Allelic loss of the BRCA1 and BRCA2 genes and other regions on 17q and 13q in breast cancer among women from Taiwan (area of low incidence but early onset)

We have examined the role of the breast cancer susceptibility genes BRCA1 and BRCA2 and other loci in the vicinity of these 2 genes on the long arms of chromosomes 17 and 13 (17q and 13q) for the presence of genomic deletions in breast cancer among Taiwanese women. Breast cancer in Taiwan is particularly characterized by its low incidence rate and its early age of tumor onset. Twelve microsatellite markers spanning the region 17q12-21 and 8 microsatellite markers spanning the region 13q12-14 were analyzed for allelic loss or loss of heterozygosity (LOH) in 90 patients with primary infiltrating ductal carcinoma. Compared with the background LOH level (10-12%) estimated by LOH at 4 unrelated loci, 17 markers (11 at 17q and 6 at 13q) demonstrated a significantly increased frequency (21-42%) of allelic loss (p < 0.05). Subsequent construction of deletion maps based on LOH at these significant loci localized the 6 smallest regions of overlap, including those harboring BRCA1, BRCA2, the retinoblastoma gene and 3 novel regions (the 1st located approximately 0.5 to 1 cM telomeric to BRCA1, the 2nd centromeric to BRCA1 flanked by D17S857/D17S846 and the 3rd closely adjacent to BRCA2), suggesting sites of susceptibility genes. Allelic loss at BRCA1 and BRCA2 was specifically associated with poorly differentiated tumors.

Artificial cells with emphasis on cell encapsulation of genetically engineered cells

Artificial cells are prepared in the laboratory for medical and biotechnological applications. Encapsulated cells are being studied for the treatment of diabetes, liver failure, and other conditions. More recently, there have been extensive studies into the use of encapsulated genetically engineered cells for gene therapy. We recently found that daily orally administered artificial cells, each containing a genetically engineered microorganism, can lower the elevated urea level in uremic rats to normal levels. This may solve the final obstacle of the lack of an effective oral urea removal system for the simple and inexpensive oral treatment of uremia. This is important because 85% of the world's uremic population cannot afford standard dialysis. Other areas of artificial cell application include use in hemoperfusion. Red blood cell substitutes based on modified hemoglobin are already in Phase 3 clinical trials in patients. Artificial cells containing enzymes are being developed for clinical trial in hereditary enzyme deficiency disease and other diseases. They are also being investigated for drug delivery and for use in other applications in biotechnology, chemical engineering, and medicine.

Adsorption of chitin derivatives onto liposomes: optimization of adsorption conditions

A 2(4) factorial design is used to optimize the adsorption conditions of the hydrophilic anionic polyelectrolytes. Carboxymethylchitin (CMC) and Carboxymethyl/Glycolchitin (CO) onto liposomes at physiological ionic strength (I) and pH using phosphate buffered saline (PBS, I = 154 mM, pH = 7.4). Positive ([+]) or high surface affinity liposomes (DSPC:CHOL:DMTAP, 5:4:1), and Neutral ([N]) or low surface affinity liposomes (DSPC:CHOL, 1:1) were used as adsorption surfaces. Results of the calculations of the main effects indicate that polymer molecular weight (mwt), Surface Affinity (S), Number of Adsorption Shots (Sh), Temperature (T), and the combinations mwt x S, mwt x Sh are the most important process parameters. Results of a study conducted at T = 37 degrees C show that no loss occurs from the positive surface at the highest particle concentration, Np = 4.043 x 10(11). Finally, the extent of polymer-induced particle aggregation is decreased when the diameter of the uncoated liposomes is doubled from 0.22 to 0.45 micron. These results are as expected, given the stiffness and the dimensions of the macromolecules.

Partial or complete circular duodenectomy with highly selective vagotomy for severe obstructing duodenal ulcer disease: an initial experience

OBJECTIVE

To evaluate partial and complete circular duodenectomy combined with highly selective vagotomy (HSV) for relief of gastric retention.

DESIGN

A retrospective, case-comparison study.

SETTING

University hospital referral center.

