Ebullition enhances chemical mass transport across the tailings-water interface of oil sands pit lakes

Base Mine Lake (BML) was the first commercial-scale demonstration oil sands pit lake established in northern Alberta, Canada. Recent studies indicate that ebullition enhances internal mass loading of dissolved constituents during settlement and dewatering of methanogenic fluid fine tailings (FFT) below the overlying water cap. Here, we describe results of integrated field measurements and numerical modelling to (i) determine potential for ebullition and enhanced mixing within BML, and (ii) assess impacts on chemical mass transport across the tailings-water interface. We observed sharp increases in [CH_4(aq)] with depth from <0.1 mg L^-1 immediately above the interface to >60 mg L^-1 over the upper 1.5 to 3.0 m of FTT. Thermodynamic modelling revealed that maximum [CH_4(aq)] values represent 60 to 80% of theoretical saturation, and corresponding total dissolved gas pressures approach or exceed fluid pressures. These findings supported integration of enhanced mixing into one-dimensional (1-D) advective-dispersive transport models, which substantially improved upon previous simulations of conservative tracer (i.e., Cl^-) profiles and chemical mass fluxes. The models revealed a positive relationship between CH_4(aq) saturation and enhanced mixing, showing that ebullition enhances internal mass loading. This information has potential to inform ongoing assessments of pit lake performance and support improved closure and reclamation planning at oil sands mines.

The crystal structures of the low-temperature and high-pressure polymorphs of nitric acid

A new high-pressure phase of pure nitric acid (HNO(3)) has been characterised at 1.6 GPa at room temperature by high-pressure neutron powder and X-ray single-crystal diffraction techniques. This is the first crystalline phase obtained upon compression of liquid nitric acid at room temperature and appears to be the stable phase up to pressures of at least 4 GPa. The crystal structure of this new phase shows some similarities to that of the low-temperature phase of nitric acid at ambient pressure, which has been redetermined as part of this study. Both structures share a herringbone packing of hydrogen-bonded molecular catemers, although the presence of disorder within the hydrogen bonds within one of the catemers of the low-temperature phase makes its structure comparatively more complex.

Comparison of the effects of caudal pole hemi-meniscectomy and complete medial meniscectomy in the canine stifle joint

OBJECTIVE

To compare the effects of caudal pole hemi-meniscectomy (CPHM) and complete medial meniscectomy (MM), specifically with respect to development of secondary osteoarthritis, in the stifle joints of clinically normal dogs.

ANIMALS

14 large-breed dogs.

PROCEDURE

Unilateral CPHM (7 dogs) or MM (7) was performed, and the left stifle joints served as untreated control joints. Gait was assessed in all dogs before surgery and at 4, 8, 12, and 16 weeks postoperatively. After euthanasia, joints were evaluated grossly; Mankin cartilage scores, subchondral bone density assessment, and articular cartilage proteoglycan extraction and western blot analyses of 3B3(-) and 7D4 epitopes were performed.

RESULTS

Weight distribution on control limbs exceeded that of treated limbs at 4 and 16 weeks after surgery in the CPHM group and at 4 and 8 weeks after surgery in the MM group; weight distribution was not significantly different between the 2 groups. After 16 weeks, incomplete meniscal regeneration and cartilage fibrillation on the medial aspect of the tibial plateau and medial femoral condyle were detected in treated joints in both groups. Mankin cartilage scores, subchondral bone density, and immunoexpression of 3B3(-) or 7D4 in articular cartilage in CPHM- or MM-treated joints were similar; 7D4 epitope concentration in synovial fluid was significantly greater in the MM-treated joints than in CPHM-treated joints.

CONCLUSIONS AND CLINICAL RELEVANCE

Overall severity of secondary osteoarthritis induced by CPHM and MM was similar. Investigation of 7D4 epitope concentration in synovial fluid suggested that CPHM was associated with less disruption of chondrocyte metabolism.

Mapping of receptive language cortex in bilingual volunteers by using magnetic source imaging

OBJECT

There are conflicting claims in the functional imaging literature concerning whether different languages are represented by distinct brain mechanisms in individuals who are proficient in more than one language. This interesting theoretical issue has practical implications when functional imaging methods are used for presurgical language mapping. To address this issue the authors compared the location and extent of receptive language cortex specific to English and Spanish in neurologically intact bilingual volunteers by using magnetic source imaging.

METHODS

Areas of the cortex that were specialized for receptive language functions were identified separately for each language in 11 healthy adults who were bilingual in English and Spanish. The authors performed exactly the same procedures used routinely for presurgical receptive language mapping. In each bilingual individual, the receptive language-specific map always encompassed the posterior portion of the superior temporal gyrus. In every case, however, substantial differences in the receptive language maps were also observed for the two languages, regardless of whether each participant's first language was English or Spanish.

CONCLUSIONS

Although the reasons for such differences and their ultimate significance in identifying the cerebral mechanisms of language are subject to continuing investigation, their presence is noteworthy and has practical implications for the surgical management of patients with lesions in the temporal and parietal regions of the dominant hemisphere.

Measures of information processing in rapid automatized naming (RAN) and their relation to reading

The letters, numbers, and objects subtests of the Rapid Automatized Naming Tests (RAN) were given to 50 first- and second-grade students. Student performance on the three RAN subtests were audiotaped and subjected to postacquisition processing to distinguish articulation and interarticulation pause times. This study investigated (1) the relations between the articulation and pause durations associated with the 50 stimuli of each RAN subtest and (2) the relations between the pause and articulation latencies of the three RAN subtests and reading. For both first- and second-grade students, pause and articulation times for RAN letters and objects were not found to be reliably related, in contrast to RAN numbers articulation and pause durations. RAN subtest pause durations were differentially related to reading; however, articulation was rarely related to reading. The RAN letters pause time was the most robust predictor of decoding and reading comprehension, consistently predicting all first- and second-grade measures. Analysis supported the view that reading is predicted by speed of processing associated with letters, not general processing speed.

