• 제목/요약/키워드: Triiodothyronine

검색결과 115건 처리시간 0.027초

핵의학 체외 검사에서 자동분주기를 이용한 Random Assay 가능성평가 (Comparison of Batch Assay and Random Assay Using Automatic Dispenser in Radioimmunoassay)

  • 문승환;이호영;신선영;민경선;이현주;장수진;강지연;이동수;정준기;이명철
    • Nuclear Medicine and Molecular Imaging
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    • 제43권4호
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    • pp.323-329
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    • 2009
  • 목적: 방사면역측정법 및 면역방사계수법은 매 실험마다 표준용액을 넣고 표준곡선에 대비하여 결과를 산출하는 batch assay가 일반화되어 있다. 비용과 시간에 대한 효율성을 증가 시키기 위해서는 선행 표준 곡선을 이용하여 검사를 진행하는 random assay의 적용이 요구된다. 방사면역측정법 및 면역방사계수법에서 자동분주기를 이용한 random assay적용 가능성을 평가 하기 위해 본 연구를 수행하였다. 대상 및 방법: Triiodothyronine (T3), free thyroxine (fT4), Prostate specific antigen (PSA), Carcinoembryonic antigen (CEA) 4가지 항목을 대상으로 하였으며 각 검사별 20명의 환자 검체를 이용하였다. 각 검사 항목별로 표준곡선을 얻기 위해 3시간 간격으로 4회 측정한 표준용액의 분당계수값(counter per minute, cpm)을 측정하였다. 이를 Friedman test를 이용하여 비교하여 검사시 마다 얻는 표준 곡선간의 차이를 평가하였다. 각 검사별 저, 중, 고농도의 대조 용액을 이용하여 5회 측정하고 이를 Friedman test를 이용하여 비교하여 측정 내 정밀도를 평가하였다. 각 검사별 저, 중, 고농도의 대조용액을 batch assay와 자동분주기를 이용한 random assay로 3시간 간격으로 각각 4회 측정하였다. 측정값을 바탕으로 평균, 표준 편차, 변이계수를 구하고 Wilcoxon test를 이용하여 비교하여 assay 방법에 따른 차이를 비교하였다. 두 assay간에 일치도(agreement)를 평가하기 위해 두 assay의 측정값 사이에 급내상관계수(Intraclass correlation coefficient, ICC)와 상관계수를 계산하였다. 결과: 모든 검사항목에서 표준 용액의 분당계수값은 측정 간에 통계적으로 유의한 차이가 없었다. T3, fT4, PSA, CEA 검사항목마다 측정한 저, 중, 고농도별 측정 내 변이계수는 T3(3.6%, 2.6%, 0.9%), fT4(4.5%, 1.1%. 1.3%), PSA(3.9%, 3.1%, 1.2%), CEA(5.0%, 4.8%, 7.6%)였다. 검사 항목별 측정방법에 따른 대조 용액을 이용한 표준 곡선의 측정 간 정밀도 평가에서 두 검사 방법간에 유의한 차이가 없었다. 각 검사항목별로 20명의 환자 검체에서 측정한 측정 간 변이계수(inter-assay precision)의 평균과 표준편차 값은 batch assay로 시행했을 때 각각 3.2$\pm$1.7%, 3.9$\pm$2.1%. 7.1$\pm$6.2%, 11.2$\pm$7.2%였고 random assay로 측정하였을 때는 2.7$\pm$1.7%, 4.8$\pm$3.1%, 3.6$\pm$4.8%, 7.4$\pm$6.2였다. Batch assay와 random assay는 서로 높은 일치도를 보였다. 측정한 급내상관계수(Intraclass correlation coefficient)는 T3, fT4, PSA, CEA 각각 0.9968, 0.9973. 0.9996, 0.9901였다. Batch assay로 측정한 값과 자등분주기를 이용한 random assay로 측정한 값 사이에 상관 계수(R$^2$)는 T3, fT4, PSA, CEA 각각 0.9924, 0.9974, 0.9994, 0.9989(p<0.005)로 모두 강한 상관관계를 보였다. 결론: T3, fT4, PSA, CEA 4가지 항목의 방사면역측정 법 (Radioimmunoassay)에서 기존의 batch assay와 자동분주기를 이용한 random assay간에 일치도와 상관성이 높았다. 결론적으로 자동분주기를 이용한 random assay를 방사면역측정법 및 면역방사계수법에 적절히 이용할 수 있을 것으로 생각된다.

