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P Mollard

Publications and source records attributed to P Mollard.

At least 19 recordsLinked to original sources
PubMed1992

Video imaging of cytosolic Ca2+ in pancreatic beta-cells stimulated by glucose, carbachol, and ATP.

In order to define the differences in the distribution of cytosolic free Ca2+ ([Ca2+]i) in pancreatic beta-cells stimulated with the fuel secretagogue glucose or the Ca(2+)-mobilizing agents carbachol and ATP, we applied digital video imaging to beta-cells loaded with fura-2.83% of the cells responded to glucose with an increase in [Ca2+]i after a latency of 117 +/- 24 s (mean +/- S.E., 85 cells). Of these cells, 16% showed slow wave oscillations (frequency 0.35/min). In order to assess the relationship between membrane potential and the distribution of the [Ca2+]i rise, digital image analysis and perforated patch-clamp methods were applied simultaneously. The system used allowed sufficient temporal resolution to visualize a subplasmalemmal Ca2+ transient due to a single glucose-induced action potential. Glucose could also elicit a slow depolarization which did not cause Ca2+ influx until the appearance of the first of a train of action potentials. [Ca2+]i rose progressively during spike firing. Inhibition of Ca2+ influx by EGTA abolished the glucose-induced rise in [Ca2+]i. In contrast, the peak amplitude of the [Ca2+]i response to carbachol was not significantly different in normal or in Ca(2+)-deprived medium. Occasionally, the increase of the [Ca2+]i rise was polarized to one area of the cell different from the subplasmalemmal rise caused by glucose. The amplitude of the response and the number of responding cells were significantly increased when carbachol was applied after the addition of high glucose (11.2 mM). ATP also raised [Ca2+]i and promoted both Ca2+ mobilization and Ca2+ influx. The intracellular distribution of [Ca2+]i was homogeneous during the onset of the response. A polarity in the [Ca2+]i distribution could be detected either in the descending phase of the peak or in subsequent peaks during [Ca2+]i oscillations caused by ATP. In the absence of extracellular Ca2+, the sequential application of ATP and carbachol revealed that carbachol was still able to raise [Ca2+]i after exhaustion of the ATP response. This may be due to desensitization to the former agonist, since the response occurred in the same area of the cell. These results reveal subtle differences in [Ca2+]i distribution following membrane depolarization with glucose or the application of Ca(2+)-mobilizing agonists.

Adenosine Triphosphate↗
PubMed1992

Limited accumulation of cyclic AMP underlies a modest vasoactive-intestinal-peptide-mediated increase in cytosolic [Ca2+] transients in GH3 pituitary cells.

The 4-chlorophenylthio analogue of cyclic AMP evoked profound and long-lasting changes in cytosolic [Ca2+] ([Ca2+]i) in pituitary-derived GH3 cells. However, vasoactive intestinal peptide (VIP), a hormone considered to act via cyclic AMP, was ineffective in modulating [Ca2+]i. The ability of VIP to modulate [Ca2+]i was enhanced by treatments that increased intracellular cyclic AMP. Much greater concentrations of intracellular cyclic nucleotides were achieved by the analogue than with VIP, under any condition. Thus cyclic AMP may play a prominent role in regulating [Ca2+]i in these cells, but the ability of hormones to stimulate its synthesis is limited, leading to a weak action on [Ca2+]i.

1-Methyl-3-isobutylxanthine↗
PubMed1992

Management of urinary incontinence in neurogenic bladder.

The treatment of children with urinary incontinence caused by a neurogenic bladder presents a challenge to the paediatric urologist. Between 1965 and 1989, 527 patients with neurogenic bladder were treated and followed-up in the Department of Paediatric Urology of Debrousse Hospital. Of these, 46 were submitted to continent cystostomy, 39 to urinary artificial sphincter and 177 to clean intermittent catheterization (CIC). This last treatment is of paramount importance in girls and can be associated with complementary procedures if cervico-urethral resistance and/or bladder compliance are poor. Urethral lengthening (Kropp's procedure) in combination with CIC represents a major means of providing dryness in girls. Our technique of urethral lengthening is detailed and the place of CIC among other incontinence treatment is discussed.

Child↗
PubMed1992

Transient but not oscillating component of the calcium mobilizing response to gonadotropin-releasing hormone depends on calcium influx in pituitary gonadotrophs.

