Spur development in chick embryos

Normal development of spurs and horny squamae have been studied in histological preparations obtained from the skin of tarsometatarsus in 8--16-day-old embryos. During the first, initial stage of development, by means of rearrangement of cellular matter and cell migration, three main parts of the spur are layed down -- the horny cover, the spur body and the fibrovascular cushion. For the second stage, vigorous growth of the spur germ at the expense of proliferative activity of its cells is characteristic. At the third stage (after hatching) in males, the spur body outgrows and the bony core is formed. Morphogenesis of the horny squama can be devided into two stages. At the initial stages by means of condensing cellular elements, squamous papilla and horny shell are layed down. The fibrovascular cushion is absent. The second stage is similar to the spur one and is characterized by growth of all the germ parts at the expense of cell proliferation. Comparing morphogeneses of the squama and the spur, it is possible to conclude that phylogenetic transformation of the squama into the spur is performed by two means (modi) of phyloembryogenesis: by means of adding new signs of development to the initial terminal stages of its morphogenesis.     

Partitioning of (13)C-photosynthate from spur leaves during fruit growth of three Japanese pear (Pyrus pyrifolia) cultivars differing in maturation date

BACKGROUND AND AIMS: In fruit crops, fruit size at harvest is an important aspect of quality. With Japanese pears (Pyrus pyrifolia), later maturing cultivars usually have larger fruits than earlier maturing cultivars. It is considered that the supply of photosynthate during fruit development is a critical determinant of size. To assess the interaction of assimilate supply and early/late maturity of cultivars and its effect on final fruit size, the pattern of carbon assimilate partitioning from spur leaves (source) to fruit and other organs (sinks) during fruit growth was investigated using three genotypes differing in maturation date. METHODS: Partitioning of photosynthate from spur leaves during fruit growth was investigated by exposure of spurs to (13)CO(2) and measurement of the change in (13)C abundance in dry matter with time. Leaf number and leaf area per spur, fresh fruit weight, cell number and cell size of the mesocarp were measured and used to model the development of the spur leaf and fruit. KEY RESULTS: Compared with the earlier-maturing cultivars 'Shinsui' and 'Kousui', the larger-fruited, later-maturing cultivar 'Shinsetsu' had a greater total leaf area per spur, greater source strength (source weight x source specific activity), with more (13)C assimilated per spur and allocated to fruit, smaller loss of (13)C in respiration and export over the season, and longer duration of cell division and enlargement. Histology shows that cultivar differences in final fruit size were mainly attributable to the number of cells in the mesocarp. CONCLUSIONS: Assimilate availability during the period of cell division was crucial for early fruit growth and closely correlated with final fruit size. Early fruit growth of the earlier-maturing cultivars, but not the later-maturing ones, was severely restrained by assimilate supply rather than by sink limitation.     

Gravity-related critical periods in vestibular and tail development of Xenopus laevis

Sensory systems are characterized by developmental periods during which they are susceptible to environmental modifications, in particular to sensory deprivation. The experiment, XENOPUS, on Soyuz in 2008 was the fourth space flight experiment since 1993 to explore whether tail and vestibular development of Xenopus laevis has a gravity-related critical period. During this flight, tadpoles were used that had developed either the early hindlimb (stage 47) or forelimb bud (stage 50) at launch of the spacecraft. The results revealed (1) no impact of microgravity on the development of the roll-induced vestibuloocular reflex (rVOR) in both stages and (2) a stage-related sensitivity of tail development to microgravity exposure. These results were combined and compared with observations from space flights on other orbital platforms. The combined data revealed (1) a narrow gravity-related critical period for rVOR development close to the period of the first appearance of the reflex and (2) a longer one for tail development lasting from the early tail bud to the early forelimb bud stage.     

