Evolutionary trends in Mio-Pliocene Leporinae, based onTrischizolagus (Mammalia, Lagomorpha)

New material ofTrischizolagus dumitrescuae from Moldova and Ukraine is described. The variation of p3 inTrischizolagus shows the gradual shift of morphotype frequencies from the ‘Hypolagus’ pattern in Turolian through the mixture of three patterns (including ‘Nekrolagus’ morphotype) in Early Ruscinian to the dominant ‘Alilepus’ pattern in the Late Ruscinian samples. These transformations took place parallel to that of the North AmericanNekrolagus. Probably North AmericanSylvilagus, Brachylagus, andRomerolagus had an North American origin fromNekrolagus, whereas Eurasiatic and AfricanOryctolagus, Caprolagus, Nesolagus, andPoelagus could have originated in the Old World fromTrischizolagus.     

Coevolution of costly mate choice and condition-dependent display of good genes.

Females often choose their mates, instead of mating at random, even when a father contributes nothing but genes to his offspring. Costly female preferences for males with exaggerated traits that reduce viability, such as the peacock's tail, are particularly puzzling. Such preferences can evolve if directly favoured by natural selection or when the exaggerated trait, although maladaptive per se, indicates high overall quality of the male's genotype. Two recent analyses suggested that the advantage to mate choice based on genetic quality is too weak to explain extreme cases of exaggeration of display traits and the corresponding preferences. We studied coevolution of a female mate-preference function and a genotype-dependent male display function where mutation supplies variation in genotype quality and mate preference is costly. Preference readily evolves, often causing extreme exaggeration of the display. Mate choice and trait expression can approach an equilibrium, or a limit cycle, or exaggeration can proceed forever, eventually causing extinction.     

Formaldehyde fixation of cells does not greatly reduce the ability to amplify cellular DNA

Formaldehyde fixation of cells is routinely used to study DNA-protein interactions in vivo. In these studies, DNA is often analyzed using a polymerase chain reaction technique. Although it is known that formaldehyde can damage DNA, no studies have been performed so far to compare the efficiency of DNA amplification between normal and fixed cells. Here we show that formaldehyde fixation results in a 15% to 20% reduction in the ability to amplify cellular DNA. The loss of amplifiability is independent of the length of the amplification region and the degree to which DNA is compacted on packaging into chromatin.     

Point Mutations in Dimerization Motifs of the Transmembrane Domain Stabilize Active or Inactive State of the EphA2 Receptor Tyrosine Kinase

The EphA2 receptor tyrosine kinase plays a central role in the regulation of cell adhesion and guidance in many human tissues. The activation of EphA2 occurs after proper dimerization/oligomerization in the plasma membrane, which occurs with the participation of extracellular and cytoplasmic domains. Our study revealed that the isolated transmembrane domain (TMD) of EphA2 embedded into the lipid bicelle dimerized via the heptad repeat motif L⁵³⁵X₃G⁵³⁹X₂A⁵⁴²X₃V⁵⁴⁶X₂L⁵⁴⁹ rather than through the alternative glycine zipper motif A⁵³⁶X₃G⁵⁴⁰X₃G⁵⁴⁴ (typical for TMD dimerization in many proteins). To evaluate the significance of TMD interactions for full-length EphA2, we substituted key residues in the heptad repeat motif (HR variant: G539I, A542I, G553I) or in the glycine zipper motif (GZ variant: G540I, G544I) and expressed YFP-tagged EphA2 (WT, HR, and GZ variants) in HEK293T cells. Confocal microscopy revealed a similar distribution of all EphA2-YFP variants in cells. The expression of EphA2-YFP variants and their kinase activity (phosphorylation of Tyr⁵⁸⁸ and/or Tyr⁵⁹⁴) and ephrin-A3 binding were analyzed with flow cytometry on a single cell basis. Activation of any EphA2 variant is found to occur even without ephrin stimulation when the EphA2 content in cells is sufficiently high. Ephrin-A3 binding is not affected in mutant variants. Mutations in the TMD have a significant effect on EphA2 activity. Both ligand-dependent and ligand-independent activities are enhanced for the HR variant and reduced for the GZ variant compared with the WT. These findings allow us to suggest TMD dimerization switching between the heptad repeat and glycine zipper motifs, corresponding to inactive and active receptor states, respectively, as a mechanism underlying EphA2 signal transduction.     

The cationic polymerization of 3-O-acetyl-β-arabinofuranose 1,2,5-orthobenzoate

Cationic polymerisation of 3-O-acetyl-β-L-arabinofuranose 1,2,5-orthobenzoate initiated by either triphenylcarbonium tetrafluoroborate or benzoylium perchlorate has been studied. The existence of living chains was demonstrated by termination of polymerisation with tritium-labelled 1-butanol. The number of growing chains reached a maximum after ≈10 min and then decreased.     

