Regulation of Akt during hibernation in Richardson's ground squirrels

Akt (or protein kinase B) plays a central role in coordinating growth, survival and anti-apoptotic responses in cells and we hypothesized that changes in Akt activity and properties would aid the reprioritization of metabolic functions that occurs during mammalian hibernation. Akt was analyzed in skeletal muscle and liver of Richardson's ground squirrels, Spermophilus richardsonii, comparing the enzyme from euthermic and hibernating states. Akt activity, measured with a synthetic peptide substrate, decreased by 60-65% in both organs during hibernation. Western blotting showed that total Akt protein did not change in hibernation but active, phosphorylated Akt (Ser 473) was reduced by 40% in muscle compared with euthermic controls and was almost undetectable in liver. Kinetic analysis of muscle Akt showed that S(0.5) values for Akt peptide were 28% lower during hibernation, compared with the euthermic enzyme, whereas S(0.5) ATP increased by 330%. Assay at 10 degrees C also elevated S(0.5) ATP of euthermic Akt by 350%. Changes in ATP affinity would limit Akt function in the hibernator since the muscle adenylate pool size is also strongly suppressed during cold torpor. Other parameters of euthermic and hibernator Akt were the same including activation energy calculated from Arrhenius plots and sensitivity to urea denaturation. DEAE Sephadex chromatography of muscle extracts revealed three peaks of Akt activity in euthermia but only two during hibernation suggesting isozymes are differentially dephosphorylated during torpor. Altered enzyme properties and suppression of Akt activity would contribute to the coordinated suppression of energy-expensive anabolic and growth processes that is needed to maintain viability during over weeks of winter torpor.     

Three new Verrucidae (Crustacea: Cirripedia) from the Upper Eocene of the Euganean Hills (Northeast Italy)

Marls with pillow lavas of Late Eocene age from Castelnuovo in the Euganean Hills (Padua, NE Italy) have yielded three new verrucid cirripede species, Verruca veneta nov. sp., Costatoverruca? seguenzai nov. sp., and Metaverruca euganea nov. sp. The stratigraphic distribution of these taxa is discussed in light of previous verrucid records and their geologic context is established. They represent the oldest known verrucids from Italy.     

Cambrian Acritarchs from the Col di Foglia (Agordo) southalpine metamorphic basement, Italian Eastern Alps: the oldest biostratigraphic record in the alps

Abstract  The Lower Palaeozoic biostratigraphic records in the Alps are briefly reviewed and the result of a new study of the acritarch assemblage found by Sassi et al. (1984) in the greenschist facies black metapelites of the Southalpine metamorphic basement at Col di Foglia, and studied by Kalvacheva et al. (1986), is presented. The new  taxonomic and biostratigraphic study indicates a late Cambrian age, which is the oldest unquestionable, recently assessed, biostratigraphic dating of the entire Alps, as well as of the Italian peninsular. Keywords Alps, Southalpine metamorphic basement, Eastern Alps, Agordo, Acritarchs, Cambrian Subject codes: G17002     

Die Regeneration der am Tibialrande oder median verstümmelten Beine bei Triton cristatus Laur. und eine Heteromorphose des langen Knochens nach Ausschneidung des Fibularrandes

Ohne ZusammenfassungEine vorläufige Mitteilung unter gleichem Titel erschien als Nr. 152 aus der Biol. Versuchsanst. (Zool. Abt., Vorstand H.Przibram) im Akad. Anz., Nr 17. Wien 4. VII. 1929.     

