Effects of mutation and growth rates on patterns of microsatellite instability.

The detection of somatic microsatellite (MS) alterations in tumors is often interpreted as a sign of underlying genomic instability. However, it is unclear why the proportions of altered MS loci vary between different mutator phenotype tumors. We present a simple mathematical analysis that can account for some of these differences, recognizing that the mutations accumulated in a tumor reflect both its mutation rate and number of cell divisions. Only a small proportion of mutated MS loci are expected in tumors with normal or low mutation rates. In contrast, tumors with high mutation rates may or may not acquire mutations depending on the numbers of divisions that proceed the onset of the mutator phenotype. The majority of MS loci should accumulate mutations if high mutation rates are acquired early in tumor progression. Somatic MS mutations provide clues to both the mode and tempo of tumori-genesis.     

Lack of correlation between expression of Epstein-Barr virus (EBV) latent membrane protein and bcl-2 oncoprotein in vivo.

AIMS--To evaluate whether there is any correlation between the expression of Epstein-Barr virus (EBV) latent membrane protein (LMP) and oncoprotein bcl-2 in the lymph node biopsy specimens of a Chinese patient with EBV-related reactive lymphoproliferation who later developed T cell lymphoma after a short period of time. METHODS--Immunohistochemistry, with a standard alkaline phosphatase antialkaline phosphatase (APAAP) method and New Fuchsin as a chromogen, was used for single staining of bcl-2 or LMP. Double immunostaining combining APAAP and indirect immunofluorescence was performed for dual labelling of LMP and bcl-2. RESULTS--bcl-2 was expressed in 10-30% of cells in the first lymph node biopsy specimen (EBV-associated lymphoproliferative disorder) and 30-50% of cells in the second lymph node biopsy specimen (T cell lymphoma). LMP was expressed in the first biopsy specimen but not in the second. Double immunostaining results showed that around 78% of LMP positive cells were bcl-2 negative and 94% bcl-2 positive cells were LMP negative. Among the very small fraction of LMP and bcl-2 double positive cells, the intensity of bcl-2 staining was heterogeneous and was not always stronger than that observed in LMP negative bcl-2 positive cells. CONCLUSIONS--The expression of bcl-2 protein is independent of LMP protein status in vivo. Several mechanisms may be involved in EBV associated lymphomagenesis, and bcl-2 induction may occur independently of LMP expression.     

Epstein-Barr virus DNA in nasopharyngeal carcinomas from Chinese patients in Hong Kong.

AIMS: To investigate the presence of Epstein-Barr virus (EBV) in cases of nasopharyngeal carcinoma (NPC) in Chinese patients living in Hong Kong. METHODS: Nasopharyngeal biopsy specimens, formalin fixed and paraffin wax embedded, from 24 patients, eight with undifferentiated nasopharyngeal carcinoma, eight with well differentiated squamous carcinoma, and eight showing normal tissue histology, were analysed for the presence of Epstein-Barr virus (EBV) DNA by slot-blot hybridisation on extracted unamplified DNA, and also after amplification of EBV specific sequences by the polymerase chain reaction (PCR). RESULTS: DNA slot-blot analysis showed viral DNA in all the undifferentiated, five of the well differentiated tumours, and none of the normal biopsy specimens. PCR studies confirmed positivity in the eight undifferentiated tumours, but six of the well differentiated tumours and three of the normal biopsy specimens showed viral DNA by this method, illustrating its greater sensitivity. CONCLUSIONS: EBV genome is present in appreciable copy number in most cases of well differentiated NPC in Chinese patients in Hong Kong.     

Platelet activating factor as a proinflammatory mediator in acetic-induced colitis in the rat

The nature of histamine receptors in peripheral tissues is still controversial. However, evidence of heterogeneous classes of binding sites for [³H]-mepyramine are reported in the literature. The aim of our study was, therefore, to investigate the nature of this heterogeneity by comparing [³H]-mepyramine study was, therefore, to investigate the nature of this heterogeneity by comparing [³H]-mepyramine binding in a central tissue (cerebellum) and in a peripheral tissue (lung) obtained from guinea pigs and to assess its dependence upon the temperature of incubation. The results revealed that the [³H]-mepyramine interaction in both tissues is temperature-dependent. At 25°C, the interaction between [³H]-mepyramine and the receptors was biphasic in the lung while only a single class of binding site was found in the cerebellum. At 0°C, [³H]-mepyramine interacted with three binding sites in the lung and two in the cerebellum. The behaviour of the reference compounds (clemastine, promethazine and histamine) also supported this temperature-dependence. Moreover, two new compounds (DF 11062 and DF 11113), synthesized in our laboratories and endowed with antihistamine activity, can differentiate between the low affinity site seen at 25°C in the lung and that seen in the cerebellum at 0°C.     

