Agyria — pachygyria and Miller-Dieker syndrome: clinical,genetic and chromosome studies

Summary Twelve cases of lissencephaly are reported. A high resolution chromosome study was performed on each in order to detect small chromosomal anomalies, undetectable with routine techniques. Only one case was shown to have an unbalanced karyotype with a microdeletion of the short arm of chromosome 17(del 17p). This child also had symptoms of the Miller-Dieker syndrome, consisting of lissencephaly, characteristic facies, pre- and post-natal growth retardation and other birth defects. As proposed by Dobyns, it seems justifiable to classify lissencephalies into four different groups, according to other clinical manifestations and results of chromosome studies.     

Bioflavonoid interaction with rat uterine type II binding sites and cell growth inhibition

Competition analysis with a number of known bioflavonoids demonstrated that these compounds (luteolin, quercetin, pelargonin) compete for [3H]estradiol binding to cytosol and nuclear type II sites in rat uterine preparations. The inhibition of [3H]estradiol binding to type II sites was specific and these bioflavonoids did not interact with the rat uterine estrogen receptor. Since estradiol stimulation of nuclear type II sites in the rat uterus is highly correlated with cellular hypertrophy and hyperplasia, we assessed the effects of these compounds on the growth of MCF-7 human breast cancer cells in culture and on estradiol stimulation of uterine growth in the immature rat. The data demonstrated that addition of quercetin (5-10 micrograms/ml) to MCF-7 cell cultures resulted in a dose-dependent inhibition of cell growth (DNA/flask). This effect was reversible by removal of quercetin from the culture medium, or by the addition of 10 nM estradiol-17 beta to these cell cultures containing this bioflavonoid. Since estradiol-17 beta (10 nM) stimulated nuclear type II sites and proliferation of MCF-7 cells, we believe bioflavonoid inhibition of MCF-7 cell growth may be mediated through an interaction with nuclear type II sites. This hypothesis was confirmed by in vivo studies which demonstrated that injection of luteolin or quercetin blocked estradiol stimulation of nuclear type II sites in the immature rat uterus and this correlated with an inhibition of uterine growth (wet and dry weight). These studies suggest bioflavonoids, through an interaction with type II sites, may be involved in cell growth regulation.     

Somatostatin as a mediator of the effect of neurotensin on pentagastrin-stimulated acid secretion in rats

Neurotensin and somatostatin have both been shown to inhibit gastric acid secretion, but no interaction between these peptides has been demonstrated. To determine whether somatostatin might be a mediator of neurotensin's effect on pentagastrin-stimulated gastric acid secretion, we performed the following three experiments. First, we collected 0.2-ml samples of portal venous blood as frequently as every 5 min, and we confirmed a significant release of somatostatin-like immunoreactivity into portal venous blood during neurotensin-induced inhibition of acid secretion. This release of somatostatin-like immunoreactivity and inhibition of acid secretion were only seen in pentobarbital-anesthetized rats, but no sustained release of somatostatin-like immunoreactivity or inhibition of acid secretion occurred in urethane-anesthetized animals. In the second experiment, we analyzed portal plasma by high pressure liquid chromatography, and found that portal somatostatin-like immunoreactivity in blood collected during neurotensin infusion was composed of a single peak corresponding to somatostatin-14. In the third experiment, we found that infusion of antibody to somatostatin prevented neurotensin from inhibiting pentagastrin-stimulated acid secretion. Taken together, these data show that somatostatin, possibly from the stomach itself, is a necessary mediator of neurotensin's inhibitory effect in pentobarbital-anesthetized rats.     

