ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

Hits per page

hits 1 - 2 | 2 hits

Sorting

Electronic Resource

Drug Release From Hydrocolloid Embeddings with High or Low Susceptibility to Hydrodynamic Stress (1995)

Lindner, Wolfram D. ; Lippold, Bernhard C.

Springer

Pharmaceutical research 12 (1995), S. 1781-1785

add to mindlist on the mindlist

Details

ISSN: 1573-904X

Keywords: hydrocolloid embeddings ; √t kinetics ; zero-order release ; hydrodynamic stress ; diffusion control ; erosion control

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract Purpose. The subject of the study was the influence of hydrodynamic stress on the drug release from direct compressed hydrocolloid embeddings. Additionally a correlation between the release kinetics and different polymer characterising parameters was attempted. Methods. The drug release was fitted to an expanded Korsmeyer equation to describe the release kinetics. The influence of the stirring rate of the paddle in the USP paddle apparatus on the Mean Dissolution Time (MDT) was expressed as quotient of the MDT's at the stirring rate of 200 and 100 min−1. Results. If the drug release followed the square root of time kinetics, nearly no effect of the agitation speed on the release rate was observed. To achieve this diffusion controlled drug release the developing gel layer had to be hydrated very well and resistant against erosion (viscosity of at least 4000 mPa · s of the 2% polymer solution and a small expansion of the swelling gel especially at the beginning of the release). The erosion controlled zero order release was generally much affected by the hydrodynamic stress except for some hydrocolloids with incomplete swelling. Thus, it was possible to define a new release mechanism, the polymer particle erosion. The drug release was controlled by the attrition of partially swollen polymer particles and not by the polymer dissolution or drug diffusion. Conclusions. Polymer particle erosion or diffusion control should be the release controlling mechanisms for negligible influence of hydrodynamic stress.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1016238427313

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

Electronic Resource

Signal perception of fibroblasts for directional migration to platelet-derived growth factor in Boyden-type chambers (1990)

Adelmann-Grill, Bernhard C. ; Cully, Zuzana

New York, NY [u.a.] : Wiley-Blackwell

Journal of Cellular Physiology 143 (1990), S. 172-177

add to mindlist on the mindlist

Details

ISSN: 0021-9541

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: Fibroblast chemotaxis has usually been determined in Boyden-type chambers with polycarbonate filters, assuming that a stable concentration gradient of the attractant develops that causes directional migration of the cells. This view has been repeatedly challenged, and development of such gradients in vivo is unlikely. The present experiments were designed to test if a stable concentration gradient was required for normal dermal fibroblasts to migrate toward platelet-derived growth factor. It was found that a brief pulse of the attractant was required and sufficient to induce chemotaxis. The pulse had to contain a specific concentration of attractant and was ineffective when not unilateral. The observed effects could not be attributed to induction of random migration or migration on a mediator-coated surface. It is not clear which machinery is regulating this cellular behaviour, but it is suggested that cells may migrate in vivo by similar mechanisms, because the establishment of stable concentration gradients of attractants in tissues is deemed unlikely.

Additional Material: 1 Ill.