Useful Principles for the Crystallization of Proteins
Hartmut Michel in Crystallization of Membrane Proteins, 1991
Polyethylene glycol is produced in a variety of polymer sizes. The low molecular weight species are oily liquids while those above 1000 at room temperature exist as either waxy solids or powders. The latter are preferable for easy dissolution. The size specified by the manufacturer is the mean molecular weight of the polymeric molecules, and the distribution of weights about that mean may vary appreciably. It is certainly broad for the very high molecular weight species. The most popular sizes currently in use are 1000, 4000, 6000, and 20,000. PEG in its commercial form does contain contaminants; this is particularly true of the high molecular weight forms such as 15,000 or 20,000. These may be removed by simple purification procedures27 or in the case of PEG 20,000 by dialysis in low-pass dialysis or collodian tubes. There have been reports that repurified PEG has proven more effective, and certainly the contiminants could be disadvantageous for some proteins.38
Bowel disorders
Henry J. Woodford in Essential Geriatrics, 2022
‘Faecal impaction' is a term for a mass of hard faeces within the rectum that cannot be easily passed (i.e. large hard stools). The mechanism that provokes FI appears to be a reduced rectal sensation capacity secondary to the faecal mass rather than the faecal mass affecting internal anal sphincter function.59 The causes are those of constipation (see page 275) and frail older people are particularly susceptible. It is often associated with multi-morbidity, polypharmacy and the prescription of constipating medications (see Table 12.1).60 It should be suspected when such a person has an unexplained clinical deterioration, especially when bowel habit alters.61 Specific presenting symptoms include nausea, vomiting, abdominal pain, paradoxical diarrhoea and subsequent FI, but non-specific presentations, such as delirium, are well recognised. The faecal bulk may precipitate urinary retention or incontinence (see page 257). Rarely, pressure on the intestinal wall may provoke ulceration, bleeding or perforation. It is usually managed with a combination of laxatives and enemas. Infrequently, failed medical therapy necessitates manual evacuation. A regimen of high-dose polyethylene glycol/electrolyte solution for up to three days has been shown to be effective in resolving impaction with minimal adverse effects.62
Constipation
John F. Pohl, Christopher Jolley, Daniel Gelfond in Pediatric Gastroenterology, 2014
An important reason for treatment failure is omitting the initial disimpaction before initiating maintenance therapy. This can result in worsening of incontinence and increase in frustration. Complete bowel evacuation is the first step and can be accomplished by oral, nasogastric, or rectal agents. High-dose polyethylene glycol (PEG) has been proven safe and effective when given at doses of 1–1.5g/kg per day for 3–6 days. For maintenance therapy enough medication should be used to reach a goal of regular, soft, and painless bowel movements and avoid reaccumulation of stool in the rectum. Options include osmotic (PEG, lactulose) or stimulant laxatives (bisacodyl and senna) or a combination of both in certain cases.
Application of titanium dioxide (TiO2) nanoparticles in cancer therapies
Published in Journal of Drug Targeting, 2019
Selin Çeşmeli, Cigir Biray Avci
Harada et al. (2013) [20] at Osaka Prefecture University, used titanium dioxide nanoparticles in the form of encapsulated inside micelle. Polyethylene glycol, a polymer which is commonly used in medical applications, was used for the stabilisation of micelles and for improving the biocompatibility also decreasing the cytotoxicity of micelles. As the far-red light used in photodynamic therapy cannot penetrate into deeper part of tissues, researchers in this study preferred ultrasound. Because ultrasound does not harm the cells and also could able to go to the further sides inside cancer cells. They found that both healthy cells and HeLa cells, an immortal cell line took up these micelles and after the ultrasound was applied to the micelles; TiO2 nanoparticles generated reactive oxygen species (ROS) that are cytotoxic agents. As a result, ultrasound energy could be used in clinic with this application in order to target and kill the only tumour.
Accelerate development of topical cream drug product using a common platform base formulation
Published in Pharmaceutical Development and Technology, 2020
Dimple Modi, Himanshu Sharma, Gossett Campbell
In this study, we focus on developing a platform of placebo formulations that can be used as systems for poorly water-soluble drugs. We use an aqueous phase comprised of water with polar co-solvents such as propylene glycol, Transcutol P, and polyethylene glycol (PEG) 40. Propylene glycol is widely used as a solubilizer. It provides soothing effect on damaged and itch skin; also used as a humectant and carrier for various emulsifier. Transcutol P is a powerful solubilizer and skin penetration enhancer in topical dosage forms. Polyethylene glycol 400 is used as a solvent/solubilizer for both active substance and excipient. It is stable, hydrophilic, and essentially non-irritant to the skin. It also helps to stabilize the emulsion when combined with other emulsifiers (Rowe et al. 2009). These three solvents have their own unique importance in topical application. The investigation was designed with varying individual concentrations of all three-solvents while targeting a fix total combined concentration of 40% w/w to ensure solubilization of poorly water-soluble drugs.
Acids produced by lactobacilli inhibit the growth of commensal Lachnospiraceae and S24-7 bacteria
Published in Gut Microbes, 2022
Emma J. E. Brownlie, Danica Chaharlangi, Erin Oi-Yan Wong, Deanna Kim, William Wiley Navarre
The Lachnospiraceae and S24-7 species are poorly studied, largely due to a paucity of cultured isolates, and their sensitivity to stress has not been extensively examined. The apparent acid sensitivity of both taxa relative to other species from the Bacteroidales and Clostridiales orders warrants further investigation. The S24-7 group of bacteria has been shown to be highly intolerant to hyperosmotic conditions.43 Indeed, osmotic-induced diarrhea caused by the administration of polyethylene glycol (as routinely occurs prior to colonoscopy procedures) leads to an extinction of these bacteria from the gut. An inability to survive acid stress could render both S24-7 and Lachnospiraceae susceptible to elimination from the gut under circumstances that lower the pH of the colon including chronic inflammation or certain drugs, food additives, or xenobiotics.
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