Iron tissue storage and hemoglobin levels of deficient rats repleted with iron bound to the caseinophosphopeptide 1-25 of beta-casein.

Caseinophosphopeptides (CPP) issued from enzyme digestion of caseins bind cations and keep them soluble in the digestive tract. They could be used as ligands to improve iron (Fe) bioavailability. Fe-deficient young rats were repleted with Fe (40 or 200 mg/kg of diet) bound either to the beta-CN (1-25) of beta-casein or to whole beta-casein or as FeSO(4). A control pair-fed group was given 200 mg of Fe (FeSO(4))/kg of diet for 6 weeks. After repletion, hemoglobin concentration of the control group was reached only by the ) animals fed 200 mg of Fe/kg; beta-CN (1-25) bound Fe (40 and 200 mg) produced higher Fe liver and spleen stores than FeSO(4). Binding Fe to the whole, nonhydrolyzed beta-casein gave results intermediate between the other experimental groups. Binding Fe to phosphoserine residues of low molecular weight CPP improved its ability to cure anemia and to restore iron tissue stores, as compared to Fe bound to the whole casein and to inorganic salts.

Oct3/4-associating proteins from embryonal carcinoma and spermatogenic cells of mouse.

The octamer-binding protein Oct3/4 was postulated to active transcription through protein-protein interactions with hypothetical cellular coactivator(s). We have used a bacterially produced Oct3/4, as a protein-binding probe, to detect by far-Western assay the Oct3/4-associating proteins (OTAPs) from the embryonal carcinoma (EC) cells F9 and pachytene spermatocytes. Both common and cell-specific OTAPs were shown to interact directly with Oct3/4. Differentiation of the EC cells results in disappearance of most of OTAPs, supporting their coactivator nature. Several OTAPs detected in pachytene spermatocyte may represent germ cell-specific Oct3/4 coactivators.

Relationships between iron and zinc metabolism: predictive value of digestive absorption on tissue storage.

The responses of animals to intake of a trace element could vary if it is ingested with a single test meal or due to chronic intake. The metabolic relationships between zinc (Zn) and iron (Fe) were assessed in the young animal by comparing their digestive absorption studied at the beginning of the study with their tissue storage after two months of being fed on experimental diet. Diets supplied adequate intakes of Fe (45 and 300mg/kg diet) and Zn (14 and 45 mg/kg). A significant effect of Fe supply (p < 0.0001) but not of Zn was displayed on Fe absorption; both Fe and Zn diet concentrations influenced Zn absorption (p < 0.01, p < 0.0001). Fe and Zn organ contents significantly correlated with the amount absorbed during the metabolic balance (p < 0.0001). There was a positive correlation between liver, bone, and muscle Fe and Fe absorption (mg/d)(p < 0.0001), and Fe absorption and bone and muscle Zn (p < 0.04) and a negative one with liver Zn (p < 0.0001); a positive correlation was displayed between Zn absorption (mg/d) and Zn organ content (p < 0.0001). There was no correlation between Zn absorption and Fe tissue content (p > 0.05). This study suggests that interactions occur at every step of Fe and Zn metabolism; Fe is more efficient in altering Zn storage than the reverse. The organism seems to be unable to diminish the consequences of an unbalanced diet and digestive absorption. Care must be taken to give the young growing balanced diets.

Effect of small variations of aluminum intake on calcium metabolism in young rats.

BACKGROUND: While in the adult Al intoxication requires high dosages, little is known on the threshold level of Al toxicity in the young. METHODS: Weaning rats were fed for 90 days ore of four diets differing by their content in Ca (7.5 vs < 0.5 g/< g diet)(Ca+/-) and Al (10.6 vs 8.4 mg/kg)(Al+/-); Al supplementation was 30% above the standard level of diet. Ca and Al levels were measured in liver, bone (femur), and brain. RESULTS: Ca- had a significant negative effect on growth which was further reduced by Al+; in Ca sufficient/Al+ animals, Al concentrations were significantly increased in bone and brain and tended to increase in liver; Ca decreases observed in these three organs were only significant in brain. Ca deficiency further enhanced the Al deposit in bone at both levels of Al intakes, and reduced Ca concentrations in these three organs in Al+ animals; in Ca-/Al- animals, the decrease in Ca displayed in the three tissues reached a significant level in brain. CONCLUSIONS: This study suggests that in the growing subject the side effects of small variations of Al intake can be enhanced when they are combined with other mineral imbalances.

