bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of intracellular creatine in erythrocytes and myoblasts: Influence of uraemia and inhibition of Na, K‐ATPase
Authors: Bennett Susan E. , Bevington Alan , Walls John 
Published: May 2005

AbstractThe regulation of intracellular creatine concentration in mammalian cells is poorly understood, but is thought to depend upon active sodium‐linked uptake of creatine from extracellular fluid. In normal human erythrocytes, creatine influx into washed cells was inhibited by 40 per cent in the absence of extracellular sodium. In washed cells from uraemic patients, sodium‐independent creatine influx was normal, whereas the sodium‐dependent component of creatine influx was 3·3 times higher than normal, possibly relecting the reduced mean age of uraemic erythrocytes. In spite of this, the intracellular creatine concentration was no higher than normal in uraemic erythrocytes, implying that some factor in uraemic plasma in vivo inhibits sodium‐dependent creatine influx. Both in normal and uraemic erythrocytes, the creatine concentration was 10 times that in plasma, and the concentration in the cells showed no detectable dependence on that in plasma, suggesting that the intracellular creatine concentration is controlled by an active saturable process. Active sodium‐dependent accumulation of creatine was also demonstrated in L6 rat myoblasts and was inhibited when transport was measured in the presence of 10−4M ouabain or digoxin, implying that uptake was driven by the transmembrane sodium gradient. However, when creatine influx was measured immediately after ouabain or digoxin had been washed away, it was higher than in control cells, suggesting that Na,K‐ATPase and/or sodium‐linked creatine transport are up‐regulated when treated with inhibitors of Na,K‐ATPase.
Mitochondrial pyruvate metabolism in liver and kidney during acidosis
Authors: Oliver F. Javier , Salto Rafael , Sola María M. , Vargas Alberto M. 
Published: May 2005

AbstractPyruvate transport and carboxylation have been determined in mitochondria from liver and kidney cortex isolated from Wistar rats with acidosis produced by three different treatments: fasting, exercise and ingestion of ammonium chloride. Fasting for 48 h or swimming for 2 h resulted in an increased rate of CO2 fixation by mitochondria from both organs incubated with pyruvate. This increase was accompanied by a rise in the rate of pyruvate transport in all cases except in mitochondria derived from the kidney of the fasted animals. Acute acidosis produced by the ingestion of ammonium chloride resulted in increases in pyruvate transport and carboxylation in kidney mitochondria, but a drop in pyruvate carboxylation was observed in mitochondria from the liver. The results are discussed in terms of the differential regulation of the mitochondria steps for gluconeogenesis from three carbon precursors in liver and kidney, taking into consideration the hormonal status of the animals and the prevailing available substrates in each condition.
Characterization of γ‐glutamyltranspeptidase in the liver of the frog: 2. Response to season, temperature and thyroid hormone in Rana pipiens
Authors: Sulakhe‐Hemmings Susan J. , Xing Hongmei 
Published: May 2005

AbstractThe impact of season and temperature on frog liver γ‐glutamyltranspeptidase was assessed by measuring the activity of this enzyme in plasma membranes isolated from the livers of Rana pipiens obtained as summer and winter frogs; subjected to short‐term (3 weeks) temperature acclimation; and subjected to multiple‐temperature shifts. Plasma levels of T3 were determined. γ‐Glutamyltranspeptidase was found to be 2·2‐fold higher in the summer frog relative to the winter frog; decreased by 44 percent in the summer frog by cold acclimation and increased by 1·7‐fold in the winter frog by warm acclimation; and increased by 1·9‐fold in the summer frog and 2·8‐fold in the winter frog subjected to multiple‐temperature shifts. Plasma T3 levels were found to be 42‐fold higher in the summer frog relative to the winter frog; decreased by 42 percent by cold acclimation and increased by 2·9‐fold by warm acclimation; and decreased by 39 percent and 38 percent in the summer and winter frogs subjected to multiple temperature shifts. T3 replacement during the last phase of the multiple‐temperature shift protocol, restored the plasma T3 levels to 75 percent of the control levels and prevented the increase evoked by the multiple‐temperature shifts in γ‐glutamyl‐transpeptidase activity. Indeed, enzyme activity in the T3 replaced state was 19 percent lower than in the control state. The involvement of thyroid hormone as a negative regulator of enzyme activity is discussed.
Differences in the G/total actin ratio and microfilament stability between normal and malignant human keratinocytes
Authors: Katsantonis J. , Tosca A. , Koukouritaki S. B. , Theodoropoulos P. A. , Gravanis A. , Stournaras Christos 
Published: May 2005

