Estrogen-Induced Synthesis of Yolk Proteins in Roosters

Vitellogenin is the serum precursor of the yolk proteins -lipovitellin,rß-lipovitellin, and phosvitin. The precursor canbe dissociated to produce the yolk proteins only by proteolyticenzymatic action, to which it is very susceptible. Denaturationin sodium dodecyl sulfate, combined with reduction of disulfidebridges and blocking of thiols, yields a complex with a molecularweight of 200,000 to 250,000. -Lipovitellin contains three polypeptides,with molecular weights of about 135,000, 105,000, and 40,000,and rß-lipovitellin is composed of two polypeptidechains with molecular weights of 135,000 and 30,000. The 40,000subunit of -lipovitellin and both rß-lipovitellinsubunits are phosphopeptides We tested RNA isolated from the liver of estrogen-treated roostersfor mRNA activity in a cell-free reticulocyte system. The vitellogeninmRNA has a sedimentation coefficient greater than 28S and thuscontains enough information to code for a long polypeptide chain.Estrogen administration to roosters induces the appearance ofvitellogenin and a lowdensity lipoprotein, the syntheses ofwhich are not coordinated. The course of vitellogenin synthesiswas calculated from accumulation and turnover data, and it wasfound that from about 25 hr after estradiol-17rß administrationthe rate of vitellogenin synthesis increases linearly for severaldays, paralleling an increase in vitellogenin-synthesizing polysomes.Thus, we estimate a constant translation rate of about 8 aminoacids per ribosome per sec. A "memory" effect is observed when a second hormone dose isgiven some time after the vitellogenin induced by the firstdose has disappeared from the blood. After the second dose vitellogeninsynthesis is detected sooner, and its initial increase is morerapid, than after the first dose. Although the synthesis ofvitellogenin starts 3 to 4 hr after the second as well as afterthe first injection, the rate of synthesis after the first injectionincreases much more slowly during the first 15 hr than duringthe subsequent period of linear accumulation, whereas afterthe second injection the linear increase in the rate of synthesisbegins immediately after the lag period of 3 to 4 hr. The "memory"effect is undiminished even 50 days after the first hormonedose; thus, the causative factor either is very stable or issynthesized in great excess during the first stimulation. Whenthe second injection is given during the descending part ofthe turnover curve, an increase in vitellogenin synthesis isobserved within 3.5 hr. There are thus at least three different effects of estradiol;(i) the "memory" effect, which probably is due to commitmentor differentiation of vitellogenin-synthesizing cells; (ii)the effect that causes the committed cells to give full responseafter the 3- to 4-hr lag period; and (iii) the effect that causesthe immediate response. To explain these results we suggestthat committed cells can synthesize vitellogenin mRNA only duringa certain period of the cell cycle.     

Specific stimulation of ribosomal RNA synthesis in E. coli by a protein factor

Summary Ribosomal RNA synthesis in a purified system is stimulated by a crude protein fraction prepared from E. coli. The positive effector which is not associated with RNA polymerase, nor is the sigma factor, increases the initiation frequency on a rRNA operon. The additional rRNA synthesis is inhibited by ppGpp to the same extent as the basal one.The evidence presented points to the existence of a positive control element for rRNA synthesis, which activity depends upon the physiological state of the cell.     

Inhibitor effect of products of metabolism on growth of Clostridium acetobutylicum

Summary The growth of Clostridium acetobutylicum was studied by three ways. 1. In batch fermentation, referred to as the control. 2. Fermentation in dialysis which permits elimination of all the products of metabolism: acids, solvents and gases. In order to test the toxic effect of acids, cultures were dialysed against 2 g l^-1 acetic acid or 2 g l^-1 butyric acid. 3. To test the toxic effect of gases only, batch fermentations were carried out under vacuum or with a continuous bubbling of nitrogen. The first method resulted in a productivity of 1.2 g l^-1 dry cell weight and a maximal specific growth rate of 0.2 h^-1; the second, 20 g l^-1 dry cell weight and a constant maximum specific growth rate (μ=0.39 h^-1) between 14 and 20 h. The toxic effect of acetic and butyric acids, starts at low concentrations and about 4 g l^-1 of both acids results in a decrease of 50% of maximal specific growth rate. The third series of experiments showed that gases produced by the bacteria have a high toxic effect, comparable to that of 5 g l^-1 of acid.     

Characterization of a polymorphism in the 3′ part of the chicken vitellogenin gene

Summary An allele giving rise to a polymorphism within the 3 part of the chicken vitellogenin gene was cloned, sequenced, and compared to the previously cloned allele. The polymorphism is formed by a perfect copy of 343 bp from intron 32 in tandem array with a perfect copy of 244 bp from intron 33; this 587-bp element is inserted in a head-to-tail arrangement in intron 33. We propose a mechanism in which an unequal crossing-over resulted in a vitellogenin gene with two exons 33, one of which was subsequently deleted. Thus, intron 33 was enlarged by the tandem repeats without affecting the protein-encoding sequence of the gene. At the boundaries of the repeated elements, two short direct repeats are found that resemble the recombination signals of immunoglobulin genes. They may have had a key role in the formation of the new allele.     

