A highly selective synthesis of new alkenylsilsesquioxanes by hydrosilylation of alkynes.

Hydrosilylation of a wide group of mono- and disubstituted (symmetrical and nonsymmetrical) alkynes with 1-dimethylsiloxy-3,5,7,9,11,13,15-heptaisobutylpentacyclo-[9.5.1.13,9.15,15.17,13]octasiloxane ((HSiMe2O)(i-Bu)7Si8O12, 1) in the presence of Karstedt's catalyst (Pt2(dvs)3) has been performed for the first time. A series of new 1,2-(E)-disubstituted and 1,1,2-(E)-trisubstituted ethenes with a silsesquioxane moiety were selectively afforded and fully characterized. On the basis of nuclear magnetic resonance (NMR) and infrared spectroscopy (in situ FT-IR and/or FT-IR), the influence of alkyne structure and reaction conditions on the stereoselectivity as well as on the progress of triple bond hydrosilylation catalyzed by Pt2(dvs)3 was explained. The results of the studies clearly indicated for which reagents the developed procedures lead to alkenylsilsesquioxanes with almost stoichiometric yields in short time, and for which other catalytic systems or methods should be considered.

Antititin antibody in early- and late-onset myasthenia gravis.

OBJECTIVES: Myasthenia gravis (MG) is an autoimmune disease caused by antibodies against neuromuscular junction proteins, 85% of patients have antibodies against acetylcholine receptor (AChR-MG). Antititin antibodies are present in a subset of patients with MG. We aimed to determine the value of antititin antibodies as severity markers and thymoma predictors in early- and late-onset MG. MATERIALS & METHODS: Two-hundred and ninety-five consecutive MG patients (188 F and 107 M) aged 12-89 years (mean 50y) were included. 164 patients had early-onset (EOMG, ≤50 years of age), 131 had late-onset MG (LOMG). Twenty-six patients had thymoma. symptoms, severity graded with MGFA scale, thymus histology, medications, and treatment results were analyzed. RESULTS: Antititin antibodies were present in 81 (27%) of all patients: 54% of thymoma MG, 0.6% of non-thymomatous EOMG, and 55% of LOMG, with proportion of titin-positive patients increasing linearly from 40% in the 6th to 88% in the 9th decade of life. Titin-positive patients had more bulbar symptoms (P = 0.003). Severity of MG, need for immunosuppression, myasthenic crisis risk or treatment results were not related to its presence. Antititin antibodies had 56% sensitivity, 99% specificity, 90% positive predictive value (PPV), and 95% negative predictive value (NPV) for thymoma diagnosis in EOMG, and 50% sensitivity, 75% specificity, 71% PPV and 55% NPV in LOMG. CONCLUSIONS: Antititin antibodies have high PPV and NPV for thymoma in EOMG. In MG without thymoma, antititin antibodies can be considered as markers of LOMG, but not of a severe course in our MG cohort.

Lambert-Eaton myasthenic syndrome in childhood.

Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder of the neuromuscular junction. LEMS can be associated with a variety of neoplasms. Patients present with proximal muscle weakness and fatigability, often combined with areflexia. Only 5% of reported cases are children. We report a case of 11-year old boy with non-neoplastic Lambert-Eaton myasthenic syndrome. Repetitive nerve stimulation test showed 83% increment after maximal voluntary contraction, presence of antibodies against voltage-gated calcium channels confirmed the diagnosis. The boy responded well to immunosuppressive treatment with prednisone and azathioprine and remains cancer-free for 4 years.

MuSK-positive myasthenia gravis is rare in the Polish population.

