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R Thomas

Publications and source records attributed to R Thomas.

At least 379 records · Page 21Linked to original sources
PubMed1995

Evidence for the involvement of cyclic AMP in the pheromonal modulation of barnacle settlement

The involvement of cyclic AMP in the settlement of the cypris larva of Balanus amphitrite amphitrite Darwin has been examined through the use of compounds that affect intracellular cyclic AMP levels. The activation of adenylate cyclase with forskolin, and the inhibition of phosphodiesterase with 3-isobutyl-1-methylxanthine, caffeine and theophylline, significantly increased the settlement of cyprids. Although the analogue dibutyryl cyclic AMP appeared to increase settlement, the effect was not significant. No marked increase in settlement resulted from the incubation of cyprids with dibutyryl cyclic GMP, 8-(4-chlorophenylthio) (CPT) cyclic AMP or papaverine (a phosphodiesterase inhibitor). Miconazole nitrate, an adenylate cyclase inhibitor, prevented settlement, but this effect appeared to be physico-chemical rather than pharmacological. Radioimmunoassay did not clearly show whether cyclic AMP levels changed following exposure of cyprids to a pulse of crude barnacle extract. However, exposure to forskolin significantly increased the cyclic AMP titre of cyprids. We conclude that compounds that alter intracellular cyclic AMP levels alter normal patterns of cyprid settlement. Whether this is because of an alteration in signal transduction is unclear.

Journal Article↗
PubMed1995

A perfluorocarbon emulsion prime additive improves the electroencephalogram and cerebral blood flow at the initiation of cardiopulmonary bypass.

Depression in electroencephalogram (EEG) has been documented clinically and is reproducible in swine at the initiation of cardiopulmonary bypass (CPB) utilizing a crystalloid prime. The physiological cause of this transient alteration in electrical brain activity appears to be associated with the transient drop in arterial pressure. The etiology is unknown but may be attributable to the bolus of the crystalloid prime or micro emboli, either air or fibrin-platelet. Thirteen swine (17-26 kg) were anesthetized and received 4 mg/kg dexamethasone, and following a tracheotomy were ventilated with halothane in 100% O2. Surgical preparation included: sternotomy and preparation for right atrial-aortic CPB. The CPB circuit consisted of a hollow fiber membrane oxygenator, a hard-shell venous reservoir, a roller pump, and PVC tubing. The circuit was randomly primed with either 1200 ml Plasmalyte-A or 10 ml/kg perfluorocarbon emulsion (PFE) and Plasmalyte-A to total 1200 ml. The animals were monitored continuously for systemic hemodynamics and electrocardiogram, and cerebral monitoring included blood flow and bitemporal EEG. Arterial blood gases were measured and PaCO2 was kept between 30-45 mmHg both before and during CPB. Cerebral blood flow (CBF) was measured pre-CPB and at 10 minutes after initiation of CPB. Bitemporal computerized EEG was analyzed every 60 seconds. Total power of each hemisphere, power in frequency bands, and spectral edge were recorded. All animals demonstrated a relative decrease in EEG total power at the onset of CPB. Animals that received PFE demonstrated a more stable arterial blood pressure, an increased CBF, and a lesser decrease and an earlier recovery of the EEG power.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Detection of Lewis, P1, and some MNS blood group system antibodies by a solid phase assay.

