To close or not to close? Wound management in emergent colorectal surgery, an EAST Multicenter prospective cohort study

BACKGROUND

To determine the clinical impact of wound management technique on surgical site infection (SSI), hospital length of stay (LOS) and mortality in emergent colorectal surgery.

METHODS

A prospective observational study (2021-2023) of urgent or emergent colorectal surgery patients at 15 institutions was conducted. Pediatric patients and traumatic colorectal injuries were excluded. Patients were classified by wound closure technique: skin closed (SC), skin loosely closed (SLC), or skin open (SO). Primary outcomes were SSI, hospital LOS and in-hospital mortality rates. Multivariable regression was used to assess the effect of wound closure on outcomes after controlling for demographics, patient characteristics, ICU admission, vasopressor use, procedure details and wound class. A priori power analysis indicated that 138 patients per group were required to detect a 10% difference in mortality rates.

RESULTS

In total, 557 patients were included (SC n = 262, SLC n = 124, SO n = 171). Statistically significant differences in BMI, race/ethnicity, ASA scores, EBL, ICU admission, vasopressor therapy, procedure details, and wound class were observed across groups (Table 1). Overall, average LOS was 16.9 ± 16.4 days, and rates of in-hospital mortality and SSI were 7.9% and 18.5%, respectively, with the lowest rates observed in the SC group (Table 2). After risk adjustment, SO was associated with increased risk of mortality (OR = 3.003, p = 0.028 in comparison to the SC group. SLC was associated with increased risk of superficial SSI (OR = 3.439, p = 0.014), after risk adjustment.

CONCLUSION

When compared to the SC group, the SO group was associated with mortality, but comparable when considering all other outcomes, while the SLC was associated with increased superficial SSI. Complete skin closure may be a viable wound management technique in emergent colorectal surgery.

STUDY TYPE

Level III Therapeutic/Care Management.

Biomarkers of oxidative stress, diet and exercise distinguish soldiers selected and non-selected for special forces training

INTRODUCTION

The metabolomic profiles of Soldiers entering the U.S. Special Forces Assessment and Selection course (SFAS) have not been evaluated.

OBJECTIVES

To compare pre-SFAS blood metabolomes of Soldiers selected during SFAS versus those not selected, and explore the relationships between the metabolome, physical performance, and diet quality.

METHODS

Fasted blood samples and food frequency questionnaires were collected from 761 Soldiers prior to entering SFAS to assess metabolomic profiles and diet quality, respectively. Physical performance was assessed throughout SFAS.

RESULTS

Between-group differences (False Discovery Rate < 0.05) in 108 metabolites were detected. Selected candidates had higher levels of compounds within xenobiotic, pentose phosphate, and corticosteroid metabolic pathways, while non-selected candidates had higher levels of compounds potentially indicative of oxidative stress (i.e., sphingomyelins, acylcarnitines, glutathione, amino acids). Multiple compounds higher in non-selected versus selected candidates included: 1-carboxyethylphenylalanine; 4-hydroxy-nonenal-glutathione; α-hydroxyisocaproate; hexanoylcarnitine; sphingomyelin and were associated with lower diet quality and worse physical performance.  CONCLUSION: Candidates selected during SFAS had higher pre-SFAS levels of circulating metabolites that were associated with resistance to oxidative stress, higher physical performance and higher diet quality. In contrast, non-selected candidates had higher levels of metabolites potentially indicating elevated oxidative stress. These findings indicate that Soldiers who were selected for continued Special Forces training enter the SFAS course with metabolites associated with healthier diets and better physical performance. Additionally, the non-selected candidates had higher levels of metabolites that may indicate elevated oxidative stress, which could result from poor nutrition, non-functional overreaching/overtraining, or incomplete recovery from previous physical activity.

Effects of energy balance on cognitive performance, risk-taking, ambulatory vigilance and mood during simulated military sustained operations (SUSOPS)

Sustained operations (SUSOPS) require military personnel to conduct combat and training operations while experiencing physical and cognitive stress and limited sleep. These operations are often conducted in a state of negative energy balance and are associated with degraded cognitive performance and mood. Whether maintaining energy balance can mitigate these declines is unclear. This randomized crossover study assessed the effects of energy balance on cognitive performance, risk-taking propensity, ambulatory vigilance, and mood during a simulated 72-h SUSOPS.

METHODS

Ten male Soldiers (mean ± SE; 22.4 ± 1.7 y; body weight 87.3 ± 1.1 kg) completed two, 72-h simulated SUSOPS in random order, separated by 7 days of recovery. Each SUSOPS elicited ∼4500 kcal/d total energy expenditure and restricted sleep to 4 h/night. During SUSOPS, participants consumed either an energy-balanced or restricted diet that induced a 43 ± 3% energy deficit. A cognitive test battery was administered each morning and evening to assess: vigilance, working memory, grammatical reasoning, risk-taking propensity, and mood. Real-time ambulatory vigilance was assessed each morning, evening, and night via a wrist-worn monitoring device.

RESULTS

Participants exhibited heightened risk-taking propensity (p = 0.047) with lower self-reported self-control (p = 0.021) and fatigue (p = 0.013) during energy deficit compared to during energy balance. Vigilance accuracy (p < 0.001) and working memory (p = 0.040) performance decreased, and vigilance lapses increased (p < 0.001) during SUSOPS, but did not differ by diet. Percentage of correct responses to ambulatory vigilance stimuli varied during SUSOPS (p = 0.019) independent of diet, with generally poorer performance during the morning and night. Total mood disturbance (p = 0.001), fatigue (p < 0.001), tension (p = 0.003), and confusion (p = 0.036) increased whereas vigor decreased (p < 0.001) during SUSOPS, independent of diet.

CONCLUSION

Prolonged physical activity combined with sleep restriction is associated with impaired vigilance, memory, and mood state. Under such conditions, maintaining energy balance prevents increased risk-taking and improves self-control, but does not improve other aspects of cognitive function or mood. Given the small sample in the present study, replication in a larger cohort is warranted.

Anthropometrics and Body Composition Predict Physical Performance and Selection to Attend Special Forces Training in United States Army Soldiers

INTRODUCTION

Anthropometrics and body composition characteristics differentiate many types of athletes and are related to performance on fitness tests and tasks in military personnel. Soldiers competing to enter elite units must demonstrate physical fitness and operational competence across multiple events. Therefore, this study determined whether anthropometrics and body composition predicted physical performance and selection for special forces training among soldiers attending the rigorous Special Forces Assessment and Selection (SFAS) course.

