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Biomedical subjects

L Post

Publications and source records attributed to L Post.

At least 19 recordsLinked to original sources
PubMed1997

Effect of transforming growth factor alpha and interleukin 8 on somatostatin release from canine fundic D cells.

BACKGROUND & AIMS: Helicobacter pylori infection in patients who have peptic ulcer disease is associated with altered regulation of gastric secretion, hypergastrinemia, and diminished somatostatin expression in gastric mucosa. Tumor necrosis factor (TNF)-alpha and interleukin (IL)-8 are the predominant cytokines produced in the gastric mucosa of patients with H. pylori infection. The aim of this study was to examine whether IL-8 and TNF-alpha could regulate somatostatin release from isolated canine gastric D cells. METHODS: Canine gastric D cells were isolated from fundic mucosa and enriched by centrifugal elutriation. Secretagogue-stimulated somatostatin release was measured by radioimmunoassay. RESULTS: TNF-alpha dose dependently increased somatostatin release after 2 hours of treatment. The stimulatory effect of TNF-alpha was additive to that of epinephrine but was unaffected by a maximal concentration of cholecystokinin. IL-8 did not alter basal or secretagogue (cholecystokinin, epinephrine)-mediated somatostatin release. The stimulatory effect of TNF-alpha (10 ng/mL) was potentiated by the addition of IL-8 (1 nmol/L), inhibited by octreotide and staurosporine, but unaffected by indomethacin. Pretreatment of D cells with TNF-alpha (10 ng/mL) for 24 hours abolished the subsequent stimulatory effect of this cytokine and secretagogues on somatostatin release. CONCLUSIONS: TNF-alpha was shown to regulate somatostatin release from cultured D cells in a divergent manner.

Animals↗
PubMed1997

Effect of Helicobacter pylori products and recombinant cytokines on gastrin release from cultured canine G cells.

BACKGROUND & AIMS: The pathophysiology of hypergastrinemia in Helicobacter pylori infection is undefined, but the infected antrum shows a marked inflammatory response with local production of cytokines. Hypergastrinemia and inflammatory infiltrate clear with successful eradication. The aim of this study was to examine whether the cytokines tumor necrosis factor alpha or interleukin 8 (IL-8), which are produced in the gastric mucosa of patients with H. pylori-induced peptic disease or H. pylori products, can stimulate gastrin release from isolated cultured canine G cells. METHODS: Canine G cells were isolated by collagenase digestion, enriched by centrifugal elutriation, incubated with cytokines, bacterial components, or both, and gastrin release was measured by radioimmunoassay. RESULTS: IL-8 (1 and 10 nmol/L) stimulated gastrin release by 34% +/- 13% and 43% +/- 23% (P < 0.05) above basal, respectively. H. pylori sonicates, water extract preparations, and lipopolysaccharide had no stimulatory actions, but the sonicates from two of four strains potentiated the effects of IL-8, leading to maximal gastrin release of 230% +/- 130% and 232% +/- 33% above basal, respectively (P < 0.05). CONCLUSIONS: IL-8 stimulated gastrin release from isolated G cells, and the effect was potentiated by H. pylori products. The interaction of cytokines and H. pylori may contribute to the hypergastrinemia seen in vivo.

Animals↗
PubMed1996

Intestinal intraepithelial lymphocytes influence the production of somatostatin.

BACKGROUND: We have previously demonstrated that intestinal intraepithelial lymphocytes (iIELs) inhibit lymphocyte proliferation. Because somatostatin also prevents lymphocyte proliferation, we hypothesized that iIELs may influence production of somatostatin. METHODS: Isolates of intestinal epithelium that were obtained from Brown Norway (BN) rats and contained an iIEL-enriched population (defined as CD45+) were incubated with irradiated Lewis splenocytes for allogeneic stimulation. BN rat splenocytes incubated with irradiated Lewis splenocytes served as a control. Supernatants were harvested after 4 days and assayed for somatostatin by using a radioimmunoassay. RESULTS: The somatostatin level in the intestinal epithelium-conditioned supernatant was significantly higher than that of the control group (176 +/- 60 versus 10 +/- 2 fmol/ml; p < 0.05). Removal of the CD45+ cell subset resulted in a fifteenfold reduction in somatostatin levels. The CD45+ cell lysates had significantly higher levels of somatostatin than did CD45+ depleted cells (1304 +/- 531 versus 128 +/- 41 fmol/ml; p < 0.05). CONCLUSIONS: The isolates of intestinal epithelium produced significant amounts of somatostatin. Removal of the CD45+ cells caused a significant loss of somatostatin production. Intracellular levels of somatostatin appeared to be highest in the CD45+ subpopulation. These data suggest that iIELs (that is, CD45+ cells) may have a significant influence on the production of somatostatin and may be a source of somatostatin production. Production of somatostatin by iIELs may help modulate immune responses in gut-associated lymphoid tissue.

