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Biomedical subjects

J B Houston

Publications and source records attributed to J B Houston.

At least 109 records · Page 6Linked to original sources
PubMed1979

Prevalence of mandibular dysfunction in young adults.

A sample of students (739) were questioned and examined for symptoms and signs associated with mandibular dysfunction. The most frequently mentioned symptoms were headache, TMJ sounds, and pain in the face or neck. No significant differences were found between men and women with symptoms other than headache. The most common dysfunctional signs were dull occlusal sounds on repeated, firm closure of the teeth, tenderness of muscles in the jaw or head, and sounds on condylar movement. Women had a higher prevalence of these signs. Subjects who were aware of bruxism (7.9%) were more likely to have tenderness of the masseter muscle and limited mouth opening. Limited mouth opening was associated with dull occlusal sounds, pain on opening the mouth, and sounds in TMJs. Headaches were associated with tenderness in muscles and joints. Subclinical signs associated with dysfunction occurred more frequently than did awareness of symptoms.

Adult↗
PubMed1978

Epinephrine absorption from retraction cord: a study in dogs.

This report re-opens the question of epinephrine absorption from gingival retraction cord during fixed prosthodontic impression procedures. The conflicting evidence exposed by this and other studies is probably related to the experimental models utilized. Some suggestions for further investigation are given.

Absorption↗
PubMed1976

Drug biotransformation interactions in man VI: acetaminophen and ascorbic acid.

Oral administration of 3 g of ascorbic acid 1.5 hr after an oral dose of 1 g of acetaminophen caused a rapid and pronounced decrease in the excretion rate of acetaminophen sulfate in five healthy adult volunteers. There was a statistically significant increase in the fractions of the dose of acetaminophen excreted as such as as acetaminophen glucuronide but a decrease in the fraction excreted as acetaminophen sulfate. The apparent biological half-life of acetaminophen increased from 2.3 +/- 0.2 (mean +/- SD) to 3.1 +/- 0.5 hr. Concomitant administration of sodium sulfate prevented these effects. Ascorbic acid, which itself is metabolized in part to the sulfate, inhibits the conjugation of acetaminophen with sulfate by competing for available sulfate in the body.

Acetaminophen↗
PubMed1976

Gastrointestinal absorption of carbenoxolone in the rat determined in vitro and in situ: deviations from the pH-partition hypothesis.

The absorption of [14C] carbenoxolone from everted rat ileum in vitro and from rat stomach and ileum in situ has been examined. The rate of its mucosal to serosal transfer in vitro increases as pH increases from 5 to 8 whereas the amount bound to ileum tissue decreases with increased pH; absorption closely parallels the drug's solubility. The uptake of carbenoxolone in situ is bi-exponential and the rate constants for the two processes, have been calculated. Absorption in situ, and biliary excretion, of the drug increases with increasing pH from 5.0 to 7.4. Tissue binding to the ileum in situ is not dependent on pH except below pH 5.0 when extensive tissue accumulation of carbenoxolone occurs because of its low solubility. Tissue binding to the stomach increases markedly with decrease of pH from 7.4 to 6.5 and at pH 6.5 is 80 times greater than binding to the intestine. The rate of absorption from the stomach, at pH 6.5-7.4, was much less than that from the intestine in situ. When allowance is made for the binding of carbenoxolone to the stomach, contrary to the pH-partition hypothesis, correlation is apparent between its absorption and the amount present in the ionized form.

Animals↗
PubMed1976

Effect of route of administration on competitive drug biotransformation interaction: salicylamide-ascorbic acid interaction in rats.

The effect of route of administration on competitive drug biotransformation interactions was explored with respect to the interaction between salicylamide and ascorbic acid. Previous studies in man have shown that this interaction involves competition for available sulfate and consequent inhibition of drug sulfate formation. Adult rats received salicylamide (100 mg/kg i.v. or 500 mg/kg orally) alone or with ascorbic acid (500 mg/kg i.v. or orally). Plasma concentrations and urinary excretion rates of salicylamide, salicylamide glucuronide and salicylamide sulfate were determined as a function of time. With i.v. salicylamide, i.v. ascorbic acid caused a modest decrease of salicylamide sulfate formation and thereby of salicylamide body clearance. Orally administered vitamin had a somewhat more pronounced effect. The vitamin had no effect on the apparent volume of distribution of salicylamide and on the renal clearances of its conjugates. With orally administered salicylamide, oral ascorbic acid caused a very pronounced decrease of salicylamide sulfate formation and salicylamide body clearance, whereas intravenous vitamin had little or no effect. These observations are consistent with the assumption that the magnitude of competitive drug biotransformation interactions, being a function of concentration, is most pronounced when the interactants are co-administered orally, due to their high concentrations in the intestinal wall and liver during the first pass.

Administration, Oral↗
PubMed1976

Effect of activated charcoal on acetaminophen absorption.