MATERIALS AND METHODS

Soldiers attending the SFAS course between May 2015 and March 2017 were enrolled in a longitudinal, observational study. Anthropometrics (height, body mass, and body mass index [BMI]; n = 795) and body composition measured by dual-energy X-ray absorptiometry (percentage body fat, fat mass, lean mass, bone mineral content [BMC], and bone mineral density [BMD]; n = 117) were assessed before the course start. Associations with physical performance were determined with correlation coefficients. Associations with selection were determined with analyses of variance and t-tests; effect sizes were calculated as Cohen's d. The U.S. Army Research Institute of Environmental Medicine Institutional Review Board (IRB) initially approved this study, and the U.S. Army Medical Research and Development Command IRB approved the continuing review.

RESULTS

Lower percentage body fat and fat mass predicted better performance on all assessments: Army Physical Fitness Test (APFT), pull-ups, SFAS run, loaded road march, obstacle course, and land navigation (P ≤ .05). Higher lean mass predicted better performance on the loaded road march (P ≤ .05). Lower body mass and BMI predicted better performance on APFT, pull-ups, run, and obstacle course; higher body mass and BMI predicted better performance on the loaded road march (P ≤ .05). Shorter stature predicted better performance on push-ups (APFT) and pull-ups; taller stature predicted better performance on SFAS run and loaded road march (P ≤ .05). On average, the selected soldiers were taller (179.0 ± 6.6 vs. 176.7 ± 6.7 cm), had higher body mass (85.8 ± 8.8 vs. 82.1 ± 9.6 kg), BMI (26.8 ± 2.2 vs. 26.3 ± 2.6 kg/m2), lean mass (67.2 ± 7.3 vs. 61.9 ± 7.6 kg), BMC (3.47 ± 0.40 vs. 3.29 ± 0.56 kg), and BMD (1.34 ± 0.10 vs. 1.28 ± 0.10 g/cm2), and lower percentage body fat (17.3 ± 3.4 vs. 20.1 ± 4.5%) and fat mass (14.2 ± 3.7 vs. 15.8 ± 4.4 kg) (P ≤ .05). Effect sizes were largest for lean mass (Cohen's d = 0.71) and percentage body fat (d = 0.70), followed by BMD (d = 0.60), body mass (d = 0.40), fat mass (d = 0.39), BMC (d = 0.37), height (d = 0.35), and BMI (d = 0.21). Body mass adjustment attenuated associations between height and selection.

CONCLUSIONS

Anthropometrics and body composition are predictors of physical performance and SFAS success. Since these measures are modifiable (excluding height), they may be the focus of intervention studies aiming to improve performance in arduous military training courses, sports that require competition in multiple events, and occupations that have varied physical demands, such as firefighting, law enforcement, and construction.

Dietary Supplement Use in US Army Personnel: A Mixed-Methods, Survey and Focus-Group Study Examining Decision Making and Factors Associated With Use

BACKGROUND

Dietary supplement (DS) use by Army personnel is high and is a safety and readiness issue.

OBJECTIVE

Our aim was to examine factors motivating use of DSs among US Army personnel and preferred safety education strategies.

DESIGN

This mixed-method study used a validated DS questionnaire and subsequent focus groups that were formed based on questionnaire-identified demographic characteristics. An embedded qualitative dominant design was used.

PARTICIPANTS/SETTING

Data were collected from April to July 2015 from active duty soldiers at 3 military installations in the United States.

MAIN OUTCOME MEASURES

A self-report questionnaire (n = 289) provided data on demographic characteristics, health, exercise, detailed use, and attitudes regarding DS safety and efficacy. Fourteen focus-group sessions (n = 129) examined factors motivating DS use, education strategies, and identified themes and DS-related behaviors.

STATISTICAL ANALYSIS PERFORMED

Descriptive statistics and χ² analyses were conducted.

RESULTS

Of the soldiers who completed questionnaires, 83% were male, 60% were enlisted, and 40% were officers; mean age ± standard deviation was 27.6 ± 0.36 years and 75% used at least 1 type of DS per week: 52% used protein/amino acids, 47% used multivitamins/minerals, and 35% used a combination of products. Focus groups indicated reasons for use included physical appearance, fitness, peer endorsement, ease of access, limited availability of healthy food, occupational demands, and health. Participants requested education from an expert on safe use that was not focused on dangerous products.

CONCLUSIONS

Soldiers are high DS users, especially products marked for purported performance enhancement. Motivating factors for DS use are fitness/appearance and occupational demands, but soldiers lack knowledge of DS regulatory requirements and safety/efficacy. Soldiers wished to receive education on DSs from trusted health care professionals, such as registered dietitian nutritionists, that was not focused on dangerous products. Study findings suggest guidance and education should occur before periods of high DS use, such as deployment.

Diet Quality Is Associated with Physical Performance and Special Forces Selection

PURPOSE

This study determined associations between diet quality measured by the Healthy Eating Index (HEI)-2015, physical performance, and successful selection following a U.S. Army Special Forces Assessment and Selection course characterized by arduous cognitive and physical demands.

METHODS

The HEI-2015 scores were calculated from usual diet assessed with a Block food frequency questionnaire among 782 soldiers attending Special Forces Assessment and Selection. Differences in HEI-2015 scores according to demographics and physical performance were determined with analysis of variance. Differences in likelihood of selection according to HEI-2015 scores were determined with logistic regression. Models were adjusted for potential confounders: age, education, body mass index (BMI), duration and type of resistance training, and smoking.

RESULTS

The HEI-2015 total score was higher among older soldiers (≥25 yr), those with more education (≥some college), higher body mass index (≥25), longer duration of resistance training (≥400 min·wk), those that reported use of free weights, suspension training, Olympic lifting, and nonsmokers (P < 0.05). The HEI-2015 total score was higher among those with higher Army Physical Fitness Test (APFT) total scores, APFT sit-up score, APFT run score, and faster loaded road march times (P < 0.05). Those with higher HEI-2015 total scores were 75% (quartile 3 vs quartile 1: odds ratio, 1.75; 95% confidence interval, 1.09-2.81) and 65% (quartile 4 vs quartile 1: odds ratio, 1.65, 95% confidence interval, 1.03-2.65) more likely to be selected. Higher scores for total vegetables, greens and beans, seafood and plant protein, and refined grains, but lower sodium scores (indicating more sodium consumed), were associated with better physical performance (P < 0.05).

CONCLUSIONS

Dietary patterns that conform to federal dietary guidelines (except sodium) are associated with physical performance and Special Forces selection.

