Stability of retrieved memory: inverse correlation with trace dominance

In memory consolidation, the memory trace stabilizes and becomes resistant to certain amnesic agents. The textbook account is that for any memorized item, consolidation starts and ends just once. However, evidence has accumulated that upon activation in retrieval, the trace may reconsolidate. Whereas some authors reported transient renewed susceptibility of retrieved memories to consolidation blockers, others could not detect it. Here, we report that in both conditioned taste aversion in the rat and fear conditioning in the medaka fish, the stability of retrieved memory is inversely correlated with the control of behavior by that memory. This result may explain some conflicting findings on reconsolidation of activated memories.     

Memory extinction, learning anew, and learning the new: dissociations in the molecular machinery of learning in cortex

The rat insular cortex (IC) subserves the memory of conditioned taste aversion (CTA), in which a taste is associated with malaise. When the conditioned taste is unfamiliar, formation of long-term CTA memory depends on muscarinic and beta-adrenergic receptors, mitogen-activated protein kinase (MAPK), and protein synthesis. We show that extinction of CTA memory is also dependent on protein synthesis and beta-adrenergic receptors in the IC, but independent of muscarinic receptors and MAPK. This resembles the molecular signature of the formation of long-term memory of CTA to a familiar taste. Thus, memory extinction shares molecular mechanisms with learning, but the mechanisms of learning anew differ from those of learning the new.     

Genetic affinity between two chemotypes of clary sage (Salvia sclarea L.)

Summary A new and unique chemotype of clary sage, Salvia sclarea L., was identified recently in wild populations of this species in the northern part of Israel. This chemotype was crossed to a cultivated form of clary sage of Russian origin which represents the standard chemotype of the species. The two chemotypes were easily intercrossed with one another and in both cross directions. The hybrids were vigorous but totally sterile despite apparent normal chromosome pairing at meiosis and regular segregation at Anaphase I. It seems, therefore, that the genetic diversity of the Israeli material can not be exploited to enrich the gene pool of clary sage. Further study is needed to determine the geographic distribution of the new chemotype and whether or not it deserves different taxonomic rank.     

Heredity of phenylpropenes in sweet basil (Ocimum basilicum L.) chemotypes and their distribution within an F2 population

Phenylpropenes play an important role in plant defense against animals and microorganisms, and in attracting pollinators and insects. We report the genetic inheritance of methyl chavicol and eugenol following a cross between the sweet basil varieties ‘Perrie’ and ‘Cardinal,’ eugenol and methyl chavicol chemotypes, respectively. Methyl chavicol was detected only in ‘Cardinal,’ accounting for more than 95% of the total phenylpropenes. Eugenol was most abundant in ‘Perrie,’ accounting for more than 99% of the total phenylpropenes. Eugenol, chavicol and methyl chavicol were detected in F₁ hybrids at intermediate levels (10%–52%) without statistical differences (p > .05) for any compound among the F₁ progeny arising from the different crossed pairs. The F₂ progeny segregated into three groups, 23%–25% to a eugenol chemotype, 23%–25% to a methyl chavicol chemotype, and the remaining (~50%) into an intermediate mixture of the two compounds. This distribution fitted a segregation ratio of 1:2:1 (χ² = 1.71; p = .4249), suggesting that the phenylpropene phenotype is regulated by a single bi‐allelic gene with incomplete dominance. A putative association with biosynthesis enzymes is discussed.     

Following the crowd: brain substrates of long-term memory conformity

Human memory is strikingly susceptible to social influences, yet we know little about the underlying mechanisms. We examined how socially induced memory errors are generated in the brain by studying the memory of individuals exposed to recollections of others. Participants exhibited a strong tendency to conform to erroneous recollections of the group, producing both long-lasting and temporary errors, even when their initial memory was strong and accurate. Functional brain imaging revealed that social influence modified the neuronal representation of memory. Specifically, a particular brain signature of enhanced amygdala activity and enhanced amygdala-hippocampus connectivity predicted long-lasting but not temporary memory alterations. Our findings reveal how social manipulation can alter memory and extend the known functions of the amygdala to encompass socially mediated memory distortions.     

Dried leaves of Rosmarinus officinalis as a treatment for streptococcosis in tilapia

Dietary application of dried Rosmarinus officinalis (rosemary) leaves as a treatment for streptococcal infection was studied in tilapia, Oreochromis sp. Feeding with dried rosemary leaves significantly reduced mortality following infection with Streptococcus iniae: 44% mortality in the group fed 8% rosemary, similar to oxytetracycline treatment (43% mortality), and significantly lower than the control (65%). Dietary administration of 16% rosemary significantly reduced mortality because of Streptococcus agalactiae infection in 44 g fish (62% and 76% in 16% rosemary and control, respectively), but not in a similar experiment conducted with 5.5 g fish. The antibacterial effect of rosemary on S. iniae was studied. Activity of rosemary cultivar Israel was reduced during the winter, but there was no significant change in cultivars Oranit and Star. Storage of powdered rosemary leaves at 50 °C resulted in fourfold and eightfold higher MIC_{24 h} values after 3 and 4.5 months, respectively. Storage at ?20 °C, 4 °C and 25 °C and autoclaving (120 °C) each resulted in a twofold increase in MIC_{24 h}. Repeated exposures of S. iniae to rosemary did not affect minimal inhibitory concentration, suggesting no development of resistance to rosemary.     

