bluuebunny/crossref_metadata_2025_split huggingface dataset:
The growth of nerves in relation to the formation of premuscle cell masses in the developing chick forelimb
Authors: Bennett M. R. , Davey D. F. , Marshall J. J. 
Published: December 2004

AbstractA description is given of the growth of segmental nerves 13 to 16 (SN13 to SN16) from the brachial myotomes into the ventral and dorsal premuscle cell masses of the chick forelimb. At stage 25 (Hamburger and Hamilton, 1951), segmental nerves have converged to form two nerve trunks which enter the ventral and dorsal premuscle cell masses. These nerves grow into the limb, parallel to its proximodistal axis. The nerve trunk in the ventral compartment, the brachialis longus inferior (bli n), grows on the brachial artery as far as the metacarpals. The nerve trunk in the dorsal compartment, the brachialis longus superior (bls n), grows on the precartilage adjacent to a dorsal premuscle density as far as the metacarpals.The brachialis longus inferior and superior nerve trunks give rise to a number of nerves during their growth to the metacarpals. Each of these nerves appears at the time of formation of a new premuscle cell density. At late stage 25, a posterior and ventral premuscle density forms in the middle of the stylopodium; posterior fascicles of the bli n diverge at this level and grow toward this new density to form the ulnar nerve. By stage 26 a posterior and ventral premuscle density is prominent over the bli n, at the junction of the stylopodium and the zeugopodium; ventral fascicles of the bli n grow into this density to form the flexor digitorum profundus nerve. At this stage a posterior and dorsal premuscle density forms just beyond the junction of the stylopodium and zeugopodium. Posterior fascicles of the bls n diverge at this level and grow toward this density to form a nerve from which the extensor metacarpi ulnaris, extensor digitorum communis, and radialis la‐terialis nerves are destined to form. At stage 29 the premuscle cell masses of the autopodium have formed. The remaining nerve fascicles comprising the bls n (the radialis profundus nerve) grow into the autopodium and branch to innervate each of the dorsal premuscles. The remaining nerve fascicles comprising the bli n (the middle nerve) grow into the autopodium and branch to innervate each of the ventral premuscles.
3H‐GABA uptake selectively labels identifiable neurons in the leech central nervous system
Authors: Cline Hollis T. 
Published: December 2004

AbstractSegment ganglia of the leech ventral nerve cord synthesize the neurotransmitter γ‐aminobutyric acid(GABA) when incubatyed in the presence of the prescursor glumate, suggesting that there may be GABA‐ergic neurons in the leech nerve cord. GABA‐accumulating neurons of the two taxonomically distant leech species, Haementeria ghilianii and Hirudo nedicinalis, have been labeled by takeing advantage of their high‐affinity uptake system for the neurotransmitter. Autoradiography of sectioned segmental ganglia previously exposed to 3H‐GABA reveals a reproducible pattern of about thirty 3labeled neurol cell bodies are bilaterally paired, although some apparently unpaired cell bodies also accumulate label. Neuronal processes were reproducibly labeled by GABA uptake and could be traced in the neuropil through commissures and fiber tracts into the segmental nerve roots and interganglionic connectives, respectively.
Morphology and migration of cultured schwann cells transplanted into the fimbria and hippocampus in adult rats
Authors: Brook Gary A. , Lawrence Jean M. , Raisman Geoffrey 
Published: December 2004

