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At least 37 records · Page 2Linked to original sources
PubMed1979

Attractants and repellents influence methylation and demethylation of methyl-accepting chemotaxis proteins in an extract of Escherichia coli.

During bacterial chemotaxis, attractants and repellents alter the methylation levels of the methyl-accepting chemotaxis proteins (MCPs). These methylation levels represent a balance between two enzymatic processes: methylation and demethylation. In vivo experiments previously have shown that chemoeffectors influence the demethylation process; effects on the methylation system have not been reported. Here we show that in a cell-free extract of Escherichia coli both methylation and demethylation of the MCPs are affected by attractants and repellents. Attractants enhance methylation and inhibit demethylation. Repellents inhibit methylation and stimulate demethylation. The cell-free system provides an opportunity for further study of the mechanisms by which attractants and repellents influence the levels of methylation of the MCPs.

Bacterial Proteins↗
PubMed1978

The structure of teleost epidermis with special reference to new qualitative and quantitative data from the guppy, Poecilia reticulata Peters.

Scales from the midlateral body region of adult male guppies, Poecilia reticulata Peters, were investigated morphometrically by light and electron microscopy. The epidermis consists of one superficial layer and, in general, two basal layers of filament-containing cells and a number of mucous cells. There are scattered chemosensory cells and unmyelinated nerve fibres. Superficial cells are flattened and form apical ridges in a fingerprint-like arrangement. The volume density of mitochondria, granular endoplasmic reticulum, and numerical density of dictyosomes are higher in superficial cells than in basal cells. The superficial cells are secretorily active. Small electron dense vesicles are transported from the dictyosomes to the body surface and yield the glycocalyx material, which is not identical with the slime produced by the mucous cells.

Animals↗
PubMed1977

Analysis of intracellular recordings from salamander olfactory epithelium.

Intracellular recordings have been obtained from provisionally identified olfactory receptor and sustentacular cells in the salamander olfactory epithelium. Two categories of membrane potential transients were recorded intracellularly in response to odor stimulation. The first category of responses, presumably recorded from receptor cell somas, were monophasis positive spikes 10-50 mV in amplitude which were superimposed on a depolarizing slow potential which ranged from 4 to 8 mV in amplitude. Graded and differential responses were recorded in response to odor stimulation. The second category of responses were depolarizing and hyperpolarizing slow membrane potential transients presumably recorded from sustentacular cells. Spiking was not observed in response to odor stimulation. Pysiological criteria and Procion dye marking in several instances have provided evidence that responses in the first category were recorded from olfactory receptors and that certain of the other responses were recorded from sustentacular cells.

Ambystoma↗
PubMed1976

Identification of the epidermal "Stiftchenzellen" of frog tadpoles by electron microscopy.

Differentiated surface epidermal cells observed in the skin of tadpoles of Rana temporaria by electron microscopy have been identified with the Stiftchenzellen originally described by Kölliker in 1885. The cells have apical microvilli or a single apical projection and appear to have synaptic associations with nerve fibres in the epidermis. The distribution, dimensions and structure of the cells are in agreement with descriptions from le cells are sensory in nature. In addition, there are fine structural resemblances to the gustatory cells of fish and of amphibians which suggest that the Stiftchenzellen are chemoreceptors.

Animals↗
PubMed1978

Replacement of receptor neurones after section of the vomeronasal nerves in the adult mouse.

Eight days after vomeronasal nerve section or removal of the accessory olfactory bulb, the majority of receptor cells of the vomeronasal neuroepithelium degenerate and disappear, leaving a regular framework consisting of supporting cells and their radial processes. The cell clusters at the boundaries of the epithelial sheet (which have been shown to be actively dividing in the normal, unoperated adult mouse) are also spared. The epithelium is subsequently repopulated by receptor cells appearing first in the basal part of the receptor cell layer and later occupying the full width of the receptor layer. These cells are anatomically fully differentiated receptor cells with normal sensory dendrites. Their axons form conspicuous intraepithelial neuromatous masses. Administration of [3H]thymidine on days 10-20 postoperatively labels some clusters of supporting cells and virtually all of the receptor cells, indicating that the repopulation of the epithelium is due to new formation of receptor cells.

