Morten Ryg

Re-evaluation of concentration levels of polychlorinated dibenzo-p-dioxins and dibenzofurans in arctic seal from spitzbergen

Abstract Levels of polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and pesticides in ringed seal blubber have been reported in Chemosphere 17 , 1291 (1988). Additional informations about sex, age and exact area which had gone lost by accident, have now been regained. They made a re-evaluation of the data necessary since the animals were caught much closer to the settlement at Ny Alesund than assumed earlier. No influence of this local source on the determined concentrations was found when they were compared with the levels in Arctic seals which have been published in the meantime.

Seasonal changes in levels of growth hormone, somatomedin and thyroxine in free-ranging, semi-domesticated norwegian reindeer [Rangifertarandus tarandus (L.)]

Abstract 1. 1. Semi-domesticated reindeer of both sexes from two adjacent herds (A and B) in the Lodingen district of Norway were studied. From Herd A jugular blood samples were collected in summer (1974), and from Herd B both in summer and in winter (1975). 2. 2. Serum levels of growth hormone, somatomedin and thyroxine were measured, and, for Herd B, conspicuous seasonal changes in the three growth promoting hormones were found, both for the calf and the adult groups. 3. 3. Levels of growth hormone were reduced in winter as compared to summer: 21.6 ± 1.6 ng/ml vs 31.9 ± 2.2 ng/ml (calves), and 20.3 ± 0.9 ng/ml vs 25.5 ± 1.5ng/ml (adults). The same was found for thyroxine: 144 ± 9 mmol/1 vs 249 ± 10 mmol/1 (calves), and 157 ± 5 nmol/1 vs 223 ±7 nmol/1 (adults). Levels of somatomedin, on other hand, were higher in winter than in summer: 1.11 ± 0.10 U/ml vs 0.67 ± 0.07 U/ml (calves), and 1.02 ± 0.09 U/ml vs 0.53 ± 0.04 U/ml (adults). 4. 4. The observed seasonal changes may reflect one aspect of the physiological adjustments involved in the adaptation of the reindeer to arctic living conditions.

Relationships between hormone-induced and compensatory weight changes in reindeer (Rangifer tarandus tarandus)

1. In connection with a study of hormonal effects on food consumption in reindeer, weight changes during treatment were compared with weight changes during a 3-week period following treatment. 2. Rates of weight change during the post-treatment period were inversely proportional to induced weight changes. 3. This inverse relationship is interpreted as evidence for a functional set-point for body weight in reindeer.

Seasonal changes in the relationship between food intake and serum triiodothyronine in reindeer

Abstract 1. 1. The relationship between serum triiodothyronine (T3) and food intake in reindeer was studied throughout the year. 2. 2. T3 was positively correlated with dry matter intake at all times of the year. 3. 3. The coefficient of regression of T3 on dry matter intake was lower in August–November (0.023) than in April–June (0.060). 4. 4. It is suggested that a less pronounced effect of food intake on T3 levels could be one cause of fat deposition in late summer and autumn.

Effects of nutrition on seasonal changes in testosterone levels in young male reindeer (Rangifer tarandus tarandus)

Food restriction during autumn in male reindeer calves decreased peak testosterone levels at 4-6 months, and also at 16-17 months of age. Peak testosterone levels at the age of 16-17 months were significantly correlated to body weight at 6 months but not to body weight at 16 months of age. There were small secondary testosterone peaks (1-3 ng/ml) in March or April in 11 of 16 animals. Testosterone levels started to increase before summer solstice in 50% of the yearlings.

