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Biomedical subjects

S Guo

Publications and source records attributed to S Guo.

At least 19 recordsLinked to original sources
PubMed2006

Effect of ammonium and nitrate nutrition on some physiological processes in higher plants - growth, photosynthesis, photorespiration, and water relations.

Ammonium and nitrate as different forms of nitrogen nutrients impact differently on some physiological and biochemical processes in higher plants. Compared to nitrate, ammonium results in small root and small leaf area, which may contribute to a low carbon gain, and an inhibition on growth. On the other hand, due to (photo)energy saving, a higher CO (2) assimilation rate per leaf area was observed frequently in plants supplied with ammonium than in those supplied with nitrate. These results were dependent not only on higher Rubisco content and/or activity, but also on RuBP regeneration rate. The difference in morphology such as chloroplast volume and specific leaf weight might be the reason why the CO (2) concentration in the carboxylation site and hence the photorespiration rate differs in plants supplied with the two nitrogen forms. The effect of nitrogen form on water uptake and transportation in plants is dependent both on leaf area or shoot parameter, and on the root activity (i.e., root hydraulic conductivity, aquaporin activity).

Biological Transport↗
PubMed2006

No association between the genetic polymorphisms in the RTN4R gene and schizophrenia in the Chinese population.

The RTN4R gene is located in the 22q11 region and it encodes a subunit of the receptor complex (RTN4R-p75NTR) which results in neuronal growth inhibitory signals in response to Nogo-66, MAG or OMG signaling. Previous studies have suggested that RTN4R might act as a potential candidate for schizophrenia susceptibility loci. We genotyped four SNPs within the gene and conducted a case-control study and TDT analysis, involving 707 schizophrenic patients, 689 controls and 372 unrelated small nuclear families with schizophrenic offspring in the Chinese population. We examined allele and genotype frequencies and haplotype distributions in both family- and nonfamily-based samples. Our results suggest that there is no significant association between the genetic polymorphisms and schizophrenia in the Han Chinese population.

Case-Control Studies↗
PubMed2006

Development of a recombinant indirect ELISA for the diagnosis of Theileria sp. (China) infection in small ruminants.

Theileria sp. (China) causes severe limitations on the development of the livestock industry in the north-west of China. An enzyme-linked immunosorbent assay (ELISA) based on merozoite homogenate of the parasite for diagnosis of infection has been established; however, cross-reactivity with other small ruminant-infecting piroplasms could not be excluded. Thus, a prerequisite for epidemiological surveys and diagnosis was the establishment of a recombinant protein-based ELISA. To this end, serum from Theileria sp. (China)-infected sheep was used to screen a Theileria lestoquardi expression library, resulting in the identification of a specifically reacting clone with a high identity to the heat shock protein 70 (HSP70) of Theileria parva and Theileria annulata and thus named TlHSP70. An HSP70 homologue was also confirmed to be expressed by Theileria sp. (China) merozoites (TcHSP70). A part of the TlHSP70 protein, found to be conserved in TcHSP70, was recombinantly expressed and used to establish an ELISA. A total of 260 field serum samples tested resulted in a sensitivity and specificity of 94.3 and 89.5%, respectively, in comparison with the merozoite homogenate ELISA. The potentials of the application of the test in epidemiological surveys to map out the prevalence of the disease and for routine diagnostics are described.

Animals↗
PubMed2006

Construction of folate-conjugated pRNA of bacteriophage phi29 DNA packaging motor for delivery of chimeric siRNA to nasopharyngeal carcinoma cells.

Nasopharyngeal carcinoma is a poorly differentiated upper respiratory tract cancer that highly expresses human folate receptors (hFR). Binding of folate to hFR triggers endocytosis. The folate was conjugated into adenosine 5'-monophosphate (AMP) by 1,6-hexanediamine linkages. After reverse HPLC to reach 93% purity, the folate-AMP, which can only be used for transcription initiation but not for chain extension, was incorporated into the 5'-end of bacteriophage phi29 motor pRNA. A 16:1 ratio of folate-AMP to ATP in transcription resulted in more than 60% of the pRNA containing folate. A pRNA with a 5'-overhang is needed to enhance the accessibility of the 5' folate for specific receptor binding. Utilizing the engineered left/right interlocking loops, polyvalent dimeric pRNA nanoparticles were constructed using RNA nanotechnology to carry folate, a detection marker, and siRNA targeting at an antiapoptosis factor. The chimeric pRNAs were processed into ds-siRNA by Dicer. Incubation of nasopharyngeal epidermal carcinoma (KB) cells with the dimer resulted in its entry into cancer cells, and the subsequent silencing of the target gene. Such a protein-free RNA nanoparticle with undetectable antigenicity has a potential for repeated long-term administration for nasopharyngeal carcinoma as the effectiveness and specificity were confirmed by ex vivo delivery in the animal trial.

