Biomedical subjects

C Yu

Publications and source records attributed to C Yu.

At least 91 records · Page 5Linked to original sources

PubMed2001

Surround modulation of perceived contrast and the role of brightness induction.

We studied iso- and cross-orientation surround modulation of perceived contrast (contrast-contrast phenomenon) with a contrast-matching method. Our results indicate (1) iso-oriented surrounds at all contrasts suppress perceived contrast of the test pattern. Cross-orientation surrounds, however, tend to enhance the perceived contrast of the test, particularly for high-contrast test patterns. Iso-orientation modulation acts over larger distances than does cross-orientation modulation. Surround modulation of perceived contrast is not accompanied by a simultaneous change of discrimination threshold. (2) Iso-orientation surround suppression is phase insensitive when brightness induction due to local luminance contrast is eliminated by a small center-surround gap. (3) Perceived contrast is similarly affected when the surround spatial frequency is equal to or higher than the center spatial frequency, but lower spatial frequency surrounds markedly enhance perceived contrast as a result of brightness induction. These data indicate that the contrast-contrast phenomenon is often mixed with brightness induction when it is measured with sinusoidal grating stimuli, and we suggest that this may account for some of the individual differences. After excluding the role of brightness induction, surround modulation of perceived contrast appears to be a second-order process that is phase independent and not tuned or very broadly tuned to spatial frequency.

Contrast Sensitivity↗

PubMed2001

Carbon monoxide of vascular origin attenuates the sensitivity of renal arterial vessels to vasoconstrictors.

Rat renal interlobar arteries express heme oxygenase 2 (HO-2) and manufacture carbon monoxide (CO), which is released into the headspace gas. CO release falls to 30% and 54% of control, respectively, after inhibition of HO activity with chromium mesoporphyrin (CrMP) or of HO-2 expression with antisense oligodeoxynucleotides (HO-2 AS-ODN). Patch-clamp studies revealed that CrMP decreases the open probability of a tetraethylammonium-sensitive (TEA-sensitive) 105 pS K channel in interlobar artery smooth muscle cells, and that this effect of CrMP is reversed by CO. Assessment of phenylephrine-induced tension development revealed reduction of the EC(50) in vessels treated with HO-2 AS-ODN, CrMP, or TEA. Exogenous CO greatly minimized the sensitizing effect on agonist-induced contractions of agents that decrease vascular CO production, but not the sensitizing effect of K channel blockade with TEA. Collectively, these data suggest that vascular CO serves as an inhibitory modulator of vascular reactivity to vasoconstrictors via a mechanism that involves a TEA-sensitive K channel.

Animals↗

PubMed2001

Spectroscopic studies and photodynamic actions of hypocrellin B in liposomes.

Hypocrellin B (HB), a lipid-soluble natural pigment of perylenequinone derivative, is considered as potential photosensitizer for photodynamic therapy. Liposomes loaded with HB can constitute a simple model system, appropriate for better understanding the photodynamic action of HB in vivo. The steady-state absorption and emission spectra, quantum yield and lifetime of fluorescence of HB incorporated into egg L-a-phosphatidyl-choline (EPC) liposome were examined. The photochemical properties (Type I and/or Type II) of HB have also been studied in aqueous dispersions of small unilamellar liposomes of EPC using electron paramagnetic resonance and spectrophotometric methods, respectively. The quantum yield of 1O2 generated by HB is ca 0.76 in chloroform solution and it did not change upon the incorporation of HB into liposomes of EPC. The superoxide anion radical was generated by the electron transfer from the anion radical of HB (HB.-) to oxygen. The disproportionation of O2.- can generate H2O2 and ultimately the highly reactive .OH via the Fenton reaction. It could be that the disproportionation proceeded too fast, so we could not detect O2.- directly in aqueous dispersions of liposome EPC. Moreover, the self-sensitized photooxygenation of HB embedded in liposomes was studied, and almost fully (87%) inhibiting this reaction of HB by p-benzoquinone (as the quencher of O2.-) in aqueous dispersion of liposome EPC indicated that the radical mechanism (Type I) might be mainly involved in this oxygenation. All these findings suggested that the photodynamic action of HB proceeded via both Type-I and -II mechanisms, but Type-I mechanism might play a more important role in the aqueous dispersion.

