bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic analysis in the dinoflagellate (Crypthecodinium (Gyrodinium) cohnii: evidence for unusual meiosis.
Authors: Himes M , Beam C A
Published: May 2006

The atypical structure and behavior of dinoflagellate chromosomes suggests that the genetics of these organisms might show comparable peculiarities. We have begun genetic analysis of the neritic, marine heterotroph Crypthecodinium (Gyrodinium) cohnii by means of motility mutants that show complementation shortly after zygote formation, permitting identification of heterozygotes. Six mutations, conferring four microscopically distinguishable phenotypes, have been isolated and investigated. These "genes" were found to complement in double heterozygotes in all pairwise combinations, indicating that the lesions are recessive and non-allelic. Clones of all possible combinations of these factors have been established and each complements only those combinations expected on the assumption that there are six independent recessive mutant "genes." Tetrad analysis following isolation of over 200 complementing zygotes showed: (1) regular segregation with recovery of parental phenotypes and genotypes; (2) independent assortment, with one possible exception; (3) segregations that were always 1:1, that is, in all tetrads showing recombination, only the two reciprocal recombinant genotypes were found; there were no tetratypes. This behavior could result from centromere linkage or the absence of crossing over in an otherwise conventional meiosis, or it could result from an unusual one-division "meiosis." Some evidence is provided that favors the latter hypothesis.
An inherited "neoplasm" in fungus.
Authors: Leonard T J
Published: May 2006

An abnormal growth form in the fungus Schizophyllum commune is described that interferes with the development of reproductive structures. The abnormality, which takes the form of relatively large, compact, hemispherical bodies, depends on a dominant Mendelian gene, mound, for its expression. When mound is expressed in a mycelium that has the potential to form fruiting bodies, the fruiting response is affected and the effect is variable within a replicate series: fruiting bodies may be normal or abnormal, abort at various stages, or not develop at all. Occasionally, fruit bodies are overgrown and are completely enveloped by the hemispherical bodies. When hyphae from hemispherical bodies are subcultured, a seemingly normal mycelium forms that eventually differentiates hemispherical structures, but the ability to form fruiting bodies in not expressed. Continuous mycelial subculture has shown this loss of fruiting expression to be a permanent transformation, which is demonstrated to be a characteristic of hemispherical bodies.
Phenomenological analysis of observed relations for low-redshift galaxies
Authors: Nicoll J. F. , Segal I. E.
Published: May 2006

Maximum-likelihood estimates are made for the exponent
p
in the phenomenological redshift-distance relation
z
[unk]

r
p

for galaxies at redshifts ≲0.03, on the basis of redshift (
z
)-magnitude (
m
)-apparent diameter (θ) observations given in the
Reference Catalogue of Bright Galaxies
[de Vaucouleurs, G. & de Vaucouleurs, A. (1964)]. The estimates are in the range 1.96 ≤
p
≤ 2.04 for the full sample of 742 galaxies having
m
-
z
- θ data, with dispersions ≲0.08, and in a similar but broader range for various subsamples. Explicit allowance for an observational cut-off in apparent magnitude in the
m
-
z
relation reinforces the result that
p
∼ 2. Independent estimation based on a cut-off independent generalized Kafka-Schmidt

V/V
m

test for a subsample in conservatively limited redshift and magnitude ranges, yields
p
= 2.05.
On some modified spherical models
Authors: Barrett Wayne W. , Kac M.
Published: May 2006

A one parameter family of models is considered which for zero value of the parameter α reduces to the familiar spherical model. The models for α > 0 have a symmetry close to that of an Ising model. A heuristic discussion of phase transitions in these models leads to the conjecture that, if the spherical model (α = 0) exhibits a phase transition, then so do the models with α > 0, and that moreover the critical temperature remains the same, at least for sufficiently small α. The conjecture is checked on a mean field model.
Spike-forming model of the neural membrane: computer simulation of some perfused axon experiments.
Authors: Wooldridge D E
Published: May 2006

This paper is an attempt to account for the action potential spikes observed when the normal axoplasm of a squid giant neuron is replaced by a postassium-free, sodium-rich fluid, and the axon is immersed in a potassiumand sodium-free, calcium-rich bath. For this purpose a recently described model of the neural membrane [Wooldridge, D. E. (1975) Proc. Nat. Acad. Sci. USA 72, 3468-3471] is extended. Allowances are made for the flow of Ca++, Cl-, and Na+ ions through some of the membrane pore configurations, as well as for some electron conductance, all of amounts too small to be significant in the normal neuron. It is also postulated that the nature of the perfusing fluid affects the rates of some of the reactions that change the convertible gates from one configuration to another, as well as the ionic permeabilities of the resulting configurations. The result of the modifications is a single membrane model that accounts for the 3-sec, 15 muA/cm2 action potential spikes of the perfused axon as well as for the 0.5-msec, 1 mA/cm2 spikes of the normal neuron.
Differential activity staining: its use in characterization of guanylyl-specific ribonuclease in the genus Ustilago.
Authors: Blank A , Dekker C A
Published: May 2006

