Seasonal Spermatogenesis in the Mute Swan (Cygnus olor)

Seasonal Spermatogenesis in the Mute Swan (Cygnus olor)
Author: H. Breucker
Publisher: Springer Science & Business Media
Total Pages: 103
Release: 2012-12-06
Genre: Medical
ISBN: 3642684602

Of all the classes in the animal kingdom, birds represent the best known. There are in total about 8600 living species, and the systematic study of this class is more or less complete. Extensive observations - to a large extent by amateur ornithologists - with respect to geographical distribution, life cycles, demands on and adaptations to the environment, breeding habits, migration, and so forth have contributed towards basic and more widely relevant knowledge, e. g. , in the areas of ethology, ecology, and evo lution and also in social biology (Hilprecht 1970; Farner and King 1971). Together, all these aspects are affected by the reproductive biology of birds, and studies have therefore been carried out for many years with special emphasis on this subject. How ever, until now this emphasis in avian reproductive biology has been physiological and in particular endocrinological (Murton and Westwood 1977; Roosen-Runge 1977). The morphology of the gonads has been treated in far less detail, and has been confined to a comparatively small number of species, compared with other classes of vertebrates. Reproduction is the section in the life cycle of an animal which is most dependent upon environmental conditions. Reproduction therefore usually takes place at a par ticular time, when stress for the adult animals is at its lowest and the chances of sur vival for the newborn are at their highest, i. e.

Current Ornithology

Current Ornithology
Author: Richard Johnston
Publisher: Springer Science & Business Media
Total Pages: 432
Release: 2012-12-06
Genre: Science
ISBN: 1461567874

Volume 5 of this series continues its coverage of currently active re search fields in ornithology. Because an editor can never be a disin terested observer of his or her own editorial efforts, any claim for su periority of this volume is not without conflict of interest. Even so, Volume 5 has certain merits that even a parent should acknowledge, and I find the current chapters not merely timely and authoritative but compelling in their demand for a reader's attention. Wolfgang and Roswitha Wiltschko provide a perceptive review of magnetic orientation in birds, a piece dedicated to Fritz Merkel, the pioneer in studies of magnetic orientation. Sergei Kharitonov and Doug las Siegel-Causey are concerned with the behavioral ecology of seabird coloniality, emphasizing their field experiences in the USSR and the United States. Ted Miller examines the application of studies of bird behavior to comparative biology, pursuing the interface of behavior and evolutionary biology adumbrated by Konrad Lorenz in the 1930s. Jeremy Raynor gives us a summary of the work over the past decade on bird flight, which is not, by turns, as complex or as simple as we had formerly believed. Carrol Henderson describes recent develop ments in nongame bird conservation, based on his pioneering work in the State of Minnesota. Alan Kamil discusses optimal experimental design for research in ornithology, a field in which experimental work is frequently difficult to pursue.

On Angiotensin-Degrading Aminopeptidases in the Rat Kidney

On Angiotensin-Degrading Aminopeptidases in the Rat Kidney
Author: P. Kugler
Publisher: Springer Science & Business Media
Total Pages: 95
Release: 2012-12-06
Genre: Medical
ISBN: 3642685528

The octapeptide angiotensin II (ANG II, Fig. 1) is the key effector substance of the renin-angiotensin system (RAS) (Werning 1972, Page and Bumpus 1974, Hierholzer 1977, Vecsei et al. 1978, Johnson and Anderson 1980 lit.). ANG II is formed in two enzymatic steps. Renin acts on renin substrate, a glycoprotein, to produce angiotensin I (ANG I, a decapeptide), which in turn is acted upon by converting enzyme to form ANG II (Skeggs et al. 1968, Fig. 1). Renin substrate (angiotensinogen) is produced mainly in the liver (Page et al. 1941) and is a constituent of the ~-globulin fraction in the circulating plasma (Plentl et al. 1943). The two enzymes involved in the formation of ANG II from renin substra te are formed at various sites in the body. Renin (E.C. 3. 4. 99. 19) is produced mainly in the granular epithelioid cells of the kidney (Cook 1971, Taugner et al. 1979, Davi doff and Schiebler 1981), and converting enzyme (CE, E.C. 3. 4. 15. 1) occurs chiefly in the lung (Ng and Vane 1967, Bakhle 1974 lit.) as well as in numerous other tissues, such as the juxtaglomerular apparatus of the kidney (Granger et al. 1969, 1972) and the brush border of the renal proximal tubule (Ward et al. 1975, 1976; Ward und Erdos 1977). The biological effects of ANG II are numerous.

Multimodal Torus in the Weakly Electric Fish Eigenmannia

Multimodal Torus in the Weakly Electric Fish Eigenmannia
Author: Henning Scheich
Publisher: Springer Science & Business Media
Total Pages: 78
Release: 2012-12-06
Genre: Medical
ISBN: 3642691668

Ever since the behavioral work of Lissrnann (1958), who showed that the weak electric discharges of some families of fish (hitherto considered useless for prey capture or for scaring away enemies) are part of a strange sensory system, these fish have attracted attention from biologists. The subsequent discovery of the electroreceptors in the skin of gymnotids and mormyrids (Bullock et al. 1961; Fessard and Szabo 1961) and the evidence that the ampullae of Lorenzini of nonelectric sharks and rays are also electro receptors (Digkgraaf and Kalmijn 1962) was a start for a lively branch of physiological, anatomical, and behavioral research. Many fmdings of general importance for these fields have made the case to which extremes the performance of the central and peri pheral nervous systems can be driven. Among those fmdings is the temporal accuracy of the pacemaker of some high-frequency fish which controls the electric organ, pro bably the most accurate biological clock (coefficient of variation

The Development of the Red Pulp in the Spleen

The Development of the Red Pulp in the Spleen
Author: V. Grouls
Publisher: Springer Science & Business Media
Total Pages: 79
Release: 2012-12-06
Genre: Medical
ISBN: 3642685145

In many aspects hematopoiesis in newborn rodents, especially in rats, resembles hema topoiesis in the human fetus in the 6th-7th month of gestation. In man the transition from the stage of liver to bone marrow erythropoiesis takes place at this time (Bessis, 1973). In rodents, however, the liver is almost the only place where hematopoiesis occurs until birth. Thereafter it is replaced to a growing extent by the bone marrow, which so far consists mainly of immature mesenchymal cells (Maximow, 1910; Cuda, 1970). Thus hematopoietic precursor cells appear in the sternum only around 30 h after birth. Just as in premature human infants, a macrocytic anemia can be demonstrat ed in normal neonatal rats (Lucarelli et aI., 1964, 1968). Beside liver (fetal) and bone marrow, the spleen is involved in hematopoiesis. In rodents like rats and mice, splenic hematopoiesis persists more or less markedly until adulthood; in man, however, it ceases after birth and reappears only under certain pathological conditions (Fischer et aI., 1970; Hennekeuser et aI., 1967; Fresen, 1960).