Decreased steady-state insulin-like growth factor binding protein-3 (IGFBP-3) mRNA level is associated with differentiation of cultured porcine myogenic cells

Insulin-like growth factor binding proteins (IGFBPs) affect the biological activity of IGF-I in several cell types, including cultured muscle cells. Additionally, at least one of the IGFBPs, IGFBP-3, has been shown to have IGF-independent effects on cell proliferation. Numerous studies have shown that immortalized muscle cell lines produce various IGFBPs, but to date no muscle cell line has been reported to produce IGFBP-3 protein or mRNA. Unlike muscle cell lines, primary cultures of porcine embryonic myogenic cells express IGFBP-3 mRNA and secrete a protein that is immunologically identifiable as IGFBP-3. Additionally, steady-state IGFBP-3 levels change significantly during differentiation. Here we report that differentiation of porcine myogenic cells in an IGFBP-3-free medium is accompanied by reduced steady-state IGFBP-3 mRNA levels. Steady-state levels of IGFBP-3 mRNA decreased approximately sevenfold (P < .05) during differentiation and then increased to predifferentiation levels once differentiation was complete. Addition of TGF-beta1 (0.5 ng/ml) to porcine myogenic cultures suppressed fusion and resulted in a sevenfold increase in steady-state IGFBP-3 mRNA and a 1.8-fold increase in IGFBP-3 protein levels as compared to untreated control cultures (P < .05). Results suggest that alterations in IGFBP-3 mRNA and protein may play a role in differentiation of porcine embryonic muscle cells.

Effect of protein intake during gestation on mammary development of primiparous sows

The effect of protein intake during gestation on mammary development was evaluated using 17 Landrace x Yorkshire gilts. On d 25 of gestation, gilts were allocated to dietary treatments consisting of levels of protein to achieve lysine intakes of approximately 4, 8, or 16 g/d. Diets provided similar amounts of ME (6.5 Mcal/d) and all other nutrients. On d 105 of gestation, gilts were bled through venipuncture to collect blood samples for analyses of blood metabolites (glucose, NEFA, blood urea nitrogen [BUN]), and metabolic hormones (insulin and IGF-I). Gilts were slaughtered between d 105 and 110 of gestation for complete collection of mammary glands. All mammary glands were carefully removed and separated from each other along the midline. One side was weighed, immediately frozen in liquid nitrogen, and stored at -70 degrees C until further processing. Frozen glands were sliced, and parenchymal tissue was separated and pooled across glands within sow, homogenized, and analyzed for DNA, RNA, and protein concentrations as indices of mammary development. Results showed no effect (P > . 10) of level of lysine intake on amount of mammary parenchymal tissue or on concentration or total amount of DNA, RNA, and protein. This experiment did not detect differences between treatments in mammary development as measured by nucleic acids and protein. Therefore, there was no effect of the amount of protein intake by gilts on mammary development. Regression analyses failed to detect any relationships between measures of mammary development and levels of metabolites or metabolic hormones.

Effect of protein intake during gestation and lactation on the lactational performance of primiparous sows

The effect of protein intake during gestation and lactation on the lactational performance of primiparous sows was evaluated using 35 Yorkshire x Landrace gilts, allocated to six dietary treatments in a 3 x 2 factorial arrangement. Treatments consisted of three protein levels during gestation, providing approximately 4, 8, and 16 g of lysine/d, and two protein levels (low [L] and high [HI), providing approximately 15 and 45 g of lysine/d, during lactation, respectively. Diets provided similar amounts of ME and all other nutrients. As dietary protein increased during gestation, sows gained more weight and tended to decrease their backfat thickness. There was no gestation x lactation treatment interaction for lactational performance of sows. Feed intake by sows during lactation was usually low but increased (P < .05) with increasing gestation and lactation protein intake and increased linearly (P < .001) as lactation progressed. This linear increase over time was greater (P < .05) in sows fed the H than in sows fed the L protein level. Increased protein intake during lactation reduced (P < .001) 21-d sow weight loss. Milk yield and pig weight gain increased as protein intake increased during gestation (P < .05) and lactation (P < .01). Milk yield did not increase as lactation progressed (P > .05). Pig weight gain increased (P < .05) from wk 1 to 2 of lactation and decreased thereafter. Simple linear regression analysis detected few important relationships between yield of milk components and metabolites or metabolic hormone concentrations. The R2 values for these relationships were < or = .30, except for some relationships between milk component yields and blood urea nitrogen (the range was between .17 and .55). Covariate adjustment for metabolite and metabolic hormone concentrations did not eliminate treatment effects in most cases. This suggests that effects of increased protein intake on milk yield are not fully mediated through metabolite and metabolic hormone concentrations.

