Biomedical subjects

Y Lin

Publications and source records attributed to Y Lin.

At least 541 records · Page 30Linked to original sources

PubMed1995

[Treatment of ototoxic auditory damage caused by kanamycin with electroacupuncture at different acupoints].

We adopted the technique and method of integrating the morphology with function to select the effective acupoints for treatment of deafness. The results show that: (1) Tinggong (SI 19), Yifeng (TE 17), Waiguan (TE 5), Shenshu (UB 23), Sanyinjiao (SP 6) and Zhubin (KI 9) etc. are the effectine acupoints for the treatment of ototoxic auditory damage caused by drug, especially, the effect of Tinggong, Sanyinjiao and Zhubin etc, is much better; (2) electroacupuncture can promote audibility, improve SDH activity and relieve progressing injury of auditory hair cells, (3) FFR method has an important significance in the determination of ototoxic damage caused by drug.

Animals↗

PubMed1995

[Measurement of respiratory muscle performance in patients with chronic obstructive pulmonary disease].

Respiratory muscle performance is measured in terms of strength and endurance. A RMSE-1 type measuring system for evaluation of respiratory muscle strength (RMS) and endurance (RME) has been developed and tested in normal subjects and patients with stable chronic obstructive pulmonary disease (COPD). The results showed that there was no significant difference between normal subjects and stable COPD patients in RMS measured as maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP). The maximum load (Load(m)), mean mouth pressure at maximum load (Pmean), and the maximum sustainable inspiratory pressure (SIP(m)) as % MIP (SIP(m)/MIP) were taken as measure of RME. All measures of RME in COPD group were much lower than those in the normal. The measurement of RME can be used to evaluate the effect of respiratory muscle training and direct the respiratory rehabilitation in COPD patients.

Adult↗

PubMed1995

Functional expression and peroxisomal targeting of rat urate oxidase in monkey kidney cells.

Humans and hominoid primates lack the enzyme urate oxidase, which catalyzes the oxidation of uric acid to allantoin. In rats and most other mammals, urate oxidase is present as a crystalloid core within the peroxisomes of liver parenchymal cells. To determine whether functionally active recombinantly expressed urate oxidase can be targeted to the peroxisome as well as display the crystalloid core-like structure, we expressed rat urate oxidase cDNA in African green monkey kidney cells (CV-1 cells) under the control of a cytomegalovirus promoter. Cell lines stably expressing urate oxidase were isolated. Northern blot analysis revealed a 1.3-kb transcript and immunoblot analysis confirmed the presence of urate oxidase in the stably transfected cells. The recombinant urate oxidase expressed in CV-1 cells was functionally active. Immunofluorescence microscopy revealed that the expressed protein was visualized as discrete granules in the cytoplasm. Electron microscopy and immunocytochemical localization studies showed that the recombinantly expressed protein formed distinct crystalloid core structures with bundles of tubules within single membrane limited cytoplasmic organelles. On cross section, the recombinant urate oxidase tubular structures are arranged as circles of 10 surrounding a slightly larger circle. This arrangement is reminiscent of urate oxidase-containing cores in rat liver peroxisomes. Immunocytochemical studies confirmed that the recombinantly expressed urate oxidase is correctly targeted to the catalase-containing peroxisomes in these CV-1 cells.

Allantoin↗

PubMed1995

Sequence requirements for alpha-fetoprotein gene expression during liver regeneration.

The alpha-fetoprotein (AFP) gene is expressed in fetal liver and in adult liver undergoing regeneration or tumorigenesis. It has been shown previously that three distal enhancers, a proximal promoter, and a dominant negative postnatal repressor element are required for the tissue-specific and developmental regulation of AFP gene expression. Using transgenic mice, we have determined the sequence requirements for AFP gene induction during liver regeneration. Two DNA sequences were found in all transgenes appropriately regulated in response to liver regeneration: a distal sequence between 1010 and 838 bp upstream of the structural gene and a proximal sequence within 118 bp of the transcriptional initiation site. In situ hybridization analysis showed that transgene expression during liver regeneration was first found in all hepatocytes and then localized to perinecrotic hepatocytes surrounding the central vein. This pattern of expression is reminiscent of that observed after birth for the transgenes, suggesting that repression of AFP gene expression after birth and liver injury may be regulated by similar mechanisms.

Animals↗

PubMed1994

Modified RNA sequence pools for in vitro selection.

