bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Chronic Lithium on Ototoxicity Induced by Gentamicin and Amikacin in Guinea‐Pigs
Authors: Sharifzadeh Mohammad , Abdollahi Mohammad , Behrooz Hodjat , Minaii Bagher , Kebriaeezadeh Abbas , Kashani Mostafa Rezvani , Dehpour Ahmad‐Reza , Aghaebrahimi Nourallah
Published: March 2009

Abstract: The effects of chronic lithium co‐therapy on the expression of gentamicin and amikacin ototoxicity were tested in guinea‐pigs. Intramuscular injection of different doses of gentamicin (5, 10 mg/kg/day) and amikacin (150, 300 mg/kg/ day) for three weeks, induced hearing loss consistent with the established pattern of aminoglycoside ototoxicity. Lithium salts remains one of the most widely used treatment for depressive illness. Administration of lithium chloride (600 mg/1, 35 days) in drinking water changed auditory brainstem response in a time‐dependent manner. Pretreatment of animals with lithium chloride after seven days induced significant alterations in wave latency and interval. The present study assesses the protective effects of chronic lithium on gentamicin‐induced ototoxicity in guinea pig. The results suggest that duration of lithium administration may be involved in auditory brainstem response changes and the observations could be accounted for, at least partially, by lithium‐ and aminoglycosides‐induced perturbations of the phosphoinositide cascade within the inner ear.
Aspects on Tail‐Flick, Hot‐Plate and Electrical Stimulation Tests for Morphine Antinociception
Authors: Gårdmark Marie , Höglund A. Urban , Hammarlund‐Udenaes Margareta
Published: March 2009

Abstract:The objective of this study was to compare the results of three nociceptive tests, tail‐flick, hot‐plate and electrical stimulation vocalisation, reflecting the responses from different sites in the CNS. A subcutaneous morphine dose (5 mg/kg) was administered to three parallel groups of rats in which the nociceptive response was measured by one of the three methods. The baseline decreased during the period of measurement for the hot‐plate test, but remained stable for the other methods. The spinally mediated tail‐flick response was more sensitive to the morphine effects as compared to the supraspinally mediated hot‐plate and electrical stimulation vocalisation responses. The electrical stimulation vocalisation‐test demonstrated more even effect‐time profiles and less variability among the rats than did the tail‐flick and the hotplate methods. In the tail‐flick group, 59% of the observations attained the cut‐off latency at this morphine dose, leading to underestimation of the peak effect, the area under the effect curve (AUEC), and the variability among the rats. In the hot‐plate group, 13% of the observations were at the cut‐off latency, and 2% in the electrical stimulation vocalisation group. Different ways of presenting the data are discussed. In conclusion, the test selected for measuring the nociceptive response will influence the effect‐time profile and subsequently any pharmacodynamic parameters describing it.
Does Blockade of Angiotensin II Receptors Offer Clinical Benefits over Inhibition of Angiotensin–Converting Enzyme?
Authors: de Gasparo Marc , Levens Nigel
Published: March 2009

Abstract:Angiotensin AT, receptor antagonists represent a new class of drugs for the treatment of hypertension. They are specific for the renin–angiotensin system, selective for the angiotensin AT1receptor, and act independently of the angiotensin II synthetic pathway. Blockade of the renin–angiotensin system at the receptor level should therefore be more complete. The high circulating levels of angiotensin II following angiotensin AT, receptor blockade could be beneficial in stimulating other unblocked angiotensin receptors, especially the AT2receptor. It has been proposed that the angiotensin AT2receptor, which is re–expressed or up–regulated during pathological circumstances, counterbalances the effect of the stimulation of the angiotensin AT1receptor. Through this mechanism, angiotensin AT1antagonists may be superior to ACE inhibitors in cardiac and vascular remodelling as well as in kidney insufficiency. Long–term trials are required to demonstrate the possible clinical superiority of this new class of antihypertensive agents.
Effects of Polyamine Synthesis Inhibition on Polyamines, Growth and Mechanical Properties in Hypertrophic Rat Urinary Bladder
Authors: Nilsson Bengt–Olof , Lindqvist Anders , Pandita Raj Kumar , Swärd Karl , Persson Katarina
Published: March 2009

Abstract: The polyamines putrescine, spermidine and spermine, are ubiquitous intracellular metabolites associated with growth and protein synthesis. In this study effects of polyamine synthesis inhibition on bladder growth, polyamine levels and mechanical properties were investigated in rat urinary bladder subjected to partial outflow obstruction that causes bladder hypertrophy. The S–adenosyl methionine decarboxylase inhibitor CGP–48664 (5 and 20 mg kg–1) was administered alone or in combination with the ornithine decarboxylase inhibitor DFMO (500 mg kg–1), starting one day before creation of partial outflow obstruction and then daily for 7 days. The bladder muscle level of putrescine was increased 38 times and that of spermine reduced by 4 times while spermidine was unchanged after treatment with CGP–48664 (20 mg kg–1). The increase in putrescine was abolished in animals receiving CGP–48664 in combination with DFMO. Treatment with polyamine synthesis inhibitors could not prevent or reduce the hypertrophy of the bladder as judged by bladder wet weight and protein contents. The effects on polyamine quantities were not associated with changes in Ca2+–force relationship or in agonist and electrically stimulated force. In summary, treatment of rats with polyamine synthesis inhibitors resulted in changes in polyamine levels in the growing urinary bladder but did not affect growth or mechanical properties.
Aluminium Distribution and Excretion: A Comparative Study of a Number of Chelating Agents in Rats
Authors: Gómez Mercedes , Esparza Jose L. , Domingo Jose L. , Corbella Jacinto , Singh Pramod K. , Jones Mark M.
Published: March 2009