Gonadotropin-releasing hormone (GnRH)-stimulated changes in the cytosolic free Ca2+ concentration ([Ca2+]i) were studied in gonadotrophs cultured from 3-week ovariectomized rat pituitaries. One animal was used per cell preparation. [Ca2+]i was monitored in individual gonadotrophs by dual emission microspectrofluorimetry, using Indo-1 as the intracellular fluorescent Ca2+ probe. A short stimulation with GnRH evoked a complex concentration-dependent Ca2+ response in individual gonadotrophs. 0.1-1 nM GnRH triggered a series of sinusoidal-like [Ca2+]i oscillations superimposed upon a modest slow [Ca2+]i rise--the oscillating response mode--while 10-100 nM GnRH caused a biphasic increase in [Ca2+]i consisting of a monophasic transient and oscillations--the transient/oscillating response mode. Despite the consistency of Ca2+ responses, an inter-preparation heterogeneity of [Ca2+]i oscillations frequency was noticed. Moreover, we observed that, within a given cell preparation, the frequency of [Ca2+]i oscillations was independent of GnRH concentration whereas both peak [Ca2+]i and area under the [Ca2+]i versus time curve were concentration-dependent. Thus, in gonadotrophs, the presence of the GnRH signal would lead to [Ca2+]i oscillations, while the amplitude of the [Ca2+]i responses would code for the concentration of agonist. Both transient and oscillating components of GnRH responses depended on releasing activity of Ca(2+)-sequestering pools in as much as GnRH responses were unaffected by brief removal of external Ca2+, but suppressed by chelating intracellular free Ca2+ with BAPTA. However, prolonged exposure to a Ca(2+)-free medium suppressed the transient component while leaving the oscillating component unaffected. We therefore propose that gonadotrophs employ Ca(2+)-sequestering pools, whose maintenance depends on a slow Ca(2+)-entry, to give an amplitude-coded Ca2+ rise in response to a short GnRH stimulation.

Animals↗
PubMed1992

[Treatment of urinary stress incontinence by a modified Pereyra procedure:Chrub's operation].

The authors report the utility of suspending the cervix by means of the pubo-urethrax ligaments anchored to Cooper's ligaments in treating exercise-related urinary incontinence. A prospective series of 40 female patients gave 97.5% of successful outcomes with regard to the incontinence. The use of the pubo-urethrax ligaments and the absence of subsphincterian dissection confers major urodynamic advantages, particularly with regard to closing pressure. These anatomical and physiological arguments appear to give the procedure an advantage over suspensions using the vagina wall, whether these make use of the upper or lower route. Anchoring to Cooper's ligaments should ensure long-term stability of the outcome.

Adult↗
PubMed1992

[Conservative treatment of cancer of the ovary].

The authors assess the potential of conservative treatment in a series of cases of ovarian cancer. Surgical evaluation is essential, in order to confirm that the conditions required for conservative treatment are present. The tumor must be a stage IA tumor, with a low histoprognostic score and small in size. Conservative treatment must be proposed in cases of tumors of potential malignancy and tumors of the sexual cords. It is debateable in epithelial tumors. The question of the necessity of further surgery to remove the genital tract after the desired pregnancies may be debateable in cases of epithelial tumors.

Adolescent↗
PubMed1991

Adenosine A1 receptor-induced inhibition of Ca2+ transients linked to action potentials in clonal pituitary cells.

Adenosine is a potent paracrine/autocrine feedback inhibitor of cell activation in a variety of tissues. Adenosine action was studied in pituitary cells, in which spontaneous electrical activity causes characteristic oscillations of the cytosolic free Ca2+ concentration, [Ca2+]i. Cells of the GH3B6 rat pituitary tumor line were studied by microspectrofluorimetry using the Ca2+ probes indo-1 and fura-2, in part in combination with electrophysiological tight seal whole cell recordings, obtained with the novel approach of patch perforation. It was demonstrated that adenosine receptor activation by N6-(R-phenyl-isopropyl)-adenosine (PIA) caused a block of electrical activity and abolished the ensuing alterations in [Ca2+]i. PIA mimicked the inhibitory action of somatostatin. Adenosine effects are mediated by A1 receptors in these cells and are antagonized by IBMX, an adenosine receptor blocker. PIA also suppressed action potentials that were elicited by the activation of protein kinase C with the phorbol ester PMA, or during the second phase of TRH action. In contrast, no interference was notable on TRH-induced intracellular Ca2+ mobilization. In addition to the abolition of Ca2+ transients, PIA lowers basal [Ca2+]i in some cells. It is proposed that in addition to the inhibition of adenylate cyclase, A1 receptor action on [Ca2+]i is an important element in the control of excitable pituitary cells.

