Effect of transient overexpression of Gq alpha on soluble and polymerized tubulin pools in GH3 and AtT-20 cells

In order to study Gq-tubulin interaction in the cytosol, GH3 and AtT-20 cells (stably expressing TRH receptor) were transiently transfected with Gq alpha cDNA. Forty-eight hours after transfection, thyrotropin-releasing hormone (TRH)-stimulated prolactin (PRL) secretion by Gq alpha-transfected GH3 cells increased by 90% compared to mock-transfected cells. In addition, using immunocytochemistry it was observed that Gq alpha-specific staining was much more prominent in Gq alpha-transfected GH3 and AtT-20 cells (also transfected with Gq alpha) compared to mock-transfected cells. Thus, transfection resulted in successful overexpression of functional Gq alpha. Forty-eight hours after transfection, cells were processed to obtain soluble and polymerized tubulin fractions. Tubulin levels were determined in these fractions by immunoblotting using polyclonal anti-tubulin antibodies. Compared to mock-transfected cells soluble tubulin levels decreased in Gq alpha-transfected GH3 and AtT-20 cells, by 33 and 52%, respectively. Moreover, compared to mock-transfected cells a 50% reduction in the ratio (an index of the flux between tubulin pools) of soluble and polymerized tubulin levels was observed in Gq alpha-transfected GH3 and AtT-20 cells. To determine whether these effects on tubulin were mediated by Gq directly, we examined the influence of purified Gq on tubulin polymerization. Gq (0.5 microM) inhibited polymerization of crude tubulin (present in GH3 cell cytosol) by 53%. In contrast to its effects on GH3 cell cytosol tubulin, Gq stimulated purified tubulin polymerization by 160%. These results suggest that Gq modulates the polymerization and depolymerization cycles of tubulin and that this modulation is in turn influenced by other unknown cellular components.

Effect of colchicine and taxol on thyrotropin-releasing hormone receptor coupling to G protein in GH(3) cells

The role of membrane-associated tubulin in TRH receptor-G protein coupling was investigated with the use of compounds that influence tubulin function. TRH-stimulated G protein GTPase activity in GH(3) cell membranes was used to determine receptor-G protein coupling. TRH-stimulated GTPase activity was abolished by G(qα) antibody, suggesting that TRH receptor coupling to G(q) results in the activation of G(qα) and the subsequent hydrolysis of GTP. TRH (1 μM) stimulated the enzymatic activity by up to 69 pmol/min/mg protein, and in the presence of 1 μM colchicine the hormone-stimulated activity was only 26 pmol/min/mg protein. Similar inhibition of TRH receptor-G protein coupling was observed with tubulin antibodies and purified tubulin, suggesting that perturbation of membrane-associated tubulin and/or tubulin-G protein interaction by these compounds disrupts receptor-G protein interaction. Next, the events occurring at the initial stages of TRH-mediated signal transduction were correlated to prolactin (PRL) secretion in GH(3) cells. Colchicine (1 μM) and taxol (1 μM) inhibited the basal PRL secretion by 38 and 44%, respectively. In addition, colchicine (1 μM) and taxol (1 μM) significantly inhibited TRH-stimulated PRL secretion. TRH-stimulated PRL secretion in control, colchicine-, and taxol-treated cells was 13.9, 9.1, and 6 ng/mL, respectively. Furthermore, polymerized tubulin levels were decreased by colchicine and increased by taxol. These results suggest that perturbation of the steady state of tubulin-G(q) interaction may disrupt the initial events in TRH-mediated signal transduction.

Endoscopic findings and overtube-related complications associated with esophageal variceal ligation

Esophageal variceal ligation (EVL) has emerged as a popular alternative to endoscopic sclerotherapy (ES), with equal efficacy as ES in control of active bleeding, rebleeding rate, and variceal eradication. The complication rate for EVL has been reported lower than for ES in several clinical trials. However, several unique complications inherent to EVL have been recognized. Overtube injury to the pharynx and proximal esophagus has been the most serious complication. Transient vocal cord paralysis, cricopharyngeal perforation, proximal esophageal laceration, varix rupture, and free esophageal perforation have also been reported. Direct banding-induced complications have been limited to rebleeding from banded ulcers, transient esophageal obstruction, and simple strictures. Pulmonary as well as serious systemic complications have yet to be reported. We report four complications of EVL, review the literature, and suggest strategies for the recognition, management, and prevention of EVL complications.

