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Biomedical subjects

Y An

Publications and source records attributed to Y An.

At least 37 records · Page 2Linked to original sources
PubMed1999

Preparation and Morphology Studies of Core-Shell Type Waterborne Polyacrylate-Polyurethane Microspheres.

Core-shell type waterborne polyacrylate-polyurethane microspheres in which polyurethane acts as the shell and acrylic polymer as the core were prepared. Hydroxyethyl acrylate and adipic dihydrazide were used as cross-linking agents introduced to the ends of the shell molecular chains, and two kinds of cross-linked structures between the core and the shell were formed. The photon correlation spectroscopy studies indicate that all the microspheres present continuous particle-size distributions and their mean particle sizes are smaller than 200 nm. The transmission electron photographs reveal that there are obvious core-shell structures for the noncross-linked type microsphere particles and different cross-linked networks between the core and shell for the two kinds of cross-linked type microsphere particles. These microspheres possess excellent storage stability, water resistance, and coating properties. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

The effects of La(III) on the peroxidation of membrane lipids in wheat seedling leaves under osmotic stress.

The physiological effects of the rare earth ion La3+ on the peroxidation of membrane lipids in wheat (Triticum aestivum L.) seedling leaves under osmotic stress were determined. With the passage of time under osmotic stress, the inhibition ability of lanthanum ions to the relative membrane permeability and concentration of malondialdehyde, superoxide radicals, and hydrogen peroxide caused by osmotic stress increased substantially, but no changes were noted in ferrous and relative water content. It indicated that lanthanum ions could not retain the water content because of osmotic stress. However, La3+ appears to decrease the production of *OH by reducing the content of O2*- and H2O2 of Haber-Weiss and Fenton reactions, which efficiently alleviated peroxidation of membrane lipids under osmotic stress and, to some degree, protected the membrane from injury of free radicals. Thus, La3+ increased the tolerance ability of plant to osmotic stress, which could assure the function of membrane normal temporally after stressed.

Hydrogen Peroxide↗
PubMed1999

Crystallization and preliminary X-ray studies of metallothionein II from rabbit liver.

Metallothionein II (Mw = 6.8 kDa), induced by cadmium and purified from rabbit liver, has been crystallized in space group P6222 or P6422. The unit-cell parameters were a = b = 113.4, c = 219.1 A, alpha = beta = 90.0, gamma = 120.0 degrees when crystallized from sodium citrate buffer and a = b = 113.4, c = 219.6 A, alpha = beta = 90.0, gamma = 120.0 degrees when crystallized from Tris-HCl buffer. There are 12 molecules per asymmetric unit and the solvent content is about 57%.

Animals↗
PubMed1998

Endotoxin-induced alteration in the expression of leptin and beta3-adrenergic receptor in adipose tissue.

Cytokines, such as tumor necrosis factor (TNF) and interleukin-6, may contribute to the anorexia and cachexia of infection, cancer, and AIDS. The present study tests the hypothesis that endotoxin alters the expression of two key fat cell proteins, leptin and beta3-adrenergic receptor (beta3-AR), through a mechanism involving TNF-alpha. Increasing doses of Escherichia coli endotoxin (lipopolysaccharide, LPS) resulted in dose-dependent elevations of plasma leptin (maximal response approximately 7-fold, half-maximal effective dose of approximately 16 microg/100 g body wt) and white fat leptin mRNA in C3/HeOUJ mice. LPS also produced a large decrease in adipose tissue beta3-AR mRNA and a parallel reduction in beta-agonist-induced activation of adenylyl cyclase. Changes in plasma leptin and beta3-AR mRNA were preceded by an approximately threefold increase in white fat TNF mRNA. TNF administration resulted in changes similar to those seen with LPS. We conclude that endotoxemia results in an induction of leptin mRNA and a decrease in beta3-AR mRNA in adipose tissue, an effect that may be mediated by alterations in TNF-alpha.

Adenylyl Cyclases↗
PubMed1998

[Distribution of substance P receptors in rat nasal mucosa of allergic rhinitis].