Physiological control of growth, reproduction and lactation in deer

The physiological mechanisms controlling the growth, lactation and reproductive cycles of cervids, and the control of allocation of energy to different organs are discussed. The growth cycle may be secondary to an appetite cycle, regulated by changes in the secretion of prolactin, gonadal steroids, and possibly unknown factors. The reproductive cycle is controlled by changes in the release at the hypothalamic hormone GnRH, and by changes in the feedback effect of gonadal steroids. These cycles are probably the result of the timing effects of nutrition and changing photoperiod on an endogenous, circannual rhythm. The effect of photopenod is mediated by the pineal hormone melatonin. The physiological mechanisms controlling the partitioning of substrates between milk production, fetal growth and the tissues of the mother are poorly understood, but may involve changes in the secretion of growth hormone, insulin and triiodothyronine.

Effect of testosterone on antler growth in yearling male reindeer

1. The effect of exogenous testosterone on ander growth in yearling male reindeer (Rangifer tarandus tarandus) was tested. 2. Testosterone (33 mg/kg) inhibited antler growth, and in one animal induced cleaning and subsequent casting of the antlers. This animal grew a new set of antlers, which were cleaned at the normal time. 3. During treatment, there was an inverse relationship between peak testosterone levels and antler growth rate. 4. There was no effect of treatment on body weight or food intake. 5. It is concluded that the effects of testosterone on antler growth are qualitatively the same in reindeer as in other deer. However, because high testosterone doses were necessary to produce effects, it is questionable whether this hormone normally is responsible for the cessation of antler growth in reindeer. Virkningen av testosteron pa gevirvekst hos ettarige reinbukker. Abstract in Norwegian / Sammendrag: 1. Virkningen av testosteron pa gevirvekst hos ett-arige reinbukker (Rangifer tarandus tarandus) ble undersokt. 2. Testosteron (33 mg/kg) hemmet gevirveksten, og hos ett dyr forte behandlingen til at geviret ble feiet og deretter felt. Deretter vokste det ut ett nytt gevir, som ble feiet til vanlig tid. 3. Det var en negativ korrelasjon mellom maksimale testosteronnivaer og gevirvekst under behandlingen. 4. Det var ingen effekt pa forinntak eller vektutvikling. 5. Det blir konkludert med at virkningen av testosteron pa gevirvekst er kvalitativt den samme hos rein som hos andre hjortedyr. Det er likevel tvilsomt om testosteron normalt er ansvarlig for avslutningen av gevirvekst hos rein, fordi store testosterondoser matte til for a fa noen virkning. Testosteronin vaikutus vuodenikaisten urosporojen sarvien kasvuun. Abstract in Finnish / Tiivistelma: 1. Tutkimuksessa seurattiin ruiskeena annetun testosteronin vaikutusta vuodenikaisten urosporojen (Rangifer tarandus tarandus) sarvien kasvuun. 2. Testosteron! (33 mg/kg) hidasti sarvien kasvua, aiheuttaen yhdessa elaimessa sarvien kelomisen ja pudottamisen. Talle elaimelle kasvoi uudestaan sarvet, jotka se keloi normaaliin aikaan. 3. Testosteronin huipputaso veressa oli kasittelyaikana kaantaen verrannollinen sarvien kasvunopeuteen. 4. Kasittely ei vaikuttanut elainten ruumiinpainoon eika niiden ruokahaluun. 5. Voidaan paatella testosteronin vaikutuksien sarvien kasvuun olevan porossa laadullisesti yhtalaiset kuin muissakin hirvielaimissa. Koska vaikutuksen aikaansaamiseksi vaadittiin korkeita testosteroniannoksia, voidaan kuitenkin pitaa kyseenalaisena, onko kyseinen hormoni normaalisti vastuussa poronsarven kasvun keskeytymisesta.

