The status of Haemogregarina mansoni Sambon and Seligmann from Zamenis flagelliformis Laurenti

Haemogregarina mansoni Sambon and Seligmann 1907, a parasite of the coachwhip snake (Masticophis flagellum) is redescribed on the basis of sporogonic stages obtained in the experimental vector Aedes aegypti and designated as Hepatozoon mansoni from hosts collected in north Florida. Gamonts average 14.7 x 4.7 (13-16 x 4-6) and are not recurved, with nuclei situated in the second quarter of the gamont. Erythrocyte cytoplasm is often thin, appearing partially dehemoglobinized, or contracted into a central mass with infected erythrocytes always distorted, longer, and more slender than uninfected cells. Sporogony occurred within the head and thorax of A. aegypti. Oocysts were spherical to ovoid, 144.2 x 126.1 (79-198 x 69-178), containing on average 29.2 (7-64) sporocysts. Sporocysts were spherical to ovoid, 33.1 x 29.8 (19-48 x 18-44), with 20.2 (12-32) sporozoites contained within. Experimental infection in Tantilla relicta produced gamonts that did not differ from those in M. flagellum, but dehemoglobinization and cytoplasmic contraction of the host erythrocyte did not occur, and persistent merogonic stages were not present in the tissues.     

Cytochrome bo(3) from Escherichia coli: the binding and turnover of nitric oxide

The reaction of nitric oxide (NO) with fast and reduced cytochrome bo(3)(cyt bo(3)) from Escherichia coli has been investigated. The stoichiometry of NO binding to cyt bo(3) was determined using an NO electrode in the [NO] range 1-14 microM. Under reducing conditions, the initial decrease in [NO] following the addition of cyt bo(3) corresponded to binding of 1 NO molecule per cyt bo(3) functional unit. After this "rapid" NO binding phase, there was a slow, but significant rate of NO consumption ( approximately 0.3molNOmol bo(3)(-1)min(-1)), indicating that cyt bo(3) possesses a low level of NO reductase activity. The binding of NO to fast pulsed enzyme was also investigated. The results show that in the [NO] range used (1-14 microM) both fast and pulsed oxidised cyt bo(3) bind NO with a stoichiometry of 1:1 with an observed dissociation constant of K(d)=5.6+/-0.6 microM and that NO binding was inhibited by the presence of Cl(-). The binding of nitrite to the binuclear centre causes spectral changes similar to those observed upon NO binding to fast cyt bo(3). These results are discussed in relation to the model proposed by Wilson and co-workers [FEBS Lett. 414 (1997) 281] where the binding of NO to Cu(B)(II) results in the formation of the nitrosonium (Cu(B)(I)-NO(+)) complex. NO(+) then reacts with OH(-), a Cu(B) ligand, to form nitrite, which can bind at the binuclear centre. This work suggests for the first time that the binding of NO to oxidised cyt bo(3) does result in the reduction of Cu(B).     

Stable isotope labelling in vivo as an aid to protein identification in peptide mass fingerprinting

Peptide mass fingerprinting (PMF) is a powerful technique for identification of proteins derived from in-gel digests by virtue of their matrix-assisted laser desorption/ionization-time of flight mass spectra. However, there are circumstances where the under-representation of peptides in the mass spectrum and the complexity of the source proteome mean that PMF is inadequate as an identification tool. In this paper, we show that identification is substantially enhanced by inclusion of composition data for a single amino acid. Labelling in vivo with a stable isotope labelled amino acid (in this paper, decadeuterated leucine) identifies the number of such amino acids in each digest fragment, and show a considerable gain in the ability of PMF to identify the parent protein. The method is tolerant to the extent of labelling, and as such, may be applicable to a range of single cell systems.     

Cell compartmentalisation in planctomycetes: novel types of structural organisation for the bacterial cell