Adenosine Monophosphate↗
PubMed2006

Effects of anti-bursin monoclonal antibody on immunosuppression in the duck (Cherry Valley duck).

To study the immunologic function of bursin, we analyzed the effects of anti-bursin monoclonal antibody (mAb) on the immunosuppression in ducks (Cherry Valley duck) by injecting various doses of the anti-bursin mAb into 13-d duck embryos. After hatch, cell-mediated immune activity and humoral responses were studied using lymphocyte proliferation test, tube agglutination test, and indirect enzyme-linked immunosorbent assay to detect anti-Escherichia coli antibodies and antibodies to Riemerella anatipestifer, respectively. Simultaneously, relative weights (BW-adjusted) of bursa of Fabricius (BF), spleen, and thymus were determined. Additionally, the morphology of BF, spleen, and thymus was examined at various ages using conventional histology. Follicle morphology of BF was analyzed by image analysis. The results indicated that anti-bursin mAb markedly decreased duck lymphocyte proliferation, the antibody-producing ability to bacteria, as well as the relative BF weight. Moreover, the anti-bursin mAb hindered the development of BF follicles.

Animals↗
PubMed2006

Dissociation of food and opiate preference by a genetic mutation in zebrafish.

Both natural rewards and addictive substances have the ability to reinforce behaviors. It has been unclear whether identical neural pathways mediate the actions of both. In addition, little is known about these behaviors and the underlying neural mechanisms in a genetically tractable vertebrate, the zebrafish Danio rerio. Using a conditioned place preference paradigm, we demonstrate that wildtype zebrafish exhibit a robust preference for food as well as the opiate drug morphine that can be blocked by the opioid receptor antagonist naloxone. Moreover, we show that the too few mutant, which disrupts a conserved zinc finger-containing gene and exhibits a reduction of selective groups of dopaminergic and serotonergic neurons in the basal diencephalon, displays normal food preference but shows no preference for morphine. Pretreatment with dopamine receptor antagonists abolishes morphine preference in the wildtype. These studies demonstrate that zebrafish display measurable preference behavior for reward and show that the preference for natural reward and addictive drug is dissociable by a single-gene mutation that alters subregions of brain monoamine neurotransmitter systems. Future genetic analysis in zebrafish shall uncover further molecular and cellular mechanisms underlying the formation and function of neural circuitry that regulate opiate and food preference behavior.

Analysis of Variance↗
PubMed2005

Enhanced fluorescence from periodic arrays of silver nanoparticles.

Electron beam lithography was used to fabricate silver nanoparticle arrays and study the effects of geometrical properties of particles on metal-enhanced fluorescence. Nanoparticle size, shape, interparticle spacing, and nominal thickness were varied in a combinatorial pattern for investigation of the particle plasmon resonance effect on enhancement of fluorescence from three different fluorophores; Fluorescein, Cy3, and Cy5. A specific geometric property for optimal enhancement from each fluorophore was determined. For interparticle spacings greater or equal to 270 nm, the enhancement matched what is expected for a single-particle model. For those particles smaller than 210 nm, the enhancement was lower than for the larger spacing in the range studied. Triangular-shaped particles gave similar enhancement to those of square-shaped particles. This combinatorial pattern by e-beam lithography was found to be useful for studying how individual parameters enhance the fluorescence that are important for rational design of enhanced fluorescence sensors.

Journal Article↗
PubMed2005

Two-dimensional and 3-dimensional optical coherence tomographic imaging of the airway, lung, and pleura.

