Proteome analysis of Rickettsia felis highlights the expression profile of intracellular bacteria

The proteome of Rickettsia felis, an obligate intracellular bacterium responsible for spotted fever, was analyzed using two complementary proteomic approaches: 2-DE coupled with MALDI-TOF, and SDS-PAGE with nanoLC-MS/MS. This strategy allowed identification of 165 proteins and helped to answer some questions raised by the genome sequence of this bacterium. We successfully identified potential virulence factors including two putative adhesins, four proteins of the type IV secretion system, four Sca autotransporters, four components of ABC transporters, some R. felis-specific proteins, and one antitoxin of the toxin-antitoxin system. Notably, the antitoxin was the first to be identified in intracellular bacteria. Only one protein containing rickettsia palindromic repeats was found, whereas none of the split genes, transposases, or tetratricopeptide/ankyrin repeats were detectably expressed. Comparison of the protein expression profiles of R. felis and 23 other bacterial species according to functional categories showed that intracellular bacteria express more proteins related to translation, especially ribosomal proteins. However, the remaining bacteria express more proteins related to energy production and carbohydrate/amino acid metabolism. In conclusion, this study reveals R. felis virulence factor expression and highlights the unique protein expression profile of intracellular bacteria.     

The moss genes <Emphasis Type="Italic">PpSKI1</Emphasis> and <Emphasis Type="Italic">PpSKI2</Emphasis> encode nuclear SnRK1 interacting proteins with homologues in vascular plants

The yeast Snf1, animal AMPK, and plant SnRK1 protein kinases constitute a family of related proteins that have been proposed to serve as metabolic sensors of the eukaryotic cell. We have previously reported the characterization of two redundant SnRK1 encoding genes (PpSNF1a and PpSNF1b) in the moss Physcomitrella patens. Phenotypic analysis of the snf1a snf1b double knockout mutant suggested that SnRK1 is important for the plant’s ability to recognize and adapt to conditions of limited energy supply, and also suggested a possible role of SnRK1 in the control of plant development. We have now used a yeast two-hybrid system to screen for PpSnf1a interacting proteins. Two new moss genes were found, PpSKI1 and PpSKI2, which encode highly similar proteins with homologues in vascular plants. Fusions of the two encoded proteins to the green fluorescent protein localize to the nucleus. Knockout mutants for either gene have an excess of gametophores under low light conditions, and exhibit reduced gametophore stem lengths. Possible functions of the new proteins and their connection to the SnRK1 kinase are discussed.     

Neuromedin U-immunoreactivity in the nervous system of the small intestine of the pig and its coexistence with substance P and CGRP

Summary In the small intestine of the pig, neuromedin U (NMU)-immunoreactivity was mainly confined to the nerve plexus of the inner submucosal and mucosal regions. After colchicine treatment, a high number of immunoreactive nerve cell bodies was observed in the plexus submucosus internus (Meissner), whereas only a low number was found in the plexus submucosus externus (Schabadasch). The plexus myentericus as well as the aganglionic nerve meshworks in the circular and longitudinal smooth muscle layers almost completely lacked NMU-immunoreactivity. Double-labeling experiments demonstrated the occurrence of distinct NMU-containing neuron populations in the plexus submucosus internus: (1) relatively large type-II neurons revealing immunoreactivity for NMU and calcitonin gene-related peptide (CGRP) and/or substance P (SP); (2) a group of small NMU- and SP-immunoreactive neurons; (3) a relatively low number of small neurons displaying immunoreactivity for NMU but not for SP. Based on its distributional pattern, it is concluded that NMU plays an important role in the regulation and control of mucosal functions.     

Spermatogenesis in the turkey (Meleagris gallopavo): quantitative approach in immature and adult males subjected to various photoperiods