Use of a water hardness test kit to measure serum calcium concentration in cattle

OBJECTIVE

To determine whether a commercially available water hardness test kit could be used to measure total serum calcium concentration and diagnose hypocalcemia in dairy cows.

DESIGN

Prospective study.

ANIMALS

30 dairy cows from 19 commercial herds.

PROCEDURE

Serum calcium concentration was determined using a water hardness test kit and a standard, laboratory-based method. Simple linear regression was used to determine whether there was a linear relationship between results of the 2 methods, and Spearman's rank correlation was used to calculate correlation between measurements. Sensitivity, specificity, and predictive values of using test kit-derived values for diagnosis of hypocalcemia (laboratory value < 8 mg/dl) were calculated.

RESULTS

There was a high correlation and significant linear relationship between results of the 2 methods. Sensitivity, specificity, predictive value of a positive test result, and predictive value of a negative test result were 100, 73, 86, and 100%, respectively. Accuracy was improved by using a test kit-derived calcium concentration of 7 mg/dl as the cut-off for determining hypocalcemia.

CLINICAL IMPLICATIONS

Results indicate that a commercially available water hardness test kit can be used as a rapid, inexpensive method of estimating serum calcium concentrations and diagnosing hypocalcemia in dairy cattle. However, the test is not practical for cow-side use, because blood samples must be centrifuged to obtain serum for use in the test kit.

Effect of insulin-like growth factor (IGF)-I and Des (1-3) IGF-I on the level of IGF binding protein-3 and IGF binding protein-3 mRNA in cultured porcine embryonic muscle cells

Insulin-like growth factor binding protein (IGFBP)-3 effects proliferation and differentiation of numerous cell types by binding to insulin-like growth factors (IGF) and attenuating their activity or by directly affecting cells in an IGF-independent manner. Consequently, IGFBPs produced by specific cells may affect their differentiation and proliferation. In this study we show that embryonic porcine myogenic cells, unlike murine muscle cell lines, produce significant quantities of a binding protein immunologically identified as IGFBP-3. Nonfusing cells subcultured from highly fused porcine myogenic cell cultures do not produce detectable IGFBP-3 protein or mRNA, thus suggesting the IGFBP-3 is produced by muscle cells in the porcine myogenic cell cultures. Treatment of porcine myogenic cultures with 20 ng of IGF-I or 20 ng of Des (1-3) IGF-I/ml serum-free media for 24 h results in a threefold reduction in the level of IGFBP-3 in conditioned media. This reduction is not affected by cell density over a sixfold range. Additionally, treatment for 24 h with 20 ng of IGF-I/ml media results in a sevenfold decrease in the steady-state level of IGFBP-3 mRNA. This IGF-I-induced decrease in IGFBP-3 mRNA level appears to be relatively unique to myogenic cells. IGF-I treatment also causes a fourfold increase in the steady-state level of myogenin mRNA. This increase in myogenin mRNA suggests that, as expected, IGF-I treatment accelerates differentiation of myogenic cells. The simultaneous decrease in IGFBP-3 mRNA and protein that accompanies IGF-I-induced myogenin expression suggests that differentiation of myogenic cells may be preceded or accompanied by decreased production of IGFBP-3.

