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Biomedical subjects

D F Wilson

Publications and source records attributed to D F Wilson.

At least 127 records · Page 7Linked to original sources
PubMed1991

Role of intramitochondrial pH in the energetics and regulation of mitochondrial oxidative phosphorylation.

The dependence of ATP synthesis coupled to electron transfer from 3-hydroxy-butyrate (3-OH-B) to cytochrome c on the intramitochondrial pH (pHi) was investigated. Suspensions of isolated rat liver mitochondria were incubated at constant extramitochondrial pH (pHe) with ATP, ADP, Pi, 3-OH-B, and acetoacetate (acac) (the last two were varied to maintain [3-OH-B]/[acac] constant), with or without sodium propionate to change the intramitochondrial pH. Measurements were made of the steady-state water volume of the mitochondrial matrix, transmembrane pH difference, level of cytochrome c reduction, concentration of metabolites and rate of oxygen consumption. For each experiment, conditions were used for which transmembrane pH was near maximal and minimal values and the measured extramitochondrial [ATP], [ADP], and [Pi] were used to calculate log[ATP]/[ADP][Pi]. When [3-OH-B]/[acac] and [cyt c2+]/[cyt c3+] were constant, and pHi was decreased from approx. 7.7 to 7.2, log [ATP]/[ADP][Pi] at high pHi was significantly (P less than 0.02) greater than at low pHi. The mean slope (delta log [ATP]/[ADP][Pi] divided by the change in pHi) was 1.08 +/- 0.15 (mean +/- S.E.). This agrees with the slope of 1.0 predicted if the energy available for ATP synthesis is dependent upon the pH at which 3-hydroxybutyrate dehydrogenase operates, that is, on the pH of the matrix space. The steady-state respiratory rate and reduction of cytochrome c were measured at different pHi and pHe values. Plots of respiratory rate vs.% cytochrome c reduction at different intra- and extramitochondrial pH values indicated that the respiratory rate is dependent upon pHi and not on pHe. This implies that the matrix space is the source of protons involved in the reduction of oxygen to water in coupled mitochondria.

Adenosine Triphosphate↗
PubMed1991

Transmastoid infralabyrinthine approach to petrous temporal bone.

The most direct approach to the anterior and inferior regions of the petrous temporal bone skull base is transmastoid infralabyrinthine. This approach provides an exposure for draining and aerating cholesterol granulomas or obtaining tissue for micropathologic diagnosis. It obviates the exposure of the intracranial space, thereby producing minimal care, as in mastoid-type surgical procedures. The procedure is described and illustrated. Two cases with petrous temporal bone cholesterol granulomas demonstrate the definitive effectiveness of this procedure.

Journal Article↗
PubMed1991

Optical measurements of the dependence of chemoreception on oxygen pressure in the cat carotid body.

The relationship between oxygen pressure (PO2) in the carotid body and carotid sinus nerve discharge was evaluated in the isolated perfused/superfused cat carotid body using the oxygen-dependent quenching of phosphorescence. Images of phosphorescence intensity arising from Pd-coproporphyrin within the microcirculation of the carotid body provided measurements of intravascular PO2. These measurements were substantiated by determining phosphorescence life-time. The carotid body was perfused in the isolated state via the common carotid artery with N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-buffered Tyrode solution, pH 7.4, at a constant pressure of 80 mmHg. Superfusion was maintained with similar media equilibrated with 100% argon. PO2 in the exchange vessels was markedly less than that in the perfusate entering the carotid artery, 23 +/- 3 and 45 +/- 3 Torr for normoxic (111 +/- 15 Torr) and hyperoxic (345 +/- 72 Torr) perfusates, respectively. Chemosensory discharge rose slowly in response to a brief interruption of perfusate flow as PO2 steadily declined from either of these capillary PO2 values to approximately 10 Torr. Between approximately 10 and 3 Torr, chemosensory discharge increased strikingly, concomitant with an enhanced rate of oxygen disappearance, from -36 +/- 4 to -69 +/- 13 (92% change) and -28 +/- 3 to -48 +/- 3 (71% change) Torr/s for normoxic and hyperoxic perfusates, respectively. As PO2 fell below approximately 3 Torr, oxygen disappearance slowed and neural activity decayed. Thus the relationships between microvascular PO2 and chemosensory discharge and between oxygen disappearance and neural discharge suggest that oxygen metabolism in the carotid body determines the expression of oxygen chemoreception.

