Biomedical subjects

C Gueuning

Publications and source records attributed to C Gueuning.

At least 19 recordsLinked to original sources

PubMed2001

Physiological concentrations of albumin stimulate chorionic gonadotrophin and placental lactogen release from human term placental explants.

This study investigates whether albumin, a major plasma protein in direct contact with the trophoblast in vivo, can modulate human chorionic gonadotrophin (HCG) and human placental lactogen (HPL) releases from placental explants. Incubating explants with a near physiological, i.e. 5%, concentration of human or bovine albumin during 30 min increased HCG and HPL release by at least 150%. This albumin effect was not mediated by any difference in hormone adsorption onto glass surfaces. In contrast to the sustained stimulation of hormone releases elicited by the addition of 10 mmol/l extracellular calcium, the albumin-mediated secretory responses were transient. However, the albumin- and calcium-stimulatory effects were abolished at 4 degrees C, depressed by 0.36 mmol/l cycloheximide or 1 mmol/l colchicine and potentiated by 40 micromol/l cytochalasin B. Moreover, the stimulatory effect of albumin on the hormone releases was not modified in the absence of Ca(2+) or in the presence of 1 or 10 mmol/l Ca(2+) in the extracellular milieu. These data suggest that albumin is involved, at physiological concentration, in the secretion of HCG and HPL by human placenta. The cellular mechanism(s) underlying the albumin-mediated secretory responses may be partly different from those involved during the calcium-mediated stimulation.

Animals↗

PubMed2000

Secretory characteristics and viability of human term placental tissue after overnight cold preservation.

Collection of human term placentae for research purposes is generally limited during working hours. Preserving placental tissue overnight might help to postpone experiments and, by extent, to increase material availability. In this study, fragments from normal placentae were incubated at 37 degrees C either immediately after delivery or after preservation at 4 degrees C in a HEPES-buffered solution or in a Roswell Park Memorial Institute (RPMI) 1640 culture medium. Protein, human chorionic gonadotrophin (HCG), human placental lactogen (HPL) and lactate dehydrogenase (LDH) contents within preserved explants were similar to those within freshly delivered ones. In contrast, HCG and HPL amounts released during incubation of preserved tissue were lower than with freshly delivered tissue. Differences were significant only during the first 3 h of incubation. Hormone releases were similarly Ca(2+)-stimulated, and Co(2+)- and low temperature-inhibited in preserved and freshly delivered tissues. After preservation, LDH leakage was also reduced. Furthermore, before and after 37 degrees C incubation during 6 h, preserved tissue was morphologically indistinguishable from freshly delivered tissue and showed neither higher incidence of DNA fragmentation, nor elevated caspase-3 activity, both of which are markers of apoptosis. This study validates an original, useful and rapid method to preserve placental tissue. Consequently, this preservation model may facilitate the study of physiological processes regulating placental hormone secretion in normal and pathological conditions.

Apoptosis↗

PubMed1999

Apoptosis in human term placenta is not increased during labor but can be massively induced in vitro.

Apoptosis in human placental villi is reported to increase until close to delivery. However, the involvement of the apoptotic process in the initiation of labor, and more particularly in relation to the decrease in placental perfusion during uterine contractions, remains unknown. The purpose of the study was to examine the reactivity of the apoptotic machinery in term placentae obtained before or after the onset of labor and after in vitro incubations. The incidence of apoptotic nuclei (< 1%) as evidenced by the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method, and the histological distribution of immunoreactive Bcl-2, Bax, and Bcl-x proteins, were similar in placentae collected after delivery and before the onset of labor and in placental explants maintained overnight at 4 degrees C in a minimal salt-Hepes medium. By contrast, 28% of nuclei contained fragmented DNA when placental explants were incubated overnight at 37 degrees C. This marked increase was associated with a decrease in the intensity of the Bcl-2 immunostaining and an increase in the intensity of Bax and Bcl-x immunostaining. In conclusion, the present study clearly evidences the presence of an active apoptotic machinery in term placental cells that is not involved in normal parturition.

Apoptosis↗

PubMed1997

Urinary neutral endopeptidase in workers exposed to cadmium: interaction with cigarette smoking.