Abstract:The present study was conducted to assess in rats the comparative effects of a number of chelating agents on the urinary excretion and tissue distribution of Al. Adult male Spraguc–Dawley rats received a single intraperitoneal dose of aluminium (Al) nitrate nonahydrate (0.24 mmol/kg). Ten min. after Al injection, l,2–dimethyl–3–hydroxypirid–4–one, 2,3–dihydroxybenzoic acid, picolinic acid, methylmalonic acid, ethylenediamine–di(o–hydroxyphenylacetic) acid, 1–benzyl–2–methyl–3–hydroxypyrid–4–one, l–(p–methylbenzyl)–2–methyl–3–hydroxypyrid–4–one, l–(p–methoxy–benzyl)–2–methyl–3–hydroxypyrid–4–one, 1 –(p–chlorobenzyl)–2–methyl–3–hydroxypyrid–4–one, 1–benzyl–2–ethyl–3–hydroxypyrid–4–one, 1–(p–methylbenzyl)–2–ethyl–3–hydroxypyrid–4–one, l–[3–hydroxy–2–methyl–4–oxopyridy]]–2–ethanesulfonic acid and l–benzyl–(4–carboxylic acid)–3–hydroxy–2–methyI–4–oxopyridine were given by gavage at 1.79 mmol/kg. A control group received similar volumes of distilled water. An additional group of rats received a subcutaneous injection of desferrioxamine at 1.79 mmol/ kg. Urine samples were collected daily for three consecutive days and the animals were killed after this period. Samples of brain, bone, liver, kidney and spleen were collected. Although desferrioxamine, l,2–dimethyl–3–hydroxypirid–4–one, 1–(p–methylbenzyl)–2–methyl–3–hydroxypyrid–4–one, l–(p–methoxybenzyl)–2–methyl–3– hydroxypyrid–4–one. l–(p–methylbenzyI)–2–elhyl–3–hydroxypyrid–4–one, l–[3–hydroxy–2–methyl–4–oxopyridyl]–2–ethanesulfonic acid and l–benzyl–(4–carboxylic acid)–3–hydroxy–2–methyl–4–oxopyridine significantly enhanced the total excretion of Al into urine, only treatment with 1–(p–chlorobenzyl)–2–methyl–3–hydroxypyrid–4– one and l–benzyl–2–ethyl–3–hydroxypyrid–4–one significantly reduced Al concentrations in all analyzed tissues. No beneficial effects of the remaining chelators on Al mobilization were observed. Further studies on the effects of some 3–hydoxrypyrid–4–ones on Al removal can be of interest for the treatment of Al accumulation and toxicity.
Effects of Bifemelane on Incomplete Cerebral Ischaemia‐Induced Reduction of Long‐Term Potentiation in Rat Hippocampal Neurones in vivo
Authors: Mori Kiyoshi , Suda Noriyuki , Togashi Hiroko , Matsumoto Machiko , Saito Hideya , Yoshioka Mitsuhiro
Published: March 2009

Abstract: In the present study, we investigated the effects of bifemelane on the reduction of hippocampal long‐term potentiation after transient ischaemia. Bilateral common carotid arteries were clamped for 10 min. in halothane‐anaesthet‐ized rats. Thirty min. before occlusion, bifemelane (25 mg/kg, intraperitoneally) or saline was administered to the rats. Four days after occlusion, we measured long‐term potentiation in Schaffer collateral‐CAl synapses and perforant path‐dentate gyrus synapses in vivo. Long‐term potentiation was significantly reduced in both the Schaffer collateral‐CAl and perforant path‐dentate gyrus synapses in the saline‐injected group. However bifemelane decreased the ischaemia‐induced reduction of long‐term potentiation in perforant path‐dentate gyrus synapses, but not in Schaffer collateral‐CAl synapses. The findings suggest that bifemelane deserves further attention with regard to possible protective role in ischaemia.
Interaction of Thalidomide with DNA of Rabbit Embryos: A Possible Explanation for its Immunosuppressant and Teratogenic Effects
Authors: Huang Peter H. T. , McBride William G. , Tuman William G.
Published: March 2009

Abstract: Although thalidomide (α‐phthalimidoglutarimide) is a potent teratogen, in recent years it has become widely used in the treatment of a variety of diseases. Despite many studies, the mechanism of its teratogenic action is still not clear. Recently we reported that only the glutarimide moiety bound to rat embryonic DNA. This result could explain our earlier observation, that thalidomide induced alteration in the secondary structure of rat embryonic DNA. In this study it was shown that [glutarimide‐2‐14C]‐thalidomide also interacts with the DNA of rabbit embryos. This interaction is a possible explanation for the diverse types of malformations caused by thalidomide and may also account for its immunosuppressant action which makes it useful in the treatment of graft‐versus‐host disease.
Glomerular Effects of Cholera Toxin in Isolated Perfused Rat Kidney: A Potential Role for Platelet Activating Factor
Authors: Monteiro Helena S. A. , Lima Aldo A. M. , Fonteles Manassés C.
Published: March 2009

