Apoptosis and apoptotic mimicry: the Leishmania connection

Different death-styles have been described in unicellular organisms. In most cases they evolve with phenotypic features similar to apoptotic death of animal cells, such as phosphatidylserine (PS) exposure, oligonucleosomal DNA fragmentation, and loss of mitochondrial transmembrane potential, hinting that similar mechanisms operate in both situations. However, the biochemical pathways underlying death in unicellular organisms are still unclear. Host recognition of PS exposed on the surface of unicellular parasites is an important feature of the process of infection and progression of the disease. Here, we discuss data showing that entirely different mechanisms of PS exposure co-exist during the life-cycle of Leishmania amazonensis: in the case of promastigotes, a sub-population dies by apoptosis; in the case of amastigotes, the entire population exposes PS, not necessarily followed by apoptotic death. This phenomenon has been called apoptotic mimicry. The elusive caspase-like activities described in protozoa are also discussed.     

A semi-automatic computerized analysis of tracks of ciliates

Summary The behavior of Protozoa can be studied by using the ethogram as a conceptual tool capable of giving an almost complete picture of the motor biology of these microorganisms. A new semi-automatic, computerized method for drawing ethograms is described here: it allows a time-saving of about 70%, in comparison with the similar manual procedure. Microorganism movements are photographed by a Pentax LX camera from the screen of a TV monitor, connected to the stereomicroscope by a TV camera, and resolved into single images using a stroboscopic apparatus. The pictorial data are introduced into the computer by means of a digitizing tablet, and the track analysis is performed semi-automatically. The measurements recorded are then processed using a commercial statistics package in order to obtain a general view of the quantitative parameters of each ethogram.     

Peristaltic movement of the tortoise intestine

Zusammenfassung Am Schildkrötendarm kann die peristaltische Bewegung weder durch Erhöhung des Binnendruckes, noch durch Kombination interner Applikation von 5-Hydroxytryptamin oder Acetylcholin mit Druck angeregt werden. Druckwirkung auf die Mucosa und Einwirkung von 5-Hydroxytryptamin oder Acetylcholin auf die Serosa war jeweils erfolgreich. Präparate von Längsmuskelstreifen reagierten nicht auf 5-Hydroxytryptamin, während die Ringmuskelstreifen mit Kontraktur antworteten.     

Science and the romantic movement

Several authors have used the expression ‘formal asymmetry’ to characterize Einstein's method of introducing conceptual innovations. Prior to his use of formal asymmetries, however, Einstein relied upon analogy to introduce his major concepts, but without satisfactory results. He gradually refined another technique, reflection upon empirical problems, into the method of formal asymmetries, with impressive results. This historical study, based upon a textual analysis of Einstein's publications, raises a series of questions regarding the place of formal asymmetries in his work.     

Aristotle, Copernicus, Bruno: centrality, the principle of movement and the extension of the Universe

This paper¹ studies the different conceptions of both centrality and the principle or starting point of motion in the Universe held by Aristotle and later on by Copernicanism until Kepler and Bruno. According to Aristotle, the true centre of the Universe is the sphere of the fixed stars. This is also the starting point of motion. From this point of view, the diurnal motion is the fundamental one. Our analysis gives pride of place to De caelo II, 10, a chapter of Aristotle’s text which curiously allows an ‘Alpetragian’ reading of the transmission of motion.In Copernicus and the Copernicans, natural centrality is identified with the geometrical centre and, therefore, the Sun is acknowledged as the body through which the Deity acts on the world and it also plays the role of the principle and starting point of cosmic motion. This motion, however, is no longer diurnal motion, but the annual periodical motion of the planets. Within this context, we pose the question of to what extent it is possible to think that, before Kepler, there is a tacit attribution of a dynamic or motive role to the Sun by Copernicus, Rheticus, and Digges.For Bruno, since the Universe is infinite and homogeneous and the relationship of the Deity with it is one of indifferent presence everywhere, the Universe has no absolute centre, for any point is a centre. By the same token, there is no place that enjoys the prerogative of being—as being the seat of God—the motionless principle and starting point of motion.     

Actin polymerization machinery: the finish line of signaling networks, the starting point of cellular movement

Dynamic assembly of actin filaments generates the forces supporting cell motility. Several recent biochemical and genetic studies have revealed a plethora of different actin binding proteins whose coordinated activity regulates the turnover of actin filaments, thus controlling a variety of actin-based processes, including cell migration. Additionally, emerging evidence is highlighting a scenario whereby the same basic set of actin regulatory proteins is also the convergent node of different signaling pathways emanating from extracellular stimuli, like those from receptor tyrosine kinases. Here, we will focus on the molecular mechanisms of how the machinery of actin polymerization functions and is regulated, in a signaling-dependent mode, to generate site-directed actin assembly leading to cell motility.These authors contributed equally to this work.Received 26 October 2004; received after revision 27 December 2004; accepted 6 January 2005 Available online 09 March 2005     

