bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mitogenic polypeptides control ion flux in responsive cells
Authors: Glaser Luis , Whiteley Brian , Rothenberg Paul , Cassel Dan 
Published: February 2005

AbstractPolypeptide growth factors (mitogens) which stimulate proliferation of fibroblasts and epithelial cells also rapidly activate transmembrane ion transport systems. The mitogen‐induced Na+ influx is due to the activation of a Na+/H+ antiport. Recent methodological developments allow, for the first time, precise measurements of the factors that control activation of the Na+/H+ antiport by these agents, and provide the tools needed to assess the physiological significance of this exchange mechanism.
Molecular biology of plasminogen activators and recombinant DNA progress
Authors: Cederholm‐Williams S. A. 
Published: February 2005

AbstractPlasminogen activators are enzymes with multiple roles. They play vital parts in maintaining the functional integrity of the vascular system and they are also involved in processes of tissue reorganization. In this review, the molecular properties of these enzymes that make them ideal targets for genetic and biochemical engineering to satisfy a potential therapeutic role are described.
Retroviral DNA integration
Authors: Skalka Anna Marie , Leis Jonathan 
Published: February 2005

AbstractThe synthesis and integration of DNA into the genome of its host cell is a normal step in the replication of the retroviruses. Previous studies have provided details concerning the structure of viral DNA and viral and host integration sites. More recent genetic and biochemical results have expanded our understanding considerably: it should soon be possible to describe the exact viral DNA sequence recognized during the integration reaction for several viruses. In addition, at least one of the viral proteins and enzymatic activities required in the reaction has been identified. Analysis of this apparently efficient and highly specific site‐directed recombination event in eukaryotic cells promises to provide insights of both fundamental and practical interest.
The role of E. coli single‐stranded DNA binding protein in DNA metabolism
Authors: Chase John W. 
Published: February 2005

AbstractSingle‐stranded DNA binding proteins have been known for some time to be crucial in many DNA metabolic reactions in both prokaryotes and eukaryotes. Despite a wealth of studies on these proteins we still do not understand their biochemical mechanism of action. Recent studies of the Escherichia coli single stranded DNA binding protein (SSB) are beginning to provide some insight into how this and similar proteins might function.
On the status of the Z‐DNA question for animal chromosomes
Authors: Hill Ronald J. 
Published: February 2005

AbstractThe Z‐conformation, recently elucidated in crystals of synthetic alternating dG‐dC polymers, is a dramatically different structure for DNA. Despite suggestive locations of alternating purine‐pyrimidine tracts in chromosomes and intriguing functional hypotheses, unequivocal demonstrations of the Z‐conformation in vivo are not proving easy. Perhaps the Z‐conformation should be considered largely as a dynamic structure transiently forming in torsionally stressed chromatin.
Control mechanisms for vitellogenin synthesis in mosquitoes
Authors: Borovsky Dov 
Published: February 2005

AbstractEarlier investigations of the hormonal control of vitellogenin (egg‐yolk protein) synthesis in mosquitoes relied on microsurgical manipulations to identify organs that secrete the various hormones that stimulate or inhibit vitellogenesis. Advances in the last 10 years, using radioimmunoassays, HPLC, mass spectrometry and tissue‐culture incubations, have shown that the control mechanism involves a complex interaction between ecdysteroids, juvenile hormones and peptide hormones.
What the papers say: Fibronectin in early embryonic development of the vertebrate
Authors: Thiery Jean Paul 
Published: February 2005

AbstractDuring development some cells are migratory whilst others are stationary. However, the same cell may change its behaviour depending upon its environment. Recent evidence has implicated the extracellular matrix protein fibronectin in the regulation of migratory behaviour. As the structure of this molecule becomes elucidated, it is also becoming possible to interpret this regulation in precise molecular terms.
Torsional stress in eukaryotic chromatin
Authors: Scott Walter A. 
Published: February 2005

