Biomedical subjects

B L Baker

Publications and source records attributed to B L Baker.

At least 19 recordsLinked to original sources

PubMed2006

The transition to school: adaptation in young children with and without intellectual disability.

BACKGROUND: Previous research has highlighted the importance of the transition to school for young children and their families. A child's successful adaptation to school is likely influenced by a number of factors, including academic, social, emotional, behavioural and cognitive competencies. Children with intellectual disability (ID) may be at heightened risk for early school difficulties, in part due to their deficits in cognitive and adaptive behaviours. METHODS: Factors associated with the adaptive transition to school in young children with (n = 24) and without (n = 43) ID were examined. Adaptive transitions were defined as having few teacher-reported problem behaviours and positive student-teacher relationships. Child self-regulatory skills and both parent- and teacher-reported social skills were evaluated to determine if they predicted positive adaptation in school for 5- to 6-year-old children. Data were gathered from child assessments, parent reports on standardized measures, direct observations of delay of gratification tasks and teacher reports on standardized measures. RESULTS: Children with ID had significantly more teacher-reported problem behaviour, poorer overall student-teacher relationships, fewer parent- and teacher-reported social skills and fewer self-regulation skills than typically developing children. Self-regulation at child age 36 months (latency to touch a desired toy) was significantly related to adaptation to school, as were parent and teacher reports of social skills. Social skills significantly predicted adaptation to school, even after accounting for the effects of child IQ and adaptive behaviour. CONCLUSIONS: Children with ID had less positive early school experiences, as indicated by multiple indices of adaptation to school. Fostering early social skills may be an important target for increasing the positive adaptation to school for young children, especially those with ID.

Adaptation, Psychological↗

PubMed2005

Preschool children with and without developmental delay: behaviour problems, parents' optimism and well-being.

BACKGROUND: Children with intellectual disability are at heightened risk for behaviour problems, and these are known to increase parenting stress. This study explored the relation of behaviour problems to less child-related domains of parent well-being (depression and marital adjustment), as well as the moderating effect of a personality trait, dispositional optimism. METHOD: Participating children (N = 214) were classified as developmentally delayed, borderline, or nondelayed. Mothers' and fathers' well-being and child behaviour problems were assessed at child ages 3 and 4 years. RESULTS: Parents of delayed and nondelayed preschoolers generally did not differ on depression or marital adjustment, but child behaviour problems were strongly related to scores on both measures. Optimism moderated this relationship, primarily for mothers. When child behaviour problems were high, mothers who were less optimistic reported lower scores on measures of well-being than did mothers who were more optimistic. CONCLUSIONS: Interventions for parents that aim to enhance both parenting skills and psychological well-being should be available in preschool. It may be beneficial for such programmes to focus not only on behaviour management strategies aimed at child behaviour change, but also on parents' belief systems, with the aim of increasing dispositional optimism.

Affect↗

PubMed2005

Preschool children with intellectual disability: syndrome specificity, behaviour problems, and maternal well-being.

BACKGROUND: Children with intellectual disability (ID) are at heightened risk for behaviour problems and diagnosed mental disorder. Likewise, mothers of children with ID are more stressed than mothers of typically developing children. Research on behavioural phenotypes suggests that different syndromes of ID may be associated with distinct child behavioural risks and maternal well-being risks. In the present study, maternal reports of child behaviour problems and maternal well-being were examined for syndrome-specific differences. METHODS: The present authors studied the early manifestation and continuity of syndrome-specific behaviour problems in 215 preschool children belonging to 5 groups (typically developing, undifferentiated developmental delays, Down syndrome, autism, cerebral palsy) as well as the relation of syndrome group to maternal well-being. RESULTS: At age 3, children with autism and cerebral palsy showed the highest levels of behaviour problems, and children with Down syndrome and typically developing children showed the lowest levels. Mothers of children with autism reported more parenting stress than all other groups. These syndrome-specific patterns of behaviour and maternal stress were stable across ages 3, 4 and 5 years, except for relative increases in behaviour problems and maternal stress in the Down syndrome and cerebral palsy groups. Child syndrome contributed to maternal stress even after accounting for differences in behaviour problems and cognitive level. CONCLUSIONS: These results, although based on small syndrome groups, suggest that phenotypic expressions of behaviour problems are manifested as early as age 3. These behavioural differences were paralleled by differences in maternal stress, such that mothers of children with autism are at elevated risk for high stress. In addition, there appear to be other unexamined characteristics of these syndromes, beyond behaviour problems, which also contribute to maternal stress.

