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Biomedical subjects

A Burg

Publications and source records attributed to A Burg.

10 recordsLinked to original sources
PubMed2000

The reaction mechanism of nitrosothiols with copper(I).

Copper and other transition metal ions and their complexes are catalysts for the decomposition of nitrosothiols. In this way they catalyze the biological functions of nitrosothiols. The kinetics and mechanism of the reaction of two nitrosothiols, S-nitrosothiolactic acid and S-nitrosoglutathione (GSNO), with copper(I) are reported. The kinetics of the reaction of Cu(MeCN)+(n) (n=0-3) with the nitrosothiols were studied. The results indicate that Cu+(aq) is the active species in the GSNO system, with k(Cu+(aq)+GSNO)=(9.4 +/- 2.0) x 10(7) dm3 mol(-1) s(-1). The results also indicate that the Cu(MeCN)+(n) (n=0-3) complexes react with S-nitrosothiolactic acid. Transient species are formed in these processes. The results suggest that these species contain copper(I) and thiol. The results shed light on the catalytic role of copper complexes in the decomposition of S-nitrosothiols.

Copper↗
PubMed1996

[0.15 mg clonidine as oral premedication in retrobulbar anesthesia].

BACKGROUND: In the present clinical study, oral premedication of 0.15 mg clonidine has been explored with view to anxiolytic effects and physiological stress parameters. METHODS: The study involved 44 patients of ASA-class I-III, all scheduled to undergo ophthalmological surgery under retrobulbar anesthesia (RBA). One hour before RBA 22 patients received 0.15 mg clonidine and 22 patients placebo p.o. The following parameters were assessed at different times perioperatively: oxygenation (SpO2), heart rate, blood pressure, intraocular pressure and anxiety. Anxiolysis was determined using the Erlanger Anxiety Scale. RESULTS: There were no significant differences among the groups in SpO2 and heart rate. Significantly decreased blood pressures were measured after clonidine premedication (p < 0.01). In contrast to clonidine after placebo the preoperative anxiety increased. Right before operation anxiety was decreased significantly (p < 0.01) by clonidine compared to placebo. CONCLUSIONS: In our opinion, oral clonidine (0.15 mg) is useful for premedication of surgery under RBA.

Administration, Oral↗
PubMedDate not supplied

Interpretation of spring recession curves.

Recession curves contain information on storage properties and different types of media such as porous, fractured, cracked lithologies and karst. Recession curve analysis provides a function that quantitatively describes the temporal discharge decay and expresses the drained volume between specific time limits (Hall 1968). This analysis also allows estimating the hydrological significance of the discharge function parameters and the hydrological properties of the aquifer. In this study, we analyze data from perennial springs in the Judean Mountains and from others in the Galilee Mountains, northern Israel. All the springs drain perched carbonate aquifers. Eight of the studied springs discharge from a karst dolomite sequence, whereas one flows out from a fractured, slumped block of chalk. We show that all the recession curves can be well fitted by a function that consists of two exponential terms with exponential coefficients alpha1 and alpha2. These coefficients are approximately constant for each spring, reflecting the hydraulic conductivity of different media through which the ground water flows to the spring. The highest coefficient represents the fast flow, probably through cracks, or quickflow, whereas the lower one reflects the slow flow through the porous medium, or baseflow. The comparison of recession curves from different springs and different years leads to the conclusion that the main factors that affect the recession curve exponential coefficients are the aquifer lithology and the geometry of the water conduits therein. In normal years of rainy winter and dry summer, alpha1 is constant in time. However, when the dry period is longer than usual because of a dry winter, alpha1 slightly decreases with time.

Fresh Water↗