[The birth of hospital biochemistry].
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Biochemistry↗
Biomedical subjects
C Dreux
Publications and source records attributed to C Dreux.
A "septide-sensitive" receptor is not involved in tachykinin-mediated secretory and inositol phosphate responses in rat parotid gland: are several transduction pathways involved after the stimulation of the NK1 receptor?
In the rat parotid gland, the neuropeptide substance P (SP), as well as SP(4-11), and septide elicited inositol phosphate production (EC50 values 0.44, 2, and 20 nM, respectively). No additivity of the maximal response to the three agonists was observed. SP, SP(4-11), and septide also stimulated protein secretion; for SP, two EC50 were determined (0.5 and 160 nM), whereas a single one could be determined for SP(4-11) and septide (EC50 values 15 and 20 nM, respectively). The selective tachykinin NK1 receptor antagonist RP67580 acted as a competitive inhibitor of both SP- and SP(4-11)-induced inositol phosphate production. Its effect on septide-induced inositol phosphate production was noncompetitive. RP67580 is apparently as potent at antagonizing septide, SP, or SP(4-11) (in all cases KB = 3 nM). These results show that in parotid gland, only NK1 receptors are activated by SP, SP(4-11), and septide. We also showed that the protein secretion stimulated by SP was inhibited competitively by RP67580, whereas the effect of RP67580 was noncompetitive on protein secretion when SP(4-11) or septide was used. Our data indicate that in rat parotid gland, the existence of a specific "septide-sensitive" receptor can be ruled out and that only the NK1 receptor is present and mediates cellular responses. Taken together, these results show that in this tissue the NK1 receptor would present at least two different binding sites that could be coupled to different transduction pathways and that would regulate protein secretion.
Animals↗
Beta-adrenergic-induced calcium efflux in rat parotid gland. Is mitochondrial Na+/Ca2+ exchange involved?
The effects of diltiazem were examined on 45Ca efflux in rat parotid glands. First, we showed that mitochondrial Na+/Ca2+ exchange occurs in rat parotid glands and that diltiazem inhibited the mitochondrial Na(+)-dependent calcium efflux. We also confirmed that in rat parotid gland, diltiazem did not modify calcium movements at plasma membrane level. Secondly, we tested the effects of diltiazem on pieces of parotid glands. Diltiazem alone induced 45Ca efflux from parotid lobules. When the effect of diltiazem was tested on isoproterenol-induced 45Ca efflux, the effects of the two drugs were less than additive. By comparison, diltiazem did not modify carbachol induced 45Ca efflux. Diltiazem was able to induce calcium efflux from an intracellular calcium pool, which is not the IP3 sensitive one. These data support the previous hypothesis that isoproterenol and carbachol do not mobilize the same calcium pool. Although we did not precisely determine the calcium pool sensitive to beta-adrenergic stimulation, we cannot rule out the hypothesis that mitochondria would be that store.
Animals↗
Simultaneous determination of all-trans and 13-cis retinoic acids and their 4-oxo metabolites by adsorption liquid chromatography after solid-phase extraction.
All-trans retinoic acid (all-trans RA), the active metabolite of vitamin A, has been demonstrated to be an efficient alternative to chemotherapy in the treatment of acute promyelocytic leukemia (APL), the AML3 subtype of the FAB cytological classification. Complete remission is obtained by inducing terminal granulocytic differentiation of the leukemic cells. To study all-trans RA pharmacokinetics in patients with APL, a rapid, precise and selective high-performance liquid chromatographic (HPLC) assay was developed. This method is easy and shows good repeatability (C.V. = 8.41-12.44%), reproducibility (C.V. = 9.19-14.73%), accuracy (C.V. = 3.5-11%) and sensitivity with a detection limit of 5 pmol/ml. The analysis is performed using normal-phase HPLC in an isocratic mode with UV detection after solid-phase extraction on octadecyl (C18) columns. The mobile phase is hexane-dichloromethane-dioxane (78:18:4, v/v) containing 1% acetic acid.
Adsorption↗
Phosphoinositide synthesis in desensitized rat pancreatic acinar cells.
