bluuebunny/crossref_metadata_2025 huggingface dataset:
The interaction of tumour‐localizing porphyrins with collagen, elastin, gelatin, fibrin and fibrinogen
Authors: El‐Far Mohamed A. , Pimstone Neville R.
Published: May 2005

We have already reported in Balb C mouse transplantable mammary carcinoma, that uroporphyrin I and III are superior as tumour localizers when compared to hematoporphyrin derivative and a derivative thereof, photofrin II. This study compares the binding of porphyrins to proteins which may be found in tumour cells or stroma to investigate whether there is a common binding determinant. Coproporphyrin III and deuteroporphyrin IX which are non‐tumour localizing porphyrins, were also part of the comparative study. The interaction of these porphyrins with acid soluble collagen and acid insoluble collagen, elastin, and fibrin was evaluated, and the binding of uroporphyrin isomers I and III and deuteroporphyrin IX to gelatin and fibrinogen, was also determined. The results suggest that collagen, especially the acid soluble form, and gelatin preferentially bind the four porphyrins which localize in mammary carcinoma tissue. The well reported observations that malignant epithelial cells, including breast cancer, produce collagen and contain a rate‐limiting enzyme in collagen biosynthesis would support the notion that de novo synthesis of this protein may in part govern the tumour uptake and retention of porphyrins. Elastin, Fibrinogen and fibrin showed non‐discriminant binding to the porphyrins under study.
Studies on mechanisms of ornithine decarboxylase activity regulation in regenerating liver
Authors: Zuretti M. F. , Gravela E. , Papino F. , Satorio L.
Published: May 2005

Rat liver (hydrocortisone‐induced) ornithine decarboxylase has been shown to be stable when the cytosolic fraction is incubated alone at 37°C, although there is a very rapid and drastic loss of activity after addition of microsomes to the incubation medium.

The present paper is concerned with the behaviour of ornithine decarboxylase induced in rat liver by a growth stimulus (partial hepatectomy); comparative studies have been carried out on the enzyme induced by sham operation, or by hydrocortisone.

Results show that ornithine decarboxylase from regenerating liver is more stable when incubated with microsomes (from the same source); this higher stability depends both on a lower microsome‐bound inactivating capacity and a limited susceptibility of the enzyme to the inactivation. A critical role in modulating the microsome‐dependent inactivation appears to be played by low molecular weight cytosolic factors, whose greater content in regenerating liver is likely to be included with the factors above in determining the relative stability of ornithine decarboxylase.
Stimulation by glucose and carbamylcholine of phospholipase C in pancreatic islets
Authors: Mathias P. C. F. , Best L. , Malaisse W. J.
Published: May 2005

Phosphoinositide hydrolysis in intact pancreatic islet cells was investigated in an indirect but dynamic manner by monitoring the efflux of radioactivity from islets prelabelled with [3H]inositol. A rise in glucose concentration provoked a rapid, modest but sustained increase in effluent radioactivity, this phenomenon being abolished in the absence of extracellular Ca2+ or presence of verapamil. The release of [3H]inositol was also stimulated at high extracellular K+ concentration, but not by gliclazide. Whether in the presence or absence of glucose, carbamylcholine provoked a marked increase in effluent radioactivity. The response to the cholinergic agent was decreased in the presence of verapamil or absence of extracellular Ca2+ and abolished in the presence of atropine or LiCl. These results suggest that an increase in cytosolic Ca activity, as caused by glucose or membrane depolarization, may cause activation of phospholipase C. In response to cholinergic agents, however, the enzymic activation, although modulated by Ca2+ availability, may result directly from the occupation of muscarinic receptors.
Human bone cell cultures: A new model for studying the mechanism of action of calcitonin
Authors: Fanó G. , Maurizi M. , Venti‐Donti G. , Paludetti G. , Donti E. , Della Torre G.
Published: May 2005

An investigation on cell cultures obtained from temporal human bone fragments showed that they provide a suitable model for studying the mechanism involved in calcitonin action on bone cells. Furthermore they demonstrated: (1) a transitory increase in 45Ca uptake that returned to control values ten minutes after the hormone was added; (2) a relation between 45Ca uptake and increased cAMP concentrations when these were measured at the same time intervals; (3) a reproduction of the salmon calcitonin (sCT) effect after incubation of the cultures with either db‐cAMP or db‐cGMP and (4) inhibition of 45Ca uptake and parallel decrease in cAMP levels with propanol.

These results suggest that in human bone cell cultures, sCT acts as a temporary promoter of 45Ca uptake, probably by activating an adenylate‐cyclase system through a β‐receptor.
The relevance of various tests for the study of specificity in immunocytochemical staining: A review
Authors: Van Der Sluis P. J. , Boer G. J.
Published: May 2005

Factors determining the specificity of immunocytochemical (ICC) tissue stainings as well as the various tests to study these factors are discussed. Since every specificity test only deals with particular aspects of the ICC procedure, a practical sequence of known test methods is proposed, which enables the determination of the specificity of the ICC tissue staining and, after possibly needed antiserum purification steps, may result in a monospecific staining. It is made clear that such a sequence has always to include a tissue‐spectrum affinity test, in which the spectrum of tissue antigens is controlled for antibody binding. A variety of such tests, consisting of separation of tissue compounds, fixation, and ICC detection, are discussed as well as their pros and cons with respect to their predictability for the actual serum specificity in the tissue section.
The inhibitory effect of 4‐hydroxy‐nonenal on DNA‐polymerases alpha and beta from rat liver and rapidly dividing Yoshida ascites hepatoma
Authors: Wawra E. , Zollner H. , Schaur R. J. , Tillian H. M. , Schauenstein E.
Published: May 2005

The purpose of this study was to determine firstly whether the isolated enzyme DNA polymerase α, which functions within the DNA replicase system, exhibits different sensitivity against the thiol‐blocking agent 4‐hydroxy‐nonenal (HNE) when adult rat liver and the rapidly dividing Yoshida ascites hepatoma were used as enzyme sources and, secondly, whether the reaction catalysed by DNA polymerase is the most sensitive step of the DNA replicase system of native cells.

