Biomedical subjects

Q Xie

Publications and source records attributed to Q Xie.

At least 91 records · Page 5Linked to original sources

PubMed1998

The maize retinoblastoma protein homologue ZmRb-1 is regulated during leaf development and displays conserved interactions with G1/S regulators and plant cyclin D (CycD) proteins.

Recent discoveries of plant retinoblastoma (Rb) protein homologues and D-type cyclins suggest that control of the onset of cell division in plants may have stronger parallels with mammalian G1/S controls than with yeasts. In mammals, the Rb protein interacts specifically with D-type cyclins and regulates cell proliferation by binding and inhibiting E2F transcription factors. However, the developmental role of Rb in plants and its potential interaction with cell cycle regulators is unknown. We show that the maize Rb homologue ZmRb-1 is temporally and spatially regulated during maize leaf development. ZmRb-1 is highly expressed in differentiating cells, but almost undetectable in proliferating cells. In vitro, both ZmRb-1 and human Rb bind all classes of plant D-type cyclins with the involvement of a conserved N-terminal Leu-x-Cys-x-Glu (LxCxE) Rb-interaction motif. This binding is strongly reduced by mutation of the conserved Cys-470 of ZmRb-1. ZmRb-1 binds human and Drosophila E2F, and inhibits transcriptional activation of human E2F. We also show that ZmRb-1 is a good in vitro substrate for all human G1/S protein kinases. The functional conservation of proteins that control the G1/S transition in mammals and plants points to the existence of plant E2F homologues. We conclude that evolution of Rb and cyclin D proteins occurred after separation of the fungi from the higher eukaryotic lineage, but preceded the divergence of plant and animal kingdoms.

Arabidopsis↗

PubMed1998

Essential pathogenic role for endogenous interferon-gamma (IFN-gamma) during disease onset phase of murine experimental autoimmune orchitis. I. In vivo studies.

We previously found that immunization of CH3/He male mice with syngeneic testicular germ cells (TGC) without the aid of any adjuvants was sufficient to induce DTH to TGC and experimental autoimmune orchitis (EAO). To evaluate the role of endogenous IFN-gamma in this model, C3H/He mice immunized subcutaneously with TGC on days 0 and 14 received a single injection of anti-murine IFN-gamma MoAb on day 15, 20 or 25. On day 45, DTH to TGC was tested, testis specimens were collected for histological examination, and blood samples collected for IFN-gamma measurement. The results showed that whilst MoAb treatment on day 15 or 25 did not influence DTH responses, EAO development, and appearance of IFN-gamma in the circulation, treatment on day 20 significantly suppressed all of them. Thus, a single injection with anti-IFN-gamma MoAb may successfully down-regulate testicular autoimmunity, provided that the treatment is given at an optimal time point during disease development.

Animals↗

PubMed1998

Effects of age on the posttranscriptional regulation of CCAAT/enhancer binding protein alpha and CCAAT/enhancer binding protein beta isoform synthesis in control and LPS-treated livers.

The CCAAT/enhancer binding protein alpha (C/EBPalpha) and CCAAT/enhancer binding protein beta (C/EBPbeta) mRNAs are templates for the differential translation of several isoforms. Immunoblotting detects C/EBPalphas with molecular masses of 42, 38, 30, and 20 kDa and C/EBPbetas of 35, 20, and approximately 8.5 kDa. The DNA-binding activities and pool levels of p42(C/EBPalpha) and p30(C/EBPalpha) in control nuclear extracts decrease significantly whereas the binding activity and protein levels of the 20-kDa isoforms increase dramatically with LPS treatment. Our studies suggest that the LPS response involves alternative translational initiation at specific in-frame AUGs, producing specific C/EBPalpha and C/EBPbeta isoform patterns. We propose that alternative translational initiation occurs by a leaky ribosomal scanning mechanism. We find that nuclear extracts from normal aged mouse livers have decreased p42(C/EBPalpha) levels and binding activity, whereas those of p20(C/EBPalpha) and p20(C/EBPbeta) are increased. However, translation of 42-kDa C/EBPalpha is not down-regulated on polysomes, suggesting that aging may affect its nuclear translocation. Furthermore, recovery of the C/EBPalpha- and C/EBPbeta-binding activities and pool levels from an LPS challenge is delayed significantly in aged mouse livers. Thus, aged livers have altered steady-state levels of C/EBPalpha and C/EBPbeta isoforms. This result suggests that normal aging liver exhibits characteristics of chronic stress and a severe inability to recover from an inflammatory challenge.

