Dynamics of the caring family

When several individuals simultaneously provide for offspring, as in families, the effort of any one individual will depend on the efforts of the other family members. This conflict of interest among family members is made more complicated by their relatedness because relatives share genetic interest to some degree. The conflict resolution will also be influenced by the differences in reproductive value between breeders and helpers. Here, we calculate evolutionarily stable provisioning efforts in families with up to two helpers. We explicitly consider that the behavioral choices are made in a life-history context, and we also consider how group sizes change dynamically; this affects, for example, average relatedness among group members. We assume two different scenarios: intact families in which the breeder is 100% monogamous and stepfamilies in which the breeder shifts mate between breeding events. The average relatedness among family members is allowed to evolve in concert with changes in provisioning effort. Our model shows that an individual's provisioning effort is not easy to predict from either its relatedness to the offspring or its reproductive value. Instead, it is necessary to consider the inclusive fitness effect of provisioning, which is determined by a combination of relatedness, reproductive value, and the reproductive value of the offspring.     

Taurine supplementation induces multidrug resistance protein 2 and bile salt export pump expression in rats and prevents endotoxin-induced cholestasis

The effect of oral taurine supplementation on endotoxin-induced cholestasis was investigated in rat liver. At 12h following lipopolysaccharide (LPS) injection (4mg/kg body weight i.p.) bile flow and bromosulfophthalein (BSP) and taurocholate (TC) excretion were determined in the perfused liver and the expression of the canalicular transporters multidrug resistance protein 2 (Mrp2) and bile salt export pump (Bsep) was analyzed. Injection of LPS induced a significant decrease of bile flow ( 2.2+/-0.2 microl/g liver wet weight/min vs 3.3+/-0.1 microl/g liver wet weight in controls), biliary BSP excretion (10.8+/-2.2 nmol/g/min vs 21.0+/-3.8 nmol/g/min), and biliary TC excretion (114+/-23 nmol/g/min vs 228+/-8 nmol/g/min). These effects were due to transporter retrieval from the canalicular membrane and downregulation of Mrp2 and Bsep expression. In taurine-supplemented rats bile flow was 30% higher than that in untreated rats and the expression of Mrp2 and Bsep protein was increased two- to threefold. In taurine-supplemented rats there was no significant reduction of bile flow or of BSP and TC excretion at 12h following LPS injection. This protective effect of taurine was due to higher Mrp2 and Bsep protein levels compared to nonsupplemented LPS-treated rats, whereas relative Mrp2 retrieval from the canalicular membrane induced by LPS was not significantly different. LPS-induced tumor necrosis factor alpha and interleukin-1beta release were lower in taurine-fed rats; however, downregulation of Mrp2 and Bsep expression by LPS was delayed but not prevented. The data show that oral supplementation of taurine induces Mrp2 and Bsep expression and may prevent LPS-induced cholestasis.     

Origin and diffusion of mtDNA haplogroup X

A maximum parsimony tree of 21 complete mitochondrial DNA (mtDNA) sequences belonging to haplogroup X and the survey of the haplogroup-associated polymorphisms in 13,589 mtDNAs from Eurasia and Africa revealed that haplogroup X is subdivided into two major branches, here defined as “X1” and “X2.” The first is restricted to the populations of North and East Africa and the Near East, whereas X2 encompasses all X mtDNAs from Europe, western and Central Asia, Siberia, and the great majority of the Near East, as well as some North African samples. Subhaplogroup X1 diversity indicates an early coalescence time, whereas X2 has apparently undergone a more recent population expansion in Eurasia, most likely around or after the last glacial maximum. It is notable that X2 includes the two complete Native American X sequences that constitute the distinctive X2a clade, a clade that lacks close relatives in the entire Old World, including Siberia. The position of X2a in the phylogenetic tree suggests an early split from the other X2 clades, likely at the very beginning of their expansion and spread from the Near East.     

Susceptibility loci for preeclampsia on chromosomes 2p25 and 9p13 in Finnish families

Preeclampsia is a common, pregnancy-specific disorder characterized by reduced placental perfusion, endothelial dysfunction, elevated blood pressure, and proteinuria. The pathogenesis of this heterogeneous disorder is incompletely understood, but it has a familial component, which suggests that one or more common alleles may act as susceptibility genes. We hypothesized that, in a founder population, the genetic background of preeclampsia might also show reduced heterogeneity, and we have performed a genomewide scan in 15 multiplex families recruited predominantly in the Kainuu province in central eastern Finland. We found two loci that exceeded the threshold for significant linkage: chromosome 2p25, near marker D2S168 (nonparametric linkage [NPL] score 3.77; P=.000761) at 21.70 cM, and 9p13, near marker D9S169 (NPL score 3.74; P=.000821) at 38.90 cM. In addition, there was a locus showing suggestive linkage at chromosome 4q32 between D4S413 and D4S3046 (NPL score 3.13; P=.003238) at 163.00 cM. In the present study the susceptibility locus on chromosome 2p25 is clearly different (21.70 cM) from the locus at 2p12 found in an Icelandic study (94.05 cM) and the locus at 2q23 (144.7 cM) found in an Australian/New Zealand study. The locus at 9p13 has been shown to be a candidate region for type 2 diabetes in two recently published genomewide scans from Finland and China. The regions on chromosomes 2p25 and 9p13 may harbor susceptibility genes for preeclampsia.     

