Absolute Removal Research Articles

Accuracy of urea removal estimated by kinetic models

The most accurate method for assessing the dialysis dose delivered during high efficiency/flux hemodialysis has not been established. Most current indices of dialysis dose are based on blood-side urea measurements, and thus estimate urea removal. Unfortunately, these methods may lead to inappropriately short dialysis during high flux or high efficiency dialysis, perhaps because of inaccuracies in estimating the amount of urea removal. It is unknown whether these clearance-based approaches can accurately predict either absolute or fractional net urea removal, the latter being equivalent to the solute removal index (SRI). Therefore, we compared the urea removal calculated by five blood-side kinetic methods: (1) urea reduction ration, (2) 1-pool, (3) 2-pool models, and the (4) Smye and (5) Daugirdas formulae. These were compared with the gold standard measurement by direct dialysate quantification. Eight stable patients receiving high-flux hemodialysis were studied over four sessions each. BUN was measured at 0, 45 minutes, 90 minutes, end dialysis, one hour after dialysis (equilibrium value), and 48 hours later. Total body water was determined from the dialysate urea removal; the urea generation rate was calculated using one hour post-dialysis and 48-hour BUN values. Both the total body water and urea generation rate were provided to the 1- and 2-pool models to optimize accuracy. The urea reduction ratio overestimated SRI. The 1-pool model overestimated both absolute urea removal and SRI in 28 of 32 sessions. The 2-pool model slightly underestimated both absolute urea removal and SRI. In contrast, the Smye and Daugirdas formulas accurately estimated SRI.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutrition support affects the distribution and organ uptake of cachectin/tumor necrosis factor in rats.

We have previously observed a potentiation of the metabolic response to cachectin/tumor necrosis factor (TNF) by total parenteral nutrition (TPN) but not in anorexic orally fed animals. We hypothesized that nutritional status might affect TNF clearance kinetics. We compared the clearance of a bolus of labeled TNF in TPN-fed animals given sufficient nutrients to grow called weight-gaining rats (WGR) with those given 50% of the WGR called weight-losing rats (WLR) and with orally fed rats (OFR). Data were analyzed using a two-compartment open system model and by linear systems analysis. The data from both types of analysis indicator that although metabolic clearance was similar, WGR had a slower fractional TNF clearance rate (FCR) as well as a larger volume of distribution than WLR or OFR. Further analysis showed that an increased proportion of the total mass of TNF resided in a plasma-associated compartment in WGR compared with WLR and OFR. In addition, WGR had reduced uptake of labeled TNF by the kidney. The data suggest that nutrition support influences either the distribution of TNF or the FCR, resulting in a greater retention in the plasma-associated compartment with intact absolute removal rates. This study has important implications concerning the type of nutrition support provided to the critically ill patient because our data suggest that clinical states with increased circulating TNF levels may be adversely affected by currently available nutritional practices.

Removal of iron dextran by hemodialysis: An in vitro study

Intravenous iron dextran is frequently prescribed for iron-deficient hemodialysis patients, a practice that has increased during the erythropoietin era. Whether iron dextran is removed by hemodialysis has been a concern, especially for high permeability membranes. The purpose of this in vitro study was to measure iron dextran clearance by nine different hemodialyzers (Fresenius F3, F8, and F80B; Baxter CF25, CA150, CA210, and CT190; Toray BK2.1P; and Hospal Filtral 16) representing six types of membranes (polysulfone, cuprophane, cellulose acetate, cellulose triacetate, polymethylmethacrylate, and polyacrylonitrile) and including membranes considered high efficiency and high flux. Clearances were assessed using a closed-loop, fixed-volume reservoir model. Absolute drug removal also was determined over the 30-minute experiments. Iron dextran clearance did not exceed 25 mL/min, and clearances also were minimal after a single automated reuse with glutaraldehyde sterilant. A maximum of 8% of iron dextran was removed during the experiment. We conclude that iron dextran clearance by the nine hemodialyzers studied was small or too low to be detected in this sensitive in vitro dialysis system and that adjusting dosing schedules is not needed.

