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Biomedical subjects

C Goddard

Publications and source records attributed to C Goddard.

At least 55 records · Page 3Linked to original sources
PubMed1991

Why are young broiler chickens fatter than layer-strain chicks?

1. The abdominal fat pads of 5 week-old broiler and layer chicks incorporated 6.0 and 3.9% of intravenously-injected 14C-labelled very low density lipoproteins respectively. 2. These proportions of total plasma lipoprotein flux were sufficient to account for about 65-70% of the rate of fat deposition in broilers, but were more than 4-fold greater than that the rate of fat deposition in layers. 3. [14C]Palmitate taken up into adipose tissue of layer chicks had a t1/2 of 2-3 days. 4. There was no significant turnover of adipose tissue triglycerides in broilers and this appears to be a major reason for their relative fatness.

Adipose Tissue↗
PubMed1991

Monoclonal antibody based sandwich enzyme-linked immunosorbent assay for chicken growth hormone.

1. Monoclonal antibodies which bind to different epitopes of chicken growth hormone (cGH) were used to develop a homologous sandwich enzyme-linked immunosorbent assay (ELISA). 2. The first antibody, which is species specific, was immobilised on microtitre plates and concentrations of cGH in biological fluids were estimated by revealing bound hormone using a second, biotinylated monoclonal antibody. 3. The sensitivity was 0.024 ng/ml, which is at least ten-fold greater than current radioimmunoassays (RIA) and there was no cross-reactivity to other chicken pituitary hormones or to growth hormone from other species. 4. The accuracy and precision of the assay were similar to RIA, and the growth hormone concentrations measured in plasma samples by both RIA and this new ELISA showed a high degree of correlation. 5. The assay takes only 4 h using pre-coated plates which can be stored at 4 degrees C in sucrose. The advantages of being rapid and non-isotopic make this method attractive to both research and industrial laboratories.

Animals↗
PubMed1991

Training general practitioners to teach psychiatric interviewing skills: an evaluation of group training.

Group teaching in problem-based interviewing based on video and audiotape feedback of the doctor's own consultations significantly improved the ability of experienced general practitioners to teach psychiatric skills to their trainees. When the GPs were randomly allocated to one of three further training experiences--video feedback of their tutorial sessions, discussion about how to teach and no further teaching, there were very few differences between the groups. The greatest impact on improving teaching skills was brought about by watching their own consultations in a group feedback setting.

Clinical Competence↗
PubMed1991

Stimulation of DNA synthesis in chicken muscle satellite cells by insulin and insulin-like growth factors: evidence for exclusive mediation by a type-I insulin-like growth factor receptor.

Insulin-like growth factors-I and -II (IGF-I and IGF-II) stimulate proliferation, differentiation, nutrient uptake and protein accretion in muscle cells. These effects are thought to be mediated through the type-I IGF receptor although a role for the type-II IGF receptor cannot be ruled out, since it has been found in most cells studied so far. Current evidence suggests that the chicken does not have a type-II IGF receptor and therefore provides a good model to study the function of IGF peptides. We have compared the effects of insulin and insulin-like growth factors on DNA synthesis with the binding of these peptides to receptors in primary chicken muscle satellite cells. Human IGF-I (hIGF-I), hIGF-II and porcine insulin increased thymidine incorporation into DNA by threefold in muscle satellite cells prepared from neonatal chickens. IGF-I and -II were almost equipotent, with half-maximum effective concentrations of 10 micrograms/l, and were 1000-fold more potent than insulin. A combination of maximum effective concentrations of all three peptides was not additive, suggesting that their effect was mediated by the same receptor. Receptor binding studies on satellite cells demonstrated the presence of specific IGF receptors. Human IGF-I inhibited the binding of 125I-labelled hIGF-I with a much higher potency than insulin, as usually observed for a type-IIGF receptor. However, unlabelled hIGF-II exhibited a higher potency than hIGF-I in displacing 125I-labelled hIGF-I. Affinity cross-linking of 125I-labelled hIGF-I and -II, followed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, showed that hIGF-I and -II bound to a receptor with the structural characteristics of a type-I IGF receptor and confirmed the lack of a type-II IGF receptor in these cells. The concentrations of IGF-I, -II and insulin required for biological action and to displace 125I-labelled hIGF-I binding were similar, and support the hypothesis that their effects on proliferation were mediated exclusively through a type-I IGF receptor.

Animals↗
PubMed1991

Regulation of DNA synthesis in chicken adipocyte precursor cells by insulin-like growth factors, platelet-derived growth factor and transforming growth factor-beta.

