Biomedical subjects

L Mei

Publications and source records attributed to L Mei.

At least 37 records · Page 2Linked to original sources

PubMed2000

Developmental myosin heavy chains in the adult human diaphragm: coexpression patterns and effect of COPD.

In preliminary experiments we noted developmental (i.e., embryonic and neonatal) myosin heavy chains (MHCs) in the diaphragms of patients with severe chronic obstructive pulmonary disease (COPD). We hypothesized that this finding represented new fiber formation secondary to injury associated with the mechanical stress of COPD or previously undescribed MHCs in the human diaphragm. To distinguish between these possibilities, we analyzed diaphragmatic biopsies obtained from 9 patients with severe COPD (forced expiratory volume in 1 s = 21 +/- 2% predicted, residual volume = 283 +/- 22% predicted) and 10 age-matched controls. First, using immunocytochemistry with specific monoclonal antibodies, we noted that control diaphragms had greater proportions of fibers expressing embryonic (50 +/- 2 vs. 28 +/- 3%, P < 0.0001) and neonatal (52 +/- 2 vs. 32 +/- 3%, P < 0.001) MHCs than COPD diaphragms. Second, SDS-PAGE demonstrated that these developmental MHCs represented only a very small fraction of the diaphragmatic MHC content. Third, the RT-PCR demonstrated mRNA coding for embryonic and neonatal MHCs in COPD and control diaphragms. Last, COPD and control diaphragms exhibited normal histology on light microscopy. We conclude that the presence of developmental MHC isoforms does not indicate new fiber formation in diaphragms of patients with severe COPD. Although these results represent the first systematic description of embryonic and neonatal MHCs in normal adult human diaphragms, their function remains to be elucidated.

Adult↗

PubMed2000

Conditioned immunosuppressive effect of cyclophosphamide on delayed-type hypersensitivity response and a preliminary analysis of its mechanism.

In the present study, camphor odor and intraperitoneal (i.p.) injection of cyclophosphamide (CY) were used as conditioned stimulus (CS) and unconditioned stimulus (US), respectively. In the unconditioned group, mice were exposed to camphor odor for 1 h followed by an i.p. injection of CY (75 mg/kg). On the next day, the above CS/US association trial session was repeated followed by smearing dinitrochlorobenzene (DNCB) on mouse abdominal skin for sensitizing the animal for delayed-type hypersensitivity (DTH) response. Five days after DNCB sensitization, mice were exposed to camphor odor (1 h), followed by an i.p. injection of CY, and then DNCB was smeared on the left ear of mice for the challenge of DTH response. Both the left/right ear weight ratio and the activity of leukocyte migration inhibitory factor (LMIF) were used as the index of DTH response, which was done 24 h after DNCB challenge. In the conditioned group, the treatment was the same as that in the unconditioned group, except that normal saline was injected on day 5 instead of CY. Furthermore, in order to analyze the mechanism of the conditioned response (CR), the mouse serum from the conditioned group (CR serum) was injected into normal mice 6 h prior to DNCB challenge. Results showed that in the conditioned group, left/right ear weight ratio and LMIF activity were statistically lower than that in the DTH group, and there was no difference between conditioned and unconditioned groups. Thus, an animal model of conditioned immunosuppressive response had been established. The results also showed that after CR serum was injected into normal mice, DTH response was also significantly suppressed. However, if CR serum was treated with dialysis (10,000 molecular weight cut-off), the suppressive effect of CR serum on DTH response disappeared. Taken together, the data suggested that a chemical compound(s) in serum, with a molecular weight less than 10,000, was important in mediating the conditioned immunosuppressive response. This may be a very important molecule(s) that could be very critical to our understanding of the interaction between the central nervous system and immune function.

Animals↗

PubMed2000

Predictive value of serum androstenedione basal levels on the choice of gonadotropin or laparoscopic ovarian electrocautery as ovulation induction in clomiphene citrate-resistant patients with polycystic ovary syndrome.

Therapeutic approaches to chronic anovulation from polycystic ovaries in clomiphene-resistant infertile patients are under debate. This study discusses evidence that supports the possible predictive value of serum basal level of androstenedione in the choice of the better therapy between laparoscopic ovarian electrocautery and ovulation induction. Lower androstenedione levels seem to be correlated with a better ovarian response after ovulation induction with gonadotropins, while high androstenedione levels are associated with a higher incidence of conception after laparoscopic ovarian electrocautery. Obesity does not seem to represent a hindrance to laparoscopic treatment.

Adult↗

PubMed2000

[Current findings on the endometrium and human reproduction].