Abstract: Cholera toxin (MW 84 kDa) is now considered a pharmacological tool to study the adenylyl cyclase system and a stimulus to generate platelet activating factor in the intestinal tract. We used this toxin to evaluate the renal haemodynamics, glomerular filtration function, tubular sodium transport and toxicity in isolated perfused rat kidney. Kidneys from adult male Wistar rats were isolated for perfusion. The perfusion fluid was modified Krebs‐Henseleit solution and the samples were analyzed for sodium, potassium, inulin and osmolality. Clearance techniques were used to calculate physiological parameters. Cholera toxin (1.0 μg/ml) caused a significant time‐dependent reduction of glomerular filtration rate and urinary flow. This toxin also caused a small, but consistent reduction in fractional proximal sodium reabsortion (toxin=67.43+2.42% versus control=79.26+5.80%; P<0.025). WEB 2086, a platelet activating factor receptor antagonist at 100 μg/ml completely blocked the effects induced by cholera toxin on glomerular filtration rate, fractional proximal sodium reabsortion and urinary flow. In contrast to cholera toxin, dibutyryl‐cyclic AMP (10−5 M) significantly increased glomerular filtration rate (Db‐cyclic AMP=0.651+0.035 versus control=0.514+0.043 ml · g−1 · min−1.; P<0.025) in isolated perfused kidneys. Db‐cyclic AMP caused a similar, but more severe reduction in fractional proximal sodium reabsortion (Db‐cyclic AMP=54.21+2.35% versus control=70.10+3.24%; P<0.025). In addition Db‐cyclic AMP increased significantly the urinary flow (Db‐Cyclic AMP=0.290+0.018 versus control=0.179+0.026 ml · g−1 · min.−1; P<0.025). WEB 2086+ Db‐cyclic AMP also caused a significant increase in the urinary flow with maximal effect at 90 min. (WEB+Db‐cyclic AMP=0.26+0.01 versus control=0.15+0.01 ml · g−1 · min.−1; n=8, P<0.025). Cholera toxin caused a decrease of urinary flow (toxin=0.034+0.004 versus control=0.145+0.02 ml · g−1 · min.−1.; P<0.025), this effect was also completely abolished by WEB 2086 when it was injected previously to toxin. When only WEB 2086 was injected, the functional parameters remained stable throughout the perfusion time. Cholera toxin had no effect on renal vascular resistance, renal perfusate flow or tissue potassium, suggesting renal integrity in kidneys treated with this toxin. The results suggest that cholera toxin effects in the perfused rat kidney are primarily mediated by platelet activating factor.
The Effect of Cimetidine on the Pharmacodynamics of Theophylline‐Induced Seizures and Ethanol Hypnotic Activity
Authors: Hoffman Amnon , Perlstein Itay , Habib Gustav , Pinto Evelyne , Gilhar Dalia
Published: March 2009

Abstract:Due to its availability as an over‐the‐counter drug, the use of cimetidine is increasing, thus adverse interactions with other commonly used agents may also increase. The aim of this study was to investigate whether acute administration of cimetidine could alter the pharmacodynamics of theophylline neurotoxicity and the hypnotic action of ethanol. To examine these questions, rats received a dose of 77 mg/kg cimetidine followed by a constant infusion of either theophylline (1.2 mg/min.) or ethanol (16.3 mg/min.) until the onset of the pharmacological end point, maximal seizure or loss of righting reflex, where samples of blood and brain were obtained and assayed for either theophylline or ethanol. We report that cimetidine in doses that may cause pharmacokinetic interactions did not affect the concentration‐effect relationship of either the stimulating action of theophylline or the depressant activity of ethanol. These outcomes emphasize the relative safety which patients using cimetidine in self‐medication rely on.
Long‐Term Alterations in Benzodiazepine, Muscarinic and α‐Amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid (AMPA) Receptor Density Following Continuous Cocaine Administration
Authors: Keys Alan S. , Ellison Gaylord D.
Published: March 2009

Abstract:Animal models of clinical phenomena, such as stimulant‐induced psychosis have focused primarily on persisting alterations that develop in brain after chronic stimulant administration. The present study utilized autoradiographic measures to examine changes in the density of benzodiazepine ([3H] flunitrazepam), muscarinic ([3H] quinuclidinyl benzilate), and non‐NMDA glutamatergic (3H α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid: AMPA) receptor binding in rats 21 days following two exposures to cocaine administered continuously for 5 days via subcutaneous pellets. A marked, selective increase in [3H] flunitrazepam binding in both the lateral and medial habenula nucleus was observed. Reduced [3H] quinuclidinyl benzilate binding was observed in various brain areas, including large decreases in the anterior cingulate cortex and ventral thalamus. A reduction in [3H]AMPA binding was observed in the ventral striatum and was suggested in the nucleus accumbens. [3H] Flunitrazepam binding was also examined 12 hr following a single 5 day cocaine exposure to determine if the long‐term habenular changes were evident at acute withdrawal. No alterations in [3H] flunitrazepam binding were observed in the habenula or any other structure analyzed at this time point. The relation of these results to persisting alterations in mesocorticolimbic pathways and previous findings of cocaine‐induced degeneration in lateral habenula circuitry is discussed.
Diazepam Inhibits Forskolin‐Stimulated Adenylyl Cyclase Activity in Human Tumour Cells
Authors: Niles Lennard P. , Wang Jane
Published: March 2009

Abstract: Previous studies have shown that the benzodiazepine agonist, diazepam, suppresses adenylyl cyclase activity in rat brain, via a G protein‐coupled benzodiazepine receptor. Since diazepam binding sites are also present in diverse non‐neuronal tissues including tumour cells, its effects on adenylyl cyclase activity were examined in membranes from human MCF‐7 (breast cancer) and M‐6 (melanoma) cells. Diazepam caused a biphasic and concentration‐dependent inhibition of forskolin‐stimulated adenylyl cyclase activity in MCF‐7 membranes. The first phase of inhibition, at picomolar to nanomolar drug concentrations (EC50=5.7×10−12M), is similar to the receptor mediated phase observed in the rat brain. At micromolar concentrations of diazepam (EC50=1.8×10−4M), the steep decrease in adenylyl cyclase activity may involve a direct action on the enzyme itself, as detected previously in rat brain membranes. Diazepam‐induced suppression of adenylyl cyclase activity was also detected in M‐6 membranes. However, in contrast to MCF‐7 findings, only micromolar concentrations of diazepam (EC50=5.2×10−4M) inhibited enzyme activity in M‐6 membranes. These findings suggest that G protein‐coupled benzodiazepine receptors, which mediate inhibition of the adenylyl cyclase‐cAMP pathway in the brain, are also expressed in MCF‐7 cells.
Growth‐Modulating Effects of Dichloro Myristic and Dichloro Stearic Acid in Cell Cultures
Authors: Høstmark Arne T. , Lystad Einar , Jebens Einar , Skramstad Jan , Frøyen Paul
Published: March 2009

