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Biomedical subjects

M Chen

Publications and source records attributed to M Chen.

At least 361 records · Page 20Linked to original sources
PubMed1999

[Expression of ET-1 and Pr ET-1 mRNA in kidney of early diabetic rats].

The purpose of this study was to explore the role of endothelin 1 (ET-1) and pr ET-1 mRNA in kidney of early diabetic rats. The location and level of ET-1 were determined by immuno-histochemical staining; ET-1 cDNA probe was used for in situ hybridization. The expressions of ET-1 and ET-1 mENA in the kidneys of 24 early diabetic rats were detected by microscopy and Mia-2000 patho-image-analysis system. The results revealed that the ET-1 mRNA and ET-1 were principally distributed in the glomerular endothelial cells, mesangial cells, smooth muscle cells of vessels, epithelial cell lining tubules and collecting ducts, showing no difference in the distribution over kidney, but the expressions of ET-1 and ET-1 mRNA were higher in the renal medulla. The levels of ET-1 and ET-1 mRNA in glomeruli significantly decreased at week 1 and week 2(P < 0.05), but increased at week 4(P < 0.05). However, the levels of ET-1 and ET-1 mRNA continually increased from week 1 to week 4 in the medulla of diabetic rats. These data suggest that ET-1 and ET-1 mRNA may induce the glomerular hyperperfusion and damage the tubulointerstitial of the kidneys in early diabetic rats.

Animals↗
PubMed1999

[Establishment of studying system cloned vernalization-putative cDNA clone by means of differential display PCR].

Differential display PCR has been developed as a tool detecting and characterizing specially expressed gene in eukaryotic cells recently. In this paper, a studying system was established which applied the novel approach of differential display PCR to clone vernalization-related cDNA clone. Here methodological details were provided which included the purification of total RNA, removal of contaminated DNA, reverse transcription of cDNAs, parameters of PCR, electrophoresis of amplified cDNAs, recovery and reamplification of cDNAs. It was also identified a vernalization-putative cDNA clone (VPC) of VPC28 which was only expressed at the key stage of vernalization for 20 d in winter wheat. These results moreover made it readily applicable to a broad spectrum of similar studies.

Cloning, Molecular↗
PubMed1999

[An experimental study on the change of adhesion between leukocyte and endothelium in acute cerebral ischemia].

The objective of this experiment was to investigate the change of leukocyte adhesion in the focus of cerebral ischemia-reperfusion injury. Immune fluorescent microscope equipped with image tube camera and high speed recording TV sets was used to study the leukocyte adhesion in the focus of cerebral ischemia-reperfusion injury. The result showed that the density index of adherent leukocyte was significantly elevated, the fracture stress between leukocyte and endothelium dropped, and the adhesion increased in the focus of cerebral ischmic-reperfusion injury. These findings indicated that leukocyte adhesion was increased significantly and leukocytes played an important role in the cerebral ischemia-reperfusion injury.

Acute Disease↗
PubMed1999

[Changes of biomechanical properties in goats at different times after ovariectomy].

