Biomedical subjects

S H Liu

Publications and source records attributed to S H Liu.

At least 91 records · Page 5Linked to original sources

PubMed1997

The in vivo effect of lipopolysaccharide on neuromuscular transmission in the mouse.

The in vivo effect of lipopolysaccharide (endotoxin) on nerve-evoked muscle contractions and neuromuscular transmission was studied in the mouse phrenic nerve-diaphragm preparations. In lipopolysaccharide-treated mouse diaphragms it was observed that indirectly induced twitch tension was unchanged while tetanic tension significantly decreased. Neostigmine (50 nM) increased the amplitude of nerve evoked muscle contractions, while it caused partial fade of tetanic contractions (Wedensky inhibition) and accelerated the run-down of end-plate potentials (e.p.ps) evoked by repetitive nerve stimulation, in the diaphragm of saline-control mice, but not of lipopolysaccharide-treated mice. These effects of neostigmine could be abolished by ouabain (5 microM). Measurement of the quantal contents of e.p.ps revealed that ouabain (5 microM) significantly increased it in the diaphragm of saline-control mice to an extent similar to that in diaphragm of lipopolysaccharide-treated mice. Moreover, ouabain-sensitive Na+, K(+)-ATPase activity in the sciatic nerve of lipopolysaccharide-treated mice was markedly decreased. The alterations in neuromuscular transmission of the diaphragm during endotoxemia could be reversed by the administration of polymyxin B (a lipopolysaccharide neutralizer) and NG-nitro-L-arginine (a nitric oxide (NO) synthase inhibitor), suggesting that NO is involved in these lipopolysaccharide-induced alterations of neuromuscular transmission mediated by an impairment of ouabain-sensitive Na+, K(+)-ATPase activity in mouse motor nerves.

Animals↗

PubMed1997

Distinct genotoxicity of phenylmercury acetate in human lymphocytes as compared with other mercury compounds.

In the present study, the frequency of sister chromatid exchanges (SCEs) was assayed to evaluate the genotoxic effects of mercury nitrate (Hg2+), methylmercury chloride (CH3HgCl and phenylmercury acetate (PMA) on human lymphocytes. The free radical scavengers, catalase (CA) and superoxide dismutase (SOD) were tested for their antigenotoxic effects toward PMA. PMA (1-30 microM) increased SCE frequency in a concentration-dependent manner. However, CH3HgCl significantly increased SCE frequency only at a concentration of 20 microM, and all concentrations treated with Hg2+ did not induce a positive effect. On the other hand, we first reported that 30 microM Hg2+, 20 microM CH3HgCl and (3-30 microM) PMA significantly increased the frequency of endoreduplicated mitosis. PMA was about 3- or 5-fold more effective in inducing endoreduplication than CH3HgCl or Hg2+ at equivalent toxic concentrations, respectively. However, neither CA nor SOD in concentrations of 75 and 150 microg/ml showed antagonistic action on the genotoxic effects of PMA. The results suggest that the mechanism of PMA-induced genotoxicity is not mediated by superoxide anion nor H2O2. It is concluded that PMA, which was more effective in inducing the elevation of both SCEs and endoreduplication, may be especially hazardous of the three mercury compounds tested.

Adult↗

PubMed1997

Primary immunolocalization of androgen target cells in the human anterior cruciate ligament.

To identify androgen target cells in the human anterior cruciate ligament, immunohistochemical localization of the androgen receptor was performed in 31 specimens of the ligament. All of the specimens were obtained at surgery. Seventeen specimens were from women, and 14 were from men: the average age of the patients was 45.2 years (range: 18-78 years). An immunoperoxidase method using monoclonal antibodies to the androgen receptor was employed to identify androgen target cells in the ligament. Consistent staining of the androgen receptor was demonstrable in six specimens obtained from young men 18-24 years old, and equivocal positive staining was seen in two other specimens from young men. No receptors were demonstrated by this method in any of the specimens from women or older men. Androgen receptors were localized to synoviocytes in the synovium and under the synovial lining, fibroblasts in the ligament stroma, and cells lining the blood-vessel walls of the anterior cruciate ligament. The demonstration of androgen receptors in the cells of the anterior cruciate ligament strongly suggests that male sex hormones may have an effect on the structure and composition of this ligament in young men.

