bluuebunny/crossref_metadata_2025_split huggingface dataset:
REPETITIVE ELECTRICAL ACTIVITY OF THE MUSCLE MEMBRANE INDUCED IN CHLORIDE‐FREE MEDIUM
Authors: Nánási P. P. , Dankó M. 
Published: June 2007

SUMMARY1. Superficial fibres of frog skeletal muscle were electrically stimulated in Ringer solution where the chloride content had been replaced by various weakly permeant anions. Changes of the membrane potential were recorded at three different time scales. The complex response was initiated by a volley of fast repetitive action potentials (10–20 ms cycle length) superimposed on the ascending phase of a transient depolarization to ‐ 35 mV. The transient depolarization was followed by a membrane potential oscillation (0.3–0.6 s cycle length). The parameters of the volley and membrane potential oscillation were not greatly affected by the substituent anion.2. The transient depolarization was fully abolished by tetrodotoxin (3 μmol/L), but left unaffected by nifedipine (5 μmol/L), or by the replacement of extracellular Ca for Ni or Co. Tetraethylammonium (20–40 mmol/L) increased the duration and amplitude of the transient depolarization. The shape of transient depolarization was uniform in a given fibre, in spite of its marked variability under different experimental conditions.3. Single outward current pulses applied in chloride‐free solution containing tetraethylammonium (20–40 mmol/L) evoked prolonged depolarizations to positive membrane potentials accompanied by increases in the specific membrane conductance. This slow response, which was also frequently observed in the absence of TEA, was mediated by Ca ions, as it was insensitive to tetrodotoxin (3 μmol/L) but abolished by nifedipine (10 4mUmol/L).4. Two populations of the muscle fibres were observed during the slow response. Some fibres repolarized completely, while others failed to produce complete repolarization but formed a plateau between ‐ 20 and ‐ 30 mV, lasting for several minutes. When the external K concentration was abruptly increased to 5 or 10 mmol/L during the plateau of the slow response, repolarization and increase in membrane conductance were observed.5. In muscle fibres, having osmotically disrupted T‐system, the duration of transient depolarization was in the range of minutes, in contrast to the range of seconds observed in intact fibres. The volley was preserved in glycerol treated fibres, however, the baseline of discharges was close to the resting potential and the rate of depolarization of the baseline was significantly less in glycerol treated than in intact fibres.6. These results are consistent with the existence of a second stable membrane potential level in skeletal muscle between ‐ 40 and ‐ 30 mV. The depolarization and repolarization during the membrane potential oscillation and transient depolarization can be regarded as a partial or full transition, respectively, between these two stable membrane potential levels, possibly due to the conductance changes of the inward rectifier K channels. It seems likely that the various types of repetitive activity are also linked to these conductance changes indicating that they are endogenous properties of the skeletal muscle membrane.
BLOOD SERUM BIOCHEMICAL CHANGES IN PHYSICALLY CONDITIONED AND UNCONDITIONED SUBJECTS DURING BED REST AND CHRONIC HYPERHYDRATION
Authors: Zorbas Yan G. , Naexu Konstantin A. , Federenko Youri F. 
Published: June 2007

