Biomedical subjects

M E White

Publications and source records attributed to M E White.

At least 19 recordsLinked to original sources

PubMed2007

Growth factor messenger ribonucleic acid expression during differentiation of porcine embryonic myogenic cells.

The growth factors, IGF-I and II, their binding proteins, IGFBP, and members of the transforming growth factor (TGF) superfamily (myostatin and TGFbeta1) are known to regulate proliferation and differentiation of myogenic cells. We hypothesized that changes in the relative expression of members of the IGF and TGFbeta systems play a significant role in regulating myogenesis in porcine embryonic myogenic cell (PEMC) cultures. Therefore, determining the expression patterns of these factors during PEMC myogenesis is important. Consequently, we used real-time PCR to explore the pattern of IGF-I; IGF-II; IGFBP-2, -3, and -5; IGF-type-I receptor; myogenin; myostatin; and TGFbeta1 mRNA expression during PEMC myogenesis. The progression of differentiation was assessed using creatine kinase activity and myogenin mRNA expression. As anticipated, creatine kinase activity was low in PEMC cultures at 48 h and increased 20-fold (P < 0.0001) between 48 h and its peak at 144 h. Similarly, myogenin mRNA was low at 48 h and increased approximately 5-fold (P < 0.0001) as differentiation progressed, peaking at 120 h and decreasing at 144 h. The patterns of IGF-I and IGFBP-2 mRNA expression were similar and were relatively lower in 48-h PEMC cultures, increasing approximately 5-fold (P < 0.0001) to their greatest levels at 120 h. In contrast, IGF-II and IGFBP-5 mRNA levels were relatively high at 48 h, peaking at 72 h, and steadily decreasing by 60 and 80%, respectively (P < 0.001), at 144 h. The level of IGF-type-I receptor mRNA was relatively high until 96 h of culture, after which it decreased 40% (P < 0.01), reaching a low at 144 h. Levels of IGFBP-3 mRNA were relatively high at 48 h, dropped approximately 40% to their lowest level at 72 h (P < 0.001), and then increased approximately 60% (P < 0.001) to their greatest levels at 144 h. Levels of TGFbeta1 mRNA decreased approximately 30% (P < 0.0001) between 48 and 96 h, then quickly rebounded to a peak at 120 h, and by 144 h had dropped to the levels seen at 72 h. Myostatin mRNA was at its greatest level at 48 h and declined rapidly between 72 and 96 h, finally decreasing by approximately 80% at 144 h (P < 0.0001). Our data demonstrate that these factors are differentially regulated during PEMC myogenesis and provide new information about their pattern of mRNA expression in cultured porcine muscle cells.

Animals↗

PubMed2006

Localization of insulin-like growth factor (IGFBP)-3 in cultured porcine embryonic myogenic cells before and after TGF-beta1 treatment.

Insulin-like growth factor binding protein (IGFBP)-3 binds IGFs with high affinity and affects their biological activity. IGFBP-3 that is not bound to IGF also affects cells via mechanisms involving binding to specific cell surface receptors and/or transport into the cell. IGFBP-3 is produced by porcine embryonic myogenic cell (PEMC) cultures. Additionally, IGFBP-3 facilitates the proliferation-suppressing actions of TGF-beta(1) and myostatin in PEMC cultures via mechanisms that do not involve IGF binding. Moreover, these mechanisms do not involve preventing myostatin or TGF-beta(1)-induced increases in phosphosmad2 or phosphosmad3 level. Consequently, the mechanism(s) by which IGFBP-3 facilitates the proliferation-suppressing actions of TGF-beta(1) and myostatin in PEMC is unclear. Since IGFBP-3 reportedly interacts with nuclear proteins that regulate transcription, TGF-beta(1) or myostatin-induced translocation of IGFBP-3 into the nucleus may facilitate the proliferation-suppressing actions of these cytokines. Here, we show that IGFBP-3 is localized in cells containing the muscle specific protein desmin, thus establishing the presence of this IGFBP in myogenic cells. IGFBP-3 is present in the cytoplasm of all myogenic cells and approximately 50% of the nuclei of proliferating PEMC. IGFBP-3 is also detectable in fused myotubes. IGFBP-3 suppresses IGF-I-stimulated differentiation of PEMC but has no affect on Long-R3-IGF-I-stimulated differentiation of PEMC. Treatment of PEMC for 24h with TGF-beta(1) (20 ng/ml) results in a 78% (p<0.01) increase in the number of nuclei that contain detectable IGFBP-3. These results suggest that translocation of IGFBP-3 into the nucleus of PEMC could play a role in mediating the proliferation-suppressing action of TGF-beta(1).

