Dynamics of plasma Ca and calcitonin levels in stonefish (Inimicus japonicus) administered a high-Ca solution into the stomach

In stonefish, changes in plasma total Ca and calcitonin levels were examined after administration of a high-Ca solution into the stomach. Blood was taken successively at 0, 1, 3, 9, 33, and 81 hr from a fine tube cannulated into the aortic bulb. Plasma Ca levels increased acutely at 1 hr and attained the peak after 3-9 hr of the administration. Although plasma calcitonin levels did not exhibit conspicuous changes for 1-3 hr, they began to rise significantly at 33 hr. The plasma Ca level began to decline significantly at 33 hr, although the level was still significantly higher than the initial level. At 33 hr, however, the plasma calcitonin level still continued to increase. At 81 hr, the plasma Ca level had returned to the initial level. At that time, the plasma calcitonin level was also significantly lower than that at 33 hr. These results suggest that, in stonefish, the ultimobranchial gland has the ability to respond physiologically to rises in plasma Ca levels, to secrete calcitonin, and to cease the secretion when the plasma Ca levels return to the initial level.     

Serum concentrations of calcitonin and parathormone in the cord blood of premature infants

Determinations of serum calcium (Ca), calcitonin (CT) and parathyroid hormone (PTH) were carried out in mixed cord blood of 23 preterm infants. Gestational age ranged between 25 and 37 weeks. 17 of theme were vaginally delivered while 6 were delivered by emergency Caesarean section. 4 neonates died because of respiratory distress syndrome. The serum was stored at -30 degrees C until the determinations. Serum Ca levels were determined by spectrophotometry while CT and PTH levels by RIA (Immuno Nuclear Co). In cord serum the mean (M +/- SE) Ca,CT and PTH concentrations of all neonates examined were respectively: 9,9 +/- 0,6 mg/dl; 176 +/- 44 pg/ml and 1100 +/- 446 pg/ml. Serum values of CT and PTH in preterm newborns delivered by emergency Caesarean section were significantly higher than in those neonates vaginally delivered (CT: 302 +/- 115 vs 94 +/- 9 pg/ml; p less than 0.005) (PTH:2655 +/- 1857 vs 466 +/- 59 pg/ml; p less than 0.05). No differences were observed between serum CT and PTH levels in preterm neonates of different gestational age. Both CT and PTH serum concentrations were higher in neonates who died. In conclusion, the preterm neonate is able to secrete both peptides and to maintain Ca homeostasis; the mode of delivery likely affects the CT and PTH secretion; unexplainable high CT and PTH serum levels were detected in poor outcome preterm infants.     

The negative correlation between prolactin and ionic calcium in cord blood of full term infants

Total serum calcium (Ca), ionic calcium (Ca++), phosphorus, magnesium, total protein, immunoreactive parathyroid hormone (iPTH), calcitonin (iCT) and prolactin (iPRL) were measured in 30 paired samples of cord and maternal blood obtained at term delivery. In the cord blood, the concentrations of Ca, Ca++, phosphorus, magnesium, albumin, iCT and iPRL were all higher, and the concentrations of total protein and iPTH lower than in the maternal blood. The calcium binding capacity of albumin assessed with the equation (Ca-Ca++)/albumin, was similar at a given concentration of Ca in both the maternal and fetal circulations. There was a significant positive correlation between cord Ca++ and maternal Ca or Ca++, and a significant negative correlation between Ca++ and iPRL in cord blood. These data suggest that there is an active system transporting calcium from mother to fetus through the placenta, and PRL is the only one of the three hormones which was correlated with ionic calcium values in the fetus. The negative relationship between Ca++ and iPRL in the cord blood suggests an inhibitory effect of the relative hypercalcemia on PRL secretion in the fetus.     

Migratory patterns and contribution of stocking to the population of European eel in Lithuanian waters as indicated by otolith Sr:Ca ratios

Otolith Sr:Ca ratios were examined to evaluate the contribution of the stocked eel Anguilla anguilla elvers, which have been stocked in Lithuanian waters and mixed with naturally recruited eels for several decades, to the native eel population. Stocked eels were identified by the freshwater signature (Sr:Ca ratios <2·24 × 10⁻³) on the otolith after the glass eel stage. Naturally recruited eels, that had migrated through the North and Baltic Seas, were characterized by an extended seawater and brackish-water signature (Sr:Ca ratios >3·23 × 10⁻³) after the glass eel stage. Of 108 eels analysed, 21 eels had otolith Sr:Ca ratio profiles consistent with stocking while 87 showed patterns of natural recruitment. The ages of naturally recruited eels arriving in Lithuanian fresh waters varied from 1 to 10 years, with a mean ±  s.d . age of 5·2 ± 2·1 years. Eels from the inland Lake Baluošai were all freshwater residents of stocked origin. Stocked eels, however, accounted for only 20% of the eels from the Curonian Lagoon and 2% of eels sampled in Baltic coastal waters. This finding does not support the hypothesis that the eel fishery in the Curonian Lagoon depends mostly on stocking.     

