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     

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.     

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.     

A characteristic Mls-1a response precedes Mls-1a anergy in vivo

T cells expressing V beta 6 variable gene segments of the T cell receptor undergo blast formation and divide in mice after injection of lymphoid cells bearing minor lymphocyte-stimulating (Mls)-1a gene products. This in vivo Mls-1a response resembles in vitro Mls-1a stimulation; it is dose dependent, not MHC-class II haplotype restricted, but requires expression of functional IE gene products. The in vivo Mls-1a response is followed by a complete and specific in vivo Mls-1a anergy and a partial in vitro Mls-1a anergy. The measurement of a Mls-1a response in vivo and of the establishment of in vivo anergy to it provides a convenient method to assay Mls-1a reactivity of T cells in vivo on a cell-by-cell basis in terms of cell surface phenotype, size, and mitotic activity.     

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.     

Effect of tranexamic acid and delta-aminovaleric acid on lipoprotein(a) metabolism in transgenic mice

The assembly of lipoprotein(a) (Lp(a)) is a two-step process which involves the interaction of kringle-4 (K-IV) domains in apolipoprotein(a) (apo(a)) with Lys groups in apoB-100. Lys analogues such as tranexamic acid (TXA) or delta-aminovaleric acid (delta-AVA) proved to prevent the Lp(a) assembly in vitro. In order to study the in vivo effect of Lys analogues, transgenic apo(a) or Lp(a) mice were treated with TXA or delta-AVA and plasma levels of free and low density lipoprotein bound apo(a) were measured. In parallel experiments, McA-RH 7777 cells, stably transfected with apo(a), were also treated with these substances and apo(a) secretion was followed. Treatment of transgenic mice with Lys analogues caused a doubling of plasma Lp(a) levels, while the ratio of free:apoB-100 bound apo(a) remained unchanged. In transgenic apo(a) mice a 1. 5-fold increase in plasma apo(a) levels was noticed. TXA significantly increased Lp(a) half-life from 6 h to 8 h. Incubation of McA-RH 7777 cells with Lys analogues resulted in an up to 1. 4-fold increase in apo(a) in the medium. The amount of intracellular low molecular weight apo(a) precursor remained unchanged. We hypothesize that Lys analogues increase plasma Lp(a) levels by increasing the dissociation of cell bound apo(a) in combination with reducing Lp(a) catabolism.     

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.     

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.     

Insulin and fructose regulate malic enzyme activity by different processes

A comparison of the regulatory processes controlling hepatic malic enzyme activity following treatment of diabetic rats with insulin or with a high fructose diet demonstrated several important differences. Insulin treatment caused a 50-fold increase in activity, due to a 12-fold increase in enzyme quantity and a 4-fold increase in specific activity(units/nmol). Dietary fructose caused a 3-fold increase in enzyme activity, due to a 3-fold increase in enzyme quantity, with no change in the specific activity of the enzyme. Thus, while fructose initiated a minor increase in malic enzyme activity, insulin was more effective, causing a substantially greater increase in enzyme activity and activating a hormone specific alteration in the catalytic activity of each enzyme molecule.     

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.     

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.     

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.     

Parastrongylus (=Angiostrongylus) cantonensis now endemic in Louisiana wildlife

Parastrongylus (=Angiostrongylus) cantonensis, a lung worm of rats, was first reported in the United States in 1987, with a probable introduction by infected rats from ships docking in New Orleans, Louisiana, during the mid-1980s. Since then, it has been reported in nonhuman primates and a boy from New Orleans, and in a horse from Picayune, Mississippi, a distance of 87 km from New Orleans. Parastrongylus cantonensis infection is herein reported in a lemur (Varencia variegata rubra) from New Iberia, Louisiana, a distance of 222 km from New Orleans, and in a wood rat (Neotomafloridanus) and in 4 opossums (Didelphis virginiana) from Baton Rouge, Louisiana, a distance of 124 km from New Orleans. The potential of a great variety of gastropods serving as intermediate hosts in Louisiana may pose a threat to wildlife as well as to domesticated animals in the areas where infected Norway rats (Rattus norvegicus) are present.     

