1. Alanine accumulation in rat hemidiaphragms is significantly inhibited by capsaicin in a dose-d... more 1. Alanine accumulation in rat hemidiaphragms is significantly inhibited by capsaicin in a dose-dependent pattern that produced maximal effect at 1 mM. 2. The inhibitory effect of capsaicin on alanine accumulation by rat hemidiaphragms was enhanced upon preincubation with 5 mM ouabain. However, preincubation with 1 mM Verapamil did not alter the inhibitory effect of capsaicin. 3. Chemical ablation of the capsaicin-sensitive primary afferent fibers abolished the inhibitory effect of capsaicin on alanine accumulation in the rat hemidiaphragms.
Intestinal nutrient transport is altered in response to changes in dietary conditions and luminal... more Intestinal nutrient transport is altered in response to changes in dietary conditions and luminal substrate level. It is not clear, however, whether an amino acid in the intestinal lumen can acutely affect its own absorption from a distant site. Our aim is to study the effect of an amino acid present in rat small intestinal segment on its own absorption from a proximal or distal site and elucidate the underlying mechanisms. The effect of instillation of alanine (Ala) in either jejunum or ileum on its own absorption at ileal or jejunal level was examined in vivo. The modulation of this intestinal regulatory loop by the following interventions was studied: tetrodotoxin (TTX) added to Ala, subdiaphragmatic vagotomy, chemical ablation of capsaicin-sensitive primary afferent (CSPA) fibers, and IV administration of calcitonin gene-related peptide (CGRP) antagonist. In addition, the kinetics of jejunal Ala absorption and the importance of Na+-dependent transport were studied in vitro after...
International journal for innovation education and research, 2021
Objectives: The authors analyzed the weaknesses and areas of opportunities with the online teachi... more Objectives: The authors analyzed the weaknesses and areas of opportunities with the online teaching imposed by the COVID19 lockdown, and the new measures adopted to control the online examinations for medical students. Method: In addition to personalized question sets we had location mapping and Open Broadcaster Software (OBS) for monitoring students during the exams as well as disabling the back-button during examination. Results: The academic year was successfully completed on time. There was no change in the exams format or scope, yet the results were similar in terms of grade distribution, average and standard deviation as well as the validity and reliability scores. The students’ perception of online teaching was evaluated through a survey. It revealed the importance and added value of online teaching but also exposed the gaps related to lecturers’ preparedness and need for training. Conclusion: The online experience was a valuable lesson for us, as we discovered not only the...
The main function of the colon is water and electrolyte absorption. Total colectomy eliminates th... more The main function of the colon is water and electrolyte absorption. Total colectomy eliminates this colonic function and may alter the absorptive capacity of the small intestine for nutrients. This study examines the effect of total colectomy on jejunal glucose absorption and investigates the potential role of aldosterone in mediating the alterations in glucose uptake post-colectomy using the aldosterone antagonist spironolactone. Total colectomy with ileo-rectal anastomosis was performed on anesthetized rats. Sham rats were identically handled without colon resection. Two days post-surgery, groups of colectomized rats were injected with either a daily subcutaneous dose of spironolactone or sesame oil for 12days. Body weight changes and food and water intake were measured in all experimental groups. Glucose absorption was measured by in-vivo single pass perfusion in the rat jejunum of control, sham, colectomized, colectomized with spironolactone, and colectomized with sesame oil treatment. Na/K ATPase, SGK1, SGLT1 and GLUT2 expressions were determined in jejunal mucosa in control, colectomized and colectomized/spironolactone injected rats by Western blot analysis. Histological assessment was performed on jejunal sections in control and colectomized groups. Glucose absorption significantly increased in colectomized rats with an observed increase in Na/K ATPase and SGK1 expression. No significant expression change in SGLT1 and GLUT2 was detected in the jejunum in colectomized rats. Spironolactone, however, significantly decreased the glucose uptake post-colectomy and normalized Na/K ATPase and SGK1 expression. Our results suggest that jejunal glucose uptake increases post-colectomy as a possible consequence of an aldosterone-mediated function.
