Absorbance-pH relationship in the steroid-tetrazolium reaction.
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Acids↗
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Results for “SALICYLAMIDE”
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Effect of an inhibitor of glucuronide formation on elimination kinetics of diphenylhydantoin in rats.
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Animals↗
Transport cell for examining solute transfer across biological membranes.
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Animals↗
Quantitative analysis of tribromsalan in blood and urine.
Tribromsalan can be quantitatively measured in whole blood and urine by a technique involving extraction with ethyl acetate, treatment with silica gel, separation by TLC, and quantitative measurement by fluorescent spectrophotometry. This method has a sensitivity down to 125 ng (25 ppb in 5.0 ml of sample) of free tribromsalan and shows an average 90% recovery of tribromsalan in blood and urine with standard deviations of 9.7 and 7.4%, respectively.
Animals↗
Mathematical description of solute velocities during dissolution from a horizontal surface.
A mathematical analysis of solute flow in a descending column following dissolution is presented. The acceleration of a solute particle from zero velocity, when it is in the solid phase, to its final equilibrium descending velocity was analyzed. The maximum velocity for N-(3-methylphenyl) acetamide developed essentially at the solid-liquid interface, contradicting the postulate of a microsize diffusional layer. The possibility of a diffusional layer existing for solids of lower solubility than N-(3-methylphenyl)acetamide is discussed.
Acetamides↗
Incidence of experimental fascioliasis on hepatic disposition of [3H]tetracycline and [14C]rafoxanide in rats.
[7-3H]Tetracycline and [carbonyl-14C]rafoxanide were injected intravenously into anesthetized controls and rats in which experimental fascioliasis had been induced by 20 Fasciola hepatica metacercariae. The biliary excretion (1 and 3 h, respectively) of the radioactivity consisted of approximately 4% of the administered dose. In 4-week infested rats, biliary excretion of [3H]tetracycline and hepatic levels of radioactivity were decreased, whereas bile flow did not vary and plasma clearance of the antibiotic was significantly decreased in comparison with control animals. These differences could be the result of the fascioliasis-induced decrease in the hepatic uptake of tetracycline and the limited active transport for its output into bile canaliculi. No change in [14C]rafoxanide disposition was shown in infested rats.
Animals↗
Rearrangement of O-acylsalicylamides via intramolecular O-to-N transacylation: rate enhancement by an adjacent carboxylic acid group.
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Acylation↗
The possible role of tightly bound adenine nucleotides in oxidative and photosynthetic phosphorylation.
The tightly bound nucleotides of the beff-heart mitochondrial ATPase are released during cold inactivation followed by ammonium sulfate precipitation. During incubation at 0 degrees C the sedimentation coefficient (S20W) of the ATPase first declines from 12.1S to 9S. Prolonged incubation or precipitation with ammonium sulfate leads to dissociation of the 9S component into subunits with S20W of 3.5S. The 9S component still bears bound nucleotides which exchange more extensively and rapidly with added nucleotides than those bound to the active 12.1S component. The bound nucleotides are lost when the 9S form dissociates into the smaller subunits. Thus, firm binding of nucleotides is a property of the quarternary structure of the enzyme. The exchangeability of the nucleotides bound to the ATPase of chloroplast membranes is greatly increased in membranes illuminated in the presence of pyocyanine. Pi can exchange into both the beta and gamma positions of the bound nucleotides when the membranes are energized in the presence of Mg2+. The exchange of the nucleotides and the incorporation of Pi are insensitive to the inhibitor Dio-9 but are inhibited by the uncoupler S13. This inhibition by S13 parallels that of the inhibition of photosynthetic phosphorylation. These findings are discussed with regard to our hypothesis that electron transfer causes release of preformed tightly bound ATP from the ATPase by inducing a conformational change.
Adenine Nucleotides↗
Insular dopamine D2 receptors and novelty seeking personality in Parkinson's disease.
Novelty seeking is a temperament trait characterized by impulsiveness and exploratory behavior. Dopamine has been suggested to be the primary neurotransmitter modulator of novelty seeking, and in young healthy subjects, a correlation between increased novelty seeking and decreased insular cortical dopamine D2 receptor availability has been reported. The proposed link between dopamine deficiency and reduction in novelty seeking in Parkinson's disease is controversial. The present study examined whether a link between insular D2 receptor availability and novelty seeking can be replicated in Parkinson's disease patients. [11C]FLB 457 positron emission tomography imaging was carried out in 28 patients with Parkinson's disease, and the data were analyzed using voxel-based statistical analysis. The results demonstrated a negative correlation between the novelty seeking score and the dopamine D2 availability bilaterally in the insular cortex (corrected P=0.001; r=-0.74 [right hemisphere]; r=-0.66 [left hemisphere]). The results provide further support for a relationship between novelty seeking and insular D2 receptors. They indicate that the association is cross-cultural, independent of age, and unaffected by dopaminergic degeneration.
