Biochemical and cytogenetic studies on the Nucleolus Organizing Regions (NOR) of Man

Summary The hybridization kinetics of DNA with labeled (18s+28s)rRNA from HeLa cells was determined in patients with trisomy 21, healthy probands with normal karyotype and in carriers of a t(DqGq) centric fusion. The results are in, accordance with the saturation values obtained earlier for these probands:Three patients with trisomy 21 showed an increased saturation level. In 2 of these patients the excess of rDNA exceeded the expected value considerably.Three of the investigated translocation carriers t(14q21q) showed significantly reduced saturation values, while results of a fourth proband with a dicentric chromosome t(15q21q) were found to be within the range of normal probands.The heterogeneous results were correlated with the cytogenetic characteristics of the acrocentric chromosomes. It is expected that these differences could be explained on the basis of family analysis.

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Zusammenfassung Hybridisierungskinetiken der DNA mit markierter (18s+28s)rRNA aus HeLa-Zellen wurden ermittelt bei Patienten mit Trisomie 21, gesunden Probanden mit normalem Karyotyp und Trägern einer zentrischen Fusion t(DqGq). Die Ergebnisse bestätigen die bereits früher ermittelten Sättigungswerte von Hybridisierungen bei diesen Probanden:3 Patienten mit Trisomie 21 zeigten erhöhte Sättigungsniveaus. Bei 2 dieser Patienten übersteigt der Überschuß an rDNA den Erwartungswert erheblich.3 der untersuchten Translokationsträger t(14q21q) hatten signifikant erniedrigte Sättigungswerte, während die vierte Probandin mit dem dizentrischen Chromosom t(15q21q) im Normbereich lag.Die unterschiedlichen Befunde werden mit den cytogenetischen Eigenschaften der akrozentrischen Chromosomen in Zusammenhang gebracht. Es wird erwartet, daß diese Unterschiede sich durch Familienuntersuchungen aufklären lassen.

     

Effects of 1-ethynylpyrene and related inhibitors of P450 isozymes upon benzo[a]pyrene metabolism by liver microsomes

The effects of three aryl acetylenes, 1-ethynylpyrene (EP), 2-ethynylnaphthalene (EN) and 3-ethynylperylene (EPE), upon the metabolism of benzo[a]pyrene (BaP) by microsomes isolated from rat liver were investigated. These aryl acetylenes all inhibited the total metabolism of BaP. Formation of BaP 7,8-dihydrodiol and BaP tetrol products by microsomal preparations from rats that had been pretreated with 3-methylcholanthrene (3MC) were preferentially inhibited. The effects of EP upon the metabolism of BaP 7,8-dihydrodiol by microsomes from rat liver were also studied. This aryl acetylene strongly inhibited the formation of BaP tetrols from BaP 7,8-dihydrodiol by liver microsomes both from untreated rats and from rats pretreated with 3MC, but enhanced the conversion of the BaP dihydrodiol into other metabolites.     

Effects of d-amphetamine on behavior maintained by signaled and unsignaled delays to reinforcement

Four pigeons responded under a progressive-delay procedure. In a signaled-delay condition, a chained variable interval (VI) 30-s progressive time (PT) 4-s schedule was arranged; in an unsignaled-delay condition, a tandem VI 30-s PT 4-s schedule was arranged. Two pigeons experienced a signaled-unsignaled-signaled sequence; whereas, two pigeons experienced an unsignaled-signaled-unsignaled sequence. Effects of saline and d-amphetamine were determined under each condition. At intermediate doses (1.0 and 1.78 m/kg) delay functions were shallower, area under the curve was increased, and, when possible, break points were increased compared to saline; these effects were not systematically related to signaling conditions. These effects on control by delay often were accompanied by decreased response rates at 0 s. These results suggest that stimulus conditions associated with the delay may not play a crucial role in effects of d-amphetamine and other stimulants on behavior controlled by reinforcement delay.     

Lipid microdomains and membrane trafficking in mammalian cells

This overview summarizes the data for how epithelial cells sort and deliver proteins and lipids to the apical and basolateral cell surface domains. The basolateral pathway uses a Rab-SNARE mechanism for docking and fusion, while the apical route employs a different machinery. This latter mechanism is based on lipid microdomains, composed of clusters of sphingolipids and cholesterol, which function as rafts for apical delivery. The sphingolipid-cholesterol raft mechanism seems to be employed generally by mammalian cells to transport raft-associated proteins to their post-Golgi destinations.