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Biomedical subjects

Y Hu

Publications and source records attributed to Y Hu.

At least 415 records · Page 23Linked to original sources
PubMed1997

Effect of Metal Ions and Compounds on the Rheological Properties of a Drag-Reducing Cationic Surfactant Solution Exhibiting Shear-Induced Structure Formation

The effect of various metal ions and compounds on the viscoelasticity of a 12.5/5 mM sodium salicylate (NaSal)/tris(2-hydroxyethyl) tallowalkyl ammonium acetate (TTAA) surfactant solution has been studied phenomenologically. This solution normally exhibits shear-induced structure formation and strong drag reduction properties. The viscosity and N1 buildup times under a constant shear rate increase monotonically with the concentration of added Zn(OH)2, Cu(OH)2, or Fe(OH)3. The magnitude of N1 and the viscosity do not change significantly with the addition of Zn(OH)2, but decrease dramatically with increasing Cu(OH)2, Cu2(OH)2CO3, and Fe(OH)3 concentrations. The effect is believed to be due to adsorption on insoluble particulates and to reaction between copper compounds and NaSal. Mg2+ and Cu2+ do not change the steady-state viscosity and N1, whereas Na+, Zn2+, and Ca2+ decrease these quantities significantly at low shear rates. The loss of viscoelasticity in the NaSal/TTAA solution due to Cu(OH)2 and Cu2(OH)2CO3 can be recovered, however, by adding the chelating agent ethylenediaminetetraacetate to the contaminated solution. The rheological results are consistent with drag reduction experiments. The results show that chemical contamination may be an important issue for drag-reducing cationic surfactant additives used in industrial applications where such contaminants are present.

Journal Article↗
PubMed1997

Identification of a specific amino acid cluster in the calmodulin-binding domain of the neuronal nitric oxide synthase.

The calmodulin (CaM) binding domain of rat neuronal nitric oxide synthase (nNOS) was analyzed using 3 synthetic peptides corresponding to different regions of the middle portion of the enzyme. One corresponding to nNOS 732-754 gave complete inhibition of NOS enzyme activity with an IC50 of about 1 microM. Kinetic analysis indicated that the inhibition was not competitive with respect to L-arginine and the peptide produced a Ca2+ dependent, electrophoretic mobility shift of CaM on 1 M urea gels. A specific hydrophobic/basic amino acid cluster in the rat nNOS sequence, Lys732 Lys Leu, that was critical for its CaM binding was also identified in this study.

Amino Acid Sequence↗
PubMed1997

HIV-1 induces cytotoxic T lymphocytes in the cervix of infected women.

Although T lymphocytes are present in the genital mucosa, their function in sexually transmitted diseases is unproven. To determine if cervical T cells mediate HIV-specific cytolysis, mononuclear cells in cytobrush specimens from HIV-1-infected women were stimulated in vitro with antigen. Resultant cell lines lysed autologous targets expressing HIV-1 proteins in 12/19 (63%) subjects, and these responses were detected intermittently on repeated visits. All 8 subjects with blood CD4+ counts > or =500 cells/microl had HIV-1-specific cervical CTL, whereas only 4/11 with counts <500 cells/microl had detectable responses (P = 0.008). Class II MHC-restricted CD4+ CTL clones lysed targets expressing Env gp41 or infected with HIV-1. Class I MHC-restricted CD8+ clones recognized HIV-1 Gag- or Pol-expressing targets, and the epitopes were mapped to within 9-20 amino acids. Comparisons of intra-individual cervical and blood CTL specificities indicate that epitopes recognized by CTL in the cervix were commonly recognized in the blood. These studies provide the first definitive evidence for an MHC-restricted effector function in human cervical lymphocytes.

Cell Line, Transformed↗
PubMed1997

Permissive role of nitric oxide in endothelin-induced migration of endothelial cells.

Endothelin (ET) synthesis is enhanced at sites of ischemia or in injured vessels. The purpose of this study was to explore the possibility of autocrine stimulation of endothelial cell migration by members of the endothelin family. Experiments with microvascular endothelial cell transmigration in a Boyden chemotactic apparatus showed that endothelins 1 and 3, as well as a selective agonist of ETB receptor IRL-1620, equipotently stimulated migration. Endothelial cell migration was unaffected by the blockade of ETA receptor, but it was inhibited by ETB receptor antagonism. Based on our previous demonstration of signaling from the occupied ETB receptor to constitutive nitric oxide (NO) synthase (Tsukahara, H., Ende, H., Magazine, H. I., Bahou, W. F., and Goligorsky, M. S. (1994) J. Biol. Chem. 269, 21778-21785), we next examined the contribution of ET-stimulated NO production to endothelial cell migration. In three independent cellular systems, 1) migration and wound healing by microvascular endothelial cells, 2) wound healing by Chinese hamster ovary cells stably expressing ETB receptor with or without endothelial NO synthase, and 3) application of antisense oligodeoxynucleotides targeting endothelial NO synthase in human umbilical vein endothelial cells, an absolute requirement for the functional NO synthase in cell migration has been demonstrated. These findings establish the permissive role of NO synthesis in endothelin-stimulated migration of endothelial cells.

