Avian sex determination: what, when and where?

Sex is determined genetically in all birds, but the underlying mechanism remains unknown. All species have a ZZ/ZW sex chromosome system characterised by female (ZW) heterogamety, but the chromosomes themselves can be heteromorphic (in most birds) or homomorphic (in the flightless ratites). Sex in birds might be determined by the dosage of a Z-linked gene (two in males, one in females) or by a dominant ovary-determining gene carried on the W sex chromosome, or both. Sex chromosome aneuploidy has not been conclusively documented in birds to differentiate between these possibilities. By definition, the sex chromosomes of birds must carry one or more sex-determining genes. In this review of avian sex determination, we ask what, when and where? What is the nature of the avian sex determinant? When should it be expressed in the developing embryo, and where is it expressed? The last two questions arise due to evidence suggesting that sex-determining genes in birds might be operating prior to overt sexual differentiation of the gonads into testes or ovaries, and in tissues other than the urogenital system.     

Coital rates,sex‐selective infanticide,and sex ratios at birth: A reply to James

Abstract

The cumulative onset curves for smoking, drinking, and sexual intercourse have been tracked through adolescence with reasonable success by recursive equations positing an “epidemic” or contagious process. The gist of these models is that the likelihood of onset in the next time period is proportional to the prevalence of the behavior among an adolescent's peers in the current time period. The present paper extends this approach to official delinquency. The fits to the data (from the Philadelphia cohort studies) are extremely tight. Several conceptual mismatches between the theory underlying the model and the model itself are discussed.     

Cellular calcium and redox regulation: the mediator of vertebrate environmental sex determination?

Many reptiles and some fish determine offspring sex by environmental cues such as incubation temperature. The mechanism by which environmental signals are captured and transduced into specific sexual phenotypes has remained unexplained for over 50 years. Indeed, environmental sex determination (ESD) has been viewed as an intractable problem because sex determination is influenced by a myriad of genes that may be subject to environmental influence. Recent demonstrations of ancient, conserved epigenetic processes in the regulatory response to environmental cues suggest that the mechanisms of ESD have a previously unsuspected level of commonality, but the proximal sensor of temperature that ultimately gives rise to one sexual phenotype or the other remains unidentified. Here, we propose that in ESD species, environmental cues are sensed by the cell through highly conserved ancestral elements of calcium and redox (CaRe) status, then transduced to activate ubiquitous signal transduction pathways, or influence epigenetic processes, ultimately to drive the differential expression of sex genes. The early evolutionary origins of CaRe regulation, and its essential role in eukaryotic cell function, gives CaRe a propensity to be independently recruited for diverse roles as a ‘cellular sensor’ of environmental conditions. Our synthesis provides the first cohesive mechanistic model connecting environmental signals and sex determination pathways in vertebrates, providing direction and a framework for developing targeted experimentation.     

Isolation and characterization of strong gene regulatory sequences from apple, Malus �� domestica

For the strong expression of genes in plant tissue, the availability of specific gene regulatory sequences is desired. We cloned promoter and terminator sequences of an apple (Malus x domestica) ribulose biphosphate carboxylase small subunit gene (MdRbcS), which is known for its high expression and used gus reporter gene expression to test the regulatory activity of the isolated promoter and terminator sequences in transgenic tobacco. The MdRbcS promoter itself seemed to be less strong than the CaMV35S promoter when both used in combination with the nos terminator. However, the combination of the promoter and terminator of MdRbcS was able to drive gus to similar expression levels as the reference construct with CaMV35S promoter and nos terminator. This observation indicates the importance of the terminator sequence for gene expression. It is concluded that the combination of the MdRbcS promoter and terminator is a suitable regulatory sequence set for the expression of transgenes to a high level in plants and for intragenesis in apple specifically.     

A gene‐based evolutionary explanation for the association between criminal involvement and number of sex partners

Abstract

Empirical research has revealed a positive relationship between number of sex partners and involvement in antisocial behaviors. Most attempts to explain this association have taken an evolutionary perspective and argued that the same traits (e.g., impulsiveness, shortsightedness, and aggressiveness) that are related to a large number of sex partners are also related to criminal involvement However, there is also reason to believe that the covariation between sex partners and crime behaviors can be partially explained by a common genetic pathway, where genes that are related to sex partners are also related to antisocial conduct. We test this possibility by using data from the National Longitudinal Study of Adolescent Health (Add Health). Specifically, we examine whether variants of the dopamine transporter gene (DAT1) are associated with number of sexual partners and with adult criminal behavior. The results of our analyses reveal two broad findings. First, and in line with prior research, we find that there is a strong positive association between sex partners and antisocial behavior. Second, DAT1 explains variation in both number of sexual partners and in criminal conduct for males. We speak to the implications of our findings.     