The in vitro effects of a local anesthetic, a membrane active drug, procaine, on some functional ... more The in vitro effects of a local anesthetic, a membrane active drug, procaine, on some functional activities of circulating human lymphocytes and monocytes were studied. Procaine inhibited spontaneous E-rosette formation between T-lymphocytes and sheep erythrocytes and EAC-rosettes with B-lymphocytes. In addition, procaine inhibited both the phagocytosis of latex particles by normal monocytes and the proliferation of lymphocytes in an allogeneic mixed leukocyte culture. Morphologically the procaine-treated cells exhibited a relative increase in the size of the cytoplasmic rim around their nuclei. The results indicated that procaine might be considered as a non-specific immunoregulator, modulating to some extent the functional expression of human peripheral blood mononuclear cells activities.
It was recently shown that vasoactive intestinal polypeptide (VIP) inhibits rat jejunal alanine a... more It was recently shown that vasoactive intestinal polypeptide (VIP) inhibits rat jejunal alanine absorption, an effect that was significantly reduced by vagotomy. This study assesses the role of capsaicin-sensitive primary afferents (CSPA) and the myenteric plexus in the inhibition of rat jejunal alanine absorption by VIP. Continuous intravenous infusion of VIP (11.2 ng . kg-1 . min-1) reduced alanine absorption by 60% in sham control rats and by 20% in rats neonatally treated with capsaicin (P < 0.01). In in vitro experiments, VIP decreased alanine uptake by jejunal strips isolated from sham control rats in a dose-dependent manner. In the presence of 40 nM VIP, alanine uptake by full-thickness jejunal strips was reduced by 54% in sham control rats and by 25% in rats neonatally treated with capsaicin (P < 0.001). On the other hand, VIP reduced alanine uptake by mucosal scrapings by 25% in sham rats compared with 9% reduction in neonatally treated rats. Chemical ablation of the ...
Comparative biochemistry and physiology. A, Comparative physiology, 1988
1. The effect of colchicine, cytochalasin-B and procaine on calcium transport across the rat smal... more 1. The effect of colchicine, cytochalasin-B and procaine on calcium transport across the rat small intestine was investigated. The results obtained show the following: 2. Colchicine and cytochalasin-B at different concentrations inhibited significantly (P less than 0.001) calcium accumulation in rat intestinal cells, whereas procaine at different concentrations increased significantly (P less than 0.001) calcium accumulation in the rat small intestine. 3. Unidirectional influx of calcium across the rat small intestine was significantly inhibited (P less than 0.01) in the presence of colchicine and cytochalasin-B in the preincubation medium. Procaine, on the other hand, caused a significant increase (P less than 0.01) in the unidirectional influx of calcium across the rat intestinal cells. 4. The cell water content was not altered in the presence of the different drugs indicating that the changes in calcium transport across the rat intestinal cells are not due to alterations in the s...
Abutract-l. The effect of aminophylline and terbutaline sulfate, separately and in combination, o... more Abutract-l. The effect of aminophylline and terbutaline sulfate, separately and in combination, on the contractility of the feline diaphragm was investigated. 2. Diaphragmatic contractility increased significantly (P < 0.05) to 28.3% above control level as long as theophylline plasma levels were maintained between 10-20 mg/l (mean 13.9 + 0.8 rag/l). 3. Diaphragmatic contractility showed a significant (P < 0.05) 41.5% increase after i.v. administration of terbutaline sulfate as a maintenance dose of 1.4/~g/kg-hr, and the increase leveled off after 180 rain. 4. Administering the two drugs in combination showed a significant (P < 0.05) 27.3% increase which suggests a non-synergistic effect of aminophylline and terbutaline sulfate on diaphragmatic contractility. 5. By enhancing the contractility of the diaphragm, aminophylline and terbutaline sulfate may improve the clinical status of patients with airway obstructive diseases and help in preventing respiratory muscle fatigue.
The effects of motilin on proline absorption and gastric and biliary secretions were examined in ... more The effects of motilin on proline absorption and gastric and biliary secretions were examined in the rat. Prolonged intravenous administration of motilin (50 pmol/kg/min) significantly inhibited (P<0.05) proline transport across the jejunum and reduced basal acid secretion to 40~o of control value. The same concentration of motilin induced choleresis and increased bile output by 32~o. Incubation of intestinal strips with different concentrations of motilin produced a dose-dependent inhibitory pattern of proline accumulation in the intestinal cells.
