bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanism of citrinin‐induced dysfunction of mitochondria. II. Effect on respiration, enzyme activities, and membrane potential of liver mitochondria
Authors: Chagas Generoso M. , Oliveira Ma. Bengna M. , Campello Annibal P. , Klüppel Ma. Lúcia W.
Published: May 2005

The mycotoxin citrinin, depressed the phosphorylation efficiency of liver mitochondria as deduced from a decrease of respiratory coefficent and of the ADP/O ratio. Citrinin (1·0 mM) inhibited some enzymes linked to the respiratory chain, namely NADH oxidase and NADH cytochrome c reductase involved with complex I. The activities of enzymes related with other enzymatic complexes of the respiratory chain were either unaffected or enhanced. ATPase activity was inhibited by the mycotoxin. Malate, glutamate, and 2‐oxoglutarate dehydrogenases were also inhibited. The transmembrane potential (Δψ), developed by energized mitochondria and depolarization on the addition of ADP, was decreased. The results suggest that citrinin promotes a partial dissipation of the transmembrane potential, different from that resulting from a classical uncoupler such as 2,4‐dinitrophenol.
Regulation of the phosphate (Pi) concentration in UMR 106 osteoblast‐like cells: Effect of Pi, Na+ and K+
Authors: Kemp Graham J. , Khouja Hamed I. , Ahmado Abdulla , Russell R. Graham G. , Bevington Alan
Published: May 2005

Osteoblast‐like cells possess Na‐dependent transporters which accumulate orthophosphate (Pi) from the extracellular medium. This may be important in bone formation. Here we describe parallel measurements of Pi uptake and cellular [Pi] in such cells from the rat (UMR 106–01 and UMR 106–06) and human (OB), and in non‐osteoblastic human fibroblasts (Detroit 532 (DET)). In UMR 106–01, cellular [Pi] was weakly dependent on extracellular [Pi] and higher than expected from passive transport alone. [32Pi]‐uptake was inhibited by Na deprivation, but paradoxically increased on K deprivation. With Na, 87 per cent of cellular 32P was found in organic phosphorus pools after only 5 min. Na deprivation also decreased cellular [Pi], in both UMR 106–01 and DET, but the decrease was smaller than that in [32Pi]‐uptake. Ouabain decreased [32Pi]‐uptake and cellular [Pi] in DET, but not in UMR 106–01. Regulation of cellular [Pi] is therefore at least partly dependent on Na/Pi co‐transport, but this does not seem to be an exclusive property of osteoblasts.
Calciotropic hormones raise the chemically detectable [Pi] in UMR 106–06 osteoblast‐like cells
Authors: Ahmado Abdulla , Khouja Hamed I. , Kemp Graham J. , Guilland‐Cumming Diane F. , Russell R. Graham G. , Bevington Alan
Published: May 2005

Uptake of orthophosphate (Pi) by osteoblast‐like cells is known to be stimulated by parathyroid hormone (PTH), but effects on intracellular [Pi] have not been investigated. Here we show in rat osteoblast‐like cells (UMR 106‐06) that PTH (10−11 to 10−7 M) increases both 32Pi uptake and cellular [Pi] by up to 50 per cent. 1,25 Dihydroxyvitamin D3 (1,25D) (10−12 to 10−6 M) and salmon calcitonin (CT) (10−12 to 10−6 g ml−1) also increased cellular [Pi] (by up to 60 per cent), but the percentage increases in total cellular 32Pi uptake were smaller. The effects of 1,25D were transient (observable at 80 min and 6 h but not 24 h), and were also observed with 24,25 dihydroxy‐ and 25 hydroxyvitamin D3. Transient degradation of organic phosphorus pools to Pi might contribute to this increased [Pi]. These pools remain to be identified but were not shown to be phospholipids. Foetal bovine serum also affected cellular [Pi]. Care is therefore needed in distinguishing direct hormonal effects on cellular [Pi] from indirect effects arising from changes in the rate of cell growth.
The effects of tunicamycin on the metabolism of acetylated low density lipoproteins
Authors: Armstrong David P. , White David A.
Published: May 2005

The effect of tunicamycin (TM) on the metabolism of acetylated low‐density lipoprotein (AcLDL) was examined to determine whether N‐linked glycosylation is required for the proper function of the AcLDL pathway. Proteolytic degradation of [125I]‐AcLDL was increased twofold in the presence of TM. This did not occur via an increase in total lysosomal enzyme activity or extracellular proteolysis; rather, the rate of uptake of [125I]‐AcLDL was increased. The enhanced degradation of AcLDL did not lead to a commensurate increase in the rate of synthesis of cholesteryl oleate. Conversely, the rate of cholesterol esterification was reduced in the presence of TM. The uptake of [125I]‐AcLDL was more sensitive to inhibition by chloroquine in TM‐treated cells. However, the presence of TM did not affect the ability of chloroquine to inhibit constitutive recycling of AcLDL binding sites. These results suggest that N‐linked glycosylation may be involved in the regulation of AcLDL metabolism in J774 cells.
Extracellular calcium modulates proliferation of factor dependent hemopoietic cells
Authors: Martínez Jorge , Santibañez Juan F.
Published: May 2005

Blockade of the calcium channel inhibited, in a dose‐dependent manner, the proliferation of the IL‐3 dependent FDCP‐1 cell line and normal murine bone marrow cells. Similar results were obtained by lowering the amount of extracellular calcium using specific chelators or a calcium‐free medium. These results suggest that factor‐dependent cell proliferation is highly sensitive to fluctuations in the concentration of extracellular calcium.
Adaptation to phosphate deprivation in osteoblast‐like cells
Authors: Ha Richard , Steenbergen Dawn K. , Kempson Stephen A.
Published: May 2005

