Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

Genetic control of rhizosheath formation in pearl millet

The rhizosheath, the layer of soil that adheres strongly to roots, influences water and nutrients acquisition. Pearl millet is a cereal crop that plays a major role for food security in arid regions of sub-Saharan Africa and India. We previously showed that root-adhering soil mass is a heritable trait in pearl millet and that it correlates with changes in rhizosphere microbiota structure and functions. Here, we studied the correlation between root-adhering soil mass and root hair development, root architecture, and symbiosis with arbuscular mycorrhizal fungi and we analysed the genetic control of this trait using genome wide association (GWAS) combined with bulk segregant analysis and gene expression studies. Root-adhering soil mass was weakly correlated only to root hairs traits in pearl millet. Twelve QTLs for rhizosheath formation were identified by GWAS. Bulk segregant analysis on a biparental population validated five of these QTLs. Combining genetics with a comparison of global gene expression in the root tip of contrasted inbred lines revealed candidate genes that might control rhizosheath formation in pearl millet. Our study indicates that rhizosheath formation is under complex genetic control in pearl millet and suggests that it is mainly regulated by root exudation.

[State of art of photobiomodulation in the management of radiotherapy adverse events: Indications and level of evidence]

PURPOSE

To evaluate the current and potential indications of photobiomodulation (PBM) and their level of evidence in the prevention or management of radiation therapy-related side effects.

MATERIALS AND METHODS

The Embase, Medline/PubMed, Cochrane, EBSCO, Scopus, and LILACS databases were systematically reviewed to include and analyze publications of clinical studies that have assessed PBM in the prevention or management of radiotherapy-related side effects. The keywords used were "photobiomodulation"; "low level laser therapy"; "acute oral mucositis"; "acute dysphagia"; "acute radiation dermatitis"; "lymphedema"; "xerostomia"; "hyposalivation"; "trismus"; "bone necrosis"; "osteoradionecrosis"; and "radiation induced fibrosis". Prospective studies were included, whereas retrospective cohorts and non-original articles were excluded from the analysis.

RESULTS

PBM in the red or infrared spectrum has demonstrated efficacy in randomized controlled trials in the prevention and management of radiotherapy-related side effects, especially acute oral mucositis, acute radiation dermatitis, and upper extremity lymphedema. The level of evidence associated with PBM was heterogeneous, but overall was still moderate. The main shortcomings were the diversity and lack of detail in treatment protocols, which could have compromised efficiency and reproducibility of PBM results.

CONCLUSION

The published data suggest that PBM may be considered as a full-fledged supportive care for patients treated with radiotherapy, or at least in the setting of a therapeutic clinical trial. However, until strong evidence has been published on its long-term safety, the use of PBM should be considered with caution, specifically when applied near areas with proven or potential tumors. The patient should be informed of the theoretical benefits and risks of PBM in order to obtain his informed consent before treatment.

Comparison of patient satisfaction measures between in-person and telemedicine postoperative appointments following third molar surgery

The goal of this study was to compare key aspects of patient satisfaction in patients who underwent in-person and telemedicine postoperative appointments following third molar surgery. A total of 69 patients undergoing the removal of third molars were randomized to receive their postoperative care either in person or via telemedicine appointments. Following the postoperative visit, patients were asked to complete a survey that assessed elements of patient satisfaction using a visual analog scale. Forty-seven patients (37 female, 10 male) completed the study (in-person n=24, telemedicine n=23). The mean total patient satisfaction score (maximum 50) was 46.46 for the in-person group and 48.78 for the telemedicine group; the difference was not statistically significant (P=0.11). There were no statistically significant differences in patient satisfaction scores between the two groups with regards to the ease of scheduling the appointment, ease of attending the appointment, perceived usefulness of the appointment, or the quality of patient education received at the appointment. However, the perceived cost-effectiveness was higher for patients in the telemedicine group (P=0.01). The results of this study suggest that for third molar extraction surgery, telemedicine and in-office postoperative visits produce similar patient satisfaction experiences, but patient perceived cost-effectiveness was greater for telemedicine visits.

