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31.
Ralph C. Mac Nally 《Oecologia》1979,42(3):293-306
Summary The socio-spatial organisation of two sympatric species of anurans was investigated by analyses of the spatial and temporal structure of breeding assemblages. Ranidella signifera breeds earlier in the year than its congener, R. parinsignifera, though there is an overlap of 6 to 8 weeks. Males of both species show high affinities for discrete spatial locations (preferred calling stations). These stations are regularly-spaced, and temporally-stable. Satellite behaviour occurs, though most satellites are past or future residential males. There appears to be a spatial-energetic limit to the number of calling residents of both species that a pond can support. There is no differentiation of calling sites between the two species, and the males of R. parinsignifera appear to displace their congeners from the preferred stations located on the land/water interface of ponds. The breeding season of R. signifera in sympatry is abbreviated relative to nearby (20 km) allopatric localities. The breeding seasons of conspecific males and females are well-synchronised, though the ratio of males to females is high early in the breeding season. 相似文献
32.
Stimulation of the adenylate cyclase of A B16 melanoma cell line by pro-opiocortin-related peptides--a structure-activity study 总被引:1,自引:0,他引:1
The ability of alpha-melanotrophin (alpha-MSH or ACTH 1-acetyl-13 amide) and other structurally related peptides derived from the common precursor, pro-opiocortin, to stimulate adenylate cyclase activity in a pigmented B16 mouse melanoma was investigated. The peptides ACTH 1-39, ACTH 1-24, alpha-MSH, ACTH 1-13 amide and beta-MSH all stimulated the enzyme to a similar maximal extent and with similar potency (ED50 = 1.3 . 10(-6) M) except that ACTH 1-39 was slightly less potent (ED50 = 5 . 10(-6) M). ACTH 4-10 (ED50 = 4 . 10(-5) M) and gamma-MSH (ED50 = 5 . 10(-6) M) were partial agonists. ACTH 1-10 was no more effective than ACTH 4-10 in stimulating the enzyme whereas ACTH 1-13 amide was a full agonist. The peptides beta-endorphin and its derivatives, Met-enkephalin and melanotrophin potentiating factor (MPF), failed to stimulate the enzyme. We suggest that the B16 melanoma requires not only the sequence ACTH 4-10 but also some part of the sequence ACTH 11-13, or a similar sequence in the terminal portion of beta-MSH, for full activation of the receptor-linked enzyme. 相似文献
33.
R.M. Maiorino A.J. Gandolfi K. Brendel J.R. Mac Donald I.G. Sipes 《Chemico-biological interactions》1982,38(2):175-188
Numerous xenobiotics are known to be bioactivated and to covalently bind to proteins, but the resulting amino acid adducts (AAAs) are unknown. In this study the AAAs of twelve 14C-labeled aliphatic halides were examined after formation in an in vitro microsomal system. After exhaustive solvent extraction of the precipitated microsomal protein, the AAAs were isolated by Pronase digestion, followed by filtration through a 500 mol. wt. exclusion membrane. The liberated AAAs were applied to a constant flow DC-4A cation exchange column, resolved by stepwise buffer elution, collected and counted for radioactivity. Column recovery for applied radioactivity was 100 ± 4%. Generally, 1–4 different AAAs (defined by eluting radioactivity) were resolved, with each organohalogen displaying a characteristic elution profile. Methyl iodide, trichloroethylene and 1,2-dichloroethylene had a single major AAA while bromotrichloromethane, 1,2-dibromoethane, 1,1,1-trichloroethane, 1,2-dichloroethane, 1,1,2-trichloroethane, 2-bromo-2-chloro-1,1,1-trifluoroethane, chloroform and carbon tetrachloride had up to 4 AAAs or more, indicating combinations of binding site(s) and reactive intermediate(s). The single AAA formed following incubation of methyl iodide with the microsomes was identified as S-methylcysteine. Thus, this method appears capable of resolving binding sites and is the initial isolation step for identifying specific adducts to proteins. 相似文献
34.
M C Apella S N González M E Nader de Macías N Romero G Oliver 《The Journal of applied bacteriology》1992,73(6):480-483
The inhibitory effect of lactobacilli on growth of Shigella sonnei was studied. The effect was not due to pH alone, as addition of hydrochloric, lactic or acetic acids to culture media did not inhibit the normal growth of the shigellas. The degree of inhibition was measured by disc assay and showed that the inhibitory substance(s) can be extracellular and diffusible, varying the degrees of inhibition depending on the media tested. When broth was inoculated with mixed cultures of Lactobacillus and Shigella strains, the inhibition began at 6 h and the death phase at 9 h. The higher inhibition was produced by the mixture of lactobacilli (35.5 +/- 2.5% at 6 h culture, 57.4 +/- 1.9% at 9 h and 91.2 +/- 1.2% at 14 h). The degree of inhibition was higher when the relationship pathogen : lactobacilli was 1:10(3). The specific growth rate of lactobacilli and shigella was different in pure or mixed cultures. When the lactobacillus alone was grown for 12 h and the shigellas then added, the numbers of shigellas began to decrease immediately at 37 degrees C. This work shows that the Lactobacillus strains employed in fermented milk can be used to inhibit the growth of Sh. sonnei. 相似文献
35.
