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M Lu

Publications and source records attributed to M Lu.

At least 271 records · Page 15Linked to original sources
PubMed1995

[A study on two gut hormones in breast milk].

OBJECTIVE: To determine if motilin and gastrin are present in breast milk and to measure their concentrations in human milk and cow milk. METHODS: The concentration of motilin was measured in 17 samples of human colostrum, 18 samples of human mature milk, 8 samples of cow colostrum and 20 samples of cow mature milk by radioimmunoassay. The concentration of gastrin in human milk was also determined by radioimmunoassay. RESULTS: Motilin concentration in human colostrum was the highest (416.34 +/- 183.95ng/L), being higher than that in human mature milk (272.91 +/- 148.73ng/L, that in cow colostrum (229.51 +/- 63.68ng/L) and that in cow mature milk (35.46 +/- 16.94ng/L). Evidently the difference in motilin concentration was very significant between human milk and cow milk. The gastrin concentration in human colostrum was 17.20 +/- 11.98ng/L, being higher than that in human mature milk (5.62 +/- 2.33ng/L). CONCLUSION: Human milk, especially human colostrum, contains high concentrations of motilin and gastrin. Breast feeding, especially early breast feeding, may promote the maturation of the developing gut in neonates and infants.

Adult↗
PubMed1995

Partitioning of proteins in dextran/hydrophobically modified dextran aqueous two-phase systems.

Partitioning of proteins was studied in aqueous two-phase systems composed of the polymers dextran and hydrophobically modified dextran. The modified dextrans were benzoyl dextran with a degree of substitution of 0.17 and valeryl dextran with a degree of substitution of 0.20. Phase diagrams for the systems of dextran/benzoyl dextran and dextran/valeryl dextran were determined at room temperature. The proteins studied were beta-galactosidase, bovine serum albumin, beta-lactoglobulin, lysozyme, myoglobin and cytochrome C. The partition coefficients of a series of salts were determined in dextran/benzoyl dextran two-phase systems. The addition of salts had strong effect on the partitioning of proteins. This effect was related to protein net charge and the position of the ions in the Hofmeister series. Cross partitioning of bovine serum albumin was studied in a dextran/benzoyl dextran aqueous two-phase system.

Animals↗
PubMed1994

Bases defining an ammonium and magnesium ion-dependent tertiary structure within the large subunit ribosomal RNA.

A 58 nucleotide RNA derived from a highly conserved domain of the large subunit ribosomal RNA (Escherichia coli 1051 to 1108) has a set of tertiary interactions that is stabilized by NH4+ and Mg2+ in preference to other ions. We have mapped the nucleotides contributing to this structure by examining the thermal denaturation of 25 sequence variants. Where necessary compensatory mutations were made to preserve the phylogenetically conserved secondary structure. Substitutions of bases or base-pairs at eight positions specifically eliminate the ion-dependent tertiary structure without affecting the secondary structure stability; most of these positions are conserved among all large subunit RNA sequences. At two positions, substitutions of bases found in other organisms stabilize the E. coli tertiary structure by substantial amounts (delta G 37 degrees becomes more favorable by -1.8 to -4.5 kcal/mol). One of these variants disrupts a potential A.U base-pair within a helix, suggesting that the tertiary structure competes with alternative structures. The results show that this rRNA domain contains an extensive, highly conserved, and very stable set of tertiary interactions. The sequence in E. coli, and probably most other organisms, has not evolved to maximum stability. It is possible that natural selection has "tuned" the tertiary structure to an optimum stability, perhaps because the structure must open and close during the ribosome cycle.

Base Composition↗
PubMed1994

SeqA: a negative modulator of replication initiation in E. coli.

In E. coli, replication initiates at a genetically unique origin, oriC. Rapidly growing cells contain multiple oriC copies. Initiation occurs synchronously, once and only once per cell cycle at all origins present. Secondary initiations are prevented by a sequestration process that acts uniquely on newly replicated origins, which are marked because they are hemimethylated at GATC sites. We report the identification of a gene required for sequestration and demonstrate that this gene, seqA, also serves as a negative modulator of the primary initiation process. All previously identified in vivo initiation factors play positive roles. Thus, precise control of replication initiation may involve a balance between positive and negative elements. We suggest that SeqA might be a cooperativity factor, acting to make the replication initiation process dependent upon cooperative interactions among components.

