Autoradiography and inmmunolabeling suggests that lizard blastema contains arginase-positive M2-like macrophages that may support tail regeneration.

BACKGROUND: The regenerating blastema of the tail in the lizard Podarcis muralis contains numerous macrophages among the prevalent mesenchymal cells. Some macrophages are phagocytic but others are devoid of phagosomes suggesting that they have other roles aside phagocytosis. METHODS: The presence of healing macrophages (M2-like) has been tested using autoradiographic, immunohistochemical and ultrastructural studies. RESULTS: Autoradiography shows an uptake of tritiated arginine in sparse cells of the blastema and in the regenerating epidermis. Bioinformatics analysis suggests that epitopes for arginase-1 and -2, recognized by the employed antibody, are present in lizards. Immunofluorescence shows sparse arginase immunopositive macrophages in the blastema and few macrophages also in the apical wound epidermis. The ultrastructural study shows that macrophages contain dense secretory granules, most likely inactive lysosomes, and small cytoplasmic pale vesicles. Some of the small vesicles are arginase-positive while immunolabeling is very diffuse in the macrophage cytoplasm. CONCLUSIONS: The presence of cells incorporating arginine and of arginase 1-positive cells suggests that M2-like macrophages are present among mesenchymal and epidermal cells of the regenerative tail blastema. M2-like macrophages may promote tail regeneration differently from the numerous pro-inflammatory macrophages previously detected in the scarring limb. The presence of M2-like macrophages in addition to hyaluronate, support the hypothesis that the regenerative blastema of the tail in lizards is an immuno-privileged organ where cell proliferation and growth occur without degenerating in a tumorigenic outgrowth.

Long-term effects of castration on the skeleton of male rhesus monkeys (Macaca mulatta).

While osteopenia (OPE) and osteoporosis (OPO) have been studied in various species of aging nonhuman primates and extensively in ovariectomized rhesus and cynomolgus macaques, there is virtually no information on the effects of castration on the skeleton of male nonhuman primates. Most information on castrated male primates comes from a few studies on the skeletons of eunuchs. This report used a subset of the Caribbean Primate Research Center's (CPRC) Cayo Santiago (CS) rhesus macaque skeletal collection to qualitatively and quantitatively compare the bone mineral density (BMD) of castrated and age-matched intact males and, thereby, determine the long-term effects of castration (orchidectomy) on bone. Lumbar vertebrae, femora, and crania were evaluated using dual-energy X-ray absorptiometry (DEXA or DXA) and digital radiography augmented, when fresh tissues were available, with autoradiography and histology. Results confirmed physical examinations of long bones that castration causes changes in the skeleton of male rhesus macaques similar to those found in eunuchs, including OPE and OPO of the vertebrae and femora, thinning of the skull, and vertebral fractures and kyphosis of the spine more severe than that caused by normal aging alone. Also like eunuchs, some castrated CS male rhesus monkeys had a longer life span than intact males or females. Based on these results and the effects of castration on other tissues and organs of eunuchs, on behavior, hormone profiles and possibly on cognition and visual perception of human and nonhuman primates, and other mammals, castrated male rhesus macaques should be used with caution for laboratory studies and should be considered a separate category from intact males. Despite these caveats, the castrated male rhesus macaque should make an excellent animal model in which to test hormone replacement therapies for boys and men orchidectomized for testicular and prostate cancer.

An autoradiogram of skeletal muscle from a pig raised on a farm within 20 km of the Fukushima Daiichi nuclear power plant.

We utilized autoradiography to visualize radioactive contamination in the skeletal muscles of a pig raised within 20 km of the Fukushima Daiichi nuclear power plant following the nuclear accident. The autoradiogram of control muscle showed relatively homogenous exposure. In contrast, the autoradiogram of affected muscle showed a heterogeneous and sporadically dense imaging pattern. Photo luminescence densities of the affected and control muscles were 3.89 ± 0.67 and 2.13 ± 0.43 PSL/mm(2), respectively. This difference indicated that radioactive cesium was distributed in the skeletal muscle of the affected pig.

The influence of trilostane on steroid hormone metabolism in canine adrenal glands and corpora lutea-an in vitro study.

