bluuebunny/crossref_metadata_2025 huggingface dataset:
Configurational chracteristics of the polysulfides, 3. Dipole moments of poly(trimethylene sulfide) and comparisons between some polysulfides and the corresponding polyoxides
Authors: Guzman J. , Riande E. , Welsh W. J. , Mark J. E.
Published: April 2003

Conformational energy calculations indicate that poly(trimethylene sulfide) (P3MS) approximates the idealized freely‐rotating chain in that gauche‐trans energy differences in this molecule are very small. This occurs because the relatively long SC bond tends to relieve congestion within the P3MS chain. The bonds in poly(trimethylene oxide) (P3MO) are much more constrained to a particular rotational state because the OC bond is shorter than the SC one, and in this sense P3MO is considerably less flexible. In this study the dipole moments 〈μ2〉0 of P3MS are measured as a function of temperature, and the results analyzed in terms of the rotational isomeric‐state theory. Using conformational energies derived from semiempirical potential energy functions, a three‐rotational‐state model gave values of the dipole moment in good agreement with experiment. Theoretical and experimental values of the temperature coefficient of 〈μ2〉0 were in disagreement, however, and a five‐rotational‐state model based on that adopted by Flory in a similar study of polymethylene failed to remove this discrepancy. Some statistical properties are tabulated for the n‐alkylene polysulfides studied to date and for structurally related polyoxides. In these types of molecules, strong preferences for pairs of gauche states in CH2SCH2SCH2 and CH2 OCH2OCH2 sequences give rise to unusually small values of the dipole moment.
A statistical analysis for stereo‐configurational sequences of vinyl polymers
Authors: Yan Deyue
Published: April 2003

In this paper, the distribution of configurational sequences in vinyl polymers is re‐treated theoretically by the aid of statistics. Various Markovian probabilities of multi‐ads are listed. A series of relationships among the frequencies of occurrence of n‐ads with different configurations is obtained, most of them have not been reported up to now. Finally, a convenient method for determination of the order of a Markovian process is established.
Unvernetzte epoxid‐amin‐additionspolymere, 6. DSC‐untersuchungen zur kinetik der stufenadditionspolymerisation von 2,2‐bis[4‐(2,3‐epoxypropoxy) phenyl] propan mit N,N′‐dibenzylethylendiamin und benzylamin
Authors: Flammersheim Hans‐Jürgen , Hörhold Hans‐Heinrich , Bellstedt Klaus , Klee Joachim
Published: April 2003

The kinetics of the linear step‐growth addition polymerization of equimolar amounts of the diglycidyl ether of bisphenol‐A 2,2‐bis[4‐(2,3‐epoxypropoxy)phenyl]propane (1) with N,N′‐dibenzylethylenediamine (2) and with benzylamine (4), respectively, is studied by means of differential scanning calorimetry (DSC). For conversions α ≤ 0,90 the experimental results of the isothermic measurements are in excellent agreement with values calculated from the rate equation dα/dt = (k1 + k2 αm) (1 − α)n with m + n = 2,5 (m ≈︁ 1,0, n ≈︁ 1,5). The first term of this rate equation takes into account both the catalytic and autocatalytic character of the addition polymerization while the exponent n ≈︁ 1,5 in the second term shows that the effective concentration of one of the addition components is given by the square root of its concentration.
Interaction between dyes and polyelectrolytes, 14. Triplet energy transfer in a cationic dye‐polyanion system
Authors: Shirai Masamitsu , Ono Yoshiki , Tanaka Makoto
Published: April 2003

Polymers with different fractions of azobenzene residues were prepared by radical copolymerization of methacrylic acid with 4′‐phenylazomethacrylanilid. The triplet excitation energy transfer from methylene blue (1) to the azobenzene residues in the polymers was investigated by using the 1‐photosensitized cis → trans isomerization of the azobenzene residue. The efficiency of the triplet excitation energy transfer from 1 to 4‐(4′‐phenylazoanilinocarbonyl)butanoic acid (4) as a monomer model compound. The number of azobenzene residues per polymer molecule and the molecular weight of the polymer were important factors for the efficient triplet excitation energy transfer. On addition of NaCl the energy transfer efficiency was lowered, suggesting that the binding of 1 to the polymer by electrostatic forces plays an important role. Binding of 1 to the polymers was investigated spectrophotometrically. Correlation with the binding of 1 to the polymers and the efficiency of triplet excitation energy transfer between 1 and azobenzene residues in the polymers is discussed.
Preparation of regularly sequenced polyamides with definite numbers of oxyethylene units and their application as phase transfer catalysts
Authors: Iwabuchi Susumu , Nakahira Takayuki , Tsuchiya Atsushi , Kojima Kuniharu , Böhmer Volker
Published: April 2003

Polyamides (1–3) having oligo(oxyethylene) segments in the main chain were prepared from α‐(2‐aminoethyl)‐ω‐aminooligo(oxyethylene)s (4) and dicarboxylic acid chlorides (5). Their ability to form complexes with alkali metal ions was examined by the picrate extraction method. The polyamides were found to catalyze the nucleophilic displacement reaction of hexyl bromide by potassium acetate in acetonitrile. An intramolecular co‐operative action of oligo(oxy‐ethylene) segments in complexation of potassium ion is proposed to account for the observed “polymer effect” in the catalytic activity.
Pharmacologically active polymers, 23. Linear and branched zwitterionic derivatives of polyethyleneimine as carriers for pharmacologically active components
Authors: Kobayashi Shiro , Gros Leo , Muacevic Gojko , Ringsdorf Helmut
Published: April 2003

