Interactions between WHITE Genes Carried by a Large Transposing Element and the ZESTE Allele in DROSOPHILA MELANOGASTER

TE146, a large transposing element of Drosophila melanogaster, carries two copies of the white and roughest genes in tandem. In consequence, z¹ w ^11E4; TE146(Z)/+ flies have a zeste (lemon-yellow) eye color. However, one in 10³ TE146 chromosomes mutates to a red-eyed form. The majority of these "spontaneous red" (SR) derivatives of TE146 have only one copy of the white gene and are, cytologically, two- to three-banded elements, rather than six-banded as their progenitor. The SR forms of TE146 are also unstable and give zeste-colored forms with a frequency of about one in 10⁴. One such "spontaneous zeste" (SZ) derivative carries duplicated white genes as an inverted, rather than a tandem, repeat. The genetic instability of this inverted repeat form of TE146 is different from that of the original tandem repeat form. In particular, the inverted repeat form frequently produces derivatives with internal rearrangements of the TE and gives a much lower frequency of SR forms. In addition, two novel features of the interaction between w⁺ alleles in a zeste background have been found. First, copies of w ⁺ can become insensitive to suppression by zeste even when paired. Second, an inversion breakpoint may disrupt the pairing between two adjacent w⁺ alleles, necessary for their suppression by zeste, without physically separating them.     

Investigation of Homologous Crossing over and Sister Chromatid Exchange in the Wheat Nor-B2 Locus Coding for Rrna and Gli-B2 Locus Coding for Gliadins

Recombination was investigated within the Nor-B2 locus of wheat chromosome 6B that contains several thousand of the 18S-5.8S-26S rRNA (rDNA) repeated units. Additionally, recombination was assessed for several chromosome regions, in arm 6Bq between the centromere and the B2 locus (awn suppressor) and in arm 6Bp between the centromere and Nor-B2, between Nor-B2 and a distal C-band and between Nor-B2 and Gli-B2 coding for gliadins. The experimental design permitted the distinction between crossing over between homologous chromosomes and exchange between sister chromatids. No homologous crossing over within the Nor-B2 locus was found in a sample of 446 chromosomes, but one exchange with the attributes of unequal sister chromatid exchange was identified. The molecular characteristics of this presumed sister chromatid exchange indicate that the spacer variants present in the Nor-B2 locus are clustered. No homologous recombination was detected within the distal Gli-B2 locus containing repeated genes coding for gliadin seed-storage proteins. Both arms of chromosome 6B showed low crossing-over frequency in the proximal regions. The distance from the centromere to Nor-B2 was only from 0.3 to 2.2 cM although it accounts for about two-thirds of the metaphase chromosome arm, which shows a great distortion of the metaphase map of the arm. The level of homologous recombination within the Nor-B2 locus is lower than in the chromosome region immediately distal to it. Whether it is comparable to that in the chromosome region proximal to it could not be determined. Recombination frequencies of different pairs of chromosome 6B in all but one interval paralleled the frequencies of their metaphase I pairing: Lower pairing at metaphase I was paralleled by lower crossing-over frequency. This relationship indicated that reduced metaphase I pairing between 6B chromosomes from different populations is due to impaired crossing-over and not due to precocious chiasma terminalization.     

3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Activity in Ochromonas malhamensis: A System to Study the Relationship between Enzyme Activity and Rate of Steroid Biosynthesis

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the key regulatory enzyme of the isoprenoid pathway, was found to be predominantly microsomal in Ochromonas malhamensis, a chrysophytic alga. Detection of HMG-CoA reductase requires the presence of 1% bovine serum albumin during cell homogenization, and the activity is stimulated by the presence of Triton X-100. The enzyme has a pH optimum of 8.0 and an absolute requirement for NADPH. When grown in 10 micromolar mevinolin, a competitive inhibitor of HMG-CoA reductase, O. malhamensis shows a 10- to 15-fold increase in HMG-CoA reductase activity (after washing) with little or no effect on cell growth rate. Cultures can be maintained in 10 micromolar mevinolin for months. O. malhamensis produces a large amount (1% dry weight) of poriferasterol, a product of the isoprenoid pathway. The addition of 10 micromolar mevinolin initially blocked poriferasterol biosynthesis by >90%; within 2 days the rate of synthesis returned to normal levels. Immediately after mevinolin was washed from the 2-day culture, there was a transient 2.5-fold increase in the rate of poriferasterol biosynthesis. The rate of poriferasterol biosynthesis and the level of HMG-CoA reductase activity both fell to control levels within hours.     

