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  • Polymer and Materials Science  (6,215)
  • Life and Medical Sciences  (1,407)
  • Humans
  • 1960-1964  (6,869)
  • 1935-1939  (581)
  • 1925-1929  (172)
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  • 1
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly-L-proline in the molecular weight range 50,000-90,000 has been synthesized from L-proline-N-carboxyanhydride. The molecular weight obtained is dependent on the initiator concentration. The rate constants for the polymerization have been determined by measuring the CO2 evolution. By observation of rotation during the polymerization, it is possible to deduce the conformation of the polymer in the polymerization solution. It is concluded that the immediate product of the polymerization is neither pure form I nor pure form II. The differences between form I and form II of poly-L-proline have been further characterized by measurements of their ultraviolet rotatory dispersion and their ultraviolet spectra.
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  • 2
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The base-catalyzed hydrolysis rate of the cationic esters obtained by quaternization of N,N,N′,N′-tetramethylethylenediamine with phenylbromoacetate was studied in buffers and in solutions of partially neutralized polymeric acids. The polyanions were found to be powerful inhibitors of the reaction. This effect was interpreted as due to the association of the ester with the polyanion, from which the catalytically active hydroxyl groups are repelled. It is shown that kinetic data may be interpreted by a procedure similar to the Lineweaver-Burk plot to yield the reactivity of the bound ester and the dissociation constant of the polymer-ester complex.
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  • 3
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of high molecular weight copolypeptides of L-proline and sarcosine have been synthesized. Experimental evidence is presented which indicates that the products are true copolymers rather than mixtures of homopolymers. In contrast to poly-L-proline I, a copolymer of L-proline-sarcosine I containing approximately 50% sarcosine is soluble in water. Two molecular conformations of the copolymers, similar to those found for polyproline, have been characterized by means of infrared spectroscopy and optical rotatory dispersion. The residue rotation of L-proline has been obtained from the copolymers and is -250°.
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  • 4
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    New York : Wiley-Blackwell
    Biopolymers 2 (1964), S. 1-8 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The results of electrophoresis experiments on aqueous solutions of native and thermally denatured DNA are reported. A significant decrease of the electrophoretic mobility has been observed following thermal denaturation, which under suitable conditions gives rise to a resolution into two peaks of 1 : 1 mixtures in the electrophoretic pattern. This result is entirely consistent with the previously reported increase of the activity coefficient of sodium counterions following thermal denaturation. The hypothesis that thermal denaturation of calf thymus DNA induces a large decrease of charge density on the macroion which has been ascribed to the population of more extended conformations of the chains in the disordered region of the molecule is therefore further confirmed.
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  • 5
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the depolymerization of native dextran in dilute hydrochloric acid at different temperatures has been followed by measurements of M̄w, M̄n, [η], 〈ρ2〉1/2, and S. The data allow the correlation of the various parameters of the total hydrolyzate at various degrees of depolymerization. At a first approximation the results conform to a random splitting of a statistical, branched polymer.
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  • 6
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The γ-ethyl-L-glutamate NCA polymerization initiated by di-n-butyl and di-isopropyl amine was studied. The experimental kinetic curves show an autocatalytic portion with 25-30% conversion, followed by a pseudo first-order region which extends up to at least 85-90%. In this linear region, the reaction order appears to be 0.5 in initiator with both amines. High degrees of polymerization and high reaction rates were observed. These results are similar to those obtained in the γ-benzyl-L-glutamate NCA polymerization initiated by sodium methoxide.
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  • 7
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dielectric constant and the electric birefringence of poly-γ-benzyl-L-glutamate in ethylene dichloride-dichloroacetic acid mixtures have been measured as functions of the solvent composition. These properties undergo a marked decrease with the addition of a small amount of dichloroacetic acid, as well as an abrupt change accompanying the helix-coil transition in the vicinity of 75 vol.-% dichloroacetic acid. The former is attributed to the apparent diminution of the dipole moment of helical poly-γ-benzyl-L-glutamate molecule, which may be due to the protonation of terminal amide groups.
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  • 8
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    Biopolymers 2 (1964) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 9
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of γ-benzyl-L-glutamate NCA initiated by n-hexylamine in DMF proceeds with two successive propagation rates whose ratio is about 1.5. The onset of the increase in rate of propagation occurred at a DPn of 7-14, which was independent of initiator to anhydride ratio and anhydride concentration and not a result of anhydride impurities. The increase in rate is likely a result of a conformational change in the polymer at a DPn of 7-14.
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  • 10
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    Biopolymers 2 (1964), S. 147-161 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The NCAs of the N-benzyl derivatives of β-alanine, β-DL-aminobutyric acid, and β-DL-aminoisobutyric acid (nonplanar six-membered rings) were prepared by reacting the corresponding N-chloroformyl derivatives, obtained on reaction of the N-benzyl amino acids with phosgene, with triethylamine. Contrary to the others, the NCA of N-benzyl-β-alanine polymerized readily on heating in vacuo or in solution, using n-hexylamine or methanolic sodium methoxide as initiators. With n-hexylamine the molecular weights of the polymers obtained in benzene, dioxan, and dimethylsulfoxide, were in accordance with DP = [NCA]/[Initiator], as was found with conventional five-membered ring NCAs of α-amino acids. With sodium methoxide initiation, DPs of the polymers obtained were smaller than the (NCA)/[Initiator] ratio, contrary to what was found previously with α-amino acid NCAs. The possibility that stereochemical factors are responsible for the differences in polymerization activity of various. N-alkyl β as well as α amino acid NCAs is discussed.
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  • 11
  • 12
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    Biopolymers 2 (1964), S. 231-236 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrophoretic mobility of DNA in the presence of tetramethylammonium and alkali metal ion chlorides has been studied as a function of ionic strength. Each cation exhibits a characteristic behavior in accord with the idea that the order of inter-action with DNA is Li+ 〉 Na+ 〉 K+ 〉 TMA+. The application of theories of the electrophoresis of polyelectrolytes is discussed, leading to an attempt to calculate the fractional charge per DNA phosphorus from the mobility data. Over the range 0.05-0.4M a constant and unique value of the DNA charge is obtained in the presence of each cation. Values of the zeta potential and of the friction factor per monomer unit are also calculated.
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  • 13
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    Biopolymers 2 (1964), S. 135-146 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple quantitative theory of inactivation of transforming DNA has been formulated. It is based on the idea that genetic recombination of the molecule of transforming DNA with the bacterial genome is possible only, from the point mutation of the gene up to the nearest hit or point of damage on the corresponding DNA molecule. Our data and the data of other authors on the kinetics of inactivation by HNO2 or U.V. light or both are consistent with these theoretical predictions. Theoretical predictions were made concerning the extent of reactivation by fusion mid annealing of damaged DNA with a diluting genetically inactive DNA. These estimates have been reasonably confirmed by our experimental results.
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  • 14
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    Biopolymers 2 (1964), S. 15-25 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to study the effect of glucose substitution on the sedimentation velocities of the T-even phage DNA's, T2 and T2*, and T6 and T6* bacteriophages were grown with H3and P32 labeling. Zone sedimentation of the DNA's isolated from these phagea showed that the glucosylated DNA's from both T2 and T6 sediment faster than the nonglucosylated molecules. Nonglucosylated DNA from TG and T2 phages sedimented with the same velocity, suggesting that the molecules of these phages are of the same length.
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  • 15
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    Biopolymers 2 (1964), S. 43-49 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report a simple method for measuring partial specific volumes, of polymers in dilute solutions with an accuracy of 3 parts per thousand. This method has been applied to 7 polypeptides in 4 organic solvents. The residue volumes deduced from these data are compared to those calculated by a differential method. The discrepancy is generally of the order of 1.5%.
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  • 16
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    Biopolymers 2 (1964), S. 283-286 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 17
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    Biopolymers 2 (1964) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 18
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that the formation of the three-strand poly (A + 2U) complex is accompanied by a decrease in optical absorbance at 280 mμ, while the format ion of poly (A + U) is not. This difference makes it possible to demonstrate that in dilute solutions (∼10-4 monomolar), a 1 : 1 mixture of poly A and poly U always forms poly (A + U) at room temperature. At higher temperatures in solutions containing more than about 0.2M sodium ion, poly (A + U) is converted to poly (A + 2U) and free poly A. These results are consistent with the observations reported by Miles and Frazier, using infrared absorption spectra, at much higher polymer concentrations. It is concluded that most of the physicochemical studies of 1 : 1 mixtures of poly A and poly U in dilute aqueous solution refer to the two-stranded species.A simple thermodynamic analysis is developed to explain the two- to three-strand conversion, and with the use of a “phase diagram” showing conditions of stability of the various poly A-poly U structures as a function of salt and temperature, it is possible to estimate the value of the enthalpy of formation of poly (A + 2U).