We report the use of modified RNA, in which the 2'-OH group of pyrimidines is replaced by a 2'-amino (2'-NH2) group to identify high affinity ligands specific for human neutrophil elastase (HNE) by in vitro selection. Compared to unmodified RNA the 2'-NH2-modified RNA ligands show enhanced stability in human serum and urine. Use of RNase T1 cleavage data in the presence of K+ and Li+ ions suggests that the modified RNA ligands selected for HNE form an intermolecular G-quartet structure.

Amino Acid Sequence↗

PubMed1994

Direct excitatory opiate effects mediated by non-synaptic actions on rat medial vestibular neurons.

Opiates increase firing of rat medial vestibular nucleus neurons. We have attempted to determine the mechanism of these excitatory opiate actions by extracellular recording of neuronal activity with ionophoretic application of opiate agonists and bath application of antagonists. The spontaneous activity of approximately 30% of medial vestibular neurons, scattered throughout the nucleus, was increased by ionophoretic application of either morphine or [D-Ala2]leucine enkephalin, implicating the presence of both mu and delta opiate receptors. The responses to both were blocked by the opiate receptor antagonist, naloxone. In only a few neurons opiates decreased firing. Most previous reports of direct opiate excitation have proven to be due to disinhibition. This is not the case here, as indicated by three observations: 1) the excitatory opiate response was sustained when gamma-aminobutyric acid (GABA) receptors were blocked by bicuculline; 2) perfusion of a solution containing 0.1 mM Ca2+ and 6.3 mM Mg2+ blocks synaptic transmission, but does not block the excitatory responses to both opiates and 3) the opiate-induced depolarization and action potential generation was evident in neurons whose spontaneous firing was almost totally depressed by adenosine. These results indicate that the excitation is neither due to disinhibition nor to a presynaptic opiate action. We conclude that medial vestibular neurons have postsynaptic opiate receptors that mediate direct neuronal excitation.

Action Potentials↗

PubMed1994

A phospholipase A2 inhibitor from the plasma of the South American rattlesnake (Crotalus durissus terrificus). Protein structure, genomic structure, and mechanism of action.

The lethal toxicity of the South American rattlesnake (Crotalus durissus terrificus) venom can be attributed mainly to the presence of a pre-synaptic neurotoxin, crotoxin, with phospholipase A2 activity. Crotoxin is a heterodimer of an acidic protein (CA) and a basic phospholipase A2 (CB). An anti-toxic protein of subunit molecular mass 23.6 kDa that neutralizes both lethal and PLA2 activity of crotalid venom and crotoxin has been previously purified from the plasma of this snake (Fortes-Dias, C., Fonseca, B. C. B., Kochva, E., and Diniz, C. R. (1991) Toxicon 29, 997-1008). The protein has been named CNF for Crotalus neutralizing factor. In the present study, we have shown that CNF exists as an oligomeric aggregate of (CNF)n, where n = 6-8, and when it interacts with crotoxin, it replaces the acidic protein CA of crotoxin to form a stable near stoichiometric complex of CNF.CB. The CNF.CB complex no longer exhibits PLA2 activity and is inert in vivo. Thus, the exchange reaction between CA.CB of crotoxin and CNF to form CNF.CB and free CA is reminiscent of the interaction of crotoxin with its target receptor at the neuromuscular transmission site in the presynaptic cells. A cDNA encoding CNF has been isolated from a liver cDNA library using an appropriate nucleotide probe. The nucleotide sequence codes for a 19-residue signal peptide, followed by a 181-residue protein of which 16 are half-cystines. Calculated molecular mass is 20.06 kDa, and there is a putative N-linked carbohydrate site at Asn157.

Amino Acid Sequence↗

PubMed1994

Protective effect of a recombinant fragment of bactericidal/permeability increasing protein against carbohydrate dyshomeostasis and tumor necrosis factor-alpha elevation in rat endotoxemia.

