Decreased respiratory muscle strength and/or excessive loads imposed on the respiratory muscles by disease may result in respiratory muscle fatigue and ventilatory failure. Once the respiratory muscles fatigue, the only treatment is rest by mechanical ventilation. However, no one has yet determined the best protocol of rest. The purpose of these studies was to develop an animal model in the hamster in order to examine the time course of recovery following fatigue of the diaphragm and specifically, to test whether mechanical ventilation or spontaneous unloaded breathing was a better mode for functional recovery. The studies required the initial development of an anesthetic regimen which produced minimal respiratory depression in the hamster. A new method of stimulating the diaphragm in small animals was developed by apposing plate electrodes directly against the diaphragm. The validity of this technique was examined and comparison of the mechanical and electrophysiological response to that of phrenic nerve stimulation were similar at maximal stimulation. The histological characteristics of the normal hamster diaphragm were determined for fibre type proportions and sizes, oxidative capacity and glycogen levels in the costal and crural regions of this muscle. The examination revealed three distinct areas of the diaphragm with different histological features: the abdominal surface of the crural region, the thoracic surface of the crural region and the sternal and costal region. Diaphragmatic fatigue was induced in vivo by repetitive electrical stimulation which resulted in both high and low frequency fatigue. The fatigue stimulus also produced muscle fibre damage, primarily along the abdominal surface of the diaphragm over the electrodes, and glycogen depletion in the type lib fibres. Rest by continuous mechanical ventilation resulted in recovery of high frequency fatigue in the hamster diaphragm whereas rest by spontaneous unloaded breathing resulted in no recovery. Sham fatigue groups rested by either mechanical ventilation or spontaneous breathing demonstrated progressive deterioration in transdiaphragmatic pressure throughout the rest period. Decreased muscle fibre damage but increased inflammation and glycogen depletion was demonstrated in all four fatigue/sham fatigue and rest groups compared to that demonstrated by the fatigue/sham fatigue only groups. The results suggest that passive rest by continuous mechanical ventilation promotes recovery following fatigue induced by electrical stimulation. Additional factors such as prolonged fasting, loads imposed on the diaphragm by the plate electrode apparatus, positive pressure ventilation, and cumulative effects of intraperitoneal urethane likely contributed to the progressive deterioration of diaphragmatic function demonstrated in the animals of the two sham groups rested by either spontaneous breathing or mechanical ventilation, and confounded the results shown by the two fatigue groups rested by either spontaneous breathing or mechanical ventilation. / Medicine, Faculty of / Pathology and Laboratory Medicine, Department of / Graduate

published_or_final_version / Anatomy / Master / Master of Philosophy

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

The tenuissimus is a long, thin hindlimb skeletal muscle which in hamsters contains about 200 extrafusal muscle fibers. Embedded in this richly innervated muscle is a continuous array of 16-20 closely packed muscle spindles suggesting that it may play a role in hindlimb proprioception. This high spindle density also makes the muscle ideal for the isolation and harvesting of these sensory receptors. In this correlative light and electron microscopic study, freshly frozen specimens were first prepared for serial microscopic analysis. Camera lucida reconstruction of spindle distribution showed a close proximity to the main artery and nerve in the central core of the muscle. Oxidative enzyme and myosin ATPase staining profiles were examined in both the intrafusal and extrafusal fiber populations. Type I and type II extrafusal fibers were present in even numbers and were distributed evenly throughout muscle cross-sections. Enzyme staining varied along the lengths of the three intrafusal fiber types. The fine structure of spindles was examined using transmission (TEM), conventional scanning (SEM), and high resolution scanning electron microscopy (HRSEM). For conventional SEM, isolated spindles were first fixed in 2.5% buffered glutaraldehyde, followed by 1% osmication, and mechanical disruption of the outer capsule under the dissecting microscope. Preparation for HRSEM included aldehyde/osmium fixation and freeze-cleavage of entire tenuissimus muscles in liquid N₂. Selective extraction of the cytosol with 0.1% OsO4 permitted the visualization of numerous intracellular structures. In these specimens, the capsular sleeve showed a multilayered pattern of vesicle-laden cells with variant surface topography in certain locations. Punctate sensory nerve endings adhered intimately to the surfaces of underlying intrafusal fibers in the equatorial and juxtaequatorial regions. By TEM and HRSEM these endings appeared crescent-shaped and were enveloped by external laminae. Each profile contained a plethora of mitochondria and cytoskeletal organelles. The methodology used in this study provides, for the first time, a three-dimensional view of the exquisite cytological architecture of this neuromuscular receptor. / Medicine, Faculty of / Graduate

