Aedes aegypti: model for blood finding strategy and prediction of parasite manipulation

Aedes aegypti mosquitoes salivate during intradermal probing of vertebrate prey before ingesting blood (Griffiths and Gordon 1952). Nonsalivating mosquitoes locate blood more slowly; this difference was ascribed to an anti-platelet activity found in the mosquito's saliva (Ribeiro et al. 1984). Mosquitoes infected with Plasmodium gallinaceum suffer pathology that specifically impairs saliva anti-hemostatic activity but without reducing volume of output (Rossignol et al. 1984). The complexity of the feeding apparatus of mosquitoes provides opportunity for a variety of strategies in which pathogens may produce specific lesions that enhance their transmission, but the variables that affect the duration of probing by mosquitoes have not been defined. We sought to resolve this complexity by identifying and quantifying relevant parameters of probing behavior. Mosquitoes thrust their mouthparts repeatedly through their host's skin while searching for blood. Female A. aegypti thrust at 7-sec intervals. If this search results in success, feeding ensues. Alternatively, the mosquito "desists," the mouthparts stylets are withdrawn, and the mosquito attempts to feed at another site. Even after previous desistance, the probability of finding blood remains undiminished. Functions for the probability of feeding success and desistance over time were derived using data from observations on 300 mosquitoes. The probability of feeding success was interpreted as being a function of the density of vessels in the skin, their geometric distribution, and the conditions locally affecting hemostasis. During each probe, the probability of desisting increased linearly with time, and after desisting once, mosquitoes tended to desist more rapidly. A model was developed incorporating Monte Carlo simulation which closely fit observed data. By changing values for the several parameters of the probability functions, we predicted modes in which parasites may manipulate their hosts to enhance transmission, both to and from the vector. In particular, parasite strategies in the vector would include induced salivary pathology; increased duration of probing thrusts; decreased desistance time; and inhibited phagoreception. Predicted parasite strategies in the reservoir host would include increased skin vascular volume and impaired host hemostasis. Our model supports the hypothesis of a mutualistic interaction of malaria and mosquitoes.     

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.     

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。     

肿瘤坏死因子受体超家族成员在免疫系统和疾病中的研究

肿瘤坏死因子受体超家族 (tumor necrosis factor receptor superfamily, TNFRSF) 是细胞因子受体的一个蛋白质超家族,其显著特征是通过细胞外富含半胱氨酸结构域结合肿瘤坏死因子(tumor necrosis factor,TNF)。肿瘤坏死因子受体(tumor necrosis factor receptors,TNFRs)是古老的细胞因子,TNFRs同源基因最早可追溯到节肢动物果蝇中。TNFRs在炎症反应、细胞凋亡、淋巴细胞稳态和组织发育中发挥重要的作用,TNFRs最主要的功能是与免疫系统相关。鉴于其在免疫系统中发挥重要的作用,肿瘤坏死因子受体家族成员已成为治疗糖尿病、动脉粥样硬化、骨质疏松、自身免疫性疾病、移植排斥反应和癌症等人类疾病的靶点。随着科学技术发展,关于TNFRs的功能有了新的进展,在无脊椎动物和低等脊椎动物中已经有大量报道。在本篇综述中,主要总结了在高等哺乳动物中发现的29种TNFR成员的相关报道,包括8种死亡受体和21种非死亡受体,主要涉及在免疫系统以及与疾病相关领域的研究。大多数研究处于基础实验阶段,少数走向临床研究的案例取得的临床效果并不理想,靶向设计针对自身免疫性疾病、炎症和肿瘤疾病的治疗方案需要更深入的理解TNFRs功能。本文旨在对TNFRs成员发挥的功能有进一步的认识。