Myocardial taurine,development and vulnerability to ischemia

Summary. Depleting intracellular taurine in heart cells improves their resistance to ischemia and reperfusion injury. The aim of this work was to see whether physiologically low levels of endogenous taurine also reflect a reduced vulnerability of the myocardium to cardiac insults. The myocardial concentration of taurine was measured during different stages of development and compared with vulnerability to ischemia and reperfusion injury in the rat and in pediatric patients undergoing cardiac surgery.Rat hearts with relatively lower levels of taurine were significantly more resistant to an ischemic inult and there was a strong negative correlation between taurine content and recovery. Childrens hearts had significantly lower taurine levels compared to infants hearts which was consistent with their known increased resistance to an ischemic cardioplegic insult (Imura et al., 2001). This work shows that the changes in the concentration of myocardial taurine during development correlate with vulnerability to ischemia where low myocardial taurine is associated with improved recovery upon reperfusion.     

The influence of NMDA, a potent agonist of glutamate receptor, on behavioral activity of rats with experimental hyperammonemia evoked by liver failure

Summary. The study was designed to investigate the effects of NMDA receptor agonist on the behavioral activity in rats with experimental hyperammonemia. The experiments were performed on adult male Wistar rats. Experimental hyperammonemia was induced by intraperitoneal injections of tioacetamide (TAA, 200mg/kg) for three consecutive days. Rats treated with saline (0.9%) served as control. Stimulation of the NMDA glutamatergic receptor was evoked by ip. injection of agonist N-methyl-D-aspartate acid (NMDA) in a dose of 30mg/kg thirty minutes before experiments. Memory motivated affectively was evaluated in the passive avoidance responses. The speculative influence of the treatment on anxiety and motor activity was tested in elevated plus-maze and in open field respectively.To show change of NMDA receptor function after various doses of agonist, the seizures evoked by N-methyl-D-aspartate acid was carried out. This experiment showed that with rise of dose of NMDA time to appear of convulsions was contracted in rats with hyperammonemia as well as in control rats. Dose of NMDA caused convulsions was three times as less in rats with hyperammonemia than dose in control. Time of duration of convulsions was proportional to applied dose of NMDA and it lengthened with rise of agonists dose in both groups of studied animals.Furthermore, we observed that NMDA increased motor activity of control rats in open field test, but not in rats with hyperammonemia (treated tioacetamide). Hyperammonemia did not have significant influence on motor activity and on a passive avoidance latency. The NMDA given in control and in hyperammonemia, increased acquisition, consolidation and recall of a passive avoidance responses. Moreover, NMDA had anxiogenic-like profile in elevated plus-maze.In rats with hyperammonemia NMDA had no influence on locomotor activity but it significantly increased memory in a passive avoidance responses. Furthermore, we observed that reactivity of NMDA glutamate receptor in rats with hyperammonemia was higher than in control rats.     

Application of metal-chelate affinity chromatography to the study of the phosphoproteome

Summary. With the increasing importance of proteome analysis, studying the phosphoproteome is a priority for functional studies. Therefore, a rational approach to simplifying the proteome is needed. In this work, we examined the use of immobilized metal affinity chromatography (IMAC) using ferric ions-chelated column for enriching crude cell extracts in phosphoproteins. The adsorption of the proteins on Fe³⁺ was obtained at an acidic pH 5.6, and their elution at a more basic pH in Tris buffer. To evaluate the separation, western blots were performed with either anti-phosphotyrosine or anti-phosphoserine/threonine. The analysis of the eluates demonstrated the selectivity of the separation, particularly for proteins phosphorylated on serine or threonine. In conclusion, the advantages and the limits of this approach are discussed.     

Protein-polyamine conjugation by transglutaminase in cancer cell differentiation: Review article

Summary. Considerable and intense progress has been made in the understanding of the chemistry, molecular biology and cell biology of transglutaminases (TGases: EC 2.3.2.13). The knowledge that very different processes such as cell growth, reproduction and death are dependent on the presence of adequate levels of these enzymes and that the amount of both free and protein-conjugated polyamines, formed by the enzyme, are capable of modulating the differentiation and proliferative capability of several cell types, has prompted a multitude of researchers to study the role of these fascinating molecules in cancer cell differentiation.     