PATIENTS

Eighteen patients with severe obstructing duodenal ulcer disease defined by failure of a saline load test and endoscopic narrowing of the gastric outlet to 5 mm or less.

METHODS

In patients with severe obstructing ulcer the diseased duodenal segment was excised with electrocautery (partial excision, 10 patients; complete excision, 8 patients). An HSV was then done. Postoperative fasting gastric residuum measurement and measurement of the emptying of liquids and solids was done at 3 months and patients were weighed at 3 and 12 months.

RESULTS

No patient experienced postoperative gastric retention or required reoperation in a 2-year follow up. The early emptying of liquid (20 minutes) in complete circular duodenectomy plus HSV was more rapid than in normal subjects and duodenal ulcer patients. The emptying of solids was slightly delayed in partial duodenectomy plus HSV compared with duodenal ulcer patients but not with normal controls. The emptying of solids in duodenal ulcer patients was more rapid than in normal controls. Weight gain was excellent at 3 and 12 months.

CONCLUSION

Partial duodenectomy and complete circular duodenectomy plus HSV are more efficacious than alternative nonresective procedures in restoring gastric emptying to near normal and restoring weight in patients with obstructing duodenal ulcer.

Modified hemoglobin-based blood substitutes: crosslinked, recombinant and encapsulated hemoglobin

Native hemoglobin in the form of stroma-free hemoglobin cannot be used as blood substitute. Hemoglobin has to be modified either molecularly or encapsulated. First generation molecularly modified ultrapure hemoglobins are now in clinical trial--some in Phase III. There are a number of these. Polyhemoglobin is formed by crosslinking hemoglobin molecules intermolecularly and intramolecularly. A crosslinked single hemoglobin molecule is formed by crosslinking hemoglobin intramolecularly. Recombinant hemoglobin from E.coli is formed by fusion of the subunits of each hemoglobin molecule. Conjugated hemoglobin is formed by crosslinking each hemoglobin molecule to soluble polymers. A second generation system formed by crosslinking hemoglobin-superoxide dismutase-catalase is being developed. A third generation hemoglobin-based blood substitute is based on microencapsulated hemoglobin, artificial red blood cells, that more closely resemble a complete red blood cell.

Artificial cells with emphasis on bioencapsulation in biotechnology

The most common use of artificial cells is for bioencapsulation of biologically active materials. Each artificial cell can contain combinations of materials. The permeability, composition and shape of an artificial cell membrane can be varied using different types of synthetic or biological materials. These possible variations in contents and membranes allow for large variations in the properties and functions of artificial cells. Artificial cells containing adsorbents have been a routine form of treatment in hemoperfusion for patients. This includes acute poisoning, high blood aluminum and iron, and supplement to dialysis in kidney failure. Artificial red blood cell substitutes based on modified hemoglobin are already in Phase I and Phase II clinical trials in patients. Artificial cell encapsulated cell cultures are being studied for the treatment of diabetes, liver failure, gene therapy and other conditions. Research on artificial cells containing enzymes includes their use for treatment in hereditary enzyme deficiency diseases and other diseases. Recent demonstration of extensive enterorecirculation of amino acids in the intestine has allowed oral administration to deplete specific amino acids. One example is phenylketonuria, an inborn error or metabolism resulting in high systemic phenylalanine levels. Preliminary clinical studies in patients using bioencapsulation of cells or enzymes have started. Artificial cells containing complex enzyme systems convert wastes like urea and ammonia into essential amino acids. Artificial cells are being used for the production of monoclonal antibodies, interferon and other biotechnological products. Other areas of biotechnological uses include drug delivery, and other areas of biotechnology, chemical engineering and medicine.

