Activation of beef-heart cytochrome c oxidase by cardiolipin and analogues of cardiolipin

Beef-heart cytochrome c oxidase lacking endogenous lipids can be prepared by cholate-mediated exchange with dimyristoylphosphatidylcholine (Powell, G. L., Knowles, P. F. and Marsh, D. (1985) Biochim. Biophys. Acta 816, 191-194). These preparations retained practically no endogenous cardiolipin (less than 0.19 mol cardiolipin per mol of oxidase) but in Tween 80 they retained unaltered electron transport activity. Resupplementation of the dimyristoylphosphatidylcholine-substituted cytochrome oxidase with cardiolipin and cardiolipin analogues with different numbers of acyl chains or with a methylated headgroup enhanced the activity of the reconstituted enzyme to an extent dependent on the structure of the cardiolipin derivative. The Eadie-Hofstee plot showed biphasic kinetic behavior for all reconstituted preparations, even those completely lacking cardiolipin. This biphasic substrate dependence of the kinetics was simulated using the model of Brzezinski, P. and Malmstr?m, B. G. (Proc. Natl. Acad. Sci. USA 83 (1986) 4282-4286), which implicates two interconverting enzyme conformations in the proton transport step. The activation of cytochrome c oxidase by the cardiolipin analogues could be explained in terms of an electrostatic enhancement of the surface concentrations of both cytochrome c and protons, and a facilitated interconversion between the two enzyme conformations.     

Specific antibodies to bovine choline acetyltransferase raised in mice immunised with small amounts of partially purified enzyme

Choline acetyltransferase was purified approximately 18,000-fold from 300 g of bovine caudate nuclei to a specific activity of 21 μmol min mg protein. The overall procedure used was: extraction of the enzyme by high salt concentration, chromatography on carboxy-methyl-Sephadex, precipitation by ammonium sulphate, affinity chromatography on Blue-Sepharose and, finally absorption on hydroxylapatite. When the enzyme absorbed on hydroxylapatite was injected into mice, it provoked reproducibly a transient production of ‘inhibitory’ antibodies, followed by higher antibody titres mainly of ‘non-inhibitory’ type. These responses were elicited by injecting less than a total of 20 μg of immunogen. The highest antibody titre was obtained less than 2 months following the initial immunisation. Species cross reactivity was investigated. This procedure should prove to be of value in the production of monoclonal antibodies to choline acetyltransferase.     

The surface microstructure of marine and terrestrial isopoda (Crustacea,Peracarida)

Summary The microstructure of the surface of thirteen marine littoral and two terrestrial isopods was investigated by scanning electron microscopy. A great diversity of surface ornamentation is present, including non-sensory microscales, pits, tubercles, and ridges, and sensory tricorns, pit organs, pores, papillae and setae. Microscales are common features of the integument surface; their shape and size are highly variable. Tricorns were not observed on the marine littoral isopods. Several hitherto undescribed structures were observed including spade-like projections from the tergite surface of Oniscus asellus, hair-like filaments associated with the microscales of Jaera and ridged conical protuberances on Edotea triloba and E. montosa. The possible function of certain surface microstructures is discussed.     

温度对干旱、盐胁迫下两种黄芪属种子萌发和幼苗生长的影响

为探讨温度对干旱、盐胁迫下黄芪属种子萌发和幼苗生长特性的影响,以黄芪属蒙古黄芪和扁茎黄芪2种种子为研究对象,纯净水处理为对照组,NaCl、PEG处理为实验组,设置4个渗透势水平(0、-0.1、-0.3、-0.5 MPa),置于5种不同的温度(10、15、20、25、30 ℃)下,每日观察并记录两种种子萌发和幼苗生长情况。结果表明：旱盐胁迫下蒙古黄芪和扁茎黄芪种子萌发最适宜的温度分别为25和20 ℃左右;蒙古黄芪耐高温不耐低温,而扁茎黄芪恰恰相反;但25和20 ℃均适宜两种幼苗生长,包括胚根、胚轴和子叶的生长。蒙古黄芪各处理组(除未发芽的种子)的平均发芽时间都比扁茎黄芪长;NaCl胁迫程度的增加使得两种种子的最终发芽率降低,但蒙古黄芪的耐盐性高于扁茎黄芪;随着PEG胁迫程度的增加,二者的发芽均受到抑制,甚至会出现完全不萌发,但扁茎黄芪的耐旱性高于蒙古黄芪;在相同的渗透势时,尤其是-0.5 MPa,PEG比NaCl对两种种子的影响大;交互胁迫作用下,随着渗透势的增加两种幼苗的鲜重、干重以及胚根、胚轴、子叶的长和宽变化较大;利用Design Expert软件预测发现：温度25 ℃、NaCl渗透势为-0.1 MPa,温度24 ℃、PEG渗透势为-0.04 MPa的处理是蒙古黄芪种子萌发和幼苗生长达到最优化的组合;而扁茎黄芪最优化的组合则为23 ℃下NaCl渗透势为-0.07 MPa的处理,20 ℃下PEG渗透势为-0.13 MPa的处理。     

Ultrastructure and isolation of glyoxysomes (microbodies) in zoospores of the fungusentophlyctis sp.

