PC program for comparing two regression lines over a specified finite interval

A method due to Tsutakawa and Hewett (Biometrics 34 (1978) 391-398) for comparing two regression lines over a specified, finite interval has been implemented. We describe and illustrate the procedure and program, and make the latter available to interested readers.

Effects of dietary thiouracil on thyroid activity, egg production, and eggshell quality in commercial layers

The effects of thyroid suppression induced during the rearing period by providing various dietary thiouracil (TU) regimens on plasma thyroxine (T4) concentrations, growth, and subsequent egg production (EP) and eggshell quality were determined in Single Comb White Leghorn chickens. Thiouracil was provided in the feed at levels of 0, .1, and .2% from 0 to 6 wk of age in Experiment 1, and at levels of 0, .05, and .1% from 6 to 16 wk of age in Experiment 2. In both experiments, T4 concentrations were reduced during TU treatment. However, T4 later became elevated at 12 and 20 wk in both dosage level groups in Experiment 1. Additionally, BW and egg weights were suppressed by both TU treatments, and EP was reduced up to Week 23 in the .1% TU-treated birds and through Week 25 in the .2% TU-treated birds. No effects on EP were noted in Experiment 2, but feed consumption (FC) was reduced during Week 6 in birds fed .05% TU and during Weeks 6, 10, and 19 in birds fed .1% TU. Both liver and thyroid weights were increased in .1% TU-treated birds relative to controls at Week 16. Eggshell quality was affected only in Experiment 2, in which birds given .05% TU had a higher relative conductance, or maximum rate of water loss, at Week 38 than 0 and .1% TU dosage levels, and .1% TU-treated birds had a higher breaking strength than 0 and .05% TU-treated birds at Week 22.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of the endothelin-1 gene in the rat thyroid gland and changes in its peptide and mRNA levels in goiter formation and iodide-induced involution

Endothelin-1 (ET-1) is a major vasoconstrictor peptide, first found in endothelial cells, and later in many other tissues, including the thyroid gland. We analysed the expression of the ET-1 gene in the rat thyroid gland and changes in ET-1 mRNA and peptide levels in goiter development and involution, two circumstances characterised by vascular changes. Thyroid hyperplasia was induced in adult Wistar rats by feeding a low iodine diet (LID) supplemented with 0.25% thiouracil for 10 days, and LID alone for 2 further days (H.12 group). Involution was induced by injecting 100 micrograms iodide and refeeding a normal diet during 6 h, 12 h, and 24 h (I.6h, I.12h, I.24h groups). Rats fed a normal iodine diet were used as controls. A specific 488 bp cDNA corresponding to the known sequence of pre-pro ET-1 was found by RT-PCR from RNA extracts in all thyroid experimental groups, as well as in lung and kidney which were used as positive controls. RP-HPLC analysis showed that ET-1 immunoreactivity eluted similarly as mature ET-1. During hyperplasia, ET-1 mRNA and peptide levels were increased 3.5- and 5-fold respectively. The relative volume of the vascular bed was more than doubled. During iodide-induced involution, the glandular ET-1 mRNA level remained elevated. The concentration of ET-1 peptide increased and was significantly greater at 12 h involution than in the H.12 group. At this time, the capillary reticulum reverted to individual capillaries and the vascular bed was significantly reduced. These data demonstrate that the ET-1 gene is expressed in the rat thyroid gland and that the ET-1 mRNA and peptide levels are increased during thyroid hyperplasia and remain elevated during a phase of rapid iodide-induced involution. These data suggest that changes in ET-1 production may play a role in control of thyroid gland trophic regulation and vascularity.

Assessing the effect of a treatment when subjects are growing at different rates

The analysis of covariance is often used in the context of premeasure/postmeasure designs to compare treatment and control groups in both randomized [1] and nonrandomized [2] studies. The intent is to adjust the difference between the changes in the 2 groups for any difference which might exist at baseline, i.e., for any difference between the premeasures in the 2 groups. An important assumption underlying the use of the analysis of covariance is that the slopes of the lines for the regression of the postmeasure on the premeasure in the 2 groups are equal. In this paper we describe a program which can be used to test the hypothesis of equal slopes; and performs an alternative analysis which does not depend on this assumption. This is done in the context of comparing treatment and control groups with respect to a measurement subject to natural maturation as in [3]. Equal slopes in this context means equal growth rates; unequal slopes implies that the 2 groups are growing at different rates. The method, known as the Johnson-Neyman procedure [4] is, however, more general than this, and can be used in any two-sample comparison where an alternative to the usual analysis of covariance is deemed appropriate. The procedure identifies a 'region of significance' which is especially useful in practice. This region consists of a set of values of the premeasure for which the treatment and the control groups are significantly different with respect to the postmeasure.

1-Aryl-2-amino/hydrazino-4-phenyl-1,6-dihydro-1,3,5-triazine-6-thione and related thiocarbamides/thiosemicarbazides as antithyroidal agents

Different 1-aryl-2-benzylmercapto-4-phenyl-1,6-dihydro-1,3,5-triazine-6- thiones have been synthesized by known methods. These triazines on treatment with ammonia/hydrazine hydrate afforded the corresponding 1-aryl-2-amino/hydrazino-4-phenyl-1,6-dihydro-1,3,5-triazine-6-thiones which on treatment with arylisothiocyanates afforded the related thiocarbamide/thiosemicarbazides. Some of these compounds show appreciable antithyroidal activity.

