Precursors of distinct size for chicken αA, αD and β globin mRNAs

The reconstitution of bovine cardiac troponin from its subunits has been investigated using hydrodynamic techniques. Gel filtration (Sephacryl S-300) and sedimentation velocity experiments indicate that troponin-C and troponin-I from a stable binary complex (1:1 mole ratio) with an apparent Stokes' radius of 36 Å (frictional ratio = 1.6). Troponin-C and troponin-T do not interact significantly while troponin-I and troponin-T undergo partial complex formation. The effect of subunit ratio on the reconstitution of whole troponin has been examined by SDS—polyacrylamide gel electrophoresis and gel filtration and the results suggest that native troponin contains the subunits in an equimolar ratio.     

Comparison of developmentally regulated lectins from three species of cellular slime mold

Extracts of the cohesive forms of the cellular slime molds Dictyostelium discoideum, Dictyostelium mucoroides and Dictyostelium purpureum contain lectin activity, assayed as hemagglutination activity. The lectin activity from each species binds quantitatively to Sepharose 4B and can be eluted with d-galactose. The resultant purified lectins are abundant proteins representing, in the case of D. purpureum, up to 5% of the total soluble protein of cohesive cells. The preparations from each species are similar but distinct in amino acid composition and other properties. Each purified preparation gives rise to two protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with the major band representing as little at 77% (D. purpureum) and as much as 96% (D. mucoroides) of the total protein in the two bands. The molecular weights of the pair of bands were different for each species, ranging between about 23 000 and 26 000. The two bands are believed to represent subunits of lectins made up of either one or a combination of these two proteins. The apparent molecular weights of the purified lectin activities determined by sucrose density gradient centrifugation were all in the range of 100 000. $\text{N-}\text{Acetyl-}\text{d}\text{-galactosamine}$ was a potent inhibitor of the hemagglutination activity of each preparation; but there were some differences in the relative inhibitory potency of a number of other saccharides. Antiserum raised against each preparation, as well as univalent antibody fragments derived from these antisera, reacted best with the antigens to which they were raised; but showed some cross reaction measured both by precipitin reactions and by inhibition of hemagglutination activity of the purified lectins. The differences between the lectins from the different species could be trivial; but they also could be important for defining specific properties of these three species which reliably segregate into colonies of a single species when grown in mixed culture.     

Variants of a cloned synthetic lactose operator: I. A palindromic dimer lactose operator derived from one strand of the cloned 40-base pair operator

Starting with one strand of the 40-bp synthetic operator (Sadler et al., 1978), we have constructed and cloned a 66-bp, palindromic DNA segment with the following sequence

where the horizontal arrows indicate the locations of the two 21-bp “core? operator sequences in this segment and the vertical arrow designates the dyad axis of symmetry. Upon denaturation and rapid renaturation, each strand of this fragment forms a hairpin molecule still retaining an EcoRI cohesive end. Two hairpin molecules can be joined with T4 DNA ligase to form a duplex DNA molecule having no ends (dumbbell form A). Denaturation and rapid renaturation of dumbbell A yields a mixture of two dumbbell forms: dumbbell A which is a substrate for EcoKL, and a new form, dumbbell B, which is not a substrate. Each of the conformations of this DNA fragment have been purified and all are active in binding lactose repressor in vitro.     

Protection of steroid hormone receptors by protease inhibitors

Steroid hormone receptors are proteolyzed by different types of enzymes present in target tissues. Effective protease inhibitors protecting steroid hormone receptors in various target tissues were investigated. Progesterone receptor (PR) in hen oviduct and estrogen receptor (ER) in cow uterus were specifically protected by relatively low concentrations (0.5 mM) of leupeptin or antipain (inhibitors of serine and thiol proteases). It was indicated that two different types of enzymes which modify native glucocorticoid receptor (GR) are present in rat liver. One was inhibited by 1 mM leupeptin or 1 mM antipain, while the other was inhibited by 1 mM phosphoramidon (inhibitor of thermolysin like proteases) or 10 mM sodium molybdate. Native PR, ER, and GR were shown to have similar Stokes radii (44 Å).     

