Showing papers by "University of Rouen published in 1993"

Pharmacokinetics and efficacy of a long-acting formulation of the new somatostatin analog BIM 23014 in patients with acromegaly.

Abstract: The treatment of acromegalics with somatostatin analogs requires continuous sc infusion using pumps or several sc injections daily. Long-acting formulations (BIM-LA) of BIM 23014 (BIM) using delayed microcapsules may provide a more convenient form of therapy. Fourteen acromegalics whose GH secretion had not been normalized by transphenoidal surgery followed, in 10 cases, by pituitary radiotherapy (performed at least 2 yr before the study) were studied. Eight of these patients participated in an initial study of the pharmacokinetics of BIM-LA, after which a 6-month efficacy study was undertaken. The 8 patients in the pharmacokinetic study had an initial blood sample collected for measurements of plasma GH and insulin-like growth factor-I (IGF-I) levels before the im injection of 30 mg BIM-LA, and blood samples were subsequently taken 2, 4, 6, and 8 h after injection and then twice a week for a month. Plasma IGF-I levels were measured on days 4, 14, 20, and 30 after the injection. Assays of plasma GH, IGF-I, and BIM levels were performed by RIAs. The results showed that plasma GH levels were markedly reduced from 26.0 +/- 2.0 to 2.5 +/- 0.2 micrograms/L 2 h after BIM-LA injection and remained lower than 5 micrograms/mL for the 11 following days. Plasma GH levels increased to 5.5 +/- 1.2 micrograms/L on day 14 and returned to basal values 23 days after injection. Similarly, plasma IGF-I decreased from an initial level of 656 +/- 43 to 324 +/- 23 ng/mL on day 4 and remained close to the normal range for the following 10 days. Plasma BIM levels reached a peak 2 h after the injection (7.2 +/- 2.3 ng/mL) and remained higher than or close to 1 ng/mL until the 14th day after injection. This initial study showed that a single injection of 30 mg BIM-LA effectively suppressed GH and IGF-I secretion for at least 14 days, in accordance with the kinetics of the drug in plasma. Based on the results of this initial study, 30 mg BIM-LA were injected twice monthly for 6 months in all 14 patients. All of the subjects had a basal evaluation before treatment with BIM-LA and were then subjected to assessment of clinical, pituitary, and hormonal parameters. Patients were evaluated after 3 and 6 months of treatment on the same basis as that previously used when starting the BIM-LA therapy. Plasma BIM levels were measured monthly. Clinical signs of acromegaly improved during the treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Pharmacokinetics of lamotrigine in patients with renal impairment: influence of haemodialysis.

Abstract: The pharmacokinetics of a single 100 mg oral dose of lamotrigine, a new anticonvulsant drug, were studied in six healthy volunteers and in twenty patients with various degrees of renal impairment. Six of these patients were regularly haemodialysed. Lamotrigine concentrations in plasma and urine were measured by the HPLC method. The mean peak plasma concentrations of lamotrigine, tmax, volume of distribution and total clearance were not significantly modified by the degree of renal impairment. The elimination half-life of lamotrigine was approximately 25 h in subjects with normal renal function and 50 h in uraemic patients. These are very large variations in uraemic patients and the results were not statistically significant. Renal clearance of lamotrigine is significantly reduced. Urinary elimination of unchanged and conjugated lamotrigine was reduced in uraemic patients. Thus it seems necessary to treat carefully patients with a very severe renal insufficiency since very large variations in pharmacokinetics were found. A 100 mg oral dose every two days is recommended if creatinine clearance is below 10 ml/min. Haemodialysis shortened the elimination half-life from 59.6 +/- 28.1 h during the interdialysis period to 12.2 +/- 6.4 h during the dialysis period; 17% of the dose was extracted by haemodialysis.

Functional subcaste discrimination (foragers and brood-tenders) in the antCamponotus vagus scop.: polymorphism of cuticular hydrocarbon patterns.

Abstract: In the antCamponotus vagus, when selected foragers that had been earlier removed from the foraging arena and brood-tenders that had been earlier removed from the nest were placed together in a foraging arena, most of the brood-tenders and only a few of the selected foragers were carried back to the nest by nonselected foragers. We hypothesize that cuticular hydrocarbons serve as a cue that allows foragers to discriminate between members of their own subcaste and brood-tenders. It has been established that the proportions of certain hydrocarbons, which are the same regardless of the colony studied, vary from one worker subcaste to another and thus constitute a specific chemical signature. These hydrocarbons belong to a wide range of chemical families (alkanes, monomethylalkanes, and dimethylalkanes). The greatest differences between the two subcastes were observed on the thorax of workers. Principal component analyses performed on the hydrocarbons (or hydrocarbon combinations) corresponding to the 45 main peaks in the cuticular profiles of the head and thorax of brood-tenders and foragers of several colonies show that there exist quantitative differences between the various signatures that characterize the colony, the worker subcastes, and the various body parts within the same species, which can be classified in a hierarchy where the differences between worker subcastes are less pronounced than those between body parts or between colonies.

