Global cell sorting is mediated by local cell–cell interactions in the C. elegans embryo

AbstractThe Caenorhabditis elegans embryo achieves pattern formation by sorting cells into coherent regions before morphogenesis is initiated. The sorting of cells is coupled to their fate. Cells move extensively relative to each other to reach their correct position in the body plan. Analyzing the mechanism of cell sorting in in vitro culture experiments using 4D microscopy, we show that all AB-derived cells sort only according to their local neighbors, and that all cells are able to communicate with each other. The directions of cell movement do not depend on a cellular polarity but only on local cell–cell interactions; in experimental situations, this allows even the reversal of the polarity of whole regions of the embryo. The work defines a new mechanism of pattern formation we call “cell focusing”

The German Savings Puzzle

Germany has one of the most generous public pension and health insurance systems of the world, yet private savings are high until old age. Savings remain positive in old age, even for most low income households. How can we explain what we might want to term the 'German savings puzzle?' We provide a complicated answer that combines historical facts with capital market imperfections, housing, tax and pension policies. The first part of the paper describes how German households save, based on a synthetic panel of four cross sections of the German Income and Expenditure Survey ('Einkommens- und Verbrauchsstichproben') collected between 1978 and 1993. The second part links saving behavior with public policy, notably tax and pension policy.

"Household Savings in Germany"

This paper describes how German households save and how their saving behavior is linked to public policy, notably pension policy. The analysis is based on a synthetic panel of four cross sections of the German Income and Expenditure Survey ("Einkommens- und Verbrauchsstichproben," EVS,1978, 1983, 1988, and 1993). The paper carefully distinguishes between several saving measures and concepts. It separates discretionary savings from mandatory savings and uses two flow measures: first, the sum of purchases of assets minus the sum of sales of assets and, second, the residual of income minus consumption. Our main finding is a hump-shaped age-saving profile with a high overall saving rate. However, savings remain positive in old age, even for most low-income households. How can we explain what may be termed the "German savings puzzle"? Germany has one of the most generous public pension and health insurance systems in the world, yet private savings are high until old age. We provide a complicated answer that combines historical facts with capital market imperfections and a distinction between the role of discretionary and mandatory savings.

CSC-1: a subunit of the aurora b kinase complex that binds to the survivin-like protein BIR-1 and the incenp-like protein ICP-1

The Aurora B kinase complex is a critical regulator of chromosome segregation and cytokinesis. In Caenorhabditis elegans, AIR-2 (Aurora B) function requires ICP-1 (Incenp) and BIR-1 (Survivin). In various systems, Aurora B binds to orthologues of these proteins. Through genetic analysis, we have identified a new subunit of the Aurora B kinase complex, CSC-1. C. elegans embryos depleted of CSC-1, AIR-2, ICP-1, or BIR-1 have identical phenotypes. CSC-1, BIR-1, and ICP-1 are interdependent for their localization, and all are required for AIR-2 localization. In vitro, CSC-1 binds directly to BIR-1. The CSC-1/BIR-1 complex, but not the individual subunits, associates with ICP-1. CSC-1 associates with ICP-1, BIR-1, and AIR-2 in vivo. ICP-1 dramatically stimulates AIR-2 kinase activity. This activity is not stimulated by CSC-1/BIR-1, suggesting that these two subunits function as targeting subunits for AIR-2 kinase

Household Savings in Germany

This paper describes how German households save and how their saving behavior is linked to public policy, notably pension policy. The analysis is based on a synthetic panel of four cross sections of the German Income and Expenditure Survey ("Einkommens- und Verbrauchsstichproben," EVS, 1978, 1983, 1988, and 1993). The paper carefully distinguishes between several saving measures and concepts. It separates discretionary savings from mandatory savings and uses two flow measures: first, the sum of purchases of assets minus the sum of sales of assets and, second, the residual of income minus consumption. Our main finding is a hump-shaped age-saving profile with a high overall saving rate. However, savings remain positive in old age, even for most low-income households. How can we explain what may be termed the "German savings puzzle"? Germany has one of the most generous public pension and health insurance systems in the world, yet private savings are high until old age. We provide a complicated answer that combines historical facts with capital market imperfections and a distinction between the role of discretionary and mandatory savings.

Cell Autonomous Expression of Perlecan and Plasticity of Cell Shape in Embryonic Muscle ofCaenorhabditis elegans

AbstractPerlecan, a component of the extracellular matrix (ECM), is essential for myofilament formation and muscle attachment inCaenorhabditis elegans.We show here that perlecan is a product of muscle and that it behaves in a cell autonomous fashion. That is, perlecan expressed in an individual muscle cell does not spread beyond the borders of the ECM underlying that cell. Using a polyclonal antibody that recognizes all isoforms of perlecan, we demonstrate that this protein first appears extracellularly at the comma stage (approx. 350 min) of development. We also show that during morphogenesis muscle cells have a heretofore undescribed plasticity of shape. This ability to regulate cell shape allows cells within a muscle quadrant to compensate for missing cells and to form a functional quadrant. A dramatic example of this morphological flexibility can be observed in animals in which the D blastomere has been removed by laser ablation. Such animals, lacking 20 of the 81 embryonic body wall muscle cells, can survive to become viable adult animals indistinguishable from wildtype animals. This demonstrates that the assembly of an embryo via a stereotypic lineage does not preclude a more general regulation during morphogenesis. It appears that embryos are flexible enough to immediately compensate for drastic alterations in tissue composition, a feature of development that may be of general importance during evolution

Cell Autonomous Expression of Perlecan and Plasticity of Cell Shape in Embryonic Muscle ofCaenorhabditis elegans

