@article{swanchara_armstrong_britt_1999, title={Effects of active immunization against growth-hormone releasing factor on puberty and reproductive development in gilts}, volume={77}, DOI={10.2527/1999.7771807x}, abstractNote={Hormones within the somatotropin cascade influence several physiological traits, including growth and reproduction. Active immunization against growth hormone-releasing factor (GRFi) initiated at 3 or 6 mo of age decreased weight gain, increased deposition of fat, and delayed puberty in heifers. Two experiments were conducted to investigate the effects of GRFi on puberty and subsequent ovulation rate in gilts. Crossbred gilts were actively immunized against GRF-(1-29)-(Gly)2-Cys-NH2 conjugated to human serum albumin (GRFi) or against human serum albumin alone (HSAi). In Exp. 1, gilts were immunized against GRF (n = 12) or HSA (n = 12) at 92 +/- 1 d of age. At 191 d of age, antibody titers against GRF were greater (P < .05) in GRFi (55.5 +/- 1.3%) than in HSAi (.4 +/- 2%) gilts. The GRFi decreased (P < .05) BW (86 +/- 3 vs 104 +/- 3 kg) by 181 d of age and increased (P < .05) backfat depth (15.7 +/- .4 vs 14.8 +/- .4 mm) by 130 d of age. At 181 d of age, GRFi reduced the frequency of ST release (1.0 +/- .5 vs 5.0 +/- .5, peaks/24 h; P < .0001) and decreased (P < .01) ST (1.1 +/- .06 vs 1.7 +/- .06 ng/mL), IGF-I (29 +/- 2 vs 107 +/- 2 ng/mL), and insulin concentrations (3.5 +/- .2 vs 6.3 +/- .2 ng/mL). The GRFi decreased (P < .05) feed conversion efficiency but did not alter age at puberty (GRFi = 199 +/- 5 d vs HSAi = 202 +/- 5 d) or ovulation rate after second estrus (GRFi = 10.7 +/- .4 vs HSAi = 11.8 +/- .5). In Exp. 2, gilts were immunized against GRF (n = 35) or HSA (n = 35) at 35 +/- 1 d of age. The GRFi at 35 d of age did not alter the number of surface follicles or uterine weight between 93 and 102 d of age, but GRFi decreased (P < .05) ovarian weight (.41 +/- .08 vs 1.58 +/- .4 g) and uterine length (17.2 +/- 1.1 vs 25.3 +/- 2.3 cm). Immunization against GRF reduced (P < .05) serum IGF-I (GRFi = 50 +/- 4 vs HSAi = 137 +/- 4 ng/mL) and BW (GRFi = 71 +/- 3 vs HSAi = 105 +/- 3 kg) and increased (P < .05) backfat depth (GRFi = .38 +/- .03 vs HSAi = .25 +/- .02 mm/kg). Age at puberty was similar in GRFi and HSAi gilts, but ovulation rate was lower (P < .05) after third estrus in GRFi (11.3 +/- .8) than in HSAi (13.8 +/- .8) gilts. Thus, GRFi at 92 or 35 d of age decreased serum ST, IGF-I, and BW in prepubertal gilts without altering age of puberty. However, GRFi at 35 d of age, but not 92 d of age, decreased ovulation rate. These results indicate that alterations in the somatotropic axis at 1 mo of age can influence reproductive development in pubertal gilts.}, number={7}, journal={Journal of Animal Science}, author={Swanchara, K. W. and Armstrong, J. D. and Britt, Jack}, year={1999}, pages={1807–1814} }
 @article{o'kane_armstrong_1997, title={Developing course materials using the World Wide Web}, volume={41}, number={2}, journal={NACTA Journal}, author={O'Kane, M. and Armstrong, J. D.}, year={1997}, pages={10–15} }
 @article{hevener_almond_armstrong_richards_1997, title={Effects of acute endotoxemia on serum somatotropin and insulin like growth factor I concentrations in prepubertal gilts}, volume={58}, number={9}, journal={American Journal of Veterinary Research}, author={Hevener, W. and Almond, G. W. and Armstrong, J. D. and Richards, R. G.}, year={1997}, pages={1010–1013} }
