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Biomedical subjects

K Chen

Publications and source records attributed to K Chen.

At least 505 records · Page 28Linked to original sources
PubMed1989

The products of the reduction of doxyl stearates in cells are hydroxylamines as shown by oxidation by 15N-perdeuterated Tempone.

The use of nitroxides in functional biological systems has increased greatly as it has become evident that such studies can provide valuable biophysical and metabolic data. This has led to a need to understand the nature of the metabolism of nitroxides and their products. This paper presents data indicating the value of 15N-perdeuterated Tempone specifically to indicate the amount of hydroxylamines that are present in a cellular system. Using this technique, we found that in the mammalian cells that we studied the principal or only products of reduction of doxyl stearates were the corresponding hydroxylamines.

Animals↗
PubMed1989

Effects of oxygen on the metabolism of nitroxide spin labels in cells.

The products of the reduction of nitroxides in cells are the corresponding hydroxylamines, which cells can oxidize back to the nitroxides in the presence of oxygen. Both the reduction of nitroxides and the oxidation of hydroxylamines are enzyme-mediated processes. For lipid-soluble nitroxides, the rates of reduction are strongly dependent on the intracellular concentration of oxygen; severely hypoxic cells reduce nitroxides more rapidly than cells supplied with oxygen. In contrast, the rates of oxidation of hydroxylamines increase smoothly with increasing intracellular oxygen concentration up to 150 microM. In order to separate the effects on the rates of metabolism of nitroxides due directly to oxygen from effects due to the redox state of enzymes, we studied the cells under conditions in which each of these variables could be changed independently. Oxygen affects the metabolism of these nitroxides primarily by interacting with cytochrome c oxidase to change the redox state of the enzymes in the respiratory chain. Our results are consistent with the conclusions that in these cells reduction of lipophilic nitroxides occurs at the level of ubiquinone in the respiratory chain in mitochondria, and oxidation of the corresponding hydroxylamines occurs at the level of cytochrome c oxidase.

Animals↗
PubMed1989

[Focal sparing around the gallbladder in fatty liver: an useful sign in the diagnosis of borderline cases by CT].

The role of CT in the diagnosis of fatty liver is well established. CT has been proved to be a useful noninvasive tool for the demonstration of fatty infiltration of the liver. The characteristic finding is a diffuse decrease in the attenuation within the liver compared with that of the spleen. Commonly, fatty infiltration of the liver is generalized and both CT scans and sonograms can easily demonstrate changes related to this condition. Sometimes, fatty infiltration of the liver is focal and occasionally, it is generalized with focal sparing of the normal liver tissue creating some problems in the diagnosis. Recently, some reports have mentioned the appearance of a focal sparing area in the generalized fatty liver. We often found a high attenuation region around the gallbladder bed in the fatty liver patients on CT examination. There appears to be some relationship between the high density around the gallbladder area and the fatty liver. A retrospective study was undertaken to evaluate the relationship. In this paper, we presented the CT scans of 57 fatty liver cases and compared them with the CT scans of 50 normal patients to discuss the possible cause of the phenomenon and its usage in the diagnosis of the fatty liver.

Adolescent↗
PubMed1989

Functional and phenotypic analysis of tumor-infiltrating lymphocytes isolated from human primary and metastatic liver tumors and cultured in recombinant interleukin-2.

