Influence of environmental hypertonicity on the induction of ureogenesis and amino acid metabolism in air-breathing walking catfish (Clarias batrachus, Bloch).

Effect of environmental hypertonicity, due to exposure to 300 mM mannitol solution for 7 days, on the induction of ureogenesis and also on amino acid metabolism was studied in the air-breathing walking catfish, C. batrachus, which is already known to have the capacity to face the problem of osmolarity stress in addition to other environmental stresses in its natural habitats. Exposure to hypertonic mannitol solution led to reduction of ammonia excretion rate by about 2-fold with a concomitant increase of urea-N excretion rate by about 2-fold. This was accompanied by significant increase in the levels of both ammonia and urea in different tissues and also in plasma. Further, the environmental hypertonicity also led to significant accumulation of different non-essential free amino acids (FAAs) and to some extent the essential FAAs, thereby causing a total increase of non-essential FAA pool by 2-3-fold and essential FAA pool by 1.5-2.0-fold in most of the tissues studied including the plasma. The activities of three ornithine-urea cycle (OUC) enzymes such as carbamoyl phosphate synthetase, argininosuccinate synthetase and argininosuccinate lyase in liver and kidney tissues, and four key amino acid metabolism-related enzymes such as glutamine synthetase, glutamate dehydrogenase (reductive amination), alanine aminotransaminase and aspartate aminotransaminase were also significantly up-regulated in different tissues of the fish while exposing to hypertonic environment. Thus, more accumulation and excretion of urea-N observed during hypertonic exposure were probably associated with the induction of ureogenesis through the induced OUC, and the increase of amino acid pool was probably mainly associated with the up-regulation of amino acid synthesizing machineries in this catfish in hypertonic environment. These might have helped the walking catfish in defending the osmotic stress and to acclimatize better under hypertonic environment, which is very much uncommon among freshwater teleosts.

Hemodynamic effects of mannitol infusion in patients with acute intracerebral hemorrhage

PURPOSE: To evaluate hemodynamic effects of mannitol infusion in patients with acute intracerebral hemorrhage. METHODS: Thirty patients with acute intracerebral hemorrhage were enrolled. Transcranial doppler was used to detect variables of bilateral middle cerebral arteria (MCA) including mean velocity (Vm) and pulsitility index (PI) before and after125ml and 250ml mannitol infusion (0, 30, 60, 90, 120, 180, 240 min). RESULTS: When 125ml or 250ml mannitol was infused in patients with acute intracerebral hemorrhage, Vm of bilateral MCA elevated, and reached the top at 30min, and then decreased. PI decreased in the affected MCA (250ml) and in the unaffected MCA (125ml and 250ml). CONCLUSION: Mannitol infusion in patients with acute intracerebral hemorrhage can improve cerebral blood flow in bilateral hemispheres and decrease intracranial pressure in the hemorrhagic hemisphere (250ml) and in the nonhemorrhagic hemisphere (125ml and 250ml).

Effect of mannitol in experimental spinal cord injury: an ultrastructural and electrophysiological study.

BACKGROUND: Although many experimental and clinical studies were performed on the pathophysiology and treatment of spinal cord injury (SCI), the electrophysiological and ultrastructural changes of the spinal cord were not precisely evaluated. AIMS: To investigate the effect of mannitol on Somatosensory Evoked Potentials (SSEP), postoperative neurological recovery and ultrastructural findings after an experimental SCI. Setting: The experimental microsurgery laboratory of a university hospital. DESIGN: A prospective, randomized animal study. MATERIAL AND METHODS: Sprague-Dawley rats were used and divided into three groups (Groups I-III) for this study. Those in Group I were control animals who underwent laminectomy only, and non-traumatized spinal cord samples were obtained 2 weeks later. SCI was produced in Groups II and III using clip compression technique, and cord samples were obtained 2 weeks later. The rats in Group II received 2 g/kg of 20% mannitol intraperitoneally, immediately and three hours after trauma was induced; and those in Group III received the same amount of 0,9% NaCl in the same manner. Preoperative and postoperative SSEP records at the end of 2 weeks were obtained. Electron microscopy examination of the cord samples was done at 2 weeks postoperatively. STATISTICAL ANALYSIS USED: Fischer's Exact Test. RESULTS: SSEP records, ultrastructural findings and clinical recovery showed that minor neural damage and significant recovery occurred in Group II. CONCLUSION: This study demonstrates that the administration of 2 g/kg of 20% mannitol produces significant improvement in the neural structures and protects the spinal cord following injury.