BDNF and its pro-peptide are stored in presynaptic dense core vesicles in brain neurons

Although brain-derived neurotrophic factor (BDNF) regulates numerous and complex biological processes including memory retention, its extremely low levels in the mature central nervous system have greatly complicated attempts to reliably localize it. Using rigorous specificity controls, we found that antibodies reacting either with BDNF or its pro-peptide both stained large dense core vesicles in excitatory presynaptic terminals of the adult mouse hippocampus. Both moieties were ~10-fold more abundant than pro-BDNF. The lack of postsynaptic localization was confirmed in Bassoon mutants, a seizure-prone mouse line exhibiting markedly elevated levels of BDNF. These findings challenge previous conclusions based on work with cultured neurons, which suggested activity-dependent dendritic synthesis and release of BDNF. They instead provide an ultrastructural basis for an anterograde mode of action of BDNF, contrasting with the long-established retrograde model derived from experiments with nerve growth factor in the peripheral nervous system.     

Dendritic morphology is altered in hippocampal neurons following prenatal compromise

Chronic placental insufficiency (CPI), a known cause of intrauterine growth restriction, can lead to structural alterations in the developing brain that might underlie postnatal neurological deficits. We have previously demonstrated significant reductions in the volumes of hippocampal neuropil layers in fetal guinea pig brains following experimentally induced growth restriction. To determine the components of the neuropil affected in the brains of growth restricted (GR) fetuses, the dendritic morphology of CA1 pyramidal neurons and dentate granule cells was examined. CPI was induced by unilateral uterine artery ligation in pregnant guinea pigs at midgestation (term approximately 67 days). Hippocampi from control and GR fetuses were stained using the Rapid Golgi technique and the growth and branching of the dendritic arbors were quantified using the Sholl method. In addition, the density of dendritic spines was determined on the apical arbors of each population. In GR brains (n = 7) compared to controls (n = 7), there was a reduction in dendritic elongation (p < 0.005) and an alteration in the branch point distribution in CA1 basal arbors, and a reduction both in the outgrowth (p < 0.05) and branch point number (p < 0.05) of CA1 apical arbors. Dentate granule cells from GR brains also demonstrated reduced dendritic outgrowth (p < 0.05). There was an increase in dendritic spine density in both neuronal populations; this might be due either to altered synaptic pruning or as a compensatory mechanism for reduced dendritic length. These findings demonstrate that a chronic prenatal insult causes selective changes in the morphology of hippocampal cell dendrites and may lead to alterations in hippocampal function in the postnatal period.     

Regulation of glucose-6-phosphate dehydrogenase by reversible phosphorylation in liver of a freeze tolerant frog

Glucose-6-phosphate dehydrogenase (G6PDH) and the pentose phosphate pathway play a key role in reductive biosynthesis and antioxidant defense, while diverting glucose from other cellular functions. G6PDH was isolated from liver of the wood frog, Rana sylvatica, a freeze tolerant species that uses glucose as a cryoprotectant. Analysis of kinetic parameters (K _m and V _max) of G6PDH showed a significant increase in K _m G6P (from 98.2 ± 3.8 to 121 ± 5.3 μM) and K _m NADP⁺ (from 65.5 ± 2.3 to 89.1 ± 4.8 μM) in frogs following freezing exposure, indicating lower affinity for G6PDH substrates in this state. Subsequent analyses indicated that differential phosphorylation of G6PDH between the two states was responsible for the altered kinetic properties. Thus, two differentially charged forms of G6PDH were resolved by DEAE ion-exchange chromatography and, compared with controls, the proportion of G6PDH activity in peak I decreased and in peak II increased in liver from frozen frogs. G6PDH in peak I had a K _m G6P of 94.1 ± 1.1 μM and K _m NADP⁺ of 61.2 ± 3.5 μM, whereas Peak II G6PDH showed higher values (K _m G6P was 172 ± 4.3 μM, K _m NADP⁺ was 98.2 ± 3.3 μM). G6PDH from each peak was incubated with ions and second messengers to stimulate the actions of protein kinases with results indicating that G6PDH can be phosphorylated by protein kinase G, protein kinase C, AMP-activated protein kinase, or calmodulin-dependent protein kinase. The data indicate that in control frogs, G6PDH is in a high phosphate form and displays a high substrate affinity, whereas in frozen frogs G6PDH is less phosphorylated, with lower substrate affinity.