Estrogen actions in the male reproductive system involve estrogen response element-independent pathways

The estrogen receptor-alpha (ERalpha) acts through multiple pathways, including estrogen response element (ERE)-dependent (classical) and ERE-independent (nonclassical) mechanisms. We previously created a mouse model harboring a two-amino-acid mutation of the DNA-binding domain (E207A, G208A) that precludes direct binding of ERalpha to an ERE. After crossing heterozygous mutant mice with an ERalpha knockout (ERKO) line, it was possible to assess the degree of physiological rescue by the isolated ERalpha nonclassical allele (-/AA; AA) when compared with ERKO mice (-/-) and to wild type (+/+; WT). In male ERKO mice up to 8 months of age, testosterone levels were high, although LH levels were similar to WT. Testosterone was normal in the AA mice, indicating that the AA allele rescues the enhanced testosterone biosynthesis in ERKO mice. Male ERKO mice exhibited distention of the seminiferous tubules as early as 2-3 months of age as a consequence of decreased water resorption in the efferent ducts. By 3-4 months of age, ERKO mice had impaired spermatogenesis in approximately 40% of their tubules, and sperm counts and motility declined in association with the histological changes. In the AA mice, histological defects were greatly reduced or absent, and sperm counts and motility were rescued. Levels of aquaporins 1 and 9, which contribute to water uptake in the efferent ducts, were reduced in ERKO mice and partially or fully rescued in AA mice, whereas another water transporter, sodium-hydrogen exchanger-3, was decreased in both ERKO and AA mice. We conclude that non-ERE-dependent estrogen pathways are sufficient to rescue the defective spermatogenesis observed in ERKO mice and play a prominent role in ERalpha action in the testis, including pathways that regulate water resorption and androgen biosynthesis.     

Chronic low back pain: non-clinical factors impacting on management by Irish doctors

Introduction  General practitioners and consultants in the Republic of Ireland manage patients with chronic low back pain (LBP), but little is known about the non-clinical factors that impact on their management. Aim  To establish the non-clinical factors that impact on the management of chronic LBP by a cohort of general practitioners and consultants. Methods  Using a multiple case study design, semi-structured interviews were conducted with general practitioners (n = 7) and consultants (n = 7). Interviews were transcribed and analysed qualitatively. Results  Two main themes emerged: policy factors (the health care system, the medico-legal system), and patient factors (need for reassurance, lack of patient adherence). Conclusions  These factors operate at national and local levels. Nationally, they underscore the lack of resources, and the impact of the medico-legal system. Local issues include changing practice by reassuring patients using evidence-based biopsychosocial strategies to maximise patient care and reduce healthcare costs. Disclaimers: none.     

Discovery of inhibitors of Escherichia coli methionine aminopeptidase with the Fe(II)-form selectivity and antibacterial activity

Methionine aminopeptidase (MetAP) is a promising target to develop novel antibiotics, because all bacteria express MetAP from a single gene that carries out the essential function of removing N-terminal methionine from nascent proteins. Divalent metal ions play a critical role in the catalysis, and there is an urgent need to define the actual metal used by MetAP in bacterial cells. By high throughput screening, we identified a novel class of catechol-containing MetAP inhibitors that display selectivity for the Fe(II)-form of MetAP. X-ray structure revealed that the inhibitor binds to MetAP at the active site with the catechol coordinating to the metal ions. Importantly, some of the inhibitors showed antibacterial activity at low micromolar concentration on Gram-positive and Gram-negative bacteria. Our data indicate that Fe(II) is the likely metal used by MetAP in the cellular environment, and MetAP inhibitors need to inhibit this metalloform of MetAP effectively to be therapeutically useful.     

Oxytocin-induced contractions within rat and rabbit ejaculatory tissues are mediated by vasopressin V1A receptors and not oxytocin receptors

Background and purpose:Oxytocin is believed to be involved in ejaculation by increasing sperm number and contracting ejaculatory tissues. However, oxytocin may mediate these effects via oxytocin or vasopressin (AVP) receptors. The aim of this study was to determine the effect of oxytocin and AVP on peripheral tissues involved in ejaculation and to identify the receptor subtype(s) involved.Experimental approach:Standard tissue bath techniques were used to measure isometric tension from tissues involved in ejaculation and erection.Key results:Oxytocin and AVP failed to elicit a tonic contractile response in rat and rabbit testes, vas deferens, epididymis, seminal vesicles and prostate. In contrast, oxytocin and AVP elicited large tonic contractions in erectile (corpus spongiosum and corpus cavernosum) and ejaculatory (prostatic urethra, bladder neck and ejaculatory duct) tissues in a concentration-dependent manner. The selective oxytocin agonist, [Thr(4),Gly(7)]-oxytocin and the V(2) agonist, [deamino-Cys(1),Val(4),D-Arg(8)]-vasopressin (dDAVP), failed to contract tissues. Oxytocin and AVP-induced contractions were weakly antagonized by the selective oxytocin antagonist, L-368899 but potently antagonized by the V(1A) antagonist, SR49059. The V(1B) antagonist SSR149415 failed to antagonize AVP contractions except in rabbit bladder neck. Neither L-368899 nor SR49059 antagonized endothelin-1-induced contractions.Conclusions and implications:The contractile effect of oxytocin on rat and rabbit ejaculatory and erectile tissues is mediated via V(1A) receptors. Endothelin-1-induced contractions are not due to endogenous oxytocin or AVP release. V(1A) receptor antagonists may have a therapeutic role in both erectile dysfunction and premature ejaculation.British Journal of Pharmacology (2008) 155, 118-126; doi:10.1038/bjp.2008.226; published online 16 June 2008.     

