Slow Fraction Research Articles

Desorption of halogenated organics from model solids, sediments, and soil under unsaturated conditions. 1. Isotherms

The mechanisms controlling desorption rates from soils and sediments were investigated by measuring TCE desorption kinetics from model solids, sediments, and soil under unsaturated conditions at 100% relative humidity. A new experimental methodology enabled measurement of desorption rates over more than 7 orders of magnitude and revealed that intraparticle pores of molecular dimensions may be responsible for the slow release of sorbed contaminants. Desorption kinetics proceeded on two distinct time scales, and all solids had both a fast and slowly released fraction. The amount of slow desorbing TCE was found to depend on the initial vapor concentration, but not in direct proportion. At TCE vapor concentrations near saturation, the fast fraction comprised the majority of the sorbed TCE and required less than 10 min for desorption, whereas the slow desorbing fraction was released over periods of months to years. Although model solids with uniform pore and particle sizes were used, a pore diffusion model was not adequate to describe both the fast and slow desorbing fractions. The measured physical properties of the solids were not useful for making a priori predictions and, in comparisons among the solids, did not correlate with the amount and the rate of slowly released TCE.more » The Freundlich isotherm exponents correlated with the fraction of slowly released TCE, but isotherm nonlinearity was not sufficient to account for the dual rate behavior. 27 refs., 18 figs., 5 tabs.« less

Ligand-induced conformational changes modify proteolytic cleavage of the adipocyte insulin-sensitive glucose transporter

The transport conformation of the human erythrocyte glucose transporter (GLUT1) modifies rates of proteolytic cleavage of this protein by a variety of enzymes. We investigated the effects of ligand-induced conformational change on the susceptibility to enzymic cleavage of the insulin-sensitive rat adipocyte glucose transporter (GLUT4). A GLUT4-enriched slow sedimenting microsomal fraction was prepared from basal adipocytes and subjected to PAGE and immunoblotting. The GLUT4 protein was detected in these immunoblots with a C-terminal-specific antiserum as an M(r)-46,000-50,000 doublet. GLUT1 protein was not detected by a GLUT1-specific antiserum in these membranes. Tryptic digestion caused loss of the GLUT4 signal in immunoblots in a time- and concentration-dependent fashion. Low-M(r) membrane-bound fragments were not observed in electrophoretic gels, whether detection was attempted by immunoblotting or by counting radioactivity in gel slices following photolabelling with [3H]cytochalasin B. Transport-specific ligands known to induce an outward-facing conformation in the human erythrocyte GLUT1 protein retarded cleavage of the GLUT4 protein by submaximal concentrations of trypsin, whereas ligands known to induce an inward-facing conformation increased the extent of cleavage. The transported substrate D-glucose retarded tryptic cleavage of GLUT4. This result contrasts with the known behaviour of GLUT1, in which D-glucose accelerates cleavage. Cleavage of GLUT4 by thermolysin was also retarded by the outward-binding analogue 4,6-O-ethylidene glucose. These results show that the conformational sensitivity to proteolysis of GLUT4 mirrors that of GLUT1, except that the glucose-loaded GLUT4 has a different steady-state configuration, which may reflect underlying kinetic differences between the two proteins.

In Situ Dry Matter, Protein, and Fiber Degradation of Perennial Forages

Eight forages (alfalfa, birdsfoot trefoil, red clover, bromegrass, orchardgrass, perennial ryegrass, quackgrass, and timothy) at three maturities were evaluated for ruminal DM, CP, and NDF degradation kinetics. Duplicate dacron bags were incubated for 0, 3, 6, 10, 13, 25, 48, and 72h in two late lactation Holstein cows fitted with ruminal cannulas over eight experimental periods. Species and maturity effects were observed for soluble, slow, and undegraded fractions; degradation rate; and ruminally degradable DM, CP, and NDF. Significant species by maturity interactions also were evident for fractions and ruminal degradabilities of DM, CP, and NDF. Legumes exhibited more extensive ruminal DM degradation than did grasses. No clear trends were evident in rate of ruminal CP degradation between legumes and grasses. Mature grasses were lowest in ruminally degradable CP. Legumes exhibited a higher undegraded fraction and faster degradation rate of slowly degraded NDF fractions, resulting in similar ruminally degraded NDF for legumes and grasses. Extensive differences in ruminal degradation kinetics existed between perennial legume and grass species and maturities. Species by maturity interactions were diverse, making categorization of degradation characteristics of legumes and grasses difficult.

