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Biomedical subjects

S Chen

Publications and source records attributed to S Chen.

At least 829 records · Page 46Linked to original sources
PubMed1997

Edema formation exacerbates neurological and histological outcomes after focal cerebral ischemia in CuZn-superoxide dismutase gene knockout mutant mice.

In a variety of studies. CuZn-superoxide dismutase (CuZn-SOD) has been shown to protect against ischemic brain injury. A possible role for CuZn-SOD-related modulation of neuronal viability has been suggested by the finding that CuZn-SOD inhibits brain edema formation following various kinds of neurological insults. We have evaluated the role of CuZn-SOD on brain edema formation following focal cerebral ischemia in mice bearing a disruption of the CuZn-SOD gene (Sod1). Homozygous mutants (Sod1-/-) had no detectable CuZn-SOD activity and heterozygous mutants (Sod1+/-) showed a 50% decrease compared to wild-type mice. Sod1-/- mice showed a high level of blood-brain barrier (BBB) disruption shortly after 1 hr of middle cerebral artery occlusion and 100% mortality at 24 hr following ischemia. Sod1+/- mice showed a moderate level of BBB disruption and 30% mortality. The Sod1+/- animals had increased infarct volume and brain swelling, accompanying exacerbated neurological deficits at 24 hr following ischemia. These results indicate the important role of superoxide anions in the development of brain edema after focal cerebral ischemia and suggest the possibility that brain edema formation may contribute to the exacerbation of ischemic brain injury and neurological deficits in knockout mutant mice.

Animals↗
PubMed1997

Anti-lipid peroxidization effect of huangdan on chronic renal failure in rats.

The activity of superoxide dismutase (SOD) in renal cortex and erythrocytes, the level of lipid peroxidant (LPO) in plasma, renal function and morphology of leftover kidney were examined in rats. The results showed that Huangdan capsule could slow down the increase of BUN and Scr, promote the SOD activity in renal cortex and erythrocytes, reduce the level of LPO in plasma and delay the renal pathological changes in 5/6 nephrectomized rats. The mechanism of Huangdan capsule's antiperoxidant effect, its effect on the renal pathological changes and relationship between the two effects were also discussed.

Animals↗
PubMed1997

Tandem mass spectrometric approach for determining structure of molecular species of aminophospholipids.

Aminophospholipids, including glycerophosphatidylethanolamine, glycerophosphatidylserine and their Lyso analogous, have been analyzed by positive and negative ion liquid secondary ion ionization coupled to tandem mass spectrometry. The mass spectra of aminophospholipids obtained by tandem mass spectrometers with different configuration (liquid secondary ion-electric-magnetic sector coupled to quadrupole mass analyzer (low-energy collision) or electric-magnetic sector (high-energy collision), as well as electrospray ionization-quadrupole mass analyzer combined with quadrupole mass analyzer (low-energy collision), are compared. The mass spectra produced by low-energy collisionally induced dissociation of the deprotonated molecules from aminophospholipids contain fragment ions for characterizing polar head moieties as well as fatty acid composition and position. The mass spectra generated by high-energy collisionally induced dissociation of both protonated and deprotonated molecules from aminophospholipids show numerous product ions for identifying polar heads, composition, and location of fatty acid chains in molecular species. Triple quadrupole mass spectrometer with electrospray ionization exhibits remarkable superiority in detection sensitivity. Liquid secondary ion with electric-magnetic sector coupled to quadrupole mass analyzer or electric-magnetic sector instrument has the advantage of the capability of properly determining location of fatty acid chains in molecular species. This paper also describes an approach for structurally analyzing aminophospholipid species as 9-fluorenylmethyloxycarbonyl derivatives by positive and negative ion liquid secondary ion mass spectrometry and high-energy collisionally induced dissociation tandem mass spectrometry. It has been found that the derivatives of glycerophosphatidylethanolamine and glycerophosphatidylserine can readily be analyzed by the negative ion liquid secondary ion and tandem mass spectrometric methods.

Lysophospholipids↗
PubMed1997

Changes in the leukocyte phenotype profile of goats infected with the caprine arthritis encephalitis virus.