Adult↗

PubMed2002

Behaviour/mental health problems in young adults with intellectual disability: the impact on families.

BACKGROUND: The present authors studied the impact of dual diagnosis [i.e. intellectual disability (ID) and mental disorder] in young adults on their mothers' perceived levels of stress and decisions about placement. METHODS: The mothers of 103 young adults with severe ID were interviewed using a 2-3-h in-depth protocol of measures designed to assess their child's adaptive functioning, maladaptive behaviour, mental health problems and negative impact on the family, as well as their own thoughts on out-of-home placement. The Scales of Independent Behavior--Revised Problem Behavior Scale assessed problem behaviours and the Reiss Screen assessed mental disorder. RESULTS: These measures were highly correlated (r = 0.64), but tapped some different domains of maladaptive behaviour and proved to be most predictive when employed together. Behaviour and/or mental health (B/MH) problems significantly predicted the mothers' perceived negative impact of the young adult on the family, even after controlling for other young adult characteristics. These problems also predicted the family's steps toward seeking out-of-home placement, as did better young adult health and the mother's higher educational attainment; stress did not predict additional variance in placement once these variables were accounted for. CONCLUSIONS: The discussion focuses on the implications for service provision to families of young adults with B/MH problems.

Activities of Daily Living↗

PubMed2001

Stepping aside for elderly persons in American versus east-Asian cultures.

In the current study, younger (15-30 years of age) and older (60+ years of age) Asian-American and European-American individuals (N = 160) were observed as they approached someone of the same ethnic group on a walkway at a city market. The interaction was recorded if one stepped aside and let the other pass. Younger Asian-Americans tended to step aside for older Asian-Americans. No such trend was observed among European-Americans. Results were discussed in terms of cultural values.

Adolescent↗

PubMed2000

Dexamethasone inhibits insulin-like growth factor signaling and potentiates myoblast apoptosis.

In the critically ill, glucocorticoids induce myopathy, combining profound protein catabolism and mild myotubular death. Insulin-like growth factors (IGFs) inhibit muscle catabolism through activation of phosphatidylinositol 3-kinase (PI3K). Using rat L6 myoblasts, we show that IGF-I also acts through PI3K to inhibit apoptosis induced by hyperosmolar metabolic stress with 300 mM mannitol. We find that the glucocorticoid dexamethasone inhibits this antiapoptotic effect of IGF-I by impairing PI3K signaling. Dexamethasone induces overexpression of the PI3K subunit p85alpha, which, in turn, competes with the complete PI3K heterodimer for binding at insulin receptor substrate-1, inhibiting PI3K activation. Dexamethasone blocks IGF-I-induced phosphorylation of Akt, a PI3K-dependent process. Increased cellular p85alpha abundance, induced by either 10 microM dexamethasone or transient transfection with a plasmid coding for p85alpha, significantly inhibits IGF-I rescue from apoptosis induced by mannitol, as indicated by both loss of cell viability and increased activity of caspase-3 by fluorogenic assay. Conversely, constitutively active PI3K inhibits death induced by mannitol, even in the presence of dexamethasone. These findings may have particular relevance in the pathogenesis of acute steroid myopathy in critical illness, in which catabolic glucocorticoid effects combine with acute metabolic stressors, including sepsis, fasting, and chemical denervation.

Animals↗

PubMed2000

Applications of the expressed emotion construct to young children with externalizing behavior: stability and prediction over time.

