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Biomedical subjects

B Liu

Publications and source records attributed to B Liu.

At least 523 records · Page 29Linked to original sources
PubMed1996

[The colorimetric method for measuring activities of lipoprotein lipase and hepatic lipase in plasma].

To study the pathogenesis of hyperlipoidemia and atheromatosis and the metabolism of lipoprotein, we have developed a colorimetric method for simultaneously determining the activities of post-heparinplasma lipoprotein lipase (LPL) and hepatic lipase (HL). The intralipid was kept for LPL and HL at 37 degrees C, pH8.3 for 30 min, with 100 microliters post-heparin plasma. The LPL and HL in the post-heparin plasma could hydrolyse the triglyceride in intralipid into glycerine and free fatty acid (FFA). Determining the amount of FFA by copper-reagent method, we could measure the activities of LPL and HL. The kinetics of LPL and HL in post-heparin plasma was observed. K(m) values for LPL and HL were 0.9 mumol/L and 2.4 mumol/L respectively. The C. V. for LPL and HL were 4.5% (n = 4), 2.9% (n = 6) and 6.4% (n = 6), 4.8% (n = 6) respectively.

Animals↗
PubMed1996

[Otoacoustic emission and auditory efferent function testing in normal subjects and patients with sensori-neural hearing loss].

OBJECTIVE: To examine the role of otoacoustic emission and function test of the auditory efferent system in evaluating of auditory functional status in both normal and diseased conditions. METHODS: Spontaneous and transient evoked otoacoustic emission and efferent function in terms of contralateral white noise induced transient evoked otoacoustic emission suppressions were tested and cross compared in 32 normal ears, 24 ears with cochlear hearing loss and 16 ears with retrocochlear hearing loss. RESULTS: Transient evoked otoacoustic emission amplitude and contralateral suppression, spontaneous otoacoustic emission incidence, peaks and frequency range were significantly reduced in cochlear hearing loss, while in retrocochlear hearing loss transient evoked otoacoustic emission and spontaneous otoacoustic emission levels were significantly higher than in cochlear hearing loss group and showed no suppression. CONCLUSION: Contralateral acoustic stimulation induced transient evoked otoacoustic emission suppression as an index of efferent function is clinically feasible. Combined otoacoustic emission and efferent tests are of great significance in evaluating cochlea status and auditory central mechanisms. Auditory efferent function is weakened in cochlear lesions and severely damaged in retrocochlear lesions.

Acoustic Impedance Tests↗
PubMed1996

[Azathioprine and its combination with methylprednisolone: preventive effect on chronic cerebral vasospasm].

OBJECTIVE: To study the effects of azathioprine alone and combined azathioprine and methylprednisolone on chronic cerebral vasospasm. METHODS: An animal model of "double subarachnoid hemorrhage" was established by two cisterna magna injections of non-heparinized autologous arterial blood (0.3 ml/kg). The preventive effect of azathioprine alone and its combination with methylprednisolone on chronic cerebral vasospasm was studied. By angiography of vertebrobasilar artery with a transfemoral catheter, assay of LPO (lipid peroxidation) was performed on BA wall. Chronic cerebral vasospasm following subarachnoid hemorrhage was noted and the drugs' effect on chronic cerebral vasospasm also observed. RESULTS: Seven days after subarachniod hemorrhage, the basilar arterial (BA) diameter was 87% +/- 26% of the original BA diameter, and LPO content of BA wall was 0.03 +/- 0.01 nmol/mg in azathioprine group and 93% +/- 20% (BA diameter) and 0.02 +/- 0.01 nmol/L (LPO content) in azathioprine plus methylprednisolone group. When the BA diameter was 53% +/- 19%, the LPO content was 0.11 +/- 0.05 nmol/mg in the control group. Pathological examination showed that azathioprine alone and its combination with methylprednisolone obviously reduced the damage to the BA wall. CONCLUSION: Azathioprine has preventive effect on chronic cerebral vasospasm, supresses the production of free radicals and reduces damage to the BA wall following subarachnoid hemorrhage. Combined azathioprine methylprednisolone has produces better effects when only lower dosage is used.

