Aptamers come of age - at last

Nucleic-acid aptamers have the molecular recognition properties of antibodies, and can be isolated robotically for high-throughput applications in diagnostics, research and therapeutics. Unlike antibodies, however, they can be chemically derivatized easily to extend their lifetimes in biological fluids and their bioavailability in animals. The first aptamer-based clinical drugs have recently entered service. Meanwhile, active research programmes have identified a wide range of anti-viral aptamers that could form the basis for future therapeutics.     

Heritability of age at first birth in captive olive baboons

The evolution of life history traits is a topic of growing interest in primatology. Traits associated with fertility, such as age at menarche and age at first birth, have great significance for natural selection, and knowing the genetic basis of such demographic traits may improve our understanding of population dynamics. Knowledge of the heritability of reproductive traits may also have practical implications for the management of captive breeding colonies. A maximum likelihood method was used to estimate heritability of age at first birth for a sample of female olive baboons resident at the Southwest Foundation for Biomedical Research. Only animals born at the Foundation that were caged in mixed sex groups and that had previously given birth were included in the sample (n = 316). There were 117 independent individuals and 199 individuals in 35 pedigrees composed of 2 to 26 members. Age at first birth ranged from 3.85 years to 13.11 years. Age at first birth is highly heritable (h² = 0.87) with no evidence for maternal effects or a dominance genetic component. This level of genetic variability in a fitness-related trait is contrary to evolutionary expectation and may reflect the uniform environment of a captive breeding situation. Thus, the heritability observed in this population may be taken as an upper bound for that in natural populations. © 1995 Wiley-Liss, Inc.     

Season of birth and recalled age at menarche.

All 8th-form schoolgirls from the municipality of Odense in Denmark were asked at what age they reached menarche, and 886 girls (97.6%) gave this information. There is no evidence for seasonality in the time of birth but for far more girls than expected menarche occurred during winter or summer and fewer than expected during spring and autumn. This pattern appears primarily in girls living in the suburbs and was not seen in those living in central Odense. The seasonality appears to be brought about by differences in mean age at menarche according to time of the year at birth.     

Parents' age at birth of their offspring and child survival

This study presents some new results on parental age as a risk factor for child survival. The study is based on individual registration forms for live births and infant deaths collected in Hungary from 1984 to 1988. Logistic regression models have been fitted for early neonatal and neonatal mortality on the one hand, and post-neonatal mortality on the other hand. Children of older males and females have significantly higher early neonatal and neonatal mortality rates compared to those of younger males and females. The impact of age of both parents remains, however, slighter than that of other biological characteristics such as previous number of fetal deaths, induced abortions, or live births. The authors discuss possible biological explanations.     

Maternal and paternal age at delivery, birth order, and risk of childhood onset type 1 diabetes: population based cohort study

ObjectiveTo estimate the associations of maternal and paternal age at delivery and of birth order with the risk of childhood onset type 1 diabetes.DesignCohort study by record linkage of the medical birth registry and the national childhood diabetes registry in Norway.SettingNorway.SubjectsAll live births in Norway between 1974 and 1998 (1.4 million people) were followed for a maximum of 15 years, contributing 8.2 million person years of observation during 1989-98. 1824 cases of type 1 diabetes diagnosed between 1989 and 1998 were identified.ResultsThere was no association between maternal age at delivery and type 1 diabetes among firstborn children, but among fourthborn children there was a 43.2% increase in incidence of diabetes for each five year increase in maternal age (95% confidence interval 6.4% to 92.6%). Each increase in birth order was associated with a 17.9% reduction in incidence (3.2% to 30.4%) when maternal age was 20-24 years, but the association was weaker when maternal age was 30 years or more. Paternal age was not associated with type 1 diabetes after maternal age was adjusted for.ConclusionsIntrauterine factors and early life environment may influence the risk of type 1 diabetes. The relation of maternal age and birth order to risk of type 1 diabetes is complex.

What is already known on this topic

Maternal age at birth is positively associated with risk of childhood onset type 1 diabetesStudies of the effect of birth order on risk of type 1 diabetes have given inconsistent results

What does this study add?

