Inhibition of mouse oocyte cyclic AMP phosphodiesterase by steroid hormones: a possible mechanism for steroid hormone inhibition of oocyte maturation

Testosterone, progesterone, and estradiol-17 beta each inhibit cAMP phosphodiesterase activity of mouse oocyte extracts in a concentration-dependent manner. This finding provides an explanation for the inhibitory effect of steroid hormones on germinal vesicle breakdown (GVBD) of mouse oocytes in vitro. Furthermore, it raises the possibility that steroid hormones present in follicular fluid participate in maintaining meiotic arrest in vivo by acting in a nonclassical manner.     

Biology of the relict fungus-farming ant Apterostigma megacephala Lattke,including descriptions of the male,gyne, and larva

Insectes Sociaux - Fungus-farming “attine” ant agriculture consists of five distinct agricultural systems characterized by a remarkable symbiont fidelity in which five phylogenetic...     

Economic impact of biofouling on a naval surface ship

In the present study, the overall economic impact of hull fouling on a mid-sized naval surface ship (Arleigh Burke-class destroyer DDG-51) has been analyzed. A range of costs associated with hull fouling was examined, including expenditures for fuel, hull coatings, hull coating application and removal, and hull cleaning. The results indicate that the primary cost associated with fouling is due to increased fuel consumption attributable to increased frictional drag. The costs related to hull cleaning and painting are much lower than the fuel costs. The overall cost associated with hull fouling for the Navy's present coating, cleaning, and fouling level is estimated to be $56M per year for the entire DDG-51 class or $1B over 15 years. The results of this study provide guidance as to the amount of money that can be reasonably spent for research, development, acquisition, and implementation of new technologies or management strategies to combat hull fouling.     

Preparation of raf-oncogene-specific antiserum with raf protein produced in E. coli

In this report we describe the expression of v-raf protein in E. coli using a tryptophan-promoter-driven expression vector and its immunological characterization by anti-peptide sera. The purified recombinant protein was used to produce raf-specific antibodies which are suitable for studying v-raf and c-raf proteins in vitro and in vivo in a variety of species ranging from mouse to man.     

Identification of a 41 kDa protein embedded in the biosilica of scales and bristles isolated from Mallomonas splendens (Synurophyceae, Ochrophyta)

Cells of the photosynthetic protist Mallomonas splendens (Synurophyceae, Ochrophyta) are encased within a highly patterned wall or scale case that consists of silicified scales and bristles. In an effort to understand the mechanisms that unicellular protists utilize to produce elaborate, mineralized structures of great complexity and hierarchical structure, we identified and characterized a 41 kDa protein from purified scales/bristles isolated from M. splendens (SP41 for Scale Protein of 41 kDa). A cDNA encoding this protein was isolated and sequence analysis indicated that it is a novel protein. Polyclonal antibodies were generated against bacterially expressed SP41 and used to localize the protein throughout scale and bristle morphogenesis. Immunoelectron microscopy confirmed the biochemical data that SP41 is a component of mature scales and bristles, the protein localizing to silicified components of the purified extracellular matrix. During scale and bristle biogenesis within the cell, SP41 is deposited into a specialized Silica Deposition Vesicle (SDV) concomitant with silica deposition, a highly regulated event during scale and bristle formation. These results argue for SP41 playing a role in morphogenesis and/or silicification within the SDV during scale and bristle biogenesis.     

Mitosis, stature and evolution of plant mating systems: low-Phi and high-Phi plants

There is a long-recognized association in plants between small stature and selfing, and large stature and outcrossing. Inbreeding depression is central to several hypotheses for this association, but differences in the evolutionary dynamics of inbreeding depression associated with differences in stature are rarely considered. Here, we propose and test the Phi model of plant mating system evolution, which assumes that the per-generation mutation rate of a plant is a function of the number of mitoses (Phi) that occur from zygote to gamete, and predicts fundamental differences between low-Phi (small-statured) and high-Phi (large-statured) plants in the outcomes of the joint evolution of outcrossing rate and inbreeding depression. Using a large dataset of published population genetic studies of angiosperms and conifers, we compute fitted values of inbreeding depression and deleterious mutation rates for small- and large-statured plants. Consistent with our Phi model, we find that populations of small-statured plants exhibit a range of mating systems, significantly lower mutation rates, and intermediate inbreeding depression, while large-statured plants exhibit very high mutation rates and the maximum inbreeding depression of unity. These results indicate that (i) inbred progeny typically observed in large-statured plant populations are completely lost prior to maturity in nearly all populations; (ii) evolutionary shifts from outcrossing to selfing are generally not possible in large-statured species, rather, large-statured species are more likely to evolve mating systems that avoid selfing such as self-incompatibility and dioecy; (iii) destabilization of the mating system-high selfing rate with high-inbreeding depression-might be a common occurrence in large-statured species; and (iv) large-statured species in fragmented populations might be at higher risk of extinction than previously thought. Our results help to unify and simplify a large and diverse field of research, and serve to emphasize the importance that developmental and genetic constraints play in the evolution of plant mating systems.