Probing the phosphoinositide 4,5-bisphosphate binding site of human profilin I

BACKGROUND

Profilin is a widely and highly expressed 14 kDa protein that binds actin monomers, poly(L-proline) and polyphosphoinositol lipids. It participates in regulating actin-filament dynamics that are essential for many types of cell motility. We sought to investigate the site of interaction of profilin with phosphoinositides.

RESULTS

Human profilin I was covalently modified using three tritium-labeled 4-benzoyldihydrocinnamoyl (BZDC)-containing photoaffinity analogs of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). The P-1-tethered D-myoinositol 1,4,5-trisphosphate (Ins(1,4,5)P3) modified profilin I efficiently and specifically; the covalent labeling could be displaced by co-incubation with an excess of PtdIns(4,5)P2 but not with Ins(1,4,5)P3. The acyl-modified PtdIns(4,5)P2 analog showed little protein labeling even at very low concentrations, whereas the head-group-modified PtdIns(4,5)P2 phosphotriester-labeled monomeric and oligomeric profilin. Mass spectroscopic analyses of CNBr digests of [3H]BZDC-Ins(1,4,5)P3-modified recombinant profilin suggested that modification was in the amino-terminal helical CNBr fragment. Edman degradation confirmed Ala1 of profilin I (residue 4 of the recombinant protein) was modified. Molecular models show a minimum energy conformation in which the hydrophobic region of the ligand contacts the amino-terminal helix whereas the 4,5-bisphosphate interacts with Arg135 and Arg136 of the carboxy-terminal helix.

CONCLUSIONS

The PtdIns(4,5)P2-binding site of profilin I includes a bisphosphate interaction with a base-rich motif in the carboxy-terminal helix and contact between the lipid moiety of PtdIns(4,5)P2 and a hydrophobic region of the aminoterminal helix of profilin. This is the first direct evidence for a site of interaction of the lipid moiety of a phosphoinositide bisphosphate analog with profilin.

Indoor air quality and acute lower respiratory infection in Indian urban slums

The present prospective study was conducted at two urban slums of Delhi, Kusumpur Pahari and Kathputly Colony, in the peak winter season from November 1994 through February 1995. We studied 642 infants to determine the incidence of acute lower respiratory infection (ALRI) and its relationship to indoor air pollution due to fuel used for cooking (wood or kerosene). In Kusumpur Pahari, there were 317 children (142 wood and 175 kerosene), including 64 controls and 78 cases of ALRI in the wood fuel group and 81 controls and 94 ALRI cases in the kerosene group (p > 0.05). Out of 316 children in Kathputly Colony (174 wood and 142 kerosene), there were 33 and 45 ALRI cases in the wood and kerosene groups, respectively (p < 0.05). Controls were children without ALRI and were used as controls in different groups. The demographic data and risk factors, namely, nutritional and immunization status, were comparable in ALRI cases and controls in both study areas. Pneumonia was the most common ailment in all the groups. Bronchiolitis was reported in 22.5% of the wood group and 27.1% of the kerosene group in Kathputly Colony versus 13.7% in the wood group and 12.1% in the kerosene group in Kusumpur Colony. Only one case of croup was reported from Kusumpur Pahari among wood users. The duration of illness was longer in the Kusumpur Pahari due to poor compliance, feeding, and child rearing habits. In conclusion, a higher incidence of ALRI was reported in kerosene users in Kathputly Colony, a high pollution area; however, the reasons for the differences observed need further elucidation.

Specific interaction of Golgi coatomer protein alpha-COP with phosphatidylinositol 3,4,5-trisphosphate

The phosphoinositide binding selectivity of Golgi coatomer COPI polypeptides was examined using photoaffinity analogs of the soluble inositol polyphosphates Ins(1,4,5)P3, Ins(1,3,4,5)P4, and InsP6, and of the polyphosphoinositides PtdIns(3,4,5)P3, PtdIns(4,5)P2, and PtdIns(3,4)P2. Highly selective Ins(1,3,4,5)P4-displaceable photocovalent modification of the alpha-COP subunit was observed with a p-benzoyldihydrocinnamide (BZDC)-containing probe, [3H]BZDC-Ins(1,3,4,5)P4. A more highly phosphorylated probe, [3H]BZDC-InsP6 probe labeled six of the seven subunits, with only beta, beta', delta, and epsilon-COP showing competitive displacement by excess InsP6. Importantly, [3H]BZDC-triester-PtdIns(3,4,5)P3, the lipid with the same phosphorylation pattern as Ins(1,3,4,5)P4, showed specific, PtdIns(3,4,5)P3-displaceable labeling of only alpha-COP. Labeling by the PtdIns(4,5)P2 and PtdIns(3,4)P2 photoaffinity probes was less intense and showed no discrimination based on PtdInsPn ligand. Thus, both the D-3 and D-5 phosphates are critical for the alpha-COP-PtdIns(3,4,5)P3 interaction, suggesting an important role for this polyphosphoinositide in vesicular trafficking.

Specific binding of phosphatidylinositol 4,5-bisphosphate to calcium-dependent activator protein for secretion (CAPS), a potential phosphoinositide effector protein for regulated exocytosis

The calcium-dependent activator protein for secretion (CAPS) is a novel neural/endocrine-specific cytosolic and peripheral membrane protein required for the Ca2+-regulated exocytosis of secretory vesicles. CAPS acts at a stage in exocytosis that follows ATP-dependent priming, which involves the essential synthesis of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2). In the present studies, CAPS is shown to bind liposomes that contain acidic phospholipids and binding was markedly enhanced by inclusion of PtdIns(4,5)P2 but not other phosphoinositides in the absence of Ca2+. PtdIns(4,5)P2, but not other phosphoinositides including PtdIns(3, 4)P2 and PtdIns(3,4,5)P3, altered the susceptibility of CAPS to proteolysis by trypsin and proteinase K, suggesting that phosphoinositide binding promoted a conformational change. Photoaffinity labeling studies with a photoactivatable benzoylcinnimidyl acyl chain derivative of PtdIns(4,5)P2 confirmed the phosphoinositide-binding properties of CAPS and suggested a hydrophobic aspect of the interaction. CAPS, as one of very few characterized proteins with a binding specificity for 4-, 5-phosphorylated inositides over 3-phosphorylated inositides, may function in regulated exocytosis as an effector of PtdIns(4,5)P2.

