Structural relatedness of lysis proteins from colicinogenic plasmids and icosahedral coliphages

The host-lysis-inducing functions of phi X174 protein E and MS2 protein L were recently shown to reside on the N-terminal and C-terminal halves of the two respective lysis proteins. In the present study it is shown that the small lysis proteins encoded in various colicinogenic plasmids share local sequence similarities and certain structural characteristics with the essential peptides of their coliphage-coded counterparts. Despite their dissimilar sizes and origins, it is suggested that the colicinogenic lysis proteins are functionally analogous and evolutionarily related to those of icosahedral single- stranded DNA and RNA phages.      

An automated assay for adenylate cyclase using reversed-phase high-performance liquid chromatography

An automated high-performance liquid chromatographic method for the assay of 3',5'-cyclic AMP was developed using octylsilica. Total analysis time was 10.1 min, with cAMP eluting at 3 min. As little as 10 pmol of cyclic AMP could be detected by absorption at 260 nm. Peak height and area were linearly related to cyclic AMP concentration over at least two orders of magnitude. The analytical procedure gave good results in the assay of crude microsomal preparations of adenylate cyclase from both bovine brain and sea urchin eggs. The method was used to demonstrate that sea urchin adenylate cyclase is a Ca2+-activated enzyme.     

Detection and localization of antigens on the surface of mouse spermatozoa. Antigen synthesis in the epididymis.

Spermatozoa achieve functional maturity during their transit through the epididymis and this maturation process is accompanied by changes in the composition and proteins of their surface. The addition of secretory products from the epididymis to the plasma membranes of the spermatozoa is considered to be a prerequisite for the acquisition by the spermatozoa of the capacities for forward motility and ovum recognition. An antibody was purified from an antiserum raised in the rabbit against fluid from the cauda epididymis of the mouse. This antibody, in combination with fluorescein isothiocyanate-conjugated goat anti-rabbit antibody, was used to demonstrate a progressive increase in the synthesis and secretion of antigens along the length of the epididymis. Immunoaffinity chromatography of [35S]methionine-labelled proteins, synthesized by segments of the epididymis maintained in vitro, showed that the predominant protein synthesized by the cauda, but not by the caput, epididymis, migrated on electrophoresis with an apparent Mr of 26,000. This same protein was the major antigen found on the plasma membrane of cauda spermatozoa that had been radioactively labelled with the non-penetrating probe isethionyl [1-14C]acetimidate.     

氟碳乳剂与右旋糖酐对犬缺血心肌侧支循环供氧的影响

本实验在14只麻醉开胸狗心脏上观察了氟碳乳剂与右旋糖酐稀释血液对心肌耗氧量与供应缺血心肌氧量关系的影响。以左室压力-时间指数(SPTI)作为心肌耗氧量的指标,根据冠脉有效侧支血流量(ECF)、PaO_2和 Hb 浓度计算供应缺血心肌的氧量。实验结果表明,低分子右旋糖酐稀释血液后,SPTI 暂时性轻度增加(稀释后30min 时较对照增加7.1±2.7%,P<0.05,稀释后60min 时增加2.8±1.2%,P>0.05),ECF 明显增多(稀释后30min 时较对照增加58.5±6.1%,P<0.01),缺血区边缘心肌氧供需关系未发生明显变化。氟碳乳剂稀释血液后,SPTI 的变化规律与右旋糖酐稀释后相同(稀释后30min 和60min 时分别较对照增加2.5±0.7%和1.9±0.8%)ECF 和 PaO_2升高(稀释后30min 时分别较对照增加53.9±6.7%和93±8.9%),供应缺血心肌的氧量显著增加,缺血区边缘心肌氧供需矛盾明显改善。     

Development ofBradyrhizobium infections in supernodulating and non-nodulating mutants of soybean (Glycine max [L.] Merrill)

Summary The early events in the development of nodules induced byBradyrhizobium japonicum were studied in serial sections of a wild type (cv. Bragg), a supernodulating mutant (nts 382) and four non-nodulating mutants (nod49, nod139, nod772, andrj ₁) of soybean (Glycine max [L.] Merrill). Cultivar Bragg responded to inoculation in a similar manner to that described previously for cv. Williams; centres of sub-epidermal cell divisions were observed both with and without associated infection threads and most infection events were blocked before the formation of a nodule meristem. The non-nodulating mutants (nod49, nod772, andrj ₁) had, at most, a few centres of sub-epidermal cell divisions. In general, these were devoid of infection threads and did not develop beyond the very early stages of nodule ontogeny. Sub-epidermal cell divisions or infection threads were never observed on mutant nodl39. This mutant is not allelic to the other non-nodulating mutants and represents a defect in a separate complementation group or gene that is required for nodulation. The supernodulating mutant nts382, which is defective in autoregulation of nodulation, had a similar number of sub-epidermal cell divisions as the wild-type Bragg, but a much greater proportion of these developed to an advanced stage of nodule ontogeny. Mutant nts382, like Bragg, possessed other infection events that were arrested at an early stage of development. The results are discussed in the context of the progression of events in nodule formation and autoregulation of nodulation in soybean.Abbreviations nts nitrate tolerant symbiosis - RT root tip (i.e., position of the tap root tip at the time of inoculation) - SERH shortest emerging root hair (i.e., position of the shortest emerging root hair on the tap root at the time of inoculation) - SCD subepidermal cell divisions     