Activation state of muscle satellite cells isolated from steers implanted with a combined trenbolone acetate and estradiol implant

Muscle satellite cells were isolated from seven yearling steers implanted for 31 d with a combined implant that contained 120 mg of trenbolone acetate (TBA) and 24 mg of estradiol (E2) and from seven nonimplanted, control steers. Implanted steers had a 28% greater ADG and a 23% greater feed efficiency than did nonimplanted steers. Implanted steers had increased (P<.001) circulating IGF-I concentrations on d 6, 14, and 31 after implantation, and circulating IGF-I concentrations in control steers remained constant or decreased (P<.05) at these times. Maximum fusion percentage was greater (P< .005) in satellite cell cultures isolated from implanted steers (ISC cultures) than in satellite cell cultures isolated from control steers (NSC cultures) (72.8% vs 54.8%, respectively). Satellite cell cultures isolated from implanted steers (ISC cultures) also contained a greater (P<.001) number of myotube nuclei than did NSC cultures (7,998 nuclei/cm2 vs 5,150 nuclei/cm2, respectively). After 72 h in culture, the number of cells (corrected for plating density) was 43% greater (P<.05) in ISC cultures than in NSC cultures. [3H]Thymidine incorporation rates per 10(5) cells at 24 and 34 h after plating were greater (P<.05) in ISC cultures than in NSC cultures; however, incorporation rates did not differ at 72 h. These data indicate that TBA + E2 implantation may result in an in vivo activation of muscle satellite cell proliferation that can be detected in cell culture. This activation may play an important role in TBA + E2-enhanced muscle growth.

Nutritional alterations and the effect of fish oil supplementation in dogs with heart failure

Alterations in body composition and nutritional status are common in humans with heart failure and are related, in part, to increases in cytokine concentrations. Cytokines have not been studied previously in dogs with naturally occurring cardiac disease nor has fish oil administration been used in this population to decrease cytokine production. The purposes of this study were to characterize nutritional and cytokine alterations in dogs with heart failure and to test the ability of fish oil to reduce cytokines and improve clinical outcome. Body composition, insulinlike growth factor-1, fatty acids, and cytokines were measured in 28 dogs with heart failure and in 5 healthy controls. Dogs with heart failure then were randomized to receive either fish oil or placebo for 8 weeks. All parameters were measured again at the end of the study period. At baseline, 54% of dogs with heart failure were cachectic and the severity of cachexia correlated with circulating tumor necrosis factor-alpha concentrations (P = .05). Cytokine concentrations at baseline, however, were not significantly increased in dogs with heart failure compared to controls. Baseline plasma arachidonic acid (P = .02), eicosapentaenoic acid (P = .03), and docosahexaenoic acid (P = .004) concentrations were lower in dogs with heart failure than in controls. Fish oil supplementation decreased interleukin-1 beta (IL-1) concentrations (P = .02) and improved cachexia (P = .01) compared to the placebo group. The mean caloric intake of the heart failure dogs as a group was below the maintenance energy requirement (P < .001), but no difference was found in food intake between the fish oil and placebo groups. Insulinlike growth factor-1 concentrations (P = .01) and reductions in circulating IL-1 concentrations over the study period (P = .02) correlated with survival. These data demonstrate that canine heart failure is associated with cachexia, alterations in fatty acids, and reduced caloric intake. Fish oil supplementation decreased IL-1 concentrations and improved cachexia. In addition, reductions in IL-1 predicted survival, suggesting that anticytokine strategies may benefit patients with heart failure.

Epidemiologic features of equine Leptospira interrogans of human significance

Leptospirosis is a zoonotic bacterial disease caused by Leptospira interrogans. There is a serologic evidence that horses are exposed to L. interrogans and, as a shedder of these organisms, can be a threat to humans. We examined risk factors associated with the risk of testing seropositive to three L. interrogans serovars (L. icterohaemorrhagiae, L. grippotyphosa, and L. canicola) in the horses of New York State, in order to understand the epidemiology of the disease and suggest strategies to control and prevent equine leptospirosis. To carry out this study, blood samples were collected from a random sample of 2551 horses and tested for the presence of antibodies to the above serovars using the microscopic agglutination test. Samples with a titer $100 were considered positive. Clinical and demographic data were collected on each horse, the farms' management practices and ecology. Logistic regression analysis was used to develop a multivariate indexing system and to identify factors significantly associated with the risk of leptospirosis. Four indices were developed based on the possible sources of exposure: rodent exposure index; wildlife exposure index; soil and water index; and management index. The soil and water index was significantly associated with the risk of exposure to all three serovars. Management was positively associated with L. icterohaemorrhagiae and L. canicola. Density of horses turned out together was positively associated with the risk of exposure to L. grippotyphosa. We concluded that indirect exposure of horses to L. interrogans through contaminated soil and water appears to be significantly associated with the risk of exposure to all three serovars. Management appears to play an important role in the exposure to L. interrogans. Modification of management practices might reduce the horses' risk of exposure and hopefully minimize the human hazards.

