Effects of ovariectomy on long-day-induced premigratory fat deposition, plasma levels of luteinizing hormone and prolactin, and molt in white-crowned sparrows, Zonotrichia leucophrys gambelii.

Long days initiate the hyperphagia, fat deposition, and nocturnal restlessness, characteristic of the vernal migratory state in white-crowned sparrows. Ovariectomy, when performed in November, but not when performed in January, prevented induction by long days (20L:4D) of vernal fat deposition, whereas autumnal fat deposition was not affected. This is consistent with results obtained previously with males. Very high plasma levels of luteinizing hormone (LH) after photostimulation of ovariectomized females did not interfere with fat deposition. During fat deposition, levels of prolactin were not different from short-day levels and similar in ovariectomized and control females. However, ovariectomy performed in November suppressed the maximum levels of prolactin produced by long-day stimulation and inhibited or disturbed postnuptial molt. These effects were absent when ovariectomy was performed in January. Long-day-induced prolactin levels were higher when birds were photostimulated during a later phase of the annual cycle. It is suggested that castration does not interfere with long-day-induced vernal fat deposition via reduced secretion of prolactin in the absence of ovarian hormones or via supernormal secretion of LH, but that vernal fat deposition, prolactin secretion, and postnuptial molt require the presence of ovarian hormones prior to photostimulation. Autumnal migratory fat deposition, which is part of the cluster of events associated with photorefractoriness, has no requirement for gonadal hormones.

Physiologic properties of steroid hormone-binding proteins in avian blood.

The physiologic properties of steroid hormone-binding proteins have been partially characterized in plasmas of 23 avian species (8 orders and 12 families). A specific sex hormone-binding protein (SBP) with high affinity and low capacity, as found in amphibians and some reptiles and mammals, could not be identified in any of the avian species investigated. In addition SBP appeared to be totally absent in the blood of posthatching and juvenile stages of two species, and in the embryonic blood of three species. For birds it is concluded that sex steroid hormones circulate bound to plasma albumins with low affinity (Kd = 10(-5) mol/liter) and very high capacity. There are two protein-binding systems for corticosterone in the blood of all species investigated, including samples collected from embryos. One is saturable and specific with low capacity (10(-8) -10(-9) mol/liter) and high affinity (Kd = 10(-7) -10(-9) mol/liter), whereas the other is a nonspecific component with very high capacity and low affinity (Kd = 10(-5) mol/liter). Specificity studies show that the high-affinity binding system for corticosterone also binds progesterone with virtually identical affinity, whereas testosterone and estradiol are bound with lower affinity. These data suggest that the high-affinity binding protein in avian blood has physiologic properties similar to mammalian corticosteroid-binding globulin (CBP).

Cytological differentiation of the interrenal tissue of the Japanese quail, Coturnix coturnix.

As reported for several other avian species there are clearly distinguishable subcapsular (SCZ) and inner (IZ) zones of interrenal tissue in the Japanese quail. The SCZ contains large columnar cells (type I) with rounded nuclei, polymorphic mitochondria with shelf-like cristae, and relatively small numbers of lipid droplets. The IZ contains two and possibly three types of cells. Type II consists of large columnar cells with moderately dense cytoplasm containing large numbers of lipid droplets and many rounded mitochondria with tubular cristae. Smooth endoplasmic reticulum (SER) and Golgi apparatus are well developed; coated vesicles occur in Golgi area and at the cell surface. Type-III cells occur in IZ and especially in its more peripheral areas. They are columnar cells with strikingly clear cytoplasm (in comparison with type II) containing mitochondria with plate-like cristae and tubular SER. Type-IV cells are sparsely distributed in IZ and occur rarely in SCZ. Type IV may be a degenerating phase of type III. After adenohypophysectomy or section of portal vessels type-I cells atrophy somewhat with a decrease in lipid droplets; type-II cells, also atrophy with conspicuous increase in size and number of lipid droplets, enlargement of mitochondria, and gradual disappearance of Ser; type-III cells decrease in number whereas type-IV cells increase. After injection of ACTH, type-I cells enlarge and their mitochondria, SER and Golgi apparatus become more conspicuous; there is a decrease in lipid droplets in type-II cells and a development of SER, polysomes and Golgi apparatus; there is also a decrease in lipid droplets and a development of SER in type-III cells after injection of 2 IU ACTH and an almost complete disappearance of lipid droplets after 4 IU ACTH; type-IV cells increase in number.

The hypothalamic neurosecretory systems of the Japanese quail as revealed by retrograde transport of horseradish peroxidase.

Within 24-48 h after injection of horseradish peroxidase (HRP) into the neural lobe or into the median eminence of adult Japanese quail dense accumulations of its reaction product (HRP-RP) can be demonstrated in axons of the hypothalamo-hypophysial tract and in the magnocellular neurosecretory perikarya of the supraoptic and paraventricular nuclei as well as in scattered neurons of the accessory hypothalamic neurosecretory nuclei. The HRP-RP-containing nerve fibers, which are beaded in appearance, occur prominently in the internal zone of the median eminence. They turn dorsally at its anterior border to become widely distributed in the retrochiasmatic region and extended to the paraventricular, supraoptic areas. These observations confirm more directly conclusions drawn earlier from Gomori-type preparations and from immunologic demonstration of arginine vasotocin, mesotocin and neurophysin. HRP-RP was also found in perikarya of parvocellular secretory neurons in the infundibular nucleus 48 h after injection of HRP into the median eminence but not after injection into the pars nervosa. This provides direct evidence that a conspicuous component of the tubero-infundibular tract is formed by axons of tuberal neurons that originate from the infundibular nucleus and pass directly into the median eminence.

Induction of Zugunruhe by photostimulation of encephalic receptors in white-crowned sparrows.

Daily 20-hour encephalic photophases (DEPP), transmitted (hours 0 to 20) via chronically implanted light-conducting fibers to selected sites in the basal hypothalamus of male white-crowned sparrows, were superimposed on daily 8-hour (hours 0 to 8) external ambient photophases (DAPP). Initially the birds displayed motor activity only during the 8-hour DAPP. After a delay of at least 2 weeks, some of the birds became intensively active during hours 8 to 20. We postulate that this period of "nocturnal" activity is equivalent to the nocturnal Zugunruhe shown by caged individuals of many nocturnally migratory species subjected to long days; such activity is generally regarded as the expression of migratory behavior.

The sites of encephalic photoreception in phosoperiodic induction of the growth of the testes in the white-crowned sparrow, Zonotrichia leucophrys gambelii.

In bilaterally enucleated White-crowned Sparrows, Zonotrichia leucophrys gambelii, testicular growth and development at rates similar to those of intact birds subjected to long days, can be induced by illumination of sites within and near the ventromedial hypothalamus from the tips of single, chronically implanted, light-conducting fibers. Essentially identical results are obtained with the same mode of encephalic illumination of birds with intact eyes held on short days that are otherwise nonstimulatory. Examination of the distribution of the sites of the fibers from which weak illumination induced testicular growth, increase in plasma level of luteinizing hormone or increase in plasma level of testosterone suggests that most of the photoreceptors must lie either within the ventromedial hypothalamus or in sites ventral thereto, such as the tuberal complex. For the time being, at least, we find it necessary to assume that some photosensitive elements of the system occur outside of the ventral hypothalamus.