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21.
T. Toga M. Hisada 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1993,173(1):77-84
Intracellular recordings and dye injections were used to examine mutual coupling among slow abdominal postural motoneurons in the 4th abdominal ganglion in crayfish (Procambarus clarkii). Intracellular current injection into one motoneuron altered the spike firing rate of some of its synergists. Depending on the polarity of the injected current, the premotor effect on the synergists was excitatory or inhibitory. The magnitude of the effect was intensity dependent. No dye coupling was found among the motoneurons following injection of Lucifer yellow. The morphological basis of the coupling was examined by differential filling of motoneuron pairs, one with horseradish peroxidase and the other with Lucifer yellow. The stained motoneurons were simultaneously visualized under light microscopy to determine the proximity of their differently colored dendrites. It was thus possible to locate the site of the presumed monosynaptic contacts between them. Combined physiological and morphological evidence suggests that these neurons are mutually coupled, forming part of an integrative system for abdominal posture control in crayfish. 相似文献
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Satnam S. Banga Akihiko H. Yamamoto James M. Mason James B. Boyd 《Molecular & general genetics : MGG》1995,246(2):148-155
The mei-41 gene of Drosophila melanogaster plays an essential role in meiosis, in the maintenance of somatic chromosome stability, in postreplication repair and in DNA double-strand break repair. This gene has been cytogenetically localized to polytene chromosome bands 14C4-6 using available chromosomal aberrations. About 60 kb of DNA sequence has been isolated following a bidirectional chromosomal walk that extends over the cytogenetic interval 14C1-6. The breakpoints of chromosomal aberrations identified within that walk establish that the entire mei-41 gene has been cloned. Two independently derived mei-41 mutants have been shown to carry P insertions within a single 2.2 kb fragment of the walk. Since revertants of those mutants have lost the P element sequences, an essential region of the mei-41 gene is present in that fragment. A 10.5 kb genomic fragment that spans the P insertion sites has been found to restore methyl methanesulfonate resistance and female fertility of the mei-41
D3 mutants. The results demonstrate that all the sequences required for the proper expression of the mei-41 gene are present on this genomic fragment. This study provides the foundation for molecular analysis of a function that is essential for chromosome stability in both the germline and somatic cells.This Paper is dedicated to the memory of Professor James B. Boyd 相似文献
24.
Fumi Katoh Kazuo Kitamura Hiromi Niina Ryuichi Yamamoto Hisanori Washimine †Kenji Kangawa Yoshitaka Yamamoto Hideyuki Kobayashi Tanenao Eto Akihiko Wada 《Journal of neurochemistry》1995,64(1):459-461
Abstract: In cultured bovine adrenal medullary cells, stimulation of nicotinic receptors by carbachol evoked the Ca2+ -dependent exocytotic cosecretion of proadrenomedullin N-terminal 20 peptide (PAMP) (EC50 = 50.1 µ M ) and catecholamines (EC50 = 63.0 µ M ), with the molar ratio of PAMP/catecholamines secreted being equal to the ratio in the cells. Addition of PAMP[1–20]NH2 inhibited carbachol-induced 22 Na+ influx via nicotinic receptors (IC50 = 2.5 µ M ) in a noncompetitive manner and thereby reduced carbachol-induced 45 Ca2+ influx via voltage-dependent Ca2+ channels (IC50 = 1.0 µ M ) and catecholamine secretion (IC50 = 1.6 µ M ). It did not alter high K+ -induced 45 Ca2+ influx via voltage-dependent Ca2+ channels or veratridine-induced 22 Na+ influx via voltage-dependent Na+ channels. PAMP seems to be a novel antinicotinic peptide cosecreted with catecholamines by a Ca2+ -dependent exocytosis in response to nicotinic receptor stimulation. 相似文献
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The dielectric dispersion of isolated intact mitochondria in suspension has been measured between 10 kHz and 500 MHz. In isotonic KCI media at 4°C, the mitochondria maintained their characteristic ‘double membrane’ structure as examined by electron microscopy, and the observed dispersion curves were successfully simulated in terms of a superposition of two sub-dispersions having different characteristic frequencies and different permittivity magnitudes. Taking these observations into account we analyzed the dispersion data on the basis of a ‘double-shell’ model in which two concentric shells are meant to represent the mitochondrial outer and inner membranes. The analyses by a computerized curve-fitting method revealed that: (i) electric capacities for the outer and the inner membrane are 1.7 and 0.5 μF/cm2, respectively, (ii) relative permittivity for the inner compartment (or the equivalent homogeneous matrical space) = 50–60, (iii) outer compartment-to-external conductivity ratio = 0.4–0.6, and (iv) inner compartment-to-external conductivity ratio = 0.14. The implications of these parameter values are discussed with due attention paid to the limitations inherent in our ‘double-shell’ model approach. 相似文献
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Abstract Passive transfer between rates of protection against cholera toxin (CT) was studied. Extracts of various organs, obtained from CT-immunized rats, were injected intravenously into non-immunized recipient rats. The ability of the extracts to inhibit CT-induced secretion in ligated jejunal loop were tested. A significant inhibition of the response to CT was achieved by extracts from hypophysis, brain and jejunal mucosa. Extracts from pancreas, spleen or adrenal glands were without effect, as were all extracts obtained from control rats. The antisecretory effects of the hypophysis extracts became intensified with increasing numbers of immunizations, and the antisecretory effect was most pronounced when the extract was injected immediately before the CT challenge. The active component of the hypophysis extract was heat-labile and negatively charged, suggesting an acidic protein as the mediator of the protective effect against CT. 相似文献
29.
Summary The transepithelial resistance, the cell membrane resistance and the ratio of resistances of the serosal (baso-lateral) to the mucosal (brush border) cell membrane were measured in rat duodenum, jejunum and ileum by means of microelectrode techniques. These measured values were not affected in the presence of actively transported solutes in the mucosal bathing fluid.Contribution of an electrical conductance through the extracellular shunt pathway to the total transepithelial conductance was quantitatively estimated using an electrically equivalent circuit analysis. These values estimated in respective tissues of small intestine were approx. 95% of the total transepithelial conductance, remaining unaffected by an active solute transport.From these data, the changes in emf's of the mucosal and serosal membrane induced byd-glucose or glycine were separately evaluated. 相似文献
30.
Summary Preadult viability and developmental time at four different temperatures, heat and cold resistances of adult flies, effects of acclimatization on heat resistance, and preferred temperature of adult flies were compared between two species of Drosophila, D. virilis and D. immigrans. Four Japanese local populations were surveyed for each species. As compared with immigrans, virilis was higher in its ability to tolerate both heat and cold stresses and was viable over a broader temperature range. On the other hand, immigrans revealed a superior ability to acclimatize and a rigid preference for gradually changing thermal environment. Differences between geographical populations are remarkable for heat tolerance in virilis and cold tolerance in immigrans. In conclusion, thermal adaptation of virilis seems to be based on the high tolerance to extreme temperatures and that of immigrans mainly on the behavioural preference for viable temperatures. 相似文献