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Biomedical subjects

L Meng

Publications and source records attributed to L Meng.

At least 73 records · Page 4Linked to original sources
PubMed1998

Dietary soy intake and urinary isoflavone excretion among women from a multiethnic population.

Isoflavones are present in soybeans and its products in concentrations up to 300 mg/100 g, have estrogenic and antiestrogenic properties, and may be protective against hormone-related cancers. The purpose of this cross-sectional study was to investigate the association between urinary isoflavone excretion and self-reported soy intake. A total of 102 women of Caucasian, Native Hawaiian, Chinese, Japanese, and Filipino ancestry completed a dietary questionnaire for soy products consumed during the last year and during the 24-h period before urine collection. Overnight urine samples were analyzed for coumestrol and the soy isoflavones genistein, daidzein, and glycitein and their main human metabolites by reverse-phase high-pressure liquid chromatography. Soy protein and isoflavone intake (predominantly from tofu) were estimated using published nutritional databases. Wilcoxon's rank-sum test scores and Spearman rank correlation coefficients were computed. Japanese women excreted more daidzein, genistein, and glycitein than did Caucasian women, whereas Caucasian women excreted slightly more coumestrol. Soy intake differed significantly among ethnic groups. Dietary soy protein and isoflavone intakes during the previous 24 h were positively related to urinary isoflavone excretion [rs = 0.61 (P < 0.0001) and 0.62 (P < 0.0001), respectively]. Urinary excretion of isoflavones was also related to annual dietary soy protein and isoflavone intake [rs = 0.32 (P < 0.0012) and 0.31 (P < 0.0016), respectively]. The strong correlation between urinary isoflavone excretion and self-reported soy intake validates the dietary history questionnaire that is now used in a study exploring dietary risk factors for breast cancer.

Adult↗
PubMed1998

Alcohol intake, body weight, and mortality in a multiethnic prospective cohort.

The purpose of this analysis was to investigate the effects of alcohol intake and body weight on mortality from all causes, cancer, and cerebrovascular and coronary heart disease. A cohort of more than 40,000 persons with Caucasian, Chinese, Filipino, Japanese, and native Hawaiian ethnicity was followed for close to 20 years. We calculated mortality rates using the person-years at risk for each gender and ethnic group as denominators. We used proportional hazards regression models to adjust for confounding variables and to estimate relative risks. Men and women with low alcohol intake (1-7 drinks per week) experienced a 20% reduction in total mortality. At higher levels of alcohol intake, women and Asian men experienced no mortality benefit. The protective effect of alcohol consumption was limited to coronary heart disease mortality. The relation between body mass index and total mortality was J-shaped for all groups. In agreement with previous reports, this study found that persons with moderate alcohol intake appear to have a lower risk of dying than nondrinkers, but the possible protective levels of alcohol for women and Asian men appear to be lower than for Caucasian men.

Adult↗
PubMed1997

The anti-angiogenic agent fumagillin covalently binds and inhibits the methionine aminopeptidase, MetAP-2.

The inhibition of new blood vessel formation (angiogenesis) is an effective means of limiting both the size and metastasis of solid tumors. The leading anti-angiogenic compound, TNP-470, has proven to be effective in in vitro and in animal model studies, and is currently being tested in phase III antitumor clinical trials. Despite many detailed pharmacological studies, little is known of the molecular mode of action of TNP-470. Using a derivative of the TNP-470 parent compound, the fungal metabolite, fumagillin, we have purified a mammalian protein that is selectively and covalently bound by this natural product. This fumagillin binding protein was found to be a metalloprotease, methionine aminopeptidase (MetAP-2), that is highly conserved between human and Saccharomyces cerevisiae. In the absence of MetAP-1, a distantly related methionine aminopeptidase, MetAP-2 function is essential for vegetative growth in yeast. We demonstrate that fumagillin selectively inhibits the S. cerevisiae MetAP-2 protein in vivo. The binding is highly specific as judged by the failure of fumagillin to inhibit MetAP-1 in vivo. Hence, these results identify MetAP-2 as an important target of study in the analysis of the potent biological activities of fumagillin.

Amino Acid Sequence↗
PubMed1997

Effects of epidermal growth factor and follicle-stimulating hormone during in vitro maturation on cytoplasmic maturation of porcine oocytes.