Prenatal cocaine exposure and prematurity: neurodevelopmental growth

The consequences of prematurity and prenatal cocaine exposure on early neurobehavior and physical growth were examined longitudinally in a sample of 20 cocaine-exposed and 20 non-exposed preterm neonates. The magnitude of the difference in physical growth acceleration related to prenatal cocaine exposure increased with increasing birth gestational age, whereas growth rate differences in irritability decreased. In contrast, prenatal cocaine exposure, independent of prematurity, was related to reduced attention skills at 36 weeks conceptional age and increased rates of neurobehavioral change. The effects of prenatal cocaine exposure differed with respect to the degree of prematurity, depending on the nature of the outcome examined, suggesting differing windows of vulnerability for different outcome domains. The usefulness of a developmental growth perspective was demonstrated.

Persistence of dyslexia: the Connecticut Longitudinal Study at adolescence

OBJECTIVE

The outcome in adolescence of children diagnosed as dyslexic during the early years of school was examined in children prospectively identified in childhood and continuously followed to young adulthood. This sample offers a unique opportunity to investigate a prospectively identified sample of adolescents for whom there is no question of the childhood diagnosis and in whom highly analytic measures of reading and language can be administered in adolescence.

DESIGN

Children were recruited from the Connecticut Longitudinal Study, a cohort of 445 children representative of those children entering public kindergarten in Connecticut in 1983. Two groups were selected when the children were in grade 9: children who met criteria for persistent reading disability in grades 2 through 6 (persistently poor readers [PPR]; n = 21) and a comparison group of nondisabled children, subdivided into average readers (n = 35) and superior readers (n = 39). In grade 9, each child received a comprehensive assessment of academic, language, and other cognitive skills.

RESULTS

Measures of phonological awareness (but not orthographic awareness) were most significant in differentiating the 3 reading groups, with smaller contributions from measures of word finding and digit-span. Academic measures that best separated good from poor readers were decoding and spelling, whereas measures of math and reading comprehension did not. Measures of phonological awareness, followed next by teacher rating of academic skills were the best predictors of decoding, reading rate, and reading accuracy. In contrast, the best predictor of reading comprehension was word finding, with digit span and socioeconomic status also contributing significantly. Using a growth curve model (quadratic model of growth to a plateau) all 3 groups demonstrated similar patterns of growth over time, with the superior group outperforming the average group, and the average group outperforming the PPR group. There was no evidence that the children in the PPR group catch up in their reading skills.

CONCLUSIONS

Deficits in phonological coding continue to characterize dyslexic readers even in adolescence; performance on phonological processing measures contributes most to discriminating dyslexic and average readers, and average and superior readers as well. These data support and extend the findings of previous investigators indicating the continuing contribution of phonological processing to decoding words, reading rate, and accuracy and spelling. Children with dyslexia neither spontaneously remit nor do they demonstrate a lag mechanism for catching up in the development of reading skills. In adolescents, the rate of reading as well as facility with spelling may be most useful clinically in differentiating average from poor readers.

Identification of sulfated oligosaccharide-based inhibitors of tumor growth and metastasis using novel in vitro assays for angiogenesis and heparanase activity

Inhibitors of tumor angiogenesis and metastasis are rapidly emerging as important new drug candidates for cancer therapy. To facilitate the identification of such drugs, we recently developed novel and rapid in vitro assays for human angiogenesis and for the extracellular matrix-degrading enzyme heparanase, which has been implicated in tumor metastasis. In this study, sulfated oligosaccharides, which are structural mimics of heparan sulfate, were investigated as drug candidates because these compounds may interfere with heparan sulfate recognition by many angiogenic growth factors and may inhibit cleavage of heparan sulfate by heparanase. In the preliminary screening studies, it was found that inhibitory activity in both assay systems was critically dependent on chain length and degree of sulfation, highly sulfated linear oligosaccharides of five or more monosaccharides in length being the most active. However, two sulfated oligosaccharides stood out as potential antitumor drugs, phosphomannopentaose sulfate (PI-88) and maltohexaose sulfate, both of these compounds having the important property of simultaneously being potent inhibitors of in vitro angiogenesis and heparanase activity. Due to the ease of manufacture of the starting material, phosphomannopentaose, PI-88 was studied in more detail. PI-88 was shown to inhibit the primary tumor growth of the highly invasive rat mammary adenocarcinoma 13762 MAT by approximately 50%, inhibit metastasis to the draining popliteal lymph node by approximately 40%, and reduce the vascularity of tumors by approximately 30%, all of these effects being highly significant. Acute hematogenous metastasis assays also demonstrated that PI-88 was a potent (>90%) inhibitor of blood-borne metastasis. Thus, by the use of novel in vitro screening procedures, we have identified a promising antitumor agent.

Memory functions in children with early hydrocephalus

Children with arrested, shunted, and no hydrocephalus were compared on verbal and nonverbal memory tasks assessing multiple components of memory. A gradient of severity was hypothesized, with the shunted hydrocephalus group expected to exhibit the most significant memory impairments and the arrested group expected to perform more poorly than children with no hydrocephalus. Etiologies of prematurity, spina bifida, and aqueductal stenosis were represented by 157 participants. Results supported the hypothesis; the shunted hydrocephalus group performed poorer on all memory measures. Differences for the arrested group were less frequently statistically significant relative to children with no hydrocephalus. Irrespective of etiology, the shunted hydrocephalus group exhibited a pattern of performance suggestive of encoding and retrieval deficits on both verbal and nonverbal tasks, showing a pervasive disturbance of memory processes.

The foundations of literacy: learning the sounds of letters

Learning the sounds of letters is an important part of learning to read and spell. To explore the factors that make some letter-sound correspondences easier for children to learn than others, we first analyzed knowledge of letters' sounds (and names) by 660 children between 3 1/2 and 7 1/2 years old. A second study examined pre-schoolers' (M age 4 years, 11 months) ability to learn various sound-letter mappings. Together, the results show that an important determinant of letter-sound knowledge is whether the sound occurs in the name of the letter and, if so, whether it is at the beginning or the end. The properties of the sound itself (consonant versus vowel, sonorant versus obstruent, stop versus continuant) appear to have little or no influence on children's learning of basic letter-sound correspondences. The findings show that children use their knowledge of letters' names when learning the letters' sounds rather than memorizing letter-sound correspondences as arbitrary pairings.

