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Biomedical subjects

F Maurice

Publications and source records attributed to F Maurice.

17 recordsLinked to original sources
PubMed1998

Effective blood flow and recirculation rates in internal jugular vein twin catheters: measurement by ultrasound velocity dilution.

The ultrasound dilution technology (Transonic Systems, Ithaca, NY) is a reliable method to assess blood flow (Qb) and recirculation rates (R) in vascular access during hemodialysis. However, the information available on these parameters for central venous dialysis catheters remains scarce at this point. Real Qb and R were evaluated in 33 well-functioning TwinCath (Medcomp, Harleysville, PA) inserted as mid- or long-term hemodialysis vascular access (mean duration since insertion, 270 +/- 253 days); all were implanted into the right internal jugular vein with their multiperforated distal tips located in the superior vena cava or right atrium. Several types of dialysis machines were used (Monitral and AK100, Hospal-Gambro, Lyon, France; 2008E and 4008E, Fresenius, Bad Homburg, Germany). Real Qb was measured with the ultrasound dilution method and compared with the set Qb (indicated by the dialysis machine); R, also evaluated by ultrasound dilution, was evaluated at various Qb with nonreversed lines; therefore, a total of 121 measures were performed. Arterial and venous pressures (PA and PV) were recorded simultaneously. The 33 measures at a set Qb of 200 mL/min showed a mean effective Qb of 210 +/- 18 mL/min and a mean R of 5.3 +/- 5.3%. At a Qb of 300 mL/min, 33 repeated measures resulted in mean effective Qb of 303 +/- 21 mL/min and R of 8.5 +/- 7.0%; 28 measures performed at a set Qb of 350 mL/min showed that the effective Qb was 336 +/- 24 mL/min and that R was 7.8% +/- 6.7%. Finally, an effective Qb of 372 +/- 26 mL/min and an R of 10.9 +/- 8.6% were found for the 27 measures performed at an indicated Qb of 400 mL/min. The difference between indicated and effective Qb was particularly significant for set Qb equal to or above 350 mL/min (P < 0.001). Variable correlations were observed between obtained parameters: Qb eff and R (r = 0.34), PV and R (r = 0.36), Qb eff and PV (r = 0.78), Qb eff and PA (r = 0.71), and PV and PA (r = 0.53). In conclusion, TwinCath delivers an effective Qb of nearly 375 mL/min when Qb is set at 400 mL/min on most dialysis machines. Mean R in TwinCath varies between 5% and 11% for Qb within the range of 200 to 400 mL/min. In well-functioning TwinCath, the ratio between PV and Qb remains usually below 0.5.

Catheterization, Central Venous↗
PubMed1995

The ovine pars tuberalis does not appear to be targeted by melatonin to modulate luteinizing hormone secretion, but may be important for prolactin release.

The pineal hormone, melatonin, transduces photoperiodic information to the neuroendocrine axis of seasonally breeding mammals to regulate reproduction. It is not known where or how melatonin achieves this effect, but the recent identification of the pars tuberalis (PT) as the area with the highest density of melatonin binding sites suggests that this pituitary subdivision may be an important target for the actions of this indoleamine on luteinizing hormone (LH) and prolactin release. The present study was designed to test this hypothesis. Ovariectomized oestradiol-implanted ewes were exposed to inhibitory long days for 85 days and then received melatonin micro-implants (Day 0) in the mediobasal hypothalamus (MBH; n = 7) or PT (Melatonin-PT; n = 5). The effect of these micro-implants was compared to ewes receiving empty micro-implants in the PT (Sham-PT; n = 5). For LH, bi-weekly jugular blood samples were collected and for prolactin, samples were collected every 20 min for 5 h, with the first hour discarded, on Days -4, 26 and 69. Melatonin implanted in the MBH stimulated LH secretion in 3 ewes by Day 46 +/- 0 after implantation, and one ewe by Day 67 after implantation. In contrast, no Melatonin-PT or Sham-PT ewes exhibited an increase in LH secretion by the end of the study (Day 70). A subsequent experiment, in which the Sham-PT ewes were implanted with melatonin both subcutaneously and in the PT showed that the micro-implants did not impair the ability of the ovine reproductive neuroendocrine axis to respond to melatonin.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1994

Evidence that melatonin binding sites in the pars tuberalis do not mediate the photoperiodic actions of melatonin on LH and prolactin secretion in ewes.

