Circadian rhythm of ornithine decarboxylase activity in small intestine of fasted rats.

The aim of this study was to determine whether the circadian changes in ornithine decarboxylase (ODC) activity of different segments of the small intestine were governed by factors other than food intake. First, the effects of fasting on mucosal ODC activity were examined. The results indicate that mucosal ODC activity in 24 hr and 48 hr fasted rats decreased significantly compared with ad libitum-fed rats. Second, the circadian rhythm of mucosal ODC activity was characterized by measuring mucosal ODC activity in fasted rats at four time points (09:00, 15:00, 21:00, and 03:00 hr; light period: 06:00-18:00 hr). The results from this study indicate that there is a detectable baseline ODC activity in different segments of fasting intestine. In duodenum, mucosal ODC activity was highest at 15:00 hr (light period), a time at which the rat was normally not eating. In jejunum and ileum, mucosal ODC activity increased between 21:00 and 03:00 hr (dark period). The observation that small intestine exhibits a distinct circadian rhythm of ODC activity in fasted rats suggests that not only food but also intrinsic factors can modulate physiologic oscillations in mucosal ODC activity.     

Complex Intramolecular Mechanics of G-actin — An Elastic Network Study

Systematic numerical investigations of conformational motions in single actin molecules were performed by employing a simple elastic-network (EN) model of this protein. Similar to previous investigations for myosin, we found that G-actin essentially behaves as a strain sensor, responding by well-defined domain motions to mechanical perturbations. Several sensitive residues within the nucleotide-binding pocket (NBP) could be identified, such that the perturbation of any of them can induce characteristic flattening of actin molecules and closing of the cleft between their two mobile domains. Extending the EN model by introduction of a set of breakable links which become effective only when two domains approach one another, it was observed that G-actin can possess a metastable state corresponding to a closed conformation and that a transition to this state can be induced by appropriate perturbations in the NBP region. The ligands were roughly modeled as a single particle (ADP) or a dimer (ATP), which were placed inside the NBP and connected by elastic links to the neighbors. Our approximate analysis suggests that, when ATP is present, it stabilizes the closed conformation of actin. This may play an important role in the explanation why, in the presence of ATP, the polymerization process is highly accelerated.     

Rapid detection of a minute amount of lipopolysaccharide from Salmonella in large volumes by poly(ethyleneimine)-cloth enzyme immunoassay

Utilizing the rapidity in capturing Salmonella lipopolysaccharide (LPS) and the macroporous nature of poly(ethyleneimine) immobilized polyester cloth (PEI-cloth), a PEI-cloth disk set in a Swinnex cartridge joined at both ends with 10 ml plastic syringes was repeatedly passed through with an LPS sample in large volumes. The captured LPS on the disk were detected at up to 1 pg, which is equivalent to the amount produced of 16 cells, by cloth enzyme immunoassay.     

Loss of Collapsin Response Mediator Protein 4 Attenuates 6-Hydroxydopamine-Induced Impairments in a Mouse Model of Parkinson’s Disease

Neurochemical Research - Parkinson's disease (PD) is a chronic neurodegenerative disorder characterized by impaired motor symptoms induced by the degeneration of dopaminergic neurons of the...     

Biological Activities of p-Ethylphenyl and p-Acetylphenyl Phosphates and their Thiono Analogs

Sixteen phosphate or phosphorothioate esters related to neurotoxic tri-p-ethylphenyl phosphate and its active metabolites were synthesized and their biological activities including inhibitory activity against cholinesterases, insecticidal activity, toxicity to mammals and neurotoxicity were examined. Dialkyl p-ethylphenyl phoshates, p-acetylphenyl phosphates and their thiono analogs showed insecticidal activity, but did not show the ataxic sign by any sublethal doses in hens. When a methyl group was introduced on p-acetylphenyl ring, the biological activity changed remarkably by its position. The introduction of a methyl group into o-position made the ester inactive, while the introduction into m-position made it active to insects selectively.     