AbstractThe bulk of the DNA in eukaryotic chromatin behaves as if it is topologically relaxed; however, a subfraction can be shown to be under suercoil tension. Endonuclease S1 cuts at specific hypersentive sites in chromatin (in the promoter regions of active genes) and this enzyme cuts in the same region in supercoiled plasmids, but not in relaxed or linearized molecules. A subfraction of the minichromosomes formed after SV40 infection or microinjection of plasmid DNA into oocytes contains supercoil tension and this subfraction is thought to play an important role in transcription.
Roots: Molecular basis of biological regulation: Origins from feedback inhibition and allostery
Authors: Pardee Arthur B. 
Published: February 2005

AbstractOne observes regulation at every biological level. Organisms, cells, and biochemical processes operate efficiently, normally wasting neither material nor energy, and adjusting their functions to external influences. Nature evidently has evolved mechanisms specifically dedicated to regulation at many levels. What is the molecular basis of this control?In the 1950s these molecular control mechanisms began to be explored seriously. The discoveries of feedback inhibition of enzyme activity were important because they gave an initial example of how regulation is achieved at the molecular level. We showed that certain enzymes are composed of two parts, one for catalysis and another distinct part present only to regulate this catalysis. Catalytic activity can be either stimulated or inhibited when a small molecule in the environment combines with the enzyme's regulatory site. In particular, a final product of a metabolic pathway generates a feedback loop which automatically limits its own excessive production, by combining with the regulatory site of an early enzyme in that pathway. Later studies showed that catalytic and regulatory structures of some enzymes could be separated physically.The discovery of regulatory sites and their interaction with molecules unrelated to their substrates was the basis for the generalized allosteric concept. This concept extends the regulatory site idea to a wide variety of processes such as control of gene expression, hormone action, and cellular growth.
The physiology of pancreatic acinar cells: Questions and perspectives on the secretory process
Authors: Romagnoli Paolo 
Published: February 2005

AbstractThe two theories of pancreatic enzyme secretion, those of exocytosis and transmembrane flow, are described. Data thought to support the theory of transmembrane flow of single molecules from pancreatic acinar cells are first reviewed, and the conditions which could allow these data to be explained by the theory of exocytosis of enzyme quanta, i.e. secretory granules, are then discussed.The evidence suggesting short‐term modulation of the composition of pancreatic juice is also considered, and its possible explanations at the organ and cellular level are discussed, in the light of suggested theories on enzyme secretion pathways.
Sequence information required for bacterial protein export
Authors: Benson Spencer A. 
Published: February 2005

AbstractGenetic analysis of the signals within bacterial exported proteins have shown that the information required for proper localization is contained in both the amino‐terminal signal sequence and the mature protein. Several types of signal sequence mutations can be isolated, suggesting that the signal sequence may be involved in more than one step in the export process. Export information within the mature portion of the protein is present at several locations.
Evolution of resistance to penicillin and cephalosporin antibiotics
Authors: Normark Staffan , Lindberg Frederik 
Published: February 2005

AbstractBacterial resistance mechanisms to the antibiotics known as β‐lactams, which include the penicillins and cephalosporins, can take several forms but frequently involve the production of β‐lactamases from either plasmid‐ or chromosomally‐encoded loci. Gram negative bacteria express a β‐lactamase from evolutionarily related chromosomal ampC genes. Genetic analysis of both inducible and constitutively expressed AmpC β‐lactamases provide insights into the mechanisms regulating production of the enzyme. Evolutionary relationships between the genes of different species are discussed, as well as the regulatory mechanisms that in both laboratory mutants and clinical isolates lead to overproduction of β‐lactamase.
Methionine or not methionine at the beginning of a protein
Authors: Sherman Fred , Stewart John W. , Tsunasawa Susumu 
Published: February 2005