The proportions of different sub-populations of leukocytes in five healthy goats and five goats infected with the caprine arthritis encephalitis virus (CAEV) were examined using immunofluorescence and flow cytometry. A panel of monoclonal antibodies that identified a monocytegranulocyte marker (GMI); the CD4, CD8, IgM, MHC Class I, MHC Class II and T19 antigens, and the gamma delta (gamma delta) T cell receptor was used. We observed a significant (P = 0.016) reduction in the proportion of monocytes in the peripheral blood of infected (5.98%) compared with healthy control goats (9.92%). There was also a decrease in the proportion of CD4+ T lymphocytes that approached significance (P = 0.076) accompanied by a slight increase in the proportion of CD8+ T lymphocytes, in infected compared with uninfected animals. Consequently, three of the five infected animals had lower CD4:CD8 ratios than any of the healthy animals and two of these three ratios were inverted. Approximately 14% of T cells in the peripheral blood of healthy goats was identified as gamma delta T cells and all expressed the T19 antigen. A significantly elevated level of gamma delta T cells (P = 0.030) and an elevated level of T19 cells were observed in infected, compared with healthy animals. The proportion of leukocytes expressing surface IgM (B cells) was also elevated, although not significantly, in CAEV-infected compared to healthy controls. The changes in peripheral blood leukocyte subsets in infected goats suggest that immune responses to the infection are probably altered in these animals with eventual progression to severe disease and death.

Animals↗
PubMed1997

Plasmalemmal ATPase calcium pump localizes to inner and outer hair bundles.

Recent studies demonstrate calcium ion influx at the tips of hair cell stereocilia during mechano-transduction. These ions must be either pumped from the cytosol into the extracellular space or endoplasmic envelope, or else sequestered by binding to specific proteins. A plasma membrane calcium pump (ATPase-type) was analysed in whole-mounts of rat organ of Corti using a monoclonal antibody to a large cytoplasmic loop of this protein. The reactivity was particularly high on the tips of longer stereocilia and was found along the shafts. Inner hair cell stereocilia had much less reactivity than outer hair cells. The reactivity lined the plasma membrane of inner hair cell bodies while a higher reactivity appeared in the cytoplasm of outer hair cells. Supporting cells were unreactive. Ultrastructural examination confirmed the plasma membrane calcium pump location on stereocilia and along the endolymph surface of receptor cells. Reaction product lined the plasma membrane of stereocilia as intense puncta. More reactive puncta occurred near the distal ends of stereocilia and the number decreased toward the ciliary base. The endolymph plasma membrane over the cuticular notch was especially reactive. The finding of more intense pump reactivity at the tips of stereocilia than the base is consistent with the hypothesis that during transduction, calcium ions enter stereocilia, distally, and the ATPase plasma membrane calcium pump rapidly extrudes these ions to the extracellular space.

Adenosine Triphosphatases↗
PubMed1997

Overlapping ipsilateral and contralateral retinal projections to the lateral geniculate nucleus and superior colliculus in the cat: a retrograde triple labelling study.

To analyze the relative proportion and distribution of retinal ganglion cells projecting ipsilaterally and contralaterally in the cat, large injections of the fluorescent tracers Fluoro Gold, Fast Blue, and Diamidino Yellow were made in the main layers of the lateral geniculate nucleus (LGN) and superior colliculus (SC). One tracer was injected in both the LGN and SC on one side, and the other two tracers were injected contralaterally, in the LGN and SC, respectively; labelled ganglion cells were charted on retinal whole mounts. Ganglion cells labelled from the LGN and SC were highly intermingled in both the ipsilateral and contralateral retinae. The adopted combinations of tracers allowed the detection of cells double labelled from the SC and LGN, supporting the occurrence of branched retino-thalamic axons to the SC. About one-fourth of the ganglion cells labelled from the LGN and SC was located in the eye ipsilateral to the injection. Retrograde labelling from the ipsilateral side was almost entirely confined to the temporal hemiretina. In the contralateral eye, labelled cells were mainly concentrated in the nasal hemiretina, but more than 10% were also detected in the temporal half of the retina. In the latter area, cells displaying the entire range of sizes of the retinal ganglion cells, labelled from the contralateral LGN and SC, were found throughout the entire hemiretina. However, more than 50% of such "wrong" projecting cells were grouped in a strip of 2 mm closest to the nasotemporal division. Control experiments, in which the tracers injections were restricted to the rostral and dorsal portions of the LGN to avoid optic tract contamination, consistently confirmed the occurrence and distribution of the "wrong" projecting cells in the temporal hemiretina. Thus, these latter cells are not grouped in a central strip, where ganglion cells would have the same chance of projecting to the same or to the opposite side, and sparsely distributed in the temporal periphery, as previously believed. Instead, the present findings indicate that the retinal ganglion cells of origin of contralateral projections are distributed more in a continuum, with a naso-temporal gradient of density, across the temporal hemiretina.

