bluuebunny/crossref_metadata_2025 huggingface dataset:
β cells occur naturally in extrahepatic bile ducts of mice
Authors: Dutton James R. , Chillingworth Naomi L. , Eberhard Daniel , Brannon Claire R. , Hornsey Mark A. , Tosh David , Slack Jonathan M. W.
Published: December 2006

Insulin-secreting β cells were thought to reside only in the pancreas. Here, we show that β cells are also present in the extra-hepatic bile ducts of mice. They are characterised by insulin and C-peptide content, the presence of secretory granules that are immunoreactive for insulin, and the ducts exhibit glucose-stimulated insulin secretion. Genetic lineage labelling shows that these β cells arise from the liver domain rather than the pancreas and, by histological study, they appear to be formed directly from the bile duct epithelium in late embryogenesis. Other endocrine cell types (producing somatostatin and pancreatic polypeptide) are also found in close association with the bile-duct-derived β cells, but exocrine pancreatic tissue is not present. This discovery of β cells outside the mammalian pancreas has implications for regenerative medicine, indicating that biliary epithelium might offer a new source of β cells for the treatment of diabetes. The finding also has evolutionary significance, because it is known that certain basal vertebrates usually form all of their β cells from the bile ducts. The mammalian bile-duct-derived β cells might therefore represent an extant trace of the evolutionary origin of the vertebrate β cell.
Ena/VASP proteins mediate repulsion from ephrin ligands
Authors: Evans Iwan R. , Renne Thomas , Gertler Frank B. , Nobes Catherine D.
Published: December 2006

Ena/VASP proteins negatively regulate cell motility and contribute to repulsion from several guidance cues; however, there is currently no evidence for a role downstream of Eph receptors. Eph receptors mediate repulsion from ephrins at sites of intercellular contact during several developmental migrations. For example, the expression of ephrin-Bs in posterior halves of somites restricts neural crest cell migration to the anterior halves. Here we show that ephrin-B2 destabilises neural crest cell lamellipodia when presented in a substrate-bound or soluble form. Our timelapse studies show that repulsive events are associated with the rearward collapse and subsequent loss of lamellipodia as membrane ruffles. We hypothesise that Ena/VASP proteins contribute to repulsion from ephrins by destabilising cellular protrusions and show that Ena/VASP-deficient fibroblasts exhibit reduced repulsion from both ephrin-A and ephrin-B stripes compared to wild-type controls. Moreover, when EphB4 and ephrin-B2 were expressed in neighbouring Swiss 3T3 fibroblasts, VASP and Mena co-accumulated with activated Eph receptors at protrusions formed by EphB4-expressing cells. Sequestration of Ena/VASP proteins away from the periphery of these cells inhibited Eph receptor internalisation, a process that facilitates repulsion. Our results suggest that Ena/VASP proteins regulate ephrin-induced Eph receptor signalling events, possibly by destabilising lamellipodial protrusions.
A B23-interacting sequence as a tool to visualize protein interactions in a cellular context
Authors: Lechertier Tanguy , Sirri Valentina , Hernandez-Verdun Danièle , Roussel Pascal
Published: December 2006

We report the characterization of a nucleolar localization sequence (NoLS) that targets the green fluorescent protein (GFP) into the granular component (GC) of nucleoli. This NoLS interacts in vitro specifically and directly with the major nucleolar protein B23 and more precisely with the region of B23 including the two acidic stretches. The affinity of NoLS for B23 is stronger than that of the HIV-1 Rev protein in vitro. Moreover, B23-NoLS interaction also occurs in vivo. Indeed, (1) NoLS confers on the GFP the behavior of B23 throughout the cell cycle, (2) the GFP-NoLS fusion and B23 remain colocalized after drug treatments, (3) a selective delocalization of B23 from nucleoli to nucleoplasm induces a concomitent delocalization of the GFP-NoLS fusion, and (4) the fusion of NoLS to fibrillarin makes it possible to colocalize fibrillarin and B23. Interestingly, by fusing NoLS to fibrillarin, both fibrillarin and the fibrillarin partner Nop56 are mislocalized in the GC of nucleoli. Similarly, by fusing the NoLS to MafG, part of the nuclear transcription factor NF-E2 composed of both MafG and p45 NF-E2, NF-E2 is redirected from the nucleoplasm to the nucleoli. Thus, we propose that the NoLS may be used as a tool to visualize and prove protein interactions in a cellular context.
Preparation of Gold and Platinum Nanoparticles Using Visible Light Activated FeIII-complex
Authors: Lee Jaesang , Ryu Jungho , Choi Wonyong
Published: December 2006

Iron(III)–citrate photochemical system can generate Au and Pt nanoparticles under the visible light illumination with playing the dual role as a precursor of reducing radicals and a stabilizer.
Electron Transfer in Tris(bipyridine)ruthenium(II) Complex Films on ITO
Authors: Kanaizuka Katsuhiko , Kato Shinji , Moriyama Hiroshi , Pac Chyongjin
Published: December 2006

The packing density of Ru(bpy)3 units was shown to be a crucial factor in constructing thin films having reversible redox functions. We have succeeded in controlling the surface of Ru(bpy)3 thin films using a bottom-up fabrication procedure. The redox function of the resulting multilayered films is highly predictable and reliable, although the productivity of the stepwise film growth of 1 is not high.
Chemical Synthesis of Face-centered-tetragonal FePt Film Using Sol–Gel Method
Authors: Su Hailin , Tang Nujiang , Wang Ruilong , Nie Bai , Tang Shaolong , Lv Liya , Du Youwei
Published: December 2006

