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Biomedical subjects

F C Yang

Publications and source records attributed to F C Yang.

18 recordsLinked to original sources
PubMed1996

CD27/CD70 interaction directly induces natural killer cell killing activity.

The CD27 molecule is expressed on a portion of natural killer (NK) cells as well as T and B cells. To provide the functional capacity of CD27 molecule on NK cells, we here highly purified CD3- CD56+ NK cells by flow cytometry (purity > 98%), and investigated their NK cell activity via CD27/CD70 interaction using a CD70-transfectant by a 4 h 51Cr-release assay. The enhancement of NK activity by purified NK cells in the presence of interleukin-2 (IL-2) or interleukin-12 (IL-12) against CD70/Nalm-6 was not recognized as compared to against mock/Nalm-6. However, after a coculture with the fixed CD70/300-19, the purified NK cells increased the NK cell activity against K562, the value being 10 to 20% higher than coculture with the mock/300-19 in the presence of IL-2 or IL-12. The enhancement of NK activity was blocked by the addition of anti-CD70 monoclonal antibody (mAb). In addition, conjugation of NK cells to the target was increased by coculture with the CD70/300-19 without increased expression of adhesion molecules. In the parallel experiment, there was no increase in the killing capacity of NK cells. These results strongly show that CD27/CD70 interaction directly enhances NK activity in the presence of IL-2 or IL-12 by increasing the effector and target conjugate formation, indicating that CD27/CD70 interaction plays an important role in the cytotoxic function of NK cells.

Antigens, CD↗
PubMed1995

CD27/CD70 interaction directly drives B cell IgG and IgM synthesis.

CD27 is a T cell activation antigen expressed on a majority of peripheral blood T cells. CD27 is also expressed on a subpopulation of human B cells, and it is reported that CD27+ B cells secrete both IgG and IgM. CD70, a ligand for CD27, is expressed on activated T and B cells, suggesting an interaction between T and B cells via CD27/CD70 ligation. Here, we analyze B cell immunoglobulin synthesis using a CD70 transfectant and present functional data showing that B cells secrete large amounts of IgG and IgM as a result of the CD27/CD70 interaction. A flow cytometric analysis showed that CD27 expression was increased and CD70 was expressed on tonsillar and peripheral blood B cells after activation with Staphylococcus aureus Cowan strain (SAC) plus interleukin (IL-2). In addition, the proliferation of B cells was enhanced mildly by the addition of CD70 transfectant, and its proliferation was blocked by anti-CD70 mAb. More importantly, the CD70 transfectant enhanced IgG and IgM production by purified B cells greatly in the presence of SAC plus IL-2. The enhancement was completely blocked by the addition of either anti-CD70 mAb or anti-CD27 mAb. Strongly suggesting that the interaction of CD27 with its ligand, CD70, on B cells plays an important role in B cell growth and differentiation to produce IgG and IgM.

Adult↗
PubMed1995

Frequent natural killer cell abnormality in children in an area highly contaminated by the Chernobyl accident.

Since January 1991, we have been performing thyroid surveys and hematologic and immunologic screening on children in Chechersk, Belarus, a city situated in one of the areas most seriously contaminated with high levels of radionuclides after the Chernobyl accident. Ten children selected from 713 children because of goiter did not show a decrease in humoral immunity or in the number and function of T cells. By contrast, natural killer (NK) cell activity against K562 cells was depressed in 4 of these 10 children. The clinical and laboratory findings indicated that previously reported diseases with NK cell dysfunction could be excluded. A comparative analysis of NK cell activity in children from areas with and without high 137Cs levels revealed a high frequency of abnormal NK cell activity only in children from the area contaminated by radioactive fallout. In addition, there was no correlation between NK cell activity and NK cell number as percentage in the children from the area with high 137Cs levels. Neither activity nor number of NK cells was correlated with the body content of 137Cs. Thus, the frequent abnormality of NK cell function may not have been due to actual internal exposure to the long-lived radionuclide.

Adolescent↗
PubMed1995

[Functional abnormalities of natural killer cells in childhood hemophagocytic syndrome].

To analyze the abnormality of natural killer (NK) cells in childhood hemophagocytic syndrome (HPS), we investigated the numbers, cytolytic functions of circulating NK cells, and responsiveness to cytokines by flow cytometry, 51Cr-releasing and single-cell assay in 13 patients. In the active phase, the relative number of CD 16+ cells was decreased in 3 patients. NK activity was depressed in 6 patients but normal in the remaining 7 in the active phase. Lymphokine-activated killer (LAK) activity showed the similar tendency. The responsiveness of NK cells to IFN-gamma was absent, but that to IL-2 was normal in the active phase. Single-cell assay showed depressed maximal recycling capacity (MRC) and killing capacity values in the active phase and in remission phase, respectively. From these results, NK cells have such functional abnormalities as the absence of responsiveness to IFN-gamma and depressed recycling capacity in the active phase of childhood HPS. Further, abnormality of killing capacity of NK cells may exist even in the remission phase.

