliance with an iron-supplementation program: a study among pregnant women in Jakarta, Indonesia.

The efficiency of an established iron-supplementation program for pregnant women in Jakarta, Indonesia was investigated. Hemoglobin, serum ferritin, and packed cell volume (PCV) were measured at the start of the study and after 2 mo supplementation with 300 mg ferrous sulphate/d. The women (n = 45) were questioned about compliance and stool samples were checked for iron content to control for tablet intake. Twelve women dropped out. Prevalence of anemia (42%) did not decrease during the study period. Of the remaining 33 women, 64% (n = 21) claimed to have taken all iron tablets. This was only confirmed by positive stool tests in 12 women. Serum ferritin and PCV increased in women with positive stool tests (P < 0.05 and P < 0.01, respectively) after supplementation. It is concluded that compliance was low and that the iron dose needs to be increased. Supplementation programs need reliable monitoring and evaluation systems.

Adult↗
PubMed1993

Decreased rate of stunting among anemic Indonesian preschool children through iron supplementation.

Effects of iron supplementation on growth and hematological status of Indonesian anemic preschool children with low weight-for-age were investigated. A treatment group (n = 39) received daily supplements of 30 mg Fe and 20 mg vitamin C, whereas a control group (n = 37) received 20 mg vitamin C only for a period of 2 mo. Supplement allocation was double blind. At the start and finish of the study, body weight, height, food intake, and hemoglobin and serum ferritin concentrations were determined. Only the treatment group showed a significant increase in all hematological values (P < 0.001). Height and weight of all children increased (P < 0.01). Increases in height and height-for-age Z score in the treatment group were larger (P = 0.001) than the increase in the control group. The positive effect of iron supplementation on linear growth was not caused by increased food intake, but seems to be influenced by decreased morbidity. Iron supplementation may be a relatively inexpensive way to help decrease the high prevalence of stunting.

Aging↗
PubMed1993

A special-purpose processor for gene sequence analysis.

Advances in computational biology have occurred primarily in the areas of software and algorithm development; new designs of hardware to support biological computing are extremely scarce. This is due, we believe, to the presence of a non-trivial knowledge gap between molecular biologists and computer designers. The existence of this gap is unfortunate, as it has long been known that for certain problems, special-purpose computers can achieve significant cost/performance gains over general-purpose machines. We describe one such computer here: a custom accelerator for gene sequence analysis. The accelerator implements a version of the Needleman-Wunsch algorithm for nucleotide sequence alignment. Sequence lengths are constrained only by available memory; the product of sequence lengths in the current implementation can be up to 2(22). The machine is implemented as two NuBus boards connected to a Mac IIf/x, using a mixture of TTL and FPGA technology clocked at 10 MHz. The boards are completely functional, and yield a 15-fold performance improvement over an unassisted host.

Algorithms↗