Thermoadaptation Characteristics of European River Lamprey Lampetra fluviatilis Smolts

Journal of Ichthyology - Thermoadaptation characteristics of smolts of European river lamprey Lampetra fluviatilis are studied in experimental conditions for the first time. The final preferred...     

Activation of Na+,H+-Exchange in Erythrocytes of the River Lamprey Lampetra fluviatilis

To study H⁺ transport, the lamprey red blood cells were acidified to pH 6.0 by a pretreatment with an ionophore, nigericin. Incubation of the acidified cells in NaCl-medium at pH 8.0 was accompanied by a rapid H⁺ efflux from the erythrocytes. There was a tenfold decrease of the H⁺ efflux rate on addition to NaCl-medium of dimethylamiloride or on replacing Na⁺ in the medium (KCl-medium, pH 8.0). A high rate of Na+ influx into the acidified erythrocytes occurred only in the presence of H⁺ gradient (pH medium 8.0), but not in its absence (pH medium 6.0). The Na⁺-dependent H⁺ efflux from the cells and H⁺-dependent Na⁺ influx into the cells were quantitatively similar (about 700 mmol/l cells/h). A rapid elevation of the intracellular Na⁺ concentration as measured by flame photometry was also observed during incubation of the acidified cells in NaCl-medium (pH 8.0). The H⁺-dependent Na⁺ influx and an increase of the Na⁺ content in the acidified cells were significantly inhibited by amiloride. The data obtained for the first time prove with certainty the presence of the Na⁺/H⁺ exchanger in erythrocytes of the river lamprey.     

Ultrastructure of the Pro-adenohypophysis of the River Lamprey,Lampetra fluviatilis,During Gonad Maturation

Abstract The pro-adenohypophysis (pro-AH) of migrating adult river lamprey, Lampetra fluviatilis, has been examined from October, when the gonads are developing slowly, until May, when the sexual maturation is completed. Two granulated cell types are dominating. One is chromophobic (C2, 95 nm), the other is basophilic (B1-B3) and probably gonadotropic. The mean diameter of the basophil secretory granules increases from 150 nm in October to 220 nm in April and May. The staining affinity of a rare, granulated cell type (D, 115 nm) has not been established. No acidophil cells are found in the pro-AH. The ultrastructural characteristics of the lead hematoxylin positive cells found sometimes in paraffin sections are unknown. Non-glandular stellate cells are common. They contain microfilaments, are probably contractile, and transform to phagocytes during the last months before spawning. This phagocytosis involves only the basophil cells. It is suggested that the stellate cells in this way destroy excess hormone. All cell types in the pituitary accumulate large irregular lipid droplets during the last month before spawning. These lipid droplets seem to be expelled from residual bodies as an end product of autolysis and phagocytosis.     

Aminergic and Indoleamine Accumulating Neurons in the Retina of the River Lamprey (Lampetra fluviatilis)

Tissues were processed for fluorescence microscopy of biogenic amines according to the method of Falck and Hillarp. Normal animals, and animals injected with α-methylnoradrenaline or 5,6-dihydroxytryptamine were used. Catecholamine containing neurons (junctional cells) occur in the innermost rows of cell bodies of the inner nuclear layer (INL) and close to the vitreous surface. Catecholamine containing fibers occur in three layers: (1) an outer layer around the innermost perikarya of the INL, which is a condition not found in retinas of gnathostome chordates; (2) a middle layer within the outer third of the inner synaptic layer (ISL), separated from the outer layer by ganglion cell axons; (3) a sparse inner layer within the innermost third of the ISL. A few catecholamine containing fibers were seen to extend from the innermost region of the INL to the outer synaptic layer. The position of the junctional cells in the lamprey corresponds to that in gnathostome chordates, but whereas all catecholamine containing fiber layers in gnathostomes are located sclerally to the optic fiber layer and within the ISL, the middle and the inner fiber layers in the lamprey occur vitreally to the optic fiber layer. Indoleamine accumulating neurons occur in the innermost row of perikarya of the INL and close to the vitreous surface. Those of the INL send fine, varicose branches to the ISL forming a network which is somewhat denser at the inner and outer borders of the ISL than in its middle. The indoleamine accumulating terminals do not ramify within the INL in contrast to the catecholamine containing terminals.     

