Impact of ocean acidification on antimicrobial activity in gills of the blue mussel (Mytilus edulis).

Here, we aimed to investigate potential effects of ocean acidification on antimicrobial peptide (AMP) activity in the gills of Mytilus edulis, as gills are directly facing seawater and the changing pH (predicted to be reduced from ∼8.1 to ∼7.7 by 2100). The AMP activity of gill and haemocyte extracts was compared at pH 6.0, 7.7 and 8.1, with a radial diffusion assay against Escherichia coli. The activity of the gill extracts was not affected by pH, while it was significantly reduced with increasing pH in the haemocyte extracts. Gill extracts were also tested against different species of Vibrio (V. parahaemolyticus, V. tubiashii, V. splendidus, V. alginolyticus) at pH 7.7 and 8.1. The metabolic activity of the bacteria decreased by ∼65-90%, depending on species of bacteria, but was, as in the radial diffusion assay, not affected by pH. The results indicated that AMPs from gills are efficient in a broad pH-range. However, when mussels were pre-exposed for pH 7.7 for four month the gill extracts presented significantly lower inhibit of bacterial growth. A full in-depth proteome investigation of gill extracts, using LC-Orbitrap MS/MS technique, showed that among previously described AMPs from haemocytes of Mytilus, myticin A was found up-regulated in response to lipopolysaccharide, 3 h post injection. Sporadic occurrence of other immune related peptides/proteins also pointed to a rapid response (0.5-3 h p.i.). Altogether, our results indicate that the gills of blue mussels constitute an important first line defence adapted to act at the pH of seawater. The antimicrobial activity of the gills is however modulated when mussels are under the pressure of ocean acidification, which may give future advantages for invading pathogens.

Mass spectrometry data from a quantitative analysis of protein expression in gills of immuno-challenged blue mussels (Mytilus edulis).

Here, we provide the dataset associated with our research article on the potential effects of ocean acidification on antimicrobial peptide (AMP) activity in the gills of Mytilus edulis, "Impact of ocean acidification on antimicrobial activity in gills of the blue mussel (Mytilus edulis)" [1]. Blue mussels were stimulated with lipopolysaccharides and samples were collected at different time points post injection. Protein extracts were prepared from the gills, digested using trypsin and a full in-depth proteome investigation was performed using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Protein identification and quantification was performed using the MaxQuant 1.5.1.2 software, "MaxQuant enables high peptide identification rates, individualized p.p.b.-range mass accuracies and proteome-wide protein quantification" [2].

Age-related effect of a single oral dose of calcium on parathyroid function: relationship with vitamin D status.

The parathyroid response to the administration of a single oral dose of 0.5 g Cal was studied in 71 normal subjects of both sexes (34 males, 37 females) aged 20-88 y. Serum 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] were measured before the intake of calcium. Serum ionized calcium (Ca++) and intact parathormone (PTH1-84) were measured before and 1, 2, and 3 h after the intake of calcium. The Ca++ maximal response (delta Ca++max), which significantly decreased with age (P = 0.0001), was correlated with both 25(OH)D (r = 0.375, P < 0.01) and 1,25(OH)2D (r = 0.284, P < 0.02). The maximal PTH1-84 suppressive response expressed as a function of basal values (delta PTH%) decreased with age. Basal PTH1-84 values were significantly increased with age (P = 0.0002) and were negatively correlated with 25(OH)D concentrations (r = 0.414, P < 0.002) which were low in elderly people. These results suggest that correction of vitamin D deficiency should improve delta Ca++max, lower basal PTH1-84, and consequently make the oral intake of calcium more efficient to decrease PTH1-84 concentrations.

Mineral water as a source of dietary calcium: acute effects on parathyroid function and bone resorption in young men.