Animals↗
PubMedDate not supplied

[The effect of ouabain on the sugar receptor of the contact chemoreceptive sensilla of the fly Protophormia terraenovae].

Studies have been made on the inhibitory effect of ouabain solutions on bioelectrical activity of the labellar sensillae of flied. It was shown that 10(-2) M ouabain solution irreversibly inhibits the activity, where as 10(-3) and 10(-4) M concentrations decrease the frequency of impulses within 40-60 min. Ouabain solution is a specific stimulator of the sugar receptor of the sensillae with a threshold of 10(-7) M; in combination with 0.2 M glucose, it inhibits impulse activity with the first 200 msec of stimulation. The effect is observed in a narrow zone of ouabain concentrations, with a maximum approximately at 10(-4) M. Differences between the effects of the inhibitor at the vicinity of the onset of generator potential and those in the impulse activity zones on the membrane of the sensory cell are suggested.

Animals↗
PubMed1976

Response plasticity in hamster olfactory bulb: peripheral and central processes.

It is a well-established fact that prolonged odor stimulation leads to marked sensory adaptation. This study demonstrates comparable electrophysiological phenomena occurring at the level of the olfactory receptor and at more central olfactory structures. Recordings of overall receptor response and of olfactory bulb unit responses were made during repeated odor stimulation. During the course of a single, continuous odor presentation response decrements were seen in the EOG (at the olfactory receptors) and were mirrored at the mitral cell layer of the bulb. When brief periods without stimulation were introduced between such odor presentations, receptor responsiveness rebounded to its original level, but mitral cell responses did not. On the basis of this dissociation it is suggested that the pattern of response decrement within the bulb represents a case of stimulus-specific habituation in a simple cortical subsystem and is well worth future investigation as a model of neural plasticity. Surgical disconnection of the olfactory bulb from one or more of its centrifugal inputs results in hyperactive, hyperresponsive mitral cells, which habituate more rapidly and show longer recovery times than do those in the intact bulb. In addition, the synchronization of such units to the inhalation cycle is markedly reduced as compared with normal preparations. These facts together suggest that the habituation of mitral cell activity does not depend on centrifugal inputs, although one or more of such inputs act indirectly in an inhibitory fashion to modulate and tune mitral cell response characteristics.

Adaptation, Physiological↗
PubMed1975

The fine structure of the olfactory and vomeronasal organs of a lizard (Tiliqua scincoides scincoides).

Olfactory epithelium in Tiliqua scinoides is of a loosely packed pseudostratified type. It receives secretion from the supporting cells and the underlying glands of Bowman. Its surface bears microvilli and cilia from sensory cells and microvilli from supporting cells. The vomeronasal epithelium is also pseudostratified but higher and more closely packed. Its surface carries microville from sensory and supporting cells but lacks cilia. Vascular connective tissue penetrates it almost to the epithelial surface but is always outlined by basal cell processes and a basal lamina. There are no secretory cells in or under the sensory epithelium but some cells in the epithelium of the mushroom body contain secretion granules. Sensory cells of both epithelia are bipolar neurons. The perikarya of the vomeronasal cells are more neuronal in character. Axonic processes are similar in both, dendrites are distinctive. Olfactory dendrites end in rounded rods bearing microvilli and cilia of an unusual type. Microville with filamentous cores occur on vomeronasal dendrites. There are no cilia, but 2-6 centrioles appear below the cell surface. Basal cells are structurally similar in both epithelia, but axonic processes of olfactory cells are surrounded by supporting cell processes, while vomeronasal axonic processes are surrounded by basal cells before they leave the epithelium. The presence of cilia and microville on the surface of the sensory cells is discussed in relation to the physical conditions surrounding them.

