bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cytophotometric analysis of alkaline phosphatase and 5′‐nucleotidase activity in regenerating rat liver after partial hepatectomy
Authors: Van Noorden Cornelis J. F. , Vogels Ilse M. C. , Houtkooper Joop M. 
Published: May 2005

AbstractAlkaline phosphatase and 5′‐nucleotidase activities were analysed cytophotometrically in cryostat sections of female rat liver after partial hepatectomy. Alkaline phosphatase activity increased rapidly after operation up to a maximum seven‐fold rise at 24 h in comparison with sham operated or control rats. There was no indication of preferential localization of alkaline phosphatase activity in either periportal or pericentral areas at any time point in control rats, sham operated rats or hepatectomized rats. Microscopical observation revealed that (a) all alkaline phosphatase activity was present at the bile canalicular surface of hepatocytes and (b) hepatocytes in mitosis did not show any increase in activity. These findings indicate that the high alkaline phosphatase activity after partial hepatectomy is not involved primarily in proliferation processes because cell division mainly takes place periportally. It may be needed for enhanced bile secretion by conversion of intracellular phosphorylcholine into choline which can be transported into the bile. The intracellular phosphorylcholine level is high after operation due to changes in phospholipid metabolism. 5′‐Nucleotidase appeared to be three times higher pericentrally than periportally under normal conditions. Partial hepatectomy caused a 40 per cent decrease in activity in pericentral areas and only a small decrease periportally. It has been suggested that 5′‐nucleotidase plays a role in breakdown of messenger RNA and its activity in control liver could be considerably lower periportally because plasma protein synthesis mainly takes place in this area. 5′‐Nucleotidase activity may well be decreased after operation for accumulation of messenger RNA for enhanced plasma protein synthesis in order to compensate for 67 per cent of the liver cell functions lost during partial hepatectomy.
New synthesis of cyclic AMP‐dependent protein kinases during liver regeneration
Authors: Pujol Maria Jesùs , Soriano Montserrat , Coll Maria Josep , Domingo Jordi , Bachs Oriol 
Published: May 2005

AbstractAs has been previously reported one surge in cytosolic calmodulin is produced between 4 and 12 h after a partial hepatectomy. Moreoever, a surge in cytosolic cyclic AMP and another in cyclic AMP‐dependent protein kinase activity can be detected during the late period of the prereplicative phase of liver regeneration after a partial hepatectomy. It is known that these three surges are involved in triggering DNA synthesis.By kinetic studies and by injecting transcription (actinomycin D) and translation (cycloheximide) inhibitors into hepatectomized rats we have demonstrated that the cyclic AMP‐dependent protein kinase surge is produced by new synthesis of the enzyme. In thyroparathyroidectomized rats subjected to a partial hepatectomy the calmodulin surge was similar to that observed in normal hepatectomized rats whereas the surge in cyclic AMP‐dependent protein kinase activity was strongly decreased suggesting that the cyclic AMP‐dependent protein kinase surge is not generated by the previous surge in calmodulin.
The effect of a native collagen gel substratum on the synthesis of collagen by bovine brain capillary endothelial cells
Authors: Scott D. M. , Kumar S. , Barnes M. J. 
Published: May 2005

AbstractCultured capillary endothelial cells, derived from bovine brain, and maintained on a plastic substratum synthesized predominantly interstitial collagens of which approximately 75 per cent were secreted into the medium. When grown on a native hydrated collagen type I gel, although no marked alteration in the ‘collagen synthetic pattern’ was observed, the overall level of collagen synthesis was increased by approximately 100 per cent. More dramatic, however, was the alteration in the distribution of these molecules between medium and cell layer. Interstitial collagens produced by cells grown on collagen gels were almost exclusively associated with the cell layer or collagenous gel. These studies, thus, demonstrate that an extracellular matrix may exert a considerable influence on the cellular synthetic activities and possibly cellular polarity of capillary endothelial cells.
Influence of long term treatment with 3‐methylcholanthrene or carbaryl on mixed‐function oxidase activity in 3T3 fibroblasts: Studies by microspectrofluorimetry on single cells
Authors: Lahmy Sylvie , Salmon Jean‐Marie , Viallet Pierre 
Published: May 2005

