Search PubMed⌕ Search

Biomedical subjects

Q Lu

Publications and source records attributed to Q Lu.

At least 235 records · Page 13Linked to original sources
PubMed1995

[Increased expression of platelet-derived growth factor beta receptor gene in hypoxic rat lungs].

The changes of platelet-derived growth factor (PDGF) beta receptor gene expression in hypoxic rats lungs was examined. Northern blots analysis revealed that normal lungs expression PDGF-beta receptor mRNA, with the longer of hypoxia the level of the mRNA increased rapidly. It reached a maximum at day 4, and was 1.34 fold as compared with the control (P < 0.05). Immunohistochemistry investigation showed that PDGF-beta receptor mainly distributed on smooth muscle cells and endothelial cells of middle and small arterial trees in rat lung. With hypoxia, the distribution of PDGF-beta receptors did not change, but it was more intense and reached a maximum at day 7, and was 2.40 fold as compared with the control (P < 0.05). The results suggested that increased expression of PDGF receptor gene may play a role in hypoxic pulmonary vascular remodeling.

Animals↗
PubMed1995

[The study of growth factors in human colostrum].

OBJECTIVE: To characterize and identify the growth factors in human colostrum and to evaluate the importance of breast-feeding. METHODS: The activity of growth factors in human colostrum was determined by technique of 3H-TdR incorporation into cultured NIH-3T3 cells. The acid growth factor (CAGF) and basic growth factor (CBGF) were purified from human colostrum by a sequence of chromatography. The study of stability and SDS-PAGE was applied to identify the CAGF and CBGF. RESULTS: 0.5% (v/v) of human colostrum and 3.0% (v/v) of bovine serum had the same activity in stimulating DNA synthesis. The specific activity of human colostrum in stimulating DNA synthesis was 20 times greater than that of bovine serum. The activity of growth factors in human colostrum was higher than that in human milk or bovine colostrum, and only human colostrum contained two different kinds of growth factors--CAGF and CBGF. CONCLUSIONS: Human colostrum contains two kinds of growth factors. CAGF is epidermal growth factor like (EGF-like) growth factor and the CBGF is platelet differentiation growth factor like (PDGF-like) growth factor. The effects of human colostrum on promoting baby growth and development is stronger than that of human milk and bovine colostrum.

3T3 Cells↗
PubMed1994

Selective nuclear transport of mu-calpain.

To study nuclear transport of purified calpains in an in vitro system, A431 cells were permeabilized with digitonin, and fluorescein-labeled calpains were introduced under conditions known to facilitate energy-dependent nuclear transport of proteins. Fluorescein-mu-calpain was transported into nuclei in an ATP-dependent fashion. The calpain-specific inhibitor protein, calpastatin, could not block mu-calpain translocation. Fluorescein-calpastatin and fluorescein-m-calpain were poorly transported at best. In the presence of rat liver cytosolic factors, accumulation of nuclear mu-calpain was maximum at approximately 1 microM Ca2+, and no transport was observed at 0.3 microM Ca2+. Rat erythrocyte and HeLa cell extracts supported transport in the absence of Ca2+.

Amino Acid Sequence↗
PubMed1994

The presence but not the sequence of the N-terminal peptide in cardiac TnC is important for function.

The most diverged region of the primary amino acid sequence between cardiac (cTnC) and fast skeletal troponin C is the N-terminal ten amino acids. We report here that major changes in the primary sequence of this region in cTnC had a minimal effect on the ability of the mutant proteins to recover maximal activity in TnC-extracted cardiac and fast skeletal muscle myofibrils. However, deletion of the N-terminal nine amino acids resulted in a 60% decrease in maximal Ca(2+)-dependent ATPase activity with only a small change in the pCa50 of activation. Deletion of the N-terminal peptide did not appear to appreciably affect the Ca(2+)-binding properties of cTnC, but it did alter the interaction with hydrophobic fluorescent probes. Thus, the presence but not the sequence, of the N-terminal extension is important for the maximal activity of cTnC. The N-terminal helix may function in a relatively non-specific manner to prevent unfavorable interactions between domains in cTnC or between cTnC and other troponin subunits.

Adenosine Triphosphatases↗
PubMed1994

Insensitivity of the present hsp26 chromatin structure to a TATA box mutation in Drosophila.

