Adhesion of Bacillus spores and Escherichia coli cells to inert surfaces: role of surface hydrophobicity

The ability of bacterial spores and vegetative cells to adhere to inert surfaces was investigated by means of the number of adherent spores (Bacillus cereus and Bacillus subtilis spores) and Escherichia coli cells and their resistance to cleaning or rinsing procedures (adhesion strength). Six materials (glass, stainless steel, polyethylene high density (PEHD), polyamide-6, polyvinyl chloride, and Teflon) were tested. Slight differences in the number of adherent spores (less than 1 log unit) were observed between materials, but a higher number of adherent E. coli cells was found on the hydrophobic materials PEHD and Teflon. Conversely, the resistance of both B. cereus and B. subtilis spores to a cleaning procedure was significantly affected by the material. Hydrophobic materials were harder to clean. The topography parameter derived from the Abbott-Firestone curve, RVK, and, to a lesser extent, the widely used roughness parameters RA (average roughness) and Rz (maximal roughness), were related to the number of adherent cells. Lastly, the soiling level as well as the adhesion strength were shown to depend largely on the microorganism. The number of adhering B. cereus hydrophobic spores and their resistance to a cleaning procedure were found to be 10 times greater than those of the B. subtilis hydrophilic spores. Escherichia coli was loosely bound to all the materials tested, even after 24 h biofilm formation.     

Expression analysis in plant and cell suspensions of CrCKR1, a cDNA encoding a histidine kinase receptor homologue in Catharanthus roseus (L.) G. Don

A full length cDNA (CrCKR1) encoding a hybrid histidine kinase was isolated from a Catharanthus roseus cDNA library. The kinase belongs to the subfamily of cytokinin receptors represented by CRE1/AHK4/WOL in Arabidopsis thaliana. In cell suspensions, the expression of CrCKR1 is not affected by various stress and hormonal treatments but is stimulated in cells continuously exposed to cytokinin. In plants, CrCKR1 is strongly expressed only in the petals of mature flowers. These data suggest that CrCKR1 could take part in the mechanisms leading to the production of secondary metabolites in C. roseus.     

The antiangiogenic factor 16K human prolactin induces caspase-dependent apoptosis by a mechanism that requires activation of nuclear factor-kappaB

We have previously shown that the 16-kDa N-terminal fragment of human prolactin (16K hPRL) has antiangiogenic properties, including the ability to induce apoptosis in vascular endothelial cells. Here, we examined whether the nuclear factor-kappaB (NF-kappaB) signaling pathway was involved in mediating the apoptotic action of 16K hPRL in bovine adrenal cortex capillary endothelial cells. In a dose-dependent manner, treatment with 16K hPRL induced inhibitor kappaB-alpha degradation permitting translocation of NF-kappaB to the nucleus and reporter gene activation. Inhibition of NF-kappaB activation by overexpression of a nondegradable inhibitor kappaB-alpha mutant or treatment with NF-kappaB inhibitors blocked 16K hPRL-induced apoptosis. Treatment with 16K hPRL activated the initiator caspases-8 and -9 and the effector caspase-3, all of which were essential for stimulation of DNA fragmentation. This activation of the caspase cascade by 16K hPRL was also NF-kappaB dependent. These findings support the conclusion that NF-kappaB signaling plays a central role in 16K hPRL-induced apoptosis in vascular endothelial cells.     

Overexpression of Galectin-7 in Mouse Epidermis Leads to Loss of Cell Junctions and Defective Skin Repair

Background

The proteins of the galectin family are implicated in many cellular processes, including cell interactions, polarity, intracellular trafficking, and signal transduction. In human and mouse, galectin-7 is almost exclusively expressed in stratified epithelia, notably in the epidermis. Galectin-7 expression is also altered in several human tumors of epithelial origin. This study aimed at dissecting the consequences of galectin-7 overexpression on epidermis structure and functions in vivo.

