Cytoskeletal filaments of heart conducting system localized by antibody against a 55,000 dalton protein.

Cow heart conducting cells characteristically contain cytoplasmic intermediate-sized filaments. We report here the preparation of a specific antibody to a 55,000 dalton protein of isolated cow Purkinje fibres. Confirmation has been obtained that these filaments consist of the 55,000 dalton protein, using the indirect immunofluorescence technique. Cross-reaction is seen with vascular endothelium and smooth muscle cells of various origin, suggesting close identity of different types of intermediate-sized filaments.     

Association of intermediate filaments with other cell organelles in carcinoid tumor of the colon.

Carcinoid tumor of the colon was studied in electron microscope. In cytoplasm, prominent intermediate-sized filaments were seen frequently attaching to nucleus and mitochondria. Direct contacts of intermediate filaments with secretory granules were not observed.     

Association of intermediate filaments with other cell organelles in carcinoid tumor of the colon

Summary Carcinoid tumor of the colon was studied in electron microscope. In cytoplasm, prominent intermediate-sized filaments were seen frequently attaching to nucleus and mitochondria. Direct contacts of intermediate filaments with secretory granules were not observed.Acknowledgments. The skilful technical assistance of Ms Tuire Koro is gratefully acknowledged. — This study was supported by grants from the Finnish Medical Research Council, Finnish Culture Foundation and J.K. Paasikivi Foundation for Cancer Research.     

Cytoskeletal filaments of heart conducting system localized by antibody against a 55,000 dalton protein

Summary Cow heart conducting cells characteristically contain cytoplasmic intermediate-sized filaments. We report here the preparation of a specific antibody to a 55,000 dalton protein of isolated cow Purkinje fibres. Confirmation has been obtained that these filaments consist of the 55,000 dalton protein, using the indirect immunofluorescence technique. Crossreaction is seen with vascular endothelium and smooth muscle cells of various origin, suggesting close identity of different types of intermediate-sized filaments.     

In vitro stability and protein composition of thick filaments from insect flight muscles

Thick and thin filaments of synchronous and asynchronous insect flight muscles were separated by density gradient centrifugation. A good release of myofilaments from myofibrils was obtained by sonication of myofibrils in relaxing solution with pH 6.1 (locust), pH 6.4 (honeybee) and pH 6.6 (fleshfly), respectively. Thick filaments but not thin filaments were dissolved, if sucrose gradient centrifugation was used to separate the filaments. Thus, sucrose gradients are the medium of choice if actin filaments are to be purified. Glycerol-containing gradients selectively dissolved myosin filaments from fleshfly muscles. The stability of the myosin filaments of all muscles was sufficient in gradients with 10–30% formamide.     

The fine structure of cloned cells from normal adult rat brain

Summary A cell clone was isolated from a normal adult rat brain culture and maintained in vitro for many passages. It possessed glial characteristics; in particular ultrastructural examination revealed astrocytic features including the presence of filaments 9–11 nm in diameter.Acknowledgments. The work was partly supported by a grant from the Cancer Research Campaign to JPR. The secretarial help of Miss Hilary A. Waddington is gratefully acknowledged.     

Transplantation of human cortex with Alzheimer's disease into rat occipital cortex; a model for the study of Alzheimer disease

Senile dementia of the Alzheimer type (SDAT) is a major problem in the human senescent population. As this pathology cannot be reproduced in animals, research into its development is greatly impeded. The technique of implantation of the nervous tissue has been utilized in order to establish an animal model and to test the possible existence of a transmissible agent. When human temporal cortex with Alzheimer's disease is implanted in the occipital cortex of 7-week-old rats, human cerebral tissue containing abundant tangles induces in the receiver cortex a reactive fibrous gliosis. In the processes of the astrocytes, twisted filaments are evident among bundles of normal filaments. These alterations could be induced by the metabolising of abnormal filament subunits or by some infectious agent introduced by the implant.     

Skeletin immunoreactivity in peripheral nerves

Summary By use of monospecific antibodies against the cow heart intermediate filament protein, skeletin, an antigenic relationship between skeletin and neurofilament protein of peripheral nerves is demonstrated. Crossreactivity is also demonstrated in the filament-containing Schwann cells. The results are consistent with the existence of several subclasses of related intermediate-sized filament proteins.Acknowledgments. The skilful technical assistence of Mrs Elisabeth Rubing, Miss Inga Johansson, and Miss Marléne Lundström is gratefully acknowledged. This work was supported by grants from Lions Research Fund, the Swedish Medical Research Council (12X-3934) and the Faculty of Medicine, University of Umeå.     

