bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stimulation of DNA synthesis by tumor promoters in primary rat hepatocytes is not mediated by arachidonic acid metabolites
Authors: Lee Chow H. , Edwards Anthony M. 
Published: August 2002

AbstractStudies in vivo using inhibitors of eicosanoid synthesis suggested that prostaglandins may play a role in mediating tumor promotion in liver by agents such as phenobarbital (PB). However, it is not clear whether any stimulation of arachidonic acid metabolism/prostaglandin formation results directly from the action of tumor promoters on hepatocytes or indirectly from effects of promoters on Kupffer cells or other non‐hepatocytes. Our laboratory has been utilizing relatively pure populations of rat hepatocytes under the defined conditions of primary cultures, to investigate growth‐stimulatory actions of tumor promoters, an important element in the promotion stage of carcinogenesis. It has been shown that most if not all liver tumor promoters tested stimulate hepatocyte DNA synthesis when added in combination with factors such as EGF, insulin, and glucocorticoid. In the present study, we sought evidence for a role of prostaglandins (PGs) in the direct growth‐stimulatory actions of tumor promoters on hepatocytes. PGE2, PGF2α, and PGD2 cause concentration‐dependent stimulation of hepatocyte DNA synthesis, while arachidonic acid was without any effect. PGE2 and PGF2α required the presence of dexamethasone to exert significant effects. These PGs did not further augment the stimulatory effect of EGF. In contrast, PGD2 stimulated DNA synthesis in the presence or absence of insulin, dexamethasone, or EGF. The effect of tumor promoters on arachidonic acid metabolism, as measured by [3H]arachidonic acid release and PGE2 production, was determined. The phorbol ester TPA significantly increased [3H]arachidonic acid release as well as PGE2 formation in hepatocytes in line with known effects in other cell types. However, liver tumor promoters phenobarbital (PB), α‐hexachlorocycohexane (HCH), 1,1‐bis(p‐chlorophenyl)‐2,2,2‐trichloroethane (DDT), and pregnenolone‐16α‐carbonitrile (PCN) were without effects. Finally, inhibitors of arachidonic acid metabolism were tested for effects on the ability of TPA or liver tumor promoters to stimulate DNA synthesis by direct action on cultured hepatocytes. In all cases, lack of selective inhibition was observed. Taken together, the results show that while prostaglandins may directly stimulate DNA synthesis in hepatocytes, they are unlikely to mediate the direct growth‐stimulatory actions of liver tumor promoters. © 2001 Wiley‐Liss, Inc.
Na+/K+ pump expression in the L8 rat myogenic cell line: Effects of heterologous α subunit transfection*
Authors: Sharabani‐Yosef Orna , Bak Asia , Nir Uri , Sampson Sanford R. 
Published: August 2002

AbstractWe have characterized the physiological and biochemical properties of the Na+/K+ pump and its molecular expression in L8 rat muscle cells. Pump properties were measured by [3H]ouabain binding and 86Rb uptake. Scatchard plot analysis of specific ouabain binding indicated the presence of a single family of binding sites with a Bmax of ∼135 fmol/ mg P and a KD of 3.3 × 10−8. 86Rb uptake due to specific pump activity was found to be 20% of the total in L8 cells. The results indicated lower affinity of L8 cells for ouabain and lower activity of the pump than that reported for chick or rat skeletal muscle in primary culture. Both the α1 and β1 protein and mRNA isoforms were expressed in myoblasts and in myotubes, while the α2, α3, and β2 isoforms were not detectable. We attempted to overcome low physiological expression of the Na+/K+ pump by employing a vector expressing an avian high affinity α subunit. This allowed identification of the transfected subunit separate from that endogenously expressed in L8 cells. Successful transfection into L8 myoblasts and myotubes was recognized by anti‐avian α subunit monoclonal antibodies. Fusion index, Na+/K+ pump activity, and the level of the transmembrane resting potential were all significantly greater in transfected L8 (tL8) cells than in non‐tL8. The total amount of α subunit (avian and rat) in tL8 cells was greater than that (only rat) in non‐tL8 cells. This relatively high abundance of the Na+/K+ pump in transfected cells may indicate that avian and rat α subunits hybridize to form functional pump complexes. © 2001 Wiley‐Liss, Inc.
Gold adsorption from cyanide solution by chitinous materials
Authors: Niu Hui , Volesky Bohumil 
Published: August 2002