AbstractThe state of polymerization of actin and the organization of actin filaments is widely believed to be related to cellular transformation. Since the intracellular monomer (G) and filamentous (F) actin content reflects the state of microfilament polymerization, we measured the G/total actin ratio in primary cultures of normal and malignant human keratinocytes. In normal keratinocytes the mean value of this ratio was 0·30 ± 0·03 (mean ± SE, n = 15), while in basal cell carcinoma (BCC) keratinocytes it was 0·49 ± 0·03 (n = 8) and in squamous cell carcinoma keratinocytes (SCC) 0·5 ± 0·07 (n = 4), indicating a 1·7‐fold increase of the G/total actin ratio in malignant cells. These results imply that the proportion of polymerized actin is decreased markedly in malignant keratinocytes, suggesting alterations of microfilament structures which probably occur during the transformation process. This was supported by the morphological changes of microfilament structures as assessed by fluorescence microscopy. A different distribution of actin filaments in normal and malignant cells became evident; stress‐fibres were converging in patches at several points in SCC cells, when compared to normal keratinocytes. Furthermore, incubation of normal and malignant keratinocytes with cytochalasin B indicated differences in the resistance of their microfilament networks. After 1 h exposure to 10−6 and 10−5 M cytochalasin B, microfilaments in normal cells appeared to be less affected than their counterparts in neoplastic cells. Even in a high excess of cytochalasin B (10−4 M), normal keratinocytes preserved their shape, while both basal cell and SCC were totally disrupted. We concluded that the G/total actin ratio was significantly increased in malignant keratinocytes. This seems to be correlated with altered microfilament morphology and resistance to cytochalasin B treatment. Our results suggest that the process of malignant transformation may be characterized by changes in the state of the polymerization of actin and in the stability of the microfilament network indicating that both features could potentially serve as markers determine the transformed state of keratinocytes.
Effect of phorbol 12‐myristate 13‐acetate (PMA) on the phosphoinositol (PI) system in Tetrahymena. Study of the 32P incorporation and breakdown of phospholipids
Authors: Kovács P. , Csaba G. 
Published: May 2005

AbstractPhorbol 12‐myristate 13‐acetate (PMA) treatment elicited an increased 32P incorporation into phospholipids namely phosphatadyl‐inositol (PI); phosphatidyl‐inositol‐4‐phosphate (PIP); phosphatidyl‐inositol‐4,5‐bis‐phosphate (PIP2); phosphatidyl‐acid (PA); phosphatidyl‐choline (PC) and phosphatidyl‐ethanolamine (PE) particularly at the 20–30th min after treatment. The ratio of members of the phosphoinositol system, especially PIP and PI, related to the total phospholipid content was increased. PMA (2 × 10−7 M) was the most effective of the three concentrations tested. The results call attention to the presence of a working phosphoinositol system in Protozoa.
Assessment of growth inhibition by aldehydic lipid peroxidation products and related aldehydes by Saccharomyces cerevisiae
Authors: Wonisch Willibald , Schaur R. Jörg , Bilinski Tomasz , Esterbauer Hermann 
Published: May 2005

AbstractThe effect of pretreatment with aldehydes on the subsequent colony forming efficiency (CFE) of Saccharomyces cerevisiae was investigated. All 21 aldehydes tested inhibited CFE in a dose‐dependent manner. The effective doses, however, differed markedly from 300 mM to 0·07 mM depending on the functional groups and chain length of the aldehydes. Amongst the nine representatives of n‐alkanals, formaldehyde was the most potent inhibitor, reducing CFE to 50 per cent at a dose of 0·3 mM (IC50). In the series of 2‐trans‐alkenals, acrolein was most effective with an IC50 of 0·08 mM and amongst the 4‐hydroxy 2‐trans‐alkenals, 4‐hydroxynonenal was most effective with IC50 of 0·07 mM. In general, effectiveness decreased in the order: 4‐hydroxyalkenals > 2‐alkenals ≫ n‐alkenals. It is proposed that S. cerevisiae is a promising target cell to elucidate further the molecular mechanisms by which aldehydes, particularly the lipid peroxidation product 4‐hydroxynonenal, inhibits cell proliferation.
Modification of frequency augmentation‐potentiation by GTPγS in the frog neuromuscular junction
Authors: Enomoto Koh‐Ichi , Maeno Takashi 
Published: May 2005