Effect of pimozide on the cytology of the eel pituitary

Pimozide, a specific blocker of dopaminergic receptors, was injected for 4 to 9 days in freshwater (FW) eels or eels acclimated to sea water (SW), for 10 to 30 days. The daily dose was 100 or 200 microgram/100 g. In FW, pimozide induces a nuclear hypertrophy in the prolactin (PRL) cells of eels; these elongated cells increase in height. The amount of erythrosinophilic granules in the cytoplasm, initially reduced, increases. Plasma electrolyte values are not modified: only the plasma sodium level slightly rises with the higher dose. In SW, PRL cells appear less active. After 10 days, this hypoactivity is not yet fully evident; pimozide stimulates PRL cells without affecting electrolyte values. After 1 month in SW, PRL cells are stimulated with pimozide and a slight regranulation may occasionally occur. The response in SW is never as marked as it is in FW; a high dose is not more effective than a low one. The higher dose significantly raises Na+, Ca2+ and Cl- plasma levels. These data suggest that prolactin synthesis and release increase with pimozide. They corroborate the hypothesis of a hypothalamic inhibitory control on PRL secretion mediated through dopaminergic fibers in the eel, but other factors may also be involved in this regulation in addition to the effect of salinity.     

Catecholamine content (as measured by the HPLC method) in brain and blood plasma of the eel: effects of 101 ATA hydrostatic pressure

The catecholamine content (noradrenaline, NA; adrenaline, A; dopamine, DA, and its metabolite, DOPAC) was measured, by the HPLC method, in brain and blood plasma of eels studied at atmospheric pressure (1 ATA) or at 101 ATA of hydrostatic pressure (HP). In the brain, HP induces a slight but significant increase (P less than 0.05) in A and DA contents but NA and DOPAC levels are not modified at 101 ATA when compared to 1 ATA. In the plasma, only A and NA are detected, adrenaline being the predominant amine. In eels exposed to 101 ATA HP, A and NA are strongly increased (+100%; P less than 0.01). The significance of the catecholamine increase in brain and plasma of the eels under HP is discussed.     

Relationship of blood concentrations of calcium, phosphate, gastrin and calcitonin to the onset of feeding in the rat.

Daily fluctuations in plasma calcium concentrations in rats trained to a closely regulated feeding pattern have been compared to corresponding plasma gastrin and calcitonin concentrations. The time period studied was that extending from 4 hr prior to the start of the feeding. Both plasma calcium and phosphate levels fedd prior to the start of the feeding period and remained low at least for the first 2 hr of feeding. This pattern was also observed in rats in which food was withheld for 2 hr past the regular feeding time. Plasma 45Ca and 32P concentrations (radionuclide injected at least one week prior to sampling) did not follow the pattern of their stable counterparts. Instead, these values rose or remained constant until after feeding had commenced, after which they fell precipitously. Both plasma calcitonin and gastrin levels rose rapidly after the start of the feeding period. The primary point of emphasis is that calcitonin secretion was produced in these rats by an intestinal related stimulus and not by a rise in plasma calcium concentration.     

Time lag of the response on the otolith strontium/calcium ratios of the Japanese eel, <Emphasis Type="Italic">Anguilla japonica</Emphasis> to changes in strontium/calcium ratios of ambient water

We conducted a laboratory experiment to validate the relationship between the otolith strontium/calcium (Sr/Ca) ratio of Japanese eels (Anguilla japonica) and water Sr/Ca ratio when the ratio in water was changed. A linear and additive mixed modeling approach was used to assess otolith Sr/Ca ratio for elver-juvenile Japanese eels when ambient water was changed from seawater to freshwater. There was a significant difference between otolith Sr/Ca ratios of eels reared in freshwater and in seawater (freshwater: 1.3–2.3; seawater: 7.0–7.8 mmol/mol). The response of otolith Sr/Ca ratios of eels was not detected until after 10 d and models suggested that it might not be completed until at least 30–60 d. This study indicated the detailed ability of otolith Sr/Ca ratio to be used as a proxy for reconstructing the individual environmental history of Japanese eels. These findings can provide some assurances for future otolith Sr/Ca studies of eels in this system or in other areas that have similar environmental conditions.     

