Biomedical subjects

Manuel de la Mata

Publications and source records attributed to Manuel de la Mata.

8 recordsLinked to original sources

PubMed2006

Model for end-stage liver disease score-based allocation of donors for liver transplantation: a spanish multicenter experience.

BACKGROUND: Prioritizing the liver transplant waiting list (WL) is subject to great variability. We present the experience of four transplant centers in Andalusia (Southern Spain) with a new consensus model of WL management based on the Model for End-Stage Liver Disease (MELD) score. METHODS: The initial criteria for local prioritizing were: a) cirrhosis with MELD score > or =24, and b) all hepatocellular carcinoma (HCC) admitted to the WL. Fourteen months later new criteria were established: a) cirrhosis with MELD score > or =18, and b) uninodular HCC between 3-5 cm or multinodular HCC (2-3 nodules <3 cm). Access to regional priority was scheduled after three months for patients with cirrhosis or six months for patients with HCC. We analyzed the WL mortality rate, posttransplant survival rate, and overall survival rate over three 14-month periods: A (before implementation of priority criteria), B (initial criteria), and C (current criteria). RESULTS: Priority was given to 36% of recipients in period B and 47% in period C. The WL mortality rate (including removals from WL) was 12.9%, 12.9%, and 10.7% in periods A, B, and C, respectively. One-year graft survival was 79.7%, 72.6%, and 81.2% in the same periods. The overall one-year survival rate for new cases on the WL was 74.9% in period A, 68.6% in period B, and 82.2% in period C. CONCLUSIONS: The allocation system and WL management with the current criteria resulted in lower waiting list mortality without reducing posttransplant survival, leading to better survival for all patients listed.

Female↗

PubMed2006

RNA polymerase II C-terminal domain mediates regulation of alternative splicing by SRp20.

Previous studies have linked the C-terminal domain (CTD) of RNA polymerase II (pol II) with cotranscriptional precursor messenger RNA processing, but little is known about the CTD's function in regulating alternative splicing. We have examined this function using alpha-amanitin-resistant pol II CTD mutants and fibronectin reporter minigenes. We found that the CTD is required for the inhibitory action of the serine/arginine-rich (SR) protein SRp20 on the inclusion of a fibronectin cassette exon in the mature mRNA. CTD phosphorylation controls transcription elongation, which is a major contributor to alternative splicing regulation. However, the effect of SRp20 is still observed when transcription elongation is reduced. These results suggest that the CTD promotes exon skipping by recruiting SRp20 and that this contributes independently of elongation to the transcriptional control of alternative splicing.

Alternative Splicing↗

PubMed2006

Daclizumab induction and maintenance steroid-free immunosuppression with mycophenolate mofetil and tacrolimus to prevent acute rejection of hepatic allografts.

Steroid-free immunosuppressive regimens reduce corticosteroid-related side effects in liver transplant recipients although their efficacy is very variable. We evaluated the efficacy and safety of a steroid-free regimen in a 6-month, open-label, multicenter, pilot study, which involved 102 liver transplant patients treated with daclizumab (2 mg/kg within 6 h following transplant and 1 mg/kg on day 7), mycophenolate mofetil (MMF, 1 g b.i.d) and tacrolimus (trough levels of 5-15 ng/ml in the first month and 5-10 ng/ml thereafter). One intra-operative dose of methylprednisolone was administered. At 6 months, the acute rejection rate was 9.8%, and patient and graft survival rates were 96% and 95%, respectively. Acute rejection rates were similar for hepatitis C-positive patients (8.6%) and hepatitis C-negative patients (10.4%). Infections occurred in 22% of patients; most cases were considered mild or moderate. Post-transplantation hypertension and diabetes mellitus developed in 37% and 14% of patients, respectively, during the study period, but were markedly less frequent (8% and 6%, respectively) at 6 months. Hypercholesterolemia was observed in only 2% of patients. In conclusion, the steroid-free immunosuppressive regimen of daclizumab, MMF, and tacrolimus effectively prevents acute rejection after liver transplantation without decreasing safety.

Acute Disease↗

PubMed2004

PGE1-induced NO reduces apoptosis by D-galactosamine through attenuation of NF-kappaB and NOS-2 expression in rat hepatocytes.

Prostaglandin E1 (PGE1) reduces cell death in experimental and clinical liver dysfunction. We have previously shown that PGE1 preadministration protects against NO-dependent cell death induced by D-galactosamine (D-GalN) through a rapid increase of nuclear factor kappaB (NF-kappaB) activity, inducible NO synthase (NOS-2) expression, and NO production. The present study investigates whether PGE1-induced NO was able to abolish NF-kappaB activation, NOS-2 expression, and apoptosis elicited by D-GalN. Rat hepatocytes were isolated following the classical method of collagenase perfusion of liver. PGE1 (1 micromol/L) was administered 2 hours before D-GalN (5 mmol/L) in primary culture rat hepatocytes. PGE1 reduced inhibitor kappaBalpha degradation, NF-kappaB activation, NOS-2 expression, and apoptosis induced by D-GalN. The administration of an inhibitor of NOS-2 abolished the inhibitory effect of PGE1 on NF-kappaB activation and NOS-2 expression in D-GalN-treated hepatocytes. Transfection studies using different plasmids corresponding to the NOS-2 promoter region showed that D-GalN and PGE1 regulate NOS-2 expression through NF-kappaB during the initial stage of hepatocyte treatment. PGE1 was able to reduce the promoter activity induced by D-GalN. In addition, a NO donor reduced NOS-2 promoter activity in transfected hepatocytes. In conclusion, administration of PGE1 to hepatocytes produces low levels of NO, which inhibits its own formation during D-GalN-induced cell death through the attenuation of NF-kappaB-dependent NOS-2 expression. Therefore, a dual role for NO in PGE1-treated D-GalN-induced toxicity in hepatocytes is characterized by a rapid NO release that attenuates the late and proapoptotic NOS-2 expression.

