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Biomedical subjects

Z Y Li

Publications and source records attributed to Z Y Li.

At least 73 records · Page 4Linked to original sources
PubMed1998

Effects of retinal laser photocoagulation on photoreceptor basic fibroblast growth factor and survival.

PURPOSE: In an unpublished study, the authors found that immunoreactivity for basic fibroblast growth factor (bFGF) is increased in rod photoreceptors adjacent to long-standing laser burns in human diabetic retinas. The goal of this study was to determine whether laser photocoagulation produces a similar increase in photoreceptor bFGF and promotes survival of these cells in dystrophic rodent retinas. METHODS: Threshold (whitening) and subthreshold (nonwhitening) laser burns were made in retinas of normal and Royal College of Surgeons (RCS) rats and normal and rds mice. The retinas were processed for immunocytochemical and morphometric analyses. RESULTS: In nonlasered normal rat and mouse retinas, bFGF immunoreactivity was prominent in the nuclei of Müller cells and astrocytes. Photoreceptors were bFGF negative except for a zone of bFGF-immunoreactive rods near the ora serrata. Some photoreceptors in nonlasered retinas of RCS rats and rds mice became bFGF immunoreactive. After laser treatment, bFGF immunoreactivity was markedly increased in all photoreceptors flanking the threshold burns and within the subthreshold burns in normal and mutant rats and mice. In RCS rat retinas, photoreceptor bFGF immunoreactivity remained elevated within subthreshold burns and flanking the threshold burns, and photoreceptor survival was prolonged. In rds mouse retinas, increased bFGF immunoreactivity in photoreceptors was not sustained and their degeneration was not retarded. CONCLUSIONS: Laser treatment of RCS rat retinas produced a sustained increase in bFGF immunoreactivity in photoreceptors and prolonged their survival, but laser treatment of rds mouse retinas did not have a long-term effect on photoreceptor bFGF immunoreactivity or survival. Although species differences in laser effects on photoreceptor bFGF and survival are apparent, the finding that rods flanking laser burns in human retinas have sustained increases in bFGF immunoreactivity suggests that laser treatment may be useful for prolonging survival of mutant photoreceptors in retinas of patients with retinitis pigmentosa.

Adult↗
PubMed1998

Rhodopsin transgenic pigs as a model for human retinitis pigmentosa.

PURPOSE: To further characterize the retinas of Pro3471Leu rhodopsin transgenic pigs, a model for human retinitis pigmentosa. METHODS: Retinas from normal and transgenic pigs, newborn to 20 months old, were processed for light and electron microscopic immunocytochemical examination. RESULTS: At birth, rod numbers were normal in the transgenic retinas, but their outer segments were short and disorganized and their inner segments contained stacks of rhodopsin-positive membranes. The newborn rod synapses lacked synaptic vesicles and ribbons and had numerous rhodopsin-positive, filopodia-like processes that extended past the cone synapses into the outer plexiform layer. Rod cell death was apparent by 2 weeks and was pronounced in the mid periphery and central regions by 6 weeks. Far peripheral rods were initially better preserved, but by 9 months virtually all rods had degenerated. Cones degenerated more slowly than rods, but by 4 weeks the cone synapses were shrunken and some mid peripheral cones had lost their immunoreactivity for phosphodiesterase-gamma, arrestin, and recoverin. From 9 months to 20 months, the cone outer segments shortened progressively, and more cones lost immunoreactivity for these proteins. CONCLUSIONS: The rhodopsin transgenic pig retina shares many cytologic features with human retinas with retinitis pigmentosa and provides an opportunity to examine the earliest stages in photoreceptor degeneration, about which little is known in humans. The finding of abnormal rhodopsin localization in newborn rods is consistent with misrouting of mutant rhodopsin as an early process leading to rod cell death. Novel changes in the photoreceptor synapses may correlate with early electrophysiological abnormalities in these retinas.

Animals↗
PubMed1997

Production and characterisation of a biosurfactant isolated from Pseudomonas aeruginosa UW-1.