 @article{armstrong_harvey_poore_simpson_miller_gregory_hartnell_1995, title={Recombinant bovine somatotropin increases milk yield and calf gain in diverse breeds of beef cattle: Associated changes in hormones and indices of metabolism}, volume={73}, DOI={10.2527/1995.73103051x}, abstractNote={In Exp. 1, Angus (A, n = 30), Charolais (C, n = 37), and Simmental (S, n = 30) multiparous cows received (s.c.) recombinantly derived bovine somatotropin (bST; sometribove, 500 mg) or vehicle (VEH) at 2-wk intervals from 124 to 228 d postpartum (DPP). Calves were weaned at 228 DPP. Bovine somatotropin increased (P < .01) milk yield and percentage of milk fat similarly in A, C, and S cows. Calf weaning weight was greater (P < .05) in cows treated with bST than in those given VEH. Administration of bST decreased deposition of fat and increased concentrations of IGF-I, insulin, glucose, and nonesterified fatty acids. In Exp. 2, we compared effects of bST initiated before or after the breeding season. Charolais (n = 33) and S (n = 40) cows were administered (at 2-wk intervals) VEH or bST beginning at 28 DPP (B-bST) or bST beginning at 105 DPP (A-bST). Calves were weaned at 243 DPP. Administration of bST before or after the breeding season increased milk yield on DPP 136 and 194; however, yields were greater in A-bST than in B-bST cows. Milk yields were similar in all cows at 236 DPP, corresponding to decreased forage availability. Calf body weight was greater (P < .05) in A-bST than VEH; B-bST calves were similar to VEH. Fat depth was greater in VEH than in bST-treated cows in C but not in S cows. Serum IGF-I was greater in A- and B-bST than in VEH cows. Mean days from calving to serum progesterone > 1 ng/mL and pregnancy rates were similar in VEH, A-, and B-bST cows. Administration of bST increased cow milk yield and subsequent calf weaning weight when initiated after 100 d postpartum. As anticipated, bST increased IGF-I, insulin, glucose, and nonesterified fatty acids. Administration of bST before and during the breeding season did not affect reproductive performance.}, number={10}, journal={Journal of Animal Science}, author={Armstrong, J. D. and Harvey, R. W. and Poore, M. A. and Simpson, R. B. and Miller, D. C. and Gregory, G. M. and Hartnell, G. F.}, year={1995}, pages={3051} }
 @article{armstrong_coffey_esbenshade_campbell_heimer_1994, title={Concentrations of hormones and metabolites, estimates of metabolism, performance, and reproductive performance of sows actively immunized against growth hormone-releasing factor}, volume={72}, DOI={10.2527/1994.7261570x}, abstractNote={Cyclic females actively immunized against growth hormone-releasing factor (GRF; n = 5) or human serum albumin (HSAi; n = 4) were used to determine the effects of reduced serum somatotropin (ST) and IGF-I on metabolism and production in gestating and lactating sows. Sows farrowed, pigs were weaned at 28 d of lactation, and sows were observed for estrus after weaning. Blood samples were collected at 15-min intervals for 5 to 6 h on d 110 of gestation and d 21 of lactation. Mean ST (nanograms/milliliter) was less (P < .05) in GRFi than in HSAi sows at d 21 of lactation, but it was similar at d 110 of gestation. Serum concentrations of IGF-I were less (P < .05) in GRFi than in HSAi sows at d 21 of lactation but not at d 110 of gestation. Serum thyroxine was greater (P < .05) in GRFi than in HSAi sows during gestation and lactation. Sows actively immunized against GRF weighed less (P < .01) and had more backfat (P < .01) at d 110 of gestation than HSAi sows; in vitro glucose oxidation and lipogenic rate of adipose tissue were greater (P < .05 for treatment x day interaction) in GRFi than in HSAi sows at d 110 of gestation. Across treatment, mammary gland oxidation of glucose and glucose clearance rates increased (P < .05), whereas adipose tissue utilization of glucose decreased (P < .05) during lactation. During lactation, GRFi sows mobilized more (P < .05) backfat than did controls.(ABSTRACT TRUNCATED AT 250 WORDS)}, number={6}, journal={Journal of Animal Science}, author={Armstrong, J. D. and Coffey, M. T. and Esbenshade, K. L. and Campbell, R. M. and Heimer, E. P.}, year={1994}, pages={1570} }