Role of eIF3a (eIF3 p170) in intestinal cell differentiation and its association with early development

Eukaryotic initiation factor 3a (eIF3a) has been suggested to play a regulatory role in mRNA translation. Decreased eIF3a expression has been observed in differentiated cells while higher levels have been observed in cancer cells. However, whether eIF3a plays any role in differentiation and development is currently unknown. Here, we investigated eIF3a expression during mouse development and its role in differentiation of colon epithelial cells. We found that eIF3a expression was higher in fetal tissues compared with postnatal ones. Its expression in intestine, stomach, and lung abruptly stopped on the 18th day in gestation but persisted in liver, kidney, and heart throughout the postnatal stage at decreased levels. Similarly, eIF3a expression in colon cancer cell lines, HT-29 and Caco-2, drastically decreased prior to differentiation. Enforced eIF3a expression inhibited while knocking it down using small interference RNA promoted Caco-2 differentiation. Thus, eIF3a may play some roles in development and differentiation and that the decreased eIF3a expression may be a pre-requisite of intestinal epithelial cell differentiation.     

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.     

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.     

microRNA-34a is tumor suppressive in brain tumors and glioma stem cells

We recently found that microRNA-34a (miR-34a) is downregulated in human glioma tumors as compared to normal brain, and that miR-34a levels in mutant-p53 gliomas were lower than in wildtype-p53 tumors. We showed that miR-34a expression in glioma and medulloblastoma cells inhibits cell proliferation, G1/S cell cycle progression, cell survival, cell migration and cell invasion, but that miR-34a expression in human astrocytes does not affect cell survival and cell cycle. We uncovered the oncogenes c-Met, Notch-1 and Notch-2 as direct targets of miR-34a that are inhibited by miR-34a transfection. We found that c-Met levels in human glioma specimens inversely correlate with miR-34a levels. We showed that c-Met and Notch partially mediate the inhibitory effects of miR-34a on cell proliferation and cell death. We also found that mir-34a expression inhibits in vivo glioma xenograft growth. We concluded that miR-34a is a potential tumor suppressor in brain tumors that acts by targeting multiple oncogenes. In this extra view, we briefly review and discuss the implications of these findings and present new data on the effects of miR-34a in glioma stem cells. The new data show that miR-34a expression inhibits various malignancy endpoints in glioma stem cells. Importantly, they also show for the first time that miR-34a expression induces glioma stem cell differentiation. Altogether, the data suggest that miR-34a is a tumor suppressor and a potential potent therapeutic agent that acts by targeting multiple oncogenic pathways in brain tumors and by inducing the differentiation of cancer stem cells.     

Brome mosaic virus RNA replication proteins 1a and 2a from a complex in vitro.

Brome mosaic virus (BMV) is a positive-strand RNA virus that encodes two RNA replication proteins, the helicaselike 1a and the polymeraselike 2a. 1a and 2a share extensive sequence similarities with proteins encoded by many other members of the alphaviruslike superfamily. While further purifying enzymatically active RNA-dependent RNA polymerase from plants infected by BMV, we observed that 1a, 2a, and the polymerase activity all cofractionated through multiple independent purification steps. Moreover, using immunoprecipitation, we found that BMV 1a and 2a proteins synthesized in rabbit reticulocyte lysates or insect cells can form a specific complex in vitro. Complex formation was more efficient when 1a and 2a were cotranslated than when they were mixed after independent synthesis. In an antibody-independent assay, in vitro-translated 1a protein was also found to bind to 2a protein fixed on a nylon membrane. A three-amino-acid insertion in 1a that blocks BMV RNA replication in vivo also blocked in vitro interaction with 2a, while another two-amino-acid insertion that renders the 1a protein temperature sensitive for RNA replication interacted in vitro with 2a at 24 degrees C but not at 32 degrees C. These results and previous genetic data suggest that the 1a-2a interaction observed in vitro is required for BMV RNA replication and may have direct implications for other members of the alphaviruslike superfamily.     

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.     

Effects of egg quality on normal fertilization and early development of the cod, Gadus morhua L

Normal cod eggs respond to insemination by a rapid cortical reaction followed by an increase in total osmolarity and a small increase in egg diameter. The chorion becomes harder, but this is a slower process reaching its maximum strength after c . 24 h. Bad eggs are characterized by a slower or incomplete cortical reaction, resulting in a slower rise in osmolarity and a softer chorion. Bad eggs rapidly lose their capacity for fertilization. In unfertilized eggs in sea water, no cortical reaction is observed. There is, however, a rise in total osmolarity and a hardening of the chorion.