PLASMA CONCENTRATION OF L. THYROXINE (T4). L. TRIIODOTHYRONINE (T3) AND CERTAIN OTHER BLOOD BIOCHEMICAL CONSTITUENTS IN GROWING CROSSBRED (B0S taurus × B0S indicus) CALVES

  • Shukla, D.C.;Varshney, V.P.;Gupta, P.S.P.;Mahapatro, B.B.
    • Asian-Australasian Journal of Animal Sciences
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    • 제7권1호
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    • pp.69-74
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    • 1994
  • The relationship of thyroid status and certain blood biochemical constituents with body weight gains (ADG) and age (13 to 96 weeks) was studied in Holstein Friesian ${\times}$ Hariana ($1/2F{\times}1/2H$) crossbred male calves by assessing their plasma triiodo thyronine ($T_3$), Thyroxine ($T_4$), sodium, potassium, total proteins and cholesterol level at two energy levels. Body weight gains (ADG) were higher during the 50 to 72 weeks of age and declined thereafter, the plasma $T_3$ conc. was aignificantly (p < 0.01) higher during this period compared to all other periods. There was no significant variation due to energy level. Overall mean plasma $T_3$ conc. was $1.19{\pm}0.12ng/ml$. Plasma $T_4$ conc. did not show any significant variation either between the different age periods or between the two energy levels. The mean plasma $T_4$ conc. was $37.34{\pm}1.32ng/ml$. The plasma sodium and potassium concentration did not vary significantly due to energy levels. But amongst the different age periods, sodium concentration was highest ($147.70{\pm}2.29mEq/L$) during 49-60 weeks of age and lowest ($134.70{\pm}1.78mEq/L$) during 13-24 weeks, where as for potassium concentration changes were nonsignificant. There was very little variation amongst other periods. Plasma protein level was higher at 100% energy level than at 75%. Amongst the different age period, it was significantly lower ($6.44{\pm}0.36$) during 13 to 24 weeks of age than at 37 to 48 weeks of age ($7.14{\pm}0.11$). Plasma cholesterol values were higher for 75% energy level than that of 100%. Between the periods it was highest during 61 to 72 weeks of age and the difference amongst the age period were highly significant.

Effects of Enzyme Addition to Broiler Diets Containing Varying Levels of Double Zero Rapeseed Meal

  • Ramesh, K.R.;Devegowda, G.;Khosravinia, H.
    • Asian-Australasian Journal of Animal Sciences
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    • 제19권9호
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    • pp.1354-1360
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    • 2006
  • Maize-soybean meal diets with 0, 100, 200 and 300 g/kg double zero rapeseed meal ('00' RSM) with and without an enzyme mixture (xylanase, pectinase, cellulase) at a level of 1.6 g/kg were evaluated with 624 day-old broiler chicks for 5 weeks. The birds were randomly allocated to eight dietary treatments with three replicates of 26 birds each. Average daily gain (ADG) and feed intake (FI) were recorded weekly and ileal viscosity, organ weights, serum enzyme activity, hormonal profile and hematological parameters were measured at the end of week 5. Average daily gain during the weekly periods was significantly influenced by the dietary level of '00'RSM (p<0.01). Inclusion of '00' RSM improved the ADG up to day 28 with the increased level; beyond that time no improvement was recorded when compared to control groups. However, ADG from 1-35 days was significantly different between 300 g/kg inclusion level of '00' RSM and the control diet. Inconsistent decline in feed intake and feed conversion ratio was observed up to day 21 and the trend was reversed thereafter. The proportion of '00' RSM in the diet had a significant ($p{\leq}0.05$) influence on thyroid weight but had no effect on the relative weights of liver and heart, serum enzyme activities (${\gamma}$-glutamyl transferase, alanine amino transferase and aspartate amino transferase), thyroid hormones ($T_3$ and $T_4$), hemoglobin level and hematocrit. Significant improvement in ADG was recorded during the 2nd week of age with the addition of enzyme, whereas for all other periods, including the whole period of the trial, higher but non-significant ADG was observed. FI and FCR were not affected by the addition of enzyme but there was a numerical reduction in FCR during the whole period. The addition of enzyme reduced the ileal viscosity at all levels of '00' RSM inclusion. The results suggest that '00' RSM can be included up to 300 g/kg in broiler diets without any adverse effects on health and performance. The addition of commercial enzyme mixture containing xylanase, pectinase, cellulase to broiler diets containing '00'RSM has some effect on growth rate and feed conversion efficiency.

