Search PubMed⌕ Search

Biomedical subjects

M L Powell

Publications and source records attributed to M L Powell.

At least 37 records · Page 2Linked to original sources
PubMed1990

Tricuspid atresia. Surgical treatment, pediatric nursing care.

Tricuspid atresia is one of the least common congenital heart defects representing less than 3% of all reported cases. The course and prognosis depends on the underlying anatomy; however, the prognosis is guarded in all cases. Intraoperative mortality is between 5% to 7%. Without surgical treatment, these children die. Of those who have surgery, more than half survive until their second decade. At approximately 15 years of age, the mortality rate increases as a result of congestive heart failure, pulmonary vascular obstructive disease, and dysrhythmias. Surgical repair for children with tricuspid atresia involves palliative surgery in infancy followed by corrective surgery when the child is three to four years of age. The Fontan procedure is the surgical procedure of choice for children undergoing corrective surgery for tricuspid atresia. It involves anastomosing the pulmonary artery to the right atrium to create a connection between the systemic venous and pulmonary circulation. Children undergoing corrective surgery for tricuspid atresia require diversified nursing care. Nurses from the cardiovascular unit, the operating room, and the pediatric intensive care unit work interdependently to facilitate the transition of the child and family through the various stages of the hospitalization. As a result of a collaborative and comprehensive nursing approach, these children and families may have a more positive experience.

Child↗
PubMed1989

Virus infection as a stressor: influenza virus elevates plasma concentrations of corticosterone, and brain concentrations of MHPG and tryptophan.

Balb/c mice were infected with influenza virus PR8 (H1N1) by the intranasal route. At various subsequent times, brain samples were examined for their content of catecholamine and indoleamine metabolites, and plasma corticosterone was measured. Virus infection was associated with a progressive loss of body and thymus weights, and an increase in plasma corticosterone. Spleen weight initially increased then decreased. There were also increases in the cerebral content of free tryptophan throughout the brain, and of MHPG, a major catabolite of norepinephrine, especially prominent in the hypothalamus. Thus influenza virus can be regarded as a stressor because, like behavioral stressors, it activates the hypothalamic-pituitary-adrenal axis, and increases cerebral concentrations of tryptophan and norepinephrine catabolites. These changes resemble those observed following administration of sheep red blood cells and Newcastle disease virus, noninfectious activators of the immune system, suggesting that noradrenergic and HPA activation are common concomitants of antigenic stimulation. The mediator of these effects may be interleukin-1 released by activated macrophages. It should be noted that animals infected with viruses can be expected to exhibit stress-like endocrine and neurochemical changes.

Animals↗
PubMed1987

Effects of Newcastle disease virus administration to mice on the metabolism of cerebral biogenic amines, plasma corticosterone, and lymphocyte proliferation.

Newcastle disease virus (NDV) administration to mice increased concentrations of plasma corticosterone, with a maximal effect at 8 h. This elevation of plasma corticosterone concentrations was not observed in hypophysectomized animals in which the completeness of the hypophysectomy was verified by functional tests. NDV administration consistently increased concentrations of free tryptophan in all brain regions examined (prefrontal cortex, hypothalamus, and brain stem). It also caused an activation of cerebral catecholamine and indoleamine metabolism as determined by measurement of the amines and their catabolites. 3-Methoxy,4-hydroxyphenylethyleneglycol (MHPG), the major catabolite of norepinephrine (NE), homovanillic acid (HVA), a major catabolite of dopamine (DA), and 5-hydroxyindoleacetic acid (5-HIAA), the major catabolite of serotonin (5-HT), were all increased in both hypothalamus and brain stem. Ratios of catabolites to the parent amine, considered to be an index of utilization of the neurotransmitters, were increased for NE, DA, and 5-HT in the hypothalamus and for DA and 5-HT in the brain stem. This pattern of changes resembles that observed following stressors such as footshock or restraint. There were also significant increases of tryptophan, HVA, dihydroxyphenylacetic acid (DOPAC), and 5-HIAA in hypophysectomized relative to sham-operated mice. The NDV treatment also increased thymus weights and markedly decreased the proliferative responses of isolated spleen cells to phytohemagglutinin, concanavalin A, pokeweed mitogen, and Escherichia coli lipopolysaccharide. These changes were not caused by increased circulating corticosterone because they were present at equal magnitude in hypophysectomized mice. Thymosin alpha 1 concentrations in the plasma were not altered by NDV or hypophysectomy. These results indicate that administration of NDV to mice can initiate neurochemical and endocrine responses like those observed during stress and can also cause immunosuppression. They are thus consistent with the hypothesis that a virus can be a stressor.