A simple sol–gel spin-coating technique was developed to prepare FePt films. The calcining temperature was found to have great influences on the film’s crystalline structure and magnetic properties. For this method, pure face-centered-tetragonal FePt film was finally obtained by calcining at 370 °C and subsequently reducing at 470 °C.
N-Terminus Methylation of Desulfovibrio vulgaris (Miyazaki) F Cytochrome c3
Authors: Iida Shin , Kawano Yusuke , Asakura Noriyuki , Tabata Kenji , Okura Ichiro , Kamachi Toshiaki
Published: December 2006

Cytochrome c3 from Desulfovibrio vulgaris (Miyazaki) F is an electron-transfer protein between hydrogenase and ferredoxin and other types of cytochromes. In this study, an N-terminus of the cytochrome c3 has been identified as an N-methylated alanine residue by cleavage with peptidase, liquid chromatography/mass spectrometry (LC/MS) and nuclear magnetic resonance (NMR) analysis. Heterologous expression of the cytochrome c3 with Shewanella oneidensis TSP-C is not methylated, this indicate that the N-methylation occur in vivo in D. vulgaris.
1,3-Dipolar Cycloaddition of Ethyl Diazoacetate to Alkynes in the Pores of Zeolite NaY
Authors: Kobayashi Keijiro , Igura Yuta , Imachi Shouhei , Masui Yoichi , Onaka Makoto
Published: December 2006

Zeolite NaY promotes 1,3-dipolar cycloaddition of ethyl diazoacetate to alkynes having an electron-withdrawing group to afford the corresponding functionalized pyrazoles in high yields. The activation of the dipolarophile inside the pores of NaY is proposed based on the 13C MAS NMR analysis.
The construction of self in online support groups for victims of domestic violence
Authors: Hurley Anna L. , Sullivan Paul , McCarthy John
Published: December 2006

In this article, we use the exemplar of domestic violence to examine the construction of self online. To do this, a positional approach to language is combined with a Bakhtinian inspired, phenomenological approach to language. Such an approach is designed to capture both the rhetorical and the intoned quality of language. This approach also draws attention to the role of the assumed community in dialogically interrupting and reflexively structuring the construction of self online. From this conceptual perspective, we examine a variety of posted messages to the public bulletin boards of a number of different online support groups for domestic violence. Three interpenetrating analytic themes emerged from this analysis: (1) The construction of self in relation to online support group members; (2) The construction of self in relation to abuser and (3) The construction of self in relation to past self. These themes are explicated over four key extracts. These extracts are also analysed in terms of the insights they offer into the phenomenological, positional and dialogical dimensions of an utterance directed at a community.
An exploratory study of the needs of staff who care for offenders with a diagnosis of personality disorder
Authors: Kurtz Arabella , Turner Keith
Published: December 2006

People with a diagnosis of personality disorder who are considered a risk to others are a current concern for public services, government and society. Healthcare provision for this group has recently increased, making it important to begin to learn about the needs of staff working in such a challenging area. An exploratory interview study with staff working in a medium secure unit for offenders with a diagnosis of personality disorder (Unit Z) is presented. Interviews were line‐coded and analysed according to the grounded theory method. A model was developed from higher order categories. This related key contextual factors to areas of concern for staff. The key contextual factors were: ‘complexity of the task’ and ‘tension in the relationship with outside’. The areas of concern were: ‘desire for more meaningful contact’, ‘contradictory attitude towards openness’, ‘feeling physically safe but emotionally vulnerable’, ‘ambivalence towards structure and control’ and ‘emphasis on staff relationships’. ‘Risk of isolation’ formed a core category and described Unit Z staff's pervading sense of distance from the outside world. These categories are described with supporting quotations and discussed in relation to the existing literature. Their implications for clinical practice and the development of services are considered.
Exercise and Calcium Combined Results in a Greater Osteogenic Effect Than Either Factor Alone: A Blinded Randomized Placebo-Controlled Trial in Boys
Authors: Bass Shona L , Naughton Geraldine , Saxon Leanne , Iuliano-Burns Sandra , Daly Robin , Briganti Esther M , Hume Clare , Nowson Caryl
Published: December 2006

We examined the combined effects of exercise and calcium on BMC accrual in pre- and early-pubertal boys. Exercise and calcium together resulted in a 2% greater increase in femur BMC than either factor alone and a 3% greater increase in BMC at the tibia–fibula compared with the placebo group. Increasing dietary calcium seems to be important for optimizing the osteogenic effects of exercise.

Introduction: Understanding the relationship between exercise and calcium during growth is important given that the greatest benefits derived from these factors are achieved during the first two decades of life. We conducted a blinded randomized-controlled exercise–calcium intervention in pre- and early-pubertal boys to test the following hypotheses. (1) At the loaded sites (femur and tibia–fibula), exercise and calcium will produce greater skeletal benefits than either exercise or calcium alone. (2) At nonloaded sites (humerus and radius–ulna), there will be an effect of calcium supplementation.

