Biomedical subjects

S Liu

Publications and source records attributed to S Liu.

At least 685 records · Page 38Linked to original sources

PubMed1997

Attenuation of leptin-mediated effects by monosodium glutamate-induced arcuate nucleus damage.

Leptin is a protein secreted by adipocytes that is important in regulating appetite and adiposity. Recent studies have suggested the presence of leptin receptors in the arcuate nucleus of the hypothalamus (ANH). Neonatal administration of monosodium glutamate (MSG) damages the ANH, resulting in obesity and neuroendocrine dysfunction. Neonatal administration of MSG was utilized to test the hypothesis that the anatomic site for many of leptin's actions is the ANH. Female control (n = 6) and MSG-treated rats (n = 7) were implanted for 14 days with osmotic minipumps containing phosphate-buffered saline or leptin (1 mg.kg-1.day-1). Leptin suppressed (P < 0.05) body weight gain in controls but did not suppress weight gain in MSG-treated rats. Leptin decreased (P < 0.05) fat depots in controls but had no effect in MSG-treated rats. Night feeding was suppressed (P < 0.05) in leptin-treated control rats. MSG-treated rats showed a suppression in food intake that was of a smaller magnitude and appeared later in the course of leptin treatment. These findings suggest that leptin mediates some physiological actions related to fat mobilization via receptors located in the ANH.

Adipose Tissue↗

PubMed1997

Reduced insulin receptor signaling in the obese spontaneously hypertensive Koletsky rat.

Insulin resistance is associated with both obesity and hypertension. However, the cellular mechanisms of insulin resistance in genetic models of obese-hypertension have not been identified. The objective of the present study was to investigate the effects of genetic obesity on a background of inherited hypertension on initial components of the insulin signal transduction pathway and glucose transport in skeletal muscle and liver. Oral glucose tolerance testing in SHROB demonstrated a sustained postchallenge elevation in plasma glucose at 180 and 240 min compared with lean spontaneously hypertensive rat (SHR) littermates, which is suggestive of glucose intolerance. Fasting plasma insulin levels were elevated 18-fold in SHROB. The rate of insulin-stimulated 3-O-methylglucose transport was reduced 68% in isolated epitrochlearis muscles from the SHROB compared with SHR. Insulin-stimulated tyrosine phosphorylation of the insulin receptor beta-subunit and insulin receptor substrate-1 (IRS-1) in intact skeletal muscle of SHROB was reduced by 36 and 23%, respectively, compared with SHR, due primarily to 32 and 60% decreases in insulin receptor and IRS-1 protein expression, respectively. The amounts of p85 alpha regulatory subunit of phosphatidylinositol-3-kinase and GLUT-4 protein were reduced by 28 and 25% in SHROB muscle compared with SHR. In the liver of SHROB, the effect of insulin on tyrosine phosphorylation of IRS-1 was not changed, but insulin receptor phosphorylation was decreased by 41%, compared with SHR, due to a 30% reduction in insulin receptor levels. Our observations suggest that the leptin receptor mutation fak imposed on a hypertensive background results in extreme hyperinsulinemia, glucose intolerance, and decreased expression of postreceptor insulin signaling proteins in skeletal muscle. Despite these changes, hypertension is not exacerbated in SHROB compared with SHR, suggesting these metabolic abnormalities may not contribute to hypertension in this model of Syndrome X.

3-O-Methylglucose↗

PubMed1997

Hodgkin-Huxley and partially coupled inactivation models yield different voltage dependence of block.

K+ channel blockers have been shown to exhibit complex time- and voltage-dependent effects on cardiac K+ currents. Whereas much attention has been focused on the state dependence of K+ channel block, how a particular channel model can alter the predicted time and voltage dependence of channel block remains unexplored. In this study, using two different model formalisms for the same cardiac transient outward current channel, we compare the effects of a theoretical open-state specific channel blocker on macroscopic currents. Model 1 is a Hodgkin-Huxley-like model, in which inactivation is an intrinsically voltage-dependent process and occurs independently of activation. Model 2 is a "partially coupled" model, in which inactivation is intrinsically voltage insensitive but requires channel activation before it can proceed. In the absence of drug (blocking agent), the two models reproduce the macroscopic current data. In the presence of blocking agent, the two models can differ substantially, with model 1 displaying much less block than model 2. We also examine simple mathematically convenient modifications to the Hodgkin-Huxley formalism, which reproduce some, but not all, of the use-dependent properties of block. Thus model formalism is important for analysis and simulation of state-specific drug-channel interactions.

