Molecular evolution of mitochondrial 12S RNA and cytochrome b sequences in the pantherine lineage of Felidae

DNA sequence comparisons of two mitochondrial DNA genes were used to infer phylogenetic relationships among 17 Felidae species, notably 15 in the previously described pantherine lineage. The polymerase chain reaction (PCR) was used to generate sequences of 358 base pairs of the mitochondrial 12S RNA gene and 289 base pairs of the cytochrome b protein coding gene. DNA sequences were compared within and between 17 felid and five nonfelid carnivore species. Evolutionary trees were constructed using phenetic, cladistic, and maximum likelihood algorithms. The combined results suggested several phylogenetic relationships including (1) the recognition of a recently evolved monophyletic genus Panthera consisting of Panthera leo, P. pardus, P. onca, P. uncia, P. tigris, and Neofelis nebulosa; (2) the recent common ancestry of Acinonyx jubatus, the African cheetah, and Puma concolor, the American puma; and (3) two golden cat species, Profelis temmincki and Profelis aurata, are not sister species, and the latter is strongly associated with Caracal caracal. These data add to the growing database of vertebrate mtDNA sequences and, given the relatively recent divergence among the felids represented here (1-10 Myr), allow 12S and cytochrome b sequence evolution to be addressed over a time scale different from those addressed in most work on vertebrate mtDNA.      

Sea urchin Hox genes: insights into the ancestral Hox cluster

We describe the Hox cluster in the radially symmetric sea urchin and compare our findings to what is known from clusters in bilaterally symmetric animals. Several Hox genes from the direct-developing sea urchin Heliocidaris erythrogramma are described. CHEF gel analysis shows that the Hox genes are clustered on a < or = 300 kilobase (kb) fragment of DNA, and only a single cluster is present, as in lower chordates and other nonvertebrate metazoans. Phylogenetic analyses of sea urchin, amphioxus, Drosophila, and selected vertebrate Hox genes confirm that the H. erythrogramma genes, and others previously cloned from other sea urchins, belong to anterior, central, and posterior groups. Despite their radial body plan and lack of cephalization, echinoderms retain at least one of the anterior group Hox genes, an orthologue of Hox3. The structure of the echinoderm Hox cluster suggests that the ancestral deuterostome had a Hox cluster more similar to the current chordate cluster than was expected Sea urchins have at least three Abd-B type genes, suggesting that Abd-B expansion began before the radiation of deuterostomes.      

Metabolic enzyme response in the pressure-overloaded heart of weanling and adult rats

Weanling and adult rats were subjected to left ventricular pressure overload induced by abdominal aortic constriction. At 5 days or 5 weeks postsurgery, the left ventricle (LV) was dissected, weighed, and metabolic marker enzyme activities (mumole/g/min) of tissue homogenates were measured. Enzymes representing glycolytic (phosphofructokinase (PFK] and mitochondrial (citrate synthase (CS) and malate dehydrogenase (MDH] metabolisms were evaluated. Five days of pressure overload had detectable, but statistically nonsignificant effects on left ventricles of both weanling and adult rats. Sustained pressure overload (5 weeks) increased LV weight by 52 and 39% in weanling and adult rats, respectively. PFK activity was 24 +/- 1 (mean +/- SE) in control weanlings and was unaltered in any of the other groups. LDH isoenzyme composition was estimated by substrate inhibition (ratio 0.33/10 mM pyruvate). With normal heart development, the LDH ratio increased from 1.89 +/- 0.06 to 2.03 +/- 0.08. Pressure overload had no influence on the adult LDH ratio. Developmental LDH responses were not observed in weanling LV after 5 weeks of aortic constriction (1.74 +/- 0.06). The product of CS activity and LV weight was used to estimate mitochondrial mass in the ventricle. Mitochondria accumulated at a rate of about 5% increase per day over the intervening 5-week period of normal heart growth. Pressure overload for 5 weeks in weanling rats elicited net accumulation of mitochondria at a rate of about 9% increase per day. Mitochondrial accumulation in the adapting adult rat heart amounted to less than 1% increase per day. The results indicate that qualitative and quantitative differences exist between young and adult animals in their heart enzyme adaptive responses to pressure overloading. Divergent metabolic adaptations may contribute to heart functional differences in the enlarged heart of weanlings and adults.