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Biomedical subjects

D G Jones

Publications and source records attributed to D G Jones.

At least 109 records · Page 6Linked to original sources
PubMed1992

A comparison of superoxide dismutase (SOD, EC:1.15.1.1) distribution in gastro-intestinal nematodes.

An examination of the distribution of superoxide dismutase (SOD) activities in whole worm homogenates from six gastro-intestinal nematodes, at different life-cycle stages, demonstrated that the third larval stages of each species contained notably more activity than the corresponding adults. Significant SOD activities were detected in culture fluids following in vitro maintenance of third and fourth larval stage and adult Trichostrongylus vitrinus and Teladorsagia circumcincta (formerly Ostertagia circumcincta). Marked interspecies variation was observed when SOD isoenzyme profiles of adult and third larval stage Nippostrongylus brasiliensis, Trichostrongylus vitrinus, Teladorsagia circumcincta and Haemonchus contortus were compared. In addition, SOD activity and isoenzyme polymorphism were greater in Nippostrongylus brasiliensis harvested from primed rats compared to parasites recovered from naive rats.

Animals↗
PubMed1992

Use of enzyme microassay to detect eosinophil potentiating activity of cytokines in sheep.

Microplate assays for eosinophil peroxidase (EPO) and arylsulphatase (EAS) have been established as indices of eosinophil survival/proliferation in sheep bone marrow cell (SBMC) cultures. Cell specificity was confirmed using density-fractionated and differentially depleted SBMC populations. Several recombinant cytokines including interleukins 3 (IL-3) and 5 (IL-5), and granulocyte macrophage-colony stimulating factor (GM-CSF), but not macrophage-CSF (M-CSF), had demonstrable eosinophil-potentiating activity on the basis of enhanced EPO and EAS activities in treated, compared with untreated, SBMC cultures. Effects of IL-5 were abrogated in the presence of a specific monoclonal anti-IL-5 antibody. The results indicate that measurement of EPO and EAS in cultured SBMC offers a simple and effective method for detecting eosinophil potentiating activity in the ovine.

Animals↗
PubMed1991

Development of an opiate-based anaesthetic technique for use in dogs with cardiomyopathy.

An opiate-based anaesthetic technique has been developed for use in dogs with end-stage heart failure due to dilated cardiomyopathy. It has been used in dogs undergoing translocation of the left latissimus dorsi around the descending thoracic aorta to create an autologous counterpulsation system. Anaesthesia was induced with barbiturate (10 mg/kg thiopentone) and fentanyl (500 micrograms) and maintained by an infusion of fentanyl (0.5 micrograms/kg/minute) [corrected] in addition to halothane (0.1 to 0.5 per cent) and nitrous oxide (20 to 60 per cent). This technique provided safe anaesthesia for major intrathoracic surgery.

Anesthesia, General↗
PubMed1991

Frequency of occurrence of perforated synapses in developing rat neocortex.

The frequency of occurrence of perforated synapses in the molecular layer of rat parietal cortex has been determined using the disector method. Perforated and non-perforated synapses were examined in electron micrographs, all quantitative procedures being carried out on adjacent sections, as required by the disector procedure. The numerical densities of perforated, non-perforated and all synapses were determined at nine ages, ranging from 0.5 to 22 months of age. The frequencies of perforated synapses were subsequently calculated. These ranged from 18.1% at 0.5 months to a peak of 37.2% at 10 months of age, and remained at around 34% up to 19 months. A frequency of 26.7% was found at 22 months of age. The mean projected height of the total perforation increased from 66 nm at 0.5 months to 133 nm at 22 months of age. These results suggest that perforated synapses are present throughout the life-span of the animal, and increase in complexity with increasing age.

Aging↗
PubMed1991

Perforated and non-perforated synapses in rat neocortex: three-dimensional reconstructions.