Animals↗
PubMed1986

Acute and subchronic toxicity of a nonsulfhydryl angiotensin-converting enzyme inhibitor.

Acute and 1-month toxicity studies with SCH 31846, a nonsulfhydryl anti-hypertensive agent which acts by inhibiting angiotensin-converting enzyme, were initiated to evaluate its toxicity. The oral LD50s in mice and rats were approximately 1.8 and 2.5 g/kg, respectively, while the iv LD50 was approximately 450 mg/kg in mice and 150 mg/kg in rats. Signs of acute toxicity in rats and mice included salivation, hypoactivity, ataxia, prostration, and convulsions. In a 1-month dog study at oral doses of 25, 75, or 150 mg/kg, there was a dose-related increase in emesis between 1 and 2 hr after dosing. Absorption studies showed peak blood concentrations occurring in dogs between 0.3 and 1 hr after dosing. No other noteworthy antemortem changes were observed. In a 1-month rat study at oral doses of 30, 180, or 600 mg/kg, the hematocrit and hemoglobin values of the 600 mg/kg-dosed female rats were slightly but significantly (p less than 0.05) decreased and the blood urea nitrogen was slightly but significantly (p less than 0.05) increased in all SCH 31846-dosed male rats and the 600 mg/kg-dosed female rats. Absorption studies in male rats at doses of 30, 180, and 600 mg/kg indicate that SCH 31846 is well absorbed in rats. The 150 mg/kg-dosed dogs and the 180- and 600 mg/kg-dosed rats had a slight increase in the number of renin-containing granules in the renal juxtaglomerular cells. No other compound-related microscopic changes were observed. These data are similar to data reported for Captopril and suggest that in the dog and rat the toxicity of ACE inhibitors is not dependent upon the presence or absence of a sulfhydryl group.

Administration, Oral↗
PubMed1985

Comparative bioavailability and pharmacokinetics of three formulations of albuterol.

Albuterol sulfate, alpha'[[1,1-dimethyl)amino]methyl]-4-hydroxy-1,3-benzenedimethanol sulfate, is a relatively selective beta-2-adrenergic bronchodilator used for the relief of bronchospasm. The bioavailability of two 4-mg tablet formulations, differing in their inactive excipients, and a syrup formulation, was evaluated. The three dosage forms were orally administered to 12 normal male volunteers in a randomized three-way crossover study. Plasma samples were collected at frequent time points through 12 h and analyzed for albuterol content by a specific GC-MS method. The drug was rapidly absorbed from all three formulations. Maximum drug concentrations were comparable for the three formulations and were obtained between 1.8-2.0 h. The areas under the plasma concentration-time curves were 68-78 h X ng/mL. The drug elimination phase half-live (t1/2 beta) ranged from 4.8 to 5.5 h. Analysis of the data showed that the bioavailability of albuterol from a tablet formulation is equivalent to that from a solution.

Administration, Oral↗
PubMed1983

Quantitative analysis of albuterol in human plasma by combined gas chromatography chemical ionization mass spectrometry.

A highly sensitive and specific quantitative assay for the determination of albuterol in human plasma, based on selected ion monitoring gas chromatography chemical ionization mass spectrometry, has been developed. The [MH]+ ions from the tri-TMS derivatives of albuterol (m/z 456) and the internal standard (2H3)albuterol (m/z 459), were assayed simultaneously by selected ion monitoring. The lower limit of quantitation is 0.25 ng ml-1 and the average assay precision (CV) for albuterol concentrations ranging from 0.25 ng ml-1 to 25 ng ml-1 is approximately 4%. This method is currently being employed for the routine quantitation of albuterol in plasma following the administration of doses therapeutically effective to man.

