Review of generic screening level assumptions for quantitative microbial risk assessment (QMRA) for estimating public health risks from Australian drinking water sources contaminated with Cryptosporidium by recreational activities

As urban communities continue to grow, demand for recreational access (including swimming) in drinking water sources have increased, yet relatively little is understood about the public health implications this poses for drinking water consumers. Preventative risk-based approaches to catchment management, informed by quantitative microbial risk assessment (QMRA), requires accurate input data to effectively model risks. A sound understanding of the knowledge gaps is also important to comprehend levels of uncertainty and help prioritise research needs. Cryptosporidium is one of the most important causes of waterborne outbreaks of gastroenteritis globally due to its resistance to chlorine. This review was undertaken by Water Research Australia to provide the most up-to-date information on current Cryptosporidium epidemiological data and underlying assumptions for exposure assessment, dose response and risk assessment for generic components of QMRA for Cryptosporidium and highlights priorities for common research. Key interim recommendations and guidelines for numerical values for relatively simple screening level QMRA modelling are provided to help support prospective studies of risks to drinking water consumers from Cryptosporidium due to body-contact recreation in source water. The review does not cover site-specific considerations, such as the levels of activity in the source water, the influence of dilution and inactivation in reservoirs, or water treatment. Although the focus is Australia, the recommendations and numerical values developed in this review, and the highlighted research priorities, are broadly applicable across all drinking source water sources that allow recreational activities.

Trypanosomiasis in an Australian little red flying fox (Pteropus scapulatus)

Case report

An adult female Australian little red flying fox (Pteropus scapulatus) presented with icterus and anaemia. Examination of a blood smear revealed numerous trypanosomes 20.4–30.8 µm long with tapered ends. Necropsy and histological findings were consistent with trypanosome infection of lymphoid tissue and intravascular haemolysis. Sequence and phylogenetic analysis demonstrated this trypanosome species to be genetically distinct and most similar to Trypanosoma minasense and Trypanosoma rangeli (with a genetic distance of 1% at the 18S rRNA locus for both).

Conclusion

To the authors’ knowledge this is the first report of a trypanosome infection associated with clinical disease in bats.

Cryptosporidium in humans and animals-a one health approach to prophylaxis

Cryptosporidium is a major cause of moderate-to-severe diarrhoea in humans worldwide, second only to rotavirus. Due to the wide host range and environmental persistence of this parasite, cryptosporidiosis can be zoonotic and associated with foodborne and waterborne outbreaks. Currently, 31 species are recognized as valid, and of these, Cryptosporidium hominis and Cryptosporidium parvum are responsible for the majority of infections in humans. The immune status of the host, both innate and adaptive immunity, has a major impact on the severity of the disease and its prognosis. Immunocompetent individuals typically experience self-limiting diarrhoea and transient gastroenteritis lasting up to 2 weeks and recover without treatment, suggesting an efficient host antiparasite immune response. Immunocompromised individuals can suffer from intractable diarrhoea, which can be fatal. Effective drug treatments and vaccines are not yet available. As a result of this, the close cooperation and interaction between veterinarians, health physicians, environmental managers and public health operators is essential to properly control this disease. This review focuses on a One Health approach to prophylaxis, including the importance of understanding transmission routes for zoonotic Cryptosporidium species, improved sanitation and better risk management, improved detection, diagnosis and treatment and the prospect of an effective anticryptosporidial vaccine.

Prevalence and pathogen load of Campylobacter spp., Salmonella enterica and Escherichia coli O157/O145 serogroup in sheep faeces collected at sale yards and in abattoir effluent in Western Australia

OBJECTIVE

Develop a multiplex quantitative PCR assay to investigate the prevalence and shedding of Escherichia coli O157/O145, Salmonella spp. and Campylobacter spp. in sheep at sale yards and abattoirs.

