The effect of cleaning procedures on fracture properties and corrosion of NiTi files.

AIM: To evaluate the effect of repeated cleaning procedures on fracture properties and corrosion of nickel-titanium (NiTi) files. METHODOLOGY: New NiTi instruments were subjected to 2, 5 and 10 cleaning cycles with the use of either diluted bleach (1% NaOCl) or Milton's solution (1% NaOCl plus 19% NaCl) as disinfectant. Each cleaning cycle consisted of scrubbing, rinsing and immersing in NaOCl for 10 min followed by 5 min of ultrasonication. Files were then tested for torsional failure and flexural fatigue, and observed for evidence of corrosion using scanning electron microscope (SEM). Four brands of NiTi files were immersed in either Milton's solution or diluted bleach overnight and evaluated for corrosion. RESULTS: Up to 10 cleaning cycles did not significantly reduce the torque at fracture or number of revolutions to flexural fatigue (P > 0.05, two-way anova), although decreasing values were noted with increasing number of cleaning cycles using Milton's solution. No corrosion was detected on the surface of these files. Files immersed in 1% NaOCl overnight displayed a variety of corrosion patterns. The extent of corrosion was variable amongst different brands of files and amongst files in each brand. Overall, Milton's solution was much more corrosive than diluted bleach. Corrosion of file handles was often extreme. CONCLUSIONS: Files can be cleaned up to 10 times without affecting fracture susceptibility or corrosion, but should not be immersed in NaOCl overnight. Milton's solution is much more corrosive than bleach with the same NaOCl concentration.

Correlations among physical activity and eating behaviors in 4- to 7-year-old Anglo- and Mexican-American children.

Physical activity and dietary behaviors are often correlated in adults and adolescents. This association was examined in 351 Anglo- and Mexican-American children between the ages of 4 and 7 years. Behaviors were assessed by structured observations and interviews at home and school. Observed physical activity was significantly correlated with energy intake (r = .43), but was unrelated to the percentage of calories from total fat or saturated fat. Thus, interventions with young children to improve dietary behavior or physical activity should not be expected to automatically lead to changes in the other.

Direct home observations of the prompting of physical activity in sedentary and active Mexican- and Anglo-American children.

Social interactions are important correlates of physical activity in children. Previous studies used global measures; the present study examined the influence of specific social interactions on immediate physical activity in children with data obtained from the Behaviors of Eating and Activity for Child Health: Evaluation System (BEACHES). The study examined parental and peer prompting of physical activity at home among 178 Mexican-American and 113 Anglo-American children at age 4 years and again at age 6.5 years. Most activity prompts came from adults interacting with children when they were sedentary. A reduction in the frequency of prompts from baseline to follow-up occurred in the prompter group (adult or child peer), gender, ethnicity, and preprompted activity level categories. Children's responses to these prompts showed that as they aged, they seemed to rely less on the interpersonal (especially adult) aspects of their environment for cues to be more active.

Physical activity levels and prompts in young children at recess: a two-year study of a bi-ethnic sample.

We investigated physical activity and encouragement for activity in a bi-ethnic cohort during recess. Activity and associated interactions of 287 children were recorded at preschool and again 2.2 years later. Children expended nearly twice as much energy at preschool recess than at elementary recess. Activity levels declined as recess time elapsed. At preschool, European-American children engaged in more moderate to vigorous activity than Mexican-Americans. As participants moved to elementary school, teachers' prompts to be active decreased and prompts from peers increased. Boys and girls received similar amounts of activity prompts at preschool, but prompts to boys increased over time. The findings suggest that school environments could be altered to promote healthful physical activity among young children.

Isolation and characterization of multiple variants of recombinant human interleukin 4 expressed in mammalian cells.

We have purified recombinant human interleukin 4 (huIL-4), formerly named B-cell stimulatory factor-1, from supernatants of COS-7 monkey kidney and L-929 cells transfected with the cDNA for huIL-4. The purified protein exhibited a specific activity of 2.6 X 10(7) units/mg in a T-cell proliferation assay and consisted of multiple components on sodium dodecyl sulfate-polyacrylamide gel electrophoresis exhibiting Mr values of 15,000, 18,000, and 19,000. All forms of huIL-4 eluted on gel filtration chromatography with an apparent Mr of 22,000. Gas-phase microsequencing identified 26 and 8 amino acid residues at the N and C termini, respectively, all of which were consistent with the cDNA sequence. The site of processing of the signal sequence was found to occur between Gly-24 and His-25. Incubation with N-glycanase converted the 18- and 19-kDa variants to a 15-kDa form. Treatment with endo-beta-N-acetylglucosaminidase H reduced the molecular mass of the 18-kDa variant to 15 kDa, but did not have any apparent effects on the mass of the 19-kDa species. The removal of oligosaccharide by any of these treatments did not affect bioactivity in the T-cell proliferation assay. Neither O-glycanase nor endo-beta-N-acetylglucosaminidase D affected the molecular weight of any of these species. These data suggest that differences in carbohydrate structure account, at least in part, for the observed microheterogeneity.