Animals↗
PubMed1997

Effect and clinical value of splanchnic nerve block of hemodynamics in ACST.

The condition of acute cholangitis of severe type (ACST) develops very rapidly and the prognosis is poor. The main clinical feature is that there is an obvious dynamic variation, which is the principal factor for the early occurrence of shock and death. In this study the Japanese long ear rabbits were used and biliary tract pressure increasing and splanchnic nervous plexus blocking experiments were conducted. Our results indicate that 0.6% of lidocaine can be used to block the right celiac plexus. It can avoid the decrease of blood pressure due to the pressure increase of the biliary tract, and the decrease of blood pressure due to the pressure increase of the biliary tract can be corrected by local anesthesia. 8 cases in conformity with the ACST diagnostic standards received the right renal capsule block injection for the purpose of stopping the celiac plexus, 6 cases of whom had a return of blood pressure to various extent, suggesting that the splanchnic nervous activity in the occurrence of ACST is of great significance. The technique may provide a new approach for the clinical treatment of ACST.

Acute Disease↗
PubMed1997

Study on oxygen supply and protection of bone marrow in acute radiation injured mice.

After irradiated by 8 Gy 60Co gamma-ray, mice were intraperitoneally injected immediately with 0.2 ml 100% compound blood-activating soup twice a day for 10 days. The in situ ulnar bone marrow partial pressure of oxygen (PbO2) was determined in vivo before, during and after irradiation respectively. The bone marrow sections in the same part were observed. Our results showed that the normal murine ulnar PbO2 was 12.72 +/- 1.05 kPa. During irradiation, the level of PbO2 decreased to 10.78 +/- 1.17 kPa (P < 0.001). And 3 days after irradiation, PbO2 decreased to 9.75 +/- 0.52 kPa, suggesting that the commonly used "blood-activating and stasis-eliminating" Chinese drugs could promote the rehabilitation and proliferation of bone marrow microvessels in the acute radiation injured mice, expand their areas, increase the oxygen supply of bone marrow microenvironment, thereby leading to PbO2 much higher increase than that of control group. It is also helpful in the proliferation and rehabilitation of hematopoietic cells.

Animals↗
PubMed1997

A quantitative study on vascular angiotensin II receptors in rats with portal hypertension.

Angiotension-II (A-II) receptor maximal binding capacity (Bmax) and dissociation constants (Kd) of different blood vessels in rats with prehepatic portal hypertension were studied by radioligand binding analysis. The results showed that the A-II receptor Bmax in the thoracic aorta, superior mesenteric artery and portal vein of portal hypertensive animals (113.7 +/- 19.4 fmol/mg protein, 206.9 +/- 39.3 fmol/mg protein and 31.5 +/- 9.2 fmol/mg protein respectively) was all significantly lower than that of controls (146.8 +/- 24.5 fmol/mg protein, 297.2 +/- 44.7 fmol/mg protein and 53.4 +/- 12.1 fmol/mg protein respectively, P < 0.01). The A-II receptor Kd in the superior mesenteric artery was markedly increased in portal hypertensive animals (1.03 +/- 0.11 nmol/L) compared with that in controls (0.88 +/- 0.08 nmol/L, P < 0.05). In the thoracic aorta and portal vein, the A-II receptor Kd in portal hypertensive animals was slightly higher than that in controls, but no significant difference was observed between the two groups. The results suggested that the vascular hyporesponsiveness to A-II in portal hypertension was caused partially by a reduction in number and a decrease in affinity of vascular A-II receptors, and these changes might possibly lead to the formation of hyperdynamic circulation.

Angiotensin II↗
PubMed1997

Coculture of human embryos with buffalo rat liver cells for women with decreased prognosis in in vitro fertilization.

