dCTP misincorporation in a Chinese hamster mutator phenotype: the role of GGA genetic context

Clone CSA7 is a CHEF18 hamster cell line that shows an increasedintracellular accumulation of dCTP. To localize the mutationsthat accumulate spontaneously in a functional gene of such amutator phenotype, independent CSA7 mutants of the hypoxanthine–guaninephosphoribosyl transferase (hprt) gene were isolated and screenedby a polymerase chain reaction–single strand conformationpolymorphism technique. Sixty-two percent of mutants produceddetectable changes of the strand migration profile and the mutationswere preferentially localized in the exons 3 (31%) and 6 (62%).The sequencing of such exons revealed that the rate of C baseincorporation was the major mutation pathway and that the Abase of a GGA sequence was the preferential site of misincorporation. ³To whom correspondence should be addressed     

Heterogeneity of human basophils and mast cells in response to muscle relaxants

We investigated thein vitro effects of increasing concentrations (10^–5–10^–3 M) of four muscle relaxants (succinylcholine, d-tubocurarine, vecuronium and atracurium) on histamine release (HR) from human peripheral blood basophils and mast cells isolated from lung parenchyma (HLMC) and skin tissues (HSMC). Basophils released less than 5% of their histamine content when incubated with any one of the muscle relaxants. In contrast, mast cells showed a marked heterogeneity in their response. Succinylcholine did not induce HR from any type of mast cell, and only high concentrations of d-tubocurarine (10^–3 M) caused HR from HSMC and HLMC. Vecuronium concentration-dependently induced HR from HLMC and HSMC. Atracurium concentration-dependently caused marked HR from HLMC and HSMC up to a maximum of 46.2±15.1% and 30.6±6.0%, respectively. From both HLMC and HSMC HR caused by atracurium and vecuronium was extremely rapid (t_1/2<1 min).=" the=" releasing=" activity=" of=" atracurium=" and=" vecuronium=" on=" hlmc=" and=" hsmc=" was=" reduced,=" but=" not=" abolished,=" by=" lowering=" the=" temperature=" of=" the=" incubation=" buffer=" to=" 22°c=" and=" 4°c.=" these=" results=" confirm=" that=" there=" are=" functional=" differences=" between=" human=" basophils=" and=" mast=" cells=" and=" among=" mast=" cells=" isolated=" from=" different=" anatomical=" sites=" in=" response=" to=" the=" muscle=" relaxants=">     

Peripheral nerve involvement in Churg-Strauss syndrome

Summary Peripheral neuropathy associated with bronchial asthma, multisystem organ dysfunction and idiopathic hypereosinophilia may be found in Churg-Strauss syndrome, hypereosinophilic syndrome and polyarteritis nodosa. Some authors have diagnosed their patients according to the presence in tissue biopsies of the three histological criteria of Churg and Strauss (necrotizing vasculitis, tissue eosinophilic infiltration, extravascular granulomas). We have observed three patients with a common history of a prodromal phase of allergic diseases (bronchial asthma and rhinitis) followed by a vasculitic phase with mononeuritis multiplex, purpura and arthritis, associated with hypereosinophilia of more than 1500 cells/mm³. All responded well to steroid treatment. Sural nerve biopsy revealed true vasculitis in two of these cases and a mild perivascular inflammatory infiltration in the other. On the basis of their characteristic clinical pattern, we think that our cases best fit the diagnosis of Churg-Strauss syndrome even though the typical histological features were not found in the sural nerves examined.     

Tuberculosis infection and disease in immigrant children

From the second half of the eighties, the cases of tuberculosis (TBC) in Italy have been constantly increasing. The increase in TBC cases in developed countries is related to different factors, including HIV epidemic and increased number of immigrants from countries with high TBC incidence and important socio-economic problems. Compared with adults few children with TBC were homeless or coinfected with HIV, nonetheless the children lived frequently in low socioeconomic status and consequently high risk of being uninsured and with adults at risk for tuberculosis (immediate relative, household members, or recently immigrated). An epidemiologic study was carried out, in order to evaluate the impact of TBC infection in immigrant children. From January 2001 to December 2002, Mantoux test (5 IU) was performed in immigrant children hospitalized or followed in two children hospitals. They included 228 children: mean age 4 years (range 1 month to 15 years). The patients came from: South America (44%) (especially from Ecuador), from Africa (20%), from Eastern Europe (19%), (especially from Middle East and North Africa), from Far East (17%). In 30 cases (13,2%) Mantoux test was positive. Among these latter, 21 presented latent infection, whereas another 9 had tuberculous disease with pulmonary localization and one of them associated with cervical adenopathy. In the study period, among all children (4426) admitted the two Units, the prevalence of tuberculous disease was 2,5% in immigrant children compared 0.2% in native children. Accurate epidemiologic monitoring, further clinical studies aimed at highlighting TBC peculiar aspects in children, and adequate therapy can lead to TBC control in the immigrant children.     