Memory functions in children with early hydrocephalus

Children with arrested, shunted, and no hydrocephalus were compared on verbal and nonverbal memory tasks assessing multiple components of memory. A gradient of severity was hypothesized, with the shunted hydrocephalus group expected to exhibit the most significant memory impairments and the arrested group expected to perform more poorly than children with no hydrocephalus. Etiologies of prematurity, spina bifida, and aqueductal stenosis were represented by 157 participants. Results supported the hypothesis; the shunted hydrocephalus group performed poorer on all memory measures. Differences for the arrested group were less frequently statistically significant relative to children with no hydrocephalus. Irrespective of etiology, the shunted hydrocephalus group exhibited a pattern of performance suggestive of encoding and retrieval deficits on both verbal and nonverbal tasks, showing a pervasive disturbance of memory processes.

Longitudinal neuropsychological outcome in infants and preschoolers with traumatic brain injury

Neuropsychological outcome was evaluated in a prospective, longitudinal follow-up study of children age 4 months to 7 years at injury with either mild-to-moderate (N = 35) or severe (N = 44) traumatic brain injury (TBI). Age-appropriate tests were administered at baseline, 6 months, 12 months, and 24 months after the injury. Performance was compared on (1) Composite IQ and motor, (2) Receptive and expressive language, and (3) Verbal and Perceptual-Performance IQ scores. In comparison to mild-to-moderate TBI, severe TBI in infants and preschoolers produced deficits in all areas. Interactions between task and severity of injury were obtained. Motor scores were lower than IQ scores, particularly after severe TBI. Both receptive and expressive scores were reduced following severe TBI. Expressive language scores were lower than receptive language scores for children sustaining mild-to-moderate TBI. While severe TBI lowered both Verbal and Perceptual-Performance IQ scores, Verbal IQ scores were significantly lower than Perceptual-Performance IQ scores after mild-to-moderate TBI. Mild injuries may produce subtle linguistic changes adversely impacting estimates of Verbal IQ and expressive language. Within the limited age range evaluated within this study, age at injury was unrelated to test scores: The impact of TBI was comparable in children ages 4 to 41 months versus 42 to 72 months at the time of injury. All neuropsychological scores improved significantly from baseline to the 6-month follow-up. However, no further change in scores was observed from 6 to 24 months after the injury. The persistent deficits and lack of catch-up over time suggest a reduction in the rate of acquisition of new skills after severe TBI. Methodological issues in longitudinal studies of young children were discussed.

Effects of intraventricular hemorrhage and hydrocephalus on the long-term neurobehavioral development of preterm very-low-birthweight infants

Measures of intelligence, neuropsychological functions, academic skills, and behavioral adjustment were obtained at school-age from children born preterm with no hydrocephalus (N=29), arrested hydrocephalus (N=19), and shunted hydrocephalus (N=17), and a term comparison group (N=23). Most children also received concurrent neurological examinations and MRI brain scans. Results revealed significantly poorer neurobehavioral development in all four domains in preterm children with shunted hydrocephalus. Despite abnormal MRI findings in virtually all children with arrested hydrocephalus, significant differences between preterm children with arrested hydrocephalus and those with no hydrocephalus were largely in areas involving attentional and academic skills. Preterm children with no hydrocephalus tended to show poorer motor development relative to term children. Neurological abnormalities were restricted to children with spasticity in the arrested (N=2) and shunted (N=10) groups. These results highlight the importance of separating cases according to residual neurological and neuroimaging abnormalities in accounting for variations in the neurobehavioral development of preterm, low-birth-weight infants.

Psychometric properties of family members' reports of parental physical aggression toward clinic-referred children

This study examined (a) differences among mothers', fathers', and children's reports of parental physical aggression toward children; (b) the reliability and validity of family members' reports of aggression using confirmatory factor analysis; and (c) the discriminant validity of the constructs of mother-child and father-child aggression. Participants were 72 dual-parent families in which the parents were seeking clinical services for their children's (ages 7-9 years) conduct behavior problems. Each participant completed the parent-child version of the Conflict Tactics Scale (P-CTS). Results indicate that children reported lower levels of mother-child and father-child aggression than either mothers or fathers reported. Although the reliability (total systematic variance accounted for by observed variables) of family members' reports on the P-CTS ranged from moderate to high, convergent validity was generally low. The constructs of mother-child and father-child aggression were highly correlated but could be distinguished from each other when relationships among rater effects were considered.

Psychometric properties of family members' reports of parental physical aggression toward clinic-referred children

This study examined (a) differences among mothers', fathers', and children's reports of parental physical aggression toward children; (b) the reliability and validity of family members' reports of aggression using confirmatory factor analysis; and (c) the discriminant validity of the constructs of mother-child and father-child aggression. Participants were 72 dual-parent families in which the parents were seeking clinical services for their children's (ages 7-9 years) conduct behavior problems. Each participant completed the parent-child version of the Conflict Tactics Scale (P-CTS). Results indicate that children reported lower levels of mother-child and father-child aggression than either mothers or fathers reported. Although the reliability (total systematic variance accounted for by observed variables) of family members' reports on the P-CTS ranged from moderate to high, convergent validity was generally low. The constructs of mother-child and father-child aggression were highly correlated but could be distinguished from each other when relationships among rater effects were considered.

Cognitive correlates of long-term cannabis use in Costa Rican men

BACKGROUND

Cognitive correlates of long-term cannabis use have been elusive. We tested the hypothesis that long-term cannabis use is associated with deficits in short term memory, working memory, and attention in a literate, westernized culture (Costa Rica) in which the effects of cannabis use can be isolated.

METHODS

Two cohorts of long-term cannabis users and nonusers were studied. Within each cohort, users and nonusers were comparable in age and socioeconomic status. Polydrug users and users who tested positive for the use of cannabis at the time of cognitive assessment after a 72-hour abstention period were excluded. The older cohort (whose age was approximately 45 years) had consumed cannabis for an average of 34 years, and comprised 17 users and 30 nonusers, who had been recruited in San José, Costa Rica, and had been observed since 1973. The younger cohort (whose age was approximately 28 years) had consumed cannabis for an average of 8 years, and comprised 37 users and 49 nonusers. Short-term memory, working memory, and attentional skills were measured in each subject.

RESULTS

Older long-term users performed worse than older nonusers on 2 short-term memory tests involving learning lists of words. In addition, older long-term users performed worse than older nonusers on selective and divided attention tasks associated with working memory. No notable differences were apparent between younger users and nonusers.

CONCLUSION

Long-term cannabis use was associated with disruption of short-term memory, working memory, and attentional skills in older long-term cannabis users.