Human endometrium is a very complex system that plays a critical role during implantation process. Several reports focused the attention on the adequate proliferative phase, particularly on mitotic and angiogenetic pathway. The growth factors and angiogenetic factors involved during the different phases of menstrual cycle are discussed and attention is drawn on the interaction between embryo and endometrium through metalloproteinases and integrins during implantation.

Endometrium↗

PubMed1999

Regulation of neuregulin-mediated acetylcholine receptor synthesis by protein tyrosine phosphatase SHP2.

Synapse-specific expression of the nicotinic acetylcholine receptor (AChR) is believed to be mediated by neuregulin, an epidermal growth factor-like trophic factor released by somatic motoneurons at the neuromuscular junction (NMJ). Neuregulin stimulates ErbB2, ErbB3, and ErbB4, members of the ErbB family of receptor tyrosine kinases. SHP2 is a cytoplasmic protein tyrosine phosphatase containing two Src homology 2 domains near its N terminus, and has been shown to be a positive mediator of mitogenic responses to various growth factors. We found that SHP2 interacted with ErbB2 and ErbB3 after neuregulin stimulation of muscle cells. Expression of SHP2 in C2C12 mouse muscle cells attenuated the neuregulin-induced expression of an AChR epsilon-promoter reporter gene, whereas a catalytically inactive SHP2 mutant or a mutant lacking the N-terminal Src homology 2 (SH2) domain enhanced reporter expression, suggesting that SHP2 negatively regulates the neuregulin signaling pathway. In fibroblast cells that express a mutant SHP2 with a targeted deletion of the N-terminal SH2 domain, neuregulin-mediated activation of the Ras/Raf/extracellular signal-regulated kinase cascade was enhanced. Furthermore, we found that SHP2 immunoreactivity colocalized with the staining of alpha-bungarotoxin, a marker of the NMJ. These results demonstrate a negative role of SHP2 in the neuregulin signal that leads to AChR gene expression at the NMJ.

Animals↗

PubMed1999

Essential roles of c-JUN and c-JUN N-terminal kinase (JNK) in neuregulin-increased expression of the acetylcholine receptor epsilon-subunit.

Neuregulin is a neural factor implicated in upregulation of acetylcholine receptor (AChR) synthesis at the neuromuscular junction. Previous studies have demonstrated that the extracellular signal-regulated kinase (ERK) subgroup of MAP kinases is required for neuregulin-induced AChR gene expression. We report here that the neuregulin-mediated increase in AChR epsilon-subunit mRNA was a delayed response in C2C12 muscle cells. Neuregulin induced expression of immediate early genes c-jun and c-fos, which followed and depended on the ERK activation. Treatment of muscle cells with cycloheximide to inhibit c-JUN synthesis at the protein level and suppression of c-JUN function by a dominant-negative mutant blocked neuregulin-induced expression of the epsilon-subunit gene, indicating an essential role of c-JUN in neuregulin signaling. Furthermore, neuregulin activated c-JUN N-terminal kinase (JNK) in C2C12 muscle cells. Blockade of JNK activation by overexpressing dominant-negative MKK4 inhibited epsilon-promoter activation. Moreover, overexpression of the JNK dominant-negative mutant inhibited neuregulin-mediated expression of the epsilon-transgene and endogenous epsilon-mRNA. Taken together, our results demonstrate important roles of c-JUN and JNK in neuregulin-mediated expression of the AChR epsilon-subunit gene and suggest that neuregulin activates multiple signaling cascades that converge to regulate AChR epsilon-subunit gene expression.

Animals↗

PubMed1999

ERK MAP kinase activation is required for acetylcholine receptor inducing activity-induced increase in all five acetylcholine receptor subunit mRNAs as well as synapse-specific expression of acetylcholine receptor epsilon-transgene.

The AChR is a pentamer of four different subunits in a stoichiometry of alpha2betagammadelta in embryonic and alpha2betaepsilondelta in adult animals. Transcription of AChR subunit genes is most active in synaptic nuclei in adult skeletal muscle cells, and is regulated by neural factors such as ARIA. We report here that ARIA up-regulated specifically the expression of all five AChR subunits in C2C12 cells. The mRNA level of erbB2, erbB3, rapsyn, MuSK, SHP-2 and beta-actin remained unchanged in response to ARIA stimulation in C2C12 cells. The ARIA-induced increase in AChR subunit expression in C2C12 cells was inhibited by the erbB kinase inhibitor tyrphostin AG1478 and the MEK inhibitor PD98059, but not by the PI3 kinase inhibitor wortmannin, suggesting an important role of the erbB protein tyrosine kinases and MAP kinase in the regulation of the expression of the five different AChR subunits. To determine the signaling pathways in vivo, we studied the expression of reporter genes driven by the epsilon-promoter in injected muscles. The in vivo expression of the epsilon-transgene was inhibited by co-expression of dominant negative mutants of key components in the MAP kinase pathway including ras, raf and MEK, but not the dominant negative mutant of PI3 kinase. These results suggest that ERK MAP kinase activation is required for ARIA-induced increase in all five AChR subunit mRNAs as well as synapse-specific expression of AChR epsilon-transgene.

