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Biomedical subjects

L Hou

Publications and source records attributed to L Hou.

At least 73 records · Page 4Linked to original sources
PubMed1999

[Investigation of the reaction of iso-propylamine on propylene oxide by Fourier transform infrared spectroscopy].

Fourier transform infrared spectroscopy method has been developed for in-situ monitoring the reaction of iso-propylamine on propylene oxide without the need to sample the reaction medium. The profile of the reaction and the influences of conditions can be directly reflected in the feature absorbance changes of the reactant and product at 826 cm(-1) and 1069 cm(-1), respectively. It is shown that the in situ infrared spectroscopy is a powerful technique to investigate the mechanism and kinetics of the reaction and to optimize the control conditions.

English Abstract↗
PubMed1998

Multislice imaging of quantitative cerebral perfusion with pulsed arterial spin labeling.

A method is presented for multislice measurements of quantitative cerebral perfusion based on magnetic labeling of arterial spins. The method combines a pulsed arterial inversion, known as the FAIR (Flow-sensitive Alternating Inversion Recovery) experiment, with a fast spiral scan image acquisition. The short duration (22 ms) of the spiral data collection allows simultaneous measurement of up to 10 slices per labeling period, thus dramatically increasing efficiency compared to current single slice acquisition protocols. Investigation of labeling efficiency, suppression of unwanted signals from stationary as well as intraarterial spins, and the FAIR signal change as a function of inversion delay are presented. The assessment of quantitative cerebral blood flow (CBF) with the new technique is demonstrated and shown to require measurement of arterial transit time as well as suppression of intraarterial spin signals. CBF values measured on normal volunteers are consistent with results obtained from H2O15 positron emission tomography (PET) studies and other radioactive tracer approaches. In addition, the new method allows detection of activation-related perfusion changes in a finger-tapping experiment, with locations of activation corresponding well to those observed with blood oxygen level dependent (BOLD) fMRI.

Artifacts↗
PubMed1998

Antibodies to mycoplasma fermentans in HIV-positive heterosexual patients: seroprevalence and association with AIDS.

There are conflicting reports concerning the prevalence of Mycoplasma fermentans in HIV-positive patients and its association with AIDS. Serum antibodies to M. fermentans were measured by a modified immunoblotting technique in 48 HIV-positive heterosexual patients and in 30 HIV-negative heterosexual controls. Antibodies to M. fermentans were detected in 19 (40%) of HIV-positive patients and in three (10%) of the HIV-negative controls (P = 0.01). The prevalence of antibodies to Mycoplasma hominis and to Ureaplasma urealyticum was similar in both groups. In the HIV-positive group, 16/19 (84%) M. fermentans-positive patients developed AIDS, compared to eight of 29 (28%) M. fermentans-negative patients (P = 0.0004). The HIV-positive patients with antibodies to M. fermentans had a lower CD4+ cell count and a higher prevalence of antibodies to the other mycoplasma tested (P = 0.007 and P = 0.03, respectively), as compared to the patients without antibodies to M. fermentans. These findings may suggest that the presence of antibodies to M. fermentans indicate an opportunistic infection. Of the 19 M. fermentans-positive patients, 11 were positive on the first examination, and eight became positive during the follow-up period. Seven out of these eight patients developed antibodies to M. fermentans before the development of AIDS. Therefore, the possibility exists that M. fermentans might influence the development of AIDS.

AIDS-Related Opportunistic Infections↗
PubMed1998

A CD4+ proliferation of large granular lymphocytes expresses the protease activated receptor-1.

The platelet-type thrombin receptor was the first member to be identified in a family of protease activated receptors (PARs) and has been designated PAR-1. We recently reported that the large granular lymphocytes (LGLs) in patients with proliferations of CD8+ cells co-expressed PAR-1 and the expression of PAR-1 correlated with the expression of CD57. Here we show, by three-colour immunofluorescence, that the LGLs from a patient with a rare CD4+ CD57+ monoclonal expansion also expressed PAR-1. Northern blot analysis confirmed the presence of high levels of mRNA for PAR-1 in these LGLs.

Aged↗
PubMed1998

Immunolocalization of protease-activated receptor-2 in skin: receptor activation stimulates interleukin-8 secretion by keratinocytes in vitro.

