Background: Dietetic students often show limited counseling skills when they enter internship pro... more Background: Dietetic students often show limited counseling skills when they enter internship programs. Research has shown that dietetic students need more training in counseling skills. This study was developed to assess students’ learning needs in counseling skills through peer-evaluations and self-reflection. Methods: Students who registered in the senior Nutrition Assessment and Counseling course from a mid-sized university in southeast Texas, United States, performed a counseling practicum at the end of the semester. Students role-playing as clients were given scenarios of common disease conditions (e.g., hyperlipidemia, hypertension, diabetes, and obesity), and students playing as counselors would interview and counsel the client with the specific condition. Each counselor rotated to four different clients, with each session lasting about 20 minutes. Each client filled out an evaluation and noted the strengths and weaknesses of each counselor they met. Each student also evalua...
Background: Dietetic students often show limited counseling skills when they enter internship pro... more Background: Dietetic students often show limited counseling skills when they enter internship programs. Research has shown that dietetic students need more training in counseling skills. This study was developed to assess students' learning needs in counseling skills through peer-evaluations and self-reflection. Methods: Students who registered in the senior Nutrition Assessment and Counseling course from a mid-sized university in southeast Texas, United States, performed a counseling practicum at the end of the semester. Students role-playing as clients were given scenarios of common disease conditions (e.g., hyperlipidemia, hypertension, diabetes, and obesity), and students playing as counselors would interview and counsel the client with the specific condition. Each counselor rotated to four different clients, with each session lasting about 20 minutes. Each client filled out an evaluation and noted the strengths and weaknesses of each counselor they met. Each student also ev...
Genetic markers of two general types have been used to assess the number of simultaneously produc... more Genetic markers of two general types have been used to assess the number of simultaneously productive stem cells in vivo, retrovirus markers and enzyme or hemoglobin variants. Use of the two techniques has led to different conclusions regarding stem-cell population organization, kinetics, and usage. To better understand this discrepancy, we have combined the two methods by retrovirally marking and transplanting stem cell populations of allophenic mice in which all tissues, including the hematopoietic system, are chimeric. Hematopoietic and lymphoid tissues of engrafted recipients were analyzed by Southern blotting to determine the number and extent of participation of individually marked stem cells. Genotypic chimerism of the same tissues was determined by quantitating electrophoretic variants of glu-
Genetic markers of two general types have been used to assess the number of simultaneously produc... more Genetic markers of two general types have been used to assess the number of simultaneously productive stem cells in vivo, retrovirus markers and enzyme or hemoglobin variants. Use of the two techniques has led to different conclusions regarding stem-cell population organization, kinetics, and usage. To better understand this discrepancy, we have combined the two methods by retrovirally marking and transplanting stem cell populations of allophenic mice in which all tissues, including the hematopoietic system, are chimeric. Hematopoietic and lymphoid tissues of engrafted recipients were analyzed by Southern blotting to determine the number and extent of participation of individually marked stem cells. Genotypic chimerism of the same tissues was determined by quantitating electrophoretic variants of glucose phosphate isomerase. This procedure permitted the genotypic identification of individual stem-cell clones. The results demonstrate the participation of few pluripotent stem cells in...
Journal of the Academy of Nutrition and Dietetics, 2014
Learning Outcome: The participant will be able to describe the association of eating disorder ris... more Learning Outcome: The participant will be able to describe the association of eating disorder risks among different psychiatric conditions, with the use of different substances, and with gambling behavior. Background: To add to existing knowledge about the coexistence of disordered eating and mental health issues, this study examined eating disorder risk and psychiatric comorbidities in a nationally representative sample. Method: Data from participants of the Canadian Community Health Survey Cycle 1.2 (CCHS 1.2) who were screened to be at eating disorder risk and completed the Eating Attitudes Test (n¼5,116) were analyzed. Mental health measures (based on The World Mental Health Composite International Diagnostic Interview) included major depression, mania (past 12 months), panic disorder, and post-traumatic stress disorder. Substance use measures included alcohol interference, and use of the following substances: cannabis/ hashish, cocaine/crack, inhalants (glue/gasoline/other solvents), amphetamines, MDMA (ecstacy), hallucinogens, heroin, and steroids. Gambling severity was based on frequency and type of gambling activities (e.g., casino games, lotteries, Internet gambling) in the past 12 months. Prevalence ratios of eating disorder risk among psychiatric comorbidities were measured using Poisson regression analysis adjusting for sex, age, marital status, income, BMI, and recent distress. Results: Findings of interest included sex differences in eating disorder risk related to gambling behavior as well as steroid and inhalant use (p's < 0.05). There were pronounced sex differences for eating disorder risk among all measurements with prevalence ratios ranging from 4.89 to 11.04 (p's < 0.0001). Conclusion: This detailed exploration of eating disorder risk among several psychiatric comorbidities in a large nationally representative sample yielded novel clinical findings including substances most likely to be used in relationship to eating disorder risk as well as binging and dieting behaviors.
