Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “fractionation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources
PubMed1991

Repopulation kinetics of rat rhabdomyosarcoma tumors following single and fractionated doses of low-LET and high-LET radiation.

Measurements were made of clonogenic cell survival in rat rhabdomyosarcoma tumors as a function of time following in situ irradiation with single or fractionated doses of 225-kVp X rays or with 557-MeV/u neon ions in the distal position of a 4-cm extended-peak ionization region. Single doses of 20 Gy of X rays or 7 Gy of peak neon ions reduced the initial surviving fraction to approximately 0.025 for each modality. Daily fractionated doses (four fractions in 3 days) of either peak neon ions (1.75 Gy per fraction) or X rays (6 Gy per fraction) achieved a cell survival of approximately 0.02-0.03 after the fourth dose of radiation. In the single-dose experiments, significant 5- and 10-fold decreases in the fraction of clonogenic cells were observed between the third and fourth days after irradiation with peak neon ions and X rays, respectively. After the sixth day postirradiation, the residual clonogenic cells exhibited a rapid burst of proliferation leading to doubling times for the surviving cell fractions of approximately 1.5 days. Radiation-induced growth delay was consistent with the cellular repopulation dynamics. In the fractionated-dose experiments with both radiation modalities, a large delayed decrease in cell survival was observed at 1-3 days after completion of the fractionated-dose schedule. Cellular repopulation was consistent with postirradiation tumor volume regression and regrowth for both radiation modalities. The extent of decrease in survival following the four-fraction radiation schedule was approximately two times greater in X-irradiated than in neon-ion-irradiated tumors that produced the same survival level immediately after the fourth dose. Mechanisms underlying the marked reduction in cell survival 3-4 days postirradiation are discussed, including the possible role of a toxic host cell response against the irradiated tumor cells.

Animals↗
PubMed1987

Enzyme distribution and transport activities in electrophoretically isolated fractions of the muscle sarcotubular system.

A simple electrophoretic method is introduced allowing to isolate five fractions of skeletal muscle ST-system vesicles. In a previous study differences in lipid content, 3H-ouabain binding and in presence of triads in individual fractions (Lehotský et. al. 1986) were analysed. In the present study biochemical characterization was extended, and (in accordance with previous results) major differences were observed to exist between fraction 1 and fractions 3 and 4. SDS-PAGE showed that fractions 3 and 4 were enriched in a protein with m.w. 100 kD, these fractions showing the highest specific activities of (Mg2+ + Ca2+)-ATPase and oxalate-supported Ca2+-uptake; activities of Mg2+-ATPase and surface membrane marker enzymes were the lowest in these fractions. On the other hand, in fraction 1 the highest activities of Mg2+-ATPase and marker enzymes of the surface membrane were observed together with a decreased content of the 100 kD protein and activities of Ca2+ transport. It could be concluded that the method is suitable to differentiate between relatively pure SR (fractions 3 and 4) and fractions rich in sarcolemma or T-tubules components (fractions 1 and 5).

Animals↗
PubMed1983

Distribution of apolipoprotein A-IV between the lipoprotein and the lipoprotein-free fractions of rat plasma: possible role of lecithin:cholesterol acyltransferase.

Plasma samples were incubated under various conditions to study the effect of in vitro incubation on apolipoprotein A-IV distribution between the lipoprotein and lipoprotein-free fractions. When plasma was fractionated immediately after bleeding, apolipoprotein A-IV was present in equal concentrations in the lipoprotein and lipoprotein-free fractions. After a 4-hr, 37 degrees C incubation, greater than 90% of total plasma apolipoprotein A-IV was present in the lipoprotein fraction and the percentage of plasma cholesterol present as cholesteryl ester increased from 58% to 74%. When plasma was incubated for 4 hr at 37 degrees C in the presence of 1.5 mM 5,5-dithiobis(2-nitrobenzoic acid) (DTNB), greater than 90% of total plasma apoA-IV was present in the lipoprotein-free fraction, whereas plasma cholesteryl ester concentration did not change. Incubating heat-inactivated plasma for 4 hr also resulted in the redistribution of apolipoprotein A-IV from the lipoprotein fraction to the lipoprotein-free fraction, concurrent with no change in cholesterol esterification. When heat-inactivated plasma was incubated in the presence of a purified lecithin:cholesterol acyltransferase preparation, cholesterol esterification was restored and apolipoprotein A-IV was redistributed from the lipoprotein-free fraction to the lipoprotein fraction in such a manner that greater than 90% was present in the lipoprotein fraction. No changes in apolipoprotein A-I and apolipoprotein E distributions were found under any of the above conditions. Thus, the in vitro plasma incubations show that apolipoprotein A-IV can move bidirectionally between lipoprotein and lipoprotein-free fractions; the direction of this movement depends on the condition of the incubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