To obtain a carrier polymer for pharmacologically active components, linear polyethyleneimine (LPEI) was chemically modified by reactions with acrylic acid (1a), acrylamide (1b), acrylic acid esters (1c and 1d), sodium chloroacetate, and hydrochloric acid. All product polymers 2a – 2e are soluble in water. Among these, 2a and 2e, β‐ and α‐amino acid derivatives, respectively, show no acute toxicity in mice up to dosages of 1 g/kg i. v. Similar types of polymers 5a and 5b and a polymer containing phosphonic acid moieties (5d) derived from branched polyethyleneimine (BPEI) were prepared. 5a and 5b are also nontoxic regardless of the molecular weight of four kinds of BPEI and of the wide range of carboxylic group content in the polymer. It is suggested that the zwitterion form contributes to the nontoxic nature of β‐and α‐amino acid type polymers. The present results show that amino acid type polymers derived from LPEI and BPEI can be used as carrier polymers for pharmacologically active components.
Untersuchung der teilschritte der ethylen‐hochdruckpolymerisation, 2. Druck‐ und temperaturabhängigkeit der einzelnen geschwindigkeitskonstanten
Authors: Lim Pe‐Chin , Luft Gerhard
Published: April 2003

In the first part of this series the individual rate constants of the radical polymerization of ethylene are reported in dependency of pressure at 405 K. By further measurements under 500 – 1750 bar and 400 – 470 K, using again the method of the rotating sector, the dependency of the rate constants on both pressure and temperature was determined. With increasing temperature the rate constant of chain growth kp as well as that of chain termination kt increases. With increasing pressure, kp increases, whereas kt decreases because of the diffusion controlled termination reaction. For the chain growth an activation energy of Ep = 37 kJ/mol and an activiation volume of Δvp≠ = ‐25,5 ml/mol was found. The activiation parameters of the chain termination are Et = 9,9 kJ/mol and Δvt≠ = 7 ml/mol. Based on these results and literature data the rate constants of different chain transfer reactions involved in the high pressure polymerization of ethylene and their dependency on temperature and pressure were evaluated.
Free radical polymerization of water‐soluble vinyl monomers in the two‐phase (water/organic) system using methylated β‐cyclodextrins as initiator‐carriers
Authors: Taguchi Hiromu , Kunieda Norio , Kinoshita Masayoshi
Published: April 2003

In the polymerization of water‐soluble vinyl monomers, such as acrylamide, sodium p‐sty‐renesulfonate, acrylic acid, and methacrylic acid, using water‐insoluble free radical initiators such as azo or peroxide compounds in the two‐phase system consisting of water and an organic solvent (chloroform/ligroin, volume ratio 1:4), the addition of a small amount of a methylated β‐cyclodextrin, heptakis(2,6‐O‐dimethyl)‐β‐cyclodextrin (DM‐β‐CD) or heptakis(2,3,6‐O‐trimethyl)‐β‐cyclodextrin (TM‐β‐CD), was found to cause a marked increase in conversion of the polymerization. Based on this finding, it may be suggested that the methylated β‐cyclodextrins act as initiator‐carriers which transport the water‐insoluble initiators from the organic phase to the aqueous phase to initiate the polymerization of water‐soluble vinyl monomers.
Preparation and properties of poly(p‐phenylene) and polynaphthylene
Authors: Sato Masa‐aki , Kaeriyama Kyoji , Someno Kazuo
Published: April 2003

Poly(p‐phenylene), poly(2,6‐naphthylene), poly(2,7‐naphthylene), poly(1,5‐naphthylene), and poly(1,4‐naphthylene) were prepared by nickel‐catalyzed polycondensation of Grignard reagents from the corresponding dibromides. The polymers were annealed in vacuo. Doping with SbF5 markedly increase the conductivity of the polymers. Annealed poly(2,6‐naphthylene) is the most conductive among the four isomers after SbF5 doping. The conductivity of doped poly(2,6‐naphthylene) and poly(p‐phenylene) is about 10−1 S · cm−1. Annealed poly(p‐phenylene) shows a broad single line ESR signal which changes to a narrow single line upon doping. Superposition of the two signals is observed at the initial stage of doping. Simultaneous conductivity and ESR measurements indicate that the narrow signal is closely related to conductivity.
Furan and pyran derivatives as modifiers of propylene polymerization catalysts
Authors: Karayannis Nicholas M. , Lee Sam S.
Published: April 2003

Studies of various tetrahydrofuran and tetrahydropyran derivatives as modifiers of Zieglertype propylene polymerization catalysts are reported. Among methyl derivatives, ethers containing two methyl substituents on carbon atoms adjacent to the etheric oxygen provied the best activity‐stereospecificity combinations (e.g. 2,5‐dimethyltetrahydrofuran (1c) and 2,2,4,4‐tetramethyltetrahydrofuran) (4). Significantly better stereospecificity with some loss in activity is realized when bulkier ethers such as isochroman (5) or 2‐(tetrahydrofurfuryloxy)tetrahydropyran (6) are used. On the other hand, combination of one of the preceding ethers with a second modifier (bis(tributyltin) sulfide, tributyl phosphite, or triethyl thiosphosphate) results in catalyst systems characterized by very attractive activity‐stereospecificity combinations. Systems of this type, containing 1c or 4, exhibit higher activity and about equal or better stereospecificity than the systems modified only with the second modifier; whereas 5 and 6 depress somewhat the activity of the latter systems but provide substantially improved stereospecificity. The steric and electronic effects introduced by the ether modifiers in the single and binary modifier systems investigated are discussed.
Synthesis of poly(ethylene‐d4oxide) with unimodal and narrow molecular weight distribution
Authors: Eisenbach Claus D. , Peuscher Manfred , Wegner Gerhard , Weiss Monika
Published: April 2003

