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Biomedical subjects

L Chen

Publications and source records attributed to L Chen.

At least 703 records · Page 39Linked to original sources
PubMed1998

Systemic and myocardial hemodynamics during periodic obstructive apneas in sedated pigs.

The effects of periodic obstructive apneas on systemic and myocardial hemodynamics were studied in nine preinstrumented sedated pigs under four conditions: breathing room air (RA), breathing 100% O2, breathing RA after critical coronary stenosis (CS) of the left anterior descending coronary artery, and breathing RA after autonomic blockade with hexamethonium (Hex). Apneas with RA increased mean arterial pressure (MAP; from baseline 103.0 +/- 3.5 to late apnea 123.6 +/- 7.0 Torr, P < 0.001) and coronary blood flow (CBF; late apnea 193.9 +/- 22.9% of baseline, P < 0.001) but decreased cardiac output (CO; from baseline 2.97 +/- 0.15 to late apnea 2.39 +/- 0.19 l/min, P < 0.001). Apneas with O2 increased MAP (from baseline 105.1 +/- 4.6 to late apnea 110.7 +/- 4.8 Torr, P < 0. 001). Apneas with CS produced similar increases in MAP as apneas with RA but greater decreases in CO (from baseline 3.03 +/- 0.19 to late apnea 2.1 +/- 0.15 l/min, P < 0.001). In LAD-perfused myocardium, there was decreased segmental shortening (baseline 11.0 +/- 1.5 to late apnea 7.6 +/- 2.0%, P < 0.01) and regional intramyocardial pH (baseline 7.05 +/- 0.03 to late apnea 6.72 +/- 0. 11, P < 0.001) during apneas with CS but under no other conditions. Apneas with Hex increased to the same extent as apneas with RA. Myocardial O2 demand remained unchanged during apnea relative to baseline. We conclude that obstructive apnea-induced changes in left ventricular afterload and CO are secondary to autonomic-mediated responses to hypoxemia. Increased CBF during apneas is related to regional metabolic effects of hypoxia and not to autonomic factors. In the presence of limited coronary flow reserve, decreased O2 supply during apneas can lead to myocardial ischemia, which in turn adversely affects left ventricular function.

Animals↗
PubMed1998

Improved oxygenation with prostaglandin F2alpha with and without inhaled nitric oxide in dogs.

Dogs of mixed breed (n = 7) were anesthetized, right lung atelectasis was established, and the cyclooxygenase pathway was blocked with ibuprofen. Measurements of pulmonary gas exchange were performed (fractional concentration of inspired O2 = 0.95) after infusions of prostaglandin F2alpha (PGF2alpha; 2 microg . kg-1 . min-1), ventilation with nitric oxide (NO; 40 ppm), or both (PGF2alpha + NO) in random order. The arterial PO2 (PaO2) under control conditions was 117 +/- 16 Torr (shunt = 33 +/- 2.5%), was unchanged with NO alone (PaO2 = 114 +/- 17 Torr; shunt = 35.7 +/- 3. 1%), but was significantly improved with PGF2alpha alone (PaO2 = 180 +/- 28 Torr; shunt = 23.2 +/- 2.8%) and with the combination of PGF2alpha + NO (PaO2 = 202 +/- 30 Torr; shunt = 20.9 +/- 2.5%). The addition of NO did not significantly enhance the effectiveness of the PGF2alpha on PaO2. Simulation of these data in a computer model, combining pulmonary gas exchange and pulmonary blood flow, reproduced the results on the basis that vasoconstriction with PGF2alpha was maximal under hypoxia in the atelectatic lung and reduced by hyperoxia in the ventilated lung, consistent with the hypothesis of O2 dependence of PGF2alpha vasoconstriction.

Administration, Inhalation↗
PubMed1998

Serum and immunoglobulin G from the mother of a child with congenital heart block induce conduction abnormalities and inhibit L-type calcium channels in a rat heart model.