Antidiuretic Effect of Eel ANP Infused at Physiological Doses in Conscious, Seawater-Adapted Eels, Anguilla japonica

Atrial natriuretic peptide (ANP) is known as a potent natriuretic/diuretic hormone in vertebrates. However, eel ANP infused at doses that did not alter arterial blood pressure (0.3-3.0 pmol/kg/min) decreased urine volume and increased urinary Na concentration in seawater (SW)-adapted eels but not in freshwater (FW)-adapted eels. The renal effects were dose-dependent and disappeared after infusate was switched back to a vehicle (0.9% NaCl). Urinary Na excretion (volume x Na concentration) did not change during ANP infusion. ANP infusion increased plasma ANP concentration, but the increase at the highest dose was still within those observed endogenously after injection of hypertonic saline. Urinary Mg and Ca concentrations increased during ANP infusion in SW eels, but urinary Ca excretion decreased in FW eels. Plasma Na concentration profoundly decreased during ANP infusion only in SW eels, suggesting that ANP stimulates Na extrusion via non-renal routes. These results indicate that ANP is a hormone which specifically extrudes Na ions and thereby promotes SW adaptation in the eel. This is in sharp contrast with mammals where ANP is a volume regulating hormone that extrudes both Na and water.     

Basal and stimulated calcitonin secretion in primary hyperparathyroidism before and after parathyroidectomy

To investigate calcitonin secretion in primary hyperparathyroidism, basal and stimulated (3 mg Ca++/kg body weight/10 min) immunoreactive calcitonin plasma levels were studied before parathyroidectomy. Plasma calcitonin levels were raised in 50% of patients regardless of sex, but a significant correlation between basal plasma calcium and calcitonin was found only in males. A reduced calcitonin response to calcium infusion was observed in all patients. Parathyroidectomy invariably induced a normalization of calcitonin basal levels. Our findings confirm the existence of a decreased parafollicular cell reserve probably as a consequence of the persistent hypercalcemic state in hyperparathyroid patients and suggest that it is more frequent in females.     

Response of prolactin cells to environmental calcium in the eel (Anguilla anguilla L.)

Prolactin (PRL) cell activity was investigated in eels kept in fresh water (FW), deionized water (DW) supplemented or not with Ca (2 mM), in Ca-enriched FW (10 mM), in normal (Ca 3.4 mM) or Ca-free 1/3 sea water (SW), and in SW (Ca 10.2 mM) or Ca-free SW (Ca 0.15 mM). Light-microscopic studies, including measurement of the nuclear area and cell height, showed that PRL cell activity, reduced in DW, is not affected by Ca supplementation. Activity is reduced in Ca-enriched FW, in 1/3 SW and in SW, conditions inducing an increase in the plasma sodium level. The lack of calcium in saline environments partly suppresses the nuclear atrophy occurring in SW. There is no significant correlation between external or total plasma calcium concentration and PRL cell activity. In artificial Ca-free SW, eels show a rapid increase in plasma osmolarity and sodium levels; there is a significant negative correlation between these two plasma values and the nuclear area or cell height of PRL cells. As in some other teleosts, plasma osmolarity and plasma sodium seem to play a more important role than external or internal calcium in controlling PRL secretion. This correlation is not apparent in eels kept in SW, having unstimulated PRL cells but active calcium-sensitive (Ca-s) cells in the pars intermedia.     

Characterization of inflammatory neutrophils induced by bacterial endotoxin in the blood of eels, Anguilla australis

Peripheral blood neutrophils were studied in eels injected with phosphate buffered saline, bacterial lipopolysaccharide (LPS), carrageenan (CAR), LPS and CAR together (CAR/LPS(T)), CAR and LPS 4 days later (CAR/LPS(S)), zymosan and latex beads. All stimuli caused a left shift toward neutrophil immaturity but LPS-elicited neutrophils, particularly in CAR/LPS stimulated eels, were often extremely basophilic, enlarged, vacuolated and had a large nucleus with poorly differentiated nuclear chromatin. These intensely basophilic neutrophils (IBN) had few granules and lower acid phosphatase and non-specific esterase, but higher PAS levels, compared to normal neutrophils. Ultrastructurally, IBN showed loss of cytoplasmic content that gave a ragged appearance, the nucleus was often immature and many rough endoplasmic reticulum profiles restricted the distribution of reduced numbers of cytoplasmic granules. These features are attributed to asynchronous development, and IBN are compared with mammalian toxic neutrophils.     

