Versailles Project on Advanced Materials and Standards interlaboratory study on intensity calibration for x-ray photoelectron spectroscopy instruments using low-density polyethylene

We report the results of a Versailles Project on Advanced Materials and Standards interlaboratory study on the intensity scale calibration of x-ray photoelectron spectrometers using low-density polyethylene (LDPE) as an alternative material to gold, silver, and copper. An improved set of LDPE reference spectra, corrected for different instrument geometries using a quartz-monochromated Al Kα x-ray source, was developed using data provided by participants in this study. Using these new reference spectra, a transmission function was calculated for each dataset that participants provided. When compared to a similar calibration procedure using the NPL reference spectra for gold, the LDPE intensity calibration method achieves an absolute offset of ∼3.0% and a systematic deviation of ±6.5% on average across all participants. For spectra recorded at high pass energies (≥90 eV), values of absolute offset and systematic deviation are ∼5.8% and ±5.7%, respectively, whereas for spectra collected at lower pass energies (<90 eV), values of absolute offset and systematic deviation are ∼4.9% and ±8.8%, respectively; low pass energy spectra perform worse than the global average, in terms of systematic deviations, due to diminished count rates and signal-to-noise ratio. Differences in absolute offset are attributed to the surface roughness of the LDPE induced by sample preparation. We further assess the usability of LDPE as a secondary reference material and comment on its performance in the presence of issues such as variable dark noise, x-ray warm up times, inaccuracy at low count rates, and underlying spectrometer problems. In response to participant feedback and the results of the study, we provide an updated LDPE intensity calibration protocol to address the issues highlighted in the interlaboratory study. We also comment on the lack of implementation of a consistent and traceable intensity calibration method across the community of x-ray photoelectron spectroscopy (XPS) users and, therefore, propose a route to achieving this with the assistance of instrument manufacturers, metrology laboratories, and experts leading to an international standard for XPS intensity scale calibration.

Aerobic exercise in water versus walking on land: effects on indices of fat reduction and weight loss of obese women

AIM

It has been suggested, that water exercise is less effective than weight-bearing exercise on land for body fat reduction.

METHODS

To test this hypothesis 38 middle-aged obese women (25-47% body fat) participated in a 13 week exercise-diet program to compare the effects of aerobic exercise in water versus walking on land on indices of fat reduction and weight loss changes. Subjects were randomly assigned to 1 of 3 exercise groups: 1) walking on land (WL), 2) swimming (SW) at 27 degrees C water temperature and 3) walking in 29 degrees C water (WW) at the shallow end of a declining pool with the water at navel height. Subjects in the SW group alternated breast-, side-, and backstroke swimming without face immersion. Exercise parameters were kept constant for all three groups. Subjects participated in supervised exercise sessions for 40 min, 4 times a week at 70% of age-predicted maximum heart rate. Subjects were tested before and after the 13-week experimental period.

RESULTS

Significant reductions in body weight, (5.9 kg), percent body fat, (3.7%), and skinfold and girth measurements, occurred in all groups. There where no significant differences between groups.

CONCLUSIONS

The results of this study indicate that there are no differences in the effect of aerobic activities in the water versus weight-bearing aerobic exercise on land on body composition components as long as similar intensity, duration and frequency are used.

An evaluation of rectal mucosal proliferation measure variability sources in the polyp prevention trial: can we detect informative differences among individuals' proliferation measures amid the noise?

We assessed components of total variability of bromodeoxyuridine (BrdUrd) and proliferating cell nuclear antigen (PCNA) assays of rectal mucosal proliferation in a subset of 390 participants from the U. S. National Cancer Institute's multicenter Polyp Prevention Trial. Biopsies were blindly double-scored by two technicians. For those participants for whom at least one evaluable biopsy was obtained, a mean of 2.0 and 2.6 biopsies, and 6.2 and 8.7 crypts/biopsy were evaluated, respectively, with the BrdUrd and PCNA assays. Factors such as clinical center, scorer, and month of biopsy collection significantly affected the observed values of the labeling index (LI) and proliferative height (PH). Therefore, it is essential to control or adjust for these variables in proliferation studies. Sources of random variation for LI and PH measures remaining after the aforementioned factors include between-participant variation and several sources of within-participant variation, including variation over time, between biopsies, and between multiple measurements on the same biopsy. Both LI and PH measurements exhibited substantial variability over time, between biopsies, and from reading-to-reading of the same biopsy. When other sources of variability have been accounted for, the PCNA LI seems to have little between-participant variation. This brings into question its utility as a marker in colorectal cancer studies. The PCNA PH showed significant between-participant variability and may hold some promise as a useful marker in colorectal cancer studies. Results for BrdUrd were less conclusive. The BrdUrd LI showed marginally significant between-participant variation, whereas the corresponding variation for PH was nonsignificant.

Activating hydroxyl groups of polymeric carriers using 4-fluorobenzenesulfonyl chloride

4-Fluorobenzenesulfonyl chloride (fosyl chloride), due to the strong electron-withdrawing property of its fluoride atom, is found to be an excellent activating agent for the covalent attachment of biologicals to a variety of solid supports (e.g. functionalized polystyrene microspheres, Sepharose beads, or cellulose rods and hollow fibers). This reagent reacts rapidly with primary or secondary hydroxyl groups, at ambient temperature and pressure, to form 4-fluorobenzenesulfonate leaving groups. The activated solid support can be used immediately or preserved for several months without loss of activity by freeze-drying or by storage at 4 degrees C in aqueous solution at pH 5. Enzymes, antibodies, avidin, and other biologicals can be covalently attached to the activated solid phase with excellent retention of biological function. Potential therapeutic applications of the fosyl chloride chemistry for bioselective separation of human lymphocyte subsets from whole blood and tumor cells from bone marrow are presented.