Dissolution and biorestoration of nonaqueous phase hydrocarbons: Model development and laboratory evaluation

A one‐dimensional numerical model is presented for simulating the enhanced biorestoration of aquifer material contaminated with residual nonaqueous phase liquid (NAPL) hydrocarbon. The model simulates the simultaneous dissolution, transport, and biodegradation of individual hydrocarbons under oxygen‐limiting conditions. Partitioning between the NAPL and aqueous phase is modeled as a linear first‐order process where the NAPL is composed of two fractions, a fast oil fraction with a high mass transfer rate and a slow oil fraction with a much lower mass transfer rate. Microorganisms are assumed to be present attached to the soil grains and are assumed to be immobile. Biodegradation of the problem compounds is simulated as a multistep process where the parent compounds are first biotransformed to oxygenated intermediates. These intermediates may then be mineralized to CO2 and H2O. Comparison of model simulations with experimental results from soil columns containing residual hydrocarbon and an active microbial population indicate that the model is capable of simulating the extent of hydrocarbon biodegradation using reasonable model parameters. Model simulations indicate that if benzene, toluene, and xylene are assumed to be completely mineralized, the model will greatly underestimate the extent of biotransformation. The model overestimated the extent of hydrocarbon biotransformation at low substrate concentrations.

Nuclear genome characterization and carrageenan analysis ofGymnogongrus griffithsiae (Rhodophyta) from North Carolina

DNA reassociation kinetics were used to determine nuclear genome organization and complexity inGymnogongrus griffithsiae (Gigartinales, Rhodophyta). Results indicate the presence of three second order components corresponding to fast (3%), intermediate (8%) and slow (89%) fractions. Thus the genome consists mainly of unique sequences. Thermal denaturation (T m) indicated a nuclear DNA base pair composition of 40 mol% G + C. Microspectrophotometry with the DNA-localizing fluorochrome DAPI was used to confirm ploidy level differences in the gametophytic and tetrasporoblastic phases. Comparisons of mean nuclear DNA (I f) values to chicken erythrocytes (RBC) resulted in an estimate of 0.32 pg/2 C genome forGymnogongrus griffithsiae. Karyological studies using aceto-orcein revealed the presence of ca. 23 bivalents during diakinesis of tetrasporangial mother cells. Total carrageenan content in water extraction was 30% dry weight. Infrared spectroscopy confirmed the isolated carrageenan to be the iota-fraction.

Nuclear genome characterization of the carrageenophyteAgardhiella subulata (Rhodophyta)

DNA reassociation kinetics were used to determine nuclear genome organization and complexity inAgardhiella subulata (Gigartinales, Rhodophyta). Results indicate the presence of three second-order components corresponding to fast (22%), intermediate (68%) and slow (10%) fractions. Thus, the genome consists of 90% repetitive sequences. Microspectrophotoometry with the DNA-localizing fluorochrome DAPI was used to confirm ploidy level differences in the gametophytic and tetrasporophytic phases. Results indicate that meiosis occurs during tetrasporogenesis. Comparison of mean nuclear DNA (If) values to chicken erythrocytes (RBC) resulted in an estimate of 0.9 pg/2C genome forAgardhiella. Karyological studies using aceto-orcein revealed a chromosome complement of 2N = 44 in carposporangia and the presence of 22 bivalents during diakinesis of tetraspore mother cells.

Evaluation of groundwater extraction for remediation of petroleum‐contaminated aquifers

ABSTRACT: Past experience has shown that restoration of an aquifer to drinking water quality by groundwater extraction and surface treatment may require many years of pumping. In this research, a mathematical model of hydrocarbon dissolution is developed to aid in the evaluation of groundwater remediation systems. The model assumes that residual hydrocarbon is distributed between two fractions: (1) a fast fraction in equilibrium with the aqueous phase and (2) a slow fraction in which mass transfer is limited. Relationships for simulating equilibrium partitioning are based on classical liquid‐liquid equilibrium theory. Column experiments were performed to test the model and examine the kinetics of aromatic hydrocarbon dissolution as residual hydrocarbon ages. The hydrocarbon dissolution process included an initial equilibrium period during which dissolved hydrocarbon concentrations were high and roughly constant followed by a rapid drop‐off period and an asymptotic period during which dissolved hydrocarbon concentrations were low and declined slowly. After passing more than 700 pore volumes of water through the column, between 8 and 10% of the original toluene and xylene isomers remained in the column. Model simulations were conducted to evaluate the effect of pulsed pumping on groundwater cleanup time.

