bluuebunny/crossref_metadata_2025_split huggingface dataset:
Localization of biotransformational enzymes along the crypt—villus axis of the rat intestine. Evaluation of two cell isolation procedures
Authors: Koster Andries Sj. , Borm Paul J. A. , Noordhoek Jan , Dohmen M. René 
Published: May 2005

AbstractRat intestinal epithelial cells were isolated by EDTA‐chelation, combined with gentle shaking (modified Weiser procedure) or with strong longitudinal vibration (Harrison/Webster procedure). Both methods yield large numbers of viable cells and are relatively easy to use. Electronmicroscopical and biochemical data indicate that cell fractions from different levels of the villous region can be obtained only by the modified Weiser procedure. When strong mechanical forces are involved (Harrison‐Webster procedure) the villus epithelium is released according to an all‐or‐nothing process. The biotransformational capacity of cell fractions, obtained from different levels of the villi by the modified Weiser procedure, was investigated. It was shown that the rate of metabolism of 7‐ethoxycoumarin and 1‐naphthol was substantially higher in lower villous cells than in cells isolated from the upper villous region. O‐Deethylation of 7‐ethoxycoumarin decreases from 145 ± 13 pmole/min mg cell protein (72 ± 4% conjugated) in lower villous cells to 62 ± 12 pmole/min mg cell protein (37 ± 6% conjugated) in tip cells. Glucuronidation of 1‐naphthol decreased from 495 ± 23 pmole/min mg cell protein (lower villous cells) to 137 ± 13 pmole/min mg cell protein (tip cells).
The effect of various aldehydes on the respiration of rat liver and hepatoma AH‐130 cells
Authors: Canuto R. A. , Biocca M. E. , Muzio G. , Garcea R. , Dianzani M. U. 
Published: May 2005

AbstractSome aldehydes, produced during lipid peroxidation of liver lipids, are able to inhibit the respiration of mitochondria and of intact cells both in normal hepatocytes and in Yoshida hepatoma. In mitochondria, the respiratory stimulation produced by addition of ADP and dinitrophenol is decreased more in hepatoma than in normal liver. Two‐ to four‐fold higher concentrations of aldehydes are needed to obtain the same degree of inhibition in normal liver mitochondria as in tumorous organs. The effect of aldehydes on intact cell respiration is absent or very low in hepatocytes, but it is consistently observed in hepatoma cells.
Lysosomal enzymes in human platelets
Authors: Leoncini Giuliana , Balestrero Flavio , Maresca Mitzi 
Published: May 2005

AbstractIn human freshly prepared platelets the following lysosomal enzymes were studied: α‐mannosidase, α‐fucosidase, β‐galactosidase, β‐glucosidase, β‐glucuronidase, β‐N‐acetylglucosaminidase and acid phosphatase. For each of the examined enzymes the conditions providing maximal activity (pH, buffer), kinetic parameters (saturating substrate concentration and Km) as well as heat stability were established. On the basis of these parameters it is suggested that many of the serum glycohydrolases may be platelet derived.
Formation of activated oxygen in the hypoxic rat liver
Authors: Räder Lutz , Siems Werner , Müller Marianne , Gerber Gerhard 
Published: May 2005

AbstractThe biliary GSSG efflux rate of normoxic perfused rat liver was 1·5 ± 0·2 nmol/min/g liver wet weight. The GSSG efflux rate as indicator for the flux through the glutathine peroxidase and, therefore, for an oxidative loading incvreased with the extent of hypoxia. 2·6 ± 0·5 nmol/min/g were released from the severely hypoxic liver. The hydroxyl radical scavenger formate as well as the xanthine oxidase inhibitor allopurinol reduced the efflux rate of GSSG.GSH was released from the perfused liver at a rate of 15·5 nmol/min/g which was nearly unchanged in severe hypoxia.The high rate of glucose liberation from the hypoxic liver declined to almost that of the normoxic organ in the presence of formate.There is an ‘oxidative stress’ during hypoxic liver perfusion which probably originates from increased generation of activated oxygen species in the degradation of purine nucleotides.
Investigation of the role of ubiquinone in rat liver subcellular compartments
Authors: Casu A. , Cottalasso D. , Pronzato M. A. , Rolla C. , Marinari U. M. , Nanni G. 
Published: May 2005

