Search PubMed⌕ Search

Biomedical subjects

W Li

Publications and source records attributed to W Li.

At least 757 records · Page 42Linked to original sources
PubMed1998

Recent declines in New York City infant mortality rates.

BACKGROUND: Although infant mortality rates have declined gradually in New York City for many years, the rate of that decline began to accelerate dramatically at the end of the 1980s. OBJECTIVE: To analyze the recent accelerated decline in infant mortality for three race/ethnicity designations in New York City and to investigate whether shifts in birth weight distribution or changes in birth weight-specific death rates were more important in determining these declines between 1988 to 1989 and 1992 to 1993. METHODS: Two complete cohorts of linked birth-death certificate files consisting of all live births in New York City in 1988 to 1989 and 1992 to 1993 were examined. For each cohort, separate multinomial logistic regressions were estimated by race/ethnicity to analyze the probability of a neonatal or postneonatal death relative to survival as a function of a spectrum of covariates. The coefficients from these regressions were used to construct direct and indirect standardization exercises to predict changes in infant mortality holding characteristics of the cohort, including birth weight distribution, constant over time, or holding the influence of determinants, including birth weight-specific death rates, constant over time. RESULTS: For whites, Hispanics, and blacks, infant mortality rates declined by 27.4%, 24.8%, and 22.7%, respectively, between 1988 to 1989 and 1992 to 1993. For whites and blacks, the largest decreases occurred for neonatal mortality rates, whereas for Hispanics, postneonatal rates fell the greatest. Although infant mortality rates among very low birth weight infants (<1500 g) fell by 27.8%, 19.3%, and 16.6% for whites, Hispanics, and blacks, the greatest decreases in rates were seen among normal birth weight infants (>2500 g). Infant mortality rate declines for this category of infants reached 31%, 31.7%, and 31.3%, respectively, for whites, Hispanics, and blacks. Direct and indirect standardization exercises indicated that the most important factor in determining these declines were decreases in birth weight-specific death rates, not improvements in the birth weight distribution over time. CONCLUSIONS: We conclude that the large decreases in infant mortality rates witnessed in New York City between 1988 to 1989 and 1992 to 1993 were attributable not to improvements in birth weight distribution of the population but to declines in birth weight-specific death rates and that normal birth weight infants showed the greatest improvement.

Black or African American↗
PubMed1998

Electromyographic investigation of masticatory muscles in unilateral cleft lip and palate patients with anterior crossbite.

OBJECTIVE: To evaluate the characteristics of masticatory muscle activity in operated unilateral cleft lip and palate (UCLP) patients with anterior crossbite compared with normal individuals. SUBJECTS: Sixteen male and 13 female Chinese patients with UCLP and anterior crossbite. Fifteen male and 13 female Chinese individuals without cleft abnormalities served as a control group. DESIGN: Electromyographic activity of the masseter muscles and anterior temporalis muscles was recorded bilaterally in different mandibular positions using bipolar surface electrodes. RESULTS: Compared to noncleft controls, patients with UCLP demonstrated (1) higher activation levels of masseter and temporalis muscles in the rest position, (2) lower potential function of masseter and temporalis, (3) inharmonious activity of the masticatory muscles during mandibular border movement, (4) a higher asymmetry index of the masseter and temporalis muscles, and (5) longer silent periods of the two muscles. CONCLUSIONS: The function of masticatory muscles is different in patients with UCLP with anterior crossbite. Muscle function should be considered when evaluating cleft patients for orthodontic treatment and orthognathic surgery.

Action Potentials↗
PubMed1998

Primary culture and characterization of enamel organ epithelial cells.

The cells of the enamel organ are programmed by signals such as growth factors and extracellular matrix components to differentiate and form dental enamel. To study how the enamel organ epithelial cells control enamel development, we have begun to characterize a primary porcine enamel organ epithelial cell culture system. The unerupted molars of 3 month old pigs were isolated, the cells were digested into a single cell suspension and grown in media either with or without serum. Expression of amelogenin and ameloblastin mRNA was monitored by RT PCR, and protein secretion was identified by immunohistochemistry. Cells grown in MEM formed a mixed cell population of epithelial- and fibroblast-like cells which grew past confluence, formed nodules, mineralized, and expressed low levels of amelogenin and ameloblastin protein. In LHC-9 media, which is selective for epithelial cells, the cells did not grow past confluence but secreted amelogenin and ameloblastin proteins more strongly. Cell viability was maintained in both serum-free and serum-containing media. However, in the serum-free media, cell proliferation proceeded slowly. Although cells grown in MEM mineralized, the mixed cell population may make studies of specific ameloblast-like cells more difficult. However, cells grown in a culture media selective for epithelial cells will require modifications such as cell immortalization to allow long term studies of cell regulation and interaction. In summary, we have established an enamel organ epithelial cell culture system which will enable us to study the role of ameloblasts in enamel matrix formation, ameloblast regulation, as well as cell-matrix interactions. Selection of specific culture conditions will depend on the questions being addressed in individual studies.