Amino Acid Sequence↗
PubMed1994

High efficiency retroviral-mediated gene transduction into CD34+ cells purified from peripheral blood of breast cancer patients primed with chemotherapy and granulocyte-macrophage colony-stimulating factor.

The hematopoietic system has been one of the major targets for designing human gene therapy protocols. In the present system, we have transduced LNL6, one of the most commonly used retroviral vectors in gene therapy, into purified CD34+ cells from peripheral blood of patients primed with chemotherapy and granulocyte-macrophage colony-stimulating factor (GM-CSF). Purification of CD34+ cells was achieved by incubation with a murine anti-CD34 monoclonal antibody (9C5), and subsequently with paramagnetic microspheres (Dynal) coated with sheep anti-mouse IgG1 (Fc). The CD34+ cells were released from the beads by treatment with chymopapain. Flow cytometry analysis using the anti-CD34 antibody HPCA-2-FITC targeted at another epitope of CD34 showed that 78-97.5% of the cells thus purified were CD34+. After retroviral-mediated gene transfer, polymerase chain reaction (PCR) analysis revealed that 67-100% of the hematopoietic colonies contained the marker gene neo, indicating that CD34+ cells purified by immunomagnetic microsphere method from peripheral mononuclear cells primed with hematopoietic growth factors are highly susceptible to retroviral-mediated gene transfer. The expression of neo as determined by reverse transcription (RT)-PCR appeared to be unstable and not persistent. Taken together, our data suggest that LNL6 is a suitable vector for gene marking of hematopoietic progenitors but not for gene therapy protocols based on persistent gene expression.

Antigens, CD↗
PubMed1994

Molecular cloning and characterization of the pgm gene encoding phosphoglucomutase of Escherichia coli.

We report here the identification and characterization of pgm, a gene in Escherichia coli that encodes the enzyme phosphoglucomutase, specifically required for the catalysis of the interconversion of glucose 1-phosphate and glucose 6-phosphate. The predicted amino acid sequence of the pgm gene is highly conserved in E. coli, Acetobacter xylinum, Saccharomyces cerevisiae, rabbits, and humans. pgm deletion mutant strains are deficient in phosphoglucomutase activity.

Amino Acid Sequence↗
PubMed1994

Stanniocalcin stimulates phosphate reabsorption by flounder renal proximal tubule in primary culture.

The effects of several hormones on transepithelial Pi transport were determined in primary monolayer cultures of winter flounder proximal tubule epithelium in Ussing chambers. Salmon stanniocalcin (STC) had a dose-dependent stimulatory effect on net Pi reabsorption within the normal plasma hormone concentration range, 12.5-50 ng/ml (0.25-1.0 nM). Net Pi transport was significantly altered by STC (200 ng/ml) within 30 min and progressively increased from slight net secretion (0.26 +/- 0.744 nmol.cm-2.h-1) in untreated controls to net reabsorption (1.96 +/- 0.729 nmol.cm-2.h-1) after 3 h. The STC effect was mimicked by 10 microM forskolin, whereas 10 microM H-89, a highly specific protein kinase A inhibitor, significantly decreased both STC- and forskolin-induced Pi reabsorption. The release of adenosine 3',5'-cyclic monophosphate (cAMP) was increased more than twofold after a 1-h exposure to STC. This hormone had no effect on transepithelial Ca2+ transport. The results indicate that STC directly stimulates net renal Pi reabsorption by a cAMP-dependent pathway. In addition to STC, bovine parathyroid hormone (100 nM) and ovine prolactin (100 nM) significantly increased net Pi reabsorptive flux.

Absorption↗
PubMed1994

Renal transepithelial phosphate secretion: luminal membrane voltage and Ca2+ dependence.

