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1.
Diana Oliveri Simona Candiani Manuela Parodi Eva Bertini Mario Pestarino 《Polar Biology》2005,28(5):366-371
The immunohistochemical distribution of serotonin-containing nerve fibres and cells has been described in the brain of the Antarctic fish, Trematomus bernacchii. The largest serotonergic system was associated with the diencephalic and rhombencephalic ventricles. In particular, serotonin-positive cells have been found in the lateral recess and neuropile zone of the diencephalic ventricle, where we have identified the serotonergic portion of the paraventricular organ. Numerous serotonin cells were localized in the dorsal nucleus of the raphe, the dorsal tegmental nucleus and the central gray. Two large cell groups, arranged in a pair of well-defined columns and connecting the central gray with the dorsal reticular formation, were immunostained in the region of the trigeminal nuclei. In addition, few positive cells have been found in the preoptic area and the cerebellar valvula, and few serotonergic nerve fibres, probably belonging to the lateral lemniscus, have been identified. The distribution of serotonin elements in the brain of T. bernacchii has been compared with that described in other fish, where it showed some modifications in the immunoreactive pattern. Finally, the lack of a serotonergic system at the level of the reticular superior formation has been reported; however, it was not possible to rule out a phylogenetic or environmental explanation. 相似文献
2.
3.
Summary DL-ethionine increases the activity of liver biotinidase, an enzyme which hydrolyzes biotinylesters and biotinylpeptides. Chronic DL-ethionine feeding increases transiently the activity of biotinidase in mouse and rat liver, after which it remains elevated in the serum. In the present work we show that both isomers of DL-ethionine are equally good enhancers of the liver biotinidase, while, 3-ethylthiopropionate, the toxic metabolite of DL-ethionine, has no effect on the biotinidase activity of either liver or serum. We have also employed two different combinations of inhibitors of the hydrolytic pathway of SAH, a transmethylation product and potent inhibitor of methylation. It was found that these inhibitors (EHNA and Ara-A, 2-deoxycoformycin and adenosine) increase the activity of serum biotinidase as was the case with ethionine. Because SAH does not ethylate biomolecules, these changes in biotinidase activity, which can not be preveneted by adenine, biotin or lecithin are most probably related to the inhibition of methylation.Abbreviations Ara-A
9--D-arabinofuranosyladenine
- EHNA
erythro-9-(2-hydroxy-3-nonyl)adenine
- SAE
S-adenosylethionine
- SAH
S-adenosylhomocysteine
- SAM
S-adenosylmethionine 相似文献
4.
C-terminal peptide identification by fast atom bombardment mass spectrometry. 总被引:1,自引:0,他引:1 下载免费PDF全文
A previously described technique [Rose, Simona, Offord, Prior, Otto & Thatcher (1983) Biochem. J. 215, 273-277] permits the identification of the C-terminal peptide of a protein as the only peptide that does not incorporate any 18O upon partial enzymic hydrolysis in 18O-labelled water. Formation of chemical derivatives followed by combined g.l.c.-m.s. was used in this earlier work. We now describe the isolation from protein digests, by reversed-phase h.p.l.c., of labelled and unlabelled polypeptides and their direct analysis by fast atom bombardment mass spectrometry. Under the conditions used, the 18O label is retained throughout the separation and analysis, thus permitting assignments of C-terminal peptides to be made. Enzyme-catalysed exchange of label into the terminal carboxy group was found to occur in some cases without hydrolysis of a peptide bond. This effect, which may be exploited to prepare labelled peptides, does not prevent application of the method (two separate digests must then be used). We have applied our method to the analysis of enzymic partial hydrolysates of glucagon, insulin and of several proteins produced by expression of recombinant DNA. 相似文献
5.