Animals↗
PubMed1997

Crx, a novel Otx-like paired-homeodomain protein, binds to and transactivates photoreceptor cell-specific genes.

The otd/Otx gene family encodes paired-like homeodomain proteins that are involved in the regulation of anterior head structure and sensory organ development. Using the yeast one-hybrid screen with a bait containing the Ret 4 site from the bovine rhodopsin promoter, we have cloned a new member of the family, Crx (Cone rod homeobox). Crx encodes a 299 amino acid residue protein with a paired-like homeodomain near its N terminus. In the adult, it is expressed predominantly in photoreceptors and pinealocytes. In the developing mouse retina, it is expressed by embryonic day 12.5 (E12.5). Recombinant Crx binds in vitro not only to the Ret 4 site but also to the Ret 1 and BAT-1 sites. In transient transfection studies, Crx transactivates rhodopsin promoter-reporter constructs. Its activity is synergistic with that of Nrl. Crx also binds to and transactivates the genes for several other photoreceptor cell-specific proteins (interphotoreceptor retinoid-binding protein, beta-phosphodiesterase, and arrestin). Human Crx maps to chromosome 19q13.3, the site of a cone rod dystrophy (CORDII). These studies implicate Crx as a potentially important regulator of photoreceptor cell development and gene expression and also identify it as a candidate gene for CORDII and other retinal diseases.

Amino Acid Sequence↗
PubMed1997

Mutations in the cone-rod homeobox gene are associated with the cone-rod dystrophy photoreceptor degeneration.

Crx is a novel paired-like homeodomain protein that is expressed predominantly in retinal photoreceptors and pinealocytes. Its gene has been mapped to chromosome 19q13.3, the site of a disease locus for autosomal dominant cone-rod dystrophy (CORDII). Analysis of the proband from a family with autosomal dominant CORD revealed an Arg41Trp substitution in the third residue of the CRX homeodomain. The sequence change cosegregated with the disease phenotype and was not detected in 247 normal controls. Recombinant CRX homeodomain containing the Arg41Trp substitution showed decreased DNA binding activity. Analysis of another 169 CORD probands identified three additional CRX sequence variations (Arg41Gln, Val242Met, and a 4 bp deletion in codons 196/7) that were not found among the controls. This data suggests that mutations in the CRX gene are associated with photoreceptor degeneration and that the Crx protein is necessary for the maintenance of normal cone and rod function.

Adult↗
PubMed1997

Aldehyde and phosphinate analogs of glutathione and glutathionylspermidine: potent, selective binding inhibitors of the E. coli bifunctional glutathionylspermidine synthetase/amidase.

INTRODUCTION: The tripeptide glutathione is converted to glutathionylspermidine (Gsp) in Escherichia coli and in trypanosomatid parasites by an ATP-cleaving Gsp synthetase activity. In parasites, an additional glutathionylation forms bis-(glutathionyl)-spermidine, trypanothione, believed to be the major surveillance thiol involved in oxidant defense mechanisms in trypanosomatid parasites. In E. coli, the Gsp synthetase is part of a bifunctional enzyme opposed by the hydrolytic Gsp amidase. RESULTS: Gsp amidase and Gsp synthetase activities of the bifunctional E. coli enzyme can be separately targeted by potent, selective slow-binding inhibitors that induce time-dependent inhibition. The inhibitor gamma-Glu-Ala-Gly.CHO most probably captures Cys59 and accumulates as the tetrahedral adduct in the amidase active site. Inhibitory Gsp phosphinate analogs are phosphorylated by ATP to yield phosphinophosphate analogs in the synthetase active site. Binding of phosphinophosphate in the Gsp synthetase active site potentiates the inhibition affinity for the aldehyde at the Gsp amidase active site by two orders of magnitude. CONCLUSIONS: Time-dependent inhibition of the Gsp amidase activity by the aldehyde substrate analog supports previous work that suggests glutathionyl acyl-enzyme intermediate formation in the Gsp amidase reaction mechanism. Use of potent selective inhibitors against Gsp amidase (aldehyde) and Gsp synthetase (phosphinate) activities provides further evidence of interdomain communication in the bifunctional enzyme from E. coli.