Animals↗
PubMed1991

In vitro perfused-superfused cat carotid body for physiological and pharmacological studies.

An in vitro perfused carotid body preparation was developed to study its chemosensory responses to physiological and pharmacological stimuli. The carotid bifurcation with the carotid body was vascularly isolated and excised from pentobarbital sodium-anesthetized cats. The CB was perfused in a chamber by gravity (80 Torr) with modified Tyrode's solution (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-NaOH at pH 7.40) equilibrated at a given Po2 and superfused with the same medium at (Po2 of 20 Torr). The temperature was maintained at 35.5 +/- 0.5 degrees C. The frequency of chemosensory discharges (CD) was recorded from the whole carotid sinus nerve (n = 24), and the responses were tested by repeated interruptions of perfusate flow (SF), perfusion with hypoxic medium, and injections of nicotine and cyanide (0.1 nmol to 1 mumol) and hypercapnic medium. During hyperoxic perfusion, SF resulted in a sigmoidal increase in CD, reaching a maximum that was 23.6 +/- 4.4-fold greater than the basal activity. Restoration of flow returned CD promptly to basal values. After normoxic perfusion, SF led to a similar maximal activity more rapidly, but the duration was shorter. Reduction of the perfusate PO2 (Po2 from 450 Torr to 150, 30, and less than 10 Torr) caused a nonlinear increase in CD. CO2 stimuli (PCo2 38-110 Torr) resulted in a linear increase in CD. Nicotine or cyanide increased CD in a dose-dependent manner. The preparation retained its initial responsiveness for 2-3 h, making extensive experimental studies feasible.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effect of hyperventilation on oxygenation of the brain cortex of newborn piglets.

A new phosphorescence imaging method (Rumsey et al. Science Wash. DC 241: 1649-1651, 1988) has been used to continuously monitor the PO2 in the blood of the cerebral cortex of newborn pigs. A window was prepared in the skull and the brain superfused with artificial cerebrospinal fluid. The phosphorescent probe for PO2, Pd-meso-tetra(4-carboxyphenyl)porphine, was injected directly into the systemic blood. The phosphorescence of the probe was imaged, and the lifetimes were measured using flash illumination and a gated video camera. The PO2 in the blood of the veins and capillary beds of the cortex was calculated from the lifetimes. Systemic blood pressure was continuously monitored while the systemic arterial PCO2, PO2, and blood pH were measured periodically. The PO2 in the blood was quantitated for 60- to 200 microns2 regions within the image (from a total field of approximately 3 mm diam). The PO2 in the microvasculature was not uniform across the viewing field but increased or decreased in each region independently of the other regions. Thus at any point in time the PO2 in a region could be substantially above or below the average value. During hyperventilation, which lowered arterial PCO2 and increased pH of the blood, the average PO2 decreased in proportion to the decrease in arterial PCO2. For example, hyperventilation, which decreased arterial PCO2 from its normal value of 40 Torr to 10 Torr, caused a rapid (within 5 min) decrease in PO2 in the blood of capillaries and veins to approximately one-third of normal.

Animals↗
PubMed1991

Argon laser stapedotomy.

Lasers have been used in otology for 10 years. There have been reports of excellent hearing results using laser energy in surgery for otosclerosis. We used the argon laser in 75 consecutive primary stapedotomy procedures. The postoperative air-bone gap was 10 dB or less in 87% of patients and 20 dB or less in 95%. One ear (1.5%) had no postoperative hearing secondary to a granulomatous reaction. Complications were otherwise uncommon and mild. Most patients were treated on an outpatient basis. Our results compare favorably with other reports of laser surgery for otosclerosis. We conclude that excellent hearing results can be obtained using the argon laser for stapedotomy procedures.

Adult↗
PubMed1990

Cellular energetics and the oxygen dependence of respiration in cardiac myocytes isolated from adult rat.

