Bovine lens aldehyde dehydrogenase. Kinetics and mechanism.

Bovine lens cytoplasmic aldehyde dehydrogenase exhibits Michaelis-Menten kinetics with acetaldehyde, glyceraldehyde 3-phosphate, p-nitrobenzaldehyde, propionaldehyde, glycolaldehyde, glyceraldehyde, phenylacetylaldehyde and succinic semialdehyde as substrates. The enzyme was also active with malondialdehyde, and exhibited an esterase activity. Steady-state kinetic analyses show that the enzyme exhibits a compulsory-ordered ternary-complex mechanism with NAD+ binding before acetaldehyde. The enzyme was inhibited by disulfiram and by p-chloromercuribenzoate, and studies with with mercaptans indicated the involvement of thiol groups in catalysis.     

Chemical basis of host selection and plant resistance in oligophagous insects

Recent investigations of the Colorado potato beetle and the alfalfa weevil reveal many similarities in their modes of host selection. Many plant chemicals influence their behavioral responses and physiological processes. Chemical stimuli influencing host finding and acceptance or rejection of plants include attractants, repellents, sign stimulants, feeding stimulants and deterrents. Both species are highly sensitive to deterrent chemicals present in many plants. Feeding stimulants are indispensible for these insects and are supplied by both primary nutrients (i.e. sugars, amino acids, phospholipids and potassium salts) and secondary plant substances. The important role played by different plant chemicals in host selection and plant resistance is discussed.

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Zusammenfassung Neuere Untersuchungen am Kartoffelkäfer und am Luzerneblattnager förderten viele Übereinstimmungen in der Art ihrer Wirtswahl zu Tage. Viele Pflanzenstoffe beeinflussen ihre Verhaltensweisen und physiologische Prozesse. Chemische Reize, welche die Auffindung des Wirtes, Annahme oder Ablehnung der Pflanzen beeinflussen, umfassen Attractants, Repellents, Signalstoffe, Fraß-Stimulatoren und Abschreckstoffe. Beide Arten sind hochempfindlich gegenüber abschreckenden Verbindungen in vielen Pflanzen. Fraß-Stimulatoren sind für beide Insekten unabdingbar notwendig und werden sowohl von primären Nährstoffen (wie Zucker, Aminosäuren, Phospholipiden und Natriumsalzen) wie von sekundären Pflanzenstoffen gestellt. Die bedeutsame Rolle, welche Pflanzenstoffe bei der Wirtswahl und der Resistenz der Pflanzen spielen, wird diskutiert.

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Journal paper No. ...., Utah Agricultural Experiment Station, Logan, Utah.     

辐射对大鼠肺巨噬细胞Fc受体表达和特异吞噬功能的影响

以往的实验表明,巨噬细胞(Macrophages简称Mф)对一定辐射剂量内的照射表现出较强的辐射抗性。因此学者们转向研究照射后时间依赖性的Mф损伤变化。这主要是涉及照射后所致的迟发损伤效应。有关大剂量照射后,短时间观察Mф损伤效应的研究报道甚少。为此本文观察了大鼠肺巨噬细胞(AlveolarMacrophages简称AM)在体外受100—500 Gy     

倭竹属地理分布的研究

倭竹属Shibataea Makino隶于禾本科之竹亚科,现已知有8种,分布于我国东南部的浙江、福建、江苏、安徽、江西等省,广东、台湾两省有少量栽培,日本产1种。苏联、西德、印尼等国所栽培的倭竹均系自我国或日本引入。我国浙-闽地区产8种,且都有野生发现,是本属的现代分布中心。倭竹属植物体型矮小,常植于庭院或公园中供观赏。近年来盆景艺术迅速发展,微型园林日益兴起,倭竹属植物体态优美,常绿,耐寒且易于栽培,为广大园林工作者所垂青。     

Tolerance of tannin by the shiitake mushroom,Lentinus edodes

Summary Tannin at 1% (w/v) did not inhibit the growth ofLentinus edodes, but did inhibitPleuroius florida, P. sajor-caju, P. cystidosus, Agaricus bisporus andVolvariella volvacea. The inhibition was not due to its acidity.

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Tolérance de Lentinus edodes aux ajouts de tannin

Résumé Le tannin à la concentration de 1% (p/v) n'inhibe pas la croissance deLentinus edodes, mais inhibe celle dePleurotus florida, P. sajor-caju, P. cystidosus, Agaricus bisporus, etVolvariella volvacea. L'inhibition n'est pas due à son acidité.

