Acquired immunological tolerance of diphtheria alum-precipitated toxoid in the domestic fowl.
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Alum Compounds↗
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The induction of experimental uveitis by means of adjuvant and ocular antigens in the domestic fowl.
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Animals↗
Anatomical defects associated with a feathering mutant (Ottawa naked) in domestic fowl.
An autosomal recessive mutation (Ottawa naked, nk) that causes abnormal feathering, fusion of the third and fourth toes, and low viability has been reported previously in the chicken. In the present study mutant individuals were examined from three different stocks: the original one in which the mutant was found and two outbred F2 stocks. Defects of the tail region were observed in all mutants from the original stock (20/20) and in 64% (16/25) of the mutants produced from the outcrossed stocks. The severity of the defects ranged from mild distortion and scoliosis of the coccygeal vertebrae to absence of all vertebrae from the lumbosacral level caudad. Forty percent (16/40) of the mutants from the original stock lacked caudal portions of the kidneys to varying degrees. Edematous areas were observed in 22% (15/67) of the embryos examined at 14 days of incubation. Other defects observed in the mutant embryos but not studied in detail are abnormal patterning or absence of scales, absence of the caudal spinal cord in embryos with severe rumplessness, and failure of the three metatarsal bones to fuse into a single element. Since all structures affected in the mutants differentiate primarily from or may be dependent upon the mesoderm, it is suggested that the site of gene action lies within this germ layer. A decrease was observed in both incidence and severity of the various defects following outcrossing, which suggests the presence of modifiers that influence the expression of the trait.
Animals↗
Morphological changes in the thecal layer during the maturation of the preovulatory ovarian follicle of the domestic fowl (Gallus domesticus).
The aim of the present study was to evaluate changes in the steroidogenic tissue, the blood vessels and the undifferentiated cell islets observed in the theca of developing follicles in the hen ovary. Samples of preovulatory follicles (F1 to F5 in order of decreasing size) and small yellow follicles (SYF) were obtained from White Leghorn hens for light microscopy studies. Cell suspensions of the whole theca obtained from follicles at the same stage of development were analyzed for 17 beta-estradiol and testosterone secretion. Typical steroidogenic cells with abundant cytoplasmic lipid droplets were identified in the theca interna beside blood vessels and nerve fibers. Islets of undifferentiated cells were observed in the theca externa. The steroidogenic tissue of the theca interna was evident in the small yellow follicle. However, considering the growth of the developing follicle, the total volume of steroidogenic cells increased from the SYF up to F1 follicle. The blood vessels reached the maximum development in the largest follicle (F1). On the other hand, undifferentiated cell islets were markedly reduced in the F1 follicle. The structural changes herein described could be correlated to modifications in the steroid hormone secretion during the maturation of the ovarian follicle.
Analysis of Variance↗
The effect of ovariectomy on concentrations of plasma prolactin and LH and parental behavior in the domestic fowl.
The role of ovarian hormones in the expression of parental behavior and in the regulation of LH secretion was investigated in incubating commercial meat-type hens. After ovariectomy, incubating hens continued to incubate eggs normally and brooded day-old chicks given to replace eggs, in a manner similar to sham-ovariectomized control hens. The concentration of plasma LH increased significantly in incubating hens after ovariectomy while the concentration of plasma prolactin remained high. Plasma LH remained depressed in sham-ovariectomized incubating control hens. The increase in plasma LH in incubating hens after ovariectomy (3.92 +/- 0.7 ng/ml) was less than that following the ovariectomy of nonincubating, nonlaying hens (5.3 +/- 1.2 ng/ml). The two groups of hens differed in that plasma prolactin concentrations were high (527 +/- 7.4 ng/ml) in the incubating hens and low (70 +/- 9 ng/ml) in the nonincubating hens. Nest deprivation resulted in an increase in plasma LH in both ovariectomized and sham-ovariectomized incubating hens with a significantly larger increase occurring in the ovariectomized hens (8.5 +/- 1.41 ng/ml compared to 2.48 +/- 0.65 ng/ml). Nest deprivation resulted in a similar rapid decrease in plasma prolactin in both ovariectomized and sham-ovariectomized hens. Replacement of eggs with day-old chicks in ovariectomized or sham-ovariectomized incubating hens resulted in a rapid decrease in plasma prolactin and after 6 days, in an increase in plasma LH in the ovariectomized but not sham-operated hens. It is concluded that once incubation behavior is established, ovarian hormones are not required for its maintenance or the readiness to brood day-old chicks. Ovarian hormones do, however, suppress LH release during incubation while the high concentration of plasma prolactin supplements this suppression.
