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Biomedical subjects

Y Fang

Publications and source records attributed to Y Fang.

At least 199 records · Page 11Linked to original sources
PubMed1996

[The dynamic change in the levels of hydroxyproline in the burned wound].

Hydroxyproline, the main component of collagen, and morphological changes were assayed dynamically in the superficial second-degree burn wounds of rats, with the aim to investigate the change in collagen and its relationship with epidermization of burn wound. The results are as follows. Epidermal layer was lacking and higher levels of OHP were noted in the early days postburn, OHP peaked on the 3rd day, declined to normal on day 10 and day 14 postburn, the latter event was in pace with the epidermization of the burn wound. These results indicated that the levels of collagen in the superficial second-degree burn wound were mainly regulated by epidermal cells. Epidermization might inhibit over-proliferation of collagen. Epidermal derived factor (EDF) might be the main factor regulating the synthesis of collagen in the superficial second-degree burn wound.

Animals↗
PubMed1996

Atomic force microscopic study on topological structures of pBR322 DNA.

Plasmid pBR322 DNA (0.5 mg/mL) isolated from Escherichia coli HB101 was suspended in Tris-HCI-EDTA (1 mol/L-0.1 mol/L, pH 8.5); then a drop of the above solution was deposited on freshly cleaved mica substrate. After adsorption for about 1 mm, the sample was stained with phosphotungstic acid. The residual solution was removed with a piece of filter paper. Afterwards the sample was imaged with a home-made atomic force microscope (AFM) in air. The AFM images of pBR322 DNA with a molecular resolution have been obtained. These images show that pBR322 DNA exists in several different topological structures: (i) relaxed circular DNA with a different diameter; (ii) supercondensed DNA with different particle sizes; (iii) dimeric catenane connected by one relaxed circular molecule and another close-compacted molecule which might be either supercoiled or intramolecular knotted form; (iv) oligomeric catenane with multiple irregular molecules in which DNA is interlocked into a complex oligomer; (v) possibly-existing intermediates formed from monomer to oligomer.

DNA, Bacterial↗
PubMed1996

[Pharmacological action of siwei shaoyao decoction].

The Siwei Shaoyao Decoction possesses a marked effect on the alleviation of trigeminal neuralgia in rats caused by penicillin G potassium injection. As shown from the hot-plate test, it also has an obvious analgesic effect on mice. To some extent, the decoction has a significant anti-inflammatory effect on the acute edema in hind paws of rats and the effect is believed to be related to the reduction of capillary permeability.

Animals↗
PubMed1996

[Shortening of Müller's muscle for the cure of sympathetic ptosis].

The procedure of shortening of Müller's muscle was performed on 23 eyes of 21 patients with sympathetic ptosis. All the patients obtained satisfactory results. The patient selection and the operation techniques were described. The pathogenesis of sympathetic ptosis and the physiological function of the Müller muscle were discussed. The authors believe that shortening of Müller's muscle is the best procedure for sympathetic ptosis.

Adolescent↗
PubMed1996

[Effects of wound wet dressing with cerium nitrate on cell-mediated immunity after severe burn].

Suppression of cell-mediated immunity (CM) and lowering of survival rate follow major thermal injury are associated with absorption of burn toxin. Wistar rats received 30% full-thickness burn, and were then treated with early burn excision or wet dressing of cerium nitrate for the wound. At day 14 postburn, both survival rates and peripheral blood Th/Ts rate were monitored. It was found that both excision and cerium nitrate could prevent marked lowering of survival rate and Th/Ts ratio were monitored. It was found that both excision and cerium nitrate could prevent markly lowering of survival rates and Th/Ts ratio induced by severe burn. This indicated that CE, in the early postburn days, may replace early burn excision to prevent the suppression of CMI following severe burn.

Animals↗
PubMed1996

[A morphometric study on hippocampus of epileptic rats induced by coriaria lactone].

This experiment was carried out with these rats were injected with 3.8 microliters (19 micrograms) convulsive dosage of coriaria lactone (CL) in the left cerebral motor cortex of the forelimb to induce acute focal epilepsy, while the other 5 rats as controls (no seizure) received normal saline solution of the same volume and at the same location. The brains were taken after seizuring for 60 min. The volume (water displacement method) and weight of the brain were measured. The brain was cut coronally and the structures of hippocampus were compared morphologically with those of the pair-matched control. The area of hippocampal formation was measured with paraffin section by test grid under 40x. The mean size (Feret's diameter) of pyramidal neurons in CA1 region was measured with semithin section by ocular micrometer under 1000x. The areal fraction of several organelles of the CA1 pyramidal cells was measured with EM negative film by magnifier. Under conditions of the consistent reference space, especially the size of CA1 pyramidal cells, the areal fraction of rough endoplasmic reticulum, lysosome and mitochondria increased significantly (P < 0.05) in epileptic rats. It indicated that their volume increased. The results show that certain ultrastructural changes have taken place after seizuring for 60 min.

