Characterizing effects of feed restriction and glucagon-like peptide 2 administration on biomarkers of inflammation and intestinal morphology.

Inadequate feed consumption reduces intestinal barrier function in both ruminants and monogastrics. Objectives were to characterize how progressive feed restriction (FR) affects inflammation, metabolism, and intestinal morphology, and to investigate if glucagon-like peptide 2 (GLP2) administration influences the aforementioned responses. Twenty-eight Holstein cows (157 ± 9 d in milk) were enrolled in 2 experimental periods. Period 1 [5 d of ad libitum (AL) feed intake] served as baseline for period 2 (5 d), during which cows received 1 of 6 treatments: (1) 100% of AL feed intake (AL100; n = 3), (2) 80% of AL feed intake (n = 5), (3) 60% of AL feed intake (n = 5), (4) 40% of AL feed intake (AL40; n = 5), (5) 40% of AL feed intake + GLP2 administration (AL40G; 75 µg/kg of BW s.c. 2×/d; n = 5), or (6) 20% of AL feed intake (n = 5). As the magnitude of FR increased, body weight and milk yield decreased linearly. Blood urea nitrogen and insulin decreased, whereas nonesterified fatty acids and liver triglyceride content increased linearly with progressive FR. Circulating endotoxin, lipopolysaccharide binding protein, haptoglobin, serum amyloid A, and lymphocytes increased or tended to increase linearly with advancing FR. Circulating haptoglobin decreased (76%) and serum amyloid A tended to decrease (57%) in AL40G relative to AL40 cows. Cows in AL100, AL40, and AL40G treatments were euthanized to evaluate intestinal histology. Jejunum villus width, crypt depth, and goblet cell area, as well as ileum villus height, crypt depth, and goblet cell area, were reduced (36, 14, 52, 22, 28, and 25%, respectively) in AL40 cows compared with AL100 controls. Ileum cellular proliferation tended to be decreased (14%) in AL40 versus AL100 cows. Relative to AL40, AL40G cows had improved jejunum and ileum morphology, including increased villus height (46 and 51%), villus height to crypt depth ratio (38 and 35%), mucosal surface area (30 and 27%), cellular proliferation (43 and 36%), and goblet cell area (59 and 41%). Colon goblet cell area was also increased (48%) in AL40G relative to AL40 cows. In summary, progressive FR increased circulating markers of inflammation, which we speculate is due to increased intestinal permeability as demonstrated by changes in intestinal architecture. Furthermore, GLP2 improved intestinal morphology and ameliorated circulating markers of inflammation. Consequently, FR is a viable model to study consequences of intestinal barrier dysfunction and administering GLP2 appears to be an effective mitigation strategy to improve gut health.

Impact of ractopamine hydrochloride on growth performance, carcass and pork quality characteristics, and responses to handling and transport in finishing pigs.

