Gestational Age at Delivery and Special Educational Need: Retrospective Cohort Study of 407,503 Schoolchildren

Background

Previous studies have demonstrated an association between preterm delivery and increased risk of special educational need (SEN). The aim of our study was to examine the risk of SEN across the full range of gestation.

Methods and Findings

We conducted a population-based, retrospective study by linking school census data on the 407,503 eligible school-aged children resident in 19 Scottish Local Authority areas (total population 3.8 million) to their routine birth data. SEN was recorded in 17,784 (4.9%) children; 1,565 (8.4%) of those born preterm and 16,219 (4.7%) of those born at term. The risk of SEN increased across the whole range of gestation from 40 to 24 wk: 37–39 wk adjusted odds ratio (OR) 1.16, 95% confidence interval (CI) 1.12–1.20; 33–36 wk adjusted OR 1.53, 95% CI 1.43–1.63; 28–32 wk adjusted OR 2.66, 95% CI 2.38–2.97; 24–27 wk adjusted OR 6.92, 95% CI 5.58–8.58. There was no interaction between elective versus spontaneous delivery. Overall, gestation at delivery accounted for 10% of the adjusted population attributable fraction of SEN. Because of their high frequency, early term deliveries (37–39 wk) accounted for 5.5% of cases of SEN compared with preterm deliveries (<37 wk), which accounted for only 3.6% of cases.

Conclusions

Gestation at delivery had a strong, dose-dependent relationship with SEN that was apparent across the whole range of gestation. Because early term delivery is more common than preterm delivery, the former accounts for a higher percentage of SEN cases. Our findings have important implications for clinical practice in relation to the timing of elective delivery. Please see later in the article for the Editors'' Summary     

Similar Impact of CD8+ T Cell Responses on Early Virus Dynamics during SIV Infections of Rhesus Macaques and Sooty Mangabeys

Despite comparable levels of virus replication, simian immunodeficiency viruses (SIV) infection is non-pathogenic in natural hosts, such as sooty mangabeys (SM), whereas it is pathogenic in non-natural hosts, such as rhesus macaques (RM). Comparative studies of pathogenic and non-pathogenic SIV infection can thus shed light on the role of specific factors in SIV pathogenesis. Here, we determine the impact of target-cell limitation, CD8+ T cells, and Natural Killer (NK) cells on virus replication in the early SIV infection. To this end, we fit previously published data of experimental SIV infections in SMs and RMs with mathematical models incorporating these factors and assess to what extent the inclusion of individual factors determines the quality of the fits. We find that for both rhesus macaques and sooty mangabeys, target-cell limitation alone cannot explain the control of early virus replication, whereas including CD8+ T cells into the models significantly improves the fits. By contrast, including NK cells does only significantly improve the fits in SMs. These findings have important implications for our understanding of SIV pathogenesis as they suggest that the level of early CD8+ T cell responses is not the key difference between pathogenic and non-pathogenic SIV infection.     

Non-phenotypic selection of N-methyl-N'-nitro-N-nitrosoguanidine-directed mutation at a predicted hotspot site

The striking mutational specificity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) exhibited in the lacI gene in Escherichia coli allows comment on the phenotypic consequences of mutation at specific sequences that are not recovered after MNNG mutagenesis. We predict that the I+ phenotype is maintained when such silent positions are substituted by amino acids whose codons are generated by the MNNG-directed G:C----A:T transition. We chose the mutationally silent Gly200 codon (an MNNG hotspot motif sequence) to test this prediction. Through MNNG mutagenesis we have generated, identified and isolated a G:C----A:T transition at position 627 (5'-G-G-C-3') under non-selective conditions which creates the Gly200----Asp substitution. The I+ phenotype is retained for this altered repressor.     

EXAMINATION OF TWO DIMENSIONAL SPATIAL PATTERN OF PERIPHYTIC DIATOMS USING AN ADHESIVE SURFICIAL PEEL TECHNIQUE1

A simple surficial peel technique using adhesive tape was developed for quantitative removal of haptobenthic diatom communities from topographically simple substrata. The method combines high removal efficiency with low peel distortion, permitting the use of spatial statistics to test whether populations are distributed in the peel randomly or form aggregated or uniform patterns. Using this technique, the microdistribution of Cocconeis placentula Ehr. on a smooth acrylic rod was examined. Using conventional nearest neighbor analyses, a clonal population of C. placentula. characterized by an indentation of the value margin, was significantly aggregated, whereas the overall C. placentula population was uniform or aggregated depending on whether the method of analysis allowed for cell size. Using refined nearest neighbor analysis, the indented population was aggregated, and the overall population was random at distances greater than cell size. The results suggest that the indented clone was weakly motile following cell division and that its directional bearing was random.     

