Biomedical subjects

Y Feng

Publications and source records attributed to Y Feng.

At least 379 records · Page 21Linked to original sources

PubMed1994

Acetylator genotype-dependent formation of 2-aminofluorene-hemoglobin adducts in rapid and slow acetylator Syrian hamsters congenic at the NAT2 locus.

Arylamine-hemoglobin adducts are a valuable dosimeter for assessing arylamine exposures and carcinogenic risk. The effects of age, sex, time-course, dose, and acetylator genotype on levels of 2-aminofluorene-hemoglobin adducts were investigated in homozygous rapid (Bio. 82.73/H-Patr) and slow (Bio. 82.73/H-Pats) acetylator hamsters congenic at the polymorphic (NAT2) acetylator locus. Following administration of a single ip dose of [3H]2-aminofluorene, peak 2-aminofluorene-hemoglobin adduct levels were achieved at 12-18 hr and retained a plateau up to 72 hr postinjection in both rapid and slow acetylator congenic hamsters. 2-Aminofluorene-hemoglobin adduct levels did not differ significantly between young (5-6 weeks) and old (32-49 weeks) hamsters or between male and female hamsters within either acetylator genotype. 2-Aminofluorene-hemoglobin adduct levels increased in a dose-dependent manner (r = 0.95, p = 0.0001) and were consistently higher in slow versus rapid acetylator congenic hamsters in studies of both time-course and dose-effect. The magnitude of the acetylator genotype-dependent difference was a function of dose; 2-aminofluorene-hemoglobin adduct levels were 1.5-fold higher in slow acetylator congenic hamsters following a 60 mg/kg 2-aminofluorene dose (p = 0.0013) but 2-fold higher following a 100 mg/kg 2-aminofluorene dose (p < 0.0001). These results show a specific and significant role for NAT2 acetylator genotype in formation of arylamine-hemoglobin adducts, which may reflect the relationship between acetylator genotype and the incidence of different cancers from arylamine exposures.

Acetylation↗

PubMed1994

Construction of Syrian hamster lines congenic at the polymorphic acetyltransferase locus (NAT2): acetylator genotype-dependent N- and O-acetylation of arylamine carcinogens.

Congenic Bio. 1.5/H-NAT2 Syrian hamster lines were constructed by introducing the NAT2r gene from MHA/SsLak inbred hamsters into a background BIO 1.5 Syrian inbred hamster line. Genetic identity of the Bio. 1.5/H-NAT2 congenic lines and nonidentity with the previously constructed Bio. 82.73/H-Pat congenic lines were determined by "DNA fingerprints" of genomic DNA derived from the different hamster lines. The N-acetylation capacity of the Bio. 1.5/H-NAT2 congenic hamster lines was clearly NAT2-dependent both in vivo and in vitro, with highest levels expressed in Bio. 1.5/H-NAT2r homozygous rapid acetylators, intermediate levels in Bio. 1.5/H-NAT2r/NAT2s heterozygous acetylators, and lowest levels in Bio. 1.5/H-NAT2s homozygous slow acetylators. The NAT2-dependent expression of N-acetyltransferase activity was evident toward p-aminobenzoic acid, 4-aminophenol, 2-aminofluorene, 4-aminobiphenyl, beta-naphthylamine, and 3,2'-dimethyl-4-amino-biphenyl in liver, kidney, colon, lung, and urinary bladder cytosols. The polymorphic acetyltransferase (NAT2) and the monomorphic acetyltransferase (NAT1) were isolated from hepatic cytosols and tested separately for their ability to catalyze arylamine N-acetyltransferase and N-hydroxyarylamine O-acetyltransferase activities. Both arylamine N-acetylation and N-hydroxyarylamine O-acetylation were clearly acetylator genotype-dependent when catalyzed by NAT2, and both were clearly acetylator genotype-independent when catalyzed by NAT1. NAT2/NAT1 activity ratios varied with the particular arylamine substrate acetylated. These studies show an important role for NAT2 acetylator genotype in Syrian hamster carcinogenic arylamine metabolism and confirm its role in the metabolic activation of N-hydroxyarylamines. The Bio. 1.5/H-NAT2 congenic lines provide a new model for investigating the precise role of the NAT2 gene locus in arylamine metabolism and toxicity.

Acetylation↗

PubMed1994

MTFA templates for quick and inexpensive assessment of display image resolution.

