Search PubMed⌕ Search

Biomedical subjects

C Wang

Publications and source records attributed to C Wang.

At least 613 records · Page 34Linked to original sources
PubMed1998

The comparative trial of TCu 380A IUD and progesterone-releasing vaginal ring used by lactating women.

The objective of this paper was to compare the efficacy, acceptability, safety, and bleeding pattern of TCu 380A intrauterine device (IUD) and progesterone-releasing vaginal ring used by breastfeeding women. The study population included 97 breastfeeding women using IUD and 100 women using vaginal ring. Of the IUD users, no insertion failure, perforation, or accidental pregnancy occurred in 12 months. There was one IUD expulsion. There were no discontinuations of IUD due to medical reasons other than expulsion. The total discontinuation rate was 2.3%. In the ring group, no accidental pregnancy occurred. The major reasons for discontinuation were ring use-related problems and vaginal problems. The total discontinuation rate was 65.4% within 1 year. The frequency of any one complaint among the ring users was higher than that among the IUD users. There were no differences in the proportion of women having no sexual activity and in the weight of their babies between the two groups. Compared with the IUD users, the median number of bleeding/spotting (B/S) episodes and B/S days of the vaginal ring users were fewer; consequently, the mean length of B/S-free interval was longer in all four reference periods; the mean length of B/S episode and segment were the same; the occurrence of amenorrhea was more frequent; in contrast, the proportions of normal bleeding patterns were fewer. The frequencies of prolonged bleeding, frequent bleeding, and infrequent bleeding patterns did not differ between the two groups. The percentage of irregular bleeding was fewer only in the first two reference periods. It is concluded that the TCu 380A IUD and progesterone-releasing vaginal ring used by breastfeeding women are safe and effective. The higher discontinuation rate of the ring users was mainly because of use-related problems. Breastfeeding women with TCu 380A IUD had better tolerance and acceptability. The TCu 380A IUD does not, but the progesterone-releasing vaginal ring does, suppress the recovery of ovarian function. However, once return of menstruation occurred, there were no differences in bleeding patterns between the two contraceptive methods.

Administration, Intravaginal↗
PubMed1998

Regulation of synaptic vesicle recycling by calcium and serotonin.

Serotonin, a neuromodulator at the crayfish neuromuscular junction, regulates neurotransmission without changing intracellular calcium levels. However, the mechanism of this regulation remains unclear. By analysis of synaptic depression using a depletion model and measurement of vesicle recycling using the styryl dye FM1-43, we show that serotonin increases the number of vesicles available for transmitter release (total synaptic vesicle pool size). This regulation is due either to an increase in the number of vesicles at each release site or to an activation of previously nonsecreting or silent synapses. We also observed that low calcium medium rendered part of the vesicle pool unavailable for release. These results suggest a new mechanism for regulating synaptic transmission.

Animals↗
PubMed1998

Dihydrotestosterone: a rationale for its use as a non-aromatizable androgen replacement therapeutic agent.

Testosterone therapy is commonly used to treat male hypogonadism, androgen deficiency of severe illness, androgen deficiency of ageing and microphallus in infancy. The effects of testosterone are mediated directly as testosterone or after conversion to either dihydrotestosterone (DHT) or oestradiol. DHT is a potent androgen and cannot be aromatized to oestrogens, therefore acting as a pure androgen. DHT has been proposed as an androgen replacement therapy, with possible advantages over testosterone in certain circumstances in the ageing population as well as in patients with gynaecomastia and microphallus. A potential advantage of DHT over testosterone as an androgen replacement therapy is the reported and seemingly paradoxically muted effects of DHT on prostate growth. The decreased effect of DHT compared with testosterone on the prostate gland of humans may be due to the decrease in intraprostatic oestradiol levels. The potential beneficial effect of less prostate growth after DHT requires substantiation and, if true, must be balanced against any negative effects that might occur on bone, lipids and sexuality when a pure androgen replaces treatment with an aromatizable androgen.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1998

Odontogenic tumors. A demographic study of 759 cases in a Chinese population.

Seven hundred fifty-nine cases of odontogenic tumors retrieved from the files of College of Stomatology, West China University of Medical Sciences were classified according to the World Health Organization's Histological Classification of Odontogenic Tumors and compared with similar reports from other countries. Among these cases, 93.9% of the tumors were benign and 6.1% were malignant. Ameloblastomas predominated (58.6%) with a predilection for the mandible, while odontomas, generally regarded as the most frequent odontogenic tumor in North America, only accounted for 6.7%, the fourth most common tumor in this series. The mandible and the maxilla were divided into eight anatomic regions, and the distribution of each odontogenic tumor type amongst these regions was recorded. The relative incidence of each tumor type, patient age and gender were also compared with data from other selected large series. Geographic differences were noted in the relative incidence of ameloblastoma, odontoma and malignant odontogenic tumors among the Chinese/African, North American and Turkish/German groups. Ameloblastoma and malignant odontogenic tumors are not considered rare in a Chinese population.