Modulation of secretin release by neuropeptides in secretin-producing cells

Nerve fibers containing bombesin (BB)/gastrin-releasing polypeptide (GRP), pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal polypeptide (VIP), or galanin are known to innervate the mucosa of the upper small intestine. Both BB/GRP and PACAP have been shown to elicit secretin secretion in vivo. We studied whether the above-mentioned neuropeptides can act directly on secretin-producing cells, including the murine neuroendocrine cell line STC-1 and a secretin cell-enriched preparation isolated from rat upper small intestinal mucosa. Secretin release from both cell types was stimulated by various agents known to elicit secretin release and by the neuropeptides BB, GRP, and PACAP, suggesting a comparable response between the two cell preparations. The effects of neuropeptides were further studied in STC-1 cells. BB, GRP, and PACAP stimulated secretin release time and concentration dependently. VIP also stimulated secretin release concentration dependently. Stimulation by BB/GRP or PACAP was accompanied by elevation of inositol-1,4,5-trisphosphate (IP3) or cAMP, respectively. The stimulatory effect of PACAP on secretin release was synergistically enhanced by BB without any synergistic increase in IP3 or cAMP production, suggesting cross talk between different signal transduction pathways downstream of the production of these two second messengers. The L-type Ca2+ channel blocker diltiazem (10 microM) and the Ca2+ chelator EGTA (1 mM) significantly inhibited BB-stimulated secretin release by 64% and 59%, respectively, and inhibited PACAP-stimulated release by 75% and 55%, respectively. The protein kinase A-specific inhibitor Rp-cAMPS (100 microM) also inhibited both BB- and PACAP-stimulated secretin release by 30% and 62%, respectively. Galanin inhibited BB- and PACAP-stimulated secretin release and production of second messengers in a concentration-dependent and pertussis toxin-sensitive manner. These results suggested that the neuropeptides BB/GRP, PACAP, VIP, and galanin can modulate secretin release in secretin-producing cells and that STC-1 cells can serve as a useful model for studying the cellular mechanism of secretin secretion elicited by luminal secretagogues and neuropeptides.

Polyhemoglobin-superoxide dismutase-catalase as a blood substitute with antioxidant properties

Polyhemoglobin-superoxide dismutase-catalase is designed to function as an oxygen carrier with antioxidant properties. This is based on cross-linking hemoglobin with superoxide dismutase and catalase (PolyHb-SOD-CAT). This study describes the structural and antioxidant properties of this solution. Our studies show that superoxide dismutase and catalase retain their enzymatic activity following glutaraldehyde polymerization with 8:1 and 16:1 glutaraldehyde:hemoglobin ratio. We have analyzed the optimal SOD/CAT ratios to prevent oxidation of hemoglobin in the presence of oxygen free radicals. The circulation half-life of crosslinked hemoglobin, SOD, and catalase in Sprague-Dawley rats correlates with the degree of polymerization as determined by high-performance molecular weight gel filtration. PolyHb-SOD-CAT decreases the formation of oxygen radicals compared with PolyHb in a rat intestinal ischemia-reperfusion model.

Secretin inhibits gastric acid secretion via a vagal afferent pathway in rats

Secretin is an enterogastrone that inhibits gastric acid secretion and motility. Recently, it was reported that secretin inhibited gastric emptying via a capsaicin (Cap)-sensitive vagal afferent pathway. However, a possible role of the sensory afferent pathway in secretin-inhibited acid secretion has not been clarified. We investigated whether or not the acid secretion suppressed by secretin is modulated by a vagal and/or splanchnic afferent pathway in rats. Subdiaphragmatic perivagal (PV) or periceliac ganglionic (PCG) application of Cap (10 mg/ml) or vehicle was performed in both conscious and anesthetized rats 2 wk before experiments. Bilateral vagotomy was performed in some conscious rats 5 days before studies. Pentagastrin was administered intravenously at 0.6 microg . kg-1 . h-1. Secretin (20 pmol . kg-1 . h-1 iv) or 0.03 N HCl (4.32 ml/h id) was infused in conscious rats with gastric cannulas or anesthetized rats with ligation of the pylorus, respectively. A rabbit antisecretin serum was injected in some anesthetized rats before duodenal acidification. Secretin significantly inhibited pentagastrin-stimulated acid secretion by 63% (P < 0.01), which was abolished by both vagotomy and PV treatment of Cap in conscious rats. In anesthetized rats, duodenal infusion of 0.03 N HCl suppressed pentagastrin-induced acid secretion by 59.4% (P < 0.01), which was reversed not only by antisecretin serum but also by PV application of Cap. However, PCG treatment with Cap did not influence the inhibition by secretin or duodenal acidification in either awake or anesthetized rats. These results indicate that the inhibition by secretin of pentagastrin-stimulated acid secretion is mediated by a Cap-sensitive vagal afferent pathway but not via a splanchnic afferent pathway in rats.

