Localization of short-term memory in the brain of the bee, Apis mellifera

ABSTRACT. Fixed honey-bees were conditioned to a scent in a one-trial learning paradigm. In contrast to free-flying colour-conditioned bees, fixed scent-conditioned bees do not show a biphasic time dependence of the conditioned response. Small metal probes were used to cool localized areas of the antennal lobes, alpha-lobes, and calyces of the mushroom bodies of the brain at various times after conditioning. Localized cooling impaired the formation of memory in all three structures. The susceptibility to impairment after conditioning lasted approximately 3 min in the antennal lobes, 7 min in the alpha-lobes, and 10 min in the calyx area. It was possible to determine the influence of the contralateral hemisphere (relative to the learning antenna) by conditioning bees with only one antenna. No contralateral impairment was found in the antennal lobes; there were minor effects in the alphalobes; contralateral cooling led to reductions of the conditioned response only in the calyx area. The temperature dependence of memory impairment was different for the antennal lobes and the mushroom bodies (alpha-lobes and calyces). The latter were most sensitive to cooling at 5°C. No correlation between cooling duration and impairment of memory was found in the antennal lobes, but there was a linear relation between impairment and cooling duration in the alpha-lobes. Brief cooling (5 or 10 s) resulted in significant impairment of memory formation only in the calyx area. A series of control experiments proved that the impairment of memory is due to a reversible block of neural activity. It was possible to show that the impairment is specific for the three neural structures analysed, by cooling the lobula of the optic system at various times after conditioning. Lesions of the brain or application of KCl also resulted in time-dependent reductions of the conditioned response. Cooling the entire animal at various times after conditioning led to similar memory impairment to that resulting from localized cooling of the alphalobes.     

Hypophysiotropic Centers in the Brain of Amphibians and Fish

The subject is the localization of three different hypophysiotropiccenters in the brain of amphibians and fish. The thyrotropic hormone-releasing hormone (TRH) in Xenapus mayoriginate from the dorsal magno-cellular neurons of the preopticnucleus. This hypothesis is based on correlative changes betweenthese cells and alterations in thyroid activity during metamorphosis.Experimental data are in support of a functional relationshipbetween certain preoptic neurons and the thyrotropic activityof the pituitary. The MSH inhibiting activity of the hypothalamus is effectedby means of an aminergic innervation of the pars intermediain amphibians, teleosts and elasmobranchs. In amphibians theaminergic fibers originate from the caudal part of the paraventricularorgan (PVO); in elasmobranchs probably from the nucleus mediushypothalamicus(NMI); in teleosts the origin still has to beinvestigated. Two centers producing gonadotropic hormone-releasing hormone(GRH) have been demonstrated. Lesion experiments lead to thehypothesis that GRH is produced in the caudal hypothalamus,i.e., in the nucleus infundibularis ventralis of amphibiansand in the nucleus lateralis tuberis of fishes. ImmunoHuorescencestudies indicate in both groups the presence of neurons, infront of the preoptic area in the telencephalon, and these neuronsare immuno-reactive with anti-mammalian LH-RH.     

Antifungal Activities of Four Fatty Acids against Plant Pathogenic Fungi

The effect of the fatty acids linolenic acid, linoleic acid, erucic acid and oleic acid on the growth of the plant pathogenic fungi Rhizoctonia solani, Pythium ultimum, Pyrenophora avenae and Crinipellis perniciosa were examined in in vitro studies. Linolenic and linoleic acids exhibited activity against all of the fungi. However, whereas linolenic acid reduced mycelial growth of R. solani and C. perniciosa at 100 microM, the concentration had to be increased to 1000 microM before any effect on mycelial growth of P. ultimum and P. avenae was observed. Linoleic acid only reduced mycelial growth of R. solani, P. ultimum and P. avenae at 1000 microM, but led to a significant reduction in growth of C. perniciosa at 100 microM. In contrast, oleic acid had no significant effect on growth of R. solani or P. avenae, but gave significant reductions in mycelial growth of P. ultimum at 100 microM and reduced growth of C. perniciosa significantly at 1000 microM. All of the fatty acids reduced biomass production by all of the fungi significantly in liquid culture when added to the media at 100 microM. Erucic acid had no effect on fungal growth at any concentration examined. The antifungal activities exhibited by linolenic, linoleic and oleic acids may be useful in the search for alternative approaches to controlling important plant pathogens, such as those examined in this study.     