Animals↗
PubMed1996

[Gas chromatographic analysis of molinate residue in rice].

We have developed a method for determining molinate residue in rice by gas chromatography. In our study, the rice sample was extracted with acetonewater (1 + 1). After filtering, the filtrate was acidified to pH 3.0-3.5 and re-extracted with petroleum. The extract was cleaned up on a florisil column and followed by analysis with GC/FPD. The linear range of the method was 0-5 micrograms/ml. the detection limit was 0.013 mg/kg for a rice sample of 20 g. The average recoveries of spiked samples ranged from 87.0%-96.7%. The relative deviation standard was less than 5.7%. The experimental verification of this method by extramural departments and its application to determination of rice samples demonstrate that this method is sensitive, reliable and suitable for analysis of molinate residue in rice.

Azepines↗
PubMed1996

[Failure in mastoidectomy with posterior canal wall preservation and tympanoplasty case analysis].

Preservation of the posterior canal wall in mastoidectomy is essential for rebuilding normal tympanum and conductive structures, and has been widely recommended. However, controversies remain about the technique due to its complications and diverse results reported. This paper analysed the causes of four failed cases in detail and proposed measure to reduce morbidities and promote success. The review includes case selection, operation staging, surgical techniques and lesion removal etc.

Adult↗
PubMed1996

[The discovery of a novel opioid-receptor-like receptor and its endogenous ligand].

A novel member of the opioid receptor family (orphan ORL receptor) was cloned in 1994, followed by the discovery of its endogenous ligand OFQ or nociceptin in 1995. ORL receptor has 50% homology with conventional opioid receptor, and OFQ is structurally homologous with dynorphin A. Whether the two systems are functionally antagonistic or synergistic with each other is a subject of future research.

Amino Acid Sequence↗
PubMed1995

Expression of synaptobrevin II, cellubrevin and syntaxin but not SNAP-25 in cultured astrocytes.

Astrocytes, a sub-type of glial cell in the central nervous system, can release the excitatory transmitters glutamate and aspartate in response to elevated levels of internal calcium. To investigate potential release mechanisms that may be present in these cells we have determined whether protein components of the neuronal secretory apparatus are expressed in astrocytes. Western blots, immunocytochemistry and RT PCR demonstrate that astrocytes express cellubrevin, synaptobrevin II and syntaxin, proteins known to form a macromolecular fusion complex. However, SNAP-25 which is another neuronal protein of the fusion complex, was not detected. Astrocyte cellubrevin and synaptobrevin II were also shown to be sensitive to the proteolytic activity of tetanus toxin. Together these data indicate that astrocytes express some proteins that are known to form a fusion complex indicating that regulated exocytosis might mediate calcium-regulated transmitter release from these cells.

Animals↗
PubMed1995

Use of non-cross-linked polyacrylamide for four-color DNA sequencing by capillary electrophoresis separation of fragments up to 640 bases in length in two hours.

Four-color DNA cycle sequencing was performed on an M13mp18 template using dye-labeled primers. Sequencing fragments were separated by capillary electrophoresis at 60 degrees C and at an electric field of 150 V/cm. The sieving medium was 5%T, non-cross-linked polyacrylamide in 7 M urea. The use of high temperature for the separation reduces formation of secondary structures in the sequencing fragments, generating a sequence that is free of compressions without the use of strongly denaturing gels. The use of high temperatures also increases the separation rate compared with room-temperature operation. Fragments up to 640 bases are separated in less than 2 h.

Base Sequence↗
PubMed1995

IL-12 inhibits IL-4 synthesis in keyhole limpet hemocyanin-primed CD4+ T cells through an effect on antigen-presenting cells.

