Experimental animal model of refractoriness to donor platelets: the effect of plasma removal and the extent of white cell reduction on allogeneic alloimmunization

Platelet transfusion effectiveness may be limited in multiply transfused patients by the development of the refractory state. White cell (WBC)-reduction filters with variable efficiency (1-3 log10 reduction) are available and have been shown to be effective in reducing the incidence of platelet alloimmunization. However, the threshold number of WBCs below which alloimmunization would no longer occur is yet to be determined. A previously established animal model was used to examine the relative efficiency of second- and third- generation filters in reducing the frequency of refractoriness to allogeneic platelets. In this model, California Black rabbits are used as blood donors and New Zealand White rabbits as transfusion recipients. Eight weekly transfusions of either second-generation or third-generation WBC-reduced blood resulted in no difference between the two groups in mean platelet survival and rate of refractoriness to allogeneic platelets. To evaluate the possible incremental benefit of removing supernatant plasma to prevent platelet refractoriness, experiments were performed in which groups of animals were given transfusion(s) with red cell suspensions that had been WBC-reduced or both plasma-depleted and WBC-reduced. A significantly lower rate of allogeneic platelet refractoriness was seen in the rabbits that received WBC-reduced and plasma-depleted red cells than in those that received red cells that had been WBC-reduced only. These data provide evidence that the combined use of plasma depletion and WBC reduction can decrease still further the frequency of refractoriness produced by allogeneic blood transfusions.     

Successful Results of a Bipolar Active Fixation Lead for Atrial Application: An Interim Analysis

Adequate atrial lead performance consists of stable sensing and pacing properties. To evaluate whether the CPI 4269 bipolar lead, covered with mannitol (Sweet Tip), in the atrial position encounters these properties, we performed a prospective study of this lead. After complete dissolution of the mannitol helix, mapping of the atrium to obtain the highest electrogram and lowest threshold was followed by screw-in into the endocardium. Intraoperative measurements were performed and long-term follow-up was scheduled every 6 to 12 months to measure threshold and perform an intracardial electro-gram. Between February 1993 and December 1996, a total number of 73 leads in the atrial position in a consecutive series of patients was implanted. Implantation was performed in 28 patients receiving an AAIR and 45 patients a DDDR pacemaker. Reason for pacemaker implantation was a third-degree AV block in 37% of patients, type II second-degree AV block in 25%, sick sinus syndrome in 35%, and drug refractory paroxysmal atrial fibrillation following His-bundle ablation in 3%. The intraoperative bipolar atrial electrogram had a mean voltage of 4.25 ± 2.1 mV. The acute atrial bipolar threshold was 0.63 ± 0.43 V, and current was 1.35 ± 0.81 mA at a 1.0-ms pulse duration. The mean acute resistance of the lead was 572 ± 86 Ohm. After a mean follow-up of 18.3 months, the bipolar intracardial electrogram was 3.37 ± 2.00 mV, the mean atrial threshold measured at the last outpatient clinic visit was 0.99 ± 0.74 V and the mean impedance was 640 ±127 Ohm. A sensing problem due to traction of the atrial lead occurred in only one patient. Acute and late dislodgement did not occur. The CPI 4269 (Sweet Tip) lead is manufactured with a dissolvable capsule covering the helix tip electrode, permitting a safe passage through the venous system. This interim analysis shows that this lead in the atrial position has favorable acute and chronic results.     

The morphofunctional characteristics of the duodenum in an osteopenic syndrome in children and adolescents

AIM: The study of duodenal morphology in children and adolescents with skeletal deformity. MATERIALS AND METHODS: Clinical, hormonal examinations, x-ray investigation of the skeleton with spinal NMR-tomography, gastroduodenoscopy with target biopsy were performed in 41 patients aged 7 to 18 on after treatment for broken spine. RESULTS: Atrophic duodenitis found in most of the patients presented without dyspepsia, with symptoms of duodenitis in 8 patients, osteoporosis in 36% of patients. NMR-tomography rejected compression-broken spine in 22 patients. CONCLUSION: Disturbed absorption of calcium and atrophic alterations in the duodenal mucosa are thought responsible for disturbance of calcium metabolism and formation of bone tissue.     

Giant combined pigmented dysplastic nevus

A giant congenital pigmented nevus combining an epidermal and a blue nevus is described in a boy. Since the lesions were extensive, multiple, and showed predominantly cell proliferation in the absence of pronounced anaplasia, the condition was diagnosed as a dysplastic nevus syndrome. Because the nevus was dysplastic, congenital, and of giant size, the child ran a high risk of developing malignant melanoma.     

