Inside-out vein graft repair compared with nerve grafting for nerve regeneration in rats

The inside-out vein graft is a vein conduit pulled through itself to invert the normal orientation and place the adventitial layer within the lumen of the conduit. Our study compares regeneration of peripheral nerves in the rat through two conduits: inside-out graft of the jugular vein and autogenous nerve graft. In 10 rats, the right jugular vein was harvested, turned inside out, and used to bridge a 10 mm defect created in the right sciatic nerve. The 10 mm nerve segment from the right was then used as a standard nerve graft to bridge a 10 mm gap created in the left sciatic nerve. Rats were sacrificed at 8 and 12 weeks. Regeneration on the inside-out vein graft side showed superior functional results (faster conduction velocities) and improved histological results (greater axon counts) compared with the nerve grafted side. We feel the adventitial surface of the wall of the vein promotes nerve regeneration by providing an environment rich with collagen, laminin, and Schwann cells and promotes increased vascularization of the new nerve.

Apoptosis occurs in lymphoma cells but not in hepatoma cells following ionizing radiation and photodynamic therapy

The aim of this study was to determine the relative role of apoptosis in photodynamically-induced cytotoxicity or radiation-induced cytotoxicity for hepatoma and lymphoma cells. Human hepatoma cells and mouse lymphoma cells were treated with either photodynamic therapy (PDT) or ionizing radiation. Dosimetry studies of immediate cell death following photodynamic therapy in the hepatoma cell line demonstrated second-order kinetics, similar to that seen in the lymphoma cells. No immediate cell death was noted in the hepatoma or lymphoma cells following ionizing radiation, but experiments measuring delayed cell death demonstrated a dose-dependent response. Maximum DNA ladder formation occurred 2 hr after PDT and 24 hr after ionizing radiation in the lymphoma cells, which was consistent with the time courses of cell death for these treatments. The hepatoma cell line did not demonstrate DNA ladder formation despite dosages of PDT or ionizing radiation sufficient to cause high levels of cytotoxicity.

Calpain inhibition: an overview of its therapeutic potential

Increasing evidence now suggests that excessive activation of the Ca(2+)-dependent protease calpain could play a key or contributory role in the pathology of a variety of disorders, including cerebral ischaemia, cataract, myocardial ischaemia, muscular dystrophy and platelet aggregation. In this review, Kevin Wang and Po-Wai Yuen discuss the evidence linking these disorders to calpain overactivation. At present, it is difficult to confirm the exact role of calpain in these disorders because of the lack of potent, selective and cell-permeable calpain inhibitors. However, given the multiple therapeutic indications for calpain, it appears that achievement of selective calpain inhibition is an important pharmacological goal.

Differential proteolysis of the full-length form of the L-type calcium channel alpha 1 subunit by calpain

This study examines the proteolysis of the carboxy terminal domain of the full-length (alpha 1(212)) and truncated (alpha 1(190)) forms of the rabbit skeletal muscle L-type calcium channel alpha 1 subunit by calpain I and calpain II. Although both forms of the alpha 1 subunit show little sensitivity to proteolysis by calpain II, alpha 1(212) is relatively more sensitive than alpha 1(190) to digestion by calpain I, the form of the enzyme regulated by micromolar concentrations of calcium. Calpain I cleaves a 37-kDa fragment from the C-terminus of alpha 1(212) in a time- and concentration-dependent manner and proteolysis is independent of the alpha 1(212) phosphorylation state. This proteolytic cleavage removes the major site of cyclic AMP-dependent phosphorylation from alpha 1(212) and may provide a mechanism for modifying the cyclic AMP-dependent regulation of L-type calcium channels in skeletal muscle.

Does performance status influence the outcome of Nd:YAG laser therapy of proximal esophageal tumors?

The value of endoscopic palliative therapy for malignant obstruction in the proximal esophagus has been questioned. To assess the importance of pre-treatment performance status on treatment outcome, we reviewed the records of patients with tumors of the proximal esophagus undergoing endoscopic laser therapy between January 1986 and December 1988. As compared with 10 patients having a good performance status, eight patients with a poor performance status had a lower frequency of obtaining complete functional relief of dysphagia (14% versus 71%), an increased rate of complications (50% versus 0%), and a shorter median survival time (24 days versus 161 days). We conclude that performance status should be considered in determining the appropriateness of laser therapy in patients with proximal esophageal cancer.

Characterization of a novel high molecular mass protein with peptidase activity purified from the human erythrocyte membrane by calmodulin affinity chromatography

A previously undescribed high molecular mass protein (HMP) from human erythrocyte membranes was solubilized by Triton X-100 and purified on a calmodulin-agarose column in the presence of Ca2+. It was shown to have a native molecular mass of 522-560 kDa, comprised of a single subunit of a molecular mass of 28 kDa (p28). The protein is associated with the lipid bilayer rather than with the cytoskeletal component of the membrane. The purified HMP showed peptidase-hydrolyzing activity toward substrates containing hydrophobic amino acids at the P1 position of the P2-P1 cleavage site. The activity was inhibited by serine proteinase inhibitors (leupeptin, phenylmethansulfonyl fluoride) and chymotrypsin inhibitors in particular (chymostatin, N-tosyl-L-phenylalanine chloromethyl ketone). The enzyme exhibited maximal activity at slightly alkaline pH (7.5-8.5) and at 37 degrees C and was stimulated over a narrow range of SDS concentrations (maximal at 0.05%). HMP was found to cross-react in Western blots with an antibody raised against the rabbit multicatalytic proteinase. The single subunit of HMP therefore contains both the catalytic activity and a sequence necessary for its association into a multimeric complex. The properties of the human erythrocyte membrane HMP described indicate that it is a novel peptidase related to the ubiquitous multicatalytic proteinase.

