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Freeze-dried samples of sucrose with buffer salts, amino acids, or dextran have been analyzed with differential scanning calorimetry (DSC) to evaluate the use of DSC thermograms in predicting the physical storage stability. The glass transition temperature, Tg, of the amorphous cake, crystallization, and melting of sucrose are observed with DSC. Tg appeared to be an important characteristic of the physical stability of the amorphous freeze-dried cake. A storage temperature above Tg results in collapse or shrinkage of the cake, which for a sucrose-based formulation, may be accompanied by crystallization of the sucrose. The Tg of the amorphous sucrose is influenced by other components present in the cake. Dextran-40 raised Tg, while the addition of glycine to the formulation lowered Tg. The residual moisture content strongly influences Tg, since water acts as a plasticizer of the system; the higher the moisture content, the lower the Tg and the less physically stable the freeze-dried cake. Crystallization of amorphous sucrose is shown to be inhibited by high molecular weight components or ionic compounds. DSC analysis of freeze-dried cakes proved to be a powerful tool in formulation studies.
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PMID:Evaluation of the physical stability of freeze-dried sucrose-containing formulations by differential scanning calorimetry. 158 94

The discovery and development of increasingly potent biological and pharmaceutical products have resulted in very small amounts of the active ingredient in final product formulations. Pediatric vaccines with sub-milliliter dose sizes pose unique problems for final formulation and lyophilization, especially when stabilizers used are present in small amounts or are hygroscopic. Lyophilized Haemophilus b Conjugate Vaccine (Meningococcal Protein Conjugate) (PedvaxHIB) has a plug weight of about 3 mg in its final formulation. Microgram amounts of water absorbed by the lyophilized plug can cause drastic changes in the moisture content of the product. In a small percentage of the final containers absorption of moisture by the vaccine may cause aesthetic defects (plug collapse) over time, or at elevated temperatures. This paper describes drying methods developed to control residual moisture levels in stoppers used as final container closures. Results on the moisture stability of the product capped with dried and non-dried stoppers are presented.
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PMID:The effects of stopper drying on moisture levels of Haemophilus influenzae conjugate vaccine. 159 70

SK&F 101926 is a synthetic octapeptide which was designed to promote free water excretion by antagonizing the action of antidiuretic hormone. The clinical and pathologic changes in rats resulting from lethal doses of SK&F 101926 have suggested that death is associated with respiratory failure and/or cardiovascular collapse. To define the relationships between respiratory failure, cardiovascular collapse, and death, respiratory and cardiovascular parameters were monitored in anesthetized rats following the intravenous administration of SK&F 101926 at a dosage (3 mg/kg) which resulted in 70% mortality. Within 5 min after receiving this dosage, mean arterial blood pressure was reduced to values between 30 and 40 mm Hg in all rats. This degree of hypotension was well tolerated by some rats and, consequently, was not considered to be the cause of death. Deaths occurred between 9 and 58 min after dosing and were preceded by respiratory depression involving marked reductions in respiratory rate and the lack of compensatory increases in tidal volume. At the time of respiratory arrest, heart rates remained above 200 beats/min, mean arterial blood pressure remained between 30 and 40 mm Hg, and there were no consistent changes in dynamic lung compliance or total pulmonary resistance. Pretreatment of rats with a mast cell stabilizing agent (disodium cromoglycate), a mast cell degranulating agent (compound 48/80), or a histamine/5-hydroxytryptamine blocking agent (cyproheptadine) prevented the reductions in respiratory rate and death caused by SK&F 101926. These pretreatments also reduced the effect of SK&F 101926 on blood pressure, but were not able to completely prevent the hypotension.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Respiratory and cardiovascular changes associated with toxic doses of a peptide antagonist of vasopressin in the rat. 160 Dec 32

An animal model of experimental perilymphatic fistula (EPLF) was developed in the guinea pig in order to study vestibular pathophysiology. In experimental animals, 4 microL of perilymph was suctioned from one cochlea via the round window membrane. Changes in vestibular function were as follows. 1) During the acute stage (5 hours postoperatively), spontaneous nystagmus directed toward the normal side was noted in 57.4% of the EPLF animals. This lasted less than 24 hours. 2) One week postoperatively, direction-fixed positional nystagmus toward the lesioned ear was present in 22.7% of the EPLF animals, especially when the lesioned ear was positioned inferiorly. 3) With the ice water caloric test, no response was present in 58.1% of the EPLF animals and an irregular response was found in 22.6% of them, 1 week postoperatively. These results tend to indicate that tests of vestibular function may differentiate between patients with Meniere's disease and those with perilymphatic fistula. Histologic findings indicate that a floating labyrinth is the cause of positional nystagmus and caloric irregularity. The absence of caloric responses was associated with collapse of the vestibular labyrinth.
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PMID:Vestibular pathophysiologic changes in experimental perilymphatic fistula. 162 10

