bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phospholipid N‐methylation in diabetic erythrocytes: Effects on membrane Na+, K+ ATPase activity
Authors: Kowluru Anjaneyulu , Kowluru Renu A. 
Published: May 2005

AbstractPhospholipid methylation was quantified in non‐diabetic and streptozotocin diabetic rat erythrocytes. While the total mass of methylated lipids remained the same in both groups, the relative abundance of individual methylated lipid species differed significantly in diabetic erythrocytes. Moreover, incubation of erythrocytes membranes with S‐adenosyl methionine, a substrate for methyl transferases, not only increased membrane lipid methylation but also decreased Na+, K+ ATPase activity significantly. These results suggest that phospholipid methylation may cause the observed depression of erythrocyte Na+, K+ ATPase activity in diabetes and could contribute to the altered rheology of erythrocytes in diabetes.
Cloturin: Effect on energy‐producing processes in ehrlich ascites and P388 murine leukaemia cells
Authors: Miko Milan , Krepelka Jiri , Melka Milan 
Published: May 2005

AbstractThe main purpose of the present investigation was to study the effect of cloturin on aerobic glycolysis, endogenous and exogenous respiration and the level of ATP in both Ehrlich ascites carcinoma (EAC) and P388 murine leukaemia cells incubated in vitro. Also its effect on the level of total (T‐SH) and non‐protein (NP‐SH) thiol groups was investigated. A significant inhibition of aerobic glycolysis was found only in P388 cells after 60 min of cloturin action. Cloturin inhibited both endogenous and exogenous respiration of EAC with succinate as substrate. Cloturin decreased the level of ATP after 2 h incubation in both types of tumour cell. The level of NP–SH was decreased more than that of T‐SH in both types of cell.
Effects of hyperthermia on intracellular calcium concentration and responses of cancerous mammary cells in culture
Authors: Furukawa Masahiko , Enomoto Koh‐Ichi , Kato Hirokazu , Ishida Tetsuya , Maeno Takashi 
Published: May 2005

AbstractEffects of hyperthermia on the intracellular calcium concentration (Cai) of an established mouse breast cancer cell line, MMT060562, were studied using fura‐2 fluorescence microscopy and the whole‐cell clamp technique. A sudden change of temperature from 37 to 45°C induced a transient increase in the fluorescence ratio permeability of the cell membrane and inward current. Deletion of extracellular calcium abolished the fluorescence ratio response to the rise in temperture. Cai of some cells increased after hyperthermia treatment at 44–48°C for 20 min, but the average increase of Cai was negligible. After hyperthermia treatment, spontaneous oscillation of Cai, chemical responses to ATP and bradykinin and the mechanically‐induced spreading reponse diminished. However, the mechanically induced increase of Cai within the stimulated cell remained even after hyperthermia treatment. Suppression of the ATP‐induced Cai response recovered to about half the original level within 12 h. Blockage of protein synthesis with cycloheximide (100 μM) had no effect on the recovery. The D‐myo‐inositol 1,4,5‐triphosphate (IP3)‐dependent increase of Cai remained intact even after hyperthermia treatment. It is concluded that hyperthermia treatment increases both the permeability of the cell membrane and Cai, but decreases the sensitivity of cells to ATP and bradykinin, presumably due to modification of the signal transduction mechanism.
Studies on the ATPase of Bacillus cereus
Authors: Higuti I. H. , Stencel M. , Nascimento K. H. , Nascimento A. J. 
Published: May 2005

AbstractThe membrane ATPase (EC 3.6.1.3) of Bacillus cereus was solubilized by a ‘shock‐wash’ process and purified. The non‐specific phosphatase contaminant was separated by glycerol density gradient centrifugation. The optimum temperature was 39·5°C and the pH optimum at 7·5. On SDS‐polyacrylamide gel electrophoresis two classes of subunits were observed in equal proportions with molecular weights of 70 K and 83 K. The effect of various compounds on the enzymatic activity was studied. The enzyme was insensitive to NaN3, oligomycin and to divalent cations, but was inhibited by citrate and oxalate.
Effect of inhibitors and activators of tyrosine kinase on insulin imprinting in Tetrahymena
Authors: Kovács P. , Csaba G. 
Published: May 2005

