bluuebunny/crossref_metadata_2025 huggingface dataset:
Does heparin inhibit renin activity?
Authors: Matsunaga Masato , Yamanaka Yoko , Nagano Noriko , Iwasaki Yuki , Saito Yumi , Ando Naoko , Kusumi Shouko , Tei Masahiko
Published: April 2011

Although heparin was reported in the 1960s to inhibit renin activity, this has not always been confirmed by other investigators. Hence, we re-examined whether heparin really inhibits renin or not. Renin activities were determined by radioimmunoassay of angiotensin I generated at pH 7.4. (i) No significant difference was found between the two kinds of plasma samples obtained with heparin and with EDTA as anticoagulant, in ARC (renin activity with addition of sheep renin substrate), TRC (ARC after activation of inactive renin by trypsin), or PRA (plasma renin activity without additional substrate), (ii) Even in higher concentrations of heparin up to 500 U/mL, neither PRA, ARC, nor TRC of plasma was affected significantly. (iii) Heparin, in concentrations up to 500 U/mL, exerted no significant effect on TRC of the media of human vascular smooth muscle cell culture. In conclusion, heparin does not exert any significant inhibitory effect on human renin nor does it affect activation of inactive renin by trypsin in the range of concentration of practical use, under the conditions employed in this study.Key words: plasma renin, tissue renin, inactive renin, vascular smooth muscle cell, trypsin.
The actions of intermediate and long-chain n-alkanols on unitary NMDA currents in hippocampal neurons
Authors: McLarnon James G. , Wong Jason H. P. , Sawyer Dale , Baimbridge Kenneth G.
Published: April 2011

The actions of the n-alkanols butanol, pentanol, and octanol on unitary currents passing through N-methyl-D-aspartate (NMDA) ion channels have been studied in cultured CA1 hippocampal neurons. The cell-attached patch clamp method, with L-homocysteic acid included in the patch pipette, was used to record single channel NMDA currents at the cell resting potential or for hyperpolarizing patch potentials. With the n-alkanols added to the bath solution, the mean open times for the NMDA channel were diminished and the channel conductance was unchanged. A decrease in mean open time to about 70% of control value was found with butanol (3 mM), pentanol (1 mM), and octanol (0.02 mM). In addition the n-alkanols had small effects to decrease the frequency of channel openings and to increase the amplitude of the unitary currents. The effects of the alcohols on intracellular calcium levels, during NMDA applications, were also measured using the fluorescent dye FURA II.Key words: patch clamp, cultured hippocampal neurons, N-methyl-D-aspartate, unitary currents, n-alkanols.
Bioavailability of aspirin and salicylamide following oral co-administration in human volunteers
Authors: Abdel-Rahman Mohamed S. , Reddi Alluru S. , Curro Frederick A. , Turkall Rita M. , Kadry Abdelrazak M. , Hansrote Julia A.
Published: April 2011

BC® powder (I) is a commercially available analgesic containing the active ingredients aspirin and salicylamide. The kinetics of I, BC® powder minus aspirin (II), and BC® powder minus salicylamide (III) were evaluated in 13 volunteers. Ten minutes after administration of I, aspirin reached a maximum concentration of 12.9 μg/mL, while salicylamide concentration reached a peak value of 3.4 μg/mL. However, when III was administered, aspirin was not detected at 10 min and only reached a concentration of 0.4 μg/mL at 2 and 6 h. Furthermore, the area under the plasma concentration versus time curve for aspirin when III was administered was sixfold less compared with treatment with I. The area under the curve for aspirin metabolites was significantly different in I versus III. After treatment with II, a delay in salicylamide peak concentration was observed. Gentisamide was not detected throughout the study. This study demonstrates that salicylamide significantly enhances plasma levels of aspirin with potential therapeutic implications.Key words: aspirin, BC® powder, bioavailability, salicylamide.
Changes in force and calcium sensitivity in the developing avian heart
Authors: Godt R. E. , Fogaça R. T. H. , Nosek T. M.
Published: April 2011

The aim of this study was to characterize the development of the contractile properties of intact and chemically skinned muscle from chicken heart and to compare these characteristics with those of developing mammalian heart reported by others. Small trabeculae were dissected from left ventricles of Arbor Acre chickens between embryonic day 7 and young adulthood (7 weeks post-hatching). At all ages, increasing extracellular calcium (0.45–3.6 mM) progressively increased twitch force of electrically stimulated trabeculae. Twitch force at 1.8 mM extracellular calcium, normalized to cross-sectional area, increased to a maximum at 1 day post-hatching, remained constant through 3 weeks post-hatching, but then decreased at 7 weeks post-hatching. The maximal calcium-activated force of trabeculae chemically skinned with Triton X-100 detergent increased to a maximum 2 days before the time of hatching and was not significantly changed up to 7 weeks post-hatching. Over the ages studied, average twitch force in 1.8 mM calcium was between 26 and 66% of maximal calcium-activated force after skinning, suggesting that the contractile apparatus is not fully activated during the twitch in normal Ringer. In skinned trabeculae, the calcium sensitivity of the contractile apparatus was higher in the embryo than in the young adult. These age-dependent changes in calcium sensitivity are correlated with isoform switching in troponin T. A decrease in pH from 7.0 to 6.5 decreased the calcium sensitivity of the contractile apparatus to a greater degree in skinned trabeculae from young adult hearts than in those from embryonic hearts. This change in susceptibility to acidosis is temporally associated with isoform switching in troponin I. Moreover, the decrease in maximal calcium-activated force with pH was also greater in trabeculae from young adult heart. Thus the contractile apparatus of embryonic chicken heart is less sensitive to the depressant effects of acidosis than that of the adult heart. These developmental changes in calcium sensitivity are analogous to those reported by others in mammalian heart.Key words: muscle contraction, heart development, acidosis, chicken, contractile proteins.
Calcium buffer solutions and how to make them: A do it yourself guide
Authors: McGuigan John A. S. , Lüthi Daniel , Buri Arlette
Published: April 2011