Regulation of PCNA and CAF-1 expression by the two tuberous sclerosis gene products

Tuberous sclerosis is an autosomal dominant tumor suppressor gene syndrome affecting about 1 in 6000 individuals. Two genes have been shown to be responsible for this disease: TSC1, encoding hamartin and TSC, encoding tuberin. A variety of tumors characteristically occur in different organs of tuberous sclerosis patients and are believed to result from defects in cell cycle/cell size control. In this study, we performed two-dimensional gel electrophoresis with subsequent mass spectrometrical identification of protein spots after overexpression of TSC1 or TSC2. We found expression of PCNA and the p48 subunit of CAF-1 to be regulated by two tuberous sclerosis gene products. CAF-1 and PCNA interact as major regulators of chromatin assembly during DNA repair. We suggest that deregulation of the control of chromatin assembly might contribute to development of tumors in tuberous sclerosis patients and provide important new insights into the molecular development, especially since deregulation of chromatin assembly and DNA repair results in genomic instability, a hallmark of tumor development.     

In vivo processed fragments of IGF binding protein-2 copurified with bioactive IGF-II

Proteolysis of insulin-like growth factor binding proteins (IGFBPs), the major carrier of insulin-like growth factors (IGFs) in the circulation, is an essential mechanism to regulate the bioavailability and half-live of IGFs. Screening for peptides in human hemofiltrate, stimulating the survival of PC-12 cells, resulted in the isolation of C-terminal IGFBP-2 fragments and intact IGF-II co-eluting during the chromatographic purification procedure. The IGFBP-2 fragments exhibited molecular masses of 12.7 and 12.9kDa and started with Gly169 and Gly167, respectively. The fragments were able to bind both IGFs. The stimulatory effect of the purified fraction on the survival of the PC-12 cells could be assigned exclusively to IGF-II, since it was abolished by the addition of neutralizing IGF-II antibodies. We suggest that in the circulation IGF-II is not only complexed with intact IGFBP but also with processed IGFBP-2 fragments not impairing the biological activity of IGF-II.     

The STC-1 cells express functional orexin-A receptors coupled to CCK release

Orexins are newly discovered neuropeptides regulating feeding and vigilance and have been detected in neuroendocrine cells of the gut. Potential neuroendocrine functions of orexin are unknown. Therefore, the effects of orexin-A on the intestinal neuroendocrine cell line, STC-1, were investigated as a model system. RT-PCR demonstrated the presence of both OX(1) and OX(2) receptors. Stimulation with orexin-A produced a dose-dependent release of cholecystokinin (CCK), which was abolished by removal of extracellular Ca(2+) or the presence of the voltage-gated L-type Ca(2+)-channel blocker diltiazem (10 microM). Orexin-A (Ox-A) elevated intracellular Ca(2+), which was dependent on extracellular Ca(2+). Furthermore, orexin-A caused a membrane depolarization in the STC-1 cells. Ox-A neither elevated cAMP levels nor stimulated phosphoinositide turnover in these cells. These data demonstrate a functional orexin receptor in the STC-1 cell line. Ox-A produces CCK release in these cells, by a mechanism involving membrane depolarization and subsequently activation of L-type voltage-gated Ca(2+)-channels.     

Ca2+ -dependent interaction of S100A1 with the sarcoplasmic reticulum Ca2+ -ATPase2a and phospholamban in the human heart

The Ca(2+)-binding S100A1 protein displays a specific and high expression level in the human myocardium and is considered to be an important regulator of heart contractility. Diminished protein levels detected in dilated cardiomyopathy possibly contribute to impaired Ca(2+) handling and contractility in heart failure. To elucidate the S100A1 signaling pathway in the human heart, we searched for S100A1 target proteins by applying S100A1-specific affinity chromatography and immunoprecipitation techniques. We detected the formation of a Ca(2+)-dependent complex of S100A1 with SERCA2a and PLB in the human myocardium. Using confocal laser scanning microscopy, we showed that all three proteins co-localize at the level of the SR in primary mouse cardiomyocytes and confirmed these results by immunoelectron microscopy in human biopsies. Our results support a regulatory role of S100A1 in the contraction-relaxation cycle in the human heart.     

ATP-citrate lyase as a substrate of protein histidine phosphatase in vertebrates

The first protein histidine phosphatase from vertebrates discovered recently was found in a variety of tissues, however, a physiological substrate protein was missing. Phosphorylation of liver extracts in the presence of EDTA, followed by SDS-PAGE and autoradiography showed labeling of three proteins. Acid- and alkaline-treatment revealed the existence of N-phosphates. Addition of histidine phosphatase exclusively resulted in dephosphorylation of a 110kDa protein (denaturing conditions). Gelfiltration revealed its native molecular mass of approximately 450kDa. That protein was purified and identified as ATP-citrate lyase. The results are in favor of histidine phosphatase playing an important yet unidentified role in metabolic processes.     

Actomyosin motility on nanostructured surfaces

We have here, for the first time, used nanofabrication techniques to reproduce aspects of the ordered actomyosin arrangement in a muscle cell. The adsorption of functional heavy meromyosin (HMM) to five different resist polymers was first assessed. One group of resists (MRL-6000.1XP and ZEP-520) consistently exhibited high quality motility of actin filaments after incubation with HMM. A second group (PMMA-200, PMMA-950, and MRI-9030) generally gave low quality of motility with only few smoothly moving filaments. Based on these findings electron beam lithography was applied to a bi-layer resist system with PMMA-950 on top of MRL-6000.1XP. Grooves (100-200nm wide) in the PMMA layer were created to expose the MRL-6000.1XP surface for adsorption of HMM and guidance of actin filament motility. This guidance was quite efficient allowing no U-turns of the filaments and approximately 20 times higher density of moving filaments in the grooves than on the surrounding PMMA.