Traditional MTFA measurements are time-consuming, expensive and cumbersome. This situation was a hindrance in the authors' work on the evaluation of the merits of MTFA as a measure of display screen image quality. A set of hard-copy MTFA templates was therefore designed to constitute an intervening variable suitable for quick quality assessments by experimental subjects. This intervening scale worked quite satisfactorily, and the present paper reports how it has been turned into an independent tool for the assessment of display image resolution.

Journal Article↗

PubMed1994

Naloxone-precipitated morphine withdrawal increases pontine glutamate levels in the rat.

Extracellular fluid (ECF) levels of glutamate (Glu) and aspartate (Asp) were measured in the locus coeruleus (LC) during morphine withdrawal by using microdialysis in conscious morphine-dependent Sprague-Dawley rats. Guide cannulae were implanted chronically and rats were given intracerebroventricular (i.c.v.) infusions of morphine (26 nmol/1 microliters/hr) or saline (1 microliters/hr) for 3 days. Microdialysis probes (2 mm tip) were inserted into the LC 24 hr before precipitation of withdrawal by i.c.v. injection of naloxone (12 or 48 nmol/5 microliters). Behavioral evidence of withdrawal (teeth-chattering, wet-dog shakes, etc.) was detected following naloxone challenge in morphine, but not in saline-infused rats. Increases (P < 0.01) in ECF levels of Glu (and Asp, to a lesser degree) were noted after naloxone-precipitated withdrawal only in the morphine group. The ECF Glu levels in the LC increased from 9.6 +/- 2.7 to 15.5 +/- 5.0 microM following 12 nmol/5 microliters naloxone, and from 9.5 +/- 1.9 to 20.5 +/- 3.3 microM following 48 nmol/5 microliters naloxone, before and in the first 15 min sample after the precipitation of withdrawal in the morphine-dependent rats, respectively. These results provide direct evidence to support the role of excitatory amino acids within the LC in morphine withdrawal.

Animals↗

PubMed1994

A mutation of the Drosophila sodium pump alpha subunit gene results in bang-sensitive paralysis.

A bang-sensitive enhancer trap line was isolated in a behavioral screen. The flies show a weak bang-sensitive paralysis, recovering after about 7 s. The P element insert is localized at 93B1-2 on the salivary chromosomes, the site of the (Na+,K+)ATPase alpha subunit gene. Molecular characterization demonstrates that the transposon is inserted into the first intron of this gene. This insertion leads to normal-sized transcripts, but reduced levels of expression. This change is also reflected in lower amounts of a normal-sized alpha subunit protein. Mutant flies show a much greater sensitivity to ouabain, likewise indicating, on a functional level, a reduction in Na+ pump activity. Furthermore, the bang-sensitive behavior can also be mimicked by injecting sublethal doses of ouabain into wild-type flies. The molecular and functional evidence indicates that the insertion has produced a hypomorphic mutation of the (Na+,K+)ATPase alpha subunit gene, opening the way to future studies of the regulation of the Na+ pump.

Animals↗

PubMed1994

Solution structure of apocytochrome b562.

The apoprotein is an important intermediate on the folding pathways of many haem proteins, yet a detailed structure of such an intermediate has remained elusive. Here we present the structure of apocytochrome b562 obtained by NMR spectroscopy. The apoprotein has a topology similar to the holoprotein. Nevertheless, significant differences in helix-helix packing between the two are evident. Much of the haem binding pocket in the apoprotein is preserved but exposed to solvent creating a large cavern. As apocytochrome b562 displays many of the physical characteristics ascribed to the molten globule state, these results help ellucidate the origin of several properties of the protein molten globule.

Apoproteins↗

PubMed1994

Plasminogen activator inhibitor-1 in the pathogenesis of delayed radiation damage in rat spinal cord in vivo.

The pathophysiology of radiation-induced damage to the central nervous system (CNS) is poorly understood. Preliminary data suggest that fibrinolytic inhibitors are involved in the development of necrosis. In this study, cervical spinal cord irradiation was studied in 90 rats by measuring plasminogen activator inhibitor (PAI)-1 on Days 2, 7, 30, 60, 90, 120, 130, or 145 after irradiation. Paralysis due to radiation necrosis developed in all animals kept alive for 140 to 150 days. Assay of PAI-1 was by Western blot, enzyme-linked immunosorbent assay (ELISA), and complex formation with 125I-labeled urokinase. No PAI-1 was detected in normal spinal cord tissue or in irradiated spinal cord up to Day 90. However, PAI-1 was detected at Day 120 and was marked by elevated ELISA levels at the time of paralysis. Western blot showed detectable PAI-1 (51 kD) at Day 120 and very significant levels at the time of paralysis. Complex formation with 125I-labeled urokinase was also detected at Day 120 with similar results. Immunohistochemical studies showed that PAI-1 was highly concentrated within and immediately adjacent to zones of necrosis at 145 days and was absent in normal tissue. This study adds considerable weight to the proposal that PAI-1 is closely associated with the pathogenesis of CNS radiation necrosis.