Structure-activity relationship of nucleobase ligands of uridine phosphorylase from Toxoplasma gondii

Seventy-nine nucleobase analogs were evaluated as potential inhibitors of Toxoplasma gondii uridine phosphorylase (UrdPase), and the apparent Ki (appKi) values for these compounds were determined. Based on the inhibition data, a structure-activity relationship for the binding of nucleobase analogs to the enzyme was formulated, using uracil as a reference compound. Two compounds were identified as very potent inhibitors of T. gondii UrdPase, 5-benzyloxybenzylbarbituric acid and 5-benzyloxybenzyluracil, which had appKi values of 0.32 and 2.5 microM, respectively. A comparison of the results from the present study, with similar studies on mammalian UrdPase and thymidine phosphorylase (dThdPase) (Niedzwicki et al., Biochem Pharmacol 32: 399-415, 1993) revealed that there are both similarities and differences between the catalytic site of T. gondii UrdPase and the catalytic sites of the mammalian enzymes with respect to binding of uracil analogs. One compound, 6-benzyl-2-thiouracil, was identified as a potent, specific inhibitor (appKi = 14 microM) of T. gondii UrdPase, relative to mammalian UrdPase and dThdPase.

Synthesis and antimicrobial properties of S-substituted derivatives of 2-thiouracil

The synthesis of 24 new 2-alkylthio and 2-(E)-N-thioalkyl-4-azachalkonyl substituted derivatives of uracil and their antimicrobial activity are reported. In particularly compounds 6o and 6p showed a good antibacterial activity against Staphylococcus aureus and Streptococcus faecalis.

Inhibition of lipid deposition in the hypercholesterolemic rat by clentiazem, a calcium channel blocker

We studied the effects of clentiazem, a calcium channel blocker (1) on the accumulation of lipid in the aorta, (2) on the level of plasma lipids, and (3) on the number of adherent intimal monocytes and foam cells. Seventy Wistar rats were assigned to one of the following groups: (1) regular diet, (2) an atherogenic diet consisting of regular chow with 2% cholesterol, 1% cholic acid, and 0.5% thiouracil (CCT), (3) CCT supplemented with 5 mg/kg/day clentiazem, and (4) CCT with 25 mg/kg/day clentiazem. Animals were sacrificed after 6 or 12 weeks of diet. Aortas were studied by light microscopy after staining with oil red O (ORO) and/or hematoxylin. ORO staining was quantified in both abdominal and thoracic regions of the aorta. The aortas of the clentiazem groups demonstrated significantly less ORO staining than CCT diet controls in thoracic aorta after 6 weeks and abdominal aorta after 12 weeks. There was no significant difference in the plasma lipid concentrations. The clentiazem-treated groups had fewer numbers of adherent monocytes and foam cells. We conclude that clentiazem inhibits lipid deposition in cholesterol-fed rats without lowering plasma lipid concentrations and that the number of intimal monocytes and foam cells is decreased in the presence of this calcium antagonist.

Kinetics of inhibition of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase by the novel HIV-1-specific nucleoside analogue [2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-3'-spiro-5 "- (4"-amino-1",2"-oxathiole-2",2"-dioxide)thymine (TSAO-T)

[2',5'-Bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-3'-spiro- 5"-(4"-amino-1",2"-oxathiole-2", 2"-dioxide)thymine (TSAO-T) is a representative of a novel class of nucleoside analogues that are endowed with a potent and specific activity against human immunodeficiency virus (HIV) type 1 and are targeted at the HIV-1 reverse transcriptase (RT). Inhibition of HIV-1 RT by TSAO-T was reversible and noncompetitive with respect to dGTP as the substrate and poly(C).oligo(dG) as the template/primer. In contrast with the nonnucleoside derivatives tetrahydroimidazo-[4,5,1-jk][1,4]- benzodiazepin-2(1H)-thione (TIBO) (R-82150), nevirapine (BI-RG-587) and the HEPT derivative I-HEPU-SdM, TSAO-T was not inhibitory to HIV-1 RT in the presence of other homopolymeric template/primers. It did not interfere with the DNA-dependent DNA polymerase function of HIV-1 RT, HIV-2 RT, herpes simplex virus type 1 DNA polymerase, or Taq polymerase. However, TSAO-T proved inhibitory to the HIV-1 RT reaction primed by Escherichia coli 16S/23S rRNA, irrespective of the nature of the radiolabeled 2'-deoxynucleotide 5'-triphosphate (dNTP) used. TSAO-T does not act as a DNA chain terminator. It interacts with HIV-1 RT at a nonsubstrate (dNTP)-binding site.

The pituitary-thyroid axis effects on ocular and orbital tissues: a histological, histochemical, and morphometric study

This work tests the notion that the effect of thyroid hormone on orbital and ocular tissues is mediated through its action on their lysosomal enzymes. Hyperthyroidism was produced in guinea pigs by thyroxin and TSH; hypothyroidism was induced by thiouracil. After treatment for 10 to 21 days, several ocular and orbital tissues were taken for histological, morphometrical, and histochemical examinations. High acid phosphatase activity was demonstrated in extraocular muscles, optic nerve and the retinal pigment epithelium of thyroxine- and TSH-treated animals. The findings fit the notion that the effects of thyroid hormones are mediated through lysosomes also in ocular and orbital tissues.