The protease-activated receptor-2 (PAR-2) is a seven transmembrane domain receptor related to the thrombin receptor, which is activated in vitro by cleavage by trypsin. Affinity-purified rabbit IgG raised against a peptide corresponding to the trypsin cleavage site of PAR-2 was used for an immunohistochemical study of skin. The expression of PAR-2 in epidermis was striking, with keratinocytes showing abundant intercellular and cytoplasmic staining. Basal cells showed the strongest staining intensity and the stratum corneum was negative. Staining with control IgG used at the same concentration was consistently negative. The functional expression of PAR-2 by the simian virus transformed human skin keratinocyte cell line SVK14 was demonstrated by Northern blot analysis, flow cytometric analysis and the measurement of intracellular calcium. Treatment of SVK14 with trypsin or a receptor agonist peptide (SLIGKV-NH2) caused a dose-dependent increase in the secretion of the chemokine interleukin-8 (IL-8) in vitro. The effect of the peptide was specific, since control acetylated peptide was without activity. We conclude that PAR-2 is highly expressed by epidermal keratinocytes and receptor activation in vitro leads to increased IL-8 secretion by keratinocytes. These data raise the possibility that PAR-2 may play a role in epidermal homeostasis and inflammatory conditions.

Blotting, Northern↗
PubMed1998

The effect of different bovine viral diarrhea virus genotypes and biotypes on the metabolic activity and activation status of bovine peripheral blood mononuclear cells.

The effects of cytopathic (cp) and non-cytopathic (ncp) bovine viral diarrhea virus (BVDV) on the cellular metabolic activity and activation status of bovine peripheral blood mononuclear cells (PBMC) were investigated. Cellular DNA and protein synthesis was determined by [3H]thymidine and [3H]valine incorporation, respectively, in phytohemagglutinin (PHA)-stimulated PBMC. All cp strains and most ncp BVDV strains significantly inhibited DNA synthesis in PHA-stimulated PBMC; however, only cp BVDV strains inhibited protein synthesis. A plaque assay and immunofluorescence test confirmed productive BVDV infection of PBMC. In addition, viral RNA synthesis was demonstrated in BVDV-infected PBMC by RT-PCR. The interleukin-2 receptor (IL-2R) was used as a marker for the activation status of BVDV-infected PBMC. The expression of IL-2R was preserved in virus-infected cells, even though DNA and protein synthesis was suppressed. These findings suggest a novel mechanism of virus-induced immune suppression in which BVDV inhibits basic metabolic activities of bovine PBMC. The activation signals, however, are maintained.

Animals↗
PubMed1998

Protease-activated receptors and their role in IL-6 and NF-IL-6 expression in human gingival fibroblasts.

The serine protease thrombin is formed at sites of coagulation and inflammation and has been shown to have important proinflammatory cellular effects relevant to the pathogenesis of periodontal disease. Thrombin acts via specific cell surface receptors termed protease-activated receptor-1 (PAR-1) and PAR-3, which have a distinctive method of activation. Proteolytic cleavage of the extracellular domain by thrombin reveals a hidden amino terminus which then acts as a "tethered ligand". A short synthetic peptide (SFLLRN) can also mimic the tethered ligand and activate PAR-1 but not PAR-3. Also, a trypsin-sensitive receptor termed PAR-2 has been described which is activated by the PAR-1 activating peptide SFLLRN. Here we show conclusively by flow cytometric and Northern blot analysis that human gingival fibroblasts (HGF) express PAR-1 but not PAR-2. In functional studies we also show that thrombin and SFLLRN stimulated increased expression of mRNA encoding nuclear transcription factor NF-IL-6 and IL-6 in vitro. At optimal concentrations, thrombin (10(-7) M) induced 7.6 +/- 0.01 ng/ml immunoactive IL-6 and PAR-1 activating peptide (5 x 10(-5) M) induced 2.2 +/- 0.2 ng/ml (mean +/- standard error of mean). A proteolytically inactive recombinant thrombin (serine 195 to alanine) was without activity. These data show that HGF express PAR-1 and suggest that PAR-1 activation stimulates increased NF-IL-6 and IL-6 gene expression and IL-6 secretion by HGF in vitro. Whether HGF express PAR-3 is unknown, but the fact that SFLLRN was not a complete replacement for thrombin raises the possibility that HGF may express additional thrombin receptors. These findings add weight to the importance of the cytokine-like role played by thrombin and raise the possibility that protease-activated receptors may play a role in the pathogenesis of inflammatory periodontal disease.

Blood Coagulation↗
PubMed1998

[Secretive activity of tumor necrosis factor alpha (TNF alpha) of marrow stromal cells in acute leukemia and its clinical significance].

OBJECTIVE: To investigate the TNF alpha secreting activity of marrow stromal cells in acute leukemia. METHODS: TNF alpha in vitro culture supernate of marrow stromal cells from 20 acute leukemia patients and 10 normal controls was detected. TNF alpha activities in patients and control serum and in patients leukemic cell culture supernate were also detected. RESULTS: TNF alpha activity in leukemic stromal cell supernate was significantly higher than that of the control (P < 0.05). Some AML cell could spontaneously secret TNF alpha. Serum TNF alpha activity of the patient group is also evidently higher than that of the control group (P < 0.001). CONCLUSION: There were qualitative and quantitative defects of marrow stromal cells in acute leukemia patients. Increased secretion of TNF alpha is probably an important factor leading to the abnormal proliferation of acute leukemia cells.