Summary A correlative approach, involving light and electron microscopic, cytochemical, and biochemical techniques, was used to study the structure and function of microbodies in zoospores ofEntophlyctis sp. The same population of microbodies already existing in the zoosporangium appeared to be segregated into zoospore initials during cytoplasmic cleavage. Microbodies laid at the anterior end of zoospores and were part of an organized assemblage of organelles, the microbody-lipid globule complex. In the microbody-lipid globule complex, endoplasmic reticulum occurred on the surface of the lipid globules toward the zoospore's exterior, and the microbody, subtended by mitochondria, was appressed to the opposite surface of the lipid globule. The organization of the microbody-lipid globule complex changed as the zoospore swam and encysted. As lipid globules coalesced, the microbody-lipid globule complex became disorganized. After lipid globule coalescence was completed, the microbody-lipid globule complex regained its order, and several microbodies were clustered adjacent to a single lipid globule. The microbodies persisted even in the encysted zoospore, but they were found on all sides of the lipid globule.Microbodies isolated from zoospores contained catalase as well as malate synthase and isocitrate lyase, two enzymes of the glyoxylate cycle. When zoospores encysted greater activities of these glyoxylate cycle enzymes could be detected. The presence of glyoxylate cycle enzymes and the close association between the microbody and lipid globule suggest that microbodies function as glyoxysomes in zoospores and encysted zoospores. The functional significance of the morphological organization of the microbody-lipid complex is discussed in terms of energy production and the conversion of storage lipid into structural components of the cell.     

Interactions of Concomitant Species of Nematodes and Fusarium oxysporum f. sp. vasinfectum on Cotton

Meloidogyne incognita, Hoplolaintus galeatus, and North Carolina and Georgia populations of Belonolaimus longicaudatus were introduced singly and in various combinations with Fusarium oxysporum f. sp. vasinfectum on wilt-susceptible ''Rowden'' cotton. Of all the nematodes, the combination of the N. C. population of B. longicaudatus with Fusarium promoted greatest wilt development. H. galeatus had no effect on wilt. With Fusarium plus M. incognito or B. longicaudatus, high nematode levels promoted greater wilt than low levels. The combination of either population of B. longicaudatus with M. incognita and Fusarium induced greater wilt development than comparable inoculum densities of either nematode alone or where H. galeatus was substituted for either of these nematodes. Nematode reproduction was inversely related to wilt development. Without Fusarium, however, the high inoculum level resulted in greater reproduction of all nematode species on cotton. Combining M. incognita with B. longicaudatus or H. galeatus gave mutually depressive effects on final nematode populations. The interactions of H. gateatus with B. longicaudatus varied with two populations of the latter.     

Isoperoxidases from tobacco tissue cultures

Two anodic isoperoxidases (A₁ and A₂) from tobacco tissue culture W-38 and two cathodic isoperoxidases (C₃ and C₄) from tobacco suspension culture WR-132 have been separated and characterized. Molecular weights for each of the isoperoxidases have been determined by two different methods. Only C₄ contained a carbohydrate component. The substrate specificity and the pH optima for the four enzymes with each of five substrates were determined.     

Epidermal differentiation governs engineered skin biomechanics

Engineered skin must be mechanically strong to facilitate surgical application and prevent damage during the early stages of engraftment. However, the evolution of structural properties during culture, the relative contributions of the epidermis and dermis, and any correlation with tissue morphogenesis are not well known. These aspects are investigated by assessing the mechanical properties of engineered skin (ES) and engineered dermis (ED) during a 21-day culture period, including correlations with cellular metabolism, cellular organization and epidermal differentiation. During culture, the epidermis differentiates and begins to cornify, as evidenced by immunostaining and surface electrical capacitance. Tensile testing reveals that the ultimate tensile strength and linear stiffness increase linearly with time for ES, but are relatively unchanged for ED. ES strength correlates significantly with epidermal differentiation (p<0.001) and a composite strength model indicates that strength is largely determined by the epidermis. These data suggest that strategies to improve ES biomechanics should target the dermis. Additionally, time-dependant changes in average ES strength and percent elongation can be used to set upper bound limits on mechanical stimulation profiles to avoid tissue damage.