AbstractPerlecan, a component of the extracellular matrix (ECM), is essential for myofilament formation and muscle attachment inCaenorhabditis elegans.We show here that perlecan is a product of muscle and that it behaves in a cell autonomous fashion. That is, perlecan expressed in an individual muscle cell does not spread beyond the borders of the ECM underlying that cell. Using a polyclonal antibody that recognizes all isoforms of perlecan, we demonstrate that this protein first appears extracellularly at the comma stage (approx. 350 min) of development. We also show that during morphogenesis muscle cells have a heretofore undescribed plasticity of shape. This ability to regulate cell shape allows cells within a muscle quadrant to compensate for missing cells and to form a functional quadrant. A dramatic example of this morphological flexibility can be observed in animals in which the D blastomere has been removed by laser ablation. Such animals, lacking 20 of the 81 embryonic body wall muscle cells, can survive to become viable adult animals indistinguishable from wildtype animals. This demonstrates that the assembly of an embryo via a stereotypic lineage does not preclude a more general regulation during morphogenesis. It appears that embryos are flexible enough to immediately compensate for drastic alterations in tissue composition, a feature of development that may be of general importance during evolution

Episodic ataxias in children and adolescents: Clinical findings and suggested diagnostic criteria

Background: The main clinical presentation of episodic ataxias (EAs) consists of vertigo and dizziness attacks lasting for minutes to hours with widely varying accompanying symptoms. The differentiation of EA and episodic vertigo/dizziness syndromes in childhood and adolescence such as vestibular migraine (VM) and recurrent vertigo of childhood (RVC) can be challenging. Furthermore, only few prospective studies of children/adolescents with EA are available. Objective: This study aims to characterize clinical and instrument-based findings in EA patients under 18 years of age, to delineate the clinical and therapeutic course in EA, and to present potentially new genetic mutations. Furthermore, the study aims to differentiate distinct characteristics between EA, VM, and RVC patients. Methods: We prospectively collected clinical and instrument-based data of patients younger than 18 years, who presented at the German Center for Vertigo and Balance Disorders (DSGZ) at the LMU University Hospital in Munich with EA, VM, or RVC between January 2016 and December 2021. All patients underwent a comprehensive evaluation of neurological, ocular-motor, vestibular and cochlear function, including video-oculography with caloric testing, video head impulse test, vestibular evoked myogenic potentials, posturography, and gait analysis. Results: Ten patients with EA, 15 with VM, and 15 with RVC were included. In EA the main symptoms were vertigo/dizziness attacks lasting between 5 min and 12 h. Common accompanying symptoms included walking difficulties, paleness, and speech difficulties. Six EA patients had a previously unknown gene mutation. In the interictal interval all EA patients showed distinct ocular-motor deficits. Significant differences between EA, VM, and RVC were found for accompanying symptoms such as speech disturbances and paleness, and for the trigger factor “physical activity”. Furthermore, in the interictal interval significant group differences were observed for different pathological nystagmus types, a saccadic smooth pursuit, and disturbed fixation suppression. Conclusion: By combining clinical and ocular-motor characteristics we propose diagnostic criteria that can help to diagnose EA among children/adolescents and identify patients with EA even without distinct genetic findings. Nevertheless, broad genetic testing (e.g., next generation sequencing) in patients fulfilling the diagnostic criteria should be conducted to identify even rare or unknown genetic mutations for EA

The German Savings Puzzle

Germany has one of the most generous public pension and health insurance systems of the world, yet private savings are high until old age. Savings remain positive in old age, even for most low income households. How can we explain what we might want to term the "German savings puzzle"? We provide a complicated answer that combines historical facts with capital market imperfections, housing, tax and pension policies. The first part of the paper describes how German households save, based on a synthetic panel of four cross sections of the German Income and Expenditure Survey ("Einkommens- und Verbrauchsstichproben") collected between 1978 and 1993. The second part links saving behavior with public policy, notably tax and pension policy

Ersparnisbildung in Deutschland : Meßkonzepte und Ergebnisse auf Basis der EVS

Eine der wichtigsten ökonomischen Entscheidungen des Haushaltes, die Aufteilung des verfügbaren Einkommens in Konsum und Ersparnis, wird durch die volkswirtschaftliche Theorie nach wie vor nur unbefriedigend erklärt. So zeigen z.B. viele Untersuchungen mit amerikanischen Daten, daß die Ersparnis „zu wenig“ auf Einkommensschwankungen reagiert, die sie nach der Theorie ausgleichen soll. Der erste Schritt zu einem besseren Verständnis der Ersparnisbildung ist eine adäquate Beschreibung des Sparverhaltens über den Lebenszyklus. Diese deskriptive Aufgabe erweist sich allerdings schon konzeptionell als schwierig. Ziel der vorliegenden Arbeit ist es zunächst, einen Rahmen für die konsistente Bestimmung von Ersparnis, Vermögen und Einkommen der privaten Haushalte zu entwicklen, der sich auf die Einkommens- und Verbrauchsstichproben (EVS) der Jahre 1978 bis 1993 anwenden läßt. Wir stellen dann die empirische Umsetzung dieser Meßkonzepte vor. Die beiden hier betrachteten Definitionen (Zu- und Abgänge im Vermögen bzw. Einkommen minus Ausgaben) ergeben sehr ähnliche Resultate für die Ersparnisbildung der privaten Haushalte in Deutschland. Wichtigstes Ergebnis ist eine im Mittel positive Sparneigung im Alter. Zwar zeigt sich ein deutlicher Rückgang der Ersparnis, doch bleibt die Geldvermögensbildung positiv