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91.
Amino acid sequence versus morphological data and the interordinal relationships of mammals 总被引:2,自引:0,他引:2
To a large extent, the mutual affinities of the mammalian orders continue
to puzzle systematists, even though comparative anatomy and amino acid
sequencing offer a massive data base from which these relationships could
potentially be adduced. In the present paper the consistency index--the
number of character states less the number of characters in a data set,
divided by the total number of changes in the character states on a
cladogram--was used to examine the relative resolving powers of recently
published morphological and molecular- sequence data. Consistency indices
were calculated for previously published alpha crystallin A chain and
myoglobin amino acid-sequence cladograms and for four original amino
acid-sequence cladograms (alpha crystallin A, myoglobin, and alpha and beta
hemoglobin); these were found to be comparable to the consistency indices
of morphologically based cladograms. Qualitative comparisons between the
morphologically based and molecularly based trees were also made; only
moderate congruence between the two was observed. Moreover, there was a
general lack of congruence between the cladograms specified by each of the
four proteins. Amino acid-sequence and morphological data agreed on the
placement of edentates as an early eutherian offshoot and on the grouping
of hyracoids, proboscideans, and sirenians. Otherwise there was only
limited congruence: morphology strongly supported the grouping of
lagomorphs and rodents and the alliance of pholidotes and edentates, but
sequence analyses did not. The placement of tubulidentates differed widely
among proteins. Morphology indicated the close association of sirenians
with proboscideans; proteins suggested a pairing of sirenians with
hyracoids. Sequence data did not identify many (morphologically
well-diagnosed) orders as monophyletic (e.g., Lagomorpha).(ABSTRACT
TRUNCATED AT 250 WORDS)
相似文献
92.
Effect of ammonia on amino acid uptake by brain microvessels 总被引:3,自引:0,他引:3
P Cardelli-Cangiano C Cangiano J H James F Ceci J E Fischer R Strom 《The Journal of biological chemistry》1984,259(8):5295-5300
NH+4 ions, at a concentration (0.25 mM) similar to that found in the plasma of patients with hepatic encephalopathy, cause, in vitro, a significant stimulation of the uptake by brain microvessels of large neutral amino acids, without any effect on the uptake of alpha-methylaminoisobutyric acid, glutamic acid, or lysine. Such a stimulation occurs essentially through an increase of the maximal transport capacity (Vmax) of the saturable component. It is apparently mediated by the intracellular formation of glutamine, which is then exchanged, through the L-system of transport, for large neutral amino acids such as leucine, phenylalanine, or tyrosine. At higher concentrations (greater than or equal to 0.5 mM), NH+4 ions cause also a decrease of carrier affinity for neutral amino acids, which counteracts the stimulatory effect on their uptake. 相似文献
93.
R. Strom P. Cardelli A. Fiori C. Cangiano D. Barra A. Cascino F. Ceci F. Rossi-Fanelli 《Amino acids》1992,2(1-2):13-23
Summary The polar long-chain amino acids glutamine and methionine can be transported across the endothelial cells of brain microvessels either by an L-system which operates by a facilitated diffusion, exchanging mechanism, or by a concentrating, energy-dependent A-system. The presence of glutamine and/or of methionine can induce a synergism between the two transport systems which results, by a transstimulation mechanism, in a net increased uptake of neutral hydrophobic aminoacids. The methionine analog S-methylthiocysteine, which is the mixed disulfide resulting from the combination of methanethiol with cysteine, behaves similarly to methionine in stimulating the uptake of neutral hydrophobic amino acids. The same transstimulating effect can even be obtained in collagenase-treated, A-system-deprived microvessels by inducing the direct formation of S-methylthiocysteine within the cytoplasmic compartment of the endothelial cells.Abbreviations MeAIB
-methylaminoisobutyric acid
- BCH
DL--aminobicyclo-2,2,1-heptanecarboxylic acid
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid 相似文献
94.
MC Chiale D Montalti MA Flamini P Fernández E Gimeno CG Barbeito 《Biotechnic & histochemistry》2016,91(1):30-37
The uropygial glands of birds are sebaceous organs that contribute to the water-repellent properties of the feather coat. We studied the histological and histochemical characteristics of the uropygial gland of chimango caracara using hematoxylin and eosin (H & E), Gomori´s trichrome, orcein, Gomori´s reticulin, periodic acid-Schiff (PAS), Alcian blue (AB) and a variety of lectins. The gland is composed of two lobes and a papilla with 20 downy feathers. It is surrounded by a capsule of dense connective tissue that contains elastic, reticular and smooth muscle fibers. The papilla is delicate and has two excretory ducts. The gland mass relative to body mass was 0.143%. Both adenomer cells and their secretions were stained with Sudan IV, PAS and AB, and were positive for numerous lectins that indicated the presence of lipids and carbohydrates. Immunohistochemical techniques to detect PCNA confirmed cell proliferation in the basal stratum of the adenomer cells. The lipids and glycoconjugates secreted by the uropygial gland serve numerous functions including protection against microorganisms. 相似文献
95.
