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Biomedical subjects

Y Han

Publications and source records attributed to Y Han.

At least 271 records · Page 15Linked to original sources
PubMed1995

Deformation and flow of red blood cells in a synthetic lattice: evidence for an active cytoskeleton.

We introduce the use of microfabrication techniques to construct on a silicon wafer a synthetic capillary bed with 2.5- to 4-micron (mu)-wide channels. Establishment of a fluid pressure gradient allowed us to observe simultaneously using optical microscopy hundreds of cells flowing through the bed at physiological speeds. We find a large distribution of mobilities among red cells flowing through the structure; smaller channels provide a greater impedance to flow than larger ones, indicating that kinetic drag variations provide the origin of the distribution. The mobility of a particular cell is not correlated with the cell diameter but appears to be inversely correlated with intracellular calcium concentration of the cell, as determined by fluorescence of the calcium-binding dye fluo-3 AM. Also, we are able to use the parallel processing nature of our arrays to observe isolated events where the rigidity of the red cell seems to change suddenly over several orders of magnitude as it blocks a channel in the array.

Capillaries↗
PubMed1995

Enzyme-linked immunosorbent assay (ELISA) using a glycolipid antigen for the serodiagnosis of melioidosis.

The serodiagnosis of melioidosis is commonly performed with tests using protein or polysaccharide as antigen. However, due to the low sensitivity, specificity and difficulty in the preparation of the antigens, more simple, precise and reproducible diagnostic tests were required. A purified glycolipid antigen (GL) which is a specific lipid component of Burkholderia pseudomallei has been used in an ELISA. With this antigen, specific immunoglobulin G (IgG) was detected in 49 out of 50 melioidosis sera. IgG was also detected in 2 out of 185 (Japanese) and 16 out of 181 (Vietnamese) control sera. Thus, the sensitivity was 98.0%, and specificity was 98.9% and 91.1% in the Japanese and Vietnamese sera, respectively. When the ELISA and indirect haemagglutination (IHA) tests were combined, a sensitivity of 100% and specificity of 97.8% were achieved. The advantages of the glycolipid antigen are ease of preparation, stability, high sensitivity and specificity.

Antigens, Bacterial↗
PubMed1995

Dynamics of accommodative vergence movements controlled by the dominant and non-dominant eye.

Accommodative vergence responses to accommodative stimuli presented at three different amplitudes in a stepwise and a sinusoidal mode to either the dominant or the non-dominant eye were studied. The motor control loop was opened by one eye viewing the target and the other eye covered. Each eye was stimulated monocularly and eye movements were recorded with an infra-red reflection system. Latency and time constant of the accommodative vergence response to step stimulation or the phase of the vergence response to sine wave stimulation, did not vary systematically with stimulus amplitude or eye stimulated. However, the gain of the accommodative vergence movements was highest in the non-dominant eye at a particular stimulus amplitude. This suggested that accommodative vergence angles can vary depending on which eye is leading and driving the accommodative vergence system in a specific fixation situation.

Accommodation, Ocular↗
PubMed1995

Eye movements in normal subjects induced by vibratory activation of neck muscle proprioceptors.

Versional eye movements, induced by neck muscle vibration at 70 Hz in 8 normal subjects, were recorded with infrared reflection technique in each eye separately with one eye fixating a target and the other covered. The direction of eye movements was horizontal when the sternocleidomastoid muscle on one side of the neck and the splenius on the other side were activated, and downward when both splenii muscles were vibrated. The direction was the same as that of the illusory movements of the target also induced by the vibration. These findings would imply that the proprioceptive messages originating in the neck muscles are processed together with visual information of eye position in determining gaze direction.

Eye Movements↗
PubMed1995

Antibody response that protects against disseminated candidiasis.