Comparison of polymerically stabilized PEG-grafted liposomes and physically adsorbed carboxymethylchitin and carboxymethyl/glycolchitin liposomes for biological applications

The stabilities of two types of polymerically stabilized liposomes consisting of PEG-grafted (DSPC:CHOL:DSPE-PEG1900, 5:4:1) and physically adsorbed carboxymethylchitin (CMC) and carboxymethyl/glycolchitin (CO) are compared. The polyelectrolyte is adsorbed on positive (DSPC:CHOL:DMTAP, 5:4:1) and neutral (DSPC:CHOL, 1:1) liposomes at different molecular weights (Mw). In PBS buffer (c(s) = 154 mM, pH = 7.4) the theoretical stability ratios (W) calculated using the classical DLVO Theory, indicate that the CMC-coated vesicles and the negative liposomes (DSPC:CHOL:DMPG, 5:4:1) are highly stable (W >> 1) compared to the PEG-grafted (W = 0.9511) and CO-coated (W = 0.9550) liposomes. Meanwhile, experimentally determined values of W, prove that the PEG-grafted is the most stable suspension (W = 5.5). Computation of the theoretical values of W for liposome-red blood cell and liposome-macrophage indicates that the electrosterically stabilized suspensions and the negative liposomes are stable. Light scattering results show that the flocculation of liposomes in blood and plasma depends on polymer molecular weight, type of polyelectrolyte and surface charge of the uncoated liposome. Neutral liposomes coated with CMC of Mw = 1.01 x 10(5) and negative liposomes provide a more effective barrier to plasma macromolecular protein adsorption than the grafted PEG groups and are easy to resuspend in blood.

Preparation of polylactic acid microcapsules containing ciprofloxacin

Microcapsules have been used as drug delivery systems in the pharmaceutical field for sustained or controlled release of drug, and for artificial cells and organs. Biodegradable polymers, especially polylactic acid, have been widely used in this field. In this study, an attempt was made to develop a new method to prepare polylactic acid microcapsules for drug delivery. The biodegradable polylactic acid microcapsules were made by the phase separation process: two types of polylactic acid, poly[(D,L)lactic acid] and poly[(L)lactic acid] were combined as the membrane material. Because of the difference of the crystal properties of the two polymers, the aggregation which happens frequently in the phase separation process was prevented. As a model drug, Ciprofloxacin was encapsulated in the polylactic acid microcapsules.

Therapeutic uses of microencapsulated genetically engineered cells

Microencapsulated genetically engineered cells have the potential to treat a wide range of diseases. For example, in experimental animals, implanted microencapsulated cells have been used to secrete growth hormone to treat dwarfism, neurotrophic factors for amyotrophic lateral sclerosis, beta-endorphin to decrease pain, factor XI for hemophilia B, and nerve growth factors to protect axotomized neurons. For some applications, microencapsulated cells can even be given orally. They can be engineered to remove unwanted molecules from the body as they travel through the intestine, and are finally excreted in the stool without being retained in the body. This application has enormous potential for the removal of urea in kidney failure, ammonia in liver failure and amino acids such as phenylalanine in phenylketonuria and other inborn errors of metabolism.

Pituitary adenylate cyclase-activating peptide stimulates rat pancreatic secretion via secretin and cholecystokinin releases

BACKGROUND & AIMS

Pituitary adenylate cyclase-activating polypeptide (PACAP) stimulates protein and/or amylase secretion from isolated rat pancreatic acini. The effect of PACAP on pancreatic secretion in vivo and its mechanism of action were studied.