AbstractSchwann cells cultured from neonatal rat peripheral nerve were injected into the fimbria and hippocampus of syngeneic adult rats by a microtransplantation technique which causes minimal disturbance to the host brain structure at the site of implantation, and thus allows the grafted cells to come into immediate contact with intact host tissue.Numerous Schwann cells could be identified for up to 6 weeks (and with decreasing frequency for up to 3 months) by intense immunoreactivity for low affinity nerve growth factor receptor. The transplanted cells adopted a distinctive elongated form, with a central, ovoid nucleus flanked by processes which were up to 300 μm long, and which ranged from swollen segments with a diameter as large as 12 μm down to thread‐like fibres of 1 μm or less. This morphology is different from that of any of the host cells. The transplanted Schwann cells migrated freely into the host tissue along blood vessels and according to the position of the grafts, they either entered the hippocampal neuropil, or migrated (for distances of up to 2 mm) along the longitudinal axis of the fimbria, where they were interspersed in parallel with the interfascicular glial rows and axons.The host astrocytes did not appear to impede the migration of the donor Schwann cells. Although the host astrocytic processes became hypertrophic, with increased glial fibrillary acidic protein and vimentin expression, the predominant longitudinal orientation of the astrocytic tract processes was maintained.The transplanted Schwann cells did not form peripheral myelin (as detected by Po immunoreactivity), and it is not clear whether they survive beyond the period at which we detect them. © 1993 Wiley‐Liss, Inc.
Astrocytic GABA receptors
Authors: Fraser Douglas D. , Mudrick‐Donnon Lori A. , Macvicar Brian A. 
Published: December 2004

AbstractGABA receptors are distributed widely throughout the central nervous system on a variety of cell types. It has become increasingly clear that astrocytes, both in cell culture and tissue slices, express abundant GABAA receptors. In astrocytes, GABA activates Cl−‐specific channels that are modulated by barbiturates and benzodiazepines; however, the neuronal inverse agonist methyl‐4‐ethyl‐6, 7‐dimethoxy‐β‐carboline‐3‐car‐boxylate enhances the current in a subpopulation of astrocytes. The properties of astrocytic GABAA receptors, therefore, are remarkably similar to their neuronal counterparts, with only a few pharmacological exceptions. In stellate glial cells of the pituitary pars intermedia, GABA released from neuronal terminals activates postsynaptic potentials directly. The physiological significance of astrocytic GABAA‐receptor activation remains unknown, but it may be involved in extracellular ion homeostasis and pH regulation. At present, there is considerably less evidence for the presence of GABAB receptors on astrocytes. The data that have emerged, however, indicate a prominent role for second‐messenger regulation by this receptor. © 1994 Wiley‐Liss, Inc.
Excitatory amino acid receptors in glial progenitor cells: Molecular and functional properties
Authors: Gallo Vittorio , Patneau Doris K. , Mayer Mark L. , Vaccarino Flora M. 
Published: December 2004

AbstractWe have analyzed the molecular and biophysical properties of glutamate‐gated channels in cells of the oligodendrocyte lineage, using both the CG‐4 primary cell line (Louis et al: J. Neurosci. Res. 31:193‐204, 1992a) and oligodendrocyte progenitors purified from the rat cerebral cortex. CG‐4 progenitor cells, as well as primary progenitors, were stained with a specific anti‐GABA antibody. In whole‐cell patch‐clamp recordings, rapid perfusion of the agonists L‐glutamate, kainate, and AMPA produced rapidly desensitizing currents in CG‐4 cells. NMDA was ineffective. Both rapidly desensitizing and steady‐state components of responses to kainate were inhibited by the kainate/AMPA receptor antagonist CNQX. Northern blot analysis of total mRNA isolated from CG‐4 cells revealed co‐expression of both AMPA‐ and kainate‐preferring glutamate receptor subunits. The activation of glutamate receptors in CG‐4 cells caused a rapid and transient elevation of mRNAs for the immediate early gene NGFI‐A. © 1994 Wiley‐Liss, Inc.
Plasticity of astrocytes
Authors: Shao Yanping , McCarthy Ken D. 
Published: December 2004

