A new method to remove hybridization bias for interspecies comparison of global gene expression profiles uncovers an association between mRNA sequence divergence and differential gene expression in Xenopus

The recent sequencing of a large number of Xenopus tropicalis expressed sequences has allowed development of a high-throughput approach to study Xenopus global RNA gene expression. We examined the global gene expression similarities and differences between the historically significant Xenopus laevis model system and the increasingly used X.tropicalis model system and assessed whether an X.tropicalis microarray platform can be used for X.laevis. These closely related species were also used to investigate a more general question: is there an association between mRNA sequence divergence and differences in gene expression levels? We carried out a comprehensive comparison of global gene expression profiles using microarrays of different tissues and developmental stages of X.laevis and X.tropicalis. We (i) show that the X.tropicalis probes provide an efficacious microarray platform for X.laevis, (ii) describe methods to compare interspecies mRNA profiles that correct differences in hybridization efficiency and (iii) show independently of hybridization bias that as mRNA sequence divergence increases between X.laevis and X.tropicalis differences in mRNA expression levels also increase.     

Transducing properties of Drosophila Frizzled proteins.

In Drosophila, two closely related serpentine receptors, Frizzled (Fz) and D-Frizzled2 (Fz2) are able to act as receptors for the secreted Wnt peptide, Wingless (Wg). In addition to transducing the Wg signal, Fz (but not Fz2) is able to transduce a second, unidentified signal that mediates planar polarity. Much attention has been focused on the structure of the N-termini of the Fz-class receptors and their role in ligand binding. Experiments using techniques of high-level expression have suggested a role for the C-termini in specifying which of the two second messenger systems the receptors are able to activate (M. Boutros, J. Mihaly, T. Bouwmeeste and M. Mlodzik (2000). Science 288, 1825-1828). We argue here that experiments involving high level expression of the receptors cannot be adequately interpreted and we have tested the ability of the receptors and chimeric forms when driven at moderate levels to rescue loss of function of the fz and fz2 genes. Under these conditions we find that all receptors tested will function as Wg receptors, but only a subset show the ability to rescue the polarity pathway. The presence of this subset implies that the N terminus is necessary but not sufficient and suggests that the ability to transduce the polarity signal is widely distributed throughout the protein.     

Predicting low testosterone in aging men: a systematic review

Background:Physicians diagnose and treat suspected hypogonadism in older men by extrapolating from the defined clinical entity of hypogonadism found in younger men. We conducted a systematic review to estimate the accuracy of clinical symptoms and signs for predicting low testosterone among aging men.Methods:We searched the MEDLINE and Embase databases (January 1966 to July 2014) for studies that compared clinical features with a measurement of serum testosterone in men. Three of the authors independently reviewed articles for inclusion, assessed quality and extracted data.Results:Among 6053 articles identified, 40 met the inclusion criteria. The prevalence of low testosterone ranged between 2% and 77%. Threshold testosterone levels used for reference standards also varied substantially. The summary likelihood ratio associated with decreased libido was 1.6 (95% confidence interval [CI] 1.3–1.9), and the likelihood ratio for absence of this finding was 0.72 (95% CI 0.58–0.85). The likelihood ratio associated with the presence of erectile dysfunction was 1.5 (95% CI 1.3–1.8) and with absence of erectile dysfunction was 0.83 (95% CI 0.76–0.91). Of the multiple-item instruments, the ANDROTEST showed both the most favourable positive likelihood ratio (range 1.9–2.2) and the most favourable negative likelihood ratio (range 0.37–0.49).Interpretation:We found weak correlation between signs, symptoms and testosterone levels, uncertainty about what threshold testosterone levels should be considered low for aging men and wide variation in estimated prevalence of the condition. It is therefore difficult to extrapolate the method of diagnosing pathologic hypogonadism in younger men to clinical decisions regarding age-related testosterone decline in aging men.Male hypogonadism is defined as the presence of low serum testosterone and spermatozoa levels, accompanied by clinical signs and symptoms.¹ The Endocrine Society divides the symptoms and signs of androgen deficiency into 2 groups, based on expert consensus.¹ The first group, which is considered more specific, includes incomplete or delayed sexual development; eunuchoidism; reduced sexual desire (libido); erectile dysfunction; gynecomastia; decreased axillary, facial and pubic hair; small testes (i.e., volume < 5 mL); infertility: low-trauma fracture; low bone mineral density; and hot flushes.¹ The second group includes less specific signs and symptoms, such as decreased energy and motivation, depressed mood, poor concentration and memory, sleep disturbance, mild anemia, reduced muscle bulk and strength, increased body fat or body mass index, and diminished physical performance. ¹ Similar definitions have recently been developed by the Canadian Men’s Health Foundation Multidisciplinary Guidelines Task Force on Testosterone Deficiency.²In young men, hypogonadism is more commonly characterized by signs and symptoms from the first group, such as reduced libido and erectile dysfunction. This condition is most often caused by testicular or pituitary pathology, including hyperprolactinemia, pituitary or hypothalamic disorders, testicular disease, radiation exposure or genetic diseases such as Klinefelter syndrome.³ Testosterone replacement is indicated in these cases of “classic hypogonadism,” as it ameliorates the clinical symptoms.⁴In contrast, although these entities exist in older men too, they are less frequent causes of low testosterone than age-related changes. There is evidence that testosterone levels decline with age in all men, regardless of symptoms, at an estimated rate of 1%–3% per year.^5,6 One study found that serum testosterone levels were below the normal range in 20% of men in their 60s and in close to 50% of men in their 80s.⁷ However, the prevalence of symptomatic low testosterone (hypogonadism) is estimated by some to be much lower in this population, at about 2%.⁸ Given the high prevalence of low testosterone and more limited correlation with symptoms in aging men, it is uncertain to what extent this represents a physiologic or pathologic event.^6,7 Moreover, symptoms typically associated with low testosterone are less specific in older men and may be caused by other comorbidities. For example, erectile dysfunction can be the result of vascular insufficiency, neurologic impairment, psychogenic causes or substance use.⁹ Conditions such as diabetes mellitus and atherosclerosis are more common in older men, with up to 40% of men over 50 years of age having evidence of vascular insufficiency as the primary cause of their erectile dysfunction.¹⁰ Low libido similarly can result from psychiatric or medical conditions that are more common in older men.¹¹Currently, many clinicians diagnose hypogonadism in older men on the basis of low serum testosterone levels, with or without symptoms, largely on the assumption that this is a pathologic condition requiring treatment. The purpose of this study was to systematically review the available literature to estimate the accuracy and operating characteristics of signs and symptoms for predicting low testosterone in aging men.     

