Brief Communication: Role of Nuclear Background and in vivo Environment in Variable Segregation Behavior of the Aging-Dependent T414G Mutation at Critical Control Site for Human Fibroblast mtDNA Replication

Previous work had shown a large accumulation (up to 50% of mtDNA) of a noninherited T414G transversion at a critical control site for mtDNA replication in skin fibroblasts from the majority of human subjects above 65 years old, and its absence in younger individuals. In the present studies, long-term in vitro culture of several fibroblasts populations carrying the heteroplasmic T414G mutation revealed an outgrowth of the mutant cells by wild-type cells. This observation supported the previous conclusion that the mutation accumulation is an in vivo phenomenon, while, at the same time, indicating intrinsic physiological differences between mutant and wild-type cells. Furthermore, subcloning experiments revealed a striking mosaic distribution of the mutation in the original fibroblasts populations, as shown by its presence, in heteroplasmic or homoplasmic form, in a fraction (18–32%) of the fibroblasts, and its absence in the others. In other investigations, transfer of mitochondria from mutation-carrying fibroblasts into mtDNA-less 143B.TK^–0 206 cells revealed the persistence of the mosaic distribution of the mutation, however, with a near-complete shift to homoplasmy. The generality of the latter phenomenon would exclude a founder effect by one or few mitochondria in the transformation experiments, and would rather point to the important role of the nuclear background in the in vitro behavior of the T414G mutation. The stability of the homoplasmic mutation in ⁰ cell transformants provides a powerful tool for analyzing its biochemical effects.     

Trisomy 8 in myelodysplasia and acute leukemia is constitutional in 15-20% of cases.

The trisomy 8 found in malignancies may derive from a constitutional trisomy 8 mosaicism (CT8M), and in these cases the trisomy itself may be regarded as the first mutation in a multistep carcinogenetic process. To assess the frequency of CT8M in hematological dysplastic and neoplastic disorders with trisomy 8, an informative sample of 14 patients was collected. The data ascertained included chromosome analyses of fibroblast cultures and of PHA-stimulated blood cultures in patients with normal blood differential count, as well as possible CT8M clinical signs. One patient showed trisomy 8 in all cell types analyzed and undoubtedly has a CT8M; a second patient consistently showed trisomy 8 in PHA-stimulated blood cultures when no immature myeloid cells were present in blood and should be considered as having CT8M; a third patient, with Philadelphia-positive chronic myelocytic leukemia, was more difficult to interpret, but the possibility that she had CT8M is likely. A few clinical signs of CT8M were also present in these three patients. Our data indicate that the frequency of CT8M in hematological dysplastic and neoplastic disorders with trisomy 8 is approximately 15-20%.     

Pathogenesis of human cytomegalovirus infection and cellular targets

In acquired immunodeficiency syndrome patients with human cytomegalovirus (HCMV), disseminated infection, and end-organ disease, autopsy findings show a generalized HCMV infection of endothelial cells. On the other hand, immunocompromised transplanted patients show presence of virus and virus products in peripheral blood leukocytes (PBL), when affected by a disseminated HCMV infection. All diagnostic assays are based on the detection of virus and viral components in PBL or whole blood, including polymorphonuclear leukocytes and monocytes. The interplay between endothelial cells and leukocytes represents the pathogenetic basis for all clinical syndromes originating during disseminated HCMV infections and is the trigger for the transmission of HCMV from mother to fetus during primary infections of pregnant women. The two biologic properties of endothelial cell tropism and leukocyte (polymorphonuclear- and monocyte-) tropism are shared by all recent clinical HCMV isolates, whereas they are missing in laboratory-adapted strains. The potential role of HCMV in the pathogenesis of atherosclerosis both in the immunocompetent (after angioplasty) and the heart transplant patient is receiving support from seroepidemiologic findings, in vivo animal models, in vitro data, and also some clinical observations. The interaction of endothelial cells and leukocytes with subsequent spreading of infection to smooth muscle cells may be a major pathogenetic mechanism at the basis of this important vascular disease.     