METHODS

A qPCR for E. coli O157/O145 was developed, validated and multiplexed with an existing qPCR for Campylobacter and Salmonella enterica. The absolute numbers of E. coli O157/O145, Campylobacter and Salmonella in control samples was determined using droplet digital PCR. These were then used as the controls in the multiplex qPCR on a total of 474 sheep faecal samples collected from two saleyards over a 4-month period (April-July 2014) and 96 effluent samples from an abattoir.

RESULTS

The mutiplex qPCR was specific with a sensitivity of 5 organisms/μL faecal DNA extract for Campylobacter, S. enterica and E. coli O157/O145. The overall prevalence of Campylobacter, S. enterica and E. coli O157/O145 in faecal samples was 5.7%, 3.6% and 8.4% and in effluent samples was 18.8%, 6.3% and 5.2%, respectively. The pathogen loads of Campylobacter, S. enterica and E. coli O157/O145 in faecal and effluent samples was also determined via mutiplex qPCR.

CONCLUSIONS

The overall prevalences of Campylobacter, S. enterica and E. coli O157/O145 were generally low (<6%), but point prevalences ranged considerably in healthy sheep (up to 26% for E. coli O157/O145). Further work to determine risk factors for shedding of bacterial organisms in meat sheep in the pre-slaughter period (on-farm, sale yards and lairage at abattoirs) could further reduce the risk of contamination of meat products.

Dynamics of Th17 associating cytokines in Cryptosporidium parvum-infected mice

Cryptosporidium parvum commonly inhabits the intestinal tract of animals and humans and can cause acute watery diarrhea and weight loss. However, host immune responses to Cryptosporidium infections are not fully understood. IL-17 (also called IL-17A) is a pro-inflammatory cytokine of Th17 cells that plays a role in the host response to Cryptosporidium baileyi infection. The present study examined levels of IL-17-specific messenger RNA (mRNA) and Th17 associating cytokines in C. parvum-infected immune-suppressed BALB/c mice using real-time quantitative PCR (qPCR). Levels of IL-17 protein were determined by ELISA. The results showed that levels of IL-17 mRNA and Th17 cell-related cytokines, namely TGF-β, IL-6, STAT-3, RORγt, IL-22, TNF-α, and IL-23, were significantly increased (P < 0.05) in gut-associated lymphoid tissue (GALT) and spleen. IL-17 protein levels in GALT were also significantly increased (P < 0.05) after infection. The present study suggested that Th17 cells play a role in host-C. parvum interaction. These results could inform future studies of the immune response against C. parvum infection in transient immunosuppressed populations.

The innate resistance of Trypanosoma copemani to human serum

Trypanosoma copemani is known to be infective to a variety of Australian marsupials. Characterisation of this parasite revealed the presence of stercorarian-like life-cycle stages in culture, which are similar to T. rangeli and T. cruzi. The blood incubation infectivity test (BIIT) was adapted and used to determine if T. copemani, like T. cruzi and T. rangeli, has the potential to grow in the presence of human serum. To eliminate any effects of anticoagulants on the complement system and on human high density lipoprotein (HDL), only fresh whole human blood was used. Trypanosoma copemani was observed by microscopy in all human blood cultures from day 5 to day 19 post inoculation (PI). The mechanism for normal human serum (NHS) resistance in T. copemani is not known. The results of this study show that at least one native Australian trypanosome species may have the potential to be infective for humans.

Identification of Anisakis species (Nematoda: Anisakidae) in marine fish hosts from Papua New Guinea

The third-stage larvae of several genera of anisakid nematodes are important etiological agents for zoonotic human anisakiasis. The present study investigated the prevalence of potentially zoonotic anisakid larvae in fish collected on the coastal shelves off Madang and Rabaul in Papua New Guinea (PNG) where fish represents a major component of the diet. Nematodes were found in seven fish species including Decapterus macarellus, Gerres oblongus, Pinjalo lewisi, Pinjalo pinjalo, Selar crumenophthalmus, Scomberomorus maculatus and Thunnus albacares. They were identified by both light and scanning electron microscopy as Anisakis Type I larvae. Sequencing and phylogenetic analysis of the ribosomal internal transcribed spacer (ITS) and the mitochondrial cytochrome C oxidase subunit II (cox2) gene identified all nematodes as Anisakis typica. This study represents the first in-depth characterisation of Anisakis larvae from seven new fish hosts in PNG. The overall prevalence of larvae was low (7.6%) and no recognised zoonotic Anisakis species were identified, suggesting a very low threat of anisakiasis in PNG.

