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Biomedical subjects

J Yan

Publications and source records attributed to J Yan.

At least 163 records · Page 9Linked to original sources
PubMed1999

Binding of interferon gamma by glycosaminoglycans: a strategy for localization and/or inhibition of its activity.

Glycosaminoglycans (GAGs) are a group of negatively charged molecules present in many tissues as components of the extracellular matrix, basement and cellular membranes. This work analysed the ability of this group of substances to interact with human interferon gamma and the effect of those interactions on its biologic activity. A variety of GAGs (heparin, heparan sulfate, chondroitin sulfate and hyaluronic acid), and a related sulfated polysaccharide (dextran sulfate), were found to interact with IFN-gamma as determined by inhibition of the binding of [125I]IFN-gamma to COLO-205 cells and binding to wells coated with GAGs. These interactions were inhibited by synthetic peptides mimicking the sequences of the basic amino acid cluster located at the C-terminal end of mouse and human IFN-gamma, or by poly-L-lysine, suggesting that ionic interactions between the positively-charged C-terminus and negatively charged groups in GAGs were involved. IFN-gamma molecules bound to plate-immobilized or endothelial cell surface GAGs retained biological activity, since they could induce major histocompatibility complex (MHC) class II expression on COLO-205 cells, suggesting that cell surface GAGs might be able to present IFN-gamma to its receptors. These results suggest important regulatory roles for GAGs on the activity of IFN-gamma in vivo.

Animals↗
PubMed1999

Bio-stretch, a computerized cell strain apparatus for three-dimensional organotypic cultures.

In the present study, a unique mechanical strain apparatus for three-dimensional organotypic cultures was developed into a computerized system. It consists of a personal computer running Windows-based software, the Bio-Stretch Manager, a Bio-Stretch Controller, and three sets of magnet boards. Cells are cultured on a Gelfoam sponge that is placed in a 35 mm petri dish with one end glued to the dish, and the other end attached to a coated steel bar. The petri dish is placed in front of a magnet, and the movement of the steel bar is controlled by dynamically changing the magnetic field. Up to five stretch patterns of variable frequency, duty cycle, and magnitude can be designed for each stretch regimen. Three different stretch regimens can be tested simultaneously. The operational characteristics of sponges were examined. Attachment of cells to the sponges was observed on several cell types. These features provide wide options for using this system to study the effects of mechanical stretch on cells.

Animals↗
PubMed1999

Therapeutic intervention with complement and beta-glucan in cancer.

Complement (C) has two major effector systems available for host defense. The membrane attack complex (MAC) generated from components C5-C9 can form membrane-penetrating lesions that lead to cell death by causing a rapid loss of cytoplasmic components. The MAC is only effective against pathogens with outer phospholipid membranes, and cannot kill gram-positive bacteria or yeast whose membranes are protected by cell walls. The most important effector mechanism of C is the opsonization of microbial pathogens with the serum protein C3 that leads to their high avidity attachment to the C3-receptors of phagocytic cells. Pathogens that activate complement are first coated with the C3b fragment of C3, which is rapidly proteolyzed into the iC3b fragment by serum factor I. These iC3b fragments serve to promote the high avidity attachment of the 'iC3b-opsonized' pathogens to the iC3b-receptors (CR3, CD11b/CD18) of phagocytic cells and natural killer (NK) cells, stimulating phagocytosis and/or cytotoxic degranulation. Host cells, including neoplastic tumor cells, have been endowed with natural mechanisms for self-protection against both the MAC and the cytotoxic activation of CR3. This review discusses a novel type of immunotherapy for cancer that uses soluble yeast beta-glucan to override the normal resistance of iC3b-opsonized tumor cells to the cytotoxic activation of phagocyte and NK cell CR3, allowing this important effector mechanism of the C system to function against tumor cells in the same way that it normally functions against bacteria and yeast. Moreover, the cytotoxic activation of beta-glucan-primed NK cell CR3 by iC3b-opsonized tumors is shown to be accompanied by a tumor-localized secretion of the cytokines TNFalpha, IFNalpha, IFNgamma, and IL-6.

Animals↗
PubMed1999

Delayed effects of prenatal low-dose irradiation in the white matter of the rat brain.

