Generation of epitope-specific antibodies to rat GHBP in the sheep using an interspecies switching strategy involving site-directed mutagenesis of ovine GHBP

Site-directed antibodies to the growth hormone receptor could be potentially useful as growth hormone mimics but, in previous attempts, we found that antisera generated using peptides derived from growth hormone receptor sequences failed to recognize the intact protein. As an alternative approach to this problem, we have now adopted a strategy of epitope-switching between rat and ovine growth hormone receptors to produce rat epitopes in the correct structural context. Using site-directed mutagenesis, we altered the two dominant linear epitopes in the ovine growth hormone binding protein to the analogous sequences in rat growth hormone binding protein. Site A, between Thr28 and Leu34, is equivalent to epitope 1 in ovine growth hormone binding protein and site B, between Ser121 and Asp124, corresponds to epitope 5. The wild-type ovine growth hormone binding protein and the two mutant proteins were bacterially expressed, refolded and, following purification by metal-chelate affinity chromatography, used to raise antisera in sheep. We showed using RIA, in which wild-type ovine growth hormone binding protein acted as a competitor for the binding of rat growth hormone binding protein, that only the site A mutant protein elicited a specific anti-rat growth hormone binding protein response. This was confirmed in subsequent RIA studies using the antiserum to the site A mutant protein in which only peptides corresponding to the site A sequences in mutant ovine growth hormone binding protein and rat growth hormone binding protein, but not that in wild-type ovine growth hormone binding protein, were able to act as competitors for rat growth hormone binding protein. Antibodies specific for rat growth hormone binding protein could be separated from the antiserum to the site A mutant protein by means of affinity chromatography using immobilized wild-type ovine growth hormone binding protein to remove antibodies which cross-reacted with the ovine protein. The work lays the foundations for further studies in which the biological effects of these antibody fractions will be investigated and demonstrates an approach with general applicability in the production of antibodies directed towards specific epitopes on protein molecules.

Characterization of the IGF axis in a rat liver-derived epithelial cell line

We have used the techniques of chemical cross-linking, Western blotting and immunoprecipitation-ligand blotting to demonstrate that insulin-like growth factor binding protein-2 (IGFBP-2) is associated with plasma membranes of an epithelial cell line derived from rat liver as well as being secreted into the medium by these cells. We demonstrate that these cells secrete IGF-I, but not IGF-II into serum free medium. Evidence from signalling, cell proliferation and cross-linking experiments indicate that these cells also express cell surface IGF-I receptors. Dose-response experiments indicate an enhanced biological activity of the IGF-I analogue des (1-3) IGF-I compared to wild-type IGF-I in both acute signalling experiments and longer-term (24 h) mitogenic assays. As this IGF-I analogue has lower affinity for IGFBPs, we believe that in this cell culture system, activity of IGF-I may be attenuated in the long and short term by the accumulation of IGFBP-2 in conditioned medium and by the presence of IGFBP-2 associated with the cell membrane and/or ECM.

Effects of complexation with in vivo enhancing monoclonal antibodies on activity of growth hormone in two responsive cell culture systems

We describe the properties of three monoclonal antibodies (MAbs) to ovine GH, two of which have previously been shown to enhance, in vivo, the biological activity of bovine and ovine growth hormone. We have examined the effects of these MAbs on GH activity in two appropriate GH-responsive cell culture systems, investigating both acute signalling effects (Janus-activated kinase (Jak)-2 tyrosine phosphorylation -5 min) and longer-term (MTT-formazan production -24 h) effects of hormone-antibody complexes. In the 3T3-F442A pre-adipocyte cell line (which has been demonstrated to be GH responsive), we show that complexation of recombinant bovine (rb) GH with either of the two enhancing anti-ovine GH MAbs (OA11 and OA15) and the non-enhancing MAb, OA14, attenuates the ability of GH to stimulate tyrosine phosphorylation of Jak-2 at a 5-min time point. Using the mouse myeloid cell line, FDC-P1, stably transfected with the full-length ovine GH receptor (oGHR), we demonstrate that rbGH causes a dose-dependent increase in MTT-formazan production by these cells. Further, we demonstrate that OA11 and OA14, but not OA15, cause a decrease in this stimulatory activity of rbGH over a hormone concentration range of 5-50 ng/ml at both 24 and 48 h. We conclude that the different in vitro activities of the two in vivo enhancing MAbs are most probably related to the time-courses over which these two assays are performed, and also to the relative affinities between antibody, hormone and receptor. In addition, the in vitro inhibitory activity of the enhancing MAb OA11 in both short- and long-term bioassay lends further support to an exclusively in vivo model for MAb-mediated enhancement of GH action.

Binding and signalling properties of a growth hormone enhancing monoclonal antibody

We have used a sequential, qualitative biosensor based assay to demonstrate that OA15, a monoclonal antibody which enhances in vivo the activity of bovine growth hormone (bGH) does not disrupt the interaction between bGH and its cognate receptor (as represented by recombinant bovine GH binding protein -rbGHBP). We have confirmed this using a classical cell-based radio-receptor assay with the GH-responsive mouse pre-adipocyte cell line 3T3-F442A. The fact that OA 15 binding to bGH still allows hormone to interact with its receptor, allows us to test the hypothesis that there is any amplification of signalling events following hormone-MAb treatment of 3T3-F442A cells. We have used as a reporter of GH activity the rapid stimulation of JAK-2 tyrosine phosphorylation which is a critical first step in GH signalling events. We demonstrate that binding of rbGH by OA15 attenuates hormone stimulation of JAK-2 tyrosine phosphorylation. We conclude that although OA15 does not disrupt GH-GH receptor (GHR) interactions it does interfere with subsequent GH activity at the molecular and cellular level. We further speculate therefore that the biological enhancing activity of this antibody is most likely due to an in vivo effect as presentation of antibody-hormone complexes to a GH-target cell inhibits hormone activity.