The present study was undertaken to investigate the influence of epidermal growth factor (EGF) and follicle-stimulating hormone (FSH) during in vitro maturation on cytoplasmic maturation of porcine oocytes as revealed by the success of fertilization and by the changes in the pattern of protein synthesis in oocytes and cumulus cells. For fertilization studies, oocyte-cumulus cell complexes (OCC) were cultured in media containing human recombinant EGF (1 ng/ml) or FSH (1.5 microg/ml) or both for 44 hr prior to fertilization with fresh sperm for 6-8 hr. The oocytes were then fixed, stained, and examined as whole mounts following an additional 14 hr of culture. Addition of EGF, FSH, and EGF + FSH significantly increased the proportion of oocytes reaching MII stage. The addition of EGF alone significantly decreased the percentage of polyspermic oocytes and increased the proportion of monospermic oocytes forming 2 normal pronuclei. FSH abolished these effects of EGF and significantly increased the percentage of polyspermic oocytes forming more than 2 pronuclei when added alone or with EGF. For protein analysis, OCC were cultured in media containing the above hormones for 6, 24, and 44 hr and exposed to 0.5 mCi/ml L-[35S]methionine during the last 3 hr of cultures. The oocytes and cumulus cells were separated prior to lysis in SDS sample buffer, and denatured polypeptides were separated by 1-dimensional SDS-PAGE. In the oocyte, addition of EGF and FSH alone stimulated the synthesis of 34, 45, and 97 kDa proteins after 6 hr of culture; however, the addition of EGF and FSH together was without any effect. After 24 hr, EGF alone inhibited the synthesis of these peptides, whereas FSH alone and with EGF maintained the stimulation of synthesis of 34 and 45 kDa proteins. Two additional peptides corresponding to 66 and 200 kDa appeared at this time as a result of exposure to FSH alone or with EGF. After 44 hr of culture, these 2 new peptides were observed in all groups and the stimulatory effect of FSH and FSH + EGF was still evident. An additional peptide of 26 kDa appeared at this time as a result of FSH and EGF + FSH treatments. In the cumulus cells, EGF and FSH each alone induced the synthesis of a new peptide of 26 kDa after 6 hr of culture. FSH when added alone or with EGF induced the synthesis of an additional peptide of 29 kDa, the synthesis of which remained unchanged at 24 and 44 hr. After 24 hr, FSH alone and in combination with EGF induced the synthesis of an additional 38 kDa peptide and its synthesis was still maintained at 44 hr. EGF alone had no effect on protein synthesis in cumulus cells at 24 and 44 hr. These studies indicate that EGF may have a physiological role in the regulation of cytoplasmic maturation of porcine oocytes.

Animals↗
PubMed1997

Ethnicity and conditional breast cancer survival in Hawaii.

The conditional survival experience of 4502 female breast cancer cases diagnosed in Hawaii between 1960 and 1983 was studied. The calculation of conditional survival is based on patients who have already survived for a specified time period. Cox proportional hazards models were used to examine the effect of ethnicity, stage at diagnosis, and menopausal, marital, and socioeconomic statuses on conditional survival prognosis. Native Hawaiian and Filipino women showed a significantly higher risk of dying from breast cancer than any other ethnic group, followed by Chinese and Caucasian women, while Japanese women had the lowest risk. The ethnic pattern of breast cancer survival changed and ethnic survival differences decreased from 17 to 4% as time progressed. Conditional survival varied greatly with stage at first diagnosis. For localized, regional, and distant disease, the conditional survival rate increased from 92, 71, and 24% after diagnosis to 95, 85, and 65% 5 years after diagnosis, respectively, indicating that stage at diagnosis becomes less important in determining survival as time progresses. Being married and of a high socioeconomic status increased survival probability. These results suggest that considering time effect, the conditional survival rate is an informative tool to assess clinical outcome of breast cancer among ethnic groups over a long follow-up period.

Breast Neoplasms↗
PubMed1997

Sperm-induced oocyte activation in the rhesus monkey: nuclear and cytoplasmic changes following intracytoplasmic sperm injection.