Aged↗
Positron emission tomography demonstrates dopamine D2 receptor supersensitivity in the striatum of patients with early Parkinson's disease.
Striatal dopamine D2 receptor binding was studied in vivo with positron emission tomography in seven patients with early Parkinson's disease using [11C]-raclopride. The patients had unilateral symptoms and none of them had received levodopa treatment. The accumulation of [11C]-raclopride in the striatum was rapid and reached a steady state at approximately 40 min after injection. The binding of [11C]-raclopride was measured in the striatum and cerebellum: The total striatal radioactivity in both hemispheres was counted and the respective striatum/cerebellum ratios were calculated. The striatum/cerebellum ratio of [11C]-raclopride binding was significantly (p less than 0.01) increased in the hemisphere contralateral to the parkinsonian symptoms as compared with the opposite hemisphere. Thus, this study demonstrates that there is denervation supersensitivity in dopamine D2 receptor binding in early Parkinson's disease.
Adult↗
PET study on striatal dopamine D2 receptor changes during the progression of early Parkinson's disease.
[11C]Raclopride uptake to dopamine D2 receptors was investigated with positron emission tomography (PET) in patients with early Parkinson's disease at the time of the diagnosis and after a half-year interval. During this progressive period of the disease, the patients received no antiparkinsonian medication. The upregulation of striatal D2 receptors, which was seen in all patients already at the time of the diagnosis, persisted. Although the patients initially showed unilateral disease, they had developed bilateral symptoms by the time of the second PET scan, but the disease was still asymmetric. The present results show that the relative increase in [11C]raclopride uptake in the striatum contralateral to the symptoms as compared with the opposite striatum will be preserved even during the progression of the disease, provided that the symptoms show clear-cut asymmetry.
Adult↗
Neurological Wilson's disease studied with magnetic resonance imaging and with positron emission tomography using dopaminergic markers.
Four patients with neurological Wilson's disease were investigated using magnetic resonance imaging (MRI) and positron emission tomography (PET). All patients had dystonia as their major clinical manifestation but also had dysarthria and at the presentation of the disease had choreoathetoid movements in at least one limb. A multitracer approach with PET was used to visualize various aspects of dopaminergic function; [11C]-(+)-nomifensine (NMF), [11C]raclopride (RAC) and [11C]-L-DOPA (one patient). Correlation analysis of RAC and NMF binding as well as putamen/caudate uptake ratios showed corresponding reductions. The patient investigated with [11C]-L-DOPA had a normal striatal uptake. Generally, structural changes as shown by MRI corresponded to reductions both in NMF and RAC binding. There was no evident correspondence between PET findings and the severity of clinical symptoms seen in the individual patient. In two patients with discrete neurological impairment at the time of investigation, PET showed serious presynaptic dopaminergic lesions in the putamen. Our data suggest that the striatal degeneration seen in Wilson's disease comprises a complex pathology involving both afferent and efferent projections. The discrete neurological impairment seen in some patients with gross striatal pathology might be due to concomitant lesions in functionally counteracting basal ganglia circuits.
Adult↗
Long-term changes of striatal dopamine D2 receptors in patients with Parkinson's disease: a study with positron emission tomography and [11C]raclopride.
We used [11C]raclopride (RACLO) and positron emission tomography (PET) to study longitudinally striatal dopamine D2 receptor binding in nine patients with Parkinson's disease (PD) at an early drug-naive stage and 3-5 years later, when motor fluctuations had appeared in seven of them. Patients were treated with a combination of levodopa and dopamine agonists. Data were compared with 10 healthy controls in the same age range. Initially, patients with PD showed a significant increase of RACLO uptake in the putamen compared with controls (p < 0.04). The caudate nucleus revealed values in the normal range. After 3-5 years, RACLO binding was significantly reduced in the putamen (p < 0.03) and caudate nucleus (p < 0.03) compared with baseline. Values were now in the control range in the putamen and reduced in the caudate nucleus (p < 0.05). The clinical score at "off" had significantly worsened (p < 0.0005) compared with the first PET scan. The nine PD patients reported here had already been investigated 3-4 months after therapy began and that time did not show a reduction of the initially increased RACLO binding capacity (data published previously). These results indicate long-term downregulation of striatal dopamine D2 receptor binding in PD. Receptor changes in the striatum of patients with PD may be induced by chronic dopaminergic therapy or occur independently of treatment, as a result of structural adaptation of the postsynaptic dopaminergic system to the progressive decline of nigrostriatal neurons.