OBJECTIVE: To explore the potential role of substance P receptor (SPR) in the initiation and development of allergic rhinitis (AR). METHODS: Twenty healthy rats were randomly divided into two groups. A model of allergic rhinitis in rat was established by using ovalbumin intraperitoneal immunization and nasal antigen challenge. The nasal mucosa obtained from seven out of ten AR models as well as ten normal controls were studied routinely by HE and immunohistochemical staining to observe the distribution and changes of SPR. RESULTS: The study showed that immunoreactivity to SPR was present both on the surface and in the cytoplasm of epithelial cells, eosinophils, glandular cells and its ducts, mast cells, plasmocyte and other monocytes. During nasal hypersensitiveness, the staining density and the positive staining cells increased significantly as compared with those in normal controls. CONCLUSION: The increase of SPR in nasal mucosa in rat AR model indicates that SPR might play a critical role in the development of AR.

Animals↗
PubMed1997

Effects of two familial hypertrophic cardiomyopathy-causing mutations on alpha-tropomyosin structure and function.

Missense mutations in alpha-tropomyosin can cause familial hypertrophic cardiomyopathy. The effects of two of these, Asp175Asn and Glu180Gly, have been tested on the structure and function of recombinant human tropomyosin expressed in Escherichia coli. The F-actin affinity (measured by cosedimentation) of Glu180Gly was similar to that of wild-type, but Asp175Asn was more than 2-fold weaker, whether or not troponin was present. The mutations had no apparent effect on the affinity of tropomyosin for troponin. The mutations had a small effect on the overall stability (measured using circular dichroism) but caused increased local flexibility or decreased local stability, as evaluated by the higher excimer/monomer ratios of tropomyosin labeled with pyrene maleimide at Cys 190. The pyrene-labeled tropomyosins differed in their response to myosin S1 binding to the actin-tropomyosin filament. The conformations of the two mutants were different from each other and from wild-type in the myosin S1-induced on-state of the thin filament. Even though both mutant tropomyosins bound cooperatively to actin, they did not respond with the same conformational change as wild-type when myosin S1 switched the thin filament from the off- to the on-state.

Actins↗
PubMed1997

Beta-3 adrenoceptor (beta-3AR) expression in leptin treated OB/OB mice.

Leptin-deficient Ob/Ob mice are hypometabolic and have reduced fat cell expression of beta-3 adrenoceptors (ARs). To determine whether leptin repletion restores beta-3 AR number, C57BL/6J Ob/Ob mice were given exogenous leptin (5 mg/kg I.P. daily) for 21 days. Leptin administration reduced body weight from 43.1+/-3.7 to 34.1+/-3.7 g in Ob/Ob animals but had no effect on weight in wildtype animals. Body weight increased by 12% in Ob/Ob mice receiving saline. Beta-3 AR mRNA concentrations were markedly reduced in Ob/Ob animals at baseline. Leptin increased beta-3 AR mRNA to control levels in Ob/Ob mice, but had no effect in wildtype animals. Adipocyte leptin mRNA was increased by 400% in Ob/Ob mice and did not suppress with exogenous leptin administration, suggesting no direct feedback regulation of leptin synthesis. We speculate that restoration of beta-3 AR expression by repleting leptin may be important in correcting hypometabolism in Ob/Ob animals.

Animals↗
PubMed1997

[The nosocomial infection in ICU: characteristics and prevention].

In 84 consecutive patients who were treated in ICU, 35 had microbiological 5 data. 117 strains (bacteria: 77; fungus: 40) were isolated from 24 of the 35 patients for 97 times. The positive rate was 68.6%, or 28.6% of 84 patients. The gram-negative bacilli were still the main source of nosocomial infection in ICU, especially the pseudomonas aeruginosa, clostridium welchii, and E. coli, but gram-positive cocci, especially MRSA infection were also increased. Mycotic infection increased very rapidly. 12 of the 24 patients were found a complicated mycotic infection. Six of the 12 (50%) died. Candida tropicalis and candida guilliermondi replaced candida albicans as the main pathogenic fungus. Sputum is still the most important specimen source of positive culture, followed by wound drainage, blood, urine, central venous catheter as well as feces. It is indicated that the respiratory system is still the main focus of nosocomial infection, and mycotic infection is most dangerous in ICU. Regular monitoring of microbial flora changes, detection correct use of antibiotics by drug sensitivity test, adequate surgical drainage, early and prevention of mycotic infection as well as improvement of ICU design will prevent or minimize the nosocomial infection in ICU.

Adult↗
PubMed1997

[The development of a CPU controlled COPD recovery training ventilator].