The objectives of this study were to identify and quantitate the germ cell populations of the testes in sexually mature male turkeys (Trial 1), determine the duration of meiosis based on BrdU labeling and stereological analyses (Trial 2), and examine the impact of various photoperiods on germinal and somatic cell populations in immature and adult males (Trial 3). In Trial 1, both testes within a male had similar stereological components (P>0.05) for all parameters analyzed. In Trial 2, the duration of Type-1 spermatocytes and round spermatids in turkeys lasted 4.5+/-0.5 and 2.0+/-0.5 days, respectively. In Trial 3, the short photoperiod (7L:17D) delayed testicular growth (in the stereological parameters analyzed). In contrast, the effect of a moderately short photoperiod (10.5L:13.5D) was comparable to the effect of a long (14L:10D) or increasing photoperiod (7L:17D to 14L:10D) on the stereological parameters examined. With the exception of the short photoperiod, all other photoperiods used in this study induced comparable early testicular maturation, with maximum testis weight at 29-35 weeks of age. As the males got older, there was a progressive, linear decline in testis weight through 60 weeks, at which time there were no significant differences among photoperiods. In conclusion, the duration of meiosis in the turkey was similar to that observed in the fowl and guinea-fowl. The existence of a threshold of photosensitivity to gonad stimulation in male turkeys is suggested to be between 7.0 and 10.5 h of light.     

Systemic Antibodies Can Inhibit Mouse Mammary Tumor Virus-Driven Superantigen Response in Mucosa-Associated Lymphoid Tissues

Many mucosal pathogens invade the host by initially infecting the organized mucosa-associated lymphoid tissue (o-MALT) such as Peyer’s patches or nasal cavity-associated lymphoid tissue (NALT) before spreading systemically. There is no clear demonstration that serum antibodies can prevent infections in o-MALT. We have tested this possibility by using the mouse mammary tumor virus (MMTV) as a model system. In peripheral lymph nodes or in Peyer’s patches or NALT, MMTV initially infects B lymphocytes, which as a consequence express a superantigen (SAg) activity. The SAg molecule induces the local activation of a subset of T cells within 6 days after MMTV infection. We report that similar levels of anti-SAg antibody (immunoglobulin G) in serum were potent inhibitors of the SAg-induced T-cell response both in peripheral lymph nodes and in Peyer’s patches or NALT. This result clearly demonstrates that systemic antibodies can gain access to Peyer’s patches or NALT.     

农田生态保留带中小林姬鼠的种群动态和结构

栖息地状况对小型兽类种群动态具有明显影响。在质量好,食物资源丰富,隐蔽条件优良的栖息地中小型兽类具有较高的存活率,种群繁殖时间更长,体重比较高。有关栖息地和种群动态方面国内外已有研究报道（Brown,1988;Corp et al．,1997;Quinn et al．,2003;Schnurr et al．,2004）。     

Nucleotide diversity of the <Emphasis Type="Italic">ZmPox3</Emphasis> maize peroxidase gene: Relationships between a MITE insertion in exon 2 and variation in forage maize digestibility

Background  

Polymorphisms were investigated within the ZmPox3 maize peroxidase gene, possibly involved in lignin biosynthesis because of its colocalization with a cluster of QTL related to lignin content and cell wall digestibility. The purpose of this study was to identify, on the basis of 37 maize lines chosen for their varying degrees of cell wall digestibility and representative of temperate regions germplasm, ZmPox3 haplotypes or individual polymorphisms possibly associated with digestibility.     

Synthesis and antiviral evaluation of thieno[3,4-d]pyrimidine C-nucleoside analogues of 2′,3′-dideoxy- and 2′,3′-dideoxy-2′,3′-didehydro-adenosine and -inosine

Several thieno[3,4-d]pyrimidine derivatives, including four hitherto unknown 2′,3′-dideoxy- and 2′,3′-dideoxy-2′,3′-didehydro-C-nucleoside analogues of adenosine and inosine have been synthesized. When evaluated in cell culture experiments against human immunodeficiency virus, none of the tested compounds exhibited any significant antiviral effect, while two of them showed some cytotoxicity.     

Modeling the response of a population of olfactory receptor neurons to an odorant

We modeled the firing rate of populations of olfactory receptor neurons (ORNs) responding to an odorant at different concentrations. Two cases were considered: a population of ORNs that all express the same olfactory receptor (OR), and a population that expresses many different ORs. To take into account ORN variability, we replaced single parameter values in a biophysical ORN model with values drawn from statistical distributions, chosen to correspond to experimental data. For ORNs expressing the same OR, we found that the distributions of firing frequencies are Gaussian at all concentrations, with larger mean and standard deviation at higher concentrations. For a population expressing different ORs, the distribution of firing frequencies can be described as the superposition of a Gaussian distribution and a lognormal distribution. Distributions of maximum value and dynamic range of spiking frequencies in the simulated ORN population were similar to experimental results.