Regulation of Gene Expression in Developing Zea mays Embryos: Protein Synthesis during Embryogenesis and Early Germination of Maize

Polypeptides synthesized in dissected embryos of Zea mays at different stages of embryogenesis and early germination have been characterized by their migration in two-dimensional gel electrophoresis. This analysis has been carried out with in vivo labeled polypeptides from excised embryos and with proteins synthesized in vitro in the rabbit reticulocyte system directed by poly(A⁺) RNA isolated from the different developmental stages. We have identified three main sets of expressed polypeptides: (a) embryonic set: this group of polypeptides is synthesized in young and mature embryos but not in early germination; (b) maturation set: this group of polypeptides is not present in young embryos and appears during the maturation period. Some of these polypeptides are still present in early germination while others disappear from stored mRNAs in dry embryos. One particular group from this set can be induced prematurely in young embryos by incubation with abscisic acid; and (c) germination set: this group of polypeptides is not expressed in the maturation period and appears after brief imbibition of the dry embryos.     

Carbon dioxide enhances the development of the ethylene forming enzyme in tobacco leaf discs

Since CO₂ is known to stimulate ethylene production by promoting the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene, the effect of CO₂ on the activity and the development of the ethylene forming enzyme (EFE) was studied in tobacco (Nicotiana tabacum L. cv Havana 425 and Xanthi) leaf discs. In addition to previous observations that EFE activity is dependent on CO₂ concentration and is saturable with 2% CO₂, present data show two saturation curves at 2% and 10% CO₂. Promotion of EFE development was dependent also on CO₂ concentration (saturated at 2% CO₂) and duration (maximum at 24 in the dark), and was abolished by 20 micromolar cycloheximide. Application of exogenous ethylene (20 microliters per liter) or light treatment further increased the CO₂-enhanced development of EFE, implying that these two factors can also affect EFE development via interaction with CO₂. The results suggest that CO₂ exerts its stimulatory effect on the conversion of ACC to ethylene by enhancing not only the activity but also the synthesis of EFE in leaf discs.     

Effect of Monochromatic Light on Proton Efflux of the Blue-Green Alga Anabaena variabilis

Light-induced proton efflux of Anabaena variabilis was found to be biphasic, the second phase being inhibited by the ATPase inhibitor nitrofen (2,4-dichloro-1-[4-nitrophenoxy]benzene). The first, fast phase was triggered by monochromatic light of 707 nanometers, whereas the second, slower phase was not. With 707 nanometers, light, respiratory O₂ uptake was inhibited. Using light composed of two wavelengths (616 and 707 nanometers) a marked enhancement of both O₂ evolution as well as the second phase of proton efflux was observed. The first phase was not enhanced. Thus, phase II is driven by both photosystems. As concluded from the action spectrum phase I is markedly determined by photosystem-I activity. Altogether the data show that two different mechanisms of light-induced proton efflux exist on the cytoplasmic membrane of Anabaena, the slower one being dependent on ATP and linear photosynthetic electron flow.     

蓖麻蚕血球细胞的体外培养及其病毒感染试验

蓖麻蚕(Philosamia cynthia ricini Donovan)由本所昆虫饲养室提供。选择健康的5龄幼虫,饥饿24小时,先用自来水洗净虫体,将幼虫放入75％乙醇中浸泡20—30分钟,体表消毒,取出幼虫以灭菌的双重蒸馏水和Hanks液各洗涤2次,置幼虫于已灭菌的滤纸平皿中,吸干体表水分。剪脚部采血,直接滴入预先盛有2毫升培养液的扁瓶中,每瓶采血1—2滴,加盖橡皮塞,轻微摇动瓶子,使培养瓶内的细胞均匀悬浮于     

人蛋白制品中辛酸与乙酰色氨酸稳定剂的定量测定

<正>在美国,大多数治疗用的人白蛋白制品是正常血清白蛋白和血浆蛋白组分。这些制品在60℃加热10小时以灭活肝炎病毒,为减少加热过程中蛋白变性,要加入稳定剂。按规定,这些稳定剂的允许量是每克蛋白中含乙酰色氨酸0.16mM或联合使用乙酰色氨酸钠与辛酸钠各0.08mM;辛酸和乙酰色氨酸与人白蛋白缔合。缔合的强度依据脂肪酸碳链的长短和色氨酸的三维结构而异,低浓度的任何稳定剂都能影响白蛋白的热稳定性,也与实验条件有关。     

