bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECT OF PHOSPHORYLATION ON L‐TYPE CALCIUM CURRENT IN VENTRICULAR MYOCYTES DIALYSED WITH PROTEOLYTIC ENZYMES
Authors: Dooley PC , Hancox JC , Chapman RA 
Published: March 2003

1. L‐Type Ca2+ channels play important roles in cardiac excitation and conduction. The present study used the whole‐cell patch‐clamp technique to investigate properties of Ca2+ channels in guinea‐pig isolated ventricular myocytes. The effects of internal application of the proteolytic enzymes trypsin and carboxypeptidase (CBP) on the whole‐cell L‐type Ca2+ current (ICa) were determined. When the effects of the enzymes on ICa had reached steady state, the effects of isoprenaline (ISP) or 2,3‐butane‐dione monoxime (BDM), which increase and decrease channel phosphorylation, respectively, were examined. The effects of these agents were compared with those observed in the absence of enzyme pretreatment.2. The amplitude and inactivation characteristics of ICa during depolarizing voltage‐clamp commands to +10 mV (0.1 Hz) were determined at 37°C.3. Trypsin and CBP (both at concentrations of 1 mg/mL in the pipette solution) increased the amplitude of ICa 4.2‐ and 2.8‐fold, respectively, and each enzyme increased the time constant of the slowly inactivating current by 50%.4. Trypsin decreased the potential at which ICa was half maximally activated from (mean±SD) −1.4±2.2 mV (n = 9) to −11.3±2.5 mV (n = 7). Although CBP increased ICa amplitude, it did not shift the half‐maximal activation voltage. Maximum conductance was increased 5.3‐fold by trypsin and 2.2‐fold by CBP.5. Isoprenaline (1 μmol/L) had no effects in myocytes dialysed with trypsin, but significantly increased the current in myocytes dialysed with CBP by 8%.6. At 12 mmol/L, BDM had no effect on current amplitude in the presence of trypsin, but decreased the time constant of slow inactivation to control values. After dialysis with CBP, BDM significantly decreased the maximum current by 11% and also decreased the rate of slow inactivation towards control values.7. These data suggest that trypsin and CBP may have digested a part of the calcium channel that normally restricts current flow, but to different extents. The enzymes interacted with BDM and ISP in a fashion suggesting that two sites may influence the amplitude of the current and at least two other sites may influence the time course of the slowly inactivating current.
PULMONARY INFLAMMATION WITHOUT BRONCHIAL HYPERRESPONSIVENESS IN VIVO OR IN VITRO AFTER SEPHADEX INSTILLATION IN PIGS
Authors: McFawn PK , Gray PR , Thomas J , Mitchell HW 
Published: March 2003

1. In rodent models, Sephadex produces pulmonary inflammation that may be associated with bronchial hyperresponsiveness. In the present study we examined whether Sephadex‐induced inflammation altered airway narrowing in pigs.2. Twenty millilitres of 10 mg/mL Sephadex suspension was instilled twice intratracheally into anaesthetized pigs (days 1 and 7 of a 9 day study). In vivo bronchial responsiveness was assessed from the effect of acetylcholine (ACh) aerosol on airways resistance and dynamic compliance before Sephadex instillation and on days 3, 5 and 9. Lung histology and in vitro bronchial responsiveness was assessed on day 9. In vitro responsiveness was assessed by measuring the reduction in flow through perfused 2 mm i.d. bronchial segments in response to ACh applied luminally and adventitially.3. Sephadex produced a focal peribronchial granulomatous reaction characterized by the presence of macrophages, eosinophils, neutrophils and giant cells. Changes in airway resistance and lung compliance in response to ACh did not change over the study period. The response of perfused bronchial segments to luminally or adventitially applied ACh was also unaltered.4. Sephadex‐induced pulmonary inflammation does not alter airway narrowing in vitro nor bronchial hyperresponsiveness in vivo in the pig.
REGULATION OF VASCULAR TONE BY ENDOTHELIUM‐DERIVED HYPERPOLARIZING FACTOR
Authors: Cheung DW , MacKay G Chen, MJ , Burnette E 
Published: March 2003

