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Biomedical subjects

D C Logan

Publications and source records attributed to D C Logan.

10 recordsLinked to original sources
PubMed2001

Mitochondrial biogenesis during germination in maize embryos.

Mitochondrial biogenesis and metabolism were investigated during maize (Zea mays) seed germination. Mitochondria from dry and imbibed seed exhibited NADH-dependent O(2) uptake that was completely inhibited by KCN and antimycin A. Mitochondria in the dry seed had a lower rate of succinate-dependent O(2) uptake relative to that measured in imbibed and germinated seed. The activities of the tricarboxylic acid (TCA) cycle enzymes, pyruvate dehydrogenase complex, 2-oxoglutarate dehydrogenase complex, NAD-malic enzyme, and citrate synthase, are similarly low in mitochondria from dry seed and this correlates with a lower relative abundance of the mitochondrial matrix-located citrate synthase and pyruvate dehydrogenase complex E1alpha-subunit polypeptides. Electron microscopy revealed that mitochondria in the dry seed have a poorly developed internal membrane structure with few cristae; following 24 h of germination the mitochondria developed a more normal structure with more developed cristae. The mitochondria from maize embryos could be fractionated into two subpopulations by Suc density gradient centrifugation: one subpopulation of buoyant density equivalent to 22% to 28% (w/w) Suc; the other equivalent to 37% to 42% (w/w) Suc. These two subpopulations had different activities of specific mitochondrial enzymes and contained different amounts of specific mitochondrial proteins as revealed by western-blot analysis. Both subpopulations from the dry embryo were comprised of poorly developed mitochondria. However, during imbibition mitochondria in the heavy fraction (37%-42% [w/w] Suc) progressively acquired characteristics of fully functional mitochondria found in the germinated seedling in terms of structure, enzymic activity, and protein complement. In contrast, mitochondria in the light fraction (22% to 28% [w/w] Suc) show no significant structural change during imbibition and the amounts of specific mitochondrial proteins decreased significantly during germination.

Gene Expression Regulation, Developmental↗
PubMed2000

Mitochondria-targeted GFP highlights the heterogeneity of mitochondrial shape, size and movement within living plant cells.

Little is known concerning the heterogeneity of mitochondrial shape, size, number, cytoplasmic distribution, and motility in planta. Ultrastructural studies using the electron microscope have shown a variety of mitochondrial shapes and sizes within fixed cells, however, it is not possible to dismiss the possibility that any heterogeneity observed resulted from preparation or fixation artefacts. Unambiguous demonstration of the extent and nature of mitochondrial heterogeneity in vivo necessitates the use of a truly in vivo mitochondrial detection system. Green fluorescent protein is an excellent in vivo marker for gene expression and protein localization studies. It is particularly useful for real-time spatiotemporal analysis of intracellular protein targeting and dynamics and as such is an ideal marker for analysing mitochondria in planta. Stably transformed Arabidopsis lines have been generated with GFP targeted to the mitochondria using either of two plant mitochondrial signal sequences from the beta-ATPase subunit or the mitochondrial chaperonin CPN-60. Mitochondrially targeted GFP, which is easily detectable using an epifluorescent or confocal microscope, highlights heterogeneity of mitochondrial shape, size, position, and dynamic within living plant cells.

Arabidopsis↗
PubMed1997

A new family of plasma membrane polypeptides differentially regulated during plant development.

Two cDNAs encoding polypeptides identified in a tobacco leaf plasma membrane fraction prepared by phase partitioning were cloned. The deduced polypeptides, P16 and P17, exhibit a striking primary structure, similar to that of P19, a previously cloned plasma membrane polypeptide. Antibodies raised to the recombinant proteins were used to probe the cellular location of P16, P17 and P19 by means of western blotting of sucrose density-gradient fractions; all three polypeptides were found to be located solely at the plasma membrane. Furthermore, P19 antigen accumulated transiently at the time of floral induction while P16 and P17 antigens accumulated towards the end of the life-cycle. These results together with sequence database searches and multiple-sequence alignments suggest that we have identified a new family of plasma membrane polypeptides that (i) are putatively plant specific and (ii) are differentially regulated during plant development. These polypeptides are termed DREPPs for developmentally regulated plasma membrane polypeptides.