A COPD recovery training ventilator controlled by micro-computer is described. The paper include the design principles of emphasizing on the expiration help and reducing the FRC, stimulating phrenic nerve to strengthen inspiration and to lay up strength, stimulating abdominal muscle or pressing on abdomen to enhance expiration and make diaphragm relaxing thoroughly, four period synchronizing control mode and the hard and soft construction.

Animals↗
PubMed1997

[Studies on serotyping of sporadic acute viral hepatitis].

Two hundred and forty-eight blood specimens collected from patients of sporadic acute viral hepatitis were serotyped with enzyme immunoassay (EIA), to study its pathogenic components during non-epidemic seasons of hepatitis A (HA). Results showed that HA accounted for 61.3% of the total sporadic acute hepatitis cases during its non-epidemic seasons, occurred mainly in youngsters and decreased with increase of their age. Hepatitis B (HB) ranked the second and accounted for 26.2%, occurred mainly in the middle-aged and the elderly and its prevalence increased with age. Hepatitis C (HC) accounted for 9.9% and hepatitis E (HE) 22.2% of the total cases, without obvious age difference. Prevalence of hepatitis D (HD) was 12.7%, with a positive rate of hepatitis D antigen (HDAg) of 12%. Superinfection accounted for 18.9%, and the viral hepatitis markers were all negative in 0.8% of the total cases. There was very significant difference in prevalence of HCV-IgG and HEV-IgG between sporadic acute hepatitis patients and blood donors during the same periods. Icterus occurred in 68% of the total cases, 86.8% in HA. Patients of HB complicated with HD were liable to chronicity.

Acute Disease↗
PubMed1996

Integral repeats and a continuous coiled coil are required for binding of striated muscle tropomyosin to the regulated actin filament.

Tropomyosin is a coiled-coil protein that binds along the length of filamentous actin and contains sequence repeats that correspond to actin monomers in the filament. Analysis of striated muscle alpha-tropomyosin mutants in which internal sequence has been deleted or replaced with non-tropomyosin sequence showed that the following parameters are important for high affinity, cooperative binding of tropomyosin-troponin to actin. 1) Tropomyosin must be a coiled coil along its entire length. 2) An integral number of repeats corresponding to the actin monomers along its length is more important than the total number. 3) In comparison, the actin affinity is relatively insensitive to changes in the sequence of the internal regions of tropomyosin. The results suggest that the internal sequence repeats function as weakly interacting spacers to allow proper alignment of the ends on the regulated actin filament.

Actins↗
PubMed1996

Application of polymerase chain reaction for diagnosing amebic liver abscess.

Polymerase chain reaction (PCR) has been applied in diagnosing amebic liver infection by detecting pathogenic Entamoeba histolytica DNA in liver aspirates. Oligonucleotide primers found to be specific for the gene encoding the 30 kDa molecule of this pathogenic ameba were used in the test. Liver aspirates obtained from 23 patients with amebic liver abscess substantiated by typical clinical manifastation or with very high titres of anti-E histolytica antibodies by ELISA were found to be positive by PCR. Fourteen control samples (3 cases of bacterial liver abscess, 1 of liver cancer and 10 of other abscess) were all found to be negative to this reaction. The results suggested PCR to be a specific and sensitive tool for diagnosing amebic liver abscess infections.

Animals↗
PubMed1996

[Management of coagulation dysfunction in critically surgical patient].

12 surgical critically ill patients were studied for a better management of perioperative coagulation dysfunction. Their primary disease, clinical manifestation as well as some coagulation tests before and after therapy were retrospectively analysed. The result showed that secondary disseminated intravascular coagulation (DIC) is the main type of perioperative coagulation disorder, especially in decompensated hepatopathy and severe sepsis patients. It should be emphasized that: control of primary disease, effective drainage of focus, strict indication for 2nd surgical hemostasis and correct operation are required. For those hepatopathy with hypofibrinogenemia, some hemostatic drugs should be prohibited or very carefully used, in order to avoid the activation of plasmin and the exhaustion of fibrin. The early administration of heparin and aprotinin after the supplement of fibrinogen has shown a great potential benifit to stop the cascade of hypercoagulation and hyperplasminogenemia by enhancing the level of AT-III and fibrinogen in plasma.