In measurements of the intracellular free calcium concentration ([Ca2+]) using either microelectrodes or fluorescent probes, calibration is normally carried out in EGTA calcium buffer solutions. In the first part of the article the general properties of calcium buffer solutions are discussed, the equations used to calculate the apparent calcium binding constant (Kapp) are derived, and the difficulties in the calculation are discussed. The effects of the purity of EGTA as well as the influence of calcium contamination on the buffer solutions are explained. Because of the difficulties in calculating Kapp, and the importance of EGTA purity and calcium contamination, it is suggested that it is easier to measure all three under the appropriate experimental conditions using the method of Bers (1982). In the second part a do-it-yourself guide to the preparation of EGTA calcium buffer solutions is given. An experimental example is provided using the Bers method to measure purity, contamination, and Kapp. It is concluded that unless all three factors are known it is not possible to prepare accurate EGTA calcium buffer solutions.Key words: Ca buffers, EGTA, CaEGTA, Ca contamination, purity of EGTA.
The effect of high buffer cardioplegia and secondary cardioplegia on cardiac preservation and postischemic functional recovery: a 31P NMR and functional study in Langendorff perfused pig hearts
Authors: Tian Ganghong , Mainwood Graham W. , Biro George P. , Smith Karen E. , Butler Keith W. , Lawrence Dominique , Deslauriers Roxanne
Published: April 2011

High buffer cardioplegia may provide protection against ischemic damage by reducing the extent of intracellular acidosis. Secondary cardioplegia may improve postischemic recovery by restoration of high energy phosphates, ionic gradients, and intracellular pH. To test these hypotheses, pig hearts were arrested with high buffer (150 mM MOPS) cardioplegia or modified St. Thomas' solution II and then kept ischemic at 12 °C for 8 h. High energy phosphates and intracellular pH were followed during the period of ischemia, using 31P nuclear magnetic resonance spectroscopy, and functional recovery was followed during reperfusion. The hearts arrested by high buffer cardioplegia showed significantly higher intracellular pH than hearts preserved with St. Thomas' solution, but there were no significant differences in high energy phosphates. There were no significant differences in functional recovery. We found, however, that secondary cardioplegia abolished ventricular fibrillation, and resulted in improved functional recovery after 8 h of ischemic preservation compared with the hearts reperfused with Krebs–Henseleit solution alone. Our results suggest that despite attenuating the decreases in intracellular pH, high buffer cardioplegia does not improve recovery following 8 h of preservation at 12 °C. Secondary cardioplegia reduces the incidence of ventricular fibrillation and improves postischemic functional recovery of the myocardium.Key words: cardioplegia, secondary cardioplegia, heart preservation, 31P NMR spectroscopy, reperfusion.
Monocyte aryl hydrocarbon hydroxylase (AHH) activity mimics Kupffer cell and hepatocyte AHH activity in an animal model of liver disease
Authors: Peterson T. C. , Williams C. N. , Malatjalian D. A.
Published: April 2011

We have previously reported that monocyte aryl hydrocarbon hydroxylase (AHH) activity is depressed in patients with liver disease and is decreased more in cirrhosis than in early stage liver disease. To determine if monocyte AHH activity reflects liver AHH activity, we studied an animal model of cirrhosis, i.e., yellow phosphorus induced cirrhosis in the pig. AHH activity was detectable in monocytes isolated from peripheral blood of normal pigs (0.32 ± 0.13 nmol∙mg−1 P∙h−1, n = 11) and was comparable to the level of AHH activity in hepatic Kupffer cells isolated from wedge or needle biopsies of livers of normal pigs (0.38 ± 0.21, n = 7). The AHH level in pig Kupffer cells was approximately 10% of the AHH level in hepatocytes and microsomes. To induce liver disease, pigs were administered yellow phosphorus (0.6 mg/kg) 5 days per week for 16 weeks. At 4 weeks of treatment, monocyte AHH activity was not different from control and liver histology was normal. Depression of monocyte AHH activity was evident at 8 weeks of treatment when liver fibrosis was seen histologically. At 12 weeks of treatment when histology revealed extensive liver fibrosis and collagen levels were elevated, the level of monocyte AHH activity was decreased 67% compared with controls. Similar changes were observed at 12 weeks in Kupffer cell AHH activity (86% decrease) and hepatocyte AHH activity (70% decrease) compared with controls. These results suggest that monocyte AHH activity reflects liver AHH activity and may be a good indicator of change in liver enzyme function in liver disease in the pig model of cirrhosis.Key words: aryl hydrocarbon hydroxylase, animal model of liver disease, monocyte, hepatocyte, Kupffer cells.
The effect of pitressin on esophageal blood flow of the dog
Authors: White S. F. , Dinda P. K. , Beck I. T.
Published: April 2011