We have studied contributions to hematopoiesis of genetically distinct stem cell populations in a... more We have studied contributions to hematopoiesis of genetically distinct stem cell populations in allophenic mice. Chimeras were made by aggregating embryos of inbred strains known to differ with respect to stem cell population kinetics. One partner strain (DBA/2) has previously been shown to normally have a stem cell (CFU-S) population of which 24% are in S-phase of the cell cycle, whereas the homologous population of the other partner strain (C57BL/6) was characterized by having only 2.6% in cycle (7). Contributions of the chimeric stem cell population to mature blood cell pools were studied throughout the life of the mice and intrinsic differences in stem cell function and aging were reflected in dynamic patterns of blood cell composition. The DBA/2 stem cell population was eclipsed by stem cells of the C57BL/6 genotype and, after 1.5-3 yr, the hemato-lymphoid composition of 22 of 27 mice studied for this long had shifted by at least 25 percentage points toward the C57BL/6 genotype...
Testicular macrophages secrete 25-hydroxycholesterol, which can be converted to testosterone by n... more Testicular macrophages secrete 25-hydroxycholesterol, which can be converted to testosterone by neighboring Leydig cells. The purposes of the present studies were to determine the mode of production of this oxysterol and its long-term effects on Leydig cells. Because oxysterols are produced both enzymatically and by auto-oxidation, we first determined if testicular macrophages possess cholesterol 25-hydroxylase mRNA and/or if macrophage-secreted products oxidize cholesterol extracellularly. Rat testicular macrophages had 25-hydroxylase mRNA and converted 14 C-cholesterol to 14 C-25-hydroxycholesterol; however, radiolabeled cholesterol was not converted to 25-hydroxycholesterol when incubated with medium previously exposed to testicular macrophages. Exposure of Leydig cells to 10 g/ml of 25-hydroxycholesterol, a dose within the range known to result in high basal production of testosterone when tested from 1 to 6 h, completely abolished LH responsiveness after 2 days of treatment. Because 25-hydroxycholesterol is toxic to many cell types at 1-5 g/ml, we also studied its influence on Leydig cells during 4 days in culture using a wide range of doses. Leydig cells were highly resistant to the cytotoxic effects of 25hydroxycholesterol, with no cells dying at 10 g/ml and only 50% of cells affected at 100 g/ml after 2 days of treatment. Similar conditions resulted in 100% death of a control lymphocyte cell line. These results demonstrate that 1) testicular macrophages have mRNA for cholesterol 25-hydroxylase and can convert cholesterol into 25-hydroxycholesterol, 2) macrophageconditioned medium is not capable of auto-oxidation of cholesterol, 3) Leydig cells are highly resistant to the cytotoxic influences of 25-hydroxycholesterol, and 4) long-term treatment with high doses of 25-hydroxycholesterol results in loss of LH responsiveness. These results support the concept that testicular macrophages enzymatically produce 25-hydroxycholesterol that not only is metabolized to testosterone by Leydig cells when present at putative physiological levels but also may exert inhibitory influences on Leydig cells when present for extended periods at very high concentrations that may occur under pathological conditions.
The bioavailability of selenium (Se) from veal, chicken, beef, pork, lamb, flounder, tuna, seleno... more The bioavailability of selenium (Se) from veal, chicken, beef, pork, lamb, flounder, tuna, selenomethionine (SeMet), and sodium selenite was assessed in Se-deficient Fischer-344 rats. Se as veal, chicken, beef, pork, lamb, flounder, tuna, SeMet, and sodium selenite was added to torula yeast (TY) basal diets to comprise Se-inadequate (0.05 mg Se/kg) diets. Se as sodium selenite was added to a TY basal diet to comprise a Se-adequate (0.10 mg Se/kg), Se-control diet. The experimental diets were fed to weanling Fischer-344 rats that had been subjected to dietary Se depletion for 6 wk. After 9 wk of the dietary Se repletion, relative activity of liver glutathione peroxidase (GSHPx) from the different dietary groups compared with control rats (100%) was: flounder 106%, tuna 101%, pork 86%, sodium selenite 81%, SeMet 80%, beef 80%, chicken 77%, veal 77%, and lamb 58%. Se from flounder was the most efficient at restoring Se concentrations in the liver and skeletal muscle. Se from sodium sel...