Aged↗
Molecular characterization and biological response to respiration inhibitors of Pyricularia isolates from ctenanthe and rice plants.
The molecular profile and the biological response of isolates of Pyricularia oryzae Cavara obtained from ctenanthe to two strobilurins (azoxystrobin, kresoxim-methyl) and the phenylpyridinamine fungicide fluazinam were characterized, and compared with isolates from rice plants. Five different isozymes (alpha-esterase, lactate, malate, isocitrate and sorbitol dehydrogenases) and five random decamer primers for RAPD-PCR were used to generate molecular markers. Using unweighted pair-group with arithmetic average analysis, ctenanthe isolates were found to form a separate group distinct from that of the rice isolates for both sets of markers. Amplified polymorphic sequences of mitochondrial cytochrome b that were digested with Fnu4HI or StyI revealed no differences among Pyricularia isolates at amino acid positions 143 or 129 which confer resistance to strobilurins in several fungi. In absence of the alternative respiration inhibitor salicylhydroxamic acid (SHAM) the three fungicides showed inferior and variable efficacy, with a trend toward the rice isolate being less sensitive. The addition of SHAM enhanced the effectiveness of all fungicides against isolates regardless of their origin. Appressorium formation was the most vulnerable target of action of the respiration inhibitors and azoxystrobin the most effective. This is the first report of a comparison between the molecular profiles and sensitivities to respiration inhibitors for Pyricularia oryzae isolates from a non-gramineous host and from rice.
Acrylates↗
A non-Mendelian inheritance of resistance to strobilurin fungicides in Ustilago maydis.
Mutants of Ustilago maydis (DC) Corda with high resistance to azoxystrobin (RF 164 to 4714, based on EC50 values), an inhibitor of mitochondrial electron transport at the cytochrome bc1 complex, were isolated in a mutation frequency of 2.3 x 10(-7) after nitrosoguanidine mutagenesis and selection on media containing 1 microgram ml-1 azoxystrobin in addition to 0.5 mM salicylhydroxamate (SHAM), a specific inhibitor of cyanide-resistant (alternative) respiration. Oxygen uptake in whole cells was strongly inhibited in the wild-type strains by azoxystrobin (1.5 micrograms ml-1) in addition to SHAM (1 mM), but not in the mutant isolates. Genetic analysis with nine such mutant isolates resulted in progeny phenotypes which did not follow Mendelian segregation, but satisfied the criteria of non-Mendelian (cytoplasmic) heredity. In crosses between three mutant isolates with the compatible wild-type strains, the sensitivity was inherited by progeny maternally from the wild-type parent strain (criterion of uniparental inheritance). In crosses between wild-type strains and remaining mutant isolates, a continuous distribution of sensitivity in the progeny was found (criterion of vegetative segregation). The third criterion of cytoplasmic resistance (criterion of intracellular selection) was fulfilled by experiments on the stability of resistance phenotypes. With two exceptions, a reduction of resistance was observed in the mutant strains when they were grown on inhibitor-free medium. Recovery of the high resistance level was observed after they were returned to the selection medium. Cross-resistance studies with other fungicides, which also inhibit electron transport through complex III of respiratory chain, showed that mutations for resistance to azoxystrobin were also responsible for reduced sensitivity to kresoxim-methyl (RF 18 to 1199) and to antimycin-A (RF 20 to 305), which act at the Qo and Qi sites of the cytochrome bc1 complex, respectively. Studies of the fitness of azoxystrobin-resistant isolates showed that these mutations appeared to be pleiotropic, having significant adverse effects on growth in liquid culture and pathogenicity on young corn plants.
Acrylates↗
A critical evaluation of the role of alternative oxidase in the performance of strobilurin and related fungicides acting at the Qo site of complex III.
