THE KINETIC ANALYSIS OF THE LOWER EXTREMITY OF NORMAL WEIGHT, OVERWEIGHT & OBESE INDIVIDUALS DURING STAIR ASCENT & DESCENT

The purpose of this study was to examine whether there is a difference in the joint moment of force between normal weight, overweight and obese participants during stair climbing. In all, 19 normal weight participants, 18 overweight participants, and 8 obese participants were recruited to perform a series of stair ascent and descent. The 3-D kinetic data were collected using 10 cameras and 4 force plates. The peak knee extensor moment was significantly higher (p=0.026) in the overweight than in the normal weight participants during descent. The obese participants also had a higher ankle abductor moment than the normal (p=0.031) and overweight participants (p=0.002) during descent. The findings from the study confirm stair climbing results in higher loading at the knee in obese/overweight individuals, which could be a potential mechanism of osteoarthritis

Identifying factors that promote tensional homeostasis in endothelial cells

Various types of mammalian cells have an exceptional ability to adapt to externally applied mechanical stresses and strains. Because of this adaptation, cells can maintain their endogenous cytoskeletal stress at a preferred (homeostatic) state. This homeostasis of mechanical stress in cells, also known as tensional homeostasis, is essential for normal physiological functions of cells and tissues and provides protection against certain diseases. Recent experimental studies revealed a novel finding that isolated endothelial cells cannot maintain tensional homeostasis, whereas multicellular clusters can. Increasing size of the multicellular clusters played a critical role in attenuating temporal fluctuations of intracellular tension as it approached homeostasis. Here, we propose to interpret these experimental results with simple mathematical models and to gain insight into factors that contribute to homeostasis. The proposed models investigate solely on how mechanical interactions between cells influence tensional homeostasis and do not consider other physical and chemical factors such as biochemical signaling and substrate rigidity. Results of our model corroborated our earlier experimental findings that tensional homeostasis is multicellular phenomenon. We were able to identify two mechanisms that influence tensional homeostasis in confluent clusters, namely statistical averaging of stress fluctuations and stress buildup in the cluster that resulted from unbalanced portion of cell-substrate tractions at the cluster boundaries. To further investigate the role of cell-cell interactions in tensional homeostasis, we conducted traction measurements in thrombin-treated endothelial cells using micropatterned traction microscopy. Our expectation was that the presence of thrombin would stimulate cellular contractility to the point of severance of cell-cell adhesions. To our surprise, the cell-cell junctions remained intact. However, the measurements revealed a threshold in the cluster size after which attenuation in cellular tension rapidly progressed. The underlying mechanism that caused the presence of a threshold is still unknown. Current efforts of our research group are dedicated to reveal and understand those mechanisms

THE MOMENT OF THE HIP AND KNEE IN OBESE AND NON-OBESE INDIVIDUALS DURING STAIR ASCENT AND DESCENT

The purpose of this study was to examine whether there is a difference in the knee and hip joint moment between obese and normal weight subjects during stair climbing. One normal weight female participant and one overweight female articipant were recruited to perform a series of stair ascent and descent. The 3-D kinetic data were collected using 9 infrared cameras and 4 force plates. Both the overweight and normal weight participants had similar peak hip extensor moments during ascent. Their peak hip flexor moment, however, was significantly different in the obese subjects (0.19 (Nm/kg)/m) than in the normal weight subjects (0.18 (Nm/kg)/m) during descent. Furthermore, the obese subjects had a higher adduction moment than the normal weight subject during ascent (obese: -0.26 (Nm/kg)/m, normal: -0.38 (Nm/kg)/m)

THE TEMPOROSPATIAL CHARACTERISTICS OF TWO TYPICAL TAI CHI MOVEMENTS

The purpose of this study was to examine and compare the three-dimensional centre of mass (COM) displacement and temporospatial features during performance of two typical Tai Chi movements, “Repulse Monkey (RM)” and “Wave-hand in Cloud (WHIC)”, with forward walking. A group of experienced male Tai Chi practitioners (n=15) between the ages of 65 to 75, participated in the study. It was found that stride width was larger for WHIC compared to walking while double-support time was longer for RM; both Tai Chi movements spent less time in single-support. RM and WHIC had larger mediolateral and vertical displacement of the COM compared to walking. The slow, gentle-shifting characteristics of two Tai Chi movements have unique biomechanical properties that may result in special training to postural control capacity

