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Biomedical subjects

N K Cheung

Publications and source records attributed to N K Cheung.

178 records · Page 10Linked to original sources
PubMed1983

Honey bee venom specific immunoglobulin G4 in honey bee sting allergic patients and bee keepers.

Honey bee venom (HBV) IgG4 antibody was studied in bee keepers and honey bee sting allergic patients on immunotherapy using mouse monoclonal anti-human IgG4 antibody in a modified microtiter solid phase radioimmunoassay (MSPIRA). The mean HBV IgG4 in bee keepers was 31 units/ml. In patients the mean HBV IgG4 pre- and post-immunotherapy were 2.9 and 11.6 units/ml, respectively, representing a mean rise of 7.3-fold as compared to a rise of 1.6-fold for total HBV IgG. The mean HBV IgG level in bee keepers was 14 micrograms/ml which was not significantly different from the mean level of 17 micrograms/ml in allergic patients at diagnosis. The percentage interference of HBV IgE detection in vitro correlated with HBV IgG but not with HBV IgG4. On the other hand, there was an inverse relationship between serum HBV IgE and HBV IgG4 levels while none was found for HBV IgE and IgG.

Antibodies, Anti-Idiotypic↗
PubMed1983

A microtiter solid-phase radioimmunoassay for platelet-associated immunoglobulin G.

An MSPRIA is described for measuring platelet-associated immunoglobulins by competitive inhibition of the binding of radiolabeled goat anti-human class-specific antibody to solid-phase immunoglobulins. PAIgG can be estimated from calibration curves constructed from soluble IgG inhibitors. The MSPRIA for IgG is antibody class-specific. The coefficient of variability is between 6% and 20%. The MSPRIA is more sensitive than other described assays. Comparative studies demonstrated that ACD-A is the preferred anticoagulant for collecting platelets for the MSPRIA and that sonicated platelets are more reliable than intact platelets in demonstrating elevated PAIgG in immune thrombocytopenias. Intact platelets from 18 normal volunteers had PAIgG ranging from 0.4 to 3.3 fg/platelet (mean +/- S.D. = 1.5 +/- 1). The same platelets when sonicated had a mean +/- S.D. PAIgG of 3.3 +/- 1 fg/platelet, with a range of 1 to 5. Only 60% of 30 adult ITP patients with presumed immune thrombocytopenia had elevated PAIgG levels when their intact platelets were studied. When these same platelets were sonicated, 87% of them had abnormal levels of PAIgG.

Antibody Specificity↗
PubMed1981

Microtiter solid-phase radioimmunoassay for specific immunoglobulin E.

A microtiter solid phase-radioimmunoassay (MSPRIA) for perennial rye grass-specific IgE is described. The assay is carried out in flexible polyvinyl chloride "u" microtiter plates by sequentially incubating antigen, albumin, test sera, and finally radiolabeled antihuman IgE. Wells are cut free of the plate with a hot wire-cutting apparatus and counted individually in a gamma counter. The amount of radioactivity bound is proportional to the amount of specific IgE in the serum. The MSPRIA is shown to be antigen and antibody specific, reproducible, and easily done. Rye-specific IgE levels assayed with the MSPRIA correlated with quantitative end point titration skin testing using perennial rye grass antigen performed on 31 volunteers with a maximum correlation coefficient of 0.92. The MSPRIA was compared with the radioallergosorbent test (RAST) method using sera from the same 31 volunteers. The rye-specific IgE levels assayed by MSPRIA correlated with those assayed by RAST with a correlation coefficient of 0.95. The MSPRIA is well suited for mass screening and represents a useful method for measuring specific IgE.

Adult↗
PubMed1981

A microtiter solid phase radioimmunoassay for total serum IgE.

A two-step microtiter solid phase radioimmunoassay (MSPRIA) for total serum IgE has been developed by the authors. Microtiter wells are coated with rabbit antihuman IgE. During the first incubation. IgE in serum samples or the standard is bound to the antibody coated wells. The wells are then overlaid with radiolabeled goat anti-IgE antibodies. The amount of radioactivity bound is proportional to the amount of IgE in the test serum. The mean IgE level of 25 cord sera was found by this assay to be 0.3 U/ml. The total serum IgE's of 40 volunteers ranged from 4 to 593 U/cc. These values agreed with the values determined by commercial PRIST assay with a correlation coefficient of 0.98. The MSPRIA is a specific, sensitive, convenient and economical means of quantitating total serum IgE.

Animals↗
PubMed1981

Changes in plasma amino acid profiles following abdominal operations.

Plasma amino acid profiles along with hemoglobin, hematocrit, albumin, protein, blood urea nitrogen and serum creatinine values for ten patients undergoing abdominal operations were studied before operation and for 16 days there-after at different intervals. Six patients in the control group were studied in a similar manner. From the observations obtained, we concluded that total amino acid valued are a more sensitive reflection of patient nutrition in both the preoperative and postoperative periods. In future, total amino acid levels may become part of the nutritional assessment of a patient undergoing an operation. The histidine levels in plasma remain low for the longest period of time, an indication of a great need for histidine. Hence, greater attention should be paid to the histidine content of a diet or solution administered parenterally, or both. In addition, branched chain amino acids, alanine, glycine, cystine, arginine, lysine, tryptophan and threonine are required in greater quantity than the other amino acids as a result of the increased catabolism and partial starvation of the patients postoperatively. In formulation hyperalimentation solutions, an increased need for these amino acids should be kept in mind.

