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Biomedical subjects

W M Liu

Publications and source records attributed to W M Liu.

At least 19 recordsLinked to original sources
PubMed1992

Unusual sequences of two old, inactive human Alu repeats.

Two human Alu repeats terminating in an oligo(T) run rather than the usual A-rich 3' tail were isolated by library screening. Base sequence comparisons reveal that these unusual Alus are also exceptionally divergent from other Alu family members implying that they are evolutionarily old. Unlike other members of the family, they are not transcribed in vitro by RNA polymerase III (Pol III) suggesting a partial explanation for how Alu source genes might become inactive with age.

Base Sequence↗
PubMed1992

Phylogenetic evidence for multiple Alu source genes.

A member of the young PV Alu subfamily is detected in chimpanzee DNA showing that the PV subfamily is not specific to human DNA. This particular Alu is absent from the orthologous loci in both human and gorilla DNAs, indicating that PV subfamily members transposed within the chimpanzee lineage following the divergence of chimpanzee from both gorilla and human. These findings and previous reports describing the transpositional activity of other Alu sequences within the human, gorilla, and chimpanzee lineages provide phylogenetic evidence for the existence of multiple Alu source genes. Sequences surrounding this particular Alu resemble known transcriptional control elements associated with RNA polymerase III, suggesting a mechanism by which cis-acting elements might be acquired upon retrotransposition.

Animals↗
PubMed1992

Preliminary human trial of inactivated golden hamster kidney cell (GHKC) vaccine against haemorrhagic fever with renal syndrome (HFRS).

An inactivated golden hamster kidney cell culture (GHKC) vaccine against haemorrhagic fever with renal syndrome (HFRS) has been developed in recent years. A monovalent GHKC vaccine (lot 88-17) was prepared with L99 strain of the rat-type hantavirus, adapted in suckling mouse brain, cultivated in GHKC, and inactivated with 0.025% formalin, and a preliminary trial of the vaccine was carried out in a small number of human volunteers with the approval of the Ministry of Public Health, PRC, in order to identify safety and antibody response of the vaccine. Three inoculations were made on days 0, 7 and 28 respectively, by the intramuscular route with 1 ml vaccine each time for every volunteer. No obvious side effect was observed in vaccinees within 3 days after each inoculation. All 12 vaccinees (10 received three inoculations, and two received two inoculations of the vaccine) showed positive seroconversion of IgG antibody (by IFAT and ELISA) and neutralizing antibody (by enzyme focus reduction neutralization test, EFRNT), and 10 of them were still seropositive 180 and 360 days after the first inoculation. These results suggest that this vaccine would be safe for human use, and could effectively induce IgG and neutralizing antibody responses.

Adult↗
PubMed1991

The embedding problem for predistance matrices.

A fundamental problem in molecular biology is the determination of the conformation of macromolecules from NMR data. Several successful distance geometry programs have been developed for this purpose, for example DISGEO. A particularly difficult facet of these programs is the embedding problem, that is the problem of determining those conformations whose distances between atoms are nearest those measured by the NMR techniques. The embedding problem is the distance geometry equivalent of the multiple minima problem, which arises in energy minimization approaches to conformation determination. We show that the distance geometry approach has some nice geometry not associated with other methods that allows one to prove detailed results with regard to the location of local minima. We exploit this geometry to develop some algorithms which are faster and find more minima than the algorithms presently used.

Algorithms↗
PubMed1991

[A study of changes in oral residual alveolar ridge under the partial denture bearing occlusal stress].

The change of oral residual alveolar ridge showing in X-ray films before and after wearing unilateral distal extension partial dentures for ten cases was observed by the image processing technique. It was demonstrated that the image processing technique is an available method for evaluating the degree of alveolar ridge resorption both quantatively and qualitatively. By the technique of pantomography of X-ray we can control the coincidence of the corresponding part of the X-ray film taking at different time. So we can use this method to study the regularity of the residual alveolar ridge resorption.

