Effects of detergents on catalytic activity of human endometase/matrilysin 2, a putative cancer biomarker

Matrix metalloproteinases (MMPs) are a family of hydrolytic enzymes that play significant roles in development, morphogenesis, inflammation, and cancer invasion. Endometase (matrilysin 2 or MMP-26) is a putative early biomarker for human carcinomas. The effects of the ionic and nonionic detergents on catalytic activity of endometase were investigated. The hydrolytic activity of endometase was detergent concentration dependent, exhibiting a bell-shaped curve with its maximum activity near the critical micelle concentration (CMC) of nonionic detergents tested. The effect of Brij-35 on human gelatinase B (MMP-9), matrilysin (MMP-7), and membrane-type 1 MMP (MT1-MMP) was further explored. Their maximum catalysis was observed near the CMC of Brij-35 (∼ 90 μM). Their IC₅₀ values were above the CMC. The inhibition mechanism of MMP-7, MMP-9, and MT1-MMP by Brij-35 was a mixed type as determined by Dixon’s plot; however, the inhibition mechanism of endometase was noncompetitive with a K_i value of 240 μM. The catalytic activities of MMPs are influenced by detergents. Monomer of detergents may activate and stabilize MMPs to enhance catalysis, but micelle of detergents may sequester enzyme and block the substrate binding site to impede catalysis. Under physiological conditions, a lipid or membrane microenvironment may regulate enzymatic activity.     

Nucleotide sequence of the ethidium efflux gene from Escherichia coli

The nucleotide sequence of the gene specifying the ethidium efflux system of Escherichia coli has been determined. The translated open reading frame has identified a membrane-bound polypeptide of 110 amino acids (11,960 Da) which shares 42% identity with a staphylococcal protein specifying resistance to ethidium.     

A tracer method to study unidirectional fluxes of lithium: Application to frog skin

We describe a new tracer method to measure unidirectional fluxes of Li⁺, despite the lack of any utilizable radioisotope of lithium. This method uses the purified stable isotopes, ⁶Li and ⁷Li, detected with an ion-probe microanalyser. The accuracy is comparable to that obtained for other ions (e.g., Na⁺) with radiotracers.The method has been applied to frog skin with both faces bathed in a 20% lithium/80% sodium medium. Sodium and lithium unidirectional fluxes have been measured simultaneously. The results are consistent with lithium being actively pumped, the outflux of lithium being, however, much larger than that of sodium.     

Hyperpolarized MRI of Human Prostate Cancer Reveals Increased Lactate with Tumor Grade Driven by Monocarboxylate Transporter 1

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Soil and plant tests for available sulfur in wetland rice soils

Summary Soil tests, plant performance, and plant tissue analyses were used to study the availability of sulfur to wetland rice in 30 Philippine soils. The critical concentrations of available sulfur by the calcium phosphate, lithium chloride, ammonium acetate, and hydrochloric acid extractions were 9, 25, 30, and 5 mg/kg, respectively. The critical total sulfur limits were 0.11% in the shoot at maximum tillering 0.055% in the straw at maturity, and 0.065% in the grain. The critical N:S ratio was 15 in the shoot at maximum tillering, 14 in the straw at maturity, and 26 in the grain. The critical sulfate-sulfur limit was 150 mg/kg in the shoot at maximum tillering and 100 mg/kg in the straw at maturity. The critical sulfate-sulfur/total sulfur percentage ratio was 15% in the shoot at maximum tillering and the straw at maturity. Plant performance, judged by appearance and yield of dry matter, straw, and grain, was generally poorer in the sulfur deficient soils than in the other soils. Although the calcium phosphate and ammonium acetate methods gave a better correlation between plant performance and available sulfur than the others, all four methods separated sulfur-deficient soils from non-deficient ones. The hydrochloric acid method merits further study because it is simple and versatile.     

