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Biomedical subjects

S Guillemant

Publications and source records attributed to S Guillemant.

At least 37 records · Page 2Linked to original sources
PubMed1993

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.

Adult↗
PubMed1992

[Laparoscopic surgery versus laparotomy. Comparative analysis of stress markers].

The place of laparoscopic surgery continues to increase in the field of surgery in our specialty. Although the advantages would seem to be obvious, it seemed to us interesting to quantify, if possible, the parameters of operative stress and compare laparoscopic surgery with conventional surgery. Markers studied are Prolactin, Cortisol, Adrenaline, Nor-Adrenaline, Dopamine and the Beta-Endorphins. The only marker that shows any difference in the two procedures in our study is Beta-Endorphin which is significantly less raised in laparoscopic surgery directly after the operation (p less than 0.01). This was very specific for pain, which is one of the benefits of this technique and shown in this parameter which confirms the clinical impression. The curves of the changes in the different markers have been analysed and discussed.

Adult↗
PubMed1991

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.

Adult↗
PubMed1991

[Exploration of the parathyroid gland function by intake or oral calcium and phosphate (only oral intake and sequential treatment with calcium-phosphate)].

The parathyroid hormone response to the oral intake of either calcium or phosphate was explored in 10 young adults (23-28 years). First, the subjects were investigated during free running diet. They ingested a single oral dose of 500 mg of calcium (as a bag of Sandocal) and 10 days later a single oral dose of phosphate (750 mg of phosphorus as a tablet of Phosphore Sandoz Forte). Samples of blood and urine were collected before and during the 4 hours following the ingestion of either calcium or phosphate. After intake of calcium an acute response was obtained with a 58% decrease in PTH 1-84 at 1 hr (p less than 0.001) and a 33% decrease in nephrogenous cAMP (p less than 0.001). After ingestion of phosphate the response was delayed and less constant with a 25% increase in PTH 1-84 at 3 hr (p less than 0.01) and a 27% increase in nephrogenous cAMP (p less than 0.001). Then, the effects of a calcium therapy (3 daily doses of 500 mg each for 20 days) and of a subsequent phosphate therapy (2 daily doses of 750 mg each for 10 days) on the parathyroid hormone response to the administration of a single dose of phosphate were studied. On days 10, 21 and 31 baseline blood and urine samples were obtained prior to calcium and phosphate administration for measuring PTH 1-84 and nephrogenous cAMP. No significant variation was found. On days 21 (after calcium therapy) and 31 (after phosphate therapy) an oral load of phosphate was administered according to the procedure described above.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1989

[Primary hyperparathyroidism: value of "intact parathormone" assay (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.

Calcium↗
PubMed1989

Effect of vitamin D3 administration on serum 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3 and osteocalcin in vitamin D-deficient elderly people.

In elderly institutionalized people, confined to bedroom and receiving no vitamin D supplementation, the frequency of vitamin D deficiency is found very high. Systematic administration of vitamin D has, therefore, been proposed to correct vitamin D deficiency. Within this context, we studied 40 elderly institutionalized subjects (mean age 80.5 + 7.2 yr) with low 25(OH)D3 concentrations (4.4 + 1.8 micrograms/l). Sixteen of them (Group I) had low serum calcium concentrations (less than 2.3 mmol/l) and 24 (Group II) had normal serum calcium concentrations (from 2.3 to 2.6 mmol/l). As hypocalcemia has been shown to regulate 1,25(OH)D3 production independent of PTH in animals and in humans, we compared their respective responses to the administration of vitamin D3. Subjects received a total dose of 15 mg (600,000 IU) of vitamin D3 divided into 3 i.m. injections at one month intervals and were explored before therapy and one and 6 months after the last dose of vitamin D3. The treatment induced a similar marked rise in 25(OH)D3 levels (from 4.1 + 1.7 to 24.4 + 8.7 micrograms/l for group I and from 5.1 + 1.8 to 27.2 + 8.0 micrograms/l for group II) in both groups but increased the 1,25(OH)2D3 concentrations only in group I (from 22.9 + 6.9 to 32.6 + 11.3 ng/l). Meanwhile serum calcium concentrations rose in group I (to low normal range i.e. 2.31 + 0.07 mmol/l) and were unaffected in group II. These results suggest that hypocalcemia is a potent stimulator of renal 1-hydroxylase in elderly people. Furthermore, a transient significant (P less than 0.01) increase in serum osteocalcin (from 10.6 + 4.1 to 14.1 + 5.9 micrograms/l) could be observed in group I which demonstrates for the first time that the osteocalcin response of osteoblasts to stimulation by 1,25(OH)2D3 is retained in very old people.