This paper presents the changes of biomechanical properties in goats at different times after ovariectomy. 14 goats were randomly divided into three groups. These goats were ovariectomized and sacrificed at 180 days (n = 4), 360 days (n = 5) and 540 days (n = 5) after the operation. The right femur, tibia and metatarsus were taken out. The structure mechanical properties of femora were measured with the three-point bending method and those of metatarsus were measured with the compressing method. The material mechanical properties of flexure, compress and tensile strength in the compact bone specimens of femora and tibiae taken from broken ends were also measured. The results showed that the one-year group, compared with the half-year group, had all the bone geometric parameters decreased, but not statistically significant (P > 0.05); the elastic modulus of three-point bending of femora decreased by 23.27% and the others had no significant difference (P > 0.05); all the material parameters of flexurel, compress and tensile strength in compact bone specimens decreased, but only the ultimate strength of tibiae of flexure, compress and tensile strength decreased obviously (P < 0.05). The one and a half year group, compared with the one year group, had the bone density of femora and tibiae decreased, but not statistically significant (P > 0.05). All the bone geometric parameters of tibiae and the thickness of bone of femora increased (P < 0.05). The break load of three-point bending of femora increased (P < 0.05). Probably, it was related to the increase of the body weight in the one and a half year group. The elastic modulus and the ultimate strength decreased, but not statistically significant (P > 0.05). When compact bone specimens were used, the ultimate strength and elastic modulus of femora and tibiae in compress and the elastic module of tibiae in flexure decreased obviously (P < 0.05); and the others had no significant changes (P > 0.05). This study indicated that the degree of osteoporosis in ovariectomized goats increased at half a year, one year, and one and a half year postoperation, and hence suggested that the ovariectomized goat be a pretty useful big animal model of osteoporosis.

Animals↗
PubMed1999

[Determination of pentachlorophenol residues in textiles and leather and leather products by gas chromatography/mass spectrometry].

A method for determination of pentachlorophenol residues in textiles and leather and leather products by gas chromatography/mass spectrometry was developed. The pentachlorophenol residues in samples was acidified with sulphuric acid solution (6 mol/L) and extracted with n-hexane. After the n-hexane layer was washed with sodium sulphate solution (20 g/L)until it was clear, determination was made by means of a gas chromatograph equipped with MSD, using external standard method. A DB-17 fused silica capillary column (30 m x 0.25 mm i.d.; 0.25 micron film thickness) was employed in the analysis, The column temperature program included a 2 min isothermal period at 50 degrees C, temperature increased at a rate of 30 degrees C/min to 220 degrees C, and hold for 1 min; temperature increased of at a rate 6 degrees C/min to 260 degrees C, and hold for 1 min. Mass spectra were obtained by electron impact at 70 eV and the determination was made by means of SIM mode, selected monitoring ion (m/z) was 264 amu. The detection limit was 0.02 mg/kg. The average recovery was from 86.7% to 93.1% and CV (n = 10) is from 4.1% to 5.9%. This method was already used to determine the mass concentration of pentachlorophenol residues in raw cotton, towel, shirt, leather gloves, leather watchguard. The method is simple, rapid and accurate.

Environmental Pollutants↗
PubMed1999

[A biomechanical study on human lataral capsular-ligament complex of temporomandibular joint].

Tensile mechanical experiments were made on 31 lateral capsular-ligament complex spencimens from 8 fresh temporomandibular joints of human cadavers aged 8-15 years. The tests included stress relaxation at different strain rates and tension test at constant strain rate. Some biomechanical material properties of the tissue were determined. The result showed that the complex had lower tensile strength and tensile stiffness, and the stress relaxatioin was the most important mechanism of spreading stress and absorbing shock. The stress relaxation function and the constitutive equation of stress and strain were obtained with Fung's Quasi-Linear Viscoelastic Theory fitting the experimental results.

Adolescent↗
PubMed1999

[A multichannel infrared telemetry system for physiological signal].

This paper introduces the multichannel infrared telemetry system for temperature, respiration and ECG measurements. The experimental results are given at the end of the paper. This infrared telemetry system can be used in the environment with high electromagnetic interference, such as the operating room with electrosurgical unit and become an important monitor device.

Electronics, Medical↗
PubMed1999

[The development and clinical application of a multipurpose neuroendoscope].

The multipurpose rigid neuroendoscope MGE-4 has been developed with the application of the self-focussing lens technology. We have been using it to examine and treat 10 neurosurgical patients who suffered from tumours, hydrocephalus, intracerebral haematomas of head injury and hypertensive cerebral haemorrhage. The short-term effect was satisfactory and there was no operative complications. It is considered that Model MGE-4 with the accessories can be used safely for the brain functional subcortical lesion or the deep-seated cystic lesions and haematomas.

