Progress 10/01/98 to 09/30/04
Outputs
We have established that vasoactive intestinal peptide (VIP) is the prolactin releasing factor (PRF) in the turkey. Any type of hypothalamic stimulation that releases PRL is dependent upon the VIPergic system. VIP-immunoreactive neurons are found throughout the hypothalamus, mainly in lateral septum (LS), anterior hypothalamus (AM), lateral hypothalamus (LHy), and infundibular nuclear complex (INF) within the turkey brain. Scattered VIP-neurons are found also in the paraventricular nucleus (PVN) and ventromedial nucleus (VMN). Only two hypothalamic areas, INF and median eminence (ME) show significant changes in VIP immunoreactivity throughout the turkey reproductive cycle. The number and intensity of VIP-immunoreactive neurons in the INF, and VIP-immunoreactive fibers in the ME are significantly increased in incubating, laying, and photorefractory hens as compared with none-photostimulated hens. Deletion analysis of turkey PRL promoter (tPRLP) indicates that the
VIP-stimulated tPRLP activity is controlled by three major positive regulatory regions and two negative regions. From the -127 to -14 Luc construct, where the 7-8 fold increase of promoter activity by VIP occurs. A 12-bp segment in the proximal prolactin promoter is found to be an important cis-element for the VIP-stimulated PRL gene expression in turkey pituitary cells.The inhibitory effect of DA on PRL secretion occurs at the transcriptional level, as DA inhibits VIP stimulated PRL promoter activity. The regulation of PRL transcription by VIP and DA involves the Ca2+ signaling pathway, mainly the extracellular Ca2+ influx. VIP receptor mRNA is expressed throughout the hypothalamus and pituitary. Only within the INF area are significant differences seen among the reproductive stages. VIP receptor mRNA is markedly reduced in reproductively quiescent (none-photostimulated) and photorefractory hypoprolactinemic hens as compared to laying and incubating hens. The most dense VIP receptor
mRNA is found in the anterior pituitary. VIP stimulates PRL promoter activity, PRL transcription and PRL mRNA stability and hypothalamic VIP transcription increases in hyperprolactinemic incubating turkeys. VIP immunoneutralization suppresses the increase in circulating PRL associated with photostimulation and prevents the induction of incubation behavior. Average weekly egg production of VIP-immunized turkeys is similar for first and second cycle turkeys (3.58 +/- 0.19 vs. 3.63 +/- 0.14 eggs per hen per wk). First-and second-cycle control hens laid 2.63 +/- 0.25 and 2.41 +/- 0.20 eggs per hen per wk, respectively. The present results show that comparable egg production was attained in first- and second-cycle hens by active immunization with VIP. Photostimulating breeder hens with a stepped up light program increased egg production by 12% during the 22 week breeder season. Also, egg production was improved (20%) by using the red spectrum (wave length) for lighting breeder hens. Egg
production of hens photostimulated with the red band of the spectrum peaked at 5.2 eggs/hen/wk compared to 4.4 eggs/hen/wk of hens photostimulated with white light.
Impacts
Reproductive efficiency in female turkeys is low when compared to chickens, mainly because the onset of incubation behavior causes an early termination of egg laying. PRL is expressed and secreted at an elevated rate during incubation and exhibits an exaggerated responsiveness to vasoactive intestinal peptide (VIP), the avian PRL-releasing factor. This PRL augmentation is involved in the ending of ovulation, the regression of the ovary, and the initiation of incubation. The neural machinery responsible for the PRL surge may be partly connected to a noticeable increase in pituitary lactotrophs and the up-regulation of their VIP receptors, which generates an increased PRL promoter gene activity and gene transcription rate. This increased PRL secretion and expression is associated with the activity of hypothalamic VIP, since VIP content in hypophyseal portal blood and VIP gene expression are highest in hyperprolactinemic incubating hens. In contrast, immunoneutralization
of VIP in the female turkey suppresses PRL release and gene expression, up-regulates LH and FSH subunit mRNAs, reduces the incident of incubation from 51% to 8.0% and increases average weekly egg production from 2.41 +/- 0.20 eggs/hen/wk to 3.63 +/- 0.14 eggs/hen/wk. This represents an increase of 32.9 eggs per hen in a 27 week reproductive season. These findings promote an agriculturally important goal of reducing the cost of market production, provide product cost benefits to consumers, and lead to increased productivity from fewer animals, thereby conserving natural resources and enhancing the environment.