SUMMARY1. It has been suggested that prolonged exposure to a rigorous bed rest regimen (hypokinesia) may induce greater serum carbohydrate and electrolyte changes in physically conditioned than unconditional subjects and that chronic hyperhydration may normalize or attenuate the development of these biochemical alterations in physically conditioned subjects.2. Serum carbohydrate and electrolyte changes were determined in 18 physically healthy male volunteers aged 19–24 years during 30 days of a rigorous bed rest regimen. The subjects were divided into three equal groups. The first g oup consisted of six unconditioned subjects with V̇o2 max of 44 mL/kg bodyweight/min, the second group consisted of six conditioned subjects with V̇o2 max of 69 mL/ kg bodyweight/ min and the third group consisted of six conditioned subjects with V̇o2 max of 69 mL/kg body weight/min who consumed daily an additional amount of 26 mL water/kg bodyweight and 0.10 mg sodium chloride/kg bodyweight.3. For the simulation of the hypokinetic effect all volunteers were kept under a rigorous bed rest regimen for 30 days. During the pre hypokinetic period of 15 days and during the bed rest period of 30 days the concentrations of cortsol, aldosterone, testosterone, tri‐idothyronine (T3), thyroxine (total; T4), glucose, potassium, sodium and chloride were determined in blood serum of volunteers.4. During the bed rest period of 30 days serum carbohydrate and electrolyte changes were more pronounced in physically conditioned than unconditioned hypokinetic subjects. In physically conditioned hyperhydrated subjects serum carbohydrate and electrolyte changes were less pronounced than in physically conditioned and unconditioned hypokinetic subjects.5. It was concluded that exposure to a rigorous bed rest regimen over a prolonged period of time induced significantly more changes in serum carbohydrate and electrolyte concentrations in physically conditioned than in unconditioned subjects and that chronic hyperhydration may be used to normalize or stabilize all serum biochemical changes in physically conditioned subjects during prolonged exposure to a rigorous bed rest regimen.
FISH OIL FEEDING SELECTIVELY ATTENUATES CONTRACTILE RESPONSES TO NORADRENALINE AND ELECTRICAL STIMULATION IN THE PERFUSED MESENTERIC RESISTANCE VESSELS OF SPONTANEOUSLY HYPERTENSIVE RATS
Authors: Chu Z. M. , Yin K. , Beilin L. J. 
Published: June 2007

SUMMARY1. The mechanism of the antihypertensive effects of n‐3 fatty acids were examined in spontaneously hypertensive rats (SHR) by feeding ‘Max EPA’ fish oil or hydrogenated coconut oil and determining the responses of perfused mesenteric resistance vessels to various contractile agents and peri‐arterial nerve stimulation.2. Fish oil feeding for 4 weeks caused a decrease in the responses to exogenous noradrenaline and electrical nerve stimulations but had no significant effect on vasopressin and KC1 (80 mmol/L) induced contractions.3. These results provide direct evidence for specific attenuation of vascular responses to sympatho‐adrenal stimulation in resistance vessels following fish oil feeding and may account for the antihypertensive effects seen in humans and in some forms of hypertension in rats.
ISOLATION AND CHARACTERIZATION OF THE RAT LIVER AVP RECEPTOR USING [125I][d(CH2)5′SARCOSINE7]AVP1
Authors: Trinder Deborah , Kelly Janice M. , Fernley Ross , Mooser Vincent , Phillips Paddy A. , Johnston Colin I. 
Published: June 2007

SUMMARY1. A vasopressin (AVP) binding protein was purified from rat liver membranes by an improved method using [125I][d(CH2)5′Sarcosine7]AVP, a selective Vi AVP radioligand and a combination of CHAPS solubilization, gel filtration, lectin affinity and FPLC ion exchange chromatography.2. The purified protein exhibited a maximum binding activity of 2480 pmol/ mg protein with a KD of 4.5 nmol/ L, which corresponds to a purification of approximately 26 700‐fold. The molecular weight of this protein was 70 000 Da.3. The binding of [125I][d(CH2)5′Sarcosine7]AVP to the solubilized membranes was dependent on the protein concentration, and was inhibited by the unlabelled peptides [d(CH2)5′Sarcosine7]AVP, AVP, and to a lesser degree by peptides with high V2 receptor affinity, such as 1‐desamino‐D‐AVP and [d(CH2)5′D‐Ileu2‐Ileu4]AVP.4. In addition, an AVP anti‐idiotypic monoclonal antibody bound to both the partially purified and purified lectin affinity AVP binding protein in a concentration‐dependent manner. These results indicate that the purified protein displays similar characteristics to the liver membrane‐bound AVP V1 receptor.
MEASUREMENT AND IDENTIFICATION OF PRORENIN AND RENIN IN OVARIAN FOLLICULAR FLUID FROM CATTLE AND PIG
Authors: Hagemann Arne , Nielsen Arne Høj , Dantzer Vibeke , Avery Birthe , Poulsen Knud 
Published: June 2007