The rat osteosarcoma cell line UMR‐106–01 has an osteoblast‐like phenotype. When grown in monolyer culture these cells transport inroganic phosphate and L‐alanine via Na+‐dependent transport systems. Exposure of these cells to a low phosphate medium for 4 h produced a 60–70 per cent increase in Na+‐dependent phosphate uptake compared to control cells maintained in medium with a normal phosphate concentration. In contrast, Na+‐dependent alanine uptake and Na+‐independent phosphate uptake were not changed during phosphate deprivation. The increased phosphate uptake was due, in part, to an increased Vmax and was blocked completely by pretreatment with cycloheximide (70 μM). In these cells recovery of intracellular pH after acidification with NH4Cl is due primarily to the Na+/H+ exchange system. The rate of this recovery process, monitored with a pH sensitive indicator (BCECF), was decreased by more than 50 per cent in phosphate‐deprived cells compared to controls indicating that Na+/H+ exchange was inhibited during phosphate deprivation.
Enzymatic, metabolic and secretory perturbations in pancreatic islets of thyroidectomized rats
Authors: Sener Abdullah , Malaisse‐Lagae Francine , Gervy‐Decoster Christine , Malaisse Willy J.
Published: May 2005

In thyroidectomized rats, the activity of FAD‐linked glycerophosphate dehydrogenase was severely diminished in liver homogenates but not affected significantly in pancreatic islet homogenates, whilst the activity of 2‐ketoglutarate dehydrogenase was decreased modestly in both liver and islet homogenates. Likewise, in intact islets of thyroidectomized rats, the generation of3HOH from [2‐3H]glycerol was not decreased, and the ratio between oxidative and total glycolysis not significantly lower than in islets from sham‐operated rats, at least in the presence of a high concentration of D‐glucose. Nevertheless impaired oxidation of both D‐[3,4‐14C]glucose and D‐[6‐14C]glucose was observed in islets of thyroidectomized rats, the relative magnitude of such a decrease being more pronounced at a low than at a high D‐glucose concentration. Such metabolic anomalies coincided with a lower level of plasma insulin and a decreased output of insulin by islets incubated at low (2·8 mM), but not higher, concentrations of D‐glucose. It is concluded that hypothyroidism does not mimic the deficiency in islet FAD‐linked glycerophosphate dehydrogenase activity found in rats with inherited or acquired non‐insulin‐dependent diabetes.
Stability and optimization of canalicular function in hepatocyte couplets
Authors: Wilton Joanne C. , Coleman Roger , Lankester David J. , Chipman J. Kevin
Published: May 2005

An enriched preparation of rat hepatocyte couplets was obtaied by collagense perfusion and subsequent elutriation (> 85 per cent couplets and triplets; viability of over 95 per cent).

Canalicular secretory activity (the ability to accumulate cholyl‐lysyl‐fluorescein, CLF) was first apparent after 2 h of culture at 37°C and was present in over 80 per cent of the total population after 5–6 h. This remained almost constant for at least 4 h in both elutriated and directly plated cells. Initial storage of freshly prepared couplets at 4°C for up to 6 h prior to incubation had no adverse effect upon secretory function.

Reduction of canalicular secretory activity occurred at a concentration of the hepatotoxic agent menadione (IC50 17 μM) that was lower than that required to induce mild plasma‐membrane blebbing (IC50 43 μM).

This study has optimized and characterized the canalicular secretory effectiveness and stability of an enriched preparation of hepatocyte couplets, and established the feasibility of studies of toxic agents on hepatobiliary function in a heterogeneous population of hepatocytes. In this preparation other biochemical parameters can be assessed, thus complementing previous techniques using individual couplets.
Differential effects of unsaturated fatty acids on phospholipid synthesis in human leukemia monocytic U937 cells
Authors: Chu Arthur J. , Nguyen Camtu T. , Moore John
Published: May 2005

The biosynthesis of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) in monocyte‐like leukemia U937 cells was monitored by adding [3H]choline, [14C]ethanolamine or [14C]glycerol to the culture media; incorporation into phospholipid (PL) increased with time. The effect of unsaturated fatty acids (UFA) on PC and PE synthesis was investigated by pretreating U937 cells for 72h with 10 μM 18:1 (n –9), 18:2 (n –6), 18:3 (n –3), 20:4 (n –6) and 20:5 (n –3). The UFA caused no alteration in cell growth, as evidenced by light microscopy and the incorporation of [3H]thymidine and [3H]leucine. Total cellular uptake of radioactive precursors remained unaffected by all the treatments. Pretreatment with 20:5 resulted in approximately 25 per cent reduction in the incorporation of [3H]choline into PL, while no significant effect was detected with the other UFAs. 18:3, 20:4 and 20:5 depressed the incorporation of [14C]ethanolamine into PL by 34 per cent, 28 per cent and 49 per cent respectively. However, there was no redistribution of label with any of the treatments. 18:3, 20:4 and 20:5 also antagonized the stimulatory effect of endotoxin (LPS) on PC and PE synthesis. In addition, the incorporation from [14C]glycerol into PC and PE was reduced by 18:3, 20:4 and 20:5.

Although the PL composition of the cells remained essentially unaffected, our study shows that chronic treatment of U937 cells with n –3 PUFA (20:5) depressed PC and PE synthesis, and 18:3 and 20:4 also caused inhibition of PE synthesis.
Continuous column culture system for adherent cells
Authors: Ishihara Yoshimi , Ohkubo T. , Shimazaki H. , El Borai Nadia , Takano J. , Yamamura M.
Published: May 2005

A new continuous column culture system for adherent cells was developed using beads. The beads were packed in a column and an appropriate medium was continuously passed through. The whole system was kept under closed conditions.