AbstractAdsorption of AuCN2− by chitinous materials such as acid‐washed crab‐shells burnt crab‐shells, as well as by chitin modified by quaternization of amine was affected by the pH of the sorption system. The maximum AuCN2− uptake by acid‐washed crab‐shells occurred at pH 3.7 corresponding to a final Au concentration of 0–0.025 mM. While this material did not bind any AuCN2− at pH 10, crab‐shells burnt in a non‐oxidizing atmosphere removed 90% of the metal under these alkaline conditions. SEM with EDXA analysis of the biosorbent showed that the heat treatment changed the ratio of C/O and created a highly porous material structure. FTIR results indicated that phenolic groups were the main sites responsible for AuCN2− binding on burnt acid‐washed shells. Chitin, the main component of crab‐shells, was modified by grafting tertiary amine to C‐3 and C‐6 on chitin to create quaternary amine groups. The presence of quaternary amine groups also made AuCN2− uptake possible at pH10. The results confirmed that certain chitinous materials are capable of effectively removing and concentrating anionic gold cyanide from both acidic and alkaline solutions if pretreated by appropriate physical or chemical methods.© 2001 Society of Chemical Industry
The use of sodium formate for the recovery of precious metals from acidic base metal effluents
Authors: Julsing Herman G , McCrindle Robert I 
Published: August 2002

AbstractZinc was used for the reduction of the platinum group metals (PGMs) in acidic effluents. Due to the increasing cost of zinc, sodium formate was investigated as an alternative reductant. In a base metal‐containing acidic effluent, called diethylenetriamine barren, sodium formate was used to precipitate the PGMs. This effluent was the filtrate obtained after a precipitation procedure had been used to remove rhodium and iridium. It was found that pH 1.5 was the optimum starting pH for sodium formate reduction. The pH increased to approximately 4.5 after the addition of sodium formate. The optimum concentration of sodium formate was found to be 30 g dm−3 at a temperature of 100 °C where the process time was 6 h. Platinum and palladium were the most effectively reduced PGMs, both exhibiting an average precipitation efficiency of greater than 99%. Difficulty was experienced with the precipitation of iridium (average precipitation efficiency of 76%). The precipitated PGMs readily dissolved in hydrochloric acid (6 M) and sodium chlorate (2%). A reduction in costs resulted from the discontinuation of the use of zinc for reduction purposes. An additional advantage was that zinc was no longer introduced into the PGM refinery circuits.© 2001 Society of Chemical Industry
The use of bacteriophages for treatment and prevention of bacterial disease in animals and animal models of human infection
Authors: Barrow P A 
Published: August 2002

AbstractA brief history of the use of lytic bacteriophages in bacterial disease therapy is presented. After early disillusionment with the idea following poor experimental work, control of phages and field trials, studies were set up in the 1980's in the UK to study their use in farm animal infections. Work with E. coli septicaemia and diarrhoea has shown that phages can be highly effective prophylactically and therapeutically and more effective than antibiotics. There is considerable potential for their use in a limited number of infection types in both man and animals.© 2001 Society of Chemical Industry
Production of lipolytic enzymes in batch cultures of Ophiostoma piceae
Authors: Tamerler Candan B , Martinez Angel T , Keshavarz Tajalli 
Published: August 2002

AbstractAfter an extensive fungal screening, an Ophiostoma piceae strain was selected for its ability to produce high concentrations of lipase and esterase to remove pitch components of wood pulp. Optimal conditions for growth and enzyme production were established first in shaken flasks. A medium containing rapeseed oil and mycological peptone resulted in a lipase activity of 736 U dm−3 and an esterase activity of 1569 U dm−3. When fermentation runs were implemented using the same medium under controlled conditions in 2‐dm3 fermenters, the lipase and esterase activities were increased to 1005 and 4006 U dm−3 respectively. Further scale‐up was carried out in two stages to 20 dm3 and 72 dm3 (pilot‐scale) stirred tank reactors. The results proved that the cultures could be scaled‐up successfully from shaken flasks to pilot‐scale with increases of 47% and 146% in lipase and esterase activities respectively.© 2001 Society of Chemical Industry
Sonographic appearance of extensive hepetic arterial calcification mimicking pneumobilia
Authors: Pai Sucheta S. , Bude Ronald O. 
Published: August 2002

AbstractPneumobilia appears sonographically as intrahepatic linear echogenic regions that often produce distal acoustic shadowing. We present a case in which extensive hepatic arterial calcification mimicked the sonographic appearance of pneumobilia. In the appropriate clinical setting, extensive hepatic arterial calcification should be considered when intrahepatic linear echogenic regions are found sonographically. © 2002 John Wiley & Sons, Inc. J Clin Ultrasound 30:38–41, 2002.
Lymphatic versus blood vascular endothelial growth factors and receptors in humans
Authors: Partanen Taina A. , Paavonen Karri 
Published: August 2002

