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Biomedical subjects

D F Wilson

Publications and source records attributed to D F Wilson.

At least 199 records · Page 11Linked to original sources
PubMed1984

Age-associated changes in neuromuscular transmission in the rat.

The physiological changes in neuromuscular transmission associated with age were examined in rats between the ages of 1 mo (28 days) and 1 yr (364 days). Intracellular recording techniques were used to monitor end-plate potentials and miniature end-plate potentials at the rat diaphragm neuromuscular junction. Muscle action potentials were blocked by cutting the muscle fibers. Neuromuscular transmission was significantly different in 28-day-old rats compared with the older rats (42-364 days). The 28-day-old rats released fewer quanta. The statistical store in the immature rats was also significantly smaller than in the older age groups. The statistical probability of release, however, was not significantly different from the older animals. Examination of the presynaptic parameters in rats between the ages of 42 and 364 days revealed no significant increases in quantal release. It is concluded that the neuromuscular junction matures physiologically by 6 wk of age in rats and remains stable through the 1st yr of life.

Action Potentials↗
PubMed1983

High affinity proline uptake in rat brain synaptosomes.

The uptake of L-proline by synaptosomes isolated from different regions of the brain was investigated. The highest rates of transport and the largest accumulation ratios were found in synaptosomes from the midbrain, striatum, hippocampus and hypothalamus, with lower activity in the cortex and medulla (+ pons) and lowest in the cerebellum. The high affinity, Na+-dependent proline uptake had a Km of 12 microM, a Vmax of 0.6 nmol . min-1 . mg protein-1 and the maximum accumulation ratio ( [proline]i/[proline]o) at 2 microM added radioactive amino acid was 40-50. Our results suggest that: (1) only 5-10% of the synaptosomal population accumulates proline through the high-affinity uptake; (2) the characteristics of the proline uptake system into the prolinergic nerve endings are remarkably similar to those of other amino acid neurotransmitters (GABA, aspartate and glutamate); (3) the behavior of proline is consistent with this amino acid being a neurotransmitter in the central nervous system.

Animals↗
PubMed1983

Evaluation of the relationship between the intra- and extramitochondrial [ATP]/[ADP] ratios using phosphoenolpyruvate carboxykinase.

The ratio of free ATP to free ADP in the mitochondrial matrix [( ATPf]/[ADPf]) has been measured in suspensions of isolated mitochondria under conditions of active phosphorylation of extramitochondrial ADP. These measurements utilized phosphoenolpyruvate carboxykinase which is present in the matrix of mitochondria from the livers of guinea pigs, chickens, and pigeons. Mitochondria isolated from these sources also contain nucleoside diphosphate kinase, malate dehydrogenase, and glutamate dehydrogenase or 3-OH-butyrate dehydrogenase. Together these enzymes catalyze the synthesis of phosphoenolpyruvate and CO2 from oxaloacetate with oxidative phosphorylation as an energy source. These reactions have been shown to be fully reversible in suspensions of mitochondria isolated from the above sources. With oxidative phosphorylation as the source of ATP, phosphoenolpyruvate was synthesized from malate and conversely addition of phosphoenolpyruvate, ADP, and CO2 led to synthesis of malate and ATP. The forward and reverse reactions were allowed to continue until the rate of change of metabolite concentrations was minimal and then the latter were measured. The intramitochondrial [Mg-ATPf]/[MgADPf] was calculated from the equilibrium constants for the reactions and the measured steady state concentrations of the metabolites in both the intra- and extramitochondrial spaces. The value of the intramitochondrial [MgATPf]/[MgADPf] was found to exceed the extramitochondrial value (adjusted to the same free Mg2+ concentration) by a factor (+/- S.E.) of 0.83 +/- 0.22 (n = 17) for the forward reaction and 1.81 +/- 0.54 (n = 11) for the reverse reaction. It is concluded that the adenine nucleotide translocase catalyzes electroneutral exchange of ATP for ADP and that this reaction does not contribute significantly to the energetics of mitochondrial oxidative phosphorylation.

Adenosine Diphosphate↗
PubMed1983

Aspartate transport in synaptosomes from rat brain.

