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Biomedical subjects

S Thompson

Publications and source records attributed to S Thompson.

At least 253 records · Page 14Linked to original sources
PubMed1987

Studies of the sialylation and microheterogeneity of human serum alpha 1-acid glycoprotein in health and disease.

The sialic acid content of alpha 1-acid glycoprotein (AGP) and its degree of microheterogeneity were investigated in AGP isolated from the pooled sera of patients with rheumatoid arthritis, or myocardial infarction or cancer (elevated AGP) or cancer (non-elevated AGP) and of healthy volunteers. Sialic acid was elevated in AGP preparations from the cancer groups and lowered in the preparation from the rheumatoid group. All preparations showed considerable charge heterogeneity by two dimensional polyacrylamide gel electrophoresis (2D-PAGE), but there was little evidence of molecular weight heterogeneity; the latter finding being also confirmed by peptide mapping studies. Each AGP preparation gave a different 2D-PAGE pattern; these differences were even more evident after partial desialylation of the samples when as many as fourteen different species could be identified. It is concluded from the sialic acid measurements and the 2D-PAGE study that the different preparations of AGP contain sialic acid in different carbohydrate structures. Using thin-layer electrofocusing (EF) and silver staining, characteristic AGP patterns could also be demonstrated after separating very small aliquots of unfractionated pooled and unpooled sera of the different groups. Therefore, EF measurements of AGP in serum may have a useful future role in clinical investigations.

Arthritis, Rheumatoid↗
PubMed1987

Elevated levels of abnormally-fucosylated haptoglobins in cancer sera.

Cancer sera have higher levels of serum protein-bound fucose than sera from healthy individuals. In an attempt to identify the cause of this increase, fucoproteins were extracted from the sera of cancer patients and healthy individuals using a fucose-specific lectin (lotus tetragonolobus) coupled to Sepharose, and were analysed by polyacrylamide gel electrophoresis and silver staining. Of the several consistent changes observed for the cancer sera, the most striking was a large increase in a component of 40-45 Kdaltons. The expression of this component in the cancer sera was related to the elevation in serum fucose levels. Two dimensional (2D) electrophoretic analysis of lectin extracts showed that this component had a similar isoelectric point to the beta chains of haptoglobin. Its identity as haptoglobin was confirmed using Western blotting and an anti-haptoglobin antibody. Fucosylated haptoglobins (FHp) were also isolated from some rheumatoid arthritis sera, but there was no correlation between serum fucose levels and the FHp expression. The FHp in cancer sera was of higher molecular weight than that found in rheumatoid sera. Serial specimens from two ovarian cancer patients undergoing chemotherapy had elevated FHp associated with increased amounts of tumour. To the best of our knowledge this is the first time a molecule of this type has been reported in cancer sera and because of its uniqueness it deserves further investigation as a potential cancer marker.

Adolescent↗
PubMed1987

Use of Ulex europaeus agglutinin I in the identification of lymphatic and blood vessel invasion in previously stained microscopic slides.

Lymphatic and blood vessel invasion is one of the most important diagnostic and prognostic parameters used by pathologists in the evaluation of neoplastic conditions. Although a variety of tissue artifacts can make the recognition of vascular, capillary, and lymphatic permeation by tumor cells extremely difficult, recent immunohistochemical studies have employed a variety of tissue markers that appear to have great value in establishing the diagnosis of lymphovascular involvement. In the present study, we applied an immunoperoxidase staining technique to previously stained microscopic tissue sections using Ulex europaeus agglutinin I lectin, an endothelial marker that can be used in paraffin-embedded tissues. Our results indicate that this technique can be successfully applied on microscopic slides previously stained with a variety of histochemical stains. It can also be used in those cases in which paraffin blocks are not available or the area in question is absent from the recut tissue sections.

Endothelium↗
PubMed1987

Purification and amino terminal sequencing of human melanoma nerve growth factor receptor.

The nerve growth factor (NGF) receptor, solubilized with Triton X-100 detergent, has been purified from human melanoma cell line A875. Purification to near-homogeneity was achieved by chromatography on wheat germ agglutinin-agarose, followed by immunoaffinity chromatography on Sepharose columns coupled with anti-NGF receptor monoclonal antibody (MAb). The purified receptor, a 75,000-dalton protein, retains the capacity to bind NGF as well as anti-receptor MAbs. Final purification was achieved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The sequence of amino acid residues at the amino terminus has been determined. Possible sequence homology between the NGF receptor and several other proteins is discussed. Using the purified receptor as immunogen, new MAbs to the NGF receptor have been produced. The NGF receptor was visualized by immunoperoxidase staining in tissue sections of dorsal root ganglia from monkeys.

