Ultrastructure of the trophic chamber and nutritive cord of Aspidiotus hederae (Homoptera,coccoidea)

Summary Each ovariole of the coccidian Aspidiotus hederae contains a single oocyte connected by means of a nutritive cord to the trophic chamber. The trophic chamber consists of three nurse cells characterized by an enlarged, ramified nucleus with a prominent nucleolus. The perinuclear cytoplasm contains nuage material, large amounts of free ribosomes, and scattered mitochondria. Occasional cisternae of the rough endoplasmic reticulum and bacteroids are found in trophocyte cytoplasm. The nutritive cord contains many microtubules in parallel array interspersed with numerous free ribosomes and a few mitochondria. The nutritive cord is strengthened by trophocyte projections which surround it. Microtubules in the projections are oriented perpendicular to the long axis of the cord.     

Occurrence of a capsule in Aeromonas salmonicida

Aeromonas salmonicida grown in a medium with excess glucose as carbon source produces both capsular and exocellular polysaccharides. The capsular polysaccharide is composed of glucose, mannose, rhamnose, N-acetylmannosamine and mannuronic acid in the molar ratios of approximately 5:3:0.75:2:1. The extracellular polysaccharide is similarly constituted, but in the molar ratios of approximately 4.75:10.5:1.5:2:1. The capsular and exocellular polysaccharides did not cross-react with monoclonal antibodies against the A-layer or the O-antigen lipopolysaccharide.     

Effect of dilution rate on the release of pertussis toxin and lipopolysaccharide ofBordetella pertussis

Summary The kinetics ofBordetella pertussis growth was studied in a glutamate-limited continuous culture. Growth kinetics corresponded to Monod's model. The saturation constant and maximum specific growth rate were estimated as well as the energetic parameters, theoretical yield of cells and maintenance coefficient. Release of pertussis toxin (PT) and lipopolysaccharide (LPS) were growth-associated. In addition, they showed a linear relationship between them. Growth rate affected neither outer membrane proteins nor the cell-bound LPS pattern.Nomenclature X cell concentration (g L^–1) - specific growth rate (h^–1) - _m maximum specific growth rate (h^–1) - D dilution rate (h^–1) - S concentration of growth rate-limiting nutrient (glutamate) (mmol L^–1 or g L^–1) - Ks substrate saturation constant (mol L^–1) - m_s maintenance coefficient (g g^–1 h^–1) - Y_x/s theoretical yield of cells from glutamate (g g^–1) - Y_x/s yield of cells from glutamate (g g^–1) - Y_PT/s yield of soluble PT from glutamate (mg g^–1) - Y_KDO/s yield of cell-free KDO from glutamate (g g^–1) - Y_PT/x specific yield of soluble PT (mg g^–1) - Y_KDO/x specific yield of cell-free KDO (g g^–1) - q_PT specific soluble PT production rate (mg g^–1 h^–1) - q_KDO specific cell-free KDO production rate (g g^–1 h^–1)     

Effects of irrigation and air humidity preconditioning on water relations, growth and survival of Rosmarinus officinalis plants during and after transplanting

The effect of different irrigation and air humidity conditioning treatments on the morphological and physiological responses of Rosmarinus officinalis in nursery conditions was investigated in order to evaluate the degree of hardening resulting from these conditions. Rosmarinus officinalis seedlings were pot-grown during 4 months in two greenhouses (nursery period), in which two irrigation treatments were used (control and deficit). In one of these greenhouses, air humidity was controlled using a dehumidifying system (low humidity), in the other greenhouse the air conditions were not artificially modified (control humidity). After the nursery period, the plants of all treatments were transplanted and well watered (100% water holding capacity for 1 month, transplanting period). After this period, they received no water (establishment period). At the end of the nursery period it was seen that deficit irrigation had altered the morphology of the R. officinalis plants by reducing plant height, stem diameter, leaf area, total dry weight, and root length, while humidity influenced the parameters related with plant water relations. Low air humidity and deficit irrigation-induced tissue dehydration and lower stomatal conductance values (gs). The plants subjected to deficit irrigation developed leaf osmotic adjustment, which was maintained during the transplanting period. At that time, the plants that had been exposed to deficit irrigation and low humidity showed efficient stomatal regulation (lower gs values). After transplanting and during the establishment period, these plants showed a better water status (higher psil and gs values). Their post-planting survival rate improved as a result of acclimation processes.     