Metabolic control at the cytosol–mitochondria interface in different growth phases of CHO cells

Metabolism at the cytosol–mitochondria interface and its regulation is of major importance particularly for efficient production of biopharmaceuticals in Chinese hamster ovary (CHO) cells but also in many diseases. We used a novel systems-oriented approach combining dynamic metabolic flux analysis and determination of compartmental enzyme activities to obtain systems level information with functional, spatial and temporal resolution. Integrating these multiple levels of information, we were able to investigate the interaction of glycolysis and TCA cycle and its metabolic control. We characterized metabolic phases in CHO batch cultivation and assessed metabolic efficiency extending the concept of metabolic ratios. Comparing in situ enzyme activities including their compartmental localization with in vivo metabolic fluxes, we were able to identify limiting steps in glycolysis and TCA cycle. Our data point to a significant contribution of substrate channeling to glycolytic regulation. We show how glycolytic channeling heavily affects the availability of pyruvate for the mitochondria. Finally, we show that the activities of transaminases and anaplerotic enzymes are tailored to permit a balanced supply of pyruvate and oxaloacetate to the TCA cycle in the respective metabolic states. We demonstrate that knowledge about metabolic control can be gained by correlating in vivo metabolic flux dynamics with time and space resolved in situ enzyme activities.     

Normalizing the thermal effects of radiofrequency radiation: body mass versus total body surface area

The current guideline for exposure to radiofrequency radiation (RFR) was developed through assessment of the biological effects data collected primarily from the rat. The consensus that a lack of hazardous biological effects occurred below a whole-body-averaged specific absorption rate (SAR) of 4.0 W/kg led to the proposition of a 0.4 W/kg guideline with a built-in safety factor of 10. This paper demonstrates that if the RFR absorption rate in the rat had been normalized with respect to total body surface area rather than body mass, the exposure guideline would be 2.3 W/m2, which translates to an SAR of approximately 0.06 W/kg for an adult human. It is further shown that a given RFR absorption rate, normalized as a fraction of a species' heat loss per unit of surface area, is independent of body mass over a range of 0.03-100 kg; however, a normalization of the RFR absorption rate to heat loss per unit of body mass is highly dependent on the species' mass. Normalizing the rate of RFR absorption to the surface area of the rat indicates that the current RFR exposure guideline of 0.4 W/kg may be too high.     

The effect of grass maturing and root decay on N2O production in soil

The N₂O flux from the surface of grass-covered pots was only significant following grass maturing. Removal of the above-ground plant material resulted in an immediate and long-lasting increase in N₂O production in the soil. The results suggest that easily available organic matter from the roots stimulates the denitrification when the plants are damaged. Grass cutting might therefore result in a marked nitrogen loss through denitrification. The quantitative effect was equal in soil with and without succinate added. The size of the anaerobic zone around the roots is therefore sufficient to allow for denitrification activity mediated by increased organic matter availability because of plant cutting.     

Luxury consumption and specific utilization rates of three macroelements in two Taraxacum microspecies of contrasting mineral ecology

Plants of Taraxacum sellandii Dahlst., a microspecies adapted to fertile, and Taraxacum nordstedtii Dahlst., adapted to infertile soils, were cultured hydroponically, either on a complete nutrient solution or on one deprived of nitrogen, phosphorus, or potassium ions. For all four treatments, the growth and internal mineral concentration of the plants was monitored. For plants cultured on a complete nutrient solution, the uptake rates of nitrate, phosphate, and potassium ions were determined. Luxury consumption of the three macronutrients was computed as the excess of ion absorption over the ion uptake rates minimally required to sustain maximum growth. In these calculations the critical N, P, or K⁺ concentrations, earlier derived, were used as parameters describing the mineral status minimally required to allow maximum growth. Efficiency in use of the three macroelements at various levels of mineral accumulation was also computed. Finally, the response to phosphate starvation as related to phosphate uptake capacity and the accumulation of P was investigated.
The physiological properies investigated provide a causal background for the superior adaptation of T. nordstedtii as compared to T. sellandii to infertile sites. Taraxacum nordstedtii had a higher relative luxury consumption of NO₃^–, H₂PO^-₄, and K⁺, a higher efficiency in N and P use at N– and (severe) P-deficiency, respectively; and, after phosphate starvation, a relatively high preservation of phosphate uptake capacity and an enlargement of P storage. In combination with the low potential growth, luxury consumption will be particularly effective in T. nordstedtii in preventing or minimizing mineral deficiency. The distribution of minerals between cytoplasm and vacuoles as a factor in mineral use efficiency is discussed.