Comparison of singlet methylene removal rates by group IV hydrides

AbstractThe technique of laser flash photolysis/laser absorption has been used to obtain an absolute removal rate constant of (3.85 ± 0.18) × 10−10 cm3 molecule−1 s−1 for singlet methylene, 1CH2 (ã1A1), with germane (GeH4) at ambient temperature. The removal rate constant is compared with the values for methane (CH4) and silane (SiH4) which have been determined previously. © 1995 John Wiley & Sons, Inc.

Singlet methylene removal by saturated and unsaturated hydrocarbons

The technique of laser flash phyotolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylene, 1CH 2 ( a ̃ 1A 1 ), with various saturated and unsaturated hydrocarbons. The removal rate constants for CH 4, C 2H 6, C 3H 8, C 2H 4, C 3H 6, C 2H 2, CH 2CCH 2, and C 6H 6 were found to be in excellent agreement with previously reported results. Removal rate constants were also measured for n-C 4H 10, i-C 4H 10, n-C 5H 12, c-C 3H 6, c-C 6H 12, 1-C 4H 8, cis-2-C 4H 8, trans-2-C 4H 8, and 1-C 4H 6, and determined to be (3.17 ± 0.15), (2.53 ± 0.11), (3.35 ± 0.24), (1.63 ± 0.08), (3.77 ± 0.21), (3.80 ± 0.20), (3.67 ± 0.16), (3.43 ± 0.16) and (4.05 ± 0.18) × 10 −10 cm 3 molecule −1 s −1, respectively. This series of hydrocarbons forms the basis of a larger series of compounds containing a wide variety of organic functional groups. The removal rate constants are reported here, both as a series within its own right, and as a reference point for future work.

Singlet methylene removal by halogen-containing organic species

The technique of laser flash photolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylne, 1CH 2 (ã 1A 1), with various halogen-containing organic species. The removal rate constants for CH 3Cl, CH 2Cl 2, CHCl 3, CCl 4, CH 3CCl 3, CH 2CHCl, CH 3Br, CH 2CHBr, ch 3F, CF 4, CHF 2CFH 2, C 2F 6 CH 2CHF, C 2F 4, C 6H 5F, p-C 6F 2 and CF 3COOCOCF 3 were measured and found to be (2.72±0.13), (3.36±0.19), (3.48±0.17), (3.35±0.21), (3.61±0.37), (3.21±0.16), (3.03±0.16), (3.54±0.19), (0.549±0.025), (0.169±0.018), (0.639±0.059), (0.212±0.031), (1.73±0.09), (0.509±0.062), (3.36±0.19), (2.59±0.26) and (2.00±0.14) × 10 −10 cm 3 molecule −1s −1, respectively. Comparisons are drawn between the reactivities of the various halide groups and with their hydrocarbon analogues.

Direct measurement of singlet methylene removal rates by organic species containing the ? O ? and > C = O moieties

The technique of laser flash photolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylene 1CH2(a1A1) with dimethyl ether (CH3OCH3), acetaldehyde (CH3CHO), acetone (CH3COCH3), acetic acid (CH3CO2H), methyl formate (HCO2CH3), acetic anhydride (CH3CO2COCH3), and dimethyl carbonate (CH3OCO2CH3). The removal rate constants were found to be (1.80 ± 0.22), (2.81 ± 0.35), (4.48 ± 0.35), (5.71 ± 0.40), (2.82 ± 0.32), (5.27 ± 0.71) and (2.68 ± 0.28)× 10–10 cm3 molecule–1 s–1, respectively. Removal rate constants for the molecules containing the > CO moiety are considerably greater than those for the corresponding alkanes, but the removal rate constant for dimethyl ether is significantly less than that for the alkane analogue, propane. Removal rate constants were also remeasured for ethane (C2H6), ethene (C2H4) and methanol (CH3OH) and found to be (1.95 ± 0.48), (2.46 ± 0.23) and (3.69 ± 0.37)× 10–10 cm3 molecule–1 s–1, respectively.

