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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 21 (1984), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Pseudomonas aeruginosa NCTC6750 and Escherichia coli K12 were used to study permeability of whole, intact cells to a series of labelled oligosaccharides. Stationary phase, oxygen depleted simple salts batch cultures were used. An efflux method was used to compare diffusion from cells of various 3H-labelled sugars (an homologous series based on isomaltitol) with diffusion of [14C]sucrose. Both plasmolysed and unplasmolysed cell suspensions were used. The data are consistent with an E. coli pore exclusion limit of approx. 833 Da for unplasmolysed cells and of about 670 Da for plasmolysed cells. For P. aeruginosa the data indicated a relatively small pore exclusion limit about the same size as sucrose with plasmolysis having little effect. These findings were confirmed with P. aeruginosa PAO1 grown in nutrient broth.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 11 (1994), S. 491-498 
    ISSN: 1573-904X
    Keywords: inhalation therapy ; rhDNase ; aerosols ; jet nebulizers ; therapeutic proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Recombinant human deoxyribonuclease I (rhDNase) is a new therapeutic agent developed to improve clearance of purulent sputum from the human airways. It is delivered by inhalation. Four jet nebulizers, T Up-Draft II (Hudson), Customized Respirgard II (Marquest), Acorn II (Marquest), and Airlife Misty (Baxter), were evaluated in vitro for their ability to deliver aerosols of rhDNase. The aerosols were generated from 2.5-mL aqueous solutions of rhDNase, at concentrations of either 1 or 4 mg/mL. In all experiments, the Pulmo-Aide Compressor (De Vilbiss) was used to supply the air to the nebulizers. Between 20 and 28% of the rhDNase dose initially placed in the nebulizers was delivered to the mouthpiece in the respirable range (1-6 µm). Evaluation of the rhDNase following nebulization in all four devices indicated that there was no loss in enzymatic activity and no increase in aggregation. Circular dichroism spectrophotometry indicated there was no change in either the secondary or the tertiary structure in rhDNase following nebulization. These results show that all four nebulizers are essentially equivalent in their ability to deliver respirable doses of rhDNase in an intact, fully active form. Changing the concentration of the solution in the nebulizer from 4 to 1 mg/mL rhDNase leads to a proportional reduction in the respirable dose delivered to the mouthpiece.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 13 (1996), S. 756-761 
    ISSN: 1573-904X
    Keywords: rhDNase ; heat denaturation ; protein ; additives ; calorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To study the thermal stability of recombinant human deoxyribonuclease I (rhDNase) in aqueous solutions. Methods. Differential scanning calorimetry (DSC) was used to measure the denaturation or melting temperature (Tm) and enthalpy (Hm) of rhDNase. The effects of denaturants (guanidine HC1 and urea) and additives (mainly divalent cations and disaccharides) were investigated at pH 6–7. Results. The Tm and Hm of rhDNase in pure water were measured as 67.4 °C and 18.0 J/g respectively, values typical of globular proteins. The melting peak disappeared on re-running the sample after cooling to room temperature, indicating that the thermal denaturation was irreversible. The latter was due to the occurrence of aggregation accompanying the unfolding process of rhDNase. Size exclusion chromatography indicated that during heat denaturation, rhDNase formed soluble high molecular weight aggregates with a molecular size 〉300kD estimated by the void volume. Of particular interest are the divalent cations: Ca2+ stabilizes rhDNase against thermal denaturation and elevates Tm and Hm while Mg2+, Mn2+ and Zn2+ destabilize it. Sugars also stabilize rhDNase. As expected, denaturants destabilize the protein and lower the Tm and Hm. All destabilization of rhDNase can be prevented by adding Ca2+ to the solutions. Conclusions. CaCl2 and sugars were found to stabilize rhDNase against thermal denaturation while divalent cations, urea and guanidine HC1 destabilize the protein. The effects could be explained by a mixture of mechanisms. For Ca2+ the protective effect is believed to be due to an ordering of the rhDNase structure in its native state, and by prevention of breaking of a disulfide bridge, thus making it less susceptible to unfold under thermal stress.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 16 (1999), S. 660-665 
    ISSN: 1573-904X
    Keywords: water ; solids ; rhDNase ; proteins ; lyophilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Development of a mathematical model to provide information about the amount of water associated with a protein and an excipient in a lyophilized product. Methods. The moisture content of the product and the mass fraction of each component were used to derive a model for the calculation of the mass of water associating with each component. The model was applied to lyophilized formulations of rhDNase containing various amounts of mannitol or lactose. The total water content was investigated by thermogravimetry, crystalline properties by X-ray powder diffraction and water uptake behaviour using a moisture microbalance system. Results. Calculations based on the model suggest that in a lyophilized rhDNase-mannitol formulation where the sugar is crystalline, most of the water is taken up by the protein. However, in the lyophilized rhDNase-lactose formulation where the sugar is amorphous, water is taken up by both the sugar and protein to a comparative extent. At high relative humidities when the amorphous sugar undergoes crystallization, the model can accommodate such a change by allowing for the formation of an additional crystalline phase. Conclusions. The rhDNase-sugar formulations show excellent conformity to the model which provides quantitative information about the distribution of water in the lyophilized binary protein-excipient products.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-904X
