Degraded Time-Frequency Acuity to Time-Reversed Notes

Time-reversal symmetry breaking is a key feature of many classes of natural sounds, originating in the physics of sound production. While attention has been paid to the response of the auditory system to “natural stimuli,” very few psychophysical tests have been performed. We conduct psychophysical measurements of time-frequency acuity for stylized representations of “natural”-like notes (sharp attack, long decay) and the time-reversed versions of these notes (long attack, sharp decay). Our results demonstrate significantly greater precision, arising from enhanced temporal acuity, for such sounds over their time-reversed versions, without a corresponding decrease in frequency acuity. These data inveigh against models of auditory processing that include tradeoffs between temporal and frequency acuity, at least in the range of notes tested and suggest the existence of statistical priors for notes with a sharp-attack and a long-decay. We are additionally able to calculate a minimal theoretical bound on the sophistication of the nonlinearities in auditory processing. We find that among the best studied classes of nonlinear time-frequency representations, only matching pursuit, spectral derivatives, and reassigned spectrograms are able to satisfy this criterion.     

Around the Mediterranean: an extreme example of loop migration in a long‐distance migratory passerine

An important issue in migration research is how small‐bodied passerines pass over vast geographical barriers; in European–African avian migration, these are represented by the Mediterranean Sea and the Sahara Desert. Eastern (passing eastern Mediterranean), central (passing Apennine Peninsula) and western (via western Mediterranean) major migration flyways are distinguished for European migratory birds. The autumn and spring migration routes may differ (loop migration) and there could be a certain level of individual flexibility in how individuals navigate themselves during a single migration cycle. We used light‐level loggers to map migration routes of barn swallows Hirundo rustica breeding in the centre of a wide putative contact zone between the northeastern and southernwestern European populations that differ in migration flyways utilised and wintering grounds. Our data documented high variation in migration patterns and wintering sites of tracked birds (n = 19 individuals) from a single breeding colony, with evidence for loop migration in all but one of the tracked swallows. In general, two migratory strategies were distinguished. In the first, birds wintering in a belt stretching from southcentral to southern Africa that used an eastern route for both the spring and autumn migration, then shifted their spring migration eastwards (anti‐clockwise loops, n = 12). In the second, birds used an eastern or central route to their wintering grounds in central Africa, shifting the spring migration route westward (clockwise loops, n = 7). In addition, we observed an extremely wide clockwise loop migration encompassing the entire Mediterranean, with one individual utilising both the eastern (autumn) and western (spring) migratory flyway during a single annual migration cycle. Further investigation is needed to ascertain whether clockwise migratory loops encircling the entire Mediterranean also occur other small long‐distance passerine species.     

Genetic analysis of autosomal and X-linked markers across a mouse hybrid zone

In this paper, we present results of the first comprehensive study of the introgression of both autosomal and sex-chromosome markers across the central European portion of the hybrid zone between two house mouse subspecies, Mus musculus musculus and M. m. domesticus. More than 1800 individuals sampled from 105 sites were analyzed with a set of allozyme loci (hopefully representing neutral or nearly neutral markers) and X-linked loci (which are assumed to be under selection). The zone center is best modeled as a single straight line independent of fine-scale local geographic or climatic conditions, being maintained by a balance between dispersal and selection against hybrids. The width (w) of the multilocus autosomal cline was estimated as 9.6 km whereas the estimate for the compound X-chromosome cline was about 4.6 km only. As the former estimate is comparable to that of the Danish portion of the zone (assumed to be much younger than the central European one), zone width does not appear to be related to its age. The strength (B) of the central barrier was estimated as about 20 km; with dispersal (sigma) of about 1 km/gen(1/2), this means effective selection (s*) is approximately 0.06-0.09 for autosomal loci and about 0.25 for X-linked loci. The number of loci under selection was estimated as N= 56-99 for autosomes and about 380 for X-linked loci. Finally, we highlight some potential pitfalls in hybrid zone analyses and in comparisons of different transects. We suggest that conclusions about parts of the mouse genome involved in reproductive isolation and speciation should be drawn with caution and that analytical approaches always providing some estimates should not be used without due care regarding the support or confidence of such estimates, especially if conclusions are based on the difference between these estimates. Finally, we recommend that analysis in two-dimensional space, dense sampling, and rigorous treatment of data, including inspection of likelihood profiles, are essential for hybrid zone studies.     

POLYPHASIC CHARACTERIZATION OF THREE STRAINS OF ANABAENA RENIFORMIS AND APHANIZOMENON APHANIZOMENOIDES (CYANOBACTERIA) AND THEIR RECLASSIFICATION TO SPHAEROSPERMUM GEN. NOV. (INCL. ANABAENA KISSELEVIANA)1

Occurrences of rare cyanobacteria Anabaena reniformis Lemmerm. and Aphanizomenon aphanizomenoides (Forti) Horecká et Komárek were recently detected at several localities in the Czech Republic. Two monoclonal strains of An. reniformis and one strain of Aph. aphanizomenoides were isolated from distant localities and different sampling years. They were characterized by a combination of morphological, genetic, and biochemical approaches. For the first time, partial 16S rRNA gene sequences were obtained for these morphospecies. Based on this gene, all of these strains clustered separately from other planktonic Anabaena and Aphanizomenon strains. They appeared in a cluster with Cylindrospermopsis Seenaya et Subba Raju and Raphidiopsis F. E. Fritsch et M. F. Rich, clustered closely together with two An. kisseleviana Elenkin strains available from GenBank. A new generic entity was defined (Sphaerospermum gen. nov., with the type species S. reniforme, based on the traditional species An. reniformis). These results contribute significantly to the knowledge base about genetic heterogeneity among planktonic Anabaena–like and Aphanizomenon–like morphospecies. Accordingly, the subgenus Dolichospermum, previously proposed for the group of planktonic Anabaena, should be revaluated. Secondary metabolite profiles of the An. reniformis and Aph. aphanizomenoides strains differed considerably from 17 other planktonic Anabaena strains of eight morphospecies isolated from Czech water bodies. Production of puwainaphycin A was found in both of the An. reniformis strains. Despite the relatively short phylogenetic distance from Cylidrospermopsis, the production of cylindrospermopsin was not detected in any of our strains.     