DNA polymerase α as well as the non‐replicative DNA polymerase β, isolated from both sources, were remarkably similar with regard to their sensitivity against HNE, as indicated by the incorporation of radioactive label from [3H]deoxy‐thymidine‐triphosphate into DNA.

The transport of [14C]thymidine through the plasma membrane and the incorporation of this precursor into DNA were studied with neonatal hepatocytes and with hepatoma cells. The incorporation of thymidine was inhibited at lower concentrations of HNE in both cell lines than the transport process and the reaction catalysed by DNA polymerase α. It was concluded that in the DNA replicase system of native liver and hepatoma cells another process different from the reaction catalysed by DNA polymerase α is more sensitive to HNE.
Enzymic heterogeneity of normal canine articular cartilage
Authors: Dunham Jane , Shackleton D. R. , Bitensky Lucille , Chayen J. , Billingham M. E. J. , Muir I. Helen
Published: May 2005

Articular cartilage is generally considered to be an homogeneous tissue. It has now been shown that, although different regions of the medial tibial cartilage of the dog have very similar oxidative enzymic activities, each region is heterogeneous with respect to these activities. The conventional histological delineation of this cartilage has been modified, to take into account a narrow band (designated zone 2a), just below the most superficial spindle‐shaped cells, that has higher oxidative enzymic activity than any other. Changes in the activity in this zone might be diluted by the lack of change in other zones if measured by conventional biochemical procedures which could not measure the activities of the different zones separately.
Role of transferrin in iron transport between maternal and fetal circulations of a perfused lobule of human placenta
Authors: Contractor S. F. , Eaton B. M.
Published: May 2005

The transfer of iron between the maternal and fetal circulations of an isolated perfused lobule of term human placenta was investigated using125I‐labelled or59Fe‐labelled diferric transferrin. There was negligible transplacental transfer of intact transferrin whereas nearly 4 per cent of the added59Fe was transferred into the fetal circulation after 2 h, where it became associated with fetal transferrin. Over 20 per cent of the added59Fe radioactivity was sequestered within the placental tissue during this period, associated with transferrin, ferritin and other uncharacterized molecules. This suggests an important role for an intracellular pool in regulating transfer. The presence of 10 mMchloroquine in the maternal circulation substantially reduced tissue accumulation of59Fe and totally inhibited transfer to the fetus. It is concluded that the initial stages of iron transfer to the fetus involve the internalization of maternal iron‐saturated transferrin bound to membrane receptors by receptor‐mediated endocytosis, which can be inhibited by the drug chloroquine. Subsequently, the transplacental transfer of iron to the fetus does not involve the concommitant movement of transferrin.
Effect of amiodarone on Na+‐, K+‐ATPase and Mg2+‐ATPase activities in rat brain synaptosomes
Authors: Rao K. S. Prasada , Rao S. B. , Camus Ph. , Mehendale H. M.
Published: May 2005

Amiodarone hydrochloride is a diiodinated antiarrhythmic agent widely used in the treatment of cardiac disorders. With the increasing use of amiodarone, several untoward effects have been recognized and neuropathy following amiodarone therapy has recently been reported. The present studies were carried out to study the effect of amiodarone on rat brain synaptosomal ATPase in an effort to understand its mechanism of action. Na+, K+‐ATPase and oligomycin sensitive Mg2+ ATPase activities were inhibited by amiodarone in a concentration dependent manner with IC50 values of 50 μM and 10 μM respectively. [3H]ouabain binding was also decreased in a concentration dependent manner with an IC50 value of 12 μM, and 50 μM amiodarone totally inhibited [3H]ouabain binding. Kinetics of [3H]ouabain binding studies revealed that amiodarone inhibition of [3H]ouabain binding is competitive. K+‐activated p‐nitrophenyl phosphatase activity showed a maximum inhibition of 32 per cent at 200 μM amiodarone. Synaptosomal ATPase activities did not show any change in rats treated with amiodarone (20mg kg−1 day−1) for 6 weeks, when compared to controls. The treatment period may be short, since the reported neurological abnormalities in patients were observed during 3–5 years of treatment. The present results suggest that amiodarone induced neuropathy may be due to its interference with sodium dependent phosphorylation of Na+, K+‐ATPase reaction, thereby affecting active ion transport phenomenon and oxidative phosphorylation resulting in low turnover of ATP in the nervous system.
Enhanced glucose consumption in erythrocytes under mechanical stress
Authors: Kodíček Milan
Published: May 2005

In this paper we study the question of whether the unique features of erythrocyte (biconcave shape, extremely high deformability etc.) result only from the specific structural characteristics of the membrane or whether the maintenance of these features is conditioned by the supply of chemical energy. It is shown that glucose, the main source of cell energy, is consumed at a markedly increased rate when there is appreciable mechanical stress of the cell. This observation supports the hypothesis that there is utilization of chemical energy for the mechanical needs of the membrane.
A microspectrofluorometric study of the effect of anthralin, an antipsoriatic drug, on cellular structures and metabolism
Authors: Kohen E. , Kohen C. , Morliere P. , Santus R. , Reyftamann J. P. , Dubertret L. , Hirschberg J. G. , Coulomb B.
Published: May 2005