The effect of feeding ractopamine hydrochloride (RAC) on growth performance, carcass and pork quality, and blood acid-base and catecholamine responses to handling and transport in finishing pigs was evaluated using a randomized complete block design to compare 2 RAC levels (0 vs. 10 mg/kg). Crossbred pigs ( = 144) were housed in single-sex pens (barrow or gilt) of 3 with 24 pens/RAC level. The study was carried out for a 28-d period from 104.0 ± 5.99 to 136.7 ± 6.44 kg BW. At the end of the growth study, pigs were subjected to handling and transport procedures that involved an initial aggressive handling procedure (pigs moved 50 m with 8 shocks from an electric prod) followed by a 30-min transport on a standard livestock trailer at a floor space of 0.46 m/pig followed by a final gentle handling procedure (pigs moved 100 m using sort boards and slap paddles). A blood sample was taken and rectal temperature was measured 2 h before (baseline) and immediately after the final handling procedure (final). Barrows ( = 72) were harvested and carcass and pork quality were measured. Feeding RAC increased ( ≤ 0.05) ADG (19.6%), ADFI (4.2%), and G:F (14.8%). The increase in plasma epinephrine levels from baseline to final was greater ( ≤ 0.05) for pigs fed RAC; there was a trend ( ≤ 0.10) for pigs fed RAC to have greater final blood lactate and to show a greater change from baseline to final in blood bicarbonate, partial pressure of and total carbon dioxide, and oxygen saturation levels. However, there were no differences between treatments for changes from baseline to final in rectal temperature, blood pH and lactate, and plasma norepinephrine levels. The incidence of physical indicators of stress and of nonambulatory, noninjured pigs during the handling and transport procedures was similar for the 0 and 10 mg/kg RAC levels. Final farm BW was 4.1 kg heavier, carcass yield was 1.4 percentage units greater, and LM area was 5.18 cm greater for pigs fed RAC compared to the control ( ≤ 0.05). Minolta a* and b* values were lower ( ≤ 0.05) and ultimate pH (0.05 units) and Warner-Bratzler shear force (0.43 kg) were greater ( ≤ 0.05) for pigs fed 10 compared to 0 mg/kg RAC. These results confirm the substantial improvement from feeding 10 mg/kg RAC in growth performance and carcass yield and suggest relatively limited effects on pork quality and on responses to the handling and transport procedures used in this study.

Conceptus, progesterone, and breed effects on uterine protein secretion in swine.

This experiment consisted of the following treatment-breed groups: 1) White crossbred gilts, 2) White crossbred gilts treated with progesterone (200 mg/d in corn oil given on d 2 and 3 after estrus), and 3) Chinese Meishan gilts. Pregnant and nonpregnant gilts (n=3 to 6) from each treatment-breed combination were assigned to be slaughtered on d 10, 11, 12, 13, and 15. At slaughter each uterine horn was flushed with 20 mL of minimal essential medium. Uterine flushings were assayed for total protein, acid phosphatase, uteroferrin, retinol-binding protein, and oxytocin. Uterine flush total protein was increased by progesterone treatment, was unaffected by pregnancy status, and was less in Meishans. Similar patterns were found for retinol binding protein and uteroferrin, except that uteroferrin was greater in pregnant than in nonpregnant gilts. Oxytocin was greater in pregnant than in nonpregnant gilts, was not influenced by progesterone treatment, and was similar in Meishan and in White crossbred gilts. These results indicate that the conceptus does not influence secretion of either total protein or retinol binding protein during pregnancy and that the onset of secretion of these uterine proteins may be controlled by progesterone. The presence of the conceptus is associated with increased uteroferrin and oxytocin production. The decreased secretion of uterine proteins in Meishan gilts may partially explain the slower embryonic development that has been reported for this breed.

Short-term effects of exogenous estradiol-17 beta on blastocyst development during the period of elongation in swine.

Objectives were to examine the effects of a single dose (4 mg) of estradiol-17 beta (E2) on blastocyst development around the period of elongation. Proestrus gilts were induced to ovulate with 750 IU of hCG and were mated before ovulation (normal mating, 24 to 32 h post-hCG) or after ovulation had begun (delayed mating, 43 h post-hCG). This difference in time of mating has been demonstrated to result in approximately a 7-h difference in time of blastocyst elongation. Normally and delay-mated gilts were ovariohysterectomized at 278 h post-hCG or injected with E2 or vehicle (corn oil) at 278 h and then ovariohysterectomized at 290 h post-hCG (five or six gilts per group). Blastocyst size was measured and concentrations of E2, retinol, uteroferrin, insulin-like growth factor-I (IGF-I), uterine plasmin/trypsin inhibitor (UPTI) and protein in uterine flushings were quantified. Blastocyst size and components of uterine flushings did not differ (P > 0.05) between normally and delay-mated gilts at 278 h post-hCG. However, at 290 h post-hCG, normally mated gilts had larger (P < 0.01) blastocysts (small spheres to filamentous) and their flushings tended to contain less (P < 0.07) amounts of retinol than those of delay-mated gilts whose blastocysts ranged from small spheres to ovoidals. Normally mated gilts receiving E2 at 278 h had smaller (P < 0.01) blastocysts and less (P < 0.05) amounts of retinol at 290 h post-hCG than gilts receiving vehicle. Conversely, delay-mated gilts treated with E2 or vehicle did not differ (P > 0.05) in blastocyst size and amounts of components of uterine flushings at 290 h post-hCG. Normally mated gilts treated with vehicle had litters in the process of elongating at 290 h post-hCG. Mean blastocyst size (P < 0.001) and amounts of components of uterine flushings (except for IGF-I) in these gilts were greater (P < 0.05, UPTI = 0.06) than in normally mated gilts at 278 h post-hCG, whose blastocysts were spherical. Among gilts not treated with E2 (278 h and 290 h pooled), mean blastocyst size was positively correlated (P < 0.05) with amounts of retinol, E2, uteroferrin and total protein. Results indicated that a single dose of E2 given before elongation altered blastocyst development depending on how close blastocysts were to onset of elongation at the time of E2 treatment.

