Polyphosphate polymers during early embryogenesis of Periplaneta americana

8 p. : il.Inorganic polyphosphates (PolyP) are linear polymers of phosphate (Pi) residues linked by high-energy phosphoanhydride bonds. Despite a wide distribution, their role during insect embryogenesis has not been examined so far. In this study, we show the mobilization of PolyP polymers during the embryogenesis of the cockroach Periplaneta americana. PolyP was detected by enzymatic and fluorimetric assays and found to accumulate in two main sizes by agarose gel electrophoresis. Confocal microscopy showed their presence in small vesicles. In addition, X-ray microanalysis of small vesicles showed considerable amounts of calcium, sodium and magnesium, suggesting an association of PolyP with these elements. Variations of the free Ca+2, Pi and PolyP levels were observed during the first days of embryogenesis. Our results are consistent with the hypothesis that phosphate ions modulate PolyP variation and that PolyP hydrolysis result in increasing free Ca+2 levels. This is the first investigation of PolyP metabolism during embryogenesis of an insect and might shed light on the mechanisms involving Pi storage and homeostasis during this period. We suggest that PolyP, mainly stored in small vesicles, might be involved in the functional control of Ca+2 and Pi homeostasis during early embryogenesis of P. Americana

Proton-pyrophosphatase and polyphosphate in acidocalcisome-like vesicles from oocytes and eggs of periplaneta americana

9 p. : il.Acidocalcisomes are acidic organelles containing large amounts of polyphosphate (poly P), a number of cations, and a variety of cation pumps in their limiting membrane. The vacuolar proton-pyrophosphatase (V-Hþ-PPase), a unique electrogenic proton-pump that couples pyrophosphate (PPi) hydrolysis to the active transport of protons across membranes, is commonly present in membranes of acidocalcisomes. In the course of insect oogenesis, a large amount of yolk protein is incorporated by the oocytes and stored in organelles called yolk granules (YGs). During embryogenesis, the content of these granules is degraded by acid hydrolases. These enzymes are activated by the acidification of the YG by a mechanism that is mediated by proton-pumps present in their membranes. In this work, we describe an Hþ-PPase activity in membrane fractions of oocytes and eggs of the domestic cockroach Periplaneta americana. The enzyme activity was optimum at pH around 7.0, and was dependent on Mg2þ and inhibited by NaF, as well as by IDP and Ca2þ. Immunolocalization of the yolk preparation using antibodies against a conserved sequence of V-Hþ-PPases showed labeling of small vesicles, which also showed the presence of high concentrations of phosphorus, calcium and other elements, as revealed by electron probe X-ray microanalysis. In addition, poly P content was detected in ovaries and eggs and localized inside the yolk granules and the small vesicles. Altogether, our results provide evidence that numerous small vesicles of the eggs of P. americana present acidocalcisome-like characteristics. In addition, the possible role of these organelles during embryogenesis of this insect is discussed

Effects of protein restriction during gestation and lactation on cell proliferation in the hippocampus and subventricular zone: Functional implications. Protein restriction alters hippocampal/SVZ cell proliferation

There is no consensus about the effects of protein restriction on neurogenesis and behavior. Here, for the first time, we evaluated the effects of protein restriction during gestation and lactation, on the two major neurogenic regions of the adult brain, the subgranular zone (SGZ) of the hippocampal dentate gyrus and the subventricular zone (SVZ), simultaneously. We also assessed different types of behavior relevant to each region. After mating, pregnant Wistar rats were divided into a control group (CG) that received a normal diet (20% protein); and a protein-restriction group (PRG) that received a low-protein diet (8% protein). After birth, the same diets were provided to the mother and pups until weaning, when some rats were analyzed and others received a normal-protein diet until adulthood. Different sets of rats were used for cellular and behavioral studies in juvenile or adult age. Brains were processed for immunohistochemistry anti-BrdU, anti-Ki67, or anti-pHisH3. Juvenile and adult rats from distinct litters also underwent several behavioral tests. Our data show that early protein restriction results in a reduction of hippocampal progenitors and deficits in object recognition during adult life. Moreover, longer periods of immobility in the tail suspension and in the forced swimming tests revealed that PRG rats show a depressive behavior at 21 days of age (P21) and in adulthood. Furthermore, we suggest that despite the reduced number/proliferation of neural stem cells (B and/or E cells) in SVZ there is a compensatory mechanism in which the progenitors (types C and A cells) proliferate in a higher rate, without affecting olfactory ability in adulthood. ► Effects of early protein restriction on cell proliferation in neurogenic niches. ► Impaired progenitor hippocampal proliferation and recognition memory, depression. ► Reduced proliferation of neural progenitor in adult SVZ without olfactory deficits