An experiment was designed to determine whether the pars tuberalis is the site of action of melatonin involved in the photoperiodic control of LH and prolactin secretion in sheep. In an attempt to produce a 'short-day' effect on these hormones (i.e. stimulation of LH secretion and inhibition of prolactin release), microimplants of melatonin were placed either around the pituitary stalk (n = 6) or in the third ventricle (n = 5) as a control for the efficacy of the microimplant. Two sham-operated groups were treated with empty microimplants around the pituitary stalk (n = 4) or in the third ventricle (n = 3). A further two control groups were given either no melatonin (n = 5) or a melatonin implant s.c. (n = 6). Administration of a melatonin implant s.c. is known to stimulate LH secretion and inhibit prolactin release in photoperiodically inhibited ewes. During the experiment (over 75 days), there was no significant increase in LH concentrations for the ewes receiving melatonin around the pituitary stalk. A similar lack of response was noted in the untreated or sham-treated ewes. In contrast, LH concentrations increased in ewes treated with the melatonin microimplant in the third ventricle on day 37 (+/- 4) and remained high until day 62 (+/- 4). Similarly, in the ewes given an implant s.c., LH concentrations rose on day 39 (+/- 4) and remained high until the end of the study. Furthermore, melatonin caused an inhibition of prolactin secretion relative to controls only when delivered to these sites (i.e. s.c. and into the third ventricle, but not around the pituitary stalk).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

[Central venous catheters: a temporary access, sometimes temporarily prolonged or even permanent].

Out of the 427 patients regularly attended to at the Centre d'Hémodialyse du Languedoc Méditerranéen, 144 have required at one stage the use of internal jugular vein for hemodialysis. Subclavian or femoral cathethers have been resorted to temporarily pending the re-establishment of a pre-existing vascular access. Jugular catheters have been reserved for lasting utilizations thanks to Carnaud's technique using two catheters. Gradually the use of such catheters has become imperative to offer vascular access for the treatment of hemodialysis or to create truly "permanent" accesses. This second solution only concerns a limited number of patients either for their private convenience, or when the establishment of an internal access would require a heavy and uncertain operation.

Actuarial Analysis↗
PubMed1994

[What is to be done in the absence of a superficial venous network compatible with the creation of an arteriovenous shunt?].

When the utilization of a simple arteriovenous fistula is out of the question, or no longer practicable, several alternative solutions have been advocated. Our own experience of surgery rests on 3000 vascular operations on dialysis patients since 1968. The solutions we have come to favour are saphenous vein homografts or heterografts with PTFE. The respective results seem to us equivalent so that either option can be held justified.

Actuarial Analysis↗
PubMed1993

Ram-induced short luteal phases: effects of hysterectomy and cellular composition of the corpus luteum.

Two experiments were conducted on Préalpes ewes to test 2 complementary hypotheses which may explain the short lifespan of corpora lutea observed in some cases after ram-induced ovulation: i) the possible role of the uterus was tested by determining the effects of hysterectomy on the duration of luteal phases after the ram effect (RE); ii) the possible difference due to characteristics of follicles before ovulation was tested by determining the cellular composition and characteristics of corpora lutea (CL) induced by the RE compared to CL of the breeding season (BS) when ovulation is synchronized by FGA-impregnated sponges. In the first experiment, 9 ewes were hysterectomized (Hys) and introduced to rams at the same time as 10 control ewes. Plasma progesterone (P4) was analyzed each day for 17 consecutive d after the introduction of rams. The number of females ovulating was not different for the 2 groups (7/9 vs 9/10, respectively), but no Hys ewes experienced short cycles compared to 5 of the 9 control ewes (P = 0.029). The second experiment involved 16 ewes subjected to the RE in June, and 5 cyclic ewes in January. The ewes were ovariectomized 82 h after the preovulatory LH surge, the CL were separated, weighted and the luteal cells enzymatically dissociated to count the relative proportions of small (< 20 mu diameter) and large cells and assess in vitro P4 secretion both with and without stimulation with 100 ng ovine LH. Plasma P4 concentration increased significantly more slowly in RE than in BS eves (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Short-day effects of melatonin on luteinizing hormone secretion in the ewe: evidence for central sites of action in the mediobasal hypothalamus.

