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.     

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.     

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.     

Photoperiodic induction of the first and the second diapause in the bean bug,Riptortus clavatus: a photoperiodic history effect

Summary In nondiapause adults raised under a long-day photoperiod, the critical daylength for diapause induction was between 13 and 14 h although some individuals did not respond to the short-day photoperiod and went on laying eggs. In postdiapause adults in which LD 1311 induced the first diapause (L13 insects), the critical daylength for diapause reinduction was between 13 and 14 h, whereas it was between 12 and 13 h in postdiapause adults in which LD 1014 induced the first diapause (L10 insects). Under LD 1311, a small proportion of L10 insects went into the second diapause after great delay as compared with L13 insects. Under LD 1014, on the other hand, L10 insects went into the second diapause more rapidly than L13 insects. Therefore, the photoperiod which had induced the first diapause affected the photoperiodic induction of the second diapause not only in the critical daylength but also in the speed of response. In Riptortus clavatus, the photoperiodic history influences the subsequent photoperiodic response even after a physiological state induced by the previous photoperiod was terminated completely.Abbreviations L13 insects postdiapause adults in which LD 1311 induced the first diapause - L10 insects postdiapause adults in which LD 1014 induced the first diapause     

CO2 and water vapour exchange in four alpine herbs at two altitudes and under varying light and temperature conditions

CO₂ and water vapour exchange rates of four alpine herbs namely: Rheum emodi, R. moorcroftianum, Megacarpaea polyandra and Rumex nepalensis were studied under field conditions at 3600 m (natural habitat) and 550 m altitudes. The effect of light and temperature on CO₂ and water vapour exchange was studied in the plants grown at lower altitude. In R. moorcroftianum and R. nepalensis, the average photosynthesis rates were found to be about three times higher at 550 m as compared to that under their natural habitat. However, in M. polyandra, the CO₂ exchange rates were two times higher at 3600 m than at 550 m but in R. emodi, there were virtually no differences at the two altitudes. These results indicate the variations in the CO₂ exchange rates are species specific. The change in growth altitude does not affect this process uniformly.The transpiration rates in R. emodi and M. polyandra were found to be very high at 3600 m compared to 550 m and are attributed to overall higher stomatal conductance in plants of these species, grown at higher altitude. The mid-day closure of stomata and therefore, restriction of transpirational losses of water were observed in all the species at 550 m altitude. In addition to the effect of temperature and relative humidity, the data also indicate some endogenous rhythmic control of stomatal conductance.The temperature optima for photosynthesis was close to 30°C in M. polyandra and around 20°C in the rest of the three species. High temperature and high light intensity, as well as low temperature and high light intensity, adversely affect the net rate of photosynthesis in these species.Both light compensation point and dark respiration rate increased with increasing temperature.The effect of light was more prominent on photosynthesis than the effect of temperature, however, on transpiration the effect of temperature was more prominent than the effect of light intensity.No definite trends were found in stomatal conductance with respect to light and temperature. Generally, the stomatal conductance was highest at 20°C.The study reveals that all these species can easily be cultivated at relatively lower altitudes. However, proper agronomical methodology will need to be developed for better yields.     

根田鼠静止代谢率特征的研究

通过实地测定分布于青海高原的根田鼠的RMR,发现其RMR水平明显高于与其体重相似的其它田鼠,而平均最小热传导值并不比后者低,说明可能是以保持高的RMR水平来适应高原寒冷气候的。同时发现,根田鼠以化学体温调节为主,以适应高原气温较大的波动。     

Effect of nitrogen form on the growth and nitrate concentration of lettuce

Summary A pot experiment with lettuce involving three N forms each at six application levels, showed that lettuce can be grown satisfactorily with a very low nitrate content when supplied with ammonium sulphate and a nitrification inhibitor. For plants growing on nitrate N, the optimum midrib sap nitrate concentration as maturity approached was about 1400 mg/1 NO₃-N. Large losses of mineral N were observed from the peat medium, even in the absence of plants. A relationship is presented which would enable a lettuce grower to estimate whole-shoot nitrate concentration from a quick test of midrib sapi.e. NO₃-N (mg/kg in fresh shoot) =0.14×NO₃-N (mg/l in sap). Tipburn was worst at intermediate levels of applied N, and was less serious with pure ammonium nutrition than with nitrate.     