Action Potentials↗
PubMed1991

High and intermediate imperforate anus: functional results and postoperative manometric assessment.

Between 1983 and 1989, 21 patients with high (12) and intermediate (9) imperforate anus were operated on according to the author's procedure. The anatomical results are satisfactory (20/21). The records of the clinical and paraclinical assessments of 13 of these patients with a follow-up of at least 5 years, is reported. The patient history demonstrates that 12 out of 13 are clean at night, with 1 to 3 bowel movements during the day. The intermediate forms have no accidental defecation and almost no soiling. Conversely, the high forms often soil but usually do not wear thick protections. Criteria of successful reconstruction as rectal examination, defecogram, CT scan or MRI, yield limited data but no formal conclusions. Manometric studies provide a better understanding of the bowel function after pull-through procedures, by studying the rectoanal inhibitory reflex threshold (RAIRT), the maximal anal resting closure (MARCP), the conscious rectal sensitivity threshold (CRST) and the maximal rectal compliance (MRC). Technical aspects of these recordings are detailed. Manometric recording from 13 of these 21 patients show that RAIRT is present in 3 out of 6 intermediate forms and 3 out of 7 high forms. CRST is normal in all the cases except 1. MARCP was normal in 5 out of 6 intermediate lesions and 5 out of 7 high lesions. MRC is good in 5 intermediate forms and 3 high forms.(ABSTRACT TRUNCATED AT 250 WORDS)

Anal Canal↗
PubMed1991

Extracellular ATP elevates cytosolic Ca2+ in cochlear inner hair cells.

The local extracellular application of ATP to isolated sensory inner hair cells (IHC) generated a rapid and transient increase in the concentration of cytosolic free Ca2+, peaking within 1 to 5 s. The dose-response curve indicated a half-max stimulation to be 5 microM ATP. The application of the structural derivatives ADP and alpha-beta-methyleneATP did not generate significant Ca2+ response. By contrast, ATP-alpha-S, an agonist for P2z receptor, was fully active in generating Ca2+ responses. In the absence of extracellular free calcium, the ATP-induced Ca2+ increase was still observed, indicating that ATP generated the liberation of Ca2+ from internal stores. These results suggest that extracellular ATP, through an activation of P2-purinergic receptors, may have a neuromodulatory role in the cochlear physiology at the level of the IHC.

Adenosine Triphosphate↗
PubMed1991

Application of the onlay island flap urethroplasty to penile hypospadias with severe chordee.

The onlay island flap urethroplasty was originally used to repair anterior hypospadias without chordee and was later used to repair penile hypospadias with a well developed urethral plate exhibiting little or no chordee after release of skin tethering. It is possible to treat all cases of penile hypospadias even with severe chordee by releasing the chordee without dividing the urethral plate and by reconstructing the urethra with an onlay island flap.

Child, Preschool↗
PubMed1991

Physiological characterization of two functional states in subpopulations of prolactin cells from lactating rats.