PTU-처치가 흰쥐대동맥의 수축 및 이완 반응에 미치는 영향 (Vascular Responses to Vasoactive Drugs in Propylthiouracil-Treated Rat Aorta)

  • 심일청;김인겸;김중영
    • 대한약리학회지
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    • 제26권2호
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    • pp.135-144
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    • 1990
  • Propylthiouracil(PTU)을 4주 및 12주간 투여한 흰쥐의 대동맥을 적출하여 혈관수축제와 이완제에 대한 반응을 관찰하여 다음과 같은 결과를 얻었다. PTU를 처치한 실험군에서는 대조군에 비해 현저한 체중저하와 혈중 갑상선호르몬의 감소를 보였다. PTU를 처치한 흰쥐의 대동맥에 대한 norepinephrine (NE)과, calcium및 potassium 이온에 의한 최대수축 반응은 대조군에 비하여 유의하게 감소되었다. 그러나 NE에 대한 중간유효량은 증가되었으나, calcium이온에 대한 중간 유효량은 유의한 차이가 없었다. 그리고 acetylcholine, histamine, isoproterenol 및 nitroprusside에 의한 대동맥의 이완작용은 대조군에 비해 증가된 경향을 보였다. PTU를 12주간 처치한 군에 있어서 acetylcholine에 의한 최대 이완반응은 대조군에 비해 유의하게 증가되었지만 다른 이완제에 의해서는 유의한 차이가 없었다. PTU를 4주간 처치한 군에 있어서는 대조군에 비하여 혈관이완제에 대한 중간억제량은 유의한 차이가 없었지만, 12주 처치군에 있어서는 isoproterenol 및 nitroprusside에 대한 중간억제량은 감소 되었으나 acetylcholine 및 histamine에 대한 중간억제량은 유의한 차이가 없었다. 이상의 결과로 미루어 보아 PTU-처치에 의한 혈관 반응성의 변화는 혈관 내피세포보다는 혈관 평활근세포자체의 변화에 기인되며, 이러한 세포내의 변화는 갑상선 기능이 저하된 후에도 계속되고 있음을 알 수 있었다.

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산란계와 비산란계의 에너지대사 비교 시험 (Comparison of Energy Metabolisms between Laying and Non- laying Hen)

  • 이영철
    • 한국가금학회지
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    • 제13권1호
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    • pp.31-40
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    • 1986
  • 정상적인 산란계와 란소 기능을 정지시킨 비산란계의 에너지 대사를 비교한 결과는 다음과 같다. 1. 절식시 열생산량(FHP)은 산란계 109.7Kcal/kg$^{0.75}$ , 비산란계 87.4 Kcal/kg$^{0.75}$ 이며 전자의 FHP가 약 25.5% 높았다. 2. 유지를 위한 ME요구량(MEm)에 있어서 산란계 149Kcal/kg$^{0.75}$ 에 대하여 비산란계는 135Kcal/kg$^{0.75}$ 이며 산란계가 10% 높았다. 이는 유지시라 하드라도 란생산을 계속하는 이상체내에서의 산란을 위해 대사작용이 계속되기 때문으로 생각된다. 3. 생산을 위한 ME의 정미이용효율(NAME)은 산란계 77%, 비산란계 83%이었다. 이 경우 체에너지 축적이 마이너스였던 산란계의 NAME은 주로 란생산을 위한 ME 이용효율이며 또 산란이 중지된 비산란계의 NAME은 증체를 위한 이용효율에 해당된다고 생각된다. 4. 산란계와 비산란계에 있어서 각각 체중과 체에너지 축적의 회귀식으로 구한 체중 1g 증감할때의 에너지치는 산란계 3.54Kcal, 비산란계5.04Kcal 가 된다. 즉, 산란계는 비산란계에 비하여 약 70%의 에너지가를 나타내어 이들은 체에너지가 란생산을 위해 이용되는 경우의 이용효율을 나타내는 것이라 생각된다. 5. 혈청중 T$_3$ 및 T$_4$ 측정결과 T$_4$농도는 유의차가 없는데 비하여 T$_3$ 농도는 산란계가 비산란계에 비하여 유의적으로 높았다. 6. 간추출액중 에너지 대사에 관여하는 효소, ATP citrate lyase, fructose diphosphate aldolase, isocitrate dehydrogenase 및 glutamic pyruvic transaminase활성을 측정한 결과 간추출액 1mg 1분간당 분해기질을 기준으로 할 때 측정한 4개 효소활성은 산란계가 비산란계에 비하여 유의적으로 증가한다. 그러나 간 1당 1분간 분해 기질을 기준으로 할 때 ICD와 APT citrate lyase만이 산란계의 활성이 현저히 증가하였다.