Animals↗
Evidence of a thyrotropin-releasing activity of ovine corticotropin-releasing factor in the domestic fowl (Gallus domesticus).
Ovine corticotropin-releasing factor (oCRF) administered to 19-day-old chicken embryos (E19) increased plasma concentration of pituitary glycoprotein alpha-subunit concentrations within 15 min for at least 4 hr. Follicle stimulating hormone levels were unchanged, while plasma luteinizing hormone concentrations only began to increase 1 hr after the oCRF treatment. Calculation of circulating thyrotropin (TSH) indicator values revealed a rapid elevation in TSH plasma levels following oCRF. Concentrations of thyroxine (T4), 3,5,3'-triiodothyronine (T3), 3,3',5'-triiodothyronine (rT3), and corticosterone increased from 1 hr postinjection. Hypothalamic outer ring deiodinating type II increased and hepatic inner ring deiodinating type III fell after 2 and 4 hr, explaining at least in part the plasma T3 increase at the end of the experiment. In a second experiment, using E18 chicks, a comparison was made between the effects of a single injection of 2 micrograms oCRF and 20 mlU bovine TSH. Both hormones increased T4, T3, and rT3 plasma concentrations, supporting the hypothesis of a TSH-releasing activity for oCRF in the embryonic chicken. The proposed TSH-mediated effect of CRF on thyroid function was further confirmed in two in vitro experiments in which oCRF did not directly influence the thyroidal T4 secretion but, when applied to pituitaries, clearly increased the alpha-subunit release. In chickens CRF is concluded to not only control the adrenal axis, but also to participate in the coordination of avian TSH release.
Adrenocorticotropic Hormone↗
The thyroid hormone, 3,5,3'-triiodothyronine, is a negative modulator of domestic fowl (Gallus gallus domesticus) adrenal steroidogenic function.
Previous work with chickens (Gallus gallus domesticus) suggests a relationship between depressed thyroid hormone status and enhanced adrenal steroidogenic function. In addition, in hypophysectomized chickens, replacement of the thyroid hormone, 3,5,3'-triiodothyronine (T3), maintains chicken adrenal steroidogenic cell sensitivity to adrenocorticotropin (ACTH) but decreases steroidogenic capacity further than that due to hypophysectomy alone. The present in vivo and in vitro studies were conducted to determine the influence of thyroid status and T3 per se on avian adrenal steroidogenic function. Chicks (1 day old) were thyroidectomized using combined surgical and chemical (6-propyl-2-thiouracil) treatments and were administered a replacement dose of T3 (0, 1.5, 4.5, 15, and 45 microg/kg body wt/day) for 5 weeks. Whereas thyroidectomy (TX) decreased adrenal weight (-20%), it increased relative adrenal weight (mg/100 g body weight) (+171%), trunk plasma corticosterone (+880%), and aldosterone (+124%). In addition, TX increased basal, maximal ACTH-induced, maximal 8-bromo-cyclic AMP-induced, and maximal 25-hydroxycholesterol-supported corticosterone production (+520, +93, +124, and +195%, respectively) and aldosterone production (+578, +288, +280, and +275%, respectively) by isolated adrenal steroidogenic cells. T3, in a dose-dependent manner, reversed the effects of TX on these in vivo and in vitro parameters of adrenal steroidogenic function. Restoration of most of these parameters to those in the sham-treated control was attained with 4.5-15 microg/kg body wt/day. Although some of the effects of TX and T3 replacement on adrenal steroidogenic function may have been mediated through changes in circulating levels of ACTH, other data suggest a direct effect on adrenal steroidogenic cell function. Adrenal steroidogenic cells from sham-treated and TX birds were preincubated (0, 4, and 12 hr) with various concentrations of T3 (0, 