PubMed Health⌕ Search

Biomedical subjects

K H Loke

Publications and source records attributed to K H Loke.

13 recordsLinked to original sources
PubMed1990

Sinus bradycardia in anorexia nervosa--a case report.

This case report highlights one of the common but usually unrecognised causes of sinus bradycardia in clinical practice. The reasons for misdiagnosis and/or delay in diagnosis of such a condition is also discussed.

Adolescent↗
PubMed1988

Spectral perturbation of human microsomal cytochrome P-450 by flavonoid binding.

Aromatase is the cytochrome P-450 complex responsible for oestrogen biosynthesis in vivo. Inhibitors of this enzyme complex might therefore serve to modulate oestrogen-dependent processes by interfering with the production of oestrogens. Thus, these agents may be useful in reproductive processes and in treating oestrogen-dependent disease states such as breast and endometrial cancer. We have demonstrated that inhibitors such as the naturally occurring flavonoids having 5,7-dihydroxy substituents can bind to human placental cytochrome P-450 with affinity comparable to their ability to inhibit aromatization of androstenedione and testosterone to oestradiol and oestrone, respectively. It appears that the mechanism of this inhibition requires the flavonoid to bind to the active site of the cytochrome P-450 without prior generation of metabolic intermediate products. Our data also suggest that the presently known differences in potency of inhibition of cytochrome P-450-mediated aromatization of steroids by different hydroxylated derivatives of 5,7-dihydroxyflavones may arise from their different binding affinity to the enzyme, particularly those compounds hydroxylated in the C3 position in ring C of the flavonoid nucleus.

Androstenedione↗
PubMed1972

The intermediary role of 5-pregnene-3 ,20 -diol in the biosynthesis of 16-unsaturated C 19 steroids in boar testis.

1. The possible involvement of 5-pregnene-3beta,20beta-diol in 16-unsaturated C(19) steroid biosynthesis has been investigated. 2. 5,16-Androstadien-3beta-ol (andien-beta) formation from [4-(14)C]pregnenolone (3beta-hydroxy-5-pregnen-20-one), 5-pregnene-3beta,20alpha-diol and 5-pregnene-3beta,20beta-diol was studied in homogenates of boar testis and the mean yields obtained were 25.6, 2.7 and 16.0% respectively. 3. Short-term kinetic studies with pregnenolone and 5-pregnene-3beta,20beta-diol separately and together suggested that the latter compound might be an intermediate in the biosynthesis of andien-beta. 4. In agreement with this interpretation, radioactive 5-pregnene-3beta,20beta-diol has been isolated during andien-beta biosynthesis from [4-(14)C]pregnenolone in the presence of NADPH, more radioactivity being trapped under limiting conditions of andien-beta formation with NADH present as cofactor. 5. Further, 5-pregnene-3beta,20beta-diol and andien-beta have been shown to inhibit the formation of the 16-unsaturated C(19) steroid from [4-(14)C]pregnenolone, the yield of radioactive 5-pregnene-3beta,20beta-diol increasing in the presence of added unlabelled andien-beta. 6. It is concluded that there may be two pathways leading to 16-unsaturated C(19) steroid formation from pregnenolone, one of these involving 5-pregnene-3beta,20beta-diol as an intermediate. Possible mechanisms are presented and discussed.

Alcohols↗