Intricate interactions among constituent components are defining hallmarks of biological systems and sculpt physiology across different scales spanning gene networks to behavioural repertoires. Whereas interactions among channels and receptors define neuronal physiology, interactions among different cells specify the characteristic features of network physiology. From a single-neuron perspective, it is now evident that the somato-dendritic plasma membrane of hippocampus pyramidal neurons is endowed with several voltage-gated ion channels (VGICs) with varying biophysical properties and sub cellular expression profiles. Structural and physiological interactions among these channels define generation and propagation of electrical signals, thereby transforming neuronal dendrites to actively excitable membrane endowed with complex computational capabilities. In parallel to this complex network of plasma membrane channels is an elegantly placed continuous intraneuronal membrane of the endoplasmic reticulum (ER) that runs throughout the neuronal morphology. Akin to the plasma membrane, the ER is also endowed with a variety of channels and receptors, prominent among them being the inositol trisphosphate (InsP3) receptors (InsP3Rs) and ryanodine receptors (RyR), both of which are calcium release channels. Physiological interactions among these receptors transform the ER into a calcium excitable membrane, capable of active propagation of calcium waves and of spatiotemporal integration of neuronal signals. Thus, a neuron is endowed with two continuously parallel excitable membranes that actively participate in the bidirectional flow of intraneuronal information, through interactions among different channels and receptors on either membrane. Although the interactions among sets of channels and receptors present individually on either membrane are very well characterized, our understanding of cross-membrane interactions among channels and receptors across these two membranes has been very limited. Recent literature has emphasized the critical nature of such cross-membrane interactions and the several physiological roles played by such interactions. Such cross-channel interactions include ER depletion-induced signaling involving store-operated calcium channels, generation and propagation of calcium waves through interactions between plasma membrane and ER membrane receptors, and the plasticity of plasma membrane VGICs and receptors induced by ER Ca2+. Such tight interactions between these two membranes have highlighted several roles of the ER in the integration of intraneuronal information, in regulating signalling microdomains and in regulating the downstream signaling pathways that are regulated by these Ca2+ signals. Yet, our understanding about the functional interactions between the ion channels and receptors present on either of these membranes is very limited from the perspective of the combinatorial possibilities that encompass the span of channels and receptors across these two membranes. In this context, the first part of this thesis deals with two specific instances of such cross-membrane functional interactions, presented as two subparts with each probing different direction of impact. Specifically, whereas the first of these subparts deals with the impact of plasma membrane VGICs on the physiology of ER receptors, the second subpart presents an instance of the effect of ER receptor activation on plasma membrane VGIC. In the first subpart of the thesis, we establish a novel role for the A-type potassium current in regulating the release of calcium through inositol triphosphate receptors (InsP3R) that reside on the endoplasmic reticulum (ER) of hippocampus pyramidal neurons. Specifically, the A-type potassium current has been implicated in the regulation of several physiological processes including the regulation of calcium influx through voltage-gated calcium channels (VGCCs). Given the dependence of InsP3R open probability on cytosolic calcium concentration ([Ca2+]c) we asked if this regulation of calcium influx by A-type potassium current could translate into the regulation of release of calcium through InsP3Rs by the A-type potassium current. To answer this, we constructed morphologically realistic, conductance-based neuronal models equipped with kinetic schemes that govern several calcium signalling modules and pathways, and constrained the distributions and properties of constitutive components by experimental measurements from these neurons. Employing these models, we establish a bell-shaped dependence of calcium release through InsP3Rs on the density of A-type potassium current, during the propagation of an intraneuronal calcium wave initiated through established protocols. Exploring the sensitivities of calcium wave initiation and propagation to several underlying parameters, we found that ER calcium release critically depends on dendrite diameter and wave initiation occurred