BACKGROUND: Calcium is a major component of mineralized tissues and is required for normal growth and maintenance of bone. Epidemiologic studies showed that a large percentage of the population fails to meet the currently recommended guidelines for optimal calcium intake. OBJECTIVE: The present study was designed to determine whether high-calcium mineral water is an efficient additional source of dietary calcium. DESIGN: Twelve healthy young men (mean +/- SD age: 21.1 +/- 1.2 y) ingested in a randomized order either 0.5 L of a mineral water containing 344 mg Ca/L or 0.5 L of a mineral water with a very low concentration of calcium (<10 mg/L) as a control. Blood samples were drawn before and 1, 2, 3, and 4 h after intake of the water. Urine was collected for 2 h before and every 2 h for 4 h after ingestion of the water. Serum concentrations of intact parathyroid hormone (iPTH) and serum concentrations and urinary excretion of a recently developed biochemical marker of bone resorption, type 1 collagen cross-linked C-telopeptide (CTx), were measured. RESULTS: Serum iPTH was significantly (P < 0.002) lower after ingestion of high-calcium water than after ingestion of the control. There was a significant (P = 0.01) progressive decrease in urinary CTx after ingestion of the high-calcium water, whereas after ingestion of low-calcium water the changes were modest and not significant. The fall in serum CTx concentrations was 34.7% 3 h after ingestion of high-calcium water, compared with 17.6% with the control. The decreases in serum CTx concentrations were significantly (P < 0.05) lower 1, 2, 3, and 4 h after ingestion of high-calcium water than after ingestion of the control. CONCLUSION: The present study showed that one oral intake of water containing a very moderate dose of calcium (172 mg) acutely inhibited iPTH secretion and bone resorption.

Effects on calcium and phosphate metabolism and on parathyroid function of acute administration of tricalcium phosphate.

The effects of the ingestion of tricalcium phosphate on calcium and phosphate metabolism and on parathyroid function were evaluated in 10 young adults. Each subject was studied during a control period of two hours before and during an experimental period of four hours after ingestion of a single oral dose of tricalcium phosphate containing 1500 mg of calcium and 770 mg of phosphorus. Serum and urinary calcium and phosphate and the nephrogenous cAMP fraction were measured. Significant rises in serum (from 2.32 +/- 0.05 to 2.44 +/- 0.08 mmol/l) and urinary (from 1.08 +/- 0.65 to 3.43 +/- 1.38 mumols/l GF) calcium and in serum phosphate (from 1.05 +/- 0.18 to 1.28 +/- 0.14 mmol/l) occurred. Unexpectedly, the acute supply of calcium in the form of tricalcium phosphate did not provoke significant alteration of nephrogenous cAMP level. In order to assess the respective effects of calcium and of phosphate, similar tests with ingestion of similar amounts either of calcium (as a glucoheptogluconate salt) or of phosphate were subsequently performed in the same subjects. Significant increases in serum total calcium were observed after calcium glucoheptogluconate as after tricalcium phosphate. However, the effects on parathyroid function differed, since a significant (p less than 0.001) decrease in nephrogenous cAMP followed the ingestion of calcium glucoheptogluconate. Otherwise, a stimulating effect of phosphate on parathyroid function was observed. These findings suggest that the respective effects of calcium and of phosphate are counterbalanced when administered as tricalcium phosphate, resulting in the absence of parathyroid suppression.

Vitamin D-dependent seasonal variation of PTH in growing male adolescents.

Twenty-eight young male adolescents (age from 13 years 6 months to 15 years 9 months) from a horseback-riding school were studied. They were studied at the end of summer (September of 1993) and, six months later, at the end of winter (March of 1994). At each timepoint their height and weight were measured and their pubertal status determined. Blood was collected and 25-hydroxyvitamin D [25(OH)D], intact parathyroid hormone (PTH1-84), and 1,25-dihydroxy-vitamin D [1,25(OH)2D] were measured. After winter, weight and height had increased by a mean of 2.9 +/- 1.3 kg and of 3.3 +/- 1.2 cm, respectively. 25(OH)D concentrations which were 29.96 +/- 7.46 micrograms/L in September had significantly (p = 0.0001) fallen by a mean of 23.31 +/- 6.6 micrograms/L in March (6.61 +/- 2.04 micrograms/L). March and September concentrations of 25(OH)D were significantly correlated (r = 0.536, p = 0.0039). March values were negatively correlated with the pubertal status (r = 0.41; p = 0.03). In the meantime, PTH had significantly (p = 0.0001) increased by a mean of 8.59 +/- 8.53 ng/L (22.8 +/- 7.44 ng/L in September vs. 30.33 +/- 8.05 ng/L in March). A statistically significant correlation between PTH and 25(OH)D concentrations (r = 0.493; p = 0.0001) was obtained. Serum 1,25(OH)2D concentrations measured in September (37.7 +/- 12.94 ng/L) and in March (38.2 +/- 7.8 ng/L) were not different. March values were positively correlated with pubertal status (r = 0.49; p = 0.008). Modulation of PTH secretion by vitamin D appears to be a physiological mechanism occurring during adolescence. In spite of a marked depletion of vitamin D stores after winter, PTH values remained within normal range. Nevertheless, we cannot exclude that a more prolonged vitamin D deficiency could adversely affect bone metabolism during this critical period of life characterized by an increased need of vitamin D.

