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Biomedical subjects

R Powell

Publications and source records attributed to R Powell.

At least 109 records · Page 6Linked to original sources
PubMed1982

Antibody mediated regulation of immune responses. I. Enhancement of specific antibody responses through IgM antibodies.

Injection of monoclonal IgM antibodies to sheep red blood cells (SRBC) 2 h before immunization with a low dose of antigen (Ag) specifically enhances the direct and indirect plaque-forming cell response. This enhancement was specific: the specific antigen had to be present; the plaque-forming cell (PFC) response to TNP-Ficoll- or bromelein-treated mouse red blood cells was not enhanced; the PFC response to SRBC was not enhanced by injections of monoclonal antibody to TNP. The optimum conditions for enhancement were found to be dependent on both the dose and the time of administration of antibody in relation to antigen. The possible mechanisms for this enhanced antibody response are discussed.

Animals↗
PubMed1982

Androgen-induced sexual dimorphism in high affinity dopamine binding in the brain transcends the hypothalamic-limbic region.

1 High affinity binding of [3H]-dopamine and [3H]-5-hydroxytryptamine ([3H]-5-HT) was measured in membrane fractions prepared from cerebral cortex, amygdala, hypothalamus, thalamus and brain stem of rats of either sex and of rats which had been either neonatally castrated or androgenized. 2 Binding was measured in rats of 8, 20 and 30 days old as well as in adults. 3 [3H]-dopamine bound with approximately 30 nM affinity ahd [3H]-5-HT with approximately 10 nM affinity to all areas of the brain tested. The relative inhibitory effects of haloperidol, apomorphine, cis-flupenthixol, unlabelled dopamine, noradrenaline, spiroperone, (+)-butaclamol, fluphenazine, pimozide and 5-HT on [3H]-dopamine binding in the cerebral cortex was consistent with receptor status for the binding components there as were the relative inhibitory effects of methysergide, dopamine, fluoxetine and ouabain on [3H]-5-HT binding in the fore brain. 4 Neither [3H]-dopamine nor [3H]-5-HT binding varied with the state of the sexual cycle in females. 5 There were no sexual differences in [3H]-5-HT binding in any of the brain areas tested nor was it affected by neonatal androgenization or neonatal castration. 6 [3H]-dopamine binding was greater in the cerebral cortex and amygdala of male than of female rats. These differences could be mimicked artificially by neonatal castration of males (female type development) or neonatal androgenization of females (male type development). Sexual dimorphism did not become overt until 20 days of age and did not extend to hypothalamus, thalamus or brain stem. 7 It is concluded that neonatal sex differences in exposure to steroid hormones has permanent effects on the number of dopamine binding sites in the cerebral cortex and is suggested that this sexual dimorphism extends to the amygdala.

Aging↗
PubMed1982

Development of sexual dimorphism in the suprachiasmatic nucleus of the rat.

Synapses develop at similar rates in the suprachiasmatic nucleus of rats of both sexes, but values are higher in male than in female animals from birth to maturity. Male-type development cannot be mimicked by neonatal androgenization but results suggest that female-type development can be induced by neonatal castration of males. The results suggested that both prenatal and postnatal androgens are essential to normal male development.

Animals↗
PubMed1982

Effective public relations that work to build your practice.

Work actively to promote your practice externally, using ideas with which you feel comfortable. Develop internal public relations that include a review of your own doctor/patient relationships, proper telephone etiquette that is effective, assistant training, and patient communications. Attend practice management seminars and always try to incorporate at least one new idea into your office routine after each meeting. Read, think about innovation, and be honest, sincere, and enthusiastic!! You and your patients will benefit!

Fees, Medical↗
PubMed1981

Menetrier's disease in childhood: report of two cases and a review of the literature.

Two new cases plus 13 previously reported cases of Menetrier's disease in childhood are reviewed. The most common features of this illness are severe upper gastrointestinal symptoms (abdominal pain, nausea, vomiting, hematemesis) followed by the onset of generalized edema and ascites. Significant laboratory findings include hypoalbuminemia, eosinophilia, and anemia. Gastrointestinal protein loss and decreased gastric acid secretion can be documented. Upper gastrointestinal radiographs demonstrate the characteristic hypertrophic gastric rugae. Histologic features include hypertrophic tortuous gastric glands, basilar cysts, and interstitial round cell inflammation. The natural course of this disease in childhood is usually benign and self-limited. Uncommonly, the course may be severe and require gastric resection. This is in contrast to the adult form, where chronicity and severity is the rule. The etiology of this problem remains unknown. Endoscopy and biopsy are the diagnostic procedures of choice, although laparotomy may be necessary in equivocal cases. Therapy should be supportive except for those few patients who require surgery to control hemorrhage.