at branch points as a consequence of high surface area to volume ratio of oblique dendrites. Further, analogous to the role of A-type potassium channels in regulating spike latency, we found that an increase in the density of A-type potassium channels led to increases in the latency and the temporal spread of a propagating calcium wave. Next, we incorporated kinetic models for the metabotropic glutamate receptor (miler) signalling components and a calcium-controlled plasticity rule into our model and demonstrate that the presence of mGluRs induced a leftward shift in a BCM-like synaptic plasticity profile. Finally, we show that the A-type potassium current could regulate the relative contribution of ER calcium to synaptic plasticity induced either through 900 pulses of various stimulus frequencies or through theta burst stimulation. These results establish a novel form of interaction between active dendrites and the ER membrane and suggest that A-type K+ channels are ideally placed for inhibiting the suppression of InsP3Rs in thin-caliber dendrites. Furthermore, they uncover a powerful mechanism that could regulate biophysical/biochemical signal integration and steer the spatiotemporal spread of signalling micro domains through changes in dendritic excitability. In the second subpart, we turned our focus to the role of calcium released through InsP3Rs in regulating the properties of VGICs present on the plasma membrane, thereby altering neuronal intrinsic properties that are dependent on these VGICs. Specifically, the synaptic plasticity literature has focused on establishing necessity and sufficiency as two essential and distinct features in causally relating a signalling molecule to plasticity induction, an approach that has been surprisingly lacking in the intrinsic plasticity literature. Here, we complemented the recently established necessity of inositol trisphosphate (InsP3) receptors (InsP3R) in a form of intrinsic plasticity by asking if ER InsP3R activation was sufficient to induce plasticity in intrinsic properties of hippocampus neurons. To do this, we employed whole-cell patch-clamp recordings to infuse D-myo-InsP3, the endogenous ligand for InsP3Rs, into hippocampus pyramidal neurons and assessed the impact of InsP3R activation on neuronal intrinsic properties. We found that such activation reduced input resistance, maximal impedance amplitude and temporal summation, but increased resonance frequency, resonance strength, sag ratio, and impedance phase lead of hippocampus pyramidal neurons. Strikingly, the magnitude of plasticity in all these measurements was dependent upon [InsP3], emphasizing the graded dependence of such plasticity on InsP3R activation. Mechanistically, we found that this InsP3-induced plasticity depended on hyperpolarization-activated cyclic-nucleotide gated (HCN) channels. Moreover, this calcium-dependent form of plasticity was critically reliant on the release of calcium through InsP3Rs, the influx of calcium through N-methyl-D -aspartate receptors and voltage-gated calcium channels, and on the protein kinase A pathway. These results delineate a causal role for InsP3Rs in graded adaptation of neuronal response dynamics through changes in plasma membrane ion channels, thereby revealing novel regulatory roles for the endoplasmic reticulum in neural coding and homeostasis. Whereas the first part of the thesis dealt with bidirectional interactions between ER membrane and plasma membrane channels/receptors within a neuron, second part focuses on cross-cellular interactions, specifically between ER membrane on astrocytes and dendritic plasma membrane of neurons. Specifically, the universality of ER-dependent calcium signalling ensures that its critical influence extends to regulating the physiology of astrocytes, an abundant form of glial cells in the hippocampus. Due to the presence of calcium release channels on ER membrane, astrocytes are calcium excitable, whereby they respond to neuronal activity by increase in their cytosolic calcium levels. Specifically, astrocytes respond to the release of neurotransmitters from neuronal presynaptic terminals through activation of metabotropic receptors expressed on their plasma membrane. Such activation results in the mobilization of cytosolic InsP3 and subsequent release of calcium through InsP3 on the astrocytes ER membrane. These ER-dependent [Ca2+]c elevations in astrocytes then result in the release of gliotransmitters from astrocytes, which bind to corresponding receptors located on neuronal plasma membrane resulting in voltage-deflections and/or activation of signaling pathways in the neuron. Although it is well established that gliotransmission constitutes an important communication channel between astrocytes and neurons, the impact of gliotransmission on neurons have largely been centered at the cell body of the neurons. Consequently, the impact of the activation of astrocytic InsP3R on neuronal