Protein-bound cyclic AMP and steroidogenesis in the adrenal gland of the rat.

Adrenocortical cyclic AMP (both total and protein-bound), and adrenal and plasma concentrations of corticosterone were measured in male rats killed at selected intervals throughout the day. The animals had previously been synchronized for 3 weeks in natural lighting. Adrenal and plasma levels of corticosterone showed similar circadian fluctuations and the onset of their ascending phases started at 13.00 h, maximum concentrations being reached at 21.00 h. On the other hand, a time-lag between the circadian variations of total cyclic AMP and protein-bound cyclic AMP could be seen in adrenocortical tissue. The onset of an increase in adrenocortical protein-bound cyclic AMP was apparent at 15.00 h and the peak occurred at 21.00 h, while total adrenocortical cyclic AMP did not begin to rise before 19.00 h and was maximal at 04.00 h. No direct link between total cyclic AMP and protein-bound cyclic AMP could be seen during the dark phase, suggesting a functional compartmentalization of cyclic AMP in the adrenal gland of the rat. While the ascending phase of the rhythm in steroidogenesis preceded the rise in total adrenocortical cyclic AMP by about 4 h an excellent synchrony between the respective patterns of corticosterone concentration and protein-bound cyclic AMP was noticed.

Acute PTH response to oral calcium load and seasonal variation of vitamin D status in healthy young adult subjects.

OBJECTIVE: The aim of the present study was to check the relationship between seasonal variations of vitamin D status and parathyroid function explored both in basal conditions and after oral calcium load. DESIGN: The calcium and parathyroid hormone response to the intake of calcium load was studied at two different seasons, before winter (November) and after winter (March-April), corresponding to different vitamin D status. SUBJECTS: Eighteen healthy young male adults (age: 25 +/- 3 y) were studied. All were medical students who were selected as having no disorders known to affect calcium metabolism. INTERVENTION: At each period an oral calcium load (1 g of elemental calcium as calcium carbonate) was administered. Blood samples were collected before and 1 h, 2 h, 3 h and 4 h after the intake of calcium. Serum ionized calcium (Ca2+) and intact parathormone (PTH1-84) were measured at each time point and 25-hydroxyvitamin D (25(OH)D) was measured before each calcium test. RESULTS: After winter, basal 25(OH)D concentrations were decreased (from 16.4 +/- 6.6 to 11.5 +/- 4.4 micrograms/l) and basal PTH concentrations were increased (from 24.1 +/- 6.5 to 31.7 +/- 9.1 pg/ ml), and the difference between pre- and post-winter basal concentrations were statistically significant for both variables (P < 0.001). A statistically significant negative correlation between PTH and 25(OH)D was obtained both before (r = -0.63; P = 0.005) and after (r = -0.64; P = 0.004) winter. The maximum decrement in PTH (delta PTHmax) was not different before (13.92 +/- 4.58 pg/ml) and after (14.14 +/- 7.79 pg/ml) winter, but as a consequence of post-winter higher basal levels of PTH, at all time points after oral calcium load, concentrations of PTH after winter were significantly higher than before. CONCLUSIONS: The present results show that PTH concentrations are physiologically linked to 25(OH)D concentrations, and emphasize the need of taking into account the vitamin D status of each subject to predict the effect of an oral calcium load on absolute concentrations of PTH.

