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Biomedical subjects

B Liu

Publications and source records attributed to B Liu.

At least 433 records · Page 24Linked to original sources
PubMed1997

The genomic 5' terminus of Manchester calicivirus.

An enteric calicivirus showing the classic cup-shaped surface morphology was identified in a stool sample obtained from a child with symptoms of acute gastroenteritis (Portishead virus, PHV). Genomic RNA was extracted directly from the PHV stool sample and amplified by RT-PCR using primers based on the Manchester isolate of HuCV. The 3' terminus of the cDNA was defined by homopolymer tailing with dATP and revealed an additional 165 nucleotides suggesting that the previously determined Manchester HuCV (MV) genome sequence was incomplete. Homopolymer tailing of MV cDNA primed using sequence data from the 5' terminus of PHV allowed extension of the MV genome by a further 165 nucleotides thereby increasing the overall genome length to 7431 nucleotides and resulting in an additional 72 amino acids at the N-terminus of the polyprotein. A conserved sequence motif typical of other caliciviruses was also identified at the extreme 5'-terminus of the genome.

Amino Acid Sequence↗
PubMed1997

The flavonoid constituents of two Polypodium species (Calaguala) and their effect on the elastase release in human neutrophils.

Five flavonoid compounds were isolated from two Polypodium species (P.decumanum and P.triseriale) with the common name Calaguala. Structure elucidation was carried out using different NMR techniques and revealed the presence of one new glycoside (kaempferol 3-O-beta-D-xylopyranosyl-(1-2)-beta-D-arabinopyranoside) (1), two known flavonoid glycosides, rutin and kaempferol 3-O-alpha-D-arabinopyranoside (2,3), the trimeric proanthocyanidin, selligueain (4), and the coumarinic acid derivative, melilotoside (5). The compounds were tested for their activity in PAF induced exocytosis in human neutrophils but none of the compounds showed PAF specific activity. Instead, they showed more general effects on the neutrophil including inhibition of the spontaneous elastase release (5) and potentiation of the release induced by PAF (1). Selligueain was found to inhibit the proteolytic enzyme, elastase in vitro.

Cells, Cultured↗
PubMed1997

Rapid elimination of low-copy DNA sequences in polyploid wheat: a possible mechanism for differentiation of homoeologous chromosomes.

To study genome evolution in allopolyploid plants, we analyzed polyploid wheats and their diploid progenitors for the occurrence of 16 low-copy chromosome- or genome-specific sequences isolated from hexaploid wheat. Based on their occurrence in the diploid species, we classified the sequences into two groups: group I, found in only one of the three diploid progenitors of hexaploid wheat, and group II, found in all three diploid progenitors. The absence of group II sequences from one genome of tetraploid wheat and from two genomes of hexaploid wheat indicates their specific elimination from these genomes at the polyploid level. Analysis of a newly synthesized amphiploid, having a genomic constitution analogous to that of hexaploid wheat, revealed a pattern of sequence elimination similar to the one found in hexaploid wheat. Apparently, speciation through allopolyploidy is accompanied by a rapid, nonrandom elimination of specific, low-copy, probably noncoding DNA sequences at the early stages of allopolyploidization, resulting in further divergence of homoeologous chromosomes (partially homologous chromosomes of different genomes carrying the same order of gene loci). We suggest that such genomic changes may provide the physical basis for the diploid-like meiotic behavior of polyploid wheat.

Chromosomes↗
PubMed1997

Cancer risk associated with germline DNA mismatch repair gene mutations.

The autosomal dominant syndrome of Hereditary Nonpolyposis Colorectal Cancer (HNPCC) is due to germline DNA mismatch repair gene mutations in most cases. However, the penetrance of such mutations outwith classical HNPCC kindreds is unknown because families studied to date have been specifically selected for research purposes. Using a population-based strategy, we have calculated the lifetime cancer risk associated with germline DNA mismatch repair gene mutations, irrespective of their family history. We identified 67 gene carriers whose risk to age 70 for all cancers was 91% for males and 69% for females. The risk of developing colorectal cancer was significantly greater for males than for females (74% versus 30%, P= 0.006). The risk of uterine cancer (42%) exceeded that for colorectal cancer in females, emphasising the need for uterine screening. Our findings give further insight into the biological effect of defective DNA mismatch repair. We have demonstrated a systematic approach to identifying individuals at high risk of cancer but who may not be part of classical HNPCC families. The risk estimates derived from these analyses provide a rational basis on which to guide genetic counselling and to tailor clinical surveillance.

Colorectal Neoplasms, Hereditary Nonpolyposis↗
PubMed1997

Determination of the volume activity concentration of alpha artificial radionuclides with alpha spectrometer.

