Perceptual speed does not cause intelligence, and intelligence does not cause perceptual speed

There is ongoing debate whether the efficiency of local cognitive processes leads to global cognitive ability or whether global ability feeds the efficiency of basic processes. A prominent example is the well-replicated association between inspection time (IT), a measure of perceptual discrimination speed, and intelligence (IQ), where it is not known whether increased speed is a cause or consequence of high IQ. We investigated the direction of causation between IT and IQ in 2012 genetically related subjects from Australia and The Netherlands. Models in which the reliable variance of each observed variable was specified as a latent trait showed IT correlations of -0.44 and -0.33 with respective Performance and Verbal IQ; heritabilities were 57% (IT), 83% (PIQ) and 77% (VIQ). Directional causation models provided poor fits to the data, with covariation best explained by pleiotropic genes (influencing variation in both IT and IQ). This finding of a common genetic factor provides a better target for identifying genes involved in cognition than genes which are unique to specific traits.     

A B220+ CD117+ CD19- hematopoietic progenitor with potent lymphoid and myeloid developmental potential

In this report, we identify in the bone marrow (BM) of normal mice a subpopulation of B220+ CD117+ CD19- NK1.1- cells with potent lymphoid and myeloid developmental potential. These cells represent 0.1-0.2% of nucleated BM cells. By limiting dilution analysis in the presence of the appropriate combination of stromal cells and cytokines, 1 in 5-10 sorted cells formed B cells, 1 in 10-15 formed T cells and 1 in 5-10 generated macrophages. When cultured on a mixture of OP9 stroma and OP9 stromal cells expressing the Notch ligand Delta-like-1, single cells generated both T and B cells. Following intravenous infusion, freshly sorted cells transiently reconstituted both the T and B cell progenitor compartments, generating cohorts of mature T and B lymphocytes. The relationship between B220+ CD117+ CD19- NK1.1- cells of wild-type mice and other multi-lineage BM progenitors is discussed.     

Overnight changes of chemoreflex control in obstructive sleep apnoea patients

We hypothesized that the numerous episodes of hypoxia, hypercapnia and arousal experienced by obstructive sleep apnoea (OSA) patients induce overnight changes in respiratory chemoreflexes. A modification of the Read rebreathing technique assessed chemoreflex characteristics in the evening and the morning of patients undergoing diagnostic assessment for OSA in a clinical sleep laboratory. Two groups were studied: those with apnoea-hypopnoea indices (AHI) greater than 30 composed the OSA group (n = 12), and those with AHI indices less than 10 composed the non-OSA group (n = 12). There was a significant (approximately 30%) overnight increase in chemoreflex sensitivities, without changes in thresholds, in the OSA group. In the non-OSA group there was a significant overnight reduction in chemoreflex thresholds (approximately 5%), without changes in sensitivities. We suggest that these changes affect the stability of the chemoreflex control system in opposite ways as the night proceeds: destabilizing breathing for patients in the OSA group, and stabilising breathing for patients in the non-OSA group.     

Influence of wet surfaces and fall height on pediatric injury risk in feet-first freefalls as predicted using a test dummy

INTRODUCTION: Falls are a major cause of morbidity and mortality in children, but are also reported falsely in child abuse. Therefore, it is of interest to understand those factors which may lead to a higher likelihood of injury in a feet-first freefall. METHODS: We used laboratory freefall experiments and a 3-year-old Hybrid III anthropomorphic test dummy (ATD) to assess head and femur injury risk. Wet and dry linoleum impact surfaces were used from three fall heights: 22, 35 and 47 in. RESULTS: For a given fall height, dry surfaces were associated with higher head injury criteria (HIC) values than wet surfaces. Changes in fall height 22-47 in. did not significantly affect HIC values for falls onto either surface. Generally, compressive and bending femur loading increased significantly for wet as compared to dry linoleum. CONCLUSIONS: In simulated feet first freefall experiments up to 47 in. using a 3-year-old test dummy, a low risk of contact type head injury and femur fracture was found. However, both fall height and surface conditions influenced femur loading and head injury measures. Future efforts should explore the risk of head injury associated with angular acceleration in freefalls.     

The Genetic Basis of Academic Achievement on the Queensland Core Skills Test and its Shared Genetic Variance with IQ

First, this study examined genetic and environmental sources of variation in performance on a standardised test of academic achievement, the Queensland Core Skills Test (QCST) (Queensland Studies Authority, 2003a). Second, it assessed the genetic correlation among the QCST score and Verbal and Performance IQ measures using the Multidimensional Aptitude Battery (MAB), [Jackson, D. N. (1984) Multidimensional Aptitude Battery manual. Port Huron, MI:Research Psychologist Press, Inc.]. Participants were 256 monozygotic twin pairs and 326 dizygotic twin pairs aged from 15 to 18 years (mean 17 years ± 0.4 [SD]) when achievement tested, and from 15 to 22 years (mean 16 years ± 0.4 [SD]) when IQ tested. Univariate analysis indicated a heritability for the QCST of 0.72. Adjustment to this estimate due to truncate selection (downward adjustment) and positive phenotypic assortative mating (upward adjustment) suggested a heritability of 0.76 The phenotypic (0.81) and genetic (0.91) correlations between the QCST and Verbal IQ (VIQ) were significantly stronger than the phenotypic (0.57) and genetic (0.64) correlations between the QCST and Performance IQ (PIQ). The findings suggest that individual variation in QCST performance is largely due to genetic factors and that common environmental effects may be substantially accounted for by phenotypic assortative mating. Covariance between academic achievement on the QCST and psychometric IQ (particularly VIQ) is to a large extent due to common genetic influences.     

