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Biomedical subjects

G Gomez

Publications and source records attributed to G Gomez.

At least 19 recordsLinked to original sources

Downregulation of prohormone convertase-1 by a phorbol ester.

Acute TPA treatment (1h, 100nM) of a human pancreatic carcinoid cell line (BON) depletes cell contents of chromogranin A (CGA) and pancreastatin (PST), a peptide derived posttranslationally from CGA. Despite removal of TPA, BON cells continue to release CGA in an unregulated fashion whereas PST secretion is reduced substantially. TPA treatment also reduced prohormone convertase-1 (PC-1) protein and increased PC-1 mRNA levels. Together, these findings indicate that the TPA-induced switch from a regulated to unregulated pattern of CGA secretion is accompanied by a decrease in the processing of CGA to PST and a decrease in the active form of a processing enzyme potentially involved in processing CGA to a smaller peptide, PST.

Aspartic Acid Endopeptidases

Decreased plasma levels of cholecystokinin in healthy males after chronic ingestion of a heat-treated soya product.

Administration of raw soya containing a trypsin inhibitor stimulated excessive release of cholecystokinin (CCK) which led to pancreatic hypertrophy, hyperplasia and cancer in the rats (Booth et al. (1964) Proc. Soc. Exp. Biol. Med., 116, 1067). More postprandial CCK release in healthy humans was observed after ingestion of a single dose of raw soya than heat-treated soya (Calam et al. (1989) Br. J. Nutr., 58, 175). The effect of chronic ingestion of a heat-treated soya product on postprandial CCK release was investigated in six healthy adult males after ingestion of a 36-oz. portion of soymilk daily for 1 month and at 2-3 months after termination of soymilk ingestion. Subjects fasted for 15 h, ingested Lipomul (1.5 g/kg) and provided blood at timed intervals for CCK analysis. The results show that 1-month ingestion of soymilk decreased the magnitude of Lipomul-induced postprandial CCK release in plasma of all six subjects by 5-60% (P < 0.05) compared to those obtained at 2-3 months after the withdrawal from soymilk ingestion. Plasma pancreatic polypeptide (PP) levels were similarly decreased in five of the six subjects by 19-67% (P = 0.03) in line with the regulation of PP by CCK. Thus, prolonged exposure of humans to a heat-treated soya inhibited slightly meal-induced CCK release in contrast to that found in rats after raw soya diets.

Adult

Comparison of cefuroxime axetil and doxycycline in treatment of patients with early Lyme disease associated with erythema migrans.

A randomized, multicenter, investigator-blinded clinical trial was undertaken in order to compare the efficacies of cefuroxime axetil and doxycycline in the treatment of patients with Lyme disease associated with erythema migrans. A total of 232 patients with physician-documented erythema migrans were treated orally for 20 days with either cefuroxime axetil, 500 mg twice daily (119 patients), or doxycycline, 100 mg three times daily (113 patients), and clinical evaluations were conducted during treatment (8 to 12 days) and at 1 to 5 days and 1, 3, 6, 9, and 12 months posttreatment. Patients were assessed as to the resolution of erythema migrans and of the signs and symptoms related to early Lyme disease as well as to the prevention of late Lyme disease. A satisfactory clinical outcome (success or improvement) was achieved in 90 of 100 (90%) evaluable patients treated with cefuroxime axetil and in 89 of 94 (95%) patients treated with doxycycline (difference, -5%; 95% confidence interval, -12 to 3%). Patients with paresthesia, arthralgia, or irritability at enrollment were at higher risk for an unsatisfactory clinical outcome at 1 month posttreatment. Of the patients with satisfactory outcomes at 1 month posttreatment who were evaluable at 1 year posttreatment, a satisfactory outcome was achieved in 62 of 65 (95%) and in 53 of 53 (100%) patients treated with cefuroxime axetil and doxycycline, respectively (difference, -5%; 95% confidence interval, -10 to 4%). Twenty-eight percent of patients treated with doxycycline and 17% of those treated with cefuroxime axetil had one or more drug-related adverse events (P = 0.041). Doxycycline was associated with more photosensitivity reactions (6% compared with 0% for patients treated with cefuroxime axetil; P=0.006), and cefuroxime axetil was associated with more cases of diarrhea (5% compared with 0% for patients treated with doxycycline; P=0.030). Jarisch-Herxheimer reactions occurred in 12% of the patients in each treatment group. In summary, cefuroxime axetil is well tolerated and appears to be equally as effective as doxycycline in the treatment of early Lyme disease and in preventing the subsequent development of late Lyme disease.

