Differential effects of the serotonin receptors on cultured rat cerebral cortical neurons

Effects of serotonin (5-HT) on cerebral cortical neurons were examined by patch clamp techniques. 5-HT produced a variety of responses such as outward (19/73 patches/neurons), slow inward (15/73 patches/neurons), fast inward (8/73 patches/neurons), and mixed currents (initially fast inward deflection followed by an outward response: 2/73 patches/neurons), with a latency of 12 sec, 15 sec, 0 sec, and 0 sec respectively, at a holding potential of −60 mV in whole-cell patches. The fast inward currents were again evoked by a selective 5-HT3 receptor agonist, 1-(m-chlorophenyl)-biguanide hydrochloride (CPBG). In the cell-attached patch clamp configuration, 5-HT inside the patch pipette elicited single channel currents with slope conductances of 42 pS and 132 pS (4/42 patches/neurons). CPBG inside the patch pipette evoked inward single channel currents with a lower slope conductance of 41 pS (3/23 patches/neurons). In contrast, application of 5-HT or a 5-HT₂ receptor agonist, α-methyl-5-hydroxytryptamine-maleate, outside the patch pipette induced outward single channel currents with a major slope conductance of 140 pS (8/30 patches/neurons) or 135 pS (6/20 patches/neurons), respectively. These results indicate that the outward and fast inward currents may be mediated respectively by the 5-HT₂ receptor, which is coupled to a G-protein, and by the 5-HT₃ receptor, which contains the non-selective cation channel, and that the mixed type may be caused by both the 5-HT₂ and 5-HT₃ receptors. Received 27 September 1996; received after revision 4 November 1996; accepted 7 November 1996     

PTC124 targets genetic disorders caused by nonsense mutations

Nonsense mutations promote premature translational termination and cause anywhere from 5-70% of the individual cases of most inherited diseases. Studies on nonsense-mediated cystic fibrosis have indicated that boosting specific protein synthesis from <1% to as little as 5% of normal levels may greatly reduce the severity or eliminate the principal manifestations of disease. To address the need for a drug capable of suppressing premature termination, we identified PTC124-a new chemical entity that selectively induces ribosomal readthrough of premature but not normal termination codons. PTC124 activity, optimized using nonsense-containing reporters, promoted dystrophin production in primary muscle cells from humans and mdx mice expressing dystrophin nonsense alleles, and rescued striated muscle function in mdx mice within 2-8 weeks of drug exposure. PTC124 was well tolerated in animals at plasma exposures substantially in excess of those required for nonsense suppression. The selectivity of PTC124 for premature termination codons, its well characterized activity profile, oral bioavailability and pharmacological properties indicate that this drug may have broad clinical potential for the treatment of a large group of genetic disorders with limited or no therapeutic options.     

De novo mutations in the gene encoding STXBP1 (MUNC18-1) cause early infantile epileptic encephalopathy

Early infantile epileptic encephalopathy with suppression-burst (EIEE), also known as Ohtahara syndrome, is one of the most severe and earliest forms of epilepsy. Using array-based comparative genomic hybridization, we found a de novo 2.0-Mb microdeletion at 9q33.3-q34.11 in a girl with EIEE. Mutation analysis of candidate genes mapped to the deletion revealed that four unrelated individuals with EIEE had heterozygous missense mutations in the gene encoding syntaxin binding protein 1 (STXBP1). STXBP1 (also known as MUNC18-1) is an evolutionally conserved neuronal Sec1/Munc-18 (SM) protein that is essential in synaptic vesicle release in several species. Circular dichroism melting experiments revealed that a mutant form of the protein was significantly thermolabile compared to wild type. Furthermore, binding of the mutant protein to syntaxin was impaired. These findings suggest that haploinsufficiency of STXBP1 causes EIEE.     