Comparative genomic hybridization analysis of hepatoblastoma reveals high frequency of X-chromosome gains and similarities between epithelial and stromal components

Hepatoblastoma (HB) is the most common liver tumor in childhood and differs in its environmental risk factors and genetic background from hepatocellular carcinoma. HB is associated with inherited conditions such as familial adenomatous polyposis and Beckwith-Wiedemann syndrome, suggesting the importance of genetic abnormalities in the pathogenesis and progression of this disease. It has a very polymorphous morphology. A diverse range of cytogenetic alterations has been reported to date, the most frequent being trisomy 2 and trisomy 20. Thirty-five HB specimens from 31 patients (22 purely epithelial, 4 purely mesenchymal, 9 mixed) were examined by comparative genomic hybridization (CGH), a technique that enables us to screen the entire tumor genome for genetic losses and gains. Our aims were as follows: (1) to characterize chromosome abnormalities that appear in this tumor and (2) to identify possible differences between different histologic subtypes of HB. We found significant gains of genetic material, with very little difference in the number and type of alterations between the different histologic components of HB. The most frequent alterations were gains of Xp (15 cases, 43%) and Xq (21 cases, 60%). This finding was also confirmed by fluorescent in situ hybridization performed on nuclei extracted from 6 specimens. Other common alterations were 1p-, 2q+, 2q-, 4q-, and 4q+. We found no difference between different histologic subtypes, a finding that may be in agreement with the hypothesis of a common clonal origin for the different components. An hitherto-unreported high frequency of X chromosome gains may support the assumption that X-linked genes are involved in the development of this neoplasm.     

Cyclosporin A regulates human NK cell apoptosis induced by soluble HLA-I or by target cells

Human natural killer (NK) cells are effectors of innate immunity, capable of killing transformed or virus-infected cells and producing pro-inflammatory cytokines. Soluble molecules of HLA-I (sHLA-I), which are significantly increased in the serum of patients affected by auto-immune or infectious or neoplastic diseases, induce NK cell apoptosis interacting with its ligands, such as CD8 or the activating isoforms of members of inhibitory superfamily receptors (IRS). This cell death is accompanied by the release of large amounts of interferon-gamma. NK cells can kill autologous target cells, including antigen presenting cells or infected or tumor cells, by engaging the natural cytotoxicity receptors (NCR) NKp30, or NKp44 and NKp46. Again, the binding between NCR on NK cells and their putative ligands on targets leads to NK cell apoptosis. FasL produced and secreted by NK cells is responsible for the NK cell apoptosis induced by either HLA-I receptors or NCR. Interestingly, cyclosporin A (CsA) blocks NK cell death consequent to interaction with target cells or with sHLA-I, without affecting the activation of cytolysis. This would indicate that CsA can maintain NK cell-dependent innate immunity by prolonging NK cell survival in an hostile environment in the presence of sHLA-I or target cells.     

Cryptosporidium parvum-specific CD4 Th1 cells from sensitized donors responding to both fractionated and recombinant antigenic proteins

T-cell-mediated immunity plays a central role in the host response to Cryptosporidium parvum. Human T-cell clones (TCC) were isolated from peripheral blood mononuclear cells of five healthy donors with prior cryptosporidiosis by use of a C. parvum crude extract, two antigen fractions obtained by ion-exchange chromatography (IEC1 and IEC2), and two recombinant peptides (SA35 and SA40) from C. parvum sporozoites. The T-cell lines derived from the one recently infected donor had a higher proportion (26 to 38%) of T cells exhibiting the gamma/delta T-cell receptor (gamma/delta-TCR) than those from donors who had recovered from cryptosporidiosis several years earlier, suggesting that the gamma/delta T-cell population is involved in the early stage of the infection. The specific TCC had the alpha/beta-TCR, had the phenotype CD45RO(+) CD4(+) CD8(-), and were characterized by either hyperproduction of gamma interferon (IFN-gamma) alone, with a Th1 profile, or IFN-gamma hyperproduction together with interleukin-4 (IL-4) or IL-5 production, with a Th0 profile. SA35, SA40, IEC1, and IEC2 may be considered good targets of the cellular response against C. parvum and may play a role in maintaining the T-cell-mediated memory response to this parasite. Furthermore, the SA35 and SA40 peptides may be regarded as immunodominant antigens involved in the maintenance of the T-cell response in healthy C. parvum-sensitized persons.