Adolescent↗
PubMed1995

Environmental stability and transmission of rat virus.

The environmental stability and transmission of a field isolate of rat virus was tested under conditions resembling those that may be encountered during the housing of laboratory rats. The rat virus kept in physiologic salt solutions at room temperature remained infective for at least 5 weeks. Similar virus preparations remained infective after drying on a plastic surface for 3 to 5 weeks, depending on initial virus concentration. Varying the protein concentration in the medium had no significant effect on stability. Bedding from cages housing infected litters induced seroconversions in sentinel rats for at least 5 weeks after storage of rat virus at room temperature. Infection was transmitted between rats housed in open cages in a Trexler isolator but not between rats housed in microisolator cages connected by tunnels partitioned by wire screens with a mesh size of 1.67 mm. The results indicate that rat virus can remain infective after prolonged exposure to an ambient environment and suggest that infection is more readily transmitted by animal-to-animal contact or by fomites than by aerosolization of exhaled virus.

Air Microbiology↗
PubMed1994

Absence of responsiveness to interferon-gamma but not to interleukin 2 and depressed recycling as natural killer cell abnormalities in childhood lymphohistiocytic syndrome.

To characterize the abnormalities of natural killer (NK) cells in childhood lymphohistiocytic syndrome (LHS), we investigated the number and cytolytic functions of circulating NK cells in 10 LHS children using flow cytometry, 51Cr-release and single-cell assays. In the active phase, the numbers of CD16+ or CD56+ cells and NK activity were normal in more than half of the patients or otherwise decreased. Despite the treatment with interferon-gamma (IFN-gamma) there was no significant increase in NK activity in the children with LHS: the values (mean +/- S.D.) of 32.2% +/- 14.2% became 35.0% +/- 13.3% (P > 0.05) when the control values changed from 45.5% +/- 8.5% to 54.2% +/- 10.1% after the stimulation. However, the NK cells normally responded to interleukin 2 (IL-2). In contrast, NK cells from 9 patients with infectious mononucleosis (IM) responded well to both IFN-gamma and IL-1 (P < 0.01). At the single-cell level, their NK cells had defective recycling capacity with normal killing capacity. The maximal recycling capacity (MRC) values (mean +/- S.D.) were 3.6 +/- 0.8 as compared to the control value of 5.5 +/- 0.9 (P < 0.01). Two of the patients studied had extremely high levels of serum IFN-gamma (9.8 U/ml and 158.0 U/ml) as compared to the control value of < 0.4 U/ml. NK cells may have been strongly stimulated by IFN-gamma in vivo, which probably yields superficially normal NK cell activity in the face of the absence of responsiveness to IFN-gamma but not to IL-2. The defective recycling may be another abnormality of NK cells in LHS.

Adolescent↗
PubMed1993

[Hemophagocytic syndrome with high level of interferon-gamma in the advanced stage].

Serum cytokines, lymphocyte subsets of peripheral blood and natural killer cell activity were serially assayed in a 3-year-old girl with hemophagocytic syndrome. Laboratory findings showed pancytopenia, increased levels of transaminases and hyperferritinemia and proliferation of histiocytes in bone marrow and pleural effusion. The administration of prednisolone resulted in a temporary improvement followed by a further exacerbation. The patient died in spite of the treatment with VP-16 and THP-adriamycin. Serum interferon-gamma (IFN-gamma) markedly increased in active phases. TNF-alpha, IL-1 beta and GM-CSF concentrations were normal or slightly elevated. The CD4/8 ratio of peripheral lymphocytes and natural killer cell activity also fluctuated according to clinical stage. These results suggested that IFN-gamma was the most important cytokine to activate histiocytes in this case.

Child, Preschool↗
PubMed1990

Studies of human platelet ultrastructure and quantitative analyses of membrane glycoprotein IIB/IIIA in shear stress-induced platelet quick release reaction.

The ultrastructural characteristics of platelets and the quantitative analysis of membrane glycoprotein (GP) IIb/IIIa quick-release reaction induced by high shear stress (HSS) were studied with transmission electron microscope and immunocolloidal gold staining. The results showed that platelets were activated and aggregated by HSS (50 dynes/cm2 or 100 dynes/cm2). Besides, HSS also caused a special platelet quick-release reaction which was called granule-membrane-fused lytic release (GFLR). GFLR differed from releases I and II which were induced by ADP and thrombin respectively. Granules were released quickly and lysis occurred when all granules had been discharged in GFLR. GFLR is a special form of platelet quick release induced by HSS and is called release III by the authors. In the process of platelet activation and lysis, the gold particles of GPIIb/IIIa were increasingly condensed. The possible reasons of increased surface expression of GPIIb/IIIa stimulated by HSS are also discussed.

