Numerical model characterization of the sound transmission mechanism in the tympanic membrane from a high-speed digital holographic experiment in transient regime

A methodology for the development of a finite element numerical model of the tympanic membrane (TM) based on experiments carried out in the time domain on a cadaveric human temporal bone is presented. Using a high-speed digital holographic (HDH) system, acoustically-induced transient displacements of the TM surface are obtained. The procedure is capable to generate and validate the finite element model of the TM by numerical and experimental data correlation. Reverse engineering approach is used to identify key material parameters that define the mechanical response of the TM. Finally, modal numerical simulations of the specimen are performed. Results show the feasibility of the methodology to obtain an accurate model of a specific specimen and to help interpret its behaviour with additional numerical simulations. STATEMENT OF SIGNIFICANCE: Improving knowledge of the dynamic behavior of the tympanic membrane is key to understanding the sound transmission system in human hearing and advance in the treatment of its pathologies. Recently we acquired a new tool to carry out experiments in transient regime by means of digital laser holography, capable of providing a large amount of information in a controlled transient test. In this work, these data are used to develop a methodology that generates a numerical model of the tympanic membrane based on numerical-experimental correlations. It is important to be able to develop models that fit specific patients. In this work, additional modal simulations are also presented that, in addition to validating the results, provide more information on the specimen.

Analyses of the Tympanic Membrane Impulse Response Measured with High-Speed Holography

The Tympanic Membrane (TM) transforms acoustic energy to ossicular vibration. The shape and the displacement of the TM play an important role in this process. We developed a High-speed Digital Holography (HDH) system to measure the shape and transient displacements of the TM induced by acoustic clicks. The displacements were further normalized by the measured shape to derive surface normal displacements at over 100,000 points on the TM surface. Frequency and impulse response analyses were performed at each TM point, which enable us to describe 2D surface maps of four new TM mechanical parameters. From frequency domain analyses, we describe the (i) dominant frequencies of the displacement per sound pressure based on Frequency Response Function (FRF) at each surface point. From time domain analyses, we describe the (ii) rising time, (iii) exponential decay time, and the (iv) root-mean-square (rms) displacement of the TM based on Impulse Response Function (IRF) at each surface point. The resultant 2D maps show that a majority of the TM surface has a dominant frequency of around 1.5 kHz. The rising times suggest that much of the TM surface is set into motion within 50 µs of an impulsive stimulus. The maps of the exponential decay time of the IRF illustrate spatial variations in damping, the least known TM mechanical property. The damping ratios at locations with varied dominant frequencies are quantified and compared.

Multiple angle digital holography for the shape measurement of the unpainted tympanic membrane

The shape of the tympanic membrane (TM) plays an important role in sound transmission through the ear for hearing. Previously we developed a high-speed holographic system employing a tunable wavelength laser for rapid TM shape measurement. However, the tunable laser illumination was not sufficient to measure the shape of the unpainted TM due to the semi-transparency of the TM and short exposure time of the camera. This paper presents a new multiple angle illumination technique that allows us to use a higher power single wavelength laser to perform shape measurements on the unpainted TM. Accuracy of the new method is demonstrated by a measure of a step gauge provided by the National Institute of Standards and Technology. We successfully applied the new shape measurement method on a fresh postmortem human TM without any paint.

Do high-frequency air-bone gaps persist after ossiculoplasty?

OBJECTIVES

Conventional reporting of postoperative hearing outcomes utilizes a pure-tone averaged air-bone gap (ABG) that is biased toward low frequencies. Consequently, a high-frequency ABG after otologic surgery may go unnoticed. In this study, we evaluate changes in low- and high-frequency ABG following ossiculoplasty.

STUDY DESIGN

Retrospective review.

SUBJECTS AND SETTING

Consecutive series of patients who underwent ossiculoplasty at a single tertiary care center. Patients with pre- and postoperative audiograms were included.

METHODS

Low-frequency ABG was calculated as the mean ABG at 250, 500, and 1000 Hz. High-frequency ABG was calculated at 4 kHz. Pre- and postoperative ABGs were compared.

RESULTS

Thirty-seven consecutive patients were included. Mean age at surgery was 38 years (range, 7-77 years). Reconstruction materials included: cartilage (N = 4), hydroxyapatite cement (N = 5), and partial or total ossicular replacement prostheses (N = 20 and N = 8, respectively). Postoperatively, the mean low-frequency ABG improved by 11.9 ± 15.1 dB (P < .0001) and the mean high-frequency ABG improved by 5.9 ± 16.0 dB (P = .030). Low-frequency ABG closure was significantly larger than high-frequency ABG closure (P = .007). Mean postoperative persistent high-frequency ABG was 22.0 ± 13.8 dB.

CONCLUSION

In this series, ossiculoplasty improved ABG across all frequencies, but greater improvements were observed at low frequencies when compared to high frequency. Current reporting standards may not identify persistent high-frequency ABG. Additional study of the mechanisms of high-frequency sound conduction in reconstructed middle ears is needed to improve high-frequency hearing outcomes in ossiculoplasty.

LEVEL OF EVIDENCE

Level 4.

High-Frequency Conductive Hearing following Total Drum Replacement Tympanoplasty

OBJECTIVES

Conventional reporting of posttympanoplasty hearing outcomes use a pure-tone averaged air-bone gap (ABG) largely representing a low-frequency sound conduction. Few studies report high-frequency conductive hearing outcomes. Herein, we evaluate high-frequency ABG in patients following temporalis fascia total drum replacement.

STUDY DESIGN

Case series with chart review.

SETTING

Tertiary care center.

SUBJECTS AND METHODS

All patients who underwent type 1 tympanoplasty using a lateral graft total drum replacement technique between August 2016 and February 2019 were identified. Patients with pre- and postoperative audiograms were included. Low-frequency ABG was calculated as the mean ABG at 250, 500, and 1000 Hz. High-frequency ABG was calculated at 4 KHz. Pre- and postoperative ABGs were compared.

RESULTS

Twenty-three patients were included, and the mean age at surgery was 44 years (range, 9-68 years). Perforation etiology was from trauma (n = 14) or chronic otitis media (n = 9). Preoperative mean low-frequency ABG was 27.8 ± 12.6 dB and mean high-frequency ABG was 21.5 ± 15.1 dB (P = .044). Postoperatively, the mean low-frequency ABG was significantly reduced by 15.5 ± 13.3 dB (P < .001) while the mean high-frequency ABG insignificantly changed (reduced by 2.6 ± 16.2 dB, P = .450).

CONCLUSION

In a series of patients undergoing temporalis fascia total drum replacement, low-frequency ABG improved; however, high-frequency conductive hearing loss persists. Conventional methods of reporting ABG may not identify persistent high-frequency ABG. These results merit further study across a range of tympanoplasty graft materials and surgical techniques.

High-Speed Holographic Shape and Full-Field Displacement Measurements of the Tympanic Membrane in Normal and Experimentally Simulated Pathological Ears

To improve the understanding of the middle-ear hearing mechanism and assist in the diagnosis of middle-ear diseases, we are developing a high-speed digital holographic (HDH) system to measure the shape and acoustically-induced transient displacements of the tympanic membrane (TM). In this paper, we performed measurements on cadaveric human ears with simulated common middle-ear pathologies. The frequency response function (FRF) of the normalized displacement by the stimulus (sound pressure) at each measured pixel point of the entire TM surface was calculated and the complex modal indicator function (CMIF) of the middle-ear system based on FRFs of the entire TM surface motions was used to differentiate different middle-ear pathologies. We also observed changes in the TM shape and the surface motion pattern before and after various middle-ear manipulations. The observations of distinguishable TM shapes and motion patterns in both time and frequency domains between normal and experimentally simulated pathological ears support the development of a quantitative clinical holography-based apparatus for diagnosing middle-ear pathologies.

[Association between Lipoprotein(a) and the characteristics of left main coronary artery plaque in patients with stable angina pectoris]

Objective: To investigate the relationship between Lipoprotein (LP) (a) level and the characteristics of tissue components of left main coronary artery (LMCA) plaque. Methods: A total of 102 patients with stable angina pectoris who underwent percutaneous coronary intervention (PCI) in the People's Hospital of Henan Province from June 2010 to October 2016 were included. We performed intravascular ultrasound-virtual histology (IVUS-VH) to their LMCAs and evaluated the tissue characteristics, and the blood level of total cholesterol (TC), triacylglycerol (TG), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), ApoB, ApoA1, LP(a) were measured. According to the value of their LP(a) level they were divided into 2 groups (high LP(a) group (>300 mg/L) (n=35) and low LP(a) group (≤300 mg/L) (n=67)), then the relationship between the above lipid values and the tissue characteristics of the LMCA plaque in the patients were evaluated. Results: Patients with a high LP(a) had a larger percentage of fibrolipid volume and a smaller percentage fibrous volume compared to patients with a normal LP(a) (25%±5% vs 13%±6%, P<0.01 and 50%±8% vs 61%±9%, P<0.01). Using multivariate linear regression analysis after adjustment for the above-mentioned confounding factors, LP(a) had a significantly positive correlation with fibrolipid volume percentage (r=0.645, β=0.29, P<0.01), and had a negative correlation with fibrous volume percentage (r=-0.467, β=-0.32,P<0.01), suggesting that the LP(a) was associated with the vulnerability of the LMCA plaque. Conclusion: For the patients with stable angina pectoris, the LP(a) has a significantly positive correlation with the percentage of fibrolipid volume and a negative correlation with the percentage of fibrous volume, suggesting that the LP(a) could predict the vulnerability of the LMCA plaque.

