Biomedical subjects

Na Li

Publications and source records attributed to Na Li.

At least 127 records · Page 7Linked to original sources

PubMed2003

Porphyrin assembly on beta-cyclodextrin for selective sensing and detection of a zinc ion based on the dual emission fluorescence ratio.

In the present paper, a new cyclodextrin/porphyrin supramolecular sensitizer for zinc ion has been proposed based on the porphyrin dual fluorescence emission ratio. In aqueous solution, meso-tetraphenylporphyrin shows weak fluorescence, while in the presence of alkylated beta-cyclodextrin, it exhibits significant fluorescence enhancement by forming a cyclodextrin/porphyrin inclusion complex. Furthermore, the formation of a supramolecular complex causes a remarkable increase of the porphyrin metalation rate following the porphyrin fluorescence emission changes at two different emission wavelengths. The fluorescence emission of tetraphenylporphyrin at 656-nm bands decreases while that at 606 nm increases upon zinc ion interaction. Thus, the inclusion complex can behave as a ratiometric fluorescent sensor. Theoretically derivative equations for fluorescent ratiometry have been proposed for the first time. The feasibility of the proposed method is demonstrated by the performance of fluorometric detection of zinc ion. With the optimum conditions described, zinc ion in aqueous solution can be determined from 5.0 x 10(-7) to 2.5 x 10(-4) M. As the porphyrin electronic absorption and fluorescence emission are located in the visible range, and the fluorescence changes upon zinc ion interaction show high selectivity over biologically relevant cations, the inclusion complex could be used for biomedical application.

Cyclodextrins↗

PubMed2003

Rayleigh light scattering study on the supramolecular interactions of beta-cyclodextrin derivatives with tetrakis(4-methoxylphenyl)porphyrin.

The supramolecular interactions of beta-cyclodextrin(beta-CD) and four kinds of alkylated beta-cyclodextrin (beta-CDs), i.e. heptakis (2,6-di-O-isobutyl)-beta-cyclodextrin (Ob-beta-CD), heptakis (2,6-di-O-n-octyl)-beta-cyclodextrin (Oc-beta-CD), heptakis (2,6-di-O-n-dodecyl)-beta-cyclodextrin (Od-beta-CD) and heptakis (2,6-di-O-n-hexadecyl)-beta-cyclodextrin (Oh-beta-CD) with tetrakis(4-methoxylphenyl)porphyrin (TMOPP) have been investigated by Rayleigh light scattering (RLS) technique. Beta-CDs form 2:1 inclusion complex with TMOPP following an obvious RLS enhancement of TMOPP. The inclusion abilities of different beta-CDs were compared. The results show that the inclusion ability of beta-CDs is related to the size of the alkylated substituent. Thus, a new mechanism of inclusion interaction has been proposed. The exact stoichiometric ratios and the association constants of the inclusion complexes have been examined by application of curve fitting method.

Cyclodextrins↗

PubMed2003

Dibenzylbutyrolactone and dibenzylbutanediol lignans from Peperomia duclouxii.

Nine new lignans (1-9), including five dibenzylbutyrolactones and four dibenzylbutanediols, were obtained from an ethyl acetate extract of the whole plants of Peperomia duclouxii. The structures of 1-9 were determined by spectroscopic methods (mainly extensive 1D and 2D NMR experiments and by mass spectral measurements). The absolute structures were elucidated as 2S,3S from their optical rotations and by chemical transformations.

4-Butyrolactone↗

PubMed2003

Modeling linkage disequilibrium and identifying recombination hotspots using single-nucleotide polymorphism data.

We introduce a new statistical model for patterns of linkage disequilibrium (LD) among multiple SNPs in a population sample. The model overcomes limitations of existing approaches to understanding, summarizing, and interpreting LD by (i) relating patterns of LD directly to the underlying recombination process; (ii) considering all loci simultaneously, rather than pairwise; (iii) avoiding the assumption that LD necessarily has a "block-like" structure; and (iv) being computationally tractable for huge genomic regions (up to complete chromosomes). We examine in detail one natural application of the model: estimation of underlying recombination rates from population data. Using simulation, we show that in the case where recombination is assumed constant across the region of interest, recombination rate estimates based on our model are competitive with the very best of current available methods. More importantly, we demonstrate, on real and simulated data, the potential of the model to help identify and quantify fine-scale variation in recombination rate from population data. We also outline how the model could be useful in other contexts, such as in the development of more efficient haplotype-based methods for LD mapping.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2003

Need to differentiate lethal toxin-producing strains of Burkholderia gladioli, which cause severe food poisoning: description of B. gladioli pathovar cocovenenans and an emended description of B. gladioli.