Electron Microscopic Analysis of the Inner Synaptic Layer in the River Lamprey (Lampetra fluviatilis)

Abstract Different types of synaptic contacts between bipolar, amacrine and ganglion cells were scored on random electron micrographs and on montages comprising the entire thickness of the inner synaptic layer. Currently accepted criteria were used when classifying the different cell processes. The percental distribution of dyads was estimated to 56 % amacrine-amacrine dyads, 34 % amacrine-ganglion dyads and 10 % ganglion-ganglion dyads. The ratio of amacrine conventional synapses to bipolar ribbon synapses was 6.8 : 1. The density per unit area of conventional synapses (0.035/μm²) and ribbon synapses (0.005/ μm²) was found markedly low as compared with other vertebrate species except the carp. The inner synaptic layer of the river lamprey is suggested to be of the intermediate type in which both simple and complex ganglion cell receptive fields may be expected.     

Feeding Habits of Larval European River Lamprey Lampetra fluviatilis from the Chernaya River (Baltic Sea Basin)

Journal of Ichthyology - The results of the analysis of the bolus of the larval river lamprey Lampetra fluviatlis caught in the Chernaya River in May are presented. A quantitative analysis of the...     

Fine Structure of the Retinal Pigment Epithelium of the River Lamprey (Lampetra fluviatilis,Cyclostomi)

The retinal pigment epithelium of Lampetra fluviatilis was studied by electron microscopy. The epithelial cells differ in many details from those of gnathostomes. The lateral cell membranes are difficult to distinguish. The smooth endoplasmic reticulum is well developed; in some animals undulated membrane complexes, comprising systems of tightly fused double membrane plates, are related to the endoplasmic reticulum. Myeloid bodies are common and well developed, but pigment granules are comparatively sparse. The intercellular space between pigment epithelium and photoreceptors is rather wide. There are only a few inclusion bodies with membranous contents. The importance of the pigment epithelium in the retinal metabolic exchange is discussed in view of the fine structure of the cells. Compared with that of hagfishes, the lamprey retina is well developed. However, any comparison must be made against the background of a diphyletic development of the two groups.     

Transmitter Sensitivity of Primary Afferent Cells of the Lamprey Lampetra fluviatilis Spinal Cord

Using dorsal sensory cells (primary afferents) of the spinal cord of the lamprey Lampetra fluviatilis, isolated by an enzymatic-mechanical method, their responses have been studied to application of excitatory amino acids (EAA), glutamate, aspartate, kainate, N-methyl-D-aspartate (NMDA), and of inhibitory amino acids, GABA and glycine, as well as of neuromodulator serotonin (5-hydroxytryptamine, 5-HT). The patch-clamp method was applied to fix either potential or current through membranes of studied cells. It was shown that of all the above substances, only NMDA and kainate could produce in dorsal cells depolarization, input current with maximal amplitude up to 16 nA, and action potential. The main attention in this work was paid to NMDA-current properties. The dose–effect curves were obtained; a blocking effect of specific antagonist of NMDA-receptors, 2-amino-5-phosphonovalerian acid (APV), was shown; passage of Ba ions through Ca²⁺-channels of dorsal sensory cell membranes at NMDA application was proven. It has been established that in a half of the studied cells under effect of NMDA there is an increase of the maximal amplitude of the potential-activated current through Ca²⁺-channels, on average, by 22.5 ± 10.5% (n = 21). It was suggested that this variation might be essential for an increase of amount of the transmitter released in synapses formed by processes dorsal sensory cells, while NMDA could be considered a modulator facilitating synaptic activity of these cells.     