In a national cohort, risk of diabetes in firstborn children was not associated with maternal ageIncreasing maternal age was a risk factor in children born second or laterThe strength of the association increased with increasing birth order     

Grandmaternal age at birth of parents of children with trisomy 21

Summary The authors investigated the age of the parents and grandmothers of 262 children with simple trisomy 21. In cases in which the mother was under 30, the mean grandmaternal age was higher than that of the controls. This might mean that some of these cases, being the children of old mothers, began their lives as trisomic zygotes.The authors assume that not only maternal but also paternal mosaicism might be significant. They evaluate their results in light of genetic counseling and in consideration of practical conclusions that can be used in prenatal genetic diagnosis.     

Covariates of age at first birth in Guyana: a hazards model analysis

Analysis of data from the Guyana Fertility Survey on the trends and covariates of age at 1st birth among various birth cohorts of women ever in union indicates that an early entry into union is associated with young age at 1st birth and higher number of children born. Multivariate analysis showed that women with higher education, urban residence, and entry into 1st birth compared to others, and that young women are delaying their 1st birth for longer durations than older women. Work status of women before 1st birth and the starting age of union seem to be the 2 major contributory factors for age at 1st birth. Noticeably, the role of education has changed and is now more significant among younger cohorts than among older ones for 1st birth timing.     

Maternal and neonatal factors influencing premature birth and low birth weight in Australia

This study identified the influences of neonatal and maternal factors on premature birth and low birth weight in New South Wales, Australia. Bivariate and multivariate analyses were used to explore the association of selected neonatal and maternal characteristics with premature birth and low birth weight. The findings of this study showed that premature birth and low birth weight rate significantly varied by infant sex, maternal age, marital status, Aboriginality, parity, maternal smoking behaviour during pregnancy and maternal hypertension. First-born infants, and infants born to mothers aged less than 20 years, or who were single, separated/divorced, Aboriginal or who smoked during the pregnancy, were at increased risk of being premature or of low birth weight. This study also found that risk factors for premature births and low birth weight were similar in both singleton and multiple births. Gestational age was confirmed to be the single most important risk factor for low birth weight. The findings of this study suggest that in order to reduce the incidence of low birth weight and premature births, health improvement strategies should focus on anti-smoking campaigns during pregnancy and other healthcare programmes targeted at the socially disadvantaged populations identified in the study.     

Maternal age and birth weight characteristics of twins born to nulliparous mothers: a population study.

In order to examine birth weight characteristics of twins delivered to nulliparous mothers in relation to maternal age, we used a population-based cohort of Israeli twins delivered between 1993-98 to select all 4793 (37.6%) nulliparas who delivered twins. Maternal age was subdivided as less than 20 years, 20-24, 25-29, 30-34, 35-39, and 40 years or more. We counted the frequencies of each total twin birth weight (twin A + twin B) in each of three categories (less than 3000, 3000-4999, and more than 5000 g) and the frequency of very low birth weight (VLBW, less than 1500 g) neonates in each of the six maternal age categories. There were significantly more nulliparas in the twin population at age groups less 30 years and significantly less at ages 30 years or more. We found a highly significant inverse correlation between the proportion of nulliparas and maternal age group, decreasing from 71.8% at less than 20 years to 18.6% at age 35-39 years (% nulliparas = 85 - 13.7 x age group, Pearson R2 = 0.98). However, this trend changed abruptly to the observed figure of 25.9% nulliparas aged 40 years or more instead of the expected 2.8%. We failed to reveal any significant difference in birth weight characteristics between the maternal age groups (all p > 0.05, all confidence intervals included 1.0). The more than tenfold deviation of the observed from the predicted frequency of nulliparas aged 40 years or more suggests that a different relationship between parity and age occurs at this age group. Maternal age of nulliparas is not associated with different birth weight characteristics of their twins.     

Progress at last

Refinement of protein structures from a correct topology to atomically detailed resolution has proven remarkably difficult. Jian et?al. (in this issue of Structure) illustrate a significant advance in this task by carefully incorporating into the refinement process many body interactions extracted from fragment statistics.