Animals↗

PubMed1994

[Study on urine ALb, serum and urine beta 2-m, IgG, and THP].

The urine ALb, serum and urine beta 2-m, IgG, and THP were serially determined with radioimmunoassay to assess the renal functions during various stages of burn in 52 patients with TBSA over 30% (mean +/- s 58.4% +/- 18.88%). It was found that the urine levels of ALb, IgG, and THP and the serum and urine levels of beta 2-m were remarkably increased and that the serum levels of IgG were decreased after burns. Our study suggested that the measurements of urine ALb, serum and urine beta 2-m, IgG, and THP using radioimmunoassay were sensitive in assessing renal glomerular permeability and tubular functions after burn. It is presumed that such methods might be used to help identify the location, the extent, and the severity of the renal abnormalities and provide valuable information about the differential diagnosis and the prognosis of the renal damage in patients with extensive burns.

Adolescent↗

PubMed1994

Elevated levels of plasminogen activators in the pathogenesis of delayed radiation damage in rat cervical spinal cord in vivo.

The pathophysiology of the cellular basis of radiation-induced demyelination and white-matter necrosis of the central nervous system (CNS) is poorly understood. Preliminary data suggest that tissue damage is partly mediated through changes in the proteolytic enzymes. In this study, we irradiated rat cervical spinal cords with single doses of 24 Gy of 18 MV photons or 20 MeV electrons and measured the levels of plasminogen activators at days 2, 7, 30, 60, 90, 120, 130 and 145 after irradiation, using appropriate controls at each time. Fibrin zymography revealed fibrinolytic bands representing molecular weights of 68,000 and 48,000 in controls and irradiated samples; these bands increased significantly at days 120, 130 and 145 after irradiation. Inhibition of these enzymatic bands with specific antibodies against tissue-type plasminogen activator (tPA) and amiloride, an inhibitor for urokinase plasminogen activator (uPA), confirmed that these bands were tPA and uPA. Enzymatic levels quantified by densitometry showed a twofold elevation in the levels of tPA and more than a tenfold increase in uPA after 120 days' irradiation. Activity of uPA was increased threefold by day 2 and increased steadily with time compared to nonirradiated control samples. Enzyme-linked immunosorbent assay (ELISA) also showed a threefold increase in the tPA content in the extracts of irradiated rat cervical spinal cords at days 120, 130 and 145. This study adds additional information to the proposed role of plasminogen activators in the pathogenic pathways of radiation damage in the CNS.

Animals↗

PubMed1993

The main chain dynamics of a peptide bound to calmodulin.

The main chain dynamics of a peptide corresponding to the smooth muscle myosin light chain kinase calmodulin-binding domain bound to calcium-saturated calmodulin have been studied by 15N relaxation techniques. Laboratory and rotating-frame spin lattice relaxation times and nuclear Overhauser effects have been determined for nine amide 15N sites in the peptide using two-dimensional NMR spectroscopy. The global motion of the 1:1 complex is shown to be isotropic and is characterized by a correlation time of 10 ns rad-1. The generalized order parameters (S2) of the nine backbone amide N-H vectors of the peptide all fall closely about a value of 0.83. The corresponding effective correlation times all tend to zero, indicating that, on the subnanosecond time scale, backbone motion of the bound peptide is highly restricted and dominated by extremely fast motions.

Amino Acid Sequence↗

PubMed1993

Effect of the arginine-82 to alanine mutation in bacteriorhodopsin on dark adaptation, proton release, and the photochemical cycle.