Aldehydes↗
PubMed1997

Methionine aminopeptidase (type 2) is the common target for angiogenesis inhibitors AGM-1470 and ovalicin.

BACKGROUND: Angiogenesis, the formation of new blood vessels, is essential for tumor growth. The inhibition of angiogenesis is therefore emerging as a promising therapy for cancer. Two natural products, fumagillin and ovalicin, were discovered to be potent inhibitors of angiogenesis due to their inhibition of endothelial cell proliferation. An analog of fumagillin, AGM-1470, is currently undergoing clinical trials for the treatment of a variety of cancers. The underlying molecular mechanism of the inhibition of angiogenesis by these natural drugs has remained unknown. RESULTS: Both AGM-1470 and ovalicin bind to a common bifunctional protein, identified by mass spectrometry as the type 2 methionine aminopeptidase (MetAP2). This protein also acts as an inhibitor of eukaryotic initiation factor 2alpha (elF-2alpha) phosphorylation. Both drugs potently inhibit the methionine aminopeptidase activity of MetAP2 without affecting its ability to block elF-2alpha phosphorylation. There are two types of methionine aminopeptidase found in eukaryotes, but only the type 2 enzyme is inhibited by the drugs. A series of analogs of fumagillin and ovalicin were synthesized and their potency for inhibition of endothelial cell proliferation and inhibition of methionine aminopeptidase activity was determined. A significant correlation was found between the two activities. CONCLUSIONS: The protein MetAP2 is a common molecular target for both AGM-1470 and ovalicin. This finding suggests that MetAP2 may play a critical role in the proliferation of endothelial cells and may serve as a promising target for the development of new anti-angiogenic drugs.

Affinity Labels↗
PubMed1997

Genetic engineering of bacteria and their potential for Hg2+ bioremediation.

Ion exchange or biosorptive processes for metal removal generally lack specificity in metal binding and are sensitive to ambient conditions, e.g. pH, ionic strength and the presence of metal chelators. In this study, cells of a genetically engineered Escherichia coli strain, JM109, which expresses metallothionein and a Hg2+ transport system after induction were evaluated for their selectivity for Hg2+ accumulation in the presence of sodium, magnesium, or cadmium ions and their sensitivity to pH or the presence of metal chelators during Hg2+ bioaccumulation. The genetically engineered E. coli cells in suspension accumulated Hg2+ effectively at low concentrations (0-20 microM) over a broad range of pH (3 to 11). The presence of 400 mM sodium chloride, 200 mM magnesium chloride, or 100 microM cadmium ions did not have a significant effect on the bioaccumulation of 5 microM Hg2+, indicating that this process is not sensitive to high ionic strength and is highly selective against sodium, magnesium, or cadmium ions. Metal chelators usually interfere with ion exchange or biosorptive processes. However, two common metal chelators, EDTA and citrate, had no significant effect on Hg2+ bioaccumulation by the genetically engineered strain. These results suggest that this E. coli strain could be used for selective removal of Hg2+ from waste water or from contaminated solutions which are resistant to common treatments. A second potential application would be to remove Hg2+ from Hg(2+)-contaminated soil, sediment, or particulates by washing them with a Hg2+ chelator and regenerating the chelator by passing the solution through a reactor containing the strain.

Cadmium↗
PubMed1997

Rectal immunization for induction of specific antibody in the genital tract of women.