Large deviations for a reaction diffusion model

Abstract: We obtain large deviation estimates for the empirical measure of a class of interacting particle systems. These consist of a superposition of Glauber and Kawasaki dynamics and are described, in the hydrodynamic limit, by a reaction diffusion equation. We extend results of Kipnis, Olla and Varadhan for the symmetric exclusion process, and provide an approximation scheme for the rate functional. Some physical implications of our results are briefly indicated.

Ischaemic preconditioning is not mediated by oxygen derived free radicals in rats.

Abstract: Objective: Although several studies have shown that ischaemic preconditioning greatly limits myocardial infarct size in the rat, the mechanisms of the beneficial effect of preconditioning in this species are not known. Experiments in dogs and rabbits have suggested that this effect could be related in part to the production of oxygen derived free radicals, as free radical scavengers partially prevent the limitation of infarct size induced by preconditioning. This study was designed to assess the contribution of oxygen derived free radicals in the infarct size limiting effects of preconditioning in rats, using the cell diffusible free radical scavenger N-2-mercaptopropionyl glycine (MPG). Methods: Open chest rats underwent 20 minutes of coronary occlusion followed by one hour of reperfusion. Preconditioning was elicited by three cycles of five minutes ischaemia and five minutes reperfusion. MPG (20 mg·kg−1) was infused for 60 minutes starting 30 minutes before preconditioning. Control hearts (with or without MPG) were treated identically but without ischaemic preconditioning. Area at risk and infarct size were determined by India ink injection and triphenyltetrazolium chloride stain, with computerised analysis of enlarged sections after colour video acquisition. Results: During preconditioning, reperfusion after the first episode of ischaemia was associated with a high occurrence of severe ventricular arrhythmias, and this was reduced by MPG. Preconditioning, however, reduced arrhythmias and mortality during subsequent episodes of ischaemia and reperfusion. In the absence of MPG, preconditioning greatly limited Infarct size (from (mean (SEM)) 59.8(3.9)% to 1.2(0.6)% of the area at risk; p < 0.01). MPG alone did not affect infarct size (60.5(6.1)%), and did not modify the infarct size limiting effect of preconditioning (infarct size: preconditioning 1.2(0.6)%; preconditioning + MPG 2.9(1.2)%. Conclusions: Preconditioning greatly reduced infarct size, and this was not affected by MPG. These experiments suggest that production of oxygen derived free radicals does not contribute to preconditioning in the rat heart. Cardiovascular Research 1993; 27 :2016-2021

Localization, characterization and activity of pituitary adenylate cyclase-activating polypeptide in the frog adrenal gland

Abstract: Pituitary adenylate cyclase-activating polypeptide (PACAP) has recently been isolated from the frog brain and the sequence of the peptide appears to be strikingly similar to that of mammalian PACAP. In the present study, we have investigated the localization of PACAP in the frog interrenal (adrenal) gland by immunocytochemistry using antisera directed against PACAP 38 or PACAP 27. Two types of PACAP-immunoreactive fibres were observed: thick varicose fibres coursing between adrenal cells and thin processes located in the walls of blood vessels irrigating the gland. Bilateral transection of the splanchnic nerves did not affect the intensity and distribution of PACAP immunoreactivity. The mean +/- S.E.M. concentration of PACAP, measured by radioimmunoassay in crude adrenal extracts, was 0.65 +/- 0.16 nmol/g wet tissue. Two molecular forms of PACAP in the adrenal gland were characterized by reversed phase high-performance liquid chromatography combined with radioimmunoassay quantification. The elution profiles revealed the existence of two peaks exhibiting the same retention times as synthetic frog PACAP 38 (fPACAP 38) and PACAP 27, the predominant form being PACAP 38. The possible involvement of PACAP in the regulation of adrenal steroidogenesis was investigated in vitro using a perifusion system for frog adrenal slices. Graded doses of fPACAP 38 (0.1-10 mumol/l) increased the secretion of both corticosterone and aldosterone in a dose-dependent manner. Administration of repeated pulses of fPACAP 38 (1 mumol/l), at 120-min intervals, led to a reproducible stimulation of corticosteroid secretion without any tachyphylaxis. Prolonged infusion (2 h) of the peptide induced a rapid increase in corticosterone and aldosterone output, followed by a gradual decline in the secretion rate, suggesting the occurrence of a desensitization phenomenon. Synthetic porcine vasoactive intestinal peptide, which is structurally related to PACAP, was about ten times less potent than fPACAP 38 in stimulating steroidogenesis while the [Des-His1]-fPACAP 38 analogue was 100 times less effective. These results demonstrate that a peptide closely related to fPACAP 38 is present in fibres innervating the frog adrenal gland and could participate in the regulation of corticosteroid secretion, particularly during neurogenic stress.

