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Biomedical subjects

U Weiler

Publications and source records attributed to U Weiler.

14 recordsLinked to original sources
PubMed2006

Influence of short-term confinement and exercise on tibia development in growing pigs.

The influence of short-term confinement and moderate exercise on tibia development was investigated in growing pigs (36-41 kg, 10 weeks at the beginning of the study). Animals were kept for 2 weeks either in individual crates of 0.8 m(2) ('confinement', n = 4) or kept in groups of four animals in large crates of 5.6 m(2) without ('control') or with additional exercise (30 min walking at 5 days/week; 'exercise'). Bone density and morphological parameters were evaluated by computer tomography (CT). Periosteal apposition and longitudinal growth were determined after polychrome sequential labelling in weekly intervals. Cortical areas of the cross sections at the mid-shaft and at 75% of the length of the bone measured distal to the carpus by CT were significantly correlated to each other (r = 0.70) and revealed a significant reduction in confined animals. This difference was explained by lower periosteal apposition rates in these animals compared with exercised and group-housed pigs. Similarly longitudinal growth and the formation and calcification of spongiosa of the tibiae were inhibited by confinement. Thus, 2 weeks of confinement led to significant differences in bone growth and metabolism in young growing piglets when compared with animals with moderate activity.

Animals↗
PubMed2003

Influence of cortisol, gonadal steroids and an energy deficit on biochemical indicators of bone turnover in Swine.

In the pig a high growth potential seems to favour a disposition for skeletal problems. Hormones of growth hormone (GH)/insulin-like growth factor (IGF)-I axis as well as cortisol and gonadal steroids are endocrine determinants of the anabolic potential but their effects on bone turnover in pigs have not been described. Thus, key hormones were either infused for 7 days (cortisol, 5alpha-dihydrotestosterone (DHT), oestradiol) or influenced by Metyrapone (inhibition of cortisol synthesis) or energy deficit (increasing GH). Each treatment was carried out in six growing barrows/treatment. Bone turnover was characterized by daily measurements indirect parameter of osteoblastic and osteoclastic activity, osteocalcin (OC) and tartrate-resistant acid phosphatase (TRAP) respectively. All treatments except cortisol infusion seemed to favour bone formation, as they led either to a pronounced increase in OC (Metyrapone: +14%) or to significantly reduced TRAP (DHT: -9%, E2: -17%, energy deficit: -25%) followed by significantly higher OC (DHT: +9%, E2: +6%, energy deficit: +18%). Cortisol infusion affected bone loss mainly by a severe inhibition of osteoblastic activity (OC: -61%). Some reactions are explained by direct effects of the infused gonadal steroids on bone cells (inhibition of osteoclasts) or of the experimentally modified cortisol levels (inhibition of osteoblasts by cortisol). Other effects seem to be mediated by concomitant changes of IGF-I (inhibition of osteoclasts after energy deficit or cortisol) and GH-secretion (increased osteoblastic activity during energy deficit), respectively. Consequences for co-ordinated bone turnover are discussed.

Acid Phosphatase↗
PubMed2000

Course of epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) in mammary secretions of the goat during end-pregnancy and early lactation.

The epidermal growth factor (EGF) plays a crucial role in mammogenesis in many species. In ruminants, studies are limited, as EGF does not occur in peripheral plasma and specific analytical systems do not exist. Therefore a heterologous radioimmunoassay based on rhEGF was set up to monitor EGF in mammary gland secretions from goats during end-pregnancy and early lactation. IGF-I was measured with an established radioimmunoassay. Samples were collected from 13 goats for 25 days ante-partum and 25 days post-partum. Mammary gland secretions were obtained ante-partum by removing a small amount of the udder secretions (control half) or milking (stimulated half). Post-partum normal milk samples were collected. Blood samples were drawn by jugular venipuncture for the same period. EGF was found to occur in different molecular weight forms in the mammary glands. For routine measurements these proteins were extracted with acetone and not further separated. IGF-I and EGF concentrations in mammary secretions and similarly IGF-I in blood were high ante-partum and decreased slightly towards birth. IGF-I but not EGF is found in the peripheral plasma. Whereas IGF-I concentrations in blood were quite constant post-partum, IGF-I and EGF dropped in mammary secretions close to the detection limits. The decrease was more pronounced in the stimulated half than in the control half. The data support a synergistic role for EGF and IGF-I for mammogenesis. Both factors are further influenced by the milking stimulus and thus the functional state of the udder.