Abdomen↗
PubMed1979

Immune suppression in vivo with antigen-modified syngeneic cells. II. T cell-mediated nonresponsiveness to fowl gamma-globulin.

Intravenous administration of syngeneic spleen cells coupled with the palmitoyl derivative of fowl gammma-globulin (p-F gamma G) results in a profound state of F gamma G-specific tolerance in C57BL/6 mice. Administration of p-F gamma G coupled syngeneic cells specifically reduces both the primary and secondary hapten and carrier-specific PFC responses to TNP-F gamma G. Since the haptenic response is affected, the tolerance functions at the level of the F gamma G-specific helper T cell. As few as 10(3) p-F gamma G spleen cells carrying only 1 ng of p-F gamma G can induce tolerance. At least a 2-day-induction period is required. This nonresponsiveness is long lived, lasting over 120 days. Spleen cells from tolerized mice can transfer suppression to normal syngeneic recipients. Treatment of tolerant spleens with anti-Thy 1.2 antiserum + C eliminates the suppressor cell activity. In addition, thymocytes and purified splenic T cells from tolerized mice can transfer suppression to normal recipients. Thus, at least a component of this nonresponsiveness is mediated by suppressor T cells. The requirement of antigen association with cell membrane components and the general applicability of this method of inducing T cell nonresponsiveness are discussed.

Animals↗
PubMed1978

Immune suppression in vivo with antigen-modified syngeneic cells. I. T-cell-mediated suppression to the terpolymer poly-(Glu, Lys, Phe)n.

The palmitoyl derivative of the linear polypeptide of poly-(L-Glu-L-Lys-L-Phe)n (GLphi) can be coupled to spleen cells directly. The intravenous administration of 2 X 10(5)--3 X 10(7) GLphi-coupled syngeneic spleen cells induces GL-phi-specific suppressor T cells in C57BL/6 nonresponder mice. The suppression is antigen specific and can be detected by the inhibition of the primary GLphi plaque-forming cell response to challenge with GLphi-fowl gamma globulin. The number of inducer cells required for suppression carry less than 0.1 microgram of antigen. Spleen cells from tolerized mice can transfer suppression to normal syngeneic recipients. The suppression is cyclophosphamide sensitive and the suppressor cells bear the Thy 1.2 marker. This method of inducing antigen-specific suppressor cells may be generally applicable to other antigen systems.

Animals↗
PubMed1978

Pyogenic liver abscess.

A review of 20 cases of pyogenic liver abscesses seen from 1971 through 1976 is presented. In this five-year interval, no amebic liver abscesses were found. The primary inflammatory processes were evenly divided among those patients with biliary, urinary, and intraperitoneal disease. Intensive antibiotic therapy was less efficient in sterilizing the abscess than the blood stream. The nebulous histories, clinical findings, and routine laboratory studies emphasize the difficulty in establishing an early diagnosis of liver abscess. Radioisotopic scanning of the liver proved to be the most reliable tool not only for the diagnosis but also for monitoring the postoperative course of the drained cavities. The overall mortality of pyogenic liver abscesses was 45% and the greatest mortality occurred in those patients over 40. Closed needle aspiration of pyogenic liver abscess in the elderly poor-risk patient in conjunction with the appropriate antibiotics may offer an acceptable alternative.

Adolescent↗
PubMed1977

Development of a hemolytic plaque assay for glutamic acid, lysine-containing polypeptides: demonstration that nonresponder mice produce antibodies to these peptides when conjugated to an immunogenic carrier.

Fowl gamma-globulin, when chemically conjugated to GLO or GL, functions as a T-dependent immunogenic carrier and stimulates anti-GLO and anti-GL antibody production in nonresponder mice. The conjugation procedure utilizes the Schiff base reaction. The anti-GL and anti-GLO responses were detected by hemagglutination and hemolytic plaque assays by using GL-coated erythrocytes. The coupling of GL to erythrocytes utilizes a novel procedure in which a palmitoyl derivative of GL is adsorbed onto red blood cells. The optimal conditions for preparing the palmitoyl derivative and for coupling to SRBC are presented. With the hemolytic plaque assay, we have verified that GLO responder animals make both IgM and IgG responses, whereas nonresponder mice fail to make either IgM or IgG plaque-forming cells.

Animals↗
PubMed1977

Colon and rectal carcinoma: clinical experience.

A 10 year clinical review of 220 patients treated for colorectal carcinoma is reported. Weight loss, abdominal pain and rectal bleeding were the leading signs and symptoms, occurring in 48.6%, 45.5%, and 42.7%, respectively. Patients treated in this series had more advanced disease, with a resectability for cure of only 37.7%. However, the overall five-year survival of 29.3% compared favorably with several other institutional reports. Earlier diagnosis and prompt treatment remain the major factors influencing ultimate survival.