Immunocytochemistry of skeletal muscle basal lamina grafts in nerve regeneration

The influence on nerve regeneration of the extracellular matrix glycoprotein laminin was studied after sciatic nerve transection in 90 outbred Sprague-Dawley rats. Nerve regeneration through basal lamina grafts was comparable with regeneration through traditional nerve grafts across gaps up to 2.0 cm in length. True axonal regeneration rather than axonal branching was demonstrated by retrograde horseradish peroxidase labeling of nerve cables. Pretreatment of basal lamina grafts with antilaminin antibodies reduced the total number of regenerated axons by 90 percent with a significant decrease of nerve conduction velocity and a significant impairment of walking track patterns. The basement membrane glycoprotein laminin serves a critical role in the regeneration of peripheral nerves through basal lamina grafts.

Endoscopic laser coagulation of radiation-induced mucosal vascular lesions in the upper gastrointestinal tract and proximal colon

Endoscopic laser coagulation effectively controls bleeding from radiation-induced rectal vascular lesions.

OBJECTIVE

To assess the outcome of endoscopic treatment of radiation-induced bleeding due to vascular lesions located proximal to the sigmoid colon.

METHODS

We identified 15 consecutive patients with such proximal radiation enteropathy treated at our Institution with Nd:YAG laser between 1984 and 1991. Ten patients (66%) had gastric and/or small bowel involvement, and five (33%) had colonic involvement with or without more proximal lesions. Bleeding first appeared at a mean of 21.2 +/- 12.5 months after completion of radiotherapy. Mean duration of gastrointestinal bleeding before laser treatment was 7.6 +/- 4.6 months.

RESULTS

After completion of laser therapy, bleeding ceased in nine (60%) patients, decreased in three (20%), and persisted in three (20%). The mean hemoglobin level increased from 8.4 +/- 0.5 g/dl to 10.4 +/- 0.6 g/dl after completion of laser treatments (p < 0.02). The mean number of transfusions per patient per year decreased from 10.5 +/- 2.8 to 0.9 +/- 0.7 (p < 0.01). No treatment-related complications or deaths occurred.

CONCLUSIONS

Endoscopic laser coagulation of radiation-induced mucosal vascular lesions in the upper gastrointestinal tract and proximal colon appears to be safe and, in most cases, effective.

Phosphorylation of connexin-32 by protein kinase C prevents its proteolysis by mu-calpain and m-calpain

Isolated connexin-32s from rat and mouse liver are proteolyzed in vitro by the intracellular Ca(2+)-dependent neutral proteases, mu-calpain and m-calpain, producing a major fragment of 26 kDa. Connexin-26 is not proteolyzed by calpain. Calpain cleaves connexin-32 at its C-terminal end as shown by 125I-calmodulin binding experiments. Connexin-32, but not connexin-26, is phosphorylated by both protein kinase A and protein kinase C in serine residues and the sites of phosphorylation by both kinases remain in the major 26-kDa fragment resulting from calpain proteolysis. Phosphorylation of connexin-32 by protein kinase C, but not by protein kinase A, prevents the proteolytic attack of mu-calpain and m-calpain. Phosphorylation of connexin-32 by protein kinase A and protein kinase C does not prevent its proteolysis by papain, alpha-chymotrypsin, proteinase K, and trypsin.

Endoscopic Nd:YAG laser coagulation of bleeding from radiation proctopathy

Hematochezia from mucosal vascular lesions usually confined to the rectum represents an uncommon but problematic late complication of pelvic radiotherapy. We studied 47 patients with medically refractory hematochezia resulting from radiation-induced rectosigmoid mucosal vascular lesions. All lesions were endoscopically coagulated with Nd:YAG laser. Median duration of hematochezia before laser therapy was 11 months, despite previous medical treatment (98%) or bypass colostomy (6%). Within 3 to 6 months after laser treatment, the number of patients with daily hematochezia fell from 40 (85%) to 5 (11%; p < 0.001), and the median hemoglobin level increased from 9.7 gm/dl to 11.7 gm/dl (p < 0.001). Complications occurred in three patients (6%); no deaths occurred. The condition in six patients (12.8%) was not improved by laser treatment. Two patients (4%) ultimately required surgical treatment for bleeding control. On the basis of symptomatic, hematologic, and endoscopic responses, Nd:YAG laser photocoagulation controlled bleeding from radiation proctopathy in most patients with an acceptably low morbidity. Patients with sigmoid colon involvement responded less favorably. Endoscopic laser photocoagulation should be considered before surgical intervention for treatment of hematochezia from radiation proctopathy.

Oral pulse prednisone therapy after relapse of severe autoimmune chronic active hepatitis. A prospective randomized treatment trial evaluating clinical, biochemical, and lymphocyte subset responses

To assess the efficacy of oral pulse prednisone therapy after relapse of severe autoimmune chronic active hepatitis and to determine the effects of such therapy on serum immunoglobulin G levels and peripheral blood lymphocyte subsets, 16 patients were randomized after relapse to therapy with prednisone 90 mg daily for 5 days each month or conventional daily dose therapy with prednisone in combination with azathioprine. Seven of the eight patients randomized to pulse therapy failed treatment after 1.9 +/- 0.7 months (range, 24 days to 6 months). Treatment failure occurred more commonly (87 vs. 0%, p < 0.01) and remission occurred less frequently (0 vs. 87%, p < 0.01) in patients receiving pulse therapy. The percentage and absolute numbers of circulating CD2 and CD4 cells decreased during relapse, while CD8 and CD20 cell counts were not significantly altered. Pulse therapy was associated with a significant increase in the percentage of CD4 cells and decrease in aminotransferase levels after 5 days. Serum immunoglobulin G levels, however, were not affected by treatment and after 1 month the biochemical findings and lymphocyte subsets were again similar to those at relapse. In contrast, serum immunoglobulin G levels decreased after 14 days of combination therapy and by 1 month the numbers in all lymphocyte subsets were higher than at relapse. We conclude that oral pulse prednisone therapy is ineffective for patients in relapse. The numbers of circulating CD2 and CD4 cells fall during relapse and increase as inflammatory activity subsides during corticosteroid therapy. Combination therapy reverses the biochemical changes and alterations in peripheral blood lymphocyte subsets that accompany relapse.

