Effect of tubulozole, a new synthetic microtubule inhibitor, on the induction of casein gene expression by prolactin

Colchicine and related drugs are known to inhibit milk secretion. They are also able to prevent stimulation of casein and DNA synthesis by prolactin in the mammary gland. The present report reports data obtained with tubulozole, a new antimitotic drug. Tubulozole C added to culture medium of isolated rabbit epithelial mammary cells strongly inhibited their multiplication. Simultaneously, at a concentration of 1 microM, it prevented almost completely the induction of beta-casein mRNA. Induced cells were rapidly deinduced by addition of the drug to the medium. A similar inhibition was observed when the induction was obtained with prolactin alone or with its two stimulators insulin and glucocorticoids. Tubulozole T, an isomer of tubulozole C which is known to be ineffective in disrupting microtubules, did not alter prolactin actions. These data and those obtained with other tubulin-binding drugs strongly suggest that the integrity of microtubules is required for prolactin to deliver its message to the mammary cell.     

Pyridoxal 5'phosphate binding site of Escherichia coli beta cystathionase and cystathionine gamma synthase comparison of their sequences

The phosphopyridoxyl peptides of beta cystathionase and cystathionine gamma synthase of Escherichia Coli were identified after reduction, carboxymethylation and proteolysis of the holoenzymes. Their comparison with those obtained from rat liver gamma cystathionase (Fearon, C.W., Rodkey, J.A. and Abeles R.H. 1982. Biochemistry 21 3790-3794.) showed a high degree of homology between the three PLP binding sites with the presence of the tripeptide sequence: Thr-Lys(Pxy)-Tyr in their structure. This homology suggests that these enzymes of methionine metabolism have probably the same origin.     

Gene amplification at a locus encoding a putative Na+/H+ antiporter confers sodium and lithium tolerance in fission yeast.

We have identified a new locus, sodium 2 (sod2) based on selection for increased LiCl tolerance in fission yeast, Schizosaccharomyces pombe. Tolerant strains have enhanced pH-dependent Na+ export capacity and sodium transport experiments suggest that the gene encodes an Na+/H+ antiport. The predicted sod2 gene product can be placed in the broad class of transporters which possess 12 hydrophobic transmembrane domains. The protein shows some sequence similarity to the human and bacterial Na+/H+ antiporters. Overexpression of sod2 increased Na+ export capacity and conferred sodium tolerance. Osmotolerance was not affected and sod2 cells were unaffected for growth in K+. In a sod2 disruption strain cells were incapable of exporting sodium. They were hypersensitive to Na+ or Li+ and could not grow under conditions that approximate pH7. The sod2 gene amplification could be selected stepwise and the degree of such amplification correlated with the level of Na+ or Li+ tolerance.     

Brain somatostatin receptors in spontaneously hypertensive rats: an autoradiographic study.

The apparent densities of brain somatostatin (SRIF) receptor sites were compared in adult spontaneously hypertensive rats (SH) and their normotensive genetic counterparts (Wistar-Kyoto; WKY) using quantitative receptor autoradiography. Globally, the distribution of brain [125I][Tyr0, D-Trp8]SRIF14 binding sites was very similar in both strains. However, apparent densities of specific labeling were either higher (subfornical organ, 3.2 x; locus coeruleus, 1.9 x; lateroanterior hypothalamic nucleus, 1.3 x) or lower (basolateral amygdaloid nucleus, 0.8 x; spinal trigeminal sensory nucleus, 0.6 x) in SH than WKY rats in areas especially relevant to CNS cardiovascular integration. This provides further evidence for the possible involvement of brain SRIF neurons in cardiovascular regulation.     

Nucleic acid hybridisation with a probe specific for 3 aminoglycoside acetyltransferase type IV: A survey of resistance to apramycin and gentamicin in animal strains of Escherichia coli

Abstract Resistance to apramycin due to production of a 3-aminoglycoside acetyltransferase type IV (AAC(3)IV) has recently been detected among Gram-negative bacteria isolated in France from bovine clinical samples. 24 apramycin-resistant Escherichia coli strains isolated over the country, and epidemiologically unrelated, were studied by colony hybridization using an intragenic probe specific for AAC(3)IV. The results obtained indicated that the structural gene for the acetyltransferase was present in all the isolates tested and in the corresponding apramycin-resistant transconjugants. This observation demonstrates that resistance to apramycin by acetylation of the antibiotic has spread very rapidly in bovine Gram-negative bacteria.     

Kinetic studies of aminoglycoside acetyltransferase and phosphotransferase from Staphylococcus aureus RPAL. Relationship between the two activities

In the Staphylococcus aureus strain harbouring the plasmid RPAL, the resistance to aminoglycoside antibiotics results from two inactivating reactions catalyzed by a 6'-N-aminoglycoside acetyltransferase and a 2"-O-amino-glycoside phosphotransferase. These enzymes are copurified with a constant ratio between the two activities, the purification process consisting in affinity chromatography, native electrophoresis and gel exclusion chromatography. The kinetic mechanisms of each activity have been determined from studies of initial velocities, as well as product and dead-end inhibitions. Both activities follow a random rapid equilibrium mechanism. The substrates and cofactors of one reaction have been tested as effectors of the other reaction. No interaction between the two activities has been observed. However, the GTP cofactor of phosphotransferase protects, at weak concentrations, the acetyltransferase against thermal inactivation, which suggests that the two activities may be associated.     

