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Biomedical subjects

J Knapp

Publications and source records attributed to J Knapp.

At least 19 recordsLinked to original sources
PubMed1997

Quantification of replication of clinical cytomegalovirus isolates in cultured endothelial cells and fibroblasts by a focus expansion assay.

A method for quantitative analysis of the growth properties of human cytomegalovirus (HCMV) in various cell culture systems was developed. Recent HCMV isolates are, in most cases cell associated, causing only limited cytopathic effect. This renders comparative analysis of the biological properties of such isolates difficult. The focus expansion assay described in this study is based on cocultivation of infected fibroblasts with a cell type of choice, relying on cell mediated infectivity. The extent of replication of a given isolate in cell culture is quantified by determining the size of resulting infectious foci. Analysis of various clinical isolates and laboratory strains indicated that this assay is a reliable and valid method to define growth properties of HCMV in cell culture. Remarkable differences in the cytopathogenicity of these isolates in fibroblasts as well as in endothelial cells were found. The assay will be useful in studies regarding cell tropism and virulence of recent HCMV isolates and for the quick and easy phenotypic characterization of HCMV deletion mutants.

Antigens, Viral↗
PubMed1997

The effect of the protein phosphatases inhibitor cantharidin on beta-adrenoceptor-mediated vasorelaxation.

1. Cantharidin, an inhibitor of protein phosphatase types 1 (PP1) and 2A (PP2A), increased basal tone of bovine isolated coronary artery rings (CARs) with and without endothelium in a time- and concentration-dependent manner with pEC50 values of about 5.1 and 5.2, respectively, for both preparations. 2. Beta-Adrenoceptor stimulation with isoprenaline (Iso; 0.03-100 microM) or inhibition of phosphodiesterase activity by 3-isobutyl-1-methylxanthine (IBMX; 10-1000 microM), respectively, relaxed CARs precontracted with KCl (75 mM). CARs with and without endothelium showed no difference in the relaxing response to Iso and IBMX, respectively. 3. Cantharidin (3 microM) attenuated vasorelaxation induced by Iso (0.03-100 microM) in CARs with and without endothelium in a time-dependent manner, whereas vasorelaxation induced by IBMX (10-1000 microM) was not attenuated by 3 microM cantharidin. 4. Cantharidin (3 microM) did not affect cyclic AMP content in bovine cultured vascular cells, i.e. coronary artery smooth muscle cells (BCs), aortic endothelial cells (BAECs) and aortic smooth muscle cells (BASMCs), either under basal conditions, after beta-adrenoceptor stimulation (Iso) or inhibition of phosphodiesterase activity (IBMX), respectively. 5. Cantharidin inhibited protein phosphatase activity in homogenates from bovine coronary artery rings with a pIC50 of about 6.0. In homogenates of bovine cultured vascular cells pIC50 values of cantharidin amounted to about 6.5 for BCs, 6.7 for BAECs and 6.7 for BASMCs, respectively. 6. It was concluded that cantharidin differently affects vasorelaxation due to stimulation of beta-adrenoceptors (Iso) or inhibition of phosphodiesterase activity (IBMX), respectively. The attenuation of beta-adrenoceptor-mediated vasorelaxation by phosphatase inhibition is not due to diminished adenosine 3':5'-cyclic monophosphate (cyclic AMP) generation but could be evidence for different subcellular compartments of cyclic AMP.

1-Methyl-3-isobutylxanthine↗
PubMed1997

Practice analysis survey: revalidation of advanced clinical practice in orthopaedic physical therapy.

The first orthopaedic physical therapy practice analysis survey was completed in 1983. Another practice analysis survey was conducted in 1993 to identify the advance practice of clinicians who practice in orthopaedic physical therapy settings. Since 10 years elapsed, a new practice analysis study was conducted to identify the practice of orthopaedic clinical specialists. The purpose of this report is to describe the results of this survey. Orthopaedic physical therapists, both specialists and nonspecialists, participated in group interviews, subject matter expert meetings, and a national practice survey to delineate important knowledges and responsibilities. The survey was.sent to a stratified convenience sample of 1,000 orthopaedic physical therapists, of which 325 were orthopaedic clinical specialists. The three-part survey contained 180 items. A total of 420 respondents, of which 241 were orthopaedic clinical specialists, rated the importance and application level for the items. The results of this study provide evidence for a core body of knowledge required by clinicians practicing with advanced skills in orthopaedic physical therapy and create the framework for the Orthopaedic Physical Therapy Specialty Exam.

Clinical Competence↗
PubMed1996

An improved questionnaire for assessing quality of life after acute myocardial infarction.