Alveolar Bone Loss↗
PubMed1990

Glial localization of adenylate-cyclase-coupled beta-adrenoceptors in rat forebrain slices.

Fluorocitrate (FC), a selective inhibitor of glial cell respiration, was used to estimate the extent to which glial cells contain adenylate cyclase-coupled beta-adrenoceptors in rat brain slices. The drug blocked 75-95% of the elevation of cyclic AMP caused by the beta-agonist, isoproterenol, in the 4 forebrain regions sampled (frontal and parietal cortex, caudate nucleus, olfactory tubercle). Intracellular recording of neurons in the treated slices confirmed that they were unaffected by FC. Treatment with the neurotoxin, kainic acid, eliminated all electrophysiological activity but did not affect the cAMP response. The results indicate that glial cells contain the preponderance of adenylate-cyclase-coupled beta-adrenoceptors in slices of the rat forebrain and may constitute an important target of the central noradrenergic system in vivo.

Adenosine Triphosphate↗
PubMed1990

Clinical diagnosis in microinvasive carcinoma of the uterine cervix.

This retrospective study collected the surgical tissues and the clinical records of 197 surgically treated patients with microinvasive carcinoma of the cervix, which was defined as a limited microinvasion not more than 3 mm in depth regardless of lymph-vascular involvement. Depth of invasion was 1 mm or less in 13.2% and 1.1 to 3 mm in 86.8%. The mean age was 47.2 years. About half of the patients were asymptomatic but suspected cytologically. Random cervical biopsy alone was inadequate for diagnosis. Cone biopsy demonstrated an accuracy of 94% in diagnosis, but failed to eliminate microinvasive carcinoma in 23.0% of the hysterectomy specimens. In 14 cases, the invasion was more extensive in the uterus than in the cone. A positive correlation has been found between the diagnostic rate of conization and the depth of stromal invasion. Cervical conization, while relatively accurate in assessing the existence of stromal invasion that characterizes microinvasion, failed to diagnose those with deeper stromal invasion, especially beyond 1 mm. The recommended approach in diagnosing microinvasion is careful colposcope-directed cone biopsy and proper examination of the conization specimen in order to exclude the possibility of more advanced disease.

Adult↗
PubMed1990

[Painless labor and instrumentation].

This report is a retrospective study of painless labor and its relation to the instrumentation. It consists of 200 cases of primigravida in labor. In the study group, 100 consecutive cases of primigravida receiving painless labor was chosen and compared to another 100 consecutive primigravida in labor without receiving painless labor. We found that painless labor with epidural analgesia would decrease the rate of cesarean section, but increase the frequency of using forceps and vacuum for labor. The rate of normal spontaneous delivery is low as compared with those not receiving epidural analgesia for painless labor. However, painless labor bears no relation to the labor course nor discernible significance to the Apgar Score of the newborn babies. We strongly recommend painless labor to those poor pain tolerated primigravida.

Adult↗
PubMed1989

Noradrenergic potentiation of cerebellar Purkinje cell responses to GABA: evidence for mediation through the beta-adrenoceptor-coupled cyclic AMP system.