AbstractIt is becoming apparent that astrocytes carry out a large number of different functions in brain and are able to modify their characteristics throughout life, that is they exhibit a high degree of plasticity in their phenotype. For example, the morphology of astrocytes changes markedly during neuronal migration, maturation, and degeneration. It is conceivable that these cells must constantly adjust their abilities to meet changes in brain environment. Several examples of astrocytic plasticity are presented in this review. First, the ability of astrocytes to recognize neuronal signals can change qualitatively as well as quantitatively; evidence suggests that the expression of glial receptors may be developmentally regulated by both intrinsic and extrinsic signals. Second, the expression of adrenergic receptors by astrocytes in adult brain can change in response to neuronal degeneration. The up‐regulation of β‐adrenergic receptors in this case suggests that these receptors play a role in function of reactive astrocytes. Finally, glial morphology can be reciprocally regulated by neurotransmitters such as norepinephrine and glutamate. This reciprocal regulation may be significant since both ß‐adrenergic receptors and glutamate transporters are found predominantly in astrocytes in the brain. The change in glial morphology may also affect neuronal activity by changing the volume of the extracellular space. © 1994 Wiley‐Liss, Inc.
Neurotransmitter‐mediated signaling between axons and glial cells
Authors: Chiu S. Y. , Kriegler S. 
Published: December 2004

AbstractNeurotransmitter‐mediated signaling is not restricted to the synaptic regions of the nervous system but also takes places along fiber tracts lacking vesicular means of releasing neuroactive substances. The first demonstration for dynamic signaling of this type came in the early 1970s from studies by Villegas and co‐workers in squid axons and their satellite Schwann cells. In this invertebrate system, glutamate has been identified as the mediator of this signaling in being first released from the active axons thus setting off a series of cascades, leading to a cholinergic activation of the Schwann cell membrane. Recent evidence suggests that receptor‐mediated signaling also exists between glial cells and axons in vertebrates. In the frog optic nerve, axonal activity facilitated the activity of glial ion channels. In the neonatal rat optic nerve, electrical activity of axons triggered oscillations in intracellular calcium in a subset of glial cells. These observations have been postulated to reflect receptor‐mediated signaling, including a mechanism in which glutamate is released from axons via the reversal of a transporter and induces intracellular calcium spiking in glial cells via metabotropic glutamate receptors. The efficacy of “axon‐to‐glia” transmission may, like that in “neuron‐to‐neuron” transmission, be modulated by co‐release of multiple neuroactive substances. One possibility is that adenosine, which is known to be released from fiber tracts, can modulate glutamate signaling in white matter by modulating the periaxonal glutamate concentration through an effect on the glial glutamate uptake system. © 1994 Wiley‐Liss, Inc.
Functional differences between auditory cortices of the two hemispheres revealed by whole‐head neuromagnetic recordings
Authors: Mäkelä J. P. , Ahonen A. , Hämäläinen M. , Hari R. , Llmoniemi R. , Kajola M. , Knuutila J. , Lounasmaa O. V. , McEvoy L. , Salmelin R. , Salonen O. , Sams M. , Simola J. , Tesche C. , Vasama J‐P. 
Published: December 2004

AbstractWe recorded auditory evoked magnetic fields from nine healthy subjects with a 122‐channel whole‐head SQUID magnetometer. This type of measurement ensures that responses from both hemispheres are collected in the same stage of vigilance. The stimuli were 50‐ms 1‐kHz tones, delivered alternately to the two ears at interstimulus intervals (ISIs) of 1, 2, 4, 8, and 16 s per ear. In both hemispheres, the prominent 100‐ms response (N100m) was, on average, 22% larger and 9 ms earlier for contralateral than ipsilateral tones. The N100m amplitude increased as a function of ISI and saturated at ISIs of 8–16 s. The average ISI dependence of N100m was similar over both hemispheres and for both contralateral and ipsilateral stimuli, implying that tones leave neural traces of similar duration in both hemispheres. Differences were observed as well: the response waveforms were clearly asymmetric in one subject, and four subjects displayed an additional right‐hemisphere‐dominant 250‐ms deflection (N250m). © 1993 Wiley‐Liss, Inc.
13C‐Kernresonanzspektroskopische und elektromotorische Untersuchungen der Wechselwirkung von neutralen Carriern mit Ionen in Membranen
Authors: Büchi Rolf , Pretsch Ernö , Morf Werner E. , Simon Wilhelm 
Published: December 2004