Aging↗

PubMed1998

Postnatal development of Leydig cells in the opossum (Monodelphis domestica): an immunocytochemical and endocrinological study.

This study involved characterization of Leydig cells of the opossum Monodelphis domestica, functionally by immunocytochemical identification of the enzyme 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and by measurement of testosterone levels using RIA. Immunostaining for 3 beta-HSD was first detected in a few Leydig cells on Day 16, was increased by Day 24, reached a peak at 4 mo, and was present even in senescent (3 yr) animals. Plasma testosterone was first measurable (0.35 nM) at prepuberty (3.5 mo). Prior to that, plasma testosterone concentrations were uniformly below the level of detection (< 0.3 nM) in both sexes from Day 5 to 2.5 mo. By 4 mo (puberty), plasma testosterone levels in males had risen significantly to 1.53 +/- 0.35 nM, continuing to increase to 1.79 +/- 0.4 nM at 6 mo and peaking at 2.71 +/- 0.29 nM in the adult (1-2 yr). Ovarian testosterone concentrations were consistently lower than those in the testis, as were those of adrenals of both sexes. Thus the testis would appear to be the major source of androgen production throughout life in this species. Our immunocytochemical study suggests that in Monodelphis, puberty is reached at 4 mo, and this was further supported by a rise in circulating testosterone levels at this time.

3-Hydroxysteroid Dehydrogenases↗

PubMed1998

Distribution of F4/80-positive cells in developing ovaries in the mouse.

The mature ovary contains a large number of macrophages. In the present study, the distribution of macrophages in murine ovaries at various developmental stages was immunohistochemically studied using a monoclonal antibody against F4/80, a highly specific antigen of murine macrophages. The results showed that definite F4/80-positive stains were hardly detectable in ovaries on day 0 after birth. On day 7, a few F4/ 80-positive cells could be identified between the developing follicles. The positive stains were irregular in shape and showed little physical contact with the primordial or primary follicles. By days 14 and 21, when the theca cell layers of growing follicles were developing, the positive cells had extended or elongated to surround the cell layer. On day 28, besides the presence of elongating positive cells surrounding the growing follicles, irregularly shaped F4/80-positive cells became apparent in the interstitium between the growing follicles and also in the capsular tissues. Thereafter, positive cells with stellate appearance were detected in the corpora lutea, which first developed around 6 weeks of age. Although the positive cells were homogenously distributed in the corpora lutea in virgin adults, only a few sporadic positive cells were found there in pregnant mice. However, the positive cells infiltrated into the corpora lutea again in the postpartum period. These results show that ovarian macrophages exhibit dramatical changes in their distribution from neonatal to postpartum periods.

Animals↗

PubMed1998

Brainstem projections of sensory fibers of the lung: a horseradish peroxidase and c-fos-like immunohistochemical study in the rat.

The brainstem projections of sensory fibers of the lung were determined in the rat by using the horseradish peroxidase (HRP) and c-fos immunohistochemical methods. Wheat germ agglutinin conjugated HRP (WGA-HRP) was injected into the parenchyma of the upper lobe of the left lung. This injection resulted in anterograde labeling in the nucleus of the tractus solitarius (NTS), area postrema (AP) and external cuneate nucleus (ECu) with slightly ipsilateral predominance. It was of interest that these labeled sensory fibers are heavily accumulated in the medial subnucleus at the rostral pole of the NTS and in the commissural subnucleus at the caudal pole. In particular, labeled fibers in the medial subnucleus were characterized by division into the ventral and dorsal portions. After formalin was injected into the parenchyma of the upper lobe of the left lung, the expression of c-fos-like immunoreactivity (FOS-LI) was observed in three nuclei of the brainstem mentioned above. In addition, this experiment resulted in the expression in the ventrolateral medulla, nucleus raphe pallidus and dorsal motor nucleus of vagus nerve bilaterally. With respect to the number of the immunoreactive cells, we could draw the conclusion that the most optimum time to induce the expression of FOS-LI is between 1.5 h and 2.0 h after noxious stimuli.

