2-(Methylseleno)benzanilide, a metabolite of ebselen, was oxidatively demethylated by rat liver microsomes to regenerate the parent compound, ebselen. The rate of this novel reaction exceeds that of ring hydroxylation, and it was inhibitable with metyrapone. The sulfur analogue, 2-(methylthio)benzanilide, was oxidized to the corresponding sulfoxide. The regeneration of ebselen from 2-(methylseleno)benzalide is suggested to result from an intermediate selenoxide and hydrolysis with formation of methanol, since only very small amounts of labeled formaldehyde were detected in incubations using 2-[(14C)methylseleno]benzanilide. In an analogous reaction, 2-(benzylseleno)benzaldehyde yielded ebselen upon oxidation with hydrogen peroxide and, as detected by gas-liquid chromatography, benzyl alcohol.

Anilides↗

PubMedDate not supplied

Early rather than recent exposure to tobacco increases bronchial reactivity.

BACKGROUND: Tobacco is well known to impair respiratory function of infants and children. This study was done to identify periods of increased vulnerability of the airways to tobacco products. PATIENTS AND METHODS: In 162 unselected schoolchildren maximum expiratory flow at 25 % of vital capacity (MEF25) was measured before and after cold air hyperventilation. Parental smoking habits were assessed by measurement of cotinine concentrations in children's urine and by interview. RESULTS: Children, whose mothers had smoked during pregnancy, showed increased bronchial reactivity at school age compared to children whose mothers had not smoked during pregnancy (median MEF25 [25th, 75th percentile] after cold air challenge as percent of baseline: 83 % [76, 95] vs. 95 % [79, 100]; p = 0.03). Similar differences were found, when the study population was divided according to the maternal smoking status during the first six months of life. On the contrary, if the cotinine excretion exceeded the group median as a measure of recent exposure to tobacco smoke, bronchial reactivity was not increased (median MEF25 [25th, 75th percentile] as percent of baseline: 88 % [76, 100] vs. 93 % [79, 100]; p = 0.25). CONCLUSIONS: Pregnancy and early infancy were found to be periods of increased vulnerability of the airways to tobacco products.

Adult↗

PubMedDate not supplied

[Optimizing the bone cement-implant interface by hydrolysis-resistant conditioning of the metal surface].

PURPOSE: The hydrolytic degradation of the implant-cement interface has to be seen as the main reason for aseptic loosening of cemented total hip replacements. Therefore, a new method of conditioning the metallic surface was developed in order to achieve a hydrolytic-resistant bound stability between the implant and bone cement. Preliminary experimental data on test bodies are presented here. METHOD: The metallic surface of 6 pairs of cylindrical test bodies each (CoCr-alloy, circular testing surface with O 6 mm) were conditioned by the method of silicoating/silanisation to gain a covalent coupling with the applied bone cement. In order to examine the initial stability and the hydrolytic resistance of the metal-cement compound, these pairs of surface-conditioned test bodies (SCT) as well as a reference series of surface-unconditioned test bodies (SUT) were immersed for 0, 30, 90, 150 days (d) in moisture environment (physiological saline solution, 37 degrees C) after coupling with bone cement. The adhesive strength of the test bodies-(bone cement-compounds) were determined by tensile tests on an universal testing machine (Typ Z030, Zwick, Ulm) with gimbal suspension. RESULTS: At time 0 d (that was without immersion of the test bodies) the mean maximum tensile bond strength of the SCT-cement-compounds was 39.5 MPa (SD +/- 4.7 MPa) and that of the SUT-cement-compounds 37.1 MPa (SD +/- 7.3 MPa) (p = 0.575). After immersion the tensile bond strength of the SUT-cement-compounds significantly decreased to an average of 13.5 MPa (SD +/- 2.7 MPa) (30 d), 10 MPa (SD +/- 1.7 MPa) (90 d) and 12.3 MPa (SD +/- 1.4 MPa) (150 d) (p < 0.01). In contrast, the SCT-cement-compounds showed a nearly unchanged high mechanical stability with tensile bond strength values of 37.0 MPa (SD +/- 4.9 MPa) after 30 d, 36.1 MPa (SD +/- 5.0 MPa) after 90 d und 30.2 MPa (SD +/- 4.7 MPa) after 150 d (p > 0.01). CONCLUSIONS: With reservation as to further in vitro and in vivo investigations the increased hydrolytic stability of the metal-cement-bound of surface-conditioned CoCr-alloy test bodies promises an improvement of the long-term stability of cement total joint replacements.

Arthroplasty, Replacement, Hip↗

PubMedDate not supplied

Physiological effects of fast oscillating magnetic field gradients.

To evaluate the physiological thresholds of neuromuscular stimulation relevant to very fast NMR imaging studies that use gradient switching at frequencies of 1-2 kHz and a maximum magnetic field of up to 10 mT, a series of studies were done with human volunteers using an experimental echo planar gradient coil set. The threshold for induction of localized and momentary sensations in the human back and abdomen for 10 subjects is 60 T/s for sinusoidally oscillating magnetic fields at 1.27 kHz. The threshold relates to an E field of 6 V/m and is shown to vary with number of oscillations and frequency in accord with theory. Using a simple model of E field induction, the threshold for stimulation of cardiac electrical events should be greater than 4 times this value.

Abdomen↗

PubMedDate not supplied

Selective MR angiography and intracranial collateral blood flow.

This study evaluates the usefulness of MR angiography (MRA) in analyzing the individual collateral flow dynamics and anatomy of the circle of Willis in patients with high-grade extracranial carotid stenosis or occlusion. Selective MRA of the carotid or vertebrobasilar territory was performed by means of presaturation of up to three of the brain-supplying arteries at the level of the middle or lower neck (angled presaturation slabs). Results obtained with selective and nonselective arterial MRA in 45 consecutive patients were compared with findings at transcranial Doppler ultrasonography and intraarterial angiography, the latter serving as the "gold standard." Sensitivity of selective MRA in detecting intracranial collateral circulation via the anterior and posterior communicating artery was 95 and 97%, respectively; sensitivity in depicting extracranial to intracranial transorbital flow was lower (67%). Nonselective arterial MRA was 100% sensitive in detecting a nonfilling of the horizontal (A1) segment of the anterior cerebral artery and in identifying an origin of the posterior cerebral artery from the intracranial carotid artery. Visibility of the posterior communicating artery at MRA predicted for pathological collateral flow via this vessel in all cases. We conclude that selective and nonselective MRA of the cerebral arteries as used here is the most powerful noninvasive method to demonstrate collateral circulation via the basal communicating arteries and to identify hemodynamically relevant anatomic variants of the circle of Willis.

Adult↗

PubMedDate not supplied

Peripheral nerve stimulation by time-varying magnetic fields.

PURPOSE: A study was performed to assess the stimulation threshold for healthy adults using sinusoidally oscillating gradients. METHOD: One hundred thirteen healthy adults were examined in the study. ECG and physiological parameters were measured. All measurements were performed of both the head and the abdomen. The subjects were measured in the supine position with the region of interest positioned in the center of the gradient coils. The measurement was performed for three orthogonal, four oblique, and double oblique orientations. RESULTS: No volunteer reported painful, severe stimulation. The mean thresholds for peripheral stimulation in head and body measurement were similar: 85.5% of stimulation during examination of the head and 87.6% during measurements of the abdomen were reported when the y-gradient was used. CONCLUSION: The greatest frequency of reported stimulations occurs when the y-gradient is used. This was confirmed by the results and supports the hypothesis that orthogonal to the y-axis the body has its largest conductive loop, resulting in the strongest peripheral stimulation.

Adult↗