Correlation of medical and neurosurgical events with neuropsychological status in children at diagnosis of astrocytoma: utilization of a neurological severity score

Neuropsychological studies of children who have brain tumors have yielded diverse results with respect to identifying factors that contribute to poor intellectual outcome. The purpose of this study was to evaluate the relationship between pre- and perioperative events, tumor-related factors, and the neuropsychological status of children diagnosed with astrocytoma. Events that could potentially be detrimental to neuropsychological outcome were quantified utilizing a new "neurological severity score." The Neurological Severity Score was developed as a research tool to test our hypothesis that ultimate intellectual outcome is a result of cumulative, interactive insults on the central nervous system. This study constitutes a first step in examining the predictive value of the Neurological Severity Score by evaluating its correlation with baseline neuropsychological status. Fifty-nine children who had astrocytoma (36 supratentorial and 23 infratentorial) received complete neurological and neuropsychological evaluations within 3 months of diagnosis. Each child's neurological history and examination results were scored by an independent observer using the Neurological Severity Score. Neuroimages obtained at diagnosis and at the time of neuropsychological testing were evaluated as well. For the group as a whole, memory, attention, and motor abilities were significantly below age-appropriate norms, whereas intelligence, language, and academic skills were preserved. Patterns of deficits were identified and related to tumor site. There were no significant differences in mean neuropsychological domain scores between groups based on gender, pre-versus post-operative status, ethnicity, tumor grade, or abnormalities on magnetic resonance imaging (MRI). The Neurological Severity Score was significantly inversely correlated with visual-spatial skills, memory, attention, performance IQ, and global IQ. In conclusion, among all the medical and neurological factors present at diagnosis, the neurological severity score had the highest correlation with neuropsychological scores. This instrument has promise as a research tool in investigations of the psychological effects of cancer and its treatment on children.

Neuropsychologic effects of chemotherapy on children with cancer: a longitudinal study

PURPOSE

A prospective study was conducted to assess the effects of chemotherapy for cancer on children's long-term neuropsychologic status.

PATIENTS AND METHODS

Ninety-nine children who received no cranial radiation therapy (CRT) completed four annual neuropsychologic assessments. Fifty-one patients received intrathecal (IT) chemotherapy (ITC); 48 received no CNS treatment. These two groups were compared using repeated-measures analysis of variance on IQ, memory, language, freedom from distractibility, academic achievement, executive functions, and fine-motor, perceptual-motor, and tactile-spatial skills. In addition, 51 of the sample of 99 patients had been examined 5 to 11 years after diagnosis. Their data were analyzed to evaluate the longer-term effects of chemotherapy. The predictability of demographic and medical variables on neuropsychologic outcome at 3-year and long-term follow-up study were assessed using multiple regression techniques.

RESULTS

Overall, the effects of chemotherapy in the absence of CRT appear to be slight. Patients who received ITC and intravenous (IV) methotrexate declined slightly on perceptual-motor skills, but were still well within the normal range. Both groups, regardless of treatment, declined on academic achievement tests, although not to a statistically significant degree. Age effects were found on performance IQ (PIQ) and perceptual-motor skills. Socioeconomic status (SES) correlated with a large number of variables. Sex effects were not significant.

CONCLUSION

The present results are largely consistent with previous findings for nonirradiated groups. Treatment effects from ITC are slightly more apparent 5 to 11 years after diagnosis than at 3-year follow-up evaluation but this does not constitute a clinically meaningful difference. More noticeable are academic declines among all groups, regardless of treatment.

Regional brain tissue composition in children with hydrocephalus. Relationships with cognitive development

OBJECTIVE

To determine whether children with shunted hydrocephalus show variations in regional brain tissue composition that relate to cognitive functions.

DESIGN

Nonequivalent control group.

PATIENTS AND METHODS

Magnetic resonance imaging (MRI) and cognitive skills assessments were obtained on 28 children, 6 to 9 years of age, with shunted hydrocephalus and 13 normal control subjects comparable in age, gender, ethnicity, and socioeconomic status. Three consecutive MRI slices below the vertex were segmented using a fuzzy clustering algorithm to separate pixels into gray matter, white matter, and cerebrospinal fluid (CSF) in quadrants representing left and right anterior and posterior brain regions. The cognitive skills assessments included the Wechsler Intelligence Scale for Children-Revised verbal and performance IQ scores, neuropsychological composites of language and visuospatial skills, a measure of visuomotor dexterity, and 2 measures of problem-solving abilities. The MRI data were analyzed in a group x tissue x hemisphere x region analysis of variance. Spearman rho correlations were computed within the hydrocephalus group between the MRI and cognitive measures.

RESULTS

Children with hydrocephalus showed reductions in overall gray matter percentages and corresponding increased CSF percentages that were more pronounced in posterior than anterior regions of both hemispheres. White matter percentages were reduced in children with hydrocephalus only in the left posterior quadrant. Correlations of posterior, but not anterior, CSF and gray matter percentages were significant with verbal and performance IQ scores and language, visuospatial, and visuomotor dexterity skills, but not with problem-solving abilities. Children with hydrocephalus who had proportionately greater posterior than anterior CSF percentages had significantly poorer visuomotor dexterity and visuospatial skills than did hydrocephalic children with proportionate CSF percentages.

CONCLUSION

Regional variations in brain tissue composition in children with shunted hydrocephalus correlate with a variety of cognitive and visuomotor functions.

Morphometric evaluation of the hydrocephalic brain: relationships with cognitive development

The effects of early hydrocephalus and related brain anomalies on cognitive skills are not well understood. In this study, magnetic resonance scans were obtained from 99 children aged from 6 to 13 years with either shunted hydrocephalus (n = 42) or arrested (unshunted) hydrocephalus (n = 19), from patient controls with no hydrocephalus (n = 23), and from normal, nonpatient controls (n = 15). Lateral ventricle volumes and area measurements of the internal capsules and centra semiovale in both hemispheres were obtained from these scans, along with area measurements of the corpus callosum. Results revealed reductions in the size of the corpus callosum in the shunted hydrocephalus group. In addition, lateral ventricle volumes were larger and internal capsule areas were smaller in both hemispheres in children with shunted and arrested hydrocephalus. The centra semiovale measurements did not differentiate the groups. Correlating these measurements with concurrent assessments of verbal and nonverbal cognitive skills, motor abilities, and executive functions revealed robust relationships only between the area of the corpus callosum and nonverbal cognitive skills and motor abilities. These results support the theory of a prominent role for the corpus callosum defects characteristic of many children with shunted hydrocephalus in the spatial cognition deficits commonly observed in these children.

