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Biomedical subjects

T Higuchi

Publications and source records attributed to T Higuchi.

At least 631 records · Page 35Linked to original sources
PubMed1981

Effects of salicylate on rectal absorption of theophylline.

The rectal absorption of theophylline in rats was facilitated by concurrent administration of salicylic acid or sodium salicylate. The absorption of theophylline depended on the simultaneous absorption of salicylate and increased with an increasing concentration of salicylate. Calcium and magnesium ions inhibited the effects of salicylate at pH 7.4 but not at pH 4.5. Sodium lauryl sulfate caused lasting changes in rectal absorption, whereas the effects of salicylate on absorption were observed only when salicylate was present Strong chelating agents, such as ethylenediaminetetraacetic acid and sodium citrate did not effect the absorption of theophylline, except at very high concentrations (30%), where membrane damage was observed. Rectal drug absorption was not enhanced by vasodilation or inflammation alone since sodium nicotinate and histamine did not facilitate the disappearance of theophylline from the perfusate.

Animals↗
PubMed1981

N-hydroxymethyl derivatives of nitrogen heterocycles as possible prodrugs II: possible prodrugs of allopurinol, glutethimide, and phenobarbital.

Solid samples of 1-hydroxymethyl- and 1,5-dihydroxymethylallopurinol, 1-hydroxymethylglutethimide, and 1-hydroxymethylphenobarbital were prepared, and equilibrium constants for their formation from formaldehyde and allopurinol, glutethimide, or phenobarbital were calculated. The N-hydroxymethyl derivatives had higher water solubilities and faster dissolution rates than the parent drugs, and they appear to be potentially useful as prodrugs.

Allopurinol↗
PubMed1981

Amino acid esters of phenols as prodrugs: synthesis and stability of glycine, beta-aspartic acid, and alpha-aspartic acid esters of p-acetamidophenol.

pH-rate profiles were calculated for the hydrolysis of the glycine (II), beta-aspartic acid (III), and alpha-aspartic acid (IV) esters of p-acetamidophenol (I) at 25 degrees and mu = 1.0 M. The hydrolysis of esters II and III occurred predominantly via intermolecular reactions involving water, hydroxide ion, and the various ionic forms of the substrates. The hydrolysis of ester IV occurred predominantly via intramolecular reactions. The catalytic effects of formate, acetate, and phosphate ions as well as of tromethamine on the degradation on ester II were similar to their effects on the hydrolysis of ethyl dichloroacetate. The efficient catalysis of the hydrolysis of ester II in bicarbonate buffers was consistent with a mechanism that involved carbon dioxide and the formation and decomposition of a carbamate intermediate.

Acetaminophen↗
PubMed1981

Immunochemical reactivity of simian sarcoma virus polypeptides isolated by preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis.

The polypeptides associated with a zonal centrifugation purified simian sarcoma virus propagated in lymphoblastoid NC-37 cells were isolated by preparative polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS) using a procedure designed to minimize the loss of immunochemical reactivity. The proteins p10, p15, p28, p36, p44, p75, and p86 were obtained in large yield and high degree of homogeneity. The electrophoretically purified p28 was analyzed by competition radioimmunoassay using antiserum to a pore exclusion and ion exchange purified simian sarcoma virus p28. Complete competition was observed with extracts of simian sarcoma virus infected cells. No competition was observed with uninfected or unrelated, infected cell extracts. The antigen-antibody affinity as measured by the slope of the competition curve using antiserum to p28 and 125I-labeled and electrophoretically purified p28 was the same as that for the p28 released from sonication-disrupted simian sarcoma virus. The data indicates that preparative purifications by polyacrylamide gel electrophoresis in the presence of SDS may be generally applicable for the isolation of proteins with essentially the same immunospecificities and affinity for a specific antiserum as proteins isolated by procedures that avoid the use of SDS and electrophoresis.

Animals↗
PubMed1981

Naltrexone-induced LH release in ovariectomized estrogen-primed rats.

In order to investigate the physiological role of endogenous opioid substances in the regulation of gonadotropin secretion, we studied the effect of Naltrexone (Nalt), a morphine antagonist, on serum luteinizing hormone(LH) concentrations in ovariectomized estrogen-treated rats. The site of action of Nalt and its interaction with other putative neurotransmitters on LH secretion were investigated in hypothalamic deafferentated rats and in animals treated with pharmacological inhibitors of the actions of neurotransmitter substances. Nalt injection increased serum LH levels at dosed 0.08 to 2 mg/kg BW. The response was dose-dependent but higher doses of Nalt had less effect. In inducing this response pattern, mediobasal connection between the anterior hypothalamus and the mediobasal hypothalamus was essential, but posterior input to the mediobasal hypothalamus was not necessary. Excepting alpha-adrenergic blocker, all the blockers used, i.e beta-adrenergic, serotonin, dopamine and acetylcholine blockers were effective in eliminating the LH release evoked by Nalt injection. These results suggest that endogenous opioid substances might inhibit LH secretion tonically through aminergic and/or cholinergic neurons and that the mediobasal neural connections to the mediobasal hypothalamus are indispensable for this inhibition.

Afferent Pathways↗
PubMed1981

Enhanced intestinal absorption of insulin in rats in the presence of sodium 5-methoxysalicylate.

Sodium 5-methoxysalicylate, previously shown to enhance the rectal absorption of several drugs, facilitates the absorption of insulin from the upper gastrointestinal tract, resulting in significantly elevated insulin levels and lowered glucose concentrations in the plasma of rats. Restricting the movement of insulin and adjuvant down the intestine by either ligation or use of a more viscous vehicle further increased the absorption of insulin.

Animals↗
PubMed1981

Enhanced renal clearance of uric acid in hepatic cirrhosis.