BACKGROUND AND PURPOSE: MuSK-positive myasthenia gravis (MG) is diagnosed in 0-48% of cases with generalized seronegative MG in different populations. The presence of anti-MuSK antibodies generally relates to a severe course and lack of response to thymectomy. We analyzed for the first time the serology and clinical characteristics of MuSK-positive MG in the Polish population. METHODS: One hundred and fifty-one patients were tested for the presence of anti-AChR and anti-MuSK antibodies: 62 with seronegative MG, including 14 with ocular seronegative MG, 48 age-matched patients with seropositive MG and 41 controls. RESULTS: All patients with seropositive MG and the disease controls were MuSK-negative. Anti-MuSK antibodies were detected only in four patients with seronegative MG (8.7% of generalized seronegative cases): three women and one man. All four had predominantly bulbar involvement, and underwent thymectomy, with no apparent benefit. All of them improved clinically after immunosuppressive treatment with remissions lasting up to 7 years. CONCLUSION: MuSK-positive MG is rare in Polish population accounting for only 8.7% of seronegative cases with generalized MG. This is consistent with emerging evidence for lower MuSK antibodies at more northerly latitudes.

Ribozymes of the hepatitis delta virus: recent findings on their structure, mechanism of catalysis and possible applications.

Although the delta ribozymes have been studied for more than ten years the most important information concerning their structure and mechanism of catalysis were only obtained very recently. The crystal structure of the genomic delta ribozyme turns out to be an excellent example of the extraordinary properties of RNA molecules to fold into uniquely compact structures. Details of the X-ray structure have greatly stimulated further studies on the folding of the ribozymes into functionally active molecules as well as on the mechanism of RNA catalysis. The ability of the delta ribozymes to carry out general acid-base catalysis by nucleotide side chains has been assumed in two proposed mechanisms of self-cleavage. Recently, considerable progress has been also made in characterizing the catalytic properties of trans-acting ribozyme variants that are potentially attractive tools in the strategy of directed RNA degradation.

The delirious cardiac surgical patient: theoretical aspects and principles of management.

Delirium, an etiologically nonspecific disorder of consciousness characterized by prominent deficits in attention, cognition, and perception, affects more than one-third of adult cardiac surgical patients. Despite the frequency of occurrence and the increased morbidity and mortality associated with it, the diagnosis is commonly late or missed, and management is less than optimal. This article addresses the recognition and management of delirium. Nurses who develop an index of suspicion for the diagnosis and acquire the diagnostic and interventional skills required to address this cerebral complication of cardiac surgery may well decrease its incidence and severity.

The changes in bile flow and its composition in sheep following liver damage by carbon tetrachloride.

Sheep were prepared surgically in a manner permitting the measurement of bile flow by preserving its enterohepatic circulation. Carbon tetrachloride (CCl4) was administered intraruminally in a dose 0.5 ml/kg b.w. After CCl4 administration a decrease in bile flow and bile acid excretion was observed. The decrease in bile flow observed after CCl4 administration was lower than the decrease in bile acid output. Thus it can be suggested that in this condition the effects of bile acid output on the bile secretion can be partially abolished and maintaining of relatively high bile flow is connected with an increase in the bile acid-independent bile flow. The increase of the bilirubin concentration in bile was observed after acute liver damage by carbon tetrachloride.

[Effects of carbachol and atropine on bile secretion in sheep]. / Wplyw karbacholu i atropiny na produkcje zólci u owiec.

Experiments were performed on rams prepared surgically to make possible the control of bile flow and the maintenance of enterohepatic circulation of bile components. Carbachol and atropine were infused into the jugular vein for 2 hours in the amounts: 0.3 and 0.7 microgram/kg b.w./min. respectively. Carbachol administration did not affect significantly the bile production. Atropine led to the significant decrease in the bile flow (p less than 0.01) by diminished concentration of bile acids in the bile. On the basis of the obtained results the role of n. vagus in the regulation of biliary secretion is discussed. It is suggested, that in physiological conditions the biliary secretion is, to some extent, maintained as a result of the muscarinic receptor stimulation. This stimulation attains the maximum level and it is not possible to evoke rise in bile production after either n. vagus stimulation or administration of parasympathomimetic agents.