Search PubMed⌕ Search

Biomedical subjects

A Picard

Publications and source records attributed to A Picard.

At least 91 records · Page 5Linked to original sources
PubMed1988

Phosphorylation of ribosomal proteins during meiotic maturation and following activation in starfish oocytes: its relationship with changes of intracellular pH.

An increased phosphorylation of ribosomal protein S6 has been shown to be correlated with an increase of intracellular pH (pHi) and with stimulation of protein synthesis in many systems. In this research changes in ribosome phosphorylation following hormone-induced meiotic maturation and fertilization or activation by ionophore A23187 were investigated in starfish oocytes. The hormone was found to stimulate, even in the absence of external Na+, the phosphorylation on serine residues of an Mr 31,000 protein identified as S6, as well as that of an acidic Mr 47,000 protein, presumably S1, on threonine residues. Phosphorylation of ribosomes was an early consequence of hormonal stimulation and did not decrease after completion of meiotic maturation. Fertilization or activation by ionophore of prophase-arrested oocytes also stimulated ribosome phosphorylation. Only S6 was labeled in this case, but to a lesser extent than upon hormone-induced meiotic maturation. Changes in pHi were monitored with ion-specific microelectrodes throughout meiotic maturation and following either fertilization or activation. The pHi did not change before germinal vesicle breakdown (GVBD) following hormone addition, but it increased before first polar body emission. It also increased following fertilization or activation by ionophore or the microinjection of Ca-EGTA. In all cases, alkalinization did not depend on activation of an amiloride-sensitive Na+/H+ exchanger. Microinjection of an alkaline Hepes buffer or external application of ammonia, both of which increased pHi, prevented unfertilized oocytes from arresting after formation of the female pronucleus and induced chromosome cycling. Phosphorylation of S6 was still observed following fertilization or induction of maturation when pHi was decreased by external application of acetate, a treatment which suppressed the emission of polar bodies. Protein synthesis increased in prophase-arrested oocytes after fertilization or activation. It also increased after ammonia addition, although this treatment did not stimulate S6 phosphorylation.

Adenine↗
PubMed1988

ATP-gamma-S (adenosine 5'-O-(3-thiotriphosphate)) microinjection increases progesterone-stimulated histone kinase activity in Xenopus oocytes.

Progesterone stimulates the activity of a potent Ca2+- and cyclic nucleotide-independent histone kinase in Xenopus oocytes. Microinjection of ATP-gamma-S during the course of meiotic maturation or after the oocytes had arrested at second meiotic metaphase resulted in a further increase of this histone kinase activity in progesterone-stimulated oocytes. ATP-gamma-S microinjection also increased and stabilized the activity of the maturation-promoting factor. The possible mechanism of ATP-gamma-S action is discussed.

Adenosine Triphosphate↗
PubMed1988

[Spastic knee flexion deformity. Results of surgical treatment].

The records of 36 children who had been treated surgically for spastic knee flexion deformity were studied. The procedures were either a modified Eggers' operation, a lowering of the patella or a combination of both. Thirty-three children were reviewed at a distance and a comparison made between their initial and final function. The results were also assessed in relation to the state of the muscles and the length of follow-up. Many patients were improved but this improvement could not reasonably be expected except in those who could walk or in whom walking had been abandoned for a short time. The indications for the type of procedure should follow systematic examination by a medical and surgical team, taking account of the strength of the gluteus maximus and the quadriceps and the response to novocaine infiltration of the sciatic nerve.

Adolescent↗
PubMed1987

Antipain microinjection prevents progesterone to inhibit adenyl cyclase in Xenopus oocytes.

