水稻小穗轴维管系统网络结构探讨

对籼型、粳型或其不育系与保持系代表品种小穗解剖观察表明：水稻小穗轴维管系统网络由中央维管束和各分枝维管束复合而成。来自小穗柄的１条大的中央主束和几条边围维管束经数次分枝、联结,不断产生新的分枝维管束进入相应的结构。一般颖片中维管束１－２条,第一稃片中１－３条,第二稃片中１－４条,第二朵退化小花残余结构中０－３条,顶生可孕小花的外稃中５条,内稃中３条,浆片中各２条,雄蕊中各１条,雌蕊中３条,主束与支     

A model for a network of phosphorylation-dephosphorylation cycles displaying the dynamics of dominoes and clocks

We consider a model for a network of phosphorylation-dephosphorylation cycles coupled through forward and backward regulatory interactions, such that a protein phosphorylated in a given cycle activates the phosphorylation of a protein by a kinase in the next cycle as well as the dephosphorylation of a protein by a phosphatase in a preceding cycle. The network is cyclically organized in such a way that the protein phosphorylated in the last cycle activates the kinase in the first cycle. We study the dynamics of the network in the presence of both forward and backward coupling, in conditions where a threshold exists in each cycle in the amount of protein phosphorylated as a function of the ratio of kinase to phosphatase maximum rates. We show that this system can display sustained (limit-cycle) oscillations in which each cycle in the pathway is successively turned on and off, in a sequence resembling the fall of a series of dominoes. The model thus provides an example of a biochemical system displaying the dynamics of dominoes and clocks (Murray & Kirschner, 1989). It also shows that a continuum of clock waveforms exists of which the fall of dominoes represents a limit. When the cycles in the network are linked through only forward (positive) coupling, bistability is observed, while in the presence of only backward (negative) coupling, the system can display multistability or oscillations, depending on the number of cycles in the network. Inhibition or activation of any kinase or phosphatase in the network immediately stops the oscillations by bringing the system into a stable steady state; oscillations resume when the initial value of the kinase or phosphatase rate is restored. The progression of the system on the limit cycle can thus be temporarily halted as long as an inhibitor is present, much as when a domino is held in place. These results suggest that the eukaryotic cell cycle, governed by a network of phosphorylation-dephosphorylation reactions in which the negative control of cyclin-dependent kinases plays a prominent role, behaves as a limit-cycle oscillator impeded in the presence of inhibitors. We contrast the case where the sequence of domino-like transitions constitutes the clock with the case where the sequence of transitions is passively coupled to a biochemical oscillator operating as an independent clock.     

Mon1a protein acts in trafficking through the secretory apparatus

Mon1a was originally identified as a modifier gene of vesicular traffic, as a mutant Mon1a allele resulted in increased localization of cell surface proteins, whereas reduced levels of Mon1a showed decreased secretory activity. Here we show that Mon1a affects different steps in the secretory pathway including endoplasmic reticulum-to-Golgi traffic. siRNA-dependent reduction of Mon1a levels resulted in a delay in the reformation of the Golgi apparatus after Brefeldin A treatment. Endoglycosidase H treatment of ts045VSVG-GFP confirmed that knockdown of Mon1a delayed endoplasmic reticulum-to-Golgi trafficking. Reductions in Mon1a also resulted in delayed trafficking from Golgi to the plasma membrane. Immunoprecipitation and mass spectrometry analysis showed that Mon1a associates with dynein intermediate chain. Reductions in Mon1a or dynein altered steady state Golgi morphology. Reductions in Mon1a delayed formation of ERGIC-53-positive vesicles, whereas reductions in dynein did not affect vesicle formation. These data provide strong evidence for a role for Mon1a in anterograde trafficking through the secretory apparatus.     

Tonic effects of stationary luminous slits on the discharge rates of some locust visual interneurones

The presence of an illuminated slit in the visual field of a locust compound eye produced changes in the tonic discharge rate of the DCMD and three other visual interneurones, recorded in a connective. The DCMD discharge peaked initially in the range of low slit subtenses, but over a period of minutes of exposure its character changed so that there was a rise at high subtenses also. When the luminance of a slit of fixed subtense was increased in steps, there was an initial rise then a sharp fall in discharge, indicating an abrupt onset of inhibition. Lateral spread of inhibition could account for the peak in response to slits, at a subtense falling well within the acceptance angle of a single ommatidium. The results show the ability of some visual interneurones to maintain a changed level of discharge in the presence of a stationary object in the visual field of the eye.     