Identification and characteristics of a 37,000 M(r) insulin-like growth factor binding protein in canine serum

Insulin-like growth factors (IGFs) are potent stimulators of cellular growth and their half-life and biological activity are regulated by specific IGF binding proteins (IGFBPs). Western ligand blots of non-reduced human, bovine, ovine and porcine sera reveal an IGFBP-2 band at approximately 34,000 M(r). However, canine sera appear to contain a unique 37,000 M(r) IGFBP and lack the 34,000 M(r) IGFBP-2 band. In order to identify and characterize the 37,000 M(r) IGFBP, adult canine serum was subjected to non-reducing SDS polyacrylamide gel electrophoresis (PAGE), transferred to nitrocellulose paper, followed by [125I]-IGF-1 ligand blotting or immunoblotting with commercially available IGFBP antibodies. The 37,000 M(r) canine IGFBP reacted with an anti-IGFBP-2 antibody indicating that it is a canine analogue of IGFBP-2. However, the large difference in apparent molecular size indicates that this is a unique molecular form of IGFBP-2. N- or O-glycanase treatment of canine sera did not alter the molecular size of canine IGFBP-2 indicating that it is not a glycosylated variant of the IGFBP. Subjecting canine sera to reducing SDS-PAGE followed by anti-IGFBP-2 western immunoblotting revealed that the actual molecular weight of the canine IGFBP-2 is similar to that of reduced IGFBP-2 from other species indicating similar peptide lengths. Thus, the increased non-reduced size of the canine 37,000 M(r) IGFBP-2 is possibly due to a unique secondary structure.

Effect of a combined trenbolone acetate and estradiol implant on steady-state IGF-I mRNA concentrations in the liver of wethers and the longissimus muscle of steers

Treatment of lambs (initial BW 28 kg) for 24 d with a combined implant containing 40 mg of trenbolone acetate (TBA) and 8 mg of estradiol (E2) increased ADG 25% (P < .05, n = 8) and feed efficiency 23% (P < .05, n = 2) compared with unimplanted lambs. By d 3 following implantation, sera from wethers implanted with TBA + E2 showed 32% (307 vs 233 ng/mL) increases (P < .001, n = 8) in IGF-I concentration compared with sera from unimplanted wethers. This increase was maintained throughout the entire 24-d study. Steady-state hepatic IGF-I mRNA levels were increased approximately 150% in implanted lambs compared with unimplanted lambs (P < .05, n = 4). These data suggest that liver may be the source of at least part of the increased circulating IGF-I in TBA + E2-implanted sheep. In steers implanted with Revalor-S (120 mg of TBA and 24 mg of E2) for 40 d, the steady-state concentration of IGF-I mRNA in the longissimus muscle was 68% greater than in the longissimus muscle of unimplanted steers (P = .013, n = 4). Consequently, increased local production of IGF-I by muscle tissue may play a role in increasing circulating IGF-I concentrations as well as an autocrine or paracrine role in stimulating muscle growth in steers implanted with Revalor-S.

Risk factors associated with the likelihood of leptospiral seropositivity in horses in the state of New York

OBJECTIVE

To determine and quantify risk factors associated with exposure of horses to the following serovars of Leptospira interrogans: pomona, autumnalis, and bratislava.

ANIMALS

2,551 horses were randomly selected from a target population during the period of May 1991 to August 1993.

PROCEDURES

Blood was collected from the horses and tested for antibodies to serovars, using the microscopic agglutination test. A titer > or = 1:100 indicated seropositivity. Information was collected on each horse, its environment, and each farm's management practices. Logistic regression analysis was used to develop a multidimensional indexing system for indices of exposure and to identify factors significantly-associated with the risk of seropositivity. These indices were: 1) rodent exposure; 2) wildlife exposure; 3) soil and water; and 4) management.

