Short- and long-term effects of maternal perinatal undernutrition are lowered by cross-fostering during lactation in the male rat.

Undernutrition exposure during the perinatal period reduces the growth kinetic of the offspring and sensitizes it to the development of chronic adult metabolic diseases both in animals and in humans. Previous studies have demonstrated that a 50% maternal food restriction performed during the last week of gestation and during lactation has both short- and long-term consequences in the male rat offspring. Pups from undernourished mothers present a decreased intrauterine (IUGR) and extrauterine growth restriction. This is associated with a drastic reduction in their leptin plasma levels during lactation, and exhibit programming of their stress neuroendocrine systems (corticotroph axis and sympatho-adrenal system) in adulthood. In this study, we report that perinatally undernourished 6-month-old adult animals demonstrated increased leptinemia (at PND200), blood pressure (at PND180), food intake (from PND28 to PND168), locomotor activity (PND187) and altered regulation of glycemia (PND193). Cross-fostering experiments indicate that these alterations were prevented in IUGR offspring nursed by control mothers during lactation. Interestingly, the nutritional status of mothers during lactation (ad libitum feeding v. undernutrition) dictates the leptin plasma levels in pups, consistent with decreased leptin concentration in the milk of mothers subjected to perinatal undernutrition. As it has been reported that postnatal leptin levels in rodent neonates may have long-term metabolic consequences, restoration of plasma leptin levels in pups during lactation may contribute to the beneficial effects of cross-fostering IUGR offspring to control mothers. Collectively, our data suggest that modification of milk components may offer new therapeutic perspectives to prevent the programming of adult diseases in offspring from perinatally undernourished mothers.

Maternal perinatal undernutrition has long-term consequences on morphology, function and gene expression of the adrenal medulla in the adult male rat.

Epidemiological studies suggest that maternal undernutrition sensitises to the development of chronic adult diseases, such as type 2 diabetes, hypertension and obesity. Although the physiological mechanisms involved in this 'perinatal programming' remain largely unknown, alterations of stress neuroendocrine systems such as the hypothalamic-pituitary-adrenal (HPA) and sympathoadrenal axes might play a crucial role. Despite recent reports showing that maternal perinatal undernutrition disturbs chromaffin cells organisation and activity in male rats at weaning, its long-term effects on adrenal medulla in adult animals are unknown. Using a rat model of maternal perinatal 50% food restriction (FR50) from the second week of gestation until weaning, histochemistry approaches revealed alterations in noradrenergic chromaffin cells aggregation and in cholinergic innervation in the adrenal medulla of 8-month-old FR50 rats. Electron microscopy showed that chromaffin cell granules exhibited ultrastructural changes in FR50 rats. These morphological changes were associated with reduced circulating levels and excretion of catecholamines. By contrast, catecholamine plasma levels were significantly increased after a 16 or 72 h of fasting, indicating that the responsiveness of the sympathoadrenal system to food deprivation was accentuated in FR50 adult rats. Among 384 pituitary adenylate cyclase-activating polypeptide-sensitive genes, we identified 129 genes (33.6%) that were under expressed (ratio < 0.7) in FR50 animals. A large number of these genes are involved in cytoskeleton remodelling and vesicle trafficking. Taken together, our results show that maternal perinatal undernutrition programmes adrenomedullary function and gene expression in adult male rats. Because catecholamines contribute to metabolic homeostasis, as well as arterial blood pressure regulation, the alterations observed in the adrenal medulla of adult male FR50 rats may participate in the programming of chronic adult diseases.

O-GlcNAcylation, an original modulator of contractile activity in striated muscle.