A representative model of the hierarchic structure of human populations]

The paper deals with the concept of a hierarchy population. The population is hierarchial, if it can be divided into a certain amount of subpopulations in such a way that the set may naturally break into classes (levels). A migration may exist from each sub-population or into a higher one. Such population structures are frequently encountered among the human populations. It is shown that in a hierarchial population a selection is more efficient than in a non-subdivided one. In this respect the role of small populations in evolution is suggested. It was possible to demonstrate that in a hierarchial population there was a higher degree of polymorphism, a higher velocity of the evolutional process, that in a non-subdivided population of the same size. Besides, the level of polymorphism in the hierarchial population increases monotomously with the growth of the amount of generations during rather a long period of time.     

The effect of a complex of meditation exercises on the psychophysiological state of young men

Using a simple motor response, a complex sensorimotor response, and a tapping test, the effect of a complex of meditation exercises on the neuromuscular coordination in healthy male students who were preliminarily trained in methods of self-regulation based on meditation techniques was studied. As a result of a 6-min session of self-regulation, a considerable decrease (by 30% or more) in the time of a simple motor response and a complex sensorimotor response (due to a decrease in the latent time at constant motor time) and a simultaneous decrease in the number of errors, as well as a considerable increase in the result of the tapping test, were recorded. A short-term effect expressed in an increase in the rate and accuracy of sensorimotor responses can be a result of a change in the functional state of the nervous system under the impact of transcendental meditation techniques.     

A prototype model structure for mixed microbial populations in homogeneous food products

An important factor which has not been included in many models in the field of predictive microbiology is the influence of a background of microflora in a food product. It is however generally known that the growth of a microorganism as a pure culture can be substantially different from its growth in a mixed culture, due to microbial interactions. Because of the importance of these interactions and the lack of suitable modeling techniques in the field of predictive microbiology to describe them, the potential of models in other research fields-namely ecology-to deal with interactions is explored in previous work of the authors. However, a model structure for microbial growth in food products cannot simply be copied from those elaborated in ecology. The structure of a predictive growth model is indeed typical, primarily due to the explicit modeling of a lag phase. The current paper proposes a prototype model structure for growth of mixed microbial populations in homogeneous food products. The model is able to describe a lag phase and reduces to a classical predictive growth model in the special case of single-species growth.     

Expression of CYP1A in liver of A/Sn and CC57BR mice differing in sensitivity to hepatocarcinogenesis induced by o-aminoazotoluene

The induction of P450 cytochromes Cyp1a1 and Cyp1a2 in the liver of male mice differing in sensitivity to the carcinogenic effect of o-aminoazotoluene (OAT) has been studied. The level of Cyp1a1 and Cyp1a2 mRNA was assayed by quantitative competitive polymerase chain reaction (PCR). In both OAT-treated strains, the level of Cyp1a1 mRNA increased more than 1000-fold, while the amount of Cyp1a2 mRNA increased only two- or threefold. Interstrain differences in the Cyp1a mRNA level were revealed. The level of Cyp1a1 mRNA in liver of OAT-induced A/Sn mice was three times higher than in CC57BR mice. The amount of Cyp1a2 mRNA in control and OAT-treated mice was 7 and 13 times higher, respectively, than in CC57BR mice. The enzyme activities of cytochromes P450 1a were assayed. An increase in Cyp1a1 mRNA level in OAT-treated mice correlated with an enhancement of the benzo[a]pyrene hydrolase and 7-ethoxyresofurin o-deethylase activities; the correlation between the level of Cyp1a2 mRNA and 7-ethoxyresofurin o-demethylase activity was much less pronounced. Interstrain variation in Cyp1a1 and Cyp1a2 activities was also shown at the enzyme activity level. We suppose that quantitative differences in the Cyp1a2 mRNA level play a key role in OAT-induced hepatocarcinogenesis.     

Stimulating role of potassium ions and ouabain on glycogen synthesis in adipose tissue.

1. Exposure of fat-pads to increasing concentrations of K+ in the presence of insulin stimulates the incorporation of labelled glucose into glycogen. In the absence of hormone, only a slight incorporation of glucose into glycogen and slight glucose oxidation were detectable. 2. Ouabain alone, up to 100 microM, had no effect on synthesis of glycogen. Ouabain reinforced the effect of insulin on the conversion of glucose into glycogen in a Na+ medium and in a equimolar Na+-K+ medium, but not in a K+ medium. In addition, ouabain modified the optimal K+/Na+ ratio for glycogen synthesis. 3. The proportion of glycogen synthase in the active form was increased in a K+ medium, and a faster rate of conversion of synthase b into a was observed under these conditions. No difference was detected in the rate of inactivation of phosphorylase in a K+ or a Na+ medium. 4. Even though these results, taken together, are consistent with the proposed role of phosphorylase a in the regulation of synthase activation, the molecular mechanism of action of K+ in adipose tissue in increasing synthesis of glycogen cannot be explained simply by a faster inactivation of phosphorylase a. It is concluded that some undetermined effector(s) or signal could itself be a primary determinant for the greater activation of synthase observed in a K+ medium.     

