Eye lens development and gamma crystallins in Discoglossus pictus (Anura).

The ontogeny and localization of the gamma crystallins in Discoglossus pictus lens development has been determined. Using antibody specific for amphibian gamma crystallins in the immunofluorescence technique, it was found that gamma crystallins first appear in primary lens fibre cells in the lens rudiment, and continue to be restricted to the fibre area as lens development progresses. Thus the role of gamma crystallins as indicators of a differentiated state remains constant in amphibian evolution, having been demonstrated in the most archaic anuran superfamily, as well as in others more recently evolved.     

Chain-proteins of the vertebrate lens

Some lens proteins exist in a chain-like form in the vertebrate lens fibre cells. They consist of globular proteins arranged on a filamentous backbone.     

Chain-proteins of the vertebrate lens

Summary Some lens proteins exist in a chain-like form in the vertebrate lens fibre cells. They consist of globular proteins arranged on a filamentous backbone.This study was supported by research grant EY-01417 of the National Institutes of Health, Bethesda, Maryland, USA.     

Transgenic mice carrying chimeric or mutated type III intermediate filament (IF) genes

Mice carrying chimeric, truncated or mutated genes encoding intermediate filament (IF) proteins type III do not show any detectable severe pathology. However, upon (over)expression of the transgene in the eye lens all animals develop lens opacification (cataract). At the cellular level the loss of visual acuity is preceded by interference with the terminal differentiation of lens fibre cells, plasma membrane damage, distorted assembly of the IF cytoskeleton and perturbation of the cytoskeleton-membrane complex. The degree of expression is paralleled by the extent of the damages. Received 4 November 1996; accepted 15 November 1996     

Eye lens development and γ crystallins in Discoglossus pictus (Anura)

Summary The ontogeny and localization of the crystallins in Discoglossus pictus lens development has been determined. Using antibody specific for amphibian crystallins in the immunofluorescence technique, it was found that crystallins first appear in primary lens fibre cells in the lens rudiment, and continue to be restricted to the fibre area as lens development progresses. Thus the role of crystallins as indicators of a differentiated state remains constant in amphibian evolution, having been demonstrated in the most archaic anuran superfamily, as well as in others more recently evolved.This research was largely accomplished during the tenure of a fellowship from the European Molecular Biology Organization to D. S. McDevitt, and was partially supported by Biomedical Research Support Grant RR 546414 to D. S. McDevitt.The authors are grateful to Prof. W. J. van Doorenmaalen for use of the laboratory facilities; and to the Hubrecht Laboratory, International Embryological Institute, Utrecht, The Netherlands, for the gift of live D. pictus eggs. We thank Miss C. M. J. Stuifsand for the normal histology and Mr Th. Hulskes for the illustrations.     

Polypeptides of the lens fibre cell intracellular matrix

Summary The cytoskeletal proteins of the vertebrate lens fibre cell comprise polypeptides ranging in mol.wt from 43,000 to 250,000 daltons. The main intermediate filament polypeptide of the pickerel, Northern frog, chick, bovine, and human lens has a mol.wt of 54,000 daltons. Peptide analysis revealed that the chick 54,000 dalton protein was more similar to the bovine protein than to the pickerel protein.Supported by grants EY 01417 (H. Maisel) and HD-06390 (J.C. Brown, University of Virginia, Charlottesville) from the National Institutes of Health, U.S.P.H.S.     

The effect of chloroquine upon the developing lens

Applied to the developing lens of the 14-day-old chick embryo, in organ culture conditions, chloroquine prevented the elongation of the primary lens fibres, destroyed the equatorial ones and provoked vacuolisation and/or destruction in the epithelial cells.     

Das Spitzenwachstum der Fasern beiLinum perenne L

Summary In shoots ofLinum perenne apical growth was observed at both ends of the fibres. Their rounded tips, rich in protoplasm, protude into the middle lamellae of adjacent fibres or parenchyma cells. In addition to their apical growth, the fibre walls undergo symplastic growth with the walls of neighbouring cells. The formation of the pointed ends of fully developed fibres is described.     

Hypophysial hormones and a G1 block in the lens epithelium of the adult frog (Rana pipiens)

Summary Mechanical injury initself may be responsible for the transition of lens epithelial cells from the G₀ to the G₁ compartment of the cell cycle. This traverse which does not depend on DNA-dependent hypophysial hormones may be in part reversible.     

