Sensory and motor innervation of bird intrafusal muscle fibers

• 1.1. Most bird muscle spindles are supplied by only one primary afferent.
• 2.2. Secondary afferents occur irregularly.
• 3.3. Sensory terminals are covered by a basal lamina and a collagenous sheath.
• 4.4. Two types of motor terminal are recognized which can be referred to specific types of intrafusal fiber.
• 5.5. The sensory and motor innervation of bird intrafusal fibers is less understood than that of mammalian intrafusal fibers.

     

Properties of the transition from short-term to long-term depression in neurons of Helix pomatia

• 1.1. Synaptic short-term depression could be transferred into long term depression by repetition of series of stimuli.
• 2.2. The transition from short-term depression to long-term depression was blocked by puromycin.
• 3.3. The majority of the transition took place during resting periods between stimulus series.
• 4.4. The initiation of the transition process was 83% completed after 5 min of stimulation.
• 5.5. Short- and long-term depression were quantitatively separated into their two serial sites of origin: afferent axons and synaptic terminals.
• 6.6. Long sequences evoked periods with increased and variable EPSPs not conforming to depression.

     

Two kinds of peripheral afferent neurons in the earthworm reflex arc

• 1.1. Two kinds of neurons were identified in the body-wall longitudinal muscle layer of the earthworm, Amynthas hawayanus, by the simultaneous potential recording and Lucifer Yellow-CH injection method with a single microelectrode.
• 2.2. Both kinds of neurons have their somata, neuntes and longitudinal processes imbedded in the longitudinal muscle layer. Those with two circular processes extending into the third segmental nerve trunk are tentatively named “intra-nerve-trunk” neurons and those with four circular processes extending into four setae shafts are tentatively named “intramural” neurons.
• 3.3. Both kinds of neurons responded to electrical and mechanical stimuli applied in an afferent direction to them.
• 4.4. The “intra-nerve-trunk” neuron decreased its response amplitudes to these stimuli after the third nerve trunk was sectioned in correlation to the response amplitude decrease recorded from the nerve trunk after it was sectioned.
• 5.5. The response amplitude decrease due to denervation implies a nonlinear structure of the earthworm reflex circuits.
• 6.6. The “intramural” neurons are believed to be primary sensory neurons connected to the mechanoreceptors in the setae.

     

Inhibiton and gamma-aminobutyric acid-induced conductance on locust (Schistocerca gregaria) extensor tibiae muscle fibres

• 1.1. Increases in membrane conductance (g_m) were induced by GABA in distal bundles 32, 33 and 34 of extensor tibiae muscles of the locust (Schistocerca gregaria).
• 2.2. Bath application of GABA (10⁻⁵−5 × 10⁻³ M) induced reductions in muscle fibre space constant (λ).
• 3.3. GABA (5 × 10⁻³ M) induced additional membrane conductance of 2.21 ± 0.03 × 10⁻⁶ S/mm, 0.38 ± 0.03 × 10⁻⁶ S/mm and 0.29 ± 0.06 × 10⁻⁶ S/mm on muscle bundles 34, 33 and 32 respectively. The greater sensitivity of muscle fibres in bundle 34 to GABA is due at least in part to a larger number of GABA receptors on bundle 34 muscle fibres.
• 4.4. The decrement of electrotonic potentials in the presence of GABA were measured over distances of both half fibre length and whole fibre length. Good agreement was obtained between changes in space constant produced by GABA using half fibre length and whole fibre length data.
• 5.5. By taking into account changes in space constant induced by GABA it was possible to demonstrate that presynaptic GABA receptors were involved in the inhibition of slow excitatory postsynaptic potentials by GABA.
• 6.6. “Slow” excitatory postsynaptic potentials recorded under current clamp were inhibited in a dose-dependent manner by GABA. This inhibition was not dependent on muscle-fibre GABA sensitivity and could not be completely accounted for by GABA-induced changes in the cable properties of the muscle fibres.

     

Distribution of opine dehydrogenases and lactate dehydrogenase activities in marine animals

• 1.1. Opine dehydrogenases (OpDHs) and lactate dehydrogenase (LDH) activities were determined in various marine animals. OpDHs were detected in six marine invertebrate phyla; Porifera, Coelenterata, Annelida, Mollusca, Arthropoda and Echinodermata in phylogenic sequence.
• 2.2. Among several OpDHs, tauropine dehydrogenase (TaDH) occurred widely in marine invertebrates, from Porifera to Echinodermata.
• 3.3. With a few exceptions, total OpDHs activities exceeded that of LDH activity in the marine invertebrates investigated.
• 4.4. With respect to anaerobic glycolysis, OpDHs are indicated to play an important role in phylogenically lower invertebrates, whereas LDH is more important in higher animals.