RESULTS

Rodent exposure index value was associated with the risk of exposure to all 3 serovars. Management index value was positively associated with the risk of exposure to serovars pomona and bratislava, but not with risk of exposure to serovar autumnalis. Soil and water index value had a positive association with risk of exposure to serovars pomona and autumnalis, but not to serovar bratislava. The wild-life index value and the population density of horses turned out together were associated with the risk of exposure to serovar autumnalis. Age of horse in years was associated nonlinearly (years) and linearly (years) with the risk of exposure to serovars autumnalis and bratislava, and only linearly with the risk of exposure to serovar pomona.

CONCLUSION

Risk of seropositivity to the 3 serovars of L interrogans varies according to age, management practices, population density of horses turned out together, and the values of the rodent exposure, wildlife exposure, and soil and water indices.

The relationship of calfhood morbidity with survival after calving in 25 New York Holstein herds

The association of owner-diagnosed calfhood diseases with the length of herd life after calving was evaluated using data collected prospectively over a ten-year period in 25 New York Holstein dairy herds. Herds selected for the study were milking between 35 and 200 Holstein cows, used dairy herd improvement records, bred cows by artificial insemination unless they needed three or more services, and had regularly-scheduled herd health visits by clinicians from the Cornell University College of Veterinary Medicine. Owners recorded occurrences of dullness, respiratory disease, and scours from birth through 90 days of age for all heifer calves that lived at least 24 h and were to be kept as replacements. Milking herd life was measured as the difference between the age at first calving and the age at death or sale. Data on cows sold when the herd went out of business or still in the herd at the end of the study were censored observations. Cox's proportional hazards model was used for statistical analysis of the data. Controlling for age at first calving, study month of birth, and sire predicted difference for milk, there was no statistically significant association of calfhood morbidity with length of herd life. The estimated hazard rate ratios for leaving the milking herd and 95% confidence intervals for dullness, respiratory disease, and scours within 90 days of birth were 1.3 (0.9, 1.9), 0.9 (0.6, 1.3), and 1.0 (0.8, 1.3), respectively. Dullness was the only disease category with an estimated hazard rate ratio greater than 1, and although it was not statistically significant, may warrant evaluation in future studies of long term effects of calfhood morbidity.

Expression of insulin-like growth factor II (IGF-II), IGF binding protein-2 and myogenin during differentiation of myogenic satellite cells derived from the turkey

Myogenic satellite cells are essential for the development of postnatal skeletal muscle. The proliferation and differentiation of these cells are, in part, regulated by the insulin-like growth factors (IGFs), and it has been shown that the IGF binding proteins (IGFBPs) are capable of modulating the actions of IGFs. We have examined the endogenous expression of IGF-II, IGFBP-2 and the myogenic regulatory factor, myogenin, during differentiation of clonally derived turkey muscle satellite cells. Cells were harvested at approximately 80% of confluent density. Additional cultures were rinsed, fed differentiation medium and harvested when approximately 20%, 60% and 80% differentiated (fused). Northern blot analyses were performed using total cellular RNA and labeled rat cDNAs specific for IGF-II, IGFBP-2 and myogenin. A single IGF-II mRNA transcript of approximately 4.0 kb was observed. The relative mRNA abundance was highest in proliferating cultures and decreased with the onset of differentiation, to approximately 60% of initial levels where it remained throughout differentiation. Use of the IGFBP-2 cDNA probe indicated a single mRNA transcript of approximately 2.0 kb. The level of expression of IGFBP-2 mRNA was highest in proliferating cells and decreased to 25%, 16% and 11% of initial levels as differentiation progressed. A single 1.8 kb mRNA transcript was detected with the myogenin probe. Expression of myogenin was undetectable in proliferating cultures and increased significantly as differentiation progressed. Serum-free medium was conditioned for 24 h (CM) at each time point and collected from similar cultures. An IGFBP species of M(r) approximately 30,000 was detected in CM by probing western blots with [125I] IGF-I (ligand blot analysis). The intensity of this band decreased with differentiation to 35%, 24% and 18% of the level for proliferating cultures. Western blots were also probed with an antibody raised against the M(r)-34,000 bovine IGFBP-2. This antibody specifically bound to the M(r)-30,000 IGFBP, and the level of antibody binding decreased as differentiation progressed. It therefore appears that IGF-II, IGFBP-2 and myogenin are expressed in a differentiation-dependent manner by turkey myogenic satellite cells and may thus be involved in the process of differentiation of avian muscle cells.