Immunolocalization of beta‐proteins and alpha‐keratin in the epidermis of the soft‐shelled turtle explains the lack of formation of hard corneous material

Immunolocalization of beta‐proteins in the epidermis of the soft‐shelled turtle explains the lack of formation of hard corneous material, Acta Zoologica, Stockholm. The corneous layer of soft‐shelled turtles derives from the accumulation of higher ratio of alpha‐keratins versus beta‐proteins as indicated by gene expression, microscopic, immunocytochemical and Western blotting analysis. Type I and II beta‐proteins of 14–16 kDa, indicated as Tu2 and Tu17, accumulate in the thick and hard corneous layer of the hard‐shelled turtle, but only type II is present in the thinner corneous layer of the soft‐shelled turtle. The presence of proline–proline and proline–cysteine–hinge dipeptides in the beta‐sheet region of all type II beta‐proteins so far isolated from the epidermis of soft‐shelled turtles might impede the formation of beta‐filaments and of the hard corneous material. Western blot analysis suggests that beta‐proteins are low to absent in the corneous layer. The ultrastructural immunolocalization of Tu2 and Tu17 beta‐proteins shows indeed that a diffuse labelling is seen among the numerous alpha‐keratin filaments present in the precorneous and corneous layers of the soft epidermis and that no dense corneous material is formed. Double‐labelling experiments confirm that alpha‐keratin prevails on beta‐proteins. The present observations support the hypothesis that the soft material detected in soft‐shelled turtles derives from the prevalent activation of genes producing type II beta‐proteins and high levels of alpha‐keratins.     

Immunocytochemical localization of sulfhydryl oxidase in mammalian epidermis suggests that the enzyme cross‐links keratins in the granular and transitional corneous layers

The epidermis of representative mammalian species including humans has been examined for the presence of sulfhydryl oxidase, an enzyme likely involved in the oxidation of corneous proteins containing sulfhydryl groups in the epidermis. A database search indicates that the enzyme shares common sequences in numerous mammalian species so that an antibody against the human sulfhydryl oxidase 2 has been utilized on other species. The immunofluorescent study on the epidermis of the platypus (monotreme), red kangaroo (marsupials), hamster and human (placentals) reveals a prevalent labelling in the granular, transitional and lowermost part of the stratum corneous layer. The detailed ultrastructural immunogold study of the human epidermis reveals a diffuse and uneven labelling in the paler component of the composite keratohyalin granules or among keratin filaments of the transitional layer while the labelling disappears in the corneous layer. The study supports the hypothesis of the participation of the enzyme in the oxidative process that determines the formation of stable disulphide groups among keratins and other corneous proteins of the stratum corneum. This process gives rise to the resistant cell corneous envelope of keratinocytes in addition to the isopeptide bonds that derive from the catalytic action of epidermal transglutaminase on several corneous proteins.     

Seasonal Changes in the Photosynthetic Rate in Apple Trees : A Comparison between Fruiting and Nonfruiting Trees

Seasonal changes in photosynthesis of apple trees (Malus domestica Borkh.) were monitored to examine the effect of source-sink interactions on photosynthesis and photorespiration. Elevated photosynthetic rates were observed during two periods of the growing season and correlated with the fruiting process. The first period of increased photosynthetic rates was during the bloom period, when spur leaves on flowering shoots exhibited up to 25% higher photosynthetic rates than vegetative spur leaves on a leaf area basis. CO₂ assimilation rates were also higher in fruiting trees than nonfruiting trees during the period of rapid fruit growth from July to September. Photorespiration, dark respiration, leaf resistance, and transpiration exhibited no seasonal changes which correlated to the presence or absence of fruit. These data represent the first comprehensive examination of the effects of flowering/fruit formation on photosynthesis and photorespiration in perennial plants.     