Adult↗
PubMed1995

[A study of the relationship between electromyographic activity of the masticatory muscles and the variations of the occlusal vertical dimension for edentulous subjects]

The study was performed in fifteen edentulous subjects with the EMG activity were recorded at the varying occlusal vertical dimension maintaining constant bite force value of 4kg.The results showed that maintaining constant bite force the amplitudes of EMG activity of the anterior temporal and masseter muscles are decreased with increasing the occlusal vertical dimension and correlation relation between them,that there is a stable region about 1.0mm for the anterior temporal muscle and about 1.5mm for the masseter muscle during the changes in electrical activity.It is represent that there is a physiological region of the occlusal vertical dimension for edentulous patient.

Journal Article↗
PubMed1995

[Detection of pathogenic Entamoeba histolytica DNA in liver abscess aspirates with polymerase chain reaction].

Polymerase chain reaction (PCR) was used to diagnose amebic liver abscess by detecting pathogenic Entamoeba histolytica DNA in liver aspirates from patients with liver abscess. Oligonucleotide primers specific for gene encoding of the 30,000 molecule of pathogenic Entamoeba histolytica were used in the test. Liver aspirates from 23 cases with amebic liver abscess as evidenced by typical clinical findings or very high titres of anti-E. Histolytica antibodies with ELISA were found to be positive with PCR. Fourteen control samples (3 cases of bacterial liver abscess, 1 of liver cancer and 10 of abscess in other sites) were all negative to PCR. The results suggest that PCR is a sensitive and useful method for diagnosing amebic liver abscess.

Animals↗
PubMed1994

Production of a standard closed fracture in the rat tibia.

In order to develop a technique for producing a standard closed transverse fracture in the rat tibia, the method of Bonnarens and Einhorn was modified and tested on 176 tibiae. A 0.9-mm Kirschner wire was inserted percutaneously near the tibial tuberosity into the intramedullary canal, and a tibial fracture was created at the junction of the middle and distal third of the tibia with a blunt guillotine driven by a dropped weight. Radiographs confirmed the production of a highly reproducible transverse mid-shaft tibia fracture in 90% of the fractures. Minimal comminution of the fracture or angulation of the Kirschner wires resulted. The Kirschner wires were removed without difficulty after the rats were put to death and did not disturb the fracture site. Mechanical testing and histological studies showed that a standard fracture healing process was obtained by using this method. The results indicate that this modified method creates a standard, reproducible transverse closed fracture of rat tibia.

Animals↗
PubMed1993

Interactions of bilirubin with isolated presynaptic nerve terminals: functional effects on the uptake and release of neurotransmitters.

1. The functional effects of bilirubin:albumin solutions (10:1, mol/mol) on several synaptosomal functions were investigated using rat cortical, striatal, and hippocampal synaptosomes prepared by iso-osmotic Percoll/sucrose gradient centrifugation. 2. Bilirubin (10-80 microM) depolarized synaptosomes in a tetrodotoxin-insensitive manner as assessed by the equilibrium distribution of tetra-[3H]phenylphosphonium. Depolarization induced by bilirubin was of a lesser magnitude than that caused by KCl or veratridine. Steady-state pH gradients across the synaptosomal membrane were determined using the transmembrane distribution of [14C]methylamine. Bilirubin (20-40 microM) did not modify the intracellular pH in physiological buffers. The pigment effected a 0.14 delta pH change when the synaptosomes were suspended in a Ca2+ and Na+ free choline medium containing ouabain. 3. Bilirubin (20-80 microM) had no effect of its own on [7,8-3H] dopamine release from striatal synaptosomes. In contrast, it inhibited the initial rate of synaptosomal uptake of the catecholamine and its intrasynaptosomal content at 10 min. The pigment (20 and 40 microM) reduced the 35 mM KCl-induced release of endogenous acetylcholine from hippocampal synaptosomes by 20 and 36%, respectively. 4. The association of bilirubin with synaptic plasma membrane vesicles was characterized by a chloroform:methanol 2:1 (v/v) extraction method. At total concentrations of 10 to 80 microM bilirubin, the molar percentage of the pigment in synaptic plasma membrane phospholipids was 1-4%. 5. It is proposed that the two main functional consequences of the bilirubin-nerve ending interaction are an impairment of specific membrane-bound neurotransmitter uptake mechanisms and a reduction of the response to depolarizing stimuli. This may be the basis for rapid alterations in synaptic transmission documented in early reversible bilirubin encephalopathy.

Animals↗