Adolescent↗

PubMed1997

Involvement of nitric oxide in the in vivo effects of lipopolysaccharide on the contractile and electrical properties of mouse diaphragm.

The contractile and electrical properties of the mouse diaphragm during endotoxemia were studied, and the possible role of nitric oxide (NO) on these changes was investigated. The mice were injected intraperitoneally with E. coli. lipopolysaccharide (endotoxin, LPS) at various times before isolation of the diaphragm to induce endotoxemia. It was observed that direct twitch tension was slightly increased, and that there was a significant increase in tetanic tension when compared with controls. The potentiation of direct twitch tension induced by a Cl--channel blocker (9-anthracene carboxylic acid), but not the potentiation by a Na+-channel activator (veratridine) or by K+-channel blockers (uranyl ion, 4-aminopyridine and tetraethylammonium ion), was attenuated in the diaphragm of LPS-treated mice. Moreover, the resting membrane potential was significantly reduced and the membrane input resistance was significantly increased, largely due to a decrease in Cl--conductance. However, the membrane K+-conductance remained unaltered. These results imply that the sarcolemmal Cl--channel is markedly affected in the mouse diaphragm during endotoxemia. These changes of contractile and electrical characteristics of the mouse diaphragm during endotoxemia could be reversed by treatment with dexamethasone and N(G)-nitro-L-arginine (NO synthase inhibitors). On the other hand, in in vitro studies, LPS (20 microg/ml), by itself, applied directly to the diaphragm, did not alter the muscle contractions or the membrane potentials. A NO donor, added to the diaphragm bath, increased the tetanus/twitch ratio and induced a transient depolarization. All of these findings suggest that LPS may, at least in part, affect the sarcolemmal electrical properties and muscle contractions during endotoxemia through the L-arginine:NO pathway.

Animals↗

PubMed1997

Enhancement by nitric oxide of neurogenic contraction in the mouse urinary bladder.

In isolated detrusor strips from the mouse urinary bladder, contractile responses to electrical field stimulation were mostly mediated by neurally released acetylcholine and ATP. The aim of this study is to investigate the possible role of nitric oxide (NO) involved in the neurogenic detrusor contraction. Repetitive electrical field stimulation evoked muscle contractions of the isolated mouse detrusor strips, which could be abolished by tetrodotoxin (TTX). NO donors including sodium nitroprusside (SNP) and S-nitroso-N-acetyl-penicillamine (SNAP) as well as exogenous NO increased, while hemoglobin and NO synthase inhibitor N(G)-nitro-L-arginine decreased the neurogenic detrusor contractions. The addition of L-arginine reversed the inhibitory effect of N(G)-nitro-L-arginine. SNP failed to affect the contractions induced by carbachol and alpha,beta-methylene ATP. These findings suggest that NO potentiated the excitatory neuromuscular transmission in electrically stimulated detrusor strips from the mouse.

Animals↗

PubMed1997

Destruction of a cyropreserved meniscal allograft: a case for acute rejection.

A cryopreserved nontissue-antigen-matched medial meniscus was transplanted arthroscopically into the knee of a 33-year-old cyclist. The patient had previously had an open medial menisectomy 19 years earlier and had significant symptoms. Ten weeks postoperatively, the patient underwent a second-look arthroscopy for a persistent effusion. Intraoperative cultures were obtained and all ultimately tested negative. The graft was found to be frayed throughout its length and significantly decreased in size. Its central portion had become detached from the peripheral repair while both the anterior and posterior bone blocks remained intact. Dense, inflammatory, hypertrophic synovium enveloped the entire joint. Histologically, the graft was found to be necrotic and acellular centrally, whereas the periphery was infiltrated with inflammatory leukocytes and giant cells. This histologic appearance is classical for an acute or subacute type rejection of allograft tissue.

Acute Disease↗

PubMed1997

Cloning and expression of bovine corneal antigen cDNA.