Pseudomonas aeruginosa UW-1 produced 17-24 g L-1 rhamnolipid in vegetable oil-containing media in shake flask cultures in 13 days. In time course studies of growth and rhamnolipid production in a salts medium containing 6% canola oil, total bacterial count reached 2.6 x 10(10) CFU ml-1 after 48 h and a maximum rhamnolipid yield of 24.3 g L-1 was obtained after 9 days. Rhamnolipid components were purified and separated by chloroform-methanol extraction and TLC chromatography. The major rhamnolipid components were characterised as L-rhamnosyl-beta-hydroxydecanoyl-beta-hydroxydecanoate and L-rhamnosyl-L-rhamnosyl-beta-hydroxydecanoyl-beta-hydr oxydecanoate by nuclear magnetic resonance and mass spectrometry. The components were separated preparatively by silica gel column chromatography. The recovered monorhamnosyl fraction contained no dirhamnosyl moiety while the recovered dirhamnosyl fraction contained 5% of the monorhamnosyl moiety when analyzed by HPLC. The ratio of mono- to dirhamnosyl components produced by P. aeruginosa UW-1 was determined by HPLC to be 4:1 by weight. Purified mono- and dirhamnosyl components had the same CMC value of 40 micrograms ml-1 and decreased the surface tension of water to 27.7 and 30.4 dynes cm-1, respectively.

Chromatography, Thin Layer↗
PubMed1997

Effects of proteinosis surfactant proteins on the viability of rat alveolar macrophages.

Pulmonary alveolar proteinosis (PAP) is a disease of unknown etiology that is characterized by the accumulation of protein- and lipid-rich insoluble material in alveoli and terminal bronchioles of the lung. Alveolar macrophages (AM) in PAP are reportedly extremely large and have low viability. We investigated substances in lavaged lung material from patients with PAP that induced these cellular changes in rat AM. Rat AM were incubated for various periods with liposomes prepared from lipids and isolated hydrophobic surfactant apoproteins, and cell size, viability, and lactate dehydrogenase release were determined. Of the hydrophobic apoproteins, a dimeric form of surfactant-associated protein-C ([SP-C]2) had the most marked effects. In addition, [SP-C]2 induced increased superoxide anion release at an early phase (6 to 12 h) and an increase in glutathione content at 24 h of incubation. At 3 d after incubation, cellular glutathione and adenosine triphosphate (ATP) content were significantly decreased in cells treated with [SP-C]2, [SP-C]2 was presumed to cause early cell death through increased formation of superoxide anion and the subsequent derangement of cellular metabolism. [SP-C]2 was not removed from cells, and SP-B and SP-C were removed at slower rates than lipids. The changes in macrophages induced by [SP-C]2 may contribute to establishing PAP.

Adenosine Diphosphate↗
PubMed1997

[Generation of human monoclonal antibodies against hemorrhagic fever with renal sydrome (HFRS) virus].

Peripheral blood lymphocytes (PBL) were obtained from healthy donors and treated with L-leucy-leucin methy (LeuLeu-OMe). The LeuLeu-OMe treated PBL were in vitro immunized with HFRS virus proteins (55kD, 67kD) for 6 days, and then fused with K6H6/B5 cells in medium containing 45% (PEG) and 7.5% DMSO. The fused cells were seeded in 96-well plates at cell density 0.5-1 x 10(5) cells/well in HAT supplemented RPMI-1640 medium. After 14-20 days, 3 positive wells were deteced by ELISA and two (1B7, 2D5) of the 3 hybridoma were stable after 4 time cloning. The hybridoma 2D5 appears to be with high ability of production of the antibodies at a concentration of 20-30 microg/ml/10(6) cells/24h. It was proved by IFAT that 2D5 McAb was specific for HFRSV.

Antibodies, Monoclonal↗
PubMed1996

Mechanisms of triggered activity induction at the border zone of normal and abnormal cardiac tissue.