Animals↗
PubMed1996

Relationships between IGF-I, cortisol, and osteocalcin in peripheral plasma of growing pigs.

Osteocalcin is a bone specific protein which is secreted by mature osteoblasts and is measurable in peripheral blood plasma. In growing female pigs (n = 6) osteocalcin was measured in daily blood samples between an age of 125 to 238 days and the values were compared to IGF-I and cortisol. Mean concentrations of osteocalcin were 158 +/- 2.7 ng/ml and the concentrations were significantly correlated to those of IGF-I (r = 0.12 p < or = 0.01 n = 581) and cortisol (r = 0.13 p < or = 0.01 n = 503). Both hormones and less pronounced osteocalcin revealed a rhythm-like pattern with a period of 10-14 days. In addition, rhythm-like variations with a period of about 5 weeks are visible. The highest correlation was found between IGF-I and cortisol both within the animals (r = 0.28, n = 508, p < or = 0.001) and between the individuals (r = 0.94, n = 6, p < or = 0.01). Thus a dialog between IGF-I and cortisol may be assumed. A possible physiological role is discussed.

Age Factors↗
PubMed1995

Consequences of selection on muscle composition. A comparative study on gracilis muscle in wild and domestic pigs.

European domestic pigs are derived from the European wild pig by genetic selection and differ in their muscular-growth ability. Thus, it was the aim of this study to investigate the consequences of genetic selection on muscle composition and fibre size in the gracilis muscle. Fibre typing based on the ATPase reaction revealed that this muscle in wild pigs is composed mainly of type-I and -IIa fibres, whereas, in domestic pigs, type-IIb fibres were predominant. For all fibre types, domestic pigs had about threefold larger fibres than wild pigs. Type-I fibres tended to be the smallest fibres in domestic pigs, but the largest fibres in wild pigs, which may be due to long-term training effects in the free-ranging animals. Giant fibres as an indicator of degeneration were obvious only in the domestic-pig samples. Their occurrence, as well as the larger fibre size and the predominance of type-IIb fibres in domestic pigs, may be ascribed to high concentrations of growth hormone. It is concluded that selection for muscular growth may favour metabolic dysbalances within the muscle and, therefore, degenerative processes.

Adenosine Triphosphatases↗
PubMed1989

Replenishment of AI-doses with oestrogens in physiological amounts: effect on sow prolificacy in a field trial.

Basing on results about physiological functions of seminal oestrogens in the genital tract of sows, the effects of an oestrogen replenishment to AI-doses were investigated in a field trial. Each ejaculate was split into two halves, which were either diluted to normal AI-doses (controls, n = 353) or diluted and replenished with oestrogens in physiological amounts (n = 384). Insemination by qualified technicians led to an improvement of the pregnancy rate (82.8% vs. 77.1%; p less than 0.05) and the litter size (10.8% vs. 10.3%; p less than 0.05) in favour of the oestrogen replenishment. These results partly explain the known differences in prolificacy between natural mating and AI and thus provide a basis for improvement of pig AI.

Animals↗
PubMed1987

Seminal oestrogens in the boar: origin and functions in the sow.

