A karyological study of Asphodelus L. (Asphodelaceae) from the Western Mediterranean

The following aspects of Asphodelus karyology are analysed: base number, polyploidy, chromosome size, chromosome morphology, satellited chromosomes, structural heteromorphism, karyotype asymmetry and karyotype evolution. The base number 0 ×= 14 is common to all species except for A. refractus , which has the derived ×= 13. Three ploidy levels occur, often in the same species; diploid, tetraploid and hexaploid, with 2n = 28, 56 and 84. Chromosomes are generally small to medium-small, with the occasional presence of medium-large chromosomes. The most frequent chromosome types are metacentric of type m and submetacentric. Metacentric chromosomes of type M occur only in sections. Verineopsis, Verinea and Plagiasphodelus ; subtelocentric chromosomes occur only in sections Asphodelus and Plagiasphodelus. There is a wide variability in relation to the number of satellited chromosomes, relative to ploidy level. There are usually two to four in diploids, four to eight in tetraploids and usually six, exceptionally up to 12, in the hexaploid. Satellites are present on the shortest arm, exceptionally on the longest arm. There is a high degree of structural heteromorphism in practically all the species which affects satellited and non satellited chromosomes. Karyotype asymmetry is generally of type 2B. Inter-and intra-chromosomal differences are estimated by the A1 and A2 indexes. Both indices vary in the karyotype evolution of the genus, with a decrease of A1 and an increase of A2. The role of polyploidy, hybridization, asymmetry and decrease of chromosome size in the evolution of Asphodelus is discussed.     

POTENTIAL RAPID BIOASSAY FOR ALIMET® USING A METHIONINE ESCHERICHIA COLI AUXOTROPH

A potential rapid bioassay for methionine hydroxy analog (MHA) feed additive (ALIMET®) was examined using a methionine auxotroph E. coli strain. Bacterial cells were grown in minimal media containing a concentration range of 0 to 26.8 μM of either L-methionine or MHA as ALIMET®. Increasing either methionine or MHA concentration increased the growth rate of the methionine auxotroph. The estimated substrate affinities for methionine compared to MHA were not significantly different (P > 0.13) and the maximum growth rate estimates were also similar (P > 0.34). Methionine and MHA standard curves yielded linear responses (R²= 0.96) to increasing concentrations of the respective substrate. Based on these results it appears that the E. coli methionine auxotroph would have potential utility for further development of a rapid bioassay of ALIMET®.     

Sexual dimorphism and interpopulation differences in lizard hind limb length: locomotor performance or chemical signalling?

Intraspecific variation in morphology has often been related to fitness differences through its effects on performance. In lizards, variation in hind limb length can be shaped by natural selection for increased locomotor performance, sexual selection on the number or size of femoral pores involved in chemical signalling, or both. Here, we analyse the selective forces involved in sexual dimorphism and differences in hind limb length between two populations of Psammodromus algirus living at different elevation. Males were more robust and had longer hind limbs and limb segments than females, and low‐elevation lizards had longer limbs than high‐elevation lizards. However, differences in locomotor performance were small and non‐significant, making natural selection for faster runs an unlikely explanation for the observed pattern. On the other hand, males had more femoral pores than females, and lizards had more pores at lower elevation, although the difference was significant only for males (which invest more in chemical signalling). In males, the number of pores, which remains constant along a lizard's life, was not correlated with hind limb length. However, femur length was positively correlated with mean pore size, allowing low‐elevation males to have larger than expected pores, which could increase the effectiveness with which they spread their signals in a dry and warm habitat where chemicals become volatile rapidly. Also, saturation of the sexual coloration of the head was higher for low‐elevation males, suggesting that sexual selection pressures may be more intense. Overall, our results indicate that sexual selection plays a significant role in shaping intraspecific variation in hind limb length. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 318–329.     

Foliar resistance to simulated extreme temperature events in contrasting plant functional and chorological types

We analysed leaf resistance of 41 Angiosperms belonging to a wide range of plant functional (PFTs) and chorological types (PCTs) to simulated frost and high‐temperature extreme events (EE). Leaf resistance was estimated as percentage of membrane electrolyte leakage under heating and freezing treatments in the lab. Leaf resistance to heating or freezing was not significantly correlated with the main resource‐use characteristics that defined PFTs, such as leaf specific area, toughness, N concentration or thickness. Leaf resistance to heating differed among PFTs (graminoids and bromeliads were the more resistant groups), but not among PCTs. In contrast, leaf resistance to freezing significantly differed among PCTs. Along a steep regional climatic gradient, climate variables (annual mean temperature, mean minimum temperature, mean maximum temperature and number of frost‐free months) at the locations where the given species were most abundant were also significantly correlated with freezing resistance. Species from colder habitats both at the sub‐continental and regional scales showed the highest leaf resistance to freezing. Our work indicates that leaf resistance to climatic EE and resource‐use strategy (assessed in previous studies) represent two different, partially decoupled axes of plant specialisation. It also suggests that changes in the frequency of very low temperature events might have regional‐scale impacts on vegetation, whereas changes in the frequency of very high temperature events might have more influence at the local scale.     

Micronucleus test applied in patients with acute leukemia, before and at different intervals during the cytostatic treatment

The micronucleus test was applied in a group of 36 patients with malignant disease of the blood (acute lymphoblastic leukemia, ALL, and acute non-lymphocytic leukemia, ANLL) in order to evaluate to what extent it may be relevant for the efficiency of the cytostatic treatment. To this end, the test was applied at the onset of the disease (when diagnosed) and at different intervals after initiating the cytostatic therapy. Determination of the incidence of micronucleated cells and immature cells (blasts) at the two moments of the study established a correlation between the frequency of micronucleated cells and blast cells, the response to the anticancerous treatment and survival duration, the data obtained reflecting the prognostic value of the test in some malignant hemopathies.