Abstract: Chloro‐containing fatty acids are a major fraction of extractable, organically bound chlorine in fish. It has been suggested that dichloro stearic acid (9,10‐dichlorooctadecanoic acid) (C18) is metabolized to dichloro myristic acid (5,6‐dichlorotetradecanoic acid) (C14) which accumulates in tissues. Hence, the biological effects of the C18 dichloro fatty acid could be due to formation of the C14 dichloro fatty acid. In this study we have compared the effects of dichloro stearic and dichloro myristic acid on growth of three widely differing cell lines. Both fatty acids inhibited cell growth; however, dichloro myristic acid had a weaker growth inhibitory effect than dichloro stearic acid. Dichloro myristic acid had a biphasic effect (i.e. growth was stimulated at low concentrations, followed by inhibition at higher concentrations) on the growth of human hepatoma cells and immortalized human kidney epithelial cells, but no such effect on human microvascular endothelial cells. The order of potency for growth inhibition by dichloro myristic acid was consistently human hepatoma cells>immortalized human kidney epithelial cells >human microvascular endothelial cells, whereas the relative potency of dichloro stearic acid was variable. Albumin alone stimulated cell growth and had a stronger protective effect against growth inhibition by dichloro myristic acid than against that of dichloro stearic acid. It seems unlikely that a major part of the effect of dichloro stearic acid on cell growth is caused by conversion to dichloro myristic acid.
Long‐Term Effects of Nicotine on Bone and Calciotropic Hormones in Adult Female Rats
Authors: Fung Yiu K. , Iwaniec Urszula , Cullen Diane M. , Akhter Mohammed P. , Haven Mary C. , Timmins Patrick
Published: March 2009

Abstract:This study determined the effects of nicotine on serum concentrations of several calciotropic hormones, and bone formation and resorption end‐points in 7 month old, adult female rats. Animals were administered either saline (n=9/group), low dose nicotine at 3.0 mg/kg/day (n=10/group) or high dose nicotine at 4.5 mg/kg/day (n=11/group) by subcutaneous osmotic minipumps. At the end of a three months treatment period, serum concentrations of calcium, phosphorus, parathyroid hormone, calcitonin, 25‐hydroxyvitamin D and 1,25‐dihydroxyvitamin D were determined. Femora, tibiae, and lumbar vertebrae (3–5) were collected and bone parameters evaluated included mineral density and content (femora and vertebrae), strength (femora and vertebrae) and histomorphometry (tibiae). Animals given nicotine had significantly lower levels of 25‐hydroxyvitamin D than controls [20.8+1.4 ng/ml for the low dose group and 20.7+1.0 ng/ml for the high dose group versus 27.6+1.3 ng/ml for the control group (mean+S.E.M.), P<0.01]. The high dose nicotine group had smaller vertebral areas (5.4+0.2 mm2versus 6.2+0.2 mm2, P<0.05) and a lower bone mineral content than the controls (0.024+0.001 g versus 0.030+0.001 g, P<0.05). Tibial endocortical mineral apposition rate was also significantly lower in the high dose nicotine group than in the control group (1.06+0.13 μm/day versus 1.42+0.08 μm/day, P<0.05). No significant treatment differences were detected in bone density, cancellous bone histomorphometry, or bone strength. Results from the present study suggest that nicotine administration may adversely affect bone formation and decrease body storage of vitamin D.
Chloroquine Inhibits Inducible Nitric Oxide Synthase Expression in Murine Peritoneal Macrophages
Authors: Park Young Chul , Pae Hyun‐Ock , Yoo Ji‐Chang , Choi Byung‐Min , Jue Dea‐Myung , Chung Hun‐Taeg
Published: March 2009

Abstract: Induction of inducible nitric oxide synthase in vivo or in vitro in response to stimuli is only temporary. However, chronic localized expression of inducible nitric oxide synthase in certain organs has been associated with the development of autoimmune diseases or chronic inflammatory diseases. Chloroquine is being used as an antiinflammatory drug, and its inhibitory effect on the synthesis of pro‐inflammatory cytokines, such as tumour necrosis factor‐α and interferon‐γ, has been reported. In this study, we examined whether chloroquine could inhibit nitric oxide synthesis in murine peritoneal macrophages stimulated with interferon‐γ and lipopolysaccharide. Although prolonged incubation of cells with high concentrations of chloroquine showed some cytotoxicity, the drug itself was not cytotoxic when macrophages were preincubated with chloroquine for 2 hr, washed and stimulated with interferon‐γ and lipopolysaccharide in the absence of chloroquine for another 48 hr. The nitric oxide production from stimulated macrophages was markedly reduced by chloroquine in a dose‐dependent manner and induction of inducible nitric oxide synthase mRNA was also suppressed by chloroquine pretreatment. These results show that chloroquine inhibits the induction of inducible nitric oxide synthase from interferon‐γ and lipopolysaccharide‐stimulated macrophages, thereby reducing nitric oxide synthesis.
The Cardiovascular Effects of Amperozide: Interactions with Cocaine
Authors: Jones Elizabeth A. , McMillen Brian A.
Published: March 2009