The pH dependence of the rate constant of dark adaptation (thermal isomerization from all-trans- to 13-cis-bR) drastically changes when Arg82 of bacteriorhodopsin is replaced by an alanine. In the wild type (WT) the rate decreases sharply between pH 2.5 and pH 5. In R82A the sharp decrease is shifted to pH > 7. This correlates with the shift in the pK of the purple-to-blue transition from pH 2.6 in the wild type to pH 7.2 in the mutant (in 150 mM KCl). We propose that the same group that controls the purple-to-blue transition, namely, Asp85, catalyzes dark adaptation. The rate of dark adaptation in the R82A mutant is proportional to the fraction of protonated Asp85, indicating that dark adaptation occurs when Asp85 is transiently protonated. Thermal isomerization is at least 2 x 10(3) times more likely when Asp85 is protonated (blue membrane) than when it is deprotonated (purple membrane). The pH dependence of dark adaptation in the WT can be explained by a model in which the rate of dark adaptation in the WT is also proportional to the fraction of protonated Asp85 and that the pK of Asp85 depends on some other group, X, which deprotonates (or moves away from Asp85) with pK9 and causes the shift in the pK of Asp85 from 2.6 to 7.2. The quantum yield of light adaptation is at least an order of magnitude less in R82A as compared to the WT. The rise time of M formation is very fast in R82A and, unlike the WT, pH independent (1 microsecond versus 85 and 6 microseconds in the WT at pH 7 and 10, respectively). The activation energy of the L to M transition is 6.9 kcal/mol versus 13.5 kcal/mol in the WT. Thus the loss of a positive charge in the active site greatly increases the rate of light-induced deprotonation of the Schiff base. In the R82A mutant, the M decay at pH > 8.8 is much faster than the recovery of initial bR, which suggests a decrease in the rate of back-reaction from N to M. In a suspension of R82A membranes the rate of proton release as measured by the pH-sensitive dye pyranine is delayed by at least 20-fold (in 2 M KCl), while the uptake of protons did not change much (12 ms in the WT versus 8 ms in R82A).(ABSTRACT TRUNCATED AT 400 WORDS)

Alanine↗

PubMed1993

Ca(2+)-dependent and thapsigargin-inhibited phosphorylation of Na+,K(+)-ATPase catalytic domain following chimeric recombination with Ca(2+)-ATPase.

Two chimeric proteins comprising the Na,K-ATPase catalytic domain (large cytosolic loop) and the two flanking regions of the Ca-ATPase were obtained by transient or stable expression in mammalian cells transfected with recombinant DNA. In the first chimera (CpNC), a large portion (containing the nucleotide-binding site) of the cytosolic loop between putative membrane spans M4 and M5 of the sarcoendoplasmic reticulum Ca2+ (SERCA) 1 (fast muscle) ATPase was replaced by the corresponding portion of the Na,K-ATPase alpha 1 subunit. In the second chimera (CNpC), an even larger portion (containing the nucleotide-binding site and the phosphorylation site) of the analogous cytosolic loop of the SERCA2 (cardiac muscle) ATPase was replaced by the corresponding portion of the Na,K-ATPase alpha 1 subunit. Steady state Ca2+ transport and coupled ATP hydrolysis by the chimeric proteins were negligible as compared to those obtained with SERCA enzymes. Nevertheless, the chimeric proteins were able to utilize ATP to form phosphoenzyme levels equal to those formed by SERCA ATPases. Chimeric and SERCA enzymes exhibited an identical Ca2+ requirement for ATP utilization and sensitivity to thapsigargin (TG) which is a specific inhibitor of SERCA ATPase and not of Na,K-ATPase. Furthermore, both SERCA and chimeric enzymes could be phosphorylated with P(i), and this reaction required removal of Ca2+. In comparative experiments, the functional pattern of seemingly unaffected phosphoenzyme formation and inhibited Ca2+ transport was produced in the SERCA ATPase even by single mutation of Pro337 to Ala, evidently due to defective protein conformation. Retention of Ca2+ and TG sensitivity by the chimeric proteins demonstrates that the Ca(2+)- and TG-binding domains do not reside within the cytosolic loop replaced by chimeric substitution and strongly support previous studies suggesting that binding of calcium required for enzyme activation occurs within the membrane-bound region of the SERCA ATPases (Clarke et al., 1989a; Sumbilla et al., 1991).

Amino Acid Sequence↗

PubMed1993

Decreased levels of glia-derived nexin/protease nexin I in irradiated rat spinal cord in vivo.

The pathophysiology of the cellular basis of radiation induced demyelination and white matter necrosis of the Central Nervous System (CNS) is poorly understood. There have been no previous studies that have shown the effect of irradiation on glia-derived nexin. In this study, rats were given cervical spinal cord irradiation, and glial derived nexin or protease nexin I (GDN/PNI) was measured on days 2, 7, 30, 60, 120, 130, and 145 after irradiation. The level of GDN/PNI significantly decreased after irradiation compared to levels in control spinal cord, and there was no detectable levels of GDN/PNI by the time paralysis developed. This study adds considerable weight to the proposal that GDN/PNI has an important role in the pathogenesis of CNS radiation damage.

