Biomedical subjects

C Zheng

Publications and source records attributed to C Zheng.

At least 109 records · Page 6Linked to original sources

PubMed1999

[The basic study of noninvasive detecting the ischemic/hypoxic cerebral injury].

The cerebrovacular diseases are important causes of mortality and disability in the world, and with the development of science and technology, many mission-oriented basic researches are aimed at the ischemic/hypoxic brain injury. This paper introduces some progress made in our research in this field, which includes: the animal experiment model of brain injury; the technique to efficiently extract evoked potentials from electroencephalogram; and the identification of the characteristic information of brain injury.

Animals↗

PubMed1999

[Multiresolution analysis based denoising algorithm for dynamic esophageal pH monitoring signal].

A denoising algorithm for dynamic esophageal pH monitoring signal is first introduced in this paper. The algorithm was developed on the basis of multiresolution analysis. The pH monitoring signal was investigated in experiments, then the algorithm was formulated by multiresolution analysis based on discrete dyadic wavelet transform combining with the results of the investigation mentioned above. Application of this algorithm to clinical data processing has proved its satisfactory denoising effect.

Algorithms↗

PubMed1999

[Vroman effect of plasma protein adsorption to biomaterials surfaces].

Fibrinogen adsorption from plasma to biomaterials surfaces passes through a maximum when studied as a function of adsorption time, plasma concentration, or column height in narrow spaces and these are called Vroman effect. Studies have demonstrated that Vroman effect is a general phenomenon of plasma proteins and reflects the competitive adsorption of plasma proteins for a limited number of surface sites. In this paper, the factors affecting Vroman effect, the relationship between contact activation and fibrinogen displacement, and the significance of the Vroman effect with respect to blood-material interactions are reviewed.

Adsorption↗

PubMed1999

[Using complexity measurement to study the EEG signal of focal ischemic cerebral injury].

In this paper, a model for SD rat focal ischemic cerebral injury is presented. Based on this experiment model, we recorded the EEG of ischemic region and normal region from before ischemia to after ischemia 30 minutes. We analyzed the complexity of these EEG signals, and found that the EEG complexity was very sensitive to focal ischemic cerebral injury. The EEG complexity on ischemic region was less than that on normal region. The difference in EEG complexity between two regions increased with the decreasing velocity. When insult took place, the EEG complexity was less than that before ischemai. These resluts agree to those we obtained by Discrete Gabor Spectrogram analysis and Heat Shock Protein (HSP) expression. The ischemic and normal regions can be clearly distinguished by analyzing their EEG complexity, and the extent can also be detected in this way.

Animals↗

PubMed1999

[The characteristic wave intervals of exercise ECG influenced by changing of heart rate].

This paper analyzes the characteristic wave intervals of exercise ECG influenced by heart rate changing under exercise test. The most influenced parameter is TP interval, the next is QT interval, and the width of P wave and QRS waves are nearly unchanging. According to the changing characteristic of these waves width mentioned above, we suggest an adaptive adjusting method for ST segment measuring position after the J point, which is of significance to recognizing the characteristic waves and determining the result of exercise test for myocardial ischemia.

Adult↗

PubMed1999

[The method of wavelet transformation used for extracting the characteristic of the exercise ECG].

This article introduces the basic rationale of wavelet transformation and the algorithm of typical dyadic wavelet transformation with mother wavelet of the first derivative of a Gaussian smoothing function, this wavelet transformation is used to recognize the characteristic parameters of the exercise ECG, it is concluded that this method make significant effects on restricting base line drifting and lessening noisy component in the exercise ECG, it provides a new way to do further research on characteristic recognition of the exercise ECG in the exercise test.

Algorithms↗

PubMed1998

[Cytogenetic study in eight cases of Fanconi anemia].