0.3, 3, and 30 nM), washed, and then incubated for an additional 2 hr in medium containing the same respective concentrations of T3, with or without a maximal steroidogenic concentration of ACTH (100 nM). T3 had no acute effects on TX-dependent enhancement of adrenal steroidogenic cell function (2-hr incubation). However, with preincubation (4 and 12 hr), T3 inhibited basal and maximal ACTH-induced corticosterone production in a dose-dependent manner. This concentration-dependent, direct effect of T3 was not observed with cells from sham-treated birds. In addition, the ostensibly inactive thyroid hormone metabolite, 3,3',5'-triiodothyronine [reverse T3; 30 nM], was without effect. Taken collectively, these studies indicate that T3 is a direct negative modulator of avian adrenal steroidogenic function.
Adrenal Cortex Hormones↗
Dietary protein restriction stress in the domestic fowl (Gallus gallus domesticus) alters adrenocorticotropin-transmembranous signaling and corticosterone negative feedback in adrenal steroidogenic cells.
Previous work with growing chickens (Gallus gallus domesticus) indicates that transient dietary protein restriction induces long-term enhancement of adrenal steroidogenic function in response to adrenocorticotropin (ACTH). The present study investigated two possible cellular functions mediating this enhanced response: (a) ACTH signal transduction and dissemination and (b) short-loop feedback inhibition of ACTH-induced corticosterone production by exogenous corticosterone. Cockerels (2 weeks old) were fed isocaloric synthetic diets containing either 20% (control) or 8% (restriction) soy protein for 4 weeks. Adrenal glands were processed for the isolation of adrenal steroidogenic cells nearly devoid of chromaffin cells ( approximately 90% adrenal steroidogenic cells). Results of experiments to assess signal transduction and dissemination indicated that protein restriction selectively enhanced ACTH-induced corticosterone production mediated by the cyclic AMP (cAMP)-dependent pathway. In addition, protein restriction substantially counteracted exogenous corticosterone-dependent inhibition of acute ACTH-induced corticosterone production (by 40.7% vs control). The proximal portion of the cAMP pathway seemed most affected by this stressor. Protein-restricted cells exhibited enhanced homologous sensitization to ACTH (136% greater than that of control cells) which appeared to be localized at a step(s) prior to or at the formation to cAMP. Also, maximal ACTH-induced cAMP production and sensitivity to ACTH in terms of cAMP production by protein-restricted cells were, respectively, 2.2 and 15.8 times those of control cells. However, variable results were obtained from other experiments designed to pinpoint the altered early steps in ACTH-transmembranous signaling. For example, with intact cells, cAMP responses to cholera toxin (CT) and forskolin (FSK) did not corroborate the results suggesting an augmentation of ACTH-signal transduction induced by protein restriction. Furthermore, basal and stimulatable (by ACTH, CT, FSK, and NaF) adenylyl cyclase activities from membranes from protein-restricted cells were, respectively, 47.2 and 40.2% less than those from control cells (normalized to 10(7) cell equivalents of crude membranes). Collectively, these findings suggest that protein restriction stress potentiates ACTH-induced corticosterone secretion by chicken adrenal steroidogenic cells in at least two ways: (1) on the proximal end, by modulating unknown factors which enhance cellular sensitivity to ACTH, ACTH receptor-adenylyl cyclase coupling, and adenylyl cyclase activity, and (2) on the distal end, by suppressing end-product corticosterone negative feedback, thus facilitating an increase in net corticosterone secretion.
