Cardiolipin biosynthesis and remodeling enzymes are altered during development of heart failure

Cardiolipin (CL) is responsible for modulation of activities of various enzymes involved in oxidative phosphorylation. Although energy production decreases in heart failure (HF), regulation of cardiolipin during HF development is unknown. Enzymes involved in cardiac cardiolipin synthesis and remodeling were studied in spontaneously hypertensive HF (SHHF) rats, explanted hearts from human HF patients, and nonfailing Sprague Dawley (SD) rats. The biosynthetic enzymes cytidinediphosphatediacylglycerol synthetase (CDS), phosphatidylglycerolphosphate synthase (PGPS) and cardiolipin synthase (CLS) were investigated. Mitochondrial CDS activity and CDS-1 mRNA increased in HF whereas CDS-2 mRNA in SHHF and humans, not in SD rats, decreased. PGPS activity, but not mRNA, increased in SHHF. CLS activity and mRNA decreased in SHHF, but mRNA was not significantly altered in humans. Cardiolipin remodeling enzymes, monolysocardiolipin acyltransferase (MLCL AT) and tafazzin, showed variable changes during HF. MLCL AT activity increased in SHHF. Tafazzin mRNA decreased in SHHF and human HF, but not in SD rats. The gene expression of acyl-CoA: lysocardiolipin acyltransferase-1, an endoplasmic reticulum MLCL AT, remained unaltered in SHHF rats. The results provide mechanisms whereby both cardiolipin biosynthesis and remodeling are altered during HF. Increases in CDS-1, PGPS, and MLCL AT suggest compensatory mechanisms during the development of HF. Human and SD data imply that similar trends may occur in human HF, but not during nonpathological aging, consistent with previous cardiolipin studies.     

The evolution of food-producing glands in eusocial bees (Apoidea,Hymenoptera)1

A food-producing role for cephalic exocrine glands has arisen independently in both taxa of highly eusocial bees, Apis and Meliponini. With several exceptions, there is little evidence that food is produced by glands of solitary bees or by most bees at lower levels of sociality. We suggest that this association with sociality is due to four adaptive features of these glands: (1) food from the glands allows feces from queens and larvae to have a small volume, (2) the queen's fecundity can be increased, (3) nutrient recovery via cannibalism can be facilitated, and (4) rearing of emergency replacement queens is accelerated. Acceleration of the rearing of other castes and of queens in the normal process of colony fission is not clearly an advantage ascribed to these glands. Trophic eggs produced by meliponine colony workers are analogous to the secretions from food-producing glands in Meliponini and Apis workers.     

Effect of Far Red Light on Drought Resistance of Cotton

The resistance of cotton (Gossypium hirsutum L.) to droughtstress was increased when plants, grown under a 9 h light period,received a 30 min far red (FR) illumination at the beginningof the dark period. With the addition of FR light, the plantsdisplayed higher stomatal resistance and lower rate of transpiration.Therefore, with the addition of FR, the plants remained at higherleaf turgor potential during the period of drought stress whencompared to plants stressed without the FR illumination. ThusFR illumination improved the water economy of the plants. (Received April 20, 1982; Accepted August 30, 1982)     

Characterization of calf liver glucosidase I and its inhibition by basic sugar analogs

Glucosidase I, the enzyme catalyzing the first step of N-linked oligosaccharide processing, has been purified from calf liver crude membranes [H. Hettkamp, G. Legler, and E. Bause, (1984) Eur. J. Biochem. 142, 85-90]. Binding experiments with concanavalin A-Sepharose suggest that glucosidase I is a glycoprotein with high-mannose carbohydrate chain(s). The enzyme has a subunit molecular mass of approximately 83 kDa and specifically hydrolyzes the terminal alpha-1,2-linked glucose residue from the natural Glc3-Man9-GlcNAc2 oligosaccharide. Studies with a variety of substrates modified in the aglycon moiety suggest that the Glc2 branch rather than the more distant domains of the substrate molecule are important for binding and hydrolysis. Glucosidase I does not require metal ions for activity and is strongly inhibited by 1-deoxynojirimycin (dNM) and its N-alkyl derivatives. Ki values range from 0.07 microM for N-methyl-dNM to 1.0 microM for dNM, measured at the pH-optimum of enzyme activity. The pH dependence of inhibition indicates that the cationic form of the inhibitors is the active species. Comparison of the Ki for N-decanoyl-dNM (approximately 70 microM) with that of N-decyl-dNM (approximately 0.4 microM) suggests that electrostatic interactions at the catalytic site of the enzyme are important for inhibitor binding. 1-Deoxymannojirimycin, previously assumed to be a specific mannosidase inhibitor, as well as its N-methyl and N-5-carboxypentyl derivatives, inhibit glucosidase I with Ki values around 190, 17, and 100 microM, respectively. This apparent lack of specificity shows that in vivo experiments on N-glycoprotein processing as well as the interpretation of results with these mannosidase inhibitors may give misleading results when these compounds are used in the millimolar range.     

Comparison of factor IX methylation on human active and inactive X chromosomes: implications for X inactivation and transcription of tissue-specific genes.

Maintenance of dosage compensation for housekeeping genes on the human X chromosome is mediated through differential methylation of clustered CpG nucleotides associated with these genes. To determine if methylation has a role in maintaining inactivity of X-linked genes which show tissue-specific expression, we examined the locus for blood clotting Factor IX. The analysis encompassed 91% of the HpaII and HhaI sites in the 41-kb region that includes the presumed promoter region, 5 kb of 5'- and 4 kb of 3'-flanking sequences. Although there are sex differences in methylation of the locus in leukocytes, the methylation pattern in liver, where the gene is expressed, is essentially the same for loci on the active and inactive X chromosome. The lack of differences in methylation of active and inactive genes makes it unlikely that methylation within the locus has a role in expression of the Factor IX gene. These findings, along with the absence of clustered CpG dinucleotides within the Factor IX locus, suggest that functional differences in DNA methylation related to X chromosome dosage compensation may be limited to CpG clusters. In any event, dosage compensation seems to be maintained regionally, rather than locus by locus.