Design, simulation and modelling of auxiliary exoskeleton to improve human gait cycle

Exoskeleton is a walking assistance device that improves human gait cycle through providing auxiliary force and transferring physical load to the stronger muscles. This device takes the natural state of organ and follows its natural movement. Exoskeleton functions as an auxiliary device to help those with disabilities in hip and knee such as devotees, elderly farmers and agricultural machinery operators who suffer from knee complications. In this research, an exoskeleton designed with two screw jacks at knee and hip joints. To simulate extension and flexion movements of the leg joints, bearings were used at the end of hip and knee joints. The generated torque and motion angles of these joints obtained as well as the displacement curves of screw jacks in the gait cycle. Then, the human gait cycle was simulated in stance and swing phases and the obtained torque curves were compared. The results indicated that they followed the natural circle of the generated torque in joints with a little difference from each other. The maximum displacement obtained 4 and 6 cm in hip and knee joints jack respectively. The maximum torques in hip and knee joints were generated in foot contact phase. Also the minimum torques in hip and knee joints were generated in toe off and heel off phases respectively.

Assessment of experimental thermal, numerical, and mandibular drilling factors in implantology

The main factors that cause an increase in the temperature of the jaw during drilling when implanting teeth are the geometric measurements of the surgical drill, its rotational speed, and its feed rate (cutting speed). Using finite element modelling we analysed the effect of the three variables - the angle of the head of the drill bit, the rotational speed, and the feed rate - on the increase in the temperature of the bone at the point of the drill. This showed that drilling with the angle of the head of the drill bit at 70° generates a lower temperature than when it is at 90° or 118°. The same is true when the drill bit is set at 200 rotations/minute (rpm) compared with 400,800, or 1200rpm. When the feed rate of the drill bit is 120mm/minute it generates less heat than when it is at 90 or 60mm/minute. An increase in temperature during drilling of the jaw has a direct relation with the rotational speed of the drill bit, and a reverse relation to its feed rate. The sharper the drill bit, the lower the temperature during drilling.

Modelling of human walking to optimise the function of ankle-foot orthosis in Guillan-Barré patients with drop foot

INTRODUCTION

This paper deals with the dynamic modelling of human walking. The main focus of this research was to optimise the function of the orthosis in patients with neuropathic feet, based on the kinematics data from different categories of neuropathic patients.

METHODS

The patient's body on the sagittal plane was modelled for calculating the torques generated in joints. The kinematics data required for mathematical modelling of the patients were obtained from the films of patients captured by high speed camera, and then the films were analysed through a motion analysis software. An inverse dynamic model was used for estimating the spring coefficient.

RESULTS

In our dynamic model, the role of muscles was substituted by adding a spring-damper between the shank and ankle that could compensate for their weakness by designing ankle-foot orthoses based on the kinematics data obtained from the patients. The torque generated in the ankle was varied by changing the spring constant. Therefore, it was possible to decrease the torque generated in muscles which could lead to the design of more comfortable and efficient orthoses.

CONCLUSION

In this research, unlike previous research activities, instead of studying the abnormal gait or modelling the ankle-foot orthosis separately, the function of the ankle-foot orthosis on the abnormal gait has been quantitatively improved through a correction of the torque.

Anandamide administration into the ventromedial hypothalamus stimulates appetite in rats

This investigation reports the possible role of the endocannabinoid anandamide in modulating appetitive behaviour. Given that cannabinoids have been used clinically to stimulate appetite in HIV and cancer chemotherapy patients, there has been a renewed interest in the involvement of cannabinoids in appetite modulation. This is the first report on the administration of anandamide into the ventromedial hypothalamus. Pre-satiated rats received an intrahypothalamic injection of anandamide (50 ng x 0.5 microl(-1)) followed by measurement of food intake at 3 h post injection. Administration of anandamide induced significant hyperphagia. Pretreatment with the selective CB1 cannabinoid antagonist SR 141716 (30 microg x 0.5 microl(-1)), 30 min prior to anandamide injection resulted in an attenuation of the anandamide-induced hyperphagia (P<0.001). This study demonstrates that intrahypothalamic anandamide initiates appetite by stimulation of CB1 receptors, thus providing evidence on the involvement of hypothalamic endocannabinoids in appetite initiation.

Dynamic simulation of the human red blood cell metabolic network

We have developed a Mathematica application package to perform dynamic simulations of the red blood cell (RBC) metabolic network. The package relies on, and integrates, many years of mathematical modeling and biochemical work on red blood cell metabolism. The extensive data regarding the red blood cell metabolic network and the previous kinetic analysis of all the individual components makes the human RBC an ideal 'model' system for mathematical metabolic models. The Mathematica package can be used to understand the dynamics and regulatory characteristics of the red blood cell.

