A Cyanobacterial Gene Encoding Peptidyl-Prolyl cis-trans Isomerase

The rotA gene encoding peptidyl-prolyl cis-trans isomerase has been identified, sequenced, and shown to be transcribed in the cyanobacterium Synechococcus sp. PCC7942. Inactivation of the gene by replacement of a region containing the open reading frame with a gene conferring kanamycin resistance resulted in merodiploids containing both the wild type and the modified genomic region. We were not able to isolate a kanamycin-resistant mutant in which all the genomic wild-type copies were substituted, which suggests that such replacement could have been lethal.     

A soluble mitochondrial protein increases the voltage dependence of the mitochondrial channel,VDAC

A soluble protein isolated from mitochondria has been found to modulate the voltage-dependent properties of the mitochondrial outer membrane channel, VDAC. This protein, called the VDAC modulator, was first found inNeurospora crassa and then discovered in species from other eukaryotic kingdoms. The modulator-containing fraction (at a crude protein concentration of 20 µg/ml) increases the voltage dependence of VDAC channels over 2–3-fold. At higher protein concentrations (50–100 µg/ml), some channels seem to remain in a closed state or be blocked while others display the higher voltage dependence and are able to close at low membrane potentials. By increasing the steepness of the voltage-dependent properties of VDAC channels, this modulator may serve as an amplifierin vivo to increase the sensitivity of the channels in response to changes in the cell's microenvironment, and consequently, regulate the metabolic flux across the outer mitochondrial membrane by controlling the gating of VDAC channels.     

Haploid plants regenerated via anther culture in wild barley (Hordeum spontaneum C. Kock)

Summary Androgenic plants have been obtained via anther culture in four natural populations of Hordeum spontaneum. Microscopic observations revealed that androgenesis started with the formation of two vegetative-type nuclei derived from the mitotic division of the uninucleate microspores. In this species androgenesis was affected by the type and concentration of the sugars added to the culture medium: the highest response (17% of callusing anthers) was observed on media containing 80 g l^–1 maltose. The highest production of androgenic plants (per 100 anthers, 5.9 green and 4.3 albino plants) was obtained from callus grown on these same media. About half of the green plants regenerated were haploid, while the others were diploid and set seed.Abbreviations IAA indolacetic acid - BAP 6-benzylaminopurine     

To lek or not to lek: mating strategies of male fallow deer

We studied the mating system of fallow deer (Dama dama) for6 years in central Italy. Males in this population could defendterritories that were either single, clumped in leks, or satelliteto leks. The most highly successful males in our study werein leks. When we considered all males, there were no significantdifferences in average copulatory success according to territorytype because many lek males did not achieve any copulations,which were seen in only a few lek territories. The variancein copulatory success, however, was much greater for leks thanelsewhere. Single territories were occupied for shorter timesduring the rut than lek territories. Fighting among males wasmore frequent in the lek, even when we excluded highly successfullek males from the analysis. Chases of nonterritorial malesand harem size were correlated with the number of copulationsachieved by individual males, but did not vary according toterritory type. Copulatory success of some individuals increasedwith age, but there were no age differences among males holdingdifferent types of territories. Satellite males switched tolek territoriality in the course of one rut, but switches fromsingle territory to lek territory were rare. We suggest thatmales in single territories are inferior competitors that selecta low-risk, lowbenefit strategy, whereas those in lek territorieswhere no copulations were seen may be attempting to establishthemselves on the lek to increase their copulatory success infuture years.     

Serotonin and γ-Aminobutyric Acid Turnover After Injection into the Median Raphe of Substance P and D-Ala-Met-Enkephalin Amide

The raphe nuclei [which contain serotonin (5-HT) cell bodies] are also known to contain axons that store substance P, met-enkephalin, and gamma-aminobutyric acid (GABA). We have previously shown that GABA has a tonic inhibitory action on 5-HT turnover. To examine other possible interactions of these neuronal systems, we assessed the effect on 5-HT turnover of injecting substance P and 2-D-ala-met-enkephalin into the median raphe nucleus, and the effects of substance P on GABA turnover. Serotonin turnover was increased by 30% in the hippocampus after the injection of substance P (4 micrograms) into the median raphe, indicating an excitatory effect of substance P on the raphe-hippocampal system. Local injection of the metabolically stable metenkephalin analog 2-D-ala-met-enkephalin amide (10 micrograms) increased the hippocampal steady state content of 5-hydroxyindoleacetic acid (5-HIAA) by 60%. The data suggest an excitatory effect of met-enkephalin within the raphe nucleus. We attempted to estimate GABA turnover from the rate of disappearance of GABA after inhibition of glutamic acid decarboxylase by isoniazid and by the rate of accumulation of GABA after inhibition of GABA transaminase by gabaculine. Isoniazid, which is a competitive inhibitor, had too short and incomplete an action to be of use when injected intranuclearly. Gabaculine, which is an irreversible inhibitor, induced a rapid-onset increase in GABA content. This accumulation was linear up to 90 min. The injection fo gabaculine (80 ng) into the raphe increased GABA content by five times the control values, but hippocampal 5-HT and 5-HIAA contents were not significantly changed. Substance P injection increased the GABA turnover by 30%. Gabaculine seems a promising tool for detecting changes in GABA turnover.     

Thiaisoleucine and protein synthesis.

Thiaisoleucine is an isoleucine analogue having the gamma-methylene group of the valerianic carbon chain substituted by a sulphur atom. It has been demonstrated that thiaisoleucine is activated and transferred to tRNAIle by rat liver aminoacyl-tRNA synthetase and inhibits isoleucine incorporation into polypeptides in protein synthesizing systems from rat liver or rabbit reticulocytes, whereas it does not affect either leucine incorporation or ribosome run-off or polypeptide chain elongation rate. All tests were performed in comparison with O-methyl-threonine, an isoleucine analogue with the gamma-methylene group substituted by an oxygen atom. In all the reactions studied, both thiaisoleucine and O-methyl-threonine act as competitive inhibitors of isoleucine. With respect to O-methyl-threonine, thiaisoleucine shows higher activity as an isoleucine inhibitor.     

Molecular structural effects involved in the interaction of anthracyclines with DNA.

Changes in DNA binding ability of daunomycin following structural modifications in the aglycone moiety have been studied by the fluorescence quenching method and by thermal denaturation of the complex. Removal of the methoxyl group at position 4 leads to a slightly stronger binding. Changes in the position of the glycosidic linkage result in a markedly weaker binding. Removal of the hydroxyl group at position 9, with the concomitant formation of a 9,10-anhydro derivative, decreases the binding ability. Methylation of hydroxyl groups at C-6 and C-11 leads to an inactive derivative and makes the binding affinity disappear almost completely. Structure-activity correlations for the DNA binding reaction deduced from these studies are in agreement with earlier findings that relate to the biological activity and confirm the general picture of the binding mechanism.