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  • 19
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    Biopolymers 2 (1964), S. 337-347 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a chromatographic technique, the adsorption of the polyribonucleotides s-RNA and poly-A provided with tri-n-butylammonium ions from an aqueous solution on to the surface of polymeric hydrocarbon granules has been demonstrated. The aqueous solution from which adsorption takes place is the aqueous phase which results on agitating together n-butanol (100), water (130), tri-n-butylamine (10), n-butyl ether (10), and glacial acetic acid (2.5) (parts by volume). Microporous polyethylene granules, microporous fluorinated polyethylene granules, and solid grains of polyethylene powder have been employed as adsorbents. The adsorbed polyribonucleotides could be eluted by aqueous solutions of sodium chloride, urea, or triethylammonium acetate. s-RXA with tri-n-butylammonium counterions could also be adsorbed on polymethacrylic acid in tri-n-butylammonium form and eluted therefrom with aqueous urea solutions. It is considered that the adsorption from aqueous solution of polyribonucleotides with tri-n-butylammonium counterions on polymeric hydrocarbon surfaces is mediated by hydrophobic bond formation. Van der Waals forces may also contribute to the bonding. It is suggested that studies on the adsorption of polynucleotides provided with counterions: possessing nonpolar groups at an aqueous solution-polymeric hydrocarbon interlace may permit the elaboration of experimental systems to serve as models for the evaluation of the role of hydrophobic and van der Waals bonding forces in the interaction of polynucleotides with cell membrane surfaces.
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  • 20
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    Biopolymers 2 (1964), S. 395-398 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 21
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    Biopolymers 2 (1964), S. 361-380 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Deoxyribonucleic acids (DNA's) extracted from several biological sources have been studied by means of the flow dichroism method, using the transparent coaxial cylinder apparatus. This study has two purposes: (1) to make clear the hydrodynamic behavior of the DNA chain, and the regularity in the orientation of purine and phrimidine bases about the molecular axis; and (2) to develop this particular flow dichroism method as an established device for the study of chain regularity of DNA and other chain polymers. The velocity gradient dependence of dichroism agrees well, to a first approximation, with the behavior of a model of a hydrodynamically equivalent ellipsoid in revolution. Differences between theoretical and empirical curves have been tentatively ascribed to the flexibility of the chain under consideration. Two kinds of data, 1 lie rotary diffusion coefficient and internal dichroism, have been evaluated by a graphical device in which the double logarithmic plots of reduced dichroism and velocity gradient of flow are compared with the theoretical curve. The data obtained have shown good reproducibility for DNA samples prepared by the same method from the same biological source. However, a remarkable difference in internal dichroism and rotary diffusion constant has been observed between DNA groups of different biological origin. The difference may be caused by fragmentation of DNA during the deproteinization procedure, bill the possibility that some of these differences originate in the biological source of the DNA cannot be denied. Orientation of purine and phrimidine bases in aqueous solution is found to be quite regular in direction, as predicted by the Watson-Crick model. Dichroic spectra have shown that the direction of the oscillator dipole corresponding to the 260 mμ absorption band has a different angular relationship to the helical axis than the oscillator dipole for the 220 mμ band.
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  • 22
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    Biopolymers 2 (1964), S. 381-393 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of the super helical structure of synthetic polypeptides, such as poly-γ-benzyl-D (or L)-glutamate (PBDG or PBLG) was carried out. The PEG was dissolved in dimethylformamide (DMF). The solution was either allowed to remain at room temperature for a long time or poured into some fatty acid, such as formic acid, acetic acid, propionic acid, or caprylic acid. Whether the polymer precipitated slowly or rapidly depended upon the aging of the solution or the nature of the acid used. The precipitated gels revealed the coiled coil fibrils, but the feature and degree of coiling varied, depending upon the length of aging or the nature of the acid used for precipitation. After a short aging of the solution, there was no helical structure in the gels. After long aging, very fine-coiled coil macrofibrils or small spindle-like fibrils were obtained. The macrofibrils consisted of the spindle-like fibrils which in turn consisted of microfibrils (diam. 60-70A.). When using the fatty acid precipitation very fine to medium fine super helices were obtained. Extremely fine super helices were obtained in propionic acid. In these gels the PBG chains have an α-helical conformation. When PMLG-DCA solution was stored for a long time, another type of precipitation was obtained, one giving evidence of so-called cross-β crystallization and no coiled coil fibrils. The precipitation of cross-β fibrils was obtained when the concentration of the solution was above 8%.
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  • 23
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    Biopolymers 2 (1964) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 24
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    Biopolymers 2 (1964), S. 399-413 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Titration studies of the 1 : 1 helical polynucleotide complex of polyinosinic acid and polycytidylic acid reveal that these two polymers form a complex when the polycytidylic acid is protonated near pH 3. Sedimentation studies show that the protonated complex also has a 1 : 1 stoichiometry. However, the protonated complex is more stable than the unprotonated neutral complex as judged by its thermal stability. The molecular structure of the protonated complex is not the same as the neutral form. Study of the kinetics of the reaction of the protonated complex with formaldehyde suggests that the amino group of cytosine is involved in hydrogen bonds which hold the polynucleotide strands together.
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  • 25
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    Biopolymers 2 (1964), S. 415-444 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The protein sequences now known have been reconstructed as a kind of intriguing logical-mathematical puzzle using information about fragments of the molecules. We wish to show that the reconstruction can be done systematically by repeating a series of elementary operations on these same data governed by a set of well-defined rules. The completely automatic reconstruction of polymer sequences by a high speed digital computer using these operations and rules is demonstrated.
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  • 26
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism of the renaturation of DNA molecules is examined on the basis of the bimolecular interaction of Gaussian chain polymers. In the nucleus formation by hydrogen bonding in segment-segment interaction, two types of interchain interaction, that is, one between complementary chains and one between noncomplementary chains, and one noncomplementary intrachain interaction are considered to be, in competition. Several previously observed characteristics of the renaturation process are displayed by this simple model. In particular it accounts for the dependence of the extent of renaturation on the heterogeneity, molecular weight, and radius of gyration of DNA, and of the ratios of the reaction rates between complementary and noncomplementary segments. Among these variables the ratio of reaction rates has shown to have a quite specific value, as high as the order of 104, which favors the complementary-strand interaction. This very great bias in favor of complementary strand interaction emphasizes that the renaturation phenomena displays the same character of biological specificity that is associated with enzyme-substrate interaction or antigen-antibody interaction. Moreover, since DNA is a good example of a one-dimensional system, it seems to provide a suitable clue for pursuing the analysis of pattern recognition at the macromolecular level.
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  • 27
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    Biopolymers 2 (1964), S. 463-481 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The polymerization of DL-β-Phenylalanine N-carboxy anhydride adsorbed on polysarcosine dimethylamide has been studied further. This unusual reaction, which is analogous kinetically to reactions catalyzed by enzymes, was called the “chain-effect.” For polymerization of N-carboxy anhydrides by this mechanism it is necessary that the initiating polymer should possess an adsorption site and a terminal base group. The effect is shown to occur with simple compounds such as amino acid dimethylamides but not with poly-L-proline due to the inability of this polymer to adsorb the anhydride. From a study of the reaction of block copolymers of L-proline and sarcosine with DL-β-phenylalanine it is concluded that the relative positions of the adsorption site and terminal base group do not greatly influence the reaction rate, but the accessibility of the adsorption sites is an important factor determining the reactivity of polysarcosine dimethylamides of various degrees of polymerization (n). At high values of n the polymer exists in a coiled form and only those sites close to the terminal base group participate in the reaction. Initial rate studies give a detailed description of the early stage of the chain-effect polymerization. With these data and by use of analog computer techniques the complete reaction has been studied. It is concluded that the poly-DL-β-phenylalanine block produced is not permanently attached to the polysarcosine chain by hydrogen bonds during its formation but that an equilibrium exists between the polysarcosine and the poly-DL-phenylalanine blocks.
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  • 28
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Del Re's method for the study of saturated compounds has been adapted so as to deal with the σ-framework of conjugated molecules. This modified procedure is used in evaluating the σ-contribution to the dipole moments of the nucleic bases and of the A-T and G-C base pairs and also to the free energy change in the tautomeric, equilibria of the bases. Associated with an appropriate Hückel method for evaluating the π-contribution, the results obtained predict a small resultant moment for A-T versus a large moment for G-C. The energy calculations predict the keto and amino forms of the bases to be the most stable forms and cytosine to be the most easily involved in tautomeric shift to the rare form.
