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Biomedical subjects

C Birch

Publications and source records attributed to C Birch.

At least 37 records · Page 2Linked to original sources
PubMed1990

Antiviral strategies in chronic hepatitis B virus infection: I. Establishment of an in vitro system using the duck hepatitis B virus model.

Primary duck hepatocyte (PDH) cultures were established from ducklings congenitally infected with the duck hepatitis B virus (DHBV), plated onto feeder cell layers of irradiated human embryonic lung fibroblasts, and observed for 2 to 3 weeks. This system permitted the survival of the PDH in a differentiated form free of fibroblastic overgrowth for at least 3 weeks. The hepatocytes were shown to contain all the replicative DNA intermediates found during DHBV replication as well as the DHBV structural proteins PRE-S1, PRE-S2, and S of duck hepatitis B surface antigen (DHBsAg). The pool of supercoiled (SC) DHBV DNA increased dramatically from days 10 to 14 postplating. This PDH-feeder cell layer cell culture model provides a convenient system to study the effects of conventional inhibitors of DHBV replication and compounds targeted at the supercoiled form of DHBV DNA. This approach should allow the evaluation of a variety of strategies for treating chronic carriers of hepadnaviruses.

Animals↗
PubMed1990

Decreased in vitro susceptibility to zidovudine of HIV isolates obtained from patients with AIDS.

This study tested isolates of human immunodeficiency virus, obtained before and after zidovudine therapy from 10 patients, for susceptibility to the drug in vitro. The isolates collected after therapy were less susceptible to zidovudine as assessed by replication in MT-2 cells and production of reverse transcriptase activity by infected mononuclear leucocytes in the presence of the drug. Furthermore, pretherapy isolates were sensitive to a range of zidovudine concentrations when 100% inhibition was used as the end point. The loss of zidovudine susceptibility did not correlate with any clinical or virologic consequences in this small group of patients.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Physicochemical stability and inactivation of human and simian rotaviruses.

The effects of various physical and chemical treatments on the stability of a human serotype 1 rotavirus and simian agent 11 (SA11) were compared by using a fluorescence focus assay. The infectivity of both strains was retained after storage at room temperature for 14 days, 4 degree C for 22 days, and -20 degree C for 32 days; lyophilization; and treatment at pH 3 to 11. Both viruses were inactivated at pH 12, as was the human virus at pH 2, although this pH resulted in only partial inactivation of SA11. The human virus also appeared to be more sensitive than SA11 to the action of ether and chloroform. The infectivity of both viruses was lost after UV irradiation for 15 min and after treatment with 8% formaldehyde for 5 min, 70% (vol/vol) ethanol for 30 min, and 2% lysol, 2% phenol, and 1% H2O2 for 1 h each.

Animals↗
PubMed1986

Antigenic analysis of rotavirus isolates using monoclonal antibodies specific for human serotypes 1, 2, 3 and 4, and SA11.

Five neutralizing monoclonal antibodies produced against human rotavirus (HRV) serotypes 1, 2, 3 and 4 and the simian rotavirus (SA11) were used to study 59 rotavirus isolates of human, simian and feline origin previously serotyped using polyclonal antisera. In neutralization tests, 19 of 26 HRV serotype 1 isolates, both strains of HRV serotype 2, 14 of 24 HRV serotype 3 isolates and all of seven serotype 4 isolates were neutralized by the homologous serotype-specific monoclonal antibodies. Use of the panel of monoclonal antibodies revealed antigenic differences between strains within serotypes 1 and 3 and, in the case of the serotype 3 strains, each variant had a unique RNA electropherotype. An enzyme immunoassay (EIA) which utilized the monoclonal antibodies essentially confirmed the neutralization results. Preliminary results show that direct serotyping in faecal extracts by EIA using these monoclonal antibodies is specific but lacks sensitivity.

Antibodies, Monoclonal↗
PubMed1985

Prolonged outbreak of Norwalk gastroenteritis in an isolated guest house.

During November and December 1982, a persistent outbreak of gastroenteritis took place in an isolated guest house. An estimated 26% of the changing population of guests and staff developed symptoms. Laboratory studies implicated Norwalk agent as the cause of illness, although the original source of the outbreak could not be established. Information on clinical features of the illness, its mode of spread, and eventual control is presented.

Adolescent↗
PubMed1984

Radioimmunofocus assay for detection and quantitation of human rotavirus.

A radioimmunofocus assay suitable for quantitation of cell culture-adapted human rotavirus was developed. The method was reproducible, more sensitive than plaque assay, and useful to detect and quantify strains of rotavirus which do not produce plaques. Preliminary results also suggested that the technique will be a useful means of serotyping cell culture-adapted strains of the virus.