The organisation of cells of the planctomycete species Pirellula marina, Isosphaera pallida, Gemmata obscuriglobus, Planctomyces maris and "Candidatus Brocadia anammoxidans" was investigated based on ultrastructure derived from thin-sections of cryosubstituted cells, freeze-fracture replicas, and in the case of Gemmata obscuriglobus and Pirellula marina, computer-aided 3-D reconstructions from serial sections of cryosubstituted cells. All planctomycete cells display a peripheral ribosome-free region, termed here the paryphoplasm, surrounding the perimeter of the cell, and an interior region including any nucleoid regions as well as ribosome-like particles, bounded by a single intracytoplasmic membrane (ICM), and termed the pirellulosome in Pirellula species. Immunogold labelling and RNase-gold cytochemistry indicates that in planctomycetes all the cell DNA is contained wholly within the interior region bounded by the ICM, and the paryphoplasm contains no DNA but at least some of the cell's RNA. The ICM in Isosphaera pallida and Planctomyces maris is invaginated such that the paryphoplasm forms a major portion of the cell interior in sections, but in other planctomycetes it remains as a peripheral zone. In the anaerobic ammonium-oxidising ("anammox" process) chemoautotroph "Candidatus Brocadia anammoxidans" the interior region bounded by ICM contains a further internal single-membrane-bounded region, the anammoxosome. In Gemmata obscuriglobus, the interior ICM-bounded region contains the nuclear body, a double-membrane-bounded region containing the cell's nucleoid and all genomic DNA in addition to some RNA. Shared features of cell compartmentalisation in different planctomycetes are consistent with the monophyletic nature of the planctomycetes as a distinct division of the Bacteria. The shared organisational plan for the planctomycete cell constitutes a new type not known in cells of other bacteria.     

Membrane type 1 matrix metalloproteinase and gelatinase A synergistically degrade type 1 collagen in a cell model

A fibrosarcoma cell line transfected with the matrix metalloproteinase MT1 MMP showed an enhanced ability to degrade 14C-labelled collagen films. As previously shown for proMMP 2 activation, TIMP 1 was an ineffective inhibitor of the process of collagenolysis whereas TIMP 2 was efficient and completely prevented collagen degradation. In the presence of the calcium ionophore, ionomycin, proteolytic processing of MT1 MMP was restricted and collagenolysis did not occur indicating that the 63 kDa form of the enzyme is not a functional collagenase. The collagenolytic activity of MT1 MMP was shown to be enhanced by the addition of proMMP 2, but TIMP 1 inhibition remained poor relative to that of TIMP 2. The study demonstrated that synergy between two non-conventional collagenases effectively degrades insoluble pericellular collagen. Due to the membrane localisation of MT1 MMP, this could potentially occur in a highly localised manner.     

Lipopolysaccharide induces Rac1-dependent reactive oxygen species formation and coordinates tumor necrosis factor-alpha secretion through IKK regulation of NF-kappa B

Reactive oxygen species (ROS) are important second messengers generated in response to many types of environmental stress. In this setting, changes in intracellular ROS can activate signal transduction pathways that influence how cells react to their environment. In sepsis, a dynamic proinflammatory cellular response to bacterial toxins (e.g. lipopolysaccharide or LPS) leads to widespread organ damage and death. The present study demonstrates for the first time that the activation of Rac1 (a GTP-binding protein), and the subsequent production of ROS, constitutes a major pathway involved in NFkappaB-mediated tumor necrosis factor-alpha (TNFalpha) secretion following LPS challenge in macrophages. Expression of a dominant negative mutant of Rac1 (N17Rac1) reduced Rac1 activation, ROS formation, NFkappaB activation, and TNFalpha secretion following LPS stimulation. In contrast, expression of a dominant active form of Rac1 (V12Rac1) mimicked these effects in the absence of LPS stimulation. IKKalpha and IKKbeta were both required downstream modulators of LPS-activated Rac1, since the expression of either of the IKK dominant mutants (IKKalphaKM or IKKbetaKA) drastically reduced NFkappaB-dependent TNFalpha secretion. Moreover, studies using CD14 blocking antibodies suggest that Rac1 induces TNFalpha secretion through a pathway independent of CD14. However, a maximum therapeutic inhibition of LPS-induced TNFalpha secretion occurred when both CD14 and Rac1 pathways were inhibited. Our results suggest that targeting both Rac1- and CD14-dependent pathways could be a useful therapeutic strategy for attenuating the proinflammatory cytokine response during the course of sepsis.     

Mycobacterium avium subspecies paratuberculosis triggers intestinal pathophysiologic changes in beige/scid mice