Investigation of the interaction of neutral carriers with ions in membranes by 13C‐NMR. and EMF.‐measurements.Applying a simple model, information on the interaction of neutral carriers with cations as well as on the ion pair formation may be obtained through 13C‐NMR. and potentiometric studies of PVC‐supported ion selective liquidmembranes in contact with aqueous solutions. The results indicate that carriers for K+ (nonactin) and synthetic ionophores for Ca2+ show an association of the carrier‐complexes with lipophilic anions. The extent of complex formation of the carrier in the presence of lipophilic anions in the sample solution is in agreement with earlier interpretations of the anion interference of cation selective liquid‐membrane electrodes.
Synthese von [D‐Alanin1, 4′ ‐azido‐3′, 5′ ‐ditritio‐L‐phenylalanin2, norvalin4]α‐melanotropin als «Photoaffinitätsprobe» für Hormon‐Rezeptor‐Wechselwirkungen
Authors: Eberle Alex , Schwyzer Robert 
Published: December 2004

Synthesis of [D‐alanine1, 4′‐azido‐3′, 5′‐ditritio‐L‐phenylalanine2, norvaline4]α‐melanotropin as a ‘photoaffinity probe’ for hormone‐receptor interactions.The synthesis of an α‐MSH derivative containing 4′‐azido‐3′,5′‐ditritio‐L‐phenylalanine is described: Ac · D‐Ala‐Pap(3H2)‐Ser‐Nva‐Glu‐His‐Phe‐Arg‐Trp‐Gly‐Lys‐Pro‐Val · NH2. This hormone analogue is being used for specific photoaffinity labelling of receptor molecules. The synthesis was performed in a way to minimize the number of radioactive steps and to introduce the radio‐active and the photoaffinity label exclusively into position 2. The dipeptide N(α)‐acetyl‐D‐alanyl‐ (4′‐amino‐3′,5′‐diiodo)‐L‐phenylalanine was tritriated and transformed into the azido compound, N(α)‐acetyl‐D‐alanyl‐(4′‐azido‐3′,5′‐ditritio)‐L‐phenylalanine which was then condensed with H · Ser‐Nva‐Glu(OtBu)‐His‐Phe‐Arg‐Trp‐Gly‐Lys(BOC)‐Pro‐Val · NH2 to the tridecapeptide. The α‐MSH analog displayed a specific activity of 11 Ci/mmol, and a biological activity of about 4 · 109 U/mmol (10% of α‐MSH).
Über die Verbreitung der stereomeren Muscarine innerhalb der Ordnung der Agaricales
Authors: Stadelmann René Josef , Eugster Conrad Hans , Müller Emil 
Published: December 2004

Investigations on the distribution of the stereoisomeric muscarines within the order of agaricales.Stereomeric muscarines (muscarine, epi‐muscarine and allo‐muscarine), albeit in low concentrations (⩽ 2 mg/100 g dry weight), have been found in fruiting bodies of the following species of agaricales: Amanita pantherina, Amanita phalloides, Boletus calopus, Boletus luridus, Clitocybe dealbata, Clitocybe hydrogramma, Clitocybe gibba (= Cl. infundibuliformis s.s. auct. plur.), Clitocybe vermicularis, Clitopilus intermedius, Collybia peronata, Hygrocybe mgrescens, Hypholoma fasciculare, Lactarius rufus, Lactarius trivialis, Mycena pelianthina, Mycena pura, Paxillus involutus, Rhodophyllus rhodopolius, Rhodophyllus sinuatus, Russula emetica, Tricholoma sulphureum, Tylopilus felleus. Collections of the same species from different sites showed pronounced variation in the relative amounts of stereoisomers, e.g. with Clitocybe dealbata and Rhodo phyllus rhodopolius. epi‐allo‐Muscarine could not be detected in any of the species tested.
13C‐NMR. Spectroscopy of Naturally Occurring Substances. XLV. Iboga Alkaloids
Authors: Wenkert Ernest , Cochran David W. , Gottlieb Hugo E. , Hagaman Edward W. , Filho Raimundo Braz , de Abreu Matos Francisco José , Lacerda Machado Madruga Maria Iracema 
Published: December 2004