Identification and characterization of a prevacuolar compartment in stigmas of nicotiana alata 总被引:3,自引:1,他引:2
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The stigmas of the ornamental tobacco plant Nicotiana alata accumulate large quantities of a series of 6-kD proteinase inhibitors (PIs) in the central vacuole that are derived from a 40-kD precursor protein, Na-PI. The sorting information that directs Na-PI to the vacuole is likely to reside in a C-terminal propeptide domain of 25 amino acids that forms an amphipathic alpha helix. Using cell fractionation techniques, we have examined transit of Na-PI through the endomembrane system and have identified a prevacuolar compartment that contains Na-PI with an intact targeting signal. In contrast, the targeting signal is not present on the predominant form of Na-PI in the vacuole. The prevacuolar compartment is marked by the presence of homologs of both the t-SNARE, PEP12p, and the putative vacuolar sorting receptor BP-80. Cross-linking and affinity precipitation studies revealed that Na-PI associates with BP-80 within this compartment, providing in vivo evidence for the function of BP-80 as a sorting receptor for a protein with a C-terminal vacuolar targeting signal. 相似文献
96.
Parturition and retention of fetal membranes were induced with PGF2α in 3 primiparous dairy cows. Starting on day 12 post partum (PP) the cows were treated with 500 μ g i.m. of ACTH-analogue (tetracosactid) every 6 h for 6 times. Changes in plasma concentrations of cortisol, progesterone and 15-ketodihydro-PGF2α were evaluated immediately after treatment. The effects on the resumption of ovarian activity were evaluated by clinical and ultrasound examinations and by progesterone and 15-ketodihydro-PGF2α analyses for 56 days after parturition. Treatment was able to induce a statistically significant (p < 0.01) similar increase in cortisol and progesterone after both the 1st and the 6th injections, in all cows. No changes in 15-ketodihydro-PGF2αconcentrations were seen after any of the injections of ACTH-analogue. The first corpus luteum (CL) was seen on day 18 PP (cow A), and 28 (cow B) and in both cases it was followed by a normal ovarian cyclicity. No CL was observed during the whole period of study in cow C. Progesterone profiles confirmed these clinical and ultrasonographic findings. The steroid output, especially progesterone, induced by the ACTH-analogue might be a stimulus for the onset of ovarian cyclicity, since 2 of the 3 animals ovulated earlier than expected. These findings point to the fact that interference with the stress system might have a positive effect on ovarian cyclicity. The different pattern of response does however demand further studies. 相似文献
97.
Marlies Cortés María J Fernández‐Aceñero MC Martínez‐Campanario Anna Esteve‐Codina Douglas S Darling Balázs Győrffy Toby Lawrence Douglas C Dean Antonio Postigo 《The EMBO journal》2017,36(22):3336-3355
Accumulation of tumor‐associated macrophages (TAMs) associates with malignant progression in cancer. However, the mechanisms that drive the pro‐tumor functions of TAMs are not fully understood. ZEB1 is best known for driving an epithelial‐to‐mesenchymal transition (EMT) in cancer cells to promote tumor progression. However, a role for ZEB1 in macrophages and TAMs has not been studied. Here we describe that TAMs require ZEB1 for their tumor‐promoting and chemotherapy resistance functions in a mouse model of ovarian cancer. Only TAMs that expressed full levels of Zeb1 accelerated tumor growth. Mechanistically, ZEB1 expression in TAMs induced their polarization toward an F4/80low pro‐tumor phenotype, including direct activation of Ccr2. In turn, expression of ZEB1 by TAMs induced Ccl2, Cd74, and a mesenchymal/stem‐like phenotype in cancer cells. In human ovarian carcinomas, TAM infiltration and CCR2 expression correlated with ZEB1 in tumor cells, where along with CCL2 and CD74 determined poorer prognosis. Importantly, ZEB1 in TAMs was a factor of poorer survival in human ovarian carcinomas. These data establish ZEB1 as a key factor in the tumor microenvironment and for maintaining TAMs’ tumor‐promoting functions. 相似文献
98.
Isticato R Cangiano G Tran HT Ciabattini A Medaglini D Oggioni MR De Felice M Pozzi G Ricca E 《Journal of bacteriology》2001,183(21):6294-6301
We developed a novel surface display system based on the use of bacterial spores. A protein of the Bacillus subtilis spore coat, CotB, was found to be located on the spore surface and used as fusion partner to express the 459-amino-acid C-terminal fragment of the tetanus toxin (TTFC). Western, dot blot and fluorescent-activated cell sorting analyses were used to monitor TTFC surface expression on purified spores. We estimated that more than 1.5 x 10(3) TTFC molecules were exposed on the surface of each spore and recognized by TTFC-specific antibodies. The efficient surface presentation of the heterologous protein, together with the simple purification procedure and the high stability and safety record of B. subtilis spores, makes this spore-based display system a potentially powerful approach for surface expression of bioactive molecules. 相似文献
99.
100.