The kinetics of RCC1 inclusion body formation in Escherichia Coli

The Regulator of Chromosome Condensation protein (RCC1) is located in both the soluble and inclusion body (IB) fractions of the whole cell lysate when expressed in Escherichia coli BL21 (pLysS) at temperatures below 30 degrees C. When bacterial growth was carried out at 20 degrees C, the majority of the RCC1 remained soluble up to 5.5 h postinduction, When the temperature was raised to 25 degrees C, RCC1 IB was dominant by 1.5 h postinduction. The shift in RCC1 IB formation with temperature suggests that in addition to increased translation rates, folding and aggregation processes may contribute to RCC1 IB formation at higher temperatures. (c) 1995 John Wiley & Sons, Inc.     

茅苍术资源再生的研究

通过对茅苍术Ａｔｒａｃｔｙ　ｌｏｄｅｓｌａｎｃｅａ（Ｔｈｕｎｂ．）ＤＣ．有性繁殖及营养繁殖后代的研究,论述其资源再生的若干生物学特性的基本规律。结果表明,茅苍术在根茎形态、干物质量、化学成分的种类和含量上都随年龄有一定的动态变化规律,并存在个体差异。繁殖方式对干物质量的增长速率无明显影响。根茎中挥发油成分的含量随年龄的变化有一下降后再缓慢增加的趋势。同时还讨论了两种繁殖方式在茅苍术生产中的意义。     

Prediction of polyelectrolyte polypeptide structures using Monte Carlo conformational search methods with implicit solvation modeling.

Many interesting proteins possess defined sequence stretches containing negatively charged amino acids. At present, experimental methods (X-ray crystallography, NMR) have failed to provide structural data for many of these sequence domains. We have applied the dihedral probability grid-Monte Carlo (DPG-MC) conformational search algorithm to a series of N- and C-capped polyelectrolyte peptides, (Glu)20, (Asp)20, (PSer)20, and (PSer-Asp)10, that represent polyanionic regions in a number of important proteins, such as parathymosin, calsequestrin, the sodium channel protein, and the acidic biomineralization proteins. The atomic charges were estimated from charge equilibration and the valence and van der Waals parameters are from DREIDING. Solvation of the carboxylate and phosphate groups was treated using sodium counterions for each charged side chain (one Na+ for COO-; two Na for CO(PO3)-2) plus a distance-dependent (shielded) dielectric constant, epsilon = epsilon 0 R, to simulate solvent water. The structures of these polyelectrolyte polypeptides were obtained by the DPG-MC conformational search with epsilon 0 = 10, followed by calculation of solvation energies for the lowest energy conformers using the protein dipole-Langevin dipole method of Warshel. These calculations predict a correlation between amino acid sequence and global folded conformational minima: 1. Poly-L-Glu20, our structural benchmark, exhibited a preference for right-handed alpha-helix (47% helicity), which approximates experimental observations of 55-60% helicity in solution. 2. For Asp- and PSer-containing sequences, all conformers exhibited a low preference for right-handed alpha-helix formation (< or = 10%), but a significant percentage (approximately 20% or greater) of beta-strand and beta-turn dihedrals were found in all three sequence cases: (1) Aspn forms supercoil conformers, with a 2:1:1 ratio of beta-turn:beta-strand:alpha-helix dihedral angles; (2) PSer20 features a nearly 1:1 ratio of beta-turn:beta-sheet dihedral preferences, with very little preference for alpha-helical structure, and possesses short regions of strand and turn combinations that give rise to a collapsed bend or hairpin structure; (3) (PSer-Asp)10 features a 3:2:1 ratio of beta-sheet:beta-turn:alpha-helix and gives rise to a superturn or C-shaped structure.     

穴蚁蛉幼虫期的食物量对各虫态历期的影响研究

穴蚁蛉在自然条件下１年发生１代,本实验证明,不同的饲食频率可影响幼虫的发育历期,在每天饲给１头米蛾成虫的情况下,１年可发生３代。１个世代可以在全历期都处于长日照和没有低温的条件下完成,其发育可以不需要光周期变化诱发,１５日饲食１次的穴蚁蛉,３龄 虫     

Does polyploidy lead to fewer and shorter microsatellites in Barbus (Teleostei: Cyprinidae)?

Screening of a hybrid Barbus barbus-B. meridionalis genome was performed for CA, GA, TAT, TCT, TAG, TGT, TATT, TACT, ATCT motifs, and simultaneously on another fish species, tilapia S. melanotheron . Sequences of positive clones were obtained for Barbus and revealed that repetitive structure significantly depends on the motif: most TAT and TATT repeats contain small numbers of repeats, and these repeats are highly heterogeneous, whereas other motifs (we mainly obtained CA and GATA repeats) form longer and much more homogeneous arrays. Polymorphism data from five loci in two different species of barbel show that perfectly repetitive loci are much more variable than imperfect loci (TAT and TATT). We compared the frequency of positive clones for different repeat motifs between barbel and tilapia. For dinucleotide repeats (CA and GA), the comparison was extended to additional fish species, trout and sea bass, which were screened in nearly identical conditions for these motifs. The most salient feature of these comparisons reveals that arrays of dinucleotide motifs are significantly under-represented and shorter in Barbus than in other fish species. We propose an explanation that can account for most features of microsatellites characterizing the genome of barbel. A bias toward deletion affecting slipped-strand mispairing events would lead to shortening and loss of microsatellite loci. Such a bias would represent an efficient way of eliminating useless DNA from polyploidized species with an excessive amount of DNA.     

