Per Rosenkilde

Function and cytology of the normal and autotransplanted pars distalis of the hypophysis in the toad Bufo bufo (L)

The functional activity of the pars distalis following heterotopic and homoiotopic autotransplantation has been studied in adult toads of both sexes in the spring, about a month after breeding, and in the autumn on toads with mature gonads. Gonadotropic Function. In males, the homoiotopic grafting of the pars distalis maintained about normal spermatogenesis and interstitial cell activity, but ectopic transplants caused a strong reduction of interstitial cell activity, though spermatogenesis was only slightly reduced. In the spring experiment, there was no significant difference in the ovaries of the two graft-bearing groups, which were intermediate between the normal and the hypophysectomized controls. In autumn females, however, the ovaries of 5 of 8 toads with homoiotopic grafts atrophied, as in the hypophysectomized controls. The 3 remaining toads had ovaries of nearly normal size filled with mature eggs, but there were strong indications that in these 3 toads also the mature eggs that were present at the time of operation degenerated immediately after the operation, and was followed by a phase of extensive growth and maturation of small oocytes during the 2 months of the experiment. All females with ectopic grafts had atrophic ovaries at the end of the experiment. Adrenocorticotropic Function. This function was normal in the toads with homoiotopic grafts. No corticotropic function could be demonstrated in the ectopic grafts although the cytological study of males in the spring experiment showed that, in general, the adrenocortical cells in the toads bearing ectopic grafts appeared more active than those in the hypophysectomized controls. Thyrotropic Function. Thyroidal uptake of 131I in the autumn experiment was used to evaluate thyrotropic function. Uptake was normal in toads with homoiotopic grafts, but reduced in the toads with ectopic grafts. In the males with ectopic grafts, the 131I accumulation in the thyroids was not significantly higher than in the thyroids of the hypophysectomized controls. Fat Bodies. In the autumn experiment, feeding was insufficient to maintain body weight, and the fat bodies were greatly reduced in both normal controls and in the toads with homoiotopic grafts. Hypophysectomized controls, however, possessed large fat bodies despite an even greater loss of body weight. In the toads with ectopic grafts, net mobilization of fat from the fat bodies was intermediate between the normal and hypophysectomized controls. In the spring experiment, feeding was efficient. All groups increased in weight, and all showed fat deposition. Cytology of Pars Distalis. Four of the five tinctorial cell types, described for the pars distalis of Bufo bufo, were observed: carminophils, orangeophils, globular basophils, and violet cells. In most of the controls the carminophils and orangeophils were storing secretory granules; the globular basophils and the violet cells showed signs of secretory activity. All four cell types remained largely unchanged in the area of the homoiotopic grafts, bordering the median eminence and pars intermedia. In the rest of such grafts and in the heterotopic transplants cysts were formed, and degeneration and dedifferentiation of cells took place; carminophils and orangeophils had slightly degranulated, globular basophils had become strongly regressed in number and granulation, and violet cells had almost completely disappeared. Generally, there existed a close correlation between the state of the target organs and the morphological signs of secretory activity of the pars distalis cells. It is suggested that not only the globular basophils, but also the violet cells have a gonadotropic function, and are responsible for the development and maintenance of the interstitial Leydig cells in the testis.

Cu uptake, metabolism and elimination in fed and starved European eels (Anguilla anguilla) during adaptation to water-borne Cu exposure

64Cu accumulation and total Cu concentrations were measured in gill filaments, plasma, liver and bile of fed and starved European eels (Anguilla anguilla) during 28 days of exposure to 12 and 94 micrograms Cu l-1. Branchial Cu uptake was found to be 0.03 and 0.13 microgram Cu g gill filament-1 h-1 at 12 and 94 micrograms Cu l-1, respectively, throughout 28 days of Cu exposure. At least during exposure to 94 micrograms Cu l-1, the basolateral membrane seemed to be the rate limiting step for branchial Cu uptake. The plasma accounted for at least 70% of the 64Cu labelled Cu present in the blood at both Cu concentrations. The plasma Cu concentration was gradually increased from 0.64 to 1.92 and 2.68 micrograms ml-1 during the first 6 days of Cu exposure; it was partly normalized to 1.07 and 1.45 micrograms ml-1 after 28 days of exposure to 12 and 94 micrograms Cu l-1, respectively, despite a constant branchial Cu uptake, indicating an increased turnover of plasma Cu. The hepatic accumulation of 64Cu was similar in fed and starved eels (0.55 microgram Cu g liver-1 h-1) at both Cu concentrations during the 28 days of exposure. The hepatic total Cu concentrations were lower in the fed fish compared to the starved fish and increased only marginally from 3 to 28 days of exposure indicating a high turnover of hepatic Cu during acclimation. Hepatic Cu elimination, measured as 64Cu in the bile, was highest in the fed fish at the highest Cu concentration and was stimulated during acclimation at least in the starved fish.