Intracytoplasmic sperm injection (ICSI) has increased the potential of the assisted reproductive technologies to propagate mammalian species and has provided an opportunity for research into cell cycle control and the mechanisms involved in sperm-induced oocyte activation. We have investigated the efficacy of ICSI in the rhesus monkey, the mechanism of fertilization following sperm injection and the cytoskeletal rearrangement that occurs upon oocyte activation. These studies were conducted on mature, and to a lesser extent, immature oocytes. Ejaculated spermatozoa, washed, capacitated and activated before immobilization, were injected into oocytes using conventional ICSI methodology. Sperm injection into mature oocytes induced oocyte activation (19/22; 86%) and pronuclear formation. In contrast, sham-injected oocytes did not activate readily (2/16; 13%). To localize oocyte activation factor(s), spermatozoa were separated mechanically into heads and tails which were then injected individually into mature oocytes. Activation occurred in 87% (20/23) of oocytes receiving heads. After tail injection, a single microtubule aster was nucleated and one pronucleus (PN) was seen in four of 21 oocytes. Intracytoplasmic injection of sperm extract (SE) resulted in oocyte activation at a significantly higher rate than occurred following sham injection (76 versus 13%). Sperm-induced oocyte activation was also evaluated in immature metaphase (MI) oocytes; activation occurred in 46% (12/26) of cases; however, only 8% of the activated oocytes exhibited 2 PN. Finally, beta-tubulin localization in untreated and taxol-treated oocytes was established as a marker for cytoplasmic changes associated with oocyte activation. These results are consistent with the hypothesis that spermatozoa contain an oocyte activating factor(s) which is primarily localized in the sperm head. Moreover, an activation response is limited to mature oocytes and is accompanied by cytoskeletal changes analogous to those seen following conventional fertilization.

Animals↗
PubMed1997

Ethnic differences and factors related to breast cancer survival in Hawaii.

BACKGROUND: Previous studies have described differences in breast cancer survival among women from various ethnic backgrounds even after adjustment for stage at diagnosis. The aim of this study is to identify factors that could explain this disparity in prognosis and to update breast cancer survival patterns in Hawaii. METHODS: The Hawaii Tumor Registry identified 3345 breast cancer cases diagnosed between 1980 and 1988. The following covariates were studied: ethnicity, stage at diagnosis, geographical residence, and menopausal, marital and socioeconomic statuses. The Kaplan-Meier method and proportional hazards regression were used to estimate survival by group. RESULTS: Native Hawaiian and Filipino women had a higher risk of dying within 5 years than women of other ethnic groups. Japanese had the highest survival probability, followed by Chinese and Caucasians. Stage was the most important prognostic factor. Married women had better survival than widowed and divorced women. Filipinos had a much greater chance of dying from localized cancer than other women with localized disease. Geographical residence, menopausal and socioeconomic statuses were not associated with survival. CONCLUSIONS: Despite an overall improvement in breast cancer survival, ethnic disparity in prognosis still exists. Other possible explanations for the differential prognosis, such as treatment, diet, genetics, obesity, oestrogen receptor and hormonal statuses need to be explored in future studies.

Adult↗
PubMed1997

Rhesus monkeys produced by nuclear transfer.

Genetically identical nonhuman primates can provide a powerful animal model for gene therapy and research activities where the physiological parameters directly or indirectly under study are heritable. Here we demonstrate that nuclear transfer is a viable technology for the production of identical rhesus macaques. Oocytes recovered from gonadotropin-treated females were enucleated by aspiration of the first polar body and underlying ooplasm, then activated by cycloheximide exposure. Individual diploid blastomeres, recovered from in vitro-fertilization-produced embryos (either fresh or frozen-thawed) and used as nuclear donors, were injected under the zona pellucida of enucleated (chromosome-free) oocytes and fused by electric pulses. The reconstituted embryos were cocultured on buffalo rat liver cells before cryostorage and transfer to synchronized host mothers. Of the 9 females receiving a total of 29 reconstituted embryos, 3 became pregnant, with two live births resulting, one male and one female. The parentage of both infants was established unequivocally by genotype analysis at 7 highly variable short tandem repeat loci.

Animals↗
PubMed1997

The mutual benefit role of liver and pancreas in combined transplantation.

The present study observed the mutual benefit role of liver and pancreas in combined hepaticopancreatic transplantation in rats. The results indicated that pancreas, when transplanted with liver, could survive for a significant long time (13.4 +/- 1.01 days) than it transplanted alone (9.2 +/- 1.14 days) (P < 0.05, t test). The interstitial rejection was mild and its rejection grade was significantly different from that of pancreas transplanted alone (P < 0.05, X2 test). The liver, when transplanted with pancreas, regenerated with strong competence and contact structure morphologically compared with liver transplanted alone. We think that pancreas could be immunologically protected against rejection and liver can be nutritionalized by pancreas in combined liver and pancreas transplantation.

