Burst morphology

Figure 13.28. Burst morphologies of E. coli and K. ozaenae colonies at low agar concentration [73]. See also Colour Plate Section.

The majority of the aforementioned capsules were either not sufficiently mechanically stable or suffered from other surface or matrix related deficiencies. These deficiencies include poor morphology, such as capsule sphericity and surface smoothness, which result from an osmolar imbalance. Membranes are also often leaky (an internal polymer slowly diffuses out through the capsule wall) or shrink in either PBS or in culture media over a period of a few hours. Exceptionally, some capsules are observed to swell excessively and burst. Furthermore, some complex membranes, although stable in water, dissolve over several days upon a contact with culture media. This is true for pectin based capsules (pectin/calcium salt) and for alginate-chitosan membranes and maybe a consequence of the polycation substitution by electrolytes present in the media [10]. In order to improve the existing binary capsules several approaches, both traditional and novel, have been considered and tested herein. These are discussed in the following sections. 

Transmission electron microscope (TEM) revealed that cellular membranes bursted during ECT and morphological changes corresponding to inhibition of cell proliferation were visible.37... 

Other models are based on electric breakdown of the oxide [Fo2, Chl2]. It is not clear whether this breakdown should be thought of in terms of an electronic or an ionic effect. However, in both cases breakdown may cause a degradation in the oxide morphology, which leads to an enhanced etch rate. An electric field strength in the order of 10 MV cm4, the observation of an electroluminescent burst associated with the current peak of the oscillation, and the presence of an electronic component in the interface current are in favor of this model [CalO, Chl2]. 

The PGO waves of REM sleep are epileptiform. Both consist of spike and wave EEG complexes that are morphologically indistinguishable. In both PGO waves and temporal lobe epilepsy, these spike and wave complexes are generated by similar mechanisms owing to a physiological decline in inhibitory modulation (REM sleep) or to structural damage (TEE), neurons are disinhibited and fire in intense bursts, of which the EEG spike and wave complex is the extracellular record. 

IFN-y also induces the costimulatory molecules on the macrophages, which increases cell-mediated immunity. As a consequence, there is activation and increase in the tumoricidal and antimicrobial activity of mononuclear phagocytes, granulocytes and NK cells. The activation of neutrophils by IFN-y includes an increase in their respiratory burst. IFN-y stimulates the cytolytic activity of NK cells. It is an activator of vascular endothelial cells, promoting CD4+ T lymphocyte adhesion and morphological alterations, which facilitates lymphocyte extravasation. IFN-y promotes opsonization by stimulating the production of IgG subclasses that activate the complement pathway. A summary of the characteristics of selected cytokines is shown in Table 2.3. 

The current burst model is potentially powerful in providing explanations for many mechanistic and morphological aspects involved in the formation of PS. However, as recognized by Foil et al. themselves, it would be extremely difficult for such a unified model to be expressed in mathematical form because it has to include all of the conditional parameters and account for all of the observed phenomena. Fundamentally, all electrochemical behavior is in nature the statistical averages of the numerous stochastic events at a microscopic scale and could in theory be described by the oscillation of the reactions on some microscopic reaction units which are temporally and spatially distributed. Ideally, a single surface atom would be the smallest dimension of such a unit and the integration of the contribution of all of the atoms in time and space would then determine a specific phenomenon. In reality, it is not possible because one does not know with any certainty the reactivity functions of each individual atoms. The difficulty for the current burst model would be the establishment of the reactivity functions of the individual reaction units. Also, some of the assumptions used in this model are questionable. For example, there is no physical and chemical foundation for the assumption that the oxide covering the reaction unit is... 

Controlled-release biodegradable PLG polymers loaded with parathyroid hormone were formulated as a freeze-dried form with particle size ranging from 27 to 47 i. The freeze-dried method did not alter the surface morphology, particle size, and parathyroid hormone content or release rate of the microspheres. The freeze-dried microspheres resuspended very rapidly and uniformly in solution. In vitro release studies indicated that except for a slight early burst ranging from 4-18%, release of parathyroid hormone from the nanoparticles was very slow over the first 14 days. At 15 days, release of parathyroid hormone accelerated rapidly. 

Chagnac-Amitai Y, Luhmann H, Prince D (1990) Burst generating and regular spiking layer 5 pyramidal neurons of rat neocortex have different morphological features. J. Comp. Neurol. 296, 598-613. 

In contrast to apoptosis, cells that die in response to tissue damage exhibit very different morphological changes, referred to as necrosis. Typically, cells that undergo this process swell and burst, releasing their intracellular contents, which can damage surrounding cells and frequently cause Inflammation. 

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