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Biomedical subjects

X Li

Publications and source records attributed to X Li.

At least 163 records · Page 9Linked to original sources
PubMed2004

Human fetal nongonadal tissues contain human chorionic gonadotropin/luteinizing hormone receptors.

Human chorionic gonadotropin (hCG), a heterodimeric glycoprotein hormone produced in abundance by placental syncytiotrophoblasts, is preferentially secreted into maternal circulation. Fetal circulation also contains low levels of hCG that are probably derived from fetal kidney, liver, anterior pituitary gland, etc. In addition, the fetus has access to hCG present in exocoelomic and amniotic fluids. hCG has been found in a number of fetal tissues known to stimulate fetal adrenal and testicular steroidogenesis and is also thought to play a role in growth and differentiation of fetal tissues. This led us to test the hypothesis that fetal nongonadal tissues, as in the adult, may also contain hCG/LH receptors. This hypothesis was tested by immunocytochemistry, Western blotting, in situ hybridization, and RT-PCR. The results demonstrate that kidney, liver, pancreas, lung, small and large intestines, and adrenals contained hCG/LH receptors. Although the role of fetal nongonadal hCG/LH receptors is not known, they may mediate the pleiotropic actions of hCG in the growing human fetus.

Blotting, Western↗
PubMed2004

Presence of luteinizing hormone/human chorionic gonadotropin receptors in male breast tissues.

Receptors for LH/human chorionic gonadotropin (hCG) have been found in a variety of nongonadal tissues including the female breast. Using in situ hybridization and immunohistochemistry, we demonstrated the presence of LH/hCG receptor mRNA and protein in normal male breast tissue obtained at autopsy (n = 4) and archival samples of benign gynecomastia (n = 14) and male breast carcinoma (n = 5). Although the function of these receptors remains to be determined, the findings suggest the possibility that LH and hCG may play a role in the pathogenesis of male breast disorders.

Adult↗
PubMed2004

Clinical and radiological features of odontogenic ghost cell carcinoma: review of the literature and report of four new cases.

OBJECTIVES: To analyse systematically the clinical and radiological features of odontogenic ghost cell carcinoma (OGCC). METHODS: Clinical and radiological features of 22 OGCCs (4 new and 18 from the literature) were analysed. RESULTS: There were 17 (77%) males and 5 (23%) females (male-to-female ratio of 3.4:1). Ages ranged from 13 years to 72 years (mean 36.7) with a peak in the fourth (40.9%) and fifth (27.3%) decades. The maxilla was involved in 68% and the mandible in 32%. Our study confirmed that OGCC is more prevalent in Asians (12/18) than in other racial groups. The mixed radiolucent and radiopaque lesion pattern was the most frequent (14/19) compared with radiolucent lesions (5/19). 89% (17/19) showed poorly defined borders and 11% (2/19) showed well defined borders. Root resorption was reported in 31% (6/19) of patients and tooth displacements in 21%. CONCLUSIONS: OGCC demonstrates clinical and radiographic features of a malignant tumour with high recurrence.

Adult↗
PubMed2004

Start up of deammonification process in one single SBR system.

A process for autotrophic nitrogen removal named aerobic/anoxic deammonification wherein NH4+ is oxidized by nearly 50% to NO2- and subsequently the ammonia is converted together with the nitrite to molecular nitrogen (N2 gas), has come to full-scale application within the last few years. In this research, sludge from a biological rotation disk located at a landfill leachate plant at Mechernich, Germany, which is capable of performing the deammonification process, was used as seed sludge for acclimating deammonification activities in laboratory scale batch-reactors. In parallel, the same tests were performed with normal activated sludge. Research results indicated that deammonification activities could be obtained from the seeded reactor and also, with limited performance, from normal activated sludge in a single SBR system after several months acclimation. It was also seen that oxygen is an important factor that influences the deammonification from both the acclimatization process and process running. Further results were approved that report an impact of nitrite as a process intermediate on the closely related process of anaerobic ammonia oxidation ("Anammox"). However, limiting concentrations on a bacteria population performing deammonification were found to be different to those reported for a pure Anammox-culture. Also the influence of another intermediate, hydrazine, was tested for speeding up the acclimating process by inducing the deammonification activities and recovering the activities of deammonification from nitrite inhibition.

Bacteria, Anaerobic↗
PubMed2003

A delta-endotoxin encoded in Pseudomonas fluorescens displays a high degree of insecticidal activity.

The short field-life of Bacillus thuringiensis (Bt) insecticidal crystal protein has limited its use. When the Bt toxin is produced in Pseudomonas fluorescens it can be encapsulated and retain its effectiveness for two to three times longer than other Bt formulations. In order to improve Bt expression, we have synthesized cryIA(c) Bt delta-endotoxin encoding region (GenBank AF537267) according to the usage codon of P. fluorescens and transformed the Bt toxin expression cassette into P. fluorescens strains. T7 RNA polymerase and the T7 promoter system were used to control expression of Bt toxin. SDS-PAGE and Western blotting assay revealed that the delta-endotoxin was expressed as 8% of the total protein in P. fluorescens. In in vitro tests, release of toxin from dead bacteria was demonstrated. Supplementation of diets with Bt toxin-containing Pseudomonas bacterium resulted in high mortality of cabbage butterfly ( Pieris brassicae) larvae.