Endotoxin (lipopolysaccharide, LPS), a component of the gram-negative bacterial cell wall, induces carbohydrate dyshomeostasis and the release of proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) when administered to experimental animals. Bactericidal/permeability increasing protein (BPI), a cationic protein found in human neutrophil granules, binds with high affinity to LPS and is capable of neutralizing its biological activity. The present study was designed to determine if a recombinant N-terminal fragment of BPI, rBPI23, attenuates LPS-induced alterations in serum glucose, lactate, and TNF-alpha in rats. In anesthetized animals challenged with a 30 min infusion of Escherichia coli O111:B4 LPS (0.25 mg/kg), there was an early transient increase in serum levels of glucose followed by a drop to 60% of those found in saline control rats. A prolonged elevation in serum levels of lactate and a transient, but marked, elevation of TNF-alpha were also observed following LPS infusion. These LPS-induced changes were inhibited significantly by simultaneous infusion of rBPI23. Different dose-response profiles of rBPI23 on LPS-induced alterations in glucose, lactate and TNF-alpha were observed. When rBPI23 was infused 30 min after the initiation of LPS infusion, it significantly inhibited the alterations in glucose and lactate, but not TNF-alpha. The rise in TNF-alpha was reduced significantly with a 15 min delayed infusion of rBPI23. A control protein failed to alter any responses to LPS. The results indicate that rBPI23 can provide significant protection against the metabolic disturbances and TNF-alpha release associated with endotoxemia. In addition, the results suggest that LPS-induced metabolic alterations in glucose and lactate are at least partially independent of TNF-alpha release.

Animals↗

PubMed1994

Cytotoxicity of the cocaine metabolite benzoylecgonine.

The NG108-15 and C6 cell lines were used in the present study as neuronal and glial models, respectively, to examine the cytotoxicity of the major metabolite of cocaine, benzoylecgonine (BE). Exposure of both cell types to varying concentrations of BE resulted in a loss of cells from the growth surface. Analysis of the unattached cells after such exposure, using a variety of techniques, revealed that these cells were not viable. Therefore, this effect could not be ascribed to BE interfering with cell-substratum interactions. The early events in BE cytotoxicity were examined by observing cells cultivated on the stage of an inverted microscope, using differential interference contrast (Nomarski) optics. Upon exposure of either cell type to 10 microM BE a retraction of cellular processes could be observed within 30 min. Within 6 h cell death was apparent. Similar analyses using 50 microM BE in the growth medium resulted in similar results, except that process retraction could be observed as early as 15 min after exposure. These results demonstrate that the major metabolite of cocaine, benzoylecgonine, is cytotoxic to in vitro models of neuronal and glial cells.

Animals↗

PubMed1994

C-reactive proteins, limunectin, lipopolysaccharide-binding protein, and coagulin. Molecules with lectin and agglutinin activities from Limulus polyphemus.

In 1964, Levin and Bang discovered that gram-negative bacterial endotoxin could rapidly induce gelation of Limulus amebocyte lysate. This observation has led to the development of the most sensitive and specific method for the detection of bacterial endotoxin in pharmaceuticals and drugs intended for human use. Over 10 years ago, Bang injected endotoxin into young horseshoe crabs and observed a time and dose-dependent coagulation of the whole hemolymph. Limunectin, LEBP-PI, and Limulus CRP are found together with coagulin as part of the hemolymph clot at the time of endotoxin-induced exocytosis of amebocytes. In this manner, these molecules with agglutinin/lectin activities could work in concert to assist in the recognition and eventual removal of invading microorganisms from the circulating system. Although the mechanism of endotoxin-induced clot formation is to a large extent understood, the mechanism of clot dissolution and removal in the Limulus hemolymph remains to be clarified.

Acute-Phase Proteins↗

PubMed1994

Proteolytic processing mechanisms of a miniprecursor of the aspartic protease of human immunodeficiency virus type 1.

The infectivity of the human immunodeficiency virus (HIV) depends upon correct proteolytic processing of viral polyprotein precursors, the Pr55gag and Pr160gag-pol polyproteins. The processing is mediated spontaneously by the viral protease unit (PR) contained within the Pr160gag-pol precursor. However, little is known about the mechanism of this process. The expression in Escherichia coli and the isolation of a 14-kDa HIV-1 PR "miniprecursor" with Ala28 mutated to serine has permitted study of the mechanism for cleavage at the N-terminus of the protease. The miniprecursor is active against a synthetic peptide substrate, and its specific activity is near that of the mutant mature protease. The rate of conversion of radiolabeled precursor to mature protease is quantitated by measuring the amounts of the two radiolabeled proteins separated by SDS-PAGE. The apparent first-order conversion rate constant, kapp, is dependent on miniprecursor concentration indicating a second-order reaction and suggesting an interdimeric processing mechanism. A significant first-order rate constant is observed when the plot of kapp versus initial precursor concentration is extrapolated to zero. This observation suggests the presence of an alternative processing mechanism involving a single active precursor dimer. The presence of both mechanisms is an advantage for the virus to ensure processing under various conditions.

