Distribution,properties, and functions of midgut carboxypeptidases and dipeptidases from Musca domestica larvae

Dipeptidase and carboxypeptidase A activities were determined in cells and luminal contents of the fore-, mid-, and hind-midgut of Musca domestica larvae. Dipeptidase activity was found mainly in hind-midgut cells, whereas carboxy-peptidase activity was recovered in major amounts in both cells and in luminal contents of hind-midguts. The subcellular distribution of dipeptidase and part of the carboxypeptidase A activities is similar to that of a plasma membrane enzyme marker (aminopeptidase), suggesting that these activities are bound to the microvillar membranes. Soluble carboxypeptidase A seems to occur both bound to secretory vesicles and trapped in the cell glycocalyx. Based on density-gradient ultracentrifugation and thermal inactivation, there seems to be only one molecular species of each of the following enzymes (soluble in water or solubilized in Triton X-100): membrane-bound dipeptidase (pH optimum 8.0; Km 3.7 mM GlyLeu, M_r 111,000), soluble carboxypeptidase (pH optimum 8.0; Km 1.22 mM N-carbobenzoxy-glycyl-L-phenylalanine (ZGlyPhe), M_r45,000) and membrane-bound carboxypeptidase (pH optimum 7.5, Km 2.3 mM ZGlyPhe, M_r58,000). The results suggest that protein digestion is accomplished sequentially by luminal trypsin and luminal carboxypeptidase, by membrane-bound carboxypeptidase and aminopeptidase, and finally by membrane-bound dipeptidase.     

Biological role of endoreplication in the process of spermatogenesis inChara vulgaris L.

Summary During cell division in antheridial filaments ofChara vulgaris an increase in DNA content occurs in both shield cells and manubria within an antheridium, reaching 16C–64C and 8C–32C levels, respectively. Endoreplication ceases prior to the formation of spermatids and initiation of spermiogenesis, probably as a result of symplasmic isolation of the antheridium from the thallus. As the DNA content of the nuclei increases, the shield cells³H-leucine incorporation increases, and they grow intensively in the tangential plane. Translation decreases considerably after termination of shield cell growth. DNA content of mature manubria is half of that in shield cells, although their size is 10 times that of manubria. Translational activity of manubria also increases as DNA content rises and cells grow. However, during spermiogenesis, this activity remains at its maximum, which is associated with the secretory function of the manubria. Spermiogenesis is also accompanied by far-reaching ultrastructural changes within the manubrial cytoplasm.The level of endopolyploidy in both shield cells and manubria of antheridia formed in the spring is higher by one replication cycle, than in autumnal antheridia. AMO-1618, at a concentration of 10^–5M reduces the DNA content in the autumnal manubria. The higher the manubrial level of endopolyploidy in spermiogenesis, the greater their size, and the higher the translational activity and number of joined spermatids. The number of spermatozoids in the antheridium is also positively correlated with the internal volume of an antheridium, which is itself dependent on the endopolyploidy level of shield cells.The results obtained confirm the assumption that endoreplication favours the higher growth dynamics and potential translational activity, which occurs in the dynamic growth phase only in shield cells, while in manubria, i.e. cells producing substances necessary to spermatozoids development, it remains high until the end of spermiogenesis.     

Functional analysis of a complex oncogene arrangement in biotype III Agrobacterium tumefaciens strains

The ubiquitous grapevine-associated octopine/cucumopine Ti plasmids of biotype III Agrobacterium tumefaciens strains carry two T regions, TA and TB, with a complex oncogene arrangement. Within the octopine/cucumopine group, two main strain types were identified: large TA strains with a TA region resembling the TL region of the biotype I octopine strain Ach5 and small TA strains with a similar T region organization as the large TA strains but with a large internal TA deletion. Structural and functional studies of the representative large TA strain Tm4 revealed six oncogenes. Each oncogene was inserted in a disarmed vector and tested for biological activity using the corresponding oncogenes of Ach5 as standards. Five Tm4 oncogenes, TA-iaaM, T-ipt, T-6b, TB-iaaH and TB-iaaM, were shown to be active, the IS-interrupted TA-iaaH gene was inactive. To study the role of each gene in the pTiTm4 context, several single and multiple pTiTm4 mutations were constructed. It was shown that whereas TA-iaaM and TB-iaaH are essential for tumour formation on grapevine, T-ipt, T-6b and TB-iaaM are not. The avirulence of the TA-iaaM ^- mutant was shown to be due to an inhibitory effect of the T-ipt gene, since a TA-iaaM ^- /T-ipt ^- double mutant was fully virulent. We conclude that the TA-iaaM gene of large TA strains is specifically required to counteract the tumour growth inhibiting activity of the T-ipt gene. Both TA-iaaM and T-ipt are absent from the small TA strains. A model on the roles and interactions of the different oncogenes in large TA and small TA strains is presented.     

NOR polymorphism in the Iberian species Chondrostoma lusitanicum (Pisces: Cyprinidae)

Chromosomal polymorphism regarding number of NOR sites in the cyprinid fish Chondrostoma lusitanicum was examined using C-banding, silver-staining (Ag), and fluorescent staining with chromomycin A₃ (CMA₃). The analysis of heterochromatic regions allowed a more precise identification of the centromeric regions and the proposal of a revised haploid chromosome formula (7M: 15S: 3A). We describe variability in the number of NOR regions per genome, number of active NOR sites per cell, and relative size of individual NORs. Individuals expressed two or four NOR-bearing chromosomes. Polymorphism was detected in all the populations studied and sex-related differences were not found. The observed chromosomal NOR phenotypes suggest the occurrence of structural rearrangements during the evolutionary process of this diploid leuciscine cyprinid.     

Colonization and deterioration processes in Roman mortars by cyanobacteria,algae and lichens

The mortars covering some walls of the Roman city of Baelo Claudia (Cadiz, Spain) support an abundant colonization of cyanobacteria, algae and lichens. The distribution of these organisms is closely related to microclimatic parameters. Furthermore, the development, specific composition and biomass of algal cryptoendolithic communities are related to the wall orientation. The effect of these communities on mortar deterioration is discussed.     

Biotransformation of monoterpenes and sesquiterpenes by cell suspension cultures of Achillea millefolium L. ssp. millefolium

The transformation capacity of Achillea millefolium L. ssp. millefolium (yarrow) cell suspension cultures was investigated using geraniol (50mg/l) and borneol, menthol, thymol and farnesols (25mg/l) as substrates. Apart from converting these substrates into several biotransformation products, the cell suspension cultures were also able to glycosylate both the substrates and the biotransformation products. aa]Key Words bb]Achillea millefolium L. ssp. millefolium bb]Yarrow bb]Compositae bb]Biotransformation bb]Glycosylation bb]Geraniol bb]Borneol bb]Menthol bb]Thymol bb]Farnesols