Changes in ovarian follicles and in vitro sex hormone release in the lizard Podarcis sicula sicula

An in vitro superfusion method was used to test sex hormone release from different kinds of ovarian follicle (growing follicles, postovulatory follicles, and atretic follicles) in the lizard Podarcis sicula sicula. Sex hormone output changes with the stage of follicle evolution and sexual cycle. Previtellogenetic follicles prevail in early-spring quiescent ovaries and secrete mainly progesterone, which is probably utilized at that phase to delay ovarian resumption. In the active ovary, progesterone output from previtellogenetic follicles decreases, whereas vitellogenetic follicles produce a significant amount of 17β-estradiol, which is necessary for sustaining vitellogenin synthesis by the liver and oviduct growth. As follicles become ripe, progesterone production is resumed, and it increases in young postovulatory follicles. This is in line with the functions assigned to the hormone at that phase of the sexual cycle, i.e., the induction of oocyte maturation and the regulation of egg retention in the oviduct. Postovulatory follicles can also synthetize 17β-estradiol. After oviposition, this hormone, which is secreted by the old postovulatory follicles, can reinitiate vitellogenin synthesis, allowing the development of a new oocyte set. Our data confirm that active, although ephemeral, corpora lutea are also formed in oviparous species. A limited contribution to ovarian sex steroid production derives also from atretic follicles, at least at the early stages of the breeding cycle. © 1993 Wiley-Liss, Inc.     

A Chronobiological Approach to Circulating Levels of Renin, Angiotensin-Converting Enzyme, Aldosterone, ACTH, and Cortisol in Addison's Disease

This study deals with a chronobiological approach to the circadian rhythm of the renin-angiotensin-aldosterone system (RAAS) and the ACTH-cor-tisol axis (ACA) in patients with Addison's disease (PAD). The aim is to explore the mechanism(s) for which the circadian rhythmicity of the RAAS and ACA takes place. The study has shown that both the RAAS and ACA are devoid of a circadian rhythm in PAD. The lack of rhythmicity for renin and ACTH provides indirect evidence that their rhythmic secretion is in some way related to the circadian oscillation of aldosterone and cortisol. This implies a new concept: a positive feedback may be included among the mechanisms which chronoregulate the RAAS and ACA.     

Circadian Rhythm of Cardiac Output, Peripheral Vascular Resistance, and Related Variables by a Beat-to-Beat Monitoring

This study aimed to explore the 24-h patterns of stroke volume, cardiac output, and peripheral vascular resistance along with other correlated variables, such as left ventricular ejection time, ejection velocity index, thoracic fluid index, heart rate, and blood pressure. The study was performed on 12 clinically healthy subjects by means of a noninvasive beat-to-beat monitoring using the thoracic electric bioimpedance technique associated with the automated sphygmomano-metric recording. Time data series were analyzed by means of chronobiological procedures. The results documented the occurrence of a circadian rhythm for all the variables investigated, giving relevance to the beat-to-beat bioperiodicity of cardiac output and peripheral vascular resistance. Temporal quantification of the investigated variables may be useful for a better insight of the chronophysiology of the cardiovascular apparatus.     

Terpenoids from Euphorbia helioscopia and Their Cytotoxic Activities against H1975 Cells

Three previously undescribed diterpenoids, helioscopnoids A–C, and eight known compounds were isolated from the whole plants of Euphorbia helioscopia. Their structures were established by extensive analysis of spectra and data comparison with previous literatures. Among them, compound 4 was identified as 24,24-dimethoxy-25,26,27-trinoreuphan-3β-ol with revised configurations of C-13, C-14, and C-17 (13R*, 14R*, 17R*). Cytotoxicity assays revealed that all compounds exhibited varying levels of cytotoxicity against H1975 cells, with compound 9 displaying the most potent activity, as indicated by cell viability rates of 18.13 % and 20.76 % at concentrations of 20 μM and 5 μM, respectively. This study expands the understanding of E. helioscopia terpenoids’ structural diversity and biological activities, contributing to the exploration of potential therapeutic applications.     

Characterization at atomic resolution of peptide helical structures.

A survey of literature for the various types of helices experimentally observed in high-resolution single crystal x-ray diffraction analyses of peptides has allowed to determine accurate conformational and helical parameters for the various secondary structures such as the alpha-helix, the 3(10)-helix, the fully extended conformation (2(5)-helix) and the beta-bend ribbon spiral. For each of these structures the characteristic phi, psi conformational parameters, n, the number of residues per turn, h, the height per residues and p, the pitch of the helix are described.     

Flow cytometric detection of mitotic cells using the bromodeoxyuridine/DNA technique in combination with 90 degrees and forward scatter measurements

Mitotic cells could be well discriminated from the cells in the G1-, S- and G2-phases of the cell cycle using pulse labeling of S-phase cells with bromodeoxy-uridine (BrdUrd) and staining of the cells for incorporated BrdUrd and total DNA content. Unlabeled G2- and M-phase cells could be measured as two separate peaks according to propidium iodide fluorescence. M-phase cells showed lower propidium iodide fluorescence emission compared to G2-phase cells. The fluorescence difference of M- and G2-phase cells was caused by the different thermal denaturation of their DNA. Best separation of M- and G2-phase cells was obtained after 30-50 min heat treatment at 95 degrees C. Mitotic index could be measured if no unlabeled S-phase cells were present in the cell culture. With additional measurements of 90 degree scatter and/or forward scatter signals, mitotic cells could be clearly discriminated from both unlabeled G2- and S-phase cells. The correct discrimination (about 99%) of mitotic cells from interphase cells was verified by visual analysis of the nuclear morphology after selective sorting. Unlabeled and labeled mitotic cells could be observed as pulse-labeled cells progressed through the cell cycle. We conclude that this modified BrdUrd/DNA technique using prolonged thermal denaturation and the simultaneous measurement of scatter signals may offer additional information especially in the presence of BrdUrd-unlabeled S-phase cells.     

Modulation of the heart rate by thyroid hormone in the newborn rat

Confirming the literature data the authors describe that the heart rate is smaller in the newborn rats than in adult ones and increases until the adult values during the first two weeks of life. On the other hand, the blood thyroid hormone exhibits the same pattern, showing an early postnatal increment. As, according the Adolph's data (1967), the heart rate enhancement is not due to the catecholamines, the authors suppose that such enhancement might conceivably depend on thyroid hormone increment.     

The importance of ecological research for ecosystem management: The case of browsing by swamp wallabies (Wallabia bicolor) in commercially harvested native forests

Summary Ecosystem management often proceeds within the context of sub‐optimal relationships between ecologists and ecosystem managers, and management outcomes could be improved with greater collaboration between members of these disciplines. This paper identifies an ecosystem management problem resulting from the interaction between timber harvesting and browsing wallabies, and this case study is used to exemplify how ecological data and expertise can contribute to the process of ecosystem management. It is argued that appropriate use of existing ecological data, establishment of strategic new research and the implementation of management actions as experimental hypothesis tests can facilitate achievement of management objectives, but greater collaboration between ecologists and managers is required before this can occur. Reasons for sub‐optimal relationships are outlined, and the potential for structural change within large State‐run ecosystem management agencies to improve interactions between managers and ecologists is discussed.