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181.
Summary. Although there are a great number of studies concerning the uptake of taurine in several tissues, the regulation of taurine
transport has not been studied in the retina after lesioning the optic nerve. In the present study, isolated retinal cells
of the goldfish retina were used either immediatly after cell suspension or in culture. The high-affinity transport system
of [3H]taurine in these cells was sodium-, temperature- and energy-dependent, and was inhibited by hypotaurine and β-alanine, but
not by γ-aminobutyric acid. There was a decrease in the maximal velocity (Vmax) without modifications in the substrate affinity (Km) after optic axotomy. These changes were mantained for up to 15 days after the lesion. The results might be the summation
of mechanisms for providing extracellular taurine to be taken up by other retinal cells or eye structures, or regulation by
the substrate taurine, which increases after lesioning the optic nerve. The in vivo accumulation of [3H]taurine in the retina after intraocular injection of [3H]taurine was affected by crushing the optic nerve or by axotomy. A progressive retinal decrease in taurine transport was
observed after crushing the optic nerve, starting at 7 hours after surgery on the nerve. The uptake of [3H]taurine by the tectum was compensated in the animals that were subjected to crushing of the optic nerve, since the concentration
of [3H]taurine was only different from the control value 24 hours after the lesion, indicating an efficient transport by the remaining
axons. On the contrary, the low levels of [3H]taurine in the tectum after axotomy might be an index of the non-axonal origin of taurine in the tectum. Axonal transport
was illustrated by the differential presence of [3H]taurine in the intact or crushed optic nerve. The uptake of [3H]taurine into retinal cells in culture in the absence or in the presence of taurine might indicate the existence of an adaptive
regulation of taurine transport in this tissue, however taurine transport probably differentially occurs in specific populations
of retinal cells. The use of a purified preparation of cells might be useful for future studies on the modulation of taurine
transport by taurine in the retina and its role during regeneration.
Received June 11, 1999/Accepted August 31, 1999 相似文献
182.
Distant enhancers stimulate the albumin promoter through complex proximal binding sites 总被引:3,自引:0,他引:3
Vorachek WR Steppan CM Lima M Black H Bhattacharya R Wen P Kajiyama Y Locker J 《The Journal of biological chemistry》2000,275(37):29031-29041
183.
184.
The main objective of this laboratory practical class was to teach students how a detergent and the best experimental conditions are chosen to solubilize a given membrane protein. Kidney Na,K-ATPase was chosen as the protein of interest and anionic, neutral and zwitterionic detergents were tested. Simple laboratory experiments were designed to study the effect of the detergent on the activity of the enzyme, the effect of detergent concentration on solubilization, the effect of protein concentration on enzyme solubilization, and the effect of time and temperature of incubation during enzyme solubilization. This resulted in the selection of an appropriate detergent for the solubilization of the protein taking into account smaller inactivation factors, more effective solubilization (more effective solubilization with a better detergent-protein relationship), lower inactivation temperature and time of incubation of the membrane protein with the detergent. The results obtained showed that instantaneous incubation of Na,K-ATPase with C(12)E(8) (1:1 w/w) at 4 degrees C resulted in a more efficient solubilization and had a smaller denaturing effect on the solubilized enzyme. 相似文献
185.
Members of Brevibacterium linens display physiological features that are relevant for cheese production. The genomes of five B. linens strains deposited on culture collections were compared by examining large restriction fragments on pulsed-field gel electrophoresis
and detection of polymorphism at the level of 16S rRNA genes. Pulsed-field analysis with the endonucleases DraI and AsnI showed a characteristic restriction profile for each strain and allowed the calculation of genome sizes ranging between
3.2 and 3.9 Mbp. No linear genomic elements were detected. Polymorphisms at the level of 16S rRNA genes were revealed by hybridization
with an oligonucleotide probe complementary to a universal domain of the 16S genes. An EcoRI fragment of 1.4 kb was identified as common to all strains under study. According to the number of positive bands detected
by the probe, at least four rRNA operons must be present on the genome of the B. linens strains here studied.
