Confirmation that GP Ib-IX complexes have a reduced surface distribution on platelets activated by thrombin and TRAP-14-mer peptide

Summary. In 1990 we reported that GP Ib-IX complexes accumulated within the surface-connected canalicular system (SCCS) of thrombin-stimulated platelets. This conclusion was reached following investigations using monoclonal antibodies (MAbs) in flow cytometry and a polyclonal antibody to GP Iba in electron microscopy with immunogold staining performed on ultrathin sections of resin-embedded platelets. Recent controversy concerning these results has prompted us to perform further studies using 14 anti-GP Ib-IX MAbs obtained from the 1993 Boston Workshop on Leukocyte Antigens. Features were the use of the MAbs in mixtures and the fact that immunogold staining was performed on frozen thin sections. Platelets were stimulated with either a-thrombin or TRAP-14-mer peptide. In all cases a decreased density of GP Ib-IX complexes on exposed areas of the activated platelet surface was accompanied by an increased expression within the SCCS. At the same time we noted that when platelets were stimulated with TRAP-14-mer they progressively exhibited a different internal morphology in comparison to that seen with thrombin. In particular, the dense central mass disappeared and large vacuoles were present throughout the cytoplasm. Overall, these studies confirm that changes in the distribution of GP Ib-IX complexes which follow thrombin-induced platelet activation (i) are indeed observed when antibody mixtures are used to detect them, and (ii) are mediated through the receptor recognized by the TRAP-14-mer peptide.     

Robot-assisted task-specific training in cerebral palsy

Our goal was to examine the feasibility of applying therapeutic robotics to children and adults with severe to moderate impairment due to cerebral palsy (CP). Pilot results demonstrated significant gains for both groups. These results suggest that robot-mediated therapy may be an effective tool to ameliorate the debilitating effects of CP and provide new opportunities for reducing impairment and improving coordination.     

The slow wave does not propagate across the gastroduodenal junction in the isolated feline preparation

Detailed spatial analysis of the propagation of individual slow waves was performed in the isolated gastroduodenal preparation of the cat. Use was made of a system that allowed the simultaneous recordings from 240 extracellular electrodes, which were positioned across the gastroduodenal region. Reconstructions of the spread of propagation (n = 31) revealed that (a) the antral slow wave never propagated into the duodenum but was blocked at the pyloric ring, (b) the duodenal slow wave did not activate the antral tissue, and (c) a quiescent zone in which no slow waves could be recorded was always present at the most proximal part of the duodenum immediately distal to the pyloric ring. Furthermore, phase density distributions of duodenal cycles revealed that antral activity had no influence on the rate of discharge of duodenal pacemakers. Light microscopic study of sections of the duodenum close to the pyloric ring and further away did not show any structural differences between the quiescent zone and the active areas. In conclusion, slow waves do not propagate across the gastroduodenal junction in the isolated feline preparation and therefore do not seem to play a role in the electro-mechanical integration between the stomach and the duodenum.     

Incidence and Predictive Factors of Atrial Fibrillation in Paced Patients

We have designed a prospective observational study to analyze the incidence and predictive factors of atrial fibrillation (AF) during a long follow-up, in a large population. Atrial fibrillation episodes were documented by the fallback mode switch (FMS) provided by implanted pacemakers. We have included 377 patients (61% men). The pacing indications were atrioventricular (AV) block (49%), sinus node disease (SND, 16%), bradycardia-tachycardia syndrome (BTS, 5%), AV block + SND (19%), AV block + BTS (6%), and BTS + SND (5%). The mean age at implant was 75 ± 12 (range 28–95). Atrial fibrillation before inclusion was documented in 10% of patients. Drug therapy at first follow-up included beta-adrenergic blockers (17% of the patients), amiodarone (13%), and others (16%). The mean follow-up was 30 ± 24 weeks. At least one AF episode was stored during follow-up in the memory of 169 pacemakers (45%). Among patients without history of AF at implant, 46% had documented FMS during follow-up. Patients with AF received more antiplatelet medications than patients without AF (P = 0.03). In patients with AF, New York Heart Association functional class was slightly higher, amiodarone and sotalol were more often prescribed, and the proportion of hypertension was higher than in patients without AF. However, these trends were not statistically significant. A significant higher incidence of premature atrial beats was observed in patients with AF than patients without AF (P < 0.0002). Patients with AF had a lower atrial percentage of paced events (55%) than patients without AF (63%, P < 0.02). These preliminary results confirm the high incidence of AF in paced patients and suggest a preventive effect of atrial pacing. The effects of other clinical variables may be confirmed with a longer follow-up in a larger population.     

