The genetic basis of human height : the role of estrogen

Height is a complex physical trait that displays strong heritability. Adult height is related to length of the long bones, which is determined by growth at the epiphyseal growth plate. Longitudinal bone growth occurs via the process of endochondral ossification, where bone forms over the differentiating cartilage template at the growth plate. Estrogen plays a major role in regulating longitudinal bone growth and is responsible for inducing the pubertal growth spurt and fusion of the epiphyseal growth plate. However, the mechanism by which estrogen promotes epiphyseal fusion is poorly understood. It has been hypothesised that estrogen functions to regulate growth plate fusion by stimulating chondrocyte apoptosis, angiogenesis and bone cell invasion in the growth plate. Another theory has suggested that estrogen exposure exhausts the proliferative capacity of growth plate chondrocytes, which accelerates the process of chondrocyte senescence, leading to growth plate fusion. The overall objective of this study was to gain a greater understanding of the molecular mechanisms behind estrogen-mediated growth and height attainment by examining gene regulation in chondrocytes and the role of some of these genes in normal height inheritance. With the heritability of height so well established, the initial hypothesis was that genetic variation in candidate genes associated with longitudinal bone growth would be involved in normal adult height variation. The height-related genes FGFR3, CBFA1, ER and CBFA1 were screened for novel polymorphisms using denaturing HPLC and RFLP analysis. In total, 24 polymorphisms were identified. Two SNPs in ER (rs3757323 C>T and rs1801132 G>C) were strongly associated with adult male height and displayed an 8 cm and 9 cm height difference between homozygous genotypes, respectively. The TC haplotype of these SNPs was associated with a 6 cm decrease in height and remarkably, no homozygous carriers of the TC haplotype were identified in tall subjects. No significant associations with height were found for polymorphisms in the FGFR3, CBFA1 or VDR genes. In the epiphyseal growth plate, chondrocyte proliferation, matrix synthesis and chondrocyte hypertrophy are all major contributors to long bone growth. As estrogen plays such a significant role in both growth and final height attainment, another hypothesis of this study was that estrogen exerted its effects in the growth plate by influencing chondrocyte proliferation and mediating the expression of chondrocyte marker genes. The examination of genes regulated by estrogen in chondrocyte-like cells aimed to identify potential regulators of growth plate fusion, which may further elucidate mechanisms involved in the cessation of linear growth. While estrogen did not dramatically alter the proliferation of the SW1353 cell line, gene expression experiments identified several estrogen regulated genes. Sixteen chondrocyte marker genes were examined in response to estrogen concentrations ranging from 10-12 M to 10-8 M over varying time points. Of the genes analysed, IHH, FGFR3, collagen II and collagen X were not readily detectable and PTHrP, GHR, ER, BMP6, SOX9 and TGF1 mRNAs showed no significant response to estrogen treatments. However, the expression of MMP13, CBFA1, BCL-2 and BAX genes were significantly decreased. Interestingly, the majority of estrogen regulated genes in SW1353 cells are expressed in the hypertrophic zone of the growth plate. Estrogen is also known to regulate systemic GH secretion and local GH action. At the molecular level, estrogen functions to inhibit GH action by negatively regulating GH signalling. GH treated SW1353 cells displayed increases in MMP9 mRNA expression (4.4-fold) and MMP13 mRNA expression (64-fold) in SW1353 cells. Increases were also detected in their respective proteins. Treatment with AG490, an established JAK2 inhibitor, blocked the GH mediated stimulation of both MMP9 and MMP13 mRNA expression. The application of estrogen and GH to SW1353 cells attenuated GH-stimulated MMP13 levels, but did not affect MMP9 levels. Investigation of GH signalling revealed that SW1353 cells have high levels of activated JAK2 and exposure to GH, estrogen, AG490 and other signalling inhibitors did not affect JAK2 phosphorylation. Interestingly, AG490 treatment dramatically decreased ERK2 signalling, although GH did stimulate ERK2 phosphorylation above control levels. AG490 also decreased CBFA1 expression, a transcription factor known to activate MMP9 and MMP13. Finally, GH and estrogen treatment increased expression of SOCS3 mRNA, suggesting that SOCS3 may regulate JAK/STAT signalling in SW1353 cells. The modulation of GH-mediated MMP expression by estrogen in SW1353 cells represents a potentially novel mechanism by which estrogen may regulate longitudinal bone growth. However, further investigation is required in order to elucidate the precise mechanisms behind estrogen and GH regulation of MMP13 expression in SW1353 cells. This study has provided additional evidence that estrogen and the ER gene are major factors in the regulation of growth and the determination of adult height. Newly identified polymorphisms in the ER gene not only contribute to our understanding of the genetic basis of human height, but may also be useful in association studies examining other complex traits. This study also identified several estrogen regulated genes and indicated that estrogen modifies the expression of genes which are primarily expressed in the hypertrophic region of the epiphyseal growth plate. Furthermore, synergistic studies incorporating GH and estrogen have revealed the ability of estrogen to attenuate the effects of GH on MMP13 expression, revealing potential pathways by which estrogen may modulate growth plate fusion, longitudinal bone growth and even arthritis.