 @article{armstrong_cohick_harvey_heimer_campbell_1993, title={EFFECT OF FEED RESTRICTION ON SERUM SOMATOTROPIN, INSULIN-LIKE GROWTH FACTOR-I-(IGF-I) AND IGF BINDING-PROTEINS IN CYCLIC HEIFERS ACTIVELY IMMUNIZED AGAINST GROWTH-HORMONE RELEASING-FACTOR}, volume={10}, ISSN={["0739-7240"]}, DOI={10.1016/0739-7240(93)90035-A}, abstractNote={Feed restriction often increases serum somatotropin (ST) and decreases insulin-like growth factor-I (IGF-I) in ruminants; however, the mechanisms responsible for this change in ST and IGF-I are not well defined. We investigated the effects of feed restriction on serum ST, IGF-I, IGF binding proteins (IGFBP), insulin and nonesterified fatty acids (NEFA) in cyclic Angus and Charolais heifers (n = 15) previously immunized against growth hormone releasing factor (GRFi) or human serum albumin (HSAi). Cows were fed a concentrate diet ad libitum (AL) or were restricted to 2 kg cotton seed hulls (R) for 4 d. Each heifer received each dietary treatment in a single reversal design. As anticipated, GRFi decreased ST, IGF-I and insulin (P < .05). In addition, GRFi decreased serum IGFBP-3 (P < .01), but increased IGFBP-2 (P < .01). Feed restriction resulted in an increase in serum ST in HSAi, but not in GRFi heifers. Regardless of immunization treatment, feed restriction decreased serum IGF-I and insulin, and increased NEFA (P < .01). In conclusion, the increase in serum ST levels observed during feed restriction was blocked by active immunization against GRF. However, feed restriction resulted in decreased serum IGF-I in GRFi heifers in spite of initial low levels of IGF-I (due to GRFi). Although GRFi decreased levels of IGFBP-3 and increased levels of IGFBP-2, feed restriction for 4 d did not alter serum IGFBP.}, number={4}, journal={DOMESTIC ANIMAL ENDOCRINOLOGY}, author={ARMSTRONG, JD and COHICK, WS and HARVEY, RW and HEIMER, EP and CAMPBELL, RM}, year={1993}, month={Oct}, pages={315–324} }
 @article{armstrong_spears_1991, title={Changes in growth hormone and luteinizing hormone following acute or chronic administration of an opioid agonist, FK33-824, in wethers}, volume={69}, DOI={10.2527/1991.692774x}, abstractNote={Two experiments were conducted to determine the effect of acute or chronic administration of an opioid agonist, (D-Ala2,MePhe4,Met(O)5-ol)-enkephalin (FK33-824), on concentrations of growth hormone (GH) and LH in castrate sheep (wethers). In Exp. 1, we evaluated the effect of acute administration (two injections or infusion for 2 h) of FK33-824 on GH and LH. Wethers (31 +/- 1 kg; n = 12) received FK33-824 or saline via one of the three following routes of deliver: 1) i.v. (8 micrograms/kg) at 0 and 60 min (i.v., n = 4), 2) s.c. (16 micrograms/kg) at 0 and 60 min (s.c., n = 4), or 3) i.v. infusion (8 micrograms.kg-1.h-1) for 120 min (inf., n = 4) preceded by a single injection (8 micrograms/kg). Wethers received FK33-824 and saline on d 1 and 2 or d 2 and 1, respectively. Concentrations of GH were consistently elevated (P less than .05) by FK33-824 regardless of route of delivery. Infusion of FK33-824 for 120 min maintained GH concentrations greater (P less than .05) than pretreatment or those during infusion of saline. Average LH was decreased consistently by FK33-824, independent of its route of administration; episodic release of LH was suppressed. In Exp. 2, crossbred wethers (36 +/- 2 kg; n = 12) were used to determine the effect of chronic administration (s.c.) of FK33-824 on the concentrations of GH and LH and retention of N and energy.(ABSTRACT TRUNCATED AT 250 WORDS)}, number={2}, journal={Journal of Animal Science}, author={Armstrong, J. D. and Spears, J. W.}, year={1991}, pages={774} }