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  • 29
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    Biopolymers 2 (1964) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 30
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Temperature jump measurements employing optical rotation to follow transients show an upper limit of 10μsec. on the half time of the helix-random coil relaxation in poly-α, L-glutamic acid. No relaxations are observed under conditions where the polymer exists in completely helical or completely random coil form. Assuming that the helix-coil transition can be described kinetically as a pure growth process, expressions for the relaxation time are derived for three special cases. A comparison is made between the rate of the helix-coil transition and the rate of imide proton exchange.
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  • 31
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    Biopolymers 2 (1964), S. 501-501 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
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  • 32
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    Biopolymers 2 (1964), S. 561-574 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Numerical calculations have been done on the exciton spectrum of a schematic model of a linear polymer. The model consists of a random sequence of two kinds of subunit whose energy levels and transition moments are almost, but not quite, the same. The orders of magnitude of parameters are taken from DNA, but the full helical geometry has not been considered. Results are given for the density of energy levels, the dipole transition strength per unit energy, and the distribution of excitation energy along the polymer in individual states. A number of localized exciton states were found.
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  • 33
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    Biopolymers 1 (1963), S. 1-1 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
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  • 34
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    Biopolymers 1 (1963), S. 25-32 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The grand-partition-function theory of the preceding paper is used to derive expressions for the number of base pairs bonded in DNA with explicit consideration of the copolymeric nature of the DNA. The following features of the DNA molecule are taken into account: (1) the DNA's from different sources have different ratios of a-t and g-c pairs; (2) the a-t pair is weaker than the g-c pair; (3) the nearest-neighbor frequencies of the two kinds of base pairs are nonrandom; (4) the stacking energies (nearest-neighbor energies) of the various combinations of pairs may be different. An ensemble is constructed in which the features (1) through (4) are introduced by means of statistical weights on the various pairs and combinations of pairs, and an expression for the corresponding partition function is written. Expressions are derived for the number of bonded base pairs and the number of helical sequences.
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  • 35
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    Biopolymers 1 (1963) 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
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  • 36
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: A method is described for formation of hydroxamic acids by direct coupling, in aqueous medium, of hydroxylamine hydrochloride and the sodium salt of a carboxylic acid. The reaction is mediated by a water-soluble carbodiimide, 1-cyclohexyl-3-[2-morpholinyl-(4)-ethyl]-carbodiimide metho-p-toluene sulfonate. Using model compounds, the production of α-, β- and γ-acyl hydroxamic acids was studied. Hydroxamic acid derivatives of α-polyglutamic and γ-polyglutamic acids were also prepared. Dinitro-phenylhydroxamate derivatives were prepared and subjected to Lossen rearrangement, and the reaction mixtures hydrolyzed. Analysis showed that α-polyglutamic acid yielded as many molecules of α,γ-diaminobutyric acid as there had been glutamic acid residues in the form of the dinitrophenylhydroxamate, and gave rise to no ammonia and succinic semialdehyde. In contrast, γ-polyglutamic acid yielded exactly twice the molar quantity of ammonia as there had been glutamic acid residues in the form of dinitrophenylhydroxamate, and also gave rise to significant quantity of succinic semi-aldehyde but no α,γ-diaminobutyric acid. Since production of the latter is characteristic of α-glutamyl hydroxamates and production of the former is associated with γ-glutamyl hydroxamates, the results indicated that the side-chain carboxyl groups of either polymer retained their identities during formation of the hydroxamic acid derivative, and no interchange had occurred between α- and γ-carboxyl groups. These methods were then used to establish that gelatin of ichthyocol contains (per 1000 total residues) at least 20 residues of glutamic acid in γ-peptide linkage. Due to the incomplete dinitrophenylation of the hydroxamic acid derivative of the protein, gelatin of calf skin collagen gave a lower figure of 10 such linkages per 1000 total amino acid residues-a value which must be considered a minimum value. These results show that γ-glutamyl peptide bonds exist in collagen.
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  • 37
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    Topics: Chemistry and Pharmacology
    Notes: A statistical thermodynamic treatment of thermally induced helix-coil transitions is formulated with the matrix method for an (ensemble) of system(s) in which one strand of a double helix consists of a homopolymeric polynucleotide and the other strand comprises a number of complementary oligonucleotides. Each oligonucleotide is considered to be completely bound to the longer chain when in the helical configuration and completely free from it when in the randomly coiled configuration. The case of partial binding; i.e., “dangling,” is treated in a later paper. Taken into account in both cases are intrachain “stacking” interactions between nearest neighbor residues and interchain hydrogen bonding.An approximate treatment of the characteristic equation of the formulation indicates that the reciprocal of the transition temperature (1/T0) is a linear function of the reciprocal of the degree of polymerization (D.P.) of the oligonucleotides. In the same approximation, 1/T0 is also a linear function of the negative logarithm of the absolute activity of the oligonucleotides. Transition curves obtained by exact calculation on a computer are presented for various degrees of polymerization of both the oligo- and polynucleotides. These curves show a sharpening of the transition with increasing D.P. of the long chain and the aforementioned reciprocal D.P. dependence of 1/T0.
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  • 38
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    Biopolymers 1 (1963), S. 171-182 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: The dielectric dispersion of polyglutamic acid (PGA) was studied in the pH range of 4-9.8. Three different dispersion curves were obtained. Above pH 6.0, where PGA has a random coil configuration, the dielectric dispersion is characterized by a large dielectric increment (ca. 450) and a relaxation time of 10-12.7 × 10-6 sec. Between pH 6.0 and 5.0, where PGA is in a transitional state with small viscosity, a dispersion curve with very small dielectric increment and also small relaxation time was observed. Below pH 5.0, where PGA has a helical configuration, the dispersion is characterized by a relaxation time of 10-12 × 10-6 sec. and a dielectric increment of about 120. The dipole moment of coil and helical forms of PGA were calculated by using Allgen's equation, and qualitative discussions of these dielectric properties are presented.
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  • 39
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    Biopolymers 1 (1963), S. 193-208 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: Ultaviolet absorption spectra down to 185 mμ are presented for a number of nucleic acids and synthetic polynucleotides in the helical and random forms, and of their constituent mononucleotides, as well as the corresponding nucleosides and free bases. A short wavelength absorption band is in all cases observed with a maximum varying between about 187 and 201 mμ. These bands are more intense than those near 260 mμ. The helical polymers show a hypochromic effect in this region of a somewhat similar magnitude to that in the 260 mμ region. Other spectral phenomena accompanying denaturation and degradation are described.
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  • 40
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    Biopolymers 1 (1963), S. 209-229 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: The inactivation of sRNA by reaction with formaldehyde has been reported as it occurs under various conditions giving differing amounts of secondary structure. The theory of inactivation of an active macromolecule by a chemical reaction is developed. Results obtained with a partially melted out secondary structure show that formaldehyde inactivates sRNA by a single reaction at any one of about ten sites, while reaction at other sites does not affect the activity of the sRNA. In the presence of Mg++ at neutral pH, a large proportion of the active molecules are completely protected against inactivation. From the correlation between the amount of secondary structure and the difficulty of inactivation, it is shown that at least a portion of the secondary structure of sRNA is essential to its amino acid acceptor ability. A comparison of results of various workers shows that formaldehyde does not alter RNA as drastically as other reagents and thus enables more discrimination between sites of reaction which are essential and those which are not essential to biochemical activity.
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  • 41
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    Biopolymers 1 (1963), S. 295-295 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 42
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    Topics: Chemistry and Pharmacology
    Notes: Infrared absorption and x-ray diffraction measurements have been made of D,L-copoly-γ-benzylglutamate fibers (cast from dioxane solutions) with various D/L ratios and with various degrees of polymerization. It was found that each chain of these copolymers consists of a random coil portion and an α-helix portion and that the conformation of the latter is similar to the α-helix of pure poly-γ-benzyl-L-glutamate. It was also found that the fraction of the α-helix portion increases with the degree of polymerization of the copolymer. A simplified polymerization mechanism has been proposed for mixtures of D- and L-amino acid N-carboxyanhydrides. A model of the molecular conformation of the D,L-copolypeptide chains derived from this proposed polymerization mechanism is in good agreement with infrared, x-ray, and other measurements. Based on the results of these observations, we discuss the number of L- or D-residues linked in succession that is required for initiating the formation of an α-helix during the course of polymerization.