Materials and Methods: Eighty-eight pre- and early-pubertal boys were randomly assigned to one of four study groups: moderate impact exercise with or without calcium (Ca) (Ex + Ca and Ex + placebo, respectively) or low impact exercise with or without Ca (No-Ex + Ca and No-Ex + Placebo, respectively). The intervention involved 20 minutes of either moderate- or low-impact exercise performed three times a week and/or the addition of Ca-fortified foods using milk minerals (392 ± 29 mg/day) or nonfortified foods over 8.5 months. Analysis of covariance was used to determine the main and combined effects of exercise and calcium on BMC after adjusting for baseline BMC.

Results: At baseline, no differences were reported between the groups for height, weight, BMC, or bone length. The increase in femur BMC in the Ex + Ca group was ∼2% greater than the increase in the Ex + placebo, No-Ex + Ca, or No-Ex + Placebo groups (all p < 0.03). At the tibia–fibula, the increase in BMC in the Ex + Ca group was ∼3% greater than the No-Ex + placebo group (p < 0.02) and 2% greater than the Ex + Placebo and the No-Ex + Ca groups (not significant). No effect of any group was detected at the humerus, ulna–radius, or lumbar spine for BMC, height, bone area, or volume.

Conclusions: In this group of normally active boys with adequate calcium intakes, additional exercise and calcium supplementation resulted in a 2–3% greater increase in BMC than controls at the loaded sites. These findings strengthen the evidence base for public health campaigns to address both exercise and dietary changes in children for optimizing the attainment of peak BMC.
Osteoporosis-Related Kyphosis and Impairments in Pulmonary Function: A Systematic Review
Authors: Harrison Robyn A , Siminoski Kerry , Vethanayagam Dilini , Majumdar Sumit R
Published: December 2006

We conducted a systematic review to examine the relationship between osteoporotic vertebral fractures, kyphosis, and pulmonary function. Findings suggest modest but predictable declines in vital capacity related to the degree of kyphosis. However, there were only four studies, and all had significant methodologic limitations. Further high-quality research is needed.

Introduction: Our objective was to systematically review the extent to which osteoporosis-related vertebral fractures and kyphosis affect pulmonary function.

Materials and Methods: We used a literature search from 1966 to 2006 (using Medline, EMBASE, and hand searches of references) for studies examining pulmonary function in patients without known lung disease who had vertebral fractures or kyphosis secondary to osteoporosis. Two reviewers independently abstracted data. Heterogeneity precluded formal meta-analysis.

Results: Initial searches yielded 453 articles. After applying eligibility criteria, only four case-control studies of limited quality (e.g., only one study was blinded) remained. Since 1966, only 109 patients (6 men) have been studied. All four studies reported reductions in vital capacity (VC), with values ranging from 68% to 94% of predicted values. This was quantified as a 9% reduction in predicted VC per vertebral fracture in one study. The degree of kyphosis clinically (one study) or radiographically (three studies) correlated with declines in VC; impairments were most notable at kyphotic angles >55°. Statistically significant differences in percent predicted VC were obtained only when arm span or recalled height, rather than measured height, was used (two studies).

Conclusions: Despite conventional teaching, the evidence relating osteoporotic vertebral fractures or kyphosis to pulmonary function is limited. On the basis of available studies, declines in VC secondary to kyphosis seem modest and directly related to the number of vertebral fractures or degree of kyphosis. Future studies need longitudinal follow-up of larger numbers of men and women, appropriate proxies for height, standardized measures for pulmonary function and kyphosis, and efforts to blind outcomes ascertainment.
Quantitative Trait Loci for BMD and Bone Strength in an Intercross Between Domestic and Wildtype Chickens
Authors: Rubin Carl-Johan , Brändström Helena , Wright Dominic , Kerje Susanne , Gunnarsson Ulrika , Schutz Karin , Fredriksson Robert , Jensen Per , Andersson Leif , Ohlsson Claes , Mallmin Hans , Larsson Sune , Kindmark Andreas
Published: December 2006

With chicken used as a model species, we used QTL analysis to examine the genetic contribution to bone traits. We report the identification of four QTLs for femoral traits: one for bone strength, one for endosteal circumference, and two affecting mineral density of noncortical bone.

Introduction: BMD is a highly heritable phenotype, governed by elements at numerous loci. In studies examining the genetic contribution to bone traits, many loci have been identified in humans and in other species. The goal of this study was to identify quantitative trait loci (QTLs) controlling BMD and bone strength in an intercross between wildtype and domestic chickens.

Materials and Methods: A set of 164 markers, covering 30 chromosomes (chr.), were used to genotype 337 F2-individuals from an intercross of domesticated white Leghorn and wildtype red junglefowl chicken. DXA and pQCT were used to measure BMD and bone structure. Three-point bending tests and torsional strength tests were performed to determine the biomechanical strength of the bone. QTLs were mapped using forward selection for loci with significant marginal effects.

Results: Four QTLs for femoral bone traits were identified in QTL analysis with body weight included as a covariate. A QTL on chr. 1 affected female noncortical BMD (LOD 4.6) and is syntenic to human 12q21–12q23. Also located on chr. 1, a locus with synteny to human 12q13–14 affected endosteal circumference (LOD 4.6). On chr. 2, a QTL corresponding to human 5p13-p15, 7p12, 18q12, 18q21, and 9q22–9q31 affected BMD in females; noncortical (LOD 4.0) and metaphyseal (LOD 7.0) BMD by pQCT and BMD by DXA (LOD 5.9). A QTL located on chr. 20 (LOD 5.2) affected bone biomechanical strength and had sex-dependent effects. In addition to the significant QTLs, 10 further loci with suggestive linkage to bone traits were identified.