Effects of genistein in the maternal diet on reproductive development and spatial learning in male rats

Endocrine disruptors, chemicals that disturb the actions of endogenous hormones, have been implicated in birth defects associated with hormone-dependent development. Phytoestrogens are a class of endocrine disruptors found in plants. In the current study we examined the effects of exposure at various perinatal time periods to genistein, a soy phytoestrogen, on reproductive development and learning in male rats. Dams were fed genistein-containing (5 mg/kg feed) food during both gestation and lactation, during gestation only, during lactation only, or during neither period. Measures of reproductive development and body mass were taken in the male offspring during postnatal development, and learning and memory performance was assessed in adulthood. Genistein exposure via the maternal diet decreased body mass in the male offspring of dams fed genistein during both gestation and lactation, during lactation only, but not during gestation only. Genistein decreased anogenital distance when exposure was during both gestation and lactation, but there was no effect when exposure was limited to one of these time periods. Similarly, spatial learning in the Morris water maze was impaired in male rats exposed to genistein during both gestation and lactation, but not in rats exposed during only one of these time periods. There was no effect of genistein on cued or contextual fear conditioning. In summary, the data indicate that exposure to genistein through the maternal diet significantly impacts growth in male offspring if exposure is during lactation. The effects of genistein on reproductive development and spatial learning required exposure throughout the pre- and postnatal periods.     

Low‐cysteine alpha‐keratins and corneous beta‐proteins are initially formed in the regenerating tail epidermis of lizard

During tail regeneration in lizards, the stratified regenerating epidermis progressively gives rise to neogenic scales that form a new epidermal generation. Initially, a soft, un‐scaled, pliable, and extensible epidermis is formed that is progressively replaced by a resistant but non‐extensible scaled epidermis. This suggests that the initial corneous proteins are later replaced with harder corneous proteins. Using PCR and immunocytochemistry, the present study shows an upregulation in the synthesis of low‐cysteine type I and II alpha‐keratins and of corneous beta‐proteins with a medium cysteine content and a low content in glycine (formerly termed beta‐keratins) produced at the beginning of epidermal regeneration. Quantitative PCR indicates upregulation in the production of alpha‐keratin mRNAs, particularly of type I, between normal and the thicker regenerating epidermis. PCR‐data also indicate a higher upregulation for cysteine‐rich corneous beta‐proteins and a high but less intense upregulation of low glycine corneous protein mRNAs at the beginning of scale regeneration. Immunolabeling confirms the localization of these proteins, and in particular of beta‐proteins with a medium content in cysteine initially formed in the wound epidermis and later in the differentiating corneous layers of regenerating scales. It is concluded that the wound epidermis initially contains alpha‐keratins and corneous beta‐proteins with a lower cysteine content than more specialized beta‐proteins later formed in the mature scales. These initial corneous proteins are likely related to the pliability of the wound epidermis while more specialized alpha‐keratins and beta‐proteins richer in glycine and cysteine are synthesized later in the mature and inflexible scales. J. Morphol. 278:119–130, 2017. ©© 2016 Wiley Periodicals,Inc.     

Immunocytochemical and autoradiographic studies on the process of keratinization in avian epidermis suggests absence of keratohyalin

The process of keratinization in apteric avian epidermis and in scutate scales of some avian species has been studied by autoradiography for histidine and immunohistochemistry for keratins and other epidermal proteins. Acidic or basic alpha-keratins are present in basal, spinosus, and transitional layers, but are not seen in the corneous layer. Keratinization-specific alpha-keratins (AE2-positive) are observed in the corneous layer of apteric epidermis but not in that of scutate scales, which contain mainly beta-keratin. Alpha-keratin bundles accumulate along the plasma membrane of transitional cells of apteric epidermis. In contrast to the situation in scutate scales, in the transitional layer and in the lowermost part of the corneous layer of apteric epidermis, filaggrin-like, loricrin-like, and transglutaminase immunoreactivities are present. The lack of isopeptide bond immunoreactivity suggests that undetectable isopeptide bonds are present in avian keratinocytes. Using immunogold ultrastructural immunocytochemistry a low but localized loricrin-like and, less, filaggrin-like labeling is seen over round-oval granules or vesicles among keratin bundles of upper spinosus and transitional keratinocytes of apteric epidermis. Filaggrin-and loricrin-labeling are absent in alpha-keratin bundles localized along the plasma membrane and in the corneous layer, formerly considered keratohyalin. Using ultrastructural autoradiography for tritiated histidine, occasional trace grains are seen among these alpha-keratin bundles. A different mechanism of redistribution of matrix and corneous cell envelope proteins probably operates in avian keratinocytes as compared to that of mammals. Keratin bundles are compacted around the lipid-core of apteric epidermis keratinocytes, which do not form complex chemico/mechanical-resistant corneous cell envelopes as in mammalian keratinocytes. These observations suggest that low amounts of matrix proteins are present among keratin bundles of avian keratinocytes and that keratohyalin granules are absent.     