Animals↗

PubMed1998

Occlusion of the femoral artery induced fos-like immunoreactive neurons in the lateral habenular nucleus projecting to the midbrain periaqueductal gray in the rat.

Wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) injection into the midbrain periaqueductal gray (PAG) resulted in heavy accumulation of retrogradely labeled neurons in the lateral habenular nucleus (LHb) bilaterally. When the left femoral artery was persistently ligated for 2 h, the expression of Fos-like immunoreactivity (FOS-LI) was also found bilaterally in the LHb. In the present study, by combining the retrograde labeling method of injecting WGA-HRP into the PAG and the immunohistochemical staining of the FOS-LI neurons in the LHb induced by occlusion of the femoral artery, it was demonstrated that there are neurons containing both HRP labeling and FOS-LI. These neurons appeared to be located mainly in the medial part and posterior half of the LHb, and constitute about 24% of the total number of all labeled cells.

Animals↗

PubMed1998

Discovery of ascomycin analogs with potent topical but weak systemic activity for treatment of inflammatory skin diseases.

Drug therapy for the major inflammatory skin diseases, which include atopic dermatitis, psoriasis and allergic contact dermatitis, is often inadequate due to poor efficacy, toxicity, or both. Much research has focused on the macrolactam T cell inhibitors as a promising new class of agents for immunotherapy, and medicinal chemistry efforts to design novel ascomycin analogs have produced clinically promising agents. A synthetic program to modify the ascomycin nucleus to alter its physicochemical properties and promote systemic clearance is described. A biologic screening strategy to identify analogs with reduced systemic activity and rapid pharmacokinetic elimination led to identification of the clinical candidate, ABT-281. A swine contact hypersensitivity model was used as a stringent indicator of skin penetration as human doses of topical corticosteroids produced inhibition only in the 50% range and ED50 values were 100-fold less potent than in rat. Also, cyclosporine was confirmed to be topically inactive in swine, as seen in human. ABT-281 had topical potency equal to tacrolimus (FK506) despite a severalfold lower potency for inhibiting swine T cells in vitro, consistent with superior skin penetration. ABT-281 was found to have a shorter duration of action after i.v. dosing in monkeys using an ex vivo whole blood IL-2 production assay. Systemic potency was reduced by 30-fold or more in rat popliteal lymph node hyperplasia and contact hypersensitivity assays. Following i.v. or i.p. administration in the swine contact hypersensitivity model, ABT-281 was 19- and 61-fold less potent, respectively, than FK506. Pharmacokinetic studies showed that ABT-281 had a shorter half life and higher rate of clearance than FK506 in all three species. The potent topical activity and reduced systemic exposure of ABT-281 may thus provide both efficacy and a greater margin of safety for topical therapy of skin diseases.

Administration, Topical↗

PubMed1998

The Sequence Attribute Method for Determining Relationships Between Sequence and Protein Disorder.

The conditional probability, P(s|x), is a statement of the probability that the event, s, will occur given prior knowledge for the value of x. If x is given and if s is randomly distributed, then an empirical approximation of the true conditional probability can be computed by the application of Bayes' Theorem. Here s represents one of two structural classes, either ordered, s (o), or disordered, s (d), and x represents an attribute value calculated over a window of 21 amino acids. Plots of P(s|x) versus x provide information about the correlation between the given sequence attribute and disorder or order. These conditional probability plots allow quantitative comparisons between individual attributes for their ability to discriminate between order and disorder states. Using such quantitative comparisons, 38 different sequence attributes have been rank-ordered. Attributes based on cysteine, the aromatics, flexible tendencies, and charge were found to be the best attributes for distinguishing order and disorder among those tested so far.

