Wayne L. Bacon

Possible roles for corticosterone and critical size in the fledging of nestling pied flycatchers

Our study was designed to see whether corticosterone (B) rises abruptly in the blood of nestling pied flycatchers (Ficedula hypoleuca) at the time they fledge, as reported recently for kestrels, and if so, why. We measured the growth and blood levels of B and selected nutrients of nestlings in broods of five, seven, and nine chicks during 1998 and 1999. In half of the broods, we clipped selected wing and tail feathers of both parents with the intention of making it more difficult for them to provide their chicks with food. We collected blood samples when the chicks were six to 10 d old (period of rapid growth) and 15 d of age or older (0–5 d before fledging). B increased substantially several days before the chicks left the nest and then declined somewhat. We found no differences in rates of growth or blood levels of B, nutrients, and hematocrit as a function of either brood size or parental handicapping. Nestlings within a day of fledging appear to have been food deprived in 1998; their glucose was significantly reduced, and B, free fatty acids, and glycerol were significantly elevated compared to levels in chicks 1–4 d younger. Such changes did not occur in 1999. Blood levels of B were significantly correlated with brood size near the day of fledging, but not earlier, in both years of the study. It was possible to predict the day on which chicks would leave the nest, using their wing length when 12 d old. These results suggest that high blood levels of B associated with food restriction and sibling competition induce chicks to fledge, provided they have reached a critical size, and that the importance of fasting, sibling competition, and B may vary from year to year.

Expression and localization of the proteoglycan decorin during the progression of cholesterol induced atherosclerosis in Japanese quail: implications for interaction with collagen type I and lipoproteins

The temporal and spatial distribution, and relative levels of the proteoglycan decorin and collagen type I were examined during the progression of atherosclerosis in the dorsal aortas of Japanese quail selected for cholesterol induced atherosclerosis. The quail were placed on either a control or 0.5% added cholesterol diet at approximately 16 weeks of age. Dorsal aortas were collected at 1- or 2-week intervals over a 15-week period after initiating cholesterol feeding. Biochemical analysis for decorin and collagen type I showed that both increased in the cholesterol-fed birds compared to control-fed birds beginning at 9 weeks and continued through the duration of the study. Through immunohistochemical staining for decorin and collagen type I, the spatial localization of decorin and collagen type I in control and less severe plaques in cholesterol-fed birds was most prominent in the arterial adventitia. However, in severe atherosclerotic plaques, decorin was localized in foam cell regions and collagen type I was found surrounding the foam cell regions where decorin accumulated. These results demonstrated a localization of decorin in the core of the atherosclerotic plaque foam cell region with collagen type I being located on the plaque surface.

Circulating IGF-I in plasma of growing male and female turkeys of medium and heavy weight lines

Plasma concentrations of insulin-like growth factor-I (IGF-I) were determined in male and female turkeys from a medium weight (RBC2) and a related heavy weight line (F) from 1 to 28 wks of age. At hatch, the concentrations of IGF-I were relatively low and not different between lines or sexes. During the neonatal period (1 to 7 wks), the concentrations of IGF-I increased and were higher in the faster growing F line and in males. During the juvenile period (8 to 15 wks) the concentrations of IGF-I were higher in males but not different between lines. During the preadolescent period (16 to 21 wks), the concentrations of IGF-I were higher in males but was not different between lines in males while the females of the RBC2 line had higher concentrations than females of the F line. During the adolescent period (22 to 28 wks) the concentrations of IGF-I were higher in males but was not different between lines in males while the females of the RBC2 line had higher concentrations than females of the F line. A phenotypic correlation (+.25) between plasma IGF-I and growth rate was present after statistical absorption of model effects during the neonatal period but not at the later ages. We conclude that IGF-I concentration was positively correlated with growth rate during the neonatal period, but that this relationship changed during the preadolescent and adolescent periods so that IGF-I concentrations were not related to growth rate in males but were negatively related to growth rate in females.