AbstractPrimary exposure of Tetrahymena cells to insulin gave rise to hormonal (insulin) imprinting in the offspring generations, as judged from the increase in binding upon reexposure to insulin. Vanadate mimicked the action of insulin, inasmuch as it also induced imprinting for insulin, whereas the other tyrosine kinase activator tested, namely H2O2, had no such effect. However, combined treatment with vanadate + H2O2 + insulin induced a more pronounced imprinting for insulin than either insulin or vanadate on their own. The tyrosine kinase inhibitor genistein, a plant flavonoid, did not change the value for insulin binding significantly relative to the control immediately after exposure, but increased it slightly in the offspring generations after 24 h at high dilution. Upon combination with insulin, 10−4 M genistein inhibited imprinting by insulin. These experimental observations suggest that there may be a key role for tyrosine kinase activity in the mechanism (development) of imprinting.
An in situ study of beta‐glucosidase activity in normal and gaucher fibroblasts with fluorogenic probes
Authors: Kohen Elli , Kohen Cahide , Hirschberg Joseph G. , Santus Rene , Grabowski Gregory , Mangel Walter , Gatt Shimon , Prince Jeffrey 
Published: May 2005

AbstractBeta‐glucosidase activity was evaluated in situ by means of fluorogenic probes in normal human fibroblasts and fibroblasts from homozygous carriers of the Gaucher trait. Probe internalization, targeting to lysosomes and post‐cleavage probe retention were the primary concerns. Internalization and targeting were attempted by in situ photosensitized labilization of lysosomal membranes, lysosomotropic detergents and the use of low density lipid (LDL) or the receptor ligand apolipoprotein E (ApoE). Post‐cleavage increase of fluorescence with fluoresceinyl (bis) betaglucopyranoside was appreciably above the rather large pre‐cleavage emission. In cells incubated overnight with nonylumbelliferylbetaglucoside (UG9) in the presence of bovine serum albumin and in the absence of ApoE, the probe was dealt with as a cytotoxic agent, accumulating in a paranuclear cap, most likely comprising elements of the endoplasmic reticulum (ER) and Golgi apparatus. Targeting of UG9 to lysosomes occurred within 1 to 3 h of preincubation in the presence of ApoE. There was some evidence of specificity, as Gaucher fibroblasts exhibited weaker cleavage of UG9 (by 50 per cent or more) compared to normal fibroblasts, but in the Gaucher cells there was some residual beta‐glucosidase activity. Cleavage of UG9 was nearly totally suppressed in Gaucher cells treated with the beta‐glucosidase inhibitor, conduritol B epoxide, for 24 h to 7 days. Suppression in the control fibroblasts was evident but to a lesser degree. The in situ method of fluorogenic assay established for beta‐glucosidase deficiency, is in principle applicable to enzyme deficiencies in other lysosomal storage diseases, or to evaluate enhanced enzyme activity following gene therapy.
Dual effects of formylpeptides on the adhesion of endotoxin‐primed human neutrophils
Authors: Bellavite P. , Chirumbolo S. , Lippi G. , Andrioli G. , Bonazzi L. , Ferro I. 
Published: May 2005

AbstractNeutrophils, treated with sequential additions of bacterial products such as endotoxin (E. Coli lipopolysaccharide, LPS) and the chemotactic peptide N‐formyl‐methionyl‐leucyl‐phenylalanine (fMLP), undergo to metabolic activation and express membrane‐anchoring proteins that promote adhesion to serum‐coated culture wells. By investigating the dose–response relationships of these phenomena, we have found that: (a) resting neutrophils do not produce a significant amount of superoxide (O) and show only minimal adhesion to serum‐coated plastic surfaces; (b) fully activatory doeses (> 5 × 10−8 M) of fMLP induce the release of O and a significant increase of the cell adhesion; (c) pretreatment of the cells for 1 h with LPS augments cell adhesion to serum‐coated culture wells in the absence of further stimulation and primes the neutrophils to enhanced fMLP‐dependent O release; (d) addition of low, substimulatory doses of fMLP (from 10−10 M to 5 × 10−9 M) inhibits and reverses the adhesion of LPS‐treated cells, (e) high fMLP doses (> 10−7 M) are additive to LPS in promoting adhesion. Phorbol‐myristate acetate (> 10−9M) increased adhesion in both normal and LPS‐treated neutrophils, but low doses of this stimulant did not inhibit adhesion. Low doses (10−9 M) of fMLP increased intracellular cyclic AMP in both normal and LPS‐treated neutrophils, suggesting that stimulus‐induced rises in cAMP may be the negative signal responsible for down‐modulation of adhesion. Low (5 × 10−9 M) and high (5 × 10−7 M) fMLP doses induced the same increase of expression of CD11/CD18 integrins, indicating that the inhibition of adhesion caused by low doses is not due to quantitative down‐regulation of integrins. These findings may provide an in vitro model of the complex biological events involved in the regulation of neutrophil adhesion.
Characterization of over‐expressed alkaline phosphodiesterase I in tumour‐derived fibroblasts from patients with neurofibromatosis
Authors: Maruyama Etsuko , Takashima Sachio 
Published: May 2005

