A DNA test to sex most birds.

PRL is an anterior pituitary hormone that, along with GH and PLs, forms a family of hormones that probably resulted from the duplication of an ancestral gene. The PRLR is also a member of a larger family, known as the cytokine class-1 receptor superfamily, which currently has more than 20 different members. PRLRs or binding sites are widely distributed throughout the body. In fact, it is difficult to find a tissue that does not express any PRLR mRNA or protein. In agreement with this wide distribution of receptors is the fact that now more than 300 separate actions of PRL have been reported in various vertebrates, including effects on water and salt balance, growth and development, endocrinology and metabolism, brain and behavior, reproduction, and immune regulation and protection. Clearly, a large proportion of these actions are directly or indirectly associated with the process of reproduction, including many behavioral effects. PRL is also becoming well known as an important regulator of immune function. A number of disease states, including the growth of different forms of cancer as well as various autoimmune diseases, appear to be related to an overproduction of PRL, which may act in an endocrine, autocrine, or paracrine manner, or via an increased sensitivity to the hormone. The first step in the mechanism of action of PRL is the binding to a cell surface receptor. The ligand binds in a two-step process in which site 1 on PRL binds to one receptor molecule, after which a second receptor molecule binds to site 2 on the hormone, forming a homodimer consisting of one molecule of PRL and two molecules of receptor. The PRLR contains no intrinsic tyrosine kinase cytoplasmic domain but associates with a cytoplasmic tyrosine kinase, JAK2. Dimerization of the receptor induces tyrosine phosphorylation and activation of the JAK kinase followed by phosphorylation of the receptor. Other receptor-associated kinases of the Src family have also been shown to be activated by PRL. One major pathway of signaling involves phosphorylation of cytoplasmic State proteins, which themselves dimerize and translocate to nucleus and bind to specific promoter elements on PRL-responsive genes. In addition, the Ras/Raf/MAP kinase pathway is also activated by PRL and may be involved in the proliferative effects of the hormone. Finally, a number of other potential mediators have been identified, including IRS-1, PI-3 kinase, SHP-2, PLC gamma, PKC, and intracellular Ca2+. The technique of gene targeting in mice has been used to develop the first experimental model in which the effect of the complete absence of any lactogen or PRL-mediated effects can be studied. Heterozygous (+/-) females show almost complete failure to lactate after the first, but not subsequent, pregnancies. Homozygous (-/-) females are infertile due to multiple reproductive abnormalities, including ovulation of premeiotic oocytes, reduced fertilization of oocytes, reduced preimplantation oocyte development, lack of embryo implantation, and the absence of pseudopregnancy. Twenty per cent of the homozygous males showed delayed fertility. Other phenotypes, including effects on the immune system and bone, are currently being examined. It is clear that there are multiple actions associated with PRL. It will be important to correlate known effects with local production of PRL to differentiate classic endocrine from autocrine/paracrine effects. The fact that extrapituitary PRL can, under some circumstances, compensate for pituitary PRL raises the interesting possibility that there may be effects of PRL other than those originally observed in hypophysectomized rats. The PRLR knockout mouse model should be an interesting system by which to look for effects activated only by PRL or other lactogenic hormones. On the other hand, many of the effects reported in this review may be shared with other hormones, cytokines, or growth factors and thus will be more difficult to study. (ABSTRACT TRUNCATED)

Prolactin (PRL) and Its Receptor: Actions, Signal Transduction Pathways and Phenotypes Observed in PRL Receptor Knockout Mice

This chapter presents basic concepts related to avian clinical biochemistry. Avian medicine and surgery is recognized as an official specialty in veterinary medicine in three continents: Europe, Australia, and North America. The increasing demand for veterinary care for individual birds with a high sentimental or economical value and efforts to conserve endangered species facilitated this awareness. The introduction of micromethods in clinical laboratories and the public demand for veterinary care for individual birds have removed many obstacles of this field. This chapter begins with discussing how blood samples of birds can be collected in the most efficient way. The chapter then discusses starvation, flight, and postprandial effects. The chapter also elaborates the biochemistry of plasma proteins, renal function, and hepatobiliary disease in birds. The chapter emphasizes that all efforts should be made to obtain a blood sample before any treatment is given. Treatments administered before samples are collected may severely affect plasma chemical values, which may jeopardize a correct diagnosis at a later stage. The time interval between restraint and blood sampling should be kept to a minimum to prevent stress-associated changes in clinical chemistry parameters. Blood samples should be obtained before an extensive clinical examination is performed to avoid iatrogenic changes in the samples.

Avian Clinical Biochemistry

/pdf/the-determination-of-clutch-size-in-birds-a-review-4kabtpyzg9.pdf

The Determination of Clutch-Size in Birds a Review

The evolution of sex created a fundamental problem for nearly all plants and animals; namely, the need to fertilize eggs. Numerous types of mating systems have evolved as solutions to this problem, each molded by particular environmental circumstances and particular species attributes. Various hypotheses have been advanced to explain each type of mating system, but an integrated theory is only now beginning to emerge. Since mating behavior is affected by nearly all other aspects of an organism’s behavioral adjustments to its environment, such a theory must fit within a composite view of animal social behavior and hence must include explicit points of contact with related bodies of theory. In particular, mating system theory must mesh with theoretical advances concerning the evolution of territoriality, parental behavior, and animal sociality. By including the appropriate theoretical work from these other areas, an integrated theory of vertebrate mating systems can be developed.