Mitochondrial respiration conserves energy by linking NADH oxidation and electron-coupled proton translocation with ATP synthesis, through a core pathway involving three large protein complexes. Strobilurin fungicides block electron flow through one of these complexes (III), and disrupt energy supply. Despite an essential need for ATP throughout fungal disease development, strobilurins are largely preventative; indeed some diseases are not controlled at all, and several pathogens have quickly developed resistance. Target-site variation is not the only cause of these performance difficulties. Alternative oxidase (AOX) is a strobilurin-insensitive terminal oxidase that allows electrons from ubiquinol to bypass Complex III. Its synthesis is constitutive in some fungi but in many others is induced by inhibition of the main pathway. AOX provides a strobilurin-insensitive pathway for oxidation of NADH. Protons are pumped as electrons flow through Complex I, but energy conservation is less efficient than for the full respiratory chain. Salicylhydroxamic acid (SHAM) is a characteristic inhibitor of AOX, and several studies have explored the potentiation of strobilurin activity by SHAM. We present a kinetic-based model which relates changes in the extent of potentiation during different phases of disease development to a changing importance of energy efficiency. The model provides a framework for understanding the varying efficacy of strobilurin fungicides. In many cases, AOX can limit strobilurin effectiveness once an infection is established, but is unable to interfere significantly with strobilurin action during germination. A less stringent demand for energy efficiency during early disease development could lead to insensitivity towards this class of fungicides. This is discussed in relation to Botrytis cinerea, which is often poorly controlled by strobilurins. Mutations with a similar effect may explain evidence implicating AOX in resistance development in normally well-controlled plant pathogens, such as Venturia inaequalis.
Drug Resistance, Fungal↗
Preproenkephalin mRNA expression in rat dorsal striatum induced by selective activation of metabotropic glutamate receptor subtype-5.
Group I metabotropic glutamate receptors (mGluR1 and mGluR5 subtypes) are positively coupled to phosphoinositide hydrolysis through G-proteins and are densely expressed in medium-sized projection neurons of striatum. Selective activation of Group I mGluRs upregulates preproenkephalin (PPE) mRNA expression in the rat dorsal striatum. This study investigated the role of one subtype of Group I receptors, mGluR5, in the regulation of PPE mRNA expression in the rat dorsal striatum using quantitative in situ hybridization. Unilateral injection of the mGluR5 selective agonist (RS)-2-Chloro-5-hydroxyphenylglycine (CHPG) into the dorsal striatum (caudoputamen) of chronically cannulated rats at doses of 50 and 200 nmol elevated basal levels of PPE mRNA in the injected dorsal striatum. The induction of PPE mRNA was evident at 1 h, remained at 3 h, and returned to normal level 6 h after CHPG injection. Pretreatment with an mGluR5 selective antagonist 2-methyl-6-(phenylethynyl) pyridine hydrochloride (MPEP) at a dose of 10 mg/kg (i.p.) blocked CHPG-stimulated PPE expression. MPEP also attenuated PPE expression induced by dopamine D(2) receptor blockade with eticlopride (0.5 mg/kg, i.p.). Administration of MPEP alone had no significant effects on basal levels of PPE mRNA in the striatum. The results from the present study demonstrate that glutamatergic tone on mGluR5 possesses the ability to positively regulate PPE gene expression in striatal neurons in vivo. Moreover, activation of mGluR5 participates in the mediation of D(2) antagonist-induced PPE expression.
Animals↗
D1 dopamine receptor regulates alcohol-motivated behaviors in the bed nucleus of the stria terminalis in alcohol-preferring (P) rats.
Recent studies have implicated the bed nucleus of the stria terminalis (BST) as a potential brain substrate for mediating drug-related behaviors. Neuroanatomical studies have demonstrated that reciprocal projections exist from the BST to the ventral tegmental area (VTA), a dopamine reward substrate proposed to play a role in alcohol abuse. In the present study, we evaluated the role of the D(1) and D(2) dopamine receptors of the BST in regulating alcohol and sucrose-motivated behaviors. Alcohol-preferring (P) rats were trained under an FR4 operant schedule to self-administer either EtOH (10% v/v) or sucrose (2% w/v). Following training, we evaluated the capacity of a competitive D(1) (SCH 23390; 0.5-20.0 microg) and a D(2) (eticlopride; 0.5-20.0 microg) dopamine antagonist to selectively reduce EtOH-maintained responding. Naltrexone, (5-30.0 microg), the nonselective opioid antagonist, was used as a reference agent. The results showed that SCH 23390 dose-dependently reduced alcohol-motivated responding. Responding was reduced with the 20.0 microg dose to about 97% of control levels. SCH 23390 also reduced sucrose responding; however, the magnitude of effects was substantially lower with the highest doses (2.5, 20.0 microg) (68-79% of control levels). In contrast, eticlopride failed to significantly alter alcohol responding and reduced sucrose responding only with the 10.0 microg dose. Unlike the dopamine antagonists, all naltrexone doses failed to alter EtOH or sucrose-maintained responding. The results suggest a salient role for the D(1), but not the D(2) and opioid receptors in selectively modulating EtOH-motivated behaviors in the BST.
Alcoholism↗