An extract of Commiphora erythraea: a repellent and toxicant against ticks

A hexane extract of the gum of an African plant, Commiphora erythraea Engler (Burseraceae), has larvicidal and repellent activity against the lone star tick, Amblyomma americanum (L.) and the American dog tick, Dermacentor variabilis (Say). Adult deer ticks, Ixodes dammini Spielman, Clifford, Piesman and Corwin, were also repelled by the extract. Concentrations of 0.02 mg/cm² of the extract impregnated onto filter paper killed 96.15 (±3.56)% of A. americanum larvae exposed to it for 24h. A concentration of 0.16 mg/cm² was needed to kill 80.3% of D. variabilis larvae. The extract was less effective as a larvicide against A. americanum and D. variabilis than permethrin. Less than 15.5% of A. americanum larvae and adults and D. variabilis and I. dammini adults entered and remained for 2 or 3 min on areas of cloth strips treated with the extract at the rate of 0.2 mg/cm². However, 73.3 to 83.3% of the ticks tested entered and remained in areas treated with hexane. Permethrin was about 1 or 2 orders of magnitude more effective against A. americanum larvae as a repellent than the extract.

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Résumé Un extrait à l'hexane de la gomme de la plante africaine, C. erythraea Engler (Burseraceae) a des effets larvicides et répulsifs contre les tiques, Amblyomma americanum L. et Dermacentor variabilis Say; les adultes de Ixodes dammini Spielman, Clifford, Piesman & Corwin, ont été aussi éloignés par l'extrait. Une concentration de 0,02 mg/cm² de l'extrait imprégnant du papier filtre a tué 96,15% (±3,56) larves de A. americanum exposées pendant 24 h. Une concentration de 0,16 mg/cm² a été nécessaire pour tuer 80,3% des larves de D. variabilis. L'extrait a été moins efficace que la perméthrine comme larvicide contre A. americanum et D. variabilis. Moins de 15,5% des larves et des adultes de A. americanum et des adultes de D. variabilis et de I. dammini pénétrèrent et séjournèrent 2 à 3 minutes dans des morceaux de tissu traités avec l'extrait à raison de 0,2 mg/cm², contre 73,3 et 83,3% qui pénétrèrent et restèrent lors de traitement avec de l'hexane. Contre A. americanum, la perméthrine est un répulsif d'un ordre de grandeur une à deux fois supérieur à l'extrait de C. erythraea.

     

Biochemical Studies of Paraquat-Tolerant Mutants of the Fern Ceratopteris richardii

Enzymes and metabolites associated with mitigation of paraquat toxicity were compared in two paraquat-tolerant mutants and a sensitive wild-type strain of the fern Ceratopteris richardii Brongn. In 21-day-old gametophytes, the specific activities of superoxide dismutase, catalase, peroxidase, glutathione reductase, dehydroascorbate reductase, and ascorbate peroxidase showed no differences that would explain mutant tolerance. Constitutive levels of ascorbate and glutathione also did not differ significantly in the three strains. An experiment testing the inducibility of paraquat tolerance revealed no change in the dose response of mutant or wild type gametophytes after exposure to sublethal concentrations of the herbicide. Uptake of paraquat by whole gametophytes was also equivalent in mutants and wild type. These data suggest that the physiological basis for tolerance in these mutants, unlike several other tolerant biotypes reported, does not lie in the oxygen radical scavenging system, in an inducible stress response, or in a block to whole-plant uptake.     

Heterogeneity of a murine B cell lymphoma. Isolation and characterization of idiotypic variants

mAb directed toward the idiotype of the 38C13 murine B cell lymphoma can be used to treat and cure a high percentage of mice challenged previously with an otherwise lethal dose of tumor cells. Tumors developing in animals despite antibody therapy were examined by immunofluorescence and found to demonstrate either loss of surface Ig, or expression of an altered idiotype that no longer bound the antibody used for treatment. Further immunofluorescence analysis of the variant tumors revealed individual patterns of cross-reactivity with anti-38C13 idiotype mAb other than that used for therapy. The variant tumor cells were fused to myeloma cells and hybrids were isolated which secreted large quantities of the altered idiotype proteins. Polyclonal antibodies and mAb prepared against the mutant proteins demonstrated cross-reactivity with the original 38C13 protein and its other variants. But the variants and wild type cells could be distinguished from each other by their patterns of reactivity with the panels of anti-idiotype antibodies. Differences in apparent m.w. were demonstrated in the L chains of each of the mutant proteins. Southern blot analysis of the H chain locus of these mutants established that they were all clonally related; however, the L chain loci were grossly different. Thus, rare cells with alteration in their Ig L chain genes and expressed proteins can give rise to idiotype variants in this B cell tumor.