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Biomedical subjects

J Ludwig

Publications and source records attributed to J Ludwig.

At least 91 records · Page 5Linked to original sources
PubMed1996

Elevation of intracellular calcium by muscarinic receptor activation induces a block of voltage-activated rat ether-à-go-go channels in a stably transfected cell line.

We have studied the properties of r-eag voltage-activated potassium channels in a stably transfected human embryonic kidney cell line. It was found that r-eag channels are rapidly and reversibly inhibited by a rise in intracellular calcium from 30 to 300 nM. The inhibition does not appear to depend on the activity of calcium-dependent kinases and phosphatases. The effect of calcium on r-eag channel activity was studied in inside-out membrane patches. Calcium inhibited r-eag channel activity with a mean IC50 of 67 nM. Activation of muscarinic receptors, generating calcium oscillations in the transfected cells, induced a synchronous inhibition of r-eag mediated outward currents. This shows that calcium can mediate r-eag current inhibition following muscarinic receptor activation. The data indicate that r-eag channels are calcium-inhibitable voltage-activated potassium channels.

Animals↗
PubMed1996

[Wilson's disease].

Explore the source record for details and available documents.

Diagnostic Errors↗
PubMed1996

Development and characterization of a rodent model of immune-mediated cholangitis.

The cholangiopathies are a group of hepatobiliary diseases in which intrahepatic bile duct epithelial cells, or cholangiocytes, are the target for a variety of destructive processes, including immune-mediated damage. We tested the hypothesis that cholangitis could be induced in rodents by immunization with highly purified cholangiocytes. Inbred Wistar rats were immunized with purified hyperplastic cholangiocytes isolated after bile duct ligation from either syngeneic Wistar or allogeneic Fischer 344 rats; control rats were immunized with bovine serum albumin (BSA) or hepatocytes. After immunization with cholangiocytes, recipient animals developed histologic evidence of nonsuppurative cholangitis without inflammation in other organs; groups immunized with BSA or hepatocytes showed no cholangitis. Immunohistochemical studies revealed that portal tract infiltrates around bile ducts consisted of CD3-positive lymphocytes, some of which expressed major histocompatibility complex class II antigen; B cells and exogenous monocytes/macrophages were essentially absent. Transfer of unfractionated ConA-stimulated spleen cells from cholangiocyte-immunized (but not BSA-immunized) rats into recipients also caused nonsuppurative cholangitis. Moreover, these splenocytes from cholangiocyte-immunized (but not BSA-immunized) rats were cytotoxic in vitro for cultured rodent cholangiocytes; no cytotoxicity was observed against a rat hepatocyte cell line. Also, a specific antibody response in sera of cholangiocyte-immunized rats was demonstrated by immunoblots against cholangiocyte proteins. Finally, cholangiograms in cholangiocyte-immunized rats showed distortion and tortuosity of the entire intrahepatic biliary ductal system. This unique rodent model of experimental cholangitis demonstrates the importance of immune mechanisms in the pathogenesis of cholangitis and will prove useful in exploring the mechanisms by which the immune system targets and damages cholangiocytes.

Animals↗
PubMed1996

Time course of histological progression in primary biliary cirrhosis.

Histological staging is used for stratification and assessment of treatment efficacy in therapeutic trials for primary biliary cirrhosis (PBC). Knowledge of the rate of progression of the histological changes would be helpful in the design (duration) and conduct of clinical trials. The histological stages were recorded for liver biopsies performed annually on 222 patients during a randomized, placebo-controlled clinical trial in which therapy with D-penicillamine (DPCA) was shown to be ineffective. These data were analyzed using a Markov model to describe the time course of histological progression in PBC. At study entry, 15 patients were stage I, 56 were stage II, 96 were stage III, and 55 were stage IV. Histological progression was observed after 1 year in 41%, 43%, and 35% of the patients, and after 2 years in 62%, 62%, and 50% of the patients who were stage I, stage II, and stage III at entry, respectively. After 4 years biopsies showed cirrhosis in 31% and 50% of the patients in stage I and stage II at entry, respectively. A minority (20%) of the precirrhotic patients showed histological stability; sustained histological regression was rarely observed (2%). Our data suggest that a majority of patients with PBC will progress histologically within 2 years. The distribution of histological stages over time may be helpful in determining the number of patients and length of time necessary to appreciate a treatment effect on histological progression in clinical trials for PBC.

