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Biomedical subjects

P Rudas

Publications and source records attributed to P Rudas.

At least 37 records · Page 2Linked to original sources
PubMed1996

Influence of a deficient intake of high and low degradable protein on body composition, metabolic adaptation, production and reproductive performance in early lactation dairy cows.

High-yielding dairy cows (n = 34) were divided into high (HD) and low (LD) protein degradability groups after delivery, and used for a feeding trial which lasted up to day 80 +/- 10 of lactation. The cows were regularly weighed, their body condition was scored (BCS), and their reproductive status assessed. Blood samples were taken simultaneously, and ruminal fluid was collected on the last day of the trial. On postpartum day 45 +/- 6 and 11 days thereafter two prostaglandin F2 alpha (PGF2 alpha) injections were administered. The ammonia and urea concentrations of the ruminal fluid were higher in cows of group HD. The C2:C3 ratio was 2.7:1 vs. 2.3:1 in HD and LD cows, respectively. The amino acid and lipid composition of blood reflected the dietary treatments. The BCS and blood urea concentration were slightly higher in HD animals. The average daily milk production of LD cows was 1.5 kg higher than that of HD cows. The pregnancy rates of the two groups at day 200 after calving did not differ, but LD cows showed their first visible oestrus and reconceived significantly (p < 0.05) later. It can be concluded that--at a marginal energy supply-a moderate (13%) deficiency of rumen-degradable protein during the first 10 weeks after calving can be more detrimental to reproductive performance than a severe (27%) deficiency of undegradable protein.

Adaptation, Physiological↗
PubMed1995

Effect of severe energy restriction and refeeding on thyroid hormones in bulls.

Fifty-three Holstein-Friesian breeding bulls (944.99 +/- 14.59 kg) were fasted for 4 weeks. The influence of feeding on thyroid hormones was studied by comparing a starting point with a 4-week fasting period and a refeeding period. Blood samples were taken via a jugular vein catheter at 8:00 a.m. one day before, then once every week during, and two times after the fasting period. Plasma thyroxine (T4) and triiodothyronine (T3) levels were determined by direct radioimmuno-assay. The concentration of T4 and T3 decreased during fasting. The concentration of T3 increased after refeeding, but that of T4 did not. These data suggest that fasting is associated with a decrease in the peripheral conversion of T4 to T3 and, consequently, less T4 is converted into T3.

Animal Feed↗
PubMed1995

Species-specificity of glial vimentin as revealed by immunocytochemical studies with the Vim 3B4 and V9 monoclonal antibodies.

Two monoclonal antibodies directed against vimentin, Vim 3B4 and V9 could distinguish between vimentins originating from certain species, when tested on cell lines (Bohn et al, 1992). Our comparative immunohistochemical studies in the rat and chicken brain with the same antibodies suggest the coexistence of two vimentin forms in the glial cells of both species. One of these forms bearing the epitope present in the respective non-glial cell lines is present in astrocytes and Bergmann glia independently of the ontogenic state of the animal. The other epitope appeared also mutually in both species, albeit its expression was more restricted. These patterns suggest that in these two species, the expression of the different vimentin forms might be differently regulated.

Aging↗
PubMed1994

Kinetic parameters of plasma thyroid hormone and thyroid hormone receptors in a dwarf and control line of chicken.

Sex-linked dwarf chickens have in plasma low triiodothyronine (T3) levels and slightly raised thyroxine (T4) concentrations and are functional hypothyroid. The kinetic parameters of T4 and T3 were investigated using 125I-labeled hormones. In addition the nuclear T3-receptors in the liver were examined using a radioreceptorassay and Scatchard analysis. Four-week-old dwarf (dw) and normal (Dw) chickens were injected with 125I-labeled T3 or T4 and blood samples taken 60, 120, 180, and 300 min after 125I-T3 injection and 120, 240, 360, and 480 minutes after 125I-T4 treatment. Labeled T4 and T3 and the degradation products were separated by paper chromatography. After the paper strips were dried, the iodinated compounds were visualized and counted in the gamma counter. The kinetic parameters, the half-life time (T1/2), the apparent distribution volume (Vd) and the metabolic clearance rate (MCR) were calculated using the natural base logarithm values of the measured radioactivity plotted against time and used for linear regression. T4 was cleared from circulation more slowly in dwarf than in control chicks and reflected a longer T1/2 (21.8%) and a reduced MCR (45%). The Vd tended to be lower (34.7%) in dwarfs. While the T1/2 of T3 was longer (28.1%) in dwarf chickens than in control animals, the MCR for T3 was considerably increased (31.8%). This results from an increased Vd (63.1%) in the dwarf chicks. The T3-receptor study in the liver of dwarf and non-dwarf chickens from Week 1 to Week 4 posthatching revealed that the total capacity and the affinity constant of the binding sites were comparable in dwarf and normal chickens. However, the occupancy of the receptors was higher in the dwarf animals.

