Biomedical subjects

Shadi Houshyar

Publications and source records attributed to Shadi Houshyar.

4 recordsLinked to original sources

PubMed2006

Synthesis of two-component injectable polyurethanes for bone tissue engineering.

The advent of injectable polymer technologies has increased the prospect of developing novel, minimally invasive arthroscopic techniques to treat a wide variety of ailments. In this study, we have synthesised and evaluated a novel polyurethane-based injectable, in situ curable, polymer platform to determine its potential uses as a tissue engineered implant. Films of the polymers were prepared by reacting two pentaerythritol-based prepolymers, and characterised for mechanical and surface properties, and cytocompatibility. This polymer platform displayed mechanical strength and elasticity superior to many injectable bone cements and grafts. Cytotoxicity tests using primary human osteoblasts, revealed positive cell viability and increased proliferation over a period of 7 days in culture. This favourable cell environment was attributed to the hydrophilic nature of the films, as assessed by dynamic contact angle (DCA) analysis of the sample surfaces. The incorporation of beta-TCP was shown to improve mechanical properties, surface wettability, and cell viability and proliferation, compared to the other sample types. SEM/EDX analysis of these surfaces also revealed physicochemical surface heterogeneity in the presence of beta-TCP. Based on preliminary mechanical analysis and cytotoxicity results, these injectable polymers may have a number or potential orthopaedic applications; ranging from bone glues to scaffolds for bone regeneration.

Aged↗

PubMed2006

Brain-derived neurotrophic factor-5-HTTLPR gene interactions and environmental modifiers of depression in children.

BACKGROUND: Child abuse and genotype interact to contribute to risk for depression in children. This study examined gene-by-gene and gene-by-environment interactions. METHODS: The study included 196 children: 109 maltreated and 87 nonmaltreated comparison subjects. Measures of psychiatric symptomatology and social supports were obtained using standard research instruments, and serotonin transporter (5-HTTLPR) (locus SLC6A4) and brain-derived neurotrophic factor (BDNF) (variant val66met) genotypes were obtained from saliva-derived DNA specimens. Population structure was controlled by means of ancestral proportion scores computed based on genotypes of ancestry informative markers in the entire sample. RESULTS: There was a significant three-way interaction between BDNF genotype, 5-HTTLPR, and maltreatment history in predicting depression. Children with the met allele of the BDNF gene and two short alleles of 5-HTTLPR had the highest depression scores, but the vulnerability associated with these two genotypes was only evident in the maltreated children. A significant four-way interaction also emerged, with social supports found to further moderate risk for depression. CONCLUSIONS: To the best of our knowledge, this is the first investigation to demonstrate a gene-by-gene interaction conveying vulnerability to depression. The current data also show a protective effect of social supports in ameliorating genetic and environmental risk for psychopathology.

Adolescent↗

PubMed2006

Adolescent girls' and boys' weight-related health behaviors and cognitions: associations with reputation- and preference-based peer status.

In this study, the authors examined associations between preference- and reputation-based peer status and weight-related behaviors and cognitions for both adolescent boys and girls. Sociometric measures of peer like-ability and peer-perceived popularity, as well as self-reported measures of body size, dieting behavior, and weight-related cognitions were collected from a sample of 441 adolescents in Grades 11 and 12. Results revealed weight-related cognitions for girls (concerning obesity) and boys (concerning musculature/fitness). Peer-perceived popularity, but not like-ability, was significantly associated with both boys' and girls' body size and dieting. Lower levels of popularity were associated with heavier body shapes for girls and with both thin and heavier body shapes for boys. Findings suggest that peer status is an important source of social reinforcement associated with weight-related behaviors and cognitions.

Adolescent↗

PubMed2004

Social supports and serotonin transporter gene moderate depression in maltreated children.

In this study, measures of the quality and availability of social supports were found to moderate risk for depression associated with a history of maltreatment and the presence of the short (s) allele of the serotonin transporter gene promoter polymorphism (5-HTTLPR). The present investigation (i) replicates research in adults showing that 5-HTTLPR variation moderates the development of depression after stress, (ii) extends the finding to children, and (iii) demonstrates the ability of social supports to further moderate risk for depression. Maltreated children with the s/s genotype and no positive supports had the highest depression ratings, scores that were twice as high as the non-maltreated comparison children with the same genotype. However, the presence of positive supports reduced risk associated with maltreatment and the s/s genotype, such that maltreated children with this profile had only minimal increases in their depression scores. These findings are consistent with emerging preclinical and clinical data suggesting that the negative sequelae associated with early stress are not inevitable. Risk for negative outcomes may be modified by both genetic and environmental factors, with the quality and availability of social supports among the most important environmental factors in promoting resiliency in maltreated children, even in the presence of a genotype expected to confer vulnerability for psychiatric disorder.

Child↗