The effect of chloroquine upon the developing lens

Summary Applied to the developing lens of the 14-day-old chick embryo, in organ culture conditions, chloquine prevented the elongation of the primary lens fibres, destroyed the equatorial ones and provoked vacuolisation and/or destruction in the epithelial cells.This work was supported by a grant from the office of the Chief Scientist, Ministry of Health, Israel     

Similar paracrystals of endoplasmic reticulum in the photoemitters and the photoreceptors of scale-worms

Summary Paracrystals of tubular endoplasmic reticulum are the characteristic of the luminous cells in the elytra of polynoïd worms, and they are the sources of luminescence as well as of fluorescence. Structurally similar paracrystals are now found to be the main constituent of the lens in the eyes of all the Aphroditidae.     

Electron microscopic observations on the innervation of the intestinal inner muscle layer

Riassunto Nella tonaca muscolare interna dell'intestino tenue di ratto si osservano numerosi fasci di fibre nervose; una distinzione tra fibre intramuscolari vere e proprie e fibre perivascolari non è possibile in quanto ogni ordine di fasci ha rapporti intimi con cellule muscolari lisce proprie della tonaca muscolare. L'osservazione di tre tipi di espansioni a vescicole distinte, senza forme di passaggio, fa ritenere verosimile l'esistenza di tre tipi differenti di fibre nervose.     

Hypophysectomy exerts a radioprotective effect on frog lens

Summary Exposure to X-rays usually causes cataracts in frogs. These cataracts are always preceded by misalignment of the structures called meridional rows (MR). When cell division is completely halted by hypophysectomy, however, irradiation no longer disturbs the orientation of the MR. Since the MR are the structures formed as lens epithelial cells differentiate into lens fibres it is reasonable to propose that radiocataractogenesis depends upon a mitosis-driven formation of pathological fibres from epithelial cells that have been rendered abnormal by exposure to X-rays.This research was supported by: NIH grant No. EY 02492-02 (HR); NIH grant No. EY 02648-02 (BVW).     

Studies on muscle fibre splitting in skeletal muscle

Summary Autoradiographic, stereological and histological studies have been carried out to determine the origin of muscle fibre splitting which supposedly occurs during muscle hypertrophy. The results obtained clearly indicate that the supposedly split fibres are a transient response probably derived from satellite cells and are not derived from pre-existing fibres by true splitting. Similarly, increases in muscle fibre size are not achieved by recruitment of satellite structures as indicated by lack of myonuclear recruitment.Acknowledgment. This work was carried out with the aid of a grant from the Medical Research Council of Great Britain. The authors are grateful for the excellent technical assistance of Miss H. Caulton, M.J. Wild and M. Fenner.     

Hemopoietic stem growth on a capillary stage

A hollow fibre capillary stage was used for the maintenance and renewal of hemopoietic stem cells in extra corporeal conditions. The partial success of this technique is due to the preservation of cell-cell contacts and interactions within the tissue sections.     

Fasergabelung durch Auftreten lokalisierter Wachstumsbezirke

Summary The formation of forked fibres cannot be explained by the theories of sliding or of symplastic growth, while the theory of local apical growth of fibre ends accounts for all the actual facts observed in xylem and phloem fibres ofSparmannia africana. In this species cambium cells with a split end are found. These cells give rise to forked fibres, the forking point of which does not show any sliding growth, but remains on its original level. This evidence is undoubtedly a proof against the theory of sliding growth during fibre elongation inSparmannia.     

Preliminary observations on pituicytes in tissue culture

Riassunto Nella presente nota preliminare sono analizzati gli aspetti ultrastrutturali di lobi neurali postipofisari in coltura organotipica ove si è evidenziata la massiccia degenerazione delle fibre neurosecretorie e la presenza di cellule simil-pituicitarie attivamente fagocitanti le fibre stesse.     

Ca-electrogenesis in mealworm muscle: A voltage clamp study

Summary The membrane current in the muscle fibre of larval mealworm,Tenebrio molitor, was characterized by an early transient inward current followed by a late outward current. The results suggest that the inward current is associated with an inward movement of Ca ions down its electrochemical gradient, and Na ions have little to contribute to the inward current in this fibre.     

Synapses of adrenergic fibres

Riassunto Nel plesso mienterico dell'ileo di cavia sono presenti numerose fibre adrenergiche. Queste fibre, riconosciute al microscopio elettronico per il contenuto in piccole vesicole a granulo denso, formano tipiche giunzioni sinaptiche, principalmente axo-somatiche, con i neuroni intramurali.     

Effects of selective intracranial section and stimulation of vago-accessory roots. III. Course and distribution of the cardio-inhibitory fibers of the bulbar root of the accessory nerve

Riassunto Le fibre cardio-inibitrici della radice bulbare del nervo accessorio spinale presentano un piano di distribuzione periferica (rami cardiaci del vago-strutture intrinseche del cuore) non distinguibile da quello delle fibre della radice del vago, che rappresentano la componente numericamente predominante.