Distribution of 125I-thyroxine in different organs and tissues of dietically obese rats

The distribution of 125I-thyroxine (% dose/g tissue; tissue/plasma radioactivity ratio) was investigated in different tissues of 28-week-old obese Wistar rats. Obesity was induced by high-fat diet (HFD) and confirmed by carcass analysis; in heavy obese animals the relative and absolute fat content is increased twofold and threefold, respectively, compared to control rats fed on a low-fat diet (LFD). Heavy HFD rats exhibit diminished 125I-T4 distribution in the "slow pool" (fat tissue, muscle) and unchanged values in the "fast pool" (liver, kidney) in comparison with LFD rats with low body weight. The differences in distribution presented here are not caused by the diet per se, but they are the consequence of the obesity of the animal, because no differences in the 125I-T4 distribution were found in the 125I-T4 between HFD and LFD rats with relatively equal body weight and body composition. The reduced T4 distribution in the fat tissue of obese rats is discussed in connection with possibly decreased lipolysis in this tissue and possible causal participation in the beginning of obesity.

Synthesis of the protected tridecapeptide (56-68) of the VH domain of mouse myeloma immunoglobulin M603 and its reattachment to resin supports

A protected tridecapeptide, representing a new peptide corresponding to residues 56-68 of the VH domain in the mouse M603 myeloma protein, has been prepared by solid phase peptide synthesis. The protected tridecapeptide was prepared using the photolabile 4-bromomethyl-(3-nitro)-benzamidomethyl-resin and the multidetachable 2-[4-bromomethyl)phenylacetoxy]propionyl-resin as solid supports. The synthetic protocol and protecting groups were the same for both syntheses. The protected tridecapeptide was removed photolytically from both supports and the sequence integrity was determined by preview analysis using the solid phase Edman degradation procedure. The protected tridecapeptide-OMPA was purified to homogeneity by DMF/H2O precipitation and LH-60 chromatography. The purity of the protected peptide was further demonstrated by high pressure liquid chromatography on the free peptide after HF deprotection. The protected tridecapeptide was reattached to 4-bromomethyl-(3-nitro)-benzamidomethyl-resin to give the photolabile Boc-(protected)peptidyl-4-oxymethyl-(3-nitro)benzamidomethyl-resin in 25% yield. The protected tridecapeptide-oxymethylphenylacetic acid derivative was reattached to aminomethyl-resin to give Boc-(protected)peptidyl-2-[4-oxymethyl)phenyl]acetamidomethyl-resin in 45% yield and to 2-bromopropionyl-resin generating the multidetachable Boc-(protected)peptidyl-2-[(4-oxymethyl)phenylacetoxy] propionyl-resin in 80% yield. The reactivity of these reattached peptides was demonstrated by the quantitative coupling of Boc-leucine to the protected peptide-resin. The advantages and disadvantages of the different resins with respect to solid phase fragment synthesis are discussed.

[Serum cholesterol and liver deiodase activity in rats of different body composition after low or high fat diet. Effect of a feeding change in fat-rich to fat-poor diet and the reverse or of an iodine deficient diet]

Male Wistar rats with an average age of 28 weeks received diets high (HFD: 50% fat) or low (LFD: 3% fat) in fat content. Rats were restricted on iodine intake by feeding pure diets without iodine addition. The relative degree of iodine shortage of rats was estimated by 131I-uptake. PB131I and ETR. Serum cholesterol, whole body lipid content and liver deiodinase activity of LFD (control)- and HFD-rats were analyzed. A change of diet feeding from high to low fat content and vice versa took place to discriminate the effect of diet fat from body fat content of rats on serum cholesterol and deiodinase activity. HFD fed rats with high body fat content showed at iodine restriction the same serum cholesterol concentration as relative lean LFD-animals. Post feeding change from diet rich to poor on fat and vice versa at 4 weeks the obese animals have lost body fat only 10-20% at calorie restriction and exhibit higher serum cholesterol levels and equal liver deiodinase activity as lean, now fat rich fed control animals. Heavy HFD-rats fed on fat rich diet for 22 weeks have approximately two times higher liver lipid content as light LFD-animals. Because liver lipid content and deiodinase activity between light LFD- and heavy HFD-rats before and after change of diet feeding are equal, a relation between liver lipid content and enzyme activity is discussed.

