Biomedical subjects
Publications and source records attributed to C Voss.
The water temperature preference of adult male albino rats was studied. Deprived and normally hydrated animals were exposed at peak hours of consumption to a choice between 12 degrees C and 30 degrees C water or to 12 degrees C and 34 degrees C water. Food intake was not restricted. There was a clear preference for the warmer water. It is concluded that oropharyngeal temperature cues influence water intake.
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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.
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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.
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.
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.
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.
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.
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Effectors and products of enzymatic diiodotyrosine (DIT) deiodination by a cytosolic fraction of pig liver hab been investigated. 13% of the degraded 131I-DIT was found as monoiodotyrosine by thin layer chromatography. The main quantity of the deiodinated DIT was found on the start point of the chromatogram bound to enzyme protein. Tyrosine as a reaction product of enzymatic deiodination of [14C]-IT could not be identified exactly. The liver cytosolic deiodinase is activated by pyruvate; the extent of activation depends on th pyruvate concentration. Diiodohydroxyphenylpyruvate as a product of transamination and theoretically possible intermediate product could be excluded. NADPH 2 and sodium dithionite activated the deiodinase to 1/3, sodium dithionite together with FAD to 1/2 the amount of which was determined for the action of pyruvate. The enzymatic activity in the presence of pyruvate and NADPH2, respectively NADPH2/FAD is identical with the sum of the single activities. The effect of dithionite and sulfite on deiodinase activity depends on the concentration: low effector concentrations increase, while high concentrations decrease the enzyme activity. The liver plasma deiodinase was inactivate quantitatively by reaction with 10(-4) M PCMB; by reaction with 10(-4) M DTNB or NEM the inactivation was 40% only. The inactivation of deiodinase by PCMB was quantitative reversible by cysteine, while inactivation by DTNB was reversible by cysteine to maximal 70% only. Differences between cytosolic and microsomal deiodinases are discussed also in regard to the mechanism of DIT-deiodination by a liver cytosolic fraction with direct participation of SH-groups.
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.
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.
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.
Male Wistar rats on 3 or 50% fat diet for 14 weeks were treated during 6 weeks with L-thyroxine (5 or 25 or 50 microgram 100 g body weight/2 times weekly, sc.) and the activity of L-thyroxine-deiodinase was determined in supernatans of liver homogenates. With increasing thyroxine lading the deiodinating activity increases statistically significantly within each diet group. The liver of animals on 50% fat diet deiodinates increasing thyroxine doses to a lesser extent than livers of animals on 3% fat diet. It is discussed that high fat diet influences thyroid function and that thyroxine shares effectiveness and undergoes deiodination also in other tissues, probably in fat tissue, to a higher extent.
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.
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.