Conclusions: Four QTLs were identified: two for noncortical BMD, one for endosteal circumference, and one affecting bone biomechanical strength. The future identification of genes responsible for these QTLs will increase the understanding of vertebrate skeletal biology.
Alterations of Cortical and Trabecular Architecture Are Associated With Fractures in Postmenopausal Women, Partially Independent of Decreased BMD Measured by DXA: The OFELY Study
Authors: Sornay-Rendu Elisabeth , Boutroy Stéphanie , Munoz Françoise , Delmas Pierre D
Published: December 2006

We assessed the role of low aBMD and impaired architecture—assessed by an HR-pQCT system—in a case-control study of postmenopausal women with fractures. Vertebral and nonvertebral fractures are associated with low volumetric BMD and architectural alterations of trabecular and cortical bone, independent of aBMD assessed by DXA.

Introduction: Alterations of bone architecture and low BMD both contribute to skeletal fragility, but the contribution of cortical and trabecular architecture, independently of areal BMD (aBMD), to the risk of fracture in postmenopausal women has not been thoroughly evaluated. We assessed the role of impaired architecture and low BMD in postmenopausal women with fractures.

Materials and Methods: A matched case-control study in women from the OFELY cohort was performed after 13 years of follow-up. One hundred one women (mean, 73.7 ± 8 years) who sustained a fragility fracture during the follow-up of the study were age-matched with one control who never had a fracture. Density and architecture at the distal radius and tibia were measured with high-resolution pQCT (HR-pQCT) using an XTreme CT (Scanco Medical AG, Bassersdorf, Switzerland). aBMD at the total hip and ultradistal radius was measured by DXA.

Results: There were 80 peripheral fractures in 72 women, 44 vertebral fractures in 34 women, and both types of fractures in 5 women over the 14 years of follow-up. At the distal radius, women with fractures had lower volumetric total (D tot) and trabecular (D trab) BMDs, BV/TV, cortical thickness (Cort Th), trabecular number (TbN), and trabecular thickness (TbTh) and higher trabecular separation (TbSp) and distribution of trabecular separation (TbSpSd) than controls without fractures. In a logistic model, each SD decrease of volumetric total and trabecular densities was associated with a significantly increased risk of fracture at both sites (ORs ranged from 2.00 to 2.47). After adjusting for aBMD measured by DXA at the ultradistal radius, differences between cases and controls remained significant for D trab, and there was a similar trend for TbN, TbSp, and TbSpSd, with adjusted ORs ranging from 1.32 to 1.50. At the distal tibia, before and after adjusting for total hip aBMD, differences between cases and controls remained significant for D tot, D trab, Cort Th, and TbTh, with adjusted ORs ranging from 1.80 to 2.09.

Conclusions: In postmenopausal women, vertebral and nonvertebral fractures are associated with low volumetric BMD and architectural alterations of trabecular and cortical bone that can be assessed noninvasively and that are partially independent of aBMD assessed by DXA.
Different Responsiveness of Alveolar and Tibial Bone to Bone Loss Stimuli
Authors: Mavropoulos Anestis , Rizzoli René , Ammann Patrick
Published: December 2006

Mandibular and systemic bone loss are poorly associated. We compared the effect of isocaloric protein undernutrition and/or ovariectomy on BMD and microstructure of mandibular alveolar and proximal tibia sites in adult rats. Mandibular bone was significantly less affected.

Introduction: Whether mandibular bone and axial or peripheral skeleton respond similarly to systemic bone loss remains a subject of controversy. We have previously shown that mechanical loading during mastication influences bone mass and architecture of the mandibular alveolar bone. Isocaloric protein undernutrition and ovariectomy are known to cause bone loss and deterioration of bone microarchitecture at various axial and peripheral skeletal sites. We studied how the mandible, which is subjected to heavy, abrupt, and intermittent forces during mastication, responds to low-protein intake and/or ovariectomy and compared this response to that of the proximal tibia in adult rats.

Materials and Methods: Forty-four 6-month-old female Sprague-Dawley rats underwent transabdominal ovariectomy (OVX; n = 22) or sham operation (n = 22) and were pair-fed isocaloric diets containing either 15% or 2.5% casein (sham 15%, n = 11; sham 2.5%, n = 11; OVX 15%, n = 11; and OVX 2.5%, n = 11) for 16 weeks. BMD and bone microarchitecture parameters (e.g., bone volume fraction [BV/TV] and trabecular thickness and number) of the mandible and the proximal tibia were measured at the end of the experiment using DXA and μCT.

Results: Mandibular alveolar bone was negatively influenced by both protein undernutrition and OVX, but to a significantly lesser extent than the proximal tibia. In sham-operated animals, low-protein intake led to a 17.3% reduction of BV/TV in the mandible and 84.6% in the tibia (p < 0.001). In normal protein diet–fed animals, OVX led to a reduction of BV/TV of 4.9% in the mandible but 82% in the tibia (p < 0.001). In the mandible, protein undernutrition resulted in thinner trabeculae (p < 0.05), whereas OVX led to a reduction of trabecular number (p < 0.05).

