Diversification of prey capture techniques among the piscivores in Lake Tana's (Ethiopia) Labeobarbus species flock (Cyprinidae)

Lake Tana harbours the only known intact species flock of large cyprinid fishes (15 Labeobarbus spp.). One of the most curious aspects of this species flock is the large number (8) of piscivorous species. Cyprinids are not well designed for piscivory (i.e. small slit-shaped pharyngeal cavity, lack of teeth in the oral jaws, lack of a stomach), which raises the question how well adapted these labeobarbs actually are to function as piscivores? In this study we analyse the kinematics of prey capture (by varied combinations of suction, swimming and jaw protrusion) among Lake Tana's piscivorous labeobarbs. Suction feeding kinematics were similar to values reported for other piscivorous fish species. A detailed analysis of several Labeobarbus species displayed distinct types of techniques (overswimming, velocity/volume suction with jaw protrusion) suited to capture elusive prey in different macro-habitats, Lake Tana's Labeobarbus species evolved a wide range of piscivorous predation techniques, a unique scenario for cyprinid fishes

Kandidatengenstudien bei Fokaler Idiopathischer Torsionsdystonie (F-ITD)

Bei der fokalen idiopathischen Torsionsdystonie (F-ITD) handelt es sich um die häufigste Form der Dystonien, wobei die Ätiologie dieser Erkrankung bisher nicht geklärt ist. Es fanden sich in klinisch-genetischen Studien Anhaltspunkte dafür, dass genetische Faktoren in der Pathogenese eine Rolle spielen. Eine Identifikation spezieller Gene ist aber bisher nicht gelungen. Basierend auf dem bisherigen Wissen über die Pathogenese der F-ITD, wurden im Rahmen dieser Arbeit Kandidatengene analysiert um einen möglichen Zusammenhang zwischen ihnen und der F-ITD zu untersuchen. Studien berichteten über einen gestörten Kupfermetabolismus bei Patienten mit Dystonie, ohne aber dieses Phänomen ätiologisch klären zu können. In dieser Arbeit wurden mit dem Menkes-Gen, dem Wilson-Gen und dem ATOX1-Gen Gene des Kupfermetabolismus analysiert. Auch über gestörte autoimmune Mechanismen bei Patienten mit F-ITD ist mehrfach berichtet worden und genetische Studien zeigten eine Assoziation von Allelen des HLA-DRB Locus mit Dystonien. Es erfolgte eine HLA-DRB Typisierung, um zu untersuchen, ob spezielle Allele des HLA-DRB Locus eine Assoziation zur F-ITD zeigen. Berichtet wurde auch über phänotypische Ähnlichkeiten zwischen tardiven Dyskinesien (TD) und Dystonien, wobei im Gegensatz zur F-ITD bei der TD genetische Susceptibilitätsfaktoren bekannt sind. Unter der Hypothese, dass sich die phänotypischen Gemeinsamkeiten auch auf genetischer Ebene widerspiegeln, wurden die für die TD bekannten Susceptibilitätsfaktoren untersucht: Dieses sind Polymorphismen im µ-Opioid Rezeptor, der