Peer navigators' role in supporting people living with human immunodeficiency virus in Australia: Qualitative exploration of general practitioners' perspectives

The redefining of human immunodeficiency virus (HIV) from an acute disease to a manageable chronic illness has reshaped the focus of care, emphasising clinical outcomes and sidelining the complex social barriers many people living with HIV (PLHIV) still face. This parallels changes in the location of HIV care in Australia, with many PLHIV seeking care from private general practitioners whose ability to address complex social issues is constrained by limitations of time and resources. In response, peer navigation has emerged as a model of care implemented by some HIV-based community health organisations seeking to support PLHIV's biomedical and psychosocial needs. However, there is limited understanding of how peer navigation operates in community settings or of the way these programmes integrate with primary care. This paper is the first to explore peer navigation from the perspective of general practitioners (GPs), with experience in treating PLHIV, to understand the role they see for peer navigators (PNs) in supporting PLHIV. Semi-structured in-depth interviews were conducted with six GPs (11.5% of specialty HIV GPs in Queensland, Australia) to examine their views and experiences of peer navigation in the context of HIV care. GPs highlighted the complexities of care for PLHIV and the need for additional resources and supports for psychosocial care. GPs valued peer navigation as part of a patient support network and bridge to health and social care systems. PNs normalised HIV, alleviating fear and stigma, educating and translating clinical information for patients. However, a key challenge was the absence of direct communication pathways with PNs. Peer navigation has clear potential in supporting the care of PLHIV, to alleviate constraints in GP settings and expand HIV care beyond the clinic.

Deletion of CD73 in mice leads to aortic valve dysfunction

Aortic stenosis is known to involve inflammation and thrombosis. Changes in activity of extracellular enzyme - ecto-5'-nucleotidase (referred also as CD73) can alter inflammatory and thrombotic responses. This study aimed to evaluate the effect of CD73 deletion in mice on development of aortic valve dysfunction and to compare it to the effect of high-fat diet. Four groups of mice (normal-diet Wild Type (WT), high-fat diet WT, normal diet CD73-/-, high-fat diet CD73-/-) were maintained for 15weeks followed by echocardiographic analysis of aortic valve function, measurement of aortic surface activities of nucleotide catabolism enzymes as well as alkaline phosphatase activity, mineral composition and histology of aortic valve leaflets. CD73-/- knock out led to an increase in peak aortic flow (1.06±0.26m/s) compared to WT (0.79±0.26m/s) indicating obstruction. Highest values of peak aortic flow (1.26±0.31m/s) were observed in high-fat diet CD73-/- mice. Histological analysis showed morphological changes in CD73-/- including thickening and accumulation of dark deposits, proved to be melanin. Concentrations of Ca²⁺, Mg²⁺ and PO₄^3- in valve leaflets were elevated in CD73-/- mice. Alkaline phosphatase (ALP) activity was enhanced after ATP treatment and reduced after adenosine treatment in aortas incubated in osteogenic medium. AMP hydrolysis in CD73-/- was below 10% of WT. Activity of ecto-adenosine deaminase (eADA), responsible for adenosine deamination, in the CD73-/- was 40% lower when compared to WT. Deletion of CD73 in mice leads to aortic valve dysfunction similar to that induced by high-fat diet suggesting important role of this surface protein in maintaining heart valve integrity.

Nucleotide metabolic mismatches in mammalian hearts: implications for transplantation

Introduction

Human donor organ shortages have led surgeons and scientists to explore the use of animals as alternative organ sources. Acute thrombovascular rejection (AVR) is the main hurdle in xenotransplantation. Disparities in nucleotide metabolism in the vessels of different species may contribute significantly to the microvascular component of AVR.

Methods

We evaluated the extent of nucleotide metabolism mismatch in selected organs and endothelial cells of different mammals with particular focus on the changes in activity of ecto-5’-nucleotidase (E5’N) elicited by exposure of porcine hearts or endothelial cells to human blood (ex vivo) or human plasma (in vitro).

Results

E5’N activity in the rat heart was significantly higher than in other species. We noted a significant difference (p<0.001) in E5’N activity between human and pig endothelial cell lines. Initial pig aortic endothelial E5’N activity decreased in vitro after a three-hour exposure to human and porcine plasma while remaining constant in controls. Ex vivo perfusion with fresh human blood for four hours resulted in a significant decrease of E5’N activity in both wild type and transgenic pig hearts overexpressing human decay accelerating factor (p<0.001).

Conclusions

This study provides evidence that mismatches in basal mammalian metabolic pathways and humoral immunity interact in a xenogeneic environment. Understanding the role of nucleotide metabolism and signalling in xenotransplantation may identify new targets for genetic modifications and may lead to the development of new therapies extending graft survival.

Closed traumatic head injury: dural sinus and internal jugular vein thrombosis

Dural sinus thrombosis (DST) has an annual incidence of 3-4 per million and can result from many aetiologies. Presentation of the disease can vary considerably, as can the aetiology and delay of symptoms to clinical detection. Symptoms on presentation include headache, seizures, focal neural deficits and altered mental status. There are many aetiological risk factors associated with DST, which include hypercoagulable states, oral contraceptive use, infection and mechanical causes such as cranial trauma. DST as a result of trauma is rare and aetiologies range from mechanical falls with or without skull fracture, firework explosions, gunshots to the head, blunt trauma to the head and closed head injury. Internal jugular vein thrombosis is also a rare disease and as with DST, traumatic aetiologies are uncommon. More common aetiologies include iatrogenic causes related to catheterisation as well as infectious causes (eg, Lemierre's syndrome). A case of thrombosis of the transverse sinus, sigmoid sinus and internal jugular vein associated with a closed head injury as the result of a motorcycle accident is presented.