The microspectrofluorometric approach has been used to investigate in single living cells in culture fundamental questions raised by the use of anthralin, a potent antipsoriatic drug. This method allows fluorescence determinations on the intracellular fate of the drug as well as the recognition of structural and metabolic alterations induced by the drug. In the absence of demonstrable adduct formation with DNA, the antipsoriatic, i.e. antiproliferative effect of anthralin, has been attributed to its action at the level of mitochondria or at the level of glucose‐6‐phosphate dehydrogenase which initiates the pentose phosphate shunt (cf. its prominent role in nucleic acid synthesis). Upon addition of 2·3 to 23 μ M anthralin to the L cell culture, the characteristic structure of the anthralin anion fluorescence spectrum is recognized almost immediately in the cytoplasm (much weaker in the nucleus) but disappears within minutes. The vital mitochondrial fluorescence probe dimethylaminostyryl‐pyridinium‐methyl‐iodine reveals striking structural alterations of the mitochondria within 15 min after addition of the drug. At the same time, there is a stimulation of the transient NAD(P)+ reduction observed upon microinjection into the L cell of the Krebs' cycle substrate malate, or the pentose cycle substrate 6‐phosphogluconate. Specially, the injection of the latter to anthralin‐treated cells suggests that upon release of the mitochondrial control, there is a tremendous disruption of metabolic activity which could have profound consequences on the proliferative activity of the cell.

These findings, while they open new possibilities for the intracellular evaluation of therapeutic agents, create also a challenge in understanding the complex and dynamic interrelationships between intracellular organelles and bioenergetic or biosynthetic pathways.
Coxsackie B4 virus induces short‐term changes in the metabolic functions of mouse pancreatic islets in vitro
Authors: Szopa T. M. , Gamble D. R. , Taylor K. W.
Published: May 2005

Mouse pancreatic islets cultured in vitro were infected with a tissue culture‐adapted or a mouse pancreas‐adapted strain of Coxsackie B4 (CB4) virus. The effects of the viruses on the islets were assessed by examination of their biochemical functions. It was found that the mouse pancreas‐adapted strain of CB4 induced a ‘leakage’ of insulin from islets incubated at a basal (2 mmol l−1) glucose concentration, both at two and four days following infection. However, at a stimulatory concentration of glucose (20 mmol l−1) the rate of insulin secretion appeared to be normal in these islets. At two days the rate of total protein synthesis in islets infected with mouse pancreas‐adapted CB4, incubated at high glucose concentration, was reduced; at four days the degree of inhibition was more severe, the rate at basal glucose concentration falling to half that of the control islets and at the stimulatory glucose concentration to a quarter of the control islets. (Pro)insulin biosynthesis was also inhibited, the rate being reduced to less than half the mean control value in islets infected with mouse pancreas‐adapted CB4 virus at 20 mmol l−1 glucose at two days; at four days the rate was greatly reduced at both 2 and 20 mmol l−1 glucose. It is concluded from this study that (1) only certain strains of CB4 virus can infect mouse pancreatic islets in vitro and (2) that infection with strains of virus tropic for the islets leads to an impairment of metabolic functions of the B‐cells, and is not necessarily lytic.
In vitro measurement and adaptive response of Fe3+ uptake by mouse intestine
Authors: Raja Kishor B. , Bjarnason Ingvar , Simpson Robert J. , Peters Timothy J.
Published: May 2005

In order to define the importance of the mucosal uptake step in the intestinal regulation of iron absorption, unidirectional uptake rates of Fe3+ from a nitrilotriacetic acid chelate were measured in duodenal fragments from mice using an in vitro technique. [57Co]‐Cyanocobalamin was used as a marker of adherent incubation medium. Uptake showed saturation kinetics over the concentration range 18–450 μM. Uptake was increased in fragments from hypoxic, dietary iron‐deficient and pregnant mice. The enhanced uptake was due to an increase in Vappmax. However, the modest increase in uptake rates in pregnancy and the gross changes observed in iron‐deficiency make the hypoxic model the most convenient. The increase in uptake in hypoxic animals was located to the duodenal region and was not associated with changes in either total mucosal iron content or epithelial cell turnover. The rate of uptake of iron via the serosa did not change with hypoxia. This study implies that flux of Fe3+ across the brush border is subject to adaptive regulation. The hypoxic model is suitable for investigation into the regulation of iron homestasis.
Microtubular protein impairment by pentanal and hexanal
Authors: Miglietta Antonella , Gabriel Ludovica , Gadoni Elena
Published: May 2005

Pentanal and hexanal are some of the aldehydes produced by lipid peroxidation, that causes damage to several subcellular structures. Lipoperoxidation products may directly attack cytoskeletal structures, the integrity of which is required for secretion mechanisms, e.g. 4‐hydroxy‐alkenals alter microtubular integrity and function.

Purified microtubular protein incubated with pentanal and hexanal at different concentrations revealed a tubulin–aldehyde interaction affecting the polymerization reaction and the colchicine‐binding activity.

These reactions apparently do not involve sulphydryl groups, and the addition of mercaptoethanol does not protect microtubules from the action of aldehydes, the effect of which is however more homogeneous, as only small differences can be noticed among the various aldehyde concentrations used.
A multiparameter analysis of the perfused rat heart: Responses to ischemia, uncouplers and drugs
Authors: Fuchs Jürgen , Zimmer Guido , Bereiter‐Hahn Jürgen
Published: May 2005

In perfused rat hearts alterations of aortic flow and mitochondrial membrane potential resulting from uncoupling of oxidative phosphorylation, hypoxia and treatment with a cardioprotective drug (2‐mercaptopropionylglycine (MPG)) have been studied.

