PubMed Health⌕ Search

Biomedical subjects

D Samuel

Publications and source records attributed to D Samuel.

At least 37 records · Page 2Linked to original sources
PubMed2001

A model to assess the infection potential of jet injectors used in mass immunisation.

Jet injectors are needleless injectors that penetrate skin with high-pressure fluid. They have potential advantages over needles and syringes in mass immunisation programs, but concerns over their capacity to transfer blood-borne viruses have been a barrier to acceptance. Hepatitis B infection can transmit in 10 pl of blood; detection of such low volumes presents severe difficulties to such assessments. A model to assess jet injector safety was developed using injection of an inert buffer into calves and assaying the next injector discharge, representing the next dose of vaccine, for blood using a highly sensitive ELISA. Four injectors were tested: two with reusable heads and direct skin contact, one with single-use injector heads and one where the injector head discharged at a distance from the skin. All injectors tested transmitted significant (over 10 pl) volumes of blood; the volumes and frequency of contamination varied with injector. The source of the contamination was consistent with contamination by efflux of injected fluid and blood from the pressurised pocket in tissue that is formed during injection. This insight should inform the design of safe jet injectors.

Animals↗
PubMed2001

Impaired glutamate uptake in the R6 Huntington's disease transgenic mice.

Huntington's disease (HD) is a late-onset neurodegenerative disease for which the mutation is CAG/polyglutamine repeat expansion. The R6 mouse lines expressing the HD mutation develop a movement disorder that is preceded by the formation of neuronal polyglutamine aggregates. The phenotype is likely caused by a widespread neuronal dysfunction, whereas neuronal cell death occurs late and is very selective. We show that a decreased mRNA level of the major astroglial glutamate transporter (GLT1) in the striatum and cortex of these mice is accompanied by a concomitant decrease in glutamate uptake. In contrast, the expression of the glutamate transporters, GLAST and EAAC1, remain unchanged. The mRNA level of the astroglial enzyme glutamine synthetase is also decreased. These changes in expression occur prior to any evidence of neurodegeneration and suggest that a defect in astrocytic glutamate uptake may contribute to the phenotype and neuronal cell death in HD.

Amino Acid Transport System X-AG↗
PubMed2001

Salvage transjugular intrahepatic portosystemic shunt for uncontrolled variceal bleeding in patients with decompensated cirrhosis.

BACKGROUND/AIMS: The place of transjugular intrahepatic porto-systemic shunt (TIPS) for variceal haemorrhage uncontrolled by sclerotherapy and medical treatment is still undefined. To investigate the outcome of early salvage TIPS for active uncontrolled variceal haemorrhage, and to identify the factors associated with mortality. METHODS: Salvage TIPS was performed in 58 patients as soon as possible after the diagnosis of variceal bleeding refractory to the combination of sclerotherapy and of pharmacological therapy. Twenty-three variables were assessed prospectively to identify predictors of mortality within 60 days of the procedure. RESULTS: The haemorrhage was controlled in 52 of 58 patients (90%). Bleeding persisted in six of 58 patients (10%), and recurred in four patients (7%). Overall, 17 (29%) and 20 (35%) patients died within respectively 30 days and 60 days of TIPS: five patients died of persistent bleeding, two patients died of recurrent bleeding, and 13 patients died of terminal liver failure. The actuarial survival following salvage TIPS was 51.7% at 1 year. On multivariate analysis, independent predictors of early mortality were: the presence of sepsis (P=0.001), the use of catecholamines for systemic hemodynamic impairment (P=0.009), and the use of balloon tamponade (P=0.04). Neither a single factor, nor a combination of factors before TIPS allowed to predict mortality confidently in a given patient. CONCLUSIONS: Early salvage TIPS is an effective treatment to stop active variceal bleeding refractory to sclerotherapy and pharmacological treatment. Pre-treatment prognostic determinants that correlate to mortality can not be used to predict the outcome in individual cases.

Bilirubin↗
PubMed2001

Primary non-Hodgkin's lymphomas of the liver with nodular and diffuse infiltration patterns have different prognoses.

