Effect of Mg2+ and spermine on the kinetics of Ca2+ transport in rat-liver mitochondria

Plots relating the initial rate of mitochondrial Ca²⁺ transport to the Ca²⁺ concentration (kinetic plots) have a hyperbolic shape in a Ca²⁺ concentration range of 2.5–100 µM as measured in sucrose or KCl media. In the presence of Mg²⁺ or a polyamine spermine, which both are competitive inhibitors of Ca²⁺ binding to low affinity sites at the membrane surface, the shape of the plots becomes sigmoidal. At higher concentrations of these agents linear kinetic plots are obtained as measured in a sucrose medium. In a KCl medium the sigmoidality of the kinetic plots is enhanced by an increase in the Mg²⁺ or spermine concentration. It is suggested that Mg²⁺ and spermine affect the kinetics of Ca²⁺ transport by interfering with Ca²⁺ binding to low affinity sites of the membrane surface and that the binding of Ca²⁺ to these sites is the first step of the mitochondrial Ca²⁺ transport.     

LSD and related drugs as DA antagonists: Receptor-mediated effects on the synthesis and turnover of DA

We have earlier shown that d-lysergic acid diethylamide, LSD and its 2-bromo derivative, BOL like the dopamine (DA) antagonists haloperidol increased the rate of the $\text{in vivo}$ tyrosine hydroxylation in the striatum measured as the accumulation of DOPA after decarboxylase inhibition.Now we have found that several agents structurally similar to LSD increase the $\text{in vivo}$ tyrosine hydroxylation in the striatum. Psilocybin (50 mg/kg i.p.) and N,N-dimethyltryptamine (50 mg/kg i.p.) caused a short-lasting increase of DOPA accumulation, while mescaline (10 – 100 mg/kg i.p.) did not increase the DOPA accumulation. A marked increase of DOPA accumulation was observed after the 5-hydroxytryptamine (5-HT) antagonist cyproheptadine. The effects of LSD and structurally related drugs on the DOPA accumulation in the striatum appear to be mediated via DA antagonism at receptor level. However, these agents may control the DOPA accumulation via other receptors than DA receptors e.g. 5-HT receptors. A control of DOPA accumulation via receptors other than DA receptors appears to be predominant after treatment with N,N-dimethyltryptamine or psilocybin.     

Methionine adenosyltransferase activity in cultured cells and in human tissues

We have investigated methionine adenosyltransferase activity (MAT) in extracts of a variety of normal and malignant human tissues and cultured cell lines. MAT activity assayed from 17 different cultured cell lines varied to a great extent. Ramos (human, Burkitt's lymphoma) and EL4 (mouse, T cell lymphoma) cell showed MAT activity near 300 pmol/mg per min. Daudi (human, Burkitt's lymphoma) and almost all monolayer cells had MAT activity below 100 pmol/mg per min. Human peripheral blood lymphocytes had MAT activity of 36 pmol/mg permin. The MAT activity of the cell lines can be related to doubling time: cell lines with short doubling times have much higher MAT activity than other cell lines. A large variation in MAT activity in different human tissues was observed. In autopsy samples MAT activity was highest in the brain and in the colon. Malignant tissue samples gave much higher MAT activity than normal tissues. Lung cancer (carcinoma squamocellulare pulmonis) had MAT activity of 30.7 pmol/mg per min, while in normal lung it was 2.4 pmol/mg per min.     