Guanylyl-specific ribonuclease can be identified by a novel technique employing electrophoresis in polyacrylamide slabs followed by differential activity staining. The technique requires as little as 7 ng of enzyme which may be grossly admixed with contaminants, including other ribonucleases. Upon electrophoresis and activity staining, a variety of ribonucleases can be visualized as light or clear bands in a colored background formed by toluidine blue complexed with oligonucleotide substrate. Guanylyl-specific ribonuclease, which is detectable when using an oligonucleotide substrate of random base sequence, does not yield a band when using oligonucleotides bearing guanylyl residues at the 3'-termini only and containing, therefore, no susceptible internucleotide bonds; in contrast, a ribonuclease with a different base specificity or no base specificity yields a band with either substrate. This differential activity staining method for establishing guanylyl specificity permits estimation of the extent of nonspecific cleavage of internucleotide linkages by a putatively guanylyl-specific enzyme and is at least as sensitive as conventional procedures for determination of base specificity. With this new technique guanyloribonuclease has been identified in the unfractionated culture medium of 10 organisms belonging to the phytopathogenic fungal genus Ustilago. It is suggested that guanylyl-specific ribonuclease is widely distributed among Ustilago species; its electrophoretic properties may be revealing of phylogenetic relationships among these plant parasites and among their hosts. The general technique of differential activity staining, developed for determination of the base specificity of ribonucleases, may be widely applicable to analysis of enzymes catalyzing depolymerization reactions.
Localization of cytoplasmic-membrane-associated DNA in human chromosomes.
Authors: Kuo M T , Meinke W , Saunders G F
Published: May 2006

In situ hybridization was used to localize the sites of the repeated sequences of cytoplasmic-membrane-associated DNA (cmDNA) in human chromosomes. cmDNA was mainly present in the heterochromatic regions of chromosomes 9. Although cmDNA has buoyant densities in neutral and alkaline CsCl gradients similar to those of human satellite C DNA, which also is localized in the heterochromatic region of chromosomes 9, cmDNA was not homologous to satellite C DNA as determined by DNA-complementary RNA hybridization. These results are in agreement with our previous studies, which indicated that cmDNA is a unique species of human DNA.
Nature of R-factor replication in the presence of chloramphenicol.
Authors: Crosa J H , Luttropp L K , Falkow S
Published: May 2006

Covalently closed circular deoxyribonucleic acid molecules of RSF1030, a nonconjugative R-factor, initiate and complete rounds of semiconservative replication in the absence of protein synthesis long after the bacterial chromosome has ceased its replication. RSF1030 replication under these conditions is sensitive to the inhibitor of ribonucleic acid synthesis, rifampicin. The product of this replication, a covalently closed DNA molecule, shows, in contrast to those molecules produced during the replication in a logarithmically growing culture of Escherichia coli, a transition to the open circular form upon treatment with ribonucleases of alkali. Analysis of the product resulting from alkali treatment indicates that there is a single break in one strand of the original circular duplex. This alkali-sensitive site occurs with equal probability in either of the complementary strands. These results are interpreted as a requirement for an RNA primer for the initiation of RSF1030 DNA synthesis and as showing that its removal from the covalently closed molecule is inhibited in the absence of protein synthesis.
Assembly of chick brain tubulin onto flagellar microtubules from Chlamydomonas and sea urchin sperm.
Authors: Binder L I , Dentler W L , Rosenbaum J L
Published: May 2006

Flagellar microtubules from Chlamydomonas and sea urchin sperm were used as in vitro assembly sites for chick brain tubulin. Brain microtubules assembled onto the A-tubules, central tubules, and, to a limited extent, onto the distal ends of the axonemes at low tubulin concentrations and onto distal and proximal ends at high tubulin concentrations; however, the rate of assembly onto the distal end was always greater. The rate of neurotubule assembly onto axonemes was shown to be dependent upon tubulin concentration and a forward rate constant for assembly was determined.
Nucleotide sequence of an RNA polymerase binding site at an early T7 promoter.
Authors: Pribnow D
Published: May 2006

Escherichia coli RNA polymerase (EC 2.7.7.6), bound in a tight complex at an early T7 promoter, protects 41 to 43 base pairs of DNA from digestion by DNase. I. The protected DNA fragment contains both the binding site for RNA polymerase and the mRNA initiation point for the promoter. The sequence of the DNA fragment and the sequence of the mRNA that it codes for are presented here. A seven-base-pair sequence, apparently common to all promoters, is implicated in the formation of a tight binary complex with RNA polymerase.
“Spshing Noise”: Biological Significance of Its Attraction and Nonattraction by Birds
Authors: Smith Neal Griffith
Published: May 2006

Many New World passerine birds, especially migrants which join mixed flocks of local species in the Neotropics, are attracted to a noise termed “spshing” used by humans to attract birds into view. The noise is effective because it mimics the vocalizations of certain bird species which play a central bonding role in mixed species flocks. Migrants join these flocks to gain local expertise about food sources and/or potential enemies in unfamiliar environments. Old World passerine migrants do not react to “spshing.” In Africa, they do not join mixed flocks of local species because of more favorable environmental conditions negating the need to do so. In tropical Asia, many migrants join mixed flocks but the local bonding species give vocalizations unlike those of their counterparts in the Neotropics, and thus not like “spshing.”
RNA of replication-defective strains of Rous sarcoma virus.
Authors: Duesberg P H , Kawai S , Wang L H , Vogt P K , Murphy H M , Hanafusa H
Published: May 2006