Conclusions: Mandibular alveolar bone was found to be less sensitive to either protein undernutrition or OVX than the proximal tibia spongiosa. We hypothesize that the mechanical loading of the alveolar process during mastication may protect the alveolar bone from the detrimental effects observed in other skeletal sites, such as the proximal tibia. Morphological and embryological differences between the two skeletal sites might also play a role.
Negative Regulation by p70 S6 Kinase of FGF-2–Stimulated VEGF Release Through Stress-Activated Protein Kinase/c-Jun N-Terminal Kinase in Osteoblasts
Authors: Takai Shinji , Tokuda Haruhiko , Hanai Yoshiteru , Harada Atsushi , Yasuda Eisuke , Matsushima-Nishiwaki Rie , Kato Hisaaki , Ogura Shinji , Ohta Toshiki , Kozawa Osamu
Published: December 2006

To clarify the mechanism of VEGF release in osteoblasts, we studied whether p70 S6 kinase is involved in basic FGF-2–stimulated VEGF release in osteoblast-like MC3T3-E1 cells. In this study, we show that p70 S6 kinase activated by FGF-2 negatively regulates VEGF release through SAPK/JNK in osteoblasts.

Introduction: Vascular endothelial growth factor (VEGF) plays an important role in bone metabolism. We have previously reported that fibroblast growth factor-2 (FGF-2) stimulates the release of VEGF through p44/p42 mitogen-activated protein (MAP) kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in osteoblast-like MC3T3-E1 cells and that FGF-2–activated p38 MAP kinase negatively regulates VEGF release. However, the mechanism behind VEGF release in osteoblasts is not precisely known.

Materials and Methods: The levels of VEGF released from MC3T3-E1 cells were measured by enzyme immunoassay. The phosphorylation of each protein kinase was analyzed by Western blotting. To knock down p70 S6 kinase in MC3T3-E1 cells, the cells were transfected with siRNA to target p70 S6 kinase.

Results: FGF-2 time-dependently induced the phosphorylation of p70 S6 kinase. Rapamycin significantly enhanced the FGF-2–stimulated VEGF release and VEGF mRNA expression. The FGF-2–induced phosphorylation of p70 S6 kinase was suppressed by rapamycin. Rapamycin markedly enhanced the FGF-2–induced phosphorylation of SAPK/JNK without affecting the phosphorylation of p44/p42 MAP kinase or p38 MAP kinase. SP600125, a specific inhibitor of SAPK/JNK, suppressed the amplification by rapamycin of the FGF-2–stimulated VEGF release similar to the levels of FGF-2 with SP600125. Finally, downregulation of p70 S6 kinase by siRNA significantly enhanced the FGF-2–stimulated VEGF release and phosphorylation of SAPK/JNK.

Conclusions: These results strongly suggest that p70 S6 kinase limits FGF-2–stimulated VEGF release through self-regulation of SAPK/JNK, composing a negative feedback loop, in osteoblasts.
The New Age of Communication Research: Discourse, Cognition and Behaviour
Authors: McDonald Skye , Togher Leanne
Published: December 2006

Research into communication disorders has been undergoing a slow revolution over the past few decades with some fascinating advances and some exciting new directions ahead. The major change in emphasis that has emerged is an interest in assessing communication as this relates to real-life everyday type situations. In particular, three major thrusts can be identified. The first is the application of socially relevant linguistic theory to communication disorders. Thus, theorists such as Halliday have provided useful frameworks for identifying patterns in discourse. In turn, these have revealed the strengths and weakness of speakers with aphasia or other communication disorders (e.g., traumatic brain injuries) and also what their conversational partners do to help or hinder this process. The second is an examination of how cognitive processes, including memory, inferential reasoning and social cognition, contribute to communicative competence in people who have communication disorders but not aphasia, such as those with Alzheimer's disease, with traumatic brain injuries and with right hemisphere lesions. The third is the adoption of a more integrated approach, whereby verbal and nonverbal behaviours are examined in detail for their communicative meaning, for both the purposes of characterising communication breakdown and for developing an integrated treatment approach.
The Impact of Varied Speaker Role and Communication Partner on the Communicative Interactions of a Person With Traumatic Brain Injury: A Single Case Study Using Systemic Functional Linguistics
Authors: Togher Leanne , Taylor Christine , Aird Vanessa , Grant Susan
Published: December 2006

This article presents preliminary findings on an investigation into the differences in communicative performance across varying speaking conditions, of an individual with a cognitive–linguistic impairment following traumatic brain injury (TBI). The article compares the communicative exchanges of an individual in a conversation with a therapist, a conversational dyad with a peer with TBI, and in a communication group task where they were interacting with other participants with TBI. The speaking conditions studied included an unstructured chat, the participant requesting information and the participant giving information. Results showed that the person with TBI responded to differences in communication partner and speaker role. He was best able to give information in the unstructured chat with the clinician and the information giving session in the group. Requesting was maximally facilitated in the information request condition with the clinician. Qualitatively, however, the most equal interactions occurred with the peer, with evidence of the person with TBI engaging in typical conversational strategies such as establishing common ground to facilitate topic development and co-constructing the discourse topics. These strategies did not occur in the clinician or group interactions, possibly due to power imbalance in the former and impaired cognitive–linguistic ability in the latter situation. Implications for clinical decision making regarding intervention strategies for patients with cognitive–communication deficits are discussed.
Gist Distinctions in Healthy Cognitive Aging Versus Mild Alzheimer's Disease
Authors: Chapman Sandra B. , Anand Raksha , Sparks Garen , Cullum C. Munro
Published: December 2006