Ameloblasts↗
PubMed1998

A kinase-defective transforming growth factor-beta receptor type II is a dominant-negative regulator for human breast carcinoma MCF-7 cells.

The role of transforming growth factor (TGF)-beta type II receptor (T beta RII) in TGF-beta resistance and tumor progression is now well recognized. To test the effects of T beta RII loss in determining malignancy, we transfected a T beta RII-expressing, TGF-beta-sensitive, MCF-7 cell strain (ME24) with a tetracycline-repressible truncated T beta RII (kdT beta RII) construct lacking the cytoplasmic domain of the receptor. Transfection of kdT beta RII into parental ME24 cells (designated ME24t6 after transfection) resulted in high expression levels of kdT beta RII mRNA and cell surface protein which were reversible by tetracycline treatment. ME24t6 cells did not respond to exogenous TGF-beta 1 as measured by inhibition of proliferation or fibronectin (FN) induction, indicating that the truncated T beta RII acted as a dominant-negative inhibitor of both the growth inhibitory and extracellular matrix (ECM) stimulatory TGF-beta effects. Furthermore, inhibition of kdT beta RII expression by tetracycline treatment led to TGF-beta 1-mediated cell growth arrest in the G1 phase of cell cycle and to the accumulation of the hypophosphorylated form of retinoblastoma (Rb) protein. However, compared to parental ME24 cells, transfectants failed to show increased tumorigenicity, indicating that loss of T beta RII itself is not sufficient to account for differences in the malignant properties of T beta RII-expressing and non-expressing MCF-7 cell strains.

Adenocarcinoma↗
PubMed1998

Antibiotic activities and affinities for bacterial cell wall analogue of N-demethylvancomycin and its derivatives.

N-Demethylvancomycin, which has been clinically used in China, is one member of vancomycin group (glycopeptide) antibiotics. It differs from vancomycin only in that methyl group on the amino group of the N-terminal residue of vancomycin has been replaced by H. By reductive alkylation of N-demethylvancomycin, we synthesized N-alkyl and N,N'-dialkyl N-demethylvancomycins, which closely correlated with vancomycin in structure. The association constants of the complexes of N-demethylvancomycin and its analogues with di-N-Ac-L-Lys-D-Ala-D-Ala and the antibiotic activity against Staphylococcus aureus of the glycopeptides were determined. Results showed that N-demethylvancomycin has higher affinity for bacterial cell wall analogue di-N-Ac-L-Lys-D-Ala-D-Ala and more potent antibiotic activity against Staphylococcus aureus than vancomycin. Both N-alkylation and N,N'-dialkylation of N-demethylvancomycin reduced the affinity and antibiotic activity. The longer the alkyl groups, the less potent antibiotic activities and lower affinities have the glycopeptides. The antibiotic activities against Staphylococcus aureus of N-demethylvancomycin and its analogues roughly parallel their affinities for di-N-Ac-L-Lys-D-Ala-D-Ala.

Alkylation↗
PubMed1998

Blood flow assessment with intravascular ultrasound catheters: the ideal tool for simultaneous assessment of the coronary haemodynamics and vessel wall?

