Diet quality does not affect resting metabolic rate or body temperatures selected by an herbivorous lizard

Diet quality can influence many aspects of digestion, but the links between diet quality and resting metabolism are poorly understood. In nature, it might be beneficial to reduce energy expenditure when only poor quality diets are available. Alternatively, animals might increase the processing capacity of the gut to more thoroughly extract energy. If maintaining the processing capacity of the gut is energetically expensive, then increasing gut size or function might result in higher resting metabolism. In ectotherms, most digestive functions are temperature dependent, thus another strategy to maintain energy balance might be to alter selected body temperatures. We tested whether differing concentrations of dietary fiber affected the resting metabolic rate or body temperatures selected by chuckwallas (Sauromalus obesus) – lizards that naturally experience marked variation in dietary fiber. Resting metabolic rates measured at two temperatures and over three time intervals did not differ between groups of lizards force-fed low- (30% neutral-detergent fiber; NDF) and high-fiber (45% NDF) diets, nor did these diet differences influence body temperatures selected in a thermal gradient. We conclude that ecologically relevant differences in diet quality may have negligible effects on resting metabolic rates and body temperatures selected by chuckwallas. Accepted: 5 January 1998     

A detailed restriction endonuclease site map of theZea mays plastid genome

Fragments produced by partial digestion of plastid DNA fromZea mays withEco RI were cloned in Charon 4A. A circular, fine structure physical map of the plastid DNA was then constructed from restriction endonucleaseSal I,Pst I,Eco RI, andBam HI recognition site maps of cloned overlapping segments of the plastid genome. These fragments were assigned molecular weights by reference to size markers from both pBR322 and lambda phage DNA. Because of the detail and extent of the derived map, it has been possible to construct a coordinate system which has a unique zero point and within which all the restriction fragments and previously described structural features can be mapped. A computer program was constructed which will display in a circular fashion any of the above features using an X-Y plotter.     

Thermal Properties of Supercritical Carbon Dioxide by Monte Carlo Simulations

We present simulation results for the volume expansivity, isothermal compressibility, isobaric heat capacity, Joule-Thomson coefficient and speed of sound for carbon dioxide (CO 2 ) in the supercritical region, using the fluctuation method based on Monte Carlo simulations in the isothermal-isobaric ensemble. We model CO 2 as a quadrupolar two-center Lennard-Jones fluid with potential parameters reported in the literature, derived from vapor-liquid equilibria (VLE) of CO 2 . We compare simulation results with an equation of state (EOS) for the two-center Lennard-Jones plus point quadrupole (2CLJQ) fluid and with a multiparametric EOS adjusted to represent CO 2 experimental data. It is concluded that the VLE-based parameters used to model CO 2 as a quadrupolar two-center Lennard-Jones fluid (both simulations and EOS) can be used with confidence for the prediction of thermodynamic properties, including those of industrial interest such as the speed of sound or Joule-Thomson coefficient, for CO 2 in the supercritical region, except in the extended critical region.     

The anticodon of the maize chloroplast gene for tRNA Leu UAA is split by a large intron.

The maize chloroplast gene encoding tRNA Leu UAA has been sequenced. It contains a 458 base pair intron between the first and second bases of the anticodon. The tRNA is 88 nucleotides long (the 3'-terminal CCA sequence included which, however, is not encoded by the gene) and differs in only four nucleotides (modified nucleotides are not considered) from the corresponding isoacceptor from bean chloroplasts. The unusual position of the intron in this maize chloroplast tRNA gene suggests a splicing model different from that generally accepted for eukaryotic split tRNA genes.