Biomedical subjects

H F Liu

Publications and source records attributed to H F Liu.

50 records · Page 3Linked to original sources

PubMed1993

[Malignant melanoma of the sole].

Ten cases of malignant melanoma on the sole are reported. Of these, 4 were acral lentiginous melanoma (ALM); 3 nodular melanoma; 2 were unclassifiable and 1 was ALM in situ. The nodular melanoma on the sole possessed a common feature with that occurring at other area of the body. ALM was considered consisting of a lump and its surrounding pigmented macular areas, while ALM in situ only appeared as a pigmented macula. Usually, the pigmented macular lesions were noticed after middle-age, and coincidentally with its gradual enlargement, its color changed from pale brown to black, while the border of the lesion was either sharp or vague with angular notches. Recognition of these features may facilitate early diagnosis and excision. Additionally, it was found that the degree of proliferation, distribution patterns and extent of atypical melanocytes in the epidermis related correspondingly to the shade variation of the pigmented maculas.

Adult↗

PubMed1992

Escherichia coli MutY protein has both N-glycosylase and apurinic/apyrimidinic endonuclease activities on A.C and A.G mispairs.

In Escherichia coli the mutY (or micA)-dependent DNA mismatch repair pathway can convert A degrees G and A degrees C mismatches to C.G and G.C base pairs, respectively, through a short repair-tract mechanism. The MutY protein has been purified to near homogeneity from an E. coli overproducer strain. Purified MutY has been shown to contain both N-glycosylase and 3' apurinic/apyrimidinic (AP) endonuclease activities. The N-glycosylase removes the mispaired adenines of A degrees G and A degrees C mismatches, and the AP endonuclease acts on the first phosphodiester bond 3' to the AP sites. The N-glycosylase and the nicking (combined N-glycosylase and AP endonuclease) activities copurified through multiple chromatographic steps without a change in relative specific activities. Furthermore, both N-glycosylase and AP endonuclease activities can be recovered by renaturation of a single polypeptide band from an SDS/polyacrylamide gel. Renaturation required the presence of iron and sulfide. These findings suggest that the MutY protein, like endonuclease III, is an iron-sulfur protein. DNA fragments with A degrees C mismatches were 20-fold less active than DNA with A degrees G mispairs as a substrate for purified MutY.

Bacterial Proteins↗

PubMed1991

Urinary glucuronide excretion of fenofibric and clofibric acid glucuronides in man. Is it polymorphic?

The possible polymorphism of the glucuronidation reaction in man has been investigated using two hypolipidaemic compounds, fenofibrate and clofibrate, as the test probes. The formation of fenofibryl and clofibryl glucuronides was identified by their susceptibility to hydrolyses by beta-glucuronidase. The urinary excretion of the glucuronides was measured in 72 healthy volunteers after a single dose of fenofibrate, and in 104 subjects given a single dose of clofibric acid. Fenofibrate was excreted at a lower rate than clofibrate, since 13.94% and 26.55% of the doses of fenofibrate and clofibrate respectively, were recovered in urine in 8 h. Correlation analysis indicated that sex and body mass index significantly influenced the formation of fenofibryl glucuronide, whereas age and oral contraceptives affected the excretion of clofibryl acid glucuronide. The 8-hour urinary excretion patterns of clofibryl glucuronide and of clofibric acid presented a Gaussian distribution, whereas those of fenofibryl glucuronide and fenofibric acid showed 2 populations. When the metabolic ratio free fenofibric acid/glucuronide was considered, 84.7% of subjects presented the ratio 0.147, and 15.3% had the 3-fold higher ratio of 0.421. The study has shown, in the human population studied, that the glucuronidation of fenofibric acid but not that of clofibric acid may present a polymorphism.

Adult↗

PubMed1991

Oral contraceptives stimulate the excretion of clofibric acid glucuronide in women and female rats.