Development of adrenocortical cyclic nucleotide (cyclic AMP and cyclic GMP) and corticosterone circadian rhythms in male and female rats.

The daily rhythm of the adrenocortical cyclic nucleotides (cyclic AMP and cyclic GMP) was studied in infant male and female Wistar rats before and after the establishment of an adult-like daily rhythm of plasma corticosterone. As in this strain the rhythm of corticosterone is known to be present on postnatal day 18, pups of 2 and 3 weeks of age were studied. The dams and the pups as well as the young adult animals were kept on a controlled 12L-12D photoperiod. Groups of 8-10 pups were killed at 4-hr intervals throughout the day. Plasma corticosterone levels and adrenal cyclic AMP and cyclic GMP concentrations were simultaneously measured and the daily patterns established. Pups of 2 weeks of age showed neither plasma corticosterone nor adrenal cyclic AMP rhythms whereas pups of 3 weeks of age exhibited a typical adult-like circadian rhythm for both variables. The patterns for adrenal cyclic GMP differed according to sex: In female pups no cyclic GMP circadian rhythm could be detected at either 2 or 3 wk. In male pups of 3 wk a typical mature rhythm for adrenal cyclic GMP was evident whereas in younger male pups (2 wk) a circadian rhythm was detected. This circadian rhythm, however, differed from mature circadian rhythm in that its peak was located at 1300 hr instead of 0700 hr. These results demonstrate that, unlike that of cyclic AMP the adrenal cyclic GMP circadian rhythm does not appear at the same time as the plasma corticosterone circadian rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effects of phosphate therapy on parathyroid gland reactivity]. / Effets d'un traitement par le phosphate sur la réactivité parathyroïdienne.

The effects of a single oral dose of phosphate (780 mg of elemental phosphorus as 100 drops of Phosphoneurol 120 from DOMS-Adrian Laboratories) on parathyroid function and on calcium and phosphate metabolism were studied in 10 young adults. The parathyroid response was checked by measurement of PTH 1-84 and of nephrogenous cAMP before and after a 10 days therapy by phosphate (780 mg of elemental phosphorus twice daily). Before treatment a 16 per cent increase in PTH 1-84 (p less than 0.05) and a 34 per cent increase in nephrogenous cAMP (p less than 0.02) was obtained. After treatment the increases were respectively 34 per cent for PTH 1-84 (p less than 0.001) and 67 per cent for nephrogenous cAMP (p less than 0.001). The responses in PTH 1-84 and in nephrogenous cAMP were significantly (p less than 0.05 and p less than 0.01) higher after than before treatment by phosphate.

[Vitamin D status in the adolescent: seasonal variations and effects of winter supplementation with vitamin D3]. / Statut vitaminique D de l'adolescent: variations saisonnières et effets d'une supplémentation hivernale par la vitamine D3.

BACKGROUND: Recently, 25 hydroxyvitamin D (25 OHD) blood concentrations measured in adolescents during or at the end of winter were found very low. A concomitant stimulation of parathyroid function was observed. The aim of the present study was to test the biological effects of a treatment with vitamin D3 during winter. POPULATIONS AND METHODS: The effects of vitamin D3 supplementation (100,000 IU, twice, at the end of November and of January) were assessed in 24 male Caucasian adolescents (mean age +/- SD: 14 y 6 m +/- 9 m). They were pupils in a lad-jockeys training center located in the countryside near Chantilly (49 degrees northern latitude). Blood concentrations of 25 OHD, calcium and intact parathormone (PTH) were measured three times: before each oral intake of vitamin D3 and 2 months after the last intake (March). A group of 32 male adolescents (mean age +/- SD: 14 y 9 m +/- 6 m), pupils in the same center, receiving no vitamin D and sampled in November and in March, served as controls. RESULTS: In March, mean concentrations of 25 OHD (8.36 +/- 2.73 micrograms/L) were very low in vitamin D-not supplemented adolescents since 34% had levels less than 6 micrograms/L. In March, PTH concentrations (40.5 +/- 12.2 ng/L) were significantly (P = 0.0001) higher than in November (28.8 +/- 9.9 ng/L). In boys receiving vitamin D3 25 OHD serum concentrations measured in January (17.5 +/- 3.2 micrograms/L) and in March (18.7 +/- 4.0 micrograms/L) remained at a level not very different from that measured in November (16.6 +/- 3.8 micrograms/L). During the same period, calcium and PTH concentrations (32.2 +/- 11.7 ng/L in November; 32.4 +/- 14.3 in January and 32.9 +/- 13.5 ng/L in March) remained at their basal level as well. CONCLUSIONS: The observation that, after winter, a relatively large number of adolescents presented low concentrations of 25 OHD suggests that, during winter, usual dietary intakes and/or vitamin D stores are not sufficient to provide for their needs. Administration of two oral doses of 100,000 IU of vitamin D3 could maintain the vitamin D status at its initial level. The efficiency of such a prophylactic treatment is also assessed by its effect on parathyroid function.

