bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fundamental motor patterns of the mammalian fetus
Authors: Robinson Scott R. , Smotherman William P. 
Published: May 2005

AbstractTechniques that permit direct observation of fetuses in vivo recently have expanded our understanding of prenatal behavioral development in mammals. Although fetal motor activity seems to lack the dynamic, goal‐directed character of postnatal behavior, the dimensions that define behavioral organization after birth are applicable to the movements expressed by fetuses. Fetal activity exhibits temporal, sequential, and spatial organization that emerges between the inception of movement and term. Fetal rodents, for example, exhibit coordinated motor patterns antecedent to postnatal righting, locomotion, suckling, maternal–infant communication and grooming behavior, while other action patterns appear to be functional adaptations to the intrauterine niche. Fetuses also are behaviorally responsive to sensory stimulation and changes in environmental conditions in utero. Expression of these behavioral properties emphasizes continuity between prenatal and postnatal life while implying an adaptive role for behavior before birth. © 1992 John Wiley & Sons, Inc.
Activity‐driven sharpening of the retinotectal projection in goldfish: Development under stroboscopic illumination prevents sharpening
Authors: Schmidt John T. , Buzzard Marlene 
Published: May 2005

AbstractBlocking or synchronizing activity during regeneration of the retinotectal projection prevents both the sharpening of the retinotopic map recorded on tectum and the refinement of the structure of individual arbors within the plane of the map, and this refinement is triggered by N‐methyl‐d‐aspartate (NMDA) receptors. We tested whether activity‐driven refinement also occurs during development of the projection in larval and young adult goldfish. Shortly after hatching, larval goldfish were placed into tanks within light‐tight chambers illuminated by a xenon strobe at 1 Hz for 14 h of each daily cycle. Fish were reared for 1.5–2 years, until large enough to record in our retinotectal mapping apparatus (6 cm length). Age‐ and size‐matched controls had normal maps with multiunit receptive fields (MURFs) recorded at each tectal point of 10.8° (0.16 S.E.M., n = 5), whereas the strobe‐reared fish had only roughly retino‐topic maps with much enlarged MURFs averaging 26.7° (1.41 S.E.M., n = 5). This enlargement represents an abnormal convergence onto each tectal point, as the maps failed to sharpen during development. The arbors of individual retinal axons were stained with horseradish peroxidase (HRP) in larval fish and in adult strobereared and control fish. They were drawn with camera lucida from tectal whole mounts, and analyzed for spatial extent in the plane of the retinotopic map, order of branching, number of branch endings, depth of termination, and caliber of the parent axon. Arbors from larval fish (1–2 weeks) were small (approximately 50 × 40 μm) with less than 10 branches, occupied a single strata, and could not be separated into different classes by caliber of axon. The 87 arbors stained in control adult fish (6 cm long) were much like previously examined adult arbors, with those from fine, medium, and coarse axons averaging 115, 166, and 194 μm in extent, respectively, and having 17–24 branch endings. The 110 arbors from 12 strobe‐reared fish were often abnormal. Although the fasciculation was normal, the extrafascicular routes were abnormal with reversing turns. The axons often had branches along their course, and these branches were scattered across a wider extent, rather than forming a distinct cluster. In contrast, neither the number of branches nor the depths of termination was significantly changed in any group. The coarse caliber arbors were most abnormal, being 64% longer and 30% wider than controls. The fine caliber arbors were also significantly larger by about 20%, but the medium caliber arbors were not enlarged. The enlarged arbors partially account for the unsharpened electrophysiological maps. Together the results show that during development, as well as during regeneration, the retinotectal map is subject to an activity‐driven sharpening process. © 1993 John Wiley & Sons, Inc.
Clusterin levels increase during neuronal development
Authors: O'Bryan M. K. , Cheema S. S. , Bartlett P. F. , Murphy B. F. , Pearse M. J. 
Published: May 2005

AbstractThe expression of clusterin has been shown to be elevated in several models of experimentally induced programmed cell death and in association with a number of neurodegenerative conditions. In order to test whether this protein is expressed in neurons during development, the expression of clusterin was examined in the developing nervous system, using immunohistochemistry and mRNA analysis. Clusterin expression was observed in the earliest neurons of the cortical plate on embryonic day (E) 12. Thereafter, the intensity of clusterin staining continued to increase in an age‐dependent manner, with the greatest intensity of staining being found in the postnatal mature brain. Virtually all neurons were clusterin‐positive and there was no evidence for the appearance of clusterin‐positive cells specifically during epochs of programmed neuronal death in the embryo. This study suggests that clusterin has a role in neuronal maturation and it is unlikely to be associated exclusively with neuronal cell death. © 1993 John Wiley & Sons, Inc.
Identification of molecules in a muscle extracellular matrix extract that promotes process outgrowth from cultured adult frog motoneurons
Authors: Kuffler Damien P. , Luethi Theres 
Published: May 2005