In situ induction of chromosome doubling in vine cacti (Cactaceae)

Vine cacti have economic potential as exotic fruits in semi-arid and arid lands due to their high water use efficiency. The goal of this study was to attain autopolyploid plants by applying the antimitotic agents colchicine and oryzalin on axillary vegetative buds and germinating seeds. The diploid Hylocereus monacanthus and the tetraploid H. megalanthus; the interspecific triploid hybrid S-75, were studied. The effects of different concentrations and exposure times on bud survival and germination rate were recorded. A negative effect on vegetative bud survival was observed in the triploid hybrid. An inhibitory effect on germinating seeds was species specific, being greater on H. monacanthus with oryzalin and on H. megalanthus with colchicine. Putative polyploids were identified by comparing stomatal density between donor plants and plants arising from treated buds or seeds. Flow cytometric analysis and chromosome counts confirmed polyploidization in 14 autotetraploid H. monacanthus, 1 autohexaploid S-75 hybrid, and 14 autooctaploid H. megalanthus. This is the first report of artificial autopolyploidization in species of vine cactus, providing valuable novel plant material for further breeding programs.     

Changes in essential oil during enzyme-assisted ensiling of lemongrass (Cymbopogon citratus Stapf.) and lemon eucalyptus (Eucalyptus citriodora Hook)

Changes in essential oil during ensiling of lemongrass and lemon eucalyptus were studied. Wilted lemongrass and eucalyptus leaves were ensiled in 0.25-L anaerobic jars. Samples consisted of a control (no additives) and a treated sample (0.5% glucose and lactic acid bacteria and 1% cellulase plus 1% hemicellulase plus pectinase). Three jars per treatment were sampled on days 2, 6, 10, and 36 for analysis of essential oil. Essential oil was obtained by extraction and by hydrodistillation. Extraction efficacy of essential oil from the lemongrass was improved by the enzyme treatment, but it was much lower than the amount obtained by distillation. The major components of the essential oil were neral and geranial. In the eucalyptus, total essential oils obtained by distillation decreased during ensiling, and the amount was similar to the amount obtained by extraction. Citronellal, which was the major component of the essential oil in the fresh eucalyptus leaves, decreased, whereas isopulegol and 3,8-terpinolhydrate increased during ensiling.     

Reduction of Botrytis cinerea sporulation in sweet basil by altering the concentrations of nitrogen and calcium in the irrigation solution

Current measures for suppressing grey mould ( Botrytis cinerea ) on sweet basil rely on fungicide applications and climate control. In this study, the nitrogen and calcium concentrations in the standard irrigation solution (7·2 and 1·3 m m , respectively) were varied in a series of experiments conducted in pots and large containers. Treatments differed in the N or Ca concentrations supplied, and effects on host response were determined in detached stem segments, individual plants and plots. Effects of the two elements on grey mould incidence, lesion size and rate of disease progression were erratic and rarely significant, but decreasing the concentration of N and increasing the concentration of Ca in the irrigation solution decreased sporulation of B. cinerea . In some cases, however, altering the standard irrigation solution resulted in significantly lower yields. Analyses of mineral contents in the shoots suggested that yields were not impaired when N content in the shoots was not reduced below 2·9% and Ca content was not raised above 1·3%. These findings were used to compose a modified irrigation solution containing half of the N (3·6 m m ) and double of the Ca (2·55 m m ) concentrations in the standard irrigation solution. The modified irrigation solution significantly reduced sporulation of B. cinerea without affecting crop yield.     

Dynamics of yield components and essential oil production in a commercial hybrid sage (Salvia officinalis x Salvia fruticosa cv. Newe Ya'ar no. 4).

The fresh yields, the essential oil content, and the quality of a sage hybrid (Salvia officinalis x Salvia fruticosa, cv. Newe Ya'ar No. 4, Lamiaceae) as affected by development and harvest time were determined. Marked increases in plant height and in the number of nodes developed per plant together with a modest increase in leaf size were accompanied by dramatic increases (more than 20-fold) in the fresh yields throughout a 50-day growth period. No major changes in the essential oil content per fresh weight and its composition were detected throughout the growth period. In contrast, the compositions of the essential oils obtained from stems, as compared to leaves and leaf-primordia, had marked differences. Developmentally controlled changes in the extractives from individual leaf pairs from the same plant were also noted. In upper young leaves, the oxygenated diterpene manool and the sesquiterpene hydrocarbons alpha-humulene and beta-caryophyllene constituted up to 20%, 8%, and 4% of the total extractives, respectively. In older leaves, the abundance of these components steadily dropped to roughly half their levels in young leaves. Conversely, the proportions of the monoterpenes, particularly the ketones camphor and alpha-thujone, steadily increased with leaf position. Minor changes in the levels of other extractives were also recorded. These studies imply independent regulatory patterns for di-, sesqui-, and monoterpenes in this sage hybrid, and suggest possible agrotechnical means to obtain preferred chemical compositions of its essential oil.