First report of Phytopythium vexans causing the “Avocado sadness” in Michoacan,Mexico

Mexico is the main producer, consumer and exporter of avocado in the world, being Michoacan the main producer state contributing more than 80% of the national production. There are phytopathogens that decimate the production causing the death of the tree. Root samples were collected in avocado trees that showed the characteristic symptomatology of the disease known as avocado sadness, the sampling was carried out in four of the main avocado producing towns, in the state of Michoacan, Mexico. The isolation consisted in sowing root tissue in Petri dishes with V8^®-PARPH culture medium, subsequently they were identified morphologically and for species level it was determined by molecular biology, with the PCR-ITS technique. Pathogenicity tests were performed in triplicate with avocado seedlings with more than six leaves. After 24 hours, the inoculated plants expressed decay in the apical part, after 120 hours the leaves showed yellowing and after 15 days there was a generalized wilt on the stem and leaves, re-isolating the phytopathogen Phytopythium vexans. This study confirms the first report of the oomycete P. vexans affecting avocado trees in the most important producing region of the Mexican Republic.     

Diversity of the dsrAB (dissimilatory sulfite reductase) gene sequences retrieved from two contrasting mudflats of the Seine estuary, France

The diversity of sulfate-reducing microorganisms was investigated in two contrasting mudflats of the Seine estuary, by PCR amplification, cloning and sequencing of the genes coding for parts of the alpha and beta subunits of dissimilatory sulfite reductase (dsrAB). One site is located in the mixing-zone and shows marine characteristics, with high salinity and sulfate concentration, whereas the other site shows freshwater characteristics, with low salinity and sulfate concentration. Diversity and abundance of dsrAB genes differed between the two sites. In the mixing-zone sediments, most of the dsrAB sequences were affiliated to those of marine Gram-negative bacteria belonging to the order of Desulfobacterales, whereas in the freshwater sediments, a majority of dsrAB sequences was related to those of the Gram-positive bacteria belonging to the genus Desulfotomaculum. It is speculated that this is related to the salinity and the sulfate concentration in the two mudflats.     

Regulation of cellular adhesion molecule expression in murine oocytes, peri-implant ation and post-implantation embryos

Expression of the adhesion molecules, ICAM-1, VCAM-1, NCAM, CD44, CD49d (VLA-4, a chain), and CDlla (LFA-1, a chain) on mouse oocytes, and pre- and peri-implantation stage embryos was examined by quantitative indirect immunofluorescence microscopy. ICAM-1 was most strongly expressed at the oocyte stage, gradually declining almost to undetectable levels by the expanded blastocyst stage. NCAM, also expressed maximally on the oocyte, declined to undetectable levels beyond the morula stage. On the other hand, CD44 declined from highest expression at the oocyte stage to show a second maximum at the compacted 8-cell/morula. This molecule exhibited high expression around contact areas between trophecto-derm and zona pellucida during blastocyst hatching. CD49d was highly expressed in the oocyte, remained significantly expressed throughout and after blastocyst hatching was expressed on the polar trophecto-derm. Like CD44, CD49d declined to undetectable levels at the blastocyst outgrowth stage. Expression of both     

Microsatellite allele frequencies in humans and chimpanzees, with implications for constraints on allele size

The distributions of allele sizes at eight simple-sequence repeat (SSR) or microsatellite loci in chimpanzees are found and compared with the distributions previously obtained from several human populations. At several loci, the differences in average allele size between chimpanzees and humans are sufficiently small that there might be a constraint on the evolution of average allele size. Furthermore, a model that allows for a bias in the mutation process shows that for some loci a weak bias can account for the observations. Several alleles at one of the loci (Mfd 59) were sequenced. Differences between alleles of different lengths were found to be more complex than previously assumed. An 8-base-pair deletion was present in the nonvariable region of the chimpanzee locus. This locus contains a previously unrecognized repeated region, which is imperfect in humans and perfect in chimpanzees. The apparently greater opportunity for mutation conferred by the two perfect repeat regions in chimpanzees is reflected in the higher variance in repeat number at Mfd 59 in chimpanzees than in humans. These data indicate that interspecific differences in allele length are not always attributable to simple changes in the number of repeats.      

Effects of ovine prolactin on iodide metabolism and thyroid activity in the eel

Summary In the eel, ovine prolactin (oPrl) treatment (0.018 IU/day·g body weight), for 8 to 13 days modifies neither iodide absorption from the water nor excretion, extrathyroidal metabolism and plasma level of iodide.Thyroid activity, evaluated by epithelial cell height, radioiodine uptake and absolute iodide uptake is approximately twice that of controls. However, the amounts of total iodine, thyroxine (T₄) and triiodothyronine (T₃) in thyroid are unaltered by oPrl. Therefore, the decrease of plasma T₄ and the increase of plasma T₃, previously observed in oPrl-treated eels, do not result from a preferential thyroidal secretion of T₃, but only from a stimulation of peripheral conversion of T₄ to T₃. Furthermore, the increased thyroid activity probably originates from a decreased feedback inhibition following the fall of circulating T₄ induced by oPrl.Abbreviations oPrl ovine prolactin - T ₄ Thyroxine - T ₃ 3.5.3 triiodothyronine - TRH thyrotropin releasing hormone - TSH thyroid stimulating hormone - PBI protein bound iodine