1. Endothelium‐derived hyperpolarizing factor (EDHF) mediates the nitric oxide (NO)‐independent component of the relaxation in rat mesenteric arteries. The relationship between hyperpolarization and vascular tone was studied by simultaneous recording of membrane potential with intracellular microelectrodes and tension in ring segments of rat mesenteric arteries.2. By depolarizing arteries with high potassium solutions, it was determined that the threshold for contraction is approximately −46 mV. Maximum contraction was attained when the arteries were depolarized to −20 mV. Thus, 1 mV depolarization resulted in an approximate 4% increase in tone. This relationship was not altered in spontaneously hypertensive rats.3. Noradrenaline (0.3 μmol/L) caused contraction and depolarized arteries by 13 mV. Acetylcholine caused endothelium‐dependent relaxation and hyperpolarization up to 14 mV. In the presence of Nω‐nitro‐L‐arginine, the EDHF‐mediated relaxation was correlated to hyperpolarization. A hyperpolarization of 1 mV corresponded to a 4.3% decrease of the induced tone.4. At concentrations (10 μmol/L) causing total relaxation, the maximum hyperpolarization induced by NO was only 7.6 mV.5. A maximum relaxation of 88% was observed with pinacidil (3 μmol/L), despite a 25 mV hyperpolarization. Relaxations to NO and pinacidil were not correlated with hyperpolarization. At similar levels of hyperpolarization, NO and pinacidil elicited more relaxation than EDHF.6. These studies show that vascular tone is very sensitive to membrane potential change in the range between −46 and −20 mV in the rat mesenteric artery. The relaxation response to EDHF, unlike that to NO and pinacidil, can be accounted for solely by its effect on the membrane potential.
ENDOMETRIAL ENDOTHELIN: REGULATOR OF UTERINE BLEEDING AND ENDOMETRIAL REPAIR
Authors: Salamonsen Lois A , Marsh Marion M , Findlay Jock K 
Published: March 2003

1. Endothelin (ET) and its mRNA are present in endometrium. Expression of ET varies across the menstrual cycle, reaching maximal levels in the premenstrual phase, suggesting a paracrine role in endometrial bleeding and/or repair.2. The major cellular source of ET is the epithelium, although endothelium and decidualized stroma are additional sites of production. Epithelial ET is the ET‐1 isoform and this is able to contract rat thoracic aortic rings ex vivo.3. Endothelin‐1 production by cultured endometrial epithelial cells is markedly increased by serum and, to a lesser extent, by transforming growth factor‐β and interleukin‐1α, but not by epidermal growth factor, oxytocin, arginine vasopressin, thrombin or angiotensin II, which stimulate ET production in other tissues.4. Endothelin‐1 has mitogenic actions on endometrial stromal cells; it stimulates the uptake of [3H]‐thymidine, acting via the AP‐1 cis element c‐jun.5. Neutral endopeptidase (NEP), a membrane‐bound ectoenzyme that is capable of degrading ET, is localized principally in endometrial stroma and immunoreactivity is maximal in the secretory phase of the cycle.6. A potential role for ET in regulating endometrial bleeding is suggested by studies on endometrium from two groups of women who were experiencing abnormal uterine bleeding: users of the contraceptive Norplant® (Leiras Co., Turku, Finland) and subjects with documented menorrhagia. In both groups, ET‐1 immunoreactivity in endometrial epithelium was markedly reduced compared with the normal menstrual cycle and did not vary cyclically, while NEP immunoreactivity, particularly in the epithelium, was increased. Thus, ET may be involved in endometrial bleeding, as a vasoconstrictor before the onset of menstruation when vasoconstriction is intense and, subsequently, when it may be required in the cessation of menstrual bleeding. Furthermore, the mitogenic actions of ET may play a role in endometrial regeneration and remodelling during the menstrual cycle, particularly following menstruation.
DIFFERENT RESPONSES TO SURGICAL STRESS BETWEEN EXTRA DOMAIN A+ AND PLASMA FIBRONECTINS
Authors: Satoi Sohei , Hiramatsu Yoshifumi , Kitade Hiroaki , Kwon A‐Hon , Matsui Kosuke , Miyashita Keiichi , Sakashita Eiji , Sekiguchi Kiyotoshi , Takahashi Hakuo , Kamiyama Yasuo 
Published: March 2003