Previous in vivo studies from our laboratory have consistently shown that iontophoretically applied norepinephrine (NE) can potentiate gamma-aminobutyric acid (GABA)-induced depressant responses of cerebrocortical, cerebellar and hypothalamic neurons. Additional experiments have further suggested that this noradrenergic facilitating action is specific for GABA and results from the activation of a beta-type adrenoceptor. The goal of the present studies was to determine if the cAMP second messenger system might also be a component of the mechanism responsible for this NE modulatory action on GABA-mediated inhibition. In one set of in vitro experiments, we examined cerebellar neuronal responses to GABA before, during and after iontophoretic application of NE, 8-bromo-3',5'-cyclic AMP (BcAMP) or 3-isobutyl-1-methyl xanthine (IBMX) or bath application of forskolin (10-30 microM). In a second group of in vivo studies, extracellularly recorded responses of individual cerebellar Purkinje (P) cells to iontophoretic pulses of GABA or beta-alanine were examined before, during and after NE or BcAMP microiontophoresis. In 20 of 25 cerebellar cells recorded from tissue slices, iontophoretically applied NE markedly enhanced responses to GABA in a manner similar to that observed previously in vivo. In these in vitro preparations, bath application of forskolin was also capable of potentiating GABA-induced inhibition in each of 4 cases tested whereas dideoxy-forskolin was not. Iontophoretic application of IBMX further enhanced the facilitating effects of NE on GABA-induced inhibition in 10 of 11 cases tested. Furthermore, under in vitro conditions, BcAMP augmented inhibitory responses to GABA in all cerebellar neurons tested. In the intact rat brain, iontophoretic administration of BcAMP caused a marked NE-like augmentation of P-cell responses to GABA in 73% of the cells tested. As with NE, BcAMP was ineffective in enhancing P-cell inhibitory responses to beta-alanine, an agent which like GABA causes hyperpolarization, by increasing Cl conductance. In summary, these results indicate that a membrane permeant analog of cAMP, a phosphodiesterase inhibitor and an agent which directly activates adenyl cyclase can mimic the previously observed GABA-potentiating actions of NE. Thus, these findings provide further support for the contention that noradrenergic enhancement of GABA inhibition results from a cascade of transmembrane events which includes beta-receptor activation, adenyl cyclase stimulation and increased intracellular production of cAMP.

1-Methyl-3-isobutylxanthine↗
PubMed1989

Epidemiological models with age structure, proportionate mixing, and cross-immunity.

Infection by one strain of influenza type A provides some protection (cross-immunity) against infection by a related strain. It is important to determine how this influences the observed co-circulation of comparatively minor variants of the H1N1 and H3N2 subtypes. To this end, we formulate discrete and continuous time models with two viral strains, cross-immunity, age structure, and infectious disease dynamics. Simulation and analysis of models with cross-immunity indicate that sustained oscillations cannot be maintained by age-specific infection activity level rates when the mortality rate is constant; but are possible if mortalities are age-specific, even if activity levels are independent of age. Sustained oscillations do not seem possible for a single-strain model, even in the presence of age-specific mortalities; and thus it is suggested that the interplay between cross-immunity and age-specific mortalities may underlie observed oscillations.

Aging↗
PubMed1989

A study of molecular epidemiology of adenovirus of types 3 and 7 on infant pneumonia in northern China.

This paper analysed 102 strains of adenovirus types 3(Ad3) and 7(Ad7) causing infant pneumonia from 1976 to 1988 in northern China. Two genotypes of Ad7, 7b and 7d, were identified by using restriction endonucleases, BamHI, BcLI, BgLI, SmaI, XbaI and HindIII. 3 genotypes of Ad3, 3I, 3II and 3III, were identified by using BgLII and BamHI. Of 56 Ad7 strains, 34 were 7b (76.8%) spread over last 10 years; 13 7d(23.2%) occurred from 1982, together with 7b. Of 46 Ad3 strains, 42 3I(91.3%) spread over the past 12 years. 3II and 3III scattered all over these years. Ad3I and Ad7b were the dominant genotypes. The results indicated that Ad7d tended to increase with time from 1982. It is possible that Ad7d will become dominant genotype and replace Ad7b.

Adenoviridae Infections↗
PubMed1989

Colposcopic assessment in microinvasive carcinoma of the cervix.

Forty of the 87 patients with microinvasive carcinoma (MIC) of the uterine cervix who underwent surgery were diagnosed colposcopically and the results were compared with the cytological and histological diagnoses. The cytology showed preinvasive carcinoma in 20 (50.0%) patients and invasive carcinoma in 19 (47.5%) patients. A correct colposcopic diagnosis was made in nine (22.5%) patients as having microinvasive carcinoma, 21 (52.5%) patients preinvasive carcinoma and eight (20%) patients invasive carcinoma, to sum up accuracy rate as 32.1%. The abnormalities most commonly observed in colposcopy were mosaic, punctuation and white epithelium. In microinvasive carcinoma, the triad co-existed in 43% of the patients. Atypical vessels, characteristic of invasion, were found in only one third of the patients. Microinvasion, therefore, may not be evident on colposcopy alone. It is therefore necessary to apply cone biopsy, prior to definite therapy, to make an accurate assessment of the maximum depth and extent of the invasion prior to definitive therapy.