To help understand the possible role of phosphoinositide turnover in the desensitization process, the availability of phosphatidylinositol 4,5-bisphosphate was investigated in normal and desensitized pancreatic acinar cells treated with carbamylcholine (Cch), caerulein (Cae), and the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA). In control acini, incorporation of [myo-3H]inositol into total phosphoinositides was maximal at 120 min, was Cch and Cae dose dependent, and was insensitive to TPA. Cch stimulation increased the proportion of [myo-3H]inositol incorporated into phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], whereas Cae specifically channeled [myo-3H]inositol incorporation into phosphatidylinositol 3,4-bisphosphate and phosphatidylinositol 3,4,5-trisphosphate. In the desensitized cells, preexposure to Cch and Cae, but not to TPA, increased the subsequent basal rate of [myo-3H]inositol incorporation into total phosphoinositol (PI) by 66 and 50% above control values. There were no subsequent responses to increasing concentrations of Cch, Cae, and TPA during a second incubation. Desensitization of the pancreatic secretory responses to Cch, Cae, and TPA does not seem to result from a decrease either in total PI or in specific PtdIns(4,5)P2 synthesis, which is needed for inositol trisphosphate and diacylglycerol production.
Animals↗
[Molecular genetics of familial and sporadic forms of human prion diseases].
Prion diseases, also known as transmissible subacute spongiform encephalopathies (TSSE), are rare neurodegenerative disorders of both humans and animals. Their biochemical hallmark is an accumulation in the brain of an abnormal form of the host-encoded prion protein (PrP). This pathological accumulation could result from a protein conformational change under the influence of unknown factors. The normal function of PrP is unknown. The abnormal form is thought to induce neurodegeneration when experimentally or accidentally introduced in recipient hosts. Such a possibility would explain the transmissible character of these diseases illustrated in humans by iatrogenic contamination. Considerable attention has been focused on the host PrP gene and its relation with the genetic susceptibility of humans and animals. Mutations in PRNP, the gene which encodes PrP in humans, are present in 17% of the patients and might be causative. In patients without any PRNP mutation, a coding polymorphism (129 Met/Val) defines a predisposing factor. Important progress in the molecular genetics of TSSE in both humans and animals have been performed for few years and point out that the development of different forms of these diseases, experimental, iatrogenic or spontaneous, are strongly dependent on the primary structure of the host PrP.
Animals↗
The impact of clinical biochemistry on university education in France.
In France, clinical biochemistry, similar to other disciplines of laboratory medicine, is taught in both the regular medical and pharmacy curricula, but medical teaching is oriented more towards the interpretation of laboratory findings than test performance. At present, there is no compulsory program of lifelong continuing education, but it is planned to introduce such an obligation in the near future. The practice of laboratory medicine is regulated strictly by the national Health Administration. Clinical laboratories are multidisciplinary, covering simultaneously clinical biochemistry, microbiology, parasitology, hematology and immunology. The only officially recognized laboratory profession is that of 'Director of a Laboratory for Medical Analysis'. The practice of this profession is only open to physicians and pharmacists, provided they graduated in 'Medical Biology' after 4 years of specialized training through a particular type of residency called the 'internat'. The 'interns' are selected by competitive examination. After completing their curriculum, specialized physicians or pharmacists can without further examination or certification either enter a career in a hospital, a university, or both, or direct or co-direct a private laboratory. In this scheme, clinical biochemistry exists as a separate academic discipline, but barely as a distinct profession.
Biochemistry↗
[Parotid gland in rats, a model for the study of regulated exocrine secretion].
In rat parotid glands protein secretion studied in vitro is weakly stimulated by carbachol (which induces Phospholipase C activation) and strongly by isoprenaline (which activates the adenylate cyclase system). We show in this work that the simultaneous activation of the two types of receptors induces a potentiation of protein secretion. This is not due to an enhanced IP3 or cAMP accumulation nor any modification on calcium movements. Potentiation of protein secretion is also mimicked by analogues of second messengers suggesting that this phenomenon is a post-receptor event which takes place at a distal step from messenger production. Furthermore we also showed that the activation of beta-adrenergic receptor led to two parallel events: cAMP accumulation and calcium movements. These two events were required to obtain maximal secretion. We also show that cholinergic induced secretion is also the result of a synergism between calcium and protein kinase C activation. At a physiological level, the synergism between two different transduction pathways must play an important role. This surely allows the cells to give maximal response, without any desensitization phenomena.
Animals↗
[Human transmissible dementia: prion diseases?].
