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221.
When isolated rat liver cells were incubated in the presence of vasoactive intestinal peptide at the concentrations ranging from 0.2 microgram to 2 micrograms per ml, glycogenolysis was maximally stimulated within 15 min. However, somatostatin inhibited the liver glycogenolysis. The combined addition to the incubation medium showed that insulin and somatostatin inhibited the stimulated glycogenolysis induced by vasoactive intestinal peptide, while vasoactive intestinal peptide plus secretin showed no additive effect on glycogenolysis, as compared with single the addition of vasoactive intestinal peptide. On the other hand, the additon of glucagon to vasoactive intestinal peptide showed additive effects on glycogenolysis. These results suggest that the receptor site for vasoactive intestinal peptide may be distinguishable from that for glucagon. Extracellular calcium ions were demonstrated to play an important role in the modulation of vasoactive intestinal peptide-induced glycogenolysis. The evidence presented in this paper indicates that glucose metabolism may be partly regulated by the direct action of vasoactive intestinal peptide on hepatocytes, which is referred to as an enterohepatic axis and that the axis is inhibited by insulin and somatostatin. 相似文献
222.
M Saito 《Experimental cell research》1979,123(1):79-86
Effect of extracellular Ca2+ on the morphogenesis of the cellular slime mold Dictyostelium discoideum was examined on agar plate. The concentration of Ca2+ in agar plate was controlled by keeping the concentration of a chelating reagent EGTA constant and varying the concentration of total calcium. From experiments in which EGTA concentration was kept at 2.0 × 10?3 M, it was found that by decreasing Ca2+ concentration the morphogenesis was modified so that development of the aggregating amebae into fruiting bodies was accelerated and the period of migrating slugs was shortened. Below 1.0 × 10?3 M of Ca2+ concentration, the total number of aggregates initially increased with decreasing Ca2+ concentration, reached a maximum at about 3.0 × 10?7 M of Ca2+ concentration and hereafter decreased with decreasing Ca2+ concentration. The number of mature fruiting bodies obtained at 36 h period after starvation depends on Ca2+ concentration and the total number of aggregates. The cell aggregation initiated at the same time period after starvation even at an extreme case of 1.0 × 10?8 M of Ca2+ concentration as under enough Ca2+ supply, while the formation of mature fruiting body was seriously inhibited. These observation suggested that the cAMP-mediated cell aggregation in D. discoideum is a Ca2+-independent phenomena, although extracellular Ca2+ is necessary for the normal development of the aggregated amebae. 相似文献
223.
224.
D-manno-3-Heptulose (5) was synthesized by dimethyl sulfoxide-phosphorus pentaoxide oxidation of 1,2:3,4:6,7-tri-O-isopropylidene-D-glycero-D-manno-heptitol (3, prepared from volemitol), followed by hydrolysis. D-ido-3-Heptulose (8) was synthesized similarly by oxidation of 1,2:4,5:6,7-tri-O-isopropylidene-D-glycero-l-galacto-heptitol (7, prepared from D-glycero-l-galacto-heptitol, 6). Another tri-O-isopropylidene derivative (11), having a free primary hydroxyl group, was produced in larger amount than 7, and 11 yielded D-glycero-l-galacto-heptose (14). Compound 8 was also synthesized by way of 1,2:4,5.6,7-tri-O-isopropylidene-D-glycero-l-gulo-heptitol (15). The production of 15 from D-glycero-l-gulo-heptitol (13) was accompanied by a larger amount of 2,3:4,5:6,7-tri-O-isopropylidene-D-glycero-D-ido-heptitol (17) which, upon oxidation followed by hydrolysis, yielded D-glycero-D-ido-heptose (18). One of the two tri-O-isopropylidene derivatives obtained by acetonation of perseitol, 2,3:4,5:6,7-tri-O-isopropylidene-D-glycero-D-galacto-heptitol (19), yielded D-glycero-D-galacto-heptose (20). 相似文献
225.
l(+)-tartrate-[U-14C] or sucrose-[U-14C] was fed into grape berries and 14CO2 evolution was determined. 14CO2 evolution front l(+)-tartrate-[U-14C] was slightly higher in mature than immature berries, and that from sucrose-[U-14C] was higher in immature than mature ones. 14CO2 evolution from l(+)-tartrate-[U-14C] was irregular throughout the day until 2 or 3 weeks after flowering. This stage shifted to regular 14CO2 evolution until 6 or 7 weeks after flowering, and the mode of 14CO2 evolution showed diurnal variation; higher in the day than at night. Then the stage without variation of 14CO2 evolution followed 10 weeks after flowering. These observations indicate that tartrate is not biochemically inert in grape berries, while the amount of 14CO2 evolution from sucrose-[U-14C] was higher at night than in the day through the whole ripening process, except in the early stage. 相似文献
226.
