Identification of molecular markers linked to the mildew resistance gene Pl-d in apple

Powdery mildew poses a serious problem for apple growers, and resistance to the disease is a major objective in breeding programmes for cultivar improvement. As selective pressure allows pathogens to overcome previously reliable resistances, there is a need for the introduction of novel resistance genes into new breeding lines. This investigation is concerned with the identification of the first set of molecular markers linked to the gene for mildew resistance, Pl-d, from the accession 'D12'. As no prior information on the map position or markers for Pl-d were available, a bulked-segregant approach was used to test 49 microsatellite primers, 176 amplified fragment length polymorphism (AFLP) primers and 80 random amplified polymorphic DNA (RAPD) primers in a progeny segregating for Pl-d resistance, 'Fiesta' (susceptible) x A871-14 ('Worcester Pearmain' x 'D12'). The segregations of the markers identified in the resistant and susceptible bulks were scored in the progeny, then the recombination fractions between Pl-d and the most tightly linked markers were calculated and a map prepared. Three AFLP, one RAPD and two microsatellite markers were identified. One AFLP was developed into a sequence-characterised amplified region marker, while the microsatellites CH03C02 and CH01D03 were flanking markers, 7 and 11 recombination units, respectively, from Pl-d. Two more distant microsatellites on the same linkage group, CH01D09 and CH01G12, confirmed the orientation of the markers on the linkage group. These microsatellites place Pl-d on the bottom of linkage group 12 in published apple maps, a region where a number of other disease resistance genes have been identified.

A non-IGF binding mutant of IGFBP-3 modulates cell function in breast epithelial cells

We demonstrated previously that IGFBP-3 alone had no effect on cell death, but dramatically modulated apoptosis in Hs578T IGF non-responsive cells. We investigated whether a non-IGF binding mutant of IGFBP-3 retained its intrinsic actions in this cell line, prior to investigating its actions in IGF-responsive cells (MCF-7 and MCF-10A). In the Hs578T cells, the ceramide analogue, C2-induced apoptosis, non-glycosylated, glycosylated or mutant IGFBP-3 alone had no effect but on co-incubation with C2, all forms of IGFBP-3 markedly accentuated triggered apoptosis. In MCF-7 cells, IGFBP-3 was unable to modulate C2-induced death. In the MCF-10A cells, IGFBP-3 acted as a potent survival factor. IGFBP-3 also affected cell growth in the MCF-10A cells (inhibiting at low doses but increasing growth at higher concentrations). These actions of IGFBP-3 in the MCF-10A cells were independent of IGF-1. IGFBP-3 has differential IGF-independent effects on cell death and growth in normal breast and breast cancer cells.

Effects of a non-IGF binding mutant of IGFBP-5 on cell death in human breast cancer cells

We have demonstrated previously that IGFBP-5 alone had no effect on cell death but modulated ceramide-induced apoptosis in Hs578T IGF non-responsive cells. To investigate if IGFBP-5 maintains its intrinsic ability to modulate apoptosis in IGF-responsive cells, we used a non-IGF binding mutant of IGFBP-5. In Hs578T cells, non-glycosylated, glycosylated or mutant IGFBP-5 alone each had no effect on cell death, whereas all forms inhibited ceramide-induced apoptosis. In IGF-responsive MCF-7 cells, each wild type form reduced ceramide-induced cell death but mutant IGFBP-5 was without effect. In the presence of mutant IGFBP-5, however, IGF-I no longer conferred survival and in the presence of wild type IGFBP-5, long R3 IGF-I was also unable to confer survival. In summary, all forms of IGFBP-5 modulated ceramide-induced apoptosis in Hs578T cells. In MCF-7 cells, IGF-I-induced survival could be facilitated by IGFBP-5, but also blocked by IGFBP-5 if association with IGFBP-5 was prevented.

Tissue transglutaminase facilitates the polymerization of insulin-like growth factor-binding protein-1 (IGFBP-1) and leads to loss of IGFBP-1's ability to inhibit insulin-like growth factor-I-stimulated protein synthesis

Insulin-like growth factor-binding protein-1 (IGFBP-1) binds to insulin-like growth factors (IGFs) and has been shown to inhibit or stimulate cellular responses to IGF-I in vitro. This capacity of IGFBP-1 to inhibit or stimulate IGF-I actions correlates with its ability to form stable high molecular weight multimers. Since the ability of some proteins to polymerize is dependent upon transglutamination, we determined if tissue transglutaminase could catalyze this reaction and the effect of polymerization of IGFBP-1 upon IGF-I action. Following incubation with pure tissue transglutaminase (Tg), IGFBP-1 formed covalently linked multimers that were stable during SDS-polyacrylamide gel electrophoresis using reducing conditions. Dephosphorylated IGFBP-1 polymerized more rapidly and to a greater extent compared with native (phosphorylated) IGFBP-1. Exposure to IGF-I stimulated transglutamination of IGFBP-1 in vitro. An IGFBP-1 mutant in which Gln(66)-Gln(67) had been altered to Ala(66)-Ala(67) (Q66A/Q67A) was relatively resistant to polymerization by Tg compared with native IGFBP-1. Tg localized in fibroblast membranes was also shown to catalyze the formation of native IGFBP-1 multimers, however, Q66A/Q67A IGFBP-1 failed to polymerize. Although the mutant IGFBP-1 potently inhibited IGF-I stimulated protein synthesis in pSMC cultures, the same concentration of native IGFBP-1 had no inhibitory effect. The addition of higher concentrations of native IGFBP-1 did inhibit the protein synthesis response, and this degree of inhibition correlated with the amount of monomeric IGFBP-1 that was present. In conclusion, IGFBP-1 is a substrate for tissue transglutaminase and Tg leads to the formation of high molecular weight covalently linked multimers. Polymerization is an important post-translational modification of IGFBP-1 that regulates cellular responses to IGF-I.