Estimation of HLA-A, -B, -DRB1 haplotype frequencies using mixed resolution data from a National Registry with selective retyping of volunteers

Large registries of volunteer hematopoietic stem cell donors typed for HLA contain potentially valuable data for studying haplotype frequencies in the general population. However the usual assumptions for use of the expectation-maximization (EM) algorithm are typically violated in these registries. To avoid this problem, previous studies using registry data have reduced the HLA typings to low-resolution and/or excluded subjects who were selected for testing on behalf of a specific patient (“patient-directed” typings). These restrictions, added to avoid bias from selection of nonrepresentative volunteers for higher-resolution typing, have limited previous results to haplotypes defined at low resolution. In this article we eliminate the need for such restrictions by formally relaxing the assumptions necessary for the EM algorithm. We show mathematically and through simulation that varying levels of resolution can be incorporated even if the level of typing resolution is chosen based on the HLA type. This allows use of intermediate and high resolution data from patient-directed typings to extend haplotype frequency estimates to the allele level for HLA-DRB1. We demonstrate the feasibility of using this computationally demanding algorithm on large datasets by applying it to more than 3 million volunteers listed in the National Marrow Donor Program Registry.     

Genetic associations in community context: a mixed model approach identifies a functional variant in the <Emphasis Type="Italic">RBP4</Emphasis> gene associated with HDL-C dyslipidemia

Background

The objective of this study was to examine individual and community factors that influence high-density lipoprotein cholesterol (HDL-C) dyslipidemia in Newfoundland and Labrador (NL), a genetically isolated population in Canada with a high prevalence of HDL-C dyslipidemia.

Methods

First, a group of single nucleotide polymorphisms from 10 metabolic trait candidate genes was tested using a multivariate logistic regression model. The significant SNPs were entered into the second phase, where a mixed logistic model incorporated the community disease risk factors together with the individual factors as the fixed part of the model and the geographic region as a random effect.

Results

Analysis of 1489 subjects (26.9% HDL-C dyslipidemia) identified rs3758539, a non-coding variant in the 5’UTR of RBP4, to be associated with HDL-C dyslipidemia (odds ratio?=?1.45, 95% confidence interval?=?1.08–1.97, p?=?0.01). The association remained significant, and the effect size did not change after the incorporation of individual and community risk factors from 17 geographic regions (odds ratio: 1.41, 95% confidence interval?=?1.03–1.93, p?=?0.03) in NL. Besides this variant, sex, BMI, and smoking also showed significant associations with HDL-C dyslipidemia, whereas no role was identified for the community factors.

Conclusions

This study demonstrates the use of community-level data in a genetic association testing. It reports a functional variant in the promoter of RBP4, a gene directly involved in lipoprotein metabolism, to be associated with HDL-C dyslipidemia. These findings indicate that individual factors are the main reason for a higher prevalence of HDL-C dyslipidemia in the NL population.

     

From taxonomy I to taxonomy II

Taxonomic development in nursing, although still in its infancy, is progressing. Taxonomy development has moved beyond subjective placement of diagnoses into categories based on an "expert" opinion alone. The taxonomy of nursing diagnoses is entering a new era whereby the assumptions and classification rules for Taxonomy I--Revised are being investigated. Alternative taxonomic structures require careful scrutiny and comparison to establish whether one structure will meet the needs of the profession or whether multiple structures of nursing diagnoses relative to outcomes are required. As members within the discipline become more sophisticated in approaches to taxonomic development, methods of handling taxonomic problems, such as varying levels of abstraction and taxonomic affinity, will be discerned.     

Mechanisms responsible for the enhanced antinociceptive effects of micro-opioid receptor agonists in the rostral ventromedial medulla of male rats with persistent inflammatory pain

This study investigated three possible mechanisms by which the antinociceptive effects of the mu-opioid receptor (MOR) agonist [d-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) and the delta-opioid receptor (DOR) agonist [d-Ala(2),Glu(4)]-deltorphin (deltorphin II) (DELT), microinjected into the rostral ventromedial medulla (RVM), are enhanced in rats with persistent inflammatory injury. Radioligand binding determined that neither the B(max) nor the K(d) values of [(3)H]DAMGO differed in RVM membranes from rats that received an intraplantar injection of saline or complete Freund's adjuvant (CFA) in one hindpaw 4 h, 4 days, or 2 weeks earlier. Likewise, neither the EC(50) nor the E(max) value for DAMGO-induced stimulation of guanosine 5'-O-(3-[(35)S]thio)triphosphate ([(35)S]GTPgammaS) binding differed in the RVM of saline- or CFA-treated rats at any time point. Microinjection of fixed dose combinations of DAMGO and DELT in the RVM of naive rats indicated that these agonists interact synergistically to produce antinociception when DAMGO is present in equal or greater amounts than DELT and, additively, when DELT is the predominant component. Thus, unlike the periphery or spinal cord, potentiation of MOR-mediated antinociception does not entail an increase in MOR number, affinity, or coupling. Rather, the data are concordant with our proposal that potentiation results from a synergistic interaction of exogenous MOR agonist with DOR-preferring enkephalins whose levels are increased in CFA-treated rats (J Neurosci 21:2536-2545, 2001). Virtually no specific [(3)H]DELT binding nor stimulation of [(35)S]GTPgammaS binding by DELT was obtained in RVM membranes from CFA- or saline-treated rats at any time point. The mechanisms responsible for the potentiation of DELT-mediated antinociception remain to be elucidated.