Ultrastructure of the nongranulated cells and morphology of the extracellular spaces in the pars distalis of adult and pouch-young tammar wallabies (Macropus eugenii)

Summary Differentiated nongranulated (folliculo-stellate) cells were observed in the centre and periphery of the cords of cells in the pars distalis of the adult tammar wallaby (Macropus eugenii). The nongranulated cells formed follicles containing a small lumen; the cell apices were joined by junctional complexes including zonulae adhaerentes and maculae adhaerentes (desmosomes). Follicles of granulated cells were also occasionally found. Follicles were rarely observed in the adult, but were numerous and generally larger in pouch-young wallabies. Moreover, whereas the involvement of granulated cells in the follicles of the adult was infrequent, they were common components of follicular structures in the pouch-young. The marginal cells at the periphery of the pars distalis in contact with the hypophysial cleft had many of the cytological characteristics of the nongranulated cells in the central pars distalis. In both adult and pouch-young wallabies, nongranulated cells at the periphery of the cell cords were juxtaposed such that they formed sinusoid-like spaces or lacunae, presumably as part of the extravascular channel system. The observations are discussed in light of the proposed phagocytotic, metabolite and/or hormone transport and stem cell roles attributed to these cells.This work was supported by a travel grant and grant-in-aid of research from the N.S.E.R.C. (J.F.L.) and from the A.R.G.C. and the N.I.H. (M.B.R.)     

Studies on the relationship between osmotic or ionic regulation and thyroid gland activity in two salmonid fishes, Salmo gairdneri Richardson and Oncorhynchus kisutch Walbaum

In freshwater-acclimated rainbow trout a single intraperitoneal injection of ovine TSH significantly elevated plasma thyroxine (T₄) levels within 1 h after the injection. In seawater adapted trout the increase in T₄ after TSH-treatment was not evident until 6 h after the injection. TSH caused a transient fall in plasma Na⁺ and Cl^- between 3 h and 9 h after the injection in seawater-adapted fish and plasma Na⁺ was lowered in freshwater-adapted trout 24 h after the injection. Although there were clear histological changes in the thyroid gland of freshwater-adapted trout after TSH-injection, no such changes were evident in seawater-adapted fish.
Plasma thyroid hormone levels and thyroid histology in freshwater-adapted rainbow trout and coho salmon transferred to sea water, and seawater-adapted trout transferred to fresh water showed no consistent changes compared with controls.
The data are interpreted to indicate that although ambient salinity may have indirect effects on thyroid activity there is no direct involvement in ionic or osmotic regulation in the two species.     

Early events in the cellular formation of proparathyroid hormone

Early events in the cellular synthesis and subsequent transfer into membrane-limited compartments of pre-proparathyroid hormone (pre-proPTH) and proparathyroid hormone (proPTH) were investigated by electrophoretic analyses of newly synthesized proteins in subcellular fractions of parthyroid gland slices pulse-labeled for 0.5-5 min with [(35)S] methionine. During these short times of incubation, both pre-proPTH and proPTH were confined to the microsomal fraction. Labeled pre-proPTH and proPTH were detected in a 30-s interval between 0.5 and 1.0 min of incubation. The radioactivity in proPTH became relatively constant between 3 and 5 min, whereas the radioactivity in ProPTH increased markedly over this period. When corrected for the known content of methionine in the prohormone and the prohormone, we found four times as much radiolabeled prohormone as prehormone between 0.5 and 1.0 min of synthesis. Sequestration of labeled prohomrone into endoplasmic reticulum compartments was shown by treatment of the microsomal fraction with chymotrypsin and trypsin, which resulted in the degradation of the prehormone but not of the prohormones. Approximately 50 percent of pre-prohormone and 25 percent of prohormone were released from the microsomes by their extraction with 1.0 M KCl, whereas 80-90 percent of both was released by treatment with Triton X-100. These results in intact cells support the signal hypothesis proposed by Blobel and his co-workers in studies utilizing cell-free systems, inasmuch as the results indicate transfer of prohormone into the cisternal space of the rough endoplasmic reticulum concomitant with the growth of the nascent polypeptide chain. Appearance of membrane-sequestered proPTH takes place without entry of pre-proPTH into the cisternal space, suggesting that proteolytic removal of the leader peptide occurs during transfer of the polypeptide through the lipid bilayer. Further evidence in support of this process is that pre-proPTH is only partly extracted from the microsomes by treatment with 1.0 M KCl, suggesting that a substantial fraction of the nascent pre-proPTH is integrally inserted into the membranes before it is cleaved to form proPTH.     

Influence of plasma lipid changes in response to 17β-oestradiol stimulation on plasma growth hormone, somatostatin, and thyroid hormone levels in immature rainbow trout

Plasma total lipids were significantly higher in 17β-oestradiol(E₂)-treated immature rainbow trout Oncorhynchus mykiss at week 4 after implantation, due to increases in polar and neutral lipids. The lipid classes responding were phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine, sterols and sterol esters, in a proportion that approximately reflected the increase in plasma vitellogenin (VtG) levels as measured by a non-competitive enzyme-linked immunosorbent assay (ELISA). Plasma non-esterified fatty acids and triacylglycerol were not affected by E₂ treatment. Plasma growth hormone GH levels were increased, and plasma somatostatin-14 (SRIF) levels decreased in E₂-treated fish, responses which could be secondary to elevated plasma lipid (VtG) content, although a direct E₂ action on somatotroph function is possible. Plasma T₄ concentrations were not affected by E₂ treatment, but plasma T₃ concentrations were significantly lower than in controls 1 week after implantation when plasma E₂ concentrations were the highest; this is in support of the hypothesis that E₂ has a suppressive action on T₃ production.     