1. Fibronectins (FN) are believed to have a role in haemorheological perturbation associated with tissue damage. Fibronectins exist in two antigenically related forms, plasma (p) and cellular fibronectin, which has the extra domain sequences A (EDA) or B (EDB). The present study was designed to determine changes in plasma p‐FN and EDA + FN under different types of surgical stress.2. Sixty‐two patients were divided into three groups: (i) group A, 33 patients undergoing hepato–pancreato–biliary surgery; (ii) group B, 19 patients undergoing laparoscopic cholecystectomy; and (iii) group C, 10 patients with postoperative complications. Plasma FN and EDA + FN levels were measured in these patients undergoing different types of surgical operation and either with or without liver cirrhosis using an enzyme‐linked immunosorbent assay.3. After surgery, a significant decrease in p‐FN levels and a significant increase in EDA + FN levels was observed in all patient groups compared with pre‐operative levels. The duration of increased EDA + FN levels, but not p‐FN levels, in group A patients was significantly longer than in group B patients. Although changes in p‐FN levels between patients with and without liver cirrhosis were significantly different, there were no significant differences in the EDA + FN levels between these two patient groups.4. In conclusion, EDA + FN and p‐FN levels were found to exhibit opposite responses to surgical stress. Furthermore, with greater surgical stress, greater increases in EDA + FN levels were seen. The presence of liver cirrhosis had no significant effect on EDA + FN levels during the perioperative period; however, p‐FN levels were significantly affected.5. Thus, it is suggested that plasma EDA + FN levels reflect the magnitude of surgical stress more closely than do p‐FN levels.
EFFECTS OF HYPOXIC EXERCISE CONDITIONING ON WORK CAPACITY, LACTATE, HYPOXANTHINE AND HORMONAL FACTORS IN MEN
Authors: Mori Masatake , Kinugawa Toru , Endo Akihiro , Kato Masahiko , Kato Tatsuo , Osaki Shuichi , Ogino Kazuhide , Igawa Osamu , Hisatome Ichiro , Ueda Mayumi , Miura Noritoyo , Ishibe Yuichi , Shigemasa Chiaki 
Published: March 2003

1. Hypoxanthine is a purine degradation product and exercise plasma hypoxanthine can be an index of ATP supply–demand imbalance during exercise. The present study determined the effects of hypoxic exercise conditioning on work capacity, blood lactate, plasma hypoxanthine and various neurohormonal factors.2. Blood lactate, plasma hypoxanthine and neurohormonal factors (catecholamines, renin–angiotensin system activity and natriuretic peptides) were measured at rest and after maximal cardiopulmonary exercise testing (at sea level) both at pre‐ and post‐hypoxic exercise conditioning in six males (40±2 years). The training protocol consisted of ergometer exercise twice weekly for 40 min in a hypobaric chamber (61.7–47.2 kPa) for 3 weeks.3. Pulmonary function and haematological and echocardiographic parameters were not altered after hypoxic exercise conditioning. Work rate at peak exercise (264±10 vs 321±31 W; P = 0.10) tended to be increased and peak O2 pulse (15.0±1.0 vs 18.4±1.4 mL/beat; P < 0.05) increased after exercise conditioning. The double product during submaximal exercise decreased and systolic blood pressure at peak exercise increased after exercise conditioning. Resting and exercise neurohormonal factors were unchanged, except for reduced resting plasma adrenaline levels. Blood lactate at peak exercise (7.4±0.7 vs 4.8±0.5 mmol/L; P < 0.05) became lower and peak plasma hypoxanthine (43.2±5.7 vs 26.4±5.0 μmol/L; P < 0.1) tended to be decreased after exercise conditioning.4. Hypoxic exercise conditioning tended to increase maximal power output with a decrease in exercise blood lactate and a trend towards a decrease in exercise plasma hypoxanthine. These data suggest that exercise conditioning under simulated altitude may improve ATP supply–demand imbalance during exercise with less anaerobiosis, which could contribute to enhanced endurance performance.
EFFECT OF HYPERINSULINAEMIA ON RENAL FUNCTION AND NITRATE/NITRITE EXCRETION IN HEALTHY SUBJECTS*
Authors: Komers Radko , Pelikanová Terezie , Kazdová Ludmila 
Published: March 2003