Efforts to control sexually transmitted infections as a means to limit HIV transmission: What is the evidence?

There is overwhelming and compelling evidence that control efforts for STI have a major role to play in the prevention of HIV transmission. Community-based randomized controlled trials are set as the highest standard of evidence for showing the efficacy of STI interventions to prevent HIV transmission. The negative results of recent randomized controlled trials have cast doubt on the positive findings of the Mwanza study. Deeper analysis of the result of these trials has improved understanding of the role of STI interventions and augmented the wealth of evidence provided by numerous epidemiological and biomedical studies. Apart from the biological impact of effective treatment of curable STIs on HIV transmission, clinical services also support the reduction of HIV-risk behaviors. STI interventions should limit the scale of the impending epidemics in Asia and Eastern Europe, depending on the priority that they are given by governments and major donor agencies.     

A multicentre randomized controlled trial of expectant management versus IVF in women with Fallopian tube patency

BACKGROUND: Although observational studies suggest that IVF is more effective than no treatment for women with Fallopian tube patency, this has not been tested rigorously in a randomized controlled trial (RCT). METHODS: Eligible consenting couples planning their first treatment cycle in five Canadian fertility clinics received either IVF, within 90 days of randomization, or a period of 90 days with no treatment. Random allocation was stratified by female age and sperm quality, and administered using numbered, opaque, sealed envelopes. Follow-up assessed live birth and associated morbidity. RESULTS: Sixty-eight couples were randomized to a first cycle of IVF and 71 couples had 3 months without treatment. The live birth rates were 20/68 (29%) and 1/71 (1%), respectively. The single delivery in the untreated group was of twins, as were six of the 20 IVF deliveries (30%). An average of 2.0 embryos were transferred and no triplet pregnancies resulted. The relative likelihood of delivery after allocation to IVF was 20.9-fold higher than after allocation to no treatment [95% confidence interval (CI) 2.8-155]. The presence of abnormal sperm did not reduce this likelihood. Treating four women (95% CI 3-6) with one cycle of IVF is required to achieve a single additional birth. CONCLUSIONS: This study provides a valid and up-to-date comparison for policy makers and patients as they make choices around IVF, accurately measuring and confirming a major benefit from treatment.     

Genetic and Environmental Sources of Covariance Between Reading Tests Used in Neuropsychological Assessment and IQ Subtests

In this study, we examined genetic and environmental influences on covariation among two reading tests used in neuropsychological assessment (Cambridge Contextual Reading Test [CCRT], [Beardsall, L., and Huppert, F. A. (1994). J. Clin. Exp. Neuropsychol. 16:232-242], Schonell Graded Word Reading Test [SGWRT], [Schonell, F. J., and Schonell, P. E. (1960). Diagnostic and attainment testing. Edinburgh: Oliver and Boyd.]) and among a selection of IQ subtests from the Multidimensional Aptitude Battery (MAB), [Jackson, D. N. (1984). Multidimensional aptitude battery, Ontario: Research Psychologists Press.] and the Wechsler Adult Intelligence Scale-Revised (WAIS-R) [Wechsler, D. (1981). Manual for the Wechsler Adult Intelligence Scale-Revised (WAIS-R). San Antonio: The Psychological Corporation]. Participants were 225 monozygotic and 275 dizygotic twin pairs aged from 15 years to 18 years (mean, 16 years). For Verbal IQ subtests, phenotypic correlations with the reading tests ranged from 0.44 to 0.65. For Performance IQ subtests, phenotypic correlations with the reading tests ranged from 0.23 to 0.34. Results of Structural Equation Modeling (SEM) supported a model with one genetic General factor and three genetic group factors (Verbal, Performance, Reading). Reading performance was influenced by the genetic General factor (accounting for 13% and 20% of the variance for the CCRT and SGWRT, respectively), the genetic Verbal factor (explaining 17% and 19% of variance for the CCRT and SGWRT), and the genetic Reading factor (explaining 21% of the variance for both the CCRT and SGWRT). A common environment factor accounted for 25% and 14% of the CCRT and SGWRT variance, respectively. Genetic influences accounted for more than half of the phenotypic covariance between the reading tests and each of the IQ subtests. The heritabilities of the CCRT and SGWRT were 0.54 and 0.65, respectively. Observable covariance between reading assessments used by neuropsychologists to estimate IQ and IQ subtests appears to be largely due to genetic effects.