BACKGROUND: Methods for obtaining real-time in vivo histologic resolution by means of noninvasive endoscopic optical imaging would be a major advance for thoracic surgical diagnostics and treatment. Optical coherence tomography is a rapidly evolving technology based on near-infrared interferometry that might provide these capabilities. The purpose of this study is to investigate the feasibility of real-time 2- and 3-dimensional optical coherence tomographic imaging of airway, pleural, and subpleural lung tissues in normal, inflammatory, and malignant animal models and patients with known or suspected airway malignancy. METHODS: Freshly excised lungs and pleural tissue obtained from rabbits with inhalation lung injury and induced empyema, metastatic sarcomas, and pleural sarcomas and from patients with airway disease were imaged by using 2- and 3-dimensional optical coherence tomography with a prototype superluminescent diode optical coherence tomographic system constructed in our laboratory. Lungs and pleural tissue were subsequently processed for standard hematoxylin and eosin histology for comparison with optical coherence tomography. RESULTS: Optical coherence tomographic imaging achieved an ex vivo resolution of 10 microm and an in vivo resolution of about 30 microm with a depth penetration of 1 to 2 mm with 2- and 3- dimensional reconstruction capabilities. Tumors as small as 500 microm were detectable with optical coherence tomography. The acquired images closely matched histologic images, demonstrating details at the level of mucosal layers, glands, alveoli, and respiratory bronchioles. CONCLUSIONS: Optical coherence tomography with near-infrared interferometric methods enables near real-time in vivo near-histologic resolution optical imaging. With further advances, optical coherence tomography has the potential for real-time accurate and early pleural and subpleural diagnostics by using small-diameter flexible fiberoptic endoscopic probes for a wide range of thoracic surgical applications.

Animals↗
PubMed2004

Evidence for the notch signaling pathway on the role of estrogen in angiogenesis.

We have investigated the molecular mechanisms involved in 17 beta-estradiol-induced angiogenic pathway. We show here that 17 beta-estradiol promoted a 6-fold increase in Jagged1 expression and an 8-fold increase in Notch1 expression by cDNA arrays in breast cancer MCF7 cells. Interestingly, Jagged1 was abrogated by incubation with the estrogen antagonist, ICI182,780. A similar up-regulation of both Notch1 receptor and Jagged1 ligand was found in endothelial cells. Additionally, imperfect estrogen-responsive elements were found in the 5' untranslated region of Notch1 and Jagged1 genes. Treatment with 17 beta-estradiol also led to an activation of Notch signaling in MCF7 cells expressing Notch1 reporter gene or by promoting Jagged1-induced Notch signaling in coculture assays. Inoculation of MCF7 cells in 17 beta-estradiol-treated nude mice resulted in up-regulation of Notch1 expression as well as increased number of tumor microvessels in comparison to placebo-treated mice. Notch1-expressing endothelial cell cultures formed cord-like structures on Matrigel in contrast to cells expressing a dominant-negative form of Notch1, emphasizing the relevance of Notch1 pathway in vessel assembly. Finally, Notch1-expressing MCF7 cells up-regulated hypoxia-inducible factor 1 alpha gene, a well-known angiogenic factor that clustered with Notch1 gene. This study implicates Notch signaling in the cross talk between 17 beta-estradiol and angiogenesis.

Animals↗
PubMed2004

The too few mutant selectively affects subgroups of monoaminergic neurons in the zebrafish forebrain.

Monoaminergic neurons are present in small numbers and in multiple distinct locations of the vertebrate CNS. They are involved in important functions such as movement coordination, motivation, and the response to environmental stress. However, the mechanisms involved in their subtype specification are not well understood. In this study, we examined the states of forebrain dopaminergic (DA) and serotonergic (5HT) neurons in larval and adult zebrafish of wild type and the too few mutant. The majority of DA and 5HT neuronal subgroups that were found in adults were established in the 6-day old larval zebrafish. Rather than affecting all monoaminergic neurons in the forebrain, selective subgroups of these neurons are reduced in the too few mutant, starting from the larval stage. Taken together, our study establishes that similar to DA neurons, distinct subtypes of 5HT neurons exist in larval as well as adult zebrafish. The development of a subset of these monoaminergic neurons is dependent on the too few gene product. Thus, this mutant is potentially important for understanding the development as well as the function of forebrain DA and 5HT neurons.

Animals↗
PubMed2004

Linking genes to brain, behavior and neurological diseases: what can we learn from zebrafish?