Threonine is the best substrate for <Emphasis Type="SmallCaps">D</Emphasis>-lactate formation in octopus tentacle

Summary. Carbon sources for D-lactate and enzyme activities related to D-lactate formation were investigated using cell-free homogenates of Octopus vulgaris tentacle tissue. The results are as follows: a) The best precursor for D-lactate formation was threonine and second best precursors were glycine and fructose-1,6-bisphosphate. Threonine and glycine served as precursors only in presence of glutathione. b) Both amino acids were precursors for methylglyoxal from which D-lactate was synthesized. Alanine, cysteine and serine were not precursors. We present a metabolic map for D-lactate formation in octopus in order to explain these experimental results.     

Branched chain amino acids as a parameter for catabolism in treated phenylketonuria

Summary. This study was performed to study an association between nutritional status on one hand and BCAA- and Phe-concentrations on the other hand in PKU patients free of infection. AA profiles from 70 PKU patients were measured. 9 patients (subgroup I) with elevated Phe- and BCAA-concentrations as well as 23 patients (subgroup II) with only elevated Phe-levels were included. Dietary records were obtained from both groups; low caloric intake in subgroup I was increased with Duocal^® or p-am ANAMIX^® without modifying total protein- and Phe-intake. AA profiles were controlled after 2 weeks.Additionally, we investigated AA profiles from 26 liver transplanted patients with increased carbohydrate and caloric intake as an example for anabolism.In subgroup I Phe- and Isoleu-concentrations decreased sign. after dietary intervention. Leu, Val and Tyr levels decreased not sign. Initial Phe-levels correlated negatively with protein and caloric intake.BCAA concentrations of liver transplanted patients receiving high amounts of carbohydrates were in the lower range of normal.Increased caloric intake lowered most of the elevated Phe- and BCAA- concentrations.     

Taurine protected myocardial mitochondria injury induced by hyperhomocysteinemia in rats

Summary. Taurine can protect against cardiovascular diseases, whereas elevated levels of plasma homocysteine are associated with atherosclerotic and thromboembolic cardiovascular diseases. To illustrate the effects of taurine on hyperhomocysteinemia, we observed the myocardial mitochondria dysfunction in the rats with hyperhomocysteinemia induced by diet methionine loading, and the therapeutic effect of taurine. A methionine diet increased plasma homocysteine concentration (133.51±27.91mol/L vs 12.31±2.58mol/L in control, P<0.01), stimulated the production of reactive oxygen species (ROS) in the myocardial mitochondria, and inhibited the activities of mitochondrial Mn-superoxide dismutase and catalase. The ⁴⁵Ca uptake and Ca²⁺-ATPase activity in the myocardial mitochondria were significantly lowered in rats with hyperhomocysteinemia. Taurine supplements effectively attenuated the hyperhomocysteinemia-induced ROS production and inhibition of Mn-superoxide dismutase and catalase activities in the myocardial mitochondria, and increased its ⁴⁵Ca uptake and Ca²⁺-ATPase activity. Thus, taurine antagonizes the oxidative stress injury in the myocardial mitochondria induced by the hyperhomocysteinemia.     

Overexpressed transglutaminase 5 triggers cell death

Summary. Transglutaminases are a class of nine different proteins involved in many biological phenomena such as differentiation, tissue repair, endocytosis. Transglutaminase 5 was originally cloned from skin keratinocytes, and a partial biochemical characterization showed its involvment in skin differentiation. Here we demonstrate that transglutaminase 5 is able to induce cell death when intracellularly overexpressed. Transfected cells show enzymatic activity, as demonstrated by fluoresceincadaverine staining. Transfected cells died due to the formation of hypodiploid DNA content, indicating the induction of cell death under these pharmacological conditions. We also show that the primary sequence of transglutaminase 5 contains GTP binding domains which are similar to those in transglutaminase 2. This raises the possibility that transglutaminase 5 is regulated by GTP in a similar fashion to transglutaminase 2.     

Use of capillary (zone) electrophoresis for determining felinine and it’s application to investigate the stability of felinine

Summary. A rapid capillary electrophoresis method was established to quantify felinine (2-amino-7-hydroxy-5,5-dimethyl-4-thiaheptanoic acid) in cat urine and used to investigate felinine stability. Synthetic felinine was stable in the presence of oxygen while 11% of the natural felinine in urine disappeared after 4 days exposure to air. Both synthetic felinine and the natural felinine (in urine) were stable for up to 3 months when stored at –5°C and 20°C. Thirty percent of the synthetic felinine was lost after 5 hours at 100°C while 95% of the natural felinine disappeared after only 2 hours at the same temperature. The recovery of felinine under certain conditions was greater than 100%. It is possible that acetyl-felinine may be present in the urine and that it is deacetylated during incubation. Overall synthetic felinine was found to be stable but the felinine in cat urine much less so. Other compounds present in the urine may contribute to the decomposition of felinine.     