Publications
- Kang, S.W., Thayananuphat, A., Rozenboim, I., Millam, J.R., Proudman, J.A. and El Halawani, M.E. 2004. Differential expression of gonadotropin releasing hormone-I mRNA in the hypothalamus during the turkey reproductive cycle. 8th International Symposium on Avian Endocrinology. 85.
- Lohmus, M., Olin, M., Sundstrom, L.F., Troedsson, M.H.T., Molitor, T.W. and El Halawani, M. 2004. Leptin increases T-cell immune response in birds. Gen Comp Endocrinol 139:245-250.
- Rozenboim, I., Mobarky, N., Heiblum, R., Chaiseha, Y., Kang, S.W., Biran, I., Rosenstrauch, A., Sklan, D. and El Halawani, M.E. 2004. The role of prolactin in reproductive failure associated with heat stress in the domestic turkey. Biol Reprod. 71:1208-213.
- Thayananuphat, A., Kang, S.W., Proudman, J.A., Youngren O.M. and El Halawani, M.E. 2004.Dopaminergic neurotransmission and mesotocin neuronal activation during the transition from egg incubation to brooding offspring in the turkey. 8th International Symposium on Avian Endocrinology. 48.
- Yupaporn, C., Youngren, O. and El Halawani, M.E. 2004. Expression of vasoactive intestinal peptide receptor mRNA in the hypothalamus and pituitary throughout the turkey reproductive cycle Biol Reprod. 70:593-599.
- El Halawani, M.E, Kang, S.W., Chaiseha, Y., Rozenboim, I., Millam, J.R., and Youngren, O.M. 2004. Dopaminergic regulation of reproduction in the female turkey. 8th International Symposium on Avian Endocrinology. 56.
- El Halawani, M.E., Kang, S.W., Chaiseha, Y. and Youngren, O.M. 2004. Neuroendocrinology of prolactin regulation in the domestic turkey. Biol. Reprod. 85.
- Kang, S.W., Al-Zailaie, K.A., Thayananuphat, A., Youngren, O.R. and EI Halawani, M.E. 2004. A neuronal pathway regulating prolactin and luteinizing hormone secretion in the turkey hypothalamus. Biol. Reprod. 220.
- Kang, S.W., Gazzillo, L.C., You, S., Wong, E.A. and El Halawani, M.E. 2004. Turkey prolactin gene regulation by VIP through 35-bp cis-acting element in the proximal promoter. Gen Comp Endocrinol. 138:157-165.
- Bakken, T., Youngren O.M., Thayananuphat, A., Kang, S.W., Proudman, J.A. and El Halawani, M.E. 2004. Activation of dopamine and vasoactive intestinal peptide neurons involved in serotonin- stimulated PRL secretionIn the turkey.8th International Symposium on Avian Endocrinology. 67.