Sincere appreciation is expressed to Dr. Shiang-Ping Yang, my major advisor and graduate committe... more Sincere appreciation is expressed to Dr. Shiang-Ping Yang, my major advisor and graduate committee chairman, for his guidance and patience throughout my graduate study. Appreciation is also extended to Dr. Donald Oberleas and Dr. David B. Wester for their valuable comments and for serving on my graduate committee. Thanks are expressed to Dr. Barbara J. Stoecker for her helpful suggestions and to Dr. Meiling T. Yang for her technical expertise. I am grateful to all my colleagues for their assistance in this research and to my dear friends, Shan-Shue Wang and Tze-Chen Hsieh, for their invaluable aids as the typists of this manuscript. Special thanks are expressed to my uncles, Raymond Chen, Fred Chen, and Michael Chen, and their families for their help, support, and encouragement. The deepest appreciation is extended to my considerate husband, Kenny Chih-Kang Wu, for his love, patience, understanding, and encouragement during my pursuit of a graduate degree. I would like to dedicate this thesis to my parents, Mr. Cheng-Jui Chen and Mrs. Yu-Chih Liao, for their support of my education. This research was supported by AMAX, Inc. n TABLE OF CONTENTS Paae ACKNOWLEDGEMENTS i i LIST OF TABLES iv CHAPTER I. INTRODUCTION 1 II. LITERATURE REVIEW 3 III. MATERIALS AND METHODS 11 IV. RESULTS 18 V. DISCUSSION 30 REFERENCES 34 m LIST OF TABLES Page 1. Composition of a semi-purified AIN-76A diet 12 2. Composition of AIN-76A vitamin mixture 12 3. Composition of AIN-76A mineral mixture 13 4. Experimental design 14 5. Effect of copper and molybdenum treatments on the activity of hepatic xanthine dehydrogenase/oxidase (XDH) (;jmoles uric acid formed/min/g fresh liver) of female rats 19 6. Effect of copper and molybdenum treatments on the activity of hepatic sulfite oxidase (SOX) (jjmoles ferricyanide reduced/min/g fresh liver) of female rats 20 7. Effect of copper and molybdenum treatments on the activity of hepatic superoxide dismutase (SOD) (units SOD/mg fresh liver) of female rats 22
Previous studies reported that the age-related decline in testosterone biosynthesis is associated... more Previous studies reported that the age-related decline in testosterone biosynthesis is associated with a decrease in the steroidogenic acute regulatory (StAR) protein which regulates the ratelimiting step of testosterone biosynthesis. To explore the possibility of delaying this decline using a dietary approach, we have examined the effect of a natural flavonoid, apigenin, on StAR gene expression in mouse Leydig cells. Incubation of these cells with the flavonoid enhanced cyclic AMP (cAMP)-induced steroidogenesis and StAR protein expression. The results from the analyses of StAR mRNA by reverse transcription-polymerase chain reaction and the luciferase assays of StAR promoter activity indicated that this flavonoid enhanced StAR gene expression at the level of transcription. Further studies showed that apigenin blocked the thromboxane A2 receptor and interrupted the signaling through the cyclooxygenase-2-thromboxane A synthasethromboxane A2-receptor pathway, resulting in a reduction of DAX-1 (dosage sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome, gene-1) protein, a transcriptional repressor of StAR gene expression. When DAX-1 protein was reduced, the sensitivity of the Leydig cells was dramatically enhanced, with sub-threshold level of cAMP being able to induce maximal levels of StAR protein expression and steroid hormone production. The present study suggests a potential application of apigenin to improve StAR protein expression and steroidogenic sensitivity of aging Leydig cells.