Serum and urinary acid were measured in 10 patients with chronic hepatitis, in 22 patients with hepatic cirrhosis, and in 11 control subjects. Significant differences were found in urinary acid excretion, uric acid clearance, and uric acid:creatinine clearance ratio between patients with hepatic cirrhosis and control subjects. Two patients with hepatic cirrhosis were found to have hypouricemia. They showed a two- to threefold increase in uric acid clearance and in the uric acid:creatinine clearance ratio compared with control subjects, but their 24-h uric acid excretion was normal. In patients with hepatic cirrhosis, a significant negative correlation was found between plasma testosterone level and either uric acid clearance or uric acid:creatinine clearance ratio. These results indicate that uric acid clearance may be increased in patients with hepatic cirrhosis and that hypouricemia may result from a change in renal handling of uric acid. Moreover, changes in plasma testosterone levels may play an important part in affecting the renal handling of uric acid in these patients.

Adult↗
PubMed1980

Antipyrine metabolism in cancer patients.

The metabolism of antipyrine was studied in cancer patients. Antipyrine elimination might be decreased in cancer patients. Increase in antipyrine half-life is not primarily due to the presence of a tumor but rather to the nutritional status and liver function of an individual.

Adult↗
PubMed1980

Effect of self-association of phenol on its transport across polyethylene film.

Phenol diffusion across a high density polyethylene film from isooctane, in which phenol self-associates, demonstrated nonideal behavior. The steady-state flux of phenol across the film was not directly proportional to its concentration in the donor phase. At higher donor phase concentrations, negative steady-state flux deviations were observed. These negative deviations were due to phenol self-association in the donor phase and the resulting decreases in thermodynamic activity. By using a monomer--pentamer model for phenol self-association in isooctane, the steady-state flux was shown to be directly proportional to the phenol monomer concentration in the donor phase. Although steady-state flux concentration deviations were observed, the diffusion time lag was independent of the permeant concentration and reflected the intrinsic diffusivity of the film to phenol.

Chemical Phenomena↗
PubMed1980

Solubility of polar organic solutes in nonaqueous systems: role of specific interactions.

The changes in solubility of several polar organic solutes when polar organic solvents are added to a relatively inert solvent such as isooctane were determined. The relative changes in solubility predicted from regular solution theory using solubility parameters often did not agree with the observed results. However, the solubilities could be rationalized mathematically by assuming the formation of specific solute-solvent complexes. Agreement of the thermodynamic data reported here with such models provides further evidence that specific interactions, when they occur, are more important than the bulk properties of the pure components in determining drug solubilities in nonaqueous systems. Specific examples demonstrate the relationship between the solubility and molecular structure of the solute and solvent. For example, solubility can be related to the hydrogen-donating and hydrogen-accepting abilities of the solute and solvent. Steric factors also appear to play a role in solubility, while structural modifications in a solute or solvent molecule far removed from the interactive functional group have little influence on molar solubility changes with the added polar cosolvent.

Anthraquinones↗
PubMed1980

Microsomal enzymes in patients with acute leukemia as determined by plasma half-life of antipyrine.

The metabolism of antipyrine was studied in five patients with acute leukemia, before and after treatment and in relapse, to ascertain the effects of treatment on hepatic microsomal enzyme activity. The mean antipyrine half-life was significantly longer in patients after treatment (15.0 +/- 3.7 h) than in patients before treatment (8.8 +/- 0.7 h) (P less than 0.02). Furthermore, the mean antipyrine half-life in patients after treatment was also significantly longer than in patients in relapse (9.2 +/- 2.7 h) (P less than 0.05). Similarly, the mean metabolic clearance rate of antipyrine was significantly lower in patients after treatment (26.9 +/- 2.2 ml/h/kg) than in patients before treatment (46.7 +/- 13.1 ml/h/kg) (P less than 0.02). The mean apparent volume of distribution was not significantly different during the course of acute leukemia. The mean transaminase activity in patients after treatment was significantly higher than that in patients before treatment and in relapse. Thus, treatment with antileukemic agents and blood transfusions might alter hepatic microsomal enzyme activity.

Adolescent↗
PubMed1980

Comparison of the effect of electrochemical stimulation of the medial preoptic area and the hypothalamic arcuate nucleus upon LH release in ovariectomized and proestrous rats.

The effect of electrochemical stimulation of the medial preoptic area (MPO) and the hypothalamic arcuate nucleus (ARC) on LH release was compared among long-term ovariectomized (OVX), ovariectomized rats treated with estradiol benzoate (OVX-E) and proestrous (PE) rats under pentobarital anesthesia. The MPO stimulation failed to facilitate LH release on OVX rats whereas the stimulation increased serum LH levels in both OVX-E and PE rats. The ARC stimulation resulted in an elevation of serum LH in OVX and PE rats. The time course of serum LH elevation after the electrochemical stimulation of the MPO or the ARC was different between OVX-E and PE rats. In PE rats serum LH concentrations began to rise 20-30 min after the stimulation of the MPO or the ARC with peak values obtained around 70-90 min. Serum LH started to elevate immediately with peak values in 10-20 min following the ARC stimulation in OVX rats and the MPO stimulation in OVX-E rats. The time courses for changes in serum LH concentrations following LH-RH administration were similar in OVX and PE rats. From these results, the lack of circadian rhythm in serum LH levels in long-term OVX rats may be due to the inability of the MPO to re- spond to the stimulus generated from circadian pacemaker(s). The cause of the delay observed between the stimulation of the MPO and LH rise in PE rats may not exist in the levels of neural transmission between the MPO and the ARC or the pituitary, but in the level of the mediobasal hypothalamus.

Animals↗