AbstractThe role of ubiquinone in the Golgi apparatus is still unknown, even if it might be considered as a lipid marker of the Golgi compartment because of its high content in these subcellular fractions. In vivo modulation of ubiquinone with ethanol and in vitro pentane extraction show that ubiquinone is not required either for NADH‐ferricyanide reductase, acetaldehyde dehydrogenase activity, or Ca2+ and Mg2+ stimulated ATPases.Since ubiquinone does not seem to be involved in these enzymic activities in Golgi compartments, other possible functions are discussed, related to a role in membrane fluidity or as a barrier to the propagation of free radicals.
Expression of a particular β‐N‐acetylgucosaminidase isoenzyme in human haematopoietic leukemic cell‐lines
Authors: Orlacchio A. , Emiliani C. , Tabilio A. , Pioda G. B. 
Published: May 2005

AbstractN‐acetyl‐β‐D‐glucosaminidase (NAG) activity and isoenzyme profiles were studied in myeloid, histiocytic, B‐lymphoid, T‐lymphoid and lymphoblastoid continuous cell lines in order to determine if N‐acetyl‐β‐D‐glucosaminidase isoenzyme expression may help to distinguish among various types of leukemic proliferation.Total NAG activity in myeloid, histiocytic, erythroleukemic cell lines were higher than Burkitt's lymphoma derived cell lines (B‐lymphoid), T‐ or lymphoblastoid cell lines.On chromatofocusing by PBE 94 coupled with an automated enzyme assay an intermediate (I) β‐N‐acetyl‐glucosaminidase form, eluting between forms B and A, was found in all leukemic and in Epstein‐Barr virus infected lymphoblastoid cell lines analysed.The different profiles recorded, the expression of the I form and the different I/B ratios may be useful as markers of tumour proliferation.
Cellular distribution of lysosomal hydrolase activities in the regenerating rat liver
Authors: Baccino Francesco M. , Barrera Giuseppina , Bonelli Gabriella , Messina Maria , Musi Marco , Tessitore Luciana 
Published: May 2005

AbstractCathepsins B and D, β‐galactosidase, and acid phosphatase activities were found to be decreased in the regenerating rat liver, the reduction being maximal around the peak of hepatocyte mitoses (30 h). To investigate whether these changes could be heterogeneously distributed among hepatic cells, total cell populations from control or two‐thirds hepatectomized rat livers were dissociated by the collagenase perfusion technique and analysed by different procedures. Isopycnic centrifugation in a Metrizamide gradient satisfactorily resolved hepatocytes and non‐parenchymal cells from control animals but was not adequate when applied to 30‐h regenerating liver cells. Colchicine treatment of the hepatectomized animals, resulted in substantial accumulation of phase M‐hepatocytes. Subpopulations considerably enriched in fast‐sedimenting phase M‐cells were obtained by sedimentation at 1 g of the total liver cell population, and subsequently analysed by isopycnic equilibration. Phase M‐hepatocytes were shown to have markedly reduced levels of β‐galactosidase, acid phosphatase, and cathepsin B activities in comparison, not only with control hepatocytes, but also with those parenchymal cells which were not metaphase‐arrested in the same regenerating livers. Therefore, in partially‐hepatectomized rats, hepatocytes progressing up to metaphase in the first mitotic cycle exhibited a selective depletion of lysosomal enzyme activities. The mechanism(s) underlying this change remain(s) presently unknown.
Cortisol succinate is slowly hydrolysed in organ cultures of porcine articular tissues and is not equivalent to cortisol
Authors: Lawrence Christopher E. , Wright Judith M. , Knight C. Graham 
Published: May 2005

AbstractThe pro‐drug cortisol succinate is frequently used as a substitute for cortisol in organ cultures. We found, however, that in Dulbecco's modified Eagle's medium the time taken for the ester to undergo 50 per cent hydrolysis (t½) to cortisol was 75 h. When 15 per cent heat‐inactivated normal rabbit serum was present t½ decreased to 47 h, but the rate of hydrolysis was not further increased in the presence of porcine articular cartilage or minced synovial tissue. When frozen and thawed synovium was present t½ decreased to 33 h, presumably due to the release of carboxyl‐esterases from the disrupted cells. The level of tetrahydrocortisol was low in all of the cultures. The slow hydrolysis of cortisol succinate resulted in the exposure of the tissues to undersirable fluctuations in the concentration of active hormone, which decreased to low levels at each medium change. Thus, in co‐cultures of porcine synovium and articular cartilage, cortisol had a greater inhibitory effect than cortisol succinate on the breakdown of cartilage matrix caused by synovial tissue.
Characterization and use of polyclonal antibody to Na+, K+‐ATPase: Immunocytochemical localization in salt glands of the duck
Authors: Russo James J. , Merchant Juanita L. , Eager Patricia R. , Barrnett Russell J. 
Published: May 2005