Cardiomyocyte growth and sarcomerogenesis at the intercalated disc

Cardiomyocytes grow during heart maturation or disease-related cardiac remodeling. We present evidence that the intercalated disc (ID) is integral to both longitudinal and lateral growth: increases in width are accommodated by lateral extension of the plicate tread regions and increases in length by sarcomere insertion within the ID. At the margin between myofibril and the folded membrane of the ID lies a transitional junction through which the thin filaments from the last sarcomere run to the ID membrane and it has been suggested that this junction acts as a proto Z-disc for sarcomere addition. In support of this hypothesis, we have investigated the ultrastructure of the ID in mouse hearts from control and dilated cardiomyopathy (DCM) models, the MLP-null and a cardiac-specific β-catenin mutant, cΔex3, as well as in human left ventricle from normal and DCM samples. We find that the ID amplitude can vary tenfold from 0.2 μm up to a maximum of ~2 μm allowing gradual expansion during heart growth. At the greatest amplitude, equivalent to a sarcomere length, A-bands and thick filaments are found within the ID membrane loops together with a Z-disc, which develops at the transitional junction position. Here, also, the tops of the membrane folds, which are rich in αII spectrin, become enlarged and associated with junctional sarcoplasmic reticulum. Systematically larger ID amplitudes are found in DCM samples. Other morphological differences between mouse DCM and normal hearts suggest that sarcomere inclusion is compromised in the diseased hearts.     

Regulation of cross-bridge detachment by Ca ions at high ionic strength in molluscan catch muscle

Changes in the profile of equatorial intensities of X-ray diffraction from an intact, anterior byssal retractor muscle (ABRM) of Mytilus were examined at rest, during contracture brought about by acetylcholine (ACh) and a subsequent rigor-like contraction caused by raising the tonicity of the external solution, and after returning the tonicity to normal. The results suggest that the cross-bridges formed between thick and thin actin filaments during the ACh-contracture were maintained in the hypertonic solution and broken on decreasing the tonicity before the recovery of spacing of the actin filament lattice. A similar rigor-like contraction was induced in glycerinated ABRM by increasing salt concentration during active contraction. The rigor-like force declined rapidly when Ca++ concentration decreased. The results suggest that the detachment of the cross-bridge from the actin filament is regulated by Ca++ at high ionic strength in the ABRM.     

Das beim Gefrieren von Gelen entstehende Eis

Summary Highly swollen gels which contain, in addition to a large amount of solvent, a spatial network formed by chains of a high polymer, show an abnormal lowering of the freezing point. This is caused by the fact that the network prevents the formation of macroscopically undisturbed crystals.If, in the course of freezing at this lower temperature, a conglomerate of microcrystals were created corresponding in size to the width of the network, one should be able to observe a broadening of the X-ray interference lines. Experiments have shown that no measurable broadening takes place.This is explained by the assumption that a crystal which is prevented from growing in the normal way by the surrounding filaments of the gel, when cooled to a suitably low temperature grows crystallites with a small cross-section corresponding to the mesh size. The crystallites thus formed are orientated in a crystallographically exact manner toward their supporting crystal and parallel to each other. Therefore, when reaching the necessary height, they unite to larger, ordered crystalline regions which incorporate the polymeric filaments. This explains the observed sharpness of the X-ray interferences as well as the observation that, upon heating of a frozen gel, the melting does not occur at the same low temperature as the freezing, but closer to the melting point of macroscopic ice.     

Some observations on bipolar filaments formed by non-muscle myosins.

Adrenal medullary and retinal myosins formed bipolar filaments in vitro. These filaments showed features suggesting flexibility in the rod region of the myosin molecules composing such filaments; in certain cases the myosin heads spread away from the filament backbone, in others the backbone itself was twisted. In addition the bare central backbone showed transverse striations.     

Transplantation of human cortex with Alzheimer's disease into rat occipital cortex; a model for the study of Alzheimer disease

Summary Senile dementia of the Alzheimer type (SDAT) is a major problem in the human senescent population. As this pathology cannot be reproduced in animals, research into its development is greatly impeded. The technique of implantation of the nervous tissue has been utilized in order to establish an animal model and to test the possible existence of a transmissible agent. When human temporal cortex with Alzheimer's disease is implanted in the occipital cortex of 7-week-old rats, human cerebral tissue containing abundant tangles induces in the receiver cortex a reactive fibrous gliosis. In the processes of the astrocytes, twisted filaments are evident among bundles of normal filaments. These alterations could be induced by the metabolising of abnormal filament subunits or by some infectious agent introduced by the implant.This study is supported by grant No. 2.4517.82 of Fonds de la Recherche Fondamentale Collective of Belgium.     