Bile duct obstruction due to portal biliopathy in extrahepatic portal hypertension: surgical management

BACKGROUND

Varices can develop in and around the bile duct in the presence of portal hypertension, especially when it is caused by extrahepatic portal vein thrombosis. The term 'portal biliopathy' is used to describe changes in the bile duct due to these varices, which may cause bile duct obstruction. This paper reviews experience of the surgical management of patients with symptomatic portal biliopathy.

METHODS

Nine patients with extrahepatic portal vein obstruction with symptomatic portal biliopathy. were reviewed retrospectively.

RESULTS

Eight patients presented with jaundice, two had abdominal pain and one had recurrent cholangitis. Endoscopic retrograde cholangiography revealed abnormality of the bile duct wall, with stricture in eight patients and bile duct calculi in two. Portasystemic shunting relieved jaundice in five of seven patients, and in two a second-stage hepaticojejunostomy was required.

CONCLUSION

Symptomatic biliary obstruction in patients with extrahepatic portal hypertension may be relieved by a portasystemic shunt. Rarely biliary bypass may be required and is rendered safer by previous portasystemic shunting to decompress the pericholedochal varices. A direct approach to the biliary tract without a preliminary shunt may be hazardous and is frequently unnecessary.

Segment III cholangiojejunostomy for carcinoma of the gallbladder

Jaundice in patients of advanced carcinoma of the gallbladder requires palliation for the distressing symptoms of pruritus and cholangitis. Intrahepatic segment III duct cholangiojejunostomy is a means for alleviating the obstruction with malignant porta block. The authors reviewed their experience with this procedure in 48 patients of carcinoma of the gallbladder. All patients had jaundice; pruritus was present in 44 (92%) and cholangitis in 14 (29%). The level of obstruction was determined preoperatively by percutaneous transhepatic cholangiography. In 32 patients the block was below the level of the bifurcation of the right and left ducts, and 16 patients had a block involving the confluence, isolating the two lobes of the liver. Following segment III cholangiojejunostomy, pruritus was relieved in all and cholangitis in 86% of patients. At the end of 6 weeks a significant fall in serum bilirubin and alkaline phosphatase levels was seen with both types of hilar obstruction. Varying degrees of pain relief was also noted in 75% of patients. Segment III biliary bypass is an effective, one-time, reliable means of palliation for carcinoma of the gallbladder with hilar obstruction. Its efficacy appears to depend on the duration and depth of the jaundice and on the anatomy of the biliary ductal system in the left hemiliver rather than on the type of hilar obstruction.

Photoaffinity analogue for the anti-inflammatory drug alpha-trinositol: synthesis and identification of putative molecular targets

alpha-Trinositol (alpha T), or Ins(1,2,6)P3, is a semisynthetic inositol trisphosphate produced commercially by the partial degradation of phytic acid with phytase. The molecular targets mediating the mechanism of action of this novel anti-inflammatory, analgesic, and antivasoconstrictive drug are unknown. A new photoaffinity analogue, 4-[3H]BZDC-alpha T, has been prepared in which the [3H]-p-benzoyldihydrocinnamoyl ([3H]BZDC) photophore is tethered through an O-(5-aminopentanoyl) linkage to the 4-OH of alpha T. Photoaffinity labeling experiments with two human tissues, umbilical cord vascular smooth muscle cells and platelet membranes, revealed proteins that were selectively labeled by 4-[3H]BZDC-alpha T. Thus, co-incubation with alpha T but not with Ins(1,3,4,5)P4 during photolysis competitively displaced labeling of a 55 kDa platelet protein. In vascular epithelial cells, alpha T and Ins(1,3,4,5)P4 both displaced labeling of a 55 and 43 kDa proteins. The identification of putative protein targets for alpha T in smooth vascular tissue may have important implications in elucidation of the mechanism of action of this unusual drug.

Reoperative surgery for choledochal cysts

BACKGROUND

Complications often follow if a choledochal cyst is treated simply by drainage, either internal or external. This study reviews 17 patients who had had previous cystoenterostomy (n = 9) or external drainage (n = 8) and who required reoperation and cyst excision.

METHODS

The study was a retrospective review including ten women and seven men managed over 9 years. The indications for reoperation were stone formation (10 patients), pancreatitis (three), portal hypertension (two) and hepatic abscess (one); two patients were asymptomatic.

RESULTS

Definitive surgery with cyst excision was possible in all patients who had previously had external cyst drainage and in seven of nine who had had previous cystoenterostomy. There were no deaths. Two postoperative biliary leaks and two duodenal fistulas resolved spontaneously.

CONCLUSION

Excision of a choledochal cyst is possible and desirable even after a previous drainage operation. In severely ill patients with a complication of choledochal cyst, external drainage may be a preferable initial manoeuvre.

Surgical management of pancreatic necrosis presenting with locoregional complications

BACKGROUND

Local complications of pancreatic necrosis may occur after surgery, but when they occur spontaneously render surgical treatment more hazardous and impair prognosis.

METHODS

A retrospective review was carried out of 83 patients who underwent surgery for pancreatic necrosis from 1988 to 1995, to determine the incidence, type, treatment and outcome of locoregional complications caused by pancreatic necrosis associated with acute pancreatitis.