Trilostane is widely used to treat hyperadrenocorticism in dogs. Trilostane competitively inhibits the enzyme 3-beta hydroxysteroid dehydrogenase (3ß-HSD), which converts pregnenolone (P5) to progesterone (P4) and dehydroepiandrosterone (DHEA) to androstendione (A4). Although trilostane is frequently used in dogs, the molecular mechanism underlying its effect on canine steroid hormone biosynthesis is still an enigma. Multiple enzymes of 3ß-HSD have been found in humans, rats and mice and their presence might explain the contradictory results of studies on the effectiveness of trilostane. We therefore investigated the influence of trilostane on steroid hormone metabolism in dogs by means of an in vitro model. Canine adrenal glands from freshly euthanized dogs and corpora lutea (CL) were incubated with increasing doses of trilostane. Tritiated P5 or DHEA were used as substrates. The resulting radioactive metabolites were extracted, separated by thin layer chromatography and visualized by autoradiography. A wide variety of radioactive metabolites were formed in the adrenal glands and in the CL, indicating high metabolic activity in both tissues. In the adrenal cortex, trilostane influences the P5 metabolism in a dose- and time-dependent manner, while DHEA metabolism and metabolism of both hormones in the CL were unaffected. The results indicate for the first time that there might be more than one enzyme of 3ß-HSD present in dogs and that trilostane selectively inhibits P5 conversion to P4 only in the adrenal gland.

Resolution, sensitivity and precision with autoradiography and small animal positron emission tomography: implications for functional brain imaging in animal research.

Quantitative autoradiographic methods for in vivo measurement of regional rates of cerebral blood flow, glucose metabolism, and protein synthesis contribute significantly to our understanding of phsysiological and biochemical responses of the brain to changes in the environment. A disadvantage of these autoradiographic methods is that experimental animals can be studied only once. With the advent of small animal positron emission tomography (PET) and with increases in the sensitivity and spatial resolution of scanners it is now possible to use adaptations of these methods in experimental animals with PET. These developments allow repeated studies of the same animal, including studies of the same animal under different conditions, and longitudinal studies. In this review we summarize the tradeoffs between the use of autoradiography and small animal PET for functional brain imaging studies in animal research.

Effects of iron supplementation on binding activity of iron regulatory proteins and the subsequent effect on growth performance and indices of hematological and mineral status of young pigs.

Two experiments were conducted to evaluate the effects of supplemental Fe on the binding activity of iron regulatory proteins (IRP) and the subsequent effect on growth performance and indices of hematological and mineral status of young pigs. In Exp. 1, male pigs (n = 10; 1.8 kg; age = 14 +/- 1 h) were allotted by BW to two treatments (five pigs per treatment). Treatments administered by i.m. injection were as follows: 1) 1 mL of sterile saline solution (Sal); and 2) 1 mL of 200 mg Fe as Fe-dextran (Fe). Pigs were bled (d 0 and 13) to determine hemoglobin (Hb), hematocrit (Hct), transferrin (Tf), and plasma Fe (PFe), and then killed (d 13) to determine spontaneous and 2-mercaptoethanol (2-ME)-inducible IRP RNA binding activity in liver and liver and whole-body mineral concentrations. Contemporary pigs (n = 5; 2.2 kg; age = 14 +/- 2 h) were killed at d 0 to establish baseline (BL1) measurements. In Exp. 2, pigs (six pigs per treatment; 6.5 kg; age = 19 +/- 3 d) were fed a basal diet (Phase 1 = d 0 to 7; Phase 2 = d 7 to 21; Phase 3 = d 21 to 35) supplemented with 0 or 150 mg/kg of Fe as ferrous sulfate and killed at d 35 (18.3 kg; age = 54 +/- 3 d). In addition, pigs (n = 5; 5.9 kg; age = 19 +/- 3 d) were killed at the start of Exp. 2 to establish baseline (BL2) measurements, and liver samples were collected and analyzed for IRP RNA binding activity. In Exp. 1, no difference (P = 0.482) was observed in ADG. On d 13, Fe-treated pigs had greater (P = 0.001) Hb, Hct, and PFe and less (P = 0.002) Tf than Sal-treated pigs. Whole-body Fe concentration was greater (P = 0.002) in Fe- vs. Sal-treated pigs. Treated pigs (Fe or Sal) had greater (P = 0.006) whole-body Cu and less (P = 0.002) whole-body Ca, Mg, Mn, P, and Zn concentrations than BL1. Liver Fe concentration was greater (P = 0.001) in Fe- vs. Sal-treated pigs, but liver Fe concentration of Sal-treated pigs was less (P = 0.001) than that of BL1 pigs. Sal-treated pigs had greater (P = 0.004) spontaneous IRP binding activity than Fe-treated pigs. In Exp. 2, spontaneous and 2-ME inducible IRP binding activities were greater (P = 0.013 and 0.005, respectively) in pigs fed diets containing 0 vs. 150 mg of added Fe/kg of diet. Moreover, pigs fed either treatment for 35 d had greater (P = 0.001) 2-ME inducible IRP binding activity than BL2 pigs. Results indicate that IRP binding activity is influenced by Fe supplementation. Subsequently, other indicators of Fe status are affected via the role of IRP in posttranscriptional expression of Fe storage and transport proteins.