Effect of concentrate source and amount in diets on plasma hormone concentrations of prepubertal heifers

Effects of concentrate source (corn or soybean hulls) and amount (40 or 80% of DMI) on plasma hormone concentrations were evaluated for 32 prepubertal Holstein heifers in a 2 x 2 factorial design. Blood samples were collected every other day from d -4 through d 28 of the experiment and were analyzed for growth hormone, prolactin, IGF-1, and glucose. Ruminal samples were collected by esophageal tube on d 0, 7, 14, 21, and 28 and were analyzed for VFA content. Serial blood samples were collected on either d 25 or 26 at 20-min intervals for 8 h and were used for profile analysis of growth hormone and prolactin. Heifers fed 80% concentrate had higher IGF-1 concentrations in serum (158.1 vs. 131.9 ng/ml) than did heifers fed 40% concentrate, and heifers fed corn tended to have higher IGF-1 concentrations than heifers fed soybean hulls. Prolactin concentrations in samples that were collected every other day were higher for heifers fed the 80% soybean hull diet than for those fed 40% concentrate diets or the 80% corn diet. Effects of source and amount of concentrate on plasma prolactin concentrations were not evident in serial samples. Concentrate source or amount had no effect on plasma growth hormone or glucose. At high concentrate intakes, the source (soybean hulls vs. corn) affected intake parameters, ruminal VFA content, and prolactin concentrations.

Serum insulin-like growth factor I (IGF-I) concentrations are increased in pigs fed antimicrobials

The effect of antimicrobial supplementation on the sera concentrations of IGF-I was determined in crossbred weanling pigs. Pigs were allotted by weight, litter, and sex to either a control diet or a diet supplemented with ASP-250 (22.7 ppm of chlortetracycline, 22.7 ppm of sulfamethazine, and 11.4 ppm of penicillin) for 5 wk. The diets contained 21.8% crude protein and 1.15% lysine. Growth performance data were collected weekly. Insulin-like growth factor I and insulin-like growth factor binding protein (IGFBP) analyses were performed on blood samples that were drawn during the final week of the trial. Feeding ASP-250 to young pigs increased their sera IGF-I concentrations by 24.8% (P < .001). A 59% increase in sera IGFBP-3 levels also was observed. The pigs fed ASP-250 had a 26% increase in average daily gain (P < .01), a 6.7% improvement in gain:feed ratio (P < .05), and a 18.5% increase in feed consumption (P < .01) compared with pigs fed the control diet. Increased serum IGF-I concentrations with antimicrobial feeding may be involved in the enhanced growth performance observed.

Hormonal regulation of IGF-binding protein-2 expression in proliferating C2C12 myoblasts

No studies have investigated the hormonal regulation of IGF-binding protein-2 (IGFBP-2) secretion and mRNA expression in myoblasts. In this study, cells of the C2C12 mouse myoblast cell line were used to examine the effects of various agents on the hormonal regulation of IGFBP-2. Conditioned medium (CM) was collected and cells were harvested at 2, 4, 6, 15 and 24 h after exposure to treatment media containing porcine insulin (pINS) or recombinant human IGF-I (rhIGF-I), and at 6, 15 and 24 h after exposure to treatment media containing dexamethasone (DEX) or prostaglandin E2 (PGE2). Relative abundance of a single 1.8 kb IGFBP-2 mRNA transcript was determined by Northern analysis using total cellular RNA and a labeled cDNA specific for rat IGFBP-2. IGFBP-2 was detected in CM by probing Western blots with 125I-IGF-I (ligand blot analysis). We have previously shown by immunoblot analysis that the predominant 32,000 M(r) protein on ligand blots is IGFBP-2. Treatment with 10(-9) or 10(-6) M pINS led to a rapid reduction (P < 0.01) in relative IGFBP-2 mRNA abundance and protein secretion relative to controls. Treatment with 7 x 10(-10) or 7 x 10(-9) M (5 or 50 ng/ml) rhIGF-I increased IGFBP-2 mRNA abundance and protein secretion (P < 0.01). Cultures treated with 10(-8) M DEX exhibited significantly increased (P < 0.001) IGFBP-2 mRNA and protein. IGFBP-2 secretion was not affected by 10(-6) M PGE2 but mRNA levels were higher than controls at 24 h (P < 0.01). These findings suggest that multiple factors, including growth factors and metabolic hormones, are involved in regulating IGFBP-2 expression in C2C12 myoblasts.