正常人末梢血淋巴细胞的电泳组分

正常人末梢血淋巴细胞是一不均一的群体。它主要由T淋巴细胞及B淋巴细胞等亚群组成。目前已有多种识别T、B淋巴细胞的方法,如E玫瑰花试验、酸性酯酶染色试验,以及检测细胞表面免疫球蛋白、Fc受体及补体受体等技术,但均因易受多种因素影响而不够完善。用细胞电泳技术分析淋巴细胞亚群国外已研究多年,但国内报道甚少。我们对50例正常人末梢血淋巴细胞进行了电泳研究,重点分析了淋巴细胞的电泳组分及其与T、B淋巴细胞亚群之间的关系。我们认为用这一方法识别淋细胞亚群是可行的。     

亲和层析法分离腺苷结合蛋白质

本文报告一种新的腺苷亲和层析凝胶的合成方法。利用这种凝胶可从大鼠心脏、肝脏及小牛主动脉平滑肌的水溶部份分离出几种腺苷结合蛋白质,其亚基分子量(据SDS-PAGE)分别为35,000、37,000、46,000、43,000及15,300Dal。现已证明,35,000Dal蛋白质是乳酸脱氢酶及苹果酸脱氢酶,43,000Dal蛋白质是腺苷激酶,46,000Dal蛋白质可能是S-腺苷同型半胱氨酸水解酶。15,000Dal蛋白质前人未有报道。它对腺苷具有高度特导性和亲和力,推测是腺苷的细胞内受体和/或载体。测定了这种低分子量腺苷结合蛋白质的氨基酸组成及某些物理常数:pI=6.5;沉降系数2.42S,微分比容0.727cm~3/g,与腺苷复合物的解离常数K_D=2.3μM。     

Design of a system for the control of low dissolved oxygen concentrations: critical oxygen concentrations for Azotobacter vinelandii and Escherichia coli

The physiological activity of microorganisms in environments with low dissolved oxygen concentrations often differs from the metabolic activity of the same cells growing under fully aerobic or anaerobic conditions. This article describes a laboratory-scale system for the control of dissolved oxygen at low levels while maintaining other parameters, such as agitator speed, gas flowrate, position of sparger outlet, and temperature at fixed values. Thus, it is possible to attribute in dilute nonviscous fermentations all physiologic changes solely to changes in dissolved oxygen. Experiments were conducted with Azotobacter vinelandii and Escherichia coli. Critical oxygen concentrations for growth (that value of oxygen allowing growth at 97% of mu max) were measured as 0.35 +/- 0.03 mg/L for A. vinelandii and 0.12 +/- 0.03 mg/L for E. coli. These values are significantly different from the commonly quoted values for critical oxygen concentrations based on respiration rates. Because of the superior dissolved oxygen control system and an improved experimental protocol preventing CO2 limitation, we believe that the values reported in this work more closely represent reality.     

The dependence of protein release from Bacillus amyloliquefaciens on the growth phase in batch culture

For the recovery of intracellular material from bacteria it is often necessary to disrupt the cells. Much work has been done on the kinetics of protein release in beadmills,(1) homogenizers,(2) and by ultrasonication.(3) In this paper we report how the growth phase of Bacillus amyloliquefaciens grown in batch culture affects the rate of protein release by ball milling, ultrasonication, and autolysis. We further suggest that autolysis is a feasible method for disrupting Bacillus.     

Effect of ultrasound treatment on the extraction of insulin

Insulin production requires a prolonged extraction process. An ultrasound method of insulin extraction was developed to increase efficiency. Application of ultrasound resulted in a significant increase in the extraction process as a result of pancreas tissue dispergation, destruction of the pancreas cells, intensive mixing, separation of particles, and increase in the interphase pancreas-extractive medium. Optimal technological parameters of insulin extraction were established: ultrasound frequency, 19.5 kHz, specific intensity of ultrasound, 3.3 W/cm(2); time of ultrasound exposure, 5-10 min; and influence of cavitation process. Effectiveness of insulin extraction depends on the properties of the extractive medium. Optimal conditions were pH, 1.6-1.7, concentration of alcohol, 75%, temperature of extractive mixture, 13-17 degrees C; ratio of ground pancreas to liquid extractive medium, 1 : 3.     

Continuous production of ethanol from fructose by immobilized growing cells of Zymomonas mobilis

Immobilized growing cells of Zymomonas mobilis were found to ferment rapidly and efficiently media containing 100 g/L fructose in a continuous reactor. A volumetric ethanol productivity of 94.8 g/L h was achieved at a substrate conversion of 75.5%. With 97% conversion of substrate the productivity was 28.4 g/L h. At fructose concentrations of 150 and 200 g/L substrate and product inhibitions limited the performance of the reactor. Ethanol production was constant over a period of 55 days.