含镍磁黄铁矿硝酸浸出液中硝酸镁与硫酸镁的分离

硝酸催化浸出是处理金属硫化物的有效方法。用这种方法在较低温度和氧压下成功地处理了含镍磁黄铁,但矿石中的氧化镁与硫酸和硝酸反应生成硫酸镁和硝酸镁,后者消耗了大量硝酸;因而需要分离硫酸镁,返回使用硝酸镁才能保证浸出过程经济地进行。本研究测定了Mg(NO_3)_2-MgSO_4-H_2O系在343K,308K,以及Mg(NO_3)_2-MgSO_4-C_2H_5OH-H_2O系在298K的平衡相图。结果表明,蒸发结晶法及乙醇结晶法均能有效地分离出硫酸镁,但后者更为节能。加10％乙醇即可使硫酸镁与硝酸镁较好分离。     

Role of the chorion as a barrier to oxygen in the diapause of the silkworm,Bombyx mori L.

Zusammenfassung Dechorionierte Diapause-Eier vonBombyx mori L. entwickeln sich in Paraffinöl. Wasseraufnahme kann also für das Brechen der Diapause keine Rolle spielen. Die Diapause könnte durch mangelnde Sauerstoffdurchlässigkeit des Chorions zustande kommen.     

Structure-activity relationship of the cardenolide,with special reference to the substituents and configurations at C-14 and C-15

Zusammenfassung Es wurden die kardiotonischen Wirkungen sechs neuer Derivate von 14-Deoxy-14H-digitoxigenin und 14-Deoxy-14-chloro-digitoxigenin auf das isolierte Froschherz untersucht, sowie die Beziehungen zwischen deren chemischen Strukturen und Wirkungen diskutiert.

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This study was supported by a research grant (No. 78 7012) from the Ministry of Education, Japan, and by a Grant-in-Aid from Tokyo Biochemical Research Foundation.     

Uptake of3H-GABA (γ-aminobutyric acid) and3H-leucine in the pancreatic islets and substantia nigra of the rat

Summary Isolated pancreatic islets and thin slices of substantia nigra (SN) of the rat were incubated in a medium containing³H-GABA or³H-leucine to test the activity of both tissues in the uptake of those substances. Pancreatic islets showed a low uptake of both³H-GABA and³H-leucine, but SN had a high activity in the uptake of³H-GABA, though not for³H-leucine. This suggests that GABA contained at high levels in the pancreatic islets plays some functional role other than in neurotransmission as in the central nervous system (CNS).     

Processivity of the single-headed kinesin KIF1A through biased binding to tubulin

Conventional isoforms of the motor protein kinesin behave functionally not as 'single molecules' but as 'two molecules' paired. This dimeric structure poses a barrier to solving its mechanism. To overcome this problem, we used an unconventional kinesin KIF1A (refs 5, 6) as a model molecule. KIF1A moves processively as an independent monomer, and can also work synergistically as a functional dimer. Here we show, by measuring its movement with an optical trapping system, that a single ATP hydrolysis triggers a single stepping movement of a single KIF1A monomer. The step size is distributed stochastically around multiples of 8 nm with a gaussian-like envelope and a standard deviation of 15 nm. On average, the step is directional to the microtubule's plus-end against a load force of up to 0.15 pN. As the source for this directional movement, we show that KIF1A moves to the microtubule's plus-end by approximately 3 nm on average on binding to the microtubule, presumably by preferential binding to tubulin on the plus-end side. We propose a simple physical formulation to explain the movement of KIF1A.     

Effect of recombinant human granulocyte colony-stimulating factor on human neutrophil adherence in vitro.

We measured the effects of recombinant human granulocyte-colony stimulating factor (rhG-CSF) on the adherence of human neutrophils by using a dacron fiber system to assay the adhesive ability of neutrophils. rhG-CSF enhanced neutrophil adherence to dacron fibers. N-formyl-methionyl-leucyl-phenylalanine (fMLP) induced neutrophil-neutrophil interaction (neutrophil aggregation) in addition to neutrophil-dacron interaction, whereas rhG-CSF did not cause neutrophil aggregation. These results indicated that rhG-CSF increases the adhesive ability of neutrophils without neutrophil-neutrophil interaction, and the action of rhG-CSF in neutrophil activation is different from the neutrophil activation caused by fMLP.