OBJECTIVE: The coculture of human embryos with epithelial cells may improve both embryo quality and pregnancy rates. In this current study we tested the efficacy of coculture with the buffalo rat liver cell line on pregnancy rates in women with a potentially poor prognosis for success with in vitro fertilization (previous in vitro fertilization failure, advanced maternal age, increased early follicular follicle-stimulating hormone levels, and anovulation). STUDY DESIGN: This prospective controlled study evaluated a total of 203 women (135 coculture, 68 controls) undergoing in vitro fertilization. Implantation rates per embryo, clinical pregnancy rates, and continuing/delivered pregnancy rates were analyzed. RESULTS: Buffalo rat liver cells, which are commercially available, are stable in coculture. Implantation rates (number of sacs with fetal heart motion per embryos transferred) were similar for coculture (19%) and control (18%) embryos. No difference in the rate of continuing/delivered pregnancies per retrieval was noted (17% coculture vs 14% control) in the group with advanced maternal age, but coculture caused a trend toward improved pregnancy rates in the group with ovulatory dysfunction (43% coculture vs 14% control) and the group with previous in vitro fertilization failure (34% coculture vs 28% control). CONCLUSION: This is the first published controlled study to our knowledge that reports the use of the buffalo rat liver cell coculture for human in vitro fertilization in a large number of patients. Our data support consideration of buffalo rat liver coculture for in vitro fertilization for women with previous in vitro fertilization failure and possibly for patients with oocyte or ovulatory dysfunction.

Adult↗
PubMed1997

Non-exocytotic GABA overflow in rat striatum inhibits gnawing.

The present study tested the hypotheses that spontaneous gamma-aminobutyric acid (GABA) efflux in anterior rat striatum is 1) independent of intra- and extracellular calcium; and 2) is physiologically relevant. Extracellular dopamine (DA) and GABA were sampled from striatum of awake, freely moving rats using in vivo microdialysis. Although dialysate concentrations of DA were 2 to 3 times greater than GABA and were decreased by at least 70% by removal of calcium, GABA was unaffected even in the presence of EGTA or the intracellular calcium chelator APTRA-AM. Functional significance of this non-exocytotic pool of GABA was tested by injecting 3-mercaptopropionic acid (3-MPA), an inhibitor of GABA synthesis, into the striatum via a guide cannula sidled alongside a microdialysis probe and measuring subsequent effects on behavior and perfusate concentrations of GABA. Results show that 3-MPA increases gnawing behavior suggesting that basal, non-exocytotic GABA overflow normally functions to suppress gnawing.

3-Mercaptopropionic Acid↗
PubMed1997

Regional vascular and cardiac responses to systemic neuropeptide-Y in normal and diabetic rats.

Diabetes is associated with altered autonomic activity, and both the peripheral and central nervous content of NPY is altered in diabetes suggesting that part of the cardiovascular dysfunction of diabetes may be associated with altered responses to NPY. We evaluated the mean arterial pressure (MAP), heart rate (HR) and regional blood flow (BF) in response to NPY in normal and diabetic rats. Male Wistar rats were made diabetic using streptozotocin and maintained without insulin treatment for 28-30 days. Normal and diabetic animals were anesthetized, the femoral artery cannulated, and flow probes placed around the iliac, renal and superior mesenteric arteries. Dose dependent responses to NPY infusion were determined for MAP, HR and BF. Conductance was calculated from BF/MAP. In normal rats NPY increased the MAP in a dose-dependent fashion but did not alter the HR. NPY decreased the BF in the iliac artery in a dose-dependent fashion while the renal BF was decreased only at the highest dose, and the superior mesenteric BF was not affected. The conductances in all vascular beds were decreased dose dependently. NPY in diabetic rats also increased MAP and did not affect HR. In diabetic rats NPY also decreased BF in iliac and renal arteries but contrastingly increased BF in the superior mesenteric artery. Again conductances in all three vascular beds were decreased by NPY. When comparing diabetic response to NPY to normals we noted that the MAP response was less in the diabetic, but the HR and regional BF were not different. The vascular conductances in response to NPY were attenuated in the diabetic vessels especially the iliac and superior mesenteric. We conclude that systemic NPY increases MAP as a result of decreased vascular conductance and this vasopressive effect of NPY is diminished in diabetics.

Animals↗
PubMed1997

Intracerebroventricular administration of NPY increases sympathetic tone selectively in vascular beds.