Vinblastine and nocodazole inhibit basal and thyrotropin-releasing hormone-stimulated prolactin secretion in GH(3) cells

To investigate the efficacy of vinblastine as a possible therapeutic agent in prolactinomas, we have examined the effects of vinblastine on GH(3) cell function. The effects of vinblastine were compared to another anti-microtubule drug, nocodazole. At 24 h, prolactin (PRL) secretion was 737±63 ng/ml in control cells. In cells treated with 0.1, 1 and 10μM: nocodazole for 24 h, PRL secretion was reduced to 200±30 ng/ml. After a 24 h incubation with the drugs, cells were washed with drug-free medium and challenged with 100NM: TRH for 10 min. TRH-stimulated PRL secretion was 35±7 ng/ml in control cells, 14±0.5 ng/ml in vinblastine-treated cells and 8.8±0.1 ng/ml in nocodazole-treated cells. [(3)H]TRH binding to GH(3) cell membrane was inhibited by about 15% by vinblastine and nocodazole. In vinblastine and nocodazole treated cells, polymerized tubulin levels decreased by 46 and 55%, respectively. These observations that vinblastine suppresses PRL secretion by GH(3) cells suggest that this drug might be useful as a therapeutic agent for prolactinomas.

Effect of thyrotropin-releasing hormone on microtubules in GH3 cells

The effect of thyrotropin-releasing hormone (TRH) on the tubulin-microtubule system in GH3 cells was investigated. Prolactin (PRL) secretion by GH3 cells was stimulated by TRH at 1, 5, and 10 min of incubation. The polymerized tubulin levels increased from 0.4 units micrograms-1 protein in control cells to 0.6 units micrograms-1 protein in cells incubated with TRH for 1 min. Soluble tubulin levels increased from 0.8 units microgram-1 protein in control cells to 1.2 units micrograms-1 protein in cells exposed to TRH for 5 min. Tubulin levels were similar in control cells and cells treated with TRH for 10 min. These results suggest that TRH-stimulated PRL secretion is accompanied by a shift in the equilibrium between tubulin pools.

Membrane-associated tubulin in the rat anterior pituitary and GH3 cells

Plasma membranes from anterior pituitary lobes of rats and GH3 cells were exposed to monoclonal anti-beta tubulin antibodies or normal mouse IgG, and treated with FITC-labeled anti-mouse IgG. Specimens were visualized with a microscope equipped with epifluorescence optics. Tubulin-specific fluorescence was very prominent in membranes incubated with tubulin antibody and was negligible in membranes incubated with normal mouse IgG or FITC-labeled anti-mouse IgG alone. Two dimensional electrophoresis revealed that 27% of the rat pituitary tubulin is beta-tubulin and 73% is alpha-tubulin; 17% of the GH3 cell tubulin is beta-tubulin and 83% is alpha-tubulin. These results suggest that tubulin is a component of plasma membranes of the rat pituitary and GH3 cells.

Gastrointestinal manifestations of amyloidosis: a case of diverticular perforation

Amyloidosis is an intriguing disorder. Its clinical presentation usually rests on the organ(s) infiltrated with the amyloid. We report a patient who presented with peritonitis secondary to a perforated large jejunal diverticulum and multiple small bowel diverticula. We believe the diverticula were a direct result of primary amyloid infiltration of the intestine in the antimesenteric location. This is the first reported case of small bowel diverticula caused by amyloidosis.

