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1.
Avian hepatic T3 generation by 5'-monodeiodination: characterization of two enzymatic pathways and the effects of goitrogens 总被引:1,自引:0,他引:1
F M McNabb L J Lyons T E Hughes 《Comparative biochemistry and physiology. A, Comparative physiology》1986,85(2):249-255
The enzymatic nature of 5'-monodeiodination (5'-D) in avian liver homogenates was demonstrated by abolishment of activity by iopanoic acid (IOP). T3 production from T4 was dependent on enzyme and substrate concentrations, incubation time, incubation temperature, and pH. Two pathways of 5'-D activity were present in avian liver and exhibited characteristics similar to those described in mammalian tissues. Type II activity was identified as propylthiouracil (PTU)-insensitive activity. Type I (PTU-sensitive) was determined by difference between Total and Type II. Km values were 1.58 microM T4 for Total activity and 0.90 nM T4 for Type II, corresponding to the characteristics of the mammalian pathways. The effects of goitrogens on avian hepatic 5'-D were equivalent to those reported for the mammalian enzyme. 相似文献
2.
Antigen inoculated intratracheally (IT) into animals can induce primary immune responses and selectively recruit specific T cells to the lung. In the current study, the role of alveolar macrophages (AM) in these two responses was investigated. Antigen-pulsed bronchoalveolar cells (BAC) inoculated IT into guinea pigs generated a population of immune T cells that proliferated in vitro on reexposure to antigen-pulsed macrophages (M?). The possibility that antigen-pulsed donor BAC shed antigen that was subsequently processed and presented by host M? was ruled out by genetic experiments. Thus, peritoneal exudate lymphocytes (PEL) from (2 X 13)F1 guinea pigs primed with antigen-pulsed BAC from strain 2 animals responded preferentially to antigen-pulsed strain 2 M? rather than to antigen-pulsed strain 13 M?. In a second set of studies, antigen-pulsed BAC inoculated IT into guinea pigs selectively recruited antigen-specific T cells to the lung. Genetic experiments verified that inoculated BAC were the source of the antigen-presenting cells responsible for selective recruitment. Thus, antigen-pulsed strain 2 BAC inoculated IT recruited a greater proportion of (2 X 13)F1 T cells that recognized antigen in the context of strain 2 M? than F1 T cells that recognized antigen on strain 13 M?. Taken together, these studies suggest that AM contribute to the regulation of pulmonary immunity by both inducing T lymphocyte immunity and selectively recruiting specific T cells to the lung. 相似文献
3.
4.
Spleen cells from rats given experimental pyelonephritis using Escherichia coli and Proteus mirabilis as infecting organisms were evaluated for their ability to respond to the mitogen Concanavalin A. Results indicate an 80% reduction in the response of animals with gross suppuration in the kidney, but no inhibition is observed in animals with kidney infection, but not renal abscesses. The inhibition is not, apparently, due to serum factors. 相似文献
5.
Over-exploitation of wildlife is a significant threat to global biodiversity, but addressing the sustainability of harvests can be difficult when trade is conducted illegally. The wildlife trade is driven chiefly by consumer demand, largely in developed nations (but increasingly in Asia), and more species are traded to meet international demand for pets than for any other purpose. We surveyed traders of amphibians and reptiles in the Indonesian provinces of Maluku, West Papua and Papua between September 2010 and April 2011. We recorded 5,370 individuals representing 52 species collected solely for the pet trade. At least 44?% were either fully protected or had not been allocated a harvest quota, making their harvest and trade illegal. Approximately half were listed within the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Trade operates via a complex chain, with hunters receiving little income compared to middlemen and exporters. Examination of Indonesian harvest quotas for amphibians and reptiles suggests limited knowledge of species distributions, with quotas often set for species in provinces where they do not occur. Illegal trade is due, partly, to an inadequate understanding of the species being traded and is facilitated by poor monitoring and enforcement at key trade hubs. As a first step to combatting illegal trade, and to better understand the effects of harvest on wild populations, we recommend the need for increased monitoring and enforcement, improving the knowledge base of species traded and educating consumers about the effects their demand for pets has on these species. 相似文献
6.
7.
