bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Spouse Support and Hostility on Trajectories of Czech Couples' Marital Satisfaction and Instability
Authors: Lorenz Frederick O. , Hraba Joseph , Pechacova Zdenka
Published: March 2004

This article examines differences in the role of spouses' hostile and supportive behaviors in predicting level and change in marital satisfaction and marital instability. We propose 2 competing hypotheses. The first hypothesis proposes that hostility is relatively volatile and support is relatively stable, and that change in hostility affects change in marital outcomes over the course of the study, whereas the overall level of support functions to maintain the level of marital outcomes. The second hypothesis argues that change in marital satisfaction is a function of change in support, whereas change in marital instability is a function of change in hostility. We tested the hypotheses by fitting growth curves to 3 waves of panel data collected from 436 Czech couples between 1994 and 1996. The results offer some support for the first hypothesis. However, the dominant pattern was for level and change in spouses' reports of their hostility to affect both wives' and husbands' level and change in marital instability, respectively, and for the level and change in husbands' reports of their support to predict level and change in wives' marital satisfaction. Other variables suggested by previous research in the United States and by the Czech transition to a market economy are examined.
Role Balance Among White Married Couples
Authors: Marks Stephen R. , Huston Ted L. , Johnson Elizabeth M. , MacDermid Shelley M.
Published: March 2004

We generate models predicting wives' and husbands' feelings of overall balance across roles. Drawing on fine‐grained data about marital lifestyles and time use, we find few predictors that are the same for both partners. Both report greater role balance when their level of parental attachment to children is higher and when their marital satisfaction is greater, but gendered time use gives rise to important differences. Wives report greater balance when they have more paid work hours but have fewer of these hours on weekends. Wives' balance is also greater when they feel less financial strain, have less leisure time alone with their children, more couple leisure alone with their husbands, and more social network involvement. Husbands' contribute to wives' balance when they report more relationship maintenance in the marriage and more leisure with their children at those times when wives are not present. Husbands' own role balance increases as their income rises, but it decreases as their work hours rise. Husbands' balance also rises with more nuclear family leisure, and it lessens as their leisure alone increases. Our discussion highlights the ways that gendered marital roles lead to these different correlates of balance.
Stress and Performance Standards: A Dynamic Approach to Time Spent in Housework
Authors: Pittman Joe F. , Kerpelman Jennifer L. , Solheim Catherine A.
Published: March 2004

Daily logs collected over a 10‐week period from a small, nonrepresentative sample of young, childless married couples were examined. Housework was conceptualized as a daily decision predicated upon personal standards, social rhythms, and stress variables that shape the perception of need for housework. Findings indicate that home‐based stress, stress from outside the home, and standards are independent, additive predictors of housework time. In addition, stress and standards interact in ways suggesting that stress modifies the meaning of performance. High home‐based stress and low imported stress lead to more critical evaluations of ones' own performance and more monitoring of one's spouse's contributions. Husbands do more when wives do more, but only when wives import little stress from outside the home or perceive high demand for housework. Results are interpreted in terms of patterns of meaning and obligation.
Gendered Resources, Division of Housework, and Perceived Fairness—A Case in Urban China
Authors: Zuo Jiping , Bian Yanjie
Published: March 2004

Drawing upon equity and gender theories, we investigate Chinese couples' perceived fairness of the wife's disproportionately heavy household responsibility. Data come from in‐depth interviews with 39 married couples in Beijing during the summer of 1998. Although housework division remained unequal among dual‐earner couples, the majority of wives and husbands saw it as fair. We explore the notion of gendered resources by examining husbands' and wives' opinions about both paid and domestic work. We find that husband's breadwinner role and wife's housekeeper role retain their primary place in the family and that gender‐role expectations produce gendered resources to both wives and husbands. These expectations release both the husbands, who have fulfilled the provider role, from the obligation to share housework equally, and the wives, who combine paid and domestic work, from an equal responsibility of breadwinning. Therefore, the failure to bring adequate gendered resources to a marriage, rather than the unequal distribution of housework, causes a sense of unfairness.
The Impact of Domestic Work on Men's and Women's Wages
Authors: Noonan Mary C.
Published: March 2004

Past research has consistently found that the negative relationship between housework and wages is stronger for women than for men. This article tests a potential explanation for this difference by focusing on the fact that men and women typically perform different types of household chores. Traditionally “feminine” and “masculine” task types are likely to interfere with work differently, because they vary as to when and how often they must be performed. Based on longitudinal data from the National Survey of Families and Households, fixed‐effects regression results show that only time spent in female housework chores has a negative effect on wages. Furthermore, gender differences in the effect of housework disappear upon disaggregating housework into task types. This research suggests that a more equitable distribution of not only the amount, but also the type, of housework performed by men and women in the home may lead to a narrowing of the gender gap in wages.
Risk Factors and Life Processes Associated with Teenage Pregnancy: Results of a Prospective Study From Birth to 20 Years
Authors: Woodward Lianne , Fergusson David M. , Horwood L. John
Published: March 2004