A Coomassie brilliant blue G-250-based colorimetric assay for measuring activity of calpain and other proteases

The activity of cytosolic calcium-dependent neutral protease (calpain) is commonly measured using casein as a substrate. A novel, modified caseinolysis assay is now developed. It involves incubation of calpain with substrate casein, followed by removal of an aliquot to which Coomassie brilliant blue G-250 dye reagent is added. The assay is based on the observation that the dye interacts only with protein but not the proteolytic products (small peptides and amino acids). Unlike the existing caseinolysis assay, this novel assay does not require separation of substrate from products and measurement is done in the visible range (595 nm). It is also more sensitive than existing colorimetric assays which use dye-conjugated protein substrates. The assay can also be used to measure the activity of other proteases such as trypsin and papain.

Inside-out vein graft promotes improved nerve regeneration in rats

Vein grafts have been used both experimentally and clinically to bridge gaps in peripheral nerves. This study describes a modification of the vein graft technique in which vein graft conduits are pulled inside-out before anastomosis with proximal and distal nerve stumps. This technique creates an autogenous vein conduit with the collagen-rich adventitial surface exposed to the regenerating axons. The inside-out technique is a fast and simple modification of the standard vein graft technique and produces an accelerated rate of nerve regeneration and significantly earlier myelination compared with the results obtained from the use of polyethylene nerve guides and standard vein graft conduits.

Sleeve insertion and collagen coating improve nerve regeneration through vein conduits

Vein grafts have been used as conduits for nerve regeneration in both research protocols and clinical situations. Results to date are encouraging. This study investigated several variations in the vein graft model in an attempt to enhance peripheral nerve regeneration. Results showed that the jugular vein, with an improved suture technique made possible by its larger diameter, is superior to the femoral vein as a conduit for regeneration of the sciatic nerve in the rat. The larger diameter of the jugular vein and its lack of valves provided less hinderance to regenerating axons. Results also showed that coating the luminal epithelium of the jugular vein with type I collagen gel greatly improved regeneration.

An unrecognized etiology for pyogenic hepatic abscesses in normal hosts: dental disease

Cryptogenic pyogenic hepatic abscesses are a diagnosis of exclusion. We have identified two patients with severe dental disease at the time of the diagnosis of their liver abscess. In both cases, oral flora was cultured from the abscess. Unlike a previous report, both patients were immunocompetent. When compared with a group of patients with liver abscesses and diverticulitis, two differences were found. In contrast to the single abscesses seen in 10 of 10 patients with diverticulitis, the patients with dental disease had multiple abscesses (p < 0.02). In addition, Fusobacterium nucleatum was cultured from both dental disease associated abscesses but only one of the diverticulitis associated liver abscesses (p < 0.05). If a liver abscess is thought to be cryptogenic, a thorough dental exam is recommended.

Calcium-activated neutral protease effects upon skeletal muscle sarcoplasmic reticulum protein structure and calcium release

In this study, the effects of Ca(2+)-activated neutral protease (CANP) upon skeletal muscle heavy sarcoplasmic reticulum (HSR) structure and function were investigated. CANP was immunolocalized to the 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid detergent-insoluble fraction of purified HSR membranes. Ca2+ activation of the endogenous membrane-bound CANP produced a characteristic partial fragmentation of the HSR 565-kDa Ca2+ release channel. Similarly, the major substrate for both micromolar and millimolar Ca(2+)-sensitive isoforms of exogenous CANP was the Ca2+ release channel with proteolysis of a 88-kDa HSR protein also observed. Ca2+ release channel proteolysis was initiated at a single cleavage site with coincidental production of 410- and 150-kDa peptide fragments. Appearance of 160- and 137-kDa limiting peptides accompanied secondary proteolysis of the primary 410- and 150-kDa fragments, respectively. Despite extensive proteolysis of the Ca2+ release channel, CANP did not dramatically alter the Ca2+ handling and ryanodine binding properties of HSR membranes. The association of CANP with isolated HSR membranes suggests that, in vivo, this protease may modify an additional property of the Ca2+ release channel. This may be related to the CANP-susceptible structural association of the Ca2+ release channel with dihydropyridine receptors at T-tubule/sarcoplasmic reticulum junctions.