Received: 13 January 2000 / Accepted: 9 February 2000 相似文献
186.
The relationship between dental morphology, sex, body length and age of small cetaceans can be used to determine ontogeny, sexual dimorphism and geographical variation. The objective of this study was to determine the relationship between dental morphology, sex, body size and age. A total of 91 specimens of P. blainvillei and 80 specimens of S. fluviatilis accidentally captured in fisheries or stranded in northern Rio de Janeiro (21 masculine37'-22 masculine25'S), from September 1988 to November 1996 were analysed. The teeth root diameter in P. blainvillei was significantly different between the sex; the values for females were larger than males. In neither species aid we observed significant in variations dimension and number of teeth, thickness of dentine and cemental layers and in the maximum width of cement as a function of body size. Age was related to increases in tooth length, root and cingulum diameters, and maximum width of cement in individuals of P. blainvillei, and tooth and crown lengths and maximum width of cement in individuals of S. fluviatilis. The observation of a linear growth between maximum width of cement and age in both species indicates that the equations obtained can be used to estimate relative age in P. blainvillei and S. fluviatilis in northern of Rio de Janeiro. 相似文献
187.
The endogenous development of Eimeria minasensis was studied in 9 coccidia-free goat kids inoculated with 10(5) sporulated oocysts/kg body weight. Kids were killed 4, 7 (2 animals), 10, 13, 16, 18, 19, and 22 days after inoculation (DAI). In tissue sections of the intestines stained with hematoxylin and eosin and examined by light microscopy, 2 generations of meronts, gamonts, gametes, and oocysts were found. The first generation of meronts developed in cells deep in the lamina propria of the jejunum and ileum. Mature giant meronts (299.4x243.8 microm) found 16 DAI were visible to the naked eye and contained a large number of crescent-shaped merozoites. The second generation of meronts developed in the epithelial cells of crypts of the ileum and above the host cell nuclei. Mature meronts (11.5x10.1 microm) with 18-28 comma-shaped merozoites were first seen 16 DAI. Gametogenesis took place in epithelial cells of the crypts and villi of the terminal part of the ileum, cecum, and colon. Macrogametes (27.8x17.6 microm), mature microgamonts (21.3x17.0 microm), microgametes, and oocysts (30.5x19.4 microm) were found 19 DAI. Sexual stages were below the host cell nucleus. 相似文献
188.
189.
Matthew Kennedy Lian Yu Maria João Lima Carla S. Ascenso Christopher Czaja Isabel Moura Jose J. G. Moura F. Rusnak 《Journal of biological inorganic chemistry》1998,3(6):643-649
Desulforedoxin and the N-terminus of desulfoferrodoxin share a 36 amino acid domain containing a (Cys-S)4 metal binding site. Recombinant forms of desulforedoxin, an N-terminal fragment of desulfoferrodoxin, and two desulforedoxin
mutant proteins were reconstituted with Fe3+, Cd2+, and Zn2+ and relative metal ion affinities assessed by proton titrations. Protons compete with metal for protein ligands, a process
that can be followed by monitoring the optical spectrum of the metal-protein complex as a function of pH. For all polypeptides,
Fe3+ bound with the highest affinity, whereas the affinity of Zn2+ was greater than Cd2+ in desulforedoxin and the N-terminal fragment of desulfoferrodoxin, but this order was reversed in desulforedoxin mutant
proteins. Metal binding in both mutants was significantly impaired. Furthermore, the Fe3+ complex of both mutants underwent a time-dependent bleaching process which coincided with increased reactivity of cysteine
residues to Ellman's reagent and concomitant metal dissociation. It is hypothesized that this results from an autoredox reaction
in which Fe3+ is reduced to Fe2+ with attendant oxidation of ligand thiols.
Received: 17 June 1998 / Accepted: 3 September 1998 相似文献
190.