Manganesesuperoxiddismutase, im Dopamin-3-Rezeptorgen, im 5HT2A-Serotonin-Rezeptor und im Gen der CYP1A2. Grundlage weiterer Analysen waren die Daten verschiedener Studien, die einen Zusammenhang zwischen Dystonien und Störungen im Homocysteinmetabolismus zeigten. Analysiert wurden hier im Speziellen funktionelle Polymorphismen in der Cystathionin-ß-Synthase (CBS), in der Methylentetrahydrofolatreduktase (MTHFR) und in der Methioninsynthetase (MS), wobei es sich hier um Gene handelt, deren Enzyme Bestandteile des Homocysteinmetabolismus darstellen. Des Weiteren wurden zwei Polymorphismen im DYT1-Gen analysiert mit der Frage, ob sie gehäuft bei Patienten mit F-ITD zu finden sind. Grundlage für die Analyse eines Polymorphismus im Dopamin-D5-Rezeptor (DRD5) war zum einen, dass Studien über Assoziationen von Allelen dieses Polymorphismus mit F-ITD berichteten und zum anderen, dass es Anhaltspunkte für eine Beteiligung des dopaminergen Systems in der Pathogenese der Dystonien gibt. Die Analyse der Kupfertransportproteine ergab keine Anhaltspunkte für eine direkte Beteiligung der untersuchten Gene an der Pathogenese der F-ITD. Auch die Analyse des HLA-DRB Locus zeigte keine signifikanten Assoziationen bestimmter Allele mit der F-ITD. Die Susceptibilitätsfaktoren der tardiven Dyskinesien zeigten keine Assoziation zur F-ITD. Bei der Analyse der Polymorphismen in Genen des Homocysteinstoffwechsels zeigte sich, neben negativen Daten zur MTHFR und MS, in der initial untersuchten deutschen Population eine Assoziation des 31bp-VNTR und der 63bp-Insertion des CBS-Gens mit der F-ITD. Diese Daten konnten jedoch in der französischen Population nicht bestätigt werden. Die Verteilung der Polymorphismen im DYT1-Gen verfehlte im Vergleich von Patienten zu Kontrollen knapp statistisch signifikante Werte. Die Ergebnisse dieser Arbeit zur Analyse des Dopamin-D5-Rezeptors konnten die positiven Daten aus anderen Studien nicht bestätigen. Eine Beteiligung der hier untersuchten Kandidatengene an der Pathogenese der F-ITD wird durch die Daten dieser Arbeit nicht unterstützt. Zu den Ergebnissen der Analyse des CBS-Gens lässt sich festhalten, dass sie nicht das wichtige Kriterium der Replikabilität erfüllen, so dass weitere Studien in anderen Populationen notwendig sein werden. Auch die Bedeutung des Polymorphismus im DRD5-Gen kann nach den negativen Daten dieser Arbeit, die im Widerspruch zu positiven Ergebnissen anderer Studien stehen, nicht abschließend beurteilt werden. Weitere Studien mit großen Studienpopulationen werden notwendig sein, diesen Widerspruch zu klären und auch andere mögliche Kandidatengene bzw. Susceptibilitätsfaktoren zur F-ITD zu identifizieren. Dieses könnte dann die Grundlage für einen möglichen therapeutischen Ansatz sein, ganz ähnlich wie es bei der DYT1-Dystonie in vitro mit Erfolg bereits praktiziert wurde