NPY is widely distributed and has broad regulatory actions in the peripheral and central nervous system (CNS) and is especially important in the regulation of cardiovascular responses. CNS administered NPY has been demonstrated to produce both increases and decreases in cardiovascular tone. In this study we evaluated the effect of intracerebroventricular (ICV) administered NPY on cardiovascular tone, regional blood flow dynamics, as well as the mechanism of this action in normal animals. Male rats were instrumented with ICV cannulas and allowed to recover. At the time of the experiment the rats were anesthetized with urethane/chloralose and the femoral artery cannulated for blood pressure determinations. The abdomen was opened and Doppler flow probes were placed around the iliac, renal, and superior mesenteric artery. Mean arterial pressure (MAP), heart rate (HR), iliac, renal, and superior mesenteric flow, as well as the calculated iliac, renal, and superior mesenteric conductance were determined. ICV administered NPY resulted in an increase in MAP and HR, which was associated with decreased flows in the iliac and superior mesenteric vessels while increasing renal flow. Conductance was decreased in the iliac and superior mesenteric vascular beds but not the renal artery. ICV administration of NPY in the presence of a systemically administered alpha1-adrenergic inhibitor, prazosin, attenuated the NPY-mediated effects on MAP as well as vascular conductance in the iliac and superior mesenteric vessels. Additionally, ICV administration of NPY in the presence of a systemically administered beta1-adrenergic inhibition, atenolol, also attenuated the NPY-mediated increase in HR and MAP. Blood flow responses and iliac and superior mesenteric vascular conductance were also attenuated by atenolol pretreatment. In these studies we conclude that lateral ventricular administration of NPY acts to increase systemic MAP and HR and the response is mediated by an increase in sympathetic tone to the heart and especially the splanchnic and skeletal muscle vasculature.

Animals↗
PubMed1997

A user-friendly method for calibrating a subcutaneous glucose sensor-based hypoglycaemic alarm.

A crucial step in developing a glucose monitoring system using a subcutaneous implanted glucose sensor is the transformation of the sensor signal (a current) into an estimation of a blood glucose concentration. We have developed an Electronic Control Unit (ECU) able to recognize, before and after a glucose load, that the sensor current presents a plateau, thus triggering an alarm asking for blood glucose determination. The system, fed with these results, subsequently transforms the current into an estimation of glucose concentration by linear extrapolation based on the sensor sensitivity and the background current computed from the two sets of current and glycaemia values (two-point calibration). In addition, the system is able to trigger an alarm when this estimation decreases below a threshold that can be set by the user. This system was evaluated in experiments performed in 12 normal rats. The quality of the calibration was assessed by comparing, by error grid analysis, the data displayed on the liquid-crystal display of the ECU to concomitant plasma glucose concentration determined at frequent intervals, 65 +/- 6 and 26 +/- 5% of the values were in zones A (good) and B (acceptable estimation) of the grid, respectively. The system was set to trigger an alarm when the estimation of glucose concentration decreased below 70 mg/dl. Following an insulin administration, the alarm was triggered when the system displayed a 64 +/- 2 mg/dl glucose concentration. The concomitant plasma glucose concentration was 59 +/- 5 mg/dl (NS). In conclusion, this work validates experimentally the new, user-friendly method for calibrating the glucose sensor integrated into the ECU, based on an automatic detection of plateaus. The quality of the sensor calibration performed with this procedure is compatible with the appropriate functioning of this continuous glucose monitoring system, which was demonstrated by its ability to detect mild hypoglycaemia following insulin injection.

Animals↗
PubMed1997

A longitudinal study of the dietary practices of black and white girls 9 and 10 years old at enrollment: the NHLBI Growth and Health Study.

PURPOSE: To determine whether there are racial differences in the frequency with which black and white girls engaged in eating practices commonly targeted for modification in weight reduction programs. METHODS: This is part of the NHLBI Growth and Health Study, a longitudinal study of preadolescent girls designed to examine the factors associated with development of obesity, and its later effects on cardiovascular risk factors. Black and white girls ages 9-10 years at entry (n = 2,379) were recruited at three clinical sites. Racial differences were examined in 11 "weight-related" eating practices such as eating with TV, eating while doing homework, and skipping meals. Multiple logistic regression analyses were then conducted for each of the dependent variables. RESULTS: Black girls were more than twice as likely as white girls to frequently engage in the targeted weight-related eating practices. The odds of a study girl frequently engaging in most of these eating practices decreased with an increase in parents' income and education level. However, even when controlling for socioeconomic and demographic effects, black girls remained more likely to engage in these eating practices than white girls. For most of the behaviors, girls who frequently practiced a behavior had higher energy intakes compared to those who practiced it infrequently. CONCLUSIONS: The finding that black girls at an early age more frequently engage in eating practices associated with weight gain may have significant implications for obesity development. For both young black and white girls, early education efforts may be necessary in helping develop good eating habits. Since it appears that black girls have a higher risk of developing adverse weight-related eating practices, culturally appropriate education materials may be required.

Black or African American↗
PubMed1997

Engineering of in vivo immune responses to DNA immunization via codelivery of costimulatory molecule genes.

