bluuebunny/crossref_metadata_2025 huggingface dataset:
Human thyroid peroxidase: complete cDNA and protein sequence, chromosome mapping, and identification of two alternately spliced mRNAs.
Authors: Kimura S , Kotani T , McBride O W , Umeki K , Hirai K , Nakayama T , Ohtaki S
Published: May 2006

Two forms of human thyroid peroxidase cDNAs were isolated from a lambda gt11 cDNA library, prepared from Graves disease thyroid tissue mRNA, by use of oligonucleotides. The longest complete cDNA, designated phTPO-1, has 3048 nucleotides and an open reading frame consisting of 933 amino acids, which would encode a protein with a molecular weight of 103,026. Five potential asparagine-linked glycosylation sites are found in the deduced amino acid sequence. The second peroxidase cDNA, designated phTPO-2, is almost identical to phTPO-1 beginning 605 base pairs downstream except that it contains 1-base-pair difference and lacks 171 base pairs in the middle of the sequence. This results in a loss of 57 amino acids corresponding to a molecular weight of 6282. Interestingly, this 171-nucleotide sequence has GT and AG at its 5' and 3' boundaries, respectively, that are in good agreement with donor and acceptor splice site consensus sequences. Using specific oligonucleotide probes for the mRNAs derived from the cDNA sequences hTPO-1 and hTPO-2, we show that both are expressed in all thyroid tissues examined and the relative level of two mRNAs is different in each sample. These results suggest that two thyroid peroxidase proteins might be generated through alternate splicing of the same gene. By using somatic cell hybrid lines, the thyroid peroxidase gene was mapped to the short arm of human chromosome 2.
Molecular cloning and analysis of functional cDNA and genomic clones encoding bovine cellular retinoic acid-binding protein.
Authors: Shubeita H E , Sambrook J F , McCormick A M
Published: May 2006

A recombinant cDNA clone, pCRABP-HS1, encoding cellular retinoic acid-binding protein was isolated from a bovine adrenal cDNA library. COS-7 cells transfected with pCRABP-HS1 produced a biologically active retinoic acid-binding protein molecule of the expected molecular mass (15.5 kDa). RNA blot hybridization analysis using pCRABP-HS1 as a probe revealed a single 1050-nucleotide mRNA species in bovine adrenal, uterus, and testis, tissues that contain the highest levels of retinoic acid-binding activity. No hybridization was detected in RNA extracted from ovary, spleen, kidney, or liver, which contain relatively low levels of cellular retinoic acid-binding protein activity. Analysis of genomic clones isolated from an EcoRI bovine genomic library demonstrated that the bovine cellular retinoic acid-binding protein gene is composed of four exons and three introns. Two putative promoter sequences were identified in the cloned 5' sequence of the gene.
Related polypeptides are encoded by Drosophila F elements, I factors, and mammalian L1 sequences.
Authors: Di Nocera P P , Casari G
Published: May 2006

The structural organization of Drosophila F elements closely resembles that of L1 sequences, a major family of repetitive DNA elements dispersed in the genome of all mammals. Members of both families are flanked by target-site duplications of different length, vary in size because of heterogeneity at one end, and invariably terminate at the other end in characteristic adenosine-rich stretches often preceded by polyadenylylation signals. The nucleotide sequence of Fw, an F element found in the white locus of wi+A flies, reveals a large open reading frame upstream of the 3' adenosine-rich terminus encoding a possible reverse transcriptase homologous to those potentially encoded by functional L1 units and Drosophila I factors. A cysteine-rich region within an interrupted frame located at the 5' terminus of Fw suggests that complete F elements might additionally encode a nucleic acid binding protein. The observation that F elements and I factors encode functionally related polypeptides, and the extensive similarity of their hypothetical reverse transcriptases to L1 open reading frames, favors the hypothesis that all these sequences are evolutionarily related and transpose upon the cDNA conversion of RNA intermediates.
General anesthetics can competitively interfere with sensitive membrane proteins.
Authors: Tas P W , Kress H G , Koschel K
Published: May 2006

It is not known whether proteins or lipids are the primary target of anesthetic action. The resolution of this problem is hampered by the fact that it is not possible to investigate the biological activity of integral membrane proteins in the absence of lipids. However, certain characteristics of membrane protein function inhibition by anesthetics cannot be explained on the basis of an indirect inhibition by disturbance of the lipid bilayer and, therefore, most likely are the result of a direct anesthetic-protein interaction. This is the case (i) when the anesthetics competitively interfere with the binding of an endogenous ligand to the membrane protein and (ii) when the size of the anesthetic molecule is of importance for the potency and/or mechanism of inhibition. The present study shows that this is true for a membrane transport system, the Na+/K+/Cl- cotransport in glial-type cells.
Expression of enzymatically active poliovirus RNA-dependent RNA polymerase in Escherichia coli.
Authors: Morrow C D , Warren B , Lentz M R
Published: May 2006