There is limited understanding of the effects of normal and abnormal aging on gist-based memory in relation to the massive evidence regarding detail-based memory. This void is striking given the widely accepted view that memory is rarely veridical, but most often abstracted. The present study examined the effects of healthy advanced aging and mild Alzheimer's disease (AD) on three distinct forms of gist. Two of these gist forms involved a passage: transformed gist (global generalised meaning of a passage) and main-idea gist (main points of a passage). The third gist form involved a word list: categorical gist (clustering of words according to semantic categories during list recall). These gist forms were assessed in immediate and delayed recall conditions. A total of 36 participants were included: 12 cognitively healthy young seniors (65–79 years), 12 cognitively healthy old seniors (80–95 years), and 12 young seniors with mild AD (65–79 years). The findings revealed that age and dementia did not equally affect all three forms of gist. Specifically, transformed gist was relatively maintained in the cognitively healthy senior groups as compared to the other two gist forms (main-idea gist and categorical gist), whereas all three gist forms were impaired in individuals with AD. The present study suggests that transformed gist operates differently than detail-based memory in the cognitively healthy senior groups. These findings have important theoretical implications in terms of informing existing models on the interrelationship between gist and detail-based memory and clinical implications in diagnosis of AD.
Self-Coaching: A Context-Sensitive, Person-Centred Approach to Social Communication After Traumatic Brain Injury
Authors: Ylvisaker Mark
Published: December 2006

Unsuccessful social communication after traumatic brain injury (TBI) is often a consequence of self-regulatory (executive function) impairments. The primary goal of this article is to describe an approach to intervention for individuals with self-regulatory impairments that is individualised, sensitive to context and to the role of everyday communication partners, and supported by personally compelling metaphors. After a brief review of the social communication outcome literature, an innovative approach to improving social competence is presented and illustrated. The article ends with a review of the evidence base for social skills and self-talk interventions.
Natural Cement in the 21st Century
Authors: Edison MP
Published: December 2006

Natural cement, the predominant hydraulic binder of the 19th century, has re-emerged in the 21st century as a restoration material. Engineers, architects, conservators, and owners must be able to rely upon modern natural cements to meet the same performance criteria as historic cement materials. In addition to the performance criteria, natural cement must provide the working characteristics demanded by contemporary tradespeople and the aesthetic results expected in high-quality historic restoration work. Historic standards for natural cement are reviewed and criteria used in developing the recently reinstated ASTM C 10 Standard Specification for Natural Cement are discussed. Recent research into the effectiveness of set and flow modifying admixtures with natural cement is presented, as well as an overview of producing color matches for natural cement mortars and stuccos.
Two Retinotopic Visual Areas in Human Lateral Occipital Cortex
Authors: Larsson Jonas , Heeger David J.
Published: December 2006

We describe two visual field maps, lateral occipital areas 1 (LO1) and 2 (LO2), in the human lateral occipital cortex between the dorsal part of visual area V3 and visual area V5/MT+. Each map contained a topographic representation of the contralateral visual hemifield. The eccentricity representations were shared with V1/V2/V3. The polar angle representation in LO1 extended from the lower vertical meridian (at the boundary with dorsal V3) through the horizontal to the upper vertical meridian (at the boundary with LO2). The polar angle representation in LO2 was the mirror-reversal of that in LO1. LO1 and LO2 overlapped with the posterior part of the object-selective lateral occipital complex and the kinetic occipital region (KO). The retinotopy and functional properties of LO1 and LO2 suggest that they correspond to two new human visual areas, which lack exact homologues in macaque visual cortex. The topography, stimulus selectivity, and anatomical location of LO1 and LO2 indicate that they integrate shape information from multiple visual submodalities in retinotopic coordinates.
Local Edge Detectors: A Substrate for Fine Spatial Vision at Low Temporal Frequencies in Rabbit Retina
Authors: van Wyk Michiel , Taylor W. Rowland , Vaney David I.
Published: December 2006

Visual acuity is limited by the size and density of the smallest retinal ganglion cells, which correspond to the midget ganglion cells in primate retina and the β-ganglion cells in cat retina, both of which have concentric receptive fields that respond at either light-On or light-Off. In contrast, the smallest ganglion cells in the rabbit retina are the local edge detectors (LEDs), which respond to spot illumination at both light-On and light-Off. However, the LEDs do not predominate in the rabbit retina and the question arises, what role do they play in fine spatial vision? We studied the morphology and physiology of LEDs in the isolated rabbit retina and examined how their response properties are shaped by the excitatory and inhibitory inputs. Although the LEDs comprise only ∼15% of the ganglion cells, neighboring LEDs are separated by 30–40 μm on the visual streak, which is sufficient to account for the grating acuity of the rabbit. The spatial and temporal receptive-field properties of LEDs are generated by distinct inhibitory mechanisms. The strong inhibitory surround acts presynaptically to suppress both the excitation and the inhibition elicited by center stimulation. The temporal properties, characterized by sluggish onset, sustained firing, and low bandwidth, are mediated by the temporal properties of the bipolar cells and by postsynaptic interactions between the excitatory and inhibitory inputs. We propose that the LEDs signal fine spatial detail during visual fixation, when high temporal frequencies are minimal.
Netrin/DCC Signaling Controls Contralateral Dendrites of Octavolateralis Efferent Neurons
Authors: Suli Arminda , Mortimer Nathan , Shepherd Iain , Chien Chi-Bin
Published: December 2006