In a previous study on canine esophagus, we reported that intravenous infusion of isoproterenol caused mucosal (i.e., mucosal + submucosal) vasodilation only in the lower esophageal sphincter (but not in the body) and muscularis vasodilation only in the body (not in the lower esophageal sphincter). In the present study, we have investigated in dogs whether these esophageal tissues also exhibit a similar difference in their vasoconstrictory response to intravenous infusion of pitressin. All measurements were made before (basal) and after infusion of 0.02 U pitressin∙min−1∙kg−1 for 15 min. Pitressin significantly decreased portal venous pressure and blood flow, and increased vascular resistance of all tissues of the esophagus. This vasoconstriction of the tissues, however, was higher in the squamous mucosa of the body than in the columnar mucosa of the lower esophageal sphincter. In contrast, it was higher in the smooth muscle of the lower esophageal sphincter than in the striated muscle of the body. These data together with those of our previous report on isoproterenol demonstrate that pitressin causes a pronounced vasoconstriction in those esophageal tissues where isoproterenol had no effect. Conversely, pitressin causes least vasoconstriction in those tissues where isoproterenol produced a significant vasodilation. These differences could be the result of partial agonist actions or differences in receptor density or in receptor-effector coupling mechanism.Key words: microspheres, portal venous pressure, esophageal body, lower esophageal sphincter.
Effects of serotonin1-like receptor agonists on autonomic neurotransmission
Authors: Park K. H. , Long J. P. , Cannon J. G.
Published: April 2011

Serotonin1A receptor agonists, 8-hydroxy-2-(di-n-propylamino)tetralin and 10-methyl-11-hydroxyaporphine, inhibited electrical stimulation-induced contraction of the guinea-pig ileum. These agonists also inhibited the pressor and tachycardiac responses to low frequency (0.25 Hz) but not to high frequency (2.0 Hz) electrical stimulation of the sympathetic nervous system in pithed rats. Serotonin1B receptor agonist RU 24969 inhibited pressor and tachycardiac responses to both low and high frequencies of stimulation in pithed rats. In the cat nictitating membrane, serotonin1A receptor agonists did not alter contractions elicited by electrical stimulation (0.1–3.0 Hz). Serotonin not only contracted the cat nicitating membrane but also facilitated contractile responses to low frequency (0.1 – 1.0 Hz) stimulation. The contractile effect of serotonin in the cat nictitating membrane was blunted by bretylium, methysergide, and ketanserin, but not by metoclopramide. The facilitatory effect of serotonin was antagonized by methysergide, but not by ketanserin, pindolol, propranolol, or metoclopramide. These results suggest that serotonin1A receptors modulate autonomic neurotransmission in the guinea-pig ileum and pithed rats, but not in the cat nictitating membrane. Serotonin contracts the cat nictitating membrane via serotonin2 subtypes, while facilitating stimulated contractile responses through the serotonin1-like receptors.Key words: guinea-pig ileum, pithed rats, nictitating membrane, serotonin receptors.
Relationship between myeloperoxidase activity and the ontogenic response of rat gastric mucosa to ethanol
Authors: Tepperman B. L. , Besco J. M. , Kiernan J. A. , Soper B. D.
Published: April 2011

We have examined the gastric luminal content of Na+, K+, and protein and mucosal levels of myeloperoxidase in rats between the ages of 10 and 60 days in response to luminal instillation of ethanol (20 and 50% w/v). In control animals the appearances of ions and protein and myeloperoxidase activities were low and similar in all age groups. Luminal content of cations and protein increased in response to both 20 and 50% ethanol and were greater in animals older than 20 days when compared with younger rats. However, ethanol treatment resulted in a significant degree of mucosal cellular disruption and erosions in both young and mature rats. Myeloperoxidase activities in response to ethanol were not greater than control until animals were older than 20 days. Treatment of rats aged 10–60 days with intraperitoneal glycogen (1%) resulted in peritoneal granulocyte infiltration. The concentration of peritoneal cells increased as animals aged. With the exception of day 15, the myeloperoxidase content of the peritoneal leukocytes did not vary significantly at other ages examined. These data suggest that (1) mucosal efflux of Na+, K+, and protein in response to luminal ethanol increase as rats age from 10 to 60 days; (2) the ontogenic development of ethanol-induced cation and protein appearance parallel the increase in myeloperoxidase activity in the gastric mucosa; and (3) the increase in mucosal myeloperoxidase activity in response to ethanol likely reflects increased granulocyte infiltration as rats age.Key words: gastric mucosa, neonate, myeloperoxidase, leukocyte, ethanol.
Energy turnover and the production of ammonium by the kidney: effect of hypernatremia
Authors: Halperin Mitchell L. , Chen Ching-Bun
Published: April 2011

The purpose of this study was to explore further the relation between the rates of oxygen consumption and ammonium (NH4+) production in the kidney during chronic metabolic acidosis. The experimental model was the dog with chronic metabolic acidosis because of the extensive background literature in this species. Chronic metabolic acidosis was produced by the ingestion of 10 mmol NH4Cl/kg body weight for 5 days. There was a significant increase in the rate of oxygen extraction when hypernatremia was present. Despite this rise in the rate of oxygen consumption, there was no increase in the rate of NH4+ production nor in the rate of glutamine extraction. These data suggest that hypernatremia might prevent a further augmentation in glutamine extraction when the rate of oxygen consumption rises. In addition, a larger proportion of the NH4+ produced was excreted in the urine during hypernatremia. This increase was associated with a rise in the urine flow rate, but not with a fall in urine pH.Key words: Acid–base, ATP, glutamine, energy metabolism, metabolic acidosis, metabolic regulation, net acid excretion, oxygen consumption.
Sodium-dependent nucleoside transport in mouse lymphocytes, human monocytes, and hamster macrophages and peritoneal exudate cells
Authors: Baer Hans P. , Moorji A. , Ogbunude P. O. J. , Serignese V.
Published: April 2011

