Biomedical subjects

H Chokshi

Publications and source records attributed to H Chokshi.

6 recordsLinked to original sources

PubMed1999

Endoscopic hemostasis in acute diverticular bleeding.

BACKGROUND AND STUDY AIMS: Early reports of urgent colonoscopy in acute lower intestinal bleeding suggest a role for endoscopic therapy for bleeding colonic lesions, but scant data exist on bleeding diverticula. We report our experience with endoscopic hemostasis in acute diverticular bleeding. PATIENTS AND METHODS: Bleeding diverticula were identified on urgent diagnostic endoscopy in five patients with acute gastrointestinal bleeding, two in the duodenum, and three in the colon. All patients had co-morbid conditions preventing more conventional therapeutic approaches. The five cases are described, including the technique of endoscopic hemostasis and outcome. RESULTS: Endoscopic therapy using epinephrine injection, thermal cautery and/or laser therapy successfully induced hemostasis in all patients. One patient died of co-morbid illness during the hospital stay, while the remaining four patients had no recurrent bleeding over a mean follow-up period of 20.6 months. CONCLUSION: Endoscopic therapy of bleeding diverticula is technically possible when the culprit diverticulum can be identified. This therapeutic modality may have a place in debilitated patients in whom other more invasive procedures are contraindicated, but further experience is needed to establish its safety.

Acute Disease↗

PubMed1996

Endoscopic management of bile duct leaks after attempted laparoscopic cholecystectomy.

Fourteen patients with symptomatic bile duct leaks following laparoscopic cholecystectomy were treated using endotherapeutic techniques. Patients presented with abdominal pain, liver test abnormalities, jaundice, leukocytosis, and fever. Twelve leaks originated from cystic duct stumps and two from right posterior hepatic ducts. Distal biliary obstruction, which may have promoted leakage, was present in five patients. Treatment methods included stent insertion with endoscopic sphincterotomy (ES), stent insertion without ES, and nasobiliary tube (NBT) placement without ES. Eleven of 14 patients had prompt resolution of their bile leaks following initial endotherapy. Three patients with continued leakage underwent successful repeat endoscopic retrograde cholangiopancreatography 4-5 days after the initial examination. Cholangiographic evidence of leak closure was documented in all patients, and all remained asymptomatic during an average follow-up period of 18.5 months. Endoscopic therapy is safe and effective treatment for clinically significant bile leaks following laparoscopic cholecystectomy. In our small group of patients, NBT alone did not appear to be as effective as endoprostheses with or without ES. The ideal endoscopic treatment method has not yet been established but will likely vary depending on the site and specific nature of the injury and any concomitant biliary ductal pathology.

Adult↗

PubMed1992

The intrinsic factor (IF)-cobalamin receptor binding site is located in the amino-terminal portion of IF.

Intrinsic factor has two binding sites, one each for cobalamin and for the ileal receptor recognizing the intrinsic factor-cobalamin complex. To obtain initial functional mapping of these domains, cDNAs encoding intact rat and human intrinsic factor or fragments thereof were expressed transiently in COS-1 cells or in an in vitro transcription/translation system. Deletion of as little as 12% of the amino acids from the carboxyl terminus resulted in loss of cobalamin binding activity. On the other hand, the receptor binding region of intrinsic factor appears localized to a restricted region in the amino-terminal portion of the protein. Only those transcription/translation fragments of rat or human intrinsic factor tested that contained amino acid residues 25 to 62 (out of 399) showed calcium-dependent binding to isolated kidney brush borders, the shortest sequence corresponding with 20 consecutive amino acids. In contrast, a 232-amino acid carboxyl-terminal fragment of rat intrinsic factor and 243- and 338-amino acid carboxyl-terminal fragments of human intrinsic factor showed no receptor binding activity.

Animals↗

PubMed1992

In vitro expression and secretion of functional mammalian intrinsic factor using recombinant baculovirus.

Intrinsic factor was produced at levels of 1-2 mg per 1 (0.25 micrograms per 10(6) cells) by growth of recombinant baculovirus-infected Sf9 cells in spinner culture. The recombinant IF showed a binding affinity for cobalamin (2.6.10(-10) M) and for the intrinsic factor-cobalamin receptor (3.5.10(-10) M) nearly identical with native IF. Purification of the recombinant intrinsic factor could be accomplished by affinity chromatography, but final purification by gel chromatography (FPLC) was necessary to separate intrinsic factor from a 62 kDa protein secreted from uninfected Sf9 cells. This protein binds selectively to the cobalamin-Sepharose column, but demonstrates no cobalamin binding activity after elution. Microgram quantities of radiolabelled protein could be produced for metabolic and autoradiographic studies. The stability of intrinsic factor to pancreatic proteinases was nearly identical with human gastric intrinsic factor, both native and recombinant as produced in mammalian cells. Glycosylation of the intrinsic factor was demonstrated by lectin binding to the recombinant protein separated on SDS-PAGE, and by a shift in apparent molecular mass from 47 kDa to 43 kDa following treatment of Sf9 cells with tunicamycin. Most of the recombinant IF was produced by Sf9 cells in the first 48 h post infection.

Animals↗

PubMed1991

Glycosylation is not required for ligand or receptor binding by expressed rat intrinsic factor.

A cDNA clone encoding rat intrinsic factor (IF), pIFQ, has been inserted into the eukaryotic expression vector pSVL and used to transfect COS-1 cells. The IF produced by the transfected cells was secreted nearly exclusively into the medium at concentrations of 0.1-0.2 micrograms/ml. Tunicamycin treatment (1-10 micrograms/ml) completely blocked N-linked glycosylation but had no effect on IF secretion. The secreted glycosylated IF retained all the properties of native IF, i.e., high affinity for cobalamin (Cbl) and for the IF-Cbl receptor and relative resistance to low pH and to proteolysis. The nonglycosylated IF also retained these properties except that it was more protease sensitive. The protease degradation was prevented by the presence of the ligand Cbl. The presence of carbohydrate may play a role in protecting IF from digestion by pancreatic proteases in the intestinal lumen.

Animals↗

PubMed1990

Chemiluminescence: a sensitive and versatile method for analyte detection.

The generation of light from the oxidation of oxalic esters with hydrogen peroxide has been applied to the detection of luminescent materials. In order to improve the efficiency of this method, which is less than 0.1%, and to enhance the selectivity for target analytes, an in-depth investigation of the oxalate ester-hydrogen peroxide reaction has been conducted. A kinetic model has been developed based on the effects of catalysts, reagents and reaction conditions for maximum light production. Application of the model to liquid chromatography through the "time-dependent emission window" concept affords a predictable maximum sensitivity for selected analytes. Application to the detection and quantitation of met- and leu-enkephalins which have been labelled with naphthalene-2,3-dicarboxyaldehyde/cyanide provides support for this methodology. Other bioanalytical applications are presented.

Humans↗