Altered cerebellum development and dopamine distribution in a rat genetic model with congenital hypothyroidism.

Thyroid hormones play crucial roles in the development and functional maintenance of the central nervous system. Despite extensive studies of the neural function of thyroid hormones, little is known about the effects of hypothyroidism on behavioural traits and the mechanisms underlying such effects. In the present study, we report an investigation of congenitally hypothyroid mutant rdw rats, revealing a novel function of thyroid hormones in the central nervous system. The rdw rats were subjected to behavioural analyses such as the rotarod test, open field test and circadian activity measurement. To determine the cause of behavioural disorders, cerebellar morphogenesis was examined by immunohistochemical analysis, and the axonal transport of dopamine in the nigrostriatal pathway was analysed by high-performance liquid chromatography and western blotting. The effects of thyroxine administration to the rdw rats were examined by behavioural analysis. The rdw rats showed severe impairment of motor coordination and balance. This could be explained by the fact that the rats showed severe retardation of cerebellar morphogenesis, which correlates with the small somata and poor dendritic arborisation of Purkinje cells and retarded migration of granule cells particularly during the first two postnatal weeks. Moreover, the rdw rats showed hypoactivity, characterised by decreased circadian locomotor activity. After weaning, thyroxine administration improved the dwarfism in rdw rats but had no effect on cerebellar function. In addition, the rdw rats showed anxiety and depression intrinsically to novel surroundings. Interestingly, the rdw rats showed high levels of dopamine in the substantia nigra and low levels in the striatum, an important centre for the coordination of behaviour. Furthermore, low levels of tubulin in the striatum were detected, indicating the aberrant axonal transport of dopamine in the nigrostriatal pathway as a result of the reduced delivery of microtubules. These findings indicate an important function of thyroid hormones in cerebellar formation and in the regulation of axonal transport of dopamine. Moreover, rdw rats will be useful for studies of brain function and behavioural disorders in congenital hypothyroidism.

A surgical navigation system for aortic vascular surgery: a practical approach.

In aortic vascular surgery, a navigation system must represent the anatomical map of individual patient in order to detect the important artery. To provide a proper fit for positions along the dorsoventral axis, the spinous process was added to a currently used anatomical point set consisting of four anterior body landmarks. In addition, we attempted to reduce the registration error by compensating for alignment errors resulting from variations in tissue thickness at each landmark. The alignment values were examined using a human phantom consisting of a skeleton model with subcutaneous tissue in the semilateral position. Using this method, a phantom simulation and five clinical trials were performed. Target errors were evaluated at the orifice of the intercostal artery. In the phantom simulation, the error at the target point was 4.1 ± 2.7 mm. However, for one patient undergoing thoracoabdominal aortic aneurysm replacement surgery, the target error was 8.0 mm using the proposed method.

Analysis of the contraction of fibroblast-collagen gels and the traction force of individual cells by a novel elementary structural model.

Based on the experimental data of the contraction ratio of fibroblast-collagen gels with different initial collagen concentrations and cell numbers, we analyzed the traction force exerted by individual cells through a novel elementary structural model. We postulate that the mechanical mechanism of the gel contraction is mainly because that populated cells apply traction force to some of the surrounding collagen fibrils with such proper length potential to be pulled straight so as to be able to sustain the traction force; this traction induce the cells moving closely to each other and consequently compact the fibrillar network; the bending force of the fibrils in turn resists the movement. By employing fiber packing theory for random fibrillar networks and network alteration theory, the bending force of collagen fibrils was deduced. The traction force exerted by individual fibroblasts in the gels was balanced by the bending force and the resistance from interstitial fluid since inertial force can be neglected. The maximum traction force per cell under free floating condition is in the range of 0.27-9.02 nN depending on the initial collagen concentration and populated cell number. The most important outcome of this study is that the traction force of individual cells dynamically varies under different gel conditions, whereas the adhesion force between cell and individual fibrils is relatively converging and stable.

Risk analysis of unruptured aneurysms using computational fluid dynamics technology: preliminary results.