We explored the utility of the Expressed Emotion (EE) construct with a community sample of young children (N = 91), studying the stability of EE scores over a 2-year period and the extent to which EE was associated with simultaneous and subsequent disruptive behavior. As part of a longitudinal study, families were assessed when the child was in preschool, 1st grade, and 3rd grade. Maternal EE was measured at preschool and 1st grade using the Five Minute Speech Sample and behavior ratings were obtained using the Child Behavior Checklist. At 3rd grade, the Diagnostic Interview Schedule for Children was used to determine DSM-IV diagnoses. The stability of the EE rating over the 2-year period from preschool to 1st grade was statistically significant although modest. At 1st grade, EE ratings were significantly related to the extent of externalizing behavior problems. Regression analyses that controlled for maternal stress levels determined that preschool EE ratings predicted classification of ADHD over 4 years later, at 3rd grade. The relationships between EE and child problem behavior were almost exclusively determined by the EE criticism dimension; the emotional overinvolvement dimension was not related to child behavior. The implications of these findings are discussed.

Attention Deficit Disorder with Hyperactivity↗

PubMed2000

Expressed emotion, parenting stress, and adjustment in mothers of young children with behavior problems.

Expressed Emotion (EE), a measure of the emotional climate of the family, predicts subsequent adjustment of adults with mental disorder (Leff & Vaughn, 1985). Despite the acknowledged importance of the family in childhood disorders, there have been relatively few studies of expressed emotion with adolescents and school-aged children and virtually none focused on preschoolers. The present study utilized the Five Minute Speech Sample (FMSS) to examine how Expressed Emotion relates concurrently and longitudinally to child problem status in a community sample of 112 preschool-aged children. At preschool, the proportion of high EE increased significantly across three child groups: Comparison (8.1%), Borderline Problem (15.8%), and High Problem (41.2%); however, preschool EE was not predictive of subsequent child status at 1st grade. Expanded FMSS codes. tapping positive affect and worry about the child, were also related to child problem group at preschool and were predictive of subsequent child status at 1st grade. Because parents' stress and adjustment were also highly related to child problem group status, we examined whether the FMSS codes were essentially a proxy for these or whether they explained unique variance. In two stepwise regressions on preschool child group status (divided by total problems and by externalizing problems), maternal stress was the only variable to enter. Also, in predicting to 1st grade externalizing child group status, only maternal stress entered. Discussion focused on the extension of the EE construct and other FMSS coding to young children, and the need to recognize that to some extent these variables may reflect maternal stress and adjustment.

Adult↗

PubMed1999

Acute saline infusion reduces alveolar-capillary membrane conductance and increases airflow obstruction in patients with left ventricular dysfunction.

BACKGROUND: Impaired alveolar-capillary membrane conductance is the major cause for the reduction in pulmonary diffusing capacity for carbon monoxide (DLCO) in heart failure. Whether this reduction is fixed, reflecting pulmonary microvascular damage, or is variable is unknown. The aim of this study was to assess whether DLCO and its subdivisions, alveolar-capillary membrane conductance (DM) and pulmonary capillary blood volume (Vc), were sensitive to changes in intravascular volume. In addition, we examined the effects of volume loading on airflow rates. METHODS AND RESULTS: Ten patients with left ventricular dysfunction (LVD) and 8 healthy volunteers were studied. DM and Vc were determined by the Roughton and Forster method. The forced expiratory volume in 1 second (FEV1), vital capacity, and peak expiratory flow rates (PEFR) were also recorded. In patients with LVD, infusion of 10 mL. kg-1 body wt of 0.9% saline acutely reduced DM (12.0+/-3.3 versus 10.4+/-3.5 mmol. min-1. kPa-1, P<0.005), FEV1 (2.3+/-0.4 versus 2.1+/-0.4 L, P<0.0005), and PEFR (446+/-55 versus 414+/-56 L. min-1, P<0.005). All pulmonary function tests had returned to baseline values 24 hours later. In normal subjects, saline infusion had no measurable effect on lung function. CONCLUSIONS: Acute intravascular volume expansion impairs alveolar-capillary membrane function and increases airflow obstruction in patients with LVD but not in normal subjects. Thus, the abnormalities of pulmonary diffusion in heart failure, which were believed to be fixed, also have a variable component that could be amenable to therapeutic intervention.