Mouse splenocytes and hamster peritoneal exudate cells (PEC), including macrophages, were shown to contain a predominantly Na+-dependent and inhibitor (6-[(4-nitrobenzyl)-mercapto]purine ribonucleoside, NBMPR)-resistant transport system for adenosine and other nucleosides. Adenosine (1 μM) was transported about equally in mouse thymocytes and human monocytes from peripheral blood by a Na+-dependent system and the NBMPR-sensitive facilitated diffusion system. Hamster PEC also transported inosine, tubercidin, formycin B, uridine, and thymidine in a NBMPR-insensitive manner. With the exception of formycin B, all nucleosides were phosphorylated intracellularly to varying degree, adenosine being almost fully phosphorylated. During the time course of routine experiments (30 s) formycin B was concentrated twofold over external medium levels (1 μM) without any drop-off in the transport rate. On the basis of metabolic studies it was estimated that uridine and tubercidin were also transported against a concentration gradient. Inosine, guanosine, 2′-deoxyadenosine, tubercidin, formycin B, and the pyrimidines uridine, thymidine, and cytidine (all 100 μM) inhibited transport of adenosine and inosine about 50–100%, while 3′-deoxyinosine showed weak inhibitory action. Transport of thymidine was strongly inhibited by nucleosides except by 3′-deoxyinosine. The Na+-dependent, active, and concentrative transport system appears to be a feature of many immune-type cells, and its presence offers particular conceptual possibilities for the therapy of infections located in these cells.Key words: immune cells, macrophage, nucleoside transport, sodium dependence, nucleoside analogs.
Cardiovascular and norepinephrine responses of men and women to two cold pressor tests
Authors: McLean J. K. , Sathasivam P. , MacNaughton K. , Graham T. E.
Published: April 2011

Two types of cold pressor tests were used to study gender differences in cardiovascular and plasma catecholamine responses. Ten male and ten female, young, healthy Caucasian subjects participated. The tests consisted of (1) 5 °C air blown at 3.5–4 m/s onto part of the face for 4 min and (2) the open right hand immersed to the wrist in water at 5 °C for 4 min. Heart rate, blood pressure (BP), and venous plasma norepinephrine were collected before, during, and 5 min after the 4 min of cold exposures. Test order was decided by a Latin square design, and the subjects rested in a quiet room for 30 min between the two tests. All parameters demonstrated significant (p < 0.01) increases from rest during the cold tests. Gender differences were significant (p < 0.01) in diastolic and systolic BP in each test with the males having a greater response, but gender differences were not found in heart rate or norepinephrine concentration. The study demonstrated that gender differences exist in the blood pressure responses to local cold, but that the mechanisms involved do not include a parallel difference in heart rate or venous plasma norepinephrine concentration.Key words: blood pressure, gender differences, stroke volume.
A study of some potential correlates of the hypotensive effects of prolonged submaximal exercise in normotensive men
Authors: Landry Jean-François , Després Jean-Pierre , Prud'homme Denis , Lamarche Benoît , Tremblay Angelo , Nadeau André , Bouchard Claude
Published: April 2011

This study was undertaken (1) to examine the relation of plasma catecholamine and insulin levels to the blood pressure response during and after submaximal exercise, (2) to verify whether the blood pressure response to an epinephrine infusion is associated with the blood pressure response to a prolonged submaximal exercise, and (3) to study some potential correlates of the hypotensive effect of prolonged aerobic exercise. Nine normotensive young men (mean age 22.0 ± 1.4 years) were subjected to a 1-h epinephrine infusion protocol and a 1-h submaximal exercise test on a cycle ergometer. The two tests were performed 1 week apart. The physiological and hormonal responses observed during the submaximal exercise test were generally greater than those observed during the epinephrine infusion test. Blood pressure responses in both tests showed no significant association with changes in plasma insulin levels. Changes in plasma norepinephrine concentration were positively correlated with changes in systolic blood pressure during the submaximal exercise test but not during the epinephrine infusion. Results also showed that the blood pressure response to epinephrine infusion was not correlated with the blood pressure response to submaximal exercise. However, post-exercise and post-infusion systolic blood pressure responses (differences between "post-test" and "resting" values) were significantly associated (r = 0.81, p < 0.01). In addition, a significant hypotensive effect of submaximal exercise was observed for both systolic and diastolic blood pressure. However, the individual differences observed in the hypotensive effect of aerobic exercise appeared to be more related to variations in vascular sensitivity than to exercise-induced variations in plasma insulin and catecholamine levels, at least in this sample of healthy normotensive young men.Key words: blood pressure, exercise, catecholamines, insulin, epinephrine infusion.
Responses of pulmonary C-fibre and rapidly adapting receptor afferents to pulmonary congestion and edema in dogs
Authors: Ravi K. , Kappagoda C. T.
Published: April 2011