Combined effects of different class I antiarrhythmic agents on maximum rate of depolarization (V max ) of action potentials in guinea-gig papillary muscles

The combination of two different kinds of class I antiarrhythmic agents (class Ia, Ib, or Ic) was examined with regard to their effects on the maximum rate of depolarization (Vmax) of action potentials in guinea-pig papillary muscles. The combinations of disopyramide plus lidocaine, disopyramide plus mexiletine, mexiletine plus flecainide, and disopyramide plus flecainide were employed to study their effects on use-dependent block of Vmax. All the combinations increased the percent of use-dependent block at most of the frequencies employed (0.1-3.3 Hz) as compared to the effects of the single use of either drug, but no decrease in use-dependent block was found with any of the combinations. The time courses of the development of use-dependent block by disopyramide, lidocaine, and mexiletine were best expressed by two exponential functions, whereas those by flecainide were expressed by a single exponential function. Disopyramide plus lidocaine and disopyramide plus mexiletine produced increases in the time constant of the fast component of the block (tau f), the fast fraction of the block (Af), and the ratio of the fast to the slow fraction (Af/As). Mexiletine plus flecainide increased tau f, Af, and As; whereas disopyramide plus flecainide caused no changes in the kinetic parameters of use-dependent block. These results suggest that there may be diverse modes of interaction between the drug and the Na+ channel, and the combination of two different types of the drug may sometimes provide different effects on the fast and slow components of the use-dependent block of Vmax.

Inter- and intraspecific variation of nuclear DNA reassociation kinetics in the Gracilariales (Rhodophyta)

DNA reassociation kinetics were used to determine inter- and intraspecific variation in genome organization and complexities in species ofGracilaria andGracilariopsis. Results indicate the presence of three second order components corresponding to fast, intermediate and slow fractions. Repeated sequences varied from 13–95%. Three geographic populations ofGracilaria tikvahiae were similar with 13–27% repeated sequences.Gracilaria sp. cultivars G-1 and G-6 with 35% and 95% repeated sequences, respectively, were distinct from each other andG. tikvahiae. No pattern of genome organization and complexity was found which permitted a distinction betweenGracilaria andGracilariopsis. Comparison of the percent of unique and repetitive sequences (U/R) indicated a wide range of ratios, withGracilaria tikvahiae populations having the highest values (2.7–7.3) andGracilaria sp. cultivar G-6,G. blodgettii andGracilariopsis lemanieformis the lowest (0.05–1.80). Unique component complexities varied one order of magnitude, from 108 forGracilaria takvahiae to 107 forGracilaria sp. cultivar G-6,G. blodgettii andGracilariopsis lemanieformis. Information for genome size, organization and complexity is used to develop a nuclear genome profile forGracilaria blodgettii andGracilariopsis lemanieformis which are characterized by commercial grade agars having high gel strengths (> 700 g cm−2) and elevated melting temperatures (99 °C).

On a Khovanskii transformation for continued fractions

Some aspects of a transformation for continued fractions due to Khovanskii are studied. It is shown that the transformation does not in general establish an identity, but has many interesting properties. It permits to transform some difficult continued fractions into suitable ones. Its even part is identical to the even part of Sn(−12) modification. It may also give acceleration for some slow continued fractions.

Regulation of the affinity state of the N-formylated peptide receptor of neutrophils: role of guanine nucleotide-binding proteins and the cytoskeleton.