Although a strong clinical association exists between congenital heart block (CHB) and an immune response to SSA/Ro and SSB/La proteins, a causative role of these antibodies in the pathogenesis is just emerging. In a preliminary report, we have demonstrated that IgG fractions isolated from the sera of mothers whose children have CHB are arrhythmogenic in the human fetal heart. To more precisely define the arrhythmogenic effect of anti-SSA/Ro-SSB/La antibodies, we used the readily available rat heart model to record: 1) ECGs from Langendorff beating hearts; 2) action potentials from atrioventricular (AV) nodal preparations; 3) L-type Ca currents, I(Ca) at the whole-cell and single channel levels; and 4) other currents such as the transient outward K+ current, I(to), the inward rectifier K+ current, I(K1), and the Na+ current, I(Na). Perfusion of hearts with purified IgG (800 microg/mL), isolated from the serum of a mother with SSA/Ro and SSB/La antibodies whose child had CHB, resulted in bradycardia associated with 2:1 AV block. Simultaneous action potentials were recorded from dissected atrial and AV nodal areas of the rat heart. Superfusion of these preparations with the same mother's IgG fraction resulted in 2:1 AV block followed by complete inhibition of AV nodal action potential. Because AV nodal electrogenesis is largely dependent on I(Ca), the effect of these antibodies on I(Ca) was subsequently determined. Superfusion of myocytes with whole serum or purified IgG (80 microg/mL) from the same mother consistently inhibited whole cell I(Ca), ensemble average Ba2+ currents (I(Ba)) and open state probability, p(o), without affecting the channel conductance. IgG had no significant effect on I(to), I(K1), or I(Na). Whole sera and IgG fractions from a healthy mother with no detectable anti-SSA/Ro or SSB/La antibodies did not inhibit I(Ca) or I(Ba). These results demonstrate that IgG containing anti-SSA/Ro and -SSB/La antibodies induces complete AV block in beating hearts and in multicellular preparations, thus implicating a preferential interaction of these autoantibodies with Ca channels and/or associated regulatory proteins. This is consistent with the observed inhibition of Ca channels that may be a critical factor contributing to the pathogenesis of CHB.

Action Potentials↗
PubMed1998

A novel PMP22 point mutation causing HNPP phenotype: studies on nerve xenografts.

BACKGROUND: Hereditary neuropathy with liability to pressure palsies (HNPP) in most cases is caused by a deletion in chromosome 17p11.2-12 or, rarely, mutations resulting in a functional loss of one copy of the peripheral myelin protein 22 (PMP22) gene. Point mutations that lie deep within transmembrane (TM) domains causing major structural changes in PMP22 are associated with severe neuropathy. METHODS: A 25-year-old asymptomatic woman with a normal neurologic examination volunteered as a control subject. Electrophysiologic studies showed multiple entrapment neuropathies, prompting a search for a genetic defect. In addition, sural nerve fascicles from the subject were grafted into the cut ends of the sciatic nerve of nude mice and studied at 2, 6, and 8 weeks and compared with controls. RESULTS: Direct sequencing of the PMP22 gene revealed a G-->A transition at position 202 in axon 3 of the PMP22 gene. To determine if this was a causative mutation rather than a polymorphism, 102 DNA samples from controls were studied; none showed a similar base pair change. In the nerve xenografts, there was a marked delay at the onset of myelination and an impairment in the regenerative capacity of the nude mice axons engulfed by the mutant human Schwann cells. The axon tips were enlarged and demonstrated neurofilament density increase. Neurofilament density distribution histograms were bimodal in xenografts as well as in the subject's sural nerve. CONCLUSION: This study provides unequivocal evidence that a base pair change causing a Val30Met substitution at the junction of the first TM domain and the extracellular loop of PMP22 results in the HNPP phenotype.

Adult↗
PubMed1998

Toxicity of holotransferrin but not albumin in proximal tubule cells in primary culture.

