Studies of three Amerindian populations using nuclear DNA polymorphisms.

Three Amerindian populations, two from Rond?nia, Brazil (Karitiana and Rond?nia Suruí), and one from Campeche, Mexico (Mayan), were typed for up to 30 nuclear restriction fragment length polymorphisms (RFLPs). Heterozygosities, both observed and expected, were compared with those of Europeans. Average heterozygosity is reduced among these Amerindians (relative to that of Europeans) by 7.0% (Mayan) to 27.1% (Karitiana). This amount of heterozygosity in the nuclear DNA is nevertheless high enough that it is unlikely that there was a severe or prolonged bottleneck.     

Le ionophore A23187

The acrosomic status of spermatozoa prepared for IVF has been evaluated by means of immunofluorescence test from Fenichel and Hsi using calcium A 23187 ionophore as inductor of acrosome reaction (AR). The spontaneous AR remains slight, even after 6 hour-incubation in Menezo B2 (6,8+2,7%). The response to ionophore, moderate before (11,2+9%), frankly increases after a 6h-capacitation (28,9+8,3%) in a group of 25 IVF couples (tubal indication, normal semen, positive fertilization). Nevertheless, it remains slight or null in 4 cases of unexplained repeated failure of fertilization. The response to ionophore A 23187 allows to explore the kinetics of capacitation of spermatozoa and their ability to perform AR. Its significance in terms of fecondance remains to be precised.     

Phycobilins of cryptophycean algae. Occurrence of dihydrobiliverdin and mesobiliverdin in cryptomonad biliproteins.

Structures of the open-chain tetrapyrrole (bilin) prosthetic groups of the cryptophycean biliproteins phycocyanin 645 (Cr-PC 645; from strain UW374), phycoerythrin 566 (Cr-PE 566; from strain Bermani) and phycoerythrin 545 (Cr-PE 545; from Proteomonas sulcata Hill & Wetherbee) were examined by absorption, 1H NMR spectroscopy, and mass spectrometry. These biliproteins carry the following covalently attached bilins: Cr-PC 645 (alpha subunit) has one mesobiliverdin, (beta subunit), two phycocyanobilins and a doubly linked 15,16-dihydrobiliverdin; Cr-PC 566 (alpha), bilin 584, (beta), phycoerythrobilin and two bilin 584 chromophores (Wedemayer, G.J., Wemmer, D.E., and Glazer, A.N. (1991) J. Biol. Chem. 266, 4731-4741); Cr-PE 545 (alpha) has one 15,16-dihydrobiliverdin and (beta), only phycoerythrobilins. This is the first report of naturally occurring biliproteins carrying either 15,16-dihydrobiliverdin or mesobiliverdin chromophores. Native cryptomonad phycobiliproteins have been classified on the basis of the position of their long wavelength absorption maxima. However, comparison of the bilins of Cr-PE 566 from strain Bermani with those of Cr-PE 566 of strain CBD shows that the two proteins carry different bilins on the alpha subunit. Consequently, the identity of the bilin prosthetic groups on cryptophycean phycobiliproteins cannot be unambiguously inferred from simple inspection of the visible absorption spectra.     

A review of methods for determining dietary range in adult parasitoids

Despite the potential importance of adult nutrition in the ecology of parasitoids, information on the range of natural foods they exploit is confined to a relatively small number of species. We provide some simple guidelines for determining dietary range in adult parasitoids, both to facilitate and to encourage further research into this aspect of parasitoid biology.      

Transient expression of a p58 protein kinase cDNA enhances mammalian glycosyltransferase activity

The effect of expression of a p58 protein kinase on mammalian beta-1,4 galactosyltransferase enzyme activity was examined in vitro and in vivo. We found that p58 protein kinase expression enhanced galactosyltransferase enzyme activity approximately three-fold in vivo when compared to reporter gene activity. Galactosyltransferase enzyme activity was also substantially reduced in vitro when dephosphorylated, or when p58 specific antibodies were used to inhibit kinase activity. These results suggest that galactosyltransferase activity is influenced by phosphorylation, and that the p58 protein kinase may mediate this effect.     