Differences in activities of the enzymes of nucleotide metabolism and its implications for cardiac xenotransplantation

Xenotransplantation is one be possible solution for a severe shortage of human organs available for transplantation. However, only a few studies addressed metabolic compatibility of transplanted animal organs. Our aim was to compare activities of adenosine metabolizing enzymes in the heart of different species that are relevant to clinical or experimental xenotransplantation. We noted fundamental differences: ecto-5' nucleotidease (E5' N) activity was 4-fold lower in pig and baboon hearts compared to the human hearts while mouse activity was compatible with human and rat activity was three times higher than human. There also were significant differences in AMP-deaminase (AMPD), adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) activities. We conclude that differences in nucleotide metabolism may contribute to organ dysfunction after xenotransplantation.

Purine metabolism in pigs and humans and its implications for xenotransplantation

We compared concentrations of nucleotide substrates and activities of enzymes of nucleotide metabolism in pig and human blood, heart, and kidney. The most important difference was lower ecto-5-nucleotidase (ESN) activity in both pig hearts and kidney. Furthermore, higher hypoxanthine, inosine, adenine, and uracil, but lower uridine and uric acid concentrations were observed in pig blood as compared to human. A twofold increase in UTP concentration has been observed in pig hearts following 4 h perfusion with human blood. Purine metabolism is an important target for genetic and pharmacological manipulation during xenotransplantations.

Exposure to human blood inactivates swine endothelial ecto-5'-nucleotidase

Ecto-5'-nucleotidase (E5'N) is an extracellular enzyme forming anti-inflammatory and immunosuppressive adenosine. We evaluated whether confrontation of pig heart and endothelial cells with human blood changes the activity of E5'N. Pig hearts were perfused ex vivo with fresh human blood for 4 h. Pig aortic endothelial cells (PAEC) were incubated in vitro with human plasma for 3 h. Ex vivo perfusion of pig heart with fresh human blood resulted in a decrease in E5'N activity to 62% and 61% of initial in wild-type and transgenic pig hearts, respectively. PAEC activity of E5'N decreased to 71% and 50% of initial after 3 h exposure to heat-inactivated and active complement human plasma, respectively, while it remained constant in controls. Pig heart activity of E5'N decreased following exposure to human blood, which may affect adenosine production and exacerbate hyperacute and vascular rejection.

Cellular Physiology of Mismatch Repair

The DNA mismatch repair system maintains genomic stability by correcting DNA sequence errors generated during DNA replication, during genetic exchanges between chromosomes i.e., recombination, and by correcting DNA lesions caused by mutagenic agents such as cis-platinum. Post-synthesis mismatch repair improves almost 1000-fold the fidelity of DNA replication; however, the functions of mismatch repair proteins extend well beyond DNA repair. Recent studies suggest that mismatch repair is part of the machinery that couples DNA damage and repair to cell cycle regulation and apoptosis. These studies indicate that tolerance to certain DNA lesions (such as methylation and cis-platinum adducts) is associated with inefficient activation of cell cycle checkpoints and inefficient activation of apoptosis in mismatch repair deficient cells. Hence, mismatch repair proteins regulate the survival threshold to DNA damage, and this function provides a novel platform for understanding the role of mismatch repair in B cells, in tumor formation, as well as in resistance to chemotherapy. In this communication, we review how mismatch repair may contribute to the physiology of cells and may be regulated by the intracellular trafficking of mismatch repair proteins.

Differences in the serum levels of acetaldehyde and cytotoxic acetaldehyde-albumin complexes after the consumption of red and white wine: in vitro effects of flavonoids, vitamin E, and other dietary antioxidants on cytotoxic complexes

After the consumption of ethanol, acetaldehyde levels increase in the serum, and the serum develops a nondialyzable cytotoxic activity caused by the formation of unstable acetaldehyde-albumin complexes. The concentration of acetaldehyde in the serum and the cytotoxic activity in serum albumin 8.5 hr after six healthy volunteers began to drink 94 g of ethanol were significantly less when the ethanol was consumed as red wine than as white wine. The serum acetaldehyde was measured by a fluorigenic HPLC assay, and the cytotoxic activity in albumin was determined using two different assays based on dissimilar endpoints: (1) detachment of adherent A9 cells and (2) impairment of the ability of A9 cells to reduce tetrazolium. When serum obtained from five other healthy volunteers after the consumption of white wine was incubated at 37 degrees C for 3 hr with a number of dietary antioxidants at a concentration of 100 mumol/liter, the cytotoxicity of the albumin was markedly reduced. The antioxidants studied consisted of six flavonoids (kaempherol, fisetin, quercetin catechin, taxifolin, and coumarin) and three nonflavonoids (salicylic acid, tannic acid, and alpha-tocopherol). In the cases of alpha-tocopherol, a statistically significant reduction of cytotoxicity was observed at a concentration of 10 mumol/liter. In addition, the cytotoxicity of artificially prepared acetaldehyde-albumin complexes was significantly reduced when such complexes were incubated with 50 to 100 mumol/liter of kaempherol, fisetin, quercetin, coumarin or salicylic acid, or 10 mumol/liter of alpha-tocopherol at 37 degrees C for 3 hr. Evidently, in vitro, flavonoid and nonflavonoid dietary constituents reduce the amount of unstable acetaldehyde-albumin complexes found in both postalcohol serum and in artificially produced acetaldehyde-albumin complexes. The difference in the amount of unstable acetaldehyde-albumin complexes found in serum after the consumption of red and white wine may therefore be caused by the higher concentration of antioxidants, including flavonoids, in red wine than in white wine. Because acetaldehyde and acetaldehyde-albumin complexes have been implicated in the pathogenesis of alcohol-mediated tissue damage, these data suggest that dietary antioxidants may influence the biological consequences of excess alcohol consumption.