Learning in the COVID-19 pandemic and beyond: development and rapid uptake of an online learning platform for vascular surgery

INTRODUCTION

With the onset of the COVID-19 pandemic, alternative methods of delivering medical education were rapidly required. An online learning platform was developed with the aim of providing high-quality, accessible learning to vascular specialty trainees. We describe the design, delivery and analysis of the first 15 months of the platform. Although originally a regional initiative, we discuss how popularity and feedback led to a rapid expansion of the training programme internationally.

METHODS

A fully online educational platform for vascular surgery specialist trainees was developed. The primary aims and ethos of the programme were that it should be easily accessible from any location, convenient, flexible, cooperative and collaborative, social and free financially to access. All learning resources were researched carefully and based on the UK vascular surgery curriculum and 20 seminal papers targeted in the Vascular Specialist Fellow of the Royal College of Surgeons (FRCSVasc) examination.

RESULTS

The project demonstrated that it is feasible to design, build and deliver a postgraduate clinical teaching platform with minimal time requirement, resources and cost while creating and maintaining high-quality content. Rapid national and international uptake has proven there is demand - in addition to overwhelmingly positive feedback from educators and learners, this demonstrates that previously perceived barriers to online education can be overcome. At present, 53 educational sessions have been delivered and are available in the online library, and in the past year (8 December 2020 to 8 December 2021) the website has been accessed 3,877 times.

CONCLUSIONS

Although the programme has grown and evolved, a strong focus is being kept on its original ethos and aims - easily accessible, collaborative, free learning resources for all vascular professionals, based on the UK vascular surgery curriculum. Making learning convenient is key. The COVID-19 pandemic may be a watershed moment for a new era of learning. It is an opportunity for people from different backgrounds to share experiences and to develop cohesion within a hospital and network, nationally and worldwide.

The entomopathogenic bacterial endosymbionts Xenorhabdus and Photorhabdus: convergent lifestyles from divergent genomes

Members of the genus Xenorhabdus are entomopathogenic bacteria that associate with nematodes. The nematode-bacteria pair infects and kills insects, with both partners contributing to insect pathogenesis and the bacteria providing nutrition to the nematode from available insect-derived nutrients. The nematode provides the bacteria with protection from predators, access to nutrients, and a mechanism of dispersal. Members of the bacterial genus Photorhabdus also associate with nematodes to kill insects, and both genera of bacteria provide similar services to their different nematode hosts through unique physiological and metabolic mechanisms. We posited that these differences would be reflected in their respective genomes. To test this, we sequenced to completion the genomes of Xenorhabdus nematophila ATCC 19061 and Xenorhabdus bovienii SS-2004. As expected, both Xenorhabdus genomes encode many anti-insecticidal compounds, commensurate with their entomopathogenic lifestyle. Despite the similarities in lifestyle between Xenorhabdus and Photorhabdus bacteria, a comparative analysis of the Xenorhabdus, Photorhabdus luminescens, and P. asymbiotica genomes suggests genomic divergence. These findings indicate that evolutionary changes shaped by symbiotic interactions can follow different routes to achieve similar end points.

Differential control of Yersinia pestis biofilm formation in vitro and in the flea vector by two c-di-GMP diguanylate cyclases

Yersinia pestis forms a biofilm in the foregut of its flea vector that promotes transmission by flea bite. As in many bacteria, biofilm formation in Y. pestis is controlled by intracellular levels of the bacterial second messenger c-di-GMP. Two Y. pestis diguanylate cyclase (DGC) enzymes, encoded by hmsT and y3730, and one phosphodiesterase (PDE), encoded by hmsP, have been shown to control biofilm production in vitro via their opposing c-di-GMP synthesis and degradation activities, respectively. In this study, we provide further evidence that hmsT, hmsP, and y3730 are the only three genes involved in c-di-GMP metabolism in Y. pestis and evaluated the two DGCs for their comparative roles in biofilm formation in vitro and in the flea vector. As with HmsT, the DGC activity of Y3730 depended on a catalytic GGDEF domain, but the relative contribution of the two enzymes to the biofilm phenotype was influenced strongly by the environmental niche. Deletion of y3730 had a very minor effect on in vitro biofilm formation, but resulted in greatly reduced biofilm formation in the flea. In contrast, the predominant effect of hmsT was on in vitro biofilm formation. DGC activity was also required for the Hms-independent autoaggregation phenotype of Y. pestis, but was not required for virulence in a mouse model of bubonic plague. Our results confirm that only one PDE (HmsP) and two DGCs (HmsT and Y3730) control c-di-GMP levels in Y. pestis, indicate that hmsT and y3730 are regulated post-transcriptionally to differentially control biofilm formation in vitro and in the flea vector, and identify a second c-di-GMP-regulated phenotype in Y. pestis.

