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Biomedical subjects

S Shen

Publications and source records attributed to S Shen.

At least 19 recordsLinked to original sources
PubMed2002

Sex differences in amino acid release from rostral trigeminal subnucleus caudalis after acute injury to the TMJ region.

The neurological basis for painful temporomandibular disorders (TMD) and the higher prevalence of TMD pain in women than men is not known. To better define the circuitry and neurochemical mechanisms in the lower brainstem associated with noxious sensory inputs from the temporomandibular joint (TMJ) region a microdialysis method was used to measure the release of amino acid transmitters from the ventral trigeminal subnucleus interpolaris/caudalis transition region (Vi/Vc-vl). The irritant chemical, mustard oil, was injected into the TMJ region (TMJ-MO) under barbiturate anesthesia in males and normal cycling female rats. Males displayed significant increases in glutamate, serine, and glycine within 15 min after TMJ-MO and increases in citrulline occurred after a delay of 15-30 min. TMJ-MO did not enhance amino acid release in diestrus or proestrus females. GABA release was not affected by TMJ-MO in males or females. Pretreatment with morphine (3 mg/kg, i.v.) prevented the increase in amino acid release seen after TMJ-MO in males. Amino acid release at the Vi/Vc-vl transition region evoked by TMJ-MO also was prevented by prior microinjection of the GABA(A) receptor agonist, muscimol, into the most caudal portion of Vc suggesting this region acted as a critical relay for nociceptive inputs from the TMJ region. These results suggest that glutamatergic mechanisms acting at the Vi/Vc-vl transition region contribute to processing of nociceptive signals that arise from the TMJ region. These results also are consistent with the hypothesis that central neural mechanisms that integrate nociceptive inputs from deep craniofacial tissues are different in males and females.

Amino Acids↗
PubMed2002

Bacterial and yeast flora of root surface caries in elderly, ethnic Chinese.

OBJECTIVES: Root caries is emerging as a significant problem in the middle aged and elderly. As little data is available on the microbiology of root caries in Chinese cohorts, we evaluated 30 such lesions in elderly, institutionalized, ethnic Chinese. METHODS: Samples of carious dentine were aseptically taken from root caries lesions of 18 subjects (five males and 13 females, mean age 79.67 +/- 8.57). The cultivable bacteria, both aerobic and anaerobic, were isolated and identified using standard methods and commercial identification kits. The yeasts were isolated on Sabouraud's agar and identified using the API system. RESULTS: The main findings were: (1) of the total isolates, 91.09% were Gram-positive and 8.91% were Gram-negative microorganisms; (2) the proportions of cocci and rods were 36.68 and 63.31%, respectively; (3) the predominant groups of organisms isolated were Streptococcus spp., Lactobacillus spp., Staphylococcus spp. and Actinomyces spp. with isolation frequencies of 100, 90.00, 73.33 and 63.33%, respectively; (4) the isolation frequency of yeasts belonging to Candida spp. (63.33%) was notably high although the proportion of yeasts within each sample was low (0.01%). Candida dubliniensis, a newly identified yeast species particularly prevalent in HIV infection, comprised 14.29% of yeasts. CONCLUSIONS: This study provides baseline information on the microbiologic features of root caries in the elderly, ethnic Chinese. Whilst our data on the most predominant bacteria isolated in root caries concur with those from other regions of the world the isolation of C. dubliniensis from these lesions has not been documented before.

Actinomyces↗
PubMed2001

Enhanced delayed-type hypersensitivity and diminished immediate-type hypersensitivity in mice lacking the inducible VPAC(2) receptor for vasoactive intestinal peptide.

