Growth-promoting technologies decrease the carbon footprint, ammonia emissions, and costs of California beef production systems.

Increased animal performance is suggested as one of the most effective mitigation strategies to decrease greenhouse gas (GHG) and ammonia (NH(3)) emissions from livestock production per unit of product produced. Little information exists, however, on the effects of increased animal productivity on the net decrease in emission from beef production systems. A partial life cycle assessment (LCA) was conducted using the Integrated Farm System Model (IFSM) to estimate GHG and NH(3) emissions from representative beef production systems in California that use various management technologies to enhance animal performance. The IFSM is a farm process model that simulates crop growth, feed production, animal performance, and manure production and handling through time to predict the performance, economics, and environmental impacts of production systems. The simulated beef production systems compared were 1) Angus-natural, with no use of growth-enhancing technologies, 2) Angus-implant, with ionophore and growth-promoting implant (e.g., estrogen/trenbolone acetate-based) application, 3) Angus-ß2-adrenergic agonists (BAA; e.g., zilpaterol), with ionophore, growth-promoting implant, and BAA application, 4) Holstein-implant, with growth implant and ionophore application, and 5) Holstein-BAA, with ionophore, growth implant, and BAA use. During the feedlot phase, use of BAA decreased NH(3) emission by 4 to 9 g/kg HCW, resulting in a 7% decrease in NH(3) loss from the full production system. Combined use of ionophore, growth implant, and BAA treatments decreased NH(3) emission from the full production system by 14 g/kg HCW, or 13%. The C footprint of beef was decreased by 2.2 kg carbon dioxide equivalent (CO(2)e)/kg HCW using all the growth-promoting technologies, and the Holstein beef footprint was decreased by 0.5 kg CO(2)e/kg HCW using BAA. Over the full production systems, these decreases were relatively small at 9% and 5% for Angus and Holstein beef, respectively. The growth-promoting technologies we evaluated are a cost-effective way to mitigate GHG and NH(3) emissions, but naturally managed cattle can bring a similar net return to Angus cattle treated with growth-promoting technologies when sold at an 8% greater premium price.

Analytical assessment of the osteoinductive material COLLOSSE.

In this study, the growth factors in COLLOSSE were analyzed, using ELISA tests, mass spectrometry, western blotting, and a 24-day cell culture experiment using osteoblast-like cells. The results of the ELISA testing, mass spectrometry, and western blotting all confirmed that TGF-beta1 was the main growth factor in COLLOSSE at 55 ng/mg. The results from the culture test showed that the cell proliferation, alkaline phosphatase activity, and matrix calcification were all drastically changed by the addition of COLLOSSE, mirroring the effects of addition of TGF-beta1. We conclude that COLLOSSE is not only a rich source of TGFbeta-1, but also contains the growth factors TGFbeta-2, BMP-2, BMP-3, BMP-7, IGF-1, and possibly VEGF. Other growth factors might be present in COLLOSSE, but were not identified due to inherent detection limits of the used ELISA and mass spectrometry techniques. The number of osteoinductive factors in COLLOSSE causes a synergistic effect, explaining the new bone formation found in previously described in vivo studies, with much lower growth factor concentrations when compared with recombinant BMPs.

Systematic assessment of growth factor treatment on biochemical and biomechanical properties of engineered articular cartilage constructs.

OBJECTIVE: To determine the effects of bone morphogenetic protein-2 (BMP-2), insulin-like growth factor (IGF-I), and transforming growth factor-beta1 (TGF-beta1) on the biochemical and biomechanical properties of engineered articular cartilage constructs under serum-free conditions. METHODS: A scaffoldless approach for tissue engineering, the self-assembly process, was employed. The study consisted of two phases. In the first phase, the effects of BMP-2, IGF-I, and TGF-beta1, at two concentrations and two dosage frequencies each were assessed on construct biochemical and biomechanical properties. In phase II, the effects of growth factor combination treatments were determined. Compressive and tensile mechanical properties, glycosaminoglycan (GAG) and collagen content, histology for GAG and collagen, and immunohistochemistry (IHC) for collagen types I and II were assessed. RESULTS: In phase I, BMP-2 and IGF-I treatment resulted in significant, >1-fold increases in aggregate modulus, accompanied by increases in GAG production. Additionally, TGF-beta1 treatment resulted in significant, approximately 1-fold increases in both aggregate modulus and tensile modulus, with corresponding increases in GAG and collagen content. In phase II, combined treatment with BMP-2 and IGF-I increased aggregate modulus and GAG content further than either growth factor alone, while TGF-beta1 treatment alone remained the only treatment to also enhance tensile properties and collagen content. DISCUSSION: This study determined systematically the effects of multiple growth factor treatments under serum-free conditions, and is the first to demonstrate significant increases in both compressive and tensile biomechanical properties as a result of growth factor treatment. These findings are exciting as coupling growth factor application with the self-assembly process resulted in tissue engineered constructs with functional properties approaching native cartilage values.