The purpose of the current study was to examine potential routes of vaccine administration for the induction of antigen-specific responses in the genital tract of women. Sixteen women were enrolled in this study, and the level of influenza-specific antibodies induced in the genital tract was measured after rectal or intramuscular immunizations. Both methods of administration induced significant increases in the concentration of flu-specific IgA found in cervical secretions within 28 days after vaccination. Initially flu-specific IgG antibodies were not induced in the genital tract by either route. As expected both IgA and IgG flu-specific antibodies were dramatically increased in serum after intramuscular vaccination. In contrast, rectal administration did not induce significant IgA responses, and only small flu-specific IgG increases in serum. Six months after administration, IgA flu-specific antibody concentrations were significantly higher than baseline levels in vaginal secretions and saliva isolated from both subject groups and flu-specific IgG concentrations in cervical secretions were high in the rectal immunization group. The long-term presence of both IgG and IgA antibody in genital secretions suggests that rectal immunization may be an effective method for induction of immune protection in the genital tract of women.

Administration, Rectal↗
PubMed1997

Inhibition of COMT induces dopamine-dependent natriuresis and inhibition of proximal tubular Na+,K+-ATPase.

The enzyme catechol-O-methyltransferase (COMT), which plays an important role for dopamine metabolism, is abundantly expressed in the kidney. To test whether the natriuretic effects of dopamine may be related to the rate of dopamine metabolism, rats were treated with nitecapone, a peripheral inhibitor of COMT. Nitecapone, given by gavage, induced a highly significant (5.6-fold) increase in sodium excretion, which was associated with an inhibition of the Na+,K+-ATPase activity in both the proximal convoluted and proximal straight tubules (PCT and PST, respectively). These effects were completely abolished if the rats were also treated with a specific dopamine 1 antagonist, SCH 23390. Furthermore, the natriuretic effect of nitecapone was also observed in rats on a high salt diet. The kidney-specific pro-drug to dopamine, glu-dopa, induced a significant, but less pronounced increase in urinary sodium excretion, associated with a dopamine-dependent inhibition of the Na+,K+-ATPase activity in the PCT but not in the PST. Nitecapone and glu-dopa had an additive natriuretic effect. It is concluded that COMT plays an important role in determining the natriuretic effects of the renal dopamine system.

Animals↗
PubMed1997

A rapid, sensitive and automated method for detection of Salmonella species in foods using AG-9600 AmpliSensor Analyzer.

The AG-9600 AmpliSensor Analyzer is an automated fluorescence-based system for detection of polymerase chain reaction (PCR) products. The principle of the AmpliSensor PCR assay involves amplification-mediated disruption of a fluorogenic DNA signal duplex (AmpliSensor) that is homologous to a target sequence within a 284-bp amplified fragment of the Salmonella invA gene. Since the assay is homogenous, the data can be obtained by direct measurement of fluorescence of the amplification mixture. The accumulation of the amplified product, reflected by the fluorescence index, is monitored cycle by cycle by the AG-9600 Analyzer. The detection limit of the assay was less than 2 colony-forming units (cfu) per PCR reaction using a pure culture of Salmonella typhimurium. In post-spiking experiments in which Salmonella was added to the overnight pre-enriched samples (chicken carcass rinses, ground beef, ground pork and raw milk), the detection limit of the assay was 2-6 cfu per PCR reaction. In pre-spiking experiments in which Salmonella was added to the samples prior to overnight pre-enrichment, the detection limit was less than 3 cfu per 25 g or 25 ml of food. The assay was up to 2 orders of magnitude more sensitive than detection by ethidium bromide-stained agarose gel electrophoresis. To further evaluate assay performance, 54 naturally contaminated chicken carcass rinses, 65 raw milk and six ground pork samples were tested in the study. Thirty-eight Salmonella-positive samples confirmed by the Modified Semi-solid Rappaport-Vassiliadis (MSRV) culture assay were found positive using the AmpliSensor assay. Two chicken carcass rinses found positive using the assay were MSRV-negative. In addition, relative quantification using the AmpliSensor assay was linear up to 3 logs of initial target concentration in artificially contaminated food samples.