Genotypes of Cryptosporidium from Sydney water catchment areas

AIMS

Currently cryptosporidiosis represents the major public health concern of water utilities in developed nations and increasingly, new species and genotypes of Cryptosporidium are being identified in which the infectivity for humans is not clear. The complicated epidemiology of Cryptosporidium and the fact that the majority of species and genotypes of Cryptosporidium cannot be distinguished morphologically makes the assessment of public health risk difficult if oocysts are detected in the raw water supplies. The aim of this study was to use molecular tools to identify sources of Cryptosporidium from the Warragamba catchment area of Sydney, Australia.

METHODS AND RESULTS

Both faecal and water samples from the catchment area were collected and screened using immunomagnetic separation (IMS) and immunofluorescence microscopy. Samples that contained Cryptosporidium oocysts were genotyped using sequence and phylogenetic analysis of the 18S rDNA, and the heat-shock (HSP-70) gene. Analysis identified five Cryptosporidium species/genotypes including C. parvum (cattle genotype), C. suis, pig genotype II, the cervid genotype and a novel goat genotype.

CONCLUSIONS

Monitoring and characterization of the sources of oocyst contamination in watersheds will aid in the development and implementation of the most appropriate watershed management policies to protect the public from the risks of waterborne Cryptosporidium.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study has shown that quantification by IMS analysis can be combined with the specificity of genotyping to provide an extremely valuable tool for assessing the human health risks from land use activities in drinking water catchments.

TGF-beta 1 reverses PDGF-stimulated migration of human aortic smooth muscle cells in vitro

Platelet-derived growth factor (PDGF) and transforming growth factor beta-1(TGF-beta 1) were tested separately or together for the ability to stimulate migration of human aortic vascular smooth muscle cells (VSMC). PDGF (10 ng/ml) stimulated migration of VSMC over a 48-h period. TGF-beta 1 (10 ng/ml) had no effect on migration during the same period. VSMC exposed simultaneously to both TGF-beta 1 and PDGF exhibited diminished migration (50%) when compared to cells treated only with PDGF. Cells that migrated in the presence of PDGF possessed short actin cables that extended from cellular processes at the leading edge of migrating cells; focal adhesions containing the alpha v beta 3/beta 5 integrins localised to the same region. Cells grown in the presence of TGF-beta 1 exhibited long, intensely stained actin filaments that spanned the entire length of the cell and were similar to untreated control VSMC. Focal adhesions containing alpha v beta 3/beta 5 distributed evenly on the basal surface in both TGF-beta 1-treated cells and control cultures. Cellular responses to PDGF were mitigated when TGF-beta 1 was present in the culture medium. VSMC grown in the presence of both PDGF and TGF-beta 1 exhibited elongated actin filaments that were similar to nonmotile TGF-beta 1-treated cultures. Concomitant exposure of VSMC to PDGF and TGF-beta 1 resulted in focal adhesions that distributed evenly on the lower cell surface. This study suggests that TGF-beta 1 can partially reverse the stimulatory effect of PDGF on VSMC migration in vitro by modifying the actin cytoskeleton and the distribution of the alpha v beta3/beta 5 integrins.

Lipopolysaccharide and tumor necrosis factor stimulate lung microvascular arginine uptake, a response attenuated by dexamethasone

BACKGROUND

Lipopolysaccharide (LPS), tumor necrosis factor-alpha, (TNF), and glucocorticoids can modulate endothelial nitric oxide (NO) production. L-Arginine is the exclusive precursor for NO biosynthesis, suggesting that NO generation and arginine transport are intimately linked.

