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Biomedical subjects

H Wong

Publications and source records attributed to H Wong.

At least 163 records · Page 9Linked to original sources
PubMed1990

Somatostatin monoclonal antibody immunoneutralization increases gastrin and gastric acid secretion in urethane-anesthetized rats.

The role of endogenous somatostatin in mediating urethane anesthesia-induced inhibition of gastric acid secretion was investigated using measurement of somatostatin messenger RNA concentrations in the antrum and the influence of somatostatin monoclonal antibody CURE.S6 on acid secretion in rats anesthetized with urethane and acutely implanted with gastric fistulas. Fifteen minutes after injection of urethane, somatostatin messenger RNA concentrations were increased by 128% compared with those in nontreated rats. The significant elevation of somatostatin messenger RNA was maintained for 2 hours after injection. Somatostatin monoclonal antibody injected intravenously (2 mg) completely reversed the inhibitory effect of somatostatin (20 micrograms/kg.h) on pentagastrin (24 micrograms/kg.h)-stimulated gastric acid secretion. The somatostatin monoclonal antibody dose dependently increased basal gastric acid secretion in urethane-anesthetized rats. Peak acid response to the somatostatin monoclonal antibody (2 mg) was observed 20 minutes after antibody injection (preinjection, 1.4 +/- 1.2 mumol/10 min; postinjection, 10.6 +/- 0.6 mumol/10 min); meanwhile, levels of plasma gastrin increased from 27 +/- 6 pg/mL to 75 +/- 8 pg/mL and were maintained elevated for the 2-hour experimental period. When gastrin monoclonal antibody 28.2 was injected together with somatostatin monoclonal antibody, the stimulatory effect of the somatostatin antibody was inhibited by 82%. A control monoclonal antibody 109-21 directed against the biologically inactive glycine-extended fragment 66-72 of progastrin did not alter basal gastric acid secretion or the inhibitory effect of somatostatin. These results indicate that one mechanism by which urethane induced low basal gastric acid secretion involved increased synthesis and release of endogenous somatostatin and associated inhibition of gastrin secretion.

Anesthetics↗
PubMed1990

TGF-beta regulates production of growth factors and TGF-beta by human peripheral blood monocytes.

Transforming growth factor beta 1 (TGF-beta 1) and its closely related homologue, TGF-beta 2, rapidly induce growth factor gene expression by freshly isolated human peripheral blood monocytes. Within 3 h of exposure to TGF-beta, mRNA species specific for interleukin-1 (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha), platelet-derived growth factor (PDGF), and basic fibroblast growth factor (bFGF) were observed. By 14-18 h, cytokine bioactivity and protein were detected in the culture supernatants. Furthermore, not only TGF-beta 1, but also TGF-beta 2 mRNA are expressed constitutively in unstimulated monocytes. However, in response to exogenous TGF-beta (beta 1 or beta 2), only TGF-beta 1 gene expression is upregulated, and the expression of TGF-beta 2 mRNA is unchanged. This selective autoinduction of TGF-beta 1 appears to be controlled at both transcriptional and post-transcriptional levels. These paracrine and autocrine activities of TGF-beta suggest potential mechanisms through which an inflammatory response can be initiated and amplified. In addition, the TGF-beta enhancement of growth factor generation may promote fibrosis and angiogenesis relevant to physiological tissue repair as well as pathological fibrotic sequelae.

Blotting, Northern↗
PubMed1989

Characterization of the carboxyl terminal flanking peptide of rat progastrin.

A peptide identical in structure to the carboxyl-terminal flanking nonapeptide of rat progastrin, predicted by cDNA sequence, was synthesized. The synthetic peptide was used for production of a rabbit antiserum. This antiserum was used to develop a radioimmunoassay specific for rat carboxyl terminal flanking peptide. This assay was used to monitor the purification of immunoreactivity from rat antral extracts. Gel permeation, anion exchange and reverse phase chromatography steps resulted in a single absorbance peak associated with the carboxyl terminal flanking peptide immunoreactivity. The purified peptide eluted in the same position as the synthetic peptide during all three types of chromatography. This material was shown to be identical in mass to Ser-Ala-Glu-Glu-Glu-Asp-Gln-Tyr-Asn, the predicted sequence of the carboxyl terminal nonapeptide of rat progastrin.

Amino Acid Sequence↗
PubMed1989

Role of growth factors in inflammation and repair.