Child↗
PubMed1980

Evidence for a subset of rheumatoid factors that cross-react with DNA-histone and have a distinct cross-idiotype.

Cross-reactivity of a monoclonal rheumatoid factor with an antigen present on IgG and DNA-nucleoprotein was demonstrated, and evidence presented that the combining site of the antibody was involved in the reaction. The antigen on the DNA-nucleoprotein was shown to involve both DNA and histone fraction H2A + H2B and was trypsin sensitive. The relative binding affinity of the antibody appeared to be greater for IgG than the DNA-histone antigen. Similar polyclonal cross-reactive rheumatoid factors were found in a variety of diseases. A high incidence was found among patients with rheumatoid arthritis and mixed connective tissue disease. None were detected in patients with systemic lupus erythematosus and idiopathic cryoglobulinemia. Studies on one representative isolated polyclonal rheumatoid factor demonstrated the same reactivity with DNA-histone H2A + H2B as the monoclonal antibody. Cross-idiotype studies using antigen-binding inhibition methods demonstrated the same cross-idiotype on the polyclonal and the monoclonal rheumatoid factor which reacted with DNA-histone. This cross-idiotype was shown to be distinct from the cross-idiotypes previously demonstrated on monoclonal IgM proteins with anti-gamma-globulin activity.

Binding Sites, Antibody↗
PubMed1980

Proliferative responses of peripheral blood lymphocytes to polyclonal activation: a comparison of young and elderly individuals.

Associated with human aging is a decline in immune activity, of both the cell-mediated and humoral types. In vivo, autoantibodies increase with aging and antibody responses to flagellin are decreased in the elderly as compared to the young. These abnormalities may be due to defects in helper or suppressor T cells, or innate defects in B cells. In vitro, the proliferative response of B cells to pokeweed mitogen (PWM) is dependent upon T cells. We studied the proliferative response of peripheral blood mononuclear cells (MNC) to polyclonal activation with PWM in young and elderly normal individuals and found that the number of IgA- and IgM-bearing B cells produced was increased in elderly subjects. This difference was statistically significant for IgA-bearing cells when MNC were placed with 5 and 15 microliter of PWM for 5 days and with 15 microliter of PWM for 6 days. Statistically significant increases in IgM-bearing cells were seen when MNC were plased with 5 microliter of PWM for 5 days and 5 and 10 microliter of PWM for 7 days. The differences in numbers of IgG-bearing cells were less consistent. Significant increases were seen when MNC were cultured with 10 microliter of PWM for 5 days and 5 microliter of PWM for 6 days. Our results suggest that in elderly normal individuals numbers of immunoglobulin-bearing cells are increased after polyclonal activation of MNC. This increase in immunoglobulin-bearing B cells associated with reports of in vivo humoral abnormalities suggests that there is loss of regulation of T cells on B cells in normal elderly individuals.

Adult↗
PubMed1976

Fatty acid variability of plasma lipids and cholesteryl esters in adult male twins and their brothers.

Variation in the fatty acid composition of fasting plasma lipids and of cholesteryl esters was studied in 69 sets of adult male twins and 25 of their brothers. Genetic variances were estimated using the twin model. In general, monozygotic (MZ) twins were characterized by the smallest within-pair variance, and brothers of twins by the largest. Variation within dizygotic pairs fell imtermediate to that of MZ twins and brothers. The present study did not reveal consistent significant (P greater than 0.05) genetic variation in plasma fatty acids from total plasma lipids or cholesteryl esters.

Adult↗
PubMedDate not supplied

Time-resolved fluorescence resonance energy transfer studies of DNA bending in double-stranded oligonucleotides and in DNA-protein complexes.

