High-resolution three-dimensional views of membrane-associated clathrin and cytoskeleton in critical-point-dried macrophages.

We obtained high-resolution topographical information about the distribution of clathrin and cytoskeletal filaments on cytoplasmic membrane surfaces of macrophages spreading onto glass coverslips by both critical-point drying of broken-open cells and preparation of rotary platinum replicas. Irregular patches of the adherent ventral surface of the plasma membrane were exposed in these cells, and large areas of these exposed membranes were covered with clathrin-coated patches, pits, and vesicles. Various amounts of cytoskeleton were attached to the plasma membranes of these spreading cells, either as distinct starlike foci, or as individual filaments and bundles radiating out from the cytoskeletal meshwork. In newly adherent cells a well developed Golgi-GERL complex, characterized by smooth, dish-like cisternae associated with rough endoplasmic reticulum, was observed. There were many coated vesicles budding off from the Golgi cisternae, and these were predominantly of the large type (150 nm) usually associated with the plasma membrane. In critical-point-dried samples, both cytoskeleton and membranes were preserved in detail comparable to that of quick-frozen samples, after appropriate fixation. Rotary replication of critical-point-dried cells provides a rapid, easily controlled, and generally easy to perform method for obtaining samples of exposed membrane large enough to permit quantification of membrane-associated clathrin and cytoskeleton under various experimental conditions

Collagenase is a major gene product of induced rabbit synovial fibroblasts.

We have investigated the effects of the tumor-promoting phorbol diester, 12-O-tetradecanoylphorbol-13-acetate (TPA), on rabbit synovial fibroblasts, and found that this agent induced a major switch in gene expression in these cells that was marked by the specific induction of the neutral proteinase, collagenase, and was always accompanied by alterations in cell morphology. Procollagenase synthesis and secretion was first observed 6-12 h after the addition of TPA. The rate of collagenase production (1-5 U, or approximately 0.2-1 micrograms secreted procollagenase protein per 10(5) cells per 24 h) depended on the TPA concentration (1-400 ng/ml) and time of exposure (1-72 h). Procollagenase was the most prominent protein visible by direct silver staining or by autoradiography after SDS PAGE of [35S]methionine-labeled proteins. The two procollagenase bands of Mr 53,000 and 57,000, which migrated as a family of spots on two-dimensional gels and were immunoprecipitated by antibodies to purified rabbit collagenase, accounted for 23% of the newly synthesized, secreted protein in TPA-treated cells. Cell-free translation of mRNA from TPA-treated cells in rabbit reticulocyte lysate produced a single band of immunoprecipitable preprocollagenase (Mr 55,000) as a major product (5% of total) that migrated as a single spot on two-dimensional gels. Secreted procollagenase, preprocollagenase , and active collagenase (purified to homogeneity; specific activity 1.2 X 10(4) U/mg protein) had related peptide maps. Two other major secreted proteins, a neutral metalloproteinase of Mr 51,000 and a polypeptide of Mr 47,000, were also induced by TPA. In contrast to the induction of these four polypeptides, TPA decreased synthesis and secretion of a number of proteins, including collagen and fibronectin. Thus, collagenase is a convenient marker for major alterations in the pattern of protein synthesis and secretion by rabbit synovial fibroblasts treated with TPA

Erklärungsansätze zum Underpricing von IPOs in der Schweiz zwischen 2000 und 2016

Bei der Notierungsaufnahme (IPO) von Aktien an organisierten Kapitalmärkten lässt sich weltweit ein zum Emissionspreis positiv divergierender Börsenkurs feststellen. Eine solche Abweichung wird in der Literatur als Underpricing bezeichnet und stellt für den Emittenten einen Opportunitätsverlust dar. In der vorliegenden Bachelorthesis wird untersucht, ob bei Schweizer Börsengängen im Zeitraum 2000-2016 ein systematisches Underpricing beobachtet werden kann. In diesem Zusammenhang werden diverse Erklärungsansätze vorgestellt, die sich diesem Phänomen widmen. In einem ersten Schritt wird der empirische Forschungsstand für den Schweizer IPO-Markt dargelegt, darauf aufbauend wird anhand einer empirischen Untersuchung neue Evidenz für den Schweizer Markt geschaffen. Als Underpricing wird die marktadjustierte Rendite bezeichnet, welche vorliegend sowohl an der Messung des Eröffnungs- als auch des Schlusskurses des ersten Handelstages ermittelt wird. Stützend auf den erhobenen Daten werden diverse Erklärungsansätze präsentiert. Auf das Winner’s-Curse-Modell, welches das Underpricing auf eine asymmetrische Informationsverteilung zurückführt, und die Hot-Issue-Markthypothese, welche einen Zusammenhang zwischen der allgemeinen Börsenstimmung und dem IPO Underpricing vermutet, wird vertieft eingegangen. Zu beiden Erklärungsmodellen wird eine Hypothese aufgestellt, die mittels statistischen Analyseverfahren verifiziert werden. Die empirische Untersuchung konnte auf dem Schweizer IPO-Markt im genannten Zeitraum ein Underpricing von 10.62 Prozent gemessen am Eröffnungskurs und ein Underpricing von 12.51 Prozent gemessen am Schlusskurs nachweisen. Die erste Hypothese, dass auf dem Schweizer IPO-Markt ein Zusammenhang zwischen dem Underpricing und der Ex-ante-Unsicherheit besteht, konnte für den Zeitraum 2000-2016 bestätigt werden. Die zweite Hypothese, dass während Hot-Issue-Marktphasen im Vergleich zu Cold-Issue-Marktphasen auf dem Schweizer IPO-Markt überdurchschnittlich hohe Anfangsrenditen erzielt werden können, konnte für die Periode 2000-2016 ebenfalls verifiziert werden . Abgeleitet aus den Hypothesentests empfiehlt es sich, gerade bei unsicheren Börsengängen sowie allgemein guter Börsenstimmung in IPOs zu investieren. Die vorliegende Bachelorarbeit zeigt auf, dass ein Investor im Untersuchungszeitraum 2000-2016 eine Überrendite von über 10 Prozent erzielen konnte, wenn er konsequent an jedem Börsengang teilnahm und die Anteile am ersten Handelstag wieder verkaufte. Eine solche Strategie bedingt jedoch, dass immer der gleiche Betrag investiert wird und dass die Zuteilung jeweils zu 100 Prozent erfolgt. Aus Sicht des emittierenden Unternehmens empfiehlt sich zudem die Schaffung einer Transparenz, die über die börsenrechtlichen Vorschriften hinausgeht, um die Markunsicherheit zu reduzieren und so das Underpricing zu verringern. Aus den Erkenntnissen der vorliegenden Bachelorarbeit lässt sich in diesem Zusammenhang die Empfehlung abgeben, in der zukünftigen Forschung im Schweizer IPO-Markt eine Analyse des IPO Underpricing unter Berücksichtigung emissionsrechtlicher Aspekte durchzuführen