AbstractThe carbon shifts of the Iboga‐type alkaloids catharanthine, voacangine, coronaridine, ibogaine, dihydrocatharanthine and epiibogamine were recorded and correlated with the conformation of the natural bases. A 13C‐NMR. analysis of heyneanine determined its C(19) configuration and a similar study of epiheyneanine proved its structure.
Carbenic Behaviour of Isocyanoamines generated by Flash Pyrolysis of 4‐Arylhydrazono‐isoxazol‐5‐ones. Rearrangement to Cyanamides and Indazoles. Preliminary communication
Authors: Reichen Werner , Wentrup Curt 
Published: December 2004

AbstractFlash pyrolysis of the 4‐arylhydrazono‐3‐methyl‐isoxazol‐5‐one (1) yields carbon dioxide, acetonitrile, and isocyanoarylamines 2 which under the reaction conditions rearrange to either arylcyanamides 3 or indazoles 4. It is shown by deuterium labelling that only the isocyanoamines not the isomeric nitrile imines are intermediates in the formation of indazoles.
Struktur des Hydrazinolyseproduktes von N‐(3‐Oxo‐1‐isoindolinyliden)‐alanin‐äthylester
Authors: Chaloupka Stanislav , Bieri Jost H. , Heimgartner Heinz 
Published: December 2004

Hydrazinolysis of N‐(3‐Oxo‐1‐isoindolinyliden)alanin Ethyl Ester, Structure of the ProductTreatment of N‐(3‐oxo‐1‐isoindolinyliden)alanin ethyl ester (6) with hydrazine hydrate leads to 4‐methyl‐2,3,4,6‐tetrahydro[1,2,4]triazino[3,4‐a]isoindole‐3, 6‐dione (8, Scheme 3) and not to the previously postulated 6‐hydroxy‐2‐methyl‐2,3‐dihydro‐imidazo [2,1‐a]phthalazin‐3‐one (7, cf. [2]). The structure of 8 has been established by an independent synthesis as well as by the X‐ray analysis of the reaction product 11 from 8 and 3‐dimethylamino‐2,2‐dimethyl‐2 H‐azirine (1, Scheme 4). A reaction mechanism for the formation of 8 from 6 is suggested in Scheme 5.
63Cu‐NMR.Studies of Copper(I)tetrapyridine and Copper(I)tetraacetonitrile Solvates
Authors: Ochsenbein Ueli , Schläpfer Carl W. 
Published: December 2004

Abstract63Cu‐NMR.‐Spectra of Cu(CH3CN)4X (X = ClO, BF, PF) and Cu(C5H5N)4X (X = ClO, BF) in solution are reported at different temperatures and concentrations. The influence of temperature on the linewidth and chemical shift indicates an equilibrium of Cu(CH3CN) and Cu(C5H5N) with another complex of lower symmetry. The preferential solvation of Cu (I) by pyridin in a mixture acetonitrile/pyridine is clearly shown.
Stereochemistry‐Odor Relationships in Enantiomeric Ambergris Fragrances
Authors: Ohloff Günther , Vial Christian , Wolf Hans Richard , Job Kurt , Jégou Elise , Polonsky Judith , Lederer Edgar 
Published: December 2004