Adult

Intestinal peptide YY: ontogeny of gene expression in rat bowel and trophic actions on rat and mouse bowel.

The purpose of this study was twofold: 1) to characterize the profile of colonic peptide YY (PYY) gene expression in rats and 2) to examine for potential trophic effects of PYY on the intestine in rats and mice. Expression of PYY mRNA (analyzed by Northern blotting and in situ hybridization) and PYY (analyzed by high-performance liquid chromatography and radioimmunoassay) was detected initially at day 17 of gestation in colonic extracts of Sprague-Dawley and Fischer rats. Expression of colonic PYY mRNA increased until 7 days of age and remained at its highest level (approximately twofold greater than the adult level) through the end of the nursing period. After weaning (21 days of age), PYY mRNA levels declined quickly to adult levels. Colonic PYY concentrations followed, in a coordinated manner, with some temporal delay after birth, the increase and decrease of its mRNA. Administration of PYY increased the weight and DNA content of the duodenum significantly in nursing rats and adult mice. In mice, PYY treatment also increased weight and DNA content of the ileum and colon. The trophic effects of PYY were dose related, peptide specific, and independent of species and sex. From these findings, we hypothesize that PYY plays an important role in intestinal development and dietary adaptation.

Aging

Phorbol ester-induced alteration in the pattern of secretion and storage of chromogranin A and neurotensin in a human pancreatic carcinoid cell line.

Brief phorbol ester treatment of BON cells results in a persistent release and cellular depletion of immunoreactive chromogranin A (CGA-IR) and neurotensin (NT-IR) cell contents. The purpose of the present study was to characterize the effects of 12-O-tetradecanoyl phorbol-13-acetate (TPA) on the secretion, biosynthesis, and steady-state messenger RNA (mRNA) levels of chromogranin A (CGA) and of a coresident peptide, neurotensin, by a novel human pancreatic carcinoid cell line, called BON. Acute TPA treatment (100 nM, 1 h) of BON cells resulted in 20- and 40-fold elevations in release of CGA-IR and NT-IR, respectively; and a 70-90% depletion of CGA-IR and NT-IR cell contents. TPA treatment also increased the biosynthetic rate of CGA-IR. Steady-state mRNA levels of CGA and NT/N (neurotensin/neuromedin N) were unchanged. Cell contents of CGA-IR and NT-IR were not replenished for a period of up to 6 days; secretion of CGA-IR and NT-IR persisted. In addition, BON cells failed to release CGA in response to stimulation by ionomycin and A23187 several days after acute TPA treatment. Our data indicate that the lack of replenishment of cell contents of CGA-IR and NT-IR is not due to decreases in steady-state CGA-IR and NT-IR mRNA levels, nor is it due to a decrease in biosynthesis of CGA-IR, but it is the result of a loss in the ability of TPA-treated BON cells to store and secrete CGA-IR and NT-IR in a regulated manner. These effects of TPA are mediated through the PKC pathway.

Analysis of Variance

Glutamine stimulates prostaglandin-sensitive Na(+)-H+ exchange in experimental porcine cryptosporidiosis.

BACKGROUND/AIMS: Recent studies of piglet cryptosporidiosis showed an injury-induced impairment of sodium-glucose cotransport and a prostaglandin-mediated inhibition of neutral NaCl absorption. Because glutamine has been shown to stimulate both neutral and electrogenic Na+ absorption, this study examined the mechanism of prostaglandin-mediated inhibition of NaCl absorption and the effect of glutamine on these processes. METHODS: Ileal mucosa from control and infected pigs was mounted in Ussing chambers for flux studies or incubated with [14C]glutamine or [14C]-glucose for metabolism studies. RESULTS: Glucose and glutamine induced equivalent increases, 2-2.5 microEq.cm-2.h-1, in Na+ absorption and short-circuit current in control ileum. Despite a reduction in villous surface area to one third of the control, glutamine enhanced both neutral and electrogenic Na+ absorption in the infected ileum by 3.5 +/- 0.5 microEq.cm-2.h-1, whereas glucose was only half as effective (P < 0.05). In addition, glutamine was oxidized to CO2 at rates three times those of glucose. Indomethacin enhanced, whereas amiloride, prostaglandin E2, and Cl-free solutions inhibited the glutamine-induced neutral Na+ transport. CONCLUSIONS: Glutamine-stimulated neutral Na+ absorption is mediated by a prostaglandin-sensitive apical Na(+)-H+ exchange mechanism. The heightened Na(+)-H+ exchange and tissue oxidation of glutamine suggest that glutamine is superior to glucose for use in oral rehydration solutions.

