Ovarian lipoxygenase activity and its regulation by gonadotropin in the rat

In our previous study a dose-dependent blockage of follicular rupture at ovulation by inhibitors of lipoxygenase was demonstrated. Here the presence of 5-lipoxygenase activity in the whole ovary and in the Graafian follicle is estimated by a chemiluminescence assay using unlabeled arachidonic acid as substrate in the presence of luminol and by conversion of 14C-arachidonic acid into lipoxygenase products as separated by HPLC. Both approaches demonstrated lipoxygenase activity in whole ovarian homogenates and in homogenates of preovulatory Graafian follicles. Furthermore, within 6 h after stimulation in vivo with hCG, lipoxygenase activity was increased by 2-fold in the whole ovarian homogenate and by 5-fold in the follicular homogenate. These results confirm the presence of lipoxygenase in rat ovaries, and its stimulation by gonadotropin and thus corroborate the suggested involvement of lipoxygenase products in follicular rupture at ovulation.     

MAJOR CLADES OF THE ANGIOSPERMS

Abstract— Our knowledge of fundamental angiosperm interrelationships is still very incomplete. The absence of a narrowly circumscribed gymnosperm outgroup, ideally the sister group, makes character evaluation, necessary for a cladistic analysis, difficult. According to current views the superorder Magnoliiflorae with a number of other groups, for example the monocotyledons, may represent a complex of families near the base of the angiosperms. Interrelationships of groups within the monocotyledons are much better understood than those between groups within the dicotyledons. A cladogram of monocotyledon orders based on earlier work by R. Dahlgren, H. T. Clifford, and F. N. Rasmussen is presented. A data matrix for a sample of the angiosperms with 61 characters for 49 taxa, mostly magnoliifloran and related families, is presented. The characters are polarized mainly according to the current view that the primitive angiosperm morphotype is a woody dicotyledon with strobiloid flowers. As an alternative the matrix is adjusted following W. C. Burger's conjecture that the primitive angiosperm was a herbaceous monocotyledon with trimerous flowers. Both matrices were run in a computerized parsimony analysis, resulting in numerous equally parsimonious solutions. This result is illustrative of the great homoplasy in the available character information, and also of how little actually is known about fundamental angiosperm interrelationships or phylogeny.     

Assignment of orthologous relationships among mammalian alpha-globin genes by examining flanking regions reveals a rapid rate of evolution

In order to study the relationships among mammalian alpha-globin genes, we have determined the sequence of the 3' flanking region of the human alpha 1 globin gene and have made pairwise comparisons between sequenced alpha-globin genes. The flanking regions were examined in detail because sequence matches in these regions could be interpreted with the least complication from the gene duplications and conversions that have occurred frequently in mammalian alpha-like globin gene clusters. We found good matches between the flanking regions of human alpha 1 and rabbit alpha 1, human psi alpha 1 and goat I alpha, human alpha 2 and goat II alpha, and horse alpha 1 and goat II alpha. These matches were used to align the alpha-globin genes in gene clusters from different mammals. This alignment shows that genes at equivalent positions in the gene clusters of different mammals can be functional or nonfunctional, depending on whether they corrected against a functional alpha-globin gene in recent evolutionary history. The number of alpha-globin genes (including pseudogenes) appears to differ among species, although highly divergent pseudogenes may not have been detected in all species examined. Although matching sequences could be found in interspecies comparisons of the flanking regions of alpha- globin genes, these matches are not as extensive as those found in the flanking regions of mammalian beta-like globin genes. This observation suggests that the noncoding sequences in the mammalian alpha-globin gene clusters are evolving at a faster rate than those in the beta-like globin gene clusters. The proposed faster rate of evolution fits with the poor conservation of the genetic linkage map around alpha-globin gene clusters when compared to that of the beta-like globin gene clusters. Analysis of the 3' flanking regions of alpha-globin genes has revealed a conserved sequence approximately 100-150 bp 3' to the polyadenylation site; this sequence may be involved in the expression or regulation of alpha-globin genes.      

P48-Triggered transmembrane signaling transduction of human monocytes:mobilization of calcium ion and activation of protein kinase C(PKC)

INTRODUCTI0NThedifferentiati0nofcelIsalongthemonocyte-macr0phagepathwayandthesig-nalsinvo1vedinthesecel1sacquiringtheabilitytokilltum0rcellsarenotfllllyundersto0d.Wehavebeenstudingamoleculewhichappearst0beanimportantmemberofthecytokinenetworkinvo1vedintheregulati0nmonocyteactivation.ThiscytokinetermedP48wasisolatedfr0mthehllmannullcellleukemiacell1ineReh.IthasbeenpurifiedtohomogeneityandfOundtobedistinctfrominterferongamma,col0nystimulatingfactors(CSFs)andTNFalphaalldbeta[1,2].Func-ti…     

Transforming growth factor-β in the early mouse embryo: Implications for the regulation of muscle formation and implantation