Lens GSH depletion and electrolyte changes preceding cataracts induced by buthionine sulfoximine in suckling mice

Cataracts were induced in suckling mice by multiple injections of L-buthionine-S,R-sulfoximine (BSO), a specific inhibitor of GSH biosynthesis, starting on post-natal day 7. The earliest visible lens aberrations began approximately 2 days after t(o), following 99% depletion of lens GSH. Cataract development then proceeded through four stages within less than 24 hr. Elevated Na+ and Ca+ and decreased K+ were first detected in pre-cataractous (stage 0) lenses. During stage 0, lens Na+ and K+ levels displayed a significant inverse correlation; by contrast, Ca2+ levels were poorly correlated with those of Na+. The initial increase in Na+ exceeded the decrease in K+. This suggested the presence of osmotic stress prior to cataract stage 1 (developing floriform). Increased lens hydration was first apparent in stage 1, coincident with a marked elevation of Ca2+, further increase in Na+ and decrease in K+. These trends persisted in the stage 2 cataract (completed floriform). Subsequent changes in lens hydration and cation content during cataract stages 3 (degenerate floriform) and 4 (amorphous translucent) suggested substantial influx of extracellular fluid into the affected lenses. The BSO cataract may represent a useful in vivo model to study the functions of GSH in maintaining normal lens cation balance and transparency.

Progressive modifications of mouse lens crystallins in cataracts induced by buthionine sulfoximine

L-buthionine-S,R-sulfoximine (BSO), a specific inhibitor of GSH biosynthesis, was administered four times daily to mouse pups on post-natal days 7 and 8, inducing initiation of opacification on day 9. The initial progression of the cataract (less than 24 hr) was divided into four stages: (1) developing floriform; (2) mature floriform; (3) degenerate floriform; and (4) amorphous translucent cataract. Following this, dense corticonuclear opacities developed within several days. Two-dimensional gel electrophoresis of water-soluble whole lens extracts indicated that the most rapid early cataractous changes, occurring mainly during stage 2, were loss of the two major components of the heavy beta-crystallin fraction, a 31-kDa basic polypeptide and an acidic component at 27 kDa, concomitant with the appearance of new species at 30 and 25 kDa. This was followed by more extensive modification of both alpha and beta-crystallins during stages 3 and 4 and the appearance of abnormal species at 26, 19 and 18 kDa, which were slightly more acidic than the major normal alpha A-crystallin polypeptide. The gamma-crystallin components, relatively unaffected at stage 4, were then lost rapidly as dense opacities ensued. By contrast with the water-soluble fraction, the normal day 9 urea-soluble fraction was deficient in gamma-crystallin polypeptides and enriched in anodic components whose relative electrophoretic mobilities were similar to those reported previously for phosphorylated bovine alpha A-crystallin and several cytoskeletal polypeptides. At stage 4 of the cataract, the modifications of normal alpha and beta-crystallin components in the urea-soluble fraction paralleled those in the water-soluble fraction, but the products seen were more numerous. In addition, the cytoskeletal proteins were no longer detectable. Substantial increases in lens Ca2+ that precede all of the above changes in lens polypeptide composition suggest that Ca(2+)-activated proteolysis may play a major role in development of BSO cataracts.

Trichosporon cholangitis associated with hyperbilirubinemia, and findings suggesting primary sclerosing cholangitis on endoscopic retrograde cholangiopancreatography

Usually, ascending cholangitis is a bacterial process. However, in the debilitated or immunocompromised patient, mycotic cholangitis must be placed in the differential diagnosis. We report a patient with cryptogenic cirrhosis whose presenting problem in his terminal hospitalization was spontaneous bacterial peritonitis, for which he was treated with broad-spectrum antibiotics. Endoscopic retrograde cholangiopancreatogram was performed during the hospital course to explain his profound hyperbilirubinemia. The findings were grossly consistent with primary sclerosing cholangitis or cholangiocarcinoma. The patient subsequently continued to deteriorate, and died with hepatic and renal failure. At autopsy, he was found to have choledocholithiasis, marked biliary duct proliferation, and ascending cholangitis, with Trichosporon demonstrated histologically to be invading the bile ducts. To our knowledge, this is the first reported case of Trichosporon cholangitis.

Role of colonoscopy in gallstone ileus:--a case report

This paper reviews the role of colonoscopy in large-bowel obstruction by a gallstone. We report the case of an elderly female with a cholecystocolonic fistula who had a large-bowel obstruction caused by a gallstone that migrated to the level of narrowing in the large bowel. After multiple attempts at removal of the stone with a snare and basket retriever, the patient was taken to the operating room and the stone was removed. Colonscopy in these circumstances can be diagnostic and possibly therapeutic.