板栗液膜保鲜剂的筛选与最佳保鲜浓度的确定

本文采用数学理论与科学试验相结合的方法,筛选了一种保鲜效果较佳的液膜保鲜剂,经此种保鲜剂处理,能使板栗贮后150天的好果率提高到95.88％．     

Gold uptake by Chlorella vulgaris

This paper describes a study on the uptake of gold (III) ions by viable and treated cells of the unicellular alga, Chlorella vulgaris. Inactivating the algal cells by various physical/chemical treatments resulted in a considerable enhancement in the uptake capacity over the pristine cells. X-ray Photoelectron Spectroscopy (XPS) analyses confirmed the deposition of elemental gold, Au (O), on the cell surface, indicating that a reduction process has taken place. XPS results also suggested an increase in the oxidized carbon species, carboxyl species in particular, on the surfaces of the treated cells. FTIR spectroscopy results revealed that the carboxyl group was involved mainly in the binding of the gold on the surface of both the viable and treated cells.     

Simultaneous NH3 oxidation and N2 production at reduced O2 tensions by sewage sludge subcultured with chemolithotrophic medium

The ammonia oxidation rate by sewage sludge was determined as a function of the dissolved oxygen tension. Samples of sludge were taken from a domestic waste water treatment pilot plant in which sludge was completely retained by membrane filtration. The samples were subcultured chemolithotrophically in recycling reactors. The gas supplied was a mixture of pure argon and oxygen. The K _O2 for ammonia oxidation was estimated to be 0.97 (±0.16) kPa dissolved oxygen. Together with ammonia oxidation and oxygen consumption, dinitrogen gas was produced. So, aerobic denitrification occurred. At dissolved oxygen tensions of 1.25 kPa and higher, the dinitrogen production rate (per N-mole) equalled 20% of the ammonia oxidation rate. This proportion was even 58% at 0.3 kPa dissolved oxygen. At 0.15 kPa dissolved oxygen, however, nitrification hardly proceeded, while dinitrogen production soon stopped. Most likely, a nitrifier concomitantly oxidized ammonia and reduced nitrite to dinitrogen.     

Behavioral sensitization and tolerance to cocaine and the occupation of dopamine receptors by dopamine

Data from the authors’ laboratory on the neural substrates of Pavlovian conditioning and behavioral sensitization to psychomotor stimulants are reviewed. The findings of a recent experiment on the role of occupation of dopamine receptors by dopamine and its association to behavioral sensitization are reported. Daily intermittent injections of cocaine produced behavioral sensitization to the locomotor response in rats, whereas continuous cocaine infusions produced behavioral tolerance. Behavioral sensitization to cocaine was blocked by coadministration of nimodipine, anL-type calcium channel blocker. The increases in locomotion produced by cocaine was associated with an increase in the occupation of striatal dopamine D₁ and D₂ receptors, measured as the density of receptors protected from denaturation byN-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). This association was not observed when rats were given a challenge injection of cocaine 10 d after withdrawal from similar treatment regimens. Rats given a cocaine challenge after withdrawal from either intermittent or continuous cocaine treatment regimens exhibited increased occupations of striatal D₁ and D₂ receptors. This increase was similar in magnitude to that observed in rats without a history of cocaine treatments after a challenge injection of cocaine. This suggests tnat the differences in occupancy of striatal dopamine receptors by dopamine observed in the prewithdrawal condition are likely the result of differences in brain levels of cocaine achieved by the two treatment regimens. Occupancy of striatals dopamine D₁ and D₂ receptors does not appear to be related to the development of sensitization to the motor-stimulating effects of cocaine.     

A simple and efficient method for clonal propagation of Casuarina sumatrana (de Vriese) L. Johnson

A new and efficient method for clonal propagation of Casuarina sumatrana by rooting stem cuttings is described. High percentage (about 60–70%) of rooting was achieved with mature softwood stem cuttings. A quick-dip of 5 s in NAA (1–10mM) solution followed by sand culture under high humidity were required for a high rate of survival and rooting of stem cuttings. A simple, closed chamber propagation system, using fluorocarbon polymer (tetrafluoroethyleneperfluoroalkyl vinyl ether) film (Neoflon PFA film), was successfully developed for the rooting of stem cuttings without mist. Rooted cuttings inoculated with Frankia were easily transplanted and established in field conditions with very low (about 3%) mortality. The significance of these findings for mass clonal propagation of C. sumatrana is discussed.Abbreviations IBA indole-3-butyric acid - NAA -naphthaleneacetic acid     

Calmodulin levels in radish (Raphanus sativus L.) seeds germinating at low calcium availability induced by EGTA treatments

Incubation of radish (Raphanus sativus L.) seeds in the presence of 1 or Smol m^?3 Ca-EGTA, which increased Ca²⁺ activity in the incubation medium (c. 0.24 or 0.37 mol m^?3 at 24 h with respect to c. 0.13 mol m^?3 in the control), did not affect germination, the restoration of K⁺ net influx, the increase in DNA and RNA levels or protein synthesis. Incubation in 1 mol m^?3 Na-EGTA, which reduced Ca²⁺ activity in the incubation medium (20 mmol m^?3 at 24 h), decreased the total Ca²⁺ level in embryo axes (-21%), but only slightly inhibited the increase in fresh weight without affecting the restoration of K⁺ net influx, the increase in DNA and RNA levels or protein synthesis. In the presence of 5 mol m^?3 Na-EGTA (Ca²⁺ activity in the incubation medium was 0.6 mmol m^?3), the decrease in the total Ca²⁺ level was greater (c. -27%) and the increases in fresh weight, DNA and RNA were inhibited by about 50, 39 and 40%, respectively. These results indicate that increased Ca²⁺ availability does not affect germination and suggest that the effect of Na-EGTA, at least up to 5 mol m^?3, is a result of an induction of Ca²⁺ deficiency. The amount and specific activity of calmodulin (CaM) present in the soluble fraction (100 000g) of radish embryo axes greatly increased during the first 24 h of incubation (c. 5-fold and 7-fold, respectively). This increase was very similar in the Ca-EGTA-treated seeds but was inhibited (c. -38%) by 1 mol m^?3 Na-EGTA, even if the increases in DNA and RNA levels and protein synthesis were not significantly reduced. The lower amount of CaM after 24 h of incubation in 1 mol m^?3 Na-EGTA (c. -30%) was due to a reduction in the fraction of CaM bound to a proteinaceous CaM inhibitor present in radish seeds [M. Cocucci & N. Negrini (1988) Plant Physiology 88, 910–914] and not involved in the metabolic reactivation of the seed. These results suggest that the level of CaM is controlled by Ca²⁺ availability and that the CaM inhibitor has a role in controlling the amount of Ca-CaM available for the Ca-CaM-dependent enzymes.     