Adenylyl Cyclases↗
Short-term stress increases testosterone secretion from testes in male domestic fowl.
Prolonged stress inhibits the hypothalamus-pituitary-gonadal (HPG) axis and reduces plasma testosterone (T). However, enhanced secretion of luteinizing hormone (LH) and T has been documented during the initial stages of acute stress in mammals. This study assayed the effect of short-term stress on plasma T and corticosterone (B) in juvenile, pubertal, and adult White Leghorn cockerels. Stress was induced by brief physical restraint of caged juvenile (7 weeks), pubertal (17 weeks), and adult (40 weeks) cockerels, as well as 40-week-old adults reared together in a room lined with wood shavings (group reared). Blood was sampled immediately before restraint (0 time), at the end of a 10-min restraint period, and at 30, 60, and 180 min after 0 time. Restraint resulted in an initial increase in plasma T in all groups, along with a rise in B. Whereas B generally reached its peak level at the end of the restraining period, T peaked 20 min later. The maximum increase of T and B relative to prestress levels (T and B ratios) was similar in all groups, with median T ratio reaching 1.25-1. 5-about half that of the B ratio. Thus, the extent of T and B response to short-term stress was not influenced by basal levels of T, which were highest in adults, and basal levels of B, which were higher in caged adults than in group-reared adults. Injection of ACTH did not induce a greater increase in plasma T than in sham-injected controls. Further, the elevation of T in response to stress was extinguished in castrated adults, indicating that T is secreted from the testes rather than the adrenals in response to stress. When the same regime of blood sampling was applied to adults not subjected to restraint, the T ratio rose by up to 11 times. It can therefore be stipulated that T response depends on the type of stress applied, a factor that should be considered when investigating androgen levels in plasma.
Adrenocorticotropic Hormone↗
Daily and circadian variation in the electroretinogram of the domestic fowl: effects of melatonin.
Visual and circadian function are integrally related in birds, but the precise nature of their interaction is unknown. The present study determined whether visual sensitivity measured electroretinographically (ERG) in 7-week-old cockerels varies over the time of day, whether this rhythm persists in constant darkness (DD) and whether exogenous melatonin affects this ERG rhythmicity. ERG b-wave amplitude was rhythmic in LD and persisted in DD with peak amplitude during mid- to late afternoon in LD and mid-subjective day in DD, indicating that the ERG rhythm is endogenously generated. No daily or circadian variation in a-wave amplitude was observed, and ERG component latency and durations were not rhythmic. Intramuscular injection of 10 micrograms/kg melatonin at ZT10 in LD significantly decreased b-wave amplitude but had no effect on a-wave. Intraocular injection of 600 pg melatonin, however, had no effect on any aspect of the ERG. These data indicate that a circadian clock regulates ocular sensitivity to light and that melatonin may mediate some or all of this effect. The level at which melatonin modulates retinal sensitivity is not known, but the present data suggest a central site rather than a direct effect of the hormone in the eye.
Animals↗
Penetration of spermatozoon into the ovum and transformation of the sperm nucleus into the male pronucleus in the domestic fowl, Gallus gallus.
The apex of the sperm head which has undergone the acrosome reaction comes in contact with the plasma membrane of the ovum. After the entire surface of the inner acrosomal membrane has come into close contact with the plasma membrane of the ovum, the two membranes fuse to form a continuous membrane. All parts of the spermatozoon that are devoid of plasma membrane penetrate into the ooplasm. As the head of the spermatozoon moves deeper into the ooplasm, the chromatin begins to disperse, and the head of spermatozoon is transformed into a large spherical nucleus with low electron density. At a later stage of the transformation, many small vesicles appear around the nucleus and subsequently fuse to form two continuous membranes. These membranes represent the male pronuclear envelope. The condensation of the chromatin occurs in places in the nucleus, so that the male pronucleus is formed. During the course of the formation of the male pronucleus, the subacrosomal rod and tail become detached from the head and disintegrate.
