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Biomedical subjects

L Cao

Publications and source records attributed to L Cao.

At least 163 records · Page 9Linked to original sources
PubMed1997

Anti-CD53 monoclonal antibody induced LFA-1/ICAM-1-dependent and -independent lymphocyte homotypic cell aggregation.

CD53 is a pan-leukocyte glycoprotein and belongs to a member of the tetraspan family of cell membrane proteins. The predicted structure and functional characteristics of CD53 suggest that it may play important roles in transmembrane signaling, but its roles in cell adhesion have not been clarified. The present study shows that anti-CD53 monoclonal antibody (mAb), HI29 induced homotypic cell aggregation of lymphoid cell lines including a B cell line from a patient with leukocyte adhesion deficiency syndrome (LAD). The homotypic cell aggregation was blocked by another anti-CD53 mAb, MEM53, in all the examined cell lines and by anti-LFA-1 (CD11a/CD18) or anti-ICAM-1 (CD54) mAbs in the cell lines except for the LAD line, but it was not blocked by anti-CD44 or anti-CD49d mAb. The induced homotypic cell aggregation was energy-dependent. These findings suggest that CD53 relates to LFA-1/ICAM-1-dependent and -independent pathways of homotypic cell aggregation of lymphocytes and that it plays an important role in lymphocyte activation and cell adhesion.

Antibodies, Blocking↗
PubMed1997

Mac-1 (CD11b/CD18) is an oligodeoxynucleotide-binding protein.

We have studied the interactions of phosphodiester and phosphorothioate oligodeoxynucleotides with Mac-1 (CD11b/CD18; alpha M beta 2), a heparin-binding integrin found predominantly on the surface of polymorphonuclear leukocytes (PMNs), macrophages and natural killer cells. Binding of a homopolymer of thymidine occurred on both the alpha M and beta 2 subunits. Soluble fibrinogen, a natural ligand for Mac-1, was an excellent competitor of the binding of a phosphorothioate oligodeoxynucleotide to both TNF-alpha-activated and nonactivated PMNs. Upregulation of cell-surface Mac-1 expression increased cell-surface binding of oligodeoxynucleotides. Binding was inhibited by anti-Mac-1 monoclonal antibodies, and the increase in cell-surface binding was correlated with a three- to fourfold increase in internalization by PMNs. An oligodeoxynucleotide inhibited beta 2-dependent migration through Matrigel, but the production of reactive oxygen species in PMNs adherent to fibrinogen dramatically increased. Thus, our data demonstrate that Mac-1 is a cell-surface receptor for oligodeoxynucleotides that can mediate their internalization and that this binding may have important functional consequences.

Antibodies, Monoclonal↗
PubMed1997

Thrombin inhibits atrial natriuretic peptide receptor activity in cultured bovine endothelial cells.

Thrombin and the atrial natriuretic peptide (ANP) possess a number of functionally antagonistic properties in vascular endothelial cells. Thus, regulatory interactions that modulate the activity of one or the other could have important sequelae with regard to cardiovascular homeostasis. Thrombin treatment effected a dose- and time-dependent reduction in ANP receptor activity (maximal 70% to 80% inhibition) in cultured bovine aortic endothelial cells. This resulted from a decrease in total receptor number as well as a modest reduction in the affinity of the receptor for its ligand. The inhibition was largely confined to the type C receptor population, in that thrombin had no effect on maximal type A receptor-linked cGMP accumulation. The protein kinase C-activating phorbol ester 12-O-tetradecanoylphorbol 13-acetate effected a similar reduction in binding activity; however, suppression of protein kinase C activity did not reverse the thrombin effect. Pretreatment of endothelial cells with cycloheximide did not completely prevent the thrombin-dependent inhibition, and thrombin did not effect a reduction in type C receptor mRNA levels, findings that argue for a postsynthetic inhibitory locus. The inhibition of receptor activity was effectively irreversible in that suspension of protein synthesis blocked the recovery of receptor density on the cell surface. Reduction in type C receptor density was accompanied by modest increases in the stability of ANP in the culture medium and enhancement of the cellular cGMP response to the peptide, particularly at low ligand concentrations. These findings demonstrate a potentially important interaction between these two agonist systems in regulating endothelial cell function within the vascular wall.

Amino Acid Chloromethyl Ketones↗
PubMed1997

[Assessment of sputum culture and serology for detection of chlamydia pneumoniae in patients with symptomatic acute respiratory tract infection].

