Biomedical subjects

B Liu

Publications and source records attributed to B Liu.

At least 289 records · Page 16Linked to original sources

PubMed2000

[A Carnobacterium-like organism isolated form a patient with multiple bacterial synergistic gangrene].

An atypical lactic-acid producing gram positive rod Y6 strain was studied in this report, which was isolated form clinic sample of a patient with multiple bacterial synergistic gangrene, and could not be identified by routine method. A 1.5 kb of 16S rDNA of Y6 strain was synthesized and sequenced. Comparative 16S rDNA sequence analyses revealed that stain Y6 is most closely related to the genus of Carnobacterium. The overall similarity value between Y6 strain and Carnobacterium species are 93% to 97%. The signature nucleotides in 16S rDNA primary sequence of strain Y6 and that of genus of Carnobacterium were identical. The biological features of Y6 strain are very similar to that of Carnobacterium, such as lactic acid as main end product of in PYG broth, no gas produced form fermentation of glucose, catalase negative, no motility. Data suggested that Y6 strain is very similar to the genus of Carnobacterium, of which no strain has been isolated form clinical sample so far. Based on the results obtained, we names Y6 strain as Carnobacterium-like organism.

Base Sequence↗

PubMed2000

[Radiofrequency treatment of hemangioma of nasal cavity under nasal endoscopy].

OBJECTIVE: To further understand the advantage of radiofrequency treatment of hemangioma of nasal cavity under nasal endoscopy. METHOD: Fifteen cases with hemangioma of nasal cavity were treated with radiofrequency under nasal endoscopy. RESULT: The hemangioma of fifteen cases could be removed completely. The complication was absent. None of them recurred in six months to four years following up. CONCLUSION: This method has many advantages such as clear operation visual field, less hemorrhage and postoperative pain, no facial scar. The radiofrequency under endoscopy is valuable in treatment for hemangioma of nasal cavity.

Adolescent↗

PubMed2000

[Immune response in Pneumocystis carinii pneumonia in rats].

OBJECTIVE: To study the inflammatory immune response to Pneumocystis canii pneumonia(PCP) in rats induced by glucocorticoid(GC). METHODS: The model of PCP was set up by injecting GC subcutanously to SD rats. Lymphocyte proportion in peripheral blood, CD4+/CD8+ T cell ratio of PBL and lymphocyte proportion in the BALF were measured. The levels of sIL-2R and TNF-alpha in the BALF were detected. RESULTS: 1. After the rats were immunospressed, the lymphocyte proportion in the peripheral blood and CD4+/CD8+ ratio of PBL, and the lymphocyte proportion in the BALF were decreased, and the levels of sIL-2R, TNF-alpha in BALF were reduced. 2. The lowest levels of TNF-alpha in BALF and CD4+/CD8+ T cells of PBL were observed in PCP group; 3. The lymphocyte proportion in the BALF was significantly higher in PCP group than in PC negative group. CONCLUSION: The reduction in the level of TNF-alpha and CD4+/CD8+ T cell ratio in rats treated with GC might result in PCP infection under immunosuppressive condition.

Animals↗

PubMed2000

[Expression of inducible nitric oxide synthase in human esophageal biopsies from carcinoma and precancerous lesions].

OBJECTIVE: To investigate the possible role of inducible nitric oxide synthase (iNOS) in esophageal carcinogenesis. METHODS: iNOS expressions in normal epithelial cells(NC), hyperplastic cells(HC), atypical hyperplastic cells(AHC) from grade I to III, carcinoma in situ(CIS), squamous cell carcinoma(SCC), and adenocarcinoma(ADC) were detected with immunohistochemistry. RESULTS: The positive rates of immunohistochemistry staining was 0 for NC, 2.5% for HC, 4.0%, 7.5% and 2.5% for AHC grade I to III respectively, 1.4% for CIS, 8.5% for SCC and 71.4% for ADC. CONCLUSIONS: There is a high expression of iNOS in human esophageal adenocarcinomas. Frequent expression of iNOS may be a potential event in ADC carcinogenesis. There is no correlation between iNOS and SCC carcinogenesis.

Adenocarcinoma↗

PubMed2000

[Distinctive infrared spectral features in human breast cancer].

