Transmission of Megatrypanum Trypanosomes to Cervus dama by Tabanidae1

Four fallow deer, Cervus dama, became infected with Trypanosoma (Megatrypanum) sp. by oral application of triturated guts from tabanids collected in an area with deer but without any cattle; four control calves remained negative. Upon challenge with triturated guts from tabanids from an area with pastured cattle, the four calves became infected with Trypanosoma (M.) theileri. The prepatent period in deer was five days or less. Haematopota spp. and Tabanus spp. were identified as vectors of the deer trypanosomes. It is concluded that the trypanosomes of C. dama belong to a Megatrypanum species that is not identical with T. theileri.     

Physical mapping of three fruit ripening genes：Endopolygalacturonase,ACC oxidase and ACC synthase from apple（Malus x domestica） in an apple rootstock A106（Malus sieboldii

The apple rootstock,A106(Malus sieboldii),had 17 bivalents in pollen mother cells at meiotic metaphase 1,and 17 chromosomes in a haploid pollen cell.Karyotypes were prepared from root-tip cells with 2n=34 chromosomes,Seven out of 82 karyotypes(8.5%) showed one pari of satellites at the end of the short arm of chromosome 3.C-bands were shown on 6 pairs of chromosomes 2,4,6,8,14,and 16 near the telomeric regions of short arms.Probes for three ripening-related genes from Malus x domestica:endopolygalacturonase(EPG,0.6kb),ACC oxidase(1.2kb),and ACC synthase(2kb)were hybridized in situ to metaphase chromosomes of A106.Hybridization sites for the EPG gene were observed on the long arm of chromosome 14 in 15 out of 16 replicate spreads and proximal to the centromere of chromosomes 6 and 11.For the ACC oxidase gene,hylridization sites were observed in the telomeric region of the short arm of chromosomes 5 and 11 in 87% and 81% of 16 spreads respectively,proxiaml to the centromere of chromosome 1 in 81% of the spreads,and on the long arm of chromosome 13 in 50% of the spreads. Physical mapping of three fruit ripening genes in an apple rootstock A106.Twenty five spreads were studied for the ACC synthase gene and hybridization sites were observed in the telomeric region of the short arm of chromosome 12 in 96% of the spreads.chromosomes 9 and 10 in 76% of the spreads,and chromosome 17 in 56% of the spreads.     

The cytokineplast: purified, stable, and functional motile machinery from human blood polymorphonuclear leukocytes

We examined the formation of motile, chemotactically active, anucleate fragments from human blood polymorphonuclear leukocytes (PMN, granulocytes), induced by the brief application of heat. These granule-poor fragments are former protopods (leading fronts, lamellipodia) that become uncoupled from the main body of the cell and leave it, at first with a connecting filament that breaks and seals itself. The usual random orientation of such filaments can be controlled by preorientation of cells in a gradient of the chemotactic peptide, N-formylmethionylleucylphenylalanine (F-Met-Leu-Phe) (2x10(-9) M- 1x10(-8)). Cytochalsin B, 2.5-5 μg/ml, prevents fragment formation; colchicine, 10(-5) M, does not. In scanning electron micrographs, fragments are ruffled and the cell body rounded up and rather smooth. In transmission electron micrographs, fragments contain microfilaments but lack centrioles and microtubules. Like intact cells, both bound and free fragments can respond chemotactically to an erythrocyte destroyed by laser microirradiation (necrotaxis); the free, anucleate fragments may do so repeatedly, even after having been held overnight at ambient temperatures. We propse the name cytokineplast for the result of this self-purification of motile apparatus. The exodus of the motile machinery from the granulocyte requires anchoring of the bulk of the cell to glass and uncoupling, which may involve heat-induced dysfunction of the centrosome. In ultrastructural studies of the centrosomal region after heat, centriolar structure remains intact, but pericentriolar osmiophilic material appears condensed, and microtubules are sparse. These changes are found in all three blood cell types examined: PMN, eosinophil, and monocyte. Of these, the first two make fragments under our conditions; the more sluggish monocyte does not. Uncoupling is further linked to centrosomal dysfunction by the observation that colchicines-treated granulocytes (10(-5)M, to destroy the centrosome’s efferent arm) make fragments after less heat than controls. If motive force and orientation are specified mainly from the organelle-excluding leading front, then endoplasmic streaming in PMN is a catch-up phenomenon, and microtubules do not provide the vector of locomotion but rather stabilize and orient the “baggage” (nucleus, granuloplasm)—i.e., they prevent fishtailing. Moreover, constraints emanating from the centrosome may now be extended to include, maintenance of the motile machinery as an integral part of the cell.     