Effect of some chelating agents on the biliary excretion of mercury. 2. Relationship between the excretion of mercury and its binding to bile fractions.

Mercury binding to bile components and the correlation between the amount of mercury bound in the bile fraction 2 and the rate of mercury biliary excretion were studied in female rats exposed to intravenously injected HgCl2 after pretreatment with a series of 14 chemical agents. After pretreatment with the tested agent, 203Hg was detectable both in the bile fraction 1 and 2. Distribution pattern of 203Hg between the two fractions appeared to be linked with the chemical structure of the formed mercury complex. Pretreatment with these agents did not inhibit the formation of the bile fraction 3. By their influence on the 203Hg distribution between the bile fractions 1 and 2, the tested agents can be roughly divided into 3 groups: the content of 203Hg in the bile fraction 2 is about 10--20% and does not change significantly within the first 24 hours after 203 HgCl2 injection (cysteine, penicillamine, disodium ethylenediaminotetraacetate -- Na2EDTA, sodium diethyldithiocarbamate, sodium alanindithiocarbamate, acrylonitrile); the the 203Hg content in the bile fraction 2 increases (thiophenolacetate); the content of 203Hg in fraction 2 is initially several times higher than that in the bile fraction 1, but then decreases during the first 24 hours (2,3-dimercaptopropanol -- BAL, sodium 2,3-dimercaptopropanesulphonate, spironolactone, Thiomestron). The rate of mercury biliary excretion (Rb) was found to be closely correlated with the relative amount of mercury present in the bile fraction 2 (a2), if a2 > 30%, both in vivo (Rb = 1.077 a2 + 0.758) and invitro (Rb = 1.067 a2 + 0.519) experiments. Practically identical values of the constant accompanying a2 in the two equations seem to indicate that one of the decisive factors influencing the rate of mercury biliary excretion in rats is rather the mercury affinity for the bile fraction 2 components than the agent-induced mercury transport mechanisms. For a2 < 30% the correlation is non-linear and the excretion is rather inhibited than enhanced.

Animals↗
PubMed1975

[Denaturation and enzymatic proteolysis in vitro of protein fractions of soya flour].

Soya, in spite of its high nutritional value and moderate cost, possesses certain undesirable qualities which limit its use in animal and human nutrition. The amendment of these qualities has resulted in much work. In this study the effects of technological treatments on the properties of certain protein fractions capable of being produced industrially were observed. Three fractions were prepared from defatted soybean flour of the "Harosoy 63" variety: an acid-precipitated fraction, a cold-insoluble fraction at 0-3 degrees C, and a water-soluble fraction. The properties of the fractions were studied both before denaturation and after denaturation by either heat or alcohol. The degree of proteolysis of each fraction by two digestive enzymes, pepsin and trypsin, was measured by the increase of non-protein nitrogen as a function of time. Several methods were used for electrophoretic analysis. The results showed that the thermal treatment at 100 degrees C and the treatment with varying concentrations of ethanol (from 10 to 100 p. 100) modified electrophoretic diagrams and the solubility of the proteins in trichloracetic acid. Moderate, moist heating of the protein fractions (100 degrees C, 20 mn) before proteolysis by pepsin and trypsin, in general, favored proteolysis. The most marked effect observed was in the acid-precipitated fraction (in which Kunitz inhibitor was concentrated treated by trypsin. Heating the fractions beyond thirty minutes had a negative effect on proteolysis: the level of proteolysis was the same, or in some cases, lower than before denaturation, especially on subsequent treatment with pepsin. The effects of the ethanol treatment were different from that of heat: the proteolysis was accelerated only with the acid-precipitated fraction.