Vasoactive intestinal peptide (VIP) and its G protein-coupled receptors, VPAC(1)R and VPAC(2)R, are prominent in the immune system and regulate many aspects of T cell-dependent immunity. In mouse T cells, VPAC(1)R is expressed constitutively, whereas VPAC(2)R is induced by immune stimuli. VPAC(2)R-null (VPAC(2)R(-/-)) mice on a C57BL/6 background are shown here to have normal basic immune characteristics, including serum Ig concentrations, blood levels of all leukocytes, and spleen number of total T cells (CD3(+)) and T cells bearing CD4, CD8, and CD28. Hapten-evoked cutaneous delayed-type hypersensitivity (DTH) was significantly enhanced in VPAC(2)R-null mice compared with age- and sex-matched wild-type mice. In contrast, generation of IgE anti-hapten antibodies and active cutaneous anaphylaxis were > or =70% lower in VPAC(2)R-null mice than in wild-type controls. Cytokine production by splenic CD4(+) T cells, stimulated with adherent anti-CD3 plus anti-CD28 antibodies, revealed higher levels of IL-2 (mean = 3-fold) and IFN-gamma (mean = 3-fold), and lower levels of IL-4 (mean = one-fifth) in VPAC(2)R-null mice than wild-type controls. Loss of VIP-VPAC(2)R maintenance of the normal ratio of Th2/Th1 cytokines thus leads to a state of enhanced DTH and depressed immediate-type hypersensitivity, which may alter both host defense and susceptibility to immune-mediated diseases.

Animals↗
PubMed2001

Further identification and characterization of novel intermediate and mature cleavage products released from the ORF 1b region of the avian coronavirus infectious bronchitis virus 1a/1b polyprotein.

The coronavirus 3C-like proteinase is one of the viral proteinases responsible for processing of the 1a and 1a/1b polyproteins to multiple mature products. In cells infected with avian coronavirus infectious bronchitis virus (IBV), three proteins of 100, 39, and 35 kDa, respectively, were previously identified as mature cleavage products released from the 1b region of the 1a/1b polyprotein by the 3C-like proteinase. In this report, we show the identification of two more cleavage products of 68 and 58 kDa released from the same region of the polyprotein. In addition, two stable intermediate cleavage products with molecular masses of 160 and 132 kDa, respectively, were identified in IBV-infected cells. The 160-kDa protein was shown to be an intermediate cleavage product covering the 100- and 68-kDa proteins, and the 132-kDa protein to be an intermediate cleavage product covering the 58-, 39-, and 35-kDa proteins. Immunofluorescent staining of IBV-infected cells and cells expressing individual cleavage products showed that the 100-, 68-, and 58-kDa proteins were associated with the membranes of the endoplasmic reticulum, and the 39- and 35-kDa proteins displayed diffuse distribution patterns.

Animals↗
PubMed2001

Reduction in DNA damage in brain and peripheral blood lymphocytes of elderly dogs after treatment with dehydroepiandrosterone (DHEA).

Steady state levels of DNA damage are substantial in vertebrate animals as a consequence of exposure to endogenous and environmental mutagens. DNA damage may contribute to organismal senescence and an increased risk for specific age-related diseases. In this study, we determined if treatment with the neuroactive adrenal steroid, dehydroepiandrosterone (DHEA), which exhibits antioxidant and anticarcinogenic properties in rodents, would reduce DNA damage in the brain and peripheral blood lymphocytes (PBLs) of elderly dogs. Elderly male dogs, physiologically equivalent to 59-69-year-old men, were randomly assigned to receive no treatment (n=9 dogs) or DHEA at 100mg/kg PO daily (n=8 dogs). Extent of DNA damage in brain cells and PBLs was measured using alkaline comet assay. The effect of DHEA treatment on the susceptibility of PBLs to H(2)O(2)-induced DNA damage was also measured. We found that elderly male dogs receiving daily DHEA treatment for 7 months had significantly less DNA damage detectable in their brain compared to age-matched control dogs. After 7 months treatment, DHEA-treated dogs also had a significant reduction in DNA damage in PBLs compared to pre-treatment levels. We also found that PBLs of dogs treated with DHEA were more resistant to H(2)O(2)-induced DNA damage than PBLs of untreated dogs. Our results did not show that basal DNA damage in PBLs was strongly correlated with DNA damage within the brain. The results of this study suggest that DHEA supplementation can significantly reduce steady state levels of DNA damage in the mammalian brain. Further evaluation of DHEA as a neuroactive agent and its effects on DNA damage and gene expression in other tissues and species is warranted.

Administration, Oral↗
PubMed2001

Right amygdala volume in adolescent and young adult offspring from families at high risk for developing alcoholism.