published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

Ball State University LibrariesLibrary services and resources for knowledge buildingMasters ThesesThere is no abstract available for this thesis.

The effect of diets with various dietary fiber sources on the plasma lipids, liver cholesterol, the histology of the gastrointestinal tract, heart, liver and kidney and the fecal neutral steroid excretion was investigated in hamsters. 155, 9-11 wk old, male Golden-syrian hamsters were fed a purified basal hypercholesterolemic diet (0.1% cholesterol, 10% fat, 4% dietary fiber) for 5 wk to elevate plasma lipid levels. Based on wk 4 plasma total cholesterol (TC) levels hamsters with elevated levels were randomly assigned, 16 animals/group, into six groups for another 4 wk: control, oat bran, guar gum, cellulose, xylan and sacrifice. After 4 wk of the fiber diets (10% dietary fiber), the plasma TC levels were significantly lowered in the oat bran, guar gum and xylan groups (16%, 12% and 15%, respectively) (p<.05). They were also significantly lower than the control and cellulose groups. Plasma HDL-C concentrations tended to be lower in all the treatment groups, but was significantly decreased only in the guar gum group (12%) (p<.05). The combined plasma VLDL-C + LDL-C was significantly lowered by the oat bran, cellulose and xylan diets (38%, 40% and 34%, respectively) (p<.05). The liver cholesterol concentration increased significantly from 1 mg cholesterol/g liver to 4.1 mg cholesterol/g liver (p<.05) after 4 wk of the control diet; this was further increased significantly only in the cellulose group (5.6 mg cholesterol/g liver), while the other treatment groups showed no significant changes or differences compared to the control diet group (wk 4). The total fecal neutral steroid excretion was significantly (p<.05) higher in the oat bran group compared to the other treatment groups. No major differences were observed in the tissue histology of the animals in the different treatment groups. In the present study, it appeared that oat bran, guar gum and xylan were effective hypocholesterolemic agents; however, their mechanism of action is still not clear. / Ph. D.