Journal Article↗

PubMed1998

[Preliminary experiment on selection of oral hygienic cleanser].

The effectiveness of three commercial chewing gums ("Hua Aikang","Cao Shanhu" and "Poli") and brushing with toothpaste on the elimination of dental plaque was observed in 31 healthy males (aged 19-25 years). Before and after chewing or brushing, evaluation of oral taste and examination of plaque were performed. The result showed that the oral taste after chewing, "hua aikang" was the best, then "po li" and "cao shanhu"; plaque indexes were substantially reduced by all four kinds of treatment (P < 0.001) as compared with the pretest values, however "hua aikang" demonstrated a better effectiveness (P < 0.001). It also indicates that plaque index is an important index revealing the hygiene status.

Adult↗

PubMed1997

Estimation of the numerical densities of neurons and synapses in cerebral cortex.

In this paper we discuss a stereological technique, 'the unfolding method', for a quantitative study of the nervous system [1,31]. Stereology implies a geometric analysis of structures and textures, and is a method to derive directly metric properties of structures from two-dimensional sections on the basis of geometrico-statistical reasoning [36,37]. Recent advances in the stereological method allow quantitative analysis [8,19,27,32]. Images on sections provide only two-dimensional information, but the stereological method can offer three-dimensional and quantitative information [19]. The need for quantitative analysis is more important and useful in the central nervous system (CNS) than in other organs. Two functional units, neurons and synapses, are of particular interest in evaluating CNS function. Numerical densities of neurons and synapses in rat visual cortex were estimated using the unfolding method at light and electron microscopic levels, respectively. Once the numerical densities of neurons and synapses were obtained, synapse-to-neuron ratios could be calculated. The ratios are interpreted as a means to obtain an index of interneuronal connectivity [9]. The unfolding method may become a powerful strategy in neuroscience research when numerical estimates are performed in restricted areas such as cortical layers II-IV, because this method is less time-consuming than other stereological methods [6,21,22].

Animals↗

PubMed1997

A novel antioxidant gene from Mycobacterium tuberculosis.

Among the major antimicrobial products of macrophages are reactive intermediates of the oxidation of nitrogen (RNI) and the reduction of oxygen (ROI). Selection of recombinants in acidified nitrite led to the cloning of a novel gene, noxR1, from a pathogenic clinical isolate of Mycobacterium tuberculosis. Expression of noxR1 conferred upon Escherichia coli and Mycobacterium smegmatis enhanced ability to resist RNI and ROI, whether the bacteria were exposed to exogenous compounds in medium or to endogenous products in macrophages. These studies provide the first identification of an RNI resistance mechanism in mycobacteria, point to a new mechanism for resistance to ROI, and raise the possibility that inhibition of the noxR1 pathway might enhance the ability of macrophages to control tuberculosis.

Amino Acid Sequence↗

PubMed1997

A novel lipopolysaccharide-response element contributes to induction of nitric oxide synthase.

The gene encoding the high output isoform of nitric oxide synthase represents a large class of alarm and defense genes transcriptionally induced in response to bacterial lipopolysaccharide (LPS). The promoters of most of these genes contain at least two LPS-response elements, one of which commonly binds transcription factors of the NF-kappaB/Rel family. Here a novel LPS-response element is identified in the inducible nitric oxide synthase promoter, termed LREAA, which contains critical adenosine residues lying 19-20 base pairs downstream of the proximal NF-kappaB binding element (NFkappaBd). Both NFkappaBd and LREAA are required for LPS-induced promoter activity. A protein partially recognized by antibody against transcription factor Oct-1 binds to the LREAA element constitutively in untreated macrophages while contributing to a DNA-protein complex that includes NF-kappaB p50 in macrophages treated with LPS. NF-kappaB p50 and the LREAA-binding proteins may together recruit an LPS-triggered transactivator of transcription.