Synthetic insulin by selective disulfide briding, II. Polymer phase synthesis of the human B chain fragments

Five protected fragments Ddz-Phe-Val-Asn(Mbh)-Gln(Mbh)-His(Dnp)-Leu-Cys(Acm)-Gly-OH [I], Ddz-Ser(But)-His(Dnp)-Leu-Val-Glu-(OBut)-Ala-OH [II], Ddz-Leu-Tyr(But)-Leu-Val-Cys(Mbzl)-Gly-OH [III], Ddz-Glu(OBut)-Arg(Tos)-Gly-OH [IV], Ddz-Phe-Phe-Tyr(But)-thr(But)-Pro-Lys(Z)-Thr(But)-OH [V] for the synthesis of the human insulin B chain, were prepared by an efficient procedure on solid phase.

[Body composition of light and heavy rats in a high or low fat diet group]

The authors studied the body composition of light and heavy male Wistar rats (approximately 11 and 21 weeks of age) from two diet groups fed a high-fat (HFD, 50 per cent (w/w) fat) and a low-fat diet (LFD, 3 per cent (w/w) fat), respectively. In both age-groups the heavy HFD rats showed a considerably higher fat proportion (as compared with light LFD rats) associated with a correspondingly reduced body water content and an approximately identical body protein concentration. On comparing light and heavy rats (11 and 21 weeks of age) from the same diet group as to their body composition, the authors found greater differences only in the 21-week-old HFD animals; as against light animals, the heavy animals exhibited a highly significant increase in body fat content and a highly significant decrease in body water content. A comparison of LFD and HFD animals of approximately the same weight revealed an increase of the relative body fat content and a decrease of the percentage of body water content in light 11-week-old and also in 21-week-old HFD animals as against heavy LFD animals.

[Effect of high-fat diet on the contents of total cholesterol, free cholesterol and esterified cholesterol in the serum and liver of rats]

Four-week-old male Wister Rats were fed a diet containing 50% of fat up to the age of 9 weeks and 6 months, respectively. The control group received a diet with 3% of fat. The fat consisted of lard (1/3) and sunflower oil (2/3). Serum cholesterol was determined according to the standard method 1 of the DAB 7 (German Pharmacopoeia); liver cholesterol was estimated by the method of Naito and Lewis. As compared to the control animals, the 9-week-old rats on the high-fat diet showed serum cholesterol values (total, free and esterified cholesterol) which were significantly lower. There was no difference in serum cholesterol level between the 6-month-old rats on the high-fat diet and the control animals. In contrast to this, the liver cholesterol levels of the 9-week-old and the 6-month-old rats on the high-fat diet were significantly increased. In both age-groups the ratio of free cholesterol to esterified cholesterol was changed in favour of the esterified cholesterol. The present results confirm the findings reported in the literature, except for the unchanged serum cholesterol values observed by the authors in the long-time dietary experiment.

Morphology and distribution of the synapses to the spinal motoneuron of the frog

The quantitative distribution of the different structural elements on the surface of the motoneurons (MN) in the spinal cord of the frog was studied in thin sections and freeze-fracture replicas. In particular, the different synaptic types and their distribution on the MN soma and dendrites are described. In thin sections three types of synapses were discerned: the S-type with spherical vesicles, the F-type with flattened vesicles, and finally the C-type synapse with spherical vesicles and a subsynaptic cistern. The synaptic covering at the MN surface as determined by thin sections is about 36%. In freeze-fracture replicas were observed boutons with and without gap junctions, and C-type boutons. When using the latter technique the synaptic covering was found to be 43%. With both techniques special attention was paied to the morphology of the C-type bouton and both the subsynaptic and extrasynaptic cisterns. The soma membrane over the sub- and extrasynaptic cisterns reveals characteristic and very similar morphological features with respect to both the distribution and size of the membrane particles. the possible functions of the two cisternal types are discussed.

