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Biomedical subjects

K R Powell

Publications and source records attributed to K R Powell.

At least 109 records · Page 6Linked to original sources
PubMedDate not supplied

Two-component arterial blood pressure conditional response in rat.

The objective of these experiments was to quantify the pattern of change in arterial blood pressure (BP) during a discriminative aversive classical conditioning paradigm in rat using a new "high resolution" computer analysis. Sprague-Dawley rats (n = 5) were restrained in a soft, conical cloth pouch and conditioned using a 6 sec. pulsed tone (CS+) followed by a 0.5 sec. tail shock; a steady tone, never followed by shock, served as a CS-. BP peaked at 16.4 +/- 6.5 mm Hg (mean +/- SD) above control at 1.5 +/- 0.1 sec. after onset of CS+. This "first component" ("C1") also occurred during CS- (12.1 +/- 3.8 mm Hg), although the magnitudes of the two were significantly (p < 0.05) different. Another group of rats (n = 8) was treated identically except the tones were 15 seconds long. The conditional BP response consisted of two components. C1 was reminiscent of that seen using the short tone: for CS+ a peak of 13.6 +/- 5.6 mm Hg at 1.5 sec. or, for CS-, of 10.0 +/- 4.3 at 1.3 sec. (p < 0.05). In CS+ trials BP peaked again ("C2," 7.4 +/- 2.5 mm Hg) at 8.3 +/- 1.2 sec. There was no statistically significant C2 for CS- trials, clearly demonstrating discrimination between tones. The unconditional BP response in both groups consisted of two large, closely spaced peaks in BP. Respiration was recorded in 3 additional rats. After shock delivery these subjects often showed a sudden shift between (1) a regular respiratory pattern with moderate chest excursion and (2) apneic episodes interspersed with single, deep breaths. This latter pattern was associated with large, low frequency fluctuations in BP. Continued development of the rat conditioning paradigm is especially warranted because of the ability to record sympathetic nerve activity in intact, awake subjects and the large number of readily available genetic strains, which model human pathological states.

Animals↗
PubMedDate not supplied

The role of dopamine in the locomotor stimulant effects and tolerance to these effects of caffeine.

Current evidence indicates that the acute locomotor stimulant effects of caffeine involve dopamine (DA) receptor activation; however, few studies have investigated the role of DA receptors in mediating the development of tolerance to caffeine. Therefore, the present study was designed to determine the degree to which DA receptors mediate the development of tolerance to the locomotor stimulant effects of caffeine. Caffeine was examined alone and in combination with haloperidol (HAL), GBR 12909, nisoxetine and fluoxetine. HAL dose-dependently and completely blocked the acute effects of caffeine on locomotor activity, and the highest dose of GBR 12909 enhanced the effects of caffeine. Neither nisoxetine nor fluoxetine altered the effects of caffeine. HAL was infused via osmotic pumps (0.1 mg/kg/day) during a 14-day regimen of chronic caffeine administered in a caffeinated drinking solution ( approximately 136 mg/kg/day). HAL did not block the development of tolerance to the locomotor stimulant effects of caffeine, but did impair the recovery from tolerance following withdrawal of caffeine. [3H]SCH 23390 (DA D(1)) binding sites were downregulated in the nucleus accumbens and striatum and were upregulated in the prefrontal cortex of caffeine-treated vs. control rats; however, the affinity of [3H]SCH 23390 for these binding sites was unaltered. There were no differences between the caffeine-treated and control rats in number or affinity of [3H]spiperone (DA D(2)) binding sites. These results suggest that, although HAL did not alter the development of tolerance to caffeine, changes in DA D(1) receptors could be one component of the mechanism underlying caffeine-induced tolerance.

Animals↗
PubMedDate not supplied

Staphylococcal protein A in the serologic diagnosis of congenital rubella and toxoplasmosis.