Effects of health status on pressure-induced changes in phocid immune function and implications for dive ability

The ability of marine mammals to cope with environmental challenges is a key determining factor in strandings and successful release of rehabilitated animals. Dive behavior is related to foraging and thus survival. While dive adaptations have been well studied, it is unknown how the immune system responds to diving and whether health status impacts immune function during diving. This study investigated the functional response of ex situ immune cells from stranded phocids to in vitro increased pressure, over the course of rehabilitation. Blood samples were drawn from stranded harbor seals (Phoca vitulina), gray seals (Halichoerus grypus) and harp seals (Phoca groenlandica) at the time of admit to the Mystic Aquarium, Mystic, CT and again after rehabilitation (pre-release). Phagocytosis, lymphocyte proliferation and immune cell activation were measured in vitro, with and without exposure to 2000 psi (simulated dive depth of 1360 m). Plasma epinephrine and norepinephrine, and serum cortisol were measured in vivo. All hormone values decreased between admit and release conditions. Under admit or release conditions, pressure exposures resulted in significant changes in granulocyte and monocyte phagocytosis, granulocyte expression of CD11b and lymphocyte expression of the IL2 receptor (IL2R). Overall, pressure exposures resulted in decreased phagocytosis for admit conditions, but increased phagocytosis in release samples. Expression of leukocyte activation markers, CD11b and IL2R, increased and the response did not differ between admit and release samples. Specific hematological and serum chemistry values also changed significantly between admit and release and were significantly correlated with pressure-induced changes in immune function. Results suggest (1) dive duration affects the response of immune cells, (2) different white blood cell types respond differently to pressure and (3) response varies with animal health. This is the first study describing the relationship between diving, immune function and health status in phocids.

A Survey Instrument to Assess Intake of Dietary Supplements, Related Products, and Caffeine in High-Use Populations

Substantial data on the use of dietary supplements by the general adult population are available, but many population subgroups have not been extensively studied. Because military service members and young people consume large amounts of dietary supplements, including for enhancement of physical performance, weight control, and bodybuilding, which can be dangerous, we developed a comprehensive questionnaire to characterize patterns of supplement use in these and other populations. The questionnaire has been used to study >7000 military service members and 1000 college students. This supplement article presents a detailed description of the questionnaire, which contains comprehensive questions on demographic characteristics, exercise habits, attitudes with regard to dietary supplements, and amount of money spent on supplements. Intakes of specific dietary supplements and caffeine, frequency of use, and reasons for use are assessed. The questionnaire was designed for studying dietary supplement and caffeine intake patterns with the use of paper-and-pencil administration to military populations and was modified for use with college students and for computer and Web administration. It is available online at https://go.usa.gov/xn9FP and in the Supplemental File for this publication. It can be used to study other populations if minor modifications are made. The online version of the questionnairewill be updated periodically as newversions become available. In conclusion, a validated, detailed, noncopyrighted questionnaire designed to assess the use of dietary supplements, energy drinks (and related products), and caffeine is available for use in diverse populations. The format of the questionnaire is adaptable to computer administration and scoring, and it can be customized for specific subpopulations, locations, and product categories including updates that reflect changes in the availability of supplements or availability of new products.

Human Health Risk from Consumption of Marine Fish Contaminated with DDT and Its Metabolites in Maputo Bay, Mozambique

Many countries with incidence of malaria, including those surrounding Maputo Bay, use dichloro-diphenyl-trichloroethane (DDT) to reduce mosquitoes. This study is the first to estimate the human health risk associated with consumption of marine fish from Maputo Bay contaminated with DDTs. The median for ∑DDTs was 3.8 ng/g ww (maximum 280.9 ng/g ww). The overall hazard ratio for samples was 1.5 at the 75th percentile concentration and 28.2 at the 95th percentile. These calculations show increased potential cancer risks due to contamination by DDTs, data which will help policy makers perform a risk-benefit analysis of DDT use in malaria control programs in the region.

Determinants of longitudinal health-related quality-of-life change in children with asthma from low-income families: a report from the PROMIS® Pediatric Asthma Study

BACKGROUND

How the longitudinal asthma control status and other socio-demographic factors influence the changes of health-related quality of life (HRQOL) among asthmatic children, especially from low-income families, has not been fully investigated.

OBJECTIVES

This study aimed to describe the trajectories of asthma-specific HRQOL over 15 months and examine the effect of asthma control status on HRQOL by taking socio-demographic factors into consideration.

METHODS

A total of 229 dyads of asthmatic children and their parents enroled in public insurance programs were recruited for assessing asthma control status and HRQOL over four time points of assessment. Asthma control status was measured using the Asthma Control and Communication Instrument, and asthma-specific HRQOL was assessed using the Patient-Reported Outcomes Measurement Information System's Pediatric Asthma Impact Scale. Latent growth models (LGMs) were applied to examine the trajectory of HRQOL and the factors contributing to the changes of HRQOL.

RESULTS

Unconditional LGM revealed that HRQOL was improved over time. Conditional LGM suggested that accounting for asthma control and participants' socio-demographic factors, the variation in the initial level of HRQOL was significant, yet the rate of change was not. Conditional LGM also revealed that poorly controlled asthma status was associated with poor HRQOL at each time point (P's < 0.05). Lower parental education was associated with lower baseline HRQOL (P < 0.05). Hispanic children had a larger increase in HRQOL over time (P < 0.01) than non-Hispanic White children.

CONCLUSIONS

Vulnerable socio-demographic characteristics and poorly controlled asthma status affect HRQOL in children. This finding encourages interventions to improve asthma control status and HRQOL in minority children.

The catecholamine neurotransmitter precursor tyrosine increases anger during exposure to severe psychological stress

RATIONALE

Acute stress produces behavioral and physiological changes modulated by central catecholamines (CA). Stress increases CA activity, and depletion of CA stores reduces responses to stress. Increasing CA activity by administration of the dietary amino acid CA precursor tyrosine may increase responsiveness to stress. This study determined whether tyrosine enhances the ability of humans to respond to severe stress.

METHODS

Severe psychological stress was generated during training at Survival, Evasion, Resistance, and Escape (SERE) School. The acute stressor consisted of two mock interrogations conducted during several days of simulated captivity. Seventy-eight healthy male and female military personnel participated in this double-blind, between-subjects study, in which they received either tyrosine (300 mg/kg, N = 36) or placebo (N = 36). Tyrosine (or placebo) was administered in food bars in two doses of 150 mg/kg each approximately 60 min before each mock interrogation. Mood (Profile of Mood States), saliva cortisol, and heart rate (HR) were assessed prior to stress exposure during a week of academic training preceding mock captivity and immediately following the mock interrogations.