Nucleic acid immunization is a novel vaccination technique to induce antigen-specific immune responses. We have developed expression cassettes for cell surface markers CD80 and CD86, two functionally related costimulatory molecules that play an important role in the induction of T cell-mediated immune responses. Coimmunization of these expression plasmids, along with plasmid DNA encoding for HIV-1 antigens, did not result in any significant change in the humoral response; however, we observed a dramatic increase in cytotoxic T-lymphocyte (CTL) induction as well as T-helper cell proliferation after the coadministration of CD86 genes. In contrast, coimmunization with a CD80 expression cassette resulted in a minor, but positive increase in T-helper cell or CTL responses. This strategy may be of value for the generation of rationally designed vaccines and immune therapeutics.

Animals↗
PubMed1997

On-column indirect photothermal interference detection for capillary zone electrophoresis.

An indirect photothermal interference detection method, which is based on the diffraction of a probe laser beam by a capillary tube, for detecting metal cations separated by capillary zone electrophoresis (CZE) is described. In this capillary photothermal interference detector, a 2 mW He-Ne probe laser is employed to provide the probe beam and an 18 mW He-Ne pump laser is used to supply the pump beam. Factors that contribute to the noise and signal in indirect photothermal interference detection in CZE, such as the noise from the scattered light caused by both the probe beam and the pump laser beam, and effects of the concentration of ethanol and NaCl on the separation efficiency, were studied. The effect of scattered light can be reduced effectively with the configuration constraints investigated for photothermal capillary absorption measurements. With Methylene Blue added to carrier electrolyte as an absorber, three typical metal cations (KI, CuII and AlIII) were separated using this system. For CuII, a 2.1 x 10(-7) mol l-1 concentration detection limit (S/N = 2) without preconcentration and a 1.02 x 10(-17) mol detection limit as absolute amount were measured, considering the optical sampling volume estimated to be 50 pl, and 1.99 x 10(6) theoretical plates were observed on the laboratory-made CE system. It was demonstrated that indirect photothermal interference detection is suitable for small capillaries and a large ionic strength range for CE analysis.

Electrophoresis, Capillary↗
PubMed1997

Specific interactions between the K domains of AG and AGLs, members of the MADS domain family of DNA binding proteins.

MADS domain (for MCM1, AG, DEFA and SRF) proteins are regulatory proteins found in all major eukaryotic kingdoms. Plant MADS domain regulatory proteins have a region of moderate sequence similarity that has been designated as the K domain, and its predicted coiled-coil structure suggests a role in establishing a protein-protein interaction. In vivo studies with the Arabidopsis AGAMOUS (AG) protein have indicated that the K domain is important for AG function. Using a bait fusion protein containing the K domain and the C-terminal region of AG in a yeast two-hybrid selection, 156 clones that encode potential AG-interacting proteins were identified. These clones each encode one of four highly related MADS domain proteins: AGL2, AGL4, AGL6 and AGL9. Additional analysis showed that the K domain of AG alone was able to bind the K domains of these AGLs. This binding was further confirmed by immunoprecipitation experiments using in vitro synthesized AG and AGL K domains. These results strongly suggest that AG interacts with AGL2, AGL4, AGL6 and AGL9 in vivo. Based on these results and previous observations, it is proposed that the AG function requires interaction with at least one of these AGL proteins, and such interactions contribute to the functional specificity of the AG protein.

AGAMOUS Protein, Arabidopsis↗
PubMed1997

Rapid changes in local extracellular rat brain glucose observed with an in vivo glucose sensor.

A needle-type electrochemically based microsensor for glucose (110 microns o.d.) is described. This sensor, designed for monitoring transient glucose content changes in response to neural stimuli, has a response time of approximately 5 s and has been shown to be free of interference from endogenous electroactive species such as ascorbate, urate, and various neurotransmitters. It exhibits linear response to glucose up to 10 mM. The usefulness of the sensor has been demonstrated by examining the time-dependent interstitial glucose concentration in the rat hippocampus in response to KCl depolarization and by stimulation of glutamate neurons through a perforant pathway. Simultaneous monitoring of oxygen is also carried out and demonstrates that for both oxygen and glucose there is substantial local depletion of both species and that their pools are replenished by increased regional cerebral blood flow. The transient initial rapid (10-13 s) decrease up to 20-34%, observed on a time scale comparable to that for neurotransmitter release, may be involved in a recently suggested astrocytic uptake for glutamate-stimulated aerobic glycolysis possibly needed to meet energy homeostasis in brain. These studies demonstrate the importance of microsensors in monitoring transient events linked to neuronal stimulation.

Animals↗