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Biomedical subjects

C L Berg

Publications and source records attributed to C L Berg.

At least 19 recordsLinked to original sources
PubMed2006

Survival after adult liver transplantation does not correlate with transplant center case volume in the MELD era.

It has been demonstrated that low-volume orthotopic liver transplant centers have poorer outcomes compared to high-volume centers. In light of the recent significant changes in liver transplantation, we performed an analysis of transplant center procedure volume and mortality with data from the Model for End-stage Liver Disease (MELD) era. We analyzed 9909 adult liver transplants performed in the United States since the beginning of the MELD allocation system. Transplant centers were categorized by volume of transplants performed per year. Multivariate survival models were constructed with raw survival as the primary endpoint for both high- and low-volume centers. Thirty percent of centers were categorized as low volume (< or =20 liver transplants per year) and 8.2% of all transplants were performed at low-volume centers. The unadjusted raw mortality rate at 1-year post-transplant at high-volume centers (9.5%, 95% CI 9.4-9.5) was significantly lower than the rate at low-volume centers (10.9%, 95% CI 10.4-11.4), p < 0.001. However, after adjusting for disease severity and multiple donor and recipient factors, transplant center volume was no longer a significant predictor of post-transplant survival (HR 0.99, 95% CI 0.99-1.00, p = 0.22). We conclude that transplant center case volume is no longer a significant predictor of post-transplant survival in the MELD era and factors which are currently unaccounted for in present survival models should be investigated.

Adult↗
PubMed2006

SRTR center-specific reporting tools: Posttransplant outcomes.

Measuring and monitoring performance--be it waiting list and posttransplant outcomes by a transplant center, or organ donation success by an organ procurement organization and its partnering hospitals--is an important component of ensuring good care for people with end-stage organ failure. Many parties have an interest in examining these outcomes, from patients and their families to payers such as insurance companies or the Centers for Medicare and Medicaid Services; from primary caregivers providing patient counseling to government agencies charged with protecting patients. The Scientific Registry of Transplant Recipients produces regular, public reports on the performance of transplant centers and organ procurement organizations. This article explains the statistical tools used to prepare these reports, with a focus on graft survival and patient survival rates of transplant centers--especially the methods used to fairly and usefully compare outcomes of centers that serve different populations. The article concludes with a practical application of these statistics--their use in screening transplant center performance to identify centers that may need remedial action by the OPTN/UNOS Membership and Professional Standards Committee.

Adolescent↗
PubMed2001

Characterization of a human plasma membrane heme transporter in intestinal and hepatocyte cell lines.

Heme is the most bioavailable form of dietary iron and a component of many cellular proteins. Controversy exists as to whether heme uptake occurs via specific transport mechanisms or passive diffusion. The aims of this study were to quantify cellular heme uptake with a fluorescent heme analog and to determine whether heme uptake is mediated by a heme transporter in intestinal and hepatic cell lines. A zinc-substituted porphyrin, zinc mesoporphyrin (ZnMP), was validated as a heme homolog in uptake studies of intestinal (Caco-2, I-407) and hepatic (HepG2) cell lines. Uptake experiments to determine time dependence, heme inhibition, concentration dependence, temperature dependence, and response to the heme synthesis inhibitor succinylacetone were performed. Fluorescence microscope images were used to quantify uptake and determine the cellular localization of ZnMP; ZnMP uptake was seen in intestinal and hepatic cell lines, with cytoplasmic uptake and nuclear sparing. Uptake was dose- and temperature dependent, inhibited by heme competition, and saturated over time. Preincubation with succinylacetone augmented uptake, with an increased initial uptake rate. These findings establish a new method for quantifying heme uptake in individual cells and provide strong evidence that this uptake is a regulated, carrier-mediated process.

Carrier Proteins↗
PubMed2000

Hepatitis C-induced hepatic allograft injury is associated with a pretransplantation elevated viral replication rate.