"Critical periods" in vestibular development or adaptation of gravity sensory systems to altered gravitational conditions?

1. A feature of sensory, neuronal and motor systems is the existence of a critical period during their development. Modification of environmental conditions during this specific period of life affects development in a long-term manner, or even irreversibly. Deprivation is the prefered approach to study the existence and duration of critical periods. For gravity sensory systems, space flights offer the only opportunity for deprivation conditions. 2. Studies in a fish (Oreochromis mossambicus) and an amphibian (Xenopus laevis) revealed a significant sensitivity of their roll-induced static vestibuloocular reflex (rVOR) to a 9- to 10-day gravity deprivation (microgravity) during a spaceflight. In some instances, the rVOR was augmented after the flight as demonstrated in young Oreochromis which were launched when their rVOR had not been developed, and in Xenopus tadpoles launched after their rVOR had developed. Fish which could perform the rVOR at launch were insensitive to microgravity exposure. A similar insensitivity to microgravity was observed in Xenopus tadpoles with normal body shape which had not yet developed their rVOR at launch. Some tadpoles, however, developed an upward bended tail during their space flight; their rVOR was significantly depressed after termination of microgravity independent of the age at onset of the flight. Hypergravity depressed the rVOR for all so far tested developmental stages in both Oreochromis and Xenopus. 3. Both adaptive processes during exposure to altered gravity as well as the existence of a critical period in vestibular development might be responsible for the modulation of the rVOR recorded after exposure to altered gravity. Deprivation studies have to be extended to older developmental stages to test the possibility of a critical period; however, this approach is limited due to the low number of space flights.     

Review: mapping epidermal beta-protein distribution in the lizard <Emphasis Type="Italic">Anolis carolinensis</Emphasis> shows a specific localization for the formation of scales,pads, and claws

The epidermis of lizards is made of multiple alpha- and beta-layers with different characteristics comprising alpha-keratins and corneous beta-proteins (formerly beta-keratins). Three main modifications of body scales are present in the lizard Anolis carolinensis: gular scales, adhesive pad lamellae, and claws. The 40 corneous beta-proteins present in this specie comprise glycine-rich and glycine-cysteine-rich subfamilies, while the 41 alpha-keratins comprise cysteine-poor and cysteine-rich subfamilies, the latter showing homology to hair keratins. Other genes for corneous proteins are present in the epidermal differentiation complex, the locus where corneous protein genes are located. The review summarizes the main sites of immunolocalization of beta-proteins in different scales and their derivatives producing a unique map of body distribution for these structural proteins. Small glycine-rich beta-proteins participate in the formation of the mechanically resistant beta-layer of most scales. Small glycine-cysteine beta-proteins have a more varied localization in different scales and are also present in the pliable alpha-layer. In claws, cysteine-rich alpha-keratins prevail over cysteine-poor alpha-keratins and mix to glycine-cysteine-rich beta-proteins. The larger beta-proteins with a molecular mass similar to that of alpha-keratins participate in the formation of the fibrous meshwork present in differentiating beta-cells and likely interact with alpha-keratins. The diverse localization of alpha-keratins, beta-proteins, and other proteins of the epidermal differentiation complex gives rise to variably pliable, elastic, or hard corneous layers in different body scales. The corneous layers formed in the softer or harder scales, in the elastic pad lamellae, or in the resistant claws possess peculiar properties depending on the ratio of specific corneous proteins.     