The Influence of Central Insulin Signals on Stress Response in Mice

Stress is an anticipatory or actual disruption of homeostasis which triggers physiological responses to prepare for the threat or to reestablish the system's internal equilibrium. Other than physical stress (e.g. blood loss, infection, pain, and cold) and psychogenic stress (e.g. novel environment (rodent) and immobilization (rodent)), nutrient (metabolic) stress such as high fat diet and fasting can also trigger stress responses. Central to the activation and regulation of the stress response in mammals is the hypothalamus, where signals from the periphery and other regions of the brain are integrated and processed. Insulin and leptin are two important hormones that provide information about the energy status of the body to the hypothalamus. The hypothalamic insulin- and leptin- sensing circuits integrate these signals to coordinate metabolic outcomes such as food intake, energy expenditure, fuel partitioning, etc. Given the tight correlation between stress axis activity and nutrient status, it raises the possibility that hypothalamic insulin- and leptin- sensing circuits may also be involved in coordinating responses of the stress axis, particularly during stress pertaining changes in energy homeostasis. My thesis research focused on understanding the roles and the interactions of hypothalamic insulin and leptin signals in regulating and coordinating metabolic and hypothalamic-pituitary-adrenal (HPA) axis functions. My first project involved understanding the role of hypothalamic insulin signals in hypothalamic leptin receptor deficient animals (L^2.1 KO) in regulating energy metabolism (Chapter 2). We observed an increase in body weight and adiposity in D^2.1 KO mice that lack both hypothalamic insulin receptor (InsR) and leptin receptor (LepRb) signals. These changes were accompanied by reduced energy expenditure, rather than an increase in food intake. Unexpectedly, there was a drastic loss in body temperature in D^2.1 KO during fasting that was significantly exacerbated by single-housing. These results suggest that interactions between hypothalamic insulin and leptin signals are important for regulating energy expenditure and body temperature. Furthermore, this study also highlights the influence of housing conditions on the evaluation of thermogenic defects in mice. My second project involved the study of hypothalamic insulin signals in regulating stress-related functions by using the non-obese hypothalamic InsR-deficient mice (I^2.1 KO)(Chapter 3). We showed that I^2.1 KOs have elevated baseline hypothalamic Avp synthesis, increased activity of the HPA axis after restraint, as well as increased anxiety-like behaviors. This study demonstrated that hypothalamic InsR signals suppress the stress response to restraint, possibly by influencing AVP release to the median eminence and decreasing hypothalamic glucocorticoid receptor (GR) signals, and may also modulate anxiety-like behaviors. My current research focuses are: to remove InsR signals by using more restrictedly expressed Cre lines in order to identify brain nuclei mediating insulin's effect on stress response and/or anxiety-like behaviors; to identify the hypothalamic AVP neuronal population affected by the loss of InsR and potential extra-hypothalamic downstream targets of these neurons; to pinpoint the hypothalamic nuclei where GR signaling is altered in I^2.1 KO. By identifying the critical anatomical and functional components mediating insulin's effects, we hope to provide more understanding of the contribution of central insulin resistance to the development of HPA axis dsyregulation and anxiety disorders in humans

PENGGUNAAN MODEL DISCOVERY LEARNING UNTUK MENINGKATKAN HASIL BELAJAR SISWA PADA TEMA 9 KAYANYA NEGERIKU SUBTEMA 3 PELESTARIAN KEKAYAAN SUMBER DAYA ALAM DI INDONESIA (Penelitian Tindakan Kelas Pada Siswa Kelas IV di Madrasah Ibtidaiyah Giriasih Kecamatan Batujajar Kabupaten Bandung Barat)

