Conformations and dynamics of surfactants in micelles and liquid crystals by nuclear magnetic relaxation

The order parameters as well as the rates of overall and internal motions of aggregated surfactants can be obtained from deuteron and carbon-13 nuclear relaxation experiments. The main contribution to the relaxation is generally the quadrupolar coupling (²H) or the short range dipolar interaction with protons (¹³C). In some cases it is convenient to derive the same information from the¹³C relaxation induced by long range dipolar interactions with a paramagnetic probe exchanging rapidly among the polar heads of surfactant molecules. This paper outlines the methods of interpretation of relaxation data by means of a rotational jump model of internal motions, taking into account most of the accessible conformers. The conformational and dynamical parameters are obtained from the magnetic field dependence of the longitudinal relaxation rates (micelles) or from the simultaneous fit of these rates and of the dipolar or quadrupolar splittings (liquid crystals). Some examples of application of these methods are given from recent works on single and double detailed surfactants.     

棉铃虫致病菌BT—931菌株的应用研究

１９９２－１９９３年,作者从菏泽、聊城棉田采集的自然罹病死亡棉铃虫幼虫体内,分离到２个较高毒效的Ｂｔ菌株,编号为ＢＴ—９３１和ＢＴ—０２１,经室内毒力测定和田间药效试验表明,防效及保蕾效果接近或超过化学农药,菌药混剂３—５天平均防治效果达８７．０－９１．６％,增效作用显著。经１９９４年大田防治示范表明,利用ＢＴ—９３１菌剂。配合化学农药防治棉铃虫,具有成本低、保护天敌、持效期长、增产效益高等优点。本研究对菌剂的田间应用技术进行了试验示范。     

Structure of the histone tetramer (H3-H4)2: 2. Position of λmax in the tyrosyl fluorescence spectra and tyrosyl accessibility to quenchers

It was shown that the histone tetramer (H3-H4)₂ fluorescence spectra were shifted by about 2 nm towards the long-wave region and had a larger halfwidth than the free tyrosine fluorescence spectra. Denaturation with 8 m urea resulted in a shift towards the short-wave region and a decrease in the halfwidth of the histone tetramer (H3-H4)₂ tyrosine fluorescence spectra. Fluorescence quenching of the histone tetramer (H3-H4)₂ by iodine ions was analysed by the Stern-Volmer equation. It was estimated that at 0.1 m NaCl and 0.3–0.8 m NaCl, 45% and 60% tyrosyl fluorescence, respectively, was quenched by I^? ions. The results obtained suggests that histone tetramer (H3-H4)₂ may have several structural forms distinguished by the amount of ‘exposed’ and ‘buried’ tyrosyls depending upon the conditions of the medium.     

Evidence for conformeric states of Rhodopsin

Spectrophotometric measurements of metarhodopsin II appearance are made on five different kinds of rhodopsin preparations. Although the preparations differ greatly in their rhodopsin: phospholipid ratio, the meta II kinetics in all of them are strikingly similar in certain respects. Meta II appearance kinetics in all of the preparations are best described by two and only two exponentials. The ratio of these two rates is always about 5. The fast fraction: slow fraction ratio depends upon temperature. These fractions are reversibly convertible in the dark, and are interconverted on a time-scale which is long compared to the meta II appearance rate. It is shown that the kinetics of the earlier step in the bleaching sequence, viz., lumi- meta I, is also described by double exponentials. Again the ratio of rates is ca. 5 and the fast-slow fractions correspond to those found in the meta I meta II step. It is proposed that these facts support an hypothesis for the existence of two conformeric states of rhodopsin which are in thermal equilibrium. Thermodynamic parameters associated with this proposed equilibrium are presented.     

Control of nematode parasites by grazing management—II. Decontamination of sheep and cattle pastures by varying periods of grazing with the alternate host

Commencing in December 1970, paddocks of a uniform series of sheep pastures were grazed for 6, 12 or 24 weeks by either yearling steers is or yearling ewes. Cattle pastures were treated similarly. All ewes and steers were pre-dosed with anthelmintic.At the conclusion of alternate grazing the effectiveness of the grazing treatments was evaluated by grazing each paddock for 1 month with either ten worm-free lambs (sheep pastures) or three wormfree calves (cattle pastures). The test animals were then slaughtered for total worm counts. The grazing of sheep pastures with cattle for 6, 12 or 24 weeks from December onwards resulted in reductions in numbers of Haemonchus contortus and Trichostrongylus colubriformis in test lambs. In comparison with continuous grazing by sheep, Nematodirus spp was only reduced after 24 weeks grazing by cattle. Cattle pastures grazed by sheep for 6 weeks showed no reduction in numbers of Ostertagia ostertagi or Cooperia oncophora in test calves. However after 12 weeks with sheep, numbers of O. ostertagi though not C. oncophora were reduced and after 24 weeks of alternate grazing both these species were reduced.Calves following the 6 week sheep treatments acquired both Haemonchus contortus and Trichostrongylus colubriformis and the calves from the 12 week sheep treatment paddock also carried H. contortus. For sheep the only evidence of cross-transmission was the occurrence of small numbers of Cooperia oncophora in test lambs from the 24 week cattle grazing treatment.The results provide evidence that sequential stocking with cattle and sheep in conjunction with anthelmintic treatment is an effective management strategy for preparing parasitologically safer pastures, but further information is required to determine the optimum timing of sequential stocking in farming situations.     

