Spectral changes in fluorescence of phycobilisomes (PBS) of A. variabilis treated with proteinase K were studied at room and liquid nitrogen temperature. In control PBS, the relative yield of 77 K fluorescence of F686 was very high, and those of F655 and F666 were low. In PBS treated with proteinase K for less than 1 h, F686 decreased, and F655 and F666 increased. In PBS treated with proteinase K for 2 h, F655 was the main peak of fluorescence emission, F686 was the second peak, the fluorescence emission peak of F666 disappeared. In PBS treated with proteinase K for more than 8 h, F655 showed only one fluorescence emission peak.We suggested that phycobiliporteins in the PBS of A. variabilis constitute an energy transfer chain, shown as follows:{fx91-1}The linkages between APC and APC-B, C-PC and APC, and C-PC and APC-B had different sensitivity towards proteinase K. 相似文献
A radioimmunoassay (RIA) was developed to measure fibroblast growth factor (FGF) using antiserum generated against a synthetic replicate of [Tyr10]FGF(1–10). The antisera, previously shown to be capable of inhibiting the biological action of FGF on bovine aortic arch endothelial cells in vitro [1], are highly specific for the amino-terminus of FGF. In the RIA, the antisera recognize the decapeptide antigen [Tyr10]FGF(1–10) and the intact mitogen on an equimolar basis and show less than 0.01% cross-reactivity with N-acetyl-[Tyr10]FGF(1–10).
Bovine adenohypophysial cells maintained in primary monolayer culture release and ir-FGF which is indistinguishable from the intact mitogen in as much as it is retained on heparin-Sepharose affinity columns and shows a dose-dependent and parallel displacement in RIA. The release of ir-FGF by the bovine adenohypophysis can be increased with forskolin (10−5 M) or KCl (50 mM). Preincubation of pituitary cells with 17β-estradiol has no measurable effects on basal ir-FGF, but increases the release after KCl treatment 2–3-fold. These results show that ir-FGF can be released by the bovine adenohypophysis in vitro and lend credence to the hypothesis that FGF plays a physiological role in the homeostatic mechanisms regulating mesoderm-derived cell growth. 相似文献
Intrathecal injection of subanalgesic doses of morphine (7.5 nmol) and dynorphin-A-(1–13) (1.25 nmol) in combination resulted in a marked analgesic effect as assessed by tail flick latency in the rat. The analgesic effect of the composite dynorphin/morphine was dose-dependent in serial dilutions so that a composition of 1/8 of the analgesic dose of dynorphin and 1/3 that of morphine produced an analgesic effect equipotent to full dose of either drug applied separately. The analgesic effect induced by dynorphin/morphine mixture was not accompanied by motor dysfunction and was easily reversed by a small dose (0.5 mg/kg) of naloxone. Contrary to the augmentatory effect of dynorphin on morphine analgesia in the spinal cord, intracerevroventricular (ICV) injection of 20 nmol of dynorphin-A-(1–13) exhibited a marked antagonistic effect on the analgesia produced by morphine (120 nmol, ICV). The theoretical considerations and practical implications of the differential interactions between dynorphin-A-(1–13) and morphine in the brain versus spinal cord are discussed. 相似文献
The subcellular localization of the enzyme invertase in Schizosaccharomyces pombe cells, both repressed and derepressed for synthesis of the enzyme, was studied. Most of the invertase was found to be located outside the plasma membrane and only a small percentage was found to be associated to membranes. A substantial portion of the external enzyme remained firmly bound to cell-wall material.All of the invertase recovered in soluble form from cellular extracts reacted with concanavalin A and with the lectin from Bandeiraea simplicifolia seeds, indicating the presence in the enzyme of a carbohydrate moiety which probably contains terminal mannosyl (or structurally related) and galactosyl residues.The possibility of the presence of two different forms of invertase in S. pombe was considered. An intracellular, soluble form of invertase, devoid of carbohydrate, similar to the small invertase of the budding yeast Saccharomyces cerevisiae, was not found in S. pombe. However, the Michaelis constant for sucrose of the enzyme present in repressed cells was smaller than that of the invertase synthesized under derepressing conditions, although this difference could also be the result of a different pattern of glycosylation of the invertase synthesized under different growth conditions. 相似文献
To examine the effects of prepubertal steroid environment on subsequent estrous cyclicity and gonadotropin secretion, Silastic implants containing 25, 50 or 100% 17 beta-estradiol (E2;n=34), 50% diethylstilbestrol (DES; n=16) or 50% testosterone (T; n=17) were placed into female rats at 12 days of age and removed on the day of vaginal opening (18-24 days of age). At 80 days of age, the percentages of regularly cycling females in the E2-(three groups combined), DES- and T-implanted groups were 59%, 0% and 59%, respectively. By 110 days of age, the percentages were reduced to 24%, 0% and 0%, and at 140 days of age 6%, 0% and 0%, respectively. Many of these females displayed irregular estrous cycles followed by a persistent estrous (PE) state. By contrast, 89% of the control females (blank implants or no implant) maintained regular cycles up to 140 days of age. At 150 days of age, an i.p. injection of gonadotropin-releasing hormone (GnRH; 100 ng/100 g BW) markedly increased serum luteinizing hormone (LH), but not follicle-stimulating hormone (FSH), in intact PE females treated prepubertally with E2 implants. After the test with GnRH, PE rats were ovariectomized (OVX). Thirty days after OVX, similar GnRH administration significantly increased serum levels of both LH and FSH, but these responses were significantly (P less than 0.01) reduced when compared with those in OVX controls. Progesterone administration to estradiol benzoate-primed, acutely (3 days) OVX, or long-term (43 days) OVX-PE females did not increase LH or FSH release. These results indicate that exposure to exogenous estrogen or T prior to puberty precipitates the decline in estrous cyclicity associated with the loss of gonadotropin surge response, presumably due to an alteration in hypothalamic GnRH release. 相似文献