Biopsy↗
PubMed1996

The role of ultrasonography and automatic-needle biopsy in outpatient percutaneous liver biopsy.

The risk of complications from percutaneous liver biopsy is low, but discomfort is common and complications require hospitalization in approximately 4% of patients. The optimal method of performing these biopsies is unknown. The goal of our study was to determine whether the use of ultrasonography in the biopsy room immediately prior to or during the procedure would lessen the risk of complications and to compare the safety and efficacy in obtaining tissue by use of a Trucut needle versus an automatic biopsy needle. Between 1992 and 1994, 836 patients were entered into a randomized study (489 in Rochester, MN; 347 in Barcelona, Spain). Patients were randomized immediately prior to liver biopsy into four groups: Trucut needle, or automatic biopsy needle, and with or without ultrasonography. Fisher's Exact Test and a logistic regression model were also used to assess the effect of needle and ultrasonography on the odds for complications. The four biopsy groups were well-matched at entry with respect to age, sex, underlying liver disease, hemoglobin, prothrombin time, and platelet count. The use of ultrasound was associated with a decreased rate of hospitalization for pain, hypotension, or bleeding (2 vs. 9, P < .05). No difference in safety was found between the two types of needles. The number of passes needed to obtain specimens was similar for all four groups. The average length of the specimen was slightly greater with ultrasonographic-guided biopsies (1.7 mm vs. 1.6 mm, P < .05) and with biopsies obtained using the automatic biopsy needle when compared with the Trucut needle (1.7 mm vs. 1.5 mm, P < .05), but this did not seem to be clinically important. The addition of ultrasonography reduces complications in patients undergoing percutaneous liver biopsy. The type of needle appears to offer little difference in safety or yield of diagnostic tissue. The use of ultrasonography for guidance of percutaneous liver biopsy will lead to a lower rate of complications. The value of this benefit must be weighed against the added cost of ultrasonographic guidance.

Adolescent↗
PubMed1996

The long-term pathological evolution of chronic hepatitis C.

Most patients infected with hepatitis C virus (HCV) develop chronic hepatitis. Unfortunately, the pathological evolution of this disease over time is not completely understood. We studied 70 HCV-positive patients, from whom 2 to 10 liver biopsy specimens (mean, 3.9) had been obtained during an interval of 1 to 26 years (mean, 8.8 years). Each biopsy specimen was evaluated independently by four pathologists who each provided a numerical score for the grade of portal/periportal necroinflammation (0-4), grade of lobular necroinflammation (0-4), their sum (final grade), and the stage of fibrosis (1-4). The scores were correlated with progression of disease, if any, and transition to cirrhosis. During follow-up, 35 patients (50%) developed cirrhosis. Cirrhosis developed in all patients with a high final grade (> or = 5) of necroinflammation on initial biopsy who were followed for 10 years and in 96% of patients with an intermediate final grade (3.5-4.9) who were followed for 17 years. Only 30.4% of patients with low final grade (< or = 3.4) on initial biopsy developed cirrhosis after 13 years. All patients with evidence of septal fibrosis with incomplete nodularity (stage 3.0-3.4) in the initial biopsy progressed to unequivocal cirrhosis by 10 years. The rate of progression to cirrhosis was accelerated in patients whose initial biopsies showed high-grade and -stage lesions. This study demonstrates the importance of grading and staging liver biopsy lesions in chronic hepatitis C, particularly for patients with high-grade necroinflammation, septal fibrosis, and regions of modularity on initial biopsy who are at high risk of developing advanced cirrhosis in the ensuing decade.

Biopsy↗
PubMed1996

Ursodeoxycholic acid or clofibrate in the treatment of non-alcohol-induced steatohepatitis: a pilot study.