We investigated whether infection of beige/scid mice with Mycobacterium avium subspecies paratuberculosis can induce intestinal pathophysiologic changes. Six-week-old beige/scid mice were inoculated intraperitoneally with M. paratuberculosis, then were killed 32 weeks after inoculation when the small intestine was evaluated for physiologic and morphologic abnormalities. All infected mice developed clinical disease. The lamina propria of the intestine from infected mice was mildly infiltrated with mononuclear cells containing acid-fast bacteria, and had significantly increased villus width. In vitro physiologic studies in Ussing chambers indicated that M. paratuberculosis infection caused significant abnormalities in intestinal transport parameters. Baseline short circuit current and potential difference were abnormally high in tissues from infected, compared with control mice, indicative of increased ion secretion. Baseline conductance was significantly decreased in infected mice, suggesting that intestinal tissue from infected mice was less permeable to ions. The change in short circuit current following transmural electrical and glucose stimulation was significantly reduced in intestines from infected mice, suggesting that inflamed intestine had neural and/or epithelial cell damage. We conclude that infection of beige/scid mice with M. paratuberculosis triggers significant intestinal pathophysiologic changes consistent with chronic inflammation. These functional abnormalities may contribute to the pathogenesis of the wasting syndrome seen in bovids with paratuberculosis. This animal model provides evidence that T cell-independent mechanisms are sufficient to cause mucosal pathophysiologic changes and inflammation in response to a specific pathogen, and may be of relevance to inflammatory bowel disease in humans.     

RNA聚合酶Ⅲ启动子的结构与功能

ＲＮＡ聚合酶Ⅲ (ｐｏｌⅢ )是真核生物催化合成ｔＲＮＡ和 5ＳｒＲＮＡ及一些核小ＲＮＡ和胞质ＲＮＡ必需的酶。ＲＮＡ聚合酶Ⅲ能够识别ｔＲＮＡ基因中一些高度保守的特征性ＤＮＡ序列而启动下游ＤＮＡ的转录 ,这些序列称为ＲＮＡ聚合酶Ⅲ启动子。ＲＮＡ聚合酶Ⅲ启动子不仅广泛存在于真核细胞中ｔＲＮＡ、Ｕ6核小ＲＮＡ(ＳＮＲ6 )等的基因中 ,也是病毒催化合成一些小片段ＲＮＡ如腺病毒ＶＡＲＮＡ所必需的。ＲＮＡ聚合酶Ⅲ启动子因其能在体内外高效快速地转录某些小片段基因 ,已被人们广泛地应用于核酶和反义ＲＮＡ技术中 ,在众多的ＲＮＡ…     

The economic costs of wildlife predation on livestock in Gokwe communal land, Zimbabwe

In areas bordering wildlife reserves in Zimbabwe, agro-pastoralists suffer livestock depredation by wild carnivores. However, the economic value of these losses, and therefore the levels of compensation required has never been calculated. Between January 1993 and June 1996 in a 33-km² area of Gokwe communal land bordering the Sengwa Wildlife Research Area, 241 livestock were killed by wild carnivores. Baboons ( Papio ursinus Kerr), lions ( Panthera leo Linnaeus) and leopards ( P. pardus Linnaeus) were the most serious predators, contributing 52%, 34% and 12% of kills, respectively. Baboons only killed young goats ( Capra hircus Linnaeus) and sheep ( Ovis aries Linnaeus) by day, while lions and leopards jumped into fortified kraals at night and killed cattle ( Bos indicus Linnaeus), donkeys ( Equus asinus Linnaeus) and smallstock. In 1995, predators killed 5% of livestock holdings, double that recorded by other African studies. The annual total value of losses depended upon the degree of lion predation on the most valuable species, cattle and donkeys. The average annual loss per livestock-owning household was US$13, or 12% of each household's net annual income. Losses could be reduced by improving kraal defences against lion and leopard predation in the dry season, when attacks were most common.     

集胞藻Synechocystissp.PCC6803利用葡萄糖生长与光合能量转化的关系

用PAM叶绿素荧光仪测定了饥饿细胞、光自养细胞和混合营养细胞的叶绿素荧光 ,并对 3种类型细胞的荧光参数 :PSⅡ实际光化学效率 φⅡ和还原型质醌Q-A 进行了比较。用双重转盘磷光机测定了光自养细胞和混合营养细胞的毫秒延迟发光。根据叶绿素荧光动力学分析和毫秒延迟发光的结果及光合电子传递抑制剂 3,4_二氯苯基二甲脲 (DCMU)、二溴百里香醌 (DBMIB)对集胞藻 6 80 3(Synechocystissp .PCC 6 80 3)混合营养生长影响进行了分析 ,集胞藻 6 80 3混合营养培养的生长速率显著高于光自养培养的原因可能在于一是外源葡萄糖没有抑制反而是促进了混合营养细胞的光自养生长 ,二是呼吸基质向质醌库提供电子 ,使光合机构的能量转化加强 ,从而促进了集胞藻6 80 3细胞的利用葡萄糖的合成代谢。