Although IL-12 is known to enhance IFN-gamma synthesis in unprimed CD4+ T cells, the effect of IL-12 on IL-4 synthesis in primed CD4+ T cells, which are thought to have relatively fixed cytokine profiles, has not been clearly examined. We examined the effects of IL-12 on cytokine production by CD4+ keyhole limpet hemocyanin (KLH)-primed memory lymph node T cells and by already established KLH-specific CD4+ T cell clones. First, we found that the presence of IL-12 greatly reduced the development of IL-4 synthesis in resting but not activated memory CD4+ T cells. Although IL-12 did not inhibit the production of IL-4 in cloned Th2 effector cells, it greatly inhibited the development of IL-4 synthesis in primed CD4+ T cells taken from the lymph nodes of mice previously immunized with KLH. Secondly, we found that IL-12 inhibited IL-4 synthesis either when directly added to cultures of T cells or when APC were preincubated in IL-12. Inasmuch as the enhancing effect of IL-12 on IFN-gamma synthesis occurred optimally only when the T cells were cultured directly in IL-12, these studies indicate that IL-12 affects IL-4 synthesis via a mechanism that involves APC, a process that differs from that by which it affects IFN-gamma synthesis. These studies also indicate that the administration of IL-12 would be clinically useful in treating patients, for example those with allergic disease or lepromatous leprosy, in whom memory T cells inappropriately overproduce IL-4.

Animals↗
PubMed1995

IL-4 synthesis by in vivo-primed memory CD4+ T cells: II. Presence of IL-4 is not required for IL-4 synthesis in primed CD4+ T cells.

Previous studies have shown that the presence of IL-4 is required for the development of IL-4 synthesis in naive CD4+ T cells. The purpose of our current studies was to investigate the role of IL-4 in the development of IL-4 synthesis in primed memory T cells. We therefore examined CD4+ T cells taken from lymph nodes of BALB/c mice immunized with keyhole limpet hemocyanin (KLH) and restimulated in vitro with KLH. Our results with such primed resting CD4+ T cells programmed to produce IL-4 indicated that the production of IL-4 did not require the presence of IL-4 (although the presence of IL-2 was absolutely necessary), and was only slightly limited by the presence of anti-IL-4 MAb. These results with resting memory T cells were not biased by the presence of activated T cells already producing substantial quantities of IL-4, since we demonstrated that high-density memory T cells could produce IL-4 in the absence of IL-4, and because T cells that actively produce IL-4 do not persist in vivo very long after antigen exposure. These results indicate that IL-4 synthesis in T cells committed to IL-4 production can indeed occur in the absence of IL-4 when culture conditions have been optimized and suggest that therapies with anti-IL-4 MAb or with soluble IL-4 receptors designed to control the development of IL-4 synthesis in memory T cells from individuals exhibiting excessive IL-4 synthesis will be unsuccessful. Therefore, other therapies, for example, utilizing IL-12, will be required to modulate the relatively fixed programs in memory T cells that direct the development of cytokine synthesis.

Adjuvants, Immunologic↗
PubMed1995

IL-4-based helper activity of CD4+ T cells is radiation sensitive.

The capacity of CD4+ T cells to induce IgG synthesis in B cells has been known to be radioresistant for more than 20 years. However, the radiation sensitivity of helper T cells with regard to their ability to induce the synthesis of isotypes other than IgG has not been studied. We therefore irradiated KLH-primed lymph node T cells and examined their capacity to induce IgG, IgM, and IgE synthesis in hapten-primed B cells. We demonstrated that while the capacity of KLH-primed lymph node cells to induce IgG synthesis was not affected by irradiation, the capacity of such T cells to induce IgE synthesis was greatly reduced by gamma-irradiation. This was consistent with our observations that IL-4 and IL-5 synthesis in such cells was greatly diminished by irradiation, whereas IL-2 synthesis was only minimally affected. A similar differential sensitivity to irradiation of the helper activity of Th1 and Th2 clones was observed with regard to their ability to induce IgE and IgG synthesis under cognate conditions. Irradiation greatly inhibited the capacity of Th2 clones to induce IgE synthesis, but only minimally affected the capacity of Th1 clones to induce IgG synthesis in primed B cells. The capacity of irradiated Th2 clones to induce IgE synthesis was restored by the addition of IL-4 and IL-5. These results taken together indicated that the sensitivity to irradiation of T helper cells with regard to the induction of IgE but not IgG synthesis was due to the sensitivity to irradiation of the production of IL-4 but not of IL-2.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Effect of selective cytosine methylation and hydration on the conformations of DNA triple helices containing a TTTT loop structure by FT-IR spectroscopy.