Experiments were designed to localize the central sites of action of melatonin involved in the control of seasonal reproduction. Ewes were exposed to long days and received microimplants of melatonin in the preoptic area (n = 9), anterior hypothalamus (n = 4), dorsolateral hypothalamus (n = 4), or mediobasal hypothalamus (n = 12). The effects of implants were determined by comparison with control ewes (untreated or sham-operated, n = 10) and with ewes treated with an s.c. implant of melatonin (n = 8) or ewes subjected to short days (n = 8). All ewes were ovariectomized and treated s.c. with a silastic capsule of estradiol. Melatonin released in the preoptic area as well as in the anterior and lateral hypothalamus did not cause any difference as compared with the controls (no stimulation of LH secretion and no inhibition of prolactin secretion). In contrast, melatonin implanted in the mediobasal hypothalamus caused an increase in LH secretion in 7 of the 12 ewes on Day 53.0 +/- 4.2 after implantation (mean +/- SEM). Their response was not different compared with that of ewes treated s.c. with melatonin or exposed to short days either in terms of timing (Day 56.3 +/- 6.2 and 59.5 +/- 3.1, respectively, for controls) or of amplitude of the LH response. Similarly, melatonin caused only a reduction of prolactin secretion in the mediobasal, s.c., and short-day groups. It is concluded that the mediobasal hypothalamus or the surrounding tissues could be the sites of action of melatonin involved in the control of seasonal reproduction.

Animals↗
PubMed1993

[Can melatonin be used in out-of-season reproduction in domestic mammals?].

Melatonin, synthetized by the pineal gland, is the chemical messenger which allows seasonal animals to perceive day length changes. The nervous message, transformed into a hormonal one, triggers pulsatile activity of the LHRH neurons. Its sites and mode of actions are not completely elucidated. The most frequent mode of distribution is the sub-cutaneous implant, which induces an advance of the cyclical ovulatory activity of ewes and goats. The date of fertilization is advanced and fecundity of females is improved. It can be used alone, or in association with other hormonal treatments, or after an artificial photoperiodic treatment. Under these conditions, it allows a quantitative and qualitative increase in out-of-season sperm production in rams and he-goats.

Animals↗
PubMed1988

Allergy in long-term hemodialysis. II. Allergic and atopic patterns of a population of patients undergoing long-term hemodialysis.

Maintenance hemodialysis is widely used throughout the world, and anaphylactic reactions appear to be increasing in number and severity. However, the exact incidence of sensitization and the role of atopy in these reactions are not yet fully understood. All of the 111 patients routinely dialyzed in a center were tested. All patients had a complete investigation of atopy, RAST to chemicals released during the procedure of dialysis (ethylene oxide (Eto), formaldehyde, phthalic anhydride, and toluene diisocyanate), skin tests with the effluent, and the titration of blood eosinophils. The incidence of atopy was found to be lower (13.5%) than in the normal population of the area. Skin tests with either histamine or allergens are significantly (p less than 0.001) smaller than those of nondialyzed subjects, and this method does not appear to be ideal in this population of patients. Eto sensitivity ranked first (5.5%), followed by phthalic anhydride sensitivity (3.6%); 5/6 patients who had a sensitivity to Eto and/or phthalic anhydride presented symptoms during dialysis, but they never were life threatening. Formaldehyde RAST was only found in one patient who had a life-threatening reaction. Finally, three patients presenting pruritus had positive skin prick tests with the effluent of the dialyzer. All patients having a first use syndrome and 80/81 symptom-free patients did not have serum-specific IgE against the released chemicals, 5/17 patients who had a pruritus during dialysis had either positive RAST to released chemicals or skin tests to the effluent, 5/8 patients who suffered from anaphylaxis had positive RAST to released chemicals, but only those who had a positive RAST presented a severe reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Allergy in chronic haemodialysis. 1. Double-blind intravenous challenge with formaldehyde.

Patients undergoing chronic haemodialysis are often exposed to formaldehyde formaldehyde (F) has been reported to cause IgE-mediated anaphylactic shock. Many other patients reported pruritus or anaphylaxis-like symptoms when dialysed with F-sterilized dialysers. Ten patients presenting such symptoms were compared with five control subjects. Intravenous double-blind challenges were performed on six consecutive occasions, with capillary flow dialysers sterilized with or without F. Dialysis was performed by an investigator who was not aware of the sterilization procedure. Among the ten F-sensitive patients, five had symptoms with F-sterilized dialysers and no symptoms with new dialysers, sterilized by ethylene oxide and free of F. Symptoms included pruritus and hypotension. These five patients were subsequently dialysed with new dialysers, not sterilized with F, and symptoms subsided. The five other patients had inconclusive challenges. The five control subjects had no symptoms during challenges. Skin-prick tests with F showed that only one of the five patients who had symptoms with F-dialysers had a strongly positive prick test. RAST to F was titrated with HSA-discs but it was negative in all patients and control subjects. Formaldehyde was shown to cause symptoms in some patients under chronic haemodialysis but an IgE-mediated mechanism was not demonstrated.