Animals↗
PubMed1996

[A study of HIA-DR antigen expression in nasopharyngeal carcinoma and its relation with clinical pathology and prognosis].

In order to clarify the relationship between HLA-DR antigen expression of nasopharyngeal carcinoma (NPC) and the clinicopathology and prognosis of NPC, immunohistochemical studies on HLA-DR antigen expression in 77 NPC cases were performed. The results showed that the positive rate of HLA-DR was 44.2% in this series. Non-neoplastic epithelium did not express this antigen. A close association was found between expression of HLA-DR antigen and the clinical staging of NPC. The positive rate of HLA-DR gradually decreased with tumor progression, showing a remarkable difference among tumors in different clinical stages (P < 0.05). Analysis of patient survival demonstrated that the prognosis of NPC patients with HLA-DR expression was significantly better than those without (P < 0.01). The above results give support to the possibility of immunomodulation of tumors.

Adult↗
PubMed1996

The expression of c-erbB-1 and c-erbB-2 oncogenes in basal cell carcinoma and squamous cell carcinoma of skin.

The expression of c-erbB-1 and c-erbB-2 oncogenes were investigated by immunohistochemistry using monoclonal antibodies to c-erbB-1 and c-erbB-2 protein in 43 cases of basal cell carcinoma (BCC) and 26 cases of squamous cell carcinoma (SCC). We found that the expression of c-erbB-1 oncogene in all BCC increased by different degrees and the expression of c-erbB-2 oncogene in BCC was significantly reduced or lost when compared to that in normal epidermal cells. Furthermore, apparent negative and positive relationships were observed respectively between the tumor differentiation and the expression of c-erbB-1 and c-erbB-2 oncogenes in SCC. It is suggested that the abnormal expression of c-erbB-1 and c-erbB-2 oncogenes in BCC and SCC may play a role in the development of skin tumors. The pattern of the c-erbB-1 and c-erbB-2 oncogenes expression in SCC may assist in distinguishing the biological behavior and prognosis of SCC.

Adolescent↗
PubMed1996

[Review of applying implant-magnetic attachments to oral and maxillofacial prostheses].

In order to evaluate the applying effect of MDIC implant-magnetic attachments on oral and maxillofacial prostheses, 38 patients, whose oral and maxillofacial defects had been restored with implant-magnetic attachments prostheses, were followed up for 1-4 years. The effects were evaluated by the measurement of the retentive force of the prostheses, X-ray and clinical examination. The results show: the successful rate of the restoration was 94.7%; two sets implant-magnetic attachments could offer an average of 14.7 N retentive force for lower complete dentures, which could meet various functional needs of the prostheses, but magnetic retentive force decreased as the applying time goes on the magnetic retainers should be changed after two years; negative rate of bone absorption on implant-bone surface was 92.6%; negative rate of gingival inflammation was 91.3%. The implant-magnetic attachments offer realize reliable retention, don't transmit lateral force to implants. Patients can insert and remove the prostheses and clean the implants and defect cavities conveniently. The above advantages are benefit to tissue health and functions of the prostheses. So, implant-magnetic attachments can be used in the restoration of various oral and maxillofacial defects.

Bone Resorption↗
PubMed1996

[Evaluation of different pathologic methods for the diagnosis of sarcoidosis].

The biopsy of different tissues were reviewed in 34 patients with intrathoracic sarcoidosis for determining their value on the diagnosis of sarcoidosis. Biopsy of different tissues was performed by routine method. The transbronchial lung biopsy (TBLB) was done under bronchoscope. The diagnosis was confirmed in 90.9% (10/11) of the biopsies of periphery lymph nodes, 75.0% (3/4) of the scalene nodes' biopsies, 68.4% (13/19) of the transbronchial lung biopsies and 70.6% (12/17) of the bronchial mucosal biopsies (BMB) through fibroptic bronchoscopy. Only 4 in 7 patients were diagnosed through skin biopsies. Kveim test was positive in 5 of 6 patients. Both TBLB and BMB were undertaken in 16 patients. The coincidence ratio between them was as high as 81.3%. The total diagnostic percentage through bronchoscopy was 87.5%. Significant differences were found between the results of TBLB or SMB before and after 1990 (P < 0.05 and 0.01 separately proved by chi 2 test). After 1990, 85.7% of TBLBs and 92.3% of BMBs were diagnostic. According to the study, TBLB and BMB were the methods that were repeatable, highly diagnostic, less invasive, and mutually compensable. They were superior over the other methods in the diagnosis of sarcoidosis. The diagnostic yield could be elevated by the accumulation of experiences and the improvement of techniques. They deserved recommending in the clinical practice.