Proliferation in the epidermis of chelonians and growth of the horny scutes

The proliferation of the epidermis in soft skin, claws, and scutes of the carapace and plastron in the tortoise (Testudo hermanni) and the turtle (Chrysemys picta) were studied using autoradiographic and immunocytochemical methods. During the growing season, a basal keratinocyte in the epidermis of soft skin and claws takes 5-9 days to migrate into the corneous layer. In the tortoise, during fall/winter (resting season) a few alpha-keratin cells are produced in soft epidermis and hinge regions among scutes and occasional beta-keratin cells in the outer scute surface. When growth is resumed in spring (growing season), cell proliferation is intense, mainly around hinge regions and tips of marginal scutes. No scute shedding occurs and numerous beta-keratin cells are produced around the hinge regions, while alpha-keratin cells disappear. Beta-cells form a new thick corneous layer around the hinge regions, which constitute the growing rings of scutes. Beta-keratin cells produced in more central parts of scutes maintain a homogeneous thickness of the corneous layer along the whole scute surface. In the turtle, a more complicated process of scute growth occurs than in the tortoise. At the end of the growing season (late fall) the last keratinocytes formed beneath the old stratum corneum of the outer scale surface and hinge regions produce more alpha- than beta-keratin. These thin alpha-keratin cells form a scission layer below the old stratum corneum, which extends from the hinge regions toward the center of scutes and the tip of marginal scutes. In the resting season (fall/winter) most cells remain within the germinative layer of the carapace and plastron and a few alpha-cells move in 7-9 days into the corneous layer above hinge regions. In the following spring/summer (growing season) a new generation of beta-keratin cells is produced beneath the scission layer from the hinge region and more central part of the scutes. The epidermis of the inner surface of scutes and hinge regions contains most of the cells incorporating thymidine and histidine, while the remaining outer scute surface is less active. It takes 5-9 days for a newly produced beta-cell to migrate into the corneous layer. These cells form a new corneous layer that extends the whole scute surface underneath the maturing scission layer. The latter contains lipids and eventually flakes off, determining shedding of the above outer corneous layer in late spring or summer.     

Effect of bax deletion on ethanol sensitivity in the neonatal rat cerebellum

The developing cerebellum is highly sensitive to ethanol during discrete neonatal periods. This sensitivity has been linked to ethanol-induced alterations in molecules of the Bcl-2 survival-regulatory gene family. Ethanol exposure during peak periods of cerebellar sensitivity, for example, results in increased expression of proapoptotic proteins of this family, while overexpression of the antiapoptotic Bcl-2 protein in the nervous system protects against ethanol neurotoxicity. For the present study, neonatal mice with a targeted deletion of the proapoptotic bax gene were used to determine whether elimination of this protein would mitigate ethanol toxicity. bax knock-out and wild-type mice pups were exposed to ethanol via vapor inhalation during the maximal period of neonatal cerebellar ethanol sensitivity and cerebellar tissue was subsequently assessed for Purkinje and granule cell number and ethanol-mediated generation of reactive oxygen species (ROS). The results revealed that: (1) ethanol exposure during the peak period of cerebellar vulnerability resulted in substantial loss of Purkinje cells in wild-type animals, but not in bax knock-outs; (2) granule cells in the bax gene-deleted animals were not similarly protected from ethanol effects; and (3) levels of ROS following acute ethanol exposure were appreciably enhanced in the wild-type animals but not in the bax knock-outs. These results imply that Bax is important to ethanol-induced Purkinje cell death during critical neonatal periods, but that ethanol effects on granule cells may function at least partially independent of this apoptosis agonist. Amelioration of ethanol-mediated increases in ROS production in the knock-outs may contribute to the observed effects.     