PURPOSE: This study is part of a general search for the anatomical bases of the severe mental retardation syndrome caused by prenatal irradiation. More specifically, it seeks reasons for the high radiosensitivity of a white matter area, the cingulum of the corpus callosum. MATERIALS AND METHODS: Pregnant primiparous Wistar rats were exposed to X-rays at 12, 13, 14 or 15 days of gestation (E12, E13, E14 or E15) with single low doses of 180 mGy. A high dose of 500 mGy was given at E15 for a complementary study. The brains of the female offspring were collected at 1 and 3 months of age. The affinity of osmium tetroxide for the white matter was used to recognize and quantify cingulum areas in a series of coronal sections made at different positions along the antero-posterior axis of the brains. RESULTS: A 180 mGy dose of X-rays caused an atrophy of the cingulum; the effect was particularly significant in the 1-month-old brains after an exposure at E13 or at E14, and increased in the 3-month-old animals exposed at E15. The axonal size distribution was unchanged in the 3-month-old cingulums treated with 500 mGy at E15. CONCLUSIONS: The atrophy of the cingulum is due to a loss of axons, which are abundant in this area. As a consequence of axon loss, a reduction of the postnatal myelination enhances the volumetric decrease of the cingulum at 3 months of age.

Animals↗
PubMed1999

Gustatory neural coding in the cortex of the alert cynomolgus macaque: the quality of bitterness.

We sought to define the gustatory neural representation in primates for stimuli that humans describe as predominantly bitter. Thus we analyzed the responses of single neurons from the insular cortex of two alert, male cynomolgus macaques in response to the oral application of four basic taste stimuli (glucose, NaCl, HCl, and quinine HCl) and fruit juice, and to a series of 15 other chemicals to which humans ascribe a bitter component. Gustatory neurons occupied a volume of 109 mm3 across an area of 4.0 mm in the anterposterior plane, 4.4 mm in the mediolateral, and 6.2 mm in the dorsoventral. Taste cells represented 161 (8.6%) of the 1881 neurons tested for chemical sensitivity. Fifty of these could be monitored throughout the delivery of the entire stimulus series, and their responses constitute the data of this study. The mean spontaneous discharge rate of the cortical gustatory cells was 3.2 +/- 3.3 spikes/s (range = 0.2-17.7 spikes/s). The mean breadth-of-tuning coefficient was a moderate 0.77 +/- 0.15 (range = 0.25-0.99). Forty-eight neurons responded to taste stimuli with excitation, and two responded with inhibition. Forty-one of the 50 neurons were able to be classified into one of four functional types based on their responses to the four basic stimuli used here. These were sugar (n = 22), salt (n = 7), acid (n = 7), and quinine (n = 5). A two-dimensional space was generated from correlations among the response profiles elicited by the stimuli array. The 16 bitter chemicals formed a coherent group that was most closely related to HCl, moderately to NaCl, and bore no relationship with glucose. Within the bitter stimuli, six formed a subgroup that was most separated from all nonbitter chemicals: quinine HCl, phenlythiocarbamide, propylthiouracil, caffeine, theophylline, and phenylalanine. Humans describe these stimuli as rather purely bitter. Of the remaining 10 bitter compounds, 4 were on the fringe of the bitter group leading to NaCl: MgCl2, CaCl2, NH4Cl, and arginine. Humans characterize these as bitter-salty. Three were on the fringe leading to HCl: urea, cysteine and vitamin B1. Humans call these bitter-sour. The remaining three (nicotine, histidine, and vitamin B2) occupied the center of the bitter group. Taste quality, inferred from the position of each stimulus in the space, correlated well with human descriptions of the same stimuli, reinforcing the value of the macaque as a neural model for human gustation.

Action Potentials↗
PubMed1999

Corticofugal amplification of facilitative auditory responses of subcortical combination-sensitive neurons in the mustached bat.

Recent studies on the bat's auditory system indicate that the corticofugal system mediates a highly focused positive feedback to physiologically "matched" subcortical neurons, and widespread lateral inhibition to physiologically "unmatched" subcortical neurons, to adjust and improve information processing. These findings have solved the controversy in physiological data, accumulated since 1962, of corticofugal effects on subcortical auditory neurons: inhibitory, excitatory, or both (an inhibitory effect is much more frequent than an excitatory effect). In the mustached bat, Pteronotus parnellii parnellii, the inferior colliculus, medial geniculate body, and auditory cortex each have "FM-FM" neurons, which are "combination-sensitive" and are tuned to specific time delays (echo delays) of echo FM components from the FM components of an emitted biosonar pulse. FM-FM neurons are more complex in response properties than cortical neurons which primarily respond to single tones. In the present study, we found that inactivation of the entire FM-FM area in the cortex, including neurons both physiologically matched and unmatched with subcortical FM-FM neurons, on the average reduced the facilitative responses to paired FM sounds by 82% for thalamic FM-FM neurons and by 66% for collicular FM-FM neurons. The corticofugal influence on the facilitative responses of subcortical combination-sensitive neurons is much larger than that on the excitatory responses of subcortical neurons primarily responding to single tones. Therefore we propose the hypothesis that, in general, the processing of complex sounds by combination-sensitive neurons more heavily depends on the corticofugal system than that by single-tone sensitive neurons.