AbstractAlkaline phosphodiesterase I from cultured fibroblasts from patients with neurofibromatosis was partially purified and characterized following extraction with Triton X‐100, and fractionation with high‐performance liquid chromatography. Some properties were compared with the enzyme extracted from normal‐appearing fibroblasts. The isoelectric points of both the tumour and normal‐appearing cell enzymes were 6·0. The enzyme required Zn2+ for its activity, was heat labile, and nicked superhelical covalently closed circular ϕX174 DNA. The activity was inhibited by GTP, DTT and EDTA. The native molecular weight of alkaline phosphodiesterase I was determined to be 430 000. No differences were found in properties of the tumour‐derived and normal cell enzymes. On purification it was observed that the peak pattern of enzyme activity corresponded to that of 125 kDa protein, which was more abundant upon SDS‐PAGE analysis in tumour cells than in normal cells. The most active fraction of isoelectric focusing, which was performed using disulfide cross‐linked polyacrylamide gel, was used to produce an antibody. The bands of 125, 60 and 40 kDa were immuno‐stained in tumour cell preparation. These results indicate that alkaline phosphodiesterase I, of which the molecular weight is probably 125 kDa, is over‐expressed in tumour‐derived fibroblasts from neurofibromatosis patients.
Stimulation of HeLa cell growth by physiological concentrations of 4‐hydroxynonenal
Authors: Zarkovic Neven , Ilic Zoran , Jurin Mislav , Schaur R. Jörg , Puhl Herbert , Esterbauer Hermann 
Published: May 2005

AbstractThe aim of this study was to analyze the growth response of HeLa cells over a prolonged period of time to a single exposure of physiological and supraphysiological concentrations of 4‐hydroxynonenal (HNE), a peroxidation product of omega‐6‐polyunsaturated fatty acids. Furthermore, the growth modulating effect of serum factors, particularly albumin, on the growth pattern was examined. The effects of HNE on the growth rate and viability of the cells, as well as on the incorporation of labelled amino acids were monitored daily over a period of four days. Fetal calf serum not only had a growth stimualting effect but also modulated the action of HNE. In neither respect was albumin able to substitute for serum indicating that the influence of serum was not exerted via an albumin–HNE conjugate.HNE had a clear dose‐dependent effect and a distinction could be made between a supraphysiological concentration (100 μM), which was primarily cytotoxic and a physiological range (below 10 μM) which showed growth modulatory effects. These effects consisted of a transient inhibition in the initial phase of the cell growth, which under optimal conditions (in presence of serum) was followed by a period of increased proliferation, compared to untreated control cultures, until confluence was attained. It is suggested that HNE is not only a toxic product of lipid peroxidation, but a physiological growth regulating factor as well.
On the association of DNA primase activity with the nuclear matrix in HeLa S3 cells
Authors: Martelli Alberto M. 
Published: May 2005

AbstractWe have reinvestigated the association of DNA primase activity with the nuclear matrix prepared from exponentially growing HeLa S3 cells. We have found that 25–30 per cent of the nuclear primase activity resists extraction with 2 M NaCl and digestion with Dnase I. Unlike previous investigations, done with the same cell line, the results showed that nuclear matrix‐bound DNA primase activity represented less than 10 per cent of the total cell activity. Association of high levels of primase activity with the nuclear matrix was strictly dependent on a 37°C incubation of isolated nuclei prior to subfractionation. Evidence was obtained that the method used for preparing nuclei can have a dramatic effect on the amount of primase activity which is recovered both in the postnuclear supernatant and in isolated nuclei, thus seriously affecting the interpretation of the results about the quantity of DNA primase activity bound to the nuclear matrix.
Enalapril maleate affects 2‐oxoglutarate metabolism in mitochondria from the rat kidney cortex
Authors: Merlin Ma. Eliane , Campello Annibal P. , Klüppel Ma. Lúcia W. 
Published: May 2005