The poliovirus genome is replicated by a virus-encoded RNA-dependent RNA polymerase (RNA polymerase). The RNA polymerase is first synthesized as a larger precursor polypeptide, which is subsequently processed by a viral proteinase, 3Cpro, to give the mature polymerase molecule, 3Dpol. To further characterize the poliovirus RNA polymerase, we have constructed plasmids that expressed this protein in Escherichia coli. The plasmids consisted of fusions between the E. coli DNA encoding the first 13 amino acids of the trp operon leader protein and viral genes encoding the 3Cpro and 3Dpol polypeptides. E. coli harboring such plasmids gave significant, inducible levels of enzymatically active RNA polymerase as determined by the poly(A).oligo(U) poly(U) polymerase assay. The purified RNA polymerase activity from E. coli corresponded to a protein with the approximate molecular weight of the mature 3Dpol protein. The availability of a recombinant, enzymatically active poliovirus RNA polymerase provides a system in which we can precisely delineate the role this enzyme plays in the regulation of poliovirus replication.
Consequences of detailed balance in a model for sensory adaptation based on ligand-induced receptor modification.
Authors: Walz D , Caplan S R
Published: May 2006

A model for exact sensory adaptation has been published by Segel and co-workers in several papers [e.g., Knox, B. E., Devreotes, P. N., Goldbeter, A. & Segel, L. A. (1986) Proc. Natl. Acad. Sci. USA 83, 2345-2349]. The model comprises a pair of states whose relative probabilities are determined by the binding of a ligand. A second pair of states related by the same ligand binding is accessible as a consequence of either a conformational change or a "covalent modification." By taking proper account of detailed balance, we show that the notion of covalent modification in this context includes three cases, two of which involve dissipation of metabolic energy. The condition for exact adaptation is dependent on metabolite concentrations in all cases of covalent modification. The performance of the model is critically examined on thermodynamic and kinetic grounds.
Evolution and maintenance of quantitative genetic variation by mutations.
Authors: Cockerham C C , Tachida H
Published: May 2006

The genotypic variance within, sigma 2w, and between, sigma 2b, random mating populations and rates and times for convergence to equilibrium values from different founder populations are formulated for an additive genetic model with an arbitrary number of alleles k, number of loci m, population size N, and mutation rate u, with unequal mutation rates for alleles. As a base of reference, the additive variance sigma 2a in an infinite equilibrium population is used. sigma 2a increases as k increases and decreases with variation in the mutation rates. Both transitional and equilibrium values of the variance within populations could be expressed as sigma 2w = (1 - theta)sigma 2a, where theta is the coancestry with mutations of individuals within populations. Thus, rates of convergence and evolutionary times are a function of those for theta, which involves both N and u. When the founder population is fixed, very long times are required to obtain a perceptible increase in sigma 2w and equilibrium values of sigma 2w are very small when 4Nu less than or equal to 10(-1). The variance between populations can be expressed as sigma 2b = 2 theta sigma 2a when the founder population is an infinite equilibrium population, and as sigma 2b = 2(theta - alpha)sigma 2a when the founder population is fixed, where alpha is a function only of u. In this latter case, rates of divergence, while affected by both N and u, are dominated by u and asymptotically a function of u only. With u = 10(-5), very long times (10(3) generations) are required for any perceptible divergence, even for N = 1-10. At equilibrium, most of the variance is between small populations and within very large populations. Migration increases the variance within populations and decreases the variance between populations.
Activated neu oncogene sequences in primary tumors of the peripheral nervous system induced in rats by transplacental exposure to ethylnitrosourea.
Authors: Perantoni A O , Rice J M , Reed C D , Watatani M , Wenk M L
Published: May 2006

Neurogenic tumors were selectively induced in high incidence in F344 rats by a single transplacental exposure to the direct-acting alkylating agent N-ethyl-N-nitrosourea (EtNU). We prepared DNA for transfection of NIH 3T3 cells from primary glial tumors of the brain and from schwannomas of the cranial and spinal nerves that developed in the transplacentally exposed offspring between 20 and 40 weeks after birth. DNA preparations from 6 of 13 schwannomas, but not from normal liver, kidney, or intestine of tumor-bearing rats, transformed NIH 3T3 cells. NIH 3T3 clones transformed by schwannoma DNA contained rat repetitive DNA sequences, and all isolates contained rat neu oncogene sequences. One schwannoma yielded a transformant with rat-specific sequences for both neu and N-ras. A point mutation in the transmembrane region of the putative protein product of neu was identified in all six transformants and in the primary tumors from which they were derived as well as in 5 of 6 schwannomas tested that did not transform NIH 3T3 cells. Of 59 gliomas, only one yielded transforming DNA, and an activated N-ras oncogene was identified. The normal cellular neu sequence for the transmembrane region, but not the mutated sequence, was identified in DNA from all 11 gliomas surveyed by oligonucleotide hybridization. Activation of the neu oncogene, originally identified [Schechter, A.L., Stern, D.F., Vaidyanathan, L., Decker, S.J., Drebin, J.A., Greene, M.I. & Weinberg, R.A. (1984) Nature (London) 312, 513-516] in cultured cell lines derived from EtNU-induced neurogenic tumors that by biochemical but not histologic criteria were thought to originate in the central nervous system in BD-IX rats, appears specifically associated with tumors of the peripheral nervous system in the F344 inbred strain.
Tissue-specific expression of insulin-like growth factor II mRNAs with distinct 5' untranslated regions.
Authors: Irminger J C , Rosen K M , Humbel R E , Villa-Komaroff L
Published: May 2006

