Ultrastructural localization of 5-methylcytosine on DNA and RNA

DNA methylation is the major epigenetic modification and it is involved in the negative regulation of gene expression. Its alteration can lead to neoplastic transformation. Several biomolecular approaches are nowadays used to study this modification on DNA, but also on RNA molecules, which are known to play a role in different biological processes. RNA methylation is one of the most common RNA modifications and 5-methylcytosine presence has recently been suggested in mRNA. However, an analysis of nucleic acid methylation at electron microscope is still lacking. Therefore, we visualized DNA methylation status and RNA methylation sites in the interphase nucleus of HeLa cells and rat hepatocytes by ultrastructural immunocytochemistry and cytochemical staining. This approach represents an efficient alternative to study nucleic acid methylation. In particular, this ultrastructural method makes the visualization of this epigenetic modification on a single RNA molecule possible, thus overcoming the technical limitations for a (pre-)mRNA methylation analysis.     

Cytochemical localization of surface carbohydrates on mycoplasma membranes

Summary Surface carbohydrate structures, containinga-D-glucosyl or sterically closely related residues, were visualized on mycoplasma membranes by a cytochemical staining procedure with concanavalin A and iron-dextran complexes.Supported by a grant from the Deutsche Forschungsgemeinschaft.     

Morphology of colloidal gold, ferritin and anti-ferritin antibody complexes.

The morphology of model complexes between colloidal gold, ferritin and anti-ferritin antibodies has been studied in order to evaluate the potential of colloidal gold as a cytochemical marker.     

An indirect demonstration of the substructure of the lamina basalis in the branchial heart of Sepia officinalis L. by means of cholinesterase reaction

Summary Using a cytochemical cholinesterase reaction, a filamentous substructure of the lamina basalis of the peripheral epithelium in the branchial heart of Sepia officinalis L. can be demonstrated. The reaction product can be identified between the probable collagenous microfilaments, so that a form of negative staining is given.This work was supported by the Deutsche Forschungsgemeingemeinschaft.     

Zur Frage der Markierung einzelner Nervenzellen durch Mikroelektroden

Summary A method of electrophoretical marking of individual neurons with methylene blue by means of a glass micropipette (used in electrophysiology) is described. In combination with a new histological crushing technique, cytochemical analysis of whole undamaged cells thus marked can be correlated with electrophysiological findings in the same neuron.     

Über die submikroskopische Organisation der Glanzstreifen (Eberthlinien) der Vorhof- und Kammermuskulatur des Herzens

Summary By means of polarization microscope, the submicroscopic structure of intercalated discs in auricle and ventricle muscles of rat heart were investigated using an imbibition method and precipitation anisotropic staining. The investigation proved that the protein and lipid parts in intercalated discs of auricle muscles are, on the contrary, arranged like intercalated discs of ventricle muscles.The ultrastructural variance revealed can be explained by mechanical effects exerted by the myofibrils on the plasma membranes which separate the adjacent heart muscle cells.     

Étude cytochimique des groupes sulfhydriles au cours des modifications de la détermination embryonnaire chez l'œuf de l'oursinParacentrotus lividus

Summary A cytochemical study of the distribution of sulfhydryl groups in animalized and vegetalized embryos of the sea-urchinParacentrotus lividus has been made by use of the Bennett's reagent. The distribution of the sulfhydryl groups appears homogeneous in these embryos. No gradient has been observed in the experimental conditions used.     

Simple apparatus for perfusion fixation for electron microscopy.

Control on duration of application and pressure of fixative is achieved with an apparatus of simple construction. This allows optimal fixation of laboratory animals for morphological and cytochemical studies.     

Effect of pancreatic secretions upon ileal disaccharidase activities of neonatal miniature pigs

Mechanisms by which pancreatic secretions influence disaccharidase activities in the distal small intestine have been investigated in 1-week-old miniature pigs. Using a combination of biochemical, cytochemical and morphological techniques it has been found that the decrease in lactase specific activity is due solely to a reduction in villus surface area. By contrast, the increased sucrase-isomaltase activities, which occur despite the reduction in villus surface area, are due entirely to increased enzyme expression during enterocyte differentiation.     

Effect of pancreatic secretions upon ileal disaccharidase activities of neonatal miniature pigs

Summary Mechanisms by which pancreatic secretions influence disaccharidase activities in the distal small intestine have been investigated in 1-week-old miniature pigs. Using a combination of biochemical, cytochemical and morphological techniques it has been found that the decrease in lactase specific activity is due solely to a reduction in villus surface area. By contrast, the increased sucrase-isomaltase activities, which occur despite the reduction in villus surface area, are due entirely to increased enzyme expression during enterocyte differentiation.     

