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C Birch

Publications and source records attributed to C Birch.

At least 19 recordsLinked to original sources
PubMed2007

A candidate precursor to serous carcinoma that originates in the distal fallopian tube.

The tubal fimbria is a common site of origin for early (tubal intraepithelial carcinoma or TIC) serous carcinomas in women with familial BRCA1 or 2 mutations (BRCA+). Somatic p53 tumour suppressor gene mutations in these tumours suggest a pathogenesis involving DNA damage, p53 mutation, and progressive loss of cell cycle control. We recently identified foci of strong p53 immunostaining-termed 'p53 signatures'-in benign tubal mucosa from BRCA+ women. To examine the relationship between p53 signatures and TIC, we compared location (fimbria vs ampulla), cell type (ciliated vs secretory), evidence of DNA damage, and p53 mutation status between the two entities. p53 signatures were equally common in non-neoplastic tubes from BRCA+ women and controls, but more frequently present (53%) and multifocal (67%) in fallopian tubes also containing TIC. Like prior studies of TIC, p53 signatures predominated in the fimbriae (80-100%) and targeted secretory cells (HMFG2 + /p73-), with evidence of DNA damage by co-localization of gamma-H2AX. Laser-capture microdissected and polymerase chain reaction-amplified DNA revealed reproducible p53 mutations in eight of 14 fully-analysed p53 signatures and all of the 12 TICs; TICs and their associated ovarian carcinomas shared identical mutations. In one case, a contiguous p53 signature and TIC shared the same mutation. Morphological intermediates between the two, with p53 mutations and moderate proliferative activity, were also seen. This is the first report of an early and distinct alteration in non-neoplastic upper genital tract mucosa that fulfils many requirements for a precursor to pelvic serous cancer. The p53 signature and its malignant counterpart (TIC) underline the significance of the fimbria, both as a candidate site for serous carcinogenesis and as a target for future research on the early detection and prevention of this disease.

Biomarkers, Tumor↗
PubMed2001

Monocytes harbour replication-competent, non-latent HIV-1 in patients on highly active antiretroviral therapy.

OBJECTIVE: To determine whether HIV-1 can be recovered from blood monocytes as well as resting, memory CD4 T lymphocytes of patients on highly active antiretroviral therapy (HAART) with undetectable plasma viraemia and whether infection is active or latent. DESIGN: Five patients with plasma HIV-1-RNA levels of less than 500 copies/ml for at least 3 months and less than 50 copies/ml at the time of sampling were initially selected, followed by an additional five patients with viral loads of less than 50 copies/ml for 3 months or more. METHODS: Monocytes were isolated from blood by plastic adherence, then further purified by a second adherence step or CD3 depletion before co-culture with CD8-depleted donor peripheral blood mononuclear cells. Virus isolates were examined for mutations conferring resistance to reverse transcriptase or protease inhibitors and for genotype. The highly purified monocytes were also analysed for the presence of proviral and unintegrated viral DNA and multiply spliced (MS) viral mRNA by polymerase chain reaction. RESULTS: Virus was recovered from monocytes of five patients. Sequencing of the recovered viruses did not reveal multiple drug resistance, and was consistent with a non-syncytium-inducing/CCR5 phenotype. Proviral DNA was detectable in monocytes from all subjects, and unintegrated HIV-1 DNA and MS RNA was found in four out of five populations examined. CONCLUSION: Recovery of replication-competent virus from some HAART patients indicates that monocytes can also harbour HIV-1. Detection of circular, viral DNA and spliced RNA, albeit at very low levels, in these cells suggests that their infection is recent and transcriptionally active rather than latent.

Antiretroviral Therapy, Highly Active↗
PubMed2001

Co-administration of drugs and blood products.

The addition of a drug to a blood product intravenous line raises the question of physical and chemical compatibility of the drug with the blood and any preservatives or additives in the blood product. This clinical scenario is encountered frequently, however the practice has not been well studied. Protocols at most institutions prohibit the addition of drugs to blood products. We investigated the addition of analgesic drugs used for patient-controlled analgesia (morphine 1 mg/ml, pethidine 10 mg/ml and ketamine 1 mg/ml) to a standard red cell concentrate, resuspended red blood cells. The red cells were analysed by a Blood Transfusion Service Haematologist and subjected to standard quality control tests. The morphology of the red cells in resuspended red blood cell preparations was unchanged by the addition of these drugs at any stage during storage. The drug concentration in the resuspended red blood cell serum was measured at 0 and at 20 minutes and there was no decrease in concentration which showed that there was no loss of free drug in the resuspended red blood cell serum. This study demonstrates that the concern regarding injury to red cells in standard red cell concentrates by addition of these drugs is unjustified.