The effects of cardiogenic and noncardiogenic pulmonary edema on the activities of rapidly adapting receptors (RARs) and pulmonary C-fibre receptors were investigated in dogs anaesthetized with chloralose. Cardiogenic pulmonary edema was produced by elevating the mean left atrial pressure by 25 mmHg (1 mmHg = 133.32 Pa) above the control value for a period of 45 min, by partial obstruction of the mitral valve. Noncardiogenic pulmonary edema was produced by injecting alloxan (100 mg/kg) intravenously. The effect of the latter was examined on RARs alone. Cardiogenic edema activated RARs (n = 8) and the activity was greatest during the first few minutes after elevation of mean left atrial pressure. The pulmonary C-fibre receptors (n = 6) were also activated by cardiogenic edema, but these responses were variable. Noncardiogenic pulmonary edema also activated RAR (n = 6), and this response was maintained during the entire recording period (20 min). The extravascular lung water (%), measured 15 min (n = 5) and 45 min (n = 5) after the elevation of the mean left atrial pressure, was significantly elevated above control values. However, these two values were not significantly different from each other. The extravascular lung water increased significantly after the injection of alloxan also (n = 5). These results show that during pulmonary edema, there is significant stimulation of the RARs and the pulmonary C-fibre receptors. It is suggested that the reflex respiratory responses observed in pulmonary edema may be due to the activation of both the RARs and the pulmonary C-fibre receptors.Key words: alloxan, cardiogenic edema, vagus.
Dietary sodium restriction and the development of two-kidney, one-clip hypertension in young versus adult rats
Authors: Wilczynski Esther A. , Yuan Baoxue , Leenen Frans H. H.
Published: April 2011

To determine the effects of moderate versus severe dietary sodium restriction on the development of 2-kidney, 1-clip (2K,1C) hypertension, young male Wistar rats were placed on diets containing 9, 26, or 101 (control) μmol sodium/g food. Three days later, a solid silver clip (i.d. 0.20 mm) was placed on the left renal artery and diets were continued up to 6 weeks. Adult rats received a 0.25-mm clip. In young clipped rats receiving the 101 μmol/g diet, blood pressure (BP), plasma renin activity (PRA), and BP response to captopril were increased as early as 1 week after clipping and increased further over time. Moderate sodium restriction (26 μmol sodium/g) led to only a slight delay in the development of hypertension; the levels of BP and PRA, the BP response to captopril, and the extent of cardiac hypertrophy achieved by 6 weeks were not different between the 2K,1C rats receiving 26 or 101 μmol sodium/g. Sodium restriction to 9 μmol/g decreased rate of growth and completely prevented the rise in BP and in left ventricular weight. At 3 and 6 weeks the severely sodium-restricted rats had significantly higher PRA levels than the 2K,1C control group. However, the BP response to captopril was attenuated relative to the other hypertensive groups. In adult rats, this level of sodium restriction had a small, but significant effect on body weight, but still prevented the increase in BP and in left ventricular weight. In conclusion, dietary sodium restriction can prevent the development of 2K,1C hypertension in both young and adult rats, but only if the restriction is severe. This effect may relate to a marked reduction in the pressor effectiveness of the renin–angiotensin system by low sodium intake per se or by associated metabolic or other changes.Key words: dietary sodium, age, renin–angiotensin system, renal hypertension, angiotensin converting enzyme inhibition.
Activation of smooth muscle in the airway wall, force production, and airway narrowing
Authors: Sparrow M. P. , McFawn P. K. , Omari T. I. , Mitchell H. W.
Published: April 2011

Airway narrowing depends on smooth muscle force production and muscle shortening, but the structural and geometric properties exhibited by individual generations of the bronchial tree largely determine the extent and characteristics of airway narrowing. Properties of major importance include the nature and integrity of the epithelium, the structural and mechanical properties of the airway wall, as well as airway diameter. The influence of these properties on airway narrowing measured as flow or flow resistance in large and small diameter segments of airways from pig lung is described using a novel preparation, the perfused bronchial segment.Key words: airway narrowing, bronchi, smooth muscle, epithelium.
Effects of inflammatory mediators on canine airway neuromuscular function
Authors: Daniel E. E. , Abela A. P. , Janssen L. J. , O'Byrne P. M.
Published: April 2011

Inflammatory mediators can both enhance or inhibit canine airway reactivity. PGE2 and PGI2 in general are inhibitory, interfering with release of acetylcholine and with responses to bronchoconstrictors. These prostaglandins may be more effective against agonists that open voltage-dependent Ca2+ channels to induce Ca2+ influx and contraction compared with those agonists that release internal Ca2+. Other mediators are excitatory: histamine, PGD2, thromboxane A2 (TxA2), and leukotrienes (LT) C4, D4, and E4. In canine airway only histamine and TxA2 have effects in the absence of indomethacin, i.e., in the presence of the large amounts of PGE2 and PGI2 produced in vitro LTs are ineffective. Effects of TxA2 and histamine may be potentiated if the synthesis of these inhibitory PGs is inhibited. Whether histamine or TxA2 normally promote synthesis and release of PGE2 and PGI2 in a kind of homeostasis remains to be explored. It is also unclear whether pre- as well as post-junctional TxA2 receptors exist and have different pharmacological sensitivities to antagonists. LTC4 and LTD4 also constrict canine bronchi but only when PGE2 and PGI2 synthesis is blocked and, again, whether this is a result of LT-induced release of inhibitory mediators is unknown. The concept that airway responsiveness can be caused by turning off PGE2 and PGI2 production and turning on TxA2 or LT production (or unmasking their actions) needs further exploration. Our recent data suggest that such a mechanism may explain ozone-induced responsiveness in dogs.Key words: histamine, thromboxane A2, leukotrienes C4 and D4, PGE2, PGI2.
Influence of arachidonic acid metabolites on cardiac α1-adrenoceptor responses in diabetic rats
Authors: Xiang Hong , McNeill John H.
Published: April 2011