Molecular architecture of the human sinus node: insights into the function of the cardiac pacemaker.

BACKGROUND: Although we know much about the molecular makeup of the sinus node (SN) in small mammals, little is known about it in humans. The aims of the present study were to investigate the expression of ion channels in the human SN and to use the data to predict electrical activity. METHODS AND RESULTS: Quantitative polymerase chain reaction, in situ hybridization, and immunofluorescence were used to analyze 6 human tissue samples. Messenger RNA (mRNA) for 120 ion channels (and some related proteins) was measured in the SN, a novel paranodal area, and the right atrium (RA). The results showed, for example, that in the SN compared with the RA, there was a lower expression of Na(v)1.5, K(v)4.3, K(v)1.5, ERG, K(ir)2.1, K(ir)6.2, RyR2, SERCA2a, Cx40, and Cx43 mRNAs but a higher expression of Ca(v)1.3, Ca(v)3.1, HCN1, and HCN4 mRNAs. The expression pattern of many ion channels in the paranodal area was intermediate between that of the SN and RA; however, compared with the SN and RA, the paranodal area showed greater expression of K(v)4.2, K(ir)6.1, TASK1, SK2, and MiRP2. Expression of ion channel proteins was in agreement with expression of the corresponding mRNAs. The levels of mRNA in the SN, as a percentage of those in the RA, were used to estimate conductances of key ionic currents as a percentage of those in a mathematical model of human atrial action potential. The resulting SN model successfully produced pacemaking. CONCLUSIONS: Ion channels show a complex and heterogeneous pattern of expression in the SN, paranodal area, and RA in humans, and the expression pattern is appropriate to explain pacemaking.

Androgen levels increase by intratumoral de novo steroidogenesis during progression of castration-resistant prostate cancer

Although systemic androgen deprivation prolongs life in advanced prostate cancer, remissions are temporary because patients almost uniformly progress to a state of a castration-resistant prostate cancer (CRPC) as indicated by recurring PSA. This complex process of progression does not seem to be stochastic as the timing and phenotype are highly predictable, including the observation that most androgen-regulated genes are reactivated despite castrate levels of serum androgens. Recent evidence indicates that intraprostatic levels of androgens remain moderately high following systemic androgen deprivation therapy, whereas the androgen receptor (AR) remains functional, and silencing the AR expression following castration suppresses tumor growth and blocks the expression of genes known to be regulated by androgens. From these observations, we hypothesized that CRPC progression is not independent of androgen-driven activity and that androgens may be synthesized de novo in CRPC tumors leading to AR activation. Using the LNCaP xenograft model, we showed that tumor androgens increase during CRPC progression in correlation to PSA up-regulation. We show here that all enzymes necessary for androgen synthesis are expressed in prostate cancer tumors and some seem to be up-regulated during CRPC progression. Using an ex vivo radiotracing assays coupled to high-performance liquid chromatography-radiometric/mass spectrometry detection, we show that tumor explants isolated from CRPC progression are capable of de novo conversion of [(14)C]acetic acid to dihydrotestosterone and uptake of [(3)H]progesterone allows detection of the production of six other steroids upstream of dihydrotestosterone. This evidence suggests that de novo androgen synthesis may be a driving mechanism leading to CRPC progression following castration.