Data gathered over the course of a 20‐year longitudinal study of 533 New Zealand women were used to (a) describe the extent and timing of pregnancies within the cohort up to age 20, and (b) examine the extent to which the risk of an early pregnancy was related to a range of social background, family, individual, and peer relationship factors measured over the course of childhood and adolescence. Results showed that by age 20, nearly a quarter of the sample had been pregnant at least once, with the majority of first pregnancies occurring between the ages of 17 and 20 years. The profile of those at greatest risk of a teenage pregnancy (<20 years) was that of an early‐maturing girl with conduct problems who had been reared in a family environment characterized by parental instability and maternal role models of young single motherhood. As young adolescents, these girls were characterized by high rates of sexual risk‐taking and deviant peer involvement. Exposure to social and individual adversity during both childhood and adolescence made independent contributions to an individual's risk of an early pregnancy. These findings were most consistent with a life course developmental model of the etiology of teenage pregnancy. Implications for teenage pregnancy prevention are discussed.
Intergenerational Transmission and the Formation of Cultural Orientations in Adolescence and Young Adulthood
Authors: Vollebergh W. A. M. , Iedema J. , Raaijmakers Q. A. W.
Published: March 2004

In this article we wanted to shed light on the intergenerational transmission and the formation of cultural orientations in adolescence. The intergenerational transmission was analyzed in different age groups in a longitudinal design (orientations of parents and their adolescent children were measured twice, with a time lapse of 3 years). Results clearly revealed that late adolescence is the “formative phase” for the establishment of cultural orientations and suggested that psychological processes such as internalization are guiding this formation. This internalization was found for all investigated orientations. In addition, as adolescents grew older, their susceptibility to parental orientations diminished, but, in contrast, parents did not become more susceptible to their children's orientations. No age effects in sociocultural influences were found. It was concluded that the investigated sociocultural influences should be seen as providing a structural context within which the formation of orientations in adolescence takes place.
Divison of Labor, Perceived Fairness, and Marital Quality: The Effect of Gender Ideology
Authors: Lavee Yoav , Katz Ruth
Published: March 2004

This study assesses the relations between division of household labor, perceived fairness, and marital quality by comparing three ethnic‐religious groups in Israel that reflect traditional, transitional, and egalitarian ideologies. The findings, based on structural equation modeling (SEM) methodology, show that sense of fairness mediates the relation between division of labor and marital quality and gender ideology moderates these relations for women but not for men. Perceived fairness is related to the division of labor for women in egalitarian and transitional families but not in traditional ones. For egalitarian women, a more segregated division of labor is linked directly with lower marital quality whereas for women in transitional families it is mediated by sense of fairness. The findings are discussed on two overlapping levels—conceptual‐theoretical and sociocultural—with implications for understanding families in cultural transition.
Physical Discipline and Behavior Problems in African American, European American, and Hispanic Children: Emotional Support as a Moderator
Authors: McLoyd Vonnie C. , Smith Julia
Published: March 2004

Using data collected over a 6‐year period on a sample of 1,039 European American children, 550 African American children, and 401 Hispanic children from the children of the National Longitudinal Survey of Youth, this study assessed whether maternal emotional support of the child moderates the relation between spanking and behavior problems. Children were 4–5 years of age in the first of 4 waves of data used (1988, 1990, 1992, 1994). At each wave, mothers reported their use of spanking and rated their children's behavior problems. Maternal emotional support of the child was based on interviewer observations conducted as part of the Home Observation for Measurement of the Environment. For each of the 3 racial‐ethnic groups, spanking predicted an increase in the level of problem behavior over time, controlling for income‐needs ratio and maternal emotional support. Maternal emotional support moderated the link between spanking and problem behavior. Spanking was associated with an increase in behavior problems over time in the context of low levels of emotional support, but not in the context of high levels of emotional support. This pattern held for all 3 racial‐ethnic groups.
Marital Conflict, Ineffective Parenting, and Children's and Adolescents' Maladjustment
Authors: Buehler Cheryl , Gerard Jean M.
Published: March 2004

Data from the 1988 National Survey on Families and Households were analyzed to examine the associations among marital conflict, ineffective parenting, and children's and adolescents' maladjustment. Parents' use of harsh discipline and low parental involvement helped explain the connection between marital conflict and children's maladjustment in children aged 2 through 11. Parent‐child conflict was measured only in families with a target teenager and also was a significant mediator. Although ineffective parenting explained part of the association between marital conflict and children's maladjustment, independent effects of marital conflict remained in families with target children aged 2 through 11 (but not for families with a teenager). With a few exceptions, this pattern of findings was consistent for mothers' and fathers' reports, for daughters and sons, for families with various ethnic backgrounds, and for families living in and out of poverty.
Psychosocial Adjustment of African American Children in Single‐Mother Families: A Test of Three Risk Models
Authors: Jones Deborah J. , Forehand Rex , Brody Gene , Armistead Lisa
Published: March 2004