Adult↗
PubMed1996

[Measurement of serum apoA I and apoA II in 438 male healthy subjects aged 40-70 in Chengdu area].

Using the method of immunoturbidimetric assay (INA) for apoA 1 and the method of radial immunodiffusion assay (RID) for apoA II developed by ourselves, we measured the serum apoA I and apoA II concentrations in 438 male healthy subjects aged 40-70 in Chengdu area. The contents of serum apoA I and apoA II for male aged 40-70 were 130.1 +/- 22.0 mg/dl (n = 438) and 29.9 +/- 4.90 mg/dl (n = 437) respectively. The serum apoA I and A II levels showed no significant increase with age and had a normal distribution.

Adult↗
PubMed1996

[Transcriptional expression of oncogenes and Rb antioncogene in experimental atherosclerotic lesions].

Atherosclerosis (AS) is characterized by the proliferation of the smooth muscle cells (SMC) in the arterial wall. Its pathogenesis might be associated with overexpression of oncogenes in SMC. Gorden and Barrett et al found that sis mRNA level elevated in human atherosclerotic plaques 5-12 fold above level present in normal artery. But the transcriptional expression of c-fos, c-myc, c-jun, H-ras, v-erb-B oncogenes and Rb antioncogene in atherosclerotic lesion has not yet been reported. A study on these oncogenes and Rb gene expression in artherosclerotic lesions in rabbits fed on high cholesterol diet were assayed by the dot blot hybridization using alpha-32P-labelled oncogenes and Rb gene fragments as the probes. After fed with the high cholesterol diet for six months, the plasma cholesterol levels in AS rabbits were significantly increased (1300 +/- 240 mg/dl vs 67.1 +/- 11.5 mg/dl). The atherosclerotic plaques covered 91% +/- 11% of the intimal aortic surface of aorta thoracalis. The results showed that the atherosclerotic plaques contained 3-4 fold more v-sis, c-fos and c-myc mRNA (P < 0.01), 2 fold more c-jun and H-ras mRNA (P < 0.01), and less Rb mRNA (P < 0.05) than those in the normal aortic arteries. But the expression of v-erb-B gene in atherosclerotic plaques remained unchanged. These results indicate that the abnormal expression of v-sis, c-myc, c-fos, c-jun, and H-ras oncogenes and Rb antioncogene may play an important role in arterial SMC proliferation and pathogenesis of atherosclerosis.

Animals↗
PubMed1996

[Regulation of purine biosynthetic genes expression in Salmonella typhimurium. V. Nucleotide sequences evidence without purJ gene].

Previous genetic analysis showed that AICAI transformylase, IMP cyclohydrolase and GAR synthetase are encoded by purJ, purH and purD respectively, and which constitute a operon, mapped on 90 min in genetic map of Salmonella typhimurium But recent study in E. coli indicated that the genes encoding for above three enzymes only have purH and purD, without purJ gene. Report here is the DNA sequences evidence for abence of purJ gene in Salmonella typhimurium.

Escherichia coli↗
PubMed1996

[Otoacoustic emissions and tinnitus].