Ultrastructural aspects of nucleolar fibrillar centres in meristematic cells ofAllium cepa

Summary This paper deals with the fine structure of the fibrillar centres of the nucleolus inAllium cepa cells in ultrathin, sections of in vivo fixed roots. The ultrastructural observations have allowed us to consider each nucleolar fibrillar centre as an active zone in the nucleolar chromatin loop, and to propose a possible model for the organization of the different components of the nucleolus within it.Acknowledgments. The author wishes to thank Dr.M. C. Risueño for her valuable comments and discussion. This work has been partially supported by the III Plan de Desarrollo of Spain and by a grant of the Foundation Rodriguez Pascual.     

Histochemical and cytochemical observations on the acetylcholinesterase (AChE) localization in the superior cervical ganglion (SCG) after preganglionic sympathectomy of the neonatal rat.

Results of histochemical and cytochemical reactions show that after the section of preganglionic nerve trunk performed in newborn animals, the appearance and the individual increase in AChE activity in non-innervated nerve cells follow the pattern of normally innervated ganglion cell.     

Histochemical and cytochemical observations on the acetylcholinesterase (AChE) localization in the superior cervical ganglion (SCG) after preganglionic sympathectomy of the neonatal rat

Summary Results of histochemical and cytochemical reactions show that after the section of preganglionic nerve trunk performed in newborn animals, the appearance and the individual increase in AChE activity in non-innervated nerve cells follow the pattern of normally innervated ganglion cell.     

Comparative ultrastructural and cytochemical analysis of the cephalopod systemic heart and its innervation

Summary The present knowledge of the morphology of cephalopod central hearts is presented. The cytological characteristics of the epicardial, myocardial and endothelial tissue layers are reviewed. Myocardial cells are characterized as obliquely striated myocytes with a high level of oxidative metabolism. The voluminous myocardium is intensively penetrated by nerve fibers controlling the myogenic heart rhythm by different chemical transmitter systems. Catecholaminergic fluorophores and acetylcholinesterase activity could be localized by means of histochemical and cytochemical investigations. A glio-interstitial cell system is shown to be present in connection with nerve fibers and also uncombined between heart muscle cells. Its content of large different-sized inclusions is described and their function discussed.     

Effects of parathyroid hormone and calcitonin on carbonic anhydrase location in osteoclasts of cultured embryonic chick bone

The ultrastructural location of carbonic anhydrase has been examined in osteoclasts of cultured embryonic chick metatarsi. In untreated cultures and in those to which parathyroid hormone (PTH) was added, the enzyme was found in close association with the plasma membrane of the ruffled border. After brief calcitonin treatment (10 min) the ruffled border disappeared and the association of carbonic anhydrase with the plasma membrane was diminished. The results indicate that the hormones employed act directly on embryonic bone to alter osteoclast structure and the intracellular location of carbonic anhydrase.     

Ultrastructural and seasonal aspects of the kidney lymphatic system of hibernating animals

The kidney lymphatic system of bat, dormouse and marmot consists of intraparenchymal (interlobar, arcuate, interlobular) and extraparenchymal (capsular) vessels sharing common ultrastructural aspects. We did not observe medullary lymphatics. The qualitative and quantitative seasonal changes in the ultrastructure of the lymphatic endothelium represent not only a species-linked feature but also (and mainly) an evident seasonal fluctuation in lymph formation. Furthermore, these ultrastructural changes emphasize the important role played by the different mechanisms involved in the translymphatic movement of proteins and interstitial fluid with particular regard to the 'vesicular route' and intraendothelial channels.     

Association of Golgi vesicles containing acid phosphatase with the chromatoid body of rat spermatids

The relationship between the Golgi apparatus and the small vesicles associated with the chromatoid body was investigated using a cytochemical technique. It was observed that in early spermatids, when the chromatoid body appears in close contact with the Golgi complex, and all through its migration to the caudal pole of the nucleus, some of the vesicles that accompany the organelle display acid phosphatase activity. It is concluded that these smooth vesicles originate in the Golgi apparatus.     

Organtypische und phasenspezifische Verteilung ungesättigter Lipoide im Schwanz der Larve vonXenopus laevis

Summary Barrollier's method for unsaturated fatty acids (u. f. a.) in paper chromatograms has been adapted for cytochemical detection of u. f. a. in the tails ofXenopus-larvae. A specific pattern in the different organs was found. It was further shown that the content in u. f. a. changes quickly, apparently indicating rapid changes in physiological conditions during growth and regeneration.