Pattern of secretion of luteinizing hormone and testosterone in the sexually mature male turkey

Whether luteinizing hormone (LH) and testosterone (T) are secreted in pulsatile patterns was determined in sexually mature male turkeys. Turkeys were chronically cannulated and serially bled for three 8-hr periods covering the 24-hr day (14L:10D, n = 7, series B), or for two 12-hr periods covering the 24-hr day (14L:10D, n = 4, series C). Pulses of both LH and T occurred during both the light and dark portions of the 24-hr day. A portion of the secretory episodes of T, where the baseline level of LH was relatively low, was associated with prior peaks of LH secretion. Secretory episodes of T also occurred, where baseline levels of LH and T were both relatively high, without detection of prior peaks of LH. No differences were found between the photophase and scotophase portions of the photoperiod for either LH or T concentration. It is concluded that T is secreted in a pulsatile pattern in sexually mature male turkeys. However, LH is secreted in a pulsatile pattern only when baseline levels of both LH and T are relatively low. Neither LH nor T secretion is entrained by the photoperiod. Corticosterone was measured in hourly samples, but no changes in concentration occurred in association with the photoperiod.

Changes in plasma luteinizing hormone concentration in Turkey hens after switching from short-day to long-day photoperiods

Luteinizing hormone (LH) has been reported to increase in plasma shortly after switching photosensitive turkey hens from short-day (SD) photoperiods (6 hr light:18 hr dark) to long-day (LD) photoperiods (14 hr light: 10 hr dark). An experiment was conducted to determine the timing and nature of these changes in plasma LH concentrations after the photostimulation of photosensitive turkey hens. The turkey hens were cannulated (jugular vein) to allow serial bleeding every 15 min for 48 hr. One group (controls) was continued under the SD photoperiod, and one group (treated) was switched to the LD photoperiod by the addition of 8 hr of light to the end of the photoperiod. In the control hens, no changes were seen in the observed or calculated baseline concentrations of LH or in the frequency and amplitude of LH peaks during the 48 hr of serial bleeding. In the treated hens, the observed and baseline concentrations of LH increased during the first LD scotoperiod, with a further increase during the second LD scotoperiod. This rapid increase was due to an increase in the baseline LH concentration, whereas no consistent changes were detected in the frequency and amplitude of LH peaks.

Responses to exogenous pulsatile turkey growth hormone by growing 8-week-old female turkeys

A study was conducted in turkeys to determine the effects of pulsatile infusion of turkey growth hormone (tGH) on growth, feed conversion, carcass component parts, carcass composition, plasma metabolite concentrations, and other hormones associated with growth. Female turkeys, 8 weeks of age, were dually cannulated via the right jugular for intermittent (10 min every 2 hr) infusion of tGH at a low dosage (4.5 micrograms tGH/infusion or 54 micrograms/day), a high dosage (18 micrograms tGH/infusion or 216 micrograms/day) or vehicle infused controls (vehicle, 0.025 M NaHCO3, 0.025 M Na2CO3 + 5 mg/ml NaCitrate, pH 9.4). Treatment was for 18 days. The second cannula was used to serially bleed the turkeys (5 or 10 min between samples) at 4 and 16 days of treatment to determine concentrations of GH, glucose, triacylglycerides (TG) non-esterified fatty acids (NEFA), and uric acid (UA). Overall GH was increased 74% above the control group in the low and 195% in the high treatment group. Baseline GH was increased 52% in the high group above the control group. The amplitude of GH peaks increased 292% in the low, and 574% in the high group above the amplitude of naturally occurring peaks in the control group. Infusion of tGH for 18 days did not affect overall daily gain, feed conversion, final body weight, tibiotarsus length, weights of pectoralis major, pectoralis minor, gastrocnemius or biceps femoris muscles, or weights of liver and offal. Abdominal fat pad weight (70% decrease), and percentages of carcass fat (4.9% decline) and carcass dry matter (2.3% decline) were lower in the high treatment group. Plasma TG and glucose were unaffected by treatment. Overall plasma NEFA concentration was increased in the high treatment group, and this increase was associated with an increased in the baseline concentration and incidence of pulses of NEFA, but not with the amplitude concentration of NEFA pulses. The dynamic nature of plasma NEFA concentration observed in this study suggests single time point measurements of this metabolite may not appropriately detect treatment effects. Plasma overall uric acid (UA) was decreased in the high treatment group in comparison to the control group, and this decrease was associated with a decrease in the baseline concentration of UA but not in the amplitude concentration nor incidence of UA pulses. Plasma insulin-like growth factor-I (IGF-I) concentrations were increased in the low treatment group at 4 but not at 16 days of treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Pulsatile secretion pattern of growth hormone in turkeys: Effects of age and sex ☆

Male and female turkeys were cannulated through the jugular vein, and blood samples were withdrawn remotely at 10-min intervals for a period of 8 hr at two points in the post-hatch growth phase (4 and 14 weeks of age). Growth hormone (GH) concentration was determined for each sample by radioimmunoassay using a recombinant chicken growth hormone preparation as standard. Data were evaluated for age- and sex-related differences. Four-week-old male and female turkeys displayed a pulsatile pattern of GH secretion. Growth hormone secretory profile characteristics differed significantly between ages with regard to overall mean, number of peaks, amplitude of peaks, interval between peaks, baseline, and total GH detected. Male four-week-old turkeys had a peak amplitude significantly greater than that of females of the same age. Older (14-week-old) male turkeys demonstrated a significantly greater number of GH secretory peaks than females during the 8-hr sampling period; however, overall it did not appear that the older birds had an organized pattern of GH secretion above baseline levels.