Animals↗

PubMed1997

Involvement of ceramide in inhibitory effect of IL-1 beta on L-type Ca2+ current in adult rat ventricular myocytes.

Interleukin (IL)-1 beta has previously been shown to decrease the L-type Ca2+ channel current (ICa,L). Because ceramide has been suggested to mediate many biological effects of IL-1 beta, we examined whether ceramide was involved in the IL-1 beta-induced suppression of ICa,L in adult rat ventricular myocytes. Exposure of myocytes to 5 ng/ml IL-1 beta elicited a 140% increase in ceramide production within 2 min, as measured with 32P phosphorylation. Whole cell patch-clamp techniques were used to measure ICa,L in myocytes internally dialyzed and externally perfused with Na(+)- and K(+)-free solutions. C2 ceramide (1 nM-1 microM), a membrane-permeable analog of ceramide, caused a concentration-dependent inhibition of ICa,L and increased the rate of ICa,L inactivation without altering its gating properties. An inactive ceramide analog failed to inhibit ICa,L. At submaximal concentrations, effects of C2 ceramide and IL-1 beta on ICa,L were additive and saturable. In the presence of a maximally effective concentration of IL-1 beta, C2 ceramide had no further effect on ICa,L. These results suggest that ceramide mediates IL-1 beta-induced suppression of cardiac ICa,L.

Animals↗

PubMed1997

Inhibition of L-type Ca2+ channel current in rat ventricular myocytes by terfenadine.

To elucidate possible mechanisms underlying the cardiotoxicity of terfenadine, the effect of this antihistamine on L-type Ca2+ channel current (ICa,L) was studied in adult rat ventricular myocytes using the whole-cell patch-clamp technique. Myocytes were held at -70 mV and internally dialyzed and externally perfused with Na(+)- and K(+)-free solutions; exposure to terfenadine (10(-9) to 5 x 10(-6) mol/L) resulted in a concentration-dependent inhibition of peak ICa,L with a half-maximum inhibition concentration (IC50) of 142 nmol/L. The terfenadine-induced inhibition of ICa,L was not mediated via effects on histamine H1 receptors, because 1 mumol/L triprolidine, a more selective and potent H1 antagonist, had no effect on ICa,L. In this study, we found that terfenadine (1) increased both the fast and slow time constants of ICa,L inactivation, (2) shifted the steady state inactivation of ICa,L to more negative potentials, and (3) elicited a tonic block and a use-dependent block of ICa,L. The terfenadine-induced tonic and use-dependent block and the steady state inhibition of ICa,L were voltage dependent. Both tonic and use-dependent blocks of ICa,L by terfenadine at -40 mV were greater than that at -70 mV, and blocks were partially released by applying a long hyperpolarizing prepulse to -90 mV. These results suggest that terfenadine binds to L-type Ca2+ channels in inactivated and rested states and inhibits ICa,L predominantly by interacting with the inactivated state with an apparent dissociation constant of 60 nmol/L. Open-state block could be observed only at high concentrations of terfenadine. The high-affinity interaction of terfenadine with the inactivated state of L-type Ca2+ channels may play an important role in its cardiotoxicity under pathophysiological conditions, such as ischemia.

Animals↗

PubMed1997

Effect of serum components from different species on destabilizing hydrogenated phosphatidylcholine-based liposomes.