Expression of a plasmin/trypsin Kunitz inhibitor by pig trophoblast.

Under the influence of progesterone, the porcine uterus synthesizes plasmin/trypsin inhibitor (PTI), a low molecular weight protein (M(r) approximately 14,000) belonging to the Kunitz family of proteinase inhibitors. Here it is demonstrated that mRNA for the same protein is produced by the developing trophoblast during early pregnancy and by the placenta throughout gestation. The transcript for PTI was represented in approximately 0.1% of total phage plaques of a day 13-17 porcine conceptus cDNA library. It shared 99% nucleotide sequence identity with the cDNA isolated from the uterine library and encoded a 112-amino-acid protein identical to the uterine-produced PTI, which has a well-defined Kunitz domain comprised of 64 residues at its amino terminus. Northern analysis and in situ hybridization studies confirmed that expression of PTI by the conceptus begins as early as day 10 of pregnancy and is continued in placental tissues until at least day 90 of gestation. Expression was trophoblast specific at day 20 of gestation, as in situ hybridization detected no mRNA in the embryo. The pattern of PTI expression during pregnancy is consistent with a role either in controlling trophoblast invasiveness or in inhibiting proteinases with trypsin-like specificity released by immune or inflammatory cells.

Purification, characterization, and cDNA cloning of a Kunitz-type proteinase inhibitor secreted by the porcine uterus.

The porcine uterus synthesizes a proteinase inhibitor (M(r) 14,000) under the influence of progesterone that is relatively specific for plasmin and trypsin, but that also has weak affinity for chymotrypsin. Several isoforms of this uterine plasmin/trypsin inhibitor were purified by a procedure whose final two steps involved affinity chromatography on immobilized chymotrypsin and cation exchange chromatography. Amino-terminal sequencing showed that at least three of the isoforms were closely related. An oligonucleotide probe based on the protein sequence was used to identify a cDNA that contained an open reading frame coding for a mature protein (M(r) 10,295) of 93 amino acids. The inhibitor had a well defined, but unique, Kunitz domain of 64 residues at its amino terminus that shared 67% sequence identity to bovine pancreatic trypsin inhibitor. Its P1 residue was arginine rather than lysine. Northern analysis showed the presence of a single mRNA species (700 bases) that in adult female pigs appeared to be confined to the uterus. During pregnancy, UPTI mRNA expression was high until Day 30 and decreased significantly thereafter. By contrast, uteroferrin mRNA reached maximal concentrations in late pregnancy. These data are consistent with an earlier hypothesis that the inhibitor serves to neutralize the activities of one or more serine proteinases generated by the proliferating trophoblast during the formation of the noninvasive placenta of the pig.

Cholecystokinin octapeptide immunization: effect on growth of barrows and gilts.