The Evolution of Mating Systems in Birds and Mammals

Breeding Biology of Birds

We examined more than 90 nests of the Common Amakihi (Hem- ignathus virens virens) from the Island of Hawaii to determine if their placement, composition, or insulation varied with meteorological conditions at the time of nesting Common Amakihi nest chiefly during the wet season The nests were always within the canopy of the nest trees and consequently were probably shielded from rain The nests from a warm rain forest on Kohala Mountain were signifi- cantly higher in the canopy and nearer each tree's center than the nests from Mauna Kea, a cold upland Savannah On Mauna Kea, nests were nearer the edge of the canopy at higher elevations, ie, in a location where they would benefit from radiant solar energy Nests from Kohala Mountain lacked liners and were more porous than those from Mauna Kea These features permitted the nests to dry rapidly Nests from Mauna Kea, in contrast, were always lined, which retarded drying and increased their insulating capacity-features appropriate for the drier, colder conditions in areas where they were built All of the nests were excellent windscreens The thermal conductance of nests from Mauna Kea diminished with altitude, ie, nests at higher elevations had more insulation than those at lower elevations This trend was associated with differences in the nests' walls, which were denser (but not thicker) at higher elevations The nest's thermal conductance can be used to estimate the energetic expense of incubation For Common Amakihi, the energy required to keep a clutch at incubation temperature may be as much as 0115 W or 47% of the birds' metabolic rate at rest The Common Amakihi (Hemignathus virens, family Drepanididae) is an abundant and widespread forest bird of the Hawaiian islands The subspecies from the Island of Hawaii (H v virens) occurs at elevations between 650 and 3,000 m Some populations nest in areas that are extremely wet and warm (rain forests), whereas others nest in relatively dry cold areas (upland savannahs); all commonly do so dur- ing the rainy season (Berger 1969, Eddinger 1970, van Riper 1978) On the Island of Ha- waii, their breeding season extends from late October through August We speculated that the small size of the ama- kihi (13-l 4 g), coupled with the extreme vari- ations in moisture and temperature to which populations are exposed while nesting, might have led to altitudinal differences in nest struc- ture For example, breeding success in rain for- ests might require a nest that will drain readily and dry quickly, but one that need not be high- ly insulated because of the mild and fairly con- stant temperatures in such habitats In fact, amakihi on the Island of Kauai sometimes brace their nests against tree trunks where they are soaked by water running down the bark during heavy rains In contrast, amakihi nest- ing at high elevations on the Island of Hawaii, where it is decidedly drier and colder, may require a more highly insulated nest, but one that is still capable of drying efficiently Here, a nest with a liner might be more adaptive In order to address these possibilities, we con- ducted qualitative and quantitative studies of m&e than 90 amakihi nests collected at many different elevations on the Island of Hawaii

Altitudinal variations in nests of the hawaiian honeycreeper hemignathus virens virens

Testosterone-Induced Singing in Female White-Crowned Sparrows

http://academic.oup.com/auk/article-pdf/97/4/816/32911277/auk0816.pdf

The Insulation in Nests of Selected North American Songbirds

-The Southwestern Willow Flycatcher (Empidonax traillii extimus; hereafter "flycatcher") is a federally listed endangered species that breeds in densely vegetated riparian habitats dominated by native and exotic plants, including introduced monotypic saltcedar (Tamarix ramosissima). Some workers have theorized that saltcedar is unsuitable habitat for the flycatcher, primarily because it generally supports a smaller and less diverse invertebrate community (the flycatcher's food base) than native habitats (e.g. Salix spp.). However, differences in insect communities between native and saltcedar habitats are not proof that saltcedar habitats are inferior. The only way to evaluate whether the habitats differ in dietary or energetic quality is to document actual food limitation or its manifestations. Measurements of an individual's body condition and metabolic state can serve as indicators of environmental stressors, such as food limitation and environmental extremes. We captured 130 flycatchers breeding in native and saltcedar habitats in Arizona and New Mexico and measured 12 variables of physiological condition. These variables included body mass, fat level, body condition index, hematocrit, plasma triglycerides, plasma free fatty acids and glycerol, plasma glucose and beta-hydroxybutyrate, plasma uric acid, total leukocyte count, and heterophil-to-lymphocyte ratio. We found substantial sex-based differences in the condition of male and female flycatchers. Ten of the 12 measures of physiological condition differed significantly between the sexes. In all cases where male and female condition differed (except mass), the differences suggest that males were in poorer condition than females. We found few habitat-based differences in flycatcher condition. Only 3 of the 12 physiological condition indices differed significantly between habitats. Our data show that, at least in some parts of the flycatcher's range, there is no evidence that flycatchers breeding in saltcedar habitats exhibit poorer nutritional condition or are suffering negative physiological affects. Received 8 April 2004, accepted 8 April 2005.

Michael D. Kern

Papers

Breeding Biology of Birds

Altitudinal variations in nests of the hawaiian honeycreeper hemignathus virens virens

Testosterone-Induced Singing in Female White-Crowned Sparrows

The Insulation in Nests of Selected North American Songbirds

Habitat and sex differences in physiological condition of breeding southwestern willow flycatchers