Adult↗
PubMedDate not supplied

In vitro antitumor activity of rebeccamycin analog (NSC# 655649) against pediatric solid tumors.

PURPOSE: This study determined the in vitro antitumor activity of a rebeccamycin analog (NSC# 655649) using tetrazolium/formazan (MTT) and clonogenic assays against established pediatric cell lines and solid tumor specimens obtained from children. MATERIALS AND METHODS: Tumor cells from 14 established cell lines and 20 patient specimens were exposed in vitro for 1 hour to NSC# 655649 at concentrations ranging from 0.015 to 15.0 microM. The cytotoxicity (IC50) of this agent against established cell lines was determined using both the MTT (cytotoxic) and clonogenic/soft agar cloning (cytostatic) assays. Tumor specimens from children undergoing biopsy or surgical resection were also evaluated in vitro against NSC# 655649 using the clonogenic assay. For studies using patient specimens, antitumor activity was measured by comparing the number of tumor colonies from NSC# 655649-treated cells with those from solvent-treated controls. RESULTS: These studies showed that the mean IC50S using the MTT and clonogenic assays using established solid tumor cell lines were 0.94 and 0.51 microM, respectively. In general, for cell lines tested using both types of assays, the clonogenic assay resulted in a smaller IC50. The overall in vitro responses (< or = 50% survival compared to controls) using patient tumor specimens and the clonogenic assay were 35% (1.5 microM), 60% (7.5 microM), and 80% (15.0 microM). Of the 9 patients with neuroblastoma, responses to NSC# 655649 were seen in 33% (1.5 microM), 58% (7.5 microM), and 92% (15.0 microM) of the specimens. Prior chemotherapy did not appear to adversely affect in vitro responses. CONCLUSIONS: NSC# 655649 appears to have broad antitumor activity in vitro against pediatric malignancies at drug concentrations achieved during adult phase I clinical trials. These studies support the further development of NSC# 655649 for solid tumors in children.

Aminoglycosides↗
PubMedDate not supplied

Quantitative imaging of I-124 using positron emission tomography with applications to radioimmunodiagnosis and radioimmunotherapy.

Positron emission tomography (PET) is potentially useful for the quantitative imaging of radiolabeled antibodies, leading in turn to improved dosimetry in radioimmunotherapy. Iodine-124 is a positron-emitting nuclide with appropriate chemical properties and half-life (4.2 days) for such studies since the radiolabeling of antibodies with iodine is well understood and the half-life permits measurements over several days. Unfortunately, I-124 has a complex decay scheme with many high-energy gamma rays and a positron abundance of only 25%. It has therefore been largely ignored as a PET-imaging nuclide. However, measurements made with phantoms and animals under realistic conditions using a BGO-based PET scanner have shown that satisfactory imaging and quantitation can be achieved. Investigations of spatial resolution, the linearity of regional observed count rate versus activity in the presence of other activity, and the visualization and quantitation of activity in spheres with different surrounding background activities were carried out with phantoms up to 22 cm in diameter. Compared with F-18, spatial resolution was only slightly degraded (13.5 mm FWHM vs 12 mm FWHM) while linearity was the same over a 10:1 activity range (0.015 to 0.15 MBq/ml for I-124). The visualization and quantitation of spheres was also slightly degraded when using similar imaging times. Increasing the imaging time for I-124 reduced the difference. To verify that the technique would work in vivo, measurements were made of human neuroblastoma tumors in rats which had been injected with I-124 labeled 3F8 antibody. Although the number of samples was small, good agreement was achieved between image-based measurements and direct measurements of excised 4-g tumors. Thus quantitative imaging of I-124 labeled antibodies appears to be possible under realistic conditions.

Animals↗
PubMedDate not supplied

Disease-specific amino acid infusion (F080) in hepatic encephalopathy: a prospective, randomized, double-blind, controlled trial.

Seventy-five patients with acute hepatic decompensation superimposed on chronic alcoholic cirrhosis were prospectively randomized for a blinded trial of the treatment of hepatic encephalopathy. The control group received 4 g of enteral neomycin daily along with 25% dextrose by a central venous catheter. The experimental group received a placebo resembling neomycin and isocaloric dextrose plus a modified amino acid mixture enriched with branched-chain amino acids to 36% and deficient in aromatic amino acids and methionine. Thirty patients in the F080 group and 29 in the control group completed the trial. The group receiving the modified amino acid mixture demonstrated a statistically significant improvement in encephalopathy as compared to the neomycin group, while maintaining nitrogen equilibrium. Survival and discharge from the hospital were statistically greater in the group treated with the modified amino acid solution and hypertonic dextrose. Treatment of hepatic encephalopathy in the presence of hepatic decompensation with an amino acid solution formulated for its treatment seems to produce faster, more complete recovery with improved capacity for nutritional support.

Adolescent↗