Burkholderia cocovenenans produces a lethal toxin (Bongkrekic acid) that leads to high fatality in food poisoning cases. However, B. cocovenenans was combined in Burkholderia gladioli in 1999. B. gladioli was originally described as a phytopathogenic bacteria that sometimes causes pneumonia in humans and that acts as an opportunistic pathogen. We thought that it was clinically dangerous to describe these two species without considering their pathogenicities. From our data of 16S rRNA sequence analysis, DNA-DNA hybridization, and fatty acid analysis, we could confirm that B. cocovenenans and B. gladioli should be categorized as a single species. However the species really weaved lethal toxin-producing strains with non-lethal strains. To emphasize that B. gladioli contains two different pathogens, we describe a new pathovar, B. gladioli pathovar cocovenenans, for the lethal toxin-producing strains. We provide characteristics that differentiate this lethal toxin-producing pathovar from other phytopathogenic pathovars within B. gladioli, together with an emended description of B. gladioli.

Animals↗

PubMed2003

Effect of immobilization site and membrane materials on multiphasic enantiocatalytic enzyme membrane reactors.

In the experimental work reported here the optical resolution of racemic naproxen methyl ester with crude lipase immobilized in a membrane reactor was studied. The multiphasic enantiocatalytic enzyme membrane reactor consisted of an organic phase that dissolved the naproxen methyl ester, a lipase-loaded membrane, and an aqueous phase that extracted the reaction product. Lipase preferentially converted the (S)-naproxen methyl ester to (S)-naproxen acid that was simultaneously separated by a membrane. The effect of the immobilization site and membrane type on the performance of the enzyme membrane reactor was studied. Capillary polyamide membrane with 10 kDa nominal molecular weight cutoff (NMWCO) and polysulfone membrane with 30 kDa NMWCO were applied, with lipase loaded in the sponge layer or on a membrane thin layer. With various immobilization sites and membrane types, the enzyme membrane reactors showed different productivity and enantioselectivity resulting from the varying amounts of immobilized enzyme and varying microenvironment of the hydrolysis reaction. Higher amounts of immobilized enzyme led to increased productivity and generally higher enantioslectivity of the membrane reactor. It seems that the location of organic/aqueous interface on membrane, which plays an important role in a multiphasic enzyme membrane reactor, was influenced by the immobilization site and membrane type and this affected the productivity and enantioselectivity. As much as 90% enantioexcess was obtained with a polyamide membrane, and lower values with a polysulfone membrane. A sponge layer of polyamide membrane is the preferred immobilization site for its higher productivity than a thin membrane layer, and for its higher enantioselectivity than a polysulfone membrane. In comparison with the unstable hydrolysis activity of free lipase in stirred tank reactor, a stable lipase activity can be obtained with the lipase-immobilized membrane reactor, irrespective of whether a polyamide or polysulfone membrane is used.

Bioreactors↗

PubMed2003

Rat corneal allograft survival prolonged by the superantigen staphylococcal enterotoxin B.

PURPOSE: The purpose of this study was to determine the optimal conditions for prolonging corneal allograft survival by inducing anergy with the superantigen staphylococcal enterotoxin B (SEB). METHODS: A rat model of penetrating keratoplasty, whereby Fisher344 donor corneas are implanted into Lewis recipients, was used to evaluate the effects of SEB on inhibiting immune-mediated allograft rejection. To induce anergy, SEB was injected into the peribulbar space of Lewis rats. Furthermore, histopathology and immunofluorescent staining were used to examine the levels of infiltrating CD4(+) and CD8(+) T lymphocytes and NK1.1(+) lymphocytes. RESULTS: By administering SEB, at doses of 90 or 120 micro g/kg 7 days before and after keratoplasty, we suppressed the episode of corneal graft rejection for a median of 12 and 30 days, respectively. In contrast, rejection was observed when 30 or 60 micro g/kg of SEB was administered. After SEB injections, lymphocyte infiltration into the corneal grafts was reduced, and the expression of NK1.1(+) lymphocytes was enhanced, suggesting that anergy may be occurring. Also, there were no differences in the number of infiltrating CD4(+) and CD8(+) T lymphocytes cells between the control group and groups injected with 30 and 120 micro g/kg SEB on postoperative days 10 and 30. CONCLUSIONS: Inducing anergy with the superantigen SEB prolonged corneal graft survival in a rat model of penetrating keratoplasty. Therefore, these results support the possibility of prolonging corneal allograft survival in a clinical setting by preventing immune-mediated rejection through the administration of the superantigen SEB.

