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At least 19 recordsLinked to original sources
PubMed1978

Dimethadione-induced fetotoxicity in rats.

The fetotoxic potential of dimethadione was studied in rats given single daily oral dosages of 0, 54, 433 or 541 mg/kg on days 1--21 or 6--15 of gestation. No maternal toxicity was observed following treatment on days 6--15. When administered from days 1 to 21 only the highest dose (541 mg/kg) produced a significant reduction in maternal body weight gain. Dimethadione caused a dose-related decrease in fetal weight and an increased incidence of umbilical hernia, ecchymoses and subcutaneous edema. There were also increased incidences of non-specific skeleton defects which consisted of unilateral or bilateral wavy ribs, additional ribs (14th rib, uni- and bilateral), retarded ossification of calvaria and a wide variety of sternal defects. Specific defects were bent radius and ulna, and bent tibia and fibula which increased with increasing dosages of dimethadione. Fetal mortality and incidence of skeletal anomalies were higher when the treatment was given on days 1--21 of gestation than on days 6--15 of pregnancy.

Abnormalities, Drug-Induced↗
PubMed1978

Consecutive gas chromatographic determination of phenytoin, phenobarbital, primidone, phenylethylmalondiamide, carbamazepine, trimethadione, dimethadione, ethosuximide, and valproate from the same serum specimen.

A quantitative gas-liquid chromatographic procedure is described for the consecutive determination of phenytoin, phenobarbital, primidone, phenylethylmalondiamide, carbamazepine, trimethadione, dimethadione, ethosuximide and valproate from a single serum specimen of 1.2 ml. After extraction from serum by two different procedures, the anticonvulsants are chromatographed without further purification on a 3% OV 17 column either with or without derivative formation by means of "on-column" methylation. Multiple internal standards are employed in order to enhance the reproducibility of drug-concentration measurement.

Anticonvulsants↗
PubMed1979

Metabolism and disposition of trimethadione in pregnant rats.

The metabolism and disposition of a suspected human teratogen, trimethadione (TMO), was studied in pregnant rats following administration of the drug at doses of 60 and 240 mg/kg/day during 6 to 15 days of gestion, with a view to understanding the fetotoxicity of the drug. Following the last dose, animals were sacrificed at 6, 12, and 24 hr, and the fetuses were removed by caesarean section. The concentrations of TMO and its N-demethylated metabolite, dimethadione (DMO), were determined by a specific GLC procedure in maternal plasma, urine, brain, and liver, as well as in placenta and whole fetus. The plasma and liver concentrations of TMO and DMO suggested that the parent drug is rapidly converted to DMO. Total 24 hr urinary recoveries of the unchanged drug and the metabolite were 61 and 82% following 240 and 60 mg/kg/day doses of TMO, respectively. The DMO concentrations in brain and all other tissues analyzed were far greater than those of TMO. The fetus to maternal plasma concentration ratios of TMO suggested that the placental transfer of the drug was greater than the clearance from the fetus over the periods examined, whereas the transfer of the metablite seemed to be independent of dose. Furthermore, the rate of decline of DMO in fetus was far slower than that of the placenta and maternal plasma, causing accumulation of DMO in the fetus. The results suggest that the fetotoxic effects produced by TMO when given to pregnant rats could be due to accumulation of DMO in fetus.

Abnormalities, Drug-Induced↗
PubMed1976

Intracellular pH of brain: alterations in acute respiratory acidosis and alkalosis.

To evaluate the metabolic adaptations of the brain to acute respiratory acid-base disturbances, a method was developed to measure intracellular pH (pHi) in the brain of dogs under conditions in which arterial pH is rapidly altered. Brain pHi was determined by measuring the distribution of 14C-labeled dimethadione (DMO) in brain relative to cortical CSF. Brain extracellular space (ECS) was evaluated as the 35SO4 = space relative to cortical CSF, and arterial Po2 was maintained at 82-110 mmHg. In normal dogs, brain (cerebral cortex) pHi was 7.05, and after 1 h of hypercapnia (arterial pH = 7.07) it fell to 6.93. However, after 3 h with arterial Pco2 maintained at 85 mmHg brain pHi was normal (7.06), and during this time brain bicarbonate had risen from 11.3 to 24.4 meq/kg H2O. These changes were not prevented by intravenous doses of acetazolamide,

Acid-Base Imbalance↗
PubMed1977

Evaluation of anticonvulsants in barbiturate withdrawal.