The boar produces considerable amounts of oestrogens in the Leydig-cells also occurring in semen. Very high oestrogen concentrations are measurable in the fluid of the tubuli, which contribute the main part of seminal oestrogens. Additionally, the accessory sex glands add 22% of the unconjugated oestrogens and 12% of conjugated oestrogens to the ejaculate. Concentrations vary considerably according to season and individuals. So far a maximum of 15.3 micrograms was measured in one ejaculate. Infusion of oestrogens (simulation of the oestrogen content of an ejaculate) at oestrus through a catheter into the uterus lumen leads to an increase of the myometrial contraction-frequency for 3 h. Additionally "inseminations" with oestradiol-17 beta (Oe 2), oestrone (Oe 1), and oestrone-sulfate (Oe 1-S) (naturally occurring in the ejaculate) in 10-micrograms amounts at oestrus may lead to an increase of PGF2 alpha concentrations in the uterine veins within a few minutes. This increase may be found after "insemination" with each of the three steroids but not after saline. A parallel rise of the "inseminated" oestrogen is measurable in the uterine vein plasma and may reach concentrations up to several thousand pg/ml. This rise also leads to significantly increased concentrations in peripheral plasma for about 30 min after the "insemination" of Oe 2 (increase of Oe 2 and Oe 1-S) and Oe 1 (Oe 1 and Oe 1-S). Consequences of seminal oestrogens for sperm transport and the timing of ovulation are discussed.

Animals↗
PubMed1985

The regulation of mitochondrial-bound hexokinases in the liver.

A functional coupling between bound hexokinase and the inner mitochondrial compartment has been shown. It is based structurally on the binding of hexokinase to a pore protein which is present in zones of contact between the two boundary membranes. The latter was observed by electron microscopic localization of antiporin and hexokinase at the mitochondrial surface. The four isoenzymes present in liver differ considerably in their activity after binding to the mitochondrial surface. This was found by binding studies using the four isoenzymes isolated from the supernatant. Isoenzyme IV did not bind at all. Isoenzymes I-III did bind and became activated: I, 5.9-fold; II, 39-fold; and III, 1.3-fold. These results suggest that the in vivo activity of hexokinase in the mitochondrial fraction is much larger than so far observed. Furthermore the binding of isoenzymes was differently affected by metabolites. Glucose-6-phosphate exclusively desorbed isoenzyme I from the mitochondrial membrane whereas free fatty acids predominantly liberated isoenzymes II and III. A reciprocal change of the levels of free fatty acids and glucose 6-phosphate in livers of starved rats therefore, can explain why exclusively mitochondrial-bound isoenzymes II and III decreased 10-fold while at the same time isoenzyme I increased.

Animals↗
PubMed1985

Influence of light and photoperiodicity on pig prolificacy.

In the wild pig mating activity is seasonal. The main breeding period is in late autumn but a second period may occur around April. It is known from other species that seasonal variations in breeding activity are mainly regulated by photoperiod. In the domestic pig seasonal influences on prolificacy still exist: for example, AI boars not only show decreased steroid synthesis, sperm counts and libido in summer compared with the optima which occur in winter but also a biphasic pattern with a transient increase in spring. In cyclic sows ovarian function may be affected with anoestrus mainly in summer and occasionally in February/March. Additionally ovulation rate may be lower in summer and the duration of oestrus prolonged compared with that in late autumn and winter. In consequence the interval from weaning to oestrus is prolonged in summer and mating during this season leads to lower conception rates and slightly smaller litters. Light programmes which extend the daily light period to a constant 15-16 h seem to be ineffective in improving reproductive characteristics of the sow but stimulate the sucking frequency of piglets and increase survival of piglets with a low birthweight. Simulation, in summer, of the decreasing photoperiod (naturally occurring in autumn) stimulates the reproductive characteristics of AI boars, optimizing testicular steroid production, libido and semen composition. Similarly, a programme of decreasing light (20 min decrease/week) from May to August removed the seasonal increase (June-August) of the weaning-to-oestrus interval which was 5.7 days (compared with 23.6 days for the controls). An interaction between photoperiod and puberty attainment seems to exist for male and female pigs. Further experiments with appropriate light programmes, however, are necessary to clarify this interaction.

Androgens↗