Gastrulation in the housefly,Musca vicina,macquart

Résumé L'«innere blastemma» de l'uf de la mouche domestique est riche en acide ribonucléique et en glycogène. Ce stratum s'incorpore dans le blastoderme et le mouvement gastrulaire commence peu après, avant même que la délimitation des cellules soit complète. La signification de ce caractère est soulignée.     

Division ofEntamoeba invadens Rodhain, 1934, in cultures

Zusammenfassung BeiEntamoeba invadens wurde eine ungleiche zellplasmatische Teilung beobachtet. Ein entsprechender Teilungsmodus gilt auch fürE. ranarum undE. moshkovskii.

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This work was done in the Department of Zoology, University of London, King's College, London WC2, England.     

Circularity,indispensability, and mathematical explanation in science

In this paper I consider the objection that the Enhanced Indispensability Argument (EIA) is circular and hence fails to support mathematical platonism. The objection is that the explanandum in any mathematical explanation of a physical phenomenon is itself identified using mathematical concepts. Hence the explanandum is only genuine if the truth of some mathematical theory is already presupposed. I argue that this objection deserves to be taken seriously, that it does sometimes undermine support for EIA, but that there is no reason to think that circularity is an unavoidable feature of mathematical explanation in science.     

Prediction,diagnosis, and causal thinking in forecasting

While forecasting involves forward/predictive thinking, it depends crucially on prior diagnosis for suggesting a model of the phenomenon, for defining‘relevant’variables, and for evaluating forecast accuracy via the model. The nature of diagnostic thinking is examined with respect to these activities. We first consider the difficulties of evaluating forecast accuracy without a causal model of what generates outcomes. We then discuss the development of models by considering how attention is directed to variables via analogy and metaphor as well as by what is unusual or abnormal. The causal relevance of variables is then assessed by reference to probabilistic signs called‘cues to causality’. These are: temporal order, constant conjunction, contiguity in time and space, number of alternative explanations, similarity, predictive validity, and robustness. The probabilistic nature of the cues is emphasized by discussing the concept of spurious correlation and how causation does not necessarily imply correlation. Implications for improving forecasting are considered with respect to the above issues.     

Immunofluorescent localization of collagen types I,III, IV,V, fibronectin,laminin, entactin,and heparan sulphate proteoglycan in human immature placenta

The distribution of eight components of the extracellular matrix in immature human placenta was studied by an indirect immunofluorescence method with monospecific antibodies. In the stroma of the term chorionic villi, collagen types I, III, IV, V, and fibronectin formed a mesh of fibers and conglomerates. Heparan sulphate proteoglycan formed multiple conglomerates, whereas laminin comprised small, scanty, discrete granules. Collagen type IV, laminin, entactin, and heparan sulphate proteoglycan were confined to the basement membrane of the trophoblast. Sometimes, only collagen type IV was identified in fetal vascular basement membrane.     

Accessibilité, solubilité et association,in situ,de la myosine

Summary myosinin situ is the more accessible to saline solutions the more finely the muscular substance has been divided, which implies its localization in structures difficult of access.This myosin exists in such structures in the form of a complex, the dissociation of which is effected by the saline solutions in proportion to their ionic strength.Fatigue does not modify the spatial accessibility of this complex but does modify its structures, so that, for some values ofp _H, solutions of equal ionic concentrations are less active on the substance of stimulated muscles than on that of normal ones.The myosin derived from that complex is much less homogenous in the Tiselius-Longworth apparatus than the myosin isolated from theWeber-Edsall myosin by fractionating with ammonium sulfate.Rabbits' muscles suddenly cooled by immersion in ice water give extracts similar to those of stimulated muscles.     

Arginine-vasopressin,lysine-vasopressin,and oxytocin,C14-labeled in the glycine residue

Zusammenfassung Die Synthese von Arginin-Vasopressin, Lysin-Vasopressin und Oxytocin, deren Glycinrest eine¹⁴C-Markierung trägt, wird mit Hilfe der Festkörpermethode nachMerrifield beschrieben.

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Supported by National Institutes of Health grants No. AM-13567 and No. AM-10080 and the Atomic Energy Commission.

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Abbreviations follow the rules of the IUPAC-IUB Commission on Biochemical Nomenclature in Biochemistry5, 2485 (1966). All optically-active amino acids are ofl-configuration. The following additional abbreviations were used: N-hydroxysuccinimide ester (OSu), ethanol (EtOH), methanol (MeOH), acetic acid (AcOH),n-butanol (n-BuOH), pyridine (Pyr) and N,N-dicyclohexylcarbodiimide (DCCI). Protected peptides and hormones were visualized on thinlayer plates according to the procedure byH. Zahn andE. Rexroth, Z. analyt. Chem.148, 181 (1955). The biological activities of the hormones were measured against the U.S.P. Posterior Pituitary Reference Standard; the four-point design was used for these bioassays and standard errors were calculated according to the method ofC. I. Bliss,The Statistics of Bioassay (Academic Press, New York, N.Y. 1952).

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Acknowledgments. The authors wish to thank Mr.D. Schlesinger for some of the amino acid derivatives used, and MissM. Wahrenburg and Mrs.A. Silverman for bioassays.     

Retropulsion,GABA, and possible hallucinatory behavior in mice

Zusammenfassung Amino-oxyacetsäure, eine Substanz welche das endogene Gehirnniveau anGABA erhöht, führte in 16 Tage alten Mäusen zu LSD-ähnlichen Verhaltensweisen wie Hypothermie: zu Krämpfen und Rückwärtslaufen.     

DNS-Synthese,Blastentransformation und Mitosen in gemischten,homologen Granulozyten-Lymphozytenkulturen

Summary Lymphocyte stimulation in vitro could be obtained with allogeneic but not autochthonous or isogeneic granulocytes. Blastoid transformation, mitosis and activated DNA synthesis measured by H³-thymidine incorporation occurred simultaneously. The cytoimmunological relevance and further applications of the findings are discussed.

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Mit Unterstützung der schweizerischen Krebsliga.     

Tightrope act: autophagy in stem cell renewal, differentiation, proliferation, and aging

Autophagy is a constitutive lysosomal catabolic pathway that degrades damaged organelles and protein aggregates. Stem cells are characterized by self-renewal, pluripotency, and quiescence; their long life span, limited capacity to dilute cellular waste and spent organelles due to quiescence, along with their requirement for remodeling in order to differentiate, all suggest that they require autophagy more than other cell types. Here, we review the current literature on the role of autophagy in embryonic and adult stem cells, including hematopoietic, mesenchymal, and neuronal stem cells, highlighting the diverse and contrasting roles autophagy plays in their biology. Furthermore, we review the few studies on stem cells, lysosomal activity, and autophagy. Novel techniques to detect autophagy in primary cells are required to study autophagy in different stem cell types. These will help to elucidate the importance of autophagy in stem cells during transplantation, a promising therapeutic approach for many diseases.