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  • 43
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    Topics: Chemistry and Pharmacology
    Notes: Poly-L-proline I and II, polyphydroxy-L-proline II, polysarcosine, and collagen, as well as two model amides have been examined by far ultraviolet spectrophotometry. Absorption spectral data are presented. Neither in solution nor in oriented films of poly-L-proline I and II is there any indication of excition resonance splitting of the peptide absorption band. In collagen there is some, in the poly-L-prolines only minimal, hypochromicity. These observations, at least in poly-L-proline II, run counter to theory. Optical rotatory dispersion measurements in the ultraviolet indicate simple dispersion in collagen and poly-L-proline II down to at least 232 mμ. The Cotton effect (trough at 233 mμ) observed in α-helical polypeptides and proteins is absent. The implications of these findings are discussed.
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  • 44
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    Topics: Chemistry and Pharmacology
    Notes: The helix - coil transition of poly-L-glutamic acid (PGA) in aqueous solutions was followed by volume changes, ΔV, and also differential refractive indices, Δn. The increase in ΔV or decrease in Δn upon mixing the sodium salt of PGA with dilute HCl gave three straight lines between pH 7 and 4, the two breaks corresponding to the transition zone observed by other physical methods. For the reaction: —COO- + H+ → —CO-OH, ΔV per mole of H+ bound was 11.4 and 11.1 ml. in 0.01 and 0.2M NaCl solutions, respectively. An additional conformational change of about 0.5-1 ml. per amino acid residue was observed for the reaction: coil → helix, after taking electrostatic interaction into consideration. This was probably due to the release of the water of hydration at the amide linkages when the polypeptide coil is converted into the α-helix, or even the occurrence of voids in the polypeptide chain as a result of imperfect packing of the atoms, although the origin of this volume change is still not fully understood at the present time. The volume changes as calculated from Δn by assuming a constant polarizability of the polymer was found to be higher for the association reaction than those mentioned above. On the other hand, the calculated ΔV for the transition was in fair agreement with those by direct measurements.
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  • 45
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    Topics: Chemistry and Pharmacology
    Notes: Dye-macromolecule complexes provide good models for the study of the effects of coupling between chromophores. In addition to modifications of the visible and UV absorption spectra of the dyes at small interchromophore distances, very efficient energy transfer has been demonstrated at longer distances. The probability of nonradiative transition increases with the number of excitation transfers so that an array of oscillators close to one another becomes nonfluorescent. The insertion of a dye molecule, acting as a trap for the excitation energy, in the highly ordered system of chromophores constituted by the purine and pyrimidine bases of native DNA has given results supporting the intercalation model of Lerman and providing an experimental approach to the problem of the path length of energy migration in the DNA molecule. The average excitation path length seems to be of the order of only ten base pairs, a result which can explain the lack of fluorescence of the DNA.
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  • 46
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    Biopolymers 1 (1963), S. 473-495 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: The sedimentation, diffusion, and osmotic behavior of poly-L-lysine hydrochloride is examined over a wide range of ionic strengths and in solutions which range in relative composition from a swamping excess of added salt (suppression of charge effect) to salt-free solutions (maximum effect). The charge effect is found to essentially obey the theoretical treatment proposed in Part I of this work. The frictional coefficient of the macroion in salt-free solutions is comparable to that of the fully stretched chain. In excess of salt the friction is appreciably smaller, its magnitude not varying greatly with ionic strength. The molecular weight is determined osmotically and also from diffusion-sedimentation, with the charge effect suppressed by addition of salt or eliminated through the use of non-ionized forms of the polymer; a reasonable agreement is obtained between the methods. The influence of small ions on sedimentation is also examined. The secondary salt effect is found to be much smaller than that predicted theoretically; on the other hand, the substitution of different counterions in the absence of secondary salt effect gives rise to changes of the expected magnitude.
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  • 47
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    Biopolymers 1 (1963), S. 500-502 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
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  • 48
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    Topics: Chemistry and Pharmacology
    Notes: Poly-β-hydroxybutyric acid has been isolated from two bacterial sources by two different procedures. Molecular weight and intrinsic viscosity for the two samples were vastly different. This was blamed on degradation occurring during polymer isolation. An optical rotatory dispersion curve for the high molecular weight sample showed a sharp increase in specific rotation at wavelengths less than 450mμ. From this fact and the reported optical activity of the monomer it is concluded that the polymer is stereo-regular. X-ray examination of the “native” and “regenerated” polymer yielded the same crystalline pattern. Electron diffraction and x-ray data on single crystals of the polymer indicate a fiber repeat of 5.9 A. The value can only be reconciled with some kind of helical conformation in the solid state.
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  • 49
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    Topics: Chemistry and Pharmacology
    Notes: It has been suggested previously that water is a nearly indifferent solvent for amylose on the basis that the exponent a of the Mark-Houwink equation is very nearly 0.50 and the second virial coefficient A2 is extremely small. It is shown that such solutions do not show the expected precipitation on cooling and the temperature coefficient of the intrinsic viscosity is small and negative. It is suggested that water is both an indifferent and a nearly athermal solvent for this polymer. Various lines of evidence suggest the polymer to exist as a very stiff coil in this and in other solvents. Variations in the intrinsic viscosity and radius of gyration in various solvents show the importance of skeletal effects in addition to the usual osmotic effects. Application of the Porod-Kratky wormlike coil model leads to unreasonably short persistence lengths if the contour length is based on a fully extended conformation but large and reasonable values of the order 40-70 A. if it is assumed that the basic conformation is the helical one observed in various amylose complexes in the crystalline state. As was previously known, the specific optical rotation decreases sharply in aqueous solutions above approximately pH 12. Accompanying this change in rotation there is first a decrease, then an increase in intrinsic viscosity. This later behavior is strikingly reminiscent of the known behavior of polyglutamic acid in the pH-dependent transition from helix to coil. It is concluded that the conformation is that of a stiff coil with essentially helical backbone contour in neutral solution, and the decrease in rotation and in intrinsic viscosity at high pH results from a partial breakdown of the helical structure with a concomitant increase in backbone flexibility. The increase in viscosity and radius of gyration in extreme alkaline solution is probably due to a polyelectrolyte expansion of the polymer coil. Some other miscellaneous observations which are in accord with this model are also pointed out.
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  • 50
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    Biopolymers 2 (1964) 
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    Keywords: Chemistry ; Polymer and Materials Science
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  • 51
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    Biopolymers 2 (1964), S. 9-14 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: A calculation based upon Gorin's equation for the electrophoresis of a rigid cylinder is used to compare the available results of electrophoresis and membrane equilibrium experiments on DNA. The distribution of chloride ions across a membrane impermeable to DXA is considered. For a reasonable choice of parameters, agreement within about 2% is obtained between the values calculated from electrophoresis and the results of membrane equilibrium studies over a twenty-fold range of NaCl concentration.
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  • 52
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    Topics: Chemistry and Pharmacology
    Notes: Light-scattering, sedimentation, viscosity, and reducing power measurements have been carried out on a sample of native dextran from Leuconostoc mesenteriodes B-512. The results are discussed in relation to the structure, polydispersity, and branching of the polysaccharide. The effect of different solvents on the behavior of native dextran has been studied. The molecular weight of the dextran remains unchanged in all the solvents used, while the radius of gyration shows a significant increase in some of them (concentrated salts, urea, and glucose solutions); in water-methanol solutions the radius of gyration slightly decreases.
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    Biopolymers 2 (1964), S. 65-68 
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    Topics: Chemistry and Pharmacology
    Notes: The statistical mechanical theory of the helix-coil transition of DNA has been recently discussed by one of the authors, who considered an assembly of DNA molecules with a Markoff distribution of nucleotide sequences. The present communication improves upon the above mentioned theory by introducing approximate normalization factors for the unnormalized statistical weights of finding a given molecule of the assembly in a given microscopic state.
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    Biopolymers 2 (1964), S. 103-103 
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  • 55
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    Biopolymers 2 (1964), S. 79-89 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: The effect of small quantities of metal ions on the electrophoretic mobility of calf thymus DNA in solutions maintained at 0.2 ionic strength with weakly interacting (CH3)4N+ ions yields information about interactions occurring in a region very close to the polymer chain. By means of this technique, it is demonstrated that the binding order to DNA is Li+ 〉 Na+ 〉 K+ for the alkali metal ions and Mn++ 〉 Mg ++ 〉 Ca++ for the divalent ions studied. The quantitative details are compared to earlier work on the long-chain polyphosphates. Close agreement between the two systems is obtained indicating that an intrinsic property of individual phosphate groups is being observed and that minor discrepancies probably arise from secondary factors. Three types of stability constants representing the binding of alkali metal ions to DNA are calculated and although differing in absolute magnitude, they all satisfactorily represent the result that the order of interaction is Li+ 〉 Na+ 〉 K+ with respective relative strengths of 1.5 : 1 : 0.8.
