Free-running rhythms of adrenocorticotropic hormone (ACTH), cortisol and melatonin in pigs.

In the domestic pig, a circadian rhythm of plasma cortisol occurs, with greatest concentrations in the morning and lowest concentrations in the afternoon. However, photic entrainment of the rhythms of ACTH and melatonin in pigs have not been defined clearly. This experiment was designed to evaluate free-running rhythms of ACTH, cortisol and melatonin in pigs housed in constant light (LL) and constant darkness (DD). Twelve crossbred barrows, maintained under ambient photoperiod, were catheterized and tethered individually in two environmentally controlled rooms, one with LL and the other with DD. For animals in LL, fluorescent lights provided 202 +/- 15 (mean +/- standard deviation) lux of light at 65 cm above the floors. Incandescent nightlights equipped with 7 watt red bulbs provided 7 +/- 2 lux and were illuminated continuously in both rooms. Pigs were given at least 14 d exposure to LL and DD, then samples of plasma and serum were obtained at hourly intervals for 48 hr. Plasma was assayed for ACTH, and serum for cortisol and melatonin. Periodograms were constructed to analyze the data. For this type of analysis, a statistic, Qp, is calculated, and circadian periodicity is suggested if maximum Qp (Qp max) occurs at or near 24 hr. The period of the free-running rhythms (tau) at Qp max for ACTH, cortisol and melatonin for pigs in LL (23.80 +/- .01, 23.78 +/- .01, and 23.21 +/- .02 hr, respectively) did not differ significantly from those for pigs in DD (23.39 +/- .01, 23.20 +/- .01, and 22.55 +/- .02 hr, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of duration of photoperiod and hemicastration on growth and testicular and endocrine functions of boars

Yorkshire boars were used to evaluate the influence of duration of photoperiod and hemicastration on growth and testicular and endocrine functions. At 10 wk of age, 5 hemicastrate (HC) and 5 intact (I) boars were assigned to either 8 or 16 hr of light daily until 6 mo of age. Body weights were recorded biweekly throughout the experiment. Venous cannulae were placed in all boars at 6 mo of age, and serum was collected at 30 min intervals from 0800 to 2000 hr. Gonadotropin releasing hormone (GnRH) was infused at 2000 hr (50 micrograms) and at 2030 hr (250 micrograms), and samples of serum were collected until 2400 hr. The following day, all boars were castrated, and the weights and sperm content of the testes and epididymides were determined. At castration, all pigs were given implants containing testosterone. Two weeks later, pigs were again canulated, and serum was obtained at 15 min intervals for 2 hr. Growth of boars was not significantly affected by duration of photoperiod or number of testes. Duration of photoperiod did not affect weight or sperm content of testes or epididymides. Hemi-castrated boars had greater testicular (P less than .01) and capita-corpora (C-C) epididymal weights (P less than .05) and more testicular and C-C sperm (P less than .01) per testis. Neither average concentrations of luteinizing hormone (LH) nor number and amplitude of pulses of LH were affected by photoperiod treatment. However, HC boars had greater average concentrations of LH (P less than .05) than I boars (.71 +/- .05 vs .52 +/- .05 ng/ml). Hemicastrated boars in 16 hr light daily had greater concentrations of FSH in serum (P less than .05) than 8I, 8HC, and 16I boars. Intact and HC boars had similar concentrations of prolactin (PRL) and testosterone. Similarly, concentrations of PRL and testosterone were not affected by duration of photoperiod. Secretion of LH and testosterone after treatment with GnRH was not significantly affected by duration of photoperiod. In general, HC boars released more LH in response to GnRH treatment than I boars. Concentrations of LH were greater (P less than .05) in HC than I boars at .5, 1, 2, and 3 hr after GnRH and tended (P less than .10) to be elevated at 1.5, 2.5, 3.5 and 4 hr after GnRH. The FSH response to GnRH was greater (P less than .05) for 16HC than 8I, 8HC, or 16I boars.(ABSTRACT TRUNCATED AT 400 WORDS)     

Contribution of the photoperiod to circadian variations in serum cortisol and melatonin in boars