The Effect of Hemodynamic Remodeling on the Survival of Arterialized Venous Flaps

Objective

To evaluate the effect of hemodynamic remodeling on the survival status of the arterialized venous flaps (AVFs) and investigate the mechanism of this procedure.

Materials and Methods

Two 7 x 9 cm skin flaps in each rabbit (n=36) were designed symmetrically in the abdomen. The thoracoepigastric pedicle and one femoral artery were used as vascular sources. Four groups were included: Composite skin grafts group and arterial perfusion group were designed in one rabbit; AVF group and hemodynamic remodeling group by ligation of the thoracoepigastric vein in the middle were outlined in another rabbit. Flap viability, status of vascular perfusion and microvasculature, levels of epidermal metabolite and water content in each group were assessed.

Results

Highly congested veins and simple trunk veins were found using angiography in the AVF group; while a fairly uniform staining and plenty of small vessels were observed in the hemodynamic remodeling group. The metabolite levels of the remodeling group are comparable with those in the arterial perfusion group. There was no statistically significant difference in the percentage of flap survival between the arterial perfusion group and hemodynamic remodeling group; however, significant difference was seen between the AVF group and the hemodynamic remodeling group.

Conclusions

Under the integrated perfusion mode, the AVFs are in an over-perfusion and non-physiological hemodynamic state, resulting in unreliability and unpredictability in flap survival; under the separated perfusion mode produced by remodeling, a physiological-like circulation will be created and therefore, better flap survival can be expected.     

In vitro evaluation of native entomopathogenic fungi and neem (Azadiractha indica) extracts on Spodoptera frugiperda

The control of Spodoptera frugiperda is based on synthetic insecticides, so some alternatives are the use of entomopathogenic fungi (EF) and neem extract. The objective of the study was to evaluate in vitro effectiveness of native EF and neem extracts on S. frugiperda larvae. Six EF were identified by DNA sequencing of ITS regions from three EF (Fusarium solani, Metarrhizium robertsii, Nigrospora spherica and Penicillium citrinum). They were evaluated in concentrations of 1 × 10⁸ spores/ mL. In addition, a second bioassay was carried out evaluating only F. solani, M. robertsii and N. sphaerica and the addition of vegetable oil. On the other hand, extraction of secondary metabolites from neem seed (Azadirachta indica) was carried out by performing, mass (g) and solvent volume (mL ethanol and water) combinations, which were subjected to microwaves and ultrasound. Subsequently, these extracts were evaluated in concentrations of 3%, 4% and 5%. A survival analysis was performed for each of the bioassays. With respect to the results of the first bioassay, F. solani obtained a probability of survival of 0.476 on the seventh day, while in the second bioassay, M. robertsii obtained 0.488 survival probability. This suggests that the expected percentage of larvae that stay alive on the sixth day is 48.8%. However, in the evaluation of the neem extract the combination 1:12/70% to 4% caused 84% mortality of larvae. The use of native HE and neem extracts has potential for the control of S. frugiperda.     

Resolution of Holliday junction substrates by human topoisomerase I

Prompted by the close relationship between tyrosine recombinases and type IB topoisomerases we have investigated the ability of human topoisomerase I to resolve the typical intermediate of recombinase catalysis, the Holliday junction. We demonstrate that human topoisomerase I catalyzes unidirectional resolution of a synthetic Holliday junction substrate containing two preferred cleavage sites surrounded by DNA sequences supporting branch migration. Deleting part of the N-terminal domain (amino acid residues 1-202) did not affect topoisomerase I resolution activity, whereas a topoisomerase I variant lacking both the N-terminal domain and amino acid residues 660-688 of the linker domain was unable to resolve the Holliday junction substrate. The inability of the double deleted variant to mediate resolution correlated with the inability of this enzyme to introduce concomitant cleavage at the two preferred cleavage sites in a single Holliday junction substrate, which is a prerequisite for resolution. As determined by the gel electrophoretic mobility of native enzyme or enzyme crosslinked by disulfide bridging, the double deleted mutant existed almost entirely in a dimeric form. The impairment of this enzyme in performing double cleavages on the Holliday junction substrate may be explained by only one cleavage competent active site being formed at a time within the dimer. The assembly of only one active site within dimers is a well-known characteristic of the tyrosine recombinases. Hence, the obtained results may suggest a recombinase-like active site assembly of the double deleted topoisomerase I variant. Taken together the presented results consolidate the relationship between type IB topoisomerases and tyrosine recombinases.     

