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Query: UMLS:C0162871 (abdominal aortic aneurysm)
 8,664 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two experiments were conducted to determine the effects of essential amino acid deficiencies on several immunological variables in male broiler chickens. Essential amino acids were classified into five groups as follows: S-containing amino acids (SAA; methionine + cysteine), aromatic amino acids (AAA; phenylalanine + tyrosine), branched-chain amino acids (BCAA; isoleucine + leucine + valine), arginine plus lysine (Arg + Lys), and other essential amino acids (OEAA; glycine + serine + histidine + threonine + tryptophan). Chickens were fed ad libitum from 10 to 24 d of age on a control diet or amino-acid-deficient diets formulated to contain each amino acid group at 50% and 16% (Expt 1) at 50% (Expt 2) of the recommended requirements (National Research Council, 1984). Effects of feed consumption on immune responses were also considered by setting pair-feeding (Expt 1) or restricted-feeding (Expt 2) groups fed on the control diet. In Expt 1, changes in lymphoid organ weights varied with the type and degree of deficiency of amino acid groups, with BCAA deficiency markedly decreasing weights. The haemagglutinin titres against sheep erythrocytes did not change in any amino-acid-deficient chickens except that the titres were lower in chickens fed on the 50%- and 16%-BCAA diets as compared with their pair-fed counterparts. In Expt 2, the splenocyte proliferative response to concanavalin A was higher in the chickens fed on the BCAA- and Arg + Lys-deficient diets and lower in chickens fed on the SAA- and AAA-deficient diets than the control chickens, independent of feed consumption. These results suggest that the effects of specific amino acid deficiencies on immune responses cannot be generalized, and that BCAA have the greatest potential to modulate immune responses among the amino acids in chickens.
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PMID:Effects of dietary essential amino acid deficiencies on immunological variables in broiler chickens. 1085 3

A 1230-bp region of the cytochrome c oxidase subunit I (COI) gene of mitochondrial DNA of each of 16 brachiopod species, representing all five living orders, was amplified by polymerase chain reaction and sequenced. Pairwise comparisons of sequence differences plotted against divergence times estimated from the brachiopod fossil record revealed that, although there are considerable variations in the expected substitution rate among different lineages, amino acid substitutions of the COI sequences may largely become saturated in 100 Ma, due mostly to multiple substitutions at the same site. Coinciding with this result, phylogenetic analysis indicated low bootstrap values for nodes corresponding to divergence events that occurred before 100 Ma, suggesting that COI sequences are suitable only for inference of phylogenetic events subsequent to the Mesozoic. Examination of brachiopod codons corresponding to invariant amino acids in the COI of various other animals suggest the nonuniversal codon relationships UGA = Trp, AUA = Met, AAA/G = Lys, and AGA/G = Ser. These are identical to those in mollusks, annelids, and arthropods, consistent with the conclusion that brachiopods are protostomes, as indicated by previous molecular analyses.
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PMID:Mitochondrial COI sequences of brachiopods: genetic code shared with protostomes and limits of utility for phylogenetic reconstruction. 1086 Jun 43

The excitotoxin, L-alpha-aminoadipic acid (L-AAA), kills primary astrocytes in the brain. The mechanism underlying the induction of cell death is not well understood although many possible mechanisms are theorized. Previous studies have reported that astrocytes die after prolonged exposure to L-AAA suggesting a delayed programmed cell death and apoptosis. In this study rat cortical astrocytes exposed to continuous 1 mM L-AAA exposure for 24-, 48-, or 72 hours demonstrated increased DNA laddering, a characteristic of apoptosis. Unexpectedly, this was not ameliorated by the presence of cycloheximide at 0.1 microg/ml medium. Because of our interest in cytoprotective heat shock proteins induced by excitoxic stress, we studied the effect of prolonged exposure of L-AAA on the synthesis of stress proteins and protein synthesis in rat cortical astrocytes. Protein synthesis as measured by [35S]-methionine labeling showed a marked and significant decrease in incorporation of radiolabel after 24 hours of exposure to L-AAA and prior to induction of significant cell death noted at 48- and 72 hours of L-AAA exposure. The inhibition of protein synthesis was partially reversible at 24 hours if cells were labeled in medium without L-AAA during the radiolabeling period. Heat shock or stress proteins, HSP70 and heme oxygenase-1 (HO-1), were analyzed after a 24 hour exposure to L-AAA and showed no significant induction of HSP70 or HO-1. The findings suggest that the prolonged inhibition of protein synthesis and associated lack of induction of HSP70 and HO-1 synthesis contributed to apoptotic cell death induced by the excitoxin L-AAA.
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PMID:Induction of cell death by L-alpha-aminoadipic acid exposure in cultured rat astrocytes: relationship to protein synthesis. 1089 21