AbstractThe molecular composition of the substrate on which neurons are cultured is critical for their attachment, survival, and extension of processes. The aim of the present experiments was to characterize the molecules in an extracellular matrix (ECM) extract that promotes the outgrowth of processes from cultured adult frog motoneurons. An extract was made of skeletal muscle ECM and tested as a substrate for cultured motoneurons. The average total process length of motoneurons cultured on this crude ECM extract is greater than when the neurons are cultured on concanavalin A, poly‐l‐lysine or mouse tumor (EHS) laminin. Gel filtration of the ECM extract yielded fractions with an increased specific activity for promoting process outgrowth. The most active fractions exhibit a single major polypeptide band of ca. 1 mD and two minor bands of ca. greater than 1 mD and 205 kD upon sodium dodecyl sulfate gel electrophoresis. Under reducing conditions, three major bands were seen of 340, 205, and 200 kD. Electron microscopy of rotary‐shadowed ECM fractions showed macromolecules with a cross‐shaped structure similar to vertebrate and invertebrate laminin, a rod‐like molecule resembling vertebrate and invertebrate collagen type IV, and a third molecule similar in appearance to vertebrate fibrillin. These results represent the first step in analyzing the role of substrate molecules in promoting neuromuscular reinnervation. © 1993 John Wiley & Sons, Inc.
Postsynaptic regulation of the development and long‐term plasticity of Aplysia sensorimotor synapses in cell culture
Authors: Glanzman David L. 
Published: May 2005

AbstractThe monosynaptic component of the neuronal circuit that mediates the withdrawal reflex of Aplysia californica can be reconstituted in dissociated cell culture. Study of these in vitro monosynaptic connections has yielded insights into the basic cellular mechanisms of synaptogenesis and long‐term synaptic plasticity. One such insight has been that the development of the presynaptic sensory neurons is strongly regulated by the postsynaptic motor neuron. Sensory neurons which have been cocultured with a target motor neuron have more elaborate structures—characterized by neurites with more branches and varicosities—than do sensory neurons grown alone in culture or sensory neurons that have been cocultured with an inappropriate target cell. Another way in which the motor neuron regulates the development of sensory neurons is apparent when sensorimotor cocultures with two presynaptic cells are examined. In such cocultures the outgrowth from the different presynaptic cells is obviously segregated on the processes of the postsynaptic cell. By contrast, when two sensory neurons are placed into cell culture without a motor neuron, thier processes readily grow together. In addition to regulating the in vitro development of sensory neurons, the motor neuron also regulates learning‐related changes in the structure of sensory neurons. Application of the endogenous facilitatory trasmitter serotonin (5‐HT) causes long‐term facilitation of in vitro sensorimotor synapses due in part to growth of new presynatpic varicosities. But 5‐HT applied to sensory neurons alone in cultuer does not produce structural changes in these cells. More recently it has been found that sensorimotor synapses in cell culture can exhibit long‐term potentiation (LTP). Like LTP of some hippocampal synapses, LTP of in vitro Aplysia syanpses is regulated by the voltage of the postsynaptic cell. Pairing high‐frequency stimulation of sensory neurons with strong hyperpolarization of the motor neuron blocks the induction of LTP. Moreover, LTP of sensorimotor synapses can be induced in Hebbian fashion by pairing weak presynaptic stimulation with strong postsynaptic depolarization. These findings implicate a Habbian mechanism in classical conditioning in Aplysia. They also indicate that Hebbian LTP is a phylogenetically ancient form of synaptic plasticity. 1994 John Wiley & Sons, Inc.
Retrograde regualtion of presynaptic development during synaptogenesis
Authors: Haydon P. G. , Zoran M. J. 
Published: May 2005