Analgesics↗
PubMed2000

Evidence for late stage compartmentalization of HIV-1 resistance mutations between lymph node and peripheral blood mononuclear cells.

OBJECTIVE: To determine the overall distribution of drug-resistance mutations to nucleoside reverse transcriptase inhibitors of HIV strains recovered from the lymph nodes (LN) and peripheral blood mononuclear cell (PBMC) compartments of four HIV-infected patients receiving zidovudine and didanosine and to compare them with antiretroviral-naive patients. DESIGN: Molecular comparison of major and minor HIV-1 env and pol region variants residing in LN and PBMC compartments. MATERIALS AND METHODS: Proviral DNA sequences were amplified by PCR from both PBMC and LN compartments, cloned into PGEM-T II Easy vector and sequenced. The clones were subjected to molecular and phylogenetic analysis. RESULTS: Comparison of PBMC and LN-derived HIV-1 variants in the env V3 region showed that nucleotide and amino acid variability was a characteristic feature of LN-derived variants. In contrast, a majority of resistance mutations to reverse transcriptase inhibitors were localized in the PBMC compartment rather than in LN, which is thought to be a reservoir of HIV. CONCLUSIONS: Distinct compartmentalization or independent evolution of pol and env gene variants between LN and PBMC could be due to the differential selection pressure imposed by the combination drug regimen, hence the bimodal distribution of resistance variants between LN and PBMC compartments.

Anti-HIV Agents↗
PubMed2000

Streptoccocus pyogenes: a forgotten cause of severe community-acquired pneumonia.

We report a case of severe community-acquired pneumonia caused by Streptococcus pyogenes (Lancefield Group A streptoccocus) that was complicated by a streptococcal toxic shock syndrome. Although this micro-organism is an uncommon cause of community-acquired pneumonia, previously well individuals may be infected and the clinical course may be fulminant. A household contact was the likely point of infection. Invasive group A streptococcal disease continues to remain an important cause of morbidity and mortality in the community and therefore will continue to be encountered by intensive care physicians. Treatment of Group A streptococcal infection remains penicillin; however, clindamycin should be added in severe infection.

Adult↗
PubMed2000

Laboratory-supported influenza surveillance in Victorian sentinel general practices.

Laboratory-supported influenza surveillance is important as part of pandemic preparedness, for identifying and isolating candidate vaccine strains, for supporting trials of anti-influenza drugs and for refining the influenza surveillance case definition in practice. This study describes the implementation of laboratory-supported influenza surveillance in Victorian sentinel general practices and provides an estimate of the proportion of patients with an influenza-like illness proven to have influenza. During 1998 and 1999, 25 sentinel general practices contributed clinical surveillance data and 16 metropolitan practices participated in laboratory surveillance. Serological, virus-antigen detection, virus culture and multiplex polymerase chain reaction procedures were used to establish the diagnosis of influenza. Two laboratories at major teaching hospitals in Melbourne provided additional data on influenza virus identification. General practice sentinel surveillance and laboratory identification of influenza provided similar data on the pattern of influenza in the community between May and September. The clinical suspicion of influenza was confirmed in 49 to 54 per cent of cases seen in general practice.

Adolescent↗
PubMed1998

Stability of human immunodeficiency virus RNA in blood specimens as measured by a commercial PCR-based assay.

We investigated the effects of conditions often encountered during handling, transit, and storage of blood specimens on the quantity of detectable human immunodeficiency virus (HIV) RNA in plasma. HIV RNA copy numbers were measured with a commercially available assay (the Amplicor HIV-1 Monitor test kit). Variables examined were the time to processing of blood and plasma, the holding temperature of blood and plasma prior to processing, the effect of freezing and thawing of plasma, and the use of different anticoagulants. The relationship between the HIV RNA copy number and the HIV isolation rate by peripheral blood mononuclear cell (PBMC) coculture was also examined. We found that RNA copy numbers were maintained to within 0.5 log10 (approximately threefold) in blood and plasma samples held at room temperature or 4 degrees C for up to 3 days and remained stable despite (limited) freezing and thawing of the plasma. HIV RNA copy numbers were also maintained after long-term storage of plasma at -70 degrees C. The ability to isolate HIV from PBMCs was directly proportional to the HIV RNA copy number.

Adolescent↗
PubMed1996

Zidovudine resistance is suppressed by mutations conferring resistance of human immunodeficiency virus type 1 to foscarnet.

