Evaluation of 10 aliphatic halogenated hydrocarbons in the mouse bone marrow micronucleus test

Ten halogenated aliphatic hydrocarbons (carbon tetrachloride, 1-chlorohexane, 2,3-dichlorobutane, 1,2-dichloroethane, 1,2-dichloroethylene, 1,3-dichloropropane, hexachloroethane, 1,1,2-trichloroethane, 1,2,3-trichloropropane and 1,1,3-trichloropropene), previously assayed in genetic assays in fungi, were evaluated in the mouse bone marrow micronucleus test in order to assess their genotoxicity in vivo. All chemicals were administered once i.p. at 40 and 70-80% of their respective LD50 to male and female CD-1 mice, 24 and 48 h before killing. All treatments produced evident clinical symptoms, but no marked depression of bone marrow proliferation. No statistically significant increases in the incidence of micronucleated polychromatic erythrocytes over the control values were observed at any sampling time with any of the 10 halogenated hydrocarbons assayed. The comparison of the results obtained in this study with the findings provided by in vitro micronucleus assays on the same chemicals, reported by other authors, indicate that mouse bone marrow is weakly sensitive to the genotoxic effects induced by halogenated hydrocarbons in other test systems. This suggests that the role of such an assay in carcinogen screening may be questionable for this chemical class. An examination of mouse bone marrow micronucleus test results with the halogenated aliphatic hydrocarbons classified as carcinogens by IARC supports this conclusion.     

Cloning and characterization of two catechol 1,2-dioxygenase genes from Acinetobacter radioresistens S13

Two novel catechol 1,2-dioxygenase (C 1,2-O) genes have been isolated from an Acinetobacter radioresistens strain that grows on phenol or benzoate as sole carbon and energy source. Designated as catA(A) and catA(B), they encode proteins composed of 314 and 306 amino acids, whose deduced sequences indicate that they have approximately 53% identity, whereas their NH2-terminal and COOH-terminal regions have no sequences in common. This may explain their different thermal and pH stability. Polyclonal antibodies raised against an amino-terminal CatA(A) peptide or the whole CatA(B) protein were used to establish their inducible and differential expression patterns upon bacterial growth in phenol or benzoate. The CatA(A) protein (IsoA) was induced by both phenol and benzoate though with different kinetics, whereas the catA(B) product (IsoB) was constitutively produced at low levels that increased only during growth in the presence of benzoate.     

Different patterns of replication in influenza virus-infected KB cells

Summary When KB cells were infected either with the fowl plague (FPV) Rostock strain (Hav1N1) or the WSN (H0N1) strain of influenza A virus the yield of cell-associated haemagglutinin and neuraminidase polypeptides was essentially comparable, but virus particles were not produced in the FPV-KB system. WSN virus-infected KB cells synthesized normal amounts of mature virus particles and had all the characteristics of a permissive replication cycle. Biosynthesis and transport of RNP antigen from nucleus to cytoplasm of infected cells were traced by immunofluorescent staining at 4 and 8 hours after the beginning of infection. While the fluorescent-stained material was totally confined to the nuclei in FPV-infected KB cells, RNP antigen migrated out of the nucleus during the replicative cycle of WSN virus in the same host cell. Patterns of virus-specific protein synthesis were studied by pulse-labelling with³⁵S-methionine. The most significant feature concerned the amplification of synthesis of virus-induced matrix (M) protein which did not occur in FPV-infected cells but occurred normally during WSN infection. The different patterns of replication in the same host cell when infected by different influenza A viruses is discussed.With 3 Figures     

Mast cell heterogeneity in response to cholinergic stimulation

Mast cell heterogeneity in response to acetylcholine has been evidentiated by the virtual lack of sensitivity or by the full reaction to nanomolar concentrations of acetylcholine, observed in samples of serosal mast cells isolated from the same animal species. The incubation with IgE of isolated rat mast cells renders the originally heterogeneous response homogeneous, the release of histamine evoked by acetylcholine being proportional to the IgE concentration. The histamine release induced by acetylcholine is due to the activation of muscarinic receptors, since it is blocked by atropine, not reproduced by acetylthiocholine and potentiated by exposure of the cells to the specific antigen.     