Mitochondrial membrane potential was followed by surface fluorimetry on DASPMI stained hearts. This fluorochrome specifically stains mitochondria in living cells; fluorescence intensity is related to the electrochemical gradient.

Aortic flow turned out to be a much more sensitive indicator of heart function than ventricular pressure or mitochondrial membrane potential. No direct relationship exists between mitochondrial membrane potential and ATP production under the different metabolic conditions. Two phases of hypoxic mitochondrial damage have been deduced: the first results in derangement of ATP synthases while membrane potential is maintained, the second in irreversible damage of mitochondrial membranes with loss of membrane potential.
Age‐dependent changes in in vivo ethanol metabolism and in the activity of hepatic enzymes involved in ethanol oxidation and microsomal functions
Authors: Fernandez V. , Kriz A. , Videla L. A.
Published: May 2005

The study of the influence of the age of the animals (13 to 53 weeks) on the rate of ethanol metabolism in vivo and the total activity of liver alcohol dehydrogenase and microsomal ethanol oxidizing system showed a progressive decline with age. These effects were observed concomitantly with a diminution in the content of cytochrome P‐450 and microsomal functions related to oxidative and free‐radical mediated reactions, namely, NADPH oxidase activity, NADPH‐dependent oxygen uptake and NADPH‐or t‐butyl hydroperoxide‐induced chemiluminescence. It is concluded that ageing is accompanied by a diminution in the total oxidative activity of the liver tissue, which would explain the depression in basal and ethanol‐induced lipid peroxidation found in the oldest group of rats studied.
Induction of alkaline phosphatase actvity by synergistic action of dibutyryl cyclic adenosine monophosphate, prednisolone, butyrate and sodium chloride in cultured cells
Authors: Sorimachi Kenji
Published: May 2005

Human urinary bladder carcinoma cells (JTC‐32) retain a low alkaline phosphatase activity. Prednisolone or a hypertonic concentration of NaCl caused a moderate increase in the activity (10‐ to 15‐fold of control), but dibutyryl cAMP or butyrate did not. Examination of the combined effect of these four agents revealed that they acted synergistically in any combination. When the cells were incubated with the four agents together, the enzyme activity increased 60‐ to 250‐fold. Serum also contributed to this synergistic increase. These agents slightly inhibited cell growth and protein synthesis. The enzyme induction was completely inhibited by cycloheximide or actinomycin D. The synergistic effect of the four agents on the enzyme activity was also observed in other strains of carcinoma cells, human urinary bladder carcinoma cells (JTC‐30) and monkey hepatocarcinoma cells (NCLP‐6E). Thus, it is concluded that the coexistence of the four agents provides general and superior conditions for the induction of alkaline phosphatase in cultured carcinoma cells.
Chromatin organization in isolated nuclei: Flow cytometric characterization employing forward and perpendicular light scatter
Authors: Papa Stefano , Maraldi N. M. , Matteucci A. , Santi P. , Vitale M. , Galanzi A. , Manzoli F. A.
Published: May 2005

Flow cytometric perpendicular and forward light scatters have been employed to evaluate whether the changes in chromatin organization due to ionic strength, Mg++ concentration and pH, visible in electron microscopy, can be monitored by flow cytometry.

The average intensity of the perpendicular light scatter signal increased as nuclear chromatin became decondensed by lowering the ionic strength or releasing H1 histone at low pH values.

These results indicate that flow cytometry signals and in particular the perpendicular light scatter allow the detection of the conformational transitions in chromatin and may therefore be useful for studying cell cycle associated morphological changes in isolated nuclei.
Effects of insulin and dexamethasone on adenine nucleotide levels in cultured hepatocytes from adult rat
Authors: Gallo G. , Mazzei M. , Voci A. , Fugassa E.
Published: May 2005

Insulin and dexamethasone, usually added to culture media, play an important role in maintaining the survival of functional hepatocytes. Adenine nucleotide concentrations and energy charge values of cultured hepatocytes were determined to investigate the relationship between the beneficial effects of these hormones and the energy status of the cells. The results indicate that insulin and dexamethasone are essential in maintaining the metabolic competence of cultured hepatocytes and that this correlates with the absolute concentration of ATP rather than with the energy charge.
Epidermal growth factor receptor numbers in male and female mouse primary hepatocyte cultures
Authors: Benveniste Robert , Danoff Theodore M. , Ilekis John , Craig H. Randall
Published: May 2005

Epidermal growth factor receptors (EGF‐R) were measured in adult male and female mouse primary hepatocyte cultures. On culture day 1, female hepatocytes had significantly fewer EGF‐R than male hepatocytes (1·3 × 104 versus 6·2 × 105 per cell). Over the next three days, morphological changes consistent with progressive heptocyte dedifferentiation were observed. During this period, EGF‐R numbers progressively increased in female cultures and decreased in male cultures, and by day 4 the sexual difference in EGF‐R numbers was obliterated. These results indicate that a relationship exists between the degree of differentiation in hepatocyte cultures and the expression of EGF‐R on the cell surface.
Improved methods for separating hydrolytic granules of neutrophil leucocytes
Authors: Takano Y. , Imai K. , Kutsukake H. , Tanaka A. , Yamamoto K.
Published: May 2005