Ethanol↗
PubMed1993

Comparison of specific blue and green fluorescence in cataractous versus normal human lens fractions.

PURPOSE: The authors compared the specific green and blue fluorescence levels in soluble and insoluble fractions (cortical and nuclear) extracted from cataractous lenses with those corresponding to clear lenses and tried to establish the nature of the role of extrinsic fluorophores in cataractogenesis. METHODS: Laser-induced fluorescence was measured with an optical-fiber sensor. The specific fluorescence was evaluated as the ratio of the fluorescence intensity to the protein concentration. Four brunescent, three pure nuclear, and four mixed nuclear-subcapsular cataractous lenses were investigated. RESULTS: Specific blue fluorescence levels in cataractous fractions were similar to those in clear lens fractions, except for the insoluble nuclear fractions in which the levels were slightly lower. The specific green fluorescence in the soluble cataractous fractions showed marked increases compared with the clear lens fractions of similar ages. The insoluble cataractous fractions had similar (cortical fractions) or slightly lower (nuclear fractions) specific green fluorescence levels compared with the normal lens fractions. CONCLUSIONS: The similarity in blue fluorescence levels suggests that the blue fluorophore(s), although increasing in concentration with age, are not indicators of cataractogenesis and may not play an active role in opacification. The levels of specific green fluorescence indicate either a dramatic increase in the fluorescence quantum efficiency and/or an increase in the number of fluorescent sites per protein unit. The green-to-blue ratios were greater by a factor of as much as six in all cataractous soluble fractions versus clear ones. This suggests an accelerated formation of the green fluorescent species in cataractous tissues.

Adolescent↗
PubMed1996

Fractionation of canine serum calcium, using a micropartition system.

OBJECTIVE: To determine usefulness of a micropartition system for calcium fractionation of canine serum, and to establish reference values for protein-bound, complexed, and ionized calcium fractions in clinically normal dogs. DESIGN: Performance characteristics of a micropartition system were evaluated, using serum from clinically normal dogs. This micropartition system was then used to determine a reference range for calcium fractions. ANIMALS: 13 clinically normal dogs. PROCEDURE: Dog serum was placed in the micropartition system, and spun for 20 minutes at 1,300 x g. Total calcium concentration, ionized calcium concentration, and pH were measured in whole serum, and total calcium concentration was measured in the ultrafiltrate. The protein-bound fraction was calculated by subtracting total calcium of the ultrafiltrate from total calcium of whole serum. The ionized calcium measurement of whole serum was subtracted from the total calcium measurement of the ultrafiltrate, determining the complexed calcium fraction. RESULTS: During validation of the ability of the micropartition system to separate calcium fractions, no significant amount of serum calcium was adsorbed by the plastic micropartition system or membrane. The micropartition membrane separated the protein-bound calcium fraction (retentate) from the ultrafiltrate, which contained ionized and complexed fractions of calcium. Concentrations of protein-bound, ionized, and complexed calcium from clinically normal dogs were determined to be 3.40 +/- 0.63, 5.49 +/- 0.17, and 1.01 +/- 0.30 mg/dl, representing 34, 56, and 10% of the total calcium concentration, respectively. CONCLUSIONS: This method is a rapid, repeatable means to completely fractionate serum calcium, and most importantly provides accurate assessment of the protein-bound and complexed calcium fractions. CLINICAL RELEVANCE: Complete assessment of calcium fractions may increase sensitivity for detection of disease processes that affect calcium metabolism.

Analysis of Variance↗
PubMed1997

Value of right ventricular ejection fraction in predicting short-term prognosis of patients with severe chronic heart failure.