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Plasma Levels of Hormones and Metabolites as Affected by the Forages Type in Two Different Types of Crossbred Holstein Cattle

  • Chaiyabutr, N.;Preuksagorn, S.;Komolvanich, S.;Chanpongsang, S.
    • Asian-Australasian Journal of Animal Sciences
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    • 제13권10호
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    • pp.1359-1366
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    • 2000
  • An experiment was carried out to study plasma levels of hormones and metabolites of crossbred Holstein cattle during late pregnancy (28 days pre partum), early lactation (30 days post partum), mid-lactation (120 days post partum) and late lactation (210 days post partum). Two breed types of Holstein $Friesian{\times}Red$ Sindhi (50:50 = 50%HF) and Holstein $Friesian{\times}Red$ Sindhi (87.5:12.5 = 87.5%HF) were divided into four groups of four animals each. Two groups of each breed were fed with either rice straw treated with 5% urea or pangola hay (Digitaria decumbens) as the source of roughage throughout the experiments. There were a substantial increases in the mean levels of total triiodothyronine ($T_3$), insulin and glucagon at the onset of lactation, and maintained in a high levels during lactation advance for all groups of experiments. The mean levels of prolactin and thyroxine ($T_4$) were not significantly different among groups of animals, but the plasma cortisol concentration was slightly higher in both groups of 50%HF in comparison with those of 87.5%HF animals. The mean levels of plasma growth hormone (GH) of both groups of 87.5%HF animals feeding on either hay or urea treated rice straw markedly rose in the early period of lactation and markedly reduced in mid- and late lactation. These changes were accompanied with changes of milk yield. In contrast to 50%HF animals, plasma GH levels were considerably higher in the late pregnant period than in the early period of lactation and it remained constant as its value at the early lactation throughout the experimental period. The high levels of both plasma progesterone and estradiol concentration significantly declined after parturition and remained low through lactating period. The plasma glucose level in the 50%HF animals feeding on either hay or urea treated rice straw was higher than the 87.5%HF animals in all periods of experiments. Changes in plasma FFA levels of both types of crossbred animals were depended on the endocrine status during late pregnancy and lactation. The levels of plasma FFA of 50%HF animals were significantly higher (p<0.05) than those of 87.5%HF animals during late pregnancy. Both plasma ${\beta}$-hydroxybutyrate and lactate concentrations were not affected by feeding on either hay or urea treated rice straw during late pregnancy and lactation. These data demonstrate that there were no differences in the physiological performances in the same crossbred animals fed either hay or urea treated rice straw. The 87.5%HF animal has the genetic potential for a high milk yield and homeorhetic adaptation for mammary function differed from 50%HF animals during periods of lactation. Altering lactation persistency in 87.5%HF is regulated mainly by chronically acting growth hormones through the period of lactation.

Influence of Rapeseed Meal on Growth Performance, Blood Profiles, Nutrient Digestibility and Economic Benefit of Growing-finishing Pigs