Animals↗
PubMed1994

Impaired local deiodination of thyroxine to triiodothyronine in dogs with symmetrical truncal alopecia.

Thyroid dysfunction causes certain dermatological alterations in dogs. Insufficient delivery of thyroid hormone to the skin may originate not only from inadequate thyroid function but also from impaired local activation of thyroxine in the target organ. Thyroid parameters and deiodination were investigated in healthy dogs (group C) and in dogs with cutaneous lesions associated with hypothyroidism (group H) or with a low-T3 syndrome (group LT). The ability of the skin to convert T4 to T3 was impaired in both groups H and LT but not in the controls. It is concluded that impaired local deiodination may contribute to skin problems in dogs.

Alopecia↗
PubMed1994

Elimination and metabolism of triiodothyronine depend on the thyroid status in the brain of young chickens.

The hypothyroid chicken brain has been found to preserve more triiodothyronine (T3) than expected from plasma T3 levels. A possible explanation is that the elimination of T3 from the hypothyroid brain is decreased. In the present experiments, the elimination rate of T3 was compared in surgically thyroidectomized animals and sham-operated controls. It was found that both T3 coming from the plasma and T3 derived locally in the cells from thyroxine have a significantly lower elimination rate in thyroidectomized chickens than in sham-operated ones. Therefore it is concluded that the adaptation of the brain to hypothyroid conditions is partly regulated by reducing the loss of the active thyroid hormone (i.e. T3) via metabolic and tissue-to-plasma exchange.

Animals↗
PubMed1994

Serum concentrations of thyroid hormones during egg laying in two types of Japanese quail (Coturnix coturnix japonica).

In the present investigation a lighter white egg-type (L) and a heavier wild meat-type (M) of female Japanese quails were compared with respect to egg production, body growth, abdominal fat pad, serum thyroxine (T4) and triiodothyronine (T3) concentrations, TRH sensitivity and T4 5'-monodeiodinase activity in liver homogenates. During the investigation period L type layed considerably more eggs and M type was heavier in body weight. Abdominal fat pad in L type quails was significantly higher than in M type ones. L type quails had lower serum T4 and T3 concentrations than M type ones and the liver T4 5'-monodeiodinase activity was higher in M type than in L type quails. Following TRH administration serum T4 and T3 concentrations increase was higher in L type quails than in M type ones. Our results suggest that lower T4 and T3 observed in L type quails reflect a possible metabolic adaptation to egg production. Different activities of 5'-monodeiodinase and of response to TRH may be inherent to these two types of quail.

Aging↗
PubMed1993

Endogenous growth hormone controls high plasma levels of 3,3',5-triiodothyronine (T3) in growing chickens by decreasing the T3-degrading type III deiodinase activity.

The influence of endogenous GH levels on peripheral monodeiodination activity has been investigated in growing chickens at the age of 4 weeks, when they normally show no T3 increase after GH injection. Injection of anti-GH serum decreased plasma T3 and increased plasma T4. Three d and 1 week after hypophysectomy, plasma T3 was also markedly decreased, while T4 was only slightly affected, hepatic 5'D-I activity showed a transient decrease, but 5D-III activity was highly increased, as were the number of hepatic GH receptor sites. Injection of GH in hypophysectomized chickens decreased 5D-III activity and increased plasma T3. GH receptor-deficient dwarf chickens had decreased plasma T3 and increased plasma T4 and hepatic 5'D-I and 5D-III activities compared to their normally-growing siblings. GH administration could only affect T3 and 5D-III in the non-dwarf siblings, which showed higher basal 5D-III activity compared to the non-responsive age-matched chickens of the Hisex strain used in the other experiments. It can be concluded that endogenous GH is an important factor in the control of plasma T3 levels in growing chickens due to its influence on the activity of the T3-degrading type III deiodinase. The effectiveness of exogenous GH administration to acutely increase plasma T3 probably depends on the balance between the injected dose and the endogenous GH concentration, the hepatic GH receptor availability and the hepatic type III deiodinase level.

Analysis of Variance↗
PubMed1993

Thyroid hormone deiodination in the brain of young chickens acutely adapts to changes in thyroid status.