Amyloid beta-Protein Precursor↗

PubMed1993

Asynaptic expression of the adult nicotinic acetylcholine receptor in long-term cultures of mammalian myotubes.

To determine whether synaptic contact is required to express adult-type nicotinic acetylcholine receptors (A-AChR) in developing mammalian muscle, we have examined single-channel AChR activity in primary muscle cultures maintained for up to 29 days. A-AChRs were first expressed after day 12 in culture (CD12), during a period characterized by the accumulation of embryonic acetylcholine receptors (E-AChR). The highest rate of A-AChR expression was observed between CD15 and 19, during a period of maximal E-AChR accumulation. Although the level of A-AChR expression between individual patches was quite variable during this period, A-AChRs accounted for up to 40% of the events produced by receptors expressed over a 3-day interval. Between CD19 and 29, the density of E-AChRs diminished while the expression of A-AChRs per patch continued to increase but at a lower rate than that observed between CD15 and 19. In 25-29-day cultures, 70.6% of patches exhibited both E-AChR and A-AChR activity, and the percentage of A-AChR events per patch ranged between 0 and 47% with a mean of 11.7 +/- 3.2%. These results demonstrate that endogenous muscle mechanisms promote developmental increases in the expression of A-AChRs in myotubes that have no history of synaptic contact. This conclusion suggests that synaptic imprinting at developing junctions is mediated in part by endogenous muscle mechanisms, and does not require direct neurotrophic activation of epsilon mRNA transcription.

Aging↗

PubMed1993

The tolerance of primate spinal cord to re-irradiation.

PURPOSE: This study was designed to assess the tolerance of the cervical spinal cord of rhesus monkeys to re-irradiation. This information is essential for treatment recommendations in previously irradiated patients. METHODS AND MATERIALS: Control animals received a single course of treatment to total doses of 70.4 Gy, 77.0 Gy, or 83.6 Gy in daily fractions of 2.2 Gy. Twelve asymptomatic animals that received 70.4 Gy were re-irradiated two years later to cumulative doses of 83.6, 92.4, or 101.2 Gy. Another group of 15 animals received 44 Gy and two years later were re-irradiated to cumulative doses of 83.6, 92.4, 101.2, or 110 Gy. The clinical endpoint was myeloparesis. A complete necropsy was performed in all animals when myeloparesis manifested or at the end of observation period. RESULTS: Only two of the 12 asymptomatic animals of the 70.4 Gy dose-response study group and two of the 15 animals that had received 44 Gy initially developed myelopathy within two years of re-irradiation. The ED50 value of the single-course irradiation was 76.1 +/- 1.9 Gy, while the extrapolated ED50 for retreatment after 44 Gy was > or = 110 Gy. The lesions of the two symptomatic animals that received 70.4 Gy initially were mixtures of white matter and vascular lesions similar to those observed after single course irradiation. However, both symptomatic animals given 44 Gy initially had hemorrhagic infarcts in the white matter. CONCLUSION: The results of this study indicate that substantial recovery of occult injuries induced by the initial 44 Gy had occurred within two years. The difference between the types of lesions observed after a single course and re-irradiation suggests that vascular injury may recover less efficiently or at slower rate than white matter damage. The dependence of the extent of recovery on the initial dose and the time course of such recovery in primates are being investigated.

Animals↗

PubMed1993

Metabolic activation and deactivation of arylamine carcinogens by recombinant human NAT1 and polymorphic NAT2 acetyltransferases.