Animals↗

PubMed2003

Synthesis of adenosine derivatives as transcription initiators and preparation of 5' fluorescein- and biotin-labeled RNA through one-step in vitro transcription.

Expanding our previous finding of an adenosine-initiated transcription system, we now demonstrate that either the 5' site or the N6 site of adenosine nucleotides can be modified extensively without abolishing their ability to initiate transcription under the T7 phi2.5 promoter. Two series of amino derivatives of adenosine nucleotides were synthesized. Fluorescein and biotin groups were coupled to AMP derivatives through linkers of different sizes and hydrophobicities. Both fluorescein- and biotin-conjugated (at either the 5' or N6 site) adenosine nucleotides can act as efficient transcription initiators, producing fluorescein- and biotin-labeled RNA at the specific 5' end by a one-step transcription procedure, eliminating posttranscriptional modification. Furthermore, N6-modified adenosine derivative-initiated transcription synthesizes 5' end modified RNA with a free phosphate group, providing the possibility for further derivatization. The current finding makes easily available a variety of site-specifically functionalized RNA, which may be used in nucleic acid detection, RNA structural and functional investigation, and generation and isolation of novel functional RNA.

Adenosine↗

PubMed2003

[Endoscopic optic nerve decompression in traumatic visual loss].

OBJECTIVE: To review our experience of treatment of optic nerve decompression in traumatic visual loss by using endoscopic technique. METHOD: Fourteen cases patients with traumatic visual loss were undergone endoscopic optic nerve decompression. All patients were followed up for 3-18 months. RESULT: Eight cases had improved visual acuity, and 6 cases did not. No complication had happened. CONCLUSION: Endoscopic optic nerve decompression is an appropriate technique for patients with traumatic visual loss. Even though high-dose steroid treatment has failed, optic nerve decompression may improve visual acuity.

Adolescent↗

PubMed2003

[Study on the auxochrome of the electronic spectrum of organic compounds and its effect mechanism (I)].

This paper discusses the effect mechanism of auxochrome of electronic spectrum. The study proves that the auxochrome does not invariably make the maximum absorption wavelength of chromophore shift towards lower photon energy. For the transition of n-->pi*, the p orbit of the auxochrome interacts with the minimum antibonding empty orbit(pi*), which will make the energy of pi* increase, while the p orbit of the auxochrome is perpendicular to the n orbit of chromophore, and the energy of the n orbit will remain steady ultimately, so the transition energy of n-->pi* will increase. For the transition of pi-->pi*, the interaction of p orbit of the auxochrome and maximum bonding orbit (pi) of the chromophore forms new orbits, so the energy of the maximum bonding orbit in new orbits will increase. In some compounds, the increase is higher than those of pi*, so the transition energy of pi-->pi* will decrease and absorption wavelength will shift towards lower photon energy, which, however, is reverse in other compounds.

English Abstract↗

PubMed2003

[The study of autonomic nervous activities in patients with obstructive sleep apnea syndrome].

OBJECTIVE: To explore the nocturnal variation of autonomic nervous system (ANS) in patients with obstructive sleep apnea syndrome (OSAS) and the transformation after surgery. METHOD: Sixty-one subjects with OSAS were recruited to undergo 7-hour nocturnal polysomnography(PSG) in sleep lab. Sixteen subjects with OSAS were performed PSG before and after UPPP. Sixteen subjects without OSAS were included as controls. Power spectrum analysis of heart rate variability (HRV) was performed in each subject. RESULT: The nocturnal of ANS activities were abnormal in patients with OSAS, especially the enhancement of sympathetic nervous activity. It increased gradually along with aggravating condition. The activities of sympathetic and vagus nerve were decreased significantly. CONCLUSION: There are abnormal ANS activities in patients with OSAS. Effective treatment of OSAS by surgery will significantly reduce the parameters of ANS, and redress the abnormality of heart rate and blood pressure.