Expression of high affinity receptors for murine interleukin 4 (BSF-1) on hemopoietic and nonhemopoietic cells.

In this report a method for the affinity purification and radiolabeling of recombinant mouse interleukin (IL)-4 is described. It is shown on the basis of several criteria that IL-4 retains full biologic activity after radioiodination and can therefore be used as a valid model for measuring the binding characteristics of native IL-4. By using Scatchard plot analysis of equilibrium binding data, it is demonstrated that 125I-IL-4 binds to a high affinity cell surface receptor which is expressed by both hemopoietic and nonhemopoietic cells. The dissociation constant for 125I-IL-4 (Kd = 20 to 60 pM) corresponds to the concentration of IL-4 which gives 50% biologic activity (i.e., 10 to 30 pM). Binding of 125I-IL-4 is rapid (t1/2 of 2 min), whereas dissociation occurs at a slow rate (t1/2 approximately 4 hr). The IL-4 receptor shows a high degree of specificity. Whereas unlabeled mouse IL-4 competed with mouse 125I-IL-4 in an equimolar fashion for binding to IL-4 receptors, several other lymphokines, including mouse IL-2, IL-3, interferon-gamma, granulocyte-macrophage colony-stimulating factor, and human IL-1, IL-2, and IL-4 were unable to inhibit, even at molar excesses of 400 to 800-fold. At 37 degrees C, 125I-IL-4 is rapidly internalized (approximately 200 molecules/cell/min) by HT-2 cells, with at least 85% of cell surface receptors being functional in this respect. Receptors for IL-4 were found to be expressed by subclasses of T and B cells, mast cells, macrophages, and by cells of the myeloid and erythroid lineages. This wide distribution of receptor expression closely matches the known spectrum of biologic activities of IL-4, including proliferation and/or differentiation of T and B cells, mast cells and granulocytes, and induction of macrophage antigen-presenting capacity. IL-4 receptors were also found on a variety of nonhemopoietic cells such as cloned stromal cell lines from the bone marrow, spleen, thymus, and brain, and on muscle, brain, melanoma, fibroblast, and liver cells. Indeed, only 5 of more than 90 cell types tested have undetectable numbers of IL-4 receptors. The biologic effects of IL-4 on nonhemopoietic cells have not yet been reported and await elucidation.

SR alpha promoter: an efficient and versatile mammalian cDNA expression system composed of the simian virus 40 early promoter and the R-U5 segment of human T-cell leukemia virus type 1 long terminal repeat.

We developed a novel promoter system, designated SR alpha, which is composed of the simian virus 40 (SV40) early promoter and the R segment and part of the U5 sequence (R-U5') of the long terminal repeat of human T-cell leukemia virus type 1. The R-U5' sequence stimulated chloramphenicol acetyltransferase (CAT) gene expression only when placed immediately downstream of the SV40 early promoter in the sense orientation. The SR alpha expression system was 1 or 2 orders of magnitude more active than the SV40 early promoter in a wide variety of cell types, including fibroblasts and lymphoid cells, and was capable of promoting a high level of expression of various lymphokine cDNAs. These features of the SR alpha promoter were incorporated into the pcD-cDNA expression cloning vector originally developed by Okayama and Berg.

Provocative tests for growth hormone release.

Subnormal growth hormone responses to both insulin-induced hypoglycemia and arginine infusion (peak response less than or equal to 5 ng/ml) were found in five male subjects (aged 10 to 14 years) with short stature but with normal interval growth rates and normal bone ages (in 4 cases). They demonstrated one or more normal GH responses to subsequent provocation by glucagon stimulation, tolbutamide-induced hypoglycemia, and repeat insulin and arginine testing following pretreatment with sex steroids. Two subjects had received exogensou GH therapy for six months prior to the subsequent assessment; each one failed to demonstrate the growth response characteristic of GH deficiency. These studies indicate the need for multiple provocative human GH testing to exclude children whose growth would not be enhanced by GH therapy despite a subnormal response to provocative tests with insulin and arginine.