Electron transfer reactions of cytochrome c confined within erythrocyte ghosts

We have prepared and characterized resealed erythrocyte ghosts in which the only discernible pigment is cytochrome c. The resealed ghosts have the normal orientation and are free of 'leaky' species; they are stable and can be maintained at 4 degrees C for many days without lysis. The internal cytochrome c participates in redox reactions with both soluble and insolubilized cytochrome c present externally, and with external cytochrome b5. No reaction was observed with plastocyanin, cytochrome c oxidase or NADPH-cytochrome c reductase. A study has been made of the reaction of the internal cytochrome c with the low molecular weight reductants, ascorbate and glutathione. Complex kinetics are observed with both reagents: with ascorbate the results are best explained by assuming the existence, in the membrane, of a redox-active species able to undergo dedimerization. A protein bound disulfide bond would satisfy the requirement.     

Sweat tests to diagnose cystic fibrosis in adults.

Twenty five patients with cystic fibrosis and 25 controls were studied to define a sweat sodium concentration in adults that could be taken as diagnostic of cystic fibrosis. Some of the controls had a sweat sodium concentration of over 50 mmol(mEq)/l, and thus cystic fibrosis should be diagnosed in an adult only when two measurements of sweat sodium concentration are above 70 mmol/l. In cases in which the sweat sodium concentration was borderline a suppression test using fludrocortisone improved the accuracy of diagnosis; this test entails recording the lowest concentration reached after administration of the drug. A scatter diagram of the baseline sweat sodium concentrations plotted against the lowest concentration attained after suppression with fludrocortisone may aid the diagnosis further.     

Structural and functional studies of the endothelial activation antigen endothelial leucocyte adhesion molecule-1 using a panel of monoclonal antibodies.

We have produced a panel of mAb to the endothelial activation Ag endothelial leucocyte adhesion molecule-1 (ELAM-1), using both a conventional immunization protocol and one involving immunosuppression. By constructing ELAM-1 mutants we have demonstrated that seven of these antibodies recognize epitopes within the lectin domain of ELAM-1 and that one binds within the complement regulatory protein domains. These studies also suggest that the EGF-like domain is important in maintaining the conformation of the neighbouring lectin domain. In functional studies, U937 cells bound to Cos cells expressing either ELAM-1 or ELAM-1 with the complement regulatory protein domains deleted. No adhesion was observed to Cos cells expressing ELAM-1 mutants lacking either the lectin or EGF-like domains. The fact that antibodies directed against the lectin domain can inhibit adhesion suggest that this domain is directly involved in cell binding.     

Estrogen induced changes in uterine sensitivity for the decidual cell reaction: Interactions between prostaglandin E2 and histamine or bradykinin

In rats receiving high doses of estrogen along with progesterone, the uterus is desensitized and does not respond to artificial stimuli with increased endometrial vascular permeability or decidualization. In addition, prostaglandin E₂ (PGE₂), the putative mediator of endometrial vascular permeability changes in sensitized uteri, is ineffective when given into the uterine lumen. The possibility that this inability of PGE₂ to increase endometrial vascular permeability may be related to the unavailability of hitamine of bradykinin was investigated. Rats were differentially sensitized for the decidual cell reaction by the daily injection of 2 mg progesterone with either 0.5 of 10 μg estrone for the 3 days preceding the unilateral intra-uterine injection of 50 μl phosphate buffered saline containing gelatin with or without 10 μg PGE₂ and with or without 1 mg histamine or 1 μg bradykinin. Prior to the intrauterine injection, all rats were treated with indomethacin to inhibit endogenous prostaglandin production. Endometrial vascular permeability changes were determined 8 h later by determining radioactivity levels in injected and non-injected uterine horns 15 min after the i.v. injection of ¹²⁵I-labelled bovine serum albumin. PGE₂ increased endometrial vascular permeability in rats receiving 0.5 μg estrone, but not in those receiving 10 μg. Histamine or bradykinin, alone or with PGE₂, did not affect endometrial vascular permeability in rats receiving either estrogen dose. The data suggest that the unresponsiveness of uteri from rats treated with high doses of estrogen is not simply due to the unavailability of bradykinin or histamine.     

Interaction of radical anion probes with glucoamylase I from Aspergillus niger.