Towards an explanation of carboxylation/oxygenation bifunctionality in Rubisco. Transition structure for the carboxylation reaction of 2,3,4-pentanetriol

We construct a theoretical model of the transition structure for the carboxylation reaction of ribulose-1,5-biphosphate catalyzed by Rubisco. This is a first-order saddle point on the energy hypersurface for the nucleophilic attack of carbon dioxide on CH₃-(CHOH)₃-CH₃ at the C2 center.Ab initio analytical gradients methods at a 4-31G basis set level are used.The carbon framework and oxygens of the stationary structure superpose with the corresponding atoms of 2-carboxyarabinitol-1,5-biphosphate, which is a transition state analog that has recently been highly refined with X-ray methods. The hydroxyl group in C3 iscis to the C2 oxygen. The C3 center is somewhat pyramidized, the dienol O2-C2-C3-O3 is not planar.The geometry of the transition state allows for simple explanations of both the enolization of Rubisco's substrate ribulose-1,5-biphosphate, O₃PO-CH2-CO-(CHOH)₂-CH₂-OPO₃ and oxygenation reaction. The former is due to the pyramidal deformation at C3 and out of plane of O2-C2-C3-O3 framework: the enoliation is intramolecular and is probably enhanced by proton tunnelling. The latter is related with the fact that a rotation around an ethylene-like bond brings the triplet state down in energy. The reactive skeleton has a stationary geometry in the triplet state not very different from the one obtained in the global transition structure. There, the triplet is only 9 kcal/mol above the singlet. The spin densities at C2 and C3 centers clearly indicate the place where oxygenation will take place.     

Differential Calcium Dependence of γ-Aminobutyric Acid and Acetylcholine Release in Mouse Brain Synaptosomes

The dependence of gamma-aminobutyric acid (GABA) and acetylcholine (ACh) release on Ca2+ was comparatively studied in synaptosomes from mouse brain, by correlating the influx of 45Ca2+ with the release of the transmitters. It was observed that exposure of synaptosomes to a Na+-free medium notably increases Ca2+ entry, and this condition was used, in addition to K+ depolarization and the Ca2+ ionophore A23187, to stimulate the influx of Ca2+ and the release of labeled GABA and ACh. The effect of ruthenium red (RuR) on these parameters was also investigated. Of the three experimental conditions used, the absence of Na+ in the medium proved to be the most efficient in increasing Ca2+ entry. RuR inhibited by 60-70% the influx of Ca2+ stimulated by K+ depolarization but did not affect its basal influx or its influx stimulated by the absence of Na+ or by A23187. The release of ACh was stimulated by K+ depolarization, absence of Na+ in the medium, and A23187 in a strictly Ca2+-dependent manner, whereas the release of GABA was only partially dependent on the presence of Ca2+ in the medium. The extent of stimulation of ACh release was related to the extent of Ca2+ entry, whereas no such correlation was observed for GABA. In the presence of Na+, RuR did not affect the release of the transmitters induced by A23187. In the absence of Na+, paradoxically RuR notably enhanced the release of both ACh and GABA induced by A23187, in a Ca2+-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)     

Monoclonal antibodies to rabbit skeletal muscle protein phosphatases C-I and C-II

Rabbit skeletal muscle protein phosphatases C-I and C-II have been previously isolated as two proteins of Mr = approximately 35,000. Both enzymes display broad substrate specificities but have distinct enzymatic properties in regard to their susceptibility to heat-stable protein inhibitor-2 and their response to divalent cations. Monoclonal antibodies against both protein phosphatase C-I and C-II were produced by fusion of spleen cells of immunized BALB/c mice with SP2/0-Ag14 mouse myeloma cells. The products of the hybrid cells were screened by solid phase radioimmunoassay for the production of antibodies to protein phosphatase C-I and C-II. Positive cells were cloned and injected into mice to produce ascitic fluids. Ten monoclonal antibodies against phosphatase C-I and eight monoclonal antibodies against phosphatase C-II were obtained. These antibodies were characterized with regard to their relative binding affinities to the two protein phosphatases and their abilities to inhibit the phosphorylase phosphatase activities of the two enzymes. All ten of the phosphatase C-I monoclonal antibodies inhibited the phosphorylase phosphatase activity of phosphatase C-I, and three of these also inhibited phosphatase C-II. Only one of the eight antibodies to phosphatase C-II was inhibitory and inhibited the activities of both phosphatase C-I and C-II. Examination of the binding of these monoclonal antibodies by a solid phase radioimmunoassay showed that eight of the ten phosphatase C-I antibodies cross-reacted with phosphatase C-II, while all eight of the phosphatase C-II antibodies cross-reacted with phosphatase C-I. These findings show that phosphatases C-I and C-II possess common antigenic determinant(s) and may, therefore, be structurally related proteins.