Abstract:Amperozide is a 5‐HT2Areceptor antagonist that significantly reduces the acquisition and expression, by rats, of a cocaine conditioned place preference. In order to rule out the possibility that amperozide affects a cocaine conditioned place preference due to effects on blood pressure or heart rate, the cardiovascular effects of amperozide were investigated. Alternating cumulative doses of amperozide (0.5, 1.0, 1.5 and 2.5 mg kg−1) or saline and phenylephrine (8 μg kg−1) were administered through the femoral vein of awake freely‐moving Sprague‐Dawley rats and blood pressure and heart rate were recorded from the femoral artery. A single dose of cocaine (5.0 mg kg−1) was administered after all the amperozide or saline doses were given. Amperozide (0.5, 1.0, 1.5 and 2.5 mg kg−1) did not have any significant effect on blood pressure compared to the saline control treatment to the same animals. However, 0.5 mg kg−1amperozide significantly decreased heart rate at 5 and 10 min. after administration, but higher doses did not further depress heart rate. Amperozide did not affect the increased blood pressure and decreased heart rate caused by phenylephrine, an a α1‐adrenoceptor agonist. In addition, amperozide did not affect the cardiovascular response to an intravenous dose of 5.0 mg kg−1cocaine. These results suggest that amperozide does not cause direct cardiovascular effects. The mechanism by which the lowest dose of amperozide caused a decrease in heart rate is unknown. Amperozide affects neither α‐adrenoceptor mediated vasoconstriction nor the increased sympathetic activity caused by the peripheral and central effects of cocaine. The significance of these results, in terms of locomotor activity and the cocaine conditioned place preference paradigm, is discussed.
The Effect of Toremifene on Bone and Uterine Histology and on Bone Resorption in Ovariectomised Rats
Authors: Karlsson Stefan , Mäntylä Eero , Hirsimäki Yrjö , Niemi Seija , Nieminen Lauri , Nieminen Kirsti , Kangas Lauri
Published: March 2009

Abstract: The effect of the selective oestrogen receptor modulator, toremifene, to inhibit ovariectomy‐induced bone loss was studied in rats. The oral doses were 0.3, 3.0 or 30 mg/kg/day for 2 months. 17β‐oestradiol (5 μg/kg/day, subcutaneously) was used as positive control. One group was also treated with a combination of 17β‐oestradiol (5 μg/kg) and toremifene (3.0 mg/kg). Biochemical markers were urinary hydroxyproline and calcium (adjusted with urinary creatinine levels) and the serum level of pyridinoline cross‐linked carboxy terminal telopeptide, a bone specific collagen breakdown product. The femoral and sternal trabecular bone thickness served as histological parameters. Ovarectomy increased the levels of hydroxyproline and pyrodinoline and decreased the trabecular bone thickness compared to the sham‐operated control group. This was inhibited by both test compounds but 17β‐oestradiol was more efficient. Toremifene did not reverse the ovariectomy‐induced reduction of urinary calcium but inhibited the 17β‐oestradiol‐related increase. When administered together with oestradiol, toremifene did not reverse the positive effect of 17β‐oestradiol on bone, however toremifene reversed the oestradiol‐related uterothrophic effects. These findings indicate that the antagonistic features of toremifene dominate in the rat uterus the agonistic properties do in the bone.
Effects on Plasma Angiotensin‐Converting Enzyme Activity and Circulating Renin of Lisinopril and Enalapril Alone and in Combination with Propranolol in Healthy Volunteers
Authors: Hansen Erik Feldager , Bendtsen Flemming , Henriksen Jens H.
Published: March 2009

The effects on plasma angiotensin‐converting enzyme activity and renin activity of the two long‐acting angiotensin‐converting enzyme inhibitors, lisinopril and enalapril, alone and in combination with propranolol were studied. In an open, randomised, cross‐over design 12 healthy volunteers received orally enalapril 20 mg alone, enalapril 20 mg in combination with propranolol 80 mg, lisinopril 20 mg alone, and lisinopril 20 mg in combination with propranolol 80 mg. Plasma angiotensin‐converting enzyme activity and plasma renin activity were measured for 24 h after each treatment period. Lisinopril and enalapril reduced plasma angiotensin converting enzyme activity substantially and equally at six hr (–70%, P<0.05) and 12 hr (–65%, P<0.05), irrespective of combination with propranolol. At 24 hr plasma angiotensin‐converting enzyme activity remained significantly suppressed only after lisinopril (–60%, P<0.05). Plasma renin activity increased almost ten times after ingestion of both angiotensin‐converting enzyme inhibitors, but the effect lasted significantly longer after lisinopril than after enalapril. β‐Adrenergic blockade blunted the effect on the increase in plasma renin activity induced by both angiotensin‐converting enzyme inhibitors. Our results show that the effect of lisinopril on plasma angiotensin‐converting enzyme activity and plasma renin activity lasted longer than that of enalapril. β‐Adrenergic blockade suppressed the effect on elevated plasma renin activity, but did not influence the effect of angiotensin‐converting enzyme inhibitors on plasma angiotensin‐converting enzyme activity.
Gender Aspects of Liver Slice Incubations with N, N, N‐Triethylene‐thiophosphamide (Thio‐TEPA) in Rats and Mice
Authors: Dale Ola , Thommesen Liv , Mortensen Bjarte , Hagen Bjørn
Published: March 2009

This study was conducted to investigate if biotransformation of N, N, N‐triethylene‐thiophosphoramide (thio‐TEPA) by liver slice incubations reflects the established gender pattern for rat and mouse. Liver slices from rat and mice of both genders were incubated with start concentrations of thio‐TEPA of 5.2, 26, 52 and 104 μM for up to 240 min. Male rat liver slices eliminated thio‐TEPA faster and formed more TEPA than female liver slices at any concentration. No gender difference was found for the elimination of thio‐TEPA in mice, however, the female liver slices formed less TEPA than the male ones. Apparently female rat liver slices formed less TEPA than female mice liver slices. It is concluded that the liver slice incubation system in a robust manner reflects gender differences in rat drug biotransformation with special reference to thio‐TEPA. It is also confirmed that these aspects of gender are less pronounced in the examined mouse species than in rats.
The Modulatory Effect of Spermine on the Glutamate‐NMDA Receptor is Regionally Variable in Normal Human Adult Cerebral Cortex
Authors: Mortensen Martin , Matsumoto Izuru , Niwa Shin‐ichi , Dodd Peter R.
Published: March 2009

