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  • Polymer and Materials Science  (37)
  • Life and Medical Sciences  (26)
  • Amphibian  (3)
  • brain  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Formation of the amphibian grey crescent: Effects of colchicine and cytochalasin B (1978)
    Springer
    Development genes and evolution 185 (1978), S. 99-104 
    Details
    ISSN: 1432-041X
    Keywords: Amphibian ; Grey crescent ; Colchicine ; Cytochalasine B
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of colchicine and cytochalasin B on grey crescent formation in frog (Rana pipiens) and toad (Bufo arenarum) eggs were determined. Colchicine prevented the appearance of the grey crescent, but this inhibition was not due to the absence of an aster. Cytochalasin B did not inhibit grey crescent formation, nor did it inhibit certain activation events such as cortical granule breakdown or cortical contraction. Cytochalasin B caused a detachment of the cortex from the cytoplasm and induced the formation of a morphological grey crescent in non-activated eggs. The results suggest that microtubules may play several roles in grey crescent formation and that a change in the attachment of the cortex to the cytoplasm may also be involved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848218
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  • 2
    Electronic Resource
    Electronic Resource
    Ultraviolet light inhibits grey crescent formation on the frog egg (1980)
    Springer
    Development genes and evolution 189 (1980), S. 73-76 
    Details
    ISSN: 1432-041X
    Keywords: Ultraviolet irradiation ; Amphibian ; Grey crescent ; Embryology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Work by others has shown that ultraviolet (UV) irradiation of the vegetal half of the uncleaved frog egg causes defects in neural development. We find that the earliest effect of irradiation ofRana pipiens eggs is to prevent grey crescent formation, the first indication of dorso-ventral polarization of the egg. The UV effect on the grey crescent and on neural development shows similarities in timing, dose-responses, and reversal by cold. We suggest that the UV effect on neural morphogenesis may be caused by the inhibition of cortical-cytoplasmic movement involved in grey crescent formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00848569
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  • 3
    Electronic Resource
    Electronic Resource
    Release of norepinephrine and dopamine from brain vesicular preparations: Effects of adenosine analogues (1982)
    Springer
    Cellular and molecular neurobiology 2 (1982), S. 193-204 
    Details
    ISSN: 1573-6830
    Keywords: adenosine ; catecholamines ; neurotransmission ; calcium ; brain ; striatum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Adenosine analogues inhibit calcium-dependent K+-evoked release of [3H]norepinephrine from guinea pig cerebral cortical and hippocampal vesicular preparations. Inhibition requires high concentrations (100µM) of the adenosine analogues and is abolished in the presence of high concentrations (2 mM) of calcium ions. The inhibitory effect of 2-chloroadenosine is blocked by theophylline. The structure activity profile (N 6-d-phenylisopropyladenosine ≥N 6-l-phenylisopropyladenosine ≥ 2-chloroadenosine 〉N 6-cyclohexyladenosine, adenosine 5′-cyclopropylcar-boxamide) is not that expected of either A1 (high-affinity) or A2 (low-affinity) adenosine receptors. 2. Calcium-dependent K+-evoked release of [3H]dopamine from guinea pig striatal vesicular preparations is inhibited by apomorphine. However, only 2-chloroadenoine causes an inhibition of K+-evoked release of [3H]dopamine. Other adenosine analogues such asd- andl-phenylisopropyladenosine and adenosine 5′-cyclopropylcar-boxamide cause a facilitation of K+-evoked release. The facilitation is abolished or reduced in the presence of high concentrations (2 mM) of calcium ions. The sites of action of adenosine analogues do not appear to have structural requirements identical to those expected of A1 (high-affinity) or A2 (low-affinity) adenosine receptors. 3. The results indicate that adenosine analogues can have either inhibitory or facilitory effects on K+-evoked release of catecholamines from central synaptic terminals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00711147
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  • 4
    Electronic Resource
    Electronic Resource
    Release of norepinephrine from brain vesicular preparations: Effects of an adenylate cyclase activator, forskolin, and a phosphodiesterase inhibitor (1982)
    Springer
    Cellular and molecular neurobiology 2 (1982), S. 179-192 
    Details
    ISSN: 1573-6830