Amino Acid Sequence↗
PubMed1987

Oligomerization and origin DNA-binding activity of simian virus 40 large T antigen.

Simian virus 40 (SV40) large tumor antigen (T antigen) exists in multiple molecular forms, some of which are separable by zone velocity sedimentation of soluble extracts from infected monkey cells. Three subclasses of this antigen from SV40-infected monkey cells have been separated and characterized: the 5S, 7S, and 14S forms. Newly synthesized T antigen occurs primarily in the 5S form. Chemical cross-linking provided evidence that the 14S form is primarily a tetramer, whereas the 5S and 7S forms could not be cross-linked into oligomers. The DNA-binding properties of each subclass were investigated after immunopurification. The affinities of the three forms for SV40 DNA and for a synthetic 19-base-pair sequence from binding site I are very similar (equilibrium dissociation constant [KD], 0.3 to 0.4 nM). The specific activity of DNA binding was greatest for the 5S and 7S subclasses and least for the 14S subclass. Moreover, the specific activity of the 5S and 7S subclasses increased sharply at about 40 h after infection, whereas the activity of the 14S subclass was maintained at a constant low level throughout infection. A model relating oligomerization and DNA binding of T antigen in infected cells is presented.

Animals↗
PubMed1987

An investigation of patients presenting with multiple physical complaints using the illness behaviour questionnaire.

The Illness Behaviour Questionnaire was used to determine whether three groups of patients who had presented with multiple symptoms in different treatment settings (Briquet's syndrome, post-viral fatigue syndrome, and a heterogeneous general practice group) could be differentiated from one another and from a mixed group of psychiatric patients on the basis of their abnormal illness behaviour. All groups completed a version of the Perley and Guze diagnostic criteria for Briquet's syndrome. The three groups presenting with multiple symptoms were more similar to each other than to the psychiatric patients. The results suggest that patients presenting with multiple symptoms include similar populations of patients who are poorly distinguished using current schemes of classification.

Adult↗
PubMed1987

Forskolin's effect on transient K current in nudibranch neurons is not reproduced by cAMP.

Forskolin, a diterpene extracted from Coleus forskolii, stimulates the production of cAMP in a variety of cells and is potentially an important tool for studying the role of cAMP in the modulation of neuronal excitability. We studied the effects of forskolin on neurons of nudibranch molluscs and found that it caused characteristic, reversible changes in the amplitude and waveform of the transient K current, IA, and also activated an inward current similar to the cAMP-dependent inward current previously described in molluscan neurons. Forskolin altered the time course of IA activation and inactivation but did not affect the voltage dependence or the reversal potential of the current. IA normally inactivates exponentially, but in forskolin the time course of inactivation can be fit by the sum of 2 exponentials with an initial rate that is faster than the control and a final rate that is much slower. On depolarization in forskolin, IA begins to activate at the normal rate, but a slower component of activation is also seen. The changes in IA in the nudibranch cells were qualitatively different than the changes caused by forskolin in Aplysia bag cell neurons (Strong, 1984). Experiments were performed to determine whether these effects of forskolin require cAMP. Intracellular injection of cAMP, application of membrane-permeable analogs of cAMP, application of phosphodiesterase inhibitors, and intracellular injection of the active catalytic subunit of cAMP-dependent protein kinase did not affect the amplitude or waveform of IA. Also, the changes in IA that are caused by forskolin were not prevented or reversed by intracellular injection of an inhibitor of cAMP-dependent protein kinase. Cyclic AMP did, however, activate inward current at voltages near the resting potential. We conclude that the changes in IA and the activation of inward current represent separate affects of forskolin. The inward current appears to depend on an increase in intracellular cAMP, while the changes in IA do not. These experiments show that, in addition to activating adenylate cyclase, forskolin may have a separate direct affect on the transient K current.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1986

Characterization of the human trophoblast-leukocyte antigenic molecules defined by a monoclonal antibody.

The murine monoclonal antibody H316 recognizes cell surface glycoproteins shared in expression by human trophoblast and peripheral blood leukocytes. It is also strongly expressed by many human tumor cell types, including choriocarcinoma and teratocarcinoma. The H316 antigenic determinant from these different cell types is carried on two wheat germ agglutinin-reactive glycoproteins of approximately 65,000 and 55,000 m.w. The antigenicity is not dependent on N-linked glycosylation. Biochemical fractionation procedures suggest that the molecules are related to each other, are not associated through intermolecular disulfide bonds, but do exhibit intramolecular disulfide interactions. These glycoproteins demonstrate m.w. heterogeneity between different cell lines and individual trophoblast membrane preparations. Such properties suggest that H316 molecules may be representative of TLX antigens (trophoblast-leukocyte common antigens), which have been suggested to influence maternofetal immunogenetic interactions.

