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Biomedical subjects

R M Sharrard

Publications and source records attributed to R M Sharrard.

26 records · Page 2Linked to original sources
PubMed1988

The identification of factors in seminal plasma responsible for suppression of natural killer cell activity.

We have identified two components of human seminal plasma which suppress natural killer (NK) cell activity in vitro. Dialysis and gel filtration experiments have shown both components to be of low molecular weight. The first will suppress NK cells following a short period of pretreatment, but this suppression is dependent upon the presence of bovine serum in the medium and is directly related to a loss of cell viability as measured by trypan blue dye exclusion. We suggest that this molecule is a polyamine. The second factor will not suppress NK activity following pretreatment of lymphocytes, but is a potent suppressor when added for the duration of the assay. This suppression is completely bovine serum independent, unrelated to toxicity and appears to be mediated by prostaglandin E2. The relevance of these results to a clinical situation is discussed.

Chromatography, Gel↗
PubMed1985

Partial purification of a factor from human synovium that possesses interleukin 1, chondrocyte stimulating and catabolin-like activities.

Human synovial explants in culture release material that stimulates the production of prostaglandin E2 (PGE2) and several extracellular enzymes by human chondrocytes. Fractionation of conditioned medium by gel filtration revealed a protein of approx. 15 kDa, which in addition to stimulating production of PGE2 and plasminogen activator by human articular chondrocytes, possessed interleukin 1 activity and induced cartilage degradation. Further purification using iso-electric focussing again showed co-elution of these activities with a major pI of 6.9 and a minor pI of 5.1-5.3. This study indicated that human synovium releases a factor that is closely related to or identical with interleukin 1 and suggests that this protein may participate in cellular interactions that occur within the rheumatoid joint.

Animals↗
PubMed1985

Polypeptide compositions of amoebae of the cellular slime mould Dictyostelium discoideum separated by partitioning during development.

Amoebae of the cellular slime mould Dictyostelium discoideum at 8 h or 10 h development were separated into two populations by countercurrent distribution in a dextran-poly (ethylene glycol), two-phase system. Two-dimensional, polyacrylamide-gel electrophoresis was then used to separate the polypeptides from the populations of amoebae. The two populations of amoebae at 8 h development differed 9n polypeptide composition as did the populations separated at 10 h development. This confirms that cell differentiation is initiated in D. discoideum prior to 8 h development.

Countercurrent Distribution↗
PubMed1985

Modulation of connective tissue metabolism by partially purified human interleukin 1.

We have investigated the relationship between the monokine interleukin 1 (IL-1) and the connective tissue-stimulating activities produced by monocytes such as mononuclear cell factor (MCF). Using almost exclusively human tissue we have monitored a wide range of MCF-like activities through the partial purification of IL-1 by gel filtration and isoelectric focusing. Activities measured include stimulation of chondrocytes to produce prostaglandins, plasminogen activator and proteoglycanase, enhancement of synovial cell proliferation, and stimulation of cartilage resorption, in addition to IL-1 (lymphocyte activating factor) activity. The activities described show the same molecular heterogeneity; the active material has similar potencies in the different systems, and removal of IL-1 activity by pretreatment with phenylglyoxal also results in loss of the connective tissue-stimulating activities. These results show that the factors responsible for this wide range of activities are very closely related to IL-1 and give further evidence in support of the possible involvement of IL-1 in the processes of joint destruction occurring in chronic inflammatory conditions such as rheumatoid arthritis.

Connective Tissue↗
PubMed1983

A possible role for calmodulin in human thyroid cell metabolism.

A protein which shared several characteristics with authentic calmodulin was extracted from human thyroid homogenates. The protein bound to fluphenazine--Sepharose and could be specifically eluted using EGTA. The eluted protein had a u.v. spectrum characteristic of calmodulin and migrated like authentic calmodulin with a calcium-dependent shift on sodium dodecyl sulphate polyacrylamide-gel electrophoresis. Calmodulin in thyroid cell extracts was shown to be biologically active, measured by its ability to activate a calmodulin-deficient cyclic GMP phosphodiesterase; this activation could be inhibited by trifluoperazine. A possible role for calmodulin in the action of TSH on the thyroid was demonstrated by studying the effects of phenothiazines and the naphthalene sulphonamide, W7, a more specific calmodulin inhibitor, on TSH-stimulated cyclic AMP levels in cultured thyroid cells. The phenothiazines and W7 were found to inhibit the accumulation of cyclic AMP in response to TSH in a concentration-dependent manner although low concentrations of W7 enhanced TSH-stimulated cyclic AMP accumulation.

3',5'-Cyclic-GMP Phosphodiesterases↗