Wall plasma in a wideband dielectric cherenkov maser

Results are reported of experimental investigations that have revealed the presence of a plasma in the interaction region of a model wideband relativistic microwave amplifier—a dielectric Cherenkov maser. The electrodynamic properties of a hybrid system—a waveguide with an annular dielectric liner and a plasma layer adjacent to its inner wall—are analyzed. Experiments with a high-current accelerator have revealed that the power of the emitted microwaves at the output of the system increases strongly when an external microwave source at different frequencies in the X-band is switched on. However, this effect was found to be hard to reproduce. Indirect evidence is obtained of the fact that, during the transport of an electron beam and under the action of the signal from a high-power pulsed magnetron, the plasma in the system is created at the surface of the dielectric. In the model of a cold magnetized plasma, a dispersion relation is derived for axisymmetric waves in a system with a wall plasma layer. The spectra of the waveguide and plasma modes in the system and the transverse structure of their electromagnetic fields are investigated thoroughly as functions of the plasma density and layer thickness. It is shown that even a very thin layer of a high-density plasma results in a large frequency shift of the dispersion curve of the waveguide mode, in which case the coupling impedance at a fixed frequency decreases sharply. On the other hand, a layer of a moderately dense plasma increases the coupling impedance for the waveguide mode. It is established that, in a configuration with a wall plasma layer, the longitudinal component of the electric field of a plasma mode whose power flux in the dielectric is of a volumetric nature reverses direction across the layer.     

Molecular cloning and expression of the col2a1a and col2a1b genes in the medaka, Oryzias latipes

The Col2a1 gene is expressed in notochord, otic vesicle, cartilaginous tissue and the anlage of endochondral bone during development in higher vertebrates. Type II collagen, a homotrimeric product of the Col2a1 gene, functions as a key regulatory protein for cartilage development and endochondral ossification. In medaka and zebrafish, a single homolog of the col2a1 gene has been identified. However, it is necessary to note that many genes are duplicated in teleost fishes. To clarify function of col2a1 genes in teleost fishes and to further understand the process of cartilage development and endochondral ossification, we cloned and mapped the gene loci of two col2a1 orthologs in medaka. The proteins encoded by both medaka col2a1a and col2a1b genes were highly conserved (85.3% and 82.6%) relative to human COL2A1, but synteny was not observed. We also examined the expression patterns of col2a1a and col2a1b during embryonic development. Whole-mount insitu hybridization data suggests that expression patterns of both medaka co2a1a and col2a1b genes are similar to that of zebrafish co2a1 in the early embryonic stages. In medaka, the two col2a1 genes show a closely correlated pattern of spatial and temporal expression. In late embryonic stages, however, there were differences in both expression patterns in the pectoral fin. This study is the first report of two homologs of col2a1 in teleosts and also the first examination of col2a1a and col2a1b expression patterns in this group.     

MiR-34a inhibits the proliferation,migration, and invasion of oral squamous cell carcinoma by directly targeting SATB2

In various kinds of carcinomas, the special AT-rich sequence-binding protein 2 (SATB2) with its atypical expression promotes the metastasis and progression of the tumor, though in the oral squamous cell carcinoma (OSCC) its inherent mechanism and the status of SATB2 remain unclear. The role played by the SATB2 expression in the OSCC cell lines and tissue samples in the target of miR-34a downstream is the intended endeavor of this study. In te OSCCs the miR-34a expression was determined by quantitative real-time polymerase chain reaction (q-PCR), while the SATB2 expression in the cell lines and tissue samples in OSCC was analyzed with the q-PCR and the western blot. Studies in both in vitro and in vivo of the effects of miR-34a on the initiation of OSCC were conducted. As a direct target of the miR-34a the SATB2 was verified with the luciferase reporter assay. In cases where the miR-34a levels were low, the SATB2 in OSCCs seemed to be overexpressed. Besides, both in the in vitro and in vivo a suppression of migration, invasion, and cell growth was caused by miR-34a by down regulating the SATB2 expression. The SATB2 being a direct target of miR-34a was confirmed by the cotransfection of miR-34a mimics specifically the decrease in the expression of luciferase of SATB2–3′UTR-wt reporter. As a whole, our study confirmed the inhibition of miR-34a in the invasion, proliferation, and migration of the OSCCs, playing a potential tumor suppressor role with SATB2 as its downstream target.     