The role of apical membrane electrical potential, the possibility of K+ channel involvement, and the role of extracellular Ca2+ in transepithelial P(i) secretion were examined in primary monolayer cultures of flounder renal proximal tubule cells in Ussing chambers. Exposure to 200 nM thapsigargin (TG) significantly increased net P(i) secretion. In TG-stimulated tissues, substitution of 100 mM KCl for 100 mM NaCl in the luminal medium depolarized the apical membrane potential from -64 +/- 2.8 to -26 +/- 3.9 mV and strongly inhibited net P(i) secretion. In 32P(i)-preloaded tissues, cell-to-lumen exit of 32P(i) was significantly decreased to approximately 50% of control by high luminal K+ while cell-to-peritubular bath movement was unchanged. Addition of BaCl2 (2 mM) or charybdotoxin (20 nM) to the luminal surface significantly reduced TG-stimulated net P(i) secretion. The elevation of bath Ca2+ from 2 to 5 mM significantly increased secretory flux and decreased reabsorptive flux. The effect of TG on net P(i) secretion was reduced by the Ca2+ channel blocker verapamil (VE, 100 microM) to 65% of control and by calmodulin antagonist W-7 (20 microM) to 35% of control but it was not blocked by the protein kinase inhibitor H-7 (100 microM). VE also significantly inhibited the P(i) secretion induced by acidification of the peritubular bathing medium. The data indicate that transepithelial P(i) secretion induced by TG is significantly influenced by apical membrane electrical polarity, which may be regulated in part by Ca(2+)-activated K+ channels.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1994

Incidence of renal failure in NIDDM. The Oklahoma Indian Diabetes Study.

The incidence of and risk factors for renal failure were determined in 912 Oklahoma Indians with non-insulin-dependent diabetes mellitus in a follow-up study conducted between 1987 and 1990. The incidence rate was 15.7/1,000 person-years after an average follow-up time of 10.2 years. Among those who had no qualitatively positive proteinuria at baseline, the incidence of renal failure was 10.3/1,000 person-years compared with 19.3- and 56.2/1,000 person-years, respectively, in those with slight and heavy proteinuria at baseline. Fasting plasma glucose (FPG) > or = 11.1 mM (200 mg/dl) increased the risk of renal failure to 2.9-fold (95% confidence interval [CI] = 1.9-4.6) higher than a level < 7.8 mM (140 mg/dl), and twofold (95% CI = 1.4-3.1) higher than a level between 7.8 (140 mg/dl) and 11.1 mM (200 mg/dl). The hypertensive patient had twice the incidence of renal failure than the normotensive subject (rate ratio = 2.1, 95% CI = 1.4-3.0). Patients with a lower blood pressure under antihypertensive medication had a lower incidence of renal failure than those whose hypertension remained uncontrolled with or without use of medication. Significant independent risk factors for renal failure, identified from Cox's proportional hazards model, were duration of diabetes, FPG, age, hypertension, and insulin use (P < 0.05). In patients without proteinuria at baseline, FPG and hypertension were significant predictors of renal failure as identified by multivariate analyses, whereas in patients who had proteinuria at baseline, insulin use was significant. Thus, hyperglycemic and hypertension control are suggested strongly for diabetic Oklahoma Indians as potential strategies to prevent the development of renal failure.

Adult↗
PubMed1994

[Modern TCM education in Shanghai].

Shanghai is a main base of the education of Chinese medicine (TCM) in modern time. A good many of famous TCM doctors, as well as TCM colleges or schools may be found in Shanghai. Many specialists and scholars of TCM gathered in Shanghai. The conditions of running TCM schools on Shanghai during 1840-1948 was introduced briefly, especially for the course and characteristic of the foundation of Shanghai Specialized School of TCM, the Chinese Medical College, the Shanghai Medicine College, the New China College of TCM and four private schools of TCM. In addition, the conditions of the correspondence schools of Shanghai in modern time were also introduced.

China↗
PubMed1994

The HOX11 homeobox-containing gene of human leukemia immortalizes murine hematopoietic precursors.

The t(10;14) chromosomal translocation of T-cell acute lymphoblastic leukemia joins the T-cell receptor delta gene to a region upstream of a diverged homeobox-containing gene called HOX11. To better understand the pathogenetic role of HOX11 in leukemogenesis, post 5-fluorouracil-treated murine bone marrow cells were infected with a replication-defective retrovirus bearing the gene. Constitutive expression of HOX11 in hematopoietic precursors yielded cell lines at high frequency consisting of immature cells belonging to the myeloid lineage. HOX11-transformed cell lines displayed a strict dependence on IL-3 for their survival and proliferation in culture and were not leukemogenic. The results support the hypothesis that the transforming capacity of HOX11 derives from its ability to alter the expression of genes regulating hematopoietic differentiation and that secondary mutations promoting cell survival or stimulating proliferation are required for progression to malignancy. The findings further suggest that the oncogenic activity of HOX11 might not be restricted to T-cell leukemias in humans.