In vitro effects of Celiptium and MR 14504 on mature rat Leydig cell testosterone production.

Percoll-purified mature rat Leydig cells have been used to evaluate the testicular toxicity of two highly potent intercalating agents (Celiptium and MR 14505). Testosterone secretion in the absence and in the presence of human chorionic gonadotropin (hCG) was measured to assess Leydig cell function. Celiptium and MR 14504 induce time- and dose-related inhibitory effects on the production of testosterone by Leydig cells, both in the presence and in the absence of hCG, whatever the concentration of hCG used. We have observed that MR 14504 is about 5 times more potent as an inhibitor of rat Leydig cell steroidogenesis than Celiptium without inducing any cell toxicity. The present study indicates that the Leydig cell is an additional potential site for the primary toxic effects of these drugs in the adult rat testis.

Equine cytochrome P450 aromatase exhibits an estrogen 2-hydroxylase activity in vitro.

Aromatase (estrogen synthetase) is a steroidogenic enzyme complex which catalyzes the conversion of androgens to estrogens (termed aromatization). This enzyme was purified from adult equine testis to homogeneity by five chromatographic steps. The ability of purified and reconstituted equine aromatase to exhibit an estrogen 2-hydroxylase activity was tested and compared to testosterone aromatization. Enzymatic activities were assessed by tritiated water release from labelled estradiol and testosterone. Kinetic analysis of estradiol 2-hydroxylation showed an apparent K(m) of 23 microM and a V(max) of 18 nmol/min/mg, whereas the values for testosterone aromatization were a K(m) of 15.7 nM and a V(max) of 34.6 pmol/min/mg. A specific antiserum raised against purified testicular equine P450arom and known to inhibit aromatase activity [1] was also found to inhibit the estrogen hydroxylase activity of equine placental microsomes in a dose-dependent manner with an IC50 value of 15 microl serum: 0.5 ml incubate. The estrogen hydroxylase activity was inhibited in a dose-dependent manner by two classes of aromatase inhibitors, i.e. steroidal-- (4-hydroxyandrostenedione and 7alpha-([4-aminophenyl]thio)-androst-4-ene-3, 17-dione)--and non-steroidal--(fadrozole and miconazole). The IC50 values were approximately 300 and 890 nM for 4-hydroxyandrostenedione and 7alpha-([4-aminophenyl]thio)-androst-4-ene-3, 17-dione, and 92 and 285 nM, for fadrozole and miconazole, respectively. Furthermore, 4-hydroxyandrostenedione caused a time-dependent inactivation of estrogen hydroxylase activity. We conclude that equine aromatase is able to use estradiol as a substrate, and converts it to catechol estradiol in vitro, possibly using the active site of aromatization. This is the first demonstration that equine aromatase functions as an estrogen 2-hydroxylase, in addition to transforming androgens into estrogen.

Enzymatic properties of adult human Sertoli cells in vitro.

The adult human Sertoli cells produced lactate, estradiol-17beta, transferrin and inhibin; germ cells modulate synthesis of these compounds. In order to study the functional features of human Sertoli cells in vitro, the aim of this study was to measure the lactic dehydrogenase (LDH), gamma-glutamyl transpeptidase (GGT), alkaline phosphatase (ALP) and creatine kinase activities (CK) in primary cultures of Sertoli cells prepared from young men (mean age: 29 years, n = 11). Five LDH isozymes have been found in Sertoli cells, the main fractions being the LDH3 and LDH4; each of them represented 30% of the total LDH activity. Furthermore, CK and ALP activities were measured in Sertoli cells. It is of note that the Sertoli cell ALP activity was 50% lower than that of germ cells. Whatever the Sertoli cell parameter measured herein, there is a great variability between patients and FSH (dbc AMP, as well as retinol, insulin, testosterone) is poorly effective in improving these enzymatic activities in vitro. We have confirmed that GGT was exclusively present in Sertoli cells and thus may be considered as a specific marker. LDH is involved in Sertoli cell glucose transformation and thus provided energetic substrates for germ cells. In contrast, the roles of CK and ALP remains to be clarified. In conclusion, we have demonstrated the existence of several enzymes namely LDH, GGT, ALP and CK in Sertoli cells prepared from adult human testis.

