mtDNA diversity in rhesus monkeys reveals overestimates of divergence time and paraphyly with neighboring species

Reconstructions of the human-African great ape phylogeny by using mitochondrial DNA (mtDNA) have been subject to considerable debate. One confounding factor may be the lack of data on intraspecific variation. To test this hypothesis, we examined the effect of intraspecific mtDNA diversity on the phylogenetic reconstruction of another Plio- Pleistocene radiation of higher primates, the fascicularis group of macaque (Macaca) monkey species. Fifteen endonucleases were used to identify 10 haplotypes of 40-47 restriction sites in M. mulatta, which were compared with similar data for the other members of this species group. Interpopulational, intraspecific mtDNA diversity was large (0.5%- 4.5%), and estimates of divergence time and branching order incorporating this variation were substantially different from those based on single representatives of each species. We conclude that intraspecific mtDNA diversity is substantial in at least some primate species. Consequently, without prior information on the extent of genetic diversity within a particular species, intraspecific variation must be assessed and accounted for when reconstructing primate phylogenies. Further, we question the reliability of hominoid mtDNA phylogenies, based as they are on one or a few representatives of each species, in an already depauperate superfamily of primates.      

Reactive sulfhydryl groups in Saccharomyces cerevisiae phosphoenolpyruvate carboxykinase

Saccharomyces cerevisiae phosphoenolpyruvate carboxykinase (ATP:oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.49) is inactivated by several thiol- and vicinal dithiol-specific reagents. Titration experiments of the enzyme with 5,5'-dithiobis(2-nitrobenzoate) (DTNB) show the presence of reactive monothiol and vicinal dithiol groups, whose modifications lead to enzyme inactivation. The enzyme is also inactivated by N-(1-pyrenyl)iodoacetamide (PyrIAM), with a binding stoichiometry of approx. 2 mol per mol of enzyme subunit. A high level of pyrene excimer fluorescence is detected on the labeled enzyme, thus implying the reaction of the reagent with two spatially close sulfhydryl groups in the protein. The carboxykinase is not completely inactivated by different vicinal dithiol-specific reagents, thus implying a catalytically non-essential character for these groups. From substrate protection experiments of the enzyme inactivation by DTNB, PyrIAM and vicinal dithiol-specific reagents, it is concluded that the loss of enzyme activity is caused by the modification of both thiol and vicinal dithiol groups in the substrate binding region.     

Toxicokinetics of di(2-ethylhexyl) phthalate (DEHP) and its effects on luteal function in sheep

The aim of the present study was to determine the toxicokinetics of short-term exposures to di(2-ethylhexyl) phthalate (DEHP) and its effects on ovarian cyclicity and luteal function using a sheep experimental model. For establishing the model, we examined the clearance of DEHP after intravenous (i.v.) and intramuscular (i.m.) administration of a single dose of 25 mg/kg body weight (b.w.) and after i.m. administration of two different doses (25 and 50 mg/kg b.w.; DEHP25 and DEHP50, respectively) three times a week for two months. Results showed a significant, dose-dependent effect of DEHP administration, when compared to the control group (CTL; untreated ewes; n = 6), on the duration of the ewes’ estrous cycles (17.1 ± 0.5 days, CTL; 15.1 ± 0.9 days, DEHP25; 12.0 ± 0.8 days, DEHP50; p < 0.05); 94.9% of the cycles were of regular duration (15–19 days) in CTL, but only 51.1% and 25.4% in DEHP25 and DEHP50, respectively. Corpora lutea (CL) were smaller in DEHP50 than in DEHP25 (p < 0.05) and were smaller in both groups than in CTL (p < 0.005), but the maximum plasma concentrations of progesterone were greater (p < 0.05) in DEHP25 and DEHP50 than in CTL. In conclusion, the exposure of cycling ewes to DEHP causes shortening of the ovulatory cycles due mainly to a reduction in the size and lifespan of CL. However, the exposure to the phthalate is also associated with an increase in circulating concentrations of progesterone, suggesting the influence of DEHP on steroid metabolism.     