Animals↗
PubMed1996

Tumour necrosis factor alpha stimulates gastrin release from canine and human antral G cells: possible mechanism of the Helicobacter pylori-gastrin link.

There is evidence that gastric Helicobacter pylori (Hp) infection promotes duodenal ulceration by releasing gastrin. We therefore asked how Hp releases gastrin. Tumour necrosis factor alpha (TNF-alpha) is up-regulated in Hp gastritis and stimulates hormone release from pituitary cells, so we tested its effect on primary cultures of canine antral G cells and human antral fragments. TNF-alpha pretreatment (100 ng mL-1) of canine G cells significantly increased both basal (by 89%: P < 0.01) and bombesin-stimulated (by 39% P < 0.05) gastrin release. A similar pattern of increase was seen following TNF-alpha (20 ng mL-1) pretreatment of human antral fragments: basal gastrin release was increased by 38% (P < 0.05) and bombesin-stimulated by 26% (P < 0.05). This effect persisted during immunoblockade with anti-somatostatin antibody S6. We propose that TNF-alpha provides the link between Hp infection and gastrin release and thus contributes to duodenal ulceration.

Animals↗
PubMed1994

Risperidone.

Explore the source record for details and available documents.

Adolescent↗
PubMed1988

Analysis of flow and vascular resistance in a model of the circle of Willis.

A very simple model of the flow in the circle of Willis is described in this paper. Disregarding pulsatility and vessel wall elasticity, fluxes in all segments of the circle of Willis and its afferent and efferent vessels are calculated by applying the Poiseuille-Hagen formula. Comparison with the fluxes calculated numerically from a more sophisticated mathematical model, including pulsatility, vessel wall elasticity and nonlinear effects, revealed only very slight differences. In short, fluxes in the afferent vessels and the segments of the circle of Willis are influenced by any change of resistance within the network, whereas the fluxes in the efferent segments are dominated by the efferent resistance distribution. However, a great advantage of the present simple model is that it offers the possibility of an analytical approach which yields both an easy sensitivity analysis of parameters and an insight into the mechanisms that govern the flow in a network like the circle of Willis. It can be concluded that these mechanisms are similar to the principles of the Wheatstone bridge, known from electrical circuit theory.

Circle of Willis↗
PubMed1986

An instrument to measure coping responses in employed mothers: preliminary results.

The purpose of this study was to develop a survey instrument to measure coping responses in working mothers. Coping responses were defined as efforts to prevent, avoid, or control emotional distress. Based on interviews, literature review, and a survey of existing instruments, items were developed to measure these three functions of coping behaviors. The instrument was distributed to 133 married mothers who worked at least 15 hours per week outside the home; response rate was 93%. Nine subscales to measure coping responses in working mothers were identified. Alpha reliability coefficients for the subscales range from .65-.90. Construct validity of the subscales was investigated by examining specified relationships between subscale scores and role strain measures. All but one of the subscales were significantly correlated in the predicted direction with at least one of the role strain measures. The final instrument, the Coping Responses Inventory (CRI), is comprised of 59 Likert format items from which nine subscale scores can be calculated. Some aspects of the reliability and validity of this instrument have been investigated, but confirmation of the findings await further study. Potential uses of the CRI are as an instrument in survey research and as an exploratory tool in counseling interventions with employed women with children.

Adaptation, Psychological↗
PubMed1986

A mathematical model of the flow in the circle of Willis.

A mathematical model of the flow in the circle of Willis has been designed and the effects of (a) the large anatomical variation of the communicating arteries and (b) physiological changes of the resistances of the vertebral arteries have been studied. The influence of the posterior perforating arteries on the flow in the posterior communicating arteries has been investigated as well, with special attention being paid to the possible occurrence of a 'dead point'. In the model, the influence of diameters of the communicating arteries on the flow in the afferent vessels and the segments of the circle turns out to be considerable, especially in the range of the anatomical variation of the diameters. Within this range flow reductions due to an increased resistance of the vertebral artery will be compensated for by the system. Assuming that the values and ratios of the peripheral resistances are within the physiological range, a dead point is not to be expected in the flow in the posterior communicating arteries.

Cerebrovascular Circulation↗
PubMed1986

The Lundia Pro 5 dialyzer, a polycarbonate membrane dialyzer.

Results of acute and long-term test runs of the Lundia Pro 5 dialyzer are presented. It is concluded that it has worked as an effective and safe dialyzer during the test period. Thoughts on future dialyzer tests are put forward for consideration.

Blood Pressure↗
PubMed1985

Nucleotide sequence of the alpha ribosomal protein operon of Escherichia coli.