Aged↗
PubMed1986

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)

Adrenal Cortex↗
PubMed1985

[Vitamin D deficiency in long-stay geriatric patients. Study of a therapeutic protocol adapted to the institutional milieu].

A vitamin D deficiency was observed in 22 women and 6 men aged 66 to 94 years, hospitalised in a long-stay department in the Paris region for an average of 5 years and incapable of going out. The diagnosis was confirmed by measuring serum 25 (OH) D: 1.89 +/- 0.18 ng/ml during the month of June (11.5 +/- 4.2 ng/ml at the same period in II healthy young adults). The patients were randomly divided into two groups of 11 (Group I) and 17 patients (Group II). The first group was given an improved diet in calcium and Vit. D; the second group received, in addition, an intramuscular supplement of 30 mg of Vit. D3 in monthly injections of 5 or 10 mg. The serum 25 (OH) D levels were measured each month in both groups. Patients with intramuscular supplements showed a slow rise until the total injected dose exceeded 20 mg, followed by a sudden rise to values greater than 30 ng/ml. Eight months after the last injection, mean serum 25 (OH) D was still 24.7 +/- 4.6 ng/ml compared to only 3.6 +/- 3 ng/ml in Group I. Vitamin D deficiency in geriatric patients cannot be corrected by dietary supplement alone, but parenteral Vit. D3 using an easily applicable therapeutic protocol is effective and well tolerated at the suggested dosage.

Aged↗
PubMed1984

Androgen metabolism in hirsute patients treated with cyproterone acetate.

Cyproterone acetate (CPA) in association with percutaneously administered estradiol has been used for the treatment of 150 hirsute patients for periods ranging from 6 months to 3 years. A spectacular clinical improvement ensued. Plasma testosterone (T) and androstenedione (A) fell from 69.0 +/- 24 to 33.0 +/- 8 and 210 +/- 103 to 119 +/- 25 ng/dl (mean +/- SD) respectively after 3 months of treatment and remained low thereafter. In contrast, T glucuronide (TG) and 3 alpha-androstanediol (Adiol) remained high during the whole course of treatment: 37 +/- 9 and 115 +/- 43 micrograms/24 h respectively. In vitro T 5 alpha-reductase activity (5 alpha-R) in pubic skin decreased from 147 +/- 34 to 79 +/- 17 fmol/mg skin after 1 year of treatment. To elucidate the discrepancy between plasma and urinary androgens levels, T production rate (PR) and metabolic clearance rate (MCR) were measured with the constant infusion technique in 7 patients before and after 6 months of treatment. PR decreased from 988 +/- 205 to 380 +/- 140 micrograms/24 h (mean +/- SD). In contrast MCRT increased from 1275 +/- 200 to 1632 +/- 360 1/24 h; this increase in MCRT explains the striking plasma T concentration fall and the high TG and Adiol excretion relative to the decrease in PR. Antipyrine clearance rate (n = 8) increased from 36.3 +/- 5.2 to 51.5 +/- 7.4 ml/min whereas 6 beta hydroxycortisol remained unchanged. In conclusion, CPA acts through several mechanisms: (1) it lowers the androgen input to the target cells by (a) depressing T production through its antigonadotropic effect and (b) accelerating T metabolic inactivation due to a partial enzymatic inducer effect on the liver; (2) at the target cell level it competes with any remaining T for the receptor binding sites; (3) the decrease in the androgen-dependent skin 5 alpha-R is a consequence of both actions of androgen suppression and androgen receptor blockade; it reinforces the antiandrogenic effect of CPA.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1983

Effect of dithiothreitol on the 1 alpha, 25-dihydroxyvitamin D3 chick intestinal receptor analyzed by polyacrylamide gel electrophoresis.