This study was an examination of the reliability and validity of a modified DINESERV instrument t... more This study was an examination of the reliability and validity of a modified DINESERV instrument to fit the needs of specific establishments. A questionnaire was administered to a convenience sample of 504 customers in an American-style restaurant (n = 226) in Taiwan and a casual Italian restaurant (n = 278) in the US. Four dimensions, titled 'Product/Service', 'Reliability', 'Greeter' and 'Physical Environment', were identified by exploratory factor analysis. Empirically, these four dimensions of service quality in foodservice operations also were supported by the structural equation model developed in this study.
During the aging process of males, testosterone biosynthesis declines in testicular Leydig cells ... more During the aging process of males, testosterone biosynthesis declines in testicular Leydig cells resulting in decreases in various physiological functions. To explore the possibility of delaying the decline using food supplements, we have studied steroidogenic effects of a natural flavonoid, chrysin, in mouse Leydig cells. Chrysin dramatically increased cyclic AMP (cAMP)-induced steroidogenesis in MA-10 mouse Leydig tumor cells. This result was confirmed using Leydig cells isolated from mouse testes. The steroidogenic effect of chrysin is not associated with an increase in expression of the P450 side-chain cleavage enzyme, required for the conversion of cholesterol to pregnenolone. In addition, when 22(R)hydroxylcholesterol was used as a substrate, chrysin induced a non-significant increase in steroid hormone, suggesting that the majority of the observed increase in steroidogenesis was due to the increased supply of substrate cholesterol. These observations were corroborated by show...
Critical Reviews in Food Science and Nutrition, 2009
The science supporting the Dietary Reference Intakes (DRI) for phosphorus, magnesium, vitamin D, ... more The science supporting the Dietary Reference Intakes (DRI) for phosphorus, magnesium, vitamin D, and fluoride was examined in this review. Along with the previous article on calcium in this series both of these reviews represent all the DRI for nutrients considered essential for bone metabolism and health, as reported in the Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (Institute of Medicine, Food and Nutrition Board (FNB), 1997). The Recomended Dietary Allowances (RDA) or adequate intake (AI), and the tolerable upper intake level (UL) were recommended for each of these essential nutrients. For adults and in the case of fluoride, for infants as well, UL were calculated since all of these nutrients have the potential for mild to detrimental side effects. Dietary intake data and controversies regarding the role these nutrients may play in other chronic diseases have also been discussed. Advances and controversies reported since the publication of the DRI for these nutrients were also addressed in this review. A recent Dietary Reference Intake Research Synthesis Workshop report identified an extensive range of suggested future research directions needed to improve our understanding of these bone-related nutrients and their contributions to human health.
Critical Reviews in Food Science and Nutrition, 2008
In this article the science relied on to establish the Dietary Reference Intakes (DRI) specifical... more In this article the science relied on to establish the Dietary Reference Intakes (DRI) specifically for calcium was examined. The latest dietary recommendations for the essential nutrients significant with respect to their roles in bone metabolism and health were reported in the Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (1997) (NIM, 1997). For calcium an adequate intake was recommended because insufficient data were available at the time to determine specific Recommended Dietary Allowances. Dietary intake data and the controversies regarding the role calcium may play in other chronic diseases have also been discussed. Advances and continued dilemmas regarding these topics reported since the publication of the DRI were also addressed in this review. A recent Dietary Reference Intake Research Synthesis Workshop report identified an extensive range of suggested future research directions needed to improve our understanding of calcium and bone and health.
Recently, we found that testicular macrophages produce 25hydroxycholesterol (25-HC) and express 2... more Recently, we found that testicular macrophages produce 25hydroxycholesterol (25-HC) and express 25-hydroxylase, the enzyme that converts cholesterol to 25-HC. In addition, 25-HC may be an important paracrine factor mediating the known interactions between macrophages and neighboring Leydig cells, because it is efficiently converted to testosterone by Leydig cells. The purpose of the present study was to determine if testosterone can regulate the production of 25-HC in rat testicular macrophages, representing a potential negative-feedback loop from Leydig cells. We found that expression of 25-hydroxylase mRNA and production of 25-HC by cultured testicular macrophages were significantly inhibited by testosterone at 10 g/ml. This dose of testosterone did not have an effect on cell viability and did not change the rate of mRNA degradation in the presence of actinomycin D. These studies indicate that production of 25-HC is negatively regulated by testosterone, which may be representative of a paracrine negative-feedback loop.