Substitutions for hydrophobic amino acids in the N-terminal domains of IGFBP-3 and -5 markedly reduce IGF-I binding and alter their biologic actions

Insulin-like growth factor-binding protein-3 and -5 (IGFBP-3 and -5) have been shown to bind insulin-like growth factor-I and -II (IGF-I and -II) with high affinity. Previous studies have proposed that the N-terminal region of IGFBP-5 contains a hydrophobic patch between residues 49 and 74 that is required for high affinity binding. These studies were undertaken to determine if mutagenesis of several of these residues resulted in a reduction of the affinity of IGFBP-3 and -5 for IGF-I. Substitutions for residues 68, 69, 70, 73, and 74 in IGFBP-5 (changing one charged residue, Lys(68), to a neutral one and the four hydrophobic residues to nonhydrophobic residues) resulted in an approximately 1000-fold reduction in the affinity of IGFBP-5 for IGF-I. Substitutions for homologous residues in IGFBP-3 also resulted in a >1000-fold reduction in affinity. The physiologic consequence of this reduction was that IGFBP-3 and -5 became very weak inhibitors of IGF-I-stimulated cell migration and DNA synthesis. Likewise, the ability of IGFBP-5 to inhibit IGF-I-stimulated receptor phosphorylation was attenuated. These changes did not appear to be because of alterations in protein folding induced by mutagenesis, because the IGFBP-5 mutant was fully susceptible to proteolytic cleavage by a specific IGFBP-5 protease. In summary, residues 68, 69, 70, 73, and 74 in IGFBP-5 appear to be critical for high affinity binding to IGF-I. Homologous residues in IGFBP-3 are also required, suggesting that they form a similar binding pocket and that for both proteins these residues form an important component of the core binding site. The availability of these mutants will make it possible to determine if there are direct, non-IGF-I-dependent effects of IGFBP-3 and -5 on cellular physiologic processes in cell types that secrete IGF-I.

Complex mediation of uterine endometrial epithelial cell growth by insulin-like growth factor-II (IGF-II) and IGF-binding protein-2

The coexpression of IGF (-I and -II) peptides, corresponding receptors, and IGF binding proteins (IGFBPs) in uterine endometrium suggests that a significant component of IGF action in this tissue is via autocrine or paracrine pathways, or both. The present study examined whether IGF-II and a major uterine-expressed IGF-II binding protein, IGFBP-2, modulate endometrial epithelial cell mitogenesis. Serum-deprived porcine endometrial glandular epithelial (GE) cells of early pregnancy were treated with various concentrations of IGFs, recombinant porcine (rp) IGFBP-2, or both, and examined for changes in cellular mitogenesis by incorporation of [(3)H]thymidine into DNA. Recombinant human (rh) IGF-II stimulated DNA synthesis in a dose-dependent manner. Human [Leu(27)]-IGF-II, an analog with selective affinity for the IGF-II (type II) receptor, increased thymidine uptake by twofold compared with untreated GE cells. When added in combination with an equimolar concentration of rhIGF-I, [Leu(27)]-IGF-II or rhIGF-II stimulated thymidine incorporation to a greater extent than did rhIGF-I alone. Ligand blot analysis of GE cell conditioned medium revealed the presence of four IGFBPs with molecular masses of 48, 31, 23, and 15 kDa. Physiological concentrations of rpIGFBP-2 (nM range) increased both basal and IGF-induced DNA synthesis in GE cells. At equimolar concentrations, Des(1-6)IGF-II (an IGF-II analog with much reduced affinity for IGFBPs) and rpIGFBP-2 had additive effects on GE cell mitogenesis, suggesting that the IGFBP-2 modulation of uterine cell growth may involve both IGF-dependent and IGF-independent pathways. Our results demonstrate the complex interplay of IGF system components in uterine endometrial epithelial growth regulation in vitro, identify IGF-II and IGFBP-2 as locally coexpressed uterine epithelial cell mitogens, and suggest the presence of a functional signaling pathway by which IGF-II stimulates epithelial cell proliferation via the type II receptor.

Hermeneutic analysis: a qualitative decision trail

Qualitative analysis is problematic from two perspectives, which exist in the science and art debate [Tesch, R., 1990. Qualitative Research. Analysis types and software tools. The Falmer Press, London; Robson, C., 1993. Real World Research. Blackwell, Oxford]. The science view claims that the absence of clear and agreed analysis processes, which can be found in the quantitative domain, attracts labels to qualitative analysis of intuitive artistry and personal journeys which are considered 'unscientific'. This thinking remains dominant despite the growth of systematic qualitative analysis supported through computer analysis systems [Tesch, 1990]. However, in the art domain there is real resistance to the development of set methods of analysis which does view qualitative analysis, "as more of an art than a science" [Robson, 1993, p. 370]. This paper offers a contribution to the qualitative analysis tension through the promotion and illustration of a decision making trail. This option supports the principles of academic rigour in qualitative research [Guba, E.G., Lincoln, Y.S., 1981. Effective Evaluation. Jossey Bass, San Francisco] as a decision trail permits the research community to make their own judgements concerning the process of analysis, the overall trustworthiness of the research and therefore its presented interpretations.

Evidence-based practice: a retrograde step? The importance of pluralism in evidence generation for the practice of health care

The origin of evidence-based medicine is explored and its connection to evidence-based practice examined. Widespread acceptance of the dominant scientific paradigm supporting evidence-based practice is challenged. Knowledge classifications and their relevance for nursing practice are considered, with the need for a critical balance to be pursued. Recommendations are made, regarding the future of evidence for practice, and a brief example of emerging evidence concerning values of professional caring is offered in redressing the balance.

