Extracellular matrix and visual cortical plasticity: freeing the synapse

The effects of monocular deprivation (MD) on the ocular dominance of visual cortical neurons are a paradigmatic example of experience-dependent plasticity. Here we review recent data showing that extracellular matrix (ECM) plays an important role in the control of experience-dependent plasticity both in the developing and adult visual cortex.     

Positional Isomerization of trans-3-Hexadecenoic Acid Employing 2-Amino-2-methyl-propanol as a Derivatizing Agent for Ethylenic Bond Location by Gas-Chromatography/Mass Spectrometry

The effect of derivatization with 2-amino-2-methyl-propanol on trans-3-hexadecenoic acid was investigated as part of the identification of the trans-3-hexadecenoic acid in two Nova Scotian seaweeds. After the extraction of the total fatty acids and their methylation, the monoenoic trans fraction was isolated by thin-layer chromatography on silica gels impregnated with silver nitrate. This fraction was first analyzed by gas chromatography and showed the presence of the trans-3-hexadecenoic acid; other fatty acids were not present. The isolated fraction was derivatized with 2-amino-2-methyl-propanol prior to analysis by gas chromatography/mass spectrometry. The chromatogram obtained showed the presence of a positional isomer formed during the derivatization of the trans-3-hexadecenoic acid. The mass spectrum showed a prominent [M + H]⁺ and diagnostic ions for the identification of the unknown isomer, corresponding to the 4,4-dimethyloxazoline (DMOX) derivative of a presumed 2-hexadecenoic acid. Definitive confirmation of the ethylenic bond position was obtained by oxidative ozonolysis of the DMOX derivatives of the fatty acids under investigation. Infrared spectroscopy showed that the artifact formed during the DMOX derivatization of trans-3-hexadecenoic acid was the DMOX derivative of cis-2-hexadecenoic acid.     

Amplitude modulation of the retinal ganglion cell impulses

Zusammenfassung Die Netzhaut decerebrierter Katzen wurde mit sinusförmig moduliertem Licht gereizt und die in den Ganglienzellen ausgelöste Erregung extracellulär registriert. Amplitude und momentane Frequenz der Aktionspotentiale ändern sich sinusförmig und besitzen zueinander eine Phasenverschiebung von 180°. Die Phasenverschiebung ist unabhängig von der Frequenz des Reizlichtes, die im Bereich von 0,1–10 Hz geändert wurde. Anhand von Kontrollmessungen wurde gezeigt, daß die Amplitudenänderung der gemessenen Aktionspotentiale auf Änderungen des Membranpotentials beruht.     

Iridoids of Cruckshanksia verticillata and their Chemosystematic importance

From Cruckshanksia verticillata, an endemic Chilean species of the family Rubiaceae, a new secoiridoid was isolated in addition to asperuloside and secologanin and identified as 7--methoxysweroside by spectroscopic means. The importance of the isolated iridoids in subfamilial classification of the genus Cruckshanksia is discussed.