An electron microscopical study of developing sympathetic neurons in man

Summary An electron microscopic study has been made of the sympathetic ganglia of a 15 and a 17 week old male human fetus. The fetal sympathetic neurons were densely packed in a scanty connective tissue matrix which also contained blood vessels. The fetal sympathetic neurons had a large, electron-light nucleus with one or two nucleoli, and was of a somewhat mottled appearance due to irregularly dispersed aggregates of fine and coarse granules. The perikaryon usually formed a thin envelope around the nucleus and contained, except for large pigment granules, all intracytoplasmic structures which were also found in mature sympathetic neurons. Adjacent sympathetic cells were either in immediate contact, or slightly separated by a wedge of electron-light satellite expansions, or lined by primitive axons. The satellite cells were in the early state of development. Electron-dense axons either stood side by side with, or were slightly engulfed by light Schwann cell expansions and formed distinct bundles surrounded by a common basement membrane. There was practically no trace of myelin formation or Schwann cell wrapping characteristic for unmyelinated fibers as seen in the adult.This investigation was supported (in whole) by United States Public Health Service Grant NB-01879-05, Institute for Nervous Diseases and Blindness.Grateful acknowledgment is made to Professor Dr. John Lind who madea vailable the fetal material through the Laboratory of Prenatal Growth and Development, Karolinska Institutet, Stockholm, Sweden.The authors wish to thank Docent Dr. Gunnar Bloom who provided the facilities necessary to prepare the fetal material for electron microscopical examination, in his laboratory for Cell Research, Karolinska Institutet, Stockholm, Sweden.     

Pigment,abnormal mitochondria and laminar bodies in human sympathetic neurons

Summary A study was made of the fine structure of neurons in lumbar sympathetic ganglia which were surgically removed from a 52 year old male patient. Some samples were fixed by direct immersion into osmium tetroxide, others were first prefixed with an aldehyde solution. Large vesiculated pigment granules were described, compared with similar particles, previously seen in human and animal autonomic neurons, and their glycogen and lipid-soluble components were tentatively identified. These granules increase numerically during aging, are probably derivatives of lysosomes, and may incorporate both lipofuscin and melanin in the same particle. Mitochondrial changes (enlargement, disappearance of cristae and deposit of opaque central material) in sympathetic perikarya occurred under all conditions of preservation, and were interpreted as hypoxia-induced structures which developed during life. Abnormal aggregates of mitochondria were seen in nerve processes. Laminar bodies, chiefly associated with mitochondria were present, especially, in aldehyde prefixed material. It remained undecided whether these structures occurred during life or were artifacts. Compared with direct osmium tetroxide fixation, prefixation with aldehyde, followed by osmium tetroxide proved to be a superior, but not entirely adequate method of preserving deep layers of neuronal tissue. This investigation was supported (in whole) by United States Public Health Service Grant NB 1879-09, Institute for Nervous Diseases and Blindness.The author is greatly indebted to Dr. Jere W. Lord, Jr., Department of Surgery, New York University Medical Center, for the surgically removed tissues used in this study; he is grateful to Dr. Sanford L. Palay, Department of Anatomy, Harvard Medical School, for suggesting the use of the then unpublished method of prefixation with the aldehyde solution. It is a pleasure to acknowledge the expert skill with which Miss Carmen DeLemos and Mr. Arnlod Cianella assisted in completing this work.     

North Carolina State University

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North Carolina State University     

Lectin binding patterns to terminal sugars of rat lung alveolar epithelial cells.

We used post-embedding cytochemical techniques to investigate the lectin binding profiles of rat lung alveolar epithelial cells. Sections from rat lung embedded in the hydrophilic resin Lowicryl K4M were incubated either directly with a lectin-gold complex or with an unlabeled lectin followed by a specific glycoprotein-gold complex. The binding patterns of the five lectins used could be divided into three categories according to their reactivity with alveolar epithelial cells: (a) the Limax flavus lectin and Ricinus communis I lectin bound to both type I and type II cell plasma membranes; (b) the Helix pomatia lectin and Sambucus nigra L. lectin bound to type II but not type I cells; and (c) the Erythrina cristagalli lectin reacted with type I cells but was unreactive with type II cells. The specificity of staining was assessed by control experiments, including pre-absorption of the lectins with various oligosaccharides and enzymatic pre-treatment of sections with highly purified glycosidases to remove specific sugar residues. The results demonstrate that these lectins can be used to distinguish between type I and type II cells and would therefore be useful probes for investigating cell dynamics during lung development and remodeling.     

The origin of polynucleotide-directed protein synthesis

Summary If protein synthesis evolved in an RNA world it was probably preceded by simpler processes by means of which interaction with amino acids conferred selective advantage on replicating RNA molecules. It is suggested that, at first, the simple attachment of amino acids to the 2′(3′)-termini of RNA templates favored initiation of replication at the end of the template rather than at internal positions. The second stage in the evolution of protein synthesis would probably have been the association of pairs of charged RNA adaptors in such a way as to favor noncoded formation of peptides. Only after this process had become efficient could coded synthesis have begun.     

A recombination event that redefines the Huntington disease region

We report both a recombination event that places the Huntington disease gene proximal to the marker D4S98 and an extended linkage-disequilibrium study that uses this marker and confirms the existence of disequilibrium between it and the HD locus. We also report the cloning of other sequences in the region around D4S98, including a new polymorphic marker R10 and conserved sequences that identify a gene in the region of interest.     

Template-directed oligomerization of 5′-deoxy-5′-nucleosideacetic acid derivatives

5-Deoxy-5-nucleosideacetic acids II–V are isostructural analogues of nucleotides with a carboxylate group in the place of the 5-phosphate group. We have studied their oligomerization in aqueous solution using a water-soluble carbodiimide as the condensing agent in the presence or absence of an appropriate polynucleotide template. Condensation of adenylic acid analogues IIa, IIIa, and Va in the presence of polyuridylic acid were found to be the most efficient reactions. Cyclization of the activated monomers to lactones and the insolubility of the oligomers in aqueous solution were found to be obstacles to the efficient formation of long oligomers.