Doctors' attitudes to patient occupation information in four hospital specialties

BACKGROUND

Although we do not know how often doctors enquire about their patients' work, evidence suggests that occupation is often not recorded in clinical notes. There is a lack of research into doctors' views on the importance of patient occupation or their educational needs in this area.

AIMS

To assess doctors' attitudes to using patient occupation information for care-planning and to determine doctors' need for specific training in occupational health.

METHODS

We undertook a cross-sectional survey of doctors in cardiology, obstetrics and gynaecology, oncology and orthopaedics. Our questionnaire explored attitudes of the doctors to asking patients about their occupational status, their training and competency to do so, and their training needs in occupational health.

RESULTS

The response rate was 42/46 (91%). Obstetrics and gynaecology 6/9 (67%) and oncology doctors 3/6 (50%) reported enquiring about the nature of patients' occupations' 'most of the time'/'always' and that it rarely influenced clinical decisions. This contrasted with orthopaedic doctors 12/12 (100%) and cardiology doctors 14/15 (93%). Although 19/42 (45%) participants felt it was important to ask patients their occupation, only 10/42 (24%) 'always' asked patients about their work. The majority of participants 29/41 (71%) reported receiving no training in occupational health, but 37/42 (88%) considered that some training would be useful.

CONCLUSIONS

Training on the importance of occupation and its' role as a clinical outcome in care-planning, might help doctors feel more competent in discussing the impact of health on work with patients.

Microwave-assisted synthesis of zinc 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin and zinc 5-(4-carboxyphenyl)-10,15,20-triphenylchlorin

The microwave-assisted synthesis of zinc 5-(4-carboxyphenyl)-10,15,20-triphenylporphyrin and zinc 5-(4-carboxyphenyl)-10,15,20-triphenylchlrorin are described and compared to classic conditions of synthesis in terms of time of reaction and yields obtained. The new experimental protocols are easy to implement required small amounts of reagents and solvents and lead to short reaction times. All compounds have been characterized by 1 H NMR, MS and spectroscopic techniques.

Increased airway iron as a potential factor in the persistence of Pseudomonas aeruginosa infection in cystic fibrosis

Iron availability is critical to many bacteria and increased iron has been described in airway secretions in cystic fibrosis (CF). The main aim of the present study was to assess the relationship between iron in CF sputum and the quantitative bacterial burden. Iron, ferritin and total cell counts (TCC) were assessed in sputum samples obtained from 15 clinically stable CF patients chronically infected with Pseudomonas aeruginosa. Sputum samples were also obtained at the commencement of episodes of acute exacerbation in 10 subjects and analyses were repeated in six of these exacerbation cases after i.v. antibiotic treatment. The relationship between iron indices and the presence of P. aeruginosa, as well as total anaerobic bacterial load, was determined. Sputum was also obtained from 10 CF patients with no evidence of infection with P. aeruginosa and 11 normal healthy controls. Sputum iron, ferritin and TCC were significantly elevated in all CF patients, even in those not infected with P. aeruginosa, compared with healthy controls. There was a strong positive relationship between sputum iron and P. aeruginosa in clinically stable patients, but not in samples obtained during an acute exacerbation. There was no relationship between sputum iron and anaerobic bacterial load. Antibiotic treatment significantly reduced sputum TCC and anaerobic bacterial load, but not iron, ferritin or the presence of P. aeruginosa during an exacerbation. In conclusion, the present study suggests that increased airway iron may be important to Pseudomonas aeruginosa persistence in cystic fibrosis.

Arabidopsis kinome: after the casting

Arabidopsis thaliana is used as a favourite experimental organism for many aspects of plant biology. We capitalized on the recently available Arabidopsis genome sequence and predicted proteome, to draw up a genome-scale protein serine/threonine kinase (PSTK) inventory. The PSTKs represent about 4% of the A. thaliana proteome. In this study, we provide a description of the content and diversity of the non-receptor PSTKs. These kinases have crucial functions in sensing, mediating and coordinating cellular responses to an extensive range of stimuli. A total of 369 predicted non receptor PSTKs were detailed: the Raf superfamily, the CMGC, CaMK, AGC and STE families, as well as a few small clades and orphan sequences. An extensive relationship analysis of these kinases allows us to classify the proteins in superfamilies, families, sub-families and groups. The classification provides a better knowledge of the characteristics shared by the different clades. We focused on the MAP kinase module elements, with particular attention to their docking sites for protein-protein interaction and their biological function. The large number of A. thaliana genes encoding kinases might have been achieved through successive rounds of gene and genome duplications. The evolution towards an increasing gene number suggests that functional redundancy plays an important role in plant genetic robustness.