[Liver deiodinase activity in rats after high and low fat iodine deficient diets]

Male Wistar rats were restricted on iodine intake by feeding pure diets, without iodine addition. The high fat diet contained 50% fat (HFD), the low fat diet 3% fat (LFD). Control animals received the same diets, but with iodine addition. After feeding the diets for 7 or 19 weeks liver deiodinase activity was estimated. The iodine deficient animals showed a diminished enzyme activity in both diet groups. But after feeding the diet without iodine addition for 7 weeks the deiodinase activity significantly decreased in the HFD-group only in relation to liver weight per 100 g body weight. After 19 weeks the liver deiodinase activity in the HFD-group was diminished significantly, but the decrease was much smaller than in the LFD-group. The estimation of relative thyroid weight and iodoamino acid distribution demonstrate that the level of iodine deficiency was in iodine restricted HFD-rats greater than in appropriate LFD-rats. This result was verified by investigations of thyroidal radio iodine uptake and iodine content, PB131I, serum iodine and T4 levels in both diet groups. The reason for the lower decrease of deiodinase activity at higher iodine deficiency in HFD-rats as compared to LFD-rats and the possible importance of food enriched with fat in endemic goiter areas is discussed.

[Cholesterol esterification in the serum of hypothyroid rats]

The ratio of unesterified to total serum cholesterol in hypothyreotic rats has been studied. Extreme rat hypothyreosis of identical degree was induced by radiothyroidectomy (group R-HT) and feeding of thyreostatics (groups MTU-HT and MMI-HT). Determination of total serum cholesterol content and the unesterified cholesterol content resulted in following changes (all changes significant for p < 0,001): 1. Higher total cholesterol in hypothyreotic rats 4 and 7 weeks after beginning the experiments as compared to the controls. 2. The ratio of unesterified cholesterol to total cholesterol was increased in all hypothyreotic groups. It is discussed, that the esterification reaction in serum catalyzed by the lecithin-cholesterol-acyltransferase (LCAT) is diminished in the hypothyreotic state.

[Changed body composition by increased total body fat content in experimentally hypothyroid rats]

Total body fat content was determined in growing normal male Wistar rats and hypothyroidized animals 7 weeks after feeding with Methimazol (group MMI-HT), Methyl-thiouracil (group MTU-HT), and performance of radiothyroidectomy by 131-iodine (group R-HT), respectively. At the end of experiments there was an extreme hypothyroid state in all treated groups, verified by external signs, growth kinetics, serum cholesterol estimation and evaluation of the iodothyrosine pattern of the thyroid glands. Changed body composition resulted in all HT-groups from significant increase of total body fat content. The relation of constituents fat : protein : water of 1 : 2 : 6 in the KT-group was changed into 1 : 1 : 3 in the HT-groups. No differences were found between the different HT-groups. Our findings are in good agreement with altered metabolism of plasma lipids described by other authors showing the existence of a highly disturbed lipid metabolism in thyroid hormone deficiency.

[Effect of diet and thyroxine on body composition in rats]

In young male Wistar rats the influence of different fat content of the diet (7 or 25 or 50 weight percent of fat) and of thyroxine (5 or 50 microgram/100 g body mass, 2 times/week, sc.) on body composition was investigated by carcass analysis. After high doses of thyroxine the percentage body fat decreases and protein and water content increases within the same diet group (7 or 25 or 50% fat diet). Smaller doses of thyroxine have only the same effect as high thyroxine doses in the 7% fat diet group; the body composition is unchanged in the 25% fat diet group, and in rats after 50% fat diet thyroxine even brings about an increase in body fat. It is concluded that the fat content of the diet makes thyroxine partly ineffective. A comparison of the different diet groups, also with or without thyroxine treatment, brings the result of significantly increased percentage body fat after 25 and 50% fat diet; body protein and body water decreases respectively. It appears from the present study that controversial results in literature concerning body composition after thyroxine treatment, may be caused by different diets, especially the fat content of the diets.

[The determination of the red cell isoenzymes 6-phosphogluconate dehydrogenase (E.C.1.1.1.44) and acid phosphatase (E.C.3.1.3.2) by means of agarosegel thinlayer electrophoresis (author's transl)]

Methods for the determination of the red cell isoenzymes 6-PGD and acP by means of agarosegel thinlayer electrophoresis are referred. Using these relatively simple techniques, results can be obtained after at least two hours. The quality of separation in both systems is higher than that obtained after starch gel electrophoresis.