Androstadienes↗

PubMed1999

Bioassay to assess the toxicity of bacillus thuringiensis to daikon leaf beetle (Coleoptera: chrysomelidae)

We developed a new method to rear daikon leaf beetles, Phaedon brassicae Baly (Coleoptera: Chrysomelidae), on a diet of Cruciferae leaves in a growth chamber. Eggs were stored at 4 degrees C for 30 days without significant loss of viability. A bioassay using artificial diet was developed to standardize the assessment of toxicity of a powdered crystal-spore preparation of Bacillus thuringiensis strain YBT-0618 to P. brassicae larvae. When the diet containing this powder preparation was stored at 4 degrees C for a period of 7 days, the coefficient of variation of the median lethal concentration (LC(50)) values in three replicates was 0.060. The reproducibility, or precision, of the bioassay results was optimal when, at each dilution, 30 neonates were exposed and incubated for 72 h at 25 degrees C, 65-75% RH, and a photoperiod of 12:12 (L:D). Copyright 1999 Academic Press.

Journal Article↗

PubMed1999

Differential signaling of glial cell line-derived neurothrophic factor and brain-derived neurotrophic factor in cultured ventral mesencephalic neurons.

In the ventral mesencephalon, two neurotrophic factors, brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor, have been shown previously to have similar effects on the survival of dopaminergic neurons. Here, we compared the signaling mechanisms for brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor, focusing on the mitogen-associated protein kinase and the transcription factor cyclic-AMP responsive element-binding protein. Double-staining experiments indicated that many neurons co-expressed the receptors for glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor, c-RET and TrkB, suggesting that they are responsive to both brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor. Although both brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor induced a rapid phosphorylation of mitogen-associated protein kinase and cyclic-AMP, responsive element-binding protein, there were significant differences in the kinetics and pharmacology of the phosphorylation. The phosphorylation of mitogen-associated protein kinase by glial cell line-derived neurotrophic factor was transient; within 2 h, the level of mitogen-associated protein kinase phosphorylation returned to baseline. In contrast, the effect of brain-derived neurotrophic factor was long lasting; the mitogen-associated protein kinase remained phosphorylated for up to 4 h after brain-derived neurotrophic factor treatment. PD098059, a specific inhibitor for mitogen-associated protein kinase kinase, completely blocked the glial cell line-derived neurotrophic factor signaling through mitogen-associated protein kinase, but had no effect on brain-derived neurotrophic factor-induced mitogen-associated protein kinase phosphorylation. Both brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor induced the phosphorylation of cyclic-AMP responsive element-binding protein in the nuclei of ventral mesencephalon neurons. However, PD098059 blocked the cyclic-AMP responsive element-binding protein phosphorylation induced by glial cell line-derived neurotrophic factor, but not that by brain-derived neurotrophic factor. These results indicate that, although both brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor act on ventral mesencephalon neurons, the two factors have different signaling mechanisms, which may mediate their distinctive biological functions.

Animals↗

PubMed1999

Lipid oxidation in emulsions as affected by charge status of antioxidants and emulsion droplets.

The influence of charge status of both lipid emulsion droplets and phenolic antioxidants on lipid oxidation rates was evaluated using anionic sodium dodecyl sulfate (SDS) and nonionic polyoxyethylene 10 lauryl ether (Brij)-stabilized emulsion droplets and the structurally similar phenolic antioxidants gallamide, methyl gallate, and gallic acid. In nonionic, Brij-stabilized salmon oil emulsions at pH 7.0, gallyol derivatives (5 and 500 microM) inhibited lipid oxidation with methyl gallate > gallamide > gallic acid. In the Brij-stabilized salmon oil emulsions at pH 3.0, low concentrations of the galloyl derivatives were prooxidative or ineffective while high concentrations were antioxidative. In SDS-stabilized salmon oil emulsions, oxidation rates were faster and the galloyl derivatives were less effective compared to the Brij-stabilized emulsions. Differences in antioxidant activity were related to differences in the ability of the galloyl derivatives to partition into emulsion droplets and to increase the prooxidant activity of iron at low pH.