Reliability of brain structure morphometry in hydrocephalic children using MR images

To assess the ability of human operators to make decisions about region boundaries in significantly malformed brains, we performed a study of the reliability of morphometric measurements of specific brain structures from MRI in children with hydrocephalus and controls. Cross-sectional area measures of the corpus callosum, internal capsules and centrum semiovale, and volumes of the lateral ventricles were made in 50 children. Independent measurements were made by two raters on T1 and T2-weighted MR images. Pearson's correlation coefficients (r) and intraclass correlation coefficients (ICC) between the two rater's sets of measures were computed for each structure across all subjects. ICCs ranged from a low of 0.7502 to a high of 0.9895. All ICCs were significant at the p < .0001 level and were generally less than or equal to the corresponding Pearson's r value in every case. Therefore, the Pearson's r may overestimate the reliability. The results of this study support the claim that the ICC should be used rather than the Pearson's r when assessing interater reliability in situations where large between-group differences are present. In addition, the results show that brains malformed by disorders, such as hydrocephalus, can be reliably assessed using morphometric measures of MR images.

Verbal and nonverbal skill discrepancies in children with hydrocephalus: a five-year longitudinal follow-up

Compared verbal and nonverbal skills of 65 children ages 5 to 7 years, with a history of shunted hydrocephalus (n = 26), arrested hydrocephalus (n = 11), and no hydrocephalus (n = 28), over a 5-year period. Comparison of these skills in 4 assessments revealed poorer average nonverbal than verbal skills on measures from the McCarthy Scales of Children's Abilities, the Wechsler Intelligence Scales for Children-Revised (WISC-R), and composites of neuropsychological skills for the shunted hydrocephalus group in comparison to the arrested-hydrocephalus and no hydrocephalus groups. There were higher rates of significant discrepancies between WISC-R Verbal IQ (VIQ) and Performance IQ (PIQ), with PIQ < VIQ in the shunted group. However, relatively few children exhibited significant discrepancies on multiple test occasions. The poorer performance of the shunted hydrocephalus group could not be attributed to motor demands of the nonverbal tasks.

Enhancement of esophageal carcinogenesis in male F344 rats by dietary phenylhexyl isothiocyanate

The purpose of this study was to evaluate the potential effects of dietary 6-phenylhexyl isothiocyanate (PHITC) on N-nitrosomethylbenzylamine (NMBA)-induced esophageal carcinogenesis in rats. Groups of 15 male F344 rats received weekly s.c. injections of NMBA in 20% dimethylsulfoxide or the vehicle alone for 15 consecutive weeks. Two weeks prior to initiation of carcinogen or vehicle injections rats were provided with modified AIN-76A diet or modified AIN-76A diet containing PHITC at levels of 0.4, 1.0 or 2.5 mumol/g diet. Experimental controls consisted of groups that received only the vehicle (vehicle controls), NMBA (carcinogen controls) or PHITC at the high dose level of 2.5 mumol/g diet. No esophageal tumors or preneoplastic lesions were detected in rats that received the vehicle or PHITC alone. In contrast, all rats treated with NMBA alone or PHITC + NMBA exhibited esophageal tumors and preneoplastic esophageal lesions. In groups that received PHITC + NMBA tumor multiplicity was increased by 21-69% when compared with rats treated with NMBA alone, indicating that PHITC enhanced esophageal tumorigenesis in this model system. These results, in conjunction with our previous work, demonstrate that arylalkyl isothiocyanates may inhibit or enhance esophageal tumorigenesis in the NMBA-treated rat. The ability of isothiocyanates to inhibit or enhance experimental tumorigenesis may depend on alkyl chain length of the isothiocyanate, the animal species examined and the specific carcinogen employed.

Perspectives of chronic pain: an evaluative comparison of restrictive and comprehensive models

The authors compare theoretical perspectives of chronic pain using a restrictive comprehensive categorization. Four of the perspectives (mind-body dualism, psychological, radical operant--behavioral, and radical cognitive) are categorized as restrictive. The other 4 perspectives (International Association for the Study of Pain, gate control, nonradical operant--behavioral, and cognitive-behavioral) that incorporate multiple facets are categorized as comprehensive. On the basis of empirical support, practical application, and issues concerning potential research design problems, the restrictive perspectives could be rejected for not providing a model in which chronic pain can be thoroughly investigated. The comprehensive perspectives, however, demonstrate greater potential for serving that role. Nonetheless, the need for additional theory development by the comprehensive perspectives is noted.

Behavioral adjustment of children with hydrocephalus: relationships with etiology, neurological, and family status

Examined the relationship of hydrocephalus and behavioral adjustment in three groups of 5- to 7-year-old children (N = 84) with a history of early hydrocephalus (spina bifida, prematurity, aqueductal stenosis) and three non-hydrocephalic comparison groups (spina bifida, prematurity, normals). Results revealed no significant group differences on measures of behavioral adjustment and a variety of family and sociodemographic variables. Children with hydrocephalus were more likely to meet criteria for behavior problems, obtained lower scores on measures of adaptive behavior, and perceived themselves as less physically competent. Categorical modeling analyses showed that hydrocephalus and its treatment, gender, family variables, and motor skills were related to the presence of behavior problems.

Neuropsychological changes in children with cancer: the treatment of missing data in longitudinal studies

Researchers conducting longitudinal studies with children or adults are inevitably confronted with problems of attrition and missing data. Missing data in longitudinal studies is frequently handled by excluding from analyses those cases for whom data are incomplete. This approach to missing data is not optimal. On the one hand, if data are missing at random, then dropping incomplete cases ignores information collected on those cases that could be used to improve estimates of population parameters (e.g., means, variances, covariances, and growth rates) and improve the power of significance tests of statistical hypotheses. On the other hand, if data are not missing at random, then dropping incomplete cases leads to biased parameter estimates and hypothesis tests that may be internally and externally invalid. This study uses three years of follow-up data from a longitudinal investigation of neuropsychological outcomes of cancer in children to demonstrate the problems presented by missing data in repeated measures designs and some solutions. In evaluating potential biasing effects of attrition, the study extends previous research on neuropsychological outcomes in pediatric cancer by inclusion of patients whose disease had relapsed, and by comparison of surviving and nonsurviving patients. Although the data presented have specific relevance to the study of neuropsychological outcome in pediatric cancer, the problems of missing data and the solutions presented are relevant to a wide variety of diseases and conditions of interest to researchers in child and adult neuropsychology.