Partially commutative magnus transformations

Abstract: Grâce a l’introduction de la notion de forme exponentielle reduite, nous montrons l’injectivite de la transformation de Magnus associee au groupe partiellement commutatif libre F(A, ϑ). Nous en deduisons la separation de la topologie p-adique de F(A, ϑ), l’existence de plus petites racines dans F(A, ϑ) et enfin la structure des centralisateurs dans F(A, ϑ). We introduce the notion of reduced exponential form in the free partially commutative group F(A, ϑ). This allows us to prove that the Magnus transformation associated with F(A, ϑ) is injective. We deduce from this result that the p-adic topology on F(A, ϑ) is Hausdorff, that there exist least roots in F(A, ϑ) and finally the exact structure of centralizers in F(A, ϑ).

Regulation of α-Melanocyte-Stimulating Hormone Release from Hypothalamic Neuronsa

Abstract: a-Melanocyte-stimulating hormone (a-MSH) is a tridecapeptide amide that was initially isolated and characterized from the intermediate lobe of the pituitary. a-MSH derives from a multifunctional precursor protein, called proopiomelanocortin (POMC), which can generate through proteolytic cleavage various regulatory peptides including corticotropin, melanotropins, lipotropins and endorphins . I The gene encoding POMC is expressed in corticotrope cells of the pars distalis, in melanotrope cells of the pars intermedia, and in two populations of neurons located respectively in the arcuate nucleus of the hypothalamus? and in the caudal portion of the nucleus s01itariu.s.~ POMC neurons of the arcuate nucleus project in a number of brain areas including several hypothalamic nuclei, the median eminence, the septum, the periventricular region of the thalamus, the amygdala, and the rh~mbencephalon.~ POMC-producing neurons of the nucleus sotitarius innervate the caudal rhombencephalon and the spinal cord.5 Processing of POMC occurs in a tissue-specific manner, depending on the enzymatic equipment that is available in each cell type. In corticotrope cells, POMC is cleaved at the level of three dibasic amino acid residues, thus generating a large terminal fragment (16 K peptide), the joining peptide, ACTH, and P-lipotropin. In melanotrope cells and in hypothalamic neurons, further processing occurs leading to the formation of several y-MSHs, a-MSH, corticotropinlike intermediate lobe peptide (CLIP), y-LPH, and P-end~rphin.~.’ A large body of evidence indicates that the neuropeptide a-MSH can be regarded as an authentic neurotransmitter and/or neuromoduiator. Intracerebral injection of a-MSH affects a number of behavioral processes8 such as learning, memory, attention, motivation, and grooming behavior. Furthermore, a-MSH exerts a trophic action on the central nervous system and induces a marked antipyretic effect. Electron microscopic studies revealed that a-MSH-immunoreactive material is sequestered in dense core secretory vesicle^.^ Concurrentiy, it

Phosphatization of calcium carbonate in phosphorites: microstructure and importance

Abstract: Fabrics of phosphatized calcium carbonate particles in various phosphorites have been studied using scanning electron microscopy coupled with X-ray dispersive microanalysis. Replacement of calcium carbonate by apatite has been observed in bivalve shell fragments and in foraminiferal tests; replacement proceeds at constant volume with excellent preservation of the original microtextures. In some deposits, replacement of carbonate by apatite is the main phosphogenic process. However, in general, the process seems to be far less important than might be believed purely on the basis of thin section observations. In many phosphorites, internal or external apatite moulds of bioclasts are common, including very small particles such as coccoliths in phosphatized chalks. Apatite precipitation was typically followed by carbonate dissolution. Later apatite precipitation within the dissolution voids may produce partial or total phosphate pseudomorphs of the original carbonate grain. In these examples direct replacement of carbonate by phosphate cannot be demonstrated.

