Tyrosine phosphatase epsilon is a positive regulator of osteoclast function in vitro and in vivo

Protein tyrosine phosphorylation is a major regulator of bone metabolism. Tyrosine phosphatases participate in regulating phosphorylation, but roles of specific phosphatases in bone metabolism are largely unknown. We demonstrate that young (<12 weeks) female mice lacking tyrosine phosphatase epsilon (PTPepsilon) exhibit increased trabecular bone mass due to cell-specific defects in osteoclast function. These defects are manifested in vivo as reduced association of osteoclasts with bone and as reduced serum concentration of C-terminal collagen telopeptides, specific products of osteoclast-mediated bone degradation. Osteoclast-like cells are generated readily from PTPepsilon-deficient bone-marrow precursors. However, cultures of these cells contain few mature, polarized cells and perform poorly in bone resorption assays in vitro. Podosomes, structures by which osteoclasts adhere to matrix, are disorganized and tend to form large clusters in these cells, suggesting that lack of PTPepsilon adversely affects podosomal arrangement in the final stages of osteoclast polarization. The gender and age specificities of the bone phenotype suggest that it is modulated by hormonal status, despite normal serum levels of estrogen and progesterone in affected mice. Stimulation of bone resorption by RANKL and, surprisingly, Src activity and Pyk2 phosphorylation are normal in PTPepsilon-deficient osteoclasts, indicating that loss of PTPepsilon does not cause widespread disruption of these signaling pathways. These results establish PTPepsilon as a phosphatase required for optimal structure, subcellular organization, and function of osteoclasts in vivo and in vitro.     

Amoralist Rationalism? A Response to Joel Marks

In a recent article, Joel Marks presents the amoralist argument against vivisection, or animal laboratory experimentation. He argues that ethical theories that seek to uncover some universal morality are in fact useless and unnecessary for ethical deliberations meant to determine what constitutes an appropriate action in a specific circumstance. I agree with Marks’ conclusion. I too believe that vivisection is indefensible, both from a scientific and philosophical perspective. I also believe that we should become vegan (unfortunately, like the two philosophers mentioned by Marks, I too am still struggling to reduce my meat and dairy consumption). However, I am in the dark as to Marks’ vision of normative deliberations in the spirit of amoralism and desirism.     

Twice daily versus four times daily insulin dose regimens for diabetes in pregnancy: randomised controlled trial

ObjectiveTo compare perinatal outcome and glycaemic control in two groups of pregnant diabetic patients receiving two insulin regimens.DesignRandomised controlled open label study.SettingUniversity affiliated hospital, Israel.Participants138 patients with gestational diabetes mellitus and 58 patients with pregestational diabetes mellitus received insulin four times daily, and 136 patients with gestational diabetes and 60 patients with pregestational diabetes received insulin twice daily.InterventionThree doses of regular insulin before meals and an intermediate insulin dose before bedtime (four times daily regimen), and a combination of regular and intermediate insulin in the morning and evening (twice daily regimen).ResultsMean daily insulin concentration before birth was higher in the women receiving insulin four times daily compared with twice daily: by 22 units (95% confidence interval 12 to 32) in patients with gestational diabetes and by 28 units (15 to 41) in patients with pregestational diabetes. Glycaemic control was better with the four times daily regimen than with the twice daily regimen: in patients with gestational diabetes mean blood glucose concentrations decreased by 0.19 mmol/l (0.13 to 0.25), HbA_1c by 0.3% (0.2% to 0.4%), and fructosamine by 41 μmol/l (37 to 45), and adequate glycaemic control (mean blood glucose concentration <5.8 mmol/l) was achieved in 17% (8% to 26%) more women; in patients with pregestational diabetes mean blood glucose concentration decreased by 0.44 mmol/l (0.28 to 0.60), HbA_1c by 0.5% (0.2% to 0.8%), and fructosamine by 51 μmol/l (45 to 57), and adequate glycaemic control was achieved in 31% (15% to 47%) more women. Maternal severe hypoglycaemic events, caesarean section, preterm birth, macrosomia, and low Apgar scores were similar in both dose groups. In women with gestational diabetes the four times daily regimen resulted in a lower rate of overall neonatal morbidity than the twice daily regimen (relative risk 0.59, 0.38 to 0.92), and the relative risk for hyperbilirubinaemia and hypoglycaemia was lower (0.51, 0.29 to 0.91 and 0.12, 0.02 to 0.97 respectively). The relative risk of hypoglycaemia in newborn infants to mothers with pregestational diabetes was 0.17 (0.04 to 0.74).ConclusionsGiving insulin four times rather than twice daily in pregnancy improved glycaemic control and perinatal outcome without further risking the mother.