Expression of insulin-like growth factor II (IGF–II) in human hepatocellular carcinomas: An immunohistochemical study

Recent results obtained using molecular biology techniques have suggested a possible role for insulin-like growth factor II (IGF-II) in the pathogenesis of hepatocellular carcinoma (HCC). To investigate this phenomenon, a monoclonal anti-body was used against IGF-II to study 54 patients with HCC. The presence of HBsAg was also tested both in serum and liver tissue. A positive immunoreaction was found in 9/15 (60%) of the HCC arising in cirrhotic livers of patients who had serum markers for HBV (HBV+ positive patients). These results provide further evidence that HBV might play a role in the expression of IGF-II. In HCC of patients without any markers of HBV infection (HBV- negative patients), IGF–II was detected in 10/39 (25.6%) of the tumors, and in some benign neoplastic lesions. It was found not only in neoplastic cells but also in some dysplastic nodules. The speculation arises that IGF–II expression may play a role in some steps of hepato-carcinogenesis.     

Dpc4 is expressed in virtually all primary and metastatic pancreatic endocrine carcinomas

DPC4/Smad4 is inactivated in about 50% of pancreatic ductal cancers. It has been recently reported that this gene is also inactivated in neoplasms arising from pancreatic islet cells, a phenomenon suggested to be related to similar progressions of malignancy found in common ductal cancers. To evaluate this possibility, we analysed 20 metastases of pancreatic endocrine carcinomas and their corresponding primary lesion for inactivation of DPC4 using immunohistochemical staining. In fact, immunohistochemical labelling has been shown to correlate with DPC4 gene status with high sensitivity and specificity. The cancers included 18 nonfunctioning tumours, one gastrinoma and one ViPoma all with liver, nodal and/or adrenal metastases. Seventeen were well-differentiated and three poorly differentiated endocrine carcinomas. Dpc4 expression was absent in only one primary well-differentiated endocrine cancer and its liver metastasis, while all the remaining 19 primary tumours and their metastases stained positive for the protein. All positively staining cases showed diffuse cytoplasmic and nuclear staining in virtually all neoplastic cells. Our data suggest that DPC4 is only rarely involved in pancreatic endocrine tumourigenesis and give further weight to the hypothesis that tumours arising from pancreatic exocrine and endocrine epithelia are genetically distinct.     

Seeing or not seeing where your hands are

Previous findings have demonstrated the existence of a visual peripersonal space centered on the hand in humans and its modulatory effects on tactile perception. A strong modulatory effect of vision on touch perception was found when a visual stimulus was presented near the hand. In contrast, when the visual stimulus was presented far from the hand, only a weak modulatory effect was found. The aim of the present study was to verify whether such cross-modal links between touch and vision in the peripersonal space centered on the hand could be mediated by proprioceptive signals specifying the current hand positions or if they directly reflect an interaction between two sensory modalities, i.e., vision and touch. To this aim, cross-modal effects were studied in two different experiments: one in which patients could see their hands and one in which vision of their hands was prevented. The results showed strong modulatory effects of vision on touch perception when the visual stimulus was presented near the seen hand and only mild effects when the vision of the hand was prevented. These findings are explained by referring to the activity of bimodal neurons in premotor and parietal cortex of macaque, which have tactile receptive fields on the hand, and corresponding visual receptive fields in the space immediately adjacent to the tactile fields. One important feature of these bimodal neurons is that their responsiveness to visual stimuli delivered near the body part is reduced or even extinguished when the view of the body part is prevented. This implies that, at least for the hand, the vision of the hand is crucial for determining the spatial mapping between vision and touch that takes place in the peripersonal space. In contrast, the proprioceptive signals specifying the current hand position in space do not seem to be relevant in determining the cross-modal interaction between vision and touch.     

Rapid Techniques in Diagnostic Electron Microscopy

This paper summarizes the rapid preparation procedures for electron microscopy published thus far and assesses their strengths and weaknesses. We also discuss whether there is a real need for rapid preparation techniques in diagnostic electron microscopic work.