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Biomedical subjects

D G Jones

Publications and source records attributed to D G Jones.

At least 199 records · Page 11Linked to original sources
PubMed1982

Changes in the intestinal enzyme activity of lambs during chronic infection with Trichostrongylus vitrinus.

The pathology and enzymology of the intestinal mucosae of lambs dosed daily with 2500 Trichostrongylus vitrinus larvae and killed at five, nine or 14 weeks were compared with worm-free animals. The proximal small intestines of the infected lambs exhibited extensive mucosal damage at five and nine weeks, but only isolated lesions were found at 14 weeks. Activities of the brush border enzymes alkaline phosphatase, leucine amino-peptidase, maltase and glycyl-L-leucine dipeptidase were all significantly depleted during infection, although the magnitude, time of onset and duration of the individual enzyme responses varied. Mucosal activities of the pancreatic enzymes, trypsin and to a lesser extent chymotrypsin were also markedly decreased particularly during the first nine weeks of infection. Specific acetylcholinesterase activity was significantly increased throughout the study, maximal levels being observed at five weeks. In contrast 'pseudo'-cholinesterase levels were consistently within the control range. During the early stages of infection (five weeks) glutamine-oxaloacetate transaminase activity was significantly decreased, while aldolase and creatine phosphokinase levels were significantly elevated. At nine weeks low glutamine-oxaloacetate transaminase activities were again detected and lactate dehydrogenase activity was also markedly reduced. At 14 weeks the mean activities of all four enzymes were within the normal range as were superoxide dismutase levels throughout. Significant correlations were found between alkaline phosphatase, trypsin, chymotrypsin, aldolase and glutamine-oxaloacetate transaminase activities and the degree of mucosal damage within the individual lambs.

Acetylcholinesterase↗
PubMed1981

The influence of protein restriction, rehabilitation and changing nutritional status on synaptic development: a quantitative study in rat brain.

Quantitative ultrastructural technique were employed to compare the development and maturation of cortical synapses in rats subjected to protein deprivation, control diet, nutritional rehabilitation and a normal-low crossover diet. Osmicated preparations of the molecular layer of occipital cortex were prepared at 15, 20, 28, 75 and 224 days postnatal in male rats. At 15 and 30 days the values for mitochondrial and synaptic densities, vesicle number and packing per terminal, synaptic length, terminal area and brain weight were lower in the protein-deprived than in the control animals. These initial deficits were progressively transformed to excesses, with the most marked crossover period occurring between 20 and 28 days. By 224 days only brain weight and presynaptic terminal area were lower in the protein-deprived material. A further parameter, synaptic curvature, showed a decrease in negativity in protein-deficient junctions between 15 days (64%) and 224 days (41%). Well-nourished tissue had fewer negatively-curved synapses during early development. These data suggest that the morphological development of the presynaptic terminals is not simply delayed, but is ultimately different in the protein-deprived animals. The nature of these changes may facilitate an adaptation to provide more efficient functioning in the adverse condition. Nutritionally rehabilitated tissue ultimately approaches the control, although significant differences occur in synaptic and mitochondrial densities and in brain weight. The normal--low crossover procedure intensities the differences noted in animals subjected to continuous deprivation.

Animals↗
PubMed1981

Synaptic parameters in developing rat cerebral cortex: comparison of anaesthetized and unanaesthetized states.

The ultrastructure of synapses from the molecular layer of parietal cortex was examined in male rats aged between 7 and 75 days. Two groups were compared, one group consisting of rats anaesthetized with 50 mg/kg pentobarbitone and the other consisting of those killed by stunning across the back of the neck. Various synaptic parameters were analyzed. In the anaesthetized material, the sectioned area of the pre-synaptic terminals decreases between 7 and 75 days, as does the number of terminals containing intraterminal profiles other than synaptic vesicles. Mean synaptic vesicle number per terminal increases, while the remaining parameters fluctuate over the developmental period. Comparing these data with those from the unanaesthetized material, the only parameters showing similar trends are the pre-synaptic terminal area, the mean vesicle number per terminal, and the length of the postsynaptic thickening. The remaining parameters are comparable up to 15 or 21 days postnatally, after which they diverge. The percentage of terminals containing intraterminal profiles, the terminal perimeter and the mean vesicle density in the unanaesthetized terminals all show increased values. The form factor indicates these terminals are more ellipsoidal by 75 days, while the mean synaptic curvature is more positive by 75 days. It is concluded that the synaptic organization of the early terminals differs from that of the older ones, and this may be related to different mechanisms of transmitter storage and release.

Age Factors↗
PubMed1981

Some effects of copper deficiency on leucocyte function in sheep and cattle.