A study was conducted to validate the previously reported growth response to cholecystokinin octapeptide (CCK-8) immunization in barrows and was extended to include gilts. Group-penned barrows and gilts were used to represent conditions in the swine industry. Thirty-two animals, 19 barrows and 13 gilts, were randomly assigned by sex to four pens and two treatments. The control groups were immunized with human serum globulin (hSG). The treated groups (CCK) were immunized with the C-terminal octapeptide of cholecystokinin conjugated to human serum globulin. Specific binding of CCK-8 was confirmed at 29 d after the primary inoculation. Antisera titers were highly variable throughout. The mean titer reached a peak on d 57 and then declined. Body weight gains during the last 49 d, the period during which titers were expressed, were compared by ANOVA. The treatment effect on gain was significant (P = .018); the sex effect approached significance (P = .071); the treatment x sex interaction effect was not significant (P = .82). Least squares mean gain of the CCK group was 8.4% greater than of the hSG group, 41.4 vs 38.2 kg, respectively. A significant linear regression coefficient for gain vs antisera titer was obtained for barrows (P = .03; r2 = .44) but not for gilts. Several carcass variables showed trends similar to that of BW gain, but the treatment effects were less robust (P < .05 to .10). These results generally confirm the findings of the previous study; CCK-8 immunization stimulated growth of barrows by 7.5% in the present and by 10.8% in the previous study.(ABSTRACT TRUNCATED AT 250 WORDS)

Porcine uterine retinol-binding proteins are identical gene products to the serum retinol-binding protein.

Retinol-binding proteins (RBP) are secreted by the porcine uterus under the influence of progesterone and consist of multiple charge forms. Evidence has been previously presented by this laboratory that these uterine RBP are distinct from serum RBP. We have followed the secretion of the uterine RBP during two stages of pseudopregnancy, examined their properties and amino acid sequences, and attempted to clone their cDNA. Analysis of the charge forms present in uterine flushes by anion-exchange chromatography showed that forms 1 (p < 0.01) and 3 (p < 0.05) predominated at Day 13, whereas forms 2 (p < 0.05) and 4 (p < 0.01) were most abundant at Day 45. All four charge forms appeared to form stable complexes with transthyretin (TTR) and were recognized by antiserum to human serum RBP on Western blots. Several cDNA clones isolated from an endometrial cDNA library all appeared to code for a protein identical to classical RBP. Off-blot amino acid sequencing of the first ten residues of two of the more divergent charge forms of uterine RBP indicated complete sequence identity with pig serum RBP. These data suggest that the uterine RBP charge forms may be slightly modified forms of a single protein product corresponding to the classical form of RBP. The change in appearance of the charge forms during pseudopregnancy is probably due to chemical modifications. These modifications do not appear to influence the binding of each charge form to TTR.

Embryo-uterine interactions in pigs during week 2 of pregnancy.

The second week of pregnancy is a particularly critical period for embryonic survival in pigs. Within that time, conceptus oestrogen synthesis is initiated, spacing and final placement of conceptuses is completed, and the signal for extending the functional lifespan of the corpora lutea is received by the mother. There is also a marked increase in blood flow to the uterus and the uterine endometrium produces and secretes nutrient histotrophe. Conceptus-derived oestrogen has been implicated in many of these events. It is also during this period that the trophoblast elongates dramatically and the inner cell mass starts to differentiate into the embryo proper. Here, we critically review the evidence that oestrogen is the sole factor initiating long-term corpus luteum maintenance in pigs. We also review the functions and general properties of the major secretory proteins in histotrophe and the role of oestrogen in controlling their expression. It is now generally accepted that asynchrony within a litter underlies much of the losses of conceptuses that are otherwise genetically normal, but which are lagging in their development; however, the underlying mechanisms remain unclear. Here we hypothesize that oestrogenic compounds derived from more advanced conceptuses or provided prematurely, either by injection or in the diet, trigger a massive increase in uterine expression and secretion of retinol-binding protein laden with retinol. We propose that less developed, smaller conceptuses are least able to contend with the sudden exposure to this potential teratogen at a time when they are particularly susceptible to imbalance in retinol supply. Hence, even though their growth proceeds for a few days, their developmental potential is irrevocably compromised.