Previous studies have indicated that the receptor for N-formylated peptides present on human neutrophils can exist in several ligand-dissociation states at least one of which is sensitive to guanine nucleotides. Human neutrophil membranes rich in cell surface enzyme markers have been isolated from cells pretreated at 37 degrees C with 5 nM fluoresceinated chemotactic peptide (N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys-fluorescein; Fl-peptide) or a buffer control and analyzed for receptor-ligand dissociation states using a previously published fluorescence assay for estimating ligand binding and dissociation rates (Sklar, L. A., et al. 1984. J. Biol. Chem. 259:5661-5669). Fractionation of crude microsomes derived from homogenates of unstimulated cells by ultracentrifugation on linear D2O gradients yielded two plasma membrane-rich fractions termed fast and slow microsomes. Analysis of Fl-peptide dissociation rates from receptor present in fast membrane fractions of unstimulated cells yielded data that could be best fit by assuming that the receptor exists in three distinct ligand-dissociation states. The intermediate ligand-dissociation state (state B) accounted for 47% of the total and was converted to the fastest ligand-dissociation state (state A) by incubation of membranes with GTP or GTP-gamma-S. The remainder of the receptor (17%) present in unstimulated membranes was in a state from which ligand was virtually nondissociable (state C). This form of the receptor was insensitive to GTP-gamma-S. When cells were stimulated with Fl-peptide, most of the receptor present in slow and fast membranes was of the state C type. In contrast to unstimulated cells, slow membranes derived from cells exposed to Fl-peptide contained the majority of the recoverable receptor indicating that receptor was transferred to a physically isolatable membrane domain after ligand binding to the intact cell. The ligand-induced formation of state C in both fast and slow microsome fractions was inhibited by treatment of cells with dihydrocytochalasin B. However, the drug had no effect on translocation of the receptor to slow membranes. Pertussis toxin treatment of intact cells had no effect on ligand-induced formation of state C in either fraction even though other cellular responses were inhibited. Both slow and fast membranes contained a 41-kD G protein as assayed by immunoblot analysis. The data suggest that ligand induces a segregation of receptor-ligand complexes into a membrane domain in which the receptor is functionally uncoupled from the 41-kD neutrophil G protein.(ABSTRACT TRUNCATED AT 400 WORDS)

Analysis of serum lactic dehydrogenase levels and its isoenzymes in ovarian dysgerminoma

The usefulness of serum lactic dehydrogenase (LDH) levels and its isoenzyme analysis as potential malignant ovarian tumor markers was investigated in 74 patients, including 5 cases of ovarian dysgerminomas. In this study 41.7% of patients with ovarian adenocarcinomas of the common epithelial types and 29.4% of cases with metastatic ovarian carcinoma had elevated preoperative serum LDH levels. In contrast all 5 cases of ovarian dysgerminomas had extremely high levels of serum LDH prior to therapy, whereas all 11 cases of benign solid ovarian tumors had normal LDH levels. The analysis of LDH isoenzymes revealed that ovarian dysgerminomas had high levels of the two fast fractions of LDH, whereas other malignant ovarian tumors had elevated levels of the two slow fractions. The present findings indicate that serum LDH levels and electrophoresis of its isoenzymes may be of value in patients with ovarian dysgerminomas.

Allocation and Turnover of Photosynthetically Assimilated 14CO2 in Leaves of Glycine max L. Clark

The allocation and turnover of photosynthetically assimilated (14)CO(2) in lipid and protein fractions of soybean (Glycine max L. Clark) leaves and stem materials was measured. In whole plant labeling experiments, allocation of photosynthate from a pulse of (14)CO(2) into polymeric compounds was: 25% to proteins in 4 days, 20% to metabolically inert cell wall products in 1 to 2 days, 10% to lipids in 4 days, and 4% to starch in 1 day. The amount of (14)C labeled photosynthate that an actively growing leaf (leaf 4) used for its own lipid synthesis immediately following pulse labeling was about 25%. The (14)C of labeled proteins turned over with half-lives of 3.8, 3.3, and 4.1 days in leaves 1, 2, and 3, respectively; and turnover of (14)C in total shoot protein proceeded with a half-life of 5.2 days. Three kinetic (14)C turnover patterns were observed in lipids: a rapid turnover fraction (within a day), an intermediate fraction (half-life about 5 days), and a slow turnover fraction. These results are discussed in terms of previously published accounts of translocation, carbon budgets, carbon use, and turnover in starch, lipid, protein, and cell wall materials of various plants including soybeans.

