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Biomedical subjects

D Cheng

Publications and source records attributed to D Cheng.

At least 91 records · Page 5Linked to original sources
PubMed1998

[Effect of tetrandrine on the collagen contents of lungs in rats with chronic hypoxia].

OBJECTIVE: To investigate the effect of tetrandrine (Tet) on the collagen contents of lung tissues in rats with chronic hypoxic pulmonary hypertension. METHOD: Using colorimetric method after oxidized by chloramine T to determine hydroxyproline contents of lung tissues and extrapulmonary arteries, using Masson method, image pattern analysis technique and gray scale scanning to observe the changes of collagen distribution in extrapulmonary arteries and lung tissues in rats with hypoxia and the effect of treatment with Tet. RESULT: Tet could remarkably reduce the mean pulmonary arterial pressure and pulmonary vascular resistance in rats with hypoxic pulmonary hypertension and could inhibit the increase of collagen contents in lung tissues and extrapulmonary arterial wall. CONCLUSION: Tet may be used as one of the main drugs in the treatment of chronic hypoxic pulmonary hypertension due to its action of reducing mPAP and collagen contents.

Alkaloids↗
PubMed1998

[Inhibition of potassium channel by chronic hypoxia on pulmonary artery smooth muscle cells in rats].

OBJECTIVE: To explore the possible effect of potassium channel in chronic hypoxic pulmonary hypertension. METHOD: Male Wistar rats were placed in the identical normobaric or hypoxic environmental chamber. In one chamber, rats were maintained in 10% +/- 0.5% O2(by displacement with N2) for 3 weeks, whereas in the other, rats were maintained in air. The single smooth muscle cell was isolated from pulmonary artery (phi 200-700 microns) of Wistar rats with acute enzymatic digestion method. Using patch-clamp technique, we recorded the outward K+ currents in pulmonary artery smooth muscle cells and identified a Ca2+.ATP activated K+ channel (K+Ca-ATP) and a delayed rectifier K+ channel among the outward K+ currents. We compared the activities of Ca2+.ATP activated K+ channel (K+Ca-ATP) or delayed rectifier K+ channel in smooth muscle cells isolated from pulmonary artery of chronic hypoxic and normoxic rats. RESULT: The activities of Ca2+.ATP activated K+ channel (K+Ca-ATP) and delayed rectifier K+ channel in chronic hypoxic group are much lower than that in normal group (T test, P < 0.01). Cromakalim (10 mmol) caused a marked enhancement of activity of the reduced K+Ca-ATP but not the delayed rectifier K+ channel in rats of hypoxic group. CONCLUSION: The persistent decrease of potassium channel activity may contribute to setting the development of chronic hypoxic pulmonary hypertension. Cromakalim, one of potassium channel openers, can decrease the pulmonary hypertension induced by chronic hypoxia and may be a new effective drug for treatment of hypoxic pulmonary hypertension.

Animals↗
PubMed1997

Identification of complexes between the COOH-terminal domains of sterol regulatory element-binding proteins (SREBPs) and SREBP cleavage-activating protein.

SREBP cleavage-activating protein (SCAP) stimulates the proteolytic cleavage of membrane-bound SREBPs, thereby initiating the release of NH2-terminal fragments from cell membranes. The liberated fragments enter the nucleus and stimulate transcription of genes involved in synthesis and uptake of cholesterol and fatty acids. Sterols repress cleavage of SREBPs, apparently by interacting with the membrane attachment domain of SCAP. In the present studies we show that SCAP, like the SREBPs, is located in membranes of the endoplasmic reticulum and nuclear envelope. The COOH-terminal domain of SCAP, like that of the SREBPs, is located on the cytosolic face of the membranes. Co-immunoprecipitation experiments show that SCAP and SREBP-2 form a complex that can be precipitated with antibodies to either component. Complex formation occurs when cells express only the COOH-terminal domain of either SREBP-2 or SCAP, indicating that the complex forms between the two COOH-terminal domains. Truncation of SREBP-2 at its COOH terminus prevents the formation of complexes with SCAP and simultaneously reduces proteolytic cleavage. We conclude that proteolytic cleavage of SREBPs requires the formation of a complex with the COOH-terminal domain of SCAP and that SCAP is therefore a required element in the regulation of sterol and fatty acid metabolism in animal cells.