How our brain is wired and subsequently generates functional output, ranging from sensing and locomotion to emotion, decision-making and learning and memory, remains poorly understood. Dys-regulation of these processes can lead to neurodegenerative, as well as neuro-psychiatric, disorders. Molecular genetic together with behavioral analyses in model organisms identify genes involved in the formation of neuronal circuits, the execution of behavior and mechanisms involved in neuro-pathogenesis. In this review I will discuss the current progress and future potential for study in a newly established vertebrate model organism for genetics, the zebrafish Danio rerio. Where available, schemes and results of genetic screens will be reviewed concerning the sensory, motor and neuromodulatory monoamine systems. Genetic analyses in zebrafish have the potential to provide important insights into the relationship between genes, neuronal circuits and behavior in normal as well as diseased states.

Animals↗
PubMed2004

Early detection of relapse in panic disorder.

OBJECTIVE: To explore predictive models of relapsing based on change in symptoms at a time when panic disorder patients are still in remission following discontinuation of antidepressants. METHOD: Forty-seven subjects, who were randomized to double-blind placebo and who had valid data at four time points: pretreatment, randomization to placebo substitution, an assessment on placebo prior to the last assessment or relapse and their last assessment (relapsers n = 15, non-relapsers n = 32) were studied using descriptive, growth curve analysis and logistic regression methodologies. RESULTS: Measures of generalized anxiety, fearfulness and disability at work and at home were better predictors of relapse than measures of panic and anxiety sensitivity. Logistic regression models using any one of these four general variables and its linear change correctly predicted relapse for 78.7-84.4% of the study subjects. CONCLUSION: It is possible to gauge, with a fair degree of accuracy, the probability of relapsing in panic disorder patients who have discontinued serotonergic antidepressants 2 months prior to the return of panic.

Adult↗
PubMed2003

Site-directed mutational analysis of the novel catalytic domains of alpha-aminoadipate reductase (Lys2p) from Candida albicans.

The alpha-aminoadipate reductase, a novel enzyme in the alpha-aminoadipic acid pathway for the biosynthesis of lysine in fungi, catalyzes the conversion of alpha-aminoadipic acid to alpha-aminoadipic-delta-semialdehyde in the presence of ATP, NADPH and MgCl(2). This reaction requires two distinct gene products, Lys2p and Lys5p. In the presence of CoA, Lys5p posttranslationally activates Lys2p for the alpha-aminoadipate reductase activity. Sequence alignments indicate the presence of all functional domains required for the activation, adenylation, dehydrogenation and alpha-aminoadipic acid binding in the Lys2p. In this report we present the results of site-directed mutational analysis of the conserved amino acid residues in the catalytic domains of Lys2p from the pathogenic yeast Candida albicans. Mutants were generated in the LYS2 sequence of pCaLYS2SEI by PCR mutagenesis and expressed in E. coli BL21 cells. Recombinant mutants and the wild-type Lys2p were analyzed for their alpha-aminoadipate reductase activity. Substitution of threonine 416, glycine 418, serine 419, and lysine 424 of the adenylation domain (TXGSXXXXK, residues 416-424) resulted in a significant reduction in alpha-aminoadipate reductase activity compared to the unmutagenized Lys2p control. Similarly replacement of glycine 978, threonine 980, glycine 981, phenylalanine 982, leucine 983 and glycine 984 of the NADPH binding domain (GXTGFLG, residues 978-984) caused a drastic decrease in alpha-aminoadipate reductase activity. Finally, substitution of histidine 460, aspartic acid 461, proline 462, isoleucine 463, glutamine 464, arginine 465, and aspartic acid 466 of the putative alpha-aminoadipic acid binding domain (HDPIQRD, residues 460-466) resulted in a highly reduced alpha-aminoadipate reductase activity. These results confirm the hypothesis that specific amino acid residues in highly conserved catalytic domains of Lys2p are essential for the alpha-aminoadipate reductase activity.

Adenosine Triphosphate↗
PubMed2003

Bacterial virus phi29 pRNA as a hammerhead ribozyme escort to destroy hepatitis B virus.

