Preparation and discharge of secretion in the subcommissural organ of the rat

Summary The secretion of the subcommissural organ (SCO) of the rat was studied by means of immunocytochemistry at the electron-microscopic level with the use of (1) the polar embedding medium Lowicryl K4M at -30° C, (2) the protein A-gold technique, and (3) a rabbit antiserum against bovine Reissner's fiber (see Sterba et al. 1981).Two different substructures of the ependymal and the hypendymal SCO-cells display a positive immunocytochemical reaction: (1) sacs containing flocculent secretion, which originate from the granular endoplasmic reticulum, and (2) vacuoles filled with fine granular secretion, which are pinched off from the Golgi apparatus. The secretory material of the sacs and the vacuoles is discharged both (i) apically into the cerebrospinal fluid and (ii) basally into intercellular spaces of the SCO-hypendyma. The apically released secretion is condensed to a lamina-like formation, which more caudally assumes the form of Reissner's fiber. The route of the basally released secretion remains, however, vague. The periodically striated bodies, which were thought to be morphological mediators of the discharge of the secretion into the capillaries, are never labeled by gold particles.Supported by grants from the Ministry for Science and Technology of the German Democratic RepublicThe expert technical assistance of Mrs. B. Wolff, Mrs. S. Mehnert, Mrs. E. Siebert, Mrs. Ch. Schneider, and Mrs. I. Seifert is gratefully acknowledged     

Vascular permeability to proteins and peptides in the mouse pineal gland

Summary The permeability of fenestrated capillaries in the mouse pineal gland to proteins and peptides was demonstrated by means of ultrastructural tracers. Horseradish peroxidase (HRP) and microperoxidase (MP) were injected intravenously and allowed to circulate for approximately 30 s, 1 min, 5 min, 1 or 2h. The tissue was then fixed by vascular perfusion or by immersion with aldehydes. In all experiments a pronounced extravasation of HRP and MP occurred. Transendothelial vesicular transport seemed to have occurred across the fenestrated capillaries. The most pronounced tracer labeling of vesicles was found after 1 min of MP- or HRP-circulation. The vesicles were uncoated and more than 70 % of the HRP-and MP-containing vesicles exhibited diameters between 50 and 110 nm. Furthermore, three other transcapillary pathways taken by the tracers are suggested: 1) via intercellular junctions, 2) through fenestrae and 3) via channels formed by fusion of vesicles with the luminal and abluminal cell membranes. Based on these results, it is assumed that the capillaries in the mouse pineal gland are also permeable to peptides synthesized and secreted by the pineal gland.Part of this study was presented at the EMCELL-76 meeting, Copenhagen, 1976     

Freeze-preservation of rice cells: A physiological study of freeze-thawed cells

Rice ( Oryza sativa L.) cells returning to in vitro culture after preservation at superlow temperature in liquid nitrogen are characterized by a number of physiological alterations. These include: reduction in respiration and glucose uptake, loss of intracellular potassium, decrease in the cellular level of key metabolites (ATP, glucose-6-phosphate and pyruvate) and fragility of protoplasts following the action of cell wall-degrading enzymes.
Nevertheless, cell growth resumes after a short lag phase (2–4 days) with an actual 70–100% cell survival, thus indicating that the observed damage is not lethal and can be repaired in a short time.     

The volar skin of primates: its frictional characteristics and their functional significance.

Friction of volar skin on wood is not proportional to load in human beings and prosimians, but to load raised to a fractional power. This meets theoretical expectations for the frictional characteristics of convex elastic surfaces. Although this enables small clawless primates to cling to steeper slopes and larger vertical supports than would otherwise be possible, the magnitude of the effect is not great enough to overcome the disadvantages of clawlessness in climbing vertical or steeply-sloping tree trunks and branches. In human subjects, friction appears to be more nearly proportional to load than in small prosimians used as experimental subjects. It is suggested that this is due to the fact that the small animals have discrete, elevated volar pads. Pad coalescence in large primates may be an adaptation for increasing the power to which load must be raised to become proportional to friction; increasing this exponent yields more friction per unit of adduction force on supports that are small relative to the animals' dimensions and weights.     

A direct observation technique for studies on rhizoplane and rhizosphere colonization

Summary A slide incubation chamber was described which allowed small plants to be grown from seed and the root systems to be observed microscopically. A fluorescence stain, the ammonium salt of 8-anilino-1-naphthalene sulfonic acid, was applied to the soil in which the roots were growing and the stained microorganisms on the roots and in the rhizosphere were counted. A statistical pattern analysis technique, the two-within-four randomization test, was used to analyze the data obtained from quadrats on the roots. Distinct colonization patterns and colony growth, especially of bacteria, were easily distinguished with the technique.     