Residual heat deposition in dental enamel during IR laser ablation at 2.79, 2.94, 9.6, and 10.6 microm

BACKGROUND AND OBJECTIVE

The principal factor limiting the rate of laser ablation of dental hard tissue is the risk of excessive heat accumulation in the tooth. Excessive heat deposition or accumulation may result in unacceptable damage to the pulp. The objective of this study was to measure the residual heat deposition during the laser ablation of dental enamel at those IR laser wavelengths well suited for the removal of dental caries. Optimal laser ablation systems minimize the residual heat deposition in the tooth by efficiently transferring the deposited laser energy to kinetic and internal energy of ejected tissue components.

STUDY DESIGN/MATERIALS AND METHODS

The residual heat deposition in dental enamel was measured at laser wavelengths of 2.79, 2.94, 9.6, and 10.6 microm and pulse widths of 150 nsec -150 microsec using bovine block "calorimeters." Water droplets were applied to the surface before ablation with 150 microsec Er:YAG laser pulses to determine the influence of an optically thick water layer on reducing heat deposition.

RESULTS

The residual heat was at a minimum for fluences well above the ablation threshold where measured values ranged from 25-70% depending on pulse duration and wavelength for the systems investigated. The lowest values of the residual heat were measured for short (< 20 micros) CO(2) laser pulses at 9.6 microm and for Q-switched erbium laser pulses at 2.79 and 2.94 microm. Droplets of water applied to the surface before ablation significantly reduced the residual heat deposition during ablation with 150 microsec Er:YAG laser pulses.

CONCLUSIONS

Residual heat deposition can be markedly reduced by using CO(2) laser pulses of less than 20 microsec duration and shorter Q-switched Er:YAG and Er:YSGG laser pulses for enamel ablation.

The protein kinases AtMAP3Kepsilon1 and BnMAP3Kepsilon1 are functional homologues of S. pombe cdc7p and may be involved in cell division

We identified an Arabidopsis thaliana gene, AtMAP3Kepsilon1, and a Brassica napus cDNA, BnMAP3Kepsilon1, encoding functional protein serine/threonine kinases closely related to cdc7p and Cdc15p from Schizosaccharomyces pombe and Saccharomyces cerevisiae, respectively. This is the first report of cdc7-related genes in non-fungal eukaryotes; no such genes have as yet been identified in Metazoans. The B. napus protein is able to partially complement a cdc7 loss of function mutation in S. pombe. RT-PCR and in situ hybridisation revealed that the A. thaliana and B. napus genes are expressed in both the sporophytic and the gametophytic tissues of the respective plant species and revealed further that expression is highest in dividing cells. Moreover, AtMAP3Kepsilon1 gene expression is cell cycle-regulated, with higher expression in G2-M phases. Our results strongly suggest that the plant cdc7p-related protein kinases are involved in a signal transduction pathway similar to the SIN pathway, which positively regulates cytokinesis in S. pombe.

Multiple O-glycoforms on the spore coat protein SP96 in Dictyostelium discoideum. Fuc(alpha1-3)GlcNAc-alpha-1-P-Ser is the major modification

