The structural plasticity of SCA7 domains defines their differential nucleosome‐binding properties

SAGA (Spt–Ada–Gcn5 acetyltransferase), a coactivator complex involved in chromatin remodelling, harbours both histone acetylation and deubiquitination activities. ATXN7/Sgf73 and ATXN7L3, two subunits of the SAGA deubiquitination module, contain an SCA7 domain characterized by an atypical zinc‐finger. We show that the yeast Sgf73–SCA7 domain is not required to recruit Sgf73 into SAGA. Instead, it binds to nucleosomes, a property that is conserved in the human ATXN7–SCA7 domain but is lost in the ATXN7L3 domain. The solution structures of the SCA7 domain of both ATXN7 and ATXN7L3 reveal a new, common zinc‐finger motif at the heart of two distinct folds, providing a molecular basis for the observed functional differences.     

Erratum to: Genomics-Guided Precise Anti-Epileptic Drug Development

Neurochemical Research -     

Enantiomeric separation by HPLC of 1,4-dihydropyridines with vancomycin as chiral selector

The macrocyclic antibiotics represent a relatively new class of chiral selectors in CE, HPLC, and TLC. We have examined the use of the macrocyclic antibiotic vancomycin as a chiral selector in HPLC for the separation of 1,4-dihydropyridines (DHPs) calcium antagonists (CAs). Chromatographic data of six 1,4-dihydropyridine calcium channel blockers obtained on the vancomycin chiral stationary phase (Chirobiotic V) were compared with those obtained on an alpha(1)-acid glycoprotein (AGP) HPLC stationary phase. Optimization of pH and organic modifier was carried out in order to modulate the retention properties of each system. All chiral neutral DHPs were resolved on the AGP column, whereas on Chirobiotic V only basic DHPs showed a split peak. The analytical chromatographic procedure on Chirobiotic V proved suitable for semipreparative separation, since the separation factor on the analytical column was high enough to obtain pure enantiomers with high yields.     

Microsatellite-AFLP for genetic mapping of complex polyploids.

In spite of the economical relevance of polyploid crops, genetic mapping of these species has been relatively overlooked. This is because of intrinsic difficulties such as the uncertainty of the chromosome behavior at meiosis I and the need for very large segregating populations. An important, yet underestimated issue, in mapping polyploids is the choice of the molecular marker system. An ideal molecular marker system for polyploid mapping should maximize the percentage of single dose markers (SDMs) detected and the possibility of recognizing allelic markers. In the present work, the marker index for genetic mapping (MIgm) of M-AFLP is compared with that of AFLP and SAMPL. M-AFLPs have the highest MIgm values (22 vs. 18.5 of SAMPL and 9.83 of AFLP) mostly because of their high power to detect polymorphism. Owing to their prevalent codominant inheritance, it is proposed that M-AFLP can be used for the preliminary identification of hom(e)ologous groups.     

Retinoic acid-induced differentiation in a human neuroblastoma cell line is associated with an increase in nitric oxide synthesis

The human neuroblastoma cell line SK-N-BE, after incubation with 10 μM retinoic acid (RA) or 20 nM phorbol 12-myristate 13-acetate (PMA), underwent biochemical and morphological signs of differentiation within 10–14 days. In parallel, SK-N-BE cells produced significantly higher amounts of nitric oxide (NO) in comparison with controls, as assessed by the measurement of nitrite and nitrate in the culture supernatant and of NO synthase (NOS) activity in the cell lysates (measured as ability to convert [³H]arginine into [³H]citrulline and as NADPH diaphorase activity). Nitrite/nitrate production was abolished by adding the NO scavenger hemoglobin in the culture medium and was inhibited by aminoguanidine (AG, a selective inhibitor of the inducible NOS isoform) but not by the less selective inhibitor N^G-nitro-L -arginine methylester (NAME). Western blotting experiments with monoclonal antibodies against the ncNOS and iNOS isoforms suggest that RA-elicited NOS activation is not attributable to an increased expression of the protein. NAME and AG were not able to revert inhibition of proliferation induced by RA, and the NO donor sodium nitroprusside did not mimic the effect of RA and PMA. These data indicate that increased NO synthesis does not mediate RA- or PMA-induced differentiation but may be an additional marker of differentiation into sympathetic-like neuronal cells. J. Cell. Physiol. 174:99–106, 1998. © 1998 Wiley-Liss, Inc.     

