DNA repair after gamma irradiation in lymphocytes exposed to low-frequency pulsed electromagnetic fields

The effect of exposure to extremely low-frequency pulsed electromagnetic fields (EMFs) on DNA repair capability and on cell survival in human lymphocytes damaged in vitro with gamma rays was studied by two different micromethods. In the first assay, which measures DNA repair synthesis (unscheduled DNA synthesis, UDS), lymphocyte cultures were stimulated with phytohemagglutinin (PHA) for 66 h and then treated with hydroxyurea (which blocks DNA replication), irradiated with 100 Gy of 60Co, pulsed with [3H]thymidine ([3H]TdR), and then exposed to pulsed EMFs for 6 h (the period in which cells repaired DNA damage). In the second assay, which measures cell survival after radiation or chemical damage, lymphocytes were first irradiated with graded doses of gamma rays or treated with diverse antiproliferative agents, and then stimulated with PHA, cultured for 72 h, and pulsed with [3H]TdR for the last 6 h of culture. In this case, immediately after the damage induced by either the radiation or chemicals, cultures were exposed to pulsed EMFs for 72 h, during which cell proliferation took place. Exposure to pulsed EMFs did not affect either UDS or cell survival, suggesting that this type of nonionizing radiation--to which humans may be exposed in the environment, and which is used for both diagnostic and therapeutic purposes--does not affect DNA repair mechanisms.     

Cytogenetical characterization of Odontesthes bonariensis (Pisces,Atherinidae), an Argentine species introduced in Italy

Giemsa and Ag-staining techniques and C-banding were performed on cytological preparations of 22 specimens of silversides (Odontesthes bonariensis) in order to extend the karyological knowledge on the family Atherinidae, to contribute cytotaxonomically to the systematics of the species and to identify possible cytogenetical markers of the introduced population.The karyotype is conservative, 2n being 48, and 44 chromosomes being uniarmed. The remaining four biarmed chromosomes show intraindividual morphological variability. This variability is sex-independent. Ag-stanining techniques reveal that NORs are located on the short arms of biarmed chromosomes and that the morphological variability is partially due to NOR activity. C-banding revealed the associations between NORs and constitutive heterochromatin which could be responsible for some apparent structural differences. The differences found could be cytogenetical markers of the introduced population.Research work supported by CNR, Italy. Special grant I.P.R.A. — Sub-project 1. Paper No. 1192.     

Atrial natriuretic factor in the vena cava and sinus node

We investigated the localization of atrial natriuretic factor (ANF) mRNA and of immunoreactive ANF in the vena cava and sinus node of rat and, for comparative purposes, in atria and ventricles. In situ hybridization with an ANF cRNA probe revealed that the supradiaphragmatic portion of the inferior vena cava contains almost as much mRNA as the atria, whereas the levels were less in the superior vena cava and higher than in ventricles in the sinus node. Immunoreactive ANF (high Mr form) was found to be 22 times less abundant in the supradiaphragmatic vena cava and 148 times less abundant in the superior vena cava than in atrial cardiocytes. The wall of the supradiaphragmatic portion of the vena cava and the valve (eustachian valve) that separates the atrial cavity from that of the vein are made up of atrial-like cardiocytes containing secretory granules. The subendothelial area of the superior vena cava also contains atrial-like cardiocytes with secretory granules, whereas the outer portion of the vein is made up of "transitional cells" without or with only a few secretory granules. Secretory granules in the vena cava and nodal cells, as well as transitional cells, contain immunoreactive ANF. With immunocryoultramicrotomy, virtually all cells, whether atrial-like, transitional, or nodal, and even those without secretory granules, were found to contain immunoreactive ANF in their Golgi complex and in secretory vesicles in the vena cava and in the sinus node.     

A karyotype analysis of the genus Dicentrarchus by different staining techniques

This study presents a cytogenetic analysis of the genus Dicentrarchus , represented by two species, D. labrax and D. punctatus . The karyotypes are very similar, even after staining with different techniques. Both species show 48 subtelocentric and acrocentric chromosomes, gradually decreasing in size. One pair of small size chromosomes has heteropycnotic and heteromorphtc short arms of longer size. These short arms are C- and Ag-positive, i.e. nucleolar organizer regions, NORs, are located there. Constitutive heterochromatin is also evident as a subcentromeric band on the long arms of a large chromosome pair. CMA₃-staining confirms the location and the heteromorphism of NORs. DAPI and quinacrine produce homogeneous staining of chromosomes. A review of cytogenetic studies on 'serranid' species is also presented.     