METHODS

To further study this relationship, we examined the effects of LPS, TNF, and dexamethasone (DEX) on arginine uptake by rat lung microvascular endothelial cells. The transport of radiolabeled arginine was assayed in confluent cells grown in 24-well plates.

RESULTS

The bulk (> 90%) of arginine transport was mediated by the Na(+)-independent carriers System y+ and System b0,+. Arginine transport was stimulated independently by LPS and TNF, a response first observed at 10 hours. Together, both agents exerted an additive effect on carrier-mediated uptake. The LPS- and TNF-induced increase in arginine transport activity was blocked by cycloheximide and actinomycin D, indicating the requirement for RNA and protein synthesis. The enhancement in transport activity was primarily due to an increase in Systems y+ maximal transport capacity (Vmax) with no change in transporter affinity and little change in System b0,+ activity. Treatment of cells with dexamethasone inhibited arginine transport activity in a time- and dose-dependent manner, an event that was abrogated by both actinomycin D and cycloheximide. The combination of DEX and LPS and TNF abrogated each other's antagonistic effects.

CONCLUSIONS

These data indicate that LPS and TNF additively stimulate arginine transport in lung microvascular endothelial cells via a pathway that requires de novo protein synthesis (possibly of the transporter protein itself) and that this response is attenuated by DEX.

Inhibition of pulmonary microvascular endothelial glutamine transport by glucocorticoids and endotoxin

BACKGROUND

During septic states, the lungs produce increased amounts of glutamine, an event that is mediated by both endotoxin and glucocorticoid hormones and is presumed to be due to accelerated intracellular glutamine biosynthesis. Because enhanced net glutamine release in vivo could also be due to a decrease in cellular uptake, we assayed glutamine transport in cultured rat microvascular pulmonary endothelial cells.

METHODS

The effect of Escherichia coli endotoxin (LPS, 1 microgram/mL), various cytokines, and dexamethasone (DEX, 0.1 mumol/L) on glutamine transport activity was studied in rat lung microvascular endothelial cells grown in varying glutamine concentrations (0, 0.1, 0.5, and 2 mmol/L). Experiments were also performed in cells treated with cycloheximide, actinomycin D, or chelerythrine chloride.

RESULTS

More than 90% of glutamine transport was mediated by the Na+ -dependent transport system ASC. DEX and LPS inhibited endothelial glutamine uptake in a time- and dose-dependent manner, a response that was only observed with incubation medium contained the lower concentrations of glutamine. Neither DEX nor LPS altered transport activity in cells cultured in medium containing 2 mmol glutamine/L. There was no synergistic or additive effect when both compounds were added together. The cytokines tumor necrosis factor alpha, interleukin (IL) 1, IL-2, and IL-6 did not alter glutamine transport. both DEX and LPS inhibited glutamine transport by decreasing transporter maximal transport velocity (Vmax) without affecting transporter affinity (Km). Cycloheximide and actinomycin D abrogated the inhibition of transport activity that was observed in DEX- or LPS-treated cells, whereas the protein kinase C inhibitor chelerythrine chloride had no effect on either control or stimulated glutamine transport.

CONCLUSIONS

These data suggest that DEX and LPS "down-regulate" glutamine uptake by lung microvascular endothelial cells by inducing the synthesis of an inhibitory protein that modulates the activity of the system ASC protein. This response in vitro appears to be influenced by the extracellular glutamine concentration. This decrease in microvascular endothelial glutamine transport may be one mechanism by which net lung glutamine release is enhanced during critical illness.