Sero-epidemiological study of cowdriosis in Moorish zebu cattle from Senegal

The seroprevalence against heartwater for maure zebus coming from Mali and Mauritania is analysed by indirect ELISA using the major antigenic protein number 1-B (MAP1-B). Sero-epidemiological results realized on maure zebu cattle give a good adequation between the abundance or absence of the vector tick in the two countries for 98% of prevalence in Mali (infected area) and 0% of prevalence in Mauritania (non infected area).     

Glucose increases cytosolic calcium concentration and inositol lipid metabolism in HIT-T15 cells

We have investigated the effects of glucose on cytosolic free calcium concentration in the insulin-secreting cell line HIT-T15. Addition of glucose (10 mM) caused a 20-75% increase in cytosolic [Ca2+] within 5 minutes compared to controls in the absence of glucose. A maximal increase in cytosolic [Ca2+] was obtained with 5 mM glucose. The magnitude of the response was markedly dependent upon the concentration of extracellular Ca2+, and the rise in cytosolic [Ca2+] was inhibited by verapamil. Cytosolic [Ca2+] was greatly increased by depolarization of the cells with KCl (50 mM), whereas carbamylcholine had no apparent effect. Glucose and KCl were also effective in stimulating insulin release from HIT cells, although carbamylcholine was again ineffective. The secretory response to glucose was also found to be directly related to the concentration of extracellular [Ca2+]. Glucose and KCl, but not carbamylcholine, were found to slightly enhance the production of [3H]-inositol trisphosphate in HIT cells pre-labelled with myo-[3H]-inositol, indicating a modest stimulation of inositol lipid hydrolysis.     

Analysis of a yeast nuclear gene involved in the maturation of mitochondrial pre-messenger RNA of the cytochrome oxidase subunit I

We have analyzed the mitochondrial RNA of a yeast nuclear pet mutant with no cytochrome oxidase activity. The product of the gene affected in this mutant appears to be necessary for the correct maturation of the mitochondrial pre-mRNA of the cytochrome oxidase subunit I. It does not affect, however, the overall splicing of cytochrome b pre-mRNA or the intron excision of the 21S ribosomal RNA precursor. This gene has been isolated by genetic complementation in yeast, and its DNA sequence has been determined. It is transcribed, as detected by S1 mapping experiments, and could encode a protein of 436 amino acids.     

Transient Hypoxia Alters Striatal Catecholamine Metabolism in Immature Brain: An In Vivo Microdialysis Study

Microdialysis probes were inserted bilaterally into the striatum of 7-day-old rat pups (n = 30) to examine extracellular fluid levels of dopamine, its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA). The dialysis samples were assayed by HPLC with electrochemical detection. Baseline levels, measured after a 2-h stabilization period, were as follows: dopamine, not detected; DOPAC, 617 +/- 33 fmol/min; HVA, 974 +/- 42 fmol/min; and 5-HIAA, 276 +/- 15 fmol/min. After a 40-min baseline sampling period, 12 animals were exposed to 8% oxygen for 120 min. Hypoxia produced marked reductions in the striatal extracellular fluid levels of both dopamine metabolites (p less than 0.001 by analysis of variance) and a more gradual and less prominent reduction in 5-HIAA levels (p less than 0.02 by analysis of variance), compared with controls (n = 12) sampled in room air. In the first hour after hypoxia, DOPAC and HVA levels rose quickly, whereas 5-HIAA levels remained suppressed. The magnitude of depolarization-evoked release of dopamine (elicited by infusion of potassium or veratrine through the microdialysis probes for 20 min) was evaluated in control and hypoxic animals. Depolarization-evoked dopamine efflux was considerably higher in hypoxic pups than in controls: hypoxic (n = 7), 257 +/- 32 fmol/min; control (n = 12), 75 +/- 14 fmol/min (p less than 0.001 by analysis of variance). These data demonstrate that a brief exposure to moderate hypoxia markedly disrupts striatal catecholamine metabolism in the immature rodent brain.