Vitamin D status of pregnant women with obesity in the United Kingdom and its association with pregnancy outcomes: a secondary analysis of the UPBEAT study

Prenatal vitamin D deficiency is widely reported and may affect perinatal outcomes. In this secondary analysis of the UK Pregnancies Better Eating and Activity Trial (UPBEAT), we examined vitamin D status and its relationship with selected pregnancy outcomes in women with obesity (BMI≥30kg/m2) from multi-ethnic inner-city settings in the UK. Determinants of vitamin D status at a mean of 17±1 weeks' gestation were assessed using multivariable linear regression and reported as percent differences in serum hydroxyvitamin D (25(OH)D). Associations between 25(OH)D and clinical outcomes were examined using logistic regression. Among 1089 participants, 67% had 25(OH)D &lt;50nmol/L and 26% had concentrations &lt;25nmol/L. In fully adjusted models accounting for socio-demographic and anthropometric characteristics, 25(OH)D was lower among women of Black (% difference = -33; 95%CI: -39 to -27), Asian (% difference= -43; 95%CI: -51 to -35) and other non-White (% difference= -26; 95%CI: -35 to -14) ethnicity compared to women of White ethnicity (n=1086; P&lt;0.001 for all). In unadjusted analysis, risk of gestational diabetes was greater in women with 25(OH)D &lt;25nmol/L compared to ≥50nmol/L (OR=1.58; 95%CI: 1.09 to 2.31), but the magnitude of effect estimates was attenuated in the multivariable model (OR=1.33; 95%CI: 0.88 to 2.00). There were no associations between 25(OH)D and risk of preeclampsia, preterm birth, or SGA or LGA delivery. These findings demonstrate low 25(OH)D among pregnant women with obesity and highlight ethnic disparities in vitamin D status in the UK. However, evidence for a greater risk of adverse perinatal outcomes among women with vitamin D deficiency was limited.</p

Interference competition in entomopathogenic nematodes: male Steinernema kill members of their own and other species

There is evidence of competition within and between helminth species, but the mechanisms involved are not well described. In interference competition, organisms prevent each other from using the contested resource through direct negative interactions, either chemical or physical. Steinernema spp. are entomopathogenic nematodes; they enter a living insect host which they kill and consume with the aid of symbiotic bacteria. Several studies have demonstrated intra- and interspecific competition in Steinernema, mediated by a scramble for resources and by incompatibility of the bacterial symbiont. Here we describe a mechanism by which male Steinernema may compete directly for resources, both food (host) and females, by physically injuring or killing members of another species as well as males of their own species. A series of experiments was conducted in hanging drops of insect haemolymph. Males of each of four species (Steinernema longicaudum, Steinernema carpocapsae, Steinernema kraussei and Steinernema feltiae), representing three of the five phylogenetic clades of the genus, killed each other. Within 48 h, up to 86% of pairs included at least one dead male, compared with negligible mortality in single male controls. There was evidence of intraspecific difference: one strain of S. feltiae (4CFMO) killed while another (UK76) did not. Males also killed both females and males of other Steinernema spp. There was evidence of a hierarchy of killing, with highest mortality due to S. longicaudum followed by S. carpocapsae, S. kraussei and S. feltiae. Wax moth larvae were co-infected with members of two Steinernema spp. to confirm that killing also takes place in the natural environment of an insect cadaver. When insects were co-infected with one infective juvenile of each species, S. longicaudum males killed both S. feltiae UK76 and Steinernema hermaphroditum. Wax moths co-infected with larger, equal numbers of S. longicaudum and S. feltiae UK76 produced mainly S. longicaudum progeny, as expected based on hanging drop experiments

Sex ratios and sex-biased infection behaviour in the entomopathogenic nematode genus Steinernema

