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Biomedical subjects

G Woodfield

Publications and source records attributed to G Woodfield.

17 recordsLinked to original sources
PubMed2000

Vaccinia topoisomerase and Cre recombinase catalyze direct ligation of activated DNA substrates containing a 3'-para-nitrophenyl phosphate ester.

DNA topoisomerases and DNA site-specific recombinases are involved in a diverse set of cellular processes but both function by making transient breaks in DNA. Type IB topoisomerases and tyrosine recombinases cleave DNA by transesterification of an active site tyrosine to generate a DNA-3'-phosphotyrosyl-enzyme adduct and a free 5'-hydroxyl (5'-OH). Strand ligation results when the 5'-OH attacks the covalent complex and displaces the enzyme. We describe the synthesis of 3'-phospho-(para-nitrophenyl) oligonucleotides (3'-pNP DNAs), which mimic the natural 3'-phosphotyrosyl intermediate, and demonstrate that such pre-activated strands are substrates for DNA ligation by vaccinia topoisomerase and Cre recombinase. Ligation occurs by direct attack of a 5'-OH strand on the 3'-pNP DNA (i.e., without a covalent protein-DNA intermediate) and generates free para-nitrophenol as a product. The chromogenic DNA substrate allows ligation to be studied in real-time and in the absence of competing cleavage reactions and can be exploited for high-throughput screening of topoisomerase/recombinase inhibitors.

Arginine↗
PubMed2000

Prevalence and phylogenetic characterisation of TT-virus in the blood donor population of Auckland, New Zealand.

TT-virus (TTV, patient initials: T.T.), a novel DNA virus, was first isolated in Japan in 1997 from serum of a patient with post-transfusion hepatitis of unknown aetiology. To date, the contribution of TTV to liver disease remains doubtful. The potential for transmission via blood and blood products makes it essential to establish the prevalence of TTV viraemia in the blood donor population. 413 blood donor serum samples were chosen randomly, the DNA was extracted and TTV-specific DNA amplified by nested polymerase chain reaction (PCR). TTV infection was present in 13 out of 413 (3.15%) blood donors in the Auckland region of New Zealand using a set of primers targeting open reading frame (ORF) 1. These 13 amplification products (264 bp) were sequenced and TTV genotypes determined. Alignment with published TTV sequences showed that seven (53.8%) of the thirteen positive serum samples belonged to genotype 1, five (38.5%) belonged to genotype 2 and one (7.7%) could not be classified as either genotype 1 or 2. One hundred twenty-seven blood donor serum samples were retested with a second set of primers targeting the 5' region of the TTV genome in a single round PCR. Forty-three samples were positive for TTV DNA with these primers resulting in a prevalence of 37%. The data demonstrate that TTV is present among New Zealand blood donors and support the need for further investigation into the natural history of TTV infection.

Blood Donors↗
PubMed1999

Malarial antibodies in Auckland blood donors.

AIM: To determine the malarial exposure characteristics of "malarial risk" blood donors and measure the potential infectivity of their donations using a commercially available malarial antibody screening kit. METHOD: Malarial risk donors were identified according to standard protocols, questioned as to their degree of exposure to malaria and blood samples were tested for malarial antibodies using an enzyme immunoassay kit. The kit used detects IgG antibodies to P. falciparum, shows 50% crossreactivity with P. vivax and some crossreactivity with P. ovale. Antibody positive samples were further checked by a direct immunochromatographic test for P. falciparum. RESULTS: We found 1.7% of the donors who were classified as a "malarial risk" to be positive for IgG malarial antibodies. None of these antibody positive samples was positive by the direct immunochromatographic test for P. falciparum. CONCLUSION: These results indicate that none of these donors tested were a risk of transmitting P. falciparum, the major and most serious cause of transfusion transmitted malaria. The introduction of malarial testing of malarial risk blood donors in Auckland, currently deferred for plasma donation only, could potentially recover 2300 units of red cells per year.

Animals↗
PubMed1998

Non-insulin-dependent diabetes mellitus in New Zealand Maori: a relationship with Class I but not Class II histocompatibility locus antigens.

AIMS: To investigate the possibility of a relationship between the major histocompatibility complex (MHC) and non-insulin-dependent diabetes mellitus (NIDDM) in Maori. Such relationships have previously been shown in non-European races with a high incidence of NIDDM. METHODS: We performed serological Class I and PCR-SSP Class II HLA typing on 44 Maori with NIDDM and renal failure and compared the results with normal Maori. RESULTS: A strong relationship with the HLA-B40 groups of antigens (relative risk 5.1 chi 2 = 16.8, p < 0.001) was found; this was mainly attributable to HLA-B48 and HLA-B60. There was no HLA Class II relationship. CONCLUSION: The relationship with HLA-B40 antigens suggests that the MHC or other genes on chromosome 6 play a role in NIDDM in Maori.

