The Genetic Factors Altered in Homozygous abo Stocks of DROSOPHILA MELANOGASTER

Females homozygous for the maternal-effect mutation abo (2-44.0) produce a large fraction of eggs which arrest during embryogenesis. Increasing doses of defined heterochromatic regions inherited by offspring of abo mothers from their fathers function zygotically to bring about a partial rescue of the abo-induced embryonic lethality. Another property of the abo mutation is that the severity of the maternal effect decreases when an abo stock is maintained in homozygous condition for a number of generations. Here, we show that the factors which change in homozygous abo stocks to result in the decrease in maternally induced embryonic lethality, act zygotically, dominantly and additively. More importantly, we show that the X and second chromosomes, but not the Y and third chromosomes, derived from homozygous abo stocks are, when inherited from males, more effective in promoting zygotic rescue of the abo-induced lethality than are the equivalent chromosomes derived from an abo stock maintained in heterozygous condition. The chromosomal locations of the factors maintained in the homozygous condition. The chromosomal locations of the factors altered in homozygous stock, as well as their behavior, strongly suggest that the same heterochromatic elements that are responsible for rescuing embryos from the abo-induced maternal effect are altered in homozygous abo flies in such a way that the maternal effect itself is less severe.     

Genetical and biochemical comparisons of alcohol dehydrogenase isozymes from Anastrepha fraterculus and A. obliqua (Diptera: Tephritidae): Evidence for gene duplication

The electrophoretic patterns of the enzyme alcohol dehydrogenase (ADH) from Anastrepha fraterculus and A. obliqua were studied. Two loci were found to code for the enzyme in A. fraterculus, and three in A. obliqua. In both species, all isozymes were active in third-instar larvae. A cationic isozyme (Adh-1) was active mainly in the visceral fat body of both species. In A. fraterculus, the locus had an anionic polymorphic isozyme (Adh-3) that was detected in the parietal fat body. In addition to these two loci, a third locus for an anionic isozyme (Adh-2), which was active in the digestive tube of larvae, was present in A. obliqua and probably resulted from gene duplication. For both species, multiple forms of the isozymes are formed by binding of an NAD-carbonyl compound, as in Drosophila melanogaster. Both larvae and early pupae of A. obliqua had almost twice the specific ADH activity as A. fraterculus. The ethanol content of the host fruit infested with A. obliqua (red mombim) was also higher than that of the host fruit infested with A. fraterculus (guava).This research was supported by grants from Conselho Nacional de Desenvolvimento Científico e Tecnologico (CNPq-PIG 40.2486/82).     

Cytometry and flow cytometry of 4',6-diamidino-2-phenylindole (DAPI)-stained suspensions of nuclei released from fresh and fixed tissues of plants

Cytometry and flow cytometry were used to study characteristics of fluorescence of the DNA-DAPI complex in nuclei released from different fresh and formaldehyde-fixed pea ( Pisum sativum L. cv. Lincoln) tissues. The two methods of isolation are compared and discussed as well as their possible use for quantitative analysis of DNA in plant tissues. With fixed tissues it is possible to obtain a number of nuclei sufficient for the flow cytometric analysis, even using small amounts of plant tissue.     

Effect of glucose on induction of delta-aminolevulinic acid synthase, ferrochelatase and cytochrome P-450 hemoproteins in isolated rat hepatocytes by phenobarbital and lead

In the present work we have been able to demonstrate that phenobarbital and lead exert an inducing effect on the biosynthesis of delta-aminolevulinic acid synthase, ferrochelatase and cytochrome P-450 hemoproteins in isolated rat hepatocytes of normal adult rats. Dibutyryl cyclic AMP enhances the induction effect produced by phenobarbital in this in vitro system. Glucose inhibits the induction of delta-aminolevulinic acid synthase and ferrochelatase. This repression effect can be reversed with increasing concentrations of dibutyryl cyclic AMP. No glucose effect was observed on the phenobarbital- and lead-mediated inductions of cytochrome P-450. he present results add more experimental evidence to support the concept that the last enzyme of the heme pathway is inducible, and as such may have a significant role in regulatory mechanisms of porphyrin and heme biosynthesis.     

Subcellular localization and glycoprotein nature of the invertase from the fission yeast Schizosaccharomyces pombe

The subcellular localization of the enzyme invertase in Schizosaccharomyces pombe cells, both repressed and derepressed for synthesis of the enzyme, was studied. Most of the invertase was found to be located outside the plasma membrane and only a small percentage was found to be associated to membranes. A substantial portion of the external enzyme remained firmly bound to cell-wall material.All of the invertase recovered in soluble form from cellular extracts reacted with concanavalin A and with the lectin from Bandeiraea simplicifolia seeds, indicating the presence in the enzyme of a carbohydrate moiety which probably contains terminal mannosyl (or structurally related) and galactosyl residues.The possibility of the presence of two different forms of invertase in S. pombe was considered. An intracellular, soluble form of invertase, devoid of carbohydrate, similar to the small invertase of the budding yeast Saccharomyces cerevisiae, was not found in S. pombe. However, the Michaelis constant for sucrose of the enzyme present in repressed cells was smaller than that of the invertase synthesized under derepressing conditions, although this difference could also be the result of a different pattern of glycosylation of the invertase synthesized under different growth conditions.     

Dion tomasellii (Zamiaceae), a new species with two varieties from western Mexico

Dion tomasellii sp. nov. occurs with an interrupted distribution from Guerrero to central Sonora. It is characterized by falcate to subfalcate leaflets. The populations from Sonora and northern Sinaloa are segregated asD. tomasellii var.sonorense on the basis of their narrower and glaucous leaflets.     

Activation of Na+/H+ exchange in lymphocytes by osmotically induced volume changes and by cytoplasmic acidification

After swelling in hypotonic solutions, peripheral blood mononuclear cells (PBM) shrink toward their original volumes. Upon restoration of isotonicity, the cells initially shrink but then regain near-normal size again. This regulatory volume increase (RVI) is abolished by removal of Na+o or Cl-o or by addition of amiloride. RVI is unaffected by removal of K+o or by ouabain and is only partially inhibited by 1 mM furosemide. As a result of increased influx, the cells gain both Na+ and K+ during reswelling. In contrast, only Na+ content increases in the presence of ouabain. Amiloride largely eliminates the changes in the content of both cations. Using diS-C3-(5), no significant membrane potential changes were detected during RVI, which suggests that the fluxes are electroneutral. The cytoplasmic pH of volume-static cells was measured with 5,6-dicarboxyfluorescein. After acid loading, the addition of extracellular Na+ induced an amiloride-inhibitable alkalinization, which is consistent with Na+/H+ exchange. Cytoplasmic pH was not affected by cell shrinkage itself, but an internal alkalinization, which was also amiloride sensitive and Na+ dependent, developed during reswelling. In isotonic lightly buffered solutions without HCO-3, an amiloride-sensitive acidification of the medium was measurable when Na+ was added to shrunken PBM. K+ was unable to mimic this effect. The observations are compatible with the model proposed by Cala (J. Gen. Physiol. 1980. 76:683-708), whereby an electroneutral Na+o/H+i exchange is activated by osmotic shrinking. Cellular volume gain occurs as Cl-o simultaneously exchanges for either HCO-3i or OH-i. Na+i is secondarily replaced by K+ through the pump, but this step is not essential for RVI.