We have used RNA from human hypothalamus as template for the production of cDNAs encoding insulin-like growth factor II (IGF-II). The prohormone coding sequence of brain IGF-II RNA is identical to that found in liver; however, the 5' untranslated sequence of the brain cDNA has no homology to the 5' untranslated sequence of the previously reported liver cDNAs. By using hybridization to specific probes as well as a method based on the properties of RNase H, we found that the human IGF-II gene has at least three exons that encode alternative 5' untranslated regions and that are expressed in a tissue-specific manner. A probe specific to the brain cDNA 5' untranslated region hybridizes to a 6.0-kilobase transcript present in placenta, hypothalamus, adrenal gland, kidney, Wilms tumor, and a pheochromocytoma. The 5' untranslated sequence of the brain cDNA does not hybridize to a 5.3-kilobase transcript found in liver or to a 5.0-kb transcript found in pheochromocytoma. By using RNase H to specifically fragment the IGF-II transcripts into 3' and 5' fragments, we found that the RNAs vary in size due to differences in the 5' end but not the 3' end.
Uptake and expression of bacterial and cyanobacterial genes by isolated cucumber etioplasts.
Authors: Daniell H , McFadden B A
Published: May 2006

The uptake and expression by plastids isolated from dark-grown cucumber cotyledons (etioplasts) of two pUC derivatives, pCS75 and pUC9-CM, respectively carrying genes for the large small subunits of ribulose bisphosphate carboxylase/oxygenase of Anacystis nidulans or chloramphenicol acetyltransferase, is reported. Untreated etioplasts take up only 3% as much DNA as that taken up by EDTA-washed etioplasts after 2 hr of incubation with nick-translated [32P]-pCS75. The presence or absence of light does not affect DNA uptake, binding, or breakdown by etioplasts. Calcium or magnesium ions inhibit DNA uptake by 86% but enhance binding (23-200%) and breakdown (163-235%) of donor DNA by EDTA-treated etioplasts. Uncouplers that abolish membrane potential (delta psi), transmembrane proton gradient (delta pH), or both do not affect DNA uptake, binding, or breakdown by etioplast. However, both DNA uptake and binding are severely inhibited by ATP. Presumably this results from the hydrolysis of ATP, because the poorly hydrolyzable analog adenyl-5'-yl imidodiphosphate does not inhibit the uptake or binding of DNA by etioplasts. beta-Lactamase specified by the ampicillin resistance gene of pCS75 can be detected only in EDTA-treated etioplasts that have been incubated with the plasmid pCS75. After the incubation of EDTA-treated etioplasts with pCS75, immunoprecipitation using antiserum to the small subunit of ribulose bisphosphate carboxylase/oxygenase from A. nidulans reveals the synthesis of small subunits; these are smaller by 2 kDa than the cucumber small subunit encoded by the nuclear genome. Treatment of etioplasts with 10 mM EDTA shows a 10-min duration to be optimal for the expression of chloramphenicol acetyltransferase encoded by pUC9-CM. A progressive increase in the expression of this enzyme is observed with an increase in the concentration of pUC9-CM in the DNA uptake medium. The plasmid-dependent incorporation of [35S]methionine by EDTA-treated organelles declines markedly during cotyledon greening in vivo.
Intramolecular recombination between partially homologous sequences in Escherichia coli and Xenopus laevis oocytes.
Authors: Abastado J P , Darche S , Godeau F , Cami B , Kourilsky P
Published: May 2006

We describe a system to analyze the individual contribution of a single physical DNA end on intramolecular recombination between partially homologous sequences. We took advantage of this partial sequence divergence to measure the distance separating the DNA end from the final recombination event. We show that a single physical DNA end stimulates recombination when located in a region of homology. Recombination frequency decreases gradually with the distance from the DNA end. A recombinational hot spot is found at the end of the region of homology. A large insertion of unrelated DNA interferes asymmetrically with this process, suggesting that a recombinogenic signal propagates along the region of homology.
Characterization of a purified nicotinic receptor from rat brain by using idiotypic and anti-idiotypic antibodies.
Authors: Abood L G , Langone J J , Bjercke R , Lu X , Banerjee S
Published: May 2006

The availability of an anti-nicotine monoclonal antibody has made it possible to further establish the nature of the nicotine recognition proteins purified from rat brain by affinity chromatography and to provide a highly sensitive assay for determining [3H]nicotine binding to the purified material. An enantiomeric analogue of nicotine, (-)-6-hydroxymethyl-nicotine, was used to prepare the affinity column. In addition, with the use of anti-idiotypic monoclonal antibody, it was confirmed that the recognition site for nicotine resides on a protein complex composed of two components with molecular masses of 62 and 57 kDa. It was also demonstrated that the same two proteins could be purified by immunoaffinity chromatography with the use of an anti-idiotypic monoclonal antibody. With the use of the anti-nicotine antibody to measure [3H]nicotine binding, the purified material was shown to bind 250 pmol/mg of protein. By utilizing a procedure in which the purified receptor protein was conjugated to membranes by disulfide bonds, a binding activity of 80 pmol/mg was obtained. With the availability of stereospecific monoclonal antibodies to (-)-nicotine as well as monoclonal anti-idiotypic antibodies derived when the anti-nicotine antibodies were used as immunogens, additional procedures became available for the further characterization of the purified nicotine receptor and examining its (-)-[3H]nicotine-binding characteristics.
UV-induced formation of pyrimidine dimers in nucleosome core DNA is strongly modulated with a period of 10.3 bases.
Authors: Gale J M , Nissen K A , Smerdon M J
Published: May 2006

