Role of de Vries in the recovery of Mendel's work. I. Was de Vries really an independent discoverer of Mendel?

Recently, doubt has been cast on the view that de Vries developed the idea of disjunction independently of Mendel. Arguments are based on de Vries' own writings that showed the F2 data of his numerous crosses are reported as 3:1 ratios only after 1900. They also show that his theory of inheritance becomes quasi Mendelian only after 1900. The authors of this review paper cannot but agree with de Vries' critics that he did not develop his law of disjunction independently of Mendel. They also raise some questions that, hopefully, will lead to a reanalysis of de Vries' theory of inheritance in 1900.     

Chi-square and Mendel's experiments: where's the bias?

Mendel has been accused of "cooking" his data to meet a particular hypothesis. The earliest time he could have formulated an hypothesis in the course of his experiments was at the end of the second year of experiments 1 and 2. If he knew what to expect as the result of his first two pea-seed experiments, one might expect the chi-square values of subsequent experiments to exhibit a trend toward smaller values. However, when the individual experiments are, each in turn, subjected to a chi-square test, there is no evidence of the expected trend. With few exceptions, the data show no systematic variation in a particular direction. In our view, the suggestion of bias is not supported.     

Ionic regulation of glutamate binding sites

Cl- and Ca2+ increase glutamate binding to rat synaptic plasma membranes (SPMs) by revealing a distinct class of L-glutamate (L-Glu) binding sites. The present study was conducted to examine both the anion specificity of this response and the nature of the interaction between Cl- and Ca2+. Of the anions tested, Br- was the most effective in increasing the levels of L-Glu binding. Other effective anions were Cl-, NO3- and formate while F-, HCO3-CIO4-, propionate, SO42- and PO43- were ineffective. The anion specificity was similar to that observed for the Cl- membrane channel, suggesting that this binding site and the ion channel may be related. In the absence of Cl-, Ca2+ has little effect on L-Glu binding. Increasing the Cl- concentration increased the apparent affinity (decreased KCa2+) of the Ca2+-stimulated, L-Glu binding component and also increased the maximal amount of the enhancement. Conversely, increasing Ca2+ levels increased the maximal enhancement of L-Glu binding brought about by Cl- without affecting the KCl- of the effect. Prior incubation of membranes with Ca2+ did not raise the level of L-Glu binding. Furthermore, EGTA was able to reverse the stimulation of L-Glu binding due to Ca2+. The results indicate that Ca2+ acts ionically to enhance L-Glu binding to rat SPMs.     

Trisomy 6q22 leads to 6qter due to maternal 6;21 translocation. Case report review of the literature

Partial trisomy for the long arm of chromosome 6, involving 6q22 leads to 6qter, was observed in a 2-month-old male infant. The mother was 6q;21p translocation carrier. A review of the previously published cases with trisomies of different 6q segments suggests that the critical segment responsible for the clinically recognizable phenotype of 6q trisomy seems to be limited to bands 6q26 and/or 6q27.     

Localization of sequences regulating ancestral and acquired sites of esterase6 activity in Drosophila melanogaster

We have broadly defined the DNA regions regulating esterase6 activity in several life stages and tissue types of D. melanogaster using P- element-mediated transformation of constructs that contain the esterase6 coding region and deletions or substitutions in 5' or 3' flanking DNA. Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and the primary sequences regulating its activity lie between -171 and -25 bp relative to the translation initiation site: deletion of these sequences decrease activity approximately 20-fold. Hemolymph activity is also modulated by four other DNA regions, three of which lie 5' and one of which lies 3' of the coding region. Of these, two have positive and two have negative effects, each of approximately twofold. Esterase6 activity is present also in two male reproductive tract tissues; the ejaculatory bulb, which is another ancestral activity site, and the ejaculatory duct, which is a recently acquired site within the melanogaster species subgroup. Activities in these tissues are at least in part independently regulated: activity in the ejaculatory bulb is conferred by sequences between -273 and -172 bp (threefold decrease when deleted), while activity in the ejaculatory duct is conferred by more distal sequences between -844 and -614 bp (fourfold decrease when deleted). The reproductive tract activity is further modulated by two additional DNA regions, one in 5' DNA (-613 to -284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to +2731 bp; threefold decrease when deleted) that probably overlaps the adjacent esteraseP gene. Collating these data with previous studies suggests that expression of EST6 in the ancestral sites is mainly regulated by conserved proximal sequences while more variable distal sequences regulate expression in the acquired ejaculatory duct site.      

Effect of recovery method on yield of bovine oocytes per ovary and their developmental competence after maturation, fertilization and culture in vitro

An important aim of an oocyte recovery method is to maximize the number of oocytes per ovary which can be employed for in vitro maturation (IVM), in vitro fertilization (IVF) and in vitro culture (IVC). In this study, primary bovine oocytes were collected by 2 methods: aspiration of visible follicles (2 to 6mm in diameter) or surface dissection in which the ovary surface is finely dissected. The oocytes were classified on the basis of cumulus cover and cytoplasmic appearance. The total number of oocytes and the yield of good-quality oocytes recovered per ovary by surface dissection and aspiration were 44.2 and 13.9 and 13.5 and 4.6 (P<0.05), respectively. When a sample group of selected oocytes recovered by each method was measured, no significant difference was found in the mean diameter (144.11m vs 142.54m). A representative sample of good-quality oocytes recovered by each method was put through the IVM/IVF/IVC procedure: no significant difference in cleavage rate, cleavage index or blastocyst yield was found. However, when the blastocyst yield was compared on a per ovary basis, a significant difference was observed in favor of surface dissection (3.30+/-0.46 vs 0.96+/-0.16;P<0.05). When unselected oocytes recovered by surface dissection of the ovaries were put through the standard embryo production system, an average of 15.4 blastocysts per dam was obtained.     

Intraspecific diversity in the fungal speciesChaunopycnis alba: Implications for microbial screening programs

Intraspecific variation among 84 isolates of the anamorphic fungusChaunopycnis alba from 26 different geographical locations was analyzed by investigating optimal growth temperatures, differences in the production of secondary metabolites and presence or absence of the cyclosporin synthetase gene. The genetic diversity was assessed using random amplified polymorphic DNA (RAPD). Analysis of these data showed high genetic, metabolic and physiological diversity within this species. Isolates from the Antarctic represented the most homogeneous group withinC. alba and together with isolates from the Arctic these polar strains differed from alpine, temperate and tropical strains by low optimal growth temperatures and by low production of secondary metabolites. Isolates from tropical climes were characterized by high optimal growth temperatures and by the production of comparatively diverse metabolite spectra. Most of the isolates that were similar in the combination of their physiological and metabolic characters were also genetically related. Isolates from different geographical origins did not show many similarities, with the exception of the cyclosporin A-producing isolates, and large diversity could be observed even within a single habitat. This leads us to the suggestion that for pharmaceutical screening programs samples should be collected from a diversity of different geographical and climatic locations. For the selection of strains for screening the RAPD assay seems to be the most powerful tool. It reflected the highest intraspecific diversity and the results corresponded well with the other characteristics.