A cross-level units-of-analysis approach to individual differences in skill acquisition

A recent multiple-stage model posits that the individual-difference factors influencing performance vary depending on skill acquisition stage (P. L. Ackerman, 1989, 1990). In the current study, the authors examine the effect of ability in early skill acquisition and extend earlier research by examining the roles of self-efficacy and task familiarity. Furthermore, learning-curve modeling with multilevel models is used to alleviate prior analytical problems. Subjects (N = 115) performed an air traffic control simulation task. Nonlinear learning-curve parameters were estimated for each subject using a negative exponential model (see D. R. Rogosa & J. B. Willett, 1985). Cognitive ability, self-efficacy, and task familiarity were then used to predict learning-curve parameters: learning-rate constant and asymptotic performance. Results revealed that ability, self-efficacy, and familiarity predicted the learning-rate constant, whereas self-efficacy predicted asymptotic performance.

Pentosan polysulphate and glycosaminoglycan polysulphate stimulate the synthesis of hyaluronan in vivo

Pentosan polysulphate (PPS) and glycosaminoglycan polysulphate (GAGPS) were examined for their ability to alter hyaluronan synthesis in vivo. The inflamed rat subcutaneous air pouch model was used for the study. PPS or GAGPS injected into the air pouch at a dose of 2.5 mg/kg daily for 7 days resulted in higher molecular weight hyaluronan in the pouch fluid compared with control non-drug-treated pouch fluid. The quantity of the hyaluronan was increased by PPS, but not by GAGPS. We concluded that both drugs could be beneficial in the treatment of inflammatory arthritides in which a decrease in normal synovial hyaluronan concentration and molecular weight occurs.

Relationship among social and intrapersonal risk, alcohol expectancies, and alcohol usage among early adolescents

Numerous studies have shown that adolescents' expectancies about the effects of alcohol influence usage. Expectancies are described as mediators between social influences (such as peer and parental influences) and alcohol use. The present study examined the relationship between social risk factors (peer influence and parental approval), intrapersonal risk factors (tolerance of deviance and sensation seeking), alcohol expectancies, and alcohol usage in a cohort of seventh graders. It was hypothesized that social risk factors affected alcohol usage indirectly through expectancies, while intrapersonal risk factors influenced usage both directly and indirectly. Structural modeling was used to examine the hypothesized relationships between these four constructs. Results indicated that the hypothesis that expectancies mediate social influences was not supported, and that social influences exerted a direct influence on usage independent of expectancies. Results suggested that the view that expectancies mediate social risk factors may need modification. Suggestions for future research in this area include the need to examine the relationships among these constructs longitudinally and with adolescents over a broader age range.

The validity of discrepancy-based definitions of reading disabilities

This study addressed the validity of distinguishing children with reading disabilities according to the presence or absence of discrepancies between intelligence test scores and academic achievement. Three definitions of reading disability were used to provide criteria for five groups of children who (a) met a discrepancy-based definition uncorrected for the correlation of IQ and achievement; (b) met a discrepancy-based definition correcting for the correlation of IQ and achievement; (c) met a low achievement definition with no IQ discrepancy; (d) met criteria a and b; and (e) met none of the criteria and had no reading disability. Comparison of these five groups on a set of 10 neuropsychological tests corrected for correlations with IQ showed that group differences were small and accounted for little of the variability among groups. These results question the validity of segregating children with reading deficiencies according to discrepancies with IQ scores.

Cerebral white matter and cognition in hydrocephalic children

Although children with hydrocephalus frequently show poor development of nonverbal cognitive skills relative to verbal skills, little is known about the neuropathologic correlates of these discrepancies. In this study, cerebral white-matter structures and lateral ventricles were measured from the magnetic resonance images of age-matched children with meningomyelocele, meningocele, and aqueductal stenosis and normal subjects. The volume of each lateral ventricle and the cross-sectional area of the corpus callosum and internal capsules were correlated with concurrent measures of verbal and nonverbal cognitive skills. The corpus callosum in the meningomyelocele and aqueductal stenosis groups was smaller. The lateral ventricles were larger, and the internal capsules were smaller, in all patient groups than in normal subjects. There were no differences in the size of the centra semiovale. Although verbal and nonverbal measures correlated positively with the size of the corpus callosum, the correlation was higher for nonverbal measures. Nonverbal measures correlated with the right, but not the left, lateral ventricle and with the area of the right and left internal capsules. Verbal measures correlated with the left, but not right, lateral ventricle and with the left, but not right, internal capsule. These results show a relationship between the corpus callosum and cognitive skills that is also influenced by hydrocephalus-related changes in the lateral ventricles and other cerebral white-matter tracts.

Verbal and nonverbal skill discrepancies in hydrocephalic children

This study evaluated a large sample (N = 90) of 5- to 7-year-old children with hydrocephalus caused by aqueductal stenosis or prematurity-intraventricular hemorrhage or associated with spina bifida. Comparison groups of normal controls, children with spina bifida and no shunt, and premature children with no hydrocephalus were also evaluated. Comparison of skill discrepancies at two occasions separated by 1 year revealed that hydrocephalic children, as a group, showed poorer nonverbal than verbal skills on measures from the McCarthy Scales of Children's Abilities, the WISC-R, and composites of neuropsychological skills. No discrepancies in verbal-nonverbal memory were found nor were any discrepancies attributable to etiology or motor demands of the tasks. Consistent with current hypotheses concerning the role of the cerebral white matter in cognitive development, these results show that hydrocephalic children in this age range generally have poorer development of nonverbal cognitive skills relative to their language development.

