The Mo-Se active site of nicotinate dehydrogenase

Nicotinate dehydrogenase (NDH) from Eubacterium barkeri is a molybdoenzyme catalyzing the hydroxylation of nicotinate to 6-hydroxynicotinate. Reactivity of NDH critically depends on the presence of labile (nonselenocysteine) selenium with an as-yet-unidentified form and function. We have determined the crystal structure of NDH and analyzed its active site by multiple wavelengths anomalous dispersion methods. We show that selenium is bound as a terminal MoSe ligand to molybdenum and that it occupies the position of the terminal sulfido ligand in other molybdenum hydroxylases. The role of selenium in catalysis has been assessed by model calculations, which indicate an acceleration of the critical hydride transfer from the substrate to the selenido ligand in the course of substrate hydroxylation when compared with an active site containing a sulfido ligand. The MoO(OH)Se active site of NDH shows a novel type of utilization and reactivity of selenium in nature.     

Serum PCB levels and congener profiles among US construction workers

Background  

The presence of PCB in caulking (sealant) material found in masonry buildings has been well-documented in several countries. A recent investigation of 24 buildings in the greater Boston area found that 8 buildings had high PCB levels in caulking materials used around window frames and in joints between masonry blocks. Workers removing caulking material have been shown to have elevated serum PCB levels.     

Dandy-Walker syndrome: a review of fifteen cases evaluated by prenatal sonography

Fifteen cases of the Dandy-Walker syndrome evaluated by prenatal sonography were reviewed retrospectively. A posterior fossa cyst communicating with the fourth ventricle was a feature in each case. Hydrocephalus was present in 53% of fetuses. Extracranial congenital malformations were documented in 60% of cases. Cardiac, genitourinary, gastrointestinal, and skeletal anomalies were noted. Of 12 available karyotypes, 4 (33%) were abnormal, including two cases of trisomy 18. Excluding terminated pregnancies, there was an overall mortality of 55%. Associated congenital defects contributed to 83% of the postnatal deaths. The Dandy-Walker syndrome can be accurately diagnosed in utero by sonographic demonstration of characteristic morphologic changes in the fetal posterior fossa. The prenatal examination should include an evaluation of associated supratentorial and extracranial defects. Coexisting structural and chromosomal anomalies occur frequently and adversely affect survival.     

Short-term distribution kinetics of intratracheally administered exogenous lung surfactant.

The short-term distribution kinetics of exogenous surfactant distribution after intratracheal instillation was investigated in surfactant-deficient neonatal piglets during assisted conventional mechanical ventilation and by high-frequency jet ventilation using exogenous calf lung surfactant extract (CLSE) labeled with 99mTc. Surfactant deficiency was induced by repeated bronchoalveolar lavage in piglets (1.2 +/- 0.4 kg, 1.4 +/- 0.7 d of age), and the short-term distribution kinetics of instilled, labeled CLSE were followed by gamma radioscintigraphy. Animals ventilated by either conventional mechanical ventilation or high-frequency jet ventilation showed similar improvement in arterial/alveolar oxygen ratios after surfactant replacement therapy (0.47 +/- 0.03 prelavage, 0.09 +/- 0.01 postlavage, 0.36 +/- 0.06 postsurfactant). This correlated directly with dynamic radioscintigraphic results showing that instilled CLSE began to distribute to the lungs within 5 s, and was present in substantial amounts in standardized symmetrical lung fields (central, right, and left; upper and lower) within 20 s of tracheal instillation. Subsequent measurements over 30 min showed continued presence of radiolabeled CLSE in all five areas of the lung, with no significant difference between conventional mechanical ventilation and high-frequency jet ventilation animals. Static (5-min) analyses at the end of this period showed that surfactant had distributed relatively symmetrically with 30% of the CLSE located in central regions, 40% in the upper lobes, and 30% in the lower lobes. In contrast, piglets receiving 99mTc in saline showed nonuniform distribution with multiple filling defects noted throughout the lungs. The rapid kinetics and ventilation independence of CLSE distribution suggest that surfactant spreading phenomena after tracheal instillation may facilitate the delivery of exogenous surfactant into aerated lungs in therapeutic applications.     

Implementation of a quality management system for the curriculum in emergency medicine education

Medical teaching, training and education in basic and advanced life support were improved by basic quality management procedures. 3rd year medical students (n = 276) of two consequent semesters were questionnaired about their acute emergency medicine curriculum. While Group A (n = 134) received a standard course, the new course for group B (n = 142) was reorganised on the basis of the results of group A. Interventive educational measures were an increased number of models provided for exercising the students skills, and an extension of megacode training possibilities. Participation of students in course design improved the overall performance in respect of knowledge, skills and decision-making (p < 0.05). Curriculum acceptance and intrinsic motivation of students however were not positively influenced by practical training compared to traditional knowledge transfer.     