AbstractUsing benzo(a)pyrene (BaP) as a probe for aryl hydrocarbon hydroxylase (AHH) activity, differences in mixed‐function oxidase (MFO) activity were observed using microspectrofluorimetry in single living cells during long term treatment with 3‐methylcholanthrene (3‐MC) or carbaryl. Although these two compounds differ in chemical structure, similar effects were observed in 3T3 cell populations.The results suggest that the two compounds activate the same enzymatic system and that individual cells of a supposed homogeneous cell population are not equally sensitive to xenobiotics, i.e. subpopulations were observed which have differences in AHH activity.
Intrarenal localization of angiotensin II specific binding in rat fetuses
Authors: Uva B. , Ghiani P. , Mandich A. , Masini M. A. 
Published: May 2005

AbstractSpecific binding sites for angiotensin II were localized in the developing rat kidney (18th day of pregnancy and immediately before birth) by autoradiography using [125I]‐ileu‐5‐angiotensin II either perfused in vivo through the fetal aorta or added in vitro to frozen sections in an incubation mixture. Specific binding was localized in the walls of the afferent and efferent arterioles, in the intraglomerular cells and in the peritubular arterioles of the subcapsular cortical zone. The immunohistochemical analysis, carried out on receptors saturated with unlabelled angiotensin II perfused through the mother's aorta, confirmed the autoradiographical localization. Antisera against ileu‐5‐angiotensin II were used in the indirect immunofluorescence technique and in the PAP method. Immunolocalization of angiotensin II was also found in the proximal tubule and in the thick ascending limb of Henle's loop.
Uptake of alpha 2‐macroglobulin–trypsin complex by human placenta is mediated by a microvillous membrane receptor
Authors: Eaton B. M. , Oakey M. P. , Sooranna S. R. , Contractor S. F. 
Published: May 2005

AbstractThe fate of native alpha 2‐macroglobulin (α2M) or its trypsin complex (α2M‐T) was studied in the isolated dually‐perfused lobule of term human placenta. [125I]‐α2M added to the maternal circuit was unchanged during the course of the perfusion with minimal activity becoming associated with the placental tissue. Transfer of radioactivity into the fetal circulation accounted for only 0·07 per cent of the initial dose after 2 h. In contrast, [125I]‐α2M‐T was rapidly taken up into the placental tissue (nearly 28 per cent of the initial dose during the 2‐h perfusion) and breakdown products were released into both maternal and fetal circulations. At the end of 2 h, radioactivity levels on the fetal side were 13 times higher than those found with the native protein. These indications of a classical receptor‐mediated uptake and breakdown pathway were confirmed in experiments in which the acidotrophic agent chloroquine was added to the maternal circuit prior to the α2M‐T. In the presence of chloroquine, tissue uptake was inhibited and the subsequent release of radioactive degradation products into the fetal circuit was similar to the levels seen with α2M. Incubation of term trophoblast cells at 37°C with [125I]‐α2M‐T revealed over three‐fold greater cell‐associated activity than was found with the native protein. In another series of experiments, a purified microvillous membrane fraction was prepared from term placentae using buffers containing 1 mM iodoacetate. In the presence of this proteolytic enzyme inhibitor, binding studies showed a single class of low affinity receptors for the α2M‐T complex capable of binding 4·8 ± 1·3 (SEM) μg of complex per mg of membrane protein. There was no binding of the native protein.
Inhibition of the glycolytic pathway by methylglyoxal in human platelets
Authors: Leoncini G. , Maresca M. , Buzzi E. 
Published: May 2005

AbstractThe incubation of human platelets with methylglyoxal and glucose produces a rapid transformation of the ketoaldehyde to D‐lactate by the glyoxalase system and a partial reduction in GSH. Glucose utilization is affected at the level of the glycolytic pathway. No effect of the ketoaldehyde on glycogenolysis and glucose oxidation through the hexose monophosphate shunt was demonstrated. Phosphofructokinase, fructose 1,6 diphosphate (F1, 6DP) aldolase, glyceraldehyde 3‐phosphate dehydrogenase and 3‐phosphoglycerate mutase were mostly inhibited by methylglyoxal. A decrease in lactate and pyruvate formation and an accumulation of some glycolytic intermediates (fructose 1,6 diphosphate, dihydroxyacetone phosphate, 3‐phosphoglycerate) was observed. Moreover methylglyoxal induced a fall in the metabolic ATP concentration. Since methylglyoxal is an intermediate of the glycolytic bypass system from dihydroxyacetone phosphate to D‐lactate, it may be assumed that ketoaldehyde exerts a regulating effect on triose metabolism.
Liposome–nucleus interactions. Flow cytometric study on the role of the nuclear surface
Authors: Caramelli E. , Papa S. , Billi A. M. , Vitale M. , Bartoletti A. , Manzoli L. , Capitani S. 
Published: May 2005