[Dietary proteins and deiodination in the liver]

The authors studied in male Wistar rats the effects of diets containing 66 and 2% (w/w) of protein on the one hand, and 18% (w/w) of protein on the other hand, on the deiodination of L-thyroxine in liver homogenate supernatants. The deiodase activity in the liver protein increased in case of low-protein diet, and decreased in case of high-protein diet; these differences were statistically significant. When the body weights of the animals were taken into account, the deiodinating power of the whole liver was significantly reduced in case of low-protein diet, but not significantly reduced in case of high-protein diet. Consequently, the reference value adopted for the calculation of the degree of deiodination is of paramount importance to validity.

[Effect of a high fat diet on the behavior of the diameter, volume, triglyceride content and number of the adipocytes in different types of fatty tissues in male Wistar rats]

The effect of a high-fat diet on the diameter, volume, triglyceride content and number of the adipocytes was studied in male Wistar rats at the age of 9 weeks and 6 months, respectively. The adipocytes were isolated by means of the method of RODBELL. The adipocyte diameters were measured using the microscopic method. The weight and the fat content of the fatty tissue were determined gravimetrically. A diet containing 50% fat increases the diameter, volume and triglyceride content of the adipocytes and also the weight and the fat content of the different types of fatty tissue. The fat content of the diet and the duration of feeding are of importance. The high-fat diet exerts no effect on the adipocyte number. However, in both age groups, the adipocyte numbers were sometimes greater in heavy animals than in light ones fed the same diet. Genetic, hormonal, and dietarily-induced factors are considered as a possible cause.

[Properties of adipocytes (diameter, volume, triglyceride content, cell number) of certain types of fatty tissue as a function of age in male Wistar rats]

The diameter, volume, triglyceride content and number of adipocytes were determined in male Wistar rats at the age of 6 weeks and 2, 3, 12 and 18 months, respectively. A standard diet and water were given ad libitum. The adipocytes were isolated by means of the method of RODBELL. The weight and fat content of the fatty tissues were determined gravimetrically. Age exerts no effect on the adipocyte parameter, nor on the weight and the fat content of the fatty tissue. In contrast to this, there are relationships between adipocyte diameter and the increases in body weight. In all age groups, the increase in size and number of the adipocytes was significantly greater in heavy animals than in light ones. Genetic, hormonal and dietarily-induced factors are discussed as a possible cause. The authors observed no difference in adipocyte size between epididymal and perirenal fatty tissues. As compared to this, the mesenteric adipocytes were smaller.

[Effect of degree of experimentally induced hypothyroidism on changes in serum albumin spectra in rats]

Extreme rat hypothyreosis of identical degree was induced by radiothyroidectomy (group R-HT) and feeding of thyreostatics (groups MTU-HT and MMI-HT). External signs, growth kinetics, serum cholesterol, thyroid weight, and the iodothyrosine pattern of the thyroid glands served as references for the quality of the hypothyreotic state. Determinations of following changes (all changes significant for p less than 0.001): 1. Higher total serum protein levels in hypothyreotic rats 4 and 7 weeks after beginning the experiemnts as compared to the controls (KT). 2. After 4 weeks the relative albumin content was diminished, the relative gamma-globulin content was elevated as compared to the KT. The absolute values of albumines did not change, alpha-1-globuline and gamma-globuline contents were increased in all hypothyreotic groups. 3. After 7 weeks normal albumine values, increase of the relative and absolute alpha-1-globuline content, and decrease of the relative beta-globuline concentrations were measured. Elevated gamma-globulins were found in MMI-HT and R-HT only, and an increased absolute albumine content in MTU-HT alone. The results confirm both hyperproteinemia and dysproteinemia as characteristics of the rat hypothyreotic state. Dynamic changes of absolute and relative contents of different serum protein fractions are demonstrated in relation to the duration of hypothyreosis. This fact can possibly explain contradictory findings on type of dysproteinemia by several authors.