Substantial differences were found in the spectral properties of surgical samples from 20 women patients with histologically normal and cancerous breast tissue. The most striking changes in the spectra were observed in the symmetric and asymmetric stretching bands of phosphodiester groups, which shifted to short wavenumber about 3 cm-1 in nu s PO2-, and to long wavenumber about 2 cm-1 in nu s PO2-. The ratio of A1,173/A1,163 increased and that of A1,025/A1,082 decreased, the intensity of symmetric and asymmetric stretching bands of CH3 decreased and those of CH2 increased in all of breast cancer tissues. Our findings indicated that in breast cancer tissue, the degree of hydrogen-bonding of oxygen atoms in the backbone of nucleic acid increased; the content of glycogen decreased; the degree of hydrogen-bonding of OH groups in serine, tyrosine, and threonine residues of cell proteins decreased; and also there were changes in the packing and the conformational structure of the methylene chains of membrane lipids.

Breast Neoplasms↗

PubMed1999

Clinical impact of molecular genetic diagnosis, genetic counseling, and management of hereditary cancer. Part I: Studies of cancer in families.

Hereditary cancer represents approximately 5-10% of the total cancer burden and may account for 60,000 to 120,000 new cancer occurrences this year in the United States. New developments in molecular genetics and the cloning of cancer-prone genes have intensely fueled interest in dealing with hereditary forms of cancer. The authors provide an algorithm that depicts the process for the identification, study, and DNA-based genetic counseling of families being investigated under a research proposal at the Hereditary Cancer Institute of Creighton University School of Medicine. They have studied 56 hereditary nonpolyposis colorectal carcinoma families; in 18 of them, associated genomic mutations have been identified in affected members. DNA-based genetic counseling has been provided for seven of these families. The authors have also evaluated 131 hereditary breast-ovarian carcinoma families. BRCA1 and BRCA2 mutation searches have been performed for 76 of these families; BRCA1 mutations were found in 38 families and BRCA2 mutations in 9. The study of cancer-prone families is a powerful approach to cancer control, particularly when the germ-line mutation is identified in the family and individuals at high risk can be tested, once they provide informed consent, and receive DNA-based genetic counseling. Discovery of the germ-line mutation for cancer proneness provides an unparalleled opportunity to predict patients' life-time risk for cancer of specific anatomic sites, inclusive of a pattern of multiple primaries. Surveillance and management protocols, when melded to the particular syndrome's natural history, can be life-saving.

Clinical Protocols↗

PubMed1999

Clinical impact of molecular genetic diagnosis, genetic counseling, and management of hereditary cancer. Part II: Hereditary nonpolyposis colorectal carcinoma as a model.

Hereditary nonpolyposis colorectal carcinoma (HNPCC) is the most common hereditary form of colorectal carcinoma (CRC) and may account for 5-10% of the total CRC burden. The discovery of DNA mismatch repair (MMR) genes, inclusive of hMSH2, hMLH1, hPMS2, and hMSH6, has enabled the identification of who has and who does not have inordinately increased susceptibility to CRC as well as a litany of extracolonic cancers. Mutation testing has focused on hMSH2 and hMLH1, the most common mutations in HNPCC. The protocol for DNA testing and DNA-based genetic counseling is described in Part I of this study. One hundred ninety-nine bloodline relatives were tested and counseled from five hMLH1 and two hMSH2 families. Their major reason for seeking genetic counseling and DNA testing was to inform their children and other loved ones of their mutation status. Those who sought counseling overestimated their risk for inheriting the mutation and showed a high rate of interest in prophylactic surgery, and many were greatly concerned about insurance discrimination. Knowledge about HNPCC, its molecular genetic diagnosis, surveillance and management opportunities, and genetic counseling implications are still emerging, all in the face of a greater need for physician education regarding all facets of hereditary cancer.

Adaptor Proteins, Signal Transducing↗

PubMed1999

Functional interaction between the cytoplasmic leucine-zipper domain of HIV-1 gp41 and p115-RhoGEF.

The long cytoplasmic tail of the human immunodeficiency virus (HIV)-1 transmembrane protein gp41 (gp41C) is implicated in the replication and cytopathicity of HIV-1 [1]. Little is known about the specific functions of gp41C, however. HIV-1 or simian immunodeficiency virus (SIV) mutants with defective gp41C have cell-type- or species-dependent phenotypes [2] [3] [4] [5] [6]. Thus, host factors are implicated in mediating the functions of gp41C. We report here that gp41C interacted with the carboxy-terminal regulatory domain of p115-RhoGEF [7], a specific guanine nucleotide exchange factor (GEF) and activator of the RhoA GTPase, which regulates actin stress fiber formation, activation of serum response factor (SRF) and cell proliferation [8] [9]. We demonstrate that gp41C inhibited p115-mediated actin stress fiber formation and activation of SRF. An amphipathic helix region with a leucine-zipper motif in gp41C is involved in its interaction with p115. Mutations in gp41C leading to loss of interaction with p115 impaired HIV-1 replication in human T cells. These findings suggest that an important function of gp41C is to modulate the activity of p115-RhoGEF and they thus reveal a new potential anti-HIV-1 target.

