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Biomedical subjects

M Li

Publications and source records attributed to M Li.

At least 1,171 records · Page 65Linked to original sources
PubMed1979

Assembly of the mitochondrial membrane system: sequences of yeast mitochondrial valine and an unusual threonine tRNA gene.

The mitochondrial DNA segments of two independently isolated rho- clones of S. cerevisiae carrying a genetic marker for a threonine tRNA have been characterized by restriction endonuclease analysis and DNA sequencing. The DNA sequences of the two segments have been used to deduce the primary and secondary structures of the tRNA. The threonine tRNA is unusual in having a leucine anticodon (3'-GAU-5'). Despite the anomalous anticodon, the tRNA is proposed to function in mitochondrial protein synthesis. One of the rho- clones contains an additional coding sequence that has been identified as a valine tRNA genes have been located on the wild-type physical map and determined to be transcribed from two different strands.

Base Sequence↗
PubMed1979

Formation of carcinogenic N-nitroso compounds in corn-bread inoculated with fungi.

DMNA, DENA and MBNA are formed in corn-bread which has been inoculated with the most common species of fungi found in foodstuffs of Lin Xian County, Henan Province, such as F. moniliforme, A. flavus and others, and then, added with small amount of NaNO2 after a few days of incubation. These carcinogenic N-nitroso compounds can induce cancer of the liver or/and esophagus in experimental animals. Results of the present study show the capability of some fungi to produce chemical carcinogens as well as mycotoxins in contaminated food, and thus, open a new field of research in cancer etiology.

Aspergillus flavus↗
PubMed1977

The effect of alpha-1-acetylmethadol hydrochloride on rat hepatic aryl hydrocarbon hydroxylase and epoxide hydrase.

Male and female Wistar rats were administered alpha-1-acetylmethadol via their drinking water for one to two weeks. Hepatic aryl hydrocarbon hydroxylase, cytochrome P-450 and epoxide hydrase activities were measured after various doses of this drug. In female rats, a significant increase in aryl hydrocarbon hydroxylase and cytochrome P-450 occurred at doses as low as 4.7 mg/Kg/day. However, no change in epoxide hydrase activity occurred. In male rats, a significant increase in epoxide hydrase activity occurred at all doses tested. From these results, it is concluded that alpha-1-acetylmethadol induces a number of hepatic drug metabolizing enzyme systems.

Animals↗
PubMedDate not supplied

Correlation between CSWS and aphasia in Landau-Kleffner syndrome: a study of three cases.

We report three typical cases of Landau-Kleffner syndrome with varied courses. The very frequent discharges in sleep EEGs, often showing the patterns of CSWS (continuous spike-waves during slow-wave sleep), either typical (spike-wave complex occupying over 85% of slow-wave sleep duration) or atypical (spike-waves occupying less than 85% of slow-wave sleep), were presented in all our cases. The CSWS seems correlated with aphasia in our cases. Since the disappearance of CSWS might be indicative of a lagged improvement in aphasia, we suggest that sufficiently long-term treatment with anticonvulsants and/or corticosteroids is worthwhile, if the EEG is improved significantly by this treatment.

Anticonvulsants↗
PubMedDate not supplied

Radiograph ordering: agreement between the triage nurse and the physician in a pediatric emergency department.

We hypothesized that the triage nurse in a busy pediatric emergency department (ED) could accurately order radiographs, ultimately reducing patient waiting time. Protocols utilized to reduce patient waiting time are of importance in busy emergency departments. All patients registering at the ED of the Children's Hospital in a one-week period were entered into the study. The triage nurse documented whether they would send the patient for a radiograph, if allowed to, and were asked to designate a specific radiograph. The radiographs that were actually ordered by the physicians were subsequently obtained from radiology records. Data were analyzed for agreement beyond chance (kappa), positive (PPV) and negative predictive values. The results showed excellent agreement for extremity radiographs and poor agreement for nonextremity radiographs.

Decision Making↗
PubMedDate not supplied

Prostaglandin E2 restores cancellous bone to immobilized limb and adds bone to overloaded limb in right hindlimb immobilization rats.

