A genomewide scan for loci involved in attention-deficit/hyperactivity disorder

Attention deficit/hyperactivity disorder (ADHD) is a common heritable disorder with a childhood onset. Molecular genetic studies of ADHD have previously focused on examining the roles of specific candidate genes, primarily those involved in dopaminergic pathways. We have performed the first systematic genomewide linkage scan for loci influencing ADHD in 126 affected sib pairs, using a approximately 10-cM grid of microsatellite markers. Allele-sharing linkage methods enabled us to exclude any loci with a lambda(s) of > or =3 from 96% of the genome and those with a lambda(s) of > or =2.5 from 91%, indicating that there is unlikely to be a major gene involved in ADHD susceptibility in our sample. Under a strict diagnostic scheme we could exclude all screened regions of the X chromosome for a locus-specific lambda(s) of >/=2 in brother-brother pairs, demonstrating that the excess of affected males with ADHD is probably not attributable to a major X-linked effect. Qualitative trait maximum LOD score analyses pointed to a number of chromosomal sites that may contain genetic risk factors of moderate effect. None exceeded genomewide significance thresholds, but LOD scores were >1.5 for regions on 5p12, 10q26, 12q23, and 16p13. Quantitative-trait analysis of ADHD symptom counts implicated a region on 12p13 (maximum LOD 2.6) that also yielded a LOD >1 when qualitative methods were used. A survey of regions containing 36 genes that have been proposed as candidates for ADHD indicated that 29 of these genes, including DRD4 and DAT1, could be excluded for a lambda(s) of 2. Only three of the candidates-DRD5, 5HTT, and CALCYON-coincided with sites of positive linkage identified by our screen. Two of the regions highlighted in the present study, 2q24 and 16p13, coincided with the top linkage peaks reported by a recent genome-scan study of autistic sib pairs.     

Cardiovascular responses to nonrespiratory and respiratory arousals in a porcine model

Spontaneous and provoked nonrespiratoryarousals can be accompanied by a patterned hemodynamic response. Toinvestigate whether a patterned response is also elicited byrespiratory arousals, we compared nonrespiratory arousals (NRA) torespiratory arousals (RA) induced by airway occlusion during non-rapideye movement sleep. We monitored mean arterial blood pressure (MAP),heart rate, iliac and renal blood flow, and sleep stage in 7 pigsduring natural sleep. Iliac and renal vascular resistance werecalculated. Airway occlusions were obtained by manually inflating achronically implanted tracheal balloon during sleep. The balloon wasquickly deflated as soon as electroencephalogram arousal occurred. As previously reported, NRA generally elicited iliac vasodilation, renalvasoconstriction, little change in MAP, and tachycardia. In contrast,RA generally elicited iliac and renal vasoconstriction, an increase inMAP and tachycardia. The frequent occurrence of iliac vasoconstrictionand arterial pressure elevation following RA but not NRA suggests thatsleep state change alone does not account for the hemodynamic responseto airway occlusion during sleep.

     

Genetic heterogeneity and localization of a familial breast-ovarian cancer gene on chromosome 17q12-q21.

In a study of 31 breast cancer families and 12 breast-ovarian cancer families, we have obtained clear evidence of linkage to markers on chromosome 17q in the families with ovarian cancer (maximum lod score 3.34 at theta = .04) but only weak evidence in those without ovarian cancer. Recombinant events indicate that the gene lies between D17S588 and D17S250.     

Foraging ofRhagoletis pomonella flies in relation to interactive food and fruit resources

Feeding behaviour of the lettuce root aphidPemphigus bursarius was monitored electronically on six lettuce varieties. Aphids, monitored for a minimum of 5 h on lettuce roots, performed recognizable feeding behaviour on the susceptible varieties, Webbs Wonderful and Borough Wonder including non probing, pattern A start of new penetration, C (stylet pathway activities) sometimes including clear B-waves (salivary sheath secretions), potential drops (intracellular penetrations), intracellular E (phloem ingestion) distinguishing E₁ and E₂ (Tjallingii, 1990) and occasionally xylem ingestion. Although aphid probing was recorded on the resistant varieties Lakeland and Grand Rapids continued penetration to the phloem elements was deterred and the time spent ingesting phloem was short. Aphids rarely probed the resistant varieties Avoncrisp and Avondefiance and all attempted penetrations quickly terminated.     

Immunocytochemical localization of a growth-associated protein (GAP-43) in rat adrenal gland

We have localized at light and electron-microscopic level the growth-associated protein GAP-43 in adrenal gland using single and double labelling immunocytochemistry. Clusters of GAP-43-immunofluorescent chromaffin cells and many immunofluorescent fibres were observed in the medulla. GAP-43-immunoreactive fibres also formed a plexus under the capsule, crossed the cortex and ramified in the zona reticulata. Double labelled sections showed the coexpression of GAP-43 with a subpopulation of tyrosine hydroxylase-and of dopamine--hydroxylase-immunoreactive chromaffin cells. Dual colour immunofluorescence for GAP-43 and calcitonin gene-related peptide (CGRP) revealed that some of the GAP-43-immunoreactive fibres also express CGRP. Pre-embedding electron microscopy showed GAP-43 immunoreactivity associated with the plasma membranes and cytoplasm of noradrenaline-producing chromaffin cells, and with processes of nonmyelin-forming Schwann cells. Immunoreactive unmyelinated axons and terminals were also observed. The immunostained terminals made symmetrical synaptic contacts with chromaffin cells. Immunoreactive unmyelinated fibres and small terminals were present in the cortex. Our results show that GAP-43 is expressed in noradrenergic chromaffin cells and in various types of nerve fibres that innervate the adrenal. Likely origins for these fibres include preganglionic sympathetic fibres which innervate chromaffin cells, postganglionic sympathetic fibres in the cortex, and CGRP containing sensory fibres.     