[Effects of two special diets on the body weight of rats]

The authors studied the effects of 2 special diets on the weight behaviour of male Wistar rats (aged 4--5 weeks) from Schönerlinde near Berlin up to the age of 35 weeks. The weight behaviour of rats fed a standard diet (commercially available pellets) lies between those of the experimental rats and near that of the rats on low-fat (3%) diet. The one special diet that contains 3% of fat is low-fat (8.4% of the gross energy of the feed) and high-protein (69.3% of the gross energy); the other diet that contains 50% of fat is high-fat (76% of the gross energy). The two diets (containing 331 and 612 kcal/100 g, respectively) are not isocaloric but the animals on the low-fat diet ate twice as much as the animals on the high-fat diet. The rats on the high-protein low-fat diet were prone to copious sweating. It was generally noticed that the animals on the high-fat diet became to a greater extent hypokinetic with increasing age. The weight difference between the two dietary groups increased with increasing age, reaching its maximum value (77%) at the age of 24 weeks and then decreasing to 60% (at the age of 35 weeks). Up to the age of 12 weeks, the rats are in the more "dynamic" phase of weight increase; and from the 16th week, in the more "static" phase of weight increase.

[Effect of protein content and thyroid hormone on body composition in growing rats]

The effects of an isocaloric control diet of high-protein and low-protein diets (in which protein amounted to 16, 62 and 2% of total calorie content, respectively) with and without simultaneous administration of Thyreotom or methylthiouracil on total body composition have been studied in growing male Wistar rats. In spite of higher average Kcal intake (per day and 100 g of body weight), the rats on the high-protein diet were weighing less than the control animals at the end of the experiment. As compared to the control animals, the rats on the high-protein diet as well as those on the low-protein diet showed a greater relative weight of the thyroid gland. The protein percentage of the body was not significantly increased by an increase in protein supply; likewise, it was not significantly reduced by a decrease in protein supply. The body fat content was by 2/3 lower in the rats on the lowprotein diet than in the control animals. This difference was statistically significant. Thyroid hormones (1 mug liothyronine + 4 mug levothyroxine/100 g body weight, administered orally for 3 weeks) produced a slight increase of body protein in the rats on the high-protein diet; they increased it significantly in the rats on the low-protein diet. Body fat was correspondingly reduced. Methylthiouracil reduces the body fat content in the control animals and in the rats on the high-protein diet; it increased the body fat content in the rats on the low-protein diet. Our results confirm the partial findings of human pathology and demonstrate clearly that nutritional diseases, especially protein deficiency, worsen considerably in case of concomitant disorders of thyroid hormone metabolism.

[Deiodination in the kidney and thyroid function)]

In homogenate supernatants of kidneys of male rats the extent of deiodination of L-diiodotyrosine (L-DJT) and L-thyroxine (L-T4) was investigated in dependence on the thyroid function (hypo- and hyperthyroidized) and also in dependence on age. In rats hypothyroidized by loading with Methylthiouracil (MTU) or Methimazol (MMI) the deiodination for L-DJT and L-T4 was significantly reduced, in rats loaded with 40 mug T4 sc. for 10 days, the deiodination was significantly enhanced compared with untreated control animals. With advancing age (6 weeks, 3 or 12 month) the deiodination activity is highly significantly reduced. The results underline relations between thyroid gland function and deiodination activity in kidney.

[Deiodase activity in rats following an overdose of thyroid hormone]

The L-DIT and L-T4 deiodinating activity in supernatants from liver or kidney homogenates of normal rats or rats loaded with T4, T3 or TSH, was investigated. Deiodination of L-DIT occurs in liver supernatants twice as much as in liver, referring to mg of protein of g of tissue, while the deiodination of L-T4 seems rather equal. The over all rate of deiodination, however, reaches in liver for L-DIT the threefold, for L-T4 the fivefold value, as compared with kidney. Short periods of loading do not alter deiodination of L-DIT in liver or kidney at all; but lead to significant elevation of L-T4-deiodination in liver tissue. Higher doses or longer periods of loading cause a significant rise of L-DIT-deiodination in liver and kidney, while the L-T4-deiodination in liver is significantly decreased and in kidney significantly elevated.