Animals↗
PubMedDate not supplied

[Protein-sensitive elements of the labellar sensillas of Musca domestica flies].

Using electrophysiological technique of registration of impulse activity in chemoreceptive cells of the labellar sensillae of the housefly, it has been demonstrated that taste hairs are not uniform in their properties. They differ from each other by the set of receptive elements which exhibit different sensitivity, range of selectivity and pattern of impulse activity. It was shown that albumen solution (10(-5) M) evokes the activity in 1--2 cells of a sensilla which are classified as water and sugar receptors. Among these receptors, protein-sensitive and protein-insensitive cells may be distinguished. Considering the inhomogeneity of sugar receptor sites, it was suggested that chemo receptive membranes in most sensitive to protein cells contain more numerous fructose receptive sites, that glucose ones.

Animals↗
PubMed1977

Fine structure of the sensilla of Peripatopsis moseleyi (Onychophora).

Three types of sensilla occurring on the lips and on the antennae of Peripatopsis moseleyi have been investigated by scanning and transmission electron microscopy. On the lips sensory spines can be found which contain numerous cilia originating from bipolar receptor cells. They reach the tip of the spine where the cuticle is modified. The perikarya of the sensory cells, a large supporting cell with a complicated surface and a second type of receptor, form a bud-like structure and are surrounded by a layer of collagen fibrils. The second receptor cell bears apical stereocilia as well as a kinocilium which are directed towards the centre of the animal -- thus the cell appears to be turned upside down. The sensilla of the antennae are 1) sensory bristles containing two or three kinds of receptor cells, one of which bears an apical cilium and one kind of supportive cell and 2) sensory bulbs located within furrows consisting of receptor cells with branched cilia and two kinds of supportive cells which are covered by a modified thin cuticle. According to the electron microscopical findings the sensory spines on the lips are presumably chemoreceptors. The sensory bristles on the antennae can be regarded as mechanoreceptors and the sensory bulbs as chemoreceptors.

Animals↗
PubMed1978

Interaction of chemosensory, visual, and statocyst pathways in Hermissenda crassicornis.

Neurons in the cerebropleural ganglia (CPG), photoreceptors in the eye, optic ganglion cells, and statocyst hair cells of the nudibranch mollusk Hermissenda crassicornis responded in specific ways, as recorded intracellularly, to stimulation of the chemosensory pathway originating at the tentacular chemoreceptors as well as to stimulation of the visual pathway originating at the photoreceptors. Synaptic inhibition of photoreceptors occurs via the chemosensory pathway. The possible significance of such intersensory interaction is discussed with reference to preliminary investigation of the animal's gustatory behavior and possible neural mechanisms of behavioral choice.

Animals↗
PubMed1975

Effects of ruthenium red, quinacrine hydrochloride, ethacrynic acid and 2,4-dinitrophenol on the water receptor of the frog tongue.

Effects of some chemicals, which are known as inhibitors of Ca2+-dependent ATPases, on the water receptor of the frog tongue were examined by using single fungiform papilla preparations. When a sufficient amount of ruthenium red, quinacrine hydrochloride, ethacrynic acid or 2,4-dinitrophenol was added to the standard stimulating solution (5mM CaCl2+100 mM NaCl), which has been shown to stimulate sufficiently the water receptor of the frog tongue, no neural response was elicited. The concentrations necessary for 50% inhibition were approximately 3 X 10(-6)M for ruthenium red, 1 X 10(-5) M for quinacrine hydrochloride, 1 X 10 (-3) M for ethacrynic acid and 2 X 10(-4) M for 2,4-dinitrophenol. Organic mercurials, mersalyl acid and p-chloromercuribenzoic acid, had no effect on the nueral response, but repeated application of these chemicals led to a permanent depression in receptor activity. Ouabain had no effect on either the neural response or receptor activity. These observations indicate that the receptor molecule of the frog water receptor has a similar property to that of the Ca2+-dependent ATPase of red-cell membrane in respect to the susceptibility to inhibitors.

Adenosine Triphosphatases↗