This is the first report of the use of non-denaturing polyacrylamide gel electrophoresis (PAGE) to measure the apparent molecular weight of the chick intestinal 1 alpha, 25-dihydroxyvitamin D3 (1, 25-(OH)2 - D3) receptor and to study the effect of dithiothreitol on it. When prepared in the absence of this factor, chick intestinal cytosol contained one major specific 1,25 - (OH)2 - D3 binding peak. Its apparent molecular weight was 95,200 +/- 1,900 (SD) daltons. Preparation of the cytosol in the presence of 5 mM dithiothreitol resulted in the appearance, besides the 95,000 daltons peak, of an additional 1,25 - (OH)2 - D3 binding peak, the molecular weight of which was 73,600 +/- 3,300 (SD). This effect of dithiothreitol could be suppressed by the simultaneous addition of 10 mM N alpha-p-tosyl-L-arginine methyl ester (TAME), a protease inhibitor.

Animals↗
PubMed1983

[The mechanism of action of cyproterone acetate in the treatment of hirsutism].

Cyproterone acetate (CPA) in association with percutaneously offinistered estradiol has been used for the treatment of 150 hirsute patients for periods ranging from 6 months to 3 years. A spectacular clinical improvement ensued. Plasma testosterone (T) and androstenedione (A) fell from 69 +/- 24 to 33 +/- 8 and 210 +/- 103 to 119 +/- 25 ng/dl (mean +/- SD) respectively after 3 months of treatment and remained low thereafter. In contrast, T glucuronide (Tg) and 3 alpha-androstanediol (Adiol) remained high during the whole course of treatment: 37 +/- 9 and 115 +/- 43 micrograms/24 h respectively. In vitro T 5 alpha-reductase activity (5 alpha-R) in pubic skin decreased from 147 +/- 34 to 79 +/- 17 fmol/mg skin after 1 year of treatment. To elucidate the discrepancy between plasma and urinary androgens levels, T production rate (PR) and metabolic clearance rate (MCR) were measured with the constant infusion technique in 6 patients before and after 6 months of treatment. PR decreased from 988 +/- 205 to 380 +/- 140 micrograms/24 h (mean +/- SD). In contrast MCRT increased from 1275 +/- 200 to 1632 +/- 360 1/24 h; this increase in MCRT explains the striking plasma T concentration fall and the high TG and Adiol excretion relative to the decrease in PR. Antipyrine clearance rate (n = 8) increased from 36.3 +/- 5.2 to 51.5 +/- 7.4 ml/min whereas urinary/6 beta hydroxycortisol remained unchanged. In conclusion, CPA acts through several mechanisms:(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1982

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.

Adrenal Cortex↗
PubMed1982

[Absorption and metabolism of labelled vitamin D3 in elderly subjects].

This study involved three adult men and six elderly individuals (3 men and 3 women). Adult subjects served as the control group. All subjects were given one dose of 10 microCi of tritiated vitamin D3 (approximately 15 IU) per os. Blood samples were taken 5 min., 1 h, 2 h, 3 h, 4 h, 6 h, 8 h, 24 h, 48 h, 72 h, 96 h, 120 h, 144 h, 168 h and 192 h after administration of vitamin D3. The concentrations of tritiated vitamin D3 and 25-hydroxyvitamin D3, its principal metabolite, were measured in each sample after extraction and purification by high performance liquid chromatography (HPLC). In addition, two adult subjects and three elderly women subjects were given an identical dose of tritiated vitamin D3 approximately 10 days following the end of the initial experience. Blood samples were collected at the times indicated above and analyzed in identical fashion. The percentage of intestinal absorption of vitamin D3 and the amount of vitamin D3 metabolized to 25-hydroxyvitamin D3 were calculated as were the time constants for vitamin D3 and 25-hydroxyvitamin D3 disappearance curves. Review of these parameters confirmed that significant individual variations exist for intestinal absorption of vitamin D3. Study results did not furnish any evidence of a decrease in 25-hydroxylation of vitamin D3, nor any increase in the rate of disappearance of vitamin D3 or 25-hydroxyvitamin D3 which might explain the very low levels of 25-hydroxyvitamin D3, often found in aged persons.

Administration, Oral↗