A decreased level of fucosylation on certain spore coat proteins of Dictyostelium discoideum alters the permeability of the spore coat. Here the post-translational modifications of a major spore coat protein, SP96, are studied in a wild type strain (X22) and a fucosylation-defective mutant (HU2470). A novel phosphoglycan structure on SP96 of the wild type strain, consisting of Fuc(alpha1-3)GlcNAc-alpha-1-P-Ser(,) was identified by electrospray ionization mass spectrometry and NMR. It was shown using monosaccharide and gas chromatography mass spectrometry analysis that SP96 in the mutant HU2470 contained approximately 20% of wild type levels of fucose, as a result of a missing terminal fucose on the novel glycan structure. The results support previous predictions, based on inhibition studies on different fucose-deficient strains, about the nature of monoclonal antibody epitopes identified by monoclonal antibodies MUD62 and MUD166, which are known to identify O-linked glycans (Champion, A., Griffiths, K., Gooley, A. A., Gonzalez, B. Y., Gritzali, M., West, C. M., and Williams, K. L. (1995) Microbiology 141, 785-797). Quantitative studies on wild type SP96 indicated that there were approximately 60 sites with phosphodiester-linked N-acetylglucosamine-fucose disaccharide units and a further approximately 20 sites with fucose directly linked to the protein. Over 70% of the serine sites are modified, with less than 1% of these sites as phosphoserine. Threonine and tyrosine residues were not found to be modified.

A novel jasmonate- and elicitor-responsive element in the periwinkle secondary metabolite biosynthetic gene Str interacts with a jasmonate- and elicitor-inducible AP2-domain transcription factor, ORCA2

Jasmonate (JA) is an important plant stress hormone that induces various plant defense responses, including the biosynthesis of protective secondary metabolites. The induction of the secondary metabolite biosynthetic gene Strictosidine synthase (Str) in Catharanthus roseus (periwinkle) cells by elicitor requires JA as a second messenger. A 42 bp region in the Str promoter is both necessary and sufficient for JA- and elicitor-responsive expression. This region is unlike other previously identified JA-responsive regions, and contains a GCC-box-like element. Yeast one-hybrid screening identified cDNAs encoding two AP2-domain proteins. These octadecanoid-derivative responsive Catharanthus AP2-domain (ORCA) proteins bind in a sequence-specific manner the JA- and elicitor-responsive element. ORCA2 trans-activates the Str promoter and its expression is rapidly inducible with JA and elicitor, whereas Orca1 is expressed constitutively. The results indicate that a GCC-box-like element and ORCA2 play key roles in JA- and elicitor-responsive expression of the terpenoid indole alkaloid biosynthetic gene Str.

Viable Cryptosporidium parvum oocysts exposed to chlorine or other oxidising conditions may lack identifying epitopes

The intestinal protozoan parasite Cryptosporidium parvum is a known cause of water-borne disease in humans. The detection of Cryptosporidium oocysts in water samples relies upon the use of fluorescently labelled antibodies, preferably using flow cytometry and epifluorescence microscopy. Here we demonstrate that four commercially available antibodies recognise a similar set of immunodominant epitopes on the oocyst wall. These epitopes appear to be carbohydrate in nature and are labile to chlorine treatment and oxidising conditions. Sodium hypochlorite and sodium meta-periodate reduced the ability of the antibodies to detect Cryptosporidium oocysts. Damage to the epitopes did not necessarily reduce the viability of oocysts. This finding may be important for the water industry, where naturally occurring oxidising conditions or sanitizing treatments could produce viable oocysts that are undetectable using standard protocols.

Karyotype and nuclear DNA content of the Australian lungfish, Neoceratodus forsteri (Ceratodidae: Dipnoi)

The karyotype of the lungfish, Neoceratodus forsteri, is described as 2n = 54, comprising 3 pairs of very large metacentrics, 1 pair of large submetacentrics, 13 pairs of smaller acrocentrics, and 10 pairs of microchromosomes. In addition to centromeric constitutive heterochromatin, C-bands were located on the arms of almost all of the macrochromosomes. The nuclear DNA content of N. forsteri was confirmed as being high (98.6-111.9 pg/nucleus).

Immunochemical, genetic and morphological comparison of fucosylation mutants of Dictyostelium discoideum