An adaptable framework for the teaching and assessment of software development across year levels

Few frameworks exist for the teaching and assessment of programming subjects that are coherent and logical. Nor are they sufficiently generic and adaptable to be used outside the particular tertiary institutions in which they were developed. This paper presents the Teaching and Assessment of Software Development (TASD) frame-work. We describe its development and implementation at an Australian university and demonstrate, with examples, how it has been used, with supporting data. Extracts of criteria sheets (grading rubrics) for a variety of assessment tasks are included. The numerous advantages of this new framework are discussed with comparisons made to those reported in the published literature.

An analysis of the determinants of job satisfaction when individuals' baseline satisfaction levels may differ.

A growing literature seeks to explain differences in individuals' self-reported satisfaction with their jobs. The evidence so far has mainly been based on cross-sectional data and when panel data have been used, individual unobserved heterogeneity has been modelled as an ordered probit model with random effects. This article makes use of longitudinal data for Denmark, taken from the waves 1995-1999 of the European Community Household Panel, and estimates fixed effects ordered logit models using the estimation methods proposed by Ferrer-i-Carbonel and Frijters (2004) and Das and van Soest (1999). For comparison and testing purposes a random effects ordered probit is also estimated. Estimations are carried out separately on the samples of men and women for individuals' overall satisfaction with the jobs they hold. We find that using the fixed effects approach (that clearly rejects the random effects specification), considerably reduces the number of key explanatory variables. The impact of central economic factors is the same as in previous studies, though. Moreover, the determinants of job satisfaction differ considerably between the genders, in particular once individual fixed effects are allowed for.

Developing a conceptual model for measuring the satisfaction levels of Malaysian contractors

The evaluation of satisfaction levels related to performance is an important aspect in increasing market share, improving profitability and enlarging opportunities for repeat business and can lead to the determination of areas to be improved, improving harmonious working relationships and conflict avoidance. In the construction industry, this can also result in improved project quality, enhanced reputation and increased competitiveness. Many conceptual models have been developed to measure satisfaction levels - typically to gauge client satisfaction, customer satisfaction and home buyer satisfaction - but limited empirical research has been carried out, especially in investigating the satisfaction of construction contractors. In addressing this, this paper provides a unique conceptual model or framework for contractor satisfaction based on attributes identified by interviews with practitioners in Malaysia. In addition to progressing research in this topic and being of potential benefit to Malaysian contractors, it is anticipated that the framework will also be useful for other parties - clients, designers, subcontractors and suppliers - in enhancing the quality of products and/or services generally.

A new approach to assessing Malaysian contractor satisfaction levels

The extent of poor project outcomes is a recurring issue for construction industries worldwide. One of the main causes of these and project failure seems to be the inability of contractors to provide a high level of service quality to the project team. In Malaysia, design failures have also been identified as a further contributory factor. To overcome this, different types of subjective performance measurement have been progressively developed. These approaches are typically concerned with client satisfaction, customer satisfaction, home buyer satisfaction and occupant satisfaction, but very seldom consider contractor satisfaction. This paper examines the implications of this, and what is involved in developing satisfaction measures based on contractor perception instead of the typical sole concern with client performance. As a result, other attributes such as participants’ performance, business performance, project performance, external factors and contractor characteristics are also examined. Several potential attributes are derived from interviews among Malaysian contractors, namely: performance (direct attributes) and contractor characteristics (indirect attributes) that possibly influence contractor satisfaction levels. These attributes are then developed to improve the existing conceptual framework. The developed framework is expected to help the project team in performing projects more efficiently, maintaining service quality and improving relationships between participants. In addition, the findings of the paper should assist contractors enhance competitiveness, improve their image and create more job opportunities in the future.

Effects of lead exposure on hippocampal metabotropic glutamate receptor subtype 3 and 7 in developmental rats

