Aspects of the biology of the euryhaline Asian cichlid,Etroplus suratensis

Synopsis Aspects of the biology of the euryhaline Asian cichlid Etroplus suratensis in a coastal lagoon of Sri Lanka were studied for a period of 15 months. Comparisons are made from the catches from the fishery of manmade, inland freshwater reservoirs. Changes in the stock structure in the sublittoral region of the lagoon indicate that recruitment takes place twice a year, during the high rainfall/low salinity periods. The feeding habits of E. suratensis were different in the two habitats. In the lagoon it fed mainly on molluscs and in the freshwater reservoirs on macrophytes. Feeding chronology based on diurnal surveys indicate that it feeds mainly during the daylight hours. The dentition of E. suratensis is adapted for both tearing and crushing (pharyngeal teeth). Distinct differences in the mean relative intestinal length between populations from the coastal lagoon and inland reservoirs were evident and these differences are correlated to their respective feeding habits. Diurnal changes in feeding activity are associated with changes in the stomach pH. The egg-diameter distribution of mature fish indicate that E. suratensis is a single spawner, that it sheds its mature eggs all at once. It is inferred that E. suratensis breeds twice a year but that an individual female is capable of spawning only once a year.     

A and alpha supernatant pretreatment of Saccharomyces cerevisiae cells affects both the kinetics and efficiency of mating.

The effects of culture supernatant treatment on subsequent matings between pretreated a and alpha Saccharomyces cerevisiae cells were studied. For each experiment, pairs of a and alpha [rho+] or [rho- rho0] cells in the logarithmic growth phase in defined minimal medium were pretreated for a total of 15 min (by exchanging their cell-free supernatants or by mixing samples of a and alpha cell cultures) and then mated in defined minimal (YNB) or enriched (YEP) liquid medium. All pretreated cells, regardless of treatment procedure, initiated cell fusion 15 to 35 min faster than did their nontreated counterparts. In all cases, pretreated cells mated 8 to 20% more efficiently than did nonpretreated ones. Regardless of the strains, the hierarchy of mating efficiency was always treated YEP greater than untreated YEP greater than treated YNB greater than untreated YNB. The cell fusion kinetics in alpha [rho+] X a [rho-] crosses were most affected by pretreatment (delta 30 to 35 min), whereas [rho+] X [rho+] crosses were least affected (delta 15 min). These results are discussed in relation to the functions known for a and alpha pheromones. The successful pretreatment regimes were used to design new rapid and efficient techniques for mating YNB-grown log-phase cells in either YNB or YEP liquid media. These techniques can be used for small- or large-scale mating, and because of their inherent media flexibility, they have many potential applications to future studies on mating-specific or intrazygotic phenomena.     

Drug Repurposing: A Systematic Approach to Evaluate Candidate Oral Neuroprotective Interventions for Secondary Progressive Multiple Sclerosis

Objective

To develop and implement an evidence based framework to select, from drugs already licenced, candidate oral neuroprotective drugs to be tested in secondary progressive multiple sclerosis.

Design

Systematic review of clinical studies of oral putative neuroprotective therapies in MS and four other neurodegenerative diseases with shared pathological features, followed by systematic review and meta-analyses of the in vivo experimental data for those interventions. We presented summary data to an international multi-disciplinary committee, which assessed each drug in turn using pre-specified criteria including consideration of mechanism of action.

Results

We identified a short list of fifty-two candidate interventions. After review of all clinical and pre-clinical evidence we identified ibudilast, riluzole, amiloride, pirfenidone, fluoxetine, oxcarbazepine, and the polyunsaturated fatty-acid class (Linoleic Acid, Lipoic acid; Omega-3 fatty acid, Max EPA oil) as lead candidates for clinical evaluation.

Conclusions

We demonstrate a standardised and systematic approach to candidate identification for drug rescue and repurposing trials that can be applied widely to neurodegenerative disorders.     

Potential role of the neuropeptide CGRP in the induction of differentiation of rat hepatic portal vein wall

The media of the rat hepatic portal vein is composed of an internal circular muscular layer (CL) and an external longitudinal muscular layer (LL). These two perpendicular layers differentiate progressively from mesenchymal cells within the first month after birth. In this paper, we studied the development of calcitonin gene-related peptide (CGRP) innervation during post-natal differentiation of the vessel. We show that CGRP innervation is already present around the vessel at birth in the future adventitia but far from the lumen of the vessel. Progressively, CGRP immunoreactive fibers reached first LL then CL. CL by itself become only innervated at day 14 after birth. This corresponds to the time at which thick filaments (myosin) are visible in electron microscopy and desmin visualisable by immunocytochemistry. Furthermore, we provide evidence by autoradiography, that binding sites for CGRP are transiently expressed on the portal vein media at day 1 and 14 after birth. Vascular smooth muscle cells were transfected with constructs containing promoters for desmin or smooth muscle myosin heavy chain (smMHC). CGRP treatment of the cells significantly increased the expression of smMHC. Overall these results suggest that CGRP can potentially influence the differentiation of smooth muscle cells from the vessel wall.     

