Stimulatory and entraining effect of melatonin on tuberoinfundibular dopaminergic neuron activity and inhibition on prolactin secretion

The aims of the present study were to determine if melatonin exerts an effect on prolactin (PRL) secretion via the tuberoinfundibular dopaminergic (TIDA) neurons and if endogenous or exogenous melatonin has an entraining effect on the rhythmic changes of TIDA neuronal activity and PRL secretion. Melatonin given in the morning (10:00 h), dose- (0.01-1 mg/kg, ip) and time- (at 15 and 60 min, but not at 30 min) dependently stimulated TIDA neuronal activity in ovariectomized (OVX), estrogen-treated rats as determined by 3,4-dihydroxyphenylacetic acid (DOPAC) levels in the median eminence (ME). Serum PRL was concurrently inhibited by the injection. Melatonin administered in the afternoon (15:00 h) was even more effective in stimulating the lowered TIDA neuronal activity and inhibiting the increased PRL level than that given in the morning (10:00 h). S-20098, a melatonin agonist was also effective in stimulating the TIDA neurons. In contrast, S-20928, a putative melatonin antagonist, while it had no effect by itself, blocked the effect of S-20098. Although S-20928 failed to prevent melatonin's effect on ME DOPAC levels, six interspaced injections of S-20928, from 18:00 to 01:30 h, significantly blocked the increase of ME DOPAC levels at 03:00 h, indicating that the endogenous melatonin may play a role. We further used rats that received daily injection of melatonin (1 mg/kg, ip) at 18:00 h for 10 days and found that the injection augmented basal TIDA neuronal activity at 11:00 h and blunted the afternoon PRL surge. In all, melatonin can have an inhibitory effect on PRL secretion by stimulating the TIDA neurons, and it may help to entrain the circadian rhythms of both TIDA neuronal activity and PRL secretion.     

Ligation of lymphocyte function-associated antigen-1 on monocytes decreases very late antigen-4-mediated adhesion through a reactive oxygen species-dependent pathway

Monocyte-endothelial adhesion plays an important role in monocyte trafficking and hence is important for immune responses and pathogenesis of inflammatory diseases including atherosclerosis. The cross-talk between different integrins on monocytes may be crucial for a coordinated regulation of the cellular adhesion during the complex process of transendothelial migration. By using monoclonal antibodies and recombinant intercellular adhesion molecule 1 (ICAM-1) to engage lymphocyte function-associated antigen 1 (LFA-1) on monocytic cells, we found that the cellular adhesion to vascular cell adhesion molecule 1 (VCAM-1) mediated by very late antigen 4 (VLA-4) was suppressed after this treatment and the suppression depended on the presence of reactive oxygen species (ROSs). Inhibition of production of ROSs through the use of inhibitor of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, but not inhibitors of mitochondrial electron transport chain or xanthine oxidase, revealed that this suppression on VLA-4-mediated cellular binding was mediated by ROSs produced by phagocyte NADPH oxidase. Activation of phosphoinositol-3 kinase and Akt appears to mediate this NADPH oxidase activation through p47phox phosphorylation and Rac-1 activation. Our results provide a novel pathway in which ROSs play a critical role in integrin cross-talk in monocytes. This signaling pathway may be important for cellular transition from firm arrest to diapedesis during monocyte trafficking.     

Obesity, leptin and blood pressure among children in Taiwan: the Taipei Children's Heart Study

BACKGROUND: Obesity is associated with the occurrence of hypertension; however, the mechanisms of obesity-induced high blood pressure (BP) remain unclear. Leptin, the obese (ob) gene product, is associated with the occurrence of obesity and related disorders in humans. The purpose of this study was to evaluate the association between plasma leptin and BP among children. METHODS: After multistage sampling, we randomly selected 1265 children (618 boys and 647 girls) with a mean age of 13.3 years (12 to 16 years old) in this cross-sectional survey. Obesity measurements included body mass index (BMI) and waist-to-hip circumference ratio (WHR). Plasma leptin levels were measured by radioimmunoassay. RESULTS: The mean and median plasma leptin levels were 4.1 and 2.4 ng/mL among boys and 10.1 and 8.8 ng/mL among girls. Children in the highest quintile of leptin level (mean, 11.1 and 19.7 ng/mL for boys and girls, respectively) had higher body weight, BMI, WHR, BP, and insulin levels than children in the lowest quintile (mean, 1.1 and 3.9 ng/mL for boys and girls, respectively). Boys had a higher BMI, WHR, and BP levels, yet had lower leptin levels than girls. In both genders, BMI and plasma leptin levels were significantly positively correlated with BP. In multivariate regression analyses, plasma leptin levels were positively associated with BP; however, this association became insignificant among girls and even inversely associated with systolic BP among boys after adjusting for BMI. CONCLUSIONS: Obesity is positively associated with BP among school children in Taiwan; however, the role of plasma leptin on the development of obesity-related hypertension is still controversial among school children.     