Some solid phase red cell adherence (SPRCA) assays are designed to detect IgG antibodies to red blood cell (RBC) antigens. These assays use anti-IgG-coated red cells as the indicator. It is reported that most antibodies to Lea, Leb, P1, M, and N fail to react by solid phase (SP), presumably because they are IgM antibodies. Those detected are assumed to be IgG. In one year, during routine testing using SPRCA to screen patients for intended RBC transfusion, 28 of 59 such examples were found to react: anti-Lea(9), -Leb(1), -M(14), -N(1), and -P1(3). A study was undertaken to determine if reactivity was due to crosslinking by IgM antibodies of antigen-positive indicator RBCs to antigen-positive reagent RBC monolayers, or due to detection of IgG antibodies. Antibodies were tested according to standard SP protocols, except where IgG-neutralized indicator RBCs were substituted for anti-IgG-active indicator cells. The 59 samples were retested with antigen-positive and antigen-negative indicator RBCs. Only 5 of 59 reacted optimally when antigen-positive indicator cells were used: anti-Lea(2), -Leb(1), -M(1), and -N(1). The reactions of all antibodies were abolished when the anti-IgG component of the indicator was neutralized by soluble IgG. These findings show that detection of most Lewis, P1, M, and N antibodies by SPRCA is dependent on the presence of an IgG antibody in the serum.

Journal Article↗
PubMed1995

[Cardiac tuberculoma; value of echocardiography and therapeutic management apropos of a case].

The authors report the case of a patient with a large mass in the right ventricle which was a tuberculoma without pulmonary disease. The severity of the right ventricular obstruction required surgical intervention with quadri-antitubercular therapy. Myocardial tuberculomas are very rare and usually reported as post-mortem findings. Only four cases resulting in cure have been previously reported. Current means of investigation such as echocardiography and endomyocardial biopsy allow rapid diagnosis of these tumours and should lead to better medical management with possible surgical intervention and a higher therapeutic success rate.

Adult↗
PubMed1995

Nursing on the net.

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Computer Communication Networks↗
PubMed1995

Pheochromocytoma and secondary erythrocytosis: role of tumour erythropoietin secretion.

Certain neoplasias can induce unregulated erythropoietin (EPO) secretion which results in secondary erythrocytosis. Pheochromocytoma associated with erythrocytosis constitute a rare condition, where the secondary red cell abnormality is believed to be due to tumour EPO secretion. In one such case of pheochromocytoma related erythrocytosis, quantitative determination of serum EPO by enzyme immunoassay was combined with immunohistochemical examination of tumour tissue sections to locate the site of EPO secretion. EPO levels were initially high but decreased after tumour surgery, while immunolocalization showed EPO to be secreted by the neoplastic cells.

Adrenal Gland Neoplasms↗
PubMed1995

The forgotten indwelling ureteral stent: a urological dilemma.

Ureteral stents are an integral part of urological practice. However, stents that migrate, fragment or are forgotten pose a management and legal dilemma. Our series consists of 31 patients, 22 with forgotten stents that were left indwelling for more than 6 months (mean 22.7) and 9 migrated stents. Of the forgotten stents 15 (68%) were calcified, 10 (45%) were fragmented, and 3 (14%) were calcified and fragmented. Procedures to render the patient stent-free were ureteroscopy in 16 (52%), percutaneous nephroscopy in 8 (26%), cystoscopic electrohydraulic lithotripsy in 6 (19%), extracorporeal shock wave lithotripsy in 10 (32%), open cysto-litholapaxy in 1 (3%) and simple nephrectomy in 1 (3%). Multiple procedures were required in 6 patients (19%). Management of such complicated ureteral stents requires a multimodal therapeutic approach incorporating the latest in extracorporeal shock wave lithotripsy and endourological techniques. These patients are at increased risk for loss of renal function. A computerized tracking registry of ureteral stents may help prevent this urological travesty.

Adult↗
PubMed1995

The start in speed skating: from running to gliding.

The purpose of this study was to describe the push-off kinematics in speed skating using three-dimensional coordinates of elite male sprinters during the first part of a speed skating sprint. The velocity of the mass center of the skater's body VC, is decomposed into an "extension" velocity component VE, which is associated with the shortening and lengthening of the leg segment and a "rotational" velocity component Vr, which is the result of the rotation of the leg segment about the toe of the skate. It can be concluded that the mechanics of the first strokes of a sprint differ considerably from the mechanics of strokes later on. The first push-offs take place against fixed location on the ice. In these "running-like" push-offs the contribution of Vr in the forward direction is larger than the extension component Ve. Later on, the strokes are characterized by a gliding push-off in which Ve increases. In these gliding push-offs no direct relation exists between forward velocity of the skater and the extension in the joints. This allows skaters to obtain much higher velocities than can be obtained during running.