Self-exchange of sodium in human lymphocytes

Self-exchanges of Na and K in human lymphocytes were measured by isotopic efflux techniques. In washed cells, K exchanged in a single slow exponential fraction, but the Na exchange had a marked curvature. It was shown that the curvature was not caused by simple bulk-phase diffusion, and it was resolved into three major fractions: fast (F) (half-time, t1/2 = 2-4 min), intermediate (I) (t1/2 = 12 min), and slow (S) (t1/2 = 125 min). Each of these appeared to follow an exponential function. The I fraction contained approximately 10 mmol Na/kg cells (25-30% of normal cellular Na), was not affected by manipulations that cause lymphocytes to gain Na, and had little or no temperature dependence. The S fraction of Na in normal cells (S1) contained approximately 10 mmol Na/kg cells, had only a slight temperature dependence, and the amount and rate of S1 were independent of external K concentration (Kex). Another slow fraction (S2) appeared when the cells underwent a net gain of Na in exchange for K, and was characterized by a steep temperature dependence and a peak rate around the transition point (the point at which half of cellular K is replaced by Na) at 0.4 mM Kex. The results are discussed within context of a theory that assigns the exchange of the major part of K in its slow exponential fraction and the Na exchange in S2 to interactions of these ions with fixed anionic sites, on intracellular macromolecules, which have been shown previously to interact cooperatively in their association with K and Na.

The permeability of human lymphocytes to chloride

The normal amount of Cl in human lymphocytes is 82 mmoles/kg wet weight. Half of this undergoes rapid self-exchange with a half-time of 3 minutes, while the remainder exchanges slowly with a half-time of 180 minutes. The fast fraction of self-exchange of Cl also undergoes a rapid net loss into medium with a low concentration of Cl. Thus, exchange of Cl in lymphocytes has properties like that of K and Na with permeability constants on the order of 10(-6) cm/sec. The results are compatible with a simple model in which the fast fractions are dissolved within ordered cellular water at concentrations less than in the external medium and the slow fractions are adsorbed onto intracellular macromolecules.

The effect of sleep deprivation on sleep in rats with suprachiasmatic lesions

The effect of 24-h sleep deprivation on sleep was investigated in rats whose circadian rest-activity rhythms were extensively disrupted by bilateral lesions of the suprachiasmatic nuclei (SCN). Sleep deprivation caused an increase in total sleep, REM sleep and the slow wave sleep fraction of non-REM sleep. It is concluded that the homeostatic component of sleep regulation is morphologically and functionally distinct from the circadian component.

Effets à court et moyen terme de chocs thermiques et influence de la cinétique de décroissance de la température consécutive au choc sur l'activité de la leucine aminopeptidase chez Scolelepis (Malacoceros) fuliginosa Claparède (Annelida: Polychaeta)

Scolelepis (Malacoceros) fuliginosa Claparède acclimated to 13 and 19 °C were subjected to thermal shocks ( ΔT) of 10 min duration and of amplitude from 8 to 14 °C for animals acclimated to 19 °C and up to 19 °C for animals acclimated to 13 °C. The effects of the thermal changes on LAP activity were detected after electrophoretic separation of LAP fractions. In most individuals two LAP fractions were demonstrable. The faster migrating fraction was sensitive to thermal shock, and the slower migrating fraction was virtually more thermostable. In individuals acclimated to 19 °C increased amplitude of thermal shocks caused a change in LAP activity with a decrease in the fast fraction, while the slow fraction was unaltered. The rate of decrease in the former fraction increased with increasing amplitude of the thermal change, and a greater decrease was observed in females than in males. In animals acclimated to 13 °C, a thermal shock of 19 °C resulted in a rapid and almost complete elimination of the fast migrating LAP fraction, and all males and females died within 24 h. The influence of the rate of decrease in temperature was studied after thermal shocks of amplitude 16 and 18 °C were applied to animals acclimated to 13 °C. The former temperature increase was not lethal but a considerable decrease in the activity of the fast migrating LAP fraction was observed in both sexes within 4 h, with a slow rate of subsequent temperature decrease. After a further 6 days there was some recovery of the activity in this fraction but activity remained lower than in control animals. With a rapid temperature decrease subsequent to the same 16 °C shock the decrease in activity did not occur until approximately 24 h after the thermal shock and a full recovery and enzyme activity was observed after 38 h. A thermal shock of 18 ° C, followed by a slow temperature decrease, was lethal for both sexes and the “fast” LAP fraction almost disappeared within 1 h. A rapid decrease in temperature, however, was only lethal to females, although the fast migrating LAP fraction, reduced after 1 h, subsequently disappeared in both sexes. In males only this fraction recovered briefly after 8 h but after a further 6 days activity remained lower than that observed in the controls. It is concluded that, according to their amplitude, thermal shocks progressively affect LAP activity. These effects can be minimized by increasing the rate of decrease in temperature after the shocks.