AbstractMajor advances are occurring in our understanding of the events leading to synapse formation. Contact between the growth cone and target tissu leads to intercellular signaling which controls both pre‐ and postsynaptic development of the synapse. The identity of retrograde signals that regualte presynaptic development are beginning to emerge, and the signal transduction cascades that are activated presynaptically are being characterized. Recent studies have shown that both the resting calcium level and activation of presynatptic protein kinase A are critical in the development of the presynaptic terminal. An understanding of these regulatory mechanisms is be ginning to provide insight into the molecular control of synaptic specificity. 1994 John Wiley & Sons, Inc.
Tumor necrosis factor‐α induces substance P in sympathetic ganglia through sequential induction of interleukin‐1 and leukemia inhibitory factor
Authors: Ding Minzhen , Hart Ronald P. , Miller Jonakait G. 
Published: May 2005

AbstractThe present study establishes that tumor necrosis factor‐α (TNF‐α) induction of sympathetic substance P (SP) requires sequential induction of both interleukin (IL‐1) and leukemia inhibitory factor (LIF). TNF‐α dose‐dependently induces SP, an induction that is secondory to an increase in the SP precursor, preprotachykinin (PPT), mRNA. Since TNF‐α conditioned medium (CM) mimics the effect of TNF‐α by raising SP, actions that are not antagonized by a neutralizing TNF‐α antibody, TNF‐α induction of SP is mediated by a soluble intermediate or intermediates. The blockade of TNF‐α action by a specific IL‐1 receptor antagonist and the induction of IL‐1 mRNA by TNF‐α suggest that IL‐1 is one of the intermediates. Moreover, because immunoprecipitation with LIF antibodies decreases SP‐inducing activity of TNF‐α CM, and because LIF mRNA is also induced by TNF‐α, LIF is a second intermediate. Furthermore, TNF‐α‐induced LIF mRNA is blocked by the IL1 receptor antagonist, whereas IL‐1‐induced LIF mRNA is not affected by TNF‐α antibodies, suggesting that TNF‐α first induces IL‐1, and IL‐1 subsequently induces LIF. These data suggest that TNF‐α induces SP in sympathetic ganglia through the sequential inductions of IL1 and LIF. © 1995 John Wiley & Sons, Inc.
Expression of engrailed in an array of identified sensory neurons: Comparison with position, axonal arborization, and synaptic connectivity
Authors: Blagburn Jonathan M. , Gibbon Charles R. , Bacon Jonathan P. 
Published: May 2005

Abstractengrailed (en) is expressed in the posterior region of embryonic segments and appendages of the cockroach, Periplaneta americana. By 23% of embryogenesis En immunoreactivity is apparent in the dorsal half of the cercus, appendages of segment A11. By 40% of development, En staining is present in the dorsomedial half of the cercus. The nucleus of the medial filiform hair sensory neuron (M), born in this region, expresses en strongly. Staining is never seen in the lateral neuron (L). En is expressed in M as the sensory axons enter the terminal ganglion and begin to form their different arborizations and synaptic connections. This pattern of expression persists through development to the second instar. In mutant animals with supernumerary filiform hair sensilla, En immunoreactivity is only seen in the medial neurons. In second‐instar and adult cerci en expression is also seen in medially located neurons. We compared the levels of En staining in the array of 25 second instar neurons with their position, axonal arbor type, and synaptic connections. Staining intensity corelates with distance from the cercal midline, suggesting that en is regulated by other circumferential positional determinants. The expression of en does not correlate with the formation of an M‐type arbor. Although 10 of 12 sensory neurons that express en form synapses with giant interneuron 5, the correlation is not precise. These results suggest that, if En does form part of a combinatorial system of positional information in the cercus, its actions are modulated by other gene products. © 1995 John Wiley & Sons, Inc.
Influence of peripheral targets on the expression of calcitonin gene‐related peptide immunoreactivity in rat cranial motoneurones
Authors: McWilliam P. N. , Maqbool A. , Batten T. F. C. , Kaye J. C. 
Published: May 2005