Active transport of aspartate by neuronal synapses has been studied using preparations of synaptosomes from rat forebrain. The maximal accumulation of labeled D-aspartate [( Asp]i/[Asp]o) was observed to increase as the second power of the transmembrane electrical potential (measured by the potassium ion concentration gradient [( K+]i/[K+]o], which indicates that aspartate is transported with a net charge of +2. The aspartate gradient also increased as the second power of the sodium ion gradient, indicating that two Na+ are transported inward with each aspartate. Measurement of total intra- and extrasynaptosomal aspartate (L-aspartate) and the specific activities of each after adding labeled D-aspartate shows the presence of two intrasynaptosomal pools, a rapidly exchanging pool in which the L-aspartate is dependent on [Na+] and [K+] in the same manner as described for D-aspartate and a slowly exchanging pool essentially insensitive to [Na+] and [K+]. Maximal activation of uptake with 50 microM aspartate causes an alkalinization of the external medium which suggests that H+ is taken up with the aspartate (or OH- is ejected) to neutralize the negative charge of aspartate at physiological pH values. The data are consistent with the transport process being: Asp- + H+ + 2Na+ o = Asp- + H+ + 2Nai+. These stoichiometries can explain the energetics of both in vitro and in vivo uptake of aspartate by the high affinity, [Na+]- and [K+]-dependent system.

Animals↗
PubMed1983

Dependence of mitochondrial oxidative phosphorylation on activity of the adenine nucleotide translocase.

The coupled reactions of electron transport and ATP synthesis for the first two sites of mitochondrial oxidative phosphorylation have been previously reported to be near equilibrium in isolated respiring pigeon heart (Erecińska, M., Veech, R. L., and Wilson, D. F. (1974) Arch. Biochem. Biophys. 160, 412-421) and rat liver mitochondria (Forman, N. G., and Wilson, D. F. (1982) J. Biol. Chem. 257, 12908-12915). Measurements are presented in this paper which demonstrate that the same relationship exists for both forward and reverse electron transport in rat heart mitochondria. This conclusion implies that adenine nucleotide translocation, a partial reaction of the system, is also near equilibrium, contrasting with proposals that the translocase is rate-limiting for oxidative phosphorylation. To resolve this controversy, the respiratory rates of suspensions of isolated rat liver and rat heart mitochondria were controlled by varying either the added [ATP]/[ADP][Pi] ratios ratios or [ADP] (by varying hexokinase in a regenerating system). Titrations with carboxyatractyloside, a high affinity inhibitor of the translocase which is noncompetitive with ADP, were carried out to assess the dependence of the respiratory rate on translocase activity. Plots of respiratory rate versus [carboxyatractyloside] were all strongly sigmoidal. In liver mitochondria, 40%-70% and in heart mitochondria 66% of the sites could be blocked with carboxyatractyloside before a 10% decrease in the respiratory rate was observed. Further analysis showed that liver and heart mitochondria have translocase/cytochrome a ratios of 1.52 and 3.20, respectively, and that at 23 degrees C the maximal turnover numbers for the translocases were 65 s-1 and 23 s-1. In all states of controlled respiration (no added inhibitor), a substantial excess of translocase activity was present, suggesting that the translocase was not normally rate-limiting in oxidative phosphorylation.

Animals↗
PubMed1983

The heat resistance of a data-encoded ceramic microchip identification system.

Samis introduced the concept of the Dentify system of personal identification. In this system, ceramic microchips embossed with metallic intelligence data are placed in teeth under dental restorations. This paper describes the results of an in vitro study aimed at testing the heat resistance qualities of this identification system when placed in teeth. Teeth were subjected to a temperature of 1,000 degrees C. The results of this study indicate that the ceramic chips and their embossed metallic intelligence data are able to withstand extremely high temperatures. The metallic identifier pins used in this study were less resistant to extreme heat. The significance of these findings is discussed.

Ceramics↗
PubMed1983

4 Nitroquinoline 1-oxide-induced carcinogenesis in the rat palate.

Most reported studies of experimental oral cancer have been carried out in the hamster. This animal is not available in certain countries and there is controversy regarding its suitability as a model for experimental oral carcinogenesis. An attempt was made to reproduce an experimental oral cancer model in rats, using a protocol based on that described by Lekholm and Wallenius (1976). The carcinogen 4 nitroquinoline 1-oxide was applied to the palates of rats for periods of up to 24 weeks. Macroscopic and microscopic examination of carcinogen-treated palatal mucosa was carried out during the experimental period. Verrucous carcinoma-like lesions of the mid-palate and squamous carcinomas of the gingival mucosa were produced, beginning at 16 and 20 weeks respectively. A variety of other macroscopic and microscopic mucosal changes were also observed during the experimental period. The findings are discussed in relation to the work of others.