Animals↗

PubMed2006

Risk factors associated with Cryptosporidium infection on dairy farms in a New York State watershed.

A cross-sectional study was carried out to determine the prevalence of Cryptosporidium parvum-like oocyst shedding on dairy farms in a watershed in New York State and to identify the factors that put animals at risk. A proportional sample of dairy herds in the targeted area was obtained, and animals were selected using a stratified sampling design to ensure representation of the population at risk. Fecal samples were collected per rectum and analyzed for the presence of C. parvum-like oocysts using the quantitative centrifugation concentration flotation technique and a proprietary enzyme-linked immunoassay. Additionally, isolates of Cryptosporidium were examined via bidirectional DNA sequencing. Data on putative risk factors were collected at the time of sampling and analyzed for association using logistic regression. The herd prevalence was 42% and the overall animal prevalence was 3.2%. The prevalence among animals less than 60 d of age was 20%. The likelihood of shedding Cryptosporidium decreased with the age of the animal and varied with the type of barn water source. Both the number of unweaned calves present at the time of the study, and whether the calves were tied vs. not tied increased the risk of infection. There was significant agreement between the flotation and PCR techniques. Sequencing revealed that 50% of the isolates were Cryptosporidium bovis, an isolate thought to be nonzoonotic.

Age Factors↗

PubMed2005

Slaughterhouse survey of pyelonephritis in dairy cows.

Twenty-one rejected kidneys from 2426 slaughtered dairy cows (0.87 per cent) had gross signs of pyelonephritis that were confirmed by histopathology. In all the kidneys the findings were consistent with a chronic rather than an acute infection. One species of bacteria was cultured from 12 of the kidneys and two species of bacteria were cultured from six. The most commonly isolated bacteria were Escherichia coli, from eight kidneys, Arcanobacterium pyogenes, from seven kidneys and Corynebacterium renale, from five kidneys. The other bacteria cultured were Corynebacterium cystitidis, Corynebacterium species, Streptococcus species group G and Enterococcus faecalis. E. coli was cultured from all the kidneys from which two species were isolated; the accompanying bacteria were A. pyogenes in three kidneys, C. renale in two and C. cystitidis in one. No bacteria were cultured from two of the kidneys and no significant bacteria were cultured from another. The kidneys with pyelonephritis were slightly larger than a comparison group of 72 kidneys without nephritis.

Abattoirs↗

PubMed2005

Insulin-like growth factor binding protein (IGFBP)-3 and IGFBP-5 mediate TGF-beta- and myostatin-induced suppression of proliferation in porcine embryonic myogenic cell cultures.

We have previously shown that cultured porcine embryonic myogenic cells (PEMC) produce both insulin-like growth factor binding protein (IGFBP)-3 and IGFBP-5 and secrete these proteins into their media. Exogenously added recombinant porcine (rp) IGFBP-3 and rpIGFBP-5 act via IGF-dependent and IGF-independent mechanisms to suppress proliferation of PEMC cultures. Furthermore, immunoneutralization of endogenous IGFBP-3 and IGFBP-5 in the PEMC culture medium results in increased DNA synthesis rate suggesting that endogenous IGFBP-3 and IGFBP-5 suppress PEMC proliferation. TGF-beta superfamily members myostatin and TGF-beta1 have also been shown to suppress proliferation of myogenic cells, and treatment of cultured PEMC with either TGF-beta1 or myostatin significantly (P < 0.01) increases levels of IGFBP-3 and -5 mRNA. We have previously shown that immunoneutralization of IGFBP-3 decreases the proliferation-suppressing activity of TGF-beta1 and myostatin. Here, we show that immunoneutralization of IGFBP-5 also significantly (P < 0.05) decreases the DNA synthesis-suppressing activity of these molecules. Simultaneous immunoneutralization of both IGFBP-3 and IGFBP-5 in TGF-beta1 or myostatin-treated PEMC cultures restores Long-R3-IGF-I-stimulated DNA synthesis rates to 90% of the levels observed in control cultures receiving no TGF-beta1 or myostatin treatment (P < 0.05). Even though immunoneutralization of IGFBP-3 and -5 increased DNA synthesis rates in TGF-beta1 or myostatin-treated PEMC cultures, phosphosmad2 levels in these cultures were not affected. These findings strongly suggest that IGFBP-3 and IGFBP-5 affect processes downstream from receptor-mediated Smad phosphorylation that facilitate the ability of TGF-beta and myostatin to suppress proliferation of PEMC.