Efficacy of aniseed extract as immune stimulant and growth promoter in broiler chicks.

Present research was undertaken to investigate the effect of different level of 6% concentrated (w/v) aniseed extract in broiler chicks at NWFP Agricultural University Peshawar Pakistan. One hundred and sixty, day old broiler chicks were randomly assigned to four treatments, as A, B, C, receiving 20, 30 and 40 mL of 6% (w/v) concentrated aniseed infusion and D was kept as control group. Each treatment was replicated four times with ten chicks per replicate. Chicks were reared in cages in an open sided house. Vaccination was done against ND and IBD. Data were recorded for growth performance, immunity and economics. The data were subjected to statistical analysis, using Completely Randomized Design and MSTATC programme. Mean feed and water intake was nonsignificant (p > 0.05). Mean weight gain, FCR and dressing percentage was found better (p < 0.05) in group C. Mean weight of giblet, intestine, breast, fat and thigh was not altered (p > 0.05) in all groups. Mean antibody titer against IBD was higher (p < 0.05) in group C and antibody titer against ND and IB was not altered. Mean percent mortality was found higher (p < 0.05) in group D. Mean feed cost including the cost of aniseed infusion was not influenced (p > 0.05), while the gross return was found better (p < 0.05) in group B and C than other groups. Findings of the research study indicated that group C, receiving aniseed infusion at the rate of 40 ml L(-1) of water shown better growth performance, immunity and gross return. Detail research work is needed to examine the effect of aniseed in ration and its different form of extracts on poultry production under different environmental conditions.

Growth and growth factor production by human nasal septal chondrocytes in serum-free media.

BACKGROUND: Tissue-engineered human cartilage offers vast possibilities as a source of graft implant material for reconstructive surgery. Serum-supplemented growth media is successful in supporting chondrocyte proliferation in vitro. Serum, however, contains exogenous growth factors that hamper the identification and quantification of growth factors autogenously produced by chondrocytes. We explore the possibility of using a commercially available serum-free medium UltraCULTURE as an alternative to modified Webber's medium (MWM), the standard media used in chondrocyte cell culture. METHODS: Human nasal septal chondrocytes were grown in UltraCULTURE containing various concentrations of basic fibroblast growth factor (bFGF; 0, 1, 10, and 100 ng/mL) with or without insulin-like growth factor and compared with chondrocytes grown in MWM. Growth curves and transforming growth factor (TGF) beta 1 production were analyzed. RESULTS: We found no differences in the ability to sustain cell viability in culture between the two base media types. We also found no statistically significant differences in TGF-beta 1 production by chondrocytes grown in either system. Finally, there were no statistically significant differences in chondrocyte proliferation between cultures supplemented with bFGF at 10 and 100 ng/mL. CONCLUSION: UltraCULTURE media is a cost-effective, serum-free alternative to standard media with compatible growth characteristics. It offers specific advantages over standard serum-containing media for the precise measurement of autogenous growth factor production by cultured chondrocytes. Furthermore, UltraCULTURE's serum-free environment would be ideal for safely producing tissue-engineered cartilage grafts.

Animal growth promoters: to ban or not to ban? A risk assessment approach.

The use of antibiotics for animal growth promotion has been controversial because of the potential transfer of antibiotic resistance from animals to humans. Such transfer could have severe public health implications in that treatment failures could result. We have followed a risk assessment approach to evaluate policy options for the streptogramin-class of antibiotics: virginiamycin, an animal growth promoter, and quinupristin/dalfopristin, a antibiotic used in humans. Under the assumption that resistance transfer is possible, models project a wide range of outcomes depending mainly on the basic reproductive number (R(0)) that determines the potential for person-to-person transmission. Counter-intuitively, the benefits of a ban on virginiamycin were highest for intermediate values of R(0), and lower for extremely high or low values of R(0).

Quantitative assessment of the integrity of the blood-retinal barrier in mice.

