Sex determination in<Emphasis Type="Italic"> Drosophila melanogaster</Emphasis> and<Emphasis Type="Italic"> Musca domestica</Emphasis> converges at the level of the terminal regulator<Emphasis Type="Italic"> doublesex</Emphasis>

Sex-determining cascades are supposed to have evolved in a retrograde manner from bottom to top. Wilkins 1995 hypothesis finds support from our comparative studies in Drosophila melanogaster and Musca domestica, two dipteran species that separated some 120 million years ago. The sex-determining cascades in these flies differ at the level of the primary sex-determining signal and their targets, Sxl in Drosophila and F in Musca. Here we present evidence that they converge at the level of the terminal regulator, doublesex (dsx), which conveys the selected sexual fate to the differentiation genes. The dsx homologue in Musca, Md-dsx, encodes male-specific (MdDSX^M) and female-specific (MdDSX^F) protein variants which correspond in structure to those in Drosophila. Sex-specific regulation of Md-dsx is controlled by the switch gene F via a splicing mechanism that is similar but in some relevant aspects different from that in Drosophila. MdDSX^F expression can activate the vitellogenin genes in Drosophila and Musca males, and MdDSX^M expression in Drosophila females can cause male-like pigmentation of posterior tergites, suggesting that these Musca dsx variants are conserved not only in structure but also in function. Furthermore, downregulation of Md-dsx activity in Musca by injecting dsRNA into embryos leads to intersexual differentiation of the gonads. These results strongly support a role of Md-dsx as the final regulatory gene in the sex-determining hierarchy of the housefly.Edited by D. Tautz     

Ethanol disrupts cell cycle regulation in developing rat cortex interaction with transforming growth factor beta1

Ethanol is a potent teratogenic agent that disrupts several aspects of neuronogenesis, including the proliferation rate of cortical precursors. With regard to corticogenesis, possible targets of ethanol toxicity include soluble factors, like transforming growth factor beta1 (TGFbeta1), that regulate cortical growth and cell cycle proteins that control the kinetics of the cell cycle. The effect of ethanol on normal cell proliferation and TGFbeta1-regulated cell proliferation in the developing cortex was assessed using an organotypic slice culture model. Ethanol elongated the cell cycle, possibly through a decrease in the expression of G1 cell cycle protein cyclin D1. Further, ethanol exposure antagonized the anti-proliferative action of TGFbeta1 and blocked TGFbeta1-dependent increases in cell cycle inhibitor p21. Collectively, this evidence suggests that disruption of appropriate cell cycle protein expression and inhibition of TGFbeta1 activity are potential mechanisms underlying the effect of ethanol on cortical development.     

Characteristics of Spinach Chloroplast Envelope, Thylakoid and Stroma Polypeptides as Revealed by Triton X-114 Phase Partition

Comparison of the SDS-PAGE profiles of the spinach chloroplaststroma, thylakoid and envelope membranes shows that severalpolypeptides have the same electrophoretic mobility. To simplifythese somewhat complex electrophoretic profiles and to verifywhether the polypeptides having similar electrophoretic mobilityare identical, we used Triton X-114 phase partition to obtaina separation of the polypeptides according to their relativehydrophobicity. The stroma polypeptides partitioned essentiallyin the aqueous phase. About half of the thylakoid and envelopemembrane polypeptides were exclusively recovered in either oneof the two phases. Therefore, the phase partitioning of membranepolypeptides proved to be useful, as the organic phase containedtrue intrinsic polypeptides, while the aqueous phase was composedof peripheral ones and stroma components. Particularly interestingwas the release of the RubisCO large subunit known to copurifywith the envelope membranes. Additional experimental approacheswere used (immunology, proteosynthesis in organello) to furthercharacterize proteins which had apparent ambiguous phase partitioning.Here, we show that Triton X-l 14 is an excellent tool to unmaskpolypeptides having identical electrophoretic mobility but differentbehaviour towards this detergent; its use leads to a clarificationof the polypeptide SDS-PAGE profiles of chloroplast membranes. (Received April 2, 1990; Accepted August 28, 1990)     

Recombinant bovine interferon alpha causes only a temporary prolongation of the lifespan of the corpus luteum

Abstract

A method is described for developing a sheep‐ vs. goat‐specific DNA marker using sequence characterized amplified regions (SCARs) derived from a random amplified polymorphic DNA (RAPD) marker from sheep DNA samples. A sheep 645 bp DNA fragment that was absent in goat DNA was identified by analyzing pools of sheep and goat DNA with RAPD primers. This fragment was cloned and partially sequenced to design extended, strand‐specific 24‐mer oligonucleotide primers. Each primer contained the original 10 bases of the RAPD primer and the following 14 internal bases. The pair of primers resulted in the amplification of a single band of 645 bp when used to amplify sheep DNA, and in no amplification when used to amplify goat DNA. These SCAR primers successfully amplified the equivalent of DNA from one nucleated sheep cell in a sample of 5000 nucleated goat cells. This level of sensitivity is especially desirable for research involving the detection of interspecific chimerism.     