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Progress 10/01/98 to 09/30/03
Outputs
We have established that vasoactive intestinal peptide (VIP) is the prolactin releasing factor (PRF) in the turkey. Any type of hypothalamic stimulation that releases PRL is dependent upon an intact VIPergic system. VIP-immunoreactive neurons are found throughout the hypothalamus, mainly in lateral septum (LS), anterior hypothalamus (AM), lateral hypothalamus (LHy), and infundibular nuclear complex (INF) within the turkey brain. Scattered VIP-neurons are found also in the paraventricular nucleus (PVN) and ventromedial nucleus (VMN). Only two hypothalamic areas, INF and median eminence (ME) show significant changes in VIP immunoreactivity throughout the turkey reproductive cycle. The number and intensity of VIP-immunoreactive neurons in the INF are significantly increased in incubating, laying, and photorefractory hens as compared with none-photostimulated hens. Although the highest number of VIP-immunoreactive neurons is observed in incubating hens, no significant
changes are observed between incubating , laying and photorefractory hens. In addition, VIP-immunoreactive fibers are widely spread in the hypothalamus including, LS, LHy, lateral mammellary nucleus, and ME. The intensity of VIP-immunoreactive fibers in the ME is significantly increased in laying, incubating, and photorefractory birds compared with none-photostimulated birds. Deletion analysis of turkey PRL promoter (tPRLP) indicates that the VIP-stimulated tPRLP activity is controlled by three major positive regulatory regions and two negative regions. From the -127 to -14 Luc construct, where the 7-8 fold increase of promoter activity by VIP occurs. A 12-bp segment in the proximal prolactin promoter is found to be an important cis-element for the VIP-stimulated PRL gene expression in turkey pituitary cells.The inhibitory effect of DA on PRL secretion occurs at the transcriptional level, as DA inhibits VIP stimulated PRL promoter activity. The regulation of PRL transcription by VIP
and DA involves the Ca2+ signaling pathway, mainly the extracellular Ca2+ influx. VIP receptor mRNA is expressed throughout the hypothalamus and pituitary. Only within the INF area are significant differences seen among the reproductive stages. VIP receptor mRNA is markedly reduced in reproductively quiescent (none-photostimulated) and photorefractory hypoprolactinemic hens as compared to laying and incubating hens. The most dense VIP receptor mRNA is found in the anterior pituitary. VIP stimulates PRL promoter activity, PRL transcription and PRL mRNA stability and hypothalamic VIP transcription increases in hyperprolactinemic incubating turkeys. VIP immunoneutralization suppresses the increase in circulating PRL associated with photostimulation and prevents the induction of incubation behavior. Average weekly egg production of VIP-immunized turkeys is similar for first and second cycle turkeys (3.58 +/- 0.19 vs. 3.63 +/- 0.14 eggs per hen per wk). First-and second-cycle control hens
laid 2.63 +/- 0.25 and 2.41 +/- 0.20 eggs per hen per wk, respectively. The present results show that comparable egg production was attained in first- and second-cycle hens by active immunization with VIP.
Impacts
Reproductive efficiency in female turkeys is low when compared to chickens, mainly because the onset of incubation behavior causes an early termination of egg laying. PRL is expressed and secreted at an elevated rate during incubation and exhibits an exaggerated responsiveness to vasoactive intestinal peptide (VIP), the avian PRL-releasing factor. This PRL augmentation is involved in the ending of ovulation, the regression of the ovary, and the initiation of incubation. The neural machinery responsible for the PRL surge may be partly connected to a noticeable increase in pituitary lactotrophs and the up-regulation of their VIP receptors, which generates an increased PRL promoter gene activity and gene transcription rate. This increased PRL secretion and expression is associated with the activity of hypothalamic VIP, since VIP content in hypophyseal portal blood and VIP gene expression are highest in hyperprolactinemic incubating hens. In contrast, immunoneutralization
of VIP in the female turkey suppresses PRL release and gene expression, up-regulates LH and FSH subunit mRNAs, reduces the incident of incubation from 51% to 8.0% and increases average weekly egg production from 2.41 +/- 0.20 eggs/hen/wk to 3.63 +/- 0.14 eggs/hen/wk. This represents an increase of 32.9 eggs per hen in a 27 week reproductive season. These findings promote an agriculturally important goal of reducing the cost of market production, provide product cost benefits to consumers, and lead to increased productivity from fewer animals, thereby conserving natural resources and enhancing the environment.
Publications
- Rozenboim I., Huisinga, R., Halevy, O. and El Halawani, M.E. 2003. Effect of embryonic photo stimulation on the posthatch growth of turkey poults. Poult. Sci. 82(7):1181-1187.