Pulsatile patterns of plasma growth hormone in Turkeys: Effects of growth rate, age, and sex

Male and female turkeys of a slow-growing, random bred line (RBC-2) and a fast-growing line (F), selected over 21 generations from RBC-2 for increased 16-week body weight, were intravenously cannulated and serially sampled at 10-min intervals for 6, 8, 9, 10, or 12 hr at 2, 4, 8, 14, and 24 weeks of age, respectively, for determination of the pulsatile pattern of plasma growth hormone (GH) concentration. Overall mean plasma GH concentration was greater for RBC-2 than F beginning at 4 weeks of age, when body weights of the two lines had diverged. Males exhibited both greater body weight and greater overall mean GH than females beginning at 4 weeks of age. Overall mean GH concentration, peak frequency and amplitude, and baseline concentrations declined with age for both lines. The RBC-2 line exhibited greater peak frequency, peak amplitude, and baseline mean concentration than the F line at 4, 8, and 14 weeks of age. Males exhibited greater peak frequency, peak amplitude, and baseline concentration than females at 4, 8, and 14 weeks of age. Peak duration was the most consistent profile parameter across lines, ages, and sexes, and averaged 68 min overall. Estimated GH pool size was consistently greater in males than females at all ages, and was greater in the F than RBC-2 line at 2 weeks of age when relative gain was maximal for both lines. Pool size was the GH parameter most highly correlated with body weight across treatment groups.

Changes in distribution of glycosaminoglycans during the progression of cholesterol induced atherosclerosis in Japanese quail

The temporal and spatial distribution and relative concentration of the proteoglycan glycosaminoglycan component were studied during the progression of atherosclerosis in the systemic arteries of Japanese quail selected for cholesterol induced atherosclerosis (CIA). The CIA quail were placed on either control or 0.5% added cholesterol diets at 3 months of age. The major systemic arteries (dorsal aorta, right and left brachiocephalic) were collected at 1- or 2-week intervals over the 10-week period of cholesterol feeding. In the cholesterol fed quail, alcian blue staining of the dorsal aorta showed elevations of glycosaminoglycans in regions of the artery with atherosclerotic plaque, beginning at the 6-week time point. By biochemical analysis, increases in glycosaminoglycan relative concentration was detected at the 10-week time point. In addition to the change in glycosaminoglycan relative concentration and distribution, the cholesterol fed animals also formed foam cells characteristic of atherosclerotic plaques. Therefore, the conclusion reached was that the CIA line of Japanese quail is a valid animal model for the study of alterations in proteoglycan metabolism in atherosclerotic plaques induced by hypercholesterolemia.

Collagen characteristics and organization during the progression of cholesterol-induced atherosclerosis in Japanese quail.

This study reports the concentration of collagen and its hydroxypyridinoline crosslinks, collagen fibril organization in the dorsal aortas, and systolic blood pressure during the progression of atherosclerosis in Japanese quail selected for cholesterol-induced atherosclerosis. The quail were placed on either a control or 0.5% cholesterol-added diet at approximately 16 weeks of age. The concentration of total collagen did not change in the control arteries during the course of the study, whereas at 5 and 10 weeks of cholesterol feeding, collagen levels decreased in the cholesterol-fed birds. Hydroxypyridinoline concentration increased during the duration of the study in the cholesterol-fed birds and by 15 and 20 weeks of cholesterol feeding, levels were significantly increased over those observed in the control arteries. Transmission electron microscopy showed changes in the organization of collagen fibrils. Increased systolic blood pressure was noted beginning at 10 weeks of cholesterol feeding, which is suggestive of other systemic changes induced by hypercholesterolemia. These results demonstrated remodeling of the collagen component of the dorsal aorta extracellular matrix during the progression of atherosclerosis and are suggestive of other systemic cardiovascular system changes.