1. Lactotroph cells from lactating female rat pituitary glands were dissociated, separated and enriched on a continuous gradient of bovine serum albumin at unit gravity. Two lactotroph subpopulations were observed in the light (F(3-5)) and the heavy (F(7-9)) fractions of the gradient. Both populations were maintained for at least 6 days in culture before experiments were performed. 2. Patch-clamp recordings, in the whole-cell mode, were performed on both lactotroph subpopulations in order to measure passive membrane properties and Ca2+ currents. Resting membrane potential as well as membrane capacitance values were found to be lower in light fraction cells. The two components of Ca2+ currents, called fast and slow deactivating (FD and SD) currents, were present with different proportions in each subpopulation; the ratio of current amplitudes, SD/FD, was 2.42 +/- 0.41 (n = 18) in light fraction cells and 1.17 +/- 0.27 (n = 17) in heavy fraction cells (P less than 0.02). 3. Reverse haemolytic plaque assay showed that in the light and heavy fractions, 68 and 47% of the lactotroph cells, respectively, were secreting. Population analysis of the plaque areas revealed a bimodal frequency distribution of plaque sizes consisting of small (1500 microns 2) and large plaques (3995 microns 2). A majority of light fraction cells produced large plaques whereas most of the heavy fraction cells produced small plaques. 4. Perifusion experiments performed on enriched prolactin cells showed that (1) basal prolactin (PRL) release was higher in light fraction than in heavy fraction cells, (2) the dopamine (10(-8)M)-induced inhibition of PRL release was greater in light fraction cells (86 +/- 15%) than in heavy fraction cells (41 +/- 21%), and (3) the thyrotrophin-releasing hormone (TRH, 10(-8)M)-induced increase of PRL release was 150 +/- 60% in light fraction versus 330 +/- 82% in heavy fraction cells. 5. Current-clamp recordings were performed using the intracellular technique. Lactotrophs were categorized according to their electrophysiological response following application of dopamine or TRH (both 10(-8)M). In the light fractions, the majority of the cells tested were hyperpolarized by dopamine (68%), whereas only 7% were depolarized by TRH application. In the heavy fractions, most of the cells (63%) responded to TRH application, while only 13% were dopamine sensitive. 6. Cytosolic free Ca2+ concentration ([Ca2+]i) measurements with the fluorescent probe Indo-1 revealed two lactotroph subtypes. Most cells in the light fractions (sixteen of twenty-two tested cells) exhibited an unstable level of [Ca2+]i with values fluctuating between 114.1 +/- 34.3 and 221 +/- 50 nM (mean +/- S.D.). Application of dopamine or of the D2 receptor agonist RU 24213 (10(-8)M) resulted in the disappearance of these fluctuations and in an accompanying decrease in basal [Ca2+]i level.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Spontaneous and corticotropin-releasing factor-induced cytosolic calcium transients in corticotrophs.

Spontaneous and CRF-stimulated changes in the cytosolic free calcium concentration ([Ca2+]i) were studied in two types of corticotrophs: 1) cultured human ACTH-secreting pituitary adenoma cells (hACTH cells), and 2) identified small ovoid corticotrophs cultured from normal rat pituitaries. [Ca2+]i was monitored in individual corticotrophs by dual emission microspectrofluorimetry using indo-1 as the intracellular fluorescent Ca2+ probe. In hACTH cells, [Ca2+]i measurements were carried out in combination with electrophysiological recordings obtained using whole cell patch-clamp techniques. It was shown that a single spontaneous Ca(2+)-dependent action potential led to a marked transient increase in [Ca2+]i in human tumoral corticotrophs. Spontaneous fluctuations in [Ca2+]i were also observed in unpatched corticotrophs whether derived from human pituitary tumors or normal rat tissue. Based on their striking kinetic features and their sensitivity to external Ca2+, we suggest that these spontaneous [Ca2+]i transients were the consequence of action potential firing. Under separate voltage-clamp (patch-clamp) conditions, tumor corticotrophs showed two Ca2+ current components: a low threshold, rapidly inactivating (T-type) current, and a higher threshold, slowly inactivating (L-type) current. The dihydropyridine Ca2+ channel blocker PN 200-110 (100 nM) abolished the L-type current without affecting the T-type current, while the inorganic Ca2+ channel blocker Cd2+ (200 microM) suppressed both Ca2+ currents. The Na+ channel blocker tetrodotoxin (5 microM) did not affect inward currents in tumor corticotrophs. Both L- and T-type voltage-gated Ca2+ channels were involved in controlling [Ca2+]i transients in both tumor and normal corticotrophs, inasmuch as Cd2+ (200 microM) abolished [Ca2+]i) transients, while PN 200-110 (100 nM) greatly diminished, but did not completely abolish, [Ca2+]i transients. The latter did not appear to depend on a voltage-dependent Na+ influx, since they were unaffected by tetrodotoxin (5 microM). Corticotrophs generate [Ca2+]i transients in response to the hypothalamic secretagogue CRF by acting on their membrane excitability. Indeed, we demonstrated in combined fluorescent and electrophysiological experiments that CRF (100 nM) had a coordinate action on human tumoral corticotrophs comprised of a modest depolarization and an increase in the frequency of both action potentials and subsequent [Ca2+]i transients. A coincident increase in the peak amplitude of the [Ca2+]i transient and after hyperpolarization was also observed in some CRF-stimulated cells. CRF (100 nM) evoked qualitatively similar [Ca2+]i patterns in human tumoral and normal rat corticotrophs not subjected to patch-clamping.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1991

[New technique for treatment of hypospadias with sutures by using an Onlay flap].

