Combined action of stem cell factor,leukemia inhibitory factor,and cAMP on in vitro proliferation of mouse primordial germ cells

In the present paper we investigated the effects of stem cell factor/mastocyte growth factor (SCF/MGF), leukemia inhibitory factor/differentiating inhibitory activity (LIF/DIA) (two growth factors known to affect primordial germ cell growth in vitro) and forskolin (FRSK) (an activator of adenylate cyclase in many cell types) alone or in combination on the survival and proliferation of primordial germ cells (PGCs) obtained from 8.5, 10.5, and 11.5 days post coitum (dpc) mouse embryos and cultured without pre-formed cell feeder layers. The results showed that both at 1 and 3 days of culture the addition of 100 ng/ml SCF, 20 μM FRSK, or in some instances 20 ng/ml LIF alone caused a significant increase of PGC number as compared with controls. The highest effects were obtained when SCF and/or LIF were used together with FRSK. Moreover, we found that FRSK elevated cAMP levels in purified 11.5 dpc PGCs and that this compound, but not SCF and LIF, stimulated PGC proliferation, as assessed by 5-bromo-2′-deoxyuridin (BrdU) incorporation. These results suggest a mechanism of combined action of cAMP with SCF and/or LIF in the control of proliferation of mouse PGCs in vitro. © 1993 Wiley-Liss, Inc.     

Fine structure of the spermatozoa of Crassostrea gigas (Mollusca,Bivalvia)

We describe sperm ultrastructure and acrosome differentiation during spermiogenesis in Crassostrea gigas (Mollusca Bivalvia). The sperm cell is a uniflagellated cell of the primitive type. The head region contains a rounded or conical nucleus surmounted by small acrosome. This organelle consists of a membrane-bound acrosomal granule, the contents of which have a homogeneous density, except in the anterior region, which is positive for PTA. The acrosome also surrounds the perforatorium, which includes oriented fibrillar elements: this is the axial body. The middle piece contains four mitochondria encircling two perpendicular centrioles. The distal centriole is provided with a system of mechanical fixation to the plasma membrane, consisting of nine fibers in radial arrangement. The tail flagellum, about 50 m?m long, contains the usual microtubular axoneme. © 1993 Wiley-Liss, Inc.     

Endoplasmic Reticulum Forms a Dynamic Continuum for Lipid Diffusion between Contiguous Soybean Root Cells

Intercellular communication between plant cells for low molecular weight hydrophilic molecules occurs through plasmodesmata. These tubular structures are embedded in the plant cell wall in association with the plasmalemma and endoplasmic reticulum (ER). Transmission electron microscopy has provided strong evidence to support the view that both the ER and plasmalemma are structurally continuous across the wall at these sites. In experiments to be described, the technique of fluorescence redistribution after photobleaching was used to examine the lateral mobility and intercellular transport capability of a number of fluorescent lipid and phospholipid analogs. These probes were shown by confocal fluorescence microscopy to partition in either the ER or plasmalemma. Results from these measurements provide evidence for cell communication between contiguous cells for probes localized predominantly in the ER. In contrast, no detectable intercellular communication was observed for probes residing exclusively in the plasmalemma. It was of particular interest to note that when 1-acyl-2-(N-4-nitrobenzo-2-oxa-l,3-diazole)aminoacylphosphatidylcholine was utilized as a potential reporter molecule for phospholipids in the plasmalemma, it was quickly degraded to 1-acyl-2-(N-4-nitrobenzo-2-oxa-1,3-diazole)aminoacyldiglyceride (NBD-DAG), which then appeared predominantly localized to the ER and nuclear envelope. This endogenously synthesized NBD-DAG was found to be capable of transfer between cells, as was exogenously incorporated NBD-DAG. Results from these investigations provide support for the following conclusions: (1) ER, but apparently not the plasmalemma, can form dynamic communication pathways for lipids across the cell wall between connecting plant cells; (2) the plasmodesmata appear to form a barrier for lipid diffusion through the plasmalemma; and (3) lipid signaling molecules such as diacylglycerol are capable of transfer between contiguous plant cells through the ER. These observations speak to issues of plant cell autonomy for lipid synthesis and mechanisms of intercellular signaling and communication.     

