A model for characterizing residential ground current and magnetic field fluctuations

The current through the residential grounding circuit is an important source for magnetic fields; field variations near the grounding circuit accurately track fluctuations in this ground current. In this paper, a model is presented which permits calculation of the range of these fluctuations. A discrete network model is used to simulate a local distribution system for a single street, and a statistical model to simulate unbalanced currents in the system. Simulations of three-house and ten-house networks show that random appliance operation leads to ground current fluctuations which can be quite large, on the order of 600%. This is consistent with measured fluctuations in an actual house. © 1994 Wiley-Liss, Inc.     

Tympanic temperature in confined beef cattle exposed to excessive heat load

Angus crossbred yearling steers (n = 168) were used to evaluate effects on performance and tympanic temperature (TT) of feeding additional potassium and sodium to steers exposed to excessive heat load (maximum daily ambient temperature exceeded 32°C for three consecutive days) during seasonal summer conditions. Steers were assigned one of four treatments: (1) control; (2) potassium supplemented (diet containing 2.10% KHCO₃); (3) sodium supplemented (diet containing 1.10% NaCl); or (4) potassium and sodium supplemented (diet containing 2.10% KHCO₃ and 1.10% NaCl). Overall, additional KHCO₃ at the 2% level or NaCl at the 1% level did not improve performance or heat stress tolerance with these diet formulations. However, the addition of KHCO₃ did enhance water intake. Independent of treatment effects, TT of cattle displaying high, moderate, or low levels of stress suggest that cattle that do not adequately cool down at night are prone to achieving greater body temperatures during a subsequent hot day. Cattle that are prone to get hot but can cool at night can keep average tympanic temperatures at or near those of cattle that tend to consistently maintain lower peak and mean body temperatures. In addition, during cooler and moderately hot periods, cattle change TT in a stair-step or incremental pattern, while under hot conditions, average TT of group-fed cattle moves in conjunction with ambient conditions, indicating that thermoregulatory mechanisms are at or near maximum physiological capacity.     

Effect of bile acids on formation of the mutagen, quercetin, from two flavonol glycoside precursors by human gut bacterial preparations

Human fecal cultures, induced with either of the flavonols, quercitrin or rutin, were grown in the presence of various concentrations of chenodeoxycholic acid, deoxycholic acid or cholic acid. Cell-free preparations (fecal preparations) from these cultures were then incubated with rutin or quercitrin. The formation of the aglycone, quercetin, was monitored by the Ames assay using tester strain TA98. The presence of chenodeoxycholic or deoxycholic acids in the quercitrin-induced culture resulted in a fecal preparation which enhanced the mutagenesis of quercitrin approximately two-fold at optimal concentrations of 0.6 mM and 0.8 mM respectively. Higher concentrations of these bile acids decreased the activity of the fecal preparations. Cholic acid gave similar results except a much higher concentration (3.0 mM) was required to achieve this effect. Analogous results with rutin-induced cultures were less clear cut: considerable variation in bile acid effect was noted among volunteers. The authors propose that bile acid in the medium may enhance the ability of rutin- and quercitrin-glycosidase elaborating organisms to successfully compete with other microbial populations. Additionally, the greater variation in results using rutin as inducer may reflect more heterogeneous populations of organisms active against this substrate. The possible role of bile acids and flavonols in bowel cancer is discussed.     

Calcium-binding modulator protein from the unfertilized egg of the sea urchin Arbacia punctulata

We have purified and partly characterized a calcium-binding protein from the unfertilized egg of the sea urchin Arbacia punctulata. This protein closely resembles the calcium-binding modulator protein of bovine brain in its molecular weight, electrophoretic mobility, amino acid analysis, and peptide map. It activates bovine brain phosphodiesterase in the presence of calcium but has no effect on the phosphodiesterase of the Arbacia egg. Densitometric scanning of acrylamide gels of arbacia egg homogenates shows the modulator protein to represent 0.1% of the total protein of the egg. At 10(-4) M free calcium, the protein binds four calcium ions per 17,000-dalton molecule. We have used a column of rabbit skeletal muscle troponin-I covalently coupled to Sepharose 4B as an affinity column to selectively purify the Arbacia egg calcium-binding protein. This column has also been used to purify bovine brain modulator protein and may prove of general use in isolating similar proteins from other sources. The technique may be particularly helpful when only small quantities of starting material are available.     

The application of toluene dioxygenase in the synthesis of acetylene-terminated resins

Summary A biotransformation procedure has been developed to prepare intermediates for the synthesis of 3-hydroxyphenylacetylene (3-HPA), a high-value specialty chemical used in the manufacture of acetylene-terminated resins. Pseudomonas putida F39/D containing toluene dioxygenase was used to oxidize a series of substituted benzenes to their respective cis-2,3-dihydroxydihydrobenzene(cis-dihydrodiol) derivatives which in turn could be converted to 3-HPA via a meta-phenol intermediate obtained by acid-catalyzed dehydration. The cis-dihydrodiols derived from the oxidation of phenylacetylene, styrene, acetophenone, and bromobenzene dehydrated to yield predominantly ortho-phenols. Three different phenyl-1,3-dioxolanes were oxidized by P. putida F39/D to three previously undescribed cis-dihydrodiols. Unlike mono-substituted cis-dihydrodiols, phenyl-1,3-dioxolane cis-dihydrodiols were dehydrated to form meta-phenols exclusively. The dehydration products, 3-hydroxyacetophenone and 3-hydroxybenzaldehyde, are suitable precursors for the chemical synthesis of 3-HPA. Offprint requests to: L. P. Wackett     

Polyamine Sparing May Be Involved in the Prolongation of Cell Division Due to Inhibition of Phenylpropanoid Synthesis in Cytokinin-Starved Soybean Cells

Effects on growth, mostly of an inhibitory nature, have been attributed to phenolic compounds in vivo and in vitro. This suggests that l-α-aminooxy-β-phenylpropionic acid (l-AOPP), a competitive inhibitor of phenylalanine ammonia-lyase (PAL), the enzyme controlling the first step in phenylpropanoid synthesis, might stimulate growth in soybean suspension cultures (Glycine max, cv. Acme). The promotive effect of l-AOPP, measured as an increase in cell number, was more clearly detected in the growth-limiting condition of cytokinin starvation. At least one more cell division cycle was completed in the presence of l-AOPP before growth by division ceased and growth continued by expansion only. Phenolic acids are known to conjugate with polyamines, modulating the free levels of these plant growth substances. Thus, the effect of l-AOPP on the titers of free and conjugated polyamines (putrescine, spermidine, and spermine) was investigated by high performance liquid chromatography in the course of cytokinin starvation. An increased level of free putrescine was detected in the presence of l-AOPP relative to controls, especially in the initial period before growth became restricted to cell expansion. The decrease in free putrescine associated with the cessation of cell division was temporarily delayed, suggesting that an interaction between phenolic acids and polyamines is involved in the mechanism of growth promotion by l-AOPP. Received July 30, 1996; accepted January 28, 1997