The effect of terbutaline sulfate on calcium transport across muscle strips isolated from rat dia... more The effect of terbutaline sulfate on calcium transport across muscle strips isolated from rat diaphragms, and its effect on this process when used in combination with aminophylline was investigated using labelled calcium in a two-compartment system. 2. The results show that terbutaline sulfate causes a dose-dependent increase in intracellular calcium concentration which reached saturation at a terbutaline sulfate concentration of 2 ng/ml. 3. The inclusion of both aminophylline and terbutaline sulfate at a concentration range of 6.25-50/~g/ml and 0.5-4 ng/ml respectively in the incubation medium, did not show a synergistic effect on intracellular calcium accumulation. 4. Although verapamil, a calcium channel blocker, inhibited significantly (P < 0.01) calcium accumulation in the muscle strips of the diaphragm, it did not inhibit completely the increase in intracellular calcium concentration noticed in the presence of aminophylline or terbutaline sulfate. 5. This would suggest that aminophylline and terbutaline sulfate have an effect on the calcium channels in the muscle strips of the diaphragm.
The effect of neurotensin (NT) on proline absorption across rat jejunum was investigated using th... more The effect of neurotensin (NT) on proline absorption across rat jejunum was investigated using the singlepass perfusion technique. This study showed that intravenous administration of NT produced a dose-dependent inhibition of proline absorption. Thus, NT at a 0.16 pmol/kg/min concentration gave 10~o decrease in proline absorption while 0.32 and 1.6 pmol/kg/min concentration gave 317o and 45?0 decrease, respectively. In the absence of Na, proline absorption decreased to 77~ o from control values. No change in proline absorption was noticed when NT at a concentration of 0.32 pmol/kg/min was intravenously injected in the absence of sodium from the perfusion solution. Water absorption did not show significant changes (P> 0.05) in presence or absence of NT. Moreover, NT did not produce a significant change (P> 0.2) in intracellular proline accumulation. NT inhibited proline absorption through an indirect mechanism that is Na-dependent and independent of changes in water absorption.
The effect of chlorpromazine on proline absorption across jejunum in anaesthetized rats was inves... more The effect of chlorpromazine on proline absorption across jejunum in anaesthetized rats was investigated. Intravenous infusion of chlorpromazine reduced significantly (P<0 .01) proline absorption across the jejunum. Intraluminal perfusion of chlorpromazine into the jejunal segment reversed net absorption of proline to net secretion. Net water absorption was increased significantly (P<0 .01) when chlorpromazine was infused intravenously or perfused intraluminally. Unidirectional influx of proline across the mucosal surface was significantly inhibited (P<0 .01) after preincubation with 1 mm chlorpromazine .
Pyridoxine binding to liver plasma membrane isolated from livers of normal and streptozotocin-ind... more Pyridoxine binding to liver plasma membrane isolated from livers of normal and streptozotocin-induced diabetic rats was investigated. The effect of increasing concentration of pyridoxine on its binding to the membranes revealed a concentration-dependent and saturable process with a significant decrease in the high affinity receptor sites of the diabetic membrane. Moreover, the incubation of the membranes with procaine, colchicine and
The effect of digoxin on calcium transport across muscle strips isolated from rat diaphragms was ... more The effect of digoxin on calcium transport across muscle strips isolated from rat diaphragms was investigated. 2. Digoxin at concentrations ranging between 0.2-5.0 ng/ml in the incubation solution increased significantly (P < 0,5) intracellular calcium in the diaphragm muscle strips in a dose-dependent pattern. 3. The inclusion of digoxin (2 ng/ral) and aminophylline (18.75 g g/ml) in the incubation medium showed a significant increase (P < 0.001) in calcium uptake suggesting a synergistic effect on intracellular calcium accumulation. 4. The presence of digoxin with verapamil in the incubation medium showed a partial alleviation of the inhibitory effect of verapamil on calcium transport. 5. The effect of increasing calcium concentration in the presence of dignxin and digoxin plus aminophylline in the incubation medium, showed a nonsaturable linear relationship between calcium concentration and intracellular calcium accumulation.
