Peripartum Cardiomyopathy Presenting With Ventricular Tachycardia: A Rare Presentation

A 25-year-old previously asymptomatic pregnant woman at 36 weeks'' gestation was noticed to have repetitive monomorphic ventricular tachycardia. A dilated left ventricle with moderately reduced systolic function was found on echocardiographic examination. This is a very rare presentation of peripartum cardiomyopathy (PPCMP) presenting with repetitive monomorphic ventricular tachycardia.     

Denisova admixture and the first modern human dispersals into Southeast Asia and Oceania

It has recently been shown that ancestors of New Guineans and Bougainville Islanders have inherited a proportion of their ancestry from Denisovans, an archaic hominin group from Siberia. However, only a sparse sampling of populations from Southeast Asia and Oceania were analyzed. Here, we quantify Denisova admixture in 33 additional populations from Asia and Oceania. Aboriginal Australians, Near Oceanians, Polynesians, Fijians, east Indonesians, and Mamanwa (a "Negrito" group from the Philippines) have all inherited genetic material from Denisovans, but mainland East Asians, western Indonesians, Jehai (a Negrito group from Malaysia), and Onge (a Negrito group from the Andaman Islands) have not. These results indicate that Denisova gene flow occurred into the common ancestors of New Guineans, Australians, and Mamanwa but not into the ancestors of the Jehai and Onge and suggest that relatives of present-day East Asians were not in Southeast Asia when the Denisova gene flow occurred. Our finding that descendants of the earliest inhabitants of Southeast Asia do not all harbor Denisova admixture is inconsistent with a history in which the Denisova interbreeding occurred in mainland Asia and then spread over Southeast Asia, leading to all its earliest modern human inhabitants. Instead, the data can be most parsimoniously explained if the Denisova gene flow occurred in Southeast Asia itself. Thus, archaic Denisovans must have lived over an extraordinarily broad geographic and ecological range, from Siberia to tropical Asia.     

Bacterial genome chimaerism and the origin of mitochondria

Many studies have sought to determine the origin and evolution of mitochondria. Although the Alphaproteobacteria are thought to be the closest relatives of the mitochondrial progenitor, there is dispute as to what its particular sister group is. Some have argued that mitochondria originated from ancestors of the order Rickettsiales, or more specifically of the Rickettsiaceae family, while others believe that ancestors of the family Rhodospirillaceae are also equally likely the progenitors. To resolve some of these disputes, sequence similarity searches and phylogenetic analyses were performed against mitochondria-related proteins in Saccharomyces cerevisiae. The 86 common matches of 5 Alphaproteobacteria (Rickettsia prowazekii, Rhodospirillum rubrum, Rhodopseudomonas palustris, Rhodobacter sphaeroides, and Ochrobactrum anthropi) to yeast mitochondrial proteins were distributed fairly evenly among the 5 species when sorted by highest identity or score. Moreover, exploratory phylogenetic analyses revealed that among these common matches, 44.19% (38) had branched most closely with O. anthropi, while only 34.88% (30) corresponded with Rickettsia prowazekii. More detailed phylogenetic analyses with additional Alphaproteobacteria and including genes from the mitochondria of Reclinomonas americana found matches of mitochondrial genes to those of members of the Rickettsiaceae, Anaplasmataceae, and Rhodospirillaceae families. The results support the idea that notable bacterial genome chimaerism has occurred en route to the formation of mitochondria.     

Polar localization of Escherichia coli chemoreceptors requires an intact Tol–Pal complex

Subcellular biomolecular localization is critical for the metabolic and structural properties of the cell. The functional implications of the spatiotemporal distribution of protein complexes during the bacterial cell cycle have long been acknowledged; however, the molecular mechanisms for generating and maintaining their dynamic localization in bacteria are not completely understood. Here we demonstrate that the trans‐envelope Tol–Pal complex, a widely conserved component of the cell envelope of Gram‐negative bacteria, is required to maintain the polar positioning of chemoreceptor clusters in Escherichia coli. Localization of the chemoreceptors was independent of phospholipid composition of the membrane and the curvature of the cell wall. Instead, our data indicate that chemoreceptors interact with components of the Tol–Pal complex and that this interaction is required to polarly localize chemoreceptor clusters. We found that disruption of the Tol–Pal complex perturbs the polar localization of chemoreceptors, alters cell motility, and affects chemotaxis. We propose that the E. coli Tol–Pal complex restricts mobility of the chemoreceptor clusters at the cell poles and may be involved in regulatory mechanisms that co‐ordinate cell division and segregation of the chemosensory machinery.     