Elimination of the antiviral drug 5-ethyl-2'-deoxyuridine by the isolated perfused rat liver

The elimination of the antiviral drug 5-ethyl-2'-deoxyuridine (EdUrd) by the isolated perfused rat liver was investigated. EdUrd (3.9-39 mumol) was injected into the perfusion reservoir and serial samples were collected for HPLC determination of EdUrd and its metabolites 5-ethyluracil (EUra) and 5-(1-hydroxyethyl)uracil (HEUra). At each dosage level, semilogarithmic plots of concentration vs. time showed apparent first order disappearance of EdUrd. However, with increasing dose, there was a progressive increase in EdUrd half-life from 18.9 to 36.4 min and decrease in total clearance from 5.5 to 2.5 ml/min, indicating dose-dependent elimination. Dose dependence was confirmed by the lack of superposition of logarithm concentration/dose vs. time plots obtained with different doses. After EdUrd administration, the concentration of EUra reached a peak value in about 1 hr, and then gradually decreased. The concentration of HEUra, which was initially much lower than that of EUra, increased throughout the experiment and appeared to approach a plateau at 2-3 hr. Biliary excretion of each ethylpyrimidine was negligible. 6-Benzyl-2-thiouracil, a thymidine phosphorylase inhibitor, slowed the disappearance of EdUrd and decreased the peak concentrations of EUra and HEUra. Cimetidine, a cytochrome P-450 inhibitor, had little effect on the rate of EdUrd disappearance, but caused a large increase in the peak EUra concentration and decrease in HeUra concentration. 3-Methylcholanthrene, a cytochrome P-450 inducer, increased the formation of HEUra but had little effect on the rate of EdUrd disappearance. The results indicate that the hepatic elimination of EdUrd is dose-dependent and involves an initial cleavage to EUra, which is then oxidized to HEUra.

Kinetics of equilibration of radioiodide in individual mouse thyroid follicles in vivo

Microdensitometric measurements were made on autoradiographs of radioiodide localized in mouse thyroids subjected to various degrees of stimulation, in which the formation of organic radioiodide was acutely blocked. Estimates were made of the relative concentrations of radioiodide in lumens and cells of follicles and in the nearby blood vessels. Simple models were introduced to interpret the data. Analysis of the ratio of radioiodide concentrations in the lumen and cells of follicles as a function of follicles size and time after injection indicated that smaller follicles equilibrated faster than larger follicles, that the equilibration was faster the more active the gland was, and that the release of radioiodide from follicles in the less active glands must be characterized by a time-dependent exit rate constant. Analysis of the relative concentration of luminal radioiodide as a function of follicle size at short time intervals and in the steady state indicated that the transport properties of the average epithelial cell were generally independent of follicle size.

Relationship of thyroid status to growth hormone and insulin-like growth factor-I (IGF-I) in plasma and IGF-I mRNA in liver and skeletal muscle of cattle

Steers were made hyperthyroid or hypothyroid to study the effects of physiological alterations in thyroid hormone status on plasma growth hormone (GH) profiles, plasma insulin-like growth factor-I (IGF-I) concentrations, and relative abundance of IGF-I mRNA in skeletal muscle and liver. Eighteen yearling crossbred steers (360 to 420 kg) were randomly allotted to hyperthyroid (subcutaneous injection 0.6 microgram/kg BW L-thyroxine for 10 d), hypothyroid (oral thiouracil; 0.25% diet plus 12.5 g capsule/d for 17 d), or control (subcutaneous injection 0.9% NaCl) treatment groups. Blood samples were taken for measurement of GH, IGF-I, thyroxine (T4) and triiodothyronine (T3) by RIA. Samples of liver and skeletal muscle were taken by biopsy for measurement of IGF-I mRNA by solution hybridization. Steers receiving thiouracil had 57 and 53% (P less than .05) lower T4 and T3, respectively, than control steers (84.1 and 1.7 ng/ml). The hyperthyroid steers had 228 and 65% greater (P less than .05) T4 and T3 than control steers. Neither increased nor decreased thyroid status had any significant effects on plasma GH profiles, liver IGF-I mRNA, or plasma concentration of IGF-I. There was no effect of thyroid hormone alteration on skeletal muscle IGF-I mRNA concentrations. The results of this study suggest that short-term changes in thyroid status of cattle had no major impact on the GH-IGF-I axis or skeletal muscle IGF-I mRNA.

Influence of diet-mediated maternal thyroid alterations on hatchability and metabolism of turkey embryos

Large White turkey breeder hens from a strain exhibiting poor hatchability were fed thyroid-altering diets. The following dietary treatments were fed to randomized groups of hens for 15 wk of egg laying: 1) 16.5% protein turkey breeder diet (control), 2) the control diet containing 2.1 ppm supplemental iodine, 3) the control diet containing .1% thiouracil, and 4) the control diet containing .5 ppm triiodothyronine (T3). Blood samples were taken from hatching embryos from hens fed each diet. Embryonic hearts and livers were weighted prior to and during pipping as well as after hatching. Blood plasma was analyzed for thyroxine (T4), T3, and glucose. Livers were assayed for glucose-6-phosphatase activity. Supplemental maternal dietary iodine elevated embryonic T4 concentrations prior to pipping. Dietary T3 and iodine increased hepatic glucose-6-phosphatase activity and blood plasma glucose concentration prior to pipping. Feeding thiouracil increased embryonic liver weights but decreased heart and body weights. Blood plasma T4 was elevated in embryos from hens fed thiouracil but blood glucose levels were depressed because of a lack of increased glucose-6-phosphatase activity. Feeding iodine decreased the enzyme activity at internal pipping. It is suggested from the data that maternal thyroid metabolism may influence hatchability via embryonic thyroid and carbohydrate metabolism during hatching.