Animals↗

PubMed2005

Effect of constitutive expression of porcine IGFBP-3 on proliferation and differentiation of L6 myogenic cells.

We have previously shown that exogenous recombinant porcine IGFBP-3 (rpIGFBP-3) suppresses proliferation and differentiation of L6 myogenic cells in an IGF-I-dependent manner and suppresses proliferation of L6 myogenic cells via an IGF-I-independent mechanism. In order to assess the effects of endogenously produced IGFBP-3, we have transfected L6 myogenic cells with a pEF6/V5 vector containing pIGFBP-3 cDNA under the control of the human elongation factor 1alpha (hEF-1alpha) promoter and with the empty vector. We have isolated a cell population that constitutively produces porcine IGFBP-3 (tL6 cells) and a stable mock transfected cell population containing the empty vector (mtL6 cells). Constitutive expression of IGFBP-3 slightly reduced the expression of IGFBP-5 but had no effect on IGFBP-4 production by L6 myogenic cells. Immunoneutralization of IGFBP-3 increased both IGF-I- and Long-R3-IGF-I-stimulated proliferation of tL6 cells (58 and 33%, respectively) (P<0.01). These data indicate endogenous pIGFBP-3, like exogenous rpIGFBP-3, suppresses the proliferation of L6 myogenic cells via both IGF-I-dependent and -independent pathways. Immunoneutralization of IGFBP-3 also increased IGF-I-stimulated differentiation (21%, P<0.05) but had no effect on Long-R3-IGF-I stimulated differentiation of tL6 myogenic cells. Results indicate that exogenous and endogenous IGFBP-3 affect proliferation and differentiation of L6 myogenic cells in a similar way. Immunohistochemical localization data reveal that pre-incubation with anti-pIGFBP-3 dramatically reduces the level of intracellular IGFBP-3 in tL6 myogenic cells indicating that endogenously produced IGFBP-3 must first be secreted before it is internalized and that anti-pIGFBP-3 prevents internalization of IGFBP-3. TL6 and mtL6 cells provide a good system to further investigate the mechanisms by which IGFBP-3 affects proliferation and differentiation of myogenic cells.

Animals↗

PubMed2005

Production of recombinant porcine IGF-binding protein-5 and its effect on proliferation of porcine embryonic myoblast cultures in the presence and absence of IGF-I and Long-R3-IGF-I.

IGF-binding protein-5 (IGFBP-5) is produced by porcine embryonic myogenic cell (PEMC) cultures and is secreted into the medium. IGFBP-5 may play some role in myogenesis and/or in changes in myogenic cell proliferation that accompany differentiation. IGFBP-5 reportedly may either suppress or stimulate proliferation or differentiation of cultured cells depending on cell type and culture conditions. Additionally, IGFBP-5 has been shown to possess both IGF-dependent and IGF-independent actions in some cell types. The goal of this study was to produce recombinant porcine IGFBP-5 (rpIGFBP-5) and assess its IGF-I-dependent and IGF-I-independent actions on the proliferation of PEMCs. To accomplish this, we have expressed porcine IGFBP-5 in the baculovirus system, purified and characterized the expressed rpIGFBP-5 and produced an anti-porcine IGFBP-5 antibody that neutralizes the biological activity of porcine IGFBP-5. rpIGFBP-5, purified to 98% homogeneity using nickel affinity chromatography and IGF-I affinity chromatography, suppressed IGF-I-stimulated proliferation of PEMCs in a concentration-dependent manner (P>0.05). rpIGFBP-5 also suppressed Long-R3-IGF-I-stimulated proliferation of PEMCs (P>0.05), even in the presence of significant molar excess of Long-R3-IGF-I compared with rpIGFBP-5, demonstrating the IGF-independent activity that rpIGFBP-5 possesses in PEMCs, since Long-R3-IGF-I is an IGF analog that has very low affinity for the IGFBPs but retains its ability to bind to the type I IGF receptor and thereby can stimulate proliferation. The anti-rpIGFBP-5 IgY produced against rpIGFBP-5 specifically recognized native porcine IGFBP-5 in PEMC media that also contained porcine IGFBP-2, -3, and -4. This antibody is capable of neutralizing the effects of both rpIGFBP-5 and endogenously produced porcine IGFBP-5 on PEMCs as well as detecting IGFBP-5 in Western blots. The production of rpIGFBP-5 and a neutralizing antibody to porcine IGFBP-5 provides a powerful tool to investigate the role of IGFBP-5 in porcine myogenic cell proliferation and differentiation. The data provided here demonstrated that IGFBP-5 has the potential to affect proliferation of PEMCs during critical periods of in vitro muscle cell development and therefore may impact the capacity for ultimate postnatal muscle mass development in vivo.