This paper introduces a method to determine the volume activity concentration of alpha and/or beta artificial radionuclides in the environment and radon/thoron progeny background-compensation based on a Si surface-barrier detector. By measuring the alpha peak counts of 218Po and 214Po in two time intervals, the activity concentration of 218Po, 214Pb and 214Bi aerosol particles were determined; meanwhile, the total beta count of 214Pb and 214Bi aerosols was also calculated from their decay scheme. With the average equilibrium factor of thoron progeny in general environment, the alpha and beta counts of thoron progeny were approximately evaluated by 212Po alpha peak counts. The alpha count of transuranic aerosols was determined by subtracting the trail counts of radon/thoron progeny alpha peaks. The total count of beta artificial radionuclides was determined by subtracting the beta counts of radon/thoron progeny aerosol particles. In our preliminary experiments, if the radon progeny concentration is less than 15 Bq m(-3), the lower limit of detection of transuranics concentration is less than 0.1 Bq m(-3). Even if the radon progeny concentration is as high as 75 Bq m(-3), the lower limit of detection of total beta activity concentration of artificial nuclides aerosols is less than 1 Bq m(-3).

Aerosols↗
PubMed1997

Investigation of the line-pair pattern method for evaluating mammographic focal spot performance.

The latest American College of Radiology (ACR) Mammography Quality Control Manual contains a new method for evaluating focal spot performance, which this paper refers to as the "line-pair pattern test." The ACR describes a variety of methods for performing this test, and does not advocate one method over another. The authors of this paper conducted an investigation to compare the optional ways for performing the test. Resolution measurements were obtained using a prototype line-pair resolution phantom imaged with a GE DMR mammography unit. Measurements were made with the line-pair pattern 4.5 cm above the breast support platforms in both conventional (contact) and magnification geometries. Both 4.5 cm of air and Lucite were tested as attenuators between the line-pair pattern and the breast support platform. Image receptors that were employed included film alone, screen-film, and screen-film that was not allowed to wait the recommended 15 min before exposure. kVp was varied as was the orientation of the line-pair pattern relative to the chest wall. For the air attenuator case, the screen degraded the measured resolution by 1-3 lp/mm when compared to the direct film. The Lucite attenuator reduced the resolution by an additional 1 1p/mm. Increasing kVp improved the resolution slightly for the conventional mode, but decreased it slightly for the magnification mode. Based upon the results of this study, recommendations are made for improving the test protocol. For a test of focal spot performance, one should use the no-attenuation with direct film detector setup. For a measure of the resolution of the entire imaging chain, one should use the Lucite attenuator with screen-film detector setup.

Bias↗
PubMed1997

Effect of nitric oxide synthase inhibitors on endothelial [Ca2+]i and microvessel permeability.

To investigate the mechanism whereby nitric oxide (NO) signaling pathways regulate microvessel permeability in vivo, we measured changes in microvessel hydraulic conductivity (Lp) and endothelial cytoplasmic calcium concentration ([Ca2+]i) in response to calcium ionophore, ionomycin (5 microM), and ATP (10 microM) before and after the use of NO synthase (NOS) inhibitors in single perfused frog mesenteric venular microvessels. Ionomycin induced a transient increase in endothelial [Ca2+]i and an associated increase in Lp. The NOS inhibitors N omega-nitro-L-arginine methyl ester (10 and 300 microM) and N omega-monomethyl-L-arginine (L-NMMA; 10, 50, and 100 microM) significantly attenuated the peak increase in Lp induced by ionomycin. A similar inhibitory effect was also observed with the increase in Lp mediated by ATP. In contrast, D-NMMA, a biologically inactive isomer of L-NMMA, showed no effect on ionomycin-induced increase in Lp L-Arginine (3 mM) reversed the inhibitory effect of L-NMMA (10 microM) on Lp. However, the NOS inhibitors did not alter the magnitude and time course of the biphasic increase in endothelial [Ca2+]i induced by both ionomycin and ATP. These data suggest that 1) calcium-dependent NO release is a necessary step to increase microvessel permeability, and 2) the action of NOS inhibitors in attenuating the permeability increase in response to ionomycin and ATP occurs down-stream from calcium entry and does not involve modification of the initial increase in endothelial [Ca2+]i.

Adenosine Triphosphate↗
PubMed1997

Ca2+ uptake by cardiac sarcoplasmic reticulum at low temperature in rat and ground squirrel.