Effects of selection on plasma thyroxine concentrations in Japanese quail under thiouracil and protein stress

Three experiments were conducted to measure changes in plasma thyroxine (T4) concentrations occurring in male and female Japanese quail in response to treatment with dietary thiouracil (TU) and different CP levels prior to sexual maturity and to determine the influence of selection for growth under TU and protein stress on this response. Selected and unselected lines of quail were fed diets containing .2% TU or two levels of CP (20 or 28%) or both from 0 to 4 wk of age. Body weight and plasma T4 were measured at 5, 7, and 9 wk of age in Experiments 1 and 2. In Experiment 3, body weight was measured at 2, 4, 5, 7, and 9 wk and T4 at 4, 7, and 9 wk. Thiouracil inhibited growth to a greater degree than did decreased dietary CP. However, offspring from selected quail were more resistant to dietary TU when selection diets contained TU. When fed as part of a selection regimen rather than to unselected birds, low CP, TU diets inhibited body weight increase to a greater degree and longer after birds were returned to control diets. Thyroxine concentrations between 4 and 9 wk were affected by TU but not by CP level. Thiouracil significantly reduced T4 during treatment; however, T4 was elevated by 3 wk after cessation of TU treatment. Increases in T4 were greater and more immediate in selected than in unselected birds. These findings reveal the ability of quail to compensate for thyroid suppression after TU is removed from the diet and the influence of selection on this compensatory response.

Photosensitized damage to supercoiled plasmid DNA induced by 334-nm radiation in the presence of 2-thiouracil consists of alkali- and piperidine-labile sites as well as frank strand breaks

A covalently closed, supercoiled plasmid was irradiated with 334-nm ultraviolet radiation in the presence of the naturally occurring photosensitizer 2-thiouracil (s2Ura). After irradiation, some DNA samples were treated to reveal labile sites. Agarose gel electrophoresis was then used to resolve the unrelaxed supercoils from the relaxed forms, and the DNA bands were quantitated by fluorescence scanning. Irradiation of the plasmid in the absence of s2Ura induced small numbers of frank DNA strand breaks (FSB), alkali-labile sites (ALS), and piperidine-labile sites (PLS). The induction of each of these lesions was enhanced 30 times when s2Ura was present during aerobic irradiation. Anoxia, as well as the hydroxyl radical scavengers acetate and formate, inhibited the formation of all three lesion types. The relative proportions of the three lesion types produced by several DNA damaging treatments were measured. Hydrogen peroxide, gamma-irradiation, and s2Ura photosensitization produced nearly identical damage proportions, with PLS: FSB ratios of 1.25:1, 0.78:1, and 0.84:1, respectively. Treatment with singlet oxygen [data from Blazek et al. (1989) Photochem. Photobiol. 48, 607-613] produced much different proportions, with a PLS:FSB ratio of 4.1:1. These results may indicate a role for hydroxyl radical in s2Ura-photosensitized DNA damage.

Stimulation of oxidative metabolism by thyroid hormones in an apodan amphibian, Gegenophis carnosus (Beddome)

Administration of different doses of L-thyroxine (T4) and triiodo-L-thyronine (T3) in vivo in G. carnosus stimulated the activities of cytochrome oxidase, alpha-glycerophosphate dehydrogenase (alpha-GPDH), succinate dehydrogenase (SDH), and Mg2+ adenosine triphosphatase (Mg2+ ATPase) and inhibited the activity of malate dehydrogenase (MDH). While a low dose of thiouracil administration produced a stimulatory effect on cytochrome oxidase and alpha-GPDH activities, a higher dose of thiouracil significantly inhibited the activities of cytochrome oxidase, alpha-GPDH, SDH, Mg2+ ATPase, and MDH. Injection of T4 or T3 into thiouracil-treated animals significantly restored the stimulatory effect of thyroid hormones on oxidative enzyme activities. It is suggested that thyroid hormones in vivo increase and that thiouracil decreases the oxidative capacity of hepatic mitochondria of G. carnosus.

Ribose-transfer activity from uridine to 5-fluorouracil in Ehrlich ascites tumor cells

Anabolism of 5-fluorouracil (5-FU) in the presence of uracil was examined using the cell-free extract of Ehrlich ascites tumor cells. FU-nucleoside formation from 5-FU with ribose 1-phosphate (R-1-P) or 2'-deoxyribose 1-phosphate was not readily inhibited even by the addition of uracil at 100 times higher concentration than 5-FU. FU-nucleotide formation from 5-FU with R-1-P and adenosine 5'-triphosphate or with 5-phosphoribosyl 1-pyrophosphate was slightly reduced as the concentration of uracil was increased. It was also found that 5-fluorouridine (5-FUR) was produced by "nucleoside N-ribosyltransferase," transferring a ribose moiety from uridine (UR) to 5-FU directly. This activity might play a role in the preferential formation of 5-FUR. However, 5-fluoro-2'-deoxyuridine was not produced by directly transferring a deoxyribose moiety. On the basis of several column chromatographies and characterization of kinetics, pH dependency, and response to inhibitors, the enzyme protein of the ribosyltransferase could not be distinguished from that of the phosphorylase.

The statistical analysis of a carcinogen mixture experiment. III. Carcinogens with different target systems, aflatoxin B1, N-butyl-N-(4-hydroxybutyl)nitrosamine, lead acetate, and thiouracil

This paper describes factorial experiments designed to determine whether two carcinogens that lead to cancers in different organ systems act synergistically to produce cancers in Fischer 344 rats. Four carcinogens, aflatoxin B1 (AFLA), N-butyl-n-(4-hydroxybutyl)nitrosamine (NBBN), lead acetate (LA), and thiouracil (THIO) were studied in pairwise combinations. Each of the six possible pairs were studied by means of a 4 X 4 factorial experiment, each agent being fed at zero and at three non-zero doses. Methods of analysis designed explicitly for this study were derived to study interaction. These methods were supplemented by standard statistical methods appropriate for single agent studies. Neither synergism nor antagonism was demonstrated in these combined exposure studies. Findings for male and female animals were consistent.