Highly efficient methods for isolating two hydrolytic granules of neutrophils are described. Neutrophil obtained from guinea pig peritoneal exudate cells were washed extensively with isotonic sucrose and then treated with heparin. More than 95 per cent of the cells so treated were disrupted with a Dounce homogenizer. Since nuclei were broken, leaving other organelles intact, homogenates were incubated with DNase to reduce viscosity. Postnuclear supernatants were centrifuged on a discontinuous gradient of Percoll. Azurophil granules, high in β‐glucuronidase activity, sedimented at fractions of d = 1·081 and showed very little activity of other marker enzymes. High neutral α‐glucosidase activity was observed in granular fractions of d = 1·038 and it is suggested that this is a marker for specific granules of neutrophils.
Significance of γ‐glutamyl transpeptidase and thiols in amino acid uptake by rat pancreatic islets: Studies with glutamine and leucine
Authors: Ammon H. P. T. , Fuß A. , Verspohl E. J.
Published: May 2005

The importance of γ‐glutamyl transpeptidase, the key enzyme of the γ‐glutamyl cycle and of thiols for the uptake of amino acids into rat pancreatic islets was investigated. Both serine–borate, an inhibitor of γ‐glutamy transpeptidase, and serine which does not inhibit this enzyme, but probabaly is a competitive inhibitor of amino acid uptake, inhibited of glutamine. The inhibitory effect of serine‐borate was not greater than that of serine alone. The uptake of glutamine was not affected by either GSH (reduced glutathione) or diamide (a thiol oxidant). Niether substances affected the uptake of leucine. The results indicate that the uptake of glutamine by rat pancreatic islets is not dependent on the functioning of γ‐glutamyl transpeptidase and that thiols are not important for the uptake of the amino acids glutamine and leucine.
Glycolysis and glutaminolysis in perifused ehrlich ascites tumour cells
Authors: Segura J. A. , Medina M. A. , Alonso F. J. , Sanchez‐Jimenez F. , De Castro I. Núñez
Published: May 2005

A perifusion system was designed in order to study glucose and glutamine metabolism by freshly harvested Ehrlich ascites tumour cells in steady state conditions. Cells were perifused in the presence of 5 mM glucose, 0·5 mM glutamine or 5mM glucose and 0·5 mM glutamine. The results in steady state reveal that both substrates glucose and glutamine are continuously wasted by tumour cells, excreting two moles of lactate per mol of glucose and one mol of glutamate and ammonia per mol of glutamine consumed into the medium. Glutamine consumption in the presence of glucose was higher than with glutamine alone.
Fatty acid composition of phospholipids in mitochondria and microsomes during diethylnitrosamine carcinogenesis in rat liver
Authors: Canuto Rosa A. , Biocca Maria E. , Muzio Giuliana , Dianzani Mario U.
Published: May 2005

Changes in lipid composition and function of subcellular organelles have been described in transplanted and primary tumours. We examine here the fatty acid composition of individual phospholipids (PL) in hyperplastic nodules and primary hepatoma induced by diethylnitrosamine (DEN), compared to that of normal liver and of transplantable Yoshida AH‐130 hepatoma.

Phosphatidylcholine and phosphatidylethanolamine fatty acid composition in mitochondria and microsomes from primary hepatoma were markedly different from normal liver; C18:0/C18:1 ratio was lower and the ratio between monounsaturated and polyunsaturated fatty acids was higher. Linoleic acid content of mitochondrial cardiolipin, usually very high in normal rat liver, was notably lower in primary hepatoma. Cholesterol/phospholipid ratio in both microsomes and mitochondria from DEN‐induced hepatoma was higher than in normal liver. Hyperplastic nodules showed no changes in cholesterol content whereas modifications in fatty acid composition were already observeable. These modifications of membrane structure may be related to the functional changes found in nodular cells.

Changes in fatty acid composition of membrane phospholipids, occurring in both primary hepatoma and preneoplastic nodules, might be one of the causes for decreased rate of lipid peroxidation peculiar to these tissues.
Action of endogenous proteases on the distribution of tyrosinase isozymes in Harding–Passey mouse melanoma
Authors: Martinez J. H. , Solano F. , Lozano J. A.
Published: May 2005

A high percentage of the total tyrosinase found in Harding–Passey mouse melanoma occurs as a soluble form. This paper shows that melanosomal tyrosinase can be solubilized by several endogenous proteases to yield active tyrosinase. This enzyme, once proteolitically solubilized, can be further degraded, leading to enzyme inactivation. The nature and specificity of the main proteases involved in the solubilization process change depending on the size and necrosis stage of the tumour. Cathepsin B could be the main protease responsible for the solubilization in small tumours (< 0·5 g). Large tumours are rich in necrotic cells, and cathepsin D and serine‐proteases are the main hydrolytic enzymes involved in the proteolytic action on mealanosomes. These results support the view that the high activity of tyrosinase found in the soluble fraction of malignant melanoma is mainly an artefact resulting from degradation of melanosomes by a variety of endogenous proteases, rather than the result of the actual occurrence of high levels of an independent cytosolic isozyme.
Atrial natriuretic peptide in heart and specific binding in organs from fetal and newborn rats
Authors: Hersey Roscoe M. , Nazir Munir A. , Whitney Kathleen D. , Klein Robert M. , Sale Robert D. , Hinton Debbie A. , Weisz Judith , Gattone Vincent H.
Published: May 2005