1. In addition to its metabolic actions, insulin acts as a vasodilator in certain vascular beds, such as skeletal muscle. It has been shown that this effect is mediated by endothelium‐derived nitric oxide (NO). Unlike in the skeletal muscle, insulin–NO interactions in the kidney, another major site of insulin action, have been less studied. The aim of the present study was to explore the role of NO in renal effects of hyperinsulinaemia in healthy subjects.2. Changes in renal function and urinary nitrate/nitrite (NO2−/NO3−; Griess method) levels as a marker of renal production of NO were assessed during euglycaemic hyperinsulinaemic clamp and compared with normoinsulinaemic isovolaemic conditions (administration of the same amount of insulin/glucose‐free vehicle) in 10 healthy male volunteers.3. Hyperinsulinaemia was associated with a decrease in renal excretion of stable metabolites of NO (mean (±SEM) 0.56±0.12 vs 0.38±0.05 μmol/min, respectively; P < 0.05). In contrast, administration of the same volume of insulin‐free vehicle resulted in elevation of urinary NO2−/NO3− (P < 0.05). The changes in renal sodium handling followed a similar pattern as changes in the renal excretion of NO2−/NO3− with a significantly different response to hyperinsulinaemia when compared with normoinsulinaemia (F = 12.2; P < 0.001). The mean arterial pressure, blood levels of low‐density lipoprotein–cholesterol and free fatty acids, possible factors influencing renal and systemic NO production, remained constant throughout both experiments.4. These results suggest that hyperinsulinaemia is associated, in healthy males, with a decrease in renal generation of NO. In contrast, mild volume expansion with insulin‐free vehicle resulted in increased excretion of NO metabolites. This insulin‐induced attenuation of renal NO synthesis may contribute to the anti‐natriuretic actions of insulin.
ROLE OF NITRIC OXIDE AND ENDOTHELIUM IN THE FLOW‐INDUCED DILATION OF RAT CORONARY ARTERIES UNDER TWO PRECONSTRICTION CONDITIONS
Authors: Véquaud Philippe , Pourageaud Fabrice , Freslon Jean‐Louis 
Published: March 2003