Combined high-speed holographic shape and full-field displacement measurements of tympanic membrane

The conical shape of the tympanic membrane (TM or eardrum) plays an important role in its function, such that variations in shape alter the acoustically induced motions of the TM. We present a method that precisely determines both shape and acoustically induced transient response of the entire TM using the same optics and maintaining the same coordinate system, where the TM transient displacements due to a broadband acoustic click excitation (50-μs impulse) and the shape are consecutively measured within <200  ms. Interferograms gathered with continuous high-speed (>2  kHz) optical phase sampling during a single 100-ms wavelength tuning ramp allow precise and rapid reconstructions of the TM shape at varied resolutions (50 to 200  μm). This rapid acquisition of full-field displacements and shape is immune to slow disturbances introduced by breathing or heartbeat of live subjects. Knowledge of TM shape and displacements enables the estimation of surface normal displacements regardless of the orientation of the TM within the measurement system. The proposed method helps better define TM mechanics and provides TM structure and function information useful for the diagnosis of ear disease.

[Effect of miR-19b on the proliferation and apoptosis of P19CL6 cells during the late-stage of cardiac differentiation]

Objective: To explore the effect of miR-19b on the function of P19CL6 cells and its molecular mechanism. Methods: Overexpression of miR-19b was carried out by transfecting miR-19b plasmid into the P19CL6 cells. MTT assay and flow cytometry were used to determine cell growth and apoptosis, respectively. Western blot was used to detect the expression level of Sox6 in P19CL6 cells. ELISA assay was used to detect the expression levels of apoptosis-related genes (Bax, Bcl-2) in P19CL6 cells at late-stage cardiac differentiation. Further online software TargetScan was used to predict the target genes of miR-19b and verified by dual luciferase reporter assay. Results: Our data showed that overexpression of miR-19b in P19CL6 cells significantly increased the cell growth rates and the apoptosis inhibition rates. The ratio of apoptosis-related proteins (Bax/Bcl-2) was significantly reduced. Results from the TargetScan and dual luciferase reporter showed that Sox6 is the direct target of miR-19b. Conclusions: We conclude that miR-19b might promote cell proliferation and inhibits cell apoptosis during the late-stage of cardiac differentiation by targeting Sox6 expression.

[Association between the ApoB/A1 ratio and the vulnerability of LMCA plaque in the patients with stable angina pectoris]

Objective: To investigate the relationship between ApoB/A1 ratio and the characteristics of tissue components of their left main coronary artery(LMCA)plaque. Methods: A total of 98 patients with stable angina pectoris who received chronic statin treatment underwentpercutaneous coronary intervention in the People's Hospital of Henan Province from June 2010 to June 2016 were included.We prospectively performed intravascular ultrasound virtualhistology (IVUS-VH) to their LMCA and evaluated the tissue characteristics, and the blood level of total cholesterol (TC) and low-density lipoprotein cholesterol(LDL-C), high-density lipoprotein cholesterol(HDL-C), triglyceride(TG), LDL-C/HDL-C ratio, ApoB, ApoA1, ApoB/A1 ratio were measured, then the association of the tissue characteristics with the aboved lipids values were analyzed. Results: According to the median value of their ApoB/A1ratios (0.80), they were divided into 2 groups [high ApoB/A1 ratio (>0.80) (n=49) and low ApoB/A1 ratio (≤0.80) (n=49)]. The patients with a high ApoB/A1 ratio had alarger fibrolipid volume and a smaller fibrous volume compared to patients with a low ApoB/A1 ratio ( 17.5%±1.2% vs 9.0%±1.0%, P=0.03 and 55.1%±2.1% vs 63.9%±1.8%, P<0.01). Using multivariate linear regression analysis after adjustment for the above-mentioned confounding factors, the ApoB/A1 ratio had a significantly positive correlation with fibrolipid volume (r=0.445, β=0.29, P=0.010)and had a negative correlation with fibrous volume (r=-0.567, β=-0.32, P=0.011), suggesting that the ApoB/A1 ratio was associated with the vulnerability of the LMCA plaque. Conclusion: For the patients with stable angina pectoris and chronic treatment of statins, a high ApoB/A1 ratio is associated with a high percentage of fibrolipid volume and a low percentage of fibrous volume in LMCA lesions, suggesting that the ApoB/A1 ratios could predict the vulnerability of the LMCA plaque.

Design, fabrication, and in vitro testing of novel three-dimensionally printed tympanic membrane grafts

The tympanic membrane (TM) is an exquisite structure that captures and transmits sound from the environment to the ossicular chain of the middle ear. The creation of TM grafts by multi-material three-dimensional (3D) printing may overcome limitations of current graft materials, e.g. temporalis muscle fascia, used for surgical reconstruction of the TM. TM graft scaffolds with either 8 or 16 circumferential and radial filament arrangements were fabricated by 3D printing of polydimethylsiloxane (PDMS), flex-polyactic acid (PLA) and polycaprolactone (PCL) materials followed by uniform infilling with a fibrin-collagen composite hydrogel. Digital opto-electronic holography (DOEH) and laser Doppler vibrometry (LDV) were used to measure acoustic properties including surface motions and velocity of TM grafts in response to sound. Mechanical properties were determined using dynamic mechanical analysis (DMA). Results were compared to fresh cadaveric human TMs and cadaveric temporalis fascia. Similar to the human TM, TM grafts exhibit simple surface motion patterns at lower frequencies (400 Hz), with a limited number of displacement maxima. At higher frequencies (>1000 Hz), their displacement patterns are highly organized with multiple areas of maximal displacement separated by regions of minimal displacement. By contrast, temporalis fascia exhibited asymmetric and less regular holographic patterns. Velocity across frequency sweeps (0.2-10 kHz) measured by LDV demonstrated consistent results for 3D printed grafts, while velocity for human fascia varied greatly between specimens. TM composite grafts of different scaffold print materials and varied filament count (8 or 16) displayed minimal, but measurable differences in DOEH and LDV at tested frequencies. TM graft mechanical load increased with higher filament count and is resilient over time, which differs from temporalis fascia, which loses over 70% of its load bearing properties during mechanical testing. This study demonstrates the design, fabrication and preliminary in vitro acoustic and mechanical evaluation of 3D printed TM grafts. Data illustrate the feasibility of creating TM grafts with acoustic properties that reflect sound induced motion patterns of the human TM; furthermore, 3D printed grafts have mechanical properties that demonstrate increased resistance to deformation compared to temporalis fascia.

Investigation of middle ear anatomy and function with combined video otoscopy-phase sensitive OCT

We report the development of a novel otoscopy probe for assessing middle ear anatomy and function. Video imaging and phase-sensitive optical coherence tomography are combined within the same optical path. A sound stimuli channel is incorporated as well to study middle ear function. Thus, besides visualizing the morphology of the middle ear, the vibration amplitude and frequency of the eardrum and ossicles are retrieved as well. Preliminary testing on cadaveric human temporal bone models has demonstrated the capability of this instrument for retrieving middle ear anatomy with micron scale resolution, as well as the vibration of the tympanic membrane and ossicles with sub-nm resolution.

Optimization of a lensless digital holographic otoscope system for transient measurements of the human tympanic membrane

In this paper, we propose a multi-pulsed double exposure (MPDE) acquisition method to quantify in full-field-of-view the transient (i.e., >10 kHz) acoustically induced nanometer scale displacements of the human tympanic membrane (TM or eardrum). The method takes advantage of the geometrical linearity and repeatability of the TM displacements to enable high-speed measurements with a conventional camera (i.e., <20 fps). The MPDE is implemented on a previously developed digital holographic system (DHS) to enhance its measurement capabilities, at a minimum cost, while avoiding constraints imposed by the spatial resolutions and dimensions of high-speed (i.e., >50 kfps) cameras. To our knowledge, there is currently no existing system to provide such capabilities for the study of the human TM. The combination of high temporal (i.e., >50 kHz) and spatial (i.e., >500k data points) resolutions enables measurements of the temporal and frequency response of all points across the surface of the TM simultaneously. The repeatability and accuracy of the MPDE method are verified against a Laser Doppler Vibrometer (LDV) on both artificial membranes and ex-vivo human TMs that are acoustically excited with a sharp (i.e., <100 μs duration) click. The measuring capabilities of the DHS, enhanced by the MPDE acquisition method, allow for quantification of spatially dependent motion parameters of the TM, such as modal frequencies, time constants, as well as inferring local material properties.