Animals↗

PubMed2004

IGF-I mRNA levels in bovine satellite cell cultures: effects of fusion and anabolic steroid treatment.

Androgenic and estrogenic steroids enhance muscle growth in a number of species; however, the mechanism by which anabolic steroids enhance muscle growth is not known. Castrated male cattle (steers) provide a particularly good model system in which to study the effects of anabolic steroids on muscle growth because they respond dramatically to treatment with both estrogens and androgens. The goal of this study was to determine if treatment of bovine satellite cell (BSC) cultures with 17beta-estradiol (E(2)) or trenbolone (a synthetic androgen) directly affects proliferation rate or level of mRNA for estrogen receptor (ER)-alpha, androgen receptor, and growth factors that have been shown to affect muscle growth (insulin-like growth factor (IGF)-I, IGF binding protein (IGFBP)-3, and myostatin). BSC cultures were established from the semimembranosus muscles of steers and then treated for 48 h with various concentrations of E(2) or trenbolone ranging from 0.001 to 10 nM. IGF-I mRNA levels in proliferating BSC cultures were significantly increased at 0.01 (1.9-times control values, P < 0.02) and at 0.1, 1, and 10 nM E(2) (2.9-, 3.5-, and 3.5-times control values, respectively, P < 0.0001). Additionally both 1 and 10 nM trenbolone increased IGF-I mRNA levels to 1.7-times control values (P < 0.02). ER-alpha mRNA was detectable in BSC cultures, and levels were increased (2.3-times control levels, P < 0.001) in cultures treated with 0.001 nM E(2) but not in cultures treated with higher concentrations of E(2). Androgen receptor mRNA levels also were increased (1.5-times control levels, P < 0.02) in cultures treated with 0.001 nM trenbolone but not by treatment with higher concentrations of trenbolone. Levels of IGFBP-3 were increased (1.4-times control values, P < 0.02) by treatment with 0.001 nM E(2) but not by treatment with high concentrations of E(2). Myostatin mRNA levels were not affected by any concentration of either of the steroids. Although, levels of IGF-I mRNA were 10-times greater (P < 0.02) in fused BSC cultures than in proliferating cultures, treatment of fused cultures for 48 h with 10 nM E(2) increased IGF-I mRNA levels (2.5-times control levels, P < 0.02). Both E(2) and trenbolone increased (3)H-thymidine incorporation rate (1.5-times control levels, P < 0.001) in BSC cultures in media containing serum from which IGFBP-3 had been removed by anti-IGFBP-3 affinity chromatography. In summary, treatment of BSC cultures with either E(2) or trenbolone increased IGF-I mRNA level and proliferation rate, thus, establishing that these steroids have direct anabolic effects on cells present in the BSC culture.

Anabolic Agents↗

PubMed2004

Effect of recombinant porcine IGFBP-3 on IGF-I and long-R3-IGF-I-stimulated proliferation and differentiation of L6 myogenic cells.