Electron Spin Resonance Spectroscopy↗

PubMed2001

Stimulating effects of low-dose fructose on insulin-stimulated hepatic glycogen synthesis in humans.

Fructose has been shown to have a catalytic effect on glucokinase activity in vitro; however, its effects on hepatic glycogen metabolism in humans is unknown. To address this question, we used (13)C nuclear magnetic resonance (NMR) spectroscopy to noninvasively assess rates of hepatic glycogen synthesis and glycogenolysis under euglycemic (approximately 5 mmol/l) hyperinsulinemic conditions (approximately 400 pmol/l) with and without a low-dose infusion of fructose (approximately 3.5 micromol. kg(-1). min(-1)). Six healthy overnight-fasted subjects were infused for 4 h with somatostatin (0.1 micromol. kg(-1). min(-1)) and insulin (240 pmol. m(-2). min(-1)). During the initial 120 min, [1-(13)C]glucose was infused to assess glycogen synthase flux followed by an approximately 120-min infusion of unlabeled glucose to assess rates of glycogen phosphorylase flux. Acetaminophen was given to assess the percent contribution of the direct and indirect (gluconeogenic) pathways of glycogen synthesis by the (13)C enrichment of plasma UDP-glucuronide and C-1 of glucose. In the control studies, the flux through glycogen synthase and glycogen phosphorylase was 0.31 +/- 0.06 and 0.17 +/- 0.04 mmol/l per min, respectively, and the rate of net hepatic glycogen synthesis was 0.14 +/- 0.05 mmol/l per min. In the fructose studies, the glycogen synthase flux increased 2.5-fold to 0.79 +/- 0.16 mmol/l per min (P = 0.018 vs. control), whereas glycogen phosphorylase flux remained unchanged (0.24 +/- 0.06; P = 0.16 vs. control). The infusion of fructose resulted in a threefold increase in rates of net hepatic glycogen synthesis (0.54 +/- 0.12 mmol/l per min; P = 0.008 vs. control) without affecting the pathways of hepatic glycogen synthesis (direct pathway approximately 60% in both groups). We conclude that during euglycemic hyperinsulinemia, a low-dose fructose infusion causes a threefold increase in net hepatic glycogen synthesis exclusively through stimulation of glycogen synthase flux. Because net hepatic glycogen synthesis has been shown to be diminished in patients with poorly controlled type 1 and type 2 diabetes, stimulation of hepatic glycogen synthesis by this mechanism may be of potential therapeutic value.

Adult↗

PubMed2001

[Expression of human anti-HBsAg-interferon fusion protein in CHO cells].

OBJECTIVE: To study the possibility of expressing human anti-HBsAg-interferon fusion protein in CHO cells as a putative targeting drug for hepatitis B. METHODS: Both the heavy and light chain genes of human anti-HBsAg antibody derived from a phage display library were fused with alpha-2b interferon (IFN-alpha-2b) gene in vitro by polymerase chain reaction. The IFN alpha-2b gene was placed at the C terminal and a 15 amino acid linker was introduced at the fusion site. The light chain-IFN expression plasmid pLIC was constructed with a mammalian expression vector pcDNA3.1(+) and the heavy chain-IFN expression plasmid pFID was constructed with another mammalian expression vector pCdhfr1. These plasmids and the anti-HBsAg full-length light and heavy chain expression plasmids (pLIC and pHFD, respectively) were transfected into CHO (dhfr-) cells by the following three combinations:I, pLIC + pHFD;II, pLIC + pFID; III, pLFC + pFID. The cultured supernatant of the transfected cells was collected and assayed for IFN activity and HBsAg affinity. RESULTS: The supernatant of combination I and II displayed IFN activity but only combination I supernatant exhibited HBsAg affinity. CONCLUSIONS: The successful expression of a fusion protein with both HBsAg affinity and interferon activity may lead to a new way to make a targeting drug for hepatitis B.