Aged↗

PubMed1999

Leaving or launching? Continuing family involvement with children and adolescents in placement.

Postplacement involvement and well-being of 53 families who had placed their child into a residential facility were studied. Parents were interviewed an average of 1, 2, and 3.5 years following placement. Visitation remained moderately high, with some type of visit reported at least monthly at Time 3 by 83% of families. Expressed attachment was high and stable, and most parents reported experiencing less guilt than at the time of placement. Parents were still thinking and talking about the child frequently. They were more likely, over time, to view the placement as permanent, and for about two thirds, the ideal placement was a residential facility. Virtually all parents reported family life to be better following placement, especially in recreation, social life, and relationships with their other children.

Adaptation, Psychological↗

PubMed1998

Carbonothioate phospholipids as substrate for a spectrophotometric assay of phospholipase A2.

A continuous spectrophotometric assay for phospholipase A2 (PLA2) was developed using novel carbonothioate phospholipids. These phospholipid analogues contain a carbonothioate bond in the place of the sn-2 ester of the natural substrates of phospholipase A2 and were synthesized in a one-pot two-step reaction. Phospholipase A2 from cobra venom (Naja naja atra) hydrolyzes carbonothioate phospholipids and liberates a free thiol, alkylmercaptan, which is reacted with 5,5'-dithiobis(2-nitrobenzoic acid) to yield a product that absorbs at 412 nm. The kinetic studies on PLA2 hydrolysis of carbonothioate phospholipids were carried out in pure phospholipid forms and in Triton X-100 mixed micelles. The hydrolysis of pure carbonothioate phospholipids exhibits an interfacial activation phenomenon. The hydrolysis of phospholipid in mixed Triton X-100 micelles follows classical Michaelis-Menten kinetics. In a mixed micellar system, the catalytic efficiency observed with this series of substrates is two orders of magnitude lower than that of the hydrolysis of the natural substrate dipalmitoyl phosphocholine. However, these substrates bind to the enzyme over 10 times tighter than does the natural substrate. Application of this carbonothioate assay to screen both reversible and irreversible enzyme inhibitors of phospholipase A2 is also demonstrated.

Elapid Venoms↗

PubMed1998

Structural characterization and optimization of antibody-selected phage library mimotopes of an antigen associated with autoimmune recurrent thrombosis.

The presence of high titers of anti-cardiolipin antibodies (ACA's) of autoimmune origin, which are known to bind to plasma beta2-glycoprotein I (aka apolipoprotein H), correlates clinically with autoimmune recurrent thrombosis. Soluble beta2-glycoprotein I binds to solid-phase ACA (immobilized on a surface plasmon resonance chip) with a Kd of 1.4 microM, but if the reactants are reversed and beta2-glycoprotein I is on the solid-phase support, then the Kd is 52 nM. This 27-fold difference in affinity reflects the avidity/entropic advantage obtained for an antibody binding to an antigen that is made multivalent because it is attached to a solid phase. A mimotope of this antigen, selected from a phage display peptide library screen with an ACA, has been shown to bind to solid-phase ACA as a phage, using surface plasmon resonance. This peptide is representative of the motif from 37 peptides obtained in a previously reported phage library screen with this ACA (1). A synthetic version of this peptide, referred to as P4, has the sequence: A1G2P3C4I5L6L7A8R9D10R11C12P13G14, and binds to its selecting antibody with a Kd of 42 nM. NMR data indicate that proline-13 is present in both cis and trans configurations, and that these two geometries dramatically affect the overall tertiary structure of the molecule. The peptide lacking this proline binds severalfold better to the ACA, consistent with at least one of these structures having low affinity for binding ACA. Replacement of the arginine-9 position with a proline decreases binding affinity to ACA 10-fold. Another phage library-selected peptide has a proline in position 9, but also has a leucine in position 5, instead of isoleucine. Since its affinity for ACA is nearly as good as that for peptide P4, the phage library screening must have selected for a non-beta-branched amino acid in this position to compensate for the adverse effects of the arginine-9 to proline-9 substitution. The solution structure of a modified version of the antibody-selected phage peptide P4 with the central proline was determined. This peptide has one turn comprised of Ala-Pro-Asp-Arg, with the proline peptide bond in the cis configuration, and another turn that contains the disulfide and adjacent residues. If the disulfide is replaced by a thioether, and the central proline by an alpha-methyl proline, in an attempt to make the peptide more biologically stable, there is little adverse effect on affinity for ACA. The thioether bond/turn is fairly well defined with a Calpha to Calpha separation of 4.9 +/- 0.8 A. The alpha-methyl proline adopts the trans configuration, and this central Ala-(alpha-methyl-Pro)-Asp-Arg turn adopts a distorted type I turn conformation with a probable i to i+3 hydrogen bond. Modeling studies suggest that the proline peptide bond configuration switched from cis to trans in the presence of the alpha-methyl group on proline because of steric hindrance with the beta-carbon of the preceding residue. Overall, this peptidomimetic molecule is structurally very similar to the peptide with natural amino acids, with an rmsd difference of only 1.37 A, when comparing backbone atoms.