Spatial and Temporal Variability during Periods of "Recovery" after Mass Bleaching on Western Atlantic Coral Reefs

Western Atlantic coral reefs were differentially affected bya mass bleaching (discoloration) event in 1987. We periodicallyassessed the "appearance" of zooxanthellate organisms betweenDecember 1987 and June 1988 at nine conspicuously affected sitesin the Bahamas, Florida, St. Croix, and Venezuela, using a standardizedpoint-count technique. Three to four months after the localinitiation of the event, the "bleached" state was still presentin one to three of the most abundant reef coral taxa and ina few of the less common species (n = 5 sites). "Recovery" occurredsomewhat faster at shallower depths, at least in the Bahamasand Florida. Scleractinian corals which were "prolonged bleachers"had foliaceous or massive, rather than branching, morphologies."Bleached" points disappeared from the point counts after $6to $8 months. Long-term field data on spatial and temporal variability inthe dynamics of zooxanthellate organisms would help us to understandthe ecological consequences of bleaching. More generally, weneed to distinguish anthropogenic changes in the structure andfunctioning of reef ecosystems from those which occur naturally.Point-count techniques are well suited for collaborative studiesinvolving rapid quantification of coloration states and healthin reef corals.     

杭州双睾虫生活史各阶段体壁的透射电镜观察

作者应用透射电镜技术观察了杭州双睾虫(Diplorchis hangzhouensis)生活史各阶段(自由生活的钩毛蚴、蝌蚪鳃上的后期幼虫、沼蛙膀胱内的成虫)体壁的超微结构,讨论了幼虫发育至成虫过程中这些结构演变的意义,并与其它单殖吸虫的体壁进行了比较。     

The effects of parasitic water mite larvae (Arrenurus spp.) on zygopteran imagoes (Odonata)

Arrenurus larvae, ectoparasitic on zygopteran imagoes, attach to the host's cuticle and tear it to obtain the host's tissue fluids. Within the host's epidermis, each larval mite produces a feeding device, the stylostome, a narrow gelatinous resilient blind sac. Heavy mite infestation brings about several wounds in close proximity, accompanied by loss of more or less extensive areas of the epidermis. Despite wound repair by congregating hemocytes, local lack of epidermis seems to enfeeble the host, presumably owing to desiccation. Heavily mite-loaded zygopterans have lost the typical agility and are easily caught. A mite-induced mortality seems to exist in zygopteran populations; the infestation contributes to reduced longevity. The study of formation and decline of the arrenurid stylostome in zygopterans renders it possible to trace cellular defence reactions under natural conditions. Most stylostomes seem to thwart the ability of the host to recognize them as foreign bodies. The host's defence appears as a two-step reaction: (1) initial hemolymph clotting and deposition of melanin associated with aggregating hemocytes at the penetration site, (2) occasional subsequent melanization and cellular encapsulation of the stylostome.     

Control of cell volume in the J774 macrophage by microtubule disassembly and cyclic AMP

We have explored the possibilities that cell volume is regulated by the status of microtubule assembly and cyclic AMP metabolism and may be coordinated with shape change. Treatment of J774.2 mouse macrophages with colchicine caused rapid microtubule disassembly and was associated with a striking increase (from 15-20 to more than 90 percent) in the proportion of cells with a large protuberance at one pole. This provided a simple experimental system in which shape changes occurred in virtually an entire cell population in suspension. Parallel changes in cell volume could then be quantified by isotope dilution techniques. We found that the shape change caused by colchicine was accompanied by a decrease in cell volume of approximately 20 percent. Nocodozole, but not lumicolchicine, caused identical changes in both cell shape and cell volume. The volume loss was not due to cell lysis nor to inhibition of pinocytosis. The mechanism of volume loss was also examined. Colchicine induced a small but reproducible increase in activity of the ouabain-sensitive Na(+), K(+)-dependent ATPase. However, inhibition of this enzyme/transport system by ouabain did not change cell volume nor did it block the colchicines-induced decrease in volume. One the other hand, SITS (4’acetamido, 4-isothiocyano 2,2’ disulfonic acid stilbene), an inhibitor of anion transport, inhibited the effects of colchicines, thus suggesting a role for an anion transport system in cell volume regulation. Because colchicine is known to activate adenylate cyclase in several systems and because cell shape changes are often induced by hormones that elevate cyclic AMP, we also examined the effects of cyclic AMP on cell volume. Agents that act to increase syclic AMP (cholera toxin, which activates adenylate cyclase; IBMX, and inhibitor of phosphodiesterase; and dibutyryl cyclic AMP) all caused a volume decrease comparable to that of colchicine. To define the effective metabolic pathway, we studied two mutants of J774.2, one deficient in adenylate cyclase and the other exhibiting markedly reduced activity of cyclic AMP-dependent protein kinase. Cholera toxin did not produce a volume change in either mutant. Cyclic AMP produced a decrease in the cyclase-deficient line comparable to that in wild type, but did not cause a volume change in the kinase- deficient line. This analysis established separate roles for cyclic AMP and colchicine. The volume decrease induced by cyclic AMP requires the action of a cyclic AMP-dependent protein kinase. Colchicine, on the other hand, induced a comparable volume change in both mutants and wild type, and thus does not require the kinase.     