Actins↗

PubMed1999

Age-related impairments in TCR/CD3 activation of ZAP-70 are associated with reduced tyrosine phosphorylations of zeta-chains and p59fyn/p56lck in human T cells.

The expression and catalytic activity of the protein tyrosine kinase (PTK) ZAP-70 are needed for normal intracellular signaling through the T-cell receptor (TCR)/CD3 complex. However, the possible effect of aging on the catalytic activity of ZAP-70 in human peripheral blood T cells stimulated via the TCR/CD3 complex is unknown. The current studies show that T cells from a substantial proportion of elderly humans (12) exhibit significant reductions in the catalytic activity, but not expression of ZAP-70 when stimulated by ligation of the TCR/CD3 with cross-linked anti-CD3epsilon monoclonal antibody OKT3. In addition, the reduced catalytic activity of ZAP-70 in T cells from elderly subjects was not restored to the normal levels in response to ligation of CD4 receptors, suggesting defects in PTKs linked to both CD3 and CD4 receptors. Other experiments demonstrated that the age-related impairments of ZAP-70 activation in anti-CD3-stimulated T cells were accompanied by decreased tyrosine phosphorylations of zeta-chains and autophosphorylations of the PTKs p561ck/p59fyn. Moreover, the age-related defects in these early TCR/CD3-mediated phosphorylation events were readily detectable in both CD45RO+ memory and CD45RA+ naive T cells. Thus, these results suggest that defects in early TCR/CD3-mediated phosphorylation events among CD45RO+ memory and CD45RA+ naive T cells from certain elderly humans may con tribute to impaired induction of ZAP-70 catalytic activity.

Aged↗

PubMed1999

Emerging HIV infections with distinct subtypes of HIV-1 infection among injection drug users from geographically separate locations in Guangxi Province, China.

Heroin users from Guangxi province, a southern province of China that borders Vietnam in the south and Yunnan province in China in the west, were studied for prevalence and risk factors for HIV-1 infection. Viral env sequences from HIV-1-positive individuals were also determined for subtypes of HIV-1. The overall HIV prevalence among 227 heroin users was 40%. Most had used drugs for < or = 3 years. Sharing of injection equipment and unprotected sex were significantly associated with HIV-1 infection. Subtypes C and E HIV-1 were detected in infected heroin users and were sharply segregated in two geographic locations: only subtype C was found in a border city with Yunnan province, whereas only subtype E was found in a city bordering northern Vietnam. HIV-1 strains within each subtype were remarkably homogenous, with a mean intersubject DNA distance of 2.32% for subtype E and 1.13% for subtype C, respectively. Phylogenetic analysis of C2-V5 region of Guangxi subtype E env sequences revealed significant clustering with subtype E sequences from southern Vietnam and Cambodia. These results suggest that HIV-1 infection among heroin users in Guangxi represents two emerging epidemics initiated from distinct sources: one from Vietnam and another from Yunnan province. Factors associated with HIV-1 infection were not restricted to injection practices. Unprotected sexual behaviors are likely to increase the probability of HIV transmission beyond this high-risk population. Designing and implementing effective intervention strategies targeted toward both injection drug use and high risk sexual behavior are urgently needed to further reduce HIV-1 spread in China.

China↗

PubMed1999

[Evidence on the carcinogenicity of silica at DNA level in human].

The alteration of p53 and K-ras gene in 36 lung cancers of workers occupationally exposed to silica (LCWS) was studied. DNA was extracted from paraffin\|embedded tissues and amplified by PCR. PCR-SS-CP analysis on exons 5, 7 and 8 of p53 gene revealed that 43.8% of mutations were clustered in exon 8 of p53 gene. In ordinary lung cancer, the mutation rate of exon 8 was fluctuated around 20%. The prevalence of mutations was the highest (70%) in small cell lung cancer (SCLC) and the lowest in adenocarcinoma(33%). In our study the mutation rate was high in adenocarcinoma(53.9%) and low in SCLC (30.8%). The K-ras gene of LCWS also revealed a different mutation pattern. Unexpectedly, no mutation was found at codon 12 in 36 LCWS by PCR-RFLP, which is the predominant mutation in K-ras gene in ordinary lung cancer. The point mutation study by DNA sequencing confirmed the absence of codon 12 mutation in K-ras gene in LCWS. The mutations observed in this study were frequently distributed in codons 13 and 15, principally a G-C transversion, instead of G-T transversion in ordinary lung cancer.