Animals↗

PubMed2001

[Accumulation, chemical fractions and phytoavailability of Cr in tannery sludge-amended soils].

The phytoavailability of various fractions in the tannery sludge amended soils was investigated employing a sequential extraction procedure as well as seedling culture experiment. The results showed that 2 mol/L HCl extractable Cr could be the major fraction of soil Cr available to the plants. When the Cr content in soil was about 220 mg/kg, the Cr concentration of in plant reached maximum of 23.5 mg/kg, which was hardly approachable in field condition.

Chromium↗

PubMed2001

[CT appearance and its diagnosis value in liver cancer after transcatheter oily chemoembolization combining with high intensity focused ultrasound therapy].

OBJECTIVE: To study the CT appearances of liver cancer after transcatheter oily chemoembolization (TOCE) combining with high intensity focused ultrasound (HIFU) therapy. METHODS: Fifty cases of clinically-proved liver cancer were included into this study. For each case, CT scanning before and after TOCE, HIFU treatment was performed. The volumes of the masses were measured. The appearances of the oily deposition and the density, shape, border of the lesions were observed. RESULTS: The lesions became smaller in 38 cases (38/50, 76%) after the treatment. The differences were detected statistically in the ratio of the tumor shrinkage between the single TOCE therapy and the combined treatment (P<0.05). The ratio of the tumor shrinkage was closely correlative with the quantity of the oily deposition, but not with the diameter of the tumor before treatment. The lowered densities were showed in 30 cases (30/50, 60%) and the borders became regular and clear in 16 cases after HIFU therapy. CONCLUSIONS: TOCE combining with HIFU therapy in the patients with liver cancer can make the tumor smaller. CT is of great value in the evaluation of efficacy and prognosis.

Adult↗

PubMed2001

[Isozyme analysis of Gastrodia elata f. elata and G. elata f. glaucca and their hybrid].

Peroxidase(POX) isozyme analysis of Gastrodia elata f. glaucca, G. elata f. elata and its hybrid were carried out. The results indicated that shoot apex meristem was optimal material for POX analysis and the determination of the hybrid. The zymogram hands were stable and clear. POX isozyme zymogram of the hybrid F1(H x W) represented the visible supplement relation between Gastrodia elata f. elata and Gastrodia elata f. glaucca.

Gastrodia↗

PubMed2001

[Study on the effects of leptin on puberty development in children].

OBJECTIVE: To study the effects of leptin on puberty development in children. METHODS: Three hundred obese and 300 healthy children without taking any medication or having evidence of endocrine or metabolic diseases were studied. Their ages of first spermatorrhea and menarche were surveyed, and blood levels of leptin, sex hormones, growth hormone (GH) and insulin (INS) were measured. RESULTS: With increased of age, blood levels of leptin appeared from low to high and from high to low again in the boys, with (1.04 +/- 0.21) nmol/L to (1.20 +/- 0.27) nmol/L and to (0.66 +/- 0.10) nmol/L in the obese group, and with (0.31 +/- 0.06) nmol/L to (0.45 +/- 0.10) nmol/L and to (0.19 +/- 0.04) nmol/L in the control group. While blood level of leptin appeared an increasing trend in girls, with (0.89 +/- 0.15) nmol/L to (1.39 +/- 0.23) nmol/L in the obese group, and (0.46 +/- 0.08) nmol/L to (0.88 +/- 0.18) nmol/L in the control group. Levels of sex hormones also appeared an increasing trend in the all groups. Levels of GH showed an abrupt increased at certain ages, different in boys from girls (14-15 years of age in boys and 13-14 in girls). In the all ages, serum levels of leptin and INS were higher in the obese group than those in the control group, while the level of GH was lower in the obese group than that in the control group. Serum level of leptin was higher in the obese group of both boys and girls than that in the control group, with (0.71 +/- 0.17) nmol/L and (0.30 +/- 0.04) nmol/L and (1.11 +/- 0.21) nmol/L and (0.70 +/- 0.18) nmol/L, respectively. Ages at first spermatorrhea and menarche were much earlier in the obese children than those in the controls, with (12.5 +/- 1.2) and (13.2 +/- 1.2) years of age in boys and (11.6 +/- 0.8) and (12.8 +/- 0.9) in the girls, respectively. Blood levels of leptin was higher in the girls than that in the boys. Age at menarche and earlier in the girls than that of first spermatorrhea in the boys. Blood level of testosterone correlated inversely with that of leptin in boys, while that of estradiol correlated with that of leptin in girls. Level of GH correlated inversely with that of leptin in boys and correlated with that in girls. Level of INS correlated with that of leptin in the control girls. CONCLUSIONS: Leptin might have an effect on initiation of puberty in children, possibly with more importance in girls than in boys. The gender difference in the degree of correlations between levels of leptin and GH may cause their difference in the ages at sudden growth in boys and girls. The gender difference in the degree of correlation between levels of leptin and sex hormone may cause their difference in the ages at first spermatorrhea and menarche in both boys and girls.