BACKGROUND AND PURPOSE: The decision as to the treatment of incidental IAs is complex. There are no certain quantitative methods that can be used to evaluate the risk of rupture in IAs. In recent years, CFD technology has been recognized as a potential risk-analysis tool. The aim of this article was to propose a hemodynamic parameter, EL, to determine the effects of stable unruptured aneurysms and of those that ruptured during the subsequent observation period. MATERIALS AND METHODS: Four incidentally found ICA-PcomA aneurysms ruptured during the period of observation (ruptured-IAs). Another 26 unruptured aneurysms (stable-IAs) with similar location, size, and morphology were compared for the differences in hemodynamic factors, such as EL and WSS. RESULTS: The EL calculated at the ruptured-IAs was nearly 5 times higher on average than that at the stable-IAs (ruptured, 0.00374 ± 0.0011; stable, 0.000745 ± 0.0001 mW/mm(3), P < .001). However, there was no difference between the ruptured and stable groups according to the results of time-averaged WSS (P = .8) for ruptured- and stable-IAs. According to flow visualization, though the mean average inflow speed of ruptured-IAs was 2 times higher than that of the stable-IAs, the flow inside ruptured-IAs appeared to undergo longer resident tracks, with stronger impact on the aneurysm wall. On the contrary, the flow inside stable-IAs passed smoothly through the aneurysms. CONCLUSIONS: These preliminary results indicated that EL may be a useful parameter for the quantitative estimation of the risks of rupture for IAs.

Two cases of nephrotic syndrome (NS)-induced acute kidney injury (AKI) associated with renal hypouricemia.

Renal hypouricemia is a clinical disorder attributed to an increased renal urate excretion rate and is well known to involve a high risk of urolithiasis and exercise-induced acute kidney injury (AKI). This report concerns two interesting cases of nephrotic syndrome (NS)-induced AKI associated with renal hypouricemia. A 64-year-old female (Case 1) and a 37-year-old male (Case 2) were hospitalized because of AKI (serum creatinine: 2.07 mg/dl and 3.3 mg/dl, respectively), oliguria and NS. They were treated with prednisolone and temporary hemodialysis. Renal function improved, but hypouricemia persisted during hospitalization. Histological findings in both cases led to a diagnosis of minimal change nephrotic syndrome and identification of the diuretic phase of tubulointerstitial damage because of findings such as acute tubular necrosis. Furthermore, distal tubules of Case 2 showed an amorphous mass, possibly a uric acid crystal. Analysis of the two cases with the URAT1 gene, encoded by SLC22A12, found a homozygous mutation in exon 4 (W258stop) of each one. Our cases show that patients with renal hypouricemia may be susceptible to AKI without involvement of exercise if they possess some facilitators. Renal hypouricemic patients should therefore be carefully examined for all complications from renal hypouricemia because of high risk of AKI.

Computational hemodynamic analysis in congenital heart disease: simulation of the Norwood procedure.

Hypoplastic left heart syndrome (HLHS) is a congenital heart disease which should be treated at neonate. Even now, its operation is one of the greatest challenges. However, currently there are no quantitative standards to evaluate and predict the outcome of the therapy. In this study, computational fluid dynamics (CFD) was used to estimate the performance of first stage HLHS surgery, the Norwood operation. An image data transfer system was developed to convert clinical images into three-dimensional geometry. To confirm software applicability, a validation process was carried out to eliminate any influence of numerical procedures. The velocities derived from echocardiography measurements were used as boundary conditions, and pressure waves measured by a cardiac catheter simultaneous with an electrocardiogram (ECG) were employed to validate the results of CFD simulation. Calculated results were congruent with the in vivo measurement results. The blood flow circulations were successfully simulated and the distribution of blood flow in each vessel was estimated. Time-varying energy losses (EL), local pressure and wall shear stress (WSS) were analyzed to estimate clinical treatment. The results indicated that pulsatile simulation is essential in quantitative evaluation. Computational hemodynamics may be applied in the surgical optimization for the treatment of HLHS.

Assessment of synchronization measures for effective ventricular support by using the shape memory alloy fibred artificial myocardium in goats.

Thromboembolic and haemorrhagic complications are the primary causes of mortality and morbidity in patients with artificial hearts, which are known to be induced by the interactions between blood flow and artificial material surfaces. The authors have been developing a new mechanical artificial myocardial assist device by using a sophisticated shape memory alloy fibre in order to achieve the mechanical cardiac support from outside of the heart without a direct blood contacting surface. The original material employed as the actuator of artificial myocardial assist devices was 100um fibred-shaped, which was composed of covalent and metallic bonding structure and designed to generate 4-7 % shortening by Joule heating induced by the electric current input. In this study, we focused on the synchronization of the actuator with native cardiac function, and the phase delay parameter was examined in animal experiments using Saanen goats. Total weight of the device including the actuator was around 150g, and the electric power was supplied transcutaneously. The device could be successfully installed into thoracic cavity, which was able to be girdling the left ventricle. The contraction of the device could be controlled by the originally designed microcomputer. The mechanical contraction signal input had been transmitted with the phase delay of 50-200 msec after the R-wave of ECG, and hemodynamic changes were investigated. Cardiac output and systolic left ventricular pressure were elevated with 20% delay of cardiac cycle by 27% and 7%, respectively, although there was smaller difference under the condition of the delay of over 30%. Therefore, it was suggested that the synchronization measures should be examined in order to achieve sophisticated ventricular passive/active support on physiological demand.