dendrites, and the role of dendritic active conductances in regulating this impact have been lacking. This lacuna in mapping the spatial spread of gliotransmission in neurons is especially striking because most afferent synapses impinge on neuronal dendrites, and a significant proportion of information processing in neurons is performed in their dendritic arborization. Additionally, given that active dendritic conductances play a pivotal role in regulating the impact of fast synaptic neurotransmission on neurons, we hypothesized that such active-dendritic regulation should extend to the impact of slower extrasynaptic gliotransmission on neurons. The second part of the thesis is devoted to testing this hypothesis using dendritic and paired astrocyte-neuron electrophysiological recordings, where we also investigate the specific roles of active dendritic conductances in regulating the impact of gliotransmission initiated through activation of astrocytic InsP3Rs. In testing this hypothesis, in the second part of the thesis, we first demonstrate a significantly large increase in the amplitude of astrocytically originating spontaneous slow excitatory potentials (SEP) in distal dendrites compared to their perisomatic counterparts. Employing specific neuronal infusion of pharmacological agents, we show that blocking HCN channels increased the frequency, rise-time and width of dendritically-recorded spontaneous SEPs, whereas blockade of A-type potassium channels enhanced their amplitude. Next, through paired neuron-astrocytes recordings, we show that our conclusions on the differential roles of HCN and A-type potassium channels in modulating spontaneous SEPs also extended to SEPs induced through infusion of InsP3 in a nearby astrocyte. Additionally, employing subtype-specific receptor blockers during paired neuron-astrocyte recordings, we provide evidence that GluN2B-and GluN2D-containing NMDARs predominantly mediate perisomatic and dendritic SEPs, respectively. Finally, using morphologically realistic conductance-based computational models, we quantitatively demonstrate that dendritic conductances play an active role in mediating compartmentalization of the neuronal impact of gliotransmission. These results unveil an important role for active dendrites in regulating the impact of gliotransmission on neurons, and suggest astrocytes as a source of dendritic plateau potentials that have been implicated in localized plasticity and place cell formation. This thesis is organized into six chapters as follows: Chapter 1 lays the motivations for the questions addressed in the thesis apart from providing the highlights of the results presented here. Chapter 2 provides the background literature for the thesis, introducing facts and concepts that forms the foundation on which the rest of the chapters are built upon. In chapter 3, we present quantitative analyses of the physiological interactions between A-type potassium conductances and InsP3Rs in CA1 pyramidal neurons. In chapter 4, using electrophysiological recordings, we investigate the role of calcium released through InsP3Rs in induction of plasticity of intrinsic response dynamics, and demonstrate that this form of plasticity is consequent to changes in neuronal HCN channels. In chapter 5, we systematically map the spatial dynamics of the impact of gliotransmission on neurons across the somato-apical trunk, also unveiling the role of neuronal HCN and A-type potassium channels in compartmentalizing such impact. Finally, chapter 6 concludes the thesis highlighting its major contributions and discussing directions of future research.

Le vascular endothelial growth factor (VEGF) un facteur de croissance essentiel du système vasculaire exerce des fonctions multiples sur les cellules nerveuses en favorisant la neurogenèse, la plasticité synaptique ou encore l'apprentissage et la mémoire. Cependant, les mécanismes impliqués dans son action régulatrice de la transmission et la plasticité synaptiques restent à élucider. Nous avons récemment mis en évidence une nouvelle interaction entre VEGFR2, le récepteur principal du VEGF, et les récepteurs NMDA (NMDAR) au cours de la migration des neurones pendant le développement du cervelet. Comme les NMDAR sont des acteurs clés de la transmission et de la plasticité synaptique, nous avons exploré le rôle du VEGF dans la régulation de l'expression et de la fonction des NMDAR synaptiques dans l'hippocampe. Nos résultats révèlent que le VEGF et son récepteur sont exprimés dans les régions CA1 et CA3 de l'hippocampe et le domaine extracellulaire de VEGFR2 peut se lier à la sous-unité GluN2B des NMDAR. Le VEGF est capable d'augmenter la transmission synaptique dépendant des NMDAR en régulant l'adressage synaptique des récepteurs exprimant la sous-unité GluN2B. Il se produit également une augmentation du nombre de synapses en présence du VEGF. Ces effets du VEGF requièrent la co-activation des récepteurs VEGFR2 et NMDAR et