Tumor-infiltrating lymphocytes (TIL) were isolated from 40 of 51 consecutive human liver tumor samples (primary hepatocellular carcinoma, 16 of 18; metastatic, 23 of 29; benign, one of four). Functional and phenotypic characteristics of fresh and recombinant interleukin-2 (rIL-2)-expanded TIL were evaluated. The expansion of TIL from hepatic tumors in the presence of 1000 units/ml of rIL-2 was possible in 60% of cases. In comparison to TIL from metastatic liver tumors, TIL obtained from primary liver tumors expanded faster and better in rIL-2 cultures. Expanded TIL from primary tumors had significantly higher cytotoxicity against K562 targets, but not Raji targets, than those from metastatic tumors. Cytotoxicity against fresh autologous tumor targets was detected in seven of eight cultures tested. TIL from primary tumors retained antitumor reactivity significantly longer in culture. The optimal in vitro cytotoxicity was achieved between days 20 and 60 of culture in the presence of rIL-2. Antitumor activity was associated with the increase in these TIL cultures of a cell population expressing the Leu19 antigen with or without the CD3 antigen. The frequency of the CD3+Leu19+ population showed a bimodal distribution during culture: the first peak of CD3+Leu19+ cells occurred between days 30 and 60 and was associated with the increased antitumor activity; the second peak occurred after day 60 and was not associated with activity. These findings demonstrate that TIL from most human hepatic tumors can be successfully isolated, cultured in rIL-2, and enriched in Leu19+ effectors. In addition, these TIL upon IL-2 activation in vitro are capable of lysing fresh autologous and/or allogeneic tumor targets.

Antigens, Differentiation↗
PubMed1989

Broad range DNA probes for detecting and amplifying eubacterial nucleic acids.

In this report we describe and characterize two oligomer probes that are broadly homologous to conserved eubacterial 16S ribosomal RNA (rRNA) sequences not present in human 18 rRNA or human mitochondrial 12S rRNA. One or both of the probes can detect all of 23 phylogenetically diverse eubacterial nucleic acids against which they were tested by dot blot hybridization. A sensitivity of about 1 bacterium per 10 eukaryotic cells was achieved. By using these oligomer sequences or their complements as primers in the polymerase chain reaction (PCR), the equivalent of 1 pg of E. coli DNA was detected in the presence of a large excess of eukaryotic DNA. Information useful for partial phylogenetic classification of detected organisms may be obtained by direct sequence analysis of the amplified DNA and comparison with known sequences or catalogs. Such broadly homologous probes offer advantages over more narrowly specific probes for detecting organisms whose identity is unknown. They could thus be employed for recognizing infection by organisms that cannot be cultured as may occur, for example, in tissue culture or in plant or animal diseases of unknown cause, provided the probes fail to hybridize with host nucleic acids.

Base Sequence↗
PubMed1989

Phenotypic characterization of mononuclear infiltrate present in liver of biliary atresia.

The liver tissue of 26 children with biliary atresia was compared to that of 20 adults with autoimmune chronic active hepatitis, 20 adults with chronic hepatitis due to hepatitis B infection, and 5 children with alpha 1-antitrypsin deficiency in terms of the number and type of mononuclear cells in portal and lobular areas of each using a panel of specific monoclonal antibodies that recognize different cell surface epitopes. All of the tissues studied were obtained at time of liver transplantation. In addition the livers of 5 adults biopsied for hepatomegaly but found to have no histologic liver disease were used as normal controls for this study. The results demonstrate that liver tissue obtained from children with end-stage biliary atresia is more like normal liver in terms of the number and type of mononuclear cells present than in either of the two types of adult liver diseases. Moreover although the liver of children with end-stage alpha 1-antitrypsin deficiency is more like that of normal liver than either of the two adult liver diseases studied in terms of the number and type of mononuclear cells within the liver, it is less similar to that of normal adult liver than is liver tissue obtained from children with biliary atresia. These findings suggest that as a morphologic basis biliary atresia is unlikely to be due to either a viral or an autoimmune attack upon the liver.

Antibodies, Monoclonal↗
PubMed1989

Recombinant human epidermal growth factor precursor is a glycosylated membrane protein with biological activity.