Mononuclear cells generate a variety of hormone-like proteins termed growth factors that are instrumental in the evolution and resolution of inflammatory reactions. Many of these growth regulatory molecules have multifunctional properties. For example, the mononuclear cell-derived growth factors, platelet-derived growth factor (PDGF), and transforming growth factor beta (TGF-beta), are potent leukocyte chemoattractants. In addition, TGF-beta, a product of platelets, T lymphocytes, and monocytes, appears to induce the transcription of other monocyte-derived growth hormone genes. In this regard, picomolar concentrations of TGF-beta stimulate peripheral blood monocytes to transcribe the genes for PDGF (c-sis), basic fibroblast growth factor (FGF), interleukin 1 (IL-1), and tumor necrosis factor (TNF). Furthermore, levels of mRNA for TGF-beta, which is constitutively expressed in resting monocytes, are also increased by exogenous TGF-beta. Each of these monocyte products exhibits a plethora of biological activities on other cell types. T lymphocytes, in response to antigen, contribute to this network by secreting growth factors and lymphokines that regulate monocyte growth factor production.

Growth Substances↗
PubMed1989

Effect of gastrin monoclonal antibody 28.2 on acid response to chemical vagal stimulation in rats.

The role of gastrin in mediating the acid response to chemical vagal stimulation was evaluated by intravenous injection of the gastrin monoclonal antibody 28.2 (2.6 mg/rat). The antibody was injected 30 min prior to the administration of vagal stimulants in urethane-anesthetized rats equipped with a double lumen gastric cannula. The gastrin monoclonal antibody 28.2 prevented gastrin-17- but not carbachol-stimulated gastric acid secretion. The gastric acid response to vagal stimulation produced by thyrotrophin-releasing hormone (TRH) injected into the cisterna magna or the dorsal vagal complex and by the GABAB agonist, baclofen, infused intravenously was reduced by 33, 22 and 33% respectively in rats administered with gastrin monoclonal antibody 28.2. These immunoneutralization studies provide evidence that approximately 75% of the acid response to vagal stimulation is not mediated by gastrin in urethane-anesthetized rats.

Animals↗
PubMed1988

Solid-phase peptide quantitation assay using labeled monoclonal antibody and glutaraldehyde fixation.

A solid-phase radioimmunoassay utilizing iodinated peptide-specific monoclonal antibody as a detection system instead of labeled peptide has been developed. Regional specific monoclonal antibodies to either gastrin-releasing peptide or gastrin were used as models to validate the general application of our modified assay. Conditions for radioactive labeling of the monoclonal antibody were determined to minimize oxidant damage, which compromises the sensitivity of other reported peptide quantitation assays. Pretreatment of 96-well polyvinyl chloride test plates with a 5% glutaraldehyde solution resulted in consistent retention of sufficient target peptide on the solid-phase matrix to allow precise quantitation. This quantitative method is completed within 1 h of peptide solid phasing. Pretreatment of assay plates with glutaraldehyde increased binding of target peptide and maximized antibody binding by optimizing antigen presentation. The hypothesis that glutaraldehyde affects both peptide binding to the plate and orientation of the peptide was confirmed by analysis of several peptide analogs. These studies indicate that peptide binding was mediated through a free amino group leaving the carboxy-terminal portion of the target peptide accessible for antibody binding. It was observed that the length of the peptide also affects the amount of monoclonal antibody that will bind. Under the optimal conditions, results from quantitation of gastrin-releasing peptide in relevant samples agree well with those from previously reported techniques. Thus, we report here a modified microplate assay which may be generally applied for the rapid and sensitive quantitation of peptide hormones.

Amino Acid Sequence↗
PubMed1988

Cholesteryl ester accumulation in smooth muscle cells after uptake of necrotic products from atherosclerotic lesions.

Cholesterol-ladened plasma membrane vesicles were used to load smooth muscle cells (SMC) with cholesterol. Plasma membrane vesicles (PMV) were isolated from rabbit atherosclerotic lesions, and characterized as to size, cholesterol content, and marker enzyme (plasma membrane, lysosome, endoplasmic reticulum) composition. PMV were regarded as a necrotic product since they are produced upon injury to cells. Degradation of PMV was proportional to the PMV protein concentration in the culture medium, suggesting bulk intake of PMV. Cholesterol accumulation of SMC varied with the cholesterol content of the vesicle. Incubation for 3 days with PMV having 0.39 and 0.62 mg cholesterol/mg protein induced the accumulation of 8 and 29 micrograms of esterified cholesterol/mg cell protein, respectively. Incorporation of oleate into cholesteryl ester during a 24-hr period under these conditions, however, was the same. The contribution of cholesterol ester synthesis to the esterified cholesterol content of SMC was 40 and 11% of the total when exposed to PMV having, respectively, low and high contents of cholesterol. This study suggests that cholesterol-bearing PMV in lesions can be utilized to load lesion-SMC. These observations suggest that lipid-bearing elements other than low density lipoprotein may be responsible for cholesterol-loaded SMC in lesions.

