Reduction of the NO-mediated response in the rat aorta by metalloporphyrins

Metalloporphyrins (MPs) have been found to affect the production of carbon monoxide (CO) and nitric oxide (NO). Unlike that for CO, little is known about the mechanism of action of MPs on the NO system. We determined the in vitro ability of ferrous protoporphyrin (heme, FePP), zinc protoporphyrin (ZnPP), and bilirubin (BR) to scavenge NO. Heme and ZnPP were studied in the rat aortic ring system for their ability to affect phenylephrine-induced contraction and methacholine-stimulated relaxation. Heme was found to be a good NO scavenger with a k s = 0.53 ± 0.19 x 10 4 M -1 ·s -1 (n = 6). ZnPP and BR did not scavenge NO. Neither heme nor ZnPP treatment affected the phenylephrine response as measured by -logEC 50 and the maximal effect. However, heme and ZnPP treatments decreased the -logEC 50 and the maximal effects of methacholine, therefore decreasing vasorelaxation. We conclude that when ZnPP is administered in vivo blood pressure should be carefully monitored.Key words: carbon monoxide, heme, NO scavenger, vasorelaxation, zinc protoporphyrin

De uitscheiding van gechloreerde bifenylen in het melkvet na orale dosering aan lakterende melkkoeien

In verband met een te verwachten tolerantie voor gechloreerde bifenylen in het melkvet is het noodzakelijk de "accumulatiefaktor" voor de individuele gechloreerde bifenylen van veevoeder naar melkvet te kennen

Irradiance levels of phototherapy devices fabricated in Nigeria

Background: Phototherapy (PT) remains difficult to deliver in many resource-constrained countries, including Nigeria due to the unavailability of devices that can deliver intensive PT (irradiance ≥30 μW/cm2/ nm) needed to treat the more severe cases of hyperbilirubinaemia. The basic equipment is expensive and replacement parts are often not available. Objective: To compare the blue light irradiance of four locally designed and fabricated PT devices with a proprietary device. Materials and Methods: Four types of intensive PT devices were locally fabricated. Irradiance was measured using an Olympic Medical Bili-Meter. The mean irradiance of triplicate measure- ments at three positions in the light footprint of each device was determine that distances of 10, 20, 30, 40, 50, 60cm from light source to meter sensor. Results: The irradiance of the fabricated devices (F1-4) and commercial device (C) measured at the most common clinically-used distance of 30 cm for intensive PT were 29.5 ±6.3, 30.3 ±5.3, 25.8 ±5.0,49.0 ±10.5 and 39.2 ± 13.6μ W/cm2/nm respectively with corresponding maximum central irradiance of 36.4, 32.1, 31.2,59.5 and 54.5 μW/cm2/nm. At a distance of 25cm, all devices delivered irradiance ≥ 30μW/cm2/nm. The cost of each local device was less than 12% of the commercial one. Conclusions: Locally fabricated devices cost much less and were suitable for delivery of intensive phototherapy (≥30 μW/cm2/nm) at a distance of 25cm

High variability and low irradiance of phototherapy devices in Dutch NICUs

<p>Objective To evaluate phototherapy practices by measuring the irradiance levels of phototherapy (PT) devices.</p><p>Design Prospective study.</p><p>Setting Tertiary neonatal intensive care units.</p><p>Patients None.</p><p>Interventions Irradiance levels of PT devices used in the 10 Dutch Neonatal Intensive Care Units (NICUs) were measured according to the local PT practice patterns. The irradiance levels of all overhead and fibre-optic PT devices were measured with a radiometer using an infant silhouette model.</p><p>Results Eight different PT devices were used in the 10 NICUs; five were overhead devices and three fibre-optic pads. The median (range) irradiance level for overhead PT devices was 9.7 (4.3-32.6) mu W/cm(2)/nm and for fibre-optic pads 6.8 (0.8-15.6) mu W/cm(2)/nm. Approximately 50% of PT devices failed to meet the minimal recommended irradiance level of 10 mu W/cm(2)/nm. Maximal irradiance levels for overhead PT spot lights were inversely related to the distance between device and infant model (R2=0.33). The distances ranged from 37 cm to 65 cm.</p><p>Conclusions PT devices in the Dutch NICUs show considerable variability with often too low irradiance levels. These results indicate that suboptimal PT is frequently applied and may even be ineffective towards reducing total serum bilirubin levels. These results underline the need for greater awareness among all healthcare workers towards the requirements for effective PT including measurements of irradiance and distance.</p>

Modeling and simulation of phase-transitions in multicomponent aluminum alloy casting

The casting process of aluminum products involves the spatial distribution of alloying elements. It is essential that these elements are uniformly distributed in order to guarantee reliable and consistent products. This requires a good understanding of the main physical mechanisms that affect the solidification, in particular the thermodynamic description and its coupling to the transport processes of heat and mass that take place. The continuum modeling is reviewed and methods for handling the thermodynamics component of multi-element alloys are proposed. Savings in data-storage and computing costs on the order of 100 or more appear possible, when a combination of data-reduction and data-representation methods is used. To test the new approach a simplified model was proposed and shown to qualitatively capture the evolving solidification front

Carbon monoxide formation in the ductus arteriosus in the lamb: implications for the regulation of muscle tone

1. We have previously shown that carbon monoxide (CO) potently relaxes the lamb ductus arteriosus and have ascribed this response to inhibition of a cytochrome P450-based mono-oxygenase reaction controlling the formation of endothelin-1 (ET-1). In the present study, we have examined whether CO is formed naturally in the vessel. 2. The CO-forming enzyme, haem oxygenase (HO), was identified in ductal tissue in its constitutive (HO-2) and inducible (HO-1) isoforms by Western immunoblotting and immunological staining procedures (both light and electron microscopy). HO-1 was localized to endothelial and muscle cells, while HO-2 was found only in muscle cells. Inside the muscle cells, HO-1 and HO-2 immunoreactivity was limited to the perinuclear region, and the Golgi apparatus in particular. However, upon exposure to endotoxin, HO-1 became more abundant, and both HO isoforms migrated towards the outer region of the cytoplasm close to the sarcolemma. 3. CO was formed enzymatically from added substrate (hemin, 50 μM) in the 10,000 g supernatant of the ductus and its formation was inhibited by zinc protoporphyrin IX (ZnPP, 200 μM). 4. ZnPP (10 μM) had no effect on the tone of the ductus under normal conditions (2.5 to 95% O(2)), but it contracted the endotoxin-treated ductus (at 2.5% O(2)). At the same concentration, ZnPP also tended to contract the hypoxic vessel (zero O(2)). 5. ZnPP (10 μM) curtailed the relaxant response of the oxygen (30%)/indomethacin (2.8 μM)-contracted ductus to bradykinin (35 nM), while it left the sodium nitroprusside (35 nM) relaxation unchanged. 6. We conclude that CO is formed in the ductus and may exert a relaxing influence when its synthesis is upregulated by an appropriate stimulus