The purpose of this study was to determine whether prostaglandin E2 (PGE2) can restore cancellous bone mass and architecture to osteopenic, continuously immobilized (IM), proximal tibial metaphysis (PTM) in female rats. The right hindlimb of three and one-half-month-old Sprague-Dawley female rats were immobilized by right hindlimb immobilization (RHLI) in which the right hindlimb was underloaded and the contralateral left limb was overloaded during ambulation. After 4 or 12 weeks of RHLI, the rats were treated with 3 or 6 mg PGE2/kg/day and RHLI for 8 or 16 weeks. Bone histomorphometry was performed on microradiographs of PTM. Immobilization (IM) induced a transient cancellous bone loss and decreased trabecular thickness, number and node density, and increased free end density that established a new steady state after 4 weeks of IM. Three or 6 mg PGE2/kg/d for 8 weeks beginning at 4 or 12 weeks of IM completely restored cancellous bone mass (+127% to +188%) and structure to the age-related control levels in spite of continuous IM. Another 8 weeks of treatment maintained bone mass and architecture at these levels. No differences in cancellous bone mass and architecture were found between the overloaded PTM or RHLI rats and the age-related controls. However, 3 and 6 mg/kg/d of PGE2 treatment started at 4 or 12 weeks for 8 weeks significantly increased cancellous bone mass in the overloaded PTM (+45 to +74% of untreated controls), and another 8 weeks of treatment maintained bone mass at these levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMedDate not supplied

Greater bone formation induction occurred in aged than young cancellous bone sites.

We have determined the differences in the effects of continual prostaglandin E2 (PGE2) treatment in aged (non-growing) and young (growing) cancellous bone sites in 7-month-old Sprague-Dawley rats. The sites involved are the aged distal tibial metaphysis (DTM) with a closed epiphysis and the young proximal tibial metaphysis (PTM) with a slow growing, open epiphysis. The study involved rats treated with 0, 1, 3 or 6 mg PGE2/kg/d for 60, 120 and 180 days. Static and dynamic histomorphometry of percent trabecular area, and tissue-referent bone formation rate (BFR/TV) were determined in both DTM and PTM. In pretreatment controls, the secondary spongiosa of the two metaphyses contain the same amount of cancellous bone (11% in DTM vs. 13% in PTM), but markedly less bone formation in DTM (0.6%/y in DTM vs. 41.5%/y in PTM). After 60 days of 6 mg PGE2/kg/d treatment, %Tb.Ar was increased 607% in DTM and 199% in PTM, BFR/TV was increased to nearly 14 fold in DTM and only 5 fold in PTM. These results indicated the aged metaphysis of the DTM was much more responsive to PGE2 treatment than young, growing metaphysis of the PTM. The results of 120 and 180 days treatment did not significantly differ from 60 days treatment in both sites, indicating that the effect of continuous daily PGE2 treatment were in equilibrium after 60 days. We concluded that aged metaphysis was much more responsive to PGE2 treatment than young growing metaphysis.

Aging↗
PubMedDate not supplied

HNF1 is critical for the liver-specific function of HBV enhancer II.

Hepatitis B virus (HBV) is a hepatotropic virus and its gene expression is highly liver-specific. It has been reported that the function of enhancer II (ENII) and the core and the core promoter (Cp) of HBV has a hepatocyte preference. To understand the effects of liver-specific nuclear factors on ENII, in this report, hepatocyte nuclear factor 1 (HNF1) was investigated for its possible action on ENII function. It was found that HNF1 transactivates ENII/Cp in HeLa cells, and antisense HNF1 suppresses it in HepG2 cells. Deletion analysis revealed that the B element of ENII is the target region responsible for the regulation of HNF1. Sequence alignment suggested the presence of the potential HNF1 binding sites in the B element of ENII. The results of electrophoresis mobility shift assay indicated that the B2 region could specifically bind a GST-HNF1 fusion protein and could compete with binding of HNF1 to the consensus motif in the rat beta-fibrinogen promoter, suggesting that the major binding site of HNF1 is located in the B2 region. Our results demonstrate that HNF1 is one of the important regulatory factors for the liver-specific function of HBV and that it transregulates ENII activity via direct binding to B2.

