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Very few experimental studies keyed to carcinogenicity have been concluded with organotins. Considerable interest has been expressed in the role, if any, of trace metals in carcinogenicity. Tin content of tumors is dramatically lower than would be expected, based on homologous nonpathogenic tissue in the cancer victim. Lowered incidence of tumor formation in rodents exposed continuously to relatively high organic or inorganic tin in their diets was indicative, when coupled with other evidence reported supra, that the body accepts xenobiotic tin, processes it into a useable anticarcinogenic or antioncogenic form, wherein it functions in repression of cancer. A logical approach would be first to discover the site of tin accumulation in the mammalian body in the hope that this would provide a key to the nature of the anticarcinogenic tin entity. Consequently, the initial experimental studies were undertaken.

A review of the hadron electromagnetic form factors obtained in a light-front constituent quark model, based on the eigenfunctions of a mass operator, is presented. The relevance of different components in the q-q interaction for the description of hadron experimental form factors is analysed.

The exclusive semileptonic decay Lambda_b -> Lambda_c + l nu_l is investigated including both radiative and first-order power corrections in the inverse heavy-quark mass, while the Isgur-Wise function is calculated within a light-front constituent quark model. It turns out that the dependence on the model parameters can be effectively constrained using recent lattice QCD results at low values of the recoil. Our final predictions for the exclusive semileptonic branching ratio, the longitudinal and transverse asymmetries, and the longitudinal to transverse decay ratio are: Br(Lambda_b -> Lambda_c + l nu_l) = (6.3 \pm 1.6) % |V_{bc} / 0.040|**2 \tau(\Lambda_b) / (1.24 ps), a_L = -0.945 \pm 0.014, a_T = -0.62 \pm 0.09 and R_L/T = 1.57 \pm 0.15, respectively. Moreover, the theoretical uncertainties both on a_L and the (partially integrated) R_L/T are found to be quite small and, therefore, the experimental determination of these quantities is a very interesting tool for testing the Standard Model and for investigating possible New Physics. In this respect the sensitivity to extract unique information both on the strength and phase of possible hadronic right-handed currents is illustrated.

A parameter-free evaluation of the $N - P_{11}(1440)$ electromagnetic transition form factors is performed within a light-front constituent quark model, using for the first time the eigenfunctions of a mass operator which generates a large amount of configuration mixing in baryon wave functions. A one-body electromagnetic current, which includes the phenomenological constituent quark form factors already determined from an analysis of pion and nucleon experimental data, is adopted. For $Q^2$ up to few $(GeV/c)^2$, at variance with the enhancement found in the elastic channel, the effect of configuration mixing results in a significant suppression of the calculated helicity amplitudes with respect to both relativistic and non-relativistic calculations, based on a simple gaussian-like ansatz for the baryon wave functions., revised version to appear in Phys. Lett. B

The charge form factor of $\ensuremath{\pi}$ and $K$ mesons is evaluated adopting a relativistic constituent quark model based on the light-front formalism. The relevance of the high-momentum components of the meson wave function, for values of the momentum transfer accessible to CEBAF energies, is illustrated. The predictions for the elastic form factor of $\ensuremath{\pi}$ and $K$ mesons are compared with the results of different relativistic approaches, showing that the measurements of the pion and kaon form factors planned at CEBAF could provide information for discriminating among various model of the meson structure.

The form factors of the $\pi \rho$ and $\pi \omega$ radiative transitions are evaluated within a light-front constituent quark model, using for the first time the eigenfunctions of a light-front mass operator reproducing the meson mass spectrum and including phenomenological Dirac and Pauli quark form factors in the one-body electromagnetic current operator. The sensitivity of the transition form factors both to the meson wave functions and to the constituent quark form factors is illustrated. It is shown that the measurement of the $\pi \rho$ and $\pi \omega$ radiative transitions could help in discriminating among various models of the meson structure.