OBJECTIVES: Structural impairment of the renal proximal tubular epithelium induced by cadmium (Cd) was investigated by measuring the concentration of neutral endopeptidase 24.11 (NEP), an ectoenzyme of the apical brush border, in the urine of 106 male workers employed in a Cd smelter (among whom 52 were occupationally exposed to Cd), and by comparing it with other tubular markers (low molecular weight proteins, lysosomal enzymes). METHODS: NEP (EC 3.4.24.11), beta-N-acetyl-glucosaminidase (NAG) (EC 3.2.1.30), and NAG-B isoenzyme activities were measured by fluorimetric assays, whereas the concentrations of retinol binding protein (RBP), beta 2-microglobulin (beta 2M), and Clara cell protein (CC16) were measured by automated latex agglutination techniques. RESULTS: An increased urinary excretion of NEP as well as microproteins was found only in subjects excreting more than 5 micrograms Cd/g creatinine. In this group, NEP concentrations were significantly higher in the subjects who smoked. This significant interaction could not be found for any other marker tested. CONCLUSIONS: The data suggest that NEP enzymuria is high even at low exposures to Cd (with a threshold of urinary cadmium excretion (U-Cd) at 5 micrograms/g creatinine), indicating early structural alterations. Moreover, its particular sensitivity to smoking could be useful in the detection of new population clusters potentially more susceptible to development of nephrotoxic insult.

Acetylglucosaminidase↗

PubMed1989

Alkaline phosphatase activities in normal and denervated, slow and fast rat muscles. Bearing on the possible participation of the enzyme in the transmembrane transport of phosphate ions.

Alkaline phosphatase (AP) activities are present in rat gastrocnemius:48.7, plantaris: 68.9, tibialis anterior: 69.1 and soleus: 96.7 nmol phenol. min-1. 100 mg muscles-1. These concentrations are one and two orders of magnitude lower than those observed in duodenum and placenta, but similar to those observed in liver. Response to activators/inhibitors and electrophoretic behaviour assign the muscle AP activities to the rat liver/placenta isoenzyme group. Motor denervation does not affect significantly the total muscle AP content within the first 30 postoperative days, however the concomitant variations in muscle weight are responsible for wide differences in AP concentrations between innervated, denervated and reinnervated muscles. Parallel determinations of radiophosphate uptake and AP activities failed to document a necessary link between the two variables, i.e. between enzyme concentration and phosphate ion transport.

Alkaline Phosphatase↗

PubMed1989

Increased muscle regeneration after repair of divided motor nerve with neuronotrophic factors containing glue.

Neuronotrophic factors (NTFs) directed to spinal cord motor neurons were collected in rats within silicone nerve regeneration chambers according to LONGO et al. (1983b). Unilateral addition of NTFs to the fibrin glue used for the repair of divided sciatic nerves improved locally nerve regeneration without affecting the controlateral side. Nerve regeneration was assessed by weight gain of the reinnervated muscles and by radioactive labelling of the acid-soluble phosphate fractions of both nerve Schwann cells and reinnervated muscle cells. Fast gastrocnemius and slow soleus muscles, the motor nerve of which had been repaired with added NTFs, were significantly heavier (21 and 28%) than their controlateral controls, and the metabolic dedifferentiation attendant on post-division nerve repair was less marked. It is suggested that this experimental nerve regeneration model is suitable to test potential nerve-active agents in vivo, under conditions close to the usual clinical setting, with, as ultimate goal, the improvement of the end-results of microsurgical repair of peripheral nerve in man.

Animals↗

PubMed1988

Alkaline phosphatase isoenzyme pattern in human amniotic fluid is dependent on the level of total activity. Implications in cystic fibrosis diagnosis.

Alkaline phosphatase activities have been examined in 500 consecutive human amniotic fluids obtained at diagnostic paracentesis between 14 and 38 wk of gestation. They were found to have a non-Gaussian, positively skewed distribution, independent of the protein concentrations. Residual activities after heat treatment or in presence of phenylalanine and levamisole allow evaluation of the placental, hepatic and intestinal isoenzyme components. It is shown that the contribution of the intestinal isoenzyme to the total activity is a linear function of the latter. This fact should be taken into account in the enzymatic diagnosis of cystic fibrosis as it is apparent that the part contributed by the intestinal isoenzyme is predictably smaller when the level of total activity is low.

Alkaline Phosphatase↗

PubMed1985

[Peripheral nerve repair: value of biological glues and epiperineural suture in late interventions. Experimental study in rats].

In order to approximate as close as possible genuine clinical conditions, the sciatic nerve of the rat was divided and then repaired after a delay of one or seven days either by application of a biological glue or by an epiperineural suture technique. The metabolic activity of the sciatic nerve Schwann cells - whether located in the distal or the proximal ends - and that of the (fast acting) white gastrocnemius and (slow acting) red soleus muscle were assessed using 32P-radiolabeled acid-soluble phosphates. Delayed repair, as judged by our biochemical criteria, was equivalent whatever method, biological glue or suture, was used. The frozen and lyophilized forms of the biological glue provided similar results.