BACKGROUND: Primary liver non-Hodgkin's lymphomas have peculiar clinical and biological patterns. This study correlates these patterns with pathology and outcome. PATIENTS AND METHODS: Clinical records and histology of patients with primary liver non-Hodgkin's lymphoma, treated at our institution over a 20-year period, were reviewed. Lymphoproliferations occurring after liver transplantation were excluded. Survival analyses were performed with patients from the other published series (62 patients). RESULTS: Our series included eight patients. Three patients had a nodular liver infiltration, corresponding to a large B-cell lymphoma. Five patients had a diffuse liver infiltration, of whom three had a T-cell lymphoma with predominant sinusoid infiltration, and two had a large B-cell lymphoma. Patients with diffuse liver infiltration presented with hepatomegaly, and two of these also had acute liver failure. Diffuse infiltration had a worse prognosis than nodular infiltration (P = 0.0033). Among these latter patients, those treated with an anthracycline-based chemotherapy had a better outcome (P < 0.0001). CONCLUSIONS: Patients with primary liver lymphomas can be classified in two groups, depending on the type of infiltration. Those with nodular infiltration may benefit from anthracycline-based chemotherapy. Diffuse infiltration has a bad prognosis, and should be suspected in patients presenting with altered liver functions and hepatomegaly.

Adult↗
PubMed2001

Low rejection rates with tacrolimus-based dual and triple regimens following liver transplantation.

We studied the outcome of 345 liver transplant patients who received tacrolimus-based immunosuppressive therapy either as a dual regimen (with corticosteroids, n=172) or as a triple regimen (with corticosteroids and azathioprine, n=173) for 3 months after transplantation (3-month cohort). A further analysis was conducted for the first 195 patients randomised (dual n=100, triple n=95) who were followed up for 12 months after transplantation (12-month cohort). For the 3-month cohort, patient survival was 90.7% (dual) and 91.9% (triple), graft survival after 3 months was 88.4% (dual therapy) and 89.6% (triple therapy). Acute rejections were experienced by 67/172, 39.0% of patients on dual therapy and by 60/173, 34.7% of patients on triple therapy; corticosteroid-resistant rejections were reported in 9 patients (5.2%) in either treatment group. The overall safety profile was similar for the two treatment groups. Significant differences, however, were found for thrombocytopenia (dual 13/172, 7.6%, triple 37/173, 21.4%, p<0.001) and leukopenia (dual 4/172, 2.3%, triple 24/173, 13.9%, p<0.001). For the 12-month cohort, patient survival was 85.6% (dual) and 88.4% (triple) after 1 year. Graft survival was 81.7% (dual) and 85.2% (triple) 12 months after transplantation. Acute rejections were reported for 38/100, 38.0% of patients on dual therapy and 36/95, 37.9% of patients on triple therapy, corticosteroid-resistant rejections were 7/100, 7.0% (dual) and 7/95, 7.4% (triple) of patients. In the 12-month cohort, no significant differences in the safety profiles of the treatment groups were found. We conclude that both tacrolimus-based dual and triple drug regimens provide effective and safe immunosuppression following orthotopic liver transplantation.

Azathioprine↗
PubMed2001

Successful tacrolimus therapy for a severe recurrence of type 1 autoimmune hepatitis in a liver graft recipient.

A 34-year-old woman underwent orthotopic liver transplantation (OLT) for decompensated type 1 autoimmune hepatitis (AIH). She was administered standard triple-drug immunosuppressive therapy (cyclosporine, steroids, and azathioprine). Ten years after OLT, she developed a recurrence of AIH, with emergence of serological markers of autoimmunity (high anti--smooth muscle antibody [ASMA] titer, high serum gamma globulin level), abnormal liver function test results, and characteristic histological features on liver biopsy. Despite intensified steroid therapy, her clinical and liver function deteriorated. The onset of cutaneous alternariosis led to a steroid dose reduction and cyclosporine replacement by tacrolimus. Clear-cut amelioration was observed, with an improvement in liver function test results and reduction in ASMA titer. One year after the recurrence of AIH, the patient has normal liver function and physical findings. Tacrolimus therefore may be effective in patients with severe recurrent autoimmune liver disease. Further studies are needed to assess tacrolimus therapy in patients who fail to respond to standard immunosuppressive therapy.