Poly(ethylene‐d4 oxide) in the molecular weight range 104 to 105 has been synthesized by anionic polymerization of highly pure ethylene‐d4 oxide with carbazolylpotassium as initiator in the presence of a cryptand in THF as solvent. The polymers show an unimodal molecular weight distribution as confirmed by high pressure liquid chromatography and a polydispersity between 0,2 and 0,5.
Structure and properties of segmented poly(ether‐ester)s, 7. Model triblock copolyesters of monodisperse block length
Authors: Schmidt Friedrich Gerog , Dröscher Michael
Published: April 2003

Synthesis and characterization of model triblock copolyesters, in which the two end‐blocks are based on tetramethylene terephthalate and the middle block is oligo(oxytetramethylene), are described. These model copolyesters, which are essentially monodisperse, and similarly prepared segmented block copolyesters with monodisperse blocks exhibit the same dependency of the melting temperature on the degree of polymerization of the ester blocks as polydisperse technical copoly(ether‐ester)s.
Die Entwicklung komplexer prospektiver Gedächtnisleistungim Kindesalter
Authors: Martin Mike , Kliegel Matthias
Published: April 2003

Zusammenfassung. Trotz der großen Bedeutung für die kognitive Entwicklung und den Alltag von Kindern, ist über die Entwicklung der prospektiven Gedächtnisleistung im Vor- und Grundschulalter bislang nur sehr wenig bekannt. In der vorliegenden Untersuchung mit insgesamt 115 Kindern im Alter von 6 bis 11 Jahren wurden mit einem computergestützten Erhebungsinstrument zunächst die Altersunterschiede in der verzögerten selbstinitiierten Ausführung zuvor gefasster Intentionen erhoben. Zusätzlich wurden die Zusammenhänge mit retrospektiver Gedächtnisleistung und der Planungsleistung analysiert. Die Ergebnisse weisen auf einen Entwicklungsverlauf mit einer altersabhängigen Veränderung prospektiver Leistung bis zum Ende des Grundschulalters, sowie Zusammenhänge mit der retrospektiven Gedächtnis- und der Planungsleistung hin.
Politische Sozialisation in der Adoleszenz
Authors: Reinders Heinz
Published: April 2003

Zusammenfassung. Für die jugendinteressierte Nachwendeforschung kann zweierlei konstatiert werden: Erstens waren Studien zumeist als Querschnitt-Untersuchung angelegt und zweitens galt das öffentliche wie wissenschaftliche Interesse vor allem den politischen Einstellungen und Handlungsweisen Jugendlicher. So kann auf einen reichhaltigen Fundus an Bestandsaufnahmen zu Jugend und Politik zurückgegriffen werden. Längsschnittliche Untersuchungen, in denen Heranwachsende im Verlauf der Adoleszenz empirisch begleitet wurden, sind demgegenüber eher selten zu finden. Im vorliegenden Beitrag werden die in den 90er Jahren in Deutschland durchgeführten quantitativen Längsschnittuntersuchungen zusammengetragen, in ausgewählten Befunden dargestellt und re-interpretiert. Dabei deutet sich als ein wichtiges Ergebnis an, dass im Jugendalter das Vertrauen in die Responsivität der politischen Ordnung sukzessive abnimmt, die Bereitschaft, an politischen Prozessen zu partizipieren aber gleichzeitig zunimmt. Dieser zunächst scheinbare Widerspruch löst sich teilweise auf, wenn angenommen wird, dass die politische Identitätsbildung stärker von den individuellen Kompetenzen als von der Perzeption demokratischer Normen abhängt.
Role of SeqA and Dam in
Escherichia coli
gene expression: A global/microarray analysis
Authors: Løbner-Olesen Anders , Marinus Martin G. , Hansen Flemming G.
Published: April 2003

High-density oligonucleotide arrays were used to monitor global transcription patterns in
Escherichia coli
with various levels of Dam and SeqA proteins. Cells lacking Dam methyltransferase showed a modest increase in transcription of the genes belonging to the SOS regulon. Bacteria devoid of the SeqA protein, which preferentially binds hemimethylated DNA, were found to have a transcriptional profile almost identical to WT bacteria overexpressing Dam methyltransferase. The latter two strains differed from WT in two ways. First, the origin proximal genes were transcribed with increased frequency due to increased gene dosage. Second, chromosomal domains of high transcriptional activity alternate with regions of low activity, and our results indicate that the activity in each domain is modulated in the same way by SeqA deficiency or Dam overproduction. We suggest that the methylation status of the cell is an important factor in forming and/or maintaining chromosome structure.
Peptide-mediated broad-spectrum plant resistance to tospoviruses
Authors: Rudolph Christoph , Schreier Peter H. , Uhrig Joachim F.
Published: April 2003