The oxygen dependence of mitochondrial respiration was investigated using suspensions of mitochondria and quiescent ventricular myocytes isolated from adult rat hearts. A new optical method was used to determine oxygen concentration in the suspending media. The P50 for respiration for coupled mitochondria at a high [ATP]/[ADP].[Pi] ratio and oxidizing glutamate/malate was 0.45 +/- 0.03 microM but was increased to 0.57 +/- 0.02 microM by the addition of succinate to the substrate mixture. This value was decreased to less than 0.06 +/- 0.01 microM when the ATP/ADP.Pi ratio was decreased with the uncoupler, carbonyl cyanide p-trifluoromethoxyphenylhydrazone. The P50 value in resting myocytes was 2.23 +/- 0.13 microM at a Vmax of 13.22 +/- 1.38 nmol of O2/g, dry weight/min. During resting conditions, the creatine phosphate/creatine and ATPfree/ADPfree ratios were high in these cells, 6.81 +/- 1.11 and 1131 +/- 185, respectively. Addition of 1 mM Ca2+ to the suspending media increased the P50 by 50% whereas respiration rose by only 10%. Respiratory rate was increased up to about 10-fold by uncoupling the cells, but the P50 increased by less than 3-fold. When these uncoupled cells were inhibited with Amytal to lower the rate of oxygen consumption to that of resting cells, the P50 fell to 1.25 +/- 0.14 microM. Diffusion models indicate that in resting myocytes, the oxygen concentration difference from sarcolemma to cell core was approximately 1.84 microM with an additional difference of about 0.27 microM attributed to the unstirred layer of media surrounding each cell. The intracellular oxygen diffusivity coefficient in myocytes was calculated to be 0.30 x 10(-5) cm2/s. The results show that the oxygen dependence of respiration is modulated by the cellular metabolic state. At near maximal levels of respiration or on recovery from hypoxic episodes, oxygen diffusion may become an important determinant of the oxygen dependence of myocardial respiration.

Animals↗
PubMed1990

Purification of neurocatin, a neuroregulatory factor from brain.

A neuroregulatory factor (neurocatin) has been isolated from bovine brain. Neurocatin is a powerful affector of catecholamine metabolism in synaptosomes isolated from rat brain, causing increased formation of norepinephrine (NE) and decreased formation of 3,4-dihydroxyphenylacetic acid (DOPAC). The ratio NE/DOPAC in synaptosomes has been used to measure the neurocatin content of samples during isolation. Neurocatin has now been purified to a single chromatographic peak by high-resolution HPLC and a preliminary amino acid content measured. It appears to be a small peptide with a molecular weight in the range of 2,000-2,500 Da.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1990

Lidocaine in the middle ear.

Anesthesia of the ear canal is produced by injection of lidocaine hydrochloride into the skin of the lateral external ear canal. Ear canal, tympanic membrane, and middle ear surgeries are performed with this injection. The fluid found in the middle ear during tympanotomy was collected and analyzed. The percentage of lidocaine in the fluid was calculated by an enzyme immunoassay technique. Fifteen surgical cases were undertaken in which perilymphatic fluid in the middle ear would not be suspected, such as tympanotomy for otosclerosis. Lidocaine was found in all middle ears in which there was sufficient fluid to collect. The authors question the validity of using the presence of clear fluid in the middle ear, even with reaccumulation, as the sole criterion for identifying perilymph and cerebrospinal fluid.

Body Fluids↗
PubMed1989

Modulation of catecholamine metabolism in synaptosomes by a neuroregulatory factor from mammalian brain.

Incubation of synaptosomes from rat brain with bovine brain extract caused inhibition of oxidative deamination of dopamine, decreased formation of 3,4-dihydroxyphenylacetic acid, increased formation of norepinephrine and its N-methyl derivatives and increased release of catecholamines. Omission of Ca2+ from the extrasynaptosomal medium completely blocked the brain extract induced release of [3H]catecholamines and decreased, by about 80%, the effect on changes in catecholamine metabolism. Chromatography of the brain extract on Sephadex-G25 columns resulted in an active compound eluting at the position expected for compounds with molecular weights in the region of 1500 to 2500 Da.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1989

Contribution of diffusion to the oxygen dependence of energy metabolism in human neuroblastoma cells.

In suspensions of normally respiring human neuroblastoma cells respiration has an oxygen dependence similar to that of suspensions of isolated mitochondria in a comparable metabolic state. When mitochondrial oxidative phosphorylation is uncoupled, respiration at limiting oxygen pressures is indicative of the oxygen pressure difference between the extracellular medium and the mitochondria. Diffusion gives a P50 proportional to the cellular respiratory rate, with a value of 0.15 torr for the respiratory rate of normal cells. The oxygen pressure difference between the cytoplasm and the mitochondria is probable only a few tens of millitorr.

Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone↗
PubMed1989

Asymptomatic fusiform aneurysm of the petrous carotid artery in a patient with von Recklinghausen's neurofibromatosis.

