Sequential study of the synaptonemal complex in rat (Rattus norvegicus) oocytes by light and electron microscopy

The progression of first meiotic prophase and synaptonemal complex (SC) formation in female rats, Rattus norvegicus S.D., is described through the analysis of the different stages of the first meiotic prophase, and confirms the high synchrony of the process in this species. Leptotene is a stage of very short duration and since pairing of the homologues begins very early, only a leptotene-zygotene stage can be distinguished. The progression of pairing during zygotene is asynchronous. The morphology of the SCs is similar to that described in other species. During diplotene and before desintegration of the lateral elements, desynapsis takes place.In some oocytes a double or even multiple nature of lateral elements was seen. Associations between SCs and nucleoli or nucleolar filaments are frequent. The presence of fragmented SCs can be interpreted as a technical artifact.     

Molecular characterization of a fourth isoform of the catalytic subunit of protein phosphatase 2A from Arabidopsis thaliana

We have recently reported the existence of multiple isoforms of the catalytic subunit of protein phosphatase 2A (PP2A) in Arabidopsis thaliana and the molecular cloning of cDNAs encoding three of these proteins (PP2A-1, PP2A-2, PP2A-3). The reported cDNA encoding PP2A-3 was truncated at the 5 terminus, lacking a short fragment of the N-terminal coding sequence. We have now isolated a near full-length cDNA encoding the entire PP2A-3 protein (313 residues). The clone includes 188 nucleotides of 5-untranslated region, where a 44 bp long poly(GA) track is found. We also describe the cloning of a cDNA encoding a fourth isoform of PP2A (PP2A-4). The polypeptide contains 313 residues being 98% identical to PP2A-3 and only 80% identical to both PP2A-1 and PP2A-2. The mRNA for PP2A-4 is 1.4 kb in length and, although predominantly expressed in roots, it is also found in other organs. It is concluded that in A. thaliana the isoforms of PP2A can be grouped in two extremely conserved subfamilies.     

IPG (inositolphosphate glycan) as a cellular signal for TGF-β1 modulation of chondrocyte cell cycle

The knowledge of transforming growth factor (TGF)-β receptors has greatly progressed in the recent years. TGF-β receptors type I and II have been implicated in the modulation of cell proliferation, whereas type III (betaglycan) may act as a component presenting TGF-β to its signaling receptors. In addition, four other proteins that bind TGF-β1 or TGF-β2 have been recently identified in some cell lines, three being anchored to the membrane through a glycosylphosphatidylinositol (GPI). Despite this knowledge, the molecular mechanism of signal transduction through the TGF-β receptors remain an enigma. TGF-β family does not signal via any of the classical pathways. As GPI anchors of membrane proteins have been implicated in the transduction of some hormonal effects, we investigated the putative role of GPI in signaling the TGF-β effects on the proliferation of rabbit articular chondrocytes (RAC). We previously showed that TGF-β1 increased DNA replication rate of RAC, with a recruitment of cells in G2/M followed by a subsequent mitosis wave. Here, we find that the factor causes specific GPI hydrolysis, with correlated increase of inositolphosphate glycan (IPG). This effect was specifically inhibited by antibodies that bind TGF-β1. Using [³H]-inositol labeling and Triton X-114 extraction, we demonstrate that a hydrophobic material from the membrane is cleaved by treatment of cell cultures with phosphatidylinositol specific phospholipase C (PI-PLC) or by exposure to TGF-β, supporting that a PI-anchored molecule gives rise to IPG by TGF-β-induced hydrolysis. The biological relevance of this hydrolysis was demonstrated by the enhancing effect of purified IPG on the DNA synthesis rate, which mimicked the TGF-β action. These results demonstrate that IPG could be an early messenger in the cellular signaling that mediates the effect of TGF-β on RAC growth. © 1993 Wiley-Liss, Inc.     

Androgen receptors in the rat epididymis and their hormonal control.

The concentrations of cytoplasmic receptor sites for androgens in the caput, corpus and cauda epididymidis, and the effect of ligation of the efferent ducts and testosterone treatment after bilateral castration on the concentration of receptors in the caput have been measured. Androgen receptors in the ventral prostate have been measured in the same animals for comparison. The caput has the highest concentration of receptor sites, the corpus the lowest. The ligation of the efferent ducts has no effect on this concentration which is dependent on testicular androgens. The present data do not yet allow explanation of the differential response of the different regions of the epididymis and of the other accessory glands to the administration of androgens.     