Direct evidence for dissociated megakaryocytic chimaerism in a Wiskott-Aldrich patient successfully allografted

Summary. We report a Wiskott-Aldrich patient who underwent allogeneic bone marrow transplantation from his HLA-identical sister at the age of 25. Conditioning regimen consisted of cyclophosphamide (180mg/kg) and thoracoabdominal irradiation (6 Grays). Cytogenetic follow-up revealed rapid and complete lymphoid chimaerism, but prolonged mixed bone marrow chimaerism. Correlative interphase cytogenetics performed on bone marrow smears using dual-colour fluorescence in situ hybridization with × and Y specific probes showed that the proportion of donor cells was significantly higher within megakaryocytes than in other lineages. This patient therefore presented with dissociated lineage engraftment, which is not exceptional in congenital diseases and aplastic anaemia, but has not previously been described in Wiskott-Aldrich syndrome. Bone marrow transplantation was successful despite this delayed engraftment which ensured adequate production in the involved cell lines.     

Crystal structure analysis of a β-turn mimic in hydrazino peptides

The crystal structures of four hydrazino peptides (Piv-Pro-h(N^α-Bzl)Gly-NHiPr 1 , Piv-Pro-hAla-NHiPr 2 , Moc-hPro-NHiPr 3 , and Boc-hPro-Gly-N(OH)Me 4 ) deriving from the hydrazino analogues of glycine (hGly), l -alanine (hAla) or l -proline (hPro) have been solved. They reveal a common folded structure of the α-hydrazino acid residue characterized by a bifurcated hydrogen bond closing an eight-membered cycle. This folded structure is topologically similar to the βII′-turn in peptides, and the CO-NH-N hydrazide link can be considered as a good turn-inducer in peptide analogues.     

Effect of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) on Influenza Virus Host Resistance in Mice

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) causes numerous immunotoxiceffects including thymic involution and an immunosuppressionof nonspecific as well as specific cell- and humoralmediatedimmunity. TCDD administration to laboratory animals also resultsin a decreased resistance to numerous bacteria, viruses, andparasites. Effects on virus host resistance appear to be amongthe most sensitive effects of TCDD immunotoxicity. However,previous studies have not achieved a no effect level. The presentstudies utilized an influenza virus host resistance model inmice to quantify the sensitivity of this model to TCDD and todetermine the NOAEL (no observed adverse effect level) of TCDDfor influenza virus. Results indicated that a single dose ofTCDD at 0.10, 0.05, or 0.01 µg/kg resulted in an increasedmortality to Hong Kong influenza virus when mice were challenged7 days after TCDD administration. Increased mortality was notcorrelated with increased virus titers in the lungs. TCDD at0.005 or 0.001 µg/kg had no effect on influenza-inducedmortality. TCDD alone did not affect thymus weight at any doseadministered in this study. TCDD also did not alter the virus-enhancedincrease in lung weight:body weight ratio nor the virus-induceddecrease in thymus weight. Thus, low levels of TCDD exposurelead to enhanced mortality to influenza virus; however, themechanism of this effect remains to be elucidated. Nonetheless,enhanced mortality to influenza virus in mice following a singledose of 10 ng TCDD/kg represents the most sensitive adverseeffect yet reported for TCDD.     

Chronic Haemolytic Anaemia in Two Patients Heterozygous for Erythrocyte Pyruvate Kinase Deficiency

Two patients with mild chronic haemolytic anaemia, a mother and her son, were found to be heterozygous for erythrocyte pyruvate kinase deficiency. In the red blood cells the enzymatic activity was reduced by about 50 % and the residual PK had normal kinetic properties, stability and electrofocusing pattern. The PK antigen concentration was also decreased by half, so that the ratio of the enzymatic activity to the immunological reactivity (i.e. the molecular specific activity) was normal. In the son's liver PK enzymatic activity was slightly reduced and, above all, an abnormal active form, more anodic than normal PK, was detected by electrofocusing. The propositus's liver PK was also slightly thermo-unstable. It is suggested that the patients were heterozygous for an unstable PK variant which is found in liver, nucleated tissue actively synthesizing proteins, but which disappeared from the erythrocytes because of its unstability.