A new mode of ammonite preservation – implications for dating of condensed phosphorite deposits

Unusual phosphatic casts of the ammonites Mortoniceras (Subschloenbachia) sp. and Stoliczkaia sp. from the upper Albian condensed phosphorite bed at Annopol, Poland, are discussed in terms of their taphonomic history. These specimens are interpreted as ‘secondary’ external casts of ammonite replicas preserved originally as attachment scars on oyster shells. The following genetic history is suggested for this previously undocumented mode of ammonite preservation: (1) settling of shells of dead ammonites on the seafloor; (2) colonization of these shells by oysters and formation of ammonite replicas on left valves of oysters; (3) dissolution of ammonite shells; (4) reworking and fragmentation of oyster shells; (5) casting of ammonite replicas by phosphatic material; and (6) separation of ammonite casts from oyster shells, either through mechanical disintegration or dissolution of the latter. The specimens studied were formed after dissolution of the ammonite conchs, not prior to this event as in the case of typical ammonite steinkerns (internal moulds). Therefore, they are here referred to as ‘pseudo‐steinkerns’. The time interval between loss of the original ammonite shells and the formation of oyster‐mediated pseudo‐steinkerns may be very extensive. Therefore, the pseudo‐steinkerns may potentially mislead in biostratigraphic dating of condensed phosphorite deposits.     

Microscopic insight into the DNA condensation process of a zwitterion‐functionalized polycation

Zwitterion‐functionalized polycations are ideal gene carriers with long circulation, high cellular uptaking and low cell viability. However, the trade‐off between the DNA condensation efficiency and the cell viability must be addressed. The purpose of this study is to provide a microscopic insight into the DNA condensation process and to explore the effect of a zwitterionic block of zwitterion‐functionalized polycation, which is of great significance in designing novel gene delivery systems. Poly[2‐(dimethylamino)ethyl methacrylate‐b‐(sulfobetaine methacrylate)] (PDMAEMA‐b‐PSBMA) copolymers were synthesized and used as the model systems. Different from the conventional concept that the PSBMA zwitterionic block act only as the “stealthy” groups, the subtle differences in physical and colloidal characteristics between the polycation/DNA polyplexes show that the PSBMA segment is capable of wrapping DNA attributed to the quaternary ammonium cations, without compromising the DNA condensation capability. On the other hand, the incorporation of PSBMA block reduces the surface charge of the polyplexes, which substantially result in the inefficient transfection and the reduced cytotoxicity.     

Microspectrophotometric measurements of DNA by automated computerized scanning in cycling cells of theChrysanthemum segetum shoot apex

Summary A new technique of exploitation of the data was proposed after DNA scanning microdensitometry. By using all of the measurements obtained from the seriated sections of a single nucleus, this method made it possible to estimate six characteristic parameters during the different phases of the cell cycle in the various shoot apical cells. The cells whose rate of proliferation was the highest showed the biggest variations of their nuclear and nucleolar volumes during the cell cycle. In the axial zone, where the cells have a slow cell cycle and display the longest duration of the G₁ phase, the volume occupied by dispersed DNA was greater than in the cells of the lateral zone and of the rib meristem, where the cell cycle and the G₁ phase were short. No matter what the cell type, the proportion of the dispersed and condensed DNA varied little when the G₁ and G₂ phases were compared. In the Z phase, characterized by a decondensation of the DNA, the mean DNA amount was 3.4 C. The evolution of the nuclear density during the interphase was also estimated. It is demonstrated that the main feature of the shoot apex zonation was the decondensation of the condensed DNA in the axial zone in both the G₁ and G₂ phases.     

Nuclear morphogenesis during spermiogenesis in the nudibranch molluscHypselodoris tricolor (Gastropoda,opisthobranchia)

An electron microscope study was carried out on Hypselodoris tricolor spermatids to describe the development of the nuclear morphogenesis and investigate the possible cause(s) of the change in the shape of the spermatid nucleus during spermiogenesis. Three different stages may be distinguished in the course of the nuclear morphogenesis on the basis of the morphology and inner organization of the nucleus. Stage 1 spermatid nuclei are spherical or ovoid in shape and the nucleoplasm finely granular in appearance. Stage 2 nuclei exhibit a disc- or cup-shaped morphology, and the chromatin forms short, thin filaments. During stage 3, a progressive nuclear elongation takes place, accompanied by chromatin rearrangement, first into fibers and then into lamellae, both formations helically oriented. A row of microtubules attached to the nuclear envelope completely surrounds the nucleus. Interestingly, the microtubules always lie parallel to the chromatin fibers adjacent to them. Late stage 3 spermatids show the highest degree of chromatin condensation and lack the manchette at the end of spermiogenesis. Our findings indicate the existence of a clear influence exerted on the chromatin by the manchette microtubules, which appear to be involved in determining the specific pattern of chromatin condensation in Hypselodoris tricolor.     

Recording mitotic chromosome cycle induction in living plant cells

Summary The presence of a prophase nucleus inHaemanthus endosperm happens to trigger the break down of the nuclear envelope in any interphase nucleus, located in its close proximity. Besides, chromosomes in the interphase nucleus start condensing gradually for the initial breaking point which is the nearest point to the prophase. The observation suggest the diffusion of an inducer, whose progression has been recorded to occur at a rate of 1.1 m/min.