We have determined the distribution of the major UV-induced photoproducts in nucleosome core DNA using the 3'----5' exonuclease activity of T4 DNA polymerase, which has been shown to stop digestion immediately 3' to UV-induced pyrimidine dimers. This assay is extremely sensitive since all DNA fragments without photoproducts (background) are reduced to small oligonucleotides, which can be separated from those fragments containing photoproducts. The results show that the distribution of UV-induced photoproducts (primarily cyclobutane dipyrimidines) is not uniform throughout core DNA but displays a striking 10.3 (+/- 0.1) base periodicity. Furthermore, this characteristic distribution of photoproducts was obtained regardless of whether nucleosome core DNA was isolated from UV-irradiated intact chromatin fibers, histone H1-depleted chromatin fibers, isolated mononucleosomes, or cells in culture. The yield of pyrimidine dimers along the DNA seems to be modulated in a manner that reflects structural features of the nucleosome unit, possibly core histone-DNA interactions, since this pattern was not obtained for UV-irradiated core DNA either free in solution or bound tightly to calcium phosphate crystals. Based on their location relative to DNase I cutting sites, the sites of maximum pyrimidine dimer formation in core DNA mapped to positions where the phosphate backbone is farthest from the core histone surface. These results indicate that within the core region of nucleosomes, histone-DNA interactions significantly alter the quantum yield of cyclobutane dipyrimidines, possibly by restraining conformational changes in the DNA helix required for formation of these photoproducts.
Brain cDNA clone for human cholinesterase.
Authors: McTiernan C , Adkins S , Chatonnet A , Vaughan T A , Bartels C F , Kott M , Rosenberry T L , La Du B N , Lockridge O
Published: May 2006

A cDNA library from human basal ganglia was screened with oligonucleotide probes corresponding to portions of the amino acid sequence of human serum cholinesterase (EC 3.1.1.8). Five overlapping clones, representing 2.4 kilobases, were isolated. The sequenced cDNA contained 207 base pairs of coding sequence 5' to the amino terminus of the mature protein in which there were four ATG translation start sites in the same reading frame as the protein. Only the ATG coding for Met-(-28) lay within a favorable consensus sequence for functional initiators. There were 1722 base pairs of coding sequence corresponding to the protein found circulating in human serum. The amino acid sequence deduced from the cDNA exactly matched the 574 amino acid sequence of human serum cholinesterase, as previously determined by Edman degradation. Therefore, our clones represented cholinesterase (EC 3.1.1.8) rather than acetylcholinesterase (EC 3.1.1.7). It was concluded that the amino acid sequences of cholinesterase from two different tissues, human brain and human serum, were identical. Hybridization of genomic DNA blots suggested that a single gene, or very few genes, coded for cholinesterase.
Identification and biochemical characterization of p70TRK, product of the human TRK oncogene.
Authors: Mitra G , Martin-Zanca D , Barbacid M
Published: May 2006

TRK is a human transforming gene generated in a colon carcinoma by a somatic rearrangement that fused a nonmuscle tropomyosin gene to sequences that shared extensive homology with members of the tyrosine-protein kinase supergene family. These sequences are likely to be derived from a transmembrane receptor gene whose putative ligand binding domain has been replaced by tropomyosin. In the present studies, we have expressed the entire coding sequences of the TRK oncogene as well as its protein kinase-related carboxyl-terminal domain in Escherichia coli. Antisera raised against these bacteria-synthesized TRK polypeptides has allowed us to identify the gene product of the TRK oncogene as a 70-kDa protein. Immunoprecipitates containing p70TRK have an associated protein kinase activity specific for tyrosine residues. Moreover, p70TRK is phosphorylated in vivo in serine (75%), threonine (20%), and tyrosine (5%) residues. Finally, immunofluorescence and cellular fractionation studies indicate that p70TRK is preferentially located in the cytoplasmic fraction.
Bacterial phytotoxin, syringomycin, induces a protein kinase-mediated phosphorylation of red beet plasma membrane polypeptides
Authors: Bidwai Ashok P. , Takemoto Jon Y.
Published: May 2006

Syringomycin, a peptide toxin and a virulence factor produced by the bacterial phytopathogen
Pseudomonas syringae
pv.
syringae
, stimulated the phosphorylation of several plasma membrane polypeptides of red beet storage tissue. Among these was a 100-kDa polypeptide, which corresponds in size to the proton pump ATPase. The phosphorylations were insensitive to hydroxylamine, indicating that the polypeptide phosphorylated intermediates involved phosphate ester bonds characteristic of protein kinase-mediated phosphorylation. Phosphorylation of the 100-kDa polypeptide and of most of the other polypeptides was reduced or eliminated by extraction of the membranes with 0.1% (wt/vol) sodium deoxycholate, a treatment that also eliminated the ability of the toxin to stimulate ATPase activity. Phosphorylation of the 100-kDa polypeptide was highest with 10-20 μg of syringomycin; the same amounts gave the highest degree of ATPase activity stimulation. Phosphorylation of some of the polypeptides was eliminated or decreased by the Ca
2+
chelator EGTA. Addition of excess Ca
2+
restored the phosphorylation of most of these polypeptides. We conclude that syringomycin acts by stimulating an endogenous membrane protein kinase activity, which results in the phosphorylation of several membrane polypeptides. One of the phosphorylated polypeptides corresponds in size to the proton pump ATPase.
Growth of human hemopoietic colonies in response to recombinant gibbon interleukin 3: comparison with human recombinant granulocyte and granulocyte-macrophage colony-stimulating factor.
Authors: Messner H A , Yamasaki K , Jamal N , Minden M M , Yang Y C , Wong G G , Clark S C
Published: May 2006