Proteinuria has been invoked as a cause of tubulointerstitial injury in chronic renal disease, and in vivo studies have suggested indirectly the particular nephrotoxicity of one urinary protein holotransferrin (Tf-Fe). However, to date there has been no direct evidence for the nephrotoxicity of Tf-Fe. To examine the potential cytotoxicity of Tf-Fe and the mechanism involved, and to compare this to another urinary protein albumin, rat proximal tubule cells were studied in primary culture. Tf-Fe at pH 6.0 caused functional and ultrastructural injury, but no cytotoxicity was seen with cells exposed to albumin, apotransferrin (transferrin), or Tf-Fe at pH 7.4. The influence of pH on Tf-Fe-induced cytotoxicity was not due to pH per se, but could be explained by an effect on Tf-Fe uptake. At pH 6.0, uptake of 125I-Tf-Fe (3.55 +/- 0.05 versus 1.25 +/- 0.10 fmol/dish, P < 0.01) and intracellular iron concentration (1.14 +/- 0.25 versus 0.46 +/- 0.23 nmol/dish, P < 0.01) were increased compared with values at pH 7.4. In contrast, pH 6.0 did not increase iron uptake from FeCl3. Lysine (100 mM) inhibited Tf-Fe uptake, decreased intracellular iron concentration, and attenuated Tf-Fe-induced cytotoxicity. The iron chelator des-ferrioxamine (200 microM) and hydroxyl radical scavenger dimethylpyrroline N-oxide (32 mM) abolished lactate dehydrogenase leakage induced by Tf-Fe at pH 6.0. Lipid peroxidation, as assessed by production of malondialdehyde, preceded lactate dehydrogenase leakage. In summary, holotransferrin, but not albumin, is toxic to rat proximal tubule cells, a pH-dependent effect involving its uptake into tubule cells, its iron moiety, and its lipid peroxidation.

Animals↗
PubMed1998

Molecular cloning of a leucine zipper motif-containing novel cDNA specifically expressed in adult mouse testis.

A novel cDNA clone was isolated from a mouse testis cDNA library. This cDNA is 2,020 nucleotides in size and predicted to encode 527 amino acid residues with a molecular weight of 59.9 kDa. Protein sequence motif analysis revealed that the predicted protein contained one leucine zipper motif in its N-terminal portion and two basic domains in its C-terminal portion. Northern blot analysis of adult ICR mouse organs using the cDNA as probe demonstrated that an approximately 2.0-kb transcript was specifically expressed in testis. We therefore termed this novel cDNA tsec-2, testis-specifically expressed cDNAs-2. Results of Southern blot analysis suggested that the tsec-2 gene may exist as a single copy in the mouse genome.

Amino Acid Sequence↗
PubMed1998

[Experimental study of fibrin glue adhesion with epineurial anchor suture to repair peripheral nerves].

To prove and improve the technique of fibrin glue adhesion repair peripheral nerve, 20 male rats were chosen. All the rats was randomly divided into two groups: Suture group (n = 10) and glue adhesion group (n = 10). Left sciatic nerves of the rats were cut with knife and repaired by suture or adhesion methods separately according to their groups. When adhesive method being used, the epineurial was fixed with a suture method similar to anchor suture for preventing suture line broken. Immediatly after the repair and 8 weeks after the surgery, the histologic and electrophysiologic changes of the repaired nerve were observed. The result showed: The axonal copation was soon improved in glue adhesion group. At the eighth week, nerve fiber alignment of the adhesion group was more regular than that of the suture group. Moreover, there were great improvement of axon cross rate and the recovery rate of sectional area of nerve fiber at the distal end in glue adhesion group (P < 0.05, P < 0.01). It was concluded that glue adhesion was prior to suture in repair of peripheral nerve, and anchor suture could improve the technique of glue adhesion method.

Animals↗
PubMed1998

[Influence of intraspinal implantation of pSVP0MCAT genetically modified Schwann cell in regeneration of injured spinal cord].

In order to observe the role of genetically modified Schwann cell (SC) with pSVP0Mcat in the regeneration of injured spinal cord, the cells were implanted into the spinal cord. Ninety SD rats were used to establish a model of hemi-transection of spinal cord at the level of T8, and were divided into three groups, randomly, that is, pSVP0Mcat modified SC implantation (Group A), SC implantation (Group B) and without cell implantation as control (Group C). After three months the presence of axonal regeneration of the injured spinal cord was examined by means of horseradish peroxidase (HRP) retrograde labelling technique and stereography. The results indicated that HRP labelled cells in Group A and B could be found in the superior region of injured spinal cord and the brain stem such as the red nuclei and oculomotor nuclei. The density of ventral hom neurons of the spinal cord and the number of myelinated axons in 100 microns of the white matter was A > B > C group. In brief, the pSVP0Mcat modified SC intraspinal implantation could promote regeneration of the injured spinal cord.