Periodization of the early postnatal development in the rat with particular attention to the weaning period

The early postnatal period is characterized by a great plasticity with critical windows in which any inadequate insult or intervention may be able to influence both positively and adversely postnatal growth and development. After birth the rat littermates enter the presuckling period (initial 6 hours terminated by the first nursing), characterized by transition from the amniotic fluid to the air, by the changes of the ambient temperature, by the termination of placental nutrition and by oxidative stress. After this stage the suckling period initiates and the littermates start to consume milk of their mothers. Comsumption of milk culminates on day 15, then decreases and terminates on postnatal day 28. The end of the suckling period and the onset of physiological weaning is determined by the moment when the youngs for the first time consume the solid food together with milk (postnatal day 17 in rats). On day 19 the first intake of drinking water occurs. The weaning period terminates by the last consumption of maternal milk - on postnatal day 28. It is necessary to stress that the duration of early postnatal periods is independent of the changes of body weight. The precise knowledge of individual ontogenetic periods critical for further development is crucial for the prediction and explanation of reactions to various pathogenetic stimuli both under experimental conditions and in clinical medicine.     

Brassinosteroids as Metahormones: Evidence for their Specific Influence during the Critical Period in Sorghum Development

Abstract: In Sorghum bicolor, the effect of brassinosteroid (BR) treatments on blade elongation depends both on concentration and on the stage of development. A specific period of increase in sensitivity to BR is reported during early vegetative development. It coincides with emergence of a critical period during which the between-organs relationship is readjusted as a function of new developmental events or new environmental conditions. Accordingly, the influence of BR cannot be completely understood without separating its effects during stable phases (phenophases) and during critical periods. A high level of redundancy exists in networks of regulation, so that modifications due to BR treatments generally remain cryptic. Nevertheless, it is shown that BR affects the pattern of relationships between organs, confirming its involvement in emergence of a new network of regulation. It is suggested that, during critical periods, brassinosteroids act as "metahormones" integrating the new emerging regulation network by triggering changes in cellular sensitivity to PGRs.     

Dark reactions in the flowering ofLemna perpusilla 6746

Summary This study concerns the effects of red and far-red light on flowering in the short day plantLemna perpusilla 6746. The critical day length for maximum flowering was found to be 10 hours. Exposure to red light near the middle of the dark period inhibited flowering, and the time of maximum sensitivity to red light occurred 9 hours after the beginning of dark periods of either 14 or 17 hours. The inhibition by red light was not reversible by far-red light, which also inhibited flowering, especially when given early in the dark period. Flowering inhibited by exposure to far-red light at the beginning of the dark period could be restored by subsequent exposure to red light. It appears that two photoperiodic partial processes in some plants may be controlled by the red, far-red reversible pigment system.With 5 Figures in the Text     

Critical periods during development as assessed by thallium-induced inhibition of growth of embryonic chick tibiae in vitro

In ovo application of thallium sulfate has been shown to produce a characteristic shortening and angulation of the tibia of the embryonic chick. The critical period for susceptibility to thallium-induced inhibition of tibial growth ends at 8 2/3 days of incubation, a time when the growth rate of the embryo declines by 55%. The aim of the present study was to expose tibiae to thallium in vitro to determine whether this response was intrinsic to the tibia. A 4-hour exposure to 400 micrograms thallium was found to be most effective. Growth of tibiae from 8-day-old embryos was inhibited, growth of tibiae from 9-day-old embryos was not, and the response of tibiae isolated from embryos of 8 2/3 days of incubation was intermediate. Therefore, the response of the tibia to thallium represents an intrinsic property and is not secondary to inhibited nerve growth as has been suggested. The critical period and its termination is also an intrinsic property of the tibia. Tibiae were exposed to thallium for 4 hours at various times after the tibiae had been established in vitro. Susceptibility to growth inhibition was shown to decline as tibiae developed beyond the critical period, a decline that could be correlated with a declining growth rate. Emphasis is placed upon critical events during development as a more useful concept than critical periods for explaining susceptibility to teratogens.     