There is growing evidence that O-linked N-acetyl-D-glucosaminylation, more simply termed O-GlcNAcylation or O-GlcNAc, is a post-translational modification involved in many cellular processes from transcription to modulation of protein properties. O-GlcNAc is a dynamic and reversible glycosylation and therefore quite similar to the phosphorylation/dephosphorylation process, with which O-GlcNAc can interplay. Since O-GlcNAc serves as a glucose sensor by the way of hexosamine biosynthesis pathway, this glycosylation is often associated with glucose toxicity and development of insulin resistance. In this way, O-GlcNAc could be involved in muscle pathological consequences of diabetes. Nevertheless, in regards of several studies performed in healthy striated muscles, O-GlcNAc seems to exert protective effects against different types of injuries. Recent new insights suggest a key implication of O-GlcNAc in skeletal and cardiac muscles contractile activity, in particular by O-GlcNAc modification of motor as well as regulating contractile proteins. While evidence linked O-GlcNAc to the regulation of calcium activation properties, its exact role remains to be defined as well as the existence of potential interference with phosphorylation. The better understanding of the exact function of OGlcNAc in this physiological process could contribute to the determination of newly markers of skeletal dysfunctions.

Childhood spinal muscular atrophy induces alterations in contractile and regulatory protein isoform expressions.

AIMS: Although modifications of the survival motor neurone gene are responsible for most spinal muscular atrophy (SMA) cases, the molecular pathophysiology and the muscular target proteins involved are still unknown. The aim of this study was to compare the expression of contractile and regulatory protein isoforms in quadriceps muscles from SMA children with age-matched control quadriceps. METHODS: The isoform patterns of myosin heavy chains (MHC), troponin subunits (T, C and I) and tropomyosin were determined by immunoblotting, reverse transcription-polymerase chain reaction and mass spectrometry analyses. Depending on the disease severity, their expression levels were followed in specific variants of SMA populations (types I, II and III), with comparison with age-matched control muscles. RESULTS: The isoform transitions in SMA muscles were different from the fast-to-faster transitions occurring in normal muscles from children aged 1 month to 5 years old. Moreover, the expression of the neonatal MHC isoform was not repressed in SMA muscles. CONCLUSIONS: The presence of the neonatal MHC isoform in SMA muscles indicates an alteration of the phenotype in these diseased muscles. It is strongly suggested that MHC and troponin T proteins may be good markers for the SMA pathology.

Dual effect of deafferentation on contractile characteristics and sarcoplasmic reticulum properties in rat soleus fibers.

The neural message is known to play a key role in muscle development and function. We analyzed the specific role of the afferent message on the functional regulation of two subcellular muscle components involved in the contractile mechanism: the contractile proteins and the sarcoplasmic reticulum (SR). Rats were submitted to bilateral deafferentation (DEAF group) by section of the dorsal roots L(3) to L(5) after laminectomy. Experiments were carried out in single skinned fibers of the soleus muscle. The maximal force developed by the contractile proteins was increased in the DEAF group compared with control, despite a decrease in muscle mass by 17%. The tension-pCa relationship was shifted toward lower calcium (Ca(2+)) concentrations. Different functional properties of the SR of DEAF soleus were examined by using caffeine-induced contractions. The caffeine sensitivity of the Ca(2+) release was decreased after deafferentation and ryanodine receptor 1 isoform was expressed at a lower level. The rate of Ca(2+) uptake was only slightly increased. The results underlined the dual effect of the afferent input on the functional regulation of both contractile proteins and SR.

Effect of natriuretic peptides on in vitro stimulated adrenocorticotropic hormone release and pro-opiomelanocortin mRNA expression by the fetal rat pituitary gland in late gestation.

OBJECTIVE AND METHODS: We investigated the effects of individual natriuretic peptides (atrial natriuretic peptide, ANP; brain natriuretic peptide, BNP, and C-type natriuretic peptide, CNP) on rat corticotropin-releasing factor stimulated adrenocorticotropic hormone (ACTH) secretion by the pituitary gland of 21-day-old rat fetuses in vitro and on pro-opiomelanocortin gene expression using in situ hybridization. RESULTS: Graded concentrations of ANP, BNP, or CNP (10(-10), 10(-9), and 10(-8) mol/l) induced a log dose dependent inhibition of ACTH secretion induced by rat corticotropin-releasing factor (10(-10) mol/l). These natriuretic peptides showed equipotent effects on a molar basis. Moreover, ANP, BNP, or CNP at 10(-10) mol/l reduced significantly the pituitary pro-opiomelanocortin mRNA expression. In addition, the immunoreactive ANP, BNP, and CNP cells were localized in the anterior lobe, but not in the intermediate lobe of the fetal pituitary gland. CONCLUSIONS: These data suggest that the fetal pituitary gland may be both a source and a target for natriuretic peptides that might control ACTH synthesis and release via an endocrine and/or paracrine mechanism. The natriuretic peptides could participate, as well as glucocorticoids, in the control of the corticotropin-stimulating activity of the fetal rat in late gestation.