Three models of risk were examined for 277 African American children from single‐mother‐headed homes: cumulative, additive, and indirect models. Risk factors were mother‐reported community risks, inadequate income, maternal depressive symptoms, and inadequate parenting. Child‐reported internalizing and externalizing difficulties served as dependent measures of adjustment. Whereas the cumulative risk model identified a subset of children within this group as at‐risk for adjustment difficulties, only more proximal family variables (maternal depressive symptoms and inadequate parenting) accounted for unique variance in child outcomes (additive risk model). However, the more distal risk factors—community risk and inadequate income—were linked to both internalizing and externalizing difficulties through the proximal family variables (indirect effects model).
Measures of Assimilation in the Marriage Market: Mexican Americans 1970–1990
Authors: Rosenfeld Michael J.
Published: March 2004

In 1965 the United States rewrote its immigration laws, and immigration increased sharply as a result. The immigrants and the children of immigrants from the post‐1965 period are slowly becoming more influential in U.S. life; the largest of these groups are the Mexican immigrants and the Mexican Americans. The rapid growth of Hispanic and Asian populations in the United States has led to a renewed interest in the question of assimilation; that is, will the new groups assimilate, and if so how long will it take? Will they become part of White America? Will some groups assimilate into the Black‐dominated urban underclass (a process Portes called segmented assimilation)? Will some groups remain permanently separate and socially isolated? In this article, I examine the behavior of Mexican Americans and Mexican immigrants in the U.S. marriage market, using census data from 1970, 1980, and 1990. The findings are that Mexican Americans are assimilating with non‐Hispanic Whites over time, and the evidence tends to reject the segmented assimilation hypothesis. The interplay between intermarriage and endogamy is studied with log linear models; some variations by geography and U.S. nativity are noted.
Predicting the Timing of Separation and Marital Satisfaction: An Eight‐Year Prospective Longitudinal Study
Authors: Kurdek Lawrence A.
Published: March 2004

Information from the growth curves (initial level and rate of change) for individual differences variables over the first 4 years of marriage was used to predict the timing of physical separation over the first 8 years of marriage and the level of marital satisfaction at the eighth year of marriage for an initial sample of 522 married couples. Overall, findings indicated that both initial level and change were needed to account for variability in each marital outcome. There was no evidence that information from wives' growth curves was sufficient to predict either marital outcome.
Toward a Greater Understanding of the Cohabitation Effect: Premarital Cohabitation and Marital Communication
Authors: Cohan Catherine L. , Kleinbaum Stacey
Published: March 2004

The goal of the present study was to examine the relationship between premarital cohabitation experience and marital communication in an effort to understand the robust finding known as the cohabitation effect, whereby couples who cohabit before marriage have greater marital instability than couples who do not cohabit. Observed marital problem solving and social support behavior were examined as a function of premarital cohabitation experience in a sample of 92 couples in the first 2 years of their first marriages. Spouses who cohabited before marriage demonstrated more negative and less positive problem solving and support behaviors compared to spouses who did not cohabit. Sociodemographic, intrapersonal, and interpersonal functioning variables did not account for the association between cohabitation experience and marital communication.
Trends and Countertrends in Sexual Permissiveness: Three Decades of Attitude Change in The Netherlands 1965–1995
Authors: Kraaykamp Gerbert
Published: March 2004

Using longitudinal data from 8 surveys on attitude change in the Netherlands, I tried to clarify trends in sexual permissiveness since the 1960s. In explaining these changes, time‐period effects proved most important, whereas cohort replacement appeared to be of minor significance. Hence, changing attitudes toward permissiveness are best understood in terms of structural developments (period effects) through which everybody in society is affected. Furthermore, this study found that churches are successful in keeping their members from developing progressive opinions. With respect to age, the growing‐conservative‐when‐growing‐older argument also holds for sexual permissiveness. A description of gender‐specific trends revealed that gender differences were relatively constant over time. Only with respect to ‘sex before marriage in a stable relationship’, was a convergence of the gap established.
Parents' Coresidence With Adult Children: Can Immigration Explain Racial and Ethnic Variation?
Authors: Glick Jennifer E. , Van Hook Jennifer
Published: March 2004