Ionic mechanisms that may be involved in inducing triggered activations at the border zone (BZTAs) of normal and abnormal Purkinje fiber segments were investigated. In a two-chamber bath, fibers were divided into a normal segment and segment treated with ethylenediaminetetraacetic acid to stimulate electrophysiologic alterations 24 hours after infarct. Interventions to normal segments included 1.8 mM lidocaine (n = 10), 3 x 10(-4) mM tetrodotoxin (n = 5), 10(-3) mM aconitine (n = 4), 3 mM cesium chloride (n = 7), 10(-2) mM verapamil (n = 4), and 6-8 mM (n = 7) of K+. Ethylenediaminetetraacetic acid (3.3 mM) prolonged action potentials and induced low diastolic potentials in the normal segment border zone. Tetrodotoxin, lidocaine, and high K+ levels suppressed BZTAs; cesium chloride and aconitine increased BZTAs; and verapamil did not reduce BZTAs. The finding that BZTAs were not abolished by verapamil suggests that abnormal automaticity is not a mechanism. Apparently, BZTAs depend on the Na+ inward current activated by depolarization of the membrane secondary to depolarization of adjacent cells.

Action Potentials↗
PubMed1996

Clinicopathologic effects of the Q64ter rhodopsin mutation in retinitis pigmentosa.

PURPOSE: To correlate retinal histopathology with functional changes caused by the rhodopsin Q64ter mutation. METHODS: A 50-year-old female heterozygote was evaluated clinically and with psychophysical and electroretinographic measurements of rod and cone function. The retinas obtained after death were examined microscopically, including immunolabeling with antibodies against the C- and N-termini of rhodopsin. RESULTS: On clinical examination 4 months before death, patient's acuity was 20/60, and she had midperipheral scotomas with retained function centrally and in the far periphery. The rod electroretinogram (ERG) was undetectable, and the cone ERG was reduced in amplitude with abnormal receptoral and postreceptoral responses. A previous study of the phenotype of mildly affected family members of the donor suggested that the rod outer segments (ROS) were shortened and that only wild-type rhodopsin was functional. The retinas contained only scattered cones in the midperiphery; the maculas and far peripheral regions contained reduced numbers of rods and cones with short to absent outer segments. The ROS appeared to contain wild-type, but not mutant, rhodopsin, and many peripheral rods had sprouted long rhodopsin-positive neurites that projected into the inner retina. Many cone synapses were abnormal, and the axons of some peripheral cones reached the inner plexiform layer. CONCLUSIONS: Microscopic changes in the donor retinas correlated well with the abnormalities in visual function in the patient donor and other family members. Postreceptoral ERG defects may relate to the abnormal photoreceptor processes found in the inner retina.

Aged↗
PubMed1996

Light-induced acceleration of photoreceptor degeneration in transgenic mice expressing mutant rhodopsin.

PURPOSE: Mutations at various loci on the rhodopsin gene have been shown to cause autosomal dominant retinitis pigmentosa (ADRP). One of the most common is a point mutation (P23H) near the N-terminus of the protein. The authors have studied the effects of light deprivation on the rate of degeneration in pigmented transgenic mice expressing the P23H mutation as well as two additional mutations near the N-terminus of opsin (V20G, P27L). METHODS: Transgenic and normal littermates were reared in darkness or in cyclic light (approximately 7 foot-candle) for periods of 2, 4, or 6 months. Retinal structure and function were evaluated by electroretinography, retinal densitometry, light microscopy, and TUNEL labeling. RESULTS: Retinas of normal animals, whether reared in darkness or in cyclic light, had no structural or functional abnormalities. The rate of photoreceptor degeneration in dark-reared transgenic mice was significantly slower than in transgenic mice raised under cyclic light conditions. Differences between the two groups of animals were evident in the retinal histology, the electroretinographically determined sensitivity to photic stimulation, and the rhodopsin levels in the retina. TUNEL labeling of retinal wholemounts showed that cyclic light-reared animals had a threefold higher incidence of photoreceptor cell death than their dark-reared counterparts; the density of apoptotic cells was greatest in the inferior retina, the region most severely affected in patients with the P23H mutation. In comparison, photoreceptor cell death was more uniformly distributed across the retina in dark-reared transgenic mice. CONCLUSIONS: These findings suggest that light activation of rhodopsin contributes to the severity of the degenerative disease resulting from the P23H opsin mutation, and they raise the possibility that minimizing exposure to light may help to prolong useful vision of patients with this form of retinitis pigmentosa.