RESULTS

The severe stress produced robust effects on mood (i.e., increased tension, depression, anger, fatigue, vigor, and confusion; p < .001), cortisol, and HR (p < .001). Tyrosine increased anger (p = .002, ANOVA treatment condition by test session interaction) during stress but had no other effects.

CONCLUSION

Tyrosine did not alter most subjective or physiological responses to severe acute stress, but it increased ratings of anger. The modest increase in anger may be an adaptive emotional response in stressful environments.

Antimicrobial management of septic arthritis of the hand and wrist

PURPOSE

The optimal antimicrobial treatment for patients with hand or wrist septic arthritis is unknown. We report the treatment outcomes in patients with these infections.

METHODS

The medical records of 40 consecutive adult patients with hand or wrist septic arthritis treated at our institution from 2000 to 2008 were retrospectively reviewed. The primary outcome measure was treatment failure (histopathologic or microbiologic evidence of relapsed infection from the same joint or a contiguous anatomic area).

RESULTS

Involved joints were the wrist (n = 10, 25 %), metacarpal-phalangeal (n = 11, 27.5 %), proximal interphalangeal (n = 8, 20 %), distal interphalangeal (n = 10, 25 %), and thumb interphalangeal (n = 1, 2.5 %). Methicillin-sensitive (n = 15, 45 %) and -resistant (n = 7, 17.5 %) Staphylococcus aureus were the most common pathogens. Surgical therapies included open arthrotomy with debridement (n = 33, 82.5 %), arthroscopic debridement (n = 2, 5 %), and aspiration alone (n = 5, 12.5 %). Most patients (23/40, 58 %) received less than 1 week of parenteral antimicrobial therapy. Only two patients developed definite antimicrobial treatment failure, one of whom had an atypical mycobacterium infection. Patients with subacute to chronic infections were at high risk for finger amputation.

CONCLUSIONS

When combined with surgical debridement, relatively short courses of parenteral antimicrobial treatment (<1 week) supplemented with oral therapy for an additional 2-3 weeks is usually sufficient antimicrobial therapy for hand or wrist septic arthritis.

Temporal changes in blood variables during final maturation and senescence in male sockeye salmon Oncorhynchus nerka: reduced osmoregulatory ability can predict mortality

This study is the first to characterize temporal changes in blood chemistry of individuals from one population of male sockeye salmon Oncorhynchus nerka during the final 6 weeks of sexual maturation and senescence in the freshwater stage of their spawning migration. Fish that died before the start of their historic mean spawning period (c. 5 November) were characterized by a 20-40% decrease in plasma osmolality, chloride and sodium, probably representing a complete loss of osmoregulatory ability. As fish became moribund, they were further characterized by elevated levels of plasma cortisol, lactate and potassium. Regressions between time to death and plasma chloride (8 October: P < 0·001; 15 October: P < 0·001) indicate that plasma chloride was a strong predictor of longevity in O. nerka. That major plasma ion levels started to decline 2-10 days (mean of 6 days) before fish became moribund, and before other stress, metabolic or reproductive hormone variables started to change, suggests that a dysfunctional osmoregulatory system may initiate rapid senescence and influence other physiological changes (i.e. elevated stress and collapsed reproductive hormones) which occur as O. nerka die on spawning grounds.

Genetics and high cognitive ability

More is known about the genetics of general cognitive ability (g) than any other trait in psychology. Recent findings on the genetics of g include the following three examples: (1) heritability increases throughout the lifespan; (2) heritabilities of performance in cognitive tests are strongly correlated with the tests' loadings on a g factor; and (3) genetic effects on scholastic achievement largely overlap with genetic effects on cognitive ability. This body of genetic research addresses the aetiology of individual differences in the normal range. Much less is known about the genetics of the high end of the distribution. Finding heritability in the normal range of cognitive ability does not imply that high ability is also genetic in origin. However, the first twin study of high IQ children, which uses a new technique that analyses the average difference between extreme groups and the rest of the population, suggests that high IQ is as heritable as individual differences in the normal range. We are currently engaged in a molecular genetic study that attempts to identify specific genes that contribute to high ability.

Geoacoustic inversion of short range source data using a plane wave reflection coefficient approach

Acoustic time series data were collected in a shallow, hard bottom lake environment located in central Texas using both short range (2 m) implosive data, obtained with the source and a single hydrophone located near mid-depth in the waveguide, along with longer range implosive and explosive data from a near surface source to a bottom mounted hydrophone. Matched field inversions using simulated annealing were performed with a ray trace plus complex plane wave reflection coefficient forward propagation model that was validated in previous work. Isolating bottom interacting paths to perform the inversions is shown to be essential to reduce parameter uncertainties in the hard bottom environment and enables a systematic approach to the inversions which establishes the number of layers needed to represent the lake environment. Measured transmission loss data from a towed source were compared through a RMS error analysis to modeled transmission loss, constructed with the parameters from inversions of data from several source types, to further establish the validity of the inversion approach for this environment. Geoacoustic parameters obtained by inversions of short range, low frequency impulsive data are used to predict transmission loss at longer ranges and higher frequencies. The range dependence of the global minimum is discussed.

Attention resources and visible speech encoding in older and younger adults

Two experiments investigated adult age differences in the distribution of attention across a speaker's face during auditory-visual language processing. Dots were superimposed on the faces of speakers for 17-ms presentations, and participants reported the spatial locations of the dots. In Experiment 1, older adults showed relatively better detection performance at the mouth area than the eye area compared to younger adults. In Experiment 2, in the absence of audible language, both age groups did not differentially focus on the mouth area. The results are interpreted in light of Massaro's (1998, Perceiving talking faces: From speech perception to a behavioral principle. Cambridge, MA: MIT Press) theoretical framework for understanding auditory-visual speech perception. It is claimed that older adults' greater reliance on visible speech is due to a reallocation of resources away from the eyes and toward the mouth area of the face.

Broadband sound propagation in shallow water and geoacoustic inversion

Part of an experiment to test a measurement package in a shallow water region in the Gulf of Mexico was designed to gather broadband acoustic data suitable for inversion to estimate seabed geoacoustic parameters. Continuous wave tow acoustic signals at multiple frequencies and broadband impulsive source signals were recorded on a horizontal line array in a high-noise environment. Simulated annealing with a normal mode forward propagation model is utilized to invert for a geoacoustic representation of the seabed. Several inversions are made from different data samples of two light bulb implosions, the measured sound speed profiles at the HLA and at the positions of the light bulb deployments, and for two different cost functions. The different cost functions, measured sound speed profiles, and measured time series result in different inverted geoacoustic profiles from which transmission loss is generated for comparison with measurements. On the basis of physical consistency and from the comparison of the transmission loss and time series, a best estimate geoacoustic profile is selected and compared to those obtained from previously reported inversions. Uncertainties in the sound speed profile are shown to affect the uncertainties of the estimated seabed parameters.