Quaternary structure of a SPATE autotransporter protein

The temperature-sensitive hemagglutinin (Tsh) is a representative of the growing subfamily of secreted bacterial virulence factors, known as serine protease autotransporters of the Enterobacteriaceae (SPATEs). Expressed by avian and human pathogenic strains of Escherichia coli Tsh acts as a serine protease and an adhesin to erythrocytes, hemoglobin, and extracellular matrix proteins. Mature Tsh is comprised of a 106-kDa secreted domain (Tshs) and a 33-kDa outer membrane beta-domain (Tshbeta). Based on the size of beta-domains and functional properties of their passenger domains, all SPATEs are considered to be conventional autotransporters. However, it is unsettled if the conventional autotransporters exist as monomers, oligomers, or multimers (e.g., hexamers). To determine the quaternary structure of Tsh in vitro, we purified Tshbeta from the outer membranes and showed that it is natively folded because it is heat modifiable and resistant to protease digestion. Blue-native polyacrylamide gel electrophoresis of Tshbeta indicated that Tshbeta exists as a monomer or a dimer. The cross-linking analysis demonstrated that purified Tshbeta exists as a monomer. The size-exclusion chromatography and cross-linking analyses of purified Tshs also showed that the passenger domain of Tsh is a monomer. Overall, our data indicated that Tsh is a monomeric protein in vitro and support the concept that the SPATE autotransporters exist as monomers rather than as multimers. Implications of our findings on the mechanism of autotransporter secretion across the outer membrane are discussed.     

Adenylate cyclase influences filamentous haemagglutinin-mediated attachment of Bordetella pertussis to epithelial alveolar cells

Attachment to epithelial cells in the respiratory tract is a key event in Bordetella pertussis colonization. Filamentous haemagglutinin (FHA) is an important virulence factor mediating adhesion to host cells. In this study, the relevance of the interaction between FHA and adenylate cyclase toxin (ACT) during bacterial attachment was investigated. Mutants lacking either FHA or ACT showed significantly decreased adherence to epithelial respiratory cells. The use of several ACT-specific monoclonal antibodies and antiserum showed that the decrease in attachment of strains lacking ACT expression could not be explained by the adhesin-like activity of ACT, or a change of any of the biological activities of ACT. Immunoblot analysis showed that the lack of ACT expression did not interfere with FHA localization. An heparin-inhibitable carbohydrate-binding site is crucial in the process of FHA-mediated bacterial binding to epithelial cells. In the presence of heparin attachment of wild-type B. pertussis, but not of the isogenic ACT defective mutant, to epithelial cells was significantly decreased. These results suggest that ACT enhances the adhesive functions of FHA, and modifies the performance of the FHA heparin-inhibitable carbohydrate binding site. We propose that the presence of ACT in the outer membrane of B. pertussis to play a role in the functionality of FHA.     

Effects of different protein concentrations on longevity and feeding behavior of two adult populations of Ceratitis capitata Wiedemann (Diptera: Tephritidae)

The effects of protein intake on two adult male and female populations of Ceratitis capitata Wiedemann were assessed. One population consisted of flies reared for twenty years in the laboratory (Lab-pop); the other population consisted both of flies reared in the laboratory for approximately fifteen years and of the periodically introduced wild flies (Hybrid-pop). Three diets were tested: a no-yeast diet and two diets containing yeast (protein source) at the concentrations 6.5 g or 1.5 g per 100 ml diet. The parameters analyzed were: adult longevity, diet intake with and without yeast, and discrimination threshold for yeast. Protein intake increased Lab-pop adult longevity and did not affect longevity of the Hybrid-pop. Longevity in each population was similar for males and females fed on the same diet. Food behavior were similar for male and female adults of both populations; all preferred diets containing protein (yeast). Males and females in both populations ingested similar amounts of each diet. The discrimination threshold for yeast was similar for all males (0.5 g yeast/100 ml diet); Lab-pop females were able to detect the presence of smaller quantities of yeast in their diet, thus having a higher discrimination capacity (0.4 g/100 ml diet) as compared to the Hybrid-pop females (0.6 g/ 100 ml diet).     

Hydrogen production by photosynthetic green algae

Oxygenic photosynthetic organisms such as cyanobacteria, green algae and diatoms are capable of absorbing light and storing up to 10-13% of its energy into the H-H bond of hydrogen gas. This process, which takes advantage of the photosynthetic apparatus of these organisms to convert sunlight into chemical energy, could conceivably be harnessed for production of significant amounts of energy from a renewable resource, water. The harnessed energy could then be coupled to a fuel cell for electricity generation and recycling of water molecules. In this review, current biochemical understanding of this reaction in green algae, and some of the major challenges facing the development of future commercial algal photobiological systems for H2 production have been discussed.     

Consequences of prenatal androgen exposure for the reproductive performance of female pheasants (Phasianus colchicus)

Maternal hormones in vertebrate eggs can mediate important forms of maternal effects. However, the function of hormone transfer to the eggs is still debated, especially because long-term fitness consequences have been little studied. We investigated the effect of prenatal exposure to physiologically elevated yolk testosterone (T) levels on reproduction of female pheasants (Phasianus colchicus) in captivity. We found that females hatching from T-injected eggs (T-females) had a lower egg-laying rate than controls, and their eggs were more frequently infertile than those laid by control females. There were no effects of prenatal maternal treatment on egg size and yolk T concentration, but eggs carrying a female embryo laid by T-females had smaller yolks than eggs with a male embryo, while there was no sex difference in yolk size among the eggs laid by control females. Progeny sex ratio was unaffected by maternal treatment. These findings suggest that the transfer of high androgen levels to the eggs by the mother is constrained by complex trade-offs between direct effects on her daughters' reproduction and by trans-generational differential consequences on male and female descendants.