Redox thermodynamics, acid-base equilibria and salt-induced effects for the cucumber basic protein. General implications for blue-copper proteins

 The reduction potential of the basic blue-copper protein from cucumber peels (CBP) was determined through voltammetric techniques in different conditions of temperature, pH and ionic composition of the medium. The most notable properties of CBP include a positive entropy change upon reduction, a low-pH protonation and detachment of a metal-binding histidine in the reduced protein, and specific binding interactions with a number of anions present in common laboratory buffers, which influence to some extent the redox thermodynamics. The enthalpy and entropy changes accompanying reduction of the Cu(II) center were compared with those for other blue-copper proteins and correlated with spectroscopic data, structural properties and theoretical calculations. This allows some general considerations to be offered regarding the determinants of the reduction potential in this protein class. It emerges, in line with previous studies of the electronic structure of blue-copper sites, that the enthalpic contribution to the reduction potential is mainly modulated by the metal-binding interactions in the trigonal N₂S ligand set, and particularly by the Cu-cysteinate bond, while the entropy term is mainly affected by solvation properties and possibly by the weak axial bond to copper. The role of solvent exposure of the metal site in the active-site protonations in reduced blue-copper proteins is discussed. Finally, it is shown that the Nernst-Debye-Huckel model qualitatively accounts for the ionic strength dependence of the reduction potential. Received: 20 December 1996 / Accepted: 26 March 1997     

Effects of dietary fats on the fluidity of human high-density lipoprotein: influence of the overall composition and phospholipid fatty acids

The present study was undertaken to analyze whether the changes induced by dietary manipulations in the chemical composition of HDL, particularly in total phospholipids, phosphatidylcholine and sphingomyelin fatty acid composition, modified their fluidity. 12 healthy women, aged 26-49 years were studied. They consumed, over periods of 5 weeks, various isocaloric diets, each containing 30% of the calories as fat. 15.6% of the total calories were provided successively by olive oil, soybean oil, corn oil, and milk fats. The HDL fluorescence anisotropy was measured with 1,6-diphenyl-1,3,5-hexatriene (DPH) by fluorescence polarization. The HDL from the monounsaturated diet, olive oil, were the most fluid particles. The HDL fluorescence anisotropy was positively correlated with their free cholesterol percentage and negatively correlated with their triacylglycerol content and their triacylglycerol/phospholipid ratio. Moreover, the HDL fluorescence anisotropy was negatively correlated with the percentage of oleic acid in their total phospholipids and particularly in the phosphatidylcholine. These results suggest that the percentages of triacylglycerol and oleic acid in phospholipids of HDL have a fluidifying effect on these lipoproteins.     

Intracranial tumor biopsy--CT-guided stereotactic surgery

A modification of Gildenberg's technique for brain tumor biopsy is described. Marking the light beam of the gantry on the scalp with a pencil, when the lesion appears on the screen, no ScoutView is necessary. With radiopaque marks on the drawn lines, the levels of the slice are transferred to a lateral conventional X-ray, for calculation of the 'Z' coordinate. 'X' and 'Y' coordinates are determined on the CT scanner.     

Uncouplers of oxidative phosphorylation a structure-activity study of their inhibitory effect on passive chloride permeability

Uncoupling agents inhibit chloride transport in red blood cells, which is a metabolism-independent process. An analysis of the molecular requirements shows that this inhibitory activity is closely correlated with the electronic and the hydrophobic bonding properties of phenols: the more lipophilic and the more electron-attracting the substituent groups are, the greater the activity they confer on the parent molecule. A recent structure-activity study concerning various classes of reversible inhibitors of chloride transport led to the same conclusion (Motais, R. and Cousin, J.L. (1977) in International Conference on Biological Membranes: Drugs, Hormones and Membranes (Bolis, L., Hoffman, J.F. and Straub, R.W., eds.), Raven Press, New York, in the press).The effects of substituents on the activity of phenols as uncouplers have been recently examined (Stockdale, M. and Selwyn, M.J. (1971) Eur. J. Biochem. 21, 565). The comparison of these results with our data shows that uncoupling depends more on electronic properties of phenols than does chloride inhibition.