Regulation of action potential duration under acute heat stress by I(K,ATP) and I(K1) in fish cardiac myocytes

The mechanism underlying temperature-dependent shortening of action potential (AP) duration was examined in the fish (Carassius carassius L.) heart ventricle. Acute temperature change from +5 to +18 degrees C (heat stress) shortened AP duration from 2.8 +/- 0.3 to 1.3 +/- 0.1 s in intact ventricles. In 56% (18 of 32) of enzymatically isolated myocytes, heat stress also induced reversible opening of ATP-sensitive K+ channels and increased their single-channel conductance from 37 +/- 12 pS at +8 degrees C to 51 +/- 13 pS at +18 degrees C (Q10 = 1.38) (P < 0.01; n = 12). The ATP-sensitive K+ channels of the crucian carp ventricle were characterized by very low affinity to ATP both at +8 degrees C [concentration of Tris-ATP that produces half-maximal inhibition of the channel (K1/2)= 1.35 mM] and +18 degrees C (K1/2 = 1.85 mM). Although acute heat stress induced ATP-sensitive K+ current (IK,ATP) in patch-clamped myocytes, similar heat stress did not cause any glibenclamide (10 microM)-sensitive changes in AP duration in multicellular ventricular preparations. Examination of APs and K+ currents from the same myocytes by alternate recording under current-clamp and voltage-clamp modes revealed that changes in AP duration were closely correlated with temperature-specific changes in the voltage-dependent rectification of the background inward rectifier K+ current IK1. In approximately 15% of myocytes (4 out of 27), IK,ATP-dependent shortening of AP followed the IK1-induced AP shortening. Thus heat stress-induced shortening of AP duration in crucian carp ventricle is primarily dependent on IK1. IK,ATP is induced only in response to prolonged temperature elevation or perhaps in the presence of additional stressors.     

Pikas (Ochotona princeps : Lagomorpha) as allogenic engineers in an alpine ecosystem

Pikas (Ochotona princeps: Lagomorpha) build caches of vegetation (“haypiles”), which serve as a food source during winter in alpine and subalpine habitats. Haypiles appear to degrade over time and form patches of nutrient-rich soils in barren talus and scree areas. We sampled soils underneath and next to haypiles, and plants growing on and near haypiles in an alpine cirque in northwestern Wyoming, USA, to determine the effects of pika food caches on N, C, and C/N ratios in soils and plants. We found that (1) haypile soils had significantly higher carbon and nitrogen levels and lower C/N ratios than both adjacent soils and soils in the general study area, (2) two of three plant species tested (Polemonium viscosum and Oxyria digyna) had significantly higher levels of tissue percent N when growing on haypile soils, and (3) total standing plant biomass at the study site increased with soil percent N suggesting that vegetation was nitrogen limited. Pikas may therefore function as allogenic ecosystem engineers by modulating nutrient availability to plants. Received: 5 July 1997 / Accepted: 30 November 1997     

Pim-1 kinase promotes inactivation of the pro-apoptotic Bad protein by phosphorylating it on the Ser112 gatekeeper site

Constitutive expression of the Pim-1 kinase prolongs survival of cytokine-deprived FDCP1 cells, partly via maintenance of Bcl-2 expression. Here, we show that Pim-1 colocalizes and physically interacts with the pro-apoptotic Bad protein and phosphorylates it in vitro on serine 112, which is a gatekeeper site for its inactivation. Furthermore, wild-type Pim-1, but not a kinase-deficient mutant, enhances phosphorylation of this site in FDCP1 cells and protects cells from the pro-apoptotic effects of Bad. Our results suggest that phosphorylation of Bad by Pim-1 is one of several mechanisms via which the Pim-1 kinase can enhance Bcl-2 activity and promote cell survival.     

A new locus for coeliac disease mapped to chromosome 15 in a population isolate

Coeliac disease is a common multifactorial disease with a strong genetic component, which is not entirely explained by the HLA association. Four previous whole-genome screens have produced somewhat inconsistent results suggesting genetic heterogeneity. We attempted to overcome this problem by performing a genome-wide scan in a Finnish sub-population, expected to be more homogeneous than the general population of Finland. The families in our study originate from the northeastern part of Finland, the Koilliskaira region, which has been relatively isolated since its founding in the 16th century. Genealogical studies have confirmed that the families share a common ancestor in the 16th century. Nine families with altogether 23 patients were genotyped for 399 microsatellite markers and the data were analysed with parametric linkage analysis using two dominant and one recessive model. A region on chromosome 15q11-q13 was implicated with a LOD score of 3.14 using a highly penetrant dominant model. Addition of more markers and one more sib-pair increased the LOD score to 3.74. This result gives preliminary evidence for existence of a susceptibility factor in this chromosomal region.     

Refuge sites of voles under owl predation risk: priority of dominant individuals?

