Mechanistic Model Describing the Time Course of Humoral Immunity Following Ad26.COV2.S Vaccination in Non-Human Primates

Mechanistic modeling can be used to describe the time course of vaccine-induced humoral immunity and to identify key biologic drivers in antibody production. We used a six-compartment mechanistic model to describe a 20-week time course of humoral immune responses in 56 non-human primates (NHPs) elicited by vaccination with Ad26.COV2.S according to either a single-dose regimen (1 × 1011 or 5 × 1010 viral particles [vp]) or a two-dose homologous regimen (5 × 1010 vp) given in an interval of 4 or 8 weeks. Humoral immune responses were quantified by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike-specific binding antibody concentrations as determined by spike protein-enzyme-linked immunosorbent assay. The mechanistic model adequately described the central tendency and variability of binding antibody concentrations through 20 weeks in all vaccination arms. The estimation of mechanistic modeling parameters revealed greater contribution of the antibody production mediated by short-lived cells as compared with long-lived cells in driving the peak response, especially post second dose when a more rapid peak response was observed. The antibody production mediated by long-lived cells was identified as relevant for generating the first peak and for contributing to the long-term time course of sustained antibody concentrations in all vaccination arms. The findings contribute evidence on the key biologic components responsible for the observed time course of vaccine-induced humoral immunity in NHPs and constitute a step toward defining immune biomarkers of protection against SARS-CoV-2 that might translate across species. SIGNIFICANCE STATEMENT: We demonstrate the adequacy of a mechanistic modeling approach describing the time course of binding antibody concentrations in non-human primates (NHPs) elicited by different dose levels and regimens of Ad26.COV2.S. The findings are relevant for informing the mechanism-based accounts of vaccine-induced humoral immunity in NHPs and translational research efforts aimed at identifying immune biomarkers of protection against SARS-CoV-2 infection.

Quantifying Antibody Persistence After a Single Dose of COVID-19 Vaccine Ad26.COV2.S in Humans Using a Mechanistic Modeling and Simulation Approach

Understanding persistence of humoral immune responses elicited by vaccination against coronavirus disease 2019 (COVID-19) is critical for informing the duration of protection and appropriate booster timing. We developed a mechanistic model to characterize the time course of humoral immune responses in severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-seronegative adults after primary vaccination with the Janssen COVID-19 vaccine, Ad26.COV2.S. The persistence of antibody responses was quantified through mechanistic modeling-based simulations. Two biomarkers of humoral immune responses were examined: SARS-CoV-2 neutralizing antibodies determined by wild-type virus neutralization assay (wtVNA) and spike protein-binding antibodies determined by indirect spike protein enzyme-linked immunosorbent assay (S-ELISA). The persistence of antibody responses was defined as the period of time during which wtVNA and S-ELISA titers remained above the lower limit of quantification. A total of 442 wtVNA and 1,185 S-ELISA titers from 82 and 220 participants, respectively, were analyzed following administration of a single dose of Ad26.COV2.S (5 × 10¹⁰ viral particles). The mechanistic model adequately described the time course of observed wtVNA and S-ELISA serum titers and its associated variability up to 8 months following vaccination. Mechanistic model-based simulations show that single-dose Ad26.COV2.S elicits durable but waning antibody responses up to 24 months following immunization. Of the estimated model parameters, the production rate of memory B cells was decreased in older adults relative to younger adults, and the antibody production rate mediated by long-lived plasma cells was increased in women relative to men. A steeper waning of antibody responses was predicted in men and in older adults.

SARS-CoV-2 binding and neutralizing antibody levels after Ad26.COV2.S vaccination predict durable protection in rhesus macaques

Several COVID-19 vaccines have recently gained authorization for emergency use. Limited knowledge on duration of immunity and efficacy of these vaccines is currently available. Data on other coronaviruses after natural infection suggest that immunity to SARS-CoV-2 might be short-lived, and preliminary evidence indicates waning antibody titers following SARS-CoV-2 infection. In this work, we model the relationship between immunogenicity and protective efficacy of a series of Ad26 vectors encoding stabilized variants of the SARS-CoV-2 Spike protein in rhesus macaques and validate the analyses by challenging macaques 6 months after immunization with the Ad26.COV2.S vaccine candidate that has been selected for clinical development. We show that Ad26.COV2.S confers durable protection against replication of SARS-CoV-2 in the lungs that is predicted by the levels of Spike-binding and neutralizing antibodies, indicating that Ad26.COV2.S could confer durable protection in humans and immunological correlates of protection may enable the prediction of durability of protection.