Acoustic Stimulation↗
PubMed1999

The human suprascapular nerve belongs to both anterior and posterior divisions of the brachial plexus.

For the sake of clarifying which division of the brachial plexus, anterior or posterior, does the human suprascapular nerve belong to, the suprascapular nerve and cervical nerves concerned were teased into bundles of fibers by the fiber analysis method in six adult human arms of cadavers. The suprascapular nerve received fibers from C4, C5 and C6 in two cases which have a communicating branch between C4 and C5, from C6 and C6 in three cases and only from C5 in one case. In contrast with the posterior root fibers, the anterior root fibers of C5 and C6 could easily be divided into anterior and posterior groups of bundles which entered the anterior and the posterior divisions of the brachial plexus and were called anterior motor and posterior motor elements respectively. The suprascapular nerve received fibers from the anterior and the posterior motor elements of C5 in all cases. In addition to the C5, the nerve received fibers from both elements of C6 in three cases or from the anterior element of C6 in two cases. From this result the suprascapular nerve is judged to be a nerve which belongs to both anterior and posterior divisions of the brachial plexus.

Adult↗
PubMed1999

[Research on immunological activity of non-immunological cells of decidua in normal early pregnancy].

OBJECTIVES: To investigate the immunological activity of non-immunological cells of decidua in normal early pregnancy. METHODS: Harvest the supernatant from cultured non-immunological cells of decidua. Inspect the effects of the supernatant on transforming function of T cells, killing activity of natural killer cells, the IgG secretion of B cells and the interleukin-2 (IL-2) secretion by lymphocytes of human peripheral blood by radioimmunological assay (RIA). RESULTS: The supernatant of the cultured non-immunological cells of decidua can inhibit the immunological function of T cells, natural killer cells and B cells to different extents, their maximum inhibiting ratio were 22.7%, 52.3% and 14.8% respectively, but there is no significant effect on the IL-2 secretion by lymphocytes. CONCLUSIONS: The non-immunological cells of decidua in normal early pregnancy have immunological inhibiting function, which might contribute to prevent fetus from being expelled by maternal immunological system.

Cells, Cultured↗
PubMed1999

[A study on the reserve capacity of endothelial tissue plasminogen activator in patients with acute coronary syndrome].

OBJECTIVE: To study the changes of the endothelial tissue plasminogen activator (tPA) reserve capacity in patients with acute coronary syndromes (ACS). METHODS: Veinous blood was sampled for determination of markers of the fibrinolytic system and hypercoagulability at admission and on the 10th day in patients with acute coronary syndrome (ACS), including acute myocardial infarction (AMI) in 15 and unstable angina pectoris (UAP) in 20. An occlusion test to determine the maximal endothelial tPA release was performed in order to evaluate the endothelial tPA reserve capacity. 20 patients with stable angina pectoris (SAP) and 12 normal subjects served as control. RESULTS: Patients with ACS had higher levels of tPA mass concentration, PAI-1 activity, D-dimers mass concentration and TAT mass concentration at admission and on the 10th day as compared with those in SAP and normal subjects. Maximal endothelial tPA release was initially reduced to (2.2 +/- 0.8) microg/L (P < 0.01, vs patients with SAP), but the levels recovered on the 10th day of follow-up to (4.5 +/- 1.2) microg/L (P > 0.05, vs patients with SAP). CONCLUSION: Endothelial tPA reserve capacity is reduced only during the acute phase and becomes normalized during follow-up. The alterations of plasma markers of systemic fibrinolysis persist longer in patients with ACS. The results demonstrated that the intravascular thrombus formation may relate more to the disturbance of endothelial fibrinolysis than to markers of the systemic fibrinolytic system. It is very important to correct the disturbances of endothelial fibrinolysis during the acute phase of ACS.

Acute Disease↗
PubMed1999

[Changes of telomere length in human nasopharyngeal carcinoma].

Using Southern hybridization, we analysed the telomere length from thirty patients with nasopharyngeal carcinoma and demonstrated telomere reduction in these individuals when compared with their age-matched controls. Of the 30 samples, 16.67% had telomere elongation, 76.67% had telomere reduction and 6.67% exhibited equal lengths as compared with the controls. Analysis of leukocytes from 30 controls indicated that the telomere length decreased (average 39 base Pairs Per year) with aging and a statistically significant correlation between the length and age was noted (r = -0.3913, P < 0.05). These results suggest that the consequences of telomere shortening in nasopharyngeal carcinoma may lead to chromosome instability.

Adult↗
PubMed1999

[Differences in haemozoin production and pathogenicity between chloroquine-sensitive and chloroquine-resistant strains of Plasmodium berghei].