Animals↗
Ultimobranchial gland of the domestic fowl. Two types of secretory cells involved in calcitonin metabolism.
The ultimobranchial gland (UBG) of birds is particularly rich in calcitonin, the hypocalcaemic hypophosphataemic hormone, that is secreted by the C-cells of the mammalian thyroid. The principal cells of the UBG have a striking resemblance with the mammalian C-cells, i.e., they possess small intracytoplasmic dense-core secretory granules, 150-300 nm in diameter. The gland also contains a second, morphologically distinct, endocrine cell type with larger granules, 500-800 nm in diameter. A sensitive immunocytochemical reaction was developed with the use of antibodies against salmon calcitonin. By means of this technique the presence of calcitonin-immunoreactive molecules was demonstrated in both secretory cell types of the UB gland of the chicken. This gland can thus be considered as a homogeneous calcitonin-producing tissue. Whether the secretory products are identical is discussed and differences in the secretory pathways are suggested.
Animals↗
Correlative light-, fluorescence- and electron-microscopic studies of catecholamine-storing cells in the adrenal medulla of the domestic fowl.
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Adrenal Medulla↗
Fine structure of the 'wulst' region of the domestic fowl in organotypic cultures.
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Animals↗
The vasomotor innervation of the inferior vena cava of the domestic fowl (Gallus gallus domesticus L.). I. Structural observations.
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Animals↗
Leptofibrils in intrafusal muscle fibres of muscle spindles in the domestic fowl.
Leptofibrils consisting of narrow dark and wide light bands at regular periods are commonly found in intrafusal muscle fibres of chicken muscle spindles. They are particularly abundant in intrafusal muscle fibres with the loose type of myofilaments. They occur either at the periphery of intrafusal muscle fibres or in deeper regions, or even close to sensory nerve terminals. Dark bands of some peripheral leptofibrils vary considerably in size and appear less regular in configuration. Lateral extensions from the dark bands may occur with or without interconnections. Lateral attachments to myofilaments at the immediate neighbourhood may also occur.
Animals↗
Scanning electron microscopic analysis of the linings of the fourth ventricle in the domestic fowl.
Surface features of the ependymal linings of the fourth ventricle in the fowl were analyzed employing the scanning electron microscope (SEM). On the floor of the median sulcus, each ependymal cell has a solitary cilium, whereas on both sides of the sulcus, cilia are so densely distributed that the details of the underlying cell surface are usually obscured. On the roof of the fourth ventricle, except for the surface of the ciliated groove where numerous cilia are present, the ependymal cells are polygonal in shape, and the center of each cell possesses an aggregate of ten to twenty cilia. Cell surfaces of the choroid tela are entirely covered with delicate microvilli and possess clumped cilia. The ependymal cell surfaces of the area postrema are dome-like in shape. Each ependymal cell has a solitary cilium and shows a smooth surface free of microvilli.
Animals↗
Phagocytosis of spermatozoa by the ovum of the domestic fowl, Gallus gallus at the time of fertilization.
Spermatozoa with intact acrosomes, as well as those coming into contact with the ovum at a smaller angle, and morphologically abnormal spermatozoa reach the plasma membrane of the ovum via an extensively dissolved zone of the inner layer of the vitelline membrane. This zone is assumed to be formed by overlapping of two or more tunnels formed by spermatozoa that had previously come into contact with the ovum. When a spermtozoon comes into contact with the plasma membrane of the ovum, many cytoplasmic processes extend outwards and cover it. Thereafter, the plasma membranes of the processes fuse, thereby phagocytizing the spermatozoon. It is assumed that the he phagocytized spermatozoa cannot undergo transformation into male pronuclei and that they degenerate soon after phagocytosis.
Animals↗