Insulin-like growth factor (IGF)-I stimulates both proliferation and differentiation of myogenic precursor cells. In vivo, IGFs are bound to one of the members of a family of six high-affinity IGF binding proteins (IGFBP 1-6) that regulate their biological activity. One of these binding proteins, IGFBP-3, affects cell proliferation via both IGF-dependent and IGF-independent mechanisms and it has generally been shown to suppress proliferation of cultured cells; however, it also may stimulate proliferation depending upon the cell type and the assay conditions. Cultured porcine embryonic myogenic cells (PEMCs) produce IGFBP-3 and its level drops significantly immediately prior to differentiation. Additionally, IGFBP-3 suppresses both IGF-I and Long-R3-IGF-I-stimulated proliferation of embryonic porcine myogenic cells. In this study, we have examined the effects of recombinant porcine IGFBP-3 (rpIGFBP-3) on IGF-I- and Long-R3-IGF-I-stimulated proliferation and differentiation of the L6 myogenic cell line. L6 cells potentially provide a good model for studying the actions of IGFBP-3 on muscle because they contain no non-muscle cells and they do not produce detectable levels of IGFBP-3. RpIGFBP-3 suppresses both IGF-I and Long-R3-IGF-I-stimulated proliferation of L6 cells, indicating that it suppresses proliferation via both IGF-dependent and IGF-independent mechanisms. Our data also show that rpIGFBP-3 causes IGF-independent suppression of proliferation without increasing the level of phosphosmad-2 in L6 cultures. Additionally, rpIGFBP-3 suppresses IGF-I-stimulated differentiation of L6 cells. In contrast, however, rpIGFBP-3 does not suppress Long-R3-IGF-I-stimulated differentiation. This suggests that rpIGFBP-3 does not have IGF-independent effects on L6 cell differentiation.

Animals↗

PubMed2003

Prevalence of Giardia spp. and Cryptosporidium spp. on dairy farms in southeastern New York state.

A prevalence study was designed to determine the presence of Cryptosporidium spp. and Giardia spp. in the soil of 37 dairy farms in southeastern New York state. A sampling design was developed and used to collect soil samples from these farms. Areas on the farms which were considered to be potential sources of contamination to the environment were evaluated quantitatively using a multidimensional scale. This scale included factors which could have the potential to contribute to the risk of contamination of the environment with Giardia or Cryptosporidium. In addition, the runoff pathway from these areas was identified and sampling points along that pathway were determined. Using a sampling grid, sampling sites were determined and soil samples collected and analyzed individually for the following: presence of Giardia and Cryptosporidium, pH, gravimetric moisture content, and volumetric moisture content. Out of 782 soil samples, 17% were positive for Cryptosporidium and 4% were positive for Giardia. The pH of the soil ranged from 3.7 to 9.8 with a mean of 7.0. There was a significant association between the pH and the likelihood of detecting Cryptosporidium spp. As the pH increased, the likelihood of detecting an oocyst decreased. Gravimetric moisture content had a mean of 40% and a range from 7 to 86%. There was a significant association between the gravimetric moisture content and the likelihood of detecting Giardia in soil samples.

Animals↗

PubMed2003

Role of insulin-like growth factor binding protein (IGFBP)-3 in TGF-beta- and GDF-8 (myostatin)-induced suppression of proliferation in porcine embryonic myogenic cell cultures.

Both transforming growth factor (TGF-beta) and growth and development factor (GDF)-8 (myostatin) affect muscle differentiation by suppressing proliferation and differentiation of myogenic cells. In contrast, insulin-like growth factors (IGFs) stimulate both proliferation and differentiation of myogenic cells. In vivo, IGFs are found in association with a family of high-affinity insulin-like growth factor binding proteins (IGFBP 1-6) that affect their biological activity. Treatment of porcine embryonic myogenic cell (PEMC) cultures with either TGF-beta(1) or GDF-8 suppressed proliferation and increased production of IGFBP-3 protein and mRNA (P < 0.005). An anti-IGFBP-3 antibody that neutralizes the biological activity of IGFBP-3 reduced the ability of either TGF-beta(1) or GDF-8 to suppress PEMC proliferation (P < 0.005). However, this antibody did not affect proliferation rate in the presence of both TGF-beta(1) and GDF-8. These data show that IGFBP-3 plays a role in mediating the activity of either TGF-beta(1) or GDF-8 alone but not when both TGF-beta(1) and GDF-8 are present. In contrast to findings in T47D breast cancer cells, treatment of PEMC cultures with IGFBP-3 did not result in increased levels of phosphosmad-2. Since TGF-beta and GDF-8 are believed to play a significant role in regulating proliferation and differentiation of myogenic cells, our current data showing that IGFBP-3 plays a role in mediating the activity of these growth factors in muscle cell cultures strongly suggest that IGFBP-3 also may be involved in regulating these processes in myogenic cells.