Postnatal Methylmercury Exposure Induces Hyperlocomotor Activity and Cerebellar Oxidative Stress in Mice: Dependence on the Neurodevelopmental Period

During the early postnatal period the central nervous system (CNS) is extremely sensitive to external agents. The present study aims at the investigation of critical phases where methylmercury (MeHg) induces cerebellar toxicity during the suckling period in mice. Animals were treated with daily subcutaneous injections of MeHg (7 mg/kg of body weight) during four different periods (5 days each) at the early postnatal period: postnatal day (PND) 1–5, PND 6–10, PND 11–15, or PND 16–20. A control group was treated with daily subcutaneous injections of a 150 mM NaCl solution (10 ml/kg of body weight). Subjects exposed to MeHg at different postnatal periods were littermate. At PND 35, behavioral tests were performed to evaluate spontaneous locomotor activity in the open field and motor performance in the rotarod task. Biochemical parameters related to oxidative stress (levels of glutathione and thiobarbituric acid reactive substances, as well as glutathione peroxidase and glutathione reductase activity) were evaluated in cerebellum. Hyperlocomotor activity and high levels of cerebellar thiobarbituric acid reactive substances were observed in animals exposed to MeHg during the PND 11–15 or PND 16–20 periods. Cerebellar glutathione reductase activity decreased in MeHg-exposed animals. Cerebellar glutathione peroxidase activity was also decreased after MeHg exposure and the lowest enzymatic activity was found in animals exposed to MeHg during the later days of the suckling period. In addition, low levels of cerebellar glutathione were found in animals exposed to MeHg during the PND 16–20 period. The present results show that the postnatal exposure to MeHg during the second half of the suckling period causes hyperlocomotor activity in mice and point to this phase as a critical developmental stage where mouse cerebellum is a vulnerable target for the neurotoxic and pro-oxidative effects of MeHg.     

Increased expression of alpha- and beta-globin mRNAs at the pituitary following exposure to estrogen during the critical period of neonatal sex differentiation in the rat

Deterioration of reproductive health in human and wildlife species during the past decades has drawn considerable attention to the potential adverse effects of exposure to xenosteroids during sensitive periods of sex development. The hypothalamic-pituitary (HP) unit is a key element in the neuroendocrine system controlling development and function of the reproductive axis; the HP unit being highly sensitive to the organizing effects of endogenous and exogenous sex steroids. To gain knowledge on the molecular mode of action and potential biomarkers of exposure to estrogenic compounds at the HP unit, we screened for differentially expressed genes at the pituitary and hypothalamus of rats after neonatal exposure to estradiol benzoate. Our analyses identified persistent up-regulation of alpha- and beta-globin mRNAs at the pituitary following neonatal estrogenization. This finding was confirmed by combination of RT-PCR analyses and in situ hybridization. Induction of alpha- and beta-globin mRNA expression at the pituitary by neonatal exposure to estrogen was demonstrated as dose-dependent and it was persistently detected up to puberty. In contrast, durable up-regulation of alpha- and beta-globin genes was not detected at the hypothalamus, cortex, cerebellum, liver and testis. Finally, enhanced levels of alpha- and beta-globin mRNAs at the pituitary were also demonstrated after neonatal administration of the anti-androgen flutamide. In summary, alpha- and beta-globin genes may prove as sensitive, pituitary-specific biomarkers of exposure to estrogenic (and/or anti-androgenic) compounds at critical periods of sex development, whose potential in the assessment of endocrine disrupting events at the HP unit merits further investigation.