PubMed Health⌕ Search

Biomedical subjects

C Ballarin

Publications and source records attributed to C Ballarin.

14 recordsLinked to original sources
PubMed2001

The metabolism and imaging in live cells of the bovine prion protein in its native form or carrying single amino acid substitutions.

Prion diseases are probably caused by an abnormal form of a cellular glycoprotein, the prion protein. Recent evidence suggests that the prion strain causing BSE has been transmitted to humans, thereby provoking a variant form of Creutzfeldt-Jacob disease. In this work, we analyzed the behavior of normal and malformed isoforms of the bovine PrP in transfected mammalian cell lines. Biochemical and immunocytochemical assays were complimented with imaging of live cells expressing fusion constructs between PrP and GFP. Bovine homologues of human E200K and D178N (129M) mutations were used as models of pathogenic isoforms. We show that the GFP does not impair the metabolism of native and mutant bPrPs and is thus a valid marker of PrP cellular distribution. We also show that each amino acid replacement provokes alterations in the cell sorting and processing of bPrP. These are different from those ascribed to both murine mutant homologues. However, human and bovine PrPs carrying the D178N genotype had similar cellular behavior.

Amino Acid Substitution↗
PubMed1996

Anion channels of the inner membrane of mammalian and yeast mitochondria.

The inner membrane of yeast and mammalian mitochondria has been studied in situ with a patch clamp electrode. Anion channels were found in both cases, although their behavior and regulation are different. In mammalian mitochondria, the principal channel is of around 100 pS conductance and opens mainly under depolarized membrane potentials. As no physiological compound able to alter its peculiar voltage dependence has yet been found, it is proposed that this channel may serve as a safeguard mechanism for recharging the mitochondrial membrane potential. Two other anion channels, each with a distinct conductance (one of approx. 45 pS, the second of at least a tenfold higher value) and kinetics are harbored in the yeast inner membrane. Matrix ATP was found to interact with both, but with a different mechanism. It is proposed that the 45 pS channel may be involved in the homeostatic mechanism of mitochondrial volume.

Adenosine Diphosphate↗
PubMed1995

An electrophysiological study of yeast mitochondria. Evidence for two inner membrane anion channels sensitive to ATP.

The inner membrane of mitochondria from various strains of Saccharomyces cerevisiae has been analyzed with the patch clamp technique for comparison with the better known homologous membrane in mammals (Sorgato, M. C., and Moran, O. (1993) CRC Crit. Rev. Biochem. Mol. Biol. 18, 127-171). Differently than in mammals, the yeast inner membrane was found to harbor essentially two channels with similar anionic selectivity but otherwise different functional behavior. One had a conductance of around 45 picosiemens (in symmetrical 150 mM KCl) and an activity only marginally sensitive to voltage. The other channel was prominent for the higher outwardly rectifying current and for the dependence upon voltage of the open probability that induced rapid closure at physiological (negative) membrane potentials. Particularly interesting was the effect of ATP (Mg2+ free) added on the matrix side of the membrane. In the case of the lower conducting channel, the nucleotide caused an immediate block of activity (IC50, 0.240 mM), whereas it locked the larger conductance in the open state at both positive and negative potentials. In proteoliposomes containing both mitochondrial membranes, the small conductance was clearly evident, whereas a larger channel, cationic and without the voltage dependence typical of that in the native inner membrane, was found.

Adenosine Triphosphate↗
PubMed1995

Mutagenicity and contents of polycyclic aromatic hydrocarbons in new high-viscosity naphthenic oils and used and recycled mineral oils.

Mutagenic activity on the Ames test was evaluated in 15 samples of naphthenic high-viscosity mineral oils and 12 samples of used lubricants (recovered and pooled) and their recycled products. Bacterial mutagenesis was assayed using both the standard technique and Blackburn's modification. The contents of polycyclic aromatic hydrocarbons (PAH) was also evaluated, as polynuclear aromatic fraction (PAF) and total PAH, determined respectively with the semi-quantitative dimethylsulphoxide-refractive index method and the Grimmer method. Only four samples (three acid-treated naphthenic oils and one recycled fraction of a used oil) showed mutagenic activity higher than 6 revertants/mg of oil, considered by Blackburn and coworkers as indicating a potential carcinogenic risk for these compounds. Limited mutagenicity was found in all used and recycled oils, but also in samples of acid- or solvent-treated oils. No hydrogen-treated naphthenic oils turned out to have any mutagenic activity. PAF contents of oils were closely correlated with those of total PAH (n = 15, r = 0.83; n = 12, r = 0.91; p < 0.01 for both naphthenic and used/recycled oils respectively). No recycled oil had high PAF contents. Eleven samples had PAF contents higher than 3%, the arbitrary danger threshold suggested by the CONCAWE (1988). Of these 11 samples, the majority were acid-treated products, although there was one hydrogen-treated oil and one used and recycled oil. No mutagenic activity could be demonstrated in almost half the oils with PAF > 3%. In this study, the presence of mutagens was not correlated wither with PAF or with total or mutagenic PAH. The difficulty of predicting the mutagenicity of mineral oils is stressed. Most naphthenic and some recycled oils clearly have components which inhibit the metabolizing system in the bacterial mutagenesis test, with consequent possible false negative results.