The guidance molecule Netrin and its receptor DCC (deleted in colorectal cancer) attract commissural axons toward the midline en route to their final destination. To test whether these molecules can also guide dendrites, we studied the contralateral dendrites of zebrafish octavolateralis efferent (OLe) neurons, which are unusual in that they navigate toward and cross the midline. We found that, at the time of dendrite outgrowth, OLe neurons expressdcc, and the hindbrain midline expressesnetrin1. Knocking downdccornetrin1function by injecting antisense morpholino oligonucleotides prevented OLe contralateral dendrites from crossing the midline, showing thatdccandnetrin1are necessary for dendrite guidance or formation. Furthermore, by transplanting cells fromdccmorphants into wild-type embryos and vice versa, we demonstrated thatdccacts cell autonomously in OLe dendrites. This work is the first evidence that Netrin/DCC signaling acts in dendrites in a vertebrate system.
Primary Afferent Synapses on Developing and Adult Renshaw Cells
Authors: Mentis George Z. , Siembab Valerie C. , Zerda Ricardo , O'Donovan Michael J. , Alvarez Francisco J.
Published: December 2006

The mechanisms that diversify adult interneurons from a few pools of embryonic neurons are unknown. Renshaw cells, Ia inhibitory interneurons (IaINs), and possibly other types of mammalian spinal interneurons have common embryonic origins within the V1 group. However, in contrast to IaINs and other V1-derived interneurons, adult Renshaw cells receive motor axon synapses and lack proprioceptive inputs. Here, we investigated how this specific pattern of connectivity emerges during the development of Renshaw cells. Tract tracing and immunocytochemical markers [parvalbumin and vesicular glutamate transporter 1 (VGLUT1)] showed that most embryonic (embryonic day 18) Renshaw cells lack dorsal root inputs, but more than half received dorsal root synapses by postnatal day 0 (P0) and this input spread to all Renshaw cells by P10–P15. Electrophysiological recordings in neonates indicated that this input is functional and evokes Renshaw cell firing. VGLUT1-IR bouton density on Renshaw cells increased until P15 but thereafter decreased because of limited synapse proliferation coupled with the enlargement of Renshaw cell dendrites. In parallel, Renshaw cell postsynaptic densities apposed to VGLUT1-IR synapses became smaller in adult compared with P15. In contrast, vesicular acetylcholine transporter-IR motor axon synapses contact embryonic Renshaw cells and proliferate postnatally matching Renshaw cell growth. Like other V1 neurons, Renshaw cells are thus competent to receive sensory synapses. However, after P15, these sensory inputs appear deselected through arrested proliferation and synapse weakening. Thus, Renshaw cells shift from integrating sensory and motor inputs in neonates to predominantly motor inputs in adult. Similar synaptic weight shifts on interneurons may be involved in the maturation of motor reflexes and locomotor circuitry.
G-Proteins Modulate Cumulative Inactivation of N-Type (CaV2.2) Calcium Channels
Authors: McDavid Sarah , Currie Kevin P. M.
Published: December 2006

Precise regulation of N-type (CaV2.2) voltage-gated calcium channels (Ca-channels) controls many cellular functions including neurotransmitter and hormone release. One important mechanism that inhibits Ca2+entry involves binding of G-protein βγ subunits (Gβγ) to the Ca-channels. This shifts the Ca-channels from “willing” to “reluctant” gating states and slows activation. Voltage-dependent reversal of the inhibition (facilitation) is thought to reflect transient dissociation of Gβγ from the Ca-channels and can occur during high-frequency bursts of action potential-like waveforms (APW). Inactivation of Ca-channels will also limit Ca2+entry, but it remains unclear whether G-proteins can modulate inactivation. In part this is because of the complex nature of inactivation, and because facilitation of Ca-channel currents (ICa) masks the extent and kinetics of inactivation during typical stimulation protocols. We used low-frequency trains of APW to activateICa. This more closely mimics physiological stimuli and circumvents the problem of facilitation which does not occur at ≤5 Hz. Activation of endogenous G-proteins reduced both Ca2+-dependent, and voltage-dependent inactivation of recombinantICain human embryonic kidney 293 cells. This was mimicked by expression of wild-type Gβγ, but not by a point mutant of Gβγ with reduced affinity for Ca-channels. A similar decrease in the inactivation ofICawas produced by P2Y receptors in adrenal chromaffin cells. Overall, our data identify and characterize a novel effect of G-proteins onICa, and could have important implications for understanding how G-protein-coupled receptors control Ca2+entry and Ca2+-dependent events such as neurotransmitter and hormone release.
Identification of Process-Localized mRNAs from Cultured Rodent Hippocampal Neurons
Authors: Poon Michael M. , Choi Sang-Hyun , Jamieson Christina A. M. , Geschwind Daniel H. , Martin Kelsey C.
Published: December 2006