  • Choi, H.B.;Jeong, J.H.;Kim, D.H.;Lee, Y.;Kwon, H.;Kim, Y.Y.
    • Asian-Australasian Journal of Animal Sciences
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    • 제28권9호
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    • pp.1345-1353
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    • 2015
  • This study was conducted to investigate the influence of dietary rapeseed meal (RSM) on growth performance, blood profiles, nutrient digestibility and economic benefit of growing-finishing pigs. A total of 120 growing pigs ($[Yorkshire{\times}Landrace]{\times}Duroc$) with an initial body weight (BW) $29.94{\pm}0.06kg$ were used in this experiment. Pigs were randomly allotted into 1 of 5 treatments in a randomized complete block design and 6 replicates with 4 pigs per pen. Treatments were divided by dietary RSM supplementation levels (0%, 3%, 6%, 9%, or 12%) in growing-finishing diets. A linear decrease (p<0.05) of BW and average daily gain (ADG) were observed at 13th wk of finishing and overall periods of pigs. Additionally, gain-to-feed ratio (G/F) tended to decrease by dietary RSM supplementation in growing-finishing diets (linear, p = 0.07 and quadratic, p = 0.08). Concentrations of serum triiodothyronine and thyroxine were not influenced by dietary RSM treatments whereas thyroid gland and liver weight were increased at 13th wk of finishing period (linear, p<0.05; p<0.01) by increasing dietary RSM supplementation level. In blood profiles, serum total cholesterol and low density lipoprotein cholesterol concentrations were not differed by dietary treatments at 13th wk of finishing period whereas concentration of serum high density lipoprotein cholesterol was affected by the supplementation level of RSM, resulting in a linear RSM level responses (p<0.05). Serum blood urea nitrogen concentration tended to decrease (linear, p = 0.07; p = 0.08) at 6th wk of growing and 13th wk of finishing periods and digestibility of dry matter tended to decrease by dietary RSM (linear, p = 0.09). Crude protein, crude fat and nitrogen retention, whereas, were not affected by dietary RSM supplementation level. In the economic analysis, feed cost per weight gain was numerically decreased when RSM was provided up to 9%. Consequently, RSM could be supplemented to growing-finishing diets up to 9% ($3.07{\mu}mol/g\;Gls$) without detrimental effects on growth performance of growing-finishing pigs.

Effects of Supplementing Brown Seaweed By-products in the Diet of Holstein Cows during Transition on Ruminal Fermentation, Growth Performance and Endocrine Responses

  • Hong, Z.S.;Kim, E.J.;Jin, Y.C.;Lee, J.S.;Choi, Y.J.;Lee, H.G.
    • Asian-Australasian Journal of Animal Sciences
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    • 제28권9호
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    • pp.1296-1302
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    • 2015
  • This study was conducted to examine the effects of supplementing brown seaweed by-products (BSB) in the diet of ruminants on ruminal fermentation characteristics, growth performance, endocrine response, and milk production in Holstein cows. In Experiment 1, the effects of different levels (0%, 2%, and 4% of basal diet as Control, 2% BSB, 4% BSB, respectively) of BSB were evaluated at 3, 6, 9, 12, and 24 h in vitro batch culture rumen fermentation. The pH tended to be higher for the higher level of BSB supplementation, with the pH at 12 h being significantly higher (p<0.05) than that of the control. The concentration of ammonia nitrogen was lower at 3, 9, 12, and 24 h incubation (p<0.05) compared with the control, and tended to be low at other incubation times. Volatile fatty acid concentration appeared to be minimally changed while lower values were observed with 4% BSB treatment at 24 h (p<0.05). In Experiment 2, effects of levels (0%, 2%, and 4%) of BSB on growth performance, endocrine responses and milk production were studied with Holstein dairy cows during transition. Dry matter intake, daily gain and feed efficiency were not affected by BSB supplementation. The concentration of plasma estrogen for the control, 2% BSB and 4% BSB after three months of pregnancy were 55.7, 94.1, and 72.3 pg/mL, respectively (p = 0.08). Although the differences of progesterone levels between BSB treatments and the control were minimal, the concentration in 4% BSB treatment increased to 157.7% compared with the initial level of the study. Triiodothyronine and thyroxine levels were also higher after both three months and eight months of pregnancy than the initial level at the beginning of the study. In addition, BSB treatments during one month after delivery did not affect daily milk yield and composition. In conclusion, the present results indicate that supplementation of BSB did not compromise ruminal fermentation, and animal performance at lower levels and hence may have potential to be used as a safe feed ingredient in dairy cows.

Effects of Dietary Dihydropyridine Supplementation on Laying Performance and Fat Metabolism of Laying Hens