AbstractThree different growth factor systems have been described acting via endothelial cell‐specific receptor tyrosine kinases (RTKs). These are vascular endothelial growth factors (VEGFs), angiopoietins, and ephrins. Recent studies on gene targeting suggest that they play critical roles in embryonic development and contribute to the integrity and responses to environmental factors in the adult vasculature. Coagulation, inflammation, immune response regulation, vascular tone, stromal component synthesis, and angiogenesis are all dependent on the physiological and pathological events that affect endothelial cells in the heart, arteries, veins, and lymphatic vessels. Angiogenesis, the formation of new blood vessels from preexisting ones, takes place in adults only during hormonal control of female reproduction. All other activation of angiogenesis in adulthood occurs in response to injury or pathological processes such as tumorigenesis, diabetes, or inflammatory conditions. Insufficient growth of collateral vessels is a major problem in atherosclerotic cardiovascular disease. Controlled stimulation of angiogenesis would be of therapeutic value. Lymphangiogenesis, the mechanisms involved in the development of lymphatic vessels, was studied intensively nearly a century ago, although since then it has been neglected, perhaps because, unlike the disorders of blood vessels, those of the lymphatic vessels are seldom life‐threatening. Interrupting this one‐way system can cause severe disorders, including liver dysfunction, genetic disease (e.g., Milroys disease), and degenerative disease (e.g., primary lymphangiosclerosis). Recently, novel growth factors, receptors, cell surface proteins, and transcription factors have been found which play a role in the lymphatic endothelium. These are VEGF‐C, VEGF‐D, VEGFR‐3, LYVE‐1, podoplanin, and Prox‐1. Until recently lymphatic vessels have been difficult to study due to a lack of appropriate tools. Monoclonal antibodies raised against VEGFR‐3 and against its ligands, VEGF‐C and VEGF‐D, have offered an insight into expression studies in tissues. In this review, we summarize the recent data on VEGFs in the human vasculature. Microsc. Res. Tech. 55:108–121, 2001. © 2001 Wiley‐Liss, Inc.
Environmental antiecdysteroids alter embryo development in the crustacean Daphnia magna
Authors: Mu Xueyan , LeBlanc Gerald A. 
Published: August 2002

AbstractThe role of ecdysteroids in crustacean embryo development and the susceptibility of the developing embryo to the antiecdysteroidal properties of an environmental chemical were evaluated. The agricultural fungicide fenarimol was shown to exhibit antiecdysteroidal activity to the crustacean Daphnia magna by lowering endogenous ecdysone levels and delaying molting in a concentration‐dependent fashion that was mitigated by co‐exposure to exogenous 20‐hydroxyecdysone. Exposure of either gravid maternal organisms or isolated embryos to fenarimol resulted in embryo abnormalities ranging from early partial developmental arrest to incomplete development of antennae and shell spines. Developmental abnormalities were associated with suppressed ecdysone levels in the embryos and the abnormalities could be prevented by co‐exposure to 20‐hydroxyecdysone. Developmental abnormalities caused by the antiecdysteroid were associated with reduced fecundity of the parental organisms. These results demonstrate that ecdysteroids are critical to normal crustacean embryo development and environmental antiecdysteroids can disrupt normal embryo development and compromise the production of viable offspring. Antiecdysteroidal activity may provide a means by which environmental chemicals impact crustacean species while not affecting vertebrates. J. Exp. Zool. 292:287–292, 2002. © 2002 Wiley‐Liss, Inc.
Effect of antiandrogen cyproterone acetate on the development of the antler cycle in Southern pudu (Pudu puda)
Authors: Bubenik George A. , Reyes Eugenia , Schams Dieter , Lobos Alejandro , Bartos̆ Ludĕk , Koerner Fernando 
Published: August 2002