Infants attend to second-order relational properties of faces

Two experiments investigated whether 7-month-old infants attend to the spatial distance measurements relating internal features of the human face. A visual preference paradigm was used, in which two versions of the same female face (one either lengthened or shortened, and one nonmodified) were presented simultaneously. In Experiment 1, infants looked longer at the nonmodified faces, which were determined to match the average distance relationships found in a sample of faces drawn from the same population. Longer looking times for modified faces were found in Experiment 2, in which the nonmodified faces were unusually long and the modified faces conformed to average distance measurements. It is proposed that infants' attention to the spatial relations of internal face features is an optimal tool for lifelong face recognition.

A genome-wide scan of 1842 DNA markers for allelic associations with general cognitive ability: a five-stage design using DNA pooling and extreme selected groups

All measures of cognitive processes correlate moderately at the phenotypic level and correlate substantially at the genetic level. General cognitive ability (g) refers to what diverse cognitive processes have in common. Our goal is to identify quantitative trait loci (QTLs) associated with high g compared with average g. In order to detect QTLs of small effect size, we used extreme selected samples and a five-stage design with nominal alpha levels that permit false positive results in early stages but remove false positives in later stages. As a first step toward a systematic genome scan for allelic association, we used DNA pooling to screen 1842 simple sequence repeat (SSR) markers approximately evenly spaced at 2 cM throughout the genome in a five-stage design: (1) case-control DNA pooling (101 cases with mean IQ of 136 and 101 controls with mean IQ of 100), (2) case-control DNA pooling (96 cases with IQ > 160 and 100 controls with mean IQ of 102), (3) individual genotyping of Stage 1 sample, (4) individual genotyping of Stage 2 sample, (5) transmission disequilibrium test (TDT; 196 parent-child trios for offspring with IQ > 160). The over all Type I error rate is 0.000125, which robustly protects against false positive results. The numbers of markers surviving each stage using a conservative allele-specific directional test were 108, 6, 4, 2, and 0, respectively, for the five stages. A genomic control test using DNA pooling suggested that the failure to replicate the positive case-control results in the TDT analysis was not due to ethnic stratification. Several markers that were close to significance at all stages are being investigated further. Relying on indirect association based on linkage disequilibrium between markers and QTLs means that 100,000 markers may be needed to exclude QTL associations. Because power drops off precipitously for indirect association approaches when a marker is not close to the QTL, we are not planning to genotype additional SSR markers. Instead we are using the same design to screen markers such as cSNPs and SNPs in regulatory regions that are likely to include functional polymorphisms in which the marker can be presumed to be the QTL.

Photochemically enhanced binding of small molecules to the tumor necrosis factor receptor-1 inhibits the binding of TNF-alpha

The binding of tumor necrosis factor alpha (TNF-alpha) to the type-1 TNF receptor (TNFRc1) plays an important role in inflammation. Despite the clinical success of biologics (antibodies, soluble receptors) for treating TNF-based autoimmune conditions, no potent small molecule antagonists have been developed. Our screening of chemical libraries revealed that N-alkyl 5-arylidene-2-thioxo-1,3-thiazolidin-4-ones were antagonists of this protein-protein interaction. After chemical optimization, we discovered IW927, which potently disrupted the binding of TNF-alpha to TNFRc1 (IC(50) = 50 nM) and also blocked TNF-stimulated phosphorylation of Ikappa-B in Ramos cells (IC(50) = 600 nM). This compound did not bind detectably to the related cytokine receptors TNFRc2 or CD40, and did not display any cytotoxicity at concentrations as high as 100 microM. Detailed evaluation of this and related molecules revealed that compounds in this class are "photochemically enhanced" inhibitors, in that they bind reversibly to the TNFRc1 with weak affinity (ca. 40-100 microM) and then covalently modify the receptor via a photochemical reaction. We obtained a crystal structure of IV703 (a close analog of IW927) bound to the TNFRc1. This structure clearly revealed that one of the aromatic rings of the inhibitor was covalently linked to the receptor through the main-chain nitrogen of Ala-62, a residue that has already been implicated in the binding of TNF-alpha to the TNFRc1. When combined with the fact that our inhibitors are reversible binders in light-excluded conditions, the results of the crystallography provide the basis for the rational design of nonphotoreactive inhibitors of the TNF-alpha-TNFRc1 interaction.

The salience of temporal cues in the developing structure of event knowledge

Two experiments used a novel method called Pathfinder to examine whether the salience of temporal cues embedded in event structure increases developmentally and whether people link event actions by simple adjacency relationships or embed them in an organized whole. A sequential format for eliciting knowledge was compared with a less structured format for dinner and bedtime events. Adults and their 8- and 10-year-old children demonstrated well-developed script organizations regardless of format, and organization improved across this age range. In Experiment 1, temporal cues were not a salient basis of comparison for 6-year-olds, but in Experiment 2 they could use temporal cues when instructed to do so. The results suggest that temporal salience increases between 6 and 10 years and that temporal knowledge of event actions is highly organized in this age range. Furthermore, children's event knowledge functions partly in the interaction between their developing event knowledge and the support provided by sequential constraints in the environment.

Context-dependent memory under stressful conditions: the case of skydiving

Two experiments examined the effect of differing levels of emotional arousal on learning and memory for words in matching and mismatching contexts. In Experiment 1, experienced skydivers learned words either in the air or on the ground and recalled them in the same context or in the other context. Experiment 2 replicated the stimuli and design of the first experiment except that participants were shown a skydiving video in lieu of skydiving. Recall was poor in air-learning conditions with actual skydiving, but when lists were learned on land, recall was higher in the matching context than in the mismatching context. In the skydiving video experiment, recall was higher in matching learn-recall contexts regardless of the situation in which learning occurred. We propose that under extremely emotionally arousing circumstances, environmental and/or mood cues are unlikely to become encoded or linked to newly acquired information and thus cannot serve as cues to retrieval. Results can be applied to understanding variations in context-dependent memory in occupations (e.g., police, military special operations, and Special Weapons and Tactics teams) in which the worker experiences considerable emotional stress while learning or recalling new information.