Adolescent↗

PubMed2001

[Microsurgical anatomy of intracranial segment of facial nerve].

OBJECTIVE: To study the microsurgical anatomy of intracranial segment of facial nerve so as to provide anatomic parameters for clinical operation. METHODS: Ten adult cadavers were fixed and perfused with color silicon. Facial nerves of these cadavers were observed and measured under operative microscope according to lateral cranial base operative approach. Ten dry skulls were dissected to observe the relationships of osseous structures. The anatomic relationship and data of different segment of facial nerve were obtained respectively. RESULTS: The facial nerve was divided into five segments, namely, cerebellopontine angle segment, internal acoustic meatus segment, labyrinthine segment, tympanum segment and mastoid segment. The cerebellopontine angle segment and internal acoustic meatus segment paralleled the vestibulocochlear nerve. The labyrinthine aegment is the finest and shortest with the lebgth of 3.8 mm +/- 0.7 mm. The tympanum segment is closely related with osseous labyrinth. The mastoid segment, 15.5 mm +/- 1.9 mm long, leaves the cranium from stylomastoid foramen. CONCLUSION: Facial nerve can be located with choroid plexus of the fourth ventricle in retrosigmoid approach. Arcuate eminence and greater superficial petrosal nerve are important mark to locate internal acoustic meatus segment and labyrinthine segment in antepetrosal approach. Tympanum segment may be exposed on the surface of petrous bone in some cases. The line between lateral semicircular canals and crista of digastric muscle is the mark of mastoid segment.

Adult↗

PubMed2001

Retrograde interlocking intramedullary nailing under arthroscopy for supracondylar femoral fracture.

OBJECTIVE: To evaluate the therapeutic effects of retrograde interlocking intramedullary nailing under arthroscopy on supracondylar femoral fractures. METHODS: From June 1999 to December 2000, 17 patients with supracondylar femoral fracture were treated with arthroscopically assisted implantation of retrograde interlocking intramedullary nail and close reduction. RESULTS: More than 6-month follow-up study after operation in 11 patients revealed that the average healing time was 3 months. Average range of the knee motion for all the patients was more than 90 degrees. There was no implant breakage and infection. CONCLUSIONS: This new method, combining the advantage of arthroscope and retrograde interlocking intramedullary nail, can provide a stable and reliable fixation, and meanwhile is less invasive to the soft tissue and knee, less operative time and blood loss, minimal disruption of the blood supply in fracture site. It is conducive to the fracture healing and the functional recovery of the knee joint and worthwhile to be recommended.

Adult↗

PubMed2001

[Treatment of the ocular burn with hormone].

OBJECTIVE: To explore new ways of the management of ocular burn with the use of hormones (human growth hormone and corticosteroid). METHODS: Twenty-one patients (30 eyes) with ocular burn were enrolled in the study. Nine cases (12 eyes) were treated with routine methods, while in 12 cases (18 eyes) corticosteroid and recombinant human growth hormone (rhGH) were used. The corticosteroid was applied immediately postburn both systemically and topically and continued for 2-4 weeks. But the rhGH was applied after 1 week postburn and continued for 2 weeks. The results in the above two groups were compared. RESULTS: Compared with those in control group, all the 18 eyes in the 12 patients with ocular burn were saved and cured with the treatments of hormones. There was significantly less incidence of corneal ulceration and perforation and better visual recovery in those treated with the hormones. CONCLUSION: Combined application of corticosteroid and rhGH might be beneficial to the management of patients with ocular burn.