Boundary spanning and identity work in the clinical research delivery workforce: a qualitative study of research nurses, midwives and allied health professionals in the National Health Service, United Kingdom

Background

Research nurses, midwives and allied health professionals are members of an important emergent profession delivering clinical research and, in the United Kingdom, have been the focus of considerable investment by the National Institute for Health Research (NIHR). This paper considers the experiences of research nurses, midwives and allied health professionals in relation to professional identity work, recognizing these are coproduced alongside others that they interact with (including patients, clinical staff and other research staff).

Methods

Semi-structured interviews were conducted with 45 nurses, midwives and allied health professionals in the UK about their experiences of working in research delivery. Interviews were transcribed verbatim and thematically coded and analysed.

Results

Our analysis highlights how research nurses, midwives and allied health professionals adjust to new roles, shift their professional identities and undertake identity work using uniforms, name badges and job titles as they negotiate complex identities.

Conclusions

Research nurses, midwives and allied health professionals experience considerable challenges as they enter and transition to a research delivery role, with implications for their sense of professional identities. A change in the work that they undertake and how they are (or perceive they are) viewed by others (including clinical non-research colleagues and patients) has implications for their sense of professional and individual identity. The tensions involved extend to their views on symbols of professional identity, such as uniforms, and as they seek to articulate and demonstrate the value of their conjoined role in research and as a healthcare professional, within the unfolding landscape of health research. We embed our study findings in the context of the newly emerging clinical research practitioner workforce, which further exacerbates and complicates the role and identity complexity for nurses, midwives and allied health professionals in research delivery.

Cerebrospinal Fluid Absorption Revisited: Do Extracranial Lymphatics Play a Role?

It would seem heretical to suggest that extracranial lymphatic vessels play a major role in the volumetric clearance of cerebrospinal fluid (CSF) from the cranial vault. It is well established that there are no lymphatics within the brain parenchyma, and it has been assumed that the drainage of CSF into the venous system occurs predominantly through the arachnoid villi and granulations. Nonetheless, a physiological association between extracellular fluid in the brain and extracranial lymph has been appreciated for more than 100 years. More important, recent studies in adult experimental animals have demonstrated that on average, one-half of the total volume of CSF absorbed from the cranial compartment was removed by extracranial lymphatics. Our objective in writing this review is to outline the experimental data that support the hypothesis that extracranial lymphatic vessels play an important role in CSF transport in the adult. Additionally, we will develop the hypothesis that lymphatic vessels may provide the primary route through which CSF is cleared from the cranial subarachnoid space in the fetus. With this new conceptual framework, we will reassess hydrocephalus from a lymphatic perspective to determine if impaired CSF transport through extracranial lymphatics might contribute to the development of this disease.

Canadian experience with the pipeline embolization device for repair of unruptured intracranial aneurysms

BACKGROUND AND PURPOSE

Flow-diverting stents, such as the PED, have emerged as a novel means of treating complex intracranial aneurysms. This retrospective analysis of the initial Canadian experience provides insight into technical challenges, clinical and radiographic outcomes, and complication rates after the use of flow-diverting stents for unruptured aneurysms.

MATERIALS AND METHODS

Cases were compiled from 7 Canadian centers between July 2008 and December 2010. Each center prospectively tracked their initial experience; these data were retrospectively updated and pooled for analysis.

RESULTS

During the defined study period, 97 cases of unruptured aneurysm were treated with the PED, with successful stent deployment in 94 cases. The overall complete or near-complete occlusion rate was 83%, with a median follow-up at 1.25 years (range 0.25-2.5 years). Progressive occlusion was witnessed over time, with complete or near-complete occlusion in 65% of aneurysms followed through 6 months, and 90% of aneurysms followed through 1 year. Multivariate analysis found previous aneurysm treatment and female sex predictive of persistent aneurysm filling. Most patients were stable or improved (88%), with the most favorable outcomes observed in patients with cavernous carotid aneurysms. The overall mortality rate was 6%. Postprocedural aneurysm hemorrhage occurred in 3 patients (3%), while ipsilateral distal territory hemorrhage was observed in 4 patients (3.4%).