Key messages

• Improving maternal glycaemic control during pregnancy is the key to better perinatal outcome
• In pregnant diabetic women insulin four times daily achieved better glycaemic control and lower rate of perinatal complications (hypoglycaemia, hyperbilirubinaemia) than insulin twice daily
• Better glycaemic control resulted from a larger total daily insulin dose
• The intensified regimen did not lead to higher rate of severe maternal hypoglycaemia

     

Ontogeny of the GnRH systems in zebrafish brain: in situ hybridization and promoter-reporter expression analyses in intact animals

The ontogeny of two gonadotropin-releasing-hormone (GnRH) systems, salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II), was investigated in zebrafish (Danio rerio). In situ hybridization (ISH) first detected sGnRH mRNA-expressing cells at 1 day post-fertilization (pf) anterior to the developing olfactory organs. Subsequently, cells were seen along the ventral olfactory organs and the olfactory bulbs, reaching the terminal nerve (TN) ganglion at 5–6 days pf. Some cells were detected passing posteriorly through the ventral telencephalon (10–25 days pf), and by 25–30 days pf, sGnRH cells were found in the hypothalamic/preoptic area. Continuous documentation in live zebrafish was achieved by a promoter-reporter expression system. The expression of enhanced green fluorescent protein (EGFP) driven by the sGnRH promoter allowed the earlier detection of cells and projections and the migration of sGnRH neurons. This expression system revealed that long leading processes, presumably axons, preceded the migration of the sGnRH neuron somata. cGnRH-II mRNA expressing cells were initially detected (1 day pf) by ISH analysis at lateral aspects of the midbrain and later on (starting at 5 days pf) at the midline of the midbrain tegmentum. Detection of red fluorescent protein (DsRed) driven by the cGnRH-II promoter confirmed the midbrain expression domain and identified specific hindbrain and forebrain cGnRH-II-cells that were not identified by ISH. The forebrain DsRed-expressing cells seemed to emerge from the same site as the sGnRH-EGFP-expressing cells, as revealed by co-injection of both constructs. These studies indicate that zebrafish TN and hypothalamic sGnRH cell populations share a common embryonic origin and migratory path, and that midbrain cGnRH-II cells originate within the midbrain. This study was supported by the US-Israel Bi-national Agricultural Research and Development (BARD) Foundation (grant 3428-03).     

Reproductive success of a marine teleost was correlated with proactive and reactive stress-coping styles

The present study investigated the relationship between reproductive success and stress-coping styles in gilthead seabream Sparus aurata in captivity. To characterise stress-coping styles, a total of 22 breeders were submitted to three different individual-based tests, one group-based test and post-handling glucocorticoid quantification. To assess spawning participation, a microsatellite analysis was performed on a total of 2698 larvae, which allowed each offspring to be assigned unambiguously to a single parental couple. Overall, S. aurata showed defined proactive and reactive behavioural traits. Proactive breeders exhibited higher levels of activity and risk taking and lower glucocorticoid blood levels than reactive breeders. The stress-coping style traits were consistent over time and context (different tests). Breeders that contributed to a higher number of progeny exhibited proactive behaviours, while those showing low progeny contribution exhibited reactive behaviour. Therefore, breeders with a high proportion of progeny (> 20%) had significantly higher activity and risk taking and lower cortisol than breeders with low progeny contribution (< 20%). In addition, males were more proactive than females and males exhibited significantly higher activity, risk taking and lower cortisol than females. This study is the first to establish in S. aurata breeders: (a) a relationship between stress-coping styles and spawning success; (b) a relationship between stress-coping styles and gender; and (c) the existence of proactive and reactive traits at the adult stage.     

Acetohydroxyacid synthase from Mycobacterium avium and its inhibition by sulfonylureas and imidazolinones

Tuberculosis (TB) remains one of the world's leading causes of death from infectious disease. It is caused by infection with Mycobacterium tuberculosis or sometimes, particularly in immune-compromised patients, Mycobacterium avium. The aim of this study was to create a tool that could be used in the search for new anti-TB drugs that inhibit branched-chain amino acid (BCAA) biosynthesis, as these are essential amino acids that are not available to a mycobacterium during growth in an infected organism. To this end, we cloned, overexpressed, purified and characterised for the first time an acetohydroxyacid synthase (AHAS), a key enzyme in the pathway to the biosynthesis of the BCAAs, from the genus Mycobacterium. Nine commercial herbicides of the sulfonylurea and imidazolinone classes were tested for their influence on this enzyme. Four of the sulfonylureas were potent inhibitors of the enzyme. The relative potency of the different inhibitors towards the M. avium enzyme was unlike their potency towards other AHASs whose inhibitor profile has been reported, emphasising the advantage of using a mycobacterial enzyme as a tool in the search for new anti-TB drugs.