Compensating for our load of mutations: freezing the meltdown of small populations

We have investigated the reduction of fitness caused by the fixation of new deleterious mutations in small populations within the framework of Fisher's geometrical model of adaptation. In Fisher's model, a population evolves in an n-dimensional character space with an adaptive optimum at the origin. The model allows us to investigate compensatory mutations, which restore fitness losses incurred by other mutations, in a context-dependent manner. We have conducted a moment analysis of the model, supplemented by the numerical results of computer simulations. The mean reduction of fitness (i.e., expected load) scaled to one is approximately n/(n+2Ne), where Ne is the effective population size. The reciprocal relationship between the load and Ne implies that the fixation of deleterious mutations is unlikely to cause extinction when there is a broad scope for compensatory mutations, except in very small populations. Furthermore, the dependence of load on n implies that pleiotropy plays a large role in determining the extinction risk of small populations. Differences and similarities between our results and those of a previous study on the effects of Ne and n are explored. That the predictions of this model are qualitatively different from studies ignoring compensatory mutations implies that we must be cautious in predicting the evolutionary fate of small populations and that additional data on the nature of mutations is of critical importance.     

Complete response of metastatic renal cell carcinoma to low-dose interferon-γ treatment

The course of metastatic renal cell carcinoma may be positively influenced by immunotherapeutic agents. We report a case of renal cell carcinoma showing a complete response to once-weekly low-dose s. c. interferon- (INF) treatment in multiple metastatic sites (lung, chest wall, abdomen, vertebral body), but concomitantly developing a solitary brain metastasis. High initial interleukin-6 (IL-6) levels returned to normal during IFN treatment suggesting that IFN may have interrupted an autocrine IL-6/IL-6-receptor loop of the tumor cells. The duration of complete remission in the extracerebral sites is now 46+ months. IFN may be less active beyond the blood/brain barrier.     

Synthesis and evaluation of unsymmetrical polyamine derivatives as antitumor agents

A series of unsymmetrically substituted polyamine derivatives were prepared and their cytotoxicities in mouse leukemia L1210, melanoma B16, and HeLa cells were investigated. The in vitro cytotoxicity revealed that these conjugates could recognize the polyamine transporter, and the N-ethyl modified homospermidine moiety may be another efficient carrier as homospermidine even though the introduction of terminal alkyl groups led to reduced cytotoxicity in comparison with the un-substituted counterpart 1. The ornithine decarboxylase and topoisomerase II inhibition experiments indicated that ODC and TOPO II were potential, but not unique targets of these conjugates. Furthermore, the in vivo antitumor activities illustrated that the representative conjugate 2f and the homospermidine analogue 1 evidently inhibited the tumor growth and significantly increased the survival time of mice-bearing sarcoma 180 cells.     

Identification and subcellular location of talin in various cell types and tissues by means of [125I]vinculin overlay, immunoblotting and immunocytochemistry

In the present study, we have examined the cellular and subcellular distribution of talin in several tissues of the chicken. By immunocytochemistry, Western Blot analysis and [125I]vinculin overlay, talin was demonstrated in most of the main tissues and cell types of the body. Corresponding to the property of talin to bind to the fibronectin receptor, talin was found to be confined to the site of the plasma membrane that abuts the extracellular matrix in various types of mesenchymal and epithelial cells. In the central nervous system talin was almost exclusively confined to cells of the connective tissue, i.e., blood vessels and the connective tissue sheaths. No evidence was obtained for the association of talin with any type of intercellular junction. In nonadhering cells such as circulating platelets and leukocytes, talin displayed a diffuse distribution throughout the cytoplasm. These findings suggest a general role for talin in certain aspects of cellular adhesion to the extracellular matrix.     

Use of mucus as a non-invasive sampling method for DNA barcoding of stingrays and skates (batoid elasmobranchs)

In this study we tested the use of mucus from five species of Neotropical marine batoid elasmobranchs to extract genomic DNA for barcoding and phylogenetic analysis. The DNA from all individuals sampled was successfully amplified and sequenced for molecular barcode, allowing 99–100% accuracy to the species level. This method proved to provide reliable and good-quality DNA for barcoding and phylogenetic analysis of Neotropical elasmobranchs, through rapid handling and with low disturbance to animals.     