The clinical and endoscopic spectrum of the watermelon stomach

The watermelon stomach is an uncommon but treatable cause of chronic gastrointestinal bleeding. We report our experience with the clinical and endoscopic features of 45 consecutive patients treated by endoscopic Nd:YAG laser coagulation. The prototypic patient was a woman (71%) with an average age of 73 years (range of 53-89 years) who presented with occult (89%) transfusion-dependent (62%) gastrointestinal bleeding over a median period of 2 years (range of 1 month to > 20 years). Autoimmune connective tissue disorders were present in 28 patients (62%), especially Raynaud's phenomena (31%) and sclerodactyly (20%). Atrophic gastritis occurred in 19 of 19 (100%) patients, with hypergastrinemia in 25 (76%) of 33 patients tested. Antral endoscopic appearances included raised or flat stripes of ectatic vascular tissue (89%) or diffusely scattered lesions (11%). Proximal gastric involvement was present in 12 patients (27%), typically in the presence of a diaphragmatic hernia. Endoscopic laser therapy after a median of one treatment (range of 1-4) resulted in complete resolution of visible disease in four patients (13%) and resolution of > 90% in 24 patients (80%). Hemoglobin levels normalized in 87% of patients over a median follow-up period of 2 years (range of 1 month to 6 years) with no major complications. Blood transfusions were not necessary after laser therapy in 86% of 28 initially transfusion-dependent patients. The characteristic clinical, laboratory, and endoscopic features allow for a confident diagnosis that can lead to successful endoscopic treatment.

Etiology and course of acute bleeding esophageal ulcers

Twenty (2%) of 1,140 patients with acute gastrointestinal bleeding had esophageal ulcers. Patients with esophageal ulcers most commonly had either melena (40%) or melena and hematemesis (40%). Fifty percent had orthostatic hypotension, and 80% required transfusions. Ulcers were associated with nonsteroidal anti-inflammatory drugs (NSAIDs) use in 50%, hiatal hernia in 60%, and esophagitis in 40%. Endoscopic stigmata of recent hemorrhage consisted of oozing blood (35%) and adherent clot (25%). Six patients had multiple ulcers. The majority of ulcers (90%) were in the distal esophagus. Nine patients were endoscopically treated without complications except for rebleeding in 1 patient. Endoscopic therapy was associated with decreased duration of hospitalization. Overall mortality was 45% in these patients, but no deaths were related to bleeding. Although uncommon, esophageal ulcers are a cause of significant acute gastrointestinal bleeding that appears to respond to endoscopic treatment.

Simultaneous reduction of the sarcolemmal and SR calcium ATPase activities and gene expression in cardiomyopathic hamster

Altered calcium regulation is a prominent feature in the hereditary cardiomyopathy of the Syrian hamster. However, the activity of the two systems necessary for intracellular calcium homeostasis in the heart, the sarcolemmal and sarcoplasmic reticulum calcium ATPase pumps, have not been correlated. Using age- and pair-matched myopathic and control hamsters, a simultaneous reduction in gene expression and enzyme activity for these two pumps has been demonstrated. The concomitant alteration in gene expression as early as 1 month of age, preceding noticeable myocytolysis suggests that the depressed activity in these two calcium ATPase systems is not due to cell necrosis but at least in part due to reduction in their mRNA levels. Reduced capacity of the calcium pumps would result in calcium overload as well as impaired contractility that leads to the eventual heart failure in this animal model.

Acute gastrointestinal bleeding. Experience of a specialized management team

The initial experience of a specialized management team organized to provide expedient care for all acute major gastrointestinal bleeding in protocolized fashion at a large referral center is presented. Of the 417 patients, 56% developed bleeding while hospitalized. Upper gastrointestinal bleeding accounted for 82%. The five most common etiologies included gastric ulcers (83 patients), duodenal ulcers (67 patients), erosions (41 patients), varices (35 patients), and diverticulosis (29 patients). Nonsteroidal anti-inflammatory drugs were implicated in 53% of gastroduodenal ulcers. The incidence of nonbleeding visible vessels was 42% in gastric and 54% in duodenal ulcers. The rates of rebleeding were 24% (20 patients) in gastric ulcers and 28% (19 patients) in duodenal ulcers. Predictive factors for rebleeding included copious bright red blood, active arterial streaming, spurting, or a densely adherent clot. The rebleeding rate for esophagogastric varices was 57%. The mortality rate overall was 6% (27 patients), with rates varying from 3% (five patients) for gastroduodenal ulcers to 40% (14 patients) for esophagogastric varices. The morbidity rate for the entire patient population was 18% (77 patients), dominated by myocardial events (34 patients). The average length of hospitalization for gastroduodenal ulcers was 5 days, for diverticulosis 8 days, and for varices 10 days. The major efforts of a specialized Gastrointestinal Bleeding Team would be best directed at both reducing the morbidity associated with acute bleeding and reducing the overall cost of care.

The plasma membrane calcium pump: a multiregulated transporter

Activation of many cells, especially nonexcitable cells, results in a Ca(2+) transient that is influenced in part by the kinetics of active extrusion of Ca(2+) across the plasma membrane. The molecular cloning of the plasma membrane Ca(2+)-pump has helped to clarify the relationship between its structure and function. The Ca(2+)-pump is controlled by multiple regulators, including calmodulin, phospholipids and various kinases. Longer term control is achieved through regulation of its gene expression, and the presence of a number of Ca(2+)-pump isoforms that differ in their regulatory domains provides potential functional diversity. In this review, we focus on the mechanisms that regulate the function of the Ca(2+)-pump, and their physiological significance.