Animals↗
PubMed1988

Somatostatin may not be a hormonal messenger of fat-induced inhibition of gastric functions.

The present study was designed to evaluate somatostatin as a hormonal inhibitor of gastric functions in humans. Seven healthy volunteers were investigated on 6 separate days. Peptone meal-stimulated gastric acid secretion was measured by intragastric titration for 2 h and gastric emptying was estimated with a dye-dilution technique. The effect of intravenous administration of somatostatin at 0, 12.5, 50, 100, and 200 pmol/kg.h was investigated and related to the effect of intragastric administration of 100 ml of vegetable oil. Plasma somatostatinlike immunoreactivity was elevated during intravenous administration of somatostatin at 100 and 200 pmol/kg.h, whereas no increase was detected in response to the oil. Somatostatin infusion at 100 and 200 pmol/kg.h significantly inhibited the acid secretion by 25% and 65%, and the oil reduced the acid output by 41%. Somatostatin at 100 and 200 pmol/kg.h significantly enhanced gastric emptying, whereas the oil inhibited gastric emptying. These observations suggest that somatostatin may not be an important hormonal messenger of fat-induced inhibition of acid secretion or gastric emptying.

Adult↗
PubMed1988

The viability and regeneration of artificial cell microencapsulated rat hepatocyte xenograft transplants in mice.

Viable hepatocytes were microencapsulated within artificial cells to form a bio-artificial liver. Trypan blue stain exclusion testing generally showed that 60% of the encapsulated hepatocytes remained viable immediately after encapsulation. To determine if xenogeneic hepatocytes can be successfully transplanted, encapsulated rat hepatocytes were implanted intra-peritoneally into mice and galactosamine induced liver failure mice. After 29 days of implantation in mice and 8 days of implantation in liver failure induced mice there was no significant change observed in the number of hepatocytes within the free floating microcapsules recovered from the peritoneal cavity. The percentage viability of the hepatocytes inside the recovered microcapsules increased from 62% to nearly 100% after 29 days of implantation in mice. The percentage viability of the encapsulated hepatocytes implanted in the liver failure induced mice was followed for 8 days. The percentage viability of the hepatocytes inside the microcapsule also increased from 42% to nearly 100%. In mice implanted with free rat hepatocytes, no viable hepatocytes were observed as early as 4 and 5 days after implantation. Instead a larger number of lymphoid cells and remnants of hepatocytes were recovered from the peritoneal cavity. In all cases the viability of the rat hepatocytes were determined with trypan blue stain.

Animals↗
PubMed1988

Phencyclidine and violence: clinical and legal issues.

Phencyclidine (PCP) abuse has diminished since PCP's intrusion into American culture in the late 1970s. One of its legacies is the assumption that it provokes violent behavior in humans with predictable regularity. This assumption is so accepted that ingestion of the drug both accidentally and knowingly prior to committing a crime has been used as a defense in criminal trials. We reviewed 81 clinical reports of toxicity in humans published chiefly in North American medical journals. We searched for descriptions of violent behavior in these reports and subjected them to the following questions: (1) Was the violent behavior corroborated or only self-reported? (2) Was the presence of PCP confirmed by analysis of bodily fluids or postmortem tissue? (3) Was the presence of other drugs excluded by similar analysis of bodily fluids? We had planned to examine the reports to see whether clinicians sought evidence of previous violent behavior, but such an inquiry was rarely conducted. Of the hundreds of patients described, only three satisfied these criteria. Further, some of the papers offered evidence that reports of violence were exaggerated. These findings plus the pre-1970 prospective evaluation of thousands of patients with PCP, in which violence was never reported, led us to conclude that clinical and forensic assumptions about PCP and violence are not warranted.

Forensic Psychiatry↗
PubMed1987

Hepatic lipase: a member of a family of structurally related lipases.

Partial amino acid sequence of rat hepatic lipase was obtained by gas-phase microsequence analysis of proteolytic fragments. Sequence comparison to bovine lipoprotein lipase and porcine pancreatic lipase reveals a highly conserved region existing among these three physiologically distinct lipolytic enzymes. In a stretch of 36 amino acid residues previously reported for pancreatic lipase (De Caro, J., Boudouard, M., Bonicel, J., Guidoni, A., Desnuelle, P. and Rovery, M. (1981) Biochim. Biophys. Acta 671, 129-138), nineteen residues are identical for all three enzymes, whereas 27 of 36 are identical in rat hepatic lipase and bovine lipoprotein lipase. The fact that this primary structural conservation extends to three different animal species emphasizes the conclusion that these lipolytic enzymes comprise a protein family originating from a common ancestral gene.

Amino Acid Sequence↗