Fusiform aneurysmal dilatation of the petrous portion of the right carotid artery was found in a young patient with von Recklinghausen's neurofibromatosis. The patient presented with sudden left-sided hearing loss, and, during the evaluation of the hearing deficit, an asymptomatic right-sided vascular abnormality was identified. This vascular abnormality is unusual because those abnormalities commonly associated with von Recklinghausen's neurofibromatosis include occlusion of the cerebral arteries, arteriovenous malformations, and intracranial aneurysms. The pathophysiology and natural history of vascular abnormalities accompanying von Recklinghausen's neurofibromatosis are discussed.

Adolescent↗
PubMed1989

Effects of DL-2-amino-5-phosphonovalerate on metabolism of catecholamines in synaptosomes from rat brain.

Incubation of synaptosomes from rat brain with DL-2-amino-5-phosphonovalerate (APV) stimulated an increased release of dopamine, and this effect was strictly dependent on the extrasynaptosomal calcium level. APV increased biosynthesis of dopamine from tyrosine by 30%, whereas monoamine oxidase activity was inhibited by 30%. When synaptosomes were incubated with radioactive dopamine, APV caused a large decrease in incorporation of label into 3,4-dihydroxyphenylacetic acid but greatly increased incorporation into norepinephrine and its N-methyl derivatives. Quantification of dopamine and its metabolites in synaptosomes, using electrochemical detection, indicated that the presence of APV resulted in changes in the absolute levels of the aforementioned dopamine metabolites similar to the changes in radiolabel incorporation. Omission of Ca2+ from the extrasynaptosomal medium greatly diminished the APV-induced changes in catecholamine metabolism. The metabolic changes appear to largely result from an increased intrasynaptosomal Ca2+ level due to the APV-induced increase in calcium permeability of the plasma membrane.

2-Amino-5-phosphonovalerate↗
PubMed1989

Lipid hydroperoxides inhibit reacylation of phospholipids in neuronal membranes.

The unsaturated fatty acids that rapidly accumulate during ischemia are thought to participate in inducing irreversible brain injury, especially because they are highly susceptible to peroxidation when the tissue is reoxygenated. Our hypothesis was that peroxidation products of unsaturated fatty acids interfere with the reacylation of synaptic phospholipids, a process essential to membrane repair. To test this hypothesis, we have examined the effect of fatty acid hydroperoxides on incorporation of [1-14C]arachidonic acid into synaptosomal phospholipids. Rat forebrain synaptosomes were incubated with arachidonic or linoleic acid hydroperoxides and [14C]arachidonate, and then lipids were extracted and separated by TLC. Both hydroperoxides inhibited [14C]arachidonate incorporation into phospholipids in a concentration-dependent manner, with 50% inhibition occurring at less than 25 microM hydroperoxide, in both the absence and presence of exogenous lysophospholipids. The inhibition was of the non-competitive type. It is concluded that (a) low levels of fatty acid hydroperoxides inhibit the reacylation of synaptosomal phospholipids, and (b) this inhibition may constitute an important mechanism whereby peroxidative processes contribute to irreversible brain damage.

Animals↗
PubMed1989

Oxygen diffusion and mitochondrial respiration in neuroblastoma cells.

Suspensions of human neuroblastoma cells consume oxygen at a constant rate when the oxygen pressure is greater than approximately 11 Torr. The rate of oxygen consumption, however, becomes dependent on the oxygen pressure below this level. The falling respiratory rate at the lower pressures gives rise to an oxygen pressure for half-maximal respiration (P50) of approximately 0.8 Torr, which is consistent with the 0.5 Torr value for suspensions of isolated mitochondria in the presence of ATP (J. Biol. Chem. 263: 2712-2718, 1988). When the cellular metabolic energy state is lowered by addition of an uncoupler of mitochondrial oxidative phosphorylation, the respiratory rate increases up to fivefold, but the P50 decreases to approximately 0.6 Torr. In the cells treated with uncoupler, the P50 decreases further when the mitochondrial respiratory rate is inhibited with amobarbital (amytal), an inhibitor of the respiratory chain. The additional decrease in P50 is proportional to the decrease in respiratory rate. Thus, for cells treated with uncoupler, the P50 appears to be limited by oxygen diffusion from the external medium to the mitochondria. When the respiratory rate of the uncoupled cells is inhibited to the level of coupled cells, the P50 for the former is less than 0.15 Torr. This indicates that for coupled cells the difference in oxygen pressure from the external medium to the mitochondria is less than 0.15 Torr at half-maximal respiratory rate and does not significantly affect the P50 for oxygen that occurs at 0.8 Torr.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