Both foscarnet (PFA) and zidovudine (AZT) select for drug-resistant variants of human immunodeficiency virus type 1 (HIV-1), but the interactions between the mutations causing such resistance are unknown. The introduction of the previously identified PFA resistance mutation W to G at codon 88 (W88G), E89K, L92I, or Q161L into an HIV-1 strain having the four known AZT resistance mutations completely reversed high-level AZT resistance. Two additional PFA resistance mutations, W88S and S156A, partially suppressed AZT resistance. Phenotypic reversion of AZT resistance by W88S, W88G, E89K, L921, and S156A was associated with a concomitant suppression of PFA resistance. The degree to which PFA resistance mutations reversed AZT resistance was directly correlated with each mutation's ability to confer high-level PFA resistance (> or = 5.0-fold) and AZT hypersusceptibility in a wild-type genetic background. Highly PFA-resistant HIV- 1 strains were hypersusceptible to AZT; conversely, AZT-resistant strains with M41L and T215Y; M41L, L210W, and T215Y; or M41L, D67N, K70R, and T215Y mutations were 2.2- to 2.5-fold hypersusceptible to PFA. Prolonged in vitro selection of wild-type or AZT-resistant HIV-1 strains with the combination AZT and PFA failed to generate coresistant virus, indicating that dual resistance was relatively difficult to achieve. Strains selected by passage in PFA plus AZT were phenotypically PFA resistant and AZT susceptible despite multiple reverse transcriptase mutations known to confer AZT resistance. These data show that PFA resistance mutations can phenotypically reverse AZT resistance and that AZT and PFA resistance might be mutually exclusive. The reciprocal interactions between AZT and PFA resistance-conferring mutations have implications for structure-function studies of the HIV-1 reverse transcriptase.

Antiviral Agents↗
PubMed1996

An in vivo mutation from leucine to tryptophan at position 210 in human immunodeficiency virus type 1 reverse transcriptase contributes to high-level resistance to 3'-azido-3'-deoxythymidine.

Sequencing of the reverse transcriptase (RT) region of 26 human immunodeficiency virus type 1 (HIV-1) isolates from eight patients treated with 3'-azido-3'-deoxythymidine (AZT) revealed a mutation at codon 210 from TTG (leucine) to TGG (tryptophan) exclusively in association with resistance to AZT. The mutation Trp-210 was observed in 15 of the 20 isolates phenotypically resistant to AZT, being more commonly observed than resistance-associated mutations at codons 67, 70, and 219. Trp-210 was never observed before the emergence of resistance-associated mutations Leu-41 and Tyr-215, and in a sequential series of five isolates from one patient the order of emergence of mutations was found to be Tyr-215, Leu-41, and then Trp-210. Trp-210 was also found in association with the Leu-41, Asn-67, Arg-70, and Tyr-215 resistance genotype. To define the role of Trp-210 in AZT resistance, molecular HIV-1 clones were constructed with various combinations of RT mutations at codons 41, 67, 70, 210, and 215 and tested for susceptibility to AZT. In clones with polymerase genes derived either from HXB2-D or clinical isolates, Trp-210 alone did not increase AZT resistance, whereas in conjunction with Leu-41 and Tyr-215, Trp-210 contributed to high-level resistance (50% inhibitory concentration of >1 microM). In HXB2-D, Trp-210 with Tyr-215 generated a virus with resistance comparable to one with Leu-41, Tyr-215, and Trp-210. Inserting Trp-210 into the genetic context of mutations at codons 41, 67, 70, and 215 further enhanced resistance from a 50% inhibitory concentration of 1.44 microM to 8.41 microM. Molecular modeling of the tertiary structure of HIV-1 RT revealed that the distance between the side chains of Trp-210 (in helix alphaF) and Tyr-215 (in strand beta11a) approximated 4 A (1 A = 0.1 nm), sufficiently close to result in significant energetic interaction between these two aromatic side chains. In conclusion, Trp-210 contributes significantly to phenotypic AZT resistance of HIV-1 by augmenting resistance at least three- to sixfold in the context of two resistant genotypes, and its effect may require an interaction with an aromatic amino acid at position 215.

Base Sequence↗
PubMed1995

Characterisation of foscarnet-resistant strains of human immunodeficiency virus type 1.

Foscarnet is a broad-spectrum viral DNA polymerase inhibitor active in vitro and in vivo against human immunodeficiency virus type 1 (HIV-1). Strains of HIV-1 resistant to foscarnet were selected by in vitro passage in increasing concentrations of drug. Reduced susceptibility to foscarnet was evident at the levels of both HIV-1 replication and reverse transcriptase. Biologically cloned, foscarnet-resistant strains with distinct genotypes were hypersensitive to zidovudine, azidodeoxyuridine, nevirapine, and R82913 but had unchanged susceptibility to zalcitibine and didanosine. The reverse transcriptase of foscarnet-resistant strains had unique substitutions Glu89-Lys, Leu92-Ile, or Ser156-Ala, the third being associated with six polymorphic changes. Introduction of these mutations into wild-type HIV-1 by site-directed mutagenesis confirmed their role in foscarnet resistance. In the three-dimensional structure of the reverse transcriptase enzyme these amino acids are located close to the template strand of the template primer and far away from the putative pyrophosphate binding site, suggesting that the mechanism by which HIV-1 becomes resistant to foscarnet is indirect. Foscarnet resistance is thus likely to be mediated through an altered interaction of the mutant enzyme with the template strand of the template primer which distorts the geometry of the polymerase active site and thereby decreases foscarnet binding.