Animals↗
PubMed1996

Sub-retinal pigment epithelial deposits in a dominant late-onset retinal degeneration.

PURPOSE: To determine the pathogenesis of an autosomal dominant late-onset retinal degeneration by studies of the retinal histopathology, phenotype of family members, and candidate genes for the disease. METHODS: The retina from an 80-year-old patient donor was prepared for light and electron microscopy, including special stains and immunocytochemistry. Family members were examined clinically and with retinal function tests. Rhodopsin, peripherin/RDS, and TIMP3 genes were screened for mutations, and linkage analysis was performed with short tandem repeat polymorphisms flanking these genes. RESULTS: Affected family members had nyctalopia in the sixth decade of life and severe visual loss developed by the eighth decade. The donor retina showed marked loss of photoreceptors except in the inferior periphery. A thick layer of extracellular deposits was present between the RPE and Bruch's membrane in all retinal regions. A 70-year-old affected family member had a retinopathy resembling retinitis pigmentosa. Her 42-year-old daughter had a patch of punctate yellow-white lesions in one fundus and abnormal dark adaptation. The 50-year-old son of the donor had normal fundi but abnormal dark adaptation and electroretinography. No mutations were detected in the coding sequence of the rhodopsin, peripherin/RDS, and TIMP3 genes. Rhodopsin and TIMP3 were further excluded with linkage analysis. CONCLUSIONS: This novel retinal degeneration shares histopathologic and clinical features with both Sorsby fundus dystrophy and retinitis pigmentosa. The sub-RPE deposits may disrupt the exchange of nutrients and metabolites between the retina and the choriocapillaris, leading to photoreceptor dysfunction and degeneration.

Adult↗
PubMed1996

Purification and characterization of lupus anticoagulant like protein from Agkistrodon halys brevicaudus venom.

By means of CM-Sephadex C-25, DEAE-Sephadex A-50, Sephadex G-200, and Sephadex G-75 chromatographies, a lupus anticoagulant like protein (LALP) from Agkistrodon halys brevicaudus was purified. On SDS-PAGE, the purified LALP had a molecular weight of 25,500 daltons under non-reducing condition and 15,000 daltons under reducing condition. The isoelectric point was pH 5.6. Its N terminal amino acid sequencing revealed a mixture of 2 sequences: DCP(P/S)(D/G)WSSYEGH(C/R)(Q/K). It was devoid of phospholipase A, fibrino(geno)lytic, 5'-nucleotidase, L-amino acid oxidase, phosphomonoesterase, phosphodiesterase and thrombin-like activities, which were found in crude venom. In the presence of LALP, PT, aPTT, and dRVVT of human plasma were markedly prolonged and its effects were concentration-dependent but time-independent. The inhibitory effect of LALP on the plasma clotting time was enhanced by decreasing phospholipid concentration in TTI test. The individual clotting factor activity was not affected by LALP when higher dilutions of LALP-plasma mixture were used for assay. Russell's viper venom time was shortened when high phospholipid confirmatory reagent was used. Therefore, the protein has lupus anticoagulant property.

Agkistrodon↗
PubMed1995

Histopathology of bone spicule pigmentation in retinitis pigmentosa.