Penelitian dilatar belakangi oleh rendahnya nilai rata-rata pembelajaran sub tema 3 pelestarian kekayaan Sumber Daya Alam di Indonesia yang dikarenakan kurangnya kesiapan guru dan pemahaman konsep siswa serta penggunaan model pembelajaran yang kurang tepat. Berdasarkan permasalahan tersebut, maka diimplementasikan suatu Penelitian Tindakan Kelas (PTK) melalui penerapan model Discovery Learning. Penelitian tindakan kelas yang terdiri dari III siklus, dilaksanakan di kelas IV MI Al-Mubarokah Batujajar dengan jumlah siswa 26 orang. Penelitian Tindakan Kelas (PTK) ini dilaksanakan dengan tujuan untuk meningkatkan hasil belajar siswa melalui penggunaan model pembelajaran discovery pada subtema pelestarian kekayaan sumber daya alam di Indonesia, baik sebelum maupun sesudah penggunaan model pembelajaran Discovery Learning. Model penelitian yang digunakan dalam Penelitian Tindakan Kelas (PTK) ini adalah model Siklus, sedangkan pola yang digunakan adalah pola kolaboratif, Teknik pengumpulan data dengan cara observasi aktivitas siswa dan guru, dokumen guru, wawancara, tes, serta angket respon siswa. Hasil penelitian menunjukkan bahwa dengan menggunakan model pembelajaran discovery dapat meningkatkan hasil belajar siswa. Pelaksanaan pembelajaran memperoleh hasil pada siklus I sebesar 68%, siklus II sebesar 72%, dan siklus III menjadi 93%, hasil belajar pada ranah afektif sikap percaya diri pada siklus I mencapai 65%, siklus II sebesar 73% dan siklus III meningkat mencapai 88%, selanjutnya pada ranah kognitif siklus I mencapai 54%, siklus II mencapai 69% dan siklus III meningkat menjadi 88%. Selanjutnya pada ranah psikomotor (keterampilan berbicara) siklus I sebesar 65%, siklus II sebesar 73% dan siklus III meningkat menjadi 85%. Itu artinya penerapan model Discovery Learning ini sangat efektif digunakan pada pembelajaran subtema pelestarian kekayaan sumber daya alam di Indonesia. Serta hasil aktivitas siswa, dan respon siwa menunjukkan kategori yang baik. Berdasarkan hasil di atas dapat disimpulkan bahwa penerapan pembelajaran penemuan dapat meningkatkan pemahmaan siswa terhadap hasil belajar siswa, diharapkan guru dapat mencoba dan menerapkan model pembelajaran pada materi yang lain dalam upaya untuk meningkatkan pemahaman konsep dan hasil belajar siswa lebih lanjut. Kata Kunci: Discovery Learning, Hasil Belajar

Females in Control: Female Sensitivity to Predation Risk Affects Courtship and Reproductive Behaviours

Even in the absence of direct killing, predators have a pervasive effect on prey populations through costly anti-predator behavioural responses. In high risk environments, animals can reduce conspicuous behaviours such as courtship displays decreasing exposure at the cost of reproduction. Previous studies typically looked at male behaviour immediately following a predator cue, thus, not considering temporal variations in risk or the impact of female receptivity on male courtship. I placed male and female brown-headed cowbirds under chronically elevated predation risk with periods of high and low risk. Under high predation risk, females performed fewer chatter calls and were more likely to reject courting males. Females also spent less time searching for host nests. Males greatly attenuated courtship displays, but male-male interactions were unaffected. I suggest that females perceive a greater risk associated with these reproductive behaviours and that it is the females that drive the predation risk effects on courtship

In vitro anti trypanosomal activity of some medicinal plants used in the treatment of trypanosomosis in Northern Nigeria

The in vitro trypanocidal activity of 13 medicinal plants used by local herdsmen in Northern Nigeria for the treatment of trypanosomosis was investigated. Forty-four different extracts prepared from the 13 plants were screened for in vitro activity against Trypanosoma brucei brucei. Four of the extracts showed activity against the parasite at minimum concentration of 8.3 mg/ml of blood. Key Words: Medicinal plants, Trypanosomosis, Trypanosoma brucei brucei African Journal of Biotechnology Vol.3(9) 2004: 481-48