Effects of valinomycin on lymphocytes independent of potassium permeability

10 −7 M valinomycin affects human lymphocytes in the following manner: (1) it is non-toxic; (2) it inhibits mitogenesis; (3) it causes a reduction in cell ATP; and (4) it causes a marked increase in steady-state Na + exchange. However, it has a minimal effect on cell ion (K +, Na +, Ca 2+, Mg 2+) contents and no effect whatever on K + exchange. Neither the fast nor the slow fraction of steady-state K + exchange is affected by 10 −7 M valinomycin. The various reported effects of valinomycin on lymphocyte functions cannot be assumed to be due to changes in plasma membrane K + permeability. The mechanism of the increase in steady-state Na + exchange, and whether or not it is related to inhibition of mitogenesis, are unsettled issues.

Migration of silver from silver-loaded polyimide adhesive chip bonds at high temperatures: Roger J. Chaffin. IEEE Trans. Components. Hybrids, Mfg Technol.Chmt-4, (2) p. 214 (June 1981)

Slow release behavior of carbon tetrachloride (CCl4) and chloroform (CHCl3) in low organic carbon (<0.1%) deep aquifer sediments was quantified by 1-D column desorption studies with intact cores. The compounds had been in contact with the sediments for 30 years. Comparison of the CCl4 distribution coefficient (Kd) from this study with those from short contact time experiments suggested that CCl4 Kd’s calculated from site contaminated sediments of long contact time are likely a factor of 10 or more higher than those calculated from short contact-time lab experiments. A significant portion of the CHCl3 mass (55% to more than 90%) was resistant to aqueous desorption in sediments with clay contents ranging from 2.0% to 36.7% and organic carbon content ranging from 0.017% to 0.088%. In contrast, CCl4 showed greatest mass retention (31% or more) only in the highest clay and organic carbon content sediment. Relatively easy solvent extraction of the residual masses of CCl4 and CHCl3 from the sediments indicated the compounds were not permanently sequestered. Tracer breakthrough in columns was well behaved, indicating interparticle diffusion was not causing the slow release behavior. Diffusion out of intraparticle pores is suggested to be the main process governing the observed behavior although, diffusion out of natural organic matter cannot be ruled out as a potential contributing factor. The half-life for release of the slow fraction of CHCl3 mass from sediments was estimated to be in the range of weeks (100 h) to months (1100 h). Neither CCl4 or CHCl3 were detected at measurable levels in the column effluent of one of the sediments even though a significant mass fraction of CHCl3 was found present on the sediment following desorption suggesting that our estimate of hundreds to thousands of hours for complete release of CHCl3 masses from such sediment is conservative.

A unitary cause for the exclusion of Na+ and other solutes from living cells, suggested by effluxes of Na+, D-arabinose, and sucrose from normal, dying, and dead muscles.

1. The effluxes of labeled Na+, D-arabinose, and sucrose from normal muscle and muscle poisoned with low concentrations of iodoacetate were studied. The procedure involved repeated loading with isotope, followed by washing of the same muscle while still normal and at different states of dying. 2. The rates of Na+ efflux in both the fast and slow fraction remained either quite constant or showed some unpredictable, minor fluctuations. This was true for both Na+ and the two sugars studied, confirming earlier conclusions that the steady levels of these solutes were not maintained by pumps. 3. In all cases studied, the efflux curves showed at least two fractions. It is the fast-exchanging fraction that steadily and consistently increased in magnitude as the muscles were dying, until finally the concentration of solute in this fraction reached and sometimes surpassed the labeled solute concentrations in the original labeled solutions in which the muscles were equilibrated. The slow fractions showed only a transient increase or none at all. These observations show that it is the fast fraction that represents solute dissolved in cell water and rate-limited by passage through the cell surface and that the partial exclusion of Na+ and the sugars have a unitary cause--a reduced solubility in the cell water which in the presence of ATP exists in the state of polarized multilayers.