Adolescent↗
PubMed1998

Paradoxical early immune activation during acceptance of liver allografts compared with rejection of skin grafts in a rat model of transplantation.

Liver allografts in many animal models are often spontaneously accepted across a complete histocompatibility barrier without requirement for immunosuppression. In contrast, skin allografts are usually rejected, even across minor histocompatibility barriers. To identify the mechanism of liver allograft acceptance we have compared skin rejection with liver acceptance in DA rat strain recipients of PVG donors, a major histocompatibility complex (MHC) class I plus II mismatch. In spite of the established role of draining lymph nodes (LN) in induction of rejection of skin allografts, there was much greater involvement of LN after liver than after skin transplantation. Few donor cells migrated to these organs from transplanted skin but many cells migrated from transplanted liver. There was also a paradoxical increase in interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) mRNA in LN and spleen of liver allograft recipients that greatly exceeded their expression in skin allograft recipients. For example, there were 2. 7+/-1.6x104 molecules of IFN-gamma per 106 molecules of beta-actin mRNA in the LN draining liver allografts 1 day after transplantation compared with 2.0+/-0.3x103 molecules/106 beta-actin in LN draining skin allografts and 8.1+/-1.8x102 molecules/106 beta-actin in LN draining skin isografts. Examination of the graft showed that infiltration and cytokine mRNA up-regulation occurred more slowly in the transplanted skin than in liver but progressed inexorably in skin grafts until rejection. These results show that liver acceptance is associated with a paradoxical marked early activation then subsequent decline of the immune response.

Animals↗
PubMed1998

Gossypol: reasons for its failure to be accepted as a safe, reversible male antifertility drug.

Following clinical trials conducted in China in the 1970s, gossypol was proposed as a drug for male contraceptive use. This review summarizes the extensive investigations on formal animal toxicology and on the recovery of fertility in men after stopping gossypol treatment which led to the decision by the Special Programme of Research, Development and Research Training in Human Reproduction (HRP) at the World Health Organization (WHO), that gossypol would not be acceptable as an antifertility drug. It is concluded that the assessment of gossypol reinforces the mandatory requirement that future contraceptive drugs must be developed by the established routes of appropriate animal toxicology and phased clinical studies.

Acetates↗
PubMed1998

Aging results in attenuated gonadotropin releasing hormone-luteinizing hormone axis responsiveness to glutamate receptor agonist N-methyl-D-aspartate.

Reproductive aging in the Brown Norway rat occurs because of testicular as well as hypothalamic-pituitary dysfunction. Excitatory amino acids (EAA) participate in the regulation of pulsatile secretion of hypothalamic GnRH and pituitary LH. In the present study, we studied the EAA-GnRH-LH axis for possible age-related alterations in prepubertal (35 days), young (3-4 months), middle-aged (12-13 months) and old (21-23 months) rats. In the first experiment, an intra-atrial cannula was implanted in rats of different ages to evaluate the pituitary response to small, physiological intravenous bolus administration of GnRH (0.5 or 1.0 nmol/100 g body weight). The results showed no age-related significant differences in in-vivo serum LH or FSH responsiveness to GnRH. In a second experiment, blood samples for the gonadotropins were withdrawn immediately before and 10 min after an iv injection of the glutamate receptor agonist N-methyl-D-aspartate (NMDA; 5 mg/kg, a dose that induces a physiological LH pulse in young rats). Administration of NMDA induced significant increases in LH and prolactin in all groups of animals (P<0.05) and a significant FSH response in young and middle-aged but not old rats. NMDA-induced LH, FSH and prolactin release was higher (P<0.05) in prepubertal rats than in all other age groups. Compared with young rats, NMDA-induced increase in plasma LH and prolactin was lower (P<0.05) in old rats. In the third experiment, to ascertain whether this reduced LH response to NMDA in old rats was exerted at the hypothalamic level, the effects of NMDA on GnRH release in vitro from preoptic area-medial basal hypothalamus (POA-MBH) fragments were compared among rats of different ages. GnRH efflux in response to NMDA was significantly attenuated with increasing age. GnRH release in vitro was higher in prepubertal and lower in old than in young rats (P<0.05). Lastly, we measured amino acid concentrations in hypothalamic tissue (POA-MBH fragments). Prepubertal rats had higher levels of glutamate and taurine than young rats. Significant reductions in glutamate and gamma-aminobutyric acid (GABA) levels were found in old compared to young rats. In conclusion, these results showed that the hypothalamic NMDA-GnRH-LH axis was altered in old rats. The decreased hypothalamic content of some of the EAA and the reduced responsiveness of GnRH neurons to NMDA (both in vivo and in vitro) may contribute to an altered LH pulsatile secretion observed in old rats.

