Development and Characterization of L-Alanyl-L-Glutamine Containing Pellets employing Extrusion-Spheronization Method and Drying Process in Fluidized Bad Equipment.

Development and Characterization of L-Alanyl-L-Glutamine Containing Pellets employing Extrusion-Spheronization Method and Drying Process in Fluidized Bad Equipment"". In this work, five formulations of L-alanyl-L-glutamine (glutamine dipeptide) containing pellets with different drug concentration were developed and evaluated: F1 (9.07%); F2 (17.70%); F3 (27.98%); F4 (37.74%) e F5 (47.53%). Pellets were prepared by extrusion-spheronization method and, further, dried in fluidized bad equipment. The following assays were carried out with the batches obtained: granulometry, friability, true density and morphologic analysis. Between the five formulations evaluated, pellets obtained from F3 present best yield (75.80%), most uniform particle size distribution (89.67% of pellets with size in the range of 0.80 to 1.18), most high true density (2.1634 g/ml) and best aspect (1.0795 +/- 0.0410). Due to these features, pellets obtained from F3 were considered adequate to further polymeric coating process in order to produce a multiparticulate system to prolong L-alanyl-L-glutamine release.

Blood pressure variability increases connexin expression in the vascular smooth muscle of rats

Aims Following sinoaortic denervation (SAD), isolated rat aortas present oscillatory contractions and demonstrate a heightened contraction for alpha-adrenergic agonists. Our aim was to verify the effects of SAD on connexin43 (Cx43) expression and phenylephrine-induced contraction in isolated aortas. Methods and results Three days after surgery (SAD or sham operation), isolated aortic rings were exposed to phenylephrine and acetylcholine (0.1-10 mu M) in the presence or absence of the gap junction blocker 18 beta-glycyrrhetinic acid (18 beta-GA, 100 mu M). Vascular reactivity to potassium chloride (KCl, 4.7-120 mM) was also examined. The incidence of rats presenting oscillatory contractions was measured. Effects of SAD on the vascular smooth muscle expression of the Cx43 mRNA by RT-PCR and western blotting for Cx43 protein were examined. Phenylephrine-induced contraction was higher in SAD rat aortas compared with the control. In the presence of 18 beta-GA, the response to phenylephrine was similar in both groups. Oscillatory contractions were observed in 10/10 SAD rat aortas vs. 2/10 controls. Relaxing response to acetylcholine was similar in both groups, but in the presence of 18 beta-GA, the response to acetylcholine decreased significantly in the sham-operated group (82.7 +/- 7.6% reduction of relaxation), whereas a half-maximal relaxation (reduction of 46.2 +/- 5.3%) took place in SAD rat aortas. KCl-induced contraction was similar in both groups. Following SAD, RT-PCR revealed significantly increased levels of Cx43 mRNA (9.85 fold, P < 0.01). Western blot analysis revealed greater levels of Cx43 protein (P < 0.05). Conclusion Blood pressure variability evoked by SAD leads to increased expression of Cx43, which could contribute to enhanced phenylephrine-induced contraction and oscillatory activity in isolated aortas.

ANALYSIS OF PRESSURE FLUCTUATIONS DURING WATER EVAPORATION IN SPOUTED BED

The aim of this work was to study the behaviour of conventional spouted beds during water evaporation and to analyze the pressure fluctuations at the maximum water evaporative capacity for different bed heights and air flow rates. The results showed that spout pressure drop could not indicate the proximity of maximum evaporative capacity; however this condition is denoted by a minimum in fountain height. The standard deviation and amplitude of the pressure fluctuations also showed a minimum point at the maximum water evaporation capacity. The frequency domain analysis of pressure fluctuations revealed that the dry bed has a dominant frequency varying from 6 to 8.2 Hz and that the peak of dominant frequency tends to disappear with the increase in water feed rate.

IDENTIFICATION OF THE STATE OF A WET SPOUTED BED THROUGH TIME-FREQUENCY ANALYSIS OF PRESSURE FLUCTUATION TIME SERIES

The feasibility of detecting instability in wet spouted beds via pressure fluctuation (PF) time-series analyses was investigated. Experiments were carried out in a cylindrical Plexiglas column of diameter 150 mm with a conical base of internal angle 60 degrees, an inlet orifice diameter of 25 mm and glass beads of diameter 2.4 mm. Transducers at several axial positions measured PF time series with incremental addition of aqueous sucrose solutions of different concentrations. Liquid addition affected the spouted bed dynamics, causing irregular spouting, increased voidage in the annulus, increased fountain height, irregular annulus height, channelling, agglomeration, and adhesion of particles to the column walls. Autocorrelations indicated the appearance of periodicities in the PF signals with increasing sucrose addition. Dominant peaks in power-spectral density developed at low frequencies with changing system dynamics. The results indicate that PF signals furnish relevant information on system dynamics, useful for monitoring and control of spouted bed operations such as particle coating and drying of paste-like materials.