Hepatitis C virus (HCV) allograft infection after liver transplantation follows a variable but accelerated course compared with the nontransplantation population. Predictors of outcome and mechanisms of reinfection remain elusive. The accelerated HCV-induced allograft injury associated with a 10- to 20-fold increase in serum viral quantity posttransplantation was hypothesized to be the result of elevated intrahepatic viral replication rates. Patients (N = 23) with HCV-induced end-stage liver disease who underwent liver transplantation between October 1995 and December 1998 were prospectively studied. HCV-induced allograft injury was defined by posttransplantation persistent biochemical hepatitis or allograft fibrosis not explained by other diagnoses. Liver biopsies (N = 92) were obtained by protocol and when clinically indicated. Negative-strand HCV RNA (putative intermediate for replication) was detected by a strand-specific reverse-transcription polymerase chain reaction (RT-PCR) assay and semiquantatively compared with constitutively expressed 18S rRNA. Recipients with increased pretransplantation replication were at increased risk for the development of posttransplantation biochemical hepatitis (P =.03), an increased rate of allograft fibrosis (P =.006), and increased mortality rate (40.0% vs. 0.0%; P =.02). There was no correlation with quantities of genomic HCV RNA in the serum with relative intrahepatic viral replication either before or after liver transplantation. The relative rate of HCV replication within the allograft was not elevated in the posttransplantation period compared with that seen within the explanted liver. Accelerated allograft injury caused by HCV may be predicted by viral replication rates within the explanted liver. The stable intrahepatic replication rate after transplantation suggests that elevated serum viral loads are the result of decreased viral clearance, possibly secondary to immunosuppressive therapy.

Adolescent↗
PubMed1999

Severe cholestasis related to intraconazole for the treatment of onychomycosis.

We describe a case of prolonged cholestasis temporally associated with the use of itraconazole for onychomycosis. Peak bilirubin level of 32.0 mg/dl was documented approximately 2 months after discontinuation of the patient's itraconazole therapy, with symptoms of cholestasis persisting more than 1 month after the peak in bilirubin. Physicians should be aware of the potential for severe cholestasis associated with itraconazole usage.

Aged↗
PubMed1998

Hepatocellular expression of glucose-6-phosphatase is unaltered during hepatic regeneration.

Gluconeogenesis and glycogenolysis are essential hepatic functions required for glucose homeostasis. During the initial phase of hepatic regeneration, the immediate-early genes (IEG) are rapidly expressed, and the IEG RL-1 encodes for glucose-6-phosphatase (G-6-Pase). G-6-Pase is a microsomal enzyme essential for gluconeogenesis and glycogenolysis. This study employs a partial-hepatectomy model to examine the expression and activity of G-6-Pase. After partial hepatectomy, rat hepatic G-6-Pase gene expression is transcriptionally regulated, and mRNA levels are increased approximately 30-fold. However, in contrast to this rapid gene induction, microsomal enzyme activity is unchanged after partial hepatectomy. Western blotting demonstrates that microsomal G-6-Pase protein expression is also unchanged after partial hepatectomy, and similar results are also noted in whole liver homogenate. Thus, despite marked induction in gene expression of the IEG G-6-Pase after partial hepatectomy, protein expression and enzyme activity remain unchanged. These data indicate that, although this hepatocyte IEG is transcriptionally regulated, the physiologically important level of regulation is posttranscriptional. This highlights the importance of correlating gene expression of IEG with protein expression and physiological function.

Animals↗
PubMed1997

Portal hypertensive stomapathy: a newly described entity and its successful treatment by placement of a transjugular intrahepatic portosystemic shunt.

We report the case of a 68-yr-old woman who had previously undergone a total colectomy and ileostomy for Crohn's disease limited to the colon. She subsequently had recurrent episodes of severe stomal bleeding and was discovered to have micronodular cirrhosis. No definite stomal varices were seen by visual inspection, stomal endoscopy, stomal endosonography, or angiography. Nevertheless, multiple discrete, punctate bleeding pints were seen on the external mucosal surface of the stoma (not at the mucocutaneous junction). Despite undergoing numerous modes of treatment, the bleeding continued. The only successful and effective form of treatment was the placement of a transjugular intrahepatic portosystemic shunt.

Aged↗
PubMed1996

Two kinetically-distinct components of UDP-glucuronic acid transport in rat liver endoplasmic reticulum.