Full-field transient vibrometry of the human tympanic membrane by local phase correlation and high-speed holography

Understanding the human hearing process would be helped by quantification of the transient mechanical response of the human ear, including the human tympanic membrane (TM or eardrum). We propose a new hybrid high-speed holographic system (HHS) for acquisition and quantification of the full-field nanometer transient (i.e., >10 kHz) displacement of the human TM. We have optimized and implemented a 2 þ 1 frame local correlation (LC) based phase sampling method in combination with a high-speed (i.e., >40 K fps) camera acquisition system. To our knowledge, there is currently no existing system that provides such capabilities for the study of the human TM. The LC sampling method has a displacement difference of <11 nm relative to measurements obtained by a four-phase step algorithm. Comparisons between our high-speed acquisition system and a laser Doppler vibrometer indicate differences of <10 μs. The high temporal (i.e., >40 kHz) and spatial (i.e., >100 k data points) resolution of our HHS enables parallel measurements of all points on the surface of the TM, which allows quantification of spatially dependent motion parameters, such as modal frequencies and acoustic delays. Such capabilities could allow inferring local material properties across the surface of the TM.

Decrease of FGF receptor (FGFR) and interstitial fibrosis in the kidney of streptozotocin-induced diabetic rats

Fibrosis is the final disorder of end-stage renal disease. Activation of fibroblast growth factor (FGF) 23-klotho axis could suppress renal fibrosis in mice. Also, a marked decrease of klotho expression was observed in the kidney of streptozotocin-induced diabetic rats (STZ rats). However, relation of FGF in renal fibrosis remained unclear. This study was aimed to screen the effect of hyperglycemia on FGF receptor (FGFR) and fibrosis in kidney of rats with diabetic nephropathy and investigate this potential mechanism in cultured Madin-Darby Canine Kidney (MDCK) epithelial cells. STZ rats were used to treat with insulin or phloridzin at the dose sufficient to correct hyperglycemia for understanding the changes of renal dysfunction. The cultured MDCK cells were also used to treat with high glucose, hydrogen peroxide, or tiron in addition to transfection of siRNA to silence the klotho. Both insulin and phloridzin reversed fibrosis and FGFR expressions in kidney of STZ rats. It was confirmed in high glucose-exposed MDCK cells. However, klotho failed to modify the level of FGFR in MDCK cells. Meanwhile, FGFR was restored by tiron in MDCK cells and in diabetic rats without changing blood glucose. In conclusion, interstitial fibrosis and decreased FGFR expression are observed in the kidney of diabetic rats. This change is reversed by tiron without the correction of blood glucose. Also, klotho has no effect on expression of FGFR. Thus, decrease of oxidative stress is useful for the recovery of FGFR expression and improvement of renal fibrosis in type-1 like diabetic rats.

Decrease of hyperglycemia by syringaldehyde in diabetic rats

Syringaldehyde is one of the active principles from the stems of Hibiscus taiwanensis (Malvaceae) that has been mentioned to lower hyperglycemia. However, the potential mechanisms for this action of syringaldehyde remain obscure. In the present study, we used streptozotocin to induce diabetic rats (STZ-diabetic rats) as type 1-like diabetic rats and fed fructose-rich chow to rats as type 2-like diabetic rats. Then, we performed the postprandial glucose test and applied the hyperinsulinemic euglycemic clamp to investigate the actions of syringaldehyde. Also, the changes of gene expressions of enzyme relating to glucose homeostasis in muscle and liver were characterized. Syringaldehyde significantly decreased the postprandial plasma glucose in rats, while the plasma insulin was not modified by syringaldehyde. The glucose infusion rate (GIR) in fructose chow-fed rats using hyperinsulinemic euglycemic clamp was markedly improved by syringaldehyde. Additionally, repeated administration of syringaldehyde for 3 days in STZ-diabetic rats resulted in a marked reduction of phosphoenolpyruvate carboxykinase (PEPCK) expression in liver and an increased expression of glucose transporter subtype 4 (GLUT 4) in skeletal muscle. Our results suggest that syringaldehyde may increase glucose utilization to lower hyperglycemia in diabetic rats.

Motion of the Human Tympanic Membrane and Stapes Velocity after Placement of TORP with Cartilage Cover

Objectives:

Investigate how prosthesis of different lengths affect tympanic membrane (TM) and footplate motion in a temporal bone model of tympanoplasty with Laser-Doppler vibrometry (LDV) and opto-electronic holography (OEH) measurements.

Methods:

Four human temporal bones without history of otologic disease were prepared using universal precautions. Preparation included removal of the bony external auditory canal to expose the majority of the TM surface, and canal wall-up mastoidectomy with wide posterior tympanotomy. Retroreflective balls were placed on the posterior crus of the stapes. Control measurements were made in bones with intact ossicular chain, then the incus and the stapes suprastructure were removed with a KTP laser. The ossicular chain was reconstructed using a total ossicular replacement prosthesis (TORP). LDV measurements of the footplate motions, together with OEH measurements of TM surface and umbo motions, were made before and after placement of different length TORPs. The effect of different sizes of a cartilage disk interposed between the TM and the prosthesis was also investigated.

Results:

A ‘Best Fit’ TORP with a small cartilage disk gave the highest stapes velocities. Either TORP with a small disk produced larger OEH determined displacements of the whole TM surface, particularly at low frequency. In general, a smaller cartilage disk resulted in higher mobility of the TM and stapes.

Conclusions:

Preliminary results indicate reconstruction length and the size of the cartilaginous disk differentially affect the mobility of the TM and the stapes. However, there is significant variation in the acoustic response of similarly reconstructed ears, even in this relatively well-controlled preparation.

Simultaneous 3D imaging of sound-induced motions of the tympanic membrane and middle ear ossicles

Efficient transfer of sound by the middle ear ossicles is essential for hearing. Various pathologies can impede the transmission of sound and thereby cause conductive hearing loss. Differential diagnosis of ossicular disorders can be challenging since the ossicles are normally hidden behind the tympanic membrane (TM). Here we describe the use of a technique termed optical coherence tomography (OCT) vibrography to view the sound-induced motion of the TM and ossicles simultaneously. With this method, we were able to capture three-dimensional motion of the intact TM and ossicles of the chinchilla ear with nanometer-scale sensitivity at sound frequencies from 0.5 to 5 kHz. The vibration patterns of the TM were complex and highly frequency dependent with mean amplitudes of 70-120 nm at 100 dB sound pressure level. The TM motion was only marginally sensitive to stapes fixation and incus-stapes joint interruption; however, when additional information derived from the simultaneous measurement of ossicular motion was added, it was possible to clearly distinguish these different simulated pathologies. The technique may be applicable to clinical diagnosis in Otology and to basic research in audition and acoustics.

Role of TNF-α in renal damage in mice showing hepatic steatosis induced by high fat diet

The present study was designed to investigate the role of TNF-α in renal damage observed in mice with hepatic steatosis. We induced hepatic steatosis in mice using high fat diet and treated mice with ectanercept at the dose sufficient to block TNF-α receptors or vehicle for 1 month. Plasma TNF-α, total cholesterol (TC), triglyceride (TG), LDL-cholesterol (LDL-C), and HDL-cholesterol (HDL-C) were determined at the end of this treatment. Renal damage was identified by histologic observation and the higher of serum blood urea nitrogen (BUN) and creatinine. Also, changes of PPAR-δ in kidney and renal mesangial cell (RMC) were analyzed using Western blot. Plasma TNF-α was markedly raised in mice showing hepatic steatosis. However, the levels of blood lipids (TC, TG, HDL-C, and LDL-C) and TNF-α were not modified by the treatment of etanercept although the hepatic steatosis has been improved. Etanercept shows renal protection from histological identification and recovery of serum BUN and creatinine levels. Moreover, restoration of PPAR-δ expression by etanercept was observed in mice kidney. Direct effect of TNF-α on PPAR-δ expression was also characterized in RMC cell. We suggest that renal damage in mice with hepatic steatosis is mainly induced by increase of TNF-α through the decrease of renal PPAR-δ. Etanercept could block TNF-α receptors to restore PPAR-δ and improve renal function in mice with hepatic steatosis.