AbstractThe antler cycle of pudu is similar to other cervids, but unlike most boreal deer, male Southern pudu (Pudu puda) exhibits two seasonal peaks of LH and testosterone. In that respect, pudu is similar to roe deer. Whereas the antler cycle in some deer species, such as roe deer or white‐tailed deer, is very sensitive to variation of testosterone, in other cervids, such as fallow deer or reindeer, a blockade of androgens with cyproterone acetate (CA) has little or no effect on the timing of the antler casting. In order to test the sensitivity of pudu antlers to variations of androgens, CA (administered 2× weekly at 50 mg/buck) was injected intramuscularly for 3 weeks in 5 adult male pudu, starting February 19 (late summer). Four other males of similar age served as controls. The experiment was performed at the University of Concepcion, Chile, latitude 36.6°S. Blood samples were taken once a week between January 19 and April 3. In CA‐treated bucks, the antlers were cast approximately 3 weeks after the initiation of CA treatment and a new antler growth began almost immediately. The antlers reached about 5 cm in length, before ceasing to grow at the end of April, when they became mineralized and were subsequently polished. CA had no effect on the already declining levels of LH. Plasma levels of testosterone in controls increased from February 15, whereas in CA‐treated bucks remained depresses until March 21. It is concluded that similarly to white‐tailed deer, the antler cycle of Southern pudu is very sensitive to manipulation of androgen levels. J. Exp. Zool. 292:393–401, 2002. © 2002 Wiley‐Liss, Inc.
Physiological changes in the spawning gilthead seabream, Sparus aurata, succeeding the removal of males
Authors: Meiri Iris , Gothilf Yoav , Zohar Yonathan , Elizur Abigail 
Published: August 2002

AbstractThe physiological effects triggered in females by the removal of males from a group of spawning fish were examined in the multiple batch spawner, the gilthead seabream, Sparus aurata. One week after the removal of males, a large portion of the oocytes underwent atresia, and sporadic release of low quality eggs continued at low frequency over a period of seven weeks. The transcript levels of the three native gonadotropin releasing hormone (GnRH) forms, salmon (s)GnRH, seabream (sb)GnRH, and chicken (c)GnRH‐II, and the two βGtH subunits were measured. Brain mRNA levels for all three GnRHs and pituitary βLH mRNA levels significantly declined in the females as a result of removing the males compared to females that were maintained with males. Pituitary βFSH mRNA levels showed the opposite trend and were significantly higher in females that were separated from males. Circulating levels of LH, testosterone, estradiol, 17α,20β‐dihydroxy‐4‐pregnen‐3‐one, and 17α,20β,21‐trihydroxy‐4‐pregnen‐3‐one all declined in the group of females without males. These results imply the existence of an endocrine response to socio‐sexual stimuli during the reproductive process in the gilthead seabream. J. Exp. Zool. 292:555–564, 2002. © 2002 Wiley‐Liss, Inc.
Sensing and transfer of respiratory gases at the fish gill
Authors: Perry Steve F. , Gilmour Kathleen M. 
Published: August 2002

AbstractThe gill is both a site of gas transfer and an important location of chemoreception or gas sensing in fish. While often considered separately, these two processes are clearly intricately related because the gases that are transferred between the ventilatory water and blood at the gill are simultaneously sensed by chemoreceptors on, and within, the gill. Modulation of chemoreceptor discharge in response to changes in O2 and CO2 levels, in turn, is believed to initiate a series of coordinated cardiorespiratory reflexes aimed at optimising branchial gas transfer. The past decade has yielded numerous advances in terms of our understanding of gas transfer and gas sensing at the fish gill, particularly concerning the transfer and sensing of carbon dioxide. In addition, recent research has moved from striving to construct a single model that covers all fish species, to recognition of the considerable inter‐specific variation that exists with respect to the mechanics of gas transfer and the cardiorespiratory responses of fish to changes in O2 and CO2 levels. The following review attempts to integrate gas transfer and gas sensing at the fish gill by exploring recent advances in these areas. © 2002 Wiley‐Liss, Inc.
Developmental and environmental regulation of chloride cells in young American shad, Alosa sapidissima
Authors: Zydlewski Joseph , McCormick Stephen D. 
Published: August 2002