[Primary hyperparathyroidism: value of "intact parathormone" assay (PTH 1-84)]. / Hyperparathyroïdie primaire: apports du dosage de la parathormone "intacte" (PTH 1-84).

In a prospective study of 20 patients with primary hyperparathyroidism the diagnostic value of the intact parathormone assay was compared with that of intermediate fragment measurement and that of nephrogenic cyclic AMP determination. In the basal state, measuring the intact parathormone is the best way of separating hyperparathyroid patients form normal subjects. During calcium infusion tests, there is good concordance between changes in intact parathormone and in nephrogenic cyclic AMP. In addition, the intact parathormone assay enables a thorough study of the relationship between ionized calcaemia and parathyroid secretion to be performed and confirms the existence, in hyperparathyroid patients, of two types of secretory response to a rise in calcaemia. Being more reliable than the measurement of a C-terminal or intermediate fragment and easier to perform than nephrogenic cyclic AMP determination, the intact parathormone assay seems to be particularly suitable for the study of primary hyperparathyroidism.

Comparison of the suppressive effect of two doses (500 mg vs 1500 mg) of oral calcium on parathyroid hormone secretion and on urinary cyclic AMP.

The respective effects of the ingestion of two different doses of calcium (500 and 1500 mg) on serum ionized calcium, intact parathyroid hormone (PTH 1-84), and the urinary excretion of 3',5'-cyclic adenosine monophosphate (cyclic AMP) were evaluated in 15 young male adults. Ionized serum calcium and PTH 1-84 were measured before and 1 hour, 2 hours and 3 hours (P1, P2, and P3) after the oral intake of calcium. Cyclic AMP was measured in 2-hour urine samples collected before and during 4 hours after the ingestion of calcium. Similar increments in serum ionized calcium (delta Ca2+) were observed except at P3 where the delta Ca2+ was significantly (P < 0.02) higher after 1500 mg (0.088 mmol/liter) than after 500 mg of (0.062 mmol/liter). In the same way, the comparison of the PTH 1-84 concentrations showed no statistical difference except at P3 (P < 0.002). When expressed as a percentage of P0, the P1 and P2 PTH 1-84 values were more suppressed after 1500 mg than after 500 mg of calcium (P1: -69% vs -59%; P < 0.02; P2: -66% vs -50%; P < 0.02). However, the simultaneous cyclic AMP responses (-24% vs -19%) were not significantly different. The results show that the respective maximal effects on PTH secretion and on urinary cyclic AMP of two very different oral doses of calcium are only slightly different.

Modification by phosphate of PTH-dependent renal cyclic AMP response.

