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Notes: Summary In rats the 3rd to 6th bronchi, measuring 500–700 μ in diameter during inspiration, were investigated by light and electron microscopy. The histological appearance of these bronchi is comparable to that of medium sized bronchioles of larger animals. The branched and lanceolate terminals are associated with the connective tissue of the lamina propria and the smooth muscle cell layer. In this way the terminals are bound to the myoelastic system of the bronchial wall. The myelinated afferent fiber is branched and the diameter measures about 4–6 microns. Besides afferent nerve terminals these are numerous efferent endings on the smooth muscle basement laminae. It is supposed that the described receptor represents the pulmonary stretch receptor of the Hering Breuer reflex.

Notes: Summary Afferent impulses were recorded from single fibers serving cold and warm receptors in the skin of the cat's nose. The receptors were carefully tested for specificity and the receptive fields localized under the microscope with a microthermode. Each single fiber served one spot-like receptive field. The field was marked without damaging the nerve ending by inserting two thin stainless steel wires into the skin on both sides of the receptor. Investigation of semithin and ultrathin serial sections by light and electron microscopy revealed beneath each cold spot a dermal papilla which contained a single small myelinated fiber dividing into a number of unmyelinated terminals. Near the epidermis the receptor branches leave their Schwann cell envelope, penetrate the basal lamina of the epithelium, and their tips are invaginated into the cytoplasm of the basal epithelial cells. The basal lamina of the epithelium fuses with that of the receptor axon. The receptor axons contain numerous mitochondria, glycogen particles and a filamentous receptor matrix with vesicles of various sizes. The described structures were absent beneath the warm spots. In addition to the cold receptors, Merkel cell neurite complexes and lamellated encapsulated endings were found that are known to be mechanoreceptors.

Notes: Summary New results as revealed by scanning and transmission electron microscopy have given us further knowledge about the structure of the olfactory region of vertebrates. With comparative studies we are now able to discuss the functional relationship of this region. In all vertebrates the olfactory cell is a primary sensory cell. The apical segment of the olfactory cell with its olfactory vesicle is involved in the formation of the olfactory border. As a rule the receptor possesses cilia or cilia-like processes. These are absent in the olfactory receptor of the shark, the microvillus receptor of the fish and the olfactory cell of Jabonsons organ of amphibians, reptiles and mammals. The odorous substances in the fish are brought to the receptor membrane by the water flow. In air breathing vertebrates a terminal film is present. This film is a product of secretion from the Bowmans glands. Gasous odorous substances must first be dissolved in the terminal film and penetrate it before reaching the receptor membrane. The cilia-like olfactory process of the fish in the proximal segment is not essentially different from the kinocilia of the supporting cell, except that they are shorter. In contrast the olfactory cell of air-breathing vertebrates form cilia-like processes with a short cilia-like proximal segment and a long and very thin distal end piece. In the amphibians and sauropsidians the end pieces can have a lenght of up to 150 μ and up to 80 μ in mammals. The olfactory vesicles with its processes undergo continuous regeneration. The olfactory epithelium of man show the same structural formation as observed in other mammals. Regressive changes in the adult can lead to a reduction in the number of sensory cells and also to a flattening of the epithelium. Morphological criteria for regenerative processes in the sensory cell structures are present. A specialized olfactory cell type has been found in some teleosts. This cell is characterized by a small pit below the olfactory border in which the cilia of the olfactory cell are redrawn. There is some evidence that this olfactory cell type may be compared with the olfactory cells in the parafollicular tubes of lamprey. The so called rod-shaped receptor in the olfactory mucosa of fishes has no axon and is therefore no olfactory cell. The same kind of cell is also present in the olfactory mucosa of airbreathing animals. We classify this cell as brush cell. Comparative electron microscopic studies reveal identical ultrastructural organization of the olfactory bulb in all classes of vertebrates, including cyclostomes and man. The size and structure of synapses in the olfactory bulb are specific for each connection type. The dark endings of the olfactory receptor cells have small axo-dendritic contacts to the bright mitral or tufted cell processes within the glomeruli. Granule cells, periglomerular cells and mitral cells interact by dendro-dendritic, dendro-axonic and somato-dendritic synaptic complexes which often have “reciprocal” arrangements. Presynaptic endings on the granule cell dendrites and somata contain a large number of small synaptic vesicles and have membrane complexes more than 0.5 μm in diameter. In the periventricular or central zone of the olfactory bulb excitatory synapses with interdigitation between the pre- and postsynaptic processes are present. We are able to give schematic representations of postulated nerve circuits with the aid of the different morphological appearances of the different synapses. The cellular composition of the taste buds of different mammals can be described from electron microscopical studies. As a rule 5 cell types which regenerate through mitosis from the basal or marginal cells can be differentiated. Only the active sensory cell forms synaptic membrane complexes. It sends rod-shaped processes into the taste pores. Growing and dying sensory cells do not possess these processes. The supporting cells surround the single sensory cell. The apical pole of the supporting cell enters the taste pore by a bundle of microvilli. Secretory granules accumulate in the apical part of the supporting cell and empty their contents into the taste pore. The terminal processes of the myelinated afferent nerve fibres form a plexus in the lamina propria and penetrate the taste bud with numerous itraepithelial branchings.