PURPOSE: A cornea-associated antigen (CO-Ag) has been found to be the target for autoantibodies in patients with Mooren's ulcer. The study goals were to isolate a full-length clone encoding CO-Ag from a bovine corneal cDNA library and to express this clone in Escherichia coli (E. coli). METHODS: A DNA fragment of CO-Ag was generated, using unique oligonucleotide primers and reverse transcription polymerase chain reaction. This fragment was used as a probe to obtain cDNA clones from a bovine corneal cDNA library. The clone with the longest cDNA insert was selected for sequence analysis. Expression of the CO-Ag protein in E. coli was induced by isopropyl beta-D-thiogalactopyranoside (IPTG). The bacterially-produced CO-Ag was partially purified by calcium (Ca2+)-dependent hydrophobic interaction chromatography. RESULTS: The cDNA insert sequence was 273 nucleotides in length for the entire mRNA coding region, 212 nucleotides in the 5' untranslated region, 83 nucleotides in the 3' untranslated region and a poly(A) tail. The DNA base sequence of this clone also contained a standard initiation codon, termination codon, and the polyadenylation signal. This cDNA predicts a protein which contains 91 amino acids with a molecular weight of 10,584 daltons. The cDNA and deduced amino acid sequence of CO-Ag are completely identical to a S-100 protein, bovine calgranulin C. The cDNA was expressed in E. coli as a fusion protein consisting of 583 N-terminal amino acids of beta-galactosidase (beta-gal), 91 amino acids of CO-Ag, and possibly a number of additional N-terminal and C-terminal residues. The bacterially produced CO-Ag was fully functional with respect to hydrophobic interaction with phenyl-Sepharose matrix for its isolation. The fusion protein was recognized by antiserum raised against bovine CO-Ag protein on Western blots. CONCLUSIONS: The isolation and analysis of a cDNA clone containing the complete coding sequence of the CO-Ag protein and the expression of the CO-Ag protein in E. coli is reported. The availability of a CO-Ag cDNA probe and larger quantities of the CO-Ag protein should aid in elucidating the possible pathogenic role of CO-Ag in Mooren's ulcer.

Amino Acid Sequence↗

PubMed1997

Morphology and matrix composition during early tendon to bone healing.

This study outlines the early morphologic phenomenon of tendon to bone healing in the rabbit model. Twelve skeletally mature, male New Zealand White rabbits received transplantation of the hallucis longus tendon into a 2-mm calcaneal bone tunnel. The morphologic characteristics of the healing tendon to bone interface were evaluated at 1, 2, 4, and 6 weeks after surgery by the use of conventional histology and immunohistochemical localization of collagen Types I, II, and III. Histologic analysis illustrated progressive maturation and reorganization of the tendon to bone interface with subsequent development of tissue collagen fiber continuity between the tendon and bone. Initially, diffuse immunolocalization of all three collagen types was observed within the scar tissue filling the space between the tendon and bone. During a 6-week period, reorganization of the scar tissue into an interface occurred, similar to an indirect insertion. Although a definitive fibrocartilage region did not form, Type II collagen was localized at the remodeling insertion site throughout the first 6 weeks of repair. In addition, Type III collagen fibers, resembling Sharpey's fibers, were noted to span this interface. The characterization of the insertion between tendon and bone is important to the understanding of healing in commonly used orthopaedic grafting procedures, such as anterior cruciate ligament reconstructions.

Animals↗

PubMed1997

Inhibition of replication of hepatitis B virus by cytallene in vitro.

The acyclic cytosine nucleoside analog cytallene [1-(4'-hydroxy-1',2'-butadienyl)cytosine], which has both (+)- and (-)-enantiomers, was evaluated for its anti-hepatitis B virus (HBV) activity in 2.2.15 cells and was found to have potent activity against HBV DNA synthesis. The R-(-)-enantiomer was found to be the more active of the cytallene enantiomers, with a 50% inhibition concentration against HBV synthesis (HBIC50) of 0.08 microM. Its antiviral activity could be reversed by deoxycytidine (dC) and less efficiently by cytidine. Upon removal of the R-(-)-enantiomer from culture medium, the synthesis of HBV DNA could reinitiate, which suggested that the antiviral action is reversible. The R-(-)-enantiomer was also found to be more cytotoxic than the S-(+)-enantiomer. The degree of cytotoxicity varied among the cell lines, with a 50% inhibition of cell growth at greater than 10 microM. The R-(-)-enantiomer had no effect on HBV RNA synthesis and mitochondrial DNA synthesis at a concentration of 10 times or more than the HBIC50. The two enantiomers cannot be deaminated by dC deaminase, and they can be phosphorylated by cytoplasmic dC kinase. The R-(-)-enantiomer of cytallene is the first acyclic cytosine analog with potent inhibitory activity against HBV similar to those of other L-(-)-ddC analogs.