Isolation and Characterization of a Natriuretic Peptide from Crotalus oreganus abyssus (Grand Canyon Rattlesnake) and its Effects on Systemic Blood Pressure and Nitrite Levels

Studies on the therapeutic potential of venom peptides have significantly advanced the development of new peptide drugs. A good example is captopril, a synthetic peptide drug, which acts as an anti-hypertensive and potentiating bradykinin, inhibiting the angiotensin-converting enzyme, whose precursor was isolated from the venom of Bothrops jararacussu. The natriuretic peptide (NPs) family comprises three members, ANP (atrial natriuretic peptide), BNP (B-type natriuretic peptide) and CNP (C-type natriuretic peptide), and has an important role in blood pressure regulation and electrolyte homeostasis. In this study, we describe, for the first time, the isolation and characterization of a novel natriuretic-like peptide (Coa_NP), isolated from Crotalus Oreganus abyssus venom. The peptide has 32 amino acids and its complete sequence is SKRLSNGCFGLKLDRIGAMSGLGCWRLINESK. The Coa_NP has an average molecular mass of 3510.98 Da and its amino acid sequence presents the loop region that is characteristic of natriuretic peptides (17 amino acids, NP domain consensus; CFGXXXDRIXXXSGLGC). Coa_NP is a natriuretic peptide of the ANP/BNP-like family, since the carboxy terminal region of CNP has its own NP domain. The functional experiments showed that Coa_NP produced biological effects similar to those of the other natriuretic peptides: (1) a dose-dependent decrease in mean arterial pressure; (2) significant increases in plasma nitrite levels, and (3) vasorelaxation in thoracic aortic rings that were pre-contracted with phenylephrine. The structural and biological aspects confirm Coa_NP as a natriuretic peptide isolated from snake venom, thus expanding the diversification of venom components.

Blood pressure and heart rate during tonic immobility in the black tipped reef shark, Carcharhinus melanoptera

Tonic immobility was induced in black tipped reef sharks (Carcharhinus melanoptera) and heart rate and ventral aortic blood pressure recorded. Without branchial irrigation, tonic immobility was correlated with a significant depression in blood pressure and heart rate irrespective of the sharks being in air or in water. Tonic immobility with branchial irrigation resulted in a significant increase in blood pressure in sharks in air, but not in water. Heart rate was unchanged when the gills were irrigated. Intra-arterial injections of atropine abolished the bradycardia and blood pressure rise associated with tonic immobility. We conclude that, during tonic immobility, sharks are able to receive afferent information from the ventilatory system and make appropriate responses via the vagus nerve.

On the mechanism of microbial cell disruption in high-pressure homogenisation

The tensions produced in the wall of a rigid, thin-walled, liquid-filled sphere as it moves with an axisymmetric straining flow are examined. This problem has not been previously addressed. A generalised correlation for the maximum wall tension, expressed in dimensionless form as a Weber number (We), is developed in terms of the acceleration number (Ac) and Reynolds number (Re) of the straining flow. At low Reynolds number We is dominated by viscous forces, while inertial forces due to internal pressure gradients caused by sphere acceleration dominate at higher Re. The generalised correlation has been used to examine the case of a typical yeast cell (a thin-walled, liquid-filled sphere) passing through a typical high-pressure homogeniser (a straining-flow device). At 56 MPa homogenising pressure, a 6 mu m yeast cell experiences tensions in the inertially dominated regime (Re = 100). The correlation gives We = 0.206, corresponding to a maximum wall tension of 8 Nm(-1). This is equivalent to an applied compressive force of 150 mu N and compares favourably with the force required to break yeast cells under compressive micromanipulation (40-90 mu N). Inertial forces may therefore be an important and previously unrecognised. mechanism of microbial cell disruption during high-pressure homogenisation. Further work is required to examine the likelihood of cell deformation in the high-strain-rate short-residence-time environment of the homogeniser, and the effect that such deformation may have on the contribution of inertial forces to disruption. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.