Presenilin-1 and -2 are molecular targets for gamma-secretase inhibitors

Presenilins are integral membrane protein involved in the production of amyloid beta-protein. Mutations of the presenilin-1 and -2 gene are associated with familial Alzheimer's disease and are thought to alter gamma-secretase cleavage of the beta-amyloid precursor protein, leading to increased production of longer and more amyloidogenic forms of A beta, the 4-kDa beta-peptide. Here, we show that radiolabeled gamma-secretase inhibitors bind to mammalian cell membranes, and a benzophenone analog specifically photocross-links three major membrane polypeptides. A positive correlation is observed among these compounds for inhibition of cellular A beta formation, inhibition of membrane binding and cross-linking. Immunological techniques establish N- and C-terminal fragments of presenilin-1 as specifically cross-linked polypeptides. Furthermore, binding of gamma-secretase inhibitors to embryonic membranes derived from presenilin-1 knockout embryos is reduced in a gene dose-dependent manner. In addition, C-terminal fragments of presenilin-2 are specifically cross-linked. Taken together, these results indicate that potent and selective gamma-secretase inhibitors block A beta formation by binding to presenilin-1 and -2.

Recent applications of polymer-supported reagents and scavengers in combinatorial, parallel, or multistep synthesis

There has been a wealth of recent reports concerning support-bound reagents and scavengers in the solution-phase synthesis of compound libraries and natural products. Important advances in 1999 include the continued development and use of novel reagents for heterocycle synthesis, the increased use of catch-and-release purification, and the development of increasingly sophisticated techniques to allow sequestering of many types of impurities from desired compounds. These techniques have all been combined to enable the complicated multistep synthesis of natural products and of libraries of novel drug-like molecules, without conventional purification.

A counterselection for the tryptophan pathway in yeast: 5-fluoroanthranilic acid resistance

The ability to counterselect, as well as to select for, a genetic marker has numerous applications in microbial genetics. Described here is the use of 5-fluoroanthranilic acid for the counterselection of TRP1, a commonly used genetic marker in the yeast Saccharomyces cerevisiae. Counterselection using 5-fluoroanthranilic acid involves antimetabolism by the enzymes of the tryptophan biosynthetic pathway, such that trp1, trp3, trp4 or trp5 strains, which lack enzymes required for the conversion of anthranilic acid to tryptophan, are resistant to 5-fluoroanthranilic acid. Commonly used genetic procedures, such as selection for loss of a chromosomally integrated plasmid, and a replica-plating method to rapidly assess genetic linkage in self-replicating shuttle vectors, can now be carried out using the TRP1 marker gene. In addition, novel tryptophan auxotrophs can be selected using 5-fluoroanthranilic acid.

Some limits on encoding visible speech and gestures using a dichotic shadowing task

Visible speech and gestures are two forms of available language information that can be used by listeners to help them understand the speaker's meaning. Previous research has shown that older adults are particularly dependent on visible speech, yet seem to profit less than younger adults from the speaker's gestures. To understand how visible speech and gestures are used when listening becomes difficult, the authors conducted an experiment with a dichotic shadowing task. The experiment examined how accurately participants could shadow the right- or left-ear input when instructed to attend selectively to a particular ear and whether performance benefited from visual input. The results indicate that older adults' shadowing performance was unaffected by visible speech and gestures. Younger adults did benefit by both visible speech and gestures. Thus, under extremely attention-demanding listening conditions, older adults are unable to use a compensatory mechanism for encoding visual language.

Parallel synthesis of prostaglandin E1 analogues

The first demonstration of the rapid parallel synthesis of diverse prostaglandin derivatives is reported. Upper (alpha-) side chain diversity was introduced to core 1 via the parallel Suzuki coupling of hydroborated alkenes. Conversion to the enones 3 and 9 was followed by the addition of the lower (omega-) side chains as higher-order cuprates 4. Upper side chains incorporating an N-acylsulfonamide protecting group were further transformed into prostaglandin amide analogues. Cleavage from support with HF/pyridine followed by scavenging provided 26 prostaglandin E1 analogues in high purity.

Neurotic butterflies in my stomach: the role of anxiety, anxiety sensitivity and depression in functional gastrointestinal disorders

This study examined the prevalence of functional gastrointestinal (FGI) disorders, and the association between FGI disorders and measures of affective distress, among a sample of 127 university students. Subjects completed a questionnaire battery including Research Diagnostic Questions for Functional Gastrointestinal Disorders, the Beck Anxiety Inventory, the Anxiety Sensitivity Index, the Beck Depression Inventory, and a medical utilization questionnaire. FGI disorders were diagnosed in 51.2% of the sample. Functional dyspepsia (22.8%), dyschezia (20.5%), functional heartburn (19.7%), functional chest pain (18.1%), and globus (12.6%) were the most frequently diagnosed disorders. Participants experiencing globus, functional dyspepsia, or functional heartburn showed significant differences in terms of anxiety, anxiety sensitivity, depression, and/or physician visits, when compared with participants without these disorders. Our results suggest that FGI disorders are strikingly prevalent among young adults, and specific FGI disorders are associated with affective distress. Implications of the observed association between psychological factors and FGI disorders are discussed.

DNA pooling and dense marker maps: a systematic search for genes for cognitive ability

Pooling DNA from subjects within a group and comparing the pooled DNA across groups for a dense map of DNA markers offers a solution to the conundrum that linkage is systematic but not powerful whereas allelic association is powerful but not systematic. We used DNA pooling to screen 66 markers on chromosome 22 in original and replication samples of children of high general cognitive ability (g) and controls of average g. Although none of these markers survived our three-stage screening design (original pooling, replication pooling, individual genotyping), the results of DNA pooling were largely confirmed by individual genotyping. We can therefore exclude associations of major effect size on chromosome 22 for g, a key variable for cognitive neuroscience research on learning and memory.

Developmental changes in the effect of dimensional salience on the discriminability of object relations

Two experiments explored three issues regarding the nature of perceptual development in 5- and 10-year-old children and adults: (a) the role of featural discriminability, (b) the facilitatory role of identity relations, and (c) the role of salience in a task context designed to minimize the likelihood of attention-switching between dimensions during perceptual processing. In Experiment 1, perceptual salience for size and achromatic color dimensions was determined for each participant based on their best-fitting triad classification task response pattern. These same persons participated in Experiment 2, which employed a speeded visual discrimination task. The primary finding was that preassessed salience significantly influenced the 5-year-olds' ability to discriminate between two objects, while salience did not affect 10-year-olds' or adults' response times. The results of both experiments support Odom & Cook's (1992) differential-sensitivity view of perceptual development, but these data contribute important information by showing that salience effects in perceptual processing occur even when the observer is selectively attending to a particular dimension, likely during early component processes prior to classification.