There is considerable racial and ethnic variation in the prevalence of intergenerational coresidence in the United States. Using data from the Current Population Surveys, we demonstrate that much of this is attributable to recent immigration and the relative economic position of immigrant parents. Multinomial logistic regression results reveal that recent immigrant parents, particularly Asian and Central and South American immigrant parents, are more likely to live in households in which their adult children provide most of the household income. The likelihood of living in this “dependent” role decreases with duration of residence in the United States. The likelihood of living in an intergenerational household in which the parent provides the majority of the household income is not as tied to nativity.
Does Marital History Matter? Marital Status and Wealth Outcomes Among Preretirement Adults
Authors: Wilmoth Janet , Koso Gregor
Published: March 2004

Data from the 1992 Health and Retirement Survey are used to specify ordinary least squares (OLS) regression models predicting wealth. Separate models are estimated for men and women. The results indicate that individuals who are not continuously married have significantly lower wealth than those who remain married throughout the life course. Remarriage offsets the negative effect of a marital dissolution. There are significant gender differences in these effects. The results demonstrate that accounting for the sequence of marital events provides a detailed picture of the life paths that lead to wealth heterogeneity among the older population.
The Community Context of Family Structure and Adolescent Drug Use
Authors: Hoffmann John P.
Published: March 2004

Using data from the National Educational Longitudinal Study (NELS), this article investigates a number of hypotheses used to explain the relationship between family structure and adolescent drug use. In particular, using linked community‐level data, an explicit examination of hypotheses drawn from a community‐context model is conducted. These hypotheses posit that the impact of family structure on adolescent behavior is, in part, explained by the different types of communities within which families reside and that community characteristics moderate the impact of family structure on drug use. The results of multilevel regression models fail to support these hypotheses; adolescents who reside in single‐parent or stepparent families are at heightened risk of drug use irrespective of community context. Moreover, adolescents who reside in single father families are at risk of both higher levels of use and increasing use over time. A significant community‐level effect involves jobless men: Adolescents are at increased risk of drug use if they reside in communities with a higher proportion of unemployed and out‐of‐workforce men.
Community Differences in the Association Between Parenting Practices and Child Conduct Problems
Authors: Simons Ronald L. , Lin Kuei‐Hsiu , Gordon Leslie C. , Brody Gene H. , Murry Velma , Conger Rand D.
Published: March 2004

Various hypotheses were identified regarding the manner in which community context might influence the association between two dimensions of parenting—control and corporal punishment—on child conduct problems. The authors used hierarchical linear modeling with a sample of 841 African American families to test these hypotheses. Consistent with the evaporation hypothesis, the results indicated that the deterrent effect of caretaker control on conduct problems becomes smaller as deviant behavior becomes more widespread within a community. The findings for corporal punishment supported the normative parenting argument. Although there was a positive relationship between caretaker corporal punishment and child conduct problems in communities where physical discipline was rare, there was no association between the two variables in communities where physical discipline was widely prevalent. These results suggest that a particular parenting strategy may be more effective in some neighborhood environments than others. The theoretical implications of this view are discussed.
Integrating Family Resilience and Family Stress Theory
Authors: Patterson Joän M.
Published: March 2004

The construct, family resilience, has been defined and applied very differently by those who are primarily clinical practitioners and those who are primarily researchers in the family field. In thisarticle, the family resilience perspective is integrated with conceptual definitions from family stress theory using the Family Adjustment and Adaptation Response (FAAR) Model in an effort to clarify distinctions between family resiliency as capacity and family resilience as a process. The family resilience process is discussed in terms of (a) the meaning of significant risk exposure (vs. the normal challenges of family life) and (b) the importance of making conceptual and operational distinctions between family system outcomes and family protective processes. Recommendations for future family resilience research are discussed.
Resilience in Midwestern Families: Selected Findings from the First Decade of a Prospective, Longitudinal Study
Authors: Conger Rand D. , Conger Katherine J.
Published: March 2004

The authors review findings related to mechanisms of resilience in an ongoing longitudinal study of a cohort of 558 focal youth and their families. The ongoing study began when the cohort of adolescents was in 7th grade. Findings demonstrate that resilience to economic adversity for the parents of the focal adolescents was promoted by marital support, effective problem solving skills, and a sense of mastery. For the cohort of youth, resilience to economic hardship was promoted by support from parents, siblings, and adults outside the family. Resilience to the difficult transitions from childhood to adolescence and from adolescence to early adulthood was especially fostered by nurturant‐involved parenting and by less angry or hostile parenting.
A Panel Study of the Associations Between Maintenance Strategies and Relational Characteristics
Authors: Canary Daniel J. , Stafford Laura , Semic Beth A.
Published: March 2004

Resilience in marriage is tied to the manner in which people strategically maintain their relationships. The associations between perceptions of five relational maintenance strategies (positivity, openness, assurances, social networks, and sharing tasks) and three fundamental relationship characteristics (liking, commitment, and control mutuality) are examined concurrently and over time. At three points in time, each separated by a month, married partners reported their perceptions of partner maintenance activities and their own beliefs regarding the relational characteristics. Results indicate that perceptions of maintenance strategies significantly add to the variance of these relational features, even when controlling for the participants' previous reports of the same measures.
The Substitution Hypothesis: The Impact of Premarital Liaisons and Human Capital on Marital Timing
Authors: Gaughan Monica
Published: March 2004