BACKGROUND: Neurobiological factors have been implicated in the increased susceptibility for developing alcohol dependence that offspring from alcoholic families exhibit. The P300 component of the event-related potential shows developmental changes during childhood and adolescence that appear to be related to risk status. The underlying structural changes that accompany these neurophysiological changes are not well understood. METHODS: Magnetic resonance imaging was used to measure cerebral, amygdala, and hippocampal volumes in 17 high-risk adolescent and young adult offspring from multiplex alcoholism families and 17 age-, gender-, and IQ-matched control subjects without a family history for alcoholism or other substance dependence. Twenty-two of the subjects are part of a longitudinal prospective study and have been followed an average of 7.3 years, making it possible to relate P300 developmental trajectories to structural volumes. RESULTS: High-risk adolescents and young adults showed reduced right amygdala volume in comparison with control subjects. Right amygdala volume was significantly correlated with visual P300 amplitude. CONCLUSIONS: Offspring from families having a high density of alcoholism differ in both neurophysiological and neuroanatomical characteristics that could not be explained by personal drinking history or particular childhood and adolescent psychopathology. Because the amygdala tends to increase in volume during childhood and adolescence, smaller volumes in high-risk children may indicate a developmental delay that parallels delays seen in visual P300 amplitude.

Adolescent↗
PubMed2001

mSiglec-E, a novel mouse CD33-related siglec (sialic acid-binding immunoglobulin-like lectin) that recruits Src homology 2 (SH2)-domain-containing protein tyrosine phosphatases SHP-1 and SHP-2.

The sialic acid-binding immunoglobulin-like lectins (siglecs) represent a recently defined distinct subset of the immunoglobulin superfamily. By using the Src homology 2 (SH2)-domain-containing protein tyrosine phosphatase SHP-1 as bait in a yeast two-hybrid screen, we have identified a new member of the mouse siglec family, mSiglec-E. The mSiglec-E cDNA encodes a protein of 467 amino acids that contains three extracellular immunoglobulin-like domains, a transmembrane region and a cytoplasmic tail bearing two immunoreceptor tyrosine-based inhibitory motifs (ITIMs). mSiglec-E is highly expressed in mouse spleen, a tissue rich in leucocytes. The ITIMs of mSiglec-E can recruit SHP-1 and SHP-2, two inhibitory regulators of immunoreceptor signal transduction. This suggests that the function of mSiglec-E is probably an involvement in haematopoietic cells and the immune system as an inhibitory receptor. When expressed in COS-7 cells, mSiglec-E was able to mediate sialic acid-dependent binding to human red blood cells, suggesting that mSiglec-E may function through cell-cell interactions. In comparison with the known members of the siglec family, mSiglec-E exhibits a high degree of sequence similarity to both human siglec-7 and siglec-9. The gene encoding mSiglec-E is localized in the same chromosome as that encoding mouse CD33. Phylogenetic analysis reveals that neither mouse mSiglec-E nor CD33 shows a clear relationship with any human siglecs so far identified.

Amino Acid Sequence↗
PubMed2001

Matrix GLA protein modulates differentiation induced by bone morphogenetic protein-2 in C3H10T1/2 cells.

Matrix GLA protein (MGP) is ubiquitously expressed with high accumulation in bone and cartilage, where it was found to associate with bone morphogenetic proteins (BMP) during protein purification. To test whether MGP affects BMP-induced differentiation, three sets of experiments were performed. First, pluripotent C3H10T1/2 cells transfected with human MPG (hMGP) or antisense to hMGP (AS-hMGP) were treated with BMP-2. In cells overexpressing hMGP, osteogenic and chondrogenic differentiation was inhibited indicating decreased BMP-2 activity. Conversely, in cells overexpressing AS-hMGP, BMP-2 activity was enhanced. Second, cells were prepared from homozygous and heterozygous MPG-deficient mice aortas. When treated with BMP-2, these cells underwent chondrogenic and osteogenic differentiation, respectively, whereas controls did not. Third, FLAG-tagged hMGP with the same biological effect as native hMGP inhibited BMP-induced differentiation, when exogenously added to culture media. Together, these results suggest that MGP modulates BMP activity. To test whether hMGP fragments would retain the effect of full-length hMGP, three subdomains were overexpressed in C3H10T1/2 cells. In cells expressing the mid-region, alone (amino acids (aa) 35-54) or in combination with the N terminus (aa 1-54) but not the C terminus (aa 35-84), osteogenic differentiation was enhanced and occurred even without added BMP-2. Thus, two subdomains had the opposite effect of full-length hMGP, possibly due to different expression levels or domain characteristics.