Treatment of gabapentin-induced myoclonus with continuous renal replacement therapy

A 56-year-old man with diabetes, hypertension, and chronic kidney disease presented to the emergency room with a complaint of pain in his right foot. He was found to have tremors. Gabapentin toxicity was suspected and the patient was found to have high gabapentin level (6.3 mcg/ml). Patient was commenced on continuous venovenous hemodiafiltration (CVVHD) and the pharmacokinetics of gabapentin was studied. The patient improved symptomatically and his tremors subsided. In this case report, we describe the successful management of gabapentin toxicity with continuous renal replacement therapy and calculate the clearance of gabapentin which will enable future treatment of gabapentin toxicity by CVVHD.

Improvement of hyperphagia by activation of cerebral I(1)-imidazoline receptors in streptozotocin-induced diabetic mice

Imidazoline I1-receptors (I1R) are known to regulate blood pressure and rilmenidine, an agonist, is widely used as antihypertensive agent in clinic. However, the role of I1R in feeding behavior is still unclear. In the present study, we used the agonist of I1R to investigate the effect on hyperphagia in streptozotocin (STZ)-induced diabetic mice. Rilmenidine decreased the food intake of STZ-diabetic mice in a dose-dependent manner. The reduction of food intake was abolished by pretreatment with efaroxan at the dose sufficient to block I1R. Intracerebroventricular (icv) administration of rilmenidine into STZ-diabetic mice also significantly reduced hyperphagia, which was reversed by icv administration of efaroxan. In addition, similar results were observed in STZ-diabetic mice, which received chronic treatment with rilmenidine 3 times daily (t.i.d.) for 7 days. Moreover, the hypothalamic neuropeptide Y (NPY) level was reduced by rilmenidine that was also reversed by pretreatment with efaroxan. In conclusion, the obtained results suggest that rilmenidine can decrease food intake in STZ-diabetic mice through an activation of I1R to lower hypothalamic NPY level.

Activation of imidazoline I-2B receptors by allantoin to increase glucose uptake into C₂C₁₂ cells

Allantoin, an active principle of the yam, belongs to the group of guanidinium derivatives and has been reported to lower plasma glucose in diabetic animals. Recent evidence indicates that activation of the imidazoline I(2B) receptor (I(2B)R) by guanidinium derivatives also increases glucose uptake; however, the effect of allantoin on I(2B)R is still unknown. Glucose uptake into cultured C₂C₁₂ cells was determined using 2-[¹⁴C]-deoxy-D-glucose as a tracer. The changes in 5'-AMP-activated protein kinase (AMPK) expression were also identified by Western blotting analysis. The allantoin-induced glucose uptake action was dose-dependently blocked by BU224, a specific I₂R antagonist, in C₂C₁₂ cells. Moreover, AMPK phosphorylation by allantoin was found to be dose-dependently increased in C₂C₁₂ cells using AICAR treatment as a reference. In addition, both actions of allantoin, the increases in glucose uptake and AMPK phosphorylation, were dose-dependently attenuated by amiloride in C₂C₁₂ cells. Moreover, compound C at concentrations sufficient to inhibit AMPK blocked the allantoin-induced glucose uptake and AMPK phosphorylation. Thus, we suggest that allantoin can activate I(2B)R to increase glucose uptake into cells, and propose I(2B)R as a new target for diabetic therapy.

Holographic otoscope for nanodisplacement measurements of surfaces under dynamic excitation

We describe a novel holographic otoscope system for measuring nanodisplacements of objects subjected to dynamic excitation. Such measurements are necessary to quantify the mechanical deformation of surfaces in mechanics, acoustics, electronics, biology, and many other fields. In particular, we are interested in measuring the sound-induced motion of biological samples, such as an eardrum. Our holographic otoscope system consists of laser illumination delivery (IS), optical head (OH), and image processing computer (IP) systems. The IS delivers the object beam (OB) and the reference beam (RB) to the OH. The backscattered light coming from the object illuminated by the OB interferes with the RB at the camera sensor plane to be digitally recorded as a hologram. The hologram is processed by the IP using the Fresnel numerical reconstruction algorithm, where the focal plane can be selected freely. Our holographic otoscope system is currently deployed in a clinic, and is packaged in a custom design. It is mounted in a mechatronic positioning system to increase its maneuverability degrees to be conveniently positioned in front of the object to be measured. We present representative results highlighting the versatility of our system to measure deformations of complex elastic surfaces in the wavelength scale including a copper foil membrane and postmortem tympanic membrane. SCANNING 33: 342-352, 2011. © 2011 Wiley Periodicals, Inc.

Holographic otoscope for nanodisplacement measurements of surfaces under dynamic excitation

We describe a novel holographic otoscope system for measuring nanodisplacements of objects subjected to dynamic excitation. Such measurements are necessary to quantify the mechanical deformation of surfaces in mechanics, acoustics, electronics, biology, and many other fields. In particular, we are interested in measuring the sound-induced motion of biological samples, such as an eardrum. Our holographic otoscope system consists of laser illumination delivery (IS), optical head (OH), and image processing computer (IP) systems. The IS delivers the object beam (OB) and the reference beam (RB) to the OH. The backscattered light coming from the object illuminated by the OB interferes with the RB at the camera sensor plane to be digitally recorded as a hologram. The hologram is processed by the IP using the Fresnel numerical reconstruction algorithm, where the focal plane can be selected freely. Our holographic otoscope system is currently deployed in a clinic, and is packaged in a custom design. It is mounted in a mechatronic positioning system to increase its maneuverability degrees to be conveniently positioned in front of the object to be measured. We present representative results highlighting the versatility of our system to measure deformations of complex elastic surfaces in the wavelength scale including a copper foil membrane and postmortem tympanic membrane. SCANNING 33: 342-352, 2011. © 2011 Wiley Periodicals, Inc.

Mediation of Endogenous β-Endorphin in the Plasma Glucose-Lowering Action of Herbal Products Observed in Type 1-Like Diabetic Rats

Recently, there have been advances in the development of new substances effective in managing diabetic disorders. Opioid receptors couple multiple systems to result in various biological effects, although opioids are best known for analgesia. In the present review, we used our recent data to describe the advance in plasma glucose-lowering action of herbal products, especially the mediation of β-endorphin in glucose homeostasis of insulin-deficient diabetes. In type 1-like streptozotocin-induced diabetic rats, we identified many products purified from herbs that show a dose-dependent plasma glucose-lowering action. Increase in β-endorphin secretion from the adrenal gland may activate peripheral opioid μ-receptors (MOR) to enhance the expression of muscle glucose transporters and/or to reduce hepatic gluconeogenesis at the gene level, thereby leading to improved glucose utilization in peripheral tissues for amelioration of severe hyperglycemia. It has also been observed that stimulation of α(1)-adrenoceptors (α(1)-ARs) in the adrenal gland by some herbal products is responsible for the increase in β-endorphin secretion via a phospholipase C-protein kinase dependent pathway. However, an increase in β-endorphin secretion from the adrenal gland by herbal products can function via another receptor. New insights into the mediation of endogenous β-endorphin activation of peripheral MOR by herbal products for regulation of glucose homeostasis without the presence of insulin have been established. Therefore, an increase in β-endorphin secretion and/or direct stimulation of peripheral MOR via an insulin-independent action might serve as the potential target for development of a therapeutic agent or promising adjuvant in intensive plasma glucose control.

The decreased expression of peroxisome proliferator-activated receptors delta (PPARdelta) is reversed by digoxin in the heart of diabetic rats

The present study is designed to investigate the role of peroxisome proliferator-activated receptors delta (PPARdelta) in the action of digoxin in diabetic rats showing cardiac hypertrophy. We used Wistar rats to induce diabetes by injection of streptozotocin (STZ-rat) and examined the effect of digoxin on PPARdelta expression in these hyperglycemic rats (STZ-rat) at 10 weeks later. We measured the changes of body weight, water intake, and food intake in three groups of age-matched rats; the vehicle treated normal control (Wistar rats), the vehicle treated STZ-rats, and the digoxin-treated STZ-rats. Cardiac output, heart rate, and blood pressure in addition to plasma insulin or glucose level were also determined. The mRNA and protein levels of PPARdelta were measured using Northern and Western blotting, respectively. Cardiac output, heart rate, and blood pressure were markedly reduced while food intake, water intake, and blood glucose were raised in STZ-rats showing lower body weight and plasma insulin as compared with the vehicle-treated controls. After a 20-day of digoxin treatment, cardiac output was raised in STZ-rats but the diabetic parameters were not modified. The PPARdelta expressions, both mRNA and protein, were markedly elevated in the hearts of STZ-rats by digoxin treatment. The related signals with PPARdelta, such as carnitine palmitoyltransferase 1B (CPT1B), acetyl-coenzyme A, carboxylase alpha (ACC1), fatty acid synthase (FAS), and troponin I, were also raised. The increase of cardiac output by digoxin was reversed by the combined treatment with PPARdelta antagonist GSK0660. Thus, we suggest a new finding that PPARdelta is involved in digoxin induced cardiac inrotropic action.