The RNA of a replication-defective (rd) mutant, isolated from stocks of nondefective (nd) Schmidt-Ruppin Rous sarcoma virus of subgroup A (SR-A) and termed SR-N8, was compared to the RNAs of SR-A, of a transformation-defective derivative of SR-A (td SR-A) and of rd Bryan Rous sarcoma virus, RSV (minus). The molecular mass of the 30-40S species of SR-N8 RNA was estimated to be 21% (congruent to 7.5 to 8 times 10-5 daltons) smaller than that of SR-A by (i) electrophoresis in polyacrylamide gels and (ii) analyses of RNA complexity based on RNase T1-resistant oligonucleotides. ST-N8 shares probably all (=14) of its large RNase T1-resistant oligonucleotides with the RNA of SR-A as judged from the chromatographic distribution and the RNase A-resistant fragments obtained from RNase T1-resistant oligonucleotides. However, SR-N8 RNA lacked six large oligonucleotides which were present in the RNAs of SR-A and td SR-A. Conversely, the RNAs of SR-A, and of SR-N8 contained two oligonucleotides not found in td SR-A. The RNA of SR-N8 was found to differ from that of RSV (minus) in its electrophoretic mobility and its fingerprint pattern. It is concluded that the RNA of SR-N8 was generated by a deletion of SR-A. The extent of this deletion is compatible with the notion that the genetic information for the large viral envelope glycoprotein (molecular mass = 70,000-85,000 daltons) has been lost from the RNA of SR-A to yield SR-N8 RNA. From a comparison of td and rd deletion mutants, it appears that loss of different functions corresponds to the absence of different oligonucleotides in their RNA.
Moments for sum of an arbitrary function of gene frequency along a stochastic path of gene frequency change.
Authors: Maruyama T , Kimura M
Published: May 2006

A diffusion model is developed to compute any moment of the sum of an arbitrary function of the gene frequency along sample paths between any two specified frequencies. This is used to calculate the mean age of a mutant of frequency chi, including or excluding the possibility of its having been at value chi equals 1 during the process, and the total frequency of heterozygotes involving an allele since its origin.
Stereochemistry of Decarboxylation of
trans
-4-Hydroxycinnamic Acid by
Aerobacter
Authors: Parry Ronald J.
Published: May 2006

The stereochemistry of the decarboxylation of
trans-p
-coumaric acid to 4-hydroxystyrene by
Aerobacter aerogenes
has been examined. The decarboxylation has been found to proceed with retention of the geometry about the
trans
-substituted double-bond.
Repetitive DNA replication of the incomplete genomes of phage T4 petite particles.
Authors: Kozinski A W , Doermann A H
Published: May 2006

The genomes of petite T4 phage particles presumably cannot circularize because they are deficient for a significant terminal segment and hence not terminally redundant like normal T4 genomes. Combined density- and 32P-labeling shows that the majority of such deficient DNA molecules can nevertheless replicate their entire length. Furthermore, the density-shift technique shows that replicated parental strands can exchange their partners for new light strands, indicating that noncircularized T4 DNA molecules replicate repeatedly. When taken together with previously published data, these results indicate that T4 replication is bidirectional from multiple, genetically fixed points of origin. Rolling circle models can, therefore, not be considered as an essential mechanism for the early rounds of T4 replication.
Molecular model of postsynaptic potential.
Authors: Dubois D M , Schoffeniels E
Published: May 2006

A molecular model of the excitatory postsynaptic membrane is given in terms of two biochemical cycles intimately associated: an acetylcholine cycle and a calcium cycle. The acetylcholine controls the Na ionophores while calcium ions control the tk ionophore. The two ionophores are spatially separated but interact in such a way that the variation in K conductance precedes that in Na conductance. Digital simulation shows that our model accounts quantitatively for both the evolution of excitatory postsynaptic potential and current in a variety of experimental conditions.
Use of biochemical lesions for selection of human cells with hybrid cytoplasms.
Authors: Wright W E , Hayflick L
Published: May 2006

Techniques for preparing large populations of anucleate cytoplasms from cultured eukaryotic cells have only recently been described. The principal value of anucleate cytoplasms derives from studies that can be done after they are fused to whole cells. Since present methods for the isolation of heterokaryons are unsuitable for the selection of hybrids between whole cells and anucleate cytoplasms (heteroplasmons), a selective system has been developed which is based on the capacity of anucleate cytoplasms containing active enzymes to rescue whole cells poisoned with iodoacetate. Ethidium bromide, a partially effective agent, was used in conjunction with iodoacetate to demonstrate the feasibility of selecting heterokaryons by producing complementary biochemical lesions in the parental cell strains. The potential for artifact in these systems is not, however, entirely precluded.
Secretion of a nerve growth factor by mouse neuroblastoma cells in culture.
Authors: Murphy R A , Pantazis N J , Arnason B G , Young M
Published: May 2006

Analyses of supernatant solutions from mouse C1300 neuroblastoma cultures by two independent immunoassays reveal that these cells secrete a factor which is immunochemically similar to mouse submaxillary gland nerve growth factor. The neuroblastoma factor is also biologically active in inducing neurite outgrowth from embryonic sensory ganglia-an effect that is completely blocked by specific antibody to nerve growth factor. Neuroblastoma cells are known to be functionally responsive to nerve growth factor, and the observation that they secrete a molecule like it may mean that these cells require or utilize the factor during growth in culture.
Third component of complement (C3): structural properties in relation to functions.
Authors: Bokisch V A , Dierich M P , Mūller-Eberhard H J
Published: May 2006