Adipose tissue growth can occur by both hypertrophy and hyperplasia. The capacity for adipocyte hyperplasia in vivo resides in a population of fibroblast-like adipocyte precursor cells but the regulation of the proliferation of these cells by growth factors has not been well characterized. This study was designed to determine the effects of the insulin-like growth factors (IGF-I and IGF-II), platelet-derived growth factor (PDGF) and transforming growth factor-beta 1 (TGF-beta 1) added alone or together on the proliferation of primary adipocyte precursor cells in vitro. Adipocyte precursor cell proliferation measured by [3H]thymidine incorporation into DNA was stimulated by all of these growth factors and was particularly marked with PDGF. IGF-I or IGF-II added together with TGF-beta 1 produced a greater than additive response and the effect of PDGF was synergistic with that of IGF-I at certain concentrations. Stimulation of proliferation of some cell types by TGF-beta has been linked to the secondary production of PDGF but the evidence we have suggests that this is unlikely in chicken adipocyte precursors. DNA synthesis in response to TGF-beta 1 required only a short exposure to the peptide, and conditioned medium from chicken adipocyte precursor cells previously exposed to TGF-beta had no effect on DNA synthesis when added to fresh batches of cells. Addition of TGF-beta 1 together with PDGF produced a synergistic effect whereas an additive effect would be expected if PDGF mediated the effect of TGF-beta 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1990

Stimulation of insulin-like growth factor I production in primary cultures of chicken hepatocytes by chicken growth hormone.

Extracts of conditioned media from primary cultures of chicken hepatocytes stimulated [3H]thymidine incorporation into chick embryo fibroblasts demonstrating that the cells released mitogen(s) into the medium. There was also a simultaneous release of insulin-like growth factor I (IGF-I) immunoreactivity into the medium. Acid chromatography of freeze-dried extracts of conditioned media by high performance gel permeation chromatography demonstrated that IGF-I immunoreactivity eluted in a major peak with a molecular weight of 7500 Da and a minor peak with a molecular weight of 55,000 Da. The release of IGF-I immunoreactivity was increased by pituitary-derived chicken growth hormone (cGH) in a dose-dependent manner with half-maximum stimulation occurring at a cGH concentration of 40 ng/ml and maximum stimulation at cGH concentrations greater than 800 ng/ml. These results demonstrate that cultured chicken hepatocytes produce IGF-I and that this can be stimulated by cGH in vitro.

Animals↗
PubMed1990

The ageing hypothalamo-neurohypophysial system. An analysis of the neurohypophysis in normal hydration, osmotic loading and rehydration.

Age-associated changes in the structure and function of the neurohypophysis may contribute to the decreased ability to conserve water in older animals. We investigated the neurohypophyses of 6 and 28-month-old male mice using radioimmunoassay and quantitative morphological techniques. The dry-weight and volume of the neurohypophysis increased significantly with age but the quantity of vasopressin in the gland remained constant. Oxytocin levels decreased with age. A quantitative morphological analysis was performed on the compartments of the neurohypophysis from male mice of 6 and 28 months of age which were either normally hydrated, osmotically loaded, or osmotically loaded and rehydrated. The absolute volumes of the axon endings, swellings, their constituent organelles and the axon terminals containing degenerating subcellular components were determined. The design of the analysis allowed us to examine both age-related changes and statistical interactions between the age of the animal and the behaviour of a variable during the osmotic loading/rehydration phase of the experiment. There was a significant age-related reduction in the volume of the neurohypophysis occupied by the endings and swellings. The diameters of the neurosecretory granules found in the endings were significantly smaller than those in the swellings in both age groups but the size difference was greater in the young animals. Dehydration and subsequent rehydration of old male mice leads to extensive re-modelling of the neurohypophysial compartments and subcellular organelles to the configuration found in the adult animal.

Aging↗
PubMed1990

Biological activity of insulin-like growth factor-I purified from chicken serum.

This study describes a rapid purification of insulin-like growth factor-I from chicken serum and the immunological, biological and receptor binding activity of the peptide. It was purified after initial extraction, by cation exchange chromatography, hydrophobic interaction chromatography and reverse phase chromatography up to 1.4 x 10(6)-fold with an overall yield ranging from 10-30%. The N-terminal amino acid sequence was the same as predicted from the nucleotide sequence of a chicken IGF-I cDNA and the partial sequence obtained from a previously reported purification. The material was both immunologically and biologically active. It had a 50% potency compared to human IGF-I in a radioimmunoassay using an antiserum raised against human IGF-I, stimulated the incorporation of [3H]-thymidine into DNA in cultured chick embryo myoblasts with a half-maximum effective dose of 5 ng/ml and displaced [125I]-labelled human IGF-I and IGF-II from binding sites in microsomal membranes prepared from both the chicken liver and the lactating rabbit mammary gland in a dose dependent manner.