Generalized diminution in the response to nutrients as insulin-releasing agents during the early neonatal period in the rat

Glucose-induced insulin secretion is diminished during the fetal and neonatal period. To investigate whether the “defect” in B-cell secretion is specific for glucose and linked to glucose metabolism, the insulin-releasing effect of three nutrient secretagogues, glucose, glyceraldehyde, and leucine, were compared at different ages of the rat in vivo (1- and 7-day neo-nates) and in vitro (1- and 7-day neonates and adult animals). Intraperitoneal injections produced a marked insulin response to glucose, glyceraldehyde, and leucine in 7-day animals but only small increments that were not significant in 1-day neonates.

The accumulation of insulin from isolated islets of 1-day neonates during 60-min incubations was slightly but significantly enhanced by 11.1-34.4 m M glucose or 40 mM leucine. No response was seen with 1-16 mM glyceraldehyde. By contrast, all three secretagogues markedly stimulated insulin secretion from 7-day and adult islets. However, quantitative relationships differed. Thus, the response from 7-day islets to the highest concentration of glucose was 20%, to glyceraldehyde 10%, and to leucine 50% of adult values. A “basal” concentration of glucose (4.4 mM) amplified glyceraldehyde- or leucine-induced insulin release, but did not influence the age-related differences in secretory response.

The nutrient secregogues induced a small percent stimulation of (32P)-orthophosphate efflux from prelabeled islets of 1-day neonates. This stimulation increased progressively with age. However, in 1- and 7-day islets glucose and leucine stimulated the efflux of 32P more than glyceraldehyde; in adult islets the nutrients were equipotent. Glucose, glyceraldehyde, and leucine increased the accumulation of (3H) cyclic AMP in prelabeled adult but not in 7- or 1-day islets.

The foregoing indicates that the obtunded insulin secretion at birth in the rat may apply to all nutrient secretagogues. Because of the difference in metabolic disposition of tested secretagogues, the secretory limitation cannot be ascribed to faulty glycolysis but must involve some communally shared, probably early, step in stimulus-secretion coupling. Continued maturation includes preferential development of the secretory responsiveness to some secretagogues.

Effect of ionophore A23187 upon membrane function and ion movement in human and toad erythrocytes

Addition of 0.1-0.3 micronM A23187, a divalent cation ionophore, to human erythrocytes suspended in a 1.0 mM 45Ca2+ -containing buffer results in a small (approximately two fold) increase in [Ca2+]i, a significant decrease in osmotic fragility, and a decrease in intracellular K+ (100 mmoles/liter of cells to 70 mmoles/liter cells) without significant alteration of intracellular [Na+]. This decrease in [K+]i is associated with a significant decrease in packed cell volume and correlates directly with the observed alteration is osmotic fragility. Increasing extracellular K+ to 125 mM prevents the A23187-induced changes in osmotic fragility, K+ content and cell volume, but does not prevent the ionophore-induced uptake of 45Ca2+. Addition of 0.1-0.3 micronM A23187 to toad erythrocytes leads to an increase in 45Ca2+ uptake comparable to that observed in human erythrocytes, but does not alter osmotic fragility, cell volume or K+ content. Higher concentrations of ionophore (3.0-10.0 micronM) cause a 30- to 50-fold increase in 45Ca2+ uptake and concomitant change in K+ content, cell volume and osmotic fragility. These changes in cell properties can be prevented by increasing extracellular [K+] to 90 mM. The difference in sensitivity of the two cell types to A23187 is attributed to the presence of additional intracellular calcium pools within toad erythrocytes that prevent an increase in cytoplasmic Ca2+ until Ca2+ uptake is increased substantially at the higher concentrations of A23187.

Calcium ion as second messenger

The role of calcium as an intracellular messenger in the activation of eukaryotic cells is discussed. Particular emphasis is devoted to: (1) the interrelationship between cell activation by chemical stimuli and alterations in intracellular calcium metabolism, and (2) the interrelated roles of calcium and the cyclic nucleotides, cyclic AMP and cyclic GMP, in achieving the final integrated, co-ordinated cellular response.

The effect of catecholamines and prostaglandins upon human and rat erythrocytes

Both human and rat erythrocytes respond to low doses (10(-11)--10(-9) M) of L-isoproterenol and L-epinephrine with an increased degree of hypotonic hemolysis and a decreased rate of filtration through standardized paper filters. The receptors in both cell types have many of the characteristics of beta-receptors for catecholamines. However, hormone-receptor interaction in the human cell does not lead to an increase in intracellular cyclic AMP concentration, but in the rat cell, hormone-receptor interaction does lead to a significant increase in cyclic AMP content. Thus, catecholamine-beta-receptor interaction, at least in the human red cell, leads to a change in red cell properties which are not mediated by adenylate cyclase activation. Likewise, prostaglandin E2, at 10(-12)--10(-10) M, causes are increased degree of hypotonic hemolysis and a decreased rate of filtration through standardized paper filters, but it also does not increase the cycliC AMP content of the human erythrocyte but does increase that of the rat erythrocyte. Nevertheless, exogenous cyclic AMP, when added at a concentration of 10(-8) M to washed human erythrocytes, increases the degree of hypotonic hemolysis. Conversely, prostaglandin E1, at 10(-12)--10(-10) M, causes a decreased degree of hypotonic hemolysis and an increased rate of filtration through a standard filter. Both prostaglandin E2 and the catecholamines decrease the size of a rapidly exchangeable calcium pool, and prostaglandin E1 increases it.