bluuebunny/crossref_metadata_2025 huggingface dataset:
Intact implicit memory for novel patterns in Alzheimer's disease.
Authors: Postle B R , Corkin S , Growdon J H
Published: June 2007

Repetition priming is a kind of implicit memory (learning without awareness) that does not depend on the medial temporal-lobe system. For example, the amnesic patient H.M., who underwent bilateral medial temporal-lobe resection, shows intact priming with novel patterns, suggesting that perceptual priming with nonverbal material does not depend on areas critical for explicit memory. A logical candidate for the neural substrate that supports this kind of priming is the peristriate cortex, an area that is relatively spared in Alzheimer's disease (AD). We therefore predicted that AD subjects would be unimpaired on pattern priming. Subjects copied each of six target figures onto dot patterns. After performing a 3-min distractor task, they were given the same dot patterns (without lines) and asked to draw the first figure that came to mind by connecting the dots with straight lines. Subsequently, in a test of recognition (explicit) memory, subjects viewed each of the six patterns of dots that they had copied previously and were asked to indicate which of four possible completions corresponded to the figure that they had copied 3 min earlier. The AD and control groups achieved comparable priming scores, but AD subjects were significantly impaired in recognizing the patterns explicitly. Our finding of intact pattern priming in AD provides, for the first time, evidence that pattern priming depends on the peristriate cortex.
Late-training amnesic deficits in probabilistic category learning: a neurocomputational analysis.
Authors: Gluck M A , Oliver L M , Myers C E
Published: June 2007

Building upon earlier behavioral models of animal and human learning, we explore how a psychobiological model of animal conditioning can be applied to amnesic category learning. In particular, we show that the late-training deficit found in Knowlton, Squire, and Gluck's 1994 study of amnesic category learning can be understood as a natural consequence of Gluck and Myers's (1993) theory of hippocampal-region function, a theory that has heretofore been applied only to studies of animal learning. When applied to Knowlton et al.'s category learning task, Gluck and Myers's model assumes that the hippocampal region induces new stimulus representations over multiple training trials that reflect stimulus-stimulus regularities in the training set. As such, the model expects an advantage for control subjects over hippocampal-damaged amnesic patients only later in training when control subjects have developed new hippocampal-dependent stimulus representations; in contrast, both groups are expected to show equivalent performance early in training. A potentially analogous early/late distinction is described for animal studies of stimulus generalization. Our analyses suggest that careful comparisons between early and late-training differences in learning may be an important factor in understanding amnesia and the neural bases of both animal and human learning.
Nonassociative and associative modification of head-waving produced by aversive tentacular stimuli in Aplysia.
Authors: Fitzgerald K K , Takacs C A , Carew T J
Published: June 2007

Head-waving, a spontaneously occurring exploratory and appetitive behavior of the marine mollusc Aplysia, provides an opportunity to examine mechanisms of learning expressed in a nonreflexive behavior. The present study explores nonassociative and associative forms of learned modification of head-waving produced using an aversive stimulus as reinforcement. Experiments on intact, freely behaving animals demonstrate that training with electric shock as an aversive unconditioned stimulus, delivered unilaterally to the anterior tentacles, produces a learned shift in head-waving behavior away from the side on which shock was applied. This behavioral change is a novel learned behavioral response that is influenced by the topographic location of an aversive stimulus. Furthermore, training with application of tentacle shock reinforcement, contingent upon the animal's head position, produces operant conditioning of head-waving. Thus, anterior tentacle shock is effective as an aversive reinforcer for both nonassociative and operant learning expressed in the head-waving behavior of Aplysia.
An autonomous kinase generated during long-term facilitation in Aplysia is related to the Ca(2+)-independent protein kinase C Apl II.
Authors: Sossin W S
Published: June 2007

Prolonged treatment with serotonin leads to long-term facilitation of sensory-to-motor neuron synapses in Aplysia. We have shown previously that there is a protein synthesis-dependent increase in an autonomous kinase activity that phosphorylates a protein kinase C substrate during an intermediate phase of this facilitation. Here, I report that the increase in autonomous activity was independent of RNA synthesis, suggesting it may play a role in the maintenance phase of synaptic facilitation. Immunoprecipitation experiments using an antibody specific to the Ca(2+)-independent protein kinase C, Apl II, demonstrated that the autonomous kinase activity increased by serotonin emanated from Apl II. Chelerythrine, an inhibitor targeted to the substrate binding site of protein kinase C, also blocked the autonomous kinase activity increased by serotonin. Using immunoblotting experiments and calphostin-C, an inhibitor targeted to the regulatory domain of protein kinase C, the autonomous activity is shown not to be a catalytic fragment of Apl II. Furthermore, a higher concentration of calphostin-C was required to inhibit autonomous kinase activity than regulated kinase activity, suggesting that calphostin-C's binding site in the regulatory domain of Apl II is modified in the autonomous kinase. These data suggest that an autonomous kinase derived from Apl II may play a role in synaptic facilitation in Aplysia.
Preserved performance by cerebellar patients on tests of word generation, discrimination learning, and attention.
Authors: Helmuth L L , Ivry R B , Shimizu N
Published: June 2007

