Adrenal steroid secretion in the Tasmanian devil (Sarcophilus harisii) and the Eastern native cat (Dasyurus viverrinus). A comparison of adrenocortical activity of different Australian marsupials

Adrenal venous and peripheral blood was collected from three Tasmanian devils and three Eastern native cats.

Ten Δ4-3-oxosteroids were identified in the adrenal venous blood of the devils and nine from the native cats. Cortisol was the major steroid and its maximum corticotrophin (ACTH) stimulated secretion rate averaged 61 μg/h/100 mg adrenal in devils and 36 μg in cats. The cortisol: corticosterone ratio in two devils and two cats was approx. 2·5 and 5, respectively. Aldosterone secretion rates in devils ranged from 0·06 to 0·12 μg/h/100 mg adrenal and in cats from 0·12 to 0·93, the response to ACTH varied in different animals. 21-Deoxycortisol was found in all animals, it increased during ACTH stimulation (maximum range in devils: 8·5–19·5 μg/h/100 mg adrenal, and 0·6–5·4 in cats). Another unusual steroid isolated from adrenal venous blood was identified as 17α-hydroxy-20β-dihydroprogesterone. Its rate of secretion was higher in devils (range approx. 2–6 μg/h/100 mg adrenal). No relationship was found between adrenal blood flow and corticosteroid secretion. In the peripheral blood plasma only cortisol and corticosterone were identified. The female of both species had a significantly higher concentration of cortisol of the order of 7 μg/100 ml plasma. The combined adrenal weights/kg body weight averaged 168 mg/kg in the devils and 132 mg in the cats.

Since all three Superfamilies of Australian marsupials have now been investigated a comparison of the results obtained from seven representative species is made and they are also considered in relation to eutherian mammals.

Identification and arrangement of coxsackievirus A1 in muscles of newborn mice

Inoculation of single legs of suckling mice with coxsackievirus type A₁ results in a high proportion of infected muscle cells in the first growth cycle of the virus. Electron microscopic study revealed 4 different arrangements of the newly synthesized virus: (i) Single virions are scattered between membranes of the ER or between filaments of the contractile material. (ii) In the vicinity of a nucleus crystal-like patterns are found which apparently are only 2-dimensional layers of viruses stretched between membranes. This kind of arrangement presents itself, according to the direction of the cutting plane, as a crystalloid structure or as a row of viruses between membranes. Serial sections were used to clear up this situation. (iii) Very infrequent 3-dimensional crystals of the close-packed type are observed, which are laying freely in the cytoplasm. (iv) In the latest stages of muscle disintegration viruses are mostly found within vacuoles which in their part, together with the remainder of the cytoplasm, are surrounded by large areas of fully disorganized myofilaments. Immunofluorescent preparations likewise demonstrated the virus antigen in early stages only around nuclei and in later stages distributed over the whole muscle fibre.

Corticosteroid secretion in kangaroos (Macropus canguru major and M. (Megaleia) rufus)

Adrenal venous and peripheral blood was collected from five adult and two immature kangaroos, anaesthetized with pentobarbitone.

Seven C-21 Δ4, 3-oxo steroids were identified in extracts of adrenal venous blood from all animals. The major component—72–92% of detected corticosteroids—was cortisol. The remainder were 11-deoxy and 21-deoxy cortisol, corticosterone, aldosterone, 11β-OH and 17α-OH progesterone. In four out of six experiments, i.v. corticotrophin caused variable degrees of increase in corticosteroid secretion. Maximum cortisol secretion rates in all the adults and the immature male were in the range 29–70 μg./hr./100 mg. adrenal, or 28–58 μg./hr./kg. body weight and 98 μg./hr./100 mg. or 114 μg./hr./kg. in the immature female.

Average aldosterone secretion rate in the adults was 0·27 μg./hr./100 mg. adrenal, or 0·18 μg./hr./kg. body weight. It was significantly higher in the immature male. However, the Na status of the animals was not known.

Cortisol was the major corticosteroid in peripheral blood plasma at concentrations of 2·0–8·1 μg./100 ml.

The unusual secretion of 21-deoxy cortisol suggests there may be differences in some aspects of adrenocortical biosynthesis, compared with eutherians.