AbstractThe effect of modifiers of guanine nucleotide‐binding proteins (G proteins) on the frequency augmentation‐potentiation of transmitter release were studied in the frog neuromuscular junction. Using GenetransferR as a carrier the mean quantal content of the endplate potential increased by penetration of GTPγS into the presynaptic nerve terminal. Neither GTPγS alone nor carrier alone had any effect. The relationship of log (mean quantal content) versus stimulation frequency changed from a single linear to a dual linear function, suggesting that the immediately releasable pool was modified. GDPβS + carrier also had similar effects, but was less potent. Aluminium fluoride was without effect. Extracellularly recorded presynaptic nerve action potentials remained unchanged with GTPγS + carrier. Also, GTPγS + carrier did not affect the action potential nor the cytosolic Ca2+ concentration in differentiated NG108–15 hybrid cells. It is suggested that some smg‐type G protein‐dependent processes are involved in determining frequency augmentation‐potentiation.
The secretion of urokinase‐like plasminogen activator is inhibited by microtubule‐interacting drugs
Authors: Santibañez Juan F. , Maccioni Ricardo B. , Martínez Jorge 
Published: May 2005

AbstractThe secretion of proteinases into the extracellular matrix is one of the main features of tumour cells, as related to their invasive behaviour. Considering the role of the microtubule cytoskeleton, and particularly the action of microtubule‐associated protein (MAPs) in mediating protein secretion, the effects of the anti‐microtubule drugs estramustine and taxol, on the secretion of urokinase‐type plasminogen activator (u‐PA) and the 72 kDa gelatinase were investigated. Treatment of 5637 bladder carcinoma cells with estramustine and taxol inhibited u‐PA secretion into the conditioned medium in a drug concentration‐dependent fashion. This inhibition was confirmed by determinations of u‐PA enzymatic activities and by measurements of the levels of immunoreactive activator. Studies using gelatin zymograms also showed an inhibition of another tumoural proteinase namely the 72 kDa gelatinase. Time‐course uptake experiments showed that estramustine was incorporated into the cells, a process which depended on temperature. On the other hand, immunofluorescence studies indicated that the microtubule network was affected by taxol with the formation of bundles of microtubules at different cell domains. Minor effects were visualized after treatment of the cells with estramustine‐phosphate, a drug that blocks primarily the action of microtubule‐associated proteins. The studies provide a way to analyse the relationships between u‐PA secretion and the integrity of the cytoskeletal network.
Cation‐induced efflux of calcium from the mitochondria of Hymenolepis diminuta
Authors: Wani Javaid H. , Siddiqui Abrar , Srivastava V. M. L. 
Published: May 2005

AbstractWe have previously reported that Ca2+ influx into the mitochondria of Hymenolepis diminuta, a rat intestinal eestode, takes place through an electrophoretic uniport system. Sodium and lithium were found to induce efflux of 45Ca2+ from the mitochondria of H. diminuta. The two cations induced the efflux in a hyperbolic and linear fashion, respectively. The efflux as well as an exchange of external Ca2+ with internal 45Ca2+ was inhibited by lanthanum. The type of Ca2+ transport system in the cestode organelle has been discussed and compared with that of the host (mammalian) counterpart.
Enzymatic, biophysical and ultrastructural changes of plasma membranes in chemical‐induced rat hepatoma
Authors: Paradisi Luciana , Losa Gabriele A. , Dianzani Mario U. 
Published: May 2005

AbstractPlasma membranes from liver of control rats or from chemical‐induced hepatoma were prepared. The basal activity of adenylate cyclase was increased significantly in the rat plasma membranes of DEN‐induced hepatoma compared to normal tissue. The glucagon‐induced response on the cellular effector systems via guanine nucleotide‐binding regulatory proteins (G proteins) was inhibited in hepatoma plasma membranes. These findings suggest that in hepatoma membranes, unlike normal hepatic membranes, the response to hormonal stimuli through regulatory G proteins results in a loss of response to glucagon, as well as to GTP plus glucagon or to GTPγS. However, the activating effects of forskolin, which catalyses the formation of cyclic AMP from ATP acting on the catalytic subunit, were to some extent retained. The methyltransferase‐I behaved in the opposite direction to the adenylate cyclase, showing a decreased activity in hepatoma plasma membranes compared to control membranes. In contrast, the activity of the ecto‐5′‐nucleotidase was significantly increased in hepatoma. These enzymatic changes have been found to influence the membrane fluidity and to be responsible for the ultrastructural modifications of hepatoma plasma membranes which are induced by chemical carcinogens.
Lovastatin induces differentiation of Mono Mac 6 cells
Authors: Weber C. , Erl W. , Weber P. C. 
Published: May 2005