  • Zou, X.T.;Xu, Z.R.;Zhu, J.L.;Fang, X.J.;Jiang, J.F.
    • Asian-Australasian Journal of Animal Sciences
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    • 제20권10호
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    • pp.1606-1611
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    • 2007
  • The experiment was conducted to investigate the effects of dihydropyridine on laying performance and fat metabolism of laying hens. Five hundred and forty laying hens, 40 weeks old, were randomly allotted to three groups, each of which included four replicates of 45 hens. The groups were given a basal corn-soybean meal diet supplemented with 0, 150 mg/kg and 300 mg/kg dihydropyridine. Results showed that compared with the control group (0 mg/kg dihydropyridine), supplements of 150 and 300 mg/kg dihydropyridine increased egg production rate by 9.39% (p<0.01) and 12.97% (p<0.01), increased mean egg weight by 3% (p>0.05) and 4.8% (p>0.05), and improved feed efficiency by 9.54% (p<0.05) and 7.25% (p<0.05), respectively; The addition of 150 and 300 mg/kg dihydropyridine decreased percentage of abdominal fat by 35.4% (p<0.05) and 46.9% (p<0.05), decreased liver fat content by 32.4% (p<0.05) and 10.5% (p<0.05), increased HSL activity of abdominal fat by 39.64% (p<0.05) and 48.48% (p<0.05), increased HSL activity of liver by 9.4% (p>0.05) and 47.34% (p<0.05) and increased the content of cAMP in adenohypophysis by 14.67% (p<0.05) and 10.91% (p<0.05), respectively; The inclusion of 150 mg/kg dihydropyridine increased liver superoxide dismutase activity by 69.61% (p<0.05), and increased hepatic apoB concentration by 53.96% (p<0.05); The supplementation of 150 or 300 mg/kg dihydropyridine decreased malondialdehyde concentration of hepatic mitochondria by 30.90% (p<0.01) and 10.39% (p<0.05), respectively; Supplemented dihydropyridine had no significant effects on TG, Ch HDL-C and VLDL-C concentrations in serum; addition of 150 or 300 mg/kg dihydropyridine increased T3 levels in serum by 15.34% (p<0.05) and 11.88% (p<0.05) and decreased insulin concentration by 40.44% (p<0.05) and 54.37% (p<0.05), respectively. The results demonstrated that adding dihydropyridine had the tendency of improving very low density lipoprotein receptor (VLDLR) content in the ovary. It was concluded that dihydropyridine could improve laying performance and regulate the fat metabolism of laying hens and that 150 mg/kg dihydropyridine is the optimum dose for laying birds in practical conditions.

한냉에 노출된 흰쥐에서 갑상선 호르몬이 체열 생산인 미치는 영향 (Effect of Cold Exposure on Thyroid Thermogenesis in Rats)

  • 황애란
    • 대한간호학회지
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    • 제13권2호
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    • pp.87-104
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    • 1983
  • It has been well documented that animals exposed to cold show increased activity of thyroid gland. The calorigenic action of thyroid hormone has been demonstrated by a variety of in vivo and in vitro studies. According to Edelman et al., the thyroid thermogenesis is due to activation of energy consuming processes, especially the active sodium transport by the hormone in target tissues. If so, the increase in thyroid activity during cold exposure should induce increased capacity of sodium transport in target tissue and the change in tissue metabolism should be precisely correlated with the change in Na+_K+_ATPase activity of the tissue. This possibility was tested in the present study: in one series, changes in oxygen consumption and Na+_K+_-ATPase activity of liver preparations were measured in rats as a function of thyroid status, in order to establish the effect of thyroid hormone on the tissue respiration and enzyme system in another series, the effect of cold stimulus on the serum thyroid hormone level, hepatic tissue oxygen consumption and Na+_K+_ATPase activity in rats. The results obtained are as follows: 1. The Na+_dependent oxygen consumption of liver slices, the oxygen consumption of liver mitochondria and the Na+_K+_ATPase activity of liver preparations were significantly inhibited in hypothyroidism and activated in hyperthyroidism. Kinetic analysis indicated that the Vmax. of Na+_K+_ATPase was decreased in hypothyroidism and increased in hyperth)'roidism. 2. In cold exposed rats, the serum triiodothyronine (T₃) level increased rapidly during the initial one day of cold exposure, then declined slowly to the control level after two weeks. The serum thyroxine (T₄) level decreased gradually throughout the cold exposure. Accordingly the T₃/T₄ratio increased. The mitochondrial oxygen consumption and the Na+_dependent oxygen consumption of liver slices increased during the first two days and then remained unchanged thereafter The activity of the Na+_K+_ATPase in liver preparations increased during cold exposure with a time course similar to that of oxygen consumption. Kinetic analysis indicated that the Vmax. of Na+_K+_ATPase increased. 3. Once the animal was adapted to cold, induction of hypothyroidism did not significantly alter the hepatic oxygen consumption and Na+_K+_ATPase activity. These results indicate that: 1) thyroid hormone increases capacities of mitochondrial respiration and active sodium transport in target tissues such as liver; 2) the increased T₃level during the initial period of cold exposure facilitates biosynthesis of Na+_K+_ATPase and mitochondrial enzymes for oxidative phosphorylation, leading to enhanced production and utilization of ATP, hence heat production.

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