AbstractThe water‐soluble probe carboxyfluorescein (CF), contained in the internal aqueous phase of liposomes, was used to investigate the interaction of phospholipid vesicles with isolated nuclei. Ultrastructural analysis indicated that adherent liposomes coated the nuclear surface, and fluorescence microscopy showed that they contained quenching concentrations of the dye. Flow cytometry revealed that the transfer of the entrapped dye from the adhering liposomes to nuclei was blocked by chilling at 0°C. Chase experiments demonstrated that the most reliable mechanism of dye transfer involved fusion phenomena between the liposomal and the nuclear membranes. After the release of the fluorophore into the nucleus, empty liposomes could withdraw the intranuclear soluble fraction of the dye.
Cytochrome P450‐dependent alkoxyphenoxazone dealkylase activity in rat alveolar type II cells: Effect of pretreatment with β‐naphthoflavone
Authors: Rabovsky J. , Judy D. J. , Sapola N. A. , Pailes W. H. , McPeek M. , Castranova V. 
Published: May 2005

AbstractCytochrome P450‐dependent alkoxyphenoxazone dealkylase activity was measured in alveolar type II cells from control and β‐naphthoflavone (ip) treated‐rats. Type II cells were isolated from collagenase/elastase‐digested lung tissue and purified by centrifugal elutriation. The specificity of the cytochrome P450‐dependent activity towards four alkoxyphenoxazones (methoxy‐, ethoxy‐, pentoxy‐, and benzyloxyphenoxazone) was measured under conditions that minimized interference by cytosolic conjugating‐ and NADPH‐dependent quinone reductase activities. Ethoxyphenoxazone dealkylase activity was induced 17‐fold following β‐naphthoflavone treatment and was further characterized by its kinetic parameters and sensitivities toward in vitro inhibitors (Km(app)=0·20 μM, Vmax = 1·74 pmoles resorufin min−1 (106 cells)−1 106 cells; I50 (α‐naphthoflavone)=0·025 μM, and I50 (methyrapone) = 72 μM). β‐Naphthoflavone pretreatment of the rats did not result in statistically significant changes in methoxy‐, pentoxy‐, or benzyloxyphenoxazone dealkylase activity of alveolar type II cells, although, a trend towards decrease activity was observed for benzyloxyphenoxazone. β‐Naphthoflavone pretreatment had no effect on oxygen consumption of trypan blue exclusion in alveolar type II cells and macrophages, or on alveolar macrophage particle‐mediated superoxide release. Furthermore, alveolar macrophage ethoxyphenoxazone dealkylase and benzyloxphenoxazone dealkylase activities were not affected by the β‐naththoflavone pretreatment. The results show that exposure to β‐naphthoflavone resulted in an increase in type II cell cytochrome P450‐dependent ethoxyphenoxazone dealkylase activity but not in other alveolar type II cell or macrophage alkoxyphenoxazone dealkylase activities or in parameters that monitor viability and cell wall integrity.
Brush border membrane non‐esterified fatty acids. Physiological levels and significance for mucosal iron uptake in mouse proximal intestine
Authors: Simpson Robert J. , Venkatesan S. , Peters Timothy J. 
Published: May 2005

AbstractBrush border membrane vesicles prepared using divalent cation precipitation methods can contain unphysiological levels of non‐esterified fatty acids. Fatty acid production from endogenous lipid during brush border membrane vesicle preparation is effectively prevented by the lipase inhibitor diethyl 4‐nitrophenylphosphate plus cooling. Vesicles prepared using this procedure have variable levels of non‐esterified fatty acids (range 22–193 nmol mg−1 protein). Changes in non‐esterified fatty acid levels in brush border membrane vesicles parallel Fe uptake by vesicles from Fe/ascorbate solutions. Brush border membrane vesicle fatty acids appear to be derived from the diet but hypoxic mice are able to maintain high brush border membrane non‐esterified fatty acid levels despite reduced dietary intake. Non‐esterified fatty acids in brush border membrane may thus provide a physiological mechanism of mucosal Fe uptake.
Effect of sodium arsentie on the induction and turnover of ornithine decarboxylase activity in erythroleukemia cells
Authors: Flamigni Flavio , Marmiroli Sandra , Caldarera Claudio M. , Guarnieri Carlo 
Published: May 2005