In vitro thymidine uptake and incorporation into thymic and bursal lymphocytes from young hypothyroidic chickens

Experiments were conducted to evaluate the ability of thymic and bursal lymphocytes from hypothyroidic chicks to take up 3H-thymidine. To produce hypothyroidism, chicks were fed a diet containing thiouracil (0.1%) from day of hatch to 3 weeks of age. At 1, 2 and 3 weeks of age, body weights were significantly lower for hypothyroid chicks, and at 2 and 3 weeks of age, the relative weights of the thymus and bursa were significantly less than those of controls. Furthermore, chicks treated with thiouracil had significantly lower serum concentrations of 3,5,3'-triiodothyronine (T3) and thyroxine (T4). Thymic cells from hypothyroid chicks incorporated less 3H-thymidine at 1 and 3 weeks of age as assessed by liquid scintillation counting and autoradiography. Liquid scintillation counts for labeled bursal cells from hypothyroid chicks were not lower at 1 week of age, but the counts were lower at 3 weeks of age. Autoradiographic studies with bursal cells revealed that 3H-thymidine incorporation was less, but not significantly less, in medium-size lymphocytes from thiouracil-treated chicks at both 1 and 3 weeks of age. Thymidine incorporation into large bursal cells was affected more by thiouracil treatment at 1 than 3 weeks of age.

Effect of hypothyroidism on methylmalonate excretion and hepatic vitamin B-12 levels in rats

The effect of hypo- and hyperthyroidism on vitamin B-12 metabolism in the rat was studied by measuring methylmalonic acid excretion, B-12 content of liver and oxidation of 2-[14C]histidine. Ten percent pectin was added to increase severity of B-12 deficiency. The addition of thiouracil to a diet containing 10% pectin decreased the excretion of methylmalonic acid suggesting an amelioration of the B-12 deficiency. It was found that part of this decreased methylmalonic acid excretion was due to a decreased food consumption with a correspondingly decreased intake of branched-chain amino acids which are precursors of methylmalonic acid. When attempts were made to increase the protein intake of animals receiving thiouracil so their amino acid intake was equal to that of the control animals, methylmalonic acid excretion was still lower than that of the controls. It was also found that the vitamin B-12 content of the liver was higher in the animals receiving thiouracil than in the controls. Thyroidectomy had the same effect as feeding thiouracil. Liver B-12 levels are rapidly depleted on a B-12 deficient diet containing 10% pectin. It appears that hypothyroidism, induced either by thyroidectomy or by feeding thiouracil, slows the rate of depletion of hepatic B-12 which in turn facilitates the metabolism of methylmalonic acid and decreases its excretion in the urine.

Effect of thiouracil in modifying folate function in severe vitamin B12 deficiency

The effects of thiouracil in correcting defects in folic acid function produced by B12 deficiency were studied. Addition of the thyroid inhibitor, thiouracil, to a low methionine diet containing B12, increased the oxidation of [2-14C]histidine to carbon dioxide, and increased liver folate levels. Addition of 10% pectin to the diet accentuated B12 deficiency as evidenced by a greatly decreased rate of histidine oxidation (0.19%) and an increased excretion of methylmalonic acid. Addition of thiouracil to the diet restored folate function as measured by increased histidine oxidation and increased liver folate levels similar to that produced by addition of methionine to a B12-deficient diet. Thiouracil decreased methylmalonate excretion, and increased hepatic levels of B12 in animals on both B12-deficient and -supplemented diets. Hepatic methionine synthase was increased by thiouracil, which may be the result of the elevated B12 levels. S-Adenosylmethionine and the enzyme methionine adenosyltransferase were also increased by thiouracil. Thus it is possible that the effect of thiouracil in increasing folate function consists both in the effect of thiouracil in decreasing levels of methylenetetrahydrofolate reductase, and also in its action in increasing S-adenosylmethionine which exerts a feedback inhibition of this enzyme.

Avian thyroid isthmus

An avian equivalent of the mammalian thyroid isthmus appeared in thiouracil-treated (.1% in feed nd hatching to 6 and 8 weeks of age) chickens. In two experiments in which chickens were fed a diet containing thiouracil, thyroid tissue was found connecting the thyroid glands. Histological examination of the connecting tissue revealed that it was of the same cellular composition as the thyroid glands.

Analogues of pyrimidine base precursors as antiphytoviral agents

Dihydroorotic acid hydrazide (DHOH) did not inhibit the replication of potatovirus X (PVX) in leaf disks of Nicotiana tabacum 'Samsun'. In contrast, 5-fluoroorotic acid (5-FOA) completely inhibited the replication of PVX, as demonstrated by a serological virus assay as well as a local lesion bioassay using Gomphrena globosa as the test plant. The corresponding base analogue 5-fluorouracil (5-FU) had only a weak inhibitory effect. Time-course inhibition experiments in synchronized virus-infected leaf disks led us to conclude that 5-FOA, as well as 5-azadihydrouracil (5-ADHU), an uracil catabolite analogue, inhibit the same early event in virus infection. Neither 5-FOA nor 5-ADHU had a direct inactivating effect on free PVX virions.

The chemical induction of PR (b) proteins and resistance to TMV infection in tobacco

Aspirin injected into Xanthi-nc tobacco leaves induces the production of PR protein and resistance to TMV. The concentration of PR protein and resistance increases with increasing aspirin concentration, up to a plateau. 2-Thiouracil and dioxohexahydrotriazine also induce PR protein when injected into tobacco leaves. Barium and manganese salts induced PR protein, but those of eight other cations did not. Certain salts were phytotoxic but did not induce PR protein, confirming that the production of PR protein is not a non-specific stress response.