To assess the possibility that atrial natriuretic peptide plays a role in salt and water balance during early mammalian development, we examined hearts from fetal and neonatal rates for the presence of this peptide and presumed target tissues for their ability to bind the hormone. Immunohistochemistry was used to localize and radioimmunoassay to quantify this peptide in heart. Immunoreactive artrial natriuretic peptide was visualized in the fetal heart on day 17·5 post‐conception. It was distributed throughout the atrial appendages and free wall and, in ventricle, in the trabeculae carnae and chordae tendineae. The concentrations of immunoreactive atrial natriuretic peptide in atria of rats on day 19·5 post‐conception were one‐tenth of those in the adult. Levels of this peptide in fetal ventricle were low and virtually absent from the adult tissue. Specific binding of radiolabelled atrial natriuretic peptide measured by whole organ counting occurred in several organs from 19·5‐day fetal and neonatal rats. A number of these tissues, including the kidney, ileum, adrenal, lung and liver, are targets for and/or bind the peptide in adult rats. Specific binding in these tissues was localized using autoradiography at anatomical sites similar to those in adult organs. Specific binding was also seen in fetal but not neonatal skin. In the kidney, binding was associated with immature as well as mature glomeruli. These findings support the proposition that atrial natriuretic peptide may function in the perinatal rat as it does in the adult and, in addition, may play a unique role during fetal life.
Distribution of 3‐hydroxy‐3‐methylglutaryl‐CoA reductase in isolated villus and crypt cells of chick duodenum, jejunum and ileum
Authors: Iglesias José , Gonzalez‐Pacanowska Dolores , Caamaño Guillermo , Garcia‐Peregrin Eduardo
Published: May 2005

3‐Hydroxy‐3‐methylglutaryl‐CoA reductase (EC 1.1.1.34), the major rate‐limiting enzyme of cholesterogenesis, was studied in epithelial cells isolated in a villus to crypt gradient from chick duodenum, jejunum and ileum, in order to resolve the apparent controversy that exists on the anatomical localization of sterol synthesis in the intestine. Consistent separation was demonstrated by using the marker enzymes alkaline phosphatase, specific to the villus cells, and thymidine kinase, specific to the crypt cells. No relative difference in stability was observed, as shown by the equal distribution of acid phosphatase. Cells were 90–95 per cent viable. The highest specific activity of reductase was located in the microsomal fraction (41 per cent of the total). The mitochondria had lower specific activity (8 per cent of the total). The distribution of reductase activity in epithelial cells of the villus–crypt axis was also studied. The specific activity in each cell fraction from chick duodenum was clearly lower than that in jejunum and ileum. The jejunal and ileal crypt regions showed lower specific activity than the villus cells. About 70 per cent of total reductase activity was found in cells from the upper and the mid villus fraction in each intestinal segment.
Dual inhibitory effect of bredinin
Authors: Kusumi T. , Tsuda M. , Katusunuma T. , Yamamura M.
Published: May 2005

Bredinin inhibition of cell growth was investigated in the mouse lymphoma cell line L5178Y. Bredinin caused the accumulation of IMP and the reduction of XMP. It was converted to the 5′‐phosphate within the cells. Bredinin 5′‐phosphate but not bredinin competitively inhibited both IMP dehydrogenase and GMP synthetase. Thus the inhibition of cell growth is probably due to bredinin 5′‐phosphate, which inhibits the consecutive enzyme reactions IMP dehydrogenase and GMP synthetase. These inhibitions result in the accumulation of IMP and the reduction of XMP.
Protein metabolism in the small intestine of the ethanol‐fed rat
Authors: Preedy Victor R. , Peters Timothy
Published: May 2005

The effects of chronic ethanol feeding on the small intestine were investigated in young rats. Rats were fed a nutritionally‐adequate liquid diet, containing 36 per cent of total energy as ethanol (treated, n = 7), or isovolumetric amounts of the same diet in which ethanol was substituted by isocaloric glucose (controls, n = 7). After six weeks the wet weight and total tissue contents of protein, RNA and DNA were significantly reduced by 21 per cent, 23 per cent, 16 per cent and 28 per cent respectively, (p < 0·014).

Rates of protein synthesis were measured with L[43H]phenylalanine and fractional rates (defined as the percentage of constituent tissue protein synthesised each hour, i.e. ks, % h−1) were calculated from the specific radioactivity of free phenylalanine in both tissue homogenates and plasma. Ethanol‐feeding reduced ks by approx 10 per cent (p < 0·181). The amount of protein synthesized unit−1 RNA was also reduced by approx 15 per cent (p < 0·059) but the amount of protein synthesis unit−1 DNA was unaffected by ethanol‐feeding (p < 1·000). In contrast, the absolute rates of protein synthesis were reduced by approximately 30 per cent (p < 0·022).

It was concluded that, as the small intestine contributes to approx. 20–25 per cent of whole body synthesis these results may have an important effect on whole body nitrogen homeostasis and may have implications for the gastrointestinal effects of ethanol seen during chronic alcoholic abuse.
Metabolic effects of acetaminophen. Studies in the isolated perfused rat liver
Authors: Itinose Ana Maria , Sakuno Marlene Leiko Doi , Bracht Adelar
Published: May 2005

The effects of acetaminophen on the metabolism of the isolated perfused rat liver were investigated. The following results were obtained:

Acetaminophen increased glucose release and glycolysis from endogenous glycogen (glycogenolysis).

Oxygen uptake, gluconeogenesis from either pyruvate or fructose and glycogen synthesis were inhibited.

In isolated rat liver mitochondria acetaminophen decreased state III and state IV respiration; it also decreased the ADP/O ratio and the respiratory control ratio.

The action of acetaminophen on glycogenolysis was not affected by N‐acetylcysteine; this compound, however, increased glycogen synthesis.

