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Biomedical subjects

B Reed

Publications and source records attributed to B Reed.

At least 55 records · Page 3Linked to original sources
PubMed1987

Effects of MHz ultrasound on electrical pain threshold perception in humans.

An electrode system was developed consisting of two 8 mm long 0.2 mm diameter silver-coated copper wires arranged parallel to each other 8 mm apart and held in contact with the skin by means of an acoustically transparent plastic adhesive tape. This system was attached to the upper arms of young adult volunteers who increased the voltage of the rectangular electrical pulses supplied to the electrodes until a reproducible sharp prickling pain sensation was perceived. A one inch diameter physiotherapy transducer was positioned over the electrode site so that ultrasound could be administered throughout the measurement period. The experiments were performed single blind to eliminate any subjective bias on the part of the volunteers. Preliminary experiments established that highly reproducible (+/- 3 to 4%) pain threshold perception values could be obtained, and that these values were not affected by changes in (a) the duration of the "on" time of the electrical pulses between 1.5 and 48 ms, (b) the contact pressure between the transducer and the electrode site, (c) the time interval between successive threshold measurements (providing that an unacceptable level of oedema was not produced around the electrodes), and (d) whether or not a test measurement was preceded by a control. Ultrasound exposure via a direct contact technique consistently produced a statistically significant (p less than 0.05) decrease in the perception threshold for electrical pain. This effect usually developed within 30-60 s and its magnitude increased both with increasing intensity (rising to 20.7 +/- 0.57% at an SATA intensity of 0.43 W/cm2 at 1.1 MHz) and with increasing frequency at the same ultrasonic intensity. Delivering the same amount of ultrasonic energy in the form of 2 ms bursts at several different peak intensities produced exactly the same reduction in pain threshold perception. These results indicate a thermal interaction mechanism, and similar threshold changes could be obtained by heating or cooling the electrode site by nonacoustic means. The inclusion of a thermocouple junction between the electrode wires showed that temperature increases of up to 10 degrees C could be produced when the transducer was in direct contact with the tape over the electrodes. The volunteers were not aware of these temperature increases which were primarily caused by heating of the transducer face. If the temperature of the skin surface is kept constant by interposing a thermostatted water path between the transducer and the electrode system, then similar ultrasound exposures had no detectable effects upon the electrical pain perception threshold.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1987

Orthodontic relapse, apical root resorption, and crestal alveolar bone levels.

This investigation examined the relationship of postorthodontic treatment relapse to crestal alveolar bone support and root resorption. Thirty-six persons having completed the retention phase of orthodontics at least 10 years earlier were divided into two groups based on the amount of relapse crowding of the mandibular anterior teeth. Eighteen subjects (relapse group) exhibited 2 mm or more of mandibular anterior relapse crowding and 18 subjects (nonrelapse group) exhibited no mandibular anterior relapse crowding. At time of recall, full-mouth series of periapical and bitewing radiographs were obtained as well as lateral cephalometric films to allow comparison with similar lateral cephalometric films obtained at pretreatment and retention time points. The radiographs were examined to assess three parameters: root resorption, crestal alveolar bone levels, and changes in the position and angulation of the maxillary incisors. The subjects in the relapse group had undergone longer periods of treatment and exhibited a greater prevalence of root resorption; they also displayed significantly greater crestal alveolar bone level distances, indicating greater loss of bone support than that observed in the nonrelapse group. The distances that teeth were translated seemed to affect the extent of root resorption and crestal bone loss with smaller amounts of tooth translation seemingly more prone to demonstrate tissue loss. The findings of this investigation suggest there may be a relationship between orthodontic relapse and the parameters of increased root resorption and decreased crestal alveolar bone levels.

Adult↗
PubMed1984

Octachlorostyrene: a 90-day toxicity study in the rat.