A vaccine carrier derived from Neisseria meningitidis with mitogenic activity for lymphocytes.

Protein carriers vary in their ability to increase the immunogenicity of poorly immunogenic or T-lymphocyte-independent antigens. We examined one such carrier, the outer membrane protein complex derived from Neisseria meningitidis serogroup B strain B11, in an attempt to determine why this outer membrane protein complex was more immunogenic in young infants and in relevant animal models than two other carriers used in conjugates made with Haemophilus influenzae type b polysaccharide, a T-cell-independent antigen. A single protein of the outer membrane protein complex, the class 2 porin protein, was purified and shown to function as a T-helper lymphocyte carrier protein. Unexpectedly, it was also found to have mitogenic activity for lymphocytes that was not due to lipopolysaccharide. This mitogenic activity appears to date to be unique to this carrier protein of the carrier proteins tested and may contribute to the ability of the H. influenzae type b conjugate vaccine made with the outer membrane protein complex to generate IgG anti-polysaccharide antibody responses in mice and infant monkeys and protective immune responses in infants less than 6 months of age.     

Epidermal growth factor‐induced COX‐2 regulates metastasis of head and neck squamous cell carcinoma through upregulation of angiopoietin‐like 4

Epidermal growth factor receptor (EGFR) expression and activation are the major causes of metastasis in cancers such as head and neck squamous cell carcinoma (HNSCC). However, the reciprocal effect of EGF‐induced COX‐2 and angiopoietin‐like 4 (ANGPTL4) on HNSCC metastasis remains unclear. In this study, we revealed that the expression of ANGPTL4 is essential for COX‐2‐derived prostaglandin E₂ (PGE₂)‐induced tumor cell metastasis. We showed that EGF‐induced ANGPTL4 expression was dramatically inhibited with the depletion and inactivation of COX‐2 by knockdown of COX‐2 and celecoxib treatment, respectively. Prostaglandin E₂ induced ANGPTL4 expression in a time‐ and dose‐dependent manners in various HNSCC cell lines through the ERK pathway. In addition, the depletion of ANGPTL4 and MMP1 significantly impeded the PGE₂‐induced transendothelial invasion ability of HNSCC cells and the binding of tumor cells to endothelial cells. The induction of molecules involved in the regulation of epithelial‐mesenchymal transition was also dependent on ANGPTL4 expression in PGE₂‐treated cells. The depletion of ANGPTL4 further blocked PGE₂‐primed tumor cell metastatic seeding of lungs. These results indicate that the EGF‐activated PGE₂/ANGPTL4 axis enhanced HNSCC metastasis. The concurrent expression of COX‐2 and ANGPTL4 in HNSCC tumor specimens provides insight into potential therapeutic targets for the treatment of EGFR‐associated HNSCC metastasis.     

Dual expression of the HA protein of H5N2 avian influenza virus in a baculovirus system

Baculovirus/insect cell system is used widely for recombinant protein production. The hemagglutinin (HA) gene of H5N2 avian influenza virus (AIV) 1209 strain and the enhanced green fluorescent protein (EGFP) gene were cloned into pFastBac DUAL vector that has two promoters and cloning sites, allowing simultaneous expression of these two genes. The HA protein of AIV was fused with a hexahistidine (His6) tag for purification. The coexpression of EGFP allowed identification of the recombinant baculoviruses in Sf-9 insect cells, eliminating cumbersome and time-consuming assays. A recombinant baculovirus, Bac-HA, was generated by transfecting pBac-HA to bacmid inside DH10B(AC)Escherichia coli by site-specific transposition, followed by transfection into the Sf-9 cells. Fluorescence in the insect cells was observed from 3 days post-infection. The expressed HA protein was confirmed by Western blot using an anti-HA monoclonal antibody. Also, different detergents and incubation times on ice were tested. The two-stage extraction with Triton X-100 or Tween 20 and incubation on ice for 2h exhibited high efficiency. Since purification of HA with ConA resin resulted in low protein recovery, lentil lectin affinity column was used and was useful for HA purification.     