OBJECTIVE: To evaluate sputum culture and serology for detection of chlamydia pneumoniae (C. pneumoniae) in adult patients with acute respiratory tract infection and normal subjects. METHODS: Microimmunoflorescence (micro-IF) test for IgG and IgM antibodies to C. pneumoniae specific antigen was performed in every subject. Thirty-seven patients also had sputum HEP-2 cell culture tested for C. pneumoniae. RESULTS: Twenty-six patients (29.7%) with micro-IF IgG titres equal to or greater than 1:512 or/and IgM titres equal to or greater than 1:32 indicated recent infection. Eight patients (21.3%) with positive sputum culture of C. pnuemoniae were identified. No similar titer was shown in control normal subjects. CONCLUSIONS: Acute infection of C. pneumoniae was common in symptomatic patients with acute respiratory tract infection and attention should be drawn to this special illness.

Adolescent↗
PubMed1997

Effect of DL111-IT on progesterone biosynthesis and viability of rat luteal cells in vitro.

AIM: To study the influence of DL111-IT on progesterone biosynthesis of cultured luteal cells (LC). METHODS: LC viability was assessed with trypan blue dye exclusion and progesterone concentration was measured with radioimmunoassay. RESULTS: DL111-IT decreased the viability of LC after 24-h incubation, its ED50 being 7.7 (95% confidence limits: 7.1-8.5) mg.L-1. DL111-IT inhibited basal secretion of progesterone in a concentration-dependent manner, and 3 mg.L-1 decreased progesterone concentration by 25% vs control. DL111-IT 3 mg.L-1 also inhibited the stimulatory effect of forskolin (cAMP activator) 10 mumol.L-1 and pregnenolone [converted to progesterone by 3 beta-hydroxysteroid dehydrogenase-isomerase complex (3 beta-HSD)] 10 mumol.L-1 on progesterone production in cultured LC, and their inhibitory rates were 43% and 155%, respectively. At the same concentration, DL111-IT did not influence hCG-induced progesterone production. CONCLUSION: DL111-IT inhibited progesterone synthesis by suppressing the conversion of pregnenolone to progesterone (inactivating 3 beta-HSD) and suppressed the activity of cAMP. DL111-IT 6-24 mg.L-1 decreased the viability of LC.

Abortifacient Agents, Nonsteroidal↗
PubMed1997

[Electrocardiographic signs of atrial overload in hypertension].

The aim of the study was to investigate the incidence of the ECG signs of atrial overload in hypertensive patients (HT) and its relationship to the state of the illness and cardiac function. ECG, mechanocardiogram and impedance cardiogram were performed in eighty-two HT and found P > 0.10, P/P-R > 1.6, P-S4 < 140 ms were more common (50%-73.2%) than PEP/LVET (46.3%) and DATI (29.1%). P/P-R = 1.96 +/- 0.588 in Stage 1 of HT, 2.204 +/- 0.678 in Stage 2 showed that P/P-R had a definite relationship to the stage of disease (P < 0.05). For those P-S4 were abnormal the PEP/LVET was increased and DATI decreased. All of these showed a simultaneity in ECG signs of atrial overload embodied the abnormal diastolic function of ventricle. In further analyses, P(ECG), A(ACG) and S4(PCG) may be changed but not keeping synchronous, so they can not be replaced with each other.

Adolescent↗
PubMed1997

[Effect of gossypol in combination with misoprostol on termination of early pregnancy in rats and mice].

Treatment of mice with misoprostol alone at doses ranging from 200 to 6400 micrograms.kg-1, qid on day 6-8 or bid on day 9 of gestation, the rate of effective early pregnancy interruption were low and showed no dose effect relation. When giving misoprostol 200-6400 micrograms.kg-1 bid on day 9 of gestation following administration of gossypol 50 mg.kg-1 qid on day 6-8, the rate of abortion increased as the dose of misoprostol increased, and the ED50 of misoprostol was 397.8 micrograms.kg-1. The ED50 of gossypol given orally on day 6-8 of gestation was 69.4 mg.kg-1. However, when gosyypol was given in combination with misoprostol 400, 800 or 1600 micrograms.kg-1 on day 9 bid, the ED50 of gossypol decreased to 63.2, 48.6 or 34.9 mg.kg-1, respectively. The results suggest that combination of gossypol and misoprostol showed synergistic effect on termination of early pregnancy in mice. Misoprostol obviously strengthened the uterine contraction of rats both in early pregnancy and estrus in vitro. The contraceptive intensity of contraction was increased as the dose of misoprostol increased from 10(-9), 10(-8) to 10(-7) mol.L-1, and the estrus group was higher than the early pregnancy group (P < 0.01). Gossypol(10(-5)-10(-6) mol.L-1) showed no effect on the uterine activity in rats, but the sensitivity of the uterus of the early pregnant rats to misoprosrol was found to be significantly increased by treatment with gossypol on day 6-8 of gestation (P < 0.01). Degeneration of the decidual was observed under light microscopy when gossypol 80 mg.kg-1.d-1, or misoprostol 800 micrograms.kg-1.d-1, or gossypol 40 mg.kg-1.d-1 combined with misoprostol 400 micrograms.kg-1.d-1 was given orally to rats on day 6-8 of pregnancy. The degeneration of cells was more remarkable when both drugs were given in combination. The assay of immunoreactivity for PR demonstrated that the distribution and content of PR in uterine decidua had no difference between the control group and the treated groups.