Taurine concentration in the brain and in the plasma following intraperitoneal injections

Summary. The effect of different taurine doses (0.050, 0.125, 0.250, 0.500 and 1.000g/kg) administered intraperitoneally to Wistar rats was studied in both the plasma and the hippocampal microdialysate content.The samples were analyzed by reverse phased HPLC for the microdialysate samples and by HPLC with ion-exchange post-column derivatization (ninhydrin) for the plasma samples.In both plasma and microdialysate, we observed a dose dependent increase of taurine concentration. The AUC curves obtained from both microdialysate and plasma samples showed that the increase of taurine concentrations were linear. The mean ratio between AUCs microdialysate and plasma was 1.63±0.21 showing thus an unbalance between plasma and brain taurine content; a mechanism which enhance taurine transfer from the plasma to the brain was assumed.     

Effects of taurine in glucose and taurine administration

Summary. Taurine has several biological processes such as hypoglycemic action, antioxidation, detoxification, etc. To assess the effect of taurine administration on the guinea pigs with hyperglycemia, blood glucose, C-peptide levels together with morphologic alterations in the pancreatic ultrastructure were investigated in terms of hypoglycemic action and malondialdehyde and total sulfhydryl group levels with regard to oxidation-antioxidation relation. Animals were divided into four groups of six. Glucose supplementation group was administrated a single dose of glucose (400mg/kg, i.p.) injection. Glucose and taurine supplementation group was administrated glucose treatment (a single dose, 400mg/kg, i.p.) following taurine (a single dose, 200mg/kg, i.p.). Taurine and glucose supplementation group was administered taurine treatment (a single dose, 200mg/kg, i.p.) following glucose treatment (a single dose, 400mg/kg, i.p.). Control animals received no treatment. Blood samples were collected at the end of the experiments for the determination of glucose, C-peptide (indicator of insulin secretion), lipid peroxidation (thiobarbituric acid reactive substances), and total sulfhydryl groups levels. Pancreatic tissue samples were then collected and processed for transmission electron microscopy. The findings showed that glucose supplementation following taurine administration significantly decreased blood glucose level by increasing C-peptide level and the pancreatic secretion stimulated morphologically and insignificantly changed thiobarbituric acid reactive substances and total sulfhydryl group levels. These observations suggest that taurine administration may be useful in hyperglycemia because of its hypoglycemic and protective effects.     

Augmented taurine release is not the mechanism of ischemic preconditioning’s cardioprotection

Summary. In ischemic preconditioning (IPC) a brief ischemic period protects the heart from a subsequent ischemic insult by an unknown mechanism. Osmotic swelling has been proposed to be a major cause of cell death when ischemic tissue is reperfused. The present study tests whether the preconditioned heart during reperfusion might release more taurine, an important osmolyte in the cardiac myocytes, to decrease cellular osmolarity, oppose swelling, and preserve viability. We collected the coronary effluent from isolated rabbit hearts for 10min before and 10min after preconditioning with 5min of global ischemia. The heart then experienced 15min of global ischemia and effluent was collected during reperfusion for 40min. A control group was studied similarly but without the preconditioning ischemia. Fifteen min of ischemia was chosen to avoid any taurine release caused by ischemic cell death. Taurine was measured with HPLC. In the IPC group there was a postischemic release over baseline of 5.09±1.51mol (approx 3.3% of the total taurine pool), whereas in the control group the release was not significantly different, 5.72±1.67mol. The percent of the taurine pool lost from each heart during reperfusion was calculated based on an assumption of a total content of 20M taurine/gm wet weight. Since the amount of taurine released by the isolated rabbit heart following ischemia was not different in preconditioned and non-preconditioned hearts, we conclude that reduced swelling through taurine release is not the mechanism of the cardioprotective effects of IPC.     

Arginine revisited: Minireview article

Summary. Arginine is a precursor of proteins and employed in urea synthesis. It is also the precursor of many other compounds, such as creatine, nitric oxide, polyamines, agmatine, proline. In this review, its transport and that of other basic amino acids are examined, along with its transformation into nitric oxide, agmatine and proline, and the mutual regulation of the individual pathways.     

