Superoxide dismutase is upregulated in <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> following protoporphyrin-mediated photodynamic inactivation and does not directly influence the response to photodynamic treatment

Background  

Staphylococcus aureus, a major human pathogen causes a wide range of disease syndromes. The most dangerous are methicillin-resistant S. aureus (MRSA) strains, resistant not only to all β-lactam antibiotics but also to other antimicrobials. An alarming increase in antibiotic resistance spreading among pathogenic bacteria inclines to search for alternative therapeutic options, for which resistance can not be developed easily. Among others, photodynamic inactivation (PDI) of S. aureus is a promising option. Photodynamic inactivation is based on a concept that a non toxic chemical, called a photosensitizer upon excitation with light of an appropriate wavelength is activated. As a consequence singlet oxygen and other reactive oxygen species (e.g. superoxide anion) are produced, which are responsible for the cytotoxic effect towards bacterial cells. As strain-dependence in photodynamic inactivation of S. aureus was observed, determination of the molecular marker(s) underlying the mechanism of the bacterial response to PDI treatment would be of great clinical importance. We examined the role of superoxide dismutases (Sod) in photodynamic inactivation of S. aureus as enzymes responsible for oxidative stress resistance.     

Annual cycle of stored spermatozoa within the ovaries of Helicolenus dactylopterus dactylopterus (Teleostei, Scorpaenidae)

The aim of this work was to analyse the ultrastructure of storage crypts and stored spermatozoa, and to describe changes during the annual reproductive cycle of the bluemouth Helicolenus dactylopterus dactylopterus , which has internal fertilization and a zygoparous mode of reproduction. Spermatozoa had elongated heads and long midpieces, two characteristics which are thought to be fairly advanced and correlated with internal fertilization, as is the case of the bluemouth. A remarkable spermatozoon feature was the retention of a significant quantity of cytoplasm around the head, a condition that appeared to be related to nourishment during the long storage period, up to 10 months in the intraovarian crystal structures of the female. Male sex cells' protection against the female immune system was ensured by junctional complexes between the crypt cells composed of tight junctions and desmosomes.     

EFFECTS OF ARSENATE ON GROWTH OF NITROGEN-AND PHOSPHORUS-LIMITED CHLORELLA VULGARIS (CHLOROPHYCEAE) ISOLATES1

The effects of arsenate on the growth characteristics of five isolates of the freshwater alga, Chlorella vulgaris Beij., were examined. Two field isolates originated from arsenic-contaminated sites in Yukon, Canada and Kyushi, Japan; two reference isolates were obtained from the University of Texas Culture Collection. One isolate was selected for arsenic-tolerance in the laboratory. All five strains survived in culture solutions containing high arsenate concentrations. Arsenate (1–25 mM As) reduced photosynthesis and cell growth, as reflected by induced lag periods, slower growth rates, and lower stationary cell yields. Field isolates had shorter lag periods, higher growth rates, and enhanced cell yields compared to lab isolates when exposed to the same arsenic concentrations. Growth of the phosphorus-limited field strains was stimulated by the addition of arsenic. The cell yield of phosphorus-limited C. vulgaris Yukon, when treated with arsenic, was two times that of the phosphorus-limited control. This pattern was not evident when photosynthesis was used as a measure of cell response.     

Body wall organization in enchytraeids

The muscle organization of the body wall in some species of oligochaetes belonging to the Enchytraeus genus is described. No differences have been detected in their circular muscles, whereas longitudinal muscles show significant differences, allowing an easy identification of the various worm species. In particular, differences are noticeable in the external longitudinal layer. These observations suggest that structural and ultrastructural muscle fiber organizations can be used as a taxonomic tool.     

Physiological integration among ramets of Lathyrus sylvestris L.