The third component of complement (C3) fulfills a pivotal role in the functions of the complement system. We have investigated the topological relationships among its polypeptide chains, physiologic fragments, enzyme attack regions, and functional sites. C3 consists of two chains (alpha and beta) which are linked by disulfide bonds and noncovalent forces and which have molecular weights of, respectively, 120,000 and 75,000. C3 is activated by action of C3 convertase on the alpha-chain. With hydrolysis of one polypeptide bonds, C3a, the 9000 dalton activation peptide is dislocated from the NH2-terminal portion of the alpha-chain. A previously concealed binding region is thereby transiently revealed in the C3b-fragment (181,000 dalton) which displays affinity for apparently nonspecific acceptors present on biological membranes. Binding of nascent C3b membranes occurs through the C3d portion of the fragment because subsequent action of the C3b-inactivator or trypsin on bound C3b causes release of C3c, but not of C3d. Bound C3b and C3d possess stable sites that are capable of binding to specific receptors present on a limited variety of cells. We propose that all known physiologically occurring fragments of C3 arise by enzymatic cleavage of the alpha-chain: C3a, C3b, C3c, and C3d. Whereas C3a (alpha1) and C3e (alpha2) consist of a single chain and C3b consists of two chains (alpha' and beta), C3c is composed of the entire beta-chain and multiple fragments of the alpha-chain, each of which is linked by disulfide bonds to the beta-chain.
On the significance of the retention of ligand by protein.
Authors: Silhavy T J , Szmelcman S , Boos W , Schwartz M
Published: May 2006

When a solution of binding protein and its ligand is dialyzed against a large volume of ligand-free medium the rate of exit of the ligand from the protein-containing compartment can be extremely slow, much slower than the rate observed in the absence of protein. This is what we call retention of ligand by protein. A simple calculation demonstrates that when the protein concentration is in large excess over the total ligand concentration, the exit of ligand follows quasi-first-order kinetics, the half-life being proportional to (1 + (P)/Kd), where (P) is the concentration of binding sites, and Kd the dissociation constant characteristic of the equilibrium between the ligand and the protein. Experimental verification of this relation is provided in the case of the periplasmic maltose-binding protein of Escherichia coli; The implications of the retention effect in biochemical techniques are discussed, as well as its possible significance in biological phenomena, such as bacterial chemotaxis and transport, mechanism of hormone action, or transmission of the nerve impulse.
Effect of chromosomal proteins extractable with low concentrations of NaCl on chromatin structure of resting and proliferating cells.
Authors: Nicolini C , Ng S , Baserga R
Published: May 2006

When quiescent WI-38 cells are stimulated to proliferate by nutritional changes, the chromatin of stimulated cells shows an increased ellipticity in circular dichroism spectra and an increased ability to bind ethidium bromide. The differences between the chromatins of quiescent and stimulated cells are abolished if both chromatins are treated with 0.25 M NaCl. However, when salt-treated chromatins are reconstituted by dialysis agains 10 mM Tris-HCl, the difference in circular dichroism spectra and ethidium bromide binding re-appear. Furthermore, addition of the 0.25 M NaCl extract from chromatin of stimulated cells to chromatin of quiescent cells causes an increased ellipticity in circular dichroism spectra similar to that of stimulated chromatin. Since only proteins (mostly nonhistones) are detectable in the 0.25 M NaCl extract, these results strongly suggest that the chromosomal proteins extractable with low concentrations of salt are responsible for the functional and structural changes occurring in chromatin of WI-38 cells stimulated to proliferate.
Interaction of f1 histone with superhelical DNA.
Authors: Vogel T , Singer M F
Published: May 2006

The superhelicity of double-stranded, closed circular SV40 DNA was altered by the addition of various amounts of ethidium bromide. The interaction of f1 histone with the series of molecules of various superhelicities was studied. The extent of interaction increases with increasing superhelicity regardless of whether it is of the positive or negative sense. The interaction of f1 histone with superhelical DNA is shown to be reversible.
Relationship of the first step in protein synthesis to ppGpp: formation of A(5')ppp(5')Gpp.
Authors: Rapaport E , Svihovec S K , Zamecnik P C
Published: May 2006

In the presence of purified Escherichia coli lysyl-tRNA synthetase [L-lysine:tRNALys ligase (AMP-forming) EC 6.1.1.6], L-lysine, and ATP, addition of the nucleotide ppGpp results in formation of a unique product-A(5')ppp(5') Gpp. The same compound is also formed very rapidly in a cell-free protein-synthesizing system when ppGpp is added. The possible significance of this reaction in the rapid turnover of ppGpp and as a more general mechanism by which an AMP residue is activated and introduced onto a 5'-diphosphorylated species, including the 5'-end of an RNA, is further discussed.
Myogenesis of avian striated muscle in vitro: role of collagen in myofiber formation.
Authors: De la Haba G , Kamali H M , Tiede D M
Published: May 2006