The aquatic fungus Blastocladiella emersonii provides a system for studying the regulation of expression of regulatory (R) and catalytic (C) subunits of cAMP-dependent protein kinase (PKA). Blastocladiella cells contain a single PKA with properties very similar to type II kinases of mammalian tissues. During development cAMP-dependent protein kinase activity and its associated cAMP-binding activity change drastically. We have previously shown that the increase in cAMP-binding activity during sporulation is due to de novo synthesis of R subunit and to an increase in the translatable mRNA coding for R (Marques et al., Eur. J. Biochem. 178, 803, 1989). In the present work we have continued these studies to investigate the mechanism by which the changes in the level of kinase activity take place. The C subunit of Blastocladiella has been purified; antiserum has been raised against it and used to determine amounts of C subunit throughout the fungus' life cycle. A sharp increase in C subunit content occurs during sporulation and peaks at the zoospore stage. Northern blot analyses, using Blastocladiella C and R cDNA probes, have shown that the levels of C and R mRNAs parallel their intracellular protein concentrations. These results indicate a coordinate pretranslational control for C and R subunit expression during differentiation in Blastocladiella. 相似文献
36.
37.
N V Shiriaeva A I Va?do N G Lopatina D A Kulagin T S Glushchenko N P Taranova 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1992,42(1):137-143
The influence was studied of 15-days stressing on the appearance of stable neurosis-like state of rats lines, selected by the excitability of the nervous system. Unconditioned and conditioned components of behaviour were tested: pain sensitivity, behaviour in the open field, level of "anxiety", passive and active defensive avoidance. Differential reactivity was shown of the rats lines to prolonged stressing, depending on the genetically determined level of the nervous system functional state. Interlinear differences in dynamics of the development of neurosis-like state were established. 相似文献
38.
J Ahlers I Cascorbi M Forêt A Gies M K?hler W Pauli E R?sick 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1991,100(1-2):111-113
1. The effects of several phenols, anilines and aliphatic alcohols on yeast plasma membrane H(+)-ATPase and purine transport system as well as on Na+, K(+)-ATPase and adenosine uptake by Chinese hamster ovary cells (CHO) were investigated. 2. In all cases an inhibition was observed, which could be correlated with the octanol/water partition coefficients of the substances tested, thus making quantitative structure-activity predictions possible. 3. The observed effects correlated well with the influence of the chemicals on cell growth. 4. The results suggest a common mechanism of toxicity by the action of hydrophobic xenobiotics on biomembranes. 相似文献
39.
Properties and partial characterization of the heat-shock factor from Tetrahymena pyriformis 总被引:2,自引:0,他引:2
M do C Avides C E Sunkel P Moradas-Ferreira C Rodrigues-Pousada 《European journal of biochemistry》1990,194(2):331-336
A heat-shock-factor-binding activity was identified in Tetrahymena pyriformis whole-cell extracts and was further purified by sequential heparin-agarose and sequence-specific oligonucleotide affinity chromatography. Tetrahymena heat-shock factor (HSF) was able to bind to the heat-shock elements (HSE) both before and after thermal stress, although heat shock altered both the HSE-binding affinity and the protein.DNA-complex mobility on polyacrylamide gels. The mobility difference was significantly reduced by treatment of the proteins with phosphatase. The HSE-binding proteins, isolated by oligonucleotide-affinity chromatography, migrated on SDS/polyacrylamide gels as a closely spaced doublet to about 70 kDa. Polypeptides with similar molecular mass were recovered from preparative band-shift gels indicating that both are components of the protein.DNA complex. 相似文献
40.
Leon Milewich Terry S. Hendricks Bettie Sue Masters Rene A. Frenkel Paul C. Mac Donald 《Archives of biochemistry and biophysics》1981,211(2):530-536
The estrogen synthetase present in human placental microsomes appears to be dependent on the cooperative interaction of the reduced cofactors NADPH and NADH for optimal activity. Using steady-state concentrations of either cofactor, it was found that while the estrogen synthetase activity followed hyperbolic saturation kinetics with NADPH (Kmapp = 14 μM), the enzyme followed sigmoidal saturation kinetics when the cofactor was NADH, with the half-maximum velocity attained at a cofactor concentration of 1.1 mm. The maximum velocity obtained with NADPH as the cofactor was greater than with corresponding concentrations of NADH. Estrogen synthetase activity in the presence of NADH was not due to NADPH contamination. NADH, in the presence of small concentrations of NADPH (0.5 to 5 μm), stimulated significantly the rate of estrogen formation from androstenedione by placental microsomes and, in addition, the enzyme saturation kinetics changed from sigmoidal to hyperbolic, thus mimicking the effect of NADPH. Estrogen synthetase activity, measured in the presence of 1 mm NADH, was stimulated in a dose-dependent manner by NADPH (Kmapp = 0.4 μM NADPH) and, when the enzyme was measured in the presence of 5 μm NADPH, the activity was stimulated in a dose-dependent manner by NADH (Kmapp = 45 μM NADH). Estrogen synthetase activity measured in the presence of NADH, without and with NADPH (1 μm) remained linear both with time of incubation for approximately 15 min and with microsomal protein concentration up to 3 mg/ml. The apparent Km of estrogen synthetase for androstenedione, when measured in the presence of NADH, was 1 μm. The synergistic interaction between NADH and NADPH in stimulating placental estrogen synthetase activity observed in vitro may, conceivably, take place in vivo in the intact placenta. 相似文献