Recent theories suggest that the human cerebellum may contribute to the performance of cognitive tasks. We tested a group of adult patients with cerebellar damage attributable to stroke, tumor, or atrophy on four experiments involving verbal learning or attention shifting. In experiment 1, a verb generation task, participants produced semantically related verbs when presented with a list of nouns. With successive blocks of practice responding to the same set of stimuli, both groups, including a subset of cerebellar patients with unilateral right hemisphere lesions, improved their response times. In experiment 2, a verbal discrimination task, participants learned by trial and error to pick the target words from a set of word pairs. When age was taken into account, there were no performance differences between cerebellar patients and control subjects. In experiment 3, measures of spatial attention shifting were obtained under both exogenous and endogenous cueing conditions. Cerebellar patients and control subjects showed similar costs and benefits in both cueing conditions and at all SOAs. In experiment 4, intra- and interdimensional shifts of nonspatial attention were elicited by presenting word cues before the appearance of a target. Performance was substantially similar for cerebellar patients and control subjects. These results are presented as a cautionary note. The experiments failed to provide support for current hypotheses regarding the role of the cerebellum in verbal learning or attention. Alternative interpretations of previous results are discussed.
Multiple subclasses of purkinje cells in the primate floccular complex provide similar signals to guide learning in the vestibulo-ocular reflex.
Authors: Raymond J L , Lisberger S G
Published: June 2007

The neural "learning rules" governing the induction of plasticity in the cerebellum were analyzed by recording the patterns of neural activity in awake, behaving animals during stimuli that induce a form of cerebellum-dependent learning. We recorded the simple- and complex-spike responses of a broad sample of Purkinje cells in the floccular complex during a number of stimulus conditions that induce motor learning in the vestibulo-ocular reflex (VOR). Each subclass of Purkinje cells carried essentially the same information about required changes in the gain of the VOR. The correlation of simple-spike activity in Purkinje cells with activity in vestibular pathways could guide learning during low-frequency but not high-frequency stimuli. Climbing fiber activity could guide learning during all stimuli tested but only if compared with the activity present approximately 100 msec earlier in either vestibular pathways or Purkinje cells.
Conditioned response timing and integration in the cerebellum.
Authors: Moore J W , Choi J S
Published: June 2007

Classical conditioning procedures instill knowledge about the temporal relationships between events. The unconditioned stimulus (US) is the event to be timed. The conditioned response (CR) is viewed as a prediction of the imminence of the US. Knowledge of the elapsed time between conditioned stimuli (CSs) and US delivery is expressed in the topological features of the CR. The peak amplitude of the CR coincides with the timing of the US. A simple connectionist network based on Sutton and Barto's Time Derivative (TD) Model of Pavlovian Reinforcement provides a mechanism that can account for and simulate CR timing in a variety of protocols. This article describes extensions of the model to predictive timing under temporal uncertainty. The model is expressed in terms of equations that operate in real time according to a competitive learning rule. The unfolding of time from the onsets and offsets of events such as CSs is represented by the propagation of activity along a sequence of time-tagged elements. The model can be aligned with anatomical circuits of the cerebellum and brain stem that are essential for learning and performance of conditioned eye-blink responses.
A model of Pavlovian eyelid conditioning based on the synaptic organization of the cerebellum.
Authors: Mauk M D , Donegan N H
Published: June 2007

We present a model based on the synaptic and cellular organization of the cerebellum to derive a diverse range of phenomena observed in Pavlovian eyelid conditioning. These phenomena are addressed in terms of critical pathways and network properties, as well as the sites and rules for synaptic plasticity. The theory is based on four primary hypotheses: (1) Two cerebellar sites of plasticity are involved in conditioning: (a) bidirectional long-term depression/potentiation at granule cell synapses onto Purkinje cells (gr-->Pkj) in the cerebellar cortex and (b) bidirectional plasticity in the interpositus nucleus that is controlled by inhibitory inputs from Purkinje cells; (2) climbing fiber activity is regulated to an equilibrium level at which the net strength of gr-->Pkj synapses remains constant unless an unexpected unconditioned stimulus (US) is presented or an expected US is omitted; (3) a time-varying representation of the conditioned stimulus (CS) in the cerebellar cortex permits the temporal discrimination required for conditioned response timing; and (4) the ability of a particular segment of the CS to be represented consistently across trials varies as a function of time since CS onset. This variation in across-trials consistency is thought to contribute to the ISI function. The model suggests several empirically testable predictions, some of which have been tested recently.
Absence of cerebellar long-term depression in mice lacking neuronal nitric oxide synthase.
Authors: Lev-Ram V , Nebyelul Z , Ellisman M H , Huang P L , Tsien R Y
Published: June 2007