Kandidatengenstudien bei Fokaler Idiopathischer Torsionsdystonie (F-ITD)

Bei der fokalen idiopathischen Torsionsdystonie (F-ITD) handelt es sich um die häufigste Form der Dystonien, wobei die Ätiologie dieser Erkrankung bisher nicht geklärt ist. Es fanden sich in klinisch-genetischen Studien Anhaltspunkte dafür, dass genetische Faktoren in der Pathogenese eine Rolle spielen. Eine Identifikation spezieller Gene ist aber bisher nicht gelungen. Basierend auf dem bisherigen Wissen über die Pathogenese der F-ITD, wurden im Rahmen dieser Arbeit Kandidatengene analysiert um einen möglichen Zusammenhang zwischen ihnen und der F-ITD zu untersuchen. Studien berichteten über einen gestörten Kupfermetabolismus bei Patienten mit Dystonie, ohne aber dieses Phänomen ätiologisch klären zu können. In dieser Arbeit wurden mit dem Menkes-Gen, dem Wilson-Gen und dem ATOX1-Gen Gene des Kupfermetabolismus analysiert. Auch über gestörte autoimmune Mechanismen bei Patienten mit F-ITD ist mehrfach berichtet worden und genetische Studien zeigten eine Assoziation von Allelen des HLA-DRB Locus mit Dystonien. Es erfolgte eine HLA-DRB Typisierung, um zu untersuchen, ob spezielle Allele des HLA-DRB Locus eine Assoziation zur F-ITD zeigen. Berichtet wurde auch über phänotypische Ähnlichkeiten zwischen tardiven Dyskinesien (TD) und Dystonien, wobei im Gegensatz zur F-ITD bei der TD genetische Susceptibilitätsfaktoren bekannt sind. Unter der Hypothese, dass sich die phänotypischen Gemeinsamkeiten auch auf genetischer Ebene widerspiegeln, wurden die für die TD bekannten Susceptibilitätsfaktoren untersucht: Dieses sind Polymorphismen im µ-Opioid Rezeptor, der Manganesesuperoxiddismutase, im Dopamin-3-Rezeptorgen, im 5HT2A-Serotonin-Rezeptor und im Gen der CYP1A2. Grundlage weiterer Analysen waren die Daten verschiedener Studien, die einen Zusammenhang zwischen Dystonien und Störungen im Homocysteinmetabolismus zeigten. Analysiert wurden hier im Speziellen funktionelle Polymorphismen in der Cystathionin-ß-Synthase (CBS), in der Methylentetrahydrofolatreduktase (MTHFR) und in der Methioninsynthetase (MS), wobei es sich hier um Gene handelt, deren Enzyme Bestandteile des Homocysteinmetabolismus darstellen. Des Weiteren wurden zwei Polymorphismen im DYT1-Gen analysiert mit der Frage, ob sie gehäuft bei Patienten mit F-ITD zu finden sind. Grundlage für die Analyse eines Polymorphismus im Dopamin-D5-Rezeptor (DRD5) war zum einen, dass Studien über Assoziationen von Allelen dieses Polymorphismus mit F-ITD berichteten und zum anderen, dass es Anhaltspunkte für eine Beteiligung des dopaminergen Systems in der Pathogenese der Dystonien gibt. Die Analyse der Kupfertransportproteine ergab keine Anhaltspunkte für eine direkte Beteiligung der untersuchten Gene an der Pathogenese der F-ITD. Auch die Analyse des HLA-DRB Locus zeigte keine signifikanten Assoziationen bestimmter Allele mit der F-ITD. Die Susceptibilitätsfaktoren der tardiven Dyskinesien zeigten keine Assoziation zur F-ITD. Bei der Analyse der Polymorphismen in Genen des Homocysteinstoffwechsels zeigte sich, neben negativen Daten zur MTHFR und MS, in der initial untersuchten deutschen Population eine Assoziation des 31bp-VNTR und der 63bp-Insertion des CBS-Gens mit der F-ITD. Diese Daten konnten jedoch in der französischen Population nicht bestätigt werden. Die Verteilung der Polymorphismen im DYT1-Gen verfehlte im Vergleich von Patienten zu Kontrollen knapp statistisch signifikante Werte. Die Ergebnisse dieser Arbeit zur Analyse des Dopamin-D5-Rezeptors konnten die positiven Daten aus anderen Studien nicht bestätigen. Eine Beteiligung der hier untersuchten Kandidatengene an der Pathogenese der F-ITD wird durch die Daten dieser Arbeit nicht unterstützt. Zu den Ergebnissen der Analyse des CBS-Gens lässt sich festhalten, dass sie nicht das wichtige Kriterium der Replikabilität erfüllen, so dass weitere Studien in anderen Populationen notwendig sein werden. Auch die Bedeutung des Polymorphismus im DRD5-Gen kann nach den negativen Daten dieser Arbeit, die im Widerspruch zu positiven Ergebnissen anderer Studien stehen, nicht abschließend beurteilt werden. Weitere Studien mit großen Studienpopulationen werden notwendig sein, diesen Widerspruch zu klären und auch andere mögliche Kandidatengene bzw. Susceptibilitätsfaktoren zur F-ITD zu identifizieren. Dieses könnte dann die Grundlage für einen möglichen therapeutischen Ansatz sein, ganz ähnlich wie es bei der DYT1-Dystonie in vitro mit Erfolg bereits praktiziert wurde

Food handling and mastication in the carp (Cyprinus carpio L.)