Foraging decisions underlying restricted space use: effects of fire and forage maturation on large herbivore nutrient uptake

Recent models suggest that herbivores optimize nutrient intake by selecting patches of low to intermediate vegetation biomass. We assessed the application of this hypothesis to plains bison (Bison bison) in an experimental grassland managed with fire by estimating daily rates of nutrient intake in relation to grass biomass and by measuring patch selection in experimental watersheds in which grass biomass was manipulated by prescribed burning. Digestible crude protein content of grass declined linearly with increasing biomass, and the mean digestible protein content relative to grass biomass was greater in burned watersheds than watersheds not burned that spring (intercept; F_1,251 = 50.57, P < 0.0001). Linking these values to published functional response parameters, ad libitum protein intake, and protein expenditure parameters, Fryxell's (Am. Nat., 1991, 138 , 478) model predicted that the daily rate of protein intake should be highest when bison feed in grasslands with 400–600 kg/ha. In burned grassland sites, where bison spend most of their time, availability of grass biomass ranged between 40 and 3650 kg/ha, bison selected foraging areas of roughly 690 kg/ha, close to the value for protein intake maximization predicted by the model. The seasonal net protein intake predicted for large grazers in this study suggest feeding in burned grassland can be more beneficial for nutrient uptake relative to unburned grassland as long as grass regrowth is possible. Foraging site selection for grass patches of low to intermediate biomass help explain patterns of uniform space use reported previously for large grazers in fire‐prone systems.     

Ethylene Production in Spinach Leaves during Floral Induction

Spinach plants were induced to flower by transferring them fromshort days to continuous light. Their leaf laminae releasedmore ethylene than those from vegetative plants. These leavesalso exhibited a greater capacity to convert exogenous ACC intoethylene. Cell wall preparations from the leaves of continuouslyilluminated plants also converted exogenous ACC into ethylenemore readily than extracts from short day plants. These effectsand also those previously reported for peroxidases appear verysimilar to these brought about by various environmental stressessuch as pollution and mechanical irritation. Key words: Ethylene, floral induction, stress, photoperiod, spinach     

Regulation of protein kinase C by lysophospholipids. Potential role in signal transduction

Certain lysophospholipids, lysophosphatidylcholine (lyso-PC) in particular, stimulated protein kinase C at low concentrations (less than 20 microM) but, conversely, inhibited it at high concentrations (greater than 30 microM). Protein kinase C stimulation by lyso-PC required the presence of phosphatidylserine (PS) and Ca2+ and was associated with a decreased Ka for PS and increased Ka for Ca2+ of the enzyme. Cardiolipin and phosphatidic acid could partially substitute for PS in supporting the stimulatory effect of lyso-PC. Lyso-PC also biphasically regulated protein kinase C activated by diolein. Of several synthetic lyso-PC preparations tested, the oleoyl, myristoyl and palmitoyl derivatives were most active. Data from the Triton X-100 mixed micellar assay indicated that 1.4 and 14.0 mol of lyso-PC/micelle produced a maximal stimulation and a complete abolishment of the stimulation of protein kinase C, respectively. Protein kinase C stimulation by lyso-PC, with a pH optimum of about 7.5, was observed for phosphorylation of histone H1, myelin basic protein, and the 35- and 47-kDa proteins from the rat brain, but not for that of other histone subfractions and protamine. Lyso-PC acted synergistically with diacylglycerol in stimulating protein kinase C, whereas the stimulation by lyso-PC was additive to that by oleic acid. Protein kinase C inhibitors (alkyllysophospholipid, sphingosine, tamoxifen, and polymyxin B) inhibited more potently the protein kinase C activity stimulated by PS/Ca2+/lyso-PC than that stimulated by PS/Ca2+. The stimulatory and inhibitory effects of lyso-PC were not observed for myosin light chain kinase and cAMP-dependent protein kinase, indicating a specificity of its actions. The present findings suggested that lyso-PC, likely derived from membrane PC by the action of phospholipase A2, might play a role in signal transduction via a dual regulation of protein kinase C, and that it could further modulate the enzyme and hence the cellular activity by interplaying with diacylglycerol and unsaturated fatty acid, the two other classes of cellular mediators also shown to be activators of protein kinase C.     