A protease-resistant form of insulin-like growth factor (IGF) binding protein 4 inhibits IGF-1 actions

Smooth muscle cells (SMC) secrete a serine protease that cleaves insulin-like growth factor (IGF) binding protein (IGFBP)-4 into fragments that have low affinity for IGF-1. When IGFBP-4 is added to monolayer cultures of cell types that do not secrete this protease, IGF-1 stimulation of DNA synthesis is significantly inhibited. In contrast, if cell types that secrete this protease are used, IGFBP-4 is a much less potent inhibitor. These studies were conducted to determine whether proteolysis of IGFBP-4 accounted for its reduced capacity to inhibit IGF-1-stimulated DNA synthesis. The cleavage site in IGFBP-4 that the SMC protease uses was determined to be lysine120, histidine121. A protease-resistant mutant form of IGFBP-4 was prepared, expressed, purified, and tested for biologic activity using porcine SMC cultures. Addition of the protease-resistant mutant resulted in inhibition of DNA and cell migration responses to IGF-1. The inhibition was concentration dependent and was maximal when 500 ng/ml (20 nM) of the mutant was added with 20 ng/ml (2.8 nM) of IGF-1. When the mutant was added in the absence of IGF-1, it had no activity. The results show that cleavage of IGFBP-4 at lysine120, histidine121 results in inactivation of the ability of IGFBP-4 to bind to IGF-1. Creation of a mutant form of IGFBP-4 that was not cleaved by the protease resulted in inhibition of IGF-1-stimulated actions. The results suggest that IGFBP-4 can act as a potent inhibitor of the anabolic effects of IGF-1 and that the variables that regulate protease activity may indirectly regulate IGF-1 actions.

Insulin-like growth factor-binding protein-5 is cleaved by physiological concentrations of thrombin

Insulin-like growth factor (IGF)-binding protein-5 (IGFBP-5) is cleaved by a serine protease that is secreted by fibroblasts and porcine smooth muscle cells (pSMC) in culture. To investigate whether other serine proteases could cleave this substrate at physiologically relevant concentrations, we determined the proteolytic effects of thrombin on IGFBP-5. Human alpha-thrombin (0.0008 NIH U/ml) cleaved IGFBP-5 into 24-, 23-, and 20-kDa non-IGF-I-binding fragments. Cleavage occurred at a physiologically relevant thrombin concentration. The effect was specific for IGFBP-5, as other forms of IGFBPs, e.g. IGFBP-1, IGFBP-2, and IGFBP-4 were not cleaved by thrombin. Although IGFBP-3 was cleaved by thrombin, this effect required a 50-fold greater thrombin concentration. [35S]Methionine labeling followed by immunoprecipitation confirmed that IGFBP-5 that was constitutively synthesized by pSMC cultures was also degraded by thrombin into 24-, 23-, and 20-kDa fragments. The binding of IGF-I to IGFBP-5 partially inhibited IGFBP-5 degradation by thrombin, and an IGF analog that does not bind to IGFBP-5 had no effect. Thrombin did not account for the serine protease activity that had been shown previously to be present in pSMC-conditioned medium. This was proven by showing that 1) no immunoreactive thrombin could be detected in the pSMC-conditioned medium; 2) the IGFBP-5 fragments that were generated by thrombin showed three cleavage sites (Arg192-Ala193, Arg156-Ile157, and Lys120-His121), whereas the serine protease in conditioned medium cleaves IGFBP-5 at a different site; and 3) hirudin had no effect on IGFBP-5 cleavage by the protease in pSMC medium; however, it inhibited IGFBP-5 degradation by thrombin. To determine the physiological significance of IGFBP-5 cleavage, the effect of an IGFBP-5 mutant that is resistant to cleavage by the pSMC protease and has been shown to inhibit IGF-I actions in pSMC was determined. This mutant inhibited IGF-I-stimulated DNA synthesis, but if thrombin was added simultaneously, IGF-I was fully active. In summary, physiological concentrations of thrombin degrade IGFBP-5. Degradation can be blocked by hirudin and is partially inhibited by IGF-I binding. Generation of active thrombin in vessel walls may be a physiologically relevant mechanism for controlling IGF-I bioactivity.

Academic validation of prior and experiential learning: evaluation of the process

This report is a summary of an AP(E)L evaluative research project conducted at the University of Southampton School of Nursing and Midwifery. The project aimed to shed light on the perceptions of candidates and teachers in conjunction with the effectiveness of the accreditation process. Through initial semi-structured interviews with teachers (n = 6) and candidates (n = 6) offering their perceptions and experiences, an emergent questionnaire was sent to the remaining active accreditation candidates (n = 60, response n = 39) and advisers/assessors (n = 36), response n = 32). The effectiveness of candidate preparation for beginning an accreditation claim, the comprehensiveness of the types of credit available to capture learning through experience, the styles of advising and feedback from assessment are all reported on. Interestingly, the data highlight how preparing an accreditation claim can affect both adviser and candidate, in terms of being more self-critical and reflective in their areas of practice.

Protease-resistant form of insulin-like growth factor-binding protein 5 is an inhibitor of insulin-like growth factor-I actions on porcine smooth muscle cells in culture