Four prototypic anticonvulsants were tested for their effectiveness against barbiturate withdrawal in cats. The effects were evaluated on a total of over 20 motor, autonomic and behavioral withdrawal signs. The animals were made physically dependent by 5 weeks of twice daily "maximally tolerable" sodium pentobarbital dosing intragastrically. Anticonvulsants were administered by intravenous infusion 25 hours after the final dose of chronic pentobarbital treatment when all withdrawal signs had become severe and grand mal type withdrawal convulsions were observed. Phenobarbital blocked withdrawal signs quite effectively at doses that caused no significant acute central nervous system depression. Trimethadione also reversed most withdrawal signs, but some signs persisted even at doses causing overt acute toxicity. Dimethadione was less effective than the parent compound, trimethadione, in reversing withdrawal but caused greater acute toxicity. Phenytoin was in effective for most withdrawal signs and some signs were made worse. The clonic phase of withdrawal convulsions was accentuated and the overall condition of the animals worsened. During withdrawal, the animals were less sensitive (tolerant) to phenobarbital but were more sensitive to acute toxicity from the other drugs tested.

Animals↗
PubMed1979

Determination of liver intracellular pH in vivo and its homeostasis in acute acidosis and alkalosis.

An in vivo method is presented for the determination of liver intracellular pH (pHi) using [14C]dimethadione (DMO) in dogs. This method differs from those previously published in that hepatic venous and portal venous blood pH were selected as the extracellular reference pH, and liver blood space corrections are applied to whole liver tissue [14C]DMO activity. Using these corrections, a normal liver pHi of 6.99 +/- 0.03 (SE) was obtained. During acute metabolic acidosis and alkalosis, as well as during acute respiratory acidosis and alkalosis, the liver pHi remained normal; metabolic acidosis was 7.04 +/- 0.04; metabolic alkalosis was 6.92 +/- 0.08; respiratory acidosis was 6.98 +/- 0.04; and respiratory alkalosis was 7.00 +/- 0.10. None of these values was significantly different from normal (P greater than 0.05). Changes in intracellular bicarbonate and lactate appeared to account in part for the observed stability of the liver pHi despite acute manipulations resulting in a range of pH values between 7.09 and 7.63 in arterial blood.

Acid-Base Imbalance↗
PubMed1976

Central nervous system pH in uremia and the effects of hemodialysis.

Rapid hemodialysis of uremic animals may induce a syndrome characterized by increased cerebrospinal fluid (CSF) pressure, grand mal seizures, and electroencephalographic abnormalities. There is a fall in pH and bicarbonate concentration in CSF, and brain osmolality exceeds that of plasma, resulting in a net movement of water into the brain. This syndrome has been called experimental dialysis disequilibrium syndrome. The fall in pH of CSF may be secondary to a fall of intracellular pH (pHi) in brain. Since changes in pHi can alter intracellular osmolality in other tissues, it was decided to investigate brain pHi in uremia, and the effects of hemodialysis. Brain pHi was measured by evaluating the distribution of 14C-labeled dimethadione in brain relative to CSF, while extracellular space was calculated as the 35504=/4 space relative to CSF. In animals with acute renal failure, brain (cerebral cortex) pHi was 7.06+/-0.02 (+/-SE) while that in CSF was 7.31+/-0.02, both values not different from normal. After rapid hemodialysis (100 min) of uremic animals, plasma creatinine fell from 11.8 to 5.9 mg/dl. Brain pHi was 6.89+/-0.02 and CSF pH and 7.19+/-0.02, both values significantly lower than in uremic animals (P less than 0.01), and there was a 12% increase in brain water content. After slow hemodialysis (210 min), brain pHi (7.01+/-0.02) and pH in CSF (7.27+/-0.02) were both significantly greater than values observed after rapid hemodialysis (P less than 0.01), and brain water content was normal. None of the above maneuvers had any effect on pHi of skeletal muscle or subcortical white matter. The data show that rapid hemodialysis of uremic dogs is accompanied by a significant fall in pH of CSF and pHi in cerebral cortex. Accompanying the fall in brain pHi is cerebral edema.