Increase of plasma insulin by racecadotril, an inhibitor of enkephalinase, in Wistar rats

Racecadotril is known as an inhibitor of enkephalinase. Increase of plasma insulin by racecadotril has been observed in rats while the mechanism of the action remains obscure. In the present study, intravenous injection of male Wistar rats with racecadotril significantly decreased blood glucose levels. However, this effect of racecadotril was not modified by naloxone at the dose sufficient to block opioid receptors. Thus, the blood glucose-lowering action of racecadotril might be through an endogenous opioid independent mechanism. Otherwise, we found that C-peptide content was also raised by racecadotril in parallel with the increase of insulin in Wistar rats. Thus, the blood glucose-lowering action of racecadotril was related to insulin secretion, but not through the inhibition of plasma insulin degradation. In addition, racecadotril showed no direct effect on insulin secretion in isolated islets or cultured HIT-T15 beta cells. The increase of plasma insulin and blood glucose-lowering action induced by racecadotril were reduced by pretreatment with atropine and enhanced by physotigmine. Direct inhibition of cholinesterase was not observed in brain homogenates treated with racecadotril. Moreover, actions of racecadotril were significantly reduced in rats receiving hemicholinium-3 at a sufficient dose to decrease endogenous acetylcholine. Activation of cholinergic tone is possibly involved in the blood glucose-lowering effect of racecadotril. Our results suggested that racecadotril increased insulin secretion to lower blood glucose mainly via regulation of parasympathetic tone in Wistar rats.

Motion of the tympanic membrane after cartilage tympanoplasty determined by stroboscopic holography

Stroboscopic holography was used to quantify dynamic deformations of the tympanic membrane (TM) of the entire surface of the TM before and after cartilage tympanoplasty of the posterior or posterior-superior part of the TM. Cartilage is widely used in tympanoplasties to provide mechanical stability for the TM. Three human cadaveric temporal bones were used. A 6 mm x 3 mm oval cartilage graft was placed through the widely opened facial recess onto the medial surface of the posterior or posterior-superior part of the TM. The graft was either in contact with the bony tympanic rim and manubrium or not. Graft thickness was either 0.5 or 1.0mm. Stroboscopic holography produced displacement amplitude and phase maps of the TM surface in response to stimulus sound. Sound stimuli were 0.5, 1, 4 and 7 (or 8)kHz tones. Middle-ear impedance was measured from the motion of the entire TM. Cartilage placement generally produced reductions in the motion of the TM apposed to the cartilage, especially at 4 kHz and 7 or 8 kHz. Some parts of the TM showed altered motion compared to the control in all three cases. In general, middle-ear impedance was either unchanged or increased somewhat after cartilage reconstruction both at low (0.5 and 1 kHz) and high (4 and 7 kHz) frequencies. At 4 kHz, with the 1.0mm thick graft that was in contact with the bony tympanic rim, the impedance slightly decreased. While our earlier work with time-averaged holography allowed us to observe differences in the pattern of TM motion caused by application of cartilage to the TM, stroboscopic holography is more sensitive to TM motions and allowed us to quantify the magnitude and phase of motion of each point on the TM surface. Nonetheless, our results are similar to those of our earlier work: The placement of cartilage on the medial surface of TM reduces the motion of the TM that apposes the cartilage. These obvious local changes occur even though the cartilage had little effect on the sound-induced motion of the stapes.

Decrease of bone morphogenetic protein-7 (BMP-7) and its type II receptor (BMP-RII) in kidney of type 1-like diabetic rats

Bone morphogenetic protein-7 (BMP-7) expression is known to be protective for renal damage during diabetic nephropathy and disappears early during the progression of diabetic nephropathy. However, changes in expression of BMP-7 and BMP-7 type II receptor (BMP-RII) during kidney nephropathy response to high glucose-induced oxidative stress remain unclear. In this study, we used streptozotocin-induced diabetic rats with diabetic nephropathy and treated them with insulin, phloridzin, or antioxidant tiron. The insulin, phloridzin, or tiron treatment improved the renal function and decreased fibronectin expression in the streptozotocin-induced diabetic rats. Both insulin and phloridzin could reverse the attenuation effects of hyperglycemia on BMP-7 and BMP-RII expressions in the kidneys of streptozotocin-induced diabetic rats through the correction of hyperglycemia. However, the decrease of BMP-7 and BMP-RII expressions in kidney of streptozotocin-induced diabetic rats could be reversed by tiron through decreasing the high glucose-induced oxidative stress but not through changing the levels of glucose. We further confirmed the effect on reversing the BMP-7 and BMP-RII expressions through decreasing oxidative stress by tiron treatment in high glucose exposed mesangial cells. Thus, we suggest that a decrease in oxidative stress is responsible for the improvement of renal function and recovery of renal BMP-7 and BMP-RII expression in streptozotocin-induced diabetic rats.

Mediation of beta-endorphin in exercise-induced improvement in insulin resistance in obese Zucker rats

BACKGROUND

Aerobic exercise including treadmill running has long been used to successfully treat and/or prevent insulin resistance and type-2 diabetes. Increase of plasma beta-endorphin is observed with exercise. The present study was designed to clarify the role of endogenous beta-endorphin in exercise-induced improvement in insulin resistance.

METHODS

We used a moderate exercise program consisting of treadmill running at 20 m/min and 0% grade for 1 h/day, 7 days/week, for 8 weeks. Plasma glucose concentration was assessed by the glucose oxidase method. The enzyme-linked immunosorbent assay was performed to quantify the plasma level of beta-endorphin-like immunoreactivity (BER). The glucose disposal rate (GDR) was measured by the hyperinsulinemic euglycemic clamp technique. Changes of the insulin signaling in isolated soleus muscle were then detected by immunoprecipitation and immunoblotting.

RESULTS

An increase of plasma BER in parallel with the reduction of plasma glucose was obtained in exercise-trained obese Zucker rats. Different from a marked reduction in sedentary obese rats, the value of insulin-stimulated GDR obtained from the exercised obese rats was reversed to near that of the sedentary lean group, eight weeks after the last period of exercise. This effect of exercise was inhibited by naloxone or naloxonazine at doses sufficient to block opioid micro-receptors. Signaling-related defects in the soleus muscle of sedentary obese Zucker rats, which impaired glucose transporter subtype 4 (GLUT 4), included decreased phosphorylation of insulin receptor substrate (IRS)-1, as well as an attenuated p85 regulatory subunit of phosphatidylinositol 3-kinase (PI3 kinase) and Akt serine phosphorylation. In contrast, exercise training failed to modify the levels of insulin receptor (IR), IRS-1, and IR tyrosine autophosphorylation in obese Zucker rats.

CONCLUSION

Enhanced insulin sensitivity via exercise training might be mediated by endogenous beta-endorphin through an increase of postreceptor insulin signaling related to the IRS-1-associated PI3-kinase step that leads to the enhancement of GLUT 4 translocation and improved glucose disposal in obese Zucker rats.

Increase of PTEN gene expression in insulin resistance

Phosphatase and tensin homologue deleted from chromosome ten (PTEN) has recently been characterized as a regulator of insulin sensitivity in the insulin target tissue. However, whether PTEN gene expression is changed in insulin resistance remains unclear. We observed that both the mRNA and protein level of PTEN in soleus muscle isolated from the obese Zucker rats (Fa/Fa) were increased compared to the age-matched lean group. Similarly, both the mRNA and protein level of PTEN in soleus muscle of the fructose-fed lean Zucker rats (Fa/Fa) showing the higher glucose-insulin index were higher than that of the regular chow fed group. These results suggest that increase of PTEN gene expression seems to be related to the development of insulin resistance.

Loperamide increases glucose ultilization in streptozotocin-induced diabetic rats

1. Loperamide has an ability to lower the plasma glucose concentration in streptozotocin (STZ)-induced diabetic rats. In the present study, we investigated the molecular mechanisms by which loperamide regulates plasma glucose concentrations in the absence of insulin. 2. Loperamide, at a dose sufficient (17.6 microg/kg) to activate mu-opioid receptors, significantly decreased plasma glucose levels in STZ-diabetic rats. The mRNA and protein levels of glucose transporter 4 (GLUT-4) in soleus muscle, detected by northern and western blotting, respectively, were increased after repeated intravenous administration of loperamide (17.6 micro g/kg) to STZ-diabetic rats over 3 days. Moreover, similar treatment with loperamide (17.6 microg/kg) for 3 days reversed the elevated mRNA and protein levels of phosphoenolpyruvate carboxykinase (PEPCK) in the liver of STZ-diabetic rats to near the levels seen in normal rats. 3. These results suggest that activation of mu-opioid receptors by loperamide can increase glucose utilization in peripheral tissues and/or reverse the higher gene expression of PEPCK to inhibit hepatic gluconeogenesis, thereby lower plasma glucose in diabetic rats lacking insulin.