Ancylostoma ceylanicum infection in female hamsters: an observation on altered reproductive function.

Reproductive performances of female hamsters were investigated during Ancylostoma ceylanicum (hookworm) infection. Animals having the highest levels of infection (34.96 +/- 1.11 worms) showed degenerative changes in the reproductive system. Ovaries of infected animals contained a few primary or secondary follicles. On cocaging with males of proven fertility, only 7-8% (80% in controls) of the infected females mated but did not conceive as evidenced by the absence of corpora lutea or implantation sites on day 10 postcoitum. Animals with low worm burdens (5.94 +/- 0.65 worms), however, showed almost normal fertility. The uterine weight bioassay and compensatory ovarian hypertrophy suggest strong suppression of pituitary gonadotrophin contents in infected females. Resorptive effects on the pregnancy outcome of infected female hamsters were also recorded.     

Expression of c-myc and c-fms oncogenes in trophoblastic cells in hydatidiform mole and normal human placenta.

AIMS: To compare the expression of c-myc and c-fms proto-oncogenes in the placenta and hydatidiform mole. METHODS: Twelve hydatidiform moles and six induced abortion cases were collected. c-myc and c-fms proto-oncogene expression was analysed by northern blot hybridisation and immunohistochemical staining. RESULTS: The results of northern blot hybridisation analysis showed that c-fms was expressed more strongly in hydatidiform moles compared with normal placenta of similar gestational age. Moreover, c-fms mRNA concentrations increased with more advanced gestational age in moles but not in normal placentas. c-myc expression was very low in hydatidiform moles and normal placentas. Both oncogenes, however, had no direct correlation with the clinical course of the molar pregnancies. CONCLUSION: The difference in c-fms expression between hydatidiform moles and normal placentas suggests that c-fms may have a role in the development of molar pregnancies.     

Chromatin interactions in differentiating keratinocytes reveal novel atopic dermatitis– and psoriasis-associated genes

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Direct detection and identification of Mycobacterium tuberculosis and Mycobacterium bovis in bovine samples by a novel nested PCR assay: correlation with conventional techniques

Mycobacterium tuberculosis and M. bovis infect animals and humans. Their epidemiologies in developed and developing countries differ, owing to differences in the implementation of preventive measures (World Health Organization, 1999). Identification and differentiation of these closely related mycobacterial species would help to determine the source, reservoirs of infection, and disease burden due to diverse mycobacterial pathogens. The utility of the hupB gene (Rv2986c in M.tuberculosis, or Mb3010c in M.bovis) to differentiate M. tuberculosis and M. bovis was evaluated by a PCR-restriction fragment length polymorphism (RFLP) assay with 56 characterized bovine isolates (S. Prabhakar et al., J. Clin. Microbiol. 42:2724-2732, 2004). The degree of concordance between the PCR-RFLP assay and the microbiological characterization was 99.0% (P < 0.001). A nested PCR (N-PCR) assay was developed, replacing the PCR-RFLP assay for direct detection of M. tuberculosis and M. bovis in bovine samples. The N-PCR products of M. tuberculosis and M. bovis corresponded to 116 and 89 bp, respectively. The detection limit of mycobacterial DNA by N-PCR was 50 fg, equivalent to five tubercle bacilli. M. tuberculosis and/or M. bovis was detected in 55.5% (105/189) of the samples by N-PCR, compared to 9.4% (18/189) by culture. The sensitivities of N-PCR and culture were 97.3 and 29.7, respectively, and their specificities were 22.2 and 77.7%, respectively. The percentages of animals or samples identified as infected with M.tuberculosis or M. bovis by N-PCR and culture reflected the clinical categorizations of the cattle (P of <0.05 to <0.01). Mixed infection by N-PCR was detected in 22 animals, whereas by culture mixed infection was detected in 1 animal.