It is accepted that some serum components play important roles in enhancing liposome permeability and in facilitating rapid liposome uptake by the mononuclear phagocytic system. In this study we systematically investigated the influence of serum components from different species on complement-mediated immune damage to hydrogenated phosphatidylcholine (HEPC)-based liposomes. Our results demonstrated that when liposomes were incubated with fresh serum from rats or bovines, there was obvious leakage of 5(6)-carboxyfluorescein (CF) from the liposome. However, when liposomes were incubated with fresh serum from humans, rabbits, guinea pigs, mice, and dogs, almost no pronounced leakage from the liposome was observed. These results indicate that the variability of damage to a liposome corresponds to the variability of the animal species from which the serum comes. In addition, leakage of CF from liposomes was completely inhibited by heating at 56 degrees C for 30 min or by treatment with EDTA. However, such leakage was not blocked by treatment with EGTA/Mg2+, suggesting that the mechanism of lysis of liposomes is due to complement activation via the alternative pathway rather than via the classical pathway. Studies on reconstitution and compatibility further confirm that some serum factors (complement activating factors, CAFs) induce the activation of the complement system, ultimately leading to the lysis of the liposomes. However, CAF from different animal species exhibited corresponding species differences. Meanwhile, under the condition of heating and dialysis experiments, it is obvious that the CAF is susceptible to heat and the dialysed serum sustains biological activity to destabilize liposome following dialysis against a buffer with Ca2+ and Mg2+, indicating that the CAF is not a type of low-molecular weight material but a serum protein.

Animals↗

PubMed1997

[The serum insulin level in severe hepatitis patients].

Serum insulin (SI) levels were determined in 36 severe hepatitis patients by RIA. The average level of SI in chronic severe hepatitis (CSH) patients was 43.18 +/- 27.12 mu.L-1, and subacute severe hepatitis (SSH) patients 28.91 +/- 12.77 mu.L-1. Both were increased significantly as compared with normal controls (P < 0.01), and the level of SI in patients died from SSH and CSH was increased significantly than those alive (P < 0.05). The level of SI at the fastiguium stage of the disease was significantly higher as compared with that of the convalescence stage (P < 0.05). The results suggest that SI may aid to evaluate the severity of the illness and to estimate the outcome of the patients.

Adult↗

PubMed1997

[Influence of cryotherapy on the concentration of malondialdehyde in rats serum].

Malondialdehyde (MDA) consistency in rats serum was measured when performing cryotherapy by means of fluorescence method. The rsult showed MDA consistency in rats serum increased after cryotherapy, and the highest MDA consistency appeared respectively in the 2nd week, 4th week and 7th week (P < 0.01). The variation of MDA consistency in mice serum is identical to that when carrying out cryotherapy, which demonstrates that lipid peroxidation involves the whole course of injury and recovery of cryotherapy.

Animals↗

PubMed1997

[One-year-result of excimer laser for photorefractive keratectomy in very high myopia].

We corrected 53 cases (84 eyes) of very high myopia using photorefractive keratectomy (PRK) with VISX 20/20 excimer laser, and followed up the cases more than one year. The rates of visual acuity more than or equal to 0.5 or 1.0 were 81.0% and 23.9%, 75.0% eyes were within +/- 2.00 diopter of the desired emmetropia. Grade 2 or more severe corneal haze were presented in 13.1% eyes. PRK with VISX 20/20 excimer laser may be an effective method to correct very high myopia from -10.00 to -16.00 diopters.

Adolescent↗

PubMed1997

[Photorefractive keratectomy to correct myopic astigmatism].

The VISX 20/20 excimer laser was used to treat 260 eyes with myopia and myopic astigmatism of 166 patients. All patients were followed up for one year. The diopter of preoperative astigmatism was from -0.25-(- 4.00 D (-1.00 +/- 0.62 D). The diopter was lowered to -0.07 +/- 0.40 D at 6 months postoperatively (P < 0.05) and -0.06 +/- 0.39 D at 12 months postoperatively (P < 0.01). Photorefractive keratectomy (PRK) is effective and safe for myopic astigmatism.

Adolescent↗

PubMed1997

[Comparison between the effects of rhCNTF on sensory and motor neuron of chicken embryo].