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    Biopolymers 2 (1964), S. 113-121 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: Birefringence relaxation times on removing the electric field characterize the rigidity of a flexible linear macromolecule structure. Electrical birefringence investigation of DNA solutions supports this view. This principal regularities displayed by relaxation times of electric birefringence decay curves in solutions of chain macromolecules are considered.
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    Biopolymers 1 (1963) 
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  • 58
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    Biopolymers 1 (1963), S. 419-429 
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    Keywords: Chemistry ; Polymer and Materials Science
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    Topics: Chemistry and Pharmacology
    Notes: The Lifson-Roig theory for the helix-random coil transition in polyglycine has been modified to take side-chain interactions into account. The modified theory is developed specifically for poly-L-alanine which probably contains a β1-α4 hydrophobic bond. A conditional probability, expressing the strength of such a hydrophobic bond, is evaluated from the Nemethy-Scheraga data for the free energy of formation of the bond. This, together with the conditional probabilities for the states of the backbone chain, permit an evaluation of the partition function and properties of the helix-random coil transition. It is seen that the hydrophobic bond renders the poly-L-alanine helix much more stable than the corresponding polyglycine one, in agreement with data obtained by Gratzer and Doty.
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    Notes: Optical, hydrodynamic, and titration properties of polyribouridylic acid (poly U) were investigated in 0.2M Na+, pH 6. Above 15°C., poly U was shown to be a randomly coiled single chain, devoid of secondary structure. There is no shear rate dependence of viscosity; molecular weight is independent of ionic strength; there is virtually no conformationally dependent hypochromicity; no anomalous optical rotatory dispersion; and no anomalous titration behavior. The dependence of the sedimentation constant and intrinsic viscosity on molecular weight was determined. Poly U was shown to be the most highly expanded of all synthetic and naturally occurring randomly coiled polynucleotides.
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    Biopolymers 1 (1963) 
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  • 61
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    Notes: Free poly-L-lysine base has been synthesized from ∊,N-trifluoroacetyl-α,N-carboxy-L-lysine anhydride via poly-∊,N-trifluoroacetyl-L-lysine (IV). No racemization occurred during the removal of trifluoroacetyl groups from IV with 1M piperidine. Measurements of optical rotatory dispersion suggest that IV exists in methanol in a helical form. The synthesis of poly-L-lysyl rabbit serum albumin is also described.
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  • 62
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    Journal of Morphology 40 (1925) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
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    Journal of Morphology 40 (1925), S. 517-557 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: An early segregation of germ cells and migration through a germ track into the gonad does not occur in the albino rat. The germ cells are produced only from the peritoneum of the genital region and their earliest formation is coincident with the thickening of the coelomic epithelium to form the genital ridge. This takes place eleven days after insemination in embryos of approximately 18 somites. Germ cells continue to form from the peritoneum during the early development of the gonad. The peritoneum of this region also produces mesenchyme, smaller cells of the gonads, and the germinal epithelium.The argument for the specific character of the germ cells in vertebrates and their continuity from the egg is based largely upon assumption, and not upon substantial observations, and must be discarded. Germ-cell origin is a problem of cellular differentiatio, and not of early segregation.
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    Journal of Morphology 41 (1925), S. ii 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Journal of Morphology 41 (1925), S. 191-216 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: Painted turtles, gopher tortoises, and terrapins were fed on various mixtures of sand, salts, dextrin, casein, cod-liver oil, wheat, eggs, lettuce, and meal worms. Each individual was weighted weekly for about a year and then killed for analysis, the water, ash, nitrogen, and fat being determined. Some individuals increased in weight as much as 75 per cent, others lost weight. Judged by growth and chemical analyses, the food requirements of chelonians, as representative poikilothermal vertebrates toward nutritive substances (including vitamines) are similar to those of homoiothermal animals.
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    Journal of Morphology 41 (1925), S. 267-281 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Of the eggs laid by Fasciolaria about 1 per cent develop into veligers, about 2 per cent more undergo a few cleavage divisions, and about 97 per cent do not divide at all. The 99 per cent that fail to develop normally are ‘swallowed’ by the veligers. This study concerns itself chiefly with the ova that do not divide. Notes on normal development and on the ova that undergo atypical cleavage are included.All of the ova are found to be typical when passed from the ovary. To each ovum one to several sperms become attached at the vegetal pole in the region of a mass of undifferentiated protoplasm - the ‘polar mass.’ A fertilization cone forms in each ovum and a fertilization membrane. In typical development a yolk lobe is formed, the sperm enters in the usual way, and fertilization is completed as in many other mollusks. In 97 per cent of the ova the yolk lobe is not formed and the sperm does not enter. In these cases the wall of the egg nucleus remains intact a long time. The nucleus itself and the ‘polar mass’ sink into the egg and meet at the center. Then the nuclear wall disappears and an atypical diaster is formed. However, cleavage is not begun and the chromosomes form vesicles that remain near the center of the ovum until it is ‘swallowed’ and digested by the veliger.
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  • 67
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The blood of Perophora viridis is found to contain six types of cells: (1) Green cells, which have green-colored fatty bodies embedded in clear cytoplasm. (2) Orange cells, with orange-colored bodies of unknown composition in the cytoplasm. (3) Colorless berry-like cells, with fluid-filled vesicles in the cytoplasm. (4) Granular amoeboid cells. (5) Compartmental amoeboid cells, which have box-like vacuoles containing brownian granules of a fatty substance. (6) Vesicular, signet-ring type of cell having a single large vacuole. The cytological structure of these cells and their reaction to various dyes are described.An effort has been made to homologize the types of cells found in the blood of other ascidians with those found in Perophora.It is concluded that the variety of colors found in the cells of ascidian blood is due to the varying chemical states of the vanadium-containing chromogen present in the cells.
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  • 68
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    Journal of Morphology 42 (1926) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 69
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    Journal of Morphology 42 (1926), S. 111-141 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Disintegration in killing agents was studied throughout development. In the unfertilized egg and cleavage stages the death gradient runs from animal to vegetal pole. In the late blastula stage the future dorsal surface and future point of gastrulation show heightened susceptibility. The gastrula has a gradient from anterior to posterior end along its dorsal surface, with a slight reverse gradient around the blastopore; lateral and ventral regions are least susceptible.Before and after the appearance of the neural groove, the dorsal surface shows increased susceptibility with gradient in it from anterior to posterior end. The neural tube is highly susceptible, with a death gradient from anterior to posterior end and a slight reverse gradient at its posterior end.During late stages and in the larva the double gradient is present; death begins at the two ends and progresses backward from head, forward from anus; from the former most rapidly. The least susceptible place is near the posterior end. The posterior reverse gradient is less developed in the lamprey than in other vertebrate embryos, due, probably, to its lack of a tail bud.Assuming that death differences indicate differences in rate of activity, it appears that such differences in activity may be causes and not results of developmental processes, for the development of certain parts (dorsal surface, blastopore, central nervous system) is indicated by heightened activity before it is evident morphologically.
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  • 70
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    Journal of Morphology 42 (1926), S. 83-109 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The summary of this paper is as follows:1A critical review of the developmental evidence shows that the branchial pouches are formed in cephalocaudal sequence subsequently to the segmentation of the dorsal mesoderm.2The pouches interrupt a continuous sheet of mesoderm to form the branchial arches.3The arches when formed do not correspond topographically to the dorsal somites.4Branchiomerism does not therefore coincide with somitic metamerism.3The branchial structures do not support the theory of head segmentation.3The nervi trigeminus, facialis, glossopharyngeus, and vagus cannot be regarded as segmental nerves.3There is no evidence that branchial pouches or arches have been elided from the series.3The problem of meristic homology is briefly discussed.
