Effects of water restriction on digestive function in two macropodid marsupials from divergent habitats and the feral goat

The effects of water restriction on digestive function in the euro (Macropus robustus erubescens) found in the arid zone of inland Australia, the eastern wallaroo (M.r.robustus) from more mesic regions of eastern Australia, and the feral goat (Capra hircus) found throughout the range of M. robustus, were compared in order to examine some physiological adaptations required by herbivores for the exploitation of arid environments. Eight animals of each species were held in individual metabolism cages in temperature-moderated rooms and given a chopped hay diet ad libitum. Half the animals were restricted to 40 ml water·kg^-0.80·day^-1. This was 40%, 32% and 57% of voluntary drinking water intake in the euro, wallaroo and goat, respectively. All species responded to water restriction by reducing faecal, urinary and evaporative water losses in association with reductions in feed intake. All animals increased urine osmolality and electrolyte concentrations but not to maximal levels, while packed-cell volume and plasma osmolality and electrolyte concentrations were unaffected by water restriction. The euro displayed a suite of characteristics that separated it from the wallaroo in terms of physiological adaptation, including lower voluntary water intake, an increase in fibre digestibility and maintenance of nitrogen balance during water restriction, and lower faecal water efflux associated with a consistently lower faecal water content (54% versus 59% water in the wallaroo during water restriction, P<0.05). The euro's colon was 37% longer (P<0.01) than that of the wallaroo. The goat had the lowest faecal water efflux (P<0.05) and the longest colon (P<0.001). Water restriction did not affect water content in digesta, nor short-chain fatty acid concentrations or production rates in vitro. Total body water, as a proportion of body mass, was depressed (P<0.05) in the macropodids, but not in the goat. The reduction in dietary nitrogen intake, which accompanied water restriction, was partially compensated by an increase in urea degradation in the gut from 68% to 76% of urea synthesis water-restricted macropodids. These responses to water restriction are discussed in relation to those reported in other macropodid and ruminant species.Abbreviations BM body mass - SCFA short-chain fatty acids - DM dry matter - PCV packed-cell volume     

Mechanisms of hyperosmotic acclimation in Xenopus laevis (salt,urea or mannitol)

The acclimation of the clawed toad Xenopus laevis to hyperosmotic solutions of NaCl (balanced solution of sea salt), urea or mannitol was studied. The animals could not be acclimated to salt solutions more concentrated centrated than 400 mosm·l^-1. Urea was tolerated till 500 mmol·l^-1. Plasma osmolality was always hyperosmotic to the environmental solution, but with diminished osmotic gradient at the highest tolerated solutions. Plasma urea concentration approached 90 mmol·l^-1, similar in the three solutions of acclimation. Urine volume was very small under all conditions. Serum aldosterone and corticosterone did not differ significantly, although there was a slight tendency towards lower aldosterone in the NaCl solution. In vivo water uptake in tap water acclimated animals was very small, and was higher in the other groups. Only the salt- and urea-acclimated, but not the tap water and mannitol-acclimated groups responded with a clear increase following injection of oxytocin or theophylline. In vitro urea fluxes were similar and invariable in both directions under all conditions. No significant effect of theophylline was observed. Sodium transport measured by the short-circuit technique in vitro was lower in salt- and mannitol-acclimation conditions, and was stimulated significantly under all conditions in response to serosal oxytocin or theopylline. It is concluded that Xenopus laevis can osmoregulate at a limited range of external solutions. It is limited in the increase of its plasma urea concentration; the transport properties of the skin do not change very much upon acclimation, except for the hydroosmotic response to oxytocin.Abbreviations I _sc short circuit current - PD potential difference - SW balanced sea water - TW tap water     

枸杞果实铁型超氧物歧化酶的纯化及性质

枸杞果实Ｆｅ－ＳＯＤ粗提液经硫酸铵盐析、离子交换柱层析及凝胶过滤,纯化到电泳单班点均一程度。纯化的Ｆｅ－ＳＯＤ分子量为４４．６ｋＤ,亚基分子量为２２．０ｋＤ。金属元素分析表明,每分子酸含１个Ｆｅ原子。该酶在紫外区最大吸收值为２７８ｕｍ。Ｈ２Ｏ２明显抑制该酶活性,ＫＣＮ对酶活性无影响。该酶氨基酸组成与高等植物和蓝绿藻的Ｆｅ－ＳＯＤ相似,但它具有较高甘氨酸,酸性氨基酸与碱性氨基酸比值高于高等植物而与低等植物及原核生物相近。     

杭州西湖水质预测方法和结果分析

本文利用二维对流扩散模型对西湖水质总磷浓度进行预测,给出方程的理论基础,编制FORTRAN77程序,在386微机上实现预测,并对预测结果作了较为详细的分析．本模型对水质环境防治决策具有实际意义．     