AbstractSodium arsenite proved effective in preventing the induction of ornithine decarboxylase (ODC) activity elicited by dilution of Friend erythroleukemia cells in fresh medium. A 50 per cent inhibition was produced at approximately 1 μM arsenite and complete inhibition was obtained at concentrations above 10 μM. However, addition of arsenite 5 h after cell dilution, i.e. when ODC was already induced, appeared to stabilize the enzyme. The half‐life of ODC activity, measured after cycloheximide treatment, increased almost six‐fold after addition of sodium arsenite. Agents known to provoke oxidative alteration of the thiol‐redox status in cells, also caused a similar effect on the induction and stability of ODC.
Blocking of human T lymphocyte activation by channel antagonists
Authors: Bono Maria Rosa , Simon Valeska , Rosemblatt Mario S. 
Published: May 2005

AbstractIt has been established that early events in lymphocyte activation involve a rise in intracellular Ca++ as well as changes in the flux of other ions. Although a Ca++ channel has been postulated to participate in the early Ca++ rise, its presence in lymphocytes remains controversial. Also although yet undetected, electrophysiological data suggest the presence of a Ca++ activated K+ channel on human peripheral blood lymphocytes (HPBL). Here we report on the effect of specific channel blockers as an approach to the identification of these channels on HPBL. At 40 nM nifedipine, an inhibitor of voltage‐gated Ca++ channels, fully inhibits the PHA‐promoted activation of HPBL. This effect is concentration dependant with a half maximum effect at approximately 10 nM and is demonstrable whether the drug is added at the same time as or up to 18 h after the addition of the mitogen. This inhibition of activation is not seen if the lymphocytes are activated using IL‐2 instead of PHA. Charybdotoxin a toxin which blocks a Ca++ activated K+ channel of muscle cells also blocks to almost 100 per cent the PHA‐induced activation of HPBL. This inhibition can be demonstrated regardless of whether the blocker is added together with or up to 4 h after PHA. As opposed to nifedipine charybdotoxin shows no effect if added 18 h after the initiation of the activation process. When nifedipine and charybdotoxin were tested on mice splenocytes we found that nifedipine fully inhibits the LPS‐promoted activation of these cells while charybdotoxin has no effect on their activation. Taken together these results strengthen the view regarding the participation of both a voltage‐gated Ca++ channel and a Ca++ activated K+ channel in human T lymphocyte activation.
The mechanism of placental alkaline phosphatase induction in vitro
Authors: Nozawa Shiro , Narisawa Sonoko , Iizuka Rihachi , Fukasawa Toshio , Kohji Takehiko , Nakane Paul K. , Hirano Kazuyuki , Millan Jose L. 
Published: May 2005

AbstractThe mechanism of placental alkaline phosphatase (PLAP) induction by prednisolone in a uterine cervical epidermoid cancer cell line SKG‐IIIa was investigated in vitro by enzyme‐cytochemistry, enzyme immunoassay, Northern and Southern blot analysis, and in situ hybridization. Enzyme‐cytochemical alkaline phosphatase (ALP) staining and immunoassay revealed increased levels of PLAP (heat‐stable ALP) in prednisolone‐treated cells. Northern blot analysis and in situ hybridization showed increased amounts of PLAP mRNA. Southern blot analysis indicated that PLAP was not a product of an amplified or rearranged gene.These findings suggest that the induction of PLAP mRNA in SKG‐IIIa cells by prednisolone in turn increased the levels of PLAP.
4‐Hydroxynonenal interacts with tubulin by reacting with its functional ‐SH groups
Authors: Olivero Antonella , Miglietta Antonella , Gadoni Elena , Gabriel Ludovica 
Published: May 2005

Abstract4‐Hydroxynonenal, which is one of the most important products of lipid peroxidation, alters microtubular organization and structure in 3T3 fibroblasts. Changes in cell shape and the disappearance of microtubules are observed by immunofluorescence after incubation with the aldehyde, and the colchicine binding activity of tubulin from 3T3 cells is modified. Moreover, the aldehyde determines a decrease in the ability of purified tubulin to polymerize and to bind colchicine. These effects may be related to the interaction of the aldehyde with functional ‐SH groups of tubulin which are necessary for protein integrity and functions. Indeed, the addition of cysteine protects against the damaging effects of the aldehyde.
ATP modifications in hexokinase deficient fibroblasts exposed to nutrient shifts
Authors: Chiarantini Laura , Vittoria Emanuela , Magnani Mauro 
Published: May 2005