Steroid regulation of the synthesis and secretion of retinol-binding protein by the uterus of the pig.

The endometrium of the pig secretes retinol-binding protein (RBP) under the influence of progesterone (P4). The objective of this study was to determine how conceptus-derived estrogen might modulate this production of RBP around days 11-13 of pregnancy when conceptuses elongate from spheres to long thread-like forms. Concentrations of retinol and RBP were low (35 +/- 7 ng/ml) in uterine flushings obtained on days 10-12 of the estrous cycle or from pregnant gilts in which conceptuses had not elongated. Concentrations of retinol and RBP increased 7- to 8-fold (P less than 0.01) in flushings where filamentous conceptuses were present. Size exclusion and ion exchange chromatography demonstrated that virtually all retinol assayed in uterine flushings was associated with RBP. Northern blot analysis with a cDNA representing uterine RBP revealed a single endometrial mRNA 1.1 kilobases in length. Expression of RBP mRNA in uterine endometrium was measured in ovariectomized prepubertal gilts after the administration of steroids according to the following regimens: I, corn oil (days 0-16; n = 10); II, estradiol benzoate (EB; days 13-14; n = 11); III, EB (days 1-2; n = 12); IV, EB (days 1-2) plus P4 (days 3-16; n = 12); and V, EB (days 1-2) plus P4 (days 3-16) plus EB (days 13-14; n = 12). EB (200 micrograms) and P4 (100 mg) were administered twice daily. Treatment IV was designed to stimulate the estrous cycle, and treatment V simulated early pregnancy. All gilts were hysterectomized on day 16, and total uterine mRNA (3 micrograms) was analyzed by Northern blotting. No RBP mRNA was detected in groups I, II, or III. In group IV, 5 of 12 gilts had detectable RBP mRNA, as measured by densitometric scanning (OD = 0.35 +/- 0.14). RNA isolated from all gilts in group V (12 of 12) gave a strong hybridization signal (OD = 1.58 +/- 0.22) for RBP. Finally, RBP mRNA was examined in the uterine endometrium of mature gilts on day 13 of the estrous cycle (n = 4), day 13 of pseudopregnancy (2.5 mg EB given on days 11-12; n = 4), or day 13 of pregnancy after conceptuses had elongated (n = 4). RBP mRNA was present in all groups, but was enhanced approximately 12-fold (P less than 0.01) in pregnant and pseudopregnant gilts compared to that in control gilts.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of weaning on concentrations of inhibin in follicular fluid and plasma of sows.

Changes in plasma and follicular fluid concentrations of inhibin were examined in sows after weaning at 28-32 days post partum. From 0 to 48 h after weaning, inhibin concentrations were 200-300 times higher in follicular fluid from small (less than 4 mm) and medium-large (greater than or equal to 4 mm) follicles than in ovarian venous plasma. Inhibin concentrations increased in follicular fluid from medium-large follicles at 24 and 48 h after weaning; concentrations in ovarian venous plasma were positively correlated with the number of medium-large follicles (r = 0.40) and with ovarian venous plasma concentrations of oestradiol (r = 0.61). Blood samples were collected for 30 days from sows (n = 6) that exhibited oestrus within 5 days after weaning and from sows (n = 5) that remained anoestrous for 11 days after weaning. Plasma inhibin concentrations rose in oestrous and anoestrous sows by 12 h and continued to rise for 60 h after weaning. Plasma inhibin concentrations rose further and were higher at 3.5-4.5 days after weaning in oestrous sows than in sows that remained anoestrous. After oestrus, plasma inhibin concentrations declined. At weaning, plasma concentrations of follicle-stimulating hormone (FSH) were higher in sows that subsequently exhibited oestrus than in sows that remained anoestrous. After weaning, plasma concentrations of FSH declined in both groups, reached a nadir at 2.5 days, and increased gradually in anoestrous sows; oestrous sows exhibited an FSH surge at oestrus. Plasma FSH returned to preweaning concentrations in both groups of sows at Days 7-8.(ABSTRACT TRUNCATED AT 250 WORDS)

The retinol-binding protein of the expanding pig blastocyst: molecular cloning and expression in trophectoderm and embryonic disc.