R L Warters L M Brizgys B W Lyons 《International journal of radiation biology and related studies in physics, chemistry, and medicine》1987,52(2):299-313
The total protein mass co-isolating with the nuclear matrix or nucleoid from Chinese hamster ovary (CHO) cells was observed to increase in heated cells as a function of increasing exposure temperature between 43 degrees C and 45 degrees C or of exposure time at any temperature. The sedimentation distance of the CHO cell nucleoid in sucrose gradients increased with increasing exposure time at 45 degrees C. Both these nuclear alterations correlated in a log-linear manner with heat-induced inhibition of DNA strand break repair. A two-fold threshold increase in nuclear matrix protein mass preceded any substantial inhibition of repair of DNA single-strand breaks. When preheated cells (45 degrees C for 15 min) were incubated at 37 degrees C the nuclear matrix protein mass and nucleoid sedimentation recovered with a half-time of about 5 h, while DNA single-strand-break repair recovered with a half-time of about 2 h. When preheated cells were placed at 41 degrees C (step-down heating; SDH) a further increase was observed in the nuclear matrix protein mass and the half-time of DNA strand break repair, while nucleoid sedimentation recovered toward control values. These results implicate alterations in the protein mass of the nuclear matrix in heat-induced inhibition of repair of DNA single-strand breaks. 相似文献
8.
Indirect evidence suggests that legumes can adjust rapidly theresistance of their root nodules to O2 diffusion. Here we describeexperiments using O2 specific micro-electrodes and dark fieldmicroscopy to study directly the operation of this diffusionbarrier. The O2 concentration sensed by the electrode decreasedsharply in the region of the inner cortex and was less than1.0 mmol m3 throughout the infected tissue in nodulesof both pea (Pisum sativum) and french bean (Phaseolus vulgaris).In a number of experiments the ambient O2 concentration wasincreased to 40% while the electrode tip was just inside theinner cortex. In 13 out of 21 cases the O2 concentration atthis position either remained low and unchanged or increasedirreversibly to near ambient values. In the remaining casesthe O2 concentration increased after 1 to 2.5 min and then decreasedto its former value. These results are ascribed to an increasein resistance of the barrier in response to increased O2 fluxinto the nodule. It was shown microscopically that air spacesboth at the boundary between the infected zone and the innercortex, and within the infected zone started to disappear 3min after nodules were exposed to high ambient O2 concentrationsand had disappeared completely after 8 min. These spaces werenot changed by exposure of the nodule for 10 min to either N2or air. Key words: Oxygen, root nodules, air spaces 相似文献
9.
Evolution of the 28S ribosomal RNA gene in anurans: regions of variability and their phylogenetic implications 总被引:1,自引:0,他引:1
Fifteen restriction sites were mapped to the 28S ribosomal RNA gene of
individuals representing 54 species of frogs, two species of salamanders, a
caecilian, and a lungfish. Eight of these sites were present in all species
examined, and two were found in all but one species. Alignment of these
conserved restriction sites revealed, among anuran 28S rRNA genes, five
regions of major length variation that correspond to four of 12 previously
identified divergent domains of this gene. One of the divergent domains
(DD8) consists of two regions of length variation separated by a short
segment that is conserved at least throughout tetrapods. Most of the
insertions, deletions, and restriction-site variations identified in the
28S gene will require sequence-level analysis for a detailed reconstruction
of their history. However, an insertion in DD9 that is coextensive with
frogs in the suborder Neobatrachia, a BstEII site that is limited to
representatives of two leptodactylid subfamilies, and a deletion in DD10
that is found only in three ranoid genera are probably synapomorphies.
相似文献
10.
M E Sant A Poiner M C Harsanyi S D Lyons R I Christopherson 《Analytical biochemistry》1989,182(1):121-128
A number of antagonists of nucleotide metabolism with anti-cancer activity affect the de novo purine pathway. To determine the biochemical mechanisms of cytotoxicity of these drugs, assay procedures have been developed for measurement of the levels of intermediates proximal to IMP in the pathway for de novo purine biosynthesis in mouse L1210 leukemia cells. Purine precursors have been synthesized in vitro from [14C]glycine using enzymes from chicken liver. These 14C-labeled intermediates have been used as marker compounds to define retention times for metabolites of leukemia cells separated by HPLC and the chromatographic mobilities of these intermediates after two-dimensional thin-layer chromatography. These new chromatographic procedures have been used in combination to determine the steady-state concentrations for purine precursors in mouse L1210 leukemia cells in the exponential phase of growth: N-formylglycineamide ribotide (16 microM); N-formylglycineamidine ribotide (4.7 microM); 5-aminoimidazole ribotide (4.0 microM); 4-carboxy-5-aminoimidazole ribotide (0.46 microM); N-succino-5-aminoimidazole-4-carboxamide ribotide (11 microM); 5-aminoimidazole-4-carboxamide ribotide (16 microM); 5-formamidoimidazole-4-carboxamide ribotide (2.7 microM); and IMP (57 microM). The metabolic effects of tiazofurin (25 microM) upon mouse L1210 leukemia cells growing in culture define a "metabolic crossover point" at the reaction catalyzed by IMP dehydrogenase (EC 1.1.1.205) which confirms previous reports of inhibition of this enzyme. 相似文献