Albuterol↗
PubMed1983

Derivatives of beta-adrenergic antagonists. N-Nitrosopropranolol and N-hydroxypropranolol and its aldonitrone.

Potential precursors to chemically reactive species derived from the beta-adrenergic antagonist propranolol were synthesized and tested for mutagenicity in the Ames Salmonella assay. N-Hydroxypropranolol (1), the corresponding aldonitrone, 3-(1-naphthoxy)-2-hydroxypropionaldehyde N-isopropylnitrone (2), and N-nitrosopropranolol (3) were prepared and tested. N-Hydroxypropranolol (1) was obtained by direct alkylation of 3-(1-naphthoxy)-1-bromo-2-propanol with N-isopropylhydroxylamine and isolated as its neutral oxalate or HBr salt. The aldonitrone (2) was obtained by mercuric oxide oxidation of the hydroxylamine. N-Nitrosopropranolol (3) was prepared by treating propranolol with nitrous acid. None of the compounds was mutagenic in the Ames assay with Salmonella typhimurium TA-98 and TA-100 strains, either in the absence or in the presence of the S-9 liver fraction from Arochlor 1254 treated rats. None of the compounds was significantly toxic to the bacteria, except for slight toxicity of the oxalate salt of 1.

Adrenergic beta-Antagonists↗
PubMed1981

Quantitative selected ion monitoring (QSIM) of drugs and/or drug metabolites in biological matrices.

From a modest beginning, QSIM has established itself with over three hundred applications in the 1970s as not only a reference technique for other methods but also as a useful method in its own right for the quantitation of drugs in biological matrices. Relative to its potential sensitivity, the actual sensitivity of QSIM drug assays is disappointing, although a number of QSIM drug assays report LOQs of 250 pg ml-1 or less. The mean reported precision of QSIM drug assays (approximately 6%) is similar to that of traditional GC and LC assays, but is an order of magnitude less than either what is theoretically possible or what has been demonstrated in a few selected QSIM assays.

Biological Availability↗
PubMed1980

Percentage of cells in the S phase of the cell cycle in human lymphoma determined by flow cytometry.

The percentage of cells with S phase DNA content (S cells) was determined by flow cytometry in cell suspensions obtained from 27 patients with non-Hodgkin's lymphomas. DNA was measured in ethanol-fixed cells stained with propidium iodide after RNase treatment. Cells from 17 samples were also exposed to [3H]-thymidine and labeling indices were determined. An excellent linear correlation was observed between the percentage of S cells calculated by flow cytometry and the labeling index (r = 0.95). To determine the relationship between the percentage of S cells and the clinical behavior of the tumors, the survival of the 27 patients was analyzed. None of the patients was undergoing antineoplastic therapy at the time of the study. The patients were separated into 2 groups according to the percentage of S cells calculated by flow cytometry: those with less than 5% S cells and those with higher than 5% S cells. Clinical follow-up ranged from 5 to 20 months. While 7 of 12 patients with tumors containing more than 5% S cells have died of lymphoma (median survival, 9 months), there has been only one death from lymphoma among 15 patients with tumors containing less than 5% S cells. The difference in survival between these two groups is statistically significant (P = 0.01).

Autoradiography↗
PubMed1980

Immunological evaluation of the tumorigenic response to implanted polymers.

This short report concentrates on a close look at the immunological status of experimental animals which were implanted with a known dose of tumor and polymer implant. The implanted polymers used represented the most common biocompatible materials employed in current surgery. The immunological studies all were done in vitro on the cellular level. The studies suggested that there is a noticeable change of the immune system when inorganic biocompatible polymers are used in experimental animals.

Animals↗
PubMed1979

Absolute configuration of glycerol derivatives. 7. Enantiomers of 2-[[[2-(2,6-dimethoxyphenoxy)ethyl]amino]methyl]-1,4-benzodioxane (WB-4101), a potent competitive alpha-adrenergic antagonist.