Monocrotaline (MCT) pneumotoxicity is known to alter the structure of pulmonary vascular wall and... more Monocrotaline (MCT) pneumotoxicity is known to alter the structure of pulmonary vascular wall and impairs endothelial cell function resulting in pulmonary hypertension. Its effect on the diaphragm muscle has not yet been elucidated. This study examines the effect of MCT pneumotoxicity on calcium transport in the rat diaphragm. Pulmonary hypertension induced by MCT pneumotoxicity caused a significant increase (PB 0.001) in calcium accumulation in strips isolated from rat diaphragms. Treatment of rats having received MCT with Indapamide reduced calcium uptake by diaphragmatic strips to levels that are not significantly different from the control (P\0.05). Treatment with Indapamide alone did not elicit any change in calcium accumulation in the diaphragmatic strips. Treatment of the animals with MCT, Indapamide or both did not produce any significant change (P \0.05) in the cell volume of the diaphragmatic strips. Pulmonary hypertension increased calcium uptake by the muscle cells in the rat diaphragm which may alter diaphragmatic contractility; an effect that was prevented by Indapamide.
The effects of macronutrient composition of the diet and glucocorticoid administration on weight ... more The effects of macronutrient composition of the diet and glucocorticoid administration on weight gain, intestinal absorption and plasma lipids were investigated. Thirty seven male Wistar rats were divided into 4 groups, implanted with pellets continuously delivering either prednisolone (0.25mg/ day) or placebo and fed two isocaloric diets providing either high fat (HF: 50% of energy) or high carbohydrate (HC: 70% of energy). The four groups [group I (HC, placebo), group II (HC, prednisolone), group III (HF, placebo), group IV (HF, prednisolone)] were pair fed and given the mean amount of food eaten by the group with the least amount of energy intake on the previous day. After 4 weeks, the animals were sacrificed and serum glucose, total cholesterol (TC), HDL-cholesterol (HDL) and triglycerides (TG) were measured. All groups showed a decrease in relative intestinal absorption with time. Prednisolone-treated groups revealed significantly lower intestinal absorption. However, prednisolone-treated high-carbohydrate (HC) fed rats showed significantly higher weight gain, concomitant with a significant increase in feed efficiency. The HC diet induced a statistically significant increase in TG concentration. The results show that prednisolone treatment induces more weight gain on a HC as compared to a high fat (HF) diet possibly through a rise in feed efficiency.
Intestinal nutrient transport is altered in response to changes in dietary conditions and luminal... more Intestinal nutrient transport is altered in response to changes in dietary conditions and luminal substrate level. It is not clear, however, whether an amino acid in the intestinal lumen can acutely affect its own absorption from a distant site. Our aim is to study the effect of an amino acid present in rat small intestinal segment on its own absorption from a proximal or distal site and elucidate the underlying mechanisms. The effect of instillation of alanine (Ala) in either jejunum or ileum on its own absorption at ileal or jejunal level was examined in vivo. The modulation of this intestinal regulatory loop by the following interventions was studied: tetrodotoxin (TTX) added to Ala, subdiaphragmatic vagotomy, chemical ablation of capsaicin-sensitive primary afferent (CSPA) fibers, and IV administration of calcitonin gene-related peptide (CGRP) antagonist. In addition, the kinetics of jejunal Ala absorption and the importance of Na+-dependent transport were studied in vitro after instilling Ala in the ileum. Basal jejunal Ala absorption [0.198 +/- 0.018 micromol x cm(-1) x 20 min(-1) (means +/- SD)] was significantly decreased with the instillation of 20 mM Ala in the ileum or in an adjacent distal jejunal segment (0.12 +/- 0.015; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001 and 0.138 +/- 0.014; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.002, respectively). Comparable inhibition was observed in the presence of proline in the ileum. Moreover, basal Ala absorption from the ileum (0.169 +/- 0.025) was significantly decreased by the presence of 20 mM Ala in the jejunum (0.103 +/- 0.027; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). The inhibitory effect on jejunal Ala absorption was abolished by TTX, subdiaphragmatic vagotomy, neonatal capsaicin treatment, and CGRP antagonism. In vitro studies showed that Ala in the ileum affects Na+-mediated transport and increases K(m) without affecting Vmax. Intraluminal amino acids control their own absorption from a distant part of the intestine, by affecting the affinity of the Na+-mediated Ala transporter, through a neuronal mechanism that involves CSPA and CGRP.