PURPOSE: To evaluate bone spicule pigmentation, a fundus feature in retinitis pigmentosa (RP) formed by migration of pigment-containing cells to perivascular sites in the inner retina. METHODS: The authors performed light and electron microscopy, including immunocytochemistry, on the retinas from ten patients with RP and five normal donors. RESULTS: The pigment-containing cells in regions of bone spicule pigmentation were derived from the retinal pigment epithelium (RPE). The translocated cells were remarkably polarized with a number of specializations characteristic of RPE cells in situ, but they did not contain lipofuscin granules and were not immunoreactive for cellular retinaldehyde-binding protein. The cells were linked by junctional complexes and formed epithelial layers around retinal vessels and next to the inner limiting membrane. Adjacent Müller cell processes contained glial fibrillary acidic protein-positive filaments and formed microvilli and intermediate junctions, resembling those in the external limiting membrane. Vascular endothelial cells adjacent to the translocated RPE cells were thin and fenestrated, resembling the choriocapillaris, and were separated from the pigmented cells by a layer of extracellular matrix similar in organization to Bruch membrane. Thickening of the matrix layer caused narrowing and occlusion of the vascular lumina. CONCLUSIONS: The lack of lipofuscin granules and cellular retinaldehyde-binding protein immunoreactivity in the translocated RPE cells is probably related to the loss of photoreceptors. The development of fenestrations in the endothelial cells correlates with the leakiness of retinal vessels to fluorescein observed in some cases of RP. Narrowing and occlusion of vascular lumina by thickening of the surrounding layer of extracellular matrix may contribute to the loss of inner retinal neurons found in RP. These changes in the RPE, blood vessels, glia, and inner neurons warrant consideration in designing therapies to restore vision to degenerate retinas.

Adult↗
PubMed1995

Rod photoreceptor neurite sprouting in retinitis pigmentosa.

In animal models for retinitis pigmentosa (RP), rod photoreceptors show abnormal distribution of rhodopsin prior to undergoing cell death. To elucidate the steps in degeneration of human photoreceptors, immunocytochemistry was performed on donor retinas from 15 RP patients and five normal subjects. Rhodopsin immunolabeling in the normal retinas was restricted to the rod outer segments. In the RP retinas, rhodopsin was present in shortened rod outer segments and in the surface membranes of the rod inner segments and somata. In regions of photoreceptor death, the surviving rods had sprouted rhodopsin-positive neurites that were closely associated with gliotic Müller cell processes and extended to the inner limiting membrane. Rods and cones in the RP maculas did not form neurites, but the axons of peripheral cones were abnormally elongated and branched. Double immunofluorescence labeling showed that the rod neurites bypassed the horizontal and rod bipolar cells that are normally postsynaptic to rod axons. To our knowledge, this is the first report of rod neurite sprouting in vivo. We were unable to find neurites on degenerate rods in old rds mice, an animal model for RP. The rod neurites in the human RP retinas resemble the long, branched processes formed by rods cultured on Müller cells or purified N-CAM. Neurite growth by surviving rods in the RP retinas may be a response to neurotrophic factor upregulation, loss of inhibitory factors, or changes in molecules associated with reactive Müller cells. Such changes in the retinal microenvironment may impede functional integration of transplanted photoreceptors. The contributions of the rhodopsin-positive rod neurites and abnormal cone axons to the functional abnormalities observed in RP are unknown.

Adult↗
PubMed1995

Dissection of LPS-induced signaling pathways in murine macrophages using LPS analogs, LPS mimetics, and agents unrelated to LPS.

The model in Figure 3 summarizes the data presented above. Using the induction of the select panel of LPS-inducible genes and the phosphorylation on tyrosine of specific MAP kinases, we have been able to dissociate three signaling pathways shared by LPS and its analogs and mimetics: a pathway that leads to tyrosine phosphorylation, one that leads to the induction of a gene subset including TNF alpha, TNFR-2, and IL-1 beta, and a pathway that results in induction of IP-10, D3, and D8 gene expression. It is still unclear if macrophage activation by non-LPS products occurs entirely through distinct yet redundant pathways or if other signaling receptors ultimately tie into the same intermediate pathways. This approach may identify particular stimuli as tools to induce specific pathways leading to select gene subsets and/or tyrosine kinase activation and, perhaps, identify a pathway deficient in C3H/HeJ macrophages.

Animals↗
PubMed1994

Complete DNA sequence of yeast chromosome II.