The complex chemical environment required for the development of the myofiber (myotube) from embryonic avian muscle myoblasts in vitro has been simplified. Myotube formation is shown to occur in the presence of insulin, a low-molecular-weight (fusion) factor obtained from embryo extract, and a collagen substratum. In the absence of collagen, globular structures are formed which are microscopically identical to the globular syncytial structures previously described [de la Haba and Amundsen (1972) Proc. Nat. Acad. Sci. USA 69, 1131-1135]. A high-molecular-weight fraction from embryo extract will also promote myotube formation in the presence of the fusion factor. This fraction is shown to contain (a) collagen, which promotes myotube formation, and (b) an additional factor which also promotes myotube formation, and which we tentatively hypothsize to be an inducer of collagen synthesis by myogenic cells.
Interlocus variation of genetic distance and the neutral mutation theory.
Authors: Nei M , Tateno Y
Published: May 2006

Theoretical distributions of genetic distance between reproductively isolated taxa are derived by means of computer simulation, taking into account mutation and random genetic drift. The distributions obtained are in good agreement with the observed distributions of interracial and interspecific genetic distances for enzymes loci in Drosophila. This indicates that the gene substitution at enzyme loci can be explained by the neutral mutation theory.
Oncornavirus-like particles from cultured bone marrow cells preceding leukemia and malignant histiocytosis.
Authors: Vosika G J , Krivit W , Gerrard J M , Coccia P F , Nesbit M E , Coalson J J , Kennedy B J
Published: May 2006

Particles with the density and enzymatic activity characteristic of known oncornavirus have been previously described in bone marrow cells from patients with leukemia in relapse and in remission. We have confirmed these findings and studied two patients in whom preleukemia was among the diagnostic considerations. Following cultivation of bone marrow from these patients for 1 week in conditioned media with dexamethasone, a high-speed pellet of the supernatant fluid and disrupted cells was prepared and analyzed on a sucrose gradient for enzymatic activity characteristic of RNA-directed DNA polymerase (reverse transcriptase). Peaks of endogenous DNA polymerase activity showing ribonuclease sensitivity and/or stimulation with the synthetic template poly(rC)-(dG)12-18 were demonstrated in both patients at densities of 1.15 to 1.19 and 1.21 to 1.24 g/ml. Subsequently, diagnosis 2 and 4 months after initial evaluation revealed acute myelogenous leukemia and malignant histiocytosis, respectively. Prior studies have suggested a possible etiological significance of such particles in human leukemia. The demonstration of similar particles preceding clinically overt disease in these patients supports this hypothesis and offers the possibility of early diagnosis and treatment.
Statistical analyses of Drosophila and human protein polymorphisms.
Authors: Ota T
Published: May 2006

By using the distribution function of allelic frequencies which was recently derived by Kimura and Ota for the model of stepwise production of neutral alleles, the observed protein polymorphisms of Drosophila and man are tested for fit to the theory of neutral protein variation. The observed and theoretical distributions of alleles agree quite well except for the excess of rare alleles in the actual distributions. In human polymorphisms, the alleles with frequencies less than 1% are more numerous than expected, whereas in Drosophila, those with frequencies less than 10% are more numerous. It is pointed out that these results support my thesis that mutational pressure rather than balancing selection is the main cause for the maintenance of protein polymorphisms.
Spectra of convolution operators on

L
p

spaces
Authors: Zafran Misha
Published: May 2006

Let 1 <
p
< ∞ with
p
≠ 2. Let
G
denote the
n
-torus or Euclidean
n
-space, and let Γ be the dual group of
G
. We show the existence of a multiplier transformation
T
on

L
p
(G)

which satisfies the following properties: (
a
) the transform
T̂
of
T
is smooth and vanishes at infinity on Γ; (
b
) the spectrum of
T
on

L
p
properly

contains
T̂
(Γ)∪{0}.
Correlation of moth sex pheromone activities with molecular characteristics involved in conformers of bombykol and its derivatives.
Authors: Kikuchi T
Published: May 2006

Molecular characteristics of bombykol and its 11 derivatives, which reveal significant correlations with biological activities for single sex pheromone receptor cells of four moth species, Bombyx mori, Aglia tau, Endromis versicolora, and Deilephila euphorbiae, were examined on the assumption of the "bifunctional unit model." Probabilities of bifunctional unit formations of those 12 compounds were assessed with frequency distribution patterns of distances between the proton acceptor, the proton donor, and the methyl group involved in a total of 1,200 conformers. A highly significant correlation exists between biological activity for each species and the probability of a particular bifunctional unit formation: a proton acceptor (A)--a methyl group (Me) unit (A--Me distances: about 6 A) for Deilephila (r = 0.94); a proton acceptor (A)--a proton donor (D)(A--D: about 11 A) for Aglia (r = 0.83); two antagonistic proton donor--methyl units (D--Me: about 14 and 5 A for favorable and adverse unit, respectively) for Bombyx (r = 0.94) and Endromis (r = 0.92).
Redox equilibria of liganded forms of methemoglobin.
Authors: Bull C , Hoffman B M
Published: May 2006

