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P Quirke

Publications and source records attributed to P Quirke.

At least 55 records · Page 3Linked to original sources
PubMed1998

Multiple genetic diagnoses from single cells using multiplex PCR: reliability and allele dropout.

We used a multiplex fluorescent PCR system containing seven primer sets on single cells from three different cell types (buccal, corneal and blastomere cells) and more than 3500 heterozygous alleles to investigate reliability and extent of allele dropout in multiplex PCRs at the single cell level. All three cell types gave similarly high reliability, accuracy and allele dropout rates, with similar reliability between singleplex and multiplex PCRs. Allele dropout was also consistent between the three cell types and did not significantly increase as allele size increased. These results indicate that multiplex fluorescent PCR is a reliable and accurate method of obtaining multiple diagnosis (eight chromosomes simultaneously) from single cells and maximizes the information available from single cell analysis.

Alleles↗
PubMed1998

Experimental models of colorectal cancer.

PURPOSE: A review of in vivo and in vitro models of colorectal cancer is presented. METHODS: A retrospective literature review was performed with reference to CD-ROM Medline and Index Medicus. RESULTS: A comparison of the advantages and disadvantages of the models is presented in addition to a summary of individual model methodology and applications. CONCLUSIONS: Such models are a useful adjunct for surgical research in colorectal oncology.

Animals↗
PubMed1998

Circumferential margin involvement after mesorectal excision of rectal cancer with curative intent. Predictor of survival but not local recurrence?

PURPOSE: This study examines the prognostic significance of circumferential margin involvement by tumor in resected specimens after potentially curative rectal cancer surgery. METHODS: During an eight-year period, all patients with rectal cancer were prospectively audited. For tumors of the middle and lower thirds of the rectum, a total mesorectal excision was performed; for tumor of the upper third, mesorectal excision proceeded at least 5 cm distal to the primary tumor. Resected specimens were subjected to careful histologic assessment, and patients undergoing curative procedures were entered into a surveillance program to detect both local and distant recurrence. RESULTS: Of 218 patients in the cohort, 9 had no resection, 14 underwent local excision, 1 had pre-operative radiotherapy, and 42 patients (20 percent) had palliative resections and were excluded from further analysis. This left 152 patients having a curative resection, of whom 20 (13 percent) had tumor within 1 mm of the circumferential margin. After follow-up until death or a median period of 41 months, recurrent disease was seen in 24 percent of patients with a negative margin and 50 percent with a positive margin. Both disease-free survival and mortality were significantly related to margin involvement (log-rank, P = 0.01 and P = 0.005, respectively). Local recurrence, however, was not significantly different in the two groups (11 and 15 percent, respectively; log-rank, P = 0.38). CONCLUSIONS: When mesorectal excision is performed, circumferential margin involvement is more an indicator of advance disease than inadequate local surgery. Patients with an involved margin may die from distant disease before local recurrence becomes apparent.

Disease-Free Survival↗
PubMed1998

Rapid trisomy diagnosis (21, 18, and 13) using fluorescent PCR and short tandem repeats: applications for prenatal diagnosis and preimplantation genetic diagnosis.

PURPOSE AND METHODS: Prenatal diagnosis of fetal trisomies is usually performed by cytogenetic analysis from amniotic fluid. This requires lengthy laboratory procedures and high costs and is unsuitable for large-scale screening of pregnant women. An alternative method, which is rapid and inexpensive and may potentially be suitable for diagnosing trisomies even from single fetal cells, is the fluorescent polymerase chain reaction (F-PCR) using polymorphic small tandem repeats (STRs). RESULTS: In this paper we present data demonstrating that fluorescent PCR amplification of STRs can be used for rapid diagnosis of trisomy 21, trisomy 18, and trisomy 13 and can be successfully applied to both prenatal diagnosis and diagnosis of single cells. This study also reports significant numbers of prenatal diagnoses using quantitative fluorescent PCR. CONCLUSIONS: We believe that further studies of greater numbers of samples will determine the absolute reliability of this technique. These results also provide a model for trisomy diagnosis from single cells using multiple STR markers for either preimplantation genetic diagnosis or, potentially, diagnosis from fetal cells isolated from maternal blood.

Chromosomes, Human↗
PubMed1998

Comparison of FISH PRINS, and conventional and fluorescent PCR for single-cell sexing: suitability for preimplantation genetic diagnosis.