Background: Dietetic students often show limited counseling skills when they enter internship pro... more Background: Dietetic students often show limited counseling skills when they enter internship programs. Research has shown that dietetic students need more training in counseling skills. This study was developed to assess students’ learning needs in counseling skills through peer-evaluations and self-reflection. Methods: Students who registered in the senior Nutrition Assessment and Counseling course from a mid-sized university in southeast Texas, United States, performed a counseling practicum at the end of the semester. Students role-playing as clients were given scenarios of common disease conditions (e.g., hyperlipidemia, hypertension, diabetes, and obesity), and students playing as counselors would interview and counsel the client with the specific condition. Each counselor rotated to four different clients, with each session lasting about 20 minutes. Each client filled out an evaluation and noted the strengths and weaknesses of each counselor they met. Each student also evalua...
Background: Dietetic students often show limited counseling skills when they enter internship pro... more Background: Dietetic students often show limited counseling skills when they enter internship programs. Research has shown that dietetic students need more training in counseling skills. This study was developed to assess students' learning needs in counseling skills through peer-evaluations and self-reflection. Methods: Students who registered in the senior Nutrition Assessment and Counseling course from a mid-sized university in southeast Texas, United States, performed a counseling practicum at the end of the semester. Students role-playing as clients were given scenarios of common disease conditions (e.g., hyperlipidemia, hypertension, diabetes, and obesity), and students playing as counselors would interview and counsel the client with the specific condition. Each counselor rotated to four different clients, with each session lasting about 20 minutes. Each client filled out an evaluation and noted the strengths and weaknesses of each counselor they met. Each student also ev...
Genetic markers of two general types have been used to assess the number of simultaneously produc... more Genetic markers of two general types have been used to assess the number of simultaneously productive stem cells in vivo, retrovirus markers and enzyme or hemoglobin variants. Use of the two techniques has led to different conclusions regarding stem-cell population organization, kinetics, and usage. To better understand this discrepancy, we have combined the two methods by retrovirally marking and transplanting stem cell populations of allophenic mice in which all tissues, including the hematopoietic system, are chimeric. Hematopoietic and lymphoid tissues of engrafted recipients were analyzed by Southern blotting to determine the number and extent of participation of individually marked stem cells. Genotypic chimerism of the same tissues was determined by quantitating electrophoretic variants of glu-
Genetic markers of two general types have been used to assess the number of simultaneously produc... more Genetic markers of two general types have been used to assess the number of simultaneously productive stem cells in vivo, retrovirus markers and enzyme or hemoglobin variants. Use of the two techniques has led to different conclusions regarding stem-cell population organization, kinetics, and usage. To better understand this discrepancy, we have combined the two methods by retrovirally marking and transplanting stem cell populations of allophenic mice in which all tissues, including the hematopoietic system, are chimeric. Hematopoietic and lymphoid tissues of engrafted recipients were analyzed by Southern blotting to determine the number and extent of participation of individually marked stem cells. Genotypic chimerism of the same tissues was determined by quantitating electrophoretic variants of glucose phosphate isomerase. This procedure permitted the genotypic identification of individual stem-cell clones. The results demonstrate the participation of few pluripotent stem cells in...
Journal of the Academy of Nutrition and Dietetics, 2014
Learning Outcome: The participant will be able to describe the association of eating disorder ris... more Learning Outcome: The participant will be able to describe the association of eating disorder risks among different psychiatric conditions, with the use of different substances, and with gambling behavior. Background: To add to existing knowledge about the coexistence of disordered eating and mental health issues, this study examined eating disorder risk and psychiatric comorbidities in a nationally representative sample. Method: Data from participants of the Canadian Community Health Survey Cycle 1.2 (CCHS 1.2) who were screened to be at eating disorder risk and completed the Eating Attitudes Test (n¼5,116) were analyzed. Mental health measures (based on The World Mental Health Composite International Diagnostic Interview) included major depression, mania (past 12 months), panic disorder, and post-traumatic stress disorder. Substance use measures included alcohol interference, and use of the following substances: cannabis/ hashish, cocaine/crack, inhalants (glue/gasoline/other solvents), amphetamines, MDMA (ecstacy), hallucinogens, heroin, and steroids. Gambling severity was based on frequency and type of gambling activities (e.g., casino games, lotteries, Internet gambling) in the past 12 months. Prevalence ratios of eating disorder risk among psychiatric comorbidities were measured using Poisson regression analysis adjusting for sex, age, marital status, income, BMI, and recent distress. Results: Findings of interest included sex differences in eating disorder risk related to gambling behavior as well as steroid and inhalant use (p's < 0.05). There were pronounced sex differences for eating disorder risk among all measurements with prevalence ratios ranging from 4.89 to 11.04 (p's < 0.0001). Conclusion: This detailed exploration of eating disorder risk among several psychiatric comorbidities in a large nationally representative sample yielded novel clinical findings including substances most likely to be used in relationship to eating disorder risk as well as binging and dieting behaviors.