     

New method to prepare single-headed heavy meromyosin with high purity and a high yield

We have developed a new method to prepare single-headed heavy meromyosin with high purity and a high yield. To examine whether the two heads on the same myosin molecule work cooperatively or not, it is important to prepare pure single-headed heavy meromyosin. Myosin was extracted from myofibrils treated with a solution containing CyDTA, a strong divalent cation chelator. CyDTA treatment was essential to the production of sHMM. Then such myosin was digested with chymotrypsin in the presence of divalent cations at high ionic strength. Crude sHMM was separated from double-headed HMM by affinity chromatography using an ADP-column. Contaminating S1 was removed by gel filtration. Heavy chain of sHMM obtained by the present method had no nick. Purified sHMM showed normal EDTA-ATPase and Ca-ATPase. It interacted with thin filament and its ATPase was activated by actin normally.     

Insulin suppresses hepatitis B surface antigen expression in human hepatoma cells

The human hepatoma Hep3B cells contain integrated hepatitis B viral genome and continually secret hepatitis B surface antigen (HBsAg). The production of HBsAg (but not alpha-fetoprotein) was suppressed by addition of low concentrations (0.1-1 nM) of insulin into serum-free medium. In addition, the suppression of HBsAg production by insulin was paralleled with the decrease in HBsAg mRNA abundance. Insulin also cause a rapid rate of disappearance of HBsAg mRNA (t 1/2, 2 h) in Hep3B cells. The Hep3B cells carry specific receptor with high affinity for insulin (Kd = 1.8 nM). The receptor showed an insulin-dependent protein tyrosine kinase activity. The half-maximal insulin concentration for the activation of the receptor kinase was about 5 nM. Only very high concentrations of insulin-like growth factor I and human proinsulin can compete for the insulin receptor binding and suppress HBsAg production, this suggests that insulin may act through its receptor binding to suppress HBsAg expression in human hepatoma Hep3B cells.     

The effects of 2-deoxy-D-glucose and sympathetic denervation of brown fat GDP binding in Sprague-Dawley rats

Central administration of 2-deoxy-D-glucose (2-DG) decreases brown fat thermogenesis. This effect is suggested to be mediated via a central control mechanism. Our study was designed to determine the importance of the sympathetic nervous system in the response of brown fat to intraperitoneal (i.p.) injection of 2-DG. Unilateral denervation of interscapular brown adipose tissue (IBAT) was performed on male Sprague-Dawley rats (300 g body weight). Nine days after surgery, rats were injected i.p. with either saline vehicle (0.9% sodium chloride) or 2-DG (360 mg/kg wt) and then killed one hour later. Sympathetic denervation resulted in 50% decreases in total IBAT protein and in mitochondrial protein recovered. In the denervated lobes, mitochondrial GDP binding (expressed as nmol/mg mitochondrial protein and as total activity recovered) was decreased to 36% and 18%, respectively. Injection of 2-DG did not change mitochondrial protein content in either the innervated or denervated IBAT. In the innervated lobes, 2-DG significantly lowered GDP binding to 55% of that in saline-treated animals, whether expressed per mg mitochondrial protein or as total recovered activity. In contrast, 2-DG did not further decrease GDP binding in the denervated lobes. In conclusion, the effects of i.p. injection of 2-DG on brown fat thermogenesis (as evidenced by GDP binding) appear to be primarily mediated via the sympathetic nervous system.     

Sucrose synthase in rice plants : growth-associated changes in tissue specific distributions

Different parts of the rice (Oryza sativa L.) plant at different growth stages were analyzed for sucrose synthase (SS) by enzyme activity assay and enzyme-linked immunosorbent assay directly on the extracts or on the eluates from a gel filtration column. On a dry matter basis, the amount of soluble protein and SS activity decreased significantly, but the amount of enzyme protein changed little in growing leaves. In the grain, the SS activity was the highest at the early ripening stage and decreased later, but the amount of SS protein increased with the increase in maturity. In the root, a low activity of SS was detectable only in the tillering but not in other stages. Immunoblotting of SS protein extracted from different parts of rice showed two bands. Elution patterns of crude extracts from a gel filtration column showed the presence of several types of SS protein. Among them, two to three types with larger elution volumes had the SS activity but others with smaller elution volumes (considered as the aggregated forms) had no activity. The SS purified from different parts of the plant showed similar but distinctly different electrophoretic mobilities in a native gel. It has been concluded that different isozymes are expressed in different tissues at different growth stages.