Structure--function relationship of the human erythrocyte plasma membrane Ca(2+)-ATPase revealed by V8 protease treatment

Treatment of the solubilized and purified Ca(2+)-translocating ATPase (Ca(2+)-ATPase) (136 kDa) from human erythrocyte plasma membranes with endoproteinase Glu-C from Staphylococcus aureus strain V8 (V8 protease) yielded transient fragments of 96 kDa and 76 kDa and more stable fragments of 60 kDa and 37/36 kDa (doublet). The presence of calmodulin did not alter the fragmentation pattern. The 60 kDa fragment contains the protein kinase C (bovine brain) phosphorylation site(s), which we previously localized in the C-terminal region [Wang, Wright, Machan, Allen, Conigrave & Roufogalis (1991) J. Biol. Chem. 266, 9078-9085]. On the other hand, the 37/36 kDa fragments possess the ability to form an acyl-phosphate intermediate. Furthermore, the presence of the 60 kDa and 37/36 kDa fragments together results in expression of calmodulin-sensitive Ca(2+)-ATPase activity. However, further degradation of the 60 kDa fragment was coupled with the appearance of calmodulin-independent activity, whereas the 37/36 kDa fragment doublet remained stable. It was concluded that the 60 kDa and the 37/36 kDa fragments: (a) together represent the C-terminal two-thirds of the enzyme, which is functional as an Ca(2+)-ATPase, (b) were produced by a single cleavage near the C-terminal side of the cytosolic catalytic domain, and (c) probably remain physically and functionally associated even after cleavage has occurred. At the C-terminus, the basic calmodulin-binding domain is flanked by two highly acidic regions (domains A and B). Our results indicate that domains A and B, despite containing many Asp and Glu residues, were not readily cleaved by V8 protease, which is known to cleave selectively peptide bonds at the C-terminal side of Asp and Glu. However, if the Ca(2+)-ATPase were pre-digested with calpain I from human erythrocytes, which removed its calmodulin-binding domain (along with domain B), multiple cleavages by V8 protease in domain A were then readily observed. We propose that the calmodulin-binding domain is closely associated with the acidic domains A and B and that these acidic domains might help to co-ordinate the stimulation of the enzyme by calmodulin.

The role of Helicobacter pylori in gastroduodenal disease

Peptic ulcers are the result of a wide variety of factors, with H. pylori probably being one of the more significant. H. pylori has been most strongly associated with gastritis and duodenal ulcer disease. The relationship of H. pylori to gastric ulcers is less substantial. The eradication of H. pylori can be achieved in the majority of patients with triple antibiotic therapy. However, resistance to metronidazole occurs readily. Eradication of H. pylori can change the course of duodenal ulcer disease by decreasing recurrence rate from 80% to zero. Nonetheless, treatment for H. pylori should only be done in randomized trials at the current time because of the lack of completely effective therapy and the high risks of side effects. The mechanism by which H. pylori influences duodenal ulcer recurrence is unclear. Pathogenic mechanisms of the organism also need to be further elucidated.

Hormone-induced phosphorylation of the plasma membrane calcium pump in cultured aortic endothelial cells

The regulation of the plasma membrane Ca2+ pump by hormones via phosphorylation in intact cells has not been clearly established. We now present evidence that the Ca2+ pump is phosphorylated on both serine and threonine residues in unstimulated and stimulated cultured rat aortic endothelial cells. Among the stimuli tested, the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) was most potent and increased the level of phosphorylation threefold, while the cAMP-dependent protein kinase activator 8-(4-chlorophenylthio)-cAMP (CPT-cAMP) stimulated the phosphorylation 1.6-fold. Two-dimensional tryptic phosphopeptide maps of the Ca2+ pump from unstimulated and CPT-cAMP-stimulated cells have identical patterns (five phosphopeptides) while PMA-stimulated cells have three additional phosphopeptides. Isoproterenol-, ATP-, angiotensin II-, and bradykinin-stimulated cells also have increased levels of Ca2+ pump phosphorylation. Stimuli-induced phosphorylation of the Ca2+ pump was rapid (5-10 min) and was concomitant with stimulated calcium efflux from the same cells. This is the first direct evidence that the plasma membrane Ca2+ pump in intact cells is regulated by various hormones or agonists via cAMP-dependent protein kinase or protein kinase C phosphorylation.

Protein kinase C phosphorylates the carboxyl terminus of the plasma membrane Ca(2+)-ATPase from human erythrocytes

Purified Ca(2+)-stimulated, Mg(2+)-dependent ATPase (Ca(2+)-ATPase) from human erythrocytes was phosphorylated with a stoichiometry of about 1 mol of phosphate/mol of ATPase at both threonine and serine residues by purified rat brain type III protein kinase C. In the presence of calmodulin, the phosphorylation was markedly reduced. Labeled phosphate from [gamma-32P]ATP was retained on an 86-kDa calmodulin-binding tryptic fragment of Ca(2+)-ATPase but not on 82- and 77-kDa non-calmodulin-binding fragments. Similarly, fragmentation of the phosphorylated Ca(2+)-ATPase by calpain I revealed that calmodulin-binding fragments (127 and 125 kDa) retained phosphate label whereas a non-calmodulin-binding fragment (124 kDa) did not. The calmodulin-binding domain, located about 12 kDa from the carboxyl terminus of the Ca(2+)-ATPase, was thus located as a site of protein kinase C phosphorylation. A synthetic peptide corresponding to a segment of the calmodulin-binding domain (H2 N-R-G-L-N-R-I-Q-T-Q-I-K-V-V-N-COOH) was indeed phosphorylated at the single threonine residue within this sequence. The additional serine phosphorylation site was carboxyl terminal to the calmodulin domain. Phosphorylation by purified type III protein kinase C (canine heart) antagonized the calmodulin activation of the Ca(2+)-ATPase, particularly at lower Ca2+ concentrations (0.2-1.0 microM). By contrast, a purified but unresolved protein kinase C isoenzyme mixture from rat brain stimulated the activity of Ca(2+)-ATPase prepared in asolectin, but not glycerol, by more than 2-fold in the presence of the ionophore A23187, without increasing its Ca2+ sensitivity. The results clearly indicate that human erythrocyte Ca(2+)-ATPase is a substrate of protein kinase C, but the effect of phosphorylation on the activity of the enzyme depends on the isoenzyme form of protein kinase C used and on the lipid associated with the Ca(2+)-ATPase.