Calibration system for pulse spectrophotometry using a double-layer pulsation flow-cell.

We have studied noninvasive devices for measuring total hemoglobin and hemoglobin derivatives such as carboxyhemoglobin (COHb) and methemoglobin (MetHb). A calibration procedure needs to be developed to evaluate or calibrate these devices and pulse oximeters for clinical practice. However, people and animals are sometimes exposed to risk when they are used for calibration. In this paper, we propose a new in vitro calibration system for a pulse photometer. This system has a novel double-layer pulsation flow-cell that incorporates both venous and arterial blood flow. Using the calibration system, we are able to measure the in vitro pulsatile optical density ratio (Phivt). The measured Phivt agrees well with the in vivo pulsatile optical density ratio (Phivi). This system simulates an in vivo environment with high accuracy and enables safe calibration. Consequently, the calibration system is able to standardize the performance and accuracy of pulse photometry.

Development of a compact mock circulation system and a new flow-cell model for pulse spectrophotometry.

We have developed an extremely compact mock circulation system. This system can simulate artery blood circulation and generate a pulse wave with a very small amount of blood. We were also able to measure the in vitro pulsatile optical density ratio (Phivt) using this system with a flow cell [1]. Results showed a difference between Phivt and the in vivo pulsatile optical density ratio (Phivi) for the same oxygen saturations. To explain this difference, we proposed a new flow-cell model that includes venous flow and arterial flow. Because these systems can simulate the in vivo environment with very accurately, they can be applied to various pulse spectrophotometry studies. Moreover, the required blood volume is very small so the system can evaluate artificial blood or artificial red cells at very low cost. Thus, this system can reduce the time and cost of developing new pulse photometry techniques and other medical equipment.

Sensorless control for a sophisticated artificial myocardial contraction by using shape memory alloy fibre.

The authors have been developing an artificial myocardium, which is capable of supporting natural contractile function from the outside of the ventricle. The system was originally designed by using sophisticated covalent shape memory alloy fibres, and the surface did not implicate blood compatibility. The purpose of our study on the development of artificial myocardium was to achieve the assistance of myocardial functional reproduction by the integrative small mechanical elements without sensors, so that the effective circulatory support could be accomplished. In this study, the authors fabricated the prototype artificial myocardial assist unit composed of the sophisticated shape memory alloy fibre (Biometal), the diameter of which was 100 microns, and examined the mechanical response by using pulse width modulation (PWM) control method in each unit. Prior to the evaluation of dynamic characteristics, the relationship between strain and electric resistance and also the initial response of each unit were obtained. The component for the PWM control was designed in order to regulate the myocardial contractile function, which consisted of an originally-designed RISC microcomputer with the input of displacement, and its output signal was controlled by pulse wave modulation method. As a result, the optimal PWM parameters were confirmed and the fibrous displacement was successfully regulated under the different heat transfer conditions simulating internal body temperature as well as bias tensile loading. Then it was indicated that this control theory might be applied for more sophisticated ventricular passive or active restraint by the artificial myocardium on physiological demand.

Morphological approach for the functional improvement of an artificial myocardial assist device using shape memory alloy fibres.

The authors have been developing a mechano-electric artificial myocardial assist system (artificial myocardium) which is capable of supporting natural contractile functions from the outside of the ventricle without blood contacting surface. In this study, a nano-tech covalent type shape memory alloy fibre (Biometal, Toki Corp, Japan) was employed and the parallel-link structured myocardial assist device was developed. And basic characteristics of the system were examined in a mechanical circulatory system as well as in animal experiments using goats. The contractile functions were evaluated with the mock circulatory system that simulated systemic circulation with a silicone left ventricular model and an aortic afterload. Hemodynamic performance was also examined in goats. Prior to the measurement, the artificial myocardial assist device was installed into the goat's thoracic cavity and attached onto the ventricular wall. As a result, the system could be installed successfully without severe complications related to the heating, and the aortic flow rate was increased by 15% and the systolic left ventricular pressure was elevated by 7% under the cardiac output condition of 3L/min in a goat. And those values were elevated by the improvement of the design which was capable of the natural morphological myocardial tissue streamlines. Therefore it was indicated that the effective assistance might be achieved by the contraction by the newly-designed artificial myocardial assist system using Biometal. Moreover it was suggested that the assistance gain might be obtained by the optimised configuration design along with the natural anatomical myocardial stream line.