Postprandial lipoprotein metabolism in normotriglyceridemic non-insulin-dependent diabetic patients: influence of apolipoprotein E polymorphism.

Non-insulin-dependent diabetes mellitus (NIDDM) is associated with postprandial lipoprotein clearance defects that are correlated with the fasting hypertriglyceridemia widely observed in NIDDM patients. The aim of this study was to determine if such postprandial disturbances are found in NIDDM patients strictly normotriglyceridemic in the fasting state, and if the apolipoprotein E (apo E) polymorphism influences postprandial metabolism of intestinally derived lipoproteins. The vitamin A-fat loading test was used in 18 normotriglyceridemic NIDDM patients and seven normotriglyceridemic obese controls, and postprandial triglyceride (TG) and retinyl palmitate (RP) concentrations were evaluated in total plasma, and in the chylomicron (Sf > 1,000) and nonchylomicron (Sf < 1,000) fractions isolated by ultracentrifugation. NIDDM patients exhibited an amplified response of both TG and RP as compared with obese controls in the three fractions. Incremental TG response to the oral fat load was strongly correlated with fasting TG level (r = .80, P < .0001) in the whole study population. Postprandial lipoprotein profiles were distinguished in NIDDM patients according to apo E phenotype: despite normal fasting TG levels in E3/3 (n = 6), E2/3 (n = 6), and E3/4 (n = 6), postprandial RP response was twofold to threefold higher in E2/3 and E3/4 patients than in the common E3/3 phenotype. Contrasting lower postprandial TG increment and lower fasting and postprandial high-density lipoprotein (HDL) and HDL3 cholesterol levels were observed in E3/4 versus E3/3 patients, possibly reflecting modifications in lipid content of the postprandial lipoproteins driven by a differential lipid transfer activity depending on apo E isoform. These data indicate an enhanced postprandial lipemia in normotriglyceridemic NIDDM patients, and demonstrate the influence of apo E polymorphism on their lipoprotein clearance. Postprandial alterations of lipoprotein remnants may thus accelerate atherogenesis even in normotriglyceridemic NIDDM patients.

Determination of metallothioneins by HPLC: application to zinc metabolism.

Metallothioneins (MT) are well known Zn and Cu tissue proteins. Their level is mainly regulated by Zn. Therefore, they have been suggested as an index of Zn status. The determination of MT has been performed by HPLC (fitted with UV-detector) following a preparation phase (heating, ultracentrifugation and filtration). This method allows direct quantification of MT in tissues and shows a good correlation between MT concentrations and peak heights (r2 = 0.995; a = 774.73; b = -148.38) from 0 to 10 micrograms/100 microL. MT determination by RP-HPLC method allows to assess the tissue zinc status as displayed by the correlation between hepatic zinc and metallothionein concentrations (r2 = 0.82; p < 0.001). Variations of MT in response to Zn intakes are observed within 24 hours and for a physiological range of dietary Zn intakes.

Steroidogenesis in the two enriched-Leydig cell populations of human testis: evidence for a positive control by seminiferous tubules secreted factor(s).