The MK‐801, glutamate and polyamine binding sites on the N‐methyl‐D‐aspartate class of glutamate receptors labelled with [3H]MK‐801 were characterized in four cortical areas (sensorimotor, superior temporal, mid‐frontal and occipital) from seven human adult control cases. Age, post‐mortem delay, tissue storage time and sex had no significant effects on any of the parameters measured. Dissociation constants (KD values) for MK‐801 showed similar mean values in the four cortical areas, whereas receptor densities (Bmax values) showed significant differences between sensorimotor or occipital and superior temporal or mid‐frontal cortex. There were marked regional differences in the profiles of the spermine‐ and glutamate‐incremented enhancement of specific [3H]MK‐801 binding. The EC50 for the glutamate enhancement was significantly higher in the occipital than in the mid‐frontal and sensorimotor cortex, whereas maximal glutamate‐enhanced binding values did not differ. The maximal enhancement of [3H]MK‐801 binding by spermine and glutamate varied between the cases, ranging from zero to 40.4+9.3 fmol · mg protein−1 for spermine, and from 85+5 to 111+10 fmol · mg protein−1 for glutamate. Maximal spermine enhancement of [3H]MK‐801 binding was significantly more variable in superior temporal or mid‐frontal than in sensorimotor or occipital cortex. The results suggest that N‐methyl‐D‐aspartate receptor sites, especially the polyamine site, are heterogeneous in human cerebral cortex, and show a high degree of regional and individual variability.
Comparison of Tobramycin Nephrotoxicity in Young Adult and Aged Female Rats
Authors: Peters‐Volleberg Gertruda W. M. , Dortant Paul M. , Speijers Gerrit J. A.
Published: March 2009

Abstract:A two week toxicity study was performed in rats to study the possible age‐dependent toxicity of tobramycin, an aminoglycoside antibiotic with well known ototoxic and nephrotoxic properties in animals and man. Young adult female Wag/Rij rats aged 12 weeks (n=10) and old female rats aged 23 to 26 months (n=14) were treated subcutaneously with 0, 10, 40 or 160 mg tobramycin sulphate/kg/day. Clinical chemistry and urinalysis revealed significant changes in renal function in young adult rats mainly at 160 mg/kg, whereas in old rats significant changes were seen at 10, 40 and 160 mg/ kg. Excretion of N‐acetyl‐β‐glucosaminidase, indicative for tubular dysfunction, was statistically significantly increased only in old animals at 160 mg/kg.Histopathology: At 40 mg/kg, tubular necrosis was increased in old animals and hyaline droplet formation in both age groups. At 160 mg/kg these lesions were increased in both age groups. For tubulonephrosis, interstitial nephritis and tubular regeneration, age‐related differences were predominantly reflected in severity, for example, at 40 mg/kg, tubular regeneration in young animals was “moderate” in 7/10 and “marked” in 2/10, while in old animals the scores were 3/14 and 11/14, respectively. Secundary treatment‐related lesions (in heart and adrenals) were also more increased in old animals. Chemistry and histopathology revealed the increased sensitivity to the toxic effects of tobramycin in old rats, which is important for the discussion of the most appropriate dosing regimen for aminoglycoside in humans. The once‐daily dosing regimen for tobramycin should not be recommended for elderly, because high peak concentrations should be avoided to minimise nephrotoxicity.
Cardiac Contractile Function and Electrolyte Regulation during Hyperosmolal Stress: An Experimental Study in the Isolated Rabbit Heart
Authors: Falck Geir , Skarra Sissel , Jynge Per
Published: March 2009

Abstract: Perturbations of the extracellular osmotic environment leads to cell volume changes. The aim of the present study was to evaluate the effects of hyperosmolality on cardiac contractile function and in particular the role of ionic mechanisms anticipated to be operative during hyperosmolal exposure. Paced rabbit hearts were perfused in the Langen‐dorff mode and were exposed to 330, 370, 410, 450 and 600 mOsm kg−1 in 10 min. intervals intervened by 15 min. isosmolal buffer perfusion (by adding mannitol). Thereafter, 370 and 600 mOsm kg−1 perfusates were chosen for investigation of the effects of inhibition of the Na‐K‐2Cl co‐transporter (bumetanide 1 μM and 10 μM), the Na+/H+ exchanger (5‐(N‐ethyl‐N‐isopropyl amiloride (EIPA)100 nM) and the Na+/K+‐ATPase (ouabain 50 nM). After a rapid and transient decrease in left ventricular developed pressure, all perfusates up to 450 mOsm kg−1 increased LVDP. The 600 mOsm kg−1 perfusate initially reduced LVDP by 50%, but LVDP increased to 85% of initial value at the end of the 10 min. perfusion. EIPA attenuated the recovery of LVDP during perfusion with 600 mOsm kg−1, whereas bumetanide did not affect cardiac contractile function. A net uptake of potassium was observed during hyperosmolal perfusion. Inhibition of the Na+/H+ exchanger resulted in a continued release of cardiac water throughout hyperosmolal perfusion. Isolated perfused rabbit hearts tolerate considerable elevations in perfusate osmolality. Our results suggest that the Na+/H+ antiporter is activated on hyperosmolal exposure with a secondary activation of the Na+/K+‐ATPase. Since inhibition with bumetanide did not affect contractility or electrolyte movements, the Na‐K‐2Cl co‐transporter does not seem to play an important role in cardiac response to hyperosmolality in rabbits.
Different Ion Channel Control pH6‐Induced Bronchoconstriction and Calcitonin Gene‐Related Peptide Release in the Guinea‐Pig Lung
Authors: Auberson Serge , Lacroix Jean S. , Lundberg Jan M.
Published: March 2009