Alkaline Phosphatase↗
PubMed2001

Characterization of murine polyreactive antigen-binding B cells: presentation of antigens to T cells.

Monoclonal polyreactive antibodies (Ab) can bind, at low affinity, a variety of different self and non-self antigens (Ag). Recent studies in humans showed that polyreactive Ab are expressed on the surface of a subset of peripheral B lymphocytes and clonal analysis revealed that a variety of different Ag can bind to single cells expressing these Ab. To see if these polyreactive Ag-binding B (PAB) cells also are present in mice, fluorescein-conjugated Ag and FACS sorting were used to identify and separate PAB cells from non-polyreactive Ag-binding B cells. Depending on the Ag used for screening, up to one-third of mouse splenic B cells displayed polyreactive Ag-binding properties. Confirmation that the Ag actually bound to surface Ig came from treating PAB cells with anti-Ig which inhibited Ag binding by up to 80 %. Further studies showed that PAB cells could present Ag to Ag-specific T cells, but despite their Ag-presenting ability, PAB cells from normal mice failed to trigger Ag-specific T cells to proliferate. Analysis of the co-stimulatory molecules B7-1 and B7-2 showed that these molecules were not expressed on PAB cells from normal mice. These findings argue that the lack of co-stimulatory molecules on PAB cells is the most likely explanation for their failure to stimulate Ag-specific T cells. The ability of PAB cells from normal mice to bind and present Ag to Ag-specific T cells, without causing them to proliferate, suggests that PAB cells may contribute to the induction and / or maintenance of immunological tolerance.

Animals↗
PubMed2001

Linear DNAs concatemerize in vivo and result in sustained transgene expression in mouse liver.

The short duration of transgene expression remains a major obstacle for the implementation of nonviral DNA vectors in clinical gene therapy trials. Here, we demonstrate stable, long-term transgene expression in vivo by transfecting a linear DNA expression cassette (LDNA) into mouse liver. Interestingly, despite similar quantities and cellular distribution of injected DNAs in their livers, mice receiving LDNA encoding human alpha1-antitrypsin (hAAT) expressed approximately 10- to 100-fold more serum hAAT than mice injected with closed circular (cc) DNA for a period of 9 months (length of study). Furthermore, when a linear human factor IX expression cassette was delivered to factor IX-deficient mice, sustained serum concentrations of more than 4 microg/ml (80% of normal) of the human clotting factor and correction of the bleeding diathesis were obtained. Southern blot analyses indicate that, unlike ccDNA, LDNA rapidly formed large, unintegrated concatemers in vivo, suggesting that transgene persistence from plasmid-based vectors was influenced by the structure of the vector in transfected cells. No differences in transgene expression or DNA molecular structures were observed when AAV ITRs were included to flank the hAAT expression cassette in both ccDNA- and LDNA-treated animals. Linear DNA transfection provides an approach for achieving long-term expression of a transgene in vivo.

Animals↗
PubMed2001

Isolation and characterization of a novel cDNA, UBAP1, derived from the tumor suppressor locus in human chromosome 9p21-22.