This study was designed to provide information on the subchronic toxicity of octachlorostyrene (OCS), a demonstrated environmental pollutant in fish from the Great Lakes of North America and the Norwegian coast in Europe. Groups of 15 male and 15 female rats were administered OCS mixed in the diet at 0.05, 0.5, 5.0, 50, or 500 ppm for 13 weeks. Increased liver weights were observed in male and female rats fed 50 ppm OCS and higher, while enlarged kidney and spleen were noted in the highest dose groups. Hepatic microsomal enzyme induction occurred at 5.0 ppm OCS and higher for the males and 50 ppm and higher for the females. The chemical produced serum biochemical changes at concentrations as low as 5.0 ppm. OCS treatment resulted in hematological disturbances starting with the 0.5-ppm dose group. Dose-dependent histological changes were observed in the thyroid, kidneys, and liver of the treated animals. OCS residues accumulated in a dose-related fashion in the liver and fat of treated animals. These results indicate that OCS produced toxic effects at low levels of exposure and accumulated in the tissues of rats.

Adipose Tissue↗
PubMed1984

Periodontal response after tooth movement into intrabony defects.

The present study was undertaken since conflicting evidence exists regarding the effect of such tooth movement on levels of connective tissue attachment. Localized intrabony pockets were produced around isolated incisors in four rhesus monkeys. The root surfaces were planned to the level of the bone at the base of the angular bony defects. An oral hygiene regime was begun and continued for the remainder of the study. The experimental teeth were moved orthodontically into, and through, the original area of the intrabony defect. Two months after cessation of active tooth movement, block specimens were removed for histologic analysis. Control specimens comprised those teeth with induced periodontal defects, but without tooth movement. In specimens not subjected to tooth movement, angular bony defects were present and epithelium lined the root surface to the apical extent of instrumentation. The alveolar bone adjacent to the orthodontically moved teeth no longer had angular defect morphology. On the pressure side, epithelium lined the root surface, was interposed between root surface and bone and terminated at the apical limit of root instrumentation. On the tension side, the crest of the bone was located apical to the level of root planing, and epithelium lined the instrumented portion of the root surface. It was concluded that orthodontic tooth movement into intrabony periodontal defects was without effect upon the levels of connective tissue attachment.

Alveolar Process↗
PubMed1983

Biochemical and physiological effects of compound 48/80 on canine trachea in vivo.

We studied changes in tracheal histamine content and tracheal muscle tension after degranulation of tracheal mast cells by compound 48/80 in 32 anesthetized dogs. In four dogs compound 48/80 caused an increase in tracheal tension [13 +/- 5 (SD) g/cm], while femoral arterial blood pressure decreased only 14 +/- 11%. Tracheal tissue histamine decreased 17 +/- 6% in five dogs receiving intra-arterial compound 48/80 (5 X 10(-3) to 10(-1) mg/kg). Chlorpheniramine, an H1-antagonist, selectively inhibited tracheal contraction to compound 48/80 and histamine. Cimetidine, an H2-antagonist, did not alter the response to intra-arterial histamine. In 11 dogs, the doses of both intra-arterial histamine and acetylcholine required to produce a threshold increase in tracheal tension of 8 g/cm were compared. Threshold doses for acetylcholine varied 10-fold, compared with 100-fold variation for histamine among these dogs. There was a significant correlation between increased tracheal tension produced by compound 48/80 and histamine (r = 0.62). We conclude that compound 48/80 causes a variable increase in tracheal tension in vivo because of marked variability in the H1-receptor response of tracheal smooth muscle to histamine and because of variability in the release of mediator from respiratory mast cells by compound 48/80.

Acetylcholine↗
PubMed1981

Effect of acute and chronic alcohol ingestion on the rate of folate catabolism and hepatic enzyme induction in mice.

