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Biomedical subjects

J R Harper

Publications and source records attributed to J R Harper.

At least 55 records · Page 3Linked to original sources
PubMed1984

Human tumor-associated antigens defined by monoclonal antibodies.

Melanoma-associated antigens extracted from cultured human melanoma cells or isolated from their spent culture medium react specifically with monoclonal antibody and are represented by glycoproteins with molecular weights of 260,000 (260K), 250,000 (250K), and 100,000 (100K). The 260 and 250K antigens are present only in spent culture medium or detergent extracts of melanoma cells, respectively. The 100K antigen is an oncofetal marker present on tumor cells of different histological type. Indirect immunofluorescence data indicate that the 250K antigen is present on the surface of melanoma cells from excised melanoma tissues when the 100K antigen appears to be present in the cytosol. Subunit structure determination indicates that the 100K antigen is a single polypeptide chain whereas the 250K antigen extracted from melanoma cells is associated with a proteoglycan fragment which is important for its cell surface expression.

Antibodies, Monoclonal↗
PubMed1983

Inhibition of anchorage-independent growth of human melanoma cells by a monoclonal antibody to a chondroitin sulfate proteoglycan.

Anchorage-independent growth of tumor cells constitutes a phenotype highly associated with malignant transformation and appears to be important in the ultimate event of tumor metastasis, i.e., secondary tumor colonization. The role of a specific, melanoma-associated chondroitin sulfate proteoglycan population in anchorage-independent growth was assessed. Melanoma cells cultured in soft agar containing monoclonal antibody (mAb) 9.2.27, which recognizes such molecules on the surface of these cells, showed a 67-74% specific decrease in their colony formation. In contrast, neither mouse myeloma IgG nor monoclonal anti-HLA-A,B,C antibody (W6/32) had any effect on colony formation of the melanoma cells grown in soft agar. Human melanoma cells cultured in the presence of mAb 9.2.27 or W6/32 did not exhibit any changes in their DNA or protein synthetic metabolism. These findings suggest that 9.2.27-defined chondroitin sulfate proteoglycans on the surface of human melanoma cells may be involved in cell--cell interaction important in anchorage-independent growth.

Antibodies, Monoclonal↗
PubMed1982

Serological and biochemical analyses of monoclonal antibodies to human melanoma-associated antigens.

Monoclonal antibodies submitted and exchanged by participating laboratories were analyzed serologically and biochemically in accordance with the goals and aims of the Workshop on Monoclonal Antibodies to Melanoma. Serological evaluation of the workshop panel revealed that when a variety of tumor and normal cell lines were tested by enzyme-linked immunoassay, a majority of antibodies reacted preferentially with melanoma cells. Indirect immunoprecipitation analysis of those antibodies that bound staphylococcal protein A provided molecular weight estimates for some antigens and additional information that suggested possible commonalities among antigens recognized by antibodies 9.2.27, 225.28S and 763.24TS. Competitive binding analyses demonstrated that antibodies 225.288 and 763.24TS bound separate and distinct epitopes from that recognized by antibody 9.2.27 on the core glycoprotein of melanoma-associated chondroitin sulfate proteoglycans. Immunoperoxidase staining of fresh frozen melanoma tissue with antibody 9.2.27 revealed a limited tissue distribution and preferential association with the cell surface of human melanoma cells.

Antibodies, Monoclonal↗
PubMed1982

Protein A-bearing Staphylococcus aureus as the solid phase in an enzyme immunoassay and its application to determination of urinary albumin.

Protein A-bearing Staphylococcus aureus was used as a solid-phase matrix in a sandwich-type enzyme immunoassay for urinary albumin. Heat-inactivated, formalin-fixed bacteria were coated with affinity-purified goat anti-human albumin, exposed to solutions containing standard or unknown concentrations of albumin, then challenged with an alkaline phosphatase/anti-human albumin conjugate obtained by periodate oxidation. Alkaline phosphatase activity bound to the bacteria was a function of albumin concentration from 25 to 1000 micrograms/L. This assay was applied to determinations of urinary albumin concentrations between 1.25 and 1000 mg/L. Between-run CV was 2.55 (63.9 mg/L concentration). Within-run CVs for albumin concentrations of 1.9, 38.1, and 638.0 mg/L were 3.7, 3.7, and 2.4%, respectively. Analytical recovery was 95 to 107% across the full working range of the assay. Bence Jones proteins and hemoglobin had no significant effect on the assay. Nonspecific binding of the enzyme-antibody conjugate was 1.3% (SD = 0.7%). Values agreed well with those by radial immunodiffusion.

Albuminuria↗
PubMed1981

Characterization of the inhibition of k absorption in oat roots by salicylic Acid.