Animals↗
PubMed1998

Clinical observation on treatment of 83 cases of posthemiplegic omalgia.

An analysis on 83 cases of posthemiplegic omalgia (shoulder pain) shows that the pathogenesis of the pain is closely related to the improper passive movement at the early stage of hemiplegia (62.7%). The large range of passive movement is a dangerous factor leading to omalgia. In the study of upper extremity complications, the incidence of shoulder-hand syndrome is relatively high (42.2%), and it is often accompanied by hand swelling (83.1%). The authors suggest that painless movement of the shoulder joint should be limited in a range of 90-120 degrees, massage be carried out immediately after acupuncture, and the affected upper extremity be moved passively during the needle retention. This therapeutic method is definitely effective for pasthemiplegic omalgia.

Acupuncture Therapy↗
PubMed1998

[A preliminary study of plasma oxidase activity by spectrophotometry on the healthy middle-aged and old volunteers in Changsha].

The plasma oxidase activities (POA) in 26 healthy volunteers were determined by spectrophotometry. The results showed that the POA value of the 26 cases was obviously lower (78.90 +/- 8.12 U.L-1) than that in Lasla's (84 +/- 5 U.L-1) (P < 0.05). A preliminary normal reference range of POA (45-60 years old) in Changsha was established. This method is an accurate (CV = 3.9%), cheaper, and easy one and applicable for clinical laboratories.

Age Factors↗
PubMed1998

[Study on the clinical diagnostic values of MCV and RDW to homolytic anemia].

In this study, the mean corpuscula volume (MCV) and the red blood cell distribution width (RDW) were measured in 21 patients with hemolytic anemia, 35 patients with non-hemolytic anemia, and 100 healthy subjects were in the control group. The result revealed that the changes of MCV and RDW in hemolytic anemia and the other proliferative anemia were special. As diagnostic criterion of HA, MCV and RDW showed high-sensitivity and specificity. It is useful for screening HA patients.

Adult↗
PubMed1998

[Expression of P62c-myc protein in breast cancer and its clinical significance].

The objective of this study was to determine the clinical significance of P62c-myc protein expression in breast cancer. P62c-myc protein was detected in 107 patients with breast cancer by immunohistochemical techniques (LSAB). The results showed that the positive rate of P62c-myc protein expression was 63.55% (68/107). The overexpression of P62c-myc protein related negatively with survival. 94.00% of the cases with overexpression of P62c-myc protein survived < or = 5 years, 65.00% survived > 5 years-< 10 years, and 21.62% survived > or = 10 years. There were significant associations of P62c-myc expression with advance clinical stage, high histological grade, and positive axillary node status in breast cancers. All of these findings suggested that overexpression of P62c-myc might be an important prognostic factor, and the detection of P62c-myc protein might be arranged as a regular pathological examination in the cases of breast cancer.

Adolescent↗
PubMed1998

[Effect of up-regulation of S-AdoMet synthetase on taxol-induced apoptosis in human breast cancer cells].

OBJECTIVE: To investigate the gene regulation of taxol-induced apoptosis. METHODS: Northern blot hybridization, enzyme activity assay of S-AdoMet synthetase and flow cytometry were performed in the investigation of expression in the mRNA level and biological action of S-AdoMet synthetase in taxol-induced apoptosis in human breast cancer cell line (BCap 37). RESULTS: Up-regulation of S-AdoMet synthetase expression was resulted by taxol treatment and the expression peaked at 48 hours. Moreover, the up-regulation of S-AdoMet synthetase was associated with cytotoxicity of antimicrotubule agents including taxol and colchicine. Inhibition rate of S-AdoMet synthetase activity by 1% DMSO was 34% in taxol-treated cells and 14% in taxol-untreated cells compared to control groups, respectively. Posttreatment with 1% DMSO following pretreatment with individual antitumor agent for 3 hr promoted apoptotic cell death of taxol-, colchicine-, and adriamycin-treated BCap37 cells. CONCLUSION: The induction of apoptosis enhanced by post-treatment with DMSO in taxol-treated cells is probably linked to its inhibition on enzyme activity of S-AdoMet synthetase, suggesting that the increased expression of S-AdoMet synthetase possibly plays an important role in protecting cells from DNA fragmentation in taxol-induced apoptosis.

