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Biomedical subjects

M M Wolfe

Publications and source records attributed to M M Wolfe.

At least 19 recordsLinked to original sources
PubMed1995

Liquid-phase combinatorial synthesis.

A concept termed liquid-phase combinatorial synthesis (LPCS) is described. The central feature of this methodology is that it combines the advantages that classic organic synthesis in solution offers with those that solid-phase synthesis can provide, through the application of a linear homogeneous polymer. To validate this concept two libraries were prepared, one of peptide and the second of nonpeptide origin. The peptide-based library was synthesized by a recursive deconvolution strategy [Erb, E., Janda, K. D. & Brenner, S. (1994) Proc. Natl. Acad. Sci. USA 91, 11422-11426] and several ligands were found within this library to bind a monoclonal antibody elicited against beta-endorphin. The non-peptide molecules synthesized were arylsulfonamides, a class of compounds of known clinical bactericidal efficacy. The results indicate that the reaction scope of LPCS should be general, and its value to multiple, high-throughput screening assays could be of particular merit, since multimilligram quantities of each library member can readily be attained.

Amino Acid Sequence↗
PubMed1995

Effects of hypochlorhydria and hypergastrinemia on structure and function of gastrointestinal cells. A review and analysis.

Since hypochlorhydria can induce hypergastrinemia, and gastrin has a trophic effect on some gastrointestinal cells, states that cause elevated plasma gastrin levels are of interest in terms of effects on cell growth and function. This article reviews the relationship between gastric mucosal cells during periods of acid stimulation and inhibition and analyses the effects of hypochlorhydria and hypergastrinemia on gastric and colonic cells and tumors. Hypochlorhydria releases the inhibitory effect of antral gastrin cells, inducing them to release gastrin in the presence of peptides or amino acids in the gastric lumen or in response to antral distension. Gastrin stimulates the oxyntic mucosa, which may lead to hyperplasia of enterochromaffin-like cells, resulting in enterochromaffin-like carcinoid tumors in aged rats and, rarely, in patients with chronic atrophic gastritis or gastrinomas. In addition to hypergastrinemia, other factors appear to be required for the progression of enterochromaffin-like hyperplasia to carcinoids; genetic factors may be involved. Gastrin elevations due to antisecretory drug therapy are indirectly proportional to the degree of acid inhibition and are reversible upon cessation of therapy. The gastrin levels during omeprazole therapy are similar to those caused by gastric vagotomy. Available evidence does not support a relationship between hypergastrinemia and the occurrence or growth of gastric carcinoma or colonic tumors.

Achlorhydria↗
PubMed1995

Role of luminal ammonia in the development of gastropathy and hypergastrinemia in the rat.

BACKGROUND/AIMS: Chronic infection with Helicobacter pylori causes persistent elevations in gastric juice ammonia levels. Thus, we studied the effects of experimentally induced increases in gastric juice ammonia levels on gastric structure and function and gastrin homeostasis. METHODS: Rats were fed either normal chow or the diet supplemented (20 g/dL) with ammonium or sodium acetate. RESULTS: Long-term dietary ammonium loading for 2 weeks or longer resulted in a 1.5-2-fold increase in the weight and mucosal thickness of the stomach and proximal duodenum with evidence of mild gastritis and enterochromaffinlike cell hyperplasia. The ammonium-containing diet also induced a significant 2-3-fold increase in both circulating gastrin levels of fed rats and an increase in the postprandial gastrin responses over control values. Antral gastrin levels were also markedly elevated by long-term ingestion of the test diet, which was increased 3-4-fold over control values in fasted animals and less so after meal stimulation. Consistent with these findings, gastrin-specific messenger RNA was increased 2.5-3-fold in the antrum of ammonium fed rats, whereas actin-specific messenger RNA was not affected or decreased. Animals fed a diet supplemented with 20 g/dL sodium acetate sustained modest increases in mucosal thickness and serum and antral gastrin concentration, suggesting that nonspecific gastric injury and inflammation is also a factor that influences G-cell function. CONCLUSIONS: Long-term exposure of the antral mucosa to elevated levels of ammonia in the gastric juice in the presence of gastritis, conditions similar to that occurring in subjects infected with H. pylori, seem to be causative factors in the development of G-cell hyperfunction.

Acetates↗
PubMed1995

Measurement of anterior and posterior circulation flow contributions to cerebral blood flow. An ultrasound-derived volumetric flow analysis.