AbstractEnalapril maleate (EM) is the salt of N‐{(S)‐1‐(ethoxycarbonyl)‐3‐phenylpropyl}‐L‐alanyl‐L‐proline, used therapeutically as an anti‐hypertensive agent. The effects of EM on some aspects of the energy metabolism and membrane properties of mitochondria from rat liver and kidney cortex were studied, but only the latter were significantly affected. With 0·8 mM of EM and 2‐oxoglutarate as oxidizable substrate for isolated mitochondria from rat kidney cortex, the findings were: (a) inhibition of the respiratory rate in state III (37 per cent) and decrease (45 per cent) in respiratory control ratio (RCR), with only one addition of ADP; (b) reinforcement of the inhibition when a second addition of ADP was made; (c) no significant effect either on the rate of respiration in state IV or on the ADP/O ratio; (d) no effect on the ATPase activity of mitochondria from liver or kidney cortex; (e) inhibition of the transmembrane potential (Δψ) after a second addition of ADP; (f) inhibition of the 2‐oxoglutarate dehydrogenase complex. It is suggested that in kidney mitochondria, EM interferes in the gluconeogenesis dependence of at least five substrates: 2‐oxoglutarate, glutamine, glutamate, lactate, and pyruvate. Also EM may inhibit Na+/H+ exchange causing natriuresis.
Mechanism by which ethanol inhibits phosphatidylcholine biosynthesis in human leukemic monocyte‐like U937 cells
Authors: Chu Arthur J. 
Published: May 2005

AbstractA previous study showing that ethanol (ETOH) blocked [3H]choline incorporation into phosphatidylcholine (PC) suggested an inhibition of PC biosynthesis in human leukemic monocyte‐like U937 cells. The mechanism of the inhibitory action of ETOH was investigated. Cells were pulsed with [3H]choline for 30 min and chased in the presence or absence of ETOH for up to 6 h. PC biosynthesis was inhibited drastically within 1 h after exposure to ETOH which increased intracellular cAMP appreciably. After a 3‐h treatment, ETOH significantly inhibited both choline kinase (CK) and the cytosolic CTP: cholinephosphate cytidylyltransferase (CT). The inactivated CT was no longer stimulated by exogenous phosphatidylglycerol (PG). There was no evidence for redistribution of CT activity between cytosol and microsomes. When cells were exposed to 8‐Bromo‐cAMP ranging from 100 to 300 μM, PC biosynthesis remained unaffected despite the drastically elevated cAMP. These results seem to suggest that the raised cAMP is not a prerequisite for the inhibition of PC biosynthesis in U937 cells. Following pretreatment with protein kinase inhibitors (H‐89 and K‐252a), PC biosynthesis was decreased significantly and the inhibitory effect of ETOH was potentiated. Taken together, our results suggest that the inhibition of PC biosynthesis and the inhibitory effect of ETOH are independent of the activation of cAMP‐dependent protein kinase. Unlike protein kinase inhibitors, pretreatment with tyrosine kinase inhibitors (erbstatin, genistein and tyrphostin 25) resulted in differential effects on PC biosynthesis and on the inhibitory action of ETOH. Genistein stimulated PC biosynthesis by 30 per cent as well as partially preventing /reversing the ETOH action, while tyrphostin 25 produced a synergistic inhibition. The relevance of tyrosine phosphorylation/dephosphorylation to the regulation of PC biosynthesis and ETOH action remains to be established.
Lidocaine inhibits choline uptake and phosphatidylcholine biosynthesis in human leukemic monocyte‐like U937 cells
Authors: Chu Arthur J. , Lee Jack M. 
Published: May 2005

AbstractThe effect of lidocaine on [3H]choline uptake and the incorporation of label into phosphatidylcholine (PC) in human monocyte‐like U937 cells was investigated. Lidocaine inhibited the rate of choline uptake in a dose‐dependent manner; at 3·2 mM it resulted in a drastic reduction, by as much as 65 per cent (n = 10; p < 0·0005) or 55 per cent (n = 10; p < 0·0006) in a 3‐ or 6‐h incubation, respectively. Lidocaine also decreased the rate of choline incorporation into PC in a dose‐dependent manner. At the highest dose, nearly 70 per cent or 45 per cent reduction was seen in a 3‐ or 6‐h incubation, respectively. Analysis of choline‐containing metabolites showed that the major label association with phosphocholine and PC was reduced to a similar extent which was also parallel to the inhibition of choline uptake. At 3·2 mM lidocaine, the reduction of choline uptake was shown to follow a competitive inhibition. In the case of [3H] choline incorporation into PC, the inhibitory pattern was shown to be of a mixed type. The pulse‐chase study dissecting the effect on choline metabolism from that on total choline uptake indicated that lidocaine exerted an additionally inhibitory effect on intracellular choline metabolism into PC. In a separate protocol in which the labelled cells were first allowed to be chased until 3H‐incorporation into PC reached a steady state, lidocaine no longer showed any effect. These results seem to exclude the possibility of enhanced PC breakdown and further suggest that the main inhibitory effect is on the CDP‐choline pathway for PC biosynthesis. After a 3‐h treatment, CTP: cholinephosphate cytidylyltransferase (CYT) in both the cytosolic and microsomal fractions was inhibited by approximately 20 per cent, while choline kinase (CK) and choline phosphotransferase (CPT) remain relatively unchanged. There was no evidence for translocation of CYT between cytosol and microsomes. Taken together, we have demonstrated a dual inhibitory function of lidocaine which inhibits PC biosynthesis in addition to its ability to block choline uptake profoundly in U937 cells.
Energy metabolism of reticulocytes: Two different sources of energy for Na+K+‐ATPase activity
Authors: Kostić Milosav. M. , Živković R. V. 
Published: May 2005