Social dominance and interrenal cell activity in rainbow trout,Salmo gairdneri (Pisces,Salmonidae)

Synopsis The relationship between standing in a dominance hierarchy and physiological stress was studied in rainbow trout. Individual fish were assigned relative dominance ranks, based on behavioral observations in a large, simulated stream tank. These ranks were compared to histometric measures of interrenal cell activity. Fish, isolated individually in the stream tank had significantly lower levels of interrenal activity than fish from the crowded holding tank. Groups of fish in the stream tank formed stable, linear dominance hierarchies. Interrenal activity correlated inversely with dominance rank, with the exception that top ranking fish had higher activity than expected. Possible cause and effect relationships are discussed.     

Determination of amitriptyline and some of its metabolites in blood by high-pressure liquid chromatography

Conditions for the determination of amitriptyline and some of its metabolites in serum on a reversed-phase material (C-8) by high-pressure liquid chromatography with UV detection at 254 nm were systematically investigated. The separation of tricyclic antidepressants is best carried out on a phase system consisting of C-8 bonded-phase material as the stationary phase and water—methanol—dichloromethane—propylamine as the mobile phase.The precision and detection limit of the method and the extraction efficiency were established. A chromatogram of a serum extract from a patient treated with amitriptyline is shown. Serum levels of amitriptyline and its four main metabolites (nortriptyline, desmethylnortriptyline, trans-10-hydroxy-amitriptyline and trans-10-hydroxy-nortriptyline) in a patient receiving 150 mg of amitriptyline daily, are reported.     

Further studies on the effect of diet on serum thyroid hormone concentrations and thyroid histology in rainbow trout,Salmo gairdneri (Pisces,Salmonidae)

Synopsis In a 3 × 2 factorial experiment examining the effects of combinations of ambient temperature (18°, 15°, 9° C) and dietary protein content (35% and 45%) on thyroid activity inSalmo gairdneri, although there was an apparent increase in activity of the thyroid in cold-adapted trout, assessed by histological appearance of the gland, there were no significant changes in serum thyroid hormone titers. In a second experiment examining the effects of combinations of ambient temperature (15°, 12.5°, 10°C) with dietary lipid content (6% and 16%) there was a similar apparent increase in thyroid activity in cold-adapted fish which was accompanied, in fish fed the higher lipid diet, with an increase in serum thyroxine (T4) and triiodothyronine (T3) levels. Trout fed an ascorbic acid-free diet (experiment 3) had lower serum T3 levels than in those given an ascorbic acid supplemented diet (1280 mg·kg^-1). In experiments 2 and 3 serum thyroid hormone concentrations were approximately inversely proportional to ambient temperature and concomitant weight gain, but no such correlation was evident in experiment 1 suggesting that the changes in hormone levels in experiments 2 and 3 were not ipso facto related to differences in either ambient temperature or weight gain but rather to the specific metabolic changes imposed by the dietary lipids or ascorbic acid deficiency.     

Testosterone and estradiol concentrations in serum, velvet skin, and growing antler bone of male white-tailed deer

The growth and mineralization of antlers correlate with the seasonal variation of serum androgens. Whereas seasonal levels of testosterone (T) in plasma are well established, steroid concentrations have not yet been determined in the tissues of growing antlers. Therefore, RIA was used to determine T and 17beta estradiol (E2) in serum, and three areas (tip, middle, and base) of the antler bone and the antler skin, called velvet. Blood and antler tissues of white-tailed deer (Odocoileus virginianus) were collected from May to August. The difference between levels of T and E2 among the sites was calculated using the square root transformation followed by a mixed model analysis with individual deer and an interaction of individual and year (individual(*)year) as a random factor. Concentrations of T in serum (799+/-82 pg/ml) were higher than T values in the velvet (589+/-58 pg/ml, P<0.01) and in the antler bone (538+/-58 pg/ml, P<0.001). Estradiol concentrations differed among antler tissues and serum (P<0.001) and between years (P<0.01). Estradiol concentrations in serum (25+/-25 pg/ml) were consistently lower than those in antler bone (208+/-11 pg/ml, P<0.001) and velvet (150+/-12 pg/ml, P<0.001). The E2:T ratio in serum was 1:10-60. The same ratio for the antler bone was only 1:2-3 and for the velvet 1:3.5. It is concluded that higher T and lower E2 concentrations found in plasma, as compared to antler bone or antler velvet, may indicate a partial metabolism of systemic androgens into estrogens xin the tissues of growing antlers.     

Impact of a diazinon calamity in 1996 on the aquatic macroinvertebrates in the River Meuse, The Netherlands

A more or less continuous load of pesticides has been noted in the River Meuse in recent years. In April 1996, when high concentrations (up toca. 1 g 1^–1) of the insecticide diazinon were measured in the River Meuse at the Belgian-Dutch border, the maximum concentration for drinking water production was exceeded. This was alerted after activity changes of fish and daphnids in the biological monitoring systems (RIZA). These observations were compared with literature toxicity data of diazinon, in order to determine the ecological impact of this diazinon discharge on the aquatic macroinvertebrates. LC₅₀ values of several aquatic macroinvertebrate species were exceeded. In addition, a high mortality was observed in bioassays with the midgeChironomus riparius and the caddisflyHydropsyche angustipennis. It is inferred that the species composition of the macrofauna community in the River Meuse is likely to be reduced by such an accident. Recolonization of the River Meuse by sensitive macrofauna species may therefore be prevented by incidental pesticide discharges.