Glycosylation genes expressed in seam cells determine complex surface properties and bacterial adhesion to the cuticle of Caenorhabditis elegans

The surface of the nematode Caenorhabditis elegans is poorly understood but critical for its interactions with the environment and with pathogens. We show here that six genes (bus-2, bus-4, and bus-12, together with the previously cloned srf-3, bus-8, and bus-17) encode proteins predicted to act in surface glycosylation, thereby affecting disease susceptibility, locomotory competence, and sexual recognition. Mutations in all six genes cause resistance to the bacterial pathogen Microbacterium nematophilum, and most of these mutations also affect bacterial adhesion and biofilm formation by Yersinia species, demonstrating that both infection and biofilm formation depend on interaction with complex surface carbohydrates. A new bacterial interaction, involving locomotory inhibition by a strain of Bacillus pumilus, reveals diversity in the surface properties of these mutants. Another biological property--contact recognition of hermaphrodites by males during mating--was also found to be impaired in mutants of all six genes. An important common feature is that all are expressed most strongly in seam cells, rather than in the main hypodermal syncytium, indicating that seam cells play the major role in secreting surface coat and consequently in determining environmental interactions. To test for possible redundancies in gene action, the 15 double mutants for this set of genes were constructed and examined, but no synthetic phenotypes were observed. Comparison of the six genes shows that each has distinctive properties, suggesting that they do not act in a linear pathway.

Caenorhabditis elegans BAH-1 is a DUF23 protein expressed in seam cells and required for microbial biofilm binding to the cuticle

The cuticle of Caenorhabditis elegans, a complex, multi-layered extracellular matrix, is a major interface between the animal and its environment. Biofilms produced by the bacterial genus Yersinia attach to the cuticle of the worm, providing an assay for surface characteristics. A C. elegans gene required for biofilm attachment, bah-1, encodes a protein containing the domain of unknown function DUF23. The DUF23 domain is found in 61 predicted proteins in C. elegans, which can be divided into three distinct phylogenetic clades. bah-1 is expressed in seam cells, which are among the hypodermal cells that synthesize the cuticle, and is regulated by a TGF-β signaling pathway.

The response regulator PhoP negatively regulates Yersinia pseudotuberculosis and Yersinia pestis biofilms

A few Yersinia pseudotuberculosis strains form biofilms on the head of the nematode Caenorhabditis elegans, but numerous others do not. We show that a widely used Y. pseudotuberculosis strain, YPIII, is biofilm positive because of a mutation in phoP, which encodes the response regulator of a two-component system. For two wild-type Y. pseudotuberculosis that do not make biofilms on C. elegans, deletion of phoP was sufficient to produce robust biofilms. In Yersinia pestis, a phoP mutant made more extensive biofilms in vitro than did the wild type. Expression of HmsT, a diguanylate cyclase that positively regulates biofilms, is diminished in Y. pseudotuberculosis strains with functional PhoP.

Uniquely insidious: Yersinia pestis biofilms

Bubonic plague, one of history's deadliest infections, is transmitted by fleas infected with Yersinia pestis. The bacteria can starve fleas by blocking their digestive tracts, which stimulates the insects to bite repeatedly and thereby infect new hosts. Direct examination of infected fleas, aided by in vitro studies and experiments with the nematode Caenorhabditis elegans, have established that Y. pestis forms a biofilm in the insect. The extracellular matrix of the biofilm seems to contain a homopolymer of N-acetyl-d-glucosamine, which is a constituent of many bacterial biofilms. A regulatory mechanism involved in Y. pestis biofilm formation, cyclic-di-GMP signaling, is also widespread in bacteria; yet only Y. pestis forms biofilms in fleas. Here, the historical background of bubonic plague is briefly described and recent studies investigating the mechanisms by which these unique and deadly biofilms are formed are discussed.

Optical mapping as a routine tool for bacterial genome sequence finishing

Background

In sequencing the genomes of two Xenorhabdus species, we encountered a large number of sequence repeats and assembly anomalies that stalled finishing efforts. This included a stretch of about 12 Kb that is over 99.9% identical between the plasmid and chromosome of X. nematophila.

Results

Whole genome restriction maps of the sequenced strains were produced through optical mapping technology. These maps allowed rapid resolution of sequence assembly problems, permitted closing of the genome, and allowed correction of a large inversion in a genome assembly that we had considered finished.

Conclusion

Our experience suggests that routine use of optical mapping in bacterial genome sequence finishing is warranted. When combined with data produced through 454 sequencing, an optical map can rapidly and inexpensively generate an ordered and oriented set of contigs to produce a nearly complete genome sequence assembly.

Caenorhabditis elegans mutants resistant to attachment of Yersinia biofilms

The detailed composition and structure of the Caenorhabditis elegans surface are unknown. Previous genetic studies used antibody or lectin binding to identify srf genes that play roles in surface determination. Infection by Microbacterium nematophilum identified bus (bacterially unswollen) genes that also affect surface characteristics. We report that biofilms produced by Yersinia pestis and Y. pseudotuberculosis, which bind the C. elegans surface predominantly on the head, can be used to identify additional surface-determining genes. A screen for C. elegans mutants with a biofilm absent on the head (Bah) phenotype identified three novel genes: bah-1, bah-2, and bah-3. The bah-1 and bah-2 mutants have slightly fragile cuticles but are neither Srf nor Bus, suggesting that they are specific for surface components involved in biofilm attachment. A bah-3 mutant has normal cuticle integrity, but shows a stage-specific Srf phenotype. The screen produced alleles of five known surface genes: srf-2, srf-3, bus-4, bus-12, and bus-17. For the X-linked bus-17, a paternal effect was observed in biofilm assays.

