Plasma melatonin profiles of Romney Marsh sheep in natural photoperiod and in acutely extended darkness.

Plasma melatonin was measured at the summer and winter solstices and the autumn and spring equinoxes in Romney Marsh sheep held under natural conditions in South Australia (35 degrees S). The amount of melatonin detected was generally related to the extent of natural darkness, though the melatonin onset was particularly delayed after dusk in winter compared with other seasons. The duration of detectable melatonin was shorter in summer than at any other season. After each initial 24 h sampling, the sheep were resampled for a further 24 h in acutely extended darkness to mark the phase and duration of suprachiasmatic nuclei activity which is believed to be the source of the melatonin signal. The onset of high plasma melatonin was earlier than the time of natural sunset in spring and summer, but not different from the time of natural sunset in autumn and winter. The offset of high plasma melatonin was later than the time of natural sunrise at all times of year and particularly so in summer. Under the extended dark conditions, the duration of detectable melatonin was longer than that under natural photoperiod at all seasons of the year and the duration of melatonin was again shorter in summer than winter. If melatonin measurements under the conditions of extended darkness do reflect the phase and duration of suprachiasmatic nuclei function then the natural light of the photoperiod can, particularly during long photoperiod conditions, mask the expression of the pacemaker. The findings may have implications for the timing of the breeding season in Romney Marsh sheep.     

Devant une OAT idiopathique: Traitement ou assistance médicale à la procréation?

Because poor success obtained with medical treatments in oligo asthenoterato-spermia (OATS) various assisted reproductive techniques (ART) have been successively proposed in these cases. Intra-uterine insemination (IUI) was the first technique to be used, and remains an interesting technique if the indication is correct: abnormal post coital test and semen characteristics no deeply altered; practically: not less than 250.000, or better 500.000 motile sperm after washing and selection of male gametes. Most pregnancies occur during the 3 or 4 first cycles, under ovarian stimulation. In vitro fertilization (IVF) was early proposed in male sterility's, since this system allows to by pass the steps of sperm migration within the female genital tract. The most important study published until now is due to FIVNAT (1995), and concerns 1218 IVF performed with semen characteristics below 500.000 motile and morphologically normal sperm per ml. Conclusions confirm previous data: compared to female indications, cleavage rates and transfer rates per transfer are equivalent. Rates of miscarriages and birth anomalies were not different. This the main difficulty consists in obtaining embryos. Chances of success were logically correlated to semen characteristics; the most discriminant factor was represented by the initial sperm concentration, with a cut-off value equal to 5 millions/ml. Conventional IVF is not indicated in cases of severe alterations of semen characteristics and/or functional sperm disturbances. Various techniques so-called “assisted micro-fertilization techniques” were proposed in order to by pass the different barriers surrounding the oocyte, but one indeed highly superior to all the others: the intracytoplasmic sperm injection (ICSI). Van Steirteghem et al. have recently reported data concerning 2820 ICSI: the fertilization rate was equal to 70%, the proportion of transfers was 91%, with a pregnancy rate equal to 34%. There was to correlation with semen characteristics. The rate of malformations was 2,7% not different of that observed after either natural conception or IVF. Nevertheless, this highly successful technique raises some ethical questions: for example, some abnormal genes, involved in spermatogenesis regulation or not, have not the ability to be transmitted to the next generations.     

Cloning and characterization of chromosomally encoded cephalosporinase gene of Enterobacter cloacae

The cephalosporinase gene, cpa, which codes for an inducible class I chromosomal beta-lactamase in Enterobacter cloacae was cloned on a fragment of 6.05 kilobase pairs inserted into plasmid pACYC184 and transferred into Escherichia coli HB101 recipient cells. The constructed hybrid plasmid, designated pGGQ101, carried a genomic fragment which retained its parental inducibility characteristics, although its expression level in transformed E. coli cells fell to 40-65% of its initial level in E. cloacae. The localization of the cpa gene on pGGQ101 plasmid was determined by Bal31 exonuclease deletion mapping and further confirmed by subcloning HindIII-AvaI restriction fragment on pMB9 plasmid vector. Labeling with [35S]methionine of pGGQ101 specified proteins in a minicell system showed that six or seven proteins are encoded by the insert. Two proteins with apparent molecular mass of 42 000 and 39 500 daltons, respectively, most probably represent the premature and mature cephalosporinase forms.     

The C system of cattle blood groups. 1. Additional factors in the system

Four additional cattle blood group antigenic factors, provisionally termed Fl, F6, F10 and F15, were shown to belong to the C system. Factor Fl appears to be a linear subtype of C"(initially designated F2, or P1B1). It is suggested that future international nomenclature should adopt C", and C"₂ in place of Fl and C . No phenogroup was found to include C" together with C₂ or C₁, but a few phenogroups lack the three factors. Thus C₁, C₂ and C"do not form a closed system within the C system as concluded by Duniec et al. (1973). The effectiveness of the additional factors to uncover the genetic variability of the C system, and to translate phenotypes into genotypes is exemplified in the Charolais breed.     

Murexide bleaching: a new direct assay method for characterizing reactive oxygen species

The murexide (5,5'-nitrilodibarbituric acid, monoammonium salt) is an efficient scavenger for superoxide and hydroxyl radicals. When exposed to oxygen radicals, murexide is converted to a colorless alloxan derivative and its absorbance at 520 nm decreases in proportion to the radicals produced. It is used to detect these reactive oxygen species in biochemical systems such as acetaldehyde oxidation by xanthine oxidase and the respiratory burst of polymorphonuclear leukocytes induced by phorbol 12-myristate, 13-acetate. The method was sensitive enough to allow direct monitoring of the production of superoxides from 10(6) phorbol 12-myristate, 13-acetate polymorphonuclear leukocyte-stimulated cells. Moreover, murexide bleaching is inhibited in the presence of radical scavengers, allowing a comparison of their scavenging activities.     

Comparison of electrophoretic distribution patterns of ribosomal RNA gene restriction fragments and of ribosomal subunit proteins of Lactococci, Streptococci, and Pediococci.

Comparison of electrophoretic distribution patterns of ribosomal RNA gene restriction fragments and of ribosomal subunit proteins are equally effective procedures for detecting differences and similarities in the Lactococci, Streptococci and Pediococci examined. Electrophoretic distribution patterns of ribosomal subunit proteins may be a useful tool in taxonomic studies.