We previously showed that surface mannans of Candida albicans function as adhesins during yeast cell attachment to mouse splenic marginal zone macrophages. The mannan adhesin fraction was encapsulated into liposomes and used to vaccinate mice over a 5- to 6-week period. Circulating agglutinins specific for the fraction correlated with increased resistance to disseminated candidiasis. Antiserum from vaccinated animals protected naive BALB/cByJ mice against C. albicans serotype A and B strains and Candida tropicalis. Antiserum also protected SCID mice against disseminated disease. The serum protective ability was stable at 56 degrees C, but this ability was adsorbed by C. albicans cells. The antiserum was divided into three fractions after separation by high-performance liquid chromatography. One fraction contained all of the agglutinin activity and transferred resistance to naive mice. A second fraction also transferred resistance. Two monoclonal antibodies (MAbs) specific for candidal surface determinants were obtained. MAb B6.1 is specific for a mannan epitope in the adhesin fraction, and MAb B6 is specific for a different epitope in the fraction. Both MAbs are immunoglobulin M, and both strongly agglutinate candidal cells, but only MAb B6.1 protected both normal and SCID mice against disseminated candidiasis. In one experiment, 10 normal mice were given MAb B6.1 and challenged with yeast cells. Six mice survived the 67-day observation period; 4 of the survivors were cured as evidenced by the lack of CFU in the kidney and spleen. Our studies show that antibodies against certain cell surface antigens of C. albicans help the host resist disseminated candidiasis.

Animals↗
PubMed1995

[Studies on the cell models of differentiation reversal phenotypes of human rhabdomyosarcoma].

We have observed the features of malignant phenotypes in human rhabdomyosarcoma RD cells. These cells exhibited high growth rate, aberrant relation between cell proliferation and myogenic terminal differentiation, blockage of myofibrillogenesis, inhibition of gap junctional intercellular communication (GJIC) and inhibition of transcriptional expression of gap junction gene, connexin 43 (Cx43). By utilization of single cell subclone separation and cDNA cell transfection techniques, we obtained several RD subclones, among them 3 were representative of differences in phenotypes and were selected for further study. They were single-cell subclone RDL6, RDL3, and a Cx43 transfectant clone of RDL6, the RDL6/C-4. Through determination of cell growth doubling time, co-stain of 3H-TdR autoradiography with myosin heavy chain (MHC) immunofluorescence, immunofluorescent cytochemical examination and slot-blot analysis, it was demonstrated that significant differences existed between each of the 3 subclones. They were differnet in cell growth rate, cell proliferation and terminal differentiation coupling relation, progress of myogenesis, functional expression of Cx43 gene, and expression of proto-oncogenes, c-myc, Ha-ras and c-met products, therefore they could be used as cell models in the study of reverse transformation of rhabdomyosarcomas. The reversal differentiation markers, their examination approaches and practical value were discussed.

Cell Transformation, Neoplastic↗
PubMed1995

Functional expression of gap junction gene Cx43 and the myogenic differentiation of rhabdomyosarcoma cells.

Rhabdomyosarcoma (RD) cells express low levels of the gap junction protein connexin 43 (Cx43), and its mRNA, and display very weak gap junctional intercellular communication (GJIC) as detected by Cx43 immunofluorescence, slot-blot and dye-transfer methods. These cells grow rapidly and show aberrant and incomplete myogenic differentiation. To investigate the role of gap junctions in these cells, the expression of Cx43 with relation to cell growth and myogenic differentiation in RD single-cell subclones-RDL3 and RDL6 is studied. The subclone RDL3 grows slowly and displays better myogenic differentiation. The expression of Cx43, its mRNA and the GJIC in RDL3 is comparable to that in normal myoblasts. Another subclone RDL6 which grows rapidly, but is poorly differentiated, expresses very low levels of Cx43 and its mRNA, and very weak GJIC. By using the calcium phosphate precipitate transfection technique, a full-length cDNA-encoding Cx43 and a pSV2neo have been introduced into the RDL6 cells. Several stably transfected clones have been obtained. A stable Cx43-transfectant clone RDL6/C-4 expresses high level of Cx43 and its mRNA, and results in dramatic increase of GJIC. These cells grow slowly but display the enhanced myogenic differentiation. A correlation between the down-regulation of Cx43 gene expression and a reduced expression of myogenic differentiation in RD cells is is demonstrated. Forced expression of Cx43 not only inhibits cell growth but also correlates with the improved myogenic differentiation of RD cells.

Cell Communication↗
PubMed1995

[Influence of age on severe pancreatitis].

Eighty-four patients of severe pancreatitis were divided by different line of age and the mortality of patients with severe pancreatitis above and below the line was comared. The results showed that the 60-year of age was the age with the lowest mortality. The analysis of 35 patients with severe pancreatitis who were older than 60 years of age indicated that multiple gallstones was the most common cause initiating the disease. The common severe concurrent diseases were hypertension, coronary disease, cerebrovascular disease, and respiratory disease. Common organ failures were ARDS, shock and heart failure. The number of failed organs in elderly patients in the fifth and seventh day after admission was obviously more than that in young patients.