PURPOSE: To clone the putative tumor suppressor gene(s) in a refined region at 9p21-22 undergoing loss of heterozygosity in nasopharyngeal carcinoma (NPC). METHODS: We systematically screened the expression patterns of 25 novel ESTs (expressed sequence tags) in a minimal common deleted region of 9p21-22 in NPC. One of these ESTs was found down-regulated in NPC. Subsequently, the corresponding gene sequence of this EST was established by cDNA cloning and RACE (rapid amplification of cDNA end) procedures. Furthermore, a mouse homologue of this gene was identified. The expression of this gene was examined using Northern blot or reverse transcription-polymerase chain reaction (RT-PCR) in various human and mouse tissues. A limited screen for mutation of coding sequence of this novel human gene was undertaken using RT-PCR and direct sequencing analysis. RESULTS: A novel gene was cloned. This gene is a new member of the UBA domain family, so we named it UBAPI for ubiquitin-associated protein 1 (HUGO Gene Nomenclature Committee-approved symbol). Northern blot and RT-PCR analysis demonstrate a ubiquitous pattern of gene expression in human and mouse tissues. The direct sequencing analysis of the coding region of hUBAP1 following RT-PCR failed to reveal any mutations in a preliminary screen of NPC cell line HNE1 and primary nasopharyngeal carcinoma samples. CONCLUSIONS: We cloned a novel gene UBAPI, which is highly conserved between human and mouse. Clearly, as a novel member of UBA domain protein family and taking its map location into account, a more extensive analysis is essential to establish whether subtle mutations are present in nasopharyngeal carcinomas.

Amino Acid Sequence↗
PubMed2001

Production of no-carrier-added 186Re via deuteron induced reactions on isotopically enriched 186W.

Rhenium-186 was produced from the reaction induced by 16 MeV deuterons on isotopically enriched 186W metal powder target. Following its separation from 187W, 183Ta and the bulk of target materials 186W through an acid alumina column, the 186Re was converted to HNO3 solution through an anion exchange column, or to ammonia solution by extracting with N-235-dimethylbenzene, and finally the no-carrier-added 186Re saline solution was obtained. The radionuclidic purity of 186Re was >99.9% and the isotopic impurities were mainly 183Re (5.0 x 10(-3)%) and 184gRe (4.6 x 10(-2)%). The experimental thick-target yield of 186Re was determined to be approximately 529 microCi/microA h and the overall chemical recovery yield was > 80%.

Kinetics↗
PubMed2001

Comparison of the 5' leader sequences of North American isolates of reference and field strains of porcine reproductive and respiratory syndrome virus (PRRSV).

The 5' leader is documented to be an important regulatory element in many (+) ssRNAvirus genome. To understand the significance of the 5' leader RNA of PRRSV, we determined the complete leader sequences of fifteen different North American strains of PRRSV and predicted their secondary structures. Viruses analysed included three reference strains and nine field strains originating from different geographic locations. To further examine the leader region, one of the field strains was adapted to grow in tissue culture, and three clones were isolated. We also predicted the secondary structures of two European strains based on their published sequences. The predicted RNA secondary structures of the leader sequences suggested the existence of three conserved domains formed by the 5' region of the leader among the North American strains, two of which were conserved in the European strains. A variable structural domain was predicted from the 3' region of the leader sequences of the North American strains, where all tissue culture-adapted isolates were characterized by a stem-loop while field isolates were characterized by an internal bulge within the stem-loop.

5' Untranslated Regions↗
PubMed2001

Increased IGFR activity and glucose transport in cultured skeletal muscle from insulin receptor null mice.

We have studied the role of the insulin receptor (IR) in metabolic and growth-promoting effects of insulin on primary cultures of skeletal muscle derived from the limb muscle of IR null mice. Cultures of IR null skeletal muscle displayed normal morphology and spontaneous contractile activity. Expression of muscle-differentiating proteins was slightly reduced in myoblasts and myotubes of the IR null skeletal muscle cells, whereas that of the Na+/K+ pump appeared to be unchanged. Insulin-like growth factor receptor (IGFR) expression was higher in myoblasts from IR knockout (IRKO) than from IR wild-type (IRWT) mice but was essentially unchanged in myotubes. Expression of the GLUT-1 and GLUT-4 transporters appeared to be higher in IRKO than in IRWT myoblasts and was significantly greater in myotubes from IRKO than from IRWT cultures. Consistent with GLUT expression, both basal and insulin or insulin-like growth factor I (IGF-I)-stimulated glucose uptakes were higher in IR null skeletal myotubes than in wild-type skeletal myotubes. Interestingly, autophosphorylation of IGFR induced by insulin and IGF-I was markedly increased in IR null skeletal myotubes. These results indicate that, in the absence of IR, there is a compensatory increase in basal as well as in insulin- and IGF-I-induced glucose transport, the former being mediated via increased activation of the IGF-I receptor.

Animals↗