5-Methylcytosines have been introduced into triplex-forming-oligonucleotides and shown to extend the pH range over which a triplex forms with a homopurine-homopyrimidine tract of duplex DNA. As a host strand, an oligodeoxypyrimidine with a base sequence of 5'-d(TC)3T4(CT)3 ([CC]) was designed to form a hairpin triplex with a 5'-d-A(GA)2G ([AG6]) purine strand at acidic pH (Tsay, et al., (1995) J. Biomol. Str. Dyn., 13, 1235-1245). We here present results obtained by FT-IR spectroscopy concerning the conformation of the hairpin triplex as a function of the selective substitution of cytosines by 5-methylcytosines in the host strand. Namely, cytosines are substituted by 5-methylcytosines in either the 3'-pyrimidine portion ([CM]) or the 5'-pyrimidine portion ([MC]) or in both ([MM]) of the host strand. The acidic-induced transitions of the equimolar mixtures of the purine target with either of the four pyrimidine oligomers gives rise to different apparent pK values, i.e., [MM].[AG6] (6.2) > [MC].[AG6] (6.0) > [CM].[AG6] (5.7) > [CC].[AG6] (5.2) > single-stranded oligopyrimidines (4.6 +/- 0.2), indicating that cytosine methylation expands the pH range compatible with the hairpin triplex formation regardless of whether the substitution is in the 5'-pyrimidine (Hoogsteen) portion or in the 3'-pyrimidine (Watson-Crick) portion. Thermal denaturation profiles indicated that all the triplexes denatured in a monophasic manner in the pH range of 4.0 to 7.0, and that cytosine methylations in any position of the 16-base pyrimidine oligomer increase the stability of the hairpin triplex DNA. IR spectra recorded in D2O and H2O solutions revealed that cytosine methylation does not significantly influence the conformation of triplex DNA in solution, i.e., all the four triplexes accept a similar sugar conformation, and predominately take on a S-type sugar pucker with a relative proportion of two S-type sugars for one N-type. Furthermore, we also investigated the effect of relative humidity (RH) on the conformation of triplex MC.AG6 in hydrated films, and found that the conformational change induced by the decrease of RH, from predominant S-type to primary N-type sugar pucker, might first occur in the purine strand at 86% RH.

Absorption↗
PubMed1995

Assessing horizontal transfer of nifHDK genes in eubacteria: nucleotide sequence of nifK from Frankia strain HFPCcI3.

The structural genes for nitrogenase, nifK, nifD, and nifH, are crucial for nitrogen fixation. Previous phylogenetic analysis of the amino acid sequence of nifH suggested that this gene had been horizontally transferred from a proteobacterium to the gram-positive/cyanobacterial clade, although the confounding effects of paralogous comparisons made interpretation of the data difficult. An additional test of nif gene horizontal transfer using nifD was made, but the NifD phylogeny lacked resolution. Here nif gene phylogeny is addressed with a phylogenetic analysis of a third and longer nif gene, nifK. As part of the study, the nifK gene of the key taxon Frankia was sequenced. Parsimony and some distance analyses of the nifK amino acid sequences provide support for vertical descent of nifK, but other distance trees provide support for the lateral transfer of the gene. Bootstrap support was found for both hypotheses in all trees; the nifK data do not definitively favor one or the other hypothesis. A parsimony analysis of NifH provides support for horizontal transfer in accord with previous reports, although bootstrap analysis also shows some support for vertical descent of the orthologous nifH genes. A wider sampling of taxa and more sophisticated methods of phylogenetic inference are needed to understand the evolution of nif genes. The nif genes may also be powerful phylogenetic tools. If nifK evolved by vertical descent, it provides strong evidence that the cyanobacteria and proteobacteria are sister groups to the exclusion of the firmicutes, whereas 16S rRNA sequences are unable to resolve the relationships of these three major eubacterial lineages.

Amino Acid Sequence↗
PubMed1995

Human alveolar macrophages present antigen ineffectively due to defective expression of B7 costimulatory cell surface molecules.

Alveolar macrophages, resident phagocytic cells in the lung that derive from peripheral blood monocytes, are paradoxically ineffective in presenting antigen to T cells. We found that antigen presentation by alveolar macrophages could be restored by the addition of anti-CD28 mAb to cultures of T cells and macrophages, indicating that costimulation by alveolar macrophages via the CD28 pathway was defective. In addition, we found that alveolar macrophages activated with IFN-gamma failed to express B7-1 or B7-2 antigens, which normally ligate CD28 on T cells and provide a costimulatory signal required for the activation of T cells. These observations are the first to demonstrate the inability of a "professional" antigen-presenting cell type to effectively express the costimulatory molecules B7-1 and B7-2. Inasmuch as immune reactions within the lung are inevitably associated with inflammatory injury to pulmonary tissue, these observations suggest that reduced expression of B7-1 and B7-2 by alveolar macrophages may be advantageous, as a critical mechanism involved in the induction of peripheral tolerance to the abundance of antigens to which mucosal tissues are continuously exposed.

Adult↗