conduisent à un enrichissement synaptique en récepteurs glutamatergiques de type AMPA qui dépend de l'activation de la CaMKII. Nos travaux démontrent pour la première fois un rôle direct de la signalisation VEGF/VEGFR2 dans la fonction de la synapse excitatrice glutamatergique / The vascular endothelial growth factor (VEGF) plays a critical role during vascular development but recent evidence indicates that it also regulates various neuronal processes in the nervous system, such as neurogenesis, hippocampal synaptic plasticity, learning and memory. Recently, we showed a novel interaction between the glutamate receptor NMDA (NMDAR) and the VEGF receptor VEGFR2 during neuronal migration in the developing cerebellum. As NMDAR have been widely implicated in synaptic transmission and plasticity, we hypothesized that VEGF might regulate NMDAR function in hippocampal synaptic transmission and plasticity, as well as in learning and memory. Our results revealed that VEGF and its receptor VEGFR2 are expressed in the CA1 and CA3 regions of the hippocampus. Biochemical exploration highlighted an interaction between the extracellular domain of VEGFR2 and the GluN2B subunit of NMDAR. In addition, whole-cell patch clamp experiments in acute hippocampal slices showed that VEGF potentiates post-synaptic GluN2B-expressing NMDAR responses. Furthermore NMDAR and VEGFR2 co-activation in hippocampal neurons increased the pool of synaptic GluN2B-NMDAR and affects synapse number. These processes are associated with an increase in AMPAR synaptic expression and an involvment of CaMKII signaling pathway. Altogether, our results demonstrated for the first time a direct effect of VEGF on the function of excitatory glutamatergic synapses

Unilateral Spastic Cerebral Palsy (USCP) is caused by an early brain lesion in which the Corticospinal Tract (CST), the primary pathway controlling upper extremity (UE) movements, is affected. The CST connectivity after early brain injury (i.e., an ipsilateral, contralateral, or bilateral connectivity) may influence treatment outcomes. Transcranial magnetic stimulation (TMS) is a common method to probe CST connectivity. However, TMS is limited to children without seizures. Mirror movements (MM), an involuntary imitation of movements by one limb during the contralateral limb voluntary movements, are common in USCP. MM may result when both UEs are controlled by the contralesional motor cortex. Here we investigated the relationship between MM and CST connectivity in children with USCP. We hypothesized that stronger MM were associated with an ipsilateral connectivity. Our secondary aim was to investigate whether the amount of MM was reduced after intensive therapy. Thirty-three children with USCP (mean age=9yrs 6mos; MACS: I-III) participated and were randomized to receive 90hrs of unimanual (n=16) or bimanual (n=17) intensive training. Assessments were measured at baseline and immediately after training. We used TMS and diffusion tensor imaging (DTI) to determine the CST connectivity. We used three approaches to quantify MM: 1) behavioral MM assessment during contralateral movements, including hand opening/closing, finger opposition, finger individuation, and finger walking, 2) involuntary grip force oscillations recorded by force transducer (FT) when the contralateral hand performed repetitive pinching, and 3) involuntary muscle contractions measured by electromyography (EMG) when the contralateral hand performed pinching. Results showed that strong MM (scores ≥3) in the more-affected hand while hand opening/closing were associated with an ipsilateral pathway (Fisher's exact test, p= 0.02). This association was not found in the remaining tasks (Fisher’s exact test, opposition, p≥ 0.99; individuation, p≥ 0.99; finger walking, p≥ 0.99). Involuntary GF oscillations were measured in a subset of 16 children. Presence of FT-measured MM in the less-affected hand (> 0.3N) was not associated with TMS-probed connectivity (Fisher’s exact test, p= 0.59). Nevertheless, presence of FT-measured MM was associated with DTI-assessed connectivity (Fisher’s exact test, p= 0.0498). Similarly, presence of EMG-measured MM in the more-affected hand was not associated with TMS-probed connectivity (Fisher’s exact test, p= 0.59). Nevertheless, presence of EMG-measured MM was associated with DTI-assessed connectivity (Fisher’s exact test, p= 0.03). The amount of MM did not change after training (p> 0.06 among all measures). In conclusion, strong MM in the more-affected hand while hand opening/closing may be indicative of an ipsilateral connectivity identified by TMS. Presence of MM measured by FT may be a predictor of DTI-assessed CST pattern. Findings of this study may help researchers and clinicians understand the relationship between the CST connectivity and its behavioral manifestation in children with USCP. Such relationship may further guide therapeutic strategies in a wider range of children with USCP.