AbstractMethionine aminopeptidases with a universal specificity have been revealed from the sequences of the amino‐terminal region of mutant forms of yeast iso‐1‐cytochrome c and from a systematic examination of the literature for amino‐terminal sequences formed at initiation sites. The aminopeptidase removes amino‐terminal residues of methionine when they precede certain amino acids, with a specificity that appears to be determined mainly by the residue adjacent to the methionine residue at the amino terminus. The result with the mutationally altered iso‐1‐cytochromes c and the results from published sequences of other proteins from a wide range of prokaryotes and eukaryotes suggest that the aminopeptidase usually cleaves amino‐terminal methionine when it precedes residues of alanine, cysteine, glycine, proline, serine, threonine and valine but not when it precedes residues of arginine, asparagine, aspartic acid, glutamine, glutamic acid, isoleucine, leucine, lysine or methionine. We suggest that the specificity is almost always determined simply by the size of the side chain of the penultimate residue; methionine is usually cleaved from residues with a side chain having a radius of gyration of 1·29 Å or less, but is not cleaved from residues with larger side chains.
The uptake and accumulation of proteins by the cell nucleus
Authors: Feldherr Carl M. 
Published: February 2005

AbstractEvidence has recently been obtained suggesting that the accumulation of specific endogenous proteins by the nucleus is due both to facilitated transport across the envelope and intranuclear binding. Using recombinant DNA methodology, polypeptide domains containing the signals required for nuclear accumulation have been identified in several karyophilic proteins.
Oncogene homologues in yeast
Authors: Wheals A. E. 
Published: February 2005

AbstractTwo different yeasts have a number of genes bearing striking structural and functional homologies to mammalian oncogenes. In yeast these genes are involved in the control of proliferation and early steps in the cell cycle. Many have putative protein kinase activity and some have been shown to control the activity of the enzyme adenylate cyclase which synthesizes cyclic AMP. Mutant forms of these yeast genes have oncogenic activity in mammalian cells.
What's new: Biosensors: Current applications and future potential
Authors: Foulds Nicola C. , Lowe Christopher R. 
Published: February 2005

AbstractBiological molecules such as enzymes and antibodies display a unique capacity to recognize and respond to other molecules in a way which can be exploited in the development of analytical devices. In a biosensor, the biological recognition system creates a physiochemical change proximal to a suitable transducer and thereby converts the concentration of the analyte into a quantifiable electrical signal. The design and construction of these devices requires an imaginative combination of biological, chemical, physical and engineering disciplines. Biosensors will find application in a variety of analytical fields.
Roots: Early explorations of the pathways of uridine diphosphate galactose in man and in microorganisms
Authors: Kalckar Herman M. 
Published: February 2005

AbstractThirty years ago, a number of human inborn errors in carbohydrate metabolism were explored with specific enzymatic tests on blood samples (hemolysates). Hereditary galactosemia was the first example. When the inoperative step in galactose metabolism was specified, the basis for the diet therapy used on the galactosemic infants, namely galactose‐free diet, could be shown to be securely founded.As far as galactose metabolism is concerned, the cells of the infant are faced with two problems: (i) the conversion of dietary lactose (galactosyl glucose) to glucose and its catabolites involved in energy metabolism, and (ii) the conversion of dietary glucose or lactose to galactosyl units of glycolipids and glycoprotein cell structures.Subsequent studies on microorganisms revealed several types of hereditary defect in galactose metabolism. One type which permits the bacteria to develop a normal carbohydrate pattern in their cell walls includes an enzyme defect, like that described in the cells of the galactosemic infant. Two other types, with the inability to synthesize UDPGlc or UDPGal from glucose, do not permit the bacteria to build the fabric of the normal bacterial cell wall. This is the subject for discussion.
Natural history of the retrovirus associated with a human leukemia
Authors: Hinuma Yorio 
Published: February 2005

AbstractA human retrovirus etiologically related to a unique leukemia, adult T‐cell leukemia, has been discovered. This retrovirus is endemic in certain areas and ethnic groups, such as the Japanese in Japan and Blacks in Africa. The virus is transmitted from mother to child and husband to wife and by blood transfusion. In addition, a virus like the human retrovirus has been found in various species of monkeys in Asia and Africa. This review describes and discusses recent results on the natural history of these primate lymphotropic retroviruses.
The pineal family of aromatic amine N‐acetyltransferases
Authors: Klein David C. , Voisin Pierre , Namboodiri M. A. Aryan 
Published: February 2005