Diabetes Mellitus, Type 2↗
PubMed1995

Mutations causing coagulation factor XIII subunit A deficiency: characterization of the mutant proteins after expression in yeast.

We identified the mutations causing factor XIII A subunit deficiency in two families. Two distinct mutations were identified in the S family: the nonsense mutation Tyr 441-->stop in exon 11, inherited through the paternal line, and the missense mutation Asn 60-->Lys in exon 3, inherited through the maternal line. Two members of the J family were heterozygous for the previously described type 3 A subunit. The substitution giving rise to the type 3 variant was found to be Gly 501-->Arg in exon 12. The Asn 60-->Lys and Gly 501-->Arg mutations were constructed in cDNA clones and expressed in yeast (Saccharomyces cerevisiae AH22). Although mRNA could be detected, protein containing the Asn 60-->Lys substitution could not be detected, suggesting extreme instability or susceptibility to proteolysis. A subunits containing the Gly 501-->Arg substitution were expressed and found to be enzymatically active in fresh yeast lysates. This variant has thermal instability and lost activity during storage or purification. Gel filtration studies suggested that the type 3 variant assembled as a dimer, as do normal A subunits. The data suggest that the Gly 501-->Arg (Type 3 variant) would cause severe factor XIII deficiency if inherited in the homozygous form or as a compound heterozygote with another deleterious mutation.

Adult↗
PubMed1994

HLA class I gene, antigen and haplotype frequencies in New Zealand Maori and Europeans.

AIM: To determine class I HLA gene, antigen and haplotype frequencies for New Zealand Maori and Europeans. METHODS: Statistical analysis was performed using accumulated data from Maori (n = 576) and European (n = 1747) parentage studies. RESULTS: HLA class I gene, antigen and haplotype frequencies are as tabulated. Significant statistical differences were shown to exist between New Zealand Maori, New Zealand Europeans and Europeans. Gene frequencies of HLA A1, 3, 9, 11, 19 and HLA B7, 8, 12, 16, 22, and 40 differed significantly between New Zealand Maori and New Zealand European data. Gene frequencies of HLA A1 and B12 differed significantly between New Zealand European and European data. CONCLUSIONS: This HLA frequency data can be used for calculating more reliable indices of paternity or for determining the potential availability of matched organs for transplantation, as well as for anthropological studies. The data may also be useful in forensic investigations.

Europe↗
PubMed1991

The hospital transfusion committee: a step towards improved quality assurance.

Quality assurance has an important contribution to make in the judicious use of scarce resources. Auckland Hospital has established a transfusion committee because there was an escalating usage of blood and blood products which are expensive prescription medicines. A pilot audit of red cell transfusions indicated that 29% of red cell transfusions may have been unnecessary. A wide range of initiatives at Auckland Hospital has reduced blood product usage. Inappropriate use of blood carries an opportunity cost and may subject patients to unnecessary risk of reactions, including potential disease transmission. Strategies which need to be employed by transfusion committees include the introduction of clinical audit, physician education, restrictions on availability, and clinical budgeting. It is recommended that transfusion committees be set up in all major hospitals.

Blood Transfusion↗
PubMed1979

Anti-N in patients undergoing regular haemodialysis: a possible association with renal transplant failure.

Six patients on regular haemodialysis in the Auckland renal dialysis unit developed the antibody anti-N. All utilised formaldehyde resterilisation dialyser procedures. Four patients with anti-N underwent renal transplantation unsuccessfully. Histological changes were difficult to interpret and could not be closely correlated with serological findings, although vessel thrombi and renal tissue infarcts were seen in some kidneys. It is recommended that renal patients should be screened at 4 degrees C and room temperature for anti-N and that resterilisation of dialysers be carefully controlled. Where transplantation is to be performed in a patient with anti-N, the organ should be warmed and perfused with warm saline prior to grafting.

Adult↗
PubMed1975

Hepatitis B antigen, alpha1 fetoprotein and liver disease in the eastern highlands of Papua New Guinea.

The sera from 89 patients from the Eastern Higlands of Papua New Guinea, all with histologically diagnosed liver disease, were tested for Hepatitis B Antigen (HB Ag) and Hepatitis B antibody (HB Ab) and alpha1 fetoprotein (AFP) by a variety of techniques which included radioimmunoassay. In the three main forms of liver disease, viral hepatitis, cirrhosis and hepatoma, HB Ag was found with a higher frequency than in patients with non specific liver disease. The frequency of HB Ab was decreased in cirrhosis and hepatoma. AFP was detected in all hepatoma patients by radioimmunoassay, levels being very high in most subjects. In hepatitis, cirrhosis and non specific liver disease, elevated levels of AFP were again frequently present, but at generally lower levels. It is conlcuded that HB Ag and AFP frequency and levels in liver disease are similar to those reported from other tropical countries. Further study is required to elicit the cellular immunological changes in liver disease.

Antibodies, Viral↗