Animals↗

PubMed2003

Effect of differentiation on levels of insulin-like growth factor binding protein mRNAs in cultured porcine embryonic myogenic cells.

Insulin-like growth factor binding proteins (IGFBPs) have been shown to affect proliferation of several cell types via insulin-like growth factor (IGF)-dependent and IGF-independent mechanisms. The goal of this study was to determine if levels of IGFBP-2, -3, -4 and -5 mRNA changed during differentiation of cultured porcine embryonic myogenic cells. Total RNA was isolated from muscle cultures at various stages of differentiation and Northern blots of this RNA were probed with 32P-labeled cDNA probes specific for individual IGFBPs. Fusion, myogenin mRNA, and creatine phosphokinase activity were used as markers of differentiation. The level of IGFBP-3 mRNA in differentiating cultures (120 h in culture) was only one-third of the level in myogenin negative, nonfused cultures (72 h in culture) (P < 0.05, n = 4). In contrast, the level of IGFBP-3 mRNA in extensively fused cultures (144 h in culture) was increased by three-fold as compared to the level in myogenin negative, nonfused cultures (P < 0.05, n = 4) and approximately seven-fold as compared to the 120-h cultures (P < 0.05, n = 4). No significant change in the level of IGFBP-5 mRNA was observed during differentiation of myogenic cultures. IGFBP-2 mRNA levels were not significantly different at 72, 96 and 120 h, but at 144 h IGFBP-2 mRNA level was increased three-fold as compared to nonfused cultures (72 h) (P < 0.05, n = 4). IGFBP-4 mRNA was not detectable on Northern blots of total RNA from porcine myogenic cultures at any stage of differentiation. Changes in IGFBP-3 and IGFBP-2 mRNA levels are associated with differentiation of embryonic porcine myogenic cells in culture and this may indicate that these IGFBPs play a role in differentiation of these cells.

Animals↗

PubMed2003

Effect of recombinant porcine IGF-binding protein-3 on proliferation of embryonic porcine myogenic cell cultures in the presence and absence of IGF-I.

IGF-binding protein (IGFBP)-3 is produced by cultured porcine embryonic myogenic cell (PEMC) cultures and is secreted into the medium. Levels of secreted IGFBP-3 and IGFBP-3 mRNA are significantly reduced during differentiation and increase after differentiation is complete, suggesting that IGFBP-3 may play some role in myogenesis and/or in changes in myogenic cell proliferation that accompany differentiation. IGFBP-3 reportedly may either suppress or stimulate proliferation of cultured cells depending on cell type. Additionally, IGFBP-3 has been shown to affect proliferation via both IGF-dependent and IGF-independent mechanisms in some cell types but not all. Currently, the effect, if any, of IGFBP-3 on myogenic cell proliferation is not known. Consequently, the goal of this study was to assess the IGF-I-dependent and IGF-I-independent actions of recombinant porcine IGFBP-3 on proliferation of cultured porcine myogenic cells. To facilitate these investigations, we have expressed porcine IGFBP-3 in the baculovirus system, purified and characterized the expressed recombinant porcine IGFBP-3 (rpIGFBP-3), and produced and characterized an anti-porcine IGFBP-3 antibody that neutralizes the biological activity of porcine IGFBP-3. rpIGFBP-3 suppressed IGF-I-stimulated proliferation of PEMCs in a concentration-dependent manner with equimolar concentrations of IGF-I and rpIGFBP-3, resulting in complete suppression of IGF-I-stimulated proliferation. rpIGFBP-3 also suppressed Long-R3-IGF-I-stimulated proliferation of PEMC, indicating that rpIGFBP-3 possesses IGF-independent activity in this cell system. These data have established that IGFBP-3 has the potential to affect proliferation of PEMCs during critical periods of muscle development that may impact ultimate muscle mass achievable postnatally.

Animals↗

PubMed2003

Time course of changes in growth factor mRNA levels in muscle of steroid-implanted and nonimplanted steers.