Women's access to health care in Ghana: Effects of education,residence, lineage and self‐determination

Abstract

Women's physical and psychological access to health care was analyzed using the 2003 Ghana Demographic and Health Survey (GDHS), a nationally representative study for monitoring population and health in Ghana. Female respondents from the 2133 cases in the couple's data set were used in this study. Women's level of education was positively related to physical but not to psychological access to health care. Residing in an urban area was positively related to both types of access. Matriliny consistently showed positive effects on physical access. In addition to these demographic factors, both physical and psychological access were positively related to women's self‐determination, i.e., women's right and ability to make real choices about their lives including their health, fertility, sexuality, childcare and all areas where women are denied autonomy and dignity in their identities as women. Self‐determination factors both mediated the effects of background factors on access and added explanatory power to the models.     

Hens,cocks and avian sex determination: A quest for genes on Z or W?

The sex of an individual is generally determined genetically by genes on one of the two sex chromosomes. In mammals, for instance, the presence of the male-specific Y chromosome confers maleness, whereas in Drosophila melanogaster and Caenorhabditis elegans it is the number of X chromosomes that matters. For birds (males ZZ, females ZW), however, the situation remains unclear. The recent discovery that the Z-linked DMRT1 gene, which is conserved across phyla as a gene involved in sexual differentiation, is expressed early in male development suggests that it might be the number of Z chromosomes that regulate sex in birds. On the other hand, the recent identification of the first protein unique to female birds, encoded by the W-linked PKCIW gene, and the observation that it is expressed early in female gonads, suggests that the W chromosome plays a role in avian sexual differentiation. Clearly defining the roles of the DMRT1 and PKC1W genes in gonadal development, and ultimately determining whether avian sex is dependent on Z or W, will require transgenic experiments.     

Relationships between pregnancy spacing,sex of infants,maternal age,and birth order,and neonatal and post‐neonatal mortality in Bangladesh

Abstract

The relationships between length of the interpregnancy interval, outcome of the pregnancy preceding the interval, sex of the infants, pregnancy order, maternal age, and maternal history of previous child deaths and neonatal and postneonatal mortality were explored in a rural Bangladeshi population using a multiple regression analysis. Specific interactions between the interpregnancy interval, outcome of the pregnancy preceding the interval, sex of the infants, and history of previous child deaths were examined. An inverse relationship was observed between postneonatal mortality and the length of the interpregnancy interval when the pregnancy preceding the interval was a surviving infant. No such trend was observed for neonatal mortality. Post‐neonatal mortality rates among children whose mothers had experienced two or more previous child deaths were essentially the same as that for infants whose mothers had experienced 0–1 child deaths when the interpregnancy intervals were more than 24 months. Although female infants have a lower neonatal mortality than male infants, the neonatal mortality rate for female infants conceived less than twelve months following a male infant birth was higher than for a male infant conceived less than twelve months following another male infant birth. Post‐neonatal mortality is consistently higher for female compared to male infants in all interval categories.     

Molecular cloning and differential expression patterns of the regulatory subunit B′ gene of PP2A in goldfish, Carassius auratus

It is well established that the protein serine/threonine phosphatase 2A (PP2A) plays very important roles in many different cellular processes, including cell proliferation and differentiation, gene expres-sion, neurotransmission, apoptosis, and aging. PP2A consists of three heterogenic subunits: the scaffold subunit A, the catalytic subunit C, and the regulatory subunit B. While both the scaffold and the catalytic subunits contain only two forms, at least four families of the regulatory subunits, B, B, B′′, and B′′′ have been identified. These regulatory subunits from different families are encoded by different genes and bear other functions besides directing the specificity of PP2A. To study the functions of the regulatory subunits of PP2A in lower vertebrates, we have cloned the full-length cDNA sequence of the gene encoding the regulatory subunit B′δ of PP2A from gold fish, Carassius auratus using 3′-RACE and 5′-RACE cloning strategies. Our results revealed that the full-length B′δ cDNA contains 2415 bp and encodes a protein of 555 amino acids. The B′δ protein displays a very high level of sequence identity with the B′δ regulatory subunit from other species of vertebrates. Regarding its expression pattern, RT-PCR revealed that the highest level of mRNA was detected in brain, a less level detected in liver, spermary, ovary, kidney and gill, and the lowest level detected in the fin. During different developmental stages of gold fish, the highest level of mRNA expression was detected at the stages of two-cell, mul-tiple-cell, blastula and gastrula, and a decreased level of B′δ ?mRNA was detected in other develop-mental stages. At the protein level, the highest expression level of B′δ protein was found in spermary, ovary, brain and heart, a less amount found in liver and the lowest level detected in kidney, gill and fin. Developmentally, B′δ protein was strongly expressed at the stages of two-cell, multiple-cell, blastula, gastrula, neurula, and optic vesicle, and then decreased at the stages of brain differentiation and eye pigmentation. These results suggest that B′δ appears to play a very important role during gold fish development and also in adult tissue homeostasis.     