Avian hepatic T3 generation by 5'-monodeiodination: characterization of two enzymatic pathways and the effects of goitrogens

The enzymatic nature of 5'-monodeiodination (5'-D) in avian liver homogenates was demonstrated by abolishment of activity by iopanoic acid (IOP). T3 production from T4 was dependent on enzyme and substrate concentrations, incubation time, incubation temperature, and pH. Two pathways of 5'-D activity were present in avian liver and exhibited characteristics similar to those described in mammalian tissues. Type II activity was identified as propylthiouracil (PTU)-insensitive activity. Type I (PTU-sensitive) was determined by difference between Total and Type II. Km values were 1.58 microM T4 for Total activity and 0.90 nM T4 for Type II, corresponding to the characteristics of the mammalian pathways. The effects of goitrogens on avian hepatic 5'-D were equivalent to those reported for the mammalian enzyme.

Synthesis of 6-anilino-2-thiouracils and their inhibition of human placenta iodothyronine deiodinase

Several 6-anilino-2-thiouracils were synthesized and tested for their ability to inhibit the inner-ring iodothyronine deiodinase from human placenta. The p-ethyl and p-n-butyl analogues were strongly inhibitory to the enzyme and were much more effective than the standard deiodinase inhibitor, 6-propyl-2-thiouracil. The degree of inhibition caused by 6-(p-n-butylanilino)-2-thiouracil was, moreover, unaffected by high concentrations of reducing agent in the enzyme assay. Attempts to prepare 3-alkyl derivatives via S-debenzylation of 2-benzylthio intermediates led to rearrangement to, for example, 3-methyl-5-benzyl-6-amino-2-thiouracil. This compound also strongly inhibited the deiodinase reaction. Preliminary results suggest that these compounds are useful to study in vitro and in vivo metabolism of thyroid hormones and may be clinically useful to enhance the availability of active thyroid hormones to certain organs.

Effect of thiouracil-induced hypothyroidism on the humoral immunity of New Hampshire chickens

Two experiments were conducted to examine the effects of feeding a diet containing .1% thiouracil to two lines of New Hampshire chickens differing in growth rate and relative bursa size. Body weight, serum 3,5,3'-triiodothyronine, and thyroxine were reduced by the thiouracil treatment. The primary total anti-sheep red blood cell (SRBC) titer in Experiment 1 was higher for thiouracil-fed (TF) chicks at 7 days postprimary immunization (PPI). In Experiment 2, the total anti-SRBC titers were higher for control chicks 3 days PPI; but from 5 to 10 days PPI, TF chicks had higher titers. During the secondary response in both experiments, the total anti-SRBC titers were not consistently higher for one dietary group over the other from 3 to 10 days postimmunization. Mercaptoethanol-resistant antibody titers were not significantly different between the two dietary groups in either experiment during the primary and secondary responses. Thiouracil-fed chicks had higher immunoglobulin G (IgG) and M (IgM) concentrations in serum during both the primary and secondary responses in Experiment 2. Although there was no genotype effect on antibody production to SRBC, serum immunoglobulins were different between lines. Small bursa line (SBL) chickens had higher serum IgG while the IgM concentrations of chicks from the Lester J. Dreesen strain were greater than those of SBL.

Thyroid and adrenal response to heat stress in chickens and quail differing in heat tolerance

Three experiments were conducted to evaluate the thyroid and adrenal response in groups of birds with altered heat tolerance. Groups of chickens that had been handled on each of 4 days and a nonhandled control group were bled on the 5th day with or without heating for 1 hr at 50 C. Handling did not affect the thyroid response as indicated by thyroxine (T4) or triiodothyronine (T3) levels. Corticosterone levels were lower in handled birds than nonhandled birds after heating. In a second experiment, groups of broilers were fed a diet containing .2% thiouracil or a control diet. After 2 weeks they were bled either with or without 1 hr of heating at 50 C. The T3 and T4 levels were reduced by thiouracil feeding both with and without heating, but adrenal function was not affected. In Experiment 3, T3 and T4 levels were compared for four lines of Japanese quail. The nongrowth-selected line had higher T3 and T4 levels than growth-selected lines but did not have elevated levels of T3 or T4 in response to heat stress. The growth-selected lines (T, S, and P) responded to heating with increased T3 and T4 levels. Levels of T4 in Line T (selected on a thiouracil diet) after heating were significantly higher than all other lines.

Depressed hypothalamic CRF immunoreactivity in 15 day old thiouracil-treated rats

Depression of thyroid status with thiouracil has been shown to delay the response of the hypothalamus-pituitary-adrenal axis to stress in young rats. In vivo and in vitro bioassay studies have indicated that the hypothalamus is the main site of axis alteration in 15 day old animals. The present study has found a significantly depressed hypothalamic content of immunoassayable corticotropin-releasing factor (CRF) in thiouracil treated young rats.

The concerted effects of thyroid function and dietary protein on growth and protein metabolism in mice at different growth stages

The effects of thyroxine (T4) and thiouracil (TU) on growth and protein metabolism were examined in male mice given diets containing different levels of protein (casein) at two different growth stages (25 and 60 days old). Changes in protein metabolism were assessed from the expiratory 14CO2 from [U-14C]leucine injected, the liver nucleic acid contents and the rates of synthesis and degradation of liver protein estimated by single injection method using [6-14C]arginine. Each mouse, excluding the control group, received daily intraperitoneal injection of 10 micrograms of L-thyroxine sodium salt per 100 g b.w. (T4 group) or were given a diet containing 0.05% 2-thiouracil (TU group). In the 25-day-old mice, growth of the T4 group was accelerated at protein levels above 15% and that of the TU group was severely retarded at protein levels below 10%. On the other hand, in the 60-day-old mice, growth of the TU group tended to be accelerated at protein levels from 10% to 25%, while it was significantly retarded at the 5%-protein level. The expiratory 14CO2 increased when the growth was retarded, and decreased when growth was accelerated by T4 or TU in both age groups, but was not significant in either case. The nucleic acid content of the liver was increased by both T4 and TU when the dietary protein level was above 15%. The rate of protein synthesis was increased, but not significantly, by T4, while it was not affected by TU. The rate of protein degradation was increased, but not significantly, by TU, while it was not affected by T4 in the 25-day-old mice. In the 60-day-old mice, the rates of both liver-protein synthesis and degradation were significantly increased by TU, while they were not affected by T4. These results definitely indicate that the growth stage and the dietary protein level change the effects of thyroid function on growth protein metabolism of mice.