We used a muscle biopsy technique in conjunction with real-time PCR analysis to examine the time course of changes in muscle IGF-I, IGFBP-3, myostatin, and hepatocyte growth factor (HGF) mRNA in the longissimus muscles of Revalor-S-implanted and nonimplanted steers on d 0, 7, 12, and 26 after implantation (nine steers/treatment group). Administration of a Revalor-S implant increased (P < 0.01) ADG and improved (P < 0.05) feed efficiency, 36 and 34%, respectively, compared with steers that received no implant during the 26-d trial. Daily dry matter intake did not differ (P > 0.15) between nonimplanted and implanted steers. Steers receiving the Revalor-S implant had increased (P < 0.001) circulating IGF-I concentrations compared with nonimplanted steers. The longissimus muscles of steers receiving the Revalor-S implant contained increased (P < 0.001) IGF-I mRNA levels compared with longissimus muscles of nonimplanted steers over the 26-d duration of the study. Longissimus muscle IGF-I mRNA levels in implanted steers were increased (P < 0.003) relative to d-0 concentrations on d 7 and 12 (101% and 128%, respectively), and byd 26, longissimus muscle mRNA levels were more than three times (P < 0.0001) those in the longissimus muscles of the same steers on d 0. There was no treatment effect on the level of IGFBP-3, myostatin, or HGF mRNA in the longissimus muscle at any time point; however, levels of IGFBP-3, myostatin, and HGF mRNA increased with time on feed. Based on current and previous studies, we hypothesize that the increased IGF-I level in muscle of implanted steers by d 7 of implantation stimulates satellite cell proliferation and maintains a high number of proliferating satellite cells at a point in the growth curve where satellite cell numbers and activity are normally dropping off. This would prolong the period of rapid muscle growth, resulting in the observed increased rate and efficiency of muscle deposition in implanted steers.

Animals↗

PubMed2003

Growth factor messenger RNA levels in muscle and liver of steroid-implanted and nonimplanted steers.

Ribonuclease protection assays were used to measure steady-state semimembranosus muscle and/or hepatic levels of IGF-I, IGFBP-3, IGFBP-5, hepatocyte growth factor (HGF), and myostatin messenger RNA (mRNA) in steers implanted from 32 to 38 d with Revalor-S, a combined trenbolone acetate and estradiol implant. Insulin-like growth factor-ImRNA levels were 69% higher (P < 0.01, n = 7) in the livers of implanted steers than in the livers of nonimplanted steers. Similarly, IGF-I mRNA levels were 50% higher (P < 0.05, n = 7) in the semimembranosus muscles of implanted steers than in the same muscles from nonimplanted steers. Hepatic IGFBP-3 mRNA levels were 24% higher (P < 0.07, n = 7) in implanted steers than in nonimplanted steers. Hepatic HGF and IGFBP-5 mRNA levels did not differ between implanted and nonimplanted steers. Similarly, muscle IGFBP-3, IGFBP-5, HGF, and myostatin mRNA levels were not affected by treatment. Previous data from these same steers have shown that circulating IGF-I and IGFBP-3 concentrations were 30 to 40% higher (P < 0.01, n = 7) in implanted steers than in nonimplanted, control steers. Additionally, the number of actively proliferating satellite cells that could be isolated from the semimembranosus muscle was 45% higher (P < 0.01, n = 7) for implanted steers than for nonimplanted steers. Viewed together, these data suggest that increased muscle IGF-I levels stimulate increased satellite cell proliferation, resulting in the increased muscle growth observed in Revalor-S implanted steers.

Anabolic Agents↗

PubMed2003

Effects of antimicrobials and weaning on porcine serum insulin-like growth factor binding protein levels.

