Effects of proteinase K on the energy transfer between phycobiliproteins in phycobilisomes

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.     

Corticotropin-releasing factor inhibits gastric emptying in dogs

The purpose of the present study was to evaluate the effect of ovine corticotropin-releasing factor (CRF) on the gastric emptying of a saline meal in conscious dogs. Intravenous infusion of CRF (220-880 pmol . kg-1 . h-1), induced a significant linear dose dependent inhibition of gastric emptying (16-71%). CRF action was not modified by naloxone and not associated with vomiting or other side effects. Intravenous infusion of sulfated cholecystokinin octapeptide (CCK-8, 50-200 pmol . kg-1 . h-1) inhibited gastric emptying by 29-52%. The relative potency of CRF with respect to CCK-8 is 4 times less. These studies demonstrated that CRF given intravenously in picomolar amount inhibits gastric emptying of a liquid meal in dogs through a mechanism unrelated to opiates. The role of endogenous CRF in stress-induced inhibition of gastric emptying needs to be investigated.     

Vasoactive intestinal peptide effects on GH3 pituitary tumor cells: high affinity binding, affinity labeling, and adenylate cyclase stimulation. Comparison with peptide histidine isoleucine and growth hormone-releasing factor

The vasoactive intestinal polypeptide (VIP) receptor was characterized on the GH3 rat pituitary tumor cell line using competitive binding studies with peptides having sequence homology with VIP. Further studies investigated receptor coupling to the adenylate cyclase complex by measurement of cAMP levels. Finally, the molecular weight of the receptor was estimated by affinity labeling techniques. Studies using 125I-VIP and unlabeled competing peptides revealed a single class of high affinity binding sites with a dissociation constant (KD) of 17 +/- 2 nM (mean +/- S.E.M.) for VIP, 275 +/- 46 nM for peptide histidine isoleucine (PHI), and 1380 +/- 800 nM for human pancreatic growth hormone releasing factor (GHRF). VIP and PHI each stimulated intracellular cAMP accumulation in a dose-dependent manner; both peptides demonstrated synergism with forskolin. In contrast, GHRF neither stimulated accumulation of cAMP nor demonstrated synergism with forskolin. VIP plus PHI (1 microM each) caused no significant increase in cAMP over either VIP or PHI alone, implying that the two peptides act through the same receptor. Covalent crosslinking of 125I-VIP to its binding site using either disuccinimidyl suberate (DSS) or ethylene glycol bis(succinimidyl succinate) (EGS) was followed by SDS-PAGE and autoradiography. The result is consistent with an Mr 47 000 VIP-binding subunit comprising or being associated with the VIP receptor of GH3 pituitary tumor cells.     

Radioimmunoassay for fibroblast growth factor (FGF): release by the bovine anterior pituitary in vitro

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.     

Identification and isolation of the primary aggregation factor from the cell membrane of the sponge Geodia cydonium

Summary The primary aggregation factor (pAF) of sponge cells is a glycoprotein that is firmly associated with the cell membrane. Polyspecific antibodies (anti-GM) prepared from sera raised against membranes of cells from the siliceous sponge Geodia cydonium were found to inhibit initial aggregation of homologous cells. The inhibition of aggregation, caused by anti-GM was neutralized by pAF. The pAF had been successfully solubilized and enriched by affinity chromatography, gel filtration and density gradient centrifugation, if checked by polyacrylamide gel electrophoresis in the presence of urea. The M_r of the native pAF was approximately 40 000 as estimated by gel filtration; under denaturing conditions three protein species (M_r: 16 500, 15 500 and 13 500) were identified in the pAF preparation. The pAF was precipitable by Ca⁺⁺ and did not cross-react with antisera against homologous purified secondary aggregation factor and lectin. It is mainly composed of protein (48.0%) and carbohydrate (50.2%). The isolated pAF restored the aggregation potency not only of factor-depleted Geodia cells but also of cells from other Demospongiae. However, the pAF displayed no aggregation enhancing effect on urea-treated cells from species belonging to the Calcispongiae or Hexactinellida. We hypothesize that in contrast to the secondary aggregation, the initial aggregation of Geodia cells is mediated by the one-component system, the bivalent and bifunctional pAF.     

A biological sampling problem illustrated by the population structure and growth patterns of Sardinella aurita at Tripoli,Libya

Synopsis Sardinella aurita were sampled from catches of the lampara fishery at Tripoli, Libya during October 1979 through to September 1980. Landings consisted mainly of adult fish with large (mode 21–26 cm total length), relatively fast growing 3–5-group individuals in winter and spring and smaller (mode 14–20 cm total length), slow growing 2- and 3-group fish in summer. Gonad growth commenced in April, when the fish were feeding on zooplankton, and continued at the expense of mesenteric fat until July. It is suggested that the older and bigger fish spawn first, probably after having moved westwards, and that this results in spatial and temporal differences in length at age within the population. There was no consistent difference in growth rate between the sexes, but because first maturity in males tends to occur earlier than in females, there were length distribution differences between the sexes in the youngest (2+) age group as sampled.     

Long-term serial cultivation and growth requirements for human umbilical vein endothelial cells

Summary Human umbilical vein endothelial cells (HUV-EC) grew rapidly in vitro in medium supplemented with epidermal growth factor, fetal bovine serum (FBS) and human diploid fibroblast-conditioned medium. The effect of FBS could be replaced partially by bovine serum albumin, cholesterol, and vitamin E, and completely by further addition of serum dialysate or refeeding every other day. Among these components, fibroblast-conditioned medium is essential for HUV-EC growth. The HUV-EC were cultured serially for over 50 population doublings in the 10% FBS containing fibroblast-conditioned medium and for over 40 population doublings in the serum-free medium. Mitogenic factor(s) present in the medium conditioned by fibroblasts may be related to endothelial cell growth factor and play an important role angiogenesis and regeneration of vascular endothelium in vitro.     

光合磷酸化偶联机制研究——Ⅸ.抗生素HP-1对光合磷酸化的解联作用

抗生素HP-1在10~(-7)～10~(-6)M时可以有效地降低光合磷酸化活力,并促进电子传递。它象氯化铵一样能降低光照射时类囊体的质子吸收,但在降低光合磷酸化活力时,既不象氯化铵那样受反应液中磷酸盐浓度的影响,又不象尼日利亚菌素那样依赖反应液中K~+存在。抗生素HP-1可以作为一种新的解联剂而用于光合磷酸化及生物能量转换反应的研究。     

高等植物叶片中的硝酸还原酶活性稳定因子

从小麦、油菜、浮萍、番茄、烟草的叶片中分离得到NR-SF。不同植物材料中NR及NR-SF能起交叉反应;不同NR-SF影响NR酶动力学性质相同;不同NR-SF的凝胶电泳谱带显示蛋白和糖蛋白性质。NR-SF广泛存在于植物细胞中。