Antibodies, Monoclonal↗
PubMed1986

Does natural sensitisation in eczema occur through the skin?

The specificities of serum IgE for the faecal and body antigens of the house-dust mite, Dermatophagoides pteronyssinus, were compared in 69 children with various combinations of asthma, eczema, and/or rhinitis. The concentration of IgE antibodies to the mite body was higher in those with eczema than in those with asthma, but the concentrations of IgE antibodies to the faecal allergen were not significantly different. The ratio of the serum concentration of anti-mite-body IgE to anti-faecal IgE was significantly greater in the children with eczema than in the children with asthma. The results in 4 subjects with rhinitis (2 with and 2 without eczema) support the view that IgE antibodies to the mite body are characteristic of eczema. Sensitisation to mite body and mite faecal particles may occur by different processes; the allergens of mite bodies may penetrate the skin, whereas faecal allergen may enter the body by other route(s).

Adolescent↗
PubMed1986

Novobiocin precipitates histones at concentrations normally used to inhibit eukaryotic type II topoisomerase.

At concentrations normally used to inhibit eukaryotic type II topoisomerase activity (100-1000 micrograms/ml) novobiocin binds core histones. Approximately 15 moles of novobiocin bind per mole of histone resulting in histone precipitation from solution in either 0.15 M or 2 M NaCl. The interaction between novobiocin and proteins appears to involve arginine residues: histones H3 and H4 (13.5 and 14 mole percent arginine) are precipitated at lower novobiocin concentrations than histones H2A and H2B (9.5 and 6.5 mole percent arginine). Furthermore, polyarginine but not polyornithine competes for novobiocin in histone precipitation. Moreover, histones with arginine residues modified with 1,2-cyclohexanedione are soluble in 1000 micrograms/ml novobiocin. Because novobiocin can remove histones from solution as well as inhibit topoisomerase activity, and because both of these events can alter DNA topology, novobiocin should be used with caution in experiments designed to implicate topoisomerase activity in chromatin dynamics.

Animals↗
PubMed1986

Cholecystokinin, diet palatability, and feeding regulation in rats.

Rats ate less food than normal on cyclic-ratio schedules following cholecystokinin and lithium chloride injections. Nevertheless, they defended this lower eating rate in the same way as under control conditions. The pattern of effects produced by cholecystokinin and lithium chloride resembled those following diet adulteration with citric acid and sucrose octa acetate and differed from the effects produced by increases in body weight. Cholecystokinin and lithium chloride injections also produced similar changes in the free-feeding patterns of non-deprived rats: Both meal size and intermeal intervals decreased in manner similar to the effects of citric acid and sucrose octa acetate adulteration. Interpreted in terms of a static regulatory model, these results suggest that cholecystokinin and lithium chloride suppress feeding by degrading the palatability of food, not by promoting satiety, discomfort, or illness.

Animals↗
PubMed1986

A computer algorithm to determine the nadir and rise time in nocturnal cortisol secretion.

The nadir concentration value and the time of the circadian rise are two important characteristics of the nocturnal cortisol secretory pattern. A computer algorithm has been developed which objectively determines these parameters, supplementing the subjective evaluating methods previously used. The algorithm smooths the cortisol values and incorporates the intra-assay variability when calculating the nadir and rise. It was tested on 156 nights of cortisol data for healthy control and depressed subjects. The algorithm results closely matched the nadir and rise time subjectively determined by the investigators. With careful screening of the computer generated results, the algorithm decreases the reliance on subjective methods to determine the actual nocturnal cortisol nadir and rise time.

Adolescent↗
PubMed1986

Murine lymphocyte and embryonal carcinoma cell surface antigens recognised by rabbit anti-murine embryonal carcinoma serum.

Some recent studies have suggested that murine embryonal carcinoma (EC) cells which lack classical H-2 molecules must express some novel class-I-MHC (major histocompatibility complex) type antigens. We have investigated whether rabbit anti-EC sera may recognize such components. Molecules of 40 and 48 kd were immunoprecipitated from EC cells and lymphocytes. The possibility that these molecules may be coded for by genes in the Qa-Tla locus which contains many MHC class-I genes or pseudogenes was investigated. The 40 and 48 kd molecules were not associated with beta 2-microglobulin on EC cells, nor with each other or other molecules through S-S bonds, although they appeared to have intradisulphide structures. Peptide map analysis suggested that the lymphocyte 40 and 48 kd molecules were related to the EC cell 40 and 48 kd molecules. However, these molecules were different from H-2, Ia or Qa-2 molecules from the same mouse strain.

Animals↗