Adrenal Cortex Hormones↗

PubMed2001

[Preliminary study on the role of vascular endothelial growth factor in pathogenesis of ovarian hyperstimulation syndrome].

OBJECTIVE: To explore the role of vascular endothelial growth factor (VEGF) in the pathogenesis of ovarian hyperstimulation syndrome (OHSS). METHODS: Fourteen moderate or severe OHSS patients and 13 non-OHSS cases were enrolled prospectively from in vitro fertilization and embryo transfer (IVF-ET) or intracytoplasmic sperm injection program. The VEGF levels of follicular fluid (FF) on the day of oocytes pick up (DOPU) and of sera on the day of human chorionic gonadotrophin (hCG) injection (DhCGI) and embryo transfer (DET) were measured by enzyme-labeled immunosorbent assay. Expression of VEGF protein and mRNA of luteinized granulosa cells obtained during OPU were detected by immunohistochemical and reverse transcription polymerase chain reaction respectively. RESULTS: The VEGF levels of FF on the DOPU and of sera on DhCGI were not significantly different between the OHSS and control groups [1257.2 +/- 648.0) ng/L Vs (1745.1 +/- 802.4) ng/L and (250.1 +/- 109.5) ng/L Vs (196.7 +/- 81.7) ng/L, respectively, P > 0.05]. However, both serum VEGF levels on DET and its increments from DhCGI to DET are significantly greater in the OHSS group as compared with the controls, so was the expression of VEGF mRNA levels of luteinized granulosa cells on DOPU. CONCLUSION: VEGF may play a role in pathogenesis of OHSS.

Adult↗

PubMed2001

[Changes and relations of leptin, growth hormone and insulin during puberty in obese and non-obese children].

In order to study the regularity of changing leptin, growth hormone (GH) and insulin (INS) during puberty and their relationships, a group of 300 obese and 300 non-obese children, aged 10-15 were selected. Leptin level increased with age and then decreased in boys, but it had only increasing tendency in girls. The GH level increased and then decreased suddenly in all groups. There was no obvious regularity in the change of INS. Serum leptin and INS levels were higher (P < 0.01) in obese children than that in non-obese children, while GH levels were significantly lower (P < 0.01) in obese boys. Results also showed that GH was negatively correlated with leptin in boys (obese group: r = -0.74, P < 0.05; non-obese group: r = -0.69, P < 0.05) and positively correlated with leptin in girls (obese group: r = 0.58, P < 0.05; non-obese group: r = 0.67, P < 0.01). There was a positive correlation between INS and leptin in non-obese girls (r = 0.54, P < 0.05). It is concluded that leptin might play an important role during the initial stage of puberty in children and the effect of leptin on pubescent development in girls is greater compared with boys. The correlation between leptin and GH are gender dependent in boys and girls, which may cause the timing differences of sudden growth in boys and girls.

Adolescent↗

PubMed2001

[Effects of chromium and fish oil on insulin resistance and leptin resistance in obese developing rats].

In order to study the effects of chromium and fish oil on insulin resistance and leptin resistance in obese rats, 50 rats were divided randomly into five groups: basal diet group was fed on normal diet, other four groups were fed on high fat diet. In addition to high fat diet, chromium group fed chromium (3 mg/kg BW), fish oil group fish oil(5 ml/kg BW) and chromium + fish oil group fed chromium(3 mg/kg BW) plus fish oil(5 ml/kg BW). Blood samples were collected in the following five weeks from tail each week to determine blood sugar, insulin and leptin. The results showed that blood sugar, insulin and leptin in fish oil group and chromium group were lower than those in high fat diet control group. Chromium and fish oil improved the insulin resistance and leptin resistance.