Influence of preexposure to sublethal levels of copper on 64Cu uptake and distribution among tissues of the European eel (Anguilla anguilla)

The effect of preexposure to copper was examined in European eels with respect to uptake and distribution of 64Cu among tissues. Eels were exposed in freshwater to 8 and 64 μg Cu · L−1 for 0, 6 and 28 days before 64Cu incubation. The accumulation of copper in gill, liver and muscle tissue was studied by the uptake of 64Cu during 67 hr of exposure to 8 and 64 μg · L−1. The Cu accumulation rate in muscle tissue was inversely related to bodyweight. Although the accumulation rates in liver and muscle tissues were significantly reduced after 6 and 28 days of preexposure to 64 μg · L−1 (but not to 8 μg · L−1), the accumulation rates in the gills were not affected by preexposure. We suggest that the excretion rate of copper was stimulated by the applied preexposure to 64 μg Cu · L−1.

Moderate exercise decreases plasma cortisol levels in atlantic salmon (Salmo salar)

Abstract 1. 1. Atlantic salmon, Salmo salar , subjected to moderate exercise (0.5 body length/sec) for 24 hr showed a significant decrease in plasma cortisol levels, after an initial sharp peak, compared to controls kept in still water. 2. 2. These findings indicate that the exercising salmon at 0.5 bl/sec have reduced stress levels which may account for the increase in growth described in trained salmonids.

Role of the preoptic-neurohypophysial system in the water economy of the toad, Bufo bufo L

Abstract The effect of neurohypophysectomy or of lesions in the preoptic region of the hypothalamus on water balance was studied in the toad Bufo bufo . In the majority of the lesion-bearing toads, few or no surviving cells were found in the preoptic nuclei, and the neurosecretory material in the pars nervosa was significantly reduced to completely absent. The operations had little effect on the antidiuretic response to moderate dehydration or on the increased cutaneous water permeability caused by severe dehydration. There was no correlation between the response to dehydration and the completeness of elimination of the preoptic-neurohypophysial system. An attempt has been made to delineate the role played by the preoptic-neurohypophysial system in the water economy of the toad. It seems that the antidiuretic response to an osmotic load and an increased permeability of the urinary bladder to water may largely depend upon a functioning preoptic-neurohypophysial system. In the absence of the neurohypophysis the system appears unable to exert its functions in the water economy of the toad.

Determination of serum thyroxine in two species of toads: Variation with season

Abstract Thyroxine concentrations were compared in two species of toads, viz., the green toad, Bufo viridis, and the common toad, B. bufo. Thyroxine was determined by means of a competitive protein-binding technique which had a detection level below 0.1 ng. The method is described and its applications are discussed. In prebreeding B. viridis, thyroxine levels were 13.6 ± 0.9 ng/ml of serum in females and 10.6 ± 0.8 ng/ml in males. In early autumn the concentration had decreased to 5.0 ± 0.4 ng/ml. B. bufo had 3.5 ± 0.3 ng/ml of serum in June and remained at that level until October. Common toads kept for the winter in a refrigerator at 5° and sacrificed in December and February had 1.7 ± 0.1 ng of thyroxine/ml of serum.