Extensive pharmacological evidence suggests that nitric oxide (NO) is a crucial transmitter for cerebellar long-term depression (LTD), a long-lasting decrease in efficacy of the synapses from parallel fibers onto Purkinje neurons, triggered by coincident presynaptic activity and postsynaptic depolarization. We now show that LTD cannot be induced in Purkinje neurons under whole-cell patch clamp in cerebellar slices from young adult mice genetically lacking neuronal nitric oxide synthase (nNOS). This genetic evidence confirms the essentiality of NO and nNOS for LTD in young adult rodents. Surprisingly, LTD in cells from nNOS knockout mice cannot be rescued by photolytic uncaging of NO and cGMP inside Purkinje neurons, although such stimuli circumvent acute pharmacological inhibition of nNOS and soluble guanylate cyclase in normal rodents. Also slices from knockout mice show no deficit in cGMP elevation in response to exogenous NO. Therefore, prolonged absence of nNOS allows atrophy of the signaling pathway downstream of cGMP.
Cerebellar guidance of premotor network development and sensorimotor learning.
Authors: Hua S E , Houk J C
Published: June 2007

Single unit and imaging studies have shown that the cerebellum is especially active during the acquisition phase of certain motor and cognitive tasks. These data are consistent with the hypothesis that particular sensorimotor procedures are acquired and stored in the cerebellar cortex and that this knowledge can then be exported to the cerebral cortex and premotor networks for more efficient execution. In this article we present a model to illustrate how the cerebellar cortex might guide the development of cortical-cerebellar network connections and how a similar mechanism operating in the adult could mediate the exportation of sensorimotor knowledge from the cerebellum to the motor cortex. The model consists of a three-layered recurrent network representing the cerebello-thalamocortical-ponto-cerebellar limb premotor network. The cerebellar cortex is not explicitly modeled. Our simulations show that Hebbian learning combined with weight normalization allows the emergence of reciprocal and modular structure in the limb premotor network. Reciprocal connections allow activity to reverberate around specific loops. Modularity organizes the connections into specific channels. Furthermore, we show that cerebellar learning can be exported to motor cortex through these modular and reciprocal premotor circuits. In particular, we simulate developmental alignment of visuomotor relations and their realignment as a consequence of prism exposure. The exportation of sensorimotor knowledge from the cerebellum to the motor cortex may allow faster and more efficient execution of learned motor responses.
Single-unit evidence for eye-blink conditioning in cerebellar cortex is altered, but not eliminated, by interpositus nucleus lesions.
Authors: Katz D B , Steinmetz J E
Published: June 2007

Many theories of motor learning explain learning-related changes in motor behavior in terms of plasticity in the cerebellar cortex. Empirical evidence, however, does not always appear to be consistent with such formulations. It is the anterior cerebellar interpositus nucleus (aINP) that seems to be essential for acquisition and retention of conditioned eye-blink responses under most circumstances and it has been therefore suggested that the aINP is the critical site of learning-related plasticity during eye-blink conditioning. Supporting this conclusion are studies demonstrating that multiple-unit conditioning-related neural activity patterns observed in many brain regions disappear after aINP lesion. The possibility that the cerebellar cortex may be involved in forming these patterns has not been assessed adequately, however. In the current study, trained rabbits received kainic acid lesions of the INP. After recovery, the animals underwent additional sessions of conditioning during which single-unit activity was recorded from the cerebellar cortex. Our results suggest that the aINP is not the sole site of plasticity during eye-blink conditioning, as a subset of the neurons recorded from lesioned animals demonstrated conditioning-related firing patterns. The lesions did change the character of these firing patterns from those observed in saline controls, however, in ways that can be generally described as a loss of organization. The normal tendency for the population of cortical cells to change firing rate together, for instance, was significantly less noticeable in lesioned animals. These results suggest that the aINP may be involved in the production of important features of conditioned responding, such as system timing function, therefore suggesting the need for more models that incorporate aINP and brain stem feedback as integral to the production of organized neural and behavioral responses.
Intact enhancement of declarative memory for emotional material in amnesia.
Authors: Hamann S B , Cahill L , McGaugh J L , Squire L R
Published: June 2007

Emotional arousal has been demonstrated to enhance declarative memory (conscious recollection) in humans in both naturalistic and experimental studies. Here, we examined this effect in amnesia. Amnesic patients and controls viewed a slide presentation while listening to an accompanying emotionally arousing story. In both groups, recognition memory was enhanced for the emotionally arousing story elements. The magnitude of the enhancement was proportional for both amnesic patients and controls. Emotional reactions to the story were also equivalent. The results suggest that the enhancement of declarative memory associated with emotional arousal is intact in amnesia. Together with findings from patients with bilateral amygdala lesions, the results indicate that the amygdala is responsible for the enhancement effect.
Neuroanatomical correlates of implicit and explicit memory for structurally possible and impossible visual objects.
Authors: Uecker A , Reiman E M , Schacter D L , Polster M R , Cooper L A , Yun L S , Chen K
Published: June 2007