Identification and characterization of a cell-surface receptor, P2Y15, for AMP and adenosine

AMP and adenosine are found in all cell types and can be released by cells or created extracellularly from the breakdown of ATP and ADP. We have identified an orphan G protein-coupled receptor with homology to the P2Y family of nucleotide receptors that can respond to both AMP and adenosine. Based on its ability to functionally bind the nucleotide AMP, we have named it P2Y15. Upon stimulation, P2Y15 induces both Ca2+ mobilization and cyclic AMP generation, suggesting coupling to at least two different G proteins. It is highly expressed in mast cells and is found predominantly in the tissues of the respiratory tract and kidneys, which are known to be affected by AMP, adenosine, and adenosine antagonists. Until now, the effects of AMP have been thought to depend on its dephosphorylation to adenosine but we demonstrate here that P2Y15 is a bona fide AMP receptor by showing that it binds [(32)P]AMP. Because AMP and adenosine have bronchoconstrictive effects that can be inhibited by theophylline, we tested whether theophylline and other adenosine receptor antagonists can block P2Y15. We found inhibition at a theophylline concentration well within the therapeutic dose range, indicating that P2Y15 may be a clinically important target of this drug.     

A sulfated galactan with antioxidant capacity from the green variant of tetrasporic Gigartina skottsbergii (Gigartinales, Rhodophyta)

The water soluble polysaccharide produced by the green variant of tetrasporic Gigartina skottsbergii was found to be composed of D-galactose and sulfate groups in a molar ratio of 1.0:0.65. (1)H and (13)C NMR spectroscopy studies of the desulfated polysaccharide showed a major backbone structure of alternating 3-linked β-D-galactopyranosyl and 4-linked α-D-galactopyranosyl units, and minor signals ascribed to 3-O-methyl-substitution on the latter unit. Ethylation analysis of the polysaccharide indicated that the sulfate groups are mainly located at position O-2 of 4-linked α-D-galactopyranosyl residue and partially located at positions O-6 of the same unit and at position O-2 of 3-linked β-D-galactopyranosyl residue, and confirmed the presence of 3-O-methyl-galactose in minor amounts (4.4%). The sulfated d-galactan presents a similar structure to λ carrageenan but with much lower sulfation at position O-6 of the α-residue and at position O-2 of β-residue. The antioxidant capacity of the sulfated d-galactan was evaluated by the peroxyl radicals (ORAC method), hydroxyl radicals, chelating activity, and ABTS(+) assays. Kinetic results obtained in these assays were compared with those obtained for the commercial λ carrageenan. The antioxidant activity toward peroxyl radicals was higher for commercial λ carrageenan, this agrees with its higher content of sulfate group. The kinetics of the reaction of both polysaccharides with hydroxyl and ABTS(+) radicals showed a complex mechanism, but the antioxidant activity was higher for the polysaccharide from the green variant of tetrasporic Gigartina skottsbergii.     

Characterization of a distinctive pattern of periovulatory leptin secretion and its relationship with ovulation rate and luteal function in swine with obesity/leptin resistance

Patterns of leptin secretion during the estrous cycle and the possible relationship of changes in circulating leptin during the periovulatory period with ovarian function in sows of obese (Iberian breed) and lean genotype (Large White×Landrace) were evaluated in two consecutive experiments. Plasma leptin concentrations throughout the estrous cycle in lean sows remain unchanged, but Iberian females showed a periovulatory increase in circulating leptin levels without associated changes in body condition and fatness. In these sows, plasma leptin concentrations at Days -1 and 0 of the cycle were found to be positively correlated with the ovulation rate (r=0.943 and r=0.987, respectively; P<0.05 for both), but the levels of leptin at Day 0 were negatively correlated with the progesterone release from Day 3 (r=-0.557; P<0.05) and, became more evident at Day 5 of the estrous cycle (r=-0.924; P<0.005). Such relationships were not observed in the females of the lean genotype. In conclusion, the present study indicates the existence of a distinctive pattern in the periovulatory leptin secretion in swine with obesity and leptin resistance, which is associated with the number and functionality of the corpora lutea present in the subsequent cycle.     

Absence of Tangentially Migrating Glutamatergic Neurons in the Developing Avian Brain

1. Download high-res image (177KB)
2. Download full-size image