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Biomedical subjects

L Tort

Publications and source records attributed to L Tort.

At least 19 recordsLinked to original sources
PubMed2000

Pituitary proopiomelanocortin-derived peptides and hypothalamus-pituitary-interrenal axis activity in gilthead sea bream (Sparus aurata) during prolonged crowding stress: differential regulation of adrenocorticotropin hormone and alpha-melanocyte-stimulating hormone release by corticotropin-releasing hormone and thyrotropin-releasing hormone.

Plasma levels of cortisol, growth hormone (GH), adrenocorticotropin hormone (ACTH), alpha-melanocyte-stimulating hormone (alpha-MSH), N-acetyl-beta-endorphin, in vitro ACTH-stimulated cortisol secretion, and in vitro corticotropin-releasing hormone (CRH)- and thyrotropin-releasing hormone (TRH)-stimulated ACTH and alpha-MSH secretion were investigated in gilthead sea bream exposed to high stocking density (30 kg m(-3)) for 23 days. Within 3 days after the onset of crowding, plasma levels of cortisol, ACTH, alpha-MSH, and N-acetyl-beta-endorphin were above control values. After 7 days, plasma parameters had returned to control levels, but at 23 days, cortisol, alpha-MSH, and N-acetyl-beta-endorphin levels were again elevated over controls, indicating a long-term activation of the melanotrope cells. In contrast, crowding stress elicited a prolonged reduction in plasma GH levels concomitant with the increased hypothalamus-pituitary-interrenal axis (HPI) activation. Crowding stress enhanced cortisol secretory activity of the unstimulated interrenal cells. However, interrenal tissue from crowded fish in vitro displayed an attenuated response to ACTH stimulation compared with tissue from control fish, indicating a desensitization of these cells to ACTH during crowding. The involvement of pituitary proopiomelanocortin-derived peptides in the HPI axis of sea bream is indicated by the observed modulation of the CRH and TRH responsiveness of the corticotropes and melanotropes in crowded fish. At day 1, when there were crowding-induced plasma increases in ACTH and alpha-MSH, there was an attenuated CRH-stimulated but not TRH-stimulated, ACTH release. However, at that time, CRH- and TRH-induced responses of alpha-MSH secretion, and the unstimulated secretory activity of the MSH cells, were enhanced in crowded sea bream. These data provide evidence for stimulatory roles of multiple hypothalamic (CRH and TRH) and pituitary (ACTH and alpha-MSH) peptides in the activation of the hypothalamus-pituitary-interrenal axis under crowding conditions in sea bream.

Adrenocorticotropic Hormone↗
PubMed1999

Quantification of calcium release from the sarcoplasmic reticulum in rainbow trout atrial myocytes.

Using the whole-cell configuration of the patch-clamp technique, we quantified calcium release from the sarcoplasmic reticulum (SR) elicited by short depolarization pulses before and after clearance of the SR Ca2+ content with 10 mM caffeine (CAF). With a loaded SR, the first detectable contraction occurred with a pulse duration of 5 ms. CAF exposure increased this pulse duration to 85 ms and slowed the inactivation of the Ca2+ current (ICa). Repolarization of the cell to -80 mV after a short depolarization elicited a tail current that was attenuated markedly after CAF exposure. The difference between the charge carried by the tail currents obtained before and after CAF exposure was taken as a measure of the Ca2+ released from the SR. SR Ca2+ release increased with increasing SR Ca2+ load over the range of loads examined. In contrast, SR Ca2+ release reached a maximum when the duration of the preceding depolarization exceeded 10 ms. Maximal Ca2+ release was 1.64 amol/pF or 62 microM and elicited a contraction that was 40 +/- 6% of the amplitude of a normal contraction. This release could account for 48 +/- 10% of the total Ca2+ required to activate contraction but only a few percent of the CAF-releasable Ca2+. Thus, contrary to the general view of excitation-contraction coupling in lower vertebrates, SR Ca2+ release in trout atrial myocytes may account for up to 50% of the total Ca2+ transient at room temperature.