Staphylococcal protein A (SPA) has been used to remove maternal IgG from cord or neonatal sera to make serologic testing for congenital infection more IgM specific. To evaluate the clinical usefulness of this procedure, sera sent for TORCH titers that had rubella hemagglutination inhibition (RHI) reciprocal titers greater than or equal to 8 or toxoplasmosis indirect fluorescent antibody (TFA) titers greater than or equal to 16 were adsorbed with SPA and retested. Nine of 109 sera were TFA positive by routine testing, and all but one from an infant with congenital toxoplasmosis became negative after SPA adsorption. A repeat TFA at 4 to 26 months of age was negative in all six children without evidence of toxoplasmosis who returned for follow-up. Fifty of 55 sera were RHI positive by routine testing, and all but one from an infant with congenital rubella became negative after SPA adsorption. The repeat routine RHI was negative in 32 of 35 children whose sera were initially negative after SPA adsorption. SPA adsorption greatly increased the specificity of routine RHI and TFA tests in the diagnosis of congenital rubella and toxoplasmosis.

Female↗
PubMedDate not supplied

Neutralizing antibodies to non-polio enteroviruses in human immune serum globulin.

Neutralizing antibodies to selected non-polio enteroviruses were found in three lots of human immune serum globulin (ISG) prepared from the sera of persons from different geographic regions. Reciprocal titers to coxsackieviruses B3 and B4 ranged from 400 to greater than or equal to 2000, whereas titers to coxsackievirus A9 and ECHO viruses 5 and 9 ranged from 100 to 400 in all three lots of ISG. The presence of neutralizing antibodies to commonly occurring (coxsackieviruses B1 to B5 and A9 and ECHO viruses 3, 4 and 9) and infrequently encountered (ECHO viruses 5 and 13) serotypes, coupled with the increasing evidence that antibodies are an important factor in preventing illness, support recommending the administration of ISG to those at high risk for serious disease.

Antibodies↗
PubMedDate not supplied

The effect of dilution during culture on detection of low concentrations of bacteria in blood.

The standard procedure for culturing blood is to inoculate 5 ml of blood into 50 ml of broth, resulting in a blood-broth ratio of 1:10. In infants, where only 0.5 to 1.0 ml of blood is available for culture, blood:broth ratios may be as dilute as 1:100. The purpose of this study was to determine whether a blood-broth ratio of 1:100 was as sensitive as a ratio of 1:10 for detecting low concentrations of bacteria in blood. Blood (0.5 ml) seeded with 2 to 30 organisms/ml of one of four common pediatric pathogens (Escherichia coli, Streptococcus pneumoniae, Group B Streptococcus or Haemophilus influenzae type b) was inoculated into culture broth so as to provide blood-broth ratios of 1:10, 1:30 or 1:100. There were no differences in the ability to recover organisms or in the time-to-positivity of cultures with different blood-broth ratios. Cultures were positive in 24 of 40 (60%) bottles at a ratio of 1:10, 28 of 40 (70%) at 1:30 and 30 of 40 (75%) at 1:100. Common pediatric pathogens can be recovered without delay from volumes of blood as small as 0.5 ml cultured at blood-broth ratios up to 1:100.

Bacteria↗
PubMedDate not supplied

An in vitro investigation of the penetrating efficacy of BIS-GMA resin pit and fissure coatings.

The frequency of complete penetration of two commercial BIS-GMA resin pit and fissure coating materials into wide and constricted fissures was assessed from photomicrographs. It was found that 334 of the 390 wide fissures examined were completely filled by the coating materials. However, in contrast, only 28 of the 650 constricted fissures examined were completely filled by these resins.

Acid Etching, Dental↗
PubMedDate not supplied

Clinical appearance of permanent successors after nonextraction treatment of grossly carious primary molars in highly anxious children.

After taking into account the local constraints, a treatment plan was devised to introduce children to dental procedures in gradual stages. An alternative nonextraction approach was adopted. Children between the ages of five and ten years were chosen for the acclimatization program; and 65 percent of their permanent successors to treated primary molars showed no defects.

Anxiety↗