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Biomedical subjects

K Chen

Publications and source records attributed to K Chen.

At least 361 records · Page 20Linked to original sources
PubMed1996

Quantification of intestinal blood flow by ultrasonic transit time flowmetry in fed and endotoxaemic rats.

OBJECTIVE: To compare the dye dilution method with ultrasonic transit time flowmetry (UTTF) for quantifying intestinal blood flow in the same experimental animals. DESIGN: Open experimental study. SETTING: University hospital, Osaka, Japan. MATERIAL: 11 (experiment 1) and 25 (experiment 2) adult male Sprague-Dawley rats. INTERVENTIONS: In experiment 1, the rats were fasted overnight. In experiment 2, endotoxin, Escherichia coli lipopolysaccharide (endotoxin) or saline (sham) was injected intraperitoneally. MAIN OUTCOME MEASURES: Superior mesenteric venous and abdominal aortic blood flow. RESULTS: Experiment 1: intestinal blood flow measured by UTTF was significantly decreased by 17% (p < 0.05) and 56% (p < 0.05) after 30 minutes infusion through the tertiary branch of the mesenteric vein and during simultaneous drawing of blood samples from both the carotid artery and the superior mesenteric vein over a 1.5 minute period, respectively. The intestinal blood flow measurements obtained by UTTF at different intervals before simultaneous drawing of blood from the carotid artery and the superior mesenteric vein differed significantly (p < 0.05) from those obtained by the dye dilution method. Experiment 2: intestinal blood flow was also decreased by 21%-34% (p < 0.05) during similar simultaneous drawing of blood. Aortic blood flow in the endotoxin group was reduced by 66% (p < 0.05) compared with fed animals and 63% (p < 0.05) compared with sham animals. Simultaneously, intestinal blood flow in the endotoxin group was also reduced by 57% (p < 0.05) compared with fed or 48% (p < 0.05) compared with sham treated animals. CONCLUSION: Real intestinal blood flow might not be measured by the procedure of simultaneously drawing blood from the carotid artery and the superior mesenteric vein in rats as is usually done in the dye dilution method. Intraperitoneal endotoxin reduced aortic as well as intestinal blood flow. We propose that UTTF is an alternative method for quantifying intestinal blood flow in fed and endotoxaemic animals.

Animals↗
PubMed1996

Chemical kinetic theory: understanding cell-cycle regulation.

Progress of a cell through its reproductive cycle of DNA synthesis and division is governed by a complex network of biochemical reactions controlling the activities of both M-phase- and S-phase-promoting factors. Standard chemical kinetic theory provides a disciplined method for expressing the molecular biologists' diagrams and intuition in precise mathematical form, so that qualitative and quantitative implications of our 'working models' can be derived and compared with experiment.

Animals↗
PubMed1996

Study on the column process of adsorption decolorization for monosodium glutamate solution in fluidized beds.

The adsorption decolorization of monosodium glutamate solution employed in multiple column fluidized beds in a series is studied. The equilibrium data, the mass transfer kinetics, and fluid flow parameters are determined. A mathematics model taking into account the effects of particle size classification, particle size distribution, external and internal diffusions, and axial mixing in the liquid and solid phases is proposed, and the simulated results are in good agreement with the experimental data.

Adsorption↗
PubMed1996

Clinical research on acute hemoptysis treated with kexue ning.

The efficacy of Kexue Ning (stopping hemoptysis) in the treatment of acute hemoptysis, and its comparison with that of the control group (treated with western medicine) are reported in this paper. The results showed that both the time for cessation of hemoptysis and the cure rate were better in the therapeutic group than in the control group. In addition, marked improvement in blood rheology after treatment was also found in the therapeutic group, but not in the control group.

Acute Disease↗
PubMed1996

[Expression of proliferating cell nuclear antigen and tumor suppressor gene P53 in mucoepidermoid carcinoma of salivary glands].