Adult↗
PubMed2001

Auxiliary partial orthotopic versus standard orthotopic whole liver transplantation for acute liver failure: a reappraisal from a single center by a case-control study.

OBJECTIVE: To reappraise the results of auxiliary partial orthotopic liver transplantation (APOLT) compared with those of standard whole-liver transplantation (OLT) in terms of postoperative death and complications, including neurologic sequelae. SUMMARY BACKGROUND DATA: Compared with OLT, APOLT preserves the possibility for the native liver to recover, and to stop immunosuppression. METHODS: In a consecutive series of 49 patients transplanted for fulminant or subfulminant hepatitis, 37 received OLT and 12 received APOLT. APOLT was done when logistics allowed simultaneous performance of graft preparation and the native liver partial hepatectomy to revascularize the graft as soon as possible. Each patient undergoing APOLT (12 patients) was matched to two patients undergoing OLT (24 patients) according to age, grade of coma, etiology, and fulminant or subfulminant type of hepatitis. All grafts in the study population were retrieved from optimal donors. RESULTS: Before surgery, both groups were comparable in all aspects. In-hospital death occurred in 4 of 12 patients undergoing APOLT compared with 6 of 24 patients undergoing OLT. Patients receiving APOLT had 1 +/- 1.3 technical complications compared with 0.3 +/- 0.5 for OLT patients. Bacteriemia was significantly more frequent after APOLT than after OLT. The need for retransplantation was significantly higher in the APOLT patients (3/12 vs. 0/24). Brain death from brain edema or neurologic sequelae was significantly more frequent after APOLT (4/12 vs. 2/24). One-year patient survival was comparable in both groups (66% vs. 66%), and there was a trend toward lower 1-year retransplantation-free survival rates in the APOLT group (39% vs. 66%). Only 2 of 12 (17%) patients had full success with APOLT (i.e., patient survival, liver regeneration, withdrawal of immunosuppression, and graft removal). One of these two patients had neurologic sequelae. CONCLUSIONS: Using optimal grafts, APOLT and OLT have similar patient survival rates. However, the complication rate is higher with APOLT. On an intent-to-treat basis, the efficacy of the APOLT procedure is low. This analysis suggests that the indications for an APOLT procedure should be reconsidered in the light of the risks of technical complications and neurologic sequelae.

Adolescent↗
PubMed2001

Residual hepatitis B virus particles in liver transplant recipients receiving lamivudine: PCR quantitation of HBV DNA and ELISA of preS1 antigen.

Lamivudine, an antiviral agent, has a potential role in the treatment of recurrent or acquired de novo hepatitis B virus (HBV) infection after liver transplantation. During lamivudine therapy, residual HBV particles in serum, PBMC, and liver were quantified in 7 patients in whom hepatitis B occurred de novo (n = 4) or recurred (n = 3). HBV DNA and preS1 antigen were measured using a sensitive PCR technique and an in-house ELISA method, respectively. The genetic and antigenic properties of HBV variants that emerged during lamivudine treatment were also examined. One month after the outset of lamivudine treatment, all 7 patients remained positive for both HBV DNA and preS1 antigen in serum, reflecting residual HBV replication. At the end of therapy, four patients were considered to be lamivudine responders, including one who seroconverted to anti-HBs but remained HBV DNA positive in the liver (> 10(3) copies/microg of DNA). Among the three patients who did not respond to lamivudine, one had pol mutations (L450P and S550C) that had not been described previously, in addition to the common mutations within the YMDD locus and B domain. Defective core and preS viral proteins and atypical sedimentation profiles of HBV DNA-positive particles were observed in all three lamivudine-resistant patients. These findings confirm the persistence of HBV in liver transplant recipients despite strong inhibition of replication by lamivudine, and show abnormal viral transcription and/or morphogenesis in lamivudine-resistant patients.

Adult↗
PubMed2001

[Autoimmune hepatitis. Physiopathologic, clinical, histological, and therapeutic features].