The genetic defect in multiple endocrine neoplasia type 2A maps next to the centromere of chromosome 10

Multiple endocrine neoplasia type 2A (MEN2A) is a rare cancer syndrome that is inherited in an apparently autosomal dominant fashion. Previous linkage studies had assigned the MEN2A locus to chromosome 10 in the pericentromeric region. We recently have described several new easily scorable RFLPs for the chromosome 10-specific alpha satellite DNA (the D10Z1) locus that is known, on the basis of previous in situ hybridization experiments, to lie at the centromere. We report here tight linkage between MEN2A and D10Z1, as demonstrated by a maximum lod score of 12.02 at the recombination frequency of zero (1-lod-unit support interval 0-4 cM), indicating that the genetic defect in MEN2A lies in the immediate vicinity of the centromere. By means of a set of ordered polymorphic DNA markers from the pericentromeric region, multipoint as well as pairwise linkage analyses place the MEN2A locus at the middle of a small region (approximately 11 cM) bracketing the centromere with FNRB (at 10p11.2) and RBP3 (at 10q11.2) on either side, providing further support for the centromeric location of the MEN2A locus. Marked sex difference in recombination frequencies exists in this pericentromeric region: significantly (P less than .01) more female than male crossovers were observed across all of the adjacent intervals D10S24-FNRB, FNRB-D10Z1, and D10Z1-RBP3. However, a sex difference was not seen in the 7-cM interval from RBP3 to D10S5, suggesting that large variation in the sex difference in recombination can occur over small chromosomal regions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Strong linkage disequilibrium between the XY274 polymorphism and the pseudoautosomal boundary.

The pseudoautosomal boundary is defined by an Alu repeat element on the Y chromosome. The Alu element is found on all Y chromosomes and on no X chromosomes, establishing it as part of Y-specific sequences. Distal to the Alu element, sequences from the X and Y are strictly homologous, suggesting that the boundary is formed by an abrupt break in sequence homology. Further investigation of the function of the boundary has been undertaken by examining the population structure of an MspI restriction-site polymorphism (XY274), which is located 274 bp distal to the Alu insertion site. Southern blot and polymerase chain reaction analysis demonstrate fixation of the high allele (noncutting or AT base pair) of XY274 on the Y chromosome in most populations, while a full range of high allele frequencies is found on the X chromosomes of different populations. Two exceptions to fixation on the Y chromosome were found in African populations. The level of linkage disequilibrium suggests that the first few hundred base pairs of the pseudoautosomal region on the Y chromosome share a single common origin more recent than the origin of the species.     

The control of seasonal changes in the pigmentation of lime aphid nymphs, Eucallipterus tiliae

Lime aphid nymphs may be found with or without bands of black pigment on the dorsal surfaces of the head, thorax and abdomen. The proportion of pigmented nymphs in a population varies during a season, although first generation nymphs are always unpigmented. The appearance of the black pigment is found to be induced by both crowding and changes in the leaves associated with leaf maturity. Since the crowding stimulus is also found to be transmitted via the leaf, this suggests that pigmentation may be ultimately controlled by a single plant-borne factor, possibly the nutritional quality of the leaves. The possible significance of this response in the life of the aphid is discussed.

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zusammenfassung Bei der Lindenblattlaus können Larven mit und ohne schwarz pigmentierten Bändern auf der Rückenseite des Kopfs, des Thorax und des Abdomens gefunden werden. Der Anteil pigmentierter Larven in einer Population schwankt während einer Saison, indessen sind die Larven der ersten Generation nie pigmentiert. Das schwarze Pigment wird induziert durch Crowding und durch Veränderungen im Blatt, welche mit der Blattreifung zusammenhängen. Da auch der Crowdingstimulus durch das Blatt übertragen wird, dürfte die Pigmentierung letztlich durch einen einzigen in der Pflanze befindlichen Faktor, möglicherweise die Nahrungsqualität der Blätter, gesteuert werden. Die mögliche Bedeutung dieses Zusammenhangs im Leben der Blattlaus wird diskutiert.

     

Factors influencing leaf vein selection in the lime aphid (Eucallipterus tiliae L.)

Summary The thickness of sclerenchyma around the veins of lime leaves varies with both size of leaf and size of vein and may provide a barrier to stylet penetration. Although small veins confer greater nutritional benefits and have no lignified barriers, there are advantages to feeding on the larger veins for those more mature aphids which can penetrate the sclerenchyma. Feeding on the large veins of the upper surface, which are situated in grooves, may provide protection against dislodgement. On the undersurfaces of small leaves, feeding on large veins promotes orientation towards the petiole and early warning of approaching predators. On the corresponding surfaces of large leaves the sclerenchyma is thicker but aphids can achieve orientation by feeding on the smallest veins.