Retinol-binding protein (RBP) is a major secretory product of the porcine conceptus. Using an oligonucleotide probe corresponding to a highly conserved region of all known mammalian RBP, we have isolated an apparently full-length cDNA clone for porcine conceptus RBP from a cDNA library constructed from pig conceptuses collected between days 13-17 of pregnancy. The cDNA was 937 base-pairs in length and coded for a protein whose inferred amino-terminal sequence was identical to that reported for both porcine conceptus RBP and porcine serum RBP. Its length was consistent with the size (approximately 1 kilobase) of the RBP message in porcine conceptuses. Porcine conceptus RBP and human serum RBP share 91% amino acid sequence identity. The inferred differences in sequence were evenly distributed throughout the length of the polypeptide. RBP mRNA was detectable within the trophoblast of day 11 porcine conceptuses by in situ hybridization with a 618-basepair 35S-labeled probe corresponding to the 3' end of porcine RBP. Silver grain density was distributed relatively uniformly over the trophoblast and the inner cell mass. Western blot analysis of conceptus culture medium demonstrated that the conceptuses of cattle (on day 19) and sheep (on day 15) as well as pigs secrete RBP during early pregnancy. Secretion of large quantities of RBP by the trophoblast of preimplantation pig conceptuses suggests important roles for vitamin A and RBP near the time of conceptus elongation.

Growth hormone and insulin-like growth factor-I responses in steers actively immunized against somatostatin or growth hormone-releasing factor.

Steers were actively immunized at 81 days of age against human serum albumin (hSA; controls) or hSA conjugated to either somatostatin (SRIF) or growth hormone-releasing factor (GRF). Binding titres were observed for the respective peptide antigens after all steers had been given booster immunizations. Although no effects of treatment were observed in SRIF-immunized steers, mean serum concentrations of GH and insulin-like growth factor (IGF-I) were suppressed (P less than 0.01) in GRF-immunized steers when compared with hSA-immunized controls. Mean concentrations of prolactin did not differ with treatment but showed seasonal fluctuations (P less than 0.001) associated with changes in the daylength. In contrast to its marked effect upon serum concentrations of IGF-I, immunization against GRF resulted in a relatively small (6%) but significant decrease in body weight gain (P less than 0.01) and an increase in carcass backfat thickness (P less than 0.05). In summary, our findings have shown the susceptibility of steers to growth modulation by GRF immunoneutralization. Secondly, the poor relationship observed between serum concentrations of IGF-I and growth rates in GRF-immunized steers suggested that circulating IGF-I may not be the principle factor determining the post-weaning growth rate in cattle.

A novel family of progesterone-induced, retinol-binding proteins from uterine secretions of the pig.

Two-dimensional polyacrylamide gel electrophoresis has revealed the presence of a group of relatively acidic proteins of molecular weight about 22,000 in the uterine flushings of pseudopregnant pigs. The proteins have been purified by a combination of gel filtration chromatography and high performance anion-exchange chromatography and shown to bind both [3H] retinol and [3H]retinoic acid. At least four protein peaks that bound retinoids could be detected in the uterine secretions of a single pig. The ion-exchange procedure also allowed the retinol-free apoproteins to be separated from the holoforms that had associated ligand. Amino acid sequencing of the NH2 termini of polypeptides within three of the peaks revealed the presence of proteins with some degree of sequence identity to serum retinol-binding proteins (RBP). The most basic polypeptides showed the least similarity (about 30% identity), while the most acidic isoform analyzed shared about 70% sequence identity with the NH2 terminus of human serum RBP. Western blotting procedures employing an antiserum raised against the most basic isoforms showed that the amount of retinol-binding protein in uterine secretions increased markedly in ovariectomized animals in response to long term progesterone treatment. These proteins appear to form part of the uterine histotroph thought to be essential for nourishment of the conceptuses during pregnancy. A simple three-step procedure for purifying retinol-binding protein from pig serum is also described. The NH2-terminal sequence of this RBP is similar to that of human RBP but different from those of the uterine forms. The study suggests that a family of RBP, distinct from the serum form, is secreted by the uterine endometrium of the pig in response to progesterone.