 @article{armstrong_esbenshade_johnson_coffey_heimer_campbell_mowles_felix_1990, title={Active immunization of pigs against growth hormone-releasing factor: Effect on concentrations of growth hormone and insulin-like growth factor 1}, volume={68}, DOI={10.2527/1990.682427x}, abstractNote={Cyclic gilts (96 +/- 1 kg) were used to determine the effect of active immunization against growth hormone-releasing factor GRF(1-29)-NH2 on concentrations of growth hormone (GH) and insulin-like growth factor 1 (IGF-1). Gilts were immunized against GRF conjugated to human serum albumin (GRF-HSA, n = 5) or HSA alone at 180 d of age (wk 0). Booster doses were administered at wk 9 and 13. Seven days after the second booster (wk 14), blood samples were collected at 15-min intervals for 6 h before feeding and 30, 60, 120, 180 and 240 min after feeding. Eight days after the second booster, all gilts were administered a GRF analog, [desNH2Tyr1,Ala15]-GRF(1-29)-NH2, followed by an opioid agonist, FK33-824. Blood samples were collected at 15-min intervals from -30 to 240 min after injection. Immunization against GRF-HSA resulted in antibody titers, expressed as dilution required to bind 50% of [125I]GRF, ranging from 1:11,000 to 1:60,000 (wk 11 and 14); binding was not detectable or was less than 50% at 1:100 in HSA gilts (P less than .05). Episodic release of GH was abolished by immunization against GRF-HSA (P less than .05). Mean GH was decreased (P less than .07), but basal GH concentrations were not altered (P greater than .15) by immunization against GRF-HSA. Serum concentrations of IGF-1 were similar at wk 0, but concentrations were lower in GRF-HSA than in HSA gilts (P less than .05) at wk 14.(ABSTRACT TRUNCATED AT 250 WORDS)}, number={2}, journal={Journal of Animal Science}, author={Armstrong, J. D. and Esbenshade, K. L. and Johnson, J. L. and Coffey, M. T. and Heimer, E. and Campbell, R. M. and Mowles, T. and Felix, A.}, year={1990}, pages={427} }
 @article{armstrong_esbenshade_coffey_heimer_campbell_mowles_felix_1990, title={OPIOID CONTROL OF GROWTH-HORMONE IN THE SUCKLED SOW IS PRIMARILY MEDIATED THROUGH GROWTH-HORMONE RELEASING-FACTOR}, volume={7}, ISSN={["0739-7240"]}, DOI={10.1016/0739-7240(90)90025-U}, abstractNote={Endogenous opioid peptides mediate the effect of suckling on LH and PRL in the domestic pig. However, the role of opioids in modulating GH during lactation in swine is not known. Primiparous sows that had been immunized against GRF(1–29) conjugated to human serum albumin (GRF-HSA, n = 5) or HSA (n = 4) were used to determine changes in GH after naloxone. Treatments were imposed in all sows on day 21 of lactation when antibody titers were 9100 ± 1629. All sows received (i.v.) naloxone (0.25 mg/kg) or saline (0.0125 ml/kg) at 15 min intervals for 165 min. Active immunization against GRF-HSA during lactation decreased (P < 0.05) mean concentration (4.8 ± 0.2 vs 2.6 ± 0.1 ng/ml) and frequency (1.5 ± 0.3 vs 0.4 ± 0.2 peaks/4 hr). Concentrations of LH and PRL were similar in GRF-HSA and HSA immunized sows. Naloxone suppressed (P < 0.05) GH in all sows. In HSA sows, naloxone abolished episodic release of GH and decreased average, but not basal, concentrations of GH. In sows immunized against GRF-HSA, naloxone decreased (P < 0.05) average and basal GH but failed to decrease frequency of GH release. Naloxone failed to alter frequency of LH release. Concentrations of PRL decreased (P < 0.05) after naloxone in all sows. In conclusion, immunization against GRF-HSA blocked most of the effect of lactation on GH. Blocking opioid receptors with naloxone decreased GH and PRL in all sows. In contrast to previous findings naloxone had no effect on LH. Opioids alter concentrations of GH through a GRF dependent and GRF independent pathway.