Acceleration↗
PubMed1994

Human peripheral blood dendritic cell subsets. Isolation and characterization of precursor and mature antigen-presenting cells.

Dendritic cells (DC) are the major APC capable of stimulating resting T cells in human peripheral blood (PB). Recent evidence suggested that various subsets of DC and monocytes might circulate in human PB, but their exact phenotype and function had not been delineated. We have previously characterized a population of human PB DC precursors that express the myeloid marker CD33, but not the monocyte marker CD14. To identify and characterize further functional myeloid APC subsets, triple color FACS analysis and sorting was used. A CD33dimCD14dimCD16+ monocyte subset, with similar APC function but less efficient accessory function than CD14bright monocytes, was isolated. In addition to the CD33+CD14dimCD16- DC precursors, a smaller population (0.1 to 0.2% of PBMC) of CD33brightCD14dimCD16- cells with potent APC function was identified. This DC population expressed greater amounts of MHC class II, adhesion, and accessory molecules, and demonstrated a greater costimulatory capacity when freshly isolated than CD33dimCD14dim DC precursors, and therefore had the characteristics of mature, possibly tissue-derived DC. When freshly isolated, however, these DC did not express B7, and up-regulation of accessory function occurred after in vitro differentiation. These data demonstrate multiple circulating myeloid accessory and APC subsets in human PB. Phenotypic and functional differences suggest that they are at different stages of differentiation, and have specialized roles in Ag presentation in vivo. Furthermore, full functional DC differentiation, associated with B7 expression and the capacity to activate T cells maximally, is likely to occur only in specific physiologic circumstances.

Antigens, CD↗
PubMed1994

[Epidemic bacterial meningitis in adults and the elderly].

Epidemic bacterial meningitis in the adult and the elderly are essentially due to Streptococcus pneumoniae. Neisseria meningitidis and Listeria monocytogenes. Their poor prognosis is mainly due to the severity of the associated encephalitis, responsible for neurological sequelae and for mortality ranging from 20 to 30% in pneumonococcal and Listeria meningitis. Treatment associates an antibiotic having rapid antibactericidal action in the CSF, suppression of possible foci of primary infections and intensive care required by the frequency of associated visceral insufficiency. Present research is centered on: 1. the appearance and progression of pneumococcal lines resistant to penicillin; 2. the trials of modulators of the inflammatory response, notably dexamethasone; 3. the improvement of antibiotic concentrations in the CSF and the cerebral parenchyma, particularly in listeria infection.

Adult↗
PubMed1994

Assessment of a positive selection technique using an avidin column to isolate human peripheral blood T cell subsets.

The current studies were designed to assess a new technique for positively selecting human T cells from whole peripheral blood mononuclear cells using the minimal amount of monoclonal antibody required to bind the T cell to an avidin column indirectly via a biotin-conjugated secondary antibody. Positive selection of T cells has previously been avoided because the saturating amounts of antibodies required for other isolation procedures can lead to aberrant results in assays of T cell activation and function. The avidin column technique for obtaining purified T cell subsets was compared to a multi-step procedure that included negative selection panning. The positive selection technique was easily performed within 4 h whereas the negative selection technique required a minimum of 12 h to complete. The avidin column technique proved to be a rapid and simple method for isolating T cell subsets of high purity and normal functional capabilities. Since minimal amounts of monoclonal antibodies were used for the purification protocol, no consistent inhibitory or stimulatory effect of the residual antibody was noted in assays of activation and proliferation of positively selected T cells compared to T cells isolated by negative selection panning.

Adult↗
PubMed1994

Reagan's revenge.

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Financing, Government↗