We have studied contributions to hematopoiesis of genetically distinct stem cell populations in a... more We have studied contributions to hematopoiesis of genetically distinct stem cell populations in allophenic mice. Chimeras were made by aggregating embryos of inbred strains known to differ with respect to stem cell population kinetics. One partner strain (DBA/2) has previously been shown to normally have a stem cell (CFU-S) population of which 24% are in S-phase of the cell cycle, whereas the homologous population of the other partner strain (C57BL/6) was characterized by having only 2.6% in cycle (7). Contributions of the chimeric stem cell population to mature blood cell pools were studied throughout the life of the mice and intrinsic differences in stem cell function and aging were reflected in dynamic patterns of blood cell composition. The DBA/2 stem cell population was eclipsed by stem cells of the C57BL/6 genotype and, after 1.5-3 yr, the hemato-lymphoid composition of 22 of 27 mice studied for this long had shifted by at least 25 percentage points toward the C57BL/6 genotype...
Testicular macrophages secrete 25-hydroxycholesterol, which can be converted to testosterone by n... more Testicular macrophages secrete 25-hydroxycholesterol, which can be converted to testosterone by neighboring Leydig cells. The purposes of the present studies were to determine the mode of production of this oxysterol and its long-term effects on Leydig cells. Because oxysterols are produced both enzymatically and by auto-oxidation, we first determined if testicular macrophages possess cholesterol 25-hydroxylase mRNA and/or if macrophage-secreted products oxidize cholesterol extracellularly. Rat testicular macrophages had 25-hydroxylase mRNA and converted 14 C-cholesterol to 14 C-25-hydroxycholesterol; however, radiolabeled cholesterol was not converted to 25-hydroxycholesterol when incubated with medium previously exposed to testicular macrophages. Exposure of Leydig cells to 10 g/ml of 25-hydroxycholesterol, a dose within the range known to result in high basal production of testosterone when tested from 1 to 6 h, completely abolished LH responsiveness after 2 days of treatment. Because 25-hydroxycholesterol is toxic to many cell types at 1-5 g/ml, we also studied its influence on Leydig cells during 4 days in culture using a wide range of doses. Leydig cells were highly resistant to the cytotoxic effects of 25hydroxycholesterol, with no cells dying at 10 g/ml and only 50% of cells affected at 100 g/ml after 2 days of treatment. Similar conditions resulted in 100% death of a control lymphocyte cell line. These results demonstrate that 1) testicular macrophages have mRNA for cholesterol 25-hydroxylase and can convert cholesterol into 25-hydroxycholesterol, 2) macrophageconditioned medium is not capable of auto-oxidation of cholesterol, 3) Leydig cells are highly resistant to the cytotoxic influences of 25-hydroxycholesterol, and 4) long-term treatment with high doses of 25-hydroxycholesterol results in loss of LH responsiveness. These results support the concept that testicular macrophages enzymatically produce 25-hydroxycholesterol that not only is metabolized to testosterone by Leydig cells when present at putative physiological levels but also may exert inhibitory influences on Leydig cells when present for extended periods at very high concentrations that may occur under pathological conditions.
The bioavailability of selenium (Se) from veal, chicken, beef, pork, lamb, flounder, tuna, seleno... more The bioavailability of selenium (Se) from veal, chicken, beef, pork, lamb, flounder, tuna, selenomethionine (SeMet), and sodium selenite was assessed in Se-deficient Fischer-344 rats. Se as veal, chicken, beef, pork, lamb, flounder, tuna, SeMet, and sodium selenite was added to torula yeast (TY) basal diets to comprise Se-inadequate (0.05 mg Se/kg) diets. Se as sodium selenite was added to a TY basal diet to comprise a Se-adequate (0.10 mg Se/kg), Se-control diet. The experimental diets were fed to weanling Fischer-344 rats that had been subjected to dietary Se depletion for 6 wk. After 9 wk of the dietary Se repletion, relative activity of liver glutathione peroxidase (GSHPx) from the different dietary groups compared with control rats (100%) was: flounder 106%, tuna 101%, pork 86%, sodium selenite 81%, SeMet 80%, beef 80%, chicken 77%, veal 77%, and lamb 58%. Se from flounder was the most efficient at restoring Se concentrations in the liver and skeletal muscle. Se from sodium sel...