The process of food handling in the common carp ( Cyprinus carpio L.) and its structures associated with feeding are analyzed. The aim of this study is to explain the relation between the the architecture of the head and its functions in food processing and to determine the specializations for some food types and the consequent restrictions for others. Such information improves our understanding of the trophic interrelations between different fish species living together in one community.- Cyprinids possess pharyngeal jaws, which are modified fifth branchial arches. These are moved by the modified branchial arch muscles against a horny chewing pad in the skull. Oral teeth and a stomach are absent. The upper jaws are protrusile and so aid in the formation of a round suction mouth. The oral and opercular cavity are highly variable in volume. The pharynx is almost fully occupied by the dorsal palatal organ. The pharyngeal floor is composed of the postlingual organ and the branchial sieve. Fibre systems of striated muscles form the bulk of these organs. The branchial arches bear numerous gill rakers. The surface of the pharyngeal roof and floor is almost fully covered by taste buds (up to 82 0/MM2 ) and mucous cells. The medullar nervous centre of these organs is of about equal size as the forebrain. The narrow slit-like space between both organs has a restricted capacity for volume change, contrary to the situation in most other fishes.- The role which these structures perform during food uptake and processing in the carp was investigated using cine- and X-ray filming techniques and by synchronously recording the electromyograms of the involved muscles (9 channels). The morphology was studied on the macroscopical and on light- and electronmicroscopical level. Food types included commercial fish pellets, barley, earthworms, tubifex, cladocerans and tubifex-soil mixtures. BaSO 4 -impregnated food was used to follow its path in the X-ray movies.- Each feeding process is composed of a variable number of stereotyped movement patterns, viz: particulate intake and gulping, selection between food and non-food material (through rinsing, repositioning and backwashing), recollection from the branchial sieve followed by food transport and filling of the chewing cavity, crushing, grinding and deglutition. Probing of the soil and spitting are considered separately.- The timing, amplitude and velocity of mouth opening, protrusion of the upper jaws, opening of the opercular valve and of the volume changes in the oral, buccal, pharyngeal and opercular cavities determine the effects of each single pattern. Food intake, selection, transport and mastication impose different demands on the head and can not be combined effectively.- Different food types are processed in sequences of movement patterns varying in frequency and type according to the specific size, consistency and soilure of the food. Handling times are read from the electromyograms and may differ widely.- The quantitative distribution pattern of taste buds, mucous cells, club cells and muscle fibers over the oro-pharyngeal surface is measured. Based on these patterns and on other structural characters six areas are distinguished in the oro-pharynx and related with the functions of the above movement patterns for food intake and processing. Scanning E.M. pictures are presented of the common epithelial cells with microridges, cornified cells, mucous cells, taste buds and sensory (?) oligovillous cells.- Particulate intake is accomplished by fast and voluminous suction, caused by expansion of the orobuccal and opercular cavities. The upper jaws are protruded to produce a fast suction flow (>60 cm/sec), aimed to the particle.Gulping, the slow and less aimed uptake of a mouthful of water with suspended foodparticles is accomplished by size increase of the oral cavity mainly. The carp finally encloses the suspension by protruding its upper jaws downward. Oral compression drives the water and food particles over the branchial sieve. The energy required for each gulp will most probably be considerably less than that needed for particulate intake.- High densities of club cells, which produce the cyprinid alarming substance in the skin, also occur in the orobuccal lining. Their alarming function in this area is doubted.- Selection between food and non-food requires the retention of edible particles and the expulsion of waste. The electromyograms and electrical stimulations indicate that this separation is achieved by momentary bulgings on the palatal organ, fixing edible particles between pharyngeal roof and floor. Waste particles are flushed through the branchial slits. The complex structure of the palatal organ, the almost maximal densities of taste buds and the cyto-architecture of its regulatory centre in the hindbrain suggest a high level of discrimination in this selection process. The slit-shaped pharynx guarantees a large contact area for selection, but limits its role in suction.