PURPOSE: The purpose of this study was to develop and characterize a quantitative assay of blood-retinal barrier (BRB) function in mice and to determine the effect of several purported vasopermeability factors on the BRB. METHODS: Adult C57BL/6J mice were treated with three regimens of increasingly extensive retinal cryopexy and subsequently were given an intraperitoneal injection of 1 microCi/g body weight of [(3)H]mannitol. At several time points, the amount of radioactivity per milligram tissue was compared in retina, lung, and kidney. Time points that maximize signal-to-background differential in the retina were identified, and the ratio of counts per minute (CPM) per milligram retina to CPM per milligram lung (retina-to-lung leakage ratio, RLLR) or kidney (retina-to-renal leakage ratio, RRLR) were calculated. This technique was then used to compare the amount of BRB breakdown that occurs after intravitreous injection of vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF)-1, prostaglandin (PG) E(1), PGE(2), interleukin (IL)-1beta, or tumor necrosis factor (TNF)-alpha. RESULTS: Twenty-four hours after retinal cryopexy, there was a higher level of radioactivity in treated than in control retinas, and the signal-to-background difference was optimal when measurements were obtained 1 hour after injection of [(3)H]mannitol. In untreated mice, the RLLR was 0.30 +/- 0.02 and the RRLR was 0.22 +/- 0.01. Twenty-four hours after one 5-second application of retinal cryopexy, the RLLR was 0.73 +/- 0.20 and the RRLR was 0.71 +/- 0.23. With increasing amounts of cryopexy, there was an increase in the RLLR and RRLR, so that after two 10-second applications, the RLLR was 1.66 +/- 0.31 and the RRLR was 1.47 +/- 0.20. Intravitreous injection of VEGF, IGF-1, PGE(1), PGE(2), IL-1beta, or TNF-alpha each caused significant increases in the RLLR and RRLR, but there were some differences in potency and time course. VEGF caused prominent BRB breakdown at 6 hours that returned to near normal by 24 hours. IL-1beta also caused relatively rapid breakdown of the BRB, but its effect was more prolonged than that caused by VEGF. There was delayed, but substantial breakdown of the BRB after injection of TNF-alpha. IGF-1, PGE(2), and PGE(1) caused less severe, relatively delayed, and more prolonged BRB breakdown. CONCLUSIONS: Measurement of the RLLR or RRLR after intraperitoneal injection of [(3)H]mannitol in mice provides a quantitative assessment of BRB function that is normalized and can therefore be compared from assay to assay. Comparison of the extent and duration of BRB breakdown after intravitreous injection of vasoactive substances shows that agents can be grouped by resultant extent and time course of leakage. Additional studies are needed to determine whether this grouping has its basis in shared mechanisms of BRB disruption.

Quantitative assessment of cerebral neocapillary network and its remodeling in mice using intravital fluorescence videomicroscopy.

To assess the responses of different growth factors on cerebral neocapillary density (NCD), cerebral angiogenesis was induced in mice using growth factors, basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) at a concentration of 6 ng/ml each. Intravital fluorescence videomicroscopy was used to quantitatively evaluate microhemodynamic parameters such as diameter and red cell velocity. The gel-nylon mesh-sandwich system was implanted over the exposed cortex. After incubation for different periods of time (days 7, 14 or 28), fluorescein isothiocyanate (FITC)-labeled red cells were injected through a carotid artery and the neocapillaries on the upper surface of the nylon mesh were observed under a fluorescence videomicroscope. Based on the recorded videoimages, we evaluated the density, diameter and red cell velocity of the neocapillaries. The NCD in the bFGF group on day 7 was significantly higher than that in the PDGF group on day 7 (P < 0.01). The NCD (index) reached 100% on day 14, while it reduced significantly in both the groups on day 28. The neocapillary diameter was greater than that of the pre-existing capillaries on day 7. On day 14, a clear difference appeared in the capillary density between large and small vessels. The red cell velocity increased with the number of days after incubation. The response of cerebral neocapillaries to acetylcholine was measured after 28 days of incubation with growth factor bFGF and with PDGF. The red cell velocity increased significantly from its basal value in the PDGF group. These results suggest that the neocapillaries in the PDGF group matured earlier than those in the bFGF group.

Assessment of oestrogenic potency of chemicals used as growth promoter by in-vitro methods.