Relationships between blood pressure and heart rate in the saltwater crocodile Crocodylus porosus

The cardiac limb of the baroreflex loop was studied in the saltwater crocodile Crocodylus porosus, The classical pharmacological methodology using phenylephrine and sodium nitroprusside was used to trigger blood pressure changes, and the resulting alterations in heart rate were analysed quantitatively using a logistic function. Interindividual differences in resting heart rates and blood pressures were observed, but all seven animals displayed clear baroreflex responses. Atropine and sotalol greatly attenuated the response. A maximal baroreflex gain of 7.2 beats min(-1) kPa(-1) was found at a mean aortic pressure of 6.1 kPa, indicating the active role of the baroreflex in a wide pressure range encompassing hypotensive and hypertensive states. At the lowest mean aortic pressures (5.0 kPa), the synergistic role of the pulmonary-to-systemic shunt in buffering the blood pressure drop also contributes to blood pressure regulation, Pulse pressure showed a better correlation,vith heart rate and also a higher gain than mean aortic, systolic or diastolic pressures, and this is taken as an indicator of the existence of a differential control element working simultaneously with a linear proportional element.

Analysis of pore-fluid pressure gradient and effective vertical-stress gradient distribution in layered hydrodynamic systems

A theoretical analysis is carried out to investigate the pore-fluid pressure gradient and effective vertical-stress gradient distribution in fluid saturated porous rock masses in layered hydrodynamic systems. Three important concepts, namely the critical porosity of a porous medium, the intrinsic Fore-fluid pressure and the intrinsic effective vertical stress of the solid matrix, are presented and discussed. Using some basic scientific principles, we derive analytical solutions and explore the conditions under which either the intrinsic pore-fluid pressure gradient or the intrinsic effective vertical-stress gradient can be maintained at the value of the lithostatic pressure gradient. Even though the intrinsic pore-fluid pressure gradient can be maintained at the value of the lithostatic pressure gradient in a single layer, it is impossible to maintain it at this value in all layers in a layered hydrodynamic system, unless all layers have the same permeability and porosity simultaneously. However, the intrinsic effective vertical-stress gradient of the solid matrix can be maintained at a value close to the lithostatic pressure gradient in all layers in any layered hydrodynamic system within the scope of this study.

Administration of growth hormone or IGF-I to pregnant rats on a reduced diet throughout pregnancy does not prevent fetal intrauterine growth retardation and elevated blood pressure in adult offspring

Increasing evidence from human epidemiological studies suggests that poor growth before birth is associated with postnatal growth retardation and the development of cardiovascular disease in adulthood. We have shown previously that nutritional deprivation in the pregnant rat leads to intrauterine growth retardation (IUGR), postnatal growth failure, changes in the endocrine parameters of the somatotrophic axis, and to increased blood pressure in later life. In the present study, we investigated whether administration of insulin-like growth factor-I (IGF-I) or bovine growth hormone (GH) during pregnancy could prevent IUGR and/or alter long-term outcome. Dams h-om day 1 of pregnancy throughout gestation received a diet of nd libitum available food or a restricted dietary intake of 30% of ad libitum fed dams. From day 10 of gestation, dams were treated for 10 days with three times daily subcutaneous injections of saline (100 mu l), IGF-I (2 mu g/g body weight) or GH (2 mu g/g body weight). Maternal weight gain was significantly increased (P

Variable temperature and pressure study of the aquation reactions of cobalt(III) and chromium(III) penta- and tetra-amines