SUMMARY1. In previous studies we have demonstrated and solved several methodological problems in relation to the measurement of prorenin by trypsin activation in rat, bovine, hog and horse plasma.2. The aim of the present study was to develop a method for the measurement of prorenin in bovine and porcine ovarian follicular fluid.3. Trypsin activation of follicular fluid generated angiotensin I immunoreactive material (AI IM) in both species.4. The AI IM interfered with the renin assay, but could be completely removed by a cation exchange resin in a batch‐wise technique.5. The enzymatic activity of trypsin‐activated prorenin and pre‐existing active renin was completely inhibited by a specific inhibitor of renin.6. The reactions were optimized and an accurate measurement of prorenin in ovarian follicular fluid was developed.7. The existence of prorenin and renin in bovine ovarian follicular fluid was established. Prorenin and renin in porcine ovarian follicular fluid was demonstrated for the first time.8. The ratio between ovarian follicular fluid and plasma was 43 for prorenin and 19 for active renin in cattle. The same ratios in pigs were 1.3 and 0.4, respectively. These findings indicate a species difference with respect to the amount of prorenin or active renin present in ovarian follicular fluid.
INCREASE IN SERUM TOTAL ANGIOTENSIN‐CONVERTING ENZYME ACTIVITY WITH ENALAPRIL THERAPY IN HUMANS: A CONTROLLED TRIAL
Authors: Stokes Gordon S. , Monaghan Judith C. , Marwood John F. , Okoro E. Obi , Johnston Heather 
Published: June 2007

SUMMARY1. In a controlled, randomized double‐blind trial, 15 patients with essential hypertension were treated with enalapril 5–20 mg/day, or doxazosin 1–8 mg/day, during a 7 week dose titration phase. This was followed by 7 weeks of combined treatment with doxazosin and enalapril.2. Blood was taken after a 2 week placebo run‐in phase, and at 3 and 7 weeks in the single‐agent and combined treatment phases, for measurement of plasma renin activity (PRA), plasma angiotensin II (All), plasma aldosterone and serum free and total angiotensin‐converting enzyme (ACE) activities.3. Doxazosin had no effect on serum free or total ACE activities.4. Enalapril reduced serum free ACE activity and increased serum total ACE activity, which at 7 weeks was significantly greater than in patients receiving doxazosin.5. In those patients who received enalapril, 10 mg/day for 3 weeks and then 20 mg/day for 4 weeks (n= 12), with or without doxazosin, mean serum total ACE activity increased by 51%. PRA was also increased in this group, but there were no changes in plasma AH or aldosterone concentrations.
POPULATION‐BASED SURVEY OF HUMAN SODIUM AND POTASSIUM EXCRETION
Authors: Beard T. C. , Eickhoff R. , Mejglo Z. A. , Jones M. , Bennett S. A. , Dwyer T. 
Published: June 2007

SUMMARY1. During the 1989 National Heart Foundation Risk Factor Prevalence Survey a subsample in Hobart collected 24 h urine samples to measure electrolyte excretion.2. The ranges were 30‐344 mmol/24 h for Na+ excretion (mean 160 mmol/24 h for men, 124 mmol/24 h for women), and 25‐119 mmol/24 h for K+ excretion (mean 77 mmol/24 h for men, 68 mmol/24 h for women).3. As in other surveys, women excreted about 20–25% less Na+ and K+ than men, although there was no significant sex difference in the ratio of Na+/K+ excretion.4. The recommended dietary intake (RDI) for Na+ and K+ was followed simultaneously by 19% of subjects, and 13% had a 24 h urinary Na+/K+ ratio ≤ 1.0.5. Observance of the RDI limited the value of iodized salt for goitre prophylaxis.6. Sodium excretion rates were outside the therapeutic range of thiazide diuretics in 22% of subjects.7. Diet groups for long‐term prospective cohort studies to test the prophylactic value of avoiding salt could apparently be recruited from existing subsamples of the population.
EFFECTS OF ARGININOSUCCINIC ACID ON NITRIC OXIDE‐MEDIATED RELAXATIONS IN RAT AORTA AND ANOCOCCYGEUS MUSCLE
Authors: Rand M. J. , Li C. G. 
Published: June 2007