Previous studies have documented the presence of protein-mediated transport of UDP-glucuronic acid (UDP-GlcUA) in rat liver endoplasmic reticulum (ER). Measurement of uptake at varying concentrations of high specific activity [beta-32P]UDP-GlcUA has revealed the presence of a two component UDP-GlcUA transporting system. Transport at low substrate concentrations occurred predominantly via a high affinity component (K(m) = 1.6 microM), whereas a low affinity component (K(m) = 38 microM) predominated at high substrate concentrations. The K(m) for the high affinity system is in agreement with that previously published, while the low affinity component is a new finding. The uptake of UDP-GlcUA was temperature-sensitive, time dependent, and saturable for both components. The high affinity transport was affected by trans-stimulation and cis-inhibition by UDP-N-acetylglucosamine (UDP-GlcNAc); however, the same concentrations of UDP-GlcNAc had less effect on the low affinity system. In order to further study the two transport components, various inhibitors of anion transport carriers were tested. The high affinity component was strongly inhibited by 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS) and furosemide, while the low affinity system was less sensitive to these reagents. Dose-dependent inhibition by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) was found for both transport systems. Probenecid was found to be a weak inhibitor of both components of the UDP-GlcUA uptake. Finally, the major metabolite of 3'-azido-3'-deoxythymidine, 3'-azido-3'-deoxythymidine monophosphate (AZTMP), was able to inhibit the uptake of UDP-GlcUA by both components. The results indicate the presence of two carrier-mediated UDP-glucuronic acid transporting components in rat liver ER.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
PubMed1996

Hepatic regeneration is associated with preservation of microsomal glucuronidation.

Significant controversy exists regarding the regulation of glucuronidation during the process of hepatic regeneration. We used a partial hepatectomy rat model to elucidate the effects of hepatic regeneration on the various components of the microsomal glucuronidation system. Hepatic microsomes were prepared by standard sucrose density centrifugation, coupled with a modified technique involving Percoll centrifugation. Microsomal uridine diphosphate (UDP)-glucuronosyltransferase (UGT) protein expression and UGT messenger RNA (mRNA) levels were measured by Western and Northern blotting. UGT enzyme activity was determined toward two prototypical aglycones, p-nitrophenol and estrone, in intact and digitonin-treated microsomes. Microsomal uptake of the cosubstrate for all glucuronidation reactions, UDP-glucuronic acid (UDP-GlcUA), was determined using a rapid-filtration assay. Microsomal enrichment after hepatectomy was preserved only when the Percoll method was used. Microsomal UGT protein expression and UGT mRNA levels were unaltered after hepatectomy. UGT enzyme activity toward estrone was unchanged 1 day posthepatectomy compared with sham laparotomy controls. Similarly, p-nitrophenol glucuronide formation was unaffected by hepatic regeneration 1, 2, and 5 days posthepatectomy when digitonin-treated microsomes were used. Glucuronidation of p-nitrophenol in intact microsomes was increased in partial hepatectomy compared with sham-operated controls at 1 and 2 days. This increase was not attributable to changes in microsomal UDP-GlcUA uptake, which was comparable in both groups. We conclude that microsomal glucuronidation, in contrast to other well characterized hepatic metabolic functions, is highly preserved during liver regeneration.

Animals↗
PubMed1995

Membrane translocation and regulation of uridine diphosphate-glucuronic acid uptake in rat liver microsomal vesicles.

BACKGROUND/AIMS: Hepatic glucuronidation is quantitatively the most important conjugation reaction by which an array of endogenous compounds and xenobiotics undergo biotransformation and detoxification. The active site of the uridine diphosphate (UDP) glucuronosyltransferases, which catalyze glucuronidation reactions, has been postulated to reside in the lumen of the endoplasmic reticulum. The aim of this study was to characterize the process whereby UDP glucuronic acid (UDP-GlcUA), the cosubstrate for all glucuronidation reactions, is transported into microsomal vesicles. METHODS: The uptake process was analyzed using rapid filtration techniques, radiolabeled UDP-GlcUA, and rat liver microsomes. RESULTS: Uptake was saturable with respect to time and concentration, inhibited by 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid and 4-acetamido-4'-isothio-cyanatostilbene-2-2'-disulfonic acid, and was osmotically sensitive. Transport was stimulated by Mg2+ and guanosine triphosphate (50 mumol/L) but not guanosine 5'-O-(3-thiotriphosphate) or adenosine triphosphate. Luminal UDP-N-acetylglucosamine (1 mmol/L) produced enhanced uptake of UDP-GlcUA (trans stimulation). In contrast to nucleotide sugar transport in the Golgi apparatus, trans uridine monophosphate and UDP did not alter UDP-GlcUA transport in microsomes, indicating distinct processes. CONCLUSIONS: These data provide unambiguous evidence for the existence of a unique, substrate-specific, regulated, carrier-mediated process that transports UDP-GlcUA into the lumen of hepatocyte microsomes. This transporter may regulate glucuronidation in vivo.