Antibodies, Anticardiolipin↗

PubMed1998

Siblings of children with mental retardation living at home or in residential placement.

Severe retardation in a child surely has an effect on all family members. Studies of non-disabled siblings in these families have indicated both emotional risks and perceived benefits. Little is known about how out-of-home placement of the child with retardation affects the siblings. Adolescent siblings of children with retardation living at home (N = 25) or in residential placement (N = 20) were contrasted with siblings of children without retardation (N = 28), on measures obtained from their mothers and themselves. Despite their different situations, these siblings were highly similar on measures of psychological adjustment, self-esteem, and family environment. Sibling relationships, however, were less intense, with less warmth but also lower conflict, in families where the child lived out of the home. Most siblings of children with retardation reported positive personal growth experiences while also expressing realistic concerns about the future. Siblings of children with retardation had beliefs and attitudes about placement that were highly consistent with the child's current living situation.

Adolescent↗

PubMed1996

Preschool children with externalizing behaviors: experience of fathers and mothers.

Childhood behavior disorders are related to family stress and maladjustment. Little is known, however, about the adjustment of families with preschool-aged children at risk for subsequent behavior disorders. Moreover, fathers' perceptions of child problem behavior and their reactions to it generally have been neglected. Subjects were mothers and fathers of 52 preschool-aged children assigned to one of three groups: control, moderate externalizing, and high externalizing. Higher child externalizing behavior was associated with greater negative family impact, lowered parenting sense of efficacy, and child-rearing practices that were more authoritarian and less authoritative. Mothers and fathers did not differ in actual perceived level of child behavior problems, although both believed that mothers saw more problems. Child Group x Parent interactions indicated that mothers experienced increased stress and a need for help with moderate as well as high child externalizing behaviors, whereas fathers were not elevated on these measures unless the child's externalizing behaviors were high. Implications of these findings for early family intervention are considered.

Adaptation, Psychological↗

PubMed1996

Family involvement in residential treatment.

Social policy stresses the importance of the family's continuing involvement with members in residential placement. We studied involvement of families with 163 children and adults in residential treatment and with their programs. Parent and staff reports of family involvement showed high agreement. The average family had 21 contacts annually with the family members; these related only marginally to the extent of involvement with the residents' programs. There was no evidence of detachment, a lessening of involvement over time. Multiple regression found three variables that accounted for 52% of the variance in contacts: higher involvement related to less distance from the facility, greater expectations that the family member would return home, and lower levels of mental retardation. Implications of findings for increasing family involvement were discussed.

Adolescent↗

PubMed1995

Enhancement of Agkistrodon piscivorus piscivorus venom phospholipase A2 activity toward phosphatidylcholine vesicles by lysolecithin and palmitic acid: studies with fluorescent probes of membrane structure.