RESULTS

Seventeen patients (20 per cent) were identified to have intra-abdominal complications with pancreatic necrosis either before operation or at the time of surgery. The majority of patients had a delay in intervention (mean 46 days). At presentation ten of the 17 patients had one or more organ system failures. Fourteen patients had gastrointestinal tract involvement, two had involvement of the biliary tract and one patient had a splenic rupture. Six patients died.

CONCLUSIONS

In patients with pancreatic necrosis, development of locoregional complications is associated with a high mortality rate. The presence of gastrointestinal bleeding, peritonitis, jaundice or pneumoperitoneum in such patients suggests the presence of a complication of the necrotic process and should prompt early intervention. Early referral of patients with severe acute pancreatitis to specialized units may reduce the risk of locoregional complications.

Phosphoinositide binding specificity among phospholipase C isozymes as determined by photo-cross-linking to novel substrate and product analogs

We tested for the presence of high-affinity phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and PI(3,4,5)P3 binding sites in four phospholipase C (PLC) isozymes (delta1, beta1, beta2, and beta3), by probing these proteins with analogs of inositol phosphates, D-Ins(1,4,5)P3, D-Ins(1,3,4,5)P4, and InsP6, and polyphosphoinositides PI(4,5)P2 and PI(3,4,5)P3, which contain a photoactivatable benzoyldihydrocinnamide moiety. Only PLC-delta1 was specifically radiolabeled. More than 90% of the label was found in tryptic and chymotryptic fragments which reacted with antisera against the pleckstrin homology (PH) domain, whereas less than 5% was recovered in fragments that encompassed the catalytic core. In separate experiments, the isolated delta1-PH domain was also specifically labeled. Equilibrium binding of D-Ins(1,4,5)P3 to PLC-delta1 indicated the presence of a single, high-affinity binding site; binding of D-Ins(1,4,5)P3 to PLC-beta1, -beta2, or -beta3 was not detected. The catalytic activity of PLC-delta1 was inhibited by the product D-Ins(1,4,5)P3, whereas no inhibition of PLC-beta1, -beta2, or -beta3 activity was observed. These results demonstrate that the PH domain is the sole high-affinity PI(4,5)P2 binding site of PLC-delta1 and that a similar site is not present in PLC-beta1, -beta2, or -beta3. The data are consistent with the idea that the PH domain of PLC-delta1, but not the beta isozymes, directs the catalytic core to membranes enriched in PI(4,5)P2 and is subject to product inhibition.

Wells' syndrome

Eosinophilic cellulitis/Wells' syndrome is a rare dermatosis with erythematous, urticarial plaques that become more indurated and eventually have grey blue discoloration. The histopathology is distinctive, with a diffuse infiltrate composed predominantly of eosinophils but admixed with lymphocytes, histicytes and occasionally multinucleated histiocytes. There is dermal edema with so called "flame figures" that is composed of collagen focally enveloped with aggregates of eosinophilic granules. These collagen fibres may be surrounded by palisading histiocyes. The course is variable with waxing and waning and eventual spontaneous resolution.

Selective photoaffinity labeling of the inositol polyphosphate binding C2B domains of synaptotagmins

Synaptotagmin (Syt) II, a synaptic vesicle protein containing two copies of highly conserved protein kinase C homology regions known as the C2A and C2B domains, acts as a Ca2+ sensor and provides both phospholipid and inositol polyphosphate (IPn) recognition domains important in endo- and exocytosis. Four photoaffinity analogues of IP3, IP4, and IP6 containing a P-1- or P-2-linked 4-benzoyldihydrocinnamidyl (BZDC) photophore were used to label glutathione S-transferase (GST) fusion constructs of the Syt II-C2A and C2B domains. The P-2-linked [3H]BZDC-IP6 showed efficient, IP6-displaceable labeling of the GST-Syt II-C2B. The rank order of photocovalent modification paralleled the order of competitive displacement: IP6 (P-2-linked) > IP4 > IP3. The P-1-linked [3H]BZDC-IP6 failed to label the C2B domains. The GST-Syt III-C2B domain, which lacks IP6 binding affinity, also failed to undergo labeling by P-2-linked [3H]BZDC-IP6. When mixtures of the 32-amino acid basic peptide corresponding to the essential IPn binding region of the Syt II-C2B domain and GST-Syt II-C2B were labeled by a stoichiometric amount of P-2-linked [3H]BZDC-IP6, the two polypeptides showed equivalent affinity for the photolabel. Although the CD spectrum of this 32-mer at two pH values showed a random coil, the photoaffinity analogue of IP6 appeared to induce a binding-compatible structure in the short peptide.

Benzophenone photoprobes for phosphoinositides, peptides and drugs

Benzophenones (BP) and related aryl ketone photophores have become established as the photoactivatable group of choice for high-efficiency covalent modification of hydrophobic regions of binding proteins, including enzymes and receptors that recognize peptide hormones, (oligo) nucleotides and nucleosides, phosphoinositides, inositol polyphosphates and a wide variety of therapeutic molecules. This review presents the advantages of BP as photoaffinity labels and provides specific examples from the last 3 years of applications of BP-containing ligands used in biochemistry.

Erythroderma: a study of incidence and aetiopathogenesis

Thirty cases of exfoliative dermatitis (22 male and 8 female) were selected at random for study. In addition to routine history and clinical examination, investigations like histopathology of skin and lymph nodes, peripheral blood smear for abnormal cells and bone marrow examinations were done. Aetiologically, the cases could be classified into 4 categories namely exfoliation in per existing dermatoses, drug-induced exfoliation, idiopathic exfoliation and exfoliation secondary to internal malignancy. Two cases showed abnormal monocytoid cells (sezary cells) in peripheral blood smear.

Current trends in the diagnosis and management of cystic hydatid disease of the liver

Cystic hydatid disease caused by Echinococcus granulosus most commonly involves the liver. Recent years have seen many changes in modalities of diagnosis and treatment of cystic disease in the liver. Currently used methods of immunodiagnosis, newer radiological modes of imaging, emerging non-surgical techniques of management and the impact of minimal access surgery in this disease are highlighted in the present review.