Animals↗
PubMed1997

Differentiation and death of premyelinating oligodendrocytes in developing rodent brain.

Previous studies have indicated that newly formed oligodendrocytes are dynamic cells whose production, survival, and differentiation depend upon axonal influences. This study has characterized the appearance and fate of newly formed oligodendrocytes in developing rat brain. Oligodendrocytes appear in predictable locations and radially extend DM-20-positive processes that cover 80-microm domains in the cortex and 40-microm domains in the corpus callosum. These premyelinating oligodendrocytes have one of two fates: they myelinate axons or degenerate. Between 7 and 21 d after birth, approximately 20% of premyelinating oligodendrocytes identified in the cerebral cortex were degenerating. Oligodendrocytes that ensheathed axons expressed and selectively targeted proteolipid protein to compact myelin and did not degenerate. These observations support the hypothesis that axonal influences affect oligodendrocyte survival, differentiation, and expression of proteolipid protein gene products.

Animals↗
PubMed1997

Undifferentiated U937 cells transfected with chemoattractant receptors: a model system to investigate chemotactic mechanisms and receptor structure/function relationships.

Transfection of either the C5a receptor or the formyl peptide receptor into undifferentiated U937 cells generated continuously growing cell lines that stably expressed these receptors. The transfected cells displayed significant numbers of cell surface receptors that had ligand binding properties similar to fully differentiated U937 cells. Undifferentiated transfected U937 cells were capable of a ligand-specific calcium flux and showed migratory responses that were qualitatively and quantitatively similar to differentiated cells and were specific for each chemoattractant. Moreover, the chemotactic response could be desensitized by preincubating the cells in a high concentration of ligand and could be blocked by pertussis toxin. These results demonstrate that undifferentiated U937 cells possess the subcellular signaling apparatus and machinery necessary to generate a motile response and that the only missing component for chemotaxis is expression of a chemoattractant receptor. In addition, the results demonstrate that undifferentiated U937 cells transfected with chemoattractant receptors provide a defined model system to study receptor structure/function relationships and may be used to investigate receptor-mediated chemotactic responses in a relevant human myeloid cell.

Antigens, CD↗
PubMed1997

Routine chest roentgenography on admission to intensive care unit after heart operations: is it of any value?

The need for routine immediate postoperative chest roentgenography after heart operations has recently been questioned. In this study we investigated the impact of routine postoperative chest roentgenography on treatment instituted in the cardiovascular intensive care unit immediately after heart operations done via median sternotomy. A total of 404 random patients admitted to the cardiovascular intensive care unit underwent clinical (positioning of endotracheal tube, nasogastric tube, and pulmonary artery catheter) and laboratory (oxygenation) assessment by a cardiovascular intensive care unit physician according to a strict protocol. After clinical assessment, chest roentgenography was done for all admitted patients and the findings reviewed by the same physician. Pathologic conditions noted were recorded on the study form together with any required treatment. Eighteen patients (4.5%) out of 404 required intervention because of abnormalities detected by the chest x-ray film but not predicted by the initial physical and laboratory assessment. None of the pathologic conditions detected was life threatening. We conclude that chest roentgenography done on admission to the cardiovascular intensive care unit should be done only if clinical and laboratory assessment indicate the possibility of underlying pathologic conditions that can only be confirmed or diagnosed by chest roentgenography.

Aged↗
PubMed1997

Determinants of reluctance to perform CPR among residents and applicants: the impact of experience on helping behavior.

