High sequence similarity within ras exons 1 and 2 in different mammalian species and phylogenetic divergence of the ras gene family

We have determined the canine and feline N-, K-, and H-ras gene sequences from position +23 to +270 covering exons I and II which contain the mutational hot spot codons 12, 13, and 61. The results were used to assess the degree of similarity between ras gene DNA regions containing the critical domains affected in neoplastic disorders in different mammalian species. The comparative analyses performed included human, canine, feline, murine, rattine, and, whenever possible, bovine, leporine (rabbit), porcelline (guinea pig), and mesocricetine (hamster) ras gene sequences within the region of interest. Comparison of feline and canine nucleotide sequences with the corresponding regions in human DNA revealed a sequence similarity greater than 85% to the human sequence. Contemporaneous analysis of previously published ras DNA sequences from other mammalian species showed a similar degree of homology to human DNA. Most nucleotide differences observed represented synonymous changes without effect on the amino acid sequence of the respective proteins. For assessment of the phylogenetic evolution of ras gene family, a maximum parsimony dendrogram based on multiple sequence alignment of the common region of exons I and II in the N-, K-, and H-ras genes was constructed. Interestingly, a higher substitution rate among the H-ras genes became apparent, indicating accelerated sequence evolution within this particular clade. The most parsimonious tree clearly shows that the duplications giving rise to the three ras genes must have occurred before the mammalian radiation. Received: 23 July 1997 / Accepted: 30 October 1997     

Genetic studies on nucleolus organizer regions (NORs) in cattle

Experimentally produced monozygotic twins, natural opposite sex blood chimeras (freemartins), and several pedigrees were used to evaluate the genetic influences on the nucleolus organizer region (NOR) patterns in cattle. In monozygotic twins, the NOR patterns of both twins are extremely similar. In chimeras, NOR patterns of genetically identical, peripheral blood lymphocytes (PBL) from the two partners resemble each other. In contrast, genetically different PBL (sib organ) differ significantly in the same environment. A high heritability of the individual NOR patterns is also demonstrated in our 23 pedigrees. In conclusion, our data demonstrate that variation in NOR expression is predominantly due to genetic factors.     

A novel metal-dye detection system permits picomolar-range h.p.l.c. analysis of inositol polyphosphates from non-radioactively labelled cell or tissue specimens.

A novel complexometric dye- and transition-metal-based post-column detection system for polyanions, called 'metal-dye detection' has been developed. This technique, combined with a new h.p.l.c. separation protocol, permits a direct highly-isomer-selective determination of bis- to poly-phosphorylated non-radioactively labelled compounds in the picomolar range, a sensitivity hitherto unknown for these substances. The application of the technique in the quantitative microanalysis of inositol polyphosphates from milligram amounts of cells or tissue specimens is described. The technique promises to answer hitherto unresolved questions about the role of inositol phosphates, especially those in intact tissues, which are not readily amenable to analysis by radioisotopic techniques.     

The Why and How of Species

The biological species concept deals both with the meaning of the sexual species as a harmonious gene pool and with its protection against deleterious outbreeding (effected by isolating mechanisms). According to the Darwin-Muller-Mayr theory isolating mechanisms are acquired by incipient species during alloparty. Isolating mechanisms are not the result of ad hoc selection, but of a change of function of properties acquired during the preceding isolation of the incipient species. The role of behavioral properties (recognition) among the isolating mechanisms has long been recognized and described by naturalists but was rejected as basis of a species definition for a number of valid reasons.     

Crystals of the NC1 domain of human type IV collagen

Crystals of the non-collagenous C-terminal region (NC1) of type IV collagen have been obtained from human placenta. These crystals diffract to 2.0 A, and belong to space group P22(1)2(1), with cell dimensions a = 81 A, b = 158 A, c = 138 A, alpha = beta = gamma = 90 degrees. The crystals contain one hexamer in the asymmetric unit; they are very stable with respect to X-rays.     

Simulation of the effect of mixing,scale-up and pH-value regulation during glutamic acid fermentation

A mixing model is coupled with fermentation kinetics in order to simulate a fermentation as a function of mixing conditions and scale-up. The mixing model for a batch stirred tank with three stirrers consists of three regions, each of them characterized by an ideally mixed compartment around the stirrer and two macromixers, i.e. cascades of tank-in-series, describing the recirculation flow. The model contains four parameters — radial and axial circulation time, volume of the ideally mixed stirrer compartment and the number of tanks in each cascade. These values, determined by Mayr et al. in function of the operational conditions and scale-up, were choosen to simulate the fermentation of glutamic acid to show the pH-fluctuation at different control and scale conditions. By choosing optimal regulation properties, such as input flow rate and/or concentration of the base, regulation span, position of the pH-electrode and base input location, etc., fluctuations of the pH-value in the bio-reactor can be minimized. However, the negative effect of insufficient mixing conditions can be reduced only by an increasing number of the base input places. In large scale fermentors, the axial circulation time is rather high, about 5–10 times larger than the radial one. This might result in a large amplitude of the pH-fluctuation. As it is shown, using an input place for base in each stirrer region, the negative impact of the insufficient axial mixing on the fermentation can be diminished perfectly. In this case ammonia should be fed into the reactor as an aqueous solution.     