IGFs are pleiotrophic mitogens for porcine smooth muscle cells (pSMC) in culture. The effects of IGFs on cells are modulated by various insulin-like growth factor-binding proteins (IGFBP). IGFBP-5 is synthesized by pSMC and binds to the extracellular matrix. However, IGFBP-5 is also secreted into conditioned medium of cultured cells and is cleaved into fragments by a concomitantly produced protease. These fragments have reduced affinity for the IGFs and cleavage makes it difficult to assess the role of intact IGFBP-5. To study the consequence of accumulation of intact IGFBP-5 in medium, we determined the cleavage site in IGFBP-5 and prepared a protease resistant mutant. Amino acid sequencing of purified IGFBP-5 fragments suggested Arg138-Arg139 as the primary cleavage site. Arg138-Arg139-->Asn138-Asn139 mutations were introduced to create protease-resistant IGFBP-5, which has the same affinity for IGF-I as the native protein. This mutant IGFBP-5 remained intact even after 24 h of incubation and it inhibited several IGF-I actions when added to pSMC culture medium. The mutant IGFBP-5 (500 ng/ml) decreased IGF-I stimulated cellular DNA synthesis by 84%, protein synthesis by 77%, and it inhibited IGF-I stimulated migration of pSMC by 77%. It also inhibited IGF-I stimulation of IRS-1 phosphorylation. In contrast, the same amount of native IGFBP-5 did not inhibit IGF-I actions. The significance of inhibitory effects of the protease resistant IGFBP-5 was further demonstrated in pSMC transfected with mutant or native IGFBP-5 cDNAs. The mutant IGFBP-5 accumulated in culture medium of transfected cells, while native IGFBP-5 was degraded into fragments, PSMC overexpressing the mutant IGFBP-5 also responded poorly to IGF-I compared with mock transfected cells. IGF-I (5 ng/ml) increased [35S]methionine incorporation into control cells by 36% above the basal level, but it did not significantly change (4%) in pSMC cultures that were producing the mutant IGFBP-5. In conclusion, the accumulation of protease-resistant IGFBP-5 in the medium was inhibitory to IGF-I actions on pSMC. This suggests that proteolysis can prevent IGFBP-5 from acting as an inhibitor of IGF-I-stimulated effects and that it serves as an important mechanism for regulating cellular responsiveness to IGF-I.

Detection of human viruses using primary cells immortalised by oncogene transfection, in comparison with primary cells and established cell lines

No single established cell line was found capable of substituting for primary baboon kidney (PBK) or primary rhesus macacque kidney (PRK) cells for detection of human viruses. Although a panel of cell lines could detect influenza, parainfluenza, and enteroviruses, which are among the most important viruses encountered in routine diagnostic laboratories, the sensitivity of this panel was not as high as that of PBK or PRK cells. However, in a promising complementary approach, PBK and PRK cells have been immortalised successfully by oncogene transfection, and some of the resulting cell lines have retained susceptibility to human viruses, and may be suitable for routine diagnostic use.

Identification of the extracellular matrix binding sites for insulin-like growth factor-binding protein 5

Fibroblast extracellular matrix (ECM) contains two forms of insulin-like growth factor-binding proteins (IGFBPs), IGFBP-3 and IGFBP-5. These studies were undertaken to identify the regions within IGFBP-5 that mediate its binding to fibroblast ECM. Synthetic peptides were prepared that were homologous with two regions of basic amino acids within IGFBP-5 (Arg201-Arg218 and Ala131-Thr141). Increasing concentrations of both peptides competed with IGFBP-5 for binding to ECM but the Arg201-Arg218 peptide was more potent. Mutagenesis was used to define the effect of substituting for these basic residues on ECM binding. Substitution for two peptide B residues K134A and R136A reduced binding by 40%. Substitution of a single basic residue within the peptide A region (K211N) reduced binding to ECM by 49%. Substitution for K211N, K134A, and R136A reduced binding by 52%. More extensive substitutions in the peptide A region, e.g. K211N,R214A,K217A,R218N, resulted in a greater (e.g. 88%) decrease. The positional location of basic residues appeared to be more important than the total number of substitutions since the mutant K202N,K206A,R207A had a 79% reduction in ECM binding. Two basic regions of IGFBP-5 contribute to its binding to ECM, but the region containing amino acids 201-218 has a greater contribution. ECM binding is mediated by charged residues and acts to stabilize IGFBP-5 by protecting it from proteolysis.

Halogenated anesthetics form liver adducts and antigens that cross-react with halothane-induced antibodies

Two halogenated anesthetics, enflurane and isoflurane, have been associated with an allergic-type hepatic injury both alone and following previous exposure to halothane. Halothane hepatitis appears to involve an aberrant immune response. An antibody response to a protein-bound biotransformation product (trifluoroacetyl adduct) has been detected on halothane hepatitis patients. This study was performed to determine cross-reactivity between enflurane and isoflurane with the hypersensitivity induced by halothane. The subcellular and lobular production of hepatic neoantigens recognized by halothane-induced antibodies following enflurane and isoflurane, and the biochemical nature of these neoantigens was investigated in two animal models. Enflurane administration resulted in neoantigens detected in both the microsomal and cytosolic fraction of liver homogenates and in the centrilobular region of the liver. In the same liver, biochemical analysis detected fluorinated liver adducts that were up to 20-fold greater in guinea pigs than in rats. This supports and extends previous evidence for a mechanism by which enflurane and/or isoflurane could produce a hypersensitivity condition similar to that of halothane hepatitis either alone or subsequent to halothane administration. The guinea pig would appear to be a useful model for further investigations of the immunological response to these antigens.

Turning experience into academic learning. The APL and APEL credit systems

1. Learning from experience can be turned into academic credit through APL and APEL. 2. The APL/APEL process is about valuing and empowering practitioners. 3. Reflection is central to developing an APEL claim. 4. An accreditation model offers a five-stage process leading to the award of credit.