The radical anions (SCN)2.- and Br2.- produced during a pulse radiolysis of the respective potassium salts have been used to study the tryptophan residues of the glucoenzyme, glucoamylase I (EC 3.2.1.3.). At neutral pH, Br2.- reacted with the tryptophan residues of glucoamylase I as expected from previous studies of proteins and free amino acids. However, (SCN)2.- at neutral and high pH was surprisingly unreactive towards the native enzyme. Reaction did occur, however, between (SCN)2.- and glucoamylase from which one-third of the covalently bound carbohydrate had been removed, producing a tryptophyl radical. Reaction also occured between (SCN)2.- and glucoamylase I inactivated by treatment with sodium dodecyl sulphate, but the tryptophan residues were not involved. It is concluded from the results that two 'types' of tryptophan residues are found in glucoamylase I; both are attacked by Br2.- but only one type is attacked by (SCN)2.-.     

Diel activity patterns in overwintering Labrador anadromous Arctic charr

Hydrobiologia - Anadromous Arctic charr, Salvelinus alpinus, migrate back to freshwater in late summer to spawn and/or overwinter. While seasonal movement patterns during the freshwater residency...     

Understorey plant community assemblage of Australian Eucalyptus woodlands under elevated CO2 is modulated by water and phosphorus availability

水分和磷调控的澳大利亚桉树林林下植物群落组合对二氧化碳浓度升高的响应 鉴于林下植物群落具有的关键性功能作用和全球范围内巨大的森林覆盖面积,研究林下群落对 CO₂浓度升高(eCO₂)的响应以及土壤资源在这些响应中的作用,对于了解CO₂浓度升高对森林生态系统造成的影响非常重要。本研究评估了在澳大利亚东部磷有限的桉树林林下群落中,两种限制性的资源(即水分和磷)在发芽、物候、覆盖率、群落组成和叶片性状等方面对eCO₂响应的作用。我们收集了含有当地土壤种子库的土壤,在温室条件下种植实验性的林下植物群落。研究结果表明,添加磷提高了植物的总体覆盖率,特别是在生长期的最初4 周以及水分含量高的条件下,而且该响应是由植物群落中的类禾本科植物所驱动。然而,随着实验的进行,不同处理方法之间的差异逐渐减小,所有处理在大约11周后均达到了80%左右的植物覆盖率。相反,植物覆盖率并未受到eCO₂ 的影响。多元分析结果反映出植物群落组成随时间的变化,盆栽从以裸土为主变为以高覆盖率的多样化群落为主。但是在实验过程中,磷的添加以及水分可利用性和CO₂之间的相互作用都对植物群落随时间的变化轨迹有所影响。CO₂浓度的升高也增加了群落水平的比叶面积,这表明植物群落对eCO₂的功能适应可能发生在成分响应开始之前。鉴于我们用种子库培育的林下群落对eCO₂ 的响应随着时间的推移而有 所变化,并且受到与磷和水分可利用性的相互作用的调节。我们的结果表明,在水分含量有限的系统中, 特别是在土壤养分可利用性低所导致的生产力响应受限的情况下,CO₂浓度的升高在塑造植物群落方面作用有限。     

Terminal Restriction Fragment Length Polymorphism for Identification of Cryptosporidium Species in Human Feces

Effective management of human cryptosporidiosis requires efficient methods for detection and identification of the species of Cryptosporidium isolates. Identification of isolates to the species level is not routine for diagnostic assessment of cryptosporidiosis, which leads to uncertainty about the epidemiology of the Cryptosporidium species that cause human disease. We developed a rapid and reliable method for species identification of Cryptosporidium oocysts from human fecal samples using terminal restriction fragment polymorphism (T-RFLP) analysis of the 18S rRNA gene. This method generated diagnostic fragments unique to the species of interest. A panel of previously identified isolates of species was blind tested to validate the method, which determined the correct species identity in every case. The T-RFLP profiles obtained for samples spiked with known amounts of Cryptosporidium hominis and Cryptosporidium parvum oocysts generated the two expected diagnostic peaks. The detection limit for an individual species was 1% of the total DNA. This is the first application of T-RFLP to protozoa, and the method which we developed is a rapid, repeatable, and cost-effective method for species identification.