1. Glucuronidation of clofibric acid, the pharmacologically active form of the hypolipidemic drug clofibrate was investigated in a human population, either in vitro with liver homogenates from biopsies, or after ingestion of the drug and determination of the urinary metabolite. No difference in the glucuronidation rate according to age of the patients was observed. Bilirubin but not clofibric acid glucuronidation was significantly higher in women (106% increase), when expressed per gram of tissue. 2. The excretion of clofibryl glucuronide in women who took oral contraceptives was significantly enhanced by 25%. 3. In female rats, treatment with the contraceptive agent norethindrone also stimulated by 48% the formation of clofibrylglucuronide in liver microsomes.

Adult↗

PubMed1989

Evaluation of a versatile reversed-phase high-performance liquid chromatographic system using cethexonium bromide as ion-pairing reagent for the analysis of glucuronic acid conjugates.

An ion-pair high-performance liquid chromatographic technique has been developed to reduce the elution times of both glucuronic acid conjugates and their free aglycones. The chromatographic system combines the use of a reversed-phase column (LiChrospher CH-18; 5 microns) and a mobile phase of methanol (70-80%)-0.01 M phosphate buffer (pH 6.0) containing 2.5 mM cethexonium bromide as counter-ion at a flow-rate of 1 ml min-1. The hydrophobicity of this quaternary ammonium ion-pairing reagent and the high content of the organic modifier in the mobile phase provide close and short elution times for a wide structural variety of compounds (i.e. alcohols, phenols, steroids, carboxylic acids) and their conjugates with glucuronic acid (capacity factors lower than 7.5), without compromising the selectivity with respect to endogenous compounds of the microsomal incubation medium and urine. Advantages of cethexonium bromide over conventional tetrabutylammonium salts are clearly demonstrated, and the described system was applied to the simultaneous quantitation of clofibric acid and its acylglucuronide in human urine and validated for a pharmacogenetics purpose.

Animals↗

PubMed1989

Experimental studies of the injurious effects of Q-switched Nd:YAG lasers and their outdoor applications.

Comparison of the dose-response relationship of retinal damage induced by Q-switched (Q-sw) Nd:YAG lasers was conducted for rabbits and monkeys. Experimental results indicated that the two probit regression lines were parallel to each other, and the damage threshold (ED50) ratio was approximately 1:3.57. Observations of the injurious effects of Q-sw Nd:YAG rangefinders--the total energy level being about 10-100 mJ--and their injurious distances are reported in this paper. A brief description is given of coagulative and hemorrhagic pathological changes under different exposure conditions and at various distances.

Accidents, Occupational↗

PubMed1989

Ocular injuries from accidental laser exposure.

This report presents 29 cases of ocular injury (31 eyes) caused by accidental laser exposure. Twenty-eight eyes were injured during laser adjustment and alignment. Nineteen eyes were damaged by Q-switched lasers at a wavelength of 1064 nm. Macula damage occurred in 25 eyes. During the early phase after injury, there were different degrees of retinal coagulation, edema or hemorrhage in exposed spots and there occurred immediate reduction of visual acuity. Effusion of blood and exudate was absorbed in most injured eyes under treatment lasting several weeks; meanwhile, gray-white scars appeared. Macular holes appeared in seven cases a week after injury, thus extending the course of the injury. Nine cases (10 eyes) were followed-up for 4-10 y, during which time the condition of eight cases (nine eyes) remained stable. The causes of the laser accidents and the relationship between the damage effects and exposure doses were analyzed.

Accidents, Occupational↗

PubMed1989

[The hypoglycemic effect of clausenacoumarine].

Clausenacoumarine is a compound isolated from the leaves of Clausena lansium (Lour.) Skeels which grows widely in South China. The studies show that clausenacoumarine can lower blood glucose level in normal mice and alloxan diabetic mice at 200 mg/kg.d for three days orally, and antagonize the elevation of blood glucose caused by injecting adrenaline in normal mice. No effect on blood lactic acid was observed.

Alloxan↗

PubMed1988