This paper reports our experience with the use of an improved self-administered questionnaire for assessing quality of life (QOL) after acute myocardial infarction. The modified questionnaire significantly increased the proportion of patients able to answer all questions from 84%-92%. The additional questions in the improved questionnaire increased the total variance explained by the Emotional, Physical and Social QOL factors from 65.8%-66.5%. Internal consistency and construct validity were assessed and found to be high. Overall, we have found that this improved questionnaire is easy to administer and that it possesses desirable properties of validity and reliability.

Factor Analysis, Statistical↗
PubMed1996

Effects of cantharidin on force of contraction and phosphatase activity in nonfailing and failing human hearts.

1. The effect of the phosphatase inhibitor, cantharidin (3-300 microM) on force of contraction was studied in isolated electrically driven right ventricular trabeculae carneae from human myocardium. 2. The positive inotropic effect of cantharidin started at a concentration of 100 microM with a positive inotropic effect to 199% and to 276% of the predrug value in nonfailing and failing human hearts, respectively. 3. Under basal conditions the contraction time parameters were prolonged in human heart failure vs. nonfailing preparations. However, the positive inotropic effect of cantharidin did not affect contraction time parameters. Thus, time to peak tension, time of relaxation and total contraction time were not shortened by cantharidin in nonfailing and failing preparations. 4. The phosphatase activity was unchanged in preparations from failing hearts compared to nonfailing hearts. 5. Cantharidin inhibited phosphatase activity in a concentration-dependent manner. The IC50 value of cantharidin was about 3 microM in both nonfailing and failing human myocardium. 6. The positive inotropic effect of cantharidin was similar in nonfailing and failing human hearts, accompanied by a similar inhibitory effect of cantharidin on the phosphatase activity. The positive inotropic effect of cantharidin in failing hearts was as strong as the effect of isoprenaline in nonfailing hearts. 7. It is concluded that the treatment with a phosphatase inhibitor may offer a new positive inotropic modality for the treatment of human heart failure.

Analysis of Variance↗
PubMed1996

Negative chronotropic and inotropic effects exerted by diadenosine hexaphosphate (AP6A) via A1-adenosine receptors.

1. Diadenosine hexaphosphate (AP6A) exerts vasoconstrictive effects. The purpose of this study was to investigate whether AP6A has any effect on cardiac function. 2. The effects of AP6A (0.1-100 microM) on cardiac contractility and frequency were studied in guinea-pig and human isolated cardiac preparations. Furthermore, the effects of AP6A on the amplitude of the L-type calcium current, on the adenosine 3':5'-cyclic monophosphate (cyclic AMP) content and on the phosphorylation of regulatory phosphoproteins, i.e. phospholamban and troponin inhibitor, were investigated in guinea-pig isolated ventricular myocytes. 3. In isolated spontaneously beating right atria of the guinea-pig AP6A exerted a negative chronotropic effect and reduced the rate of contraction maximally by 35% (IC20 = 35 microM). 4. In isolated electrically driven left atria of the guinea-pig AP6A exerted a negative inotropic effect and reduced force of contraction maximally by 23% (IC20 = 70 microM). 5. In isolated electrically driven papillary muscles of the guinea-pig AP6A alone was ineffective, but attenuated isoprenaline-stimulated force of contraction maximally by 23% (IC20 = 60 microM). Furthermore, AP6A attenuated the relaxant effect of isoprenaline. 6. In human isolated electrically driven ventricular preparations AP6A alone was ineffective, but attenuated isoprenaline-stimulated force of contraction by maximally 42% (IC20 = 18 microM). Moreover, AP6A attenuated the relaxant effect of isoprenaline. 7. All these effects of AP6A were abolished by the selective A1-adenosine receptor antagonist 1,3-dipropyl-cyclopentyl-xanthine (DPCPX, 0.3 microM), whereas the M-cholinoceptor antagonist atropine (10 microM) and the P2-purinoceptor antagonist suramin (300 microM) failed to abolish the effects of AP6A. 8. AP6A 100 microM had no effect on the amplitude of the L-type calcium current, but attenuated isoprenaline-stimulated L-type calcium current. The maximum of the current-voltage relationship (I-V curve) was shifted to the left by isoprenaline and additional application of AP6A shifted the I-V curve back to the right to the control value. The phosphorylation state of phospholamban and the troponin inhibitor was unchanged by AP6A alone, but was markedly attenuated by AP6A in the presence of isoprenaline. Cyclic AMP levels remained unchanged by AP6A, even after stimulation with isoprenaline. 9. In summary, AP6A exerts negative chronotropic and inotropic effects in guinea-pig and human cardiac preparations. These effects are mediated via A1-adenosine receptors as all effects were sensitive to the selective A1-adenosine receptor antagonist DPCPX. Furthermore, the effects of AP6A on cyclic AMP levels, protein phosphorylation and the L-type calcium current are in accordance with stimulation of A1-adenosine receptors.

