Operant conditioning of cortical steady potential responses in rats

This study was conducted to determine if amplitudes of rat corticol steady potential (SP) response to an auditory stimulus could be altered by operant conditioning procedures using food reinforcement. The negative SP responses to the 5-sec tone alone diminished with repeated presentation of the stimulus. When food reinforcement was given immediately following the tone, SP response amplitudes increased and stabilized after 4–5 sessions. Thereafter, the animals were required to increase or decrease the amplitudes of response in order to obtain reinforcement. Two of three rats required to increase amplitudes were successful and three of four rats required to decrease amplitudes were successful. It is concluded that changes in cortical SP responses can be operantly conditioned.     

Metabolite and enzyme contents of freeze-clamped liver of the marine fish Stenotomus chrysops

Hepatic metabolites and enzymes in the marine fish, scup or porgy (Stenotomus chrysops), were determined in freeze-clamped tissue taken either within a day of removing fish from their natural habitat or after scup were held in captivity for 6-8 months. The same determinations were made for liver from fed or 48 hr-starved rats (Mus norvegicus albinus). Compared with rat liver, both groups of fish had, per gram of liver, higher contents of AMP, inorganic phosphate, glucose, glucose-6-phosphate, malate, glutamate and NH4+. ATP was lower in fish liver, and ADP, lactate and pyruvate contents were similar in rats and fish. Fish held in captivity had significantly lower pyruvate, alpha-ketoglutarate, and cytosolic free NAD+/NADH and higher cytosolic free NADPH/NADP+. These decreases were similar to those seen when starved rats were compared with fed ones. In scup liver, glucose-6-phosphate dehydrogenase was 3-8 times, malic enzyme about 2 times, and alanine aminotransferase 2-4 times higher than those activities in rat liver. Those results and a higher cytosolic free NADPH/NADP+ are consistent with the liver being the major site of lipogenesis in fish.     

Distinction between mouse DNA polymerases alpha and beta by tryptic peptide mapping.

Results presented here and in a previous paper (Tanabe et al. (1979) Biochemistry 18, 3401--3406) indicate that mouse beta-polymerase is a single polypeptide with an apparent molecular weight of 40,000. This polypeptide has now been analyzed by tryptic peptide mapping. Comparison of the results with identical analysis of mouse alpha-polymerase reveals that the tryptic peptides derived from the two enzymes are different. These results indicate that beta-polymerase is neither a subunit of alpha-polymerase nor a proteolytic degradation product of alpha-polymerase.     

Adventitious Root Formation in Veronica Spp.

Species of the genus Veronica differ in habitat preferences,growth form and in adventitious root production. The annualspecies rarely or never produce adventitious roots in intactplants in the field but some, for example V. persica and V.arvensis will root vigorously from single node stem segmentsin culture. Others, such as V. agrestis require the presenceof IAA for substantial levels of root formation to occur incultured stem segments. Veronica hederifolia cuttings rarelyproduce roots. Stem cuttings of the perennial species, in general,rooted more vigorously than those of annual plants. Both V.fihiformis and V. serpyllifolia root very strongly. The position of root production from the stem cuttings differedfrom species to species. Roots arose either from the node, theregion of the base or at some intermediate point. Veronica arvensis,V. chamaedrys and V. persica rooted mainly from the basal regionwhereas V. filiformis rooted mainly from the node. Veronicaserpyllifolia cuttings rooted at both of these locations. Veronica filiformis, a perennial species that is infertile inBritain, produces root primordia in intact plants at nodes whichare close to the shoot apex. Thus, even very young stem segmentshave ‘preformed’ root primordia. For this reason,detached stem segments of V. filiformis root very rapidly andthis probably has been of great significance in its successfulinvasion and spread in lawns and short turf areas. Veronica spp., adventitious roots, indol-3-ylacetic acid, root primordia, vegetative reproduction     

Cloning of the Zea mays controlling element Ac from the wx-m7 allele

Summary The cloning of the controlling element Ac from the wx-m7 allele of Zea mays is described. The cloned fragment carries a 4.3 kb insertion that by restriction analysis is indistinguishable from the Ac insertion in Ac wx-m9. It is located approximately 2.5 kb upstream of the Ac wx-m9 insertion. Offprint requests to: P. Starlinger     

A comparative study of the characteristics of eIF-2 and eIF-2-ancillary factor activities from yeast Saccharomyces cerevisiae and rabbit reticulocytes

The characteristics of yeast eukaryotic initiation factor 2 (eIF-2) and Co-eIF-2A have been studied and compared with those of the corresponding factors from rabbit reticulocytes. 1) Unlike eIF-2r, purified eIF-2y did not contain bound GDP. 2) Purified eIF-2y preparation contained GTPase activity and dephosphorylated GTP to GDP. 3) An anti-eIF-2r preparation which predominantly precipitated the gamma-subunit (Mr 54,000) of eIF-2r also precipitated the larger subunit (Mr 54,000) of eIF-2y. 4) Unlike eIF-2r, ternary complex formation by eIF-2y was not inhibited by Mg2+. 5) Both Co-eIF-2A20y and Co-eIF-2r significantly enhanced Met-tRNAf binding to eIF-2y and, again, Mg2+ did not have any effect on this stimulated Met-tRNAf binding to eIF-2y. 6) Both Co-eIF-2A20y and Co-eIF-2r were similarly effective in stimulating Met-tRNAf binding to eIF-2r in the absence of Mg2+. However, in the presence of Mg2+, Co-eIF-2A20y was significantly less effective than Co-eIF-2r as Co-eIF-2A20y did not promote displacement of GDP from eIF-2r X GDP. 7) eIF-2y bound [3H]GDP and this binding was significantly enhanced in the presence of Mg2+. Also, [3H]GDP in the preformed eIF-2y X [3H]GDP complex was rapidly exchanged with exogenously added unlabeled GDP in the presence of Mg2+. Co-eIF-2A20y had no effect on GDP binding to eIF-2y nor on GDP exchange reactions. 8) Reticulocyte heme-regulated protein synthesis inhibitor, which phosphorylated almost completely (in excess of 80%) the alpha-subunit (Mr 38,000) of eIF-2r, also phosphorylated similarly the smaller subunit (Mr 36,000) of eIF-2y. However, such phosphorylation had no significant effect on ternary complex formation, GDP binding, and GDP exchange reactions.