Adult↗

PubMed2003

[Repair of severe blepharoptosis with a frontalis muscle complex suspension technique].

OBJECTIVE: To search an ideal method for treatment of severe blepharoptosis. METHODS: Fifty-four eyes of 47 patients with severe blepharoptosis were undergoing for the treatment with a frontalis muscle complex flap, included in the frontalis muscle, orbicularis oculi muscle and SMAS membranes, to suspend the dropped eyelids. RESULTS: The 54 eyes with severe blepharoptosis were successfully treated with the frontalis muscle complex suspension technique. Although the lagophthalmos in different degrees was shown in 3 months after the operation, it usually disappeared 6 months after the operation. The results were shown good appearance without recurrence. CONCLUSION: The above mentioned technique may be a good and effective method for treatment of the severe blepharoptosis, compared with the traditional technique.

Adolescent↗

PubMed2002

Transcriptional regulation of Fcgr2b gene by polymorphic promoter region and its contribution to humoral immune responses.

FcgammaRIIB1 molecules serve as negative feedback regulator for B cell Ag receptor-elicited activation of B cells; thus, any impaired FcgammaRIIB1 function may possibly be related to aberrant B cell activation. We earlier found deletion polymorphism in the Fcgr2b promoter region among mouse strains in which systemic autoimmune disease-prone NZB, BXSB, MRL, and autoimmune diabetes-prone nonobese diabetic, but not NZW, BALB/c, and C57BL/6 mice have two identical deletion sites, consisting of 13 and 3 nucleotides. In this study, we established congenic C57BL/6 mice for NZB-type Fcgr2b allele and found that NZB-type allele down-regulates FcgammaRIIB1 expression levels in germinal center B cells and up-regulates IgG Ab responses. We did luciferase reporter assays to determine whether NZB-type deletion polymorphism affects transcriptional regulation of Fcgr2b gene. Although NZW- and BALB/c-derived segments from position -302 to +585 of Fcgr2b upstream region produced significant levels of luciferase activities, only a limited activity was detected in the NZB-derived sequence. EMSA and Southwestern analysis revealed that defect in transcription activity in the NZB-derived segment is likely due to absence of transactivation by AP-4, which binds to the polymorphic 13 nucleotide deletion site. Our data imply that because of the deficient AP-4 binding, the NZB-type Fcgr2b allele polymorphism results in up-regulation of IgG Ab responses through down-regulation of FcgammaRIIB1 expression levels in germinal center B cells, and that such polymorphism may possibly form the basis of autoimmune susceptibility in combination with other background contributing genes.

Alleles↗

PubMed2002

Studies on a high encapsulation of colchicine by a niosome system.

To prepare niosomes which have high encapsulation capacity for soluble drugs, starting from Span 60 and cholesterol, an improved method, evaporation-sonication method, was proposed. The corresponding niosomes show a good stability at least 40 days. Colchicine was chosen as a model drug for examining the capsulation capacity of these niosomes. To obtain the highest encapsulation efficiency, several factors including the structure of surfactant, level of lipid, content of drug and cholesterol were investigated and optimized. The inner cause was also discussed. The results indicate that the Span 60 is the most ideal surfactant among four kinds of Span. Furthermore, the release studies of colchicine and 5-fluorouracil (5-FU) in vitro from niosomes exhibited a prolonged release profile as studied over a period of 24 h. The results demonstrated that niosomes prepared in this way not only have high encapsulation capacity but also is expected that side effects of drugs may be reduced. It still suggests that this method may be used extensively in the field of encapsulation soluble drugs.

Antimetabolites↗

PubMed2002

Intrapreoptic microinjection of TNF-alpha enhances non-REM sleep in rats.

Tumor necrosis factor-alpha (TNFalpha) is involved in sleep regulation. Peripheral or central administration of TNFalpha induces non-rapid eye movement sleep (NREMS) in many species. However, the brain site responsible for TNF-enhanced NREMS remains unclear. Thus, we tested the hypothesis that the preoptic area (POA) of the anterior hypothalamus, a crucial site for sleep regulation, is involved in TNF-induced sleep responses in rats. Unilateral microinjection of TNFalpha (2, 20 and 100 ng) or a TNF receptor fragment (TNFRF; 1.25, 5.0 and 12.5 microg) into the POA was performed at dark onset and light onset, respectively. The two higher doses of TNFalpha increased NREMS and brain temperature with little effect on REMS and EEG slow wave activity. These effects were lost after the heat-treatment of TNFalpha. The two higher doses of the TNFRF decreased NREMS without affecting the other parameters measured. Combined with previous results showing diurnal variations of TNFalpha in the hypothalamus, the present data suggest that POA TNFalpha is involved, in part, in the regulation of physiological sleep.