We have examined the redox equilibria of azidomethemoglobin (low-spin) and fluoromethemoglobin (high-spin). We have derived a modified Hill equation which includes the tetramer--dimer equilibrium of the oxidized form, and also generalized the two-state model to incorporate ligand binding to the ferriheme. The pH dependence of the redox Hill's constant for fluoromethemoglobin is the same as that for methemoglobin, demonstrating that this dependence and the marked cooperativity achieved (n = 2.2) are not coupled to changes of the ferriheme spin state. The redox Hill's constant for azidomethemoglobin, however, is as large as the oxygenation Hill's constant (n approximately 2.7) and is also roughly pH independent.
A spike-forming model of the neural membrane.
Authors: Wooldridge D E
Published: May 2006

A model of the neural membrane is described, based on a set of "convertible gates" on its inner surface. The atomic arrangement of a gate is specified to be subject to modification by a set of chemical reactions, sometimes permitting sodium ions, sometimes potassium ions, sometimes neither, to have access to the transmembrane channel it guards. Reaction rate and current/voltage equations are developed, values assigned to the parameters, and computer solutions obtained. Under pulse or continuous stimulating current the model is found to generate action potential spikes closely similar in height and shape to those of real neurons. Other electrical properties are also relatively neuron-like.
Mechanism of removal of senescent cells by human macrophages in situ.
Authors: Kay M M
Published: May 2006

Mechanisms by which macrophages discriminate between "mature-self" and "senescent-self" were investigated using the human red blood cell (RBC) system as a model. Conditions simulating those encountered in situ were adhered to as closely as possible by using short term culture techniques and incubating with autologous macrophages and immunoglobulins (Ig). It was found that RBC aged in vitro were phagocytized when they were incubated in pooled, normal human IgG, allogeneic Ig, autologous IgG or Ig, washed with medium, and then incubated with autologous macrophages. RBC treated in the same way but incubated in IgM or Iga, Ig-depleter serum, or Medium 199 alone were not phagocytized. This indicates that Ig is required for phagocytosis and suggests that the Ig which attaches to RBC is IgG. When freshly drawn RBC were separated into young (Y) and old (O) RBC according to density and incubated with autologous macrophages, less than 5% of the Y-RBC were phagocytized, whereas greater than 30% of the O-RBC were phagocytized, independent of whether the final incubations were performed in medium without serum (Y-RBC, 5 +/- 2% phagocytized; O-RBC, 33 +/- 1.5%), or autologous Ig-depleted serum (Y-RBC, 2 +/- 2.5%; O-RBC, 51 +/- 17%), or whole serum (Y-RBC, 0%; O-RBC, 43 +/- 5%). This indicates that (1) the Ig is attached in situ to the old RBC, and (2) that phagocytic recognition is not inhibited by other serum components. Scanning electron microscopy, employing labeled anti-IgG, IgM, and IgA reagents, revealed that Y-RBC had essentially no Ig on their surface, whereas old RBC had IgG on their surface. These findings indicate that IgG attaches in situ to senescent human RBC, making them vulnerable to phagocytosis by macrophages.
In vitro infection of lymphoid cells by thymotropic radiation leukemia virus grown in vitro.
Authors: Haas M , Hilgers J
Published: May 2006

Murine lymphoid cells were infected in vitro with purified leukemogenic radiation leukemia virus (RadLV) produced by virus-induced lymphoblast cell lines. Thymocytes were shown to be highly susceptible to infection by the virus, whereas murine or other fibroblasts were refractory to it. Murine bone marrow and spleen cells were shown to be much less sensitive to infection by this thymotropic RadLV. By comparison, a B-tropic RadLV isolate (RadLV), propagated on a mouse fibroblast cell line, was noninfectious for lymphoid cells but infected fibroblasts. A correlation was shown to exist between in vitro infection of thymocytes, as assayed by immunofluorescence, and in vivo leukemogenicity of the thymotropic RadLV. This constitutes a rapid in vitro test for in vivo leukemogenicity of a natural lymphatic leukemia virus.
Analysis of incipient reproductive isolation within a species of Drosophila.
Authors: Dobzhansky T
Published: May 2006

Drosophila willistoni and its subspecies quechua are morphologically indistinguishable, but differ in relative frequencies of certain allozyme genes. The cross quechua female X willistoni male produces nearly or completely sterile males, while the reciprocal cross gives fertile males. Hybrid females are fertile. Analysis of the sterility with the aid of chromosomes marked with mutant genes shows that the second and X-chromosomes have major and third chromosomes minor effects. Backcross males of the same chromosomal constitution may be either fertile or sterile; the threshold effect may be due to environmental variations or to gene variants present in the strains crossed. Only a trace of ethological isolation between the subspecies is present. In contrast to a narrowly localized and geographically isolated subspecies bogotana of D. pseudoobscura, the subspecies quechua of D. willistoni is fairly widespread, although its geographic area is not accurately known. Neither with bogotana nor with quechua are there valid reasons to suppose that these subspecies are of very recent origin.
Energy-dependent binding of dansylgalactoside to the lac carrier protein: direct binding measurements.
Authors: Schuldiner S , Weil R , Kaback H R
Published: May 2006