Preparation of a series of specific penta- and tetra-amine derivatives of Co-III and Cr-III with a neutral leaving ligand has been carried out in order to accomplish a fine tuning of the associativeness/dissociativeness of their substitution reactions. Spontaneous aquation reactions of the neutral ligands have been studied at variable temperature and pressure. Although rate constants and thermal activation parameters show an important degree of scatter, the values determined for the activation volumes of the substitution process illustrate the mechanistic fine tuning that may be achieved for these reactions. In all cases, in the absence of important steric constraints in the molecule, electronic inductive effects seem to be the most important factor accounting for the dissociative shifts observed both for pentaamine (i.e.Delta V double dagger=+4.0 or +14.0 cm(3) mol(-1) and +5.2 or +16.5 cm(3) mol(-1) for the aquation of cis- or trans-[Co(MeNH2)(NH3)(4)(DMF)](3+) and cis- or trans-[CoL15(DMF)](3+) respectively, where L-15 represents a pentaamine macrocyclic ligand), and tetraamine systems (i.e.Delta V double dagger=+4.1 or +8.4 cm(3) mol(-1) and -10.8 or -7.4 cm(3) mol(-1) for the aquation of cis-[Co(NH3)(4)Cl(DMAC)](2+) (DMAC=dimethylacetamide) or cis-[Co(en)(2)Cl(DMAC)](2+) and cis-[Cr(NH3)(4)Cl(DMF)](2+) or cis -[Cr(en)(2)Cl(DMF)](2+)). From the results, clear evidence is obtained which indicates that, only when the situation is borderline I-a/I-d, or the steric demands are increased dramatically, dissociative shifts are observed; in all other cases electronic inductive effects seem to be dominant for such a tuning of the substitution process.

Changes in intra-abdominal pressure during postural and respiratory activation of the human diaphragm

In humans, when the stability of the trunk is challenged in a controlled manner by repetitive movement of a limb, activity of the diaphragm becomes tonic but is also modulated at the frequency of limb movement. In addition, the tonic activity is modulated by respiration. This study investigated the mechanical output of these components of diaphragm activity. Recordings were made of costal diaphragm, abdominal, and erector spinae muscle electromyographic activity; intra-abdominal, intrathoracic, and transdiaphragmatic pressures; and motion of the rib cage, abdomen, and arm. During limb movement the diaphragm and transversus abdominis were tonically active with added phasic modulation at the frequencies of both respiration and limb movement. Activity of the other trunk muscles was not modulated by respiration. Intra-abdominal pressure was increased during the period of limb movement in proportion to the reactive forces from the movement. These results show that coactivation of the diaphragm and abdominal muscles causes a sustained increase in intra-abdominal pressure, whereas inspiration and expiration are controlled by opposing activity of the diaphragm and abdominal muscles to vary the shape of the pressurized abdominal cavity.

Quantification of free mycophenolic acid by high-performance liquid chromatography-atmospheric pressure chemical ionisation tandem mass spectrometry

To facilitate the investigation of free mycophenolic acid concentrations we developed a high-performance liquid chromatography tandem mass spectrometry method using indomethacin as an internal standard. Free drug was isolated from plasma samples (500 mul) using ultrafiltration, The analytes were extracted from the ultrafiltrate (200 mul) using C-18 solid-phase extraction. Detection was by selected reactant monitoring of mycophenolic acid (m/z 318.9-->190.9) and the internal standard (m/z 356.0-->297.1) with an atmospheric pressure chemical ionisation interface. The total chromatographic analysis time was 12 min. The method was found to be linear over the range investigated, 2.5-200 mug/l (r>0.990, n=6). The relative recovery of the method for the control samples studied (7.5, 40.0 and 150 mug/l) ranged from 95 to 104%. The imprecision of the method, expressed in terms of intra- and inter-day coefficients of variation, was

In vivo measurement of the effect of intra-abdominal pressure on the human spine

In humans, intra-abdominal pressure (IAP) is elevated during many everyday activities. This experiment aimed to investigate the extent to which increased IAP-without concurrent activity of the abdominal or back extensor muscles-produces an extensor torque. With subjects positioned in side lying on a swivel table with its axis at L3, moments about this vertebral level were measured when IAP was transiently increased by electrical stimulation of the diaphragm via the phrenic nerve. There was no electromyographic activity in abdominal and back extensor muscles. When IAP was increased artificially to similar to 15% of the maximum IAP amplitude that could be generated voluntarily with the trunk positioned in flexion, a trunk extensor moment (similar to6 Nm) was recorded. The size of the effect was proportional to the increase in pressure. The extensor moment was consistent with that predicted from a model based on measurements of abdominal cross-sectional area and IAP moment arm. When IAP was momentarily increased while the trunk was flexed passively at a constant velocity, the external torque required to maintain the velocity was increased. These results provide the first in vivo data of the amplitude of extensor moment that is produced by increased IAP. Although the net effect of this extensor torque in functional tasks would be dependent on the muscles used to increase the IAP and their associated flexion torque, the data do provide evidence that IAP contributes, at least in part, to spinal stability. (C) 2001 Elsevier Science Ltd. All rights reserved.