Amino acids within the extracellular matrix (ECM) binding region (201-218) of rat insulin-like growth factor binding protein (IGFBP)-5 are important determinants in binding IGF-I

The highly conserved N-and C-terminal domains of IGFBPs are believed to participate in IGF binding, but only recently have some of the critical residues in the IGFBP sequence involved in ligand binding been identified. Here we describe two highly conserved amino acids in the C-terminal domain of rat IGFBP-5 that are involved in binding IGF-I. Site-directed mutagenesis was used to produce two mutants, G203K and Q209A, of rIGFBP-5. Relative to wild-type rIGFBP-5, an 8-fold reduction in affinity for human IGF-I was found for recombinant G203K protein in both IGF-I ligand blots and solution phase ligand binding assays, and a 7-and 6-fold reduction for Q209A respectively. This shows that Gly203 and Gln209 in IGFBP-5 are important determinants in binding IGF-I, and due to their complete conservation in all IGFBP sequences, we suggest that they are likely to be involved in binding IGF-I in all six binding proteins. In addition, these two non-basic residues lie within the ECM binding region (201-218) of IGFBP-5, demonstrating that the C-terminus contains partially overlapping IGF-I and ECM binding sites. We therefore propose that heparin binding to basic amino acids in IGFBP-5 between 201-218 may physically occlude subsequent interaction between IGF-I and Gly203/Gln209, and that this may explain previous work of others showing reduced affinity of ECM bound IGFBP-5 for IGF-I.

Identification of novel sites in the ovine growth hormone receptor involved in binding hormone and conferring species specificity

Using site-directed mutagenesis we mutated the extracellular domain of the ovine growth hormone receptor (oGHR) to the corresponding amino acids in the rat GHR at two different sites: site A is between Thr28 and Leu34 and represents a major immunogenic epitope, while site B is between Ser121 and Asp124 and is involved in the interaction of the human GHR with growth hormone (GH). Native and mutant receptors were bacterially expressed and refolded, and then RIA and GH-binding assays were carried out on the purified recombinant proteins. Mutations at the N-terminal site A of oGHR led to greatly reduced binding to bovine GH and, in addition, to significant loss of recognition by a polyclonal antiserum to bovine GHR which recognizes site A as a major epitope. The crystal structure of human GH bound to human GHR did not resolve this extreme N-terminal region of the receptor but our data indicate that the N-terminal loop undertakes a 180 degrees turn bringing it into close proximity to the hormone-binding domain in a fashion analogous to the prolactin receptor. A fourfold decrease in affinity for binding bovine GH was also observed after mutation of site B. However, this change from the ovine sequence to the equivalent sequence in the rat GHR at site B caused a 2.4-fold increase in the affinity of binding to rat GH. Taken together, the changes in binding affinity of the site-B mutant for rat and bovine GH demonstrate that this site is involved in conferring species specificity for binding GH.

Workforce dilemmas: a comparison of staffing in a generalist and a specialist intensive care unit

Intensive care units are arguably one of the most costly resources a hospital has to maintain in terms of nursing staff, skills and technology. Given that the Government's agenda on quality remains one of obtaining cost-effective healthcare, it is imperative that nursing managers consider the implications of the new policy shift for how they currently provide services. The purpose in this paper is to compare the different staffing levels adopted by managers in generalized and neurosurgical intensive care in an acute hospital trust. The dilemmas facing managers making staffing decisions without any definitive guidelines for resourcing these specialized units are examined.

Immunological manipulation of body composition

Hormonal growth promoters (e.g., growth hormone [GH], beta-adrenergic agonists, steroids), which improve growth rate and/or lean:fat ratios in the carcass, have received considerable adverse publicity and are either banned or have no licence for their use in the EC. This has led to the development of a number of techniques, involving the use of antibodies, aimed at regulating metabolic processes involved in determining growth and body composition. A different approach to the problem of excess fat deposition involves the use of antibodies directed against the plasma membranes of adipocytes in order to elicit their destruction and thereby limit the capacity for fat storage. This technique has been demonstrated in rats, sheep and pigs in both passive and active immunisation techniques. This promising approach is, however, limited by the lack of a commercially suitable vaccine. The identification of individual membrane proteins that are antigenic has been achieved and this affords the prospect of producing recombinant DNA-derived vaccines. Whether these new approaches will be perceived as acceptable to the general public remains a serious concern and a potential limitation to their development as many would-be sponsors withdraw their support for research in these areas.

A case of hyperzincemia with functional zinc depletion: a new disorder?

We report the case of an 1l-y-old boy with a plasma Zn concentration greater than 200 micromol/L, but with symptoms consistent with Zn deficiency. He has had hepatosplenomegaly, rashes, stunted growth (<3rd centile), anemia, and impaired immune function since infancy. He also has vasculitis and osteoporosis. A plasma Zn-binding protein has been separated and characterized by a combination of size exclusion and ion exchange chromatography and electrophoretic studies and by immunologic methods. Antibodies to the partially purified protein have been raised in rabbits. Size exclusion chromatography shows that Zn is bound to a protein with a mass 110000-300000 kD. Electrophoretic and mass spectrometry studies suggest that the protein may be composed of several subunits. One component of the isolated protein reacts with antiserum to alpha2-macroglobulin; immunoprecipitation studies confirm that the protein is not alpha2-macroglobulin or a histidine-rich glycoprotein. Kinetic studies of zinc metabolism in the patient and his mother with stable Zn isotopes show the presence of increased exchangeable Zn, with a rapid flux from plasma to a stable pool. Liver and muscle Zn and Cu concentrations are raised, but with no abnormal liver histology. Immunoreactive metallothionein in the liver is increased. We suggest that this boy may suffer from a previously unrecognized inborn error of Zn metabolism causing symptomatic zinc deficiency.