Electron paramagnetic resonance and other properties of hydrogenases isolated from Desulfovibrio vulgaris (strain Hildenborough) and Megasphaera elsdenii

The hydrogenases of Desulfovibrio vulgaris and Megasphaera elsdenii are compared with respect to some of their physical properties. In addition to Fe the only metal ions that are present in significant amounts are Ni and Cu. From cluster extrusion experiments it follows that the D. vulgaris enzyme contains three 4 Fe-4S clusters, while M. elsdenii hydrogenase only releases part of its Fe-S clusters. The resting D. vulgaris enzyme shows only a small 3 Fe-xS type of EPR signal (maximum 5% electron equivalent). This amount can be increased to approximately 25% by treatment with ferricyanide, with a concomitant large decrease in activity. The M. elsdenii enzyme shows in its oxidized state a normal Hipip (high-potential iron-sulphur protein) type of EPR spectrum. After a reduction/oxidation cycle the D. vulgaris enzyme also shows a weak Hipip type of EPR spectrum. In the reduced state both enzymes show complex spectra. By integration of those spectra it is shown that 1.5 electron equivalents are present. The complex spectra do not arise from nuclear hyperfine interactions but are partially due to electron spin interactions. It is proposed that the spectrum of reduced D. vulgaris hydrogenase consists of a sum of three different ferredoxin-like spectra.     

A new cluster model for the FeMo-cofactor of nitrogenase.

A new structural model for the FeMo-cofactor of nitrogenase, consisting of two Fe₄S₄ clusters bridged by an S₂Mo₂ unit, is proposed. Available chemical, spectroscopic, and EXAFS data are shown to be consistent with the proposed structure. In particular, EXAFS data are in agreement with m(Mo-Fe):n(Mo-S) of either 2:4 or 3:4; comparison with known Mo-Fe-S and Fe-S systems leads us to favor the former. Based on the proposed structural model, a possible mechanism of reduction of N₂ is suggested.     

Quantitative assessment of the quality of medical care provided in five family practices before and after attachment of a family practice nurse.

The standards of patient care were maintained in five urban medical practices after the introduction of family practice nurses. Evaluations were achieved before and after their appointment by the indicator condition method. Minimal explicit criteria for the management of patients with 12 indicator conditions and by the use of 14 drugs were approved by an ad hoc peer group of community physicians. These cirteria were applied to the five practices by the use of a single-blind design and the abstraction of unaltered medical records. A standardized score for each practic e permitted comparison of scores for the management of indicator conditions and for the clinical use of drugs before and after attachment of the family practice nurses. For each of the indicator conditions and the drugs assessed in the five practices similar levels of adequacy were observed in the two study periods. These explicit (objective) audit resutls agreed with the implicit (subjective) assessments of the family practice nurses by their physician colleagues.     

Sensitization to the cytotoxicity of adriamycin by verapamil and heat in multidrug-resistant Chinese hamster ovary cells.

Development of multidrug resistance to anticancer agents is a major limitation for the success of cancer chemotherapy. The chemosensitizer verapamil increases intracellular accumulation of drugs such as adriamycin in certain multidrug-resistant cell lines. When combined with verapamil, hyperthermia should be able to alter membrane permeability to adriamycin and to enhance the cytotoxicity of the drug. Verapamil increased the cytotoxicity of adriamycin in multidrug-resistant Chinese hamster ovary cells (CH(R)C5) but not in drug-sensitive cells (AuxB1). Hyperthermia (42 degrees C) alone clearly increased the cytotoxicity of adriamycin in AuxB1 cells. There was also a small increase in CH(R)C5 cells at 42 and 43 degrees C. In drug-resistant cells, the cytotoxicity of adriamycin increased considerably when verapamil was combined with heat. This effect was dependent on temperature and increased with time of incubation. At 37 degrees C, verapamil increased the uptake of adriamycin in CH(R)C5 cells, while drug efflux decreased. When verapamil was combined with hyperthermia, drug efflux decreased even further. These results led to an overall increase in intracellular accumulation of the drug. In drug-sensitive cells, hyperthermia increased both the uptake and efflux of adriamycin, but verapamil had no effect. Verapamil plus heat increased the cytotoxicity of adriamycin in drug-resistant cells, and this was accompanied by altered permeability of the membrane to the drug. Hyperthermia combined with verapamil could be beneficial by increasing the effectiveness of adriamycin in the elimination of multidrug-resistant cells in a localized target region.     

Forest tree growth is linked to mycorrhizal fungal composition and function across Europe

Most trees form symbioses with ectomycorrhizal fungi (EMF) which influence access to growth-limiting soil resources. Mesocosm experiments repeatedly show that EMF species differentially affect plant development, yet whether these effects ripple up to influence the growth of entire forests remains unknown. Here we tested the effects of EMF composition and functional genes relative to variation in well-known drivers of tree growth by combining paired molecular EMF surveys with high-resolution forest inventory data across 15 European countries. We show that EMF composition was linked to a three-fold difference in tree growth rate even when controlling for the primary abiotic drivers of tree growth. Fast tree growth was associated with EMF communities harboring high inorganic but low organic nitrogen acquisition gene proportions and EMF which form contact versus medium-distance fringe exploration types. These findings suggest that EMF composition is a strong bio-indicator of underlying drivers of tree growth and/or that variation of forest EMF communities causes differences in tree growth. While it may be too early to assign causality or directionality, our study is one of the first to link fine-scale variation within a key component of the forest microbiome to ecosystem functioning at a continental scale.Subject terms: Microbial ecology, Forest ecology, Fungal ecology, Biogeochemistry