Merits of Modelling Multivariate Survival Data Using Random Effects Proportional Odds Model

Recently, there has been a great deal of interest in the analysis of multivariate survival data. In most epidemiological studies, survival times of the same cluster are related because of some unobserved risk factors such as the environmental or genetic factors. Therefore, modelling of dependence between events of correlated individuals is required to ensure a correct inference on the effects of treatments or covariates on the survival times. In the past decades, extension of proportional hazards model has been widely considered for modelling multivariate survival data by incorporating a random effect which acts multiplicatively on the hazard function. In this article, we consider the proportional odds model, which is an alternative to the proportional hazards model at which the hazard ratio between individuals converges to unity eventually. This is a reasonable property particularly when the treatment effect fades out gradually and the homogeneity of the population increases over time. The objective of this paper is to assess the influence of the random effect on the within‐subject correlation and the population heterogeneity. We are particularly interested in the properties of the proportional odds model with univariate random effect and correlated random effect. The correlations between survival times are derived explicitly for both choices of mixing distributions and are shown to be independent of the covariates. The time path of the odds function among the survivors are also examined to study the effect of the choice of mixing distribution. Modelling multivariate survival data using a univariate mixing distribution may be inadequate as the random effect not only characterises the dependence of the survival times, but also the conditional heterogeneity among the survivors. A robust estimate for the correlation of the logarithm of the survival times within a cluster is obtained disregarding the choice of the mixing distributions. The sensitivity of the estimate of the regression parameter under a misspecification of the mixing distribution is studied through simulation. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Equilibrium constants for the formation of glyoxylate thiohemiacetals and kinetic constants for their oxidation by O2 catalyzed by l-hydroxy acid oxidase

Glyoxylate thiohemiacetal formation constants (defined as the concentration of thiohemiacetal divided by the concentration of thiol and the total concentration of hydrated and unhydrated glyoxylate) were determined at 25°C and pH 7.4 for a variety of thiols using two independent methods, and were found to be in the range of 0.2 to 1.7 mm^?1. Under the same conditions the hydration constant for glyoxylate (defined as the concentration of the hydrate divided by the concentration of the free aldehyde) was determined to be 163 ± 7. This information is used in conjunction with kinetic data to calculate kinetic constants for the oxidation of the thiohemiacetals by O₂ catalyzed by rat kidney l-hydroxy acid oxidase. The results further indicate that several such thiohemiacetals are excellent substrates, and suggest that one or more of them may be the physiological reactant for this enzyme.     

Establishment and characterization of a cell line from embryos of the Indianmeal moth,Plodia interpunctella

A cell line, UMN-PIE-1181, initiated in November, 1981, from embryos of a malathion-resistant strain of Indianmeal moth, Plodia interpunctella, was in the 83rd passage on January 28, 1985. The line consists of single, small, fibroblastlike cells that are polyploid with chromosome numbers ranging from 56 to 180. Growth rate is dependent on seeding density, there being no growth at or below seeding densities of $\text{2 ×}\text{10}{}^5\text{5}\text{,}\text{ml}$; optimum growth requires a fetal bovine serum concentration of at least 5%. Twenty-nine isozymes were examined. Five enzymes from the cell lines resolved well and subsequently were compared to enzymes extracted from 4-day-old embryos and other life stages of the insects. Phosphomannose isomerase, malic enzyme, malate dehydrogenase, phosphoglucose isomerase, and glucose-6-phosphate dehydrogenase in extracts from the cultured cells and from the insects had identical patterns. Two bands for glutamate-oxalacetate transaminase, present in the cell line, were not observed in the tissue extracts. Furthermore, lactate dehydrogenase from the cultured cells appeared as four bands but was not detectable in any of the samples run from the various life stages of the insects.     

Methylation analysis of mesophyll,epidermis, and fibre cell-walls isolated from the leaves of perennial and italian ryegrass

Intact, finely milled mesophyll, epidermis, and fibre cell-walls prepared from the leaves of perennial and Italian ryegrass have been subjected to methylation analysis. Methylation of the cell-walls led to a consistently higher recovery of glucose residues than that obtained by analysis of monosaccharide residues as their alditol acetates. Values for other sugars were in close agreement. The partially methylated sugars formed were consistent with the presence, in order of decreasing concentration, of cellulose, (glucurono)arabinoxylan, xyloglucan, rhamnogalacturonan, (1→3),(1→4)-linked glucan, (1→4)-linked galactan, and (1→3),(1→6)-linked galactan. The relative proportions of these polysaccharides differed between the various types of cell. Arabinoxylan comprised 21.6%, 26.7%, and 36.5% of the total sugars recovered from mesophyll, epidermis, and fibre cell-walls, respectively. Mixed-linked glucan and rhamnogalacturonan were found in epidermis walls in amounts 2- to 3-fold higher than in other cell-walls. The xylan backbone of arabinoxylan was more heavily substituted in primary than in secondary-thickened (fibre) cell-walls. Arabinose, found largely as terminal residues in the cell-walls, carried various amounts of alkali-labile substituents, particularly at position 5. The extent of 5-substitution reflected the phenolic content and was substantially higher in fibre cell-walls. The methylation data, coupled with the analytical data for uronic acids and non-carbohydrate components, accounted for ～98% of the cell-wall dry matter.