}, number={2}, journal={DOMESTIC ANIMAL ENDOCRINOLOGY}, author={ARMSTRONG, JD and ESBENSHADE, KL and COFFEY, MT and HEIMER, E and CAMPBELL, R and MOWLES, T and FELIX, A}, year={1990}, month={Apr}, pages={191–198} }
 @article{armstrong_kraeling_britt_1988, title={Morphine suppresses luteinizing hormone concentrations in transiently weaned sows and delays onset of estrus after weaning}, volume={66}, DOI={10.2527/jas1988.6692216x}, abstractNote={Lactating sows were used to evaluate effects of morphine and suckling on secretion of LH and prolactin (PRL) and occurrence of estrus after weaning. In the first experiment, crossbred multiparous sows nursing 7.9 +/- .4 pigs per litter at 25.2 +/- .3 d of lactation were subjected to one of three treatments during the middle 8-h segment of a 24-h experimental period. Treatments were infusion (i.v.) of morphine (200 mg/h) with the litter present (n = 4) or transiently weaned (n = 4), or transient weaning of litters without morphine (n = 4). Transient weaning decreased (P less than .05) prolactin and increased (P less than .05) the frequency of LH pulses and average concentration of LH. Infusion of morphine caused transient hyperthermia and suppressed (P less than .05) LH release in two of four sows nursing litters and in four sows whose litters were absent. Infusion of morphine, in the presence or absence of litters, suppressed PRL during the middle and last 8-h segments. A second experiment was conducted to test the hypothesis that chronic administration of morphine delays onset of estrus after weaning. Primiparous Duroc sows were assigned at weaning (53 to 63 d postpartum) to receive morphine (n = 10) or saline (n = 11). Saline (1.5 ml) or morphine (75 mg) was administered s.c. three times a day for 5 d after weaning. Onset of estrus after weaning was delayed in sows given morphine compared with those given saline (9.7 +/- .4 vs 5.2 +/- .3 d, respectively; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)}, number={9}, journal={Journal of Animal Science}, author={Armstrong, J. D. and Kraeling, R. R. and Britt, J. H.}, year={1988}, pages={2216} }
 @article{armstrong_1987, title={Season, suckling and nutrition alter ovarian function in swine through control of gonadotropin-releasing hormone}, volume={47}, number={8}, journal={Dissertation Abstracts International. B, Sciences and Engineering}, author={Armstrong, J. D.}, year={1987}, pages={3178} }
 @article{armstrong_britt_cox_1986, title={Seasonal differences in function of the hypothalamic-hypophysial-ovarian axis in weaned primiparous sows}, volume={78}, DOI={10.1530/jrf.0.0780011}, abstractNote={Primiparous sows were fed to appetite during lactations that occurred during winter or summer, and 11.4 +/- 0.4 pigs per litter were weaned at 23.5 +/- 0.1 days of age. Sows were slaughtered at 0 or 72 h after weaning or blood samples were collected until 24 h after onset of oestrus. Sows that lactated during summer consumed less food and lost more (P less than 0.05) weight, heartgirth and backfat than those that lactated during winter. Weaning-to-oestrus interval was greater (P less than 0.05) in summer (224 +/- 25 h) than in winter (93 +/- 13 