Yersinia pestis YrbH is a multifunctional protein required for both 3-deoxy-D-manno-oct-2-ulosonic acid biosynthesis and biofilm formation

Bubonic plague is transmitted by fleas whose feeding is blocked by a Yersinia pestis biofilm in the digestive tract. Y. pestis also block feeding of Caenorhabditis elegans by forming a biofilm on the nematode head, making the nematode an experimentally tractable surrogate for fleas to study plague transmission. Arabinose 5-phosphate isomerase (API), encoded by Y. pestis yrbH, catalyses the conversion of ribulose 5-phosphate into arabinose 5-phosphate (A5P), the first committed step in the 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) biosynthesis pathway. Here we show that Y. pestis YrbH is a multifunctional protein required for both Kdo biosynthesis and biofilm formation on C. elegans. The YrbH protein contains four functional components: biofilm-related region 1 (B1), a sugar isomerase domain (SIS), biofilm-related region 2 (B2) and a cystathionine beta-synthase domain pair (CBS). B1, SIS and B2 are all required for API function, but any of the three is sufficient for a biofilm-related function. The CBS domain appears to negatively regulate the biofilm-related function.

Identification of gmhA, a Yersinia pestis gene required for flea blockage, by using a Caenorhabditis elegans biofilm system

Yersinia pestis, the cause of bubonic plague, blocks feeding by its vector, the flea. Recent evidence indicates that blockage is mediated by an in vivo biofilm. Y. pestis and the closely related Yersinia pseudotuberculosis also make biofilms on the cuticle of the nematode Caenorhabditis elegans, which block this laboratory animal's feeding. Random screening of Y. pseudotuberculosis transposon insertion mutants with a C. elegans biofilm assay identified gmhA as a gene required for normal biofilms. gmhA encodes phosphoheptose isomerase, an enzyme required for synthesis of heptose, a conserved component of lipopolysaccharide and lipooligosaccharide. A Y. pestis gmhA mutant was constructed and was severely defective for C. elegans biofilm formation and for flea blockage but only moderately defective in an in vitro biofilm assay. These results validate use of the C. elegans biofilm system to identify genes and pathways involved in Y. pestis flea blockage.

Yersinia pestis is viable with endotoxin composed of only lipid A

Lipopolysaccharide (LPS) is the major outer membrane component of gram-negative bacteria. The minimal LPS structure for viability of Escherichia coli and Salmonella enterica serovar Typhimurium is lipid A glycosylated with 3-deoxy-D-manno-octulosonic acid (Kdo) residues. Here we show that another member of the Enterobacteriaceae, Yersinia pestis, can survive without Kdo in its LPS.

Interactions with microbial pathogens

A wide variety of bacterial pathogens, as well as several fungi, kill C. elegans or produce non-lethal disease symptoms. This allows the nematode to be used as a simple, tractable model host for infectious disease. Human pathogens that affect C. elegans include gram-negative bacteria of genera Burkholderia, Pseudomonas, Salmonella, Serratia and Yersinia; gram-positive bacteria Enterococcus, Staphylococcus and Streptococcus; and the fungus Cryptococcus neoformans. Microbes that are not pathogenic to mammals, such as the insect pathogen Bacillus thuringiensis and the nematode-specific Microbacterium nematophilum, are also studied with C. elegans. Many of the pathogens investigated colonize the C. elegans intestine, and pathology is usually quantified as decreased lifespan of the nematode. A few microbes adhere to the nematode cuticle, while others produce toxins that kill C. elegans without a requirement for whole, live pathogen cells to contact the worm. The rapid growth and short generation time of C. elegans permit extensive screens for mutant pathogens with diminished killing, and some of the factors identified in these screens have been shown to play roles in mammalian infections. Genetic screens for toxin-resistant C. elegans mutants have identified host pathways exploited by bacterial toxins.

A movable surface: formation of Yersinia sp. biofilms on motile Caenorhabditis elegans

Bubonic plague is transmitted by fleas whose feeding is blocked by a mass of Yersinia pestis in the digestive tract. Y. pestis and the closely related Y. pseudotuberculosis also block the feeding of Caenorhabditis elegans by forming a biofilm on the nematode head. C. elegans mutants with severe motility defects acquire almost no biofilm, indicating that normal animals accumulate the biofilm matrix as they move through a Yersinia lawn. Using the lectin wheat germ agglutinin as a probe, we show that the matrix on C. elegans contains carbohydrate produced by Yersinia. The carbohydrate is present in bacterial lawns prior to addition of nematodes, indicating that biofilm formation does not involve signaling between the two organisms. Furthermore, biofilm accumulation depends on continuous C. elegans exposure to a lawn of Yersinia bacteria.