AbstractThe mammalian pineal gland contains two types of N‐acetyltransferases which act on aromatic amines. One type preferentially acetylates arylamines such as phenetidine and aniline, whereas the other preferentially acetylates arylalkylamines such as tryptamine and phenylethylamine. The two enzymes can be distinguished by (1) molecular size, (2) regulation, and (3) inactivation characteristics. Arylalkylamine N‐acetyltransferase is involved in the regulation of melatonin synthesis in the pineal gland. A specific function of pineal arylamine N‐acetyltransferase has not been established; it may function as a nonspecific detoxification mechanism.
What's new?: The AMBIS beta scanning system
Authors: Smith Ivor 
Published: February 2005

AbstractAMBIS is a complete identification system which includes (1) a highly reproducible electrophoresis unit; (2) a beta‐scanner with the ability to rapidly locate and measure beta particle emission data from a variety of isotopes and surfaces; and (3) an IBM computer with a massive data storage capacity for the emission data plus subsequent manipulation of that data. Hence it provides a rapid facility for (1) classification of all types of micro‐organisms, (2) examination of cells of multicellular plants and animals, (3) routine determination of molecular weights of one or more proteins in a complex mixture, (4) quantification of single or mixed compounds in a band, (5) scanning and quantification of dot and other blots, immunodiffusion precipitates and probes, (6) direct counting of radioactive solutions from RIA, column fractions, etc., without the need of expensive scintillation fluids with their consequent hazards, (7) circumventing the need of much time‐consuming auto‐radiography, and (8) setting up databases plus exchange and transference of data between AMBIS systems in different locations via floppy disk, modem or other forms of rapid transmission.
Non‐radioactive nucleic acid probes for the diagnosis of virus infections
Authors: Pereira H. G. 
Published: February 2005

AbstractNucleic acid hybridization is being increasingly used in viral diagnosis. Most of the assays described so far for this purpose require the use of radioactive probes. Their replacement by Non‐radioactive assays has many advantages and makes the technique feasible in routine diagnostic work. Non‐radioactive assays have had limited use but their diagnostic value has been demonstrated for a number of virus infections. They have the main advantages of employing stable probes, of avoiding safety hazards and of being easy and rapid to perform with limited laboratory facilities. Their main disadvantage compared to radioactive assays is in having relatively low sensitivity. Improvements in probe construction, in labelling and detecting methods, in sample treatment and in hybridization conditions may well increase their usefulness.
Replication origins in yeast chromosomes
Authors: Kearsey Stephen 
Published: February 2005

AbstractDNA replication initiates at many sites in eukaryotic chromosomes. It has been difficult to isolate such replication origins, but a family of sequences from the yeast genome have properties which suggest that they may serve this function. The identification of these sequences together with sophisticated methods of genetic analysis, make yeast a useful organism for the study of eukaryotic DNA replication.
Molecular basis of antigenic variation in african trypanosomes
Authors: Ashall Frank 
Published: February 2005

AbstractAfrican trypanosomes, which cause sleeping sickness in man and other mammals, are able to evade immune destruction in their hosts by altering the expression of a major cell surface molecule, the variant surface glycoprotein (VSG). The VSGs are encoded by a multigene family, and antigenic variation occurs when the trypanosome switches from expression of one VSG gene to another. This switching process involves changes in the arrangement of the trypanosome genomic DNA.
Molecular biology of complement
Authors: Colten Harvey R. 
Published: February 2005