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  • 71
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    Journal of Morphology 43 (1927), S. 521-546 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The literature on the general subject of freezing and survival both in plants and in animals is briefly reviewed and a bibliography given. Insects representing three ecological groups, (1) the oak borers - exposed to temperature extremes normally; (2) stored-products insects representing supposedly a tropical or subtropical group, and, (3) aquatic insects never exposed to temperatures lower than 0°C., were chosen for this study. Determinations of the freezing and undercooling points were made during the yearly cycle.Both the stored-products insects and the aquatic insects studied showed no periodicity in freezing or undercooling. The oak borers showed marked periodicity. The freezing-point varies directly with the moisture content. Cold-hardiness was produced experimentally by, (1) exposure of insects to low temperatures and, (2) by dehydration. Loss of cold-hardiness was produced experimentally by combinations of high temperature, food, and high relative humidity. The freezing-point ordinarily found corresponds with that of the blood. Repeated freezings of the same insect or tissue showed no hysteresis. There exists in certain insects a secondary freezing-point below that ordinarily found. Oak borers in summer condition die at the first freezing-point; in fully hardened condition they die at the secondary freezingpoint.
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  • 72
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    Journal of Morphology 44 (1927), S. 1-20 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ant Formica exsectoides F. builds mounds with some reference to sunlight, and measurements of internal temperatures have shown them higher in upper parts of the mound, but different in different faces of the mound - all higher than the earth outside the mound.Inside temperatures are not constant; they are due to the sunshine. The mound is so fabricated that the internal temperatures are conserved during the night. The ants make use of the differential internal temperatures for rearing broods.Some mounds show bilateral symmetry dependent upon sun exposure.Measurements of rate of running of these ants show a falling off with lower temperatures, and possibly this is one factor in the smaller development of northerly aspects of these mounds.
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  • 73
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    Journal of Morphology 44 (1927), S. 117-125 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the early cleavage stages of Ascaris the homologous chromosomes are of unequal length. Measurements show that these homologues fall into two sharply defined groups suggesting their biparental origin. The shorter are considered to have come from the male.As the age of the embryo increases, these differences between the chromosome mates tend to become less, and it is suggested that at some later period in the history of the animal this difference will entirely disappear in response to the effect of continued existence in a common environment. The length of the chromosomes is very slightly shortened during the early cleavage divisions, while the area of the equatorial cross-section of the cells becomes enormously reduced.
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  • 74
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    Journal of Morphology 44 (1927), S. 313-339 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The rates of oxygen consumption of single pupae of blowflies (Phormia terraenovae, Phormia regina, Lucilia sericata), of the flesh fly (Sarcophaga sarracenioides Aldrich), of the Mediterranean flour moth (Ephestia kuehniella), and of the bee moth (Galleria mellonella) during metamorphosis, until emergence, have been determined. The record for each pupa, with the exception of those of blowflies, is practically continuous day and night during the period of pupal development which lasted from 140 to 300 hours, according to the species, at the temperatures used. During pupal development there is first a period of decrease in rate, which is later followed by a steady increase until a short time before emergence, when a sudden decrease occurs.The ‘oxygen curves’ of the blowfly pupae (Diptera) are quite different from those of the flour-moth and bee-moth pupae (Lepidoptera), although all are of the same general U-shaped type. There are strong indications of a specific difference in the curves of the blow-fly pupae. The flour-moth pupae curves differ slightly from those of the bee-moth pupae. During the major part of development the rates of O2 consumption of pupae of both sexes of bee moth and flour moth are about the same, but near the end of metamorphosis the females have higher rates than the males. No such sex difference appears among the dipterous pupae used.
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  • 75
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    Journal of Morphology 44 (1927), S. 363-372 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The history of investigations on the contractile vacuole is reviewed briefly and brought up to date.The study of the contractile vacuole in Amoeba proteus is considered from standpoints of origin, structure, behavior, and function. The results are obtained from a prolonged study of normal organisms and from their reactions when introduced into conductivity water.The origin of vacuoles is studied by means of dark-field illumination which reveals the vacuole to be formed from a fusion and coalescence of extremely minute droplets.The retaining ‘wall’ of the contractile vacuole is not a permanent structure, but is in the nature of a condensation membrane, totally disappearing with each contraction.The loci of the contractile vacuoles are not permanent, but vacuoles are formed more or less at random. It is unlikely that they are supported in gelated areas, for amoebae with a dozen vacuoles are quite active and there is no interference with amoeboid movement.Conductivity water increases the size, number, and rate of contraction of contractile vacuoles, which suggests that they may function in maintaining an osmotic gradient as well as in the elimination of metabolic waste.
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  • 76
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    Journal of Morphology 44 (1927), S. 467-514 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The eggs of Corella develop in the atrial chamber of the parent at a pH below that of normal sea-water (pH 7.4 ±). When removed to normal sea-water in early stages and under certain other experimental conditions, larval development is more or less inhibited, the tail being most inhibited, the dorsal region somewhat less. The free larval stage may be eliminated and later development and metamorphosis may proceed normally to an advanced stage in the chorion and give rise to normal ascidians. The region most inhibited are, in general, those which possess the highest reducing power, as indicated by KMnO4. Experiments made in the attempt to control development all agree in indicating that the early stages are adjusted to a certain CO2 concentration approximately that of the atrial chamber and presumably near that of the body. Solutions of the same pH may or may not inhibit development according to their CO2 content.The tail, the region of highest reducing power in the embryo during its development, is most inhibited; the dorsal region, the next most rapidly reducing region, is next in degree of inhibition. All differences in reducing power disappear when, or soon after, the animals are killed by other agents before treatment with KMnO4.
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  • 77
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    Notes: The claspers of Centrina are adnate with the pelvic fin and bear a spine as in other Spinacidae. Mustelus canis resembles M. lunulatus rather than M. vulgaris. The claspers of Chiloscyllium end in a pointed spike. Pseudotriakis resembles the Carchariidae. The three North American Atlantic species of the genus Raia are considered, and R. laevis and R. erinacea are placed in the pseudogenus containing R. batis, and a new pseudogenus erected for R. ocellata. A gross and histological account is given of the Cowper's glands of Homo, and they are shown to be homoplastic with clasper glands, similar in structure, arrangement, development, and function.
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  • 78
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: In the golden-mantled ground-squirrel, Callospermophilus, a spatulate glandular area has been noted in the skin of the back. It has been found in the following species: C. l. lateralis, C. l. arizonensis, C. l. caryi, C. l. saturatus, C. l. tescorum, C. c. chrysodeirus, and C. bernardinus. Probably it is common to the genus.The individual glands making up this area are modified and enlarged sudoriparous glands. They are divided into a tightly coiled and branched fundus, a large sinus, and a duct which passes caudad and outward to its exit at the surface.The glands secrete a strongly smelling oil, which is probably left on vegetation and other objects in the animal's environment and serves as a source of information to other members of the species. The glands are more active in spring and summer than in winter. They are stimulated by excitement. While present in both sexes, both adult and juvenile, they are best developed in adult males.Callospermophilus has three anal glands. These have flat-topped, straight-sided nipples which are protruded from the anus if the animal is frightened. A milky substance with a very weak odor can be extruded.
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  • 79
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: The study is divided into three parts. Part I deals with the chromosome number and morphology in the amniotic cells of rabbit embryos. The number of chromosomes has been found essentially constant in amniotic cells of young, but more variable in older embryos. The somatic number is 44. Part II deals with the chromosomes of race crosses (Flemmish Giant X Polish) in which the homologous chromosomes were found to be alike. Part III deals with spermatogenesis. There are forty-four chromosomes in spermatogonia, and twenty-two in primary spermatocytes. The sex chromosomes are of the usual X-Y type.
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  • 80
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: 1Monovalent cation salts induce reversal in the direction of the stroke of the cilia; bivalent and trivalent cation salts with a few exceptions do not. Some acids induce reversal, others do not.2The duration of reversed action varies with the kind of salt and with the concentration. As the concentration increases, the duration of reversed action increases to a maximum and then decreases to zero.3Bivalent and trivalent cation salts neutralize the effect of monovalent cation salts. The relative amount required varies with the kind of salt used and with the concentration.4The amount of a given salt required to neutralize another salt is not proportional to the concentration of the salt neutralized. Weber's law does not hold.5The results seem to indicate that ciliary reversal is associated with differential adsorption and consequent changes in electric potential, but that there are also other factors involved.