Item does not contain fulltext Mutations in the Forkhead box G1 (FOXG1) gene, a brain specific transcriptional factor, are responsible for the congenital variant of Rett syndrome. Until now FOXG1 point mutations have been reported in 12 Rett patients. Recently seven additional patients have been reported with a quite homogeneous severe phenotype designated as the FOXG1 syndrome. Here we describe two unrelated patients with a de novo FOXG1 point mutation, p.Gln46X and p.Tyr400X, respectively, having a milder phenotype and sharing a distinctive facial appearance. Although FoxG1 action depends critically on its binding to chromatin, very little is known about the dynamics of this process. Using fluorescence recovery after photobleaching, we showed that most of the GFP-FoxG1 fusion protein associates reversibly to chromatin whereas the remaining fraction is bound irreversibly. Furthermore, we showed that the two pathologic derivatives of FoxG1 described in this paper present a dramatic alteration in chromatin affinity and irreversibly bound fraction in comparison with Ser323fsX325 mutant (associated with a severe phenotype) and wild type Foxg1 protein. Our observations suggest that alterations in the kinetics of FoxG1 binding to chromatin might contribute to the pathological effects of FOXG1 mutations.

The purpose of this study was to evaluate the awareness of sports as risk factor of dental injuries, the emergency management when a tooth avulsion occurs and the compliance about mouthguards.Two hundred children and youngsters 8- to 15-year-old (147 boys and 53 girls) attending Sports Societies in Isernia, a town in Southern Italy, participated to the investigation. The sports involved were soccer, martial arts, tennis, swimming, volleyball, basketball and cycling. The questionnaire was structured into three parts: 1) questions about age, sex, type and time of sports practice; 2) questions about dental injuries, particularly personal experience, awareness of first aid and procedure about tooth avulsion; 3) questions about knowledge and use of mouthguards.Sixty-five per cent of the athletes were aware of the possibility of oral injuries during sports practice and 8.5% referred an experience of dental trauma; 71.5% of the participants think that the immediate management of dental injuries by a dentist is very important to increase the rate of success; 31% know that the avulsed tooth may be reimplanted: 33.9% would reimplant the tooth within an hour and 62.9% would keep it in a wet storage medium. Finally, 80.5% of the athletes knew about mouthguards as protective devices, but only 5% actually used them; eight out of ten were provided by the dentist.Educational programs organized by the sports dentistry community are needed to inform coaches, teachers, athletes and parents about dental injuries and to promote the mouthguards use, especially in contact sports practice.

Anaemia is a common complication of chronic kidney disease (CKD), particularly in dialysis patients. The recent European guidelines for anaemia treatment in CKD indicate the percentage of hypochromic red cells (%HYPO) and reticulocyte haemoglobin content (CHr) calculated by Siemens ADVIA haematology analysers as a useful tool indicating iron deficiency. The aim of this study was to evaluate the agreement between CHr and %HYPO parameters and the reticulocyte haemoglobin equivalent (RET-He) and red blood cell haemoglobin equivalent (RBC-He) calculated by the Sysmex XE-2100 haematology analyser in a cohort of 200 dialysis patients referred to the Nephrology Unit of our hospital. Furthermore, we evaluated a new index, the DF-Hypo XE, obtained from haemoglobin (Hb), haematocrit (Hct) and RET-He, provided by the Sysmex XE-2100, as a new potential marker of %HYPO in dialysed patients.Blood samples collected in EDTA anticoagulant from 200 CKD patients receiving erythropoietin and iron to maintain haemoglobin level between 10 and 12 mg/dL were analysed on both the Siemens ADVIA 2120 and the Sysmex XE-2100 within 2 h of collection.There was good correlation between CHr and RET-He (r = 0.88; p0.0001), %HYPO and DF-Hypo XE (r = 0.89; p0.0001) and between RBC-He and CH (r = 0.96; p0.0001), but there was a lower correlation, even though statistically significant, between RBC-He and %HYPO (r = -0.59; p0.0001). The Altman-Bland analysis showed a very good level of agreement between CHr and RET-He (mean bias = 1.04 pg), %HYPO and DF-Hypo XE (mean bias = 1.73). Using a cut-off value of 29.4 pg for the RET-He and of 10.2 for the DF-Hypo XE, 15 out 17 patients with a CHr29.0 pg and 9 out 11 patients with a %Hypo10.0% were respectively correctly identified.Our study shows good correlation and agreement between CHr and RET-He and between %HYPO and DF-Hypo XE in evaluating CKD patients needing iron support.