Comparison of opioid and alpha-2 adrenergic receptor binding in horse and dog brain using radioligand autoradiography.

OBJECTIVE: To test the hypothesis that the distribution, density, and subtype of opioid and alpha (alpha)-2 adrenergic receptors within the central nervous system (CNS) are significantly different between horse and dog. STUDY DESIGN: Prospective experimental study. ANIMALS: Three dogs (3 years of age) and three horses (2-5 years of age). Animals were opioid- and alpha-2 agonist-free at the time of euthanasia. METHODS: Brain tissue was obtained at 126 days post-surgery from dogs and 72 days post-surgery from horses. The brains were removed, sectioned coronally into 1-cm slabs, frozen in methylbutane, which was cooled by liquid nitrogen, and stored at -70 degrees C. Receptor autoradiography was performed using established techniques. [3H]DAMGO, [3H]U-69593, and [3H]RX821002 were used for mu ( micro )-opioid, kappa (kappa)-opioid, and alpha-2 adrenergic-binding assays, respectively. Species differences were analyzed separately for each major brain region by repeated measures anova for subregions followed by Fisher's protected Latin square design (LSD). p < 0.05 was considered significant. RESULTS: There was higher binding of micro -opioid receptors in the frontal cortex, left somatosensory cortex, colliculus (mid-brain), and granule cell layer of the cerebellum of horses than that of dogs. There was higher binding to kappa-opioid receptors in the frontal cortex of dogs compared to horses, whereas binding to kappa-opioid receptors in the cerebellum was higher in horses. Binding to alpha-2 adrenergic receptors in the mid-brain was significantly higher in dogs than in horses. There was higher binding of alpha-2 adrenergic receptors in the dorsomedial and dorsolateral periaqueductal grey of dogs as compared to that of horses. CONCLUSION: The results of this study show that the distribution of these receptors is different between horses and dogs. Further work is needed to understand the relevance of these differences to clinical responses to opioids and alpha-2 adrenergic agonists in these species.

Flumequine in Atlantic salmon Salmo salar: disposition in fish held in sea water versus fresh water.

14C-labeled flumequine was administered as a single oral (5 mg kg(-1), 86 microCi kg(-1)) or intravenous (5 mg kg(-1), 82 microCi kg(-1)) dose to Atlantic salmon Salmo salar held in sea water or in fresh water. The absorption, tissue distribution and elimination were determined by means of liquid scintillation counting and whole-body autoradiography. The drug was rapidly absorbed and extensively distributed in all groups of fish. Radiolabeled compound was present in blood and muscle for more than 8 wk in the freshwater groups. In the seawater groups, however, no radioactivity was detected in the blood and muscle after 4 d and 2 wk, respectively. It was concluded that flumequine was eliminated at a substantially higher rate from Atlantic salmon in sea water than in fresh water.

Muscarinic receptors in equine airways.

The distribution of muscarinic receptors in equine airways was investigated using autoradiography. Frozen sections of tissue from six different levels in the bronchial tree, from the trachea to the distal bronchioles, were incubated in vitro with 1.5 nmol/L of the muscarinic receptor antagonist 1-[N-methyl-3H]scopolamine methyl chloride (3H-NMS). In addition, the subtype pattern of muscarinic receptors was investigated in equine tracheal smooth muscle using radioligand binding with methoctramine, tripinamidc, 4-DAMP-methiodide and pirenzipine as competitors against the binding of 1.3 nmol/L 3H-NMS. The autoradiograms showed specific labelling indicating a high density of muscarinic receptors in smooth-muscle tissue in all levels of the airway tree investigated. Besides muscle tissue, subepithelial glands were the only structures specifically labelled. The dominating subtypes in tracheal smooth muscle investigated with radioligand binding studies were found to be M2 and M4, as both methoctramine (pKd = 8.5) and tripinamide (pKd = 8.6 and 6.7 for two different sites) showed high affinity. The density of the M3-muscarinic receptor subtype was low, but this subtype could be detected with statistical significance when methoctramine was used as the competitor against 3H-NMS binding.