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  • 81
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Notes: A special type of cell, called ‘Lichtzellen’ by Hesse, was found in the photosensitive regions of the earthworm. Wherever the epidermis is most sensitive to light these cells are most abundant. They are found in the epidermis of all segments of the body and also in nerve enlargements of the prostomium and the caudal segment, but the intersegmental and ventral regions of the different segments, except the more distal ones, contain none of them. They are supplied by nerves and each contains a characteristic inner structure, the optic organelle, composed of a large central hyaline structure, the lens, which is surrounded by a dense network of nerve fibrillae, the retinella. In hanging drops the lens was found to focus light in the region of the retinella irrespective of the direction of the rays.These cells are similar in structure and function to the visual cells in leeches. Available data indicate that these cells function as photoreceptors and that the fibrillae of the retinella are the direct receptors of light stimuli.Pigment is not associated with the photoreceptors in a way that suggests direct functional relationship, but there is a subepidermal pigment layer through which pinhole windows admit light along the path of nerves to each of the nerve enlargements containing photoreceptor cells. These windows open in such directions as to determine the direction of withdrawal of the worm.
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  • 82
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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    Topics: Biology , Medicine
    Notes: The effect of removal of the liver has been noted in fishes, frogs, and turtles. As in the higher vertebrates, removal of the liver produced a fall in blood sugar and a loss in muscular tone. The lower vertebrates failed to respond to intravenous injections of glucose, as do the birds and mammals. They also fail to respond to maltose or levulose. The liver maintained the blood-sugar level in the lower vertebrates, which is necessary for the maintenance of life.The mechanism of carbohydrate metabolism in the lower vertebrates may be different from that in the higher ones, in that glucose, when injected intravenously, apparently exercises a progressively less beneficial effect on the characteristic hypoglycemic condition which follows the removal of the liver of mammals and cold-blooded vertebrates.
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    Journal of Morphology 41 (1925), S. 239-265 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This paper reports experiments with Fundulus heteroclitus to modify larval development by means of ultraviolet radiation. Eggs were exposed to radiation at various intervals after fertilization for varying periods of time. The results accord with previous work on fish teratology, and the developmental types obtained are essentially similar to those produced by chemicals, cold, and hybridization. The deviations from normal development occur in the same body regions as do those in other vertebrates whose early development has been modified by the action of radiation (x-rays, radium, etc.).The results of these experiments indicate that there is a non-specificity in susceptibility relations with the production of similar types of monsters for widely different reagents. That these eggs are differentially susceptible to the action of ultraviolet radiation is indicated by the fact that those regions which have the highest metabolic activity when an inhibiting influence is active are the ones most generally affected. Thus modifications of the nervous system, sense organs, circulatory system, tail region, and body axis result, respectively, in the production of varying degrees of cyclopia, inadequate circulation, short, stubby or bent, non-motile tails (some bifid), and anterior twinning.As these modifications may be produced by applying inhibiting influences during the first few minutes after fertilization, it is evident that there is in the egg at this stage some constitutional or physiological basis which determines early differences in susceptibility of its various parts.
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    Journal of Morphology 41 (1926), S. 427-439 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Webbing of toes or fingers in man is produced by a local arrest of development, causing retention of the normal embryonic webbing. This type of digital fusion involves only the skin, the skeleton being unaffected. The extensor tendons of the toes may sometimes be fused.Webbed digits occur normally in some marsupials, rodents, and insectivores, in a number of lemurs and catarrhines, and in the siamang and gorilla. They also may occur in varying degree in other Primates, notably Hylobates. An analysis of five new pedigrees together with those already published demonstrates that webbing of toes in man may be inherited in either a mendelian or sex-linked manner. In one case this character follows the course of the Y-chromosome.
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  • 85
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    Journal of Morphology 45 (1928) 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
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  • 86
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Amoeba proteus was raised in a modified and diluted Ringer solution. When the pH of this culture medium became less than 6.0, the normal activities of the amoebae were interfered with; and when a still lower pH was attained, the amoebae died off. The same was true when the pH became greater than 8.0. At neutrality the activities were subnormal, very dark, and rounded. The rate of locomotion of amoebae raised in solutions with a pH less than 7.0 showed a maximum rate of locomotion at pH 6.6, which decreased as the pH changed in either direction, dropping to a very low rate at pH 7.0 and above and also below 6.0. For amoebae raised at a pH above 7.0 the rate was maximum at pH 7.6 and decreased as the pH changed in either direction; it was low at pH 7.0 and below and also above 8.0.On increasing the external osmotic pressure of the medium it was found that the effects caused varied somewhat with the hydrogen-ion concentration. Small increases in osmotic pressure decreased the rate from the normal at pH 6.0 and 8.0, increased it at pH 6.6 and 7.6, and did not affect it at pH 7.0. Osmotic pressures above that produced by M/20 lactose caused locomotion to cease in a short time at all pH values.
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    Journal of Morphology 45 (1928), S. 209-231 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The highly specialized cranial musculature of the toadfish is characterized by the following features: 1Absence of intermandibularis and branchiomandibularis muscles.2Presence of levator premaxillaris muscle.3Very large branchial chamber, the outer wall of which is formed by seven branchiostegal rays connected by a strong fascia provided with muscles (oblique levators and adductors).4Highly developed masticator muscles (adductor mandibularis and pterygoids).5The rectus abdominis, sternohyoid, and hyohyoid muscles are attached by a median aponeurosis to the hyoid and basibranchial elements and directly to the hypobranchial cartilages; this muscle complex depresses the buccal floor in opposition to the geniohyoid.6The pelvic fins are in the jugular position.7Two narrow muscles connect the cleithrum with the fourth ceratobranchial.8The cranial musculature is obviously adapted to a carnivorous habit and particularly for increasing respiratory capacity under asphyxial conditions.
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    Journal of Morphology 45 (1928), S. 293-398 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Blindfolded persons walk, run, swim, row, and drive automobiles in clock-spring spiral paths of greater or less regularity when attempting a straightaway. The spirals turn either right or left in one and the same individual, and may do so even in one experiment. But either right or left turns predominate in the great majority of individuals, often to a high degree. The paths show marked individuality, and there is some ground for thinking there exists a correlation between temperamental differences and general character of path.The mechanism which produces the spiral path is not located in the locomotor organs, but in the central nervous system and is probably identical essentially with the spiral mechanism in other motile organisms, all of which move in spiral paths when there are no guiding senses to direct the path. The clock-spring spiral in man is interpreted as the expression in two dimensions of space of a helical spiral mechanism which seems to exist in all motile organisms moving in three dimensions of space and in amebas which move in two dimensions. In a large number of lower organisms the number of body lengths per spiral turn is almost constant, being about 4.5. The smallest regular swimming spirals in man are very close to this value, but the smallest regular walking spirals are somewhat larger. The fundamental spiral mechanism seems to be of molecular dimensions, and there seems to exist a demonstrable locomotor bilateral asymmetry in very nearly, if not quite, all organisms.
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    Journal of Morphology 45 (1928), S. 473-503 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A detailed study has been made of the anatomy of one of the fingernail shells, and preliminary observations on the life-history have been carried out. In its general organization Sphaerium notatum is very similar to the larger fresh-water lamellibranchs. A gastric shield, crystalline style, and style sac, very similar to those found in the stomach and intestine of Lampsilis, are present. A pair of slender muscles extending from the dorsal side of the body into the gills, and evidently not previously described, have been found. The nervous system consists of the typical three pairs of lamellibranchiate ganglia, with their connectives, accessory ganglia, and nerve fibers. Particular study was given to the statocysts and osphradia, and attention is called to the fact that the function commonly ascribed to the osphradia is incompatible with their position in the roof of the cloacal chamber.S. notatum, like all the Sphaeriidae, is hermaphroditic and viviparous. The gonads are paired racemose glands lying behind and below the stomach. The sperm-producing follicles form the anterior portion of each gonad and are somewhat smaller and more numerous than the ova-producing follicles which form the posterior portion. The young pass through the early stages of development in brood pouches in the gills and are expelled as relatively enormous individuals.Preliminary observations on the life-history indicate that reproduction reaches its height in the summer and that fertilization probably takes place during the late summer and fall.
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    Journal of Morphology 45 (1928), S. 579-597 
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    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: When Menidia eggs are fertilized with Prionotus sperm, the Prionotus chromosomes react in the Menidia cytoplasmic medium just as they do in the cytoplasm of Fundulus eggs. There is lagging, non-disjunction, and elimination of chromosomes during the early cell divisions. The mitotic behavior of the Prionotus sperm in the Menidia egg also resembles the behavior of the sperm of Ctenolabrus in the same medium. This behavior which was expected from what was known concerning the mitotic behavior of the reciprocal crosses between Menidia and Fundulus and between Ctenolabrus and Prionotus and other intercrosses between the members of these two groups is regarded as a function of the physical state of the egg cytoplasm during the division phase of mitosis. This physical character forms the earliest differential factor in the development of these hybrids and shows no correlation with the width of the cross.A comparison of nine teleost crosses, in which both the development and the early mitotic behavior are known, with a rough numerical estimate of the width of the cross brought out the fact that development is most successful in crosses between nearly related species if mitosis is normal and in distantly related crosses if mitosis is abnormal. This indicates that nuclear relationship is also a factor in the development of hybrids.