Diagnosis and outcome of isolated rectal tuberculosis

PURPOSE

Segmental colonic tuberculosis commonly involves the ascending, transverse, or sigmoid colon. Rectal involvement in tuberculosis is uncommon and poorly characterized. This study describes the clinical presentation, endoscopic features, and outcome of isolated rectal tuberculosis.

METHODS

Isolated rectal tuberculosis was defined as focal lesions of the rectum in the absence of radiologically demonstrable lesions in the small and large bowel on barium contrast studies. Diagnosis of rectal tuberculosis was based on characteristic endoscopic appearance of lesions, histopathologic features of tuberculosis in biopsy/ resected material, and response to antitubercular therapy.

RESULTS

Eight patients with rectal tuberculosis were seen during a four-year period at our hospital. Hematochezia was the most common presenting feature (88 percent), followed by constitutional symptoms (75 percent) and constipation (37 percent). Rectal examination revealed a tight stricture within 10 cm of the anal verge in seven patients. Barium enema showed stricture of variable length, with focal areas of deep mucosal ulceration and increase in presacral space. Proctoscopic findings were tight stricture (7), nodularity with ulceration (6), and multiple aphthous ulcers (1). Granulomatous infiltration was detected in seven of eight patients in biopsy material obtained at endoscopy (6) or surgery (1). Cessation of hematochezia, resolution of constitutional symptoms, and weight gain were seen in all patients following treatment with antitubercular drugs.

CONCLUSION

Our data suggest that tubercular involvement of rectum, although uncommon, is an important cause of rectal strictures in India. Response to antitubercular chemotherapy is uniformly good, and surgery is seldom required in these patients.

Internal pancreatic fistulae with serous effusions in chronic pancreatitis

BACKGROUND

Serous effusions in chronic pancreatitis are infrequent but persistent. These occur usually as a consequence of internal pancreatic fistulae and commonly involve the pleural cavity or peritoneum.

METHODS

To assess strategies in operative management, the records of 12 patients who underwent surgery for internal pancreatic fistula with underlying chronic pancreatitis were reviewed retrospectively. Seven patients had pancreatic ductal calculi. Three cases underwent external drainage. Three cases with leaking pseudocysts underwent cystojejunostomy-en-Y. Three cases with ductal dilatation or calculi underwent lateral pancreaticojejunostomy and three patients had caudal pancreatectomy for distal disease.

RESULTS

Eight patients were completely controlled of all symptoms, with no sequelae. One case each had recurrent pancreatitis and ascites but did not require re-operation. There were two deaths: one with massive haematemesis and one with pre-existent multi-organ failure and sepsis.

CONCLUSIONS

Pancreatic duct stones may be causally associated with internal pancreatic fistulae. Delineation of ductal anatomy and pathological aberrations of the pancreas, including determination of the leak site, was of paramount importance in planning surgery. Peroperative ductography proved the most useful in this regard.

Choledochal cysts--differences in children and adults

Choledochal cysts in children and adults may behave differently. To identify these differences the records of 49 patients (22 children and 27 adults) who underwent surgery for choledochal cysts over a period of 7 years were analysed retrospectively. In two adult patients who had undergone a previous cholecystectomy an acquired malformation could not be excluded. Cholangitis was more common in adults. Choledochal cysts in children were predominantly Type I cystic lesions, whereas Type IV cysts were more common in adult patients. Anomalies of the pancreatic duct and associated hepatobiliary problems were seen exclusively in adults and the latter can make excision of the cyst more difficult and complicated. To prevent the development of complications choledochal cysts should be excised as soon as they are detected.

Coeliac artery aneurysm: a case report

Coeliac artery aneurysms are rare. A case of coeliac artery aneurysm treated successfully by endoaneurysmorrhaphy is presented. Although excision with arterial reconstruction is usually recommended, endoaneurysmorrhaphy can also be considered in selected cases.

Elective surgery for corrosive-induced gastric injury

Gastric cicatrization is a well recognized late sequela of corrosive gastric injury, but the optimum timing and type of surgery for this complication are still unclear. Over a 7-year period (1988-1994) 34 patients underwent elective surgery for gastric lesions secondary to corrosive ingestion. A total of 18 (53%) patients had an associated esophageal stricture and presented with dysphagia, 15 (44%) patients had features of gastric outlet obstruction, 6 (18%) had diffuse gastric injury, and 28 (82%) had a segmental lesion. A tube jejunostomy was done in 23 (68%) patients to improve nutrition and resulted in a significant increase in weight and in the serum protein level after 8 weeks of tube feeding. Elective surgery was performed 3 to 24 months (average 7 months) after ingestion of the corrosive substance. Gastric resection was done in 20 (59%) patients and gastrojejunostomy (without vagotomy) in 11 (32%); at follow-up the latter group did not exhibit development of a stomal ulcer. In patients with an associated esophageal stricture, endoscopic dilatation was successful in 89% patients and simplified the surgical approach. In conclusion, the success of surgery for corrosive-induced gastric injury depends on selecting the right procedure and intervening at the appropriate time.

Percutaneous catheter drainage in pancreatic pseudocysts

Percutaneous catheter drainage (PCD) was performed in 12 pancreatic pseudocysts in 11 patients. The procedure was performed under realtime ultrasound guidance adopting a direct transperitoneal approach in all cases. Complete cure was achieved in 9 (75%) of the Pseudocysts drained. Success rate was higher in pseudocysts not communicating with the main pancreatic duct (MPD), 7 of 8 (87.5%) as compared to those with ductal communication, 2 of 4 (50%). The mean duration of catheter drainage was 14.2 days in the first group while it was significantly longer, (42.5 days) in the latter group. No death or major complication related to the procedure was encountered in the study. A single pseudocyst got infected after catheter insertion but it was treated successfully with antibiotics. The follow up period was 3-18 months with a mean of 6.8 months. PCD failed in 2 pseudocysts communicating with MPD and associated strictures in the MPD. In one case having no communication with MPD the procedure failed because the cyst had thick debris which could not be drained properly. PCD may be a safe and effective therapy in the management of pseudocysts with best results in those not communicating with the MPD. Communicating pseudocysts, also having strictures in MPD, should not be subjected to PCD.