The phenolic compounds salicylic acid (o-hydroxybenzoic acid) and ferulic acid (4-hydroxy-3-methoxycinnamic acid) inhibited K(+) ((86)Rb(+)) absorption in excised oat (Avena sativa L. cv. Goodfield) root tissue. Salicylic acid was the most inhibitory. The degree of inhibition was both concentration- and pH-dependent. With decreasing pH, the inhibitory effect of the phenolic increased. During the early stages of incubation, the time required to inhibit K(+) absorption was also pH- and concentration-dependent. At pH 4.0, 5x10(-4) molar salicylic acid inhibited K(+) absorption about 60% within 1 minute; whereas, at pH 6.5, this concentration affected absorption only after 10 to 15 minutes. However, at 5 x 10(-3) molar and pH 6.5, salicylic acid was inhibitory within 1 minute. The capacity of the tissue to recover following a 1-hour treatment in 5 x 10(-4) molar salicylic acid ranged from no recovery at pH 4.5 to complete recovery at pH 7.5. The absorption of salicylic acid was pH-dependent, also. As pH decreased, more of the phenolic compound was absorbed by the tissue. The increased absorption of the compound at low pH most likely contributed to apparent tissue damage at pH 4.5 and might have accounted for the lack of recovery of K(+) absorption as pH decreased.Under the proper conditions of pH and concentration, phenolic acids such as salicylic acid could significantly affect mineral absorption by plants in the field.

Journal Article↗
PubMed1980

Membrane potentials of vallisneria leaf cells and their relation to photosynthesis.

A study has been made of the effects of the inhibitors carbonylcyanide m-chlorophenylhydrazone (CCCP), 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU), and of anoxia on the light-sensitive membrane potential of Vallisneria leaf cells. The present results are compared with the known effects of these inhibitors on ion transport and photosynthesis (Prins 1974 Ph.D thesis). The membrane potential is composed of a diffusion potential plus an electrogenic component. The electrogenic potential is about -13 millivolts in the dark and -80 millivolts in the light. The inhibitory effect of DCMU and CCCP on the electrogenic mechanisms strongly depends on the light intensity used, the inhibition being less at a higher light intensity. This is of significance in view of the often conflicting results obtained with these inhibitors. With ion transport in Vallisneria the electrogenic pump derives its energy from phosphorylation; however, the process which causes the initial light-induced hyperpolarization and the process that keeps the membrane potential at a steady hyperpolarized state in the light have different energy requirements. The action of photosystem I alone is sufficient to induce the initial hyperpolarization. For continuous operation in the light the activity of photosystem II also is needed.

Journal Article↗
PubMed1980

Effects of amrinone, a cardiotonic drug, on calcium movements in dog erythrocytes.

Dog erythrocytes (RBC) have a system for passive Ca and Na movements that resembles the Ca-Na exchanger first described in cardiac muscle. Amrinone, a new cardiotonic drug active in humans with congestive heart failure, is shown to stimulate net Ca uptake by dog RBC. Amrinone's action is on Ca influx rather than efflux. The influence of Amrinone on Ca uptake is enhanced when the cells are placed in low Na media; raising external Na or lowering intracellular Na both abolish the effect of the drug. The data suggest that amrinone potentiates passive Ca entry into the cells by a Na-dependent pathway. If Ca moves through myocardial sarcolemma as it does through dog RBC membranes, then the inotropic action of amrinone can be explained on the basis that the drug increases intracellular Ca levels.

Aminopyridines↗
PubMed1979

Adriamycin inhibits Ca permeability and Ca-dependent K movements in red blood cells.

Normal human red blood cells show a prompt, large increase in K permeability when their cytoplasmic Ca concentration is increased by various in vitro manipulations. Adriamycin, in concentrations greater than 0.02 mM, inhibits this response. Although the mechanism of adriamycin's action is not clear, experiments with dog red blood cells suggest that the drug inhibits passive Ca permeability. The importance of Ca-gated K movements in red blood cells is obscure, but in excitable tissues such ion currents play an important role in membrane repolarization. The influence of adriamycin on this ion conductance pathway may be related to the acute cardiotoxic and neurotoxic effects of the drug.

Animals↗
PubMed1977

Rapid Hormone-induced Hyperpolarization of the Oat Coleoptile Transmembrane Potential.

The effects of the plant growth substances indoleacetic acid (IAA) and fusicoccin on the transmembrane potential of Avena coleoptile cells (at 27-29 C) were studied. Fusicoccin caused hyperpolarization of the membrane potential which started after a lag of less than 20 seconds, and which on average reached -49 mv at an external K(+) concentration of 1 mm and -75 mv at 0.1 mm K(+). IAA caused a hyperpolarization of -25 mv starting after a lag of 7 to 8 minutes. These results suggest that fusicoccin and IAA both activate electrogenic H(+) extrusion.

Journal Article↗
PubMed1977

Natural sleep as an aid to electroencephalographic diagnosis in young children.

A total of 300 children aged five years and under, referred for routine EEG investigations, were included in this study. It was possible to obtain recordings during natural sleep in 250 of the 300 children, using stick-on electrodes. Of the 250 with natural-sleep recordings, 110 children had normal records both awake and asleep. In 73 cases the awake record was normal but the asleep record showed abnormalities, the most common being spike discharges (60 children). Of these 60 children, 52 had a history suggestive of epilepsy or of febrile convulsions. A further 27 children had recordings which were equally abnormal awake and asleep, and 37 showed abnormalities while awake but greater abnormalities while asleep. It is concluded that useful additional information can be obtained from the EEG if young children are encouraged to sleep naturally during the recording, and that this can be done without sedation, even in a busy, routine EEG department.

Child Behavior Disorders↗