Amino Acid Sequence↗
PubMed1995

Effect of algal food concentration on toxicity of two agricultural pesticides to Daphnia carinata.

The effects of algal concentration (Selanastrum capricornatum) on the toxicity of the organochlorine pesticide endosulfan and the synthetic pyrethroid esfenvalerate to Daphnia carinata was investigated. The study progressed through four stages: (1) A dose-response experiment on the effects of endosulfan and esfenvalerate on the survival, growth, and reproduction of D. carinata at a single nonlimiting food level. (2) An experiment to investigate the effects of five different food concentrations on survival, growth, and reproduction of D. carinata at sublethal concentrations of endosulfan and esfenvalerate compared with nonexposed controls. (3) An experiment to investigate the effects of route of exposure (water, food-borne, or water+food-borne exposure) on the toxicity of endosulfan to D. carinata. (4) An experiment to investigate the effects of algal concentration on persistence of endosulfan in the water column and on the relative toxicity of the alpha and beta isomers and of endosulfan sulfate to D. carinata. In the first experiment all daphnids exposed to 500 ng/liter esfenvalerate died within 3 days. There was a significant effect of esfenvalerate on reproduction at 50 ng/liter by the second brood. Endosulfan did not cause significant mortality to daphnids but brood size was reduced at 320 micrograms/liter. In the second experiment the toxicity of esfenvalerate increased significantly with decreasing food concentration. In contrast, the toxicity of endosulfan to D. carinata was greatest at the higher food concentrations. Direct water-borne exposure to endosulfan was the most toxic route of exposure and the presence of algae decreased toxicity of this pesticide. The total amount of endosulfan (alpha + beta + endosulfan sulfate) persisting in the water column after 24 hr was greater at high food levels, suggesting that this may be one mechanism for increased toxicity at high food concentrations. The 48-hr LC50s of technical endosulfan, endosulfan sulfate, alpha-endosulfan, beta-endosulfan, and a 50:50 mixture of alpha, and beta endosulfan were 478, 756, 249, 205, and 234 micrograms/liter, respectively.

Analysis of Variance↗
PubMed1983

Pentachlorophenol poisoning.

Pentachlorophenol (PCP) is a pesticide commonly used as a wood preservative. Although exposure has been well controlled in large chemical manufacturing plants, over-exposures have recently becomes a concern at smaller facilities. Five cases of PCP poisoning, including two fatalities, occurred in two small wood preservative plants. All cases presented with fever, including severe hyperpyrexia in two; an increased anion gap and renal insufficiency were noted in two others. PCP may uncouple oxidative phosphorylation, resulting in a poisoning syndrome characterized by hyperpyrexia, diaphoresis, tachycardia, tachypnea, abdominal pain, nausea, and even death.

Adult↗
PubMed1976

Uric acid catabolism in the woolly monkey.

The degradation and excretion of 2-14C-uric acid were examined in three adult woolly monkeys (Lagothrix lagothrichia) to determine the basis for the relatively high serum and urinary uric acid concentrations previously reported in this species. Like man and the great apes which lack uricase, but in distinction to most other mammals, these animals converted very little urate to allantoin. Uric acid turnover, as has been reported for other New World monkeys, was several times that of normal man. Renal urate excretion as well as disposition by extrarenal mechanisms may protect Lagothrix vrom hyperuricemia. The capacity to convert urate to allantoin appears to have been lost late in the evolution of New World monkeys. The woolly monkey deserves further study as a primate model for investigations of enzyme replacement strategies.

Animals↗
PubMedDate not supplied

Reproduction and the workplace: an industry perspective.

The main issue confronting industry in addressing reproductive health and the workplace is how to obtain needed data. The advantages and limitations of four methods of data collection--literature reviews, toxicology, epidemiology, and medical surveillance--are described, and recommendations made for improving reproductive health monitoring by industry.

Animals↗