- Protrusion of the upper jaws with the mouth closed plays a crucial role in selection by resuspending food and non-food in the expanding oral cavity. Alternative expansion and compression of the oral cavity creates a for- and backward flow through the pharyngeal slit and the branchial sieve. Repetition of such 'closed protrusions' and selection effects are graded increasing purification. Closed protrusion movements also serve for merely repositioning of large particles and for recollection of the filtrate from the branchial sieve.- Cells producing low-viscosity mucus (sialomucines) are found rostrally in the oro-pharynx. It probably serves in lowering the resistance of the wall for the flow of water and in protection of the underlying tissue.Cells producing large quantities of highly viscous mucus (sulfomucines) are found in regions were aggregation and clustering of food particles prior to transport is expected.- Transport of food enveloped in mucus is effected by a peristaltic type of movement in the palatal and postlingual organs. These also propel the food into the chewing cavity being enlarged by depression of the pharyngeal jaws.- The pharyngeal jaws are suspended in muscular slings from the caudal part of the skull and pectoral girdle. Except an antero-ventral gliding joint with the branchial basket no articulations are present. The symphysis of the jaws allows intrinsic movements. Food is crushed and ground between the pharyngeal teeth and a cornified chewing pad, fixed to the base of the skull. Mastication of grains of maize produces distinct sounds, even distinct close to the experimental tank.- The epaxial muscles of the carp contribute through rotation of the skull high forces to crushing and grinding. The hypaxial muscles transfer their forces to the pharyngeal teeth by retraction of the pectoral girdle, which provides a large moment-arm. The pharyngeal masticatory apparatus is built for producing and resisting high forces.- Contrary to these 'power muscles', the hypertrophied pharyngeal jaw muscles act more like 'steering muscles'. They direct and stabilize the pharyngeal jaw movements around four anatomical rotational axes.- The chewing construction with the rotating skull renders a single Weberian ossicle connecting the sound receiving swimming bladder and the internal ear inside the skull almost impossible. The chain of Weberian ossicles running close to the rotation centre of the skull seems to be a constructive necessity.- Deglutition is accomplished by compression of the chewing cavity. Bulging of the palatal and postlingual organs closes the entrance and thus direct the transport to the esophagus. Movements of the pharyngeal jaws support transport.- The apparatus for food uptake and food processing of the carp appears to be specialized to deal with medium-sized and hard food particles (e.g. seeds and shelled mollusks), from 250 pm to about 3% of its standard body length, but also for food items mixed with unedible material. These specializations for bottomfeeding are most likely basic to the present wide distribution of the common carp and facilitate fish farming.Large, fast and struggling preys as well as large and flat plant material can hardly be utilized by the carp. Thus, also this 'omnivorous' fish is limited by its specializations in the utilization of the available food items in its environment.- A tentative scheme relates characters from different parts of the head and unique to the cyprinid family in a functional and structural context. The development of the masticatory apparatus may well have been a key adaptation in the origin of the cyprinid feeding mechanism.- The present research of the carp provides a new and detailed startingpoint for investigation of the regulatory mechanisms in feeding and for comparisons with native cyprinids like bream roach, tench etc. Knowledge of abilities and restrictions of their structural specializations associated with feeding eludidates which plasticity the fish has to utilize different types of food. This plasticity is a crucial factor for the survival of the species in conditions of food scarcity and co-determines its position in competition. The obtained knowledge thus aids in predicting the effects of environmental changes on the trophic interactions and composition of the fish fauna