Neuroanatomical and physiological evidence for the involvement of pituitary adenylate cyclase-activating polypeptide in the regulation of the distal lobe of the frog pituitary

Abstract: Pituitary adenylate cyclase-activating polypeptide (PACAP) is a 38 amino-acid peptide which belongs to the glucagon/secretin/ vasoactive intestinal peptide superfamily. The sequence of PACAP is identical in all mammalian species studied so far but frog PACAP differs by one amino-acid from mammalian PACAP. The aim of the present study was to investigate the presence of PACAP in the hypothalamo-pituitary complex of the frog Rana ridibunda and to determine the biological activity of frog PACAP on homologous pituitary cells. The distribution of PACAP-containing neurons and fibers was examined by the indirect immunofluores-cence method using an antiserum raised against the N-terminal region of the peptide. In the hypothalamus, PACAP-immunoreactive perikarya were localized in the preoptic nucleus and the dorsal and ventral infundibular nuclei. Beaded nerve fibers were observed coursing from the ventral infundibular nucleus to the external vascular layer of the median eminence. A dense network of immunoreactive axons terminated in the vicinity of the capillaries of the hypophysial portal system. The neurointermediate lobe and the distal lobe of the pituitary were devoid of immunoreactive elements. The amount of PACAP-like immunoreactive material in hypothalamus extracts was measured by radioimmunoassay; the apparent concentration of PACAP was 4.5 ng/mg protein. Synthetic frog PACAP38 and PACAP27 induced a similar dose-dependent stimulation of cAMP production in isolated frog distal lobe pituitary fragments (ED50= 2 × 10−8 M). At the maximum dose tested (5 × 10−6 M), both frog PACAP38 and PACAP27 produced a 4-fold increase in cAMP production. In contrast, the truncated form [Des-His1frog PACAP38 did not affect adenylate cyclase activity demonstrating therefore that the N-terminal histidyl residue is essential for the biological activity of the peptide. [Des-His1]frog PACAP38 did not antagonize the stimulatory effect of frog PACAP38 or PACAP27 on cAMP production. Taken together, these data support the concept that, in amphibians as in mammals, PACAP may act as a hypophysiotropic neuropeptide.

Cell immobilization in composite agar layer microporous membrane structures: growth kinetics of gel-entrapped cultures and cell leakage limitation by a microporous membrane

Abstract: Agar discs containing different amounts of viable Escherichia coli cells (from 10 to 106 organisms·g−1 agar) were incubated in a nutrient medium and the growth of agar-entrapped bacteria and free (released) cells was monitored. The study was repeated with composite immobilized-cell structures obtained by placing a microporous membrane filter between the gel matrix and the incubation medium. In both cases, immobilized cells grew exponentially and reached a peak concentration an order of magnitude higher than that of free (suspended) cell cultures. The maximum specific growth rates of entrapped bacteria, ranging between 0.0115 min−1 and 0.0145 min−1, i.e., slightly higher than that of control free cultures (0.011 min−1), showed no clear dependence on the initial cell loading (ICL). The microporous filter proved efficient in limiting cell leakage since it noticeably lengthened the leakage time at a given ICL. This efficiency, however, decreased at high ICL and high growth rate of immobilized organisms.

Physical methods to locate metal atoms in biological systems.

Abstract: Publisher Summary Metal elements are involved in a number of cellular processes such as enzyme activation, transmembrane transport, water exchange, signal transduction, and intercellular communication. For instance, the alkaline and alkaline earth cations Na + , K + , Mg 2+ , and Ca 2+ play a key role in the functioning of living systems; Cu, Fe, Zn, or Mn may be associated with proteins; heavy metals and radioactive Sr 2+ or Cs + can be dangerous pollutants; and lithium or cobalt may be used as specific inhibitors of biological processes. Quantitatively mapping, or depth-profiling, metal atoms in biological systems can thus help toward an understanding of physiological mechanisms. A variety of physical methods are progressively being adapted to the study of biological specimens. This chapter discusses X-ray fluorescence, analytical electron microscopy (X-ray microanalysis, electron energy loss spectrometry, and Auger spectrometry), analysis of tracks originating from nuclear events, nuclear probes, and secondary ion imaging methods. Among these different methods, some can detect most chemical elements, whereas others apply to only a few elements. Some are useful mainly on a histological scale, whereas, in other cases, the spatial resolution may be good enough for considering subcellular localizations. In vivo measurements may be possible in a few cases, but most often, the methods are meant for fixed preparations. It is then clearly requisite that the techniques used for sample preparation—fixation, dehydration, and staining—do not disturb the natural distribution of the metal ions under observation.