4-Nitroquinoline-1-oxide↗
PubMed1983

Bioenergetics of Na+ transport across frog skin: chemical and electrical measurements.

Enzymatically prepared split frog skins consisted purely of epithelial cells. Electrical parameters and the cell contents of ATP, ADP, phosphocreatine (PCr), creatine, inorganic phosphate, protein, and water were measured in skins maintained at room temperature. Studies were conducted under base-line conditions, 15 and 60 min after adding vasopressin, and 30 min after adding amiloride. Intracellular ionic activities and concentrations were obtained from previous results. The data demonstrated that 1) the base-line concentration ratio of PCr/ATP was 0.53 +/- 0.03; 2) the average molar free energy of hydrolysis of intracellular ATP was approximately 15.0 kcal X mol-1 under control conditions, changing by less than or equal to 3% with changes in transport; and 3) the free energy of extruding 3 mol of Na+ and accumulating 2 mol of K+ was approximately 9.8 kcal X mol-1 under base-line conditions; the difference between the molar free energies of ATP hydrolysis and of transport work remained large, despite large changes in transepithelial transport. The simplest conclusion is that the Na+ pump of frog skin operates far from equilibrium.

Amiloride↗
PubMed1983

Malignant Schwannoma of cranial nerves.

The clinical presentation and histopathological features of 5 cases of malignant Schwannoma of cranial nerves are described. The ultrastructural appearances of one case and the pattern of nerve sheath cell differentiation of these tumours are also discussed. These uncommon tumours often are not diagnosed at initial presentation. Since the cases provide evidence that early diagnosis and surgical treatment are vital in the management of patients with this tumour criteria for its diagnosis are suggested.

Adult↗
PubMed1983

Effects of 4-aminopyridine and 3,4-diaminopyridine on transmitter release at the neuromuscular junction.

The presynaptic effects of 4-aminopyridine (4-AP) and 3,4-diaminopyridine (3,4-DAP) were investigated at the rat diaphragm neuromuscular junction using intracellular recording techniques. 4-AP caused only minor increases in miniature end-plate potential frequency at junctions depolarized with elevated potassium levels. Calcium ions antagonize this excitatory effect. 4-AP (20-200 microM) enhanced evoked transmitter release and the amplitude of the end-plate potentials (EPPs), but this effect was considerably less than predicted from earlier reports. 4-AP (100 microM) enhanced quantal content of the first EPP by only 97% and 3,4-DAP by 95%. 4-AP and 3,4-DAP also enhanced transmitter release during maintained stimulation at 50 Hz. The APs did not exhaust the output capabilities of the nerve terminal. 4-AP and 3,4-DAP blocked facilitation. This is attributed to the observation that 4-AP and 3,4-DAP increases the statistical probability of release to its maximum level (1.0). Increased transmitter release by 4-AP and 3,4-DAP is attributed primarily to their ability to increase the releasable store of transmitter and mobilization activity. It was observed that 4-AP and 3,4-DAP enhances the duration of the EPP. This observation supports the suggestion that 4-AP prolongs the time course of the presynaptic spike. The effects of 4-AP and 3,4-DAP on quantal release are compatible with the hypothesis that these drugs enhance calcium entry indirectly by blocking voltage sensitive potassium channels.

4-Aminopyridine↗
PubMed1982

Labeling of succinate-cytochrome c reductase with 125I. Accessibility of the peptides to the aqueous phases on the cytosolic and matrix sides of the mitochondrial membrane.