Microinjection of antipain, an inhibitor of thiol and Ca2+-dependent proteases, in immature Xenopus oocytes inhibited meiotic maturation induced by progesterone, but not by transfer of cytoplasm taken from maturing oocytes. Oocytes could be released from antipain inhibition by increasing progesterone concentration. alpha-32P-ATP was microinjected to study adenylcyclase in ovo. As already reported, neosynthesis of cAMP was decreased following progesterone application. This decrease was not observed, or it was considerably reduced, in oocytes previously injected with antipain. In amphibian, full-grown ovarian oocytes are arrested at first meiotic prophase, and have a large nucleus known as the germinal vesicle. Progesterone induces the production of a cytoplasmic maturation-promoting factor (MPF), which itself triggers germinal vesicle breakdown (GVBD), and subsequent events of meiotic maturation (Masui and Markert, 1971; Gerhart et al., 1984). A considerable body of evidences support the view that release from prophase block is due to inactivation of a cAMP-dependent protein kinase (reviewed by Maller, 1983). On the other hand, progesterone has been shown to induce a transient decrease in cAMP level (Speaker and Butcher, 1977; Schorderet-Slatkine et al., 1982; Cicirelli et al., 1985), and this initial drop of cAMP, along with a number of studies indicating a decrease in adenylate cyclase activity (Mulner et al., 1979; Baltus et al., 1981; Sadler and Maller, 1981; Finidori-Lepicard et al., 1981; Jordana et al., 1981), provided key support to the theory that an early drop in cAMP led to the dephosphorylation of a hypothetical protein which initiates maturation.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗
PubMed1987

[Renal manifestations in dermatomyositis and polymyositis].

Renal involvement is usually considered to be rare in dermatomyositis and polymyositis. The aim of this prospective study was to reevaluate the renal changes which may occur in these two conditions. Twenty patients, 12 with dermatomyositis and 8 with polymyositis of the adult type, were investigated to determine the incidence, the severity and course of renal disease. The 24 hour proteinuria was over 0.1 g in 14 cases and greater than 1 g/24 hours in 6 cases, including one patient with the nephrotic syndrome. Microscopic haematuria was noted in 3 cases and pyuria in 8 cases. Endogenous creatinine clearance was significantly decreased (p less than 0.001) in patients with dermatomyositis compared with a control group of subjects paired for age, sex, weight and serum creatinine concentration. Renal biopsy (5 cases) showed minimal glomerular lesions (2 cases), endocapillary proliferation and extramembranous glomerulonephritis (1 cases) and amyloid deposits (1 case). Although the proteinuria, haematuria and pyuria responded to steroid therapy (except in 1 case), the creatinine clearance remained decreased during the course of steroids.

Adult↗
PubMed1986

Changes in the activity of the maturation-promoting factor during meiotic maturation and following activation of amphibian and starfish oocytes: their correlations with protein phosphorylation.

Changes in the extent of protein phosphorylation and their possible correlation with changes in the activity of maturation-promoting (MPF) factor were investigated throughout meiotic maturation and following activation of amphibian and starfish oocytes. Despite several exceptions in the pattern of phosphorylation of individual proteins, high and low levels of protein phosphorylation were found to be correlated with high and low levels of MPF activity. Both the extent of protein phosphorylation and MPF activity were found to drop upon parthenogenetic activation and to cycle synchronously thereafter in the amphibian. In contrast no drop in MPF activity or in the extent of protein phosphorylation was observed following activation of starfish oocytes with ionophore A23187. This suggests that changes of protein phosphorylation and of MPF activity are rather related to the progression of the cell cycle than directly to Ca2+-dependent activation reaction. In amphibians global protein kinase activity in homogenates was found to drop with MPF activity following activation. Changes in the ratio of threonine vs serine phosphorylation were also investigated during the course of meiotic maturation and activation in both amphibian and starfish oocytes: changes in the activity of MPF were found to be better correlated with changes in threonine than serine phosphorylation.

Adenosine Triphosphate↗
PubMed1985

Parthenogenetic activation decreases the polyphosphoinositide content of frog eggs.