The activity of phospholipase A2 from snake venom to hydrolyze bilayers of phosphatidylcholines is greatly enhanced by the presence of the hydrolysis products, lysolecithin and fatty acid, in the bilayer. The fluorescence of several probes of membrane structure was used to monitor changes in bilayer physical properties during vesicle hydrolysis. These changes were compared to emission spectra and fluorescence polarization results occurring upon direct addition of lysolecithin and/or fatty acid to the bilayer. The excimer to monomer ratio of 1,3-bis(1-pyrene)propane was insensitive to vesicle hydrolysis, suggesting that changes in the order of the phospholipid chains were not relevant to the effect of the hydrolysis products on phospholipase activity. The fluorescence of 6-propionyl-2-(dimethylamino)-naphthalene (Prodan) suggested that the polarity of the bilayer in the region of the phospholipid head groups increases as the hydrolysis products accumulate in the bilayer. The fluorescence of 6-dodecanoyl-2-(dimethylamino)naphthalene (Laurdan) confirmed that such effects were restricted to the bilayer surface. Furthermore, the lysolecithin appeared to be the product most responsible for these changes. These results suggested that lysolecithin increases the activity of phospholipase A2 during vesicle hydrolysis by disrupting the bilayer surface, making the phospholipid molecules more accessible to the enzyme active site.

2-Naphthylamine↗

PubMed1995

Reduced alveolar-capillary membrane diffusing capacity in chronic heart failure. Its pathophysiological relevance and relationship to exercise performance.

BACKGROUND: The pulmonary diffusing capacity for carbon monoxide (DLCO) is reduced in chronic heart failure (CHF) and is an independent predictor of peak exercise oxygen uptake. The pathophysiological basis for this remains unknown. The aim of this study was to partition DLCO into its membrane conductance (DM) and capillary blood volume components (Vc) and to assess if alveolar-capillary membrane function correlated with functional status, exercise capacity, and pulmonary vascular resistance. METHODS AND RESULTS: The classic Roughton and Forster method of measuring single-breath DLCO at varying alveolar oxygen concentrations was used to determine DM and Vc in 15 normal subjects and 50 patients with CHF. All performed symptom-limited maximal bicycle exercise tests with respiratory gas analysis; 15 CHF patients underwent right heart catheterization. DLCO was significantly reduced in CHF patients compared with normal subjects, predominantly because of a reduction in DM (7.0 +/- 2.6 versus 12.9 +/- 3.8 versus 20.0 +/- 6.1 mmol.min-1.kPa-1 in New York Heart Association class III, class II, and normal subjects, respectively, P < .0001), even when the reduction in lung volumes was accounted for by the division of DM by the effective alveolar volume. The Vc component of DLCO was not impaired. DM significantly correlated with maximal exercise oxygen uptake (r = .72, P < .0001) and inversely correlated with pulmonary vascular resistance (r = .65, P < .01) in CHF. CONCLUSIONS: Reduced alveolar-capillary membrane diffusing capacity is the major component of impaired pulmonary gas transfer in CHF, correlating with maximal exercise capacity and functional status. DM may be a useful marker for the alveolar-capillary barrier damage induced by raised pulmonary capillary pressure.

Blood-Air Barrier↗

PubMed1995

Staff attitudes toward family involvement in residential treatment centers for children.

OBJECTIVES: The goals of this study were to determine the extent of staff members' support for family involvement in residential treatment centers for children, to examine staff members' beliefs about families and the consequences of their involvement, and to examine the relationship between staff members' support of family involvement and their characteristics, experiences, and beliefs. METHODS: A total of 267 staff members at three residential treatment centers for children with psychiatric disorders or mental retardation or both responded to a survey about their experiences with families, beliefs about families, and support for family involvement. RESULTS: Staff members were very supportive of greater family involvement, although they showed more support for families in the role of service recipients than as decision makers. However, staff members did not believe in family reunification as a goal for the majority of children served. The strongest predictors of staff support for family involvement were positive general beliefs about clients' families, the perception that family involvement was advantageous, and the endorsement of fewer reasons to discourage family involvement. CONCLUSIONS: Residential programs seeking to create a more receptive climate for families should help staff members establish positive attitudes about the families they serve and about families' potential role in successful treatment.

Adult↗