Adolescent↗
PubMed1995

[Effects of thermal injury on production of nitric oxide in rat heart].

To elucidate the relationship between thermal injury and production of nitric oxide (NO), we measured the levels of heart No2-/NO3- (the stable and products of NO) and GMP in rats with full thickness burn of 30% TBSA. A higher level of heart tissue NO2-/NO3- was observed from 3 to 24 hours after burn injury. Parallel to the changes of NO2-/NO3-, there were increases of tissue cGMP level and heart tissue water content in burned rats. L-NMMA, a specific inhibitor of NO synthetase (NOS), can block the rise of heart NO2-/NO3- and the enhancement of heart water content. The results indicate that the heart injury caused by burn injury may be associated with induction of NOS and formation of NO.

Animals↗
PubMed1995

[Effect of lysostaphin on phagocyte function in burn mice].

The ability of lysostaphin to prevent immunosuppression of phagocyte was assessed in burn mice. A full thickness burn covering 20% of TBSA was created on back of mouse, Lysostaphin was given intraperitoneally (400 micrograms/kg/day) for 3 days in treatment group. The results showed that lysostaphin treatment could restore the depression of phagocytosis of chick RBC by peritoneal macrophages. In the group treated by lysostaphin, peritoneal macrophage chemiluminescence expressed much greater peak value than that in both burn and normal groups. The a-value, which is a criterion of carbon clearance, was 1.63 x 10(-2) in lysostaphin treated mice, while that in burn and normal mice were 8.13 x 10(-4) and 2.76 x 10(-3), respectively. Results of the study indicated that lysostaphin was effective in improving phagocytosis by phagocytes.

Adjuvants, Immunologic↗
PubMed1994

Cardiac contraction and intramyocardial venous pressure generation in the anaesthetized dog.

1. Two hypotheses relating to the influence of contraction of the heart on coronary venous pressure (Pv) were tested. The first assumes a direct transmission of left ventricular pressure (PLV). According to the alternative hypothesis the Pv is caused by cyclical changes in the elastance of the surrounding tissue. 2. A small epicardial vein was cannulated retrogradely in eight open-chest dogs deeply anaesthetized with fentanyl. The duration of diastoles was varied after induction of a heart block with formaldehyde. Coronary arterial inflow and perfusion pressure were controlled by a perfusion system connected to the left main coronary artery by a Gregg cannula. Stopped-flow Pv was studied with intrinsic coronary tone (IT) and after maximal dilatation with adenosine. 3. The Pv pulse in the first contraction after a long diastole was not significantly correlated to the PLV pulse, with a slope of 0.5, in any dog, either with IT or during adenosine treatment. Comparing the first contraction after the long diastole with the last beat before, systolic Pv pulse decreased significantly in seven out of eight dogs, but systolic PLV pulse increased in five dogs and was unaltered in three dogs in both conditions. In contrast, end-diastolic Pv was significantly correlated to the systolic Pv in each individual animal under either condition. 4. The results indicate that pressure generation in the small coronary veins can be explained on the basis of the time-varying elastance hypothesis and that a direct transmission of PLV to Pv is absent.

Adenosine↗
PubMed1994

A DNA-binding activity, TRAC, specific for the TRA element of the transferrin receptor gene copurifies with the Ku autoantigen.

We have previously described purification and characterization of a nuclear protein, TREF, which interacts specifically with the transcriptional control element, TRA, of the human transferrin receptor (TR) gene. In this report we show that TREF can be separated into two functionally distinct DNA-binding activities. The first DNA-binding activity (TRAC) is highly specific for the 8-bp element TRA and the related Escherichia coli cAMP receptor binding site. This motif is homologous to the phorbol 12-tetradecanoate 13-acetate- and cAMP-responsive elements of eukaryotic genes and the regulatory proximal sequence elements of the U1 small nuclear RNA gene and is also present in the promoter of the Drosophila melanogaster yolk protein factor 1 gene. In striking contrast, the second activity exhibits high affinity for the ends of double-stranded DNA in a sequence-unspecific manner and is attributable to the heterodimeric Ku autoantigen. Notably, transcription of Ku is induced during mid-late G0/G1 with kinetics similar to the TR gene. Ku is a highly abundant nuclear protein possessing nonspecific affinity for the ends of DNA, whose biological role remains to be elucidated. A transcriptional role for this protein has been proposed, however, on the basis of studies attributing DNA sequence-specific binding activity, notably for TRA-like sequences described above, directly to the Ku heterodimer. The observation that Ku-mediated nonspecific DNA-binding activity copurifies with the TRA-specific activity, TRAC, clearly has implications for these and related studies. The unusual properties of TRAC activity and its relationship, if any, with the enigmatic Ku protein, are discussed.