L cells and C6 cells were cultured by this new system. The number of cells increased linearly up to 16 days and reached a maximum at around 18 days. As the heat production remained constant for 16 days, it can be concluded that cells grown in this system had identical characteristics. The final concentration of cells reached was 1.0 × 108ml−1. The cells could grow both in the upward and the downward direction.

Advantages of this system are: (1) Cells can be recovered in their adherent form on the beads; (2) cells can easily be collected from the column by trypsinization, and (3) cells remaining in the column after trypsinization can grow again.
Characterization of γ‐glutamyltranspeptidase in the liver of the frog: 1. Comparison to the rat liver enzyme
Authors: Sulakhe‐Hemmings Susan J. , Xing Hongmei
Published: May 2005

The characteristics of the enzyme γ‐glutamyltranspeptidase were determined in frog liver and compared to those of the rat. In Rana pipiens, tissue distribution studies indicated the order of activity to be: kidney >>> liver >> nerve > egg > lung > heart > skeletal muscle in homogenates. In the Rana pipiens relative to the Fischer 344 rat, the activity of the liver enzyme was somewhat greater (1·8‐fold) and the kidney enzyme substantially less (25‐fold). Frog liver γ‐glutamyltranspeptidase displayed strain‐dependent differences in activity with Rana pipiens and Rana sylvatica exhibiting comparable activities and Xenopus laevis exhibiting 20‐fold lower activities. No influence of sex was apparent in Rana pipiens in contrast to the sex dependent differences observed in the Fischer 344 rat: ♀ : ♂ = 7:1. In homogenates and plasma membrane fractions of Rana pipiens, Xenopus laevis and the Fischer 344 rat, high, and comparable relative specific activities, were observed, 8–11, coupled with protein yields of 2·2–2·5 per cent indicating the enzyme to be plasma membrane bound and associated with the sinusoidal surface of the liver cell. Both the frog Rana pipiens and Xenopus laevis and Fischer 344 rat liver plasma membrane enzymes displayed comparable temperature‐induced activation (1·51–1·74‐fold) but with a peak for the frogs at 60°C and for the rat at 50°C. Both Acivicin and maleate inhibited the liver plasma membrane γ‐glutamyltranspeptidase of both Rana pipiens and the Fischer 344 rat, but the frog enzyme was less sensitive (89 per cent decrease versus 97 per cent decrease) to 150 μM Acivicin and more sensitive (65 per cent decrease versus 35 per cent decrease at 150 mM maleate) to maleate. Kinetic studies indicated that the liver plasma membrane enzyme from Rana pipiens had a Km of 0·61 mM and Vmax of 55·6 nmol mg−1 min−1 and that from the Fischer 344 rat had a Km of 3·57 mM and Vmax of 71·4 nmol mg−1 min−1.
Binding of the lipid peroxidation product 4‐hydroxynonenal to human polymorphonuclear leukocytes
Authors: Curzio M. , Ferretti C. , Stephens R. J. , Esterbauer H. , Dianzani M. U.
Published: May 2005

4‐Hydroxynonenal (HNE) is produced during peroxidation of polyunsaturated fatty acids. It exerts a chemokinetic effect on human polymorphonuclear leukocytes (PMN). Investigations of this mechanism were performed. The results indicate that [3H]‐HNE binding to PMN results both in non‐specific bonds to the numerous SH groups of the cells and in binding to a saturable, reversible and specific HNE site. Scatchard analysis revealed that this is a single site with an apparent affinity constant of 319 nM and a density of 1·57 pmol (106)−1 cells. This specific binding site may be involved in the chemokinetic effect of HNE.
Sperm phospholipid methyltransferase activity during preparation for exocytosis
Authors: Llanos Miguel N. , Ronco Ana María
Published: May 2005

The present report describes experiments to evaluate phospholipid methyltransferase activity in golden hamster spermatozoa incubated under different conditions. Washed cauda epididymal sperm were incubated with taurine, in the presence or absence of epinephrine. At various times, the sperm were separated, and phospholipid methyltransferase activity measured. Also, at each time, aliquots of the sperm suspension were assayed for motility, and acrosome reactions. Some sperm incubated in the presence of taurine and epinephrine were capacitated by 3·5 h, because about 40 per cent of them can undergo the acrosome reaction 10 min after addition of the fusogen lysophosphatidylcholine. In epinephrine‐free incubations the fusogen failed to stimulated acrosome reactions. On the other hand, epinephrine stimulated by twofold phospholipid methyltransferase activity from ‘0 time’ incubated sperm, in comparison to that observed in taurine‐treated cells. Enzyme activities from both taurine or epinephrine plus taurine‐treated cells decreased as the incubation time of the sperm suspension increased. Kinetic properties of the sperm phospholipid methyltransferase acvity were modified by the presence of taurine and epinephrine when S‐adenosylmethionine was used as the substrate. These results suggest that refined molecular events occur in the sperm cell during the acquisition of fertilizing ability.
Effects of β1‐integrin antisense phosphorothioate‐modified oligonucleotide on myoblast behaviour in vitro
Authors: Carraro U. , Bruson A. , Catani C. , Libera L. Dalla , Massimino M. L. , Rizzi C. , Rossini K. , Sandri M. , Cantini M.
Published: May 2005