Sincere appreciation is expressed to Dr. Shiang-Ping Yang, my major advisor and graduate committe... more Sincere appreciation is expressed to Dr. Shiang-Ping Yang, my major advisor and graduate committee chairman, for his guidance and patience throughout my graduate study. Appreciation is also extended to Dr. Donald Oberleas and Dr. David B. Wester for their valuable comments and for serving on my graduate committee. Thanks are expressed to Dr. Barbara J. Stoecker for her helpful suggestions and to Dr. Meiling T. Yang for her technical expertise. I am grateful to all my colleagues for their assistance in this research and to my dear friends, Shan-Shue Wang and Tze-Chen Hsieh, for their invaluable aids as the typists of this manuscript. Special thanks are expressed to my uncles, Raymond Chen, Fred Chen, and Michael Chen, and their families for their help, support, and encouragement. The deepest appreciation is extended to my considerate husband, Kenny Chih-Kang Wu, for his love, patience, understanding, and encouragement during my pursuit of a graduate degree. I would like to dedicate this thesis to my parents, Mr. Cheng-Jui Chen and Mrs. Yu-Chih Liao, for their support of my education. This research was supported by AMAX, Inc. n TABLE OF CONTENTS Paae ACKNOWLEDGEMENTS i i LIST OF TABLES iv CHAPTER I. INTRODUCTION 1 II. LITERATURE REVIEW 3 III. MATERIALS AND METHODS 11 IV. RESULTS 18 V. DISCUSSION 30 REFERENCES 34 m LIST OF TABLES Page 1. Composition of a semi-purified AIN-76A diet 12 2. Composition of AIN-76A vitamin mixture 12 3. Composition of AIN-76A mineral mixture 13 4. Experimental design 14 5. Effect of copper and molybdenum treatments on the activity of hepatic xanthine dehydrogenase/oxidase (XDH) (;jmoles uric acid formed/min/g fresh liver) of female rats 19 6. Effect of copper and molybdenum treatments on the activity of hepatic sulfite oxidase (SOX) (jjmoles ferricyanide reduced/min/g fresh liver) of female rats 20 7. Effect of copper and molybdenum treatments on the activity of hepatic superoxide dismutase (SOD) (units SOD/mg fresh liver) of female rats 22
Previous studies reported that the age-related decline in testosterone biosynthesis is associated... more Previous studies reported that the age-related decline in testosterone biosynthesis is associated with a decrease in the steroidogenic acute regulatory (StAR) protein which regulates the ratelimiting step of testosterone biosynthesis. To explore the possibility of delaying this decline using a dietary approach, we have examined the effect of a natural flavonoid, apigenin, on StAR gene expression in mouse Leydig cells. Incubation of these cells with the flavonoid enhanced cyclic AMP (cAMP)-induced steroidogenesis and StAR protein expression. The results from the analyses of StAR mRNA by reverse transcription-polymerase chain reaction and the luciferase assays of StAR promoter activity indicated that this flavonoid enhanced StAR gene expression at the level of transcription. Further studies showed that apigenin blocked the thromboxane A2 receptor and interrupted the signaling through the cyclooxygenase-2-thromboxane A synthasethromboxane A2-receptor pathway, resulting in a reduction of DAX-1 (dosage sensitive sex reversal-adrenal hypoplasia congenita critical region on the X chromosome, gene-1) protein, a transcriptional repressor of StAR gene expression. When DAX-1 protein was reduced, the sensitivity of the Leydig cells was dramatically enhanced, with sub-threshold level of cAMP being able to induce maximal levels of StAR protein expression and steroid hormone production. The present study suggests a potential application of apigenin to improve StAR protein expression and steroidogenic sensitivity of aging Leydig cells.