The role of the TATA element in establishing the chromatin structure and inducible transcription of the Drosophila melanogaster hsp26 gene has been analyzed. An hsp26/lacZ fusion gene with a mutant promoter, in which the TATA box sequence TATAAA was changed to CCCAAA, was introduced into Drosophila by P-element transformation. The mutation had little effect on formation of the preset chromatin structure observed prior to induction. However, the mutation dramatically reduced transcription levels following heat shock. Northern analysis indicated that weak, inducible expression of the mutant promoter occurred within the same period of heat shock as for the normal promoter, suggesting that TFIID was associated with the mutant promoter prior to heat shock. Biochemical analysis showed that the mutant promoter still bound TFIID in vitro, but with 3-5-fold less affinity than the normal promoter. DNase I footprinting revealed that the conformation of the TFIID-DNA complex differed significantly from that of the normal promoter. These results indicate that alterations in the conformation or the stability of the TFIID-DNA complex drastically reduce the level of induction, but do not dramatically affect chromatin structure formation. Formation of the requisite chromatin structure is either independent of, or highly tolerant of, changes in the TFIID-DNA complex.

Animals↗
PubMed1994

Abnormal phosphorylation of tau proteins associated with bovine brain microtubules: activation by excess ATP and tyrosine dephosphorylation.

Phosphorylation of tau protein has been suggested as a major mechanism regulating its functions. In assembled brain microtubules, tau is phosphorylated, but additional phosphorylation can be induced in vitro. Supply of excess ATP alone was sufficient to reduce migration of tau on SDS gels, diminish Tau-1 immunostaining, and induce the expression of epitopes recognized by the PHF-1 antibody, suggesting that Alzheimer-type phosphorylation may have occurred. Okadaic acid had no further effect. However, treatment with tyrosine kinase inhibitors modifies the phosphorylation profiles of tau proteins. Most evidently, migration of the largest tau isoform was further retarded on SDS gels and PHF-1 immunostaining was enhanced. The profound effect of tyrosine kinase inhibitors on tau phosphorylation was also demonstrated in living cells following microinjection of cultured hippocampal neurons. Identification of proline-directed protein kinases and their regulatory factors associated with assembled microtubules indicated the presence of multiple phosphorylation pathways in microtubules. Our results are consistent with the hypothesis that sequential phosphorylation of tau proteins is at least partially mediated through tyrosine phosphorylation/dephosphorylation mechanisms.

Adenosine Triphosphate↗
PubMed1994

In vitro analysis of microtubule assembly of isotypically pure tubulin dimers. Intrinsic differences in the assembly properties of alpha beta II, alpha beta III, and alpha beta IV tubulin dimers in the absence of microtubule-associated proteins.

Microtubule assembly of different beta tubulin isotypes in the presence of 4 M glycerol and 6 mM magnesium ion demonstrates significantly different characteristics. alpha beta II and alpha beta IV assembled faster and to a greater extent than did unfractionated phosphocellulose-purified tubulin (PC-tubulin). Microtubule assembly from alpha beta III showed a distinctive delay in nucleation, proceeded at a slower rate than those of the other beta tubulin isotypes, and had the highest critical concentration. However, treatment of beta tubulin isotypes with subtilisin to remove the C-terminal domain of the tubulin dimer abolished these differences in microtubule assembly pattern and enhanced self-assembly. The kinetic analysis of microtubule elongation of different beta tubulin isotypes also showed significant differences. Elongation of alpha beta III from microtubule seeds had a lower apparent K alpha and a lower apparent Kd than did alpha beta II and alpha beta IV. The dynamic behaviors of different beta tubulin isotypes were qualitatively similar to each other and fit the dynamic instability model. However, microtubules formed from alpha beta III appeared to be less dynamic than microtubules formed from other beta tubulin isotypes. Our results suggest that the beta III isotype might have a different conformation than do the other beta tubulin isotypes. The distinctive nucleation and elongation behaviors of the alpha beta III dimers demonstrated in vitro may have a significant influence on microtubule functions in vivo.

Animals↗
PubMed1994

Architectural variations of inducible eukaryotic promoters: preset and remodeling chromatin structures.

The DNA in a eukaryotic nucleus is packaged into a nucleosome array, punctuated by variations in the regular pattern. The local chromatin structure of inducible genes appears to fall into two categories: preset and remodeling. Preset genes are those in which the binding sites for trans-acting factors are accessible (i.e. in a non-nucleosomal, DNase I hypersensitive configuration) prior to activation. In response to the activation signal, positive factors bind to cis-acting regulatory elements and trigger transcription with no major alterations in the chromatin structure of the promoter region. In contrast, remodeling genes are those in which some of the required cis-acting regulatory elements are packaged into nucleosomes. The nucleosomes must be perturbed in response to an activation signal in order for the trans-acting factors to gain access to cis-acting elements; a chromatin remodeling process which forms DNase I hypersensitive sites must occur. In both cases, precise positioning of nucleosomes along the promoter region of a gene appears to be critical for appropriate regulation of expression.