In experimentally infected insects, the sex ratio of first generation nematodes of five species of Steinernema was female-biased (male proportion 0.35-0.47). There was a similar female bias when the worms developed in vitro (0.37-0.44), indicating that the bias in these species is not due to a lower rate of infection by male infective juveniles (IJs). Experimental conditions influenced the proportion of males establishing in insects, indicating that male and female IJs differ in their behaviour. However, there was no evidence that males are the colonising sex in any species, contrary to what has previously been proposed. Time of emergence from the host in which the nematodes had developed influenced sex ratios in experimental infections. In three species (Steinernema longicaudum, Steinernema glaseri and Steinernema kraussei), early emerged nematodes had a higher proportion of males than those that emerged later, with the reverse trend for Steinernema carpocapsae and Steinernema feltiae. In a more detailed in vitro study of S. longicaudum, the proportion of males was similar whether or not the nematodes passed through the developmentally arrested IJ stage, indicating that the female bias is not due to failure of males to exit this stage. The sex ratio in vitro was independent of survival rate from juvenile to adult, and was female-biased even when all juveniles developed, indicating that the bias is not explained by failure of males to develop to adults. The female-biased sex ratio characteristic of Steinernema populations appears to be present from at least the early juvenile stage. We hypothesise that the observed female bias is the population optimal sex ratio, a response to cycles of local mate competition experienced by nematodes reproducing within insect hosts interspersed with periods of outbreeding with less closely related worms following dispersal

Lethal Fighting in Nematodes Is Dependent on Developmental Pathway: Male-Male Fighting in the Entomopathogenic Nematode <i>Steinernema longicaudum</i>

<div><p>Aggressive encounters occur between competitors (particularly males) throughout the animal kingdom, and in some species can result in severe injury and death. Here we describe for the first time lethal interactions between male nematodes and provide evidence that the expression of this behaviour is developmentally controlled. Males of the entomopathogenic nematode <i>Steinernema longicaudum</i> coil around each other, resulting in injuries, paralysis and frequently death. The probability of death occurring between pairs of males was affected by the developmental pathway followed, being much greater among males that had passed through the infective juvenile (IJ, or dauer) stage than among males that had not. Post-IJ males are found only in newly colonised hosts, typically with few competing males present. Killing those few competitors may secure valuable resources (both females and a host cadaver for nourishment of offspring). Non-IJ males develop in subsequent generations within a host cadaver, where the presence of many closely related male competitors increases the risk:benefit ratio of fighting. Thus, passage through the IJ stage primes males for enhanced aggression in circumstances where this is more likely to result in increased reproductive success. Fighting occurred between males developing in mixed-sex social groups, indicating that it is an evolved trait and not an abnormal response to absence of females. This is supported by finding high mortality of males, but not of females, across a range of population densities in insect cadavers. We propose that these nematodes, with their relatively simple organization, may be a useful model for studies of aggression.</p></div

Mortality (mean ± S.E.) of male <i>S. longicaudum</i> 24 h and 2–4 days after being placed in groups of 1–32.

1<p>Males were reared separately in hanging drops each inoculated with one infective juvenile before being placed in groups.</p

Mortality (mean ± SE) of <i>S. longicaudum</i> males and females developing together for 4–5 days in hanging drops of insect haemolymph inoculated with infective juveniles.

<p>Mortality (mean ± SE) of <i>S. longicaudum</i> males and females developing together for 4–5 days in hanging drops of insect haemolymph inoculated with infective juveniles.</p

Developmental pathway affects killing.

<p>Effect of developmental pathway on fatal fighting in <i>Steinernema longicaudum</i>. Percentage of pairs in which at least one male was paralysed or dead 24 hours after they were placed together. Differences between the IJ and non-IJ pathways significant at <i>P</i><0.001 (chi-square, 1 d.f. = 41.049 for dead, 61.016 for total affected (paralysed or dead). Numbers on the bars are numbers of pairs. A maximum of 3% of single males suffered paralysis or death, significantly different to pairs for IJ (chi-square  = 34.239, 1 d.f., <i>P</i><0.001), but not for non-IJ (chi-square  = 2.064, 1 d.f., <i>P</i> = 0.151)</p

Time course of killing in IJ-derived males.

<p>Percentage of pairs of male <i>Steinernema longicaudum</i> in which one male was either paralysed or dead at various times after the males were placed together; N = 36 pairs. None of the 36 single male controls was paralysed or dead after 24 h.</p

Fighting nematodes.

<p>Fighting in <i>Steinernema longicaudum</i> in a drop of insect haemolymph <b>A</b>. A male wrapped around the tail end of another male (the victim). The victim is moving rapidly at this stage, resulting in blurring of the image. <b>B</b>. The same pair ten minutes later. Here, the victim has slowed movement and is paralysed. Scale bar: 1 mm.</p

Effect of competitor density on killing in vivo.

<p>Percentage mortality (mean ± S.E.) of first generation adult males and females of the nematode <i>Steinernema longicaudum</i> in cadavers of the wax moth <i>Galleria mellonella</i>, with varying density, classed by number of males found in each cadaver. The number above the bar is the number of cadavers in each class.</p