Implicit memory refers to nonconscious retrieval of past experience demonstrated by facilitation in test performance on tasks that do not require intentional recollection of previous experiences. Explicit memory, in contrast, refers to the conscious retrieval of prior information, as demonstrated during standard recall and recognition tasks. In this experiment, positron emission tomographic (PET) measurements of regional cerebral blood flow (CBF), a marker of local neuronal activity, were used to identify and contrast brain regions that participate in the perception, implicit memory, and explicit memory for structurally possible and impossible visual objects. Ten CBF images were acquired in 16 normal women as they made possible/impossible and old/new recognition decisions about previously studied (old) and nonstudied (new) structurally possible and impossible objects. As reported previously, object decisions for familiar possible objects were associated with increased CBF in the vicinity of the left inferior temporal and fusiform gyri and recognition memory for familiar possible objects was associated with increased CBF in the vicinity of the right hippocampus. In this report, we provide more extensive analyses of the roles of the inferior temporal cortex, the hippocampus, the parahippocampus, and the pulvinar in encoding and retrieval operations. Additionally, patterns of CBF increases and decreases provide information regarding the neural structures involved in implicit and explicit memory.
Reactivation-dependent changes in memory states in the terrestrial slug Limax flavus.
Authors: Sekiguchi T , Yamada A , Suzuki H
Published: June 2007

The change in memory state in the terrestrial slug Limax flavus was studied using cooling-induced retrograde amnesia. Slugs were first conditioned to avoid carrot odor and then a second conditioning procedure was applied 1, 3, 6, or 7 days after the first conditioning trial. Cooling the slugs to approximately 1 degrees C on day 7 immediately after the presentation of the odor used in the conditioning resulted in retrograde amnesia in the slugs that were subject to a second conditioning on day 6 or 7, but not in slugs that were subject to a second conditioning on day 1 or 3. Next, second-order conditioning was used as the second conditioning procedure to distinguish the memory acquired in the first conditioning from that acquired in the second conditioning and similar results were obtained. These results suggest that the reactivation of memory altered the memory state from a cooling-insensitive state to a cooling-sensitive one. A possible model for memory states is discussed.
Deficit in learning of a motor skill requiring strategy, but not of perceptuomotor recalibration, with aging.
Authors: McNay E C , Willingham D B
Published: June 2007

We investigated the effect of aging on different aspects of motor skill learning using two computer-presented perceptuomotor tasks. The relationship between visual and proprioceptive feedback was transformed in the first task, which was open to the formation and use of strategies. This task was designed to lead to perceptuomotor adaptation that was then measured by performance on a very similar second task that was not open to the use of strategy task. Older participants showed impaired learning of the strategic task but not of the nonstrategic task. This is in line with the suggestion that the effect of aging on learning and memory may be to reduce working memory resources.
A model of cerebellar metaplasticity.
Authors: Schweighofer N , Arbib M A
Published: June 2007

The term "learning rule" in neural network theory usually refers to a rule for the plasticity of a given synapse, whereas metaplasticity involves a "metalearning algorithm" describing higher level control mechanisms for apportioning plasticity across a population of synapses. We propose here that the cerebellar cortex may use metaplasticity, and we demonstrate this by introducing the Cerebellar Adaptive Rate Learning (CARL) algorithm that concentrates learning on those Purkinje cell synapses whose adaptation is most relevant to learning an overall pattern. Our results show that this biologically plausible metalearning algorithm not only improves significantly the learning capability of the cerebellum but is very robust. Finally, we identify several putative neurochemicals that could be involved in a cascade of events leading to adaptive learning rates in Purkinje cell synapses.
Habitat‐related heterogeneity in breeding in a metapopulation of the Iberian lynx
Authors: Fernández Néstor , Delibes Miguel , Palomares Francisco
Published: June 2007

Identifying attributes associated with good breeding habitat is critical for understanding animal population dynamics. However, the association between environmental heterogeneity and breeding probability has been often overlooked in habitat analyses. We evaluated habitat quality in a metapopulation of the endangered Iberian lynxLynx pardinusby analyzing spatiotemporal patterns in breeding records. Data summarizing successful production of litters after emergence from dens over four years within 13 lynx territories were examined. We designed a set of generalized linear mixed models representing different hypotheses regarding how patterns in breeding records relate to environmental heterogeneity. Environmental heterogeneity was described by two characteristics: 1) a landscape index measured in lynx territories indicative of time‐averaged prey availability and 2) yearly variability in prey abundance not captured with this index. By including the random effect of the lynx territory we also accounted for other territory‐specific effects on reproduction. We found significant differences in yearly prey density dynamics among lynx territories. However, temporal variation in prey density contributed poorly to explaining lynx breeding. The most parsimonious model included the landscape structure as the only effect explaining breeding patterns. A multinomial‐model‐representation of the landscape hypothesis explained nearly 50% of variability in breeding records. Results pointed to the existence of a habitat quality gradient associated with particular landscape structures influencing lynx habitat selection and breeding performance. Underlying this gradient was time‐averaged prey availability. Probably as a result of long‐term fitness strategies in long‐lived territorial species, the short‐term fluctuations in prey availability had a minor influence. Our results illustrate how habitat inferences can be enhanced by incorporating the link between spatiotemporal patterns in reproduction and environmental heterogeneity.
Parents' and service providers' perceptions of family‐centred practice in a community‐based, paediatric disability service in Australia
Authors: Raghavendra P. , Murchland S. , Bentley M. , Wake‐Dyster W. , Lyons T.
Published: June 2007

Background  For children who have physical disabilities and their families, involvement with a variety of providers of rehabilitation services is the norm rather than the exception. Despite family‐centred practice (FCP) being recognized as the ‘best practice’ model, families experience models of service provision that range from ‘expert’ to ‘collaborative’. After adopting FCP at Novita Children's Services in South Australia, it was imperative to determine the effectiveness of the implementation of FCP.

