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Biomedical subjects

S Bowden

Publications and source records attributed to S Bowden.

At least 19 recordsLinked to original sources
PubMed1997

Hepatitis B virus polymerase mutations during antiviral therapy in a patient following liver transplantation.

BACKGROUND/AIMS: The purpose of this study was to investigate possible resistance mutations which arose in the polymerase gene of hepatitis B virus (HBV) in a patient with severe recurrent HBV infection following liver transplantation. The patient's management included antiviral chemotherapy for almost 4 years comprising ganciclovir, foscarnet and famciclovir. In the last 2.5 years of famciclovir treatment, an increase in serum HBV DNA levels and a reduced sensitivity of the virion-associated DNA polymerase to penciclovir triphosphate were observed. METHODS: The viral polymerase gene and X gene were sequenced from serum samples collected at representative time intervals covering the entire treatment period. RESULTS: No mutations were detected in the X gene. Three nucleotide mutations, each of which resulted in an altered amino acid sequence, were detected in the polymerase gene after 816 days of total antiviral therapy (370 days of famciclovir). Two of these mutations were detected by direct sequencing and the third was detected after cloning and was present in 10% of the clones. All three mutations occurred in "region B" of RNA-dependent DNA polymerases. The HBV polymerase has similarities to both RNA and DNA polymerases. These mutations in the HBV polymerase gene were located in a similar area to the penciclovir-induced mutations observed in the herpes simplex virus DNA polymerase gene. CONCLUSIONS: Three mutations within the HBV polymerase gene were detected which were associated with a reduced penciclovir sensitivity.

2-Aminopurine↗
PubMed1996

Retransplantation for precore mutant-related chronic hepatitis B infection: prolonged survival in a patient receiving sequential ganciclovir/famciclovir therapy.

Retransplantation for hepatitis B-related liver allograft failure is rarely successful. Recurrence of infection is almost universal, and the second allograft is invariably lost more rapidly than the first. In a recent multicenter study, only 1 of 20 hepatitis B virus (HBV)-positive patients who underwent liver retransplantation survived beyond 6 months. This report describes the long-term effect of antiviral therapy in a 56-year-old man who was retransplanted for HBV-related allograft loss 14 months after his initial liver transplant. He was treated after the second transplant with intravenous daily ganciclovir. After 10 months of this therapy HBV recurrence was detected. After a change to oral famciclovir therapy, there was a decrease in serum HBV DNA and amino-transferase levels and an improvement in the patient's clinical condition. Famiciclovir therapy has now been continued for 26 months, and the patient remains well 3 years after his second transplant, despite persistent HBV infection and progression to cirrhosis. These observations indicate that the use of long-term antiviral therapy offers promise for improving outcomes in patients who undergo retransplantation after HBV-related liver allograft failure.

2-Aminopurine↗
PubMed1995

Reversion of duck hepatitis B virus DNA replication in vivo following cessation of treatment with the nucleoside analogue ganciclovir.

In order to define, in more detail, the virological events which occur after completion of antiviral chemotherapy, ducks congenitally infected with the duck hepatitis B virus (DHBV) were treated for 4 weeks with the nucleoside analogue ganciclovir and followed up over a 7-day period. Specimens of serum and liver were collected daily during follow-up for virological analysis. Treatment resulted in a substantial reduction in both viraemia and liver DHBV DNA replicative intermediates. However, after cessation of treatment, viraemia returned to detectable levels within 4 days. In the liver, the viral supercoiled DNA (SC DNA) was the form least affected by therapy and returned to near control levels by day 2 post-treatment. The other hepatic replicative intermediates reached pretreatment levels within 4 days of cessation of therapy. This study has defined the kinetics of relapse of viral replication after completion of antiviral therapy in the duck hepatitis B model. Of all viral replicative forms, the SC DNA appears to be the one which is most resistant to nucleoside analogue therapy and is presumably responsible for the relapse phenomenon observed post-treatment.

Animals↗
PubMed1995

Inhibition of duck hepatitis B virus DNA replication by antiviral chemotherapy with ganciclovir-nalidixic acid.

The aim of this study was to examine the effects of ganciclovir and nalidixic acid either alone or in combination on duck hepatitis B virus DNA replication in vivo with particular reference to production of viral supercoiled DNA and RNA. The most effective antiviral response was observed in the livers of ducks treated by the combination therapy for 28 days, which resulted in a substantial decrease in the amounts of viral supercoiled DNA, relaxed circular and single-stranded DNA, and also viral RNA. This combination treatment was not hepatotoxic over the study period.