Nonmarital romantic and sexual relationships occur concurrently with the human capital acquisition process and contribute to delaying or forgoing marriage. Event history analysis is used to model the marital hazard rate of 341 White women born between 1960 and 1963 in a Western metropolitan area. In addition to family background, adolescent characteristics, and employment and educational histories, the structure of the women's premarital liaisons is shown to play an important role in the timing of first marriage. The greater a woman's involvement in nonmarital romantic and sexual activity, the less likely she is to be married by age 27–30. Human capital characteristics and the dynamics of relationship histories operate independently to explain marital timing. This supports the theory that women substitute premarital liaisons for marriage early in the adult life course. However, there is no evidence that highly educated women, or those who are students, are more or less likely to do so than others.
The Effects of Marital and Nonmarital Union Transition on Health
Authors: Wu Zheng , Hart Randy
Published: March 2004

This study examines the effects of marital and nonmarital union transition on health. Utilizing Canadian longitudinal data, we find that exiting both marriage and cohabitation seems to have similar effects: Dissolving either union tends to be associated with a decrease in physical health, mental health, or both. With possible selection effects eliminated and protection effects held constant, we find that remaining in either type of union generally is associated with poorer health. We speculate that decreased union quality may account for this inverse relationship, and that protection effects may explain much of the reported health gains associated with union life.
Compatibility, Leisure, and Satisfaction in Marital Relationships
Authors: Crawford Duane W. , Houts Renate M. , Huston Ted L. , George Laura J.
Published: March 2004

This study challenges the prevailing view that marital companionship promotes marital satisfaction. By following a cohort of married couples for over a decade and by incorporating several methodological improvements—such as refining the measurement of marital satisfaction, determining how much spouses enjoy doing the leisure activities they pursue together and apart, and using diary data to portray marital leisure patterns—we found that the association between companionship and satisfaction is less robust than previously believed, and that it depends on how often spouses pursue activities that reflect their own and their partner's leisure preferences. Over time, involvement in leisure liked by husbands but disliked by wives, whether as a couple or by husbands alone, is both a cause and a consequence of wives' dissatisfaction.
Temperamental Vulnerability and Negative Parenting as Interacting Predictors of Child Adjustment
Authors: Morris Amanda Sheffield , Silk Jennifer S. , Steinberg Laurence , Sessa Frances M. , Avenevoli Shelli , Essex Marilyn J.
Published: March 2004

This study examines parenting by temperament interactions in predicting child adjustment. Participants included 40 first and second graders, their mothers, and teachers. Child report of maternal psychological control and hostility was assessed using the Child Puppet Interview. Mothers completed temperament scales from the Child Behavior Questionnaire, and teachers provided information on child adjustment. As expected, among children high in irritable distress, maternal psychological control was associated with internalizing problems and maternal hostility was associated with externalizing problems. Among children with poor effortful control, maternal hostility was associated with externalizing behavior. This study offers evidence that the effects of negative parenting are accentuated among children with temperamental vulnerabilities.
Social Fathering in Low‐Income, African American Families with Preschool Children
Authors: Jayakody Rukmalie , Kalil Ariel
Published: March 2004

Although research increasingly focuses on nonresident biological fathers, little attention has been given to the role of other men in children's lives. The authors examine the factors associated with social father presence and their influence on preschoolers' development. Findings indicate that the majority of children have a social father and that mother, child, and nonresident biological father characteristics are all related to social father presence. These associations differ depending on whether the social father is the mother's romantic partner or a male relative. The social father's influence on children's development also depends on his relationship to the child. Male relative social fathers are associated with higher levels of children's school readiness, whereas mothers' romantic partner social fathers are associated with lower levels of emotional maturity.
Structural and Supportive Changes in Couples' Family and Friendship Networks Across the Transition to Parenthood
Authors: Bost Kelly K. , Cox Martha J. , Burchinal Margaret R. , Payne Chris
Published: March 2004

