Attention deficit/hyperactivity disorder children with a 7-repeat allele of the dopamine receptor D4 gene have extreme behavior but normal performance on critical neuropsychological tests of attention

An association of the dopamine receptor D4 (DRD4) gene located on chromosome 11p15.5 and attention deficit/hyperactivity disorder (ADHD) has been demonstrated and replicated by multiple investigators. A specific allele [the 7-repeat of a 48-bp variable number of tandem repeats (VNTR) in exon 3] has been proposed as an etiological factor in attentional deficits manifested in some children diagnosed with this disorder. In the current study, we evaluated ADHD subgroups defined by the presence or absence of the 7-repeat allele of the DRD4 gene, using neuropsychological tests with reaction time measures designed to probe attentional networks with neuroanatomical foci in D4-rich brain regions. Despite the same severity of symptoms on parent and teacher ratings for the ADHD subgroups, the average reaction times of the 7-present subgroup showed normal speed and variability of response whereas the average reaction times of the 7-absent subgroup showed the expected abnormalities (slow and variable responses). This was opposite the primary prediction of the study. The 7-present subgroup seemed to be free of some of the neuropsychological abnormalities thought to characterize ADHD.

Nest site selection by Black-necked Crane Grus nigricollis in the Ruoergai Wetland, China

From 5 May 2003 to early June 2005, nest site selection of Black-necked Cranes Grits nigricollis was studied at the Ruoergai Wetland Nature Reserve (RWNR), an important breeding area for the species in China. Results showed that the crane nests only in we

Manipulation of host density affects infestation of a peritrich ciliate (Epistylis lacustris) on a calanoid copepod (Leptodiaptomus minutus) in Crystal Lake, Wisconsin, USA

Specimens of the calanoid copepod, Leptodiaptomus minutus, collected in June 1994 in oligotrophic: north temperate Crystal Lake, were infested with the stalked ciliate Epistylis lacustris. E. lacustris was highly specific to L. minutus and no other coexisting zooplankters were infested. Excluding nauplii, nearly 70% of copepods carried 1-20 ciliates, although the maximum load was as high as 250 ciliates. A lower percentage of nauplii were infested by the ciliate; those that were infested had a lower ciliate load than other copepod stages. Infestation by ciliates had no significant influence on the average egg number of female copepods. In a field experiment, higher copepod densities in enclosures resulted in a significantly higher infestation rate, but the ciliate load per individual copepod did not differ significantly among treatments.