BACKGROUND: The prognosis of chronic heart failure has been studied extensively, but factors predicting short-term outcome in patients with severe chronic heart failure are still poorly defined, and the current indications for heart transplantation as a treatment for end-stage heart failure need on objective analysis. METHODS: Purpose of the study was to identify the determinants of short-term prognosis in a group of 142 consecutive ambulatory patients (mean age 49.8 +/- 11 years). Referred for heart transplantation because of severe chronic heart failure, the patients were admitted with left ventricular ejection fraction markedly depressed and had had symptoms in spite of an optimal standardized medical therapy for at least 1 month. Baseline clinical and instrumental evaluation included right-sided heart catheterization with a flow-directed multilumen thermodilution catheter, which enables determination of pressures, cardiac output, right ventricular volumes, and ejection fraction. RESULTS: Most patients were in New York Heart Association class III (61%) and IV (24%), and the hemodynamic profile was characterized by mean left ventricular ejection fraction of 20.2% +/- 6%, cardiac index of 2.13 +/- 0.6 l/min/m2, pulmonary capillary wedge pressure of 23.1 +/- 11 mm Hg, right atrial pressure of 7.9 +/- 6 mm Hg, right ventricular ejection fraction of 23.2% +/- 12.4%. During a mean follow-up of 11.1 +/- 9.4 months, 33 patients underwent transplantation (23.4%), 41 died (28.8%), and 68 were still alive (47.8%). There was a substantial overlap in left ventricular ejection fraction between patients divided on the basis of outcome, whereas right ventricular ejection fraction was significantly lower in patients who died or underwent transplantation. Cox multivariate analysis showed three independent prognostic variables: cause (p = 0.03), heart failure score (p = 0.001), and right ventricular ejection fraction (p = 0.000). Short-term survival (10 months) was significantly (p = 0.000) different in patients with > or = 24% or < 24% right ventricular ejection fraction. Statistical analysis identified right ventricular ejection fraction as the single variable to be highly correlated with an increased risk of early death. CONCLUSIONS: This study suggests that right ventricular function is a crucial determinant of short-term prognosis in severe chronic heart failure. Statistical analysis identified right ventricular ejection fraction, determined by thermodilution during right-sided heart catheterization, as the single most important predictor of short-term prognosis in a large cohort of patients who had symptoms in spite of a standardized, optimized, multipharmacologic treatment. The variable allows a useful risk stratification in patients with severe chronic heart failure and uniformly depressed left ventricular ejection fraction and provides guidance in the assessment of indications and timing for transplantation.

Adolescent↗
PubMedDate not supplied

[Coronary score in patients with low ejection fraction after myocardial infarct].

INTRODUCTION: The most frequent cause of heart failure is ischemic heart disease (1). This paper was aimed at comparing the coronary score of patients with low ejection fraction whose ejection fraction was not significantly changed after sustained myocardial infarction. MATERIAL AND METHODS: The study involved patients after sustained myocardial infarction treated at the Institute of Cardiovascular Diseases in Sremska Kamenica. Total coronary score and score of each individual coronary artery were emphasized. RESULTS: The investigation study comprised 56 patients aged 33-83 years of various occupations. Patients were divided into two groups: the first--A group consisted of 28 (50%) patients with ejection fraction 35% or lower; the second--B group also consisted of 28 (50%) patients with ejection fraction higher that 35%. Table 1. shows the dominant coronary artery in investigated groups of patients. Table 2. shows values of total and scores of each coronary artery. The right coronary artery was dominant in 75% of patients from the A group and in 82.1% of patients from the B group. A significantly higher individual score of coronary arteries, as well as the total score, was established in the group of patients with low ejection fraction, and especially the score of the anterior descendent artery which is almost twice higher in regard to the second group of examined patients. Table 3. describes the analyzed score in male and female patients. DISCUSSION: Patients with low ejection fraction after sustained myocardial infarction have more changes of coronary arteries than patients with better ejection fraction. The total score, score of the right coronary artery (ACD), circumflex artery (RCX) and especially anterior descendent artery (LAD) are significantly higher in patients with ejection fraction lower than 35%. There are no differences in the dominant coronary artery in investigated patients. In both investigated groups women had a smaller score of ACD and RCX and a higher score of LAD, but the difference is not significant. In regard to total score there were no differences in men and women. Numerous investigations also point to the fact that patients with lower ejection fraction and ischemic heart disease have more changes on coronary artery than patients with better ejection fraction. CONCLUSION: 1. Patients with low ejection fraction after sustained myocardial infarction have a higher total score and scores of ACD. LAD and RCX. 2. There are no differences in coronary score of men and women within the same investigated groups. 3. There are no differences in dominant coronary artery in investigated groups of patients.