A 72-year-old male diabetic patient admitted to our operative unit of nephrology and dialysis underwent hemodialytic treatment because of rapidly progressive renal failure. A moderate hypertensive state was associated to nephrotic proteinuria and microematuria. Renal angiography showed a severe stenosis of the right renal artery and a smaller left kidney. Right renal artery stenting induced a significant reduction in serum creatinine (Cr) and the patient discontinued with the dialytic treatment.

The 2 principal factors implicated in late kidney allograft failure are chronic rejection (also called chronic allograft nephropathy) and death of the patient with a functioning graft (mainly from cardiovascular causes). Despite lifelong immunosuppression of the recipient, immunological responses remain the leading factor in the pathogenesis of chronic rejection and both cellular and humoral immune mechanisms have been shown to play important roles. In this review, we highlight the relevance of humoral mechanisms of rejection to the pathogenesis of late allograft loss. Non immunological factors, such as donor organ quality, initial ischemic injury, calcineurin inhibitor (CNI) toxicity, hypertension, and hyperlipidemia, also contribute to progressive chronic allograft injury, but will not be reviewed in detail here. Possible strategies to stabilize or improve allograft function in patients with already established "chronic rejection/chronic allograft nephropathy" (CR/CAN) are the addition of mycophenolate mofetil (or sirolimus) with or without a reduction of cyclosporine dosage, or conversion from cyclosporine to tacrolimus. However, prospective randomized clinical trials are needed to test the efficacy of these strategies. A major current challenge for transplant physicians is to develop regimens that prevent CR/CAN, since, once established, the process typically progresses inexorably to renal allograft loss in most recipients. Evidence is now accumulating that new immunosuppressive regimens must control not only T cell but also B cell responses (i.e. limit antidonor antibody production) in order to prevent CR/CAN and improve long-term allograft survival.

The effects of SU(6) breaking on the nucleon elastic form factors are investigated within the constituent quark model formulated on the light-front. It is shown that the kinematical SU(6) breaking caused by the Melosh rotations of the quark spins as well as the dynamical SU(6) breaking due to the mixed-symmetry component generated in the nucleon wave function by the spin-dependent terms of the quark-quark interaction, can affect both GEn(Q**2) and GMp(Q**2)/GMn(Q**2). The calculated GEn(Q**2) is found to be qualitatively consistent with existing data. while the calculations of GM(Q**2) based on the plus component of the current are found to be plagued by spurious effects related to the loss of the rotational covariance in the light-front formalism. These unwanted effects can be avoided by considering the transverse y-component of the current. In this way our light-front predictions are found to be consistent with the data on both GEn(Q**2) and GMp(Q**2)/GMn(Q**2). Finally, it is shown that a suppression of the ratio GEp(Q**2)/GMp(Q**2) with respect to the dipole-fit prediction can be expected in the constituent quark model provided the relativistic effects generated by the Melosh rotations of the constituent spins are taken into account., Comment: latex 27 pp., 7 postscript figures

We present an investigation of the Isgur-Wise form factor relevant for the semileptonic decay Lambda_b -> \Lambda_c + l nu_l performed within a light-front constituent quark model. Adopting different baryon wave functions it is found that the Isgur-Wise form factor depends sensitively on the baryon structure. It is shown however that the shape of the Isgur-Wise function in the full recoil range relevant for the Lambda_b -> \Lambda_c + l nu_l decay can be effectively constrained using recent lattice QCD results at low recoil. Then, the Lambda_b -> \Lambda_c + l nu_l decay is investigated including both radiative effects and first-order power corrections in the inverse heavy-quark mass. Our final predictions for the exclusive semileptonic branching ratio, the longitudinal and transverse asymmetries, and the longitudinal to transverse decay ratio are: Br(Lambda_b -> \Lambda_c + l nu_l) = (6.3 +/- 1.6) % |V_bc / 0.040|**2 ~ tau(Lambda_b) / (1.24 ps), a_L = -0.945 +/- 0.014, a_T = -0.62 +/- 0.09 and R_L/T = 1.57 +/- 0.15, respectively. Moreover, both the longitudinal asymmetry and the (partially integrated) longitudinal to transverse decay ratio are found to be only marginally affected by the model dependence of the Isgur-Wise form factor as well as by first-order power corrections; therefore, their experimental determination might be a very interesting tool for testing the SM and for investigating possible New Physics.