Cerebral venous thrombosis in adult nephrotic syndrome due to systemic amyloidosis.

Although venous thrombosis is one of the common complications in nephrotic patients, cerebral venous thrombosis (CVT) is rarely reported. CVT is so difficult to be detected by conventional diagnostic methods that it is sometimes overlooked despite its potential severity. We report a 79-year-old female with nephrotic syndrome due to systemic amyloidosis who suddenly altered mental status during her hospitalization. The underlying etiology had been not identified by physical examinations, various laboratory data, and repeated computed tomography, and finally she died. The post-mortem examination showed a massive thrombus impacted in intracranial left-sided transverse and sigmoid sinus. This case suggests that CVT can occur in a nephrotic patient who presents unexplained neurological signs and symptoms, which might not be detected only through conventional diagnostic tests.

An innovative approach to evaluate a cardiac function based on surface measurement.

Major function of the heart is to pump blood flow up to all tissues or organs in the body, and it is generally recognized that cardiac function under various diseased conditions are mainly represented by a relationship between blood flow and pressure inside of the heart. In this report, an original proposal of evaluation method on cardiac function is introduced through a simultaneous measurement of various points of cardiac muscular surface. An optical three-dimensional location sensor was employed to measure a displacement change of anatomically specific points on heart surface. Then, changes in strain in each regional surface area were quantitatively obtained. This result indicated similar tendency obtained from echocardiogram. It was also indicated that there was a difference in displacements and phrases between control and arrhythmia. Moreover, strain change in regional area was coincident with a contraction of natural heart. It was found that an attempt to superimpose the data of strain change onto the video images of natural heart was extremely helpful to understand a cardiac function visually.

Development of an Artificial Myocardium using a Covalent Shape-memory Alloy Fiber and its Cardiovascular Diagnostic Response.

The authors have been developing a newly-designed totally-implantable artificial myocardium using a covalent shape-memory alloy fibre (Biometal®, Toki Corporation), which is attached onto the ventricular wall and is also capable of supporting the natural ventricular contraction. This mechanical system consists of a contraction assistive device, which is made of Ti-Ni alloy. And the phenomenon of the martensitic transformation of the alloy was employed to achieve the physiologic motion of the device. The diameter of the alloy wire could be selected from 45 to 250μm. In this study, the basic characteristics of the fiber of 150μm was examined to design the sophisticated mechano-electric myocardium. The stress generated by the fiber was 400gf under the pulsatile driving condition (0.4W, 1Hz). Therefore it was indicated that the effective assistance might be achieved by using the Biometal shape-memory alloy fiber.

Relation between hematocrit and optical density in pulse oximetry -In vitro study with Waseda mock circulatory system-.

Optical properties of living tissues have not been well established even today, and bioopticinstrumentations have to be based on empirical formulae. In order to examine optical properties of the tissue having pulsating blood perfusion, we investigated the relation between optical density (defined as O.D.) of whole blood and hematocrit by transmission spectrophotometry. We used Waseda mock circulatory system that simulates blood circulation in the tissue. It was found that with increasing light path length, O.D. per unit light path length due to scattering and absorption effect, tended to become constant in each hematocrit. For wavelengths of 660, 805 and 940 nm, the relations between O.D. of whole blood and hematocrit predicted by Twersky's equation, Loewinger's equation and photon diffusion equation fitted to the data obtained. Meanwhile, for 1300 nm, the relation predicted by Loewinger's equation gave the best fit to the data.

Compression-induced changes on physical structures and calcification of the aromatic polyether polyurethane composite.

It is generally accepted that stress causes calcification in both bio-prosthetic and polyurethane heart valves. However, simple uni-axially- and bi-axially-stretched samples did not yield a feasible model for the elaboration of the stress-induced calcification. In this study, heat compaction combined with the incorporation of polyethylene has been explored. Specimens of polyurethane were solution cast onto a porous bi-axially-drawn ultra-high-molecular-weight polyethylene film and then heat compacted under a pressure of 18 MPa at a chosen temperature for 1.5 h. The heat-compaction-induced calcification and physical changes of the polyurethane composite were evaluated using a 28-day in vitro calcification model and Attenuated Total Reflection-Fourier Transform-Infrared (ATR-FT-IR) spectroscopy. The calcification results indicated that heat-compaction-induced calcification was double that achieved without heat compaction. Heat-compacted polyurethane composite showed higher affinity to calcium ions than the non-heat compacted sample. The ATR-FT-IR results showed that the heat-compaction-induced physical changes include distortions of polymeric molecules and permanent changes of microstructures. The distortions of polymeric molecules could be deteriorated in contact with different media. The relaxation of the stressed structures of the polyether moiety might serve as a calcium trap and a heterogeneous nucleation site for calcification. The permanent changes of microstructures resulted from high distortions also served as affinity sites attracting calcification.

