Differential effects of magnesium on the hydrolysis of ADP and ATP in human term placenta. Effect of substrates and potassium

Genetic Dissection of ICP-Detected Nutrient Accumulation in the Whole Seed of Common Bean (Phaseolus vulgaris L.)

Nutrient transport to grain legume seeds is not well studied and can benefit from modern methods of elemental analysis including spectroscopic techniques. Some cations such as potassium (K) and magnesium (Mg) are needed for plant physiological purposes. Meanwhile, some minerals such as copper (Cu), iron (Fe), molybdenum (Mo), and zinc (Zn) are important micronutrients. Phosphorus (P) is rich in legumes, while sulfur (S) concentration is related to essential amino acids. In this research, the goal was to analyze a genetic mapping population of common bean (Phaseolus vulgaris L.) with inductively coupled plasma (ICP) spectrophotometry to determine concentrations of and to discover quantitative trait loci (QTL) for 15 elements in ground flour of whole seeds. The population was grown in randomized complete block design experiments that had been used before to analyze Fe and Zn. A total of 21 QTL were identified for nine additional elements, of which four QTL were found for Cu followed by three each for Mg, Mn, and P. Fewer QTL were found for K, Na and S. Boron (B) and calcium (Ca) had only one QTL each. The utility of the QTL for breeding adaptation to element deficient soils and association with previously discovered nutritional loci are discussed.

PKA tightly bound to human placental mitochondria participates in steroidogenesis and is not modified by cAMP

INTRODUCTION

Protein phosphorylation plays an important role in the modulation of steroidogenesis and it depends on the activation of different signaling cascades. Previous data showed that PKA activity is related to steroidogenesis in mitochondria from syncytiotrophoblast of human placenta (HPM). PKA localization and contribution in progesterone synthesis and protein phosphorylation of HPM was assessed in this work.

METHODS

Placental mitochondria and submitochondrial fractions were used. Catalytic and regulatory PKA subunits were identified by Western blot. PKA activity was determined by the incorporation of (32)P into proteins in the presence or absence of specific inhibitors. The effect of PKA activators and inhibitors on steroidogenesis and protein phosphorylation in HPM was tested by radioimmunoassay and autoradiography.

RESULTS

The PKAα catalytic subunit was distributed in all the submitochondrial fractions whereas βII regulatory subunit was the main isoform observed in both the outer and inner membranes of HPM. PKA located in the inner membrane showed the highest activity. Progesterone synthesis and mitochondrial protein phosphorylation are modified by inhibitors of PKA catalytic subunit but are neither sensitive to inhibitors of the regulatory subunit nor to activators of the holoenzyme.

DISCUSSION

The lack of response in the presence of PKA activators and inhibitors of the regulatory subunit suggests that the activation of intramitochondrial PKA cannot be prevented or further activated.

CONCLUSIONS

The phosphorylating activity of PKA inside HPM could be an important component of the steroidogenesis transduction cascade, probably exerting its effects by direct phosphorylation of its substrates or by modulating other kinases and phosphatases.

Maternal smoking is associated with mitochondrial DNA depletion and respiratory chain complex III deficiency in placenta

Maternal smoking during pregnancy is often associated with a decrease in placental function, which might lead to intrauterine growth retardation. Because tobacco is known to alter the mitochondrial respiratory function in cardiomyocytes and lung tissue, we hypothesized that placental mitochondrial function could be altered by maternal smoking. Placental mitochondria from 9 smoking and 19 nonsmoking mothers were isolated by differential centrifugation. Mitochondrial oxygen consumption was measured by polarography, and the enzymatic activity of each complex of the electron transport chain was assessed by spectrophotometry. In addition, the relative content in mitochondrial DNA (mtDNA) was determined by real-time quantitative PCR in placentas from seven smoking and seven nonsmoking mothers. We observed a 29% reduction in the enzymatic activity of complex III in the placental mitochondria from smokers compared with nonsmokers (P = 0.03). The relative content of mtDNA (with respect to the beta-globin gene) was reduced by 37% in the placental tissue from smokers compared with nonsmokers (P < 0.02). Both the enzymatic activity of complex III and mtDNA content were inversely related with the daily consumption of cigarettes, and mtDNA content was correlated with cord blood insulin-like growth factor-binding protein-3 (r = 0.74, P < 0.01), a marker of fetal growth. These results show that maternal smoking is associated with placental mitochondrial dysfunction, which might contribute to restricted fetal growth by limiting energy availability in cells.