Supernatants of COS-1 cells transfected with gibbon cDNA encoding interleukin 3 (IL-3) with homology to sequences for human IL-3 were tested for ability to promote growth of various human hemopoietic progenitors. The effect of these supernatants as a source of recombinant IL-3 was compared to that of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) as well as to that of medium conditioned by phytohemagglutinin-stimulated leukocytes. The frequency of multilineage colonies, erythroid bursts, and megakaryocyte colonies in cultures containing the COS-1 cell supernatant was equivalent to the frequency observed in the controls and significantly higher than found in cultures plated with recombinant GM-CSF. G-CSF did not support the formation of multilineage colonies, erythroid bursts, and megakaryocyte colonies. In contrast, growth of granulocyte-macrophage colonies was best supported with GM-CSF, while recombinant IL-3 yielded colonies at lower or at best equivalent frequency. The simultaneous addition of higher concentrations of GM-CSF to cultures containing IL-3 in optimal amounts did not enhance the formation of multilineage colonies, erythroid bursts, and megakaryocyte colonies. However, the frequency of such colonies and bursts increased with GM-CSF when cultures were plated with suboptimal concentrations of IL-3. Growth of colonies within the granulocyte-macrophage lineage is optimally supported by GM-CSF and does not increase with further addition of IL-3.
Recovery from ultraviolet light-induced inhibition of DNA synthesis requires umuDC gene products in recA718 mutant strains but not in recA+ strains of Escherichia coli.
Authors: Witkin E M , Roegner-Maniscalco V , Sweasy J B , McCall J O
Published: May 2006

Ultraviolet light (UV) inhibits DNA replication in Eschericia coli and induces the SOS response, a set of survival-enhancing phenotypes due to derepression of DNA damage-inducible genes, including recA and umuDC. Recovery of DNA synthesis after UV irradiation ("induced replisome reactivation," or IRR) is an SOS function requiring RecA protein and postirradiation synthesis of additional protein(s), but this recovery does not require UmuDC protein [Khidhir, M. A., Casaregola, S. & Holland, I. B. (1985) Mol. Gen. Genet. 199, 133-140]. IRR occurs in strains carrying either recA718 (which does not reduce recombination, SOS inducibility, or UV mutagenesis) or umuC36 (which eliminates UV mutability), but not in recA718 umuC36 double mutants. In recA430 mutant strains, IRR does not occur whether or not functional UmuDC protein is present. IRR occurs in lexA-(Ind-) (SOS noninducible) strains if they carry an operator-constitutive recA allele and are allowed to synthesize proteins after irradiation. We conclude the following: (i) that UmuDC protein corrects or complements a defect in the ability of RecA718 protein (but not of RecA430 protein) to promote IRR and (ii) that in lexA(Ind-) mutant strains, IRR requires amplification of RecA+ protein (but not of any other LexA-repressed protein) plus post-UV synthesis of at least one other protein not controlled by LexA protein. We discuss the results in relation to the essential, but unidentified, roles of RecA and UmuDC proteins in UV mutagenesis.
Explanation of parity nonconservation
Authors: Segal I. E. , Ørsted B. , Paneitz S. M. , Vogan D. A.
Published: May 2006

Space inversion and other discrete symmetries are treated within the frame of a theory of fundamental forces based only on general considerations of causality, symmetry, and stability, without ad hoc differential equations. The basic space-time ˜M is the Einstein universe
R
1
×
S
3
as a causal (or conformal) rather than a pseudo-Riemannian manifold. Its connected symmetry group is then a 15-parameter group ˜G locally equivalent to
SO
(2, 4), while the isometry group ˜K of the Einstein universe is a 7-parameter subgroup. Correlation with conventional relativistic theory is based on a canonical imbedding of Minkowski space M
0
into ˜M, together with the unique extendability of all transformations of the scaling-extended Poincaré group ˜P from M
0
to global transformations on ˜M. The fundamental fermion field F and boson field B are here restricted to be real and are fully invariant under ˜G
e
, where the superscript e denotes the inclusion of space and time inversions. The role of
C
on F is taken over by a real matrix having the eigenvalues ±
i
, that commutes with ˜G but anticommutes with space inversion. The spin space for B consists of the real linear transformations on that for F. There is a corresponding natural total Lagrangian that is both ˜G
e
and
O
(2)-gauge invariant, the latter leading to lepton and baryon number conservation, and which is nonparametric except for scale. The Weyl and Maxwell equations are deduced, and compelling identifications made for neutrinos and the photon. The
e
and μ neutrino pairs occur in strikingly inequivalent positions in F, appearing symmetric only in the conventional relativistic limit
R
→ ∞, where
R
is the (˜G-invariant) fundamental length interpretable as the radius of the space
S
3
. The photon occurs as the lowest member of a coherent subfamily of B that includes natural candidates for bare versions of the
W
and
Z
particles. In the relativistic limit the interaction Lagrangian becomes a sum over all elementary processes, one of which appears as quantum electrodynamics with Majorana-type electrons.
Lateral diffusion of lipids in complex biological membranes.
Authors: O'Leary T J
Published: May 2006