Abortifacient Agents, Nonsteroidal↗
PubMed1997

[The effects of gossypol on rat luteal cells, human decidual cells and cytotrophoblasts].

The direct effects of gossypol on the serum-free primary cultures of rat luteal cells and cytotrophoblasts were observed. The results indicate that: (1) Gossypol affected the viability of the cultured rat luteal cells, LD50: 1.6 (0.4-2.9) micrograms.ml-1. (2) The basal secretions of progesterone were significantly inhibited at low and high concentrations. The activities of 3 beta-HSD, adenyl cyclase and hCG-stimulated progesterone production were inhibited by higher concentrations of gossypol. (3) Gossypol damaged cultured human decidual cells and cytotrophoblasts, the LD50 were 3.5(0.4-6.6) micrograms.ml-1 and 4.1(0.6-7.6) micrograms.ml-1, respectively. These results suggest that the luteolytic effect is the main mechanism of action for the termination of early pregnancy by gossypol, while the direct damaging effects on decidual cells and cytotrophoblasts may also play a role in the termination of early pregnancy.

Animals↗
PubMed1997

[Analysis of semi-volatile organic compounds in chemical waste by gas chromatography/mass spectrometry].

According to US EPA 8270 method the semi-volatile organic compounds in chemical waste were analysed by internal standard method which could eliminate the systematic and injection errors and increase the accuracy of the results. Through this experiment, ten prior pollutants of US EPA and eleven organic chlorinated compounds with concentrations between 0.4 microg/g and 80 microg/g in the waste were determined. It is concluded that the waste was hazardous and could not be disposed without proper treatment.

Gas Chromatography-Mass Spectrometry↗
PubMed1997

[Study on the tribochemistry of antiwear additive BA1 by FTIRM].

This paper studied the tribochemistry of antiwear additive BA1 by FTIR microscope technique. We observed the changes of physical properties, interpreted the infrared spectra of the products in the track and concluded the chemical mechanism through the change of BA1 concentration, load and rubbing time. The results shows that the BA1 was decomposed, oxided and a thin film was produced when rubbed. This film makes the rubbing efficiency less.

English Abstract↗
PubMed1997

[Expression of foreign tyrosine hydroxylase gene in the rat model of Parkinson's disease].

A total of 75 adult rats were used to produce hemiparkinson's disease (PD) model by unilateral injection of 6-hydroxydopamine (6-OHDA) into the right substantial nigra. Four weeks following the lesions, rats were tested for apomorphine (APO) -induced asymmetric rotation. Only rats that showed more than seven turns per minute were selected as PD models for transplantation. A tyrosine hydroxylase expression plasmid (pSVK3-TH) mixed with lipofectin was transplanted into the right striatum of 15 PD rats. Another 20 PD rats transplanted either with lipofectin or with pSVK3-TH served as controls. Every three days following transplantation, the performance of asymmetric rotation were tested and stained with the TH-immunohistochemistry. Only the animals grafted with pSVK3-TH mixed with lipofectin were found to show the decreased rotational behavior and a few TH-positive cells in the right striatum at the postgraft day 3-12, but not day 18. The results indicate that there exists a correlation between amelioration of asymmetric rotation and the TH gene expression in the denervated striatum. It is suggested that the lipofectin may mediate foreign TH gene expression in the PD rat brain.

Animals↗
PubMed1996

Nitric oxide stimulates both the basal and reflex release of vasopressin in anesthetized rats.

In view of the fact of the high concentration of neuronal nitric oxide synthase (NOS) in the supraoptic and paraventricular nuclei as well as the posterior pituitary, it has been supposed that nitric oxide (NO) may be involved in the regulation of hormone secretion from these sites. In the present study, L-arginine, the precursor of NO, and N(omega)-nitro-L-arginine methyl ester (L-NAME), the NOS inhibitor, were intracerebroventricularly (i.c.v.) administered into the pentobarbital anesthetized rats. The results showed that plasma arginine vasopressin (AVP) concentration increased after the injection of L-arginine (1.0 mg in microliters, i.c.v.) and decreased after the L-NAME (270 micrograms in 5 microliters, i.c.v.). The elevated plasma AVP level in response to short-term hypotension induced by intravenous infusion of sodium nitroprusside was also significantly reduced by i.c.v. administration of L-NAME. The results indicate that NO acts as a stimulating factor to both the basal and reflex release of AVP, opposing the view that NO plays an inhibitory role in the regulation of AVP secretion.

