Emerging Patterns in Adolescent Drug Use: The Belfast Youth Development Study 2000-2002

This paper reports the findings from the first 2 years of the Belfast Youth Development Study. The Belfast Youth Development Study is a 5-year longitudinal investigation of the onset and development of adolescent drug using behaviours, the findings of the first 2 years from the study in relation to drug use patterns among the young people participating in the research are reported here. The findings show that while the majority of young people have not yet used an illicit substance, the study has seen a substantial increase in the numbers using such substances between year 1 and year 2. Boys still make up the majority of drug users in this period but there has been a substantial increase in the number of girls using illicit drugs and, more generally, an increase in the frequency of use among all those using such substances during this period.     

Non-operative management of retroperitoneal fibrosis

It is generally recognized that in many patients the ureteric obstruction and other manifestations of non-malignant retroperitoneal fibrosis will respond to treatment with corticosteroids. However, most surgeons are reluctant to use steroids as the primary treatment for patients with this condition, mainly because of the risk of mismanagement of malignant retroperitoneal fibrosis. Our experience in the care of 17 patients with non-malignant retroperitoneal fibrosis has led us to believe that an initial non-surgical approach is both safe and preferable.     

Fine mapping of X-linked clasped thumb and mental retardation (MASA syndrome) in Xq28

The MASA syndrome is an X-linked disorder with mental retardation, spastic paraparesis, and adducted thumbs as the most characteristic features. We performed linkage analysis, using Xq28 markers, on a large MASA syndrome family. The maximum lodscore was 6.37 at 0 recombination for DXS52 and 5.99 at 0 recombination for DXS305. Crossovers were demonstrated between the disorder and DXS455. Clinical and linkage data from this family further support the hypothesis that the MASA syndrome and X-linked hydrocephalus are allelic disorders.     

Cardiovascular effects of 5-HT1A receptor agonists injected into the dorsal raphe nucleus of conscious rats

The aim of this study was to investigate the cardiovascular effects of the 5-HT1A receptor agonists, 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin), flesinoxan and 5-carboxamidotryptamine (5-CT) following injection into the dorsal raphe nucleus of conscious rats. 8-OH-DPAT (0.5-2.5 micrograms), hypotension, bradycardia and flat body posture. In contrast, injection of 8-OH-DPAT (0.5 microgram) into the median raphe nucleus caused no cardiovascular changes or flat body posture. (-)Pindolol (0.5 microgram dorsal raphe nucleus) had little effect on cardiovascular parameters, but significantly attenuated the cardiovascular effects of 8-OH-DPAT (0.5 microgram dorsal raphe nucleus). N-Methylatropine (1 mg/kg i.v.) antagonised the cardiovascular effects of 8-OH-DPAT (0.5 microgram dorsal raphe nucleus), suggesting these were vagally mediated. Both pretreatments also appeared to reduce 8-OH-DPAT-induced flat body posture. The results suggest that 8-OH-DPAT activates 5-HT1A receptors in the dorsal raphe nucleus to cause hypotension and bradycardia.     

Reperfused myocardial infarctions on T1- and susceptibility-enhanced MRI: Evidence for loss of compartmentalization of contrast media

The purpose of this study was to characterize the contrast caused by a susceptibility MRI contrast agents, on spin echo T₂-weighted imaging of reperfused myocardial infarction. Our interest in this model focused on the expected requirement that such agents be compartmentalized in the tissue to cause signal loss on spin echo images, a condition which may not be present in reperfused infarcted myocardium. Accordingly, nine rats were subjected to 2 h of left coronary artery occlusion followed by 3 ± 0.5 h of reperfusion prior to administration of contrast media. Three sets of MR images were acquired: (a) baseline axial images at the midventricle, both T₁-weighted (TR/TE = 300/20) and T₂-weighted (TR/TE = 1500/60); (b) T₁-weighted images after administering a T₁-enhancing agent, Gd-DTPA-BMA (0.2 mmol/kg), to document that contrast media is delivered to the reperfused infarction; and (c) T₂-weighted images after administering the susceptibility agent, Dy-DTPA-BMA (1.0 mmol/kg). Gadolinium-enhanced T₁ images depicted reperfused infarction as regions with greatly enhanced signal intensity compared with unin-farcted myocardium, indicating that contrast agent was delivered to the infarcted zone. Dysprosium-enhanced T₁ images depicted the injury as a region of persistent signal intensity relative to depletion of signal in normal myocardium, consistent with failure of the contrast agent to cause signal loss. Similar infarction sizes were observed for unenhanced T₂-weighted images (33 ± 5%), gadolinium-enhanced T₁ weighted images (36 ± 5%) and postmortem staining (30 ± 6%); strong correlations (r > 0.9) were noted in comparisons of these data. Dysprosium-enhanced images exhibited a smaller region of differential signal presumed to be infarction (20 ± 5%, P < 0.05) and weak correlations (r < 0.75) with the other measurements. We conclude that the smaller infarction depicted on dysprosium-enhanced images is a subregion of the true infarction in which myocardial necrosis is sufficiently advanced that the agent is homogeneously distributed throughout all tissue compartments, preventing T₂*-dependent phase loss on spin echo images.     

Poly(2,6-Dimethyl-1,4-Phenylene oxide)/crosslinked polystyrene semi-interpenetrating networks: Synthesis and properties

Semi-interpenetrating networks (semi-IPN's) based on linear poly(phenylene ether)s and crosslinked polystyrene can be prepared by reactive moulding of crosslinkable polymeric mixtures. These materials show thermomechanical properties which strongly depend on both the ratio of the two polymeric matrices and the degree of crosslinking in the polystyrene network. Samples based on a 50/50 weight ratio of poly(2,6-dimethyl-1,4-phenylene oxide)/crosslinked polystyrene show glass transition temperatures (T_g) which are very dependent on the degree of crosslinking. It is therefore possible to obtain materials with desired T_g, ranging from the T_g of the corresponding linear blend to that of poly(2,6-dimethyl-1,4-phenylene oxide) alone.