Magnetic-field flux density and spectral characteristics of motor-driven personal appliances

Flux density and spectral measurements were carried out on magnetic fields generated by several types of motor-driven personal appliances used near the body. Among the units tested were several for which the average flux densities, as determined at the surfaces of the appliance, exceeded 0.4 mT. Time-rates-of-change (dB/dt) for several units exceeded 1000 T/s, and several units exhibited high-frequency components in the low-MHz range. Use of such appliances, although normally of short duration, can represent exposure to magnetic fields of relatively high flux density, which may also have high-frequency components. Compared to other household and commercial sources of magnetic fields, those generated by certain motor-driven personal appliances may represent a significant contribution to time-weighted average exposure and may represent an important source of local induced currents in the body. Furthermore, high-frequency transients that represent only a minor contribution to time-weighted average exposure may generate significant instantaneous induced currents. © 1994 Wiley-Liss, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Concordance between Parental Origin of Chromosome 13q Loss and 6p Duplication in Sporadic Retinoblastoma

Two hypotheses are capable of explaining nonrandom loss of one parent's alleles at tumor suppressor loci in sporadic cases of several pediatric cancers, including retinoblastoma—namely, preferential germ-line mutation or chromosome imprinting. We have examined 74 cases of sporadic retinoblastoma for tumors in which at least two genetic events—loss of heterozygosity for chromosome 13q markers and formation of an isochromosome 6p—have occurred. Sixteen cases were found to contain both events. In 13 of 16 such tumors, the chromosomes 13q that were lost and chromosomes 6p that were duplicated are derived from the same parent. These data may be explained within the framework of the genome imprinting model but are not predicted by preferential germ-line mutation.     

Fast single-channel measurements resolve the blocking effect of Cs+ on the K+ channel.

The Cs+ block of K+ channels has often been investigated by methods that allow only indirect estimation of the rate constants of blocking and re-opening. This paper presents single-channel records with high temporal resolution which make the direct observation of the fast transitions between the blocked and the unblocked state possible. The rate constants kOGb, kGbO of Cs(+)-dependent blocking and of re-opening are evaluated from the time constants found in the open-time and closed-time histograms. The blocking rate constant kOGb between 1000 and 50000 s-1 depends linearly on the Cs+ concentration and strongly on voltage, increasing by a factor of 1.44 per 10 mV hyperpolarization. The re-opening rate constant kGbO approximately 30000 s-1 is independent of Cs+ concentration and only slightly voltage-dependent. Formally, the results can be described by a Woodhull-model. The strong voltage dependence with d > 1, however, weakens its plausibility. The results are interpreted in terms of a molecular framework emerging from recent results on the structure of voltage-gated channels.     

Biogeochemical cycling of sulfur and iron in sediments of a south-east Asian mangrove,Phuket Island,Thailand

Benthic sulfate reduction and sediment pools of sulfur and iron were examined during January 1992 at 3 stations in the Ao Nam Bor mangrove, Phuket, Thailand. Patterns of sulfate reduction rates (0–53 cm) reflected differences in physical and biological conditions at the 3 stations, and highest rates were found at the vegetated site within the mangrove (Rhizophora apiculata) forest. Due to extended oxidation of mangrove sediments, a large portion of the added³⁵S-label was recovered in the chromium reducible pools (FeS₂ and S⁰) (41–91% of the reduced sulfur). Pyrite was the most important inorganic sulfur component, attaining pool sizes 50–100 times higher than acid volatile pools (FeS). HCl-extractable (0.5 M HCl) iron pools, including Fe(II)_HCl and Fe(III)_HCl, were generally low and Fe(III)_HCl was only present in the upper surface layers (0–5 cm). Maximum concentrations of dissolved Fe²⁺ (35–285 M) occurred just about the depth where dissolved H₂S accumulated. Furthermore Fe²⁺ and H₂S coexisted only where concentrations of both were low. There was an accumulation of organic sulfur in the deep sediment at 2 stations in the inner part of the mangrove. The reoxidation of reduced sulfides was rapid, and storage of sulfur was minor in the upper sediment layers, where factors like bioturbation, the presence of roots, or tidal mixing enhance oxidation processes.Author of correspondence.     