We present the potentials of a novel method of intracoronary flow visualization and quantification that is based on conventional intravascular ultrasound (IVUS) imaging catheters. The quantification of flow is obtained from analysis of the rate of decorrelation of digitized radiofrequency ultrasound echo signals. Flow information is superimposed on the IVUS image using a colour scale. Integration of the blood velocity components normal to the scan plane permits calculation of the volume flow. Validation using IVUS and electromagnetic (EM) flowmeter recordings were obtained in vivo from instrumented pigs. IVUS flow (IVUS(f)) compared favourably to EM flow (EM(f)): IVUS(f)=1.0 EM(f)+5.72 cc/min, r2=0.98. Clinical results for the first five patients investigated are reported. A Doppler wire was used to measure the flow in four coronary arteries and one renal artery in baseline and hyperaemia conditions. IVUS flow and derived coronary flow reserve (CFR) demonstrated a very good agreement with the data derived from the combination of quantitative angiography and velocity when measured with the Doppler wire (DOP(f)): IVUS(f)=1.01 DOP(f)-20 cc/min, r2=0.90 and IVUS(cfr)=1.03 DOP(cfr)-0.03, r2=0.93. This demonstrates that simultaneous morphological and physiological assessment of coronary or peripheral arteries with one IVUS catheter is feasible. This method should be very useful for the evaluation of intermediate coronary stenoses or the results of revascularization procedures.

Angina Pectoris↗
PubMed1998

Characteristics of transient outward K+ current in human atrial cardiomyocytes.

AIM: To study the properties of transient outward potassium current (Ito) in human atrial myocytes. METHODS: The patch-clamp whole-cell recording techniques were used. When the calcium inward current was blocked by CdCl2 (0.1 mmol.L-1), the transient outward potassium current (Ito) was recorded by depolarizing cells. RESULTS: The current was voltage dependent, it was activated quickly and inactivated rapidly too. 4-Aminopyridine (4-AP) 10 mmol.L-1 (a selective blocker of Ito) blocked the current completely. The IC50 (95% confidence limits) of 4-AP on Ito were 0.67 (0.58-0.80) mmol.L-1, 4-AP 1 mmol.L-1 shifted the activation curve of Ito to positive potential, therefore a higher membrane potential was required to activate Ito. CONCLUSION: Ito, a major K+ channel current in human atrial cells, is blocked by 4-AP.

4-Aminopyridine↗
PubMed1998

[The pathological action of surrounding connective tissues of alar cartilage in the cleft lip nose].

OBJECTIVE: This study was to explore the pathological action of the adjacent connective tissues of alar cartilage in unilateral cleft lip nose. METHODS: Anatomic-histological and pathoanatomical study was carried on 40 normal cadavers and 30 patients with secondary deformities of unilateral cleft lip during their operations. RESULTS: Six kinds of connective tissues with different histological features were found between the alar cartilage and adjacent skin, cartilage or bone. There was no histological difference in each connective tissue between the normal and the cleft lip nose. In the cleft lip nose, due to histological differences among the six connective tissues, there existed various changes of pathological dislocations between the alar cartilage and adjacent skin, cartilage or bone. CONCLUSION: The authors suggest that the surrounding connective tissues of the alar cartilage play an important role and be the intrinsic basis to produce the characteristic deformities of the cleft lip nose. The result is helpful in understanding the anatomical and histological features of the connective tissues around the alar cartilage and the deformities of the unilateral cleft lip nose so as to select a reasonable operation method.

Abnormalities, Multiple↗
PubMed1998

[Anatomic study of the musculus depressor septi nasi in unilateral cleft lip nasal deformity].

OBJECTIVE: This study was to investigate the nasal musculature and its relationship with the deformities of the unilateral cleft lip nose. METHOD: The anatomic and histological examination and comparison of the musculus depressor septi nasi (MDSN) were performed in 33 normal cadavers and 30 patients with unilateral cleft lip undergoing the operation for secondary nasal deformities. RESULT: It was found that the MDSN in the cleft side of a unilateral cleft lip nose is lacking. CONCLUSION: Because of the anatomic deficiency on the cleft side, the function of the normal side is pathologically increased. The functional imbalance between the normal and abnormal side may bring about dislocation and malformation of the base of nasal columella as well as the septal structures.

Abnormalities, Multiple↗
PubMed1998

[Determination of copper, zinc, iron and calcium in wheat and maize and three nitrogen compounds in high and low risk areas of esophageal cancer].

This study reports the concentrations of copper, zinc, iron and calcium in wheat and maize from high risk area Linzhou and low risk area Yuzhou of esophageal cancer and three nitrogen compounds of four types of drinking water in Linzhou. The results showed that the concentrations of zinc and calcium in wheat and maize from Linzhou were significantly lower than these from Yuzhou, the copper concentrations in grains were higher and the iron in maize was lower. The nitrate-N concentrations in four types of drinking water from Linzhou were below the national standard but the nitrite and NH3-N concentrations were higher than the national limits. The results suggest that the low concentrations of zinc, iron and calcium and high concentrations of copper in grains as well as the high concentrations of nitrite and NH3-N may be related to the etiology of esophageal cancer.