Investigation on the mechanical properties of contracted collagen gels as a scaffold for tissue engineering.

In this article the mechanical properties of contracted collagen gels were investigated thoroughly by means of uniaxial tensile test. Large type I collagen-Dulbecco's Modified Eagle Medium (DMEM) gels (each was 26 ml in volume, 1.67 mg/ml collagen concentration), each populated with about 2.5 x 106 human fibroblasts, were made in 100 mm diameter plastic dishes precoated with albumin for floating the gels in DMEM. Such identically treated gels were divided into three groups for the mechanical measurements at different culture periods (2, 4, and 10 weeks). Rapid contraction occurred within the first 3 days and then the contraction went slowly in the rest period until it reached about 13% of its original size. The stress-strain curve of the contracted collagen gels demonstrated an exponential behavior at low stress region, followed by linear region, a point of yielding, and finally an ultimate stress point at which the maximum stress was reached. The mechanical strength increased in the first few weeks and then decreased as the culture went on. It is obvious that the collagen fibrils formed and were forced to orientate to the tensile direction after the test. The stress relaxation and cyclic creep phenomena were observed. Based on the morphological analysis of transmission electron microscopy (TEM) of the gels, a nonlinear visco-elastic-plastic constitutive formula was proposed, which was able to reproduce the rheological phenomena of the gels. This experiment shows that the human fibroblasts significantly contracted collagen gels so as to achieve certain mechanical strength, which makes it possible to be a scaffold for tissue engineering. However, a further method to reinforce the mechanical strength by several folds must be considered. Meanwhile, the rheological phenomena should be taken into account in the fabrication and application of the structure.

Characteristics of infertility in female hypothyroid (hyt) mice.

Female hypothyroid (hyt) mice are infertile, but the reason for this infertility is not yet known. The present study was conducted to determine whether hypothyroidism induced infertility in immature and mature hyt mice. Furthermore, animals were treated with thyroxine and gonadotrophins at different times to determine whether infertility was due to failure of follicular development, implantation or pregnancy. There were no significant differences in the numbers of ovulated eggs induced by gonadotrophin treatment or the percentages of eggs developed in vitro among immature normal controls, hyt and thyroxine-treated hyt mice. Mature hyt mice showed continuous dioestrus, and ovulated significantly fewer eggs after gonadotrophin treatment and failed to establish pregnancy after mating compared with mature control mice. Mature hyt mice had significantly fewer corpora lutea > 500 microm in diameter and significantly lower progesterone concentrations. Thyroxine treatment before mating in hyt mice resulted in well-developed corpora lutea, an increase in progesterone and normal pregnancy, regardless of subsequent thyroxine administration. In conclusion, infertility occurs in mature rather than immature hyt mice, is due to the failure of follicular development and pregnancy, and can be reversed by thyroxine treatment before mating.

The role of diastolic pump flow in centrifugal blood pump hemodynamics.

We tried to verify the hypothesis that increases in pump flow during diastole are matched by decreases in left ventricular (LV) output during systole. A calf (80 kg) was implanted with an implantable centrifugal blood pump (EVAHEART, SunMedical Technology Research Corp., Nagano, Japan) with left ventricle to aorta (LV-Ao) bypass, and parameters were recorded at different pump speeds under general anesthesia. Pump inflow and outflow pressure, arterial pressure, systemic and pulmonary blood flow, and electrocardiogram (ECG) were recorded on the computer every 5 ms. All parameters were separated into systolic and diastolic components and analyzed. The pulmonary flow was the same as the systemic flow during the study (p > 0.1). Systemic flow consisted of pump flow and LV output through the aortic valve. The ratio of systolic pump flow to pulmonary flow (51.3%) did not change significantly at variable pump speeds (p > 0.1). The other portions of the systemic flow were shared by the left ventricular output and the pump flow during diastole. When pump flow increased during diastole, there was a corresponding decrease in the LV output (Y = -1.068X + 51.462; R(insert)(2) = 0.9501). These show that pump diastolic flow may regulate expansion of the left ventricle in diastole.