Biomedical subjects

X F Xu

Publications and source records attributed to X F Xu.

At least 19 recordsLinked to original sources

PubMed2006

Fast blind extraction of arbitrary unknown phase shifts by an iterative tangent approach in generalized phase-shifting interferometry.

A novel fast convergent algorithm to extract arbitrary unknown phase shifts in generalized phase-shifting interferometry (PSI) is proposed and verified by a series of computer simulations. In this algorithm an error function is introduced and then the unknown phase shifts are found by an iterative tangent approach. In combination with the statistical method, this algorithm can give the most exact results in the fewest iteration steps. It can be used for generalized PSI of arbitrary frames for both smooth and diffusing objects and can usually reach the exact phase shifts with only four or five iterations for three- or four-frame PSI.

Journal Article↗

PubMed2006

Two-step phase-shifting interferometry and its application in image encryption.

Conventional phase-shifting interferometry (PSI) needs at least three interferograms. A novel algorithm of two-step PSI, with an arbitrary known phase step, by which a complex object field can be reconstructed with only two interferograms is proposed. This algorithm is then applied to an information security system based on double random-phase encoding in the Fresnel domain. The feasibility of this method and its robustness against occlusion and additional noise attacks are verified by computer simulations. This approach can considerably improve the efficiency of data transmission and is very suitable for Internet use.

Journal Article↗

PubMed1992

[Changes in T lymphocytes and their subpopulations and IgG in peripheral blood from mice infected with Trichinella spiralis].

Acid alpha-naphthyl esterase (ANAE), a cytoplasmic marker, was used to identify the T lymphocytes and their subpopulations in peripheral blood of mice infected with Trichinella spiralis, and Dot-ELISA was used to identify the serum IgG antibody of the infected mice. The results showed that T lymphocytes increased on the d3 after infection, reaching the peak on d14, and then remained in number greater than normal up to d77. The spotted granular ANAE positive cells (Help T cells, Th) decreased and the scattered granular ANAE positive cells (Suppressor T cells, Ts) increased, leading to a drop of the Th/Ts ratio. The reduction in host immune function during T. spiralis infection might be related to the drop of Th/Ts ratio. At the same time, the serum IgG antibody increased on d7 after infection, reaching the peak on d28, and remained higher up to d140. The results indicated that the host's cellular immunological level was lower while the host's IgG antibody level was higher during T. spiralis infection.

Animals↗

PubMed1991

Delayed recovery from NG-nitro-L-arginine in the conscious sheep.

1. In the chronic, awake, instrumented sheep model NG-nitro-L-arginine (NOLA) an inhibitor of nitric oxide synthesis, injected at a dose of 40 mg/kg, produced a significant increase in systolic blood pressure (from 110 +/- 6 to 145 +/- 8 mmHg after 5 min) which persisted for at least 1 h but returned to baseline after 24 h. 2. When NOLA was repeated 1 and 4 days after the first injection, the blood pressure response was significantly attenuated, and at 1 day was no greater than the response to an equivalent volume of saline. The blood pressure response returned to the initial response with an 8 day interval between injections. 3. There was no significant blood pressure response to 100 mL of saline before the NOLA injection; however, 1 and 4 days after NOLA there was a significant rise in blood pressure.

Adrenergic alpha-Antagonists↗

PubMed1991

Testosterone increases lipolysis and the number of beta-adrenoceptors in male rat adipocytes.

The influence of androgen status on the regulation of lipolysis and number of beta-adrenoceptors in isolated adipocytes was studied in male rats. Castration resulted in decreased catecholamine-induced as well as forskolin-induced lipolysis. beta-adrenoceptor number, examined by a whole cell cyanopindolol binding assay, was also diminished to a similar extent. Testosterone treatment of castrated rats normalized lipolysis as well as beta-adrenoceptor number. These results demonstrate that testosterone stimulates catecholamine-induced lipolysis in vivo by increasing the number of beta-adrenoceptors as well as the activity of adenylate cyclase, confirming previous in vitro studies performed in adipose precursor cells.

Adipose Tissue↗

PubMed1991

The effects of exercise, training on body composition and metabolism in men and women.