Porcine reproductive and respiratory syndrome (PRRS): a review, with emphasis on pathological, virological and diagnostic aspects

Despite early attempts to control the spread of the disease, porcine reproductive and respiratory syndrome (PRRS) has now become endemic in many countries including Britain. The occurrence of subclinical herd infections, the prolonged circulation of virus within herds and probable aerogenic virus spread all mitigated against the success of control measures. The origin of the disease is unknown but the causative agent has been shown to be an arterivirus with shared features to lactate dehydrogenase virus of mice. There is evidence of extreme genetic and antigenic variability between American and European isolates. PRRS virus has a predilection for alveolar macrophages and does not grow in most cell lines. In infected pigs, viraemia can persist for many weeks in the face of circulating antibodies and little is known about the mechanisms by which immunity to infection develops. A wide spectrum of disease has been reported from the field, accompanied in some cases by heavy economic losses. Reproductive and perinatal losses were most prominent when the disease first appeared. In the endemic phase, PRRS may be more significant as a contributory factor to a post-weaning respiratory syndrome of young pigs of 3-8 weeks. On-farm techniques have been developed to reduce the recycling of PRRS virus from older infected nursery pigs to the younger newly weaned pig. Vaccines are now marketed for the control of PRRS, but are not licensed for use in Britain. Improvements in knowledge of virion composition and antigenic stability and in the nature of the immune response of the pig should result in genetically engineered subunit vaccines becoming available. Diagnosis of PRRS is still difficult as many animals do not show clinical signs and may only be detected by serology and often only when other respiratory diseases are being investigated. Now that the infection is widespread, serological testing must be properly targeted and interpreted to give meaningful results about virus circulation. An increasing arsenal of diagnostic methods are becoming available to detect virus in both fresh and fixed specimens. The pathogenic mechanisms of PRRS remain poorly defined and more work is needed to reveal the nature of the interaction between PRRS virus and other factors in disease.

Molecular cloning and sequence analysis of the porcine insulin-like growth factor binding protein-5 complementary deoxyribonucleic acid

We report here for the first time the isolation of a cDNA clone containing the open reading frame sequence for porcine insulin-like growth factor binding protein-5 (pIGFBP-5) and the complete deduced amino acid sequence for this porcine IGFBP. The cDNA sequence shares 94%, 90% and 91% identity to its human, mouse and rat counterparts, respectively. The deduced amino acid sequence consists of 252 amino acids and a putative 19 amino acid signal and shares 97%, 96%, and 96% identity to the human, mouse and rat peptides, respectively. The mature peptide contains the 18 conserved cysteines found in all of the IGFBPs. Northern blot analysis of total RNA isolated from porcine heart, muscle and spleen using a 315 base pair cDNA insert derived from the pIGFBP-5 open reading frame sequence revealed a single mRNA transcript of 6.0 kilobases.

Lack of association between calf morbidity and subsequent first lactation milk production in 25 New York Holstein herds

The association of owner-diagnosed calfhood diseases with first lactation milk production was evaluated using data collected prospectively for 728 heifers from 25 New York dairy herds. Cows diagnosed with one or more occurrences of dullness, respiratory disease, or scours within 90 d of birth had first lactation milk production that was similar to that of unaffected herdmates. Estimates for the effects of dullness, respiratory disease, and scours on second test milk production were -1.0, 1.0, and .4 kg/d, respectively (adjusted for season and age at calving, times milked per day, study month on birth, sire PTA for milk production, and the other two calfhood diseases). Estimates for the effects on 305-day mature equivalent production were -139, 123, and 158 kg for dullness, respiratory disease, and scours, respectively (adjusted for study month of birth, sire PTA for milk production, and the other two calfhood diseases). These results were based on data of heifers that were selected as replacements and remained in the herd long enough to have milk production recorded. There was no significant detrimental effect of owner-diagnosed calfhood disease on first lactation milk production, but affected heifers had higher mortality before calving and were less likely to enter the milking herd.

