Search PubMed⌕ Search

Biomedical subjects

D Wrede

Publications and source records attributed to D Wrede.

11 recordsLinked to original sources
PubMed1993

Oxygen concentration and asexual development of Eimeria tenella in cell cultures.

Primary chicken kidney cells in Flexiperm cultures were either inoculated with Eimeria tenella sporozoites or incubated as noninoculated controls. Oxygen concentration was reduced (10 or 15 vol% O2, 5 vol% CO2) or increased (25 or 30 vol% O2, 5 vol% CO2) in a triple gas incubator (Heraeus B 5061 EK/O2) and retained in a CO2-air incubator (20 vol% O2, 5 vol% CO2) 24 hours post inoculation (hpi). Mature second generation schizonts (mS2) were counted microscopically at 120 hpi and numbers were compared either as mS2 or mS2/cm2 confluent cells. Asexual development of Eimeria tenella was neither stimulated nor inhibited by different oxygen concentrations, indicating that higher numbers of schizonts in cultures under reducing conditions reported earlier are probably a result of increased invasion rates of sporozoites.

Animals↗
PubMed1992

Clonal p53 mutation in primary cervical cancer: association with human-papillomavirus-negative tumours.

Analyses of cancer cell lines and of anal cancers suggest an inverse correlation between infection with human papillomavirus (HPV) and somatic mutation of the p53 tumour-suppressor gene. We have investigated this association in primary cervical tumours. Tumour-tissue samples from 28 women with primary cancer of the cervix were analysed for presence of HPV sequences and for somatic mutations of the p53 gene. Southern blot analysis and the polymerase chain reaction (PCR) showed that 25 of the tumours contained HPV sequences; 20 were HPV16 positive and 5 HPV18 positive. 17 tumours subjected to restriction fragment length polymorphism analysis for the short arm of chromosome 17 showed no evidence of allelic deletion. Sequencing of the entire coding region of the p53 gene by asymmetric PCR detected heterozygous point mutations in only 3 HPV-negative tumours. By contrast, in 21 HPV-positive cancers the p53 sequence was wild-type throughout. Our data indicate that loss of wild-type p53 function is important in the pathology of cervical cancer and that in the absence of an HPV-encoded gene product that mediates loss of p53 function, somatic mutation of the gene is required. This pattern of p53 mutation may partly explain the apparently worse prognosis of HPV-negative cervical cancers.

Adenocarcinoma↗
PubMed1992

Absence of HPV 16 and 18 DNA in breast cancer.

The finding that human papillomavirus (HPV) genes can immortalise breast epithelial cells has led to suggestions that HPV could be involved in the pathogenesis of breast cancer. Using the polymerase chain reaction (PCR) we have been unable to demonstrate the presence of HPV DNA in a series of 80 breast carcinomas.

Adult↗
PubMed1991

Expression of RB and p53 proteins in HPV-positive and HPV-negative cervical carcinoma cell lines.

Mutations within the tumor suppressor genes Rb-1 and p53 are commonly found in many human malignancies, and loss of wild-type function of both p53 and RB appear to be important events in the development of these malignancies. Interference with normal RB and p53 function in the cell has apparently also been exploited by the oncogenic genital human papillomaviruses (HPVs), which encode transforming proteins capable of binding cellular RB and p53 proteins. We have investigated the expression of RB and p53 in a series of eight cervical carcinoma cell lines, six of which contain HPV sequences and two of which have arisen apparently independently of HPV infection. In the six HPV-positive lines, no evidence of abnormal RB or p53 protein could be detected. However, there was evidence for abnormal RB and p53 in the two HPV-negative lines. These data are consistent with the hypothesis that loss of wild-type RB and p53 function is necessary for tumor development and that such loss can occur either by mutation within the cellular gene or by expression of viral proteins capable of complexing wild-type cellular proteins.

Carcinoma↗
PubMed1991

p53 point mutation in HPV negative human cervical carcinoma cell lines.

Clinical and experimental evidence is consistent with a key role for transforming human papilloma viruses (HPVs) in the aetiology of anogenital carcinoma. Cervical carcinoma does, however, occasionally occur in the absence of HPV sequences (Riou et al., 1990). We have used a direct cDNA/PCR sequencing protocol to analyse the sequence of p53 mRNA expressed by HPV positive and negative cervical carcinoma cell lines. Six cell lines which contain HPV sequences express p53 mRNA which has wild-type sequence throughout conserved boxes 2, 3, 4 and 5. The two HPV negative cell lines (C33a and HT3) express mutant p53 mRNA. In each case the mutation occurs in an evolutionarily conserved amino acid. Our data suggest that loss of wild-type p53 function is important in development of cervical carcinoma, and that this might be achieved either by mutation within the p53 gene or the presence of a virally encoded p53 binding protein.

Base Sequence↗
PubMed1991

Status of c-myc, p53 and retinoblastoma genes in human papillomavirus positive and negative squamous cell carcinomas of the anus.

We have examined a series of squamous cell carcinomas (SCC) of the anus, anal intraepithelial neoplasia grade III (AINII) lesions and haemorrhoids for the presence of sequences from transforming human papillomavirus (HPV) types by polymerase chain reaction (PCR)/Southern blotting. In addition, the same DNAs have been analysed for abnormalities in the c-myc, p53 and retinoblastoma (Rb-1) gene loci by Southern blotting. HPV16 sequences were detected in a total of 38 of 50 (76%) and HPV18 sequences in 4 of the 50 cancers (8%). Of 12 haemorrhoids examined, none contained HPV16 or HPV18 sequences. Amplification of c-myc was demonstrated in 15 of the 50 cancers (30%), of which 13 were HPV16 positive, and one also positive for HPV18. Amplification of c-myc was not observed in the 5 AINIII or any of the 41 haemorrhoid DNAs analysed. Rearrangement of c-myc was not seen in any of the DNAs. Gross rearrangement, or loss of p53 or Rb-1 loci was not observed in any normal or tumor tissue. However, in preliminary analysis of p53 sequence, three tumours negative for HPV were heterozygous for p53 point mutation whereas six HPV positive tumours and two haemorrhoids were wild-type sequence throughout exons four to ten.

Anus Neoplasms↗
PubMed1979

An intercomparison between two methods of obtaining percentage depth doses for irregular shaped fields and comparison of each method with experimental data for 60Co and 10 MV X rays.

Measurements of central ray tissue-air ratio (TAR) for 60Co for a large number of irregularly shaped fields typically encountered in the cancer clinic were compared with TAR values either calculated by the Clarkson method using scatter air ratios or obtained from tables of square field data using the area/perimeter approach. Irregular field shapes included the "L", pentagonal, rectangular, upper and lower mantle and split fields. Agreement between both calculational methods and direct measurement is within +/- 2% if careful attention is given to central ray position as affected by the proper use of off-centre ratios in air. In the case of 10 MV X-rays, eight randomly chosen irregular fields again yielded an average agreement between both methods of calculation and experimental data of less than 1% and an agreement of less than 0.5% between the A/P and Clarkson calculations.

Cobalt Radioisotopes↗