Animals↗
PubMed1995

The covalently closed duplex form of the hepadnavirus genome exists in situ as a heterogeneous population of viral minichromosomes.

Replication of hepadnaviruses requires a persistent population of covalently closed circular (CCC) DNA molecules in the nucleus of the infected cell. It is widely accepted that the vital role of this molecule is to be the sole DNA template for the synthesis by RNA polymerase II of all viral transcripts throughout the infection process. Since the transcriptional activity of eukaryotic nuclear DNA is considered to be determined in part by its specific organization as chromatin, the nucleoprotein disposition of the hepadnavirus CCC DNA was investigated. These studies were undertaken on the duck hepatitis B virus (DHBV) CCC DNA present in the liver cell nuclei of DHBV-infected ducks. The organization and protein associations of the DHBV CCC DNA in situ were inferred from sedimentation, micrococcal nuclease digestion, and DNA superhelicity analyses. These three lines of investigation demonstrate that the DHBV CCC DNA is stably associated with proteins in the nuclei of infected liver cells. Moreover, they provide compelling evidence that the viral nucleoprotein complex is indeed a minichromosome composed of classical nucleosomes but in arrays that are atypical for chromatin. When the DHBV chromatin is digested with micrococcal nuclease, a ladder of viral DNA fragments that exhibits a 150-bp repeat is produced. This profile for the viral chromatin is obtained from the same nuclei in which the duck chromatin shows the standard 200-bp ladder. The superhelicity of the DHBV CCC DNA ranges from 0 to 20 negative supertwists per molecule, with all possible 21 topoisomers present in each DNA preparation. The 21 topoisomers of DHBV CCC DNA are inferred to derive from an identically diverse array of viral minichromosomes. In the DHBV minichromosomes composed of 20 nucleosomes, 96.7% of the viral DNA is calculated to be compacted into these chromatin subunits spaced on average by 5 bp of linker DNA; other minichromosomes contain fewer nucleosomes and proportionately more linker DNA. Two major subpopulations of DHBV minichromosomes are detected with comparable prevalence. The two groups correspond to minichromosomes which contain essentially a full or half complement of nucleosomes. The functional significance of this minichromosome diversity is unknown but is suggestive of transcriptional regulation of the viral DNA template.

Animals↗
PubMed1994

The role of Raf-1 in the regulation of extracellular signal-regulated kinase 2 by the T cell antigen receptor.

Triggering of the T cell antigen receptor (TCR) complex activates the serine/threonine kinase Raf-1 whose function is necessary for TCR induction of the interleukin 2 gene. Raf-1 has been identified as a candidate mitogen-activated protein (MAP) kinase kinase kinase (MKKK) and thus has the potential to couple the TCR to the activation of the MAP kinases such as ERK2. In the present study, the role of Raf-1 in ERK2 regulation of ERK2 in T cells has been explored. A constitutively active Raf-1 kinase, v-raf, or a dominant inhibitory Raf-1 mutant were expressed transiently from the pEF BOS vector in Jurkat cells and the effects of these Raf-1 mutants on a coexpressed ERK2 reporter was assessed. The action of the constitutively active Raf-1 was to stimulate the ERK2 kinase, whereas the dominant negative version of Raf-1 inhibited the ERK2 activation induced by triggering of the TCR. These data indicate a role for Raf-1 in the regulation of ERK2 in T cells.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1994

Detection of hepatitis B virus DNA in tears by polymerase chain reaction.

OBJECTIVE: To assess the possibility of transmission of hepatitis B virus (HBV) via tears. METHODS: Tear and plasma specimens were collected from 36 carriers of HBV, and the presence of HBV DNA was investigated using the polymerase chain reaction (PCR). RESULTS: Ten (29.4%) of the 34 carriers of chronic HBV and one of the two patients with acute hepatitis B had plasma specimens that were positive for HBV DNA using PCR. Sixteen (47.1%) of the 34 carriers of chronic HBV had tear specimens that were repeatedly positive for HBV DNA using PCR, 10 (29.4%) had tear specimens that were repeatedly negative, and the remaining eight (23.5%) had tear specimens that were equivocal. Both of the patients with acute hepatitis B had tear specimens that were positive for HBV DNA using PCR. CONCLUSION: Hepatitis B virus DNA can be demonstrated in the tears of carriers, even those who were asymptomatic.