Loss of srf-3-encoded nucleotide sugar transporter activity in Caenorhabditis elegans alters surface antigenicity and prevents bacterial adherence

During the establishment of a bacterial infection, the surface molecules of the host organism are of particular importance, since they mediate the first contact with the pathogen. In Caenorhabditis elegans, mutations in the srf-3 locus confer resistance to infection by Microbacterium nematophilum, and they also prevent biofilm formation by Yersinia pseudotuberculosis, a close relative of the bubonic plague agent Yersinia pestis. We cloned srf-3 and found that it encodes a multitransmembrane hydrophobic protein resembling nucleotide sugar transporters of the Golgi apparatus membrane. srf-3 is exclusively expressed in secretory cells, consistent with its proposed function in cuticle/surface modification. We demonstrate that SRF-3 can function as a nucleotide sugar transporter in heterologous in vitro and in vivo systems. UDP-galactose and UDP-N-acetylglucosamine are substrates for SRF-3. We propose that the inability of Yersinia biofilms and M. nematophilum to adhere to the nematode cuticle is due to an altered glycoconjugate surface composition of the srf-3 mutant.

Caenorhabditis elegans: plague bacteria biofilm blocks food intake

Bubonic plague is transmitted to mammals, including humans, by the bites of fleas whose digestive tracts are blocked by a mass of the bacterium Yersinia pestis. In these fleas, the plague-causing bacteria are surrounded by an extracellular matrix of unknown composition, and the blockage depends on a group of bacterial genes known as the hmsHFRS operon. Here we show that Y. pestis creates an hmsHFRS-dependent extracellular biofilm to inhibit feeding by the nematode Caenorhabditis elegans. Our results suggest that feeding obstruction in fleas is a biofilm-mediated process and that biofilms may be a bacterial defence against predation by invertebrates.

Comparative metabolism of genistin by human and rat gut microflora: detection and identification of the end-products of metabolism

1. Biotransformations by gut microflora play a pivotal role in determining the biological activity of isoflavones that occur in soya-based foods predominantly as betaglycosyl conjugates. Microflora prepared from rat caecae and human faeces were used to investigate the metabolic fate of genistein beta-glycosides extracted from soya flour. The end-products of such metabolism were determined by parallel incubations of microflora with [2',3,5',6'-3H] and [4-14C]-labelled genistein. 2. Quantitative analysis by LC-MS/IS indicated very rapid and complete degradation of genistin, which was associated with a transient increase in genistein. Qualitative studies indicated that the malonyl and acetyl glycosides of genistein were also degraded by the microflora. 3. Incubation of caecal and faecal microflora with [3H] and [14C]genistein yielded similar radiolabelled metabolites, which were identified by radio-LC-MS(n) as the intermediates dihydrogenistein and 6'-hydroxy-O-desmethylangolensin and end-product 4-hydroxyphenyl-2-propionic acid. This profile of genistein metabolites indicated selective hydrolysis of 6'-hydroxy-O-desmethylangolensin between carbon atoms 1' and 1 to yield the end-products 4-hydroxyphenyl-2-propionic acid and 1,3,5-trihydroxybenzene. 4. The biological significance of the products of genistein metabolism warrant further investigation since they may play an important role in mediating the beneficial antioxidant health effects associated with the consumption of isoflavones in food.

Mimicry of a G protein mutation by pertussis toxin expression in transgenic Caenorhabditis elegans

Pathogens produce virulence factors that interact directly with host molecules, but in many cases the host targets are unknown. The genetic and molecular identification of these orphan targets is often not feasible with mammalian experimental models. However, a substantial number of known targets are molecules and pathways that are conserved among eukaryotes, and therefore the use of nonmammalian model hosts to identify orphan targets may prove useful. To demonstrate the feasibility of this approach, we transformed the nematode Caenorhabditis elegans with a gene encoding the catalytic subunit of pertussis toxin (PTX), which in mammals inactivates G(o/i)alpha proteins. Expression of PTX in C. elegans produced phenotypes almost identical to those of a null mutation in the nematode gene encoding G(o/i)alpha. Furthermore, PTX suppressed the phenotype of a constitutively active form of nematode G(o/i)alpha protein. These results indicate that PTX is functional in nematodes and acts specifically on the C. elegans homologue of the mammalian target.

The role of performance measures for improving quality in managed care organizations

OBJECTIVES

To understand how managed care plans use performance measures for quality improvement and to identify the strengths and weaknesses of currently used standardized performance measures such as the Health Plan Employer Data and Information Set (HEDIS) and the Consumer Assessment of Health Plans (CAHPS) survey.

DATA SOURCES/STUDY SETTING

Representatives (chief executive officers, medical directors, and quality-improvement directors) from 24 health plans in four states were surveyed. The overall response rate was 58.3 percent, with a mean of 1.8 respondents per plan.