- Lohmus M., Sundstrom, L.F., El Halawani, M. and Silverio, B. 2003. Leptin depresses food intake in great tits (parus major). Gen. Comp. Endocrinol. 131(1):57-61.
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Progress 01/01/02 to 12/31/02
Outputs
While investigating vasoactive intestinal peptide response elements in the promoter of the prolactin gene, we found that pituitary cells from turkey hens highly expressed endogenous beta-galactosidase. Therefore, we developed a new protocol for determining transfection efficiency using the beta-lactamase gene, which is present on many expression vectors. Transcript levels of beta-lactamase were measured by RT- PCR after transfection of different amounts of the pGL3-basic and pGL3-control vectors. A high correlation was observed between the amount of plasmid transfected and beta-lactamase mRNA levels. Although no eukaryotic promoter was present, there was apparently leaky expression of the beta-lactamase gene. Expression of beta-lactamase was independent of expression from the simian virus 40 or turkey prolactin promoters cloned upstream of the luciferase gene. DA (10 nmol/min for 40 min) was infused into the third ventricle of laying turkey hens to study its effect on
circulating PRL, hypothalamic VIP and pituitary PRL and LH beta subunit mRNA levels. Plasma PRL was significantly elevated after 20 min of DA infusion and remained elevated 30 min after cessation of infusion. Hypothalamic VIP mRNA content was significantly greater in the INF of DA-infused birds than it was in the INF of vehicle-infused control birds. No increase in VIP mRNA due to DA infusion was noted in the preoptic area. Pituitary PRL and LH beta subunit mRNA were increased in DA-infused hens as compared to vehicle-infused controls but the rate of increase was more in PRL than LH beta subunit.
Impacts
The new protocol for determining transfection efficiency, will over come the limitation to using beta-galactosidase reporter gene for cells that express edogenous beta-galactosidase We further demonstrated that exogenous DA activated hypothalamic VIP gene expression and this increased expression was limited exclusively to the avian INF. The increased VIP mRNA in the INF is correlated with increased levels of circulating PRL suggesting that VIP neurons in the INF are involved in PRL regulation.
Publications
- Al-Zailaie, K. and El Halawani, M. 2002. Alterations in GnRH-l within the turkey hypothalamus throughout the reproductive cycle. Poultry Sci. 80 (suppl. 1):29.
- Chaiseha, Y., Youngren, O.M. and El Halawani, M.E. 2002. Expression of vasoactive intestinal peptide receptor mRNA in the hypothalamus and pituitary throughout the turkey reproductive cycle. Poultry Sci. 80 (suppl. 1):45.
- Kang, S.W., Bakken, T. and El Halawani, M.E. 2002. The suppressive effect of prolactin on prolactin promoter activity in primary anterior pituitary cells from turkey hens. Poultry Sci. 80 (suppl. 1):45.
- Kang, S.W., You, S., Wong, E.A. and El Halawani, M.E. 2002. Transfection efficiency nonnalization using the j3-Lactamase Gene of the pGL3 Luciferase vector in primary anterior pituitary cells. BioTechniques 33: 326-330.
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Progress 01/01/01 to 12/31/01
Outputs
We isolated cDNA encoding turkey inhibin-a (tINHa) and -betaA (tINH-betaA) subunits from the turkey ovary using reverse transcription-polymerase chain reaction (RT-PCR). Northern blot analysis revealed that the transcripts of tINH-? mRNA was highly expressed in small white follicles as compared to postovulatory and regressed follicles, whereas tINH-betaA mRNA was predominantly expressed in preovulatory F5 follicles. Hens immunized with rtINH showed increased FSH beta subunit mRNA content, but no change in the content of LH beta subunit or PRL mRNA. Hens immunized with VIP or rtINH + VIP had significant increases in both pituitary LH beta subunit and FSH beta subunit mRNA contents, accompanied by a decline in PRL mRNA abundance. These data suggest that active immunization of female turkeys with INH neutralizes endogenous INH and increases both circulating FSH and the number of preovulatory follicles. However, no significant increase in egg production was observed in
INH-immunized hens. Ambient temperature modulates prolactin (PRL) secretion in birds. Chronic exposure to either 32 degrees or 10 degrees had no effect on the rise in serum PRL that followed photostimulation in both sham-operated controls and ovariectomized hens. Acute overexposure to 10 degrees or 32 degrees altered the photoperiodically stimulated rise in plasma PRL. Birds switched from 10 degrees to 32 degrees showed a significantly greater PRL increase than birds shifted from 32 degrees to 10 degrees. Ovariectomy enhanced the PRL response to the gonadal stimulating photoperiod. The effect was most pronounced in hens photostimulated prior to ovariectomy. These findings suggest that ambient temperature and/or ovariectomy have a modulating effect on the PRL response to long days.