Four pubertal (25 wk) crossbred boars were used to evaluate the role of the photoperiod in the organization of secretion of cortisol and melatonin throughout a 24-hr period. Boars were exposed to a 16-hr photoperiod in an environmentally controlled room and temperature was kept constant at 22 C. For the first 15 d, the onset of the photophase (light phase) and scotophase (dark phase) was 0200 hr and 1800 hr, respectively (ON2). During the final 15 d, the onset of the photophase and scotophase was advanced by 6 hr (0800 hr and 2400 hr, respectively; ON8). Samples of serum were obtained from catheterized boars at hourly intervals for 24 hr between the 14th to 15th d in both ON2 and ON8 photoperiods. Samples of serum were frozen and later assayed for cortisol and melatonin. The data were normalized to the clock time of onset of the photophase, fit to polynomial equations, and the profiles of cortisol and melatonin in ON2 and ON8 were tested for heterogeneity of regression. A circadian rhythm of cortisol was observed in both ON2 and ON8 and the fitted profiles were parallel, suggesting that the rhythm had shifted with the 6-hr shift in lights-on, lights-off. Generally, higher concentrations were observed during the late subjective evening and scotophase, whereas lower concentrations occurred about 6 to 10 hr after onset of the photophase. Although the profiles of melatonin did not differ in ON2 and ON8, there was no evidence of a nocturnal rise in melatonin in either treatment. It is suggested that some characteristic of the photoperiod organizes the circadian rhythm of cortisol in boars, but melatonin is not secreted in a rhythmic fashion in long photoperiods.     

Circulating cortisol, tumor necrosis factor-alpha interleukin-1beta, and interferon-gamma in pigs infected with Actinobacillus pleuropneumoniae

This study evaluated the time course of systemic cytokine concentrations in an acute model of pneumonia in pigs challenged intranasally with Actinobacillus pleuropneumoniae. Feed intake and serum cortisol were measured as overt clinical and systemic markers of disease onset, respectively, and serum tumor necrosis factor-alpha, interleukin-1beta, and interferon-gamma as representative systemic inflammatory markers. Crossbred barrows (n = 15), approximately 5 wk of age, were used in the study. Pigs were housed in an environmentally controlled facility at 25 degrees C and under continuous illumination in pens measuring approximately 1.5 m2. Pigs had free access to water and an unmedicated diet. Approximately 1 wk prior to disease challenge, pigs were fitted nonsurgically with venous catheters. At challenge, pigs were given 5 x 10(8) CFU Actinobacillus pleuropneumoniae intranasally (n = 8) or a similar volume of sterile growth media intranasally (Control; n = 7). Feed intake was estimated by the change in feeder weight at 12-h intervals from -12 to 72 h relative to the time of disease challenge. Blood sampling began 12 h prior to challenge and continued until 72 h after challenge. Pigs were sampled at -12, -6, and 0 h, then at 90-min intervals until 12-h post-challenge, continuing at 3-h intervals until 24-h post-challenge, then again at 6-h intervals until 72 h after challenge. Serum was harvested and frozen until assayed for cortisol, tumor necrosis factor-alpha, interleukin-1beta, and interferon-gamma. Feed intake was reduced in Actinobacillus pleuropneumoniae pigs during the intervals 0 to 12 h (P < 0.001), 24 to 36 h (P < 0.001), 48 to 60 h (P <0.05), and 60 to 72 h (P < 0.05). TheActnobacillus pleuropneumoniae-challenged pigs had elevated serum cortisol from 180-min to 18-h post-challenge (P < 0.001) and also at 36 (P < 0.05), 42 (P < 0.001), and 60 (P < 0.05) h following infection. Circulating cytokines were not affected by disease challenge. Thus, in this experimental model of pneumonia, weaned pigs demonstrated expected behavioral and endocrine characteristics of disease in the absence of significant changes in circulating inflammatory cytokines.     