The PTH response and the renal cAMP response obtained after oral administration of either tricalcium phosphate or calcium gluconolactate were compared in 12 young adult males. Each subject was studied during a control period of two hours before and during an experimental period of four hours after ingestion of a single oral dose of calcium salt. The respective dosages (1.2 g of calcium plus 0.6 g phosphorus for tricalcium phosphate; 0.5 g of calcium for gluconolactate calcium) were chosen to provide similar significant (p = 0.0001) increases in serum ionized calcium (from 1.23 to 1.29 mmol/l vs from 1.23 to 1.28 mmol/l). After tricalcium phosphate a modest (10%) but significant (p < 0.001) rise in serum phosphate was observed. In both series of experiments similar inhibitory effects on PTH circulating levels were obtained (from 22.6 to 12.4 pg/ml after tricalcium phosphate and from 24.1 to 10.6 pg/ml after calcium gluconolactate). After ingestion of calcium gluconolactate the renal secretion of cAMP fell from 12.68 to 8.64 nmol/l GF (p < 0.001), whereas no significant alterations of the mean values of nephrogenous cAMP were detected after ingestion of tricalcium phosphate. In accordance with the role of cAMP as a second messenger, after calcium gluconolactate we obtained a significant increase in tubular maximal reabsorption of phosphate (p < 0.0001) contrasting with the absence of significant effect after tricalcium phosphate. The present results confirm that suppression of PTH secretion only depends on the rise of serum ionized calcium and suggest that additional phosphate administration could have a decoupling effect between PTH and renal cAMP secretion.

Effect of dexamethasone on steroidogenesis and on adrenocortical cyclic AMP and cyclic GMP responses to ACTH.

The inhibitory action of dexamethasone on the adrenal steroidogenic response to ACTH was confirmed by im administration of graded doses (5, 10 and 30 ng) of synthetic beta 1-24 ACTH to young adult male rats which had received dexamethasone (0.1 mg/100 g bw) 4 hr prior to sacrifice. Following this, kinetic studies were performed by measuring plasma corticosterone, adrenocortical cyclic AMP and cyclic GMP before and 4, 12 and 30 min after administration of either 10 or 30 ng of ACTH. These doses were selected because their effects could be either completely or partially inhibited by dexamethasone. In rats without dexamethasone all the doses of ACTH which were checked induced an increase in both corticosterone and cyclic AMP and a decrease in cyclic GMP. With the smallest dose of ACTH the earlier administration of dexamethasone resulted in complete suppression of both the steroidogenic response and the cyclic AMP response. With the largest dose of ACTH both responses were diminished. In dexamethasone-treated rats the decrease in cyclic GMP was significantly less pronounced 4 min after ACTH than it was in non-treated rats. These results support the view that cyclic AMP and cyclic GMP might both be concerned with the mechanism of acute adrenal steroidogenesis.

Circadian variation of adrenocortical cyclic nucleotides (cyclic AMP and cyclic GMP) in hypophysectomized rats.

The existence of a circadian variation in the adrenocortical concentrations of cyclic AMP and cyclic GMP in male adult Wistar rats examined 10 days after hypophysectomy is demonstrated. The results suggest that the circadian variations of adrenocortical cyclic nucleotides observed previously in intact rats might not entirely depend upon pituitary corticotrophin.

Acute effects of an oral calcium load on markers of bone metabolism during endurance cycling exercise in male athletes.

Although sport and physical activity are generally considered as positive factors for bone metabolism some endurance trainings such as running and bicycling have few or no beneficial or even deleterious effects on bone mineral density. The present study was designed to investigate the acute effect of an intensive endurance cycling exercise on biochemical bone markers. Furthermore, the effect of the oral intake of 1 g calcium load, by drinking high-calcium mineral water, just prior to and during the exercise was checked. Twelve well-trained elite male triathletes aged 23-37 years were explored. The serum concentrations of calcium, phosphate, PTH, bone alkaline phosphatase (BALP) and C-terminal cross-linking telopeptide of type 1 collagen (CTX) were measured before, during and after a 60 min 80% VO2max cycle ergometer exercise. Since cycling exercise was accompanied by a reduction in plasma volume the total amount of biochemical bone markers was calculated. When the exercise was performed without calcium load both serum concentrations and total amount of CTX began to increase progressively 30 min after the start of the exercise and were still significantly elevated, by 45-50%, 2h after the end of the exercise. Ingestion of high-calcium mineral water completely suppressed the CTX response. By contrast serum concentrations and total amount of BALP fluctuated and showed no significant difference with or without calcium load. The present study demonstrates that the burst of osteoclastic activity acutely induced by an endurance cycling exercise can be suppressed by the previous intake of a calcium load afforded by drinking high-calcium mineral water.