Stem and Progenitor Cell Expansionin Co-culture of Mobilized CD34~ Cells and Osteopetrotic Mouse Stroma

1 IntroductionCulture systems capable of expanding and/or maintaining hematopoietic stem cells will not only facilitate our understanding of stem cell biology, but also broaden clinical applications. Among various in vitro hematopoietic culture systems, co-cultures of marrow or CD34~ cells with an adherent stromal layer that can produce cytokines and extracellular matrix components most effectively supports long-term hematopoiesis (LTC), mimicking the bone marrow micro-environment.The OP-9 stromal cells ar...     

Effect of Whitening Agents on Dentin Bonding

Background: Several studies have shown a reduction in enamel bond strengths when the bonding procedure is carried out immediately after vital bleaching with peroxides. This reduction in bond strengths has become a concern in cosmetic dentistry with the introduction of new “in‐office” and “waiting‐room” bleaching techniques. The aim of this in vitro study was to evaluate the effect of three bleaching regimens: 35% hydrogen peroxide (HP), 35% carbamide peroxide (CP), and 10% CP, on dentin bond strengths. Materials and Methods: One hundred and twenty fresh bovine incisors were used in this study. The labial surface of each tooth was ground flat to expose dentin and was subsequently polished with 600‐grit wet silicon carbide paper. The remaining dentin thickness was monitored and kept at an average of 2 mm. The teeth were randomly assigned to four bleaching regimens (n = 30): (A) control, no bleaching treatment; (B) 35% HP for 30 minutes; (C) 35% CP for 30 minutes; and (D) 10% CP for 6 hours. For each group, half of the specimens (n = 15) were bonded with Single Bond/Z100 immediately after the bleaching treatment, whereas the other half was bonded after the specimens were stored for 1 week in artificial saliva at 37°C. The specimens were fractured in shear using an Instron machine. Results: For the groups bonded immediately after bleaching, one‐way analysis of variance (ANOVA) followed by the Duncan's post hoc test revealed a statistically significant reduction in bond strengths in a range from 71% to 76%. For the groups bonded at 1 week, one‐way ANOVA showed that group B (35% HP for 30 min) resulted in the highest bond strengths, whereas 10% CP resulted in the lowest bond strengths. Student's t‐test showed that delayed bonding resulted in a significant increase in bond strengths for groups B (35% HP) and C (35% CP); whereas the group bleached with 10% CP (group D) remained in the same range obtained for immediate bonding. Storage in artificial saliva also affected the control group, reducing its bond strengths to 53% of the original.     

Beta-adrenergic signalling and threshhold adrenaline concentration for induction of fibrillation in the perfused heart pretreated with antihypertensive drugs

Recent investigations have shown that antihypertensive drug treatment leads to enhanced myocardial #-adrenoceptor sensitivity. This study was therefore conducted to establish whether or not such hypersensitivity might trigger myocardial arrhythmia subsequent to adrenaline exposure. Adult male Wistar rats (n=6 per group) were treated with either placebo (vehicle), metoprolol (2.40 mg·kg^-1·day^-1), timolol (0.075 mg·kg^-1·day^-1), verapamil (5.50 mg·kg^-1·day^-1) or enalapril (0.50 mg·kg^-1·day^-1) for 20 consecutive days. Hearts were excised and perfused ad modum Langendorff in the presence of an adrenaline gradient (0-300 nM) for 20 min with either 3.0 mM or 5.9 mM of potassium in the perfusion buffer. Adrenaline threshold concentration (ATC, nanomolar) at myocardial fibrillation was recorded, as well as tissue cAMP contents, #-adrenoceptor number, G-protein levels and signalling effector enzyme activities. The main findings were: (1) ATC and cAMP levels were affected in hearts perfused with low-concentration potassium buffer only. In terms of ATC, the beneficial effect of each drug regimen appeared to be in the rank order of: placebo=enalapril>verapamil>timolol>metoprolol. There was an inverse correlation between ATC and myocardial cAMP contents at the start of fibrillation; (2) Subsequent to fibrillation, #-adrenoceptor number, hormone-elicited adenylate cyclase activities and G_s!:G_i2!-ratio were no different from preperfusion values; (3) Significant inverse correlations between #₁-adrenoceptor numbers and ATC were observed. We conclude that alterations in #-adrenoceptor number, G proteins and cAMP induced by antihypertensive drugs are predictive of the myocardial sensitivity to adrenaline in terms of time to continuous and irrevocable fibrillation.