Lateral diffusion of lipids in biological membranes may be influenced by polypeptides, proteins, and other nonlipid membrane constituents. Using concepts from scaled-particle theory, we extend the free-volume model for lipid diffusion to membranes having an arbitrarily large number of components. This theory clarifies the interpretation of the free-volume theory, better reproduces the free-area dependence of lipid lateral diffusion rates, and quantitatively predicts the experimental observation that the lateral diffusion rates of membrane lipids are significantly reduced when proteins or polypeptides are incorporated in the membrane.
Can free energy be transduced from electric noise?
Authors: Astumian R D , Chock P B , Tsong T Y , Chen Y D , Westerhoff H V
Published: May 2006

Recently, it was shown that free energy can be transduced from a regularly oscillating electric field to do chemical or transport work when coupled through an enzyme with appropriate electrical characteristics. Here we report that randomly pulsed electric fields can also lead to work being done, giving rise to speculation as to whether appropriately designed enzymes can extract and convert free energy from the inherent fluctuations in their environment. The paradox is resolved by showing that equilibrium electrical noise resulting from the environment around an enzyme cannot be completely random but is correlated to the state that the enzyme is in. If the noise has the appropriate reciprocal interaction with the enzyme, its potential to serve as a free-energy source disappears. This is shown by Monte Carlo and other numerical calculations and is proven analytically by use of the diagram method. This method also is used to provide an explicit equation showing that, under a range of conditions, our model enzyme will be induced by uncorrelated ("autonomous") noise to undergo net cyclic flux. That work can be transduced from the "random" noise is demonstrated by using numerical methods.
Cytoplasts made from human blood polymorphonuclear leukocytes with or without heat: preservation of both motile function and respiratory burst oxidase activity.
Authors: Malawista S E , Van Blaricom G
Published: May 2006

Anucleate fragments (cytoplasts) from polymorphonuclear leukocytes (PMN) are simplified systems that can be used to elucidate specific pathways by which cell function is altered. PMN cytoplasts in current use are defective either in activatable respiratory burst oxidase activity or in motile function. By centrifugation of PMN on discontinuous gradients of Ficoll without cytochalasin B, we have created granule-poor cytoplasts in which both these capacities are preserved. Specifically, they generate superoxide anion (O2-.) and reduce nitroblue tetrazolium dye on appropriate stimulation; they respond chemotactically to erythrocytes destroyed by laser microirradiation or to the specific chemoattractants fMet-Leu-Phe (10 nM) and C5a (zymosan-activated serum); and they ingest and kill staphylococci. We can improve the yield of these fragments progressively by preheating (45 degrees C) the cells in suspension for increasing periods of time, but those treatments are attended by a decreasing percentage of cytoplasts with activatable oxidase activity, and a progressive inability of the cytoplasts to ingest and to kill staphylococci. These easily made and multipotent cytoplasts readily lend themselves to studies of PMN physiology.
Evolution of the genus Leishmania as revealed by comparisons of nuclear DNA restriction fragment patterns.
Authors: Beverley S M , Ismach R B , Pratt D M
Published: May 2006

Restriction endonuclease DNA fragment patterns have been used to examine the relationships among 28 isolates of Leishmania as well as Crithidia, Endotrypanum, and Trypanosoma cruzi. Fragments of nuclear DNA were generated with six restriction enzymes, and blots were hybridized with probes from three loci. Among the major lineages the fragment patterns are essentially completely different, while within the major lineages various degrees of divergence are found. Molecular evolutionary trees were constructed using the method of Nei and Li to estimate the percent nucleotide sequence divergence among strains from the fraction of fragments shared. Defined groups, such as species or subspecies within the major lineages, are also grouped by nuclear DNA comparisons. Within the donovani complex, we find Leishmania donovani chagasi and Leishmania donovani infantum to be as similar as strains within Leishmania donovani donovani, consistent with the proposal by other workers that New World visceral leishmaniasis originated quite recently.
Niemann-pick variant disorders: comparison of errors of cellular cholesterol homeostasis in group D and group C fibroblasts.
Authors: Butler J D , Comly M E , Kruth H S , Vanier M , Filling-Katz M , Fink J , Barton N , Weintroub H , Quirk J M , Tokoro T
Published: May 2006

Fluorescence microscopic examination of filipin-stained cultured skin fibroblasts derived from two brothers with group D Niemann-Pick disease revealed abnormal storage of low density lipoprotein (LDL)-derived cholesterol. LDL stimulation of intracellular cholesteryl ester synthesis was severely compromised in the Niemann-Pick D fibroblasts, as it also was in fibroblasts obtained from Niemann-Pick C patients. Cholesteryl ester synthesis was intermediately deficient in cells derived from an obligate group-D heterozygous carrier. Activity of acyl-CoA:cholesterol acyltransferase was within the normal range in cell-free extracts of both LDL-depleted and LDL-supplemented cultures of Niemann-Pick C and D fibroblasts. Incubation of Niemann-Pick D fibroblasts with LDL did not lead to as high a level of intracellular cholesterol accumulation as the excessive storage observed with Niemann-Pick C fibroblasts. These findings suggest that the Niemann-Pick variant disorders may represent a family of specific and possibly individual mutations that disrupt cellular cholesterol homeostasis.
Tyrosine radicals are involved in the photosynthetic oxygen-evolving system.
Authors: Barry B A , Babcock G T
Published: May 2006