Protective effects of the SOD-mimetic SC-52608 against ischemia/reperfusion damage in the rabbit isolated heart

An experimental model of myocardial ischemia/reperfusion injury was used to assess the cardioprotective effects of SC-52608, a low molecular weight superoxide dismutase mimetic. Langendorff perfused rabbit isolated hearts were subjected to 30 min of global ischemia followed by 45 min of reperfusion. Hearts perfused in the presence of 20 microM SC-52608 exhibited a decrease in the release of creatine kinase and intracellular potassium compared to hearts receiving vehicle (control). A progressive increase in left ventricular end-diastolic pressure developed upon reperfusion in all hearts, but was significantly greater in control hearts when compared to hearts treated with SC-52608 (P < 0.05). In addition, results obtained with a radiolabeled monoclonal antibody to the intracellular protein myosin, indicate an increased degree of irreversible damage in vehicle-treated hearts. Myocardial protection was not significant in an additional group of hearts treated with 10 microM SC-52608. The hemodynamic, biochemical, morphological, as well as the antimyosin binding data, demonstrate that pretreatment with SC-52608 protects the myocardium from damage associated with global ischemia and reperfusion. The mechanism by which SC-52608 mediates the observed protective effect is most likely related to its ability to scavenge superoxide.

Interaction of mAb to angiotensin-converting enzyme (ACE) with antigen in vitro and in vivo: antibody targeting to the lung induces ACE antigenic modulation

We previously described that mAb to angiotensin-converting enzyme (ACE), mAb 9B9, accumulates in the rat lungs after systemic injection. In the present work we have documented that mAb 9B9 cross-reacts with human, monkey, rat, cat and hamster ACE, while other ACE antibodies did not cross-react with the rat, cat and hamster enzyme. Anti-ACE mAb 3A5 and I2H5 inhibit human ACE in vitro, while mAb 9B9 does not inhibit ACE activity. Radiolabeled mAb 9B9, but not other antibodies, accumulates selectively in rat, cat and hamster lungs after systemic administration. No accumulation of mAb 9B9 has been observed in hamster kidney, while hamster kidney ACE activity is higher than that in the lung. mAb 9B9 does not induce complement-mediated injury to cultured endothelial cells. No pathological changes were detected in organs of animals after mAb 9B9 injection (10-100 mg/kg). However, injection of these amounts of mAb 9B9 leads to a decrease in ACE activity in the lung homogenates and an increase in serum. In cultured human endothelial cells treatment with mAb 9B9 increases ACE activity in cell medium and decreases in cell lysates. Therefore, while mAb 9B9 does not kill endothelial cells, at high dose it may induce ACE shedding from the cell. The results obtained support the potential of anti-ACE mAb 9B9 for targeting to the lung and for investigations of the pulmonary endothelium.

Endogenous xanthine oxidase does not significantly contribute to vascular endothelial production of reactive oxygen species

The contribution of xanthine oxidoreductase (XDH + XO) to the extracellular release of hydrogen peroxide (H2O2) and intracellular H2O2 concentration in cultured bovine aortic endothelial cells (BAEC) was determined. Intracellular H2O2 concentration was measured by the aminotriazole-mediated inactivation of catalase, while extracellular H2O2 release was measured by the horse-radish peroxidase-mediated oxidation of p-hydroxyphenyl acetic acid to a fluorescent dimer. Supplementation of reaction systems with xanthine did not increase H2O2 production by cells. Inhibition of XO activity with allopurinol did not decrease either intracellular concentrations or the extracellular release of H2O2. Similarly, inactivation of XO by culture of cells with tungsten did not have any effect on intracellular levels of H2O2, while it increased extracellular release of H2O2 by 86 and 103% from cells cultured in Medium 199 (M199) and Dulbecco's modified Eagle's medium (DMEM), respectively. Cells cultured in DMEM had an average of 8 times greater XDH + XO specific activity, compared to M199 cultured cells, and had a threefold greater rate of release of H2O2 than M199-grown cells. However, DMEM-cultured cells did not have a greater rate of myxothiazole-resistant respiration, suggesting that this increase in H2O2 release comes from sources other than XO. These results show that cellular XO does not contribute significantly to basal H2O2 production in bovine endothelial cells. Analysis of XDH + XO activity of endothelial cells derived from vessels of various species showed a relatively low specific activity of this potential oxidant source in human-derived cells compared with cells cultured from other species such as rodents.