Plant viruses have a significant impact on agronomic losses worldwide. A new strategy for engineering virus-resistant plants by transgenic expression of a dominant interfering peptide is presented here. This peptide of 29 aa strongly interacts with the nucleocapsid proteins (N) of different tospoviruses. Transgenic
Nicotiana benthamiana
lines expressing the peptide fused to a carrier protein were challenged with five different tospoviruses that have a nucleocapsid protein interacting with the peptide. In the transgenic plants, strong resistance to tomato spotted wilt virus, tomato chlorotic spot virus, groundnut ring spot virus, and chrysanthemum stem necrosis virus was observed. This therefore demonstrates the feasibility of using peptide “aptamers” as an
in vivo
tool to control viral infection in higher plants.
Solution structure of a functionally active fragment of decay-accelerating factor
Authors: Uhrinova Stanislava , Lin Feng , Ball Graeme , Bromek Krystyna , Uhrin Dusan , Medof M. Edward , Barlow Paul N.
Published: April 2003

The second and third modules of human decay accelerating factor (DAF) are necessary and sufficient to accelerate decay of the classical pathway (CP) convertase of complement. No structure of a mammalian protein with decay-accelerating activity has been available to date. We therefore determined the solution structure of DAF modules 2 and 3 (DAF∼2,3). Structure-guided analysis of 24 mutants identified likely contact points between DAF and the CP convertase. Three (R96, R69, and a residue in the vicinity of L171) lie on DAF∼2,3's concave face. A fourth, consisting of K127 and nearby R100, is on the opposite face. Regions of module 3 remote from the semiflexible 2–3 interface seem not to be involved in binding to the CP convertase. DAF thus seems to occupy a groove on the CP convertase such that both faces of DAF close to the 2–3 junction (including a positively charged region that encircles the protein at this point) interact simultaneously. Alternative pathway convertase interactions with DAF require additional regions of CCP 3 lying away from the 2–3 interface, consistent with the established additional requirement of module 4 for alternative pathway regulation.
Timing of neural responses in cortical organotypic slices
Authors: Buonomano Dean V.
Published: April 2003

Timing is a fundamental part of sensory and motor processing. However, little is known about the neural mechanisms underlying timing in the range of tens to hundreds of milliseconds. Although many theoretical hypotheses have been put forth on the possible underpinnings of temporal processing, there is little cellular experimental data, particularly
in vitro
, as to the neural mechanisms that could potentially function as timers. We use organotypic cortical slices to show that reliably timed action potentials (or excitatory postsynaptic potentials) can be observed up to 300 ms after a single stimulus. There was no relationship between the latency of the late responses and distance from the stimulating electrode. Paired recordings and pharmacological manipulations suggest that the timed late responses are the result of the propagation of activity throughout functionally defined networks. These results show that cortical networks may be intrinsically able to process temporal information.
α-Synuclein maps to a quantitative trait locus for alcohol preference and is differentially expressed in alcohol-preferring and -nonpreferring rats
Authors: Liang Tiebing , Spence John , Liu Lixiang , Strother Wendy N. , Chang Hwai Wen , Ellison Julie A. , Lumeng Lawrence , Li Ting-Kai , Foroud Tatiana , Carr Lucinda G.
Published: April 2003

Total gene expression analysis (TOGA) was used to identify genes that are differentially expressed in brain regions between the alcohol-naïve, inbred alcohol-preferring (iP), and -nonpreferring (iNP) rats. α-Synuclein, expressed at >2-fold higher levels in the hippocampus of the iP than the iNP rat, was prioritized for further study.
In situ
hybridization was used to determine specific brain regions and cells expressing α-synuclein in the iP and iNP rats. Similar to α-synuclein mRNA levels, protein levels in the hippocampus were higher in iP rats than iNP rats. Higher protein levels were also observed in the caudate putamen of iP rats compared with iNP rats. Sequence analysis identified two single nucleotide polymorphisms in the 3′ UTR of the cDNA. The polymorphism was used to map the gene, by using recombination-based methods, to chromosome 4, within a quantitative trait locus for alcohol consumption that was identified in the iP and iNP rats. A nucleotide exchange in the iNP 3′ UTR reduced expression of the luciferase reporter gene in SK-N-SH neuroblastoma cells. These results suggest that differential expression of the α-synuclein gene may contribute to alcohol preference in the iP rats.
Amino acids determining enzyme-substrate specificity in prokaryotic and eukaryotic protein kinases
Authors: Li Lewyn , Shakhnovich Eugene I. , Mirny Leonid A.
Published: April 2003

The binding between a PK and its target is highly specific, despite the fact that many different PKs exhibit significant sequence and structure homology. There must be, then, specificity-determining residues (SDRs) that enable different PKs to recognize their unique substrate. Here we use and further develop a computational procedure to discover putative SDRs (PSDRs) in protein families, whereby a family of homologous proteins is split into orthologous proteins, which are assumed to have the same specificity, and paralogous proteins, which have different specificities. We reason that PSDRs must be similar among orthologs, whereas they must necessarily be different among paralogs. Our statistical procedure and evolutionary model identifies such residues by discriminating a functional signal from a phylogenetic one. As case studies we investigate the prokaryotic two-component system and the eukaryotic AGC (i.e., cAMP-dependent PK, cGMP-dependent PK, and PKC) PKs. Without using experimental data, we predict PSDRs in prokaryotic and eukaryotic PKs, and suggest precise mutations that may convert the specificity of one PK to another. We compare our predictions with current experimental results and obtain considerable agreement with them. Our analysis unifies much of existing data on PK specificity. Finally, we find PSDRs that are outside the active site. Based on our results, as well as structural and biochemical characterizations of eukaryotic PKs, we propose the testable hypothesis of “specificity via differential activation” as a way for the cell to control kinase specificity.
Positive selection in the egg receptor for abalone sperm lysin
Authors: Galindo Blanca E. , Vacquier Victor D. , Swanson Willie J.
Published: April 2003