1. Alanine accumulation in rat hemidiaphragms is significantly inhibited by capsaicin in a dose-d... more 1. Alanine accumulation in rat hemidiaphragms is significantly inhibited by capsaicin in a dose-dependent pattern that produced maximal effect at 1 mM. 2. The inhibitory effect of capsaicin on alanine accumulation by rat hemidiaphragms was enhanced upon preincubation with 5 mM ouabain. However, preincubation with 1 mM Verapamil did not alter the inhibitory effect of capsaicin. 3. Chemical ablation of the capsaicin-sensitive primary afferent fibers abolished the inhibitory effect of capsaicin on alanine accumulation in the rat hemidiaphragms.
Intestinal nutrient transport is altered in response to changes in dietary conditions and luminal... more Intestinal nutrient transport is altered in response to changes in dietary conditions and luminal substrate level. It is not clear, however, whether an amino acid in the intestinal lumen can acutely affect its own absorption from a distant site. Our aim is to study the effect of an amino acid present in rat small intestinal segment on its own absorption from a proximal or distal site and elucidate the underlying mechanisms. The effect of instillation of alanine (Ala) in either jejunum or ileum on its own absorption at ileal or jejunal level was examined in vivo. The modulation of this intestinal regulatory loop by the following interventions was studied: tetrodotoxin (TTX) added to Ala, subdiaphragmatic vagotomy, chemical ablation of capsaicin-sensitive primary afferent (CSPA) fibers, and IV administration of calcitonin gene-related peptide (CGRP) antagonist. In addition, the kinetics of jejunal Ala absorption and the importance of Na+-dependent transport were studied in vitro after...
International journal for innovation education and research, 2021
Objectives: The authors analyzed the weaknesses and areas of opportunities with the online teachi... more Objectives: The authors analyzed the weaknesses and areas of opportunities with the online teaching imposed by the COVID19 lockdown, and the new measures adopted to control the online examinations for medical students. Method: In addition to personalized question sets we had location mapping and Open Broadcaster Software (OBS) for monitoring students during the exams as well as disabling the back-button during examination. Results: The academic year was successfully completed on time. There was no change in the exams format or scope, yet the results were similar in terms of grade distribution, average and standard deviation as well as the validity and reliability scores. The students’ perception of online teaching was evaluated through a survey. It revealed the importance and added value of online teaching but also exposed the gaps related to lecturers’ preparedness and need for training. Conclusion: The online experience was a valuable lesson for us, as we discovered not only the...
The main function of the colon is water and electrolyte absorption. Total colectomy eliminates th... more The main function of the colon is water and electrolyte absorption. Total colectomy eliminates this colonic function and may alter the absorptive capacity of the small intestine for nutrients. This study examines the effect of total colectomy on jejunal glucose absorption and investigates the potential role of aldosterone in mediating the alterations in glucose uptake post-colectomy using the aldosterone antagonist spironolactone. Total colectomy with ileo-rectal anastomosis was performed on anesthetized rats. Sham rats were identically handled without colon resection. Two days post-surgery, groups of colectomized rats were injected with either a daily subcutaneous dose of spironolactone or sesame oil for 12days. Body weight changes and food and water intake were measured in all experimental groups. Glucose absorption was measured by in-vivo single pass perfusion in the rat jejunum of control, sham, colectomized, colectomized with spironolactone, and colectomized with sesame oil treatment. Na/K ATPase, SGK1, SGLT1 and GLUT2 expressions were determined in jejunal mucosa in control, colectomized and colectomized/spironolactone injected rats by Western blot analysis. Histological assessment was performed on jejunal sections in control and colectomized groups. Glucose absorption significantly increased in colectomized rats with an observed increase in Na/K ATPase and SGK1 expression. No significant expression change in SGLT1 and GLUT2 was detected in the jejunum in colectomized rats. Spironolactone, however, significantly decreased the glucose uptake post-colectomy and normalized Na/K ATPase and SGK1 expression. Our results suggest that jejunal glucose uptake increases post-colectomy as a possible consequence of an aldosterone-mediated function.
