Reference

Corticosteroids as effectors of lipid polymorphism of dielaidoylglycerophosphoethanolamine

Corticosteroids as effectors of lipid polymorphism of dielaidoylglycerophosphoethanolamine. A study using phosphorus-31 NMR and differential scanning calorimetry. Gallay, Jacques; De Kruijff, Ben (Cent. "De Uithof", State Univ. Utrecht, Utrecht, Neth.). Eur. J. Biochem., 142(1), 105-12 (English) 1984. CODEN: EJBCAI. ISSN: 0014-2956. DOCUMENT TYPE: Journal CA Section: 2 (Mammalian Hormones) The influence of corticosteroids on the lipid polymorphism of dielaidoylglycerophosphoethanolamine [19805-18-6] was studied by 31P NMR spectroscopy and differential scanning calorimetry. Both techniques evidenced 2 transitions in the pure lipid samples. The 1st one corresponded to the gel?liq. cryst. phase transition. It occurred at a temp. of 38.9°, as measured by differential scanning calorimetry and at 35-40° as detected by 31P NMR. The 2nd transition corresponded to the bilayer?hexagonal H11 phase transition. It occurred at 64.2° as measured by differential scanning calorimetry and at 60° as detected by NMR. Addn. of corticosteroids led to different specific effects on the bilayer?hexagonal H11 phase transition, according to their chem. structure. These effects appear to be the result of low amts. of incorporated steroids, according to binding studies (partition coeff. values range 5-54). The presence of a conjugated 3-keto group in the steroid mol. (progesterone [57-83-0]) promoted a downward shift in the bilayer?hexagonal H11 phase transition temp. by ~6-7° as compared to the 3b-OH-bearing compd. (pregnenolone [145-13-1]), which did not exhibit any appreciable effect. No change in the DH of transition could be measured. The presence of the 21-OH group (like in deoxycorticosterone [64-85-7]) induced the formation of a structure, characterized by an isotropic lineshape of the 31P NMR spectrum at temps. where the hexagonal type of lineshape is present, without steroid. The transition from the bilayer to this other structure occurred at a slightly higher temp. than the bilayer?hexagonal H11 phase transition. It corresponded to a peak in differential scanning calorimetry scans than a DH of 2.1 kJ/mol. The presence of the 17b-OH group as present in 17b-OH-progesterone [604-09-1], and 11-deoxycortisol [152-58-9] suppressed the 2 former effects. These compds. had no influence on the bilayer?hexagonal H11 phase transition. The addnl. presence of the 11b-OH group like in corticosterone [50-22-6] and cortisol [50-23-7], evoked a stabilization of the bilayer organization as the bilayer?hexagonal H11 phase transition temp. is shifted upward by ~10°. This was accompanied by a decrease of the DH to 0.8 kJ/mol. Besides this, the corticosteroids did not affect to a large extent the gel?liq. cryst. phase transition: a general slight downward shift of the transition temp. and a small broadening of the transition were obsd. without significant change in the DH. The effects of corticosteroids on the bilayer?hexagonal H11 phase transition are qual. correlated with their influence on biol. membranes.

The influence of photoperiod on the reproductive activity of female Honey possums, Tarsipes rostratus (Marsupialia: Tarsipedidae): assessed by fecal progestagens and oestradiol-17b

The influence of photoperiod on the reproductive activity of female Honey possums, Tarsipes rostratus (Marsupialia: Tarsipedidae): assessed by fecal progestagens and oestradiol-17b. Oates, J. E.; Bradshaw, F. J.; Bradshaw, S. D. (School of Animal Biology and Centre for Native Animal Research, The University of Western Australia, Perth 6009, Australia). General and Comparative Endocrinology, 139(2), 103-112 (English) 2004 Elsevier. CODEN: GCENA5. ISSN: 0016-6480. DOCUMENT TYPE: Journal CA Section: 2 (Mammalian Hormones) Section cross-reference(s): 13 Six female Honey possums were kept on a 15L:9D light regime to simulate a long daylength over summer. 604-09-1 and 128-20-1 which are cas registry numbers are also used here. After seven weeks, three females (Group 2) were changed to a shorter daylength of 10L:14D, while the other three females (Group 1) were maintained on the long daylength. Fecal estradiol-17b and progestagen levels were measured during the expt. to detect any changes in reproductive rhythm, such as resumption of blastocyst development. Group 2 females were found to have very large and greatly expanded blastocysts with significantly higher levels of progestagens after the change to short photoperiod (p < 0.05). In contrast, the Group 1 females had very small diapausing blastocysts and progestagen levels did not change throughout the study. Overall estradiol levels also increased significantly in Group 2 females (p < 0.05) but not in Group 1 females. These results demonstrate that a change from long to short days stimulates increased progestagen output (and estradiol-17b to a lesser extent) that supports the growth and expansion of the blastocysts. Photoperiod, in particular its change to a shortening daylength, appears to be a stimulus for terminating diapause in the Honey possum during its first reprodn. of the year. However, as subsequent breeding later in the year occurs when daylength is increasing, a similar role for photoperiod cannot be attributed and females may be entrained to other factors such as food resources. .