A doença de Charcot-Marie-Tooth (CMT) caracteriza-se por comprometimento dos nervos periféricos de predomínio distal, tendo curso clínico variável. Observa-se quadro de evolução lenta de atrofia e fraqueza distal em membros inferiores, seguidos por diminuição da sensibilidade. Os reflexos estão em geral abolidos, mas podem estar exaltados e acompanhados de sinal de Babinski. É frequente o encontro de atrofia do terço distal das pernas, de pes cavos e de deformidades em artelhos. A doença de CMT pode ser classificada, com o auxílio da eletroneuromiografia, em desmielinizante (CMT1) ou axonal (CMT2). A CMT1 possui velocidade de condução motora do nervo mediano < 38 m/s e a CMT2 > 38m/s. A CMT1 é de herança autossômica dominante, e a CMT2 pode ser de herança dominante ou recessiva. A CMT2 é geneticamente heterogênea e conhecem-se até o momento 13 loci associados a essa condição, com nove genes identificados. O objetivo deste estudo é investigar do ponto de vista clínico, neurofisiológico e genético uma família com muitos portadores de CMT2. A família multigeneracional que apresenta CMT2 é procedente de Tobias Barreto, SE. Foi feita avaliação neurológica de 50 indivíduos e eletroneuromiografia em 22 pacientes. Com dados da avaliação clínica e eletroneuromiográfica foi aplicado o escore que avalia a gravidade da doença, o CMTNS. Para o estudo genético, foram coletadas 42 amostras de sangue de indivíduos afetados e de familiares não afetados. Entre os 50 indivíduos avaliados, 30 tinham sinais clínicos de neuropatia sensitivo-motora de predomínio distal. Paresia dos músculos distais foram os sinais clínicos mais precoces. Redução da sensibilidade superficial e profunda foi detectada nos segmentos distais. O sinal de Babinski estava presente em 14 indivíduos. A eletroneuromiografia demonstrou alterações compatíveis com polineuropatia axonal sensitiva e motora. O estudo genético demonstrou que, nesta família, CMT2 não está ligada a nenhum dos loci já conhecidos para esta condição, más o lócus do gene responsável não foi identificado até o momento. Em conclusão, as características clínicas e neurofisiológicas dessa família não diferem significativamente das observadas em outras formas de CMT, exceto pela alta prevalência de sinal de Babinski, e nossos resultados indicam a existência de um novo locus para CMT2 / Charcot-Marie-Tooth (CMT) disease is characterized by predominantly distal peripheral neuropathy with variable clinical course. Initial presentation is of a slowly progressive distal atrophy and weakness in lower limbs, followed by sensory compromise. Reflexes are usually abolished, but might be brisk and accompanied by Babinski sign. It is frequent to find distal atrophy of lower limbs, pes cavus and toe deformities. Electromyography can recognize two patterns of CMT: demyelinating (CMT1), which has a conduction median nerve velocity < 38 m/s and axonal (CMT2), with velocity > 38m/s. CMT1 is inherited as an autosomal dominant trait, and CMT2 might be transmitted as an autosomal dominant or recessive. CMT is genetically heterogeneous, and, up to now, 13 loci have been recognized and nine genes identified. The aim of this study was to conduct an investigation of clinical, genetics and neurophysiological investigation of a multigenerational family with several individuals with CMT2 and to characterize phenotype, neurophysiological pattern and genetic basis of this condition. Fifty individuals were clinically evaluated and nerve conduction velocity studies and distal muscular activity in lower limbs using concentric needle were performed in 22 patients. A blood sample was collect from 42 individuals, in order to perform linkage analysis. Thirty, among the 50 evaluated individuals, had clinical signs of predominantely distal sensory motor neuropathy. Distal muscle paresis was an early clinical sign. Reduction of superficial and deep sensory was detected distally. Babinski sign was present in 14 affected individuals. Neurophysiological study was characteristic of axonal sensory-motor neuropathy. Linkage analysis demonstrated that in this family, CMT2 was not linked to any already known loci for this condition, but the responsible gene locus was not identified so far. In conclusion, clinical and neurophysiological characteristics of this family did not differ substantially from other forms of CMT, except by the high prevalence of Babinski sign. Our study also suggests the presence of a new locus for CMT2

Families of children with autism spectrum disorder (ASD) in developing countries may not have as much access to needed behavioral services as families living in developed countries. Caregivers of children with ASD in developing countries would benefit from an affordable, efficient parent training to teach them behavior techniques to use with their children. Pyramidal training is a cost-efficient method of training individuals through peers and would be a supportive intervention for families in developing countries. This study used a repeated acquisition design across three variables to examine whether a caregiver could train another caregiver on three behavioral interventions. These interventions were appropriately redirecting repetitive behaviors, using praise, and requesting eye contact. The study also examined if the caregivers could acquire the three skills and the extent caregivers were receptive to this training model based on their comments about the training. The participants were six ethnic Macedonians or Albanians between the ages of 38 and 43 who were caregivers of a child with ASD. The results indicate the caregivers were able to train another caregiver on three skills for working with their child with autism, all the caregivers were able to acquire the three skills, and the training model's goals were socially appropriate based on participants' comments. This implicates professionals such as doctors, social workers, behavioral therapists, or school psychologists could use this form of parent training to share information throughout a family in order to benefit children with disabilities and their families.

