Investigation of cis-acting sequences regulating expression of the gene encoding yolk protein 3 in Drosophila melanogaster.

Summary The regulatory sequences leading to the ovarian and fat body expression of yolk proteins 1 and 2 (YP1 and 2) of Drosophila melanogaster have been characterised in some detail. These genes (yp1 and yp2) share many enhancer elements, and some important regulatory sequences lie within the coding regions. We have begun to investigate the cis-regulation of the gene encoding yolk protein 3 (yp3). We describe a system for P element transformation using the complete and unaltered yp3 gene rather than reporter genes and describe sequences conferring correct expression in the ovary and carcass.     

35S-β-glucuronidase gene blocks biological effects of cotransferred iaa genes

The iaaM and iaaH genes of Agrobacterium tumefaciens and Agrobacterium rhizogenes play an important role in crown gall and hairy root disease. The iaaM gene codes for tryptophan monooxygenase which converts tryptophan into indole-3-acetamide (IAM). IAM is converted into the auxin indole-3-acetic acid (IAA) by indoleacetamide hydrolase, encoded by the iaaH gene. In functional studies on the activity of the iaa genes of the TB region of the A. tumefaciens biotype III strain Tm4, the frequently used 35S--glucuronidase (35S-UidA or GUS) marker gene was found to inhibit IAA synthesis and root induction encoded by the TB iaa genes. To exert this inhibition, the 35S-UidA gene must be cotransferred with the iaaH gene. The 35S promoter alone is sufficient to cause the inhibitory effect.     

Transformation of Nicotiana tabacum,N. debneyi,and N. rustica: Inheritance and protoplast expression of antibiotic resistance

Agrobacterium tumefaciens strains harbouring plasmid vectors pBCAT1, pVU1011 or pMON806 were used to transform leaf explants of Nicotiana tabacum cultivars Delgold and Candel, N. debneyi, and N. rustica var. NRT. Transgenic plants resistant to the selective agents kanamycin, hygromycin or methotrexate were regenerated and used as sources of leaf mesophyll protoplasts. Protoplasts divided and regenerated plants in the presence of selective agents at levels inhibitory to protoplasts of non-transformed plants. Cross-resistance of protoplasts to more than one selective agent was not observed in this study which suggests that this approach may lead to an efficient interspecific somatic hybrid selection system.     

Processing of multi-dimensional NMR data with the new software PROSA

Summary The new program PROSA is an efficient implementation of the common data-processing steps for multi-dimensional NMR spectra. PROSA performs linear prediction, digital filtering, Fourier transformation, automatic phase correction, and baseline correction. High efficiency is achieved by avoiding disk storage of intermediate data and by the absence of any graphics display, which enables calculation in the batch mode and facilitates porting PROSA on a variety of different computer systems; including supercomputers. Furthermore, all time-consuming routines are completely vectorized. The elimination of a graphics display was made possible by the use of a new, reliable automatic phase-correction routine. CPU times for complete processing of a typical heteronuclear three-dimensional NMR data set of a protein vary between less than 1 min on a NEC SX3 supercomputer and 40 min on a Sun-4 computer system.     

高原鼢鼠挖掘取食活动的能量代价及其最佳挖掘取食行为

高原鼢鼠(Myospalax baileyi)是青藏高原典型的地下鼠,它主要挖掘取食杂类草之地下根茎,在挖掘过程中形成取食洞道。本文根据此特点,建立了挖掘取食过程中能量代价(E_(?))与取食道结构参数(土丘间距S、侧道长L、取食道半径b及洞道深度D)之间以及取食获能E_(fg)与S和b之间的两个函数关系。分别以挖掘效率极大和取食效率极大为优化目标,导出同样的结果,即相同的最佳土丘间距S_(opt)。通过实验观测,计算出在矮嵩草(Kobresiahumilis)草甸生境条件下,最佳土丘间距S_(opt)=127.4厘米,与野外实测土丘间距(126.30±47.85厘米)无显著差异(t=0.312,P>0.50),表明高原鼢鼠的挖掘及取食行为符合最佳化原则。     