Base Sequence↗
PubMed1994

Alterations in intrahepatic expression of duck hepatitis B viral markers with ganciclovir chemotherapy.

Ducks congenitally infected with duck hepatitis B virus (DHBV) were treated with the guanosine analogue, ganciclovir, and the effect on serum and intrahepatic expression of DHBV DNA and viral proteins was examined. After 21 days of ganciclovir treatment, a substantial reduction in viraemia occurred; in contrast, the level of circulating DHBV surface antigen was unchanged. Ganciclovir therapy also substantially reduced the level of DHBV DNA replicative intermediates and the expression of viral core and surface antigen in hepatocytes. However, despite the antiviral treatment some liver cells, including the bile duct epithelial cells and putative oval cells, maintained their intense staining for the viral proteins. Furthermore, DHBV-infected cells in extrahepatic sites such as the pancreas, kidney and spleen were also unaffected by ganciclovir treatment. These results suggest that monotherapy with nucleoside analogues is unlikely to eliminate chronic hepadnaviral infection, and antiviral programs should be designed to target all cell populations infected by the virus.

Animals↗
PubMed1994

Alcohol, thiamin deficiency, and neuropsychological disorders.

In this paper, two of the major themes in contemporary neuropsychological research are reviewed. These are the nature of cognitive impairment observed in alcohol related brain injury, and the cause or causes of alcohol related brain injury. Two experiments are briefly reported which address these issues. The first experiment concerns the nature of abilities which are involved in a test of memory (delayed matching to sample), which is fundamental to current experimental models of human amnesia. The second experiment involves preliminary data from a randomised, double-blind, multi-dose trial of intra-muscular thiamin for the treatment of alcohol related brain injury, in alcohol dependent subjects who do not show any overt signs of Wernicke-Korsakoff syndrome.

Adult↗
PubMed1993

The use of ampligen alone and in combination with ganciclovir and coumermycin A1 for the treatment of ducks congenitally-infected with duck hepatitis B virus.

Ampligen, a known immunomodulator and interferon inducer, was used alone and in combination with other antiviral agents to treat ducks congenitally-infected with duck hepatitis B virus. These antiviral agents included the conventional nucleoside analogue ganciclovir and the prokaryotic DNA gyrase B inhibitor coumermycin A1. When used alone, ampligen decreased the amount of serum and liver viral DNA, but had no effect on circulating duck hepatitis B surface antigen (DHBsAg). In combination with ganciclovir, the antiviral effect appeared at least additive with a greater inhibition of viral DNA replication within the liver. The combination of ampligen with coumermycin A1 also resulted in inhibition of viral replication but to a lesser extent than ampligen alone. When all three agents were used together, viral DNA replication was again inhibited, but as with previous treatment regimes, serum DHBsAg levels remained unchanged. At the end of the treatment period for all regimes, analysis of viral DNA forms in the liver showed that the viral relaxed circular and supercoiled DNA forms had persisted. Within 1 week of cessation of therapy, viral replication had often returned to pre-treatment levels. Interferon-like activity was detected in the sera of the majority of the treated ducks during the ampligen therapy, but no clear relationship between the presence of interferon and antiviral effect could be established. These observations in the duck hepatitis B model may provide a rational basis for the use of combinations of antiviral and immunomodulatory regimes for the management of chronic hepatitis B infection in man.

Aminocoumarins↗
PubMed1993

Function of the ypt2 gene in the exocytic pathway of Schizosaccharomyces pombe.

The ypt2 gene of the fission yeast Schizosaccharomyces pombe encodes a member of the ypt/rab family of small GTP-binding proteins, related in sequence to Sec4p of Saccharomyces cerevisiae but closer to mammalian rab8. We have introduced a mutation into the gene corresponding to a mutation identified in ypt1, in which a conserved valine residue was altered to asparagine. The mutated ypt2 gene was introduced into the S. pombe genome by gene replacement. The resulting strain was temperature-sensitive for growth. Normal growth was restored by introduction of a plasmid-borne wild-type ypt2 cDNA or by cDNA for rab8 but not by various other rab or ypt sequences. At restrictive temperature the mutant cells accumulated the secretory protein acid phosphatase in a form that appeared to be fully glycosylated and acquired a population of vesicles detectable by electron microscopy. Thus the ypt2 protein, and by inference rab8, appear to function in the last stage of the secretory pathway.