In a search for functions of transforming growth factor-β during early embryonic development we used two different experimental approaches. In the first we made use of embryonic stem (ES) cells. ES cells in culture differentiate to derivatives of all three germ layers and mimic some aspects of organogenesis when grown as aggregates in suspension to form embryoid bodies. Differentiation procedes further when the embryold bodies attach to suitable substrates. Muscle and neuronal cells are among the most readily identified cell types then formed. We examined the effect of all-trans retinoic acid (RA) and members of the transforming growth factor-β family(TGF-βl, TGF-β2) under these conditions in an assay where single aggregates formed in hanging microdrops in medium supplemented with serum depleted of lipophilic substances which would include retinoids. Endoderm-like cells formed under all conditions tested. RA at concentrations of 10⁸ M and 10⁷ M induced the formation of neurons but in the absence of RA or at concentrations up to 10?⁹ M, neurons were not observed. Instead, beating muscle formed in about one-third of the plated aggregates; this was greatly reduced when RA concentrations increased above 10?⁹ M. Immunofluorescent staining for muscle specific myosin showed that two muscle cell types could be distinguished: elongated, non-contractile myoblasts and mononucleate flat cells. The mononucleate flat cells appeared to correspond with rhythmically contracting muscle. The number of non-contractile myoblasts increased 3-fold over controls in the presence of 10?⁹ M RA. TGF-βs increased the number of contractile and non-contractile muscle cells by a factor 3 to 7 over controls, depending on the TGF-β isoform added and the muscle cell type formed. TGF-β2 also invariably increased the rate at which contracting muscle cells were first observed in replated aggregates. The stimulatory effect of TGF-βs on the formation of mononucleate flat cells was completely abrogated by RA at 10?⁹ M while the number of myoblasts under similar conditions was unchanged. These data suggest that a complex interplay between retinoids and TGF-β isoforms may be involved in regulation of differentiation in early myogenesis. In the second approach, neutralizing polyclonal rabbit antibodies specific for TGF-β2 were injected into the cavity of mouse blastocysts 3.5 days post coitum (pc). After 1 day in culture, embryos were transferred to pseudopregnant females. The number of decidua, embryos and resorptions were counted at day 8.5–9.5 pc. Control antibody injected embryos implanted with high efficiency (87%) compared with anti-TGF-β2 injected embryos which implanted with an efficiency of only 43%. If empty decidua (resorptions) were included, the overall recovery was 71% and 32% for control and experimental embryos, respectively. Embryos that were recovered showed no overt macroscopic abnormalities. These results together impiy functions for TGF-βs in implantation as well as in later development of the embryo. © 1993Wiley-Liss, Inc.     

Performance of a new dynamic model for predicting diurnal time courses of stomatal conductance at the leaf level

Under natural conditions, plants are subjected to continuous changes of irradiance that drive variations of stomatal conductance to water vapour (g_s). We propose a dynamic model to predict the temporal response of g_s at the leaf level using an asymmetric sigmoid function with a unique parameter describing time constants for increasing and decreasing g_s. The model parameters were adjusted to observed data using Approximate Bayesian Computation. We tested the model performance for (1) instant changes of irradiance; or (2) continuous and controlled variations of irradiance simulating diurnal time courses. Compared with the two mostly used steady‐state models, our dynamic model described daily time courses of g_s with a higher accuracy. In particular, it was able to describe the hysteresis of g_s responses to increasing/decreasing irradiance and the resulting rapid variations of intrinsic water‐use efficiency. Compared to the mechanistic model of temporal responses of g_s by Kirschbaum, Gross & Pearcy, for which time constants were estimated with a large variance, our model estimated time constants with a higher precision. It is expected to improve predictions of water loss and water‐use efficiency in higher scale models by using a small number of parameters.     

An improved neutral landscape model for recreating real landscapes and generating landscape series for spatial ecological simulations

Many studies have assessed the effect of landscape patterns on spatial ecological processes by simulating these processes in computer‐generated landscapes with varying composition and configuration. To generate such landscapes, various neutral landscape models have been developed. However, the limited set of landscape‐level pattern variables included in these models is often inadequate to generate landscapes that reflect real landscapes. In order to achieve more flexibility and variability in the generated landscapes patterns, a more complete set of class‐ and patch‐level pattern variables should be implemented in these models. These enhancements have been implemented in Landscape Generator (LG), which is a software that uses optimization algorithms to generate landscapes that match user‐defined target values. Developed for participatory spatial planning at small scale, we enhanced the usability of LG and demonstrated how it can be used for larger scale ecological studies. First, we used LG to recreate landscape patterns from a real landscape (i.e., a mountainous region in Switzerland). Second, we generated landscape series with incrementally changing pattern variables, which could be used in ecological simulation studies. We found that LG was able to recreate landscape patterns that approximate those of real landscapes. Furthermore, we successfully generated landscape series that would not have been possible with traditional neutral landscape models. LG is a promising novel approach for generating neutral landscapes and enables testing of new hypotheses regarding the influence of landscape patterns on ecological processes. LG is freely available online.     

Evaluation of candidate genes in case-control studies: a statistical method to account for related subjects

Traditional case-control studies provide a powerful and efficient method for evaluation of association between candidate genes and disease. The sampling of cases from multiplex pedigrees, rather than from a catchment area, can increase the likelihood that genetic cases are selected. However, use of all the related cases without accounting for their biological relationship can increase the type I error rate of the statistical test. To overcome this problem, we present an analysis method that is used to compare genotype frequencies between cases and controls, according to a trend in proportions as the dosage of the risk allele increases. This method uses the appropriate variance to account for the correlated family data, thus maintaining the correct type I error rate. The magnitude of the association is estimated by the odds ratio, with the variance of the odds ratio also accounting for the correlated data. Our method makes efficient use of data collected from multiplex families and should prove useful for the analysis of candidate genes among families sampled for linkage studies. An application of our method, to family data from a prostate cancer study, is presented to illustrate the method's utility.