Aim  To investigate parents' and staff's perceptions of FCP at Novita as part of ongoing quality assurance activity, and to identify any gaps in the services provided.

Methods  The Measures of Processes of Care (MPOC) for parents/caregivers and service providers were utilized. A total of 189 families stratified by the three age groups of clients (<6, 6–12 and 13–18 years) and home location (metropolitan and rural) completed the MPOC‐20 questionnaire. A total of 145 staff, allied health therapists, rehabilitation engineers, managers and other staff who have direct contact with clients and their families completed the MPOC – service providers (MPOC‐SP) questionnaire.

Results  Parents generally rated the family‐centred behaviours of staff as positive. Respectful and supportive care received the highest rating, while providing general information received the lowest. There were significant differences in scores for all five scales of the MPOC between metropolitan and rural families and the age of the child. Service providers also generally rated their family‐centred behaviours as positive. There were significant differences among the professions in areas of showing interpersonal sensitivity and providing general information.

Conclusions  The findings suggest that parents and service providers perceive FCP as positive at Novita, with some areas for improvement. The MPOC‐20 and MPOC‐SP can be used to measure FCP and to identify service delivery gaps, which warrant further exploration.
The mechanisms determining the nucleolar‐organizing regions inactivation of domestic horse chromosomes
Authors: Slota E. , Wnuk M. , Bugno M. , Pienkowska‐Schelling A. , Schelling C. , Bratus A. , Kotylak Z.
Published: June 2007

Cytogenetic investigations of the nucleolar‐organizing regions (NORs) show that there is variation in the transcriptional activity of rDNA in many organisms. As a consequence, genetic polymorphism of these regions has been detected. The aim of the present study was to evaluate the hypothetic genetic mechanisms determining the NORs polymorphism of the domestic horse chromosomes. Molecular cytogenetic analyses were carried out on Hucul horses and the following techniques were used: fluorescence in situ hybridization (FISH), telomere primed in situ synthesis (PRINS), in situ nick‐translation with HpaII, silver staining (AgNOR) and C‐banding technique (CBG). The obtained results suggest that variation in the number and size of silver deposits is related to the number of rDNA copies, DNA methylation and the localization of ribosomal DNA loci in telomeric regions. Moreover, we have found that chromosome pairs 28 and 31 are characterized by higher variation in the NORs number.
SNP discovery, expression and association analysis for the SDHD gene in pigs
Authors: Guimaraes S.E.F. , Rothschild M.F. , Ciobanu D. , Stahl C.H. , Lonergan S.M.
Published: June 2007

The SDHD gene was examined for single nucleotide polymorphisms (SNP) as well as for expression changes in the Longissimus dorsi muscle of commercial pigs with different potential for growth. Three SNPs, including one previously described in the coding region and two new ones in the 3′‐UTR, were found. The normalized expression of SDHD was correlated with growth, meat quality and sensory traits (p < 0.05). For the commercial pigs used in this study, as well as a Berkshire × Yorkshire resource population, the SNPs have been associated (p < 0.05) with: growth, carcass composition, meat quality and sensory traits. Despite the fact that the described SNPs were not significantly associated with the normalized expression values, the SDHD SNPs and expression were associated with growth and meat quality traits in pigs.
Effect of polymorphisms linked to LEP gene on its expression on adipose tissues in beef cattle
Authors: Passos D.T. , Hepp D. , Moraes J.C.F. , Weimer T.A.
Published: June 2007

In cattle, genetic markers at the leptin (LEP) gene and at those linked to the gene have been described as affecting calving interval (markers LEPSau3AI and IDVGA51), or daily weight gain (BMS1074 and BM1500). This work investigated the effect of these alleles on LEP mRNA levels in cattle subcutaneous and omental adipose tissues. A sample of 137 females of a Brangus‐Ibage beef cattle herd was analysed to evaluate the distribution of the polymorphisms; then, animals having at least one of the IDVGA51*181 (allele 181 at marker IDVGA51; six animals), LEPSau3AI*2 (four), BMS1074*151 (13), BM1500*135 (six) alleles and a control group composed of animals without any of these alleles (four animals) were submitted to surgery to obtain omental and subcutaneous adipose tissues. Leptin mRNA expression was quantified by TaqMan RT‐PCR, using 18S rRNA as internal control and adjusted for the effect of body condition score, through regression analysis. Omental fat had LEP gene expression 33% lower than the subcutaneous tissue. Carriers of IDVGA*181 and BMS1074*151 showed subcutaneous fat leptin mRNA levels higher than the controls. Leptin controls feed intake and coordinates reproduction; therefore, animals with higher LEP gene expression will probably have lower daily weight gain than others with similar forage offer and nutritional condition and probably will also have longer calving interval.
Spontaneous induction of tetraploidy in hop using adventitious shoot regeneration method
Authors: Sˇkof S. , Bohanec B. , Kastelec D. , Luthar Z.
Published: June 2007