Signals in the activation of opioid mu-receptors by loperamide to enhance glucose uptake into cultured C2C12 cells

In an attempt to understand the signal pathways of opioid mu-receptors for glucose metabolism, we used loperamide to investigate the glucose uptake into the myoblast C2C12 cells. Loperamide enhanced the uptake of radioactive deoxyglucose into C2C12 cells in a concentration-dependent manner that was abolished in cells pre-incubated with naloxone or naloxonazine at concentrations sufficient to block opioid mu-receptors. Pharmacological inhibition of phospholipase C (PLC) by U73122 resulted in a concentration-dependent decrease in loperamide-stimulated uptake of radioactive deoxyglucose into C2C12 cells. This inhibition of glucose uptake by U73122 was specific since the inactive congener, U73343, failed to modify loperamide-stimulated glucose uptake. Moreover, both chelerythrine and GF 109203X diminished the action of loperamide at concentrations sufficient to inhibit protein kinase C (PKC). The obtained data suggest that an activation of opioid mu-receptors in C2C12 cells by loperamide may increase glucose uptake via the PLC-PKC pathway.

Increase in adenosine A1 receptor gene expression in the liver of streptozotocin-induced diabetic rats

BACKGROUND

Adenosine A1 receptor (A1-AR) activation can lower plasma glucose in diabetic rats lacking insulin. We investigated the change in A1-AR gene expression in diabetic rats.

METHODS

The incorporation of [U-(14)C]-glucose into glycogen was carried out to evaluate the effect of N(6)-cyclopentyladenosine (CPA) on glucose utilization in vitro. The plasma glucose concentration was assessed by the glucose oxidase method. The mRNA and protein levels of A1-AR in isolated liver were detected by Western blotting analysis and Northern blotting analysis, respectively.

RESULTS

The effect of CPA, an agonist of A1-AR, on glycogen incorporation in hepatocytes isolated from streptozotocin-induced diabetic rats (STZ-diabetic rats) was more marked than that from the normal rats. However, similar glycogen synthesis was not modified by 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, in the isolated hepatocytes from both the normal and the STZ-diabetic rats. A change in response at the receptor level can thus be considered. The mean level of liver mRNA transcripts encoding A1-AR was increased in STZ-diabetic rats to about 250% of that in normal rats. Exogenous insulin at a dose sufficient to normalize the plasma glucose of STZ-diabetic rats reversed the mRNA level of A1-AR in the liver after a four-day treatment. Similar results were also observed in STZ-diabetic rats that received treatment with phlorizin for four days. Moreover, the protein level of A1-AR was higher in the liver of STZ-diabetic rats than that in the normal rats. Similar treatment with exogenous insulin or phlorizin reversed the elevated protein level of A1-AR in the liver of STZ-diabetic rats to near the normal level. Therefore, correction of hyperglycemia in STZ-diabetic rats can reverse the higher gene expression of A1-AR in liver.

CONCLUSIONS

The obtained results suggest that an increase in plasma glucose is responsible for the higher gene expression of A1-AR in the liver of STZ-diabetic rats.

Release of beta-endorphin by caffeic acid to lower plasma glucose in streptozotocin-induced diabetic rats

The role of alpha 1A -adrenoceptors in the regulation of opioid secretion from the adrenal glands of streptozotocin-induced diabetic rats (STZ-diabetic rats) was examined in an attempt to determine the mechanism of plasma glucose-lowering action of caffeic acid. In agreement with a previous report, we showed that caffeic acid produced a dose-dependent lowering of the plasma glucose concentration in STZ-diabetic rats along with an increase of plasma beta-endorphin-like immunoreactivity (BER). These actions of caffeic acid were abolished by pretreatment with WB 4101 or RS 17 056 at doses sufficient to block alpha 1A -adrenoceptors. In addition, naloxone and naloxonazine at doses effective for blocking opioid micro -receptors abolished the plasma glucose-lowering action of caffeic acid. Also, unlike that in wild-type diabetic mice, caffeic acid failed to produce a plasma glucose lowering effect in opioid micro -receptor knockout diabetic mice. We observed that caffeic acid could enhance BER release from isolated rat adrenal medulla in a concentration-dependent manner; inhibitors of alpha 1A -adrenoceptors such as WB 4101 and RS 1705 abolished this action. Investigations of the signal pathways further supported that activation of alpha 1A -adrenoceptor is responsible for the stimulatory effect of caffeic acid on BER secretion from the adrenal medulla. In the presence of U73312, a specific inhibitor of phospholipase C, the caffeic acid-induced increase of BER was reduced in a concentration-dependent manner, but it was not affected by U73343, the negative control of U73312. Chelerythrine and GF 109203X also diminished the action of caffeic acid at concentrations sufficient for inhibiting protein kinase C. Moreover, bilateral adrenalectomy in STZ-diabetic rats resulted in the loss of this plasma glucose-lowering effect of caffeic acid, and there was no increase in plasma BER with caffeic acid. Therefore, beta-endorphin release from the adrenal gland appears to be responsible for the lowering of plasma glucose in STZ-diabetic rats induced by caffeic acid, through the activation of alpha 1A -adrenoceptors.

Effect of thiopental, propofol, and etomidate on vincristine toxicity in PC12 cells

Neurotoxicity is the dose-limiting side-effect of vincristine in cancer therapy. Using the nerve growth factor (NGF)-dependent neurite outgrowth and cell proliferation of the PC12 pheochromocytoma cell line as an in vitro assay, the protective effect of different intravenous anesthetics was assessed. Vincristine (1 nmol/L) significantly decreased the percentage of neurite-forming cells from 68% +/- 9% to 27% +/- 7% within a 3-day incubation period. The longer neurites (> 2 x cell body) in particular proved to be extremely sensitive to vincristine (from 17% +/- 4% to 0% of total neurite-expressing cells). Flow cytometry results revealed an S-phase percentage of 15.85% +/- 3.25% after NGF induction, with vincristine reducing this percentage to 0.68% +/- 0.38%. Reversal of the inhibitory effect of vincristine was noted in the cells treated with thiopental or propofol but not etomidate. Bicuculline partially antagonized the protective effect of thiopental and propofol in both studies. We conclude that thiopental and propofol, but not etomidate, have a protective effect in vincristine-induced neurotoxicity. The protective effect produced by thiopental and propofol is probably secondary to activation of GABAA receptors.

Plasma glucose-lowering effect of beta-endorphin in streptozotocin-induced diabetic rats

The effect of beta-endorphin on plasma glucose levels was investigated in streptozotocin-induced diabetic rats (STZ-diabetic rats). A dose-dependent lowering of plasma glucose was observed in the fasting STZ-diabetic rat fifteen minutes after intravenous injection of beta-endorphin. The plasma glucose-lowering effect of beta-endorphin was abolished by pretreatment with naloxone or naloxonazine at doses sufficient to block opioid mu-receptors. Also, unlike wild-type diabetic mice, beta-endorphin failed to induce its plasma glucose-lowering effect in the opioid mu-receptor knock-out diabetic mice. In isolated soleus muscle, beta-endorphin enhanced the uptake of radioactive glucose in a concentration-dependent manner. Stimulatory effects of beta-endorphin on glycogen synthesis were also seen in hepatocytes isolated from STZ-diabetic rats. The blockade of these actions by naloxone and naloxonazine indicated the mediation of opioid mu-receptors. In the presence of U73312, the specific inhibitor of phospholipase C (PLC), the uptake of radioactive glucose into isolated soleus muscle induced by beta-endorphin was reduced in a concentration-dependent manner, but it was not affected by U73343, the negative control of U73312. Moreover, chelerythrine and GF 109203X diminished the stimulatory action of beta-endorphin on the uptake of radioactive glucose at a concentration sufficient to inhibit protein kinase C (PKC). The data obtained suggest that activating opioid mu-receptors by beta-endorphin may increase glucose utilization in peripheral tissues via the PLC-PKC pathway to lower plasma glucose in diabetic rats lacking insulin.

Intrathecal clonidine decreases spinal nitric oxide release in a rat model of complete Freund's adjuvant induced inflammatory pain

A long-lasting antihyperalgesic effect has been demonstrated for intrathecal (IT) clonidine, an alpha2-adrenergic agonist. In the present study, the mechanism and antihyperalgesic effects of IT clonidine were examined post-treatment in a rat model of Complete Freund's Adjuvant (CFA)-induced inflammatory hyperalgesia. Using a chronic model of spinal cord dialysis, we examined the effect of the adjuvant-induced inflammation on spinal release of nitric oxide (NO) and the development of chronic pain and assessed the antinociceptive effects and mechanisms of the alpha2-adrenergic agonist, clonidine (IT). Chronic, persistent inflammatory pain was induced by left hind paw injection of 0.3 ml CFA prepared in a mixture with Mycobacterium butyricum. Rats were randomly assigned to groups receiving IT clonidine in discrete doses of 1, 10 or 50 microg, 3 or 24 hr post-inflammation. Measurement of total NOx (NO + NO2- + NO3-) was used to determine NO release into the cerebrospinal fluid. Rat thermal antinociception was assessed using a radiant heat thermal hyperalgesia model. CFA injection resulted in significant thermal hyperalgesia throughout the four days of observation. A dose-dependent suppression of thermal hyperalgesia and spinal NO release was observed after IT clonidine treatment. Evidence from this CFA-induced inflammatory pain model suggests that clonidine's spinal antihyperalgesic mechanisms act through inhibition of spinal NO release.