Animals↗
PubMed1998

L-type Ca2+ current and excitation-contraction coupling in single atrial myocytes from rainbow trout.

We have examined the contribution of L-type Ca2+ current (ICa) to the activation of contraction in trout atrial myocytes under basal and phosphorylating conditions. The average myocyte length was 197 +/- 14 micrometer, width was 5.5 +/- 0.2 micrometer, and cell capacitance was 36.2 +/- 2.2 pF. With 25 microM EGTA in the patch pipette and a stimulation frequency of 0.125 Hz, ICa was 2.6 +/- 0.4 pA/pF and it carried a total charge of 0.10 +/- 0.01 pC/pF, giving rise to a contraction of 15.2 +/- 2.8% of the resting cell length. With a cell volume of 2.4 +/- 0.3 pl, the charge carried by ICa corresponded to 14.7 +/- 2.2 micromol Ca2+/l nonmitochondrial cell volume (microM). This can account for only 30-40% of the Ca2+ binding to the myofilaments during a contraction. Increasing the stimulation frequency from 0.25 to 2 Hz decreased ICa amplitude and charge by 66 +/- 5 and 80 +/- 3%, respectively. Elevating the pipette EGTA concentration from 25 microM to 5 mM increased ICa amplitude and charge by approximately 290%. Both isoproterenol and cAMP increased ICa by approximately 230%. The total charge carried by the isoproterenol- or cAMP-stimulated current was increased by 170%. We conclude that the use of high-EGTA concentration may overestimate the total Ca2+ carried by ICa under physiological conditions. Furthermore, the results suggest that, in contrast to previous reports from other lower vertebrates, Ca2+ flux through L-type Ca2+ channels alone is not sufficient to fully activate contraction in trout atrial myocytes at room temperature.

Adrenergic beta-Agonists↗
PubMed1998

Quantification of Ca2+ uptake in the sarcoplasmic reticulum of trout ventricular myocytes.

We measured Ca2+ uptake by the sarcoplasmic reticulum (SR) in trout ventricular myocytes, measuring indo 1 fluorescence in permeabilized cells or ionic currents in single myocytes subjected to voltage clamp. Titration of the SR Ca2+ pumps with thapsigargin gave a pump site density of 454 pmol/mg cell protein. Lowering the temperature from 20 degreesC to 10 or 5 degreesC reduced the SR Ca2+ uptake rate in permeabilized myocytes by 50 and 63%, respectively. Surprisingly, Ca2+ leak from the SR also decreased with decreasing temperatures. Exposure of single myocytes to 10 mM caffeine (Caf) induced a cell contracture and an inward ionic current. Neither contracture nor current decreased significantly after rest periods of 120 and 320 s. The inward current was due to Ca2+ extrusion by the Na+/Ca2+ exchanger (NCX), and the time integral of the exchange current (INCX) was used to calculate the SR Ca2+ content. This gave a steady-state SR Ca2+ content of 22.5 +/- 2.8 amol Ca2+/pF or 750 microM. When the SR was loaded by depolarizing the cell to +50 mV, the Ca2+ content increased with increasing length of the depolarization, reaching a maximum of 52.0 +/- 5.9 amol Ca2+/pF. When the cell was depolarized to different voltages for 3 s, a subsequent Caf-induced INCX increased with increasing voltage. At +100 mV, the Ca2+ content was 36.6 +/- 3.8 amol/pF, giving a maximal SR Ca2+ uptake rate of 12.2 +/- 1.2 amol Ca2+. pF-1. s-1 or 417 microM/s. We conclude that maximal SR Ca2+ content and Ca2+ uptake rates can be estimated using specific SR Ca2+ loading protocols. Contrary to the general assumption that contraction in lower vertebrates depends largely on transsarcolemmal Ca2+ fluxes, we found that although the L-type Ca2+ current is insufficient to fully activate contraction, the SR is capable of participating in the regulation of the cytosolic Ca2+ during the excitation-contraction coupling in trout ventricular myocytes.