Role of insulin-like growth factor binding proteins in the control of IGF actions

The insulin-like growth factor binding proteins have been shown to modify IGF actions. IGFBP-5 binds to extracellular matrix (ECM) and its ability to potentiate IGF activity is dependent upon the amount that is ECM associated. To determine the specific regions of IGFBP-5 that are required for ECM association, site directed mutagenesis has been used to prepare several forms of IGFBP-5. Mutants that have had the amino acids between positions 201 and 218 altered have been useful. Mutation of the lysine 211 resulted in no change in the affinity of IGFBP-5 for ECM or heparin Sepharose; however, it resulted in a major reduction in affinity for IGF-I following heparin binding. Other mutations which disrupted heparin binding also resulted in loss of this affinity shift. Most distruptive were mutations of amino acids 211, 214, 217 and 218 and 202, 206 and 207. Mutation of residues 201 plus 202 had some effect, but substitution for 207, 211, 217 and 218 had no effect. When binding to intact ECM was analyzed, similar results were obtained. This suggests that amino acids 202, 206 and 214 are definitely involved in heparin and ECM binding. When binding to proteoglycans such as tenascin and heparin sulfate proteoglycan was analyzed, similar results were obtained. IGFBP-5 also binds to other proteins in ECM, including type IV collagen and plasminogen activator inhibitor-I. Specific antisera for plasminogen activator inhibitor-1 can coprecipitate IGFBP-5. IGFBPs are degraded by specific proteases. Three proteases that degrade IGFBP-2, -4 and -5 have been characterized. They are serine proteases that cleave these proteins at basic residues. Although several well characterized serine proteases cleave IGFBP-4 or -5, the proteases in cell conditioned media appear to be distinct.

CCAAT box binding protein NF-Y facilitates in vivo recruitment of upstream DNA binding transcription factors

NF-Y binds a CCAAT motif found in many eukaryotic polymerase II-dependent promoters. In the HLA-DRA promoter it has been demonstrated that stereo-specific alignment between this motif and the upstream elements X1 and X2 is required for activation. To study the underlying mechanism for this requirement, a panel of transfected cell lines that maintained integrated, wild-type and mutant promoters were analyzed by in vivo genomic footprinting. Cell lines harboring a mutated CCAAT element exhibited a loss of interactions at the CCAAT site, as expected, and no transcriptional activity. Most importantly, mutation of the CCAAT sequence nearly abolished in vivo binding at the X1 and X2 sites, while mutations of X1 and X2 had little effect on CCAAT box binding. However, X1 and X2 binding was interdependent. In vitro, X1 binding activities are known to be stabilized by NF-Y binding. Interaction between NF-Y and X box binding proteins was demonstrated by reciprocal co-immunoprecipitation in the absence of DNA and co-affinity purification in the presence of DNA. Collectively, these studies indicate that occupancy of the CCAAT element represents an early event affecting other protein-DNA interactions and suggest that NF-Y stabilizes and interacts with X box factors to mediate this function. These findings may represent a common theme among promoters containing a CCAAT element.

Identification of the dihydrolipoamide acetyltransferase subunit of the human pyruvate dehydrogenase complex as an autoantigen in halothane hepatitis. Molecular mimicry of trifluoroacetyl-lysine by lipoic acid

Trifluoroacetylated (CF3CO-) proteins, elicited upon exposure of animals or humans to halothane, were recognized by anti-CF3CO antibody, monospecific for the hapten derivative N6-trifluoroacetyl-L-lysine. Anti-CF3CO antibodies cross-reacted with the dihydrolipoamide acetyltransferase (E2 subunit) of pyruvate dehydrogenase, indicating that epitopes on the E2 subunit of pyruvate dehydrogenase molecularly mimic those on CF3CO-proteins. Lipoic acid, the prosthetic group of the E2 subunit of pyruvate dehydrogenase was essential in this process, in that only the lipoylated form of the recombinantly expressed inner lipoyl domain of the human E2 subunit of pyruvate dehydrogenase, but not the unlipolyated form, was recognized by anti-CF3CO antibody. Furthermore, based on a high degree of structural relatedness, both CF3CO-Lys and (6RS)-lipoic acid, as well as the lipoylated peptide ETDK(lipoyl)ATIG specifically inhibited the recognition by anti-CF3CO antibody of the E2 subunit of pyruvate dehydrogenase, of trifluoroacetylated rabbit serum albumin and of human liver CF3CO-proteins. In sera of patients with halothane hepatitis, autoantibodies with properties identical to those of anti-CF3CO antibody were identified which could not discriminate between CF3CO-proteins and the E2 subunit of pyruvate dehydrogenase. These data suggest that the E2 subunit pyruvate of dehydrogenase is an autoantigen in halothane hepatitis and that molecular mimicry of CF3CO-proteins by the E2 subunit of pyruvate dehydrogenase is due to the similar structures of CF3CO-Lys and lipoic acid.

Immunogenicity studies of a synthetic antigen of alpha methyl dopa

Since the idiosyncratic liver toxicity of methyl dopa (L-alpha-methyl-3,4- dihydroxy-phenylalanine) may be due to immune mediated mechanisms, immunologic tools are needed to detect methyl dopa induced antibody and antigen. Hapten (methyl dopa)--carrier (albumin) conjugates were synthesized to generate antibodies reactive with this drug. Studies were also conducted to test the immunogenicity of this hapten-carrier conjugate and its cross reactivity with methyl catechol and levodopa. Methyl dopa (MD), levodopa (LD) or methyl catechol (MC) were conjugated to rabbit serum albumin (RSA) under high pH (base) conditions or by a tyrosinase (tyr) catalyzed reaction. Under the base conjugation conditions, MD-RSA, LD-RSA and MC-RSA conjugates were produced at higher hapten: carrier ratios than conjugates produced by the enzyme catalyzed reaction. Rabbits were subsequently immunized with either MD-RSA(base) or MD-RSA(tyr). Antibodies elicited by MD-RSA(base) had marked reactivity to the carrier protein, albumin, whereas antibodies elicited by MD-RSA(tyr) did not. In addition, reactivity of anti-MD antibody was equal to or greater with MC-RSA than reactivity with either MD-RSA or LD-RSA. This work suggests that the conjugation method using the tyr catalyzed reaction produces the optimal immunogen with minimal modification of the carrier protein. In addition, the catechol moiety of MD, MC and LD appears to be the immunogenic epitope on these haptens.

Ethical issues in health education

Moral dilemmas abound during health education practice and ethical decisions have to be made. This article examines the contribution of the four guiding ethical principles (respect for autonomy, beneficence, non-maleficence and justice) to nurse decision making. Multidisciplinary ethical guidelines to assist health educators to serve the best interests of patients and clients are suggested.