Amino Acid Sequence↗
PubMed1990

Haemodynamic and neurohumoral responses in elderly patients with postural hypotension.

Haemodynamic and neurohumoral responses to head-up tilt were measured in 28 elderly patients with postural hypotension (EPPH) and 12 healthy elderly subjects (HE). There were no differences in catecholamines between the groups and only noradrenaline increased on tilt (P less than 0.001). Plasma renin activity and aldosterone were similar in HE and EPPH in the supine and tilt positions. In both groups vasopressin increases (P = 0.032), and plasma volume decreases were the same (P = 0.673). Supine EPPH had higher heart rates (P = 0.019) but similar cardiac indices (P = 0.621). Both had similar changes on tilting (P = 0.975 and P = 0.341). Stroke volume decrease was higher in HE (35%) than EPPH (23%; P less than 0.001). HE showed an increase in peripheral resistance on tilting with no change in EPPH (P = 0.005). EPPH had larger coefficients of variation for all variables. The differences in haemodynamic responses and the similarity of neurohumoral responses during tilting suggest end-organ failure in EPPH with individual variations. Postural hypotension in old age is not a single entity.

Aged↗
PubMed1990

Recombinant transforming growth factor type beta 3: biological activities and receptor-binding properties in isolated bone cells.

We have recently cloned the cDNA for transforming growth factor type beta 3 (TGF-beta 3), a new member of the TGF-beta gene family. We examined the biological effects of recombinant TGF-beta 3 protein in osteoblast-enriched bone cell cultures. In this report we demonstrate that TGF-beta 3 is a potent regulator of functions associated with bone formation, i.e., mitogenesis, collagen synthesis, and alkaline phosphatase activity. In a direct comparison between TGF-beta 3 and TGF-beta 1, TGF-beta 3 appeared to be three- to fivefold more potent than TGF-beta 1. Our cross-linking experiments with iodinated TGF-beta showed that in osteoblast-enriched bone cell cultures, both TGF-beta 3 and TGF-beta 1 associated with the same three cell surface binding sites. Scatchard analysis of receptor competition studies indicated the presence of high-affinity binding sites for TGF-beta 3 in the picomolar range. TGF-beta 3 showed an approximately fourfold-higher apparent affinity than TGF-beta 1 in overall binding.

Alkaline Phosphatase↗
PubMed1990

Insulin-like growth factor receptors in chicken liver membranes: binding properties, specificity, developmental pattern and evidence for a single receptor type.

Two distinct receptors for the insulin-like growth factors (IGF-I and IGF-II) have been identified in mammalian tissues, but so far only a receptor structurally related to the type I receptor has been identified in chicken embryonic tissues. This study was designed to characterize binding sites for IGF peptides in chicken liver microsomal membranes prepared from hatch to 10 weeks of age which is the period of most rapid growth. Binding of both human (h) IGF-I and hIGF-II was displaceable by either peptide and exhibited similar pH, time and temperature dependency. Human IGF-II was more potent than hIGF-I in competing for the binding of the iodinated ligands with half-maximum effective concentrations of 3-5 micrograms/l and 7-13 micrograms/l respectively. Porcine insulin was also a potent competitor. Affinity cross-linking studies, followed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis under reducing conditions demonstrated that both IGF peptides were linked to a protein with a molecular weight of about 130,000 Da characteristic of the alpha-subunit of the type I receptor. There was no evidence for the presence of a type II receptor similar to that found in mammals. Specific binding of both peptides was low on the day of hatch, increased about threefold by day 3 of age and remained high for the first 3 weeks of life before returning to a lower steady state level up to 10 weeks of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1990

Purification and biological activity of a single charge isomer of pituitary-derived chicken growth hormone.

The chicken pituitary gland contains a number of naturally occurring, developmentally regulated forms of GH which have identical molecular weights but differ in their isoelectric points. In order to characterize their biological properties, each must be separated from non-GH proteins and other forms of GH. Chickens GH (cGH) was separated from other pituitary proteins by immunoaffinity chromatography using an anti-GH monoclonal antibody covalently linked to Sepharose 4B. The cGH eluted from this column as a single peak and migrated as a single band during sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), but showed multiple bands on isoelectric focussing. This material was chromatographed on a high-performance cation exchange column, and separation of charge isomers was monitored by a combination of isoelectric focussing and immunoblotting. Chicken GH eluted from this column in two distinct peaks. The minor peak (cGH P1) contained an isomer with an isoelectric point of 6.86 and the major peak (cGH P2) an isomer with an isoelectric point of 7.52. Each isomer migrated as a single band during isoelectric focussing and SDS-PAGE (Mr = 23,500), and as a single peak during high-performance gel permeation chromatography and reverse-phase high-performance liquid chromatography. Analysis of cGH P2 through 30 cycles in a gas-phase microsequencer gave an amino acid sequence identical to that predicted by translation of the GH complementary DNA nucleotide sequence. This single charge isomer increased the rate of lipolysis in chicken adipose tissue explants by about fourfold and was able to displace 125I-labelled cGH from binding sites in liver membranes with a dissociation constant of about 4 nmol/l.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1989

High affinity binding of an N-terminal myristoylated p60src peptide.