Metyrapone-induced glucocorticoid depletion modulates tyrosine hydroxylase and phenylethanolamine N-methyltransferase gene expression in the rat adrenal gland by a noncholinergic transsynaptic activation.

The hypothalamic corticotropin-releasing hormone system and the sympathetic nervous system are anatomically and functionally interconnected and hormones of the hypothalamic-pituitary-adrenocortical axis contribute to the regulation of catecholaminergic systems. To investigate the role of glucocorticoids on activity of the adrenal gland, we analysed plasma and adrenal catecholamines, tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) mRNA expression in rats injected with metyrapone or dexamethasone. Metyrapone-treated rats had significantly lower epinephrine and higher norepinephrine production than control rats. Metyrapone increased TH protein synthesis and TH mRNA expression whereas its administration did not affect PNMT mRNA expression. Dexamethasone restored plasma and adrenal epinephrine concentrations and increased PNMT mRNA levels, which is consistent with an absolute requirement of glucocorticoids for PNMT expression. Adrenal denervation completely abolished the metyrapone-induced TH mRNA expression. Blockage of cholinergic neurotransmission by nicotinic or muscarinic receptor antagonists did not prevent the metyrapone-induced rise in TH mRNA. Finally, pituitary adenylate cyclase activating polypeptide (PACAP) adrenal content was not affected by metyrapone. These results provide evidence that metyrapone-induced corticosterone depletion elicits transsynaptic TH activation, implying noncholinergic neurotransmission. This may involve neuropeptides other than PACAP.

Activities of the pituitary-adrenal and gonadal axes during the estrous cycle in adult female rats prenatally exposed to morphine.

The present investigation concerns 80-90-day-old female rats born from morphine-exposed mothers (2x10 mg/kg per day from day 11-18 of gestation) or saline-treated ones (controls). The former showed reduced size and activity of the adrenals at birth. At adult stage, they present: (1) higher increase of plasma adrenocorticotrophic hormone level on proestrus; (2) significant rise of plasma corticosterone level on diestrus morning and estrus evening; (3) adrenal atrophy which was significant only on diestrus and estrus morning; (4) more corticosterone binding sites of type I (mineralocorticoid receptors) on proestrus morning in the hippocampus; (5) more corticosterone binding sites of type II (glucocorticoid receptors) in the hippocampus on proestrus morning and in the hypothalamus on estrus morning. In both experimental groups, B(max) for hypothalamic mineralocorticoid receptors were drastically higher on estrus morning than on the other stages of the estrous cycle. The activity of the pituitary-gonadal axis is poorly affected by prenatal morphine-exposition. In both experimental groups drastic and comparable surges of both plasma progesterone and luteinizing hormone were observed during proestrus. Nevertheless morphine-exposed females showed higher levels of plasma estradiol on diestrus morning but lower levels on metestrus morning. In conclusion, prenatal exposition to morphine has long-term effects mainly on pituitary-adrenal axis as well as on binding sites for corticosterone in the hypothalamus and the hippocampus which are dependent on the estrous cycle stages in adult females.

Plasticity of monkey triceps muscle fibers in microgravity conditions.

We examined the changes in functional properties of triceps brachii skinned fibers from monkeys flown aboard the BION 11 satellite for 14 days and after ground-based arm immobilization. The composition of myosin heavy chain (MHC) isoforms allowed the identification of pure fibers containing type I (slow) or type IIa (fast) MHC isoforms or hybrid fibers coexpressing predominantly slow (hybrid slow; HS) or fast (hybrid fast) MHC isoforms. The ratio of HS fibers to the whole slow population was higher after flight (28%) than in the control population (7%), and the number of fast fibers was increased (up to 86% in flight vs. 12% in control). Diameters and maximal tensions of slow fibers were decreased after flight. The tension-pCa curves of slow and fast fibers were modified, with a decrease in pCa threshold and an increase in steepness. The proper effect of microgravity was distinguishable from that of immobilization, which induced less marked slow-to-fast transitions (only 59% of fast fibers) and changed the tension-pCa relationships.