OBJECTIVE: To study the clinical, hematological and cytogenetical characteristics in Fanconi anemia (FA). METHODS: Culture the peripheral lymphocytes with Mitomycin C (MMC) induction to count the chromosome breakages and to count the sister chromatid exchanges (SCE) in FA. RESULTS: The clinical and hematological manifestations in FA varied at all. Spontaneous chromosome break and MMC induced break in FA were significantly higher than those in normal. Spontaneous and induced SCE were also higher in FA. CONCLUSION: Owing to genetic heterogeneity in FA, the phenotypes in FA are diversified also. So, chromosome breakage study is a very important method in the diagnosis of FA, and gene complementation analysis may identify which complementation group the patient carries.

Adolescent↗

PubMed1998

Differential stimulation of proline-rich tyrosine kinase 2 and mitogen-activated protein kinase by sphingosine 1-phosphate.

Sphingosine 1-phosphate (SphP), a metabolite of cellular sphingolipids, has been shown to induce cell proliferation by activating the mitogen-activated protein kinase (MAPK) pathway. Proline-rich tyrosine kinase 2 (Pyk2) is a novel cytosolic tyrosine kinase which mediates activation of the MAPK or c-Jun N-terminal kinase (JNK) signaling pathways in response to a variety of stimuli that elevate intracellular calcium. In this report, we show that SphP stimulates both tyrosine phosphorylation of Pyk2 and MAPK activation in a transient and dose-dependent manner in rat aortic smooth muscle cells. Further studies indicate that Pyk2 phosphorylation, but not MAPK activation, is dependent on a pertussis toxin-sensitive G-protein-coupled receptor as well as partially on actin cytoskeleton. In addition, both intracellular calcium mobilization and protein kinase C (PKC) are required for optimal Pyk2 phosphorylation while either calcium increase or PKC activation is sufficient for MAPK activation in response to SphP. Finally, we show that a tyrosine kinase(s) other than Pyk2 is necessary for MAPK activation by SphP. Together, these results suggest that SphP stimulates tyrosine phosphorylation of Pyk2 through a G-protein coupled receptor, which is dissociated from its activation of the MAPK pathway in these cells.

Animals↗

PubMed1998

Differential regulation of Pyk2 and focal adhesion kinase (FAK). The C-terminal domain of FAK confers response to cell adhesion.

Pyk2 is a recently described cytoplasmic tyrosine kinase that is related to focal adhesion kinase (FAK) and can be activated by a variety of stimuli that elevate intracellular calcium. In this report, we showed that Pyk2 and FAK tyrosine phosphorylation are regulated differentially by integrin-mediated cell adhesion and soluble factors both in rat aortic smooth muscle cells, which express endogenous Pyk2 and FAK, and in transfected Chinese hamster ovary cells. We also found that Pyk2 is diffusely present throughout the cytoplasm, while FAK is localized in focal contacts as expected, suggesting that the different localization may account for their differential regulation. By analyzing a chimeric protein contain N-terminal and kinase domains of Pyk2 and C-terminal domain of FAK, we provided evidence that the distinctive C-terminal domains of Pyk2 and FAK were responsible for their differential regulation by integrins and soluble stimuli as well as their subcellular localization. Finally, we correlated FAK, Pyk2, and the chimeric protein binding to talin, but not paxillin, with their regulation by integrins and focal contact localization. These results demonstrate that the distinctive C-terminal domain of Pyk2 and FAK confer their differential regulation by different subcellular localization and association with the cytoskeletal protein talin.

Amino Acid Sequence↗

PubMed1998

Gamma-irradiation-induced cell cycle arrest and cell death in a human submandibular gland cell line: effect of E2F1 expression.