Animals↗
PubMed1995

In vivo isoproterenol treatment leads to downregulation of the mRNA encoding the cAMP response element binding protein in the rat heart.

The expression of different myocardial regulatory proteins is altered in human heart failure, e.g., beta 1-adrenoceptors, G-proteins and others. Similar changes in rats after 4 days treatment with isoproterenol led to the hypothesis of the cAMP pathway involved in these changes. In different cell types cAMP-dependent transcriptional activation is mediated by the cAMP-response element binding protein (CREB) which was recently shown to be expressed and phosphorylated in the human heart. Here, by the reverse transcriptase-polymerase chain reaction two alternatively spliced isoforms of CREB mRNA were found to be expressed in rat ventricles. Both isoforms were down-regulated in the ventricles of rats treated in vivo with isoproterenol (2.4 mg/kg per day) for 4 days proposing a possible mechanism involved in expressional changes mentioned above.

Adrenergic beta-Agonists↗
PubMed1995

cAMP response element binding protein is expressed and phosphorylated in the human heart.

BACKGROUND: In end-stage failing human hearts and in rat hearts after prolonged in vivo beta-adrenergic treatment, several proteins involved in the cAMP-dependent signal transduction are altered on the protein, mRNA, or transcriptional level, eg, beta-adrenoceptors, G-proteins, or proteins of Ca2+ homeostasis. In many tissues, cAMP-dependent transcriptional regulation occurs through the cAMP response element binding protein (CREB) and related transcription factors binding as dimers to cAMP response elements (CREs) in the promoter regions of regulated genes. METHODS AND RESULTS: To investigate a possible role of CREB in the human heart, nuclear protein of explanted failing and nonfailing human hearts was used to test for CRE specific binding properties in gel mobility shift assays. CRE specific binding was found in competition studies, and CREB and its phosphorylated form were immunologically identified in supershift experiments. The alternatively spliced CREB isoforms CREB327 and CREB341 were found to be expressed on the mRNA level by the reverse transcriptase-polymerase chain reaction. CONCLUSIONS: We conclude that in the failing and nonfailing human heart, CREB is expressed on the protein and mRNA levels and that CREB is phosphorylated and able to bind to CREs, indicating a functional role of CREB in the human heart.

Animals↗
PubMed1994

Autogenic-feedback training: a potential treatment for orthostatic intolerance in aerospace crews.

Postflight orthostatic intolerance has been identified as a serious biomedical problem associated with long-duration exposure to microgravity in space. High priority has been given to the development of countermeasures for this disorder that are both effective and practical. A considerable body of clinical research has demonstrated that people can be taught to increase their own blood pressure voluntarily, and that this is an effective treatment for chronic orthostatic intolerance in paralyzed patients. The current pilot study was designed to examine the feasibility of adding training in control of blood pressure to an existing preflight training program designed to facilitate astronaut adaptation to microgravity. Using an operant conditioning procedure, autogenic-feedback training (AFT), three men and two women participated in four to nine training (15-30-minute) sessions. At the end of training, the average increase in systolic and diastolic pressure, as well as mean arterial pressures, that the subjects made ranged between 20 and 50 mm Hg under both supine and 45 degrees head-up tilt conditions. These findings indicate that AFT may be a useful alternative treatment or supplement to existing approaches for preventing postflight orthostatic intolerance. Furthermore, the use of operant conditioning methods for training cardiovascular responses may contribute to the general understanding of the mechanisms of orthostatic intolerance.

Adult↗
PubMed1994

Sensitization by dexamethasone of lymphocyte cyclic AMP formation: evidence for increased function of the adenylyl cyclase catalyst.

