Biomedical subjects

Sajjad A Khan

Publications and source records attributed to Sajjad A Khan.

4 recordsLinked to original sources

PubMed2006

The genetics of ADHD: a literature review of 2005.

Investigations into the genetic basis of attention-deficit/hyperactivity disorder (ADHD) continue to yield compelling results as candidate gene studies reveal more information about this elusive disorder. Family, twin, and adoption studies further the notion that ADHD is a highly heritable disorder with direct genetic and environmental influence. The year 2005 saw many ADHD candidate gene studies, with most focused on the catecholaminergic candidates. Although many genes were studied in 2005, a large portion of findings has been supportive of the roles of dopaminergic genes' relationship to clinical phenotypes and drug response. These studies often require replication. Clinical implications continue to be speculative, as larger sample sizes are needed to validate findings to the general population. Further understanding of endophenotypes and the impact of comorbidities also is necessary for proper clinical intervention. Forthwith, we provide a summary of ADHD genetic studies published in 2005.

Attention Deficit Disorder with Hyperactivity↗

PubMed2006

Candidate gene studies of attention-deficit/hyperactivity disorder.

A growing body of behavioral and molecular genetics literature has indicated that the development of attention-deficit/hyperactivity disorder (ADHD) may be attributed to both genetic and environmental factors. Family, twin, and adoption studies provide compelling evidence that genes play a strong role in mediating susceptibility to ADHD. Molecular genetic studies suggest that the genetic architecture of ADHD is complex, while the handful of genome-wide scans conducted thus far is not conclusive. In contrast, the many candidate gene studies of ADHD have produced substantial evidence implicating several genes in the etiology of the disorder. For the 8 genes for which the same variant has been studied in 3 or more case-control or family-based studies, 7 show statistically significant evidence of association with ADHD based on pooled odds ratios across studies: the dopamine D4 receptor gene (DRD4), the dopamine D5 receptor gene (DRD5), the dopamine transporter gene (DAT), the dopamine beta-hydroxylase gene (DBH), the serotonin transporter gene (5-HTT), the serotonin receptor 1B gene (HTR1B), and the synaptosomal-associated protein 25 gene (SNAP25). Recent pharmacogenetic studies have correlated treatment nonresponse with particular gene markers, while preclinical studies have increased our understanding of gene expression paradigms and potential analogs for human trials. This literature review discusses the relevance and implications of genetic associations with ADHD for clinical practice and future research.

Attention Deficit Disorder with Hyperactivity↗

PubMed2004

Liquid-crystal-deflector based variable fiber-optic attenuator.

A compact, low-component-count, no-moving-parts variable optical attenuator (VOA) is demonstrated for the first time by means of beam spoiling that is implemented via an electrically reconfigurable nonpixelated nematic liquid-crystal deflector. The VOA design features an in-line alignment polarization-insensitive design that does not use bulky polarization splitting and combining optics. The proof-of-concept VOA at 1550 nm demonstrates a 30-dB attenuation range, a 2.5-dB insertion loss, a < or = 0.8-dB polarization-dependent loss, and a 1-s maximum attenuation reset time. The VOA design can counter performance-reducing environmental effects such as excess-loss increases due to temperature variations.

Journal Article↗

PubMed2003

Programmable high-speed polarization multiplexed optical scanner.

A fast digital-analog control polarization-based optical scanner with complete three-dimensional beam-forming programmability is described. Its features include low power consumption and large-aperture liquid-crystal-based optics, digital repeatability, and time-multiplexed accurate analog beam forming. Analog frequency and amplitude control of the nematic liquid-crystal beam-former cells permits continuous fine-scan programmability over a 0.66-mrad horizontal deflection, a 0.75 mrad vertical deflection, and an infinity-to-1.84-m focal-length longitudinal scan. First demonstrations included an 8-point volumetric scan and a 2-bit digital lens scan, both at 1310 nm, with a 35-micros random-access time.

Journal Article↗