The effects of subtherapeutic antimicrobial supplementation and weaning on serum levels of IGF-I and insulin-like growth factor binding proteins (IGFBP)-2, -3 and -4 were determined in crossbred weanling pigs. At weaning, pigs were allotted to a diet containing 21.8% crude protein and 1.15% lysine with or without Aureozol (110 mg/kg of Aureomycin chlortetracycline, 110 mg/kg of sulfathiazole, and 55 mg/kg of penicillin) for 4 wk. Insulin-like growth factor-binding proteins and IGF-I analyses were performed on blood samples that were drawn weekly. Weaning decreased serum IGFBP-3 levels in both control and Aureozol-treated groups on d 6 and d 14 (P < 0.05) relative to preweaning levels. The IGFBP-3 values returned to preweaning levels by d 21. Although the circulating levels of both the 43-kDa and the 39-kDa glycosylation variants of IGFBP-3 were affected by weaning, the level of the 39-kDa IGFBP-3 was affected relatively more than that of the 43-kDa IGFBP-3 (P < 0.05). Compared with circulating IGFBP-3 levels in control pigs, Aureozol-treated pigs had higher circulating IGFBP-3 levels on d 21 (43%, P < 0.05) and d 27 (46%, P < 0.05). In direct contrast to the effect of weaning on serum IGFBP-3 level, serum IGFBP-2 levels increased on d 6 and d 14 after weaning (P < 0.05) and decreased to preweaning levels by d 21. The IGFBP-2 levels continued to decline and were less than preweaning levels by d 27 (P < 0.05). Aureozol treatment had no effect on serum IGFBP-2 levels at any time. Serum levels of nonglycosylated IGFBP-4 were not affected by either weaning or Aureozol supplementation. Weaning decreased circulating IGF-I concentration on d 6 in both control and Aureozol-treated pigs (76 and 73%, respectively, P < 0.05) and on d 14 (62%, P < 0.05) and d 21 (32%, P < 0.05) in control pigs. Aureozol-supplemented pigs had higher serum IGF-I concentrations than control pigs on d 14 (82%, P < 0.05), d 21 (55%, P < 0.05), and d 27 (36%, P < 0.05). The Aureozol-fed pigs had a 14.2% increase in BW gain (P < 0.05) and a 59.6% increase in ADG (P < 0.05) compared with pigs fed the control diet. Both Aureozol-supplementation and weaning cause changes in serum IGFBP levels and IGF-I concentrations that might be involved in regulating rate and efficiency of growth.

Animal Feed↗

PubMed2003

Factors associated with the likelihood of Giardia spp. and Cryptosporidium spp. in soil from dairy farms.

A study was conducted to identify factors associated with the likelihood of detecting Giardia spp. and Cryptosporidium spp. in the soil of dairy farms in a watershed area. A total of 37 farms were visited, and 782 soil samples were collected from targeted areas on these farms. The samples were analyzed for the presence of Cryptosporidium spp. oocysts, Giardia spp. cysts, percent moisture content, and pH. Logistic regression analysis was used to identify risk factors associated with the likelihood of the presence of these organisms. The use of the land at the sampling site was associated with the likelihood of environmental contamination with Cryptosporidium spp. Barn cleaner equipment area and agricultural fields were associated with increased likelihood of environmental contamination with Cryptosporidium spp. The risk of environmental contamination decreased with the pH of the soil and with the score of the potential likelihood of Cryptosporidium spp. The size of the sampling site, as determined by the sampling design, in square feet, was associated nonlinearly with the risk of detecting Cryptosporidium spp. The likelihood of the Giardia cyst in the soil increased with the prevalence of Giardia spp. in animals (i.e., 18 to 39%). As the size of the farm increased, there was decreased risk of Giardia spp. in the soil, and sampling sites which were covered with brush or bare soil showed a decrease in likelihood of detecting Giardia spp. when compared to land which had managed grass. The number of cattle on the farm less than 6 mo of age was negatively associated with the risk of detecting Giardia spp. in the soil, and the percent moisture content was positively associated with the risk of detecting Giardia spp. Our study showed that these two protozoan exist in dairy farm soil at different rates, and this risk could be modified by manipulating the pH of the soil.

Agriculture↗

PubMed2001

Partnerships in international applied epidemiology training and service, 1975-2001.

In 1951 the Centers for Disease Control and Prevention created the Epidemic Intelligence Service to provide training and epidemiologic service on the model of a clinical residency program. By January 2001, an additional 28 applied epidemiology and training programs (AETPs) had been implemented around the globe (with over 945 graduates and 420 persons currently in training). Field Epidemiology Training Programs and Public Health Schools Without Walls are the most common models. Applied epidemiologists, or field epidemiologists, use science as the basis for intervention programs designed to improve public health. AETPs train people by providing them with health competencies through providing service to public health intervention programs and strengthening health systems. AETPs are relatively expensive to create and maintain, but they are highly sustainable and can produce immediate benefits. Of the 19 programs that began before 1997, 18 (95%) continue to produce graduates. The Training Programs in Epidemiology for Public Health Interventions Network was organized in 1997 to provide support, peer review, and quality assurance for AETPs. In 2001, new programs are planned or in development in India, Argentina, China, and Russia.

Centers for Disease Control and Prevention, U.S.↗