In an aviary experiment, we studied whether body size or habitatfamiliarity of field voles (Microtus agrestis) affected predationrisk by Tengmalm's owls (Aegolius funereus). In the field, wecompared the body size of field voles snap-trapped in good (covered)and poor (open) habitats in 1992 and 1994 to determine whetherthere were habitat-related differences in the body size of voles.In the aviary, large individuals occupied the good habitat significantlymore than small individuals both in the control (owl not present)and experimental treatments (owl present). Furthermore, habitat-familiarvoles inhabited the good habitat more than habitat-unfamiliarvoles did when an owl was present Our field data were consistentwith our aviary data: larger field voles were more frequentlyfound in good habitats than in poor habitats. In the aviary,Tengmalm's owl predation risk was higher for small and habitat-unfamiliarvoles. This suggests that large field voles may have priorityto sheltered habitats. Furthermore, habitat familiarity mayplay a central role in avoiding risky habitats.     

DNA family shuffling within the chicken avidin protein family - A shortcut to more powerful protein tools

Avidins represent an interesting group of proteins showing high structural similarity and ligand-binding properties but low similarity in primary structure. In this study, we show that it is possible to create functional chimeric proteins from the avidin protein family when applying DNA family shuffling to the genes of the avidin protein family: avidin, avidin related gene 2 and biotin-binding protein A. The novel chimeric proteins were selected by phage display biopanning against biotin, and the selected enriched proteins were characterized, displaying diverse features distinct from the parental genes, including binding to cysteine.     

The Wnt pool of glycogen synthase kinase 3beta is critical for trophic-deprivation-induced neuronal death

Glycogen synthase kinase 3 (GSK-3) is implicated in neuronal death through a causal role, and precise mechanisms have not been unambiguously defined. We show that short hairpin RNA (shRNA) knockdown of GSK-3β, but not GSK-3α, protects cerebellar granule neurons from trophic-deprivation-induced death. Using compartment-targeted inhibitors of the Wnt-regulated GSK-3 pool, NLS-FRAT1, NES-FRAT1, and axin-GSK-3-interacting domain (axin-GID), we locate proapoptotic GSK-3 action to the cytosol and regulation of Bim protein turnover despite constitutive cycling of GSK-3 between the cytosol and nucleus, revealed by leptomycin B. We examine the importance of Ser21/9 (GSK-3α/β) phosphorylation on proapoptotic GSK-3 function. Neurons isolated from GSK-3α/β^S21A/S9A knock-in mice survive normally and are fully sensitive to trophic-deprivation-induced death. Nonetheless, inhibition of GSK-3 catalytic activity with lithium or SB216763 protects GSK-3α/β^S21A/S9A neurons from death. This indicates that dephosphorylation of GSK-3β/Ser9 and GSK-3α/Ser21 is insufficient for GSK-3 proapoptotic function and that another level of regulation is required. Gel filtration reveals a stress-induced loss of neuronal GSK-3β from a high-molecular-mass complex with a concomitant decrease in axin-bound GSK-3β. These data imply that Wnt-regulated GSK-3β plays a nonredundant role in trophic-deprivation-induced death of neurons.     

Gender‐dependent progression of systemic metabolic states in early childhood

Little is known about the human intra‐individual metabolic profile changes over an extended period of time. Here, we introduce a novel concept suggesting that children even at a very young age can be categorized in terms of metabolic state as they advance in development. The hidden Markov models were used as a method for discovering the underlying progression in the metabolic state. We applied the methodology to study metabolic trajectories in children between birth and 4 years of age, based on a series of samples selected from a large birth cohort study. We found multiple previously unknown age‐ and gender‐related metabolome changes of potential medical significance. Specifically, we found that the major developmental state differences between girls and boys are attributed to sphingolipids. In addition, we demonstrated the feasibility of state‐based alignment of personal metabolic trajectories. We show that children have different development rates at the level of metabolome and thus the state‐based approach may be advantageous when applying metabolome profiling in search of markers for subtle (patho)physiological changes.     

Cardiac outflow tract defects in mice lacking ALK2 in neural crest cells

Cardiac neural crest cells are multipotent migratory cells that contribute to the formation of the cardiac outflow tract and pharyngeal arch arteries. Neural crest-related developmental defects account for a large proportion of congenital heart disorders. Recently, the genetic bases for some of these disorders have been elucidated, and signaling pathways required for induction, migration and differentiation of cardiac neural crest have emerged. Bone morphogenetic proteins comprise a family of secreted ligands implicated in numerous aspects of organogenesis, including heart and neural crest development. However, it has remained generally unclear whether BMP ligands act directly on neural crest or cardiac myocytes during cardiac morphogenesis, or function indirectly by activating other cell types. Studies on BMP receptor signaling during organogenesis have been hampered by the fact that receptor knockouts often lead to early embryonic lethality. We have used a Cre/loxP system for neural crest-specific deletion of the type I receptor, ALK2, in mouse embryos. Mutant mice display cardiovascular defects, including persistent truncus arteriosus, and abnormal maturation of the aortic arch reminiscent of common forms of human congenital heart disease. Migration of mutant neural crest cells to the outflow tract is impaired, and differentiation to smooth muscle around aortic arch arteries is deficient. Moreover, in Alk2 mutants, the distal outflow tract fails to express Msx1, one of the major effectors of BMP signaling. Thus, the type I BMP receptor ALK2 plays an essential cell-autonomous role in the development of the cardiac outflow tract and aortic arch derivatives.