Zebrafish embryo, a tool to study tumor angiogenesis

Zebrafish (Danio rerio) represents a powerful model system in cancer research. Recent observations have shown the possibility to exploit zebrafish to investigate tumor angiogenesis, a pivotal step in cancer progression and target for anti-tumor therapies. Experimental models have been established in zebrafish adults, juveniles, and embryos, each one with its own advantages and disadvantages. Novel genetic tools and high resolution in vivo imaging techniques are also becoming available in zebrafish. It is anticipated that zebrafish will represent an important tool for chemical discovery and gene targeting in tumor angiogenesis. This review focuses on the recently developed tumor angiogenesis models in zebrafish, with particular emphasis to tumor engrafting in zebrafish embryos.     

Competing interactions in DNA assembly on graphene

We study the patterns that short strands of single-stranded DNA form on the top graphene surface of graphite. We find that the DNA assembles into two distinct patterns, small spherical particles and elongated networks. Known interaction models based on DNA-graphene binding, hydrophobic interactions, or models based on the purine/pyrimidine nature of the bases do not explain our observed crossover in pattern formation. We argue that the observed assembly behavior is caused by a crossover in the competition between base-base pi stacking and base-graphene pi stacking and we infer a critical crossover energy of 0.3-0.5 eV. The experiments therefore provide a projective measurement of the base-base interaction strength.     

Met overexpression confers HGF-dependent invasive phenotype to human thyroid carcinoma cells in vitro

The proto-oncogene c-MET encodes the tyrosine kinase receptor for hepatocyte growth factor (HGF), a pleiotropic cytokine controlling growth, survival, motility, invasive migration, and differentiation of epithelial cells. Like several other epithelial neoplasms, thyroid carcinomas have been found to overexpress c-MET at both the mRNA and protein level. The biological relevance of Met overexpression to thyroid carcinoma natural history, however, remains to be elucidated. Therefore, we analyzed Met expression and response to HGF in two cell lines established from human thyroid carcinomas. In both lines we observed that the overexpressed and constitutively tyrosine phosphorylated HGF receptor maintained biochemical responsiveness to the ligand. Both cell lines were also found to respond to HGF by consistently increasing their motility and invading in vitro reconstituted basal membranes. Conversely, no effect of HGF could be observed in proliferation and survival assays. These data show that overexpression of Met specifically confers to transformed thyroid cells a motile-invasive phenotype that is dependent on exogenous HGF stimulation. J. Cell. Physiol. 180:365–371, 1999. © 1999 Wiley-Liss, Inc.     

Early stimulation of ATP turnover induced by growth factors : Synergistic effect of EGF and insulin and correlation with DNA synthesis

Addition of a mixture of EGF + insulin to quiescent cell cultures synergistically stimulates the cells to reinitiate DNA synthesis and cell division. We have previously demonstrated that this mixture rapidly increases ATP turnover in quiescent cells. The present work shows that each of the two growth factors, EGF and insulin, when added separately to quiescent cells was able to stimulate the phosphorylation of the organic acid-soluble compounds (Po) pool and ATP turnover. The stimulation of ATP turnover was closely correlated with the increase in phosphorylation of the Po pool which suggests that Po labelling reflects the ATP turnover. In many experiments, the synergy between the two growth factors on the early increase in phosphorylation of the Po pool was clearly shown. Doubling the concentration of EGF (12-24 ng/ml) or insulin (50-100 ng/ml) did not increase early stimulation of phosphorylation of the Po pool, whereas simultaneous addition of the two growth factors induced a greater stimulation than that of each growth factor separately added. The augmentation in Po labelling after addition of EGF or insulin alone was transient. The synergistic effect of the two growth factors was more significant when determined 150 or 300 min after growth-factor addition. In our experimental conditions, each of the two growth factors, EGF and insulin, was able to induce a stimulation of DNA synthesis. However, the best stimulatory effect was observed with the mixture of the two which synergistically increased DNA synthesis determined between 6 and 24 h after growth-factor addition. The comparison between DNA replication and Po labelling suggests a correlation between the increase in DNA replication and in the total ATP synthesized in the first 5 h after cell stimulation by growth factors added separately or in combination.     