Adult↗
PubMed1979

Characteristics of transcriptionally active and inactive neuronal and nonastrocytic glial rat brain chromatin fractions.

Rapid and reliable fractionation of neuronal and nonastrocytic glial (NAG) cerebral rat brain chromatin in transcribable and repressed portions was achieved employing the DNAase II/Mg++-solubility method of Gottesfeld et al. (1974). Compositional and transcriptional properties of these fractions have been investigated. Compared to transcriptionally repressed fractions, template-active neuronal and NAG chromatin fractions are associated with an increased content of nonhistone chromosomal (NHC-) proteins. Both of the transcribable as well as both of the repressed fractions are strikingly different in their composition as assessed by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. Comparative acid urea gel electrophoretic patterns of histones revealed that histone fraction H 1 is almost completely absent in actively transcribed neuronal chromatin and reduced in the corresponding NAG fraction while in template-inactive neuronal and NAG chromatin all five main histone fractions are present in equal amounts. The total number of RNA initiation sites available for exogenously added homologous RNA polymerase on template-active and -inactive neuronal and NAG chromatin was quantitatively measured under assay conditions completely eliminating reinitiation. Unlike the template-active neuronal and NAG fractions which are differently enriched in RNA initiation sites, transcriptionally more repressed neuronal and NAG fractions demonstrated a minimal ability to initiate RNA synthesis. Under assay conditions allowing repeated initiation of RNA chains at the same initiation site, rat brain RNA polymerase molecules were found to utilize neuronal initiation sites more frequently than NAG ones.

Animals↗
PubMed1976

Association of a protease (plasminogen activator) with a specific membrane fraction isolated from transformed cells.

The intracellular distribution of specific protease, plasminogen activator (PA), has been examined in Rous sarcoma virus-transformed chick embryo fibroblasts (RSV-CEF). Cellular homogenates were fractionated by differential centrifugation followed by sucrose gradient centrifugation. The activities and the percent distribution of a series of marker enzymes, specific for different subcellular organelles, were compared to those of PA. Normal CEF have been similarly fractionated and the relatively low amount of PA activity present in these cells has been analyzed in terms of its subcellular distribution. A membrane fraction was isolated from the RSV-CEF that contained the bulk of the PA activity and less than 8% of the total cellular protein. The specific activity of the PA in this fraction is 40-fold higher than that of a comparable fraction isolated from companion cultures of normal cells. This fraction contains little or no nuclear and cytoplasmic material and is contaminated only to a relatively small degree with mitochondria, lysosomes, endoplasmic reticulum. Significant amounts of a putative Golgi membrane marker are present in this fraction. The relatively high specific activities of Na+,K+-ATPase, 5'-nucleotidase, and [3H]fucose indicate that the fraction is enriched in surface membrane. Further purification of the fraction by equilibrium centrifugation on shallow sucrose gradients reduces further the contaminating activities and results in a PA distribution that closely parallels the distribution of the membrane enzyme, 5'-nucleotidase. PA was not released from its membrane association by hypotonic and hypertonic extraction and ultrasonication, while granule-bound enzymes were released by these treatments. The PA activity from hamster SV40 cells fractionated the same way as that of RSV-CEF. These results suggest that a protease that is dramatically enhanced upon malignant transformation is associated with "plasma membrane-like" elements of the cell and may serve as an intrinsic modifier of cell surface proteins after malignant transformation.