Myoblasts gene‐engineered in vitro and then injected in vivo are safe, efficient options for gene therapy. While isolation of satellite cells is routinely achieved, their proliferation potential in vitro remains a limiting factor for cell transplantation under clinical conditions. We have studied the role of reversible inhibition of gene expression by antisense oligonucleotides on the proliferation of the myogenic cells. Addition of antisense oligonucleotides to myoblast cultures has been used to inhibit specifically the expression of the β1‐integrin subunit gene. Here we show that the effects of multiple pulses of a phosphorothioate oligodeoxinucleotide antisense on the attachment to substrata and on the proliferation of myoblasts are dose‐dependent. The addition of antisense to rat myoblasts caused rounding up of the cells and most of the cells became detached after several days in culture. A single pulse did not show any consistent effect, while in the presence of continously administered antisense, the relative numbers of myoblasts in the treated muscle culture increased. We have no evidence of inhibition of myoblast fusion under these conditions. On the other hand, [3H]‐TdR incorporation, total DNA and total number of cells decreased in antisense‐treated cultures thus demonstrating an inhibitory effect of the phosphorothioate oligonucleotides on DNA synthesis. These side‐effects could be overcome by substituting the phosphorothioate by unmodified oligonucleotides, so decreasing the half‐life of the antisense, but also its toxicity. The overall results suggest a potential role of integrin antisense strategy in modulating the potential of myoblasts to proliferate.
Protein synthesis in the hypertrophied heart of spontaneously hypertensive rats and a comparison of the effects of an ACE‐inhibitor and a calcium channel antagonist
Authors: Patel V. B. , Siddiq T. , Richardson P. J. , Preedy V. R.
Published: May 2005

The aim of the investigation was to assess and compare the effects of a calcium channel antagonist, (i.e. amlodipine) and an ACE‐inhibitor (i.e. lisinopril) in reducing chronic left ventricular hypertrophy in 15‐week old spontaneously hypertensive rats (SHR). Changes in cardiac hypertrophy were assessed after 8 weeks by measuring the fractional rates of protein synthesis using a ‘flooding dose’ of [3H]‐phenylalanine for 10 min. Blood pressure was monitored throughout the treatment period in both SHR and Wistar‐Kyoto control rats (WKY). The results showed a decrease in blood pressure by amlodipine after 1 week of treatment which was further reduced at 4 to 8 weeks. Lisinopril caused immediate and sustained reductions in blood pressure (190 mmHg to 130 mmHg, P < 0·001). After 8 weeks of treatment in SHR rats, amlodipine had no significant effect on left ventricular weight (P > 0·05), whereas lisinopril caused a marked reduction. The protein content and RNA were also not changed by amlodipine. In contrast, lisinopril significantly lowered the tissue protein, RNA and DNA content (P < 0·001). The changes in the left ventricles of lisinopril‐treated SHR rats were accompanied by an increase in the fractional synthesis rate of left ventricular myofibrillar proteins (+12 per cent, P < 0·025). The synthesis rate per unit RNA was also increased in right ventricular tissue of lisinopril‐treated SHR rats. However, amlodipine had no effect on the fractional synthesis rates of any of the left‐ventricular fractions of SHR rats (P > 0·05). The cellular efficiency in the right ventricle was also increased in amlodipine‐treated SHR rats, indicating a moderate effect on protein metabolism. In conclusion, amlodipine had minimal effects in the reduction of established left ventricular hypertrophy (LVH), despite reducing the blood pressure, whereas lisinopril caused regression of LVH. These events were associated with small changes in protein synthesis rates, with the contractile protein showing an increase.
Glutathione reductase (EC 1.6.4.2.) in experimental trypanosomiasis
Authors: Nok Andrew J. , Onyenekwe Paul C. , Ibrahim Sani , Bature Asabe , Ogbadoyi Emmanuel
Published: May 2005

The activity of glutathione reductase (GHSR) in extracts of kidney, liver and testis of rats infected with Trypanosoma congolense decreased with every wave of parasitemia. The implications of these observations as they relate to the risk of oxidative stress are discussed.
Glucocorticoid‐induced changes in liver: Inhibition of nuclear Ca2+, Mg2+‐dependent endonuclease activity in response to dexamethasone administration
Authors: Goodlad George A. J. , Clark Catherine M.
Published: May 2005

The endogenous Ca2+, Mg2+‐dependent endonuclease activity in nuclei from livers of rats receiving daily injections of the synthetic glucocorticoid dexamethasone was examined with respect to the production of both single and double strand breaks in chromatin DNA. The ability to form single strand breaks was measured by means of a nick translation assay and double strand breaks by following the appearance of nucleosomal ladders. A fall in the activity causing double strand breaks to approximately 50 per cent of the control value was apparent at 12 h after the first injection of the steroid. A fall of 25–30 per cent was also observed in the nicking activity but this was not apparent until 24 h after the first steriod injection. Both endonuclease activities remained at these lower levels for the remainder of the period of treatment. Nuclear extracts from dexamethasone‐treated rats also showed a reduced ability to produced nucleosomal ladders when incubated with rat muscle nuclei, indicating that the inhibition observed in intact nuclei from treated animals was independent of any changes in chromatin structure. On the other hand the nick translation activity of the two extracts was the same when calf thymus DNA was used as the substrate suggesting that steriod‐induced alterations in chromatin structure may be a critical factor in the reduced level of this activity observed in intact nuclei.
Cooperation of protein disulfide isomerase and redox environment in the regulation of NF‐κB and AP1 binding to DNA
Authors: Clive Diana R. , Greene James J.
Published: May 2005