Prophylactic Effects of the Glucagon-Like Peptide-1 Analog Liraglutide on Hyperglycemia in a Rat Model of Type 2 Diabetes Mellitus Associated with Chronic Pancreatitis and Obesity

The objective of this study was to investigate the effects of liraglutide, an analog of human glucagon-like peptide 1 (GLP1), on WBN/Kob-Lepr^fa (fa/fa) rats, which spontaneously develop type 2 diabetes mellitus with pancreatic disorder and obesity. Male fa/fa rats (age, 7 wk) were allocated into 4 groups and received liraglutide (37.5, 75, 150 μg/kg SC) or saline (control group) once daily for 4 wk. All rats in the control group became overweight and developed hyperglycemia as they aged. Although the rats given liraglutide showed a dose-dependent reduction in food intake, no significant effects on body weight or fat content occurred. In the liraglutide groups, the development of hyperglycemia was suppressed, even as plasma insulin concentrations increased in a dose-dependent manner. Intravenous glucose tolerance testing of the liraglutide-treated rats confirmed improvement of glucose tolerance and enhanced insulin secretion. Histologic examination revealed increased numbers of pancreatic β-cell type islet cells and increased proliferation of epithelial cells of the small ducts in the liraglutide-treated groups. Although our study did not reveal a significant decrease in obesity after liraglutide administration, the results suggest a marked antidiabetic effect characterized by increased insulin secretion in fa/fa rats with pancreatic disorders.Abbreviations: GLP1, glucagon-like peptide-1; IVGTT, intravenous glucose tolerance testing; T2DM, type 2 diabetes mellitusThe number of patients diagnosed with diabetes has more than doubled over the last 30 y, and diabetes has become an important public health concern worldwide.⁶ Approximately 90% of patients with diabetes are diagnosed with type 2 diabetes mellitus (T2DM).³¹ The onset of T2DM is determined by multiple factors that lead to reduced insulin secretion or insulin resistance, including genetic predisposition and lifestyle-associated habits such as lack of exercise, overeating, and obesity. Many drugs are already used clinically to treat T2DM;^9,11 nevertheless, the search and development of more efficient and safe drugs is currently underway. In this regard, incretin has recently gained attention as a member of a class of drugs used to treat T2DM.^9,11Enteroendocrine cells secret incretin hormones, which augment glucose-induced insulin secretion in response to food ingestion, in a glucose-dependent manner. Currently, the 2 confirmed incretins are glucose-dependent insulinotropic polypeptide and glucagon-like peptide 1 (GLP1). Research has shown that GLP1 derivatives have functions in addition to the promotion of insulin secretion, including facilitation of β-cell proliferation,²⁸ suppression of β-cell apoptosis,¹² and promotion of β-cell differentiation or de novo formation of β cells.^29,30 GLP1 derivatives have been reported to have multiple nonpancreatic functions, including suppression of appetite and body weight,^7,13 suppression of gastric secretions,¹⁹ reduction of lipid accumulation in the liver,¹⁷ and promotion of sensitivity to insulin in adipose cells and skeletal muscle.^8,22WBN/Kob-type male rats are a relevant animal model for diabetes without obesity. These rats typically show disease conditions including chronic pancreatitis and pancreatic endocrine disorders.^18,26 A new model rat for diabetes was established recently by crossing rats carrying the Lepr^fa obesity gene with wild-type WBN/Kob rats, yielding a fa/fa congenic strain.¹ The obesity gene (Lepr^fa) is a spontaneous mutation derived from Zucker-fatty rats that leads to dysfunction of the leptin receptor. Rats homozygous for this gene are obese, resistant to insulin, and hyperinsulinemic.^4,16,32 Male WBN/Kob-Lepr^fa rats (hereafter referred to as fa/fa rats) represent a new animal model in which the animals spontaneously develop diabetes in addition to endogenous insulin resistance. Compared with the parental strains, fa/fa rats are characterized by an earlier onset of diabetes and more severe pancreatic complications.^1,2 Our previous investigations have revealed that fa/fa rats present with hyperinsulinemia at a prediabetic stage as a compensatory response to insulin resistance, but these rats show high blood glucose levels because of a difficulty in maintaining blood insulin concentrations as a consequence of declining pancreatic β-cell function associated with advancing age.¹⁴In the current study, to further validate fa/fa rats as a T2DM model, we investigated the effects of a GLP1 analog in fa/fa rats with hyperglycemia (age, 7 to 11 wk). We used liraglutide, a human GLP1 analog, which has been shown to be clinically effective in T2DM patients.^9,11