Animals↗
PubMed1983

Cryptosporidiosis in hospital patients with gastroenteritis.

Among 884 hospital patients with gastroenteritis, 36 (4.1%) were excreting Cryptosporidium oocysts in their stools; only 5 of the 36 patients were also excreting other enteropathogens, while none of 320 hospital patients without gastroenteritis were excreting Cryptosporidium oocysts. Children were more commonly infected with Cryptosporidium (4.8%) than were adults (1.6%). The prevalence of infection was higher (7%) during the summer period of February-May 1981 than in the remainder of the observation period to the beginning of June 1982 (1.9%). The most common clinical manifestation of gastroenteritis in Cryptosporidium-infected patients was diarrhea, lasting from 3 to over 14 days, accompanied by vomiting, anorexia, and abdominal pain. The results show that a small proportion of patients with gastroenteritis are infected with Cryptosporidium, and the importance of the infection needs to be examined.

Adolescent↗
PubMed1981

Adenovirus eye infections in an Australian city, 1972-9.

A number of adenovirus serotypes have been associated with both sporadic cases and outbreaks of conjunctivitis and pharyngoconjunctival fever but only adenovirus type 8 and adenovirus type 19 have been responsible for wide-spread epidemic kerato-conjunctivitis. In Melbourne, Australia, in the past eight years these two serotypes have been prevalent, resulting in an outbreak of adenovirus type 8 kerato-conjunctivitis in 1976-7 followed by adenovirus type 19 kerato-conjunctivitis in 1978-9. During these two periods of peak incidence, 53 cases of adenovirus type 8 and 43 cases of adenovirus type 19 kerato-conjunctivitis were confirmed by isolation.

Adenoviridae Infections↗
PubMed1981

Molecular epidemiology of human rotaviruses in Melbourne, Australia, from 1973 to 1979, as determined by electrophoresis of genome ribonucleic acid.

Rotaviruses contain a double-stranded ribonucleic acid genome consisting of 11 segments. Gel electrophoresis separates genome segments and allows identification of strain differences. This electrophoretic typing technique was applied to rotavirus specimens from 116 children and 72 newborn babies. Between 1973 and 1979, 17 different electropherotypes of rotavirus were observed in children with acute gastroenteritis. These electropherotypes showed a sequential pattern of appearance, with a limited number of electropherotypes present at any given time. By contrast, only two electropherotypes were identified from isolates from newborn babies in seven hospitals during 1975 to 1979. These two electropherotypes were very similar and were never identified in children with acute gastroenteritis. One of the neonatal electropherotypes was found in the nurseries of five different hospitals and persisted in one hospital for 4 years. Electrophoretic typing techniques can be applied routinely and reproducibly to small samples of feces and could prove to be of value in epidemiological studies of rotavirus infection

Australia↗
PubMedDate not supplied

Baseline antiretroviral drug susceptibility influences treatment response in patients receiving saquinavir-enhancing therapy.

PURPOSE: To relate baseline plasma HIV genotypic and virtual phenotypic antiretroviral drug susceptibility to subsequent virological response in patients receiving saquinavir (SQV)-enhancing therapy. Individuals were randomized to receive stavudine (d4T), SQV, and one of ritonavir, nelfinavir, or delavirdine to enhance SQV blood levels. METHOD: The protease and reverse transcriptase baseline sequences of 31 treatment-experienced patients were analyzed by genotype and virtual phenotype and were related to viral load at weeks 12 and 24. Genotypic resistance to SQV was defined by the presence of G48V and/or L90M mutations in the protease gene. Potential cross-resistance to d4T in zidovudine (ZDV)-experienced individuals was defined by the presence of thymidine-associated mutations in the reverse transcriptase gene. RESULTS: ZDV-associated mutations did not affect the virological response at 24 weeks. Individuals who were sensitive to SQV at baseline as determined by either genotyping or virtual phenotyping showed a greater decrease in viral load at week 24 than those resistant to SQV, irrespective of treatment arm. By genotyping, SQV-sensitive individuals had a median log decrease of 1.12 compared to 0.32 for those individuals who were SQV resistant. By virtual phenotyping, SQV-sensitive individuals had a median log decrease of 1.0 compared to a rise of 0.08 in resistant individuals. CONCLUSION: Thymidine analogue-associated mutations at baseline did not influence the response to subsequent therapy involving d4T. Individuals who were sensitive or resistant to SQV by genotyping or virtual phenotyping responded to SQV-enhancing regimens, but the virological response was greater in those who were sensitive.

Anti-HIV Agents↗