METHODS

Rats were prepared with pancreatic duct cannulation, pyloric ligation, and bile diversion into duodenum, and 2.5, 5, and 10 nmol/kg PACAP-27 was administered intravenously while pancreatic juice was collected for 30 minutes. In other groups of rats, the effect of 10 nmol/kg PACAP-27 was studied under the influence of either atropine; loxiglumide, an antisecretin serum; a combination of both loxiglumide and the antiserum; or a PACAP antagonist (PACAP 6-38). Plasma secretin and cholecystokinin concentrations were measured by radioimmunoassay.

RESULTS

(1) PACAP dose-dependently increased pancreatic secretion of fluid, bicarbonate, and protein; (2) the increase in pancreatic secretion paralleled that of plasma secretin and cholecystokinin; (3) a combination of loxiglumide and antisecretin serum eliminated the PACAP-stimulated pancreatic secretion, whereas loxiglumide or antisecretin serum alone partially but significantly blocked pancreatic secretion; (4) atropine failed to influence PACAP-induced pancreatic secretion; and (5) PACAP antagonist profoundly suppressed the PACAP action.

CONCLUSIONS

PACAP-27 dose-dependently stimulates pancreatic secretion of fluid, bicarbonate, and protein in rats. This effect is mediated by release of both secretin and cholecystokinin and is independent of cholinergic tone.

Absence of hemoprotein-associated free radical events following oxidant challenge of crosslinked hemoglobin-superoxide dismutase catalase

Crosslinking hemoglobin with superoxide dismutase and catalase (PolyHb-SOD-CAT) helps to limit free radical reactivity of modified hemoglobin red blood cell substitutes. In the present study, in vitro oxidant challenge experiments were performed with exogenous hydrogen peroxide (H2O2) and xanthine oxidase-derived superoxide (O2.-). PolyHb-SOD-CAT was compared to PolyHb for the presence of secondary hemoprotein-free radical events. PolyHb-SOD-CAT prevents ferrylhemoglobin formation, measured as Na2S-induced absorbance at 620 nm. Similarly, PolyHb-SOD-CAT inhibited ferrozine-detectable iron release at high oxidant-heme ratios. The formation of oxygen radicals, monitored by salicylate hydroxylation, was prevented at high oxidant-heme ratios with PolyHb-SOD-CAT. The peroxidation of liposomal membranes was also inhibited in PolyHb-SOD-CAT mixtures subject to oxidant challenge. These results show that PolyHb-SOD-CAT prevents secondary hemoprotein-associated free radical events. This new type of modified hemoglobin oxygen carrier with antioxidant activity may reduce the potential toxicity of hemoglobin-based substitutes in certain applications, especially during reperfusion of ischemic tissues.

Pharmaceutical and therapeutic applications of artificial cells including microencapsulation

Artificial cells for pharmaceutical and therapeutic applications started as microencapsulation on the micron scale. This has now expanded up to the higher range of macrocapsules and down to the nanometer range of nanocapsules and even to the macromolecular range of cross-linked hemoglobin as blood substitutes. This author first reported microencapsulation of biologically active material in 1957 (T.M.S. Chang, Hemoglobin corpuscles. Research Report for Honours Physiology, Medical Library, McGill University, 1957. (Also reprinted as part of 30th anniversary in Artificial Red Blood Cells Research, J. Biomater. Artif. Cells Artif. Organs 16 (1988) 1-9.) and 1964 (T.M.S. Chang, Semipermeable microcapsules, Science 146 (1964) 524-525). While pharmaceutical research has made use of these approaches for drug delivery, this author has been concentrating on the encapsulation of biotechnological products for therapeutic applications. Therefore, there was little interaction between the two approaches. In the last 10 years, pharmaceutical research, as in other areas of research, has become increasingly interested in biotechnology. Because of this interest, this article is a brief overview of developments of artificial cells for biotechnological products with emphasis on hemoglobin, enzymes, cells and genetically engineered microorganisms.

Evidence for the existence of CCK-producing cells in rat pancreatic islets

BACKGROUND

Although the existence of cholecystokinin-like immunoreactivity (CCK-LI) in rat pancreas had been reported previously, it was never clearly demonstrated whether CCK is produced in rat pancreatic islets.

AIMS

The purpose of this study was to elucidate the source of the CCK-LI, the molecular properties of CCK, and the expression of the CCK gene in islet cells.