Animals↗

PubMed1982

Systemic effects of N,N-dimethyl-paraphenylenediamine hydrochloride on phosphate metabolism in innervated and denervated, slow and fast muscles of the rat.

N, N-dimethyl-paraphenylenediamine (DMPPD) hydrochloride increases the inorganic and organic acid-soluble phosphate (Pi and POAS) uptakes in the innervated gastrocnemius muscle of the rat but not in the innervated soleus. In the denervated gastrocnemius muscle, the effects of DMPPD and denervation are not additive, Pi uptake being even lower than on the controlateral innervated side. It is suggested that DMPPD acts only on the innervated fast fibre (white fibre, type II anaerobic fibre), as far as the permeability to Pi is concerned. Histological evidence of a severe myopathic process affecting slow and fast fibres, irrespective of denervation has been documented. Severe degenerative changes were still manifest after a 20-day DMPPD treatment. There is no obvious relation between the biochemical alterations in phosphate metabolism and the morphological lesions. The increased Pi and POAS uptakes observed in the innervated gastrocnemius and soleus muscles during generalized convulsions induced by DMPPD are independent of a direct drug action on the muscle fibre.

Animals↗

PubMed1982

[Metabolic recovery of rat muscle after reparative microsurgery of peripheral nerves as a function of suture technics].

In the rat, a characteristic response to motor denervation is an increased flow of inorganic phosphate across the muscle cell membranes. This reaction is specific for the neurogenic atrophy and is fully reversible on reinnervation. In the present study, the muscle cell permeability to inorganic phosphate has been used as a criterion in assessing the efficiency of four different techinques. Microsurgery was carried out on peroneal nerve using a Zeiss OMP I operating room microscope. The technique were: I. Bringing together the two nerve segments with two epineural stitches (Ethilon 11/0 thread). II. Tight suture with eight epineural stitches (Ethilon 11/0 thread). III. As in II but with SSC 11/0 thread. IV. As in III but combined with postoperative corticotherapy. 32P radiophosphate incorporation was measured in the extensor digitorum longus and in the tibialis anterior. The best results were obtained with the first and simpler procedure. However, in some respects, equivalent results were observed with the fourth procedure associating a tight suture with postoperative corticotherapy. It follows that in the rat, it is indicated either to minimize the surgical trauma or to counteract the fibrosis attending the surgical trauma.

Animals↗

PubMed1980

Systemic effects of colchicine on phosphate metabolism in innervated and denervated, slow and fast muscles of the rat.

A single systemic injection of 75 micrograms colchicine/100 g body weight increases the permeability to inorganic phosphate of both fast gastrocnemius and extensor digitorum longus muscles and of the slow soleus muscle. In the two fast muscles, there is a significant interaction between colchicine treatment and 5-d- or 30-d- surgical denervation. In the slow soleus muscle there is no interaction between 5-d-colchicine treatment and the initial decrease in phosphate flow due to 5-d-surgical denervation but a significant interaction between colchicine treatment and the secondary increase in phosphate permeability observed after a 30-d-surgical denervation. Thirty days after a single systemic injection of colchicine the muscle phosphate metabolism is still perturbed especially in the slow soleus muscle in which the initial decrease in radioactive uptake associated with a 5-d-surgical denervation is inapparent. It is proposed that colchicine induces denervation-like alterations in the Pi- and POAS metabolism of skeletal muscles through mechanisms which are also activated -- partly or entirely -- by surgical denervation. These alterations do not result from the interruption of the axonal flow. A direct effect on the muscle membrane seems less likely than a disinhibition or activation of the muscle protein synthesis system.

Animals↗

PubMed1980

Systemic effects of podophyllotoxin on phosphate metabolism in innervated and denervated, slow and fast muscles of the rat.

The systemic administration of podophyllotoxin gives qualitatively the same results as the administration of colchicine. It increases the specific activities and isotope uptakes of the inorganic phosphate and acid-soluble organic-bound phosphate fractions of slow and fast muscles. In the extensor digitorum longus muscles these increases are slowly reversible. In the two fast muscles -- gastrocnemius and extensor digitorum longus muscles -- significant interactions between podophyllotoxin treatment and 3 d-surgical denervation are observed. It is proposed that, like colchicine, podophyllotoxin induces denervation-like alterations in the Pi and POAS metabolism of skeletal muscle. In view of their structural dissimilarities it is further proposed that their action on muscle phosphate metabolism is mediated through a common property : i.e. binding to muscle free tubulin.

Animals↗

PubMed1980

Early and late systemic effects of colchicine on muscle permeability to inorganic phosphate.