Animals↗

PubMed2000

Impaired preneoplastic changes and liver tumor formation in tumor necrosis factor receptor type 1 knockout mice.

Hepatic stem cells (oval cells) proliferate within the liver after exposure to a variety of hepatic carcinogens and can generate both hepatocytes and bile duct cells. Oval cell proliferation is commonly seen in the preneoplastic stages of liver carcinogenesis, often accompanied by an inflammatory response. Tumor necrosis factor (TNF), an inflammatory cytokine, is also important in liver regeneration and hepatocellular growth. The experiments reported here explore the relationship among the TNF inflammatory pathway, liver stem cell activation, and tumorigenesis. We demonstrate that TNF is upregulated during oval cell proliferation induced by a choline-deficient, ethionine-supplemented diet and that it is expressed by oval cells. In TNF receptor type 1 knockout mice, oval cell proliferation is substantially impaired and tumorigenesis is reduced. Oval cell proliferation is impaired to a lesser extent in interleukin 6 knockout mice and is unchanged in TNF receptor type 2 knockout mice. These findings demonstrate that TNF signaling participates in the proliferation of oval cells during the preneoplastic phase of liver carcinogenesis and that loss of signaling through the TNF receptor type 1 reduces the incidence of tumor formation. The TNF inflammatory pathway may be a target for therapeutic intervention during the early stages of liver carcinogenesis.

Animals↗

PubMed2000

15N NMR relaxation studies of free and ligand-bound human acidic fibroblast growth factor.

15N NMR relaxation data have been used to characterize the backbone dynamics of the human acidic fibroblast growth factor (hFGF-1) in its free and sucrose octasulfate (SOS)-bound states. (15)N longitudinal (R(1)), transverse (R(2)) relaxation rates and (1H)-(15)N steady-state nuclear Overhauser effects were obtained at 500 and 600 MHz (at 25 degrees C) for all resolved backbone amide groups using (1)H- detected two-dimensional NMR experiments. Relaxation data were fit to the extended model free dynamics for each NH group. The overall correlation time (tau(m)) for the free and SOS-bound forms were estimated to be 10.4 +/- 1.07 and 11.1 +/- 1.35 ns, respectively. Titration experiments with SOS reveals that the ligand binds specifically to the C-terminal domain of the protein in a 1:1 ratio. Binding of SOS to hFGF-1 is found to induce a subtle conformational change in the protein. Significant conformational exchange (R(ex)) is observed for several residues in the free form of the protein. However, in the SOS-bound form only three residues exhibit significant R(ex) values, suggesting that the dynamics on the micro- to millisecond time scale in the free form is coupled to the cis-trans-proline isomerization. hFGF-1 is a rigid molecule with an average generalized parameter (S(2)) value of 0.89 +/- 0.03. Upon binding to SOS, there is a marked decrease in the overall flexibility (S(2) = 0.94 +/- 0.02) of the hFGF-1 molecule. However, the segment comprising residues 103-111 shows increased flexibility in the presence of SOS. Significant correlation is found between residues that show high flexibility and the putative receptor binding sites on the protein.

Binding Sites↗

PubMed2000

Functional expression of NAD(P)H oxidase p47 in lung microvascular endothelial cells.

Vascular endothelial cell superoxide (O(*)(2)) has an important role in intracellular signaling, in interaction with other reactive species such as nitric oxide, and in vascular dysfunction. Little is known regarding the source and function of O(*)(2) from microvascular endothelial cells from specific tissues. Mouse lung microvascular endothelial cells stimulated with phorbol ester (PMA) or NADPH generated significant O(*)(2), which was inhibited by diphenyleneiodonium (DPI) but not by allopurinol, rotenone, indomethacin, or quinacrine. Optimal O(*)(2) generation required cytosolic as well as particulate cell fractions of cells. In parallel studies, PMA induced increased expression of the p47 component of the NAD(P)H oxidase in the particulate fraction, which was inhibited by staurosporine and calphostin. These data demonstrate that NAD(P)H oxidase is an important source of O(*)(2) generation in lung microvascular endothelial cells.

Allopurinol↗