Oxygen consumption, carbon dioxide excretion and respiratory quotient of larval lampreys (Mordacia mordax) in air

The standard rates of O2 consumption of larval Mordacia mordax (weight range 1.3-2.3 g), after these ammocetes had been in humidified air for 18 hr, were 26.8, 46.3 and 71.2 microL x g(-1) x hr(-1) at 10, 15 and 20 degrees C, respectively. The corresponding rates of CO2 excretion were 20.7, 35.6 and 54.1 microL x g(-1) x hr(-1). The RQs at the three temperatures were essentially identical (0.76 or 0.77) and similar to that of adults of the lamprey Geotria australis in air at 15 degrees C. The above RQs for ammocoetes, which are probably similar to those that would be recorded in water, are consistent with the view that the aerobic respiration of these animals relies predominantly on lipid as an energy source, but that some energy is derived from carbohydrate and/or protein. The RQs for larval and adult lampreys in air lie well within the range recorded for amphibious fishes in air.     

Towards Metal-Mediated G-Quartet Analogues: 1,2,4-Triazole Nucleotides

We proposed that metal-coordinating nucleotides could be used to control the assembly of G-quadruplexes through the formation of an artificial metal-centered quartet. Several guanine-rich DNA sequences containing 1,2,4-triazole-functionalized nucleotides were investigated. These oligonucleotides were designed to form quartets mediated by metal-triazole bonding both on the surface of and within the G-quadruplex core. In contrast to duplex studies in which 1,2,4-triazole nucleosides serve as a mimic of Watson-Crick base-pairs, our results show that these nucleosides are not suitable components of an artificial metal-centered quartet.     

A plate-based high-throughput activity assay for polysialyltransferase from Neisseria meningitidis

Polysialyltransferases (PSTs) assemble polysialic acid (PSA) and have been implicated in many biological processes. For example, certain bacteria such as neuroinvasive Neisseria meningitidis decorate themselves in a PSA capsule to evade the innate immune system. Identifying inhibitors of PSTs therefore represents an attractive therapeutic goal and herein we describe a high-throughput, robust, and sensitive microtiter-plate-based activity assay for PST from N. meningitidis. A trisialyl lactoside (GT3) serving as the acceptor substrate was immobilized on a 384-well plate by click chemistry. Incubation with PST and CMP-sialic acid for 30 min resulted in polysialylation. The immobilized PSA was then directly detected using a green fluorescent protein (GFP)-fused PSA-binding protein consisting of the catalytically inactive double mutant of an endosialidase (GFP-EndoNF DM). We report very good agreement between kinetic and inhibition parameters obtained with our on-plate assay versus our in-solution validation assay. In addition we prove our assay is robust and reliable with a Z′ score of 0.79. All aspects of our assay are easily scalable owing to optimization trials that allowed immobilization of acceptor substrates prepared from crude reaction mixtures and the use of cell lysates. This assay methodology enables large-scale PST inhibitor screens and can be harnessed for directed evolution screens.     

Comparative physiology of Australian quolls (Dasyurus; Marsupialia)

Quolls (Dasyurus) are medium-sized carnivorous dasyurid marsupials. Tiger (3,840 g) and eastern quolls (780 g) are mesic zone species, northern quolls (516 g) are tropical zone, and chuditch (1,385 g) were once widespread through the Australian arid zone. We found that standard physiological variables of these quolls are consistent with allometric expectations for marsupials. Nevertheless, inter-specific patterns amongst the quolls are consistent with their different environments. The lower T _b of northern quolls (34°C) may provide scope for adaptive hyperthermia in the tropics, and they use torpor for energy/water conservation, whereas the larger mesic species (eastern and tiger quolls) do not appear to. Thermolability varied from little in eastern (0.035°C °C⁻¹) and tiger quolls (0.051°C oC⁻¹) to substantial in northern quolls (0.100°C oC⁻¹) and chuditch (0.146°C oC⁻¹), reflecting body mass and environment. Basal metabolic rate was higher for eastern quolls (0.662 ± 0.033 ml O₂ g⁻¹ h⁻¹), presumably reflecting their naturally cool environment. Respiratory ventilation closely matched metabolic demand, except at high ambient temperatures where quolls hyperventilated to facilitate evaporative heat loss; tiger and eastern quolls also salivated. A higher evaporative water loss for eastern quolls (1.43 ± 0.212 mg H₂O g⁻¹ h⁻¹) presumably reflects their more mesic distribution. The point of relative water economy was low for tiger (−1.3°C), eastern (−12.5°C) and northern (+3.3) quolls, and highest for the chuditch (+22.6°C). We suggest that these differences in water economy reflect lower expired air temperatures and hence lower respiratory evaporative water loss for the arid-zone chuditch relative to tropical and mesic quolls.     

Mapping the mutation causing lens luxation in several terrier breeds

Primary lens luxation (PLL), a painful and blinding inherited condition, is common in several breeds of terrier. Here we have examined the Veterinary Medical Database of patient encounters and Canine Eye Registration Foundation (CERF) cases records for the last 10 years and found the diagnosis recorded in 85 breeds. We have performed association analysis using a genome-wide microsatellite screen to map mutations underlying the condition in miniature bull terriers and Lancashire heelers. These studies show microsatellite alleles in disequilibrium with disease status with highest support in a 6.3-Mbp region in the central part of chromosome 3 (-log P(max) = 6.4). The same region also shows an association to the disease in Tibetan terriers. Tight junction protein-1 (TJP1) is a positional candidate to contain the PLL mutation. All recognized exons and splice junctions of TJP1 have been sequenced from affected, obligate carrier and control Lancashire heeler dogs. Several polymorphisms have been found, but these are not likely to cause the disease.     

Quantification of global transcription patterns in prokaryotes using spotted microarrays

We describe an analysis, applicable to any spotted microarray dataset produced using genomic DNA as a reference, that quantifies prokaryotic levels of mRNA on a genome-wide scale. Applying this to Mycobacterium tuberculosis, we validate the technique, show a correlation between level of expression and biological importance, define the complement of invariant genes and analyze absolute levels of expression by functional class to develop ways of understanding an organism's biology without comparison to another growth condition.