Removal rates of CHF (Ã 1A″ (0, 0, 0)) by alkenes

Absolute removal rates of CHF (à 1A″ (0, 0, 0)) by ethene (C 2H 4), propene (C 3H 6), 1-butene (1-C 4H 8), isobutene( i-C 4H 8), 1,3-butadiene (C 4H 6), difluoromethane (CH 2F 2), nitric oxide (NO) and argon (Ar) have been measured at room temperature. CHF in the à 1A″ state was produced by infrared multiphoton dissociation of CH 2F 2 forming the CHF (X̃ 1A′) state and further pumping to the à 1A″ state by absorption of a visible dye laser pulse. Removal processes were found to be second order with the following rate constants in units of 10 −10 cm 3 molecule −1 s −1: k(C 2H 4) = 0.9 ± 0.2. k(C 3H 6) = 1.0 ± 0.2; k (1−1C 4H 8) = 1.1 ± 0.2; k( i-C 4H 8) = 1.1 ± 0.2; k(C 4H 6) = 1.0 ± 0.2; k(Ar) = 0.27 ± 0.02; k(NO) = 0.8 ± 0.1; k(CH 2F 2) = 1.3 ± 0.1. The Parmenter—Seaver correlation for collisional removal of à 1A″ CHF is discussed.

Predictability of low‐density lipoprotein levels during apheretic treatment of hypercholesterolemia

The efficiency and efficacy of low-density lipoprotein (LDL) apheresis performed with a dextran sulphate cellulose (DSC) regenerating unit were tested in five familial hypercholesterolaemic patients. LDL apheresis was repeated four times at both bi-weekly and weekly intervals, processing one plasma volume each time. The efficiency of the procedure (i.e., the extent of lipoprotein removal) was nearly identical with both schedules. Efficacy parameters, i.e., decreases of plasma total and LDL cholesterol (TC and LDL-C) and apo B, were highly correlated (r greater than 0.96) with preapheresis levels, allowing an accurate prediction of the absolute lipid removal in the single individual. Plasma triglycerides, high-density lipoprotein cholesterol, apo A-I and apo A-II recovered rather rapidly, reaching 91-96% of the pre-apheresis values in 48 hours; the recovery of TC, LDL-C and apo B was much slower, with a relatively rapid early phase (80% recovery after about 7 days) followed by a successive slower rise. This pattern was highly reproducible in the single patient, allowing the definition of a simple mathematical model for an accurate (error less than 20%) prediction of the individual process. Based on this model one can design the treatment schedule necessary to maintain lipid levels within the desired range in the single individual. The hypolipidaemic efficacy of DSC apheresis appears, otherwise, not to be dependent upon the procedure per se, but on other individual factors, e.g. the amount of removable lipoproteins and the rate of lipid recovery; both can be predicted with sufficient accuracy.

Direct measurement of methylene removal rates by species containing the OH functional group

The technique of laser flash photolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylene (1CH2) with N2, ketene (CH2CO), H2O, D2O, methanol (CH3OH), ethanol (C2H5OH), and n-propanol (n-C3H7OH) at 296 ± 2 K. The rate constants were found to be (0.130 ± 0.012), (2.38 ± 0.18), (1.60 ± 0.17), (1.05 ± 0.13), (2.20 ± 0.19), (2.61 ± 0.23) and (4.15 ± 0.44)× 10–10 cm3 molecule–1 s–1, respectively. The removal rate constants for the alcohols are consistently greater than those for the corresponding alkanes.

Supplemental Carbon Use by Microorganisms Degrading Toxic Organic Compounds and the Concept of Specific Toxicity

Biological treatment can be used to decontaminate soil and water polluted by toxic organic compounds. Some compounds are metabolized too slowly under natural conditions to be effectively removed from the contaminated system. The technical literature contains several examples where nutrient manipulation has been used to enhance microbial metabolism. One promising technique for increasing absolute biodegradation rates of organic toxins is to augment microbial biomass by adding a supplemental carbon substrate. Simultaneous metabolism of the toxic and supplemental substrates requires maintenance of growth limiting carbon concentrations in culture to avoid catabolite repression. Populations of microorganisms can metabolize very low levels of organic toxins at accelerated rates when an ancillary carbon source is supplied. Cell-specific degradation rates may remain unchanged, but absolute removal rates are increased by virtue of increased biomass. Ancillary carbon can also stabilize a population of microorganisms in the presence of high and otherwise inhibitory concentrations of organic toxins. In such cases where organic toxin levels are high and biomass is augmented by supplemental carbon a measure of toxicity is required which accounts for microbial population density as well as toxin concentration. This second order parameter is called specific toxicity.