Acid-Base Imbalance↗
PubMed1979

Intracellular pH changes during the cell cycle in Tetrahymena.

The equilibrium distribution of 5,5-dimethyloxazoladine 2,4-dione (DMO) between intra- and extracellular volume was used to estimate intracellular pH (pHi) in Tetrahymena pyiformis. In control experiments, DMO was found to equilibrate rapidly in response to a pH gradient. Under normal growth conditions, pHi was constant over a finite range of external pH, being maintained near pH 7.1 over the external pH range 5.2 to 7.3. This same range of external pH was also optimal for growth. pHi was monitored during the cell cycle of a synchronous population of T. pyriformis GL. The cells were synchronized either by starvation/refeeding or heat shock. Under both conditions, there were two alkaline shifts of approximately 0.4 pH units per cell cycle. These shifts in pH retained a constant remporal relationship to S phase and were not affected by changes in the time, duration, or magnitude of cytokinesis.

Cell Cycle↗
PubMed1978

Transport of heterocyclic acids across rat small intestine in vitro.

A study has been made of the steady-state fluxes of barbituric acid, six of its substituted derivatives, and 5,5-dimethyloxazolidinedione (DMO) across the wall of rat jejunum in vitro. For each of the compounds tested the mucosal (M) to serosal (S) flux was significantly larger than the S to M flux. Both M to S and S to M fluxes increased linearly with concentration, and the transport of one acid was not influenced by the presence of a tenfold greater concentration of a second heterocyclic acid. The fluxes decreased as the pH of the incubation saline was increased, but neither the M to S, nor the S to M fluxes could be described in terms of simple nonionic diffusion. It was found that the relation between the flux ratios of the transported acids and their pKalpha values could be described by an equation derived from consideration of the transport of a weak acid in a series three compartment system, and it has been concluded that the three compartment system provides a good working hypothesis for the mechanism of heterocyclic acid transport across rat jejunum. It was found that the best fit of the theoretical curve to the experimental data was obtained when the ratio of permeabilities to the ionized and nonionized forms of a weak acid at one of the barriers was assigned the value 5 X 10(-1). It is suggested that this value may be characteristic of a noncellular restriction to diffusion, such as a layer of connective tissue, and substantiates previous suggestions that the intermediate compartment of the intestinal three compartment system is a component of the sub-epithelial extracellular space.

Amobarbital↗
PubMed1976

Myocardial ischemia and cell acidosis: Modification by alkali and the effects on ventricular function and cation composition.

Myocardial cell pH was measured with 5, 5 dimethyl-2, 4-oxazolidinedione (DMO) in intact anesthetized dogs by a transient indicator dilution technique. Bolus injections of labeled DMO, vascular, extracellular and water indicators were made into the left anterior descending coronary artery, and blood samples were collected from the great cardiac vein. The steady state distribution of DMO between cells and plasma was calculated from the mean transit times of the indicator. Normal myocardial cell pH averaged 6.94 and changed by 58% of the concomitant alterations in plasma pH after infusions of acid or alkali. Myocardial ischemia induced by inflation of a balloon tip catheter in the left anterior descending coronary artery resulted in progressive decreases in cell pH to 6.59 by 1 hour. Infusions of sodium carbonate diminished intracellular acidosis. Hemodynamic studies during 4 hours of ischemia with blood pH at 7.55 to 7.60 indicated a significantly reduced left ventricular end-diastolic pressure and increased stroke volume by comparison with findings in animals given infusions of saline solution. Ventriculograms revealed improved wall motion in the ischemic segment after infusion of alkali. Precordial mapping showed a significant reduction in the number of leads with S-T segment elevation as well as in the sum of S-T segment elevations, but R wave amplitudes did not differ from those in control studies. Calculations of extracellular space, tissue water and cation content revealed a reduced gain of cell sodium ion and loss of cell potassium ion during ischemia after alkali treatment. The latter may account for the S-T segment responses, whereas enhanced ventricular performance may be related to reduced competition of hydrogen ion with calcium ion for binding sites on contractile protein.

