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Weight Substances (weight + substance)

Distribution by Scientific Domains
Medical Sciences75%

Kinds of Weight Substances

  • molecular weight substance
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    Selected Abstracts

    Enhanced ethanol production from enzymatically treated steam-exploded rice straw using extractive fermentation

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2001
    Yoshitoshi Nakamura
    Abstract Alcohol fermentation of an enzymatic hydrolyzate of exploded rice straw was studied experimentally. Rice straw was treated under variable conditions, such as steam pressure and steaming time. The exploded rice straw was separated into water-soluble material, methanol-soluble lignin, Klason lignin, and a mixture of cellulose and a low molecular weight substance. The effects of steam explosion on the characteristics of the exploded rice straw were clarified from the point of view of the amounts of extractive components. Steam explosion was found to be effective for the delignification of rice straw and for increasing its susceptibility to enzyme hydrolysis and alcohol fermentation. The polysaccharides (cellulose and hemicellulose) in the rice straw treated at a steam pressure of 3.5,MPa with a steaming time of 2,min were hydrolyzed almost completely into monosaccharides, (ie glucose and xylose) by a mixture of Trichoderma viride cellulase (Meicelase) and Aspergillus aculeatus cellulase (Acucelase). The enzymatic hydrolyzate of exploded rice straw was converted into ethanol efficiently by Pichia stipitis and the ethanol yield from sugar was about 86%(w/w) of the theoretical value. The ethanol concentration in a membrane bioreactor coupled with a pervaporation system reached 50,gdm,3 and was about five times higher than that in the culture broth. The energy efficiency (ratio of combustion energy of ethanol produced to energy for steam explosion) reached a maximum value at a pressure of 3.5,MPa for 2,min. © 2001 Society of Chemical Industry [source]

    Fallacies of High-Speed Hemodialysis

    HEMODIALYSIS INTERNATIONAL, Issue 2 2003
    Zbylut J. Twardowski
    Chronic hemodialysis sessions, as developed in Seattle in the 1960s, were long procedures with minimal intra- and interdialytic symptoms. Financial and logistical pressures related to the overwhelming number of patients requiring hemodialysis created an incentive to shorten dialysis time to four, three, and even two hours per session in a thrice weekly schedule. This method spread rapidly, particularly in the United States, after the National Cooperative Dialysis Study suggested that time of dialysis is of minor importance as long as urea clearance multiplied by dialysis time and scaled to total body water (Kt/Vurea) equals 0.95,1.0. This number was later increased to 1.3, but the assumption remained unchanged that hemodialysis time is of minimal importance as long as it is compensated by increased urea clearance. Patients accepted short dialysis as a godsend, believing that it would not be detrimental to their well-being and longevity. However, Kt/Vurea measures only removal of low molecular weight substances and does not consider removal of larger molecules. Besides, it does not correlate with the other important function of hemodialysis, namely ultrafiltration. Whereas patients with substantial residual renal function may tolerate short dialysis sessions, the patients with little or no urine output tolerate short dialyses poorly because the ultrafiltration rate at the same interdialytic weight gain is inversely proportional to dialysis time. Rapid ultrafiltration is associated with cramps, nausea, vomiting, headache, fatigue, hypotensive episodes during dialysis, and hangover after dialysis; patients remain fluid overloaded with subsequent poor blood pressure control, left ventricular hypertrophy, diastolic dysfunction, and high cardiovascular mortality. Short, high-efficiency dialysis requires high blood flow, which increases demands on blood access. The classic wrist arteriovenous fistula, the access with the best longevity and lowest complication rates, provides "insufficient" blood flow and is replaced with an arteriovenous graft fistula or an intravenous catheter. Moreover, to achieve high blood flows, large diameter intravenous catheters are used; these fit veins "too tightly," so predispose the patient to central-vein thrombosis. Longer hemodialysis sessions (5,8 hrs, thrice weekly), as practiced in some centers, are associated with lower complication rates and better outcomes. Frequent dialyses (four or more sessions per week) provide better clinical results, but are associated with increased cost. It is my strong belief that a wide acceptance of longer, gentler dialysis sessions, even in a thrice weekly schedule, would improve overall hemodialysis results and decrease access complications, hospitalizations, and mortality, particularly in anuric patients. [source]

    Urinary macromolecules and renal tubular cell protection from oxalate injury: Comparison of normal subjects and recurrent stone formers

    INTERNATIONAL JOURNAL OF UROLOGY, Issue 3 2006
    MASAO TSUJIHATA
    Aim:, To determine whether urinary macromolecules (UMM), which are the high molecular weight substances in urine, can provide protection against the oxalate-associated injury to the renal tubular cells. Methods:, UMM were extracted from 24-h urine of 12 healthy adult male volunteers and 13 recurrent-stone-former male patients. Urine parameters in relation to urolithiasis were measured, including the level of glycosaminoglycans (GAG) in the UMM. Madin-Darby canine kidney (MDCK) cells were used to evaluate the protective activity of UMM from oxalate-induced cytotoxicity by LDH release measurement and methyl-thiazolyl tertrazolium (MTT) assay. Results:, Considering urinary parameters, citrate was significantly higher in urine from normal subjects than stone-former subjects; the other parameters show no differences between the groups. Total UMM and the level of GAG in the UMM were also significantly higher in the normal subject group. Compared with normal subject and stone-former subject UMM, after cells were treated with the UMM and then exposed to oxalate solution, LDH release was significantly higher in stone-former group. In the MTT assay, we found that more viable cells were observed after treatment with UMM compared to control in both groups. Moreover, UMM from the normal subjects showed higher protective activity against oxalate-related cytotoxicity than UMM from the stone-former subjects. Conclusion:, UMM protected renal epithelial cells from oxalate-related injury. This protective activity was found to be higher in normal subject UMM than stone-former UMM. Among other factors, a higher concentration of GAG and citrate in normal subject UMM might affect some parts in this finding. [source]

    Low molecular weight analysis of tears using matrix assisted laser desorption ionization-time of flight mass spectrometry

    CLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 3 2000
    Irene Mulvenna BSc
    ABSTRACT Many low molecular weight substances in human tears, including protein and lipid species, have yet to be characterized. Some of these uncharacterized substances may well be important in the pathogenesis of ocular surface disease or in ocular discomfort. The aim of this study was to build a biochemical profile of low molecular weight species in tears, and to determine its repeatability. A total of 80 tear samples were collected from 11 subjects. Tear samples were dialysed to remove salts, added to a matrix of ,-cyano-4- hydroxycinnamic acid, and analysed using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. Species were separated based on their mass to charge ratio (m : z). The repeatability of the appearance of the different species was analysed using logistic regression and diurnal and day-to-day repeatability were ascertained. Peptides were identified in the range of 848,3897 Da. Of these, 39 peptides were found to be present in more than 10 / 80 samples. There was no diurnal variation in the peptides. All species were found to occur repeatably, with the exception of peptide 1653 Da. This study has demonstrated that the majority of low molecular weight species in tears are repeatably present and do not exhibit diurnal variation. Further study aims to characterize these species and to identify changes in tear profiles between subject groups. [source]