STUDY DESIGN

This exploratory qualitative research used a purposive sample of respondents. Two study authors conducted separate one-hour tape-recorded telephone interviews with multiple respondents from each health plan.

PRINCIPAL FINDINGS

All managed care organizations interviewed use performance measures for quality improvement but the degree and sophistication of use varies. Many of our respondent plans use performance measures to target quality-improvement initiatives, evaluate current performance, establish goals for quality improvement, identify the root cause of problems, and monitor performance.

CONCLUSION

Performance measures are used for quality improvement in addition to informing external constituents, but additional research is needed to understand how the benefits of measurement can be maximized.

Are managed care plans organizing for quality?

This article examines the degree to which managed care organizations (MCOs) are reorganizing to take responsibility for the quality of care and service they provide. Specifically, factors prompting plans to focus on quality improvement (QI) and how they may be building the capacity to improve quality are considered. The authors' analysis is based on executive interviews with the plan medical directors, QI directors, and chief executive officers (CEOs) in a sample of 24 health plans. The overall response rate was 58.3 percent (medical director = 62.5 percent, QI director = 79.2 percent, CEO = 33.3 percent). The authors queried respondents about (1) perceived drivers and obstacles to the development of an effective QI program, (2) plan organizational structure for QI, and (3) technical capacities for data collection, management, and performance measurement. The results suggest that MCOs are responding to outside pressures to engage in QI. They are reorganizing their management structures and more slowly and tentatively are building technical capacity for QI.

Co-inheritance of mutations in the uroporphyrinogen decarboxylase and hemochromatosis genes accelerates the onset of porphyria cutanea tarda

Porphyria cutanea tarda is a skin disease caused by photosensitization by porphyrins whose accumulation is caused by deficiency of hepatic uroporphyrin- ogen decarboxylase activity. Mutations in the uroporphyrinogen decarboxylase gene are present in the low-penetrant, autosomal dominant familial form but not in the commoner sporadic form of porphyria cutanea tarda. We have investigated the relationship between age of onset of skin lesions and mutations (C282Y, H63D) in the hemochromatosis gene in familial (19 patients) and sporadic porphyria cutanea tarda (65 patients). Familial porphyria cutanea tarda was identified by mutational analysis of the uroporphyrinogen decarboxylase gene. Five previously described and eight novel mutations (A80S, R144P, L216Q, E218K, L282R, G303S, 402-403delGT, IVS2 + 2 delTAA) were identified. Homozygosity for the C282Y hemochromatosis mutation was associated with an earlier onset of skin lesions in both familial and sporadic porphyria cutanea tarda, the effect being more marked in familial porphyria cutanea tarda where anticipation was demonstrated in family studies. Analysis of the frequencies of hemochromatosis genotypes in each type of porphyria cutanea tarda indicated that C282Y homozygosity is an important susceptibility factor in both types but suggested that heterozygosity for this mutation has much less effect on the development of the disease.

ETK2 receptor tyrosine kinase promotes survival of factor-dependent FDC-P1 progenitor cells

By virtue of its high expression in both developing hematopoietic tissues and many myeloid leukemia cells lines, the embryonic tyrosine kinase receptor ETK2 (also known as Tyro3, Sky, and Rse) has been postulated to play a role in early hematopoiesis. To investigate this role, we expressed murine ETK2 in the interleukin 3 (IL-3) dependent myeloid progenitor cell line FDC-P1 and examined its effect on growth factor dependence.ETK2 cDNAs encoding full-length or kinase domain-deleted receptor were retrovirally transduced into murine FDC-P1 cells. Survival, cell cycle status, and proliferative responses of ETK2 expressing clones were studied at normal and reduced growth factor concentrations. ETK2 was expressed as a functional tyrosine kinase of 110 and 150 kDa. This proto-oncogene altered the growth of FDC-P1 cells, allowing survival at reduced growth factor concentrations and delaying apoptosis after IL-3 withdrawal. ETK2-expressing clones contained a higher fraction of cells in the S/G2/M phases of the cell cycle, both after cytokine withdrawal and in the presence of IL-3. Furthermore, these cells had a modestly enhanced proliferative response to IL-3 and granulocyte-macrophage colony-stimulating factor, suggesting that ETK2 intracellular signaling may converge with that of hematopoietic growth factors. The effects of ETK2 expression on viability and proliferation were largely dependent on a functional intracellular tyrosine kinase domain. These results support a role for ETK2 in the survival and/or expansion of primitive hematopoietic cells and suggest that this tyrosine kinase may be implicated in myeloid leukemogenesis as well.