Animals↗
PubMed2003

Efficient operation of double-clad Yb3+-doped fiber lasers with a novel circular cladding geometry.

A highly efficient double-clad Yb3+-doped fiber laser with a novel cladding geometry is described. A round double-clad fiber with a small D-shaped hole for breaking a circular symmetry in a cladding combines the advantages of ease of manufacture and handling round fibers with efficient absorption of pump light. Fiber lasers with a double-D cladding shape and a D-hole cladding are compared. We report what are to our knowledge the highest slope efficiencies of 73% and 69%, respectively, pumping at 915 nm. Output powers in excess of 13 W are demonstrated.

Journal Article↗
PubMed2003

Amperometric glucose sensors based on ferrocene containing polymeric electron transfer systems-a preliminary report.

In this paper we introduce a preliminary work in which a redox mediator containing polyvinylferrocene immobilized on silica gel particles is synthesized. Carbon paste electrodes prepared with this polymeric mediator were studied for their stability in aqueous media for a month. The results indicated that approximately 70% of the initial activity was retained after a month. A steady state amperometric measurement of this carbon paste electrode containing this mediator and glucose oxidase at different potentials showed a linear relationship at elevated glucose concentration.

Adsorption↗
PubMed2003

Purification, crystallization and preliminary X-ray analysis of human pirin.

Pirin is a novel highly conserved nuclear protein, but very little is known about its cellular function. Human pirin has been cloned, expressed, purified and crystallized using PEG as precipitant. The crystal belongs to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 42.3, b = 67.0, c = 107.3 A, alpha = beta = gamma = 90 A. It contains one molecule per asymmetric unit and diffracts to 2.0 A under cryoconditions (100 K) using an in-house Cu rotating-anode X-ray generator.

Amino Acid Sequence↗
PubMed2003

Cognitive performance and MR markers of cerebral injury in cognitively impaired MS patients.

OBJECTIVE: To relate neuropsychological performance to measures of cerebral injury in persons with MS selected for cognitive impairment. METHODS: Participants were 37 individuals with relapsing-remitting (59.5%) and secondary progressive (40.5%) MS. They were tested at baseline as part of a clinical trial to enhance cognition with an acetylcholinesterase inhibitor. Eligibility criteria included at least mild cognitive impairment on a verbal learning and memory task. A modified Brief Repeatable Battery of Neuropsychological Tests formed the core of the behavioral protocol. Neuroimaging measures were central (ventricular) cerebral atrophy, lesion volume, and ratios of N-acetyl aspartate (NAA) to both creatine and choline. RESULTS: A clear, consistent relation was found between cognitive and MR measures. Among neuroimaging measures, central atrophy displayed the highest correlations with cognition, accounting for approximately half the variance in overall cognitive performance. NAA ratios in right hemisphere sites displayed larger correlations than those on the left. Multiple regression models combining the MR measures accounted for well over half the variance in overall cognitive performance. The Symbol Digit Modalities Test was the neuropsychological task most strongly associated with the neuroimaging variables. CONCLUSIONS: If a strong and stable association can be firmly established between cognitive and MR variables in appropriate subsets of MS patients, it might aid in the investigation of interventions to enhance cognition and modify the course of the disease.

Adult↗
PubMed2003

Wave initiation through spatiotemporally controllable perturbations.

We study the initiation of pulses and fronts in a two-dimensional catalytic reaction-diffusion system: CO oxidation on Pt(110). Using a computer-controlled mobile focused laser beam, we impart various patterns (in space and time) of localized temperature "kicks" to the surface. We explore, and also rationalize through modeling, the cooperativity of such individually subcritical perturbations in both the excitable and the bistable regime.

Journal Article↗
PubMed2003

Age dependence of in situ termostability of collagen in human bone.

The hypothesis of this study is that the in situ thermostability of collagen in bone changes with age and such changes relate to the structural properties of collagen and/or the interaction between the collagen and mineral phases. To test the hypothesis, the effect of age on the in situ thermostability of collagen in human bone and its correlation with the mineral and collagen phases were investigated. In this study, 30 human cadaveric femurs were collected and divided into three age groups: young adults (20-45 years), middle aged (46-69 years), and elderly (over 70 years of age). The in situ thermostability of collagen was assessed using high performance liquid chromatography (HPLC) in terms of the amount of heat-induced collagen denaturation at eight temperatures between 25 degrees C and 140 degrees C. In addition to the density and weight fraction of the mineral and organic phases, the concentration of collagen crosslinks was measured to assess the structural integrity of collagen. The results of this study indicate that the in situ thermostability of collagen increases with increasing age, and such age-related changes correlate with the following: collagen molecular structure, amount of noncalcified collagen, and the fraction and density of the mineral phase in bone. These results suggest that the age-related changes in the in situ thermostability of collagen most likely relate to the collagen structure and its interaction with the mineral phase. In addition, the bone remodeling process may play a role in the age-related changes in collagen thermostability because noncalcified collagen is commonly associated with this process.