In the framework of the EU genome-sequencing programmes, the complete DNA sequence of the yeast Saccharomyces cerevisiae chromosome II (807 188 bp) has been determined. At present, this is the largest eukaryotic chromosome entirely sequenced. A total of 410 open reading frames (ORFs) were identified, covering 72% of the sequence. Similarity searches revealed that 124 ORFs (30%) correspond to genes of known function, 51 ORFs (12.5%) appear to be homologues of genes whose functions are known, 52 others (12.5%) have homologues the functions of which are not well defined and another 33 of the novel putative genes (8%) exhibit a degree of similarity which is insufficient to confidently assign function. Of the genes on chromosome II, 37-45% are thus of unpredicted function. Among the novel putative genes, we found several that are related to genes that perform differentiated functions in multicellular organisms of are involved in malignancy. In addition to a compact arrangement of potential protein coding sequences, the analysis of this chromosome confirmed general chromosome patterns but also revealed particular novel features of chromosomal organization. Alternating regional variations in average base composition correlate with variations in local gene density along chromosome II, as observed in chromosomes XI and III. We propose that functional ARS elements are preferably located in the AT-rich regions that have a spacing of approximately 110 kb. Similarly, the 13 tRNA genes and the three Ty elements of chromosome II are found in AT-rich regions. In chromosome II, the distribution of coding sequences between the two strands is biased, with a ratio of 1.3:1. An interesting aspect regarding the evolution of the eukaryotic genome is the finding that chromosome II has a high degree of internal genetic redundancy, amounting to 16% of the coding capacity.

Base Composition↗
PubMed1994

Autosomal dominant retinitis pigmentosa caused by the threonine-17-methionine rhodopsin mutation: retinal histopathology and immunocytochemistry.

The retinas from a 68-year-old man with autosomal dominant retinitis pigmentosa caused by the threonine-17-methionine rhodopsin mutation were studied. Patients with this mutation have a characteristic clinical phenotype that shows intra- and interfamilial consistency. The retinas were examined by light and electron microscopy, including immunocytochemistry with markers for rods, cones, the retinal pigment epithelium, the interphotoreceptor matrix and Müller cells, and the results were correlated with those from visual function tests performed fourteen months before death. Grossly, both retinas had heavy deposits of bone spicule-like pigmentation inferiorly, but the superior retinas showed much less pigmentation. The maculas contained no rods and an incomplete monolayer of cone somata, consistent with the patient's severely reduced central vision. The inferior retinas contained no rods and rare cone somata, correlating with an absolute scotoma in the superior field. The superior retinas had near-normal-appearing rods and cones in the far periphery and a gradient from the midperipheral to central retina of progressively shortened outer segments and loss of photoreceptors, consistent with the patient's reduced rod and cone electroretinograms and retained rod and cone sensitivities in the inferior peripheral field by perimetry. Immunocytochemistry with rod-specific markers was qualitatively normal in the superior mid to far peripheral retina. Electron microscopic immunogold labeling with anti-rhodopsin revealed similar densities of gold particles over rod outer segments of the RP and a normal donor retina. Degenerate photoreceptors in the superior equatorial region of the RP retina had short outer segments, and some rods had surface labeling with anti-rhodopsin of the inner segments, somata and synapses. The results indicate regional retinal differences of disease severity in this genotype and that rods in the superior peripheral retina have normal morphology despite the presence of the mutant allele. To the authors' knowledge, this is the first detailed study of rod photoreceptors in the retina of an RP patient with a rhodopsin mutation.

Aged↗
PubMed1994

Production of docosahexaenoic acid by Thraustochytrium roseum.

When three Thraustochytrium stains were cultivated in liquid media containing 2.5% starch and 0.2% yeast extract, initial pH 6.0, with shaking under fluorescent light for five days at 25 degrees C, similar biomass yields were observed (9.7-10.3 g L-1). Contents of docosahexaenoic acid (DHA) in biomass varied: 0.15, 3.55 and 6.40% w/w for T. striatum ATCC 24473. T. aureum ATCC 34304 and T. roseum ATCC 28210, respectively. In further studies, T. roseum produced a maximum titer of 0.85 g of DHA per liter of culture broth. The DHA content of total lipids ranged from 46-49% w/w.

Culture Media↗