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Biomedical subjects

W Feng

Publications and source records attributed to W Feng.

106 records · Page 6Linked to original sources
PubMed1993

Low follicular oestrogen levels in New Zealand women consuming high fibre diets: a risk factor for osteopenia?

AIMS: To study effects of anthropometry, diet and exercise on plasma 17 beta-oestradiol concentrations in healthy premenopausal women. METHODS: Fifty-five healthy female volunteers aged 19-29 (Mean (SD) = 22.2 (2.6) years) were studied. Anthropometric measurements were made, food intakes were estimated using a food frequency questionnaire, physical activity was assessed, menstrual histories were taken and blood 17 beta-oestradiol values were measured in the follicular and luteal phases of the menstrual cycle. RESULTS: Adiposity and dietary fat intake did not influence circulating plasma 17 beta-oestradiol but dietary fibre intake was negatively correlated with both follicular (r = -0.43, p < 0.001) and luteal (r = -0.28, p < 0.05) 17 beta-oestradiol concentrations. Follicular oestradiol values were abnormally low in 53% of the population. Subjects with high fibre intakes (> or = 25 g fibre daily) had significantly lower concentrations of 17 beta-oestradiol in the follicular phase of the menstrual cycle (p < 0.01). Physical activity was similar in groups consuming high and low fibre diets. Subjects with oligomenorrhoea or amenorrhoea (n = 7) had higher fibre intakes/energy (p < 0.05) than subjects with eumenorrhoea (n = 48). CONCLUSION: Our study suggests that healthy New Zealand women of premenopausal age have lower 17 beta-oestradiol levels on high fibre diets than on low fibre diets. Because hypoestrogenism is a known risk factor for osteoporosis we propose that high fibre intakes may influence bone mass adversely and be a risk factor for osteoporosis. The effects of high fibre intakes on bone mass warrant further investigation.

Adult↗
PubMed1993

Quantum chemical and molecular mechanics studies on the binding of stereoisomers of the oligopeptide antibiotics amidinomycin and noformycin to the minor groove of B-DNA.

Ab initio calculations (Hartree-Fock) using the 6-31G basis set have been performed on two chiral oligopeptide antitumor antibiotics amidinomycin 5 and noformycin 6. The latter are DNA minor groove binding agents related to the A.T recognizing netropsin 4 and distamycin 3 but, unlike the latter, bear stereocenters (two for 5 and one for 6) that may be expected to affect binding to the B-DNA receptor. Geometry optimized conformations, energies and distribution of electrostatic charges within the molecules were derived. The rotational barrier for bond C3-C6 in 6 was calculated to be ca. 6 kcal.mole-1 and the dipole moment for 6 was 7.69D and for 5 was 5.58D. The ab initio derived parameters of the geometry optimized conformations of the different possible stereoisomeric forms of 5 and 6 were used to interpret their different interactions with the minor groove of DNA at both A.T and G.C sequences and the results were compared with molecular mechanics calculations. The order of binding of the four stereoisomers of 5 at the preferred (A.T)n sequences by both ab initio and molecular mechanics calculations is 1S,3R > RR > RS > SS. The predicted energy differences for complexation with DNA of the other stereoisomers from that of 1S,3R are: RR (4.2%); RS (6.7%) and SS (21.5%). In the case of noformycin the 4R structure binds more effectively than the enantiomer. Considerations of phasing in the computed distances between hydrogen bond donating sites in the DNA-bound antibiotics provide further insight into the binding processes. In the complexes of noformycin 6 the N-N1-N4 and N1-N5 distances (9.05 and 9.15 A respectively for 4R-6 and 9.23 and 9.26 A respectively for 4S-6) are close to the optimum value of 9.1 A for effective binding. In the case of amidinomycin 5 the best agreement with the optimum value occurs with the strongest binding diastereomer 1S,3R (N1-N3 = 8.91, N1-N4 = 9.41 A). The unexpected result, consistent in both ab initio and molecular mechanics treatments, is that, in contrast to the cases of kikumycin 1 and anthelvencin 2, the natural 3S configuration of 5 and 4S of 6 do not confer maximal binding efficiency. This suggests that biogenetic factors in the generation of the oligopeptide antibiotics lead to maximum DNA binding in the cases of kikumycin and anthelvencin but not in the cases of amidinomycin and noformycin.