Mutations in three loci in Dictyostelium discoideum which affect fucosylation are described. Mutations in two of these loci resulted in the simultaneous loss of two separate carbohydrate epitopes. The GA-X epitope, which was competed by L-fucose, was absent in strains carrying a modC354, modD352 or modE353 mutation. These strains exposed a new carbohydrate epitope, competed by N-acetylglucosamine, and the size of several glycoproteins was reduced. A second epitope (GA-XII) was also absent in strains carrying the modC354 or modE353 mutations, reducing the size of the glycoprotein which normally expresses it. Fucose content was reduced in the three mutants, suggesting that each mutation affected a separate step in fucosylation. The lesions did not appear to inhibit synthesis of the underlying carbohydrate, because detergent extracts of mutant vesicles were more active than normal vesicles at transferring [14C]fucose from GDP-[14C]fucose to endogenous acceptor species. The modD352 and modE353 mutant strains incorporated exogenous [3H]fucose poorly, suggesting that lesions in the modD and modE genes interfere with the biosynthesis of fucoconjugates downstream from the previously described GDP-fucose synthesis defect of the modC mutation. Intact modE353 mutant vesicles were relatively inefficient in in vitro assays, suggesting a global fucosylation defect (which is consistent with the loss of both glycoantigens, GA-X and GA-XII, in this mutant). Finally, the modC354 mutation led to delayed accumulation of slime sheath in vitro. The three genetic loci define a fucosylation pathway in D. discoideum comprising defined biochemical steps which contribute to multicellular morphogenesis in this organism.

Application of flow cytometric methods for the routine detection of Cryptosporidium and Giardia in water

Cryptosporidium and Giardia are common causes of waterborne disease. The currently used methods of detecting these organisms in water rely on filtration capture, immunofluorescence labelling, and epifluorescence microscopy. These methods are inefficient, labour intensive, and require a highly skilled microscopist. We describe an alternative technique using flocculation concentration, followed by flow cytometry with fluorescence activated cell sorting. Environmental samples were analysed, and protozoan-like particles were sorted and collected before confirmation with epifluorescence microscopy. The technique was found to be significantly more sensitive and considerably faster than the conventional methods.

Comparison in different tissue preparations of the in vitro pharmacological profile of RP 67580, a new non-peptide substance P antagonist

We describe the effects of RP 67580, a new non-peptide substance P (SP) antagonist, on tachykinin-induced contractions of guinea-pig ileum, trachea and urinary bladder, rabbit pulmonary artery and rat portal vein. All NK1 agonists tested (SP, Septide, SPOMe and [Pro9]SP) contracted guinea-pig ileum, trachea and urinary bladder (pD2 = 7.5 to 9.1), but they had no effect on rabbit pulmonary artery or rat portal vein (pD2 < 6). RP 67580 inhibited these effects: guinea-pig ileum, pA2 = 7.1 to 7.6; guinea-pig trachea and urinary bladder, pKB = 6.3 to 6.8. The difference in RP 67580 activity in these tissues might be due to the existence of subtypes of NK1 receptors. RP 67580 (1 microns) did not affect the contractions induced by the two NK2 agonists, NKA and [Lys5, MeLeu9, Nle10]NKA(4-10) (pA2 < 6), except in guinea-pig ileum (pA2 = 7.3-7.5) where these two NK2 agonists interact apparently with NK1 receptors. In the tissue preparations used, RP 67580 (1 micron) was without effect on contractions induced by the NK3 agonists: NKB and senktide. These results indicate the high selectivity for NK1 receptors of RP 67580. In all cases, similar results were obtained with another non-peptide SP antagonist, (+/-) CP-96,345. The present work provides further evidence that RP 67580 and (+/-) CP-96,345 exert in vitro a potent, selective and competitive antagonistic action on NK1 receptors and suggests the existence of at least two distinct NK1 receptor subtypes in some guinea-pig peripheral organs.

Immunodominant carbohydrate determinants in the multicellular stages of Dictyostelium discoideum

Two families of glycoprotein are defined in Dictyostelium discoideum by the presence of different glycoconjugates, both of which are highly immunogenic in mice. The previously described monoclonal antibodies MUD50 and MUD62 recognize the glycoconjugates and identify the respective glycoprotein families. Both types of glycosylation occur on vegetative and developmentally regulated glycoproteins. The immunodominant components of both families are reportedly O-linked sugars, but Western blots do not identify any glycoprotein that has both O-glycans, suggesting that there are two independently processed types of O-linked glycosylation in D. discoideum. The synthesis of the two O-glycan families is affected by glycosylation-defective mutations. Strains with a mutation at the modB locus lack one of these glycosylation types (that recognized by MUD50) and this mutation alters the size of two minor glycoproteins in the second family. Two new mutants, HU2470 (mod-352) and HU2471 (mod-353), lack the epitope recognized by MUD62. The two mutations map to different chromosomes. The mod-353 mutation also affects the size of PsA, a cell surface glycoprotein carrying the modB-dependent O-glycan.