To explore the expression of proliferating cellnuclear antigen (PCNA) and tumor suppressor gene P53 product in mucoepidermoid carcinoma of the salivary glands, we studied 41 cases by immunohistochemical method. All of the cases were PCNA positive. The positive index, distribution pattern and cellular staining intensity for PCNA expression were correlated with carcinoma grade. P53 protein expression was found in 17 (41.5%) of the 41 cases; among them the expressions were weak in 9 cases. These results indicate that positive index, distribution pattern and cellular staining intensity of PCNA expression may be served as an indicator for evaluating the differentiating degree of the tumor.

Carcinoma, Mucoepidermoid↗
PubMed1995

The human urinary epidermal growth factor (EGF) precursor. Isolation of a biologically active 160-kilodalton heparin-binding pro-EGF with a truncated carboxyl terminus.

In this report, we describe the isolation from human urine of a predominant 160-kDa epidermal growth factor (EGF)-immunoreactive glycoprotein that exhibits affinity for heparin. The purification procedure involved concentration and dialysis of 20-30-liter batches of fresh urine on a high capacity ultrafiltration apparatus followed by chromatography on DEAE-Sephacel, heparin-agarose, and Sephacryl S-300. A nearly homogeneous preparation of 160-kDa protein was obtained with a yield of approximately 1 mg of 160-kDa protein from 25 liters of urine. The amino-terminal sequence of the purified 160-kDa protein, H2N-SAPQHXSXPEGTXA-, matched residues 21-34 of the predicted sequence of human prepro-EGF and established that the 160 kDa protein (pro-EGF) is a product of the prepro-EGF gene. Characterization of the carboxyl terminus of the purified protein by digestion with carboxypeptidase B and by immunoblotting with antisera against synthetic carboxyl-terminal and juxtatransmembrane peptides of prepro-EGF indicated that the carboxyl terminus has been truncated at an arginine residue that corresponds, most likely, to the carboxyl-terminal arginine of the EGF moiety. The intact 160-kDa pro-EGF is biologically active as evidenced by its specific binding to the EGF receptor and activation of the EGF receptor tyrosine kinase in A-431 cell membranes. Purified pro-EGF competitively inhibited the binding of 125I-EGF to human fibroblasts, and it stimulated the proliferation of these cells in culture. When immobilized onto culture dishes, the heparin-binding pro-EGF appeared to function both as an adhesion molecule and as a growth factor for serum-free mouse embryo cells.

Amino Acid Sequence↗
PubMed1995

Angiotensin II-mediated renal vasoconstriction amenable to alpha 1-adrenoceptor blockade.

Renal adrenergic interactions of intravenously and intrarenal arterially administered angiotensin II were studied in the anesthetized rabbit. Systemic arterial blood pressure and left renal blood flow were monitored. Bolus doses of angiotensin II, 50 and 100 ng/kg given intravenously, caused an immediate reduction in renal blood flow followed by a more sustained vasoconstrictor response. Prazosin, 5 micrograms/kg/min, infused intrarenal arterially, decreased both components of the reduced renal blood flow, suggesting adrenergic contribution to the response. Renal denervation reduced significantly the immediate response to angiotensin II without affecting the sustained response; administration of prazosin after denervation caused a further decrease in the response. Left adrenalectomy had no significant effect on the angiotensin II-induced renal blood flow response, ruling out the possible contribution of adrenal catecholamine release via the adrenal rete. In animals that had undergone renal denervation and left adrenalectomy, the renal blood flow response to intrarenal arterial injection of subpressor doses of angiotensin II (5 and 10 ng/kg) was reduced by the infusion of prazosin. It is concluded that angiotensin II-induced renal vasoconstriction is contributed to by adrenergic actions dependent in part on intact renal nerves, but also by a component not requiring an intact nerve supply.

Adrenalectomy↗
PubMed1995

Localization of protein disulfide isomerase to the external surface of the platelet plasma membrane.

