The origin of naturally occurring perchlorate: the role of atmospheric processes

Perchlorate, an iodide uptake inhibitor, is increasingly being detected in new places and new matrices. Perchlorate contamination has been attributed largelyto the manufacture and use of ammonium perchlorate (the oxidizer in solid fuel rockets) and/or the earlier use of Chilean nitrate as fertilizer (approximately 0.1% perchlorate). However, there are regions such as the southern high plains (Texas Panhandle) where there is no clear historical or current evidence of the extensive presence of rocket fuel or Chilean fertilizer sources. The occurrence of easily measurable concentrations of perchlorate in such places is difficult to understand. In the southern high plains groundwater, perchlorate is better correlated with iodate, known to be of atmospheric origin, compared to any other species. We show that perchlorate is readily formed by a variety of simulated atmospheric processes. For example, it is formed from chloride aerosol by electrical discharge and by exposing aqueous chloride to high concentrations of ozone. We report that perchlorate is present in many rain and snow samples. This strongly suggests that some perchlorate is formed in the atmosphere and a natural perchlorate background of atmospheric origin should exist.     

Effect of halofuginone lactate on the occurrence of Cryptosporidium parvum and growth of neonatal dairy calves

Thirty-one Holstein bull calves were purchased at birth from 3 dairy farms in Eastern Ontario. Each calf was assigned at random to oral treatment with either 5 mg of halofuginone lactate in 10.0 mL of aqueous carrier solution (Halocur, base comprised 10 mg of benzoic acid, 100 mg of lactic acid, and 0.3 mg of tartrazine) or 10 mL of placebo (Halocur base minus the active ingredient, halofuginone lactate) administered 15 to 30 min after morning milk feeding for the first 7 d of life. Intakes of milk, calf starter, and water, and fecal consistency score were recorded daily for 56 d. Calf weights were recorded weekly for 56 d. Fecal samples were taken from all calves at approximately 2, 7, 14, 21, and 28 d of age for isolation of Cryptosporidium parvum oocysts. Logistic and linear regression analyses were used to assess the effect of treatment on the incidence of diarrhea and C. parvum infection status. The odds of C. parvum shedding among calves in the halofuginone lactate-treated group was 70% lower than the odds of shedding among calves in the placebo group. In calves treated with halofuginone lactate, no oocyst shedding occurred until 2 wk of age, whereas 12.5% of calves in the placebo group began shedding oocysts during wk 1. From all ages of placebo-treated calves, 31 of 73 samples (42.5%) were positive for C. parvum, whereas only 15 of 67 samples (22.4%) from all ages of halofuginone lactate-treated calves tested positive. The largest number of C. parvum-positive samples occurred in the third week of life. There was a significant delay of 3.1 d in the incidence of diarrhea among calves treated with halofuginone lactate. Intake of milk and starter, body weight gains, and age at weaning were not significantly different between treatment groups.     

Effect of calcium and magnesium on binding of beta, gamma-methylene ATP to sarcoplasmic reticulum

Isolated sarcotubular membranes (SR) from skeletal muscle bound 3.7 nmol of beta, gamma-methylene [8-3H]ATP (AMP-PCP) per mg of membrane protein. Only one class of binding site was identified and the dissociation constant (K) for this site was 1.5 X 10(-5) M. Addition of 0.05% Triton X-100 increased the number of binding sites to 5.7 nmol/mg. ATP and ADP competitively inhibited AMP-PCP binding. The dissociation constants for ATP and ADP were 3.5 X 10(-5) M and 3.3 X 10(-6) M, respectively. Since this data was obtained in the presence of 5 mM EDTA, it was established that the sarcoplasmic reticulum has a high affinity for the metal free forms of ATP, ADP, and AMP-PCP. Magnesium concentrations in excess of 1 X 10(-4) M inhibited AMP-PCP binding. Lower concentrations of magnesium had little effect on AMP-PCP binding. The effect of calcium on AMP-PCP binding was biphasic. Calcium concentration between 1 X 10(-6) and 1 X 10(-4) M inhibited AMP-PCP binding. Inhibition was maximal at 1 X 10(-5) M. Calcium concentration above 1 X 10(-4) M facilitated analogue binding. Possible sites of magnesium and calcium actions are discussed.     

Interpretation of regional geochemistry using optimal interpolation parameters

A collection of data analysis procedures is presented which are derived from estimation of geographic interpolation parameters. Several interpolation models are discussed along with a procedure to obtain the best model. The power parameter, p, and the search radius, c, are the standard parameters in inverse distance weighting interpolation which is appropriate for sampling patterns that are not highly irregular. The power parameter is shown to characterize the regional behavior of geochemical measurements. This characterization process can be used to associate similar types of geochemical measurements, produce optimal contour maps, derive meaningful residual maps, and highlight unusual geochemical areas by a weighted sum variable. The computer program. BESTP, (used to estimate the optimum inverse distance weighting interpolation parameters) is presented, along with an example using reconnaissance groundwater data from the Plainview Quadrangle, Texas.     

Sexual and reproductive health among primary and secondary school pupils in Mwanza, Tanzania: need for intervention

A cross-sectional questionnaire survey was conducted among 892 randomly selected pupils, aged 12 and above, attending 18 primary schools (PS) and five secondary schools (SS) in four communities of Mwanza Region in Tanzania. The goals were to assess the level of knowledge adolescents have about sexual and reproductive health (SRH), to assess the magnitude of SRH problems and to help design appropriate interventions. Median age of respondents was 15 years (range 12-20 years) and 14 years (range 12-19 years) for PS boys and girls, respectively, and 19 years (range 16-24 years) and 17 years (range 14-19 years) for SS boys and girls. Eighty per cent of PS boys and 68% of PS girls were already sexually active; the corresponding figures were 89% for SS boys and 48% for SS girls. Vaginal sex was the most common first sexual act reported by SS pupils, but 40% of PS pupils reported orogenital sex and 9% of PS pupils reported anal sex as their first sexual act. Almost half of PS girls have had sex with adults, including teachers and relatives. 'Forced sex' was reported by nearly half of PS and SS girls. Fourteen per cent of PS girls had already been pregnant, and over half of these pregnancies ended in illegally induced abortions. Despite a rather high (30%) lifetime rate of condom use, 33% and 25% of PS boys and girls, respectively, reported past experience of sexually transmitted diseases (STDs). STD rates were lower among SS pupils who had a better knowledge of STDs/HIV and fertility issues and reported higher condom use. The survey demonstrated the great vulnerability of school-going adolescents of Mwanza Region to consequences of sexual intercourse. The response should urgently come in the from of comprehensive adolescent SRH programmes.     

Conformational change and assembly through edge beta strands in transthyretin and other amyloid proteins

Numerous diseases are characterized by the formation of insoluble, amyloid protein fibrils. Intensive investigations are beginning to unravel the detailed molecular and structural principles that underlie the spontaneous formation of these fibrils. The amyloid protein transthyretin serves as an excellent system for dissecting the conformational changes and ensuing subunit-subunit associations that lead to amyloid. One working model for tranthyretin amyloid involves the exposure of an "unprotected" edge beta strand, followed by symmetric assembly of subunits to give head-to-head and tail-to-tail protofibrils. The models and principles emerging from studies on transthyretin lead to connections to other amyloid systems.