Unravelling the life-history patterns and habitat preferences of the Japanese eel (Anguilla japonica) in the Pearl River,China

Eels have fascinated biologists for centuries due to their amazing long-distance migrations between freshwater habitats and very distant ocean spawning areas. The migratory life histories of the Japanese eel, Anguilla japonica, in the waters of south China are not very clear despite its ecological importance, and the need for fishery regulation and management. In this study, strontium (Sr) and calcium (Ca) microchemical profiles of the otoliths of silver eels were measured by X-ray electron probe microanalysis based on data collected from different habitats (including freshwater and brackish habitats), in the large subtropical Pearl River. The corresponding habitat preference characteristics were further analysed using redundancy analysis (RDA). A total of 195 Japanese eels were collected over 6 years. The collected individuals ranged from 180 to 771 mm in total length and from 8 to 612 g in body weight. Two-dimensional pictures of the Sr:Ca concentrations in otoliths revealed that the A. japonica in the Pearl River are almost entirely river eels, spending the majority of their lives in fresh water without exposure to salt water, while the catadromous migration time has delayed about 1 month in the Pearl River estuary in the past 20 years. RDA analysis further indicated that juveniles and adults preferred water with high salinity and high tide levels. Youth preferred habitats with high river fractals. Our findings contribute to a growing body of evidence showing that the eels are extremely scarce currently and conservation measures against them are imminent, including the protection of brackish and freshwater areas where they live in south China.     

Ca2+-activated adenosinetriphosphatase activity in the gills of freshwater-and seawater-adapted eels (Anguilla rostrata).

1. Ca2+ -activated ATPase activity was higher in the gills of freshwater acclimated eels than in the gills of seawater acclimated eels. 2. The properties of the enzyme and the amount of protein extracted were identical in freshwater and seawater acclimated eels.     

Seasonal changes in the relationship of blood calcium levels to immunoglobulins and some of the blood proteins in schoolchildren

Blood and saliva were collected in the autumn and spring from a group of schoolchildren (39 girls, 35 boys) with a mean age of 11.4 years. Serum immunoglobulin IgG, IgA, IgM and IgE, alpha 1-antitrypsin (A 1-AT), alpha 2 macroglobulin (A 2M), transferrin (TRF), ceruloplasmin (CPL), lysozyme (LYS) and pertussis (PE) antibody levels were determined. Calcium (Ca2+) and total serum protein levels were also determined. Secretory IgA (sIgA) and secretory lysozyme (sLYS) levels were assessed in the saliva. A highly significant drop in Ca2+ levels was found in the spring in boys, while in girls there was only a greater scatter of the values. Mean IgG, IgA and IgM values fell significantly in the spring in both sexes, but IgE levels fell significantly only in boys. PE levels rose significantly in the spring in girls. Among the other proteins, all the values rose in boys, except for TRF, whose levels fell. In girls, LYS and TRF levels rose, but all the other values fell. The coefficients of correlation between Ca2+ and the tested proteins showed a significant relationship only for A 2M and PE in girls and only for the total protein level in boys; in boys, the determination coefficient for sIgA and IgM was over 10%. The results do not testify to the existence of a close relationship between blood Ca2+ levels and Ig and other blood protein levels.     

Differences in the Trace Element Deposition in Otoliths Between Marine- and Freshwater-resident Japanese Eels, Anguilla japonica, as Determined by Laser Ablation ICPMS

Synopsis In order to determine whether the trace element composition in otolith of the Japanese eel Anguilla japonica could be used to determine its habitat use, we used laser ablation inductivity coupled plasma mass spectrometry (LA-ICPMS) to assay sectioned otoliths of both marine-resident (sea eels) and freshwater-resident (river eels) eels. A close linear relationship in the Sr:Ca ratios between EPMA (X-ray analysis with an electron microprobe) and LA-ICPMS analyses was found, suggesting that the latter technique could be used to separate the marine and freshwater life phases. Elemental signatures in the otolith outside the elver mark showed significant differences in Cr:Ca, Mn:Ca, and Ba:Ca ratios as well as Sr:Ca ratios between sea and river eels. These results indicate that the elemental compositions may reflect environmental variability between marine and fresh water masses. Thus, those elemental ratios determined by LA-ICPMS analysis seem to have the potential to help distinguish the habitat of the eel.     