Enhanced DNA fragmentation in the thymus of spontaneously hypertensive rats

The mechanisms contributing to organ injury in hypertension have been incompletely defined. The thymus gland of the spontaneously hypertensive rat (SHR) shows significant atrophy at the age of 15 wk compared with its normotensive control, the Wistar-Kyoto rat (WKY). The aim of the present study was to examine the thymus of SHR for evidence of DNA nicking as one of the mechanisms for thymic atrophy. SHR and WKY were subjected to adrenalectomy or sham surgery at 12 wk and studied at 15 wk. Adrenalectomy served to normalize the blood pressure in the SHR. DNA nicking was detected by in situ nick-end labeling (ISEL) of fixed tissue sections. Tissue sections were treated with proteolysis, and terminal deoxyribonucleotidyl transferase was used to incorporate biotinylated deoxynucleotides into DNA nick end in situ. Separately, DNA fragmentation was evaluated by measuring the level of released mono- and oligonucleosomes to the cytoplasm. A higher number of thymic ISEL-positive cells and a higher level of cytoplasmic mono- and oligonucleosomes were observed in SHR than in WKY. After adrenalectomy the enhanced level of ISEL and cytoplasmic mono- and oligonucleosomes in SHR was reduced to the level in WKY. Dexamethasone treatment (0.05 mg. kg-1. day-1) in WKY serves to decrease the thymus weight and significantly elevate the level of mono- and oligonucleosomes. Thus increased DNA fragmentation represents one of the mechanisms associated with thymic atrophy, a feature that reflects immune suppression in SHR.

Xanthine oxidase activity associated with arterial blood pressure in spontaneously hypertensive rats

Recent evidence in vivo indicates that spontaneously hypertensive rats (SHR) exhibit an increase in oxyradical production in and around microvascular endothelium. This study is aimed to examine whether xanthine oxidase plays a role in overproduction of oxidants and thereby may contribute to hypertensive states as a consequence of the increasing microvascular tone. The xanthine oxidase activity in SHR was inhibited by dietary supplement of tungsten (0.7 g/kg) that depletes molybdenum as a cofactor for the enzyme activity as well as by administration of (-)BOF4272 [(-)-8-(3-methoxy-4-phenylsulfinylphenyl)pyrazolo(1,5-alpha)-1,3, 5-triazine-4-monohydrate], a synthetic inhibitor of the enzyme. The characteristic elevation of mean arterial pressure in SHR was normalized by the tungsten diet, whereas Wistar Koto (WKY) rats displayed no significant alteration in the pressure. Multifunctional intravital videomicroscopy in mesentery microvessels with hydroethidine, an oxidant-sensitive fluoroprobe, showed that SHR endothelium exhibited overproduction of oxyradicals that coincided with the elevated arteriolar tone as compared with WKY rats. The tungsten diet significantly repressed these changes toward the levels observed in WKY rats. The activity of oxyradical-producing form of xanthine oxidase in the mesenteric tissue of SHR was approximately 3-fold greater than that of WKY rats, and pretreatment with the tungsten diet eliminated detectable levels of the enzyme activity. The inhibitory effects of the tungsten diet on the increasing blood pressure and arteriolar tone in SHR were also reproducible by administration of (-)BOF4272. These results suggest that xanthine oxidase accounts for a putative source of oxyradical generation that is associated with an increasing arteriolar tone in this form of hypertension.

Expression and disulfide-bond connectivity of the second ligand-binding repeat of the human LDL receptor

The human LDL receptor (LDLR) has a binding domain which consists of seven contiguous ligand-binding (LB) repeats, each approximately 40 amino acids long with three disulfide bonds. The second LB repeat, which is required for full binding of LDL, has been expressed, purified and folded to yield a single, fully oxidized isomer. By selective reduction and alkylation, we have shown that the cysteine residues have a I-III, II-V, IV-VI connectivity, matching that recently determined for the amino-terminal repeat. We suggest that the first two LB repeats of the LDLR, with their unique disulfide-bonding pattern, serve as a structural paradigm for other LB repeats.

Expression studies of pigmentation and POU-domain genes in human melanoma cells

Human melanoma cell lines have been used to examine the regulation of the tyrosinase (TYR) and tyrosinase-related protein genes TRP-1 and TRP-2 in response to differentiating chemicals and UV irradiation. TRP-1 mRNA levels can be repressed by treatment with the differentiating chemicals DMSO and HMBA. There is little effect of UV irradiation on pigment synthesis by human melanoma cell lines or tyrosinase activity, with variable effects on the levels of the TYR, TRP-1, and TRP-2 gene transcripts. The human TRP-1 gene promoter has been isolated and its activity tested by transient cell transfection to begin an examination of signal transduction mechanisms operating in response to pigmenting and differentiating agents. To identify transcription factors that may be involved in melanocytic gene expression, we studied the N-Oct-3 and N-Oct-5 octamer-binding activities normally expressed in the neuroectodermal cell lineage and which are expressed at high levels in melanoma cells. POU-domain-containing cDNA have been isolated from the A2058 human melanoma cell line that are homologous to the brn-2 gene that encodes N-Oct-3 and N-Oct-5.