The mechanism of speciation is a central problem in evolutionary biology. In free-spawning animals with no complex mating behavior, prezygotic reproductive isolation (speciation) could result from the rapid divergence of genes coding for sperm and egg proteins that bind each other during fertilization. In abalone, sperm lysin evolves rapidly by positive Darwinian selection. The egg vitelline envelope receptor for lysin had previously been shown to evolve neutrally and be subjected to concerted evolution. Several mathematical simulations predict that both male and female reproductive proteins should evolve rapidly by positive selection. Here we report that the sequence diversity of the amino-terminal end of the egg vitelline envelope receptor for lysin has been promoted by positive Darwinian selection. These data provide molecular support for theoretical models showing that the two sexes are locked in a “coevolutionary chase” that could be driven by processes such as sexual selection, sexual conflict, or microbial attack (pathogen avoidance). The result of this continuous coevolution of the gamete recognition system could be the splitting of one population into two that are reproductively isolated (speciation).
Inhibition of Contraction and Myosin Light Chain Phosphorylation in Guinea‐Pig Smooth Muscle by p21‐Activated Kinase 1
Authors: Wirth A. , Schroeter M. , Kock‐Hauser C. , Manser E. , Chalovich J. M. , de Lanerolle P. , Pfitzer G.
Published: April 2003

The p21‐activated protein kinases (PAKs) have been implicated in cytoskeletal rearrangements and modulation of non‐muscle contractility. Little, however, is known about the role of the PAK family members in smooth muscle contraction. Therefore, we investigated the effect of the predominant isoform in vascular smooth muscle cells, PAK1, on contraction and phosphorylation of the regulatory light chains of myosin (r‐MLC) in Triton‐skinned guinea‐pig smooth muscle. We also investigated which of the three putative substrates at the contractile apparatus ‐ MLCK, caldesmon or r‐MLC ‐ is phosphorylated by PAK1 in smooth muscle tissue. Incubation of Triton‐skinned carotid artery and taenia coli from guinea‐pig with an active mutant of PAK1 in relaxing solution for 30–60 min resulted in inhibition of submaximal force by about 50 %. The mechanism of inhibition of force was studied in the Triton‐skinned taenia coli. In this preparation, inhibition of force was associated with a respective inhibition of r‐MLC phosphorylation. In the presence of the myosin phosphatase inhibitor, microcystin‐LR (10 μm), the rate of contraction and r‐MLC phosphorylation elicited at pCa 6.79 were both decreased. Because under these conditions the rate of r‐MLC phosphorylation is solely dependent on MLCK activity, this result suggests that the inhibitory effect of PAK1 on steady‐state force and r‐MLC phosphorylation is due to inhibition of MLCK. In line with this, we found that MLCK was significantly phosphorylated by PAK1 while there was very little 32P incorporation into caldesmon. PAK1 phosphorylated isolated r‐MLC but not those in the skinned fibres or in purified smooth muscle myosin II. In conclusion, these results suggest that PAK1 attenuates contraction of skinned smooth muscle by phosphorylating and inhibiting MLCK.
NEW APPLICATION OF THERMO FIELD DYNAMICS IN SIMPLIFYING THE CALCULATION OF WIGNER FUNCTIONS
Authors: FAN HONGYI
Published: April 2003

We find that the Thermo Field Dynamics, invented by Takahashi and Umezawa, can simplify calculations of Wigner functions for density matrices ρ. Using the coherent thermal state representation (Phys. Lett.A246, 242 (1998)), we show that the Wigner function W = Tr (Δρ) (an ensemble average of the Wigner operator Δ) can be expressed as a matrix element of ρ in the pure coherent thermal states. Wigner functions for some complicated density matrices are derived in this way.
GRAVITATIONALLY INDUCED NEUTRINO ASYMMETRY
Authors: SINGH PARAMPREET , MUKHOPADHYAY BANIBRATA
Published: April 2003

We study the propagation of Dirac neutrinos in gravitational backgrounds and show that the gravitational interaction can lead to neutrino asymmetry due to modifications in dispersion relation. We give some examples of spacetime geometries where such asymmetry can arise. This asymmetry would have contributed to the relic neutrino asymmetry through the interaction of neutrinos with primordial black holes before neutrinos decoupled. In the present epoch it may be generated in accretion around high temperature rotating black holes.
Topographic Position of Forelimb Motoneuron Pools Is Conserved in Vertebrate Evolution
Authors: M. Ryan James , Cushman Jeremy , Jordan Becky , Samuels Amy , Frazer Heather , Baier Christopher
Published: April 2003