Calcium↗
PubMed1998

[Changes of cerebral blood flow during hypoxicischemic encephalopathy in newborn pigs].

This study was designed to explore the change of cerebral blood flow during hypoxic-ischemic encephalopathy (HIE). Sixteen newborn pigs were devided into four groups: the normal control, 15 minutes after HIE, 30 minutes after HIE and 60 minutes after HIE. The shapes of the cerebral blood vessels were obsessed by the prepared Chinese ink irrigation and the width and volume fraction of capillary were tested and analyzed by stereographic method respectively. The results showed the small blood vessels were interrupted with the passage of time. At the time of 60 minutes after HIE, capilaries almost disappeared from view, only a few ends of blood vessels in the sheap of a broken tree were seen. The width of capillaries and small veins became more and more narrow as time went on. The percentages of capillary volume fraction and small vein volume fraction became smaller and smaller (P < 0.05). These demonstrate that the fall of cerebral blood flow plays an important role in the development of HIE.

Animals↗
PubMed1998

[The changes and significance of the intensity of transcription of endothelial nitric oxide synthase-mRNA in placental tissue from cases of pregnancy induced hypertension].

OBJECTIVE: To determine the cause of decreasd expression of endothelial nitric oxide synthase (eNOS) in placental tissue from cases of pregnancy induced hypertension (PIH). METHODS: 9 placentae of normal pregnant women and 12 placentae of patients with PIH were studied. eNOS-mRNA was measured in placental tissue by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: (1) There was eNOS-mRNA in placental tissue of normal pregnancy as well as PIH cases. (2). The intensity of transcription of eNOS-mRNA in placental tissue of PIH cases decreased significantly when compared with that of normal pregnancy (P < 0.05). CONCLUSION: The decrease of the intensity of transcription of eNOS-mRNA in placental tissue of PIH patients may result in reduction of expression of eNOS in placental tissue of PIH.

Female↗
PubMed1998

[A computerized information system for gynecological patients].

OBJECTIVE: Clinical experiences in the fields of general gynecology, gynecological oncology and reproductive endocrinology had been accumulated over a long period of time. All of the recorded information was written on various kinds of sheets that could easily be damaged and lost with frequent reading. Statistical works were done manually. This is the situation may encountered by all of the hospitals in China, so a computerized information system for gynecological patients is eagerly needed. METHODS: The program was designed on the basis of Foxpro 2.6 for Windows. RESULTS: The interfaces were specially designed for every of 72 databases to be like the style of patient's records which can be easily operated with mouse pressing buttons. Some of the databases such as basal body temperature, metastasis of lymph nodes and classification of endometriosis were carefully designed. Because the program will be used in China, the interfaces were all in Chinese. A dictionary was used to simplify the importing of the data. When import, one can easily press the line with the appropriate meaning in the dictionary. A strong statistical function was attached to the program. With its friendly interface, statistical work can be done with ease. This system is capable of further development and fit into needs of various hospitals and departments. CONCLUSION: This program is very useful for clinical doctors as well as scientific research personnel. With the help of this program, efficacy of our medical work can be raised, clinical experiences can be summarized in time and the clinical level can thus be improved.

Female↗
PubMed1998

[Association of fragile histidine triad gene (FHIT) with susceptibility to esophageal cancer. A preliminary study].

OBJECTIVE: To identify loss of heterozygosity(LOH) and homozygous deletion on loci of fragile histidine triad gene(FHIT). METHODS: Gene regions have been detected in 73 pairs of esophageal cancer samples using microsatellite DNA markers. Deletions of FHIT cDNA on 14 fresh esophageal cancer(EC) samples and 2 EC cell lines were screened by RT-PCR and DNA sequencing. RESULTS: High frequency of LOH was detected on loci D3S1480, D3S1481, D3S1234. Of 14 esophageal cancer samples 9(64.3%) had deletions of the FHIT gene, 7 of them were deletions in exon 1-4, and 5 of them were deletions in exon 5-9, the coding region. The whole FHIT gene was found deleted in an EC cell line, EC8733. CONCLUSION: It is suggested that the FHIT gene may play an important role in the genesis of EC. However, further study is needed to ascertain whether FHIT gene is indeed an EC susceptibility gene.

Acid Anhydride Hydrolases↗