Acetaminophen intoxication can cause hepatic, renal, and myocardial necrosis which is often fatal. These lesions develop very rapidly, perhaps during the first pass of the drug through the liver. In case of acute ingestion of an overdose it is therefore essential to employ measures for reducing the absorption of acetaminophen. The effect of activated charcoal on acetaminophen absorption by normal volunteers was determined as a function of the dose of charcoal, the dosage form of acetaminophen, and the charcoal-to-acetaminophen dose ratio. The results indicate that activated charcoal can be an effective antidote for acute acetaminophen intoxication, if administered promptly and in sufficient quantity.

Acetaminophen↗
PubMed1976

Potentiation of isoproterenol effect by ascorbic acid.

Intraduodenal administration of isoproterenol together with ascorbic acid caused a much greater increase in the heart rate and pulse pressure, and a greater decrease in the mean blood pressure of anesthetized dogs than was observed after intraduodenal administration of isoproterenol alone. No potentiating effect was observed when isoproterenol and the vitamin were injected intravenously.

Animals↗
PubMed1975

Effect of various alcohols on intestinal net water flux and theophylline absorption in rats.

Previous studies in this laboratory demonstrated that the rate of intestinal absorption of theophylline in rats is increased significantly by ethanol in low concentrations and that this absorption enhancing effect is associated with an increased net water flux from the intestine. It is now shown that other alcohols, namely methanol, n-propanol, n-butanol, glycerin, propylene glycol, and, to a lesser extent, mannitol and sorbitol, can also increase net water flux from the small intestine of anesthetized rats. Polyethylene glycol 200 and 400 had no such effect, suggesting that these compounds do not penetrate to a site of action that elicits the increased net water flux. At initial concentrations of 0.1 and 1.0 M, glycerin and propylene glycol increase significantly the intestinal absorption rate of theophylline from the small intestine of anesthetized rats. The results show that the theophylline absorption enhancing effect of ethanol is not limited to that particular alcohol.

1-Propanol↗
PubMed1975

Effect of carbonated beverages and of an antiemetic containing carbohydrate and phosphoric acid on riboflavin bioavailability and salicylamide biotransformation in humans.

Two carbohydrate-phosphoric acid solutions, one a widely used beverage (Solution C) and the other a pharmaceutical product used as an antiemetic (Solution E), administered together with riboflavin-5'-phosphate or salicylamide to healthy human adults, significantly increased the bioavailability of riboflavin and appreciably altered the metabolic fate of salicylamide (increased conversion to the sulfate and decreased formation of the glucuronide). A beverage containing phosphoric acid but no carbohydrates (Solution T) also increased the bioavailability of riboflavin but not as much as Solution C. These effects are attributed to a decrease of the gastric emptying rate caused by carbohydrates and phosphoric acid, consistent with the empirical use of Solution C syrup and Solution E as antinauseants and antiemetics. The results demonstrate also that the choice of beverage to be taken with medication can affect the bioavailability and/or metabolic fate of medicinals with saturable absorption and/or biotransformation characteristics.

Adult↗
PubMed1975

Pharmacokinetics and metabolism of two carbamate insecticides, carbaryl and landrin, in the rat.

1. A pharmacokinetic model for distribution of carbaryl and landrin (0-5 mg/kg) in male rat has been derived. Distribution of both compounds is adequately described in terms of two kinetically distinct compartments equilibrating slowly or rapidly with the blood circulatory system. The role of the slowly equilibrating tissue compartment is particularly important for carbaryl and as a result this carbamate has a longer half-life (77 min) than landrin (42 min). 2. Less than 1% of the carbamate was excreted unchanged. The kinetics of metabolism have been studied by decline in plasma carbamate concentrations, urinary excretion, and production of 14CO2 from the 14C-carbamyl group. Enterohepatic circulation of carbamate metabolites prolongs the duration of radioactivity in the body. 3. Comparison of different routes of administration shows that oral or hepatic portal administration results in lower plasma carbamate levels than those achieved by jugular vein injection, due to a liver first-pass effect.

Animals↗
PubMed1975

Prediction of post-freshman year dental student performance.

The orientation of the remedial education program was changed as a result of this study. By using freshman achievement to aid in prediction of later performance it was found that inefficient students could be identified much earlier with reliable accuracy (R equal to 0.9). Although the computer program did not produce a reliable formula for the prediction of specific problem disciplines, it allowed a preventive as well as a remedial mechanism to assist the inefficient student.

Education, Dental↗
PubMed1975

Further studies using carbamate esters as model compounds to investigate the role of lipophilicity in the gastrointestinal absorption of foreign compounds.

In order to examine the validity of models proposed previously for the gastrointestinal absorption of foreign compounds, the absorption behavior of a series of N-methylated carbamates has been studied in the rat. An optimal partition coefficient for the intestinal absorption of these compounds was demonstrated but this value was approximately one order higher than that reported earlier for a related series of unsubstituted carbamates. It is suggested that this difference is due to the modification in hydrogen bonding arising from N-methyl substitution. In contrast, an optimal partition coefficient for gastric absorption could not be demonstrated within the range of the apparent partition coefficient studied. The absorption behavior of the N-methylated carbamates tends to confirm the different trends previously observed between drug absorption from the intestine and that from the stomach.

Absorption↗