Charles University in Prague

About: Charles University in Prague is a education organization based out in Prague, Czechia. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 32392 authors who have published 74435 publications receiving 1804208 citations.

Polyaniline nanotubes: conditions of formation

Abstract: The courses of aniline oxidation with ammonium peroxydisulfate in aqueous solutions of strong (sulfuric) and in weak (acetic) acids, followed by temperature and acidity changes, are different. In solutions of sulfuric acid, granular polyaniline (PANI) was produced; in solutions of acetic acid, PANI nanotubes were obtained. The external diameter of the nanotubes was 100–300 nm, the internal cavity 20–100 nm, and the length extended to several micrometres. The morphology of PANI, granular or tubular, depends on the acidity conditions during the reaction rather than on the chemical nature of the acid. PANI nanotubes were also produced when aniline was oxidized in the absence of any acid. The bulk conductivity of PANI prepared in solutions of acetic acid was 0.08–0.27 S cm−1, depending on the acid concentration. Protonated PANI prepared in sulfuric and acetic acids were deprotonated with ammonium hydroxide to obtain PANI bases and the ammonium salt of the protonating acid. FTIR spectroscopy showed the differences in the molecular structure of the PANI bases. Irrespective of whether the polymerization was performed in solutions of sulfuric or acetic acid, PANI had hydrogen sulfate counter-ions only. The PANI morphology is thus not controlled by the nature of counter-ions. The acidity of the reaction medium determines the protonation of monomer, oligomer and polymer species. The chemistry of aniline oxidation is likely to be affected especially by the protonation of an intermediate in the pernigraniline form. It is proposed that, in the course of aniline oxidation, pH-dependent self-assembly of aniline oligomers predetermines the final PANI morphology. Copyright © 2005 Society of Chemical Industry

Effect of cadmium salts on testicular tissue.

Abstract: THE physiological action of cadmium salts has been studied extensively by many authors. Morphological disturbances have been described in various organs (liver, kidney, etc.). While studying the effect of cadmium salts on protein metabolism one of us (J. P.) observed that cadmium chloride administered subcutaneously to rats produces macroscopic lesions of the testes. This seems to have escaped the notice of previous authors and therefore this phenomenon was studied more closely.

Progesterone vaginal gel for the reduction of recurrent preterm birth: primary results from a randomized, double‐blind, placebo‐controlled trial

Abstract: Objective Preterm birth is the leading cause of perinatal morbidity and mortality worldwide. Treatment of preterm labor with tocolysis has not been successful in improving infant outcome. The administration of progesterone and related compounds has been proposed as a strategy to prevent preterm birth. The objective of this trial was to determine whether prophylactic administration of vaginal progesterone reduces the risk of preterm birth in women with a history of spontaneous preterm birth. Methods This randomized, double-blind, placebo- controlled, multinational trial enrolled and randomized 659 pregnant women with a history of spontaneous preterm birth. Between 18 + 0 and 22 + 6 weeks of gestation, patients were assigned randomly to once-daily treatment with either progesterone vaginal gel or placebo until either delivery, 37 weeks' gestation or development of preterm rupture of membranes. The primary outcome was preterm birth at ≤ 32 weeks of gestation. The trial was analyzed using an intent-to-treat strategy. Results Baseline characteristics were similar in the two treatment groups. Progesterone did not decrease the frequency of preterm birth at ≤ 32 weeks. There was no difference between the groups with respect to the mean gestational age at delivery, infant morbidity or mortality or other maternal or neonatal outcome measures. Adverse events during the course of treatment were similar for the two groups. Conclusion Prophylactic treatment with vaginal progesterone did not reduce the frequency of recurrent preterm birth (≤ 32 weeks) in women with a history of spontaneous preterm birth. The effect of progesterone administration in patients at high risk for preterm delivery as determined by methods other than history alone (e.g. sonographic cervical length) requires further investigation. Copyright © 2007 ISUOG. Published by John Wiley & Sons, Ltd.

Friedrich Sigmund Merkel and his "Merkel cell", morphology, development, and physiology: review and new results.

Abstract: Merkel nerve endings are mechanoreceptors in the mammalian skin. They consist of large, pale cells with lobulated nuclei forming synapse-like contacts with enlarged terminal endings of myelinated nerve fibers. They were first described by F.S. Merkel in 1875. They are found in the skin and in those parts of the mucosa derived from the ectoderm. In mammals (apart from man), the largest accumulation of Merkel nerve endings is found in whiskers. In all vertebrates, Merkel nerve endings are located in the basal layer of the epidermis, apart from birds, where they are located in the dermis. Cytoskeletal filaments consisting of cytokeratins and osmiophilic granules containing a variety of neuropeptides are found in Merkel cells. In anseriform birds, groups of cells resembling Merkel cells, with discoid nerve terminals between cells, form Grandry corpuscles. There has been controversy over the origin of Merkel cells. Results from chick/quail chimeras show that, in birds, Merkel cells are a subpopulation of cells derived from the neural crest, which thus excludes their development from the epidermis. Most recently, also in mammals, conclusive evidence for a neural crest origin of Merkel cells has been obtained. Merkel cells and nerve terminals form mechanoreceptors. Calcium ions enter Merkel cells in response to mechanical stimuli, a process which triggers the release of calcium from intracellular stores resulting in exocytosis of neurotransmitter or neuromodulator. Recent results suggest that there may be glutamatergic transmission between Merkel cell and nerve terminal, which appears to be essential for the characteristic slowly adapting response of these receptors during maintained mechanical stimuli. Thus, we are convinced that Merkel cells with associated nerve terminals function as mechanoreceptor cells. Cells in the skin with a similar appearance as Merkel cells, but without contact to nerve terminals, are probably part of a diffuse neuroendocrine system and do not function as mechanoreceptors. Probably these cells, rather than those acting as mechanoreceptors, are the origin of a highly malignant skin cancer called Merkel cell carcinoma.