理解运动行为抑制调控的新视角：乙酰胆碱门控氯离子通道受体

Acetylcholine, the first identified neurotransmitter, plays crucial roles in various brain functions. One well-known case is its involvement as an activating neurotransmitter in the regulation of locomotion. However, its inhibitory regulatory role, particularly in locomotion, remains poorly understood. In a study conducted by Polat et al., the authors investigated the inhibitory role of acetylcholine in locomotion in C. elegans. In this organism, the acetylcholine-gated chloride channel receptor consists of four subunits. The authors thoroughly examined the loss-of-function of each subunit in movement regulation. Interestingly, the mutant worms were still capable of performing various movements such as forward, backward crawling, and turning, suggesting that the overall movement was not significantly affected. However, quantitative behavior analysis revealed subtle yet significant differences in the timing and postures of the movement in these mutants. Furthermore, the authors employed optogenetics to stimulate a specific neuron involved in backward crawling and demonstrated that the loss-of-function of the receptors in individual neurons affects the transitioning between locomotion modes. This work provides evidence for the inhibitory regulatory role of acetylcholine in locomotion. The loss-of-function of acetylcholine-gated chloride channel receptors likely disrupts the balance of neuronal and circuit physiology, thereby affecting the regulation of locomotion. Moreover, this study highlights the powerful role of quantitative behavior analysis in discovering and understanding more sophisticated functions of neural circuits.     

Engineering approach to mixing quantification in bioreactors

Homogeneity-time is defined and introduced as the criterion for mixing quality in bioreactors. The criterion could replace the mixing time, in the case, when more than one measuring point (sensors) is included in the measuring system. Results based on the homogeneity-time and the temperature pulse method, achieved in stirred tank reactors under aerated conditions as well as in a jet-mixed tank, are presented.List of Symbols C _p,p kJ/kg K Heat capacity of the pulse medium - C _p,s kJ/kg K Heat capacity of the reactor-medium - F m³/s Flow rate of the pulse-input - i Inhomogeneity - I _N Inhomogeneity-number - M (t) °C Ideal response curve - m deNumber of combinations for certain number of sensors acc. to Table 1 - n Number of sensor - _p kg/m³ Density of the pulse medium - kg/m³ Density of the tank medium - s ₁ °C Mean absolute deviation of the sensor temperatures related on the ideal response curve s₂ s Mean absolute deviation of the homogeneity-times related on the time achieved with 6 sensors - t s Time - t (i) s Homogeneity-time - t _ps s Starting time of tracer injection - t _PE s End time of tracer injection - T _E °C Mean medium temperature at the end of experiment - T _k °C Temperature at k-th sensor position - T _p °C Pulse temperature - T _s °C Mean medium temperature before the tracer injection - V _s m³ Tank volume before pulse input     

栓孔菌属漆酶高产菌株的初步筛选及其产酶条件的优化

利用显色反应对栓孔菌属(Trametes)进行了漆酶高产菌株的筛选,并对目标菌株的产酶条件进行了优化,在添加愈创木酚的固体培养基中,通过显色反应初步筛选出漆酶高产菌株东方栓孔菌Trametes orientalis Cui 6300;进一步通过单因子分析、正交试验和ABTS法确定了菌株Cui 6300的最适产酶条件:麦芽糖15 g/L,蛋白胨3 g/L,pH 4.8,Cu2+2.0 mmol/L,培养温度28°C,接种饼直径1.5 cm,此时酶活最高可达19.923 U/mL;同时探索了Cu2+浓度及添加时间对其菌丝生物量和漆酶活力的影响。研究表明,Cu2+最适添加浓度为2.0 mmol/L,添加时间为接种后第3天。     

瘦蛋白与皮肤创伤愈合

自1994年瘦蛋白（leptin）被发现以来,其生理作用得到广泛的研究。近年的研究表明,在高等动物的皮肤创伤愈合过程中,胶原与血管的生成、肉芽组织与上皮的再生以及组织的重建等因子,对皮肤的创伤愈合发挥着至关重要的作用,了解瘦蛋白与上述因子之间的相互关系与作用机制,有助于指导治疗,改善预后。