Variations of membrane cholesterol alter the kinetics of Ca2(+)-dependent K+ channels and membrane fluidity in vascular smooth muscle cells

The patch-clamp technique and fluorescence polarization analysis were used to study the dependence of Ca2(+)-dependent K+ channel kinetics and membrane fluidity on cholesterol (CHS) levels in the plasma membranes of cultured smooth muscle rabbit aortic cells. Mevinolin (MEV), a potent inhibitor of endogenous CHS biosynthesis was used to deplete the CHS content. Elevation of CHS concentration in the membrane was achieved using a CHS-enriching medium. Treatment of smooth muscle cells with MEV led to a nearly twofold increase in the rotational diffusion coefficient of DPH (D) and to about a ninefold elevation of probability of the channels being open (Po). The addition of CHS to the cells membrane resulted in a nearly twofold decrease in D and about a twofold decrease in Po. Elementary conductance of the channels did not change under these conditions. These data suggest that variations of the CHS content in the plasma membrane of smooth muscle cells affect the kinetic properties of Ca2(+)-dependent K+ channels presumably due to changes in plasma membrane fluidity. Our results give a possible explanation for the reported variability of Ca2(+)-dependent K+ channels kinetics in different preparations.

Synthesis and binding of lactose-specific lectin by isolated lung cells

Neonatal maturation of alveolar structure in rat lung temporally coincides with the peak activity of a beta-galactoside-specific endogenous lung lectin of the type that has been linked to developmental processes in other tissues. To learn more about the lung lectin we examined four cell types for their ability to synthesize and bind the lectin. Cultured lung fibroblasts and pulmonary artery endothelial cells synthesized and bound the lectin, alveolar macrophages bound but did not synthesize it, and alveolar epithelial type II cells neither bound nor synthesized it. Pulmonary macrophages made a different lactose-binding protein that did not agglutinate or bind trypsin-treated red blood cells, a property of lung lectin that is the means of its assay.

Isolation and characterization of monoclonal antibodies reactive with endothelial cells

Monoclonal antibodies were generated to antigens on cultured human umbilical vein endothelial cells. Spleen cells from BALB/c mice, immunized with low passage cultures of human umbilical vein endothelial cells, were fused with the non-secretory myeloma line, P3 x 63Ag 8.653. Hybridoma supernatants were screened for the desired immunological reactivity using ELISA binding assays. Hybridomas secreting antibodies reacting with the immunizing endothelial cells, but not with peripheral blood mononuclear cells, were cloned by limiting dilution and three stable clones were chosen for study. Further testing by ELISA revealed that each antibody displayed a unique pattern of reactivity. One antibody, 14E5, reacted with the macrophage-like cell line DHL-2, cultured macrophages derived from peripheral blood monocytes, and macrophages derived from malignant effusions. The antibody failed to react with fibroblasts or bovine endothelial cells. The second antibody, 12C6, reacted with human and primate fibroblasts and endothelial cells derived from bovine arteries, but not with mature macrophages. The third clone, 10B9, reacted only with the immunizing endothelial cells and the immature-macrophage line U-937. All three antibodies failed to react with long-term human B or T lymphoblastoid cell lines, leukemic cell lines, or murine macrophage lines. None of the antibodies reacted with a battery of human epithelial derived cell lines or primary cultures of human epithelial cells. Indirect immunofluorescence assays revealed that the antigens were expressed on the cell surface. These antibodies should prove useful as differentiation markers of human endothelial cells and in studies of endothelial cell function.

Research into the anatomy and X-ray diagnostics of the fibular ligaments at the ankle joint

In the literature widely differing statements are found as to the extent of the radiographically seen tilt of the talus after rupture of the fibular ligaments. Our studies on cadavers showed that there can be no exact correlation between the instability found on X-ray investigation and the intraoperatively ascertained damage of the ligamentous structures. The intraoperatively found damage is usually greater than presumed on X-ray investigation. The main reason for these findings is to be seen in the various anatomical shapes of the fibular ligaments. We have certified this in our studies on 20 amputated feet. For clinical purpose it is not of interest which of the ligaments is damaged, but it is of great importance to know whether there is a rupture or not. Anamnesis and clinical state may be important in deciding whether to operate or not.