Shared molecular genetic characteristics other than DNA and protein sequences can provide excellent sources of phylogenetic information, particularly if they are complex and rare and are consequently unlikely to have arisen by chance convergence. We have used two such characters, arising from changes in mitochondrial genetic code, to define a clade within the Platyhelminthes (flatworms), the Rhabditophora. We have sampled 10 distinct classes within the Rhabditophora and find that all have the codon AAA coding for the amino acid Asn rather than the usual Lys and AUA for Ile rather than the usual Met. We find no evidence to support claims that the codon UAA codes for Tyr in the Platyhelminthes rather than the standard stop codon. The Rhabditophora are a very diverse group comprising the majority of the free-living turbellarian taxa and the parasitic Neodermata. In contrast, three other classes of turbellarian flatworm, the Acoela, Nemertodermatida, and Catenulida, have the standard invertebrate assignments for these codons and so are convincingly excluded from the rhabditophoran clade. We have developed a rapid computerized method for analyzing genetic codes and demonstrate the wide phylogenetic distribution of the standard invertebrate code as well as confirming already known metazoan deviations from it (ascidian, vertebrate, echinoderm/hemichordate).
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PMID:Changes in mitochondrial genetic codes as phylogenetic characters: two examples from the flatworms. 1102 35

The flatworm mitochondrial genetic code, which has been used for all species of the Platyhelminthes, is mainly characterized by AUA codon for isoleucine, AAA codon for asparagine and UAA codon for tyrosine. In eight species of cestodes (Echinococcus multilocularis, Echinococcus granlosus, Taenia solium Taenia saginata, Taenia hydatigena, Taenia crassiceps, Hymenolepis nama and Mesocestoides corti), the cytochrome c oxidase subunit I (COI) genes were partially sequenced to verify this genetic code. Comparison of the COI-encoding nucleotide sequences with those of human, sea urchin, fruit fly, nematode and yeast indicated that the assignments of AUA and AAA codons are adequate for cestodes. In addition, the nucleotide sequences of ATPase subunit 6 (ATP6) gene and its flanking region were compared to examine initiation and stop codons. In the related species of T. solium and T. saginata, the deduced amino acid sequences of ATP6 were homogeneous; however, the conversion of initiation codon AUG into GUG was observed in T. saginata. We also found the similar conversion in T. crassiceps. The C-terminal sequences of putative ATP6 proteins were highly conserved among the eight species and the stop codon UAG was altered to UAA in all Taenia species. The features of the gene-junctional region between NADH dehydrogenase subunit 4 (ND4) and glutamine tRNA (tRNAGln) genes also supported that UAA serves as a stop codon. Based on these results, we propose that the flatworm mitochondrial code should be modified for cestodes, particularly, in an initiating methionine codon (GUG) and a terminating codon (UAA).
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PMID:Mitochondrial genetic code in cestodes. 1116 47

The clinical manifestations of atherosclerosis include coronary artery disease (CAD), stroke, abdominal aortic aneurysm and peripheral vascular disease. World-wide, CAD and stroke are the leading causes of death and disability. The recognition of atherosclerosis as an inflammatory disease in its genesis, progression and ultimate clinical manifestations has created an interesting area of vascular research. Apart from those well-known traditional risk factors for atherosclerosis, novel and potentially treatable atherosclerotic risk factors such as homocysteine (an amino acid derived from the metabolism of dietary methionine that induces vascular endothelial dysfunction) and infections have emerged. In fact, the century-old 'infectious' hypothesis of atherosclerosis has implicated a number of micro-organisms that may act as contributing inflammatory stimuli. Although cytomegalovirus, Helicobacter pylori and Chlamydia pneumoniae are the three micro-organisms most extensively studied, this review will focus on C. pneumoniae. Collaborative efforts from many disciplines have resulted in the accumulation of evidence from seroepidemiological, pathological, animal model, immunological and antibiotic intervention studies, linking C. pneumoniae with atherosclerosis. Seroepidemiological observations provide circumstantial evidence, which is weak in most prospective studies. Pathological studies have demonstrated the preferential existence of C. pneumoniae in atherosclerotic plaque tissues, while animal model experiments have shown the induction of atherosclerosis by C. pneumoniae. Finally, immunological processes whereby C. pneumoniae could participate in key atherogenic and atherothrombotic events have also been identified. Although benefits of the secondary prevention of atherosclerosis have been demonstrated in some antibiotic intervention studies, a number of negative studies have also emerged. The results of the ongoing large prospective human antibiotic intervention trials may help to finally establish if there is a causal link between C. pneumoniae infection and atherosclerosis.
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PMID:Chlamydia pneumoniae and atherosclerosis -- what we know and what we don't. 1190 95