Animals↗

PubMed1997

Expression and phosphorylation of a MARCKS-like protein in gastric chief cells: further evidence for modulation of pepsinogen secretion by interaction of Ca2+/calmodulin with protein kinase C.

In gastric chief cells, agents that activate protein kinase C (PKC) stimulate pepsinogen secretion and phosphorylation of an acidic 72-kDa protein. The isoelectric point and molecular mass of this protein are similar to those for a common PKC substrate; the MARCKS (for Myristoylated Alanine-Rich C Kinase Substrate) protein. We examined expression and phosphorylation of the MARCKS-like protein in a nearly homogeneous suspension of chief cells from guinea pig stomach. Western blotting of fractions from chief cell lysates with a specific MARCKS antibody resulted in staining of a myristoylated 72-kDA protein (pp72), associated predominantly with the membrane fraction. Using permeabilized chief cells, we examined the effect of PKC activation (with the phorbol ester PMA), in the presence of basal (100 nM) or elevated cellular calcium (1 microM), on pepsinogen secretion and phosphorylation of the 72-KDa MARCKS-like protein. Secretion was increased 2.3-, 2.6-, and 4.5-fold by incubation with 100 nM PMA, 1 microM calcium, and PMA plus calcium, respectively. A PKC inhibitor (1 microM CGP 41 251) abolished PMA-induced secretion, but did not alter calcium-induced secretion. This indicates that calcium-induced secretion is independent of PKC activation. Chief cell proteins were labeled with 32P-orthophosphate and phosphorylation of pp72 was detected by autoradiography of 2-dimensional polyacrylamide gels. In the presence of basal calcium, PMA (100 nM) caused a > two-fold increase in phosphorylation of pp72. Without PMA, calcium did not alter phosphorylation of pp72. However, 1 microM calcium caused an approx. 50% attenuation of PMA-induced phosphorylation of pp72. Experiments with a MARCKS "phosphorylation/calmodulin binding domain peptide" indicated that calcium/calmodulin inhibits phosphorylation of pp72 by binding to the phosphorylation/calmodulin binding domain and not by inhibiting PKC activity. These observations support the hypothesis that, in gastric chief cells, interplay between calcium/calmodulin binding and phosphorylation of a common domain on the 72-kDa MARCKS-like protein plays a role in modulating pepsinogen secretion.

Animals↗

PubMed1997

Structure of chain d of the gigantic hemoglobin of the earthworm.

The extracellular hemoglobin of the earthworm has four major O2-binding chains, a, b, c and d, together with additional non-heme structural chains that are required for assembly. Although the abc trimer self-associates extensively at least to (abc)10, addition of chain d results in the formation of a discrete 280 kDa complex corresponding to (abcd)4. Thus a primary function of chain d is to cap the abc association and convert an abc trimer that binds O2 with weak cooperativity to a highly cooperative (abcd)4 complex. Amino-acid sequences of the major globin chains a, b, c have been determined previously by peptide and cDNA analysis. However, the peptide sequence reported for the major chain d (Shishikura, F., Snow, J.W., Gotoh, T., Vinogradov, S.N. and Walz, D.A. (1987) J. Biol. Chem., 262. 3123-3131), has a calculated molecular mass 134-167 Da higher than masses for components of chain d determined by mass spectrometry (Owrby, D.W., Zhu, H., Schneider, K., Beavis, R.C., Chait, B.T. and Riggs, A.F. (1993) J. Biol. Chem. 268, 13539-13547). Reverse-phase HPLC confirms the presence of two distinct polypeptides, d1 and d2, together with d'1, a variant of d1, cDNA derived amino acid sequences have been determined for chains d'1 and d2 by application of the polymerase chain reaction with primers based on the NH2-terminal sequences and oligo-dT. Each of the two cDNA-derived sequences has 140 residues and they differ by 28 substitutions. The data show that the sequence originally reported had been derived from peptides generated from both polypeptides.