Apparent nuclear localization of unoccupied receptors for 1,25-dihydroxyvitamin D3

Previous studies have demonstrated that unoccupied 1,25-dihydroxyvitamin D₃ receptors are associated with crude chromatin under hypotonic conditions $\text{in}\text{vitro}$. The data presented herein show that unoccupied 1,25-dihydroxyvitamin D₃ receptors appear to be associated with chromatin prior to solubilization by dilution/homogenization in both high and low salt buffers. Additionally the unoccupied receptors are recovered nearly quantitatively from purified nuclei. These results suggest that unoccupied 1,25-dihydroxyitamin D₃ receptors may be localized within nuclei $\text{in}\text{vivo}$.     

Cloning of chemically synthesized lactose operators. II. EcoRI-linkered operators.

A 40 base, mainly duplex DNA segment, with the following sequence pAATTCCACATGTGGAATTGTGAGCGGATAACAATTTGTT (3') GGTGTACACCTTAACACTCGCCTATTGTTAAACACCTTAAp (5') has been synthesized by combination of chemical and enzymatic methods. It consists of a wild-type lactose operator sequence (boxed) bracketed by "linker" sequences which permit excision of the segment from plasmid vehicles by the EcoRI restriction endonuclease. This segment has been ligated into the pMB9 plasmid and the resulting operator plasmids used to transform E. coli K-12. Among the transformant products were strains carrying plasmids with one, two, three, or four operator segments in tandem. Derepression of the lactose operon effected by these plasmids in vivo as well as the lifetimes of complexes formed between repressor and these plasmids in vitro increase with increasing numbers of operators per plasmid.     

白蚁翅面微刻点的扫描电镜观察：堆砂白蚁属、楹白蚁属和原白蚁属

用扫描电镜观察了3种木白蚁(平阳堆砂白蚁Cryptotermes pingyangensis、叶额堆砂白蚁C.Havilandi和侧角楹白蚁Incisistermes laterangularis)和2种草白蚁(东方原白蚁Hodotermopsis orientalis和尤氏原白蚁H.Yui的翅面微刻点。微刻点类型有：乳突：基部宽5.0-20.6μm,长3.0-19.7μm,翅面中央密度可达2070-3375乳突mm²;瘤状突起：基部直径15.0-58.6μm,翅面中密度282-356突起/mm²;粉刺状突起：基部直径2.4-4.8μm。此外,还发现有长11一57μm的毛。同种白蚁的前、后翅和翅的背、腹面之间,微刻点类型没有明显的差异。最后初步讨论了白蚁翅面微刻点的分类学和生物学意义。     

马尾松毛虫蛋白质、核酸酶和羧酸酯酶与耐药性的关系

马尾松毛虫(Dendrolimus Punctatus Walder)幼虫蛋白质含量,羧酸酮酶和多酚氧化酶活力与虫龄大小成正相关;氰戊菊酯处理后,兴奋期的蛋白质含量和羧酸酯酶活力上升,到抑制期均降低到正常虫体的水平,而多酚氧化酶的变动不大。正常虫体中脱氧核糖核酸酶(Dnase)和核糖核酸酶(Rnase)的活力存在差异：Dnase从3-5龄幼虫随虫体增大而上升,到6龄时明显降低;Rnase与虫龄大小成负相关;氰戊菊酯处理后,Dnase便开始下降并低于正常虫体的水平,而Rnase在兴奋期上升,到抑制期下降亦低于正常虫体水平。结果说明,除多酚氧化酶外,蛋白质、核酸酶和羧酸酯酶均与耐药性存在一定的相关性,研制酶的抑制剂具有实用意义。根据毒力测定结果,马尾松毛虫幼虫随虫龄增大而耐药力增加,氰戊菊酯对5龄幼虫是3龄的2.8倍,6龄是4龄的2.3倍。因此,掌握在4龄前进行药物防治是合理的。     