Alprostadil↗

PubMed2004

Multiple links between transcription and splicing.

Transcription and pre-mRNA splicing are extremely complex multimolecular processes that involve protein-DNA, protein-RNA, and protein-protein interactions. Splicing occurs in the close vicinity of genes and is frequently cotranscriptional. This is consistent with evidence that both processes are coordinated and, in some cases, functionally coupled. This review focuses on the roles of cis- and trans-acting factors that regulate transcription, on constitutive and alternative splicing. We also discuss possible functions in splicing of the C-terminal domain (CTD) of the RNA polymerase II (pol II) largest subunit, whose participation in other key pre-mRNA processing reactions (capping and cleavage/polyadenylation) is well documented. Recent evidence indicates that transcriptional elongation and splicing can be influenced reciprocally: Elongation rates control alternative splicing and splicing factors can, in turn, modulate pol II elongation. The presence of transcription factors in the spliceosome and the existence of proteins, such as the coactivator PGC-1, with dual activities in splicing and transcription can explain the links between both processes and add a new level of complexity to the regulation of gene expression in eukaryotes.

Alternative Splicing↗

PubMed2003

A slow RNA polymerase II affects alternative splicing in vivo.

Changes in promoter structure and occupation have been shown to modify the splicing pattern of several genes, evidencing a coupling between transcription and alternative splicing. It has been proposed that the promoter effect involves modulation of RNA pol II elongation rates. The C4 point mutation of the Drosophila pol II largest subunit confers on the enzyme a lower elongation rate. Here we show that expression of a human equivalent to Drosophila's C4 pol II in human cultured cells affects alternative splicing of the fibronectin EDI exon and adenovirus E1a pre-mRNA. Most importantly, resplicing of the Hox gene Ultrabithorax is stimulated in Drosophila embryos mutant for C4, which demonstrates the transcriptional control of alternative splicing on an endogenous gene. These results provide a direct proof for the elongation control of alternative splicing in vivo.

Adenoviridae↗

PubMed2003

Antiviral therapy of patients with decompensated cirrhosis to prevent recurrence of hepatitis C after liver transplantation.

BACKGROUND/AIMS: After liver transplantation (LT) infection of the graft with the hepatitis C virus (HCV) is almost universal and chronic hepatitis and cirrhosis develop in a significant proportion of patients. One of the possible strategies to prevent HCV infection recurrence is to eradicate HCV before LT. METHODS: We evaluated the efficacy and safety of antiviral therapy to prevent HCV recurrence in 30 HCV-cirrhotic patients awaiting LT. At the time of inclusion 15 patients were Child-Pugh A and 15 Child-Pugh B/C. The infecting genotype was 1b in 25 patients. Treatment with interferon alpha-2b 3 MU/day and ribavirin 800 mg/day was initiated when the expected time for LT was less than 4 months and continued until LT. The median duration of treatment was 12 weeks. RESULTS: Nine patients (30%) achieved a virological response and 21 did not respond to therapy. In nine (43%) of the 21 non-responders viral load decreased > or =2 log10 during treatment. A viral load decrease > or = 2 log10 at week 4 of treatment was the strongest predictor of virological response. All nine virological responders have already undergone LT; six patients remain free of infection after a median follow-up of 46 weeks and HCV infection recurred in three patients after LT. In one of these patients HCV-RNA was still detectable in the explanted liver. Side effects were frequent and dose reduction was necessary in 19 (63%) of the 30 patients; no patient died while on therapy. CONCLUSIONS: Our data support the utilization of antiviral therapy in HCV-infected patients awaiting LT as one of the strategies to prevent hepatitis C recurrence after transplantation.

Adult↗

PubMedDate not supplied

Control of alternative pre-mRNA splicing by RNA Pol II elongation: faster is not always better.

The realization that the mammalian proteomic complexity is achieved with a limited number of genes demands a better understanding of alternative splicing regulation. Promoter control of alternative splicing was originally described by our group in studies performed on the fibronectin gene. Recently, other labs extended our findings to the cystic fibrosis, CD44 and CGRP genes strongly supporting a coupling between transcription and pre-mRNA splicing. A possible mechanism that would fit in these results is that the promoter itself is responsible for recruiting splicing factors, such as SR proteins, to the site of transcription, possibly through transcription factors that bind the promoter or the transcriptional enhancers. An alternative model, discussed more extensively in this review, involves modulation of RNA pol II (pol II) elongation rate. The model is supported by findings that cis- and trans- acting factors that modulate pol II elongation on a particular template also provoke changes in the alternative splicing balance of the encoded mRNAs.

Alternative Splicing↗