AbstractThe proliferation of human monocytic Mono Mac 6 cells was significantly retarded by treatment with lovastatin (LOV, 10 μM) for 72 h. Treatment of Mono Mac 6 cells with LOV increased surface protein expression of monocyte‐associated CD14 and the integrin‐chain CD11b towards levels found in isolated human blood monocytes. These effects were dose‐dependent and completely reversed by the isoprenoid precursor mevalonate (MVA). LOV failed to induce growth retardation and upregulation of CD11b or CD14 in the less mature premonocytic U937 cell line. While CD11b expression was comparable in Mono Mac 6 cells treated with LOV (10 μM), TNF (100 U ml−1) or LPS (10 ng ml−1), upregulation of CD14 by LOV was less pronounced. Basal CD23 expression was unaffected by LOV but markedly reduced by treatment with TNF or LPS. Moreover, LOV enhanced Mono Mac 6 adhesiveness to human umbilical vein endothelial cells to levels found in isolated human blood monocytes, probably due to the increased CD11b and CD14 expression. In conclusion, LOV can induce differentiation of monocytic cells which is reflected by the retardation of growth, expression of CD14 and CD11b, and enhanced adhesiveness.
Microdensitometric measures of cytoplasmic RNA and total protein in pyramidal neurons of the insular cortex and midfrontal gyrus in patients with Alzheimer's disease
Authors: Colurso Gloria J. , Kan Robert K. , Anthony Adam 
Published: May 2005

AbstractScanning and integrating microdensitometry of azure B‐ and Coomassie brilliant blue G‐stained tissue sections was used to measure the levels of RNA and protein, respectively, in pyramidal neurons of the insular cortex (INS) and midfrontal gyrus (MFG) in patients with Alzheimer's disease (AD) and age‐matched, nondemented control subjects. AD was associated with a decreased neuronal RNA (by 7·4 per cent) and protein (by 28·7 per cent) content in INS. Although the neuronal RNA content was maintained at the control amounts in MFG, the average protein level was lower (14·7 per cent) in AD patients. These results demonstrate a disease‐related impairment in metabolic function in two brain regions connected via discrete corticocortical pathways. Such findings support the hypothesis that a primary site of pathology occurs in AD, and specific neural deficits occur secondarily in certain connected brain regions.
Proteoglycan alterations in skin fibroblast cultures from patients affected with pseudoxanthoma elasticum
Authors: Passi A. , Albertini R. , Contri M. Baccarani , de Luca G. , de Paepe A. , Pallavicini G. , Ronchetti I. Pasquali , Tiozzo R. 
Published: May 2005

AbstractProteoglycans (PGs) were investigated in fibroblast cultures from both apparently normal and involved areas of skin from two patients affected with Pseudoxanthoma elasticum (PXE) and compared to control normal cells. Biochemical analysis showed that cells from the PXE‐affected patients produced a PG population with stronger polyanion properties, as well as a markedly increased amount of high hydrodynamic‐size PGs. Moreover, PGs from PXE‐affected cells showed abnormal hydrophobic interaction properties when examined under associative conditions and included heparan sulphate (HS)‐containing populations with anomalous electrophoretic mobility. These phenomena were particularly evident in the case of PGs secreted into the growth medium. In agreement with these findings immunohistochemical study showed alterations affecting decorin and biglycan, as well as a different content and distribution of HS‐PGs in PXE‐affected cells. The same biochemical and morphological alterations were confirmed for both patients on different cell cultures and were present in cells from both apparently normal and affected skin areas, being more pronounced in the latter. Our results indicate that PXE‐affected fibroblasts in culture exhibit an abnormal PG metabolism, which could affect the normal assembly of extracellular matrix.
Long‐term treatment of swiss 3T3 fibroblasts with dexamethasone attenuates MAP kinase activation induced by insulin‐like growth factor‐I (IGF‐I)
Authors: Hansson Anders , Hehenberger Karin , Thorén Marja 
Published: May 2005