    Keywords: rhDNase ; dornase alpha ; powder aerosol ; spray drying ; inhalation ; powder blends
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. We have used rhDNase to investigate the feasibility of developing a dry protein powder aerosol for inhalation delivery. Methods. Powders of rhDNase alone and with sodium chloride were prepared by spray drying. Powder blends were obtained by mixing (tumbling and sieving) pure rhDNase powder with 'carrier' materials (lactose, mannitol or sodium chloride). The weight percent of drug in the blends was between 5 and 70%. The particle size distributions and crystallinity of the spray dried powders were obtained by laser diffraction and X-ray powder diffraction, respectively. Particle morphology was examined by scanning electron microscopy. The ability of the powders and powder blends to be dispersed into respirable aerosols was measured using a Rotahaler™ connected to a multistage liquid impinger operating at 60 L/min. Results. Pure rhDNase powder was quite cohesive with a fine particle fraction (FPF or 'respirable fraction': % wt. of particles 〈 7 μm in the aerosol cloud) of about 20%. When particles also contained NaCl, the powders were dispersed better to form aerosols. A linear relationship was observed between the NaCl content and FPF for a similar primary size (~3 μm volume median diameter) of particles. The particle morphology of these powders varied systematically with the salt content. For the blends, SEM revealed a monolayer-like adhesion of the fine drug particles to the carriers at drug contents ≥50 % wt. An overall 2-fold increase in FPF of rhDNase in the aerosol cloud was obtained for all the blends compared to the pure drug aerosols. Conclusions. The aerosol properties of spray dried rhDNase powders can be controlled by incorporation of a suitable excipient, such as NaCl, and its relative proportion. Coarse carriers can also enhance the performance of rhDNase dry powder aerosols.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nuclear medicine 13 (1987), S. 183-186 
    ISSN: 1619-7089
    Keywords: Aerosols ; Radioaerosols ; Aerosols-delivery systems ; Aerosols-evaluation ; Aerosols-diagnostic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effective delivery (ED) in MBq/min of a 100 MBq/ml nebuliser solution was defined as the rate of delivery of droplets in the respirable size range (aerodynamic diameter below 3.3 μm) to the mouthpiece of the aerosol delivery system (ADS). Wasted delivery (WD) was defined as the rate of delivery of droplets above 3.3 μm. ED and WD were measured on four types of commercially available ADS. The aerosols were sampled at the mouthpiece of each system and droplet size distribution measured with a seven stage cascade impactor. The effect of ambient air humidity on the droplet size produced by the Cadema delivery system was also evaluated. The ED values ranged from 6 to 15 MBq/min and WD values from 0.01 to 15 MBq/min. Two ADS produced low ED and WD values (6.1–9.0 and 0.01–0.07 MBq/min, respectively) due to a low output, while another produced higher ED and WD values [11.3±0.2 (SD) and 15.4±0.5 (SD) MBq/min, respectively] due to a larger droplet size. The Cadema delivery system gave the optimum characteristics of high ED [13.9±0.8 (SD) MBq/min] and low WD [1.24±0.61 (SD) MBq/min] values. The mass median aerodynamic diameter (MMAD) of the Cadema ADS fell by 22% (P〈 0.01) as the ambient dilution air was dried from a high relative humidity (RH) (88%–100%) to a low RH (12%–17%). The variability of both MMAD and geometric standard deviation (σg) was increased with dry dilution air (P〈 0.01).
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nuclear medicine 18 (1991), S. 860-860 
    ISSN: 1619-7089
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nuclear medicine 18 (1991), S. 511-513 
    ISSN: 1619-7089
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 321-321 
    ISSN: 1573-8744
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pharmacokinetics and pharmacodynamics 12 (1984), S. 525-534 
    ISSN: 1573-8744
    Keywords: pharmacokinetics ; Michaelis-Menten model ; steady state predictions ; sensitivity analysis ; experimental design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Linear sensitivity theory is used to estimate the reliability of predictions of the minimum and maximum concentrations at steady state in the Michaelis-Menten model with i.v. bolus. The dependence of the relative errors in the predictions on the errors in the pharmacokinetic parameters is derived in an analytical form. It is shown that the quality of the predictions is not equally sensitive to all errors in parameters, and that the sensitivity factors vary with the degree of saturation of the system. An example of application for a drug, such as phenytoin, is discussed. It is suggested that sensitivity analysis may be useful in design of pharmacokinetic experiments aimed at the control of steady state levels for drugs with Michaelis-Menten kinetics.
    Type of Medium: Electronic Resource
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