The effects of acetaminophen are reversible.

It was concluded that glycogen depletion by acetaminophen can be produced by two mechanisms. The first, as previously demonstrated by several workers, depends on irreversible binding of a reactive metabolite. The second, however, is reversible and depends primarily on an inhibition of mitochondrial energy metabolism.
Cytochrome P450 in highly purified suspension of nonparenchymal liver cells
Authors: Rich K. , Lodola A.
Published: May 2005

Rat liver nonparenchymal cells (NPC) were prepared by pronase digestion and purified on discontinuous gradients on Nycodenz. Morphological and biochemical characterization of cell suspensions showed that they were free of contamination by hepatocytes. We have confirmed the usefulness of pyruvate kinase activity in monitoring the degree of hepatocyte contamination of NPC and we have derived an equation which allows this carry‐over to be calculated. Using highly purified suspensions of NPC we have shown that they contain glucose‐6‐phosphatase in low but detectable levels. Spectrophotometric studies showed that they contain cytochrome P450, with a specific content of 24 +/− 5 pmole mg−1 cell protein. A potential source of error in previous studies was recognized; namely that peroxidase, present in NPC in high concentration, is able to mask the absorption due to cytochrome P450. Both the presence and inducibility of this enzyme in NPC prepared from rats pretreated with phenobarbital or 3‐methylcholanthrene have been confirmed using Western blot analysis.
Synthesis of proteoglycans and hyaluronic acid by long‐term cultures of testicular cells from immature and pubertal rats
Authors: Rodríguez J. Pablo , Minguell José J.
Published: May 2005

Long‐term cultures of somatic testicular cells derived from immature and pubertal rats were used to study the synthesis of proteoglycans (PG) and hyaluronic acid (HA). Labelled PG and HA in the culture medium, membrane‐associated and intracellular pools were characterized by gel fitration, ion exchange chromatography and selected enzymatic and chemical treatments. Somatic cells synthesize a PG containing both heparan and chondroitin/dermatan sulfate (CS/DS) chains and a PG containing only CS/DS chains. No major qualitative changes in the type of PG were observed in cells derived from immature and pubertal animals. However, significant age‐dependent differences in the cell distribution pattern of PG and HA were determined. This may have implications in the regulation of spermatogenesis.
Evidence for a differential distribution of reducing equivalents from NADPH in cartilage
Authors: Nahir A. M. , Boussidan F. , Shomart D.
Published: May 2005

It has been suggested that the NADPH, generated from the activity of glucose 6‐phosphate dehydrogenase, may be utilized by two different routes, namely either for biosynthetic purposes (type 2) or for microsomal respiration (type 1). This concept has been tested in the rabbit ear model in which an injection of papain into the rabbit causes loss of proteoglycans of the auricular matrix followed by its restoration over the following eight days. It is shown that whereas the type 1 pathway was either unaltered or diminished, the doubling of the glucose 6‐phosphate dehydrogenase activity was related solely to the type 2 pathway.
Identification of a nuclear antigen with molecular weight of 48 000 differentially expressed in tumour and normal cells
Authors: Krajewska Wanda M. , Lipińska Anna , Marszałek Małgorzata , Kiliańska Zofia , Wojtkowiak Zbigniew , Kłyszejko‐Stefanowicz Leokadia
Published: May 2005

A non‐histone protein with mol. wt of 48 000 differentially expressed in normal and tumour cells was identified using immunological criteria. Antibodies were raised against a component specific for Kirkman‐Robbins hepatoma of mol. wt about 48 000 separated from hepatoma non‐histone proteins by preparative electrophoresis in polyacrylamide gel. It was demonstrated by immunoblotting that Morris hepatoma 7777 and Ehrlich ascites cells share an antigenic non‐histone protein with Kirman‐Robbins hepatoma. Tumour cells when compared with normal cells, i.e. hamster and rat liver, are characterized by significant enrichment of this component. Intracellular distribution of the polypeptide with mol. wt 48 000 suggests that this component may be a structural protein the biosynthesis of which increases or the antigenic determinants of which change in tumour cells.
Influence of 4‐hydroxynonenal on chemiluminescence production by unstimulated and opsonized zymosan‐stimulated human neutrophils
Authors: Di Mauro C. , Cavalli G. , Amprimo M. C. , Paradisi L. , Scano G. , Curzio M. , Dianzani M. U.
Published: May 2005

The lipid peroxidation product 4‐hydroxy‐2,3‐trans‐nonenal (HNE) has a spectrum of biological effects on different cell types depending on the concentrations tested. In particular micromolar HNE concentrations stimulate neutrophil migration and polarization whereas higher doses inhibit.

In our experimental conditions, fMet‐Leu‐Phe (fMLP) increased CL production of both unstimulated and zymosan‐stimulated neutrophils, whereas cell stimulation with low HNE concentrations as well as zymosan addition to HNE incubated cells did not enhance light emission. In contrast 10−4 M HNE reduced CL emission by unstimulated cells nearly to background values, completely depressed CL production by zymosan‐stimulated cells and reduced phagocytosis. Cysteine was found to be able to counteract the HNE effect by about 70 per cent. The possibility that this aldehyde could exert its inhibitory effect through the alkylation of NADPH‐oxidase SH‐groups is postulated. Moreover, our present data on differences observed between fMLP and HNE indicate a different chemotactic mechanism induced by these two classes of compounds and lead to the conclusion that the local functional features of the attracted cells may be different.
Reduced oxidative activity of circulating neutrophils in patients after myocardial infarction
Authors: Guarnieri Carlo , Melandri Giovanni , Caldarera Ilaria , Scheda Mauro , Ligabue Amedeo , Guizzardi Sandro , Branzi Angelo
Published: May 2005