Peripheral blood leucocytes from copper-deficient (less than 8 mumol per litre plasma) and copper-sufficient (more than 8 mumol per litre) ewes and lambs were tested for their ability to ingest and kill Candida albicans in vitro. Killing capacity was significantly reduced in both copper-deficient ewes and lambs, although phagocytic capacity was apparently unimpaired. Similar results were obtained with copper-deficient calves, in which it was further shown that copper repletion restored candidacidal activity. Leucocyte and erythrocyte superoxide dismutase (LSOD and ESOD respectively) activities were both significantly decreased in hypocupraemic ewes and there was a linear relationship between their activities in the two cell types: LSOD activities were reduced by approximately 35 per cent and ESOD activities by 67 per cent. Cyanide inhibition tests indicated that the manganese-dependent form of the enzyme contributed little to the total activity of LSOD or ESOD. There was a tendency for leucocytes from copper-deficient ewes to release greater amounts of superoxide anion after stimulation with opsonised zymosan. Their viability was similar to that of leucocytes from control sheep and was unaffected for up to three hours after stimulation.

Animals↗
PubMed1980

Quantitation of terminal parameters and their inter-relationships in maturing central synapses: a perspective for experimental studies.

The development and maturation of synapses in the molecular layer of the occipital cortex of rats at 15, 20, 28, 75 and 224 days postnatal were examined and quantitative ultrastructural techniques were employed. The parameters evaluated display a diverse set of trends. A steady increase in mean terminal area is noted, the proportions of the smallest terminals declining progressively over this period. The mean length of the postsynaptic thickening fluctuates throughout the developmental series. A close association is found between terminal area and junction lengthlarger junction lengths being consistently associated with larger areas. Synaptic vesicle numbers within each terminal increase markedly between 15 and 28 days. There is an increase in the frequency of flat and positively curved junctions with increasing age, the bimodal distribution of negative and positive curvatures at 15 days being replaced by a normal distribution in the adult. When synaptic length is compared with curvature, flat junctions emerge as the longest and the most highly curved junctions as the shortest. The terminal areas of positive junctions are greater than those of negative ones. The consequences of these results for the flat disc model of synapses are discussed, and it is postulated that negatively curved synaptic junctions may be non-functional.

Aging↗
PubMed1980

A strain marker in Rhizobium trifolii based on the absorption of congo-red.

It is widely recognized that most rhizobia absorb congo-red weakly when grown on agar media containing this dye. In contrast to this generalized behaviour, an ineffective strain of Rhizobium trifolii (Coryn) has been found which strongly absorbs the dye, producing growth of a very deep-red colour on yeast-extract mannitol agar, supplemented with congo-red (0.025 g/l). Assays for dye absorption characteristics on this medium with 21 strains of R. trifolii showed that Coryn could be readily differentiated from all the other strains examined. Supplementary fluorescent antibody tests with Coryn confirmed the reliability of differential absorption of congo-red as a strain-marker system. Data are presented which demonstrate the potential of this characteristic as a strain identification method in nodulation and competition studies under aseptic growth conditions, using mixed inocula.

Absorption↗
PubMed1979

Limbless: a new genetic mutant in the chick.

A mutation in the chicken resulting in total amelia is described. Genetic analysis indicates that the limbless condition is due to an autosomal recessive gene. In the limbless embryos the apical ectodermal ridge is lacking. However both the pectoral and pelvic girdles as well as the respiratory and excretory systems are normal. In the affected embryos usually the upper beak is shorter than the lower beak.

Animals↗
PubMed1979

Synaptic terminal parameters in unanesthetized rat cerebral cortex.

The ultrastructure of synapses from the molecular layer of parietal cortex was examined in two groups of unanesthetized rats. Rats of the first group were killed by stunning across the back of the neck, and those of the second group by the introduction of fixative through a preimplanted carotid artery cannula. Comparison of synapses from the two groups revealed that the distribution of synaptic types was the same. A larger percentage of synapses of the cannulated group has vesicle attachment sites than did those of the stunned group. The area and perimeter of the presynaptic terminals were significantly larger in synapses from the cannulated group, although the equivalent length of the postsynaptic thickening was less. The mean value for synaptic curvature was greater in the cannulated group, although over 80% of synapses in both groups had positive curvatures. No significant differences were found between the groups for the relationships between presynaptic terminal area and synaptic vesicle number, and between postsynaptic thickening length and synaptic curvature. Membrane recycling is suggested as a mechanism of accounting for the differences. The preponderance of postively-curved synapses in unanesthetized material may indicate a preponderance of functioning synapses.

Anatomy↗