Three in-vitro bioassays were used to compare the oestrogenic potency of chemicals used as growth promoter in beef cattle in certain non-European Union countries (17beta-oestradiol, alpha-zearalanol, testosterone, trenbolone, trenbolone acetate, melengestrol acetate) or found as food contaminant such as the mycotoxin zearalenone and some of their metabolites (17alpha-oestradiol, oestrone, 17alpha-epitestosterone, 19-nortestosterone, androstendione, zearalanone, alpha-zearalanol, beta-zearalanol, alpha-zearalenol, beta-zearalenol). The strong oestrogens 17alpha-ethinyl oestradiol and diethylstilboestrol were used as standards. The first bioassay was based on the activation of a reporter gene by oestrogens in recombinant yeast expressing human or rainbow trout oestrogen receptor. In the second bioassay, the vitellogenin gene induction of rainbow trout hepatocyte cultures was used as a biomarker for the exposure to oestrogens. The third bioassay was based on the alkaline phosphatase gene induction by oestrogens in the human endometrial Ishikawa cell line. The assessment of oestrogenic potency of these chemicals clearly demonstrates the strong oestrogenicity of the mycotoxin zearalenone and its metabolites and particularly alpha-zearalenol which was as potent as ethinyl oestradiol and diethylstilboestrol in the human endometrial Ishikawa cell line.

Oestrogenic potencies of Zeranol, oestradiol, diethylstilboestrol, Bisphenol-A and genistein: implications for exposure assessment of potential endocrine disrupters.

We have compared the oestrogenic potency of the synthetic oestrogen Zeranol, used as a growth promoter in meat production, and five related compounds, with the potency of 17beta-oestradiol, diethylstilboestrol (DES), genistein, and Bisphenol-A. The potency was assayed by analysing differences in expression levels of endogenous oestrogen-regulated genes in human MCF7 cells, treated with different concentrations of the compounds. Zeranol, 17beta-oestradiol and DES were about equally potent, genistein was four to six orders of magnitude less potent than 17beta-oestradiol but an order of magnitude more potent than Bisphenol-A. There were gene specific differences, the PS2 and TGFbeta3 genes were about equally sensitive to Zeranol, 17beta-oestradiol and DES whereas a down-regulation of MRG1/p35srj could be detected at fmol/l concentrations of Zeranol whereas 17beta-oestradiol was several orders of magnitude less potent. GST mu3 was sensitive to fmol/l concentrations of 17beta-oestradiol but much less sensitive to Zeranol and DES. The very high potency of Zeranol compared with other potential endocrine disrupters suggests that Zeranol intake from beef products could have greater impact on consumers than the amounts of the known or suspected endocrine disrupters that have been found in food. Since little data is available in man, there is an urgent need for reliable measurements of the concentration of Zeranol in human serum after ingestion of meat products from treated animals.

The role of growth factor administration and T-cell recovery after peripheral blood progenitor cell transplantation in the treatment of solid tumors: results from a randomized comparison of G-CSF and GM-CSF.

BACKGROUND: Peripheral blood progenitor cell (PBPC) transplantation (PBPCT) combined with post-PBPCT administration of myelopoietic growth factors is a valid therapeutic intervention to rapidly restore hematopoiesis after the delivery of intensive, myeloablative cancer chemotherapy. On the other hand, the best growth factor regimen to potentiate PBPC-mediated immunohematopoietic recovery has yet to be determined. STUDY DESIGN AND METHODS: In a randomized evaluation, the effects produced by post-PBPCT G-CSF and GM-CSF on myeloid/lymphoid recovery and transplant outcome in women with chemosensitive cancer were compared. Thirty-seven ovarian cancer patients and 34 breast cancer patients ranging in age from 24 to 60 years were treated with carboplatin, etoposide, and melphalan (CEM) high-dose chemotherapy and then randomly assigned to receive G-CSF (5 microg/kg subcutaneously) or GM-CSF (5 microg/kg subcutaneously) until Day 13 after PBPCT. Patients were compared in regard to hematopoietic recovery, posttransplant clinical management, and immune recovery. Finally, clinical outcome was estimated as time to progression and overall survival. RESULTS: Hematopoietic recovery and posttransplant clinical management were comparable in both the G-CSF and GM-CSF series. Conversely, significantly higher T-cell counts were observed in G-CSF-treated patients during the early and late posttransplant follow-up. Patients who received G-CSF showed a significantly longer median time to progression. A parallel analysis revealed that patients in whom a higher CD3+ count was recovered had a significantly longer overall survival and time to progression. CONCLUSION: The enhancement of post-PBPCT T-cell recovery observed in G-CSF-treated patients encourages the use of G-CSF to ameliorate immune recovery, which seems to play a role in post-PBPCT control of disease in cancer patients. GM-CSF might be administered to prolong immunosuppression after autologous PBPCT for autoimmune diseases or allogeneic PBPCT.

