bluuebunny/crossref_metadata_2025_split huggingface dataset:
Continuous cultivation of micro‐organisms: A new approach and possibilities for its use
Authors: Slezák Josef , Sikyta Bohumil 
Published: May 2005

AbstractWhen trying to turn a batch fermentation process into a continuous process, many important factors must be repected. A new approach is presented by means of which it is possible to reproduce in a continuous system those changes (both inside the cells and in the environment) which are functions of elapsed time (lag‐type changes, sudden changes occurring at a constant growth rate of the micro‐organisms, etc.). Special attention is paid to lag‐type changes. In the hitherto described apparatuses for continuous cultivation it was difficult to follow changes which are functions of time. The use of a multi‐stage apparatus is therefore suggested, and a method of cultivation, which through adjusting retention times in individual cultivation vessels allows a detailed study of such changes, is proposed. Basic equations concerning the growth of microorganisms in the described apparatus are derived and some examples of the possible practical use of the new approach are presented.
The disintegration of bacteria and other micro‐organisms by the M.S.E.‐Mullard Ultrasonic disintegrator
Authors: Hughes D. E. 
Published: May 2005

AbstractTwo commercially available ultrasonic instruments are described, in which micro‐organisms and other cells may be disintegrated.Sound waves (20 kc/s) are generated in the cell suspension by means of titanium velocity transformers (probes) coupled to a magnetostriction transducer. One instrument operating at 500 W will disintegrate from 2 to 500 ml, the other operating at 50 W from 1 ml to 30 ml.Yeast was used as a test organism but results on some other organisms are also given. Cell rupture is shown to be independent of sonically generated free radicals, but enzyme inactivation (alcohol dehydrogenase) is accelerated by free radicals. Increasing the viscosity, decreasing surface tension of the suspending medium, or the presence of CO2 decreases disintegration. The addition of solid nuclei such as powdered glass, as well as small air bubbles, increases disintegration.This is consistent with disintegration being due to cavitation, but does not indicate the precise mechanism of cell rupture. Some effects of sonic disruption are compared with disruption by other methods.
Expression and regulation of pOb24 and lipoprotein lipase genes during adipose conversion
Authors: Dani C. , Amri E.‐Z. , Bertrand B. , Enerback S. , Bjursell G. , Grimaldi P. , Ailhaud G. 
Published: May 2005

AbstractLipoprotein lipase (LPL) and pOb24 mRNAs are known to be early markers of adipose cell differentiation. Comparative studies of the expression of pOb24 and LPL genes during adipose conversion of Ob1771 preadipocyte cells and in mouse adipose tissue have shown the following: (1) the expression of both genes takes place at confluence; this event can also be triggered by growth arrest of exponentially growing cells at the G1/S stage of the cell cycle; (2) In contrast to glycerol‐3°phosphate dehydrogenase mRNA, the emergence of pOb24 and lipoprotein lipase mRNAs requires neither growth hormone or tri‐iodothyronine as obligatory hormones nor insulin as a modulating hormone; (3) in mouse adipose tissue, pOb24 mRNA is present at a high level in stromal‐vascular cells and at a low level in mature adipocytes, and in contrast LPL mRNAs are preferentially expressed in mature adipocytes. Thus, these two genes do not appear to be regulated in a similar manner, as also shown by the differential inhibition of their expression by tumor necrosis factor (TNF) and transforming growth factor‐β (TGF‐β ).
Involvement of a highly polyvalent Glycan in the cell‐binding of the aggregation factor from the marine sponge Microciona prolifera
Authors: Misevic Gradimir N. , Burger Max M. 
Published: May 2005

AbstractA proteoglycan‐like aggregation factor from the marine spongeMicrociona prolifera (MAF) mediates cell‐cell recognition via a cell‐binding and a self‐association domain. After repetitive and prolonged treatment of MAF with glycopeptide‐N‐glycosidase (PNGase) the specific binding of MAF to homotypic cells was decreased by 72%. Polyacrylamide gel electrophoresis and gel filtration analysis of such PNGase digests showed that: (1) the enzyme released a single glycan type of Mr = 6 × 1032 (G‐6) from MAF, (2) 1 mole of MAF contains at least 830 moles of N‐linked chains of G‐6 glycan. The correlation between the loss of the binding activity of MAF and the extent of the release of the repetitive G‐6 polysaccharide strongly suggests its involvement in MAF‐cell association via highly polyvalent interactions.
Differentiation of BC3H1 and primary skeletal muscle cells and the activity of their endogenous insulin‐degrading enzyme are inhibited by the same metalloendoprotease inhibitors
Authors: Kayalar Celik , Wong William T. , Hendrickson Lisa 
Published: May 2005