METHODS

Immunohistochemical studies of rat pancreas were carried out with different rabbit antisera against CCK-8 and CCK-related peptide including N-terminal CCK-33 (1-22) and gastrin-17, and colocalization with known islet hormones including insulin, glucagon, somatostatin, and pancreatic polypeptide was investigated. The major molecular form of CCK in the islets was determined by HPLC. RT-PCR and in situ hybridization were performed to demonstrate the presence of the CCK transcript in the pancreas.

RESULTS

CCK-LI was found in the center of the islets, colocalized with insulin in B cells. The major molecular form of CCK in the islets was CCK-8. A 350-nucleotide fragment of PCR-amplified CCK cDNA was detected in the islet as well as the duodenum by RT-PCR. In situ hybridization showed that CCK messenger RNA was located in a large portion of the islets, and this was consistent with the immunohistochemical findings.

CONCLUSION

CCK messenger RNA and immunoreactivity are expressed in adult rat pancreatic islets, indicating that CCK-producing cells are present in adult rat islets.

Growth and survival of renal failure rats that received oral microencapsulated genetically engineered E. coli DH5 cells for urea removal

In our earlier reports we have introduced a new method for urea removal in renal failure. This is based on the oral administration of polymeric artificial cells containing nonpathogenic genetically engineered E. coli DH5 cells to renal failure rats. This resulted in the lowering of systemic uremic urea level to normal range without elevation of ammonia. The present article deals with the safety study of this approach. Microscopic study follows changes in microcapsule morphology with time are described. Two parameters, the body weight of the renal failure rats and, the survival for of the renal failure rats receiving microcapsules containing genetically engineered E. coli DH5 cells are discussed in this article. Result shows that there is no significant difference between the weight profile of uremic rats receiving oral therapy and normal control rats. Also the treated group of uremic rats survived longer than the untreated uremic rats.

Artificial cells and bioencapsulation in bioartificial organs

The most common use of artificial cells is for bioencapsulation of biologically active materials. Many combination of materials can be bioencapsulated. The permeability, composition and configurations of artificial cell membrane can be varied using different types of synthetic or biological materials. These possible variations in contents and membranes allow for large variations in the properties and functions of artificial cells.

Allelic loss at BRCA1, BRCA2, and adjacent loci in relation to TP53 abnormality in breast cancer

Cells with abnormal TP53 lose cell cycle checkpoints, resulting in genomic instability and neoplastic transformation. However, the evidence linking the tumor-specific targets of genomic alteration to an abnormal TP53 is limited. The present study tested the hypothesis that TP53 abnormalities are correlated with an increased frequency of deletion of breast cancer susceptibility loci (17q and 13q) in breast carcinomas. Tumors from 90 patients were examined for TP53 abnormality and loss of heterozygosity (LOH) at 11 loci on 17q (17q11.2-21) and 13q (13q12-14), including the loci for BRCA1 and BRCA2. A higher frequency of LOH was consistently found at 17q or 13q loci in tumors with an abnormal TP53. The increased LOH in relation to TP53 abnormality was statistically significant at the BRCA1, D17S588, and D13S267 loci (P < 0.05) but not at the locus for BRCA2 (P = 0.64). These observations imply a possible link between an abnormal TP53 and specific genomic deletions of breast cancer susceptibility loci, which may provide clues to the role of TP53 during breast tumorigenesis.

Cloning and sequence analysis of the gene (eprA1) encoding an extracellular protease from Aeromonas hydrophila

A gene (eprA1) encoding the extracellular protease of Aeromonas hydrophila AH1 has been cloned and sequenced. Nucleotide sequence analysis of eprA1 predicted a single open reading frame (ORF) of 1038 bp encoding a 346 amino acid (aa) polypeptide, with a potential 21-aa signal peptide. When the eprA1 gene was expressed in minicells, one major band of approx. 37 kDa was identified, while protease activity staining experiments identified a caseinolytic band of approx. 29 kDa determined by SDS-PAGE analysis of the minicells. The deduced C-terminal aa region (Arg-290 to Gly-313) showed sequence homology to partial C-terminal sequences of other zinc metalloproteases including Penicillium citrinum metalloprotease (PlnC), Aspergillus oryzae metalloprotease (NpII), Aspergillus flavus metalloprotease (MepA), and Aspergillus fumigatus metalloprotease (Mep20), particularly with respect to zinc-binding residues.