Anti-Bacterial Agents↗
PubMed1992

Preoperative chemotherapy and radiation therapy for stage IIIa carcinoma of the lung.

Thirty-six patients with stage IIIa histologically proven non-small cell carcinoma (T3 N2 or T2 N2) underwent concomitant radiation therapy and chemotherapy before pulmonary resection. The therapy consisted of two cycles of continuous infusion of cis-platinum, 25 mg.m-2.day-1 (days 1 through 4) every 4 weeks and concomitant irradiation, 55 Gy, of the tumor and mediastinum. Two to 3 weeks after treatment, the patients were reevaluated for thoracotomy and pulmonary resection. Five patients were found to have unresectable lesions. Thirty-one patients had complete resection, 27 by radical pneumonectomy and 4 by radical lobectomy, giving a resectability rate of 86%. Complete sterilization of lung tumor and mediastinal nodes proven histologically was achieved in 10 patients (28%) and 17 patients (47%). The 3-year survival rate is 61.7% for patients who had resection. Median follow-up is 27 months (range, 6 to 61 months). The preliminary study indicates that preoperative cis-platinum and concomitant radiation therapy is tolerated, appears to increase resectability, and may improve survival in patients with stage IIIa lung cancer.

Adult↗
PubMed1992

Tamoxifen in the rat prevents estrogen-deficiency bone loss elicited with the LHRH agonist buserelin.

In young women chronic use of luteinizing hormone releasing hormone (LHRH) agonists such as buserelin to treat endometriosis leads to estrogen-deficiency bone loss. Tamoxifen citrate is an estrogen agonist/antagonist which protects the skeleton from osteopenia when ovarian hormones are depleted. The present study was undertaken to determine whether tamoxifen citrate (20 mg/kg body wt/week s.c.) could prevent the osteopenic effect of buserelin (25 micrograms/kg body wt/day s.c.). Four groups of rats with 45Ca-labelled bones were studied for 4 weeks: group A--placebo controls; group B--buserelin; Group C--tamoxifen; group D--buserelin+tamoxifen. Bone resorption was monitored by measuring the urinary excretion of 45Ca and hydroxyproline. Interestingly buserelin lowered both blood 17 beta-estradiol values and uterine weights in the presence and absence of tamoxifen. However, tamoxifen slowed bone breakdown and inhibited the bone-thinning effects of buserelin. Total body calcium values (mg; means +/- S.D.) were: 2227 +/- 137; 1926 +/- 124; 2233 +/- 94 and 2268 +/- 163, in groups A to D respectively. Osteopenia was thus present only in group B (P less than 0.001). Because tamoxifen inhibits estrogen-deficiency bone loss in buserelin-treated rats without depressing the hypoestrogenic actions of this LHRH-agonist, we suggest that use of tamoxifen to protect the skeleton during LHRH-agonist therapy in young women should be explored. Tamoxifen citrate might also help to prevent postmenopausal osteoporosis.

Animals↗
PubMed1992

Antitumor activity of Hypsizigus marmoreus. I. Antitumor activity of extracts and polysaccharides.

Antitumor activity of Hypsizigus marmoreus, one of the most popular Japanese edible mushrooms, was investigated. The aqueous and methanol extracts were tested against allogeneic tumor, solid sarcoma 180 and syngeneic tumor, Meth A fibrosarcoma. The aqueous extract was highly active in inhibiting growth of solid sarcoma 180, but not as much for Meth A fibrosarcoma. Fractionation of antitumor substances of the aqueous extract isolated four polysaccharides. Chemical analysis revealed one of them to be beta-(1-3)-glucan with a remarkable inhibitory effect against tumor-growth of sarcoma 180.

Animals↗
PubMed1992

Radial keratotomy. 1. The wound healing process and measurement of incisional gape in two animal models using in vivo confocal microscopy.