Phorbol ester induces both gene expression and phosphorylation of the plasma membrane Ca2+ pump

Regulation of the plasma membrane Ca2+ pump in the cell is of critical importance in maintaining calcium homeostasis. Since protein kinase C is known to regulate functions of cellular proteins by direct phosphorylation or by inducing their gene expression, we investigated the possible involvement of protein kinase C in the regulation of the plasma membrane Ca2+ pump. The Ca2+ pump was isolated by immunoprecipitation from [32P]orthophosphate-labeled cultured rat aortic endothelial cells grown in the absence or presence of phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C. PMA treatment of cells led to a rapid increase in the phosphorylation level (1.3-fold) within 5 min and a further increase to 2.9-fold after 3 h. Prolonged PMA treatment also induced the accumulation of the Ca2+ pump mRNA, followed by increased levels of the pump protein. The peak level of the pump mRNA induction occurred at 4 h and was 8-20-fold higher than the control culture without PMA. The rate of the Ca2+ pump protein accumulation was slower, reaching a maximum of 3.5-fold after 6 h. Induction of the pump mRNA was suppressed by the protein kinase C inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine and by down-regulation of protein kinase C. Inactive phorbol ester 4 alpha-phorbol didecanoate also failed to mimic the PMA effect. These results suggest that the induction of Ca2+ pump expression is mediated by a protein kinase C-dependent mechanism. Furthermore, since the induction of the Ca2+ pump mRNA was blocked when cycloheximide and PMA were added together, this suggests that newly synthesized protein factor is needed to produce the mRNA induction. Our results suggest that protein kinase C is involved in the regulation of the Ca2+ pump in endothelial cells. At the protein level, it modifies the Ca2+ pump by phosphorylation, and at the gene level, it stimulates the expression of its mRNA and thereby increases the amount of the pump protein.

Persistent Ca2(+)-induced activation of erythrocyte membrane Ca2(+)-ATPase unrelated to calpain proteolysis

Preincubation of human erythrocyte membranes with calcium in the submillimolar to millimolar concentration range resulted in an increase of the Ca2+ affinity and apparent maximum velocity of the Ca2(+)-stimulated Mg2(+)-dependent ATPase (Ca2(+)-ATPase). The activation was persistent, as it was not reversed when the Ca2(+)-preincubated membranes were washed with ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid-containing buffers. Magnesium was not required for the activation, whereas greater than 2 mM Mg2+ partially antagonized the activation by Ca2+. In some membrane preparations ATP was required in addition to Ca2+ for activation of the Ca2(+)-ATPase, but nonhydrolyzable analogs of ATP had the same effect. Calmodulin prevented the activation by Ca2+ over the same concentration range in which it interacts with the Ca2(+)-ATPase. Taken together the results obtained provided strong evidence that the Ca2+ activation of the enzyme was not due to proteolytic cleavage by endogenous calpain. Thus, activation by Ca2+ was not blocked by leupeptin (100-200 microM), did not require dithiothreitol, and occurred at Ca2+ concentrations greater than those required for activation of calpain I. Furthermore, Ca2+ activation did not result in change in the mobility the native 136-kDa species of the Ca2(+)-ATPase on SDS-gel electrophoresis. Moreover, solubilization of the Ca2(+)-pretreated membranes with Triton X-100 reversed the Ca2+ activation of the Ca2(+)-ATPase. On the other hand, Ca2(+)-pretreatment of the membranes modified the susceptibility of the Ca2(+)-ATPase to both cleavage and activation by exogenously added calpain I. We conclude that pretreatment of Ca2(+)-ATPase in erythrocyte membranes with millimolar Ca2+ activates the enzyme by inducing a persistent conformational change of the enzyme which is, however, subsequently reversed by detergent solubilization.

Calpain I activates Ca2+ transport by the reconstituted erythrocyte Ca2+ pump

Calpain I purified from human erythrocyte cytosol activates both the ATP hydrolytic activity and the ATP-dependent Ca2+ transport function of the Ca2(+)-translocating ATPase solubilized and purified from the plasma membrane of human erythrocytes and reconstituted into phosphatidylcholine vesicles. Following partial proteolysis of the enzyme by calpain I, both the initial rates of calcium ion uptake and ATP hydrolysis were increased to near maximal levels similar to those obtained upon addition of calmodulin. The proteolytic activation resulted in the loss of further stimulation of the rates of Ca2+ translocation or ATP hydrolysis by calmodulin as well as an increase of the affinity of the enzyme for calcium ion. However, the mechanistic Ca2+/ATP stoichiometric ratio was not affected by the proteolytic treatment of the reconstituted Ca2(+)-translocating ATPase. The proteolytic activation of the ATP hydrolytic activity of the reconstituted enzyme could be largely prevented by calmodulin. Different patterns of proteolysis were obtained in the absence or in the presence of calmodulin during calpain treatment: the 136-kDa enzyme was transformed mainly into a 124-kDa active ATPase fragment in the absence of calmodulin, whereas a 127-kDa active ATPase fragment was formed in the presence of calmodulin. This study shows that calpain I irreversibly activates the Ca2+ translocation function of the Ca2(+)-ATPase in reconstituted proteoliposomes by producing a calmodulin-independent active enzyme fragment, while calmodulin antagonizes this activating effect by protecting the calmodulin-binding domain against proteolytic cleavage by calpain.