Impacts
The studies gave us an insight into the mechanism by which high ambient temperature inhibits egg production
Publications
- Ahn, J., You, S., Kim, H., Chaiseha, Y. and El Halawani, M.E. 2001. Effects of active immunization with inhibin a subunit on reproductive characteristics of turkey hens. Biol Reprod 65: 1594-1600
- Gahali, K., El Halawani, M.E. and Rosenboim, I. 2001. Photo stimulated Prolactin release in the turkey hen: Effect of ovariectomy and environmental temperature. Gen Comp Endocrinol 124: 166-172
- You, S., Hsu, C., Kim, H., Kho, Y., Choi, Y., El Halawani, M.E., Farris, J. and Foster, D. 2001. Molecular cloning and analysis of the turkey vasoactive intestinal peptide receptor. Gen Comp Endocrinol 124: 53-65
- Farnell, M.B., El Halawani, M.E., You, S., McElroy, A.P., Hargis, B.M. and Caldwell, D.J. 2001. In vivo biologic effects of recombinant-turkey interferon-gamma in neonatal leghorn chicks: protection against Salmonella enteritidis organ invasion. Avian Dis. 45 (2): 473-478.
- Ahn, J., You, S., Kim, H., Foster, D.N. and El Halawani, M.E. 2001. Molecular cloning and expression of turkey inhibin-a and - betaA subunits. Poultry Science 80: 1690-1694
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Progress 01/01/00 to 12/31/00
Outputs
The objective of this study was to compare the effect of vasoactive intestinal peptide (VIP) immunization on first- and second-cycle turkey hens. Hens received four antigen injections beginning the day of photostimulation. The maximum titers of VIP antibodies in first-cycle and second-cycle hens were comparable. After photostimulation, plasma prolactin of first- and second-cycle control hens peaked between 484 and 630 ng/mL. In contrast, prolactin changed very little in VIP-immunized turkeys. Expression of incubation behavior was 50.0 and 52.6% in first- and second-cycle control hens, respectively, upon termination of the study. In contrast, only 11.1% first-cycle and 5.2% second-cycle VIP-immunized turkeys exhibited the hormonal and behavioral characteristics of incubating hens. Average weekly egg production of first- and second-cycle VIP-immunized turkeys was similar (3.58 +/- 0.19 vs. 3.63 plus/minus 0.14 eggs per hen per wk). First- and second-cycle control hens
laid 2.63 +/- 0.25 and 2.41 +/- 0.20 eggs per hen per wk, respectively. The present results show that comparable egg production was attained in first- and second-cycle hens by active immunization with VIP. A Northern blot was used to examine turkey prolactin receptor (PRL-R) transcript isoform expression in laying hens. A 3.1-kb band was found in the pineal, infundibulum, magnum, isthmus, kidney, and intestine. In addition, 10.7- and 7.3-kb bands were detected in the pineal, magnum, isthmus, and intestine. Turkey PRL-R mRNA levels were also compared during the reproductive cycle. Turkey PRL-R mRNA levels were greatest in laying hen pineal glands (P < 0.05) and in incubating hen oviducts. This study provides the first evidence for multiple PRL-R mRNA transcript isoforms in turkeys.