In order to examine whether there are sex-differences in the response of energy balance to physical training slightly obese men and women participated in the same 3 months physical training program with the same individual relative intensity. The men became somewhat lighter (-2 kg) and leaner (-2.9 kg body fat) and showed decreases in sum of insulin and sum of C-peptide values during an oral glucose tolerance test as well as cholesterol values. The women showed decrease of 2.6 kg body fat, and also increased lean body mass (1.9 kg) and similar metabolic changes. The women had, however, a larger body fat mass at the outset. When women with similar body fat mass as that of men were analysed separately, no change in body weight or body fat had occurred, and the metabolic adaptations were less pronounced. No compensatory increase of energy intake could be discovered in any of the groups, the most obese women actually showed a decrease. Taken together with previous information these results suggest that men, like male rats, become leaner during physical training due to a lack of energy intake compensation. Women with similar body fat mass, however, like female rats, may react with such a compensation, causing a protection of their body fat. Women usually have more body fat than men, however. Obese women in this study showed a decrease of body fat.

Adult↗

PubMed1990

Up-regulation of androgen receptor binding in male rat fat pad adipose precursor cells exposed to testosterone: study in a whole cell assay system.

Binding of androgens to adipocytes has previously been evaluated using cytosol fractions without taking into account nuclear binding, although the latter is suggested to be close to the physiological site of action. In the present study, performed in differentiated fat pad adipose precursor cells, we describe a simple, reliable and reproducible androgen binding assay in a system with intact cells. Tritiated and unlabeled methyltrienolone (R1881) were used to define specific and unspecific androgen binding. Triamcinolone acetonide was added to prevent the binding of R1881 to other types of receptors. Differentiated adipose precursor cells contain a homogeneous class of high affinity androgen binding sites, and binding is saturable and reversible. Binding apparently occurs at one site, with a Kd in the range of physiological androgen concentration (about 4 nM). Competition studies indicate that the receptor is specific for R1881, testosterone and dihydrotestosterone, which have approximately the same affinity, while progesterone, estradiol and dexamethasone show much lower affinity. Androgen binding was markedly enhanced after cellular exposure to R1881 and testosterone but not dihydrotestosterone, and this increase was dependent on protein synthesis, suggesting the formation of new receptors by these androgens. In conclusion, fully differentiated adipocytes contain a specific, high affinity receptor, the density of which is dependent on androgens.

Adipose Tissue↗

PubMed1990

Progestin binds to the glucocorticoid receptor and mediates antiglucocorticoid effect in rat adipose precursor cells.

The binding of progestin and glucocorticoid hormones was examined in the cytosol of rat adipose precursor cells. Progestin binding sites of high affinity and limited capacity were present in the cytosol of adipose precursor cells from female rats, but not from male rats, by using [3H]R5020 as radioligand. Glucocorticoid binding sites of high affinity and limited capacity were present in the cytosol of these cells from both male and female rats by using [3H]dexamethasone and [3H]triamcinolone acetonide as radioligands. The dissociation constants were in the physiological concentration range. Studies of competitive binding showed that progestin could compete with glucocorticoids at glucocorticoid binding sites. In a serum free medium glucocorticoid effect on cellular differentiation, monitored by glycerophosphate dehydrogenase (GPDH), was effectively counteracted by progesterone which by itself had no effect. These results demonstrate that progestin receptor exists only in rat adipose precursor cells from female rats, while glucocorticoid receptor exists in rat adipose precursor cells of both sexes. Glucocorticoid effects on cellular differentiation in these cells are mediated by the glucocorticoid receptor. Progestin binds to the glucocorticoid receptor and antagonizes glucocorticoid effect on cellular differentiation in these cells.

Adipose Tissue↗

PubMed1990

Effects of dexamethasone on multiplication and differentiation of rat adipose precursor cells.

The effects of dexamethasone (DEX) on adipose precursor cells from rat adipose tissue were studied in primary culture. When added from the beginning of culture in media containing untreated fetal calf serum (SM), serum treated with charcoal to remove steroid hormones (CSM), or serum-free medium (SFM), DEX inhibited cellular growth. Lipoprotein lipase (LPL) as well as glycerophosphate dehydrogenase (GPDH) activities, markers of cellular differentiation, were also inhibited, except in CSM where LPL was stimulated. When added after cellular confluence, however, DEX had opposite effects and now stimulated cellular differentiation. This effect was highly dependent on insulin. These studies demonstrate that DEX affects adipose precursor cells in several ways, depending on the type of culture medium, the time period of exposure, and the presence of insulin.

Adipose Tissue↗

PubMed1990

A survey of cigarette smoking among middle school students in 1988.

A survey of the prevalence of smoking in middle school students aged 13-21 years in Harbin city, China, was undertaken in the Spring of 1988. A random sample of 4712 students was selected using proportional stratified clustering. A self-administered confidential questionnaire relating to smoking habits and certain family and school factors was administered. The results showed that 1.29% of the students (2.21% boys and 0.38% girls) smoked regularly, 5.62% (10.52% boys and 0.76% girls) were light smokers and 13.77% (24.29% boys and 2.92% girls) smoked only occasionally. Smoking habits were related to the type of school and to age, there being a higher proportion of smoking in senior grade students. Students were significantly more likely to smoke if they were male and if their siblings smoked. Prevalence of regular smoking was not related to parental occupation or family income. It is suggested that anti-smoking education in the school curriculum should be directed towards students in middle school.