There is evidence that one or more metabolites of arachidonic acid can produce positive inotropic effects and may also be implicated in the enhanced α1-adrenoceptor responses in hearts from diabetic rats. We therefore carried out a study to investigate the possibility that arachidonic acid metabolites could be involved in the altered cardiac α1 -effect of norepinephrine (in the presence of propranolol) in chronic streptozotocin-diabetic rats. Our results have shown that in the presence of the cyclooxygenase inhibitor indomethacin or the thromboxane synthetase inhibitor imidazole, the norepinephrine-stimulated positive inotropic effect and the formation of inositol 1,4,5-trisphosphate were significantly increased in control hearts but were unaltered in hearts from diabetic rats. The addition of the prostacyclin synthetase inhibitor tranylcypromine reduced the norepinephrine-stimulated positive inotropic effect and inositol 1,4,5-trisphosphate formation only in diabetic hearts and had no effect in the controls. The nature and physiological significance of the enhanced positive inotropic effect and inositol 1,4,5-trisphosphate formation in the control heart with the addition of indomethacin and imidazole are still unclear. The effect of tranylcypromine may indicate the participation of prostacyclin in mediating the enhanced α1-inotropic effect of norepinephrine in the chronic diabetic heart.Key words: norepinephrine, positive inotropic effect, inositol 1,4,5-trisphosphate.
Neuronal regulation of renal function: A model system for nervous system interactions
Authors: Wyss J. Michael
Published: April 2011

The kidney is the most highly innervated peripheral organ, and both the excretory and endocrine functions of the kidney are regulated by renal nerve activity. The kidney plays a dominant role in body fluid homeostasis, blood ionic concentration, and pH and thereby contributes importantly to systemic blood pressure control. Early studies suggested that the neural-renal interactions were responsible only for short-term adjustments in renal function, but more recent studies indicate that the renal nerves may be a major contributor to chronic renal defects leading to established hypertension and (or) renal disease. The neural-renal interaction is also of considerable interest as a model to elucidate the interplay between the nervous system and peripheral organs, since there is abundant anatomical and physiological information characterizing the renal nerves. The investigator has easy access to the renal nerves and the neural influence on renal function is directly quantifiable both in vivo and in vitro. In this symposium that was presented at the 1990 annual convention of the Society for Neuroscience in St. Louis, Missouri, three prominent researchers evaluate the most recent progress in understanding the interplay between the nervous system and the kidney and explore how the results of these studies relate to the broader questions concerning the nervous system's interactions.First, Luciano Barajas examines the detailed anatomy of the intrarenal distribution of the efferent and afferent renal nerves along the nephron and vasculature, and he evaluates the physiological role of each of the discrete components of the innervation. His basic science orientation combined with his deep appreciation of the clinical consequence of the failure of neural-renal regulation enhances his discussion of the anatomy. Ulla C. Kopp discusses the role of the renorenal reflex, which alters renal responses following stimulation of the contralateral kidney. She also considers her recent findings that efferent renal nerve activity can directly modify sensory feedback to the spinal cord from the kidney. Finally, J. Michael Wyss examines the functional consequences of neural control of the kidney in health and disease. Although the nervous system has often been considered as only an acute regulator of visceral function, current studies into hypertension and renal disease suggest that neural-renal dysfunction may be an important contributor to chronic diseases.Together, these presentations examine most of the recent advances in the area of neural-renal interactions and point out how these data form a basis for future research into neuronal interactions with all visceral organs. The relative simplicity of the neural-renal interaction makes this system an important model with which to elucidate all neural-peripheral and neural-neural interactions.
Anatomy of the renal innervation: intrarenal aspects and ganglia of origin
Authors: Barajas Luciano , Liu Li , Powers Kenneth
Published: April 2011

The intrinsic innervation of the kidney is described based on studies using ultrastructural, fluorescent, immunocytochemical, and autoradiographic techniques. The efferent sympathetic innervation reaches all the segments of the renal vasculature and to a much lesser extent the tubular nephron. The afferent renal nerves are localized predominantly in the pelvic region, the major vessels, and the corticomedulary connective tissue. The pathways of the renal innervation to the corresponding ganglia, as reported from observations resulting from the combination of axonal transport labeling and immunocytochemical methods, are presented. In the rat the ganglia of origin of the sympathetic efferent innervation include T13–L1 ipsilateral and contralateral paravertebral ganglia and the prevertebral superior mesenteric and celiac ganglia. The sensory afferent innervation presents a different segmental distribution of the dorsal root ganglia for the right and left kidney. For the left kidney, the corresponding ganglia extend from T8 to L2 with the greatest numbers in T12 and T13. For the right kidney, ganglia as high as T6 and as low as L2 harbor neurons innervating the kidney. Current knowledge of the anatomical bases of the function of the renal nerves is discussed.Key words: autoradiography, immunocytochemistry, electron microscopy, axonal transport labeling.
Neuronal control of the kidney: Contribution to hypertension
Authors: Wyss J. Michael , Oparil Suzanne , Sripairojthikoon Wanida
Published: April 2011