Prognosis of corticosteroid-treated hepatitis B surface antigen-negative chronic active hepatitis in postmenopausal women: a retrospective analysis

To determine the consequences of corticosteroid treatment in postmenopausal patients with severe hepatitis B surface antigen-negative chronic active hepatitis, the findings in 43 such patients (mean age, 59 +/- 2 yr) were compared retrospectively to those in 46 premenopausal counterparts (mean age, 31 +/- 2 yr) after similar durations of initial (19 +/- 2 vs. 18 +/- 2 mo) and subsequent (48 +/- 8 vs. 63 +/- 11 mo) therapy. Postmenopausal patients entered remission as frequently as premenopausal women during initial treatment (81% vs. 83%, p = 0.9), deteriorated as commonly (7% vs. 7%), and developed drug-related complications as frequently (49% vs. 33%, p = 0.14). Postmenopausal women, however, had a higher cumulative frequency of complications (77% vs. 48%, p less than 0.01) and a greater occurrence of multiple complications (44% vs. 13%, p less than 0.01) than premenopausal counterparts during follow-up. Vertebral compression occurred more frequently (23% vs. 7%, p = 0.05), and lumbar spine densities were below the spontaneous fracture threshold more commonly (85% vs. 22%, p less than 0.002). Longer initial and cumulative durations of therapy were associated with the development of complications. We conclude that initial corticosteroid treatment is as safe and effective in postmenopausal women as in premenopausal counterparts. Postmenopausal women, however, have a higher cumulative frequency of complications long-term and a lower net benefit-risk ratio than comparably treated premenopausal women.

Characterization of the fragmented forms of calcineurin produced by calpain I

Calcineurin, a calmodulin-stimulated phosphatase from bovine brain, was hydrolyzed by calpain I from human erythrocytes. In the absence of calmodulin, calpain rapidly transformed the 60-kilodalton (kDa) catalytic subunit of calcineurin into a transient 57-kDa fragment and thereafter a 43-kDa limit fragment. In the presence of calmodulin, the 60-kDa subunit was sequentially proteolyzed to a 55-kDa fragment and then a 49-kDa fragment. Upon proteolysis in the absence or presence of calmodulin, the p-nitrophenyl phosphatase activity (assayed in the presence of calmodulin) was increased by 300%. The 43- and the 49-kDa fragments were found to (i) remain associated with the small subunit (17 kDa), (ii) have lost the ability to bind and to be activated by calmodulin, and (iii) have phosphatase activity that was still stimulated by Mn2+ or Ni2+. The 43- + 17-kDa form had similar Km values for various substrates, but the Vmax values were increased compared with the native enzyme. It is proposed that (i) a 43-kDa core segment of the 60-kDa subunit of calcineurin contained the catalytic domain, the small subunit-binding domain, and the metal ion (Mn2+ and (or) Ni2+) binding site; and (ii) two distinct types of inhibitory domains exist near the end(s) of the large subunit, one of which is calmodulin regulated, while the other is calmodulin independent.

Calmodulin-binding proteins as calpain substrates

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Extrahepatic malignancy following long-term immunosuppressive therapy of severe hepatitis B surface antigen-negative chronic active hepatitis

To determine the frequency, predisposing factors and consequences of extrahepatic malignancy following long-term immunosuppressive therapy of severe HBsAg-negative chronic active hepatitis, 149 patients who had received prednisone (20 mg daily) or prednisone (10 mg daily) in combination with azathioprine (50 mg daily) for at least 6 months were evaluated systematically for 109 +/- 5 months (range: 7 to 223 months). Seven neoplasms involving cervix (2), lymphatic tissue (1), breast (1), bladder (1), soft tissue (1) and unknown site (1) developed in seven patients after 116 +/- 23 months (range: 18 to 164 months). The incidence of extrahepatic neoplasm was 1 per 194 patient-years of surveillance, and the probability of tumor occurrence was 3% after 10 years. Tumor frequency was similar in men and women and the risk was 1.4-fold greater than that in an age- and sex-matched normal population (95% confidence interval, 0.6- to 2.9-fold normal). Patients with extrahepatic malignancy were not distinguished by age, sex, treatment regimen, cumulative duration of treatment (42 +/- 9 vs. 60 +/- 4 months, p = 0.7) or individual features of the liver disease. Five of the seven patients survived during 48 +/- 25 months of follow-up, including two patients who have lived for at least 5 years after the diagnosis of malignancy. We conclude that extrahepatic malignancy develops infrequently during long-term immunosuppressive therapy. Its occurrence is not related to the type or duration of treatment, and long-term survival after tumor detection is possible. The low but probably increased risk of extrahepatic neoplasm does not militate against the use of immunosuppressive therapy in these patients.

Further characterization of calpain-mediated proteolysis of the human erythrocyte plasma membrane Ca2+-ATPase

The membrane-bound form and a solubilized and purified form of the Ca2+-ATPase from human erythrocyte have been proteolyzed under controlled conditions by highly purified Ca2+-dependent neutral cysteine-protease, calpain I, in the absence and in the presence of the calmodulin-calcium complex. In the absence of calmodulin the 136-kDa enzyme was transformed into a group of fragments of 125-124 kDa, followed by the slower formation of a second group of fragments of 82-80 kDa. These heterogeneous fragments were capable of forming an acylphosphate intermediate. The 125- and 82-kDa minor components of each heterogeneous group of fragments (125-124 and 82-80 kDa) were capable of binding calmodulin, whereas the 124- and the 80-kDa major components did not. In the presence of calmodulin, however, the native enzyme was transformed into a 127-kDa fragment followed by the slower formation of an 85-kDa fragment. Both fragments (127 and 85 kDa) formed an acylphosphate intermediate and were capable of binding calmodulin. The presence of calmodulin during calpain action effectively protected the Ca2+-ATPase from proteolytic activation (K.K.W. Wang, A. Villalobo, and B.D. Roufogalis (1988) Arch. Biochem. Biophys. 260, 696-704) and prevented the formation of the calmodulin-insensitive 124- and 80-kDa fragments. Smaller fragments not capable of forming the acylphosphate intermediate were also produced, in particular a 39-37 kDa doublet band retaining the capacity to bind calmodulin. In contrast to the membrane-bound form, the purified form of the Ca2+-ATPase was proteolyzed by calpain at a slower rate.