published_or_final_version / Anatomy / Master / Master of Philosophy

Chiu Chi Pang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 121-134). / Abstracts in English and Chinese. / DECLARATION --- p.i / ACKNOWLEDGEMENTS --- p.ii / ABBREVIATIONS --- p.iii / ABSTRACT --- p.vi / 摘要 --- p.viii / Chapter CHAPTER 1: --- GENERAL INTRODUCTION --- p.1 / Chapter 1.1 --- Cholesterol --- p.1 / Chapter 1.1.1 --- History of cholesterol --- p.1 / Chapter 1.1.2 --- Structure of cholesterol --- p.1 / Chapter 1.1.3 --- Biological function of cholesterol --- p.3 / Chapter 1.1.4 --- Sources of cholesterol in our body --- p.3 / Chapter 1.2 --- Lipid hypothesis --- p.4 / Chapter 1.2.1 --- Relationship between dietary cholesterol and plasma cholesterol --- p.4 / Chapter 1.2.2 --- "Hypercholesterolemia , atherosclerosis and coronary heart disease (CHD)" --- p.4 / Chapter 1.2.3 --- Individual variation --- p.5 / Chapter 1.3 --- Cholesterol homeostasis --- p.7 / Chapter 1.3.1 --- SREBPs up-regulates the expression of LDL-receptor and HMG-CoA reductase --- p.7 / Chapter 1.3.2 --- HMG-CoA reductase as the rate-limiting enzyme in cholesterol synthesis --- p.11 / Chapter 1.3.3 --- LDL-receptor as the major protein removing plasma cholesterol …… --- p.12 / Chapter 1.3.4 --- LXR-α as an activator of CYP7A1 --- p.14 / Chapter 1.3.5 --- CYP7A1 controls the classical pathway for the elimination of hepatic cholesterol --- p.16 / Chapter 1.3.6 --- Bile acids as the metabolites of CYP7A1 --- p.17 / Chapter 1.4 --- Previous works in our laboratory --- p.20 / Chapter 1.5 --- Objective of this project --- p.22 / Chapter CHAPTER 2: --- INCREASED EXPRESSION OF LDL-RECEPTOR IS RESPONSIBLE FOR THE HYPO-RESPONSIVENESS OF RATS TO DIETARY CHOLESTEROL --- p.23 / Chapter 2.1 --- Introduction --- p.23 / Chapter 2.2 --- Objective --- p.24 / Chapter 2.3 --- Methods and materials --- p.25 / Chapter 2.3.1 --- Animals --- p.25 / Chapter 2.3.2 --- Diets --- p.25 / Chapter 2.3.3 --- Determination of serum cholesterol --- p.26 / Chapter 2.3.4 --- Western blot --- p.26 / Chapter 2.3.5 --- Probe production for LDL-receptor --- p.27 / Chapter 2.3.5.1 --- Extraction of total RNA --- p.27 / Chapter 2.3.5.2 --- Reverse-transcription reaction of total RNA --- p.28 / Chapter 2.3.5.3 --- Polymerase chain reaction (PCR) of LDL- receptor fragment from cDNA template --- p.28 / Chapter 2.3.5.4 --- Separation and purification of PCR products --- p.29 / Chapter 2.3.5.5 --- Polishing of purified PCR products --- p.29 / Chapter 2.3.5.6 --- Ligation of PCR products and pPCR-script Amp SK(+) cloning vector --- p.30 / Chapter 2.3.5.7 --- Transformation --- p.30 / Chapter 2.3.5.8 --- Preparing glycerol stocks containing the bacterial clones --- p.31 / Chapter 2.3.5.9 --- Plasmid DNA preparation --- p.31 / Chapter 2.3.5.10 --- Clones confirmation by restriction enzyme digestion --- p.32 / Chapter 2.3.5.11 --- Clones confirmation by automatic sequencing --- p.32 / Chapter 2.3.5.12 --- Linearization of the plasmid DNA --- p.33 / Chapter 2.3.5.13 --- DIG-labeling of RNA probe --- p.35 / Chapter 2.3.5.14 --- Testing of DIG-labeled probe --- p.35 / Chapter 2.3.6 --- Probe production for HMG-CoA reductase --- p.36 / Chapter 2.3.7 --- Probe production for GAPDH --- p.37 / Chapter 2.3.8 --- Northern blot --- p.38 / Chapter 2.3.9 --- Determination of hepatic cholesterol --- p.39 / Chapter 2.3.10 --- Statistics --- p.40 / Chapter 2.4 --- Results --- p.42 / Chapter 2.4.1 --- Growth and food intake --- p.42 / Chapter 2.4.2 --- Effect of cholesterol supplements on serum cholesterol --- p.42 / Chapter 2.4.3 --- Effect of cholesterol supplements on liver cholesterol content --- p.45 / Chapter 2.4.4 --- "Stimulatory effect of high cholesterol diet on nSREBP-2, LDL-receptor and HMG-CoA reductase in rats" --- p.45 / Chapter 2.4.5 --- "Effect of high cholesterol diet on nSREBP-2, LDL-receptor and HMG-CoA reductase in hamsters" --- p.49 / Chapter 2.4.6 --- The regulation of LDL-receptor and HMG-CoA reductase existed at transcriptional level --- p.54 / Chapter 2.5 --- Discussion --- p.59 / Chapter CHAPTER 3: --- RATS ARE HYPO-RESPONSIVE TO DIETARY CHOLESTEROL DUE TO EFFICIENT ELIMINATION OF CHOLESTEROL --- p.67 / Chapter 3.1 --- Introduction --- p.67 / Chapter 3.2 --- Objective --- p.69 / Chapter 3.3 --- Methods and materials --- p.70 / Chapter 3.3.1 --- Animals and diets --- p.70 / Chapter 3.3.2 --- Western blot --- p.70 / Chapter 3.3.3 --- Probe production for CYP7A1 and LXR-α --- p.71 / Chapter 3.3.4 --- Northern blot --- p.71 / Chapter 3.3.5 --- Determination of fecal neutral and acidic sterols --- p.71 / Chapter 3.3.5.1 --- Separation of neutral and acidic sterols --- p.71 / Chapter 3.3.5.2 --- Neutral sterols analysis --- p.72 / Chapter 3.3.5.3 --- Acidic sterols analysis --- p.72 / Chapter 3.3.5.4 --- GLC analysis of neutral and acidic sterols --- p.73 / Chapter 3.3.6 --- Statistics --- p.73 / Chapter 3.4 --- Results --- p.76 / Chapter 3.4.1 --- Effect of cholesterol supplements on fecal total neutral sterols --- p.76 / Chapter 3.4.2 --- Effect of cholesterol supplements on fecal total bile acids --- p.76 / Chapter 3.4.3 --- CYP7A1 protein on rats showed a concentration-dependent increase with response to dietary cholesterol while hamsters did not --- p.79 / Chapter 3.4.4 --- The regulation of CYP7A1 was at transcriptional level --- p.79 / Chapter 3.4.5 --- LXR-α demonstrated a parallel changes in its expression at both translational and transcriptional level --- p.84 / Chapter 3.5 --- Discussion --- p.88 / Chapter CHAPTER 4: --- MECHANISM FOR INDIVIDUAL VARIATION OF SERUM CHOLESTEROL LEVEL IN RATS AND HAMSTERS FED A HIGH CHOLESTEROL DIET --- p.94 / Chapter 4.1 --- Introduction --- p.94 / Chapter 4.2 --- Objective --- p.96 / Chapter 4.3 --- Methods and materials --- p.97 / Chapter 4.3.1 --- Diet and animals --- p.97 / Chapter 4.3.2 --- Western blot --- p.97 / Chapter 4.3.3 --- Statistics --- p.97 / Chapter 4.4 --- Results --- p.99 / Chapter 4.4.1 --- Growth and food intake --- p.99 / Chapter 4.4.2 --- Change of serum cholesterol --- p.99 / Chapter 4.4.3 --- Correlation between various protein expression and serum cholesterol --- p.99 / Chapter 4.4.3.1 --- Correlation between LDL-receptor and serum total cholesterol in rats --- p.99 / Chapter 4.4.3.2 --- Correlation between CYP7A1 and serum total cholesterolin rats --- p.99 / Chapter 4.4.3.3 --- Correlation between nSREBP-2 and serum total cholesterolin rats --- p.105 / Chapter 4.4.3.4 --- Correlation between LXR-a and serum total cholesterol in rats --- p.105 / Chapter 4.4.3.5 --- Correlation between HMG-CoA reductase and serum total cholesterol in rats --- p.105 / Chapter 4.4.3.6 --- Correlation between LDL-receptor and serum total cholesterol in hamsters --- p.105 / Chapter 4.4.3.7 --- Correlation between CYP7A1 and serum total cholesterolin hamsters --- p.109 / Chapter 4.4.3.8 --- Correlation between nSREBP-2 and serum total cholesterolin hamsters --- p.109 / Chapter 4.4.3.9 --- Correlation between HMG-CoA reductase and serum total cholesterol in hamsters --- p.109 / Chapter 4.5 --- Discussion --- p.114 / Chapter CHAPTER 5: --- CONCLUSION --- p.117 / REFERENCES --- p.121