The brain represents a special organ in respect of thyroid hormone handling. This was analyzed in one-week-old chickens. The effect of sham-operation (SH), thyroidectomy (TX) and thyroidectomy plus thyroxine supplementation (TX+T4) on the intracerebral triiodothyronine (T3) content and on the activity of different types of deiodinases was investigated. it was found that in spite of very low T3 levels in the serum of TX animals, the brain displayed close to normal tissue T3 levels. Kinetic studies of the deiodinase system showed an increase in type II activity (increased T4 to T3 conversion) and decreased type III activity (decreased degradation of intracellular T3) in the brain of TX animals vs. SH or TX+T4. It is concluded that a considerable part, if not the total of the T3 preserved in hypothyroidism may be ascribed to adaptive changes of the deiodinase system in the brain of young chickens.

Animals↗
PubMed1993

Thyroxine and triiodothyronine uptake by the brain of chickens.

The instant uptake of 125-I-labelled triiodothyronine and 125-I-thyroxine by the brain tissue was measured in sham-operated (SH) controls, thyroidectomized (TX) and thyroidectomized plus iodothyronine supplemented (TX+T3 or TX+T4) young chickens. It was found that thyroidectomy significantly increases the uptake of iodothyronines, and iodothyronine supplementation returns the uptake close to sham-operated levels. The characteristics of the inhibition of the uptake of labelled hormones by non-labelled iodothyronines speak in favour of the presence of specific, separate uptake sites for T3 and T4 in the blood-brain barrier of young chickens.

Animals↗
PubMed1991

Thyrotropin-releasing hormone (TRH) is not thyrotropic but somatotropic in fed and starved adult chickens.

Adult fed and starved Warren chickens, 2 yr of age, and approaching the end of the second laying year, were injected iv with 1 of the following products: 10 micrograms of thyrotropin releasing hormone (TRH); 100 micrograms of bovine thyrotropin (bTSH); 100 micrograms of ovine growth hormone (oGH); saline. The influence on plasma concentrations of thyroxine (T4), triiodothyronine (T3) or chicken GH (cGH) were followed. Prior to injection, it was clear from the control values that starvation for 3 d decreased plasma levels of T3 and increased cGH, whereas 7 d of fasting increased T4 and cGH. The plasma levels of cGH were elevated greater than 10-fold at 15 min following the TRH challenge in food-deprived chickens compared to a less than 4-fold increase in normal fed hens. This increase was followed by a rise in T3 after 1 h, which was also more pronounced in the starved animals, whereas T4 decreased or remained unaffected. Increases in T4 can, however, be obtained with 100 micrograms TSH in normal fed (2-fold) or starved animals (greater than 3-fold). Following injection of 100 micrograms oGH, a significant increase in T3 levels was observed which in fed animals was already present at 30 min, but the higher levels persisted for 1 and 2 h in fed and starved hens. At the same time, a decrease in T4 was observed in both groups of GH-treated chickens. It is concluded that TRH at the dose used is not thyrotropic but has a somatotropic effect and is responsible for the peripheral conversion of T4 into T3.

Animals↗
PubMed1991

Effect of hypophysectomy and acute administration of growth hormone (GH) on GH-receptor binding in chick liver membranes.

The effects of hypophysectomy on GH binding to liver membranes of young chicks were studied 3 days and 1 week after surgery. Specific binding of 125I-labelled chicken GH (cGH) to MgCl2-treated liver microsomal fractions of hypophysectomized animals was two- to fivefold greater than to those of sham-operated or control (non-operated) birds. This effect was due to a rise in binding capacity rather than a change in binding affinity of the GH receptor. Two daily injections of cGH (20 micrograms/animal) returned the number of hepatic GH receptors from hypophysectomized chicks to the level of the sham-operated ones. Administration of GH to the latter group did not cause a significant lowering of specific binding or number of receptors. No positive correlation between GH binding and plasma concentrations of insulin-like growth factor-I (IGF-I) was observed; although GH binding increased, IGF-I levels were lower for the hypophysectomized group. Since the number of hepatic GH receptors and the plasma GH levels were inversely correlated, it was concluded that the GH receptors in the liver of the chicken can be down-regulated by GH. This possibly explains why GH binding is low in posthatch and young chicks, because circulating GH concentrations are high during this period.

Animals↗
PubMed1990

Effects of congenital hypothyroidism on microtubule-associated protein-2 expression in the cerebellum of the rat.