Acidosis↗
PubMed1977

Factors determining human chorion laeve permeability in vitro.

An increased mean diffusion permeability across human chorion laeve in vitro was measured for meperidine (D = 5.26 x 10(-6) cm.2 sec.-1) and diazepam (D = 4.51 X 10(-6) cm.2 sec.-1). These values corresponded to large chloroform-buffer partition coefficients (49 and 29) measured for these two compounds. Diffusion permeability values of 3.98 and 2.18 x 10-6 cm.2 sec.-1 measured for urea and glucose corresponded to their relative insolubility in lipid, as indicated by chloroform-buffer partition coefficients of 0.05 and 0.0004, respectively. An increase in placental permeability in vitro to the weak organic acid 5,5-dimethyl, 2,4-oxazalidinedione at lower pH's corresponded to an increase in the fat-soluble nonionized fraction of this compound. These data support the concept that this tissue is most permeable to compounds of relatively small molecular size and/or with a high level of lipid solubility. The large diffusion permeability values measured for meperidine and diazepam suggest that these compounds will diffuse rapidly between mother and fetus at a maximal rate limited only by uterine blood flow.

Cell Membrane Permeability↗
PubMed1976

An estimation of the light-induced electrochemical potential difference of protons across the membrane of Halobacterium halobium.

The light-dependent uptake of triphenylmethylphosphonium (TPMP+) and of 5,5-dimethyloxazolidine-2,4-dione (DMO) by starved purple cells of Halobacterium halobium was investigated. DMO uptake was used to calculate the pH difference (deltapH) across the membrane, and TPMP+ was used as an index of the electrical potential difference, deltapsi. Under most conditions, both in the light and in the dark, the cells are more alkaline than the medium. In the light at pH 6.6, deltapH amounts to 0.6-0.8 pH unit. Its value can be increased to 1.5-2.0 by either incubating the cells with TPMP+ (10(-3) M) or at low external pH (5.5). --deltapH can be lowered by uncoupler or by nigericin. The TPMP+ uptake by the cells indicates a large deltapsi across the membrane, negative inside. It was estimated that in the light, at pH 6.6, deltapsi might reach a value of about 100 mV and that consequently the electrical equivalent of the proton electrochemical potential difference, deltamuH+/F, amounts under these conditions to about 140 mV. The effects of different ionophores on the light-drive proton extrusion by the cells were in agreement with the effects of these compounds on --deltapH.

Biological Transport, Active↗
PubMed1976

Relationship between medium pH and that of the lysosomal matrix as studied by two independent methods.

1. The method of estimating the intralysosomal pH by measuring the distribution of [14C]methylamine in lysosomes isolated from the livers of Triton WR 1339-treated rats has been critically examined. 2. In lysed lysosomes, methylamine is bound to the membrane fragments, but this binding can be completely suppressed by increasing the concentration of monovalent cations in the medium. 3. In intact lysosomes, the binding of [14C]methylamine is only partly inhibited by monovalent cations at 25 degrees C. 4. THe accumulation of [14C]methylamine in intact lysosomes is progressively inhibited as the concentration of methylamine is increased. A similar inhibition of [14C]methylamine accumulation is obtained with NH4Cl. 5. Similar values for the intralysosomal pH were obtained from measurements of the distribution of methylamine, dimethylamine and trimethylamine, which are accumulated in the lysosomes, and of 5,5-dimethyloxazolidinedione-2,4, which is excluded. 6. The breakdown of endocytosed 123I-labelled bovine serum albumin by intact isolated lysosomes is much less sensitive to the pH of the medium than the breakdown of added protein by lysed lysosomes. 7. The intralysosomal pH has been estimated by comparing the rate of breakdown of endocytosed 125I-labelled albumin in intact lysosomes as a function of medium pH with that of added 125I-labelled albumin by lysed lysosomes at different pH values. The values obtained agree well with those calculated from the distribution of [14C]methylamine. 8. Methylamine and NH4Cl inhibit the breakdown of 125I-labelled albumin in intact lysosomes, particularly at high medium pH, but have no effect on the breakdown by lysed lysosomes. 9. It is concluded that a pH difference across the lysosomal membrane (more acidic inside than outside) is maintained by the presence of indiffusible negatively charged groups within the lysosomes, and by the permeation across the lysosomal membrane of protons together with permeant anions (or of OH- in exchange for anions).