Antigens, Nuclear↗
PubMed1994

Co-evolution of ligand-receptor pairs.

Specific receptors for lutropin (luteinizing hormone; LH) and follitropin (follicle-stimulating hormone; FSH) mediate the actions of human chorionic gonadotropin (hCG) and FSH5 on the gonads. Here we report that short independent sequences of the beta-subunit enable hCG to distinguish between the receptors for FSH and LH. Residues between the 11th and 12th cysteines restrict FSH receptor binding; residues between the 10th and 11th cysteines and, to a much lesser extent, residues carboxy-terminal to the 12th cysteine also affect LH receptor binding. CF101-109, an hCG analogue containing hFSH beta residues between the 11th and 12th cysteines, had high affinity for both LH and FSH receptors. Modifications to CF101-109 that reduce binding to either LH or FSH receptors yield gonadotropin analogues having differing ratios of LH:FSH activity. Ligand-binding specificity of the LH receptor is determined by residues encoded by parts of exons 2-4 and 7-9 which prevent hFSH binding but have little effect on hCG binding. FSH receptor specificity is controlled primarily by residues encoded by exons 5 and 6 that prevent hCG binding but have little effect on hFSH binding. These determinants can be interchanged to create receptor analogues that bind hCG and hFSH. Our observations support a model in which distinct negative determinants restrict ligand-receptor interaction. This explains coevolution of binding specificity in families of homologous ligands and their receptors. Natural or designed manipulation of these determinants leads to the 'evolution' of new, specific protein-protein interactions.

Amino Acid Sequence↗
PubMed1994

Iron deficiency reduces the efficacy of tryptophan as a niacin precursor.

A niacin-deficient purified amino acid diet that contained adequate (40 mg/kg) or deficient (10 or 15 mg/kg) iron was used to assess the growth promoting efficacy of tryptophan as a niacin precursor. Basal diets contained 1400 mg/kg tryptophan, a level that was established as meeting the requirement for tryptophan per se in diets containing excess nicotinic acid. Chicks fed the iron-deficient diets had markedly lower hemoglobin concentrations than those fed the iron-adequate diets. Regardless of iron level, chicks exhibited linear growth responses to either nicotinic acid or tryptophan supplementation. Using multiple-linear regression of weight gain on supplemental tryptophan or nicotinic acid intake, the efficiency (wt:wt) of tryptophan conversion to niacin activity (i.e., tryptophan slope divided by nicotinic acid slope) was a mean of 1.77% (56:1) for chicks fed the iron-deficient diet. This was significantly (P < 0.05) lower than the 2.39% (42:1) efficiency calculated for chicks fed the iron-adequate diet. Thus, iron deficiency reduced tryptophan utilization (for NAD synthesis) but had no effect on nicotinic acid utilization. The results suggest that pellagra in populations having endemic anemia and protein-energy malnutrition may be due not only to inadequate intakes of bioavailable niacin but also to inadequate intakes of bioavailable iron.

Animals↗
PubMed1994

Mouse sialoadhesin is not responsible for Candida albicans yeast cell binding to splenic marginal zone macrophages.

Candida albicans hydrophilic yeast cells specifically adhere to mouse macrophages in the splenic marginal zone and in lymph node subcapsular and medullary sinuses. These macrophages express sialoadhesin that binds erythrocytes, but binding of yeast cells is not mediated by sialoadhesin because (i) erythrocytes did not block yeast cell binding, (ii) yeast cell adherence was unaffected by sialoadhesin-specific monoclonal antibodies, (iii) the purified sialoadhesin did not bind to yeast cells, and (iv) an Fc-sialoadhesin chimera immobilized on plastic did not bind yeast cells. These data give further support for a unique macrophage adhesion system that binds C. albicans.

Adhesiveness↗