Subacute transmissible spongiform encephalopathies (STSE) represent a cause of presenile dementias, found in man (Creutzfeldt-Jakob disease, Gerstmann-Straussler syndrome, Kuru), in sheep and goats (scrapie), in cattle (bovine spongiform encephalopathy) and in various mammals. It seems that the frequency of the human spongiform encephalopathy (HSE) is more frequent than thought up to now and an alimentary origin is not to be discarded. Many discussions are held concerning the nature of the transmissible agent: virus, virino, prion? Isolation of an abnormal protein, the isoform PrPSc resulting from an unknown alteration of a protein PrPc encoded in man by the chromosome 20 is presently the basis for seeking the cause of transmissible dementias. Molecular genetic studies of the gene PrP have demonstrated the existence of many mutations: are they the actual cause of the STSE or only a favouring factor? The existence of familial sporadic or infectious forms of HSE might be explained by alterations of the conformation of PrPc into PrPSc, able to induce this structure modification to last when thereafter the synthesis of the normal protein is achieved. The "chaperone" protein model can be questioned in this respect. For the moment the research work is developed into characterization of humoral or genetic markers able to detect the predisposed subjects in high-risk families. HSE are also an interesting model for other types of dementias, especially the Alzheimer disease which is still the preferred target of research in this field.
Animals↗
Some aspects of the use of dextran sulfate-cellulose columns for the treatment of familial hypercholesterolemia.
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Adolescent↗
First heterotransplantation of a human carcinoid tumor into nude mice.
The first successful heterotransplantation of a human carcinoid tumor into nude mice is reported. CSH, a voluminous hepatic metastasis of a primary bronchial carcinoid tumor (CSB) was resected and transplanted into three irradiated nude (Swiss-nu/nu) mice both by subcutaneous (SC) and intramuscular (IM) routes; the success rate was five of six. Heterotransplanted tumors took 4 to 5 months to appear in the mice and 1 month to attain a width of 0.5 cm. Both human and mouse tumors (named CSH-SC and CSH-IM) were studied by light and electron microscopy. They were Grimelius-positive, neuron-specific enolase-positive, and bombesin-negative by immunocytochemistry. Furthermore, CSH-SC cells presented characteristic (pear-shaped, rod-shaped, or tadpole-shaped) neurosecretory granules. Although CSB and CSH were slightly serotonin positive by immunocytochemistry, only a few serotonin-positive cells were found in CSH-SC and none in CSH-IM, suggesting partial loss of differentiation or an increase in serotonin catabolism during transplantation.
Aged↗
Process of re-establishment of beta-adrenergic induced protein secretion after cytochalasin D inhibition in rat parotid gland. Effect of cholinergic agonist, phorbol ester and calcium.
In rat parotid gland, 3H-protein secretion is stimulated by beta-adrenergic receptor activation (via cAMP) and also by cholinergic receptor activation (via IP3, calcium and diacylglycerol). The disorganization of microfilament system by cytochalasin D induced an inhibition of beta-adrenergic induced 3H-protein secretion whereas it did not modify the cholinergic muscarinic one. Cytochalasin D induced the formation of vacuoles in the parotid cell. In this work we show that the activation of muscarinic receptors (with carbachol) partially abolished the inhibitory effect of cytochalasin D on beta-adrenergic induced secretion. Since carbachol induced both intracellular calcium increase and protein kinase C activation, we decided to test separately the effect of calcium (using the calcium ionophore A23187) and protein kinase C activation (using phorbol ester) on the inhibitory effect of cytochalasin D on beta-adrenergic induced secretion. A23187, in the presence of calcium in the external medium was able to partially abolish cytochalasin D effect (ie re-establishing protein secretion) whereas activation of protein kinase C by phorbol 12-13 di-butyrate had no effect. These results suggest that protein kinase C is not involved in re-establishing a 'normal' secretion phenomenon whereas calcium does interfere. Furthermore, our fluorescence study shows that, when cytochalasin D is present in the incubation medium, the actin network is disturbed even in the presence of carbachol. This indicates that a calcium entry in the cell is not sufficient to restore a 'normal' actin network.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Pharmacokinetics of oral all-trans retinoic acid in patients with acute promyelocytic leukemia.
It has been shown that patients with acute promyelocytic leukemia (AML3 subtype) treated with all-trans retinoic acid (all-trans RA), 45 mg/m2/day, achieve complete remission through differentiation of the leukemic clone to mature myeloid cells, which die spontaneously. The pharmacokinetics of all-trans RA given by mouth were studied in 15 AML3 patients. Blood samples were drawn for 24 h following a single oral dose of 45 mg/m2 and assayed for all-trans RA and 13-cis retinoic acid (13-cis RA) plasma concentrations by specific high-performance liquid chromatography. In one patient all-trans RA and 13-cis RA levels were below the detection limits at all times. In the other patients, the time to peak concentration of all-trans RA was between 60 and 210 min (median 90 min) after ingestion, with maximum concentrations between 0.03 and 2.5 micrograms/ml (median 0.4 micrograms/ml). These concentrations were within the in vitro differentiating concentration range of all-trans RA for these patients' cells. In nine patients, enterohepatic cycling was suggested by the presence on the concentration versus time curve of a secondary peak that occurred at meal times. The apparent plasma elimination half-life was between 16.8 and 77.4 min (median 30 min). Detectable plasma levels of 13-cis RA in 12 patients indicated in vivo isomerization of all-trans RA. Despite the high inter-individual variability of all-trans RA pharmacokinetics in these patients, high blast cell counts and failure to respond to differentiation treatment tended to be associated with low all-trans RA Cmax values and high clearance estimates.