The neuromotor conservatism hypothesis predicts that neuromotor patterns in homologous tetrapod muscles are conserved evolutionarily despite the musculoskeletal modifications of vertebrate limbs. A complete description of the anatomical organization of the neurons innervating homologous limb muscles is a prerequisite to any test of the neuromotor conservatism hypothesis. This study uses the retrograde neuronal tracer WGA-HRP to selectively label the motor neuron pools of seven homologous forelimb muscles in mice (Mus musculus) and iguanas (Iguana iguana): Mm. pectoralis, spinodeltoideus, biceps brachii, lateral and long heads of triceps brachii, and the supraspinatus and infraspinatus (in mice) or their reptilian homolog, the supracoracoideus (in iguanas). In vertebrates, motoneurons are arranged in longitudinal columns of cells in the ventral horn of the spinal cord. Mouse motor pools average 1,952 μm in length, except the pectoralis pool which averaged 2,949 μm in length. Iguana pools average 3,196 μm in length. The number of neurons per pool ranged from 70–199 in mice and from 58–114 neurons in iguanas. In both iguanas and mice the motor pools for the spinodeltoids, biceps, and the supracoracoideus (or its mammalian homologs) lie anterior to the pectoralis and triceps motor pools. In the transverse plane, the pectoralis pool lies medial to those of the triceps. The pools of the biceps and spinodeltoids are located dorsal and lateral to those of the pectoralis and supracoracoideus (or its homologs in mammals). The resulting motor pool maps support the hypothesis that the anatomical organization of motoneurons in ancestral reptiles has been retained in these two tetrapod descendents.
Convergence of Thalamic and Cholinergic Projections in the ‘Dentate Area’ of Lizards
Authors: V. Hoogland Piet , Martinez-Garcia Fernando , Geneser Finn , Vermeulen-VanderZee Eefke
Published: April 2003

The small-celled part of the medial cortex (Cxms) in lizards is comparable to the hippocampal area dentata in mammals. As in mammals, most of the afferents to this cortical area are arranged in sharply delimited laminae. In reptiles this lamination pattern is species-specific. In the lizard Tupinambis nigropunctatus projections from the multisensory dorsolateral thalamic nucleus (Dla) terminate in the middle one-third of the outer plexiform layer throughout the whole rostrocaudal extent of Cxms. In Podarcis hispanica the thalamic projections terminate not only in the middle one-third of Cxms but also in the inner plexiform layer. To find out whether the species-related variation of thalamic projections to Cxms is a solitary phenomenon or is related to variations of other afferents of Cxms, we studied the relationships between the thalamic and cholinergic projections from the basal telencephalon in the medial cortex of three lizard families: the Lacertidae, the Teiidae and the Gekkonidae. In the gekkonid lizards Gekko gecko and Eublepharius macularius, Dla projections were studied with the anterograde tracer Phaseolus vulgaris-leucoagglutinin. Projections were found in only the rostral one-third of Cxms where the fibers terminate in the superficial half of the outer plexiform layer and in the deep half of the inner plexiform layer. From acetylcholinesterase staining in the Cxms of representatives of these three lizard families, it appeared that the main cholinergic afferents terminate in the same subregions and the same laminae as the Dla projections. Therefore, there seems to be a close association between thalamic and cholinergic afferents in the Cxms of lizards, irrespective of their precise location in the cortex of the various species. This suggests a functional relationship between these two afferents of the dentate area in lizards.
The Effects of Telencephalic Lesions on Visually Mediated Prey Orienting Behavior in the Leopard Frog (Rana pipiens)
Authors: Patton Paul , Grobstein Paul
Published: April 2003

Unilateral removal of the telencephalon in the leopard frog, Rana pipiens, produces a contralateral deficit in visual prey orienting behavior [Patton and Grobstein, 1997]. In mammals, such deficits are most commonly associated with damage to the isocortex, a pallial derived structure. In contrast, we here report that in leopard frogs, lesions that remove substantial areas of one telencephalic lobe, including virtually the entire pallium, have no discernible effect on visual orienting behavior. Restricted lesions to the ventrocaudal telencephalon, however, produce an effect that closely resembles that produced by the complete removal of one telencephalic lobe. The ‘critical area’ that is both included in all lesions that are effective in producing a severe deficit and excluded from all ineffective lesions includes a portion of the caudal striatum. The striatum is known to play a significant role in anuran vision. It thus seems likely that the deficit produced by unilateral removal of the telencephalon in the leopard frog is due specifically to the removal of the caudal striatum. Unilateral lesions to the striatum have previously been shown to produce a contralateral deficit in visual orienting behavior in cats, and a role for the striatonigral pathway in the production of the visual orienting deficit that follows visual cortex lesions has been proposed. The current findings call attention to the possible general importance of the striatum in the control of vertebrate visual orienting behaviors.
Organization of the Caudal Rhombencephalic Alar Plate of the Ribbed Newt Pleurodeles waltl: Evidence for the Presence of Dorsal Column and Lateral Cervical Nuclei
Authors: Muñoz A. , Muñoz M. , González A. , ten Donkelaar H.J.
Published: April 2003

As part of a recent program on the evolution of somatosensory systems in vertebrates, the cytoarchitecture, chemoarchitecture, and fiber connections of the caudal rhombencephalic alar plate were studied in the ribbed newt, Pleurodeles waltl. This part of the brain stem includes ill-defined dorsal column and lateral cervical nuclei. A cytoarchitectonic analysis revealed that the caudal medullary alar plate consists of an inner and an outer cell layer. The dorsomedial part of the outer cell layer at the obex level contains the dorsal column nucleus (DCN), whereas its ventrolateral part constitutes the lateral cervical nucleus (LCN). NADPH-diaphorase histochemistry and calbindin D-28k immunohistochemistry clearly delineate the main components of the compact inner cell layer, i.e. the nucleus of the solitary tract dorsally and the nucleus of the descending trigeminal tract ventrally. Neither NADPH-diaphorase-labeled nor calbindin D-28k positive neurons were observed in the DCN and LCN. With anterograde and retrograde tracing, the DCN and LCN were further delineated. Labeling of ascending dorsal root projections showed that the dorsal column and the DCN are somatotopically arranged: lumbar primary afferent fibers terminate on medial DCN neurons, whereas cervical primary afferent fibers terminate on lateral DCN neurons. The LCN is densely innervated by the dorsolateral funiculus. Retrograde tracing showed extensive, predominantly contralateral projections of both the DCN and LCN to the torus semicircularis and the ventral thalamus. These data show that even in the poorly segregated caudal rhombencephalic alar plate of urodeles a DCN and LCN can be distinguished with afferent and efferent projections comparable to those in anurans and other terrestrial vertebrates.
Central Trigeminal and Posterior Eighth Nerve Projections in the Turtle Chrysemys picta Studied in vitro
Authors: Herrick James , Keifer Joyce
Published: April 2003