Enhancement of FSH bioactivity in vivo using site-specific antisera

The ability of site-specific antipeptide antisera to enhance the biological activity of ovine FSH (oFSH) in vivo was investigated using hypopituitary Snell dwarf mice. These animals were shown to respond to increasing doses of oFSH (3.3-90 micrograms/day), administered in two daily injections over a 5-day treatment period, in a highly significant dose-dependent fashion. The responses measured were increases in uterine weight, ovarian weight and the index of keratinisation in vaginal smears. The dose-dependent response to oFSH confirmed the suitability of this animal model for these investigations and suggested the suboptimal dose of oFSH (20 micrograms/day) for use in enhancement studies. Five peptides derived from the beta subunit of bovine FSH (bFSH) (A, residues 33-47; B, 40-51; C, 69-80; D, 83-94; E, 27-39) were used to generate polyclonal antipeptide antisera. Of these peptides, only A and B produced an antiserum (raised in sheep) capable of recognising 125I-bFSH in a liquid phase RIA. Antisera prepared against peptide A or peptide B were found to significantly enhance the biological activity of 20 micrograms oFSH/day over a 5-day treatment period. The response to antipeptide antisera alone did not differ significantly from that observed in PBS-injected control animals, neither did the response to FSH alone differ from that observed in animals treated with FSH plus preimmune serum. Thus the enhanced responses are dependent upon the presence of FSH plus antipeptide antiserum. Peptides A and B are located in a region thought to be involved in receptor recognition, this may have implications for the mechanism underlying this phenomenon and/or the structure/function relationships of FSH. That FSH-enhancing antisera can be generated by immunisation of animals with peptides A and B suggests that it may be possible to develop these peptides as vaccines capable of increasing reproductive performance, such as ovulation rate. The high degree of sequence homology between ovine, bovine and porcine (and to a lesser extent human and equine) FSH in the region covered by peptides A and B suggests that these peptides could also be used to promote and regulate ovarian function in all of these species.

The politics of collaboration as viewed through the lens of a collaborative nursing research project

Collaborative research has much to offer nursing. However, the collaborative research process is fraught with issues arising from the 'politics of collaboration'. Such politics operate at the individual and institutional levels and can have debilitating effects on the research enterprise if they are not dealt with. This paper explores what is meant by collaboration and the politics of collaboration. Drawing on a critical perspective, it uses Brookfield's themes of impostorship, cultural suicide and roadrunning as the theoretical framework for the analysis. The paper uses an actual collaborative research project to ground the discussion provided.

Growth hormone stimulates the secretion of insulin-like growth factor binding protein-2 (IGFBP-2) by monolayer cultures of sheep costal growth plate chondrocytes

Using monolayer cultures of costal chondrocytes established from four week old Clun Forest lambs, we have demonstrated that, under serum free conditions the cells release three IGFBPs (32, 29 and 21 kDa) into the medium. The most abundant of these--the 32 kDa BP--was shown to be IGFBP-2 by Western blotting. Furthermore we demonstrate that the levels of IGFBP-2 in conditioned medium are acutely increased (6, 12 and 24 h time points) following treatment of cells with bovine GH (1-100 ng/ml). In a parallel set of experiments, using ovine fibroblasts (derived from dermis) we show that IGFBPs of Mr 32, 29 and 21 kDa are also secreted by this cell type. However the relative abundance of these BPs differed from that seen in the chondrocyte cultures, with the 21 kDa species now the most abundant. In addition, prolonged exposure of autoradiographs indicated that fibroblasts secreted a higher Mr IGFBP (most probably ovine BP-3) that was not detected in any of our chondrocyte cultures. Most significant however was the demonstration that bGH did not dramatically affect the levels of IGFBPs in fibroblast cell cultures. We conclude that GH stimulates BP-2 production from chondrocytes and this is a cell-type specific effect in as much as it is not replicated in cultures of dermal fibroblasts.

Objects, decision considerations and self-image in men's and women's impulse purchases

Current theories in economics, marketing, and psychology fail to explain underlying reasons for impulse buying and, crucially, why certain goods (e.g., clothes) are bought impulsively more than others (e.g., basic kitchen equipment). We propose and examine a social psychological model, which predicts that people impulse buy to acquire material symbols of personal and social identity. We predict that consumers will differ systematically in the goods they buy on impulse, and in their reasons for doing so, depending on their attitudes towards shopping, and also along important social categories, such as gender. Specifically, our theoretical model-drawing on a social constructionist model of material possessions (e.g., Dittmar, 1992) and symbolic self-completion theory (e.g. Wicklund and Gollwitzer, 1982)-leads to three sets of hypotheses: (i) some consumer durables are more likely to be bought on impulse than others, and there may be gender differences in object choices, (ii) differences will emerge in the buying considerations (e.g., functional, emotional, symbolic) that are used for impulse and planned buying, and (iii) magnitude of self-discrepancies will predict relative impulse buying frequency and the buying considerations used, if the individual uses consumption as a self-completion strategy. These predictions were expected to hold particularly strongly for individuals high in compulsive shopping tendencies. We test our model in a questionnaire study with a sample of British consumers (n = 61). The results lend support to all three sets of hypotheses. The implications of these findings are discussed with respect to economic and consumer theory, and the treatment offered to the increasing number of 'addicted' shoppers.