Animals↗
PubMed1997

[Purification and behavior of recombinant human gamma-interferon on reversed-phase high performance liquid chromatography].

A high performance liquid chromatographic system is described for the purification to homogeneity of recombinant human gamma-interferon (gamma-IFN) from the inclusion bodies produced in genetically transformed Escherichia Coli cells. Crude products of gamma-IFN obtained from typical preparative liquid chromatographic separation on Sephacryl S200 column was applied to analytical HPLC with RP-C18 column and eluted with convex gradient of 0-82% acetonitrile in 30 min followed by linear gradient of 82%-100% in 30 min. A constant level of 0.1% trifluoroacetic acid was maintained throughout the gradient process. The retention of gamma-IFN was investigated as a function of pH, temperature as well as concentration of salt in the mobile phase. For denatured and renatured gamma-IFN the chromatographic profiles were analyzed under various conditions. The retention time of renatured gamma-IFN was compared with that of denatured gamma-IFN and a significant difference in the retention time of profiles was observed. Both biological activities were reduced to different degree followed with incorrect disulfide bond gamma-IFN or oligomer gamma-IFN. The purified gamma-IFN has a specific activity about 6 x 10(6) units/mL. The eluats were assayed for identification of gamma-IFN using Enzyme-Linked Immunosorbent Assays (ELISA). Its molecular weight was 17.5 kD, as determined by SDS-PAGE. The results support that renatured sample with tR = 24.8 min and denatured one with tR = 30.1 min were identical protein with different conformation. The chromatographic behavior is explained by the change in net charge and polarity of gamma-IFN when the mobile phase condition and the conformation vary. The oligomer or incorrect disulfide bonds were formed during gamma-IFN renaturation and also the biological activity was found to be native conformation dependent.

Chromatography, High Pressure Liquid↗
PubMed1997

Mammography screening and the increase in breast cancer incidence in Hawaii.

This ecological study investigated the association between mammography utilization and breast cancer incidence in Hawaii with the hypothesis that geographic areas with high mammography use have higher breast cancer incidence than geographic areas with low mammography use. Insurance claims for mammograms received during 1992 and 1993 were combined with breast cancer incidence data from the Hawaii Tumor Registry and data from the 1990 Census ZIP File. The claims data were obtained from four private and three public health plans and covered approximately 85% of women 40 years of age and older. Age-specific breast cancer incidence rates for the 79 ZIP code areas were regressed on mammography rates and selected aggregate demographic variables using multiple linear regression. An estimated 42% of women 40 years of age and older had received at least 1 mammogram during 1992 and 1993, with the highest rate (45%) in women ages 50-64 years old. Overall, 23% of the variation in age-specific breast cancer incidence could be predicted by mammography utilization, 23% by increasing age, and 4% by higher education. The relationship between mammography use and breast cancer incidence was strongest for women 50-64 years old and for localized disease. The magnitude of the association between breast cancer incidence and mammography utilization was comparable to the increase in breast cancer rates observed in Hawaii during the mid-1980s, supporting the hypothesis that the sharp increase in breast cancer incidence was attributable to screening and early detection. However, the long-term 1% increase in breast cancer incidence requires alternate explanations.

Adult↗
PubMed1997

[Construction, expression and activity of a single chain antibody to gastric cancer cells].

OBJECTIVE: To construct single chain antibody from McAb 3H11, which has been successfully used in clinical radioimmunoimage, for its widel application in biological treatment of human cancer. METHOD: Reversetranscription and polymerize chain reaction (RT-PCR) were used to clone the V region genes of McAb 3H11 (VH, VL). The cloned VH and VL were sequenced and recombined through a (Gly4Ser) 3 linker. The constructed single chain antibody gene was joined with glutathione-S-transferase gene (gst) and its fusion proteins (GS3H11) were expressed in E. coli. The activity of GS3H11 was characterized with competition experiments after its denature and renature treatment. RESULTS: The recombinant GS3H11 was highly produced in inclusion bodies and the activity was recovered after being renatured. The competition experiments showed that GS3H11 could competitively inhibit the McAb 3H11 binding to gastric tumor cells MGC803. The inhibition was complete when the molecular ratio of GS3H11 to McAb 3H11 reached to 30:1. However, the GS3H11 did not interfere in binding of McAb PD4 and 3G9 to MGC803. CONCLUSION: The specific binding activity of McAb 3H11 is retained in single chain antibody which is potentially useful for therapeutic application.