Recent electrophysiological studies in the turtle Chrysemys picta have suggested that a neural correlate of the eye-blink reflex can be evoked in an in vitro brainstem-cerebellum preparation by electrical rather than natural stimulation of the cranial nerves. Discharge recorded in the abducens nerve, which is similar to EMG recordings from extraocular muscles during eye retraction, is triggered by a brief electrical stimulus applied to the ipsilateral trigeminal nerve. Evidence also suggests that pairing a one-second electrical stimulus applied to the posterior eighth nerve immediately prior to a single shock to the trigeminal nerve results in classically conditioned abducens nerve discharge in response to the previously neutral eighth nerve stimulus. In view of these physiological findings, the aim of the present study was to examine the central projections of trigeminal and posterior eighth nerve inputs to elucidate the anatomical substrates that may underlie the in vitro eye-blink reflex and possible pathways involved in reflex conditioning. Neurobiotin (NB) or fluorescein dextran (FD) was pressure injected into the cut end of either the trigeminal or posterior eighth nerve of the in vitro brainstem-cerebellum. Following trigeminal nerve injections, both tracers showed label in the ipsilateral trigeminal nuclear complex. Direct projections to the ipsilateral principal and accessory abducens motor nuclei were observed, suggesting that the eye-blink reflex is monosynaptic. Trigeminal nerve axons were also observed to terminate in the ipsilateral cerebellar cortex. The results of the posterior eighth nerve injections showed axonal projections and terminals in the cochlear, vestibular and principal sensory trigeminal nuclei. Terminal label was also observed in the ipsilateral cerebellar cortex, deep cerebellar nuclei, and in the principal and accessory abducens motor nuclei. Results from the NB cases suggested transneuronal transport of this tracer substance, whereas the FD cases did not. The present findings suggest that convergence of trigeminal and posterior eighth nerve inputs occurs in the ipsilateral cerebellar cortex, the principal sensory trigeminal nucleus, and the principal and accessory abducens motor nuclei. These regions of convergence may therefore be considered as potential sites of synaptic modification during in vitro studies of the conditioned abducens nerve reflex.
The Diencephalon and Pretectum of the White Sturgeon (Acipenser transmontanus): A Cytoarchitectonic Study
Authors: Rupp Barbara , Glenn Northcutt R.
Published: April 2003

The cytoarchitecture of the diencephalon and pretectum of the white sturgeon, Acipenser transmontanus, was studied utilizing cresyl violet stained serial paraffin sections. The identified cell groups were assigned to the preoptic area, hypothalamus, thalamus and posterior tubercle, epithalamus, synencephalon and pretectum. The outlines of the diencephalic and pretectal nuclei were projected graphically onto a midsagittal section of the brain, thus providing a reconstruction of the relative positions of the major cell groups. This facilitated comparisons with the diencephalic and pretectal nuclei of other ray-finned fishes. Our cytoarchitectural analysis indicates that the diencephalon and pretectum of the white sturgeon is intermediate to that described for cladistians and neopterygians. The preoptic area in Acipenser is relatively conservative compared to other ray-finned fishes but lacks distinct subdivisions in the magnocellular periventricular preoptic nucleus and includes a unique migrated rostral accessory nucleus. The hypothalamic walls are rather thin, and due to the presence of extensive lateral and posterior recesses and the lack of migrated nuclei, they superficially resemble the condition seen in sharks. The dorsal and ventral thalamic nuclei do not exhibit much variation compared to other ray-finned fishes, except for the presence of a small lateral posterior thalamic nucleus, the absence of a distinct ventrolateral thalamic nucleus, and slight differences in the internal organization of the ventromedial thalamic nucleus. The posterior tubercle in Acipenser clearly comprises more migrated cell groups than that of Polypterus, however, these cell groups are considerably less well defined than in neopterygians. As in other nonteleost actinopterygians, the habenular nuclei are highly asymmetrical with the right side larger than the left side. The cytoarchitectonic complexity of the pretectum in Acipenser is intermediate to that observed in Polypterus and neopterygians in that a magnocellular component within the superficial pretectal nucleus is clearly present but cannot be delineated as a distinct magnocellular superficial pretectal nucleus. Also, the posterior pretectal nucleus which is absent in Polypterus but which has been identified as a small nucleus both in Lepisosteus and Amia is represented in Acipenser by a small group of scattered cells.
Sonic / Vocal Motor Pathways in Catfishes: Comparisons with Other Teleosts
Authors: Ladich Friedrich , H. Bass Andrew
Published: April 2003