Adenocarcinoma↗

PubMed1999

Age-related defects in Th1 and Th2 cytokine production by human T cells can be dissociated from altered frequencies of CD45RA+ and CD45RO+ T cell subsets.

The present study investigated whether age-related changes in the production of Th1 and Th2 cytokines by human T cells might be linked to altered frequencies of naive (CD45RA+) and memory (CD45RO+) T cell subsets. T cells from healthy elderly humans (n = 32) stimulated with anti-CD3epsilon monoclonal antibody OKT3 plus PMA produced significantly lower levels of IL-2 and IFNgamma (Th1 type) and of IL-4 (Th2 type) cytokines compared with T cells from young subjects. Although considerable heterogeneity was observed in the levels of cytokines produced by activated T cells from elderly individuals, linear regression analysis failed to demonstrate any significant shift in Th1 to Th2 type cytokine profiles of human T cells during aging. Sufficient T cells were available from eighteen elderly subjects to quantitate the levels of cytokine production in parallel with flow cytometry analysis of the frequencies of CD45RA+ naive and CD45RO+ memory T cells. Compared with the group of young subjects, the elderly group exhibited significant decreases in the frequencies of naive T cells with reciprocal increases in memory T cells. However, defects in Th1 and Th2 cytokine production were not significantly correlated with altered frequencies of naive/memory T cells among elderly individuals. In addition, those elderly individuals with normal frequencies of naive/memory T cells exhibited decreases in cytokine production comparable to the reductions observed for elderly donors with alterations in the frequencies of naive/memory T cells. These findings suggest that age-related defects in Th1 and Th2 cytokine production cannot be attributed entirely to alterations in the frequencies of naive/memory T cell subsets and point toward intrinsic aberrancies within human T cell cytokine networks during aging.

Aged↗

PubMed1999

[Effects of unarmed marching in dry-heat desert environment on the heat shock protein 27 in human blood].

To explore the variation of blood heat shock protein 27(HSP27) for unarmed marching in dry-heat environment, plasma HSP27 levels of 57 marchers and 14 controls were detected. The results revealed a significant difference between exposed and control groups (P < 0.01), and no significant difference among different time exposures at the same speed. HSP27 levels increased slightly with the increase of speed. During the second hour of marching, HSP27 levels were slightly lower, and kept steady in the third hour.

Adolescent↗

PubMed1999

Isolation of human salivary mucin MG2 by a novel method and characterization of its interactions with oral bacteria.

Human salivary mucin MG2 was purified from submandibular/sublingual gland secretion by ultrafiltration and sequential gel filtration chromatography on Sephadex G-200, Superose 6 (prepgrade), and Superose 6. This method differs from earlier procedures in that all steps are performed in the presence of 4 M guanidine hydrochloride and do not involve covalent modification of the mucin molecule. Electrophoretic analyses and Western blotting showed that purified MG2 did not contain detectable levels of other salivary proteins. Amino acid analysis showed that the composition of purified MG2 was in excellent agreement with the deduced sequence of MG2 apomucin encoded in the MUC7 gene. The yield of purified MG2 was 10-15 mg from 750 ml of salivary secretion. Binding of purified MG2 to Streptococcus mutans in vitro was not significantly affected by reductive methylation, but was nearly abolished by reduction and alkylation. These data identified a functional determinant for mucin-bacterial interactions in the N-terminal region where the only two cysteines (Cys45 and Cys50) in the MG2 apomucin occur. Additionally, purified MG2 bound to four strains of oral Streptococci, indicating that the binding is not dependent on complexing with other salivary proteins, such as secretory immunoglobulin A. The purification procedure described in this work will facilitate investigation of the role of MG2 in the oral environment.

Adult↗

PubMed1999

Subnuclear partitioning and functional regulation of the Pit-1 transcription factor.

Subnuclear compartmentation is postulated to play an important role in many aspects of nuclear metabolism. To directly test an application of this model to transcription factor function, we examined the subnuclear partitioning behavior of Pit-1, a tissue-specific, POU-class transactivator. Biochemical and in situ assays indicate the nuclear pool of Pit-1 is normally divided between two compartments: the majority being differentially soluble in detergent, and a significant insoluble fraction (approximately 20%) bound to the nuclear matrix. Examination of Pit-1 deletion mutants and chimeric fusions reveal the highly conserved 66 amino acid POU-specific domain contains a necessary and sufficient nuclear matrix targeting signal. The nuclear partitioning behavior of several natural or engineered point mutations of Pit-1 was also examined. Surprisingly, the inactive point mutants were completely matrix-bound, irrespective of their ability to bind Pit-1 specific DNA. These results suggest that dynamic partitioning of Pit-1 is a component of its normal transactivator function that takes place upon the insoluble nuclear substructure where transcription occurs.