Effects of nutrition on serum levels of thyroxine and triiodothyronine in reindeer (Rangifer tarandus tarandus)

We have investigated effects of qualitative and quantitative differences in feed on serum concentrations on the thyorid hormones, thyroxine (T4) and triiodothyronine (T3). We have recorded hormone levels in groups of animals of different sex, age and weight. They were fed either a pelleted reindeer feed (RF 71, 13,7% protein) or lichen (3,4 protein), or a combination of RF 71 and lichen. 1. When going over from restricted to ad lib. feeding with the same kind of feed (RF 71), serum T3 increased, but nok T4. 2. Serum T3 or T4 did nok change when feed was changed from RF 71 to the same amount of dry matter of a combination of RF 71 and lichen. Neither were there any significant differences between a group fed RF 71 and a group fed a combination of RF 71 and lichen. 3. Serum T3 and dry matter intake were well correlated. We conclude that seasonal differences in T4 are partly independent of nutrition, while T3 was heavily influenced by nutrition, specifically the amount of dry matter consumed. Serum T3 can possibly be used to estimate dry matter intake. Ravitsemuksen vaikutus poron (Rangifer tarandus tarandus) seerumin tyroksiini ja trijodityroniinitasoon. Abstract in Finnish / Yhteenveto: Olemme tutkineet poron ravinnonsaannissa esiintyvien kvalitatiivisten ja kvantitathvisten erojen vaikutusta seerumin kilpirauhashormonien trijodityroniinin (T3) ja tyroksiinin (T4) konsentraatioon. Olemme rekisteroineet hormonipitoisuuksia ian, sukupuolen ja painon perusteella erilaisissa ryhmissa. Ruokinnassa on kaytetty pelletoitua poronrehua (RF 71, 13,7% proteiini ja/tai jakalaa (3,4% proteiinia). 1. Siirryttaessa rajoitetusta rehunsaannista ad lib. ruokintaan samalla rehulla (RF 71), seerumin T3-taso kohosi, mutta ei T4-taso. 2. Siirryttaessa ruokinnassa RF 71-rehun kaytosta kuiva-ainepitoisuudeltaan vastaavan RF 71-rehun ja jakala-yhdistelman kayttoon ei havaittu merkitsevia muutoksia T3- tai T4-tasoisaa. Verrattaessa RF 71-rehua kayttanytta ryhmaa ja toista ryhmaa, jota ruokittiin rehun ha jakalan yhdistelmalla ei myoskaan havaittu merkitsevia eroja. 3. Nautitun kuiva-ainemaaran ja seerumin T3-konsentraation valilla vallitsee selva korrelaatio. Me paattelemme, etta T4-tason vuodenaikaisvaihtelut ovat osittain riippumattomia ravitsemuksesta, kun taas ravinto selvasti vaikuttaa T3-tasoon. Seerumin T3-arvoa voidaan ehka kayttaa poron nauttiman kuiva-ainemaaran arvioimiseen. Virkninger av ernaering pa serumnivaer av thyroxin og triiodothyronin hos rein (Rangifer tarandus tarandus) Abstract in Norwegian / Sammendrag: Vi har undersokt virkningen av kvalitative og kvantitative forskjeller i naeringstilgang pa konsentrasjonene av skjoldbruskkjertelhormonene triiodothyronin (T3) og thyroxin (T4) i serum hos rein. Vi har registrert hormonnivaer hos grupper av dyr med forskjellig alder, kjonn og vekt. De har vaert foret med et pelletert reinfor (RF 71, 13,7% protein), og/eller lav (3,4% protein). 1. Ved overgang fra begrenset til ad lib. foring med samme for (RF 71) okte serum T3, men ikke T4. 2. Ved overgang fra RF 71 til samme torrstoffmengde av en kombinasjon av RF 71 og lav, var det ikke signifikante endringer i T3 eller T4. Det var heller ikke signifikante forskjeller mellom en gruppe som ble foret med RF 71 og en som ble foret med RF 71 og lav. 3. Det var en god korrelasjon mellom torrstoffinntak og serumkonsentrasjon av T3. Vi konkluderer med at arstidsvariasjonene i T4 delvis er uavhengige av ernaering, mens T3 er strengt ernaeringsregulert. Serum T3 kan kanskje brukes til a estimere torrstoffinntak hos rein.