Animals

Glucose metabolism, triglyceride and glycogen levels, as well as eicosanoid production in isolated uterine strips and in embryos in a rat model of non-insulin-dependent diabetes mellitus during pregnancy.

Spontaneous contractile activity, glucose (Glu), glycogen (GLY), triglyceride (TG) metabolism and eicosanoid production, was evaluated in isolated uterine strips from control and non-insulin-dependent diabetic rats on day 10 of pregnancy. Metabolism of Glu, levels of GLY and TG and eicosanoid production were also studied in day 10 embryos obtained from both experimental groups. "In vitro" isometric developed tension (IDT), was similar at 0 hr in control and diabetic uterine preparations, but IDT was decreased after a 60 min incubation in the diabetic group. The frequency of contractions (FC) was similar at 0 hr and after 60 min incubation in both experimental groups. On the other hand, the production of 14CO2 from U14C-glucose was lower in isolated uteri and embryos obtained from diabetic rats than in controls. Initial TG levels were similar in uteri isolated from control and diabetic rats, and higher in embryos obtained from diabetic mothers than in controls. Levels of TG in uterine strips suspended in Glu or Glu-free medium did not differ at 0 hr or at 60 min either in controls or in diabetic rats. On the contrary GLY levels in uterine strips from diabetic animals were higher than in controls, whereas in embryos from diabetic mothers GLY levels were similar to controls. Levels of GLY in uterine strips from controls and diabetic animals decreased after 60 min incubation only in the absence of Glu in the incubation medium. Production of PGE2, PGE1, 6-keto-PGF1 alpha, PGF2 alpha, TXB2 and LTB4 was studied in uterine strips and embryos obtained from control and diabetic rats. No differences were found between control and diabetic uterine prostanoid production, but lower production of LTB4 was observed in diabetic uteri. However production of PGE2 and PGF2 alpha was greater in embryos obtained from diabetic mothers than in controls. In this study, we observed lower uterine metabolic alterations than in the pancreatectomized diabetic rat model studied previously, but important anomalies in the embryos obtained from non-insulin-dependent diabetic mother were found.

Animals

Bombesin inhibits growth of pancreatic ductal adenocarcinoma (H2T) in nude mice.

Bombesin (BBS), a tetradecapeptide, stimulates growth of various types of cells, including fibroblasts and human small cell lung cancer, and has been termed the universal "on-switch" due to its ability to stimulate the release of numerous hormones. In addition, BBS receptors have been identified in normal and neoplastic pancreatic tissue. A pancreatic ductal adenocarcinoma cell line (H2T), established in our laboratory, possesses specific binding sites for BBS. The purpose of this study was to examine the effect of BBS on the growth of H2T tumors transplanted into athymic nude mice. H2T cells (5 x 10(6) cells/mouse) were injected s.c. into the interscapular region of the nude mice and then the mice were randomized into two groups (n = 10/group). Mice received either 0.1 ml of saline with 0.1% bovine serum albumin (BSA) (control) or 0.1 ml BBS (5 micrograms/kg) intraperitoneally, three times/day. Tumor area was measured twice weekly until the mice were killed (day 32), when tumor and normal pancreas were removed, weighted, and assayed for DNA and protein content. Administration of BBS significantly inhibited H2T tumor area, weight, and DNA and protein content. Conversely, growth of normal pancreas, removed as an in vivo bioassay so as to ensure the efficacy of BBS, was stimulated. We conclude that BBS is a growth inhibitory factor for H2T tumors and that different mechanisms may be responsible for the differential growth effects elicited by normal and neoplastic pancreas in response to BBS.

Animals

Neural regulation of peptide YY secretion.