NIH 3T3 cells were transfected with cDNA corresponding to human kidney prepro-epidermal growth factor (preproEGF) under control of the inducible mouse metallothionein promoter. The synthesis of recombinant human EGF precursor by these cells has provided us with a model system for analysis of the structure and activity of this precursor. In transfected cells, the precursor was present as an intrinsic 170-kilodalton membrane protein as well as a soluble protein in the extracellular medium; both forms were N glycosylated. Glycosylation of the EGF precursor was determined by (i) the direct incorporation of [3H]mannose and [3H]glucosamine, (ii) metabolic labeling in the presence or absence of glycosylation inhibitors, (iii) enzymatic cleavage of the precursor by N-glycanase or endoglycosidase II, and (iv) lectin chromatography. Recombinant human preproEGF was purified by affinity chromatography, using wheat germ lectin and antibodies to human EGF. The intact precursor was biologically active. Purified preparations of preproEGF (i) competed with 125I-labeled EGF for binding to the EGF receptor in intact fibroblast cells, (ii) activated the intrinsic tyrosine kinase activity of the EGF receptor in membrane preparations, and (iii) sustained the growth of a mouse keratinocyte cell line that is dependent on EGF for growth. These results suggest that proteolytic processing of the precursor may not be essential for its biological function.

Binding, Competitive↗
PubMed1989

[Clonidine stimulates central nervous alpha 2 adrenoceptors not mediating Ca2+ channels].

Seven renal hypertensive (2 kidneys--2 clipped) and 8 normotensive conscious dogs were given icv clonidine. After the medication the mean arterial blood pressure (MAP) were lowered and the heart rate (HR) and plasma norepinephrine (NE) were decreased. The magnitude of the decrease of MAP was greater than normotensive dogs; while no differences of decrease of NE was found. Nicardipine (10 micrograms/kg) icv caused significant increases of MAP and HR in both hypertensive and normotensive groups. The decrease of MAP induced by clonidine was not changed by the pretreatment of nicardipine icv in both groups. It is thus concluded that clonidine stimulates central nervous alpha adrenoceptors not mediating Ca2+ channels.

Animals↗
PubMed1989

[Pharmacodynamics and pharmacokinetics of nifedipine in patients with congestive heart failure].

Twenty-seven cases of congestive heart failure (CHF) were treated with nifedipine (Nif) 20 mg po. Significant improvements in resting hemodynamics were found in 22 cases. The higher the basal systemic vascular resistance (SVR) and pulmonary artery end diastolic pressure (PAEDP) were, the greater the magnitudes of reduction found (r = 0.84 and 0.77, P less than 0.01, respectively). Exercise hemodynamic investigation showed that Nif led to a lowering of SVR, PAEDP and pulmonary vascular resistance (PVR), with increases in SV and concentration of 5-10 ng/ml, with a maximum being observed at the concentration of 20 ng/ml. No further vasodilation was found when the plasma concentration exceeded 20 ng/ml. No remarkable deviations from the normal ranges of Nif pharmacokinetics were found in CHF patients. The plasma norepinephrine level decreased markedly 2 and 7 h after Nif. Thus, it is concluded that oral Nif is beneficial in severe CHF patients having low cardiac output and high SVR.

Adolescent↗
PubMed1989

[Evaluation of mailed epidemiologic inquiries].

The mailed inquiry is a economical and useful epidemiologic survey method. Comparison and discussion of data from the mailed inquiries and home interviews were done. More than 60 items which included general questions, height and weight, sources of drinking water, dietary habits, histories of smoking and alcohol consumption, physical activities, medical histories, parents medical histories and income were analysed, there was no significant difference in 45 items of the above data and a very significant relative coefficients between there two methods. Only 16 items which focused on alcohol and oil consumption, income, etc. had significant differences, but the most still had positive-relative correlation (P less than 0.05). The response rate of the mailed inquiries was 87.1 percent. In addition, the mailed questionnaire also was discussed.

Epidemiologic Methods↗
PubMed1989

[Effects of an ever-young pill on decreased intelligence and symptoms associated with aging].