Membrane Potential Oscillations Produced by Excitatory Amino Acids in Isolated Spinal Neurons of the Lamprey Lampetra fluviatilis

Membrane potential (MP) oscillations produced by excitatory amino acids (EAA) have been studied in branching neurons isolated by an enzymatic-mechanical method from the lamprey spinal cord. It was shown that (1) all studied EAA (glutamate, kainate, NMDA, aspartate, and quisqualate) evoke an ion current and a short-term reversible depolarization in studied cells; (2) EAA added to perfusion solution may produce MP oscillations, with kinetic parameters and duration of the oscillation depending on the amino acid used (the most effective are kainate and NMDA, the least effective, quisqualate); (3) oscillations can be irregular (of the type of a synaptic noise or of a long-term plateau of depolarization with action potentials—AP) or regular, with frequency of 0.5–1.5 Hz. Amplitude of both oscillation types depends on MP level, frequency is more steady for each cell and less depends on MP. In 68 out of 128 studied cells, oscillations could be evoked, which indicates that a significant part of lamprey spinal neurons have intrinsic capability for MP oscillations and probably pacemaker properties. The functional role of oscillations can be different. They can take cells out from the profound inhibition state, synchronize activity of rhythm generation neurons and/or be the base for trigger signals (AP firing) sent by locomotor neuronal circuits to trunk muscles.     

The intestinal blood circulation in the River lamprey, Lampetra fluviatilis

Serial sections, injections with india ink and latex, and observations on fresh material, have been used to determine the pattern of blood circulation within the intestine of larval and adult lampreys. Attention has also been paid to resolving the variable terms previously applied to many of the blood vessels, and to the possible functional significance of the differences found between the two life cycle stages. In the larva, the main arterial supply to the intestine consists of a typhlosolar artery, while the venous return is comprised of a posterior and a left and right anterior intestinal vein that usually unite before entering the liver. Although a typhlosolar artery is also present in the adult, the main venous return of the ammocoete is replaced at metamorphosis by a newly formed typhlosolar vein. Moreover, in the ammocoete a considerable amount of blood is discharged into the haemopoietic sponge-work of the typhlosole and the arterial supply to the intestine is poorly developed. By contrast, the typhlosolar sponge-work is lost in the adult and a more efficient arterial supply is developed within the lamina propria of the various intestinal regions. Furthermore, vascular couples are developed in the adult which facilitate the flow of blood in opposite directions in the intestinal wall. Since, during both life cycle stages, the arterial blood passes into tissue spaces, there is no true capillary network in the intestine and no evidence was found for the presence of a lymphatic system. It is suggested that the changes which take place in the intestinal blood supply and the internal structure of the gut during metamorphosis result in improvements both to the vascular system and to the assimilation efficiency.     

Role of Oxidative Metabolism in the Energy Suppply of Active Potassium Transport in Erythrocytes of the Lamprey Lampetra fluviatilis

To study role of glycolysis and oxidative metabolism in providing active transport of monovalent cations, isolated erythrocytes of the lamprey Lampetra fluviatlis were incubated at 20°C in the presence of various metabolic inhibitors. The active (ouabain-sensitive) K⁺ (⁸⁶Rb) influx into erythrocytes did not change after cell incubation for 1–2 h in the absence of glucose or in the presence of 10 mM deoxy-D-glucose or 1 mM monoiodoacetate. Inhibitors of oxidative phosphorylation (antimycin A, rotenone, sodium azide, cyanide) produced a significant decrease (on average, by 74% ) in the active K⁺ transport in the lamprey erythrocytes. All blockers of oxidative phosphorylation produced the same degree of inhibition of the K⁺ transport after the cell pre-incubation with them for 30 and 60 min. In experiments with rotenone, the K⁺ influx was reduced statistically significantly as early as in 5 min of cell incubation and reached a maximal effect after 10–20 min. The intracellular ATP content in erythrocytes decreased by 17, 37, and 45% after 5, 10, and 20 min of cell incubation with rotenone, respectively. The active K⁺ transport in the lamprey erythrocytes is most likely to be closely associated with the intracellular ATP concentration. The data obtained indicate that the energy supply of the Na,K-pump in the lamprey erythrocytes is due exclusively to oxidative phosphorylation processes.     