Beta-glucoside (bgl) operon of Escherichia coli K-12: nucleotide sequence, genetic organization, and possible evolutionary relationship to regulatory components of two Bacillus subtilis genes.

Wild-type Escherichia coli cells are unable to grow on beta-glucosides. Spontaneous mutants arise, however, which are able to utilize certain aromatic beta-glucosides such as salicin or arbutin as carbon sources, revealing the presence of a cryptic operon called bgl. Mutations activating the operon map within (or close to) the promoter region of the operon and are due to the transposition of an IS1 or IS5 insertion element into this region. This operon was reported to consist of three genes coding for a phospho-beta-glucosidase, a specific transport protein (enzyme IIBgl), and a positively regulating protein. We have defined the extent and location of three structural genes, bglC, bglS, and bglB, and have determined their DNA sequence. The amino acid sequences deduced from the open reading frames together with deletion and subcloning analyses suggest that the first gene, bglC, codes for the regulatory protein, the second, bglS, codes for the transport protein, and the third, bglB, for phospho-beta-glucosidase. A fourth gene may exist which codes for a product of unknown function. We discuss structural features of the DNA sequence which may bear on the regulation of the operon. Homologies to sequences preceding the gene for an excreted levansucrase of Bacillus subtilis, which are known to be involved in the regulation of this gene, and to sequences preceding the gene for an excreted beta-endoglucanase of B. subtilis, for which data pertaining to regulation are not yet available, suggest a close evolutionary relationship among the regulatory components of all three systems.     

Functional morphology of the asterionic region in extant hominoids and fossil hominids

Asterionic sutural patterns in Plio-Pleistocene hominid crania have never been examined in detail. We present an analysis of this anatomical region in Australopithecus and Homo and relate different sutural patterns to functional changes in the masticatory apparatus. The great apes and A. afarensis share the common adult higher primate sutural pattern referred to as the "asterionic notch," which develops in response to the hypertrophy of posterior temporalis muscle fibers and the consequent formation of compound temporal/nuchal crests. This sutural configuration also appears to be present on the early Homo cranium KNM-ER 1805. In contrast, adult male A. boisei crania exhibit a unique pattern where the temporal squama overlaps the parietal which, in turn, overlaps the par mastoidea and the upper scale of the occipital bone. We relate this arrangement to the need to reinforce the rear of a thin-walled braincase against the net tensile forces exerted by the temporalis and nuchal muscles. The common juvenile hominoid edge-to-edge asterionic articulation is maintained in adult A. africanus, A. robustus, female A. boisei, and most Homo crania. We discuss the latter pattern in regard to anterior temporalis hypertrophy in A. africanus, A. robustus, and A. boisei and to craniofacial paedomorphosis in Homo.     

Detection of platelet-associated IgG in chronic immune thrombocytopenic purpura using antibody-coated polyacrylamide beads

Platelet-associated IgG (PAIgG) was detected by means of anti-human IgG coated polyacrylamide beads ("Immunobeads") technique in 32 patients with chronic ITP. Both a direct test (with in vivo sensitized platelets) and an indirect test (with in vitro loaded platelets) were carried out. The percent of rosette forming beads was both in the direct test (41.2%) and in the indirect test (32.6%) significantly higher in the cases of chronic ITP patients than in the controls (2.5% and 3.2%, respectively). These results confirm the diagnostic value of this new, relatively simple and rapid method in routine clinical practice.     

A 3.6-kbp segment from the vir region of Ti plasmids contains genes responsible for border-sequence-directed production of T region circles in E. coli

The vir region of Ti plasmids is responsible for the transfer of the T region from Agrobacteria to plant cells; previous experiments suggested that formation of independent T region DNA circles is one step in this process. To study this step in Escherichia coli, we developed a binary vector system. One plasmid (= substrate) contains correctly oriented right and left borders from octopine plasmid pTiAch5. A gene with a counterselectable function (galK) was cloned between these borders. The galK gene is under control of the tac promoter-operator and the lac repressor with the laci gene also in the selection cassette. This construction allows determination of substrate plasmid mutants which have lost the selectable galK function. The second component of the system is one of a set of compatible plasmids harbouring various cloned parts from the vir region of nopaline plasmid pTiC58. A 3.6-kbp segment of the vir region turned out to be necessary and sufficient for production of substrate plasmid mutants which represented the equivalent of the T region containing a complete left border. From this vir region fragment four discrete proteins were expressed in minicells. The coding regions were mapped to a part conserved in nopaline and octopine plasmids; in the latter it appears to correspond to virC/D.