Animals↗

PubMed1999

Two different gene elements are required for glucose regulation of S14 transcription.

Carbohydrate feeding increases the transcriptional activity of the hepatic S14 gene. The region of the S14 promoter between -1384/-1275 contributes to the transcriptional regulation by carbohydrate. A previously identified element (-1303/-1289) within this region is required but is not sufficient for the carbohydrate effect. Therefore, we ligated -1384/-1275 to a heterologous promoter and created mutants in this region to identify other potential responsive sequences. We found that mutation within -1365/-1350 eliminated the response to high glucose (27.5 mM). However, three copies of this element ligated to a mouse mammary tumor virus-luciferase vector did not respond to glucose indicating the -1365/-1350 element is insufficient to confer a glucose response in isolation. Nevertheless. mutating the -1365/-1350 element in the native promoter led to a loss of response to glucose, proving this element is necessary. Electrophoretic mobility shift assays (EMSA) using three copies of the element showed significant binding to rat hepatic nuclear extracts, but no difference between the dietary states. Competition EMSA studies showed that the previously identified element at -1303/-1289 was unable to compete for proteins that bind to the -1365/-1350 element. Therefore, we have demonstrated two separate elements within the -1384/-1275 region of the S14 gene that bind different proteins and interact to elicit the carbohydrate effect.

Animals↗

PubMed1999

The histopathology of fibrous dysplasia of bone in patients with activating mutations of the Gs alpha gene: site-specific patterns and recurrent histological hallmarks.

Gs alpha mutations and histopathology have been analysed in a series of 13 patients with fibrous dysplasia (FD) of bone, including 12 patients with the McCune-Albright syndrome (MAS) and one patient with monostotic FD. Activating mutations (either R201C or R201H) of the gene encoding the alpha subunit of the stimulatory G protein, Gs, were detected in all cases, including the case of monostotic FD, using a variety of techniques [reverse transcription-polymerase chain reaction (RT-PCR) with allele-specific primers, allele-specific oligonucleotide hybridization, and DNA sequencing]. A spectrum of bone lesions associated with such mutations was identified and it was possible to recognize three primary, but distinct, histological patterns, defined here as Chinese writing type, sclerotic/Pagetoid type, and sclerotic/hypercellular type, which are characteristically associated with the axial/appendicular skeleton, cranial bones, or gnathic bones, respectively. Features of FD histopathology were characterized by confocal fluorescence microscopy, which allowed the definition of osteogenic cell shape changes and 'Sharpey fibre bone' as common denominators of all histological subtypes. Defining characteristics of the different subtypes, two of which diverge from standard descriptions of FD and have never been characterized before, were dependent on the amount and structure of bone tissue within the FD lesion. These data emphasize the non-random (site-specific) variability of FD histopathology in patients carrying activating mutations of the Gs alpha gene and provide additional evidence for the occurrence of Gs alpha mutations in cases of FD other than typical MAS.

Adolescent↗

PubMed1999

Gamma-tubulin in Chlamydomonas: characterization of the gene and localization of the gene product in cells.

In addition to their role in nucleating the assembly of axonemal microtubules, basal bodies often are associated with a microtubule organizing center (MTOC) for cytoplasmic microtubules. In an effort to define molecular components of the basal body apparatus in Chlamydomonas reinhardtii, genomic and cDNA clones encoding gamma-tubulin were isolated and sequenced. The gene, present in a single copy in the Chlamydomonas genome, encodes a protein with a predicted molecular mass of 52,161 D and 73% and 65% conservation with gamma-tubulin from higher plants and humans, respectively. To examine the distribution of gamma-tubulin in cells, a polyclonal antibody was raised against two peptides contained within the protein. Immunoblots of Chlamydomonas proteins show a major cross-reaction with a protein of Mr 53,000. In Chlamydomonas cells, the antibody stains the basal body apparatus as two or four spots at the base of the flagella and proximal to the microtubule rootlets. During cell division, two groups of fluorescent dots separate and localize to opposite ends of the mitotic apparatus. They then migrate during cleavage to positions known to be occupied by basal bodies. Changes in gamma-tubulin localization during the cell cycle are consistent with a role for this protein in the nucleation of microtubules of both the interphase cytoplasmic array and the mitotic spindle. Immunogold labeling of cell sections showed that gamma-tubulin is closely associated with the basal bodies. The flagellar transition region was also labeled, possibly indicating a role for gamma-tubulin in assembly of the central pair microtubules of the axoneme.

Amino Acid Sequence↗