In view of the defective neurotubule assembly observed in congenital hypothyroidism and the striking morphological abnormalities of the cerebellum in this condition, we have investigated the expression of microtubule-associated protein-2 (MAP2) in the cerebellum of rats with congenital hypothyroidism. Analysis included the measurement of immunoreactive MAP2 and its mRNA. In addition, the intracellular distribution of MAP2 was studied by immunostaining of the appropriate histological preparations. The results showed that the developmental increase in MAP2 is delayed in congenital hypothyroidism, but eventually the concentration of this protein reached normal levels in animals with this condition, even if untreated. These abnormalities in the immunoreactive protein are not paralleled by abnormalities in the abundance of MAP2 mRNA, which was not affected by the thyroid status of the animals. In spite of the normalization of the content of the protein, the distribution of MAP2 in the Purkinje cells of hypothyroid rats remained abnormal. Whereas in euthyroid rats the protein rapidly migrated into the dendrites, in the Purkinje cells of hypothyroid pups, MAP2 remained largely confined to the body and the most proximal part of the dendrites. These results suggest that thyroid hormone affects the expression of MAP2 at translation or posttranslational levels. The abnormality in distribution may result from some posttranslational abnormality of the protein itself or some underlying defect in the function of the neurons. These observations are probably relevant to the abnormalities in cerebellar function seen in animals and humans with untreated congenital hypothyroidism.

Animals↗
PubMed1990

Correlation between thyroid hormone level and blood pH in cows and in their offspring.

Thyroid hormone levels in the plasma and blood pH were compared in 38 newborn calves and their dams immediately at parturition, then 24 and 72 h thereafter. Both thyroid hormone levels and pH exhibit much higher variation in calves than in cows. Applying a linear model at different sampling times, a weak (r = -0.112 to -0.397) but significant (P less than 0.05) negative correlation was found between thyroid hormone levels and blood pH in calves 24 and 72 h postpartum. At birth, when no correlation was found with linear approach, a polynomial regression model showed curvilinear relationship between thyroid hormone levels and blood pH in calves. Since these correlations could not be substantiated by comparing data of different sampling times, one can conclude that the possible relationship of thyroid hormone levels and blood pH is a complex one. Revealing the underlying mechanism of the above observations requires further study.

Animals↗
PubMed1989

Effect of malabsorption syndrome on pancreatic function in broilers.

The effect of "malabsorption syndrome" on pancreatic function was studied in newly hatched broiler chicks orally inoculated during the first few hours of life with intestinal homogenates from birds with naturally occurring malabsorption syndrome. The control groups were treated with saline. Tissue samples were collected at 0, 2, 4, 6, 9, 13, 17, and 29 days of age from both groups. The BW of inoculated birds decreased significantly relative to that of controls as early as 9 days of age. Pancreatic amylase activity was significantly greater than that in controls by 2 days. Protease activity of inoculated birds increased significantly over that in controls on the 2nd day and decreased significantly on the 6th and 9th days. Reoviruses were detected in the fecal samples of inoculated birds on the 2nd and 3rd days and did not appear in control samples. Reoviruses were also isolated from the pancreatic tissue of two inoculated birds on the 3rd day. Symptoms characteristic of malabsorption syndrome may be elicited by maldigestion; in the present study, this probably resulted from reduced digestive enzyme production of the pancreas. Similarities of changes in plasma triiodothyronine and pancreatic protease levels suggested a possible relationship between thyroid and pancreatic dysfunction in the condition of the malabsorption syndrome.

Amylases↗
PubMed1989

Adaptation of 5'-deiodination to hypothyroid conditions following surgical and/or radiothyroidectomy in chickens.

The effect of thyroidectomy on serum levels of thyroid hormones (thyroxine, T4; triiodothyronine, T3) and on tissue levels of T3 as well as on 5'-deiodination (5'-DI) in liver, kidney and brain of chickens was investigated. The most effective way of thyroidectomy was a combined surgical (Tx) plus radiothyroidectomy (RTx) with low amounts of 131-I (NaI). The latter destroyed extra-thyroidal hormone production. It was found that even if after Tx and RTx the serum levels of T4 and T3 were close to the detection limit, the tissue T3 level was only half of normal in liver and kidney and remained normal in the brain. It is suggested that lowered 5'-deiodination is an important but not exclusive factor contributing to this adaptation of cells to hypothyroid conditions.

Animals↗
PubMed1989

Restricted feed intake influences thyroid hormone production and peripheral deiodination in chickens.

Thyroid hormones are of major importance in determining metabolic state both in mammals and in birds. Whether or not feed intake itself has an autoregulatory role in adjusting the setpoint of thyroid hormone activity is yet not well understood. The present work investigates the effects of restricted feed intake on the serum levels and on the peripheral metabolism of thyroid hormones. Also, the sensitivity of the pituitary-thyroid axis was looked at by means of thyrotropin releasing hormone provocation test. Several groups of Hunniahybrid chickens aged 2-6 weeks were used. Restriction was made by providing the experimental animals 70 and 85 percent of the amount of food consumed in the ad libitum fed control group. It was found that feed restriction lowers circulating concentration of triiodothyronine probably by inhibiting the activity of liver deiodinase and also decreases the sensitivity of the pituitary-thyroid axis meaning that both central and peripheral regulatory mechanisms of thyroid economy are affected by feed restriction.

Animals↗