PURPOSE: Although conventional polymerase chain reaction (PCR) was the first method used for sexing in preimplantation genetic diagnosis, fluorescent in situ hybridization (FISH) has become the method of choice. Recently two new techniques, primed in situ synthesis (PRINS) and fluorescent PCR, have been developed. This study compares the reliability and accuracy of these four techniques in single cells. RESULTS: In buccal cells, fluorescent PCR and FISH had similar reliability (94 and 93%) and accuracy (97 and 96%) rates. The reliability and accuracy of PRINS (91 and 25%) and conventional PCR (79 and 89%) were lower. In human blastomeres, FISH and fluorescent PCR had similar reliability (100%, 717; 95%, 190/201) rates. Accuracy rates were 71% (517) and 99% (188/190) for FISH and fluorescent PCR, respectively, however, too few blastomeres were analyzed by FISH for meaningful comparison. However, when these data are compared with published data, the method of choice for blastomere sexing appears to be fluorescent PCR. CONCLUSIONS: Flouroscent PCR has major implications for PGD.

Biotin↗
PubMed1998

Rapid determination of trisomy 18 parental origin using fluorescent PCR and small tandem repeat markers: case reports.

Trisomy 18 is the second most common genetic defect after trisomy 21, almost 90% of which are due to additional chromosome from the mother. The parental origin of the additional chromosome can, if required, be determined by two methods: karyotyping, which takes several weeks; or, more recently, by polymerase chain reaction (PCR) which is often problematic. Fluorescent PCR of small tandem repeats (STRs) can determine the parental origin in the majority of cases within 5 h. Although the incidence of paternal origin is known for both trisomy 21 and trisomy 18, this technique can rapidly determine the parental origin in cases where there is insufficient samples to perform conventional tests. Determining parental origin by these methods may also have clinical significance in the diagnosis of chromosomal translocations or in the diagnosis of genetic disease using linkage analysis.

Chromosomes, Human, Pair 18↗
PubMed1998

Frequency of replication errors in colorectal cancer and their association with family history.

BACKGROUND: Replication errors (RERs) characterise tumours of hereditary non-polyposis colorectal cancer (HNPCC). RER status may therefore improve identification of such families previously diagnosed by family history alone. AIMS: To assess RER and HNPCC frequency within a population of colorectal cancer patients and a regional population of family history defined (Amsterdam criteria) HNPCC families. METHODS: Family history was assessed by personal interview in a population of 479 patients with colorectal cancer attending one follow up clinic. Seven fluorescently labelled microsatellites were used to investigate RER frequency in colorectal cancers from 89 patients of this population with varying degrees of family history and 20 Amsterdam criteria positive families (four with a known germline mutation, 16 with unknown mutation status) from the regional population. RESULTS: Only four of the follow up population (0.8%) came from families meeting the Amsterdam criteria with only one showing RERs. The frequency of RERs was similar in the early onset cancer group (less than 50 years of age), those with a family history, and those with no family history of colorectal cancer. From the regional population, RERs were identified in 4/4 families with a mutation but only 8/16 families with unknown mutation status. CONCLUSIONS: No correlation was seen between RER status and strength of family history except in HNPCC families. Results also indicate that half of the Amsterdam criteria defined families do not exhibit RERs, perhaps suggesting a different mechanism of tumorigenesis.

Adult↗
PubMed1998

Prenatal detection of trisomy 21 and 18 from amniotic fluid by quantitative fluorescent polymerase chain reaction.

Prenatal diagnosis of fetal trisomies is usually performed by cytogenetic analysis on amniotic fluid. This requires lengthy laboratory procedures and high costs, and is unsuitable for large scale screening of pregnant women. An alternative method, which is both rapid and inexpensive and suitable for diagnosing trisomies even from single fetal cells, is the fluorescent polymerase chain reaction using polymorphic small tandem repeats (STRs). In this paper we present the preliminary results of a larger study comparing parallel prenatal diagnoses of trisomies 21 and 18 using cytogenetics with quantitative fluorescent polymerase chain reaction using STR markers. The results obtained by the two techniques were concordant in all cases. This is the first study reporting significant numbers of prenatal diagnoses using the quantitative fluorescent polymerase chain reaction. We believe that further studies on greater numbers of samples will determine the absolute reliability of this technique. These results also provide a model for diagnosis of trisomy from single fetal cells isolated from maternal blood.

Amniocentesis↗
PubMed1998

Same day diagnosis of Down's syndrome and sex in single cells using multiplex fluorescent PCR.