BACKGROUND: Though mouth-to-mouth resuscitation (MMR) is widely endorsed as a useful lifesaving technique, studies have shown that health care professionals are reluctant to perform it. To characterize the circumstances which facilitate this reluctance among physicians, we have surveyed current and future residency trainees regarding attitudes toward providing ventilation by this method to strangers experiencing arrest in the community. METHODS: A total of 280 categorical emergency medicine (EM) and internal medicine (IM) house officers and respective program applicants at a 655 bed Brooklyn, New York teaching hospital were anonymously surveyed regarding their willingness to attempt resuscitation in five hypothetical scenarios of cardiopulmonary arrest. RESULTS: A direct relationship was observed between residency training level and reluctance to perform MMR in each scenario. Applicants expressed greater overall willingness to perform MMR than all residents (56 versus 34%, P < 0.00001). Willingness among experienced residents was lower than for junior-level residents (29 versus 40%, P = 0.01). EM and IM physicians were statistically indifferent in their responses. There were no differences in willingness to perform MMR by age in MD applicant or resident groups. CONCLUSIONS: Many physicians and future doctors are reluctant to perform MMR on arrest victims in the community, a trend that increases in prevalence among those with more residency training. These data support the hypothesis that diminished helping behavior occurs gradually over the training period and may occur as a direct consequence of the training experience. A model for characterizing the elements that make up a rescuer's decision process is proposed.

Accidents, Traffic↗
PubMed1997

Acyl-coenzyme A:cholesterol acyltransferase.

Due to its presumed role in regulating cellular cholesterol homeostasis, and in various pathophysiological conditions, acyl-coenzyme A:cholesterol acyltransferase (ACAT) has attracted much attention. Cloning the ACAT gene provides the necessary tool to advance molecular studies of this enzyme. The topics reviewed in this chapter include the pathophysiological roles of ACAT, the biochemistry and molecular biology of the ACAT protein and the ACAT gene, and the mode of regulation by sterol or nonsterol agents in mammalian cells. In addition, we present a working model linking the presumed allosteric property of ACAT with cholesterol trafficking into and out of the endoplasmic reticulum.

Amino Acid Sequence↗
PubMed1997

[Expression and distribution of bFGF in rat lung tissue of chronic hypoxic pulmonary hypertension].

OBJECTIVE: To evaluate the role of bFGF in the development of hypoxic pulmonary hypertension. METHOD: Rat models with chronic hypoxia induced pulmonary hypertension were established, the pulmonary hemodynamics were measured and the pulmonary arterioles change were studied with morphometric analysis under light microscopes, immunohistochemical staining with monoclonal antibody against human recombinant bFGF was performed in the paraffin section of rat lung. RESULT: (1) The mean pulmonary artery pressure (mPAP), and the ratio of the thickness of pulmonary arteriolar wall to external diameter of pulmonary arterioles (MT%) were 3.96 +/- 0.47 kPa and 33.8% +/- 3.5% in rats exposed to hypoxia for 3 weeks respectively, both were significant higher than those in normal control group, P < 0.01. (2) The positive staining for bFGF in the wall of pulmonary arterioles in hypoxic rats was stronger than that of control group (P < 0.01), there was a statistical relationship between increase of staining for bFGF and MT% in rats exposed to hypoxia. CONCLUSION: (1) Hypoxia can induce formation of pulmonary hypertension and structual remodeling of pulmonary arterioles. (2) bFGF may modulate the structure remodeling of pulmonary arterioles in chronic hypoxic pulmonary hypertension.

Animals↗
PubMed1997

[The identification of banding chromosomes by computer image analysis].

The analysis system for banding chromosomes (SYSTEM), an image analysis software, was programmed. By the SYSTEM the photos of Chinese G banding chromosomes were analyzed. It showed that the karyotype of the chromosomes of persons was recorded in high speed and efficiency, and that the chromosomes of alike ordinal number from different persons could be compared directly. That would presage, by this kind of the high effective operation, a favorable condition was created for the application of the polymorphism of the chromosomes to the parentage diagnosis.

Chromosome Banding↗
PubMed1997

[Diagnostic value of pleuro-examination with fiberoptic bronchoscope in indefinite pleural effusions].

The diagnostic value of pleuro-examination with fiberoptic bronchoscope in indefinite pleural effusions was studied. Pleuro-examination with fiberoptic bronchoscope has been performed in 10 cases with indefinite pleural effusions, and its diagnostic value and complications have been observed. The results showed that the diagnoses were confirmed in 9 of 10 patients submitted to pleuro-examination, and no severe complications were found. The results suggest that pleuro-examination with fiberoptic bronchoscope is an effective and safe procedure and might be performed on patients with pleural effusions when routine examinations fail to provide a diagnosis.

Adenocarcinoma↗
PubMed1997

[The value of erythromycin pleurodesis in the treatment of malignant pleural effusions].