The effect of chemical pretreatment on the aerobic microbial degradation of PCB congeners in aqueous systems

A series of experiments was conducted to examine the effects of chemical pretreatment on biodegradation of¹⁴C-labeled PCB congeners in aqueous systems. Fenton's reagent was used to generate hydroxyl radicals (OH) which were successful in partially oxidizing/transforming otherwise recalcitrant molecules of tetrachlorinated PCB, but had little or no impact on the biodegradation of a monochlorinated congener. Application of Fenton's reagent (1% H₂O₂, 1 mM FeSO₄) followed by inoculation with pure culturesPseudomonas sp, strain LB 400 andAlcaligenes eutrophus, strain H850 resulted in the removal of approximately 38% of 2-chlorobiphenyl and 51% of 2,2, 4,4-tetrachlorobiphenyl in the form of¹⁴CO₂. Comparison of the rate and extent of biodegradation of 2,2, 4,4-tetrachlorobiphenyl after the application of Fenton's reagent with the dynamic and final level of radioactivity in the aqueous phase of experimental system suggests two possible means of microbial utilization of tetrachlorinated PCB congener altered by chemical oxidation: (a) consumption of the partially oxidized chemical dissolved in the aqueous phase, and (b) direct microbial attack on the transformed compound, which may still be adhered to the solid surface.     

Properties of unusual phospholipids. III: Synthesis, monolayer investigations and DSC studies of hydroxy octadeca(e)noic acids and diacylglycerophosphocholines derived therefrom

Diacylglycerophosphocholines containing (R)-3-, (R)-12-, (R)-17-hydroxy octadeca(e)noic acids and the corresponding racemates were synthesized and purified to homogeneity. The influence of the position of the hydroxy group on the monolayer packing properties of these fatty acids and their phosphatidylcholines was studied by Langmuir techniques and 1,2-di-[(R)-12-hydroxy-octadec-cis-9-enyl]-sn-glycero-3-phosphocholine displayed the largest lift-off area (330 Ų/molecule). This result was in line with the thermotropic phase behavior of these phospholipids, as measured by differential scanning calorimetry (DSC): the gel- to liquid-crystalline phase transition temperature (T_m) passed through a minimum of −15.1°C for 1,2-di-[(R)-12-hydroxy-octadec-cis-9-enyl]-sn-glycero-3-phosphocholine.     

Oral/aboral ectoderm differentiation of the sea urchin embryo depends on a planar or secretory signal from the vegetal hemisphere

A monoclonal antibody that recognizes oral ectoderm and esophagus of sea urchin larvae was newly produced. Distribution of the antigen, named Hpoe, was examined by indirect immunofluorescence microscopy. Hpoe did not exist in eggs and appeared during the cleavage stage. In hatched blastulae, Hpoe was detected on the apical surface of all cells. As embryogenesis progressed, Hpoe disappeared from the primary mesenchyme, archenteron and aboral ectoderm. Hpoe reappeared in foregut at the prism stage and was restricted to the oral ectoderm and esophagus at the pluteus stage. Using this antigen as a molecular marker of oral/aboral ectoderm differentiation, the role of the vegetal hemisphere in ectoderm differentiation was examined. All animal hemispheres isolated from 16-cell stage embryos, mesenchyme blastulae, early gastrulae and mid gastrulae developed into epithelial balls and every cell expressed Hpoe. These epithelial balls failed in oral/aboral ectoderm differentiation. Twenty millimolar LiCI-treated whole embryos developed into exo-gastrulae but Hpoe restriction in ectoderm occurred in these exo-gastrulae. These results show that oral/aboral ectoderm differentiation requires an inductive interaction from the vegetal hemisphere and indicate that the inductive interaction depends on a planar or secretory signal, rather than the contact of the esophagus and ectoderm.     

Biosynthesis and biotechnological production of degradable polyhydroxyalkanoic acid

The use of biodegradable polymers is one of the key solution to environmental problems and the development of biocompatible material. The impact of such a large commercial opportunity is one of the primary reasons for much interest in the field of microbial polyester, polyhydroxyalkanoic acid (PHA). Its valuable properties of biodegradability, biocompatibility and thermoplasticity have attracted considerable commercial interest, and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] has been launched as the first market product. Recent advances in molecular genetics and microbial physiology of PHA biosynthesis have been uncovering the biosynthetic mechanics at molecular level, and extensive efforts for the developments of practical applications and cost-effective mass production of PHA will profell the commercialization of PHA towards the commodity market for biodegradable plastics. The biosynthesis of new members of PHA family with new monomer or unusual composition will also lead to the biotechnological production of tailor-made biopolymer for various applications.