The effect of calmodulin on the interaction of carbodiimides with the purified human erythrocyte (Ca2+ + Mg2+)-ATPase

The activity of the solubilized and purified (Ca2+ + Mg2+)-ATPase from human erythrocyte membranes was inhibited by N,N'-dicyclohexylcarbodiimide in a concentration-dependent manner. The carbodiimide prevented formation of the phosphorylated intermediate during the catalytic cycle of the enzyme. Treatment of the enzyme with N,N'-dicyclohexyl[14C]carbodiimide resulted in the formation of a 14C-labelled polypeptide corresponding to the enzyme monomer (molecular weight 136,000). The tryptic fragmentation of this 14C-labelled enzyme resulted in the formation of three major 14C-labelled fragments with molecular weights of 58,000, 36,500 and 23,000, the latter two probably representing transmembrane and calmodulin-binding domains of the enzyme, respectively. In the absence of calmodulin, 6.7 molecules of N,N'-dicyclohexyl[14C]carbodiimide covalently bound to each molecule of Ca2+-ATPase; in the presence of calmodulin, the number of molecules of carbodiimide bound was 13.1. The binding of N,N'-dicyclohexylcarbodiimide to the (Ca2+ + Mg2+)-ATPase greatly reduced its ability to bind to a calmodulin-agarose gel.

Hepatocellular carcinoma in corticosteroid-treated severe autoimmune chronic active hepatitis

To determine the frequency of hepatocellular cancer in corticosteroid-treated severe autoimmune chronic active hepatitis and to identify risk factors for its development, 124 patients who were selected by uniform criteria, treated comparably and followed systematically for 111 +/- 6 months were evaluated. Hepatocellular cancer was diagnosed in three patients (2%) after 66, 99 and 174 months of observation, respectively. The incidence of hepatocellular cancer was 1 per 350 patient-years of follow-up. All three patients with hepatocellular cancer had cirrhosis for at least 5 years. The frequency of neoplasm in patients with cirrhosis of at least 5 years' duration was 7%. The incidence of hepatocellular cancer in these patients with cirrhosis was 1 per 182 patient-years of follow-up, and the probability of tumor was 29% after 13 years. Late elevation of the serum alpha-fetoprotein level was associated with the presence of neoplasm but normal levels did not exclude the diagnosis. We conclude that patients with corticosteroid-treated severe autoimmune chronic active hepatitis are at risk for hepatocellular cancer. This risk is greatest in patients with cirrhosis for at least 5 years. Such patients are candidates for cancer surveillance.

Activation of the Ca2+-ATPase of human erythrocyte membrane by an endogenous Ca2+-dependent neutral protease

Limited proteolysis of the plasma membrane calcium transport ATPase (Ca2+-ATPase) from human erythrocytes by trypsin produces a calmodulin-like activation of its ATP hydrolytic activity and abolishes its calmodulin sensitivity. We now demonstrate a similar kind of activation of the human erythrocyte membrane Ca2+-ATPase by calpain (calcium-dependent neutral protease) isolated from the human red cell cytosol. Upon incubation of red blood cell membranes with purified calpain in the presence of Ca2+ the membrane-bound Ca2+-ATPase activity was increased and its sensitivity to calmodulin was lost. In contrast to the action of other proteases tested, proteolysis by calpain favors activation over inactivation of the Ca2+-ATPase activity, except at calpain concentrations more than 2 orders of magnitude higher. Exogenous calmodulin protects the Ca2+-ATPase against calpain-mediated activation at concentrations which also activate the Ca2+-ATPase activity. Calcium-dependent proteolytic modification of the Ca2+-ATPase could provide a mechanism for the irreversible activation of the membrane-bound enzyme.

Collagenous colitis: a clinicopathologic correlation

Collagenous colitis is an unusual cause of chronic, watery diarrhea. To characterize this disease, we reviewed biopsy specimens and the clinical records of 17 patients (9 women and 8 men) with this diagnosis. Intermittent diarrhea with symptom-free intervals lasting years was found in 7 of the 17 patients. Two patients had incapacitating arthralgias, and nine had a mild weight loss. Collagen deposition beneath the surface epithelium formed a continuous layer in 11 but was discontinuous in 5 of the 16 patients who had undergone rectal or colonic biopsies at our institution. The thickness of the collagen band was variable (maximum, 93 microns). The symptoms of the patients did not correlate with the thickness of the collagen layer. Variability in collagen thickness may be related to disease phase and increases the need to obtain multiple biopsy specimens from the sigmoid colon and rectum. The optimal treatment for collagenous colitis is difficult to determine because three of six patients treated only symptomatically in our study had resolution of their diarrhea.

Pulmonary infiltrates and eosinophilia associated with sulfasalazine

Asymptomatic pulmonary infiltrates and eosinophilia developed in a patient with chronic ulcerative colitis 1 month after therapy with sulfasalazine had been instituted. The abnormalities resolved completely after use of the drug was discontinued. The sulfapyridine component of the sulfasalazine was the likely causative agent because 41 years earlier, the patient had experienced fever, myalgias, and eosinophilia after taking a sulfonamide. Ten previous cases of sulfasalazine pulmonary toxicity, including one fatality, have been reported.