Fibrillogenesis of apomyoglobin facilitated by aggregation sequence of yeast Sup35 in various regions

To examine the effect of aggregation sequence QGGYQQQYNP from yeast Sup35 on fibril formation of sperm whale apomyoglobin (apoMb), we constructed several mutants via substitution. Urea-induced unfolding of apoMb confirms that the substitution of the aggregation sequence does not significantly affect the stability of the mutants compared to wild type (WT) at pH 4.2. Under this condition, however, despite the difference in rate most apoMb mutants form fibrils more readily than WT with distinct morphology. These results suggest that the aggregation sequence facilitates fibril assembly of apoMb at acidic pH in vitro and this facilitation depends on the regions replaced.     

Photosynthetic Prokaryotes. Cell Differentiation and Functions : Edited by G.C. Papageorgiou and L. Packer Elsevier Biomedical; New York, 1983 405 pages. $65.00

A protein (designated as luffin) with an app. M_r of 26000, which inhibits protein synthesis in rabbit reticulocyte lysate, was purified to homogeneity from the seeds of Luffa cylindria roem by extraction with 20 mM Na phosphate buffer (pH 7.2) containing 0.2 M NaCl, ammonium sulfate fractionation, and chromatography on Sephacryl S-200 and CM-Sephadex C-25. Luffin exhibited 10-times as strong inhibitory activity against protein synthesis in rabbit reticulocyte lysate (IC₅₀, 0.42 ng/ml) as that of ricin A-chain, but it showed only a weak cytotoxicity against murine leukemia L1210 cells, an activity of 1/10⁶ to 1/10⁵ that of ricin.     

Rapid purification of plasmid DNA by a single centrifugation in a two-step cesium chloride-ethidium bromide gradient

A procedure for rapid, preparative purification of plasmid DNA is described and compared with a conventional equilibrium centrifugation method. A discontinuous, two-step CsCl-ethidium bromide gradient is used, with the starting position of the plasmid-containing extract being at the bottom of the tube. During centrifugation in a fixed angle rotor, covalently closed circular plasmid DNA is separated from contaminating protein, RNA, and chromosomal DNA in 5 hr. Plasmids purified by this method are considerably less contaminated with RNA than when purified by a 48-hr equilibrium run in a homogeneous gradient, as determined by agarose gel electrophoresis and 5'-end-labeling studies. Plasmid DNA purified in two-step gradients can be used directly for restriction endonuclease analysis and DNA sequencing.     

Pituitary metabolism of 5alpha-androstane-3beta-17beta-diol: intense and rapid conversion into 5alpha-androstane-3beta,6alpha,17beta-triol and 5alpha-androstane-3beta,7alpha, 17beta-triol.

In the male rat pituitary, 5alpha-androstane-3beta, 17beta-diol (3beta-diol) is extensively metabolized into polar steroids. They were identified as 5alpha-androstane-3beta, 6alpha-17beta-triol (6alpha-triol) and 5alpha-androstane-3beta, 7alpha, 17beta-triol (7alpha-triol). 6-alpha-Triol represents 53% and 7alpha-Triol 28% of the total 3beta-diol metabolites. The remaining percentage is related to 6beta and 7beta isomers. The biological role of triols is still unknown.     

Nuclear 115cadmium: uptake and disappearance correlated with cadmium-binding protein synthesis.

The intracellular distribution of ¹¹⁵cadmium was determined following a pulsed exposure to the metal. The uptake and disappearance of label from rat liver nuclei was correlated with the appearance of a cytoplasmic Cd-binding protein. By coupling $\text{in}\text{vivo}$ - $\text{in}\text{vitro}$ experiments it was shown that unspecifically bound cadmium is free to enter the nucleus while specifically bound cadmium remains in the cytoplasm.