Nebivolol enhances the effect of alendronate against methylprednisolone‐induced osteoporosis in rats

This study aimed to assess the possible modulatory effect of nebivolol against methylprednisolone‐induced osteoporosis in rats. Weekly administration of methylprednisolone (7 mg/kg), for six consecutive weeks caused significant increases in serum calcium, bone malondialdehyde, and hydroxyproline as well as serum alkaline phosphatase, but it significantly decreased serum phosphorous and osteocalcin, bone reduced glutathione, and nitric oxide (NO) as well as bone antioxidant enzymes activities compared with the control group. The results were confirmed by histopathological findings of femur bone. On the other hand, administration of alendronate (1 mg/kg) with nebivolol (1.5 mg/kg) orally and daily for seven consecutive days after methylprednisolone treatment caused marked mitigation in the above‐mentioned parameters compared with methylprednisolone group. In conclusion, nebivolol proved to enhance the effect of alendronate in modulating methylprednisolone osteoporotic effect, which might be attributed to its release of NO together with its profound reducing capability in the oxidative cascade of bone tissue.     

The effect of methylation on DNA replication in Salmonella enterica serovar typhimurium

The DNA adenine methylase of Salmonella typhimurium methylates adenine at GATC sequences. Strains deficient in this methylase are not well transformed by methylated plasmids, but unmethylated plasmids transform them at high frequencies. Hemimethylated daughter molecules accumulate after the transformation of dam(-) strains with fully methylated plasmids, suggesting that hemimethylation prevents DNA replication. It will also be shown that plasmids isolated from dam(-) bacteria are hemimethylated by restriction enzyme digestion. These results may explain why newly formed daughter molecules are not substrates for immediate reinitiation of DNA replication in dam(-) bacteria.     

Description of Lamellodiscus confusus n. sp, (Monogenea: Diplectanidae), parasite of Sarpa salpa (Teleostei: Sparidae)

Lamellodiscus confusus n. sp., a diplectanid gill parasite of Sarpa salpa Linnaeus, 1758 (Sparidae) from the coast of Algeria, is described. This monogenean has been previously reported in Sarpa salpa, by various authors, under the name L. ignoratus. L. confusus n. sp. is included (among other Lamellodiscus of Mediterranean sparids) in the "ignoratus" sub-group (Amine & Euzet, 2005). L. confusus n. sp. can be distinguished from L. ignoratus by the shape and size of the haptoral ventral bar and the male copulatory organ. For comparison, illustrations of the ventral bar and the male copulatory organ of all Mediterranean species of the "ignoratus" sub-group are provided. The question of the host specificity of L. ignoratus is discussed.     

The high-resolution NMR structure of the R21A Spc-SH3:P41 complex: Understanding the determinants of binding affinity by comparison with Abl-SH3

Background  

SH3 domains are small protein modules of 60–85 amino acids that bind to short proline-rich sequences with moderate-to-low affinity and specificity. Interactions with SH3 domains play a crucial role in regulation of many cellular processes (some are related to cancer and AIDS) and have thus been interesting targets in drug design. The decapeptide APSYSPPPPP (p41) binds with relatively high affinity to the SH3 domain of the Abl tyrosine kinase (Abl-SH3), while it has a 100 times lower affinity for the α-spectrin SH3 domain (Spc-SH3).     

Protein Disulfide Isomerase Is Required for Platelet-derived Growth Factor-induced Vascular Smooth Muscle Cell Migration, Nox1 NADPH Oxidase Expression, and RhoGTPase Activation

Vascular Smooth Muscle Cell (VSMC) migration into vessel neointima is a therapeutic target for atherosclerosis and postinjury restenosis. Nox1 NADPH oxidase-derived oxidants synergize with growth factors to support VSMC migration. We previously described the interaction between NADPH oxidases and the endoplasmic reticulum redox chaperone protein disulfide isomerase (PDI) in many cell types. However, physiological implications, as well as mechanisms of such association, are yet unclear. We show here that platelet-derived growth factor (PDGF) promoted subcellular redistribution of PDI concomitant to Nox1-dependent reactive oxygen species production and that siRNA-mediated PDI silencing inhibited such reactive oxygen species production, while nearly totally suppressing the increase in Nox1 expression, with no change in Nox4. Furthermore, PDI silencing inhibited PDGF-induced VSMC migration assessed by distinct methods, whereas PDI overexpression increased spontaneous basal VSMC migration. To address possible mechanisms of PDI effects, we searched for PDI interactome by systems biology analysis of physical protein-protein interaction networks, which indicated convergence with small GTPases and their regulator RhoGDI. PDI silencing decreased PDGF-induced Rac1 and RhoA activities, without changing their expression. PDI co-immunoprecipitated with RhoGDI at base line, whereas such association was decreased after PDGF. Also, PDI co-immunoprecipitated with Rac1 and RhoA in a PDGF-independent way and displayed detectable spots of perinuclear co-localization with Rac1 and RhoGDI. Moreover, PDI silencing promoted strong cytoskeletal changes: disorganization of stress fibers, decreased number of focal adhesions, and reduced number of RhoGDI-containing vesicular recycling adhesion structures. Overall, these data suggest that PDI is required to support Nox1/redox and GTPase-dependent VSMC migration.