Administration, Oral↗
Greater conversion of testosterone to 5 alpha-dihydrotestosterone, reflecting increased peripheral 5 alpha-reductase activity in nude mice treated with high doses of cyclosporine A.
Following cyclosporine A (CsA) immunosuppressive therapy in kidney grafts, increased body hair growth (hypertrichosis and/or hirsutism) without significant variation in normal circulating plasma androgen levels (as observed in idiopathic hirsutism) has been reported by several authors. Other authors have described increased hair growth in nude mice treated with CsA. In order to evaluate the action of this drug in target tissues, using dorsal skin homogenates from nude mice treated with various doses of CsA, we measured the metabolic conversion of testosterone (T) to its 5 alpha-reduced products, reflecting 5 alpha-reductase activity (5 alpha-RA). Three groups of 5 female nude mice were treated with an oral suspension containing CsA 5 mg/kg (group 1), 25 mg/kg (group 2) and 100 mg/kg (group 3), respectively, and the results, including 5 alpha-DHT and Adiol formation, were compared with those obtained in a control group (n = 5) receiving only the olive oil vehicle. Cutaneous metabolic conversion of T was determined using tritiated T as substrate. After 1 h of incubation, 5 alpha-DHT and other 5 alpha-reduced products formed were separated and quantified using a reverse-phase chromatography column fitted to a flow-through radioactivity detector. Mean +/- SD 5 alpha-DHT formation (expressed as pmol per 100 mg of protein per h) was found to be increased in the treated groups (group 1: 3.17 +/- 0.37, group 2: 3.10 +/- 0.13, group 3: 4.26 +/- 0.20), respectively 7.5% (NS), 5.10% (NS) and 44.4% (P = 0.01) higher than in the control group (2.95 +/- 0.13). In addition to 5 alpha-DHT, enhanced formation of delta 4-androstenedione (delta 4), 5 alpha-androstan-3 beta,17 beta-diol (3 beta-diol) and 5 alpha-androstan-3 alpha,17 beta-diol (3 alpha-diol) were also observed in the treated groups. These results show a significantly increased formation of 5 alpha-DHT (and Adiol) in nude mice treated with high dose-levels of CsA.
3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
[Plasma releasing factors in common migraine].
Many platelet abnormalities have been described in migraine, but they are now regarded as secondary phenomena rather than primary causative factors. In this study, we attempted to assess the presence of bioamine-releasing factors in the plasma of patients with common, non-dietary migraine. Blood samples were collected from 17 such patients, either during attacks (n = 9) or during attack-free periods (n = 8). Ten healthy volunteers served as controls. Release experiments were performed by adding 1 volume as controls. Release experiments were performed by adding 1 volume of migraineur's platelet-poor plasma to 1 volume of either control's whole blood (histamine release) or isolated platelets (catecholamines or serotonin release). Endogenous unconjugated bioamines were measured in whole blood and in isolated platelets from migraineurs' blood collected during and between attacks. We also measured plasma levels of histamine and of unconjugated and conjugated serotonin and catecholamines, as well as the inhibition of serotonin uptake and labelled serotonin release from controls' platelets in the presence of migraineurs' plasma collected during or between attacks. The results obtained suggest the presence of two plasma bioamine-releasing factors: a histamine-releasing factor present in migraineurs' blood during and between attacks, and a catecholamine and serotonin releasing factor present only during attacks in migraineurs' platelet-poor plasma. The latter factor is thermolabile and dialysable, with an apparent molecular weight lower than 16 kd. Gel-filtered fractions of semi-purified catecholamine-serotonin releasing factor induced the same events as the migraineurs' platelet-poor plasma from which they were obtained.
Adult↗
Increase in plasma 5 alpha-androstane-3 alpha,17 beta-diol glucuronide as a marker of peripheral androgen action in hirsutism: a side-effect induced by cyclosporine A.