The effects of rhCNTF on dorsal root ganglia (DRG) sensory neurons and spinal cord (SC) motor neurons of 10-day chicken embryos were observed with serum-free culture. The results indicated that rhCNTF supported the survival and differentiation of these neurons and showed certain dose-dependent manners. No effect was found at 0.5 ng/ml rhCNTF concentration, a little survival promotive effect at 1.0-1.5 ng/ml, peak effect at 4 ng/ml and no more effects from 8.0 to 100 ng/ml. The survival number of neurons on 7th day was compared, and results showed higher sensitivity of sensory neuron to CNTF shortage than that of motoneuron. This suggests that survival effect of CNTF on motoneuron is only small part of its neurotrophic effects.

Animals↗

PubMed1997

[Cell culture of human lamina cribrosa in vitro].

OBJECTIVE: To investigate the physiology and pathology of the biosynthesis of extracellular matrix (ECM) by lamina cribrosa cells (LCC) and to establish a model of cultured LCC. METHODS: The LCC of 10 human dead fetal eyes were cultured with enzyme digestion procedures in vitro. The cultured cells were identified by immunohistochemistry assays and electron microscopy. RESULTS: The cultured cells were flat, polygonal in shape, and their cytoplasm contained abundant perinuclear granules. The nuclei were relatively transparent and nucleoli were clear, there were basement membrane-like material and ECM surrounding the cell membrane. The immunofluorescent staining was positive for collagen type I, III, IV, fibronectin and laminin, negative for glial fibrillar acid protein and factor-VIII. The characteristics mentioned above were coincident with the morphology of LCC. This cell line has been cultured to its fourth generation. CONCLUSION: We have successfully cultured a cell line of LCC, and it may be utilized in the study of pathogenesis of glaucoma.

Cells, Cultured↗

PubMed1997

[The setting up of human serum calcitonin radioimmunoassay and its clinical application].

This study deals with the setting up of human serum calcitonin radioimmunoassay (hCT-RIA) using the high titer and specific antibody which was prepared by our own laboratory. The final dilution of the antibody titer was 1:1,200,000 when the binding rate of Bo/T was 30%. The antibody's affinity constant (Kd) was 2.25 x 10(11) L/M. No cross reaction was found between the antibody and the following eight different peptide hormones and proteins, viz.: TSH, T3, T4, ACTH, PTH, BGP, Insulin and Gastrin. The coefficients variation of intra and inter assay were 3.2% and 9.0%, respectively. The mean recovery rate of CT was 99.8%. The sensitivity of this assay was 9.4 pg/ml. The examination of this methodology showed that all its indices met the demands of RIA. There was no difference in the mean value of serum CT between the two sexes in 232 normal subjects, but the serum CT concentration in those aged of sixty and over of men and women, were much lower than those aged of fourty group. Mean CT concentration was low in the patients with primary osteoporosis, but were significantly higher in those suffering from medullary thyroid carcinoma, primary hyperparathyroidism crisis and chronic renal failure.

Adult↗

PubMed1997

[The inhibitory effects of antioxidant vitamins on serum oxLDL and experimental atherosclerosis of rabbits].

OBJECTIVE AND METHODS: In order to study the inhibitory effects of antioxidant vitamins on serum (low oxidative density lipoproteins, oxLDL) and experimental atherosclerosis in rabbits, 20 rabbits were fed on cholesterol rich diet and antioxidant vitamins (vitamin E, vitamin C and beta carotene) for 12 weeks. oxLDL were tested by ELISA at the beginning of experiment and after 4 weeks 8 weeks. RESULTS: The results showed that supplement of antioxidant vitamins can decrease the oxLDL level significantly and inhibited development of atherosclerosis lesion around aorta in rabbits.

Animals↗

PubMed1997

[Separation and purefied of calf osteocalcin, set up radioimmunoassay for osteocalcin].

