A recombinant foot-and-mouth disease virus antigen inhibits DNA replication and triggers the SOS response in Escherichia coli

Abstract The 3D gene of foot-and-mouth disease virus encodes the viral RNA dependent RNA polymerase, also called virus infection associated (VIA) antigen, which is the most important serological marker of virus infection. This 3D gene from a serotype Cl virus has been cloned and overexpressed in Escherichia coli under the control of the strong lambda lytic promoters. The resulting 51 kDa recombinant protein has been shown to be immunoreactive with sera from infected animals. After induction of gene expression, an immediate and dramatic arrest of cell DNA synthesis occurs, similar to that produced by genotoxic doses of the drug mitomycin C. This effect does not occur during the production of either a truncated VIA antigen or other related and non-related viral proteins. The inhibition of DNA replication results in a subsequent induction of the host SOS DNA-repair response and in an increase of the mutation frequency in the surviving cells.     

Molecular basis of the Keap1–Nrf2 system

Nrf2 (NF-E2-related factor 2) is a master regulator of cellular responses against environmental stresses. Nrf2 induces the expression of detoxification and antioxidant enzymes, and Keap1 (Kelch-like ECH-associated protein 1), an adaptor subunit of Cullin 3-based E3 ubiquitin ligase, regulates Nrf2 activity. Keap1 also acts as a sensor for oxidative and electrophilic stresses. Keap1 retains multiple sensor cysteine residues that detect various stress stimuli. Increasing attention has been paid to the roles that Nrf2 plays in the protection of our bodies against drug toxicity and stress-induced diseases. On the other hand, Nrf2 is found to promote both oncogenesis and cancer cell resistance against chemotherapeutic drugs. Thus, although Nrf2 acts to protect our body from deleterious stresses, cancer cells hijack the Nrf2 activity to support their malignant growth. Nrf2 has emerged as a new therapeutic target, and both inducers and inhibitors of Nrf2 are awaited. Studies challenging the molecular basis of the Keap1–Nrf2 system functions are now critically important to improve translational studies of the system. Indeed, recent studies identified cross talk between Nrf2 and other signaling pathways, which provides new insights into the mechanisms by which the Keap1–Nrf2 system serves as a potent regulator of our health and disease.     

Satiation and the functional response: a test of a new model

Abstract. 1. A model of the functional response to prey density is derived to include the reduction in time available for search, T_s , resulting from predator satiation.
2. For larger prey items predator satiation occurs at each prey capture and T_s is reduced by the attack time and digestive pause of a series of attack cycles. For small prey items predator foraging is continuous at low densities with T_s reduced solely by attack time. At higher densities predator satiation occurs after the capture of several small prey items and T_s is reduced by the attack time and digestive pause of a series of foraging cycles.
3. A comparison of the predicted asymptotic level of prey capture using experimentally estimated parameter values, with the maximum consumption of aphids by larval and adult coccinellids provides a test of the satiation model.
4. The limitation of prey capture by predator satiation is discussed with reference to handling time and the success of coccinellids in biological control.     

Infection of the gonads of Glaucosoma hebvaicum by the nematode Philometva lateolabracis: occurrence and host response

The prevalence of infection of the West Australian dhufish Glaucosoma hebraicum off the lower west coast of Australia by Philometra lateolabracis was greater among females than males, which contrasts with the situation with Pagrus auratus in waters off New Zealand. Live P. lateolabracis were represented solely by females and were found only in the gonads of fish of mature size ( L ₅₀ at first maturity = c . 300 mm) caught between December and April and thus during the spawning period of dhufish. Since the gonads were largest during that period, they, and particularly ovaries, would provide an abundant food source in the form of blood. The prevalence of the parasite (live + dead individuals) increased with host body size to reach a maximum of c . 80% in the 700–799 mm length class of females and c . 50% in the largest length class of males. During the spawning period of G hebraicum, P. lateolabracis developed from small, non-gravid females to large gravid females, representing an increase in mass of more than 200 times. The maximum length of P. lateolabracis (470 mm) in G hebraicum is the greatest yet recorded for this species. Gonadosomatic indices provided no evidence that infection by P. lateolabracis leads to a conspicuous atrophy of the ovaries, which contrasts with the situation with the gonads of some of the teleosts infected by Philometra species, and presumably reflects, in part, the small volume of the ovary occupied by P. lateolabracis (c . 3%) and the low intensity of infection (mean = 2.0, maximum = 7). Although the presence of live P. lateolabracis did not stimulate an obvious tissue response by the ovaries during the spawning period of G. hebraicum , both the dead and any live parasites that remain after spawning become encapsulated in fibrous tissue.     

Describing Ordinal Odds Ratios for Stratified r × c Tables

For an r × ctable with ordinal responses, odds ratios are commonly used to describe the relationship between the row and column variables. This article shows two types of ordinal odds ratios where local‐global odds ratios are used to compare several groups on a c‐category ordinal response and a global odds ratio is used to measure the global association between a pair of ordinal responses. When there is a stratification factor, we consider Mantel‐Haenszel (MH) type estimators of these odds ratios to summarize the association from several strata. Like the ordinary MH estimator of the common odds ratio for several 2 × 2 contingency tables, the estimators are used when the association is not expected to vary drastically among the strata. Also, the estimators are consistent under the ordinary asymptotic framework in which the number of strata is fixed and also under sparse asymptotics in which the number of strata grows with the sample size. Compared to the maximum likelihood estimators, simulations find that the MH type estimators perform better especially when each stratum has few observations. This article provides variances and covariances formulae for the local‐global odds ratios estimators and applies the bootstrap method to obtain a standard error for the global odds ratio estimator. At the end, we discuss possible ways of testing the homogeneity assumption.     