Lentivirus-mediated overexpression of microRNA-199a inhibits cell proliferation of human hepatocellular carcinoma

microRNA-199a (miR-199a) is a highly conserved miRNA, always deregulated in numerous human tumors. The results of microarray analysis indicated that miR-199a was frequently downregulated in hepatocellular carcinoma (HCC). The expression levels of miR-199a in 11 pairs of matched HCC neoplastic and adjacent non-neoplastic tissues, 5 HCC cell lines and liver cell line L02 were examined by quantitative real-time PCR analysis. We found miR-199a was significantly down-regulated in HCC tissues when compared with pair-matched adjacent non-tumor tissues. We also found the expression level of miR-199a was also substantially decreased in several human HCC cell lines including SMMC-7721, BEL-7402, BEL-7701, MHCC97H, and HepG2. To investigate the role of miR-199a in tumorigenesis, we developed a lentiviral vector for the expression of pre-miR-199a (Lenti-miR-199a). Lenti-miR-199a inhibited HCC cell proliferation in vitro and in vivo. Compared to parental cells or cells transfected with a control vector, the overexpression of microRNA-199a in the HCC cell lines HepG2 stably was showed to reduce cell proliferation in vitro and in vivo. Luciferase reporter assay revealed the regulation of miR-199a on 3’-UTR of HIF-1α. Further investigation confirmed that miR-199a significantly reduced the endogenous protein level of HIF-1α in hypoxia. MiR-199a inhibits cell proliferation in vitro and in vivo partly through down-regulation of HIF-1α in human HCC. Thus, these studies provide an important new insight into the pathogenesis of human HCC and it may open a new perspective for the development of effective gene therapy for human HCC.     

Is there a weak H‐bond → LBHB transition on tetrahedral complex formation in serine proteases?

The transformation of a weak hydrogen bond in the free enzyme into a low-barrier hydrogen bond (LBHB) in the tetrahedral intermediate has been suggested as an important factor facilitating catalysis in serine proteases. In this work, we examine the structure of the H-bond in the Asp102-His57 diad of serine proteases in the free enzyme and in a covalent tetrahedral complex (TC) with a trifluoromethylketone inhibitor. We apply ab initio quantum mechanical calculations to models consisting of a large molecular fragment of the enzyme active site, and the combined effect of the rest of the protein body and the solvation by surrounding bulk water was simulated by a self-consistent reaction field method in our novel QM/SCRF(VS) approach. Potential profiles of adiabatic proton transfer in the Asp102-His57 diad in these model systems were calculated. We conclude that the hydrogen bond in both the free enzyme and in the enzyme-inhibitor TC is a strong ionic asymmetric one-well hydrogen bond, in contrast to a previous suggestion that it is a weak H-bond in the former and a double-well LBHB in the latter.     

Role of calcium in secretion of chorionic gonadotropin by first trimester human placenta.

The role of calcium in regulation of secretion of human chorionic gonadotropin (hCG) by first trimester human placental minces in vitro has been investigated. Depletion of calcium in the medium by addition of EGTA resulted in a drastic decrease in the levels of immunoreactive hCG in the medium with consequent of accumulation of hCG in the tissue. Addition of A 23187 which is a calcium ionophore resulted in a dose dose dependent increase in the hCG in the medium and this stimulatory response could not be observed in the absence of calcium. Use of lanthanum (a calcium antagonist) in place of calcium in the medium used resulted in a significant decrease in the levels of hCG in the medium. Addition of veratridine (a sodium channel activator) stimulated hCG secretion in a dose dependent manner. These results suggest that calcium is essential for normal secretion of hCG by human placenta.     

Properties of polyglutamine expansion in vitro and in a cellular model for Huntington's disease.