Cell Fractionation↗
PubMed2002

Localization of metallic ions with gingival fibroblast subcellular fractions.

Nickel-based alloys have been in use since the 1930s; however, there are concerns regarding the release of metal ions (Be(+2), Cr(+6), Cr(+3), Ni(+2), Mo(+6)) from these alloys into surrounding tissues. Therefore, the objective of this study was to determine the cellular location and accumulation of ions using atomic absorption spectroscopy and correlate location with the cytotoxic, morphologic, and ultrastructural evaluations reported previously. Human gingival fibroblasts were exposed to the metal ions for 72 h. Controlled atomic absorption spectroscopy studies were used to determine the intracellular location of these ions reported as parts per million metal ions per milligram protein. Enzymatic markers were shown to correspond to the appropriate fraction indicating success in fractionation of the gingival fibroblasts. These results correspond with the cytotoxic, morphologic, and ultrastructural alterations reported previously for fibroblasts exposed to these ions. The highest concentration of beryllium ions occurred in the low-density molecule fraction, where lipofuscin granules were found, which has been shown to contain metal ions. The highest concentrations of hexavalent chromium ions occurred in the plasma membrane and nuclear fractions followed by the mitochondria fraction, which is supported by the ions' ability to oxidize to trivalent chromium accumulating at the membrane as well as the alterations in nuclear and mitochondrial function. For trivalent chromium, the highest concentrations occurred in the low-density molecule and the plasma membrane fractions, which correlates with the ions' inability to readily cross membranes. The highest concentration of molybdenum ions occurred in the plasma membrane fraction correlating with alterations in membrane morphology and increased numbers of myelin figures. The highest concentration of nickel ions was associated with the cytosol fraction where lipid droplets seen in the transmission electron micrographs were located. The current study demonstrates that a successful subcellular fractionation was obtained on gingival fibroblasts and that the location of metallic ions within the fractions correlated with cellular alterations reported previously.

Beryllium↗
PubMed1981

Composition of axolemma-enriched fractions isolated from bovine CNS myelinated axons.

Axolemma-enriched fractions were isolated from the white matter of bovine corpus callosum via a purified preparation of myelinated axons which were osmotically shocked and fractionated on a discontinuous density gradient. Two membrane fractions of differing density were obtained: both were somewhat enriched over white matter whole homogenate in specific activity of acetylcholinesterase and 5'-nucleotidase and maximal binding capacity for saxitoxin. Both membrane fractions contained appreciable amounts of 2', 3'-cyclic nucleotide 3'-phosphohydrolase; the specific activity of antimycin-sensitive NAPH-cytochrome c reductase and cytochrome c oxidase indicated low levels of contamination by microsomal and mitochondrial membrane. The myelin which is concomitantly isolated with the axolemma-enriched fractions has a lipid and protein composition comparable to that of myelin isolated by other procedures. Both axolemma-enriched fractions contain about one half of their dry weight as lipid comprised of approximately 25% cholesterol, 25% galactolipid (cerebrosides and sulfatides in a molar ratio of about 4:1) and 50% phospholipid, mostly choline phosphatides and ethanolamine phospholes in an equimolar ratio. The axolemma fractions are also enriched in ganglioside content relative to the myelin fraction. The polypeptides of the axolemma-enriched fractions range from 20,000 to over 200,000 in molecular weight; the predominant proteins are in the range from 50,000 to 69,000. The most dense axolemma-enriched fraction is over fourfold enriched in glycoprotein content compared with myelin, with at least 10 different molecular-weight classes of glycoproteins as identified by Schiff stain of polyacrylamide gel protein profiles. The differences and similarities in the molecular composition of axolemma-enriched preparations which have been characterized to date are discussed.

Animals↗
PubMed1988

Isolation and initial characterization of myelin-like membrane fractions from the nerve cord of earthworms (Lumbricus terrestris L).