Cloning and sequence analysis of a novel hemolysin gene (vllY) from Vibrio vulnificus

A gene (vllY) encoding a novel hemolysin of Vibrio vulnificus CKM-1 has been cloned and sequenced. When the vllY gene was expressed in minicells, a unique peptide of approximately 40 kDa was identified. Subcellular fractionation of Escherichia coli cells carrying the vllY gene indicated that the VllY protein was distributed in both the cytoplasmic and the periplasmic fractions, with the notable ability to appear in the latter compartment. Nucleotide sequence analysis predicted a single open reading frame of 1,071 bp encoding a 357-amino acid polypeptide with an estimated pI of 5.02. The deduced amino acid sequence of VllY showed high similarity to the sequence of legiolysin, responsible for hemolysis, pigment production, and fluorescence in Legionella pneumophila. The enzyme also exhibited sequence homology to the MelA protein sequence of Shewanella colwelliana and the sequences of 4-hydroxyphenylpyruvate dioxygenase family proteins from various organisms. PCR screening and Southern blotting of V. vulnificus strains revealed that all of the 41 V. vulnificus clinical isolates contained vllY-like genes.

Mechanism of gastric acid hypersecretion in patients with islet cell tumor without hypergastrinemia: studies in rats

BACKGROUND & AIMS

A nongastrin acid-stimulating peptide (NGASP) has been found in ulcerogenic pancreatic tumor syndrome without hypergastrinemia. The mechanism of gastric acid hypersecretion by NGASP was investigated in rats.

METHODS

In vivo, gastric acid secretion and in vitro histamine release from enterochromaffin-like (ECL) cells in responses to tumor extract (TE) and synthetic human gastrin-17 I or pentagastrin (PG) were studied. Whether the 2 secretagogues potentiate each other was determined.

RESULTS

TE dose-dependently stimulated histamine release, which was not blocked by a cholecystokinin (CCK)-B receptor antagonist. When TE was incubated with trypsin, the activity was abolished but was not affected by antibody. However, when rats were pretreated with antigastrin serum or CCK-B receptor antagonist, the acid secretion by TE was virtually abolished. The dose response of acid secretion to TE in the rats receiving PG in a threshold dose was significantly greater than that achieved by TE alone. Similarly, the dose response to PG combined with a threshold dose of TE was significantly greater than that produced by PG alone.

CONCLUSIONS

NGASP stimulates histamine release from ECL cells, but the release is not mediated via CCK-B/gastrin receptor. NGASP and gastrin may potentiate each other to produce acid hypersecretion in ulcerogenic pancreatic tumor syndrome.

Mouse skin damage caused by a recombinant extracellular metalloprotease from Vibrio vulnificus and by V. vulnificus infection

Vibrio vulnificus wound infection is characterized by an intense acute cellulitis which spreads along the subcutaneous tissue with severe tissue destruction. Toxins produced by the bacteria appear to be involved in the pathogenesis of skin necrosis and to facilitate microbial dissemination in vivo. We report microscopic studies of mouse skin damage caused by a single intradermal injection of V. vulnificus or of an extracellular metalloprotease isolated from this organism. The gene encoding this metalloprotease has been cloned and expressed in Escherichia coli. The crude metalloprotease extract obtained from the periplasmic fraction by osmotic shock was used in this study. Intradermal injection of this preparation resulted in marked edematous changes of the skin, which extended throughout the dermis and subcutaneous tissues and into adjacent muscles. The collagen and elastic fibers degenerated and some muscle cells even appeared necrotic. Blood vessels became congested, with moderate perivascular neutrophil and mononuclear cell infiltration. There was no evidence of necrotic changes in the blood vessel itself. These results show that the damage to the connective tissues caused by V. vulnificus is at least partly attributable to its protease. Therefore, the protease seems to be an important virulence factor of this microbe.