AbstractLocation, abundance, and morphology of gill chloride cells were quantified during changes in osmoregulatory physiology accompanying early development in American shad, Alosa sapidissima. During the larval‐juvenile transition of shad, gill chloride cells increased 3.5‐fold in abundance coincident with gill formation, increased seawater tolerance, and increased Na+,K+‐ATPase activity. Chloride cells were found on both the primary filament and secondary lamellae in pre‐migratory juveniles. Chloride cells on both the primary filament and secondary lamellae increased in abundance (1.5‐ to 2‐fold) and size (2‐ to 2.5‐fold) in juveniles held in fresh water from August 31 to December 1 (the period of downstream migration) under declining temperature. This proliferation of chloride cells was correlated with physiological changes associated with migration (decreased hyperosmoregulatory ability and increased gill Na+,K+‐ATPase activity). Increases in chloride cell size and number of fish in fresh water were delayed and of a lower magnitude when shad were maintained at constant temperature (24°C). When juveniles were acclimated to seawater, chloride cell abundance on the primary filament did not (though size increased 1.5‐ to 2‐fold), but cells on the secondary lamellae disappeared. Na+,K+‐ATPase was immunolocalized to chloride cells in both fresh water and seawater acclimated fish. The disappearance of chloride cells on the secondary lamellae upon seawater acclimation is evidence that their role is confined to fresh water. The proliferation of chloride cells in fresh water during the migratory‐associated loss of hyperosmoregulatory ability is likely to be a compensatory mechanism for increasing ion uptake. J. Exp. Zool. 290:73–87, 2001. © 2001 Wiley‐Liss, Inc.
EM studies of female meiosis in wood lemmings with different sex chromosome constitutions
Authors: Akhverdyan Mikhayil , Fredga Karl 
Published: August 2002

AbstractThe chromosomes were studied throughout meiotic prophase by electron microscopy of surface‐spread oocytes from one XX, four X*X, and three X*Y female wood lemmings, Myopus schisticolor. The X* chromosome had originated from X by a deletion and an inversion in the short arm. The deletion was confirmed in pachytene cells from X*X females; a D‐loop was present in the sex bivalent in 16.8% of the cells, and asynapsis of unequal ends was seen in 9.1% of other cells. At late pachytene the D‐loop underwent synaptic adjustment. The breakpoints of the deletion are in G‐light bands. No inversion loop was seen, which also is in agreement with Ashley’s (’88) hypothesis; at least one of the presumed breakpoints of the inversion is in G‐dark chromatin. Various types of synaptic abnormalities, such as nonhomologous pairing (triple pairing, interchange, self‐synapsis), univalents, foldbacks, and broken lateral elements, were encountered in all types of female. X*Y females showed a high frequency of abnormal oocytes (70.7%), which significantly exceeded that of X*X (23.1%) and XX (8.1%). Univalents were particularly common in the X*Y females. J. Exp. Zool. 290:504–516, 2001. © 2001 Wiley‐Liss, Inc.
Effects of some steroids and other compounds on ovarian growth of the red swamp crayfish, Procambarus clarkii, during early vitellogenesis
Authors: Rodríguez Enrique M. , Medesani Daniel A. , Greco Laura S. López , Fingerman Milton 
Published: August 2002

AbstractThe effects of spiperone, a dopaminergic receptor blocker, the terpenoid JHIII, and the steroids 17α‐hydroxyprogesterone and 17β‐estradiol (10–7 mol/crayfish) were assayed in vivo on females of the red swamp crayfish, Procambarus clarkii, during early vitellogenesis. All these compounds were injected twice a week for 3 weeks. The rate of molting in response to these compounds was also determined. At the end of the experiment the ovaries were dissected out, in order to determine the gonadosomatic indexes and oocyte diameters. Spiperone, 17α‐hydroxyprogesterone, and 17β‐estradiol produced a significant increase in the gonadosomatic index, while only the first two compounds were able to significantly increase the oocyte diameter; therefore, the effect of 17β‐estradiol the on gonadosomatic index could be merely due to increased water uptake by the ovary. Spiperone could be causing a decrease in secretion of the gonad and/or mandibular inhibiting hormones from the eyestalks, and 17α‐hydroxyprogesterone could be having a direct stimulatory effect on vitellogenin production. Concerning molting, of the compound tested, only JHIII had a significant (P < 0.05) stimulatory effect, producing a 100% molting rate versus 66.7% among the controls. J. Exp. Zool. 292:82–87, 2002. © 2002 Wiley‐Liss, Inc.
Convex‐round graphs are circular‐perfect
Authors: Bang‐Jensen Jørgen , Huang Jing 
Published: August 2002

AbstractWe show a connection between two concepts that have hitherto been investigated separately, namely convex‐round graphs and circular cliques. The connections are twofold. We prove that the circular cliques are precisely the cores of convex‐round graphs; this implies that convex‐round graphs are circular‐perfect, a concept introduced recently by Zhu [10]. Secondly, we characterize maximal Kr‐free convex‐round graphs and show that they can be obtained from certain circular cliques in a simple fashion. Our proofs rely on several structural properties of convex‐round graphs. © 2002 Wiley Periodicals, Inc. J Graph Theory 40: 182–194, 2002