Hypothalamic control of thyroid function in Amphibia

Abstract The regulation of thyroid activity in Amphibia is characterized by a wide range of variation in the dependence of the thyroid upon the pars distalis of the pituitary and in the dependence of the pars distalis upon the central nervous system. In Bufo bufo , thyroid activity is dependent upon TSH secretion from the pars distalis. Pars distalis thyrotropic activity is fully dependent upon contact with the hypothalamus. Hypothalamic influence includes a stimulatory part (TRH-secreting cells), situated in the hypothalamus at or behind the level of the optic chiasma, and an inhibitory part, originating above the level of the optic chiasma. The implications of this system are discussed. In most other Amphibia, thyroid activity—measured as iodine uptake—depends upon a functional pars distalis, but thyrotropic secretion shows a higher degree of autonomy, in that ectopic pars distalis grafts can maintain at least normal thyroid activity, and partial extirpation of the hypothalamus does not abolish thyrotropic activity. In some amphibian species a hypothalamic inhibitory influence upon thyroid activity is indicated. Triturus cristatus shows a further increase in autonomy, insofar as hypophysectomy does not result in immediate decrease in iodine uptake, as in other amphibian species. After some weeks, however, thyroid activity declines. The presence of hypothalamic inhibition in several amphibian species together with the fact that hypothalamic stimulation of thyrotropic function is necessary to complete amphibian metamorphosis, indicates that the basal pattern of thyroid regulation in Amphibia includes both inhibitory and stimulatory influences from the central nervous system.

Effect of extirpation of median eminence on function of pars distalis of the hypophysis in the toad Bufo bufo (L.)

Abstract In order to test the hypothesis that in vertebrates the hypothalamic neuro-humoral control of the pars distalis of the hypophysis is mediated by the median eminence and the hypophysial portal circulation, the effect of extirpation of these structures on the function of pars distalis was investigated in the toad Bufo bufo (L.). In nine toads out of eleven with extirpated median eminence of the neurohypophysis and in thirty toads out of sixty-four with completely extirpated neurohypophysis, the pars distalis was functioning for one to several months after the operation. Extirpation of the median eminence was compatible with normal survival for at least one year; toads with totally extirpated neurohypophysis died within 5 months. Apparently, the pars distalis resumed functioning only when it obtained contact with the cut ends of the hypothalamic tracts normally terminating in the median eminence. It is suggested that the pars distalis activating substances that are normally liberated in the median eminence are produced in hypothalamic centres as neurosection.

Iodine metabolism in normal, hypophysectomized, and thyrotropin-treated river lampreys, Lampetra fluviatilis (Gray) L. (Cyclostomata)

Iodine metabolism in adult male and female river lampreys was studied before and during sexual maturation. Intact and hypophysectomized (pro- and mesoadenohypophysis) lampreys were included in the study. The effect of treatment with thyroxine and thyrotropin was evaluated. The following parameters were investigated: 131I uptake (in the thyroid gland, the gonads, and the notochord), iodinated compounds in the thyroid tissue, protein-bound iodine in blood, ordinary histology, and autoradiography of the thyroid follicles. It was concluded that iodine metabolism was similar to that of other vertebrates, but no evidence was found of hypophysial control of thyroid function nor of any specific inhibitory action of thyroxine on iodine metabolism.

Formation of phosphatidylethanolamine as a putative regulator of salt transport in the gills and esophagus of the rainbow trout (Oncorhynchus mykiss)

Abstract Rainbow trout ( Oncorhynchus mykiss ) adapted to brackish water (BW) showed 32 P-phospholipid patterns in gill and esophagus tissues dominated by phosphatidylcholine (PC) when the fish were incubated in vivo either in fresh water (FW) at 5, 16°C or in BW at 5°C, and corresponding patterns dominated by phosphatidylethanolamine (PE) when the fish were incubated in vivo either in seawater (SW) at 5, 16°C or in BW at 16°C, in both cases with ( 32 P) phosphate as the precursor labeling the polar headgroups. Equivalent incorporations in the same fish with (1 14 C) acetate as precursor, labeling the lipophilic moiety, showed 14 C-phospholipid patterns in gill and esophagus tissues dominated by PC, practically independent of ambient salinity and temperature. Eels ( Anguilla anguilla ) similarly incubated in vivo in FW at 18°C showed 32 P-phospholipid patterns in gill tissue dominated by PE after preadaptation to either FW or SW; corresponding patterns after preadaptation to BW showed PE = PC. We suggest that PE participates in a stabilization of the integral membrane proteins that regulate the function of apical ion channels. The absence of PE dominated 32 P-phospholipid patterns in FW after preadaptation to isosmotic BW would indicate that the fish do not experience an osmotic challenge under these circumstances.