In the process of breeding triploid hop cultivars, diploid varieties need to be raised to the tetraploid level. Existing methods are predominantly based on treatment of the apices with antimitotic substances, in vivo or in vitro, resulting in a reported maximum of 26% tetraploids and a large proportion (over 60%) of mixoploids. This study was set‐up to test whether an adventitious shoot regeneration protocol can be used as an alternative. In the first part of the experiments, regeneration media and a choice of explants (internodes, petioles and leaf discs) were optimized using three hop cultivars with putatively low, medium or high adventitious shoot regeneration capacity. On an optimized induction medium supplemented with 6 mg/l N6‐(2‐isopentenyl) adenine (2iP), a regeneration rate up to 17.7% was obtained from cultured internodes, even of the most recalcitrant ‘Aurora’, while the regeneration rate of the most responsive ‘Tettnanger’ was 56.9%. Flow cytometric analysis of ploidy level revealed a high frequency of tetraploid induction, the highest (58.6%) being in ‘Savinjski golding’. In 616 regenerants of all three cultivars, 30.4% were found to be tetraploid, the others were diploid. Cytokinin content was found to be of minor importance in tetraploid induction. The high frequency of spontaneous tetraploid induction and, in particular, the complete absence of mixoploids makes this protocol an alternative to the currently established methods of chromosome doubling based on the use of antimitotic substances. The occurrence of a high proportion of tetraploid adventitious regenerants in hop is discussed in view of certain other biotechnological applications.
Genic microsatellite markers for discrimination of spinach cultivars
Authors: Khattak J. Z. K. , Christiansen J. L. , Torp A. M. , Andersen S. B.
Published: June 2007

A set of simple sequence repeat (SSR or microsatellite) markers was used to discriminate a collection of 33 Spinacia oleracea hybrid cultivars from seven different breeding stations all over the world. All SSR markers were genic microsatellite markers located in coding or non‐coding regions of genes of known function. Cluster analysis based on 13 of the SSR markers showed that the spinach hybrids grouped into three clusters. The first two clusters consisted of European spinach types, which were well discriminated according to their origin from different breeding stations. The third cluster was a mixture of Asian as well as European types of spinach. Subclusters in this group did not reflect differences in morphology, earliness or company origin. The data show that genic microsatellites are a powerful tool for discrimination of spinach cultivars.
Effect of mannitol pretreatment to improve green plant regeneration on isolated microspore culture in Triticum turgidum ssp. durum cv. ‘Jennah Khetifa’
Authors: Labbani Z. , De Buyser J. , Picard E.
Published: June 2007

The use of doubled haploids improves the efficiency of cultivar development in many crops and can be helpful in genetic and molecular studies. The major problem with this approach is the low efficiency of green plant regeneration. We describe here an efficient method for inducing embryos and regenerating green plants directly from isolated microspores of durum wheat cv. ‘Jennah Khetifa’. Tillers from donor plants were pretreated in 0.3 m mannitol and were stored at 4°C at various times: 3, 5, 6, 7, 8, 10 and 12 days. Our results showed clearly that the novel pretreatment combined mannitol 0.3 m and cold for 7 days had a strong effect on the number of embryos produced and regenerated green plants. Under this condition 13 475 mature embryos were produced from 2 693 500 microspores. Moreover, 85 green plants were obtained. High green plants regeneration frequency was recorded. As an average 11.55 green plants were produced per 100 000 microspores (about the equivalent of six plants per spike). Therefore, this study showed clearly that our results are the best ones published until now in durum wheat.
Neurology of Fabry disease
Authors: Low M. , Nicholls K. , Tubridy N. , Hand P. , Velakoulis D. , Kiers L. , Mitchell P. , Becker G.
Published: June 2007

Background: Fabry disease has diverse neurological manifestations, many of which influence morbidity and quality of life.

Aims: The aim of the study was to document the clinical and subclinical neurological manifestations in a cohort of Australian patients with Fabry disease, using multiple clinical tools and a multidisciplinary approach.

Methods: Participants completed focused questionnaires and underwent clinical neurological examination, Neurocognitive testing using Mini Mental State Examination and Neuropsychiatry Unit Cognitive Screen, Quantitative Sensory Testing (QST), autonomic assessment using RR interval variation, intracranial magnetic resonance imaging (MRI) and audiology. In subsets of patients who had previously undergone QST and/or prospective serial quality‐of‐life assessments over the previous 5 years, results before and after enzyme replacement therapy were compared.

