Workshop report. Health risks of drinking water chlorination by-products: report of an expert working group

Studies of water chlorination by-products have suggested a possible increased risk of bladder and colon cancers, as well as adverse reproductive and developmental effects such as increased spontaneous abortion rates and fetal anomalies. A workshop for an expert working group was convened to advise Health Canada on the need for further action. Participants were given background papers and a set of key questions to review prior to the meeting. At the workshop, experts presented an overview of what was known to date on water chlorination by-products from toxicologic studies, epidemiologic studies of cancer and adverse reproductive/developmental effects, and risk assessment. This paper summarizes the information provided in the background papers and presentations, describes the consensus arrived at regarding assessment of evidence for level of risk and presents a number of suggestions for future research.     

Young children's active and passive graphing

Abstract This paper reports on the graphing work of children, aged 8 and 9 years, who have immediate and continuous access to portable computers across the whole curriculum. They have been using their computers to generate graphs and charts from experimental data. The unit of analysis is a learning sequence in which the progress of a small group of children on a specific coherent task was recorded over a period of several weeks. The paper describes two such learning sequences to illustrate two types of graphing, which can occur in computer-rich environments. In one sequence, the children collected data after which they explored the graphing facilities on the computer whereas in the other learning sequence graphing is used iteratively as an integral part of the ongoing task.     

Human stress protein hsp70: overexpression in E coli, purification and characterization

The gene encoding the stress-inducible member of human heat shock protein hsp70, was expressed in E. coli using the bacteriophage T7 RNA polymerase-based gene expression system. Recombinant hsp70 (R-hsp70) was purified from inclusion bodies after solubilization and refolding, using a combination of ATP-agarose affinity chromatography and ion-exchange chromatography. R-hsp70 was shown to be monomeric and free of its structurally similar E. coli counterpart, DnaK. In addition, R-hsp70 is functional as demonstrated by its ability to bind to peptides and to ATP. The availability of pure, correctly folded R-hsp70 in sufficient quantity will assist in the structural and functional characterization of hsp70. Furthermore, an understanding of the cytoprotective function of hsp70 and its role in immune responses during infections will be facilitated by the availability of pure R-hsp70.     

The neuronal growth-associated protein GAP-43 interacts with rabaptin-5 and participates in endocytosis

Structural plasticity of nerve cells is a requirement for activity-dependent changes in the brain. The growth-associated protein GAP-43 is thought to be one determinant of such plasticity, although the molecular mechanism by which it mediates dynamic structural alterations at the synapse is not known. GAP-43 is bound by calmodulin when Ca2+ levels are low, and releases the calmodulin when Ca2+ levels rise, suggesting that calmodulin may act as a negative regulator of GAP-43 during periods of low activity in the neurons. To identify the function of GAP-43 during activity-dependent increases in Ca2+ levels, when it is not bound to calmodulin, we sought proteins with which GAP-43 interacts in the presence of Ca2+. We show here that rabaptin-5, an effector of the small GTPase Rab5 that mediates membrane fusion in endocytosis, is one such protein. We demonstrate that GAP-43 regulates endocytosis and synaptic vesicle recycling. Modulation of endocytosis by GAP-43, in association with rabaptin-5, may constitute a common molecular mechanism by which GAP-43 regulates membrane dynamics during its known roles in activity-dependent neurotransmitter release and neurite outgrowth.     

Aging and movement: Variability of force pulses for saccadic eye movements.

Age-related differences in the trajectories of saccadic eye movements were examined. Younger and older adult subjects produced saccades to predictable target locations. Detailed features of the movements were examined such as the time of peak acceleration and the variability in the magnitude of the peak velocity. These and other measures reveal important details of the force pulses underlying the eye movements and the mental mechanisms that control them. Although minor differences were apparent between the eye movements of younger and older adults, the general patterns were the same across age groups. These results suggest that fundamental details of the brain mechanisms involved in the control of movement are the same for younger and older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Salivary PAF in acute myocardial infarction and angina: changes during hospital treatment and relationship to cardiac enzymes

Salivary levels of platelet activating factor (PAF) were measured together with serum CPK and interleukin 2 receptor in 30 patients admitted to the coronary care unit, 9 patients with pulmonary tuberculosis, 10 with acute severe asthma and 8 normal controls. 16 of the 30 C.C.U. patients had sustained a acute myocardial infarction (M.I.) 5 had acute angina and the remaining 9 had non cardiac chest pain. Salivary PAF on admission was significantly higher in the M.I. Patients than in the normal subjects, asthmatics, tuberculosis patients and those with non cardiac chest pain (p < 0.001 in all cases) but not those with angina. After 48 hours PAF levels fell in the subjects with M.I. (p < 0.01) and no significant difference was seen between any group. PAF levels did not show any relationship with CPK levels or site of infarct in the M.I. patients. Interleukin 2 receptor was not significantly raised in the M.I. group as a whole but some individual patients showed markedly increased serum levels, but these levels did not correlate with either salivary PAF or serum CPK.     

Mothers and fathers teaching 3-year-olds: Authoritative parenting and adult scaffolding of young children's learning.

Investigated variations in parental tutoring of children on the basis of Vygotsky's (1978) theorizing and concept of parental scaffolding of children's learning. Twenty-four couples and their 3-year-old children participated. Mothers and fathers worked separately with the child on three difficult tasks: a block construction task, a matrix classification task, and a story retelling task. Parental interventions were classified by level of support and were used to define the region of sensitivity to instruction, following the work of Wood (1980). Independent observers rated each parent separately on authoritative/uninvolved and authoritarian/permissive styles, following Baumrind's (1967, 1973) typology. Both mothers and fathers adjusted their support of the child as predicted. Later portions of the tutoring interactions demonstrated more fine tuning of interventions by parents than earlier portions. However, authoritative mothers and fathers were generally more likely than nonauthoritative parents to focus interventions in the region of sensitivity across tasks and to shift their interventions contingent on child success or failure. These patterns were also associated with more dyadic success on task as predicted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Murine model for human secondary amyloidosis: genetic variability of the acute-phase serum protein SAA response to endotoxins and casein

The serum precursor SAA of the secondary amyloid protein AA has been detected by solid-phase radioimmunoassay as a normal serum alpha-globulin of mol wt 160,000, which dissociates to a more stable 12,500 dalton moiety on treatment with formic acid. In 12 strains of mice, including T-cell-deficient nude mice, treated with the amyloid-inducing agents lipopolysaccharide (LPS) or casein, SAA behaved as an acute-phase reactant. SAA concentration rose to about 750 mug/ml by 24 h and returned to less than 1 mug/ml by 48 h. Since the amyloid-resistant colchicine-treated mice and AJ mice had a normal SAA response to LPS, it appears that their resistance to amyloid induction is due to the nature of their SAA processing rather than decreased SAA production. C3H/HeJ mice, which have defective B-lymphocyte responses to LPS, required extremely high dosages of LPS to cause SAA elevation, although their SAA response to casein was normal. This suggests that SAA is an acute-phase protein produced as a result of B-lymphocyte stimulation. Preliminary evidence suggests that at the height of an acute SAA response, liver homogenates are particularly rich in protein AA cross-reacting material.