Initial events during phagocytosis by macrophages viewed from outside and inside the cell: membrane-particle interactions and clathrin.

ABSTRACT The initial events during phagocytosis of latex beads by mouse peritoneal macro-phages were visualized by high-resolution electron microscopy of platinum replicas of freezedried cells and by conventional thin-section electron microscopy of macrophages postfixed with I % tannic acid. On the external surface of phagocytosing macrophages, all stages of particle uptake were seen, from early attachment to complete engulfment. Wherever the plasma membrane approached the bead surface, there was a 20-nm-wide gap bridged by narrow strands of material 12.4 nm in diameter. These strands were also seen in thin sections and in replicas of critical-point-dried and freeze-fractured macrophages. When cells were broken open and the plasma membrane was viewed from the inside, many nascent phagosomes had relatively smooth cytoplasmic surfaces with few associated cytoskeletal filaments. However, up to one-half of the phagosomes that were still close to the cell surface after a short phagocytic pulse (2-5 min) had large flat or spherical areas of clathrin basketwork on their membranes, and both smooth and clathrin-coated vesicles were seen fusing with or budding off from them. Clathrin-coated pits and vesicles were also abundant elsewhere on the plasma membranes of phagocytosing and control macrophages, but large flat clathrin patches similar to those o

Psychoneuroendocrine evaluation of an acceptance and commitment based stress management training

Acceptance and Commitment Therapy (ACT), a behavioral therapy that targets psychological flexibility (PF), has been shown to be efficacious across a wide range of problems, including chronic work-related stress and perceived stress. ACT's effect on the multiple levels of the acute stress response (i.e., subjective and biological) is less well understood. The aim of the current study was to test whether ACT, by working toward PF, would reduce both the endocrine and subjective evaluations of participants' acute stress response.; Participants (n = 35) were randomized to an ACT condition or waitlist (WL). Participants in the ACT condition received a two-day ACT workshop on how to flexibly deal with stress. All participants completed a standardized laboratory stress test.; The ACT and WL groups did not differ on main comparisons of the endocrine response (i.e., cortisol) or subjective evaluation. Baseline levels of PF moderated some outcomes. Avoidant participants had a stronger endocrine stress reaction if they received the ACT intervention.; The control condition was a WL and not an active intervention comparison.; ACT is not useful in reducing the acute stress response and may even be iatrogenic, at least during tasks with little real-world impact for their personal values

Role of the cytoskeleton in laminin induced mammary gene expression

The differentiation of rat mammary epithelial cells is characterized both by morphologic changes and by the expression of a group of milk protein genes. We have previously shown that by culturing these cells on the basement membrane glycoprotein laminin, the synthesis of the milk proteins, transferrin, Α-casein, and Α-lactalbumin is induced. In order to determine if this effect is mediated through the cytoskeleton, we have treated these cells with cytochalasin D and colchicine. Treatment with cytochalasin D or colchicine for 24 h inhibits the accumulation of Α-casein, transferrin, and Α-lactalbumin without significant effect on general protein synthesis. Pulse chase studies show that cytochalasin D does not alter the intracellular turnover of Α-casein or transferrin. Additionally, treatment with cytochalasin D causes an early (within 1 h) increase in secretion of Α-casein and transferrin suggesting that the actin cytoskeleton provides a meshwork for secretory vesicles. The disruption of this network enhances the secretion of preformed proteins. However, long term (24 h) treatment with cytochalasin D inhibits synthesis of these milk proteins. Northern blot analysis indicates that treatment with cytochalasin D or colchicine inhibits the laminin induced increase in Α-casein, Α-lactalbumin, and transferrin mRNAs. These studies indicate that the major effect of the cytoskeleton on laminin induced milk protein gene expression occurs at the level of accumulation of mRNAs for these proteins. We conclude that the expression of laminin induced milk protein gene expression in primary rat mammary cultures depends on the integrity of the actin and microtubule cytoskeleton.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49876/1/1041350103_ftp.pd