Animals↗
PubMed1994

[Regulative role of hypocapnia on cerebral blood flow under hypoxia in rats].

The experiments were performed on urethane anesthetized and artificially ventilated SD rats using a gascous mixture of 11.9% O2 and 88.1% N2. The PaCO2 was regulated by changing the volume of ventilation. The items to be studies are: (1) The correlation between hypocapnia and CBF under hypoxia; (2) the value of PaCO2 that can keep CBF at the level of hypoxic adapters; (3) the CBF change during a 5 h hypoxia-hypocapnia and (4) the reactivity of isolated basilar artery strips on hypoxia-hypocapnia. The results showed: (1) There was a significant correlation between the degree of hypocapnia and CBF under hypoxia. The correlation curve was steeper than that of normoxia. (2) When the ventilation was controlled at 25.5% above normoxic control value and the PaCO2 was about 2/3 of normoxic level under hypoxia, the CBF is near to the level of normoxic control. (3) When the PaCO2 was controlled at 2/3 of normoxic level, the CBF could still keep at the level of normoxic control for 5 h. (4) The tension of artery strip was decrease under hypoxia-normocapnia but increased under hypoxia-hypocapnia. Artery stripes with or without endotheliocyte make no difference in their tension changes due to changes of O2-CO2 tension.

Animals↗
PubMed1994

[Measurement of rCBF by hydrogen gas clearance with lower H2 concentration in rats].

H2 clearance method in measuring regional cerebral blood flow (rCBF) on animals has been widely used in experimental research. It was found that 3% H2 which is lower than the lower concentration limit guarded against occurrence of explosion could be mixed with any concentration ratio of N2 to O2 without causing transient hypoxia as often found by inhaling 100% H2 and thus made clearance measurement more accurate and safe. Comparison studies between inhaling 100% H2 and 3% H2 as well as inhaling 3% H2 for 1-1.5 min and 3% H2 for 5 min were undertaken. Repeated measurements of 3% H2 clearance for 1.5 min further showed that clearance test using low H2 concentration for short term periods reflected better the rCBF of experimental animals.

Animals↗
PubMed1993

Specific ammonium ion requirement for functional ribosomal RNA tertiary structure.

In compactly folded RNAs, coordination or hydrogen bonding of cations in specific sites is a potentially important aspect of the tertiary structure. NH4+ specifically stabilizes the tertiary structure of a conserved, 58-nt fragment of the large subunit ribosomal RNA, as judged in two ways: a melting transition associated with tertiary interactions is sharpened and stabilized more effectively by NH4+ than by any alkali metal cation, and the affinity of the RNA fragment for ribosomal protein L11 or the antibiotic thiostrepton is approximately 10-fold stronger when measured in NH4+ than in Na+. The dependence of the melting temperature on NH4+ concentration shows that a single bound ion is responsible for these effects. The requirement of different ribosome functions for NH4+ suggests that other such sites exist in ribosomal RNAs.

Cations, Monovalent↗
PubMed1993

Structure of a parallel-stranded tetramer of the Oxytricha telomeric DNA sequence dT4G4.

We report here the determination of the solution structure of the single-copy tetramer of the sequence dT4G4, the unit repeat in telomeres of the ciliated protozoan Oxytricha, in the presence of potassium ions. This is accomplished by a combination of sequential assignments and distance determinations from 2D proton NMR with model building, based on conformational analysis of the structure using a full-matrix NOESY simulation and molecular dynamics. Each strand in this tetramer structure has an identical environment and conformation: a parallel-stranded, right-handed helix, with all nucleotides in the C2'-endo, anti configuration. The T flanking the G cluster stacks in a 4-fold symmetrical helical array, while the remaining T's become increasingly flexible and sample multiple stacked configurations.

Animals↗