How to Test Mandatory Text Templates: The European Patient Information Leaflet

The structure of patient information leaflets (PILs) supplied with medicines in the European Union is largely determined by a regulatory template, requiring a fixed sequence of pre-formulated headings and sub-headings. The template has been criticized on various occasions, but it has never been tested with users. This paper proposes an alternative template, informed by templates used in the USA and Australia, and by previous user testing.The main research question is whether the revision better enables users to find relevant information. Besides, the paper proposes a methodology for testing templates. Testing document templates is complex, as they are “empty”. For both the current and the alternative template, we produced a document with bogus text and real headings (reflecting the empty template) and a real-life document with readable text (reflecting the “filled” template). The documents were tested both in Dutch and in English, with 64 British and 64 Dutch users. The test used a set of scenario questions that covers the full range of template (sub)topics; users needed to indicate the text locations where they expected each question to be answered. The revised template improved findability of information; this effect was strongest for the “filled” template with readable text. When participants were shown both filled templates, there was a clear preference for the revised template. A closer analysis of the findability data revealed question-specific effects of topic grouping, topic ordering, subtopic granularity and wording of headings. Most of these favoured the revised template, but our revision led to adverse effects as well, for instance in the new heading Check with your doctor. Language-specific effects showed that the wording of the headings is a delicate task. Generally, we conclude that document template designs can be analyzed in terms of the four parameters grouping, ordering, granularity and wording. Furthermore, they need to be tested on their effects on information findability, with template translations requiring separate testing. The methodology used in this study seems an appropriate one for such tests. More specifically, we find that the new patient information leaflet template proposed here provides better information findability.     

MtZR1, a PRAF protein,is involved in the development of roots and symbiotic root nodules in Medicago truncatula

PRAF proteins are present in all plants, but their functions remain unclear. We investigated the role of one member of the PRAF family, MtZR1, on the development of roots and nitrogen‐fixing nodules in Medicago truncatula. We found that MtZR1 was expressed in all M. truncatula organs. Spatiotemporal analysis showed that MtZR1 expression in M. truncatula roots was mostly limited to the root meristem and the vascular bundles of mature nodules. MtZR1 expression in root nodules was down‐regulated in response to various abiotic stresses known to affect nitrogen fixation efficiency. The down‐regulation of MtZR1 expression by RNA interference in transgenic roots decreased root growth and impaired nodule development and function. MtZR1 overexpression resulted in longer roots and significant changes to nodule development. Our data thus indicate that MtZR1 is involved in the development of roots and nodules. To our knowledge, this work provides the first in vivo experimental evidence of a biological role for a typical PRAF protein in plants.     

SIMPLE: implementation of recommendations from international evidence-based guidelines on caesarean sections in the Netherlands. Protocol for a controlled before and after study

Background

Caesarean section (CS) rates are rising worldwide. In the Netherlands, the most significant rise is observed in healthy women with a singleton in vertex position between 37 and 42 weeks gestation, whereas it is doubtful whether an improved outcome for the mother or her child was obtained. It can be hypothesized that evidence-based guidelines on CS are not implemented sufficiently. Therefore, the present study has the following objectives: to develop quality indicators on the decision to perform a CS based on key recommendations from national and international guidelines; to use the quality indicators in order to gain insight into actual adherence of Dutch gynaecologists to guideline recommendations on the performance of a CS; to explore barriers and facilitators that have a direct effect on guideline application regarding CS; and to develop, execute, and evaluate a strategy in order to reduce the CS incidence for a similar neonatal outcome (based on the information gathered in the second and third objectives).

Methods

An independent expert panel of Dutch gynaecologists and midwives will develop a set of quality indicators on the decision to perform a CS. These indicators will be used to measure current care in 20 hospitals with a population of 1,000 women who delivered by CS, and a random selection of 1,000 women who delivered vaginally in the same period. Furthermore, by interviewing healthcare professionals and patients, the barriers and facilitators that may influence the decision to perform a CS will be measured. Based on the results, a tailor-made implementation strategy will be developed and tested in a controlled before-and-after study in 12 hospitals (six intervention, six control hospitals) with regard to effectiveness, experiences, and costs.

Discussion

This study will offer insight into the current CS care and into the hindering and facilitating factors influencing obstetrical policy on CS. Furthermore, it will allow definition of patient categories or situations in which a tailor-made implementation strategy will most likely be meaningful and cost effective, without negatively affecting the outcome for mother and child.

Trial registration

http://www.clinicaltrials.gov: NCT01261676