The neutron charge form factor GEn(Q**2) is investigated within a constituent quark model formulated on the light-front. It is shown that, if the quark initial motion is neglected in the Melosh rotations, the Dirac neutron form factor F1n(Q**2)$ receives a relativistic correction which cancels exactly against the Foldy term in GEn(Q**2), as it has been recently argued by Isgur. Moreover, at the same level of approximation the ratio of the proton to neutron magnetic form factors GMp(Q**2) / GMn(Q**2) is still given by the naive SU(6)-symmetry expectation, -3/2. However, it is also shown that the full Melosh rotations break SU(6) symmetry, giving rise to GEn(Q**2) =/ 0 and GMp(Q**2)/GMn(Q**2) =/ -3/2 even when a SU(6)-symmetric canonical wave function is assumed. It turns out that relativistic effects alone cannot explain simultaneously the experimental data on GEn(Q**2)$ and GMp(Q**2)/GMn(Q**2)., Comment: final version with one minor correction and updated references; to appear in Physics Letters B

The momentum distributions of the constituent quarks inside the nucleon and the prominent electroproduced nucleon resonances are investigated in the two most sophisticated, available quark potential models, based respectively on the assumption of the valence + gluon dominance and on the exchange of the pseudoscalar Goldstone-bosons arising from the spontaneous breaking of chiral symmetry. It is shown that both models predict a large, similar content of high-momentum components, due to the short-range part of the interquark interaction, which affect the behaviour of both elastic and transition electromagnetic form factors at large values of the momentum transfer. The electromagnetic form factors are calculated within a relativistic approach formulated on the light-front, adopting a one-body current with constituent quark form factors. The results suggest that soft, non-perturbative effects can play a relevant role for explaining the existing data on elastic as well as transition form factors (at least) for Q 2 ≲ 10 ÷ 20 (GeV/c)2.

The space-like elastic form factors of baryons containing a heavy quark are investigated within a light-front constituent quark model in the limit of infinite heavy-quark mass, adopting a gaussian-like ansatz for the three-quark wave function. The results obtained for the Isgur-Wise form factors corresponding both to a spin-0 and a spin-1 light spectator pair are presented. It is found that the Isgur-Wise functions depend strongly on the baryon structure, being sharply different in case of diquark-like or collinear-type configurations in the three-quark system. It is also shown that the relativistic effects lead to a saturation property of the form factors as a function of the baryon size. Our results are compared with those of different models as well as with recent predictions from QCD sum rules and lattice QCD simulations; the latter ones seem to suggest the dominance of collinear-type configurations, in which the heavy-quark is sitting close to the center-of-mass of the light quark pair., Comment: latex, 15 pp., 6 figures with epsfig.sty

The parameter-free predictions for the $N - P_{11}(1440)$ and $N - P_{33}(1232)$ electromagnetic transition form factors, obtained within our light-front constituent quark model using eigenfunctions of a baryon mass operator which includes a large amount of configuration mixing, are reported. The effects due to small components in the baryon wave functions, such as S'- and D-wave, are also investigated., to appear in the Proceedings of the International Workshop on Hadron Dynamics with the new DAPHNE and CEBAF facilities, Frascati, Italy, 11-14 November 1996

A parameter-free evaluation of the $N - \Delta$ electromagnetic transition form factors is carried out in a light-front constituent quark model, based on $N$ and $\Delta$ eigenstates of a mass operator which reproduces a large set of hadron energy levels. A one-body electromagnetic current, including the constituent quark form factors previously determined within the same approach from nucleon and pion experimental data, is used. Our prediction for the magnetic transition form factor is compared with the results both of phenomenological analyses of experimental data for the $\Delta$ electroproduction, and of an analysis which includes the effects of off-energy-shell $\pi - N$ final state interaction., Comment: 13 pages as .uu encoded postscript file; to appear in Phys. Lett. B