白及块茎铜,锌超氧物歧化酶的纯化及其性质

白及（Ｂｌｅｉｌｌａｓｔｒｉａｔａ（Ｔｈｕｎｂ．）Ｒｅｉｃｈｂ．ｆ．）的ＳＯＤ同工酶只有一条较宽的谱带,确认为Ｃｕ·Ｚｎ－ＳＯＤ。其块茎ＳＯＤ总活性和比活性都高,且含有丰富的白及胶;经丙酮分级沉淀,ＳｅｐｈａｄｅｘＧ１００凝胶过滤和ＤＥＡＥ－纤维素柱层析分离纯化,获得对ＣＮ￣－敏感的淡兰色Ｃｕ·ＺｎＳｏＤ粉末。在凝胶电泳染色图谱上,纯化后的酶与粗酶液的ＳＯＤ区带相对应,且其酶活性染色带与蛋白染色带位置对应,表明已纯化到均一程度。该酶分子量约３３ＫＤ,亚基分子量约为１６．４ＫＤ;紫外光区的吸收峰在２６４．６ｎｍ,等电聚焦电泳呈现一条蛋白区带,ｐＨ值在４．３５左右;该酶在ｐＨ６．０～１０．０,温度在５０℃范围内具稳定性。纯化后的酶为４５６３．２ｕ／ｍｇ·蛋白,纯化了５１倍,活力回收为２２．３％。上述酶没有过氧化氢酶活性。提取过程中还得到高质量的副产品白及胶。     

不同感染状态下EB病毒核抗原亚型表达的研究

本实验用免疫印迹法纯化的抗ＥＢＮＡ亚型抗体,结合显微荧光分光光度检测技术,检测在不同感染状态下,三种亚型ＥＢＮＡ抗原在细胞中的表达程度。结果表明,处于潜伏感染状态下的Ｒａｊｉ细胞ＥＢＮＡ－１表达量较大,经巴豆油和正丁酸诱导进入钝挫感染状态后ＥＢＮＡ－１表达减少,而ＥＢＮＡ－２的表达增强。Ｂ＿（９５－８）细胞也有相似的趋势。表明ＥＢ病毒的激活可能与不同ＥＢＮＡ亚型表达量的改变有关。     

小球藻RubisCO的纯化及其在异养向自养转变过程中的含量变化

经硫酸铵分部沉淀、ＳｅｐｈａｃｒｙｌＳ－３００和ＤＥＡＥ－纤维素柱层析纯化了小球藻ＲｕｂｉｓＣＯ,得率为１５％,比活力达１．２３２μｍｏｌＣＯ２ｍｓ－１ｍｉｎ－１,分子量是５００ｋＤ,它和菠菜叶片ＲｕｂｉｓＣＯ在分子量、亚基组成和免疫特性等方面相似,反映ＲｕｂｉｓＣＯ在高等和低等植物中有较高的同源性。自养小球藻ＲｕｂｉｓＣＯ占细胞可溶性蛋白质的２４％。而异养转变后的小球藻细胞内不含ＲｕｂｉｓＣＯ。异养小球藻向自养生长转变过程中,２０ｈ后细胞内叶绿素含量逐渐增加,２４ｈ时细胞内出现ＲｕｂｉｓＣＯ,２４ｈ后大量增加,至４１ｈ时含量达最高峰;标志着小球藻细胞光合作用能力的恢复和加强。     

Physico-chemical characteristics of a permanent Spanish hypersaline lake: La Salada de Chiprana (NE Spain)

La Salada de Chiprana Lake, located in the Ebro River basin, northeastern Spain, is the only permanent and deep water hypersaline ecosystem in all of western Europe. With a total surface of 31 ha and a maximum depth of 5.6 m, it has several basins bounded by elongated sandstone-bodies or ribbons which are paleochannels of Miocene age. Its salinity varied from 30 to 73 g 1^–1 during the 1989 hydrological cycle and the most abundant ions were magnesium and sulphate. Depth-time distributions of major physico-chemical variables demonstrated that the lake was stratified in two distinctive layers during most of the year. The chemocline disappeared only in October, with the complete overturn of the water column. In the deep water, three conditions occurred which allowed development of green sulphur bacteria populations: (1) oxygen depletion, (2) presence of hydrogen sulphide and (3) presence of light. Benthic microbial mats covered the sediments of shallow shores of moderate slope.     

Properties of polyphosphatase ofAcinetobacter johnsonii 210A

Polyphosphatase, an enzyme which hydrolyses highly polymeric polyphosphates to P_i, was purified 77-fold fromAcinetobacter johnsonii 210A by Q-Sepharose, hydroxylapatite and Mono-Q column chromatography. The native molecular mass estimated by gel filtration and native gel electrophoresis was 55 kDa. SDS-polyacrylamide gel electrophoresis indicated that polyphosphatase ofAcinetobacter johnsonii 210A is a monomer. The enzyme was specific for highly polymeric polyphosphates and showed no activity towards pyrophosphate and organic phosphate esters. The enzyme was inhibited by iodoacetamide and in the presence of 10 mM Mg²⁺ by pyro- and triphosphate. The apparent K_m-value for polyphosphate with an average chain length of 64 residues was 5.9 µM and for tetraphosphate 1.2 mM. Polyphosphate chains were degraded to short chain polymers by a processive mechanism. Polyphosphatase activity was maximal in the presence of Mg²⁺ and K⁺.