     

Synaptic transmission at high pressure: Effects of [Ca2+]o

• 1.1. The effects of pressure on synaptic currents were examined in crayfish abdominal muscles.
• 2.2. Helium pressure (10.1 MPa) considerably decreased extracellulariy-recorded excitatory junctional potentials associated with increased short-term facilitation.
• 3.3. These effects could be mimicked by a reduction of [Ca²⁺]_o, and partially compensated by an increase in [Ca²⁺]_o.
• 4.4. Pressure also reduced the amplitude of the extracellular nerve terminal potentials (ENTP) by up to 25%, and significantly increased synaptic delay in a [Ca²⁺]_o-dependent manner.
• 5.5. The interaction between compression and various [Ca²⁺]_o were analysed in terms of an existing model of transmitter release. The results were consistent with the hypothesis that high pressure decreases the maximal Ca²⁺ influx into nerve terminals.
• 6.6. The decreased ENTP and increased synaptic delay suggest that additional processes may be involved in pressure effects on synaptic transmission.

     

Evidence for a molecular polymorphis of cholinesterase in Sepia officinalis (cephalopoda: decapoda)

• 1.1. Three forms of cholinesterase were sequentially extracted from head and tentacles of Sepia officinalis and noted as low-salt (LSS), detergent (DS) and high-salt (HSS) soluble. They represent about 24, 30 and 46% of total activity.
• 2.2. All enzyme forms seem to be amphiphilic proteins with hydrophobic domains interacting with non-ionic detergent (Triton X-100) and giving self-aggregation (LSS form).
• 3.3. The DS form is membrane-anchored by a phosphatidylinositol, while the HSS form is likely linked to some proteoglycan molecule of the extracellular matrix by ionic interactions.
• 4.4. According to V_max/K_m values, all the enzymes are acetylcholinesterases, even if hydrolyze propionylthiocoline at the highest rate.
• 5.5. Some kinetic and molecular properties of the studied enzymes are compared with those of other cholinesterases from vertebrates and invertebrates. Possible phylogenic and adaptive features are discussed.

     

A comparative study of vertebrate eye lens crystallins using isoelectric focusing and densitometry

• 1.1. The crystallin proteins of numerous species belonging to different classes of vertebrates have been studied.
• 2.2. Species-specific crystallin patterns are revealed which unequivocally characterize the different species.
• 3.3. A marked variability in the number and percentage of alpha-, beta- and gamma-crystallins were found in the various species.
• 4.4. The gamma-crystallin family, with a meagre number of common bands, has proved to be most representative of the species. The beta-crystallins, with their greater number of common bands, have been best preserved throughout vertebrate evolution.
• 5.5. From the similarity coefficient matrix a dendrogram is drawn up, a visual phylogenetic summary of the interrelationships between the vertebrates considered.
• 6.6. In the Discussion, other aspects are considered, such as lens morphology, functionality, animal age, post-synthetic modifications and genetic factors.

     

Extraction and rapid identification of law molecular weight compounds from marine organisms

• 1.1. Different methods for extraction of low molecular weight compunds (lipids, terpenoids, steroids, glycosides, etc.) from Black Sea invertebrates and algae were examined.
• 2.2. The composition and quantity of the extracts were found to depend strongly on the type of the organisms and on the solvents used for extraction.
• 3.3. Thin-layer chromatography was found to be convenient for rapid identification of low molecular weight compounds in the extracts.
• 4.4. An approach has been developed which was suitable for field experimentrsand was successfully applied for the analysis of five algae and seven invertebrates from the Black Sea.

     

Phase reversal in the lateral line of the ruff (Acerina cernua) as cue for directional sensitivity

• 1.1. The afferent response recorded from single fibres innervating canal neuromasts on the head of the ruff shows phase shifts of 180°, depending on stimulus location.
• 2.2. Based on these recordings it is shown, that in the flow field of a nearby moving object, the cupulae of adjacent neuromasts can be deflected in opposite directions.
• 3.3. This information may, in addition to other cues, enable localization of the stimulus source.

     

Transduction and transmission in ampullary electroreceptors of catfish

• 1.1. Transduction and transmission in catfish ampullary electroreceptors is mediated by sensory cells bearing microvilli, chemically mediating synapses, nerve terminals and one axon. Although some aspects still remain to be clarified, a number of properties have been found.
• 2.2. Spike generation per seand the modulation of spike frequency by electrical stimuli behave differently with respect to a number of experimental factors.
• 3.3. Stimulus current enters presumably through non-voltage-sensitive or non-specific ion channels.
• 4.4. Fluctuations of the spike frequency may be used as a measure for proper functioning of this sense organ.

     

The biochemical ecology of Biomphalaria glabrata,a freshwater pulmonate mollusc: The uptake and assimilation of exogenous glucose and maltose

• 1.1. The rates at which the pulmonate snail B. glabrata takes up soluble glucose and maltose from a defined medium were evaluated by measuring the buccal mass pulsation rate, the drinking rate, net changes in the concentrations of sugars in the medium and the rate of accumulation of ¹⁴C labelled maltose.
• 2.2. It was demonstrated that B. glabrata was capable of net accumulation of maltose and glucose via the mouth and integument, respectively.
• 3.3. Some of the maltose in the medium was also hydrolysed to glucose by exogenous snail enzymes.
• 4.4. The mechanisms involved in the accumulation of the sugars and the relevance of the results to the biochemical ecology of the snails and other aquatic invertebrates are discussed.