Stimulation of food intake and growth of swine by cholecystokinin immunization.

Experimental superalimentation at 30% above ad libitum intake increased growth 40% and confirmed that voluntary food intake is a growth-limiting factor in swine. A sequence of contingent hypotheses was proposed for swine: cholecystokinin (CCK) is a regulator of food intake; food intake is enhanced by reduction of serum CCK; serum CCK is reduced by anti-CCK antibodies: anti-CCK antibodies are raised by active immunization. The objectives of this study were to determine if antibodies were raised in immunized swine and if the anti-CCK titers were sufficient to increase food intake and growth. Twelve young growing swine were immunized against cholecystokinin (CCK-8) to test the hypothesis that anticholecystokinin antibodies in serum would suppress cholecystokinin inhibition of appetite (food intake). An equal number of control animals (hSG) were immunized against the antigenic carrier protein by the same protocol. Specific binding of [125I]CCK-8, the C-terminal octapeptide, by sera diluted 1:181 increased to a peak value on day 43. Food intake and body weight gain were similar for the two groups during the first phase of the study. However, food intake was 8.2% greater and body weight gain was 10.6% greater for the CCK-8 than for the hSG group during the second phase (d 43 to d 77). Total food intake over the 77-day study was 5.4% greater for the CCK-8 group (P = .08): body weight gain was 8.3% greater (P = .006). Regression analyses confirmed that gain over the 34-day second phase increased .076 kg (P = .045; R2 = 0.34) for each percentage unit increase of serum binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Immune, growth and carcass responses of ram lambs to active immunization against desulfated cholecystokinin (CCK-8).

This study explored feed intake and carcass responses to active immunization against desulfated cholecystokinin-octapeptide (CCK-8) in ram lambs. Antibody titers 8 wk following primary immunization and booster immunizations given at 4 and 6 wk averaged greater than 1:1,000. Titers increased to greater than 1:10,000 by 16 wk following a final booster immunization at 11 wk. The antibodies developed against desulfated CCK-8 exhibited 29% and 13% cross-reactivities for sulfated CCK-8 and gastrin-17, respectively. Immunization against desulfated CCK-8 had no effect on feed intake, ADG, carcass weight or carcass quality grade. Backfat thickness and carcass yield grade were reduced (P less than .05) by immunization. Organ weights at slaughter, including those of the pancreas and small intestines, were not affected by CCK-8 immunization, with the exception of the lungs, which were 16% lighter (P less than .01) in immunized lambs. In conclusion, active immunization against desulfated CCK-8 resulted in development of high antibody titers against desulfated and sulfated CCK-8. Immunization against CCK-8 decreased fat content of the carcass but failed to affect feed intake, carcass weight or ADG.

Specific binding of naloxone to ovine brain tissue: comparison of brain regions and endocrine states.