An immobilised peptide array identifies antibodies to a discontinuous epitope in the extracellular domain of the bovine growth hormone receptor

Using an array of overlapping decapeptides representing the extracellular domain of the bovine (b) growth-hormone receptor (GHR) we have mapped the continuous, dominant epitopes defined by five rabbit and one guinea pig polyclonal antisera to recombinant bovine growth-hormone-binding protein (rbGHBP). We report that six major epitopes are identified by these antisera and that these largely occur in areas of non-ordered secondary structure, although there is some contribution from the extensive beta-sheet structure of GHBP. Similar to our previously described studies for growth hormone (GH), we have again found slight differences between animals in the exact location of these epitopes. Using peptide-affinity chromatography we have isolated a population of antibodies reactive with epitope 1 (the N-terminal epitope:GHBP residues 21-38). Analysis of these antibodies by further peptide affinity chromatography and competitive radioimmunoassay experiments indicated cross-reactivity of epitope-1-specific antibodies with epitope 4 (in the interdomain hinge region of the GHBP:residues 111-126). We suggest that, although separate in the primary structure of the molecule, the tertiary fold exhibited by GHBP may bring into close proximity areas of sequence representing epitope 1 and epitope 4 such that they represent a conformational epitope. Under these conditions our experiments indicate that peptides 1 and 4 may represent partial functional epitopes for this antibody population and consequently demonstrate that this approach may be useful in describing discontinuous epitopes.

Determination of the structure of the N-terminal splice region of the cyclic AMP-specific phosphodiesterase RD1 (RNPDE4A1) by 1H NMR and identification of the membrane association domain using chimeric constructs

A 25-residue peptide representing the membrane targeting N-terminal splice region of the cyclic AMP phosphodiesterase RD1 (RNPDE4A1) was synthesized, and its structure was determined by 1H NMR. Two independently folding helical regions were identified, separated by a highly mobile "hinge" region. The first helical region was formed by an N-terminal amphipathic alpha-helix, and the second consisted of multiple overlapping turns and contained a distinct compact, hydrophobic, tryptophan-rich domain (residues 14-20). Chimeric molecules, formed between the N-terminal region of RD1 and the soluble bacterial protein chloramphenicol acetyltransferase, were used in an in vitro system to determine the features within the splice region that were required for membrane association. The ability of RD1-chloramphenicol acetyltransferase chimera to become membrane-associated was not affected by deletion of any of the following regions: the apolar section (residues 2-7) of the first helical region, the polar part of this region together with the hinge region (residues 8-13), or the polar end of the C-terminal helical region (residues 21-25). In marked contrast, deletion of the compact, hydrophobic tryptophan-rich domain (residues 14-20) found in the second helical region obliterated membrane association. Replacement of this domain with a hydrophobic cassette of seven alanine residues also abolished membrane association, indicating that membrane-association occurred by virtue of specific hydrophobic interactions with residues within the compact, tryptophan-rich domain. The structure of this domain is well defined in the peptide, and although the region is helical, both the backbone and the distribution of side chains are somewhat distorted as compared with an ideal alpha-helix. Hydrophobic interactions, such as the "stacked" rings of residues Pro14 and Trp15, stabilize this domain with the side chain of residue Leu16 adopting a central position, interacting with the side chains of all three tryptophan residues 15, 19, and 20. These bulky side chains thus form a hydrophobic cluster. In contrast, the side chain of residue Val17 is relatively exposed, pointing out from the opposite "face" of the peptide. Although it appears that this compact, tryptophan-rich domain is responsible for membrane association, at present the target site and hence the specific interactions involved in membrane targeting by the RD1 splice region remain unidentified.

The effect of non-insulin-dependent diabetes mellitus and obesity on glucose transport and phosphorylation in skeletal muscle

Defects of glucose transport and phosphorylation may underlie insulin resistance in obesity and non-insulin-dependent diabetes mellitus (NIDDM). To test this hypothesis, dynamic imaging of 18F-2-deoxy-glucose uptake into midthigh muscle was performed using positron emission tomography during basal and insulin-stimulated conditions (40 mU/m2 per min), in eight lean nondiabetic, eight obese nondiabetic, and eight obese subjects with NIDDM. In additional studies, vastus lateralis muscle was obtained by percutaneous biopsy during basal and insulin-stimulated conditions for assay of hexokinase and citrate synthase, and for immunohistochemical labeling of Glut 4. Quantitative confocal laser scanning microscopy was used to ascertain Glut 4 at the sarcolemma as an index of insulin-regulated translocation. In lean individuals, insulin stimulated a 10-fold increase of 2-deoxy-2[18F]fluoro-D-glucose (FDG) clearance into muscle and significant increases in the rate constants for inward transport and phosphorylation of FDG. In obese individuals, the rate constant for inward transport of glucose was not increased by insulin infusion and did not differ from values in NIDDM. Insulin stimulation of the rate constant for glucose phosphorylation was similar in obese and lean subjects but reduced in NIDDM. Insulin increased by nearly twofold the number and area of sites labeling for Glut 4 at the sarcolemma in lean volunteers, but in obese and NIDDM subjects translocation of Glut 4 was attenuated. Activities of skeletal muscle HK I and II were similar in lean, obese and NIDDM subjects. These in vivo and ex vivo assessments indicate that impaired glucose transport plays a key role in insulin resistance of NIDDM and obesity and that an additional impairment of glucose phosphorylation is evident in the insulin resistance of NIDDM.

SH2 domain protein interaction and possibilities for pharmacological intervention

SH2 domain containing proteins play a key role in the process of intracellular transmission of signalling events initiated at the cell surface. As a pre-requisite in the fulfillment of this function, these proteins bind to a variety of phospho-tyrosine (pY) containing target molecules. Delineation of these binding sites as essentially short linear peptides (both structurally and functionally) has led to the suggestion that the activity of these signalling complexes may be manipulated by the development of relatively simple peptide reagents. This review examines the range of possibilities open on this approach and the extent to which positive results have already been realised.