Animals↗
PubMedDate not supplied

Synthesis, metal chelate stability studies, and enzyme digestion of a peptide-linked DOTA derivative and its corresponding radiolabeled immunoconjugates.

By directly coupling a tetrapeptide to DOTA through an amide bond, we synthesized a novel DOTA derivative, DOTA-glycylglycylglycyl-L-p-nitrophenylalanine amide. We converted this new precursor bifunctional chelating agent to DOTA-glycylglycylglycyl-L-p-isothiocyanatophenylalanine++ + and conjugated it to monoclonal antibody Lym-1. Serum stability studies show that the radiolabeled conjugates are kinetically inert under physiological conditions. The rates of loss of radiometals in human serum are 0.1 +/- 0.1% per day for InIII, 0.02 +/- 0.15% per day for YIII, and 0.3 +/- 0.2% per day for CuII labeled immunoconjugates. In the presence of the liver enzyme cathepsin B, an in vitro digestion of 114mIn-labeled conjugate yields a small fragment containing 114mIn. Characterization of the cleavage products shows that this liver enzyme hydrolyzes the peptide linkage before the phenylalanine residue, freeing the In-DOTA-triglycine complex from the conjugate. However, the liver enzyme cathepsin D does not cleave the linkage over the span of 7 days.

Amino Acid Sequence↗
PubMedDate not supplied

Labeling monoclonal antibodies with 90yttrium- and 111indium-DOTA chelates: a simple and efficient method.

Yttrium-90 and indium-111 have been attached to a monoclonal antibody with a bifunctional chelating agent (DOTA-peptide). Using the unique features of this DOTA-peptide and its complexes with trivalent yttrium and indium, the bifunctional chelating agent was prelabeled with either radiometal and then conjugated to chimeric monoclonal antibody L6. Both radiolabeling procedures and yield are suitable for the practical preparation of radiopharmaceuticals. Biodistribution studies in tumor-bearing mice showed that, e.g., on day 3 after intravenous injection of a 90Y immunoconjugate, liver uptake was 5.4 +/- 1.5% ID/g, bone uptake 2.0 +/- 0.5% ID/g, and tumor uptake 18.0 +/- 8.0% ID/g.

Animals↗
PubMedDate not supplied

Fluorogenic N-nitrosoamides: active-site labeling reagents for chymotrypsin-like proteases.

Two fluorogenic N-nitrosoamides, N-nitroso-N-((7-methoxycoumarin-4-yl)methyl)-N'-isobutyrylalaninamide (6a) and N-nitroso-N-((6-methoxyquinolin-2-yl)methyl)-N'-isobutyrylalani namide (6b), were synthesized. Both N-nitrosoamides inhibited alpha-chymotrypsin irreversibly; they show promise as labeling reagents for the active sites of chymotrypsin-like proteases.

Binding Sites↗
PubMedDate not supplied

Amine-reactive forms of a luminescent diethylenetriaminepentaacetic acid chelate of terbium and europium: attachment to DNA and energy transfer measurements.

An isothiocyanate form of a lanthanide chelate which is highly luminescent when bound to terbium or europium has been synthesized. The chelate consists of diethylenetriaminepentaacetic acid (DTPA) covalently joined to a chromophore, 7-amino-4-methyl-2(1H)-quinolinone (cs124), and to L-p-aminophenylalanine, in which the aromatic amine was further converted to an isothiocyanate group. Ethylenediamine was also used in place of aminophenylalanine, but the isothiocyanate formed from the aliphatic amine was significantly less reactive. Site-specific attachments to triglycine and to the 5' ends of amine-modified DNA oligomers have been made. In addition, as an alternative method of coupling to macromolecules, DTPA anhydride-cs124 can be used to react specifically with a 5' amine group on base-deprotected synthetic DNA oligomers. Synthesis and purification is relatively straightforward in both cases, and luminescent properties are favorable for several applications, including as nonisotopic labels, as long-lifetime alternatives to fluorophores in imaging and diagnostics and particularly as donors in luminescence resonance energy transfer. Energy transfer measurements are consistent with previously reported measurements using different attachment mechanisms.

Amines↗