SUMMARY1. Argininosuccinic acid (ASA), a naturally occurring NG derivative of arginine, and the nitric oxide synthase (NOS) inhibitor JVG‐nitro‐L‐arginine methyl ester (l‐NAME) were compared for their ability to reduce responses to nitric oxide (NO) derived from endothelial cells (aorta) and nitrergic nerves (anococcygeus muscle).2. In isolated rings of rat aorta, endothelium‐dependent relaxation responses to acetylcholine were abolished by l‐NAME (0.1 mmol/L) and were reduced by ASA (0.1 and 0.3 mmol/L). Relaxations induced by sodium nitroprusside (SNP) were not affected by l‐NAME but were reduced by ASA.3. In rat isolated anococcygeus muscles, relaxations elicited by nitrergic nerve stimulation at 1 Hz were abolished by l‐NAME (0.1 mmol/L) but were only slightly reduced by ASA (1 mmol/L). The effect of ASA was not sustained. l‐Arginine (1 mmol/L) prevented the effect of L‐NAME but not that of ASA. Neither ASA or l‐NAME inhibited SNP‐induced relaxation in the anococcygeus muscle.4. The results suggest that ASA inhibits NOS but this does not totally account for its effects in reducing NO‐mediated relaxations produced by the endothelium‐dependent vasodilator acetylcholine in rat aortic rings and stimulation of nitrergic nerves in the rat anococcygeus muscle.
POLYMERASE CHAIN REACTION‐BASED DNA FINGERPRINTING IN THE SPONTANEOUSLY HYPERTENSIVE RAT: POTENTIAL SOURCE OF cDNA LIBRARY PROBES
Authors: Di Nicolantonio Robert , Imai Takashi , Ikeda Katsumi , Sawamura Makoto , Yamori Yukio , Murakami Kazuo 
Published: June 2007

SUMMARY1. Using the Polymerase Chain Reaction with a primer homologous to a repetitive unit found at irregular distances in the rat genome, we were able to synthesize DNA fragments spanning such units and visualize them as a ladder of discrete bands following electrophoresis.2. Differences between fingerprint patterns generated using SHR, WKY and SD DNA, in the form of band deletions or duplications, were readily detected.3. Unlike traditional fingerprinting, PCR fingerprints allow the ready extraction and characterization of polymorphic bands. Such bands could then be used as probes with which to screen a cDNA library that might, in turn, identify expressed genes involved in the development of hypertension.
THE HETEROGENEITY OF 11‐β‐HYDROXYSTEROID DEHYDROGENASE ACTIVITIES IN THE RAT HIPPOCAMPUS IMPLIES A COMPLEX REGULATION OF STEROID HORMONE ACTION
Authors: Smith R. E. , Mercer W. R. , Provencher P. H. , Obeyesekere V. , Krozowski Z. S. 
Published: June 2007

SUMMARY1. The rat hippocampus 1l‐β‐hydroxysteroid dehydrogenase (11‐HSD) displays a different substrate specificity to that of other tissues. S1 nuclease analysis was used to determine whether the hippocampal messenger RNA is different from that found in other tissues.2. SI nuclease analysis using probes spanning the full length cDNA demonstrated that there were no differences in sequence between the hippocampal 11‐HSD and the enzyme originally cloned from the liver.3. These results suggest that there may be multiple 11‐HSD isoforms in the hippocampus with different substrate specificities.
DA‐1 RECEPTORS MEDIATE RENAL EFFECTS OF THE DOPAMINE PRODRUG, GLUDOPA, IN CONSCIOUS RABBITS
Authors: Wang Zhi‐Qin , Way Diana , Trigg Lisbeth , McGrath Barry P. 
Published: June 2007