Lactoperoxidase-catalyzed radioiodination was used to study the arrangement of the component peptides of succinate-cytochrome c reductase with respect to the aqueous phases on each side of the mitochondrial inner membrane. Mitochondria depleted of their outer membrane and inside-out vesicles purified from submitochondrial particles by the lectin-affinity procedure (D'Souza, M. P., and Lindsay, J. G. (1981) Biochim. Biophys. Acta 640, 463-472) were iodinated using immobilized preparations of lactoperoxidase. The labeled membranes were solubilized in detergent and the succinate-cytochrome c reductase was purified by immunoprecipitation with specific IgG. Analysis of the radioiodine distribution after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and comparison with peptide stain patterns show that bands 2 (64 kilodaltons), 6 (30 kilodaltons), 9 (15 kilodaltons), and 11 (less than 10 kilodaltons) are labeled from the cytoplasmic surface of the membrane. Bands 1 (72 kilodaltons), 4 (48 kilodaltons), and 8 (20 kilodaltons) appear to be labeled on the matrix side of the membrane, while bands 3 (52 kilodaltons), 5 (35 kilodaltons), 7 (25 kilodaltons), and 10 (11 kilodaltons) are labeled from both sides of the membrane. Tentative identification of the labeled bands suggests that band 1 is the large subunit of succinate dehydrogenase. Bands 3 and 4 represent proteins which have been referred to as core proteins I and II. Bands 5 and 6 are the proteins associated with cytochromes b and c1, respectively; band 7 is the Rieske iron-sulfur protein.

Animals↗
PubMed1982

Energetics of gamma-aminobutyrate transport in rat brain synaptosomes.

The energetics of active transport of gamma-aminobutyric acid (GABA) by neuronal synapses has been studied using preparations of synaptosomes from rat brain. The maximal (steady state) accumulation of GABA by synaptosomes was measured as a function of the transmembrane potassium concentration gradient (which is equal to the transmembrane electrical potential in this system), the sodium concentration gradient, and the external chloride concentration. The steady state [GABA]i/[GABA]o increased as the second power of [K+]i/[K+]o which indicates that GABA is transported with a net charge of +2. The GABA gradient was dependent on [Na+]o/[Na+]i to a power of between 1.2 and 2.1 but was almost independent of [Cl-]. It is concluded that a neutral GABA molecule is cotransported with 2 Na+ to give a net charge of +2. The coupling of GABA transport to the transmembrane electrical potential and the Na+ concentration gradient is sufficient to provide the energy for the measured GABA concentration gradient in rat brain synaptosomes.

Animals↗
PubMed1982

Coulometric and potentiometric evaluation of the redox components of cytochrome c oxidase in situ.

A new coulometric-potentiometric titration cuvette is described which permits accurate measurements of oxidation-reduction components in membranous systems. This cuvette has been utilized to measure the properties of cytochrome c oxidase in intact membranes of pigeon breast muscle mitochondria. The reducing equivalents accepted and donated by the portion of the respiratory chain with half-reduction potentials greater than 200 mV are equal to those required for the known components (cytochrome a3 and the high-potential copper plus cytochrome a, 'visible copper', cytochrome c1, cytochrome c, and the Rieske iron-sulfur protein). Titrations in the presence of CO show that formation of the reduced cytochrome a3-CO complex requires two reducing equivalents per cytochrome a3 (coulometric titration). Potentiometric titrations indicate (Lindsay, J.G., Owen, C.S. and Wilson, D.F. (1975) Arch. Biochem. Biophys. 169, 492--505) that both cytochromes a3 and the high-potential copper must be reduced in order to form the CO complex (n = 2.0 with a CO concentration-dependent half-reduction potential, Em). By contrast, titrations in the presence of azide show that the Em value of the high-potential copper is unchanged by the presence of azide and thus azide binds with nearly equal affinity whether the copper is reduced or oxidized.

Animals↗
PubMed1982

Oxidation-reduction potentials of respiratory chain components in Thiobacillus A2.

(1) Cells of Thiobacillus A2 grown chemoautotrophically on thiosulfate or heterotrophically on succinate with oxygen contained b-, c-, o-, a- and a3-type cytochromes. The amount of cytochrome per mg of cell protein was much greater in thiosulfate-grown cells and differences in the relative concentrations of cytochromes were observed for the different growth conditions. (2) The half-reduction potentials at pH 7.0 (Em,7.0) and spectral maxima of c-, b-, a- and a3-type cytochromes were similar in cells grown aerobically with thiosulfate or with succinate as the growth substrate. (3) The half-reduction potential of the 'invisible', or high-potential copper, as determined from the potentiometric behavior of the carbon monoxide-reduced cytochrome a3 complex at pH 8.0, was 365 mV. (4) Reducing equivalents from thiosulfate appear to enter the respiratory chain at the cytochrome c level; however, studies in cell-free extracts were limited due to a loss in respiratory activity with thiosulfate as a substrate upon cell disruption.

Carbon Monoxide↗