Abstract:We have studied the bronchoconstriction and the release of calcitonin gene‐related peptide‐like immunoreactivity induced by perfusion of pH6 buffer in the isolated guinea‐pig perfused lung. Both bronchoconstriction and peptide release were completely abolished after systemic capsaicin pretreatment. Ca2+‐free pH6 buffer infusion also completely inhibited the bronchial response, whereas the calcitonin gene‐related peptide‐like immunoreactivity overflow was significantly reduced. ω‐Conotoxine and ω‐agatoxin IVA known as N‐, L‐ and P‐type Ca2+channel blocker, respectively, and the Na+channel blocker tetrodotoxin decreased significantly the pH6‐induced bronchial response and calcitonin gene‐related peptide like immunoreactivity overflow. Nifedipine was without influence suggesting the involvement of both P‐ and N‐type Ca2+channel as well as the activation of an axon reflex. Ruthenium red had a more pronounced reduction effect on the functional response than on the peptide release. Ryanodine and caffeine are both agents known to influence Ca2+release from sarcoplasmic reticulum. Ryanodine significantly reduced both bronchoconstriction and calcitonin gene‐related peptide‐like immunoreactivity overflow. Caffeine as well as theophylline and the Na+‐H+ blocker, dimethylamiloride, largely depressed the functional response while producing a significant increase of calcitonin gene‐related peptide‐like immunoreactivity basal value. The pH6‐induced peptide overflow was slightly inhibited after caffeine and dimethylamiloride pretreatment whereas no significant change was observed after theophylline. It is concluded that multiple ion channels including different type of Ca2+channels appear to participate in pH6‐induced bronchoconstriction and calcitonin gene‐related peptide‐like immunoreactivity release in the guinea‐pig lung.
Lack of Protective Effects of Dietary Silicon on Aluminium‐Induced Maternal and Developmental Toxicity in Mice
Authors: Bellés Montserrat , Albina M. Luisa , Sánchez Domènec J. , Domingo Jose L.
Published: March 2009

Abstract: In recent years, it has been demonstrated that oral aluminium (A1) exposure can produce growth retardation, delayed ossification and an increased incidence of foetal abnormalities in rats and mice. On the other hand, it has been also suggested that silicon may have a protective effect in limiting oral A1 absorption. The aim of the present study was to assess whether dietary silicon could prevent against A1‐induced maternal and developmental toxicity in mice. On gestation days 6–15. A1 nitrate nonahydrate (398 mg/kg/day) was given by gavage to three groups of pregnant animals, which also received silicon in drinking water at concentrations of 0, 118 and 236 mg/l on days 7–18 of gestation. Three additional groups of pregnant mice received respectively: 270.6 mg/kg of sodium nitrate (gavage), and silicon in drinking water at 118 and 236 mg/l. Although silicon adiministration at 236 mg/l significantly reduced the percentage of A1‐induced deaths, abortions and early deliveries, neither 118 nor 236 mg/l of silicon produced significant ameliorations on A1‐induced foetotoxicity. Under the current experimental conditions dietary silicon was not effective in protecting against A1‐induced developmental toxicity.
Effects of P2Purinoceptor Agonists on Membrane Potential and Intracellular Ca2+of Human Cardiac Endothelial Cells
Authors: Zünkler Bernd J. , Gräfe Michael , Henning Berthold , Kühne Stephan , Ott Tilmann , Fleck Eckart , Hildebrandt Alfred G.
Published: March 2009

Abstract:Vasoactive agonists like adenosine‐5′‐triphosphate (ATP) increase intracellular Ca2+([Ca2+]i) in vascular endothelial cells with an initial peak due to inositol 1,4,5‐triphosphate‐mediated Ca2+release from intracellular stores followed by a sustained plateau that is dependent on the presence of extracellular Ca2+, thus leading to an increased synthesis and release of prostacyclin and nitric oxide. We studied the effects of nucleotides on membrane potential and [Ca2+]iin confluent human microvascular cardiac endothelial cells obtained from patients with dilated cardiomyopathy. The whole‐cell configuration of the patch‐clamp technique and a confocal laser scanning microscope employing fluo‐3 as a Ca2+indicator were used. Both uridine‐5′‐triphosphate (UTP) and 2‐methylthioadenosine‐5′‐triphosphate (2MeSATP) induced depolarizations in human microvascular cardiac endothelial cells and increased [Ca2+]iwith a rank order of potency 2MeSATP>ATP=UPP (EC50values (in μM) were 0.084 2MeSATP, 0.67 ATP and 1.1 UTP). This suggests that both P2uand P2ypurinoceptors are present on human microvascular cardiac endothelial cells. Maximal [Ca2+]iresponses of confluent human microvascular cardiac endothelial cell monolayers to UTP were lower when compared to 2MeSATP. Nucleotide‐induced increases in [Ca2+]iconsisted of a transient peak, which was also observed in the absence of extracellular Ca2+, and a sustained [Ca2+]iplateau. This plateau, which was not observed in all monolayers studied, was not markedly influenced by increasing extracellular [K+]. Previous incubation with thapsigargin abolished ATP‐induced increases of [Ca2+]i. It is concluded that human microvascular cardiac endothelial cells express both P2yand P2upurinoceptors. P2purinoceptor agonists release Ca2+from intracellular thapsigargin‐sensitive stores and stimulate capacitative Ca2+influx pathways. K+efflux through Ca2+‐dependent K+(Kca) channels does not play a major role in the regulation of nucleotide‐induced Ca2+influx in human microvascular cardiac endothelial cells, which might be related to an impaired function of the cells.
Role of Metallothionein on Ag Accumulation in Hepatic and Renal Cytosol after Ag Injection to Rats
Authors: Saito Shigeru , Okabe Masashi , Yoshida Katsumi , Kurasaki Masaaki
Published: March 2009

Abstract: To examine the role of metallothionein on Ag accumulation in liver or kidney of rat after Ag injection, the relative Ag‐binding capacity of Ag‐induced metallothionein in hepatic or renal cytosol of rat after Ag injection was determined. The greater part of Ag increment in hepatic cytosol was attributable to a low molecular weight protein, while the main part of Ag increment in renal cytosol was ascribed to high molecular weight proteins. The low molecular weight, metal‐binding protein was identified as metallothionein using ELISA. The maximal levels of hepatic and renal metallothionein mRNA induced by Ag occurred at 7 hr after Ag injection. There was a close relationship between Ag contents in the hepatic or renal cytosol and metallothionein after Ag injection. In dose‐response and time‐course studies, approximately 60–70% of the Ag increments in hepatic cytosol and approximately 30% of the Ag increments in renal cytosol were bound to metallothionein. These results suggest that the role of metallothionein on Ag accumulation in the liver after Ag injection is different from that of metallothionein on Ag accumulation in the kidney.
The Relationship between Activation of Phosphoinositide‐Specific Phospholipase C and Growth Stimulation by Ca2+‐Mobilizing Hormones in Hepatocytes
Authors: Sandnes Dagny , Dajani Olav , Bjørneby Andreas , Christoffersen Thoralf
Published: March 2009