Gene expression in Brassica campestris showing a hypersensitive response to the incompatible pathogen Xanthomonas campestris pv. vitians

Xanthomonas campestris pv. vitians, a pathogen of lettuce, elicits a hypersensitive response within 12 hours of inoculation into Brassica leaves, characterized by tissue collapse, loss of membrane integrity, vein blockage and melanin production. In contrast, the compatible pathogen, X. c. pv. campestris, has no visible effects on leaves for 48 hours, after which inoculated areas show chlorosis which eventually spreads, followed by rotting.mRNA was prepared from leaves inoculated with suspensions of both pathovars or with sterile medium up to 24 hours following inoculation. In vitro translation of total and poly A⁺ RNA in rabbit reticulocyte lysate in the presence of ³⁵S methionine followed by separation of the polypeptide products by 2D-PAGE, allowed comparison of the effects of these treatments on plant gene expression. Major changes in gene expression were observed as a consequence of the inoculation technique. In addition, after inoculation with X. c. vitians, up to fifteen additional major polypeptides appeared or greatly increased by four hours. Some of these had disappeared by nine hours and several more had appeared. No major polypeptides disappeared or decreased greatly in intensity following inoculation with X. c. vitians.     

The establishment,growth, phenology and longevity of two species of Helianthemum in the Negev Desert Highlands,Israel

Summary The hills of the Negev highlands, west of Sede Boqer, are typically covered by various half-shrub communities, including the deciduous species of Helianthemum vesicarium Boiss., an Irano-Turanian element that grows only on north facing slopes, and H. ventosum Boiss., a Saharo-Arabian element which grows on both slopes but mainly on those facing south. Upon irrigation, plants of H. vesicarium preserve their natural rhythm of activity during winter and remain deciduous throughout the summer. On the other hand, under a similar irrigation treatment, the growth and flowering season of H. ventosum is modified and is extended well into the summer. Thus, H. ventosum shows a high phenological plasticity, while H. vesicarium seems to be very conservative. The different response of the two species to an improved water regime may partly explain the differences in their natural habitats: H. vesicarium on the more humid north facing slopes and H. ventosum mostly on the more arid and extreme south facing ones. Plants of both species which grow near boulders attain larger sizes and denser stands than those on the slopes.Age analysis based on xylem ring counts of 859 plants of the two natural populations showed that the plants did not exceed 14 years and most of them reached the age of some 5 years only. In general more seedlings are established during rainy year-clusters than during dry ones. However, no direct correlation between seedling establishment and the annual rainfall of specific years could be found.The rapid turnover of plants in the stands of both species of Helianthemum resembles the behavior of desert annuals rather than that of most desert shrubs.     

The Chlamydomonas cell cycle is regulated by a light/dark-responsive cell-cycle switch

Cultures of the unicellular green alga Chlamydomonas reinhardii can be synchronized by light/dark cycling not only under photoautotrophic but also under mixotrophic growth conditions. We observed that cultures synchronized in the presence of acetate continue to divide synchronously for one cell-cycle period when transferred to heterotrophic growth conditions. This finding enabled us to investigate the differential effects of light on cell growth and cell division. When cells were exposed to continuous light at the beginning of the growth period they entered the division phase earlier than dark-grown cells as a consequence of an increased growth rate. Illumination at the end of the growth period, however, caused a considerable delay in cell division and an extended growth period. The light-induced delay in cell division was also observed in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), an inhibitor of photosystem II. This finding demonstrates that cell division is directly influenced by a light/dard-responsive cell-cycle switch rather than by light/dark-dependent changes in energy metabolism. The importance of this light/dark control to the regulation of the Chlamydomonas cell cycle was investigated in comparison with other control mechanisms (size control, time control). We found that the light/dard-responsive cell-cycle switch regulates the transition from G1-to S-phase. This control mechanism is effective in cells which have attained the commitment to at least one round of DNA replication and division but have not attained the maximal cell mass which initiates cell division in the light.Abbreviations dCTP deoxycytidine 5-triphosphate - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea     

Cladocera in space and time: Analysis of lake sediments

Shells of Bosminidae and Chydoridae are quantitatively preserved in lake sediments. The chronological deposition of these remains provides the means for longterm observation of these Cladocera, both in terms of species and communities. Chydorid analysis, as based on subfossil assemblages, is an analysis of community and provides direct observation of community dynamics over extended periods of time. It has proved to be a valuable method to obtain information on the influence of environmental factors and time on community characteristics. Morphological variation inBosmina (Eubosmina) has been followed for some thousand years. This is of special interest for the evaluation of taxonomic rank (species, forms) if closely related taxa have co-existed. Bosmina successions, as well as shifts in the chydorid fauna, are related to environmental change. Thus, cladoceran analysis of lake sediments provides information on the developmental history of lakes and allows observation of the effects of longterm environmental changes, such as climatic changes and eutrophication.