    Keywords: adenylate cyclase ; catecholamines ; adrenergic receptors ; cyclic AMP ; phosphodiesterase ; neurotransmission ; calcium ; brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. The calcium-dependent K+-evoked release of [3H]norepinephrine from guinea pig cerebral cortical vesicular preparations is inhibited by norepinephrine, clonidine, and epinephrine. Isoproterenol has no effect and phentolamine prevents the inhibition by norepinephrine. The results indicate that anα-adrenergic receptor mediates an inhibitory input to the calcium-dependent release process. The inhibition by norepinephrine is prevented by high concentrations (3.0 mM) of calcium ions. 2. A cyclic AMP phosphodiesterase inhibitor, ZK 62771, slightly elevates [3H]cyclic AMP levels in the guinea pig cerebral cortical preparation and potentiates the marked elevation of [3H]cyclic AMP elicited by the adenylate cyclase activator, forskolin. 3. Neither ZK 62771 nor forskolin alone has significant effects on K+-evoked release of [3H]norepinephrine from the cerebral cortical vesicular preparation; however, a combination of ZK 62771 and forskolin inhibits K+-evoked release by as much as 60%. The inhibition is reversed by high concentrations (2.0 mM) of calcium ions. The results suggest that a marked accumulation of cyclic AMP elicited via both activation of adenylate cyclase and inhibition of phosphodiesterase can be inhibitory to neurotransmitter release from central synaptic terminals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00711146
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  • 5
    Electronic Resource
    Electronic Resource
    Release of norepinephrine and dopamine from brain vesicular preparations: Effects of calcium antagonists (1982)
    Springer
    Cellular and molecular neurobiology 2 (1982), S. 205-213 
    Details
    ISSN: 1573-6830
    Keywords: calcium ; catecholamines ; neurotransmission ; brain ; striatum ; calcium antagonists
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. The calcium antagonists D-600 (1–10µM) and diltiazem (10–25µM) inhibit K+-evoked release of [3H]norepinephrine from guinea pig cerebral cortical vesicular preparations. The inhibition of release is partially reversed by increasing concentrations of calcium to 2 mM. Diltiazem at 100µM has no effect on K+-evoked release of [3H]norepinephrine at 0.15 mM calcium but does inhibit release at 2.0 mM calcium. 2. The calcium antagonist nifedipine and dantrolene, an agent purported to antagonize release of calcium from intracellular storage sites, have no effect on K+-evoked release of [3H]norepinephrine. 3. The calcium antagonists D-600 (1µM) and diltiazem (10µM) inhibit K+-evoked release of [3H]dopamine from guinea pig striatal vesicular preparations. Higher concentrations of drug, namely, 10µM for D-600 and 100µM for diltiazem, cause a potentiation rather than an inhibition of K+-evoked release. The potentiation is reduced in magnitude upon raising the extracellular calcium to 2.0 mM. Indeed, 10µM D-600 then inhibits K+-evoked release of [3H]dopamine. 4. The results indicate that putative calcium antagonists can have both inhibitory and facilitory effects on calcium-dependent K+-evoked release of catecholamines from central synaptic endings. Furthermore, certain peripheral calcium antagonists such as nifedipine and dantrolene may prove ineffective in central systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00711148
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  • 6
    Electronic Resource
    Electronic Resource
    Cytoplasmic inclusions of Trichamoeba and their reaction to vital dyes and to osmic and silver impregnation (1930)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 49 (1930), S. 139-151 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In Trichamoeba sp two types of inclusions are recognized on the basis of reaction to vital dyes and tomethods of osmic and silver impregnation. Globular inclusions, which are stained selectively with neutral red, may be blackened under direct observation by exposure to osmic vapor in hanging-drop preparations and demonstrated by osmic and silver impregnation. Rod-like and granular mitochondria, stainable vitally with Janus green, may be distinguished from the neutral-red globules in preparations stained with a mixture of Janus green and neutral red, and are demonstrated by Regaud's chondriosome method.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1050490104
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  • 7
    Electronic Resource
    Electronic Resource