Results: Twenty hemizygotes and two heterozygotes were recruited. The age (mean ± standard deviation (SD)) of male participants was 40.4 ± 11.9 years (range 20–62 years); the women were aged between 20 and 56 years. Increasing age was strongly associated with increasing neurological disability. Clinical peripheral neuropathy predominantly affected thermal sensation in all patients, with variable involvement of pinprick and light touch. QST confirmed these findings. Clinical cerebellar tests were commonly abnormal: this has not been previously reported in the absence of symptomatic cerebrovascular disease. There was hearing loss was in 90% of patients and no patient older than 44 years had normal hearing. MRI lesion prevalence increased with age. Despite neurological complications being common, formal cognitive testing was basically normal. QST thresholds for pain showed a significant change after enzyme replacement therapy.

Conclusions: Neurological complications in Fabry disease are common, complex and may be devastating. All patients studied had neurological involvement, with protean and diverse manifestations.
Effect of long‐term nebulized colistin on lung function and quality of life in patients with chronic bronchial sepsis
Authors: Steinfort D. P. , Steinfort C.
Published: June 2007

Recurrent Gram‐negative bacterial infection is a significant cause of death in patients with bronchiectasis and severe chronic obstructive pulmonary disease (COPD). Nebulized colistin in cystic fibrosis has shown maintenance of pulmonary function and improved symptom scores. We prospectively followed 18 patients with chronic bronchial sepsis treated with nebulized colistin 30 mg daily. Mean decline in forced expiratory volume in 1 s was significantly slower following commencement of inhaled colistin (44 mL/year vs 104 mL/year, P = 0.035). Mean decline in forced vital capacity was also significantly slower following commencement of colistin (48 mL/year vs 110 mL/year, P = 0.033). Patient‐reported quality of life improved following commencement of colistin (3.6 vs 6.2, P = 0.001). No patient had isolates resistant to colistin. No side‐effects were reported by patients in the cohort. Use of inhaled colistin in the treatment of bronchiectasis and severe (COPD) in patients with recurrent Gram‐negative infections is safe. Inhaled colistin may improve quality of life and slow decline in forced expiratory volume in 1 s and forced vital capacity.
Population dynamics of marine magnetotactic bacteria in a meromictic salt pond described with qPCR
Authors: Simmons Sheri L. , Bazylinski Dennis A. , Edwards Katrina J.
Published: June 2007

Magnetotactic bacteria (MTB) contain membrane‐bound magnetic iron minerals and are globally abundant in the suboxic/anoxic portions of chemically stratified marine and freshwater environments. However, their population dynamics and potential quantitative contribution to the biogeochemical cycles that they influence (iron, sulfur, carbon) have not been previously considered. Here we report the first quantitative description of the distribution of individual species of magnetite‐ and greigite‐producing MTB in a natural system. We developed a quantitative polymerase chain reaction assay targeting 16s rRNA genes to enumerate four major groups of marine MTB, and applied the assay to samples collected with respect to geochemical parameters during summer 2003 in seasonally stratified Salt Pond, MA. Using catalysed reporter deposition‐fluorescent in situ hybridization, we also show that a large greigite‐producing bacterium is distantly related to Thiomicrospira pelophila in the Gammaproteobacteria. Ribosomal RNA copy numbers obtained with quantitative polymerase chain reaction indicate that MTB comprise up to 10% of total Bacteria and that each organism has a characteristic distributional profile with respect to the chemocline.
Novel hopanoid cyclases from the environment
Authors: Pearson Ann , Flood Page Sarah R. , Jorgenson Tyler L. , Fischer Woodward W. , Higgins Meytal B.
Published: June 2007

Hopanoids are ubiquitous isoprenoid lipids found in modern biota, in recent sediments and in low‐maturity sedimentary rocks. Because these lipids primarily are derived from bacteria, they are used as proxies to help decipher geobiological communities. To date, much of the information about sources of hopanoids has come from surveys of culture collections, an approach that does not address the vast fraction of prokaryotic communities that remains uncharacterized. Here we investigated the phylogeny of hopanoid producers using culture‐independent methods. We obtained 79 new sequences of squalene‐hopene cyclase genes (sqhC) from marine and lacustrine bacterioplankton and analysed them along with all 31 sqhC fragments available from existing metagenomics libraries. The environmental sqhCs average only 60% translated amino acid identity to their closest relatives in public databases. The data imply that the sources of these important geologic biomarkers remain largely unknown. In particular, genes affiliated with known cyanobacterial sequences were not detected in the contemporary environments analysed here, yet the geologic record contains abundant hopanoids apparently of cyanobacterial origin. The data also suggest that hopanoid biosynthesis is uncommon: < 10% of bacterial species may be capable of producing hopanoids. A better understanding of the contemporary distribution of hopanoid biosynthesis may reveal fundamental insight about the function of these compounds, the organisms in which they are found, and the environmental signals preserved in the sedimentary record.
Fusarium solani species complex isolates conspecific with Fusarium solani f. sp. cucurbitae race 2 from naturally infected human and plant tissue and environmental sources are equally virulent on plants, grow at 37°C and are interfertile
Authors: Mehl Hillary L. , Epstein Lynn
Published: June 2007