In addition to the reaction-center chlorophyll, at least two other organic cofactors are involved in the photosynthetic oxygen-evolution process. One of these cofactors, called "Z," transfers electrons from the site of water oxidation to the reaction center of photosystem II. The other species, "D," has an uncertain function but gives rise to the stable EPR signal known as signal II. Z+. and D+. have identical EPR spectra and are generally assumed to arise from species with the same chemical structure. Results from a variety of experiments have suggested that Z and D are plastoquinones or plastoquinone derivatives. In general, however, the evidence to support this assignment is indirect. To address this situation, we have developed more direct methods to assign the structure of the Z+./D+. radicals. By selective in vivo deuteration of the methyl groups of plastoquinone in cyanobacteria, we show that hyperfine couplings from the methyl protons cannot be responsible for the partially resolved structure seen in the D+. EPR spectrum. That is, we verify by extraction and mass spectrometry that quinones are labeled in algae fed deuterated methionine, but no change is observed in the line shape of signal II. Considering the spectral properties of the D+. radical, a tyrosine origin is a reasonable alternative. In a second series of experiments, we have found that deuteration of tyrosine does indeed narrow the D+. signal. Extraction and mass spectral analysis of the quinones in these cultures show that they are not labeled by tyrosine. These results eliminate a plastoquinone origin for D+.; we conclude instead that D+., and most likely Z+., are tyrosine radicals.
Antigen-specific drug-targeting used to manipulate an immune response in vivo.
Authors: Abu-hadid M M , Bankert R B , Mayers G L
Published: May 2006

The administration of dextran-conjugated cytosine arabinonucleoside (araC) to BALB/c mice at various times prior to but not subsequent to immunization with native dextran renders mice unresponsive to this thymic-independent antigen. These results demonstrate that the primary immune response to an antigen can be selectively and efficiently suppressed or eliminated in vivo by the delivery of a single dose of an appropriate antigen-cytotoxic drug conjugate. Evidence presented here indicates that the dextran-araC conjugate (toxogen) acts directly and selectively upon unprimed dextran-specific antibody-forming cell precursors, presumably by binding to their receptors and subsequent internalization of the resultant receptor-toxogen complexes. The resistance of antigen-primed mice to the cytotoxic effect of the toxogen could result from the failure of dextran-primed cells to reexpress antigen-specific receptors, from an alternative processing of the toxogen, or from the inability of the antigen-primed cells to internalize a second round of receptor-ligand complexes. We also determined that B cells responding to thymic-dependent antigens were not affected by the prior exposure to a toxogen. The inability to eliminate or suppress the primary response to a thymic-dependent antigen via the administration of a cytotoxic drug-antigen conjugate distinguishes the thymic-independent set of B cells from the thymic-dependent B-cell repertoire. The difference between these two B-cell compartments could be due either to differences in the amount of ligand bound to receptors or to differences in the trafficking patterns of receptor-ligand complexes within each cell type.
Structural changes and metal binding by proalbumins and other amino-terminal genetic variants of human serum albumin.
Authors: Takahashi N , Takahashi Y , Putnam F W
Published: May 2006

Proalbumins are rare genetic variants of human serum albumin containing a basic propeptide that is not removed during post-transcriptional processing because of a mutation in the site of excision, an Arg-Arg sequence. We have identified the amino acid substitutions in three different types of proalbumins designated Gainesville, Taipei, and Takefu. The first two proalbumins are identical to previously described proalbumins of the Christchurch and Lille types, respectively, and exhibit the characteristic properties of susceptibility to tryptic cleavage and of lower metal-binding affinity. Takefu is a third type of proalbumin and resists tryptic cleavage because of the substitution Arg-1----Pro. Each of the first two types of proalbumins has been identified in geographically separate, ethnically diverse populations and therefore must have arisen by independent mutations. There is some tendency for mutations in albumin to cluster in the propeptide sequence. Although the substitution His3----Gln in the genetic variant albumin Nagasaki-3 decreases metal-binding affinity, mutations further down the polypeptide chain have no such effect, nor is there any reduction of copper-binding affinity in albumin from patients with Wilson disease.
Elevated DNA topoisomerase II activity in nitrogen mustard-resistant human cells.
Authors: Tan K B , Mattern M R , Boyce R A , Schein P S
Published: May 2006

A human Burkitt lymphoma cell line, Raji-HN2, made 10-fold more resistant to nitrogen mustard (HN2) than the parental Raji cell line, exhibited the following characteristics when compared to the parental Raji cells: (i) decreased HN2-induced DNA interstrand crosslinking; (ii) increased (3-fold) DNA topoisomerase II [DNA topoisomerase (ATP-hydrolyzing), EC 5.99.1.3] activity; (iii) increased (4- to 11-fold) sensitivity to topoisomerase II inhibitors; (iv) increased (2-fold) glutathione content; and (v) increased (2-fold) cell doubling time. The resistant phenotype was unstable and was maintained by weekly treatment of the cells with HN2. Growing the resistant cells in the absence of HN2 resulted in a time-dependent decrease in both resistance to HN2 and topoisomerase II activity and an increase in DNA interstrand crosslinking induced by HN2. We hypothesize that HN2 resistance is due to enhanced monoadduct repair with resultant decreased DNA crosslinking and that this process is mediated by topoisomerase II.
Role of platelet-derived growth factor in wound healing: synergistic effects with other growth factors.
Authors: Lynch S E , Nixon J C , Colvin R B , Antoniades H N
Published: May 2006