Corneal morphology in vitro after superficial keratectomy with q-switched Er:YSGG and free-running Er:YAG lasers

PURPOSE: Examination of morphology in corneal ablation induced by a q-switched Er:YSGG (2.79 microm) laser and a free-running Er:YAG laser (2.94 microm). METHODS: Defined ablation of 6-mm diameter and 15, 30, 55, 90, and 120-microm depth was performed on freshly enucleated swine eyes. Er:YSGG laser parameters: fluence 1.6 J/cm2, frequency 6 Hz, spot-size 465 microm FWHM, scanning-mode, pulse number 1520 to 6210. Er:YAG laser parameters: fluence 3 J/cm2, frequency 1.5 Hz, spotsize 6 mm, wide area ablation, pulse number 2 to 13. Corneal morphology was analyzed by gross photography, histology, scanning electron microscopy, and scanning nearfield acoustic microscopy. RESULTS: Histology showed thermal damage of 5 to 15 microm in depth caused by the Er:YSGG laser in comparison with 10 to 20 microm by the Er:YAG laser. Average roughness of the ablated surface measured with scanning nearfield acoustic microscopy was 20 to 40 microm for the Er:YSGG laser and 5 to 15 microm for the Er:YAG laser. These data confirm the subjective impression of images created by scanning electron microscopy and gross photography. CONCLUSIONS: Although the Er:YAG laser system appeared to demonstrate a smoother corneal surface than the q-switched Er:YSGG laser, the thermal damage in either case poses a potential limitation for clinical use in lamellar refractive surgery.     

Retinal nerve fibre layer loss in patients with type 1 diabetes mellitus without retinopathy

BACKGROUND/AIM: There is evidence suggesting the occurrence of neurovisual abnormalities in patients with diabetes without retinopathy. However, the determination of abnormalities in the neural and glial elements in vivo is difficult. The aim of this study was to investigate whether a retinal nerve fibre layer (RNFL) defect (as determined by scanning laser polarimetry, SLP) is present in patients without clinical manifestations of diabetic retinopathy. METHODS: 12 patients with type 1 diabetes mellitus (DM) without retinopathy or other diabetes induced microvascular complications, underwent a complete ophthalmological examination, including automated perimetry and RNFL measurements with a nerve fibre layer analyser GDx. The data were compared with a normal control group matched for age and sex. RESULTS: The superior segment retardation in patients with diabetes was lower than in the control group, based on the superior integral (0.19 (SD 0.06) v 0.23 (0.04) mm(2), p=0.03) and the superior average (71.0 (11.05) v 84.27 (10.56) microm, p=0.007) parameters. CONCLUSION: This finding may be indicative of significant nerve fibre loss in the superior segment of the retina in patients with type 1 diabetes mellitus but without retinopathy. The meaning of intraretinal differences in RNFL retardation, indicating asymmetric NFL loss, in patients with diabetes is yet not understood.     

A phase II study of Irofulven (MGI 114) in patients with stage IV melanoma

Sixteen patients with stage IV melanoma,who were heavily pretreated, received11 mg/m²/day of intravenous Irofulvenfor five consecutive days every 28 days.There were no objective tumor responses,although one patient exhibited stabledisease after 4 cycles. The most commontoxicities were grade 1/2 nausea, vomiting,fatigue, anemia, and thrombocytopenia. Onepatient required a dose reduction for anelevated creatinine while another patientrequired cessation of treatment because ofacute ataxia that may have been related toIrofulven. Based upon these data, Irofulvendoes not demonstrate significant antitumoractivity to warrant further investigationin advanced melanoma.     

Mg2+ sensitizes KATP channels to inhibition by DIDS: dependence on the sulphonylurea receptor subunit

1. ATP-sensitive potassium channels (K(ATP) channels) consist of pore-forming Kir6.x subunits and of sulphonylurea receptors (SURs). In the absence of Mg(2+), the stilbene disulphonate, DIDS, irreversibly inhibits K(ATP) channels by binding to the Kir subunit. Here, the effects of Mg(2+) on the interaction of DIDS with recombinant K(ATP) channels were studied in electrophysiological and [(3)H]-glibenclamide binding experiments. 2. In inside-out macropatches, Mg(2+) (0.7 mM) increased the sensitivity of K(ATP) channels towards DIDS up to 70 fold (IC(50)=2.7 micro M for Kir6.2/SUR2B). Inhibition of current at DIDS concentrations > or =10 micro M was irreversible. 3. Mg(2+) sensitized the truncated Kir6.2Delta26 channel towards inhibition by DIDS only upon coexpression with a SUR subunit (SUR2B). The effect of Mg(2+) did not require the presence of nucleotides. 4. [(3)H]-glibenclamide binding to SUR2B(Y1206S), a mutant with improved affinity for glibenclamide, was inhibited by DIDS. The potency of inhibition was increased by Mg(2+) and by coexpression with Kir6.2. 5. In the presence of Mg(2+), DIDS inhibited binding of [(3)H]-glibenclamide to Kir6.2/SUR2B(Y1206S) with IC(50)=7.9 micro M by a non-competitive mechanism. Inhibition was fully reversible. 6. It is concluded that the binding site of DIDS on SUR that is sensed by glibenclamide does not mediate channel inhibition. Instead, Mg(2+) binding to SUR may allosterically increase the accessibility and/or reactivity of the DIDS site on Kir6.2. The fact that the Mg(2+) effect does not require the presence of nucleotides underlines the importance of this ion in modulating the properties of the K(ATP) channel.