Morphine-induced stimulation of pituitary-adrenocortical activity is mediated by activation of nitric oxide in the early stages of postnatal life in the rat.

OBJECTIVE: The first aim of the present study was to determine if morphine, a prototypic mu-opioid agonist drug, affects pituitary-adrenocortical activity in developing rat pups (first and second weeks of postnatal life). The second aim of this study was to explore, in vivo, if nitric oxide (NO) could be involved in the neurohormonal response to morphine in the early stages of postnatal life. METHODS: Plasma ACTH and corticosterone concentrations were determined by RIA in rat pups (n=5-14 rats/experimental group) after they had been killed by decapitation. In a first experiment, 1-day and 1- and 2-week-old rats were treated s.c. with morphine (20 mg/kg) or with vehicle (0.9% NaCl) and killed 5-90 min later. In a second experiment, 2-week-old pups were pretreated s.c. with naltrexone (NAL; 0.4 mg/kg or 10 mg/kg), and injected 1 h later with either morphine (20 mg/kg) or vehicle, and killed 30 min later. Some pups injected with only NAL were killed 60 or 90 min later. On the other hand, pups injected with NAL (10 mg/kg) or NAL and morphine were killed 30 min later. In a third experiment, 2-week-old pups were pretreated s.c. with N-omega-nitro l arginine methyl-ester (L-NAME; 30 mg/kg or 100 mg/kg), and injected 1 h later with either morphine (20 mg/kg) or vehicle, and killed 30 min later. Moreover, some pups injected with L-NAME (100 mg/kg) or L-NAME with morphine were killed 30 min later. In a final experiment, pups were injected s.c. with either S-nitroso-N-acetylpenicillamine (SNAP; 5 mg/kg) or vehicle, and killed 60 or 90 min later. RESULTS: Morphine administered to rat pups elicited marked rises in both ACTH and corticosterone secretion. Moreover, these responses increased with advancing postnatal age. In 2-week-old rat pups, NAL, a competitive antagonist at mu-opioid receptors, administered alone increased both plasma ACTH and corticosterone concentrations 30 min later. L-NAME, a specific NO synthase inhibitor, did not affect plasma ACTH and corticosterone concentrations 30 min later when administered alone. NAL, when concomitantly administered with morphine, was unable to block morphine responses. In contrast, morphine responses were blocked by pretreatment (60 min before) with NAL or with L-NAME. Acute injection of SNAP increased both ACTH and corticosterone release. CONCLUSION: Our results suggest that opioids have controversial effects on pituitary-adrenocortical activity in the early postnatal period in the rat, and that endogenous NO is one of the major factors in the response of the pituitary-adrenocortical axis to morphine.

Heat-shock protein 90: intrinsic peptidase activity and in vitro long-term self-processing.

When tested on Suc-Leu-Leu-Val-Tyr-MCA as substrate, purified full-length hsp90 displays a low "chymotrypsin-like" peptidase activity which is activated by Ca++ and Mg++ ions. On the other hand, using long-term in vitro experiments, we demonstrate the ability of hsp90 to convert into a 73 kDa truncated product. This autocatalytic degradation proceeds from the C-terminal end of the full-length hsp90 and shifts the oligomers toward monomeric truncated forms. This corresponds to an intermolecular process as addition of exogenous 73 kDa product speeds up the maturation kinetics. The peptidase activity is enhanced in the 73 kDa product and is sensitive to peptide aldehyde inhibitors but only partially to lactone compounds. The degradation process itself presents a great degree of similarity with the peptidase activity toward either the inhibitors or the tested ions. Neither 20S proteasome nor m-calpain are responsible for the observed activities. Indeed, the self-processing is a consequence of the peptidase activity which appears to be an intrinsic property of the chaperone. The functional importance of these findings is discussed.

Diazepam-like effects of a fish protein hydrolysate (Gabolysat PC60) on stress responsiveness of the rat pituitary-adrenal system and sympathoadrenal activity.