Ethnonationalism,ethnic nationalism,and mini‐nationalism: A comparison of Connor,Smith and Snyder

Some terms have been coined to highlight the important relation between nationalism and ethnicity. However, there has been much confusion as to the meaning of such concepts as ‘ethnonationalism’, ‘ethnic nationalism’ and ‘mini‐nationalism’. This article compares the three terms, as used respectively in the works of Walker Connor, Anthony Smith and Louis Snyder. These scholars are selected not only because of their well‐respected position in the study of nationalism but also because their works are representative of each of the three concepts. The comparison finds that since both Connor and Smith emphasized the ethnic dimension of nationalism, their ideas can be presented in one analytical framework. In fact, Connor's ‘ethnonationalism’ and Smith's ‘ethnic nationalism’ overlap with each other. However, Smith's theory of nationalism is comprehensive enough to take care of the fact that the nationalisms of many new states of today's world have no ethnic base at all, whereas Connor's analysis makes no mention of this. In this respect, Smith's model is preferred to that of Connor. Finally, Snyder's ‘mini‐nationalism’ is seen as the least useful concept, since the use of size rather than ethnicity to classify nationalisms does not increase our understanding of the concept.     

Reproductive and socioeconomic determinants of child survival: Confounded,interactive, and age‐dependent effects

Abstract

Studies of infant and child mortality have evolved to distinguish between two sets of explanatory variables—factors related to reproductive or maternal characteristics and socioeconomic factors, generally described as characteristics of the family or household. Almost all multivariate analyses include variables from each of these two sets, but there has been little consideration of the relationship between them. We examine how these two sets of variables jointly affect mortality. We test first for confounded effects by examining socioeconomic effects while excluding and then including reproductive variables in nested multivariate models. Next, we look for age‐dependent effects among the explanatory variables and find that reproductive and socioeconomic factors affect mortality at differing ages of children. Finally, we examine interactive effects of the two sets of variables. We conclude that the higher mortality observed among the low status groups is not a result of greater concentration of poor reproductive patterns in those groups. Instead, higher status groups probably have more resources available for combating the negative effects of the same high‐risk reproductive patterns.     

Building‐Site Camps and Extended Work Hours: A Two‐Week Monitoring of Self‐Reported Physical Exertion,Fatigue, and Daytime Sleepiness

Large‐scale construction work often requires people to work longer daily hours and more than the ordinary five days in a row. In order to minimize transportation times and optimize the use of personnel, workers are sometimes asked to live in temporary building‐site camps in the proximity of the work site. However, little is known about the biological and psychological effects of this experience. The objective of the present study was to investigate whether exposure to long work hours and extended workweeks while living in building‐site camps in between work shifts was associated with a build‐up of increased complaints of poor sleep, daytime sleepiness, physical exertion, and fatigue across a two‐week work cycle. Two groups of construction workers were examined. The camp group of 13 participants (mean age: 42±11 S.D. yrs) lived in building‐site camps and worked extended hours (between 07:00 and 18:00 h) and extended workweeks (six days in a row, one day off, five days in a row, nine days off). The home group of 16 participants (mean age 40±9 yrs) worked ordinary hours between 07:00 and 15:00 h and returned home after each workday. Self‐ratings of daytime sleepiness (Karolinska Sleepiness Scale), physical exertion (Borg CR‐10), and mood were obtained six or seven times daily during two workweeks. Fatigue ratings were obtained once daily in the evening, and ratings of sleep disturbances were obtained once daily in the morning with the Karolinska Sleep Diary. Data were evaluated in a repeated measures design. The results showed that both groups reported a similar level of daytime sleepiness, physical exertion, and mood across workdays and time points within a workday (all three‐way interactions had p>0.898). Although the home group reported earlier wake‐up times, the pattern of sleep disturbance ratings across the workdays did not differ between the groups. Both groups reported few sleep disturbances and good mood. However, the camp group reported higher physical exertion already at the start of work and showed a more gentle increase in ratings during the work shift and a smaller decline between the end of work and bedtime. The camp group also reported higher fatigue scores than the home group. However, none of the groups showed signs of increasing ratings in the progress of the two workweeks. For both groups, the ratings of daytime sleepiness formed a U‐shaped pattern, with the highest scores at awakening and at bedtime. Yet, the camp group reported higher daytime sleepiness than the home group at lunch break and at the second break in the afternoon. In conclusion, there were no signs of fatigue build‐up or accumulation of daytime sleepiness, physical exertion, or sleep disturbances in either group. Despite the fact that the camp group showed some signs of having trouble in recuperating in between work shifts, as indicated by the higher physical exertion ratings at the start of work, higher fatigue scores, and higher daytime sleepiness, the results constitute no real foundation for altering the camp group's current work schedule and living arrangements.     