Aging↗
PubMed1998

Preoperative autologous blood deposition in support of gynaecological repair procedures.

Autologous blood transfusion was evaluated in gynaecological repair procedures including abdominal/ vaginal hysterectomy with vaginal repair, post-hysterectomy vaginal suspension and fixation, uni/bilateral salpingo-oophorectomy with vaginal colpopexy and sling procedures. A total of 247 autologous units were collected from 95 patients at the regional blood centre with 1-3 units (mean 2-6 units) deposition from each patient. One hundred and ninety of all collected units were transfused (collection/transfusion ratio = 1.3). Of these patients, 86 (90.5%) received autologous blood; 12 (13%) being transfused with 1 unit, 44 (46%) with 2 units and 30 (32%) with 3 units. Two of these patients received additional homologous blood. The average preoperative haemoglobin level was 119 g L-1 and average post-operative haemoglobin level was 105 gL-1. The post-operative Hb level was used as a retrospective indicator for the requirement for blood transfusion. The results show that overall 75% of patients had post-operative haemoglobin levels < or = 110 and 33% of patients with Hb levels < 100, respectively. These results suggest that preoperative autologous blood deposition may be appropriate in the patients undergoing reconstructive gynaecological repair procedures since there was a high rate of usage of autologous blood and low post-operative haemoglobin in a significant proportion of patients.

Adult↗
PubMed1998

Excitatory convergence of Y and non-Y channels onto single neurons in the anterior ectosylvian visual area of the cat.

Numerous functional and hodological studies of the anterior ectosylvian visual area (AEV) of the cerebral cortex of the cat suggest that this area plays an important role in processing information about visual motion. In the present study, in cats with selective conduction block of Y fibres in one optic nerve, we have examined the extent of the excitatory convergence of Y (presumed 'motion channel') and non-Y information channels on single neurons in AEV, as well as the contribution of the Y channel to the receptive field properties of AEV neurons. While in normal cats all neurons recorded from AEV were binocular, i.e. could be photically activated via either eye, in cats with selective conduction block of Y fibres in one optic nerve, a significant proportion (about 15%) of AEV cells could be photically activated only via the normal eye. In comparison to those in normal cats, the peak discharge rates of AEV neurons in the Y-blocked cats were drastically reduced not only when photic stimuli were presented via the Y-blocked eye, but also when they were presented via the normal eye. Selective block of Y input also resulted in a significant shift in velocity preferences towards the lower velocities. However, the direction selectivity indices of AEV neurons were not affected by selective Y block. Thus: (i) the responses of AEV neurons to a high velocity of motion are dependent on the integrity of the Y input; (ii) the 'spontaneous' (i.e. not photically evoked) discharges of Y retinal ganglion cells exert a facilitatory influence on the responses of AEV cells to photic stimuli; (iii) although the responses of AEV neurons are dominated by the Y inputs, AEV neurons also receive significant non-Y excitatory inputs; and (iv) the strong direction selectivity revealed in most AEV neurons does not dependent on the integrity of Y input.

Animals↗
PubMed1998

Effects of phytoestrogens on DNA synthesis in MCF-7 cells in the presence of estradiol or growth factors.

Phytoestrogen effects on estrogen action and tyrosine kinase activity have been proposed to contribute to cancer prevention. To study these mechanisms, a number of phytoestrogens and related compounds were evaluated for their effects on DNA synthesis (estimated by thymidine incorporation analysis) in estrogen-dependent MCF-7 cells in the presence of estradiol (E2), tamoxifen, insulin, or epidermal growth factor. We observed that 1) at 0.01-10 microM, genistein and coumestrol enhanced E2-induced DNA synthesis, as did 10 microM enterolactone. Chrysin at 1.0-10 microM and 10 microM luteolin or apigenin inhibited E2-induced DNA synthesis, as did all compounds at > 10 microM, 2) tamoxifen enhanced genistein-induced DNA synthesis but inhibited DNA synthesis induced by all other compounds, and 3) genistein enhanced insulin- and epidermal growth factor-induced DNA synthesis at 0.1-1.0 and 0.1-10 microM, respectively. At higher concentrations, inhibition was observed. Similar effects were seen with coumestrol. In conclusion, the effects of phytoestrogens in the presence of E2 or growth factors are concentration dependent and variable. At low concentrations, genistein and coumestrol significantly enhanced E2-induced and tyrosine kinase-mediated DNA synthesis; at high concentrations, inhibition was observed. Differing effects were observed with the other compounds. The variable effects of phytoestrogens on DNA synthesis must be considered when their roles in cancer prevention or treatment are evaluated.