1. Pressure‐induced tone and flow‐induced dilations were studied in a rat perfused epicardial coronary artery mounted in an arteriograph. Spontaneous tone was assessed in arteries submitted either to 60 or 90 mmHg intraluminal pressure either under control conditions, after incubation with NG‐nitro‐L‐arginine methyl ester (L‐NAME; 100 μmol/L) or after endothelial denudation. Flow‐induced dilation was quantified under these conditions in preparations either submitted to 60 mmHg and preconstricted with 10 μmol/L 5‐hydroxytryptamine (5‐HT) or exhibiting spontaneous tone at 90 mmHg.2. Spontaneous tone was greater at 90 mmHg compared with tone obtained at 60 mmHg (21±2 vs 10±2% reduction of the fully dilated diameter after sodium nitroprusside incubation, respectively). Incubation with L‐NAME or removal of the endothelium significantly increased spontaneous tone at both pressures compared with control.3. In arteries submitted to 60 mmHg and preconstricted with 10 μmol/L 5‐HT, flow (0–800 μL/min) induced a continuous dilation (maximal value 63±4%). As a function of flow, shear stress first increased and then plateaued at values of approximately 76±6 dyn/cm2. After L‐NAME incubation or endothelial denudation, the flow‐induced dilation was reduced to the same extent and was obtained for higher values of shear stress (172±14 and 150±14 dyn/cm2, respectively).4. In arteries exhibiting spontaneous tone, starting flow led, first, to a constriction followed by a dilation up to 76±4% of the initial tone. Incubation with L‐NAME greatly altered flow‐ induced dilation. Endothelium removal further reduced the dilation obtained for very high values of shear stress (up to 300 dyn/cm2).5. The present study shows that different patterns of vasodilation induced by flow can be observed, depending on the initial vasoconstrictor stimulus. In 5‐HT‐preconstricted arteries, flow‐induced dilation appears to be fully dependent on the synthesis and release of nitric oxide. In arteries with spontaneous tone, a vasoconstrictor substance could be released for low values of flow. Nitric oxide is mainly, but not exclusively, responsible for the vasodilation. For both experimental conditions, removal of the endothelium greatly reduced the response, but a dilation was still observed.
HYPERGLYCAEMIA ABOLISHES THE ANTIHYPERTROPHIC EFFICACY OF BRADYKININ IN RAT VENTRICULAR MYOCYTES
Authors: Dusting Ac Rosenkranz, Gj , Ritchie Rh 
Published: March 2003

1. Bradykinin inhibits hypertrophy of rat ventricular myocytes, but only in the presence of endothelial cells.2. The influence of hyperglycaemia on the ability of bradykinin to prevent hypertrophy was investigated in adult rat ventricular myocytes cocultured with bovine aortic endothelial cells (BAEC).3. In myocytes cocultured with normal BAEC, angiotensin II (AngII; 1 μmol/L) significantly increased [3H]‐phenylalanine incorporation (an in vitro marker of hypertrophy) by 32±2%. This was abolished by bradykinin (10 μmol/L).4. Pretreatment of BAEC with high glucose (25 mmol/L for 24 h) prior to coculture with myocytes reduced the antihypertrophic effect of bradykinin, but did not modulate the hypertrophic effect of AngII.5. Pretreatment of BAEC with hyperglycaemia abolishes the antihypertrophic efficacy of bradykinin in rat ventricular myocytes cocultured with BAEC. This has implications for the action of angiotensin‐converting enzyme inhibitors.
IMPLICATION OF HYPERTENSIVE RAT MODELS FOR PRIMORDIAL NUTRITIONAL PREVENTION OF CARDIOVASCULAR DISEASES
Authors: Yamori Yukio 
Published: March 2003

1. Various substrains maintained during selective sib‐mating contributed to the establishment of spontaneously hypertensive rats (SHR) with a variety of clinical features.2. Stroke‐prone SHR (SHRSP), developing haemorrhagic and/or ischaemic stroke spontaneously, are regarded as a model for osteoporosis.3. The genetic mechanisms of spontaneous hypertension have been attributed pathophysiologically to neural and structural vascular alterations.4. The mechanisms of stroke are ascribed to the limited regional oxygen and nutrient supplies to the brain areas fed by perforating arteries.5. The genome‐wide linkage analysis on the F2 obtained by crosses of SHRSP with normotensive strains has demonstrated different gene loci contributing to the development and maintenance of hypertension during the ageing process and also genes influencing the susceptibility to stroke without any effect on blood pressure.6. Experimental studies in SHRSP revealed that stroke could be prevented by protein, Ca‐ or Mg‐supplemented diets, particularly if given in the early stage, indicating the importance of primordial nutritional prevention of cardiovascular diseases (CVD).7. Experimental findings in SHRSP as well as epidemiological studies on nutrition and CVD indicate the future avenue towards ‘predictive‐preventive medicine’ for CVD.
GENE RELATED TO STROKE IN STROKE‐PRONE SPONTANEOUSLY HYPERTENSIVE RATS
Authors: Ikeda Katsumi , Yamori Yukio 
Published: March 2003

