Transcontinental latitudinal variation in song performance and complexity in house wrens (Troglodytes aedon)

There is growing interest in latitudinal effects on animal behaviour and life history. One recent focus is on birdsong, which is hypothesized to be more elaborated or complex in the north temperate zone compared with the tropics. Current evidence is mixed and based on cross-species comparisons, or single species with restricted distributions. We circumvent these limitations using a transcontinental sample of 358 songs from house wrens (Troglodytes aedon) at 281 locations spanning more than 100° of latitude (52° N–55° S) across the Americas. We found a significant latitudinal gradient in several basic elements of song performance and complexity between north temperate and tropical populations. Furthermore, we document convergence in song patterns between populations at higher latitudes in the Northern and Southern Hemispheres. Effects were strongest for the number of elements in a song, and the rate of element production, both increasing towards the poles, with similar but weaker effects for other song dimensions (e.g. number of unique elements, trills and trill rate). We consider possible causes related to variable habitats and morphology, concluding that the shorter breeding seasons at higher latitudes in both hemispheres may favour greater song elaboration to mediate territory competition and mate choice.     

Aging attenuates the coronary blood flow response to cold air breathing and isometric handgrip in healthy humans

The purpose of this echocardiography study was to measure peak coronary blood flow velocity (CBV(peak)) and left ventricular function (via tissue Doppler imaging) during separate and combined bouts of cold air inhalation (-14 ± 3°C) and isometric handgrip (30% maximum voluntary contraction). Thirteen young adults and thirteen older adults volunteered to participate in this study and underwent echocardiographic examination in the left lateral position. Cold air inhalation was 5 min in duration, and isometric handgrip (grip protocol) was 2 min in duration; a combined stimulus (cold + grip protocol) and a cold pressor test (hand in 1°C water) were also performed. Heart rate, blood pressure, O(2) saturation, and inspired air temperature were monitored on a beat-by-beat basis. The rate-pressure product (RPP) was used as an index of myocardial O(2) demand, and CBV(peak) was used as an index of myocardial O(2) supply. The RPP response to the grip protocol was significantly blunted in older subjects (Δ1,964 ± 396 beats·min(-1)·mmHg) compared with young subjects (Δ3,898 ± 452 beats·min(-1)·mmHg), and the change in CBV(peak) was also blunted (Δ6.3 ± 1.2 vs. 11.2 ± 2.0 cm/s). Paired t-tests showed that older subjects had a greater change in the RPP during the cold + grip protocol [Δ2,697 ± 391 beats·min(-1)·mmHg compared with the grip protocol alone (Δ2,115 ± 375 beats·min(-1)·mmHg)]. An accentuated RPP response to the cold + grip protocol (compared with the grip protocol alone) without a concomitant increase in CBV(peak) may suggest a dissociation between the O(2) supply and demand in the coronary circulation. In conclusion, older adults have blunted coronary blood flow responses to isometric exercise.     

Guarana Provides Additional Stimulation over Caffeine Alone in the Planarian Model

The stimulant effect of energy drinks is primarily attributed to the caffeine they contain. Many energy drinks also contain other ingredients that might enhance the tonic effects of these caffeinated beverages. One of these additives is guarana. Guarana is a climbing plant native to the Amazon whose seeds contain approximately four times the amount of caffeine found in coffee beans. The mix of other natural chemicals contained in guarana seeds is thought to heighten the stimulant effects of guarana over caffeine alone. Yet, despite the growing use of guarana as an additive in energy drinks, and a burgeoning market for it as a nutritional supplement, the science examining guarana and how it affects other dietary ingredients is lacking. To appreciate the stimulant effects of guarana and other natural products, a straightforward model to investigate their physiological properties is needed. The planarian provides such a system. The locomotor activity and convulsive response of planarians with substance exposure has been shown to provide an excellent system to measure the effects of drug stimulation, addiction and withdrawal. To gauge the stimulant effects of guarana we studied how it altered the locomotor activity of the planarian species Dugesia tigrina. We report evidence that guarana seeds provide additional stimulation over caffeine alone, and document the changes to this stimulation in the context of both caffeine and glucose.     