AbstractCalcitonin gene‐related peptide‐like immunoreactivity (CGRP‐ir) is displayed by motoneurons that innervate striated muscle but is absent from preganglionic parasympathetic motoneurons. One hypothesis to explain this is that CGRP gene expression in motoneurons is, in part, dependent on influences from the innervated organ. To test this hypothesis, we cross‐anastomosed the right hypoglossal and cervical vagal nerves of rats so that the vagal motoneurons grew to innervate the musculature of the tongue. Following a recovery period of 17 to 52 weeks, the distribution of CGRP‐ir in the dorsal motor vagal nucleus was determined in both cross‐anastomosed animals and self‐anastomosed control animals. Successful reinnervation of the tongue musculature by vagal motoneurons was demonstrated by showing that electrical stimulation of the central vagus/peripheral hypoglossal nerve produced a twitch of the tongue muscles. Motoneurones of the dorsal motor vagal nucleus, which now innervated the tongue were found to express CGRP‐ir, which was evident from the double labeling of neurons with both horseradish peroxidase and CGRP‐ir. Motoneurones of the dorsal motor vagal nucleus contralateral to the cross‐anastomosis remained CGRP negative. Similarly, motoneurons of the dorsal motor vagal nucleus in control animals where the vagus nerve was self‐anastomosed remained CGRP negative, showing that an induction of CGRP expression is not a result of nerve section itself. We suggest that a signal from the striated muscle transported retrogradely via the motor axon regulates expression of CGRP‐ir in motoneurons. © 1995 John Wiley & Sons, Inc.
Carbon‐13 nuclear magnetic resonance spectra of some mesoionic xanthine analogs
Authors: Mbagwu G. O. , Bass R. G. , Glennon R. A. 
Published: May 2005

AbstractNatural abundance 13C NMR chemical shifts have been experimentally determined for a series of mesoionic thiazolo[3,2‐a]pyrimidine‐5,7‐diones. The spectral data are compared with those of related mesoionic dihydrothiazolo[3,2‐a]pyrimidine‐5,7‐diones and mesoionic 1,3,4‐thiadiazolo[3,2‐a]pyrimidine‐5,7‐diones. Resonable correlation between the observed 13C NMR chemical shifts and CNDO/2 total charge densities have been obtained for the different carbon atoms of 8‐methylthiazolo[3,2‐a]pyrimidine‐5,7‐dione.
1H and 13C NMR studies on 3‐aryl‐2‐thioxo‐4‐oxazolidinones and 3‐arylrhodanines
Authors: Aksaç Zihni , Pinar Esat , Içli Sîddîk 
Published: May 2005

Abstract3‐Aryl‐2‐thioxo‐4‐oxazolidinones and 3‐arylrhodanines have been studied for magnetic non‐equivalence of diastereotopically related proton and 13C nuclei in rotational isomers, and for steric interactions between the aryl and heterocyclic moieties of these compounds. For the majority of rotational isomers the barriers to internal rotation about the aryl CN bond were >100 kJ mol−1, due to the steric bulk of the thiocarbonyl group. Chemical isolation of several of the diastereomers was achieved. The enhanced steric effect and the difference in the electronic effect of the sulphur atom in relation to the oxygen atom appeared to have no influence on the small chemical shift differences of the rotational isomers, detected for some 1H and some 13C nuclei.
Hydroxy group substituent effects on 1H NMR chemical shifts in the structural elucidation of spirostanes
Authors: Jaffer Jaffer A. , Crabb Trevor A. , Turner Christopher H. , Blunden Gerald 
Published: May 2005

Abstract1H NMR chemical shifts in spirostanes have been determined by spin‐decoupling difference spectroscopy. Substituent effects of 7β‐OH on 15‐methylene proton shifts, 1β‐OH on 11α‐ and 2α‐proton shifts and 6α‐OH on 4α‐proton shifts have been determined and used in the structural assignment of spirostanes.
Mass spectrometry in structural and stereochemical problems—CLXIV. Electron impact promoted fragmentation of some thiosemicarbazones
Authors: Sheikh Younus M. , Duffield A. M. , Djerassi Carl 
Published: May 2005

AbstractThe mass spectral fragmentation of thiosemicarbazone derivatives of some typical aliphatic, alicyclic and aromatic aldehydes and ketones has been rationalized using high resolution mass spectrometry supplemented by deuterium labeling. Thiosemicarbazone derivatives of carbonyl compounds yield mass spectra which have little in common with those generated by their semicarbazone analogs.
On the mass spectra of some alkyl digermanium compounds
Authors: De Ridder J. J. , Dijikstra G. 
Published: May 2005

AbstractThis paper reports the monoisotopic mass spectra of the compounds (CH3)GeGe(CH3)3,(C2H5)3GeGe(C2H5)3 and (CH3)3GeGe(C2H5)3. With the aid of metastable ion transitons and appearance potentials the fragmentation patterns can be given.The dominant reactions are explained in terms of the valence of the metal atom. According to the valence rule the possibility of forming an ion in which two germanium atoms are bonded to five other groups (alkyl or hydrogen) determines greatly the spectra, while successive elimination of the methyl groups appears to be difficult and elimination of the ethyl groups is a predominant process.
Stereoisomeric effects on mass spectra—I. A Review
Authors: Meyerson Seymour , Weitkamp A. W. 
Published: May 2005