Homocysteine (Hcy) is a non-protein forming sulfur amino acid, synthesised from methionine (Met), whose metabolism is at the junction of two metabolic pathways: remethylation and transsulfuration. Increased Hcy serum concentration is a well established independent risk factor of cardiovascular diseases and a known feature of end stage renal disease. Hcy plasma level is influenced by folate, vitamin B6 and genetic factors. Mutation C677T in gene encoding methylenetetrahydrofolate reductase (MTHFR), an enzyme involved in Hcy remethylation has been associated with elevated Hcy in homozygous carriers (TT genotype). Several amino acids take part in metabolism of Hcy. There are abnormalities of concentration of the non essential and essential of amino acids in serum of patients treated with hemodialysis (HD). It is possible that these abnormalities of amino acids can change the Hcy metabolism. The aim of this study was the evaluation of some aspects of Hcy metabolism. We examined the MTHFR gene polymorphism and its relationship with plasma Hcy concentration. The plasma levels of total amino acids and amino acids connected with Hcy metabolism: methionine (Met), seryne (Ser), cysteine (Cyst) and tauryne (Tau) were evaluated in hemodialysis patients. The study was conducted in 71 (35 male, 36 female) patients, mean age 56.2 +/- 12.4 years. They were dialysed for a mean duration of 87.7 +/- 84.7 months (range 2-302). The control group (CG) in which Hcy and amino acids levels were examined consisted of 12 healthy subjects. Serum (EDTA) Hcy levels were measured by EIA-Hcy ELISA kit. The MTHFR gene polymorphism was evaluated by means of the polymerase chain reaction (PCR). The amino acids were measured by chromatography in amino acid analyser AAA 400. Mean concentration of Hcy was significantly higher in patients than in CG (31.1 +/- 9.1 vs 11.9 +/- 2.9 mumol/L; p < 0.01). Genotype frequencies in patients were: 42.8% for CC, 48.5% for CT and 8.7% for TT. Mean concentration of Hcy were similar in above genotype groups: 31.2 +/- 9.4; 30.7 +/- 10.7; 32.8 +/- 5.1 mumol/L, respectively. We did not find any correlation between Hcy level and the mutation in gene coding for MTHFR in our study group of patients. Mean total amino acid concentrations were significantly lower in plasma patients than in CG: 3624.48 +/- 140.32 vs 4454.45 +/- 774.91 mumol/L; p < 0.05. Mean plasma level of Tau was significantly lower in patients than in CG: 93.01 +/- 43.73 vs 286.75 +/- 57.02 mumol/l; p < 0.01. Also mean plasma level of Ser was significantly lower in patients than in CG; 125.71 +/- 24.25 vs 233.61 +/- 44.55 mumol/L; p < 0.01. Mean concentration of Cys were significantly higher in hemodialysis patients than in CG: 100.82 +/- 43.53 vs 31.31 +/- 21.31 mumol/L; p < 0.01. Mean Met concentrations were not significantly different between two studied groups. We found significant positive correlation between plasma Hcy levels and plasma Cys level (r = 0491; p < 0.05). Also there was a significant positive correlation between plasma Hcy level and duration of hemodialysis (r = 5411; p < 0.05). We concluded that in our studied population of hemodialysis patients there was no significant association between mutation in the gene coding for MTHFR and hyperhomocysteinemia and hypercysteinemia. There are abnormalities of plasma level of amino acids which are take part in Hcy metabolism in hemodialysis patients.
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PMID:[Some aspects of homocysteine metabolism in hemodialysis patients]. 1268 44

Integration of cytochrome b(5) (b5), a tail-anchored protein located in the endoplasmic reticulum (ER) membrane, into the membrane was studied. Mutation of three amino acids, -Leu-Met-Tyr, at the carboxy-terminal end of the transmembrane segment of b5 to alanines resulted in localization of the mutated protein, b5LMY/AAA, in the cytosol as well as in the ER membrane. When an N-glycosylation site was introduced at the carboxy-terminal end of b5LMY/AAA, a substantial amount of the glycosylated form of the mutant protein was recovered in the cytosol fraction. A portion of the mutant protein recovered in the ER was released from the membrane by incubation with the cytosol fraction, but no further release was observed in the second incubation, suggesting that b5 is present in two different states, loosely-bound and firmly-integrated forms, in the ER membrane. These results suggest that b5 is integrated into the ER membrane via the loosely bound state, in which the carboxy-terminal end of the molecule is inserted into the luminal side of the vesicle but is easily translocated back to the cytosol, and that the three amino acids are important for conversion of the loosely-bound state to the firmly-integrated state.
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PMID:Integration of cytochrome b5 into endoplasmic reticulum membrane: participation of carboxy-terminal portion of the transmembrane domain. 1276 Nov 89