The in vitro effects of a local anesthetic, a membrane active drug, procaine, on some functional ... more The in vitro effects of a local anesthetic, a membrane active drug, procaine, on some functional activities of circulating human lymphocytes and monocytes were studied. Procaine inhibited spontaneous E-rosette formation between T-lymphocytes and sheep erythrocytes and EAC-rosettes with B-lymphocytes. In addition, procaine inhibited both the phagocytosis of latex particles by normal monocytes and the proliferation of lymphocytes in an allogeneic mixed leukocyte culture. Morphologically the procaine-treated cells exhibited a relative increase in the size of the cytoplasmic rim around their nuclei. The results indicated that procaine might be considered as a non-specific immunoregulator, modulating to some extent the functional expression of human peripheral blood mononuclear cells activities.
It was recently shown that vasoactive intestinal polypeptide (VIP) inhibits rat jejunal alanine a... more It was recently shown that vasoactive intestinal polypeptide (VIP) inhibits rat jejunal alanine absorption, an effect that was significantly reduced by vagotomy. This study assesses the role of capsaicin-sensitive primary afferents (CSPA) and the myenteric plexus in the inhibition of rat jejunal alanine absorption by VIP. Continuous intravenous infusion of VIP (11.2 ng . kg-1 . min-1) reduced alanine absorption by 60% in sham control rats and by 20% in rats neonatally treated with capsaicin (P < 0.01). In in vitro experiments, VIP decreased alanine uptake by jejunal strips isolated from sham control rats in a dose-dependent manner. In the presence of 40 nM VIP, alanine uptake by full-thickness jejunal strips was reduced by 54% in sham control rats and by 25% in rats neonatally treated with capsaicin (P < 0.001). On the other hand, VIP reduced alanine uptake by mucosal scrapings by 25% in sham rats compared with 9% reduction in neonatally treated rats. Chemical ablation of the ...
Comparative biochemistry and physiology. A, Comparative physiology, 1988
1. The effect of colchicine, cytochalasin-B and procaine on calcium transport across the rat smal... more 1. The effect of colchicine, cytochalasin-B and procaine on calcium transport across the rat small intestine was investigated. The results obtained show the following: 2. Colchicine and cytochalasin-B at different concentrations inhibited significantly (P less than 0.001) calcium accumulation in rat intestinal cells, whereas procaine at different concentrations increased significantly (P less than 0.001) calcium accumulation in the rat small intestine. 3. Unidirectional influx of calcium across the rat small intestine was significantly inhibited (P less than 0.01) in the presence of colchicine and cytochalasin-B in the preincubation medium. Procaine, on the other hand, caused a significant increase (P less than 0.01) in the unidirectional influx of calcium across the rat intestinal cells. 4. The cell water content was not altered in the presence of the different drugs indicating that the changes in calcium transport across the rat intestinal cells are not due to alterations in the s...
Abutract-l. The effect of aminophylline and terbutaline sulfate, separately and in combination, o... more Abutract-l. The effect of aminophylline and terbutaline sulfate, separately and in combination, on the contractility of the feline diaphragm was investigated. 2. Diaphragmatic contractility increased significantly (P < 0.05) to 28.3% above control level as long as theophylline plasma levels were maintained between 10-20 mg/l (mean 13.9 + 0.8 rag/l). 3. Diaphragmatic contractility showed a significant (P < 0.05) 41.5% increase after i.v. administration of terbutaline sulfate as a maintenance dose of 1.4/~g/kg-hr, and the increase leveled off after 180 rain. 4. Administering the two drugs in combination showed a significant (P < 0.05) 27.3% increase which suggests a non-synergistic effect of aminophylline and terbutaline sulfate on diaphragmatic contractility. 5. By enhancing the contractility of the diaphragm, aminophylline and terbutaline sulfate may improve the clinical status of patients with airway obstructive diseases and help in preventing respiratory muscle fatigue.
The effects of motilin on proline absorption and gastric and biliary secretions were examined in ... more The effects of motilin on proline absorption and gastric and biliary secretions were examined in the rat. Prolonged intravenous administration of motilin (50 pmol/kg/min) significantly inhibited (P<0.05) proline transport across the jejunum and reduced basal acid secretion to 40~o of control value. The same concentration of motilin induced choleresis and increased bile output by 32~o. Incubation of intestinal strips with different concentrations of motilin produced a dose-dependent inhibitory pattern of proline accumulation in the intestinal cells.