CONCLUSIONS

Flow-diverting stents represent an important tool in the treatment of complex intracranial aneurysms. The relative efficacy and morbidity of this treatment must be considered in the context of available alternate interventions.

Transretinal degeneration in ageing human retina: a multiphoton microscopy analysis

AIM

Retinal cell remodelling has been reported as a consistent feature of ageing. However, the degree to which this results in transretinal degeneration is unclear. To address this, the authors used multiphoton microscopy to quantify retinal degeneration in post-mortem human eyes of two age groups.

METHODS

Retinas from six young subjects (18-33 years old) and six older subjects (74-90 years old) were prepared as wholemount preparations. All retinas were stained with 4,6-diamidino-2-phenylindole and imaged by multiphoton confocal microscopy to quantify neuron densities in the retinal ganglion cell layer (RGCL), inner nuclear layer (INL) and outer nuclear layer (ONL). Neurons were counted using automated cell identification algorithms. All retinas were imaged hydrated to minimise tissue artefacts.

RESULTS

In both groups, 56% of the area within the central 4 mm eccentricity and 27% of the area with eccentricity between 4 mm and 7 mm were imaged. Compared with young subjects, the peak RGCL neuron loss in the aged subjects (25.5%) was at 1 mm eccentricity. INL and ONL neuron densities significantly decreased at 1-2 mm eccentricity (8.7%) and 0.5-4 mm eccentricity (15.6%) respectively (P <0.05). The reduction in neuron density in the INL corresponded, spatially, to the region with the greatest neuron loss in the RGCL and ONL.

CONCLUSIONS

This is the first study to correlate neurodegeneration in different populations of cells in the ageing retinas. These data confirm that the greatest neuronal loss occurs in the RGCL and ONL in human ageing retinas, whereas the INL is relatively preserved.

Topography of neuron loss in the retinal ganglion cell layer in human glaucoma

AIM

To determine if retinal ganglion cell (RGC) loss influences the loss of surrounding RGCs to generate clustered patterns of cell death in human glaucoma. It is hypothesised that retinal ganglion cell loss accelerates the loss of surrounding cells to generate, at a local, cellular scale, clustered patterns of retinal of RGC death. The absence of these interactions would result in a diffuse pattern RGC loss.

METHOD

Six glaucomatous retinas (67-83 years old) and six age-matched control retinas (61-89 years old) were prepared as wholemounts and stained by 4',6-diamidino-2-phenylindole (DAPI) solution (3 microg/ml in PBS). An area corresponding to central 14 degrees of the visual field was imaged. The nearest-neighbour distribution was determined for cells in both normal and glaucomatous RGCL.

RESULTS

Clustered RGC loss in human glaucoma was observed on a background of diffuse loss. The mean nearest-neighbour distance (NND) of the glaucomatous retinas was significantly higher than with controls (p<0.001). The distribution of NND in glaucomatous retinas was skewed to the higher values with a higher positive kurtosis relative to controls. The quantitative analysis of the pattern of cell loss is supported by the visual inspection of the patterns of cell loss.

DISCUSSION

The nearest-neighbour analysis is consistent with the presence of two patterns of cell loss in the RGCL in glaucoma. While the diffuse of cell loss can account for an overall reduction in the RGC population, an additional non-random pattern is consistent with the hypothesis that RGC loss has a local influence on the viability of surrounding cells.

Surveillance of Trend and Distribution of Stroke Mortality by Subtype, Age, Gender, and Geographic Areas in Tianjin, China, 1999–2006

Background

The purpose of this study was to analyze the epidemiological trend and distribution of stroke mortality in the city of Tianjin, China, in order to provide evidence for the prevention and control of stroke.

Methods

The study was based on 102 718 cases of stroke mortality in Tianjin between 1999 and 2006. The cause of death was coded according to the International Classification of Diseases into stroke subtypes. Standardized mortality rates were calculated for stroke and its subtypes, adjusted for age and gender using the year 2000 world standard population. The age, gender, and geographic distribution of stroke and subtype mortality were analyzed. χ2-tests were used to determine the statistical significance of differences in mortality trends.