AbstractThe amount of Na+, K+‐ATPase of the avian salt gland increased concomitantly with plasma membrane surface area during salt feeding of ducklings (adaptation), and both enzyme content and membrane surface area decreased upon return to fresh water (deadaptation). In a further study of the enzyme, a marker for plasma membrane biogenesis, polyvalent antibodies were raised to the denatured α‐subunit of the purified ATPase. Antisera did not inhibit enzymatic activity but immunoprecipitated the phosphorylated intermediate of the α‐subunit. Furthermore, the α‐subunit, which was not glycosylated, was immunoprecipitated from homogenates of tissue slices metabolically labelled with [35S]‐methionine, using antisera raised against either duck salt gland or dog kidney α‐subunit. The former antisera also recognized the α‐subunit in the brain, heart, kidney, liver, intestine and skeletal muscle of the duck.Immunocytochemistry with the antisera raised to the duck salt gland α‐subunit revealed reaction at basolateral as well as apical plasma membrane in the duck salt gland principal cells, with essentially no deposits no deposits on peripheral cells, fibroblasts, erythrocytes, endothelial cells and neural elements. Within the principal cells, immunolabelling was also detected on small vesicles, multivesicular bodies and lysosomes; deposits on extracellular debris and vesicles in the lateral and lumenal spaces were also apparent. The labelling patterns were qualitatively but not quantitatively similar in salt glands of control, adapted and deadapted ducklings, and are discussed in the context of a model for plasma membrane biogenesis and turnover in which degradative events may play a major role.
Growth hormone binding and stimulation of amino acid uptake in epithelial cells of rat ventral prostate
Authors: Prieto J. C. , Carmena M. J. 
Published: May 2005

AbstractThe binding of [125I]‐human growth hormone (hGH) was studied in epithelial cells isolated from rat ventral prostate. Binding and degradation were dependent on time and temperature. The effect of a lysosomotropic agent suggested internalization and lysosomal degradation of the hormone. Dissociation and stoichiometric studies indicated the existence of a single class of GH receptors with a Kd of 0·7 nM and a binding capacity of 46 fmol hGH bound mg−1 cell protein. The receptor appeared to possess a somatotrophic nature since lactogenic hormones such as human placental lactogen and rat prolactin exhibited a very low degree of competition (whereas a variety of unrelated hormones and neuropeptides showed no effect). GH‐stimulated leucine uptake by the cells in a time‐ and dose‐dependent manner, half maximal effect being observed at 0·32 nM GH thus suggesting a direct relationship with the binding step.
Biochemistry of Entamoeba: A review
Authors: Avron Boaz , Chayen Ann 
Published: May 2005

AbstractEntamoeba histolytica, the protozoan parasite causing amoebiasis, is carried by approximately 10% of the world's population although only a minority of carriers of the organism present active clinical symptoms.Although Entamoeba are classified as eukaryotes, the biochemistry of these organisms has a number of unusual facets which are reminiscent of prokaryotes. It has indeed been suggested that these cells represent early evolutionary forms that have been successful in surviving unchanged in the protected environment in which they reproduce (the intestine).Glycolysis in Entamoeba lacks several of the typical eukaryotic glycolytic enzymes. The pentose phosphate shunt enzymes are missing completely. Another unusual feature of the glycolytic path is the utilization of PPi instead of ATP in a number of enzyme reactions e.g. phosphofructokinase. Entamoeba is the only eukaryote in which one of these PPi utilizing enzymes, phosphoenolpyruvate carboxytransferase, has been found.The respiratory pathway is also an unusual one. Entamoeba are classified as anaerobes but the cells do have an affinity for oxygen. The oxygen is reduced to water at the end of a respiratory chain which is not well understood but which operates withough cytochromes or mitochondria.The nucleic acid, protein and lipid metabolic pathways have not been well studied and interest has mainly focused on the proteolytic processes of the amoeba which have been implicated in the pathogenic, histolytic behaviour of the parasite. Despite these efforts the mechanism of attack of the parasite and the stimuli that cause it to invade the host are not yet clear. This understandably is the goal of much of the present studies concerning E. histolytica but the organism also deserves study in its own right as an example of an organism that has an unusual biochemistry and may represent an early stage in the evolution of eukaryotic cells.
Adenylate cyclase in membrane fractions of RIN‐A2‐cells: Studies with forskolin, NaF, GppNHp and NEM
Authors: Trier J. K. , Kühn M. , Ammon H. P. T. 
Published: May 2005