Regulation of cross-bridge detachment by Ca ions at high ionic strength in molluscan catch muscle

Summary Changes in the profile of equatorial intensities of X-ray diffraction from an intact, anterior byssal retractor muscle (ABRM) ofMytilus were examined at rest, during contracture brought about by acetylcholine (ACh) and a subsequent rigor-like contraction caused by raising the tonicity of the external solution, and after returning the tonicity to normal. The results suggest that the cross-bridges formed between thick and thin actin filaments during the ACh-contracture were maintained in the hypertonic solution and broken on decreasing the tonicity before the recovery of spacing of the actin filament lattice. A similar rigor-like contraction was induced in glycerinated ABRM by increasing salt concentration during active contraction. The rigor-like force declined rapidly when Ca⁺⁺ concentration decreased. The results suggest that the detachment of the cross-bridge from the actin filament is regulated by Ca⁺⁺ at high ionic strength in the ABRM.     

La structure de certaines terminaisons nerveuses montre des variations cycliques

Summary All sensory endings of the trigeminal nerve in the dura mater of the rat are formed by a small swelling, from which continues themetaterminal apparatus, fine filaments at the limit of visibility. Periodically the fine granules at the extremity of the filaments swell, whereas the fibrils themselves disappear, leaving a small, round, argentophil mass. Later the filaments reappear, then redeposit their debris, which persists for a time.Thus the metaterminal apparatus manifests cyclic variations, which recall the transitory existence of collaterals observed duringin vivo orin vitro development of nerve fibres.     

Isolation of filaments of the chick lens

Summary A preparation of intermediate filaments isolated from the chicken lens is enriched with a 50,000 dalton polypeptide.This study was supported by research grant EY 01417 of the National Institutes of Health, Bethesda, Maryland, USA.     

Isolation of filaments of the chick lens

A preparation of intermediate filaments isolated from the chicken lens is enriched with a 50,000 dalton polypeptide.     

Some observations on bipolar filaments formed by non-muscle myosins

Summary Adrenal medullary and retinal myosins formed bipolar filaments in vitro. These filaments showed features suggesting flexibility in the rod region of the myosin molecules composing such filaments; in certain cases the myosin heads spread away from the filament backbone, in others the backbone itself was twisted. In addition the bare central backbone showed transverse striations.We thank G. Devilliers for assistance with electron microscopy, D. Thiersé for technical assistance during purification of adrenal medulla myosin and Professor P. Mandel for his interest and support J.E.H. gratefully acknowledges receipt of a Royal Society European Exchange Fellowship and a grant from INSERM. N.V. is chargée de recherches au CNRS, D.A. is chargé de recherches à l'INSERM.     

Ultrastructural aspects of the cell fusion induced by Visna virus on sheep choroid plexus cell in culture]

Sheep choroid plexus cells infected with low multiplicities of infection of Visna Virus were stellate and had long and thin processes containing filaments and forming cytoplasmic bridges between adjacent cells. Enlargement of the bridges resulted in the formation of multinucleated cells. Some glycoproteins were clustered on filaments outside the cell. The cytoplasmic changes showed : an intensive protein synthesis; numerous mitochondria closely associated with filaments and some lysosomes and numerous vesicules near the plasma membrane.     

Nuclear envelope and nuclear matrix: interactions and dynamics

The peripheral nuclear lamina is located near the nuclear inner membrane and consists of lamin filaments and integral membrane proteins, including the lamin B receptor and various isoforms of lamina-associated polypeptides (LAP) 1 and 2. Several nuclear membrane proteins also interact with chromatin proteins BAF and Hp1. Lamins in the nuclear interior associate with at least one soluble (non-membrane-bound) LAP2 isoform named LAP2alpha. The internal lamins, together with Tpr-based filaments that connect to nuclear pore complexes, are proposed to be major structural elements of the internal nuclear matrix. We describe the structural links between the peripheral lamina and the internal nuclear matrix that are thought to be mediated by LAP2 family members, filament protein Tpr and nucleoporin Nup153. These findings are discussed in relation to human diseases that arise from mutations in nuclear lamina proteins.