Sterols and steryl esters in some Brassica and Sinapis seeds

The qualitative and quantitative composition of sterols in the free form and esterified to fatty acids was studied in seed oils from Brassica napus, B. campestris, B..iuncea, B. nigra, Sinapis alba and S. aruefisis (Brassica kaber). Sitosterol, followed by campesterol, predominated in both the free and the esterified sterols. The free sterols were richer in brassicasterol (ca 10–20%) than the steryl esters (3–10%). Small amounts of δ⁵-avenasterol and δ⁷-stigmastenol were also found in the Brassica oils, often more in the esterified than in the free form. The quantity of sterols was studied only in Brassica campestris, which had ca 0.3 % in the free as well as in the esterified form. In Sinapis alba, ca 10% of the sterols in the free form and 20 % in the esterified sterols were δ⁵-avenasterol. This compared to only a few per cent in both the free and esterified sterols in the Brassica oils. Similarly, ca 2 % of cholesterol was found among the sterols of Sinapis alba but only traces in the Brassica oils. The similarity of sterol compositions among the cultivated brassicas and wild mustard (Sinapis arvensis), and the specific characteristics of the sterols in white mustard (Sinapis alba) adds further weight to the suggestion that wild mustard should be treated as Brassica kaber and strengthens the generic separation of Sinapis alba.     

Digestion and absorption of trioleoyl-thioglycerol in the rat

A triacylglycerol analogue, rac-1,2-di-O-oleoyl-3-S-oleoyl-3-thioglycerol, was fed to rats and chyle acylglycerols were analyzed. Triacylglycerol was the dominating chyle lipid but X-triacyl-1-thioglycerol constituted approx. 6% of total chyle lipids. Its identity was verified by ultraviolet and mass spectra and its stereochemical structure by ORD and CD. The proportions of triacyl-1-thio-sn-glycerol/triacyl-3-thio-sn-glycerol were $\text{63}\text{37}$ and $\text{78}\text{22}$ in two experiments. Possible reasons for this stereospecificity are discussed. The study shows that the stereochemical configuration of lipids isolated from biological material can be assessed by ORD and CD.     

赤眼蜂的产卵行为

赤眼蜂能在多种宿主卵中产卵寄生,并且还具有在人工物体上产卵的习性。Holloway早在1912年即观察到秋葵植物汁滴干燥结膜后,广赤眼蜂(Trichogramma evanescen)企图在其表面产卵。Salt(1935)观察到赤眼蜂有企图将产卵器插入玻璃珠,水银滴,植物种子等表面的行为。Hagen等(1965)试制人工蜡卵饲喂草蛉幼虫时,偶然发现赤眼蜂可以产卵在这种蜡卵内。近年来,Rajendram和Hagen(1974)曾用上述蜡卵引诱赤眼蜂产卵于盐水或氨基酸溶液内。总之,赤眼蜂可在不少的非天然的宿主或物体上产卵,并且所报道产过卵的物体都是球形的。Salt(1937)认为决定赤眼蜂产卵的因素是化学感觉,夜蛾中促使赤眼蜂产卵的物质是22—25碳的直链烷烃成分。但影响产卵行为的各种因素尚缺乏详细的分析。