Non-alcohol-induced steatohepatitis (NASH) is characterized by elevated serum aminotransferase activities with hepatic steatosis, inflammation, and occasionally fibrosis that may progress to cirrhosis. No established treatment exists for this potentially serious disorder. Our aim was to conduct a pilot study to evaluate the safety and estimate the efficacy of ursodeoxycholic acid (UDCA) and clofibrate in the treatment of NASH. Forty patients were diagnosed with NASH based on a compatible liver biopsy with other causes of liver disease, including alcohol abuse, excluded by history, serum tests, and use of ultrasound. Twenty-four patients received 13 to 15 mg/kg/d of UDCA for 12 months. Sixteen patients with hypertriglyceridemia were placed on clofibrate, 2 g/day for 12 months. Twenty-five women and 15 men entered the study. Six of 40 patients (15%) withdrew because of side effects. Four additional patients were withdrawn because of noncompliance; one of them later required liver transplantation. In the UDCA group, the decreases in mean serum levels of alkaline phosphatase, alanine transaminase (ALT), and gamma-glutamyl transpeptidase (GGT) as well as histological grade of steatosis were significant. Among the patients treated with clofibrate, no change from baseline was found in mean ALT, aspartate transaminase (AST), GGT, bilirubin, triglycerides, and cholesterol, or in histological grade of steatosis, inflammation, or fibrosis after 12 months of treatment as compared with entry. Alkaline phosphatase activities decreased significantly from baseline. Despite the known lipid-lowering effects of clofibrate, it did not appear to be of clinical benefit in the treatment of NASH in this 1-year pilot study. However, treatment of NASH with UDCA for 12 months resulted in significant improvement in alkaline phosphatase, ALT, GGT, and hepatic steatosis. The possible benefit of UDCA therapy should be further investigated in the context of a randomized, controlled trial.

Alanine Transaminase↗
PubMed1996

Failed allografts and causes of death after orthotopic liver transplantation from 1985 to 1995: decreasing prevalence of irreversible hepatic allograft rejection.

Mayo Clinic pathology files from March 1985 to March 1995 contained records of 584 orthotopic liver transplantations in 515 patients. The most common indication for liver transplantation was primary sclerosing cholangitis (PSC), followed by primary biliary cirrhosis (PBC), and cryptogenic cirrhosis. In 59 patients, a total of 69 single or repeated retransplantations became necessary. Vascular complications necessitated retransplantation in 35 cases, followed by irreversible rejection in 16 cases, and primary graft failure in 8 cases. Ninety-nine patients died, 25 of them after one or more retransplantations. Infectious complications caused death in 38 cases, followed by graft-related complications (excluding rejection) in 22 cases, noninfectious systemic diseases such as intracerebral hemorrhage (21 cases), malignancies in 13 cases, and irreversible rejection in 5 cases. In the decade from 1985 to 1995, only 14 patients had irreversible rejection that often was associated with other complications such as ischemic cholangitis. Furthermore, the rate of irreversible rejection decreased dramatically. Thus, although 5 deaths were caused by irreversible rejection, none occurred since March 1991, and of the 16 retransplantations for irreversible rejection, only one needed to be performed during these last 4 years. The disappearance of irreversible rejection, which can be described as the "vanishing vanishing bile duct syndrome," must be considered when new immunosuppressants are tested, because graft loss and death from rejection are no longer suitable criteria.

Adult↗
PubMed1996

Extracellular Mg2+ regulates activation of rat eag potassium channel.

The rat homologue of Drosophila ether à gogo cDNA (rat eag) encodes voltage-activated potassium (K) channels with distinct activation properties. Using the Xenopus expression system, we examined the importance of extracellular Mg2+ on the activation of rat eag. Extracellular Mg2+ at physiological concentrations dramatically slowed the activation in a dose- and voltage-dependent manner. Other divalent cations exerted similar effects on the activation kinetics that correlated with their enthalpy of hydration. Lowering the external pH also resulted in a slowing of the activation. Protons competed with Mg2+ as the effect of Mg2+ was abolished at low pH. A kinetic model for rat eag activation was derived from the data indicating that all four channel subunits undergo a Mg2+-dependent conformational transition prior to final channel activation. The strong dependence of rat eag activation on both the resting potential and the extracellular Mg2+ concentration constitutes a system for fine-tuning K channel availability in neuronal cells.

Animals↗
PubMed1996

Pharmacokinetics of a synthetic, chemically modified hammerhead ribozyme against the rat cytochrome P-450 3A2 mRNA after single intravenous injections.