Localisation of metallothionein isoform mRNAs in rat hepatoma (H4) cells

The localisation of metallothionein isoform mRNAs in rat hepatoma (H4) cells was investigated using two approaches, namely Northern hybridisation of total RNA extracted from free, cytoskeletal-bound and membrane-bound polysomes isolated by a sequential detergent/salt extraction procedure and in situ hybridisation. The cytoskeletal-bound polysomes were enriched in metallothionein-I (MT-I) and c-myc mRNAs but showed a significantly lower enrichment in MT-II mRNA. These findings indicate that the MT-I mRNA is localised to the cytoskeleton during translation. In situ hybridisation using a biotin-labelled oligonucleotide probe revealed a predominantly perinuclear localisation for the MT-I mRNA.

Glucocorticoids regulate the secretion of a 21kDa-IGF-binding protein by sheep adipose tissue explants

Using a solution phase assay we have demonstrated that sheep adipose tissue explants secrete insulin-like growth factor binding proteins (IGFBPs) when cultured in serum-free medium over a 24 h period. Further, we demonstrate that secretion of IGFBP(s) is inhibited (up to 50%) by incubation of the cultures in the presence of 10(-8) M dexamethasone. This inhibitory effect is overcome when insulin (10 ng/ml) and ovine growth hormone (100 ng/ml) are incubated together (but not separately) with glucocorticoid. Further characterisation of this IGF binding activity by high performance size exclusion chromatography and Western ligand blot analysis indicated that under our culture conditions sheep adipose tissue explants secrete one predominant 21 kDa IGFBP and it is this BP which is hormonally regulated as described above. We discuss our results in the context of endocrine/paracrine/autocrine control of adipose tissue metabolism and differentiation.

Identification and characterization of the type-IVA cyclic AMP-specific phosphodiesterase RD1 as a membrane-bound protein expressed in cerebellum

An antiserum was generated against a dodecapeptide whose sequence is found at the C-terminus of a cyclic AMP (cAMP)-specific, type-IVA phosphodiesterase encoded by the rat 'dunc-like' cyclic AMP phosphodiesterase (RD1) cDNA. This antiserum identified a single approximately 73 kDa protein species upon immunoblotting of cerebellum homogenates. This species co-migrated upon SDS/PAGE with a single immunoreactive species observed in COS cells transfected with the cDNA for RD1. Native RD1 in cerebellum was found to be predominantly (approximately 93%) membrane-associated and could be found in isolated synaptosome populations, in particular those enriched in post-synaptic densities. Fractionation of lysed synaptosomes on sucrose density gradients identified RD1 as co-migrating with the plasma membrane marker 5'-nucleotidase. Laser scanning confocal and digital deconvolution immunofluorescence studies done on intact COS cells transfected with RD1 cDNA showed RD1 to be predominantly localized to plasma membranes but also associated with the Golgi apparatus and intracellular vesicles. RD1-specific antisera immunoprecipitated phosphodiesterase activity from solubilized cerebellum membranes. This activity had the characteristics expected of the type-IV cAMP phosphodiesterase RD1 in that it was cAMP specific, exhibited a low Km cAMP of 2.3 microM, high sensitivity to inhibition by 4-[3-(cyclopentoxyl)-4-methoxyphenyl]-2-pyrrolidone (rolipram) (Ki approximately 0.7 microM) and was unaffected by Ca2+/calmodulin and low concentrations of cyclic GMP. The phosphodiesterase activities of RD1 solubilized from both cerebellum and transfected COS cell membranes showed identical first-order thermal denaturation kinetics at 50 degrees C. Native RD1 from cerebellum was shown to be an integral protein in that it was solubilized using the non-ionic detergent Triton X-100 but not by either re-homogenization or high NaCl concentrations. The observation that hydroxylamine was unable to cause the release of RD1 from either cerebellum or COS membranes and that [3H]palmitate was not incorporated into the RD1 protein immunoprecipitated from COS cells transfected with RD1 cDNA, indicated that RD1 was not anchored by N-terminal acylation. The engineered deletion of the 25 residues forming the unique N-terminal domain of RD1 caused both a profound increase in its activity (approximately 2-fold increase in Vmax) and a profound change in intracellular distribution. Thus, immunofluorescence studies identified the N-terminal truncated species as occurring exclusively ion the cytosol of transfected COS cells. The cDNA for RD1 thus appears to encode a native full-length type-IVA phosphodiesterase that is expressed in cerebellum.(ABSTRACT TRUNCATED AT 400 WORDS)

Production of insulin-like growth factor binding protein (IGFBP), IGFBP-3 protease, and expression of IGF-I receptors by cells of the sheep immune system

Single-cell suspensions of sheep thymus cells were cultured in serum-free medium with or without polyclonal activators (phytohaemagglutinin or concanavalin A) and the resultant conditioned medium was assayed for insulin-like growth factor binding protein (IGFBP) activity by binding of [125I]IGF-I, using charcoal to separate free from bound. All cultures produced IGFBP but mitogen stimulation significantly increased IGFBP concentrations, indicating production by lymphoid cells. Conditioned medium also degraded recombinant human [125I]IGFBP-3, suggesting IGFBP-3 protease production within the thymus. This degradation was inhibited by several protease inhibitors (phenylmethylsulphonyl fluoride, aprotinin, N-alpha-p-tosyl-L-lysine chloromethyl ketone), suggesting the presence of a serine protease. Cell surface [125I]IGF-I binding was demonstrated on cells from thymus, mesenteric lymph node, peripheral blood mononuclear cells and platelets. The [125I]IGF-I binding to platelets could be inhibited by unlabelled peptides, with relative potencies IGF-I > IGF-II >> insulin. Scatchard analysis of IGF-I competitive binding revealed a Kd of 266 pmol/l and approximately 40 receptor sites per cell. The high-affinity binding of IGF-I and competition by insulin suggested that the [125I]IGF-I binding was to an IGF-I receptor rather than to a membrane-associated IGFBP, to which insulin does not bind. These data provide further support for the role of the IGF-IGFBP axis in the immune system, particularly in relation to the thymus.