RATIONALE: Gabolysat PC60 is a fish protein hydrolysate with anxiolytic properties commonly used as a nutritional supplement. OBJECTIVE: The diazepam-like effects of PC60 on stress responsiveness of the rat pituitary-adrenal system and on sympathoadrenal activity were studied. METHODS: The activity of the pituitary-adrenal axis, measured by plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone (B) of the sympathoadrenal complex, measured by circulating levels of noradrenaline (NA) and adrenaline (A), and the gamma aminobutyric acid (GABA) content in the hippocampus and the hypothalamus were investigated in male rats which received daily, by an intragastric feeding tube, for 5 days running either diazepam (1 mg/kg) or PC60 (300 or 1,200 mg/kg). Controls received only solvent (carboxymethylcellulose 1%). Six hours after the last force-feeding, the rats were subjected to 3 min ether inhalation or 30 min restraint and killed by decapitation 30 min after ether stress or at the end of restraint. RESULTS: Baseline plasma levels of ACTH, B, NA and A were not affected by either diazepam or PC60. Both ether- and restraint-induced release of ACTH, but not B, were similarly and drastically reduced by diazepam and PC60 (1,200 mg/kg). Both diazepam and PC60 (1,200 mg/kg) deleted restraint-induced NA and A increases. Both treatments also reduced the ether-induced rise of A. Basal levels of GABA were significantly increased in both the hippocampus and the hypothalamus in PC60-treated rats and only in the hippocampus in diazepam-treated ones. In controls, ether inhalation as well as restraint increased GABA content of these two brain structures. In contrast, such stress procedures performed in PC60-treated rats reduced GABA content slightly in the hippocampus but significantly in the hypothalamus. In diazepam-treated rats, GABA content of the hypothalamus was unaffected by stresses but that of the hippocampus was slightly decreased. CONCLUSIONS: Present data suggest diazepam-like effects of PC60 on stress responsiveness of the rat pituitary adrenal axis and the sympathoadrenal activity as well as GABA content of the hippocampus and the hypothalamus under resting and stress conditions. These effects of PC60 agree with anxiolytic properties of this nutritional supplement, previously reported in both rats and humans.

Atrial natriuretic peptide and aldosterone secretions, and atrial natriuretic peptide-binding sites in kidneys and adrenal glands of pregnant and fetal rats in late gestation in response to a high-salt diet.

OBJECTIVE: This study aimed at determining, in the term pregnant rat, whether maternal and fetal plasma atrial natriuretic peptide (ANP) concentrations were modified in response to an oral sodium load, and to investigate whether any changes in plasma concentrations were able to modify the density and affinity of the different ANP-binding site subtypes in maternal and fetal kidneys and adrenal glands. METHODS: Pregnant rats kept in metabolic cages were divided into two groups. The normal sodium diet group had free access to rat chow and tap water whereas the high sodium diet group received 1% NaCl as drinking water for 10 consecutive days from day 11 to day 21 of gestation with free access to standard rat chow. Pregnant rats from both groups were killed by decapitation on day 21 of gestation. The plasma ANP and aldosterone concentrations were determined by RIA. The density and affinity of ANP receptors were determined in the maternal and fetal adrenal glands and kidneys. RESULTS: In the pregnant rats on the high-salt diet, the sodium and water intakes, as well as the urine volume and sodium excretion, were significantly higher than in the control group. After 10 days of high-salt intake, water and sodium retentions were not significantly different in the two groups, indicating that the pregnant rats were able to excrete excess salt. The high sodium intake did not change the body weight of the pregnant rats but did increase the body weight of the fetal rats. Maternal and fetal hematocrits remained unchanged in both groups, the high sodium intake did not modify plasma sodium concentration in the maternal rats but increased that of the fetuses, indicating an accumulation of sodium in the fetal rats. The dietary sodium intake did not change the plasma ANP concentrations but significantly decreased the plasma aldosterone concentrations in both the maternal and fetal rats. In response to the high-salt diet, the density and affinity of total ANP, ANPb and ANPc receptors were not altered in the maternal isolated renal glomeruli or the adrenal zona glomerulosa membranes or the fetal adrenal gland and kidney membrane preparations. CONCLUSION: These results suggest that ANP is not involved in the regulation of water and electrolyte balance in maternal and fetal rats during salt-loaded intake.