Plasma calcium and calcitonin in the marine teleost, Gadus morhua

Total, free and ionic plasma levels of calcium as well as total plasma magnesium and inorganic phosphate levels were studied in the Atlantic cod, Gadus morhua, in relation to salmon calcitonin injections. Plasma ion levels and endogenous levels of calcitonin were studied during environmentally induced hypercalcemia. It is concluded that no apparent relationship between calcitonin and calcium levels was found, and it is implied that calcitonin in fish may have a physiological function not related to blood calcium regulation.     

Responses of the ultimobranchial body in eels (Anguilla anguilla L.) maintained in sea water and experimentally matured,to injections of synthetic salmon calcitonin

The effect of a synthetic salmon calcitonin (SCT) treatment on ultimobranchial body (UB) activity in eels (Anguilla anguilla L.) maintained in seawater and submitted to experimental maturation, has been studied histologically. 2. The activity of the glands of a control group of eels maintained in sea water was taken as a reference. 3. The UB parenchyma showed a marked atrophy in the fish treated with SCT alone and serum calcium decreased significantly in this group. 4. Immature female silver eels receiving carp pituitary extract (CPE 1 mg/100 g body wt. per injections) until complete maturation presented high hypercalcemia associated with cellular hypertrophy and hyperplasia in the UB. 5. SCT treatment did not prevent the hypercalcemia provoked by CPE injections. UB activity was strongly increased in this case. 6. These data indicate that the activity of the UB in eels varies with both physiological and experimental hypercalcemia, and responds to SCT injections.     

Development of hypothermia in rats at increase of [Ca2+] in the blood

In rats, data on influence of i. v. administration of calcium chloride on the level of [Ca2+] in the blood and on process of oppression ofthermoregulatory and respiratory functions in rats in hypothermia. 0.18 or 0.135 mmol Ca2+ on the 3rd minute from beginning of the administration increased [Ca2+] in the blood from 1.01 +/- 0.03 to 2.56 +/- 0.08 mM (or 2.27 +/- 0.06 mM). Then [Ca2+] was reduced gradually, in 20 minutes from administration, solution of CaCh [Ca2+] exceeded the initial level by 20-30 %. The increase of concentration of ionized calcium in the rat blood strengthened the cold oppression of breathing and cold shivering as compared with the control (administration of physiological solution). Arrest of breathing in rats after administration of CaCl2 solution occurred at higher rectal temperatures (21 +/- 0.03 degrees C) as compared with control experiments (18 +/- 0.4 degrees C), p < 0.05. It is suggested that increase of [Ca2+] in the blood strengthens effects of cold in the form of oppression of thermoregulatory and respiratory functions.     

Stanniectomy attenuates the renin–angiotensin response to hypovolemic hypotension in freshwater eels (<Emphasis Type="Italic">Anguilla rostrata</Emphasis>) but not blood pressure recovery

Plasma Angiotensin II (ANG II) concentrations were measured in SHM (sham-operated 2 weeks) and CSX (corpuscles of Stannius removed 2 weeks) eels before and after the induction of hypovolemic hypotension (HH) by the rapid withdrawal of 8 ml kg bw⁻¹ of caudal venous blood. Baseline (before exsanguination) plasma ANG II concentrations were similar in SHM and CSX eels (81.3 ± 18.8 fmol ml⁻¹ cf. 106 ± 31.6 fmol ml⁻¹, respectively) but the elevation in plasma ANG II following HH (1,732 ± 82 fmol ml⁻¹) was attenuated by CSX (368 ± 127 fmol ml⁻¹) showing that the CS are linked to plasma ANG II concentrations. Plasma ANG II in both groups returned to baseline levels within 48 h. Dorsal aortic blood pressures (DABP) were measured in both experimental groups before, and during the 60 min after, blood withdrawal. A 44% decrease in mean DABP was observed in both SHM and CSX eels within 2 min and followed by similar rapid patterns of recovery of systolic, diastolic, and pulse pressures in both groups during the next 60 min showing that short-term recovery of DABP is not CS-dependent. Stanniectomy increased plasma Ca and K⁺ and decreased plasma Mg, Na⁺, Cl⁻ and osmolality which confirms some earlier observations in eels and other freshwater teleosts.