Animals↗
PubMed1997

Diversity of the third form of complement, C3, in fish: functional characterization of five forms of C3 in the diploid fish Sparus aurata.

We have recently shown that Sparus aurata, the gilthead sea bream (a diploid species), similarly to rainbow trout (a quasi-tetraploid species), possesses multiple forms of the third form of complement (C3). In the present study we have evaluated the ability of the gilthead sea bream proteins to function as active C3 molecules. All five C3 isoforms could be fixed covalently to sheep erythrocyte ghosts and were able to bind to various complement-activating surfaces in the presence of MgEGTA. In the absence of MgEGTA their binding capacities generally increased, presumably as a result of classical-pathway activation by the natural antibodies present in the serum. The presence of EDTA abrogated the binding of all C3 isoforms to the various surfaces tested. The C3 isoforms differed in the efficiency of their binding to complement-activating surfaces: the two most abundant C3 isoforms (C3-1 and C3-2) bound to zymosan as well as to sheep and rabbit erythrocyte ghosts, whereas C3-3, C3-4 and C3-5 were unable to bind to zymosan. Upon complement activation, all five C3 isoforms were cleaved to 'iC3b' by factor H and I-like proteins, generating fragments similar to those generated from C3 molecules of other species. Furthermore the degradation of methylamine-hydrolysed C3 isoforms to iC3b was significantly inhibited by EDTA. The structural and functional diversity that we have observed in the C3 isoforms of S. aurata would increase the capacity of this fish to recognize a broader spectrum of potential pathogens and reinforce a specific immune response, which in fish is delayed compared with that of higher vertebrates, and is based on a single Ig type (IgM).

Animals↗
PubMed1997

Structural C3 diversity in fish: characterization of five forms of C3 in the diploid fish Sparus aurata.

In virtually all species examined to date, the functionally active third component of complement (C3) is encoded by a single gene. We have recently demonstrated, however, that trout possess three structurally and functionally distinct active C3 that represent the products of at least two different C3 genes. In the present study, we provide evidence that multiple forms of functional C3 occur not only in the rainbow trout (Salmo gairdneri), a quasi-tetraploid old teleost fish, but also in the diploid gilthead sea bream (Sparus aurata), a modern teleost fish. In the gilthead sea bream, we have characterized five different forms of C3 (C3-1, C3-2, C3-3, C3-4, and C3-5); in addition, we have identified and isolated a C5-like molecule. Each of the six proteins was composed of an alpha-chain and a beta-chain; however, only the C3 isoforms contained a thioester bond in their alpha-chains. These proteins all differed in the molecular masses of their alpha- and beta-chains and in their glycosylation patterns, reactivity with various Abs, tryptic peptide maps, and NH2-terminal sequences of their chains. These observations together with the fact that each of the six proteins were also purified from a single fish suggest that the C3 isoforms represent the products of several genes. The presence of multiple forms of C3 in a modern diploid fish, very distant in evolutionary time from the trout, strongly suggests that the C3 isoforms generated once from a single C3 gene have remained functional in the genomes of these animals. These findings not only have important consequences for our understanding of the evolution of the C3 protein, but also provide evidence for the formation and generation of a new C3-related gene family.

Amino Acid Sequence↗
PubMed1997

Cortisol and glucose responses after acute stress by net handling in the sparid red porgy previously subjected to crowding stress

In red porgy Pagrus pagrus subjected to 3 weeks of chronic stress by crowding, plasma cortisol remained significantly higher in crowded fish compared to controls. There was no significant effect of crowding on plasma glucose levels. When the crowded fish were subjected to an acute handling the plasma cortisol response was similar to that of the uncrowded fish. No significant differences were found between the groups. The changes in plasma glucose following acute handling were also similar in both crowded and uncrowded fish.