Influence of morphine treatment in pregnant rats on the mineralocorticoid activity of the adrenals in their neonates.

Exposure of pregnant rats to morphine, from day 11 to day 18 of gestation, was previously reported to induce both an adrenal atrophy and hypoactivity of the glucocorticoid function in newborns at term, but did not affect, in vitro, the responsiveness of those glands to adrenocorticotrophin hormone (ACTH) concerning corticosterone release. Moreover, these effects were mediated by maternal hormones from the adrenal glands. In the present work, we investigated the effects of a prenatal morphine exposure on the mineralocorticoid activity of the adrenals in neonates. The first aim of the present study was to determine in these newborns 1) the adrenal and plasma aldosterone concentrations at birth time and during the early postnatal period 2) the plasma levels of Na+ and K+ at birth time, 3) the in vitro responsiveness of the newborn adrenals to angiotensin II (A(II)) and ACTH. The second aim of our study was to investigate the mineralocorticoid activity of the adrenals in newborns from adrenalectomized mothers treated with morphine during gestation. According to present data morphine given to intact mothers induced in newborns a severe adrenal atrophy but increased adrenal aldosterone content and plasma aldosterone level. However, prenatal morphine was unable to affect significantly Na+/K+ ratio in both mothers and newborns. In vitro, the adrenals of neonates from morphine-treated mothers were unresponsive to An and ACTH for promoting aldosterone release; in contrast, aldosterone secretion was significantly stimulated by high potassium levels (55 mEq). Maternal adrenalectomy performed one day before the beginning of morphine treatment prevented morphine-induced adrenal atrophy but was unable to affect significantly the adrenal mineralocorticoid function of the offspring. Such data suggest that a prenatal morphine exposure stimulated both aldosterone synthesis and release in neonates. However, this basal hyperfunction did not appear to be coupled with an enhanced adrenal responsivity to AII or ACTH. Prenatal morphine-induced hyperactivity of the mineralocorticoid function of the newborn adrenals, which drastically contrast with hypoactivity of the glucocorticoid one, was independent of adrenal factors from maternal origin.

Effect of spaceflight on single fiber function of triceps and biceps muscles in rhesus monkeys.

Primates appeared to be a good model for investigating muscle contractile and biochemical properties, as well as EMG recordings. The purpose of our study was to examine the effects of microgravity on the contractile properties of the slow-type triceps and fast-type biceps muscles during the 14-day Bion 11 spaceflight.

Effects of water deprivation on atrial natriuretic peptide secretion and density of binding sites in adrenal glands and kidneys of maternal and fetal rats in late gestation.

The effects of water deprivation for 3 days were studied in pregnant rats and their fetuses on day 21 of gestation. Maternal water deprivation induced a significant decrease of the body weight in both maternal and fetal rats. This weight loss was accompanied by significant increases in plasma osmolality and haematocrit in both maternal and fetal rats. Similarly, dehydration significantly decreased plasma atrial natriuretic peptide (ANP) concentrations and increased plasma aldosterone concentrations in maternal and fetal rats. Water-deprived maternal rats presented a significant increase in total ANP receptor density in isolated renal glomeruli and adrenal zona glomerulosa membranes. This increase was due to a significant increase in ANPc receptor density in both renal glomeruli and adrenal zona glomerulosa. The densities of total ANP, ANPb and ANPc receptors in fetal kidneys and adrenal glands were not affected by maternal dehydration. These results suggest that the dehydrated maternal rat is able to up-regulate the number of its ANP receptors in its kidneys and adrenal glands, in response to a decrease in plasma ANP concentrations. In contrast, the fetal rat does not seem to be able to regulate its own ANP receptors in response to maternal dehydration, in spite of a decrease in plasma ANP concentrations.

Effect of high hydrostatic pressures on 20S proteasome activity.