AbstractUpon reduction of serum in their media, mouse BC3H1 muscle cells withdraw from the cell cycle and begin to differentiate. In differentiating cells, the induction of muscle‐specific genes is accompanied by a distinct morphological chance. However, differentiated BC3H1 cells do not fuse with each other; they remain mononucleated. Metalloendoprotease inhibitors selectively block the differentiation of BC3H1 cells while inhibitors of other protease types are ineffective. In these cells, the degradation of the internalized insulin is initiated by a 110 kDa, non‐lysosomal protease known as the insulin‐degrading enzyme. The same metalloendoprotease inhibitors that block BC3H1 differentiation also inhibit, with a similar specificity and potency, the in vitro and the in vivo degradation of insulin by the insulin‐degrading enzyme. When the serum in the medium is reduced, the activity of the insulin‐degrading enzyme in the cell cytoplasm increases rapidly. This increase precedes any detectable change in the differentiation state of these cells by about 12 hours. These results, together with very similar ones obtained with primary rat skeletal muscle cells, support our earlier proposal that the insulin‐degrading enzyme is the metalloendoprotease involved in the initiation of the morphological and biochemical differentiation of muscle cells in culture.
Characterization and partial purification of human epithelial transforming growth factor
Authors: Dunnington Damien J. , Scott Robert G. , Anzano Mario A. , Greig Russell 
Published: May 2005

AbstractA polypeptide growth factor has been partially purified from medium conditioned by the human adrenocortical carcinoma cell line SW13. This factor, designated h‐TGFe, stimulates anchorage‐independent growth of the SW13 cells. Similar activity was observed in human milk, and in conditioned media from seven of 14 epithelial cell lines. The SW13‐derived activity is stable to low pH and 8M urea but labile to dithiothreitol and 2% sodium dodecyl sulfate. Human TGFe does not bind to heparin and fails to stimulate growth of endothelial cells in monolayer culture. The apparent molecular weight of h‐TGFe is 59k by size exclusion chromatography in the presence of 8M urea and the activity binds strongly to cation exchangers. The activity elutes at 15–30% acetonitrile from a C18 reversephase column and has been partially purified by using a four‐step chromatographic procedure. TGFe appears to be a novel growth factor produced by many epithelial cells and tissues.
Cellular senescence: A reflection of normal growth control, differentiation, or aging?
Authors: Peacocke Monica , Campisi Judith 
Published: May 2005

AbstractNormal cells, with few exceptions, cannot proliferate indefinitely. Cell populations—in vivo and in culture—generally undergo only a limited number of doublings before proliferation invariably and irreversibly ceases. This process has been termed the finite lifespan phenotype or cellular senescence. There is long‐standing, albeit indirect, evidence that cellular senescence plays an important role in complex biological processes as diverse as normal growth control, differentiation, development, aging, and tumorigenesis. In recent years, it has been possible to develop a molecular framework for understanding some of the fundamental features of cellular senescence. This framework derives primarily from the physiology, genetics, and molecular biology of cells undergoing senescence in culture. Our understanding of senescence, and the mechanisms that control it, is still in its infancy. Nonetheless, recent data raise some intriguing possibilities regarding potential molecular bases for the links between senescence in culture and normal and abnormal growth control, differentiation, and aging.
GMP‐140: A receptor for neutrophils and monocytes on activated platelets and endothelium
Authors: McEver Rodger P. 
Published: May 2005