Most transcription factors are multimeric complexes whose subunits depend on strict conformational requirements to form the active unit. Among these requirements is the presence of appropriate sulfhydryl interactions that are critical to transcription factor binding to cognate DNA recognition sites. Our experiments now suggest that modulation of these sulfhydryls may involve the action of thiol‐modifying oxido‐reductases such as protein disulfide isomerase (PDI). Electrophoretic mobility shift titration experiments incorporating different ratios of GSH:GSSG indicated that changes in GSH and GSSG concentrations corresponding to redox potential differences of as little as ±15 mV enabled or abolished binding of NF‐κB and AP1 to their cognate DNA sites. Moreover, this binding range was modulated significantly by the addition of purified protein disulfide isomerase (PDI). Collectively, these results suggest that a reversible oxidation/reduction signalling pathway may exist in the cell whereby localized changes in redox potentials and/or oxido‐reductase activity can be functionally relevant in the regulation of critical gene expression events.
Modulation of murine osteoarthritis
Authors: Chayen J. , Bitensky Lucille , Chambers M. G.
Published: May 2005

Up to nine out of 10 male STR/ORT mice develop osteoarthritis (OA) of the medial tibial cartilage at an early age. This has now been shown to be related to changes in the activity and distribution of monoamine oxidase which is related to the metabolism of catecholamines. Treatment with diclofenac sodium tended to normalize this activity but there was no significant histological improvement. It was therefore postulated that two influences were involved in the development of OA: a cellular and an extracellular factor. The first was improved by diclofenac sodium; the second, namely oedema of the matrix, was improved by tribenoside. In very preliminary studies, feeding the two drugs simultaneously resulted in 7/9 mice having no sign of OA.
JAR human placental choriocarcinoma cells actively synthesize, take up and release polyamines
Authors: Fontana L. , Cravanzola C. , Colombatto S. , Grillo M. A.
Published: May 2005

Uptake of polyamines has been investigated extensively in many cells, but not in placenta, where the polyamine– polyamine oxidase system is supposed to have an immunoregulatory function in pregnancy. Due to the importance of the transfer in this tissue, we have started this study. JAR human placental choriocarcinoma cells in monolayer at confluency were used as a model for measuring the key enzymes of polyamine synthesis and interconversion, rate of uptake and efflux, and the polyamine content. Polyamines were taken up by JAR cells and released by an independent mechanism. Ornithine decarboxylase and spermidine acetyltransferase activities and the rate of transport in and out of the cell were much higher than in other cells, such as L1210 cells. However the systems used for uptake and release appear in many respects to be similar to those observed in L1210 cells, but different from others. The uptake appears to be regulated by an inhibitory protein. Moreover, protein kinase C appears to be involved in the process. The efflux also is regulated as in L1210 cells, through control of H+ and Ca2+ concentration. In conclusion, this study shows that, in JAR cells, ornithine decarboxylase and spermidine acetyltransferase activities were much higher than in other cells, and so was the rate of transport in and out of the cells. As a result, a much higher polyamine content was observed.
Discrepancy between the initial DNA damage and cell survival after camptothecin treatment in two murine lymphoma L5178Y sublines
Authors: Grądzka Iwona , Szumiel Irena
Published: May 2005

Two L5178Y (LY) murine lymphoma cell sublines, LY‐R, resistant, and LY‐S, sensitive, to X‐irradiation display inverse cross‐sensitivity to camptothecin (CPT): LY‐R cells were more susceptible to this specific topoisomerase I inhibitor than LY‐S cells. After 1 h incubation with CPT, the doses that inhibited growth by 50 per cent (ID50) after 48 h of incubation were 0·54μM for LY‐R cells and 1·25 μM for LY‐S cells. Initial numbers of DNA–protein crosslinks (DPCs) measured at this level of growth inhibition were two‐fold higher in LY‐R (5·6 Gray‐equivalents) than in LY‐S cells (3·1 Gray‐equivalents), which corresponds well with the greater in vitro sensitivity of Topo I from LY‐R cells to CPT.1,2 Conversely, the initial levels of single‐strand DNA breaks (SSBs) and double‐strand DNA breaks (DSBs) were lower in LY‐R cells (4·2 Gray‐equivalent SSBs and 5·8 Gray equivalent DSBs) than in LY‐S cells (8·0 Gray‐equivalent SSBs and 12·0 Gray‐equivalent DSBs). Dissimilarity in the replication‐dependent DNA damage observed after 1 h of treatment with CPT was not due to a difference in the rate of DNA synthesis between the two cell lines, but may have arisen from a substantially slower repair of DNA breaks in LY‐S cells.3 Release from G2 block by caffeine co‐treatment significantly increased cell killing in the LY‐S subline, and only slightly inhibited growth of LY‐R cells. These results show that after CPT treatment cells arrest in G2, allowing them time to repair the long‐lived DSBs. As LY‐S cells are slower in repairing the DSBs, they were more susceptible to CPT in the presence of caffeine.
The control of mitochondrial respiration in yeast: A possible role of the outer mitochondrial membrane
Authors: Ahmadzadeh Mojgan , Horng Andrew , Colombini Marco
Published: May 2005

Mitochondrial respiration in yeast (S. cerevisiae) is regulated by the level of glucose in the medium. Glucose is known to inhibit respiration by repressing key enzymes in the respiratory chain. We present evidence that the early events in this inhibition include the closure of VDAC channels, the primary pathway for metabolite flow across the outer membrane. Aluminum hydroxide is known to inhibit the closure of VDAC. Addition of aluminum acetylacetonate to yeast cells, which should elevate the aluminum hydroxide concentrations in the cytoplasm, caused the inhibition of cell respiration by glucose to be delayed for up to 100 min. No significant effect of aluminum was observed in cells grown on glycerol. Yeast cells lacking the VDAC gene were also unresponsive to the addition of aluminum salt in the presence of glucose. Therefore, the closure of VDAC channels may be an early step in the inhibition of the respiration of yeast by glucose.
Carboxymethylated beta‐1,3‐glucan inhibits the binding and degradation of acetylated low density lipoproteins in macrophages In Vitro and modulates their plasma clearance In Vivo
Authors: Dushkin Michail I. , Safina Alfija F. , Vereschagin Evgenij I. , Schwartz Yakov Sh.
Published: May 2005