Antiviral Agents↗

PubMed1997

Contribution of the anterolateral joint capsule to the mechanical stability of the ankle.

Published reports describe the clinical efficacy of modified Brostrom anatomic repairs, surgical procedures that involve repair and fortification of the lateral capsuloligamentous complex of the ankle for patients suffering from chronic lateral instability of this joint. A cadaveric serial sectioning study of the anterior talofibular ligament, the calcaneofibular ligament, and the remainder of the anterolateral joint capsule was completed to quantitate the contribution of the superior portion of the anterolateral joint capsule, independent of the other two structures, to the overall mechanical stability of the lateral ankle. Using 20 fresh frozen specimens, talar tilt and anterior drawer stress radiographs were taken before and after sectioning these anatomic structures in an order established by one of two protocols. Sectioning of the superior anterolateral joint capsule caused 17% to 18% of the total displacement in a Grade II sprain simulation and 29% to 33% of the total displacement in a Grade III sprain simulation. This work suggests that disruption of the segment of ankle joint capsule superior to the anterior talofibular ligament creates approximately 30% of the overall laxity encountered in a Grade III inversion sprain, substantiating the principle of restoring the integrity of the entire anterolateral joint capsule when operating on a chronically unstable ankle.

Ankle Joint↗

PubMed1997

Fibroblast growth factor and epidermal growth factor receptors in ligament healing.

Although recent in vivo studies indicate that basic fibroblast growth factor hastens the healing and strength of the medical collateral ligament after injury, in vitro studies with epidermal growth factor and basic fibroblast growth factor have shown increased fibroblast proliferation with the exogenous administration of these growth factors. Using an established spontaneously healing rabbit injury model, the surgical transection of the medial collateral ligament was undertaken in 12 anesthetized male adult rabbits. Immunohistochemical localization using monoclonal antibodies to the basic fibroblast growth factor receptor and epidermal growth factor receptor were used to identify the distribution and relative concentrations of the individual receptors at 3, 7, 14, and 28 days after surgery. Realizing that the trophic effects of basic fibroblast growth factor and epidermal growth factor are determined exclusively by their individual receptors, this study confirms the hypothesis that basic fibroblast growth factor and epidermal growth factor receptor proteins are present and increase during the early stages of medial collateral ligament healing. The understanding of this rabbit ligament injury model has far reaching implications to ligament healing seen in humans. By elucidating the spatial and temporal regulation of the basic fibroblast growth factor and epidermal growth factor receptor proteins, exogenous growth factor therapy, once approved for human use, potentially can be synchronized with maximal protein receptor levels.

Animals↗

PubMed1997

Cloning and sequence analysis of human and bovine corneal antigen (CO-Ag) cDNA: identification of host-parasite protein calgranulin C.

PURPOSE: The primary structure of a cornea-associated antigen (CO-Ag) has been identified and has been implicated in the pathogenesis of Mooren's ulcer. The study designs were to isolate full-length clones encoding CO-Ag from a bovine and a human corneal cDNA library so that complete sequence analyses might further define the possible role of this protein in Mooren's ulcer. METHODS: DNA fragments of bovine and human CO-Ag were generated using unique oligonucleotide primers and reverse transcription polymerase chain reaction. These fragments were used as probes to obtain cDNA clones from a bovine and a human corneal cDNA libraries. The clones with the longest cDNA inserts were selected for sequence analyses. Human cDNA fragment was digested with Stu I and Hind III and cloned into a expression vector, pPROEXHT, at the same restriction enzyme sites. The plasmid was transformed into E. coli cells. Correct cloning and the full-length sequence of human CO-Ag were determined by sequencing the insert cDNA. RESULTS: The bovine cDNA insert sequence was 273 nucleotides in length for the entire mRNA coding region, 212 nucleotides in the 5' untranslated region, 83 nucleotides in the 3' untranslated region and a poly(A) tail. The DNA base sequence of this clone also contained a standard initiation codon, termination codon, and the polyadenylation signal. This cDNA predicts a protein which contains 91 amino acids with a molecular weight of 10,584 daltons. Plasmid expression vector, pPROEXHT-CO-Ag, was constructed that direct the synthesis of human CO-Ag in E. coli as fusion protein. Human CO-Ag fusion protein was purified to 90% pure with a yield of 17.2 mg per liter of the bacterial cell lysate. The nucleotide sequence of the CO-Ag cDNA insert was completely identical to human neutrophil calgranulin C. The deduced amino acid sequence was completely identical to a Ca(2+)-binding protein isolated on the surface of filarial nematodes. CONCLUSIONS: The isolation and analysis of cDNA clones containing the complete coding sequence of bovine and human CO-Ag proteins is reported. The proteins identified by deduced amino acid sequences demonstrate 100% sequence homology with human and bovine calgranulin C. Immune recognition of calgranulin C to a filarial nematode may lead to a hyperactive autoimmune response to CO-Ag in the cornea leading to a Mooren's ulcer.