Assessment of growth factor effects on post-thaw development of cryopreserved mouse morulae to the blastocyst stage.

The objective of this study was to assess the influence of specific factors on post-thaw development of mouse cryopreserved morulae. Thawed morulae (n = 206) were randomly distributed between 10 treatment groups: medium alone control (CT), Vero (VR) cells, leukaemia inhibitory factor (1 ng/ml), interleukin-6 (1 ng/ml), transforming growth factor (TGF) alpha (2 ng/ml), epidermal growth factor (EGF) (4 ng/ml), platelet-derived growth factor (1 ng/ml), insulin-like growth factor (IGF)-I (30 ng/ml), IGF-II (1 ng/ml) and TGFbeta (2 ng/ml). At 4, 8, 20, 30 and 48 h, a digitized image of each thawed embryo was captured and stored for later analysis. The following parameters were examined: blastocoel formation, blastocyst expansion, zona thickness and hatching. At termination of the experiment, cell number per embryo was determined by bisbenzimide staining. When contrasted to the medium alone control, co-culture consistently accelerated the development of frozen-thawed morulae to the hatched blastocyst stage, allowing embryos to recover rapidly from any damage sustained during the cryopreservation process. While no single growth factor/cytokine was able to completely mimic the results achieved with co-culture, all of the growth factors impacted positively on at least one of the morphological parameters studied. Cell proliferation was significantly stimulated by just 48 h exposure to growth factors, either through co-culture or by direct media supplementation. Co-culture again yielded the best results with a mean cell count of 217 +/- 76 cells per blastocyst as compared with 131 +/- 36 in control medium alone. Amongst the factors tested, IGF-I, IGF-II and EGF had the greatest impact, with mean cell counts of 172 +/- 50, 168 +/- 50 and 179 +/- 55 respectively. Whereas only 5% of CT embryos developed to blastocysts with > 200 cells, 51% of thawed embryos placed on co-culture monolayers and 25-32% of embryos cultured with IGF-I, IGF-II or EGF had > 200 cells. This study for the first time systematically describes the effect of culture regimen and growth factor additives on the post-thaw development of cryopreserved embryos.

The protein hydrolysate, Primatone RL, is a cost-effective multiple growth promoter of mammalian cell culture in serum-containing and serum-free media and displays anti-apoptosis properties.

The tryptic meat digest Primatone RL is a low-cost medium supplement of a complex nature which serves as a source of amino acids, oligopeptides, iron salts, some lipids and other trace low molecular weight substances. Its addition to mammalian and insect cell culture media significantly improves the cell growth properties of many cell lines. In this work the growth promoting effects of Primatone RL are described in more detail using different mouse hybridomas, a mouse myeloma cell line, and human promyelocytic leukemia HL-60 cells. The positive effects on cell growth induced by Primatone were observed in the presence of serum but were even more pronounced in serum-free culture. In addition the adaptation time from high serum to low (1%) or serum-free growth in the presence of Primatone is also significantly reduced. Primatone RL, when added to HL and DHI medium, improves cell growth under low serum or serum-free conditions by increasing the maximum cell numbers and in particular the viability of the culture. The observed decrease in cell death (apoptosis) induction leads to a significant improvement in antibody (recombinant protein) production by increasing the volumetric yields during long-term batch culture. The so-called anti-apoptotic effects of Primatone RL for mouse hybridomas, which is concentration dependent, is not fully understood.

Rat gro/melanoma growth-stimulating activity. Assessment of the structure responsible for chemotactic activity by use of its fragments prepared by proteolysis and chemical synthesis.

Rat gro/melanoma growth-stimulating activity is a dimer composed of two identical subunits. Each subunit consists of 72 amino-acid residues and contains two disulfide bridges. In order to obtain information on the structure responsible for chemotactic activity, various fragments of gro were prepared and tested for their ability to induce chemotaxis. None of the fragments corresponding to residues 1-6, 1-21, 12-31, 36-50 or 52-72 was active as a chemoattractant. Reduced and carboxymethylated gro as well as the tryptic peptide consisting of three peptides, residues 9-21, 28-45 were and 49-61, linked by two disulfide bonds Cys-9-Cys-35 and Cys-11-Cys-51, were inactive. Also, these, peptides did not inhibit the chemotactic activity of gro. Rat gro lacking the N-terminal 6 residues had a reduced activity and the one lacking the C-terminal Lys was as active as intact gro. Therefore, an almost entire portion of the molecule including disulfide cross-links is required for chemotactic activity.