This study examined the effect of gamma-irradiation (5 and 10 Gy) on the human submandibular cell line (HSG). Radiation treatment (5 Gy and 10 Gy) induced a dose-dependent decrease in cell proliferation, with a G2/M arrest of the cell cycle, and an increase in cell death (cells with <2n DNA increased from 7% in control cells to 34% and 40% in 5 and 10 Gy irradiated cells, respectively). [Ca2+]i measurements demonstrated that the status of internal Ca2+ stores, and muscarinic receptor-mediated Ca2+ mobilization, in irradiated cells was comparable to that in non-irradiated cells. These data suggest that 1) irradiated HSG cells maintain normal physiology and 2) internal Ca2+ store depletion does not account for the decreased cell proliferation. To manipulate the radiation-induced cell cycle arrest, we examined the effect of the transcription factor E2F1, which has been shown to induce cell cycle progression in HSG cells (Lillibridge and O'Connell, 1997, J. Cell. Physiol., 1 72:343-350). The ability of irradiated HSG cells to express and appropriately route proteins was demonstrated by using adenovirus-mediated expression of beta-galactosidase, alpha1-antitrypsin, and aquaporin-1. Infection of HSG cells with an adenoviral vector encoding E2F1, either 12 h before or immediately following irradiation, but not post-irradiation, induced maintenance of cells in the S phase of the cell cycle, reduced the number of cells arrested at G2/M, and decreased the rate of appearance of cells with <2n DNA. While the mechanism of irradiation-induced cell death has not yet been confirmed, these data suggest that expression of the E2F1 gene product in HSG cells can be a useful strategy to manipulate cell cycle events and reduce the initial loss of cells due to radiation.

Adenoviridae↗

PubMed1998

Growth factor regulation of the amylase promoter in a differentiating salivary acinar cell line.

Salivary glands contain two major epithelial cell types: acinar cells which produce the primary salivary secretion, including amylase, and ductal cells which reabsorb electrolytes but also secrete kallikrein. Here we investigated salivary acinar cell differentiation in vitro using the activity of the salivary amylase and tissue kallikrein promoters as markers of acinar cell and ductal cell differentiation, respectively. Each of the promoter sequences was cloned into a replication-deficient adenoviral vector containing the luciferase reporter gene. Previous studies showed that a human submandibular gland cell line (HSG) differentiated into acinar cells when cultured on a reconstituted basement membrane matrix (Matrigel). The luciferase activity of the amylase promoter vector (AdAMY-luc) was low in HSG cells cultured on plastic, where they grow as an epithelial monolayer. The promoter activity increased approximately tenfold when HSG cells were cultured on Matrigel and developed an acinar phenotype. Under the same conditions, the luciferase activity of the kallikrein promoter (AdKALL-luc) was not induced. Because HSG cells demonstrate acinar cell morphology, but not amylase gene expression, when cultured on laminin-1, certain soluble components of Matrigel were tested for their ability to induce the amylase promoter during in vitro differentiation of acinar cells. We find that epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha), which are present in the basement membrane, and hepatocyte growth factor (HGF) increase activity of the amylase promoter. Other basement membrane-derived growth factors such as TGF-beta, basic fibroblast growth factor (bFGF), and platelet-derived growth factor (PGDF), as well as tumor necrosis factor (TNF-alpha), keratinocyte growth factor (KGH), nerve growth factor (NGF) and interferon gamma (IFN-gamma) were inactive. This system will be further exploited to study the mechanisms by which extracellular matrix molecules and growth factors regulate salivary acinar cell differentiation.

Amylases↗

PubMed1998

A polarized salivary cell monolayer useful for studying transepithelial fluid movement in vitro.

There are no reported, convenient in vitro models for studying polarized functions in salivary epithelial cells. Accordingly, we examined three often-used salivary cell lines for their ability to form a polarized monolayer on permeable, collagen-coated polycarbonate filters. Only the SMIE line, derived from rat submandibular gland, had this ability. The SMIE cell monolayer exhibited junctional complexes, with a tight-junction-associated protein, ZO-1, localized to cell-cell contact areas. The Na+/K+-ATPase alpha1-subunit was detected predominantly in the basolateral membranes, while the Na+/H+ exchanger isoform 2 appeared primarily in the apical membranes. Using adenovirus-mediated cDNA transfer, SMIE cells were shown to be capable of routing marker proteins (beta-galactosidase +/- a nuclear targeting signal, alpha1-antitrypsin, aquaporin-1) to appropriate locations. Furthermore, this salivary cell monolayer provided a convenient tool for studying aquaporin-1-mediated, osmotically directed, transepithelial fluid movement in vitro. Thus, SMIE cells appear to be a useful experimental model with which to study some polarized functions in a salivary epithelial cell line.