Effects of Ascophyllum nodosum extract on growth performance and immune function of young pigs challenged with Salmonella typhimurium

Ninety-five pigs (initially 7.1 kg and 24 d of age) were used in a 28-d experiment to determine the effects of Ascophyllum nodosum seaweed extract (ANOD) on young pig growth performance and immune function in response to enteric disease challenge with Salmonella typhimurium (ST). Experimental treatments were arranged in a 2 x 4 factorial with main effects of disease challenge (control vs ST-challenge) and dietary addition of ANOD (0, 0.5, 1.0, and 2.0% of diet). Pigs were fed ANOD diets for 14 d and then challenged orally with ST or sterile media. There were no main effects of ANOD on growth performance end points, although there were significant quadratic effects of ANOD on ADG (P < 0.04) and final weight (P < 0.003), both being greatest at 1.0% ANOD. There was a positive linear effect of ANOD inclusion on ADFI (P < 0.07) and a negative linear effect on the gain-to-feed ratio (G/F) (P < 0.05). ST-challenge reduced ADG (P < 0.05), ADFI (P < 0.05), and G/F (P < 0.05) in the first week following challenge. Daily estimates revealed reductions in feed intake in ST-infected pigs on d 2 to 4 following infection (P < 0.05). Rectal temperature was increased maximally 2 d following ST-infection (P < 0.05). A disease challenge x time interaction (P < 0.001) was observed for serum haptoglobin and alpha1-acid glycoprotein. Serum immunoglobulin M (IgM) was not influenced by disease challenge, but IgM declined (P < 0.001) in all pigs over time. Serum immunoglobulin G (IgG) also was not influenced by disease challenge, but IgG tended (P < 0.08) to increase over time. In vitro culture of porcine alveolar macrophages with 10 mg/mL ANOD elevated (P < 0.05) prostaglandin E2 (PGE2) production over that of controls at 3 and 24 h of culture. There was no interleukin-10 response by porcine splenocytes cultured in vitro with 0.005, 0.05, 0.5, or 5 mg/mL ANOD. We conclude that this model of enteric disease elicits an acute phase response that is accompanied by increased rectal temperature and diminished feed intake. Furthermore, our results indicate some beneficial effects of dietary ANOD on growth performance and no influence of dietary ANOD on immune response in the presence or absence of ST-challenge. However, high ANOD concentrations are capable of activating porcine alveolar macrophages in vitro to secrete PGE2.     

Influence of the duration of photoperiod on growth,testicular characteristics and endocrine function of boars

Crossbred boars were used to evaluate the influence of exposure to 8 or 16 hr of light daily from 75 to 175 days of age on growth rate, testicular characteristics and endocrine function. At 160 days of age, concentrations of testosterone in serum (P<.10), the areas under plotted 12 hr testosterone profiles (P<.10) and the number (P<.05) and magnitude (P<.10) of testosterone secretory spikes were increased in boars exposed to 16 hr of light compared to boars in 8 hr light, but concentrations of LH in serum were similar in boars exposed to both treatments. Treatment with GnRH resulted in similar concentrations of LH in serum for both groups of boars. Testosterone in serum after GnRH-mediated LH release was greater at .5 (P<.05) and 1.0 (P<.10) hr following GnRH in boars exposed to 16 hr of light compared to boars at 8 hr, but concentrations of testosterone were similar for both treatments from 1.5 to 4.0 hr after GnRH. Growth rate and testicular and epididymal weights and sperm reserves at 175 days of age were not significantly altered by duration of photoperiod. Boars exposed to 8 hr of light had more hair per unit area than boars exposed to 16 hr of light. We conclude that exposure of prepubertal boars to longer daily photoperiods results in increased concentrations of testosterone in serum at 160 days of age.     

Repeated restraint and isolation stress in lambs increases pituitary-adrenal secretions and reduces cell-mediated immunity.

Rambouillet crossbred ewe lambs were used to evaluate the effect of repeated restraint and isolation stress (RIS) on endocrinological and immunological functions. Lambs were blocked by weight and assigned to either RIS (n = 6) or to control (CON; n = 6) treatments. All lambs were tethered in environmentally controlled rooms at 22 degrees C with constant light and, at this time (d 0), were given 1 mg of ovalbumin in adjuvant. On d 12, catheters were placed nonsurgically into the jugular vein of all lambs, and they were reimmunized with .5 mg of ovalbumin in incomplete adjuvant. Each lamb in the RIS treatment group was removed from its home stanchion, isolated from visual and tactile (but not auditory and olfactory) contact with other lambs, and restrained for 6 h on d 14, 15, and 16. Lambs in CON treatment remained undisturbed in their home stanchions. Lymphocyte blastogenic function and production of interleukin-2 (IL-2) were assessed in samples of blood collected before and at the conclusion (0 and 6 h) of each of the three stress bouts. In addition, ACTH and cortisol secretion in response to RIS was evaluated in samples of plasma and serum collected at .5-h intervals on the first and last days of stress (d 14 and 16). Finally, antibody production in response to immunization against ovalbumin was assessed in samples of serum obtained 14 d after reimmunization on d 12 of the study. Polynomial curves fit to the ACTH and cortisol data differed (P less than .005) on both d 14 and 16 between RIS and CON treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Poor reproductive response of anestrous Suffolk ewes to ram exposure is not due to failure to secrete luteinizing hormone acutely