Biotransformation↗
PubMed1993

Reconstitution of the native mitochondrial outer membrane in planar bilayers. Comparison with the outer membrane in a patch pipette and effect of aluminum compounds.

Detergent-free rat brain outer mitochondrial membranes were incorporated in planar lipid bilayers in the presence of an osmotic gradient, and studied at high (1 M KCl) and low (150 mM KCl) ionic strength solutions. By comparison, the main outer mitochondrial membrane protein, VDAC, extracted from rat liver with Triton X-100, was also studied in 150 mM KCl. In 1 M KCl, brain outer membranes gave rise to electrical patterns which resembled very closely those widely described for detergent-extracted VDAC, with transitions to several subconducting states upon increase of the potential difference, and sensitivity to polyanion. The potential dependence of the conductance of the outer membrane, however, was steeper and the extent of closure higher than that observed previously for rat brain VDAC. In 150 mM KCl, bilayers containing only one channel had a conductance of 700 +/- 23 pS for rat brain outer membranes, and 890 +/- 29 pS for rat liver VDAC. Use of a fast time resolution setup allowed demonstration of open-close transitions in the millisecond range, which were independent of the salt concentration and of the protein origin. We also found that a potential difference higher than approx. +/- 60 mV induced an almost irreversible decrease of the single channel conductance to few percentages of the full open state and a change in the ionic selectivity. These results show that the behavior of the outer mitochondrial membrane in planar bilayers is close to that detected with the patch clamp (Moran et al., 1992, Eur. Biophys. J. 20:311-319). The neurotoxicological action of aluminum was studied in single outer membrane channels from rat brain mitochondria. We found that microM concentrations of Al Cl3 and aluminum lactate decreased the conductance by about 50%, when the applied potential difference was positive relative to the side of the metal addition.

Aluminum↗
PubMed1992

Ionic permeability of the mitochondrial outer membrane.

The ionic permeability of the outer mitochondrial membrane (OMM) was studied with the patch clamp technique. Electrical recording of intact mitochondria (hence of the outer membrane (OM], derived from mouse liver, showed the presence of currents corresponding to low conductances (less than 50 pS), as well as of four distinct conductances of 99 pS, 152 pS, 220 pS and 307 pS (in 150 mM KCl). The latter were voltage gated, being open preferentially at positive (pipette) potentials. Very similar currents were found by patch clamping liposomes containing the isolated OM derived from rat brain mitochondria. Here a conductance of approximately 530 pS, resembling in its electrical characteristics a conductance already attributed to mitochondrial contact sites (Moran et al. 1990), was also detected. Immunoblot assays of mitochondria and of the isolated OM with antibodies against the outer membrane voltage-dependent anion channel (VDAC) (Colombini 1979), showed the presence of the anion channel in each case. However, the typical electrical behaviour displayed by such a channel in planar bilayers could not be detected under our experimental conditions. From this study, the permeability of the OMM appears different from what has been reported hitherto, yet is more in line with that multifarious and dynamic structure which apparently should belong to it, at least within the framework of mitochondrial biogenesis (Pfanner and Neupert 1990).

Animals↗
PubMed1992

Chromosome aberrations and micronuclei in lymphocytes of workers exposed to low and medium levels of styrene.

In the present study we analysed 19 workers exposed to styrene in two factories where polyester resins were used. Because of the different sizes of the pieces undergoing resin processing, the environmental styrene concentrations and urinary mandelic acid (MA) levels of the analysed subjects were quite different in the two plants examined. Cytogenetic monitoring was performed by analysis of chromosome aberrations (CAs) and micronuclei (Mn) in peripheral blood lymphocytes. Cytogenetic analysis revealed a significant increase in the percentage of aberrant cells and total aberrations in the group with higher styrene exposure (group 2) and no increase in the group with lower exposure (group 1), as compared with matched controls. Mn frequencies were not significantly increased in the two exposed populations. No correlations between length of exposure and CA or Mn frequency were found, and a weak correlation was found between exposure levels, measured as urinary MA, and Mn frequencies. Only 5 of the 12 exposed workers examined in group 2 had urinary MA levels higher than the limit recommended by the ACGIH in 1990-91 [1]. Significant increases in DNA damage are therefore already found at urinary MA levels lower than the internationally suggested exposure limits.

Adult↗
PubMed1992

Micronucleated cells in nasal mucosa of formaldehyde-exposed workers.