High specific activity 6'-N-[3H]dansyl)aminohexyl 1-thio-beta-D-galactopyranoside (Dns6-Gal) has been synthesized, and its binding to Escherichia coli membrane vesicles measured directly by flow dialysis. With ML 308-225 vesicles containing the lac carrier protein, specific binding is not detected in the absence of D-lactate or reduced phenazine methosulfate. In the presence of these electron donors, binding is observed, and the binding constant and number of binding sites are approximately 4 muM and 1.5 nmol/mg of membrane protein, respectively. These values are in excellent agreement with those obtained by fluorescence titration. p-Chloromercuribenzenesulfonate, which directly inactivates the lac carrier protein, and carbonylcyanide m-chlorophenylhydrazone, which collapses the membrane potential, cause release of bound Dns6-Gal. Moreover, significant binding is not observed with membrane vesicles that are devoid of the lac carrier protein. The results provide qualitative and quantitative confirmation of previous studies which indicate that changes in dansylgalactoside fluorescence observed on "energization" of membrane vesicles reflect binding of the probe to the lac carrier protein.
Free energy levels and entropy production associated with biochemical kinetic diagrams.
Authors: Hill T L , Simmons R M
Published: May 2006

"Basic" and "gross" free energy levels are defined for the discrete states of a macromolecular biochemical kinetic system such as a free energy transducing enzyme (e.g., myosin or Na,K-ATPase). Basic free energy level differences are related to the first-order rate constants for transitions between states while gross free energy differences, along with the corresponding fluxes, determine the rate of entropy production in the system. In muscle contraction the analysis is complicated by the possibility of the system doing external mechanical work. The question of the sign of the flux or of the gross free energy level change in a given transition is examined for both single-cycle and multi-cycle models. More definite statements can be made in single-cycle cases. Some numerical examples are included. The more complicated cases are reserved for a subsequent paper.
Deep inelastic scattering of leptons
Authors: Schwinger Julian
Published: May 2006

The description of deep inelastic scattering as an extrapolation between resonance production and diffractive scattering is extended to give successful quantitative representations for the structure functions of unpolarized electron scattering on protons and neutrons, and of neutrino, antineutrino scattering on nucleons. The same ideas also supply a prediction for the polarization asymmetry in deep inelastic electron-proton scattering (paper no. 2, to be published).
A structural model of radiation effects in living cells.
Authors: Neyman J , Puri P S
Published: May 2006

The chance mechanism of cell damage and of repair in the course of irradiation involves two details familiar to biologists that thus far seem to have been overlooked in mathematical treatment. One of these details is that, generally, the passage of a single "primary" radiation particle generates a "cluster" of secondaries which can produce "hits" that damage the living cell. With high linear energy transfer, each cluster contains very many secondary particles. With low linear energy transfer, the number of secondaries per cluster is generally small. The second overlooked detail of the chance mechanism is concerned with what may be called the time scales of radiation damage and of the subsequent repair. The generation of a cluster of secondary particles and the possible hits occur so rapidly that, for all practical purposes, they may be considered as occurring instantly. On the other hand, the subsequent changes in the damaged cells appear to require measurable amounts of time. The constructed stochastic model embodies these details, the clustering of secondary particles and the time scale difference. The results explain certain details of observed phenomena.
Stepwise biosynthesis in vitro of globin genes from globin mRNA by DNA polymerase of avian myeloblastosis virus.
Authors: Rougeon F , Mach B
Published: May 2006

Two approaches have been explored for the synthesis of double-stranded DNA from single-stranded DNA template complementary to rabbit 9S globin mRNA (cDNA). (i) cDNA was elongated with dCMP or dTMP homopolymeric tracts using terminal deoxynucleotidyltransferase (EC 2.7.7.31; nucleosidetriphosphate:DNA deoxynucleotidylexotransferase). cDNA-dC, in the presence of an oligo(dG)10 primer, was an efficient template with either DNA polymerase of Escherichia coli (EC 2.7.7.7; deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase) or RNA-directed DNA polymerase of avian myeloblastosis virus. cDNA-dT [ with an oligo(dA)10 primer] functioned as template only with E. coli polymerase. (ii) cDNA, without homopolymeric tails, was also efficiently copied in the absence of oligonucleotide primer, by DNA polymerase of avian myeloblastosis virus or of E. coli. The product of the reaction consisted of long hairpin molecules which could be converted into DNA duplex (melting temperature, 93 degrees) by digestion with single-strand nuclease S1. The data indicate that a loop structure on the 3' end of cDNA allowed DNA synthesis to take place by a "self-priming" mechanism. Some of the double-stranded DNA synthesized corresponded to the entire sequence of the 9S mRNA template. The synthesis of full-length double-stranded DNA from mouse globin mRNA and immunoglobulin light chain mRNA is also discussed.
Choleragen-mediated release of trapped glucose from liposomes containing ganglioside GM1.
Authors: Moss J , Fishman P H , Richards R L , Alving C R , Vaughan M , Brady R O
Published: May 2006