Haploids adapt faster than diploids across a range of environments

Despite a great deal of theoretical attention, we have limited empirical data about how ploidy influences the rate of adaptation. We evolved isogenic haploid and diploid populations of Saccharomyces cerevisiae for 200 generations in seven different environments. We measured the competitive fitness of all ancestral and evolved lines against a common competitor and find that in all seven environments, haploid lines adapted faster than diploids, significantly so in three environments. We apply theory that relates the rates of adaptation and measured effective population sizes to the properties of beneficial mutations. We obtained rough estimates of the average selection coefficients in haploids between 2% and 10% for these first selected mutations. Results were consistent with semi-dominant to dominant mutations in four environments and recessive to additive mutations in two other environments. These results are consistent with theory that predicts haploids should evolve faster than diploids at large population sizes.     

Characterization of activity and binding mode of glycyrrhetinic acid derivatives inhibiting 11β-hydroxysteroid dehydrogenase type 2

Modulation of intracellular glucocorticoid availability is considered as a promising strategy to treat glucocorticoid-dependent diseases. 18β-Glycyrrhetinic acid (GA), the biologically active triterpenoid metabolite of glycyrrhizin, which is contained in the roots and rhizomes of licorice (Glycyrrhiza spp.), represents a well-known but non-selective inhibitor of 11β-hydroxysteroid dehydrogenases (11β-HSDs). However, to assess the physiological functions of the respective enzymes and for potential therapeutic applications selective inhibitors are needed. In the present study, we applied bioassays and 3D-structure modeling to characterize nine 11β-HSD1 and fifteen 11β-HSD2 inhibiting GA derivatives. Comparison of the GA derivatives in assays using cell lysates revealed that modifications at the 3-hydroxyl and/or the carboxyl led to highly selective and potent 11β-HSD2 inhibitors. The data generated significantly extends our knowledge on structure-activity relationship of GA derivatives as 11β-HSD inhibitors. Using recombinant enzymes we found also potent inhibition of mouse 11β-HSD2, despite significant species-specific differences. The selected GA derivatives potently inhibited 11β-HSD2 in intact SW-620 colon cancer cells, although the rank order of inhibitory potential differed from that obtained in cell lysates. The biological activity of compounds was further demonstrated in glucocorticoid receptor (GR) transactivation assays in cells coexpressing GR and 11β-HSD1 or 11β-HSD2. 3D-structure modeling provides an explanation for the differences in the selectivity and activity of the GA derivatives investigated. The most potent and selective 11β-HSD2 inhibitors should prove useful as mechanistic tools for further anti-inflammatory and anti-cancer in vitro and in vivo studies. Article from the Special issue on Targeted Inhibitors.     

Peptidoglycantyp und Zusammensetzung der Zellwandpolysaccharide vonCellulomonas cartalyticum und einigen coryneformen Organismen

Cellulomonas cartalyticum was found to contain a peptidoglycan type different from that of the other species ofCellulomonas. The diamino acid is lysine instead of ornithine and the interpeptide bridge consists ofd-Asp-d-Ser. The same peptidoglycan type occurs inCorynebacterium manihot, Brevibacterium liticum andArthrobacter luteus. These non cellulolytic organisms are most likely not closely related withCellulomonas cartalyticum, as indicated by the very different G+C content of their DNA, although they formed a narrow cluster includingC. cartalyticum when numeric taxonomical methods were applied.

     

The aminergic control of cockroach salivary glands

The acinar salivary glands of cockroaches receive a dual innervation from the subesophageal ganglion and the stomatogastric nervous system. Acinar cells are surrounded by a plexus of dopaminergic and serotonergic varicose fibers. In addition, serotonergic terminals lie deep in the extracellular spaces between acinar cells. Excitation-secretion coupling in cockroach salivary glands is stimulated by both dopamine and serotonin. These monoamines cause increases in the intracellular concentrations of cAMP and Ca(2+). Stimulation of the glands by serotonin results in the production of a protein-rich saliva, whereas stimulation by dopamine results in saliva that is protein-free. Thus, two elementary secretory processes, namely electrolyte/water secretion and protein secretion, are triggered by different aminergic transmitters. Because of its simplicity and experimental accessibility, cockroach salivary glands have been used extensively as a model system to study the cellular actions of biogenic amines and to examine the pharmacological properties of biogenic amine receptors. In this review, we summarize current knowledge concerning the aminergic control of cockroach salivary glands and discuss our efforts to characterize Periplaneta biogenic amine receptors molecularly.