Identification of two splice variant forms of type-IVB cyclic AMP phosphodiesterase, DPD (rPDE-IVB1) and PDE-4 (rPDE-IVB2) in brain: selective localization in membrane and cytosolic compartments and differential expression in various brain regions

In order to detect the two splice variant forms of type-IVB cyclic AMP phosphodiesterase (PDE) activity, DPD (type-IVB1) and PDE-4 (type-IVB2), anti-peptide antisera were generated. One set ('DPD/PDE-4-common'), generated against a peptide sequence found at the common C-terminus of these two PDEs, detected both PDEs. A second set was PDE-4 specific, being directed against a peptide sequence found within the unique N-terminal region of PDE-4. In brain, DPD was found exclusively in the cytosol and PDE-4 exclusively associated with membranes. Both brain DPD and PDE-4 activities, isolated by immunoprecipitation, were cyclic AMP-specific (KmcyclicAMP: approximately 5 microM for DPD; approximately 4 microM for PDE-4) and were inhibited by low rolipram concentrations (K1rolipram approximately 1 microM for both). Transient expression of DPD in COS-1 cells allowed identification of an approx. 64 kDa species which co-migrated on SDS/PAGE with the immunoreactive species identified in both brain cytosol and membrane fractions using the DPD/PDE-4-common antisera. The subunit size observed for PDE-4 (approx. 64 kDa) in brain membranes was similar to that predicted from the cDNA sequence, but that observed for DPD was approx. 4 kDa greater. Type-IV, rolipram-inhibited PDE activity was found in all brain regions except the pituitary, where it formed between 30 and 70% of the PDE activity in membrane and cytosolic fractions when assayed with 1 microM cyclic AMP, PDE-4 formed 40-50% of the membrane type-IV activity in all brain regions save the midbrain (approx. 20%). DPD distribution was highly restricted to certain regions, providing approx. 35% of the type-IV cytosolic activity in hippocampus and 13-21% in cortex, hypothalamus and striatum with no presence in brain stem, cerebellum, midbrain and pituitary. The combined type-IVB PDE activities of DPD and PDE-4 contributed approx. 10% of the total PDE activity in most brain regions except for the pituitary (zero) and the mid-brain (approx. 3%. The isolated cDNAs for DPD and PDE-4 appear to reflect transcription products which are expressed in vivo in brain. The unique N-terminal domain of PDE-4 is suggested to target this PDE to membranes in brain. Type-IVB PDEs are differentially expressed in various brain regions, indicating that there are tissue-specific controls on both the expression of the gene and the splicing of its products.

Location of an epitope defined by an enhancing monoclonal antibody to growth hormone: some structural details and biological implications

We have previously shown that a murine monoclonal antibody (MAb OA15) prepared against ovine GH (oGH) can enhance the somatogenic activity of bovine GH (bGH), as determined by increased incorporation of 35SO4(2-) into costal cartilage of hypopituitary Snell dwarf mice in vivo We have now established that MAb OA15 can also enhance the biological activity of oGH and porcine GH (pGH) in vivo. Using multiple pin peptide synthesis techniques a set of overlapping immobilized octamers representing the entire bGH sequence were synthesized and tested for their ability to bind MAb OA15 using an enzyme-linked immunosorbent assay. The pattern of binding showed that OA15 defined a functionally continuous epitope comprising residues 91-102. This region includes the C-terminal end of helix 2 plus a portion of the adjacent loop linking helices 2 and 3. Polyclonal antisera to a synthetic peptide representing this epitope mimicked the ability of MAb OA15 to enhance oGH, bGH, and pGH. Window size analysis showed that the heptapeptide 94-100 (SRVFTNS) represents the minimum unit to retain full recognition of MAb OA15. The fact that pGH, bGH, and oGH have identical sequences in this region also explains the ability of OA15 to both cross-react with and enhance the biological activity of each of these GHs. Replacement net analysis (where each residue in the heptamer is substituted with each of the 19 naturally occurring L-amino acids) demonstrated that residues R95 and T98 are critical for antibody binding and also indicated that the substitution of V96 with I, as found in rat GH, would permit the observed binding of OA15 to this hormone.(ABSTRACT TRUNCATED AT 250 WORDS)

Several insulin-like growth factor-I analogues and complexes of insulin-like growth factors-I and -II with insulin-like growth factor-binding protein-3 fail to mimic the effect of growth hormone upon lactation in the rat

Lactation was suppressed in rats using a combined treatment of bromocriptine (to reduce prolactin concentrations) and a specific antiserum to rat GH administered twice daily for 2 days. When milk production had ceased, as determined by litter weight loss and the absence of milk in the stomachs of pups, attempts were made to reinitiate lactation using prolactin, GH, insulin-like growth factor-I (IGF-I) precomplexed to recombinant human IGF-binding protein-3 (hIGFBP-3) or IGF-I plus IGF-II precomplexed to hIGFBP-3. Despite the fact that all treatments except prolactin led to increases in serum IGFs and IGFBP-3, only prolactin and GH provoked the reinitiation of milk production as determined by increased litter weight gain, milk in the stomach of pups and a significant increase in the weight of the mammary glands. Since the mammary gland has been shown to produce IGFBPs which may inhibit IGF action we also tested three IGF-I analogues, R3-IGF-I, Long-IGF-I and Long-R3-IGF-I. R3-IGF-I has a single amino acid substitution (Glu to Arg) at position 3 whereas Long-IGF-I has a 13 amino acid N-terminal extension. These modifications dramatically reduce the ability of these analogues to bind to IGFBPs although they remain active at the IGF-I receptor. Such IGF analogues would therefore be expected to be active irrespective of the production of inhibitory IGFBPs. However, none was effective in reinitiating lactation, even at doses which have been shown to be biologically effective in terms of nitrogen retention.(ABSTRACT TRUNCATED AT 250 WORDS)

Integrated care for patients with asthma: views of general practitioners

BACKGROUND

In 1989, a shared or integrated care scheme was developed for hospital outpatients with asthma, using the computerized patient record system of Grampian Health Board, Scotland. Patients with asthma attending hospital clinics were entered into this scheme and were invited to attend their general practitioner instead of an outpatient clinic for review of their asthma. Three-monthly questionnaires covering clinical aspects of asthma were sent to these patients and their general practitioners; the latter then returned them to the specialist. Patients could be recalled to the hospital clinic if either the general practitioner or consultant felt this was necessary and all patients were reviewed after one year by the specialist. The success of integrated care for patients with asthma relies on the cooperation of general practitioners.