The mechanism of movement of the gill-filaments in Teleostei

Zusammenfassung Bei ruhiger Atmung sind die Kiemenspalten der Teleostier sowohl während der Ein- wie während der Ausatmung dadurch verschlossen, daß je zwei einander zugekehrte Filamentreihen der angrenzenden Kiemen sich mit ihren Filamentspitzen berühren. Nur durch die ganz feinen Spalten zwischen den Lamellen der Filamente hindurch kann das Atmungswasser vom Ein- zum Ausatmungsraum strömen.Die Zusammenziehung der Adduktormuskeln bringt die Spitzen der Filamente zweier auf einem Kiemenbogen stehenden Filamentreihen zur Adduktion, und zwar entweder durch die Drehung des ganzen Filaments oder durch die Streckung seines freien Teiles. Ein- und Ausatmungsraum stehen dann durch breite Spalten miteinander in Verbindung.Diese Kontraktion der Adduktormuskeln tritt bei den Hustbewegungen auf, sowohl beim Husten nach vorne wie auch beim Husten nach hinten. Die Muskeln haben also eine Bedeutung für die Kiemenreinigung und spielen weder bei der Bewegung des Blutes durch die Kiemengefäße (Riess, 1881,Woskoboinikoff, 1932) noch bei der Erneuerung des Atmungswassers (Elfriede Schöttle, 1932) eine Rolle.     

Effect of sodium deoxycholate on net transintestinal movement in the uraemic rat: Acute experiments

Zusammenfassung In vivo gelingt der Nachweis, dass der Transport von Kreatinin, Phosphor, Natrium und Kalium vom Blut in das Lumen des Dünndarms bei urämischen Ratten durch Natriumdesoxycholat gesteigert wird.

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This work has been supported in part by a research grant from the Deutsche Forschungsgemeinschaft Nr. Dr 74/2     

New technique for movement analysis: Application to biological systems

Summary A new system for motion analysis is described. Modulation of light intensity by an organism's movement over an opaque and transparent checkerboard grid is monitored by a photocell. The photocell's output is proportional to the organism's amplitude and frequency of movement. This output is analyzed by a continuous interval dot display and spectral analysis. The system was tested by analyzing the activity of 4 Drosophila strains which are known to differ in their activity. General applicability of the system is discussed.This research was supported by a grant from the United States-Israel Binational. Science Foundation (BSF), Jerusalem, Israel.     

Neuronal degeneration in the striatum of the groggy rat: A new mutant with a movement disorder

A new mutation displaying abnormal movement was obtained in the progeny of a female Wistar rat which had been given 10 mg/kg methylnitrosourea at an early stage of the gestational period. Genetic studies revealed that the character is inherited by an autosomal single recessive gene, and we designated this mutationgroggy (gene symbolgr). The abnormal movement of the groggy rat was first apparent around postnatal day 15, while the histological studies revealed the appearance of numerous necrotic neurons in the striatum of the groggy rat on postnatal days 60 and 120.     

New technique for movement analysis: application to biological systems

A new system for motion analysis is described. Modulation of light intensity of an organism's movement over an opaque and transparent checkerboard grid is monitored by a photocell. The photocell's output is proportional to the organism's amplitude and frequency of movement. This output is analyzed by a continuous interval dot display and spectrum analysis. The system was tested by analyzing the activity of 4 Drosophila strains which are known to differ in their activity. General applicability of the system is discussed.     

Lithium and rubidium: Effects on the rhythmic swimming movement of jellyfish (Aurelia aurita)

Summary The effects of adding LiCl, RbCl, KCl or NaCl to sea water at concentrations up to 30 mmoles/1 on the frequency of contraction of jellyfish (Aurelia aurita) suggest that studies on phylogenetically low animals with relatively simple nervous systems may be of use to determine mechanisms of action of lithium and rubidium on movements.Acknowledgments. We thank P. Carl Petersens Fund and the Danish Medical Research Council for financial support and Henning Petersen for permission to carry out our experiments at Mols Laboratory.     

Demonstration of a net movement of water through the lens

Résumé Des cristallins de lapins couvés dans des diméthylsilicones sécrètent un fluide à leur surface antérieure. Ce fluide peut prendre le même aspect et la même réticulation qu'un morceau du tissu de la surface postérieure, si le cristallin est excisé promptement après la mort.

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This work was supported in part by a grant from the Institute of Neurological Diseases and Blindness N.I.H., No. NBO1979. The technical assistance ofR. Lukanen and CarolynMcDonald with picture taking and lens preparation respectively is gratefully acknowledged. The author gives a special thanks to Prof.J. E. Harris for helpful discussions and encouragement wihch led to this work.     

Lithium and rubidium: effects on the rhythmic swimming movement of jellyfish (Aurelia aurita).

The effects of adding LiCl, RbCl, KCl or NaCl to sea water at concentrations up to 30 mmoles/1 on the frequency of contraction of jellyfish (Aurelia aurita) suggest that studies on phylogenetically low animals with relatively simple nervous systems may be of use to determine mechanisms of action of lithium and rudidium on movements.