In two different enriched populations of Leydig cells (called FI and FII) obtained from human testes (young patients: mean age 36 +/- 3 years, n = 6; aged men: mean age 73 +/- 2 years, n = 5), the dehydroepiandrosterone and testosterone in vitro outputs were increased in a dose- and time-related manners by hCG. Similar results were obtained when the Leydig cells were incubated in presence of either dbcAMP or 22R-hydroxycholesterol. In presence of either hCG or dbcAMP, the coefficient of stimulation (in terms of steroid outputs) was higher in FII when compared to FI. Conversely, the basal production of steroids was greater in FI than in FII, mainly for testosterone. The addition of increasing amounts of seminiferous tubule culture medium (STM) to the Leydig cell incubation medium led to a dose-related enhancement of the steroid production in both enriched-Leydig cell fractions under basal and hCG-stimulated conditions. Similar results were obtained in presence of increased seminiferous tubules length. Additional experiments realized with either concentrated STM or the coculture of seminiferous tubules with purified Leydig cells have confirmed the existence of a paracrine control of Leydig cell steroidogenesis by seminiferous secreted factor(s). A paracrine factor (or factors) from seminiferous tubular origin influences positively and with a high efficiency the Leydig cell function in humans, whatever the age.

Germ cell and Sertoli cell interactions in human testis: evidence for stimulatory and inhibitory effects.

In human Sertoli cell preparations obtained from healthy men (mean age 31.8 +/- 6.8 years; n = 6), we have measured the productions of lactate, 17 beta-oestradiol, transferrin and inhibin between day 4 and day 5 after plating, either in the presence or absence (hypotonic treatment of plated cells on day 2) of germ cells. The results, expressed per 10(6) of cells plated/24 h, showed that lactate production was unchanged, whether or not germ cells were present. However, if we calculated the lactate production per mg protein/24 h, the lactate output was decreased (30-60%) in the presence of germ cells. Whatever the mode of expression, Sertoli cell 17 beta-oestradiol synthesis was diminished 1.5-fold in the presence of germ cells. Conversely, the transferrin output was increased 3.2-fold in non-treated Sertoli cell preparations when compared to the hypotonic-treated plates. A similar observation was recorded for the in-vitro production of inhibin by Sertoli cells, which was enhanced 1.4-fold when germ cells were present. These results, together with a likely potentializing role of germ cells on follicle stimulating hormone control of Sertoli cell function, strongly suggest that germ cells exert both stimulatory and inhibitory effects in regulating human Sertoli cell function through either direct contact and/or via secreted factors.

[Physiological variations of LpA1, HDL2 and principal lipid markers in athletes]. / Variations physiologiques de la LpA1, des HDL2 et des principaux marqueurs lipidiques chez l'homme sportif.

An original approach of the influence of physical activities on lipid metabolism is presented in this work: the authors studied the physiological variations of the lipoparticle LpA1, high-density lipoprotein subfraction HDL2 and the most important lipid markers in serum of a presumably healthy population of 55 high-level sportsmen. They were 18-45 years old and practised endurance sports, whether individual (cycling, long-distance running), or collective activities (soccer, basketball). The authors observed an important increase of LpA1 (+20%, p < 0.001) and C-HDL2 (+23.3%, p < 0.01) after an intense physical activity (CK = 430 +/- 312 U/l); they also found a good correlation between LpA1 and HDL2 (r = 0.85, p < 0.0001) and between LpA1 and CK (r = 0.62, p < 0.001).

[Sertoli cells. Functional aspects compared in rats, pigs and man]. / La cellule de Sertoli. Aspects fonctionnels comparés chez le rat, le porc et l'homme.

In the mammalian testis, the Sertoli cell plays a key role in the development and maintenance of spermatogenesis. Indeed, within the seminiferous tubule, the structure of the Sertoli cells and the specialized junctions between them and the neighbouring germ cells, contribute to create the sophisticated microenvironment and to bring all the nutriments require for a full development of germ cells. In this review, we have compared the main Sertoli cell functions in the rat and the pig to the available data concerning the human. We have included our recent results obtained from testicular tissues of 15 young men (mean age: 29 years) from which we have prepared the Sertoli cells. In addition to the lactate and estradiol-17 beta syntheses, the human Sertoli cell produces several proteins, namely transferrin, ferritin and inhibin under the control of germ cells.