Female reproductive fluid concentrations affect sperm performance of alternative male phenotypes in an external fertilizer

There is growing evidence that the female reproductive fluid (FRF) plays an important role in cryptic female choice through its differential effect on the performance of sperm from different males. In a natural spawning event, the male(s) may release ejaculate closer or further away from the spawning female. If the relative spatial proximity of competing males reflects the female pre-mating preference towards those males, then favoured males will encounter higher concentrations of FRF than unpreferred males. Despite this being a common situation in many external fertilizers, whether different concentrations of FRF can differentially influence the sperm performance of distinct male phenotypes (favoured and unfavoured by the female) remains to be elucidated. Here, we tested this hypothesis using the grass goby (Zosterisessor ophiocephalus), a fish with distinct territorial-sneaker reproductive tactics and female pre-mating preference towards territorial males, that consequently mate in an advantaged position and whose sperm experience higher concentrations of FRF. Our findings revealed a differential concentration-dependent effect of FRF over sneaker and territorial sperm motility only at low concentrations (i.e. at the distance where sneakers typically ejaculate), with increasing FRF concentrations (i.e. close to the eggs) similarly boosting the sperm performance of both sneaker and territorial males. The ability to release sperm close to the eggs is a prerogative of territorials, but FRF can likewise advantage the sperm of those sneakers that are able to get closer, allowing flexibility in the direction of female post-mating choice.     

Evolutionary rescue under demographic and environmental stochasticity

Populations suffer two types of stochasticity: demographic stochasticity, from sampling error in offspring number, and environmental stochasticity, from temporal variation in the growth rate. By modelling evolution through phenotypic selection following an abrupt environmental change, we investigate how genetic and demographic dynamics, as well as effects on population survival of the genetic variance and of the strength of stabilizing selection, differ under the two types of stochasticity. We show that population survival probability declines sharply with stronger stabilizing selection under demographic stochasticity, but declines more continuously when environmental stochasticity is strengthened. However, the genetic variance that confers the highest population survival probability differs little under demographic and environmental stochasticity. Since the influence of demographic stochasticity is stronger when population size is smaller, a slow initial decline of genetic variance, which allows quicker evolution, is important for population persistence. In contrast, the influence of environmental stochasticity is population-size-independent, so higher initial fitness becomes important for survival under strong environmental stochasticity. The two types of stochasticity interact in a more than multiplicative way in reducing the population survival probability. Our work suggests the importance of explicitly distinguishing and measuring the forms of stochasticity during evolutionary rescue.     

Phylogenetic analysis of Starmerella apis in honey bees (Apis mellifera)

Honey bees are among the most effective pollinators that promote plant reproduction. Bees are highly active in the pollen collection season, which can lead to the transmission of selected pathogens between colonies. The clade Starmerella comprises yeasts that are isolated mainly from bees and their environment. When visiting plants, bees can come into contact with Starmerella spp. The aim of this study was to determine the prevalence and phylogenetic position of S. apis in bee colonies. Bee colonies were collected from nine apiaries in three regions. Ten colonies were sampled randomly from each apiary, and pooled samples were collected from the central part of the hive in each colony. A total of 90 (100%) bee colonies from nine apiaries were examined. Starmerella apis was detected in 31 (34.44%) samples, but related species were not identified. The 18S rRNA amplicon sequences of S. apis were compatible with the GenBank sequences of Starmerella spp. from India, Japan, Syria, Thailand, and the USA. The amplicon sequences of S. apis were also 99.06% homologous with the sequences deposited in GenBank under accession numbers JX515988 and NG067631 .This is the first study to perform a phylogenetic analysis of S. apis in Polish honey bees.     