dCMP-aminohydrolase activity during early sea urchin development. An example of negative enzyme control during embryogenesis

In sea urchin, unfertilized eggs have a very high level of dCMP-aminohydrolase (dCMPase) activity, which decreases gradually and at the pluteus stage it is only about a quarter of that found in the unfertilized egg. But in abnormal embryos and in disaggregated cells from embryos, no decrease in the dCMPase activity takes place. To understand the control mechanism involved in this enzyme activity during development, we have analyzed the effect of various drugs which interfere with information transfer, such as actinomycin C, puromycin, 5-azacytidine, 2-thio-uracil and p-fluoro-DL-phenylalanine on dCMPase activity in embryos of Paracentrotus lividus and Sphaerechinus granularis. Among these drugs only actinomycin induces a remarkable increase of the dCMPase activity in embryos with respect to unfertilized eggs. Puromycin has a differential and dose-dependent effect. Other drugs, although they affect normal development and macromolecular synthesis, do not significantly alter the dCMPase activity. On the basis of these results we suggest the presence of a repressor mechanism in the control of dCMP-aminohydrolase level during early embryogenesis of sea urchin.

Long-term effects of triiodothyronine and thiouracil on myocardial beta-adrenergic receptor numbers and cyclic AMP concentration in rats

Long-term (35 days) effects of thyroid hormone on the number of myocardial beta-adrenergic receptors and the c-AMP concentration were studied in the rat. The ventricles from triiodothyronine-administered rats (T3 rats) showed an increase in the number of beta-receptors compared to controls (54.3 +/- 3.1 vs 39.3 +/- 1.8 fmole of [125I]-iodohydroxybenzylpindolol (IHYP) binding sites/mg protein p less than 0.001) on the 35th day. Conversely, the ventricles from thiouracil-administered rats (TU rats) showed a decrease in the number of beta-receptors compared to controls (31.4 +/- 1.6 vs. 38.4 +/- 2.6 fmole/mg protein, p less than 0.05). The equilibrium dissociation constants (Kd) for the interaction of receptors with IHYP did not differ significantly (0.10 to 0.15 nM). The myocardial concentration of cyclic AMP was not significantly different (T3 rats, 1.09 +/- 0.09 nM/g wet weight tissue; T3 controls, 1.12 +/- 0.07; TU rats, 1.13 +/- 0.07; TU controls, 1.16 +/- 0.12) on the 35th day. On serial effects of triiodothyronine from the first to the 35th day, the number of beta-receptors of T3 rats increased significantly on the 24th and the 35th day, but the c-AMP concentration was not significantly different from that in control rats. These results demonstrated that thyroid hormone affects the number of myocardial beta-receptors in rats, and suggested a different mechanism of action of thyroid hormone on the myocardium from that of catecholamines.

Mode of action of the antiphytoviral compound 2,4-dioxohexahydro-1,3,5-triazine (5-azadihydrouracil)

The time course of inhibition of potato virus X ( PVX ) synthesis by the newly developed antiphytoviral compound 2,4- dioxohexahydro -1,3,5-triazine (DHT) was determined in mechanically inoculated leaves of Nicotiana tabacum L. cv. ' Samsun '. At the permissive temperature (22 +/- 3 degrees) DHT inhibited the synthesis of PVX almost 100% within 8 h postinoculation, after which the inhibition declined. In leaves maintained at a temperature of 5 +/- 2 degrees for 5 days, DHT inhibited PVX synthesis about 65% immediately after the shift to permissive temperature. This time course of inhibition was almost identical to that of 2-thiouracil. Uracil completely overcame the inhibition of PVX replication caused by DHT when added within 2 h after incubation of leaf disks with DHT. These results indicate that DHT acts as an analogue of the pyrimidine base uracil.

Perinatal thiouracil exposure depresses corticotropin-releasing factor activity in 15 day old rats

Although previous in vivo studies have shown thiouracil to delay maturation of the hypothalamus-pituitary-adrenal (HPA) axis response to stress, the nature of the developmental deficit was not determined. By in vitro methods we determined which HPA components are influenced by thiouracil-induced hypothyroidism in 15 day old rats. Our results indicate that adrenal response to ACTH stimulation and adenohypophysial ACTH content were not significantly modified by thiouracil exposure. On the other hand, the corticotropin-releasing factor-like activity of median eminence extracts was severely depressed by thiouracil-induced hypothyroidism. Thus, the delayed maturation of functional capacity of the central nervous system caused by hypothyroidism includes synthesis of biologically active corticotropin-releasing factor.

Effect of thiouracil on response to heat stress of White Leghorn lines selected for fast and slow gain in two temperatures

Four lines of White Leghorns previously selected for fast and slow gain from 5 to 9 weeks of age in a hot (32.2 C) and in a cold (21.1 C) selection environment were grown from 5 to 9 weeks in the same two temperature environments. Samples of 32 females from each line of the third generation grown in each temperature environment from 5 to 9 weeks of age were divided into two groups; one received .2% thiouracil in the diet for a 5-day period and the other did not. The temperature was then increased to 40.6 C until 52.8% of all birds had died. The percentages of mortality of lines, rearing environments, and thiouracil treatments were then analyzed. An increase of 64.8% mortality from acute heat stress for birds reared in the cold environment was significant, but the differences among the four selected lines were not. The presence of thiouracil in the diet significantly reduced mortality from heat stress by 16.4%. There were no significant interactions between thiouracil treatments and selected lines or rearing environments.