Insect herbivory on an inland brackish wetland

Standing crop measurements were made in emergent wetland vegetation following acute herbivory by 2 species of leaf-chewing caterpillars,Cisseps fulvicula (Ctenucidae) andAcronicta leporina (Noctuidae). Significant weight differences were found between grazed and ungrazed stands of alkali bulrush, cattail, Olney’s bulrush, and saltgrass, respectively. The greatest absolute removal was 2050 kg/ha (43%) in cattail stands and the smallest was 783 kg/ha (47%) in Olney’s bulrush. Mincral conlent of cattail leaf parts remaining after grazing was greater than that of similar but ungrazed stands, suggesting non-random feeding by these insects. Herbivory removed enough plant material to significantly change the standing crop and alter plant stand architecture of these 4 emergent species.

ChemInform Abstract: Absolute Rate Constants for Silylene Reactions with Hydrocarbons at 298 K.

The authors report absolute removal rate constants for silylene by reaction with alkanes, olefins, 1,3-butadiene, and acetylene at ambient temperature and 5-Torr total pressure. Rate constants were determined by laser resonance absorption flash kinetic spectroscopy. The results show that silylene is unreactive with alkanes and reacts rapidly and unselectively with unsaturated hydrocarbons.

Frictional interactions in machining: comparisons between transparent sapphire and steel cutting tools

This paper is concerned with the frictional interactions at the chip/tool interface in machining. Lead, aluminium, copper, iron, and nickel have been machined over a range of cutting speeds and times. Steel, cemented carbide, and transparent sapphire cutting tools have been used; the last allowing the interface to be observed directly. When used in this way in an earlier investigation it was found that relative motion, or sliding, occurred between chip and tool. However, a wider range of experiments has now shown that the conditions can vary between interfacial sliding and full sticking friction or seizure. The physical differences between sliding and seizure are discussed in detail. In the latter case the bond between chip and tool is sufficiently strong for relative motion to occur within the chip, and material is transferred to the tool face. When cutting aluminium with the sapphire tools, comparatively long cutting times and high speeds promote transfer. The key feature of such a process is the absolute removal of organic contaminants. When cutting with metal tools, the transfer will be further enhanced if the chip can also remove the oxide films from the rake face and form metal-metal bonds with the parent tool material. The difference in hardness between tool and work material is the major factor in this process. At the rear of the chip-tool contact length, the interaction between the atmosphere and the chip can cause transfer of a different nature. However, this may be eliminated if the cutting speed is increased.

Particulate retention by bacteria retentive membrane filters

Membranes are widely used in and accepted by industry as capable of 0.2 and 0.22 μm absolute removal of bacteria and particulates. Conditions are establised in this study under which these membranes pass latex spheres 0.5 μm and larger in diameter. The conditions of penetration, as a function of membrane type, challenge conditions, and pH are reported, and the interactions between the membrane pore surfaces and the latexes are related to DLVO theory. The study indicates that membranes of pore diameter substantially smaller than those now in common use increase the probability of obtaining microbial sterility.

Filtration Effects on Ball Bearing Life and Condition in a Contaminated Lubricant

Ball bearings were fatigue tested with a noncontaminated MIL-L-23699 lubricant and with a contaminated MIL-L-23699 lubricant under four levels of filtration. The test filters had absolute particle removal ratings of 3, 30, 49, and 105 microns. Aircraft turbine engine contaminants were injected into the filter’s supply line at a constant rate of 125 milligrams per bearing hour. Bearing life and running track condition generally improved with finer filtration. The experimental lives of 3- and 30-micron filter bearings were statistically equivalent, approaching those obtained with the noncontaminated lubricant bearings. Compared to these bearings, the lives of the 49-micron bearings were statistically lower. The 105-micron bearings experienced gross wear. The degree of surface distress, weight loss, and probable failure mode were dependent on filtration level, with finer filtration being clearly beneficial.