High affinity open channel block by dofetilide of HERG expressed in a human cell line

In the long QT syndrome, excessive prolongation of the cardiac action potential leads to polymorphic ventricular tachycardia (torsades de pointes) and sudden death. Mutations in HERG have been identified as one of the causes of the chromosome 7-linked form of congenital long QT syndrome. The biophysical properties of currents recorded from HERG expressing Xenopus oocytes are similar to those of a cardiac K+ current, I(Kr), but the characteristic nanomolar methanesulfonanilide sensitivity has not been demonstrated. To determine the biophysical and pharmacological properties of HERG under experimental conditions similar to those used to study native cardiac currents, we examined currents expressed after expression of HERG in a human cell line, human embryonic kidney 293. Transfected cells display K+-selective outward currents that activated at membrane potentials positive to -50 mV with strongly voltage-dependent kinetics [time constant (tau) = 2 sec at -20 mV and 188 msec at +20 mV]. Marked inward rectification was observed for depolarizations positive to +0 mV, which was due to rapid channel inactivation (tau = 6 msec at +50 mV). The subsequent tail currents at -40 mV displayed an initial rising phase with tau = 10 msec, followed by a slow multiexponential decline. The EC50 for the methanesulfonanilide I(Kr) blocker dofetilide was 12 +/- 2 nM. Induction of block depended on depolarization beyond the threshold for channel opening. Time-dependent block developed slowly, with tau = 5.2 +/- 0.6 sec (300 nM) at +10 mV, and was delayed by stronger depolarizations. This pattern suggested that dofetilide preferentially blocks open (or activated) channels and that the fast inactivation may competitively slow the binding kinetics. The latter occurrence was further supported by a simplified mathematical model that addressed the impact on binding kinetics of fast inactivation. These results indicate that the HERG gene product encodes an alpha subunit that, when expressed in mammalian cells, displays both the major functional and pharmacological properties of native I(Kr). Dofetilide acts as a slow-onset/slow-offset open channel blocker of this current at nanomolar concentrations.

Surgery in perforation after endoscopic sphincterotomy: sooner, later or not at all?

During a period of 8 years we managed ten patients with perforations resulting from endoscopic sphincterotomy. Four patients underwent operation within 24 h of the perforation, while six underwent operation later than 24 h. All the deaths and complications occurred in the latter group. Our experience underscores the importance of early diagnosis of perforation after endoscopic sphincterotomy and supports an aggressive surgical approach.

Purification and properties of levanase from Rhodotorula sp

Levanase, a slime dissolving enzyme of Rhodotorula sp., was purified to approx. 26-fold by ammonium sulphate precipitation, DEAE and gel filtration (Sephacryl S-200) chromatography. The molecular mass of the enzyme was 39 kDa. The purified levanase showed maximum activity at pH 6.0 and 40 degrees C. Enzyme was quite stable at 4 degrees C and at pH 5.5 to 6.5. Hg2+ at a level of 10 mM completely inhibited the levanase activity, while 2-mercaptoethanol at the same concentration showed a 2.93-times increase in activity. In addition to levan, the enzyme also showed substrate specificity towards inulin.

Functional differences in Kv1.5 currents expressed in mammalian cell lines are due to the presence of endogenous Kv beta 2.1 subunits

The voltage-sensitive currents observed following hKv1.5 alpha subunit expression in HEK 293 and mouse L-cells differ in the kinetics and voltage dependence of activation and slow inactivation. Molecular cloning, immunopurification, and Western blot analysis demonstrated that an endogenous L-cell Kv beta 2.1 subunit assembled with transfected hKv 1.5 protein. In contrast, both mRNA and protein analysis failed to detect a beta subunit in the HEK 293 cells, suggesting that functional differences observed between these two systems are due to endogenous L-cell Kv beta 2.1 expression. In the absence of Kv beta 2.1, midpoints for activation and inactivation of hKv1.5 in HEK 293 cells were -0.2 +/- 2.0 and -9.6 +/- 1.8 mV, respectively. In the presence of Kv beta 2.1 these values were -14.1 +/- 1.8 and -22.1 +/- 3.7 mV, respectively. The beta subunit also caused a 1.5-fold increase in the extent of slow inactivation at 50 mV, thus completely reconstituting the L-cell current phenotype in the HEK 293 cells. These results indicate that 1) the Kv beta 2.1 subunit can alter Kv1.5 alpha subunit function, 2) beta subunits are not required for alpha subunit expression, and 3) endogenous beta subunits are expressed in heterologous expression systems used to study K+ channel function.

Endoscopic biliary endoprosthesis for palliation of gallbladder carcinoma

BACKGROUND

Carcinoma of the gallbladder is a major cause of malignant obstructive jaundice in India. It usually presents at an advanced stage and endoscopic palliation is the mainstay of treatment. We prospectively studied our results with endoscopic stenting in patients with carcinoma of the gallbladder.

METHODS

Patients unfit for surgery were included in the study. Straight 10F plastic prostheses were placed endoscopically. Patients were assessed for procedure success, early and late complications, and stent patency.

RESULTS

The success rate of stent placement was 84% (27 of 32). The five failures were caused by an inability to pass the guide wire across the stricture. Relief of pruritus and reduction in jaundice was seen in 25 of 27 (92%) patients. Double stents were placed in three patients. Four patients (11%) developed cholangitis in the first 30 days. Stent occlusion was detected in four patients after longer follow-up. The 30-day mortality was 5 of 27 (18%). There were no procedure-related deaths.