AbstractGMP‐140 is a membrane glycoprotein located in secretory granules of platelets and endothelium. When these cells are activated by agonists such as thrombin, GMP‐140 is rapidly translocated to the plasma membrane. GMP‐140, along with ELAM‐1 and the peripheral lymph node homing receptor, defines the selectin family of structurally related molecules that regulate interactions of leukocytes with the blood vessel wall. Each of these molecules contains an N‐terminal lectin‐like domain, followed by an EGF‐like region, a series of consensus repeats related to those in complement‐binding proteins, a transmembrane domain, and a short cytoplasmic tail. The genomic structures of the selectins suggest that they arose by duplication and modification of exons encoding specific structural domains. GMP‐140 is a receptor for neutrophils and monocytes when it is expressed on activated platelets and endothelium. This property facilitates rapid adhesion of leukocytes to endothelium at regions of tissue injury as well as platelet‐leukocyte interactions at sites of inflammation and hemorrhage. Like other leukocyte adhesion molecules, GMP‐140 may also participate in pathologic inflammation, thrombosis, and tumor metastasis. Confirmation of such pathologic roles may lead to design of new drugs that block adhesive receptor function in human disease.
The specific protein phosphatase inhibitor okadaic acid differentially modulates insulin action
Authors: Hess Susan L. , Suchin Craig R. , Saltiel Alan R. 
Published: May 2005

AbstractThe pleiotropic nature of insulin action suggests diverse mechanisms of signal transduction for the hormone. The specific protein phosphatase inhibitor, okadaic acid, is utilized to differentiate metabolic pathways that may be regulated by phosphorylation or dephosphorylation of key enzymes. In H‐35 hepatoma cells, okadaic acid inhibits insulin‐stimulated glycogen synthesis with an IC50 of 400 nM. In contrast, activation of lipogenesis by insulin is inhibited with an IC50 of 50 nM okadaic acid. The toxin also inhibits stimulation of lipogenesis in these cells by the insulin‐sensitive inositol glycan enzyme modulator. In isolated rat adipocytes, insulin‐stimulated lipogenesis is also inhibited by okadaic acid with an IC50 of approximately 1,700 nM. The antilipolytic effect of insulin in these cells is more sensitive to okadaic acid, exhibiting an IC50 of 150 nM. Maximal activation of lipogenesis by insulin is dramatically reduced by okadaic acid with no effect on the concentration required for half‐maximal activation, whereas the sensitivity of insulin‐induced antilipolysis is attenuated by okadaic acid, with no apparent reduction in the maximal effect of the hormone. Taken together, these data suggest that specific phosphatases may be differentially involved in some of the metabolic pathways regulated by insulin.
Neutral metalloendopeptidase associated with the smooth muscle cells of pregnant rat uterus
Authors: Ottlecz Anna , Walker Susan , Conrad Matt , Starcher Barry 
Published: May 2005

AbstractThe pregnant rat uterus contains a membrane‐bound metalloendopeptidase that is biochemically and immunologically similar to kidney enkephalinase (E.C.3.4.24.11). The uterus enzyme readily cleaved specific neutral endopeptidase substrates and oxytocin as well as the synthetic elastase substrate, Suc(Ala)3‐pNA, yet did not digest native elastin. Using specific inhibitors, the uterus endopeptidase was identified as a metallopeptidase and not a serine protease, having an absolute requirement for zinc and perhaps calcium for maximal activity. The uterus endopeptidase cross‐reacted with polyclonal antiserum to kidney microvillar endopeptidase and a monoclonal antibody to common acute lymphocytic leukemia antigen. Immunohistochemical localization of the enzyme in a 17 day pregnant uterus indicated that the enzyme was localized on the smooth muscle bundles of the myometrium and the endometrial epithelium. Total enzyme activity was 25 times higher in the late‐term pregnant uterus (17th day of pregnancy) than in the nonpregnant uterus. Enzyme levels dropped rapidly prior to parturition and within 4 days after delivery the enzyme activity had returned to control levels. Inhibition of NEP in uterine strips with phosphoramidon resulted in a marked potentiation of oxytocin‐induced contractions. Our results suggest that the uterine endopeptidase may have an important role in regulating uterine smooth muscle cell contraction during the latter stages of pregnancy through its action on oxytocin and perhaps other biologically active peptides.
Na+‐dependent, active nucleoside transport in S49 mouse lymphoma cells and loss in AE‐1 mutant deficient in facilitated nucleoside transport
Authors: Plagemann Peter G. W. 
Published: May 2005