The effect of EGF application in gel form on histamine content of experimentally induced wound in mice

Summary. The factors participating to the wound healing are complex and still obscure. Among these factors, epidermal growth factor (EGF) and histamine by increasing reepithelization and reparation tissue strength via enhancing collagen deposition to the wound site have a beneficial effect. This study was performed to investigate the effect of EGF dosage forms on the histamine content of the experimentally induced wound and some wound healing criters in the mice.Histological investigation of reepithelization, wound tensile strength for healing and collagen maturation, and histamine levels were assessed in the present study. Thirty two mice were divided into control, and EGF treated groups. Controls included three subgroups; untreated (n=5), 0.9% NaCl applied (n=5), and gel applied (n=5). Experimental groups were treated with two forms of EGF; EGF, solution form in 0.9% NaCl (n=5) and the gel form in 0.2% w/w in carbopol 940 (n=7). The discrepancy between these forms were evaluated. This evaluation was done by the application of two forms of EGF for 15 days on experimentally induced wound healing.Gel form of EGF by sustained release from bioadhesive polymer is found to be more effective than the soluble form, on the healing of the wound, by acceleration of reepithelization and increment of wound tensile strength. The tensile strength of the wound indicates the rate of repair and collagen maturation. It has been observed that when physiological saline and carbopol 940 exposed to incision without EGF causes a significant increase in tissue histamine content.According to the results of the present investigation; the histamine content is found to be decreased by EGF gel dosage form treatment, therefore preventing abnormal collagen formation has a beneficial effect on wound healing.     

L-Histidine is a beneficial adjuvant for antiepileptic drugs against maximal electroshock-induced seizures in mice

Summary. Endogenous histamine has been reported to be involved in regulation of seizure susceptibility. Enhancement of histamine neurotransmission engendered by L-histidine treatment produces anticonvulsant effects in experimental animals. The present study investigated the influence of L-histidine on the protective effects of carbamazepine and phenytoin against maximal electroshock-induced seizures in mice.L-Histidine, administered at the doses that did not influence the threshold for electroconvulsions (250–500mg/kg), enhanced by nearly 30% the protective effects of carbamazepine against maximal electroshock-induced seizures. D-Histidine (1000mg/kg), an inactive isomer of histidine, was without any effect in this regard. L-Histidine (500mg/kg) also augmented the protective effects of phenytoin. Importantly, the enhancement of the anticonvulsant effects of these antiepileptic drugs produced by L-histidine co-administration was not associated with augmentation of their unwanted effects on memory and motor performance. A pharmacokinetic interaction was also excluded since the free plasma levels of these antiepileptics remained unchanged in the presence of L-histidine. It may be suggested that L-histidine could serve as a beneficial adjuvant for selected antiepileptic drugs.Present address: Integrative Neuroscience Section, Behavioral Neuroscience Branch, NIDA/NIH, 5500 Nathan Shock Drive, Baltimore, MD 21224, U.S.A.     

Hoe 140 abolishes the blood pressure lowering effect of taurine in high fructose-fed rats

Summary. High fructose feeding induces moderate increases in blood pressure of normal rats, associated with hyperinsulinemia, insulin resistance and impaired glucose tolerance. Increased vascular resistance, and sodium retention have been proposed to contribute to the blood pressure elevation in this model. Taurine, a sulphur-containing amino acid has been reported to have antihypertensive and antinatriuretic actions. In addition, taurine is shown to increase the excretion of nitrite and kinin availability and hence would be expected to improve the vascular tone. In the present study, the involvement of kinins in the blood pressure lowering effect of taurine was investigated by coadministration of Hoe 140, a kinin B₂ receptor antagonist along with taurine. The effects of taurine on plasma and urinary concentrations of sodium and tissue kallikrein activity were studied in high fructose-fed rats. Fructose-fed rats had elevated blood pressure and decreased levels of sodium in urine. Treatment with 2% taurine in drinking water prevented the blood pressure elevation and coadministration of Hoe 140 abolished this effect of taurine in high fructose-fed rats. The findings confirm the antinatriuretic action of taurine and also suggest a role for the kinins in the mechanism of taurine action in diet-induced hypertension.     

