Effects of adriamycin on respiratory chain activities in mitochondria from rat liver, rat heart and bovine heart. Evidence for a preferential inhibition of complex III and IV

The inhibition of respiratory chain activities in rat liver, rat heart and bovine heart mitochondria by the anthracycline antibiotic adriamycin was measured in order to determine the adriamycin-sensitive sites. It appeared that complex III and IV are efficiently affected such that their activities were reduced to 50% of control values at 175 +/- 25 microM adriamycin. Complex I displayed a minor sensitivity to the drug. Of the complex-I-related activities tested, only duroquinone oxidation appeared sensitive (50% inhibition at approx. 450 microM adriamycin). Electron-transfer activities catalyzed by complex II remained essentially unaltered up to high drug concentrations. Of the activities measured for this complex, only duroquinone oxidation was significantly affected. However, the adriamycin concentration required to reduce this activity to 50% exceeded 1 mM. Mitochondria isolated from rat liver, rat heart and bovine heart behaved essentially identical in their response to adriamycin. These data support the conclusion that, in these three mitochondrial systems, the major drug-sensitive sites lie in complex III and IV. Cytochrome c oxidase and succinate oxidase activity in whole mitochondria exhibited a similar sensitivity towards adriamycin, as inner membrane ghosts, suggesting that the drug has direct access to its inner membrane target sites irrespective of the presence of the outer membrane. By measuring NADH and succinate oxidase activities in the presence of exogenously added cytochrome c, it appeared that adriamycin was less inhibitory under these conditions. This suggests that adriamycin competes with cytochrome c for binding to the same site on the inner membrane, presumably cardiolipin.     

Molecular and classical genetic analyses of his-3 mutants of Neurospora crassa. I. Tests for allelic complementation and specific revertibility

A collection of 81 his-3 mutants of Neurospora crassa was analyzed in assays for allelic complementation and specific revertibility. In these studies, the linearity of the complementation map of the his-3 cistron (Webber, 1965) was confirmed and mutants were classified as complementing with non-polarized or polarized complementation patterns, or non-complementing. In the assays for spontaneous or induced revertibility, 89% (71/80) of the mutants reverted either spontaneously or after treatment with the chemical mutagens N-methyl-N'-nitro-N-nitrosoguanidine, ethyl methanesulfonate, 2-methoxy-6-chloro-9-(3-[ethyl-2-chloroethyl]aminopropylamino) acridine dihydrochloride, nitrous acid or hydroxylamine. The frequency of revertible mutants among the non-polarized complementing mutants was 96% (45/47), and 79% (15/19) for the polarized complementing and 79% (11/14) for the non-complementing mutants. The results of these classical genetic assays for allelic complementation and specific revertibility suggest a correlation between complementation pattern and presumptive genetic alterations at the molecular level among his-3 mutants similar to that found with ad-3B mutants induced by nitrous acid (Malling and de Serres, 1967), ethyl methanesulfonate (Malling and de Serres, 1968), or ultraviolet (Kilbey et al., 1971).     

TheRhizobium-legume symbiosis Two methods to discriminate between nodules and other root-derived structures

Summary Two methods have been developed in order to discriminate between lateral roots, nodules and root-derived structures which exhibit both root and nodule histological features and which can develop on legumes inoculated with certainRhizobium mutants. The first method, known as the clearing method, allows the observation by light microscopy of cleared undissected root-structures. The second, known as the slicing method, is a complementary technique which provides a greater degree of structural information concerning such structures. The two methods have proved invaluable in defining unequivocally the nature of the interaction between a rhizobial strain and a legume host.     

A division inhibitor and a topological specificity factor coded for by the minicell locus determine proper placement of the division septum in E. coli

The E. coli minicell locus (minB) was shown to code for three gene products (MinC, MinD, and MinE) whose coordinate action is required for proper placement of the division spetum. Studies of the phenotypic effects of expression of the three genes, alone and in all possible combinations, indicated the following: cell poles contain potential division sites that will support additional septation events unless specifically inactivated; the minC and minD gene products act in concert to form a nonspecific inhibitor of septation that is capable of blocking cell division at all potential division sites; and the minE gene codes for a topological specificity factor that, in wild-type cells, prevents the division inhibitor from acting at internal division sites while permitting it to block septation at polar sites.     