Lethal paralysis of Caenorhabditis elegans by Pseudomonas aeruginosa

Identification of host factors that interact with pathogens is crucial to an understanding of infectious disease, but direct screening for host mutations to aid in this task is not feasible in mammals. The nematode Caenorhabditis elegans is a genetically tractable alternative for investigating the pathogenic bacterium Pseudomonas aeruginosa. A P. aeruginosa toxin, produced at high cell density under control of the quorum-sensing regulators LasR and RhlR, rapidly and lethally paralyzes C. elegans. Loss-of-function mutations in C. elegans egl-9, a gene required for normal egg laying, confer strong resistance to the paralysis. Thus, activation of EGL-9 or of a pathway that includes it may lead to the paralysis. The molecular identity of egl-9 was determined by transformation rescue and DNA sequencing. A mammalian homologue of EGL-9 is expressed in tissues in which exposure to P. aeruginosa could have clinical effects.

Activation of three classes of nonreceptor tyrosine kinases following Fc gamma receptor crosslinking in human monocytes

Fc gamma receptors on monocytes/macrophages play an important role in both host defense and autoimmune disorders. Fc gamma receptor signaling can lead to such downstream events as phagocytosis and the release of intracellular cytokines and reactive oxygen species. Freshly isolated human monocytes express two major classes of Fc gamma receptor proteins, Fc gamma RI (CD64) and Fc gamma RII (CD32). Crosslinking of Fc gamma RI and Fc gamma RII gives rise to rapid and transient phosphorylation of multiple monocyte intracellular proteins including proteins of 40, 68-72, 75-85, 95, and 115-165 kDa. A 72-kDa protein was earlier identified as the tyrosine kinase Syk. Here we identify one of the proteins in the 115- to 165-kDa cluster as FAK, a protein tyrosine kinase localized to focal adhesions. A 68-kDa phosphoprotein was identified as paxillin, a cytoskeleton associated substrate for tyrosine kinases, and a 95-kDa protein was found to be the proto-oncogene product Vav. The Src family protein tyrosine kinase Fgr (p58) also displayed enhanced tyrosine phosphorylation after Fc gamma RI and Fc gamma RII crosslinking. Although Fc gamma RIIA utilizes tyrosines within its own cytoplasmic domain for signaling while Fc gamma RI utilizes the cytoplasmic tyrosines of its associated gamma subunit, our results indicate sharing of several proteins for signaling in monocytes by these Fc receptors. These molecules include three distinct classes of tyrosine kinases, Syk, FAK, and Fgr, and the functionally diverse proteins Vav and paxillin.

Prospective randomised study comparing tacrolimus (Prograf) and cyclosporin (Neoral) as primary immunosuppression in cadaveric renal transplants at a single institution: interim report of the first 80 cases

As part of an ongoing study, 80 patients undergoing cadaveric renal transplantation were randomised to receive either Prograf [PTT (patients receiving Prograf); n = 40]- or Neoral [NTT (patients receiving Neoral); n = 40]-based immunosuppression as part of a triple therapy regimen. Prograf was commenced at a dose of 0.2 mg/kg per day and Neoral at 8 mg/kg per day. Both groups received identical azathioprine and corticosteroid regimens. Trough levels for Prograf were maintained between 5 and 15 ng/ml and for Neoral between 100 and 200 ng/ml. During the 3-month follow up 40% of PTT and 33% of NTT experienced biopsy-proven acute rejection. In each group 81% of rejection episodes were classified as either borderline or grade 1. The median 3-month serum creatinine levels were 128 mumol/l and 135 mumol/l, respectively, for PTT and NTT. Six grafts were lost in the NTT group including three deaths with functioning grafts whilst none were lost in the PTT group (chi 2, P < 0.02). The prevalence of other complications was similar for the two groups. We conclude that Prograf represents an effective and safe therapy as a primary immunosuppressive agent following cadaveric renal transplantation and appears to have a similar side-effect profile to Neoral.

Screening of patients with iron overload to identify hemochromatosis and porphyria cutanea tarda

OBJECTIVE

To assess the importance of iron overload as a risk factor for porphyria cutanea tarda (PCT).

DESIGN

Prospective study during a 4-month period.

SETTING

Departments of emergency care, gastroenterology, and dermatology in a tertiary referral center.

PATIENTS

Patients were deemed eligible for inclusion in the study if serum ferritin levels were greater than 500 micrograms/L (normal range: females, < 125 micrograms/L; males, < 325 micrograms/L).

MAIN OUTCOME MEASURES

Porphyrin excretion profiles were analyzed on all patients included in the study, where clinically relevant. A diagnosis of PCT was confirmed biochemically in all cases. The HLA typing was then performed on newly diagnosed cases of PCT.

RESULTS

Of 4127 patients tested, 240 patients with an elevated serum ferritin level were identified, of whom 74 had an elevated serum ferritin level of more than 500 micrograms/L. Of the latter group, 17.5% had hemochromatosis and 6.7% had PCT. The incidence of PCT in the hemochromatosis group was 23%; HLA typing revealed the presence of at least 1 of the hemochromatosis markers.

CONCLUSIONS

A high serum ferritin level in the absence of evident cause should prompt investigation for both hemochromatosis and PCT. The HLA heterozygosity for hemochromatosis in some patients with PCT may be a cause of hepatic siderosis.