In atherosclerotic lesions, macrophages are transformed into foam cells accumulating modified low density lipoproteins (LDL) via the scavenger receptor pathway. We have investigated the effects of carboxymethylated beta‐1,3‐glucan (CMG) on acetylated LDL (AcLDL) metabolism in murine peritoneal macrophages in vitro and upon the clearance of AcLDL by rat liver in vivo. In cultured murine peritoneal macrophages, CMG reduced substantially the AcLDL‐induced synthesis of cholesteryl esters, decreased the binding and degradation of [125I]‐AcLDL in a dose‐dependent manner with complete inhibition at 20–30 nM, but had no effect on the binding and degradation of native [125I]–LDL. In contrast, other polysaccharides studied, namely zymosan, lipopolysaccharide, non‐modified glucan and mannan Rhodexman, had a slight effect at concentrations significantly exceeding the concentrations of CMG. [125I]‐AcLDL injected intravenously into rats was cleared from the blood with a half‐life of 3.7 min. About 56 per cent of the label of injected [125I]‐AcLDL was recovered in the liver 15 min after administration. Co‐injection of the labelled AcLDL with CMG (25 mg kg−1 b.w.) decreased the rate of AcLDL clearance so that the half‐life increased to 6.0 min. Injections of CMG (25 mg kg−1 b.w.) 48 and 24 h before the determination increased the rate of [125I]‐AcLDL clearance (with a half‐life of about 2.3 min) and increased the uptake of AcLDL by the liver. We suggest that CMG competed with AcLDL for scavenger receptors in vitro and in vivo and repeated CMG injections before the measurements of AcLDL resulted in the induction of scavenger receptor function.
Target factor analysis of parameters influencing solute‐monomeric stationary phase interactions
Authors: Howery Darryl G. , Soroka Joseph M.
Published: May 2005

Retention indices for 18 monomeric stationary‐phase solvents and 33 organic solutes are factor analyzed. Six factors reproduce the data matrix near experimental error. The solvents diglycerol and zonyl E‐7 are shown to be highly unique, whereas none of the solutes behaves uniquely. Combination sets of solvent vectors and of solute vectors from the data matrix lead to models having errors within experimental error. Basic factors which might influence the solute—solvent interactions are identified by the least‐squares method of target testing. For the solvents, a number of properties, including McReynolds' constants and molecular weight, test successfully. For the solutes, carbon number and group dipole moment are representative properties which test successfully. The best combination of solvent basic factors gives errors about twice the experimental error. Combination sets composed only of McReynolds' constants do not model the data well.
Coating of TiO2 particles by chemical vapor deposition of SiO2
Authors: Powell Quint. H. , Kodas Toivo. T. , Anderson Bruce M.
Published: May 2005

A simple CVD process for coating titanium dioxide particles to improve dispersion, pigment durability, and resistance to viscosity increases in paints is presented. The conventionally used liquid‐phase routes are complicated and expensive and often lead to porous layers, which have high oil absorption, whereas the continuous, high temperature gas phase route described here produces dense layers of silica. The Figure shows a possible mechanism for the coating process.

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Study of a cobalt‐based surface modified glassy carbon electrode: Electrocatalytic oxidation of sugars and alditols
Authors: Cataldi Tommaso R. I. , Guerrieri Antonio , Casella Innocenzo G. , Desimoni Elio
Published: May 2005

Sugars and alditols undergo an electrocatalytic oxidation in alkaline solution at cobalt‐oxide‐based glassy carbon (Co/GC) electrodes. The catalytic deposit was investigated by cyclic voltammetry and scanning electron microscopy (SEM). It is pointed out that, at relatively low coverage of cobalt, two main redox processes, CoII → CoIII and CoIII → CoIV, are observed in 0.2 M NaOH. The redox behavior of the Co/GC electrode is strongly dependent on hydroxide ion concentration, and no electrocatalytic activity is observed at pH lower than 11.5. Under voltammetric conditions the modified electrode exhibits a non‐Nernstian potential/pH shift (−88 ± 3 mV per pH unit). A reasonable explanation of the E/pH behavior in alkaline solution is given and an oxidation mechanism of CoII to CoIII is proposed in terms of hydrous cobalt oxides. No detrimental effects on the electrocatalytic oxidation of polyhydric compounds are observed in the presence of high acetonitrile concentrations (up to 40%). Inspection by SEM of the cobalt‐based deposit evidenced the presence of grain‐like microcrystallites on the glassy carbon surface.
Optimum conditions for polarographic studies of mixed‐ligand complex formation
Authors: Zelić Marina
Published: May 2005

Some characteristics of bi‐ligand systems, important for the design and performance of studies on mixed‐ligand complex formation, are given. The problem of the optimum ligand concentration is discussed using published results. In the experimental work the concentration range of the stronger complexant (at a constant level of the weaker) seems to be critical. The measurements should start under conditions where the increase in the half‐wave potential shift (with respect to the situation in the presence of only the weaker ligand) is virtually absent and finish at concentrations where it is pronounced. Small changes at the beginning reflect the ‘contribution’ of ternary species to the composite signal, whereas the big shifts at higher concentrations are mainly produced by simple species with only a minor contribution from mixed‐ligand complexes.
Mediated amperometric biosensor for nicotinic acid based on whole cells of Pseudomonas fluorescens
Authors: Takayama Katsumi , Ikeda Tokuji , Nagasawa Toru
Published: May 2005