SUMMARY1. Eight male rabbits were implanted with Doppler flow probes around the lower abdominal aorta and left renal artery. A 2 week recovery period was allowed prior to the experiment.2. Normal saline, gludopa at 25 μmg/kg per min and at 100 μg/ kg per min were each infused i.v. for 60 min. One week later the same protocol was administered to four of these animals in addition to DA‐1 antagonist SCH 23390 (0.3 mg/kg i.v.) before gludopa infusion.3. Gludopa elicited significant increases in urine flow, urinary sodium excretion and renal blood flow, and decreased renal vascular resistance. These changes were abolished by the DA‐1 antagonist. Blood pressure, heart rate and hindlimb blood flow remained unchanged.4. Urine dopamine excretion was increased 1200‐fold and 7800‐fold after gludopa administration at 25 μg/kg per min and 100 μg/kg per min, respectively, while plasma dopamine concentration and plasma renin activity (PRA) were not significantly altered. However, PRA was elevated by gludopa with DA‐1 antagonism.5. The renal vasodilation, natriuresis and diuresis produced by gludopa in conscious rabbits appears to be mediated by locally generated dopamine via DA‐1 receptors.
COMPARISON OF PARATHYROID HORMONE AND CALCITONIN ON RAT RENAL CALCIUM AND MAGNESIUM TRANSPORT
Authors: Carney S. L. 
Published: June 2007

SUMMARY1. Because in vitro adenylate cyclase activity studies suggest that parathyroid hormone (PTH) and calcitonin (CT) increase renal tubular calcium and magnesium reabsorption by stimulating the same transport mechanism, the separate and combined effects of these hormones on calcium and magnesium transport was assessed in the rat.2. Fractional excretion of calcium was 9.5 ±0.5% in calcium‐infused thyroparathyroidectomized (TPTX) rats and was reduced to 5.1 ±0.6 and 4.1 ±0.6% by maximal hypocalciuric concentrations of PTH and CT, respectively.3. Combined administration of maximal PTH and CT produced an effect on fractional and absolute calcium excretion similar to that recorded with maximal CT alone. The combined administration of half‐maximal concentrations of PTH and CT also produced a comparable fall in the fractional excretion of calcium to 3.0 ± 0.7%, which was similar to that observed in the ‘maximal CT’ and ‘maximal PTH plus CT’ groups. The magnesium reabsorption data were comparable.4. These results support biochemical data suggesting that PTH and CT act upon the same transport site, presumably within the thick ascending limb of Henle's loop, to facilitate calcium and magnesium reabsorption.
CAPTOPRIL MAGNIFIES THE INCREASE IN ANGIOTENSIN I‐CONVERTING ENZYME ACTIVITY IN RATS WITH AMINONUCLEOSIDE NEPHROSIS
Authors: Pedraza‐Chaverri José , Maciel Avril H. , Cruz Cristino , Peña José Carlos 
Published: June 2007

SUMMARY1. Serum, tissue and urine angiotensin I‐converting enzyme (ACE) activity was estimated in the following groups of rats: saline‐injected rats (controls); captopril‐treated (CAP) control animals (CONTROL‐CAP); puromycin aminonucleoside (PAN)‐induced nephrotic syndrome (NS); and CAP‐treated animals with NS (NS‐CAP).2. Serum ACE activity increased in the CONTROL‐CAP, NS, and NS‐CAP groups. The increase in the NS‐CAP group was significantly higher compared with the NS or CONTROL‐CAP groups.3. In the CONTROL‐CAP group, tissue ACE decreased in brain, heart and adrenal glands, and remained unchanged in the lung, testis, kidney, small intestine and liver. In the NS group, tissue ACE activity increased in the lung and testis, decreased in the brain and heart, and remained unchanged in the small intestine, adrenal glands, kidney and liver. Tissue ACE activity increased significantly in the NS‐CAP group compared with the other groups. This increase in tissue ACE may contribute to an increase in the serum ACE activity in the NS‐CAP group compared with the NS group.4. Urine ACE activity increased in the NS and NS‐CAP groups, although the rise in the NS‐CAP group was significantly higher. The urine ACE correlated significantly with the circulating levels of this enzyme in the NS and NS‐CAP groups. The loss of ACE in the urine in the presence of an increased serum ACE activity indicates that the biosynthesis of tissue ACE and its release into the bloodstream must be elevated.
BRONCHODILATORY ACTIVITY AND PHARMACOKINETICS OF NEW XANTHINES IN GUINEA‐PIGS
Authors: Takagi Kenzo , Hasegawa Takaaki , Nadai Masayuki , Sakai Ryousuke , Miyamoto Kenichi 
Published: June 2007