A view of the phenomenon of caring in nursing practice

Care is regularly used as a suffix to nursing, in such well-known phrases as 'total nursing care' and 'holistic nursing care'. While most care is provided by lay persons, there is little nursing research which focuses on the meaning of care, particularly in relation to the United Kingdom. This small-scale study investigates the meaning of care from the experience of six practising staff nurses in a British hospital and leads to a view of this phenomenon. Phenomenology was the chosen methodology, which facilitated the emergence of an essential structure of caring which incorporated four major categories described as 'being supportive', 'communicating', 'pressure' and 'caring ability'. It is suggested that, through gaining perspectives to enhance our understanding of the meaning of care, it will ultimately develop our understanding of nursing itself.

Conjugation of dinitrofluorobenzene to plasma proteins in vivo in the rat

The extent of protein dinitrophenylation was determined in plasma and other tissues of anesthetized rats after administration of the model immunogen [3H]dinitrofluorobenzene (DNFB) (25 mg/kg; 5-25 microCi). DNFB was given by the intravenous, intraportal, intramuscular, or oral route. Irreversible binding was determined radiometrically after exhaustive solvent extraction of plasma or organ proteins. The extent of binding was high in plasma after parenteral administration (approximately 1% dose/ml plasma), but less (approximately 0.1% dose/ml) if DNFB was given orally. Low levels of radioactivity were bound irreversibly in liver (0.01-0.13% dose/g) and kidney (0.03-0.10% dose/g) and only residual amounts in other organs. Western blotting was used to identify target proteins in plasma, liver, and kidney using a specific antidinitrophenyl antiserum. No dinitrophenylation could be detected in liver or kidney samples, but strong recognition of two protein bands was observed in plasma. Bands with the same apparent molecular masses (67 and 44 kDa) were seen when DNFB was incubated with rat plasma in vitro. Preliminary evidence for these proteins being albumin and alpha 1-acid glycoprotein, respectively, is presented. The latter may be important for interindividual variability in immune responsiveness, because it is an acute phase protein whose levels fluctuate widely during disease states.

The B cell-specific nuclear factor OTF-2 positively regulates transcription of the human class II transplantation gene, DRA

The promoter of the major histocompatibility class II gene DRA contains an octamer element (ATTTGCAT) that is required for efficient DRA expression in B cells. Several DNA-binding proteins are known to bind this sequence. The best characterized are the B cell-specific OTF-2 and the ubiquitous OTF-1. This report directly demonstrates that OTF-2 but not OTF-1 regulates the DRA gene. In vitro transcription analysis using protein fractions enriched for the octamer-binding protein OTF-2 demonstrate a positive functional role for OTF-2 in DRA gene transcription. In contrast, OTF-1-enriched protein fractions did not affect DRA gene transcription although it functionally enhanced the transcription of another gene. Recombinant OTF-2 protein produced by in vitro transcription/translation could also enhance DRA gene transcription in vitro. In vivo transient transfection studies utilizing an OTF-2 expression vector resulted in similar findings: that OTF-2 protein enhanced DRA gene transcription, and that this effect requires an intact octamer element. Together these results constitute the first direct evidence of a positive role for the lymphoid-specific octamer-binding factor in DRA gene transcription.

The mechanism of bioactivation and antigen formation of amodiaquine in the rat

A glutathione conjugate of amodiaquine has been isolated and characterized from rat bile after administration of [14C]amodiaquine (50 mumol/kg, 5.0 muCi/rat) to anaesthetized male Wistar rats. Thioether conjugates of amodiaquine in rat bile accounted for a total of 12% of the dose, 5 hr after administration of the drug. In addition, 1% of the dose remained in the liver covalently bound to tissue proteins after 5 hr. These findings provide direct evidence that a chemically reactive metabolite, amodiaquine quinoneimine, has been formed from the drug in vivo. A second major metabolite, desethylamodiaquine, accounting for 14% of the given dose, was present in the liver after 5 hr. Enzyme inhibition studies with ketoconazole-pretreated rats showed that both amodiaquine quinoneimine and desethylamodiaquine formation can be catalysed by cytochrome P450. The demonstration that amodiaquine readily and extensively forms a metabolite in vivo, with strong reactivity towards protein and non-protein thiol groups, may help to explain the idiosyncratic toxicity observed in man.

Detection of antidrug IgG antibodies in patients with adverse drug reactions to amodiaquine

Antidrug IgG antibodies have been detected in some patients receiving amodiaquine (AQ). Antidrug antibodies were detected in 6/7 patients who experienced serious well-defined adverse drug reactions during malaria prophylaxis and in 7/22 patients who received comparable doses of the drug (at least 400 mg weekly x 6) but did not present with clinical adverse drug reactions. In contrast antidrug antibodies were not detected in 7 patients who received the drug for treatment (1.0-1.2 g total over 3 days). The specificity of the IgG response was defined by hapten inhibition experiments (IC50 value for AQ ranged between 0.050 and 0.282 microM) which suggest that the antibody recognised the drug linked to cysteine residues in protein via the 4-hydroxyanilino side chain. The data show that AQ is immunogenic in man and are consistent with the hypothesis that idiosyncratic adverse reactions to the drug have an immunological aetiology.

The effect of bioreactor configuration on production of HIV and cell-virus interaction

In an attempt to establish a bioreactor system for generation of HIV that is practicable, efficient, biologically contained, and capable of scale up, the production of two strains of this virus was examined in suspension culture and the 'Porosphere' fixed bed system. HIV 1 and HIV 2 were grown successfully in both these types of reactor. The porosphere reactor theoretically appears to offer a better environment for HIV production, but evidence for significantly improved yields from this system, compared to suspension, was equivocal. However, this configuration facilitated media changes during culture. The data clearly showed that the culture system and cell environment significantly affected cell-virus interrelationships. Switches between lytic--and persistent--type infections, and changes in the virus population were observed.