Impacts
Immunization with vasoactive intestinal peptide increased egg production of recycled turkey hens to that of the first cycle birds.
Publications
- Bluhm, C., Rozenboim, I., Silsby, J. and El Halawani, M. 2000. Sex related differences in the effects of late winter pairing activity and seasonal influences on neuroendocrinology and gonadal development of mallards. Gen. Comp. Endocrinol. 118:310-321.
- El Halawani, M.E., Whiting, S.E., Silsby, J.L., Pitts, G.R. and Chaiseha, Y. 2000. Active immunization with vasoactive intestinal peptide in turkey hens. Poultry Sci. 79:349-354.
- Pitts, G.R., You, S., Foster, D.N. and El Halawani, M.E. 2000. Evidence for multiple prolactin receptor transcripts in the turkey. Poultry Sci. 79:355-362.
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Progress 01/01/99 to 12/31/99
Outputs
Circulating prolactin (PRL) levels increase when dynorphin (DYN) is infused into the turkey brain. When a highly selective kappa opioid receptor antagonist was given prior to DYN injection, the PRL response to DYN was almost totally blocked. The co-infusion of a serotonin (5-HT) receptor antagonist prevented the increase in PRL observed in control birds when DYN was infused alone. When DYN was co-infused with a selective D1 dopamine (DA) receptor antagonist, DYN was unable to effect any increase in PRL. In hens actively immunized against VIP, infused DYN was unable to increase plasma PRL levels. Thus, DA, 5-HT, and DYN stimulate PRL secretion via a common synaptic pathway expressing DAergic, 5-Htergic, and opioid receptors at synapses arranged serially in that functional order. While peptide histidine isoleucine (PHI) stimulated PRL secretion from anterior pituitary cells in a dose dependent manner, it was 100-fold less potent than tVIP in stimulating maximum PRL
secretion. Immunization against tVIP blunted the normal PRL increases associated with the turkey reproductive cycle. Turkeys immunized with tPHI did not differ from control birds. Incubation behavior was significantly reduced in tVIP-immunized turkeys as compared to controls or tPHI-immunized turkeys. Egg laying was similar between the control group and the group immunized against tPHI, while birds immunized against tVIP laid more eggs. These findings suggest that tPHI has little or no neuroendocrinological relevance in avian PRL secretion.
Impacts
Peptide histidine isoleucine has no physiological significance in controlling PRL secretion; and dynorphin, serotonin and dopamine regulate PRL secretion via common hypothalamic pathway.
Publications
- Ahn, J., You, S. and El Halawani, M.E. 1999. Active immunization against inhibin-alpha subunit increases the number of non-graded ovarian yellow follicles in the turkey. Poult. Sci. 78 (Suppl. 1):65.
- Farnell, M.B., You, S., El Halawani, M.E., Hargis, B.M. and Caldwell, D.J. 1999. Effect of rtINF-gamma on Salmonella enteritidis organ invasion in leghorn chicks. Poult. Sci. 78 (Suppl. 1):107.
- Kulick, R., Whiting, S., Pitts, G., You, S. and El Halawani, M. 1999. Vasoactive intestinal peptide but not peptide histidine isoleucine as a physiological regulator of prolactin in the domestic turkey. Poult. Sci. 78 (Suppl. 1):65.
- Stone, E., Millam, J.R., El Halawani, M.E., Phillips, R.E. and Redig, P. 1999. Determinants of reproductive success in cockatiels (Nympicus hollandicus). Appl. An. Behav. Sci. 63:209-218.
- Youngren, O.M., Pitts, G.R., Chaiseha, Y. and El Halawani, M.E. 1999. An opioid pathway in the hypothalamus of the turkey that stimulates prolactin secretion. Neuroendocrinology 70(5):317-323.
- Youngren, O., Pitts, G. and El Halawani, M. 1999. Partial characterization of an opiate pathway modulating prolactin secretion in the turkey. Poult. Sci. 78 (Suppl. 1):65.
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