The effect of terbutaline sulfate on calcium transport across muscle strips isolated from rat dia... more The effect of terbutaline sulfate on calcium transport across muscle strips isolated from rat diaphragms, and its effect on this process when used in combination with aminophylline was investigated using labelled calcium in a two-compartment system. 2. The results show that terbutaline sulfate causes a dose-dependent increase in intracellular calcium concentration which reached saturation at a terbutaline sulfate concentration of 2 ng/ml. 3. The inclusion of both aminophylline and terbutaline sulfate at a concentration range of 6.25-50/~g/ml and 0.5-4 ng/ml respectively in the incubation medium, did not show a synergistic effect on intracellular calcium accumulation. 4. Although verapamil, a calcium channel blocker, inhibited significantly (P < 0.01) calcium accumulation in the muscle strips of the diaphragm, it did not inhibit completely the increase in intracellular calcium concentration noticed in the presence of aminophylline or terbutaline sulfate. 5. This would suggest that aminophylline and terbutaline sulfate have an effect on the calcium channels in the muscle strips of the diaphragm.
The effect of neurotensin (NT) on proline absorption across rat jejunum was investigated using th... more The effect of neurotensin (NT) on proline absorption across rat jejunum was investigated using the singlepass perfusion technique. This study showed that intravenous administration of NT produced a dose-dependent inhibition of proline absorption. Thus, NT at a 0.16 pmol/kg/min concentration gave 10~o decrease in proline absorption while 0.32 and 1.6 pmol/kg/min concentration gave 317o and 45?0 decrease, respectively. In the absence of Na, proline absorption decreased to 77~ o from control values. No change in proline absorption was noticed when NT at a concentration of 0.32 pmol/kg/min was intravenously injected in the absence of sodium from the perfusion solution. Water absorption did not show significant changes (P> 0.05) in presence or absence of NT. Moreover, NT did not produce a significant change (P> 0.2) in intracellular proline accumulation. NT inhibited proline absorption through an indirect mechanism that is Na-dependent and independent of changes in water absorption.
The effect of chlorpromazine on proline absorption across jejunum in anaesthetized rats was inves... more The effect of chlorpromazine on proline absorption across jejunum in anaesthetized rats was investigated. Intravenous infusion of chlorpromazine reduced significantly (P<0 .01) proline absorption across the jejunum. Intraluminal perfusion of chlorpromazine into the jejunal segment reversed net absorption of proline to net secretion. Net water absorption was increased significantly (P<0 .01) when chlorpromazine was infused intravenously or perfused intraluminally. Unidirectional influx of proline across the mucosal surface was significantly inhibited (P<0 .01) after preincubation with 1 mm chlorpromazine .
Pyridoxine binding to liver plasma membrane isolated from livers of normal and streptozotocin-ind... more Pyridoxine binding to liver plasma membrane isolated from livers of normal and streptozotocin-induced diabetic rats was investigated. The effect of increasing concentration of pyridoxine on its binding to the membranes revealed a concentration-dependent and saturable process with a significant decrease in the high affinity receptor sites of the diabetic membrane. Moreover, the incubation of the membranes with procaine, colchicine and
The effect of digoxin on calcium transport across muscle strips isolated from rat diaphragms was ... more The effect of digoxin on calcium transport across muscle strips isolated from rat diaphragms was investigated. 2. Digoxin at concentrations ranging between 0.2-5.0 ng/ml in the incubation solution increased significantly (P < 0,5) intracellular calcium in the diaphragm muscle strips in a dose-dependent pattern. 3. The inclusion of digoxin (2 ng/ral) and aminophylline (18.75 g g/ml) in the incubation medium showed a significant increase (P < 0.001) in calcium uptake suggesting a synergistic effect on intracellular calcium accumulation. 4. The presence of digoxin with verapamil in the incubation medium showed a partial alleviation of the inhibitory effect of verapamil on calcium transport. 5. The effect of increasing calcium concentration in the presence of dignxin and digoxin plus aminophylline in the incubation medium, showed a nonsaturable linear relationship between calcium concentration and intracellular calcium accumulation.