Circulating neutrophils isolated from patients 3–4 h after a myocardial infarction produced less \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm O}\frac{ \cdot }{{\rm 2}} $\end{document} compared with controls, when stimulated with phorbol myrystate acetate or formyl‐methionine‐leucine‐phenylalanine. Three days after the infraction the \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm O}\frac{ \cdot }{{\rm 2}} $\end{document} generation elicited by both stimuli further decreased markedly. Seven and 15 days after infarction the \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm O}\frac{ \cdot }{{\rm 2}} $\end{document} stimulated production was only slightly lower than or similar to the control values. The neutrophils of infarcted patients showed an augmented latency period before \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm O}\frac{ \cdot }{{\rm 2}} $\end{document} production compared with controls in response to exogenous stimuli, particularly three days after infarction. Electron microscopy revealed that the neutrophils isolated from the infarcted patients displayed signs of cell exhaustion with few alterations of the plasma membranes when stimulated with phorbol ester. In contrast, control neutrophils displayed alterations of the plasma membranes characteristic of active neutrophils. The results of this study indicate that the circulating neutrophils appear exhausted and functionally inhibited immediately after myocardial infarction.
Extracellular sodium is required for methacholine‐induced secretion of mucus glycoconjugates from canine tracheal explants
Authors: Barsigian Carl , Barbieri Edward J.
Published: May 2005

Extracellular sodium is known to influence secretion by certain secretory cells, possibly by mobilizing calcium from cellular stores or by altering intracellular pH via regulation of a Na+ ‐H+ antiport system. Using canine tracheal explants, we determined whether agents which alter sodium fluxes are capable of modulating basal or cholinergically‐induced secretion of mucus glycoconjugates. Methacholine, a cholinergic agonist, increased mucus secretion from explants incubated in the presence or absence of calcium, but had no effect on secretion when incubated in sodium‐deficient media, indicating (a) that cholinergically‐induced secretion can be mediated by mobilization of cellular calcium and (b) that extracellular sodium was required for this stimulatory effect. Several agents which increase intracellular sodium were tested for their effect on mucus secretion. Ouabain, a sodium pump inhibitor, and veratridine, a sodium channel activator, did not significantly affect control or methacholine‐induced secretion; gramicidin, a sodium ionophore, also had no effect on basal release. Tetrodotoxin, a sodium channel inhibitor, was also without effect on basal or methacholine‐stimulated mucus release. Agents which alter intracellular pH were also examined for their effects on basal or methacholine‐induced glycoconjugate secretion. Amiloride, which decreases intracellular pH by inhibiting Na+ ‐H+ exchange, produced a 19 per cent increase in basal secretion (not statistically significant), but had no effect on methacholine‐induced secretion. An agent, 4,4′‐diisothiocyanostilbene‐2,2′‐disulfonic acid (DIDS), which decreases intracellular pH by inhibiting HCO3−−Cl− exchange, elicited decreases in both basal and methacholine‐induced secretion, but the inhibition did not reach statistical significance. Thus extracellular sodium is required for cholinergically‐induced glycoconjugate secretion from canine tracheal explants and the underlying mechanism does not involve sodium influx into the cell, but may possibly be mediated by alterations in intracellular pH.
Effects of vanadate on 6‐phosphofructo 2‐kinase activity and fructose 2,6‐bisphosphate levels in cultured rat hepatocytes
Authors: Miralpeix Montserrat , Katz Norbert R. , Bartrons Ramon
Published: May 2005

The presence of vanadate in primary cultures of rat hepatocytes produced a significant increase in the concentration of fructose 2,6‐bisphosphate and in the activity of 6‐phosphofructo 2‐kinase. Compared with insulin, vanadate had a more potent action on the metabolite increase, but a similar effect on the 6‐phosphofructo 2‐kinase activity. Both the insulin‐ and the vanadate‐dependent enhancements of 6‐phosphofructo 2‐kinase were inhibited by cycloheximide which specificially blocks protein synthesis on the translational level, suggesting that the increase of the enzyme activity was due to induction rather than to a change in the catalytic activity.
Efflux of inorganic phosphate from rat hepatocytes: Lack of effect of insulin
Authors: Parkash Mukesh , Butterworth Peter J.
Published: May 2005

Efflux of Pi from rat hepatocytes suspended in phosphate free‐medium was studied by chemical assay of released Pi and by monitoring the loss in radioactivity of cells pre‐labelled with [32P]‐Pi. The release follows first‐order kinetics fairly closely with a rate constant of 7 × 10−3min−1 approximately. Insulin at a concentration of 10−8M had no effect on the rate of Pi release and it is concluded therefore, that the insulin‐stimulated accumulation of Pi described in the literature is the result of hormone action on Pi uptake by liver rather than on its release.
Mitoxantrone toxicity on ehrlich ascites tumour cells: Inhibition of the transplasma membrane redox activity
Authors: Medina Miguel Angel , Luque Pilar , De Castro Ignacio NÚñez
Published: May 2005

This study focused on the potent cytotoxic effect that mitoxantrone produces on Ehrlich ascites tumour cells. Host mice treated with mitoxantrone showed a life span three times higher than control non‐treated host mice. Mitoxantrone also showed a potent cytotoxic effect on Ehrlich cells incubated in vitro for only a few hours. Studies on the effect of mitoxantrone on a plasma membrane redox system showed that mitoxantrone inhibits this activity, which is apparently related to cell proliferation.