We report here the isolation of fractions enriched in components of the myelin-like membranes surrounding the giant axons of the earthworm. Lumbricus terrestris L. The composition and purity of the fractions have been assessed using SDS-protein electrophoresis, Western immunoblots, and electron microscopy. Preliminary enzyme assays indicated that the mitochondrial marker, succinate dehydrogenase, has a similar specific activity distribution in earthworm nerve cord and in mouse liver sedimentation velocity fractions, however, the distribution of the total units of activity among the fractions seems to indicate the existence of smaller mitochondria in earthworm nerve cord compared with mouse liver mitochondria. In earthworm nerve cord fractions, Na+/K+ ATPase and Ca2+/Mg2+ ATPase were found to be enriched exclusively in the fraction containing large plasma and myelin-like membranes, while in the mouse liver fractions, the total units of these two enzymes were found to be distributed broadly among fractions. 5'-Nucleotidase activity in the earthworm nerve cord seemed to be restricted to the microsomal fractions (endomembrane network), with a very low activity associated with the large plasma and myelin-like membrane fraction. We have established the presence of keratins or prekeratins in the myelin-like membranes, probably in the form of tonofilaments. However, we could not show that the desmosome-like structures, characteristic of these membranes, are composed of those proteins described for vertebrate epithelial desmosomes.

Animals↗
PubMed2003

Size fractionation of non-volatile dissolved organic compounds and metal species in German white wines by combining on-line tangential-flow multistage ultrafiltration, a home-built carbon analyser, and inductively coupled plasma mass spectrometry.

Organic metal species and their size fractions in three German white wines were characterized by combining multistage ultrafiltration (MST-UF), determination of non-volatile dissolved organic carbon (NV-DOC) by a home-built carbon analyser, and metal quantification by inductively coupled plasma mass spectrometry (ICP-MS). First, NV-DOC and metal species in selected "dry" German white wines were fractionated on-line using MST-UF in the size range of >100 kDa to <1 kDa. For this purpose a 20 mL sample of the wine under study diluted 1:10 with high-purity water was processed through a cascade system of hydrophilized polyethersulfone-based flat membranes of decreasing cut-off (100, 50, 10, 5, and 3 kDa). An aliquot of the fraction <3 kDa was additionally processed through a commercial UF tube (MidGee system, cut-off: 1 kDa) to obtain low-molecular size fractions also. A home-built carbon analyser was applied to determine NV-DOC in the wines and their size fractions. The NV-DOC found in a German reference wine and its size fractions was as follows: total NV-DOC: 8.97 mg mL(-1); F(1) (>100 kDa), 0.15%; F(2) (50-100 kDa), 0.44%; F(3) (10-50 kDa), 0.74%; F(4) (5-10 kDa), 0.76%; F(5) (5-3 kDa), 0.7%; F*(6) (3-1 kDa), 0.9%; F(7) (<1 kDa), 81.6% (related to total NV-DOC). The NV-DOC recovery was 85.2%. Accordingly, most of the NV-DOC in this wine consists of low-molecular mass organic compounds of <1 kDa, presumably carboxylic acids as typical in wine. Parallel metal determinations in these wines and their fractions were performed by ICP-MS. The measurements showed that the major part of the metals investigated, up to 25 elements, were dissolved in the size fraction of <1 kDa except Ba, Sr and Pb which appeared also in other fractions. In addition, conventional UV-VIS spectroscopy was applied to characterise the studied wines and their size fractions. According to this, the UV absorbance between 254 and 280 nm of these white wines shows a parallel trend to their NV-DOC.

Barium↗
PubMed2006

Fractionation and sequential extraction of heavy metals in the soil of scrapyard of discarded vehicles.