A 23-year-old male with complete collapse of the right lung due to spontaneous pneumothorax was admitted 11 days after its onset. Paying close attention to the re-expansion pulmonary edema (REPE), water seal drainage was performed. Following couple episodes of persistent severe cough, four hours later, he developed dyspnea and began to expectorate frothy massive sputum. Chest X-ray revealed pulmonary edema of the entire right lung field. Measurement of total proteins and neutrophil elastase in airway exudates showed 5.5 g/dl (ratio to plasma, 0.89) and 7000 micrograms/l, respectively. Because of marked difference of compliance between bilateral lungs, management with right and left-separated mechanical ventilation and PEEP applied only to the right lung was performed. Although transient mediastinal deviation to the left was observed, successful management was achieved by the maneuver. High concentrations of total proteins and neutrophil elastase in edema fluid suggest that increased vascular permeability due to endothelial cell injury via activated neutrophils is mainly responsible for REPE. In the present case, rapid expansion of the collapsed lung accelerated by severe cough seems to be a predisposing factor of REPE. In patient with prolonged pneumothorax, suppression of cough is thought to be important for the prevention of REPE even with water seal drainage.
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PMID:[A case of re-expansion pulmonary edema following water seal drainage for spontaneous pneumothorax--management with right and left-separated mechanical ventilation]. 163 63

The term "caloric irregularity" was coined to refer to a gross irregularity in the amplitude and/or frequency of a caloric-induced nystagmus, having a variable slow-phase velocity and prolonged duration. Twelve of 46 guinea pigs with experimentally induced perilymphatic fistula had irregular responses to the ice-water caloric test 1 week after creation of a fistula. The long-term vestibular consequences in animals with caloric irregularities were either resolution and return to normal function (i.e. caloric return) or continuing deterioration to canal paresis. Morphological examination of ears with caloric irregularity revealed that there had been partial collapse of the membranous labyrinth and the creation of a floating labyrinth.
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PMID:Caloric irregularity in experimentally induced perilymphatic fistula. 164 73

Gd-DTPA (Gd) enhanced Magnetic Resonance (MR) early images and delayed images of 28 patients with pulmonary or mediastinal tumors were analyzed and compared with the computed tomography scans and the plain MR images. Numbers of relative signal intensity of the tumors, secondary lesions (adjacent pneumonia or collapse) and pleural effusions were calculated and graphed on time intensity curves. Gd-enhanced MR early images were more useful than other methods in delineating viable areas from necrotic areas. However, Gd-enhanced MR delayed images better delineated margins of necrotic areas than Gd-enhanced MR early images did in some cases. In distinguishing tumors from secondary lesions, Gd-enhanced MR early images were the most useful, too. We considered Gd gradually penetrated into pleural effusions after intravenous administration, just in the same way into necrotic areas. Therefore pleural effusions showed very high intensity on Gd-enhanced MR delayed images. Time intensity curves of the tumors and pleural effusions showed characteristic patterns, but those of secondary lesions showed different patterns among the individual cases. We presumed this was due to the variances of the water and fibrous components among them.
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PMID:[Clinical value of Gd-DTPA enhanced MRI of pulmonary and mediastinal tumors]. 165 71

It is hypothesized that (cAMP, ATP) is the elusive, universal Turing morphogenetic couple, which defies the second law of thermodynamics, i.e. the inexorable march towards homogeneity. cAMP and ATP can be distributed nonhomogeneously because the whole of the intermediary metabolism is so organized that they mutually satisfy the Turing bifurcation conditions upon nonlocalized application of an extracellular ligand, in particular a soluble peptide growth factor, which is nature's distinguished universal bifurcation parameter, acting homogeneously in space and removing the substrate inhibition from adenylate cyclase and thus triggering embryonic induction by triggering the (cAMP, ATP) Turing system. The hypothesis predicts that although the extracellular signal, the growth factor, is applied homogeneously, an organized "dissipative structure" will emerge spontaneously in the responding tissue; this "symmetry breaking" in a reaction-diffusion system occurs precisely in the manner envisaged by Turing, where (cAMP, ATP) constitutes the "reaction-diffusion system". This Turing bifurcation explicates the recent experiments where a differentiated embryoid emerges from the mere immersion of frog animal caps in an homogeneous growth factor solution, and similar experiments on chicks. The "metabolic" patterns found by Child and colleagues also reflect dissipative structures arising in a (cAMP, ATP) reaction-diffusion system when interpreted in the light of modern biochemistry: in particular, the localized glycogen depletion reflects localized cAMP; localized redox, respiratory or susceptibility activity reflects localized ATP. The dramatic collapse of organized structure found by Child and colleagues, for example, when Planaria or a section of it is exposed to an homogeneous environment of a narcotic solution, and the reemergence of structure upon return to water, are explained on the basis of the violation or satisfaction of the Turing bifurcation conditions with respect to (cAMP, ATP), respectively. cAMP is the "activator", ATP is the "inhibitor", and together they mutually satisfy the four activator-inhibitor inequalities, including the all-important autocatalytic cAMP production, as well as the lateral inhibition condition. The functional significance of gap junctions is to generate a multicellular purely reaction-diffusion system for (cAMP, ATP) as envisaged by Turing. It is emphasized that localization and pattern formation occur intracellularly in gap junction-coupled cells and not, as often suggested, extracellularly, the latter localization being too fragile to be maintained for long enough, and soon succumbing to the mixing effect of convection and movement. The activator-inhibitor property of (cAMP, ATP) means that the spatial distribution of cAMP and ATP could be not only nonhomogeneous but also of the same shape.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:An hypothesis: phosphorylation fields as the source of positional information and cell differentiation--(cAMP, ATP) as the universal morphogenetic Turing couple. 165 48