    The vacuome of the flagellate Chlamydomonas (1931)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 51 (1931), S. 527-543 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A vacuome (‘Golgi apparatus’) consisting of small globular inclusions has been demonstrated in Chlamydomonas sp. These inclusions may be seen in the living, unstained organism; they are stainable vitally with neutral red; they have been stained vitally with neutral red and then blackened with osmic vapor under direct observation, and they have been impregnated by osmic and silver methods without previous treatment with neutral red.The reaction of these inclusions to the iodin test for starch suggests that they may play some rǒle, possibly one of storage, in the cycle of starch metabolism.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1050510207
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  • 8
    Electronic Resource
    Electronic Resource
    Fertilization and aqueous development of the puerto rican terrestrial-breeding frog, Eleutherodactylus coqui (1987)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 193 (1987), S. 217-224 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The Puerto Rican tree frog, Eleutherodactylus coqui, has internal fertilization and direct development on land. In light of these reproductive adaptations, the events of fertilization and early development were studied. Cytological examination of just-fertilized eggs showed that sperm entry is restricted to about 10% of the surface of these large, yolky eggs, and all nuclear events of the first cell cycle occur near the animal pole. Although the oocytes have cortical granules, a number of polyspermic fertilizations were found. One clutch consisted of eggs with a high frequency of polyspermy and of normal development. This raises the possibility that normal development can occur despite multiple sperm entry, a situation not found in other anuran amphibians. With respect to saline requirements, the sperm and the embryo are similar to those in amphibians with external fertilization and aqueous development. Sperm motility was high in low-tonicity conditions, and the normally terrestrial embryo could develop completely from a fertilized egg to a froglet in a low-tonicity aqueous solution.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051930208
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  • 9
    Electronic Resource
    Electronic Resource
    Configurational entropy of polyethylene and other linear polymers (1966)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 4 (1966), S. 869-880 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The configurational entropy of the polyethylene chain at the melting points calculated in two ways. In both calculations, tetrahedral angles and discrete trans and gauche arrangements of all bonds are assumed, and trans bonds are assumed more stable than gauche by energy U1. First, calculations are made on chains of up to N = 18 bonds, disallowing all configurations having overlapping atoms, and the result is extrapolated to large N. Second, a calculation is made directly for long chains, with overlaps excluded only over every short chain segment. The results are in almost exact agreement, suggesting that the second method can be safely used with other molecules. The calculated configurational entropy is in line with that suggested by the entropy of fusion, assuming the chains to acquire a configurational freedom in the melt which approaches that of independent chains.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1966.160040604
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  • 10
    Electronic Resource
    Electronic Resource
    Equation of state and the thermodynamic properties of liquid polymers: Application of the Hirai-Eyring modelPresented at Symposium on Thermodynamic Properties of Bulk Polymers, National Bureau of Standards, Gaithersburg, Md., March 10-12, 1969. (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 1337-1360 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is shown that the Hirai-Eyring model for the liquid state is capable of accurately describing the p, V, T behavior of liquid polymers in the temperature range over which measurements are now made, and below. Once the parameter choices necessary to accomplish the fit are made for a particular polymer, the excess thermodynamic functions (differences in properties, liquid less solid) are determined by the same parameters. Above the glass transition temperature Tg the volume, excess enthalpy, and square of the excess entropy are predicted by the model to be essentially linear with temperature, in agreement with experiment. Below Tg, these functions do not remain linear (as is usually assumed in extrapolating the equilibrium behavior to low temperatures), but instead they rapidly approach zero in a continuous way as the temperature is lowered. These remarks apply to glass-forming materials composed of small molecules, as well as to polymers. The “paradox” raised by Kauzmann is thus resolved, and the Gibbs-DiMarzio second-order transition appears to be unnecessary.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160080807
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