This study was an examination of the reliability and validity of a modified DINESERV instrument t... more This study was an examination of the reliability and validity of a modified DINESERV instrument to fit the needs of specific establishments. A questionnaire was administered to a convenience sample of 504 customers in an American-style restaurant (n = 226) in Taiwan and a casual Italian restaurant (n = 278) in the US. Four dimensions, titled 'Product/Service', 'Reliability', 'Greeter' and 'Physical Environment', were identified by exploratory factor analysis. Empirically, these four dimensions of service quality in foodservice operations also were supported by the structural equation model developed in this study.
During the aging process of males, testosterone biosynthesis declines in testicular Leydig cells ... more During the aging process of males, testosterone biosynthesis declines in testicular Leydig cells resulting in decreases in various physiological functions. To explore the possibility of delaying the decline using food supplements, we have studied steroidogenic effects of a natural flavonoid, chrysin, in mouse Leydig cells. Chrysin dramatically increased cyclic AMP (cAMP)-induced steroidogenesis in MA-10 mouse Leydig tumor cells. This result was confirmed using Leydig cells isolated from mouse testes. The steroidogenic effect of chrysin is not associated with an increase in expression of the P450 side-chain cleavage enzyme, required for the conversion of cholesterol to pregnenolone. In addition, when 22(R)hydroxylcholesterol was used as a substrate, chrysin induced a non-significant increase in steroid hormone, suggesting that the majority of the observed increase in steroidogenesis was due to the increased supply of substrate cholesterol. These observations were corroborated by show...
Critical Reviews in Food Science and Nutrition, 2009
The science supporting the Dietary Reference Intakes (DRI) for phosphorus, magnesium, vitamin D, ... more The science supporting the Dietary Reference Intakes (DRI) for phosphorus, magnesium, vitamin D, and fluoride was examined in this review. Along with the previous article on calcium in this series both of these reviews represent all the DRI for nutrients considered essential for bone metabolism and health, as reported in the Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (Institute of Medicine, Food and Nutrition Board (FNB), 1997). The Recomended Dietary Allowances (RDA) or adequate intake (AI), and the tolerable upper intake level (UL) were recommended for each of these essential nutrients. For adults and in the case of fluoride, for infants as well, UL were calculated since all of these nutrients have the potential for mild to detrimental side effects. Dietary intake data and controversies regarding the role these nutrients may play in other chronic diseases have also been discussed. Advances and controversies reported since the publication of the DRI for these nutrients were also addressed in this review. A recent Dietary Reference Intake Research Synthesis Workshop report identified an extensive range of suggested future research directions needed to improve our understanding of these bone-related nutrients and their contributions to human health.
Critical Reviews in Food Science and Nutrition, 2008
In this article the science relied on to establish the Dietary Reference Intakes (DRI) specifical... more In this article the science relied on to establish the Dietary Reference Intakes (DRI) specifically for calcium was examined. The latest dietary recommendations for the essential nutrients significant with respect to their roles in bone metabolism and health were reported in the Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (1997) (NIM, 1997). For calcium an adequate intake was recommended because insufficient data were available at the time to determine specific Recommended Dietary Allowances. Dietary intake data and the controversies regarding the role calcium may play in other chronic diseases have also been discussed. Advances and continued dilemmas regarding these topics reported since the publication of the DRI were also addressed in this review. A recent Dietary Reference Intake Research Synthesis Workshop report identified an extensive range of suggested future research directions needed to improve our understanding of calcium and bone and health.
Recently, we found that testicular macrophages produce 25hydroxycholesterol (25-HC) and express 2... more Recently, we found that testicular macrophages produce 25hydroxycholesterol (25-HC) and express 25-hydroxylase, the enzyme that converts cholesterol to 25-HC. In addition, 25-HC may be an important paracrine factor mediating the known interactions between macrophages and neighboring Leydig cells, because it is efficiently converted to testosterone by Leydig cells. The purpose of the present study was to determine if testosterone can regulate the production of 25-HC in rat testicular macrophages, representing a potential negative-feedback loop from Leydig cells. We found that expression of 25-hydroxylase mRNA and production of 25-HC by cultured testicular macrophages were significantly inhibited by testosterone at 10 g/ml. This dose of testosterone did not have an effect on cell viability and did not change the rate of mRNA degradation in the presence of actinomycin D. These studies indicate that production of 25-HC is negatively regulated by testosterone, which may be representative of a paracrine negative-feedback loop.
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Papers by Jau-Jiin Chen