Protein disulfide isomerase (PDI) is an enzyme that catalyzes the formation as well as the isomerization of disulfide bonds. In this study, antibodies against PDI were used to show PDI antigen on the platelet surface by indirect immunofluorescence microscopy and by flow cytometry. The platelets were not activated, as evidenced by the absence of staining by an antibody against P-selectin. Permeabilized platelets showed little cytosolic PDI by indirect immunofluorescence microscopy, suggesting that the majority of platelet PDI is localized to the platelet surface. PDI activity against "scrambled" RNase was shown with intact platelets. The activity was inhibited by inhibitors of PDI and by an antibody against PDI. Other blood cells showed little PDI. Platelet surface PDI may play a role in the various physiological and pathophysiologic processes in which platelets are involved.

Animals↗
PubMed1995

Contrasting roles for Myc and Mad proteins in cellular growth and differentiation.

The positive effects of Myc on cellular growth and gene expression are antagonized by activities of another member of the Myc superfamily, Mad. Characterization of the mouse homolog of human mad on the structural level revealed that domains shown previously to be required in the human protein for anti-Myc repression, sequence-specific DNA-binding activity, and dimerization with its partner Max are highly conserved. Conservation is also evident on the biological level in that both human and mouse mad can antagonize the ability of c-myc to cooperate with ras in the malignant transformation of cultured cells. An analysis of c-myc and mad gene expression in the developing mouse showed contrasting patterns with respect to tissue distribution and developmental stage. Regional differences in expression were more striking on the cellular level, particularly in the mouse and human gastrointestinal system, wherein c-Myc protein was readily detected in immature proliferating cells at the base of the colonic crypts, while Mad protein distribution was restricted to the postmitotic differentiated cells in the apex of the crypts. An increasing gradient of Mad was also evident in the more differentiated subcorneal layers of the stratified squamous epithelium of the skin. Together, these observations support the view that both downregulation of Myc and accumulation of Mad may be necessary for progression of precursor cells to a growth-arrested, terminally differentiated state.

Animals↗
PubMed1995

Aggressive behavior and altered amounts of brain serotonin and norepinephrine in mice lacking MAOA.

Deficiency in monoamine oxidase A (MAOA), an enzyme that degrades serotonin and norepinephrine, has recently been shown to be associated with aggressive behavior in men of a Dutch family. A line of transgenic mice was isolated in which transgene integration caused a deletion in the gene encoding MAOA, providing an animal model of MAOA deficiency. In pup brains, serotonin concentrations were increased up to ninefold, and serotonin-like immunoreactivity was present in catecholaminergic neurons. In pup and adult brains, norepinephrine concentrations were increased up to twofold, and cytoarchitectural changes were observed in the somatosensory cortex. Pup behavioral alterations, including trembling, difficulty in righting, and fearfulness were reversed by the serotonin synthesis inhibitor parachlorophenylalanine. Adults manifested a distinct behavioral syndrome, including enhanced aggression in males.

Aggression↗
PubMed1995

Epidermal growth factor induces the tyrosine phosphorylation and nuclear translocation of Stat 5 in mouse liver.

Intraperitoneal injection of epidermal growth factor into mice results in the appearance of multiple tyrosine-phosphorylated proteins in liver nuclei within minutes after administration. We have previously identified three of these proteins as Stat 1 alpha, Stat 1 beta (p91, p84), and Stat 3 (p89). In the present report we demonstrate that Stat 5 (p92), the recently described prolactin inducible transcription factor detected in mammary glands, is the major tyrosine-phosphorylated protein translocated to the nucleus in mouse liver in response to epidermal growth factor. Furthermore, gel-shift analysis and affinity purification revealed that Stat 5, Stat 1 alpha, and Stat 1 beta specifically bind to the prolactin inducible element upstream of the beta-casein promoter.

Animals↗
PubMed1995

Assay of pancreatic lipase with the surface acoustic wave sensor system.

A new type of surface acoustic wave sensor system for assaying the activity of pancreatic lipase has been proposed. The assay of this enzyme is based on the change in conductance of the solution caused by the release of a fatty acid, using triolein as a substrate. A linear relationship between frequency response and enzyme concentration is obtained. Kinetic parameters of pancreatic lipase, i.e., the Michaelis constant for triolein and the corresponding maximum initial rate, are estimated to be 5.46 mM and 7551.6 Hz/min, respectively. The effects of temperature and pH value are also investigated.

Acoustics↗