Disposition of 14C-flumequine in eel Anguilla anguilla, turbot Scophthalmus maximus and halibut Hippoglossus hippoglossus after oral and intravenous administration.

The absorption, distribution and elimination of 14C-labelled flumequine were studied using whole body autoradiography and liquid scintillation counting. Flumequine was administered to eel Anguilla anguilla, turbot Scophthalmus maximus and halibut Hippoglossus hippoglossus intravenously and orally as a single dose of 5 mg kg(-1), corresponding to 0.1 mCi kg(-1). The turbot and halibut studies were performed in salt water (salinity of 32%) at temperatures of 16 +/- 1 degrees C (turbot) and 9.5 +/- 0.5 degrees C (halibut). The eel study was conducted in fresh water at 23 +/- 1 degrees C. In the intravenously administered groups flumequine was rapidly distributed to all major tissues and organs. After oral administration flumequine also appeared to have rapid and extensive absorption and distribution in all 3 species. After the distribution phase, the level of flumequine was higher in most organs and tissues than in the blood, except in muscle and brain. The most noticeable difference between the species was the slow elimination of flumequine from eel compared to turbot and halibut. In orally administered eels, substantial amounts of flumequine remained in all major organs/tissues for 7 d. At 28 d significant levels of flumequine were present in liver, kidney and skin (with traces in muscle), and at the last sampling point (56 d) in eye, bone, bile and posterior intestine. In orally administered turbot significant levels of flumequine were observed over 96 h in bile, urine, bone, skin, intestine and eye, and traces were detected over 28 d in bone and eye in addition to a significant level in bile. In orally administered halibut, significant levels of flumequine were observed in bile, skin, intestine and eye over 96 h. Traces were present in skin and eye over 7 d. The maximal flumequine concentrations in blood were calculated to be 2.5 mg equivalents l(-1) (eel at 12 h), 0.8 mg l(-1) (turbot at 6 h) and 0.6 mg l(-1) (halibut at 6 h) after oral administration.

Plasma and bile antibodies of the teleost Trematomus bernacchii specific for the nematode Pseudoterranova decipiens.

We investigated the occurrence of antibodies against protein antigens of the nematode parasite Pseudoterranova decipiens in the plasma and bile of the Antarctic teleost Trematomus bernacchii. Three different P. decipiens protein solutions were prepared: excreted/secreted proteins from live larvae (ESP); surface-associated proteins obtained by mild extraction of larval bodies (SAP); and cuticular soluble proteins recovered by extraction in strong reducing conditions (CSP). Using different immunoassays, these 3 preparations were tested for their ability to bind fish antibody. As determined by ELISA, the specific antibody binding activity was higher in SAP than in CSP. As determined by dot-blot immunoassay, the specific antigen binding activity versus SAP was higher in bile than in plasma antibodies. A different number of antigenic components of SAP and ESP were identified by immunoblotting performed with plasma or bile antibodies. These results led to the conclusion that T. bernacchii parasitism by nematodes involves plasma and bile anti-parasite antibodies. Furthermore bile antibodies were found to be more reactive and more heterogeneous than plasma.

Time course and magnitude of synthesis of heat-shock proteins in congeneric marine snails (Genus tegula) from different tidal heights.