AIM

The aim of this study was to investigate how this scheme worked in general practice, and general practitioners' perceptions of it, in order to identify factors that enhance or inhibit integrated care for patients with asthma in general practice.

METHOD

A qualitative survey was carried out with a random, stratified sample of 38 of the 317 general practitioners in the region. Semi-structured interviews were designed to elicit general practitioners' accounts of their operation of integrated care and their attitudes towards the scheme.

RESULTS

General practitioners perceived the scheme to have several advantages: the continuity and quality of care provided was improved; and the transmission of information between general practitioner and specialist was enhanced. Regular general practitioner reviews, instigated by standard letters generated by computer, were favoured as being clearly structured. Concerns were raised about the processing of paperwork, and the possibility that unnecessary reviews might be generated.

CONCLUSION

Integrated care for asthma patients is an acceptable management option among general practitioners.

Life-threatening right ventricular thrombosis in association with phospholipid antibodies

An 18 year old man presented with cough and dyspnoea caused by pulmonary infarction. A large friable mass of organising thrombus in an anatomically normal right ventricle was identified as an embolic source. The acute illness was associated with raised titres of anticardiolipin antibodies, one of the antiphospholipid group. This thrombus recurred after surgical removal but subsequently was dissipated after treatment with oral corticosteroids and long-term oral anticoagulation.

An immuno-dominant sequential epitope recognized by mouse anti-recombinant bovine growth hormone antisera

The sequential epitopes on bovine growth hormone (bGH) recognised by five polyclonal mouse antisera have been identified by scanning with multiple pin-bound peptides. Four main epitopes were identified at residues 29-40, 101-110, 139-152 and 181-191. Of these, only epitope 139-152 is recognised by all five mouse antisera indicating that, for the mouse, this may represent an immuno-dominant region of the bGH molecule.

Diabetes induces selective alterations in the expression of protein kinase C isoforms in hepatocytes

Membrane and cytosol fractions from hepatocytes of both normal and streptozotocin-induced diabetic animals were probed with a panel of polyclonal anti-peptide antisera in order to identify protein kinase C (PKC) isoforms. Immunoreactive species were noted with antisera specific for alpha (approximately 81 kDa), beta-II (approximately 82 kDA), epsilon (approximately 95 kDa) and epsilon (approximately 79 kDa). In addition, a species migrating with an apparent size of approximately 94 kDa was also detected in cytosol fractions using an antiserum specific for PKC-alpha. Each of these species was specifically displaced when the PKC-isoform specific peptide was included in the immunodetection system. No immunoreactive species consistent with the presence of the beta-I, gamma, delta and eta isoforms of protein kinase C was observed. Induction of diabetes using streptozotocin invoked selective alterations in the expression of PKC isoforms which were reversed upon insulin therapy. In the cytosol fraction, marked increases of approximately 3-fold occurred in levels of the beta-II isoform and the approximately 90 kDa (upper) form of PKC-alpha, with no apparent/little change in the levels of the approximately 81 kDa (lower) form of PKC-alpha and those of PKC-zeta. Diabetes induction also appeared to have elicited the translocation of PKC-beta-II and the approximately 81 kDa (lower) form of PKC-alpha to the membrane fraction where immunoreactivity for these species was now apparent. The level of PKC-epsilon, which was noted only in membrane fractions, was also increased upon induction of diabetes. It is suggested that the selective alterations in the expression of PKC isoforms occurring upon streptozotocin-induced diabetes may lead to altered cellular functioning and underly defects in inhibitory G-protein functioning and insulin action which characterise this animal model of diabetes.

Scaling of cursoriality in mammals

Data on limb bone lengths from 64 mammalian species were combined with data on 114 bovid species (Scott, '79) to assess the scaling of limb lengths and proportions in mammals ranging from 0.002 to 364 kg. We analyzed log-transformed data using both reduced major axis and least-squares regression to focus on the distribution across mammals of two key traits-limb length and metatarsal/femur ratio--associated with cursorial adaptation. The total lengths of both fore and hindlimbs scale in a manner very close to the M0.33 predicted by geometric similarity. Thus the relative limb lengths of large mammals, including bovids, generally regarded among the most cursorial of mammals, are very similar to those of the rodents and insectivores in this sample. Metatarsal/femur ratio also shows little change with changing mass, although bovids tend to have relatively longer metapodials than do other families in the sample. We argue that many of the remaining morphological traits associated with cursoriality (e.g., reduction in joint mobility and number of distal limb bone elements) promote cursoriality only at large body sizes. These results lead us to question the general perception that cursoriality is most widespread among large mammals. We also suggest that discussions of cursoriality should focus explicitly on the two partially independent aspects of performance that are otherwise confounded under this general term--speed and the ability to cover substantial distance.