This article prospectively examined the patterns of change in couples' family and friend networks and supports across the transition to parenthood as well as stability in individual differences over time. Additionally, parental adjustment and depression were examined with respect to changes in couples' social systems. Participants included a total of 137 couples recruited prior to the birth of their first child from prenatal clinics in rural North Carolina. Couples were interviewed about their social networks and supports at four different time periods: prenatally and when target children were 3, 12, and 24 months of age. Couples also completed measures of depression and adjustment at each of the time periods. Across‐time correlations computed for the social network, support, and parental functioning variables revealed that there was considerable stability in the rank ordering of husbands and wives from the prenatal period through 24 months postpartum documenting continuity in parental networks in the context of change. However, growth curve analyses revealed dynamic changes in mothers' and fathers' social systems during this transition and that many of these changes were related to parental adjustment and depression. The discussion highlights the contribution of these data to understanding continuities and discontinuities in mothers' and fathers' social networks over time.
Activation of single heteromeric GABAA receptor ion channels by full and partial agonists
Authors: Mortensen Martin , Kristiansen Uffe , Ebert Bjarke , Frølund Bente , Krogsgaard‐Larsen Povl , Smart Trevor G.
Published: March 2004

The linkage between agonist binding and the activation of a GABAA receptor ion channel is yet to be resolved. This aspect was examined on human recombinant α1β2γ2S GABAA receptors expressed in human embryonic kidney cells using the following series of receptor agonists: GABA, isoguvacine, 4,5,6,7‐tetrahydroisoxazolo[5,4‐c]pyridin‐3‐ol (THIP), isonipecotic acid, piperidine‐4‐sulphonic acid (P4S), imidazole‐4‐acetic acid (IAA), 5‐(4‐piperidyl)‐3‐isothiazolol (thio‐4‐PIOL) and 5‐(4‐piperidyl)‐3‐isoxazolol (4‐PIOL). Whole‐cell concentration–response curves enabled the agonists to be categorized into four classes based upon their maximum responses. Single channel analyses revealed that the channel conductance of 25–27 pS was unaffected by the agonists. However, two open states were resolved from the open period distributions with mean open times reduced 5‐fold by the weakest partial agonists. Using saturating agonist concentrations, estimates of the channel shutting rate, α, ranged from 200 to 600 s−1. The shut period distributions were described by three or four components and for the weakest partial agonists, the interburst shut periods increased whilst the mean burst durations and longest burst lengths were reduced relative to the full agonists. From the burst analyses, the opening rates for channel activation, β, and the total dissociation rates, k−1, for the agonists leaving the receptor were estimated. The agonist efficacies were larger for the full agonists (E∼7−9) compared to the weak partial agonists (∼0.4–0.6). Overall, changes in agonist efficacy largely determined the different agonist profiles with contributions from the agonist affinities and the degree of receptor desensitization. From this we conclude that GABAA receptor activation does not occur in a switch‐like manner since the agonist recognition sites are flexible, accommodating diverse agonist structures which differentially influence the opening and shutting rates of the ion channel.
Does gender affect human pulmonary gas exchange during exercise?
Authors: Olfert I. Mark , Balouch Jamal , Kleinsasser Axel , Knapp Amy , Wagner Harrieth , Wagner Peter D. , Hopkins Susan R.
Published: March 2004

Women may experience greater pulmonary gas exchange impairment during exercise than men. To test this we used the multiple inert gas elimination technique to study eight women and seven men matched for age, height and V̇O2 max (∼48 ml kg−1 min−1) during normoxic and hypoxic (inspired PO2= 95 Torr) cycle exercise. Resting lung function was similar between the sexes, except for a lower carbon monoxide diffusing capacity (DLCO) in women (P < 0.05). Arterial PO2,PCO2 and alveolar–arterial O2 difference (A−aDO2) were not significantly different in men and women. Despite a lower diffusing capacity for O2 (DLO2) in women, the ratio DLO2/βQ̇ (which estimates pulmonary end‐capillary diffusion equilibrium) was similar between men and women and estimates of diffusion limitation during hypoxic exercise were not different between the sexes. Ventilation–perfusion inequality (described by the second moment of the perfusion distribution, logSD) increased during both normoxic and hypoxic exercise. Surprisingly, logSD values were slightly lower for women under all conditions (P < 0.05), but this did not significantly affect gas exchange. These data indicate that these active women, despite a lower DLCO and DLO2, do not experience greater exercise‐induced abnormalities in gas exchange than men matched for age, height, aerobic capacity and lung size. Possibly fitness level and lung size are more important in determining whether or not pulmonary gas exchange impairment occurs during exercise than sex per se.
Changes in extracellular K+ concentration modulate contractility of rat and rabbit cardiac myocytes via the inward rectifier K+ current IK1
Authors: Bouchard Ron , Clark Robert B. , Juhasz Alexander E. , Giles Wayne R.
Published: March 2004