Amino Acid Sequence↗

PubMed1994

Stimulation of the ATP-dependent interaction between actin and myosin by a myosin-binding fragment of smooth muscle caldesmon.

We reported previously that smooth muscle caldesmon stimulates the ATP-dependent interaction between actin and phosphorylated smooth muscle myosin, as monitored by ATPase measurement and in vitro motility assay. Furthermore, this effect changes from stimulatory to inhibitory with increasing concentrations of caldesmon [Ishikawa et al., 1991: J. Biol. Chem. 266:21784-21790]. The N-terminal (myosin-binding) fragment and the C-terminal (actin-binding) fragment were purified from digests of caldesmon. The effects of the myosin-binding fragment and the actin-binding fragment on the interaction were stimulatory and inhibitory, respectively, indicating that stimulatory and inhibitory domains are localized in the myosin-binding domain and actin-binding domain of caldesmon, respectively. The effect of the myosin-binding fragment on the interaction was exclusively stimulatory when the interaction was challenged by caldesmon, both at lower and higher concentrations. However, the actin-binding fragment had no effect on the interaction at lower concentrations and inhibited the interaction at higher concentrations. Thus, the stimulatory effect of caldesmon that is observed at lower concentrations can be explained by the hypothesis that the stimulatory effect of the myosin-binding domain predominates over the inhibitory effect of the actin-binding domain when the concentration of caldesmon is low. With uncleaved caldesmon, we also emphasized the role of the myosin-binding domain in the stimulation as follows; the stimulatory effect of caldesmon became obscured when binding of caldesmon to myosin was competed by the exogenous caldesmon-binding fragment of myosin.

Actins↗

PubMed1994

Structure of trichosanthin at 1.88 A resolution.

Trichosanthin (TCS) is one of the single chain ribosome-inactivating proteins (RIPs). The crystals of the orthorhombic form of trichosanthin have been obtained from a citrate buffer (pH 5.4) with KCl as the precipitant. The crystal belongs to the space group P2(1)2(1)2(1) with a = 38.31, b = 76.22, c = 79.21 A. The structure was solved by molecular replacement method and refined using the programs XPLOR and PROLSQ to an R-factor of 0.191 for the reflections within the 6-1.88 A resolution range. The bond length and bond angle in the protein molecule have root-mean-square deviations from ideal value of 0.013 A and 3.3 degrees, respectively. The refined model includes 247 residues and 197 water molecules. The TCS molecule consists of two structural domains. The large domain contains six alpha-helices, a six-stranded sheet, and an antiparallel beta-sheet. The small domain has a largest alpha-helix, which shows a distinct bend. The possible active site of the molecule located on the cleft between two domains was proposed. In the active site Arg-163 and Glu-160, Glu-189 and Arg-122 form two ion pairs, Glu-189 and Gln-156 are hydrogen bonded to each other. Three water molecules are bonded to the residues in the active site region. The structures of TCS molecule and ricin A-chain (RTA) superimpose quite well, showing that the structures of the two protein molecules are homologous. Comparison of the structures of the TCS molecule in this orthorhombic crystal with that in the monoclinic crystal indicates that there are no essential differences of the structures between the two protein crystals.

Amino Acid Sequence↗

PubMed1994

Use of superoxide dismutase (SOD) in patients with temporomandibular joint dysfunction--a preliminary study.

The aim of this preliminary study was to investigate and assess the effect of intra-articular injection of superoxide dismutase (SOD) in patients with temporomandibular joint (TMJ) dysfunction who had not responded to conservative therapy in a first study. Thirty joints in 29 patients were studied. The results showed that intra-articular injection of superoxide dismutase was effective in 25 joints (83%). It was concluded that intra-articular injection of superoxide dismutase may be an alternative therapy for patients with TMJ dysfunction who fail to respond to conservative treatment.

Adult↗

PubMed1994

Magnetic resonance imaging assessment of the temporomandibular joint in disk displacement.

