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1.
D L Epstein G A Nolen J L Randall S A Christ E J Read J A Stober M K Smith 《Teratology》1992,46(3):225-235
Dichloroacetic acid (DCA) is a by-product of the chlorine disinfection of water and may occur in treated water at levels exceeding 100 micrograms/L. Previous studies revealed teratogenic effects, particularly heart malformations, at high doses (900-2,400 mg/kg given on days 6-15 of pregnancy). In a series of three studies, groups of 7-10 Long-Evans rats were dosed with 1,900 mg/kg of DCA on days 6-8, 9-11, or 12-15; with 2,400 mg/kg on days 10, 11, 12, or 13; and with 3,500 mg/kg on days 9, 10, 11, 12, or 13, in an attempt to determine the most sensitive period and further characterize the heart defect. In a fourth study, six dams were treated with 1,900 mg/kg of DCA days 6-15 of pregnancy, and 56 fetuses were harvested for light microscopy of the heart. Eight control fetuses from four litters were also examined. No heart malformations were seen in the groups treated with 1,900 mg/kg DCA days 6-8 but were present in the group treated on days 9-11 and 12-15, with the higher incidence occurring on days 12-15. Single doses of 2,400 mg/kg DCA given on days 10, 11, 12, or 13 resulted in a much lower incidence of cardiac malformations, which occurred only on days 10 and 12. The high dose of DCA (3,500 mg/kg) did not increase the incidence of heart defects but showed that dosing on day 9 as well as on days 10 and 12 would produce the defect. The defects seen were characterized as high interventricular septal defects (H-IVSD). Light microscopy showed that the defect was caudal to the semilunar valves, with the anterior right wall of the aorta communicating with the right ventricle. Another aspect of the defect is at the level of the semilunar valves, with the right cusp or sinus of Valsalva in communication with the right ventricle. The defects are discussed more fully and methods for further study suggested. 相似文献
2.
[14C]Glucose release either from endogenous 14C-prelabelled glycogen or from added 14C-labelled glucose 6-phosphate was measured in filipin-treated, permeabilized hepatocytes in 48 h culture. [14C]Glucose output from prelabelled glycogen was not altered by the addition of 5 mM glucose 6-phosphate to the incubation medium. Conversely, [14C]glucose release from 5 mM labelled glucose 6-phosphate was not influenced by different glycogen concentrations in the cells. Moreover, in the permeabilized cells the anion transport inhibitor DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid) inhibited only the liberation of [14C]glucose from labelled glucose 6-phosphate but not from glycogen. It is therefore concluded that there exist at least 2 separate, mutually non-accessible glucose 6-phosphate pools in cultured rat hepatocytes, one linked to glycogenolysis and the other to gluconeogenesis. 相似文献
3.
Atrial trabeculae (studied in voltage-clamping conditions and in the presence of 0.5 mmol/l BaCl2 to abolish gK1) responded to 1 s hyperpolarizations to beyond approximately E = -140 mV (from HP of about E = -80 mV) with an inwardly directed current increasing with time. Quite similar results were obtained with enzymatically dissociated frog atrial cells studied in whole cell voltage clamp with a patch-clamp pipette. This behaviour could be accounted for by assuming the presence of an "if" current at this quite negative range of potentials or by the fact that the cell membrane may undergo reversible electropermeabilization when its potential is brought to values negative to about -140 mV (St?mpfli 1958). When a brief (1 ms) and large (150 mV) hyperpolarization was applied 1 s before the test pulse, an inwardly directed current increasing with time was elicited by test pulses to beyond approximately E = -120 mV. This current was neither abolished in the presence of 1 mmol/l CsCl nor greatly reduced in the absence of Na+ ions, unlike "if" (Di Francesco 1981). We conclude that this current having a time course similar to that of "if" is of different nature and we argue that it might be accounted for by electropermeabilization of the membrane (reversible within about 2.5 min) due to the electrical shock represented by a brief and large hyperpolarization. 相似文献
4.
H Christ 《Peptides》1985,6(1):139-148
Administration of 10 and 30 micrograms methionine-enkephalin (MET-ENK)/g bw (n = 10/dose) affected the propensity towards fighting in H. bimaculatus; 10 micrograms increased, while 30 micrograms decreased the aggressive behavior. MET-ENK also affected a number of behavior patterns displayed by the fish. Moreover, the "wet-dog-shakes" observed suggest that MET-ENK acts on opiate-receptors. Treatment with substance P (SP)/g bw (n = 10/dose) induced chafing movements in the fish slightly. It also decreased fighting and increased biting of the air stone, which is evidence that H. bimaculatus is still aggressive, directing its attacks to different objects. When 4, 8, 12 micrograms somatostatin (SRIF)/g bw (n = 10/dose) were injected, H. bimaculatus stopped fighting for several hours after the onset of treatment, depending on the dosage. Somatostatin reduces blood glucose concentration, causing a sudden stop of aggressive behavior, 0.04, 0.1, 0.6, 1.0 and 3.0 IU prolactin (PRL)/g bw (n = 5/dose) eventually decreased fighting and affected a number of behavior patterns displayed by the fish. 相似文献
5.