Simultaneous analysis of skin response to the different L.E.T. regions of a 55 MeV helium ion beam

Summary Rat tail epidermis was used to analyze the in vivo response of a biological system to heavy particle irradiation. The conical configuration of the rat tail gives rise to a variable energy degradation of the beam thus yielding information on the damage elicited by 2 different L.E.T. regions of the helium beam at different sites on the same sample. Cytochrome oxidase activity and epidermal thickness were used to analyze the metabolic and structural radioinduced response. Quantitative evaluation of radiation damage revealed marked variations within a few micrometers of tissue.     

Differential effects of the destruction of Leydig cells by administration of ethane dimethane sulphonate to postnatal rats

Ethane dimethane sulphonate (EDS) is a cytotoxic drug that selectively destroys Leydig cells in adult testes. This study has examined the effect of a single injection of EDS on the Leydig cell populations present in the testes of rats aged 5, 10, or 20 days. Microscopic examination of the tissue demonstrated that the fetal Leydig cell population was destroyed at all ages, but that subsequent development of the adult population of Leydig cells was not affected. Whilst the destruction of the fetal Leydig cells in this acute phase of EDS on 5-day-old rats was accompanied by a decline in serum testosterone levels, there was no apparent effect on this hormone when EDS administered at 10 or 20 days of age, despite the destruction of fetal Leydig cells in these rats. The long-term effects of EDS on Day 5 of age resulted in proliferation of the intertubular tissue in which more Leydig cells were observed, but serum testosterone and testosterone levels in response to human chorionic gonadotropin stimulation in vitro were normal despite moderate or severe disruption of the seminiferous epithelium. These data show that the fetal Leydig cells of immature testes are sensitive to the cytotoxic effects of EDS in the adult, but the response of the testes differs depending on the age at which the drug is administered.     

Reduced neuroexcitatory effect of domoic acid following mossy fiber denervation of the rat dorsal hippocampus: further evidence that toxicity of domoic acid involves kainate receptor activation

Domoic acid, an excitatory amino acid structurally related to kainic acid, has been shown to be responsible for the severe intoxication presented, in 1987, by more than one hundred and fifty people having eaten mussels grown in Prince Edward Island (Canada). Unitary extracellular recordings were obtained from pyramidal neurons of the CA3 region of the rat dorsal hippocampus. The excitatory effects of microiontophoretic applications of domoic acid and of the agonists of the two other subtypes of glutamatergic receptors, quisqualate and N-methyl-D-aspartate, were compared on intact and colchicine-lesioned sides. Similar to what has been previously found for kainate, the colchicine lesion of the mossy fiber projections induced a 95% decrease of the neuronal responsiveness to domoic acid, whereas the effect of quisqualate was unchanged and that of N-methyl-D-aspartate was only slightly decreased. These results provide further electrophysiological evidence that domoic acid is a potent agonist of kainate receptors and that it may produce its neuroexcitatory and neurotoxic effects, in the hippocampal CA3 region, through activation of kainate receptors located on the mossy fiber terminals.     

Incontinentia pigmenti: Xp breakpoint is not the same in a case of r(X) and in X/autosome translocations

X-specific DNA probes were used to characterize the r(X) of a 45,X/46,X,r(X) female patient with Incontinentia pigmenti. It was found to be of maternal origin. Breakpoints were shown to be in or distal to p11.22 and between q12.2 and q13.1. When considering all known cases of Incontinentia pigmenti and X rearrangements at least four different break sites on the X have been shown.     

Substrate oxidation by the heme edge of fungal peroxidases. Reaction of Coprinus macrorhizus peroxidase with hydrazines and sodium azide

The peroxidase from Coprinus macrorhizus is inactivated by phenylhydrazine or sodium azide in the presence of H2O2. Inactivation by phenylhydrazine results in formation of the delta-meso-phenyl and 8-hydroxymethyl derivatives of the prosthetic heme group and covalent binding of the phenyl moiety to the protein but not in the detectable formation of Fe-phenyl- or N-phenylheme adducts. Alkylhydrazines are catalytically oxidized but do not inactivate the enzyme. Catalytic oxidation of sodium azide produces the azidyl radical and results in its addition to the delta-meso position of the prosthetic heme group. Comparison of the heme adducts obtained with C. macrorhizus peroxidase with those generated by horseradish peroxidase shows that the regiochemistry of the addition reactions is the same in both cases. The results suggest that substrates interact primarily or exclusively with the heme edge rather than the ferryl oxygen of C. macrorhizus peroxidase and indicate that the interaction occurs with the same sector of the heme edge as in horseradish peroxidase. The active-site topologies of this pair of plant and fungal peroxidases thus appear to be similar, although the observation that alkylhydrazines add to the heme edge of horseradish but not C. macrorhizus peroxidase clearly shows that there are significant differences in the two active sites.