Noninvasive assessment of the viscoelasticity of peripheral arteries

Currently used methods of examining the mechanical properties of blood vessel walls are either indirect or invasive, or measure vessel diameter and pressure waveforms at different sites. We developed a noninvasive technique to assess the mechanical properties and viscoelasticity of peripheral arteries. The pressure-strain elastic modulus (Ep) and the viscoelastic properties (energy dissipation ratio, EDR) of the common carotid artery (CCA), brachial artery (BA), radial artery (RA) and dorsalis pedis artery (DPA) were determined by means of palpating pressure and diameter distension waveforms extracted from high-resolution ultrasonography. The methodology was validated in vitro using an elastic tube phantom, as well as in vivo. In vivo study in 10 healthy volunteers (mean age 22 y) showed that the pressure-diameter curves were nonlinear, with an inflection at about 85–90 mmHg, and routed clockwise with slight hysteresis. The CCA (n = 5) had a mean diameter of 6.74 mm and the pulsatile diameter distension was 12.2%. The Ep calculated at the CCA was 0.44 × 10⁶ dyne/cm² with an EDR of 7.18%. The BA, RA and DPA (n = 10) had mean diameters of 3.91 mm, 2.21 mm and 2.12 mm; arterial strains of 4.60%, 4.25% and 8.91%; mean Ep of 1.39, 1.45, 0.90 × 10⁶ dyne/cm²; and mean EDRs of 6.34%, 6.15% and 5.60%, respectively. The method presented is relatively simple to implement clinically and has potential as a new diagnostic tool for detecting local vascular changes.     

Intrinsic Mode Analysis of Human Heartbeat Time Series

The human heartbeat interval is determined by complex nerve control and environmental inputs. As a result, the heartbeat interval for a human is a complex time series, as shown by previous studies. Most of the analysis algorithms proposed for characterizing the profile of heartbeat time series, such as detrended fluctuation analysis and multi-scale entropy, are based on various characteristics of dynamics. In this study, we present an empirical mode decomposition-based intrinsic mode analysis, which uses the appearance energy index (AEI) to quantify the property of long-term correlation, and structure index (SI) to characterize the internal modulation of data. This presented algorithm was used to investigate the human heartbeat time series downloaded from PhysioBank. We found the profiles of human heartbeat time series of subjects with congestive heart failure (CHF) or atrial fibrillation (AF) are significantly different from those of healthy subjects in internal modulation as shown by SI. Moreover, AEI is the critical characteristics for verifying subjects with CHF from subjects with AF in a degree of long-term correlation. Both AEI and SI contribute to presenting the characteristic profiles of a human heartbeat time series.     

A Mediated Glucose Biosensor Incorporated with Reverse Iontophoresis Function for Noninvasive Glucose Monitoring

The objective of this study was to develop a ferrocene mediated glucose biosensor for reverse iontophoresis. An amperometric ferrocene mediated glucose biosensor based on a three electrodes planar configuration was constructed using screen printing technique. Different combinations of glucose oxidase and ferrocene loading were drop coated onto the surface of the amperometric transducer. The amperometric transducer was characterized electrochemically using cyclic voltammetry and its electrochemical characteristics (ΔE _p = 70 mV, I _pa/I _pc = 0.89) were found close to an ideal amperometric transducer. The biosensor on the detection of glucose at 200 mV (vs. Ag/AgCl) showed a linear response range (0–4 mM). The response time of the biosensor was about 10 s. Finally, the biosensor was used together with reverse iontophoresis technique. By the use of an actual model for evaluation, an excellent linear relationship (r ² = 0.99) was found between the glucose concentration of the actual model and the biosensor current response. In conclusion, a ferrocene mediated glucose biosensor incorporated with reverse iontophoresis function was developed.