The DNA-packaging pRNA of bacterial virus phi29, which forms dimers and then hexamers, contains two independent tightly self-folded domains. Circularly permuted pRNAs were constructed without impacting pRNA folding. Connecting the pRNA 5'/3' ends with variable sequences did not disturb its folding and function. These unique features, which help prevent two common problems - exonuclease degradation and misfolding in the cell, make pRNA an ideal vector to carry therapeutic RNAs. A pRNA-based vector was designed to carry hammerhead ribozymes that cleave the hepatitis B virus (HBV) polyA signal. The chimeric HBV-targeting ribozyme was connected to the pRNA 5'/3' ends as circularly permuted pRNA. Two cis-cleaving ribozymes were used to flank and process the chimeric ribozyme. The hammerhead ribozyme including its two arms for HBV targeting was able to fold correctly while escorted by the pRNA. The chimeric ribozyme cleaved the polyA signal of HBV mRNA in vitro almost completely. Cell culture studies showed that the chimeric ribozyme was able to enhance the inhibition of HBV replication when compared with the ribozyme not escorted by pRNA, as demonstrated by Northern blot and e-antigen assays. pRNA could also carry another hammerhead ribozyme to cleave other RNA substrate. These findings suggest that pRNA can be used as a vector for imparting stability to ribozymes, antisense, and other therapeutic RNA molecules in vivo.

Base Sequence↗
PubMed2003

Prognostic indicators for outcome following rotator cuff tear repair.

PURPOSE: To examine the prognostic indicators associated with outcome following rotator cuff surgery. METHODS: A retrospective evaluation of records on 1120 shoulders (1067 patients) with rotator cuff tear treated by surgery was performed. Preoperative, intra-operative and postoperative factors were analysed by Kendall's Tau-b correlation analysis and logistic regression analysis. RESULTS: Positive correlations were seen between the type of tear and the number of tendons involved, retraction, age, degeneration, subacromial bone spur, surgical technique, preoperative and postoperative muscle power, surgical outcome, and preoperative abduction on Kendall's Tau-b analysis. There was a positive correlation seen between degenerative change and age, number of tendons involved, retraction, preoperative pain, tear type, and preoperative musclepower on logistic regression analysis. Additionally, positive correlations were seen between good surgical postoperative outcome and postoperative activities of daily living, preoperative pain, postoperative muscle power, preoperative activities of daily living, tear type, preoperative external rotation, preoperative muscle power, number of tendons involved, preoperative pain, and duration of symptoms. CONCLUSION: Ageing was found to be the major factor in progressive degeneration of the rotator cuff, and should be considered the single most important contributing factor in the pathogenesis of rotator cuff tears. In addition, degenerative tendonopathy appeared the primary pathology in rotator cuff tear, preceding hypertrophic spur formation. Rotator cuff tears are therefore unlikely to be initiated by impingement; rather, they develop as an intrinsic degenerative tendonopathy.

Adolescent↗
PubMed2001

Electronic communication in oligometallic complexes with ferrocene-based tris(1-pyrazolyl)borate ligands.

Ferrocene-based tris(1-pyrazolyl)borate ligands 1R-Li and 1R-Tl have been synthesized and used to generate a variety of heterotrinuclear transition metal complexes, 3R-M [R = H, SiMe(3), cyclohexyl, (cyclohexyl)methyl, phenyl; M(II) = Mn, Fe, Co, Ni, Cu, Zn]. The poor solubility of 3H-M is greatly enhanced by the introduction of large organic substituents into the 4-positions of all pyrazolyl rings. The unsubstituted ligand 1H-Li and the trinuclear complex 3Cym-Cu [Cym = (cyclohexyl)methyl] have been investigated by X-ray crystallography. 1H-Li, which represents the first example of a structurally characterized lithium tris(1-pyrazolyl)borate, forms centrosymmetric dimers in the solid state. A severe Jahn-Teller distortion was observed for the (Bpz(3))(2)Cu fragment in 3Cym-Cu. Compared to the parent compounds [(HBpz(3))(2)M], the presence of uncharged ferrocenyl substituents in 3R-M tends to shift the M(2+)/M(3+) redox potential to significantly more cathodic values. The opposite is true if the ferrocenyl fragments are in their cationic state, which results in an anodic shift of the M(2+)/M(3+) transition. Most interestingly, the two ferrocenyl fragments in 3R-Cu appear to be electronically communicating.

Journal Article↗