Malignant pleural effusion is a frequent complication of patients with advanced malignant tumors. For many patients suffering from malignant pleural effusion that increases rapidly and may be life threatening, it is important to control the effusions. To investigate the value of erythromycin as a pleural sclerosant, a dose of 1 g erythromycin in 30 ml of 5% glucose was injected into the pleural cavity of 26 patients with malignant pleural effusion. The results were assessed by Miller's standards. After treatment, numerous adhesions were present in 15 cases; Pleural effusion reduced in 7 patients, and no effect was noted in 4 patients. The total response rate was 84.6%, and there were no severe side-effects. The erythromycin-induced pleurodesis is probably the result of induced chemical inflammation in the locality. This study suggests that erythromycin is a useful pleural sclerosant.

Adenocarcinoma↗
PubMed1997

[Effect of different hypoxic duration on changes of pulmonary circulation].

In order to assess the relationship between the hypoxic duration and pulmonary hypertension, we investigated the pulmonary hemodynamics and right ventricular hypertrophy and pulmonary vascular structure changes in rats with hypoxic exposure for 1 day to 3 weeks. After hypoxic treatment, the pulmonary artery pressure of rats increased in 3 days, and it was up to peak at 2 weeks later. The weight of right ventricle of rats significantly increased after 1 week. The endothelium of pulmonary vascular of rats became swollen in 3 days, and then increased in extracellular matrix deposition. Vessel wall thickening was found in 1 week hypoxic rats, and it was very significant in 3 week hypoxic rats. The results suggest that the duration of hypoxic treatment is related to the change of pulmonary circulation in 3 weeks in rats.

Animals↗
PubMed1997

[Study on conversion degree of double bonds of dental composites by Fourier transform infrared spectroscope].

Conversion degrees (CDs) of double bonds of 8 dental composites were measured by Fourier transform infrared spectroscope. Also, effects of disc-sampling method and film-sampling method on CD were compared. The results showed that CDs of 8 composites ranged from 45% to 75%. CDs of visible-light-cured (VLC) composites were higher than those of chemically-cured (CC) ones. In VLC composites, those with hybrid fillers had higher CDs than those with superfine fillers. In VLC composites, CDs obtained by disc-sampling method were higher than by film-sampling method; in CC composites, there were no differences between CDs obtained by both sampling methods.

Composite Resins↗
PubMed1997

The construction and expression of deletion mutant of human pro-urokinase cDNA.

The human pro-urokinase mutant deleting 150-156 amino acids was constructed by overlap-extension PCR and other molecular cloning techniques. The mutant was expressed transiently in COS-7 cells and constitutively in CHO cells; the expression level is 450-500 IU/10(6) cells/24 h. SDS-PAGE and Western blotting analysis showed that the molecular weight of the expression product is 54 kDa, which is similar to that of the mature pro-UK and recombinant pro-UK (rPro-UK) expressed by full-length cDNA. Most of the products exist in the form of single chain; the percentage of single chain is much higher than that of rPro-UK. In addition, the mutant product is more resistant to proteinases and its affinity to fibrin is also improved slightly.

Animals↗
PubMed1997

[TGF-beta 1 gene expression in the healing process of skin wound in rat].

For observation of the change of transforming growth factor-beta 1 (TGF-beta 1) gene expression in the process of skin wound healing, the following experiments were performed. Sixteen Wistar rats were chosen. At each side of the rat's back, a 1 cm x 1.5 cm middle-thick skin wound was made. After 3, 6, 9 and 12 days, the specimens were taken from the wounds. For each specimen, half of it was used for RNA extraction, and underwent dot blotting; and the other half was frozen immediately and underwent in situ hybridization. The probes were dig-labeled PDGF-BB cDNA probe and TGF-beta 1 probe. The results showed that TGF-beta 1 gene was expressed mainly in fibroblast, epithelial cell and capillary endothelial cell. The peak of TGF-beta 1 mRNA content was in the 6th day postoperatively. After that, the content of TGF-beta 1 decreased to normal. It was suggested that TGF-beta 1 gene expression was in close relation with healing process. TGF-beta 1 may play an important regulatory role in the skin wound healing.

Animals↗