Platelet-derived growth factor (PDGF) in vitro stimulates DNA synthesis and chemotaxis of fibroblasts and smooth muscle cells and stimulates collagen, glycosaminoglycan, and collagenase production by fibroblasts. These in vitro properties suggest that PDGF, delivered by platelets to the site of injury in vivo, may play an important role in the initiation of the wound repair process. Studies presented here show that the addition of pure PDGF to a wound site involving the epidermis and dermis has little effect on the morphology or biochemistry of the healing wound. In contrast, the addition of partially purified PDGF resulted in significant dose-dependent increases in the width of the newly synthesized connective tissue and epidermal layers. Autoradiography using [3H]thymidine revealed increased numbers of labeled cells in the new connective tissue and epithelial layers. Furthermore, addition of partially purified PDGF resulted in significant increases in the rate of protein and DNA synthesis and the total content of these components in biopsies taken from the wound site. Similar effects were obtained when insulin-like growth factor I was added in combination with pure PDGF. This combination of factors caused a 2.4-fold increase in the width of the newly formed connective tissue layer and a 95% increase in epidermal thickness compared with controls. Insulin-like growth factor I alone caused no significant morphologic changes. Epidermal growth factor alone or in combination with PDGF resulted in a thickening only of the epidermis. These results indicate that the synergistic actions of other factors with PDGF are important in the modulation of the wound healing process.
Antiatherogenic effect of probucol unrelated to its hypocholesterolemic effect: evidence that antioxidants in vivo can selectively inhibit low density lipoprotein degradation in macrophage-rich fatty streaks and slow the progression of atherosclerosis in the Watanabe heritable hyperlipidemic rabbit.
Authors: Carew T E , Schwenke D C , Steinberg D
Published: May 2006

It has been postulated that low density lipoprotein (LDL) becomes fully atherogenic only if it first undergoes oxidative modification. The oxidatively modified form, but not native LDL, is recognized by the acetyl-LDL or "scavenger" receptor and could, therefore, be taken up rapidly by tissue macrophages to generate the fatty-streak lesion of atherosclerosis. However, there is thus far very little direct evidence for oxidative modification in vivo. The studies reported here take advantage of the fact that probucol is an effective antioxidant transported in lipoproteins, including LDL, and blocks the oxidative modification of LDL in vitro. We now show that the rate of degradation of LDL in the macrophage-rich fatty-streak lesions of the LDL receptor-deficient rabbit treated with probucol (1% by weight in the diet) is reduced to about one-half of that in the lesions of receptor-deficient rabbits not given probucol (but matched for plasma cholesterol levels). In contrast, the rates of degradation in the nonlesioned areas of the aorta were no different in probucol-treated and control animals. Most of the LDL degradation in fatty-streak lesions takes place in macrophages, whereas in nonlesioned aorta, which contains very few macrophages, the degradation is almost exclusively in endothelial cells and smooth muscle cells. Thus, the results are compatible with the postulate that the native LDL taken up and degraded by foam cells in the developing fatty-streak lesions was in part first converted to a form recognized by the scavenger receptor (by oxidative or analogous modification). Finally, and most importantly, we show that treatment with probucol significantly reduced the rate of development of fatty-streak lesions even though plasma cholesterol levels were no lower than lovastatin-treated (control) rabbits.
Reduction, the trace formula, and semiclassical asymptotics
Authors: Guillemin Victor , Uribe Alejandro
Published: May 2006

We state a theorem that relates the theory of dimensional reduction in Hamiltonian mechanics to the spectral properties of elliptic operators with symmetries on compact manifolds. As an application, we show that the spectrum of the Schrödinger operator, -[unk]hΔ +
V
, as [unk]h → 0, contains geometric information about the closed trajectories of a classical particle with Hamiltonian ‖
p
‖
2
+
V
(
q
). More generally, we show that this is true for particles with internal degrees of freedom and subject to an external Yang-Mills field, the classical limit being the Wong-Sternberg-Weinstein system for such particles.
Control of A-system amino acid transport by a second regulatory gene R2 in Chinese hamster ovary cells CHO-K1 and the possible connection of this gene with insulin activity.
Authors: Moffett J , Périer F , Jones M , Englesberg E
Published: May 2006

Evidence based on a study of alanine-resistant (Alar), constitutive mutants of CHO-K1 cells and the conditions that favor stimulation of the A system of amino acid activity supports the model that the A system of amino acid transport in these cells is repressible and under negative control of regulatory gene R1. In this study, we show that mutant Alar6, when grown under conditions of repression, has an A system of amino acid transport activity similar to that of the derepressed parental cell line, CHO-K1 (wild type) and of the fully constitutive mutant in gene R1, Alar4. However, the A system of Alar6 is further derepressible. The Vmax for proline transport through this system in mutant Alar6 is four times that of the parental culture, with no significant change in Km. Analysis of hybrids produced by crossing mutant Alar6 with the parental culture and with Alar4 shows that mutant Alar6 is recessive to wild type and complements mutant Alar4. Although the amino acid transport A system of CHO-K1 is stimulated by insulin, mutant alar6 is not stimulated by insulin. These results support the hypothesis that mutant alar6 results from mutation in another regulatory gene, R2, that, in conjunction with gene R1, negatively controls the expression of a structural gene for the A-system transport. Evidence also indicates that R2 gene product is not responsive to amino acids and that insulin stimulation of the A system may result from insulin inactivation of this repressor.