Tissue and Cell Culture of 'Passe Crassane' Pears: Amylase Pattern of Cultured Tissues Compared with Whole Fruit

Calluses and cell suspension cultures were initiated from young and fully developed fruits and from stem and petiole tissues of ‘Passe Crassane’ pears. On a dry weight basis, proliferation is significantly higher in tissues from full-grown fruits and petioles. Cullus tissues grown in vitro have a protein content up to 25 times higher than the initial quiescent organ. Three amylase fractions (2 β amylases E, and E₂: 1 α amylase E₃) were isolated by gel filtration on Sephadcx G-100 and isoenzymes revealed in these fractions after polyacrylamide gel electrophoresis. Comparison of amylase activity in actively growing cells and in auxin-starved cell suspensions shows that β-amylase activity is mainly a function of cell growth, while α-amylase activity is more related to the age of the cells. The presence of two isoenzymes in the β-amylase E₂ fraction was found to be highly characteristic of young fruits. The same polymorphism was found in all the strain of tissues thus indicating that tissues grown in vitro retain or revert to a juvenile biochemistry. The growth hormone. 2,4-dichlorophenoxyacetic acid, used to support cell division, is demonstrated to be responsible for the reversion of the β-amylase polymorphism from a mature to a juvenile phenotype in mature fruit explants incubated in vitro. The interest of fruit tissue and cell culture for the study of fruit physiology is questioned and discussed.     

Benthic and hyporheic invertebrate assemblages along a flow intermittence gradient: effects of duration of dry events

1. A large proportion of the total river length on Earth comprises rivers that are temporary in nature. However, the effects of periodical dry events have received far less attention from ecologists than those of floods and low flows. 2. This study concomitantly examined the effects of flow intermittence on invertebrates from the streambed surface and from a depth of 30 cm in the hyporheic zone. Invertebrates were collected during 3 years in the Albarine River, France, before and after summer dry events from 18 sites (seven were perennial) distributed along a longitudinal flow intermittence gradient. 3. I predicted benthic and hyporheic density and taxonomic richness to decrease, and assemblage composition to shift from desiccation‐sensitive to desiccation‐resistant taxa with increased dry event duration. Second, I predicted benthic and hyporheic assemblages from sites that dried for longer periods to be nested subsets of assemblages from sites that dried for shorter periods. Last, I predicted a convergence in benthic and hyporheic assemblage composition with increasing duration of dry events, resulting from increased vertical migration of benthic taxa into the hyporheic sediments to cope with dry events. 4. Increased dry event duration in the Albarine River led to a decrease in both benthic and hyporheic density and taxonomic richness. Invertebrate assemblage composition shifted along the gradient of increasing flow intermittence, but broad taxonomic overlap between perennial and temporary reaches and nestedness patterns indicated that these shifts were because of the loss of taxa susceptible to drying rather than selection for desiccation‐resistant specialists. 5. Assemblage composition between benthic and hyporheic invertebrates diverged with increasing dry event duration, suggesting that the hyporheic zone did not act as a refuge during dry events in this river. 6. Quantitative studies on the relationships between ecology and intermittence are still rare but are needed to predict the consequences of future changes in flow intermittence. The relationships found in this study should be tested across a wide range of temporary rivers to better evaluate the generality of these findings.     

The diet of young Lammergeiers Gypaetus barbatus in Corsica: its dependence on extensive grazing

This paper describes the diet of young Lammergeiers Gypaetus barbatus during the nesting period on the island of Corsica. From 1985 to 1990, food items were collected from 10 nests after the young had fledged. These nests were from five territories where the potential food supply was estimated using a range of 'large mammal' counts. Feathers, bones and isolated hooves were used to identify prey. For each nest, the minimal number of food portions was quantified, ignoring material that provided no food value. The diet consisted mainly of limb extremities of domestic ungulates (c. 36% by number of portions of sheep and goat; 33% of cattle, mostly calves). Pigs, both wild and domestic, yielded c. 16% of the items. Where present on the territory, mouflon occurred frequently in nests (c. 12% of items). Birds and small mammals were scarce in the diet. For three territories, samples varied less among years than among territories. There was a strong association between the diet of the young and the food available in the territories. We examined the possible links between known 20th century changes in stock rearing activities and the Corsican Lammergeier's diet.     

Phylogeny of Acomys spinosissimus (Rodentia, Muridae) from north Malawi and Tanzania: evidence from morphological and molecular analysis

New specimens of Acomys spinosissimus from northern Malawi and southern Tanzania were subjected to morphological, molecular (cytochrome b mitochondrial gene) and cytogenetical analysis in order to establish the phylogenetic position of these populations among A. spinosissimus, as well as their relationships with other species (A. subspinosus and A. wilsoni). The monophyly of the spinosissimus clade is supported by morphological and molecular phylogenies. Cytogenetics and morphology, but not the cytochrome b phylogeny show the possible existence of two sibling species within spinosissimus. Incongruences are noted between molecular and morphological trees, especially concerning the position of the Transvaal specimens. Two different biogeographic scenarios for the origin and dispersal of A. spinosissimus are discussed in the light of available palaeontological data.     

Expression of Three Gastrula Cell Surface Glycoproteins during Embryonic and Larval Development in the Amphibian Pleurodeles waltlii

We have previously reported the identification of cell surface glycoproteins in Pleurodeles waltlii gastrulae. In an attempt to study the expression of three of these cell surface glycoproteins (proteins referred to 1, 11 and 14), we have produced monoclonal and polyclonal antibodies by immunizing mice with the spots of the three selected glycoproteins excised from 2D-gels. Expression of the three glycoproteins was detected on the surfaces of all cells during embryonic development. Before hatching, proteins 1, 11 and 14 become expressed in a limited number of tissues.     

A Two-Dimensional Separation of Proteins from Chloroplast Thylakoids and Other Membranes

• 1 A two-dimensional, highly reproducible, analytical separation procedure for Triton/urea extractable proteins, using isoelectric focusing in the first dimension and gelelectrophoresis with sodium dodecylsulfate (SDS) in the second, is described. The separation of erythrocyte membrane proteins compares the reliability with that of published procedures.
• 2 From the thylakoid membranes of the green alga Chlamydomonas reinhardii and of spinach, two-dimensional maps of the Triton/urea extractable proteins were established, containing 58 and 33 peptide spots, respectively, which were characterized by their molecular weights and apparent isoelectric points. In Chlamydomonas some of the spots could be attributed to the photosystem I and II particles. A few major spots in the maps of the thylakoid proteins from the two non-related plants were found at the same relative positions.
• 3 A one-dimensional electrophoretic comparison of the SDS and the Triton/urea-extractable proteins showed that in the Triton/urea extract of thylakoid membranes some proteins of the photosystem II region, and in that of erythrocyte membranes, some components of the band 3 and 5 region are reduced or missing.