Perforated and non-perforated synapses in the molecular layer of rat parietal cortex have been assessed morphologically and quantitatively using three-dimensional reconstructions of the postsynaptic terminal. Perforated synapses were analyzed at nine ages, ranging from 0.5 to 22 months of age, and non-perforated synapses at three ages--0.5, 12, and 22 months. Examination of the reconstructions shows that perforated synapses increase in size and complexity with increasing age. This increasing complexity is reflected in a break-up of the postsynaptic density, which is punctuated by larger, branched perforations. In the most extreme cases the result is the appearance of isolated islands of postsynaptic density separated by, and also surrounded by, a synaptic contact zone. Spinules are especially prominent at around 12 months of age in perforated synapses, and the overall negative curvature of the young junctions is replaced by positively curved junctions from 4 months onwards. The non-perforated synapses are relatively small and show few changes with increasing age. Using the measurement option in the reconstruction program, the following trends emerged. All parameters of perforated synapses increased in size with increasing age, whereas the corresponding parameters of non-perforated synapses remained relatively unchanged over this age range. In addition, the percentage of the synaptic contact zone surface area occupied by the postsynaptic density decreased with increasing age in perforated synapses, but increased in non-perforated synapses. The total postsynaptic density surface area of non-perforated synapses per unit volume of molecular layer was double that of perforated synapses at 0.5 months, but the situation was reversed at 12 months. This parameter was similar in the 2 populations at 22 months. This suggests that perforated synapses contribute more to the total surface area of the postsynaptic density in mid- to late-adulthood than do non-perforated synapses, despite non-perforated synapses outnumbering perforated by 2-3:1 at these ages. These data provide more specific evidence that perforated and non-perforated synapses constitute separate synaptic populations from early in development, and that perforated synapses are responsible for the maintenance of neuronal postsynaptic density surface area from mid-adulthood onwards.

Animals↗
PubMed1991

Neuronal survival and neurite growth in cultured cerebral explants: assessment of the effect of cytosine arabinoside using improved stereology.

Using improved stereological procedures, based on measurements of the total reference volume, the effect of cytosine arabinoside (AraC) on neurons and non-neuronal cells in rat cerebral explants has been reinvestigated. These analyses revealed that, in the AraC-treated explants, neurons support a significantly increased volume of neurites, while the volume of non-neuronal cells in the outgrowth zone is significantly decreased. The total number of neurons is similar in the control and treated explants. Since AraC primarily affects dividing cells, these data suggest that the increased volume of neurites per neuron may be mediated through a curtailment of non-neuronal cell division in the AraC-treated explants. This volumetric approach represents a major improvement on current morphometric approaches for quantifying cultured explants of nervous tissue, and provides important evidence that the previously postulated effects of AraC are real ones.

Animals↗
PubMed1991

Perforated synapses and plasticity. A developmental overview.

Against a background of existing models relating perforated synapses to synaptic plasticity, the numerical density and frequency of perforated synapses in rat neocortex have been assessed from 1 d to 22 mo of age using the disector procedure, and changes in their morphology were assessed using 3-D computer reconstructions. The data point toward perforated and nonperforated synapses being separate synaptic populations from early in development, and with perforated synapses playing a part in the maintenance of neuronal postsynaptic density surface area from mid-adulthood onwards. This suggests that they play a crucial role in synaptic plasticity, although its nature may be different from that postulated by most recent workers.

Animals↗
PubMed1991

Molecular cloning, characterization and analysis of the regulation of the ARO2 gene, encoding chorismate synthase, of Saccharomyces cerevisiae.

We describe here the cloning, characterization and analysis of the regulation of the ARO2 gene of Saccharomyces cerevisiae, the first reported study of a eukaryotic gene encoding chorismate synthase (E.C. 4.6.1.4). The gene contains an ORF of 1128 bp, encoding a protein with a calculated molecular mass of 40.8 kDa. ARO2 is regulated under the 'general control system' for amino acid biosynthesis by the transcriptional activator GCN4 which binds in vitro at three sites within the ARO2 promoter. The ARO2 gene product is highly similar to its Escherichia coli counterpart, with a 47% identity distributed over the entire length of the peptide. We therefore suggest that the S. cerevisiae chorismate synthase, in contrast to the Neurospora crassa enzyme, but like other chorismate synthases, is a monofunctional peptide, solely possessing chorismate synthase activity.

Amino Acid Sequence↗
PubMed1991

A computational model for the overall pattern of ocular dominance.