Animals↗
PubMed1994

Nucleosome positioning and gene regulation.

Recent genetic and biochemical studies have revealed critical information concerning the role of nucleosomes in eukaryotic gene regulation. Nucleosomes package DNA into a dynamic chromatin structure, and by assuming defined positions in chromatin, influence gene regulation. Nucleosomes can serve as repressors, presumably by blocking access to regulatory elements; consequently, the positions of nucleosomes relative to the location of cis-acting elements are critical. Some genes have a chromatin structure that is "preset," ready for activation, while others require "remodeling" for activation. Nucleosome positioning may be determined by multiple factors, including histone-DNA interactions, boundaries defined by DNA structure or protein binding, and higher-order chromatin structure.

Base Sequence↗
PubMed1994

Hirsutoid papillomas of vulvae: absences of human papilloma virus (HPV) DNA by the polymerase chain reaction.

We have analyzed the specimens from 16 women with hirsutoid papillomas of the vulvae for the presence of HPV DNA using the polymerase chain reaction. The subjects' ages ranged from 27 to 43 years. In all cases, smooth or filiform papules were symmetrically located on the inner surface of both labia minora. Histologically, the lesions consist of acanthosis or papillomatosis without koilocytes and mitotic activity. Eight of 16 specimens were studied by transmission electron microscopy (TEM). No HPV granules were found in the nuclei of keratinocytes. HPV DNA could not be detected in all specimens. Positive controls were present in each assay. These results suggest that the papules of hirsutoid papillomas of the vulvae are unrelated to HPV. Chronic irritants and inflammation may play an important role in pathogenesis.

Adult↗
PubMed1994

Bombesin protects against bacterial translocation induced by three commercially available liquid enteral diets: a prospective, randomized, multigroup trial.

OBJECTIVE: To test the hypothesis that certain commercially available liquid diets would cause bacterial translocation and that this diet-induced translocation could be reduced with bombesin (an intestinal hormone stimulant). DESIGN: Prospective, multigroup trial in which animals fed each test diet were randomized to receive either bombesin or saline for 7 days. On day 7, the mice were killed and their organs were cultured for translocating bacteria, their cecal bacterial population concentrations were measured, and ileal and jejunal mucosal protein content was determined. SETTING: Small animal laboratory. SUBJECTS: Outbred ICR mice weighing 25 to 35 g. INTERVENTIONS: Mice received bombesin (10 micrograms/kg) or saline subcutaneously three times daily for 7 days before sacrifice. MEASUREMENTS AND MAIN RESULTS: The incidence of bacterial translocation to the mesenteric lymph node was significantly increased (p < .05) in mice fed Vivonex (53%), Criticare (67%), or Ensure (60%) compared with chow-fed controls (0%). All three liquid diets were associated with the development of cecal bacterial overgrowth and loss of jejunal and ileal mucosal protein content. Bombesin reduced the incidence of bacterial translocation and loss of mucosal protein content in all three liquid diet groups (p < .05), but did not prevent diet-induced cecal bacterial overgrowth. CONCLUSIONS: Three different liquid diets induced bacterial translocation to the mesenteric lymph node. Since bombesin was effective in reducing bacterial translocation, it appears that bacterial translocation induced by these liquid diets can be modulated hormonally.

Animals↗
PubMed1994

Characterization of the autophosphorylation of Era, an essential Escherichia coli GTPase.

Era is an essential protein in Escherichia coli which binds both GTP and GDP and has an intrinsic GTPase activity. Studies on the role of GTP/GDP binding and GTPase activity in an attempt to understand its function lead to the observation that Era is autophosphorylated. The autophosphorylation reaction is specific for GTP and cannot use ATP as a phosphoryl group donor. The reaction velocity is of first order with respect to protein concentration, suggesting an intramolecular mechanism. Autophosphorylation occurs at serine and threonine residues. The major phosphorylated tryptic peptide isolated after autophosphorylation has been identified as ISITSR, from residue 33 to 38. The peptide contains the site of phosphorylation and two potential sites for serine and threonine phosphorylation. Subsequently, both the threonine residue at position 36 and the serine residue at position 37 were altered to alanine. The double mutant Era, but not individual single mutants, was unable to functionally complement the growth of an E. coli strain which cannot produce wild-type Era protein at high temperature. This suggests that either threonine 36 or serine 37 has to exist for the function of Era in vivo. In vivo phosphorylation of Era was also examined by two-dimensional gel electrophoresis. Era has been previously assigned two distinct positions having two different X-Y co-ordinates: one of the spots (H032.0) was identified as phosphorylated Era, indicating that a substantial portion of Era in the cell is indeed phosphorylated. Therefore, Era autophosphorylation is likely to play an important physiological role in the cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Fusion with E2A converts the Pbx1 homeodomain protein into a constitutive transcriptional activator in human leukemias carrying the t(1;19) translocation.