Methods of objective tinnitus testing exploration causes of tinnitus and the relationship between OAE and tinnitus are reported. In 306 ears with tinnitus (with or without hearing loss), Distortion Products Otoacoustic Emission (DPOAE), Spontaneous OAE (SOAE) and Transiently Evoked OAE (TEOAE) were tested by ILO92 Otodynamics Analyzer. Results indicated that 1. In these cases there was no correlation between the frequency of tinnitus and SOAE. 2. In 94.8% of sensorineural hearing loss with tinnitus the DPOAE-gram presented lower amplitude or was absent within the frequency range of elevated pure-tone-thresthold; In 59% of cases with normal hearing and tinnitus the amplitude of DPOAE at nearby frequencies of tinnitus was decreased and there was no SOAE detectable. At frequencies other than that of tinnitus, the amplitude of DPOAE was normal and SOAE could be recorded. So OAE could reflect cochlear lesion in early stage.

Adolescent↗
PubMed1995

Topochemical catalysis achieved by structure-based ligand design.

Recently, a cyclic peptide ligand, cyclo-Ac-[CHPQG-PPC]-NH2, that binds to streptavidin with high affinity was discovered by screening phage libraries. From the streptavidin-bound crystal structures of cyclo-Ac-[CHPQGPPC]-NH2 and of a related but more weakly binding linear ligand, FSHPQNT, we designed linear thiol-containing streptavidin binding ligands, FCH-PQNT-NH2 and Ac-CHPQNT-NH2, which are dimerized catalytically by the streptavidin crystal lattice of space group I222, as demonstrated by high performance liquid chromatography and mass spectrometry. The catalytic dimerization relies on presentation of the ligand thiols toward one another in the lattice. The streptavidin crystal lattice-mediated catalysis achieved by structure-based design is the first example of catalysis of a chemical reaction by a protein crystal lattice. The spontaneous and crystal catalyzed rates of disulfide formation were determined by high performance liquid chromatography at pH 3.1, 4.0, 5.0, and 6.0. The ratio of the catalyzed to uncatalyzed rate was maximal at pH 3.1 (kcat/kuncat = 3.8), diminishing to 1.2 at pH 6.0. The crystal structures of the streptavidin-bound dimerized peptide ligands, FCHPQNT-NH2 dimer at 1.95 A and Ac-CHPQNT-NH2 dimer at 1.80 A, are described and compared with the structures of streptavidin-bound FSHPQNT monomer and cyclo-Ac-[CHPQGPPC]-NH2 dimer.

Amino Acid Sequence↗
PubMed1995

Melanoma cell lines express VEGF receptor KDR and respond to exogenously added VEGF.

Tumour-secreted vascular endothelial growth factor (VEGF) exerts a number of effects which are important in tumour pathology, including stimulation of angiogenesis and permeabilisation of tumour-associated vasculature. In this study we have examined the possibility that VEGF may also play an autocrine role in tumour growth. Using reverse-transcriptase polymerase chain reaction (RT-PCR), the expression of VEGF was found in 15/15 human tumour cell lines examined, while the VEGF receptor KDR was detected only in three melanoma cell lines (MeWo and A375, both wild type and metastatic variant). Exogenously added VEGF (10ng/ml) was able to stimulate up to 40% increased proliferation of A375 M melanoma cells following a 48-h period of quiescence, suggesting that VEGF may indeed play a role in autocrine, as well as paracrine, stimulation of melanoma growth.

Base Sequence↗
PubMed1995

DNA elements with AT-rich core sequences direct pituitary cell-specific expression of the pro-opiomelanocortin gene in transgenic mice.