The mechanisms underlying the inotropic effect of reductions in [K+]o were studied using recordings of membrane potential, membrane current, cell shortening and [Ca2+]i in single, isolated cardiac myocytes. Three types of mammalian myocytes were chosen, based on differences in the current density and intrinsic voltage dependence of the inwardly rectifying background K+ current IK1 in each cell type. Rabbit ventricular myocytes had a relatively large IK1 with a prominent negative slope conductance whereas rabbit atrial cells expressed much smaller IK1, with little or no negative slope conductance. IK1 in rat ventricle was intermediate in both current density and slope conductance. Action potential duration is relatively short in both rabbit atrial and rat ventricular myocytes, and consequently both cell types spend much of the duty cycle at or near the resting membrane potential. Rapid increases or decreases of [K+]o elicited significantly different inotropic effects in rat and rabbit atrial and ventricular myocytes. Voltage‐clamp and current‐clamp experiments showed that the effects on cell shortening and [Ca2+]i following changes in [K+]o were primarily the result of the effects of alterations in IK1, which changed resting membrane potential and action potential waveform. This in turn differentially altered the balance of Ca2+ efflux via the sarcolemmal Na+–Ca2+ exchanger, Ca2+ influx via voltage‐dependant Ca2+ channels and sarcoplasmic reticulum (SR) Ca2+ release in each cell type. These results support the hypothesis that the inotropic effect of alterations of [K+]o in the heart is due to significant non‐linear changes in the current–voltage relation for IK1 and the resulting modulation of the resting membrane potential and action potential waveform.
Acid‐sensing ion channels ASIC2 and ASIC3 do not contribute to mechanically activated currents in mammalian sensory neurones
Authors: Drew Liam J. , Rohrer Daniel K. , Price Margaret P. , Blaver Karen E. , Cockayne Debra A. , Cesare Paolo , Wood John N.
Published: March 2004

The molecular basis of mechanosensory transduction by primary sensory neurones remains poorly understood. Amongst candidate transducer molecules are members of the acid‐sensing ion channel (ASIC) family; nerve fibre recordings have shown ASIC2 and ASIC3 null mutants have aberrant responses to suprathreshold mechanical stimuli. Using the neuronal cell body as a model of the sensory terminal we investigated if ASIC2 or 3 contributed to mechanically activated currents in dorsal root ganglion (DRG) neurones. We cultured neurones from ASIC2 and ASIC3 null mutants and compared response properties with those of wild‐type controls. Neuronal subpopulations [categorized by cell size, action potential duration and isolectin B4 (IB4) binding] generated distinct responses to mechanical stimulation consistent with their predicted in vivo phenotypes. In particular, there was a striking relationship between action potential duration and mechanosensitivity as has been observed in vivo. Putative low threshold mechanoreceptors exhibited rapidly adapting mechanically activated currents. Conversely, when nociceptors responded they displayed slowly or intermediately adapting currents that were smaller in amplitude than responses of low threshold mechanoreceptor neurones. No differences in current amplitude or kinetics were found between ASIC2 and/or ASIC3 null mutants and controls. Ruthenium red (5 μm) blocked mechanically activated currents in a voltage‐dependent manner, with equal efficacy in wild‐type and knockout animals. Analysis of proton‐gated currents revealed that in wild‐type and ASIC2/3 double knockout mice the majority of putative low threshold mechanoreceptors did not exhibit ASIC‐like currents but exhibited a persistent current in response to low pH. Our findings are consistent with another ion channel type being important in DRG mechanotransduction.
The elementary events of Ca2+ release elicited by membrane depolarization in mammalian muscle
Authors: L. Csernoch  , Zhou J. , Stern M. D. , Brum G. , Ríos E.
Published: March 2004

Cytosolic [Ca2+] transients elicited by voltage clamp depolarization were examined by confocal line scanning of rat skeletal muscle fibres. Ca2+ sparks were observed in the fibres' membrane‐permeabilized ends, but not in responses to voltage in the membrane‐intact area. Elementary events of the depolarization‐evoked response could be separated either at low voltages (near −50 mV) or at −20mV in partially inactivated cells. These were of lower amplitude, narrower and of much longer duration than sparks, similar to ‘lone embers’ observed in the permeabilized segments. Their average amplitude was 0.19 and spatial half‐width 1.3 μm. Other parameters depended on voltage. At −50 mV average duration was 111 ms and latency 185 ms. At −20 mV duration was 203 ms and latency 24 ms. Ca2+ release current, calculated on an average of events, was nearly steady at 0.5–0.6 pA. Accordingly, simulations of the fluorescence event elicited by a subresolution source of 0.5 pA open for 100 ms had morphology similar to the experimental average. Because 0.5 pA is approximately the current measured for single RyR channels in physiological conditions, the elementary fluorescence events in rat muscle probably reflect opening of a single RyR channel. A reconstruction of cell‐averaged release flux at −20 mV based on the observed distribution of latencies and calculated elementary release had qualitatively correct but slower kinetics than the release flux in prior whole‐cell measurements. The qualitative agreement indicates that global Ca2+ release flux results from summation of these discrete events. The quantitative discrepancies suggest that the partial inactivation strategy may lead to events of greater duration than those occurring physiologically in fully polarized cells.
Different vasodilator responses of human arms and legs
Authors: Newcomer Sean C. , Leuenberger Urs A. , Hogeman Cynthia S. , Handly Brian D. , Proctor David N.
Published: March 2004