Molasses is widely used as a substrate for commercial yeast production. The complete hydrolysis of raffinose, which is present in beet molasses, by Saccharomyces strains requires the secretion of α-galactosidase, in addition to the secretion of invertase. Raffinose is not completely utilized by commercially available yeast strains used for baking, which are Mel−. In this study we integrated the yeast MEL1 gene, which codes for α-galactosidase, into a commercial mel0 baker's yeast strain. The Mel+ phenotype of the new strain was stable. The MEL1 gene was expressed when the new Mel+ baker's yeast was grown in molasses medium under conditions similar to those used for baker's yeast production at commercial factories. The α-galactosidase produced by this novel baker's yeast strain hydrolyzed all the melibiose that normally accumulates in the growth medium. As a consequence, additional carbohydrate was available to the yeasts for growth. The new strain also produced considerably more α-galactosidase than did a wild-type Mel+ strain and may prove useful for commercial production of α-galactosidase. 相似文献
6.
Multiple attractors,catastrophes and chaos in seasonally perturbed predator-prey communities 总被引:2,自引:0,他引:2
A classical predator-prey model is considered in this paper with reference to the case of periodically varying parameters.
Six elementary seasonality mechanisms are identified and analysed in detail by means of a continuation technique producing
complete bifurcation diagrams. The results show that each elementary mechanism can give rise to multiple attractors and that
catastrophic transitions can occur when suitable parameters are slightly changed. Moreover, the two classical routes to chaos,
namely, torus destruction and cascade of period doublings, are numerically detected. Since in the case of constant parameters
the model cannot have multiple attractors, catastrophes and chaos, the results support the conjecture that seasons can very
easily give rise to complex populations dynamics. 相似文献
7.
Urs Thalmann Thomas Geissmann Arsène Simona Thomas Mutschler 《International journal of primatology》1993,14(3):357-381
During a short field trip to the Special Reserve of Anjanaharibe-Sud in northeastern Madagascar, data concerning pelage coloration, behavior (especially vocalization), and ecology of indris were collected. Anjanaharibe-Sud is the northernmost locality of indri distribution. In comparison to the better-known indris from the southern part of their distribution, the indris in this region show different pelage coloration. Several types of loud vocalizations are analyzed, based on a small sample of tape recordings. Their song structure is more complicated than previously reported, containing distinct sequences of duetting. Data on behavior and ecology were collected by interviewing guides and local inhabitants. Some information contrasts with reports on the more southern indri populations. The conservation status of indris in Anjanaharibe-Sud and the future of the reserve are outlined. 相似文献
8.
Othman Al Musaimi Sophie V. Morse Lucia Lombardi Simona Serban Alessandra Basso Daryl R. Williams 《Journal of peptide science》2023,29(2):e3448
Successful manual synthesis of the TD2.2 peptide acting as a blood–brain barrier shuttle was achieved. TD2.2 was successfully synthesised by sequential condensation of four protected peptide fragments on solid-phase settings, after several unsuccessful attempts using the stepwise approach. These fragments were chosen to minimise the number of demanding amino acids (in terms of coupling, Fmoc removal) in each fragment that are expected to hamper the overall synthetic process. Thus, the hydrophobic amino acids as well as Arg(Pbf) were strategically spread over multiple fragments rather than having them congested in one fragment. This study shows how a peptide that shows big challenges in the synthesis using the common stepwise elongation methodology can be synthesised with an acceptable purity. It also emphasises that choosing the right fragment with certain amino acid constituents is key for a successful synthesis. It is worth highlighting that lower amounts of reagents were required to synthesise the final peptide with an identical purity to that obtained by the automatic synthesiser. 相似文献
9.
Simona Picardi Briana Abrahms Emily Gelzer Thomas A. Morrison Tana Verzuh Jerod A. Merkle 《Ecology letters》2023,26(1):157-169
Site fidelity—the tendency to return to previously visited locations—is widespread across taxa. Returns may be driven by several mechanisms, including memory, habitat selection, or chance; however, pattern-based definitions group different generating mechanisms under the same label of ‘site fidelity’, often assuming memory as the main driver. We propose an operational definition of site fidelity as patterns of return that deviate from a null expectation derived from a memory-free movement model. First, using agent-based simulations, we show that without memory, intrinsic movement characteristics and extrinsic landscape characteristics are key determinants of return patterns and that even random movements may generate substantial probabilities of return. Second, we illustrate how to implement our framework empirically to establish ecologically meaningful, system-specific null expectations for site fidelity. Our approach provides a conceptual and operational framework to test hypotheses on site fidelity across systems and scales. 相似文献