Ammonium Chloride↗
PubMed1977

Weak acid accumulation in the serosal extracellular compartment of the frog gastric mucosa.

The dimethyloxazolidine dione distribution in the extracellular compartments of the frog gastric mucosa was analyzed by washout kinetics. The volumes of the two extracellular compartments, serosal and mucosal, were estimated by inulin washout as 0.435 +/- 0.019 and 0.176 +/- 0.018 microliter/microliter tissue water, respectively. In the serosal extracellular space, significant dimethyloxazolidine dione accumulations of 2.63 +/- 0.25, 2.28 +/- 0.16, and 1.86 +/- 0.08 times that of the bathing media were found for bathing solutions with pH values of 6.9, 7.4, and 7.9 respectively. A high pH of the serosal extracellular fluid by itself could not account for the high values of dimethyloxazolidine dione accumulation. A difference in the total dimethyloxazolidine dione accumulation requires: (a) the existence of differences in the pH values and also the existence of a difference in the diffusion coefficient of the two forms of dimethyloxazolidine dione; or (b), a binding of one of the two forms, i.e., binding of dimethyloxazolidine dione form by fixed charges.

Animals↗
PubMed1975

Determination of mean whole body intracellular pH in unanesthetized dogs.

In order to determine mean whole body pHi in unanesthetized dogs, assumptions on the urinary and intestinal excretion of DMO, the total loss of an injected single dose of [14C] DMO, and the distribution kinetics of DMO were tested experimentally. Urinary excretion of DMO was almost negligible. The best assumption on the total loss of DMO was based on the exponential decay observed over a period of 1 to 4 weeks. The biological half-life of DMO was 5 days, the time constant being --0.14 d-1. The extracellular distribution of DMO was considered to equal that of [3H] inulin. Between 1 and 7 hours after an injection of inulin in nephrectomized dogs the distribution volume increased linearly from 16% of the body weight after 2 hours to 21% after 6 hours. Based on these experimental results, pHi was determined in 16 unanesthetized dogs. 120 min after the injection of DMO pHi was 7.05 and 430 min after the injection pHi was 7.11. It is concluded that the assumption made allow the estimation of pHi in unanesthetized dogs over a period of 1 to 7 hours.

Acid-Base Equilibrium↗
PubMed1975

Intracellular pH in unanesthetized dogs during panting.

Intracellular pH, arterial blood gases and several plasma enzymes were estimated in unanesthetized dogs during a 3-hour exposure to 30 degrees C/50% relative humidity, and 40 degrees C/50% relative humidity. No change occurred during mild heat stress, whereas during severe heat stress a profound respiratory alkalosis developed together with an increase in intracellular pH from 7.03 to 7.29. Most plasma enzymes increased by about 300% or more. In spite of extreme panting body temperature rose to 42.2 degrees C. Exposure to 40 degrees C/50% relative humidity with 4% CO2 in the climatic chamber inhibited the respiratory alkalosis and the increase of plasma enzymes. Though the panting frequency was lower the ventilatory heat dissipation was more efficient. Body temperature rose to only 39.8 degrees C. It is concluded that the intracellular buffering is not able to prevent marked changes of the intracellular pH during panting.

Acid-Base Equilibrium↗