Inhibitory action of saturated fatty acids and their derivatives

The inhibitory effects of some saturated fatty acids on the growth of Avena coleoptile segments were attributed to the co-existence of a hydrophili     

The Role of Structural Dynamics of Actin in Class-Specific Myosin Motility

The structural dynamics of actin, including the tilting motion between the small and large domains, are essential for proper interactions with actin-binding proteins. Gly146 is situated at the hinge between the two domains, and we previously showed that a G146V mutation leads to severe motility defects in skeletal myosin but has no effect on motility of myosin V. The present study tested the hypothesis that G146V mutation impaired rotation between the two domains, leading to such functional defects. First, our study showed that depolymerization of G146V filaments was slower than that of wild-type filaments. This result is consistent with the distinction of structural states of G146V filaments from those of the wild type, considering the recent report that stabilization of actin filaments involves rotation of the two domains. Next, we measured intramolecular FRET efficiencies between two fluorophores in the two domains with or without skeletal muscle heavy meromyosin or the heavy meromyosin equivalent of myosin V in the presence of ATP. Single-molecule FRET measurements showed that the conformations of actin subunits of control and G146V actin filaments were different in the presence of skeletal muscle heavy meromyosin. This altered conformation of G146V subunits may lead to motility defects in myosin II. In contrast, distributions of FRET efficiencies of control and G146V subunits were similar in the presence of myosin V, consistent with the lack of motility defects in G146V actin with myosin V. The distribution of FRET efficiencies in the presence of myosin V was different from that in the presence of skeletal muscle heavy meromyosin, implying that the roles of actin conformation in myosin motility depend on the type of myosin.     

Block of sodium conductance by n-octanol in crayfish giant axons

The block of the Na⁺ current by $\text{n-}\text{octanol}$ was studied in crayfish giant axons under axial wire voltage-clamp conditions. Standard kinetic analysis of the Na⁺ currents was undertaken to test the hypothesis that the $\text{n-}\text{octanol-induced}$ block of the Na⁺ current could be accounted for on the basis of changes in the voltage dependence of the kinetic parameters. Alterations in the membrane dipolar potential arising from rearrangement of membrane lipids would be the anticipated source of changes in the voltage dependence. Although some changes in voltage dependence did evolve with the block by $\text{n-}\text{octanol}$, the changes were not of sufficient magnitude to account for the block. In conclusion, although higher concentrations of $\text{n-}\text{octanol}$ produced shifts along the voltage axis of the kinetic parameters, direct blocking action of $\text{n-}\text{octanol}$ on the channel appears to be the most important mechanism of the block.     

Effects of combined β-adrenergic and cholinergic blockade on the initial ventilatory response to exercise in humans

To elucidate whether combined adrenergic and parasympathetic blockade would affect the ventilatory response to exercise, especially at the initial stage (phase I), six healthy subjects performed a brief and light voluntary bilateral leg extension exercise and passive movements under the conditions of control (before the blockade) and after intravenous administration of combined β-adrenergic (propranolol, 0.2 mg · kg⁻¹) and muscarinic (atropine, 0.04 mg · kg⁻¹) receptor antagonists. The movements were continued only within two breaths after the onset of the motion. Ventilation increased immediately and significantly (P<0.05) within the first breath at the onset of voluntary exercise in all conditions as compared with at rest. However, the magnitude of increase in mean ventilation within two breaths at the start of exercise as against the resting value (delta ventilation) was significantly less (P<0.05) after the combined blockades (2.5 l · min⁻¹) than in the control condition (3.7 l · min⁻¹). Passive movements showed a similar but smaller change as compared with voluntary exercise. The heart rate response to exercise was attenuated by the combined blockade while cardiac output showed a slight change at the onset of exercise. It is concluded that phase I should occur despite the inhibited activity of the β-adrenergic and the cholinergic systems; nevertheless, the response was attenuated by the combined blockade. These results suggest a possible role of the β-adrenergic and/or cholinergic systems in the rapid increase in ventilation that occurs at the start of exercise. Accepted: 2 March 1997     

Antibacterial and Inducer Activities for Tetracycline Resistance by Its Derivatives and Analogues

Antibacterial and inducer activities of thirteen TC derivatives were investigated for tetracycline (TC) resistance in staphylococcus aureus. Four compounds of the TC derivatives were not able to induce the resistance to TC in Staphylococcus aureus MS3937 r_ms7 (TC)⁺ harboring an inducible TC resistance determinant located on a plasmid. The 12a-hydroxy position seems to be essential for the inducer activity.