Ultrasound-derived volumetric flow analysis may be useful in answering questions of basic physiological interest in the cerebrovascular circulation. Using this technique, the authors have sought to describe quantitatively the complete concurrent flow relations among all four arteries supplying the brain. The aim of this study of normal subjects was to determine the relative flow contributions of the anterior (internal carotid arteries) and posterior (vertebral arteries) cerebral circulation. Comparisons between the observed and theoretically expected anterior and posterior flow distribution would provide an opportunity to assess traditional rheological conceptions in vivo. Pulsed color Doppler ultrasonography was used to measure mean flow rates in the internal carotid and vertebral arteries in 21 normal adults. The anterior circulation (internal carotid arteries bilaterally) carried 82% of the brain's blood supply and comprised 67% of the total vascular cross-sectional area. These values demonstrate precise concordance between observations in vivo and the theoretically derived (Hagen-Poiseuille) expected flow distribution. These cerebrovascular findings support the traditional conception of macroscopic blood flow. Further studies using ultrasound-derived volumetric analysis of the brain's arterial flow relations may illuminate the vascular pathophysiology underlying aging, cerebral ischemia, and dementias.

Adult↗
PubMed1994

Regulation of glucose-dependent insulinotropic peptide gene expression by a glucose meal.

Glucose-dependent insulinotropic peptide (GIP) enhances insulin secretion by pancreatic beta-islet cells. Its release has been demonstrated predominantly after the ingestion of carbohydrate and fat. We have recently cloned a rat intestinal GIP cDNA and in the present studies have used this cDNA as a probe for measuring rat duodenal GIP mRNA after nutrient administration. Rats were fasted overnight, after which they were permitted to drink water or 10% glucose. The duodenum was then removed, GIP mRNA was measured by Northern hybridization analysis, and duodenal mucosa and serum GIP levels were determined by radioimmunoassay. In response to oral 10% glucose, duodenal mucosal GIP mRNA concentrations increased from 2 to 4 h, and at the end of 4 h a threefold increase was detected. Serum and mucosal GIP concentrations increased earlier, starting at 60 min, and levels remained elevated at 4 h. In separate studies, nuclear run-on assays were performed to compare the effects of glucose and water ingestion on transcription of the GIP gene. Whereas no increase in GIP gene transcription was detected in rats ingesting water, the rate of transcription doubled in glucose-fed rats. Actin gene transcription was nearly identical in both groups, indicating genomic specificity. The results of these studies indicate that duodenal GIP gene expression is stimulated at both the pre- and posttranslational levels by glucose-containing meals. These studies further suggest that the release of GIP from cellular storage granules might account for the initial increase in serum GIP levels after oral glucose ingestion.

Animals↗
PubMed1994

The effect of recombinant cytokines on [14C]-aminopyrine accumulation by isolated canine parietal cells.

Interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha) have been shown to inhibit basal and pentagastrin-stimulated gastric secretion in rats and histamine-stimulated secretion in dogs. IL-1 also reduces the severity of ethanol and stress-induced gastroduodenal damage. The aim of this study was to examine the effects of human recombinant IL-1 alpha and TNF-alpha on enzymatically dispersed and enriched (> 90%) parietal cells stimulated with histamine, histamine plus 3-isobutyl-1-methylxanthine (IMX) or carbachol (all 10(-5) M). Acid secretion was assessed indirectly by quantitating [14C]-aminopyrine (AP) accumulation. IL-1 alpha (500 and 1000 ng/ml) inhibited histamine-stimulated AP uptake by 53% and 60% respectively, and it inhibited IL-1 alpha (1500 ng/ml) by 69%. IL-1 alpha (500 and 1000 ng/ml) inhibited histamine plus IMX-stimulated AP uptake by 36% and 34%, respectively. IL-1 alpha (500 ng/ml) also inhibited carbachol-stimulated AP accumulation. TNF-alpha (100 and 250 ng/ml) inhibited histamine-stimulated AP accumulation by 38% and 36%, respectively. TNF-alpha also significantly inhibited histamine/IMX- and carbachol-stimulated AP uptake (P < or = .01). Indomethacin did not affect IL-1 alpha-induced inhibition. These results show that IL-1 alpha and TNF-alpha inhibit histamine- and carbachol-stimulated isolated parietal cell secretion and that, for IL-1 alpha, this effect does not depend on mucosal prostaglandin synthesis.