Modulation of gene expression via nucleic acid sequence-specific intervention represents a new paradigm for drug discovery and development. Ribozymes are small RNA structures capable of cleaving RNA target molecules in a catalytic fashion. A 2'-O-allyl-modified hammerhead ribozyme designed to cleave the messenger RNA of cytochrome P-450 3A2 was administered to rats via 0.25 mg intravenous injections to investigate the disposition of this compound. The chemically modified ribozyme binds to serum albumin and can be displaced by phosphorothioate oligonucleotides. A biphasic plasma clearance with a distribution half-life of 12 min and an elimination half-life of 6.5 h was observed. A volume of distribution of 2.1 l/kg indicates perfusion into tissues well beyond the vascular system. The chemically modified ribozyme can be detected intact in the plasma up to 48 h after injection. Metabolic degradation of the chemically modified ribozyme occurs at unmodified ribonucleotides, leaving the 2'-O-allyl-modified sites intact. Recovery of intact chemically modified ribozyme was 1.9% of the administered dose at 12 h along with significant metabolites. The renal clearance of the intact ribozyme is an average 34.3 ml/h. The tissue distribution of the chemically modified ribozyme at 48 h is primarily to kidney and liver but the only detected material is a single 27-mer metabolite that has been cut in the unmodified GAAA region. The brain concentration of the prominent 27-mer metabolite is greater than that observed in the lung or spleen. Examination of tissues reveals no morphological evidence of toxicity. These data strongly support the potential utility of synthetic, 2'-O-allyl-modified hammerhead ribozymes as therapeutic agents in vivo.

Animals↗
PubMed1995

[The risks of percutaneous endoscopic gastrostomy].

AIM OF STUDY: Percutaneous endoscopic gastrostomy (PEG) having established itself as the standard procedure and preferred method for artificial long-term intestinal nutrition, a retrospective study was undertaken to evaluate the complications and course after PEG. PATIENTS AND METHODS: 1299 patients in whom PEG had been performed between 1.8. 1984 and 1.8. 1993 were sent a standardised questionnaire, 1182 of which could be evaluated (954 males, 228 females; mean age 56.7 [3-94] years). RESULTS: Total duration of PEG was 279830 days, with a mean of 216.2 days per patient. Mortality rate due to the procedure was 0.5%. Severe complications (peritonitis, perforation or faulty puncture) occurred in 9 patients (0.9%). The most common relatively minor complications were peristomal wound infection (8.7%) and brief periods of abdominal pain (4.8%). Typical side effects specific to nutrition were gastrointestinal symptoms, like constipation, diarrhoea, meteorism, vomiting and other signs of illness (39.3%). CONCLUSION: Long-term intestinal nutrition via PEG is a safe, efficacious and cost-effective form of treatment which decreases demands on hospital care and reduces costs.

Adolescent↗
PubMed1995

Biological response to ligament wear particles.

In ligament replacement cases where the artificial ligament has worn and partially or totally ruptured, the released wear particles have been associated with a chronic synovitis that inhibits integration of the ligament and contributes to the ultimate failure of the device. In this study, the biological response to ligament wear particles from nine different artificial ligaments was quantitatively evaluated in vivo. Wear particles, the majority of which were < 7 microns, were generated in vitro. These particles were injected into rabbit knee joints, and the biological response as well as the systemic migration of the particles were evaluated histologically after 4 weeks. The extent of the inflammatory reaction to the ligament wear particles was found to be significantly (p < 0.05) influenced by the type of material implanted. No particles were found in the regional lymph nodes or in the spleen, liver, kidney, or lung.

Animals↗
PubMed1995

Recent-onset autoimmune hepatitis. Biopsy findings and clinical correlations.