Thesis (Ph.D.)--University of Toledo, 2007. / "In partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biomedical Sciences." Major advisor: Elizabeth Tietz. Includes abstract. Title from title page of PDF document. Bibliography: pages 88-94, 130-136, 178-189, 218-266.

Acute brain cell swelling (cytotoxic edema) can occur in the first minutes of stroke, presumably as a result of brain cells taking up water. In extreme hypo-osmotic situations such as excessive water-loading by patients, uptake by brain cells can expand the brain, causing seizures. But is ischemic brain cell swelling the same as hypo-osmotic swelling? Water can passively diffuse across the plasma membrane. However the presence of water channels termed aquaporins (AQP) facilitates passive water diffusion by 10-100 times. Unlike astrocytes, there is no evidence of water channels on neuronal plasma membrane. However, there is still much debate about which cells (neurons or astrocytes) swell during over-hydration or during stroke and if neurons and astrocytes can volume-regulate during osmotic stress. The purpose of this study was to examine and compare the volume responses of PyNs and magnocellular neuroendocrine cells (MNCs) to acute osmotic challenge and to OGD. We examined MNCs because they are intrinsically osmosensitive to small changes (2-3 mOsm) of plasma osmolality. We also examined if the same neurons behave similarly in brain slices or when dissociated and if they respond differently to acute osmotic stress and stroke-like stress. Our results indicate that during acute osmotic stress (±40 mOsm) half of dissociated PyNs and MNCs tended to show appropriate responses. MNCs in brain slices showed similar responses to when they were dissociated, while brain slice PyNs were less responsive than when dissociated. Exposure to OGD resulted in obvious differences between the two types of in vitro preparations. Dissociated PyNs and MNCs showed no consistency in their volume responses to 10 minutes of OGD. Dissociated neurons swelled, shrunk or were unchanged in about equal numbers. In contrast, brain slice PyNs underwent profound swelling whereas, brain slice MNCs showed minor volume decreases. We conclude that about half of our dissociated neurons were too variable and unpredictable in their osmotic volume responses to be useful for osmotic studies. They also were too resistant to stroke-like stress to be good models for ischemia. Brain slice neurons were similar in their osmotic responses to dissociated neurons but proved to have consistent and predictable responses to stroke-like stress. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2011-02-07 17:55:08.333

Copies of author's previously published articles inserted. / Bibliography: leaves 193-228. / xvi, 235 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The aim of this thesis is to provide evidence of a training related effect on neural control of a muscle in individuals who have long standing different patterns of use of their muscles. The study examines the motor unit (MU) discharge properties in first dorsal interosseous muscle of individuals who had experienced very different usage patterns of their hand muscles and explores the relationship between different muscle usage patterns and involuntary force fluctuations (tremor). It evaluates the importance of the shared branched-axon inputs to motor neurons in the production of common drive and investigates the relationship between different measures of MU sychronization. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physiology, 1997?

Thesis (Ph. D.)--University of Alabama at Birmingham, 2008. / Title from first page of PDF file (viewed Sept. 16, 2008). Includes bibliographical references.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2009. / Title from PDF title page (viewed Mar. 31, 2010). Additional advisors: N. Shastry Akella, James E. Cox, Gitendra Uswatte, Victor W. Mark. Includes bibliographical references (p. 50-60).