Animals↗

PubMed2002

[Treatment of xerophthalmia by transplantation of autologous vascularized submandibular gland].

OBJECTIVE: To investigate the feasibility of treatment of xerophthalmia by transplantation of autologous vascularized submandibular gland (SMG). METHODS: The SMGs of 19 patients with severe keratoconjunctivitis were transferred to their temporal region by microsurgery. The arteries and veins of the SMGs were anastomosed to the super-temporal arteries and veins, the SMG ducts were implanted into the conjunctival fornix of the eye. The saliva secreted by the SMG was used as the substitute of tear. RESULTS: The transplantation succeeded in 14 patients and failed in 4. Follow up lastred for 3 months to 2 years. The symptom of corneal xerosis disappeared, the symptoms of photophobia and anemophobia were alleviated, and artificial tear substitutes were not used any more. Epiphora appeared in 4 cases and disappeared after partial resection of the transplanted gland. Atresia of orifice occurred in one case and was cured by reconstruction of the duct. CONCLUSION: Transplantation of autologous vascularized SMG is effective in treating severe keratoconjunctivitis sicca.

Adolescent↗

PubMed2002

Molecular spectroscopic studies on the interaction of glycosaminoglycans with brilliant cresol blue and its analytical application.

The interaction of brilliant cresol blue (BCB) with glycosaminoglycans (GAGs), such as heparin (Hep) and chondroitin 4-sulfate (CS), in aqueous solution has been studied by spectrophotometry and light scattering spectroscopy. Absorbance of BCB at 632 and 594 nm decreased on addition of Hep or CS with the appearance of a new blue-shifted absorption band at 550 nm, which indicated that new metachromatic complex formed. The linear decrease in absorbance of BCB at 632 nm was observed. In addition, Hep was more effective than CS (1.7 times) in decreasing absorbance of BCB. The stoichiometry of Hep or CS with BCB was determined by spectrophotometric titration and the MacIntosh extraction method. The result showed that the stoichiometry of BCB/Hep was 1.8 times that of BCB/CS. These results suggested that the interaction between GAGs and BCB was the result of electrostatic forces, and the differences between Hep and CS were attributed to the different negative charge numbers on repetitive disaccharides unit. Studies on the effects of alcohol and urea indicated that GAGs only interacted with the aggregates of BCB. Moreover, a strong light scattering signal was observed after mixing BCB with GAGs. Furthermore, the light scattering intensity at light scattering bands was proportional to the concentration of Hep or CS added when the concentration of BCB was constant.

Chondroitin Sulfates↗

PubMed2002

Spectroscopic studies on the spontaneous assembly of phenosafranin on glycosaminoglycans templates.

Spectroscopic studies showed that binding of phenosafranin (PSF) molecules to glycosaminoglycans (GAGs) resulted in the following observations: (i) appearance of a 52.6 nm hypsochromic shift of the visible absorption band; (ii) static quenching of fluorescence from PSF; (iii) induction of strong circular dichroism (CD) signal of PSF. Stoichiometry of the PSF-GAGs complex was determined by spectrophotometric titration, spectrofluorimetric titration and MacIntosh extraction method. These studies demonstrated the formation of the extended helical PSF array aligned on the helical backbone of GAGs templates by electrostatic force, and the dimeric binding mode of PSF to each anionic site was proposed. The comparative studies between PSF-heparin (Hep) and PSF-chondroitin 4-sulfate (CS) complexes revealed that: (i) stoichiometry of PSF-Hep complex was 1.8 times of PSF-CS complex; (ii) Hep was more effective than CS (1.8 times) in decreasing the absorbance of PSF; and (iii) Stern-Volmer constants of the Hep-PSF system were greater than that of the CS-PSF system. These differences were attributed to the different charge density on the Hep and CS molecules, which in turn suggested that the electrostatic force was dominant in the interaction between PSF and GAGs.

Binding Sites↗