1. Folate deficiency is commonly found in alcoholic subjects although the causative mechanism is uncertain. It has been suggested that microsomal enzyme induction resulting from chronic alcohol ingestion might accelerate the rate of folate catabolism thus causing deficiency. 2. By using an experimental animal model to determine the rate of catabolism of [3H]pteroylglutamate (folic acid) by the quantitative estimation of the two urinary catabolites p-[3H]aminobenzoylglutamate and [3H]acetamidobenzoylglumate, we have measured both the rate of folate catabolism and the extent of microsomal-enzyme induction in mice after acute and chronic alcohol ingestion. 3. Despite significant evidence of enzyme induction in the chronic alcohol group, there was no difference in the rate of folate catabolism after acute or chronic alcohol ingestion when compared with that of the controls.

4-Aminobenzoic Acid↗
PubMed1981

Bile acid inhibition of vitamin B12 binding by intrinsic factor in vitro.

The effect of conjugated and unconjugated bile acids on the binding of vitamin B12 to intrinsic factor was investigated. The dihydroxy bile acids (deoxycholic, glycodeoxycholic, taurodeoxycholic, glycochenodeoxycholic, and taurochenodeoxycholic) inhibit the binding of intrinsic factor to vitamin B12 at physiological concentrations. On the other hand, the trihydroxy bile acids (cholic, glycocholic, and taurocholic) are not effective in this respect. The inhibition is dependent both on concentration and time, and its pattern is similar to that previously reported for duodenal juice. On column chromatography, there is a close correlation between the degree in intrinsic factor inhibition and the total acid concentration in the duodenal juice. The binding of vitamin B12 by R protein in saliva is not affected by bile acids. The results show that bile acids at concentrations found in duodenal juice inhibit intrinsic factor vitamin B12 binding. It is suggested that this observation may have physiological significance for vitamin B12 absorption.

Bile Acids and Salts↗
PubMed1981

Developing bilingual patient education materials. Problems and solutions.

The bilingual format presents a challenging set of problems for media producers. Four factors seem to be of primary importance to the success of bilingual materials: 1. Identifying the unique educational and cultural characteristics of the target audience. 2. Developing strategies to establish credibility with the target audience. 3. Determining the most appropriate dialect for non-English scripts. 4. Designing a 'tri-script' to allow all project planners to easily follow the script in both languages. The article describes the development of a series of bilingual patient education materials on Renal Transplantation, particularly focussing on the efforts of the development team in regard to each of the four factors listed above.

Audiovisual Aids↗
PubMed1979

Effect of anticonvulsant drugs on the rate of folate catabolism in mice.

An increase in folate catabolism has been suggested as the cause of the folate deficiency observed in many clinical conditions, including chronic anticonvulsant therapy. Previous studies have shown that the radioactive catabolites, excreted after an equilibration period of 3 d, consisted exclusively of folates that had been cleaved to produce pteridines and p-aminobenzoylglutamate, most of which was excreted as acetamidobenzoylglutamate. We have developed an experimental animal model using mice to determine the rate of catabolism of [3H]pteroylglutamate (folic acid) by the quantitative estimation of [3H]p-aminobenzoylglutamate and [3H]acetamidobenzoylglutamate in urine. Administration of diphenylhydantoin at three different doses (0.5, 20, and 50 mg/kg) significantly increased the rate of catabolism as measured by an increase in both the mean daily excretion and the cumulative excretion of these catabolites. Administration of intramuscular phenobarbitone on the other hand, did not affect the rate of catabolism, when compared with controls.

Animals↗
PubMed1978

The occurrence of folate-derived pteridines in rat liver.

1. It has previously been shown that folate polyglutamates in the rat are catabolized almost exclusively via cleavage of the C-9--N-10 bond, resulting in the formation of pteridines and p-aminobenzoylglutamate. The latter catabolite is rapidly excreted, appearing in the urine as acetamidobenzoylglutamate and is undetectable in rat liver. 2. The pteridines catabolites on the other hand are retained to a much greater extent by the liver, forming an ever-increasing proportion of the retained radioactive tracer. 3. A possible role for these pteridines as cofactors in brain metabolism is discussed.

Animals↗