Background A complete explanation of the mechanisms by which Pb2+ exerts toxic effects on developmental central nervous system remains unknown. Glutamate is critical to the developing brain through various subtypes of ionotropic or metabotropic glutamate receptors (mGluRs). Ionotropic N-methyl-D-aspartate receptors have been considered as a principal target in lead-induced neurotoxicity. The relationship between mGluR3/mGluR7 and synaptic plasticity had been verified by many recent studies. The present study aimed to examine the role of mGluR3/mGluR7 in lead-induced neurotoxicity. Methods Twenty-four adult and female rats were randomly selected and placed on control or 0.2% lead acetate during gestation and lactation. Blood lead and hippocampal lead levels of pups were analyzed at weaning to evaluate the actual lead content at the end of the exposure. Impairments of short -term memory and long-term memory of pups were assessed by tests using Morris water maze and by detection of hippocampal ultrastructural alterations on electron microscopy. The impact of lead exposure on mGluR3 and mGluR7 mRNA expression in hippocampal tissue of pups were investigated by quantitative real-time polymerase chain reaction and its potential role in lead neurotoxicity were discussed. Results Lead levels of blood and hippocampi in the lead-exposed rats were significantly higher than those in the controls (P < 0.001). In tests using Morris Water Maze, the overall decrease in goal latency and swimming distance was taken to indicate that controls had shorter latencies and distance than lead-exposed rats (P = 0.001 and P < 0.001 by repeated-measures analysis of variance). On transmission electron microscopy neuronal ultrastructural alterations were observed and the results of real-time polymerase chain reaction showed that exposure to 0.2% lead acetate did not substantially change gene expression of mGluR3 and mGluR7 mRNA compared with controls. Conclusion Exposure to lead before and after birth can damage short-term and long-term memory ability of young rats and hippocampal ultrastructure. However, the current study does not provide evidence that the expression of rat hippocampal mGluR3 and mGluR7 can be altered by systemic administration of lead during gestation and lactation, which are informative for the field of lead-induced developmental neurotoxicity noting that it seems not to be worthwhile to include mGluR3 and mGluR7 in future studies. Background

A preliminary investigation of the role of the Phenylalynine: Tyrosine Ratio in children with early and continuously treated phenylketonuria : toward identification of “safe” levels

Children with early and continuously treated phenylketonuria (ECT-PKU) remain at risk of developing executive function (EF) deficits. There is some evidence that a high phenylalanine to tyrosine ratio (phe:tyr) is more strongly associated with impaired EF development than high phenylalanine alone. This study examined EF in a sample of 11 adolescents against concurrent and historical levels of phenylalanine, phe:tyr, and tyrosine. Lifetime measures of phe:tyr were more strongly associated with EF than phenylalanine-only measures. Children with a lifetime phe:tyr less than 6 demonstrated normal EF, whereas children who had a lifetime phe:tyr above 6, on average, demonstrated clinically impaired EF.

The effect of graded levels of exercise on energy intake and balance in free-living men, consuming their normal diet

Objective: To assess the effect of graded increases in exercised-induced energy expenditure (EE) on appetite, energy intake (EI), total daily EE and body weight in men living in their normal environment and consuming their usual diets. Design: Within-subject, repeated measures design. Six men (mean (s.d.) age 31.0 (5.0) y; weight 75.1 (15.96) kg; height 1.79 (0.10) m; body mass index (BMI) 23.3(2.4) kg/m2), were each studied three times during a 9 day protocol, corresponding to prescriptions of no exercise, (control) (Nex; 0 MJ/day), medium exercise level (Mex; ~1.6 MJ/day) and high exercise level (Hex; ~3.2 MJ/day). On days 1-2 subjects were given a medium fat (MF) maintenance diet (1.6 ´ resting metabolic rate (RMR)). Measurements: On days 3-9 subjects self-recorded dietary intake using a food diary and self-weighed intake. EE was assessed by continual heart rate monitoring, using the modified FLEX method. Subjects' HR (heart rate) was individually calibrated against submaximal VO2 during incremental exercise tests at the beginning and end of each 9 day study period. Respiratory exchange was measured by indirect calorimetry. Subjects completed hourly hunger ratings during waking hours to record subjective sensations of hunger and appetite. Body weight was measured daily. Results: EE amounted to 11.7, 12.9 and 16.8 MJ/day (F(2,10)=48.26; P<0.001 (s.e.d=0.55)) on the Nex, Mex and Hex treatments, respectively. The corresponding values for EI were 11.6, 11.8 and 11.8 MJ/day (F(2,10)=0.10; P=0.910 (s.e.d.=0.10)), respectively. There were no treatment effects on hunger, appetite or body weight, but there was evidence of weight loss on the Hex treatment. Conclusion: Increasing EE did not lead to compensation of EI over 7 days. However, total daily EE tended to decrease over time on the two exercise treatments. Lean men appear able to tolerate a considerable negative energy balance, induced by exercise, over 7 days without invoking compensatory increases in EI.