The regulated translation of localized mRNAs in neurons provides a mechanism for spatially restricting gene expression in a synapse-specific manner. To identify the population of mRNAs present in distal neuronal processes of rodent hippocampal neurons, we grew neurons on polycarbonate filters etched with 3 μm pores. Although the neuronal cell bodies remained on the top surface of the filters, dendrites, axons, and glial processes penetrated through the pores to grow along the bottom surface of the membrane where they could be mechanically separated from cell bodies. Quantitative PCR and immunochemical analyses of the process preparation revealed that it was remarkably free of somatic contamination. Microarray analysis of RNA isolated from the processes identified over 100 potentially localized mRNAs.In situhybridization studies of 19 of these transcripts confirmed that all 19 were present in dendrites, validating the utility of this approach for identifying dendritically localized transcripts. Many of the identified mRNAs encoded components of the translational machinery and several were associated with the RNA-binding protein Staufen. These findings indicate that there is a rich repertoire of mRNAs whose translation can be locally regulated and support the emerging idea that local protein synthesis serves to boost the translational capacity of synapses.
Apparent Encoding of Sequential Context in Rat Medial Prefrontal Cortex Is Accounted for by Behavioral Variability
Authors: Euston David R. , McNaughton Bruce L.
Published: December 2006

Simple sequences can be represented via asymmetrically linked neural assemblies, provided that the elements of the sequence are unique. When elements repeat, however (e.g., A-B-C-B-A), the same element belongs to two separate “sequential contexts,” and a more complex encoding mechanism is required. To enable correct sequence performance, some neural structure must provide a disambiguating signal that differentiates the two sequential contexts (i.e., B as an element of “A-B” as opposed to “C-B”). The disambiguating signal may derive from a form of working memory, or, in some cases, a simple timing mechanism may suffice. To investigate the possible role of medial prefrontal cortex in complex sequence encoding, rats were trained on a spatial sequence containing two adjacent repeated segments (e.g., A-B-C-D-B-C-E). The double-repeat procedure minimized behavioral differences in the second leg (C) of the repeat subsequence that arise in the first leg (B) because of differences in the entry point (e.g., A-Bvs D-B). Far more cells were context sensitive along the first leg than along the second (36 vs 9%), and most of the differences were accounted for by systematic variations in the rat's trajectory, which were much larger along the first leg. There is thus little evidence for sequential context-discriminative activity in the medial prefrontal cortex that cannot plausibly be accounted for by context-dependent behavior. The finding that the rodent medial prefrontal cortex is highly sensitive to sensory–behavioral variables raises doubts about previous experiments that purport to show working memory-related activity in this region.
Modulation of Neural Activity during Observational Learning of Actions and Their Sequential Orders
Authors: Frey Scott H. , Gerry Valerie E.
Published: December 2006

How does the brain transform perceptual representations of others' actions into motor representations that can be used to guide behavior? Here we used functional magnetic resonance imaging to record human brain activity while subjects watched others construct multipart objects under varied task demands. We find that relative to resting baseline, passive action observation increases activity within inferior frontal and parietal cortices implicated in action encoding (mirror system) and throughout a distributed network of areas involved in motor representation, including dorsal premotor cortex, pre-supplementary motor area, cerebellum, and basal ganglia (experiments 1 and 2). Relative to passive observation, these same areas show increased activity when subjects observe with the intention to subsequently reproduce component actions using the demonstrated sequential procedures (experiment 1). Observing the same actions with the intention of reproducing component actions, but without the requirement to use the demonstrated sequential procedure, increases activity in the same regions, although to a lesser degree (experiment 2). These findings demonstrate that when attempting to learn behaviors through observation, the observers' intentions modulate responses in a widely distributed network of cortical and subcortical regions implicated previously in action encoding and/or motor representation. Among these regions, only activity within the right intraparietal sulcus predicts the accuracy with which observed procedures are subsequently performed. Successful formation of motor representations of sequential procedures through observational learning is dependent on computations implemented within this parietal region.
Cross-Whisker Adaptation of Neurons in the Rat Barrel Cortex
Authors: Katz Yonatan , Heiss Jaime E. , Lampl Ilan
Published: December 2006

Neurons in the barrel cortex and the thalamus respond preferentially to stimulation of one whisker (the principal whisker) and weakly to several adjacent whiskers. Cortical neurons, unlike thalamic cells, gradually adapt to repeated whisker stimulations. Whether cortical adaptation is specific to the stimulated whisker is not known. The aim of this intracellular study was to determine whether the response of a cortical cell to stimulation of an adjacent whisker would be affected by previous adaptation induced by stimulation of the principal whisker and vice versa. Using a high-frequency stimulation that causes substantial adaptation in the cortex and much less adaptation in the thalamus, we show that cortical adaptation evoked by a train of stimuli applied to one whisker does not affect the synaptic response to subsequent stimulation of a neighboring whisker. Our data indicate that intrinsic mechanisms are not involved in cortical adaptation. Thalamic recordings obtained under the same conditions demonstrated that an adjacent whisker response was not generated in the thalamus, indicating that the observed whisker-specific adaptation results from diverging thalamic inputs or from cortical integration.