A test was carried out to evaluate the effect of Ever-Young Pill (EYP) on decreased fluid intelligence and symptoms associated with aging. Nootropil and placebo were used as control drugs. Random, single-blind and self-control observation methods were applied. 90 days were spent for the clinical study. 154 older persons were divided into three groups (EYP 63, nootropil 60, placebo 31). The method of measuring intelligence was talking between man and computer. The computerized program was worked out by our department. The measure included eight parameters. A semi-quantitative method was used to evaluate the symptoms of aging. The main results were as follows: In the group of EYP, there were significant differences (P less than 0.01) in speed of calculation (SC, 5.92 +/- 2.5, 5.1 +/- 2.1), speed of digits and pictures (SDP, 24.2 +/- 6.2, 21.7 +/- 6.7), two digits span (2.8 +/- 1.0, 3.2 +/- 0.8) and other two parameters before and after treatment. In the group of nootropil, SDP and SC were also improved significantly. In the normal control's there was not any evident change. In the early declined health group treated with EYP and nootropil separately, four parameters were improved in each group. The best effect of EYP obtained was on Kidney Yang deficiency and Kidney and Heart Qi Yang deficiency Syndromes. In other syndromes, the results were less satisfactory. By using EYP for treating symptoms of aging the total effective rate was 96.8%, nootropil 71.7% and placebo 44.2%. There were noticeable differences in three groups. Those results suggested that EYP was one of the effective therapies for decreased fluid intelligence with aging.

Aged↗
PubMed1988

Activation of a cytosolic serine protein kinase by epidermal growth factor.

Exposure of A-431 cells to epidermal growth factor (EGF) results in a rapid enhancement (approximately 10-fold) of cytosolic serine protein kinase activity. The increase in serine kinase activity may be detected using a number of peptide and protein substrates. Enhancement of kinase activity occurs within 1 min of exposure of the cells to EGF and reaches a maximum in 5 min. Similar results were obtained with a variety of cell lines. We have partially purified the EGF-activated kinase from A-431 cells. It has an apparent molecular mass of approximately 100 kDa by gel filtration. One distinguishing property of the enzyme is its sensitivity to inhibition by micromolar quantities of polyarginine; polylysine has no effect. The EGF-activated kinase is unaffected by cyclic nucleotides, Ca2+/calmodulin, Ca2+/diolein/phosphatidylserine, or heparin. The enhancement of cytosolic serine kinase activity in A-431 cells appears to be an early event in cell "activation" by a number of biological response modifiers including EGF, bradykinin, 12-O-tetradecanoylphorbol-13-acetate, and histamine.

Animals↗
PubMed1988

Kinetics of enzyme-mediated reduction of lipid soluble nitroxide spin labels by living cells.

Nitroxide spin labels can be reduced to the corresponding hydroxylamines in cells. The selective action of inhibitors, and thermal and chemical inactivation demonstrate that the reduction of nitroxides in cells is an enzymatic or enzyme-mediated process. The kinetics of reduction of doxylstearates are affected by the position of the doxyl moiety along the stearic acid chain. The doxyl moiety of 5-doxylstearate is close to the membrane surface, and its reduction is first order with respect to the nitroxide, whereas the doxyl moieties of 10- and 12-doxylstearate are in the membrane hydrocarbon region and their reduction is a zero-order process. The reduction of 16-doxylstearate which usually has a mixture of first- and zero-order kinetics becomes zero order with addition of an extracellular broadening agent, potassium trioxalatochromiate(III). These results suggest that the rate of reduction of doxyl moieties is controlled by their accessibility to reducing equivalents, i.e., the rate-limiting step for the reduction of the doxyl moiety deep in the membrane is the diffusion of reducing equivalents within or into the membrane. The reduction of doxylstearates in cells is inhibited by rotenone but not antimycin A, cyanide, propyl gallate or SKF-525A. It appears that the reduction of doxylstearates takes place at the level of the ubiquinone in the respiratory chain in mitochondria in these cells.

Animals↗