Acid Phosphatase↗
PubMed1993

Schizosaccharomyces pombe ypt5: a homologue of the rab5 endosome fusion regulator.

The ypt/rab proteins are a family of small GTP-binding proteins thought to be required for different stages of membrane traffic. From the fission yeast Schizosaccharomyces pombe we have isolated and characterized ypt5, a gene encoding a homologue of rab5, a mammalian protein apparently involved in regulating fusion of early endosomes. Recombinant ypt5 protein bound GTP. The ypt5 gene was found to be essential for viability on minimal media, but ypt5-disrupted cells grew slowly on some rich media and accumulated a population of small vesicles not observed in wild-type cells. Canine rab5 cDNA could replace the ypt5 gene in S. pombe and restore normal growth and viability. Ypt5 protein expressed in mammalian cells colocalized with the transferrin receptor to early endosomes. Thus, molecular aspects of the early endocytic pathway may be conserved between mammalian cells and S. pombe and hence may be amenable to genetic analysis.

Amino Acid Sequence↗
PubMed1993

Is there a need for improved pharmacy services to the operating theatre?

A study to assess the control and handling of drugs within an operating theatre complex (10 theatres) of an 850-bed hospital, has revealed the presence of unusable medication and thus highlighted the need for improved pharmacy services. The aims and objectives of the pharmacy department to enhance such services included improvement of drug control of stock medication and the introduction of clinical pharmacy services within the operating theatre. To undertake this, three systems were evaluated with reference to systems already in use in the U.S.A. Operating theatre visits by a clinical pharmacist, coupled with the expansion of the existing drug distribution service, were identified as the most cost-effective methods that would allow the objectives to be met. Consequently, this has now been implemented within the operating theatre complex.

Evaluation Studies as Topic↗
PubMed1992

A homologue of the ras-related CDC42 gene from Schizosaccharomyces pombe.

A cDNA was isolated from the fission yeast, Schizosaccharomyces pombe, using mixed oligodeoxyribonucleotides encoding part of the GTP-binding site of the ras superfamily. The encoded protein is the homologue of the budding yeast CDC42 gene product and the human proteins, CDC42Hs and G25K.

Amino Acid Sequence↗
PubMed1992

Neuropsychological functioning in adolescents with diabetes.

Investigated the relationship between disease variables, neuropsychological performance, and psychosocial status in adolescents with Insulin Dependent Diabetes Mellitus (IDDM). The study group consisted of 85 adolescents, aged 14 to 16.5 years who had been diabetic for longer than 12 months. Parameters of both recent and long-term metabolic control were determined, including diabetic incidents such as severe hypoglycemia or ketoacidosis. The mothers completed standardised measures of adolescent adjustment, and the adolescents provided self-reports of psychosocial status. Neuropsychological functioning was evaluated with standardised tests of verbal and nonverbal intelligence, memory and new learning, visuo-graphic skills, mental flexibility, and problem-solving ability. Using retrospective accounts of disease history, there was no relationship between neuropsychological functioning and variables such as age of onset, chronic poor control, or major metabolic crises. The findings emphasise the need for a long-term, prospective study of a cohort of diabetic children from the time of diagnosis to clarify causal relationships, if any, between illness variables, neuropsychological performance, and psychosocial factors.

Adolescent↗
PubMedDate not supplied

Combination antiviral therapy controls severe post-liver transplant recurrence of hepatitis B virus infection.

The authors have successfully used combination ganciclovir and foscarnet chemotherapy to control viral replication following liver transplantation in a patient with severe recurrence of hepatitis B virus (HBV) infection. The disease was characterized by extremely high viraemias, deteriorating liver function, and high levels of intra-hepatic hepatitis B core antigen (HBcAg) and hepatitis B surface antigen (HBsAg). Treatment resulted in a greater than 30-fold reduction in serum HBV DNA and HBsAg levels. Liver function tests returned to normal and the histological progression of the disease was arrested. Hepatic cytoplasmic HBsAg decreased substantially but there was little change in HBcAg, implicating HBsAg rather than HBcAg in the liver injury. Combination antiviral chemotherapy using agents such as ganciclovir and foscarnet may offer a new approach to the management of post-transplant recurrence of HBV.

Adult↗