Polyphosphoinositides were quantified in metaphase II-arrested eggs of the amphibian Xenopus laevis and 8-10 min later in eggs activated by pricking. The content of phosphatidylinositol 4,5-biphosphate (PIP2) was remarkably high in metaphase II-arrested eggs with respect to that of phosphatidylinositol 4-phosphate (PIP). It was found to drop dramatically at activation. In contrast PIP content did not change significantly.

Animals↗
PubMed1985

Inositol 1,4,5-triphosphate microinjection triggers activation, but not meiotic maturation in amphibian and starfish oocytes.

Inositol 3,4,5-triphosphate (InsP3) brought about cortical granule exocytosis and elevation of a fertilization membrane, due to a rapid increase of free calcium in cytoplasm, when injected into oocytes of the amphibian Xenopus laevis arrested at second meiotic metaphase. The same result was observed when injection was performed into oocytes of the starfish Marthasterias glacialis arrested either at the first meiotic prophase or after completion of meiosis. Although meiotic maturation was induced in both animals by specific hormones which have been previously shown to release Ca2+ within cytoplasm, InsP3 microinjection into prophase-arrested oocytes did not release them from prophase block.

Adenine↗
PubMed1985

Role of protein synthesis and proteases in production and inactivation of maturation-promoting activity during meiotic maturation of starfish oocytes.

In starfish oocytes, activity of the maturation-promoting factor (MPF) and that of a major cAMP-independent protein kinase dropped at the time of meiotic cleavage, and rose again after the first but not the second meiotic cleavage. Protein synthesis was required before the first meiotic cleavage for both MPF and protein kinase activity to rise again after the first meiotic cleavage. Microinjection of either leupeptin or soybean trypsin inhibitor early enough prior to first polar body emission suppressed both the meiotic cleavage and the associated drop of MPF activity. Microinjection of leupeptin or soybean trypsin inhibitor during the 10-min period before the first meiotic cleavage also suppressed cytokinesis but did not prevent a decrease in MPF activity at the normal time of cytokinesis. The lysosomotropic inhibitor ammonia neither suppressed cytokinesis nor the drop of MPF activity at the time of first meiotic cleavage. Activity of neutral proteases sensitive to leupeptin and soybean trypsin inhibitor was demonstrated in oocyte homogenates prepared at the time of first meiotic cleavage. It is proposed that such proteases might be involved in degradation of protein kinase(s) and in the drop of MPF activity at the time of first meiotic cleavage.

Animals↗
PubMed1984

The role of the germinal vesicle in producing maturation-promoting factor (MPF) as revealed by the removal and transplantation of nuclear material in starfish oocytes.

In starfish, oocytes are released from prophase block by a hormone, which has been identified as 1-methyladenine. The action of 1-methyladenine is indirect in inducing oocyte maturation: it acts on the oocyte surface to produce a cytoplasmic maturation-promoting factor (MPF), the direct trigger of germinal vesicle breakdown (GVBD). Less than 5 min after hormone addition, thus about 10 min before appearance of the cytoplasmic maturation-promoting factor, a factor appears in the germinal vesicle, which triggers the production of cytoplasmic MPF, GVBD, and the subsequent events of meiotic maturation when transferred in the cytoplasm of any fully grown oocyte of the starfishes Marthasterias glacialis and Asterias rubens. Before hormone action, the germinal vesicle also contains a factor capable of inducing meiosis reinitiation in recipient oocytes, but in contrast with nuclear MPF, this factor acts exclusively when transferred in the cytoplasm of a special category of oocytes (the "competent" oocytes). In contrast to other oocytes (the "incompetent" oocytes) the competent oocytes are capable of producing MPF to some extent after enucleation, upon hormonal stimulation. Transfer of either nuclear or cytoplasmic MPF initially produced in hormone-treated maturing oocytes triggers the production of both cytoplasmic and nuclear MPF in non-hormone-treated recipient oocytes of both categories.

Adenine↗
PubMed1984

Rise and fall of protein phosphorylation during meiotic maturation in oocytes of Sabellaria alveolata (polychaete annelid).