SUMMARY1. The in vitro biological activities and the effect of protein binding on the relaxant effects in vivo of N‐3‐alkylxanthine and N‐3‐alkyl‐N‐1‐methylxanthine derivative were investigated in guinea‐pigs.2. A significantly positive correlation was observed among the in vitro muscle relaxant activity, the cyclic adenosine monophosphate (cAMP) phosphodiesterase (PDE) inhibitory activity and the protein‐binding potency of xanthine derivatives. However, there was a weak relationship between these activities and affinity for adenosine receptors.3. When theophylline, enprofylline and 1‐methyl‐3‐propylxanthine (MPX) were injected intravenously in guinea‐pigs, their ED50 values were 6.1, 3.3 and 1.0 mg/kg, respectively. Plasma concentrations of these drugs obtained following the intravenous injection of the ED50 approximated the theoretically effective concentration (EC50) predicted from both the relaxant effects in vitro and the protein binding parameters. A good linear correlation was observed between bodyweight in four species (rats, guinea‐pigs, rabbits and humans) and certain pharmacokinetic parameters of enprofylline and theophylline.4. The present study indicates that differences in the relaxant effects of these drugs in vitro and in vivo can be explained in part by protein binding, and that the protein binding of these xanthine bronchodilators is an important determinant for their pharmacological activity. Guinea‐pigs provide a useful model for studying pharmacodynamic‐pharmacokinetic relationships of new bronchodilators.
A comparison of guanfacine, bunazosin, atenolol and nadolol on blood pressure and plasma noradrenaline responses to cold pressor testing
Authors: Koshiji Masatoshi , Ito Hiroyasu , Minatoguchi Shinya , Watanabe Hiroko , Imai Yoko , Kakami Masao , Hirakawa Senri 
Published: June 2007

b1. The role of the presynaptic adrenoceptor subtypes in man was investigated based on observation of the changes in blood pressure (ΔBP) and plasma noradrenaline concentration (ANA) with the cold pressor test (CPT).2. The CPT was well reproducible for BP and NA when performed at a 2 week interval in patients with mild hypertension.3. After administration for 4 weeks, guanfacine (Gf; (α‐adrenoceptor agonist) decreased the ΔNA response to CPT.4. After administration for 2 or 4 weeks, bunazosin (Bu; α1‐adrenoceptor antagonist) atenolol (At; β1‐adrenoceptor antagonist) and nadolol (Nd; non‐selective β‐adrenoceptor antagonist) did not affect the ΔNA response to CPT.5. Both Gf and Bu decreased the systolic blood pressure response (ΔSBP) to CPT after 4 weeks of the administration. Neither At nor Nd significantly changed the ΔSBP response to CPT.6. It is likely that Gf stimulated the presynaptic α2 adrenoceptors at the sympathetic nerve endings as well as the central α2 adrenoceptors, inhibiting the release of noradrenaline. It is unlikely that Bu, At and Nd exerted any clearly defined action on the presynaptic adrenoceptors in human hypertensive subjects.
EFFECTS OF ACUTE SUPERIOR CERVICAL GANGLIONECTOMY ON CEREBRAL BLOOD FLOW AND METABOLISM IN STROKE‐PRONE SPONTANEOUSLY HYPERTENSIVE RATS SUBJECTED TO CEREBRAL ISCHAEMIA
Authors: Nagao Tetsuhiko , Sadoshima Seizo , Ishitsuka Takao , Kusuda Kenji , Shiokawa Osamu , Lbayashi Setsuro , Fujishima Masatoshi 
Published: June 2007

b1. The effects of acute bilateral superior cervical ganglionectomy on cerebral blood flow and metabolism were investigated in stroke‐prone spontaneously hypertensive rats (SHRsp), before and during cerebral ischaemia.2. The resting cerebral blood flow was comparable between the control and denervated animals.3. There was no significant difference in cerebral blood flow or concentration of tissue energy metabolites (adenosine triphosphate [ATP], lactate and pyruvate) between the sham‐operated control and denervated animals during ischaemia.4. The results suggest that sympathetic innervation of cerebral vessels originating from superior cervical ganglia may not play a major role in the progression of cerebral ischaemia in SHRsp.