Notes: Abstract Measurements of the γ-ray anisotropy of recoil-implanted52Mn ions in pure Au down to 3 mK indicate marked deviations from free-ion behavior in low applied fields. The effective hyperfine field that explains the anisotropy is found to decrease below 10 mK. Although this behavior could be a signature of a “bound” Kondon state with a lower effective hyperfine coupling constant, it is better explained as arising from a combination of Kondo and relaxation effects. The data indicate that the Mn local moment relaxation timeT 1 is comparable to or larger than the Larmor precession time of the Mn nuclei at 3 mK. Other possible reasons for an attenuated γ-ray anisotropy, such as nuclear quadrupole and second-order crystal field effects, are also considered.

Notes: Abstract Nuclear adiabatic demagnetization experiments have been performed in the Van Vleck paramagnet PrCu6 in order to determine the very-low-temperature nuclear magnetic properties of this material and to test its efficiency as a very low-temperature refrigerator. It is found that a temperature of 2.7 mK can be reached from an initial temperature of 40 mK and an initial field of 20 kOe. Susceptibility and specific heat measurements above 2.7 mK indicate the presence of both nuclear quadrupole and exchange interactions. The transition to an antiferromagnetically ordered state among the Pr nuclei is expected to occur below 2.7mK.

Notes: Summary Scintigraphic experiments and radioactivity measurements of tissues have shown that the radioactivity of 51Cr-labelled and neuraminidase-treated rabbit erythrocytes is rapidly accumulated in liver and spleen. Sequestration of these erythrocytes by liver and spleen was demonstrated by light and electron microscopy of these tissues after perfusion of the rabbits with solutions for tissue fixation. In liver the phagocytic activity of Kupffer cells was increased after injection of desialylated erythrocytes, while in spleen a significantly enhanced number of erythrocytes was found attached to the sinusoidal walls and in the reticulum of the red pulp. It was shown by scanning electron microscopy that neuraminidasetreatment did not influence the shape of erythrocytes. Desialylated and 51Cr-labelled erythrocytes from the cow are rapidly cleared from the blood-stream with a half-life time of about 3 h. It was shown in an in-vitro test that they adsorb to surviving slices from liver and spleen derived from the same animal. The amount of radioactivity adsorbed is appreciably enhanced in the presence of homologous serum when compared with buffer only. Human neuraminidase-treated erythrocytes are agglutinated in the direct and especially in the indirect Coombs-tests. The involvement of T-antigen in this phenomenon was largely excluded. The in vitro experiments and antibody consumption tests suggest that immunoglobulins (IgG) and complement from serum may be involved in recognition and sequestration of desialylated erythrocytes by macrophages in vivo.