Whole cells of Pseudomonas fluorescens TN5 were immobilized on the surface of carbon paste electrodes containing p‐benzoquinone or its derivatives. The electrodes produced anodic currents for nicotinic acid due to the electrocatalytic action of the bacterial cells using the quinone compounds as an electron transfer mediator. The characteristics as a nicotinic acid sensor were studied of the electrode containing p‐benzoquinone. It could measure nicotinic acid in the range 5μM to 6mM with a response time of 80s and with high selectivity in the solution of pH between 4 and 10. The electrode was stable for at least two weeks when used for the measurment of nicotinic acid at the concentration below 1 mM. An alternative method of measuring nicotinic acid, which is based on the respiration reaction ofP. fluorescens, is also described.
Determination of indium in bismuth indium telluride materials by anodic stripping voltammetry. Method development
Authors: Kotrlý Stanislav , Pravda Miloslav , Šrámková Jitka , Vytŕas Karel
Published: May 2005

Differential‐pulse anodic‐stripping voltammetry with the use of a pen‐type hanging mercury‐drop electrode was investigated for the determination of indium as dopant in milligram samples of thermoelectric bismuth‐telluride material. After dissolving a milligram sample in dilute HN03, telluric acid present in a great excess was oxidized by H2O2in ammoniacal medium to the less interfering Te(VI). In contrast with the supporting electrolytes containing sulfuric, nitric, perchloric, and hydrochloric acid, respectively, a higher sensitivity was achieved with a citrate buffer (of pH 2.6–2.9). The calibration plot was linear up to a concentration of about 2μg In(III)per 1 mL of the measured solution; the corresponing detection limit was 5.6 ng/mL (49 nmol/L). A standard bismuth telluride material containing 2.94% w./w. In was used to compare the results of the method with applications of flame atomic absorption spectrometry, extraction spectrophotometry and scanning energy dispersive X‐ray analysis.
Electrochemical biosensors for inhibitor determination: Selectivity and sensitivity control
Authors: Budnikov Herman C. , Evtugyn Gennady A.
Published: May 2005

The behavior of cholinesterase based potentiometric and amperometric biosensors with renewable membranes toward irreversible inhibitor determination has been investigated. Tracing paper, gelatin and cellulose nitrate were examined, as membrane materials. The membranes are replaced in the biosensor assembly after 15–20 inhibition measurements. The detection limits as well as other analytical characteristics of inhibitor determination for different enzyme supports and detection systems are compared and discussed.
Sonoelectrochemical processes: A review
Authors: Compton Richard G. , Eklund John C. , Marken Frank
Published: May 2005

The considerable progress made in the development of fundamental and applied aspects of sonoelectrochemistry, the coupling of power ultrasound into an electrochemical experiment, is reviewed with respect mainly to the measurement and analysis of effects observed in conventional sonoelectrochemical experiments in homogeneous environments. Based on the tools and methods now available it is hoped that the application of ultrasound in areas as diverse as electroanalytical and synthetic electrochemistry will be beneficial and new innovative approaches employing the various mechanical and chemical effects of ultrasound will result.
Indirect voltammetric determination of lanthanides in the presence of mordant red 19
Authors: Lee Sang Kwon , Chung Tack Dong , Kim Hasuck
Published: May 2005

Complexes of lanthanide with Mordant Red 19 (MR19) are shown to be adsorbed and can be electrochemically reduced at mercury electrodes at a more negative potential than where MR19 is reduced. Based on these properties, an analytical application for the determination of lanthanides is demonstrated by linear sweep voltammetry (LSV) and by highly sensitive adsorptive stripping voltammetry (AdSV). By applying AdSV, the detection limit of several lanthanides is about 5.0 × 10−10 M with an accumulation time of 5 min and the linear response range is from 5.0 × 10−8 M to 1.0 × 10−6 M. A typical relative standard deviation is found to be 5.2% at the 5.0 × 10−8 M level. The results from LSV show that the difference in peak potentials (δEp) between complex and MR19 increases when the atomic number of lanthanide ion is increased. Because the smallest δEp due to the presence of La3+ is still large enough to distinguish the complex peak from dye peak, it is possible to recognize all members of lanthanide ions selectively with MR19, regardless of whether they are light or heavy ones. It is also possible to perform simultaneous analysis for some mixtures. In addition, the range of lanthanide concentration, for which quantitative analysis is valid, becomes wider as a result of using LSV as well as AdSV.
Layer‐layer assembly for extremely stable glucose sensors
Authors: Khan Golam Faruque
Published: May 2005

A novel fabrication of an amperometric glucose sensor by layer after layer approach is described. The sensor electrode is fabricated by arranging a layer of Pt black, a layer of glucose oxidase (GOD) and a layer of stabilizer gelatin on a shapable electro‐conductive (SEC) film surface. Finally, the dried layered‐assembly is cross‐linked by exposing to a diluted glutaraldehyde solution. The performance of the developed sensor is evaluated by a FIA system at 37°C and under a continuous polarization at 0.4 V (vs. Ag/AgCl). The sensitivity of the sensor was dependent on the amount of GOD loaded. The highest sensitivity (3.6 μA/mM cm−2) of the sensor was obtained at a GOD loading of 160 μg/cm2, and the linear dynamic range was extended to 80 mM level when the sensor was covered with a polycarbonate membrane. The sensor shows an extremely stable response for several weeks and a storage stability of over 2 years.
Flow injection, amperometric determination of ethanol in wines after solid‐phase extraction
Authors: Chen Zuliang , Yu Ji Jin , Hibbert D. Brynn
Published: May 2005