Alternative ligands as probes for the carotenoid-binding site of lobster carapace crustacyanin

The apoproteins of the lobster carotenoprotein, crustacyanin, show single high-affinity binding sites for the hydrophobic fluorescence probes 8-anilo-1-naphthalenesulphonic acid and cis-parinaric acid, and exhibit fluorescence transfer from tryptophan to the ligands. These results, together with information from the amino acid sequences, infer that the native carotenoid, astaxanthin, is bound to each apoprotein within an internal hydrophobic pocket, or calyx.

Influence of glutathione conjugation on the immunogenicity of dinitrophenyl derivatives in the rat

The role of metabolic detoxication (glutathione conjugation) in the humoral response to three model haptens, dinitrofluorobenzene (DNFB), dinitrochlorobenzene (DNCB) and dinitrobenzenesulphonate (DNBS), was investigated in male Wistar rats. All three haptens produced a measurable anti-dinitrophenyl IgG antibody response over a wide dose range (2.7 nmol/kg to 0.27 mmol/kg) given for 4 days. A significant difference in antibody titre was only observed at the highest dose (DNFB greater than DNCB = DNBS), despite a marked difference in reactivity towards a protein carrier (albumin) and N-acetyl-lysine in vitro. These observations can be partly explained by the fact that the most reactive hapten (DNFB) conjugates most rapidly with glutathione in vitro and in vivo.

Immunogenicity of amodiaquine in the rat

Amodiaquine is an antimalarial drug that has been associated with adverse reactions which may be immune mediated. Specific IgG anti-amodiaquine antibodies were detected after administration of the drug to rats (269 mumols/kg for 4 days), using an enzyme-linked immunosorbent assay employing amodiaquine conjugated to metallothionein as an antigen. A positive immune response was observed regardless of the route of administration, but the magnitude of the response in terms of antibody titre was in the order intraperitoneal administration greater than intramuscular administration greater than oral administration. Hapten inhibition experiments with structurally related drugs defined the specificity of the antibody which appears to recognize a conjugate of amodiaquine quinone imine and cysteine residues present in protein. Amodiaquine was converted to a protein-reactive species by activated human polymorphonuclear leucocytes in vitro, and this may provide a mechanism for immunogen formation in vivo. A humoral immune response was observed with doses of amodiaquine that did not produce either direct hepatotoxicity or leucopenia. Thus an animal model has been developed with which to investigate the toxicological consequences of amodiaquine immunogenicity.

Chipping hammer vibration

An investigation was carried out to determine the factors influencing the vibration of chipping hammers and to find ways of reducing the vibration at the operator's hand. It showed that substantially higher vibration levels are produced at the chisel of a chipping hammer than at its handle. Typical weighted values for the two areas were 24 and 8 m/s2, respectively. This finding agrees with medical observations showing that invariably the hand holding the chisel exhibits the more severe symptoms of vibration-induced white finger. A sleeve which fits onto the chisel was developed which can effect a reduction in vibration of up to 66%. A prototype hammer was developed incorporating an isolating material which reduced the weighted vibration value from 7 to 3 m/s2. Vibration isolating gloves were tested and resulted in an additional reduction in vibration of up to 63% when used with the chisel sleeve. A unique mounting device using rubber isolators was designed which protects the accelerometer from very intense high-frequency vibration but allows accurate measurement of chisel vibration in the frequency range of interest.

Mechanism of action of rabbit liver phosphoglucomutase

Induced-transport tests with comparatively undegraded rabbit liver phosphoglucomutase show that the enzyme possesses a phosphoenzyme mechanism and that any interconversion of phosphoenzyme forms is very rapid. A relatively stable 32P-labelled phosphoenzyme was isolated, which exchanged label rapidly with substrates. The phospho group appears to be bonded to a serine residue on the enzyme.

An investigation into causes of resistance of a cloned line of BHK cells to a strain of foot-and-mouth disease virus

The reduced ability of foot-and-mouth disease virus (FMDV) strain Asia 1 Iran 1/73 to replicate in the cloned BHK cell line AA7 was not due to lack of virus attachment at the cell surface. Instead, the main restriction in the viral growth cycle occurred during synthesis and processing of viral macromolecules, and/or during the earliest stages of their assembly. Reduced efficiency of penetration and uncoating of virus attached to the cells may also have contributed to inhibition of virus replication. Viral components or subviral particles did not accumulate and defective interfering particles were not detected. The reduced number of infective virions produced was released from infected cells at the normal rate. No interferon production could be demonstrated.

Variation in the susceptibility of BHK populations and cloned cell lines to three strains of foot-and-mouth disease virus

BHK monolayer and suspension cell populations maintained in different laboratories were found to vary in their susceptibility to infection with three strains of foot-and-mouth disease virus (FMDV). The susceptibility of parent cell populations was compared with that of individual clones of cells derived from them. The populations tested in this way consisted of a number of cell types, each expressing a different capacity to produce FMDV. The relative numbers of susceptible and insusceptible cells in each population appeared to determine the overall susceptibility of that population. The ability of the FMDV strain Asia 1 Iran 1/73 to multiply was an indicator of the general FMDV susceptibility of a BHK cell population.

The equilibrium constant of the phosphoglyceromutase reaction

The equilibrium constant of the phosphoglyceromutase reaction was determined over a range of pH (5.4-7.9), in solutions of different ionic strength (0.06-0.3) and in the presence of Mg(2+), at 30 degrees C and at 20 degrees C. The values obtained (8.65-11.65) differ substantially from previously published values. The third acid dissociation constants were redetermined for 2- and 3-phosphoglycerate, and in contrast with previous reports the pK values (7.03 and 6.97 respectively at zero ionic strength) were closely similar. The Mg(2+)-binding constants were measured spectrophotometrically and the values, 286mm(-1) and 255mm(-1) for 2- and 3-phosphoglycerate at pH7 and ionic strength 0.02, were also very similar. From the relative lack of effect of temperature, pH and ionic strength it is concluded that the equilibrium constant differs from unity largely because of entropic factors. At low ionic strength, in the neutral region, the pH-dependence can be attributed to the small difference in the acid dissociation constants, but the difference in dissociation constants does not explain the pH-dependence in the acid region or at high ionic strength. Within physiological ranges of pH, Mg(2+) concentration and ionic strength there will be little variation in equilibrium constant.