Porphyrin abnormalities in acquired immunodeficiency syndrome

OBJECTIVE

To examine prospectively porphyrin metabolism in a human immunodeficiency virus (HIV)-positive population.

SETTING

Specialist referral unit at the Department of Genitourinary Medicine, St James's Hospital, Dublin, Ireland.

PATIENTS

Twenty-eight men and 5 women (age range, 18-35 years). Twenty-nine were current or previous intravenous drug abusers. Four were thought to have sexually acquired HIV infection. All had a history of acquired immunodeficiency syndrome-defining illnesses. The patients were selected as a consecutive sample from the inpatient department. Eligibility criteria were cooperation with urine and stool collection and confirmed HIV seropositivity. The patients were matched to 2 groups: 1 with normal results of porphyrin studies and the other with abnormal findings from porphyrin studies.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Plasma, urine, and stool porphyrin excretion patterns.

RESULTS

Of the 33 patients in the study, 13 (40%) had increased urinary porphyrin excretion. All but 2 of these patients were seropositive for hepatitis C virus. No study patient had clinical evidence of porphyria. Four patients (12%), however, had urine and stool porphyrin excretion patterns that were classic for porphyria cutanea tarda. All 4 of these patients were hepatitis C virus-positive. Patients with porphyrinuria had a greater degree of immunosuppression (P = .002) than those with normal porphyrin metabolism, and they were more likely to be taking zidovudine (P = .009).

CONCLUSIONS

Commonly, porphyrin metabolism is abnormal in persons with established HIV infection. Hepatitis C may contribute to abnormal porphyrin metabolism. An unexpected number of patients studied had porphyrin excretion patterns that were characteristic of porphyria cutanea tarda, and all of these were hepatitis C virus-positive. A diagnosis of porphyria cutanea tarda, especially in a young patient, should prompt investigation for underlying HIV and hepatitis C virus infections. Dermatologists should be aware of the infectious risk associated with the vesicles and erosions in these patients. Porphyrin studies should be performed in any patient with HIV and photosensitivity.

Cytomegalovirus causing acute colonic pseudo-obstruction in a renal transplant recipient

A female patient presented with pyrexia and features of large intestinal obstruction, 10 weeks posttransplantation, with biopsy-proven colitis caused by cytomegalovirus (CMV) and positive CMV antigenaemia and IgM tests. The symptoms resolved after treatment with ganciclovir, nasogastric aspiration and intravenous fluid replacement.

Porphyrin metabolism in hepatitis C infection

Hepatitis C virus has been implicated as a major precipitating factor in porphyria cutanea tarda (PCT). To determine whether hepatitis C infection alone is sufficient to induce PCT, we screened two groups of patients with hepatitis C infection. The first group comprised women who had become HCV positive secondary to immunization with anti-D immunoglobulin (group 1). Group 2 included males and females who were HCV positive but HIV negative secondary to intravenous drug abuse. Though both groups had very abnormal liver function tests, we found no significant abnormalities in porphyrin metabolism in these groups of patients. Therefore, in this study population, we conclude that HCV infection alone is insufficient to cause porphyrin metabolic derangement.

Stimulation of macrophage Fc gamma RIIIA activates the receptor-associated protein tyrosine kinase Syk and induces phosphorylation of multiple proteins including p95Vav and p62/GAP-associated protein

The role of tyrosine phosphorylation during signal transduction by the phagocytic macrophage (Mphi) FcR Fc gamma RIIIA was investigated. Cross-linking Fc gamma RIIIA on pulmonary Mphi or cultured monocytes used as in vitro model for differentiated Mphi induced rapid and transient phosphorylation of multiple protein substrates. The lymphocyte/mast cell 72-kDa protein tyrosine kinase (PTK) designated PTK72 or Syk, whose expression in Mphi was previously unknown, was identified as a major substrate by immunoprecipitation and phosphopeptide mapping. Activation of Fc gamma RIIIA stimulated a fourfold increase in Syk kinase activity assessed by autophosphorylation. Under mild lysis conditions several specific proteins were co-precipitated with the gamma subunit of Fc gamma RIIIA. Tyrosine kinase activity was also co-precipitated with gamma, as shown by in vitro phosphorylation of gamma. One of these kinases was identified as Syk by phosphopeptide mapping, suggesting a physical association between this PTK and the receptor. Two additional phosphoproteins induced by Fc gamma RIIIA cross-linking were identified: the hematopoietic proto-oncogene product p95Vav, previously implicated in B lymphocyte and mast cell signaling; and p62, a protein associated with p21Ras-GAP. Our results also establish that there are important functional similarities in signal transduction between a phagocytic Mphi FcR and other multi-subunit Ig gene family receptors in diverse cell lineages.