Modulation of ventral pallidal dopamine and glutamate release by the intravenous anesthetic propofol studied by in vivo microdialysis

Summary. The intravenous anesthetic propofol is reported to have various psychological side effects as hallucinations, sexual disinhibition, or euphoria. Hedonic and rewarding states like these are modulated by the dopaminergic system in the nucleus accumbens, prefrontal cortex and also in the ventral pallidum and by the glutamatergic system in the neocortex and limbic system. In the present study, propofol was administered either alone or in combination with the GABAA receptor antagonist bicuculline via reverse microdialysis into the ventral pallidum of freely moving rats. Dialysis fractions were taken every 20min and analyzed for dopamine and glutamate using high performance liquid chromatography. Application of propofol decreased dopamine levels in the ventral pallidum. This effect seems to be mainly mediated through GABAA receptors, since it was compensated by the GABAA receptor antagonist bicuculline. Propofol and propofol plus bicuculline exerted no effect on glutamate release in this brain region. The reduced dopamine release in ventral pallidum was most probably mediated through a GABAergic feedback loop from the ventral pallidum via the nucleus accumbens to the dopaminergic neurons of the ventral tegmental area or by long loop feedback. As an increase but not a decrease of dopamine release in the ventral pallidum is involved in hedonic and rewarding properties, similar symptoms induced by propofol seem to be unrelated to an action of propofol in the ventral pallidum.     

Arginine pathways and the inflammatory response: Interregulation of nitric oxide and polyamines: Review article

Summary. An early response to an acute inflammatory insult, such as wound healing or experimental glomerulonephritis, is the conversion of arginine to the cytostatic molecule nitric oxide (NO). This anti-bacterial phase is followed by the conversion of arginine to ornithine, which is the precursor for the pro-proliferative polyamines as well as proline for the production of extracellular matrix. This latter, pro-growth phase constitutes a repair phase response. The temporal switch of arginine as a substrate for the cytostatic iNOS/NO axis to the pro-growth arginase/ ornithine/polyamine and proline axis is subject to regulation by inflammatory cytokines as well as interregulation by the arginine metabolites themselves. Arginine is also the precursor for another biogenic amine, agmatine. Here we describe the capacity of these three arginine pathways to interregulate, and propose a model whereby agmatine has the potential to serve in the coordination of the early and repair phase pathways of arginine in the inflammatory response by acting as a gating mechanism at the transition from the iNOS/NO axis to the arginase/ODC/polyamine axis. Due to the pathophysiologic and therapeutic potential, we will further examine the antiproliferative effects of agmatine on the polyamine pathway.     

Interaction of aluminium ions with some amino acids present in human blood

Summary. The interaction of aluminium with some amino acids present in human blood was studied combining ion-chromatography (IC), atomic absorption spectrometry (AAS) and ultrafiltration (UF) techniques. An IC system for simultaneous determination of ornithine, lysine, glutamic acid, aspartic acid and tyrosine was developed. By adding aluminium to standard solutions of the amino acids and keeping the pH at 6 and 7 it was possible to verify that aluminium caused a reduction on the amino acid chromatographic signals. Similar experiment, carried out for copper showed the same behaviour (with different percentage of signal reductions) and validated the results for aluminium, considering that the interaction Cu-amino acid is well-established. The AAS analysis of sample fractions (500l) after the IC separation showed that aluminium (as copper as well) is not present in the fractions in which the amino acid peaks appear in the chromatogram. These approaches carried out with serum samples after UF showed that part of the free fraction of serum aluminium is distributed, besides other ligands, among these amino acids. It was found that in serum the affinity for aluminium followed the sequence Lys>Orn>Tyr>GluAsp.     

Tryptophan administration increase contractility and change the ultrastructure of mice duodenum

Summary. Serotonin (5-HT) is a metabolite of tryptophan (TRP). 5-HT has been shown to induce contractions in rat duodenum and ileum. We planned to investigate the in vivo effects of TRP administration on duodenal contractility and ultrastructure together.Two equal groups of adult male Swiss-albino mice were used in the experiments.Controls (CONT) and TRP treated (100mg/kg/24hr in 0.2ml. saline solution ip, 7 days).Body weights were recorded at the beginning and at the end of experiments. Duodenum tissues contractility responses to different concentration of KCl and acethycholine (ACh) were recorded on polygraph. The ultrastructural changes in duodenum observed by transmission electron microscopic (TEM) method and 5-HT levels determined by immunohistochemical method.Body weights decreased and duodenal contractile response of ACh increased significantly by TRP treatment. The duodenal ultrastructural changes in TRP group illustrated partially loss of apical surface and fusion in microvilli. Immunohistochemical detection showed that 5-HT increased by TRP treatment.There is a relation between duodenal contractility increased by TRP treatment and changes in the duodenal tissue 5-HT level and ultrastructure.