OBJECTIVE AND METHODS: We extracted and purified osteocalcin (BGP) from calf femur by gel filtration, FPLC and HPLC subsequently. The rabbits were immunized by this antigen and produced antibody. With this antibody (final 1: 35,000 dilution) we established RIA for BGP. This assay is stable and sensitive, the kd was 2.29 x 10(11). The intra assay variation was 2.1% and the inter assay variaton was 5.6%. It has no crossreaction with insulin, parathyroid hormone or calcitonin. RESULTS: The serum BGP values were detected in normal subjects and six kinds of bone metabolic diseases. In 81 normal subjects, the average serum BGP level was (5.3 +/- 1.5) ng/ml and in postmenopausal osteoporosis the serum BGP level [(6.2 +/- 1.9) ng/ml, n = 42] was higher than the normal (P < 0.05). The serum BGP levels were increased much in primary hyperparathyroidism [(12.8 +/- 7.0) ng/ml, n = 21, P < 0.001]. Increased values of BGP were also found in patients with chronic renal failure [(8.5 +/- 2.4) ng/ml, n = 18, P < 0.01] and Paget's disease [(6.7 +/- 2.2) ng/ml, n = 12, P < 0.05]. Decreased serum BGP values were found in Cushing syndrome [(2.9 +/- 0.9) ng/ml, n = 16, P < 0.001] and hypoparathyroidism [(3.4 +/- 1.1) ng/ml, n = 42, P < 0.001]. This result showed that in diseases with high bone turnover, the serum BGP levels were increased and in diseases with low bone turnover, the serum BGP levels were decreased. CONCLUSION: The data suggest that serum BGP is a sensitive marker for bone turnover. It is very improtant in studying bone metabolic diseases.

Adult↗

PubMed1997

[Traumatic ascending ischemic injury of the spinal cord].

We report five cases that the paraplegic level showed ascending from the segment of spinal injury upward to the higher level. In T10-11 fracture-dislocation, the paraplegic level ascended gradually to C2-3 in case 1 within 10 days and death due to breathing paralysis. In case 2, the paraplegic level ascended to cervical cord with loss of strength in both arms within 14 days. The remaining 3 cases were Ti2(in 2 cases) and L3(1 case) fracture. Their paraplegic level ascended to T8(2 cases) and T9(1 case). There were lower motor neuron paralysis in all cases. Observation on spinal cord specimen of case 1 showed thrombosis of dorsal vessels at T9-10 segment and multiple thrombosis were found in anterior spinal vessels, central spinal vessels and intramedullar small vessels upward to C3 and downward to S1 segments. The whole cord underwent ischemic necrosis.

Adult↗

PubMed1997

[Immunohistochemical and quantitative analysis of expression of basement membrane in squamous cell carcinoma of the oral cavity].

Fifty seven cases of oral squamous cell carcinoma (OSCC) were studied by immunohistochemical ABC method using type IV collagen and laminin antibodies and computer image analysis system to investigate the expression of basement membrane and its relation to clinicopathologic characteristics of the OSCC. The results demonstrated that: 1. in OSCC there were defects basement membrane in continuity of varying extents to complete loss of; 2. there was no correlation between the loss of basement membrane and tumor clinical stage (P > 0.05) by computer image analysis, while there was a highly significant correlation between the loss of basement membrane and histologic grading (P > 0.05). The well-differentiated tumor was associated with a low frequency of basement membrane loss. Therefore, the expression of basement membrane may be a useful parameter to evaluate tumor histologic differentiation.

Basement Membrane↗

PubMed1997

[Preparation of chromosomal DNA from whole blood without use of phenol].

We describe in this paper a simple and efficient procedure for preparing peripheral blood DNA without pre-isolation of white blood cells. The method also avoids the hazard of organic solvent extraction. Routinely it yields 20 to 28 micrograms of chromosomal DNA from per ml whole blood. The A260/A280 ratio for DNA sample is 1.80 to 1.85. The undigested DNAs migrate above the 21 kb pair, while the endonucleasedigested samples appear characteristically in the smear form. These data illustrate the consistency and quality of the chromosomal DNA isolated using this procedure. The DNA prepared by this method was used for analysis of beta-thalassemia mutation and prenatal diagnosis in our laboratory.

Blood Chemical Analysis↗