Blood Platelets↗
PubMed1989

[A quantitative study of human platelet membrane glycoproteins using immunocolloidal gold under the electron microscope].

Two human platelet membrane glucoproteins (GP) and the quantitative changes of them induced by high shear stress (HSS) were studied using SZ-2 and SZ-21 monoclonal antibodies against GPIb and GPIIb/IIIa respectively by means of immunocolloidal gold technique with electron microscopy. Exposure to HSS (50 dynes/cm2, 5 min; 100 dynes/cm2, 3 min) resulted in the transformation of platelets from native smooth discs to activated spiny spheres followed by the centralization of organelles and lysis or aggregation of platelets. The results showed that resting platelets with few gold probes were turned into activated platelets by HSS with increased gold probes which represent the quantity of GPIb or GPIIb/IIIa. HSS also caused a specific platelet reaction--lysis. In the process of platelet lysis, platelet GPIIb/IIIa were increasingly condensed. On the contrary, GPIb reduced gradually. It suggests that the increase of GPIIb/IIIa under HSS may be one of the causes inducing platelet adhesion, release and aggregation at the opening of branched vessels, curved arteries, stenosed or partially occluded arteries due to local spasm.

Adult↗
PubMed1981

Barbiturates--structure versus RIA reactivity.

Over 90 different compounds having structural similarities to barbituric acid were analyzed by radioimmunoassay (RIA) using 125I-secobarbital reagents (Roche). Affinities were compared with molecular structures and a number of observations are made. It was found that all definitive components of the 5,5-dialkyl barbituric acid ring structure were essential for reactivity with the Roche RIA reagents; structural changes at any position of the ring reduced reactivity. No compounds studied were found to be more reactive than secobarbital [5-allyl-3-(1-methylbutyl) barbituric acid] and RO-2-1126[5-allyl-5-(1-carbamoylisopropyl) barbituric acid (the hapten used to prepare the RIA antibody)]. Changes in the 5-allyl and/or the 5-(1-methylbutyl) groups of secobarbital resulted in decreased reactivity.

Barbiturates↗
PubMed1980

Mass screening and confirmation of methaqualone and its metabolites in urine by radioimmunoassay-thin-layer chromatography.

A sensitive, rapid, and specific procedure is described for the mass screening and confirmation of methaqualone (Quaalude) in urine specimens. The method is sensitive to 1.0 microgram/ml levels of total methaqualone excretion products (free methaqualone, free hydroxylated methaqualone metabolites, and conjugated hydroxylated methaqualone metabolites). The raw urine is screened directly by radioimmunoassay, which is reactive to all the methaqualone excretion products. Specimens that are screened positive are confirmed by thin-layer chromatography using a solvent system of ethyl acetate-1,2-dichloroethane-chloroform (75:15:10) which separates methaqualone and its four major metabolites without interference from other drugs or urinary substances. The distinctive spot pattern produced by the methaqualone metabolites makes false positive results nearly impossible.

Chromatography, Thin Layer↗
PubMed1980

TLC analysis of urine for benzoylecgonine and norpropoxyphene.

A thin-layer chromatography (TLC) procedure has been developed for the analysis of urine samples for benzoylecgonine and norpropoxyphene, the major metabolites of cocaine and propoxyphene, respectively. Urine is made slightly acidic and methylated with dimethyl sulfate to convert the difficult-to-extract benzoylecgonine back into the much more readily extractable cocaine. The urine is then chilled, made basic, and extracted with chloroform/isopropanol. The organic layer containing the cocaine and norpropoxyphene is separated and evaporated to dryness. The residue is reconstituted and spotted on a TLC plate which is developed in hexane:chloroform:diethylamine (80:10:10) which separates the two substances without interference from other drugs, metabolites, and urinary substances. The two substances are visualized with acidified iodoplatinate spray and can be detected down to levels of 2.0 microgram/mL for benzoylecgonine and 1.0 microgram/mL for norpropoxyphene.

Chromatography, Thin Layer↗
PubMed1980

RIA opiates: structure versus reactivity.

Twenty-six different opiates were analyzed by radioimmunoassay (RIA) at five different concentrations. At attempt is made to relate structural differences to the affinity of the compounds for the Roche RIA morphine antibody. The effects of substituent placement on the morphine molecule are studied. As expected, the basic 5-ring opiate structure is essential for reactivity. Addition of an alkyl group to the oxygen in the 3-position increased affinity, but alteration of other key functional groups had a reverse affect.

Narcotics↗