Adult↗
PubMed1999

[Microwave acid-digestion ICP-MS method for the determination of sixteen elements in marine products].

Microwave acid-digestion samples and ICP-MS method were established for the determination of Na, Mg, Al, P, Cr, Mn, Fe, Ni, Cu, Zn, As, Sr, Mo, Cd, Pb and Hg in marine product. According standard sample GBW08571 mussel, we cheek the method accuracy and precision. The accuracy average values are 96.7%. These results are very suitable for the reference values. The RSDs of all elements are less than 5%. We use several internal standard correction method to correct the matrix interference. The method is simple, rapid, accurate and reliable.

Animals↗
PubMed1999

[Fluorescence spectra of lanthanide coordination compounds].

In this paper, the recent progress in fluorescence spectra of lanthanide coordination compounds including photophysics and photochemistry is briefly reviewed and the application of lanthanide complexes as fluorescent probes to structural analysis of coordination compounds and biomolecular systems is summed up.

English Abstract↗
PubMed1999

[Bonding behavior of 4f orbital].

In this paper, the bonding behavior of 4f orbital in lanthanide coordination compounds was discussed and corresponding theory and research methods were summed up with 36 references.

English Abstract↗
PubMed1998

The Alzheimer's plaques, tangles and memory deficits may have a common origin. Part IV: can calpain act as alpha-secretase?

Abnormality of protease activities and imbalance of intracellular calcium are two most salient aberrant events in Alzheimer's disease (AD). As such, calcium-dependent proteases such as calpain, as a critical link between these two events, must play a key role in the pathogenesis of AD, particularly in the abnormal processing of beta-amyloid precursor protein. Because alpha-secretase in this process appears to be a calcium-dependent protease and its enzymatic characteristics are impressively similar to those of calpain, a challenging possibility arises: Calpain might act as alpha-secretase in vivo. However, as the experimental evidence both for and against this possibility is compelling, the issue currently remains as a theoretical dilemma in which a central question is whether calpain, a cytosolic enzyme, can somehow reach the cell surface. This difficult issue needs to be addressed now. As a first attempt to explore the issue, we propose a working model for the membrane orientation of calpain and suggest several experiments that will critically test this model. The quest to this dilemma will not only impact our understanding of AD, but may also expand the current knowledge about Ca2+ signal transduction pathway. Finally, we discuss several competing models and the potential role of presenilins as "regulators" of alpha-secretase. It is of interest to note that some of our previous theoretical predictions have been experimentally observed.

Alzheimer Disease↗
PubMed1998

Comparison of the intranuclear distributions of herpes simplex virus proteins involved in various viral functions.

Herpesviral transcription, DNA synthesis, and capsid assembly occur within the infected cell nucleus. To further define the spatial relationship among these processes, we have examined the intranuclear distributions of viral DNA replication, gene regulatory, and capsid proteins using dual label immunofluorescence and confocal microscopy. We observed that several of the viral DNA replication proteins localize preferentially to punctate structures within replication compartments while the major transcriptional activator, ICP4, and the ICP27 regulatory protein show a more diffuse distribution within replication compartments. The viral proteins that show a punctate distribution in replication compartments redistribute from these compartments to prereplicative sites when viral DNA replication is inhibited, whereas viral proteins that show a diffuse distribution remain within replication compartments when viral DNA replication is inhibited. Thus the sites of viral DNA replication and late transcription appear to be distinct but codistribute within the boundaries of replication compartments. The major capsid protein, ICP5, also localizes initially to a diffuse distribution within replication compartments, but during the time of maximal progeny virus assembly, ICP5 becomes localized to punctate structures within replication compartments that are often near the punctate structures occupied by viral DNA replication proteins. Hence the processes of viral DNA replication, late transcription, and capsid assembly show a general overlapping distribution within replication compartments but appear to be located at distinct sites within these regions of the infected cell nucleus.

Animals↗