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  • 1
    Electronic Resource
    Electronic Resource
    Development and Evaluation of Sustained-Release Ibuprofen–Wax Microspheres. II. In Vitro Dissolution Studies (1994)
    Springer
    Pharmaceutical research 11 (1994), S. 575-579 
    Details
    ISSN: 1573-904X
    Keywords: ibuprofen ; microspheres ; dissolution ; matrix drug release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A modified USP paddle method using minibaskets was used to study the effects of various formulations on in vitro dissolution of ibuprofen microspheres. Formulations containing waxes such as paraffin or ceresine wax without modifiers exhibited very slow dissolution profiles and incomplete release, which did not improve with increased drug loading or the preparation of smaller microspheres. The addition of modifiers such as stearyl alcohol and glyceryl mono-stearate greatly increased the dissolution rate, with 20% (w/w) near the optimum for predictable dissolution. Higher drug loading and decreased microsphere size increased the dissolution rate from microspheres containing modifier. Optimum formulations contained ceresine wax or microcrystalline wax and stearyl alcohol as a modifier, with a drug content of 17%. An increase in the encapsulation dispersant concentration had little effect on the dissolution profiles. The dissolution data from narrow size fractions of microspheres indicated spherical matrix drug release kinetics; the 50% dissolution time decreased with the square of the microsphere diameter. With appropriate modifiers, wax microsphere formulations of drugs with solubility characteristics similar to those of ibuprofen can offer a starting basis for predictable sustained release dosage forms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018931002991
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  • 2
    Electronic Resource
    Electronic Resource
    Middle-ear development: II. Morphometric changes in the conducting apparatus of the chick (1992)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 212 (1992), S. 257-267 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The ontogeny of various middle-ear structures was examined in 11 groups of chicks between 10 days embryonic and adult. Measurements of the tympanic membrane surface area and height, columella length, and that of the columella footplate, annular ligament, and oval window area were obtained using video micrographs and computer digitization techniques. The oval window matures first at 53 days post-hatching, whereas the columella achieves adult size at 74 days. The tympanic membrane surface area is the last middle-ear variable studied to reach adult size (79 days post-hatch). The columella increases its length from 0.63 mm (10 days embryonic) to 2.73 mm in the adult. The tympanic membrane area expands by 280% whereas the columellar footplate area increases by 11x. As a result, the pressure amplification of the middle ear due to the tympanic membrane/columellar footplate area ratio improves by over 400%. These data further contribute to our understanding of the functional development of the middle ear. © 1992 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052120305
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  • 3
    Electronic Resource
    Electronic Resource
    Development and Evaluation of Sustained-Release Ibuprofen-Wax Microspheres. I. Effect of Formulation Variables on Physical Characteristics (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 1377-1383 
    Details
    ISSN: 1573-904X
    Keywords: ibuprofen ; waxes ; microspheres ; modifiers ; size analysis ; thermal analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A congealable disperse phase encapsulation method was used to prepare sustained-release ibuprofen-wax microspheres. Microspheres prepared with paraffin wax, such as ceresine and micro-crystalline waxes, using polyvinylpyrrolidone (PVP) as dispersant had a tendency to aggregate, but the addition of wax modifiers (stearyl alcohol and glyceryl monostearate) greatly reduced aggregation. Optimum modifier and dispersant concentrations were 20% (w/w) and 5% (w/v), respectively. The particle size distribution of the microspheres was log-normal. An increase in modifier, dispersant concentration, emulsification stirring speed, or temperature shifted the size distribution toward finer particles. Microcrystalline wax required a higher emulsification temperature and produced finer particles than ozokerite wax. The recovery of drug from the different microsphere formulations varied between 71 and 92%. Differential scanning calorimetry (DSC) of the single components and physical mixtures showed endothermic peaks at the respective melting-point ranges. The DSC of the ceresine and microcrystalline wax microspheres was similar to rescans of ternary mixtures of components of the microspheres with less prominent and lower melting temperatures than individual components or physical mixtures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015845022112
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of Drug Loading and Molecular Weight of Cellulose Acetate Propionate on the Release Characteristics of Theophylline Microspheres (1991)
    Springer
    Pharmaceutical research 8 (1991), S. 1396-1400 
    Details
    ISSN: 1573-904X