1. In order to study genes related to stroke in stroke‐prone spontaneously hypertensive rats (SHRSP), linkage analysis was performed using F2 rats (SHRSP/Izm × WKY/Izm). The brainweight that reflected cerebral stroke in F2 rats showed cosegregation with three genetic markers, D4Mit19 (P < 0.0015), D4Mgh7 (P < 0.0014) and D4Mgh8 (P < 0.004) on chromosome 4, but not blood pressure.2. These results suggest that a chromosomal region other than the region responsible for hypertension contributes to the development of stroke in SHRSP.
NEW MEMBERS OF UNCOUPLING PROTEIN FAMILY IMPLICATED IN ENERGY METABOLISM
Authors: Hosoda Kiminori , Itoh Hiroshi , Son Cheol , Doi Kentaro , Tanaka Tokuji , Fukunaga Yasutomo , Yamori Yukio , Nakao Kazuwa 
Published: March 2003

1. The regulation of energy metabolism involves food intake and energy expenditure. Mitochondrial uncoupling proteins (UCP) are implicated in energy expenditure.2. cDNA of a homologue of UCP highly expressed in rat skeletal muscle, UCP‐3, is isolated and sequenced. Rat UCP‐2 cDNA is also isolated and sequenced.3. Rat UCP‐3 cDNA probe hybridized two bands, a major band at 2.5 kb and a minor band at 2.8 kb in rat tissues. The mRNA was expressed at the highest level in the skeletal muscle, and moderately in the interscapular brown adipose tissue (BAT). Only weak signals were detected in the epididymal white adipose tissue (WAT) and the heart. Rat UCP‐2 cDNA probe hybridized a 1.7 kb band detected widely in the whole body, especially abundant in the lung and the spleen. In contrast to the UCP‐3 gene expression, the UCP‐2 gene expression was expressed at substantial levels in the WAT and only at slight levels in the skeletal muscle and BAT.4. The UCP‐3 gene expression is augmented two‐fold in the gastrocnemius muscle from rats fed a high‐fat diet (P < 0.05). The UCP‐3 mRNA levels remained unchanged in the interscapular BAT, and epididymal WAT. The levels of the UCP‐2 gene expression are augmented significantly in the epididymal WAT (1.6‐fold; P < 0.05), while no significant increase is observed in the gastrocnemius muscle and interscapular BAT.
HUMAN ERYTHROCYTE BUT NOT BRAIN ACETYLCHOLINESTERASE HYDROLYSES HEROIN TO MORPHINE
Authors: Salmon Asher Y , Goren Zafrir , Avissar Yaniv , Soreq Hermona 
Published: March 2003

1. In human blood, heroin is rapidly hydrolysed by sequential deacylation of two ester bonds to yield first 6‐monoacetylmorphine (6‐MAM), then morphine.2. Serum butyrylcholinesterase (BuChE) hydrolyses heroin to 6‐MAM with a catalytic efficiency of 4.5/min per μmol/L, but does not proceed to produce morphine.3. In vitro, human erythrocyte acetylcholinesterase (AChE) hydrolyses heroin to 6‐MAM, with a catalytic efficiency of 0.5/min per μmol/L under first‐order kinetics. Moreover, erythrocyte AChE, but not BuChE is capable of further hydrolysing 6‐MAM to morphine, albeit at a considerably slower rate.4. Both hydrolysis steps by erythrocyte AChE were totally blocked by the selective AChE inhibitor BW284c51 but were not blocked by the BuChE‐specific inhibitor, iso‐OMPA (tetraisopropylpyrophosphoramide).5. The brain synaptic form of AChE, which differs from the erythrocyte enzyme in its C‐terminus, was incapable of hydrolysing heroin.6. Heroin suppressed substrate hydrolysis by antibody‐immobilized erythrocyte but not by brain AChE.7. These findings reveal a new metabolic role for erythrocyte AChE, the biological function of which is as yet unexplained, and demonstrate distinct biochemical properties for the two AChE variants, which were previously considered catalytically indistinguishable.