Adolescent↗

PubMed1990

The effects of steroid hormones on adipocyte development.

Corticosteroids inhibit the differentiation of adipocyte precursor cells in the presence of fetal calf serum. This inhibition is more pronounced in serum-free media or in the presence of serum, extracted free from steroid hormones. Progesterone antagonized this inhibition in serum-free media and in media with extracted serum, and caused an increased differentiation in media with sera where corticosteroids had not been removed. Corticosteroid hormones bind specifically to these cells. The binding is saturable and has a Kd in the order of circulating hormonal concentrations. Progesterone competes effectively with this binding at physiological concentrations. Progesterone is also bound to these cells but 17-beta-estradiol, is not. Neither of these hormones shows effects alone or in combination with each other on the development of new adipocytes in the system in question. It was speculated that the effect of progesterone to release corticosteroid inhibition of adipose precursor cell differentiation might be of importance during pregnancy, and contribute to the risk of development of hyperplastic obesity.

Adipose Tissue↗

PubMed1990

[Soluble protein and esterase isozyme analysis of adult female Anopheles stephensi after Plasmodium yoelii yoelii-infected blood meal].

In this paper, the system of Anopheles stephensi and Plasmodium yoelii yoelii was used as animal model. The soluble protein and esterase isozymes of adult female mosquitoes at various times after taking noninfected and plasmodia-infected blood meal were investigated. The result shows that the amount of soluble protein in plasmodia-infected mosquitoes was lower than that in noninfected ones (P less than 0.01); the activity and electrophoretic patterns of EST in infected mosquitoes being also different from those of the noninfected ones.

Animals↗

PubMed1987

Effects of sex steroid hormones on differentiation of adipose precursor cells in primary culture.

The effects of estradiol-17 beta and progesterone on multiplication, differentiation and lipid filling of adipose precursor cells were examined in primary cell cultures of cells prepared from adipose tissue of both male and ovariectomized female rats. Progesterone down to a concentration of 10(-7) mol/liter, alone or in the presence of estradiol-17 beta stimulated the development of glycerophosphate dehydrogenase and lipoprotein lipase activity. Estradiol-17 beta alone had no effects. These effects were essentially parallel to increases in the rate of lipid filling of the cells. Furthermore, the formation of cells with a lipid vacuole greater than 20 micron was markedly stimulated, suggesting that new fat cells were formed by the stimulation of differentiation of the adipose precursor cells. No effects of the sex steroid hormones were seen on the rate of multiplication. These results suggest a role of sex steroid hormones in the regulation of triglyceride storage capacity in adipose tissue by facilitating the differentiation of precursor cells to form new adipocytes.

Adipose Tissue↗

PubMed1987

Effects of age, obesity and growth-hormone on adipogenic activity in human plasma.

The potential was examined for insulin, growth hormone and insulin-like growth factor (IGF-1) alone or in combinations to stimulate glycerophosphate dehydrogenase (GPDH) activity, a sensitive marker of differentiation of adipose precursor cells in primary culture. Insulin, but not growth hormone or IGF-1, stimulated GPDH in the presence of fetal calf serum and cat serum. The content of growth hormone in adult rat heparinised plasma seemed, however, important for such stimulation, but was also dependent on feeding status of the plasma donor, and was abolished by hypophysectomy of the cell donor. GPDH activity was then analysed in heparinised plasma in the over-night fasting state in humans to examine a potential influence of age, obesity and pregnancy. In comparison with non-obese adults, GPDH-stimulatory activity was higher in plasma from infants and small children. A similar trend was seen in plasma from teenagers. This activity was probably partly dependent on growth hormone, because this increase of activity could be inhibited by excess of anti-human growth hormone antiserum. Obesity in adulthood or among teenagers was not associated with any difference in plasma activity to stimulate cellular differentiation, and plasma from women during late pregnancy had a low stimulating capacity. Simultaneous analyses of the potential of plasma to stimulate lipid accumulation in adipose precursor cells was proportional to the triglyceride concentration. Overall, the inhibitory effect of antihuman growth hormone antiserum on the differentiating capacity of human plasma was small or non-existing. It is therefore suggested that in human plasma, factors other than growth hormone might be important for the differentiation of adipocyte precursor cells.

Adipose Tissue↗

PubMed1986