Autoimmune hepatitis is characterized by an inflammation of the portal tract with lymphocytes and plasma cells, an hypergammaglobulinemia and a variety of circulating autoantibodies. The presence of smooth muscle antibodies and/or antinuclear antibodies define type 1. Type 2 is characterized by the presence of liver-kidney--microsomal antibodies. Environmental, genetic and infectious factors may explain the autoreactivity of T cells. Different non specific clinical features may be present. Sometimes the presentation may be an acute hepatitis; in the remainder, the disease may not be recognized until liver damage is advanced. Hypergammaglobulinemia and presence of circulating autoantibodies are the key for diagnosis. The association of prednisolone in combination with azathioprine remains the established treatment. If relapse or non response occur, other immunosuppressive therapy such as cyclosporin may be useful. Liver transplantation is reserved for (sub)fulminant forms and end stage liver disease.

Hepatitis, Autoimmune↗
PubMed2000

Influence of liver hepatitis C virus RNA and hepatitis C virus genotype on FAS-mediated apoptosis after liver transplantation for hepatitis C.

BACKGROUND: Recurrent hepatitis C virus (HCV) infection after liver transplantation is characterized by a high level of intrahepatic HCV replication and more severe liver damage in case of genotype 1b infection. We investigated the involvement of apoptosis in recurrent HCV liver disease, and its possible links with histological findings, HCV genotype, liver HCV RNA level, and liver Fas mRNA level. METHODS: We studied 61 liver graft biopsy specimens from 25 patients transplanted for HCV-related cirrhosis. DNA fragmentation was determined semi-quantitatively by in situ end labeling. HCV RNA and liver Fas mRNA were determined in parallel by quantitative polymerase chain reaction, with ribosomal 28S RNA as internal standard. RESULTS: Apoptotic lesions were predominantly portal (nonhepatocytic) or lobular (hepatocytic). Both were correlated with serum aminotransferase levels. The degree of portal apoptosis correlated with acute rejection (P<0.001), although lobular apoptosis was associated with lobular hepatitis (P<0.02), and HCV genotype 1b (P=0.04). In multivariate analysis, liver Fas mRNA level independently correlated with HCV-related chronic active hepatitis (P=0.04), age (P=0.01), and liver HCV RNA level (P=0.0007). CONCLUSIONS: After liver transplantation, 1) apoptosis is involved in HCV-related liver damage; 2) HCV type 1b may induce more severe apoptotic lesions than other genotypes; and 3) Fas transcription may be up-regulated by intrahepatic HCV replication.

Apoptosis↗
PubMed2000

Identification and characterization of an equilibrium intermediate in the unfolding pathway of an all beta-barrel protein.

The guanidinium hydrochloride (GdnHCl)-induced unfolding of an all beta-sheet protein, the human acidic fibroblast growth factor (hFGF-1), is studied using a variety of biophysical techniques including multidimensional NMR spectroscopy. The unfolding of hFGF-1 in GdnHCl is shown to involve the formation of a stable equilibrium intermediate. Size exclusion chromotagraphy using fast protein liquid chromatography shows that the intermediate accumulates maximally at 0.96 m GdnHCl. 1-Anilinonapthalene 8-sulfonate binding, one-dimensional (1)H NMR, and limited proteolytic digestion experiments suggest that the intermediate has characteristics resembling a molten globule state. Chemical shift perturbation and hydrogen-deuterium exchange monitored by (1)H-(15)N heteronuclear single quantum coherence spectra reveal that profound structural changes in the intermediate state (in 0.96 m GdnHCl) occur in the C-terminal, heparin binding region of the protein molecule. Additionally, results of the stopped flow fluorescence experiments suggest that the kinetic refolding of hFGF-1 proceeds through the accumulation of an intermediate at low concentrations of the denaturant. To our knowledge, the present study is the first report wherein an equilibrium intermediate is characterized in detail in an all beta-barrel protein.

Anilino Naphthalenesulfonates↗
PubMed2000

Structural events during the refolding of an all beta-sheet protein.