Ethanol in wines was determined by flow injection analysis with an amperometric detector using an oxidized nickel wire. Solid‐phase extraction with a strong anion exchanger was used to remove interferences such as organic acids from the matrix, and the residue of the extraction was injected directly into the FIA system. The recoveries of ethanol from wines spiked with standards ranged from 101% to 103%. The response of the nickel electrode to ethanol is dependent on the applied potential and the pH of the carrier. The optimal conditions for the detection of ethanol were an applied potential of +0.60 V (vs. Ag/AgCl) in a carrier of 100 mM sodium hydroxide solution. The electrode exhibited a linear response from 10−5 to 10−3 M, with a detection limit of 1 × 10−6 M. The method was demonstrated by the determination of ethanol in wines.
Coulometric stripping potentiometry for arsenic(III)
Authors: Ratana‐ohpas Roongroje , Jagner Daniel , Ma Feng
Published: May 2005

Calibration‐free determination of AsIII in the presence of AsV using coulometric stripping potentiometry is described. AsIII, in the concentration range 0.01‐2 mg/L, is quantitatively reduced to elemental arsenic and simultaneously dissolved in gold codeposited onto a glassy carbon substrate by electrolysis for 4 minutes at −0.50 V (vs. Ag/AgCl (0.01 MCl−)) in 12 μL samples containing 3 M hydrochloric acid and 10 mg/L gold(III). Selectivity between arsenic(III) and (V) is achieved by proper control of the deposition potential and by minimizing the gold(III) concentration and the time between addition of gold(III) and commencement of analysis.
Determination of chloride by stripping chronopotentiometry with silver‐film electrode
Authors: Suturović Zvonimir J. , Marjanović Nikola J. , Dokić Petar P.
Published: May 2005

The experimental parameters of cathodic stripping chronopotentiometry of chloride at a silver‐film electrode are investigated and optimized. The chloride preconcentration is achieved in the form of silver chloride by a controlled potential oxidation of the working electrode under vigorous stirring. Cathodic stripping of the deposit is obtained by the constant current, under the condition of diffusive mass transfer. Deaeration of the solution is not necessary. A detection limit of 35 μ dm−3 (10−6 mol dm−3) is obtained at a deposition time of 180 s, with a reproducibility of 6.7 % (expressed as relative standard deviation, RSD).
Determination of dissociation constants by affinity electrophoresis: Complexes between human serum proteins and concanavalin A
Authors: Bøg‐Hansen Thorkild C. , Takeo Kazusuke
Published: May 2005

The general equation for determination of dissociation constants by affinity electrophoresis is given. Dissociation constants of macromolecular complexes may be determined irrespectively of the mobility of the complex. Complexes between two macromolecular components may be studies. Dissociation constants are given for concanavalin A‐complexes of human serum proteins: two components of alpha1‐antitrypsin, two components of orosomucoid (alpha1‐acid glycoprotein), high density lipoprotein‐associated arylesterase, haptoglobin, alpha2‐HS‐glycoprotein, and transferrin. When the affinity electrophoresis is performed as lectin interaction electroimmuno precipitation (crossed immunoelectrophoresis with lectin in the first dimension gel) prior purification is unnecessary.
A new technique for eluting proteins from polyacrylamide gels: Flat‐bed electrophoretic elution in Sephadex via isoelectric focusing
Authors: Lasky Marvin , Manrique Albert
Published: May 2005

We have developed a new technique, flat‐bed electrophoretic elution in Sephadex via isolectric focusing for the removal of proteins from polyacrylamide gels subsequent to electrophoresis. A narrow slice of the polyacrylamide gel, which contains the protein to be eluted, is finely ground and applied to a horizonatal bed of Sephadex G‐200 SF containing carrier ampholytes. Upon focusing the Sephadex plate, the protein rapidly elutes and migrates to its isoelectric point where it bands and concentrates. This method, by circumventing many of the problems and limitations of current elution methods and apparatus, ensures the recovery of proteins in concentrated form with a high yield.

Conditions for optimal rates of elution were developed. For best results, a finely chopped slice of the gel, which contains the protein, is mixed in with some of the Sephadex G‐200 SF which has been removed from a narrow rectangular application zone of a flat‐bed plate. The application zone is chosen several pH units from the isoelectric point of the eluting material. The use of a broad pH carrier ampholyte in the bed generally proves superior to a narrow range interval. High voltage can be used due to the excellent cooling capacity of the system and the even conductivity of the Pharmalyte® carrier ampholytes. The technique is relatively mild and should only minimally influence the biological activity of the eluted material.
Determination of protein‐ligand dissociation constants of their pH dependence by combined isoelectric focusing‐electrophoresis (titration curves): Binding of phosphorylases a and b to glycogen
Authors: Ek Kristina , Righetti Pier Giorgio
Published: May 2005

Affino‐titration curves, a variant of conventional affino‐electrophoresis techniques, allow the simultaneous determination of protein‐ligand dissociation constants (Kd) and of their pH‐dependence in the pH range 3–10. If the ligand is a macromolecule, it is simply entrapped in the gel matrix; if it is a small molecule, it is covalently bound to the gel fibers. When a titration curve of a protein is run in presence of increasing amounts of ligand in the gel, the progressively decreasing mobilities, when plotted against the ligand molarity in the gel, can be used to calculate Kd's at any pH value. This technique has been used to measure the dissociation constants of glycogen with phosphorylases a and b, and their pH‐dependence.