AIM: To better understand the differences in haemozoin formation and pathogenicity between chloroquine-sensitive(N) and chloroquine-resistant(RC) strains of Plasmodium berghei. METHODS: IRC mice were grouped as follows: group Xba I (Normal control, NC), group II (control treated with chloroquine alone, CC), group III (mice infected with N strain), group IV (mice infected with RC strain, RC) and group V (mice infected with RC strain and treated with chloroquine, RCC). Morphologic features of the parasites, parasitaemia, histological and ultrastructural changes of livers among the groups were compared. RESULTS: Severe damages of the hepatic cells of the N group including increased lysosomes and swollen and fused mitochondria were detected. On the contrary, the prominent features in liver section of the RC group were inflammatory cell (notably mononuclear) infiltration and Kupffer cell activation. Numerous trophozoites and schizonts were sequestrated in hepatic sinusoids and less degeneration of parenchymal cells was found except for some swollen and vacuolated mitochondria. Internal food vacuoles containing haemozoin were found in the parasites of the N group, whereas external food vacuoles without haemozoin granules were arranged in foamy appearance within the parasitized cell of the RC group. CONCLUSION: P. berghei RC strain may modify the mode of ingestion and degradation of hemoglobin in the parasites, resulting in impeding haemozoin formation. The difference in virulence between the N and RC strain of P. berghei is probably attributed to the significant differences in the induction of immune response of the host.

Animals↗
PubMed1999

[The correlation analysis of obstructive sleep apnea syndrome and the size of oropharyngeal cavity].

OBJECTIVE: To explore the relationship between obstructive sleep apnea syndrome (OSAS) and the size of oropharyngeal cavity. METHOD: The distance from uvula basis to tongue, the distance between anterior and posterior tonsillar pillars and the uvula area were measured for 30 OSAS patients and 30 healthy controls. RESULT: The study data indicated that there was very significant difference between patients and healthy controls (P < 0.001). The results of correlation analysis indicated that there was a nagetive correlation between the distance from uvula basis to tongue, the distance from anterior to between posterior tonsillar pillars and apnea hypopnea index (AHI) (P < 0.05), but there was a positive correlation between uvula area and AHI (P < 0.01). The patient's height, weight were measured, the body mass index was positive correlation with AHI (P < 0.001). CONCLUSION: These observations suggest that the obesity, smaller pharyngerl area can play an important role in the pathogenesis of OSAS.

Adult↗
PubMed1999

[Effects of pure and crude Lycium barbarum polysaccharides on immunopharmacology].

Effects of pure Lycium barbarum polysaccharides (LBP-X) on immunological activity were compared with crude LBP. The pure LBP-X were divided into different doses, lower doses (5-20 mg/kg.d) of pure LBP-X showed a remarkable effect on immunological enhancement. Especially, LBP-X 10 mg/kg.d had a highly significance difference compared with crude LBP on immune indices in mice. Lycium barbarum polysaccharides have the best pharmacological effect when it was the best dose.

Adjuvants, Immunologic↗
PubMed1999

Differentiation of embryonic stem cells into neurons and retina-like structure in nude mice.

PURPOSE: To investigate the intraocular growth and biological characteristics of mice embryonic stem cells in nude mice. METHODS: Murine embryonic stem cells (D3 cell line) were cultured and maintained in an undifferentiated state in vitro, then transplanted into the anterior chamber of nude mice. Mophological and immunohistochemical examinations were implemented. RESULTS: Two to three days after transplantation, yellow-white floating granules, sheets and masses were seen inside the anterior chamber and vitreous cavity, and enlarged gradually. 14-20 days later, the mice were executed. Morphological examination showed that there were undifferentiated cells and some round or polygonal differentiated cells in anterior chamber and vitreous cavity. The morphology of these differentiated cells were similar to that of the retina. The cells were highly positive in NSE staining. CONCLUSION: The transplanted embryonic stem cells could grow in the eyes of nude mice with tendency to differentiate into neurons and retina-like structure.

Animals↗
PubMed1999

Corneal topographical changes following strabismus surgery.

PURPOSE: To study corneal topographical changes after strabismus surgery. METHODS: Computer-aided corneal topography was used in 43 strabismus patients (45 eyes) one or two days prior to and six or seven days after strabismus surgery. The spherical and cylindrical equivalents were calculated based on the simulated keratometry. RESULTS: After the surgery, only the changes at 3 mm in the inferior quadrant were statistically significant. The changes at 3 mm in the rest quadrants and the changes at 7 mm were not significant. Significant changes in spherical equivalent were found post-operatively. Neither the horizontal nor the vertical meridional equivalent showed significant changes after surgery. CONCLUSIONS: The results of corneal topographical changes following strabismus surgery in our preliminary study indicated the little effect of strabismus surgery on corneal curvature and corneal astigmatism.

Adolescent↗