Amino Acid Sequence↗

PubMed1996

Inhibition of Epstein-Barr virus replication by a novel L-nucleoside, 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil.

A novel L-nucleoside analog, 2'-fluoro-5-methyl-beta-L-arabinofuranosyluracil (L-FMAU), was found to be a potent and selective inhibitor of Epstein-Barr virus (EBV) replication. The decrease in the amount of viral production was concentration dependent with a 90% inhibitory concentration of approximately 5 muM. Upon removal of the drug from treated cells, virus production resumed in 21 days. Metabolism studies indicated that L-FMAU could be converted to its mono-,di- and triphosphate metabolites in both EBV producing and non-producing cells than in EBV non-producing cells. The mechanism of selectivity of L-FMAU against EBV producing cells. However, the amount of L-FMAU nucleotides formed was three times larger in EBV producing cells than in EBV non-producing cells. The mechanism of selectivity of L-FMAU against EBV does not appear to be due solely to the preferential phosphorylation of L-FMAU in EBV producing cells. The triphosphate of L-FMAU could not be utilized as a substrate by EBV DNA polymerase or the human DNA polymerases alpha, beta, gamma, or delta. Therefore, the incorporation of L-FMAU residues into viral DNA may not be the mechanism of antiviral activity. This compound appears to have a mechanism of action different from that of any other antiherpes virus nucleoside analogs. In addition, L-FMAU has very low cytotoxicity with 50% inhibition of cell growth occurring at a concentration of 1mM. Given the potent inhibitory activity of this compound against EBV and its inability to be incorporated into cellular DNA, L-FMAU analogs should be explored as a new class of anti-EBV agents.

Arabinofuranosyluracil↗

PubMed1996

Suppression of potassium currents by cyanide on the mouse motor nerve terminals.

NaCN at low concentrations markedly depressed the potassium currents in the motor nerve terminal of mouse triangularis sterni neuromuscular junction pretreated with potassium channel blockers 4-aminopyridine (4-AP), tetraethylammonium (TEA) or glucose-free medium. Neither azide nor dinitrophenol nor ouabain mimicked the effect of cyanide. This inhibitory effect of cyanide on nerve terminal spikes was correlated to its dramatic increase in spontaneous transmitter release under glucose-free condition. These results suggest that the effect of cyanide on the electrogenesis of nerve terminals is due to the direct suppression of ATP-sensitive K+ current since the effect was antagonized by ATP-sensitive K+ channels opener diazoxide and this may modulate the transmitter release.

2,4-Dinitrophenol↗

PubMed1996

Primary immunolocalization of estrogen and progesterone target cells in the human anterior cruciate ligament.

To identify estrogen and progesterone target cells in the human anterior cruciate ligament immunohistochemical localization of both estrogen and progesterone receptors was performed in 17 specimens of human anterior cruciate ligament. All ligament specimens were obtained at surgery. Thirteen specimens were from women, and four were from men: the average age was 57 years (range, 18-78 years). Eleven specimens (from nine women and two men) came from total knee replacements for osteoarthritis of the knee: three (from two women and one man), from reconstructions of the anterior cruciate ligament: two (both from women), from medial meniscectomies; and one (from a man), from an amputation secondary to chondrosarcoma of the pelvis. An immunoperoxidase method using monoclonal antibodies to the estrogen and progesterone receptors was employed to identify estrogen and progesterone target cells in the anterior cruciate ligament. Staining of both receptors was demonstrable in 14 specimens and in the remaining three specimens less than 15% of the cells were stained. Both estrogen and progesterone receptors were localized to synoviocytes in the synovial lining, fibroblasts in the anterior cruciate ligament stroma and cells in the blood vessel walls of the ligament. This demonstration of receptors for estrogen and progesterone in the cells of anterior cruciate ligament suggests that female sex hormones may have an effect on its structure and composition.