Capillary endothelial cell multiplication in adipose tissue pads on the thyroid during the feeding of thiouracil

It has been reported that blood capillaries in adipose tissue pads on the upper and lower poles of the thyroid gland enlarge when Fischer rats are fed thiouracil (TU) in a low iodine diet. To test whether the enlargement is accompanied by proliferation of the endothelial cells, [3H]thymidine was injected into rats fed the TU-containing diet, and labeling of the endothelial cells was studied by autoradiography. Nuclear labeling of the capillary endothelial cells was observed in the mixed brown and white adipose tissue (BAT and WAT, respectively) pads on the thyroid. After a single pulse of [3H]thymidine, 10% of the nuclei were labeled at 10 days (the peak labeling), and labeling decreased thereafter. To test whether the adipose tissue was stimulated because of the poor nutritional quality of the low iodine diet, Purina Laboratory Chow (a nutritionally adequate diet) was tested and produced the same result. To test whether TU had a direct effect, 5 micrograms T4/100 g BW were given daily; there was then no response to the TU, suggesting that the effect was due to an elevated circulating concentration of TSH. The effect was generally restricted to the adipose tissue pads on the thyroid. There was no response in interscapular BAT, epididymal WAT, or sc WAT. However, there was a response in small clusters of adipocytes embedded in inguinal sc WAT. The results are consistent with the idea that the effects are directly or indirectly due to elevated circulating TSH levels.

The influence of environmental temperature, thyroid status and a synthetic oestrogen on the induction of fatty livers in chicks

1. Hepatic lipid content, lipogenic enzyme activity and plasma lipid concentration were measured in chicks reared at 21 degrees or 34 degrees C and after thyroxine (T4), thiouracil (TU), propylthiouracil (PTU), dienestrol diacetate (DD) or PTU with DD had been given for 14 d. 2. At 34 degrees C there was a significant increase in the total liver lipid and triglyceride content. 3. Injections of T4 decreased liver lipid content whereas it was increased by feeding PTU or DD. The effects of PTU were more pronounced at 21 degrees C while those of DD were more pronounced at 34 degrees C. 4. There were significant interactions between temperature, thyroid status and synthetic oestrogen treatments on total lipid and triglyceride content of the liver. Fatty liver with marked steatosis could be produced through synergic actions of PTU and DD in chicks maintained at 21 degrees C.

Effect of 2-thiouracil on RNA and protein synthesis in synchronous and asynchronous infections of tobacco mosaic virus

Examination of the effect of 2-thiouracil on tobacco mosaic virus (TMV) RNA and protein synthesis in synchronous and asynchronous systems of replication in tobacco leaves demonstrated that 2-thiouracil does not prevent synthesis of TMV RNA, as suggested by previous studies, but inhibits some earlier function. When added at different times after mechanical inoculation, 1 mM 2-thiouracil partially inhibited both viral RNA and protein synthesis, with greater inhibition when treatment began nearer the time of inoculation. In leaves systemically inoculated with TMV using a differential temperature inoculation procedure to synchronize the infection, 1 mM 2-thiouracil inhibited viral protein and RNA synthesis totally when treatment began within the first 4 h after initiation of replication, but not at all when treatment began at 12 h or later, even though earlier reports had shown that most RNA and protein synthesis occurred after 12 h.

Lipid-lowering effects of N-[4-methylbenzylthiocarbonyl]-L-phenylalanine (KF1492), a new phenylalanine derivative

Lipid-lowering effects of KF1492, N-[4-methylbenzylthiocarbonyl]-L-phenylalanine, were evaluated in comparison with clofibrate. This compound lowered serum cholesterol (s-CL) and triglyceride(s-TG) in cholesterol-fed, Triton-injected and glycerol-fed rats as well as in normal rats. The dose of KF1492 required to show these effects was almost equal to that of clofibrate. In addition, KF1492 produced significant reductions of s-CL and s-TG in thiouracil-fed rats and decreasing phase of Triton-induced hyperlipemia of rats. In these models, clofibrate produced no significant reductions. Clofibrate produced a marked increase of liver size and shortened the pentobarbital-induced sleeping time in rats. On the contrary, the increase of liver size by KF1492 was less marked than clofibrate, and KF1492 caused no change in the sleeping time. Thus, it is apparent that KF1492 is a new lipid-lowering compound with less hepatic effect than clofibrate and that the lipid-lowering profile of KF1492 differs from that of clofibrate in some points.

Shedding of dense cell fragments into the follicular lumen early in involution of the hyperplastic thyroid gland

Membrane-bounded fragments of thyroid epithelial cells are found in the lumen of the thyroid follicle at early stages of involution of the hyperplastic gland. To demonstrate this, thyroid glands were made hyperplastic by feeding rats a low iodine diet containing thiouracil for 3 weeks. Involution was induced by the feeding of a high iodine diet. Three types of dense cell fragments were observed in the lumen at its periphery within 5 hours after the change of diet: (1) single, relatively large fragments that contained vesicles occasionally, (2) a cluster of rounded fragments of relatively small size. Some of these had a narrow tail, and (3) elongated narrow fragments in a row parallel to the apical surface of one or more epithelial cells. The fragments are probably derived from the thyroid epithelial cells since no other cell types were generally present. By 14 hours the fragments were distributed randomly throughout the lumen. Fragments were no longer present by 12 days of involution in most follicles. Fragment formation may be a mechanism for disposal of excess plasma membrane deposited by exocytic vesicles during rapid secretion of thyroglobulin into the follicular lumen early in involution.