In vitro assessment of the effects of granulocyte-macrophage colony-stimulating factor on primary human tumors and derived lines.

One hundred eighty-nine human tumor specimens were tested in a human tumor cloning assay to determine their growth response to human recombinant granulocyte-macrophage colony-stimulating factor. Of these samples 48 were evaluable for response. Growth stimulation to greater than 150% of controls was noted in 1 of 12 lung cancers (8%) and 1 of 14 breast cancers (7%) but in no other instances for an overall rate of 2 of 48 (4.2%). A dose-response effect was not seen with each of the two stimulated samples responding only at the two lowest concentrations tested. In addition, 7 cell lines derived from human tumors were tested using a metabolic CO2 production assay without evidence of growth stimulation. Samples of normal bone marrow displayed the usual dose-dependent stimulation whether grown in agar or assayed metabolically. We conclude that human recombinant granulocyte-macrophage colony-stimulating factor has minimal effect on the growth of the solid tumors tested and that clinical trials to reduce chemotherapy-associated myelo-suppression may proceed without undue concern for enhancement of tumor growth.

Improving food quality through new technology.

New technological developments make it possible to improve the quality of animal disease therapy, prophylaxis and diagnosis, and to improve animals' growth and fertility. The term 'quality' includes not only objective measurements, such as the fatness or leanness of meat, but also organoleptic factors such as flavour and others which are of increasing importance to consumers, such as animal welfare. Is new technology consistent with the improvement of quality? For example, beta-agonists and porcine somatotrophin reduce the fatness and increase the protein content of carcases, but there are also subtle positive relationships between fatness and eating quality. In contrast, bovine somatotrophin appears to have no effect on milk composition but there are indications that it may affect the perception of milk quality by some consumers. Improved vaccines can increase food quality by improving animal health and welfare and increasing the uniformity of the product; immunological techniques may also be used to improve meat quality. A gulf has developed between the benefits from new technology and consumer perceptions; indeed there is evidence of political resistance to some technological advances. Despite the stringent regulation of veterinary medicinal products in the United Kingdom and other countries, there is continued pressure for greater political control over their approval. The exchange of information between scientists, industry, the legal regulators and consumers must be improved so that advances in technology are acceptable to the majority and used to the advantage of all.

Involvement of cell surface transferrin receptor in the assessment of estradiol stimulating effect on cultured breast cancer cells.

In order to find the reasons for the conflicting results depicted during the estradiol stimulations of cultured MCF7, breast cancer cells we investigated, besides cell counts, the cell surface transferrin receptor as an additional means of assessing the effect of estradiol. In this study we report results obtained using different culture conditions, i.e. short-term or long-term phenol-red withdrawn cells grown either in calf-serum supplemented media or defined media. Our results point out concurrent variations of cell counts and transferrin receptors when short-term phenol-red withdrawn cells were grown in defined media. Discrepancies were, however, observed when short-term phenol-red withdrawn cells were grown in serum-supplemented media or when long-term phenol-red withdrawn cells were grown in defined media. In both cases, only transferrin receptors account for estradiol stimulation. These results highlight the importance of transferrin receptor measurement in cultured breast cancer cell experiments and suggest cell kinetic perturbations due, in all likelihood, to serum factors or factors secreted by long-term phenol-red withdrawn cells.

Assessment of biological activity of synthetic fragments of transforming growth factor-alpha.

Transforming growth factor-alpha (TGF-alpha) is a single chain polypeptide hormone of 50 amino acids that stimulates growth of some human cancer cells via an autocrine mechanism. The domain(s) of TGF-alpha that bind and activate its receptor have not been reported. Hydrophilicity plots of TGF-alpha indicate three discrete sequences that are theoretically exposed on the hormone's surface and thus potentially able to interact with the TGF-alpha receptor. Fragments of TGF-alpha encompassing these hydrophilic domains were prepared by using solid-phase peptide synthesis (SPPS) techniques and purified by use of high performance liquid chromotography (HPLC). Assessment of biological activity of the TGF-alpha fragments indicated that none of the fragments significantly inhibited binding of EGF to the receptor, stimulated DNA synthesis of cells, inhibited EGF-induced DNA synthesis of cells, stimulated growth of cells in soft agar, or induced phosphorylation of the receptor or p35 protein. These results indicate that the receptor binding domain of TGF-alpha is not totally encompassed by any of the separate fragments tested and probably is formed by multiple separate regions of TGF-alpha.