A five-factor model for motor, psychomotor, and visual-spatial tests used in the neuropsychological assessment of children

Previous confirmatory factor analysis has supported a distinction between simple and complex motor skill tests in a modified and expanded Halstead Reitan test battery (HRB). The present study used a sample of 722 right-handed boys and girls, aged 9 through 12, and expanded the sample of motor, psychomotor, and visual-spatial tests to further clarify this distinction. Restricted maximum-likelihood factor analysis resulted in correlated factors of Simple Motor Skill, Complex Visual-Spatial Relations, Simple Spatial Motor Operations, Motor Steadiness, and Speeded Motor Sequencing. These results provide additional evidence for the discriminant validity of this particular battery of tests, and explicate further the skills and abilities measured in neuropsychological assessments of children referred for evaluation.

Defining patterns of drinking in adolescence: a cluster analytic approach

Most empirical approaches to defining patterns of adolescent alcohol consumption focus on frequency of drunkenness. In an attempt to define patterns of drinking in a more comprehensive way, the present study used measures of social context in addition to frequency and quantity of alcohol use. Subjects' scores on frequency, quantity and five social context variables were cluster analyzed separately for males and females. Results yielded four socially appropriate drinking patterns and three problem drinking patterns (two for males and one for females). Socially appropriate patterns for both sexes were light drinkers, light party drinkers, family drinkers and dating drinkers. Problem drinking patterns included school drinkers and solitary/stranger drinkers for males, and solitary/school drinkers for females. These groups of subjects showed significant differences on reasons for drinking and on drinking consequences even after differences due to frequency and quantity were statistically controlled. Effects of drinking primarily attributable to frequency and quantity appeared to be limited to differences concerning the physiological effects of alcohol.

Neurobehavioral outcomes in diseases of childhood. Individual change models for pediatric human immunodeficiency viruses

The growing incidence of human immunodeficiency virus-1 (HIV-1) and acquired immunodeficiency syndrome (AIDS) in children is a major public health problem. Current research emphasizes treatments for ameliorating deleterious effects on the child's neurological and behavioral development. This article outlines approaches to the assessment of individual change that may provide alternatives to more traditional approaches to the assessment of neurobehavioral outcomes in children with chronic diseases. These approaches provide more precise conceptualizations of changes that lead directly to statistical designs and measurement strategies for assessing effects of HIV-1 and AIDS on development. Such assessments can be superimposed on current clinical trial methodologies to evaluate the efficacy of pharmacological and behavioral interventions designed to improve quality of life in HIV-1 infected children.

Absence of synergistic effects of CNS treatments on neuropsychologic test performance among children

Three hypotheses are proposed to account for neurobehavioral impairments following treatment with cranial radiation therapy (CRT) and intrathecal (IT) chemotherapy: CNS treatments exert a synergistic effect (A x B), an additive effect (A + B), or a single-agent effect (A or B). Eighty-five long-term survivors of non-CNS cancers aged 6 to 16 years were classified into groups on the basis of CNS treatments: CRT-IT (n = 25), CRT-No IT (n = 11), No CRT-IT (n = 24), and No CRT-No IT (n = 25). Study I findings did not provide support for synergistic mechanisms; nonorthogonal analysis of variance showed interaction effects (CRT x IT) restricted to tactile-perceptual speed. However, main effects were significant for a single agent (CRT) across a wide range of measures. General intelligence, academic achievement, verbal knowledge and reasoning, and perceptual-motor abilities were found to be significantly lower among CRT-treated groups. Study II findings provided additional support for the role of CRT; Pearson correlations within the CRT-No IT group indicated significant negative associations between CRT dose estimates for cortical regions and perceptual-motor abilities.

Analysis of change: modeling individual growth

Research on change is complicated by problems of measurement and analysis stemming from a conceptualization of change as a series of accumulating increments and decrements. In contrast, individual growth curves depict change as a continuous process underlying individual performance. These two perspectives are reviewed, and some problems with the use of difference scores in the study of change are clarified. Traditional methods are contrasted with growth curve analysis for the purposes of measuring change and studying its correlates. An illustrative example of the use of growth curves is provided from research on recovery of cognitive function following pediatric closed head injury.

Neurobehavioral outcomes in diseases of childhood: Individual change models for pediatric human immunodeficiency viruses

The growing incidence of human immunodeficiency virus-1 (HIV-1) and acquired immunodeficiency syndrome (AIDS) in children is a major public health problem. Current research emphasizes treatments for ameliorating deleterious effects on the child's neurological and behavioral development. This article outlines approaches to the assessment of individual change that may provide alternatives to more traditional approaches to the assessment of neurobehavioral outcomes in children with chronic diseases. These approaches provide more precise conceptualizations of changes that lead directly to statistical designs and measurement strategies for assessing effects of HIV-1 and AIDS on development. Such assessments can be superimposed on current clinical trial methodologies to evaluate the efficacy of pharmacological and behavioral interventions designed to improve quality of life in HIV-1 infected children.

Application of an enzyme-linked immunosorbent-inhibition assay to quantitate the release of KS peptides into fluids of the rat subcutaneous air-pouch model and the effects of chondroprotective drugs on the release process

The effects of the chondroprotective agents (Arteparon, SP-54 and DH40J) on the release of proteoglycan degradation products (as keratan sulphate peptide fragments) from articular cartilage implanted into rat subcutaneous air pouches have been investigated by using an enzyme-linked immunosorbent-inhibition assay (ELISIA). The ELISIA technique was capable of quantitating the keratan sulphate peptides (KS peptides) in fluids within the range of 100-2,000 ng/ml by using the monoclonal antibody line 1/20/5-D-4 and human articular cartilage KS peptides as standard reagents. It was found that the levels of KS peptides present in the air-pouch fluid of rats treated with the chondroprotective drugs was significantly less than in fluid aspirated from the pouches of non-drug-treated control animals. On the basis of these findings we suggest that the assessment of KS peptide by ELISIAs may provide a useful means of monitoring proteoglycan breakdown products in biological fluids (e.g. synovial fluids or blood) and for evaluating the effects that antiarthritic drugs may have on this process.