CONCLUSION

Endoscopic endoprosthesis is a safe and relatively effective palliative measure for the majority of patients with unresectable carcinoma of the gallbladder.

Interactions among GYKI-52466, cyclothiazide, and aniracetam at recombinant AMPA and kainate receptors

We examined the actions of cyclothiazide, aniracetam, and 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine (GYKI-52466) on recombinant alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) and kainate receptors. Receptors expressed in Xenopus oocytes or human embryonic kidney 293 cells were characterized using voltage and patch-clamp electrophysiology. Aniracetam and cyclothiazide potentiated AMPA receptor currents by slowing or blocking desensitization. Cyclothiazide was more potent at receptors consisting of flip subunits compared with receptors consisting of flop subunits, whereas aniracetam appeared to be more efficacious at flop receptors. The potency of GYKI-52466 did not differ in heteromeric flip or flop containing AMPA receptors, but GYKI-52466 was less potent at homomeric GluRAi and GluRDi receptors. At heteromeric AMPA receptors, 50 microM cyclothiazide increased the IC50 value for GYKI-52466 significantly. The increase was largest in GluRBi/Di receptors where the IC50 value shifted from 21.9 microM (95% confidence interval, 12.0-39.8 microM) to 126 microM (95% confidence interval, 72.4-214 microM) in the presence of cyclothiazide. In contrast, 100 microM GYKI-52466 did not alter the EC50 of cyclothiazide at GluRBi/Di receptors nor did it markedly change the maximal potentiation induced by cyclothiazide. At GluRBi/Di receptors transiently expressed in human embryonic kidney 293 cells, 30 microM GYKI-52466 inhibited the steady state and the peak current evoked by 300 microns L-glutamate to the same extent (34.5 +/- 12% and 27.3 +/- 13.0%, respectively; five experiments), and GYKI-52466 did not alter the apparent rate of desensitization (tau = 15.7 +/- 4.7 and 17.5 +/- 8.3 msec in the absence and presence of GYKI-52466, respectively; five experiments). GYKI-52466 inhibited L-glutamate currents in the presence and absence of 10 microM cyclothiazide, but GYKI-52466 never restored the desensitization that was blocked by cyclothiazide. Furthermore, GYKI-52466 inhibited L-glutamate currents mediated by homomeric Glu6 receptors, which are not potentiated by cyclothiazide. Our data suggest that the effect of cyclothiazide on the affinity of GYKI-52466 for its binding site is allosteric and that the positive modulatory effect of cyclothiazide and the negative modulatory effect of GYKI-52466 result from binding to separate sites on recombinant subunits.

Disposition of lorazepam in diabetes: differences between patients treated with beef/pork and human insulins

The pharmacokinetics of lorazepam was examined in 10 male patients with insulin-dependent diabetes mellitus before and following treatment with neomycin and cholestyramine. Neomycin and cholestyramine were given in an attempt to block the enterohepatic circulation of lorazepam and so to permit an in vivo estimate of hepatic glucuronidation. The volume of distribution and clearance of free lorazepam in diabetic patients were not significantly different from the corresponding estimates in 14 normal controls. Neomycin and cholestyramine increased the clearance of lorazepam by 63% consistent with their effect in non-diabetic controls. However, patients on beef/pork insulin exhibited a greater than normal increase on this interupting regimen (125%), and had a significantly greater neomycin/cholestyramine cycling-interrupted clearance of lorazepam than either normal controls or patients on human insulin (15.4 vs. 6.96 and 7.87 ml.min-1.kg-1). The clearance was correlated positively and significantly with HbA1c and glycated proteins (fructosamine), but only in patients on human insulin. Thus, the pharmacokinetics of lorazepam was not altered in patients with insulin-dependent diabetes mellitus. However, it is possible that there are differences in the rate and extent of hepatic glucuronidation and enterohepatic circulation of lorazepam between patients treated with beef/pork and human insulins and between diabetics treated with beef/pork insulin and non-diabetic controls.

Course of severe ulcerative colitis in northern India

Thirty patients with severe ulcerative colitis were studied prospectively. Sixty percent (18/30) of severe ulcerative colitis were in remission after mean duration of 9.2 days (range 2-20 days) of intensive intravenous therapy without major side effects of steroids. Factors predicting poor response to medical therapy on admission are: stool frequency > or = 9 per day, pulse rate > or = 120/minute, temperature > or = 38 degrees C, Albumin < or = 2 gm, mucosal tags on plain x-ray abdomen and pancolitis.

Lipofuscin accumulation in neurons with restraint stress

Stress induced lipofuscinosis was studied in rat cerebellum. 3 month old wistar rats were subjected to restraint stress by keeping them immobile for 24, 48 and 72 hours duration. This was achieved in specially prepared cages which allowed no space for the rats to move; giving a stress to the animal. The cerebella from the stressed groups rats were removed after the experiment and were processed for fluorescent microscopical, histochemical and fluorimetric study of lipofuscin. The lipofuscin content in the Purkinje neurons was compared with that of the control rats which were of the same age, size and weight as of the experimental rats. The results showed that the lipofuscin content in the neurons of the experimental rats was more than that of the control ones. In gist, while 24 hrs. stress caused a 28.9% increase in lipofuscin content, 48 hrs. stress resulted in a 38.3% increase. This shows that restraint stress can be a good experimental model for lipofuscinogenesis and ageing studies.

Percutaneous transluminal balloon angioplasty in suprahepatic IVC obstruction--Budd-Chiari syndrome

Encouraging results of Transluminal Angioplasty for Budd-Chiari Syndrome due to obstruction of Suprahepatic inferior vena cava have been reported in the last decade. We present our experience with two such patients, treated with balloon dilatation producing dramatic clinical improvements and control of disease on follow-up.