Amino Acid Sequence↗
PubMed1995

Reverse transcriptase mutations in sequential HIV-1 isolates in a patient with AIDS.

Sequential human immunodeficiency virus type 1 (HIV-1) isolates were obtained over a 29-month period from a person before, during, and after AZT therapy. DNA sequence analysis of polymerase chain-amplified reverse-transcriptase gene showed a gradual accumulation of mutations to peak resistance (IC50 2.13 microM AZT) in association with mutations at codons 44, 210, and 369, as well as at 41, 67, 70, and 215. Eight months after cessation of AZT therapy, when an HIV-1 isolate from the patient was again sensitive to AZT, these mutations had all returned to the pretherapy sequence.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Long-term foscarnet therapy not associated with the development of foscarnet-resistant human immunodeficiency virus type 1 in an acquired immunodeficiency syndrome patient.

Sequential human-immunodeficiency virus type 1 (HIV-1) isolates from an acquired immunodeficiency syndrome (AIDS) patient on long-term foscarnet and zidovudine therapy were examined for the emergence of foscarnet resistance. One isolate obtained before therapy, and three post-foscarnet therapy HIV isolates had similar foscarnet sensitivity profiles, despite the emergence of foscarnet-resistant herpes simplex virus type 2 (HSV-2) during the period of therapy. Virion reverse transcriptases from these isolates were also equally inhibited by foscarnet. In contrast, sequential HIV isolates taken pre- and postzidovudine therapy showed a gradual increase in IC50 to this drug. In this patient, long-term foscarnet and zidovudine therapy selected foscarnet-resistant HSV and zidovudine-resistant HIV; in contrast, HIV remained susceptible to foscarnet. Concurrent administration of other anti-HIV drugs (zidovudine and interferon-alpha) may have hindered the development of foscarnet resistant HIV-1 in vivo.

Acquired Immunodeficiency Syndrome↗
PubMed1994

Use of a flavivirus RNA-dependent RNA polymerase assay to investigate the antiviral activity of selected compounds.

We have developed an assay using flavivirus RNA-dependent RNA polymerase to test the inhibitory activity of potential antiviral agents. The effects of antiviral agents on RNA synthesis were examined in this assay using extracts of Vero cells infected with dengue virus type 2 or Kunjin virus. Several different classes of known polymerase inhibitors were tested. The synthesis of double-stranded replicative form RNA was inhibited in a dose-dependent fashion in the presence of the polyoxometalate HPA-23 [(NH4)18(NaW21Sb9O86)17].14 H2O and several structurally related compounds.

Animals↗
PubMed1993

Cellular topoisomerase I activity associated with HIV-1.

Topoisomerase I activity was detected in detergent-disrupted human immunodeficiency virus type 1 (HIV-1) particles. The enzyme did not require ATP for its conversion of SC DNA to an RC form, had divalent cation requirements similar to those of eukaryotic topoisomerase I, and was significantly inhibited by the specific topoisomerase I inhibitor camptothecin. However, camptothecin failed to inhibit replication of HIV in infected cells at nontoxic concentrations, and an active site motif for topoisomerase I could not be detected on the HIV genome. These results suggests that HIV does not encode a novel topoisomerase I, but rather packages the cellular enzyme.

Amino Acid Sequence↗
PubMed1992

Incidence of zidovudine-resistant human immunodeficiency virus isolated from patients before, during, and after therapy.

The zidovudine sensitivity of 372 isolates of human immunodeficiency virus (HIV) obtained from 237 patients before, during, and after treatment with zidovudine was examined. Virus resistant to > 0.5 micrograms/mL (1.87 microM) zidovudine was isolated from most patients (93%) after 36 months of therapy. Zidovudine-sensitive virus was isolated from 5 of 15 patients who had ended antiretroviral therapy but had previously shed resistant virus. The emergence of sensitive virus after end of therapy appeared to be influenced by both the duration of treatment and the time off drug. Patients with resistant virus tended to have low CD4 cell counts and HIV antigenemia at the commencement of therapy, suggesting that these two factors are important in the development of drug resistance.

CD4 Antigens↗