The renal nerves contribute to hypertension in experimental models of the disease, and appear to play a role in human hypertension. Several lines of evidence indicate that both in spontaneously hypertensive rats and in deoxycorticosterone acetate–NaCl rats, the full development of hypertension is dependent on renal efferent nerves and their induction of excess sodium retention. Renal sensory (afferent nerve) feedback to the central nervous system does not contribute to either of these forms of hypertension. In contrast, renovascular hypertension in rats and aortic coarctation hypertension in dogs are mediated, at least in part, by overactivity of renal afferent nerves and a resultant increase in systemic sympathetic nervous system activity. These forms of hypertension are not associated with sodium retention, and selective sensory denervation of renal afferent nerves by dorsal rhizotomy and total renal denervation result in similar reductions in hypertension. Surprisingly, the renal nerves do not contribute to dietary NaCl exacerbated hypertension in the spontaneously hypertensive rat, dietary NaCl-induced hypertension in the Dahl NaCl-sensitive rat, or the chronic hypertensive and nephrotoxic effects of cyclosporine A therapy in the rat, despite the finding that in all three forms of hypertension, overactivity of the sympathetic nervous system is prominent. Clinical studies indicate that the renal afferent and efferent nerves contribute to hypertension of different etiologies. Together these data point to the complex role that the renal nerves likely play in human essential hypertension.Key words: kidney, cyclosporine, spontaneously hypertensive rat, renal deafferentation, renal denervation.
Ca2+ transport through the brush border membrane of human placenta syncytiotrophoblasts
Authors: Brunette M. G. , Leclerc M.
Published: April 2011

The calcium (Ca2+) uptake by brush border membrane vesicles isolated from fresh human placentas has been characterized. This process was saturable and time- and concentration-dependent. It exhibited a double Michaelis–Menten kinetics, with apparent Km values of 0.17 ± 0.03 and 2.98 ± 0.17 mM Ca2+, and Vmax values of 0.9 ± 0.13 and 2.51 ± 0.45 pmol∙μg−1∙5 s−1. It was not influenced by the presence of Na+ or Mg2+ in the incubation medium. It was not increased by K+ or anion diffusion potentials, inside negative. At a steady state of 1 mM Ca2+ uptake, a large proportion (approximately 94%) of the Ca2+ was bound to the internal surface of the membranes. Preincubation of these membrane vesicles with voltage-dependent Ca2+ channel blockers (nifedipine and verapamil) had no influence on Ca2+ uptake. However, this uptake was very sensitive to pH. In the absence of a pH gradient, the Ca2+ uptake increased with alkalinity. When the intravesicular pH was kept constant while the pH of the incubation medium was increased, Ca2+ uptake was also stimulated by alkaline pH. In contrast, when the pH of the incubation medium was kept constant and the intravesicular pH was progressively increased, Ca2+ uptake was diminished with alkaline pH. Therefore, H+ gradient (H+ in trans-position > H+ in cis-position) favored Ca2+ transport, suggesting a H+/Ca2+ exchange mechanism. Finally, in contrast to the basal plasma membrane, the brash border membrane did not show any ATP-dependent Ca2+ transport activity.Key words: calcium transport, brush border membranes, placenta.
Differences in myocardial ischemic tolerance between 1- and 7-day-old rabbits
Authors: Lopaschuk Gary D. , Spafford Marguerite A.
Published: April 2011

Between 1 and 7 days of life, the newborn rabbit heart shifts from predominantly using carbohydrates to predominantly using fatty acids as an energy substrate. We therefore used isolated working hearts from 1- or 7-day-old rabbits to determine the effects of fatty acids on myocardial glucose use and the ability of hearts to recover following various periods of transient no-flow ischemia. One-day-old hearts were perfused via the inferior vena cava and ejected buffer through the cannulated aorta and pulmonary artery. Seven-day-old hearts were perfused via the left atrium and ejected buffer through the cannulated aorta. To measure glucose use, hearts were perfused with 11 mM [3H,14C]glucose, 3% albumin, and 500 μU insulin/mL, in the presence or absence of 0.4 mM palmitate. In the absence of fatty acids, glycolytic rates were similar in 1- and 7-day-old hearts, whereas glucose oxidation rates were 5 times greater in 7-day-old hearts. Palmitate did not have any major effects on overall glucose use in 1-day-old hearts, but did markedly inhibit glycolysis and glucose oxidation in 7-day-old hearts. A series of hearts were also subjected to periods (25–60 min) of no-flow ischemia, followed by 30 min of aerobic reperfusion. In the absence of palmitate, 1-day-old hearts subjected to ischemic periods of up to 60 min recovered some degree of mechanical function during reperfusion, whereas 7-day-old rabbit hearts failed to recover if hearts were subjected to ischemic periods of 35 min or longer. Palmitate did not affect reperfusion recovery of 1-day-old rabbit hearts, but did improve recovery of 7-day-old hearts subjected to 40 min of ischemia. This effect in 7-day-old hearts was accompanied by a decrease in tissue lactate during ischemia. In 1-day-old hearts, a greater increase in lactate levels at the end of ischemia was seen, compared with 7-day-old hearts, and the increase was unaffected by the presence or absence of palmitate. These results demonstrate that the sensitivity of the rabbit heart to ischemia increases in the 1st week after birth. This increased sensitivity may be related to a combination of a decrease in glycolytic rates and an increase in sensitivity of hearts to glycolytic product accumulation during ischemia.Key words: newborn, ischemia, heart, fatty acids, glucose.
Effect of streptozotocin diabetes on motor and inhibitory transmission in rat anococcygeus
Authors: Luheshi G. N. , Zar M. A.
Published: April 2011