Partially folded intermediates during trypsinogen denaturation

The equilibrium unfolding of bovine trypsinogen was studied by circular dichroism, differential spectra and size exclusion HPLC. The change in free energy of denaturation was delta GH2O = 6.99 + ou - 1.40 kcal/mol for guanidine hydrochloride and delta GH2O = 6.37 + ou - 0.57 kcal/mol for urea. Satisfactory fits of equilibrium unfolding transitions required a three-state model involving an intermediate in addition to the native and unfolded forms. Size exclusion HPLC allowed the detection of an intermediate population of trypsinogen whose Stokes radii varied from 24.1 + ou - 0.4 angstron to 26.0 + ou - 0.3 angstron 1.5 M and 2.5 M guanidine hydrochloride, respectively. During urea denaturation, the range of Stokes radii varied from 23.9 + ou - 0.3 angstron to 25.7 + ou - 0.6 angstron for 4.0 M and 6.0 M urea, respectively. Maximal intrinsic fluorescence was observed at about 3.8 M urea with 8-aniline-1-naphthalene sulfonate (ANS) binding. These experimental data indicate that the unfolding of bovine trypsinogen is not a simple transition and suggest that the equilibrium intermediate population comprises one intermediate that may be characterized as a molten globule. To obtain further insight by studying intermediates representing different stages of unfolding, we hope to gain a better understanding of the complex interrelations between protein conformation and energetics.

Manitol- fundamentos para sua utilizaçäo / Mannitol- reasons for its utilization

O diurético osmótico manitol é uma droga amplamente utilizada em neurociruriga e neurologia a fim de diminuir a pressäo intracraniana e melhorar a microcirculaçäo cerebral. As teorias sobre seu mecanismo de açäo säo revisadas: gradiente osmótico pela barreira hematoencefálica, auto-regulaçäo vascular e neutralizaçäo dos radicais livres do oxigênio. Sua posologia é empírica, segunda a experiência própria de cada autor. O conhecimento dos critérios básicos para o uso do manitol e de sua reposiçäo hidreletrolítica é fundamental para a manutençäo da osmolaridade sérica em valores terapêuticos

Influencia de los diuréticos en el resultado de los análisis clínicos / Influence of diuretics on the result of clinical analysis

En este trabajo se realizó una revisión de los principales grupos de diuréticos, sus sitios y mecanismos de acción y sus efectos sobre las pruebas de laboratorio. Se analizó el efecto de los diuréticos sobre: el estado ácido base, los electrolitos séricos y urinarios, el ácido úrico sérico y urinario y sobre la glucemia. También se describió la influencia de los diuréticos sobre los análisis de orina. Finalmente, los efectos hematológicos de los mismos. El objetivo de este trabajo fue estudiar la influencia de los diuréticos en los análisis clínicos, buscando los mecanismos fisiopatológicos o metodológicos de los casos citados

Influência do acréscimo de manitol à solução nutriente no desempenho mecânico e no grau de edema miocárdico de coraçoes isolados de ratos / Influence of Mannitol Added to the Perfusion Solution on Mechanical Properties and Myocardial Edema of Isolated Rat Hearts

PURPOSE--To analyse the influence of mannitol added to Krebs-Henseleit (KH) solution on the myocardium edema and myocardial function. METHODS--Isolated rat heart under isovolumetric contractions studied according to Langendorff's technique were perfused with KH solution at constant flow during 90 min. The coronary perfusion pressure, diastolic and systolic pressures were recorded at every 15 min. At the end of the experiment, myocardium water content was measured in hearts perfused with KH solution (group I, n = 9) and in hearts perfused with KH solution plus 8mM mannitol (group II, n = 8). These results were compared to non-perfused control heart (n = 9). RESULTS--Myocardial water content was statistically higher in group I (80.8 +/- 1.3) compared to group II (78.1 +/- 0.7) and control group (75.5 +/- 0.5). Systolic arterial pressure was statistically higher in group I (86.2 +/- 11.5mmHg) compared to group II (72.7 +/- 21.1mmHg). There was no difference in the diastolic pressure between the two groups. Coronary perfusion pressure (Pp) increased progressively during the experiment in both groups. However, Pp was lower in group II than in group I. CONCLUSION--Mannitol added to KH solution significantly attenuates the myocardium edema in the isolated perfused rat heart.

Avanços terapêuticos em cardiologia; Parte 2. Diureticos: estado atual em cardiologia / Therapeutic advances in cardiology; Part 2. Diuretics: up-to-date cardiology

Os diuréticos constituem-se na principal arma no tratamento da insuficiência cardíaca e da hipertensäo arterial sistêmica. Os pacientes têm uma boa e prolongada resposta com alívio da dispnéia, reduzem a pressäo venosa e a congestäo hepática. Chamamos atençäo para os efeitos adversos e o uso indevido em pacientes com edema e obesidade