森林土壤氮转化的微生物功能研究

本文研究了不同林型下土壤(A+6层和A_1层)微生物、土壤酶活性在森林土壤氮转化中的作用。结果表明不同林型下土壤具有不同的固氮作用、反硝化作用、氨化作用和硝化作用速率,即阔叶林>针阔混交林>针叶林。已经证明,固氮作用主要存在于森林土壤的A_1层,反硝化作用主要存在于A_0层。森林土壤存在2种硝化作用过程,即由自养微生物所引起的自养硝化作用过程和异养微生物所引起的异养硝化作用过程。它的存在与林型有关,某些森林土壤中这2种硝化作用过程都存在,如针阔混交林下的A_0层和A_1层。有些林型下土壤,则以异养硝化作用过程为主,如针叶林的A_0层。     

Cellular Localization of the Molecular Forms of Acetylcholinesterase in Primary Cultures of Rat Sympathetic Neurons and Analysis of the Secreted Enzyme

The secretion and cellular localization of the molecular forms of acetylcholinesterase (AChE) were studied in primary cultures of rat sympathetic neurons. When cultured under conditions favoring a noradrenergic phenotype, these neurons synthesized and secreted large quantities of the tetrameric G4, and the dodecameric A12 forms, and minor amounts of the G1 and G2 forms. When these neurons adopted the cholinergic phenotype, i.e., in the presence of muscle-conditioned medium, the development of the cellular A12 form was completely inhibited. These neurons secreted only globular, mainly G4, AChE. Both cellular and secreted A12 AChE in adrenergic cultures aggregated at an ionic strength similar to that of the culture medium, raising the hypothesis that this form was associated with a polyanionic component of basal lamina. In noradrenergic neurons, 60-80% of the catalytic sites were exposed at the cell surface. In particular, 80% of G4 form, but only 60% of the A12 form, was external, demonstrating for the A12 form a sizeable intracellular pool. The hydrophobic character of the molecular forms was studied in relation to their cellular localization. As in muscle cells, most of the G4 form was membrane-bound. Whereas 76% of the cell surface A12 form was solubilized in the aqueous phase by high salt concentrations, only 50% of the intracellular A12 form was solubilized under these conditions. The rest of intracellular A12 could be solubilized by detergents and was thus either membrane-bound or entrapped in vesicles originating from, e.g., the Golgi apparatus.     

Suppression of the Escherichia coli dnaA46 mutation by amplification of the groES and groEL genes

Summary A hybrid phage (Sda1), containing an 8.1 kb EcoRI DNA fragment from the Escherichia coli chromosome, was selected on the basis of its ability to suppress bacterial thermosensitivity caused by the dnaA46 mutation. We have shown that this suppression is due to a recA ⁺-dependent amplification of the 8.1 kb fragment; consistent with this observation, cloning of the 8.1 kb fragment into a high copy number plasmid (pBR325) leads also to suppression of dnaA46. In the suppressed strains growing at high temperature, bidirectional replication starts in or near the oriC region and requires the presence of the DnaA polypeptide. These findings suggest that the overproduction of a gene product(s), encoded by the cloned 8.1 kb fragment, can restore dnaA-dependent initiation of replication at high temperature in the oriC region. Genetic mapping shows that the groES (mopB) and groEL (mopA) genes are located on the 8.1 kb suppressor fragment. Further analysis, including in vitro mutagenesis and subcloning, demonstrates that the amplification of the groES and groEL genes is both necessary and sufficient to suppress the temperature sensitive phenotype of the dnaA46 mutation.     

Membrane and cytoplasmic resistivity properties of normal and sickle red blood cells

The cytoplasmic resistivities and membrane breakdown potentials of normal (AA), sickle-cell-trait (AS), and sickle (SS) red blood cells have been measured by the biophysical methodology of resistive pulse spectroscopy over a range of osmolalities. At isotonicity, the average membrane breakdown potentials are virtually identical for the three types of cells occurring at about 1150 V/cm. Average isotonic cytoplasmic resistivities are somewhat higher for the SS cells (166.7±7.49 ohm-cm) compared to the AA (147.6±1.98 ohm-cm) or AS cells (148.7±1.79 ohm-cm). As medium osmolality is varied, the differences in resistive properties become enlarged, especially at very low and very high osmolalities. At high osmolalities, both types of sickle cells show a large increase in internal resistivity compared to the normals; at low osmolality, the SS samples exhibit a distinctly different membrane breakdown characteristic, decreasing in this parameter, whereas the other two groups increase. Of the 15 SS samples tested, three displayed much higher cytoplasmic resistivities at isotonicity: 218.2±5.25 ohm-cm, compared to an average of 153.5±3.46 ohm-cm for the other 12. The relationship between these high resistivities and the subfraction of irreversibly sickled cells in the sample is discussed.