Amino Acid Sequence↗

PubMed1997

Resorption of mandibular canal wall in the edentulous aged population.

STATEMENT OF PROBLEM: The mandibular canal wall may be affected by the progress of residual ridge resorption after tooth extraction. Little knowledge is available regarding the relationship of specific systemic factors and the resorption of the mandibular canal wall. PURPOSE: The purpose of this study was to assess the status of the mandibular canal in the edentulous mandible and to determine whether there is any relationship between the resorption of the mandibular canal wall and selected health indices in the elderly. MATERIAL AND METHODS: The status of the mandibular canal was assessed from panoramic radiographs of 128 edentulous elderly subjects (32 men and 96 women). RESULTS: The superior border of the mandibular canal was more frequently resorbed in women (32.6%) than in men (9.8%). Resorption in the mandibular canal wall was significantly more prevalent in subjects with asthma (odds ratio: 6.0), with thyroid disease (odds ratio: 3.04), and with a cortical thickness at the mandibular angle less than 1 mm thick (odds ratio 2.74). CONCLUSION: The findings suggest that gender, asthma, and thyroid disease play important roles in resorption of the mandibular canal wall.

Aged↗

PubMed1997

Different susceptibility of three clinically isolated strains of Cryptococcus neoformans to the fungicidal effects of reactive nitrogen and oxygen intermediates: possible relationships with virulence.

We investigated the susceptibility of three clinically isolated strains of Cryptococcus neoformans with different virulences to reactive nitrogen and oxygen intermediates (RNI and ROI, respectively), representing two important mediators of macrophage microbicidal activity. All mice infected with the highly virulent strain of C. neoformans, YC-11, died within 3 to 6 weeks because of rapid multiplication of the organism in the lungs and dissemination to the brain. In contrast, a weakly virulent strain, YC-13, was almost completely eradicated from the lungs and did not disseminate to the brain, leading to survival of all infected animals during the period of observation (15 weeks). The virulence of the third strain, YC-5, was intermediate between the other two strains. To examine the susceptibility of C. neoformans to the fungicidal effect of nitric oxide (NO) and superoxide anions (O2-), the organisms were exposed to these oxidants, which were chemically generated in a cell-free system. Interestingly, the number of live YC-13 yeast cells was markedly reduced after exposure to NO and O2-. In contrast, YC-11 was almost completely resistant to the killing effect of these oxidants. YC-5 showed an intermediate susceptibility. Our results demonstrate that the resistance of C. neoformans to the fungicidal effects of RNI and ROI is related to virulence, and suggest that the resistance to nitrogen- and oxygen-derived oxidants may be one of the factors to determine the outcome of infection with C. neoformans.

Animals↗

PubMed1997

Assessment of the effect of an oscillating/rotating electric toothbrush on oral health. A 12-month longitudinal study.

The aim of this 12-month parallel design controlled clinical trial was to assess the effect of the Braun Oral-B Plak Control electric toothbrush on supragingival plaque and gingival health, and to compare it with a conventional soft manual toothbrush (Jordan). A total of 111 patients aged between 20 and 63 years, from a general population, with bleeding on probing at 30% or more of all sites examined were entered into the study. At baseline, immediately after periodontal examination, all volunteers received a thorough scaling of their teeth. Volunteers in both groups were told to brush their teeth for 2 min 2 x a day. Oral hygiene instruction was given at the start of the study and was not repeated. At 3, 6 and 12 months, assessments were carried out by a single clinician who was not aware which group the volunteers belonged to. Analysis of results demonstrated that over the 12 months of the study, the Braun Oral-B Plak Control was significantly more effective in improving gingival health than the manual toothbrush. There was, however, no difference between the 2 groups in terms of plaque removal, with the number of sites with visible plaque decreasing by a similar amount in both groups. In conclusion, results indicate that the Braun Oral-B Plak Control toothbrush is safe and more effective than a manual toothbrush in improving gingival health.

Adult↗