Summary Lathyrus sylvestris is a pioneer legume often found in disturbed habitats. Mainly reproduced through vegetative propagation, this clonal species presents a system of ramets that remain connected for several years. The existence of carbon transfer among ramets within a clone has been studied using ¹⁴C in situ. Assimilate translocation from primary to secondary ramets was observed in all clones when the primary ramet was exposed to ¹⁴CO₂. The amount of transfer ranged from trace up to 90% of the total ¹⁴C incorporated. However, in only half of the clones there was consistent enrichment of the secondary ramet (5 to 89%) suggesting that interramets transfer of carbon may be facultative. Furthermore, when significant export occurred from the primary ramet, it was always principally towards only one ramet even when the clone included more than one. The transfer of ¹⁴C from secondary to primary ramets was shown to be significant only when photosynthesis of the latter was decreased by shading. In this case import of carbon was never more than 60% of the incorporated ¹⁴C.No correlation was found between age or size of the ramets and the intensity of transfer. The shading effect let suppose that transfers are mainly driven by carbon limitation due to changing environmental conditions and not to the state of ramet maturity. The adaptative advantage of such facultative physiological integration between ramets of a clone is discussed.     

Altered protein-chromophore interaction in dicyclohexylcarbodiimide-modified purple membrane sheets

Previous studies of N,N'-dicyclohexylcarbodiimide (DCCD)-modified bacteriorhodopsin (Renthal, R. et al. (1985) Biochemistry 24, 4275-4279) used reaction conditions (detergent micelles) that are not optimal for subsequent physical studies. The present work describes new conditions for reaction of bacteriorhodopsin with DCCD in intact purple membrane sheets in the presence of 4.5% (v/v) diethylether and light. Like the detergent reaction system, the reaction is light induced, incorporates approximately 1 mol [14C]DCCD per mol bacteriorhodospin, and results in a bleached chromophore. Peptide mapping indicates that the likely site of modification in intact membranes is identical to the site in the detergent reaction system: Asp 115. The retinal chromophore of DCCD-modified purple membrane has an absorbance maximum at 390 nm and very little induced circular dichroism. The retinal is easily extracted in hexane, yielding a 3:1 ratio of all-trans to 13-cis retinal. Borohydride reduces the retinal onto the protein within the 1-71 region of the amino acid sequence. These results suggest that Asp-115 is near the retinal binding cavity of bacteriorhodopsin. When DCCD reacts with Asp 115, retinal is displaced from its binding site.     

Insulin-like growth factor-I supports proliferation of autocrine thymic lymphoma cells with a pre-T cell phenotype

We have studied the phenotypic characteristics and growth properties of murine T lymphoma cell lines derived from primary x-ray-induced thymic lymphomas at the earliest stage at which they can be detected, and well before spreading to other organs has occurred. These cell lines serve as model systems for the earliest events in T cell lymphoma induction, before tumor cell progression and spreading to other organs. We find that primary x-ray-induced T cell lymphoma lines have phenotypic characteristics of thymic pre-T cells and show no proliferative response to any of the IL tested nor to other hematopoietic growth factors. However, they do proliferate in response to insulin-like growth factor I (IGF-I) and to a small autocrine peptide distinct from IGF-I, which we term lymphoma growth factor. One of the earliest lesions in T cell lymphoma induction may therefore be an inhibition of differentiation at one of several specific points. In its early stages, T lymphoma cell growth may be restricted to an environment where local concentrations of specific growth factors such as IGF-I or lymphoma growth factor are sufficiently high.     

The surface charge of NKLy ascitic tumor cells differing in their proliferative activity, in their place in the cell cycle and in their ploidy

The NKLy ascitic tumor cells in the stationary phase of growth were fractionated by velocity sedimentation method. Cells from the obtained fractions were characterized by measurements of DNA contents and 3H-thymidine incorporation. The surface properties of the cells from five fractions, differing in proliferative capacity, stage of the cell cycle and ploidy were considered using cell electrophoresis, two polymer aqueous phase system and Alcian blue sorption. A correlation between electrophoretic mobility and cell partition constant for these fractions has been obtained. No correlation was found between these parameters and dye absorption. The surface charge of the cells from G0/G1 and S fractions was higher than that of other cells. The polyploid NKLy cells demonstrated a lower surface charge. The surface properties of the tumor cells differing in proliferative capacity, stage of the cell cycle and ploidy are discussed.     

Inhibition of CI857-controlled recombinant gene expression in Escherichia coli at very low concentrations of glucose

Summary The effects of glucose on biomass and temperature-mediated recombinant gene expression has been studied in Escherichia coli batch cultures. Glucose, above 2 g/L, has inhibitory effects on aerobic cell growth and specially on gene expression. Although lower concentrations have no influences on biomass, a tenuous, but still remarkable concentration-dependent reduction of gene expression levels was observed even at about 0.1 g/L.