Adolescent↗
PubMed1997

Proteinase-activated receptor-2: expression by human neutrophils.

Neutrophils were shown to express the proteinase-activated receptor-2 (PAR-2), a seven transmembrane domain receptor, which is activated by cleavage by trypsin. Granulocytes from 14 donors stained positively for PAR-2 with affinity-purified rabbit antibodies raised against a peptide corresponding to the trypsin cleavage site of human PAR-2. Neutrophil activation in response to a receptor activating peptide (RAP) varied between donors. RAP (Ser-Leu-Ile-Gly-Lys-Val-NH2) alone induced an increase in the forward and side light scatter after 5-10 minutes and a small increase in the expression of the activation molecule CD11b. The increased expression of CD11b induced by RAP was markedly enhanced by priming the neutrophils with a low concentration (1 nM) of formyl-Leu-Met-Phe. Trypsin and RAP also induced an increase in intracellular calcium, but there were large variations in the magnitude of responses between donors also in this assay. The effects of RAP in the different assays were specific; acetylated RAP was completely without activity.

Adult↗
PubMed1997

[Effects of overdose fluoride on metabolism of extracellular matrix collagen and proteoglycan in condylar cartilage].

The study was conducted to evaluate the effects of chronic fluorosis on the metabolism of extracellular matrix in the development of rabbit condylar cartilage using the technique of pathology, biochemistry and radiographs. The results demonstrated that collagen content of condylar cartilage and the bone under condylar cartilage decreased (P < 0.01), and the proteoglycar contents increased significantly during the process of fluorosis (P < 0.01). The chondroprogenitor was obviously thin, and the cells of maturation zone increased in number. All the results indicated that overdose of fluoride retarded the growth of the condyle and ramus of the mandible.

Animals↗
PubMed1997

Antiproliferation effects of hexadecylphosphocholine on solid tumour and leukaemia selectively in vitro.

Hexadecylphosphocholine (HePC), an alkylphospholipid analogue representing a new class of antitumor agents, exerts sufficient oncolytic potencies that it might be developed as a selective antitumour drug. This paper reports that 12 cell lines of leukaemia and solid tumour employed in this study were inhibited by HePC in vitro. This result indicated that HePC possessed general antitumour properties, but did not interfere significantly with cell proliferation of normal BMC in tests of colony formation in granulocytic-macrophage colonies (CFU-GM). Because of these advantages, we suggest that HePC would be an excellent antitumour agent for selectively killing tumour cells and is of low toxicity as compared to conventional cytotoxic agents.

Animals↗
PubMed1997

Antiganglioside antibodies in cerebrospinal fluid of children with neuropsychiatric lupus erythematosus.

OBJECTIVE: To determine antiganglioside antibodies (AGA) in cerebrospinal fluid (CSF) of children with neuropsychiatric lupus erythematosus (NPLE), and to investigate their association with clinical manifestations and other laboratory tests. METHODS: An enzyme linked immunoabsorbent assay was used to detect AGA in 22 CSF samples obtained from 18 children with systemic lupus erythematosus (SLE). These patients were further classified into clinical active NPLE (9 patients) and SLE (9 patients) groups. Indirect immunofluorescent assay was used for determination of CSF antinucleus antibodies (ANA). RESULTS: AGA could be found in CSF of all the 9 active NPLE children who had neuropsychiatric manifestations within 6 months before or after AGA was tested. A clear association was observed between AGA and brain CT scan. No detectable ANA was found in CSF samples even though high titer of ANA was present in corresponding serum samples of SLE patients. CONCLUSION: Detection of AGAs in CSF, more sensitive and specific than routine CSF examination and EEG, and positively associated with brain CT scan, is a simple and practical test for early judgment of childhood NPLE.

Adolescent↗
PubMed1996

Early Adaptive Radiation of Birds: Evidence from Fossils from Northeastern China

Late Jurassic and Early Cretaceous birds from northeastern China, including many complete skeletons of Confuciusornis, provide evidence for a fundamental dichotomy in the class Aves that may antedate the temporal occurrence of the Late Jurassic Archaeopteryx. The abundance of Confuciusornis may provide evidence of avian social behavior. Jurassic skeletal remains of an ornithurine bird lend further support to the idea of an early separation of the line that gave rise to modern birds. Chaoyangia, an ornithurine bird from the Early Cretaceous of China, has premaxillary teeth.

Journal Article↗