Corticotrophs are the first fully differentiated cells to appear in the anterior pituitary during organogenesis and are distinguished by pro-opiomelanocortin (POMC) gene expression. Earlier studies in our laboratory defined three DNA regions (sites 1, 2 and 3) within promoter sequences at the 5'-end of the rat POMC gene (-323/-34) that cooperatively targeted cell-specific gene expression to corticotrophs and melanotrophs in transgenic mice. In this study we analysed the DNA-nuclear protein interactions underlying this functional activity. We demonstrated that the transcriptional activator SP1 interacts with GC-rich regions in sites 1 (-146/-136) and 2 (-201/-192) and an unidentified protein, which we call PP1 (putative pituitary POMC1), interacts with AT-rich regions in sites 2 (-202/-193) and 3 (-262/-253). The PP1-binding activity appears to be specific to cells that express the POMC gene because it was detected in nuclear extracts prepared from AtT20 corticotroph cells and mouse melanotroph tumours but not from GH4 pituitary tumour cells, HeLa cells or liver. Site-directed mutagenesis of core binding sequences demonstrated that PP1 is required for the correct cell-specific expression of the POMC gene in the pituitary gland of transgenic mice and SP1 appears to support such an expression. The best core binding sequence for PP1 is TAAT, a possible transcription factor homeodomain contact site. However, PP1 is distinct from Brn 3.0, a POU protein that also binds to site 3. We conclude that PP1 is a transcriptional activator for pituitary-specific POMC gene expression.

Animals↗
PubMed1995

An ospA frame shift, identified from DNA in Lyme arthritis synovial fluid, results in an outer surface protein A that does not bind protective antibodies.

Passive immunization with murine or human Abs to outer surface protein A (OspA) can protect mice against Borrelia burgdorferi, but OspA Abs elicited during natural infection in mice or humans are unable to clear the spirochete from the infected host. To examine Ab binding by OspA during the course of human infection, we amplified the operon encoding full-length ospA and ospB from synovial fluids of a patient with chronic Lyme arthritis, the first such recoveries from human material, at four separate time points over 4.5 mo, and expressed OspA in Escherichia coli. OspA mAbs that passively protected mice from infection did not bind one of the expressed OspAs, because of a deletion in ospA that resulted in a frame shift and premature stop codon near the carboxyl terminus. However, expressed OspA from a later synovial fluid sample did not contain this deletion. Thus, although altered forms of OspA, which potentially can influence host immune effectiveness, do occur in the human host, they cannot be the only factors responsible for microbial persistence.

Adolescent↗
PubMed1995

Microsatellite instability and mutations of the transforming growth factor beta type II receptor gene in colorectal cancer.

The TGF beta type II receptor (RII) was found to be mutated within a polyadenine tract in 100 of 111 (90%) colorectal cancers with microsatellite instability. Other polyadenine tracts of similar length were mutated in these samples but not as frequently as RII. In most cases, the polyadenine tract mutations affected both alleles of RII, and in four tumors heterozygous for the polyadenine mutations, three had additional mutations that were expected to inactivate the other RII allele. These genetic data support the idea that RII behaves like a tumor suppressor during CR cancer development and is a critical target of inactivation in mismatch repair-deficient tumors.

Animals↗
PubMed1995

Tamoxifen treatment of ovariectomized mice alters dopamine release from striatal tissue fragments superfused in vitro.

In this report we examined the effect of tamoxifen upon the nigrostriatal dopaminergic system. Ovariectomized mice were subjected to one of the following treatments: two subcutaneous injections administered on successive days of the sesame oil vehicle (control), estradiol benzoate (EB-10 micrograms), tamoxifen citrate (TMX 125 micrograms) or a combination of EB+TMX. At 24 h after the second injection, the caudate nucleus was superfused in vitro to evaluate the effects of these treatments upon basal as well as potassium stimulated (30 mM) dopamine release rates. In addition, uteri were weighed from each animal. Basal and total fractional dopamine release rates from the caudate nucleus of control mice were significantly lower than those of the other three treatments, which failed to differ among each other. Potassium minus (-) basal stimulated dopamine release rates failed to differ significantly among the four treatment conditions. Uterine weights of the TMX treated mice were significantly greater than controls, but significantly lower than EB and EB+TMX animals. These data show that TMX can significantly increase caudate nucleus dopamine release to levels observed in EB treated mice. These agonistic effects of TMX upon nigrostriatal dopaminergic function can be contrasted with its relatively weak estrogenic effects upon uterine weights and indicate the discriminatory, system specific effects that can be exerted by this anti-estrogen. This demonstration of TMX's ability to modulate central nervous system function is of particular relevance in light of pending clinical trials for the prophylactic use of TMX in the treatment of women for breast cancer.

Animals↗