Methods

We established transgenic mice specifically overexpressing galectin-7 in the basal epidermal keratinocytes and analyzed the consequences on untreated skin and after UVB irradiation or mechanical injury.

Results

The intercellular cohesion of the epidermis is impaired in transgenic animals, with gaps developing between adjacent keratinocytes, associated with loss of adherens junctions. The epidermal architecture is aberrant with perturbations in the multilayered cellular organisation of the tissue, and structural defects in the basement membrane. These transgenic animals displayed a reduced re-epithelialisation potential following superficial wound, due to a defective collective migration of keratinocytes. Finally, a single mild dose of UVB induced an abnormal apoptotic response in the transgenic epidermis.

Conclusion

These results indicate that an excess of galectin-7 leads to a destabilisation of adherens junctions associated with defects in epidermal repair. As this phenotype shares similarities with that of galectin-7 null mutant mice, we conclude that a critical level of this protein is required for maintaining proper epidermal homeostasis. This study brings new insight into the mode of action of galectins in normal and pathological situations.     

Analytical subcellular distribution of cAMP-dependent protein kinase activity in bull sperm

The distribution of the cAMP-dependent protein kinase activity in bull ejaculated sperm has been investigated. This activity proved to be mainly present in a soluble form inside the cell. Sperm fractionation into heads and flagellar fragments, using differential centrifugation or centrifugal elutriation, has shown that the particulate cAMP-dependent protein kinase activity was mainly associated with the flagellar structures. A much activity was shown to be associated with the head fraction. Some activity could also be detected in the purified plasma membrane fraction.     

The discovery of the potent aurora inhibitor MK-0457 (VX-680)

The identification of a novel series of Aurora kinase inhibitors and exploitation of their SAR is described. Replacement of the initial quinazoline core with a pyrimidine scaffold and modification of substituents led to a series of very potent inhibitors of cellular proliferation. MK-0457 (VX-680) has been assessed in Phase II clinical trials in patients with treatment-refractory chronic myelogenous leukemia (CML) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph + ALL) containing the T315I mutation.     

Structural and functional analysis of SGT1 reveals that its interaction with HSP90 is required for the accumulation of Rx, an R protein involved in plant immunity

SGT1 (for suppressor of G2 allele of skp1) and RAR1 (for required for Mla12 resistance) are highly conserved eukaryotic proteins that interact with the molecular chaperone HSP90 (for heat shock protein90). In plants, SGT1, RAR1, and HSP90 are essential for disease resistance triggered by a number of resistance (R) proteins. Here, we present structural and functional characterization of plant SGT1 proteins. Random mutagenesis of Arabidopsis thaliana SGT1b revealed that its CS (for CHORD-SGT1) and SGS (for SGT1 specific) domains are essential for disease resistance. NMR-based interaction surface mapping and mutational analyses of the CS domain showed that the CHORD II domain of RAR1 and the N-terminal domain of HSP90 interact with opposite sides of the CS domain. Functional analysis of the CS mutations indicated that the interaction between SGT1 and HSP90 is required for the accumulation of Rx, a potato (Solanum tuberosum) R protein. Biochemical reconstitution experiments suggest that RAR1 may function to enhance the SGT1-HSP90 interaction by promoting ternary complex formation.     

Iron-sulphur cluster composition and redox properties of two ferredoxins from Desulfovibrio desulfuricans Norway strain

Two ferredoxins from Desulfovibrio desulfuricans, Norway Strain, were investigated by EPR spectroscopy. Ferredoxin I appears to be a conventional [4Fe-4S]^2+;1+ ferredoxin, with a midpoint reduction potential of ?374 mV at pH 8. Ferredoxin II when reduced, at first showed a more complex spectrum, indicating an interaction between two [4Fe-4S] clusters, and probably, has two clusters per protein subunit. Upon reductive titration ferredoxin II changed to give a spectrum in which no intercluster interaction was seen. The midpoint potentials of the native and modified ferredoxin at pH 8 were estimated to be ?500 and ?440 mV, respectively.