Induction of mutations by replication of malondialdehyde-modified M13 DNA in Escherichia coli: determination of the extent of DNA modification, genetic requirements for mutagenesis, and types of mutations induced

The mutagenicity of the lipid peroxidation product, malondialdehyde (MDA), was measured in the lacZ alpha forward mutation assay using a recombinant M13 phage, M13MB102. Single-stranded M13MB102 DNA was reacted with MDA at neutral pH and the modified DNA was transformed into strains of Escherichia coli induced for the SOS response. Increasing concentrations of MDA led to an increase in lacZ alpha-mutations coincident with an increase in the level of the major MDA-deoxyguanosine adduct. Spontaneous and MDA-induced M13MB102 mutants were collected and the lacZ alpha target region was subjected to automated DNA sequence analysis. The most common sequence changes induced by MDA were base-pair substitutions (76%). Of these, 43% (29/68) were transversions, most of which were G-->T (24/29). Transitions account for 57% of the base-pair substitutions (39/68) and were comprised exclusively of C-->T (22/39) and A-->G (17/39). Frameshift mutations were identified in 16% of the induced mutants and were comprised of mainly single base additions occurring in runs of reiterated bases (11/14). The diversity of base-pair substitution and frameshift mutations induced by MDA at low levels of adduction suggests it may be an important contributor to endogenous mutagenesis and carcinogenesis in aerobic organisms.

Disposition of lorazepam in Gilbert's syndrome: effects of fasting, feeding, and enterohepatic circulation

The effects of fasting and feeding of a high-carbohydrate, low-fat diet on the glucuronidation and enterohepatic circulation (EHC) of lorazepam were examined in seven healthy men (age 18-30 years) and seven matched patients with Gilbert's syndrome. A simultaneous intravenous/oral dosing regimen was used, with half of each group receiving treatment with neomycin and cholestyramine (neo/chol) to block the EHC of the drug. Feeding increased the clearance of free lorazepam from 10.96 +/- 0.56 (mean +/- SD) to 14.11 +/- 1.21 mL/min/kg (P = 0.05) in patients with Gilbert's syndrome when examined in the presence of neo/chol. Clearances, on the other hand, decreased with feeding in control Gilbert's patients (7.61 +/- 0.54 versus 8.82 +/- 0.48 mL/min/kg), although the differences were not significant (P = 0.09). In contrast to both of these groups, feeding decreased lorazepam clearances (13.33 +/- 0.32 to 12.45 +/- 0.52 mL/min/kg, P = 0.17) in neo/chol-treated normals and increased clearances (9.95 +/- 1.84 to 12.38 +/- 2.05 mL/min/kg, P = 0.04) in control normals. Lorazepam clearances were also 20-40% lower in patients with Gilbert's syndrome compared with normals when studied fasting and with neo/chol, or fed and in the control state (P < 0.05 for both). Thus, the glucuronidation and EHC of lorazepam is sensitive both to diet and to the presence or absence of the Gilbert's trait.

Biosynthesis of 12(S)-hydroxyeicosatetraenoic acid by B16 amelanotic melanoma cells is a determinant of their metastatic potential

BACKGROUND

We have previously demonstrated that the metastatic potential of tumor cells can be increased by treatment with exogenous 12(S)hydroxyeicosatetraenoic acid [12(S)-HETE], a lipoxygenase metabolite of arachidonic acid. However, the biosynthesis of the authentic lipid mediator by tumor cells, and especially the correlation of its biosynthesis to tumor cell metastatic capacity have not been characterized. In addition, a role for other mono HETEs in influencing tumor cell metastatic behavior has been suggested, but conclusive evidence is lacking. In this study, we analyzed the biosynthesis of mono HETEs from arachidonic acid in tumor cells of different metastatic ability and correlated biosynthesis to metastatic potential.

EXPERIMENTAL DESIGN

The biosynthesis of mono HETEs by low and high metastatic subpopulations of B16 amelanotic melanoma (B16a) cells was analyzed by high performance liquid chromatography (HPLC). The identity of biosynthetic 12-HETE was confirmed by gas chromatography/mass spectrometry (GC/MS) and its stereochemical structure assigned by chiral phase HPLC. The effect of a lipoxygenase inhibitor on the biosynthesis of mono HETEs and its effect on metastatic behavior was examined.

RESULTS

HPLC analysis revealed that low (LM180) and high (HM340) metastatic B16a cells exhibited different profiles and efficiencies for conversion of arachidonic acid to mono HETEs. LM180 cells produced equal quantities of 12-HETE and 5-HETE. In contrast, HM340 cells synthesized predominantly 12-HETE and small amounts of 15-, 11- and 5-HETEs. At equal concentrations of substrate, four times more 12-HETE was synthesized by HM340 cells than by LM180 cells. The identity of biosynthetic 12-HETE was confirmed by gas chromatography/mass spectrometry and chiral phase HPLC demonstrated that it was the S enantiomer. The biosynthesis of 12(S)-HETE, but not other HETEs, was significantly inhibited by a lipoxygenase inhibitor, N-benzyl-N-hydroxy-5-phenylpentanamide. N-benzyl-N-hydroxy-5-phenylpentanamide, in a dose-dependent manner, decreased the adhesion of HM340 cells to murine pulmonary microvessel endothelium in vitro and lung colony formation in vivo. Furthermore, re-introduction of 12(S)-HETE, but not other mono HETEs, to HM340 cells pretreated with N-benzyl-N-hydroxy-5-phenylpentanamide, increased their adhesion to endothelium.

CONCLUSIONS

Biosynthesis of 12(S)-HETE by tumor cells is a determinant of their metastatic potential and inhibition of 12(S)-HETE biosynthesis in tumor cells may be a crucial target for intervening in metastasis.

