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The paper aims to improve the Thurstone scaling method by reducing the workload of data collection and simplifying the procedures of application. It proposes a hierarchical structure for organizing items that are to be scaled. Instead of making paired comparisons, the respondents would be asked to rank the items. The ranks of the items would then be transformed into paired comparisons. Workload of data collection can hence be greatly reduced. As an alternative to Thurstone model, the use of three models, i.e., linear, exponential and information, to compute serious scores is also demonstrated.

Desmoplastic small round cell tumor (DSRCT) is a rare undifferentiated neoplasm. The prognosis is poor, even if therapy is instituted promptly, and thus it is important to differentiate it from other histologically and cytologically similar-looking malignancies of the young adult. We present a case of DSRCT in a 17-yr-old male with disseminated peritoneal disease and peritoneal effusion. The cytology sample showed a malignant small round cell tumor, the classical cytological features of DSRCT, and immunohistochemistry performed in the prepared cell block exhibited an antibody expression profile in keeping with DSRCT. Further material from the effusion was prepared for RNA extraction, following which a reverse-transcriptase polymerase chain reaction (RT-PCR) and sequencing of the t(11;22)(p13;q11 or q12) were carried out. The result showed the presence of the reciprocal translocation and thus confirmed the diagnosis of DSRCT. This case shows how molecular techniques (including sequencing) can be applied to cytology in clarifying and confirming certain difficult diagnosis of undifferentiated neoplasms, DSRCT in this particular case., (Copyright 2003 Wiley-Liss, Inc.)

This study investigated whether or not the genotypes glutathione S-transferase theta (GST T1) and mu (GST M1) correlated with low white blood cell (WBC) count found in benzene exposed workers. We found that individuals with genotypes positive for both GST T1 and GST M1 showed the highest prevalence of low WBC [odds ratio (OR) = 4.67, P = 0.046, 95% confidence interval (CI) = 1.02-24.15] when the benzene exposure was high. Multiple logistic regression showed that benzene exposure (OR = 2.81, P = 0.062, 95% CI = 0.96-8.30) was associated with increased OR on low WBC and interactions between the benzene exposure and the genotype of GST T1 were also observed. These observations suggest that GST T1 and GST M1 may play important roles in the biotransformation of benzene, the effect which leads to its hematotoxicity.

Neuroblastoma is a tumour derived from the sympathoadrenal progenitors of the neural crest. It is one of the most malignant solid tumours in childhood with an annual incidence of 9.4 per 10(6) children under 15 years of age. Recent studies suggest that immunocytological detection of neuroblastoma cells in bone marrow and circulating neuroblasts during treatment may predict clinical outcome and correlate with tumour relapse. The present methods of diagnosing metastasis in neuroblastoma include histological, biochemical and immunohistological analysis. Morphological distinction between tumour cells and primitive lymphoblasts in bone marrow is often difficult, and these methods may also not always be sensitive enough for early detection of the residual and minimally circulating tumor cells. A sensitive assay for detection of such residual cells using two tissue-specific markers, NFM and SYN, by reverse transcriptase-polymerase chain reaction (RT-PCR) is reported here. Analysis of the specificity of this assay in three neuroblastoma cell lines, namely IMR 32, SK-N-SH and SY5Y showed positive expression while control peripheral blood mononuclear cells (HL 60) were negative. In reconstituted cell spiking tests, this method has the ability to detect 1-10(3) neuroblastoma cell in 10(7) normal peripheral blood mononuclear cells (PBMC), as shown by serial dilution and limiting dilution. The NFM marker was found to be a more sensitive marker. The specificity and sensitivity of this technique makes it suitable for future application in detection of minimally disseminated tumour cells in neuroblastoma patients.

Retinoblastoma (Rb) is a paediatric intraocular tumour in which predisposition can be inherited. Cases of Rb tumours can be divided into three types: familial cases, sporadic bilateral cases and sporadic unilateral cases. Familial and sporadic bilateral cases are usually categorised as hereditary while sporadic unilateral cases as non-hereditary. In both familial and non-familial forms of Rb, loss of heterozygosity of the Rb locus has been reported although its frequency in tumours has not so far been accurately determined. The cloning of the gene responsible for retinoblastoma (Rb1) has facilitated DNA studies and genetic counselling of patients. We have examined forty-five cases of retinoblastoma at five intragenic sites of the Rb1 locus, namely intron 1/BamH1, intron 17/Xba1, intron 24/TthIII1, intron 25/Dra1 and Rb1.20 VNTR. Thirty-six out of the forty-five cases (80%) were informative for these markers. Comparison of results between genomic DNA from peripheral blood and from tumours revealed that loss of heterozygosity of alleles could be detected in 50% of cases studied in which tumour samples were available. Investigation of parental origin of retained alleles showed that in all these cases, the paternal alleles were preferentially retained. The analysis of the genetic origin of mutations predisposing to retinoblastoma can facilitate new approaches for identifying recessive mutant genes that lead to cancer as well as to provide a conceptual basis for accurate prenatal predictions of cancer predisposition.

Dinucleotide polymorphisms are short tandem repeat sequences that can be used as probes for haplotype analysis in Duchenne's muscular dystrophy (DMD). There are approximately a total of 50,000 to 100,000 such loci in the human genome, and they are highly informative due to the variability of allele lengths at these loci. Primers can be designed to amplify across such repeats located in the dystrophin gene to provide diagnostic information when RFLP analysis is uninformative. We report the usefulness of three such loci for analysis of DMD families in Singapore. The STR50 marker consists of (CA)n repeats located in intron 50 of the dystrophin gene while DYS1 marker is located upstream to the transcriptional start site for the brain dystrophin promoter and BSTRH marker is identified in the 3' untranslated region of the gene. End-labeled PCR products were resolved on 6% denaturing polyacrylamide sequencing gel. Alleles were identified by comparison with sequencing markers. PCR product typically ranged between 174 bp to 255 bp with five to six alleles observed. The heterozygosity rates estimated from 50 X chromosomes of unrelated individuals were 76.0% (BSTRH), 86.6% (DYS1) and 93.3% (STR50). In 38 DMD families studied, the results obtained show that these markers were highly informative and reveal Mendelian mode of inheritance. They were useful for linkage analysis, identification of deletion mutations, confirmation of paternity and mapping of gene recombination.

Plasma from patients with thrombotic thrombocytopenic purpura (TTP) caused the aggregation of washed human platelets, which was inhibited by preincubation with normal plasma. Using salt fractionation, ion exchange chromatography, and preparative agarose gel electrophoresis, we purified a protein from normal plasma which inhibited the platelet aggregation caused by TTP plasma. On SDS polyacrylamide gel, the purified inhibitor gave a single band with a M.W. of 150,000. The antiserum against the purified protein neutralized the activity of the inhibitor and formed an identical precipitin line against normal and TTP plasma.