Dopamine markers and general cognitive ability

Because general cognitive ability (g) is among the most heritable behavioural traits, it is a reasonable target for a search for quantitative trait loci (QTLs). We used a selected-extremes design to test candidate genes for allelic association with g. Polymorphisms in four genes in the dopamine system (DRD2, DRD3, DRD4, DAT1) were genotyped for 51 high g children with IQ scores > 130 and for 51 average g control children. No significant allelic or genotypic differences were found between the high g and average g groups for these markers of the dopamine system, even though the selected-extremes design provides power to detect QTL associations that involve a relative risk of about 1.5.

What is so special about special education?

There is nothing special about special education. Educational methods have not changed significantly in at least 2,500 years. IQ tests were developed to identify those in need of special education, with the intention of developing appropriate educational methods. Effective special educational methods have yet to be developed. IQ tests are diagnostic but not prescriptive. Effective special educational methods will not be developed until (a) individual differences in student characteristics beyond IQ scores are recognized and understood and (b) educators focus on specific and realistic goals for outcome.

What is so special about special education?

There is nothing special about special education. Educational methods have not changed significantly in at least 2,500 years. IQ tests were developed to identify those in need of special education, with the intention of developing appropriate educational methods. Effective special educational methods have yet to be developed. IQ tests are diagnostic but not prescriptive. Effective special educational methods will not be developed until (a) individual differences in student characteristics beyond IQ scores are recognized and understood and (b) educators focus on specific and realistic goals for outcome.

No association between general cognitive ability and the A1 allele of the D2 dopamine receptor gene

Berman and Noble (1995) reported significantly reduced visuospatial performance in children with the TAQI A1 allele of the D2 dopamine receptor (DRD2) gene. Given that visuospatial performance loads highly on an unrotated principal component indexing general cognitive ability, we tested the association between DRD2 and WISC-R IQ comparing 51 high-IQ, 51 average-IQ, and 35 low-IQ children in the IQ Quantitative Trait Loci (QTL) Project. No statistically significant association between the TAQI A DRD2 alleles and IQ was found. Given that a statistically significant portion of genetic variance for specific cognitive abilities is independent of general cognitive ability, it is possible that the TAQI DRD2 association is specific to visuospatial performance and independent of general cognitive ability.

Cortical localization of human sustained attention: detection with functional MR using a visual vigilance paradigm

PURPOSE

Our goal was to determine whether functional MRI on a standard 1.5 T system can localize activation during a visual vigilance sustained attention task and whether this corresponds to results described in a PET investigation of a similar task.

METHOD

Sixteen volunteers were studied on a 1.5 T system using a gradient echo technique. A single axial section was oriented within a stereotaxic coordinate space, 40 mm superior to the anterior-posterior commissure line. Images with eyes closed were followed by images during subject concentration on a small dim spot. Motion correction and pixel-by-pixel statistical analysis were performed. Talairach grids were applied for summary statistical analysis and comparison to PET data, with analysis using a series of planned contrasts within a repeated measures analysis of variance.

RESULTS

Predominantly right-sided frontal and parietal activation was observed, with statistical significance across subjects in the right frontal lobe (F > or = 5.9, p < or = 0.041). Comparison with previously reported PET data yielded a very similar pattern of activation (F = 13.2; df = 1,8; p = 0.007).

CONCLUSION

Activation of the right middle frontal gyrus and right parietal lobe during visual vigilance is detectable across functional imaging modalities.

Information integration in cross-modal pattern recognition: an argument for acquired modularity

Three experiments addressed the issue of whether modularized operations (Fodor, 1983) in pattern recognition could be acquired. In Experiment 1, blind and sighted individuals were compared in the speech-tactile domain of pattern recognition. The results were inconsistent with the assumptions of the fuzzy logical model of perception (FLMP) (Oden and Massaro, 1978) and with the assumptions of modularized pattern recognition processes, but were consistent with the assumptions of 'penetrability' into non-modularized operations. Experiments 2 and 3 compared sighted individuals across speech-visual and speech-tactile domains, revealing fundamentally different patterns of performance that we argue demonstrate modularized and non-modularized FLMP operations in pattern recognition, respectively.

The independent prediction of general intelligence by elementary cognitive tasks: genetic and environmental influences

Current theories of intelligence have, in some cases, begun to include elementary cognitive tasks. Behavioral genetic studies of intelligence have not taken these theories into account. The current study includes 135 MZ and 128 DZ twin pairs from the Western Reserve Twin Project. The 11 WISC-R subtests as well as 6 elementary cognitive tasks were employed. Using a Schmid-Leiman (1957) transformation, analyses indicate a four-group factor model, supported by a second-order general factor at both phenotypic and biometric levels. Results indicate that the general factor, group factors, and specific residuals are necessary when examining additive genetic variance. Common environmental variance can be collapsed into a single general factor.

Encoding and memory for visible speech and gestures: a comparison between young and older adults

Two experiments explored whether older adults have developed a strategy of compensating for slower speeds of language processing and hearing loss by relying more on the visual modality. Experiment 1 examined the influence of visual articulatory movements of the face (visible speech) in auditory-visual syllable classification in young adults and older adults. Older adults showed a significantly greater influence of visible speech. Experiment 2 examined immediate recall in three spoken-language sentence conditions: speech alone, with visible speech, or with both visible speech and iconic gestures. Sentences also varied in meaningfulness and speech rate. In the old adult group, recall was better for sentences containing visible speech compared with the speech-alone sentences in the meaningful sentence condition. Old adults' recall showed no overall benefit of the presence of gestures. Young adults' recall on meaningful sentences was not higher for the visible speech compared with the speech-alone condition, whereas recall was significantly higher with the addition of iconic gestures. In the anomalous sentence condition, both young and old adults showed an advantage in recall by the presence of visible speech. The experiments provide converging evidence for old adults' greater reliance on visible speech while processing visual-spoken language.