    Keywords: microspheres ; encapsulation ; drug loading ; dissolution ; cellulose acetate propionate ; molecular weight ; theophylline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Microspheres with 40, 50, and 60% drug loading of anhydrous theophylline core material were prepared by the emulsion-solvent evaporation method. Three different molecular weights of cellulose acetate propionate were used as encapsulating polymers. The geometric mean diameter of the microspheres increased with drug loading for all polymers. Dissolution rate for a given particle size fraction also increased with drug loading for all polymers. Higuchi/Baker-Lonsdale spherical matrix dissolution kinetics were followed by narrow particle size fractions of the microspheres. A linear relationship between the T-50% (time required for 50% of the drug to be released) and the square of microsphere diameter was observed with all three molecular weights of the encapsulants. The slowest drug release was obtained with the high molecular weight polymer, which also produced the smoothest microspheres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015801207091
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  • 5
    Electronic Resource
    Electronic Resource
    The passage of exogenous peroxidase from blood capillaries into the intestinal epithelium (1967)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 159 (1967), S. 159-169 
    Details
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Horseradish peroxidase was injected into the spleens of mice and the animals were sacrificed ten minutes after injection. The tissues were reacted with 3-3′ diaminobenzidine hydrochloride and the distribution of the reaction product was studied with both the light and electron microscope. The peroxidase was localized between epithelial cells up to the region of the tight junction and within vacuoles in the absorptive cells Granules ranging in size from ca. 40A to 600A were observed in the cytoplasm of epithelial cells in numbers far in excess of that found in control specimens. It appeared that the diffuse light brown staining observed in epithelial cells with the light microscope could be attributed to large numbers of granules of reaction product free in the cytoplasm. When corn oil was given by stomach tube and an intravascular injection of perioxidase was given ten minutes later, absorbed lipid was found to pass from interepithelial cell spaces to lamina propria at the same time that peroxidase was traversing the same compartments in the reverse direction. Hence, it was shown that exogenous peroxidase and probably other substances of vascular origin required for the metabolism of epithelial cells are exposed to both the basal and lateral epithelial cell membranes, even when absorbed lipid is traversing the same spaces in the opposite direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1091590205
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  • 6
    Electronic Resource
    Electronic Resource
    Middle-ear development VI: Structural maturation of the rat conducting apparatus (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 239 (1994), S. 475-484 
    Details
    ISSN: 0003-276X
    Keywords: Middle ear ; Auditory ; Hearing development ; Ossicles ; Tympanic membrane ; Rat (Long Evans strain) ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Background: The contribution of middle-ear development to the overall development of hearing has not been explored in great detail. This presentation describes the maturation of conductive elements in the rat middle ear, and provides the basis on which future studies of middle-ear functional development will follow.Methods: The middle-ear apparatus was examined at nine different ages (between 1 and 80 days postpartum) in Long Evans rats. At each age elements of the conducting apparatus were observed with either light or scanning electron microscopy (SEM), and quantitative measurements were made from video enhanced photomicrographs. Tympanic membrane area and cone depth, the length of the malleus and incus arms, ossicular weight, stapes foot plate and oval window areas, and bulla volume were all measured. Development of the area and lever ratios were derived from these measurements. The data were fitted to exponential equations and the time in days required to reach 90% of the adult level determined.Results: The pars tensa achieved 90% of total area by 17 days. The oval window achieved the 90% criterion by 13 days, while the area ratio was within 10% of its adult size by 8 days. The ossicles took between 26 and 34 days, while bulla volume took 59 days to reach the 90% level.Conclusions: Middle-ear growth was very orderly and systematic in the data reported. When maturation of the area ratio was considered against development of the endocochlear potential or the round window compound action potential, it was clear that the growth of this important aspect of the middle ear preceded the onset of cochlear function. © 1994 Wiley-Liss, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092390413
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  • 7
    Electronic Resource
    Electronic Resource
    A morphological and histochemical study of the primary and secondary immune responses in the rat spleenThis project received support from a General Research Support Grant to the University of Wisconsin Medical School from the National Institutes of Health, Division of Research Facilities and Resources. (1967)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 121 (1967), S. 305-317 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Macrophages and cells of the plasmocyte series were studied in the rat's spleen during the primary and secondary immune responses to particulate antigen. Evidence is presented to suggest that the plasma cell precursors are located in the marginal zones surrounding the lymphoid nodules and that less than one day following injection of antigen, these cells migrate into the nodules, where mitosis and subsequent differentiation into hemocytoblasts occurs in the presence of nodular macrophages. The hemocytoblasts then migrate across the marginal zone into the red pulp where differentiation into mature plasma cells occurs in the presence of red pulp macrophages. It is suggested that the initiation of the antibody-forming process occurs in the lymphoid nodules where marginal zone cells come into close contact with the marginal metalophils or with germinal center macrophages. The process initiating the migration of cells from the marginal zone to the nodules is unknown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001210209
