L’Equipement chromosomique du spermatozoïde

Cytogenetics of human sperm chromosomes has been developped by few laboratories during the last decade, in order to investigate dysfuncitons of meiosis in normal men and in carriers of chromosomal abnormalities. On the basis of pooled data, it can be established that normal men produce almost 10% of abnormal spermatozoa, including a majority of structural aberrations (6.5%). Frequency of hyperhaploïdies, resulting from chromosome malsegregations, seems to be equally distributed among all chromosome groups. A study of in vivo recently irradiated patients demonstrates that despite a high incidence of multiple rearrangements, the sperm fertilizing ability is not reduced. Segregation of additional chromosomes can also be studied in fertile carriers; such as study has demonstrated that, in a mosaic patient, 47 XXY germ cells are able to complete meiosis. Finally the major application of the technique consists in direct segregation analysis of structural chromosome rearrangements. The sperm of such carriers exhibits a higher proportion of unbalanced spermatozoa than generally expected in offsprings.     

Mouse oocyte maturation is affected by lithium via the polyphosphoinositide metabolism and the microtubule network

The incubation of mechanically denuded mouse oocytes in medium containing LiCl delayed both germinal vesicle breakdown (GVBD) and polar body extrusion in a dose-dependent and reversible manner. When myo-inositol alone was added to the culture medium, we observed that it accelerated GVBD and increased the rate of polar body extrusion, whereas, when combined with LiCl, the normal timing of GVBD was recovered. In the same way, when inositol trisphosphate (InsP₃) was microinjected into the ooplasma, we observed an important improvement of the rate of GVBD, as compared to control oocytes, and prevention of lithium inhibition. However, neither myo-inositol nor InsP₃ were able to rescue totally the oocytes from the negative effect of lithium on polar body extrusion. Moreover, lithium induced some important changes in microtubule and chromosome organizations. Before extrusion of the first polar body, the reduction of the spindle size or the appearance of short individualized chromosomes dispersed around a large aster of microtubules were often observed, whereas, after polar body extrusion, the spindle appeared smaller and chromosomes were often trapped in the midbody. Thus lithium affects mouse oocyte maturation at two different levels: GVBD and polar body extrusion. Whereas the former seems to be affected via polyphosphoinositide turnover, the latter is InsP₃-independent and seems to be influenced negatively via underdevelopment of microtubular structures. © 1994 Wiley-Liss, Inc.     

The Value of a hoard: not just energy

We present a stochastic dynamic programming model of the contributionof stored food to winter survival. Using the acorn woodpecker(Melanerpes formtcivorus) as a model organism, we demonstratethat a hoard of small energetic value can impart considerableimprovement in the probability of surviving the winter and soimprove fitness. With this model we hope to resolve Koenig andMumme's paradox, that acorn woodpeckers expend much time andeffort to create and maintain hoards of acorns which provideno more that 16% of their energetic needs over the period inwhich they are used. We further demonstrate that the contributionof hoarded acorns to survival depends on the variability inforaging outcome, independently of the energetic value of thehoard in absolute terms. We point out that the results applyin principle to all hoarding animals and suggest a number offurther elaborations of the model.     

The Presence of (+)-S-Adenosyl-l-Methionine in the Rat Brain and Its Lack of Effect on Phenylethanolamine N-Methyltransferase Activity

Abstract: (+)-S-Adenosyl- l -methionine [(+)-SAM] was isolated from rat brain and was quantified by HPLC followed by UV spectrophotometric measurements and by ¹H-NMR. Its estimated ratio in brain is 3% of total SAM. Because of its commercial unavailability, (+)-SAM was also prepared from chemically synthesized SAM by separation of the two diastereoisomers on a preparative reverse-phase Nucleosil C8 column. The (+) diastereoisomer thus obtained was then assayed in vitro both as an inhibitor and a substrate of phenylethanolamine N -methyltransferase. Enzymatic activity was measured by HPLC analysis. It was shown that (+)-SAM has no effect on phenylethanolamine N -methyltransferase activity; therefore, it is unlikely that (+)-SAM plays any possible role in regulation of adrenaline synthesis in the brain.     

Casein kinase II in signal transduction and cell cycle regulation

Molecular and Cellular Biochemistry - Casein kinase II is a protein serine/threonine kinase that is ubiquitously distributed in eukaryotes. Molecular cloning studies and protein sequence analysis...     