4-Butyrolactone↗
PubMed1998

Magnetic starch microspheres in the MR imaging of hepatic metastases. A preclinical study in the nude rat.

PURPOSE: To evaluate reticular endothelial system-specific magnetic starch microspheres (MSM) as an i.v. contrast agent for MR imaging in a model of experimental liver metastases. MATERIAL AND METHODS: The study comprised 15 nude rats, 7 of which were carrying hepatic metastases from a human colonic cancer. The 15 rats were examined at 0.5 T using a T1-weighted spin-echo (SE) sequence and a gradient-echo sequence. The examinations were performed before and 15 min after the administration of accumulated doses of MSM at 0.25-2.5 mg Fe/kg b.w. The images were compared with corresponding serial liver specimens. RESULTS: A loss of liver signal intensity was obtained at all MSM dose levels. No metastases were detected in the pre-contrast images. The optimum detection rate of hepatic metastases was reached with the SE sequence at a dose of 1.0 mg Fe/kg b.w. MSM and the diameters of the smallest lesions depicted were 1 mm. However, in the SE sequence, the measured lesion-to-liver contrast and liver signal damping were highest at the largest dose, indicating a possible image degrading effect of MSM at high doses. Administration of MSM as a short bolus over 30 s resulted in congestion of the liver with dilatation of the hepatic veins. When MSM was instead injected slowly over 5 min, this adverse effect was not seen. CONCLUSION: The use of MSM dramatically increased the detection of experimental hepatic metastases.

Animals↗
PubMed1998

Effect of selective substitution of 5-bromocytosine on conformation of DNA triple helices.

Three triplex DNAs containing 5-bromocytosine[BrC] were studied by vibrational spectroscopy and molecular modelling. Firstly, three oligodeoxypyrimidines of 5'-(TC)3-T4-(BrCT)3 [CBrC], 5'-(TBrC)3-T4-(CT)3 [BrCC] and 5'-(TBrC)3-T4-(BrCT)3 [BrCBrC] were synthesized and then reacted with an oligodeoxypurine of 5'-(AG)3 at pH=4.5 in phosphate buffer respectively to form three comparative hairpin triplex named CY,YC and YY. The results of FT-Raman and IR revealed that YY is almost in A-like form, CY and YC are combinations of A-like form and B-like form, but A-form dominates in CY while B-form is equivalent as A-form in YC. The result is consistent with the theoretical analysis.

Cytosine↗
PubMed1998

Myelopathy secondary to spinal epidural abscess: case reports and a review.

Spinal epidural abscess (SEA) is a rare disease with an unknown incidence rate. This paper will illustrate that early diagnosis and rehabilitation may result in improved outcomes for patients with neck or back pain presenting with neurological deficits. Three cases of SEA in individuals without the commonly acknowledged risk factors of intravenous drug abuse (IVDA), invasive procedures, or immunosuppression were seen at our institution during a 10-month period between October 1995 and July 1996. The patients presented with neck or thoracic back pain and progressive neurological deficits without a febrile illness. Predisposing factors were thought to be urinary tract infection with underlying untreated diabetes mellitus in the first case, a history of recurrent skin infection in the second, and alcoholism without a definite source of infection in the third. Leukocytosis, elevated sedimentation rate, and confirmatory findings reported on magnetic resonance imaging (MRI) led to the diagnosis of SEA in all three cases. Immediate surgical drainage and decompression followed by proper antibiotic treatment and early aggressive rehabilitation led to good functional outcomes. All the individuals became independent in activities of daily living, wheelchair mobility, and bowel and bladder management. Two eventually became ambulatory.

Abscess↗
PubMed1998

An observational study of hand washing and infection control practices by healthcare workers.

During a 6-week period, a medical student conducted an observational study of hand washing and infection control practices in a community teaching hospital. There was no difference in the prevalence of handwashing practices among the three work shifts. The prevalence of hand washing was higher in surgical (56.4%) and medical intensive-care units (39.2%) than in intermediate (30.0%) or general units (22.8%).

Gloves, Protective↗