Effect of the globus pallidus on hippocampal epilepsy in the cat

The action of the pallidum on electrically induced afterdischarge of the hippocampus (HAD) was studied. Significant facilitatory influences on HAD duration were observed when pallidal conditional stimulation immediately preceded hippocampal test stimulation. The phenomenon appeared to be into correlation with the interval between conditioning and test stimulation. Experimental data are discussed as strongly presumptive of a functional interrelationship between the inhibitory role played by the caudate on both pallidum and hippocampus; facilitatory influence of the pallidum on HAD duration is discussed too.     

Acetylcholine and Dopamine Promote the Production of Platelet Activating Factor in Immature Cells of Chick Embryonic Retina

We have previously shown that platelet-activating factor (PAF), a naturally occurring lipid mediator of cell-to-cell communication, was produced by 3-day-old chick retina stimulated with acetylcholine (ACh) and dopamine (DA), but not with other neurotransmitters. ACh and DA stimulated PAF synthesis via a dithiothreitol (DTT)-insensitive cholinephosphotransferase, without affecting the acetyltransferase pathway, which was stimulated only by the calcium ionophore A23187. Therefore, we attempted to study the effects of neurotransmitters on PAF production and on the activities of the DTT-insensitive cholinephosphotransferase and acetyltransferase in the developing chick embryo retina up to hatching. Our results show that PAF was produced already at 8 days of development, when retinal cells are still rather immature and ganglion and Mueller cells are the only differentiated cells. The stimulation of PAF production occurred with ACh and not with other neurotransmitters. In older stages, DA also stimulated PAF production, as already described in the chick after hatching. DTT-insensitive cholinephosphotransferase and acetyltransferase activities were present in 8-day-old embryos, the earliest stage analyzed. Both enzymatic activities increased with age; DTT-insensitive cholinephosphotransferase increased rapidly from day 12 up to day 18, whereas acetyltransferase activity increased linearly up to the time of hatching. To promote PAF production, ACh and DA activate DTT-insensitive cholinephosphotransferase, but not acetyltransferase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mechanical properties of the triceps surae tendon and aponeurosis in relation to intensity of sport activity

The purpose of the present study was to investigate whether the mechanical properties (i.e. force strain relationship) of the triceps surae tendon and aponeurosis relate to the performed sport activity in an intensity-dependent manner. This was done by comparing sprinters with endurance runners and subjects not active in sports. Sixty-six young male subjects (26+/-5 yr; 183+/-6 cm; 77.6+/-6.7 kg) participated in the study. Ten of these subjects were adults not active in sports, 28 were endurance runners and 28 sprinters. All subjects performed isometric maximal voluntary plantar flexion contractions (MVC) on a dynamometer. The distal aponeuroses of the gastrocnemius medialis (GM) was visualised by ultrasound during the MVC. The results showed that only the sprinters had higher normalised stiffness (relationship between tendon force and tendon strain) of the triceps surae tendon and aponeurosis and maximal calculated tendon forces than the endurance runners and the subjects not active in sports. Furthermore, including the data of all 66 examined participants tendon stiffness correlated significantly (r=0.817, P<0.001) with the maximal tendon force achieved during the MVC. It has been concluded that the mechanical properties of the triceps surae tendon and aponeurosis do not show a graded response to the intensity of the performed sport activity but rather remain at control level in a wide range of applied strains and that strain amplitude and/or frequency should exceed a given threshold in order to trigger additional adaptation effects. The results further indicate that subjects with higher muscle strength possibly increase the margin of tolerated mechanical loading of the tendon due to the greater stiffness of their triceps surae tendon and aponeurosis.