The enantiomers of 2-[[[2-(2,6-dimethoxyphenoxy)ethyl]amino]methyl]-1,4-benzodioxane (4) were prepared from the chiral 2-[(tosyloxy)methyl]-1,4-benzodioxanes [(2S)- and (2R)-5]. The corresponding (2R)- and (2S)-2-(aminoethyl)-1,4-benzodioxanes [2R)- and (2S)-7] were prepared by a modified Gabriel synthesis and converted to the enantiomers of 4 by condensation with 2,6-dimethoxyphenoxyacetaldehyde (8) and reduction of the intermediate imine with NaBH4. The enantiomer (2S)-4 was 40--50 times as potent as the enantiomer (2R)-4 in antagonizing the alpha-adrenergic response of methoxamine-induced contraction of rabbit aortic strips, showing a pA2 = 9.0. This result is consistent with the previous observation that S enantiomers of 2-[(alkylamino)methyl]benzodioxanes are more potent antagonists at a alpha-adrenergic receptors than the R enantiomers.

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

Comparative steady state bioavailability of conventional and controlled-release formulations of albuterol.

A new controlled-release (CR) dosage formulation of albuterol has been developed which is suitable for twice-a-day dosing. The present study was conducted in twelve healthy adult male volunteers to compare the steady state plasma levels obtained following repeated administration of a 4 mg CR tablet (q12h) compared to a 2 mg conventional table (q6h) for 5 consecutive days. The mean steady state plasma level-time curves for both the CR and conventional tablet treatments were comparable over time and reproducible. There were no significant differences in the AUC or Cmax values between the two treatments. The mean 48-h AUC values were 240.7 and 231.3 h X ng ml-1 for the conventional and CR tablets, respectively, while the corresponding Cmax values ranged from 5.3 to 6.8 ng ml-1 and 5.4 to 6.5 ng ml-1. There were no significant differences in Cmin values except for one 12-h (day 4) value. Cmin values ranged from 3.8 to 4.3 ng ml-1 and 3.0 to 4.8 ng ml-1 for the conventional and CR tablets, respectively. The data show that the 4 mg albuterol CR tablet (q12h) is bioequivalent to a 2 mg conventional albuterol tablet (q6h). The CR tablet formulation will offer the advantage of increased patient compliance; additionally, the CR formulation may prove to be especially beneficial in the treatment of nocturnal asthma.

Adult↗
PubMedDate not supplied

Quantitative determination of a new anticonvulsant (CGS 18416A) in human plasma using capillary gas chromatography/mass spectrometry.

An analytical method has been developed for the determination of a new antiepileptic drug, CGS 18416A, in human plasma. CGS 18416A is a new anticonvulsant representative of a novel class of water-soluble agents being developed for the treatment of epilepsy. Preclinical trials indicate sustained efficacy at relatively low oral doses, indicating a need for a sensitive assay. The method is based on capillary gas chromatography/mass spectrometry and utilizes stable isotope-labelled CGS 18416A as the internal standard. Samples (1 mL) are acidified, then washed with pentane/ethyl acetate, followed by liquid/liquid extraction at pH 11 with pentane/ethyl acetate. Extracts are then concentrated and analysed directly by gas chromatography/mass spectrometry. Separation is accomplished on a thick film methylsilicone capillary column. Mass spectrometry was carried out under positive ion ammonia Cl conditions with selected ion monitoring of the protonated molecular ions (m/z = 248 and 252) for CGS 18416A and the 13CD3-CGS 18416A, respectively. Specificity was demonstrated by the lack of interfering peaks at the retention time of CGS 18416A and the internal standard. Recovery and reproducibility assessments indicate good accuracy and precision over the validated concentration range of 0.2-51 ng/mL. The limit of quantification is 0.2 ng/mL and the method has sufficient sensitivity to support clinical trials. This is illustrated with an example of quantification in a normal volunteer following oral dosing.

Anticonvulsants↗