A genetic polymorphism at the NAT2 gene locus, encoding for polymorphic N-acetyltransferase (NAT2), segregates individuals into rapid, intermediate or slow acetylator phenotypes. Both rapid and slow acetylator phenotypes have been associated with increased incidence of cancer in certain target organs related to arylamine exposure, suggesting a role for acetylation in both the activation and deactivation of arylamine carcinogens. A second gene (NAT1) encodes for a different acetyltransferase isozyme (NAT1) that is not subject to the classical acetylation polymorphism. In order to assess the relative ability of NAT1 and NAT2 to activate and deactivate arylamine carcinogens, we tested the capacity of recombinant human NAT1 and NAT2, expressed in Escherichia coli XA90 strains DMG100 and DMG200 respectively, to catalyze the N-acetylation (deactivation) and O-acetylation (activation) of a variety of carbocyclic and heterocyclic arylamine carcinogens. Both NAT1 and NAT2 catalyzed the N-acetylation of each of the 17 arylamines tested. Rates of N-acetylation by NAT1 and NAT2 were considerably lower for heterocyclic arylamines such as 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ), particularly those (e.g. IQ) with steric hindrance to the exocyclic amino group. For carbocyclic arylamines such as 4-aminobiphenyl and beta-naphthylamine, the apparent affinity was significantly (P < 0.05) higher for NAT2 than NAT1. NAT1/NAT2 activity ratios and clearance calculations suggest a significant role for the polymorphic NAT2 in the N-acetylation of carbocyclic arylamine carcinogens. Both NAT1 and NAT2 catalyzed acetyl coenzyme A-dependent O-acetylation of N-hydroxy-2-aminofluorene and N-hydroxy-4-aminobiphenyl to yield DNA adducts. NAT1 catalyzed paraoxon-resistant, intramolecular N,O-acetyltransferase-mediated activation of N-hydroxy-2-acetylaminofluorene and N-hydroxy-4-acetylaminobiphenyl at low rates; catalysis by NAT2 was not readily detectable in the presence of paraoxon. In summary these studies strongly suggest that the human acetylation polymorphism influences both the metabolic activation (O-acetylation) and deactivation (N-acetylation) of arylamine carcinogens via polymorphic expression of NAT2. These findings lend mechanistic support for human epidemiological studies suggesting associations between both rapid and slow acetylator phenotype and cancers related to arylamine exposure.

Acetylation↗

PubMed1993

Effect of myocardial ischemia on stimulation-evoked noradrenaline release. Modulated neurotransmission in rat, guinea pig, and human cardiac tissue.

The effect of myocardial ischemia and its major metabolic changes, such as anoxia, acidosis, and hyperkalemia, on exocytotic noradrenaline release was investigated in rat, guinea pig, and human cardiac tissue. Noradrenaline release was evoked by electrical field stimulation, and the effect of each experimental intervention on stimulation-evoked noradrenaline release (S2) was intraindividually compared with the release induced by a control stimulation (S1). In perfused hearts, 10 minutes of global ischemia caused a reduction of noradrenaline overflow in rat hearts (mean S2/S1, 0.31), whereas the overflow was increased in guinea pig hearts (S2/S1, 1.89). This species-dependent effect may be caused by quantitatively different responses to facilitating and suppressing factors of noradrenaline release in both species. Anoxia and substrate-free perfusion increased noradrenaline overflow in guinea pig hearts (S2/S1, 2.40) but had no significant effect in rat hearts (S2/S1, 0.75). Acidosis (pH 6.0) resulted in a suppression of noradrenaline release in rat hearts (S2/S1, 0.16), whereas it had only a minor inhibiting effect in guinea pig hearts (S2/S1, 0.67). Hyperkalemia had a comparable effect in both species (S2/S1 at 15 mmol/L K+, 1.17 in rat and 1.14 in guinea pig; and S2/S1 at 20 mmol/L K+, 0.64 in rat and 0.41 in guinea pig). To obtain results regarding the modulation of noradrenaline release in human myocardium, human atrial tissue was incubated, and the effect of anoxia, acidosis, and hyperkalemia on stimulation-evoked noradrenaline release was investigated.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidosis↗

PubMed1993

[Structure analysis of the mitochondrial tRNA(Cys) gene and the original region of light-strand replication from carp].

In this study, we have determined the nucleotide sequences of the cysteine tRNA gene and the original region of light-strand replication from carp (Cyprinus carpio L.) mitochondrion, which were further represented respectively in cloverleaf secondary structure and stem loop structure. By comparing the nucleotide sequences of 5 vertebrate tRNA(Cys) genes, it is found that carp mitochondrial tRNA(Cys) gene have many unusual structural features differing from those of cytoplasmic tRNA(Cys) gene. The carp mitochondrial original region of light-strand replication consists of 36 bases which include 11 base pairs in its stem and 14 bases in its loop. By making a comparison between the nucleotide sequences of the carp original region of light-strand replication and those of other 10 vertebrates, it is further found that stem sequence of carp is very conservative while loop sequence is very variable. This result indicates that stem structure may play an important role in the replication of light strand.

Animals↗