Adenoviridae↗

PubMed1998

[Doppler echocardiographic studies on fetal cardiac function of diabetic mothers].

OBJECTIVE: To assess fetal cardiac function by Doppler echocardiography in diabetic pregnancies. METHODS: We investigated the changes of cardiac function in 54 normal fetuses and 23 fetuses of diabetic mothers. Cardiac anatomic datas were obtained by measuring the diameter of the aortic (AO), the pulmonary artery (PA), the mitral valve(MV), the tricuspid valve (TV) and interventricular septal thickness (IVS). Blood flow evlocity were obtained from the AO, PA, atrioventricular valves. The following variables were measured: peak flow velocity (PFV), accelerate time (ACT), systolic volume (SV) and ForceF. These indices respresented the systolic function. The peak early flow velocity (PFVe), peak late flow velocity (PFVa), PFVe/PFVa(E/A), mean velocity (V) of MV or TV respresented the diastolic function. RESULTS: The results revealed that in fetuses of diabetic mothers, IVS became thickness. The diameter of AO, PA, MV, TV were wider than that of normal fetases. The PFV, SV, ForceF of AO or PA increased significantly. There was no different in ACT between two groups. The PFVa of MV or TV increased significantly, whereas the E/A of both atrioventricular valves decreased. CONCLUSION: It showed that the fetal hyperinsulinemia triggered by maternal hyperglycemia result in fetal weight increasing, as well as hyperplasia and hypertrophy of myocardial cells. An iacreased contractility is compatible with relatively larger size of such fetuses. The intracardiac flow volume increased secondary to the more needs of fetal development. Abnormal thickenning IVS might impair ventricular diastolic function.

Adult↗

PubMed1998

Bletilla striata as a vascular embolizing agent in interventional treatment of primary hepatic carcinoma.

OBJECTIVE: To evaluate Bletilla striata as a vascular embolizing agent in interventional treatment of primary hepatic carcinoma. METHODS: We made a vascular embolizing agent from a Chinese medicinal herb, Bletilla striata (bai ji). From October 1991 to January 1995, 56 patients with primary hepatic carcinoma were treated by hepatic arterial chemoembolization with Bletilla striata angioembolus, and 50 patients with primary hepatic carcinoma who were treated by conventional gelfoam embolization served as controls. All patients were followed up for 10-48 months. RESULTS: Embolization with the Bletilla striata powder produced extensive and permanent vascular obstruction, resulting in marked shrinkage of the tumor and significant decrease of serum alpha fetoprotein (AFP) level. After embolization, less collateral circulation formed later. The treatment interval was prolonged to an average of 7 months. The 1-, 2- and 3-year survival rates were 81.9%, 44.9%, and 33.6%, respectively, with a mean survival period of 19.8 months. All the clinical parameters were better than those in the control group treated by conventional gelfoam embolization. CONCLUSION: Bletilla striata angioembolus is a good vascular embolizing agent for treating PHC.

Adult↗

PubMed1998

[Relationship between endothelin-1 and ischemic brain damage after subarachnoid hemorrhage and protective effect of Ginkgo biloba extract].