Journal Article↗
PubMed1997

Adrenergic stimulation of sea bream (Sparus aurata) red blood cells in normoxia and anoxia: effects on metabolism and on the oxygen affinity of haemoglobin

The metabolic response of sea bream (Sparus aurata) red blood cells to adrenergic stimulation was determined in normoxia and anoxia. In the presence of oxygen, red blood cells swelled and then recovered their resting volume. Continuous monitoring of oxygen uptake displayed the kinetics of the increase in the oxygen affinity of haemoglobin. Cell volume recovery correlated with an activation of ATP consumption, and the energy equilibrium was restored by increasing the rates of respiration and glycolysis. When the respiratory chain was blocked, adrenergic stimulation increased the rates of ATP consumption and glycolysis of red blood cells. Moreover, adrenergic stimulation of deoxygenated erythrocytes also increased cell volume but did not enhance glycolysis or ATP consumption, and the cells remained swollen. Our results suggest that there is an oxygen-linked signal transducer that activates ATP-consuming processes, provided that the adrenergic stimulation occurs in the presence of oxygen.

Journal Article↗
PubMed1996

Crowding stress induces changes in serum haemolytic and agglutinating activity in the gilthead sea bream Sparus aurata.

Sea bream Sparus aurata were subjected to crowding for 3 weeks and the levels of plasma cortisol and glucose were determined in order to ascertain the occurrence of stress. At the same time, selected indicators of the immune response were monitored through blood lymphocyte counting and selected humoral responses such as the haemagglutination activity (HA) of serum towards rabbit erythrocytes (RaRBC) and the alternative complement pathway (ACP) levels. The results show an initial moderate increase in cortisol followed by hyperglycaemia and recovery to basal levels. A pattern of immunodepression was detected afterwards as shown by decreases in ACP levels after 5 days and haemagglutination titre and circulating lymphocytes after 9 days. Nevertheless, ACP levels showed a significant increase after 9 days, and HA titres and circulating lymphocyte numbers also increased after 15 days. Normal values were recovered after 15 days for lymphocytes and ACP and 21 days for agglutination. Results are discussed in view of the incidence of stress on indicative parameters of endocrine and immune systems.

Agglutination↗
PubMed1995

Natural hemolytic and bactericidal activities of sea bream Sparus aurata serum are effected by the alternative complement pathway.

Sea bream serum displayed bactericidal and hemolytic activities. These activities were depleted when serum was incubated with different activators of the alternative complement pathway (ACP). Ethylenediaminetetraacetic acid (EDTA) inhibited both the hemolytic and bactericidal activities, while ethyleneglycol-bis (B-aminoethyl ether)-N, N, N'-tetraacetic acid (EGTA) was not inhibitory. An antibody against the putative third component of sea bream component (C3) was produced. It was observed by immunoelectrophoresis that the sea bream C3 and human C3 migrated in the same position. Crossed immunoelectrophoresis showed that sea bream C3 exhibited a similar pattern of activation when compared with its human counterpart. The anti-sea bream C3 antibody inhibited both bactericidal and hemolytic activities. It was concluded that both serum actions were displayed by the ACP. The best conditions for the sea bream ACP titration were investigated. Of all mammal erythrocytes tested, rabbit erythrocytes (RaRBC) were found to be the best ACP activators and thus were used for the titration. Sea bream showed very high ACP titers when compared with those of mammals. Absorption of naturally occurring antibodies against rabbit RaRBC did not influence the ACP titers. Enzymatic removal of sialic acid from different mammalian erythrocytes increased the sensitivity of these cells to hemolysis mediated by the sea bream ACP.

Animals↗
PubMed1994

Computing heart rate variability using spectral analysis techniques: HRVUAB, a ready-to-use program.

The application of spectral analysis techniques to study the nervous modulation of the vertebrate heart have given interesting results in clinical studies although nearly nothing is known in lower vertebrates. A program to compute this heart rate variability is described in detail and preliminary results are shown. Data is first statistically qualified and fragmented in smaller segments, each being further processed through linear trend removal and normalization before the application of the Fast Fourier Transform algorithm to estimate the interval spectrum. All consecutive periodograms are averaged and the interval spectrum plotted and saved.