The purpose of these experiments was to investigate the neural control of peptide YY (PYY) secretion. The effects of various pharmacological manipulations and vagotomy on peptide YY (PYY) secretion was examined in dogs. Atropine, hexamethonium and atropine plus hexamethonium treatment blocked food-induced release of PYY significantly. Integrated release of PYY in response to food alone and in combination with atropine, hexamethonium and atropine plus hexamethonium were 8.8 +/- 2.2, -1.1 +/- 2.3, -2.7 +/- 2.2 and -3.2 +/- 3.1 (ng (0-150) min/ml), respectively. beta-Adrenergic blockade with propranolol or depletion of nerve terminal stores of catecholamines with reserpine did not affect food-stimulated release of PYY. Truncal vagotomy resulted in significant elevations of basal and food-induced release of PYY. IV administration of bethanechol, a cholinergic agonist, and electrical stimulation of the vagus nerve resulted in release of PYY. Together, these data suggest that food-stimulated PYY secretion is dependent on ganglionic transmission and an atropine-blockable postganglionic parasympathetic pathway; and that PYY release is inhibited tonically, probably through a vagal cholinergic mechanism. Adrenergic pathways do not participate in food-stimulated PYY release; however, electrical stimulation of the splanchnic nerves increased basal levels of PYY, suggesting that the sympathetic nervous system affects release of PYY.

Animals

Glucose, glycogen and triglyceride metabolism, as well as prostaglandin production in uterine strips and in embryos from diabetic pregnant rats. Influences of the presence of substrate in the incubation medium.

"In vitro" isometric developed tension (IDT) and frequency of contractions (FC), glucose (Glu), glycogen (GLY) and triglyceride (TG) metabolism, as well as prostaglandin PGE2 and PGE1 production, were studied in uterine strips and in embryos isolated from controls and diabetic rats at day 10 of pregnancy. The IDT and the FC, at 0 time or after a 60 min incubation, were not different in controls and in preparations from diabetic animals when the uterine strips were incubated in glucose or in glucose-free medium (p > 0.05). The production of 14CO2 and 14C-lactate from 14C-glucose were lower in the diabetic group than in controls (p < or = 0.05). Indomethacin (10(-6) M), an inhibitor of prostaglandin synthesis, failed to modify these results. Labelled Glu metabolism by isolated embryos was similar (p > 0.05) in controls and in embryos obtained from diabetic mothers. On the other hand, the initial TG and GLY levels were higher (p < or = 0.05) in diabetic uterine tissues than in controls. However, the values of TG and GLY in embryos obtained from both experimental groups were similar (p > 0.05). TG levels in uterine strips suspended in Glu or in Glu-free medium did not differ (p > 0.05) at 0 time (postisolation) and at 60 min, either in controls or in diabetic rats. However, Gly levels in uterine strips from diabetic animals, decreased significantly at 60 min in tissues incubated in Glu or in Glu-free medium (p < or = 0.05). In controls, uterine Gly content decreased (p < or = 0.05) only at 60 min time when the strips were incubated in Glu-free medium. Finally, uterine tissue from controls as well as from diabetic pregnant rats release more PGE2 than PGE1 into the incubation medium (p < or = 0.001). Nevertheless, secretion of PGE2 and PGE1 was similar in both experimental groups and was not modified by the presence or absence of glucose. In summary, we found differences in uterine metabolism of glucose, glycogen and triglycerides in controls and in diabetic rats, but metabolic differences have not been detected between embryos obtained from controls and from diabetic mothers.

Alprostadil

Eicosanoid production by uterine strips and by embryos obtained from diabetic pregnant rats.

Eicosanoid production by uterine strips and by embryos obtained from normal and diabetic rats at day 10 of pregnancy was studied. It was found that the release of 6-keto-PGF1 alpha (representing PGI2 synthesis) and of LTB4 was less in preparations from diabetic animals than in controls. The production of TXB2 (indicating the formation of TXA2) by uterine tissue obtained from diabetic rats was almost double that of controls. The synthesis and release of eicosanoids when tissues were incubated in glucose-containing solution or in glucose-free medium were similar, with the exception of LTB4, which was diminished with uterine strips from diabetic rats. The mean number of embryos in control pregnant rats (12.4 +/- 0.5) and in diabetic mothers (10.1 +/- 1.3) was not significantly different, but in 4 of the 14 diabetic rats studied, all of their embryos were resorbed. Although embryos released large amounts of PGF2 and PGE2, and small amounts of 6-keto-PGF1 alpha, TXB2 and LTB4, the amounts of each eicosanoid in control and diabetic groups were similar. The present results indicate that the diabetic state, which induces alterations in uterine eicosanoid production, do not influence arachidonic metabolism in their corresponding embryos.