Animals↗
PubMed1997

Stem cells of the corneal epithelium lack connexins and metabolite transfer capacity.

The stem cells of the corneal epithelial lineage are confined to the basal cell layer of the limbus, a vascularized outer corneal rim. These slow cycling cells of great proliferative potential maintain the corneal epithelial mass. Since cell-cell communication plays an important role in development and differentiation, we conducted a comparative examination of the expression of two corneal connexins, C x 43 and C x 50, and the tracer transfer capacity of the limbal and corneal epithelia using the scrape loading technique. C x 43 is abundantly expressed in the basal cell layer of the epithelium covering the cornea, but is essentially absent from the mouse, human, neonatal rabbit, and chicken limbal epithelium. In the adult rabbit the limbal epithelium displays an overall weak C x 43 immunoreactivity, but C x 43-free isolated basal cells can be distinguished. C x 50 is expressed throughout the corneal epithelium of the three mammalian corneas, but is not detectable in the limbus. Scrape loading experiments in the rabbit yielded results which were consistent with the immunohistological findings; limbal epithelium lacked tracer (lucifer yellow) transfer capacity, strongly suggesting the absence of functional gap junctions. Altogether, our results demonstrate the incompetence of stem cells for gap junction-mediated cell-to-cell communication. This property may reflect the need of these unique cells to maintain a distinct intracellular environment.

Aged↗
PubMed1997

A low conductance chloride channel in the basolateral membranes of the non-pigmented ciliary epithelium of the rabbit eye.

PURPOSE: Chloride efflux plays an important role in aqueous humor production. Chloride currents have been described in bovine non-pigmented ciliary epithelium (NPE), in transformed cultured human NPE, and in bovine volume-activated chloride channels described in the latter. It is the basolateral membranes of the NPE of ocular ciliary processes that comprise the exit pathway for the process of aqueous secretion performed by the double syncytial layer of ciliary epithelium, however. Therefore, we studied both cell-attached, and, excised, inside-out patches from basolateral membranes of the NPE. METHODS: Cell-attached and cell-free excised patches were formed from the basolateral membranes of NPE and single channel currents recorded with a Dagan 3900A patch clamp amplifier. RESULTS: A low conductance channel of 14 pS was observed and recorded in 30% of cell attached patches and in 35% of excised inside out patches under symmetrical conditions (160 mM chloride). This channel displayed a nearly linear current-voltage relationship, with an open probability that was not voltage-dependent. The channel was chloride-selective: N-methyl-D-glucamine (NMDG) used as cation did not alter the current profile nor the reversal protein. Further, with inside-out patches, the reversal potential was close to zero (0.3 +/- 0.5 mV (10) in symmetrical (160 mV) chloride, but shifted to -32.3 +/- 0.5 mV (5) when the concentration of chloride in the bathing solution was reduced to 40 mM while the recording pipette was held at 160 mM. This value approaches the theoretical equilibrium potential of chloride for these conditions. The channel anion permeability sequence was: I- > NO3- > or = Br- > Cl- > gluconate- approximately equal to aspartate-. Three different chloride-channel blockers inhibited the channel activity. CONCLUSION: A low conductance channel, selective for chloride, and, modulated by beta adrenergic and VIP stimulation, based on it sensitivity to exogenously added cAMP, ATP and the catalytic subunit of PKA, is present in the exit basolateral membranes of rabbit NPE and contributes to the process of aqueous humor formation.

Adenosine Triphosphate↗
PubMed1997

Isolation and characterization of anti morphine analgesic peptide from canine brain.

The anti-morphine peptide from canine brain, which is homologous to alpha subunit of hemoglobin of canine, has been isolated and characterized. The canine brain was homogenized and extracted in 0.1 M acetic acid. The supernatant was collected, and purified by chromatography of Sephadex G-50 and ion-exchange and RP-HPLC. A polypeptide was then obtained, which is termed as AMP5. It shows prominent antimorphine analgesic activity. AMP5 has an apparent molecular mass of 10.23kD. The isoelectric point was estimated to be around pH 6.7 by IEF. The amino acid composition of AMP5 and sequence of the N-terminal 50 amino acid residues was determined.

Amino Acid Sequence↗