N-Myristoyl and non-myristoyl peptides corresponding to the N terminus of p60src were used to examine whether N-myristoylation facilitates the binding of p60src to specific protein sites at the plasma membrane. We discovered high affinity protein acceptor sites (Kd = 2.7 nM) to a 15-amino acid N-myristoylated N-terminal p60src peptide in red cell membrane vesicles. Binding was not competed by the non-myristoylated analog of the peptide nor by shorter N-myristoyl src peptides and peptides homologous to the N terminus of other N-myristoylated proteins. Binding was not evident after treatment of vesicles with proteolytic enzymes. Raising the salt concentration of the buffer to 50 mM NaCl caused an apparent inhibition of binding. However, no significant effect of salt was observed on the off-rate of bound ligand under these conditions. The results indicate the existence of N-myristoyl-dependent p60src protein acceptor sites at or near the plasma membrane/skeleton interface of red cells which could be responsible for the localization of p60src to this region and may represent new regulatory components for p60src-mediated tyrosine kinase activity.

Amino Acid Sequence↗
PubMed1989

Chemical characterization of p17gag from human immunodeficiency virus as an N-terminally myristoylated protein.

The N-terminal p17gag protein of the human immunodeficiency virus has been shown to incorporate radioactivity following labelling of infected cell lines with [3H]myristic acid. We investigated p17gag to determine whether the incorporated radioactivity was the consequence of N-terminal myristoylation. The virus was purified by density gradient centrifugation after labelling chronically infected H9 cells with [3H]myristic acid. The p17gag was isolated by immunoprecipitation and subjected to partial acid hydrolysis. [3H]Myristoylglycine generated by the hydrolysis was derivatized to 4-(p-nitrobenzylidene)-2-tridecanoyloxazol-5-one and identified against a co-eluting, derivatized, unlabelled N-myristoylglycine standard by reverse-phase high-performance liquid chromatography. This study unequivocally demonstrates that p17gag is an N-myristoylated protein.

Cell Line↗
PubMed1989

The effect of food restriction on circulating insulin-like growth factor-I in mice divergently selected for high or low protein or fat to body mass ratios.

1. Plasma insulin-like growth factor-I (IGF-I) was measured in mice divergently selected for high and low lean tissue gain or high and low fat to body weight ratio, both before and after fasting and refeeding. 2. Selection for high lean tissue resulted in increased body weight and a higher basal IGF-I concentration at 10 weeks of age. 3. Selection resulting in a difference in fatness had no effect on IGF-I concentration. 4. Circulating IGF-I decreased more rapidly in response to 24 hr food withdrawal in growing (5-week-old) than in almost fully grown (10-week-old) animals from all lines.

Adipose Tissue↗
PubMed1989

Insulin-like growth factor-I binding proteins in serum from the domestic fowl.

This investigation describes the presence of insulin-like growth factor-I (IGF-I) binding proteins in chicken serum. Whole blood was collected from broiler chickens of 7-9 weeks of age and analysed for binding proteins after gel permeation chromatography under both neutral and acidic conditions, and by polyacrylamide gel electrophoresis in the presence of 12.5% sodium dodecyl sulphate (SDS-PAGE). When serum was chromatographed under neutral conditions, about 70% of the IGF-I immunoreactivity was associated with a large protein complex (Mr = 150,000) and 20-25% was associated with an intermediate-sized protein complex (Mr = 45,000). Up to 6% of the serum IGF-I immunoreactivity was eluted in a fraction which corresponded to an Mr of about 7500 and was presumably free IGF-I. Chromatography under acidic conditions dissociated the IGF-I/protein complexes and revealed the presence of an acid-stable binding protein (Mr = 50,000-60,000). After analysis of serum by SDS-PAGE, three monomeric IGF-I binding proteins (Mr = 28,800, 33,200 and 40,700) were detected. The largest monomer (Mr = 40,700) is probably the binding protein component of the intermediate-sized IGF-I/protein complex. The relationship between the other monomers and both the large IGF-I/protein complex and the acid-stable binding protein is not known. Although the pattern of binding proteins in chicken serum is similar to that observed in mammals, a major difference is the presence of up to 6% of the serum IGF-I immunoreactivity in an unbound form.

Animals↗