A single systemic injection of 75 micrograms colchicine/100 g body weight in the lumbar muscles increases within 6 h the permeability of the extensor digitorum longus muscle to inorganic phosphate. Twenty four hours after the injection the specific activities and isotope uptakes of both inorganic and organic-bound acid-soluble phosphates are markedly increased. By the third day a maximal four-fold increase in rate of inorganic phosphate exchange is reached. The observed effects are slowly reversible, a near normal situation obtaining after 30 days. They are qualitatively different from those observed after administration of vincristine sulphate and bupivacaïne (Marcaine).

Animals↗

PubMed1978

Effects of denervation on the rate of entry of inorganic phosphate into rat slow and fast muscles: selective inhibition of denervation changes by actinomycin D.

Actinomycin D abolishes the post denervation increase in inorganic phosphate flow observed in the fast gastrocnemius muscle. In the slow soleus muscle, the initial decrease in phosphate flow is unaffected but the secondary rise is suppressed in the same manner as in the fast muscle. These observations put the post denervation increase in inorganic phosphate flow on a par with the development of extrajunctional cholinergic receptors in being the result of the synthesis of new proteins. It has the added advantage of being suitable to quantitative assessment at the whole muscle level.

Animals↗

PubMed1978

Effect of increasing duration of denervation on the rate of entry of inorganic phosphate into rat gastrocnemius muscle.

The increased inorganic phosphate flow, characteristic of denervated gastrocnemius muscle, is shown to have no direct relation with either the loss of muscle mass or with the concentrations of the acid-soluble phosphate fractions. It is shown to increase hyperbolically with the time elapsed since the nerve section. The asymptotic value reached after thirty days suggests the presence of a saturable mechanism.

Animals↗

PubMed1978

[Neurotoxicity of acrylamide in rats. I. Subacute intoxication. Absence of effect on incorporation of plasma phosphates into the acid-soluble phosphates of the sciatic nerve and the gastrocnemius muscle, in anatomic continuity and after neural section].

The subcutaneous injection of acrylamide (30 mg kg-1 day-1) in adult male rats induces a severe impairment of the general state of health and a progressive polyneuropathy at the cumulative dose of 180 mg/kg. At the cumulative dose of 400 mg acrylamide does not interfere with the incorporation of plasma inorganic phosphate into the inorganic and organic acid-soluble phosphate fractions of either the gastrocnemius muscle or the sciatic nerve Schwann cells. Nor does it modify the characteristic metabolic response of these fractions to Wallerian degeneration and neurogenic muscle atrophy.

Acrylamides↗

PubMed1978

Unlike effects of denervation on the rate of entry of inorganic phosphate into rat slow and fast muscles.

The increased inorganic phosphate flow, characteristic of denervated gastrocnemius muscle is shown to be present in additional denervated fast muscles, i.e. the plantaris, tibialis anterior and extensor digitorum longus muscles. The response of the soleus, a slow muscle, to denervation is biphasic. After an initial decrease of the phosphate flow at the end of the first postoperative day, there is a secondary rise which has the same general characteristics as the rise observed in fast muscles i.e. an exponential or hyperbolic increase to an asymptotic value reached after thirty days. The denervated fast and slow muscles are not converging to an intermediate metabolic pattern. The changes in phosphate flow induced by denervation are reversible in the soleus as well as in the gastrocnemius muscles.

Animals↗

PubMed1977

[Incorporation of plasma radiophosphate into the inorganic, organic acid-soluble and phospholipid phosphate fractions of the normal rabbit sciatic nerve and during Wallerian degeneration].

Inorganic phosphate exchanges between plasma and sciatic nerve have been measured in the rabbit using a 32PO4 tracer technique. Inorganic phosphate is taken up at the rate of 0.13 microng per hour and per 100 mg fresh weight. Incorporation of plasma radiophosphate is markedly increased into the inorganic and organic acid soluble phosphate fractions of the distal part of the sectioned sciatic nerve. This increase is already signficant within one hour after surgical division, spreading at least 3 cm distally within 6 hours. This high level of incorporation persists until the 29th day of degeneration. These results favour the hypothesis that the axonal continuity maintains the metabolic activity of the Schwann cells at an inframaximal level. We confirm the rapid decrease in total phospholipid concentration in the nerve undergoing Wallerian degeneration as well as the marked increase in their specific activity. We show however that this increase in specific activity is due partly to the increased specific activities of the precursors (organic acid soluble phosphates), partly to the disappearance of a metabolically insert pool (myelin phospholipids). The Schwann cells of the nerve undergoing Wallerian degeneration do not have a more active phospholipid metabolism than their normal counterparts.

Animals↗