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  • 91
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Virulent hay-infusion cultures of Bacillus pyocyaneus are toxic to pure-line races of three species of paramecia, but these races may acquire a tolerance for this toxic agent. Races with acquired tolerance have been grown for long periods of time in toxic, pure cultures of B. pyocyaneus by means of the daily-isolation culture method, and here the average division rate is as high as, or higher than, in the chance-mixed bacterial cultures in which these protozoa are usually maintained in the laboratory. The tolerance is lost, however, when the paramecia are removed from the toxic cultures and grown for a number of generations in cultures of non-toxic bacteria.The toxic agent that is lethal to paramecía is probably the soluble toxin of B. pyocyaneus. The investigation shows that the agent is soluble and either thermolabile or volatile. It also shows that all deleterious substances, other than the soluble toxin, known to be produced in cultures of this bacillus, are non-lethal to paramecia.Hay-infusion cultures of Bacillus enteritidis were lethal to paramecia. All attempts to develop tolerance in paramecia for the toxic agent in these cultures failed.Under the experimental conditions that prevailed, diphtheria toxin was found to have no appreciable effect upon the division rate or death rate in three species of paramecia.
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  • 92
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    Journal of Morphology 57 (1935), S. 1-29 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Two kinds of spermatozoa are formed in the testis of Goniobasis laqueata, typical (eupyrene) and atypical (apyrene); a similar dimorphism is noted in several other related genera. The development of each type of spermatozoon is described in Goniobasis. The apyrene spermatozoa do not appear in the testis until eupyrene spermatogenesis has progressed to the formation of mature eupyrene spermatozoa. After this time apyrene spermatogenesis becomes predominant. It is suggested that this condition is indicative of a modified protandric hermaphroditism, according to a recent theory of spermic dimorphism. The anatomy of the reproductive system of Goniobasis is described briefly, and the behavior and fate of the two types of spermatozoa are noted. Only the eupyrene spermatozoa are inclosed in a spermatophore formed in a special organ of the male, the apyrenes being somehow excluded. Thus the latter do not reach the female in copulation and can have no necessary functional relationship to the ova at the time of fertilization. The delayed formation of the apyrene spermatozoa, and other facts, indicate that they are probably not concerned with the nutrition or transport of the eupyrene spermatozoa.
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  • 93
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    Journal of Morphology 57 (1935), S. 61-89 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Three pairs of thymus primordia are found at 6 to 6.5 mm. on the dorsal lateral ends of the second, third and fourth visceral pouches. Those on each side after fusing by growth and migratin come to lie above the third visceral pouch, whence the thymus migrates upward and backward; growing in size, it stretches above the ends of all the gill pouches. It pushes inward into the mesenchyme at 12 to 13 mm. and becomes perforated and surrounded by blood vessels and connective tissue which separate it almost completely from the epithelium. No septa are found; occasionally the third primordium fails to fuse and forms a separate lobe.The early thymus is a syncytium in which are found lymphoblasts, identified by structure of the cytosome and its behavior during mitosis. Evidence is presented that lymphoblasts migrate into the thymus where they increase in number with corresponding increase in length of cytoplasmic bridges and size of intercellular spaces. At 10 mm. begins a rapid increase in size of the thymus and in number of lymphoblasts and decrease in size of the latter, culminating at 12 to 13 mm. in their transformation into thymocytes. A medulla associated with blood vessels is unmistakable at 30 mm.
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  • 94
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A study of the development of the sense organs of the larva of Botryllus schlosseri to determine, if possible, any homologies between its sense organs and those of other types of ascidians such as Molgula and Ammaroucium, which have sense organs structurally very different.The statolith appears in the Botryllus embryo as a single club-shaped cell. The lightsensitive organs have their primordia slightly later as five small filaments, each developed from a ganglion cell. A cavity appears in the statolith into which the light-sensitive filaments penetrate. Later development is concerned with pigmentation of the statolith, and a twisting process which orients it into the position in which it is found in the free-swimming larva. The three tactile papillae develop from evaginations of ectoderm at the anterior end of the embryo. The ectodermal cells at the center of a papilla are differentiated into rod-shaped sensory receptors and ganglion-like masses of nerve tissue. Nervous connections are established between these peripheral ganglia and the central nervous system.Results of the investigation indicate that the statoliths of the different ascidian larvae are homologous; the direction eyes probably are not, but have evolved independently from a light-sensitive area in the primitive larva of a common ancestral ascidian. The larvae of Molgula and Ammaroucium possess no structures comparable to the sensory papillae of Botryllus.
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  • 95
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 57 (1935) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 96
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    Journal of Morphology 57 (1935), S. 335-351 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A study of the brinchial epithelium in representative specimens of Cyclostomata Elasmobranchii and Teleostei fishes has been made, with special reference to the following: 1) the importance of physiological role of osmotic regulation effected by the gills; 2) the presence or absence of specialized secretory tissue; 3) progressive evolution of the fishes and the possible phylogenetic difference between them. In regard to these topics we find: 1) There is no indication of any specialization in the branchial epithelium of fishes indicating a special role in extrarenal excretion. 2) In the respiratory epithelium of fishes widely separated phylogenetically or in fishes in living in fresh or salt water, the only significant differences are that in general the teleosts have a squamous type of epithelium, whereas, the elasmobranchs have in general a thicker polyhedral investment. 3) Mucous cells appear large and numerous on the filament proper, smaller and less numerous in the interlamellar spaces, and on the free surface of the lamellae. These are the only specialized secretory cells which occur in the gills.
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  • 97
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    Journal of Morphology 57 (1935), S. 461-471 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The exeretory system of Typhlocoelum cucumerinum consists of three pairs of longitudinal channels communicating by a single ventral vessel with the excretory vesicle. Branches subdivide extensively and anastomose forming a dense network of tubules throughout the body. The vessele possess many of the features characteristic of lymph systems as described in amphistome trematodes. They have cuticular walls, come into intimate association with the intestine and contain a granular coagulum and cellular elements suspended in the lumen. The single system of vessels appears to be functioning as a combined lymph and excretory system. Typhlocoelum americanum Manter and Williams ('28) is regarded as a synonym of Typhlocoelum cucumerinum (Rud. 1809).
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  • 98
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    Journal of Morphology 57 (1935), S. 597-615 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The development of the thyroid has been briefly described from an example of each of the four urodele families and comparisons drawn. An attempt has been made toward clarifying previous and conflicting accounts. The thyroid arises as a solid bud from the floor of the pharynx in the region of the first visceral pouches. This bud grows backward until it reaches the pericardium. Division of the primordium into lateral portions is inaugurated and the anterior end of the splitting thyroid loses its connection with the pharynx before the separation of the parts is completed. Some of the undivided anterior portion may persist as an accessory thryroid. After the two lateral thyroid masses are separated the yolk disappears from the cells which then form cell columns and enlarge as a result of the fusion of adjacent vesicles. A thyroid [release] occurs at the time of metamorphosis except in Necturus. After the [release] the follicles refill. Similarities in development and general histological picture are closer between Necturus and Cryptobranchus as a pair than between either of these forms and Amblystoma or Eurycea. Amblystoma and Eurycea also resemble each other in histological picture. It is suggested that Necturus produces the thyroid hormone in sufficient quantity to induce metamorphosis but that some other factor or factors serve to inhibit the response.
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  • 99
    Electronic Resource
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 58 (1935) 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 100
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    New York, NY : Wiley-Blackwell
    Journal of Morphology 58 (1935), S. 41-85 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Extensive measurements were made on skeletal configurations and muscles of several forms of Hemiptera-Homoptera from the early nymphal instars to the adults, inclusive. It has been shown that several of the muscles actually decrease in length (i.e., contract) as the animal grows as a whole. Such a state of affairs has never before been observed, so far as the writer knows. The most marked increase in length of a skeletal invagination often coincides with the greatest amount of contracture of the muscle which is attached to its extremity. The characteristics of the arthropod skeleton, which consist of invaginations and evaginations are probably, in the forms studied, due to muscular contraction or to the prolonged sustenance of muscular tonicity.The form of muscular contraction described probably belongs to the ‘catch’ type rather than to the metabolic type. The direct cause of these muscular contractions is probably due to changes in physico-chemical constitution of the haemolymph.
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