Elastin production by cultured calf pulmonary artery endothelial cells

Calf pulmonary artery (CPA) endothelial cells synthesize and secrete soluble elastin when incubated in medium conditioned by arterial smooth muscle cells. Endothelial cell tropoelastin cross-reacts with antiserum to bovine ligamentum nuchae elastin and comigrates on SDS-PAGE with tropoelastins from fetal bovine ligamentum nuchae fibroblasts, aortic smooth muscle cells, and ear chondroblasts at an apparent molecular weight of 70,000. Endothelial cells synthesize only one-third as much elastin as these other cell types, however. Approximately 80% of the elastin synthesized by endothelial cells in confluent culture is released into the culture medium. The remaining 20% remains associated with the cell layer and is readily extractable with dilute acetic acid as un-cross-linked, 70,000-dalton tropoelastin. The addition of beta-aminopropionitrile to culture medium did not alter the ratio of tropoelastin in the medium and cell layer, suggesting that cross-linking of tropoelastin does not occur in culture. Immunofluorescent staining of confluent endothelial cell cultures with antielastin serum demonstrated elastin occurring as a web-like network of fine filaments extending throughout the extracellular space. The fibrous elastin was different in organization and distribution from fibers stained with antifibronectin serum, which were localized primarily beneath the cell layer and in regions of cell-cell contact. Extracellular matrix remaining after solubilization of cellular material with Triton X-100 stained positive for fibronectin, but not for elastin.

Immunocytochemical localization of HLA-DR in human islets of Langerhans

Previous reports of allogeneic transplantation studies in rodents have postulated that the primary carriers of Ia antigen in islets of Langerhans are passenger leukocytes. We sought to demonstrate directly the localization of the analogous human antigen, HLA-DR, in islet-enriched fractions (IEFs), utilizing a nonpolymorphic monoclonal anti-DR (alpha DR) antibody. The presence of DR in the IEFs was first demonstrated by radioimmunobinding assay. Light microscopic immunocytochemistry, in frozen sections of intact (unfixed) human pancreas, revealed a staining pattern suggestive of a vascular distribution of DR in islets. Ultrastructural localization of DR was then carried out by indirect immunoperoxidase labeling in the presence of NaN3 (to prevent internalization of bound alpha DR). The major site of DR expression in the islet was the endothelial cell surface. Endocrine cells were entirely devoid of alpha DR binding. Nonislet endothelium was also heavily labeled, but acinar and ductal cells were completely negative. Leukocytes bound alpha DR but were relatively rare in the IEFs. Human islets, therefore, clearly express HLA-DR, but predominantly on insular endothelial cells. Isolation of pure endocrine cell populations, specifically free of endothelium, would appear to be a rational approach to reducing immunogenicity in allogeneic transplantation.

Metabolism of prostaglandin f 1 alpha in the pulmonary circulation

3-H5,6-Prostaglandin F1alpha is largely eliminated from the circulation during a single passage through the pulmonary vascular bed. Its elimination requires cellular uptake. The volume of distribution and the mean transit time of the radioactivity are greater than those of an intravascular marker, blue dextran. The lungs retain 25-30% of the radioactivity, most in the form of a metabolite less polar that PGF1alpha itself. The pulmonary venous effluent contains the same metabolite along with some unmetabolized PGF1alpha. The metabolite can be distinguished from prostaglandins of the A, B, D, E and F series. It is reduced on reaction with borohydride, but reduction does not yield PGF1alpha. NaOH has no effect on the metabolite, a finding that rules out the presence of a beta-hydroxy-ketone configuration of the ring structure. The chromatographic behavior of the metabolite and its reaction with borohydride are those expected of 9,11-hydroxy-15-ketoprostanoic acid.