Animals

Bombesin stimulates growth of colon cancer in mice and decreases their survival.

Bombesin (BBS) stimulates cellular proliferation of both normal and transformed cells. The mouse colon cancer cells (MC-26) possess specific binding sites for BBS. The purpose of this study, therefore, was to examine the effect of chronic administration of BBS on in vivo growth of MC-26 tumours in Balb/c mice and on survival of tumour-bearing mice. Three groups of mice (n = 10 each) inoculated with MC-26 cells received either saline containing 0.1% bovine serum albumin (BSA), or BBS (5 micrograms kg-1 or 20 micrograms kg-1) dissolved with 0.1% BSA saline by intraperitoneal route three times a day for 15 days. BBS increased weight, DNA and RNA contents of MC-26 tumours. To examine the effect of BBS on survival rates of mice with MC-26 tumours, three groups of mice (n = 20 each) were treated for 31 days, as above. One group of mice inoculated with MC-26 cells received 0.1% BSA saline; the other group of MC-26-inoculated mice and the control group without tumour received BBS (5 micrograms kg-1) dissolved with 0.1% BSA saline. BBS significantly decreased the survival rate of mice bearing MC-26 tumours (median survival; saline group: 42.5 days, BBS group: 32.0 days, P = 0.037). None of the mice in the control group died during the experiment. BBS may stimulate in vivo growth of MC-26 cells through specific receptors.

Animals

Pituitary adenylate cyclase activating polypeptide stimulates release of peptide YY.

The purpose of these experiments was to examine the effects of the recently discovered gastrointestinal peptide, pituitary adenylate cyclase activating polypeptide (PACAP), and two structurally related peptides, vasoactive intestinal polypeptide and secretin, on release of peptide YY (PYY) in conscious dogs. Intravenous administration of PACAP-27 or -38 stimulated a dose-related release of PYY; PACAP-27 was more potent than PACAP-38. PACAP-stimulated release of PYY was inhibited significantly by atropine, whereas ganglionic or beta-adrenergic blockade with hexamethonium and propranolol treatment, respectively, did not affect PACAP-induced release of PYY significantly (P > 0.05). These results indicate that PACAP-induced release of PYY is cholinergic dependent and that beta-adrenergic tone and ganglionic transmission do not participate in PACAP-induced release of PYY. PACAP may play a role in the neural regulation of PYY release.

Animals

Changes in mononuclear peripheral blood cells in cattle with foot-and-mouth disease.

The percentages and absolute numbers of mononuclear peripheral blood cells (MNC) were studied in vaccinated (Vac) and non-vaccinated (control) cattle, challenged with foot-and-mouth disease virus (FMDV). All Vac cattle but none of the controls resisted challenge. Cell populations were studied immediately before and one week after challenge, by direct and indirect immunofluorescence, using polyclonal and monoclonal antibodies against different bovine markers. Total B-lymphocytes, as assessed with polyclonal anti-IgG (H + L) antisera, as well as total mononuclear cells, were normal before and after infection, and did not change in Vac or control groups. Before challenge Vac cattle had higher numbers of ILA-29+ (a putative marker for null cells or, alternatively, for gamma delta T-cells) than control cattle. After challenge, in control cattle, the number of total T-cells, BoT4-bearing (helper) T-cells and BoT8-bearing (cytotoxic/suppressor) T-cells were decreased, while IgM-bearing B-lymphocytes, as well as monocyte/macrophage cells were increased. The number of IL-A29-bearing T-cells did not change after infection in either group. After challenge, Vac cattle also showed increased numbers of IgM-bearing B-lymphocytes and monocyte/macrophage cells, whereas T-subpopulations did not change significantly.

Animals

Early stages of gallstone formation in guinea pig are associated with decreased biliary sensitivity to cholecystokinin.