Chemical and physical size fractionation of heavy metals were carried out on 20 soil samples from the scrap yard area. Tessier method was used in sequential extraction. Cadmium showed the highest levels among the other elements studied in the exchangeable fraction (about 33%), while other elements showed low levels in this fraction (> or =1%). Lead and manganese were mostly found in the Fe-Mn oxide fraction, zinc and iron were mostly in residual fraction, while copper was mostly found in the organic fraction of the soil. Soil samples were size-fractionated into four sizes: 1000-500, 500-125, 125-53, and less than 53 microm. The highest levels of Fe, Cu, Pb, Mn, and Cd were found in the medium fraction (500-125 mum), while zinc showed its highest levels in the fine fraction (125-53 microm). The order of heavy metal load in the size fractions was found to be medium > fine > coarse > silt for Fe, Mn, Cu, Pb, and Cd, where it was found as fine > medium > coarse > silt for zinc.

Chemical Fractionation↗
PubMed1980

Plasma membrane heterogeneity in ascites tumor cells. Isolation of a light and a heavy membrane fraction of the glycogen-free Ehrlich-Lettré substrain.

In this work we report on the isolation of two plasma membrane fractions of a glycogen-free substrain of Ehrlich-Lettré ascites cells, a light fraction sedimenting in a sucrose gradient at 1.10 g/ml, and a heavy fraction sedimenting at nuclei by a combination of short-term swelling and mild Dounce homogenization. A 12 000 X g postnuclear pellet (PII) containing major portions of the plasma membrane marker enymes, 5'-nucleotidase, ouabain-sensitive (Na+ + K+)-ATPase and the alkaline phosphatase, was prepared by differential centrifugation. The two plasma membrane fractions were obtained by centrifugation on a discontinuous sucrose gradient, from which they were further purified on a linear sucrose gradient applying sedimentation velocity conditions only. Enrichment factors for the three marker enzymes were between 5- and 14-fold for the light fraction and between 3- and 7-fold for the heavy fraction with an overall yield of 1--4% and 0.5--1.7%, respectively, of cellular protein. Contamination of both fractions with nuclear material was minor. Mitochondrial contamination was about 8% for the light material and somewhat higher for the heavy material. In the light fraction, co-sedimentation of lysosomal and Golgi marker enzymes was detected. The presence of membrane structures of these organelles could not be confirmed definitely by electron microscopy. Differences in sialic acid content and phospholipid composition within the two fractions, especially in the relative proportion of lecithin to sphingomyelin, suggests differences in membrane fluidity. The light material showed mostly unit membrane vesicles in thin-section and freeze-etch electron microscopy, whereas the heavy fraction mainly consisted of sheet-like membrane fragments.

5'-Nucleotidase↗
PubMed1992

Ca(2+)-binding proteins in rat synaptic fractions surveyed by the 45Ca2+ overlay method.

Ca(2+)-binding proteins in the synaptic and subsynaptic fractions (P2, synaptosome, synaptic plasma membrane, and postsynaptic density [PSD]-enriched fractions) and soluble fraction of rat brain were surveyed by a 45Ca2+ overlay method. The PSD-enriched fraction from cerebral cortex contained two major Ca(2+)-binding proteins (55,000 M(r) and 19,000 M(r)) and a distinct group (in 140,000 M(r) region), and two minor ones (66,000 M(r) and 16,000 M(r)); and the fraction from cerebellum contained two (55,000 M(r) and 19,000 M(r)). The proteins with 55,000 M(r) and 19,000 M(r) were identified as tubulin and calmodulin, respectively, and present in all the fractions investigated. The Ca(2+)-binding proteins of 140,000 M(r) region were found only in the PSD-enriched fraction isolated from cerebral cortex: neither the PSD-enriched fraction isolated from cerebellum nor other subcellular fractions prepared from cerebral cortex and cerebellum contained the proteins. The 140,000 M(r) Ca(2+)-binding proteins were the substrates for the Ca2+/calmodulin-dependent protein kinase II associated with PSD, and no change in the Ca(2+)-binding was detected by the 45Ca2+ overlay method after phosphorylation of the proteins by the protein kinase. The 16,000 M(r) Ca(2+)-binding protein might be the beta-subunit of calcineurin. Calretinin and calbindin-D28k were also detected as Ca(2+)-binding proteins in the soluble fractions of both cerebral cortex and cerebellum.

Animals↗