Decrease in catechol-O-methyltransferase activity in the liver of streptozotocin-induced diabetic rats

1. The present study compared the activity of catechol- O-methyltransferase (COMT) in the liver and plasma of streptozotocin (STZ)-induced diabetic rats with that in normal rats. The activity of COMT was estimated by the metabolism of noradrenaline to metanephrine (MN), both measured by high-performance liquid chromatography with electrochemical detection. 2. Formation of MN was decreased in the liver of STZ- diabetic rats compared with normal rats. The amount of MN was also decreased in plasma obtained from STZ-diabetic rats. A Michaelis-Menten plot showed a reduction in the maximum velocity and an increase in the Km for COMT in liver samples from STZ-diabetic rats. 3. The role of hyperglycaemia in the lowering of COMT activity was then investigated using phlorizin or insulin at doses sufficient to normalize plasma glucose from STZ-diabetic rats. Both insulin and phlorizin treatment of STZ-diabetic rats for 4 days restored the activity of COMT to that seen in normal rats. Thus, correction of hyperglycaemia in STZ-diabetic rats can reverse the decrease in COMT activity. The activity of COMT is lower in STZ-diabetic rats than in normal rats mainly due to the higher plasma glucose.

Stimulatory effect of paeoniflorin on the release of noradrenaline from ileal synaptosomes of guinea-pig in-vitro

The effect of paeoniflorin (an active principle of Paeoniae Radix, commonly used in traditional Chinese medicine) on the release of noradrenaline (norepineprhine) from nerve terminals was investigated using guinea-pig isolated ileal synaptosomes. Release was determined as the amount of noradrenaline, quantified by high-performance liquid chromatography-electrochemical detection, from samples incubated with paeoniflorin or vehicle. Paeoniflorin stimulated the release of noradrenaline in a concentration-dependent manner without an effect on the level of lactate dehydrogenase in the bathing medium. Tetrodotoxin abolished the action of paeoniflorin at concentrations sufficient to block sodium channels. The depolarizing effect of paeoniflorin on the membrane potential was also illustrated by a concentration-dependent increase in the fluorescence of bisoxonol. Moreover, the effect of paeoniflorin on bisoxonol fluorescence in ileal synaptosomes seems more potent than that of 4-aminopyridine. That paeoniflorin causes influx of calcium ions via the depolarization of nerve terminals could be considered. The noradrenaline-releasing action of paeoniflorin was abolished by removal of calcium chloride from the bathing medium. This action of paeoniflorin was also attenuated by Rp-cAMP atconcentrations sufficientto inhibitthe action of cyclicAMP. Therefore, paeoniflorin could induce a calcium-dependent and cyclic-AMP-related release of noradrenaline from sympathetic nerve terminals of guinea-pig ileum. Guanethidine inhibited the noradrenaline-releasing action of paeoniflorin in a concentration-dependent manner. The effect of paeoniflorin on the increase of bisoxonol fluorescence was not modified by atropine. Release of noradrenaline by paeoniflorin from noradrenergic nerve terminals was characterized. These findings suggest that paeoniflorin can stimulate tetrodotoxin-sensitive depolarization of membranes to result in a calcium-dependent and cyclic-AMP-related release of noradrenaline from noradrenergic nerve terminals.

Fluid flow through nanometer-scale channels

We describe studies of the pressure driven flow of several classical fluids through lithographically produced channels in which one dimension, the channel height h, is in the micron or nanometer size range. The measured flow rates are compared with theoretical predictions assuming no-slip boundary conditions at the walls of the channel. The results for water agree well with this prediction for h as small as 40 nm (our smallest channels). However, for hexane, decane, hexadecane, and silicone oil we find deviations from this theory when h is reduced below about 100 nm. The observed flow rates for small h are larger than theoretical expectations, implying significant slip at the walls, and values of the slip length are estimated. The results are compared with previous experimental and theoretical work.

Role of hypothalamic neuropeptide Y (NPY) in the change of feeding behavior induced by repeated treatment of amphetamine

Neuropeptide Y (NPY), an orexigenic peptide, is involved in the control of food intake. Repeated administration of amphetamine (AMPH), an anorectic agent, results in an anorectic effect on day 1 and a tolerant anorectic effect on the followings. In an attempt to know the role of hypothalamic NPY in these effects of AMPH, contents of hypothalamic NPY were determined by radioimmunoassay at first. In AMPH-treated groups, the contents of hypothalamic NPY decreased rapidly on day 1 but restored gradually to the normal level on the following days as observed in repeated AMPH. An involvement of hypothalamic NPY in the feeding change of repeated AMPH can thus be considered. Moreover, daily injection of NPY antisense oligonucleotide into brain (10 microg/10 microl/day, i.c.v.) to inhibit the gene expression of hypothalamic NPY were performed at 1 hour before daily 2 mg/kg AMPH. The reversion of food intake from the anorectic level to the normal level (tolerant anorexia) was abolished by this antisense pretreatment. It is suggested that hypothalamic NPY may play a role in the change of feeding behavior induced by repeated AMPH administration.

Metformin-like effects of Quei Fu Di Huang Wan, a Chinese herbal mixture, on streptozotocin-induced diabetic rat

Effect on plasma glucose concentration of Quei Fu Di Huang Wan (Quei Fu DHW), the herbal mixture widely used to treat diabetic disorder in Chinese traditional medicine, was investigated in diabetic rats deficient in insulin. Changes of plasma glucose in streptozotocin-induced diabetic rats (STZ-diabetic rats) receiving repeated oral administration of Quei Fu DHW were determined. Also, the mRNA level (by Northern blotting) and protein level (by Western blotting) of phosphoenolpyruvate carboxykinase (PEPCK) in liver from STZ-diabetic rats were measured to compare differences between groups receiving repeated oral administration of Quei Fu DHW, metformin, and two active herbs (Zou Guei or Fuzei) at effective dosages. In STZ-diabetic rats, acute oral administration of Quei Fu DHW decreased the plasma glucose level significantly in a dose-dependent manner from 5 mg/kg to 26.0 mg/kg. Similar treatment with Quei Fu DHW also brought on a plasma glucose-lowering effect in normal rats, although the effectiveness was not as significant as in STZ-diabetic rats. Repeated oral treatment of Quei Fu DHW at 26 mg/kg every 8 h, three times daily for 3 days, produced a plasma glucose-lowering activity similar to that of metformin-treatment in STZ-diabetic rats. Oral administration of Zou Guei (Cinnamomi Cortex) or Fuzei (Aconiti Tuber), the individual constituent of Quei Fu DHW, at the dose of 50 mg/kg into STZ-diabetic rats for 3 days normalized hyperglycemia. Similar to the repeated treatment with Quei Fu DHW, Fuzei at the effective dose reversed the elevated mRNA and protein levels of PEPCK in liver from STZ-diabetic rats. This is consistent with findings that metformin restored the increased gene expression of PEPCK in liver from STZ-diabetic rats. However, the gene expression of PEPCK in STZ-diabetic rats was not influenced by similar treatment with Zou Guei. The present study found that oral administration of Quei Fu DHW could decrease hepatic gluconeogenesis in a way similar to metformin in lowering plasma glucose in diabetic rats lacking insulin. Thus, this preparation may be a helpful adjuvant for the treatment of diabetic disorders in clinical practice.

Plasma glucose-lowering effect of tramadol in streptozotocin-induced diabetic rats

The effect of tramadol on the plasma glucose level of streptozotocin (STZ)-induced diabetic rats was investigated. A dose-dependent lowering of plasma glucose was seen in the fasting STZ-induced diabetic rats 30 min after intravenous injection of tramadol. This effect of tramadol was abolished by pretreatment with naloxone or naloxonazine at doses sufficient to block opioid mu-receptors. However, response to tramadol was not changed in STZ-induced diabetic rats receiving p-chlorophenylalanine at a dose sufficient to deplete endogenous 5-hydroxytrptamine (5-HT). Therefore, mediation of 5-HT in this action of tramadol is ruled out. In isolated soleus muscle, tramadol enhanced the uptake of radioactive glucose in a concentration-dependent manner. The stimulatory effects of tramadol on glycogen synthesis were also seen in hepatocytes isolated from STZ-induced diabetic rats. The blockade of these actions by naloxone and naloxonazine indicated the mediation of opioid mu-receptors. The mRNA and protein levels of the subtype 4 form of glucose transporter in soleus muscle were increased after repeated treatments for 4 days with tramadol in STZ-induced diabetic rats. Moreover, similar repeated treatments with tramadol reversed the elevated mRNA and protein levels of phosphoenolpyruvate carboxykinase in the liver of STZ-induced diabetic rats. These results suggest that activation of opioid mu-receptors by tramadol can increase the utilization of glucose and/or decrease hepatic gluconeogenesis to lower plasma glucose in diabetic rats lacking insulin.

