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Background An essential determinant of a neuron’s functionality is its neurotransmitter phenotype. We previously identified a defined subpopulation of cholinergic neurons required for social orienting behavior in zebrafish. Results We transcriptionally profiled these neurons and discovered that they are capable of synthesizing both acetylcholine and GABA. We also established a constellation of transcription factors and neurotransmitter markers that can be used as a “transcriptomic fingerprint” to recognize a homologous neuronal population in another vertebrate. Conclusion Our results suggest that this transcriptomic fingerprint and the cholinergic-GABAergic neuronal subtype that it defines are evolutionarily conserved. more...

Previous investigations in our laboratory have shown that leaf developmental programming in tobacco is regulated by source strength. One hypothesis to explain how source strength is perceived is that hexokinase acts as a sensor of carbohydrate flux to regulate the expression of photosynthetic genes, possibly as a result of sucrose cycling through acid invertase and hexokinase. We have turned to Arabidopsis as a model system to study leaf development and have examined various photosynthetic parameters during the ontogeny of a single leaf on the Arabidopsis rosette grown in continuous light. We found that photosynthetic rates, photosynthetic gene expression, pigment contents and total protein amounts attain peak levels early in the expansion phase of development, then decline progressively as development proceeds. In contrast, the flux of 14CO2 into hexoses increases modestly until full expansion is attained, then falls in the fully expanded leaf. Partitioning of carbon into hexoses versus sucrose increases until full expansion is attained, then falls. The in vitro activities of hexokinase, vacuolar acid invertase, and cell wall acid invertase do not change until the late stages of senescence, when they increase markedly. At this time there are also dramatic increases in hexose pool sizes and in senescence-associated gene (SAG) expression. Taken together, our results suggest that invertase and hexokinase activities do not control the partitioning of label into hexoses during development. We conclude that our data are not readily compatible with a simple model of leaf development, whereby alterations in photosynthetic rates are mediated directly by hexose flux or by hexose pool sizes. Yet, these factors might contribute to the control of gene expression. more...

Previous investigations have shown that increased source strength as a result of elevated CO2 can alter the timing of the phases of change that occur in photosynthetic rates during dicot leaf ontogeny [Miller et al. (1997) Plant Physiol 115: 1195–1200]. To evaluate the converse situation of decreased source strength, we examined leaf development in rbcS antisense mutants of tobacco. These mutants have depressed Rubisco levels and decreased rates of carbohydrate production. We found that antisense leaves are longer-lived than wild type leaves and that this appeared to be due to a prolongation of the senescence phase of development, as monitored by photosynthetic rates, chlorophyll content, and the abundance and activity of Rubisco. Declines in these parameters during leaf ontogeny in both the wild type and mutant plants were generally accompanied by coordinate reductions in the levels of rbcS mRNA and rbcL mRNA, as well as by reductions in chloroplast rRNA, chloroplast DNA and total protein. We suggest that the prolongation of senescence in the antisense leaves is due to an impact of source strength on leaf developmental programming that occurs, at least in part, at the level of transcript abundance of nuclear and chloroplast genes for chloroplast rRNAs and proteins. We hypothesize that plants are capable of sensing a range of source strength conditions to initiate and modulate leaf developmental programming. more...

With a selection paradigm, three experimental groups of 10 Ss each learned six conjunctive concepts successively under three learning conditions: attribute identification (AI), rule learning (RL), or their combination (CL). Only for AI did learning sets form and were strategies near optimum efficiency. Experimental Ss learned two additional disjunctive concepts under the three learning conditions, and three control groups learned only the disjunctive concepts. For a measure of response frequency, positive transfer occured for RL and CL, indicating the importance of rule learning for transfer. For a measure of strategy efficiency, negative transfer occurred for AI and positive transfer for RL. more...

This study examined the effects of counterconditioning, neutral conditioning, and extinction, and different amounts of each, upon reshifting the rated meaning of nonsense syllables. For 120 Ss only counterconditioning was significantly effective at changing meaning. more...

This study analyzed the effects of extinction, counterconditioning and the number of trials of each upon the degree of rated meaning for words and nonsense syllables. For 200 Ss counterconditioning was effective, but extinction and trials were not, in changing meaning. Awareness was unrelated to meaning change. more...

With a group procedure, 72 Ss learned associations between pairs of colored figures and nonsense words taken from a 4 by 4 miniature system. In a factorial design, the number of different associations from the system that were learned was varied at two levels, and an extinction procedure that followed learning was applied in three ways. Systems learning occurred. The number of different associations that were learned was not related to accuracy in reproducing the system. For Ss who learned half of the system, the extinction procedure was effective on those associations produced without learning. more...