Using in vivo confocal microscopy, corneal wound healing was evaluated in both rabbit and cat eyes after radial keratotomy. A total of six rabbit and six cat eyes were evaluated sequentially over time for 1 mo after surgery by in vivo confocal microscopy, and quantitative measurements of changes in incisional wound gape were determined. In vivo histopathologic changes were correlated with conventional histopathologic findings in 18 rabbit and 4 cat eyes; the animals were killed at various intervals from 0-30 days after surgery. In the rabbit, in vivo corneal wound healing was characterized by the initial ingrowth of corneal epithelium followed by persistence within the wound without a marked fibrotic response. Measurement of incisional wound gape showed increasing gape from 144 +/- 32 microns on day 0 to 976 +/- 155 microns on day 26 at a distance of 2.4 mm from the optical zone. These in vivo measurements were not significantly different (P = 0.996) from those obtained using conventional histopathologic techniques which showed an incisional wound gape of 252 +/- 112 microns on day 0 and 917 +/- 216 microns on day 26 at 2.5 mm from the optical zone. In the cat eyes, healing of radial keratotomy wounds showed an initial increase in incisional wound gape from 135 +/- 56 microns on day 0 to 245 +/- 88 microns on day 7 at a distance of 2.4 mm from the optical zone. Starting at day 14 and continuing to day 30, there was a progressive decrease in incisional wound gape from 198 +/- 41 microns to 92 +/- 35 microns. Sequential, in vivo histopathologic analyses indicated that increasing incisional wound gape correlated with the retention of corneal epithelium in the wound. Initiation of decreasing incisional wound gape was associated with replacement of the incisional epithelial plug with fibroblastic tissue. These changes in the incisional wound gape observed in the cat suggest that healing of radial keratotomy wounds involves contraction of the wound in response to the ingrowth of fibroblastic cells. Furthermore, the contractile response appears to be biphasic involving a precontractile and contractile phase. Overall these data indicated that in vivo confocal microscopy provides quantitative histopathologic data on living tissue comparable with that obtained with conventional techniques on dead, fixed, and sectioned tissue. Additionally, the absence of wound fibrosis in the rabbit radial keratotomy model raises important questions as to the appropriateness of this experimental model for human radial keratotomy.

Animals↗
PubMed1991

The binding of prototype lexitropsins to the minor groove of DNA: quantum chemical studies.

Ab initio calculations (Hartree-Fock) using the 6-31 G basis set have been performed on two prototype lexitropsins or information-reading molecules. The latter are DNA minor groove binding agents related to the A.T recognizing netropsin in which each of the two N-methylpyrrole moieties is replaced in turn by 1-methylimidazole and which thereby confers the property of recognizing G.C sites.Ab initio treatment was possible by examining composities of separate non-conjugated segments of the molecules. Geometry optimized conformations, energies and distribution of electrostatic charges within the molecules were derived. The ab initio derived parameters of the geometry optimized conformations of these lexitropsins were used to interpret their interaction with different sequences within the minor groove of B-DNA.

Base Sequence↗
PubMed1991

[Effect of Tibetan drug Arenavia kansuensis Maxim. var. ovatipetala Tsui on inflammation and immunological function].

It has been found that the Tibetan drug Arenaria kansuensis has significant inhibitory action on edema in the ears of mice induced by cotton oil and granuloma, on acute inflammation in the form of swollen feet of rats induced by albumen injection and carrageenan, on phagocytosis of histiocytes in the abdomen of mice, and on the formation of antibody (serum HC50). Being low in toxicity, the drug is conducive to the smooth functioning of the liver and kidney.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1987

Function of the diabetic retina after panretinal argon laser coagulation.