Twenty Polypay-sired ewes (Group P) and 14 Suffolk ewes (Group S) were bled at 48-h intervals for 10 d beginning on April 6, 1989, and the serum was assayed for progesterone to determine which ewes were anestrous; 9/20 Group P ewes were anestrous, compared with 14/14 Group S ewes (P less than .001). Catheters were placed into the jugular vein of anestrous ewes from both breed groups (eight of Group P, seven of Group S), and samples of serum were collected at 12-min intervals for 4 h. Then, the ewes were exposed to mature, intact rams, and additional samples were taken at 12-min intervals for 4 h after ram exposure. The serum was later analyzed to determine the secretion of LH in response to ram introduction. After the acute bleeding period, all Group P and Group S ewes were commingled and exposed to a ram continuously for 42 d. Samples of serum were collected thrice weekly and analyzed for progesterone to monitor ovulatory response to ram introduction through the 42-d period. In addition, breeding activity and lambing data were recorded. When all Group P ewes were compared to Group S ewes, a greater proportion (P less than .001) of Group P ewes were mated (20/20 vs 3/13; one Group S ewe died during the 42-d mating period) by the end of the 42-d period and more (P less than .001) ewes lambed in the fall (17/20 Group P vs 2/13 Group S).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of isoenergetic infusions of propionate and glucose on portal-drained visceral nutrient flux and concentrations of hormones in lambs maintained by total intragastric infusion

Three lambs were used in a repeated Latin square design to determine the influence of isoenergetic infusions of propionate or glucose on portal-drained visceral flux (PDV) of nutrients and concentrations of insulin, glucagon, growth hormone and prolactin. Lambs were fitted with appropriate catheters for blood sampling and maintained on total intragastric infusion of nutrients. Basal VFA, casein, mineral and vitamin infusions (isocaloric and isonitrogenous) were supplemented with an additional 22 +/- .5 kcal/h from propionate, glucose or a combination of propionate plus glucose. Ruminal fluid proportion and arterial blood concentration and PDV flux of propionate increased (P less than .10) by 17 mol/100 mol, .02 mM and 40 mmol/h, respectively, with infusion of an additional 61 mmol/h of propionate. Regression equations predicted that, on a net basis, 67% of ruminally infused propionate and 43% of abomasally infused glucose appeared in portal blood. Arterial L-lactate, beta-hydroxybutyrate and acetate concentrations, and beta-hydroxybutyrate flux were increased (P less than .10) by .34 mM, .20 mM, .50 mM and 4.2 mmol/h, respectively, with infusion of 33 mmol/h of added glucose. Net utilization of glucose by the PDV was approximately 4.4 mmol/h when no glucose was infused. Increased infusion of propionate resulted in a 22.2-micrograms/h increase in PDV flux of insulin (P less than .08) but had no effect on arterial insulin, glucagon and prolactin concentrations (P greater than .10). Arterial growth hormone increased by 3.8 ng/ml with increasing glucose infusion (P less than .08).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ringlike structure of the Deinococcus radiodurans genome: a key to radioresistance?

The bacterium Deinococcus radiodurans survives ionizing irradiation and other DNA-damaging assaults at doses that are lethal to all other organisms. How D. radiodurans accurately reconstructs its genome from hundreds of radiation-generated fragments in the absence of an intact template is unknown. Here we show that the D. radiodurans genome assumes an unusual toroidal morphology that may contribute to its radioresistance. We propose that, because of restricted diffusion within the tightly packed and laterally ordered DNA toroids, radiation-generated free DNA ends are held together, which may facilitate template-independent yet error-free joining of DNA breaks.