Inhibitory effect of stevioside on calcium influx to produce antihypertension

Stevioside is a sweet-tasting glycoside occurring abundantly in the leaves of Stevia rebaudiana (Compositae). It has been used popularly in Japan and Brazil as a sugar substitute for decades. Previous study has shown that it lowered blood pressure in spontaneously hypertensive rats (SHRs) when administered intravenously. This study shows that intraperitoneal injection of stevioside 25 mg/kg also has antihypertensive effect in SHRs. In isolated aortic rings from normal rats, stevioside could dose-dependently relax the vasopressin-induced vasoconstriction in both the presence and absence of endothelium. However, stevioside had no effect on phenylephrine- and KCl-induced phasic vasoconstriction. In addition, stevioside lost its influence on vasopressin-induced vasoconstriction in Ca(2+)-free medium. The results indicate that stevioside caused vasorelaxation via an inhibition of Ca(2+) influx into the blood vessel. This phenomenon was further confirmed in cultured aortic smooth muscle cells (A7r5). Using 10(-5) M methylene blue for 15 min, stevioside could still relax 10(-8) M vasopressin-induced vasoconstriction in isolated rat aortic rings, showing that this vasorelaxation effect was not related to nitric oxide. The present data show that the vasorelexation effect of stevioside was mediated mainly through Ca(2+) influx inhibition.

Genetic variation of the nucleocapsid genes of waterfowl parvovirus

Duck parvovirus (DPV) and Goose parvovirus (GPV) isolated from infected waterfowls with Derzsy's disease in the year 1999 were identified by polymerase chain reaction and sequencing. The nucleotide sequences of their viral capsid proteins (VPs) show that they share 77% similarity at the DNA, and 84.6% at the protein level. The most variable region between DPV and GPV resides in the N-terminal of VP2 before the initiation codon of VP3 with 35% (19/54) amino acids divergence. Viral capsid protein sequences diverge 4.1 to 4.4% among 1990-99 isolated strains. Variant amino acids cluster in the common regions of VP3 at residues 203-266 and 482-534 which overlaps with the regions proposed to expose on the outer surfaces of parvoviral particles, implying that selective pressure from host immune system might play a part. These data provide useful information for antigenic epitope prediction. This study also reveal the presence of conserved strain-specific residues in VPs and these residues seldom vary among different viral isolates, suggesting that they might be functionally important and worth further investigation.

Stimulatory effect of phenylephrine on the secretion of beta-endorphin from rat adrenal medulla in vitro

In an attempt to investigate the role of alpha1-adrenoceptors in the regulation of opioid secretion from adrenal gland, phenylephrine was employed to investigate the effect on secretion of beta-endorphin-like immunoreactivity (BER) from adrenal medulla of rat in vitro. Phenylephrine enhanced the BER from isolated adrenal medulla in a concentration-dependent manner and this action was abolished by the antagonists of alpha1-adrenoceptors, prazosin and tamsulosin. Investigations of signal pathway further support that an activation of alpha1-adrenoceptors is responsible for the stimulatory effect of phenylephrine on BER secretion from adrenal medulla. In the presence of U73312, the specific inhibitor of phospholipase C (PLC), phenylephrine-induced change of BER was reduced in a concentration-dependent manner but it was not affected by U73343, the negative control of U73312. Moreover, chelerythrine and GF 109203X diminished the action of phenylephrine at concentration sufficient to inhibit protein kinase C (PKC). In conclusion, our results suggest that an activation of alpha1-adrenoceptors in adrenal medulla by phenylephrine may enhance the secretion of opioids from adrenal gland of rat via signals of PLC-PKC pathway.

Free radical-triggered hepatic injury of experimental obstructive jaundice of rats involves overproduction of proinflammatory cytokines and enhanced activation of nuclear factor kappaB

Excessive production of hydroxyl radicals in blood and liver has previously been demonstrated by us in rats with obstructive jaundice induced by common bile duct ligation (CBDL). In this study, we demonstrate overproduction of superoxide radicals in circulating blood of CBDL rats by the lucigenin-amplified chemiluminescence technique. To pinpoint the molecular agents that mediate these processes, we measured circulating proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta ( IL-1beta), and interleukin-6 (IL-6) in controls and CBDL rats. Concentrations of these cytokines in blood of CBDL rats were markedly elevated when compared to the controls (TNF-alpha: 36.7 +/- 5.0 vs 13.8 +/- 0.5 pg/mL; IL-6: 2,814 +/- 1,740 vs 0 pg/mL; IL-1beta: 11.9 +/- 2.6 vs 0 pg/mL). The overproduction of free radicals triggered by elevated cytokines in CBDL rats was correlated with the activation of NF-kappaB in hepatic tissue. Using the TdT-mediated dUTP nick-end label staining technique, we showed that hepatic tissue sections from CBDL rats had an increase in the apoptotic index (AI). Based on these findings, we propose that the severe hepatic injury in CBDL rats is mediated by a cycle that involves the activation of NF-kappaB by combined action of proinflammatory cytokines and reactive oxygen species (ROS). NF-KB, in turn, initiates the transcription of cytokine genes (eg, IL-6, IL-8, TNF-alpha), which triggers hepatic injury, at least in part, by a free radical-mediated apoptotic mechanism. Elevated ROS may be as a positive-feedback signal that triggers NF-KB reactivation; the severe hepatic injury of CBDL rats may result from perpetuation of this vicious cycle.

Protein kinase C and changes in manganese superoxide dismutase gene expression in cultured glial cells

1. To study the role of protein kinase C (PKC) in the increase in manganese superoxide dismutase (Mn-SOD) gene expression following transient hypoxia in glial cells, we examined the mRNA levels of Mn-SOD using northern blot analysis. 2. The Mn-SOD mRNA levels were markedly increased after exposure to nitrogen gas for 5 min. 3. Pretreatment with chelerythrine or GF109203x, inhibitors of PKC, attenuated the increase in Mn-SOD mRNA following hypoxia in a concentration-dependent manner. 4. Incubation with phorbol 12-myristate 13-acetate, the PKC activator, enhanced the increase in Mn-SOD gene expression in response to transient hypoxia. 5. The results suggest that hypoxia increases Mn-SOD gene expression in cultured glial cells mainly through activation of a PKC pathway.

Folate deficiency-induced oxidative stress and apoptosis are mediated via homocysteine-dependent overproduction of hydrogen peroxide and enhanced activation of NF-kappaB in human Hep G2 cells

Folate coenzymes are critical for de novo synthesis of purine and thymidine, and for interconversion of amino acids. Folate deficiency inhibits cellular proliferation, disturbs cell cycling, causes genetic damage and eventually results in cell death. Previously, we demonstrated that the demise of human hepatoma Hep G2 cells mediated by folate deficiency proceeded via a p53-independent apoptosis, and the perturbation of intracellular calcium homeostasis was also shown to be involved. To further delineate the mechanism associated with this observed phenomenon, Hep G2 cells were cultivated in the control or folate-deficient media (control media lacking folate, glycine, thymidine and hypoxanthine) for 4 weeks. At the end of this cultivation period, we found that TBARS (an index of lipid peroxidation) concentrations in the folate-deficient cells were drastically increased as compared to the control cells (0.04 vs 0.01 nmole/10(6) cells), indicating that a severe oxidative stress of the former cells had occurred. This phenomenon was also shown to coincide with the ability of these folate-deficient cells to elaborate increased amounts of H2O2 as compared to its folate-supplemented cells (2.87 vs 0.98 nmole/10(5) cells/h). Furthermore, the accelerated production of H2O2 by the folate-deficient cells was also closely correlated with the elevated homocysteine concentrations released in the culture medium (15.37 +/- 2.4 vs 3.58 +/- 2.4 micromole/L; P< 0.001). Finally, we demonstrated that folate deficiency was indeed capable of activating a redox-sensitive transcription factor, NF-kappaB, which is crucial in the control of a reactive oxygen species-mediated apoptosis. In summary, we show that folate deficiency-induced apoptosis is proceeded via the enhanced activation of NF-kappaB, which is the resulting form of the homocysteine-mediated overproduction of hydrogen peroxide.