Maximal exercise capacity in adolescent European and Amerindian high-altitude natives

Forty-seven highland natives were given maximal exercise tests on a treadmill ergometer at 3,600 m. The subjects were grouped into four subsamples on the basis of ethnicity (European vs. Aymara) and age (young vs. old adolescent). Two-way ANOVA indicated that VO2max adjusted for body size did not differ significantly between ethnic groups but was significantly larger in older than younger boys within each ethnic group (p less than .05). This finding does not support the hypothesis that Amerindian highland natives have adapted genetically to hypoxia but is consistent with the hypothesis that the relatively high VO2max's of highlanders are acquired by developmental adaptation. Several measures of ventilation and oxygen transport capacity differed significantly between ethnic groups, suggesting that growing European and Aymara boys may respond somewhat differently to the stress of high-altitude hypoxia. However, despite these differences, VO2max, an integrated measure of the overall functional capacity of the oxygen transport system, did not differ significantly between ethnic groups, suggesting that both groups are equally capable of meeting the body's oxygen requirements during maximal exercise at high altitude.     

Kinetic parameters of nitrogen mineralization rates of leguminous crops incorporated into soil

Summary Fresh leguminous plant residues were incorporated into soil columns and incubated at 23°C for up to 20 weeks. The N released from specific fractions (foliage, stems, and roots) of each residue were monitored at specific time intervals. Relationships between organic carbon, total nitrogen, CN ratio, lipids, and lignin content of the plant materials and the cumulative amount of N mineralized in soil were investigated. Statistical analyses indicated that the rates of N mineralized were not significantly correlated with the organic C nor lipid content of the residues. However, the cumulative amount of N released was significantly correlated with the total N content of the plant material (r=0.93^***). The percentage of organic N of the legumes mineralized in soil ranged from 15.9 to 76.0%. The relationship between the percentage of N released and the CN ratio of the plant material showed an inverse cuvilinear response (r= 0.88^***). It was also evident that the composition of lignin in the residue influenced N mine-ralization rates of the leguminous organs incorporated into soil.There was a curvilinear relationship between the cumulative amount of N released from the residues and time of incubation. Nitrogen mineralization rates were described by first-order kinetics to estimate the N mineralization potential (N₀), mineralization rate constant (k), and the time of incubation required to mineralize one-half of N₀ (t_1/2). The kinetic parameters were calculated by both the linear least squares (LLS) and nonlinear least squares (NLLS) transformations. The N₀ values among the crop residues varied from –35 to 510 g Ng^–1 soil. Statistical analyses revealed that the N₀ values obtained by both LLS and NLLS methods were significantly correlated (r=0.93^***). The mineralization rate constants (k) of the residues ranged from 0.045 to 0.325 week^–1. The time of incubation required to mineralize one-half the nitrogen mineralization potential (t_1/2) of the legumes incorporated into soil ranged from 2.1 to 15.4 weeks.     

The effect of soil water status on critical phosphorus concentrations inStylosanthes hamata cv. Verano

Summary The effect of soil water status on the critical phosphorus concentration (CPC) determined in apices and whole tops ofStylosanthes hamata cv. Verano was investigated in a glasshouse trial. The species was grown with six rates of P and three ranges of soil water potential and was harvested at 10 and 14 weeks after germination. The CPC of both whole tops and apices decliced between the two harvests. At the first harvest the CPC of both whole tops and apices increased as the soil water potential decreased but at the second harvest there was no effect of soil water potential on CPC. It is suggested that at the earlier harvest water stress was delaying physiological development, resulting in a CPC characteristic of chronologically younger tissue, but that by the second harvest the decline in CPC with age had ceased for all water treatments.