Biomedical subjects

G J Bijloo

Publications and source records attributed to G J Bijloo.

5 recordsLinked to original sources

PubMed1990

Copper complexes of 1,10-phenanthroline and related compounds as superoxide dismutase mimetics.

In a preliminary study we tested CuSO4.5H2O, (Cu(II]2[3,5-diisopropylsalicylate]4.2H2O and a number of copper complexes of substituted 1,10-phenanthrolines for superoxide anion dismutase activity. It appeared that this activity depends on the ligands involved and might be governed by the redox potential of the Cu(I) complex/Cu(II) complex couple. The strong superoxide anion dismutase activity of Cu(II)[DMP]2 complex can be expected considering its high redox potential. Rather surprisingly is the superoxide anion dismutase activity of the Cu(I)[DMP]2 complex since it involves oxidation to Cu(II)[DMP]2 complex. From regression analysis it was established that steric and field effects of the substituents of the investigated phenanthrolines play an important role in SOD activity and therefore it is concluded that complex formation is important for the superoxide dismutase-like activity.

Copper↗

PubMed1988

Paracetamol, 3-monoalkyl- and 3,5-dialkyl-substituted derivatives. Antioxidant activity and relationship between lipid peroxidation and cytotoxicity.

The analgesic drug paracetamol is known to cause lipid peroxidation and hepatotoxicity after overdosage. In this paper, the relationship between lipid peroxidation and toxicity in freshly isolated hepatocytes was studied using paracetamol and three 3-monoalkyl-substituted derivatives of paracetamol. Paracetamol was found to induce both toxicity and lipid peroxidation in the hepatocytes. 3-Monoalkyl substitution of paracetamol (R = CH3, C2H5 and iso-C3H7) did not influence its cytotoxicity but, in contrast, inhibited the lipid peroxidation. This effect may be caused by the antioxidant activity of the substituted derivatives. Apart from 3-monoalkyl substitution, 3,5-dialkyl substitution of paracetamol was also found to potentiate the antioxidant activity of paracetamol. The antioxidant activity of paracetamol and its alkyl derivatives was found to be highly correlated to their lipophilicity.

Acetaminophen↗

PubMed1987

HA autoreceptor assay with superfused slices of rat brain cortex and electrical stimulation.

Slices of rat brain cortex previously loaded with [3H]histamine ([3H]HA) via de novo synthesis from [3H]histidine released tritiated histamine ([3H]HA) Ca2+ dependently in a superfused system. Both electrical field stimulation and high levels of K+ ions elicited this release. The extent of release depended on stimulation intensity. Rather strong stimuli, either by high frequency or longer stimulation, were required to elicit sufficient HA release for proper assessment of the concentration-dependence of release inhibition by drugs. The system showed marked depletion (less response per pulse) upon long-continued or successive stimulations. HA added to the superfusion medium inhibited the release evoked by stimulation at frequencies up to 10 Hz or with 30 mM K+ but not the release at higher frequencies or with 45 mM K+. The inhibition was mediated by H3 receptors, was concentration-dependent (pD2 = 7.4) and was complete at 10(-6) M. The H2 agonist impromidine antagonized the inhibition competitively (pA2 = 7.1). It is concluded that this assay in a superfusion system with electrical stimulation is suitable for the assessment of H3 receptor activity of drugs.

Animals↗

PubMed1987

H3 receptor assay in electrically-stimulated superfused slices of rat brain cortex; effects of N alpha-alkylated histamines and impromidine analogues.

The release of the putative neurotransmitter histamine (HA) from rat brain cortex slices is under negative feedback control by an HA autoreceptor. This autoreceptor has been postulated to belong to a new class of HA receptors, H3. To verify this hypothesis we have developed an assay using superfused rat brain cortex slices. The HA transmitter pool is labelled by incubation of the slices with the precursor 3H-histidine; 3H-HA is estimated after separation by column chromatography. Release of HA was found both after K+-induced depolarization and electrical field stimulation. The latter resulted in higher and more reproducible HA release. Electrically induced HA release could be fully inhibited in a concentration dependent way by exogenous HA in the superfusion buffer. N alpha-alkylated histamines also showed agonistic activity. The action of exogenous HA was totally blocked by the potent H2 agonist impromidine and some of its analogues.

Animals↗

PubMed1979

Determination of erythrocyte membrane-buffer partition coefficients by numerical analysis of multicomponent spectra.

A method suitable for the measurement of erythrocyte membrane-buffer partition coefficients by u.v.-spectrophotometry is described. This method is characterized by a proper correction for inconstant background absorption in case of bad signal to noise ratios. For this purpose the multicomponent u.v.-spectrum of a compound in the presence of absorbing materials lost by erythrocyte membranes is decomposed into its constituent spectra by means of numerical analysis. Application of this method to the determination of partition coefficients of benzhydrol, 4-bromophenol and benzyl alcohol yields satisfactory agreement with literature values for the latter two coefficients.

Benzhydryl Compounds↗