Polarized distribution of γ interferon-stimulated MHC antigens and transferrin receptors in a clonal cell line isolated from Fisher rat thyroid (FRT cells)

Summary The fine structure of single identified muscle fibers and their nerve terminals in the limb closer muscle of the shore crab Eriphia spinifrons was examined, using a previous classification based on histochemical evidence which recognizes a slow (Type-I) fiber and three fast (Type-II, Type-III, Type-IV) fibers. All four fiber types have a fine structure characteristic of crustacean slow muscle, with 10–12 thin filaments surrounding each thick filament and sarcomere lengths of 6–13 m. Type-IV fibers have sarcomere lengths of 6 m while the other three types have substantially longer sarcomeres (10–13 m). Structural features of nerve terminals revealed excitatory innervation in all four fiber types but inhibitory innervation in Type-I, Type-II, and Type-III fibers only. Thus fibers with longer sarcomeres receive the inhibitor axon but those with shorter sarcomeres do not. Amongst the former, synaptic contact from an inhibitory nerve terminal onto an excitatory one, denoting presynaptic inhibition, was seen in Type-I and Type-II fibers but not in Type-III and Type-IV fibers. Inhibitory innervation of the walking leg closer muscle is therefore highly differentiated: some fibers lack inhibitory nerve terminals, some possess postsynaptic inhibition, and some possess both postsynaptic and presynaptic inhibition.     

The IS4 family of insertion sequences: evidence for a conserved transposase motif

The eight IS 231 variants characterized so far (IS 231 A-F, V and W) display similar transposases with an overall 40% identity. Comparison with all the proka-ryotic transposable elements sequenced so far revealed that the IS231 transposases share two conserved regions with those of 35 other insertion sequences of wide origins. These insertion sequences, defining the IS4 family, have a common bipartite organization of their ends and are divided into two similarity groups. Interestingly, the transposase domains conserved within this family display similarities with the well known integrase domain shared by transposases of the IS3 and IS15 families, and integrases of retroelements. This domain is also found in IS30- related elements and Tn7 TnsB protein. Amino acid residues conserved throughout all these prokaryotic and eukaryotic mobile genetic elements define a major transposase/integrase motif, likely to play an important role in the transposition process.     

Organization of the genes necessary for hydrogenase expression in Rhodobacter capsulatus. Sequence analysis and identification of two hyp regulatory mutants

A 25kbp DNA fragment from the chromosome of Rhodobacter capsulatus B10 carrying hydrogenase (hup) determinants was completely sequenced. Coding regions corresponding to 20 open reading frames were identified. The R. capsulatus hydrogenase-specific gene (hup and hyp) products bear significant structural identity to hydrogenase gene products from Escherichia coli (13), from Rhizobium liguminosarum (16), from Azotobacter vinelandii (10) and from Alcaligenes eutrophus (11). The sequential arrangement of the R. capsulatus genes is: hupR2-hupU-hypF -hupS-hupL-hupM-hupD -hupF -hupG -hupH -huoJ -hupK -hypA-hypB-hupR1-hypC -hypD -hypE -ORF19 -ORF20 , all contiguous and transcribed from the same DNA strand. The last two potential genes do not encode products that are related to identified hydrogenase-specific gene products in other species. The sequence of the 12 R. capsulatus genes underlined above is presented. The mutation site in two of the Hup^? mutants used in this study, RS13 and RCC12, was identified in the hypF gene (deletion of one G) and in the hypD qene (deletion of 54 bp), respectively. The hypF gene product shares 45% identity with the product of hydA from E. coli and the product of hypF from R. leguminosarum. Those products present at their N-terminus a Cys arrangement typical of zinc-finger proteins. The G deletion in the C-terminal region of hypF in the RS13 mutant     

Synthesis and evaluation of the antidepressant activity of the enantiomers of bupropion

The synthesis of the enantiomers of bupropion, (rac)-2-tert-butylamino-3′-chloropropiophenone 1 (Wellbutrin®) is described. The enantiomers were compared with the racemate in both the tetrabenazine-induced sedation model and the inhibition of uptake of biogenic amine assay. No significant differences were found in their potencies to reverse tetrabenazine-induced sedation in mice or in their IC₅₀ values as inhibitors of biogenic amine uptake into nerve endings obtained from mouse brain. © 1993 Wiley-Liss, Inc.