The construction in vitro of derivatives of bacteriophage lambda carrying the amidase genes of Pseudomonas aeruginosa

Summary The amidase genes of Pseudomonas aeruginosa were inserted into a replacement vector following cleavage with the restriction endonuclease HindIII. The recombinant ami was detected by enhanced growth of Escherichia coli around plaques of the recombinant phage on minimal medium containing acetamide as the nitrogen source. Low levels of amidase activity were detected in E. coli cultures infected with ami and these were sufficient to allow growth with acetamide as nitrogen source. Lysis-defective derivatives of ami were made by introducing Q ^-, S ^- mutations. Cultures of E. coli infected with amiQ ^- S ^- synthesised amidase as the major protein. The amidase produced by these cultures was identical to that produced by PAC strains of P. aeruginosa in substrate specificity, thermal stability and immunological crossreaction.     

Structure of a B-DNA dodecamer. II. Influence of base sequence on helix structure

Detailed examination of the structure of the B-DNA dodecamer C-G-C-G-A-A-T-T-C-G-C-G, obtained by single-crystal X-ray analysis (Drew et al., 1981), reveals that the local helix parameters, twist, tilt and roll, are much more strongly influenced by base sequence than by crystal packing or any other external forces. The central EcoRI restriction endonuclease recognition site, G-A-A-T-T-C, is a B helix with an average of 9.8 base-pairs per turn. It is flanked on either side by single-base-pair steps having aspects of an A-like helix character. The dodecamer structure suggests several general principles, whose validity must be tested by other B-DNA analyses. (1) When an external bending moment is applied to a B-DNA double helix, it bends smoothly, without kinks or breaks, and with relatively little effect on local helix parameters. (2) Purine-3′,5′-pyrimidine steps open their base planes towards the major groove, pyrimidine-purine steps open toward the minor groove, and homopolymer (Pur-Pur, Pyr-Pyr) steps resist rolling in either direction. This behavior is related to the preference of pyrimidines for more negative glycosyl torsion angles. (3) CpG steps have smaller helical twist angles than do GpC, as though in compensation for their smaller intrinsic base overlap. Data on A-T steps are insufficient for generalization. (4) G.C base-pairs have smaller propellor twist than A · T, and this arises mainly from interstrand base overlap rather than the presence of the third hydrogen bond. (5) DNAase I cuts preferentially at positions of high helical twist, perhaps because of increased exposure of the backbone to attack. The correlation of the digestion patterns in solution and helical twist in the crystal argues for the essential identity of the helix structure in the two environments. (6) In the two places where the sequence TpCpG occurs, the C slips from under T in order to stack more efficiently over G. At the paired bases of this CpG step, the G and C are tilted so the angle between base planes is splayed out to the outside of the helix. This TpC is the most favored cutting site for DNAase I by a factor of 4.5 (Lomonossoff et al., 1981). (7) The EcoRI restriction endonuclease and methylase both appear to prefer a cutting site of the type purine-purine-A-T-T-pyrimidine, involving two adjacent homopolymer triplets, and this may be a consequence of the relative stiffness of homopolymer base-stacking observed in the dodecamer.     

Central nervous system regulation of mammalian hibernation: implications for metabolic suppression and ischemia tolerance