AbstractIn crude membrane fractions of rat pancreatic islets and of RIN‐A2‐cells, forskolin and NaF stimulated adenylate cyclase activity. Basal and stimulated enzyme activity was approximately 3 to 6 fold higher in membranes of RIN‐A2‐cells than in membranes of islet cells. In RIN‐A2‐cells GppNHp and NEM inhibited forskolin‐stimulated cyclase system of RIN‐A2‐cells contains inhibitory and stimulatory N‐proteins and that there are critical thiols related to Ni, Ns and/or the catalytic unit. Thus, membrane fractions of RIN‐A2‐cells may be an appropriate model for studies on the adenylate cyclase system of insulin‐producing cells.
Methotrexate: Studies on cellular metabolism. II—Effects on mitochondrial oxidative metabolism and ion transport
Authors: Yamamoto Nair , Lopes Luiz Carlos Vieira , Campello Annibal Paiva , Klüppel Maria Lucia Wambier 
Published: May 2005

AbstractEffects of methotrexate (MTX) on mitochondrial oxidative metabolism and ion transport were studied. MTX decreases the membrane potential (Δψ) upon energization of the mitochondrial membrane by NAD+‐linked substrates and decreases the amplitude and velocity of swelling induced by glutamate and α‐ketoglutarate. MTX also has an inhibitory effect on the activities of the oxidation enzymes of NAD+‐linked substrates without interfering with the oxidation systems of FAD‐linked substrates. The effects of MTX could be interpreted as a consequence of a decrease in the ionic conductivity of the mitochondrial inner membrane.
Methotrexate: Studies on cellular metabolism. IV. Effect on the mitochondrial oxidation of cytosolic‐reducing equivalents in HeLa cells
Authors: Bastos Ma. Teresa C. C. , Oliveira Ma. Benigna M. , Campello Annibal P. , Klüppel Ma. Lúcia W. 
Published: May 2005

AbstractThe effect of methotrexate (MTX) on the mitochondrial oxidation of cytosolic‐reducing equivalents in HeLa cells was studied. MTX inhibited (100 per cent) malate dehydrogenase activity, but no effect was observed on that of GOT. MTX (0.5 mM) inhibited (100 per cent) the activity of reconstituted enzymatic system MDH–GOT, probably as a consequence of inhibition of malate dehydrogenase activity. MTX decreased pyruvate production (54 per cent), demonstrating its inhibitory action on the malate‐aspartate shuttle. Blockage of the malate–aspartate shuttle by MTX accounts for the decrease in cellular energetic gain. The results obtained are consistent with the view that in HeLa cells, as well as in other tumour cells, the trasport of reducing equivalents from cytoplasmic NADH into the respiratory chain of mitochondria is via the malate‐aspartate shuttle.
Interaction of captan with mammalian microtubules
Authors: Stournaras Christos , Saridakis Ioannis , Fostinis Yannis , Georgoulias Vassilis 
Published: May 2005

AbstractUsing turbidometry, electron microscopy and immunofluorescent microscopy experiments we studied the effect of captan, a widely used pesticide on mammalian microtubules and microfilaments. Turbidometry at 350 nm showed a dose‐dependent inhibition of tubulin assembly incubated with captan. The pesticide, given at equimolar concentration with tubulin (30 μM), caused the total inhibition of microtubule formation, while at lower concentrations (5–20 μM) the inhibition of tubulin polymerization was less extensive. At the same concentration range (5–30 μM), captan also promoted the disassembly of performed microtubules. The results of the in vitro effects of captan with microtubules were confirmed in parallel by electron microscopic studies. In vivo, captan caused also depolymerization of microtubules in cultured mouse fibroblasts as shown by indirect immunofluorescent staining of tubulin. The extent of microtubules disassembly was concentration‐ and time‐dependent. While incubation of the cells with 10 μM captan for 3 h disturbs totally the microtubular structures, incubation with 5 μM captan needs 12 h for the same effect. Recovery of microtubules was observed, when preincubated cells were extensively washed. No interaction of this drug with equimolar concentration of G‐ or F‐actin could be observed in vitro, as shown by polymerization experiments. In line with this, the fluorescent actin pattern in mouse fibroblasts incubated with 10 mM captan for up to 12 h did not seem to be altered. From these results it is concluded that captan interacts in equimolar concentrations with tubulin affecting the assembly and disassembly of microtubules in vitro and in cultures of mammalian cells.
In vivo and in vitro evidence concerning the role of lipid peroxidation in the mechanism of hepatocyte death due to carbon tetrachloride
Authors: Biasi Fiorella , Albano Emanuele , Chiarpotto Elena , Corongiu Francesco P. , Pronzato Maria A. , Marinari Umberto M. , Parola Maurizio , Dianzani Mario U. , Poli Giuseppe 
Published: May 2005