In layer IV of the primary visual cortex, in both the macaque monkey and the cat, geniculocortical terminals representing the two eyes are segregated into alternating zones known as ocular dominance bands. Viewed tangentially, in the monkey these bands take the form of a series of branching parallel stripes that run roughly perpendicular to the border of striate cortex. In the cat, the overall ocular dominance pattern consists of irregularly branching, beaded bands that exhibit no predominant orientation. If the striking differences in the appearance of these two patterns reflect important differences in the basic rules governing cortical ocular dominance, then this poses a problem for attempts to formulate general principles of visual cortical organization. However, it has been suggested that the differences in the appearance of the ocular dominance patterns in these two species could result simply from known differences in the boundary conditions of their geniculocortical pathways. This article describes the formulation and testing of a single computational model that accurately predicts the quite dissimilar ocular dominance patterns in cats and monkeys. This model also generalizes to predict the different ocular dominance patterns observed in young and old three-eyed frogs, supporting the notion that the overall pattern of ocular dominance is governed by a common set of rules. The significance of these results is discussed in terms of previous models, which have focused largely on local processes underlying the development of ocular dominance segregation. Although the present model is not a developmental one, it does shed some light on potential mechanisms for establishing retinotopy in striate cortex and on possible developmental relationships between the geniculostriate pathway and intrinsic modularity of the striate cortex.

Animals↗
PubMed1990

Isolation of a novel protein kinase-encoding gene from yeast by oligodeoxyribonucleotide probing.

We have identified a novel protein kinase-encoding gene, KIN3, in the genome of the budding yeast Saccharomyces cerevisiae. The gene was isolated from a library of cloned genomic fragments by probing with an oligodeoxyribonucleotide mixture corresponding to part of a highly-conserved region in the catalytic domain of protein serine-threonine kinases. KIN3 is unique in the yeast genome, maps to chromosome VI and is actively expressed in mitotically dividing cells to produce a 1400 nucleotide (nt) message. The nt sequence of KIN3 predicts a protein product of 43.4 kDa which contains all of the conserved elements found in known protein serine-threonine kinases, although the organisation of these elements in the KIN3 gene product differs significantly from the consensus. The function of the KIN3-encoded protein kinase is unclear although it appears not to be essential for growth, conjugation or sporulation.

Amino Acid Sequence↗
PubMed1990

Stimulation of adult chondrocyte metabolism by a thyroid-derived factor.

This paper reports the effects of adding partially purified bovine thyroid calcitonin, thyrocalcitonin, to adult bovine articular cartilage cells. Thyrocalcitonin stimulated chondrocyte proliferation fourfold under low serum (0.5%) culture conditions. In serum-free medium, thyrocalcitonin stimulated cell proliferation more than twofold. With high-density cultures in serum-free medium, chondrocyte glycosaminoglycan (GAG) synthesis was stimulated 60% by thyrocalcitonin. Cell-associated radioactivity was increased twofold. In contrast to thyrocalcitonin, addition of human and salmon calcitonin peptides as well as the thyroid hormones T3 and T4 had no effect on adult cartilage cell proliferation or GAG synthesis. The data reported here suggest the existence of a thyroid-derived factor, independent of calcitonin peptides or thyroid hormones, which stimulates adult articular chondrocyte metabolism.

Animals↗
PubMed1990

Studies on the presence and release of proteolytic enzymes (proteinases) in gastro-intestinal nematodes of ruminants.

The proteolytic activity of worm homogenates prepared from the third stage larval (L3) and adult stages of the ovine gastro-intestinal nematodes, Nematodirus battus, Ostertagia circumcincta, Trichostrongylus colubriformis, Trichostrongylus vitrinus and Haemonchus contortus, and the rodent intestinal nematode, Nippostrongylus brasiliensis, has been examined using the protein substrates azocasein, azocoll and elastin-orcein. Activity detected in third stage larvae was usually higher than that observed in the adult. Species and stage differences were demonstrated. The in vitro release of proteolytic activity, detected using protein substrates and specific low molecular weight peptide substrates, was, similarly, shown to exhibit a degree of species and stage specificity. Acetylcholinesterase and lactate dehydrogenase activities were determined as reference 'secretory' and 'non-secretory' enzymes, respectively. Three separate peaks of 'tryptic' activity were detected following anion-exchange chromatography of culture fluids derived from adult Ostertagia circumcincta. These peaks could be ascribed to different proteinase classes on the basis of inhibitor sensitivity.

Animals↗