Biopsy, Needle↗
PubMed1989

Simultaneous endometrioid carcinoma of the uterine corpus and ovary.

The carcinoma with simultaneous involvement of the endometrium and the ovary is an uncommon but well recognized event. The determination of clinical stage depends on which of the two sites is considered to be the primary. Combined involvement may occasionally represent independent primary neoplasm. A review of all cases with a tissue diagnosis of endometrioid ovarian carcinoma and concomitant endometrial carcinoma was undertaken to identify those cases which possibly had independent primaries. Three such cases with disease confined to the pelvis were identified on the basis of pathologic features. The incidence of endometrial carcinoma in patients with endometrioid ovarian carcinoma was 15.8% (3/19). They were treated surgically with adjuvant therapy. Two patients died of disseminated carcinoma 1 and 4 years later respectively. The only one patient alive had been free of disease for 25 months after initial therapy. These endometrioid neoplasms simultaneously occurring in ovary and endometrium are considered to be primary tumors. The morphologic reasons for this view are discussed.

Aged↗
PubMed1988

Trichinella spiralis: quantitative relationships between intestinal worm burden, worm rejection, and the measurement of intestinal immunity in inbred mice.

The effect of widely different doses of Trichinella spiralis muscle larvae on time to rejection of intestinal adults and on host survival was assessed in mice of the three rejection phenotypes; strong, intermediate, and weak. Rejection is weak with doses of less than 50 larvae per mouse. At these doses all mice rejected worms at a similar rate and no phenotypic variation was evident among strains. In contrast, rejection time was shortest for all strains and phenotypic variation among strains was evident in the range 50-100 muscle larvae/mouse. Above this dose the time taken to rejection increases monotonically with dose for all mouse strains examined. Despite this, the relative strength of rejection (i.e., phenotype) of a given strain of mouse was not changed at higher doses. Based on an end point of 98% rejection of the infective dose, time to rejection was predictable to +/- 1 day for all mouse strains and doses tested over the range 100-1000 worms administered. The principal reason for the increased time to complete rejection with larger worm doses was a delay in the initiation of intestinal rejection. This delay was evident above a dose of 50-100 larvae per mouse and occurred in all strains. Once begun, rejection was faster and eliminated more worms in unit time at higher doses (400-800 more) than at lower doses of worms. This appeared to be due to a stronger immune response of the host at higher doses. However, the increase in the rate of rejection was still not as great as the increase in the dose. We postulate that the delay in rejection with increased dose is due to a requirement for a "critical mass" of effectors/worm required to cause rejection. As dose increases, more time is required to reach the level at which worm rejection commences. Deaths due to higher doses of worms also occurred in a strain-specific manner and were temporally biphasic. The intestinal phase of infection produced mortality from 1 to 5 days after infection and the strongest rejection phenotype (NFS) was also the most resistant to intestinal deaths. Deaths occurring after Day 5 were due to the parenterally migrating newborn larvae. The weakest rejection phenotype, that of the B10 congenics, was also the least resistant to intestinal deaths. An experimental formula describing 98% worm rejection time with different doses was derived from the data.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Dynamical behavior of epidemiological models with nonlinear incidence rates.

Epidemiological models with nonlinear incidence rates lambda IpSq show a much wider range of dynamical behaviors than do those with bilinear incidence rates lambda IS. These behaviors are determined mainly by p and lambda, and secondarily by q. For such models, there may exist multiple attractive basins in phase space; thus whether or not the disease will eventually die out may depend not only upon the parameters, but also upon the initial conditions. In some cases, periodic solutions may appear by Hopf bifurcation at critical parameter values.

Biometry↗