Twenty-four patients (48 joints) presenting signs and symptoms of internal derangement of the temporomandibular joint (TMJ) were studied, combinations of coronal and sagittal magnetic resonance imaging (MRI) being used for assessment of the TMJ disk. In the coronal MRI, lateral or medial disk displacement was confirmed in 10/48 joints (20.8%). Disk displacement in a lateral direction was confirmed in six joints, and in a medial direction in four joints, while, in the sagittal images, anterior displacement of the disk without reduction (ADWR) was observed in 20/48 joints (17/24 cases), among which bilateral ADWR were found in three cases. Rotational disk displacements were observed in eight joints, and of these cases six were anterior and lateral disk displacements, while the remaining two were anterior and medial disk displacements. The disks tended to be displaced in a lateral direction in cases of rotational disk displacement.

Adolescent↗

PubMed1994

A hyaluronidase activity of the sperm plasma membrane protein PH-20 enables sperm to penetrate the cumulus cell layer surrounding the egg.

A typical mammalian egg is surrounded by an outer layer of about 3,000 cumulus cells embedded in an extracellular matrix rich in hyaluronic acid. A current, widely proposed model is that the fertilizing sperm, while it is acrosome intact, passes through the cumulus cell layer and binds to the egg zona pellucida. This current model lacks a well-supported explanation for how sperm penetrate the cumulus layer. We report that the sperm protein PH-20 has a hyaluronidase activity and is present on the plasma membrane of mouse and human sperm. Brief treatment with purified, recombinant PH-20 can release all the cumulus cells surrounding mouse eggs. Acrosome intact mouse sperm incubated with anti-PH-20 antibodies can not pass through the cumulus layer and thus can not reach the zona pellucida. These results, indicating that PH-20 enables acrosome intact sperm to penetrate the cumulus barrier, reveal a mechanism for cumulus penetration, and thus provide the missing element in the current model.

Animals↗

PubMed1994

Transient, meiosis-induced expression of the rec6 and rec12 genes of Schizosaccharomyces pombe.

Two meiotic recombination genes, rec6 and rec12, from Schizosaccharomyces pombe have been cloned by genetic complementation and their DNA sequences determined. Gene replacements demonstrated that the cloned fragments contained the rec6 and rec12 genes. Further analysis showed that the functional rec6 gene was within a 1.3-kb fragment and rec12 within a 1.7-kb fragment. The nucleotide sequences of these fragments revealed open reading frames (ORFs) predicting 143 amino acids for the rec6 gene product and 139 amino acids for the rec12 gene product. After pat1-114 temperature-induced meiosis, the transcripts of rec6 and rec12 were induced to maximal levels at 2-3 hr, at about the time of premeiotic DNA synthesis, but were present at much lower levels before and after this time. The transient induction of the transcripts and the phenotypes of the mutants suggest that the rec6 and rec12 gene products are involved primarily in the early steps of meiotic recombination in S. pombe. Near the rec6 gene are two additional ORFs potentially encoding proteins with homology to ribosomal protein S7 of Saccharomyces cerevisiae (ORF137) and to the homeodomain of developmental regulatory proteins (ORF201). The roles of these S. pombe ORFs remain to be determined.

Amino Acid Sequence↗

PubMed1994

The regulatory role of myosin light chain kinase as an actin-binding protein.

Myosin light chain kinase (MLCK) is present in muscle cells including those of smooth muscle as an actin-binding protein. By avoiding complication introduced as a result of kinase activity of MLCK, we have demonstrated regulatory role of MLCK through its actin-binding activity [Kohama et al. (1992) Biochem. Biophys. Res. Commun. 184, 1204-1211]. To analyze such a regulatory role of MLCK, we compared the effects of MLCK on the velocity of the movement of actin filaments on a surface coated with smooth muscle myosin with those of another actin-binding proteins in smooth muscle, namely, caldesmon (CaD) and calponin (CaP). Both CaD and CaP stimulated movement when their concentrations were low, but they inhibited movement as their concentrations were increased. Calmodulin (CaM) in the presence of Ca2+ (Ca-CaM) antagonized the inhibition but hardly affected the stimulation. The effect of MLCK, by contrast, was simply inhibitory when Ca-CaM was not present. No stimulation was observed until Ca-CaM was added. The inhibitory ability of these actin-binding proteins increased in the following order: CaD < CaP < MLCK. The effect of MLCK and CaD on movement was further examined on surfaces coated with skeletal muscle myosin. The basic effect was similar to that observed with smooth muscle myosin. However, 10-fold greater concentrations of MLCK and CaD were required for a comparable effect. Such an increase in the required concentration was also observed when the velocity of movement was increased by elevation of the temperature during the assay with smooth muscle myosin. Thus, it is the velocity of movement itself that determines the required concentrations of MLCK and CaD.

Actins↗