Sequential morphologic changes in adult Echinococcus granulosus during complement-mediated lysis In vitro

Herd R. P., Ko L., Weisbrode S. E. and Heath D. D. 1984. Sequential morphologic changes in adult Echinococcus granulosus during complement-mediated lysis in vitro. International Journal for Parasltology14:141–149. Sequential changes (5,10, 20, 30,40, 50 min, 1, 2, 3, 4, 5, 6, 7, 8, h) were observed by light, scanning and transmission electron microscopy after 38-day-old adult Echinococcus granulosus were exposed to 50% guinea pig serum in vitro. Early changes within 3 h included contraction of worms, fusion of microtriehes, vacuolization and vesiculization of the distal cytoplasm, followed by rupture of vesicles leading to erosion and loss of the distal cytoplasm. This was most marked in the terminal proglottid but ultimately there was complete erosion of the distal cytoplasm of all proglottids and the scolex. After 3 h there was loss of definition of organelles, apparent edema of the perinuclear cytoplasm and, in some instances, rupture of the circular muscle layer with extrusion of parenchyma. Adult tape-worms exposed to heat-inactivated complement showed none of these changes. Lysis and death of the parasite was attributed to osmotic changes subsequent to the formation of trans-membrane channels induced by complement-mediated attack of the tegument after activation of the alternate pathway by factors present in the cestode tegument.     

Larval rearing of fringe-lipped carp,Labeo fimbriatus (Bloch) with low cost diets including green bottle fly Lucilia sericata (Meigen) larvae meal incorporated diet

A study was conducted with non-conventional ingredients to test their efficacy as fishmeal (FM) replacers in the diet of fringe- lipped carp. Labeo fimbriatus first feeding larvae and fry were reared for 30 and 60 days in indoor, 50 L, aerated, circular plastic tanks at 100 and 30 numbers tank⁻¹, respectively. In the first feeding larvae to fry rearing experiment (Exp. 1), the fish were fed with either of the following isonitrogenous and isocaloric diets – live plankton, FM diet, green bottle fly (Lucilia sericata) larvae meal (GBFLM) diet and silkworm pupa (SWP) diet. The fry to fingerling rearing (Exp. 2), was also conducted using the same diets described above except live plankton. All compounded diets were formulated to contain 40% crude protein for the experiment 1 and 35% for experiment 2 and were fed ad libitum. Triplicate tanks were maintained for each treatment in both the experiments. In Exp. 1, the mean final weight of fry was higher with plankton and FM diets, while no difference (p > .05) was observed between FM and GBFLM diets. Weight of fish fed SWP diets was not statistically different from those fed GBFLM diet. No difference (p > .05) in final length, survival and condition factor was recorded. Analysis of digestive enzyme activity of whole fish revealed lower (p < .05) activity of amylase in fish fed plankton. In Exp. 2, no difference (p > .05) was observed between the different diet groups in terms of mean final weight, length, survival and condition factor. Analysis of digestive enzyme activity of whole fish revealed no difference (p > .05) in the activity of digestive enzymes between the treatments except a lower (p < .05) activity of trypsin in FM diet and lipase in FM and GBFLM diets. Since the survival and condition factors of animals is the most important aspect during nursery rearing, similar (p > .05) values recorded in different treatments indicate the possibility of incorporation of these non-conventional protein sources in the diet of L. fimbriatus during first feeding larvae to fry and fry to fingerling rearing.     

Kinetic Formulations for the Reduction of Ketomalonate by Lactate Dehydrogenase

Abstract

Initial rate kinetic studies of lactate dehydrogenase with ketomalonate and NADH as substrates suggest that this enzymatic system is adapted to a rapid equilibrium ordered bi-bi ternary complex mechanism. The application of the reaction product inhibition method reveals the existence of the enzyme-NADH-hydroxy-malonate and enzyme-NAD⁺-ketomalonate abortive complexes. This kinetic behaviour is confirmed by the differential inhibition induced by several alternate products on the pyruvate-lactate dehydrogenase-NADH and ketomalonate-lactate dehydrogenase-NADH systems.