The time course and magnitude of the heat-shock response in relation to severity of thermal stress are important, yet poorly understood, aspects of thermotolerance. We examined patterns of protein synthesis in congeneric marine snails (genus Tegula) that occur at different heights along the subtidal to intertidal gradient after a thermal exposure (30 degrees C for 2.5 h, followed by 50 h recovery at 13 degrees C) that induced the heat-shock response. We monitored the kinetics and magnitudes of protein synthesis by quantifying incorporation of 35S-labeled methionine and cysteine into newly synthesized proteins and observed synthesis of putative heat-shock proteins (hsp's) of size classes 90, 77, 70, and 38 kDa. In the low- to mid-intertidal species, Tegula funebralis, whose body temperature frequently exceeds 30 degrees C during emersion, synthesis of hsp's commenced immediately after heat stress, reached maximal levels 1-3 h into recovery, and returned to prestress levels by 6 h, except for hsp90 (14 h). In contrast, in the low-intertidal to subtidal species, Tegula brunnea, for which 2.5 h at 30 degrees C represents a near lethal heat stress, synthesis of hsp's commenced 2-14 h after heat stress; reached maximal levels after 15-30 h, which exceeded magnitudes of synthesis in T. funebralis; and returned to prestress levels in the case of hsp90 (50 h) and hsp77 (30 h) but not in the case of hsp70 and hsp38. Exposures to 30 degrees C under aerial (emersion) and aquatic (immersion) conditions resulted in differences in hsp synthesis in T. brunnea but not in T. funebralis. The different time courses and magnitudes of hsp synthesis in these congeners suggest that the vertical limits of their distributions may be set in part by thermal stress.

Y-specific microsatellite polymorphisms in a range of bovid species.

At least five dinucleotide (CA)n microsatellite repeat arrays have been assigned to the bovine Y-chromosome, with one marker (INRA124) shown to be polymorphic. We describe here the assessment of a panel of four Y-specific microsatellite markers for polymorphism in a range of cattle and related species. It was possible to amplify all the markers in the animals sampled and all showed variation. Three of the microsatellite loci (INRA124, INRA189 and BM861) displayed putative taurine- and zebu-specific alleles which can be useful indicators of male-mediated gene flow in hybrid populations. In the future these microsatellites, in combination with other Y-specific markers should provide a high-resolution Y haplotype system for evolutionary studies in both domesticated cattle and other related species.

32P-postlabelling analysis of DNA adducts and EROD induction as biomarkers of genotoxin exposure in dab (Limanda limanda) from British coastal waters.

Dab (Limanda limanda) were sampled from a number of polluted and unpolluted areas in British coastal waters. The 32P-postlabelling assay was used to analyse the level of aromatic/hydrophobic DNA adducts in pooled samples of liver tissue. The mean levels of DNA adducts detected from areas known to receive anthropogenic pollutants ranged from 4.0 to 26.8 adducts per 10(8) nucleotides, with all sites containing samples displaying DNA adduct profiles consisting of diagonal radioactive zones. In contrast no DNA adducts were detectable in samples from an unpolluted reference site. The ranking of polluted sites based on DNA adduct levels did not correspond with the ranking of sites based on sediment associated polycyclic aromatic hydrocarbon levels, highlighting the problem of linking the presence of contamination with detectable biological responses. No correlation could be found in this study between EROD activity and the level of DNA adducts.

Haematology of foetal sheep.

OBJECTIVE: To describe the ontogeny of blood cells throughout foetal development in sheep. DESIGN: A haematological study on blood and bone marrow from 42 sheep foetuses aged between 19 days gestation and full term. PROCEDURE: Virgin Merino ewes were mated and the developing foetuses removed surgically at different stages of gestation. Blood and bone marrow samples were collected, stained for cytological examination or processed for electron microscopy. Blood samples were also examined haematologically. Foetuses were incubated with 3H-thymidine and autoradiographed. RESULTS: During the first 4 weeks of development primitive erythroblast constituted the majority of the circulating blood cells. Definitive erythroid cells, originating in the liver, first appeared in the blood at around 27 days gestation and entirely replaced the primitive erythroblasts by 50 days gestation. Leukocyte numbers, especially lymphocyte count, increased rapidly after 49 days gestation. Erythropoiesis predominated in the marrow of all foetuses older than 70 days. In more marrow, myelopoiesis was the major activity and lymphopoiesis was not significant. CONCLUSIONS: Red blood cell numbers and haemoglobin content progressively increases during foetal development. Primitive erythroblasts are not the precursors of the definitive erythroblasts. There are no significant differences in morphological features or maturation sequence between hepatic and bone marrow erythroblasts. Myelopoiesis is a major activity of bone marrow rather than of foetal liver.

Distribution of substance P binding sites in equine airways.