Adolescent↗

PubMed1996

The effects of uranyl ions on neuromuscular transmission in the urinary bladder of the normal and streptozotocin-diabetic mouse.

The depressant effects of uranyl nitrate on the nerve-evoked muscle contraction of urinary bladder isolated from normal and streptozotocin-diabetic mice were compared. The non-cholinergic component of the evoked bladder contraction (in the presence of atropine) was specifically sensitive to the suppressive effect of uranyl nitrate. In contrast, the cholinergic component remaining after treatment with alpha, beta-methylene ATP was rather insensitive to uranyl nitrate. The contractile responses induced by KCl, acetylcholine and ATP were also not affected by uranyl nitrate, indicating a presynaptic site of action. High Ca2+ and calmodulin inhibitors (trifluoperazine, diltiazem and W7) antagonized the suppressive effects of uranyl ions. These results suggest that the depressant effects of uranyl nitrate is mediated by a reduction of prejunctional non-cholinergic transmitter release through the calcium-calmodulin pathway. In contrast to the normal bladder, the urinary bladder of streptozotocin-diabetic mice revealed not only weaker neurogenic contractile responses to electrical field stimulation, but also a profound reduction in the depressant effect of uranyl nitrate. These findings suggest that the Ca2+ regulation of non-cholinergic neurotransmission in mouse urinary bladder may be impaired in the diabetic state.

Animals↗

PubMed1996

Mutual interactions among ingredients of betel quid in inducing genotoxicity on Chinese hamster ovary cells.

The purpose of this study is to explore the mutual interactions among the chemical ingredients of betel quid including arecoline, sodium fluoride, catechin and glycyrrhizin in producing genotoxicity on Chinese hamster ovary (CHO) cells using the micronucleus method. Our results show that arecoline at a rather low concentration of 0.2-2 microM which could be in the oral cavity during betel quid chewing and NaF(0.8-2.4 mM) significant elevated the number of micronucleated cells in a concentration-dependent manner. In addition, significant prolongation of cell cycles was observed by treatment with arecoline (> or = 2.0 microM) or NaF (2.4 nM) in CHO cells. Both catechin and glycyrrhizin could antagonize not only the increased micronucleated cells induced by arecoline and NaF but also the prolonged cell cycle induced by arecoline in CHO cells. This find implies that the adjuvant ingredients, catechu and liquorice root extract provide not only a flavor but also an antagonist against the genotoxicity of arecoline and fluoride containing betel quid.

Animals↗

PubMed1996

Isolation, cloning, and characterisation of a trp homologue from squid (Loligo forbesi) photoreceptor membranes.

The invertebrate phototransduction system is a valuable model of the ubiquitous inositol lipid signalling system. Taking advantage of the ability to obtain relatively large amounts of retinal material from the cephalopod eye, partial protein sequence data were obtained for a 92-kDa component isolated from a detergent-insensitive cytoskeletal fraction of a squid retinal microvillar membrane preparation. Degenerate oligonucleotides, designed on the basis of these sequence data, were used to isolate a full-length cDNA, encoding the 92-kDa component, using both cDNA library screening and 5'-rapid amplification of cDNA ends (5'-RACE) techniques. Comparison of the amino acid sequence encoded by this cDNA with entries in the OWL composite protein sequence database reveals greatest sequence similarity with the products of the Drosophila trp and trpl genes. Greatest variation from the Drosophila Trp protein is seen in the carboxyl-terminal region, which is considerably truncated in the squid protein and which accounts for most of the substantial difference in molecular weight seen between these proteins. This variation may be significant as the carboxyl-terminal domain has been shown to be in the regulation of several ligand-gated channels. The carboxyl-terminal domain has been expressed and shown to interact with calmodulin in a calcium-dependent fashion, thereby supporting this hypothesis. The likely occurrence of other homologues in a variety of systems suggests that this is a novel and important family of regulated ion channels involved in calcium signalling.

Animals↗