Influence of sialic acid on cell surface properties in I-cell disease fibroblasts

Summary Fibroblasts derived from patients with I-cell disease have been shown to accumulate many natural substrates including a three to fourfold increase in sialic acid content compared to that found in normal fibroblasts. This diverse accumulation of storage material is due to a massive deficiency of multiple lysosomal hydrolases as they are preferentially excreted into the culture fluid. There is evidence that the I-cell plasma membrane itself is abnormal with respect to certain transferase activities and in its sensitivity to freezing and Triton X-100. In this study, we have shown that a neuraminidase-sensitive substrate, and perhaps others in I-cell fibroblasts, contribute to an increased electronegativity of the I-cell fibroblast surface and to the cells' sensitivity to freezing. We also found that neuraminidase treatment of I-cell fibroblasts before preservative freezing in liquid nitrogen enables the cells to adapt more easily to subculture upon thawing. This project was supported in part by National Institutes of Health (NIH) BRSG Grant RR-05493, NIH Grant 1-R01-HD-11453-01-A1, National Science Foundation Grant PCM 77-05733, and Maternal and Child Health Service Project 417. Georgirene D. Vladutiu is the recipient of Research Career Development Award 1K04 HD 00312-01A1 from the National Institutes of Health.     

Immunocytochemical identification of proctolinlike immunoreactivity in the terminal ganglion and hindgut of the cockroach Periplaneta americana (L.)

Summary In the American cockroach, the distribution and connections of neuronal elements of the terminal ganglion-proctodeal nerve-hindgut system were investigated by means of immunohistochemical methods and axonal CoCl₂ iontophoresis. Proctolinlike immunoreactivity was localized within neurons of the terminal ganglion projecting into the proctodeal nerve on the one hand, and in nerve cells without a direct connection to this system on the other. Immunohistochemically, in whole mount preparations fibres of the proctodeal nerve and terminal structures in the hindgut musculature exhibit strong proctolinlike immunoreactivity. At the light- and electron-microscopic levels the pathways of about 30 somata of the proctodeal neural system were characterized by cobalt chloride iontophoresis. The relationships of cobalt filled and immunoreactive neuronal structures are discussed.For the preparation of tritiated proctolin we thank Dr. S. Reißmann, WB Biochemie, Sektion Biologie, FSU JenaThe authors wish to thank G. Schörlitz, Film- und Bildstelle, FSU Jena, for photographs of whole mount preparations and Ms. A. Zinßer and Mrs. B. Cosack for excellent technical assistance.     

Sensory cells in the head skin of pond snails

Summary Several types of receptor endings were identified with scanning electron microscopy and silver-impregnation techniques in the skin of the tentacles, lips, dorsal surface of the head and mouth region of the pond snails Lymnaea stagnalis and Vivipara viviparus. Sensory endings at the tips of dendrites of primary receptor neurones, scattered below the epithelium, differ in structure, i.e., the endings exposed to the surface of the skin possess different proportions of cilia and microvilli, which vary in number, length, and packing. Type-I endings have microvilli and a few (1–5) cilia, 5–12 m in length. Type-2 endings have abundant (20–40), interwoven long (9–12 m) cilia and random microvilli. Type-3 endings show typical packing of 10–25 cilia in the form of bundles or brushes. They may be composed either of long (9–18 m) or short (2–7 m) cilia, or of both long and short ones. Microvilli here are absent. Type-4 endings have only microvilli. Two other types of skin receptors do not extend their sensory endings to the surface and can be indentified only in silver-stained preparations. Type-5 endings are branching dendrites of skin receptors cells that terminate among epithelial cells. In type-6, the sensory endings also terminate among epithelial cells but their cell bodies are located outside of the skin. In both species all skin regions examined possess the receptors of all six types differing only in their relative proportion. Possible functional roles of different receptors are discussed.     

The effect of stretching on formation of myofibroblasts in mouse skin

Summary Wound contraction results from the contractile activity of modified fibroblasts, termed myofibroblasts, which are present in the granulation tissue of the healing wound. This study examines the relative role of mechanical tension (stretching) and wound healing as events capable of stimulating the formation of myofibroblasts in mouse skin. The skin of hairless mice was subjected to mechanical stretching and to a small incisional wound either separately or in combination. Animals were killed at intervals between 1 and 6 days and the dermis examined with the electron microscope. Stretching alone produced little evidence of inflammation at any time interval but cells with the ultrastructural characteristics of myofibroblasts were present at 4 days and abundant at 6 days. Skin that had been both stretched and wounded showed a marked inflammatory response and also contained myofibroblasts, but they were less frequent than in the skin subjected to stretching alone. Very few myofibroblasts were evident in skin that had only been wounded. It is suggested that the effect of mechanical tension alone may initiate formation of myofibroblasts in a tissue.     

Fine structure of Merkel cells in lampreys

Summary The structure of Merkel cells occurring in the epidermis of adult and larval stages of Lampetra spp. is described; it is comparable to that reported from the gnathostome classes. The cells bear microvilli, grouped on the distal and proximal aspects, and are associated with sparsely branching and varicose nerve fibres. One branch of the neurite bears a spur-like process which indents the proximal side of the Merkel cell. Most of the specific Merkel granules are situated in the vicinity of this neurite projection; the cell membrane adjacent to the tip of the spur process bears structures resembling presynaptic densities. Occasionally, desmosome-like junctions are found between the neurite and the Merkel cell.The authors thank the Fresh Water Biological Association and the Department of Biological Sciences, University of Bath, for supplying the material, Dr. H. Fox for giving some prepared blocks of Lampetra planeri adults, Mr. B.L. Pirie for technical assistance, and the Science Research Council for support through grant GR/A/3740.6