The effect of streptozotocin diabetes of 4-week duration on the adrenergic motor transmission and on the nonadrenergic, noncholinergic, inhibitory transmission in the rat anococcygeus was investigated by recording contractile and relaxant activity of isolated muscle preparations taken from diabetic and age-matched control animals. The neurogenic contractile responses to electrical field stimulation were significantly reduced in the preparations from diabetic rats. The inhibitory transmission remained unaffected in the diabetic rats. Concentration–response curves showed no change in sensitivity of the diabetic anococcygei to noradrenaline. The maximum tension generated was also similar in preparations from diabetic and nondiabetic animals. The contractile responses to electrical field stimulation were significantly greater in preparations from diabetic rats treated for 4 weeks with either sorbinil (20 mg∙kg−1∙day−1 orally) or myo-inositol (667 mg∙kg−1∙day−1 orally) when compared with the untreated diabetic controls; the sensitivity to noradrenaline was identical in all three groups. It is concluded that streptozotocin diabetes causes a significant reduction of adrenergic contractile responses of the anococcygeus to electrical field stimulation by a prejunctional mechanism, and the reduction can be prevented by treating the animals with the aldose reductase inhibitor sorbinil or with myo-inositol.Key words: streptozotocin; autonomic neuropathy; adrenergic transmission; nonadrenergic, noncholinergic transmission; sorbinil; myo-inositol.
Incidence of multinucleated and polyploid aortic smooth muscle cells cultured from different age groups of spontaneously hypertensive rats
Authors: Lee Robert M. K. W. , Conyers Roop B. , Kwan Chiu-Yin
Published: April 2011

Cell size and incidence of multinucleated, polyploid cells in cultured aortic smooth muscle cells from different age groups of spontaneously hypertensive rats (SHR) and normotensive Wistar–Kyoto rats (WKY) were compared. Smooth muscle cells from SHR were generally larger than those from WKY, and the percentage of multinucleated smooth muscle cells was always higher in SHR than WKY in the three age groups of rats studied (3–4, 10–12, and 28–30 weeks). In smooth muscle cells from the 3- to 4-week group, there was a positive correlation between cell diameter and the percentage of multinucleated smooth muscle cells. Microdensitometric measurements also showed that the incidence of polyploid smooth muscle cells was always higher in SHR than WKY in the three age groups. There was a positive correlation between DNA density and nuclear area measurements in all the age groups of SHR and WKY. We conclude that cultured aortic smooth muscle cells from different age groups of SHR and WKY contained heterogeneous populations of cells and that, under our culture conditions, the polyploidy of the smooth muscle cells found in vivo was maintained in the SHR and WKY.Key words: hypertension, cultured smooth muscle cells, aorta, polyploidy.
Absence of hepatic p-nitrophenol UDP-glucuronosyltransferase induction by spironolactone in male rats: possible involvement of testosterone
Authors: Catania Viviana A. , Luquita Marcelo G. , Pozzi Enrique J. Sánchez , Ferri Alejandro M. , Mottino Aldo D.
Published: April 2011

This study was performed to determine whether the lack of spironolactone induction of hepatic p-nitrophenol UDP-glucuronosyltransferase in male rats could be attributed to a presumed interaction between spironolactone and testosterone. The effect of spironolactone was evaluated in four experimental groups: normal females, normal males, castrated males, and castrated males that received testosterone. Enzyme activity was measured in native microsomes and in microsomes activated with UDP-N-acetylglucosamine or Triton X-100. When the nucleotide was included in the incubations, it was observed that enzyme activity in castrated male rats decreased to values approaching those obtained in normal females. Treatment of castrated animals with testosterone enhanced enzyme activity so that no significant difference existed between this group and normal males. This suggests that testosterone may act as an endogenous inducer of hepatic p-nitrophenol glucuronidation. It was also found that only females and castrated males showed an increase in enzyme activity in response to spironolactone treatment. Thus, the absence of an additive effect of endogenous or exogenous testosterone and spironolactone on UDP-glucuronosyltransferase activity suggests that these compounds could share a common induction mechanism, which appears to reach its maximal capacity in male rats. Possible explanations of this observation are discussed. From the analysis of enzyme activity in native and Triton X-100 activated microsomes, it can be postulated that spironolactone enzyme induction in female and castrated male rats could be attributed to an enhancement in the transferase synthesis rather than to an alteration of the membrane environment.Key words: UDP-glucuronosytransferase, spironolactone, enzyme induction, testosterone, p-nitrophenol.
Low concentrations of hydrogen sulphide alter monoamine levels in the developing rat central nervous system
Authors: Skrajny B. , Hannah R. S. , Roth S. H.
Published: April 2011

The central nervous system is one of the primary target organs for hydrogen sulphide (H2S) toxicity; however, there are limited data on the neurotoxic effects of low-dose chronic exposure on the developing nervous system. Levels of serotonin and norepinephrine in the developing rat cerebellum and frontal cortex were determined following chronic exposure to 20 and 75 ppm H2S during perinatal development. Both monoamines were altered in rats exposed to 75 ppm H2S compared with controls; serotonin levels were significantly increased at days 14 and 21 postnatal in both brain regions, and norepinephrine levels were significantly increased at days 7, 14, and 21 postnatal in cerebellum and at day 21 in the frontal cortex. Exposure to 20 ppm H2S significantly increased the levels of serotonin in the frontal cortex at day 21, whereas levels of norepinephrine were significantly reduced in the frontal cortex at days 14 and 21, and at day 14 in the cerebellum.Key words: hydrogen sulphide, monoamines, serotonin, norepinephrine, neurotoxicity.