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91.
Liposome-mediated labeling of adrenocorticotropin fragments parallels their biological activity 总被引:2,自引:0,他引:2
To test our hypothesis that specific interactions of ACTH peptides with model lipid membranes reflect the biological importance of similar interactions on target cells, we investigated the liposome-mediated labeling of ACTH fragments with the extremely hydrophobic photolabel, 3-trifluoromethyl-3-(m-[125I]iodophenyl)diazirine. Correlations were found between the labeling rates and the agonistic and antagonistic potencies of the peptides for in vitro steroidogenesis and inhibition of a synaptosomal protein kinase. A model for the cross-reactivity between ACTH and opioid peptides is discussed. 相似文献
92.
W A Murphy V A Lance J Sueiras-Diaz D H Coy 《Biochemical and biophysical research communications》1983,112(2):469-474
Synthetic human pancreatic growth hormone-releasing factor containing 40 amino acids ([hpGRF (1-40)]-OH) significantly stimulated plasma growth hormone (GH) levels in both sodium pentobarbital and urethane anesthetized rats. Synthetic secretin, gastric inhibitory polypeptide (GIP), and glucagon significantly decreased plasma GH levels while synthetic vasoactive intestinal peptide (VIP) had no effect. Secretin and GIP also altered the in vivo plasma GH response to [hpGRF(1-40)]-OH. Whether this effect is the result of an interaction at the pituitary level or is due to an extra-pituitary effect of secretin and GIP awaits further study. 相似文献
93.
We previously demonstrated inhibition of Na+-dependent 32Pi transport in canine renal brush-border membranes in association with NAD+-induced ADP ribosylation of membrane protein(s) and postulated that NAD+ inhibits Pi transport across the brush-border membrane via ADP ribosylation. Recently it was shown that incubation of rat brush-border membrane with NAD+ resulted in release of Pi which was prevented by EDTA. It was proposed that NAD+-mediated inhibition of 32Pi transport might occur through this mechanism. To determine whether NAD+ inhibited 32Pi transport by a mechanism other than or in addition to release of Pi, we compared Na+-dependent 32Pi counterflow in brush-border membrane equilibrated with Pi or with Pi generated from NAD+. Release of Pi from NAD+ incubated with brush-border membrane was confirmed. The increased uptake of 32Pi which was demonstrated in brush-border membrane equilibrated with Pi was not measured when intravesicular Pi was generated from a concentration of NAD+ which effected ADP-ribosylation of brush border membranes (100 μM NAD+). In contrast, increased uptake of 32Pi was demonstrated when intravesicular Pi was generated from 1 μM NAD+ which did not effect ADP ribosylation. Mg2+-dependent ADP ribosylation of brush-border membrane incubated with NAD+ was demonstrated which persisted during the time interval of 32Pi uptake measurements. Our findings are compatible with the hypothesis that NAD+-induced ADP ribosylation of brush-border membrane protein(s) results in inhibition of Pi transport across the membrane in vivo. EDTA may act to prevent this inhibition in brush-border membrane by chelation of Mg2+ and decreased ADP ribosylation. 相似文献
94.
Cerebroside and Sulfatide Biosynthesis in the Brain of Snell Dwarf Mouse: Effects of Thyroxine and Growth Hormone in the Early Postnatal Period 总被引:1,自引:1,他引:0
Snell dwarf mice (dw/dw) and normal mice (+/?) were injected with thyroxine (T4) (1 μg/animal, four injections) and growth hormone (GH) (20 μg/animal, four injections) from the 5th to the 15th day of life. In the untreated dw/dw mouse brain, the specific activities of UDP-galactose:ceramide galactosyltransferase (CGalT), PAPS:cerebroside sulfotransferase (CST), and 2′,3′-cyclic nucleotide 3′-phosphohydrolase (CNP) were decreased by 28, 25, and 37%, respectively, compared with the control untreated +/? mice. The major effect of T4 was an increase of the brain CNP in the +/? mice (+40%) and dw/dw mice (+111%). The treatment with T4 also brought to normal the level of CGalT in dw/dw brain; a somewhat less marked effect on CST was observed. The treatment with GH had a great stimulatory effect on CNP: the specific activity of this enzyme increased by 40 and 69% in +/? and dw/dw mouse brain, respectively. On the contrary, no effect of GH on the CGalT activity was observe in this study. Our results suggest that T4 and GH may have both independent and complementary actions on the myelin-associated enzymes during the early postnatal period of brain development. 相似文献
95.