An examination of communication across cultures in news media and at informal/personal levels : with concentration on relations among two South East Asian countries and Australia and those two countries and Germany

In the age of globalisation dominated by mass communication, the flow of information contributes to a big extent to the worldviews of its "global citizens". From this point of view the mass media can be seen as one of the most salient sources of cross-cultural communication. This study investigates mass communication across cultures, focusing on South East Asia (Malaysia and Singapore), Australia and Germany. The centre of attention is the Western media coverage of South East Asia and vice versa. In this context a content analysis of newspapers of the three regions has been conducted. In addition, working practices and conditions of Western foreign correspondents in South East Asia have been examined. Apart from the investigation of inter-cultural media coverage, another focus of attention will be the examination of two levels of communication: The business level, concentrating on issues like e.g. the Asian business etiquette; and the private level, looking into the transition to a different culture from the perspective of Australian and German expatriates. Apart from investigating mass communication across cultures and to provide a written analysis of the findings, a series of radio documentaries in English and in German has been produced. They cover the following issues: Foreign correspondents in South East Asia, the expatriate-lifestyle of Australians and Germans in South East Asia, business etiquette in Asia, student exchange Germany-Asia, image and prejudices East-West and Tourism.

Reducing high levels of communication apprehension among primary school students

This study focused on a group of primary school teachers as they implemented a variety of intervention actions within their class programs aimed towards supporting the reduction of high levels of communication apprehension (CA) among students.Six teachers and nine students, located across three primary schools, four year levels,and six classes, participated in this study. For reasons of confidentiality the schools,principals, parents, teachers, teacher assistants, and students who were involved in this study were given fictitious names. The following research question was explored in this study: What intervention actions can primary school teachers implement within their class programs that support the reduction of high CA levels among students? Throughout this study the term CA referred to "an individual's level of fear or anxiety associated with either real or anticipated (oral) communication with another person or persons" (McCroskey, 1984, p. 13). The sources of CA were explained with reference to McCroskey's state-trait continuum. The distinctions between high and appropriate levels of CA were determined conceptually and empirically. The education system within which this study was conducted promoted the philosophy of inclusion and the practices of inclusive schooling. Teachers employed in this system were encouraged to create class programs inclusive of and successful for all students. Consequently the conceptual framework within which this study was conducted was based around the notion of inclusion. Action research and case study research were the methodologies used in the study. Case studies described teachers' action research as they responded to the challenge of executing intervention actions within their class programs directed towards supporting the reduction of high CA levels among students. Consequently the teachers and not the researcher were the central characters in each of the case studies. Three principal data collection instruments were used in this study: Personal Report of Communication Fear (PRCF) scale, semistructured interviews, and dialogue journals. The PRCF scale was the screening tool used to identify a pool of students eligible for the study. Data relevant to the students involved in the study were gathered during semistructured interviews and throughout the dialogue journaling process. Dialogue journaling provided the opportunity for regular contact between teachers and the researcher, a sequence to teacher and student intervention behaviours, and a permanent record of teacher and student growth and development. The majority of teachers involved in this study endeavoured to develop class programs inclusive of all students.These teachers acknowledged the importance of modifying aspects of their class programs in response to the diverse and often multiple needs of individual students with high levels of CA. Numerous conclusions were drawn regarding practical ways that the teachers in this study supported the reduction of high CA levels among students. What this study has shown is that teachers can incorporate intervention actions within their class programs aimed towards supporting students lower their high levels of CA. Whilst no teacher developed an identical approach to intervention, similarities and differences were evident among teachers regarding their selection, interpretation, and implementation of intervention actions. Actions that teachers enacted within their class programs emerged from numerous fields of research including CA, inclusion, social skills, behaviour teaching, co-operative learning, and quality schools. Each teacher's knowledge of and familiarity with these research fields influenced their preference for and commitment to particular intervention actions. Additional factors including each teacher's paradigm of inclusion and exclusion contributed towards their choice of intervention actions. Possible implications of these conclusions were noted with reference to teachers,school administrators, support personnel, system personnel, teacher educators, parents, and researchers.