AbstractTwelve tricyclic ethers of the labdane and ent‐labdane series, 5–16, have been synthesized; compounds 6–15 are new. The intramolecular C18‐acetals 1–4 and the tricyclic ethers 5–16 were submitted to an olfactory test which was characterized by an exceptionally high percentage of ‘wrong’ answers (cf. Table 1, footnote b). For most compounds specific anosmia, rapidly ensuing fatigue and a high percentage of odor deviation were the most salient features.Pronounced ambergris‐like odors were only noted in compounds of the labdane series, and were strongest in ethers 1, 5 and 15, followed by the ethers 9 and 11. In contrast, both labdane derivatives 3 and 7 were practically odorless. Their enantiomers 4 and 8, on the other hand, have relatively strong odors which can only to a limited extent be associated with ambergris‐type odors. The pairs of ethers 3/4 and 7/8 are the first recorded examples of optical antipodes in which only one isomer possesses olfactory properties.
Some Comments on the Conformations of Methyl Phenyl Sulfides, Sulfoxides and Sulfones
Authors: Mohraz Manijeh , Jian‐qi Wang , Heilbronner Edgar , Solladiéa‐Cavallo Arlette , Matloubi‐Moghadam Firouz 
Published: December 2004

Abstract13C‐NMR. and He (Iα) photoelectron spectra of alkyl phenyl sulfides, sulfoxides and sulfones have been used to probe how their conformations depend on the size of the alkyl groups R. The results are interpreted to indicate that in the sulfides the S, R‐bond is twisted out of the planar conformation with increasing size of the alkyl group, whereas in the sulfoxides and sulfones the preferred conformation with the S, R‐bond perpendicular to the phenyl group plane seems to be independent of the size of R. These conclusions are in agreement with previous work on the alkyl phenyl sulfides and provide strong support for previous conjectures concerning the preferred conformations of alkyl phenyl sulfoxides and sulfones.
Hindered Nucleophilic Displacement (SN 2) Reactions of 2exo‐ and 2endo‐ Norbornyl Derivatives. Norbornane) Series 4
Authors: Grob Cyril A. , Lutz Erich 
Published: December 2004

AbstractThe reactions of 2exo‐ and 2endo‐norbornyl bromide (1e and 2e, respectively) in 90% ethanol with a large excess of potassium hydroxide, and of 2exo‐norbornyl p‐toluenesulfonate (1g) with excess sodium thiophenolate in methyl cellosolve, have been studied. They obey the first order rate law and are zero order with respect to the base‐nucleophile. However, the ratio of 1,2‐ and 1,3‐elimination to exo‐substitution products depends strongly on the base‐nucleophile concentration. Ion pair intermediates are indicated. The extreme inertness of 2‐norbornyl derivatives in displacement reactions is due to severe steric hindrance of rearside nucleophilic attack, a feature they have in common with other bi‐ and tricyclic molecules bearing nucleofugal groups adjacent to one or two bridgehead atoms.
Photochemische Reaktionen 119. Mitteilung [1] Zur Photospaltung konjugierter γ,δ‐Epoxyenone. UV.‐Bestrahlung von 3‐(1′,2′‐Epoxy‐2′‐methyl‐prop‐1′‐yl)‐5,5‐dimethyl‐2‐cyclohexen‐1‐on
Authors: De Weck Guy , Wolf Hans Richard 
Published: December 2004

Photocleavage of Conjugated π,π‐Epoxyenones. UV.‐Irradiation of 3‐(1′,2′‐Epoxy‐2′‐methyl‐prop‐1′‐yl)‐5,5‐dimethyl‐2‐cyclohexene‐1‐oneOn 1π,π*‐excitation (δ = 254 nm) 9 undergoes cleavage of the C(δ), C(δ)‐bond yielding 17 and a, which gives 18 by photofragmentation. In presence of maleinic ester the photolysis of 9 yields 20, in presence of methanol 21 and 22 are obtained. By photocleavage of the C(δ), O‐bond 9 is converted into b giving 14. Photolysis of 14 yields 15 (A + B) and 16.On 1n,π*‐excitation (δ λ⩾ 347 nm) of 9 cleavage of the C(δ), O‐bond (9 → b) seems to be the preferred reaction, whereas products of a are formed in traces, only.