Inoculation with native soil improves seedling survival and reduces non-native reinvasion in a grassland restoration

Losses of grasslands have been largely attributed to widespread land-use changes, such as conversion to row-crop agriculture. The remaining tallgrass prairie faces further losses due to biological invasions by non-native plant species, often with resultant ecosystem degradation. Of critical concern for conservation, restoration of native grasslands has been met with little success following eradication of non-native plants. In addition to the direct and indirect effects of non-native invasive plants on beneficial soil microbes, management practices targeting invasive species may also negatively affect subsequent restoration efforts. To assess mechanisms limiting germination and survival of native species and to improve native species establishment, we established six replicate plots of each of the following four treatments: (1) inoculated with freshly collected prairie soil with native seeds; (2) inoculated with steam-pasteurized soil with native seeds; (3) noninoculated with native seeds; or (4) noninoculated/nonseeded control. Inoculation with whole soil did not improve seed germination; however, addition of whole soil significantly improved native species survival, compared to pasteurized soil or noninoculated treatments. Inoculation with whole soil significantly decreased reestablishment of non-native invasive Bothriochloa bladhii (Caucasian bluestem); at the end of the growing season, plots receiving whole soil consisted of approximately 30% B. bladhii cover, compared to approximately 80% in plots receiving no soil inoculum. Our results suggest invasion and eradication efforts negatively affect arbuscular mycorrhizal hyphal and spore abundances and soil aggregate stability, and inoculation with locally adapted soil microbial communities can improve metrics of restoration success, including plant species richness and diversity, while decreasing reinvasion by non-native species.     

Induction Patterns of an Extensin Gene in Tobacco upon Nematode Infection

When sedentary endoparasitic nematodes infect plants, they induce complex feeding sites within the root tissues of their host. To characterize cell wall changes induced within these structures at a molecular level, we studied the expression of an extensin gene (coding for a major structural cell wall protein) in nematode-infected tobacco roots. Extensin gene expression was observed to be induced very early upon infection. This induction was weak, transient, and probably due to wounding during penetration and migration of the tobacco cyst nematode Globodera tabacum ssp solanacea-rum. In contrast, high extensin gene expression was observed during the whole second larval stage (an ~2-week-long phase of establishment of the feeding site) of the root knot nematode Meloidogyne javanica. During later stages of this interaction, expression gradually decreased. Extensin gene expression was found in at least three different tissues of the gall. We propose that distinct mechanisms lead to induced expression in these different cell types. The significance of these results for the understanding of plant-nematode interactions as well as the function of structural cell wall proteins, such as extensin, is discussed.     

pS2—A new cytosolic protein recognized by monoclonal antibodies as a marker of hormone sensitivity in breast cancer

Using a new immunoradiometric assay (ELSA pS2 Cis-France), a total of 200 cytosols obtained from primary breast tumors were examined for pS2 content, which is an estrogen-regulated protein actually studied as a marker of hormone sensitivity and favorable prognostic factor in breast cancer. In our patient group, the median pS2 value corresponding to 5.3 ng/mg of cytosolic proteins was used as cutoff. pS2 content was not related to menopause status, tumor size, or nodal involvement, whereas a positive correlation was found between pS2 and ER/PgR status. Moreover, the association of pS2 with steroid receptors seems to identify subgroups of patients better than ER/PgR alone.     

A trait-based approach to assess niche overlap and functional distinctiveness between non-indigenous and native species

Our understanding of the community assembly processes acting on non-indigenous species (NIS), as well as the relationship with native species is limited, especially in marine ecosystems. To overcome this knowledge gap we here develop a trait-based approach based on the functional distinctiveness metric to assess niche overlap between NIS and native species, using high-resolution data on benthic invertebrate communities in the Baltic Sea. Our results show that NIS retain a certain degree of similarity with native species, but display one or a few singular unique traits (e.g., bioturbation ability). Furthermore, we demonstrate that community assembly processes, including both environmental filtering and limiting similarity affect NIS establishment, but that their effects may be highly context dependent, as illustrated by pronounced spatial patterns in distinctiveness. Finally, our trait-based approach provides a generic framework applicable to other areas and organisms, to better understand and address biological invasions.