Binding of [3H]naloxone ([3H]NAL) to brain membranes was quantified by Scatchard analysis using two methods of separating bound from free [3H]NAL. In the centrifugation method, membranes that were soluble at 1,000 x g, but sedimented at 20,000 x g, were incubated with [3H]NAL. For filtration, all membranes that sedimented at 20,000 x g were incubated and filtered through glass filter fibers. Nonspecific binding was estimated using greater than 500-fold excess of unlabeled naloxone (10(-6) M). Specific binding of [3H]NAL was used to generate linear multiple-point Scatchard plots, which indicated a single class of high-affinity sites. In Exp. 1, 10 ovariectomized (OVX) ewes were injected with estradiol-17 beta alone or in combination with progesterone. Compared with OVX controls, these hormonal treatments did not affect binding of [3H]NAL (centrifugation method) to combined hypothalamus (HYP) + preoptic (POA) tissues. In cyclic ewes (Exp. 2, filtration method), affinity constants (2.4 +/- .2 x 10(8) M-1) did not differ among HYP, POA and basal forebrain (BF) tissues, but BF had more sites (39 +/- 3 fmol/mg) than either HYP (14 +/- 1) or POA (17 +/- 1). Binding affinity and concentration of sites within each brain area (HYP, POA, BF) did not differ between d 8 and d 16 (preovulatory but after luteolysis) in normally cycling ewes. Overall, neural tissue dissected from BF had a greater concentration of binding sites than HYP or POA. Exogenous and endogenous fluctuations in ovarian steroids did not affect binding of [3H]NAL to these tissues.

Quantification of naloxone binding sites in brains from suckled beef cows during postpartum anestrus and resumption of estrous cycles.

Thirty beef cows, approximately 3 yr of age, were randomly assigned to be slaughtered on d 7, 14, 28, 42 or 56 postpartum. Each cow suckled one calf until slaughter. Data from cows slaughtered on d 42 and 56 were pooled and further classified as anestrous or cyclic based on the presence of a corpus luteum and elevated serum concentrations of progesterone at slaughter. Specific binding of [3H]naloxone (3H-NAL) to homogenates of tissue from hypothalamus (HYP), preoptic area (POA) and basal forebrain (BF) was assessed using multiple-point Scatchard analyses. Nonspecific binding was estimated in the presence of 10(-6) M naloxone. Separation of bound from free 3H-NAL was achieved by centrifugation at 20,000 X g. Concentration (fmol/mg original tissue wet wt) of 3H-NAL binding sites in POA tissue was higher (P less than .05) on d 28 postpartum in anestrous cows than in cyclic cows on d 42 + 56 postpartum (2.58 +/- .32 vs 1.58 +/- .10). When all anestrous cows were compared with cyclic cows, concentrations of 3H-NAL binding sites in POA tissues and in BF tissue were higher (P less than .05) in anestrous cows (anestrous POA, 2.12 +/- .17, cyclic POA, 1.58 +/- .10; anestrous BF, 2.94 +/- .41, cyclic BF, 2.19 +/- .16). Compared across brain regions for all cows, the concentration of specific binding sites for 3H-NAL was greater (P less than .01) in BF (2.5 +/- .2) than in POA (1.9 +/- .1) and greater (P less than .01) in POA than in HYP (1.5 +/- .1).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of exogenous estradiol-17 beta and progesterone on naloxone-reversible inhibition of the release of luteinizing hormone in ewes.

The role of endogenous opioids in controlling luteinizing hormone (LH) secretion was studied by injecting the opioid antagonist naloxone into intact and ovariectomized ewes that were treated with estradiol-17 beta (E2) and progesterone (P4). The existence of a naloxone-reversible inhibition of LH release was examined in five experiments using a total of 52 mature ewes. Naloxone at a dosage of 1 mg/kg disinhibited release of LH and abruptly increased serum concentrations of LH in a variety of experimental models. This naloxone-reversible inhibition of LH secretion was apparent in all experimental models that involved P4-induced inhibition of basal LH secretion but not in one model in which P4 inhibited the LH surge. Specific effects of E2 on naloxone-reversible inhibition of LH varied among experimental models. When prolonged administration of P4 alone appeared to lose its LH-inhibitory potency, E2 restored inhibition of LH as well as the naloxone-reversible state. Whenever E2 acted synergistically to suppress basal LH secretion in models involving brief (5 d) exposure to P4, E2 appeared to antagonize the naloxone-reversible state. In summary, P4-induced suppression of LH secretion appeared to be mediated by endogenous opioids, but the apparent interaction of E2 and opioids in LH suppression varied among experiments.