The Ca2+ uptake by isolated cardiac sarcoplasmic reticulum (SR) was compared between Richardson's ground squirrels and rats at 37, 25, 15, and 5 degrees C. The rate of SR Ca2+ uptake in ground squirrels was significantly higher than in rats over the temperature range. This marked species difference was observed over a Ca2+ concentration range from 0.1 to 10 microM. The Arrhenius plot for Ca2+ uptake was linear for ground squirrels between 37 and 5 degrees C but showed a depression from linearity for rats at 5 degrees C. This temperature sensitivity was also reflected in rat SR Ca2+-adenosinetriphosphatase activity. Analysis of [3H]ryanodine binding in SR suggests that more Ca2+ release channels are in an open state at low temperatures in rats than in ground squirrels. Together, these results suggest that species differences in the response of SR to low temperature may account for the rise in cytosolic free Ca2+ in cold-sensitive species and may be responsible, at least in part, for the inability of cold-sensitive hearts to function at low temperature.

Acclimatization↗
PubMed1997

Identification and characterization of a mouse homolog for decidual/trophoblast prolactin-related protein.

Decidual/trophoblast PRL-related protein (d/tPRP) is one member of a large placental PRL gene family composed of at least nine members in the rat and four in the mouse. Only placental lactogen I and II have been characterized in both rat and mouse. The identification of mouse homologs for rat placental PRL family members will facilitate gene manipulation studies aimed at identifying functions for these hormones. In this report, we establish the presence of d/tPRP in the mouse and characterize its complementary DNA, protein, and pattern of expression during mouse gestation. Evaluation of the National Center for Biotechnology Information database of expressed sequence tags resulted in the identification of several mouse complementary DNA clones exhibiting significant homology to rat d/tPRP. One of these clones was obtained from IMAGE Consortium and Research Genetics for further investigation. The full-length mouse clone was found to have an 81% nucleotide homology with rat d/tPRP and to encode a 239-amino acid protein. Like rat d/tPRP, the mouse protein contains two putative N-linked glycosylation sites and six homologously located cysteine residues. Mouse d/tPRP maps to chromosome 13 along with other members of the mouse PRL family. Like the rat, mouse d/tPRP messenger RNA and protein are expressed by antimesometrial decidual cells and spongiotrophoblast and trophoblast giant cells in the junctional zone of the placenta. In summary, we have established the presence of d/tPRP in the mouse and demonstrated its similarity in structure and pattern of expression to rat d/tPRP. This level of conservation between species expands the biological significance of d/tPRP during pregnancy and provides additional opportunities for evaluating its function.

Animals↗
PubMed1997

Electrophysiologic effect of enalapril on guinea pig papillary muscles in vitro.

AIM: To study the direct effect of enalapril on cellular electrophysiology of myocardium. METHODS: Conventional microelectrodes technique was used to record the action potentials (AP) of guinea pig papillary muscles. RESULTS: Enalapril caused an increase of the AP amplitude (APA) and the resting potential (RP) in a concentration-dependent manner without any significant change of AP duration, Vmax and overshoot of AP. Superfusion of ouabain 0.5 mumol.L-1 reduced APA and RP, induced stable delayed after-depolarizations (DAD) at different basic cycle lengths (BCL) in a frequency-dependent manner. At BCL 200 ms, the amplitude of DAD was large enough to induce nonsustained triggered activity (TA). In additional presence of enalapril 10 mumol.L-1, the DAD amplitude at 500, 400, 300, and 200 ms were decreased from 5.3 +/- 2.3, 5.9 +/- 2.8, 7.4 +/- 2.1, and 8.9 +/- 1.3 to 2.6 +/- 0.7, 3.1 +/- 1.0, 3.7 +/- 1.5, and 5.3 +/- 1.1 (mV) respectively, all P < 0.01. The compensation intervals were increased in a similar frequency-dependent manner. The number of TA induced at BCL 200 ms was decreased from 3.6 +/- 0.7 to 0.8 +/- 0.2 (P < 0.05). CONCLUSION: Enalapril directly inhibits DAD and TA induced by ouabain through increasing RP and APA, which may contribute to its anti-arrhythmic effect.

Action Potentials↗
PubMed1997

[Contrast analysis of clinical and pathological staging of supraglottic carcinomas].

To evaluate the accuracy of clinical staging of supraglottic carcinomas, a retrospective histopathological study of larynges from 53 patients who had undergone total laryngectomy was adopted. All larynges were processed as whole-organ serial sections in coronal plane. The results showed that clinical underestimation had been made in 24.5% of all laryngeal cancer cases. Clinical underestimation occured in 54.5%, 33.3% of T2, T3 laryngeal cancer cases, respectively. There was no overestimation in clinical staging. The important factors that affected clinical underestimation were invasion of the pre-epiglottic space and thyroid cartilage. It is suggested that the pre-epiglottic space should be resected in early supraglottic carcinoma. The thyroid cartilage involvement should be suspected in laryngeal cancer with extensive invasion of anterior commisure or extensive invasion of the paraglottic space accompanied by cartilage ossification.