Incorporation of [32P]phosphate into proteins was monitored, in preloaded Sabellaria oocytes, during meiosis. After a fourfold increase during the transition from prophase to metaphase I, the incorporated radioactivity decreased steadily by 25% during completion of meiosis, while it slowly increased in metaphase I-blocked oocytes. Measurements of the amount and specific activity of nucleotide pools showed no variation, while total alkali-labile protein-bound phosphate was found to increase and then decrease during meiosis. Autoradiography of sodium dodecyl sulfate slabgels showed that some proteins have peculiar phosphorylation-dephosphorylation kinetics. The changes in the level of phosphorylation of proteins may be related to similar changes in maturation-promoting factor (MPF) activity.

Adenosine Triphosphate↗
PubMed1984

[Disorders of horizontal gaze motility in the cerebral palsy patient].

The authors studied voluntary and reflex horizontal eyes movements, median and lateral fixation, pursuit movements, binocular and monocular optokinetic nystagmus, and vestibulo-ocular reflex suppression by fixation in a group of 66 cases of cerebral palsy. Horizontal gaze is normal in only 26% of the cases. Pursuit movements and vestibulo-ocular reflex suppression by fixation are the most affected. These anomalies are more frequent in ex-premature babies. Only 2 of 32 ex-premature babies were normal. Whereas, 15 of 34 term babies had no anomaly of horizontal gaze. The frequency and intensity of the troubles seem to correlate with the extent and onset of the neurological lesions.

Adolescent↗
PubMed1984

[Acute fatal non-occlusive intestinal ischemia during treatment with a cardiotonic glucoside].

After presenting the case of a 70 year old woman who presented a massive mesenteric infarction as a result of non-occlusive intestinal ischaemia ( NOII ), the authors review the principal features of this particular form of intestinal ischaemia. This condition is seen principally in elderly people with a syndrome of low cardiac output, resulting in marked mesenteric vasoconstriction. It is a complication of either severe decompensated heart disease treated with digitaloids or to a state of hypovolaemic or septic shock. The diagnosis of NOII should be suggested by the combination of abdominal signs with a state of shock and/or treated heart disease. The diagnosis is confirmed by selective mesenteric arteriography which reveals a patent but spastic vessel. The treatment is initially medical, consisting of the correction of haemodynamic disturbances and the in situ injection of vasodilator products, which may need to be completed by a surgical operation. However, the prognosis of NOII remains serious, particularly because of the frequent delay in making the diagnosis.

Acetyldigitoxins↗
PubMed1983

Intracellular microinjection of alkaline buffers reversibly inhibits the initial phase of hormone action in meiosis reinitiation of starfish oocytes.

Intracellular microinjection of alkaline Hepes-KOH buffers, which increases intracellular pH (pHI) from 6.92 to 7.70 in fully grown prophase-blocked oocytes of the starfish Marthasterias glacialis, like external application of ammonia and other weak bases (M. Doree, K. Sano, and H. Kanatani, 1982, Dev. Biol. 90, 13-17), inhibited meiosis reinitiation induced by 1-methyladenine (1-MeAde) or dithiothreitol (DTT), a mimetic of the hormone. Oocytes could be released from inhibition by raising the concentration of hormone or of its mimetic. Increasing pHI to 7.70 neither inhibited nor delayed meiosis reinitiation when pH was clamped after the end of the hormone-dependent period, the period during which 1-MeAde is required in the external medium for meiosis to occur, whereas it blocked the action of the hormone at low concentration when performed before the end of the hormone-dependent period. When hormone concentration was higher, germinal vesicle breakdown (GVBD) occurred, but duration of the hormone-dependent period was increased. Delay introduced by alkalinization for oocytes to reach GVBD after 1-MeAde addition was smaller at high than at medium concentrations of the hormone. Increasing pHI did not inhibit action of MPF, the cytoplasmic maturation factor which induces GVBD and the subsequent process of meiotic maturation following hormonal treatment of prophase-blocked oocytes.

Adenine↗