     

Ion transport in crab gills: A new method using isolated half platelets of Eriocheir gills in an ussing-type chamber

• 1.1. A half platelet preparation from Chinese crab (Eriocheir sinensis) gill is described which allows electrophysiological investigations of ion transport by gill epithelial monolayer when mounted in a modified Ussing chamber.
• 2.2. The resistance of these preparations equals half that of complete gill platelets (containing the gill epithelium and cuticle twice) indicating that cell damage during preparation of half platelets is negligible.
• 3.3. The transepithelial resistance (resistance of cuticle subtracted previously) was determined to be about 140 Ω cm² when both sides are bathed with identical salines.
• 4.4. Similarities to the results obtained with perfused complete gills demonstrates the reliability of this preparation.
• 5.5. When identical salines are applied on both sides of the epithelium an outside positive transepithelial potential difference (PD_te) up to 40 mV was measured.
• 6.6. The occurrence of such a high PD_te under symmetric conditions and its sensitivity to CN⁻ suggests the PD_te to be generated by active transport processes.

     

Ultrahistopathology of enchytraeid oligochaetes (annelida) after exposure to pesticides—A means of identification of sublethal effects?

• 1.1. The effects of the commonly used insecticides E605f (parathion), Ripcord 10 (cypermethrin) and the fungicide DuPont Benomyl on chloragocytes of an enchytraeid species were studied by transmission electron microscopy.
• 2.2. Animals were exposed to concentrations varying between 0.1 × and 100 × the minimum concentration recommended for agricultural application.
• 3.3. Ultrastructural changes regarding nuclei, mitochondria and other cytoplasmic compartments were obvious and were correlated to concentration and exposition time of the pesticides.
• 4.4. The importance of ultrahistopathology for terrestrial bioassays and monitoring is discussed.

     

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Binding and detoxification of heavy metals in lower vertebrates with reference to metallothionein

• 1.1. The metabolism of Cu, Zn, Cd and Hg in lower vertebrates is described, using fish as a model.
• 2.2. The main part of this review deals with metallothionein and the role of this protein for the storage and detoxification of these metals.
• 3.3. Factors influencing the bioavailability and probable uptake routes are identified.
• 4.4. The distribution of the metals within the organism is outlined. The distribution between tissues is described and the subcellular distribution discussed with reference to metallothionein.

     

Crayfish retinular cells: Influence of extracellular sodium and calcium upon receptor potential

• 1.1. In crayfish, light stimulation of the retinular cells induces a depolarizing receptor potential.
• 2.2. Experiments were designed to determine the role of Na⁺ and Ca²⁺ on receptor potential during dark And light states.
• 3.3. Depolarization depends on Na⁺ and Ca²⁺ availability to the retinular cell.
• 4.4. Repolarization velocity and response duration depend on extracellular Ca²⁺ availability.
• 5.5. Light adaptation increases receptor potential dependence on calcium and sodium ions.
• 6.6. We analyse these results with respect to other invertebrate photoreceptors.

     

Driving forces for the uphill transport of amino acids into epidermal brush border membrane vesicles of the sea anemone,Anemonia sulcata (Cnidaria,anthozoa)

• 1.1. The transport of amino acids into membrane vesicles prepared from epidermal tentacle tissue of the sea anemone, Anemonia sulcata, depends on an electrochemical potential difference caused, e.g. by sodium chloride gradients.
• 2.2. Potassium or choline chloride gradients energized the transport less effectively than sodium chloride gradients. Both Na⁺-ions and Cl⁻-ions were required for the amino acid transport.
• 3.3. The uphill transport of amino acids along the downhill movement of driver ions (sodium chloride gradient conditions) was characterized by an overshoot; under sodium chloride equilibrium conditions, however, an accumulation of amino acids within the vesicles could not be measured.
• 4.4. Potassium diffusion potentials in combination with valinomycin indicated that hyperpolarization (vesicle inside negative) and hypopolarization (vesicle inside positive) enhanced or depressed the accumulation of amino acids within the vesicles.
• 5.5. Being at the phylogenetic base of the Eumetazoa, cnidarians show characteristics for the transmembrane transport of amino acids comparable to those established for vertebrates.

     

Optical and neural pooling in visual processing in crustacea

• 1.1. Optical pooling is common in crustacean vision, both pooling in the single ommatidium and pooling inputs from many ommatidia by overlapping visual fields.
• 2.2. Optical and neural pooling work together subdividing the eye into different surface regions with different tasks.
• 3.3. Small-fiber and large-fiber systems with corresponding small and large dendritic branching provide a parallel processing system.
• 4.4. Several parallel, integrating channels process that visual information which is needed for high-speed reactions.
• 5.5. Visual fibers receive contributions from other modality inputs like vibration, olfaction or attention neurons. Inputs from mechanoreceptors transmitted over integrating fibers seem to join the signals in the intergrating visual fibers.
• 6.6. The signal for a particular channel is expressed by the pattern of spikes (rather than changes in the mean frequency of spikes) which is modulated by any input variation.
• 7.7. A particular discharge pattern may then be recognized by a command neuron or a muscle ensemble.