Gut Microbiota-Produced Tryptamine Activates an Epithelial G-Protein-Coupled Receptor to Increase Colonic Secretion

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Integrin Ligation Results in Nephrin Tyrosine Phosphorylation In Vitro

Nephrin is expressed at the basolateral aspect of podocytes and is an important signaling protein at the glomerular slit diaphragm. In vitro studies have demonstrated that Nephrin phosphorylation-dependent signaling is able to assemble a protein complex that is able to polymerize actin. However, proximal signaling events that result in nephrin tyrosine phosphorylation are not well understood. Nephrin deletion in mice and human nephrin mutations result in developmental failure of the podocyte intercellular junction resutling in proteinuria. This has been presumed to be due to a failure to respond to an external polarized cue in the absence of nephrin or a failure to transduce an outside-in signal in patients with nephrin mutations. The nephrin extracellular domain binds to itself or neph1 across the foot process intercellular junction. Nephrin is tyrosine phosphorylation-silent in healthy glomeruli when presumably the nephrin extracellular domain is in an engaged state. These observations raise the possibility of an alternate proximal signaling mechanism that might be responsible for nephrin tyrosine phosphorylation. Here we present data showing that integrin engagement at the basal aspect of cultured podocytes results in nephrin tyrosine phosphorylation. This is abrogated by incubating podocytes with an antibody that prevents integrin β1 ligation and activation in response to binding to extracellular matrix. Furthermore, nephrin tyrosine phosphorylation was observed in podocytes expressing a membrane-targeted nephrin construct that lacks the extracellular domain. We propose, integrin-activation based signaling might be responsible for nephrin phosphorylation rather than engagment of the nephrin extracellular domain by a ligand.     

The induction of allophanate lyase during the vegetative cell cycle in light-synchronized cultures of Chlamydomonas reinhardi.

Allophanate lyase can be induced by urea or acetamide 20-40-fold within 4 h in NH4 + -deprived cultures of Chlamydomonas reinhardi. In light-synchronized cultures, allophanate lyase induction appeared to be limited to the light phase of the cell cycle, provided that culture samples were induced under ongoing illumination conditions (i.e. light induction of light phase cells and dark induction of dark phase cells). However, when culture samples were induced under constant light conditions this cell cycle pattern was abolished. Light was found to be required for allophanate lyase induction and this was shown to be due, in part, to the light requirement for inducer uptake. The relationship between allophanate lyase induction and gametogenesis is discussed.     

Improved microscopic observation of mammalian cells on microcarriers by fluorescent staining

Many microcarriers used for the cultivation of animal cells do not allow for convenient microscopic observation of cell morphology and viability due to their optical properties. Using fluorescent viable stain combining fluorescein diacetate and ethidium bromide, we observed the distribution, morphology and viability of cells on various microcarriers.     

The nucleolar protein Esf2 interacts directly with the DExD/H box RNA helicase, Dbp8, to stimulate ATP hydrolysis

While 18 putative RNA helicases are involved in ribosome biogenesis in Saccharomyces cerevisiae, their enzymatic properties have remained largely biochemically uncharacterized. To better understand their function, we examined the enzymatic properties of Dpb8, a DExD/H box protein previously shown to be required for the synthesis of the 18S rRNA. As expected for an RNA helicase, we demonstrate that recombinant Dbp8 has ATPase activity in vitro, and that this activity is dependent on an intact ATPase domain. Strikingly, we identify Esf2, a nucleolar putative RNA binding protein, as a binding partner for Dbp8, and show that it enhances Dbp8 ATPase activity by decreasing the K_M for ATP. Thus, we have uncovered Esf2 as the first example of a protein co-factor that has a stimulatory effect on a nucleolar RNA helicase. We show that Esf2 can bind to pre-rRNAs and speculate that it may function to bring Dbp8 to the pre-rRNA, thereby both regulating its enzymatic activity and guiding Dbp8 to its site of action.