AbstractBone formation is reduced in hyperglucocorticoid states, e.g. Cushing's syndrome or long‐term treatment with synthetic glucocorticoids during rheumatic diseases. Possibly related to decreased sensitivity of the target to insulin‐like growth factor‐I (IGF‐I). In this study, we have sought to identify postreceptor‐mechanisms for glucocorticoid‐induced resistance to insulin‐like peptides in a model system. Treatment of Swiss 3T3 fibroblasts with 100 nM dexamethasone for 48 h reduced IGF‐I‐induced activation of mitogen‐activated protein kinase (MAP kinase). The level of insulin receptor substrate‐1 (IRS‐1) was reduced in dexamethasone‐treated cells, as measured by Western blot; however, the pattern of tyrosine‐phosphorylated protein subsequent to stimulation with IGF‐I (1 min) was not altered. No inhibitory effect of dexamethasone was observed on the level of phosphotyrosine in IRS‐1 in extracts from IGF‐I‐treated cells. The amount of IGF‐I‐induced association of insulin receptor substrate‐1 and phosphatidylinositol 3‐kinase was increased in steroid treated cells. Addition of IGF‐I increased the synthesis of lipid, glycogen and protein, and the reduction of a tetrazolium dye, MTS, in untreated cells. The response to IGF‐I in terms of glycogen synthesis was blunted, whereas the effect of IGF‐I was unaffected for the other three parameters in cells pretreated with dexamethasone. These findings indicate that the activation of MAP kinase may be dissociated from IGF‐I‐induced anabolic pathways and tyrosine phosphorylationof IRS‐1. The results agree with the previously proposed role for the activation of MAP kinase in the regulation of glycogen synthesis. Furthermore, they suggest that dexamethasone‐induced reduction of IRS‐1 expression may be important for the impaired activation of MAP kinase by insulin‐like peptides in steroid‐treated cells.
High glucose and hyperosmolarity increase heparin‐binding epidermal growth factor‐like growth factor (HB‐EGF) production in cultured human aortic endothelial cells
Authors: Asakawa Hideki , Miyagawa Jun‐Ichiro , Higashiyama Shigeki , Goishi Katsutoshi , Hanafusa Toshiaki , Kuwajima Masamichi , Taniguchi Naoyuki , Matsuzawa Yuji 
Published: May 2005

AbstractHeparin‐binding epidermal growth factor‐like growth factor (HB‐EGF) has been shown to be a potent smooth muscle cell (SMC) mitogen and chemoattractant, and might be a candidate factor for the progression of atherosclerosis. We have investigated the effects of high glucose and hyperosmolarity on HB‐EGF production in cultured human aortic endothelial cells. Following the culture of the cells for 2 days with high concentrations of glucose or in the hyperosmolar conditions, we measured the content of HB‐EGF and the rate of production in the cells using a semi‐quantitative immunofluorescent technique and a metabolic radiolabelling method. With high glucose (16.6 mmol) and hyperosmolar conditions (glucose 5.5 mmol + mannitol 11.1 mmol or glucose 5.5 mmol + raffinose 11.1 mmol), the content of HB‐EGF was significantly increased and the metabolic rate was also significantly increased (more than a twofold increase, compared to that of 5.5 mmol glucose). In conclusion, conditions of high glucose or hyperosmolarity increase HB‐EGF production in human aortic endothelial cells. These results suggest that diabetic macroangiopathy might be attributed at least in part to HB‐EGF‐related vascular changes which may be induced by glucose.
Insulin treatment can abolish changes in glucose and glutamine metabolism of lymphocytes and macrophages caused by the implantation of the walker 256 tumour
Authors: Fernandes Luiz Claudio , Mattozo Carlos Alberto , Machado Ubiratan Fabres , Rosa Luis Fernando B. P. Costa , Curi Rui 
Published: May 2005

AbstractActivation of lymphocytes and macrophages by the implantation of tumour cells (107 cells per rat) into the left flank of rats increased the conversion of glucose to lactate and of glutamine to glutamate and aspartate and the decarboxylation of [U‐14C]‐glucose and [U‐14C]‐glutamine in incubated cells. In addition, the amount of GLUT1 was increased in macrophages. The effect of insulin treatment on glucose and glutamine metabolism of lymphocytes and macrophages activated by Walker 256 tumour implantation was also examined. For this purpose, insulin was injected subcutaneously (4 U/100 g b.w. daily) after the fourth day of tumour implantation and the rats were killed 10 days afterwards. Insulin treatment fully reverted the changes due to tumour implantation in the metabolism of glucose and glutamine in lymphocytes and of glucose in macrophages.
Palmitoyl‐CoA synthetase on the external surface of isolated rat hepatocytes
Authors: de Groote Katrien , Velghe Griet , Stals Hedwig K. , Baes Myriam I. , Declercq Peter E. 
Published: May 2005

AbstractAfter incubating isolated rat hepatocytes with [1‐14C]palmitic acid, CoA and ATP (+MgCl2), a significant amount of [1‐14C]palmitoyl‐CoA was found in the incubation medium. There was no correlation between its rate of synthesis and the degree of intactness of the cells. The results indicate that there is a long‐chain fatty acyl‐CoA synthetase active on the external surface of the hepatocyte plasma membrane. The activity of this enzyme was negligible in primary cultures of rat hepatocytes, suggesting that the exofacial long‐chain acyl‐CoA synthetase is an artifact of the collagenase perfusion technique used to prepare the hepatocytes.