In Escherichia coli some 19 transcription units encoding the 52 ribosomal proteins are scattered throughout the genome. One of the units, the alpha operon, encodes genes for the ribosomal proteins S13, S11, S4 and L17 as well as the alpha subunit of RNA polymerase. We report here the complete 3.0 kb nucleotide sequence of the alpha operon. In addition, we have determined by S1 nuclease mapping the site of transcription termination in this operon.

Amino Acid Sequence↗
PubMed1984

Requirement for the 3' flanking region of the bovine growth hormone gene for accurate polyadenylylation.

We examined whether the sequence extending 3' to the polyadenylylation site of the bovine growth hormone gene contains any signal that affects the polyadenylylation of the growth hormone mRNA. For this purpose, cloned copies of this gene, each containing a different length of growth hormone-specific sequence 3' to the wild-type polyadenylylation site, were used to transfect COS-1 cells. The polyadenylylation site on the mRNAs produced from the exogenously added growth hormone genes were analyzed with an S1 nuclease mapping procedure. We found that a gene containing 84 base pairs of its own 3' flanking sequence is capable of producing an accurately polyadenylylated mRNA. On the other hand, genes containing only 1, 10, or 13 base pairs of 3' flanking sequence were principally polyadenylylated at discrete sites either upstream or downstream from the wild-type position. Using a computer program, we examined whether secondary structures on the primary growth hormone transcript correlated with the site where the mRNA is polyadenylylated.

Animals↗
PubMed1977

Characterization of hybrid plasmids carrying individual ribosomal ribonucleic acid transcription units of Escherichia coli.

We have screened the strains with ColE1 hybrid plasmids constructed by Clarke and Carbon (Cell 9:91-99, 1976) for the presence of ribosomal ribonucleic acid (rRNA) genes on the plasmids and identified 16 strains whose plasmids carry rRNA genes. The structures of these 16 plasmids were compared by heteroduplex analysis, and the plasmids were classified into six groups on the basis of their chromosomal origins. Homology with known transducing-phage deoxyribonucleic acids and genetic mapping have assigned locations on the Escherichia coli chromosome to three of the six groups. These are rrnB near rif at 88 min, rrnC near ilvE at 83 min, and rrnD near aroE at 71 min. A fourth group is probably rrnA at 85 min (T. Ikemura and M. Nomura, Cell, 11:779-793, 1977). We conclude that the minimum number of rRNA transcription units per haploid chromosomes is seven, that is, the six groups identified in this work plus a known operon (rrnE near metA at 89 min) that we failed to find among the hybrid plasmids. This heteroduplex analysis also suggests that there are only two kinds of rRNA operons with respect to their spacer region; three of the six rRNA operon groups studied here have one kind, whereas the remaining three have the other kind.

Bacterial Proteins↗
PubMed1977

Neonatal ophthalmoplegia with microfibers: a reversible myopathy?

An infant born with marked hypotonia showed prompt regression of skeletal muscle weakness, but by 7 weeks of age had total external ophthalmoplegia. Biopsy of the gluteus muscle at 14 days showed marked variation in fiber size with a large proportion of very small fibers (less than 3 mu). By 10 months of age, biopsy of the vastus was virtually normal. The inferior oblique muscle was replaced by fibrous tissue containing a few remaining degenerating fibers. The child was normal at 2 years of age except for mild facial weakness and ophthalmoplegia. This syndrome may be the result of a reversible intrauterine process.

Child, Preschool↗
PubMed1976

DNA-dependent in vitro synthesis of fibosomal proteins, protein elongation factors, and RNA polymerase subunit alpha: inhibition by ppGpp.

We have previously shown that the synthesis of ribosomal proteins (r proteins) in E. coli cells is under stringent control (Dennis and Nomura, 1974). Since guanosine tetraphosphate (ppGpp) has been implicated in stringent control, we examined the effects of ppGpp on the in vitro synthesis of r proteins directed by DNA from transducing phage lambdafus3 and lambdarifd18. lambdafus3 carries genes for protein elongation factors EF-Tu and EF-G, and RNA polymerase subunit alpha, in addition to genes for approximately 27 r proteins. lambdarifd18 carries genes for EF-Tu, RNA polymerase subunits beta and beta1, and a set of rRNAs, in addition to genes for approximately five r proteins. We have shown that low concentrations of ppGpp (0.2-0.3 mM) specifically inhibit DNA-dependent r protein synthesis in this system, and that this inhibition takes place directly, rather than as a consequence of the inhibition of rRNA synthesis by ppGpp. In addition, we have also shown that ppGpp inhibits the synthesis of EF-G, EF-Tu, and RNA polymerase subunit alpha, as well as rRNAs.

Colicins↗