The refolding kinetics of the 140-residue, all beta-sheet, human fibroblast growth factor (hFGF-1) is studied using a variety of biophysical techniques such as stopped-flow fluorescence, stopped-flow circular dichroism, and quenched-flow hydrogen exchange in conjunction with multidimensional NMR spectroscopy. Urea-induced unfolding of hFGF-1 under equilibrium conditions reveals that the protein folds via a two-state (native <--> unfolded) mechanism without the accumulation of stable intermediates. However, measurement of the unfolding and refolding rates in various concentrations of urea shows that the refolding of hFGF-1 proceeds through accumulation of kinetic intermediates. Results of the quenched-flow hydrogen exchange experiments reveal that the hydrogen bonds linking the N- and C-terminal ends are the first to form during the refolding of hFGF-1. The basic beta-trefoil framework is provided by the simultaneous formation of beta-strands I, IV, IX, and X. The other beta-strands comprising the beta-barrel structure of hFGF-1 are formed relatively slowly with time constants ranging from 4 to 13 s.

Fibroblast Growth Factor 1↗
PubMed2000

Fulminant non--A-G viral hepatitis leading to liver transplantation.

BACKGROUND: All hepatotropic viruses are known to cause fulminant hepatic failure (FHF). However, in 30% to 40% of patients with FHF, the precise cause remains unknown. We aimed to better define this subgroup. METHODS: We evaluated the clinical course and outcome of 7 patients admitted during a 22-month period with fulminant viral hepatitis leading to liver transplantation; none had serologic or molecular evidence of hepatitis A, B, C, D, E, or G viral infection, thus the term non-A-G viral hepatitis. All known etiologies of FHF were excluded. RESULTS: All patients had prodromal symptoms suggestive of viral causes. Mean age was 30 years. The interval between onset of jaundice and appearance of encephalopathy was 23 days (range, 4-50 days). Five patients had grade III/IV encephalopathy. Serum alanine aminotransferase levels showed a single peak of activity. The duration between first symptoms and liver transplantation was 28 days (range, 12-71 days). Results of histological study of the explanted liver showed submassive (4 patients) or massive (3 patients) hepatocyte necrosis. In all patients, results of polymerase chain reaction analysis did not detect hepatitis B virus DNA, hepatitis C virus RNA, or hepatitis G virus RNA in the explanted liver. After transplantation, 2 patients showed (6 months later) increased liver enzyme levels of undetermined cause, and results of a liver biopsy showed mild lobular hepatitis; 1 patient had lymphoproliferative disorder (Epstein-Barr virus-originated); and 1 patient, aplastic anemia, which is known to be associated with seronegative viral hepatitis. The latter patient died, whereas the other 6 patients are alive (survival rate, 86%). CONCLUSIONS: Our patients with non-A-G viral hepatitis had a severe acute onset with progressive FHF requiring liver transplantation. There is some suggestion of recurrent viral disease after transplantation implicating other unknown viruses in the etiology.

Adolescent↗
PubMed2000

Age-related resistance to alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid-induced hippocampal lesion.

This study compares the effects of acute alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) administration in the hippocampus in adult (3 months) and middle-aged (15 months) rats at 15 days postinjection. Injection of 1 and 2.7 mM AMPA produced dose-dependent neurodegeneration, assessed by Nissl staining; a glial reaction shown by glial fibrillary acidic protein immunocytochemistry; and calcification, revealed by alizarin red staining. Furthermore, at both doses, these alterations were significantly greater in 3-month-old rats. Finally, at AMPA 2.7 mM, no significant changes in the density of hippocampal parvalbumin- or calbindin-immunoreactive neurons or in choline acetyltransferase, glutamate uptake, or GABA uptake activities were found in 15-month-old animals, whereas significant reductions in parvalbumin (-76%) and calbindin (-32%) immunostaining and in GABA uptake (-27%) were observed in 3-month-old animals compared to the respective sham-operated or control animals. In conclusion, this study clearly demonstrates that in rats the vulnerability of hippocampal neurons and the glial and calcification reactions to AMPA-induced injury decreased with age between 3 and 15 months. Our results also indicate that hippocampal cholinergic, glutamatergic, and GABAergic systems show an adaptive response to excitotoxic damage in both adult and middle-aged animals.

Aging↗