Post‐dispersal seed predation and its relations with seed traits: a thirty‐species‐comparative study

Post‐dispersal seed predation is a key process determining the variability in seed survival in forests, where most seeds are handled by rodents. Seed predation is thought to affect seedling regeneration, colonization ability and spatial distribution of plants. Basic seed traits are the essential factors affecting rodent foraging preferences and thus seed survival and seedling recruitment. Many studies have discussed several seed traits and their effects upon seed predation by rodents. However, the results of those previous studies are usually equivocal, likely because few seed traits and/or plant species tend to be incorporated into these studies. In order to elucidate the relationships between seed predation and seed traits, we surveyed the predation of 48 600 seeds in a natural pine forest, belonging to 30 species, for three consecutive years. The results demonstrated that: (i) seed size and seed coat hardness did not significantly affect seed predation; (ii) total phenolics had a negative effect upon seed predation; (iii) positive effects of nitrogen content upon seed predation were found. From our study, it seems that the better strategy to prevent heavy predation is for plants to produce seeds with higher total phenolics content rather than physical defenses (i.e. hard seed coat) or larger seeds. Additionally, rodent foraging preference may depend more on Nitrogen content than other nutrient content of seeds.     

Intersubunit bridge formation governs agonist efficacy at nicotinic acetylcholine α4β2 receptors: unique role of halogen bonding revealed

The α4β2 subtype of the nicotinic acetylcholine receptor has been pursued as a drug target for treatment of psychiatric and neurodegenerative disorders and smoking cessation aids for decades. Still, a thorough understanding of structure-function relationships of α4β2 agonists is lacking. Using binding experiments, electrophysiology and x-ray crystallography we have investigated a consecutive series of five prototypical pyridine-containing agonists derived from 1-(pyridin-3-yl)-1,4-diazepane. A correlation between binding affinities at α4β2 and the acetylcholine-binding protein from Lymnaea stagnalis (Ls-AChBP) confirms Ls-AChBP as structural surrogate for α4β2 receptors. Crystal structures of five agonists with efficacies at α4β2 from 21-76% were determined in complex with Ls-AChBP. No variation in closure of loop C is observed despite large efficacy variations. Instead, the efficacy of a compound appears tightly coupled to its ability to form a strong intersubunit bridge linking the primary and complementary binding interfaces. For the tested agonists, a specific halogen bond was observed to play a large role in establishing such strong intersubunit anchoring.     

哀牢山常绿阔叶林水源涵养功能及其在应对西南干旱中的作用

为了解云南哀牢山中山湿性常绿阔叶林在2010年初西南地区特大干旱中是否遭遇水分胁迫,及其水源涵养功能在应对干旱中的作用,测定了该森林土壤和主要树种在2010年旱季的水分状况,并对比研究了原生林和森林经砍伐烧垦后形成的毛蕨菜-玉山竹群丛的土壤持水、凋落物持水、水面蒸发和土壤水分季节动态。结果表明:常绿阔叶林主要树种在2010年初西南特大干旱中并未遭受水分胁迫(最旱月叶片凌晨水势高于-0.4 MPa)。虽然常绿阔叶林土壤含水量和地下水位在最旱月都达到了有观测以来的最低点,但主要根系分布区的土壤水势仍不低于-0.5 MPa,并高于毛蕨菜-玉山竹群丛。森林较好的水分状况和原生常绿阔叶林较好的水源涵养功能有关。常绿阔叶林的土壤总持水量尤其是非毛管持水量要显著大于毛蕨菜-玉山竹群丛,同时也大于云南地区的一些次生林和人工林。常绿阔叶林地表丰富的凋落物通过持水和抑制土壤蒸发也对水源涵养有一定作用。哀牢山常绿阔叶林良好的水源涵养功能,充足的土壤地下水储存弥补了旱季和特大干旱中降水的不足。结果指示原生林在水源涵养中不可替代的作用,以及加强原生林保护在提高区域抗干旱能力中的重要意义。