Psychrophilic <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> requires <Emphasis Type="Italic">trans</Emphasis>-monounsaturated fatty acid for growth at higher temperature

A psychrophilic bacterium, Pseudomonas syringae (Lz4W) from Antarctica, was used as a model system to establish a correlation, if any, between thermal adaptation, trans-fatty acid content and membrane fluidity. In addition, attempts were made to clone and sequence the cti gene of P. syringae (Lz4W) so as to establish its characteristics with respect to the cti of other Pseudomonas spp. and also to in vitro mutagenize the cti gene so as to generate a cti null mutant. The bacterium showed increased proportion of saturated and trans-monounsaturated fatty acids when grown at 28°C compared to cells grown at 5°C, and the membrane fluidity decreased with growth temperature. In the mutant, the trans-fatty acid was not synthesized, and the membrane fluidity also decreased with growth temperature, but the decrease was not to the extent that was observed in the wild-type cells. Thus, it would appear that synthesis of trans-fatty acid and modulation of membrane fluidity to levels comparable to the wild-type cells is essential for growth at higher temperatures since the mutant exhibits growth arrest at 28°C. In fact, the cti null mutant-complemented strain of P. syringae (Lz4W-C30b) that was capable of synthesizing the trans-fatty acid was indeed capable of growth at 28°C, thus confirming the above contention. The cti gene of P. syringae (Lz4W) that was cloned and sequenced exhibited high sequence identity with the cti of other Pseudomonas spp. and exhibited all the conserved features.     

N-(1-Benzylpyrrolidin-3-yl)arylbenzamides as potent and selective human dopamine D4 antagonists

A series of N-(1-benzylpyrrolidin-3-yl)arylbenzamides 8 has been prepared, and their structure-activity relationships studied. Potent ligands selective for human D(4) (hD(4)) over hD(2) and alpha(1) have been identified. One example was determined to be an antagonist in a cAMP assay, with an IC(50) of 1500 nM.     

Structural organisation of the head-to-tail interface of a bacterial virus

In tailed icosahedral bacteriophages the connection between the 5-fold symmetric environment of the portal vertex in the capsid and the 6-fold symmetric phage tail is formed by a complex interface structure. The current study provides the detailed analysis of the assembly and structural organisation of such an interface within a phage having a long tail. The region of the interface assembled as part of the viral capsid (connector) was purified from DNA-filled capsids of the Bacillus subtilis bacteriophage SPP1. It is composed of oligomers of gp6, the SPP1 portal protein, of gp15, and of gp16. The SPP1 connector structure is formed by a mushroom-like portal protein whose cap faces the interior of the viral capsid in intact virions, an annular structure below the stem of the mushroom, and a second narrower annulus that is in direct contact with the helical tail extremity. The layered arrangement correlates to the stacking of gp6, gp15, and gp16 on top of the tail. The gp16 ring is exposed to the virion outside. During SPP1 morphogenesis, gp6 participates in the procapsid assembly reaction, an early step in the assembly pathway, while gp15 and gp16 bind to the capsid portal vertex after viral chromosome encapsidation. gp16 is processed during or after tail attachment to the connector region. The portal protein gp6 has 12-fold cyclical symmetry in the connector structure, whereas assembly-na?ve gp6 exhibits 13-fold symmetry. We propose that it is the interaction of gp6 with other viral morphogenetic proteins that drives its assembly into the 12-mer state.     

Identification by microscopically controlled comet assay of peritoneal macrophages in a mixture of peritoneal exudate for DNA strand break analysis

A simple modification of the alkaline comet assay allows the study of DNA damage in a specific cell type in a mixture of primary cells. Peritoneal macrophages from mice are selected from other peritoneal exudate cells without complex preparation and separation steps by their size and shape of the nuclei and their comets. The DNA damage can be well characterised by the manually monitored parameter 'tail length'. Complex measurement of the 'tail moment', often used for characterising DNA damage is not required, a fact which further simplifies the protocol. The distribution of tail length within one sample is symmetric and can be described by a Gaussian distribution and the mean tail length. As a first application, UV-A sensitivity of resident and stimulated macrophages was studied. The resident macrophages were more sensitive to UV-A than the stimulated ones. DNA damage repair follows the same simple monoexponential time course for both cell types. The simplicity of results, i.e., applicability of tail lengths and Gaussian statistics as well as monoexponential kinetics, suggest that microscopically controlled comet assay is well suited to study elementary processes of DNA damage induction and repair.     