In 19 anesthetized piglets 3 ventilatory modes were studied after inducing pulmonary insufficiency by bronchoalveolar lavage by the method of Lachmann. The lavage model was considered suitable for reproduction of severe respiratory distress. This model was reproducible and stable with respect to alveolar collapse, decrease in static chest-lung compliance and increase in extravascular lung water. The ventilatory modes studied were volume-controlled intermittent positive-pressure ventilation (IPPV), pressure-controlled inverse ratio ventilation (IRV), and pressure-controlled high-frequency positive-pressure ventilation (HFPPV). The 3 ventilatory modes were used in random sequence for at least 30 min to produce a ventilatory steady state. Ventilation with no PEEP, permitting alveolar collapse, was interposed between each experimental mode. The ability to open collapsed alveoli, i.e. alveolar recruitment, was different. The recruitment rate for IPPV was 74%, but for IRV and HFPPV it was 95%, respectively. Although IRV provided the best PaO2, this was at the expense of high airway pressures with circulatory interference and reduced oxygen transport. In contrast to this, HFPPV provided lower airway pressures, less circulatory interference and improved oxygen transport. In the clinical setting there might be negative effects on vital organs and functions unless the ventilatory modes are continuously and cautiously adapted to the individual requirements in different phases of severe respiratory distress. Therefore, one ventilatory strategy could be to "open the airways" with IRV, but then switch to HFPPV in an attempt to maintain the airways open with lesser risk of barotrauma and with improved oxygen transport.
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PMID:An experimental study of different ventilatory modes in piglets in severe respiratory distress induced by surfactant depletion. 174 8

Descriptions of the functional significance of carbohydrates based on the familiar equilibrium thermodynamics of very dilute solutions fail for pragmatical time scales and conditions, which are far from equilibrium. This is not too surprising, since limiting partial-molar properties reflect the independent behavior of solute in the limit of infinite dilution where free volume is maximum at a given temperature, while Tg'-Wg' properties reflect the cooperative behavior of solute-plasticizer blends at the limiting minimum value of free volume to observe relaxation within experimental time scales. Carbohydrate-water systems, with well-characterized structure and MW above and below the entanglement limit, provide a unique framework for the investigation of non-equilibrium behavior. Thermal analysis by DSC reveals the central role of water as a plasticizer for carbohydrates and of the glass transition as a physicochemical parameter that governs their properties, processing, and stability. A classical polymer science approach is used to study structure-property relationships of carbohydrates as water-compatible food polymers, which are treated as homologous systems of polymers, oligomers, and monomers with their plasticizers and solvents. Mechanical relaxation behavior is described by a "transformation map" of the critical variables of moisture content, temperature, and time. The glass curve is a reference contour, which represents the limiting isogram for free volume, local viscosity, relaxation rates, and rotational and translational mobility. Map domains are discussed as aspects of "water dynamics," to dispel the myth of "bound water," and "glass dynamics," to relate to macroscopic structure and collapse phenomena. A particular glass with invariant composition and Tg (prepared by freeze-concentration) is identified as a pivotal and practical reference state. The Tg observed during DSC analysis is often an effective Tg, resulting from instantaneous relative relaxation rates and non-uniform distribution of total sample moisture. Non-equilibrium melting, annealing, and gelation/recrystallization of kinetically metastable, partially crystalline carbohydrate systems exhibit non-Arrhenius kinetics which depend on the magnitude of delta T above the appropriate Tg, as defined by WLF relaxation transformations. Thermally reversible aqueous gels (crystallized from an under-cooled, rubbery melt) are described by a "fringed micelle" structural model for a three-dimensional polymer network, composed of microcrystalline junction zones crosslinking plasticized amorphous regions of flexible-coiled, entangled chain segments.
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PMID:A food polymer science approach to structure-property relationships in aqueous food systems: non-equilibrium behavior of carbohydrate-water systems. 174 35


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