Characterization of proteoglycans synthesized by rabbit articular chondrocytes in response to transforming growth factor-beta (TGF-beta)

The effect of transforming growth factor-beta (TGF-beta, 1 ng/ml) on proteoglycan synthesis by rabbit articular chondrocytes in culture was studied in the presence of fetal bovine serum. Exposure of confluent cells for 24 h to the factor resulted in a marked increase of 35S-labeled sulfate incorporation in the newly synthesized proteoglycans (PG), as estimated by glycosaminoglycan (GAG) radioactivity (+58%). The onset was observed 6 h after addition of the factor but was significant after 12 h. TGF-beta also enhanced the uptake of [35S]sulfate by chondrocytes, but had no effect on the release of PG by these cells. The effect of TGF-beta on the distribution of PG between the medium and the cell layer was shown to be dependent on the serum concentration in the medium: the relative proportion of cell-layer associated GAG of TGF-beta-treated cells decreased with increasing concentration of fetal bovine serum. The proportion of aggregated PG, the hydrodynamic size of PG monomers and GAG chains were not modified by TGF-beta, but the relative distribution of disaccharides 6- and 4-sulfate in GAG chains was altered by the factor: the proportion of chondroitin 6-sulfate (C6S) was decreased while that of chondroitin 4-sulfate (C4S) was augmented in presence of TGF-beta, leading to a decrease of the ratio C6S/C4S (-11 to -22%, P less than 0.01). The present study indicates that TGF-beta promotes the synthesis of a modified extracellular matrix in cultured articular chondrocytes. This mechanism could be relevant to some aspects of cartilage repair in osteoarticular diseases.     

Effects of lesions in the pontine tegmentum on the sleep stages in the rat]

1. Limited coagulations of the locus coeruleus and subcoeruleus nuclei have been performed in rats and the sleep-waking cycle was continuously monitored during 9 days. The cortical and diencephalic noradrenaline content was mesured at the termination of the experiment, on the 10th post lesion day. 2. The bilateral destruction of the locus coeruleus is followed by the appearance of a uro-genital syndrome consisting of hema turia, bladder distension and penile erection. The states of sleep are disturbed during the first two days (increase of slow-wave sleep and decrease of paradoxical sleep times) and thereafter return to normal. Additionally, an hyperthermia appears during the third experimental day. The cortical and diencephalic noradrenaline content decrease to 70%. 3. The simultaneous lesion of both locus coeruleus and subcoeruleus nuclei is followed by the appearance of an aphagia adipsia syndrome in addition to the uro-genital syndrome. After these lesions, it is no long possible to find paradoxical sleep episodes in polygraphic recordings while the amount of slow wave sleep is normal. Cortical and diencephalic noradrenaline content decrease more than 50%. 4. In normal rats direct injection of 6 hydroxydopamine directly in both locus coeruleus and nuclei subcoeruleus had no discernable effects either on the behaviour or on the states of sleep. The cortical noradrenaline content decreased 30% below control values. 5. These results are consistent with but do not prove the hypothesis that part of the pontine tegmentum might play an important role in triggering paradoxical sleep episodes. The role of these regions in the regulation of internal temperature, food consumption and bladder motricity is also discussed.     

Population genetics and phylogenetics of DNA sequence variation at multiple loci within the Drosophila melanogaster species complex

Two regions of the genome, a 1-kbp portion of the zeste locus and a 1.1- kbp portion of the yolk protein 2 locus, were sequenced in six individuals from each of four species: Drosophila melanogaster, D. simulans, D. mauritiana, and D. sechellia. The species and strains were the same as those of a previous study of a 1.9-kbp region of the period locus. No evidence was found for recent balancing or directional selection or for the accumulation of selected differences between species. Yolk protein 2 has a high level of amino acid replacement variation and a low level of synonymous variation, while zeste has the opposite pattern. This contrast is consistent with information on gene function and patterns of codon bias. Polymorphism levels are consistent with a ranking of effective population sizes, from low to high, in the following order: D. sechellia, D. melanogaster, D.mauritiana, and D. simulans. The apparent species relationships are very similar to those suggested by the period locus study. In particular, D. simulans appears to be a large population that is still segregating variation that arose before the separation of D. mauritiana and D. sechellia. It is estimated that the separation of ancestral D. melanogaster from the other species occurred 2.5-3.4 Mya. The separations of D. sechellia and D. mauritiana from ancestral D. simulans appear to have occurred 0.58- 0.86 Mya, with D. mauritiana having diverged from ancestral D. simulans 0.1 Myr more recently than D. sechellia.      

<Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> inhibits <Emphasis Type="Italic">in-vitro Candida</Emphasis> biofilm development

Background  

Elucidation of the communal behavior of microbes in mixed species biofilms may have a major impact on understanding infectious diseases and for the therapeutics. Although, the structure and the properties of monospecies biofilms and their role in disease have been extensively studied during the last decade, the interactions within mixed biofilms consisting of bacteria and fungi such as Candida spp. have not been illustrated in depth. Hence, the aim of this study was to evaluate the interspecies interactions of Pseudomonas aeruginosa and six different species of Candida comprising C. albicans, C. glabrata, C. krusei, C. tropicalis, C. parapsilosis, and C. dubliniensis in dual species biofilm development.