Algorithms↗
PubMed1994

Plasma glucose and lactate and hematological changes after handling stresses in the dogfish.

Hematological variables as well as blood glucose and lactate levels are determined in the Mediterranean dogfish after either cannulation surgery or handling by capture. The results show that both types of stress generate similar metabolic changes but somehow different hematological responses, since a cell loss is detected in cannulated fish, whereas an increase of cell volume is observed after handling. At the same time, surgery stress requires longer time to recover the basal levels than handling stress.

Animals↗
PubMed1991

Cadmium induction of metallothioneins in several dogfish organs.

Dogfish Scyliorhinus canicula were exposed to 50 mg/l Cd for 4 days for inducing metallothionein synthesis. Spleen, pancreas, kidney and gonads were dissected out and metallothionein presence was checked by means of gel filtration chromatography in Sephadex G-75 and sodium dodecyl sulphate polyacrylamide electrophoresis. In pancreas and kidney, a cadmium-binding protein with spectroscopical and electrophoretic properties similar to those of dogfish liver metallothionein was found. In the other organs, the existence of an analogue protein but at very low concentrations is feasible.

Animals↗
PubMed1987

Effects on dogfish haematology and liver composition after acute copper exposure.

1. Dogfish Scyliorhinus canicula was subjected to experimental acute copper pollution. At the lowest concentration no changes were recorded on haemoglobin levels whilst decreases of the erythrocyte number and haematocrit was found. 2. At higher concentrations near to the lethal doses, a general reduction of all blood parameters was observed. 3. Liver composition (protein, glycogen and lipid levels) was not affected by any copper concentration, over the duration of the experiments. 4. Results are discussed in relation to physiological responses of fish, acute concentration and metal action.

Animals↗
PubMed1987

Acute toxicity of copper to mediterranean dogfish.

Acute copper toxicity to dogfish (Scyliorhinus canicula) was determined. Median lethal concentrations (LC50) for 24 and 48 hr were respectively 16 and 4 mg/l. These results are compared with those for zinc in dogfish and with the values for copper toxicity in several teleosts obtained by other authors.

Animals↗
PubMed1986

Effects of confinement stress and additional zinc treatment on some blood parameters in the dogfish Scyliorhinus canicula.

Several blood parameters were studied in the dogfish Scyliorhinus canicula subjected to different confinement conditions (transport and maintenance) and zinc contamination. Confinement stress significantly decreased erythrocyte counts (RBCC), haematocrit (Ht), haemoglobin (Hb), leucocrit (Lt), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC). Mean corpuscular volume (MCV) did not change with this stress and plasma glucose concentration significantly increased. In fish subjected to confinement stress conditions, Zn treatment significantly decreased Hb, MCH and MCHC and plasma glucose concentration. Ht and MCV did not change and Lt and RBCC significantly increased. Results are discussed related to other stress effects and effects of zinc treatment on fish confined in non-stressful conditions.

Animals↗
PubMed1986

Statistical relations of some blood parameters along recovery from imposed stress in dogfish.

Selected blood parameters (arterial pH, O2 and CO2 tensions, oxygen content, bicarbonate and lactate concentrations, haematocrit, haemoglobin, red blood cell count, mean corpuscular haemoglobin, mean corpuscular volume and mean corpuscular haemoglobin concentration), oxygen consumption and ventilatory frequency were measured 0, 3 and 24 hours after cannulation of the dorsal aorta of 22 dogfish. Correlations were calculated between all pairs of variables along the post-operational recovery period. Results are discussed in terms of the integrated dynamics of the recovery process subsequent to handling, anaesthesia and surgery stress. It is suggested that erythrocyte swelling plays an important role in maintaining tissue oxygen supply during recovery from operational procedures.

Anesthesia↗