The purpose of this study was to measure differences in gallbladder sensitivity to cholecystokinin (CCK) in vivo during the early stages of gallstone formation and to correlate these findings to gallbladder CCK receptors. Guinea pigs were placed on either a normal diet or a two-week cholelithogenic diet, after which gallbladder emptying pressure to exogenously administered CCK was measured in vivo, according to the presence or absence of gallstones. At all doses of CCK tested (except 10(-10) mol/kg), the gallbladder response to CCK of guinea pigs that did not develop gallstones (on the cholelithogenic diet) was more sensitive than that of guinea pigs that did develop gallstones. Neither group was different from guinea pigs on a normal diet. In a second experiment, CCK receptors were measured on gallbladder muscularis from guinea pigs after two weeks on the same diet as in the first experiment. Those guinea pigs that did not develop gallstones had greater concentrations of CCK receptors (149 +/- 9 fmol/mg protein) than those that did develop gallstones (70 +/- 23 fmol/mg protein). Neither group was different from normal diet guinea pigs (119 +/- 57 fmol/mg protein). At the time point measured, there were no differences in the lipid chemistry or protein concentrations of gallbladder bile between the guinea pigs on the cholelithogenic diet that did or did not develop gallstones, or those on normal guinea pig chow. We conclude that the early stages of gallstone formation in guinea pigs are associated with decreased gallbladder sensitivity to CCK and that this change may be due to a lower concentration of CCK receptors on the gallbladder smooth muscle.

Animals

Comparison of high titer Edmonston-Zagreb, Biken-CAM and Schwarz measles vaccines in Peruvian infants.

In an effort to identify the optimal dose and strain of measles vaccination for early immunization, Peruvian infants were randomly assigned to receive one of three measles vaccines in varying doses at 5 to 6 or 8 to 9 months of age. Edmonston-Zagreb vaccines were significantly (P < 0.001) more immunogenic than equivalent or higher titers of Schwarz or Biken-CAM vaccines as determined by neutralization antibody response 3 months after vaccination. Eighty-two percent of infants who received high titer Edmonston-Zagreb vaccine at 5 to 6 months of age developed protective concentrations of measles antibody, a response rate similar to that observed after standard titer Schwarz (81%) or high titer Biken-CAM vaccine (81%) at 8 to 9 months of age. No significant differences in the rates of fever, rash or other adverse events were noted by vaccine group 10 to 14 days after vaccination. Although the high titer vaccines are more immunogenic in young infants than standard vaccines, long term safety must be assured before these vaccines can be put into widespread use.

Antibodies, Viral

Chronic effect of oral cholestyramine, a bile salt sequestrant, and exogenous cholecystokinin on insulin release in rats.

Oral cholestyramine, a bile salt sequestrant, stimulates pancreatic exocrine secretion and growth chiefly by increasing cholecystokinin (CCK) release. In this report, we examine pancreatic insulin content and insulin release from the isolated perfused pancreas in rats given oral cholestyramine (4%, wt/wt) or subcutaneous CCK-8 (1 micrograms/kg every 8 h) for 2 weeks. Cholestyramine significantly increased pancreatic weight by 32%. CCK administration significantly increased pancreatic weight by 15%. Total pancreatic content of protein and DNA were also increased significantly by cholestyramine and pancreatic protein content was increased significantly by CCK administration. Total pancreatic insulin content was not affected by cholestyramine or CCK. Both cholestyramine and CCK significantly increased the first phase of glucose (8.4 mM)-stimulated release of insulin [mean insulin output (ng/min): control, 2.0 +/- 0.1; cholestyramine, 2.7 +/- 0.2; CCK, 2.6 +/- 0.2]. Cholestyramine also significantly enhanced the second phase of glucose-stimulated release of insulin. Insulin release stimulated by CCK-8 (10(-10) M) was not affected by oral cholestyramine or CCK treatment. These findings indicate that oral cholestyramine and exogenous CCK have a stimulatory effect on beta cell function. Since pancreatic insulin content was not affected by cholestyramine and CCK treatment, cholestyramine and CCK may increase the sensitivity of beta cells to glucose. The absence of a stimulatory effect of cholestyramine and CCK administration on insulin release in response to CCK-8 may be related to a down-regulation of CCK receptors on beta cells.

Administration, Oral