Autoradiography with [125I]-Bolton Hunter substance P ([I]-BHSP) was used to detect substance P binding sites in the equine lung. Specific [I]-BHSP binding sites were very dense over small bronchial vessels, tracheobronchial glands and airway epithelium in large and small airways. The density of [I]-BHSP binding sites over airway smooth muscle was much lower than in the preceding tissues. Competition with an excess of either a specific neurokinin 1 receptor agonist, or a specific neurokinin 2 receptor agonist indicated that most specific [I]-BHSP binding sites in the equine lung represent neurokinin 1 receptors. The receptor-mediated effects of substance P in the equine lung are most likely to involve regulation of vascular tone and airway secretions based upon the density of specific [I]-BHSP binding sites in these tissues. Activation of intrapulmonary afferent nerves containing Substance P by noxious stimuli such as inhaled allergens or irritants may lead to increased mucus secretion and decreased airway diameter due to vascular congestion.

Increases in insulin-like growth factor binding protein-2 accompany decreases in proliferation and differentiation when porcine muscle satellite cells undergo multiple passages.

Subjecting cloned porcine myogenic satellite cells to multiple passages leads to decreased rates of cell division and myotube formation. Because IGF have been implicated in the regulation of muscle cell proliferation and differentiation, the present study was conducted to characterize secretion of IGF-I and IGF-binding proteins (IGFBP) in cultures of cloned porcine satellite cells at two stages of multiple passaging. To this end, we obtained a single porcine satellite cell clone that demonstrated relatively high capacities for cellular proliferation and differentiation into myotubes at the fifth passage but that had greatly diminished capacities for proliferation and myotube formation by the seventh passage. The predominant IGFBP secreted by this satellite cell clone was immunologically identified as IGFBP-2, and quantities of it were increased in medium from seventh-passage cultures. Quantities of IGF-I in medium were determined with a newly developed "titration" radioimmunoassay in which interference from IGFBP was minimized by adding a range of saturating quantities of IGF-II. Medium IGF-I concentrations in seventh-passage cultures were also increased relative to the fifth-passage cultures when expressed per unit of DNA. It is hypothesized that the observed increase of IGF-I in medium likely resulted from protective sequestration of IGF-I by IGFBP-2 rather than from enhanced IGF-I secretion. In summary, these data suggest that multiple passaging of cloned porcine satellite cells results in increased secretion of IGFBP-2, which is associated with depressed cell proliferation and myotube formation, perhaps because the increased IGFBP-2 sequestered IGF-I and reduced its bioactivity.

An analysis of sex and breeding stage differences in prolactin binding activity in brain and hypothalamic GnRH concentration in Wilson's phalarope, a sex role-reversed species.

Wilson's Phalarope (Phalaropus tricolor) is a sex role-reversed species in which incubation of eggs and care of young is performed exclusively by the male. Plasma levels of prolactin (PRL), the hormone most associated with parental care in birds, are higher in incubating males than in nonincubating males or females. Conversely, plasma testosterone levels are reduced in males during incubation. In an attempt to characterize the physiological basis of this unusual parental care system we used quantitative film autoradiography and densitometry to measure the specific binding in vitro of 125I-ovine PRL to 12 brain regions in females, nonincubating males, and incubating males during the normal breeding season. We also measured hypothalamic chicken gonadotropin-releasing hormone I (cGnRH-I) in three brain areas in these same birds, as well as plasma levels of PRL and testosterone. Analysis revealed that cGnRH-I concentrations in the preoptic area and plasma testosterone levels were significantly lower in incubating males than in nonincubating males. Specific binding of 125I-ovine PRL was detected in choroid plexus and in several diencephalic brain regions of both sexes, with highest binding activity recorded in the dorsolateral thalamus, medial habenula, nucleus subrotundus, and preoptic area. When adjustments were made for the large number of comparisons performed, specific binding did not vary significantly by sex or breeding stage in any single brain region. However, average specific binding values in nonincubating males exceeded those of incubating males in 9 of the 11 PRL-sensitive regions examined. Increased occupancy of the receptor by endogenous PRL during incubation could have contributed to this result, since plasma PRL levels were elevated in incubating males. In addition, PRL binding activity in several of these brain regions tended to correlate negatively with plasma PRL. The two exceptions to this general pattern were the preoptic area and the lateral septum, where mean specific binding was 14-15% higher in incubating males than in nonincubating males. This raises the interesting possibility that PRL sensitivity is up-regulated during incubation in some regions of the male phalarope brain, such as the preoptic area and lateral septum, that have been implicated in PRL-modulated changes in behavior and reproductive activity during this breeding stage.