AbstractIsolated rat hepatocytes exposed to CCl4 showed a stimulated formation of malonaldehyde after only 30–60 min incubation. Conversely, the onset of hepatocyte death was a relatively late event, being significant only after 2–3 h of treatment. A cause–effect relationship between the two phenomena has been demonstrated by using hepatocytes isolated from rats pretreated with alpha‐tocopherol. Comparable results were obtained in vivo where supplementation with alpha‐tocopherol 15 h before CCl4 dosing induced a partial or complete protection against the drug's necrogenic effect, depending on the concentration of the haloalkane used. Moreover, the vitamin supplementation prevented the CCl4‐induced increase of liver total calcium content, probably by blocking alterations in the liver cell plasma membranes due to lipid peroxidation.
Chromatin phospholipid changes during rat liver development
Authors: Albi Elisabetta , Magni Mariapia Viola , Lazzarini Remo , Gahan Peter B. 
Published: May 2005

AbstractThe chromatin extracted from rat hepatocytes of different ages has been shown to contain a phospholipid fraction representing 0·47–0·59 per cent of total chromatin in newborn animals and 0·22 per cent in 45‐day‐old animals. No such age‐related differences are observed in the nuclei.The phospholipid composition of the nuclei at different ages shows a higher level of sphingomyelin and a lower level of phosphatidylserine in newborn than in adult animals. Chromatin phospholipids have a completely different composition from that of nuclei with respect to age, particularly in newborn rats, where there is a decrease in phosphatidylcholine and an increase in phosphatidylserine.
Comparative subcellular distribution of benzaldehyde and acetaldehyde dehydrogenase activities in two hepatoma cell lines and in normal hepatocytes
Authors: Ferro Margherita , Muzio Giuliana , Bassi Anna M. , Biocca Maria E. , Canuto Rosa A. 
Published: May 2005

AbstractThe NAD‐ and NADP‐dependent aldehyde dehydrogenase (ALDH) activities were evaluated in two rat hepatoma cell lines, namely the well‐differentiated MH1C1 line and the less differentiated HTC line. Each activity was determined in parallel in isolated rat hepatocytes, for comparison. The aliphatic aldehyde acetaldehyde (ACA) and the aromatic aldehyde benzaldehyde (BA) were used as substrates. With the first substrate the ALDH activities found in the crude cytoplasmic extracts were lower in hepatoma cells than in normal hepatocytes, especially when measured with NADP as coenzyme (ACA/NADP). Otherwise, with benzaldehyde as substrate the NAD‐dependent enzyme activity (BA/NAD) was increased about 9‐fold in HTC cells over hepatocytes and decreased in MH1C1 cells, while the NADP‐dependent (BA/NADP) activity was increased 38‐ and 2·5‐fold in HTC and MH1C1 cell lines, respectively. Studies on the subcellular distribution of these enzyme activities showed that the activity measured with acetaldehyde and NAD (ACA/NAD) was almost equally distributed between the cytosol and the subcellular particles in the three cell populations, but the ACA/NADP activity was shifted towards the cytosolic compartment in hepatomas, especially in HTC cells. The BA/NAD and BA/NADP ALDH activities found in the organelles of hepatoma cells were markedly reduced in comparison with hepatocytes, in favour of the cytosol. The most striking difference between the normal and the transformed cells was the 94‐fold increase over hepatocytes of the BA/NADP activity, found in the cytosolic fractions of HTC cells. MH1C1 cells showed a less pronounced (7·5‐fold) enhancement of this tumour‐associated specific activity. These results confirm that the cytosolic NADP‐dependent benzaldehyde dehydrogenase activity can be considered as a tumour marker, the activity being inversely correlated with the degree of differentiation of the two hepatoma cell lines.