h). Content of GnRH in the hypothalamus and concentrations of LH in the anterior pituitary and serum were lower (P less than 0.05) after weaning in summer than winter. The numbers of visible ovarian follicles less than 5 mm in diameter at weaning were lower (P less than 0.05) in summer than in winter. In contrast to LH, FSH concentration in serum was higher (P less than 0.10) in summer than winter, but FSH values in the anterior pituitary were lower (P less than 0.05) in summer than in winter. Post-weaning patterns of secretion of oestradiol and follicular development differed between winter and summer. For example, in some sows weaned during the summer, transient surges of oestradiol occurred repeatedly during 0 to 280 h after weaning without provoking surges of LH. These results indicate that the period of post-weaning anoestrus in summer is prolonged because of altered activity of the hypothalamic-pituitary axis, possibly because of changes in sensitivity to the feedback of oestradiol. Lower feed intake during lactations that occur during summer may predispose the endocrine system to the aberrations.}, number={1}, journal={Journal of Reproduction & Fertility}, author={Armstrong, J. D. and Britt, J. H. and Cox, N. M.}, year={1986}, pages={11} }
 @article{armstrong_britt_1985, title={PULSATILE ADMINISTRATION OF GONADOTROPIN-RELEASING HORMONE TO ANESTROUS SOWS - ENDOCRINE CHANGES ASSOCIATED WITH GNRH-INDUCED AND SPONTANEOUS ESTRUS}, volume={33}, ISSN={["0006-3363"]}, DOI={10.1095/biolreprod33.2.375}, abstractNote={Tbit experim~llt detumiDcd wbubn pulAtile administration of JOlladolropiDffleuinS hormone (GnRK) would induce estrUs and ovulation in SCa$(lnally anesuotU prirnipuou. sow. .nd complRd endoc::rinc responses of GIlRH-induced sows with those of primipllOUI so_ that abibitrd .pOD­ u.nc-ou. e5IrUS afta" wc:aninf. Sn'Cntttn priinipllOU' Landrac~ X Lute Whit~ sow. fllfOwe'd in August 1982, IlI;:tlt~d 23.8 t 0.4 da~ (mean t SEM), and weaned 9.0 t. 0.3 pip pn litter. 8100d for detCTlTlinaoon of proptnoDe, Iuuinizin, hormon~ (LH), and estradiol-17fJ (E) was coUeo::ted every 6 b from 1 day before to 12 day. aft~r wc:aninf. Twelve so_ exhibited spOllu.neous esuu. 135 t 9 h attn w~.nin" and these sows wn~ cunsidcr~d to be normal. Fiv~ sows wnc: anestrous for at leut 23 d.ys postwelllin, lIId failed to oyullt~, u indkued by concentration. of prosesttrone that were Jell than 1.0 nJ'mJ in blood samples coUeo::ted daily durin, thit period. From Day 0 to D.y 30 pOStweaninJ, levels of estradiol in anestrou. sow. varied betwttn 3 and 30 pJ/ml, con<:~n­ aation. of LH wa-e low, and preovulatory·like LH RIfF' did not oc::c:ur. 8q:inoin, on Day 30 postwe1l..ll.i.nJ, four l.Destrou, sow. wac: Jiven 1.5", GoRH (i.v.) hourly until on.t of atru5 ltId blood was collected every 6 h durin, GnRH trnDn~nt. Th~ .vcr. interval from beainnin, of GnRH un.anent to onset of estrUs was 84 t 5 h (ran~ 72 to 96 h). Pan~11IJ of Htradiollild LH secretion lIound eslrUS were limitll in nonnal sow. and thote trnted with CoRH. Esaadiol rcmli.n~d devated abaft bual cODc~naatiooa (25 pJ'mJ) for 49.6 t 4.0 h in nofUla.l sows e~pared to 48.0 t 0 h in CnRH-tretted sows.. Ave~ in~rval (h) ITom peak estradiol to th~ preovulatory LH sufJ'C wu similar in nonnal (23.5 1; 4.2) and GnRK-induced sow. (18.0 t 4.2). We eooelude the admilliltration of hourly pulses of GnRH to wcan~d anem-aus primiparous sow. impoted a proper stimulation to th~ anterior pituitary that in tum led to an in(f~ued JOnadoaopin ~tion that indu~d estrus and OYIIlltioo.}, number={2}, journal={BIOLOGY OF REPRODUCTION}, author={ARMSTRONG, JD and BRITT, JH}, year={1985}, pages={375–380} }