IgG-dependent generation of platelet-activating factor by normal and low density human eosinophils

We have compared normal and low density human eosinophils for their ability to generate platelet activating factor (PAF) in response to IgG-dependent and nonimmunologic stimulation. After 45 min incubation with IgG-coated Sepharose beads the concentrations of cell-associated PAF recovered from normal density eosinophils were significantly greater than from low-density eosinophils or neutrophils. Moreover, eosinophils stimulated with calcium ionophore A23187 had a considerably greater capacity to generate PAF than had previously been described. Although the quantities of cell-associated PAF recovered from normal and low density eosinophils and neutrophils after A23187 stimulation were similar, the amounts of extracellular PAF recovered from both eosinophil populations were significantly greater than from neutrophils. The amounts of PAF recovered from the low density eosinophils may not reflect the full synthetic capacity of these cells, because PAF-turnover was found to be more rapid than that observed with normal density eosinophils. When exogenous [3H]PAF was added to the two stimulated eosinophil populations subsequent analysis of the [3H]PAF metabolites by DIOL-HPLC revealed that low density eosinophils incorporated PAF into the phosphatidylcholine (PC) pool more rapidly than did normal density eosinophils or neutrophils. Alkaline hydrolysis of the PC fraction from whole cell extracts followed by treatment with acetic anhydride resulted in all the PC-associated radioactivity being converted to [3H]PAF, confirming PAF incorporation to PC via this pathway. These findings suggest that the contribution of eosinophils to inflammatory processes through the generation of PAF may be greater than previously appreciated, and that Ig-mediated stimulation may be important in initiating generation of the mediator. Low density eosinophils, that are presumed to be similar to tissue eosinophils, may have a role in regulating PAF concentrations in tissues through their enhanced rate of metabolism.

IgG-dependent generation of platelet-activating factor by normal and low density human eosinophils

We have compared normal and low density human eosinophils for their ability to generate platelet activating factor (PAF) in response to IgG-dependent and nonimmunologic stimulation. After 45 min incubation with IgG-coated Sepharose beads the concentrations of cell-associated PAF recovered from normal density eosinophils were significantly greater than from low-density eosinophils or neutrophils. Moreover, eosinophils stimulated with calcium ionophore A23187 had a considerably greater capacity to generate PAF than had previously been described. Although the quantities of cell-associated PAF recovered from normal and low density eosinophils and neutrophils after A23187 stimulation were similar, the amounts of extracellular PAF recovered from both eosinophil populations were significantly greater than from neutrophils. The amounts of PAF recovered from the low density eosinophils may not reflect the full synthetic capacity of these cells, because PAF-turnover was found to be more rapid than that observed with normal density eosinophils. When exogenous [3H]PAF was added to the two stimulated eosinophil populations subsequent analysis of the [3H]PAF metabolites by DIOL-HPLC revealed that low density eosinophils incorporated PAF into the phosphatidylcholine (PC) pool more rapidly than did normal density eosinophils or neutrophils. Alkaline hydrolysis of the PC fraction from whole cell extracts followed by treatment with acetic anhydride resulted in all the PC-associated radioactivity being converted to [3H]PAF, confirming PAF incorporation to PC via this pathway. These findings suggest that the contribution of eosinophils to inflammatory processes through the generation of PAF may be greater than previously appreciated, and that Ig-mediated stimulation may be important in initiating generation of the mediator. Low density eosinophils, that are presumed to be similar to tissue eosinophils, may have a role in regulating PAF concentrations in tissues through their enhanced rate of metabolism.

The contribution of an adult educationalist to a trainers' group

I have summarized my findings as a non-medically qualified educationalist attending regularly at meetings of a group of general-practitioner trainers. I believe that it is essential for trainers to learn to draw general principles from specific examples in order to help trainees to learn. Two other contributions an educationalist can make are promoting counselling relationships and helping trainers understand more deeply their own relationships with their patients.