Abstract: Since evidence is now available to support a nonendocrine autonomic function for thyrotropin-releasing hormone (TRH), quantitative measurements of TRH were made in nuclei of the vagal complex and other areas of the caudal medulla oblongata of the rat. Regions containing the dorsal motor nucleus of the vagus (DMN), nucleus tractus solitarius (NTS), hypoglossal nucleus, dorsal column nuclei, descending nucleus V (DNV), nucleus ambiguus (NA), raphe nuclei (MR) dorsomedial and ventromedial reticular formation, and inferior olivary nuclei were isolated from 300-μm-thick frozen sections of medulla by the micropunch technique. Each region was pooled bilaterally, homogenized in 0.1 M HCl, and vacuum-dried. Extracts were assayed for TRH by specific radioimmunoassay (RIA). TRH levels varied 100-fold among medulla nuclei. Highest content (ng/mg protein ± SEM) was found in DMN (14 ± 1.38) and NTS (4.7 ± 0.68), whereas lowest levels occurred in the DNV and MR (0.13, 0.06). Nearly 65% of the total medullary TRH was localized in nuclei associated with vagal complex (DMN, NTS, NA). Characterization of tissue immunoreactivity (TRHi) in these regions suggests the presence of TRH, since (1) medullary tissue extracts competed with 125I-TRH for antibody binding sites with the same affinity as authentic TRH; (2) TRHi in tissue extracts co-migrated with synthetic TRH when subjected to reverse-phase high performance liquid chromatography and Sephadex G-10 chromatography; and (3) rat serum TRH peptidases degraded TRHi and authentic TRH at similar rates. Another group of rats was subjected to unilateral (right side) vagotomy. At 33 weeks post-vagotomy, the vagal preganglionic cell population in the ipsilateral DMN was depleted 50–75%, while the contralateral side was unaffected. Interestingly, the content of TRH in the ipsilateral (right) DMN remained unchanged, whereas TRH in the contralateral DMN increased by 50%. In contrast, TRH was significantly elevated in the NA on the ipsilateral side of the lesion. TRH in both ipsi- and contralateral NTS was unchanged when compared with sham-operated controls. These results indicate that (1) TRH is present in several specific loci of the medulla; (2) very high levels are found in the vagal complex; and (3) vagotomy may alter TRH in the contralateral DMN and ipsilateral NA. 相似文献
96.
When adult apterous viviparous females of Myzus persicae, reared in short night conditions at 21–23°C, are treated with the precocene analogue 6-methoxy-7-ethoxy-2,2-dimethylchromene, they deposit males towards the end of their reproductive lives. The first-born normal daughters of the treated females also deposit some males at various times in their reproductive lives. Karyotypic analysis was used to investigate the sequence of male and female embryos in the ovarioles of precociously metamorphosed aphids. The experiments support the hypothesis (Mittler et al., 1979) that juvenile hormone level controls the sex determination process in aphids. Since male aphids have an XO sex chromosome constitution, this implies that juvenile hormone level influences the behaviour of the X-chromosomes at or before the single maturation division of the egg. At this division one X-chromosome is eliminated from eggs which will develop as males. Aphids provide the first example of a specific endocrine influence on chromosome behaviour in sex determination. 相似文献
97.
Corpora allata from Diploptera punctata females at adult ecdysis or at the end of the last-larval stadium, when implanted into decapitated females, underwent a cycle of juvenile hormone synthesis similar in timing and magnitude to that of glands implanted into control animals which had been starved and allatectomized. Starvation did not alter the cycle in rates of juvenile hormone synthesis of sham-operated animals.Decapitation of ovariectomized animals resulted in no cycle in rates of juvenile hormone synthesis by implanted adult corpora allata; however, implantation of an ovary along with the corpora allata into decapitated, ovariectomized hosts resulted in a cycle of juvenile hormone synthesis. In control animals, which retained their heads but were starved and allatectomized as well as ovariectomized, the implanted corpora allata showed a cycle of juvenile hormone synthesis only when implanted with an ovary. The maximal rates of juvenile hormone synthesis by the corpora allata in both experimental and control conditions were lower than normal, likely due to the repeated trauma of surgery. However, at no time from eclosion to the end of the first gonotrophic period was the brain necessary for the cyclic response of the corpora allata to the presence of the ovary. 相似文献
98.
Molting in a parasitic nematode, Phocanema decipiens—VII. The mode of action of the ecdysial hormone
The cycle of aminopeptidase activity demonstrated by histochemical methods in the activated excretory gland could not be detected in homogenates. In the electron microscope, the secretory granules in dormant glands were dense and irregular in shape and the mitochondria elongate, relatively dense, and with a crenellated outer membrane. The excretory gland was activated when the neuroendocrine system was stimulated by farnesyl methyl ether. In activated glands the secretory granules became larger, less dense and the membranes began to fuse with membranes of the ductules which ramify through the gland. The mitochondria became swollen. Aminopeptidase activity was displayed by a large uniformly less dense granules but not by the denser granules, and was seen in the endoplasmic reticulum, Golgi apparatus and in the lumen of the ducts. It is suggested that the ecdysial hormone from the neurosecretory cells sets in train a sequence of events which leads to entry of water into the gland and consequent activation of the enzyme in the granules, and to changes in the membranes of the granules which facilitate fusion with the membrane lining the ducts. 相似文献
99.
100.
T Suda N Horiuchi S Sasaki E Ogata I Ezawa 《Biochemical and biophysical research communications》1973,54(2):512-518
Kidney mitochondria were isolated from rachitic chicks and their activity in the metabolism of 25-OH-D3 was studied in relation to the amount of calcium added . The addition of 0.050.2 mM calcium to a mitochondrial suspension caused a marked and dose-related stimulation of 1-hydroxylation. A sharp decline in the activity was induced by higher concentrations (0.3-0.5 mM) of calcium. The rate of 24-hydroxylation was not influenced by calcium. In these effects, calcium was relatively specific among various divalent cations. These data strongly suggest that calcium is directly involved in the regulation of the vitamin D activation in kidney mitochondria. 相似文献