Electrophysiological properties and thermosensitivity of mouse preoptic and anterior hypothalamic neurons in culture

Responses of mouse preoptic and anterior hypothalamic neurons to variations of temperature are key elements in regulating the setpoint of homeotherms. The goal of the present work was to assess the relevance of culture preparations for investigating the cellular mechanisms underlying thermosensitivity in hypothalamic cells. Our working hypothesis was that some of the main properties of preoptic/anterior hypothalamic neurons in culture are similar to those reported by other authors in slice preparations. Indeed, cultured preoptic/anterior hypothalamic neurons share many of the physiological and morphological properties of neurons in hypothalamic slices. They display heterogenous dendritic arbors and somatic shapes. Most of them are GABAergic and their activity is synaptically driven by the activation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate receptors. Active membrane properties include a depolarizing "sag" in response to hyperpolarization, and a low threshold spike, which is present in a majority of cells and is generated by T-type Ca2+ channels. In a fraction of the cells, the low threshold spike repeats rhythmically, either spontaneously, or in response to depolarization. The background synaptic noise in cultured neurons is characterized by the presence of numerous postsynaptic potentials which can be easily distinguished from the baseline, thus providing an opportunity for assessing their possible roles in thermosensitivity. An unexpected finding was that GABA-A receptors can generate both hyper- and depolarizing postsynaptic potentials in the same neuron. About 20% of the spontaneously firing preoptic/anterior hypothalamic neurons are warm-sensitive. Warming (32-41 degrees C) depolarizes some cells, a phenomenon which is Na+-dependent and tetrodotoxin-insensitive. The increased firing rate of warm-sensitive cells in response to warming can be prepotential and/or synaptically driven. Overall, our data suggest that a warm-sensitive phenotype is already developed in cultured cells. Therefore, and despite obvious differences in their networks, cultured and slice preparations of hypothalamic neurons can complement each other for further studies of warm-sensitivity at the cellular and molecular level.     

Management of patients with carotid stenosis

Carotid atherosclerosis is one of the main risk factors for ischemic stroke. The annual risk of ipsilateral stroke for asymptomatic, albeit severe stenoses is as low as 1 to 2%, but increases to 13% in patients with recent ischemic symptoms. However the risk decreases after the first 2-3 years from the symptomatic episode, dropping to 3%. Echo-color Doppler ultrasonography is the screening method of choice, being highly accurate, noninvasive and low-cost. Carotid angiography still represents the gold standard, however, less invasive techniques as RM angiography and Angio-CT are becoming increasingly common. Based on NASCET, ECST and ACAS results, carotid endarterectomy (CE) is strongly recommended for severe symptomatic stenoses, while for the moderate symptomatic and the severe asymptomatic ones the benefit in terms of stroke risk reduction is modest and surgery should be restricted to selected cases in surgical centers of high experience. For severe asymptomatic stenoses NNT is too high to recommend indiscriminate surgery; we are waiting for the results of ACSRS trial, designed to identify a subset of patients at risk of ipsilateral stroke greater than 4%/y, that may be considered for CE, while patients at low risk will be spared from unnecessary operation. Apart from surgery, in all patients with carotid atherosclerosis correction of cardiovascular risk factors is mandatory. Antiplatelet therapy (ASA alone or with dypiridamole, ticlopidine) is effective in secondary prophylaxis of athero-thrombotic stroke; its use in asymptomatic carotid stenoses can be recommended, even if more because of a plausible rationale than of clinical trial-based evidences.     

Analysis of the structure and distribution of chromatin in interphase nuclei of different cell types from a pleural effusion of tumoral origin in man. Cytophotometric and electron microscopic studies

The authors have studied the distribution and the structure of the chromatin in the different cell types from a human pleural effusion of tumoral origin (mammary adenocarcinoma). The results show that in the entire nuclei the distribution and the structure of the chromatin cannot be considered as characteristic morphological features of the cells of the same cellular type. Thus making a clear distinction among differentiating cells and cells in DNA synthesis or in G2 period, only based on these properties of the chromatin, is very debatable. On the other hand, the distribution and the structure of the chromatin permit to characterize the different cell types in G1 period. The authors discuss the possible differential cytological diagnosis of the smears from human effusions of tumoral origin.     

Ultrastructural and biochemical aspects of liver mitochondria during recovery from ethanol-induced alterations. Experimental evidence of mitochondrial division.

To study the morphologic and biochemical changes occuring in liver mitochondria during recovery from ethanol-induced injury, rats fed a 6-month high-alcohol regimen plus a nutritionally adequate diet which did not induce fatty liver were compared with isocalorically fed controls. After this period the alcohol-fed animals displayed striking ultrastructural changes of liver mitochondria and a decreased respiratory activity with succinate or malate-glutamate as substrate. On the contrary, the respiratory rate with I-glycerophosphate was 50% increased. Regression changes were studied after alcohol was withdrawn from the diet. Enlarged mitochondria rapidly disappeared (in 24 hours), although a few megamitochondria were still present after 8 days of abstinence. A similar recovery was observed for the functional alterations. At the end of the experimental period, only a slight decrease of the maximal respiratory rate using malate-glutamate as a substrate was noted. The ultrastructural findings and the morphometric data suggest that the way in which mitochondrial normalization takes place is based on partition of these organelles.