Solid-state ethanol fermentation by means of inert gas circulation

A new method for solid-state ethanol fermentation (the SSEF system) was experimented on for the ethanol production from solid starchy materials, where a packedbed-type fermentor was used. Both cultivation of Aspergillus saitoi and enrichment of a saccharifying enzyme were effective for hydrolysis of the starch. Ethanol production was set in by a form of parallel fermentation using a respiration-deficient mutant of Saccharomyces cerevisiae. Produced ethanol was simultaneously stripped by circulating inert gas and separated in a condenser. Average ethanol concentration in the condensate was over 200 g/L, and over 90% of produced ethanol was recovered from the packed bed during 15 or 16 days of stripping. The fermentation efficiency was about 80%, which was evaluated much higher than those of conventional solid-state fermentations. The residue had lesser volume and a higher solids content compared with the distillery wastewaters of conventional liquid-state fermentations. This means an advantage for the treatment and the effective conversion of the residue into fetilizers or animal feeds.     

Performance of hydrophobic chromatography in purification of alpha-amylase

Hydrophobic ligands were introduced onto agarose beads, and the adsorption capacity of the beads was measured. The adsorption capacity increased with increase in the carbon number of the ligand, ionic strength of the buffer solution, and temperature. Crude alpha-amylase was purified with these hydrophobic adsorbents and the breakthrough and elution curves were estimated based on the mass transfer theory. Under strongly hydrophobic conditions, impurities contained in crude feeds and the lack of uniformity of packing caused by aggregation of beads affected adsorption and elution behaviors.     

Gas holdup in an external-loop air-lift fermentor with a contaminated gas distributor

Contamination of the porous-plate gas distributor was observed in an air-lift fermentor used for Aspergillus fumigatus fermentations. Comparisons between gas holdups measured with uncontaminated distributors and the contaminated one showed that the contamination had no effect on gas holdups in water but reduced the holdups in sodium chloride and sodium sulfate solutions, probably due to increased bubble coalescence. A correlation for gas holdups with clean distributors(2) could be used to represent the results for the comtaminated distributor by changing the values used for the characteristic velocities of the electrolyte solutions.     

Noninferior periodic operation of the biological reactor

The optimal periodic operation of the biological reactor was studied from the standpoint of the two-objective programming problem. The noninferior set with respect to the cell productivity and the conversion of the substrate into the biomass was determined by use of the optimization technique due to Miele. It was shown that the noninferior set was composed in general of the repeated batch branch and the repeated fed-batch branch, which occupy the high-productivity portion and the high-conversion portion of the noninferior set, respectively. However, the latter branch disappears in the case of growth kinetics with no substrate inhibition. In addition, the extreme points of the noninferior set yielding the maximal productivity and the maximal conversion represent such operations that are equivalent to the steady-state operation (chemostat culture) and the batch operation, respectively.     

The Effect of Sugars on the Binding of [Hg]-p-Chloromercuribenzenesulfonic Acid to Leaf Tissues

Replacement of mannitol with sucrose decreases the binding of [²⁰³Hg]-p-chloromercuribenzenesulphonic acid (PCMBS) to Vicia faba leaf discs without epidermis. This decrease is optimal for 20 minutes on incubation, is concentration-dependent, and is also found with maltose and raffinose. In parallel experiments, the addition of sucrose, maltose, and raffinose during PCMBS pretreatment was shown to increase subsequent uptake of [U-¹⁴C]sucrose. In contrast, d- or l-glucose, 3-O-methylglucose, galactose, fructose, palatinose, turanose, or melibiose had no effect either on PCMBS binding or on [¹⁴C]sucrose uptake. The sucrose-induced decrease of PCMBS binding is retained after a cold and ionic shock. Measurements of specific activities of membrane fractions prepared from tissues incubated in labeled PCMBS show that the decrease concerns the 120,000 gravity pellet, but that very mild procedures must be chosen to prevent redistribution of label in the supernatant. Altogether, the data provide new support to the hypothesis that the active site of the sucrose carrier contains a group sensitive to PCMBS.