The 20S proteasome is the catalytic core of the ubiquitin proteolytic pathway, which is implicated in many cellular processes. The cylindrical structure of this complex consists of four stacked rings of seven subunits each. The central cavity is formed by two beta catalytic subunit rings in which protein substrates are progressively degraded. The 20S proteasome is isolated in a latent form which can be activated in vitro by various chemical and physical treatments. In this study, the effects of high hydrostatic pressures on 20S proteasome enzymatic activity were investigated. When proteasomes were subjected to increasing hydrostatic pressures, a progressive loss of peptidase activities was observed between 75 and 150 MPa. The inactivation also occurred when proteasomes were pressurized in the presence of synthetic peptide substrates; this may be the result of the dissociation of the 20S particle into its subunits under pressure, as was shown by PAGE. Pressurized proteasomes also lost their caseinolytic activity. In contrast, in the presence of casein, the pressure-induced inactivation and the dissociation of the 20S particles were prevented. In addition, in comparison to that observed at atmospheric pressure, their caseinolytic activity was increased under pressure. Following depressurization, the caseinolytic activity returned to basal levels but was further enhanced following an additional pressurization treatment. Thus, the structure of the 20S particle exhibits a certain degree of plasticity. This pressure-induced activation of the 20S proteasome is discussed in relation to its hollow structure, its currently accepted proteolytic mechanism and the general effect of high pressures on the biochemical reactions and structures of biopolymers.

Hypothalamic-pituitary-adrenocortical and gonadal axes and sympathoadrenal activity of adult male rats prenatally exposed to morphine.

The present investigation concerns 80-90 day-old male rats born from morphine-exposed mothers (2 x 10 mg/kg per day from days 11 to 18 of gestation which showed at birth reduced size and activity of the adrenals). This prenatal treatment did not significantly disturb under resting conditions: (1) the postnatal body growth up to week 10 after birth, (2) the activity of the pituitary gonadal axis (circulating luteinizing hormone (LH) and testosterone (T), weight of the testicles and seminal vesicles), (3) the activity of the hypothalamo-pituitary-adrenal axis (HPA) (hypothalamic corticoliberin (CRF) content, plasma adrenocorticotrophic hormone (ACTH) level, adrenal weight and corticosterone (B) content, plasma B level) as well as Bmax and Kd of mineralocorticoid (type I) and glucocorticoid (type II) receptors to B in both the hippocampus and the hypothalamus. In contrast these rats showed reduced content of adrenals in noradrenaline (NA) and adrenaline (A) but increased circulating levels of A.

Degradation of an ubiquitin-conjugated protein is associated with myoblast differentiation in primary cell culture.

At the early stages of myogenesis, myoblasts fuse to form multinucleated myotubes. This morphological differentiation is the result of dynamic changes in gene regulation and expression. The ubiquitin proteasome-dependent pathway has been reported to play an important role in many aspects of cellular functions such as regulation of growth and cell cycle progression. In this study, we showed that the amount of mRNA's corresponding to the iota subunit of the 20S proteasome, the level of the S4 subunit of the 19S complex and the 20S and 26S proteasomes peptidase activities increased during myoblast fusion. Cell permeable 20S proteasome inhibitor prevented fusion with concomitant accumulation of ubiquitin-conjugated protein. On the other hand, inhibition of ubiquitin ligase E3 enzymes prevented the formation of ubiquitin conjugate and decreased the fusion process. These results strongly support the involvement of the ubiquitin-proteasome proteolytic pathway in the events leading to myoblast fusion.

20S proteasome, hsp90, p97 fusion protein, PA28 activator copurifying oligomers and ATPase activities.

Whether hsp90 acts in an ATP-dependent or independent way is of crucial importance for understanding the molecular mechanism of this chaperone and, to day, the involvement of ATP hydrolysis in hsp90 function is still a controversial subject. ATPase activities may be detected in partially purified hsp90's preparations from rabbit muscle. We demonstrate that the major contaminant associated with hsp90 is the p97 fusion protein and that these oligomeric structures are copurifying together with the 20S proteasome and its PA28 activator. Improving the purification procedure permits to separate hsp90 and p97 to homogeneity. Then, our attempts failed to detect any significant ATPase activity in the hsp90 fraction. Thus, p97 would be principally responsible for the ATPase activity detected in partially purified hsp90 preparations from rabbit muscle.