Effect of mifepristone (RU 486) on concentrations of prostaglandin E-2 binding sites in the rat endometrium

Progesterone implants in ovariectomized rats increased endometrial concentrations of PGE-2 receptors. The increase was completely inhibited by simultaneous daily injection (7.5 mg/kg) of mifepristone (RU 486). A single injection of mifepristone on the morning of Day 1 of pseudopregnancy (day of oestrus) decreased the amount of PGE-2 receptors found in the endometrium on Day 5 by 64%. This inhibitory effect probably resulted from the antiprogesterone activity of this compound since it was not counteracted by simultaneous treatment with dexamethasone, shown to reverse totally the antiglucocorticoid action of mifepristone. The inhibition by mifepristone lasted only for 1 day; endometrial PGE-2 receptor levels on Day 6 of pseudopregnancy returned to the high values present in controls. Under these conditions, administration of the mifepristone did not affect the plasma oestradiol and progesterone concentrations during the 1st week of pseudopregnancy. The administration of mifepristone on Days 2 and 3 of pseudopregnancy kept the endometrial PGE-2 receptor levels low, even by 4 days after the end of treatment. We therefore concluded that, in the rat, progesterone priming leading to uterine receptivity can be delayed, at least by 1 day. In contrast, interruption of the progesterone action for a longer period later during the early pseudopregnant period resulted in an altered subsequent evolution of the endometrium, in terms of acquisition of the PGE-2 binding sites.     

Improving protein extraction yield in reversed micellar systems through surface charge engineering

The mechanism of extraction of rat cytochrome b(5) from water into a sodium dioctylsulfosuccinate (AOT) micellar organic phase was studied using protein engineering of surface charged residues. The extraction behavior of native cytochrome b(5) and modified proteins with substitutions of the type glutamic acid --> lysine at positions 44 (E44K), 56 (E56K), and 92 (E92K), was studied as a function of pH. The results indicate that an important mechanism of extraction is an electrostatic interaction of this protein with the negatively charged surfactant. We demonstrate that it is possible to improve extraction by engineering the protein surface charge, increasing the driving force responsible for the protein transfer to the micellar phase. (c) 1994 John Wiley & Sons, Inc.     

Heterogeneity of twoBeauveria bassiana strains revealed by biochemical tests,protein profiles and bio-assays ofLeptinotarsa decemlineata (Col.: Chrysomelidae) andColeomegilla macultata lengi (Col.: Coccinellidae) larvae

Biochemical profiles on API Rapid CH^* strips and protein profiles on polyacrylamide gels in the presence of sodium dodecyl sulfate were used to distinguish two strains of the entomopathogenic fungusBeauveria bassiana (Balsamo) Vuillemin, ARSEF 2991 and ATCC 44860. Next, the toxicity of these two strains was determined at concentrations of 10², 10⁴, 10⁶ and 10⁸ blastospores/ml on larvae of the Colorado potato beetleLeptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) and of its predator, the spotted ladybird beetle,Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Both strains were highly toxic toL. decemlineata larvae. However, the two strains exhibited different levels of toxicity forC. maculata larvae: ARSEF 2991 was toxic, whereas ATCC 44860 caused little coccinellid larval mortality.

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Résumé Les profils biochimiques sur galeries API Rapid CH^* et les profils protéiques sur gels de polyacrylamide ont été utilisés pour distinguer deux souches du champignon entomopathogèneBeauveria bassiana (Balsamo) Vuillemin. La toxicité de ces deux souches a été déterminée à des concentrations de 10², 10⁴, 10⁶ et 10⁸ blastospores/ml sur des larves du doryphore,Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) et de la coccinelle maculéeColeomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae). Les deux souches deB. bassiana se sont avérées actives à l'égard des larves deL. decemlineata. Toutefois la souche ARSEF 2991 s'est avérée pathogène pour les larves deC. maculata, alors que la souche ATCC 44860 a provoqué une faible mortalité des larves.

     

The Presence and Role of Transmembrane Transforming Growth Factor-α in Cultures of Rat Liver Epithelial Cells

We assessed the presence and the role of membrane TGF-α in two rat liver epithelial cell lines, either parental or transfected with c-fos proto-oncogene. c-fos overexpressing cells had more TGF-α-like activity in their membranes. When TGF-α was removed by elastase or neutralized, the growth rates of both cell lines were markedly reduced, but to a higher extent for parental cells. If membrane TGF-α seemed to play a key contribution in normal cell growth, both cell lines were unable to react to the addition of soluble TGF-α, showing that these two forms of growth factors are not equivalent.