Animals↗
PubMed1995

Evidence for a low Km transporter for non-transferrin-bound iron in isolated rat hepatocytes.

Non-transferrin-bound iron (NTBI) plays an important role in the hepatocellular injury induced by iron overload. However, the mechanism responsible for NTBI uptake into hepatocytes remains poorly defined. The purpose of this study was to define the kinetics of NTBI uptake by isolated rat hepatocytes and to characterize the uptake process. NTBI uptake was time and temperature dependent, exhibited a Michaelis-Menten constant (Km) value of 1.25 microM and maximum uptake of 241 pmol.10(6) cells-1.min-1, and 55Fe was incorporated in part into intracellular ferritin. Uptake was Ca2+ dependent, exhibiting 15 and 80% of maximal uptake in the presence of 0.6 and 0.75 mM CaCl2, respectively. The putative NTBI transporter was highly specific; divalent (Zn2+, Mn2+, Cd2+, and Co2+) or trivalent (La3+) cations did not inhibit Fe3+ uptake. Reduction from Fe3+ to Fe2+ was not essential for uptake or the process occurred deep within the membrane bilayer, since the Fe2+ chelator ferrozine did not influence 55Fe uptake. These data provide evidence for a low Km plasma membrane transporter for NTBI, which should be functional at physiological serum concentrations and saturated in iron-overload diseases, such as hemochromatosis.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1993

Blood pressure comparison in a selected Native American and white population.

This study compared the frequency of blood pressure elevation in a selected Native American and white population. Three hundred individuals participated: 87 Native Americans, 210 whites, and 3 others. Data were gathered using a questionnaire that addressed residence, sex, age, race, occupation, height, smoking, alcohol use, tea/coffee consumption, medications, and past or present illness. Weight and blood pressure were measured by the researchers at the time of data collection. The sample mean for systolic blood pressure (SBP) was 124 mm Hg (SD 14.78) and diastolic blood pressure (DBP) was 77 mm Hg (SD 10.13). One-way analysis of variance showed age groups and sex to affect blood pressure significantly (P = 0.0001). Stepwise multiple regression indicated weight significantly predicted blood pressure (SBP multiple R = 0.39, P = 0.001; DBP multiple R = 0.43, P = 0.00001). The interaction of age, sex, tobacco, alcohol, and caffeine influenced SBP and DBP. Obviously, these findings have limited generalizeability due to the sampling frame used in this study.

Adult↗
PubMed1992

Total blood cholesterol and contributory risk factors in an adolescent population.

Total blood cholesterol (TBC) levels and contributory risk factors in an adolescent population were investigated. Existing TBC screening records were reviewed on 452 10th grade students in two schools. The sample consisted of 52% males and 48% females whose mean age was 15.47 years. Blood samples were analyzed by the Reflotron. Risk factors investigated included age, gender, ethnicity, individual and family history of high cholesterol, history of high blood pressure, smoking tobacco products, and oral contraceptive use. The sample mean for TBC was 150.61. The only significant factors identified by ANOVA were gender and use of oral contraceptives. Females had higher TBC levels than males, and females who used oral contraceptives had higher TBC levels than nonusers.

Adolescent↗
PubMed1992

Primary biliary cirrhosis: new therapeutic directions.

The immunologic mechanisms responsible for the development of primary biliary cirrhosis (PBC) remain poorly defined, although recent investigations have provided new clues as to the role of cellular membrane proteins such as the mitochondrial autoantigens and intercellular adhesion molecules. Additionally, new therapeutic agents have become available that markedly enhance the prospect for medical management of both hepatic and extrahepatic manifestations of PBC. Definitive therapy with ursodeoxycholic acid and/or methotrexate, and symptomatic relief of pruritus with rifampicin or metronidazole may become standard in the years ahead. The results of their use to date in the treatment of PBC are detailed in this review. Successful therapy of hepatic osteodystrophy associated with PBC has yet to be achieved, although early data suggest a role for ursodeoxycholic acid, estrogen, calcium, and vitamin D in the management of this debilitating problem. Orthotopic liver transplantation continues to be successful for the management of advanced disease (greater than 70% 5-year survival) and will remain an essential therapeutic tool until definitive medical therapy for PBC becomes available.

Bone Diseases, Metabolic↗