Whereas the histologic findings in clinically "chronic" autoimmune hepatitis have been well established, with piecemeal necrosis as a hallmark lesion, the histologic findings of clinically "acute" or recent-onset autoimmune hepatitis remain undefined. The goal of this study was to define more fully the liver histomorphology in patients with recent-onset autoimmune hepatitis. Twenty-six patients were identified at our institution who had well-characterized autoimmune hepatitis and had undergone a liver biopsy within 6 months of clinical presentation. A detailed histologic evaluation revealed evidence of chronic liver disease in 25 (of 26) patients despite the lack of correlating clinical chronicity. The histologic evidence of chronicity included, in addition to a portal lymphoplasmacytic infiltrate, bridging (septal) fibrosis (11 patients) and overt cirrhosis (four patients). Eighteen of these 25 cases with evidence of chronicity also showed zone 2 and 3 lobular hepatitis, including disarray and hepatocyte necrosis. A single case showed lobular hepatitis with confluent hepatocyte necrosis (submassive hepatocellular necrosis), but no evidence of chronic liver disease. Although autoimmune hepatitis remains in the differential diagnosis of lobular hepatitis, these data show that most patients with autoimmune hepatitis who undergo biopsy early in its clinical course will have histologic evidence of chronic liver disease. Most of these patients probably have a lobular "flare" in disease activity, which likely precipitated the clinical presentation. The findings herein reinforce the concept that autoimmune hepatitis is by definition a chronic disease and supports the proposal that the modifier "chronic" be eliminated from autoimmune hepatitis.

Adult↗
PubMed1995

Chronic hepatitis. An update on terminology and reporting.

The terms chronic active hepatitis (CAH), chronic persistent hepatitis (CpH), and chronic lobular hepatitis (CLH) have become obsolete, and their use without further specifications should be discontinued. This recommendation has become necessary because these names have changed from descriptive terms, intended for grading, to terms that are used either as morphologic diagnoses or disease designations or both, depending on individual preferences. Because this practice has caused serious misunderstandings, many authors and two international groups have recommended the use of a clear etiologic terminology. For the reporting practice of pathologists, we recommend that the pathologist routinely sign out biopsy samples with features of chronic hepatitis by indicating etiology, grade, and stage. An example would be autoimmune hepatitis, severe, stage 3. The stage in this case would indicate the presence of well-developed septal fibrosis but no nodular regeneration. Obviously, for the etiologic diagnosis, morphologic findings must be integrated with clinical and laboratory data. If this information is not available, clear morphologic diagnoses should be reported. Thus, instead of CPH, the diagnosis should be portal hepatitis, cause undetermined. This reporting practice eliminates ambiguous terminology and avoids the risk of inappropriate treatment as might occur, for example, when a term such as CAH is used to describe Wilson's disease and is misunderstood to mean autoimmune hepatitis. For a transitional period and to facilitate relearning, the terms CAH, CPH, and CLH can be reported in parentheses behind the etiologic diagnosis.

Chronic Disease↗
PubMed1995

Two cases from the spectrum of nonalcoholic steatohepatitis.

Nonalcoholic steatohepatitis is a poorly understood disease that mimics alcoholic liver disease histologically. Its natural history is not well defined, although gradual progression to cirrhosis has been described. Most patients with this condition have been obese, with or without associated diabetes or hyperlipidemia. No known effective treatment exists for nonalcoholic steatohepatitis, although weight loss may have a beneficial effect. We report two cases of nonalcoholic steatohepatitis. One patient with well-established nonalcoholic steatohepatitis had cirrhosis with a complete loss of fat on subsequent liver biopsy despite a gain in weight, simulating cryptogenic cirrhosis. In another patient, the condition improved after use of ursodeoxycholic acid; this agent may be a potential therapeutic agent for the treatment of nonalcoholic steatohepatitis. We believe these two cases represent the spectrum of this condition: on the one end is a progressive liver disease that in some instances may be a cause of cryptogenic cirrhosis; at the other end, a potentially treatable liver condition.

Adult↗
PubMed1995

Multiple abdominal telangiectases and lymphangiectases. A limited form of Osler-Weber-Rendu disease?

We describe a 23-year-old man with protein-losing enteropathy, iron deficiency anemia, and recurrent gastrointestinal bleeding. The patient eventually developed disseminated intravascular coagulation, portal vein thrombosis, and extensive small bowel infarction. The autopsy showed multiple telangiectases in the intestines, mesentery, liver, gallbladder, renal pelves, and diaphragm. In addition, lymphangiectases were found in the retroperitoneal space, intestines, and liver. These lesions appeared to have been the cause of the gastrointestinal bleeding and the protein-losing enteropathy. The case most likely represents Osler-Weber-Rendu disease without the usual manifestations in the skin and oral-nasal cavities.

Adult↗