A Fluorescence Microscopic Study of the Retina of the River Lamprey (Lampetra fluviatilis) and the Atlantic Hagfish, (Myxine glutinosa)

During the last few years many facts have been revealed about the neural structure in the retina of several vertebrate groups, particularly with regard to the monoamine containing neurons. A number of investigations have been made on mammals, birds and teleost fishes by the Falck-Hillarp method for the cellular demonstration of such amines. The present study has paid attention to two cyclostomes, the river lamprey, Lampetra fluviatilis, and the atlantic hagfish, Myxine glutinosa.     

The estuarine phase in the spawning run of the River lamprey Lampetra fluviatilis

The biology of the very early stages in the upstream migration of the River lamprey has been studied using samples taken from the cooling water intake screens of the Oldbury Power Station in the Severn Estuary. Examination of the numbers of lampreys caught at different times indicate that an increase in freshwater discharge is the predominant environmental factor responsible for initiating the movement from the sea into the estuary, although temperature may also be a contributory factor. The migrants could be separated on the basis of size into typical and praecox forms whose mean lengths during peak abundance were approximately 300 and 240 mm respectively, the corresponding weights being about 53 and 22 g respectively. The typical forms were occasionally found in the estuary as early as July and as late as April, with peak abundance generally being reached in November, whereas the praecox forms were present mainly between January and March. The ratio of typical to praecox forms over the four years of sampling was estimated as 3.3 : 1. In both size categories, the gonadosomic and hepatosomic ratio was greater in females than males. Evidence was also found in the typical forms for a correlation between high numbers and an increased proportion of males. Measurement of a number of different characters, including lengths, weights and condition factors, as well as gonadosomic, hepatosomic and gut ratios, suggest that, although the typical forms enter the estuary over a long period of time, the onset of the changes leading to sexual maturity are more synchronous. A small number of the later typical migrants, however, exhibited different characteristics to those of the majority of the animals comprising this size category. Measurements made on typical animals from Oldbury in November indicate that they can regulate their plasma ions in salinities as high as 70% of full strength sea water.     

The Ultrastructure of the Accessory Olfactory Organ in the River Lamprey (Lampetra Jiuviatilis)

The accessory olfactory organ of Lampetra fluviatilis was found to consist of clusters of interconnected vesicles in tenuous connection with the exterior medium via the cavity of the olfactory organ. The walls of the vesicles are composed of two types of cells. One type are primary sense cells that resemble the olfactory sense cells in that their nucleus is situated peripherally and their axons pass directly into the brain. They differ from the olfactory sense cells in the size and number of cilia they bear, and also in the internal structure of the cilia. The second cell type are supporting and/or secretory cells. It is concluded that this sense organ is capable of responding to a “special kind” of chemical stimulus and its possible function is discussed.     

Liver monoamine oxidase activity of the lamprey Lampetra fluviatilis. The substrate-inhibitor specificity

Based on the data of substrate-inhibitor analysis with the use of specific inhibitors-deprenyl, chlorgilin, and specific substrates-serotonin, noradrenalin, benzylamine, β-phenylethylamine and N-methylhistamine, one molecular form of monoamine oxidase (MAO) was suggested to possibly exist in liver of mature individuals of the European lamprey Lampetra fluviatilis. The kinetic parameters of monoamine oxidase deamination of eight substrates were determined, which indicates the large spectrum of substrate specificity of MAO from the lamprey liver. The studied enzyme does not deaminate histamine and putrescine and is not sensitive to 10^?2 M semicarbaside. Results of the study of the substrate-inhibitor specificity allow us to suggest some resemblance in catalytic properties of the lamprey liver MAO and the mammalian MAO of the form A. The low activity of the enzyme revealed at deamination of all used substrates seems to be associated with low detoxifying function of the lamprey liver.