Adult↗
PubMed1986

Anaphylactic shock caused by formaldehyde in a patient undergoing long-term hemodialysis.

Formaldehyde (F) elicits contact dermatitis and asthma in subjects who are exposed to this chemical when it is applied on the skin or inhaled. An immediate-type hypersensitivity reaction was never confirmed in these reactions. F is widely used in hemodialysis to sterilize adhesives, surgical devices, or reconditioned dialyzers. A 20-year-old woman who was subjected to hemodialysis for the past 4 years had a contact dermatitis to F. When hemodialysis was performed with a new dialyzer not sterilized with F, there were no symptoms. She had minor symptoms of anaphylaxis characterized by rhinitis, wheezing, and headache on the first use of a reconditioned dialyzer. Two days later, she was dialyzed with the same reconditioned dialyzer and developed within minutes a severe anaphylactic shock requiring resuscitation. The patient had no personal or family history of atopy. Prick tests and RAST to common food and inhlant allergens were negative. Prick tests performed with 0.1% and 1% F were positive in the patient, whereas they were negative in control subjects. RAST to F was performed with discs specially prepared and coated with human serum albumin. RAST was strongly positive. RAST to ethylene oxide was negative. A patch test with F was performed and induced an anaphylactic shock 26 hours after the skin application of F. The patient did not present any anaphylactic symptoms with the use of nonreconditioned dialyzers. An immediate-type allergy to F mediated by IgE may be envisaged in this patient.

Adult↗
PubMed1986

Bronchiectasis: assessment by thin-section CT.

To assess the accuracy of computed tomography (CT) in the evaluation of bronchiectasis, we performed thin-section CT in 36 patients with clinical findings suggestive of this diagnosis. CT was performed with 1.5-mm section thickness and 10-mm intersection spacing. Bilateral (eight patients) and unilateral (28 patients) bronchograms were obtained. CT and bronchographic findings were correlated in 44 lungs. In 15 lungs no bronchiectasis was observed on CT scans and bronchograms. In 25 lungs both examinations accurately indicated the presence and extent of bronchiectasis. In two lungs the extent of disease was underestimated on CT, which failed to indicate bronchiectasis in one segment of the affected lobe. In one case CT findings suggested focal bronchial disease, but the lung was misinterpreted as not bronchiectatic; the bronchogram showed cylindric bronchiectasis. In one case CT disclosed cylindric bronchiectasis in a lobe that was bronchographically normal, but in this case the bronchogram was probably misinterpreted as false negative. In two cases lung findings were better visualized on CT scans than on bronchograms. It is concluded that thin-section CT is an accurate procedure in the recognition of bronchiectasis.

Adolescent↗
PubMed1986

[Spontaneous fracture of the sacrum due to "insufficiency". An overlooked cause of low lumbago in elderly women].

A case of insufficiency fracture of the sacrum is reported. These fractures usually occur in elderly women and are secondary to various conditions, mainly postmenopausal or steroid-induced osteoporosis and radiation therapy. They are often overlooked or confused clinically and radiographically with metastatic disease. Findings on plain films are often subtle. Radionuclide bone scan shows a characteristic H or butterfly shaped pattern of increased uptake in the sacral alae. The diagnosis is confirmed by conventional tomograms or CT which show the fracture always surrounded by prominent sclerosis.

Aged↗
PubMed1984

[Anaphylactic reactions during hemodialysis: responsibility of the dialysis membrane (cuprophane)].

Iterative hemodialysis causes only exceptionally anaphylactic reactions. In those cases it has been possible to incriminate sterilizing agents (ethylene oxide, formaldehyde) and in a few cases the membrane. We report the case of one patient suffering from a chronic renal failure who had been undergoing hemodialysis treatment for more than six years in whom we noticed anaphylactic reactions at the beginning of each dialysis session carried on with cuprophan. We were able to use three different types of dialysis membranes: cuprophan, polyacrylonitrile and cellulose acetate, and two means of sterilization: ethylene oxide and gamma rays. The disorders we observed do not seem to be related to the phenomena usually observed during hemodialysis. The clinical signs linked with hypereosinophilia (13,000/mm3), hyperbasophilia (140/mm3) and an increase in total serum IgE disappeared when cuprophan membrane was replaced by cellulose acetate. One year later, hypereosinophilia had disappeared, hyperbasophilia had subsided, total IgE remained high. We conclude that IgE dependent anaphylaxis might be due to one component of the cuprophan membrane.

Adult↗