Immunocytochemical localization of atrial natriuretic factor (ANF)-like peptides in the brain and heart of the treefrog Hyla japonica: Effect of weightlessness on the distribution of immunoreactive neurons and cardiocytes

Abstract: The localization of atrial-natriuretic factor (ANF)-like immunoreactivity was investigated in the brain and heart of the treefrog Hyla japonica by the indirect immunofluorescence technique. Concurrently, the effect of weightlessness on the distribution of ANF-containing neurons and cardiocytes was studied in frogs that were sent into space for 9 days on the space station "MIR." In control animals, the amygdala contained the most prominent group of ANF-immunoreactive cells and fibers. ANF-positive neurons and nerve processes were also detected in other areas of the telencephalon such as the nucleus olfactorius, the pallium mediale, and the striatum. In "space frogs," the intensity of labeling of the amygdala and nucleus olfactorius was similar to that seen in control animals. In contrast, the pallium and the striatum of "space frogs" were totally devoid of positive cell bodies. In the diencephalon, of all animals, numerous ANF-immunoreactive perikarya and fibers were seen in the hypothalamus, the anterior thalamus, the infundibulum, and the median eminence. ANF-positive cell bodies were also noted in the lateral forebrain bundle of control frogs but were absent in "space frogs." The major difference between control and "space frogs" was observed in the posterior nuclei of the thalamus. In "space frogs," the nucleus posterocentralis thalami and the nucleus posterolateralis thalami exhibited large ANF-immunoreactive perikarya, while, in control frogs, these nuclei only contained scarce positive nerve fibers. In the mesencephalon, ANF-positive cell bodies and nerve processes were seen in the nucleus tegmenti mesencephali, the interpeduncular nucleus, and the nucleus cerebelli of all animals. However, stained perikarya were only observed in the nucleus reticularis isthmi of control frogs. In the heart, atrial cardiocytes exhibited intense ANF-like immunoreactivity. ANF-positive myocytes were also detected in the subpericardial region of the ventricle. The density and distribution of the staining were identical in the heart of control and "space frogs." These data support the concept that prolonged exposure to microgravity affects biosynthesis and/or release of ANF-related peptides in discrete regions of the amphibian brain.

Multihormonal regulation of pituitary melanotrophs.

Abstract: The pars intermedia of the pituitary is composed of one predominant category of endocrine cells, the melanotrophs, which synthesize the precursor protein proopiomelanocortin (POMC). 1,2 In lower vertebrates a-melanocyte stimulating hormone (a-MSH), which plays a pivotal role in skin color adaptation, is considered as the major peptide hormone secreted by melanotrope cells. Early experiments demonstrated that the release of MSH from the intermediate lobe is primarily under an inhibitory control from the hypothalamus. In particular, hypoth~amic lesions, pituitary stalk section, and autotransplantation of the pituitary all induce darkening of the animal^.^.^ However, Wilson and Morgan have observed that the concentration of MSH in the plasma of black-adapted Xenopus laevis was higher than in pituitary stalk-sectioned animals,’ suggesting the involvement of stimulatory hypothalamic factor(s) in the control of MSH release. The purpose of the present review is to summarize our current knowledge on the regulatory mechanisms that are involved in the control of the activity of amphibian pituitary meianotrophs.

Immunohistochemical distribution, biochemical characterization, and biological action of tachykinins in the frog adrenal gland

Abstract: The distribution of tachykinin-like immunoreactivity (LI) was studied in the adrenal gland of the frog Rana ridibunda using the immunofluorescence technique. A dense network of varicose fibers immunoreactive to both substance-P (SP) and neurokinin-A (NKA) was found in the adrenal tissue. In contrast, no positive fibers could be detected using antineurokinin-B (NKB) antibodies. At the electron microscope level, the immunogold technique revealed that tachykinin-LI was sequestered in dense core vesicles of 50-70 nm. Bilateral transection of either splanchnic or vagus nerves or total lesion of celiac sympathetic ganglion did not suppress tachykinin-LI. A combination of HPLC analysis and RIA detection was used to characterize tachykinin-LI in frog adrenal extracts. Two major peaks were resolved, which coeluted, respectively, with synthetic ranakinin, a novel tachykinin previously isolated from the frog brain, and [Leu3,Ile7]NKA previously isolated from the frog gut. No NKB could be detected in the extracts. Th...