Saito Masahiko; Kondo Noriaki; Yamaguchi Hisao; Hashimoto Tohru 《Plant & cell physiology》1976,17(3):411-416
Nine bibenzyls and 10 stilbenes were synthesized as analoguesof batatasin III, a growth inhibitor isolated from dormant yambulbils, and examined for their plant growth-regulating activities.The bioassays used were the elongation of dark-grown intactrice coleoptiles, auxin-induced elongation of excised oat coleoptiles,and germination of rape and barnyard grass seeds. In the elongationof intact rice coleoptiles, 3,3'-dihydroxy-5-methoxy- (batatasinIII), 3,5-dimethoxy-3'-nitro-, 4'-bromo-3-nitro-, 3-amino-3'-chloro-,3-amino-4'-chloro-bibenzyls and 3-benzyloxy-4'-bromo-5-methoxy-,3-benzyloxy-3',4'-dichloro-5-methoxy-stilbenes were inhibitory,and 4'-bromo-3-nitrostilbene was promotive at a concentrationof 100 mg/liter. The results obtained by the other bioassayswere qualitatively consistent with these findings, although3-amino-4'- chlorobibenzyl and 4'-bromo-3-nitrostilbene werenot tested in all the bioassays. In the seed germination, which was rather tolerant to the testanalogues, batatasin III was inactive but 3-benzyloxy-4'-bromo-5-methoxy-and 3-benzyloxy-3',4'-dichloro- 5-methoxystilbenes were veryactive. Thus, if substituted properly, bibenzyls and stilbenes are activewithout hydroxyl and methoxyl group(s) as the functional group.
3 Present address: The National Institute for EnvironmentalStudies, Yatabc, Ibaraki 300-21, Japan. (Received November 19, 1975; ) 相似文献
227.
Takehiko Saito Kyōsuke Tenma 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1976,111(1):39-53
1. | Stimulation to left and right vagi caused an almost equal amount of inhibitory, and occasionally excitatory, effects on pacemaker activity. Both inhibitory and excitatory effects were abolished by atropine. Vagal stimulation hyperpolarized the resting membrane potential of pacemaker fibers in the sino-atrial valve, but did not change their action potential profile. |
2. | The atrial action potential showed a prominent decrease in the action potential amplitude and duration in response to vagal stimulation. The atrial region surrounding the sino-atrial valve was more sensitive to right vagal stimulation. |
3. | The fibers in the atrio-ventricular ring muscle were less sensitive to vagal stimulation than the atrial fibers. Some fibers showed a decrease in the action potential amplitude and duration by vagal stimulation, and other fibers showed a decrease in the amplitude, but a prolongation of the duration as the result of a slowing of the rate of upstroke. The atrial-ventricular conduction delay or block by vagal stimulation may depend on these properties of the action potential of the atrio-ventricular ring muscle. |
4. | The sino-atrial conduction block is explained by the fact that the atrial fibers are more sensitive to vagal stimulation than pacemaker fibers. |
5. | The possible pathways for the sino-ventricular conduction during vagal stimulation are discussed. |
228.
In rat cerebellum the major portion of guanylate cyclase was found to be particulate-bound. The properties of particulate and supernatant guanylate cyclases from the cerebellum were comparatively examined. Both enzymes required the same optimal concentration of Mn2+ and were stimulated by Ca2+ in the presence of a low concentration of Mn2+. But dispersion of the particulate enzyme with Triton X-100 altered the Mn2+ concentration producing maximum activity and the inhibitory effect of Ca2+. The subcellular distributions of guanylate and adenylate cyclases were also studied in rat cerebellum. The major portions of the two cyclases were found in the mitochondrial fraction. The submitochondrial fractions separated by sucrose gradient showed that the major activities of both cyclases were concentrated in the fraction containing mainly nerve ending particles. 相似文献
229.
230.
Tetsuya Fukui Akio Yoshimoto Mamoru Matsumoto Shunji Hosokawa Terumi Saito Hiroko Nishikawa Kenkichi Tomita 《Archives of microbiology》1976,110(2-3):149-156
The enzyme activity synthesizing poly--hydroxybutyrate (PHB) was mainly localized in the PHB-containing particulate fraction ofZoogloea ramigera I-16-M, when it grew flocculatedly in a medium supplemented with glucose. On the other hand, the enzyme activity remained in the soluble fraction, when the bacterium grew dispersedly in a glucose-starved medium.The soluble PHB synthase activity became associated with the particulate fraction as PHB synthesis was initiated on the addition of glucose to the dispersed culture. Conversely, the enzyme activity was released from the PHB-containing granules to the soluble fraction when the flocculated culture was kept incubated without supplementing the medium with glucose.PHB synthase was also incorporated into the newly formed PHB fraction when partially purified soluble PHB synthase was incubated withd(-)--hydroxybutyryl CoA in vitro.Although attempts to solubilize the particulate enzyme were unsuccessful, and the soluble enzyme became extremely unstable in advanced stages of purification, both PHB synthases had the same strict substrate specificity ford(-)--hydroxybutyryl CoA, and showed the same pH optimum at 7.0.Non-Standard Abbreviations PHB
poly--hydroxybutyrate 相似文献