125I-Labeled choleragen was bound to liposomes containing galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosylglucosylceramide (GM1), but not in large amounts to ganglioside-free liposomes nor to those containing N-acetylneuraminylgalactosylglucosylceramide (GM3), N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosylglucosylceramide (GM2), or N-acetylneuraminylgalactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosylglucosylceramide (GD1a). Choleragen released trapped glucose only from GM1-liposomes. This choleragen-induced glucose release from GM1-liposomes was relatively rapid for the first few minutes, then continued more slowly. The amount of glucose released from liposomes in 30 min was dependent on both the GM1 content and choleragen concentration. Prior incubation of GM1-liposomes with anti-GM1 antiserum prevented the choleragen-dependent release of trapped glucose. After incubation of GM1-liposomes with choleragen, addition of anticholeragen antibodies and complement led to more extensive glucose release. Under these latter conditions a much smaller glucose release was observed also from liposomes containing GM1 or N-acetylneuraminylgalactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosylglucosylceramide in the absence of choleragen. These releases were attributed to naturally-occurring antiganglioside antibodies in the antiserum and complement. Ganglioside-free liposomes did not release glucose in response to anticholeragen and complement. It appears that choleragen in the absence of other proteins binds specifically to liposomes containing GM1 and can induce permeability changes.
RNase sensitivity of an anterior morphogenetic determinant in an insect egg (Smittia sp., Chironomidae, Diptera).
Authors: Kandler-Singer I , Kalthoff K
Published: May 2006

In chironomid midges, the development of head and thorax in the embryo requires the function of cytoplasmic determinants localized near the anterior pole of the egg. Experimental inactivation of these determinants causes a dramatic switch in the developmental program of the embryo. Instead of the normal segment pattern, the aberrant pattern "double abdomen" is formed. Head, thorax, and anterior abdominal segments are then replaced by an additional set of posterior abdominal segments joined in mirror image symmetry to the original abdomen. Such double abdomens have been produced, with a maximum yield of 29%, by application of RNase (ribonuclease I, ribonucleate 3'-pyrimidino-oligonucleotidohydrolase, EC 3.1.4.22) to the anterior pole region of the egg. This was achieved by microinjection or puncturing the eggs during submersion in RNase. Control experiments with inactive RNase S fragments reliably proved that double abdomen formation resulted from RNase activity. Neither application of other enzymes to the anterior pole region nor application of RNase to other egg regions produced double abdomens in significant yields. The effects of RNase concentration and stage of development were determined. The data from these and earlier experiments are compatible with the idea that stored cytoplasmic RNP particles act as anterior determinants. Similarities to genetically caused switches in developmental pathways (homeotic mutations) are discussed.
Analogue solution for electrical capacity of membrane-covered cubes in cubic array at high concentration.
Authors: Cole K S
Published: May 2006

Earlier measurements have shown that the equations derived for the resistance of suspension of spheres apply up to a volume concentration of 100% for close-packing forms. They have also shown, by a resistance-capacitance analogue, that they apply for the capacity of a close-packing of membrane-covered square cylinders in square array, approximating muscle and nerve. The present work is an extension of the two-dimensional to a three-dimensional array of membrane-covered cubes in a cubic array. It is found by measurements of a three-dimensional electrolytic analogue that the capacitance is indeed expressed by an extension of the analytic solution at low concentrations up to 100% volume concentration of the membrane-covered form, such as epithelial tissues. There is thus at least one example each of two-and three-dimensional forms which conform to the low concentration analysis up to 100% volume and so give a basis for the extensions to other and more complicated forms to complete a survey to work begun by Fricke in 1923.
Role of antigenic structure in cell to cell cooperation.
Authors: Schwartz M , Hooghe R J , Mozes E , Sela M
Published: May 2006

Two synthetic polypeptides which differ only in the order of amino acids in their NH2-terminal side chains, namely, (Tyr-Tyr-Glu-Glu)-poly(DLAla)- -poly(LLys) and (Tyr-Glu-Try-Glu)-poly(DLAla)- -poly(LLys), were found to be under different genetic control. By three different in vivo systems for thymus-derived cell depletion, it was demonstrated that (Tyr-Tyr-Glu-Glu)-poly(DLAla)- -poly(LLys), which represents the random poly(Tyr,Glu)-poly(DLAla)- -poly(Lys) in the pattern of immune responses and in the quality of antibodies they elicit, is thymus-dependent whereas (Tyr-Glu-Tyr-Glu)-poly(DLAla)-poly(LLys) does not require thymus-derived cell help for efficient antibody production. Therefore, the two ordered polypeptides which are similar chemically differ in parameters, not yet determined, which affect their capability to trigger bone marrow-derived cells.
Renal CO2 production from glutamine and lactate as a function of arterial perfusion pressure in dog.
Authors: Baruch S B , Eun C K , MacLeod M , Pitts R F
Published: May 2006

The energy cost of renal function in the intact kidney of the dog was assessed at a series of arterial perfusion pressures. Pressure was varied by partially inflating a balloon at the tip of a catheter positioned in the aorta above the origins of the renal arteries.Either L-[U-14C]-lactate was infused intravenously in tracer amounts throughout each experiment. Total renal CO2 production and 14CO2 production from each isotope permitted assessment of total renal oxidative metabolism and the proportions derived from the two major substrates of the kidney. Stepwise inflation of the aortic balloon progressively lowered glomerular filtration rate, renal blood inflow, filtered and consequently reabsorbed Na+, total renal CO2 production, and 14CO2 derived from glutamine and lactate. The percent of total CO2 derived from lactate decreased more or less in proportion to the decrease in percent of total CO2 produced. Results were consistent with the view that reabsorption of sodium is the major energy sink of the kidney. They suggest that the oxidation of glutamine supplies energy for tubular transport and basal demands such as synthesis of hormones and maintenance of structure, whereas the oxidation of lactate supplies energy mainly for transport activities.