Micronuclei frequencies in hospital workers occupationally exposed to low levels of ionizing radiation: influence of smoking status and other factors

In the context of a medical surveillance program aimed at preventing cancer risk from exposure to ionizing radiation, we investigated chromosomal damage in peripheral lymphocytes from 37 hospital workers exposed to low levels of ionizing radiation and 37 controls. The micronuleus (MN) assay was used as a biomarker of genetic damage. The influence of confounding factors like smoking status, age and gender was investigated by multiple regression analysis. The results indicated that, overall, MN frequency was higher in exposed workers than in controls, although the difference was not statistically significant. Interestingly, smoking status significantly raised MN frequency among the exposed workers but not among controls. This suggests that smoking can influence chromosomal damage induced in humans by ionizing radiation. Among both exposed workers and controls, MN frequency was found to increase with age. Female gender influenced the increase in MN frequency in the exposed group. Our results suggest that the effect of cigarette smoking should be carefully factored into genetic monitoring studies assessing the risks associated with low level radiation exposure.     

Functional properties of grasping-related neurons in the dorsal premotor area F2 of the macaque monkey

We investigated the properties of neurons located in the distal forelimb field of dorsal premotor area F2 of macaque monkey using a behavioral paradigm for studying the neuronal discharge during observation (object fixation condition) and grasping of different 3-dimensional objects with and without visual guidance of the movement (movement in light and movement in dark conditions, respectively). The main result is that almost all studied neurons were selective for both the type of prehension and the wrist orientation required for grasping an object. Three categories of neurons were found: purely motor, visually modulated, and visuomotor neurons. The discharge of purely motor neurons was not affected by either object presentation or by the visual feedback of the hand approaching to and interacting with the object. Visually modulated neurons presented a different discharge in the 2 movement conditions, this determining a decrease in selectivity for the grip and wrist orientation in the movement in dark condition. Visuomotor neurons typically discharged during the object fixation task even in the absence of any grasping movement. Nine of them also displayed a different discharge rate between the 2 movement conditions. Congruence was observed between the neuron response during the most effective type of prehension and the neuron response during observation of the object requiring that particular prehension. These results indicate an important role of F2 in the control of goal-related hand movements.     

Apoptotic DNA binds to HLA class II molecules inhibiting antigen presentation and participating in the development of anti-inflammatory functional behavior of phagocytic macrophages

Resident macrophages are mainly responsible for the clearance of apoptotic cells from tissue by phagocytosis. Phagocytosis of apoptotic cells is not accompanied by activation of inflammatory mechanisms, unlike what happens when necrotic phenomena occur. We analyzed the effect of phagocytosis of apoptotic bodies on macrophage cell functions. After phagocytosis of apoptotic cells macrophages were unable to present an exogenous antigen to autologous antigen-specific T-cell lines. The inhibition was mediated by different mechanisms including binding of apoptotic DNA to human leukocyte antigen (HLA) class II molecules of macrophages, decreased expression of co-stimulatory molecules and increased secretion of tumor growth factor beta (TGFbeta). When dendritic cells were cultured with macrophages phagocytosing apoptotic cells, or with their supernatant, impaired dendritic cell antigen presenting activity and reduced tumor necrosis factor alpha (TNFalpha) secretion were found. Our results suggest that: (1) the phagocytosis of apoptotic bodies inhibits macrophage antigen presentation; (2) such inhibition is mediated by the binding of apoptotic DNA to macrophage HLA class II molecules as well as by the activation of biological mechanisms that induce an anti-inflammatory functional behavior in macrophages; and (3) macrophages phagocytosing apoptotic cells inhibit antigen presentation of neighboring dendritic cells via TGFbeta secretion. These events are likely related to the preservation of healthy tissues from the onset of inflammation.     

Quantification of HIV DNA in the brain by PCR: differences between fresh frozen and formalin fixed tissue.

HIV-1 DNA extracted from frozen and formalin fixed brain tissue can be detected using PCR. This work has been extended by amplifying, using semiquantitative PCR, HIV DNA extracted from frontal lobe tissue of 16 patients with AIDS (eight positive and eight negative for p24 antigen). DNA was amplified using HIV-1 pol gene digoxigenin labelled primers and detected by chemiluminescence and densitometry. Cloned standards were amplified in parallel for quantification. HIV DNA levels detected in frozen tissue showed a correlation with p24 positivity and the severity of the histological diagnosis. This correlation was less clear in the formalin fixed material.     

Age-dependent changes in the susceptibility to apoptosis of peripheral blood CD4+ and CD8+ T lymphocytes with virgin or memory phenotype

Susceptibility to apoptosis changes with age and most of the available data on lymphocytes refer to mitogen stimulated cells. We studied this susceptibility in quiescent, purified CD4+ or CD8+ T cells from a group of Italian old people compared with a group of young people. We found that an apoptotic agent such as 2-deoxy-D-ribose (dRib), which acts via glutathione depletion and oxidative stress, was more effective in CD4+ T cells from young donors, while no difference was found in CD8+ T cells. On the contrary, another agent such as TNF-alpha, which acts via receptor engagement, was more effective in CD8+ T cells from old subjects, and no difference was found in CD4+ T cells. When marker of activation-memory were investigated, no difference between young and old subjects was found when dRib was used. Differently, when TNF-alpha was used, memory and activated CD4+ T cells from old donors were less sensitive than younger counterparts, while memory CD8+ T cells from old donors were more sensitive than younger counterparts. This suggests that age-related changes in susceptibility to apoptosis of resting T cells largely depend on the type of the apoptotic stimulus which is used as well as on the memory phenotype of the cells. These results may also account, at least in part, for the deep remodelling of T cell repertoire that occurs during ageing.     