Torpor during hibernation defines the nadir of mammalian metabolism where whole animal rates of metabolism are decreased to as low as 2% of basal metabolic rate. This capacity to decrease profoundly the metabolic demand of organs and tissues has the potential to translate into novel therapies for the treatment of ischemia associated with stroke, cardiac arrest or trauma where delivery of oxygen and nutrients fails to meet demand. If metabolic demand could be arrested in a regulated way, cell and tissue injury could be attenuated. Metabolic suppression achieved during hibernation is regulated, in part, by the central nervous system through indirect and possibly direct means. In this study, we review recent evidence for mechanisms of central nervous system control of torpor in hibernating rodents including evidence of a permissive, hibernation protein complex, a role for A1 adenosine receptors, mu opiate receptors, glutamate and thyrotropin-releasing hormone. Central sites for regulation of torpor include the hippocampus, hypothalamus and nuclei of the autonomic nervous system. In addition, we discuss evidence that hibernation phenotypes can be translated to non-hibernating species by H(2)S and 3-iodothyronamine with the caveat that the hypothermia, bradycardia, and metabolic suppression induced by these compounds may or may not be identical to mechanisms employed in true hibernation.     

Improving N2 fixation from the plant down: Compatibility of Trifolium subterraneum L. cultivars with soil rhizobia can influence symbiotic performance

Plant genotypes of Trifolium subterraneum L. (subterranean clover) were evaluated for differences in symbiotic N₂ fixation with soil rhizobia, with the long-term aim of using plant selection to overcome sub-optimal N₂ fixation associated with poorly effective soil rhizobia. Symbiotic performance (SP) was assessed for 49 genotypes of subterranean clover with each of four pure Rhizobium strains isolated from soil. Plants were grown in N free media in the greenhouse and their shoot dry weights measured and expressed as a percentage of dry weight with R. leguminosarm bv. trifolii WSM1325, the recommended commercial inoculant. Average SP with two Rhizobium strains (H and J) ranged from completely ineffective to 80% of potential for the subterranean clover genotypes. Two clover cultivars with high (cv. Campeda) and low (cv. Clare) SP values were investigated in more detail. Campeda typically fixed more N₂ than Clare when inoculated with 30 soil extracts (4.2 vs 2.4 mg N₂ fixed/shoot) and with 14 pure strains isolated from those soils (4.2 vs 2.2 mg N₂ fixed/shoot). The poor performance of Clare could be attributed to interruptions at multiple stages of the symbiotic association, from nodule initiation (less nodules), nodule development (small, white nodules), through to reduced nodule function (N₂ fixed/mg nodule) depending on the inoculation treatment. Through the careful use of subterranean clover genotypes by plant breeders it should be possible to make significant gains in the SP of future subterranean clover cultivars.     

Hsp110 over-expression increases the immunogenicity of the murine CT26 colon tumor

Several studies have suggested a positive correlation between heat shock protein (hsp) expression and tumor immunogenicity. Independently, many studies have shown that hsp purified from tumors can be used as a tumor-specific vaccine. In this study, we have explored the connection between hsp expression and anti-tumor immunity by transducing murine CT26 colon carcinoma cells with the cDNA of a major hsp, i.e. hsp110. We have shown that over-expression of hsp110 has no effect on CT26 tumor cell growth in vitro, and does not inhibit their anchorage-independent growth capacity. However, in situ, hsp110 over-expressing CT26 tumor (CT26-hsp110) grew at a significantly reduced rate as compared to the wild-type CT26 tumor in immunocompetent mice. Moreover, immunization of mice with inactivated CT26-hsp110 cells significantly inhibited the growth of wild-type CT26 tumor. This immunity was associated with an increased frequency of tumor-specific T cells after vaccination. An in vivo antibody depletion assay demonstrated that inactivated CT26-hsp110 cells elicited anti-tumor responses involving CD8(+) T cells and natural killer (NK) cells, but not CD4(+) T cells. Lastly, the effect of the addition of granulocyte-macrophage colony stimulating factor (GM-CSF) to these vaccine formulations was determined. Mice immunized with irradiated CT26-hsp110 cells combined with GM-CSF-producing bystander cells revealed a complete inhibition of CT26 tumor growth, indicating a synergy between inactivated CT26-hsp110 vaccine activity and GM-CSF. These observations demonstrate that manipulation of hsp110 expression in tumors, specifically when combined with GM-CSF, represents a potentially powerful approach to cancer vaccine formulation.