Chromium and parenteral nutrition in children.

Chromium (Cr) dosage was assayed in i.v. nutrition, serum, and losses of five children on total parenteral nutrition for > or = 4 weeks. The Cr supply (4.7 +/- 1.2 micrograms/kg/day) was above recommended levels (0.5 microgram/kg/day). Serum (18.2 +/- 1.8 micrograms/L) and urine (37.4 +/- 10.5 micrograms/L) were also higher than control values (0.7-0.9 microgram/L and 0.2-0.8 microgram/L, respectively). Serum and urine Cr concentrations displayed a positive correlation. Serum Cr and Fe showed a negative correlation. These results confirm the potential toxicity of Cr previously reported in animals. Cr levels of i.v. nutrition solutes should be checked thoroughly.

Human Sertoli cells in vitro. Lactate, estradiol-17 beta and transferrin production.

Human Sertoli cell parameters, namely lactate, estradiol-17 beta, and transferrin production, were determined after a 24-hour incubation with either human follicle stimulating hormone (FSH) or dbcAMP in the presence or absence of testosterone plus a phosphodiesterase inhibitor (1-methyl-3-isobutylxanthine; MIX). Testicular tissues were obtained from 10 young patients (mean age, 29 years); using a 3-step enzymatic treatment, Sertoli cell enriched preparations (> 92%) were studied after 4 days as primary cultures. No significant changes in lactate, estradiol-17 beta, and transferrin outputs have been observed according to age in patients ranging in age from 16 years to 47 years. Sertoli cell production of the compounds is controlled by testosterone plus MIX; FSH (or dbcAMP) treatment only slightly improves their synthesis. It is suggested that human Sertoli cell function, as far as the parameters measured in this study are concerned, is likely regulated by cAMP-dependent and independent pathways.

Germ cell-Sertoli cell interactions and production of testosterone by purified Leydig cells from mature rat.

The addition of seminiferous tubule (ST) culture medium (STM) prepared from testes of either busulfan-treated (Bus) or cryptorchid (Cryp) or genetically sterile (hd) rats, to Percoll purified Leydig cells leads to a further increase of LH-stimulated testosterone (T) output (26, 43 and 14%, respectively). Taking into account that the Sertoli cell number per cm of ST is 2.6, 1.8 and 1.4-fold greater in Bus, Cryp and hd rats than in controls, the above STM effects on T output, expressed per 10(6) Sertoli cells are in fact lower (63, 44 and 43%, respectively) that those of control STM. Similar results have been obtained for the STM transferrin levels which are decreased, 74, 67 and 45%, respectively in Bus, Cryp and hd animals. So, it is likely that the Sertoli cell secretion of both the paracrine factor involved on Leydig cell T production and the transferrin is influenced mainly by spermatids and to a lesser extent by spermatocytes of mature rat testis.

Chromium status of full-term and preterm newborns.

In order to obtain reference values from normal babies, Cr status of full-term newborns has been studied. Plasma and urine values were (mean +/- SEM) 0.7 +/- 0.1 micrograms/L and 0.9 +/- 0.3 micrograms/L, respectively, for the first month of life (n = 19), and 0.6 +/- 0.1 micrograms/L and 0.8 +/- 0.2 micrograms/L for the second-to-third-month period (n = 31). Premature newborns (gestational age 28-36 wk) were compared to these control values; concentrations were 0.9 +/- 0.1 micrograms/L and 1.1 +/- 0.2 micrograms/L for the first month (n = 47), and 1.0 +/- 0.2 micrograms/L and 1.5 +/- 0.3 micrograms/L for the second to third months (n = 27). For the whole group, there was a positive correlation between plasma and urine concentrations (p = 0.0001); multiple regression analysis was performed between plasma levels and gestational age at birth (p = -0.002) and postnatal age (NS). Plasma levels of prematures and full terms were statistically different (p = 0.03) only for the second- to third-month period. It is suggested that these high Cr levels result from high dietary intakes and/or high absorption rates.