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  • 8
    Electronic Resource
    Electronic Resource
    Marginal zone and germinal center development in the spleens of neonatally thymectomized and nonthymectomized young ratsThis project received support from a General Research Support grant to the University of Wisconsin Medical School from the National Institutes of Health, Division of Research Facilities and Resources. (1968)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 123 (1968), S. 489-499 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Spleens from neonatally thymectomized and nonthymectomized young rats were studied histologically and histochemically to elucidate the development of the splenic immune system with and without thymus.In intact animals primitive germinal center activity could be elicited with antigen as early as 13 days of age. More definitive germinal centers lacking tingible body macrophages were observed at 18 days of age. Germinal centers containing tingible body macrophages did not develop until 35 days of age in response to antigenic stimulation. This coincided with maximal development of the marginal zone of medium-sized lymphocytes and the mature development of nodular macrophages possessing strong acid phosphatase activity.Neonatally thymectomized rats developed marginal zones and germinal centers similar to control littermates when the young animals were maintained on tetracycline. Thymectomized animals not given tetracycline showed disturbances in splenic development. These are discussed.The results suggest that the thymus may be critical to the immune system in rats from birth to about 30 days of age but is not essential to its function beyond this period. Marginal zone lymphocytes and germinal center cells proliferate normally and mature to the plasma cell stage in the absence of a thymus if the animals are maintained on tetracycline beyond this critical age.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001230306
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  • 9
    Electronic Resource
    Electronic Resource
    Immunohistochemical localization of atrial natriuretic peptide in the developing and adult mammalian kidney (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    American Journal of Anatomy 190 (1991), S. 182-191 
    Details
    ISSN: 0002-9106
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The discovery, within the last decade, of atrial natriuretic peptide (ANP), a family of peptides with natriuretic/diuretic and vasorelaxant properties, has prompted much research into the mechanisms and sites of action of ANP within the kidney. In the present study, ANP was localized in the kidneys of several mammalian species by immunohistochemical techniques (1) to identify possible sites of synthesis; (2) to compare the localization of ANP to known physiological effects; (3) to determine species differences, if any, in ANP localization; and (4) to study the development of ANP immunoreactivity in the fetal and neonatal rat kidney. Using an antibody against rat ANP IV, ANP was localized exclusively on the proximal convoluted tubule (PCT) brush border and within intercalated cells of the outer medullary and cortical collecting tubules and ducts of adult mouse, rat, pig, monkey, and human kidneys. The development of ANP immunoreactivity paralleled the differentiation and maturation of collecting duct epithelium in rat fetal kidney. Atrial natriuretic peptide found within intercalated cells of the cortical and outer medullary collecting ducts may be the result of endogenous synthesis and, following secretion, may be available to receptors in the inner medullary collecting ducts.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aja.1001900207
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of pulsed microwaves on passive electrical properties and interspike intervals of snail neurons (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 14 (1993), S. 503-520 
    Details
    ISSN: 0197-8462
    Keywords: constant temperature ; intracellular recording ; time series ; regression analysis ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The effects of pulsed microwaves (2.45 GHz, 10 μs, 100 pps, SAR: 81.5 kW/kg peak, 81.5 W/kg average) on membrane input resistance and action potential (AP) interval statistics were studied in spontaneously active ganglion neurons of land snails (Helix aspersa), at strictly constant temperature (20.8±.07°C worst case). Statistical comparison with sham-irradiated neurons revealed a significant increase in the mean input resistance of neurons exposed to pulsed microwaves (P ≪ .05 ). Pulsed microwaves had no visible effect on mean AP firing rate; this observation was confirmed by analysis of interspike intervals (ISIs). Using an integrator model for spontaneously active neurons, we found the net input current to be more variable in neurons exposed to pulsed microwaves. The mean input current was not affected. The standard deviation of ISIs and the autocorrelation of the input current were marginally affected, but these changes were not consistent across neurons. Although the observed effects were less obvious than those reported in other studies, they represent evidence of a direct interaction between neurons and pulsed microwaves, in the absence of macroscopic temperature changes. The data do not suggest a single, specific mechanism for such interaction. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250140603
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