1. Glucocorticoids and elevations of intracellular adenosine 3':5'-cyclic monophosphate (cyclic AMP) may affect lymphocyte activation, proliferation and effector functions in similar ways. Therefore, we have investigated the effects of the glucocorticoid, dexamethasone, on human lymphocyte cyclic AMP formation. 2. Treatment of resting human lymphocytes with the glucocorticoid, dexamethasone, sensitized prostaglandin E2-stimulated cyclic AMP accumulation in a time- and concentration-dependent manner. 3. In membranes of lymphocytes treated for 24 h with 100 nM dexamethasone, maximal adenylyl cyclase activity stimulated by prostaglandin E2, isoprenaline, guanosine 5'-triphosphate (GTP), forskolin and MnCl2 was significantly enhanced; the EC50 for these agents was not significantly altered. 4. beta 2-Adrenoceptor density, immunodetectable alpha-subunits of the G-proteins Gs and Gi, and pertussis toxin-substrates were not significantly altered by dexamethasone treatment. 5. In dexamethasone-treated lymphocytes, prostaglandin E2-mediated inhibition of concanavalin A-induced Ca2+ elevations was doubled compared to control cells. 6. Based on these data and the observation that enhancement of forskolin- and MnCl2-stimulated adenylyl cyclase activity could quantitatively account for the enhancement of prostaglandin E2-, isoprenaline- or GTP-stimulated adenylyl cyclase activity, we conclude that dexamethasone treatment sensitizes cyclic AMP formation in resting human lymphocytes by altering the adenylyl cyclase catalyst rather than G-proteins or hormone receptors. This results in an enhanced capability of cyclic AMP generating agonists to inhibit early steps of lymphocyte activation.

Adenylyl Cyclases↗
PubMed1993

Do not resuscitate.

Explore the source record for details and available documents.

Congenital Abnormalities↗
PubMed1990

Chloroquine poisoning in a child.

Chloroquine poisoning in children, although infrequent, is extremely dangerous because of the narrow margin between therapeutic and toxic doses. Children clinically present with apnea, seizures, and cardiac arrhythmias. We present the case of a 12-month-old infant, the second-youngest patient reported in the US literature to die from chloroquine poisoning. A serum level of 4.4 mg/L (13.64 mumol/L) was obtained after the infant ingested only one tablet (300 mg). This establishes a new minimal lethal dose/blood level for children. Although some pediatric and adult pharmacokinetic and clinical similarities exist, the outcome is different. Pediatric mortality is 80%, whereas adult mortality is only 10%. Pediatric ingestion cases are primarily unintentional, and most adult cases are suicide attempts. Current treatment in adults includes a protocol of diazepam and epinephrine. Further studies involving children and these medications and other modalities are needed to improve survival.

Apnea↗
PubMed1988

Identification and sequence determination of a cDNA clone for tomato pectin esterase.

Cell wall softening during tomato fruit ripening is brought about through the action of a number of pectolytic enzymes. We have reported previously the cloning and characterisation of the cDNA for the major cell wall softening (degrading) enzyme, polygalacturonase [Grierson, D., Tucker, G. A., Keen, J., Ray, J., Bird, C. R. and Schuch, W. (1986) Nucleic Acids Res. 14, 8595-8603]. We have now isolated a cDNA clone for tomato pectin esterase, an enzyme also implicated in cell wall softening. Here we report the structure of this cDNA and compare it with the structure of pectin esterase derived from amino acid sequence experiments [Markovic, O. and Jornvall, H. (1986) Eur. J. Biochem. 158, 455-462]. We have used the pectin esterase cDNA clone to analyse pectin esterase gene expression during development and ripening of normal and mutant fruit.

Amino Acid Sequence↗
PubMed1988

Aromatase is concentrated in the proximal pars distalis of tilapia pituitary.

Aromatase has been identified in the telostean, avian, and mammalian pituitaries, although its cellular location(s) is not yet certain. To address this question, experiments were performed in tilapia (Oreochromis mossambicus), a species which has been well characterized with respect to the intraglandular distribution of the different pituitary cell types. To estimate aromatase, glands were microdissected into rostral pars distalis (RPD), proximal pars distalis (PPD), and neurointermediate lobe (NIL) and organs were cultured in the presence of [3H]androstenedione for 16-24 hr. [3H]Estrogen products were isolated and quantified after ether extraction, hydrolysis with glucuronidase-sulfatase, thin-layer chromatography, and phenolic partition. Authentic estrone or estradiol-17 beta were produced by all pituitary regions and also by the urophyseal region of the spinal cord. Aromatase was two to five times higher in PPD than in RPD or NIL and similar to activity in adjacent hypothalamus-preoptic area (HPOA). Much lower estrogen yields were obtained in cultures of cerebellum, urophysis, and other cord regions. Since the PPD contains most of the somatotropes, these data are consistent with earlier studies implicating GH3/GH4 cell strains as an enriched enzyme source, although its presence in other cell types cannot be ruled out. The unusually high and localized aromatase in tilapia pituitary renders this species a useful model for studying the targets and functional importance of estrogen as a parahormone in the pituitary.

Androstenedione↗