In a previous taxonomic study based on multilocus sequencing of Fusarium from clinical specimens and hospital environments, the most common lineage was Fusarium solani species complex group 1 (FSSC 1) which is conspecific with F. solani f. sp. cucurbitae race 2, a pathogen of cucurbit fruits. The aims of our study were to determine if clinical and environmental isolates of FSSC 1 are plant pathogens and members of the same biological species as cucurbit isolates, and to determine if all isolates can germinate, grow and sporulate at 37°C. Isolates from the different sources did not differ in virulence on zucchini fruits. All FSSC 1 isolates were pathogenic and produced more rot than FSSC isolates from plant hosts other than cucurbits. Both mating types were found among isolates from each of the sources, and all isolates were sexually compatible with cucurbit isolates. All isolates germinated, grew and sporulated at 37°C. This is the first report in which plant pathogenicity has been verified for a collection of human clinical isolates. Our data are consistent with the hypothesis that all FSSC 1 isolates, regardless of source, are a single biological species, equally virulent plant pathogens and tolerant of the human body temperature.
Interpartner Legitimacy in the Alliance Development Process*
Authors: Kumar Rajesh , Das T. K.
Published: June 2007

abstract  We propose a framework to understand interpartner legitimacy in strategic alliances. Interpartner legitimacy is the mutual acknowledgment by the alliance partners that their actions are proper in the developmental processes of the alliance. We argue that interpartner legitimacy is needed for cooperation to achieve alliance objectives. We propose three types of interpartner legitimacy – pragmatic, moral, and cognitive legitimacy – and discuss the dynamics of these three types in the formation, operation, and outcome stages of alliance development. Further, we discuss the salience of interpartner legitimacy in different alliance types. Finally, we derive propositions for further research, and discuss strategies that alliance managers can adopt to develop interpartner legitimacy.
Boardroom Strategizing in Professional Associations: Processual and Institutional Perspectives*
Authors: Parker Lee D.
Published: June 2007

abstract  This study examines strategic decision‐making at the boardroom level of two non‐profit professional associations, penetrating directors' strategic orientations, discourse and decisions in their holistic context. In comparison with the predominantly survey and interview based literature on board level strategy behaviour, this study employs a longitudinal complete member researcher, participant observer methodology. Its findings are analysed from an institutional theory perspective and reveal selective championing of strategies by directors, the evaluation of strategic proposals and progress in predominantly financial resource/outcome terms, and directors' attention to navigating strategic initiatives through organizational politics. Also revealed are private sector philosophies imported into the non‐profit boardroom, the predominantly ceremonial role of formal strategic plans, and an informally enacted strategic discourse. This study offers a unique insider view of strategizing at the highest organizational level.
Socioeconomic gradients predict individual differences in neurocognitive abilities
Authors: Noble Kimberly G. , McCandliss Bruce D. , Farah Martha J.
Published: June 2007

Socioeconomic status (SES) is associated with childhood cognitive achievement. In previous research we found that this association shows neural specificity; specifically we found that groups of low and middle SES children differed disproportionately in perisylvian/language and prefrontal/executive abilities relative to other neurocognitive abilities. Here we address several new questions: To what extent does this disparity between groups reflect a gradient of SES‐related individual differences in neurocognitive development, as opposed to a more categorical difference? What other neurocognitive systems differ across individuals as a function of SES? Does linguistic ability mediate SES differences in other systems? And how do specific prefrontal/executive subsystems vary with SES? One hundred and fifty healthy, socioeconomically diverse first‐graders were administered tasks tapping language, visuospatial skills, memory, working memory, cognitive control, and reward processing. SES explained over 30% of the variance in language, and a smaller but highly significant portion of the variance in most other systems. Statistically mediating factors and possible interventional approaches are discussed.
The development of prudence in the face of varying future rewards
Authors: Lemmon Karen , Moore Chris
Published: June 2007

The choice to delay gratification, opting for a greater reward later instead of a smaller reward now, has been used as a measure of preschoolers’ ability to make future‐oriented decisions. The present studies investigated to what extent these choice tasks reflect children's ability to make choices in favour of their future self. In Experiment 1, preschoolers were presented with choices between a smaller immediate reward of one sticker and larger delayed rewards varying in amount from two to five stickers. Whereas 3‐year‐olds showed no increased tendency to choose the delayed option as quantity increased from two to five, 4‐year‐olds’ future‐oriented choices reflected the value of the delayed reward. In Experiment 2, preschoolers chose between immediate and delayed rewards that were equal in amount and varied between one and four stickers. Three‐year‐olds reliably chose the immediate reward and showed no differentiation among rewards, whereas 4‐year‐olds chose in a manner that suggested they were trying to satisfy both immediate and future desires. Together these results support the notion that future‐oriented prudence reflects growth in concern for the future self.