An inexpensive insoluble chromogenic substrate for the determination of proteolytic activity

Summary A new insoluble chromogenic substrate for the determination of proteolytic activity was developed. This substrate was prepared by incorporating black drawing ink into casein and heating this complex at 200°C for 4 h. It is especially suitable for determining the activity of alkaline bacterial proteinases.     

Gradient-tailored excitation for single-quantum NMR spectroscopy of aqueous solutions

Summary A novel approach to tailored selective excitation for the measurement of NMR spectra in non-deuterated aqueous solutions (WATERGATE, WATER suppression by GraAdient-Tailored Excitation) is described. The gradient echo sequence, which effectively combines one selective 180° radiofrequency pulse and two field gradient pulses, achieves highly selective and effective water suppression. This technique is ideally suited for the rapid collection of multi-dimensional data since a single-scan acquisition produces a pure phase NMR spectrum with a perfectly flat baseline, at the highest possible sensitivity. Application to the fast measurement of 2D NOE data of a 2.2. mM solution of a double-stranded DNA fragment in 90% H₂O at 5 °C is presented.     

国产五种菊属植物的核型研究

本文对国产5种菊属植物的核型进行了研究,结果为:D. indicum 2n=2x=18=16m 2st,2n=4x=36=28m 6sm 2st;D. lavandulifolium 2n=2x=18=14m 4sm,2n=4x=36=28m 6sm 2st;D. lavandulifolium var.seticuspe 2n=2x=18=12m 6sm;D. chanetii 2n=4x=36=20m 14sm 2st,2n=6x=54=38m 14sm 2st;D. potentilloides2n=2x=18=14m 2sm 2st;D. vestitum 2n=6x=54=38m 16sm.核型分析的结果表明,本文所研究类群中出现的多倍体多为异源多倍体;根据对核型资料、形态特征及地理分布特点的综合分析,作者认为多倍化是菊属野生种进行的主要途径。     

Pigmentation changes in Brevibecteria induced by mutagenic treatment

Inducible pigmentation changes were observed in pigmented strains of Brevibacterium sp. M27 and B. flavum treated with N-methyl-N'-nitro-N-nitrosoguanidine. The highest frequency of induction was reached already at a survival of 30-40% with the maximal yield of 6-10%. As compared with the initial yellow colour, three new pigmentation types, viz. white, pink and orange, were observed. The yellow pigmented parent strains are most resistant to the lethal effects of UV radiation. By selecting pigmented mutants of all types on media containing antibiotics it was possible to obtain strains that were resistant either to tetracycline or to streptomycin. Auxotrophic pigmented mutants were also isolated. In multiple mutant strains of Brevibacterium sp. M27 a number of strainsexhibited a changed L-lysine production. In some strains the production was variable, whereasother strains did not produce L-lysine at all and stains with a limited production of other amino acids were also detected.     

Enzymatic down regulation with exercise in rat skeletal muscle

Maximal activities of rat skeletal muscle mitochondrial citrate synthase (CS), malate dehydrogenase (MDH), and alanine aminotransferase (ALT), as well as several other mitochondrial enzymes involved in various metabolic functions were significantly suppressed after a single bout of acute or exhaustive treadmill running. This enzymatic "down regulation" was maintained 24 and 48 h post exhaustion, especially in the untrained rats. Neither muscle cytosolic nor hepatic enzymes exhibited down regulation after exercise. Proteolysis was increased with exercise as assessed by the clearance of [3H]leucine previously incorporated into the proteins of the rats. Decreased CS, MDH, and ALT activities correlated with a significant loss of mitochondrial total protein sulfhydryl (r = 0.67, 0.68, 0.59, respectively, P less than 0.001) in untrained rats and both CS and MDH could be partially restored by incubation with dithiothreitol. Endurance-tested untrained and trained rats had significantly higher glutathione peroxidase (GPX) activity in both muscle mitochondria and cytosol which correlated significantly with endurance time (r = 0.70 and 0.74, respectively). It is concluded that enzymatic down regulation is not caused by proteolysis alone; i.e., peroxides and oxygen free radicals produced in prolonged exercise may alter the intramitochondrial redox state by oxidizing free thiols that may be required at active sites of these enzymes. Training may enhance the ability of the muscle to resist the toxic oxygen species by increasing GPX activity.     

Reduction of nitrite to nitric oxide by enteric bacteria

Seven bacteria representing seven genera of enteric bacteria, in addition to Escherichia coli, were shown to reduce nitrite to NO under anaerobic conditions when the cells were grown as nitrate respirers. NO production was inhibited by nitrate and azide and was self limiting, just as was found to be the case previously with E. coli and its nitrate reductase. Maximum initial rates of NO production were observed at pH 5.5-6.     

Serial propagation of mammalian cells on gelatin-coated microcarriers

The ability to serially propagate mammalian cells in microcarrier cultures is essential for large-scale operation. The success of such serial propagation depends on viable dissociation of cells from microcarriers and the normal growth and product formation after subsequent reinoculation. The high pH treatment developed for dissociating cells from DEAE-derivatized microcarriers was not as effective for a number of cell strains cultivated on gelatin-coated microcarriers. By prewashing the cell-laden microcarriers with buffer containing a chelating agent, bovine kidney cells, BK, human embryonic foreskin fibroblasts, FS-4, and continuous human kidney cells, TCL-598 which produces prourokinase, were viably dissociated from commercially available gelatin-coated microcarriers, Cytodex-3. Cells dissociated from microcarriers reattached and grew on micro-carriers subsequent to inoculation into subcultures. However, after subculturing, cells may attach at different rates to newly added beads and to conditioned microcarriers which cells had previously grown. It resulted in an uneven cell distribution on microcarriers and inferior growth kinetics. This effect was more profound for BK and FS-4 cells which are propagated with a low multiplication ratio. Specifically, BK cells attach to conditioned beads at a faster rate than to new beads, while FS-4 cells attach to new beads faster than to conditioned beads. Thus, for these two cell strains, a separator was used to separate the microcarriers from the suspension of dissociated cells before subsequent inoculation. For TCL-598 cells, which are propagated at a high multiplication ratio, this dissociation technique can be applied directly without the separation of dissociated cells and conditioned microcarriers. All the three cell lines tested exhibit normal growth kinetics in serial propagation on microcarriers. Furthermore, the production of prourokinase by TCL598 cells serially propagated on microcarriers was comparable to that inoculated from roller bottles.     

Improved performance of intensive semicontinuous cultures of Scenedesmus by biomass recirculation

The microscopic green alga, Scenedesmus obliquus, was used in a semicontinuous culture system for the tertiary treatment of urban wastewater, with the simultaneous production of usable biomass. Partial biomass recycling was used to increase the productivity of the system by overcoming the limits imposed by the low maximal growth rate of the alga. The biomass to be recycled was collected by simple gravity settling of the removed culture.The culture system was operated at different dilution rates and its productivity measured at each rate. An evaluation of the crude nutrient composition of the algae produced at each dilution rate was also carried out.The system was found to operate stably at dilution rates of up to 0.8 day(-1) which represents a 20% net increase over the maximum dilution rate allowed under the same conditions in a system without recirculation. The composition of the biomass produced varied little over a range of dilution rates, which may be of relevance to its projected end-use.The study indicated that such a system can exploit available light to the full and should be of particular value for the treatment of low-strength wastes such as we employed.