The use of multiple-pin peptide synthesis in an analysis of the continuous epitopes recognised by various anti-(recombinant bovine growth hormone) sera. Comparison with predicted regions of immunogenicity and location within the three-dimensional structure of the molecule

A recently developed technology called epitope scanning permits the rapid and accurate delineation of continuous stretches of amino acids in a protein which constitute the sequential epitopes recognised by an antiserum raised to that protein. In the present report, we describe the use of this technique to identify the epitopes in the recombinant bovine growth-hormone (rbGH) molecule recognised by three polyclonal guinea-pig antisera and two polyclonal rabbit antisera. The results obtained show that, for guinea-pig antisera, 3 or 4, very-well-defined major continuous epitopes are present. As would be expected given the intrinsic genetic factors (major histocompatibility restriction, antigen processing and presentation) controlling the immune response in individual animals, subtle differences are evident in the precise location and relative reactivities of these epitopes in different guinea-pig antisera. Nevertheless, there is a large degree of overlap in these epitopes, such that immunodominant regions of the antigen can be clearly delineated. In a structural sense, these epitopes share a common motif in that they are sited in areas of the protein antigen with little secondary structure (loop/coil), although there is some contribution by neighbouring alpha-helices. For the two rabbit antisera, the response tends to be rather more heterogeneous, with recognition of more peptides and less clearly defined epitopes than was the case with the guinea-pig antiserum. Comparison of the four guinea-pig epitopes, identified by our experimental methods with computer predictions for this molecule (Jameson-Wolf antigenic index), indicate that two are strongly predicted, one is weakly predicted and one is not predicted. These observations, together with the displayed intraspecies and interspecies variation clearly indicate the limitations of these predictive methods. In conclusion, we have demonstrated that, despite the expected variation in the exact location of continuous epitopes defined by different anti-rbGH sera, there are large regions of overlap defining immunogenic core regions within the molecule. We believe that studies of this nature, together with further understanding of antigen processing and peptide presentation to immune cells, may have a role to play in the development of candidate peptide vaccines.

The nature of professional child abuse

The care study Care of a child with hypospadias: ethical issues in practice in the last issue of British Journal of Nursing (Vol 1(8): 393-8) raises many interesting issues, not least the question of what constitutes child abuse.

Investigation of the solid- and solution-phase binding reactivities of continuous epitopes recognized by polyclonal guinea-pig anti-recombinant bovine growth hormone antisera

We have used the technique of multiple pin peptide synthesis to identify three major continuous epitopes in the recombinant bovine (rb) GH molecule. We have synthesized these peptides, residues 24-40, 139-152 and 179-189, as N-terminally acetylated, C-terminal amides and confirmed their reactivity in a standard solid-phase ELISA. Subsequently, for epitope 139-152, we have synthesized a peptide affinity column and used this to isolate antibodies with this epitope specificity from whole antiserum. In addition, we demonstrate that under native conditions in a liquid phase RIA, these antibodies will precipitate [125I]rbGH. Further, peptide 139-152 itself also cross-reacts in an rbGH RIA inhibiting binding by up to 20%. Our data suggest that during the immune response to rbGH in guinea-pigs a substantial part of the B-cell response is directed to the 139-152 region and that this part of the protein is a native epitope.

Investigation of the mechanism of action of growth hormone in stimulating lactation in the rat

The role of GH was examined using an antiserum to rat GH (anti-rGH). When administered to lactating rats on day 2 of lactation it was without effect, whereas bromocriptine markedly suppressed milk production, with no additional effect of combined treatment. On day 6 of lactation, treatment with anti-rGH was also without effect, whilst bromocriptine again suppressed milk production. Combined treatment, however, suppressed milk synthesis completely, suggesting that GH was capable of maintaining about 50% of normal milk yield in the absence of prolactin at day 6 of lactation. By day 14 of lactation, anti-rGH treatment alone was capable of decreasing milk yield by about 20%, and again milk secretion only stopped completely when GH and prolactin were suppressed. These data suggest that the role of GH in supporting lactation increases as lactation progresses. The effects of GH in stimulating growth and in increasing milk yield in ruminants have been proposed to be mediated via insulin-like growth factor-I (IGF-I). In rats treated with anti-rGH, both IGF-I and IGF-II were decreased in serum. The concentration of the major IGF-binding protein (IGFBP-3) was not, however, affected by inhibition of GH or prolactin individually, but was decreased in animals treated with bromocriptine and anti-rGH. In animals given both bromocriptine and anti-rGH, concurrent treatment with recombinant bovine GH maintained milk yield at 50% of control values and normalized serum IGF-I, IGF-II and IGFBP-3 concentrations. By contrast, concurrent treatment with IGF-I or IGF-II, despite normalizing their respective concentrations in serum, failed to affect milk yield.(ABSTRACT TRUNCATED AT 250 WORDS)

Critical evaluation of a theory of molecular recognition using human insulin-like-growth-factor-I fragment 21-40 and its complementary peptide

Using solid-phase methods we have synthesized human insulin-like-growth-factor-I (IGF-I) fragment 21-40 (IGF-I 21-40) and the peptide derived from the 5'----3' translation of the complementary nucleic acid of this peptide, 'I-FGI 20-40' (the complementary peptide). According to a recently proposed theory of molecular recognition, these two peptides should bind specifically to each other. We have tested this theory by using both solid- and solution-phase direct-binding assays for this complementary-peptide pair. We have also investigated the ability of I-FGI 20-40 to interfere with native IGF-I binding during radioimmunoassay (r.i.a.), radio-receptor (r.r.a.) assay and ligand-blot analysis of IGF-binding proteins. We have obtained no evidence of any interaction between IGF-I 21-40 and I-FGI 20-40 in either solid- or solution-phase assays. In addition, I-FGI 20-40 does not interfere in the assays used to detect IGF-I binding antibodies (r.i.a.), receptors (r.r.a.) or binding proteins (ligand blots). Our data therefore question the universality of this particular theory of molecular recognition.