Retardation of articular cartilage degradation by glycosaminoglycan polysulfate, pentosan polysulfate, and DH-40J in the rat air pouch model

The rat subcutaneous air pouch model was adapted to examine the in vivo degradation of implanted rabbit articular cartilage, both with and without induced air pouch inflammation, over a 7-day period. The effects of 3 drugs, glycosaminoglycan polysulfate (Arteparon), pentosan polysulfate (SP-54), and zinc-chelated pentosan polysulfate (DH-40J), on inflammation-induced cartilage degradation were also examined. Implanted articular cartilage from noninflamed air pouches showed a reduction in total proteoglycan (PG) content (as hexuronic acid), but not in PG extractability or aggregation, compared with cartilage maintained in tissue culture. The injection of peptone into the air pouch as an inflammogen caused an influx of leukocytes and plasma exudate and a reduction in implanted articular cartilage PG content, extractability, and aggregation, which was significantly greater than that which occurred in noninflamed air pouches. In vitro experiments demonstrated that peptone did not have a direct effect on cartilage PG degradation. Daily injection of Arteparon, SP-54, or DH-40J (10 mg/kg) into peptone-inflamed air pouches significantly increased the PG content, extractability, and aggregation in implanted articular cartilage, compared with that in cartilage from non-drug-treated control animals. The infiltration of leukocytes into the peptone-inflamed air pouches was significantly reduced by daily administration of Arteparon, 10 mg/kg. At an equivalent dose, DH-40J increased leukocyte numbers in the pouch fluid, whereas SP-54 had no significant effect on leukocyte accumulation.

Discriminant validity of lateral sensorimotor tests in children

The discriminant validity of left- (LH) and right-hand (RH) sensorimotor measures from a comprehensive neuropsychological battery was tested using confirmatory factor analysis. A group of children (primarily learning disabled) was divided into analysis (n = 488) and cross-validation (n = 400) samples and the following measures were taken for both the LH and the RH Tactile Perception, Finger Agnosia, Fingertip Number Writing, Tactile Form Recognition, Finger Tapping, Grip Strength, Grooved Pegboard, and Mazes. RH- and LH scores from these tests, and scores from five WISC subtests (Information, Similarities, Vocabulary, Block Design, and Object Assembly) were analyzed in a series of four nested confirmatory factor models. Models distinguished between LH and RH skill factors, and/or between simple- and complex-skill factors. Models were compared using incremental fit ratios and chi 2 difference tests (Bentler & Bonnett, 1980). Model comparisons revealed little evidence for discriminant validity of LH and RH measures, but strong support for distinctions between measures of simple- and complex-skills. These findings were replicated in the cross-validation sample.

An introduction to structural equation models

This paper provides an overview of structural equation models, and their potential for advancing neuropsychological theory and practice. Four topics are covered: (1) an overview of the various classes of models, and an introduction to the terminology and diagrams used to describe them, (2) an outline of the steps involved in applying structural equation modeling to any research problem, (3) an overview of the information used in assessing model fit, and a discussion of the role of significance tests in structural models, and (4) an outline of the advantages and disadvantages of structural equation models, and their potential contribution to neuropsychology. The paper is intended to help researchers (1) assess the relevance of these advanced statistical techniques to their own research, and (2) begin the process of successful application.

A prospective study of neuropsychological sequelae in children with brain tumors

Surgery and radiotherapy are the primary modalities of treatment for pediatric brain tumors. Despite the widespread use of these treatments, little is known of their acute effects (within one year posttreatment) on neuropsychological functions. An understanding of acute treatment effects may provide valuable feedback to neurosurgeons and a baseline against which delayed sequelae may be evaluated. This study compares pre- and posttherapy neuropsychological test performance of pediatric brain tumor patients categorized into two groups on the basis of treatment modalities: surgery (n = 7) and radiotherapy (n = 7). Treatment groups were composed of children aged 56 to 196 months at the time of evaluation with heterogeneous tumor diagnoses and locations. Comparisons of pretherapy findings with normative values using confidence intervals indicated that both groups performed within the average range on most measures. Outstanding deficits at baseline were observed on tests of fine-motor, psychomotor, and timed language skills, and are likely to be attributable to tumor-related effects. Comparisons of pre- versus posttherapy neuropsychological test findings indicated no significant interval changes for either group. Results suggest that surgery and radiotherapy are not associated with acute effects on neuropsychological functions.

Ultrastructure of cystosarcoma phyllodes and fibroadenoma. A comparative study

Electron microscopic studies were conducted on 11 cases of cystosarcoma phyllodes (6 benign, 3 malignant, 2 recurrent), 1 stromal sarcoma, and 15 cases of fibroadenomas. Particular emphasis was placed on examination of the epithelial-stromal junction. The epithelial cells were basically similar in all cases. The basal lamina of fibroadenomas tended to be reduplicated, whereas in cystosarcoma phyllodes the basal lamina was less reduplicated and even focally absent. A continuous layer of delimiting fibroblasts was not present in either type of tumor. Stromal cells were generally fibroblasts, with 2 of 15 being fibroadenomas and 2 of 11 cystosarcoma phyllodes showing myofibroblastic differentiation. The stromal sarcoma also showed smooth muscle differentiation. The authors conclude that the epithelial-stromal junction is abnormal in both fibroadenomas and cystosarcomas, but the abnormality is different in these two tumors. Increasing prominence of stromal cell junctions and of lysosomes also correlated with the diagnosis of cystosarcoma, particularly the malignant variant.

Construct validity of various memory testing procedures

The construct validity of Wechsler Memory Scale Logical Memory, Paired Associate Learning and Visual Reproduction subtests was evaluated, as well as the validity of the Benton Visual Retention Test, and the two memory factor scales of the Luria-Nebraska Neuropsychological Battery (LNNB). The results of a series of factor analyses based on test performances of 102 subjects indicated that delayed reproduction measures of visual memory were more valid than the traditional immediate reproduction administrations, which were more closely associated with visual-perceptual-motor abilities. Construct validity was also demonstrated for Logical Memory and Paired Associate Learning. Although both LNNB measures loaded on a memory factor, item heterogeneity and brief sampling of items raised serious questions about the clinical utility of these scales.

Catecholamines and anxiety

Plasma catecholamines and heart rate were determined in drug-free groups of anxious patients and normal controls before and 20 min after intramuscular injection of 0.01 mg/kg of 1/1000 diluted epinephrine. Levels of anxiety after the injection were determined via the State Anxiety Scale of State Trait Anxiety Inventory. Both groups showed substantial increases in plasma levels of epinephrine and norepinephrine and heart rate after the injection. However, there were no significant differences between anxious patients and controls on plasma catecholamines and heart rate before or after the injection and post injection levels of State Anxiety. The anxious subjects showed a significant correlation between post injection heart rate and State Anxiety.