AbstractHuman fibroblasts from a patient homozygous for hexokinase (HK) deficiency and normal controls were submitted to different nutrient shifts to investigate the role of glucose metabolism on ATP levels. HK‐deficient cells maintained in the presence of both glucose and L‐glutamine had 20 per cent less ATP than controls and an ATP/ADP ratio of 18 instead of 37–40. Glucose alone was not able to maintain normal ATP levels neither in the controls nor in the HK‐deficient cells. However while in control cells the ATP/ADP ratio was not modified, it was reduced to 10 in HK deficiency. The effect of several hexoses on ATP levels was also investigated. Mannose, which is metabolized by HK phosphorylation, was the least efficient for ATP maintenance in HK‐deficient cells. In contrast galactose, which is metabolized by a specific galactokinase, provided ATP values close to those observed in the presence of glutamine. These results suggest that glucose metabolism is an important determinant in the maintenance of ATP levels in cultured cells and that glutamine, although being a good metabolic substrate, is not sufficient to maintain normal ATP concentrations.
Effects of inositol 1,4,5‐trisphosphate on calcium release from the endoplasmic reticulum and golgi apparatus in mouse mammary epithelial cells: A comparison during pregnancy and lactation
Authors: Yoshimoto Akio , Nakanishi Keiko , Anzai Tadashi , Komine Senichi 
Published: May 2005

AbstractIt has been established that inositol 1,4,5‐trisphosphate(IP3) is responsible for the mobilization of calcium(Ca2+) from intracellular locations in a wide variety of tissues, and that this response triggers the stimulation of several hormones and neurotransmitters. However, these phenomena have yet to be examined in the mammary epithelium.Ca2+ uptake from the medium into the endoplasmic reticulum(ER) and Golgi apparatus in vitro in both pregnant and lactating mouse mammary epithelial cells was studied and a strong Ca2+ release from these organelles into the medium with the use of IP3 was shown. The Ca2+ uptake and its release due to IP3 was also usually greater during pregnancy than lactation.
Impairment of ATP‐linked reactions in mitochondria isolated from skeletal muscle of halothane‐sensitive pigs
Authors: Ayoub S. , Monin G. , Rock E. , Younes A. 
Published: May 2005

AbstractOxygen consumption was depressed in mitochondria isolated from halothane sensitive pig (HP) muscle. The calculation of the respiratory control ratio (RCR) indicated that mitochondria were more affected at the site‐I level of the respiratory chain. Calcium accumulation in these mitochondria was not altered when driven by the oxidation of succinate. This process was abolished when linked to ATP as a source of energy. ATP transport was completely inhibited in (HP) mitochondria.
Decarboxylation of branched‐chain α‐ketoacids in hepatocytes from alloxan‐diabetic rats. The effect of insulin
Authors: Sterniczuk Anna , Wałajtys‐Rode Elżbieta I. , Wojtczak Anna B. 
Published: May 2005

AbstractThe flux through branched‐chain α‐ketoacid dehydrogenase and the activity of the branched‐chain α‐ketoacid dehydrogenase complex were measured in hepatocytes isolated from fed, starved and alloxan diabetic rats. The highest rate of branched‐chain α‐ketoacid oxidation was found in hepatocytes isolated from starved rats, slightly lower in those from fed rats, and significantly lower in diabetic hepatocytes. The amount of the active form of branched‐chain α‐ketoacid dehydrogenase was only slightly diminished in diabetic hepatocytes, whereas the flux through the dehydrogenase was inversely correlated with the rate of endogeneous ketogenesis. The same was observed in hepatocytes isolated from starved rats when branched‐chain α‐ketoacid oxidation was measured in the presence of added oleate. In both cases the diminshed flux through the dehydrogenase, restored by a short preincubation of hepatocytes with insulin, was parallelled by a decrease of fatty acid‐derived ketogenesis. The significance of these findings is discussed in relation to the role of insulin in branched‐chain α‐ketoacid oxidation in liver of diabetic rats.