Preparation and properties of a phosphoenzyme from the phosphoglucomutase of Micrococcus lysodeikticus

1. Phosphoglucomutase from Micrococcus lysodeikticus was incubated with (14)C- and (32)P-labelled glucose 1,6-diphosphate and separated from the cofactor on a Sephadex column. (32)P-labelled phosphate (0.7mol/mol of enzyme) was associated with the enzyme, but no (14)C label was. 2. The (32)P-labelled enzyme exchanged its label with the substrates. When the labelled enzyme was incubated in Tris buffer, pH8.3, at 30 degrees C the proportion of exchangeable label slowly fell indicating a half-life of the phosphoenzyme of about 50h. 3. When HClO(4) was added to the labelled phosphoenzyme all of the label was precipitated with the protein and none was released as P(i). On alkaline hydrolysis P(i) was released at a rate comparable with the rate of hydrolysis of the phosphoenzyme from rabbit muscle. 4. We conclude that the phosphoenzyme from Micrococcus lysodeikticus yields a relatively stable, catalytically active phosphoenzyme when treated with cofactor, and that there is no evidence for the formation of an enzyme-glucose 1,6-diphosphate complex. The properties of the phosphoenzyme, which resemble those of rabbit muscle phosphoglucomutase, suggest that the phosphate may be bound to serine.

The mechanism of phosphoglucomutase from Micrococcus lysodeikticus

The mechanism of the phosphoglucomutase from Micrococcus lysodeikticus was investigated. Induced-transport tests at low substrate concentrations (0.15mm) showed co-transport of the (32)P label but no induced transport of the (14)C label, which is in quantitative agreement with a phosphoenzyme mechanism with a rapid isomerization of the phosphoenzyme. The results excluded an intramolecular transfer of phosphate and could only have been compatible with a sequential mechanism if the K(m) for glucose 1-phosphate had been over 20 times smaller than the measured value. The results of induced-transport tests at intermediate concentrations (1mm) with both labels agreed quantitatively with a phosphoenzyme mechanism, and induced-transport tests with (14)C-labelled substrates at high concentrations (26mm) indicated that the rate constants for isomerization of the phosphoenzyme must be greater than about 3x10(6)s(-1). Consistent with these findings is the fact that (14)C label exchanged between the substrates twice as rapidly as the (32)P label at chemical equilibrium. Further, since the (14)C label exchanged between the substrates about ten times more rapidly than between the substrates and glucose 1,6-diphosphate, glucose 1,6-diphosphate is not an obligatory intermediate in the interconversion of the substrates. It is concluded that, contrary to previous evidence, the mechanism of the enzyme from M. lysodeikticus is essentially that of the rabbit muscle enzyme. To account for the rapid isomerization of the phosphoenzyme in both cases a mechanism is proposed in which there is no formal isomerization of the phosphoenzyme.

The reactive serine residue in phosphoglucomutase of Micrococcus lysodeikiticus

1. Phosphoglucomutase of Micrococcus lysodeikticus was labelled at the active site by exchange with (32)P-labelled substrates of high specific radioactivity. 2. Partial acid hydrolysis gave rise to radioactive peptides; serine phosphate was identified as one of the derivatives. 3. Comparison of the other (32)P-labelled peptides with the peptides obtained from the (32)P-labelled rabbit muscle phosphoglucomutase indicates that the sequence around the reactive serine residue is identical in both enzymes.

Mechanism of the 2,3-diphosphoglycerate-dependent phosphoglycerate mutase from rabbit muscle

1. The properties and kinetics of the 2,3-diphosphoglycerate-dependent phosphoglycerate mutases are discussed. There are at least three possible mechanisms for the reaction: (i) a phosphoenzyme (Ping Pong) mechanism; (ii) an intermolecular transfer of phosphate from 2,3-diphosphoglycerate to the substrates (sequential mechanism); (iii) an intramolecular transfer of phosphate. It is concluded that these mechanisms cannot be distinguished by conventional kinetic measurements. 2. The fluxes for the different mechanisms are calculated and it is shown that it should be possible to distinguish between the mechanisms by appropriate induced-transport tests and by comparing the fluxes of (32)P- and (14)C-labelled substrates at chemical equilibrium. 3. With (14)C-labelled substrates no induced transport was found over a wide concentration range, and with (32)P-labelled substrates co-transport occurred that was independent of concentration over a twofold range. (14)C-labelled substrates exchange at twice the rate of (32)P-labelled substrates at chemical equilibrium. The results were completely in accord with a phosphoenzyme mechanism and indicated a rate constant for the isomerization of the phosphoenzyme of not less than 4x10(6)s(-1). The intramolecular transfer of phosphate (and intermolecular transfer between two or more molecules of substrate) were completely excluded. The intermolecular transfer of phosphate from 2,3-diphosphoglycerate would have been compatible with the results only if the K(m) for 2-phosphoglycerate had been over 7.5-fold smaller than the observed value and if an isomerization of the enzyme-2,3-diphosphoglycerate complex had been the major rate-limiting step in the reaction. 4. The very rapid isomerization of the phosphoenzyme that the experiments demonstrate suggests a mechanism that does not involve a formal isomerization. According to this new scheme the enzyme is closely related mechanistically and perhaps evolutionarily to a 2,3-diphosphoglycerate diphosphatase.