Bioremediation of a petroleum‐contaminated cryic soil: Effects of phosphorus,nitrogen, and temperature

Bioremediation has been shown to be an effective means of treating petroleum‐contaminated soils in cold areas, although the conditions required to maximize bioremediation in cold region (cryic) soils are not well documented. A laboratory study was conducted to investigate the effects of nitrogen and phosphorus levels and temperature on petroleum bioremediation. A cryic entisol contaminated with diesel fuel was treated with nitrogen (0, 400, 800, or 1200 mg/kg of soil) and phosphorus (0, 60, 120, or 180 mg/kg of soil) and incubated at two temperatures (10 and 20°C). At 10°C, bioremediation rates were not affected by fertility treatments. At 20°C, reaction rates were increased by the addition of P, but unaffected by N. Regardless of fertility regime, the rate of diesel loss was much greater in soil incubated at 20°C than in soil incubated at 10°C.     

Predicting the fate of a living fossil: how will global warming affect sex determination and hatching phenology in tuatara?

How will climate change affect species'' reproduction and subsequent survival? In many egg-laying reptiles, the sex of offspring is determined by the temperature experienced during a critical period of embryonic development (temperature-dependent sex determination, TSD). Increasing air temperatures are likely to skew offspring sex ratios in the absence of evolutionary or plastic adaptation, hence we urgently require means for predicting the future distributions of species with TSD. Here we develop a mechanistic model that demonstrates how climate, soil and topography interact with physiology and nesting behaviour to determine sex ratios of tuatara, cold-climate reptiles from New Zealand with an unusual developmental biology. Under extreme regional climate change, all-male clutches would hatch at 100% of current nest sites of the rarest species, Sphenodon guntheri, by the mid-2080s. We show that tuatara could behaviourally compensate for the male-biasing effects of warmer air temperatures by nesting later in the season or selecting shaded nest sites. Later nesting is, however, an unlikely response to global warming, as many oviparous species are nesting earlier as the climate warms. Our approach allows the assessment of the thermal suitability of current reserves and future translocation sites for tuatara, and can be readily modified to predict climatic impacts on any species with TSD.     

Homology of a 130-kb region enclosing the α-globin gene cluster,the α-locus controlling region,and two non-globin genes in human and mouse

The human -globin gene cluster (30 kb) is embedded in a GC-rich isochore very close to the telomere of Chromosome (Chr) 16p. The -Locus Controlling Region (-LCR) is located upstream of the adult -globin genes and has been shown to be essential for their expression. In this study we have been looking for expressed genes in the region upstream of the -globin cluster to understand the role of the LCR-like element in the expression and replication timing of flanking gene clusters. We show that the upstream -globin region is conserved over a 75-kb range and includes at least two oppositely transcribed non-globin genes, here referred to as Mid1 and Dist1. Complementary DNA sequences of 250 bp and 2.5 kb from Mid1 (coordinate-68) and Dist1 (coordinate-90 to-99), respectively, were isolated from human and mouse. The deduced partial amino acid sequences of these cDNAs are 81% and 95% identical for the Mid1 and Dist1 gene respectively. We have cloned a mouse cosmid contig which includes Dist1, Mid1, and the entire murine -globin cluster. The murine homolog of the -LCR was mapped upstream of the mouse globin genes at approximately the same position as in the human locus. Our results indicate that, in mouse and human, the -globin loci and their flanking sequences are homologous over a range of at least 130 kb. The structural homology of this region in both mammals suggests also a functional one and indicates the mouse as a potential model for studying the role of the -LCR controlling element in the regulation of expression and replication timing of the flanking gene clusters.The nucleotide sequence data reported in this paper have been submitted to GenBank and have been assigned the accession numbers M99623, M99624, M99625, and M99626.