Among teleost fishes, representatives of several distantly related groups have sound-producing (sonic/vocal) muscles associated with the swimbladder or pectoral girdle/fin. Here, the diversity of vocal organs and central motor pathways in four families of catfish, order Siluriformes, is compared to that in families from two distantly related orders, the Scorpaeniformes and Batrachoidiformes. Several catfish families have two sonic mechanisms – a swimbladder vibration established by ‘drumming muscles’ that differ in origin and insertion between families, and a pectoral spine stridulatory apparatus. In ariids, mochokids and doradids, sonic swimbladder muscles originate at various cranial or postcranial elements and insert onto an ‘elastic spring’ that vibrates the swimbladder, while in pimelodids the muscles insert ventrally at the swimbladder. Sonic motoneurons are located along the midline, ventral to the fourth ventricle/central canal in doradids and mochokids but lateral to the medial longitudinal fasciculus in ariids; pimelodids have motoneurons in both locations. The axonal trajectory for the lateral motoneurons in pimelodids and ariids implies that they are a migrated, midline population of sonic motoneurons. Pectoral spine-associated motoneurons are located in the ventral motor column. Unlike catfishes, a diversity of sonic mechanisms in Scorpaeniformes is not associated with different positions for sonic motoneurons. Cottids (sculpin) lack a swimbladder but have sonic muscles that originate at the occipital cranium and insert at the pectoral girdle; sonic motoneurons are located within the ventral motor column. Some triglids have intrinsic swimbladder muscles, although ontogenetic data indicate a transient association with the pectoral girdle; sonic motoneurons are in the same location as in cottids. Among Batrachoidiformes, all known representatives have intrinsic swimbladder muscles that are never associated with the pectoral girdle and are innervated by midline sonic motoneurons. The results suggest two patterns of organization for sound-producing systems in teleost fishes: pectoral fin/girdle-associated muscles are innervated by sonic motoneurons positioned within the ventral motor column, adjacent to the ventral fasciculus; non-pectoral associated muscles are innervated by sonic motoneurons located on or close to the midline, adjacent to the medial longitudinal fasciculus.
Forebrain Differentiation and Axonogenesis in Amphibians: I. Differentiation of the Suprachiasmatic Nucleus in Relation to Background Adaptation Behavior
Authors: Eagleson Gerald W. , Ubink Ruud , Jenks Bruce G. , Roubos Eric W.
Published: April 2003

Functional forebrain development is the result of a complex series of early developmental processes which include cell division, cellular rearrangements, tissue-tissue interactions, cellular determinative and differentiation events, and axonogenesis. In these studies, Xenopus laevis embryos were examined for early forebrain neuronal determination, differentiation and axonogenesis with special emphasis on the hypothalamic area known to be involved in regulating pars intermedia function. Whole brain acetylcholine esterase (AChE) histochemistry was used to follow the early pattern of forebrain neuronal differentiation, and whole brain acetylated-tubulin immunocytochemistry was done to follow early forebrain axonogenesis. AChE histochemistry indicated that the source of the tract of the postoptic commissure (stpoc) was the first forebrain area to begin differentiation (stage 22). Whole brain immunocytochemistry for acetylated-tubulin indicated that the tpoc is also the first forebrain tract to develop (at stage 25/26). The main forebrain tracts have developed and become interconnected by stage 35/36. The forebrain undergoes a pronounced extension, with much cellular mixing and rearrangement during stages 37/38 to 43/44. This results in bending and contortions in the already developed tracts. Whole brain immunocytochemistry for tyrosine hydroxylase and extirpation of the stage 14 presumptive suprachiasmatic (SC) area indicated that the dopaminergic cells of the SC are determined by stage 14 and initially undergo differentiation between stages 37/38 and 40. Tadpoles with stage 14 presumptive SC extirpated lacked TH-positive tracts to the pars intermedia, lacked most midline TH-positive forebrain cells, and also failed to background adapt to white background. Thus, the SC tracts to the pars intermedia that inhibit melanotrope secretion probably form during the extension stages of 37/38 and contact the pars intermedia by stage 40 when animals are first capable of background adaptation.
Glutamatergic Neurotransmission from the Optic Tectum to the Contralateral Nucleus Rotundus in Pigeons
Authors: Huang Li-Hua , Li Jian-Li , Wang Shu-Rong
Published: April 2003

Neuronal responses of 114 cells to electrical stimulation of the optic tectum were extracellularly recorded from the contralateral nucleus rotundus (nRt) in pigeons (Columba livia), and the effects of two glutamatergic antagonists CNQX and CPP, as well as those of GABA, were examined on rotundal cells. The results show that tectal stimulation evokes excitation in neurons of the contralateral nRt and that the excitatory responses are blocked by microiontophoretically applied CNQX, CPP and GABA. It is suggested that the contralateral tectorotundal transmission is excitatory in nature and mediated by both glutamatergic AMPA and NMDA receptors and that GABA is an inhibitory transmitter within the nucleus as well. We also review our previous findings in discussing transmitters participating in the tectofugal pathway.
Molecular Evolution of the Brain of Chordates
Authors: Williams Nic A. , Holland Peter W.
Published: April 2003

The molecular basis of regionalisation and patterning of the developing brain is an area of current intense interest. Members of the Otx, Pax-2/5/8 and Hox gene families appear to play important roles in these processes in vertebrates, but functional divergence and genetic redundancy arising from gene duplication events obscures our view of the roles played by these genes during the evolution of vertebrate brains. Determination of the ancestral gene copy number in chordates through molecular phylogenetics, accompanied by gene expression analysis in all three chordate subphyla (vertebrates, cephalochordates and urochordates) may distinguish between ancestral and derived expression domains and give clues to the roles played by these genes in chordate ancestors. Application of this comparative approach indicates evolutionary homologous brain regions (fore-/midbrain, isthmus/cerebellum and hindbrain) in chordates and supports homology of the frontal eye of cephalochordates to the paired eyes of vertebrates.