Antineoplastic Agents, Phytogenic↗
PubMed1998

[Strategy on the prevention and treatment of chronic diseases among residents in Dongcheng District, Beijing].

Chronic diseases, in particular, circulatory diseases characterized by high mortality, morbidity, and lack of special treatment have become serious problems to the residents living in the Beijing communities. To learn the above mentioned diseases among people at the community level and to investigate treatment and preventive method concerned studies on chronic circulatory system diseases among people living in communities in Dongcheng where few disease were under special control studies were carried out between 1981 and 1997. We found that the studied residents who had received and adopted a series of preventive measures as health education, giving up smoking, reducing alcohol and salt consumption, diet balance and practicing physical exercises, had greatly improved their health condition. Because of the positive results, we addressed some long-termed suggestions on the treatment and prevention for chronic patients with circulatory system diseases which is believed to have established a solid ground for the future.

Cardiovascular Diseases↗
PubMed1998

[Correlation of interleukin 1 beta-converting enzyme(ICE) gene expression with gut epithelial cell apoptosis in septic mice].

OBJECTIVE: To investigate the correlation of gut epithelial cell apoptosis with ICE, IL1 beta gene expression in septic mice. METHODS: Sepsis was induced in mice by cecal ligation and puncture(CLP). Sham-operation group underwent the same manipulation but without CLP. 1, 3, 6 hours after CLP, gut epithelial cells, were isolated. IL1 beta, ICE gene expression was detected quantitatively by RT-PCR. Epithelial cell apoptosis was assessed by flow cytometric method and biochemically by DNA electrophoresis. RESULTS: The survival rate of CLP mice was 1/10 as compared to 10/10 of sham-operation mice. IL1 beta, ICE mRNA expression in CLP mice was significantly higher than that in the sham-operation group(P < 0.01); IL1 beta mRNA expression was parallel to ICE mRNA expression. The number of epithelial cell apoptosis was correlated excellently to the level of ICE, IL1 beta mRNA expression. Epithelial cell apoptosis could not be detected in sham-operation group at the indicated time points. CONCLUSION: ICE, IL1 beta gene overexpression may be involved in the vulnerability of epithelial cell apoptosis in septic mice.

Animals↗
PubMed1998

Clinical and bacteriologic study of eighty-six patients with systemic lupus erythematosus complicated by infections.

OBJECTIVE: To investigate the clinical and bacteriologic features of patients with systemic lupus erythematosus (SLE) complicated by bacterial and/or fungal infections. METHODS: Statistical analysis was made on basis of the clinical and bacteriologic data of 86 patients with SLE complicated by bacterial and/or fungal infections. RESULTS: One hundred and thirty-three episodes of infections occurred in 86 patients with SLE, in which 51.13% were nosocomial infections and 76.69% occurred in the blood system, respiratory tract, lungs and urinary tract. Gram-negative bacilli, gram-positive cocci, fungal and other bacterial infections accounted for 39.85%, 31.58%, 18.80% and 9.77%, respectively. In the bacterial infections, 18.52% were caused by L-form bacteria and more than 60% of the patients had no apparent toxic manifestations. The odds ratio (OR) of infection increased significantly in patients with damaged functions of the heart, lungs and kidneys, and in those who received high-dosage steroids. CONCLUSIONS: Patients with SLE tend to develop nosocomial infections with gram-negative bacilli which are the most common pathogens. The clinical manifestations of the infection are atypical. Careful inspection and monitoring, timely collecting the specimens for L-form bacterial culture can reduce misdiagnosis and missed diagnosis of the infection.

Adolescent↗