AbstractTotal energy production in rabbit reticulocytes amounted to 136·52 ± 6·50μmol ATP h−1ml−1 of reticulocytes: 88·3 per cent was provided by oxidative phosphorylation, whereas only 11·7 per cent by aerobic glycolysis. Na+K+‐ATPase accounted for 23 per cent, i.e. 27·65 ± 2·55μmol ATP h−1ml−1 of reticulocytes, in the overall energy consumption in reticulocytes of rabbits. Under basal conditions ATP for Na+K+‐ATPase activity was derived exclusively from oxidative phosphorylation. However, when the activity of Na+K+‐ATPase was increased due to the stimulation of adenylate cyclase by (−)‐isoprenaline, the additional energy required was provided by aerobic glycolysis. These results indicate that two different compartments, one cytosolic and the other mitochondrial, provide energy for Na+K+‐ATPase activity in reticulocytes.
Effect of omeprazole on secretion, synthesis and the gene expression of pepsinogen in the guinea pig stomach mucosa
Authors: Tsukada Shinko , Ichinose Masao , Kakei Nobuyuki , Tatematsu Masae , Tezuka Noriaki , Matsushima Masashi , Miki Kazumasa , Kurokawa Kiyoshi , Nozawa Masayuki , Kageyama Takashi , Takahashi Kenji , Fukamachi Hiroshi , Nakane Paul K. 
Published: May 2005

AbstractThe effects of omeprazole, a proton pump inhibitor, on gene expression, protein synthesis, intracellular storage and secretion of pepsinogen in guinea pig stomach were investigated.After treatment with omeprazole for five days, acid and pepsinogen secretion into the gastric lumen was significantly reduced. Concomitant with this, there was an increase in intracellular pepsinogen as demonstrated by increased pepsin activity in the gastric mucosa, more intense immunohistochemical staining by antibodies specific of pepsinogen and accumulation of secretory granules in the cells producing pepsinogen. In these cells, the amount for pepsinogen mRNA was reduced as revealed by Northern blotting and in situ hybridization. Ultrastructurally the endoplasmic reticulum of these cells was poorly developed, the findings being consistent with a reduction in protein synthesis. It appears that omeprazole inhibits the secretion of pepsinogen, increasing the intracellular store and leading to the reduction in gene expression probably by a feedback mechanism and consequent reduction in pepsinogen synthesis. Since these changes were most evident in the acid‐secreting fundic gland mucosa, as compared with other mucosae secreting only pepsinogen, namely pyloric and duodenal mucosa, it appears probable that these changes are linked with omeprazole‐induced reduction in the acid secretion.
N‐3 but not N‐6 fatty acids reduce the expression of the combined adhesion and scavenger receptor CD36 in human monocytic cells
Authors: Pietsch A. , Weber C. , Goretzki M. , Weber P. C. , Lorenz R. L. 
Published: May 2005

AbstractCD36, a multifunctional adhesion receptor e.g. for thrombospondin and collagen, as well as a scavenger receptor for oxidized low density lipoprotein, is expressed e.g. on platelets and monocytes. By this dual role it might be involved in early steps of atherosclerosis like the recruitment of monocytes and formation of foam cells. We therefore studied the effects of n‐3 fatty acids on CD36 expression in human monocytic cells. Incorporation of eicosapentaenoic acid (EPA, C20:5n‐3) and docosahexaenoic acid (DHA, C22:6n‐3) into cellular phospholipids resulted in a significant reduction of CD36 expression at the mRNA and protein level, whereas arachidonic acid (AA, C20: 4n‐6) and linoleic acid (LA, C18:2n‐6) tended to increase CD36 expression compared to the control. This specific down‐regulation of CD36 by n‐3 fatty acids in cells involved in the initiation and progression of atherogenesis and inflammation, represents a further mechanism that may contribute to the beneficial effects of n‐3 polyunsaturated fatty acids (PUFA) in these disorders.