Vascular endothelial growth factor and neo-angiogenesis in H. pylori gastritis in humans

Host response plays a major role in the pathogenesis of Helicobacter pylori-induced gastroduodenal disease including adenocarcinoma of the distal stomach. Vascular endothelial growth factor (VEGF) is an important modulator of gastric mucosal repair and is overexpressed in gastric cancer. The present study sought to evaluate the expression of VEGF in the gastric mucosa of H. pylori-infected and H. pylori-non-infected dyspeptic patients. Fifteen H. pylori-infected and 15 H. pylori-non-infected dyspeptic patients were studied. Diagnosis of H. pylori infection was based on rapid urease test and histology. VEGF protein expression was assessed by western blotting. VEGF mRNA expression was assessed by RT-PCR. VEGF localization in the gastric mucosa and neo-angiogenesis were determined by immunohistochemistry. VEGF protein and mRNA expression was significantly greater in H. pylori-infected than in non-infected patients. Immunohistochemistry showed that VEGF expression was more intense in the gastric gland compartment of H. pylori-infected mucosa than in the non-infected mucosa. The increase in VEGF expression was associated with a significant increase in neo-angiogenesis as assessed by determination of CD34-positive micro-vessels. H. pylori gastritis is therefore associated with up-regulation of VEGF expression, which parallels the increased formation of blood vessels in the gastric mucosa. It is postulated that increased VEGF expression and neo-angiogenesis may contribute to H. pylori-related gastric carcinogenesis.     

Glycosylphosphatidylinositol-linked proteins are required for maintenance of a normal peripheral lymphoid compartment but not for lymphocyte development

Surface proteins tethered to the membrane through a glycosylphosphatidylinositol (GPI) anchor are deficient in the blood cells of patients with paroxysmal nocturnal hemoglobinuria (PNH) as result of a somatic mutation, in a hematopoietic stem cell, of the X-linked phosphatidylinositolglycan complementation group A (PIG-A) gene. In PNH patients, compared to the large numbers of GPI-deficient myeloid cells, the proportion of GPI-deficient lymphocytes tends to be low, and therefore the impact of GPI deficiency on immune function has been unclear. We have obtained complementation by Pig-a(-) embryonic stem (ES) cells of Rag(-/-) blastocysts, and we show that Pig-a(-) ES cells are able to reconstitute the T cell and B cell compartments of Rag(-/-) mice. Although these mice were immunologically competent, by comparison with appropriate controls we detected several abnormalities: (1) increased levels of IgG; (2) high frequency/titers of anti-nuclear antibodies; (3) markedly reduced delayed hypersensitivity; and (4) impaired activation-induced lymphocyte death in vitro. In some cases, aging Pig-a(-)/Rag(-/-) chimeric mice developed lymphadenopathy and polyclonal T cell and B cell expansion. Thus, GPI-linked proteins are not required for lymphocyte development but they are required for normal lymphocyte function and for maintaining normal peripheral lymphoid homeostasis.     

Morphological observations and morphometric analysis in three human fetuses with bilateral cervical cystic hygroma

Three human fetuses (crown-rump length, CRL, ranging from 71 to 77 mm), presenting bilateral cervical cystic hygroma were examined. The specimens were cleared and double-stained with alcian blue and alizarin red S for detecting the ossification growth patterns in the vertebral column, ribs, ischium, limbs, and face. Longitudinal measurements of some long bones in the upper (humerus, ulna, radius) and lower (femur, tibia, fibula) limb were taken. The values of both the total length (TL) and the ossified part (OL) of each long bone, as well as the OL/TL per cent ratio were considered. Reference points were located on the mandible, i.e. condylar process (Pcl), coronoid process (Pco), gnathion (GN), gonion (GO), inferior interdental point (IDI) for measuring linear dimensions. All values obtained were related with those relative to a group of fetuses, without any detectable malformation and chromosomal abnormalities, with CRL mean value 75 mm, in order to assess the presence of further anomalies, besides the cystic hygroma, in the three fetuses considered.     

Regional mapping of RBP4 to 10q23→q24 and RBP1 to 3q21→q22 in man

The human gene coding for RBP4 has been assigned to 10q2324 using a panel of somatic cell hybrids and in situ hybridization experiments. The mapping of the human RBP1, previously assigned by our group to chromosome 3 using a panel of somatic cell hybrids, was restricted to the region 3q2122 using in situ experiments and Southern blots of genomic DNA from a hybrid retaining a portion of chromosome 3.R.F. is recipient of a Research Grant from A.I.R.C.