AbstractComplementary DNA clones corresponding to most of the proteins of a major amplification and effector of immune host defenses, the complement system, have been isolated and characterized. Availability of these molecular probes has substantially increased our information about and understanding of the structure of the complement proteins and regulation of complement gene expression. Information about the proteins has led to the generation of potential pharmacological agents for the selective control of inflammation. Understanding of the regulatory mechanism has provided insights into the mechanisms accounting for the response to several cytokines including interferon‐gamma, interleukin‐1 and tumor necrosis factor. Finally, complement molecular genetics has been stimulated so that the basis for several complement deficiency disorders has been elucidated.
What the papers say: The influence of immunoglobulin genes in lymphoid oncogenesis
Authors: Adams Jerry M. 
Published: February 2005

AbstractIlluminating insights into lymphoid oncogenesis came with the finding that the chromosome translocations characteristic of many tumors of immunoglobulin‐producing cells represent conjunction of an immunoglobulin gene locus with the myc oncogene. The potency of this combination has been underlined by recent studies in which DNA regions mimicking certain chromosome junctions of lymphomas were shown to be highly tumorigenic when inserted into the mouse germline. Nevertheless, the mechanism by which an immunoglobulin locus activates the oncogene remains largely an enigma, particularly in those cases where the two loci remain at some distance.
Mutations affecting sodium channels in Drosophila
Authors: Ganetzky Barry 
Published: February 2005

AbstractIon channels play key roles in the generation and propagation of nerve impulses by mediating ionic fluxes across excitable membranes. Elucidation of the structure and function of these proteins is a major goal in understanding the molecular mechanisms of membrane excitability. Much work has focused on sodium channels, whose activity is of primary importance in producing nerve impulses. Despite the recent cloning and sequencing of a sodium channel structural gene, many unanswered questions remain. To address some of these question genetically, Drosophila mutants with altered sodium channels are being isolated and subjected to multidisciplinary analyses. Ultimately, these can provide novel approaches for understanding the function and regulation of sodium channels at a molecular level.
Multiple levels of gene regulations in the control of amino acid biosynthesis in Saccharomyces cerevisiae
Authors: Hinnebusch Alan G. 
Published: February 2005

AbstractIn the yeast Saccharomyces cerevisiae, the regulation of expression of many of the enzymes for amino acid biosynthesis involves an interlinked general control system. Molecular and genetic analyses of this system reveal an underlying set of hierarchical transcriptional controls and a novel translational regulatory mechanism for governing expression of a key activator gene.
The tubulin and histone genes of Physarum polycephalum: Models for cell cycle‐regulated gene expression
Authors: Laffler Thomas G. , Carrino John J. 
Published: February 2005

AbstractAlthough the great majority of genes are not subject to cell‐cycle controls, those that are could play a very important role in regulation of the cell cycle itself. The tubulin and histone genes of the naturally synchronous myxomycete, Physarum polycephalum, provide an excellent paradigm for such regulation. The transcription of both is highly periodic within the Physarum cycle, and curiously, both sets of genes appear to be activated at the same time. This activation appears to function as part of a developmental program, since it serves to meet future needs for each gene's product. The significance of this activation event for cell‐cycle regulation is discussed with particular regard to the nature of the mitotic oscillator.
Lymphocyte homing receptors and the immune response in vivo
Authors: Weissman Irving L. 
Published: February 2005

AbstractAn important aspect of the developmental maturation of lymphocytes is their capacity to locate and enter lymphoid organs with great rapidity and specificity and to follow certain routes within these organs for the attainment of particular immunological capabilities. It is now known that this “homing response” to lymphoid organs involves specific glycoprotein receptors on the lymphocyte cell surface. The biochemistry of these receptors and their significance in normal and pathological immune responses are discussed.
Regulation of enzymes in isolated plant nuclei
Authors: Datta Neeraj , Roux Stanley J. 
Published: February 2005

AbstractPurified nuclei are being used as a test system to study the regulation of nuclear enzymes in plants. Regulatory agents such as light, hormones and polyamines can stimulate kinases or phosphatases that control nuclear protein phosphorylation and they can modulate the activity of as yet unidentified enzymes required for transcript synthesis and/or stabilization. This essay summarizes current findings and discusses the advantages and pitfalls of using isolated nuclei to investigate how nuclear functions are controlled.