Search PubMed⌕ Search

Biomedical subjects

J Dickson

Publications and source records attributed to J Dickson.

At least 55 records · Page 3Linked to original sources
PubMed1993

Costs of on-call.

Explore the source record for details and available documents.

Costs and Cost Analysis↗
PubMed1992

Purification and characterization of a sperm motility-dynein ATPase inhibitor from boar seminal plasma.

A sperm motility inhibitor from boar seminal plasma was purified. The purification procedure included dialysis against 0.1 M Tris-HCl containing 0.1 mM DTT and chromatographies on SP-Sephadex C-25 and Phenyl-Sepharose CL-4B. With this procedure, the seminal plasma motility inhibitor (SPMI) preparation was highly purified with a 18% recovery of inhibitory activity. The molecular weight of SPMI in native conditions has been estimated at 50,000 by molecular sieving, but 3 polypeptides with molecular weights of 14,000, 16,000 and 18,000 were observed following polyacrylamide gel electrophoresis in denaturing conditions. SPMI is a thermolabile basic protein that is stable between pH 6 and pH 11. The observations that SPMI effects on motility of demembranated spermatozoa are reversed by Mg.ATP and that SPMI inhibited bull dynein ATPase in a concentration-dependent manner suggest that this protein blocks the motility of demembranated spermatozoa by interfering with dynein arm function.

Animals↗
PubMed1992

Disruption of synchrony between parasite growth and host cell division is a determinant of differentiation to the merozoite in Theileria annulata.

The multinucleated macroschizont stage of the protozoon Theileria annulata is an intracellular parasite of bovine leukocytes. The parasite induces the host cell to proliferate, and divides in synchrony with the immortalised host cell. Differentiation to the next stage occurs within the host cell culminating in the release of merozoites and destruction of the leukocyte. In this study clones of Theileria annulata macroschizont-infected cell lines were isolated by limiting dilution and tested for differentiation to the merozoite stage (merogony). Two cloned cell lines underwent differentiation with enhanced efficiency, while two others were of lower efficiency. Quantification was carried out using monoclonal antibodies, which showed that over 90% of the cells in an enhanced cloned cell line could be induced to differentiate. By carrying out induction at 41 degrees C for limited periods of time followed by culture at 37 degrees C evidence was obtained that differentiation to the merozoite is a two-step process: a preliminary reversible phase, followed by a second irreversible phase of differentiation. Analysis of the nuclear number of the macroschizont and the growth rate of the cloned cell lines showed that the ability to differentiate was associated with an increase in nuclear number (size) of the macroschizont, generated by a disruption in the synchrony between parasite growth and host cell division. We believe that these results reveal a relationship between a reduction in parasite division and differentiation, and that there are similarities between stage differentiation in parasites and cellular differentiation in higher eukaryotes.

Animals↗
PubMed1990

New diagnostic method for cystic fibrosis.

We report 3 cases where the diagnosis of cystic fibrosis (CF) was either confirmed or refuted by studies of chloride secretion in intestinal mucosal biopsies. In one case a heterozygous state was indicated and later confirmed by gene probe studies. The technique clearly distinguishes between CF and control patients and can provide a rapid diagnosis even in the neonatal period.

Child, Preschool↗
PubMed1989

Defective T-cell activation by Mycoplasma arthritidis mitogen is restored by interferon-gamma.

A mitogen derived from supernatants of Mycoplasma arthritidis (MAS) has been shown to induce both T-cell activation and the production of interferon-gamma (IFN-gamma). MAS-induced response required the presence of accessory cells and is under the genetic control associated with the major histocompatibility complex (MHC). We found that recombinant IFN-gamma restored the proliferative response to MAS mitogen in unreactive mice strains, including H-2b and H-2s haplotypes. We postulated that these T-cells fail to respond since they lack part of the I-E molecules on their accessory cells. Our data suggest that interferon-gamma may be able not only to increase the levels of Ia antigens but also to promote the appearance of MHC products that are not usually present on the cell surface. Since Ia antigens have a central role on T-cell activation, we examined the effect of the level of IFN-gamma on MAS-induced T-cell activation. We analyzed the acquisition of responsiveness to IL-2 and IL-2 activity in cells pretreated with IFN-gamma and found that both the steps of T-cell activation were restored to the MAS mitogen in the unreactive mice strains by IFN-gamma.

Animals↗
PubMed1989

Interaction of retinal glial cells with collagen matrices: implications for pathogenesis of cell-mediated vitreous traction.

Traction retinal detachment results in severe visual loss in many proliferative vitreoretinal disorders. Retinal glial cells participate in nearly all of the proliferative diseases involving the retina. In order to better understand the mechanism of vitreous traction we used phase-contrast and scanning electron microscopy to study the interaction of human retinal glial cells and rabbit dermal fibroblasts with collagen gels. To modify this interaction, we placed a peptide containing the arginine-glycine-aspartic acid sequence that competes for the cellular binding site of fibronectin onto the collagen gels. We found that both glial cells and fibroblasts attached to collagen fibers and pulled them centripetally. The cells extended their processes toward adjacent cells in the gel creating "strands" and traction in a self-promoting fashion. Despite a dramatic effect on fibroblast-mediated traction, the peptide had little effect on glial cells even at 3 mg/ml.

Animals↗
PubMed1987

Nerve fibers surrounding intracranial and extracranial vessels from human and other species contain dynorphin-like immunoreactivity.

Dynorphin B(20-32) was visualized by immunohistochemistry in guinea-pig and rat perivascular nerve fibers and was measured by radioimmunoassay within the walls of feline, canine, bovine and human cephalic and systemic arteries and veins. Canine vessels contained the highest levels. When human blood vessels or trigeminal ganglia were subjected to reverse-phase high-performance liquid chromatography, dynorphin immunoreactivity exhibited a retention time identical to that of synthetic dynorphin B. No differences in dynorphin-like immunoreactivity were measurable between feline systemic arteries and veins, or between cephalic and systemic vessels. The highest amounts were present in leptomeninges devoid of large pial arteries. Relatively high levels were also measured in feline and human trigeminal ganglia and feline superior cervical and sphenopalatine ganglia, three sources of projecting perivascular axons. Levels did not diminish, however, in ipsilateral feline cephalic vessels following either unilateral trigeminal or superior cervical ganglionectomies. Hence, dynorphin-containing fibers may project from parasympathetic cell bodies or perhaps from intrinsic brain sources. Previously published reports indicate that the kappa agonist dynorphin does not modify vessel tone when added in vitro but does inhibit release of neurotransmitters from afferent and sympathetic axons via prejunctional receptors. These observations suggest a pharmacological role for dynorphin on sensory and autonomic functions of the vasculature.

Aged↗
PubMed1985

Response of merino sheep to inoculation with a caprine retrovirus.

Maedi-visna has never been recorded in Australia. However, caprine retroviruses have been isolated which cause clinical disease similar to caprine arthritis-encephalitis and produce antibodies in goats similar to those caused by maedi-visna virus. Merino lambs in close contact for up to 109 weeks with three goats experimentally infected with a caprine retrovirus did not seroconvert or show any significant pathological lesions. No viruses were isolated from any of these sheep though the goats seroconverted and two out of the three developed a non-suppurative bursitis and arthritis. Merino lambs inoculated with a caprine retrovirus showed no significant clinical signs or pathological lesions over a period of 140 weeks though nine out of the 12 seroconverted and viraemia was demonstrated in seven.

Animals↗