The relationship of the interval from breeding to uterine palpation for pregnancy diagnosis with calving outcomes in holstein cows

This study used data collected prospectively at 32 dairy herds to examine the effect of interval from breeding to uterine palpation for pregnancy diagnosis on calving interval and likelihood of calving. Multivariable statistical models were used to control for other factors that were significantly associated with the outcomes of interest. Cows diagnosed pregnant from 30 to 36 d post breeding had 2-wk longer calving intervals than cows palpated at later intervals. The interval from breeding until a cow was diagnosed open had a significant positive association with the calving interval. The interval to palpation was not associated with the probability of remaining in the herd to calve when controlling for the effects of herd, season of freshening, number of services, days to first service and mature equivalent milk production. Among cows diagnosed pregnant, 3.4% subsequently were bred and 1.5% were diagnosed open by palpation at a later date. About 5% of the cows diagnosed open calved at a time consistent with being pregnant when the diagnosis was made.

Lectin binding distinguishes between neuroendocrine and neuronal derivatives of the sympathoadrenal neural crest

Lectin cytochemistry was used to identify surface epitopes selectively expressed by chromaffin cell chemoreceptors (glomus cells) in the rat carotid body. Unexpectedly, these studies revealed that binding sites for peanut agglutinin (PNA; Arachis hypogea) were highly expressed by all neuroendocrine-derivatives of the sympathoadrenal neural crest, including glomus cells, small, intensely fluorescent cells, and adrenal chromaffin cells in situ. In contrast, principal sympathetic neurons did not express PNA receptors. PNA binding was inhibited by 2% galactose. To determine whether expression of PNA receptors was selectively induced by neuroendocrine differentiation of sympathoadrenal precursors, we compared PNA labeling of embryonic sympathoblasts in the presence of either nerve growth factor (NGF) or the synthetic glucocorticoid dexamethasone (DEX). DEX-treated cells, which expressed several neuroendocrine traits, bound PNA, whereas NGF-treated neuronal derivatives did not. In addition, to examine whether expression of existing PNA receptors was down-regulated by neuronal differentiation of chromaffin cells, we compared labeling of PC12 cells, which normally bind PNA, in the presence and absence of NGF. Although PC12 cells acquired characteristic neuronal morphologies in the presence of NGF, they did not lose PNA labeling, even after 8 days of NGF treatment. These findings indicate that neuronal and neuroendocrine derivatives of the sympathoadrenal lineage can be distinguished by differential expression of carbohydrate epitopes and suggest that PNA receptors are induced by neuroendocrine differentiation.

The onset of maternal diabetes in swine induces alterations in the development of the fetal preadipocyte

Diabetes induced during gestation has previously been demonstrated to increase adipose accretion in the fetal pig. The present experiment examined whether maternal diabetes alters the proliferation and differentiation of the fetal preadipocyte. Seven crossbred gilts were injected with alloxan (50 mg/kg) at d 75 of gestation to induce diabetes and seven additional gilts were injected with buffer (controls). All gilts underwent Caesarean section of d 105 of gestation. Cells obtained from adipose tissue of fetuses of diabetic swine (FDS) at d 105 of gestation demonstrated a greater (P < .05) proliferative response (57%) and higher (P < .05) rates of differentiation as determined by sn-glycerol-3-phosphate dehydrogenase (142% increase) and lipoprotein lipase (80% increase) activities than cells acquired from fetuses of control swine (FCS). Adipogenic activity of the sera from these two groups of fetuses did not differ when tested on adipose tissue from fetuses at 105 d of gestation. However, use of these sera on cells derived from normal fetuses at 75 d of gestation resulted in detection of an increase (P < .05) in adipogenic activity within the sera from FDS. This study suggests that maternal diabetes causes alterations in the preadipocyte fraction of cells within the developing adipose tissue that result in formation of more adipocytes and thus permits greater capacity for lipid accumulation in the growing fetus of the diabetic pig. These alterations in the preadipocyte result from the activity of factors that transitionally function during the latter half of gestation.