Abstract:Previous studies have shown that while vasopressin and angiotensin II are markedly more effective than norepinephrine and prostaglandin F2αin eliciting an acute elevation of inositol 1, 4, 5‐trisphosphate (IP3), norepinephrine and prostaglandin F2αproduce larger enhancement of DNA synthesis. This suggests that the initial activation of phosphoinositide‐specific phospholipase C is not a common factor for the growth response to these agonists, but does not exclude a role of the integral of phospholipase C activity over a prolonged part of the prereplicative period, during which agonist‐specific changes in responsiveness might occur. We show that vasopressin and angiotensin II also cause a prolonged elevation of cellular IP3levels, which remain elevated for at least 60 min., while norepinephrine and prostaglandin F2αelevate IP3levels slightly and transiently. For vasopressin the dose‐effect curves for IP3accumulation and stimulation of DNA synthesis were closely parallel, while this was not the case for angiotensin II, norepinephrine, or prostaglandin F2α. After cultivation of the hepatocytes, hormone‐stimulated IP3accumulation rapidly declined, particularly in response to norepinephrine and prostaglandin F2α. When the IP3response to norepinephrine and prostaglandin F2αwas completely down‐regulated, these agonists still enhanced the DNA synthesis. These results suggest that other mechanisms in addition to IP3accumulation and Ca2+release are likely to be involved in the growth stimulatory effects of the Ca2+‐mobilizing agonists studied here, in particular for angiotensin II, norepinephrine, and prostaglandin F2α.
Effects of Salicylic Acid Derivatives on Red Blood Cell Membranes
Authors: Li Anlan , Seipelt Hubert , Müller Cornelia , Shi Yongde , Artmann Gerhard Michael
Published: March 2009

AbstractSalicylamide, sodium salicylate and acetylsalicylic acid are salicylic acid derivates. They differ in their substitution on the benzene ring and may have different effects on membranes. Red blood cells were used as a prototypical cellular system regarding drug mediated plasma bilayer effects. Established photometric methods sensing tiny changes of red blood cell morphology at rest (red blood cell shape) and at very low shear forces (red blood cell stiffness, red blood cell relaxation time) were applied. The derivative induced effects were detected in a time‐ and dose‐dependent manner. Salicylamide induced a most pronounced echinocytic shape at 5 mM. The shape effect was smaller above as well as below 5 mM. Sodium salicylate induced echinocytes with increasing concentrations showing a saturation above 10 mM. In contrast, the shape was not affected by acetylsalicylic acid. All shape changes occurred within 2 min. and were reversible. The above tendencies were in parallel to a slight red blood cell stiffening. The relaxation time continuously increased with increasing concentrations in both salicylamide and sodium salicylate, with salicylamide always acting stronger. Acetylsalicylic acid again showed no effect. We hypothesize that the observed effects of sodium salicylate and salicylamide are due to their phenolic character mediating a molecular hydrophobicity. According to the bilayer couple hypothesis this would lead to an insertion into the red blood cells outer plasma bilayer leaflet. The extension induced here would cause a positive membrane bending leading to echinocytic shapes and the observed loss of red blood cell fluidity. In contrast, the hydrophilic aspirin would penetrate and thus not affect the red blood cell plasma membrane.
Thapsigargin Enhances Camptothecin‐Induced Apoptosis in Cardiomyocytes
Authors: Kong Jennifer Y. , Rabkin Simon W.
Published: March 2009

Abstract Topoisomerase I inhibitors are promising new chemotherapeutic agents for the treatment of certain malignancies. The present study investigated the impact of the topoisomerase I inhibitor camptothecin on cell death in cardiomyocytes and sought to determine whether the sesquiterpene gamma‐lactone – thapsigargin, that alter sarcoplasmic reticulum calcium flux, modulates the effect of camptothecin on the cardiomyocyte. Camptothecin‐induced cell death was demonstrated in cardiomyocytes maintained in culture, from 7 day old embryonic chick hearts, by the trypan blue and the MTT (3‐[4,5‐dimethylthiazol‐2‐yl]‐2,5‐diphenyl tetrazolium bromide) assay, two independent indicators of the loss of cell viability. The type of cell death was attributed to apoptosis based on cell structure, DNA fragmentation and flow cytometry studies. Camptothecin‐treated cardiomyocytes were shrunken with membrane blebs and nuclear fragmentation. Camptothecin produced a dose‐dependent increase in DNA fragments of 180 base pairs, or multiples thereof, which are characteristic of apoptosis. A two‐fold increase in this type of DNA fragmentation was produced by camptothecin (10 μM) compared to control (diluent‐treated) cells. Flow cytometry analysis of populations of 10,000 cardiomyocytes stained with propidium iodide demonstrated a significant increase in the proportion of the population with alterations of DNA content consistent with apoptosis. Pretreatment of cells with thapsigargin, which selectively inhibits sarcoplasmic reticulum and endoplasmic reticulum Ca+2‐dependent ATPase, significantly augmented camptothecin‐induced apoptosis. Exploring further the role of calcium in camptothecin‐induced cell death, we found that the Ca+2 chelator EGTA decreased camptothecin‐induced DNA fragmentation. These data indicate the potential for cardiotoxicity from camptothecin through the process of apoptosis and suggest that agents which affect cellular calcium regulation enhance camptothecin‐induced apoptosis.