Effects of forced distribution rating systems on workforce productivity and potential in companies with internal promotion: A Monte-Carlo simulation

How to improve performance of workforce and productivity is perhaps one of the most challenging issues for companies today. Rating systems can be used to improve performance potential by identifying high and low performers. Probably the determination of who shall or who shall not be promoted is the most important use of ratings (Odiorne, 1963). Performance rating systems can be classified into two general categories: absolute and relative systems (Cascio, 1991). Absolute ratings assess individuals against the same standards, and relative ratings are required to assess individuals in relation to another. Heneman (1986) and Nathan&Alexander (1988) examined the differences between relative and absolute ratings, and found out that relative formats have stronger correlations with results orientated criteria like production quantity and sales volume. Forced Distribution Rating Systems (FDRS) are relative rating systems which evaluate performance, forcing raters to assign ratees into at least three categories (top, middle and bottom) and are often tied to termination decisions. The most basic approach of FDRS is sometimes referred as a “totem pole” because it involves ranking all employees in a particular workgroup from best to worst (Grote, 2005). FDRS and other relative approaches have been argued to be more accurate than absolute systems as FDRS require raters to objectively find differences between ratees and leave distributional biases behind (Goffin, Gellatly, Paunonen, Jackson, & Meyer, 1996; Heneman, 1986; Jelley & Goffin, 2001; Nathan & Alexander, 1988; Roch, Sternburgh, & Caputo, 2007). When it comes to performance improvement, proponents and critics of forced ranking have both found support for their positions within the limited available existing research. Even FDRS supporters acknowledge that their fairness and usefulness largely depend on how they are implemented and whether or not they are accompanied by other changes in the overall performance management system. While there are no hard and fast statistics regarding which companies have succeed with the process and which have not, most observers agree that FDRS is more favorably in companies with a high-pressure, results orientated culture (Bates, 2003) and seemed to be more acceptable at high-tech, manufacturing and financial service organizations, rather than in the public sector and retail sector (Todd & Ramachandran, 2007). When done correctly, FDRS ensures that company resources are directed toward those who contribute the most or have the potential to make a positive difference. These resources include compensation and other rewards like internal promotions. “Forced Distribution Rating Systems are probably the most controversial issue in management today" (D. Grote in Bates, 2003, p. 64). Since 2000, articles about FDRS (also known as forced ranking) have appeared in such prominent international media outlets like The New York Times, The Economist, The Chicago Tribune, Financial Times and so on. The practice of FDRS gained fame based on the endorsement of General Electric CEO Jack Welch. The latest estimate is that up to 20 percent of all U.S. business organizations and up to 25 percent of Fortune 500 firms use some type of FDRS (Sears & McDermott, 2003)). As many as a quarter of the Fortune Page 2 500 companies, including Cisco Systems, Hewlett-Packard, Microsoft, Lucent, Conoco, EDS, and Intel, may be currently using some type of performance management system built around that principle (Melsler, 2003). Nevertheless given the intense interest in FDRS, it is surprising that there is virtually no published research that can inform practitioners about their effectiveness. A prominent study on the field of FDRS was conducted by Scullen, Bergey and Aiman-Smith (2005). Scullen et al. demonstrated for the first time the efficacy of FDRS by means of a simulation obtaining performance potential in a scope of 30 years. The present study sought to extend Scullen’s study attending the limitations they highlighted in their discussion. Our study comprehends the following improvements: a) inclusion of a non-zero correlation between turnover and potential b) firing the lowest performers of the company (instead of firing the poorest performers of each workgroup) and c) evaluation of productivity by adding the costs per hire and the costs of replacement. Furthermore to emulate the reality of modern companies we decided to define a multilevel structure (executives, managers and workers) and we also considered the effects of using internal promotion or not.Outgoin

Very Late Stent Thrombosis 42 Months after Implantation of Sirolimus-Eluting Stent and Discontinuation of Antiplatelet Therapy

Although safety profiles of sirolimus-eluting stents do not seem to differ in short-to-medium term from those of bare-metal stents, late stent thrombosis after deployment of drug-eluting stents has emerged as a potential safety concern in the era of high-pressure stent implantation. Here, we describe the case of a patient with acute myocardial infarction due to stent thrombosis of a sirolimus-eluting stent 42 months after stent deployment and 5 weeks after discontinuation of aspirin treatment. To the best of our knowledge, this is one of the most delayed cases of sirolimus-eluting stent thrombosis described so far. The case emphasizes the potential risk that late stent thrombosis can unpredictably occur at any time point after drug-eluting stent deployment

De-Escalation of P2Y(12) Receptor Inhibitor Therapy after Acute Coronary Syndromes in Patients Undergoing Percutaneous Coronary Intervention

Dual antiplatelet therapy (DAPT) - a combination of a P2Y(12) receptor inhibitor and aspirin - has revolutionized antithrombotic treatment. Potent P2Y(12) inhibitors such as prasugrel and ticagrelor exhibit a strong and more consistent platelet inhibition when compared to clopidogrel. Therefore, ticagrelor and prasugrel significantly reduce ischemic events, but at an expense of an increased bleeding risk in acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI). These observations have engaged intensive clinical research in alternative DAPT regimens to achieve sufficient platelet inhibition with an acceptable bleeding risk. Our review focusses on P2Y(12) receptor therapy de-escalation defined as a switch from a potent antiplatelet agent (ticagrelor or prasugrel) to clopidogrel. Recently, both unguided (platelet function testing independent) and guided (platelet function testing dependent) DAPT de-escalation strategies have been investigated in different clinical studies and both switching strategies could be possible options to prevent bleeding complications without increasing ischemic risk. In light of the still limited data currently available, future large-scale trials should accumulate more data on various DAPT de-escalation regimens with both ticagrelor and prasugrel in unguided and guided de-escalation approaches. In the current review we aim at summarizing and discussing the current evidence on this still emerging topic in the field of antiplatelet treatment