Adult↗
PubMed1997

[PCR-SSCP and sequencing analysis on mutations of anti-oncogene p53 in asbestos-related lung cancer].

To explore the carcinogenic effect of asbestos at molecular level, we directly analyzed the mutations of exon 5, 7 and 8 of anti-oncogene p53 in paraffin-embedded human lung tissue affected by asbestos for the first time. Mutations of p53 gene located in exon 5, 7 and 8 were detected in 7 of 10 cases by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. The mutation rate found in this study is 70%. Two cases were analyzed by PCR product direct sequencing and C-->A and T-->A transformations were detected. Mutation of p53 gene may be one of the characteristics of asbestos-related lung cancer.

Asbestos↗
PubMed1997

[The research on p53 gene mutation in lung cancer tissue of silicotic patients by PCR-SSCR].

Using polymerase chain reaction single strand conformation polymorphism analysis (PCR-SSCP), the authors mutations in exon 5, 7 and 8 of the p53 gene in lung cancer tissue from 15 of 36 silicotic patients. Mutations existed in exon 5, exon 7 and exon 8, but occured more frequently in exon 8. The authors also found that p53 gene mutation rate in lung adenocarcinomas of silicotic patients was higher than that of those without silicosis. A single base substitution was found by DNA sequencing analysis in sample C8. As a result, No. 144 codon was mutated from CAG to AAG, so Gln was substituted by Lys. The authors' data suggest that p53 mutation may play an important role in the pathogenesis of lung cancer of silicotic patients.

Adenocarcinoma↗
PubMed1997

[Pathological features of hepatocellular carcinoma carrying hepatitis C virus antigen].

OBJECTIVE: To analyze the pathological features of hepatocellular carcinomas (HCCs) carrying different hepatitis virus antigens histopathologically and systematically. METHODS: PAP and ABC kits were used in the immunohistochemical study, and CAS-200 System was applied in the image cytometry. RESULTS: As compared with HCCs carrying HBV marker(s), the HCCs carrying HCV marker showed more cases of clear cell type (7/9 vs 4/33), better differentiation of cancers, less necrosis of hepatocytes, milder lymphocyte infiltration in the hepatic sinuses or periportal areas (P < 0.01), higher incidence of bile ductule damages, and bore a close relation to the formation of lymphoid follicle in the surrounding tissues (P < 0.05). These patients were elder, with lower grade of symptoms and better prognosis after operation. CONCLUSION: HCCs carrying only HCAg have different pathological features and clinical characteristics from which carrying HBV marker(s). The results of image cytometry are in accordance with the biological behaviour of HCC.

Adult↗
PubMed1997

[The usefulness of dye endoscopy in diagnosis esophageal diseases].

OBJECTIVE: To investigate the usefulness of Dye endoscopy in the diagnosis of the esophageal disorders. METHODS: 87 cases with esophageal diseases underwent dye endoscopy examination with Toluidin-staining and Iodine-staining or double-staining method. RESULTS: In the conventional group, the conformity rate of the endoscopy to biopsy results is 80%, but in the Dye one is 95% and the accurate rate of diagnostic is 100%. Under the guiding of Dye endoscopy, the occurrence rate of Ca cell on the incisal edge is 0%. CONCLUSION: The methods enable diffentinal diagnose of benign and malignant lesion, conforming the type of esophagitis. And it is more helpful to conform the area of surgical resection and when conventional endoscopy cannot satisfactorily diagnosis. We think it is a useful and simple diagnostic method for esophageal diseases.

Diagnosis, Differential↗
PubMed1997

[Subperiosteal implantation of block coral on the rabbit cavarial bone].

The aim of this study was to evaluate osteoconductive effect of coral implanted on surface of the cortical bone. The 2 mm thick block corals were implanted on the surface of one side of rabbits cavarial bone, the another side were used as blank control. The specimen was examined by light microscopy, histometry and scanning electron microscopy at 2, 4, 8, 12 weeks after operation respectively. The results show that the new bone growth into the pore of the coral at 2 weeks after implantation. The coral was progressively absorbed and replaced by new bone. Up to 12 weeks, most of the coral was absorbed and newly formed bone had been remodeled. The reconstructed height of new bone in coral group was significantly higher than that of blank control and lower than the thickness of block coral. The study demonstrated good osteoconductive property of coral implanted on surface of cortical bone.

Animals↗