The Onlay island flap urethroplasty was originally described for repair of anterior hypospadias without chordee. Then the technique was used for repair of penile hypospadias with a well developed urethral plate and exhibiting little or no chordee after release of skin tethering. In fact, it is possible to treat all penile hypospadias even with severe chordee using: 1) release of the chordee without dividing the urethral plate and 2) reconstruction of the urethra with an onlay island flap.

Humans↗
PubMed1990

Galanin evokes a cytosolic calcium bursting mode and hormone release in GH3/B6 pituitary cells.

The effects of galanin on secretion and cytosolic free Ca2+ concentration ([Ca2+]i) have been studied in GH3/B6 pituitary cells. Prolactin (PRL) and growth hormone (GH) release was measured in column perifusion experiments; [Ca2+]i was monitored in single cells by dual emission microspectrofluorimetry using indo-1 as intracellular Ca2+ probe. Galanin (0.1-1 nM) caused PRL and GH release coincident with a modest rise in [Ca2+]i. The increase in [Ca2+]i comprises the establishment of characteristic long-lasting bursts of [Ca2+]i transients. Galanin acts on Ca2+ entry through voltage-gated Ca2+ channels since there was no response to the peptide when Cd2(+)-a Ca2+ channel blocker-was added to the bath solution. The stimulation of bursting activity by galanin may provide a fine Ca2(+)-signalling mechanism which maximally stimulates hormone release while avoiding refractory periods.

Animals↗
PubMed1990

Thyrotropin-releasing hormone activates a [Ca2+]i-dependent K+ current in GH3 pituitary cells via Ins(1,4,5)P3-sensitive and Ins(1,4,5)P3-insensitive mechanisms.

The role of Ins(1,4,5)P3 in receptor-induced Ca2+ mobilization in pituitary cells was studied at the single-cell level. Experimental strategies were developed which allowed a comparative analysis of the effects of Ins(1,4,5)P3 with those of receptor activation under identical conditions. These include microfluorimetry as well as a novel technique which permits the controlled and rapid application of intracellular messenger molecules to individual cells. This latter approach is based on the tight-seal whole-cell recording (WCR) technique, and utilizes two patch-clamp micropipettes, one for electrical recording and the second for the controlled pressure injection. Ins(1,4,5)P3, when applied with this dual-WCR (DWCR) technique, leads rapidly to a marked rise in cytosolic free Ca2+ [( Ca2+]i) and a concomitant stimulation of Ca2(+)-activated K+ current; Ins(1,4,5)P3 can thus mimic the effects of thyrotropin-releasing hormone (TRH) in the same cells under identical conditions. In cells dialysed intracellularly with heparin, a potent antagonist of Ins(1,4,5)P3 action, the rapid response to extracellular stimulation with TRH was abolished, as were the effects of intracellular application of Ins(1,4,5)P3. Heparin, which abolished Ins(1,4,5)P3 action completely, blocked responses to TRH in some cells only partially, revealing that Ca2+ mobilization response to TRH is in part slower in onset than the response to Ins(1,4,5)P3. It is concluded (1) that Ins(1,4,5)P3 is an essential element for the action of TRH, providing a rapid mechanism for Ca2+ mobilization induced by the releasing hormone and (2) that TRH action in mobilizing intracellular Ca2+ is sustained by a slower mechanism which is independent of Ins(1,4,5)P3.

Animals↗
PubMed1990

Urethral lengthening for neurogenic urinary incontinence (Kropp's procedure): results of 16 cases.

Kropp and Angwafo described a urethral lengthening reimplantation operation for the correction of urinary incontinence. We used this technique in 16 girls with neurogenic incontinence with successful results in 13. We describe the problems encountered during the operation, especially with ureters but also with the tube. Sometimes we resected half to all of the muscular layer to obtain a thin and pliable tube. The procedure was used only in girls.

Adolescent↗
PubMed1990

[Indications and results of the MAGPI intervention in the treatment of minor hypospadias].

In order to clarify the indications of MAGPI procedure (Meatal Advancement and Glanuloplasty Incorporated), 18 patients operated upon have been reassessed after a long follow-up (mean: 30 months). The cosmetic and functional results are good in 16 cases, 2 non-satisfactory results are noticed with a wrong meatal position. The initial position of the meatus (glanular or coronal), the absence of chordee and the initial aspect of the glans (broad and flat) are the three main conditions to obtain a good result.

Esthetics↗