We have got you 'covered': how the meninges control brain development

The meninges have traditionally been viewed as specialized membranes surrounding and protecting the adult brain from injury. However, there is increasing evidence that the fetal meninges play important roles during brain development. Through the release of diffusible factors, the meninges influence the proliferative and migratory behaviors of neural progenitors and neurons in the forebrain and hindbrain. Meningeal cells also secrete and organize the pial basement membrane (BM), a critical anchor point for the radially oriented fibers of neuroepithelial stem cells. With its emerging role in brain development, the potential that defects in meningeal development may underlie certain congenital brain abnormalities in humans should be considered. In this review, we will discuss what is known about assembly of the fetal meninges and review the role of meningeal-derived proteins in mouse and human brain development.     

Influence of Ozone on the Stable Carbon Isotope Composition, deltaC, of Leaves and Grain of Spring Wheat (Triticum aestivum L.)

The relative composition of stable carbon isotopes, δ¹³C, was determined in flag leaves and grain of spring wheat (Triticum aestivum L. cv Albis) grown in open-top field fumigation chambers and exposed to different O₃ levels during the growing season. The aim of the study was to establish exposure-response relationships for the radiation-weighted seasonal mean O₃ concentration and δ¹³C (relative deviation of the ¹³C/¹²C ratio) values of the two plant parts. Samples were collected at harvest in 1986, 1987, and 1988. With increasing O₃ concentration, δ¹³C values increased (became less negative) proportionally. Year to year δ¹³C differences at equivalent O₃ concentrations were small. The shift in δ¹³C caused by O₃ was more pronounced in grain than in leaves. According to models of ¹³C discrimination in C₃ plants, these results indicate increasing limitation of photosynthesis by CO₂ diffusion relative to limitation by carboxylation with increasing O₃ exposure. This conclusion is not in agreement with results from gas exchange analysis. Water use efficiency in green flag leaves tended to decrease with increasing O₃, indicating a dominating effect of O₃ on CO₂ carboxylation.     

Alteration in the acyl lipid composition of thylakoids induced by aging and its effect on thylakoid structure

The alteration in both the lipid composition and chlorophyll proteins obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of detergent solubilized thylakoids was investigated on differentially aged spinach (Spinacia oleracea L.) chloroplasts. Freshly isolated material demonstrated seven major bands upon electrophoretic fractionation. Membranes aged in vitro showed a diminution and/or a disappearance of some bands concomitant with changes in the acyl lipid composition of these membranes. The extent of these changes was influenced by the purity of the preparation. Low temperature fluorescence measurements (77K) showed that upon aging, the photochemical capacity of photosystem II decreased prior to alterations in the molecular organization of the photochemical apparatus as indicated by the energy distribution between the two photosystems.     

Changes in the binding and inhibitory properties of urea/triazine-type herbicides upon phospholipid and galactolipid depletion in the outer monolayer of thylakoid membranes

The binding characteristics and the inhibitory power of atrazine and DCMU towards uncoupled electron flow activity were studied in acyl lipid-depleted thylakoid membranes from atrazine-susceptible and-resistant biotypes of Solanum nigrum L. For this purpose, phospholipase A₂ from Vipera russelli and the lipase from Rhizopus arrhizus were used to obtain a selective lipid class (phospholipids or galactolipids) depletion which was restricted to the outer monolayer. Neither phospholipid nor galactolipid removal affected the dissociation constant and the number of binding sites of atrazine. In contrast, the dissociation constant of DCMU was increased in phospholipid-depleted thylakoid membranes but remained unchanged after galactolipid depletion. The number of DCMU binding sites decreased significantly after both lipase treatments, but only in the resistant biotype. The inhibitory effectiveness of the herbicide was either decreased or increased (to different extents) depending on the lipid class which was removed from the membrane and on the biotype considered. These results are discussed with reference to the possible conformational changes of the 32 kDa herbicide-binding polypeptide occurring after lipase treatments.Abbreviations Atrazine 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine - BSA bovine serum albumin - DCMU diuron, 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DGDG digalactosyldiacylglycerol - LRa lipase from Rhizopus arrhizus - MGDG monogalactosyldiacylglycerol - PC phosphatidylcholine - PG phosphatidylglycerol - PLA₂ phospholipase A₂ - R atrazine-resistant - S atrazinesusceptible