Abnormal Hepatic Transport of Indocyanine Green in Gilbert's Syndrome

The plasma fractional disappearance rate of indocyanine green (kICG, min-1) and the absolute hepatic ICG removal rate (VICG, mg per kg per min) were determined in 26 patients with Gilbert's syndrome (GS) and 19 normal control volunteers following intravenous administration of doses of 0.5, 2.0, 3.5, and 5.0 mg per kg of dye. The diagnosis of GS was based on studies of radiobilirubin kinetics in all cases and liver biopsy in 22 cases. The patients were further classified into 3 subgroups, based on patterns of sulfobromophthalein (BSP) kinetics, as follows: GS I (15 patients) had normal BSP metabolism; GS II (5 patients) had a defect in BSP metabolism beyond the stage of initial hepatic uptake; and GS III (6 patients) had a defect in the initial hepatic uptake of BSP (Gastroenterology 63:472-481, 1972). Both kICG and VICG were significantly reduced, compared to normal controls, in the GS III group with defective BSP uptake, but did not differ significantly from normal in the GS I and GS II groups. Michaelis-Menten analysis of the data indicated that VMAX for ICG uptake in the GS III group (1.2 +/- 0.6 mg per min per kg) was significantly reduced compared to the previously established normal value of 3.6 +/- 0.6 mg per min per kg; (P less than 0.01). For the total population of 26 patients with Gilbets' syndrome, there was a highly significant correlation (r= 0.77, P less than 0.01) between kICG and lambda21BSP, the fractional hepatic uptake rate for BSP. These studies confirm previous work indicating that patients with Gilbert's syndrome constitute a heterogeneous population with regard to defects in hepatic organic anion transport, some of the defects not being attributable to glucuronyl transferese deficiency. Future studies of Gilbert's syndrome must take into account the existence of these subgroups, since they may have different underlying pathogenetic mechanisms.

Removal of exogenous plasma triglycerides in forearm muscle and subcutaneous tissue of hyper-and normotriglyceridaemic men.

Absolute arterio-venous removal and fractional removal of blood-borne exogenous triglyceride particles by skeletal and subcutaneous tissues were determined in eight normotriglyceridaemic and six hypertriglyceridaemic men. Estimations were made by simultaneously sampling blood from catheters inserted into a brachial artery, and in the distal direction, into a superficial and deep vein, draining subcutaneous tissue and skeletal muscle respectively. During the infusion of the fat emulsion IntralipidR for 3 hours steady arterial concentrations of exogenous TG particles were found, indicating first order kinetics. In all subjects absolute arterio-venous and fractional removal of triglycerides were about twice as high in skeletal muscle as in subcutaneous tissue. In skeletal muscle the fractional removal and absolute removal were significantly higher in normotriglyceridaemic than in hypertriglyceridaemic subjects (p less than 0.001). No decrease in removal with time was observed, which would have suggested saturation of removal sites. Mean fractional removal in skeletal muscle was significantly correlated with the k2 value determined by an intravenous fat tolerance test before the infusion study (r = 0.61, p less than 0.05). In subcutaneous tissue fractional removal was also significantly higher in normotriglyceridaemic subjects (p less than 0.05). The results suggest that in both skeletal muscle and subcutaneous tissue the removal system is impaired in hypertriglyceridaemic subjects. This finding supports the concept that a decreased elimination capacity in these tissues may partly account for triglyceride elevation in hypertriglyceridaemic subjects.

A PLEA FOR EAREY VAGINAL HYSTERECTOMY FOR CANCER OF THE UTERUS.Read in the Section of Obstetrics and Diseases of Women, at the Forty-first Annual Meeting of the American Medical Association, held in Nashville, Tenn., May, 1890.

It is, at present, a generally conceded fact that cancer can be permanently eradicated from the human body if the parts of primary development and subsequent invasion can, early in the progress of disease, be absolutely separated and removed from the surrounding normal tissue. This implies that the operation for cancer which will go the farthest beyond the diseased limits, is the one most liable to accomplish absolute removal, consequently the one by which the most satisfactory curative results must be expected. With this fact well established, we can have no hesitancy in making the assertion that the operation which will obtain the best ultimate results in cancer of any portion of the uterus is the one which will accomplish its total removal, together with as much of the tissue which lies in close proximity to it as can be removed without unduly increasing immediate mortality. Hence my first proposition