Forearm vascular responses to intra‐arterial infusions of endothelium‐dependent and ‐independent vasodilators have been thoroughly characterized in humans. While the forearm is a well‐established experimental model for studying human vascular function, it is of limited consequence to systemic cardiovascular control owing to its small muscle mass and blood flow requirements. In the present study we determined whether these responses could be generalized to the leg. Based upon blood pressure differences between the leg and arm during upright posture, we hypothesized that the responsiveness to endothelium‐dependent vasodilators would be greater in the forearm than the leg. Brachial and femoral artery blood flow (Q, ultrasound Doppler) at rest and during intra‐arterial infusions of endothelium‐dependent (acetylcholine and substance P) and ‐independent (sodium nitroprusside) vasodilators were measured in eight healthy men (22–27 years old). Resting blood flows in the forearm before infusion of acetylcholine, substance P or sodium nitroprusside were 25 ± 4, 30 ± 7 and 29 ± 5 ml min−1, respectively, and in the leg were 370 ± 32, 409 ± 62 and 330 ± 30 ml min−1, respectively. At the highest infusion rate of acetylcholine (16 μg (100 ml tissue)−1 min−1) there was a greater (P < 0.05) increase in Q to the forearm (1864 ± 476%) than to the leg (569 ± 86%). Similarly, at the highest infusion rate of substance P (125 pg (100 ml tissue)−1 min−1) there was a greater (P < 0.05) increase in Q to the forearm (911 ± 286%) than to the leg (243 ± 58%). The responses to sodium nitroprusside (1 μg (100 ml tissue)−1 min−1) were also greater (P < 0.05) in the forearm (925 ± 164%) than in the leg (326 ± 65%). These data indicate that vascular responses to both endothelium‐dependent and ‐independent vasodilator agents are blunted in the leg compared to the forearm.
Contribution of cone photoreceptors and post‐receptoral mechanisms to the human photopic electroretinogram
Authors: Friedburg C. , Allen C. P. , Mason P. J. , Lamb T. D.
Published: March 2004

We recorded the electroretinogram (ERG) from human subjects with normal vision, using ganzfeld stimulation in the presence of rod‐suppressing blue background light. In families of responses to flashes of increasing intensity, we investigated features of both receptoral and post‐receptoral origin. Firstly, we found that the oscillatory potentials (OPs, that have long been known to be post‐receptoral) exhibited a time course that was invariant over a range of bright flash intensities. Secondly, we found that the photopic b‐wave (which probably originates in cone ON bipolar cells) was most pronounced after test flashes of around 20 Td s, and could be suppressed either by increasing the test flash intensity or by applying a second flash after the test flash. We obtained estimates of the time course of the cone photoreceptor response using the paired‐flash technique, in which an intense ‘probe’ flash was delivered at different times after a test flash. The response to the probe flash was recorded and, its amplitude was measured at early times after the probe flash. Estimates obtained in this way were of normalized amplitude, but could be scaled to an absolute amplitude by making an assumption about the level of probe‐flash response that corresponded to complete suppression of photoreceptor current. For moderately bright test flashes the estimated cone photoreceptor response at early times coincided closely with the a‐wave of the test flash ERG. However, the maximal size of this estimated response accounted for only about 70% of the peak a‐wave amplitude in the case of bright flashes, and for an even smaller proportion after flashes of lower intensity, and we take this to indicate the existence of a third substantial post‐receptoral contribution to the a‐wave. For dim flashes, the time‐to‐peak of the cone response was around 15–20 ms, and for saturating flashes the dominant time constant of recovery was about 18 ms. The intensity dependence of the estimated cone response amplitude at fixed times followed an exponential saturation relation. We provide a comparison between our estimates of photoreceptor responses from human cones, and recent estimates from monkey cones obtained using related ERG approaches, and earlier single‐cell measurements from isolated primate cones.
Stress Redistribution for Increased Creep Life in the GE MS6001 B Second-Stage Blade
Authors: DiCristoforo P. E. , Elledge M.
Published: March 2004

When a hot end blade for a gas turbine is designed, several failure criteria must be considered to insure reliability. The criteria include (but are not limited to) creep rupture, low-cycle fatigue, high-cycle fatigue, and creep deflection. This paper will focus on the second-stage turbine blade for the GE MS6001 industrial gas turbine. BP Amoco has experienced failure of this blade due to excessive creep deflection. Creep deflection rate is a function of stress level and metal temperature. A typical approach to reducing creep deflection is to reduce the bulk temperature in the blade. In this paper a design is reviewed that has had the stress redistributed, so that the high-temperature regions of the airfoil are at a lower stress level, thereby reducing the creep rate to an acceptable level.