OBJECTIVE: To investigate the role of endothelin-1 (ET-1) in development of ischemic brain damage after subarachnoid hemorrhage (SAH), and the protective effect of Ginkgo biloba extract (GBE). METHODS: Wistar rat noncraniotomy models of SAH were divided into SAH group and GBE treated group, the diameter of basilar artery (BA) and dynamic changes of regional cerebral blood flow (rCBF) and ET-1 content of intracranial plasma within 24 hours after SAH of both groups were determined. And pathological examination of CA1 region of hippocampus was performed 3 days later. RESULTS: rCBF decreased and ET-1 content increased obviously and retained in 24 hours after SAH. Spasm of BA occurred half an hour after SAH and neurons of hippocampus CA1 region was damaged severely. GBE could antagonize the above-mentioned pathological changes effectively. CONCLUSION: Increase of ET-1 is an important factor leading to ischemic brain damage after SAH. GBE exerts its protective effect by antagonizing pathological increase of ET-1.

Animals↗

PubMed1998

[Pressure control system for the hermetically sealed cabin of the recoverable satellite].

There are many precision instruments and equipment for scientific researches and experiments in the hermetically sealed cabin of satellite. Appropriate pressure must be controlled in the cabin in order to ensure the instruments and equipment from the adverse space environment. This paper describes a pressure control system for the hermetically sealed cabin in the recoverable scientific detect and experimental satellite. The cabin pressure is regulated automatically into the specific levels by venting or supplying the air from or to the cabin during launch, on orbit and before reentry of the satellite. The system has low mass, low power consumption and high reliability. It was used successfully in the recoverable satellite first in September 1987 and had been used many times since then. It is the first active pressure control system for the hermetically sealed cabin of the satellite in China.

Atmospheric Pressure↗

PubMed1998

[Bispectral analysis of EEG signal during focal cerebral ischemia].

Early noninvasive detection of cerebral ischemia is important for fighter pilots as well as in clinical diagnosis. In this paper, a model of focal cerebral ischemia was presented. Bispectrum of EEG signals recorded from ischemic region and normal region after 30 min ischemia was analyzed using the third-order recursion method, which possesses higher frequency resolving ability. It can resolve two closely spaced peaks in the bispectrum and detect the presence or absence of quadratic phase coupling at frequency pairs that are very close to each other. It was found that some characteristics of such bispectrum are very sensitive to focal cerebral ischemia. The maximum bispectrum magnitude of EEG and the weighted center of bispectrum (WCOB) changed sensitively to the different ischemic regions and ischemic stages. The ischemic and normal regions as well as the degree of ischemia can be clearly distinguished by analyzing their bispectrum of EEG. It demonstrates that this method can be used as a quantitative method for the detection of focal cerebral ischemia in the early phase.

Acceleration↗

PubMed1998

[Coexisting pheochromocytoma and renal artery stenosis].

OBJECTIVE: To improve the diagnosis of coexisting pheochromocytoma and renal artery stenosis. METHOD: Four patients with coexisting pheochromocytoma and renal artery stenosis were treated. RESULT: After removal of the pheochromocytoma, the blood pressure became normal in two patients combined with resection of kidney with renal artery stenosis, and one patient with local adhesion loosened. The hypertension, however, persisted in another patient after the resection of pheochromocytoma even though the long segment of renal artery stenosis was relieved. CONCLUSION: After pheochromocytoma was diagnosed with its known position, coexisting renal artery stenosis should be suspected according to one of the following conditions: (1) Vascular murmurs are noted at the area of the upper abdomen or back; (2) One of the kidneys becomes less sized; (3) Using the inhibitor of receptor alpha only has no effect lowering blood pressure and it is necessary to add the inhibitor of angiotension; (4) Postoperative hypertension does not resolve when no remaining pheochromocytoma is present. the renal artery stenosis can be reversed after both removal of pheochromocytoma and loosening of adhesion in case of stenosis due to the pressure of the tumor and adhesion caused renal artery angling and local stricture. Extensive stenosis or closure, however, can not be corrected with severe atrophy of renal parenchyma due to pheochromocytoma, and the resection of kidney should be indicated.

Adolescent↗