Animals↗

PubMed1999

Neuregulin-increased expression of acetylcholine receptor epsilon-subunit gene requires ErbB interaction with Shc.

Selective transcription of acetylcholine receptor (AChR) subunit genes by neuregulin is one of the mechanisms involved in the synaptic localization of AChRs to the neuromuscular junction. Neuregulin stimulates ErbB receptor tyrosine kinases and subsequently activates the Ras/ERK pathway, which is required for neuregulin-mediated induction of AChR subunit genes in muscle cells and synapse-specific expression in vivo. Here we investigated the neuregulin transduction mechanism that leads to ERK activation after ErbB receptor tyrosine phosphorylation. Neuregulin increases the association of the adaptor proteins Grb2 and Shc with both ErbB2 and ErbB3 in C2C12 muscle cells. Dephosphorylation of the tyrosine-phosphorylated ErbB proteins abolished their association with both Grb2 and Shc, suggesting a tyrosine phosphorylation-dependent interaction. The interaction of Shc with the ErbB receptors is mediated by Shc's phosphotyrosine-binding domain. In addition, neuregulin increased tyrosine phosphorylation of Shc. Mutagenesis approaches demonstrated that tyrosine phosphorylation of Shc is required for neuregulin induction of AChR subunit gene expression. Taken together, these data indicate that the interaction of ErbB receptors with Grb2 alone is insufficient for neuregulin-activated transcription, but that ErbB receptor signaling via Shc is necessary and important.

Adaptor Proteins, Signal Transducing↗

PubMed1999

[Impact of counseling on the sexual habits and reproductive decisions in HIV-1-positive subjects].

BACKGROUND: To assess the results of counselling on sexual behavior and reproductive choices of couples discordant for HIV-1, in South-Eastern Italy. SETTING: University Hospital, Apulia region, South-Eastern Italy. METHODS: In the period March 1985-December 1995, one hundred and forty-four HIV-1 discordant couples were enrolled. They were followed up for a median period of 39 months (range 12-60 months). Behavioural counselling was performed at each visit of the infected case and the sexual partner was periodically tested for HIV-1 antibodies. RESULTS: Sixty percent of couples pursued in unprotected sex intercourse, 30 new infections being diagnosed during the study period (cumulative incidence rate = 21%). In addition, 49 pregnancies in 38 women were recorded. Termination was very seldom the choice of pregnant women. CONCLUSIONS: There is a clear indication for a failure in the counselling process. A change in population characteristics is to be pointed out as the main factor of the results. More appropriate counselling modalities need to be introduced for the different targets of sexual behaviour of our population.

Adult↗

PubMed1999

[The correlation between idiopathic leukocytospermia, embryo quality and outcome in the FIVET and ICSI procedures].

BACKGROUND: An adverse effect of leukocytospermia in seminal fluid on motility and fertilizing power of spermatozoa has been described. This detrimental effect could be mediated by radical oxygen species (ROS). Recently, a direct effect on nuclear DNA of sperm induced by ROS has been described, although the chance of fertilization did not seem altered during ICSI procedure. Aim of this prospective case-control study was to compare the outcome of results in term of fertilization rate and embryo quality in patients with and without idiopathic leukocytospermia during IVF and ICSI cycles. METHODS: Seventy-two patients selected for a program of IVF and ICSI were admitted in the study. Fourty-two patients underwent IVF procedure, 14 with idiopathic leukocytospermia and 28 without, and thirty underwent ICSI procedure, 16 with leukocytospermia and 14 without leukocytospermia. RESULTS: Statistical significant differences on cleavage rate of embryos between leukocytospermia and control group in IVF cycles were observed. In ICSI procedure a low fertilization, cleavage rate and percentage of good embyros in the presence of leukocytospermia were evidenced. CONCLUSIONS: The presence of a significant number of leukocytes in semen, even in idiopathic condition, could affect the results of IVF and ICSI procedure. An adverse effect of lipoperoxidation process of plasma membrane and damage of nuclear chromatin of sperm, as result of leukocyte contamination could be hypothesized and future studies needed in order to verify the role of ROS on sperm functions.

Adult↗

PubMed1999

Cultivation of encapsulated yeast cells in NaCS-PDMDAAC polyelectrolyte complexes.