Eight neurodegenerative diseases have been shown to be caused by the expansion of a polyglutamine stretch in specific target proteins that lead to a gain in toxic property. Most of these diseases have some features in common. A pathological threshold of 35-40 glutamine residues is observed in five of the diseases. The mutated proteins (or a polyglutamine-containing subfragment) form ubiquitinated aggregates in neurons of patients or mouse models, in most cases within the nucleus. We summarize the properties of a monoclonal antibody that recognizes specifically, in a Western blot, polyglutamine stretches longer than 35 glutamine residues with an affinity that increases with polyglutamine length. This indicates that the pathological threshold observed in five diseases corresponds to a conformational change creating a pathological epitope, most probably involved in the aggregation property of the carrier protein. We also show that a fragment of a normal protein carrying 38 glutamine residues is able to aggregate into regular fibrils in vitro. Finally, we present a cellular model in which the induced expression of a mutated full-length huntingtin protein leads to the formation of nuclear inclusions that share many characteristics with those observed in patients: those inclusions are ubiquitinated and contain only an N-terminal fragment of huntingtin. This model should thus be useful in studying a processing step that is likely to be important in the pathogenicity of mutated huntingtin.     

Ewens' sampling formula and related formulae: combinatorial proofs, extensions to variable population size and applications to ages of alleles

Ewens' sampling formula, the probability distribution of a configuration of alleles in a sample of genes under the infinitely-many-alleles model of mutation, is proved by a direct combinatorial argument. The distribution is extended to a model where the population size may vary back in time. The distribution of age-ordered frequencies in the population is also derived in the model, extending the GEM distribution of age-ordered frequencies in a model with a constant-sized population. The genealogy of a rare allele is studied using a combinatorial approach. A connection is explored between the distribution of age-ordered frequencies and ladder indices and heights in a sequence of random variables. In a sample of n genes the connection is with ladder heights and indices in a sequence of draws from an urn containing balls labelled 1,2,...,n; and in the population the connection is with ladder heights and indices in a sequence of independent uniform random variables.     

Dynamics of Scroll Wave in a Three-Dimensional System with Changing Gradient

The dynamics of a scroll wave in an excitable medium with gradient excitability is studied in detail. Three parameter regimes can be distinguished by the degree of gradient. For a small gradient, the system reaches a simple rotating synchronization. In this regime, the rigid rotating velocity of spiral waves is maximal in the layers with the highest filament twist. As the excitability gradient increases, the scroll wave evolutes into a meandering synchronous state. This transition is accompanied by a variation in twisting rate. Filament twisting may prevent the breakup of spiral waves in the bottom layers with a low excitability with which a spiral breaks in a 2D medium. When the gradient is large enough, the twisted filament breaks up, which results in a semi-turbulent state where the lower part is turbulent while the upper part contains a scroll wave with a low twisting filament.     

Female-induced sexual arousal in male mice and rats: behavioral and testosterone response

Exposure of a male mouse to a female mouse separated from it by a holed partition induced specific behavior and an increase in blood testosterone in the male. The male made more approaches to the partition and spent more time at it. The time spent by the male mouse over the first 10 min at the partition, behind which an estrus female was placed, was increased sixfold compared to the time spent by a male mouse exposed to the vacant neighboring compartment; and 1.5-fold compared to that spent by a male mouse exposed to a nonreceptive female or a male. Increased blood testosterone level was detected at 20 min of exposure to a receptive female in winter and at 40 min in summer. No variation in blood testosterone levels in the male mouse exposed to a nonreceptive female or a male was observed. Similar response to a receptive female placed in the neighboring compartment was shown in a male rat. The time spent by the male rat at the partition was 12 times higher when there was an estrus female behind it than in control. Blood testosterone in the male rat increased in response to a female rat and did not change in response to a male rat indicating female-induced motivation. It was concluded that the partition time might serve as a quantitative measure of sexual motivation in the males and that the model of female-induced sexual arousal used was suitable for studying both motivational and hormonal components of sexual arousal in male mice and rats.     

Temperature-induced phase transitions in proteins and lipids. Volume and heat capacity effects

The partial specific heat capacity and volume of globular proteins and dispersions of phosphatidylcholines in aqueous solutions have been determined over a broad temperature range using a precise scanning microcalorimeter and a vibrational densimeter. It is shown that the temperature-induced, gel-to-liquid crystalline phase transition in phosphatidylcholines proceeds without a noticeable change in heat capacity but with a significant increase in the specific volume, whereas heat denaturation in proteins takes place without a noticeable change in the volume but with a significant increase in heat capacity. This principal difference between temperature-induced conformational phase transitions in proteins and lipids demonstrates clearly that heat denaturation of proteins, in contrast to the gel-to-liquid crystalline phase transition in lipids, cannot be regarded as a process similar to melting. Consequently, the 'molten globule' does not appear to be a suitable model for a heat-denatured protein.