AbstractThe unimolecular reactions that give rise to mass spectra are controlled by spatial relationships and energy considerations. In molecules that contain a heteroatom, elimination reactions, involving bond‐making as well as breaking, are often prominent, e.g. loss of water from alcohols. The ease of such reactions depends on spatial relationships in the molecule, and the resultant ion intensities in the spectra of geometric isomers can consequently be correlated with differences in geometry and hence furnish a basis for assigning structures. Processes that do not involve bond‐making do not have such rigorous geometric requirements, but depend rather on attainment of a transition state defined in terms of a minimum energy content. Common product ions from stereoisomeric hydrocarbons seem often to arise via a common transition state. When this condition holds, the difference between the enthalpies of the isomers is reflected in the relative appearance potentials and–though the cause‐and‐effect relationship here is less direct and more readily obscured by other factors–relative intensities of the common product derived from the isomers. In both classes of processes, the spectra of stereoisomers can be simplified and made more distinctive by lowering source temperature and ionizing voltage.
Electron impact‐induced rearrangement of trimethylsilyl groups in long chain compounds
Authors: Draffan G. H. , Stillwell R. N. , McCloskey James A. 
Published: May 2005

AbstractMass spectra of trimethylsilyl (TMS) derivatives of long chain dicarboxylic acids, hydroxy acids, cyano acids, and terminal diols, dithiols and diamines have been examined. A number of fragmentation pathways involving rearrangement of partial or intact TMS groups between the termini or remote points in the chain have been determined, using deuterium and carbon‐13 labeling, and high resolution mass spectrometry. Knowledge of the occurrence of functional group migrations of this type is essential to the correct interpretation of mass spectra of TMS derivatives, which are now in wide use in mass spectrometry and gas chromatography. These data in addition provide further evidence for the general ability of remote functional groups to interact, by winding or coiling of long chains. A number of interesting doubly‐charged ions are reported, in which the charges are reported, in which the charges are located at opposite ends of long chains, and for which no singly‐charged counterparts are observed.
Electron‐impact studies of organometallic molecules—VII. Some transition metal complexes derived from 3,3,3‐trifluoroprop‐1‐yne
Authors: Bruce M. I. 
Published: May 2005

AbstractThe mass spectra of ten complexes derived from 3,3,3‐trifluoroprop‐1‐yne, namely (CF3CCH)CO2(CO)6, (CF3CCH) [πC5H5Ni]2, (CF3CCH)3Co2(CO)4, CF3CH2C[Co(CO)3]3,

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are discussed in terms of their structures. The major processes observed can be satisfactorily explained in terms of (i) loss of carbonyl groups, if present; (ii) loss of one fluorine atom from the parention (iii) elimination of neutral metal fluorides, with ligand transfer reactions in the case of the iron complexes; (iv) elimination of neutral fluorocarbon molecules.
Zur Massenspektrometrie von Nitrophenylverbindungen—I. Nitrophenylphydrazone Aromatischer Aldehyde und Ketone und Verweandte Verbindungen
Authors: Seibl J. , Völlmin J. 
Published: May 2005

AbstractDie Fragmentierung von Nitrophenylhydrazonen aromatischer Aldehyde und Ketone, von Nitrostillbenen, Nitrobenzalacetophenonen und analogen Verbindungen unter Elektronenbeschuss wird entscheidend durch intramolekulare Oxidationsreaktionen beeinflusst, sofern sich eine Nitrogruppe in o‐Stellung zum ungesättigten substituenten befindet. Es findet eine Sauerstoffübertragung von der o‐Nitrogruppe auf die Hydrazon‐ oder Stilbendoppelbindung statt; ein wesentlicher Teil der charakterisierenden Fragmente in den Massenspektren dieser Verbindungen stammt aus dem Zerfall dieser Sauerstoffübertragungsprodukte. 20 Spektren von 40 untersuchten Verbindungen werden präsentiert und diskutiert. Eine Reihe weiterer umlagerungsreaktionen werden beobahtet. Eine konjugierte zusätzliche Dopplbindung in der Hydrazonkette ändert die Reaktivität der Verbindung vollsändig. auch die Fragmentierung gesättigter Substituenten (Cyclopropyl) kann durch eine o‐Nitrogruppe entscheidend beeinflusst werden.