The major reason for prenatal diagnosis lies in the detection of trisomies, particularly trisomy 21 (Down's syndrome). Current techniques require lengthy laboratory procedures and high costs. Furthermore, diagnosis is often not possible if the sample is of small size or is contaminated. An alternative method, quantitative fluorescent polymerase chain reaction (PCR) of short tandem repeats (STRs), can also be used to diagnose trisomies and it has the advantage that a result is obtained within five to eight hours. However, this method is currently limited to relatively large amounts of sample, which restricts diagnostic confidence and value. Recently, genetic diagnosis using fluorescent PCR has been applied at the single cell level but is limited to sex or single gene defect diagnosis. This study, using quantitative multiplex fluorescent PCR, provides for the first time simultaneous diagnosis and confirmation of sex and trisomy in single cells. Two markers for chromosome 21 increase diagnostic confidence, informativeness, and confirmation. This system is rapid (five hours), reliable, and accurate and we believe that it will be more cost effective than alternative methods. The technique has direct application to preimplantation genetic diagnosis, early prenatal diagnosis, and other diagnostic systems where sample size is limited.

Down Syndrome↗
PubMed1998

Prenatal detection of trisomy 13 from amniotic fluid by quantitative fluorescent polymerase chain reaction.

Prenatal diagnosis of fetal trisomies is usually performed by cytogenetic analysis from amniotic fluid. However, this requires lengthy laboratory procedures, high costs and is unsuitable for large-scale screening of pregnant women. An alternative method, which is rapid, inexpensive and suitable for diagnosing trisomies, even from single fetal cells, is the fluorescent polymerase chain reaction (PCR) using polymorphic small tandem repeats (STRs). In this paper, we present the method of rapid prenatal detection of trisomy 13 from amniotic fluid using fluorescent PCR and two highly polymorphic STRs (D13S258 and D13S631). The results obtained by quantitative fluorescent PCR amplification of fetal DNA were concordant with amniocyte karyotyping results in all cases. Two cases of trisomy 13 were detected from 212 amniotic fluids and the results obtained from D13S631 and D13S258 amplification are presented. In the first trisomy 13 case, a triallelic pattern was detected by both markers, and in the second case, D13 markers showed a characteristic 2:1 dosage allele ratio, both of which demonstrate trisomy 13 status. All other heterozygous disomic samples showed an allele intensity ratio of 1:1.

Amniocentesis↗
PubMed1997

Assessment of microsatellite alterations in young patients with gastric adenocarcinoma.

BACKGROUND: Genetic factors are probably important in the development of gastric carcinoma in young patients (younger than 40 years). The authors investigated early onset primary gastric adenocarcinomas for the presence of microsatellite instability, which is a phenotypic marker for the hereditary nonpolyposis colon carcinoma syndrome. METHODS: DNA was extracted from archival microdissected carcinoma and corresponding normal tissue from 10 British gastric carcinoma patients age 19 to 39 years at the time of diagnosis. A panel of 12 microsatellite loci were amplified by fluorescent polymerase chain reaction and analyzed using an automated DNA sequencer. RESULTS: There was no evidence of microsatellite instability. In contrast, allelic imbalance was recorded at D3S966, D3S1076, D10S197, D11S904, P53, NM23, and DCC microsatellite loci. CONCLUSIONS: The authors reported ten cases of early onset gastric carcinoma that demonstrated allelic imbalance but no evidence of instability at microsatellite loci. It is unlikely that defective DNA mismatch repair is important in this group of young patients.

Adenocarcinoma↗
PubMed1997

Prognostic significance of microsatellite instability in patients with gastric carcinoma.

A proportion of gastric adenocarcinomas exhibit replication errors manifested as microsatellite instability. The clinicopathological and prognostic significance of this abnormality remains uncertain. This study aimed to determine the importance of microsatellite instability by analysing a large series of gastric carcinomas from an English population. Using a novel fluorescent polymerase chain reaction technique, we amplified 11 microsatellite sequences from paired normal and carcinoma DNA from 101 patients who underwent a potentially curative resection for gastric carcinoma. Overall, 21% of cases demonstrated microsatellite instability in at least one locus. At least four loci were examined in each case. A replication error positive phenotype (minimum of 29% of loci affected) was detected in 9% of cases. There was no statistically significant association between the presence of microsatellite instability or replication error positive phenotype and the patient's age, sex, tumour site, stage, node status, histological subtype or grade. Carcinomas confined to the mucosa or submucosa (T1) showed a significantly higher frequency of instability and replication error positive phenotypes than T3 lesions (P = 0.03 and P = 0.05, respectively). A larger proportion of patients who were microsatellite instability or replication error positive were alive at 5 years compared with those who were negative but this did not reach statistical significance (P = 0.15 and P = 0.16, respectively). We identified a subset of gastric carcinomas from a relatively low-risk population which showed evidence of microsatellite instability. There were no statistically significant 5-year survival advantages in cases demonstrating microsatellite instability or replication error positive phenotypes. The detection of microsatellite instability is of limited prognostic value in gastric carcinoma.

Adult↗