In-vivo precipitation

Young What about the other CRYs in your in vivo precipitation ... 

If a crystallization-inhibitory polymer is incorporated into the amorphous solid dispersion, the in vivo precipitation may be delayed or completely eliminated, resulting in much improved oral absorption. It is ideal if the polymeric carrier can function as a precipitation (crystallization) inhibitor during in vivo dissolution (Zhang et al. 2009). 

Methods of detection, metabolism, and pathophysiology of the brevetoxins, PbTx-2 and PbTx-3, are summarized. Infrared spectroscopy and innovative chromatographic techniques were examined as methods for detection and structural analysis. Toxicokinetic and metabolic studies for in vivo and in vitro systems demonstrated hepatic metabolism and biliary excretion. An in vivo model of brevetoxin intoxication was developed in conscious tethered rats. Intravenous administration of toxin resulted in a precipitous decrease in body temperature and respiratory rate, as well as signs suggesting central nervous system involvement. A polyclonal antiserum against the brevetoxin polyether backbone was prepared a radioimmunoassay was developed with a sub-nanogram detection limit. This antiserum, when administered prophylactically, protected rats against the toxic effects of brevetoxin. 

We used outdated human CPD (citrate-phosphate-dextrose) blood from the Dayton Community Blood Center. At 21 days, CPD blood still retains 78% survival of the red blood cells and would fairly well simulate in vivo physiological conditions. During these tests, many enzymes and proteins may denature and/or precipitate. Even after suffering that trauma, the resulting fluid is more suitable for material testing than other pseudo-physiological fluids, since it still contains most of the salts, lipids, hormones, oligomers, nucleotides, saccharides, etc., found in whole blood in vivo. 

In the late 1970s and early 1980s there was a flurry of interest in precipitation techniques as a method of keeping ions in their in vivo locations, and thus avoid the problems mentioned in Subheading 3.1. The idea was simply to add a precipitant to the fixative, which reacted with the ion in question, and hopefully kept it where it was in the tissue. The most popular technique was to use a silver salt to precipitate chloride ions (35). Two problems emerged loss of ions was not totally prevented (36) and quantification was not possible. This led to the almost complete... 

In any case, through the propensity and specificity for aggregation (e.g., by jS-sheet formation in amyloids), proteins, silk, or otherwise, they will precipitate and form disordered aggregates or fibrils under the appropriate conditions (whether in vivo or in vitro Dobson, 1992 Fandrich et al., 2001 Uversky and Fink, 2004). 

Many factors may confound the assessment of the D DI potential of early discovery compounds [93], Limited or no solubility data exist to understand the likelihood that the compound will precipitate out of an in vitro incubation. The compounds have generally not been analyzed from a spectroscopic perspective their characteristics may interfere with a fluorogenic DDI assay. Metabolism data are typically not available. The binding of a compound to plasma proteins or microsomal incubation constituents is not well understood, which may lead to underprediction of its inhibitory potential. The compounds are typically delivered in DMSO, which may cause solvent-related inhibition of the enzymatic assay. Also, since little is known about in vivo concentrations or projected dose, framing the consequences of an early DDI in vitro experiment may be difficult. With these factors in mind, general experimental paradigms have been developed to help minimize their potential impact. 

Kinetic solubility This pragmatic approach starts with a concentrated compound solution in pure DM SO further diluted in a buffer medium. The amount of compound in solution is measured after a few minutes incubation either by recording its UV absorbance (with or without a chromatographic step) or precipitate formation using an optical method (turbidimetry, nephelometry or flow cytometry). This approach mimics the typical path of the compound in biochemical, cellular assays or in vivo animal models. Kinetic solubility usually serves as a quality filter prior to cell based assays (see paragraphs on solubility, permeability and cellular assays). 

Under neutral conditions, fluoride is also able to induce nucleation and growth of apatite crystals without the involvement of OCP [72]. This requires fluoride concentrations of 0.5 ppm or higher, which are rarely achieved in vivo except in cases where fluorosis may result. It is significant that in severe cases of fluorotic enamel, ultra-structural studies [73] have shown the occurrence of a proliferation of apatite nuclei, suggesting that the presence of fluoride may act to encourage precipitation of crystals of fluorapatite. 

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