Multiple-dose lorazepam kinetics: shuttling of lorazepam glucuronide between the circulation and the gut during day- and night-time dosing intervals in response to feeding

Lorazepam kinetics were examined in seven healthy males age 18 to 30 years after single- and multiple-dose lorazepam administration and in the presence and absence of neomycin and cholestyramine to block the enterohepatic circulation of the drug. Methods used a simultaneous i.v./p.o. dosing regimen with provision to measure lorazepam clearance during day- and night-time dosing intervals. The day-time steady-state clearance of free lorazepam measured 7.55 +/- 1.95 ml/min/kg (mean +/- S.D.) and was identical to that observed after single-dose administration (7.68 +/- 3.19 ml/min/kg). Neomycin and cholestyramine increased lorazepam clearances 5 to 45% (P < or = .05) as would be expected for interruption of an enterohepatic circulation and in keeping with previous observations under nonsteady-state conditions. Lorazepam clearances were the same during the day as during the night, except in the presence of neomycin and cholestyramine, where night-time clearances were significantly greater (10.16 +/- 3.52 vs. 8.77 +/- 2.43 ml/min/kg, P < or = .05). Urinary recoveries of lorazepam glucuronide, on the other hand, were greater during the day than during the night (114 +/- 11 vs. 77 +/- 15%, P < or = .05) and in all cases were greater than 100% of the administered dose for that interval. Thus, there is a diurnal variation in lorazepam elimination consistent with a fasting-induced increase in hepatic glucuronidation during the night. This, combined with the relative inactivity of the gut during this period, serves to trap the glucuronide and delay its transfer back to the systemic circulation and urine.

Histological and immunological analysis of gastric and intestinal lymphomas

Immunophenotyping of 28 gastrointestinal non-Hodgkin's lymphomas was done using specific antibodies. Twenty six of these were successfully classified using this technique.

Tubeless, drainless, short-stay cholecystectomy

Of 340 patients undergoing elective cholecystectomy for gallstone disease, 41 (12%) required an abdominal drain and 22 (65%) required a nasogastric tube postoperatively to control vomiting. Eighty six percent patients were discharged on the third post-operative day; 53% were satisfied with the early discharge. In our opinion, routine use of nasogastric tube and abdominal drain is not necessary and patients can be safely discharged on the third postoperative day after an uncomplicated cholecystectomy.

Devascularization following endoscopic sclerotherapy of oesophageal varices: dangers and difficulties

Twenty-three patients underwent devascularization operations for acute variceal bleeding. All had received endoscopic sclerotherapy, either long-term or just before surgery. The oesophagus and peri-oesophageal tissues showed either oedematous or fibrotic reaction depending on the number and duration of sessions of sclerotherapy. These changes in the oesophagus and surrounding tissues were responsible for intraoperative oesophageal perforation and postoperative anastomotic leaks. To obviate these problems, stapling of the anterior and posterior walls of the stomach was tried and found to be safer than stapled transection of the oesophagus. During follow-up, varices reappeared in over 75 per cent of patients and were managed by further sclerotherapy. Patients who did not receive sclerotherapy had a higher incidence of rebleeding.

Small bowel adenocarcinoma mimicking tubercular stricture. Role of enteroscopy in early diagnosis

We report a patient with high jejunal stricture initially thought to be tubercular in origin. There was, however, no response to antitubercular treatment and enteroscopic biopsy revealed it to be an adenocarcinoma. This case illustrates the role of enteroscopy and biopsy in the definitive diagnosis of high small bowel strictures.

Giant perforations of duodenal ulcer

Over a period of eleven years, eight patients were treated for duodenal ulcer perforation measuring more than one centimetre in diameter. In five of these patients, the perforation was sealed using a jejunal loop as serosal onlay patch; one patient underwent gastrectomy and in two patients catheter duodenostomy was done. Two patients died, both due to renal failure. The six surviving patients were discharged with the advice for a subsequent 'ulcer-curing' operation after six months. Two patients developed life threatening complications during this waiting period and one of these died. Giant perforations of duodenal ulcer can safely be closed using a jejunal loop as serosal patch. Delay in doing the second stage definitive surgery for the ulcer may be dangerous.

Post-cholecystectomy syndrome due to a broken T-tube

Breaking of a biliary T-tube during removal is unusual. One such case who presented with features of post-cholecystectomy syndrome is presented.

Colonoscopic polypectomy. North Indian experience

Colonoscopic snare polypectomy was carried out in 70 patients (40 children, 30 adults). There was a male preponderance in both the groups with a combined male: female ratio of 4.4:1. The majority of patients (85%) were aged 20 years or below. All patients presented with intermittent bleeding per rectum, ranging from 2 months - 6 years (mean 1.2 +/- 1.1 years) in children and 1-14 years (1.9 +/- 2.3) in adults. The majority of patients polyps were located in the rectum (73%) or in the rectosigmoid region (21%). Polyps were significantly more common in the rectum (80% vs 63%; P less than 0.01) and less frequent in the rectosigmoid (15% vs 30%; p less than 0.01) in children as compared to adults. A single polyp was present in 49 (70%) patients; 17 (24%) had 2-10 polyps, while 4 patients (2 children, 2 adults) had more than ten polyps. Most patients (94%) had polyps of less than 2 cm size. Histologically, the most polyps (91.5%) were of the juvenile variety; 39 (97.5%) children and 25 (83%) adults had this variety of polyp. The remaining 5 (17%) adults and one (2.5%) child had adenomatous polyps. The difference in the polyp histology between the two age groups was statistically significant (p less than 0.05). Only one patient (1.4%) had excessive bleeding following polypectomy. The present study suggests two important differences in the nature of polyps as compared to the West: 1) our patients were much younger, and polyps were rare after 40 years; and (2) histologically, the commonest polyps were of the juvenile variety (91.5%) while adenomatous polyps were rare (8.5%).

Choledocho-duodenal fistula due to tuberculosis

An unusual case of caseating nodal tuberculosis causing a choledocho-duodenal fistula is reported. Anti-tubercular treatment led to closure of the fistula.