The frequency of micronuclei (MN) and cytology of respiratory nasal mucosa cells were evaluated in 15 non-smokers exposed to formaldehyde in a plywood factory. Each subject was paired with a control matched for age and sex. Mean levels of exposure to formaldehyde ranged from about 0.1 mg/m3 in the sawmill and shearing-press departments to 0.39 mg/m3 in the warehouse area. There was a contemporary exposure to low levels of wood dust (inspirable mass ranged from 0.23 mg/m3 in the warehouse to 0.73 mg/m3 during sawing operations). Nasal respiratory cell samples were collected by an otorhinolaryngologist near the inner turbinate using a brush for endocervical cytology. After staining (Feulgen plus Fast Green and Papanicolaou's method for MN analysis and cytology, respectively), about 6000 cells were screened for micronuclei and scored in parallel for cytology according to a histopathological scale. A higher frequency of micronucleated cells was observed in the exposed group than in the controls (0.90 +/- 0.47 vs. 0.25 +/- 0.22, Mann-Whitney U test: p less than 0.01). Cytological examination indicated chronic phlogosis in the nasal respiratory mucosa of plywood factory workers, with a high frequency of squamous metaplasia cells (mean score 2.3 +/- 0.5 vs. 1.6 +/- 0.5 in the control group, Mann-Whitney U test: p less than 0.01).

Adult↗
PubMed1991

Influence of smoking habit on the frequency of micronuclei in human lymphocytes by the cytokinesis block method.

To evaluate the frequency of micronucleated lymphocytes in a normal population, 45 healthy subjects were analysed by using a modified cytochalasin B block method; the influence of some confounding factors (sex, age, smoking, etc.) were taken into account. Using a stepwise regression test smoking habits were found to have a statistically significant influence on the frequency of micronucleated cells and micronuclei. In addition, the mitotic and proliferative indexes, and the frequency of micronucleated lymphocytes, at different culture times, were studied in four healthy subjects. Based on the results we suggest that cytochalasin B be added to cultures no later than the 42nd hour.

Adult↗
PubMedDate not supplied

[The prevention of tumors in the aluminum industry].

Aluminium industry workers are exposed to various carcinogenic substances, the most important of which are asbestos and coal pitch and tar fumes. Primary prevention of cancer risk can be achieved either by eliminating the carcinogenic agent from the working environment, or by reducing the exposure levels or the number of exposed workers. In the aluminium industry the first type of approach is possible in the case of asbestos, which can be substituted with MMMF (man made mineral fibers), with the cancer risk thus passing from group 1 to group 2b of the IARC Classification. Complete abolition of exposure to pitch and coal-tar fumes is not feasible, but a reduction in risk can be achieved by using the pre-bake anode cell process instead of the Söderberg process, since the former reduces exposure of potroom workers to pitch and coal-tar fumes. A further reduction of exposure in pot-rooms can be achieved, as demonstrated by direct experience in an aluminium plant at Port Marghera (Province of Venice). Environmental monitoring performed from 1978 to 1989 showed a decrease in levels of total dust concentrations and thus of PAH and BaP concentrations as a result of a series of technical and/or organisational improvements. In biological monitoring, which can detect any skin absorption of the carcinogen, the concentrations of urinary hydroxypyrene confirmed low levels of exposure in the plant under study, excluding the pitch plant workers.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants, Occupational↗
PubMedDate not supplied

The vasotocinergic system in the hypothalamus and limbic region of the budgerigar (Melopsittacus undulatus).

We report a morphological and biochemical analysis on the presence, distribution and quantification of vasotocin in the hypothalamus and limbic region of the budgerigar Melopsittacus undulatus, using immunohistochemistry on serial sections and competitive enzyme linked immunoadsorbent assay measurements on tissue extracts. Analysis of the sections showed large vasotocin-immunoreactive neurons in three main regions of the diencephalon, of both male and female specimens. Vasotocinergic cell bodies were located in the ventral and lateral areas of the hypothalamus, dorsal to the lateral thalamus and medial to the nucleus geniculatus lateralis. Immunoreactive neurons were placed also periventricularly, close to the walls of the third ventricle, at the level of the magnocellular paraventricular nucleus. Well evident bundles of immunoreactive fibers were placed ventral to the anterior commissure in the same regions of the hypothalamus and thalamus where vasotocinergic perikarya are localized. Fibers were identified close to the third ventricle, and in the lateral hypothalamic area along the lateral forebrain bundle. In contrast to what reported for other oscine and non-oscine avian species, we were not able to identify immunopositive neurons in any region above the anterior commissure, or detect relevant differences on the distribution of the vasotocin immmunoreactivity between sexes. Competitive enzyme linked immunoadsorption assay and image analysis of the extension of immunoreactivity in the tissue sections were consistent with the qualitative observations and indicated that there is no statistically significant dimorphism in the content of vasotocin or in the location and distribution of vasotocinergic elements in the investigated areas of male and female parrot brains.

Animals↗