Dose-dependent hypertrichosis is a common dermatological side-effect affecting the majority of patients treated with cyclosporine A (CSA). Previous studies have not demonstrated the influence of CSA on specific sex hormone levels. The aim of this study is to investigate whether CSA increases the activity of 5 alpha-reductase, an enzyme which transforms androgens into dihydrotestosterone in peripheral tissues. The metabolite which best reflects this activity is 5 alpha-androstane-3 alpha,17 beta-diol glucuronide (Adiol G). The study was carried out on 49 insulin-dependent diabetes patients participating in the double-blind "Cyclosporine-Diabète-France" clinical trial, of which 28 were treated with CSA (16 males and 12 females), and 21 received only placebo (10 males and 11 females). All patients underwent extensive clinical and laboratory evaluations prior to and during the present study. In addition to Adiol G, testosterone (T), dehydroepiandrosterone sulfate (DHEA S) and sex hormone-binding globulin (SHBG) were assayed. Levels of Adiol G increased significantly in CSA-treated groups: males, 11.86 +/- 2.58 vs 7.83 +/- 2.30 nmol/l; females, 4.48 +/- 2.70 vs 2.10 +/- 1.22 nmol/l; P less than 0.02 (comparison of means). There were no significant differences in this parameter before and during treatment in either the male or female placebo groups (paired t-test). During the treatment period, T, DHEA S, SHBG and the T/SHBG ratio did not significantly change with respect to their baseline values in any of the groups studied (comparison of means). Comparison (using paired t-test) showed a significant increase of DHEA S in CSA-treated groups: males, delta = 3.08 +/- 3.33 nmol/l, P less than 0.01; females, delta = 0.98 +/- 1.13 nmol/l, P less than 0.05. In conclusion, it is possible that CSA induces hypertrichosis or hirsutism by increasing 5 alpha-reductase activity in peripheral tissues. Nevertheless the role of increased DHEA S as a possible Adiol G precursor cannot be excluded.
3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
Circadian variations in plasma levels of hypophyseal, adrenocortical and testicular hormones in men infected with human immunodeficiency virus.
Alterations in the circadian time structure of the secretion of several hormones were investigated in 13 male patients infected with human immunodeficiency virus (HIV). Seven were asymptomatic (classified CDC II, according to the criteria of the Atlanta Centers for Disease Control), and 6 had acquired immunodeficiency syndrome (CDC IV). Ten healthy males volunteered as controls. Plasma levels of dehydroepiandrosterone (DHEA) and its sulfate (DHEA-S), cortisol, testosterone, ACTH, and beta-endorphin were determined by RIA in blood samples obtained every 4 h from 0830-0830 h the next morning. Data were analyzed both by two-way analysis of variance and the cosinor method. Circadian rhythms were statistically validated for each of the six hormones in each of the three groups of subjects. Compared with the control subjects, mesors (24-h adjusted means) were significantly higher for cortisol and lower for DHEA, DHEA-S, and ACTH (P less than 0.001 for all four hormones) in all HIV-infected patients. Plasma testosterone mesors were similar in controls and CDC II patients, but decreased significantly in the CDC IV patient group (P less than 0.05). Analysis of the circadian rhythms of plasma hormone levels clearly indicated an altered adrenal hormonal state in HIV-infected male patients, even during the asymptomatic period of the infection. For instance, plasma cortisol at 0430 h was more than twice as high in HIV-infected patients as it was in time-qualified controls. Although patients already had elevated plasma cortisol and lowered adrenal androgen levels at this stage, hypogonadism was not observed, as gauged by plasma testosterone concentrations. We speculate that the primary hormonal defect in HIV-infected patients is increased cortisol secretion resulting from circadian-varying stimulation of the adrenal cortex by a factor other than pituitary ACTH. This factor might be a stimulating substance secreted primarily by infected immune cells. Excess cortisol would lower adrenal androgen secretion by shifting adrenal steroid biosynthesis toward glucocorticoids and decreasing pituitary ACTH secretion via a negative feedback mechanism.
Acquired Immunodeficiency Syndrome↗
[Proteins, genes and early diagnosis of Alzheimer's disease].
Proteic (neuritic plaques, amyloid substances...) and genetic characteristics of Alzheimer's disease are reviewed. An infectious origin appears unlikely. After production of specific antibodies, the reported abnormal Tau proteins might represent peripheral markers of the disease. Changes in olfactory neurons, accessible for biopsy specimens, might give rise to new biological diagnosis of Alzheimer's disease.
Alzheimer Disease↗