AbstractS49 murine lymphoma cells were examined for expression of various nucleoside transport systems using a non‐metabolized nucleoside, formycin B, as substrate. Nitrobenzylthioinosine (NBTI)‐sensitive, facilitated transport was the primary nucleoside transport system of the cells. The cells also expressed very low levels of NBTI‐resistant, facilitated nucleoside transport as well as of Na+‐dependent, concentrative formycin B transport. Concentrative transport was specific for uridine and purine nucleosides, just as the concentrative nucleoside transporters of other mouse and rat cells. A nucleoside transport mutant of S49 cells, AE‐1, lacked both the NBTI‐sensitive, facilitated and Na+‐dependent, concentrative formycin B transport activity, but Na+‐dependent, concentrative transport of α‐aminoisobutyrate was not affected.
A new perspective on ornithine decarboxylase regulation: Prevention of polyamine toxicity is the overriding theme
Authors: Morris David R. 
Published: May 2005

AbstractThe polyamines are essential cellular components for growth. Control of a key regulated enzyme of polyamine biosynthesis, ornithine decarboxylase (ODC), as a function of growth, is an area of intense interest. A unique regulatory property of ODC is the short half‐life of the protein, which has been suggested to be an important factor in rapid activation of polyamine biosynthesis after cells are mitogenically stimulated. In this paper, it is argued that the biological significance of the short half‐life of ODC is unrelated to the rate of its induction to a new steady state by growth factors, which is in fact limited by the relatively long half‐life of the ODC mRNA. Instead, I suggest that the rapid turnover of ODC protein becomes of significance when cells cease growth and expeditious downregulation of the enzyme is important in preventing polyamine overproduction, which would result in cytotoxicity in the arrested cells. Although mitogenic activation of ODC expression has been studied extensively, there is very little known about the mechanisms controlling downregulation of polyamine biosynthesis during the arrest of animal cell growth. These considerations suggest that this would be a fertile area of future inquiry.
Mutational analysis of leucine 47 in human epidermal growth factor
Authors: Matsunami Risë K. , Yette Margaret L. , Stevens Audrey , Niyogi Salil K. 
Published: May 2005

AbstractSeven site‐specific mutants (including changes to other hydrophobic, charged, and heterocyclic amino acids) of leucine 47 of human epidermal growth factor (EGF) were generated by protein engineering and characterized for their activity in three assays: radioreceptor competition binding in membrane fractions, the stimulation of the EGF receptor's tyrosine kinase activity, and the stimulation of thymidine uptake in tissue culture cells. K½ (concentration required for half maximum response) values for each of the mutants are reported in the three assays. The results show that the native leucine residue is quite important for EGF activity. Substitutions are tolerated to different degrees, depending upon hydrophobicity and size of the side chain. Substitution with ionic residues led to the most drastic reduction in activity. One‐dimensional nuclear magnetic resonance spectroscopy, at physiological pH, of several of the mutants did not detect any major structural perturbations which would account for the loss of activity. The results suggest that the side chain of leucine 47, because of its charge neutrality, size, and hydrophobicity, is highly important, although not absolutely essential for the interaction of EGF with its receptor. A striking finding was the lower (compared with wild type) Vmax values of the mutants in the tyrosine kinase reaction, but these low Vmax mutants, in cell culture experiments, were able to stimulate at high concentrations a growth response equivalent to wild type EGF.
PCR analysis of dystrophin gene mutation and expression
Authors: Chamberlain Jeffrey S. , Farwell Nancy J. , Chamberlain Joel R. , Cox Gregory A. , Caskey C. Thomas 
Published: May 2005

AbstractDuchenne muscular dystrophy (DMD) is caused by mutations that impair normal production of dystrophin in muscle and brain tissues. The dystrophin gene is expressed at extremely low levels in both humans and mice, which makes analysis of the 14kb mRNA a difficult task. In addition, 30% of all cases of DMD (and the genetic lesion in all three known mdx mouse models for DMD) are thought to arise from single base mutations, yet methods are not available to routinely identify and analyze these mutations and their effects on disease progression. We have been using the polymerase chain reaction (PCR) to analyze the expression of the murine dystrophin gene. A simple assay is described that distinguishes the murine dystrophin transcripts expressed from either the muscle or brain promoter. In addition, amplification of overlapping segments from the 5′ end of the murine transcript has enabled the identification of DNA sequence variations between wild‐type and mdx mice. These results demonstrate that the mutation in the original strain of mdx mice is distinct from those in two newer mdx isolates and that three independently isolated mdx mutants are available for study of DMD.
Vascular permeability factor: A unique regulator of blood vessel function
Authors: Connolly Daniel T. 
Published: May 2005