Monocrotaline (MCT) pneumotoxicity is known to alter the structure of pulmonary vascular wall and... more Monocrotaline (MCT) pneumotoxicity is known to alter the structure of pulmonary vascular wall and impairs endothelial cell function resulting in pulmonary hypertension. Its effect on the diaphragm muscle has not yet been elucidated. This study examines the effect of MCT pneumotoxicity on calcium transport in the rat diaphragm. Pulmonary hypertension induced by MCT pneumotoxicity caused a significant increase (PB 0.001) in calcium accumulation in strips isolated from rat diaphragms. Treatment of rats having received MCT with Indapamide reduced calcium uptake by diaphragmatic strips to levels that are not significantly different from the control (P\0.05). Treatment with Indapamide alone did not elicit any change in calcium accumulation in the diaphragmatic strips. Treatment of the animals with MCT, Indapamide or both did not produce any significant change (P \0.05) in the cell volume of the diaphragmatic strips. Pulmonary hypertension increased calcium uptake by the muscle cells in the rat diaphragm which may alter diaphragmatic contractility; an effect that was prevented by Indapamide.
The effects of macronutrient composition of the diet and glucocorticoid administration on weight ... more The effects of macronutrient composition of the diet and glucocorticoid administration on weight gain, intestinal absorption and plasma lipids were investigated. Thirty seven male Wistar rats were divided into 4 groups, implanted with pellets continuously delivering either prednisolone (0.25mg/ day) or placebo and fed two isocaloric diets providing either high fat (HF: 50% of energy) or high carbohydrate (HC: 70% of energy). The four groups [group I (HC, placebo), group II (HC, prednisolone), group III (HF, placebo), group IV (HF, prednisolone)] were pair fed and given the mean amount of food eaten by the group with the least amount of energy intake on the previous day. After 4 weeks, the animals were sacrificed and serum glucose, total cholesterol (TC), HDL-cholesterol (HDL) and triglycerides (TG) were measured. All groups showed a decrease in relative intestinal absorption with time. Prednisolone-treated groups revealed significantly lower intestinal absorption. However, prednisolone-treated high-carbohydrate (HC) fed rats showed significantly higher weight gain, concomitant with a significant increase in feed efficiency. The HC diet induced a statistically significant increase in TG concentration. The results show that prednisolone treatment induces more weight gain on a HC as compared to a high fat (HF) diet possibly through a rise in feed efficiency.
Intestinal nutrient transport is altered in response to changes in dietary conditions and luminal... more Intestinal nutrient transport is altered in response to changes in dietary conditions and luminal substrate level. It is not clear, however, whether an amino acid in the intestinal lumen can acutely affect its own absorption from a distant site. Our aim is to study the effect of an amino acid present in rat small intestinal segment on its own absorption from a proximal or distal site and elucidate the underlying mechanisms. The effect of instillation of alanine (Ala) in either jejunum or ileum on its own absorption at ileal or jejunal level was examined in vivo. The modulation of this intestinal regulatory loop by the following interventions was studied: tetrodotoxin (TTX) added to Ala, subdiaphragmatic vagotomy, chemical ablation of capsaicin-sensitive primary afferent (CSPA) fibers, and IV administration of calcitonin gene-related peptide (CGRP) antagonist. In addition, the kinetics of jejunal Ala absorption and the importance of Na+-dependent transport were studied in vitro after instilling Ala in the ileum. Basal jejunal Ala absorption [0.198 +/- 0.018 micromol x cm(-1) x 20 min(-1) (means +/- SD)] was significantly decreased with the instillation of 20 mM Ala in the ileum or in an adjacent distal jejunal segment (0.12 +/- 0.015; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.0001 and 0.138 +/- 0.014; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.002, respectively). Comparable inhibition was observed in the presence of proline in the ileum. Moreover, basal Ala absorption from the ileum (0.169 +/- 0.025) was significantly decreased by the presence of 20 mM Ala in the jejunum (0.103 +/- 0.027; P &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01). The inhibitory effect on jejunal Ala absorption was abolished by TTX, subdiaphragmatic vagotomy, neonatal capsaicin treatment, and CGRP antagonism. In vitro studies showed that Ala in the ileum affects Na+-mediated transport and increases K(m) without affecting Vmax. Intraluminal amino acids control their own absorption from a distant part of the intestine, by affecting the affinity of the Na+-mediated Ala transporter, through a neuronal mechanism that involves CSPA and CGRP.
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