The cultivation of encapsulated S. cerevisiate and C. utilis in NaCS-PDMDAAC Polyelectrolyte Complexes was studied. The results showed that these two kinds of encapsulated microorganisms showed the same growing properties as in their free cell cultures, and thus NaCS-PDMDAAC microcapsules were suitable for the encapsulation of biological substances. The encapsulated S. cerevisiate cells were fermented sequentially for 16 batches. The highest cell density in the capsules reached 2.64 x 10(10) cells/mL and ethanol concentration reached 47.0 g/L. The encapsulated C. utilis produced the same amount of GSH as the free cell culture.

Ammonium Chloride↗

PubMed1998

Caspase-3 cleaves the expanded androgen receptor protein of spinal and bulbar muscular atrophy in a polyglutamine repeat length-dependent manner.

Spinal and bulbar muscular atrophy (SBMA) is one of a group of human inherited neurodegenerative diseases caused by polyglutamine expansion. There is increasing evidence that generation of truncated proteins containing an expanded polyglutamine tract may be an important step in the pathogenesis of these disorders. We have previously demonstrated that the SBMA gene product, the androgen receptor (AR) protein, is toxic when truncated. We now report that in vitro translated full-length AR proteins containing different sized polyglutamine repeats (24, 65 and 97 repeats, respectively) are specifically cleaved by recombinant caspase-3, liberating a polyglutamine containing fragment, and that the susceptibility to cleavage is polyglutamine repeat length-dependent. These findings suggest that AR protein is one of the "death substrates" cleaved by caspase-3 and that caspase-3 might be involved in the pathogenesis of SBMA.

Bulbar Palsy, Progressive↗

PubMed1998

Reversible regulation of SHP-1 tyrosine phosphatase activity by oxidation.

Increasing evidence indicates that redox regulation is an important signaling mechanism. Protein tyrosine phosphatases (PTPases) are sensitive to oxidative inactivation and are potential targets of redox regulation. In this study, we analyzed the reversibility of oxidative inactivation of the PTPase SHP-1, which negatively regulates protein tyrosine kinase signaling. H2O2 inactivated SHP-1 in vitro. Incubation of the H2O2-inactivated SHP-1 with dithiothreitol recovered 44-99% of the PTPase activity, depending on the H2O2 concentrations used to inactivate SHP-1. Glutathione and N-acetylcysteine also reactivated H2O2-treated SHP-1. Stimulation of SHP-1-transfected HeLa cells with H2O2 rapidly decreased SHP-1 activity, which was completely reversed within 15 min. Thus, oxidative inactivation of SHP-1 is a reversible process.

Acetylcysteine↗

PubMed1998

Regulation by ARIA/neuregulin of acetylcholine receptor gene transcription at the neuromuscular junction.

Transcription of genes encoding nicotinic acetylcholine receptor (AChR) subunits (alpha, beta, gamma or epsilon, and delta) is highest in nuclei localized to the synaptic region of the muscle which contributes to maintain a high density of AChRs at the postjunctional membrane. ARIA (AChR inducing activity) is believed to be the trophic factor utilized by motor neurons to stimulate AChR synthesis in the subsynaptic area. ARIA stimulates tyrosine phosphorylation of the erbB proteins and activates the MAP kinase pathway which is required for the ARIA-mediated induction of AChR genes.

Animals↗

PubMed1998

Cloning and characterization of glial cell line-derived neurotrophic factor receptor-B: a novel receptor for members of glial cell line-derived neurotrophic factor family of neurotrophic factors.

Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor with diverse biological functions. Signal transduction of GDNF is mediated by binding to a glycosyl-phosphatidylinositol (GPI)-linked receptor GDNFR-alpha and activation of c-RET tyrosine kinase. The recent discovery of a new GDNF homolog neurturin raises the possibility that multiple receptors exist for the members in the GDNF family. Here we report isolation of the gene encoding a new receptor called GDNFR-beta. Sequence analysis indicated that GDNFR-beta is also a GPI-linked protein, with 47% identity to GDNFR-alpha. The GDNFR-beta transcript was preferentially expressed in the brain, spleen and lung, but moderate levels of GDNFR-beta mRNA were also found in kidney and the entire gastrointestinal track. In situ hybridization revealed high expression levels in the entorhinal cortex and olfactory bulb, followed by cortex, septum, inferior and superior colliculus, and zona inserta. A laminar pattern of expression was detected in layer III of the cortex. Treatment with GDNF of PC12 cells transfected with the GDNFR-beta gene activated mitogen-activated protein kinase (MAPK) and elicited neurite outgrowth. GDNFR-alpha and GDNFR-beta together form a new family of GPI-linked receptors for GDNF-like molecules.

Amino Acid Sequence↗