Anesthesia↗
PubMed1996

Scavenger receptor-mediated adhesion of microglia to beta-amyloid fibrils.

A pathological hallmark of Alzheimer's disease is the senile plaque, containing beta-amyloid fibrils, microglia and astrocytes. Beta-amyloid fibrils exert a cytotoxic effect on neurons, and stimulate microglia to produce neurotoxins, such as reactive oxygen species. Mononuclear phagocytes, including microglia, express scavenger receptors that mediate endocytosis of oxidized low-density lipoproteins, and adhesion to glucose-modified extra-cellular matrix proteins. Here we report that class A scavenger receptors mediate adhesion of rodent microglia and human monocytes to beta-amyloid fibril-coated surfaces leading to secretion of reactive oxygen species and cell immobilization. Thus, class A scavenger receptors are potential therapeutic targets in Alzheimer's disease.

Alzheimer Disease↗
PubMed1996

The value of perioperative echocardiography in percutaneous balloon mitral valvuloplasty.

In order to investigate the value of perioperative echocardiography in percutaneous balloon mitral valvuloplasty (PBMV), two-dimensional echocardiography (2-DE), Doppler echocardiography and color Doppler flow imaging (CDFI) were employed prior to PBMV in 52 patients and during or after PBMV in 15 patients. The results showed that TTE and TEE were helpful in the selection of candidates for 2-DE transseptal and balloon dilation procedures. Continuous monitoring of 2-DE, Doppler echocardiography and CDFI during PBMV could make this procedure safer and more effective, reduce X-ray exposure and avoid complications. Echocardiography was useful in fluoroscopy and could be used for evaluation of the effects of operation.

Adult↗
PubMed1996

The Fas antigen is detected on immature B cells and the representative cell lines show Fas-mediated apoptosis.

The expression and functions of Fas antigen, a major regulator of apoptosis, in T-cell selection have been intensively investigated, but little is known about its expression i immature B cells which are also selected in the bone marrow, and plasma cells which are at the terminal stage of B-cell differentiation and are designed to die. We examined bone marrow cells and found Fas antigen on these cells at low levels. Next we analysed Fas expression and susceptibility to anti-Fas antibody-mediated apoptosis on B-cell lines representing various stages of differentiation. We also examined the expression of Bcl-2 and Bax on these lines, which were intimately related to apoptosis. Fas antigen was almost negative on pre-pre-B cell lines and was detected on pre-B-cell lines at low levels. All plasma cell lines expressed Fas at a low to moderate level. Some cell lines with peripheral B-cell phenotype expressed Fas antigen. Except for the Burkitt cell lines and one plasma cell line, susceptibility to Fas-mediated apoptosis depended on Fas expression. Bcl-protein was detected on all but one cell line and Bax was detected on 15/23 lines, but neither were related to cellular differentiation or Fas expression.

Apoptosis↗
PubMed1996

Sodium-glucose cotransporters display sodium- and phlorizin-dependent water permeability.

Expression of Na(+)-glucose cotransporters of the SGLT-1 type by Xenopus laevis oocytes increased the osmotic water permeability (Pf) of oocytes by a factor of 1.9-2.8, in the presence and in the absence of 5 mM extracellular glucose. The Pf increase was correlated with the amount of SGLT-1 cRNA injected. In oocytes expressing SGLT-1, either addition of phlorizin to the medium or the replacement of Na+ by choline inhibited the uptake of methyl-alpha-D-glucopyranoside, a specific substrate for SGLT-1, and returned oocyte Pf to its level in uninjected oocytes. Phlorizin inhibited the SGLT-1-attributable increase in Pf with an inhibition constant (Ki) of 6.1 microM, a value analogous to the Ki for phlorizin inhibition of sugar uptake. However, neither the presence of phlorizin nor the absence of extracellular Na+ significantly affected the increase in Pf elicited in oocytes expressing GLUT-1, a facilitative glucose transporter. These findings suggest that SGLT-1 forms a pore that allows the transmembrane passage of water and that water and glucose traverse the protein through this pore. The finding that removal of extracellular Na+ abolishes the increase in Pf attributable to SGLT-1 suggests that extracellular Na+ is required to maintain patency of this transporter's water-permeable transmembrane pore.

Animals↗