Time-resolved Förster resonance energy transfer (trFRET) has been used to obtain interdye distance distributions. These distributions give the most probable distance as well as a parameter, sigma, that characterize the width of the distribution. This latter parameter contains information not only on the flexibility of the dyes tethered to macromolecules, but on the flexibility of the macromolecules. Both the most probable interdye distance as well as sigma provide insight into DNA static bending and DNA flexibility. Time-resolved fluorescence anisotropy and static anisotropy measurements can be combined to provide a measure of the cone angle within which the tethered dyes appear to wobble. When this motion is an order of magnitude faster than the average lifetime that characterizes transfer, an average value of the dipolar orientational parameter kappa2 can be calculated for various mutual dye orientations. The resulting kappa2 distribution is very much narrower than the limiting values of 0 and 4, allowing more precise distances and distance changes to be determined. Static and time-resolved fluorescence data can be combined to constrain the analyses of DNA-protein kinetics to provide thermodynamic parameters for binding and for conformational changes along a reaction coordinate. The parameter sigma can be used to model multiple DNA-protein complexes with varying DNA bend angles in a global fitting of trFRET data. Such a global fitting approach has shown how the range of bends in single base DNA variants, when bound by the TATA binding protein (TBP), can be understood in terms of two limiting forms. Time-resolved FRET, combined with steady-state FRET, can be used to show not only how osmolytes affect the binding of DNA to proteins, but also how DNA bending depends on osmolyte concentration in the DNA-protein complexes.

DNA↗
PubMedDate not supplied

Forensic toxicology of some orphenadrine-related deaths.

Toxicological data for orphenadrine in ten cases of fatal poisoning are presented together with results for a further eight cases in which orphenadrine was present in combination with alcohol or another drug. Collapse and convulsions occur within an hour of ingestion of an overdose and death supervenes soon after. Autopsy blood concentrations of orphenadrine in such acute fatal poisonings range from 5.5-37 mug/ml. The unchanged drug was found in the bile and urine and the concentrations in the liver, lung and kidney, though differing between cases, were of the same order in any one case.

Adolescent↗
PubMedDate not supplied

Association of foreign DNA with porcine spermatozoa.

The aim of this project was to establish if DNA molecules bind to porcine spermatozoa after incubation in vitro. In an initial experiment, the DNA was mixed with porcine spermatozoa to test for the presence of DNases. From bacterial transformation and gel electrophoresis studies, it was established that the presence of DNases within the sperm or in the sperm suspension was negligible. By the addition of radiolabeled DNA, spanning a large size range, it was demonstrated that the DNA molecules interacted with the sperm during a 15 to 20 min period of incubation. These samples were centrifuged and washed extensively to confirm that the DNA was closely associated with the sperm. Under the experimental conditions used, it was calculated that approximately 3.8 x 10(2) DNA molecules were associated with each spermatozoon. Percoll gradient experiments, which allowed differentiation between motile and nonmotile sperm, showed that motile sperm were more efficient at capturing DNA molecules than nonmotile sperm. In situ hybridization studies revealed that approximately 30% of the motile sperm carried the DNA on their surface, and the associated DNA was attached only to the sperm head with no attachment to the sperm tails. Heterologous foreign DNA can become closely associated in a nonrandom manner with porcine spermatozoa.

Animals↗
PubMedDate not supplied

Effects of electropermeabilization on the association of foreign DNA with pig sperm.

This study was conducted to evaluate the effects of an electric pulse (electroporation/electropermeabilization) on the binding of foreign DNA molecules to porcine spermatozoa. We previously examined various parameters involved in the association of foreign DNA with sperm after a simple incubation procedure and now report the effects of electroporation on this association. Using end-labeled and random primer labeled lambda HindIII DNA fragments (23-0.125 kb), it was demonstrated that the DNA fragments interacted with the sperm after electroporation. These samples were then centrifuged and washed extensively to establish if any of the labeled DNA was associated with the spermatozoa. It was determined that approximately 10(8) molecules of DNA were associated with 1.5 x 10(7) mL-1 motile spermatozoa after five medium washes. After each wash, samples were withdrawn for gel analysis and scintillation counting. Gel analysis followed by autoradiography revealed the distinctive band pattern of lambda HindIII DNA associating with sperm. In situ visualization studies with biotin-labeled DNA revealed that approximately 75% of motile sperm carried DNA bound to the post-acrosomal region. However, the intensity of the binding varied, with some sperm being more strongly stained than others. Using [3H]dCTP-labeled DNA followed by light microscope autoradiography, approximately 70% of the sperm were strongly stained in the post-acrosomal region. There was a 5-10% increase in the amount of DNA bound by sperm when the samples were electroporated.

Animals↗