Relationship between cardiac protein tyrosine phosphorylation and myofibrillogenesis during axolotl heart development

The axolotl, Ambystoma mexicanum, is a useful system for studying embryogenesis and cardiogenesis. To understand the role of protein tyrosine phosphorylation during heart development in normal and cardiac mutant axolotl embryonic hearts, we have investigated the state of protein tyrosine residues (phosphotyrosine, P-Tyr) and the relationship between P-Tyr and the development of organized sarcomeric myofibrils by using confocal microscopy, two-dimensional isoelectric focusing (IEF)/SDS-polyacrylamide gel electrophoresis (PAGE) and immunoblotting analyses. Western blot analyses of normal embryonic hearts indicate that several proteins were significantly tyrosine phosphorylated after the initial heartbeat stage (stage 35). Mutant hearts at stages 40-41 showed less tyrosine phosphorylated staining as compared to the normal group. Two-dimensional gel electrophoresis revealed that most of the proteins from mutant hearts had a lower content of phosphorylated amino acids. Confocal microscopy of stage 35 normal hearts using phosphotyrosine monoclonal antibodies demonstrated that P-Tyr staining gradually increased being localized primarily at cell-cell boundaries and cell-extracellular matrix boundaries. In contrast, mutant embryonic hearts showed a marked decrease in the level of P-Tyr staining, especially at sites of cell-cell and cell-matrix junctions. We also delivered an anti-phosphotyrosine antibody (PY 20) into normal hearts by using a liposome-mediated delivery method, which resulted in a disruption of the existing cardiac myofibrils and reduced heartbeat rates. Our results suggest that protein tyrosine phosphorylation is critical during myofibrillogenesis and embryonic heart development in axolotls.     

Establishment of asymptomatic Leishmania donovani infection in Indian langurs (Presbytis entellus) through intradermal route

Indian langurs, which were previously reported to be highly susceptible, were infected intradermally using variable numbers of promastigotes along with different doses, 1/2 pair, 5 pairs and 10 pairs respectively of salivary gland lysate (SGL). Although, all the monkeys developed mild infection and remained subclinically infected throughout the observation period, which later resolved, none of them could develop the classical disease. No marked antigen specific antibody or lymphoproliferative response was noticed throughout the experimental period. However, a late IFN-gamma response (by day 90 pi.) was demonstrated in monkeys infected with 2 x 10(6) promastigotes +10 pairs SGL. It seems that a single intradermal dose of promastigotes with or without SGLs had a vaccines like effect. Perhaps, multiple frequent inoculations, as happens in the natural situation, may be necessary for the development of full-blown disease.     

Comparison of measured and predicted residual lung volume in determining body composition of collegiate wrestlers

This investigation compared percent fat obtained via underwater weighing using measured and predicted residual lung volume (RLV) in euhydrated and hypohydrated collegiate wrestlers (N = 67). RLV was measured using O(2) rebreathing or O(2) dilution and predicted using 3 equations-Equation 1: (0.019 x height [cm]) + (0.0115 x age [years]) - 2.24; Equation 2: (0.017 x age [years]) + (0.06858 x height [in.]) - 3.477; and Equation 3: (0.0275 age [years]) + (0.0189 height [cm]) - 2.6139. Percent fat determined using RLV Equation 2 did not differ from the value obtained using measured RLV in the euhydrated (10.9 +/- 5.1 vs. 11.5 +/- 5.6% fat) or hypohydrated (10.8 +/- 5.1 vs. 12.3 +/- 5.6% fat) trials. All other percent fat values differed (p < 0.05) from the value obtained using measured RLV in euhydrated subjects. The use of RLV Equation 2 may be a practical alternative to measured RLV in determining percent fat in euhydrated and hypohydrated collegiate wrestlers.     

Regulation of siderophore production by iron Fe(III) in certain fungi and fluorescent pseudomonads

Regulation of siderophore production in response to iron concentration in the medium was examined. Threshold concentration was recorded for twenty fungi and three rhizobacterial pseudomonads. Organisms showed difference in threshold values at which they stopped siderophore elaboration. In nine fungi (3 aspergilli, 1 penicillium, N. crassa, F. dimerum and 3 mucors) siderophore production was repressed at 3 microM Fe(III). Siderophore production was repressed at 27 microM of Fe (III) in 3 aspergilli, 2 penicillia and 3 pseudomonads. Rest of the fungi had cut off values at 6, 9, 15, 21 microM of Fe(III) concentration.     

Influence of termites on the soil seed bank in an African savannah

In savannah ecosystems, termites drive key ecosystem processes, such as primary production through creation of patchiness in soil nutrients availability around their nests. In this study, we evaluated the role of termites in altering the soil seed bank size, an important ecosystem component that has often been overlooked in previous work. Data on above ground vegetation and soil seed bank samples were collected from four microhabitats, that is, the wooded mound, unwooded mound, tree sub‐canopy and the open grassland matrix in a protected game reserve in south‐central Zimbabwe. The seedling emergence method was then used to identify species present in the soil samples. One‐way analysis of variance followed by Tukey's multiple comparison tests was executed to test for significant differences in plant species richness among the four microhabitats. The results indicate that plant species richness was high on wooded termite mound but did not differ between the unwooded and the sub‐canopy microhabitats. The open grassland microhabitat had the lowest plant species richness. The influence of termites on the soil seed bank composition was also life form specific. The herb and woody life forms had significantly (α = 0.05) higher species richness in the soil seed bank at wooded and unwooded termite mounds when compared to the other two microhabitats. Overall, these results imply that termites alter the soil seed bank and the findings enhance our understanding of the significant role termites play in regulating processes in savannah ecosystem.