Contribution of single motoneurons to renshaw cell activity

Single spinal alpha motoneurons driven by injected current are shown to increase the activity of Renshaw cells. This fact is a necessary condition for the validity of hypotheses concerning the functional significance of recurrent inhibition which are based on the conception that individual motoneurons can interact with each other.     

Distribution of tritium label in the neonate rat brain following intracisternal or subcutaneous administration of [H]6-OHDA. An autoradiographic study

The present report describes the distribution of tritium label after injection of newborn rats with [³H]6-hydroxydopamine ([³H]6-OHDA). The animals were injected either intracisternally (i.c.) or subcutaneously (s.c.), with or without pretreatment with nomifensine, which blocks the high-affinity uptake of both noradrenaline (NA) and dopamine (DA), and sacrificed at intervals from 40 min to 24 h post-injection (p.i.). In i.c. injected animals, tritium label is demonstrable as early as 40 min p.i. in neurons of all known NA and DA cell groups. In NA neurons, it is taken up into cell body, dendrites, preterminal and terminal axons. The intensity of neuronal labeling is highest within the first 4 h p.i. and decreases in most neurons with longer postinjection intervals. A significant proportion of both NA and DA neurons degenerate beginning 6 h p.i., the majority show morphological signs of the axon reaction 24 h p.i. Uptake of [³H]6-OHDA into serotonergic and non-catecholaminergic neurons is not demonstrable.[³H]6-OHDA is accumulated by the following extraneuronal cells of the CNS: ependymal cells, epithelial cells of the choroid plexus, subependymal macrophages, smooth muscle cells in the wall of large intraparenchymal blood vessels, meningeal cells and glial cells. The time course of accumulation and disappearance of the label varies among these extraneuronal elements. The meningeal cells show the highest labeling intensity and degenerate within 24 h p.i.After pretreatment of the animals with nomifensine, the uptake of [³H]6-OHDA into NA and DA neurons is totally blocked; by contrast uptake of the labeled drug into extraneuronal cells is not prevented.These findings show that [³H]6-OHDA is not only accumulated by neurons possessing the high-affinity uptake for NA or DA, but by numerous other, extraneuronal cells which also participate in the metabolism of catecholamines.     

Polymere mit phosphor-stickstoff-bindungen, 6. Zur polymerisation von hexakis(2,2,2-trifluorethoxy)cyclotriphosphazen bei anwesenheit von bortrichlorid

Hexakis(2,2,2-trifluorethoxy)cyclotriphosphazene ( 1b ) reacts with borontrichloride at elevated temperatures to give a mixture of polymeric phosphazenes containing imino dichloro and imino bis(trifluoroethoxy)phosphoranetriyle units. The reaction was investigated by ³¹P NMR. Separation of several fractions of polymers was achieved by hexane/benzene solvent extraction. Molecular weights have been determined by means of membrane and/or vapor pressure osmometry. A reaction mechanism is discussed.     

Thion- und Dithioester, 41. Mitt. Zur Reaktion von Dithionmalonsäureestern mit Elektrophilen

Thiono and Dithio Esters, 41. - Reaction of Dithiono Malonic Esters with Electrophiles Dithiono malonic esters 1 react with alkali alkoxides to form the stable alkali salts 2 . According to an X-ray analysis for the N,N,N′,N′-tetramethylformamidinium salt 18 their anions adopt a trans,s-trans configuration in the crystalline state. By NOE experiments the same configuration is confirmed for solutions ([D₆]DMSO or D₂O). Alkylation of 2 , however, gives rise to the Z-configurated thiono acrylic esters 4 , By oxidation of 1a with tert.-butyl hypochlorite or iodine the 1,2-dithiolium salts 5 and 7 were obtained. The reaction of 1a with N,N-dimethylformamide diethylacetal ( 8 ) in ethanol leads to the formation of the dimethylaminomethylene compound 12 , in ether the formamidinium salt 18 precipitates. The latter decomposes to N,N-dimethyl thioformamide 20 and the thiono acrylic ester 21 .     

Chiral Compounds of Essential Oils,VII: Quality Evaluation of Mentha Oils,Using Enantioselective CGC-Analysis of Monoterpenoid Constituents

Combinations of two or three capillary columns, coated with modified cyclodextrins are used as chiral CGC-separation systems for the direct stereo-differentiation of menthone ( 1 ), isomenthone ( 2 ), menthol ( 3 ), and menthyl-acetate ( 4 ), to evaluate their enantiomeric ratios in mentha oils. Optical purity of 1–4 is discussed as an indicator of the natural origin of mint and peppermint oils.     

Stereokontrolle. III. Geschwindigkeitskonstanten der iso- und syndiotaktischen anlagerung

The rate constants of isotactic and syndiotactic addition can be calculated from the rate constant k_w of the propagation reaction and the fractions of isotactic and syndiotactic dyads and triads. Corresponding equations are given for BERNOULLI trials and MARKOV trials of first order with respect to monomer dyads. The temperature dependence of dyad formation is discussed for MARKOV trials.     

Polymere mit phosphor-stickstoff-bindungen, 5. Zu reaktion und polymerisation von (NPCI2)3 in gegenwart von elementhalogeniden und borsäureestern

Hexachlorocyclotriphosphazene ( 1 ) reacts with SbCl₅ or BCl₃ to produce long chain polymers, whereas AlCl ³ gives phosphazenyl cations. TiCl₄ does not react and boric acid esters lead to an exchange of one ester group for one chlorine. ³¹P NMR-spectra were used to identify the reaction products. The molecular weights of the polymeric compounds were measured.     

Löusungsverhalten niedermolekularer polydimethylsiloxane mit methylendgruppen

Poly(dimethyl siloxanes) with methyl endgroups undergo association in chloroform and toluene according to measurements by vapour pressure osmometry. The virial coefficients measured in bromocyclohexane point to a structure of an interrupted helix. Accordingly, the values of [η]/M^0,5 strongly drop down at low molecular weights.