E2A-PBX1 is a chimeric gene formed by the t(1;19)(q23;p13.3) chromosomal translocation of pediatric pre-B-cell leukemia. The E2A-Pbx1 fusion protein contains sequences encoding the transactivation domain of E2A joined to a majority of the Pbx1 protein, which contains a novel homeodomain. Earlier, we found that expression of E2A-Pbx1 causes malignant transformation of NIH 3T3 fibroblasts and induces myeloid leukemia in mice. Here we demonstrate that the homeodomains encoded by PBX1, as well as by the highly related PBX2 and PBX3 genes, bind the DNA sequence ATCAATCAA. E2A-Pbx1 strongly activates transcription in vivo through this motif, while Pbx1 does not. This finding suggests that E2A-Pbx1 transforms cells by constitutively activating transcription of genes regulated by Pbx1 or by other members of the Pbx protein family.

Adenovirus E2 Proteins↗
PubMed1994

Bacterial translocation is bacterial species dependent: results using the human Caco-2 intestinal cell line.

BACKGROUND: Because of in vivo limitations, the mechanisms underlying the process of bacterial translocation are poorly understood. Thus, an in vitro model system to study the translocation process was developed. METHODS: Transformed human colonic carcinoma (Caco-2) intestinal cells were grown as a polarized monolayer on semi-permeable membranes contained in the upper compartment of a two-compartment system. Once the Caco-2 monolayer had reached confluence, the ability of six different species of bacteria to translocate across the monolayer was tested using a dose-response curve of bacteria (10(2), 10(4), or 10(6)) organisms. RESULTS: At inocula of 10(4) or 10(6) but not 10(2) organisms, bacteria crossed the monolayer. Bacterial passage across the monolayer was bacterial species specific, with gram-negative enterics being the best, gram-positive aerobes being intermediate translocators, and strict anaerobes being the poorest translocators. CONCLUSION: The results of this study indicate that bacteria translocate across the Caco-2 monolayer in a dose-dependent and species-related fashion and support the use of this in vitro epithelial cell culture system as a model for studying bacterial transport.

Bacterial Physiological Phenomena↗
PubMed1993

Nerve growth factor synthesis by mouse submandibular gland cells in culture.

Mouse submandibular gland (SMG) cells in culture rarely retain functional properties of SMG cells in vivo. We demonstrate that both primary SMG cells and the mouse SMG cell line SCA-9 secrete biologically active nerve growth factor (NGF). However, primary cells secrete 40-fold more NGF than SCA-9 cells, demonstrating that SCA-9 cells cannot substitute for primary SMG cells for the study of SMG NGF in vitro.

Animals↗
PubMed1993

p44mpk MAP kinase induces Alzheimer type alterations in tau function and in primary hippocampal neurons.

Abnormally phosphorylated tau protein is a major component of the cytoskeletal pathology of Alzheimer's disease (AD) found in the neurofibrillary tangle (NFT) and neuritic plaque (NP). Identification of the kinase responsible for this phosphorylation has been difficult. In the test tube, several proline-directed kinases, particularly mitogen-activated protein (MAP) and cdc2 kinase, phosphorylate tau on sites that appear to mimic the abnormally phosphorylated sites in AD. Important unanswered issues include: 1) whether this phosphorylation event occurs in the tightly regulated environment of a living cell; 2) whether this phosphorylation of tau affects its functional properties; and 3) what is the subcellular relationship of proline-directed kinases and tau. We show here that tau can be phosphorylated in cultured hippocampal neurons by the MAP kinase p44mpk, and phosphorylation of tau compromises its functional ability to assemble microtubules. We show further that MAP kinase copurifies with microtubule fractions where it is tyrosine phosphorylated and presumably active. These studies address and raise several important issues regarding the regulation of tau phosphorylation in normal and AD brain.

Alzheimer Disease↗
PubMed1993

Proline-directed kinase systems in Alzheimer's disease pathology.

Immunohistochemical analysis was used to assess the distribution of the proline-directed kinase, cdc2, in Alzheimer's disease (AD) pathology. A robust signal was most prominent in the neurofibrillary tangle (NFT) of affected neurons that also contained abnormally phosphorylated tau protein. Biochemical analysis identified a pool of cdc2 in bovine brain microtubules that contain normal tau. These results strongly support the hypothesis that cdc2 is involved in the abnormal phosphorylation of tau in AD pathology and they raise important issues regarding regulation of tau phosphorylation in normal and diseased neurons.

Aged↗