1-Methyl-3-isobutylxanthine↗
PubMed1993

Effects of histamine type 2-receptor antagonists cimetidine and famotidine on left ventricular systolic function in chronic congestive heart failure.

Twelve patients with stable congestive heart failure and left ventricular dysfunction were enrolled in a double-blind, randomized crossover trial of famotidine, cimetidine and placebo to determine whether histamine type 2 (H2) antagonists adversely affect left ventricular systolic performance. Two-dimensional echocardiograms were obtained at baseline, after 4 days of oral treatment with standard doses of famotidine and cimetidine, and placebo, and at the conclusion of the trial. The baseline mean ejection fraction was 19 +/- 7%. The changes in ejection fraction were +2 +/- 11% (95% confidence interval [CI] -5 to 9%) with famotidine, +3 +/- 10% (95% CI -3 to 10%) with cimetidine, and -3 +/- 7% (95% CI -8 to 2%) with placebo. There were no significant differences in changes in ejection fraction among the 3 experimental treatments (p = 0.22; analysis of variance). The changes in end-systolic wall stress/volume ratios from baseline were +6 +/- 21% (95% CI -6 to 18%) for famotidine, +8 +/- 29% (95% CI -8 to 25%) for cimetidine, and +2% +/- 29% (95% CI -15 to 18%) for placebo (p = 0.69; analysis of variance). No patient had a worsening of symptoms during therapy. Despite previous reports that H2 antagonists may depress left ventricular systolic function, at standard doses these agents result in no decrease in left ventricular systolic function in patients with chronic congestive heart failure.

Aged↗
PubMed1993

Glucose-dependent insulinotropic peptide: structure of the precursor and tissue-specific expression in rat.

Glucose-dependent insulinotropic peptide (GIP) is a 42-amino acid gastrointestinal regulatory peptide that stimulates insulin secretion from pancreatic beta cells in the presence of glucose. Approximately 7.8 x 10(5) recombinant clones of a neonatal rat intestinal cDNA library were screened by using plaque hybridization, and three clones were identified and sequenced with the dideoxynucleotide chain-termination method. The translated amino acid sequence deduced from the nucleotide sequence of the cDNA indicated that rat GIP was derived by proteolytic processing of a 144-amino acid precursor polypeptide. The mature peptide is flanked by a 43-amino acid NH2-terminal peptide that contains a 21-amino acid signal peptide and by a 59-amino acid COOH-terminal peptide. Analysis of the nucleotide and amino acid sequence of rat GIP revealed only two substitutions from the known human GIP peptide. The use of high-stringency RNA blot-hybridization analysis of total RNA extracted from various organs demonstrated expression of the GIP gene in the duodenum and jejunum and, to a lesser extent, in the ileum. In addition, expression of the GIP gene was observed in the submandibular salivary gland both by RNA analysis and RIA. In response to duodenal perfusion of a 20% Lipomul meal for 60 min, duodenal mucosal GIP mRNA concentrations increased by 42.8% and 48.2% at 30 and 60 min, respectively.

Amino Acid Sequence↗
PubMed1992

Somatostatin inhibition of gastrin gene expression: involvement of pertussis toxin-sensitive and -insensitive pathways.

These studies were performed to determine the intracellular pathways involved in regulating gastrin gene expression. The inclusion of 10(-4) M forskolin or 10(-4) M dibutyryl cyclic AMP (DBcAMP) in incubation medium containing dog antral mucosa resulted in 249% and 323% increases, respectively, in gastrin mRNA levels. The stimulatory effects of forskolin and DBcAMP were both inhibited significantly by 10(-6) M somatostatin. Preincubation of antral mucosa with pertussis toxin nearly abolished the inhibitory effects of somatostatin on gastrin mRNA stimulated by forskolin, but had no effect following DBcAMP. To examine whether calcium-dependent pathways might be involved in regulating gastrin gene expression, antral mucosa was incubated with increasing concentrations of calcium or the ionophore ionomycin. Both agents produced only modest increases in gastrin mRNA, which were abolished by the addition of somatostatin to the incubation medium. These studies indicate that somatostatin appears to inhibit gastrin gene expression through mechanisms involving both pertussis toxin-sensitive and -insensitive pathways.

Animals↗