The effects of membrane compartmentalization of csk on TCR signaling

The TCR signal transduction is initiated by the activation of Src-family kinases (SFK) which phosphorylate Immunoreceptor tyrosine-based activation motifs (ITAM) present in the intracellular parts of the T-cell receptor (TCR) signaling subunits. Numerous data suggest that after stimulation TCR interacts with membrane rafts and thus it gains access to SFK and other important molecules involved in signal transduction. However, the precise mechanism of this process is unclear. One of the key questions is how SFK access TCR and what is the importance of non-raft and membrane raft-associated SFK for the initiation and maintenance of the TCR signaling. To answer this question we targeted a negative regulator of SFK, C-terminal Src kinase (Csk) to membrane rafts, recently described “heavy rafts” or non-raft membrane. Our data show that only Csk targeted into “classical” raft but not to “heavy raft” or non-raft membrane effectively inhibits TCR signaling, demonstrating the critical role of membrane raft-associated SFK in this process.     

Estimation of the quantity of bacteria encapsulated in Lentikats Biocatalyst via phospholipid fatty acids content: a preliminary study

The content of phospholipid fatty acids (PLFA) was determined in samples of polyvinyl alcohol lenses (Lentikats Biocatalyst, LB) with encapsulated Paracoccus denitrificans withdrawn during long-term denitrification experiments. The total PLFA content correlated highly with specific denitrification activities of LB as well as biomass estimation based on image analyses of microscopic photos. The results confirmed the applicability of PLFA determination for estimation of the amount of living encapsulated microbial biomass during biotechnological applications.     

Is <Emphasis Type="Italic">Testudo werneri</Emphasis> a distinct species?

Sequence variation of a 1066 bp long mtDNA fragment (cytochrome b gene, adjacent part of tRNA-Thr gene) of four known-locality samples of Testudo kleinmanni (Tripolitania, Libya) and of four samples of T. werneri (Negev, Israel) is compared with additional five sequences of pet trade tortoises allegedly representing T. kleinmanni. Four haplotypes, differing in one to four mutation steps occur. The most common haplotype was shared by all known-locality samples of T. kleinmanni and three T. werneri. Sequence variation within each nominal species and in the pooled sample of T. kleinmanni, T. werneri and pet trade tortoises is the lowest known for any Testudo species. We conclude there is no support for the validity of T. werneri Perälä, 2001.     

Inefficient cross-presentation limits the CD8+ T cell response to a subdominant tumor antigen epitope

CD8(+) T lymphocytes (T(CD8)) responding to subdominant epitopes provide alternate targets for the immunotherapy of cancer, particularly when self-tolerance limits the response to immunodominant epitopes. However, the mechanisms that promote T(CD8) subdominance to tumor Ags remain obscure. We investigated the basis for the lack of priming against a subdominant tumor epitope following immunization of C57BL/6 (B6) mice with SV40 large tumor Ag (T Ag)-transformed cells. Immunization of B6 mice with wild-type T Ag-transformed cells primes T(CD8) specific for three immunodominant T Ag epitopes (epitopes I, II/III, and IV) but fails to induce T(CD8) specific for the subdominant T Ag epitope V. Using adoptively transferred T(CD8) from epitope V-specific TCR transgenic mice and immunization with T Ag-transformed cells, we demonstrate that the subdominant epitope V is weakly cross-presented relative to immunodominant epitopes derived from the same protein Ag. Priming of naive epitope V-specific TCR transgenic T(CD8) in B6 mice required cross-presentation by host APC. However, robust expansion of these T(CD8) required additional direct presentation of the subdominant epitope by T Ag-transformed cells and was only significant following immunization with T Ag-expressing cells lacking the immunodominant epitopes. These results indicate that limited cross-presentation coupled with competition by immunodominant epitope-specific T(CD8) contributes to the subdominant nature of a tumor-specific epitope. This finding has implications for vaccination strategies targeting T(CD8) responses to cancer.     

Secondary alcohol dehydrogenase catalyzes the reduction of exogenous acetone to 2-propanol in Trichomonas vaginalis

Secondary alcohols such as 2-propanol are readily produced by various anaerobic bacteria that possess secondary alcohol dehydrogenase (S-ADH), although production of 2-propanol is rare in eukaryotes. Specific bacterial-type S-ADH has been identified in a few unicellular eukaryotes, but its function is not known and the production of secondary alcohols has not been studied. We purified and characterized S-ADH from the human pathogen Trichomonas?vaginalis. The kinetic properties and thermostability of T.?vaginalis S-ADH were comparable with bacterial orthologues. The substantial activity of S-ADH in the parasite's cytosol was surprising, because only low amounts of ethanol and trace amounts of secondary alcohols were detected as metabolic end products. However, S-ADH provided the parasite with a high capacity to scavenge and reduce external acetone to 2-propanol. To maintain redox balance, the demand for reducing power to metabolize external acetone was compensated for by decreased cytosolic reduction of pyruvate to lactate and by hydrogenosomal metabolism of pyruvate. We speculate that hydrogen might be utilized to maintain cytosolic reducing power. The high activity of Tv-S-ADH together with the ability of T.?vaginalis to modulate the metabolic fluxes indicate efficacious metabolic responsiveness that could be advantageous for rapid adaptation of the parasite to changes in the host environment.