AbstractVascular permeability factor (VPF), also known as vascular endothelial growth factor (VEGF), is a potent polypeptide regulator of blood vessel function. VPF promotes an array of responses in endothelium, including hyperpermeability, endothelial cell growth, angiogenesis, and enhanced glucose transport. VPF regulates the expression of tissue factor and the glucose transporter. All of the endothelial cell responses to VPF are evidently mediated by high affinity cell surface receptors. Thus, endothelial cells have a unique and specific spectrum of responses to VPF. Since each of the responses of endothelial cells to VPF are also elicited by agonists, such as bFGF, TNF, histamine and others, it remains a major challenge to determine how post‐receptor signalling pathways maintain both specificity and redundancy in cellular responses to various agonists.
Effect of phospholipases and proteases on the [3H]N6‐(R)‐phenylisopropyladenosine ([3H]R‐PIA) binding to A1 adenosine receptors from pig cerebral cortex
Authors: Casadó Vicent , Mallol Josefa , Lluis Carmen , Canela Enric I. , Franco Rafael 
Published: May 2005

AbstractThe effect of phospholipases and proteases on the membrane‐bound and solubilized A1 adenosine receptor has been studied. Phospholipids modulate the [3H]N6‐(R)‐phenylisopropyladenosine binding to A1 adenosine receptors in crude membranes and in soluble preparations, because changes in the phospholipid environment decrease both the binding capacity and the affinity for the ligand. It has become clear that (1) there is co‐solubilization of receptor and phospholipids; (2) the phospholipid requirements are different for the coupled and the uncoupled receptor; (3) a net charge in the polar head produced by phospholipase D prevents the agonist binding to the receptor‐G protein complex; alternatively, when the whole polar head is removed by phospholipase C the uncoupled receptor is altered; and (4) the protease action upon the receptor suggests that receptor coupled to G protein is more protected by the membrane than the uncoupled receptor. In kinetic experiments performed on membranes it was demonstrated that phospholipase C and trypsin increased the Kd value of the high‐affinity state by modifying both k1 and k−1. In contrast they only modified the dissociation constant of the low‐affinity state. In conclusion it should be noted that phospholipids play a key role for the binding of R‐PIA to A1 adenosine receptor. Also, a different disposition within the membrane of the coupled and uncoupled receptor is encountered.
Regulation of transcription‐factor activity during growth and differentiation: Involvement of the nuclear matrix in concentration and localization of promoter binding proteins
Authors: Stein Gary S. , Lian Jane B. , Dworetzky Steven I. , Owen Thomas A. , Bortell Rita , Bidwell Joseph P. , van Wijnen Andre J. 
Published: May 2005

AbstractSeveral lines of evidence are presented which support involvement of the nuclear matrix in regulating the transcription of two genes, histone and osteocalcin, that are reciprocally expressed during development of the osteoblast phenotype. In the 5′ regulatory region of an H4 histone gene, which is expressed in proliferating osteoblasts early during the developmental/differentiation sequence, a dual role is proposed for the nuclear matrix binding domain designated NMP‐1 (−589 to −730 upstream from the transcription start site). In addition to functioning as a nuclear matrix attachment site, the sequences contribute to the upregulation of histone gene transcription, potentially facilitated by concentration and localization of an 84kD ATF DNA binding protein. A homologous nuclear matrix binding domain was identified in the promoter of the osteocalcin gene, which is expressed in mature osteoblasts in an extracellular matrix undergoing mineralization. The NMP binding domain in the osteocalcin gene promoter resides contiguous to the vitamin D responsive element. Together with gene and transcription factor localization, a model is proposed whereby nuclear matrix‐associated structural constraints on conformation of the osteocalcin gene promoter facilitates vitamin D responsiveness mediated by cooperativity at multiple regulatory elements.