Chaperone-mediated activation in vivo of a Pseudomonas cepacia lipase

An extracellular Pseudomonas cepacia lipase, LipA, is inactive when expressed in the absence of the product of the limA gene. Evidence has been presented that LimA is a molecular chaperone. The lipA and limA genes have been cloned in separate and independently inducible expression systems in Escherichia coli. These systems were used to test the molecular chaperone hypothesis by investigating whether LimA could activate presynthesized prelipase and whether presynthesized LimA could activate newly synthesized prelipase. The results show that LimA cannot activate presynthesized prelipase and that presynthesized LimA can activate only a limited number of de novo synthesized prelipase molecules. Co-immunoprecipitation of prelipase/lipase with LimA generated a 1:1 complex of prelipase/lipase and LimA. The results suggest that a 1:1 complex of LipA and LimA is required for prelipase processing and secretion of active lipase.     

Gene technology-based antimetabolite design: the use of an in vitro protein expression system to facilitate antimetabolite design for virally-induced human diseases and malignant conditions

A precondition for the chemotherapeutic treatment of a variety of virally-induced human diseases and malignant conditions is a highly selective interaction of the drug molecule to be used with it's biological target. To ensure the development of novel, effective drugs, it is essential that the biological target is well characterised with regard to it's structure and activity. Such characterisation relies upon adequate amounts of pure target being available. One of the most important enzymatic importers for antimetabolites is the enzyme thymidine kinase. In this article an in vitro protein expression system is described which facilitates the production of milligram amounts of pure and biologically active thymidine kinase, from a number of important biological sources. Results have shown that the in vitro produced enzyme has the exact biochemical propeties of the in vivo enzyme. Thus the in vitro protein expression system is an ideal vechicle to facilitate an in depth investigation of the enzyme's biological properties.     

Observations on the influence of glutamine,asparagine and peptone on growth and t-PA production of Chinese hamster ovary (CHO) cells

When a transfected CHO cell, that produces tissue-type Plasminogen Activator, t-PA, was transferred from a medium based on 5% Fetal Calf Serum, FCS, to a medium based on 0.8% casein peptone with variable glutamine and asparagine content, it was observed, that the growth of the cells changed from anchorage dependant to suspension culture giving more reproducible cultivations. In the FCS culture t-PA was unstable, observed as a decline in t-PA concentration after 250 h. This decline in t-PA concentration was not observed in the serum free culture, although there was a decline in productivity after 200 h. This change in production profile may be attributed to either no proteolytic attack from serum or by scavenging of proteolytic activities produced by the cells from the peptone peptides. Increasing amounts of glutamine/asparagine gave higher production of t-PA in synchrony with an increasing production of ammonia/ammonium ions. Ammonia inhibition does not seem to be a key factor for this cell line as seen with many others.     

The genus Ptyssiglottis (Acanthaceae). A taxonomic monograph

A taxonomic treatment of the genus Ptyssiglottis including Ancylacanthus, Hallieracantha, Oreothyrsus , and Polytrema is given. The phylogeny is briefly dealt with. Leaf morphology, inflorescence morphology and pollen morphology yield important characters. The distribution of selected characters is mapped. The distribution of all species is mapped. Eight new species are published viz. P. campanulata, P. decurrens, P. fusca, P. glandulifera, P. longisepala, P. mucronata, P. pubescens , and P. stamino-difera . Fifteen new combinations are made viz. P. caudata, P. creaghii, P. cuprea, P. cyrtandroides, P. dulcamarioides, P. fastidiosa, P. glabrisepala, P. granulata, P. nigrescens, P. peranthera, P. psychotriifolia, P. pubisepala, P. salicifolia, P. sanguinolenta , and P. undulata .     

Mallomonas palaestrica sp. nov. (Synurophyceae), a new member of sect. Torquatae from Denmark

Mallomonas paluestrica sp. nov., a new member of sect. Torquatae ser. Pumilae , was found in a small Danish pond and is described and illustrated with TEM and SEM micrographs.     

High-affinity folate binding in human prostate

Binding of³H-folate in Triton X-100 solubilized human prostate homogenate was of a high-affinity type and displayed apparent positive cooperativity typical of specific folate binding. Radioligand dissociation was slow at pH 7.4, but rapid at pH 3.5. Gel chromatography reveled two major folate binding proteins (M_r100 and 25kDa), but only one single band (M_r65–70 kDa) was detectable on SDS-PAGE and immunoblotting with rabbit-anti human milk folate binding protein. Concentration of folate binding protein in prostate homogenate expressed as maximum³H-folate binding was 1.10 nmol/g protein, and the cross-reactivity with rabbit-anti human milk folate binding protein serum was 15% as determined by an enzyme-linked immunosorbent assay (median values; n=6).