G J Christ 《Life sciences》1990,47(20):1867-1874
Steady-state contractile responses elicited by activation of the proportional 1-adrenergic and 5-HT2 receptors in isolated rat and rabbit aorta, respectively, were analyzed. Agonist dissociation constants (KA's) obtained by the method of partial irreversible receptor inactivation were compared to KA values determined by fits of the operational model of pharmacological agonism to single concentration response curves (CRCs). The observed nature of the KA estimates obtained with the Furchgott method for phenylephrine (PE) and oxymetazoline (OXY) at the proportional 1-adrenergic receptor and for 5-hydroxytryptamine (5-HT) at the 5-HT2 receptor in isolated rat aorta, and for PE and 5-HT at the proportional 1-adrenergic and 5-HT2 receptors, respectively, in isolated rabbit aorta, was consistent with the hypothesis that the density of membrane receptors is greatly in excess of the density of transducer proteins (i.e., [Ro] much greater than [To]) in these systems. Therefore, KA, efficacy and slope factor estimates were also obtained by computer fits of the operational model to single agonist CRCs in both rat and rabbit aorta, with the empirically determined tissue maximal response (Tmax) substituted for the theoretical parameter Em. In all cases, the mean pKA estimates obtained with the operational model closely approximated and were strongly correlated with the mean pKA estimates determined by the Furchgott method. These studies suggest that, at least in some vascular preparations, Tmax is a good estimate of Em, and moreover, that Em may be not only a specific characteristic of a given receptor-effector system as previously demonstrated by Black and Leff, but that Em may also describe a more general feature of tissue responsiveness that is shared among distinct membrane receptors coupled to similar effector systems. In conclusion, when receptor inactivation studies have indicated that the condition [Ro] much greater than [To] exists, Tmax can be substituted into the operational model to provide valid estimates of agonist KA values at distinct receptor subtypes, in the absence of receptor alkylation. 相似文献
6.
R. Bender R. Fundele M. A. Surani L-L. Li R. Kothary D. O. Fürst B. Christ 《Development genes and evolution》1995,204(7-8):436-443
Parthenogenetic cells are lost from fetal chimeras. This may be due to decreased proliferative potential. To address this question, we have made use of combined cell lineage and cell proliferation analysis. Thus, the incorporation of bromodeoxyuridine in S-phase was determined for both parthenogenetic and normal cells in several tissues of fetal day 13 and 17 chimeras. A pronounced reduction of bromodesoxyuridine incorporation by parthenogenetic cells at both developmental stages was only observed in cartilage. In brain, skeletal muscle, heart and intestinal epithelium, this reduction was either less pronounced or observed only at one of the developmental stages analysed. No difference between parthenogenetic and normal cells was observed in epidermis and ganglia. Our results show that a loss of proliferative potential of parthenogenetic cells during fetal development contributes to their rapid elimination in some tissues. The analysis of the fate of parthenogenetic cells in skeletal muscle and cartilage development demonstrated different selection mechanisms in these tissues. In skeletal muscle, parthenogenetic cells were largely excluded from the myogenic lineage proper by early post-midgestation. In primary hyaline cartilage, parthenogenetic cells persisted into adulthood but were lost from cartilages that undergo ossification during late fetal development. 相似文献
7.
Alteration of apparent restriction endonuclease recognition specificities by DNA methylases. 总被引:14,自引:10,他引:4 下载免费PDF全文
An in vitro method of altering the apparent cleavage specificities of restriction endonucleases was developed using DNA modification methylases. This method was used to reduce the number of cleavage sites for 34 restriction endonucleases. In particular, single-site cleavages were achieved for Nhe I in Adeno-2 DNA and for Acc I and Hinc II in pBR322 DNA by specifically methylating all but one recognition sequence. 相似文献
8.
9.
Gruber Véronique Berna Patrick P. Arnaud Thierry Bournat Philippe Clément Christèle Mison Dominique Olagnier Béatrice Philippe Laurence Theisen Manfred Baudino Sylvie Bénicourt Claude Cudrey Claire Bloës Carole Duchateau Nathalie Dufour Sylvie Gueguen Catherine Jacquet Séverine Ollivo Catherine Poncetta Christine Zorn Nathalie Ludevid Dolores Van Dorsselaer Alain Verger Robert Doherty Annette Mérot Bertrand Danzin Charles 《Molecular breeding : new strategies in plant improvement》2001,7(4):329-340
A recombinant dog gastric lipase with therapeutic potential for the treatment of exocrine pancreatic insufficiency was expressed in transgenic tobacco plants. We targeted the protein using two different signal sequences for either vacuolar retention or secretion. In both cases, an active glycosylated recombinant protein was obtained. The recombinant enzymes and the native enzyme displayed similar properties including acid resistance and acidic optimum pH. The proteolytic maturation and the specific activity of the recombinant proteins, however, were found to be dependent on subcellular compartmentalization. Expression levels of recombinant dog gastric lipase were about 5% and 7% of acid extractable plant proteins for vacuolar retention and secretion respectively. This expression system already has allowed the production of tens of grams of purified lipase through open-field culture of transgenic tobacco plants. 相似文献
10.
Marion Fiorentino Guillaume Bastard Malick Sembène Sonia Fortin Pierre Traissac Edwige Landais Christèle Icard-Vernière Frank T. Wieringa Jacques Berger 《PloS one》2013,8(12)