Cryopreservation of human oocytes and fertilization by two techniques: in-vitro fertilization and intracytoplasmic sperm injection

Human oocyte cryopreservation results in poor survival and subsequent fertilization rates. It has been suggested that freeze-thaw-induced changes in the zona pellucida may impair sperm penetration or attachment. The aim of this study was to compare fertilization and cleavage rates in cryopreserved oocytes inseminated by conventional in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). A total of 220 oocytes, obtained from volunteers who had undergone ovarian stimulation, were cryopreserved using a slow freeze-rapid thaw protocol with 1.5 M propanediol as the cryoprotectant. Surviving oocytes (n = 74, 34.4%) were randomly allocated for fertilization by conventional IVF (group 1) or ICSI (group 2) using cryopreserved spermatozoa from a single donor of proven fertility. Fertilization was achieved in five (13.5%) of the oocytes in group 1 and 17 (45.9%) in group 2 (P < 0.005), with only one oocyte in group 1 exhibiting normal fertilization as opposed to 16 (43.2%) in group 2 (P < 0.001). Similarly, one oocyte fertilized by IVF cleaved, while all fertilized with ICSI cleaved (P < 0.001). We conclude that although the survival of oocytes is poor following cryopreservation, fertilization and cleavage rates can be enhanced significantly using ICSI. These data also suggest that the method of cryopreservation used in this study affected the zona pellucida, such that normal sperm attachment or penetration was impaired.

A twin study of competence and problem behavior in childhood and early adolescence

The Child Behavior Checklist (CBCL) was completed by parents of 181 pairs of same-sex twins ages 7-15 (mean age = 11.0 years). Correlations between scores on the CBCL scales for 99 pairs of monozygotic twins and 82 pairs of dizygotic twins indicated significant genetic influences that varied according to the specific area of competence and problem behavior. Model-fitting estimates derived from multiple regression analyses indicated significant genetic influence on competence in school and on all areas of problem behavior. In addition, significant shared environmental influence was detected for amount and quality of participation in activities, quality of social relationships, performance in school, anxiety/depression, and delinquent behaviour. Implications for future work on the mechanisms underlying these effects are discussed.

Current attitudes towards egg donation among men and women

Recent widespread concern has led to legislation in the UK preventing the use of fetal ovarian tissue for the treatment of infertile women. This questionnaire-based study aimed to assess the attitudes of both fertile and infertile men and women as well as egg donors and recipients towards the use of donated eggs for treatment, diagnosis and research. Fertile individuals were significantly less aware of egg donation but the majority in both the fertile and the infertile groups approved the use of eggs for research (89 and 95% of women and 88 and 92% of men respectively) and treatment (similar percentages). However, fetal sources of oocytes were acceptable to only 15% of women in the fertile, 21% in the infertile, 35% in the recipient and 19% in the donor groups. Cadaveric sources of oocytes were slightly more acceptable (28% fertile, 28% infertile, 50% recipient and 42% donors). Both these sources of oocytes were slightly more acceptable to men. Education had little influence on attitudes, although men and women of tertiary education level said they would be less likely to have gamete donation themselves. Thus there would appear to be widespread approval for the use of donor eggs in research and treatment but not if the source of eggs is fetal or cadaveric.

Encoding and memory for visible speech and gestures: a comparison between young and older adults

Two experiments explored whether older adults have developed a strategy of compensating for slower speeds of language processing and hearing loss by relying more on the visual modality. Experiment 1 examined the influence of visual articulatory movements of the face (visible speech) in auditory-visual syllable classification in young adults and older adults. Older adults showed a significantly greater influence of visible speech. Experiment 2 examined immediate recall in three spoken-language sentence conditions: speech alone, with visible speech, or with both visible speech and iconic gestures. Sentences also varied in meaningfulness and speech rate. In the old adult group, recall was better for sentences containing visible speech compared with the speech-alone sentences in the meaningful sentence condition. Old adults' recall showed no overall benefit of the presence of gestures. Young adults' recall on meaningful sentences was not higher for the visible speech compared with the speech-alone condition, whereas recall was significantly higher with the addition of iconic gestures. In the anomalous sentence condition, both young and old adults showed an advantage in recall by the presence of visible speech. The experiments provide converging evidence for old adults' greater reliance on visible speech while processing visual-spoken language.

The genetic and environmental variance underlying elementary cognitive tasks

Although previous studies have examined the genetic and environmental influences upon general intelligence and specific cognitive abilities in school-age children, few studies have examined elementary cognitive tasks in this population. The current study included 149 MZ and 138 same-sex DZ twin pairs who participated in the Western Reserve Twin Project. Thirty measures from the Cognitive Abilities Test (CAT; Detterman, 1986) were studied. Results indicate that (1) these measures are reliable indicators of general intelligence in children and (2) the structure of genetic and environmental influences varies across measures. These results not only indicate that elementary cognitive tasks display heterogeneous genetic and environmental effects, but also may demonstrate that individual differences in biologically based processes are not necessarily due to genetic variance.

A comparison of the effects of different biopsy strategies on the post-thaw survival of 8-cell-stage mouse embryos: implications for preimplantation diagnosis

The aim of this study was to investigate the effects of two different biopsy strategies, zona slitting and zona piercing, on the post-thaw survival and subsequent in-vitro development of 8-cell mouse embryos. From control experiments it was determined that neither biopsy by zona slitting nor zona piercing adversely affected embryo development in vitro, as similar rates of blastocyst formation and hatching were found between biopsied and zona-intact embryos; there was, however, a trend towards a lower rate of blastocyst hatching in embryos biopsied by zona piercing (78.3% compared with 91.9% of zona-intact embryos). When biopsy was followed by cryopreservation a different picture was seen: similar rates of freeze-thaw survival were found for zona-slit, zona-pierced and zona-intact embryos (84.2, 88.5 and 87.2% respectively), but this was superseded by a significant (P < 0.05) reduction in the blastocyst formation rates (61.4% zona-slit and 63.9% zona-pierced versus 78.7% zona-intact) and hatching rates (51% zona-slit and 52.5% zona-pierced versus 72.3% zona-intact) of the biopsied embryos. When the effects of zona slitting and piercing were considered in isolation, i.e. without performing biopsy, it was found that the larger holes produced by zona slitting rendered embryos more susceptible to freeze-thaw damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Dimensional strategies dominate perceptual classification

The nature of perceptual classification was investigated in children ranging between 4 and 10 years, and in young adults. Triad classification task responses were categorized as consistent or inconsistent with several classification rules, including: overall-similarity, size-dimensional, brightness-dimensional, pure identity, and all combinations of a switch from one rule to another midway through the experiment. The rule with the highest proportion of responses consistent with it reflected each person's best-fitting rule pattern. The higher this value, the higher the assumed consistency of rule usage. Data from the majority of individuals in every age group conformed best to one of the three dimensional rules. In addition, the consistency values for individuals' best-fitting rule became significantly higher as age increased. It is concluded that most children have a tendency to attend selectively to one stimulus dimension when making perceptual classification judgments. The developmental trend in perceptual classification does not appear to be a holistic-to-analytic shift; instead, it is a trend toward greater consistency in following a given classification rule.