Adult↗
PubMed2003

Gentle dragging of reaction waves.

Using a recently realized "addressable catalyst surface" [Science 294, 134 (2001)]] we study the interaction of chemical reaction waves with prescribed spatiotemporal fields. In particular, we study how a traveling chemical pulse is "dragged" by a localized, moving temperature heterogeneity as a function of its intensity and speed. The acceleration and eventual "detachment" of the wave from the heterogeneity is also explored through simulation and stability analysis.

Journal Article↗
PubMed2003

Changes in amount of bacteria during gut passage of leaf litter and during coprophagy in three species of Bibionidae (Diptera) larvae.

To elucidate the interaction between bacteria and saprophagous Diptera larvae, the amounts of bacteria in leaf litter, individual gut compartments, and feces of three species of Bibionidae (Bibio pomonae, Bibio marci, and Penthetria holosericea), feeding either directly on leaf litter or on fecal pellets produced from leaf litter by larvae of the same species, were assessed by determining total direct counts and viable counts on solid media at different pH. In P. holosericea, the effect of various cultivation temperatures on direct counts of bacteria in individual compartments was also demonstrated. In all species, the amount of bacteria in the anterior mesenteron was lower than in the consumed food, regardless of whether the larvae were feeding on leaf litter or feces, and increased again in the posterior part of the gut. The amount of bacteria in these compartments was generally higher in larvae feeding on feces than in those feeding on leaf litter, whereas the amount of bacteria found in the ceca varied. In B. marci, the amount of bacteria in the mesenteron sections able to grow on alkaline medium (pH 9) was higher than that of bacteria able to grow on slightly acidic medium (pH 5.5) during both the first and the second gut passage. In B. pomonae and P. holosericea, this increase was observed only during the second gut passage. The effect of gut passage in P. holosericea on changes in direct counts of bacteria was more pronounced when the larvae were fed at 5 degrees C as compared to 20 degrees C. Radiolabeled bacteria were digested in the gut and utilized as a source of energy and nutrients by the larvae; digested bacteria represented up to 10% of the material assimilated by the larvae. Lysozyme activity in whole-gut extracts of P. holosericea had a pH optimum of at pH 7, indicating a low in situ activity in the alkaline mesenteron. Proteinase activity, however, had an optimum at pH > 12, suggesting that the digestion of bacteria in the bibionid gut is caused by a combination of digestive proteinases and alkaline pH in the anterior mesenteron.

Animals↗
PubMed2003

The shape parameter of liposomes and DNA-lipid complexes determined by viscometry utilizing small sample volumes.

A minicapillary viscometer utilizing <0.5 ml of sample at a volume fraction of <0.1% is described. The calculated a/b of DPPC/DPPG multilamellar liposome was 1.14 as prolate ellipsoids and a/b of dioleoylpropyltrimethyl ammonium methylsulfate-DNA complex at a charge ratio of 4:1 (+/-) was 3.7 as prolate ellipsoids or 4.9 as oblate ellipsoids. The deviation of shape from perfect sphere is thus expressed quantitatively in more than two significant figures. In these measurement, the necessary amount of DNA is <0.5 mg.

Capillary Action↗
PubMed2003

Heme oxygenase type 2 modulates behavioral and molecular changes during chronic exposure to morphine.

The heme oxygenase (HO) enzyme system has been shown to participate in nociceptive signaling in a number of different models of pain. In these experiments we investigated the role of the HO type 2 (HO-2) isozyme in tolerance to the analgesic effects of morphine, and the hyperalgesia and allodynia which are measurable upon cessation of administration. Wild type C57Bl/6 wild type mice or HO-2 null mutants in that background strain were treated with morphine for 5 days. The morphine administration protocol consisted of either twice daily repeated s.c. boluses of 15 mg/kg or s.c. implantation of a morphine pellet. At the end of the treatment period wild type mice treated by either protocol exhibited tolerance, but the HO-2 null mutants did not. The HO-2 null mutants also exhibited less mechanical allodynia following cessation of morphine administration, though only modest differences in thermal hyperalgesia were noted. There was no correlation between the degree of tolerance obtained in the bolus and pellet protocols and the degree of hyperalgesia and allodynia observed after cessation of morphine administration in the wild type mice. Our final experiments analyzed increases in expression of mRNA for nitric oxide synthase type 1, N-methyl-D-aspartate (NMDA) receptor NMDAR1 subunit and prodynorphin in spinal cord tissue. In pellet-treated mice two- to three-fold increases were observed in the abundance of these species, but very little change was observed in the null-mutant mice. Taken together our results indicate that HO-2 participates in the acquisition of opioid tolerance, the expression of mechanical allodynia after cessation of opioid administration and in gene regulation occurring in the setting of treatment with morphine. Furthermore, these studies suggest that the mechanisms underlying analgesic tolerance and opioid-induced hypersensitivity are at least somewhat distinct.

Animals↗