The finding that a lens under oxidative stress accumulated free and protein-bound cysteine (protein-S-S-cysteine) in the fiber cells prompted us to examine if there is an alternative source for cysteine pools besides the active cysteine transport system in the lens, namely, the transsulfuration pathway of homocysteine-cystathionine-cysteine, which utilises methionine through transmethylation. We examined the presence of the gene for cystathionine-beta-synthase (CBS), the rate limiting enzyme that converts homocysteine to cystathionine in the transsulfuration pathway, in human lens epithelial (HLE) B3 cells using PCR with primers designed based on the sequence of human liver CBS (Forward 5'-CCA CAC TGC CCC GGC AAA AT-3'; Reverse 5'-CTG GCA ATG CCC GTG ATG GT-3'). The purified DNA fragment (586 bp) from PCR analysis was sequenced and confirmed the homology with CBS gene from other human tissues. The CBS protein band (67 kDa) was present in the HLE cells, which reacted positively with the human liver anti-CBS antibody. The enzyme protein was detected in the pig and human lenses with the highest intensity in the epithelial layer, lower but equal quantities of CBS was present in the cortical and nuclear regions. Human nuclear CBS increased while epithelial CBS decreased with aging. Oxidative stress transiently upregulated the gene expression of CBS both in HLE cells (0.1 mMH2O2) and in pig lens cultured in TC 199 medium (0.5 mMH2O2). The catalytic activity for CBS, which was assayed by measuring the production of C14-cystathionine from C14-serine in the presence of homocysteine, S-adenosyl-methionine and pyridoxal phosphate, was detectable in the HLE cells and transiently activated with H2O2. Free cystathionine accumulated when HLE B3 cells were treated with propargylglycine (PGG), an inhibitor of cystathionase, the downstream enzyme that converts cystathionine to cysteine. More cystathionine accumulation occurred when the cells were simultaneously exposed to PGG and 0.1 mMH2O2. We have shown that oxidative stress of H2O2 could increase the flux of this transsulfuration pathway by committing more homocysteine to cysteine and glutathione production as H2O2 (0.1 mM) inhibited the remethylation enzyme of methionine synthase while concurrently activating the CBS enzyme. This is the first evidence that a transsulfuration pathway is present in the lens, and that it can be upregulated under oxidative stress to provide additional redox potential for the cells.
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PMID:The presence of a transsulfuration pathway in the lens: a new oxidative stress defense system. 1564 25

In humans, eight types of histone H1 exist (H1.1-H1.5, H1 degrees , H1t and H1oo), all consisting of a highly conserved globular domain and less conserved N- and C-terminal tails. Although the precise functions of these isoforms are not yet understood, and H1 subtypes have been found to be dispensable for mammalian development, it is now clear that specific functions may be assigned to certain individual H1 subtypes. Moreover, microsequence variations within the isoforms, such as polymorphisms or mutations, may have biological significance because of the high degree of sequence conservation of these proteins. This study used a hydrophilic interaction liquid chromatographic method to detect sequence variants within the subtypes. Two deviations from wild-type H1 sequences were found. In K562 erythroleukemic cells, alanine at position 17 in H1.2 was replaced by valine, and, in Raji B lymphoblastoid cells, lysine at position 173 in H1.4 was replaced by arginine. We confirmed these findings by DNA sequencing of the corresponding gene segments. In K562 cells, a homozygous GCC-->GTC shift was found at codon 18, giving rise to H1.2 Ala17Val because the initial methionine is removed in H1 histones. Raji cells showed a heterozygous AAA-->AGA codon change at position 174 in H1.4, corresponding to the Lys173Arg substitution. The allele frequency of these sequence variants in a normal Swedish population was found to be 6.8% for the H1.2 GCC-->GTC shift, indicating that this is a relatively frequent polymorphism. The AAA-->AGA codon change in H1.4 was detected only in Raji cells and was not present in a normal population or in six other cell lines derived from individuals suffering from Burkitt's lymphoma. The significance of these sequence variants is unclear, but increasing evidence indicates that minor sequence variations in linker histones may change their binding characteristics, influence chromatin remodeling, and specifically affect important cellular functions.
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PMID:Characterization of sequence variations in human histone H1.2 and H1.4 subtypes. 1600 66


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