Panretinal photocoagulation has been demonstrated to have a beneficial effect on the natural history of diabetic retinopathy. However, it is associated with detectable loss of retinal function. To determine the best coagulation technique we conducted a prospective study in 32 eyes of 16 patients. We investigated retinal function in relation to spot size and scatter density after panretinal laser coagulation. One eye was treated with approximately 400 comparatively large laser spots (0.6-0.8 mm diameter), whereas the fellow eye was coagulated with approximately 1500 small spots (0.2-0.4 mm diameter), so that the total coagulated area was almost the same in both eyes. Subjective parameters (visual acuity, perimetry, dark adaptation, photostress), as well as objective functions (electroretinogram, ERG; electro-oculogram, EOG), were studied preoperatively and then postoperatively over a time span of 6 months. Pronounced impairment of retinal function was detected, which recovered after 3 months on the average. When the pairs of eyes were compared, persistent visual field scotomas as detected by computerized static perimetry, occurred less frequently in eyes subjected to small coagulation spots, although this tendency was not statistically significant.

Adult↗
PubMedDate not supplied

Studies on silica-bonded monoclonal antibody packing material for separation of recombinant interferon by high performance immunoaffinity chromatography.

A method for the preparation of a new packing material for high performance liquid chromatography by bonding an anti-interferon monoclonal antibody to the surface of silica gel is described. The high coupling efficiency and activity of the interferon-alpha A-monoclonal antibody (IFN-alpha A-McAb) column were obtained by activated diol-silica gel with an activating agent. After purification with this packing material, the specific activity of recombinant human interferon-alpha A rose by up to 1.03 x 10(7)IU/mg protein and the purification efficiency was increased by approximately 100 times.

Antibodies, Monoclonal↗
PubMedDate not supplied

The action of carboxyl modifying reagents on the ryanodine receptor/Ca2+ release channel of skeletal muscle sarcoplasmic reticulum.

In this work we show that ryanodine binding to junctional sarcoplasmic reticulum (SR) membranes or purified ryanodine receptor (RyR) is inhibited in a time- and concentration-dependent fashion by prior treatment with the carboxyl reagent dicyclohexylcarbodiimide (DCCD). Exposure of the membrane-bound RyR to the water soluble carboxyl reagents 1-ethyl-3 (3-(dimethylamino) propyl carbodiimide (EDC) or N-ethyl-pheny-lisoxazolium-3'-sulfonate (WRK) only slightly affects their ryanodine binding capacity. The amphipathic reagent N-ethoxy cabonyl-2-ethoxy-1,2-dihydroquinaline (EEDQ) inhibited ryanodine binding at relatively high concentrations. DCCD-modification of the SR decreased the binding affinities of the RyR for ryanodine and Ca2+ by about 3- and 18-fold, respectively. The single channel activity of SR membranes modified with DCCD and then incorporated into planar lipid bilayers is very low (5-8%) in comparison to control membranes. Application of DCCD to either the myoplasmic (cis) or luminal (trans) side of the reconstituted unmodified channels resulted in complete inhibition of their single channel activities. Similar results were obtained with the water soluble reagent WRK applied to the myoplasmic, but not to the luminal side. The DCCD-modified non-active channel is re-activated by addition of ryanodine in the presence of 250 microM Ca2+ and is stabilized in a sub-conductance state. With caffeine, ryanodine re-activated the channel in the presence of 100 microM of Ca2+. The results suggest that a carboxyl residue(s) in the RyR is involved either in the binding of Ca2+, or in conformational changes that are produced by Ca2+ binding, and are required for the binding of ryanodine and the opening of the Ca2+ release channel.

Animals↗
PubMedDate not supplied

Historical demography in China: review and perspective.

"This paper argues that the development of historical demography in China will not only contribute greatly to our understanding of the particular population and social development dynamics in China, but will also enhance our understanding of the role of population for social and economic development in general.... After a review of the recent development of population studies in China, this paper will review the current state of Chinese historical demography and examine some research issues and data sources which can help broaden the horizons of population research in China."

Asia↗
PubMedDate not supplied

Characterization of Haemophilus paragallinarum isolates from China.

The biochemical and serological properties of 11 isolates of Haemophilus paragallinarum from outbreaks of infectious coryza in the People's Republic of China are described. All 11 isolates had the typical biochemical properties of H. paragallinarum, and all belonged to Page serovar A.

Animals↗