Antibodies, Monoclonal↗
PubMed1996

Amphetamine releases dopamine from synaptic vesicles by dual mechanisms.

Low concentrations of D-amphetamine (AMPH) released [3H]dopamine (DA) from purified, rat brain synaptic vesicles with exponential kinetics and a half-time of 4 min. Slight alkalinization of the vesicles by AMPH seemed unable to account for this release. Instead, it is likely that AMPH partially inhibits DA uptake after which DA escapes by an uptake-independent pathway. At high concentrations the proton gradient was severely reduced by AMPH and DA was released with a half-time of < 1 min. Loss of the proton gradient was sufficient to account for this DA release. These results show that low concentrations of AMPH release DA from synaptic vesicles and suggest that release occurs by different mechanisms at low and high AMPH concentrations.

Amphetamine↗
PubMed1996

Role of germinal vesicle on protein synthesis in rat oocyte during in vitro maturation.

To investigate the role of the germinal vesicle (GV) on in vitro maturation (IVM) of rat oocytes, we examined protein synthesis during IVM by comparing polypeptide patterns in control and enucleated oocytes using one and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Separation of polypeptides extracted from the cytoplasm of GV by one-dimensional SDS-PAGE revealed that a 55 kDa polypeptide was present only in the GVs of rat oocytes. At 0, 12, 24, 36, and 44 hr after PMSG injection, prior to the initiation of maturation, enucleated oocytes synthesized the same major polypeptides as cumulus intact (CI) oocytes. During meiotic maturation, no major changes were detected in protein synthesis from prophase (GV stage) to prometaphase I (0-6 hr IVM). However, after entry into prometaphase I (7 hr IVM), striking changes were seen; a 24 kDa polypeptide disappeared and expression of a 34 kDa polypeptide became stronger. This pattern lasted until metaphase II. We detected no major differences in the pattern of protein synthesis between CI and enucleated oocytes using two-dimensional PAGE. These results indicate that protein synthesis in the maturing rat oocyte is controlled by cytoplasmic regulators rather than intrinsic nuclear components.

Animals↗
PubMed1996

Detection of p53 gene abnormality by sequence analysis of archival paraffin tissue. A comparison with fresh-frozen specimens.

This parallel study was designed to compare the sensitivity and specificity of detection of point mutations in fresh-frozen and formalin-fixed, paraffin-embedded breast cancer tissue. Sequence analysis of exon 5 of p53 gene was performed on polymerase chain reaction-amplified DNA from 25 infiltrating ductal carcinomas of the breast. Four tumor showed mutations with identical base substitutions in their respective codons of both frozen and paraffin-embedded specimens. We conclude that subtle genetic alterations can be detected in archival paraffin tissue with an accuracy comparable to that of fresh-frozen histologic samples.

Breast Neoplasms↗
PubMed1996

[Data analysis on the causes of death through disease surveillance program in Gansu province in the early 1990's].

In order to observe the changes of the causes of death among the residents in Gansu, mortality and years of porential life lost (YPLL) are used in this article to analyse the data of causes of death in 1990-1994. Data indicates that the average mortality of residents was 591.98 per 100,000. The main sequence were as below: respiratory diseases, cardiorasculor and cerebrovascalar diseases, neoplasms, injuries and pediatric diseases. Chronic diseases take up 74.4% of an mortalities. Average YPLL was 55.84/1000. YPLL sequence was as follows: injuries, neoplasms, respiratory system diseases, infectious diseases, cardiorascular diseases.

Accidents↗
PubMed1995

Hybridization of DNA targets to glass-tethered oligonucleotide probes.

Hybridization of nucleic acids to surface-tethered oligonucleotide probes has numerous potential applications in genome mapping and DNA sequence analysis. In this article, we describe a simple standard protocol for routine preparation of terminal amine-derivatized 9-mer oligonucleotide arrays on ordinary microscope slides and hybridization conditions with DNA target strands of up to several hundred bases in length with good discrimination against mismatches. Additional linker arms separating the glass surface from the probe sequence are not necessary. The technique described here offers a powerful tool for the detection of specific genetic mutations.

Base Sequence↗