Stimulation of macrophage Fc gamma RIIIA activates the receptor-associated protein tyrosine kinase Syk and induces phosphorylation of multiple proteins including p95Vav and p62/GAP-associated protein

The role of tyrosine phosphorylation during signal transduction by the phagocytic macrophage (Mphi) FcR Fc gamma RIIIA was investigated. Cross-linking Fc gamma RIIIA on pulmonary Mphi or cultured monocytes used as in vitro model for differentiated Mphi induced rapid and transient phosphorylation of multiple protein substrates. The lymphocyte/mast cell 72-kDa protein tyrosine kinase (PTK) designated PTK72 or Syk, whose expression in Mphi was previously unknown, was identified as a major substrate by immunoprecipitation and phosphopeptide mapping. Activation of Fc gamma RIIIA stimulated a fourfold increase in Syk kinase activity assessed by autophosphorylation. Under mild lysis conditions several specific proteins were co-precipitated with the gamma subunit of Fc gamma RIIIA. Tyrosine kinase activity was also co-precipitated with gamma, as shown by in vitro phosphorylation of gamma. One of these kinases was identified as Syk by phosphopeptide mapping, suggesting a physical association between this PTK and the receptor. Two additional phosphoproteins induced by Fc gamma RIIIA cross-linking were identified: the hematopoietic proto-oncogene product p95Vav, previously implicated in B lymphocyte and mast cell signaling; and p62, a protein associated with p21Ras-GAP. Our results also establish that there are important functional similarities in signal transduction between a phagocytic Mphi FcR and other multi-subunit Ig gene family receptors in diverse cell lineages.

Conserved cytoplasmic tyrosine residues of the gamma subunit are required for a phagocytic signal mediated by Fc gamma RIIIA

Fc receptors for immunoglobulins are found on many cells and are important in host defense. We transfected Fc gamma RIIIA, present on macrophages and natural killer (NK) cells, into COS-1 cells to study its role in phagocytosis and calcium mobilization in the absence of other Fc gamma receptors. Human Fc gamma RIIIA-alpha (CD16) was cotransfected with its associated chains, either Fc gamma RIIIA gamma or zeta. Both gamma and zeta were observed to induce a phagocytic signal, but gamma was at least sixfold more effective than zeta. Conservative substitution by phenylalanine of either one of the two cytoplasmic tyrosine residues in the gamma chain resulted in markedly diminished phagocytosis and calcium mobilization. Tyrphostin 23, an inhibitor of tyrosine kinases, reversibly inhibited phagocytosis. Further, in vitro kinase assays with the wild type and mutant gamma chains demonstrated that the wild type gamma chain, but not the mutant gamma chains, is phosphorylated. These results suggest that the cytoplasmic tyrosine residues and tyrosine phosphorylation are required for Fc gamma RIIIA to mediate two signal transduction events: phagocytosis and calcium mobilization.

In vivo glucocorticoid modulation of guinea pig splenic macrophage Fc gamma receptors

Although glucocorticoids are widely used in the treatment of immunohematologic disease, their relative efficacy is uncertain. We used an animal model, which has helped to elucidate the role of splenic macrophage Fc gamma receptors in the clearance of IgG-coated cells, to investigate whether each Fc gamma receptor is modulated by glucocorticoids to the same extent and to examine the relative potency of three commonly used glucocorticoids. Cortisol, prednisone, and dexamethasone all impaired the clearance of IgG-coated erythrocytes. However, dexamethasone was more effective than either prednisone or cortisol (P less than 0.001). Furthermore, splenic macrophages isolated from glucocorticoid-treated animals expressed impaired Fc gamma receptor function. This effect was greater in macrophages isolated from dexamethasone-treated animals, as compared to either cortisol- or prednisone-treated animals (P less than 0.001). To assess the effect of glucocorticoids on the two types of guinea pig splenic macrophage Fc gamma receptors, Fc gamma R1,2 and Fc gamma R2, specific immunoglobulin isotypes were used to measure macrophage binding of IgG-sensitized erythrocytes. Cortisol and prednisone primarily affected Fc gamma R2, whereas dexamethasone inhibited the function of both guinea pig Fc gamma receptors. Furthermore, dexamethasone was more effective (P less than 0.01) than either prednisone or cortisol in inhibiting the ability of both receptors to bind IgG-sensitized cells. Fluorescence-activated cell sorter analysis and fluorescence microscopy with monoclonal antibodies specific for each of these two receptors demonstrated that essentially all splenic macrophages expressed both receptors, and that these glucocorticoids decreased the level of each Fc gamma receptor protein expressed, rather than altering receptor mobility and clustering in the macrophage membrane. The effect on both Fc gamma receptors was greatest with dexamethasone and least with cortisol. These studies demonstrate the significant role of guinea pig splenic macrophage Fc gamma R2 in immune clearance and in the binding of IgG-coated cells. They demonstrate a differential effect of glucocorticoid hormones on Fc gamma receptor function and on surface receptor protein. Furthermore, they suggest that dexamethasone may be a more effective glucocorticoid than either prednisone or cortisol in inhibiting the clearance of IgG-coated cells by its effect on splenic macrophage Fc gamma receptors.