Results

The stroke mortality rate in Tianjin declined from 133·52/100000/year in 1999 to 102·52/100000/year in 2006. The stroke mortality rate for males was higher than that for females. Stroke mortality rates increased with increasing age. The subtypes of stroke have changed considerably in Tianjin. Hemorrhagic was major in 1999–2001, while cerebral infarction attained the first rank and accounted for more than 50% of stroke mortality in 2002–2006. The most pronounced finding was that the proportion of ischemic stroke was 66·65% in the urban population and over 20% higher than that in the rural area. Stroke in the suburban area was mainly hemorrhagic stroke, up to 62·67%.

Conclusions

There are significant differences in the distribution of stroke mortality by subtype, age, gender, and geographic areas in Tianjin, China. Various subtypes of stroke are associated with different risk factors and therefore require different public health prevention and control measures. This study provides pertinent information for formulation of measures for the prevention and control of stroke.

VEGF-A regulates the expression of VEGF-C in human retinal pigment epithelial cells

AIM

To determine the expression and regulation of vascular endothelial growth factor C (VEGF-C), and its receptor VEGFR-3, in human retinal pigment epithelial (RPE) cells and to consider their angiogenic role in choroidal neovascularisation (CNV).

METHOD

The expression of VEGF-C and VEGFR-3 in cultured human RPE was confirmed by immunostaining, PCR, western blotting, and ELISA. Cultured RPE cells were exposed to VEGF-A and glucose and VEGF-C and VEGFR-3 changes in gene expression determined by RT-PCR. Secreted VEGF-C protein in conditioned media from RPE was examined by western blotting and ELISA analysis. The ability of VEGF-C to elicit tube formation in choroidal endothelial cells was assayed by an in vitro Matrigel model.

RESULT

VEGF-A and glucose upregulated VEGF-C mRNA expression and increased the secretion of VEGF-C protein into the culture medium. VEGF-A, but not glucose alone, stimulated VEGFR-3 mRNA expression. VEGF-C acted synergistically with VEGF-A to promote in vitro tube formation by choroidal endothelial cells.

CONCLUSION

VEGF-A has a critical role in the orchestration of VEGF-C expression in RPE cells and the synergistic action of VEGF-C with VEGF-A may play an important part in the aetiology of CNV.

Evidence of a distinct lipid fraction in historical parchments: a potential role in degradation?

Parchment, a biologically based material obtained from the processed hides of animals such as cattle and sheep, has been used for millennia as a writing medium. Although numerous studies have concentrated on the structure and degradation of collagen within parchment, little attention has been paid to noncollagenous components, such as lipids. In this study, we present the results of biochemical and structural analyses of historical and newly manufactured parchment to examine the potential role that lipid plays in parchment stability. The lipid fraction extracted from the parchments displayed different fatty acid compositions between historical and reference materials. Gas chromatography, small-angle X-ray scattering, and solid-state NMR were used to identify and investigate the lipid fraction from parchment samples and to study its contribution to collagen structure and degradation. We hypothesize that the origin of this lipid fraction is either intrinsic, attributable to incomplete fat removal in the manufacturing process, or extrinsic, attributable to microbiological attack on the proteinaceous component of parchments. Furthermore, we consider that the possible formation of protein-lipid complexes in parchment over the course of oxidative degradation may be mediated by reactive oxygen species formed by lipid peroxidation.

Angiopoietin concentrations in diabetic retinopathy

BACKGROUND/AIM

Angiopoietin 1 and 2 interact with vascular endothelial growth factor (VEGF) to promote angiogenesis in animal and in vitro models. Although VEGF concentrations are elevated, there is little information regarding angiopoietin concentration in the vitreous of patients with diabetic retinopathy.

METHODS

Angiopoietin concentrations were measured by luminescence immunoassay in vitreous samples from 17 patients with non-proliferative diabetic retinopathy (NPDR) and clinically significant diabetic macular oedema (CSMO), 10 patients with proliferative diabetic retinopathy (PDR), and five patients with macular hole (controls) obtained at pars plana vitrectomy.

RESULTS

Angiopoietin 1 concentrations were low in patients with macular hole (median 17 pg/ml) while in NPDR with CSMO they were 2002 pg/ml (range 289-5820 pg/ml) and in PDR 186 pg/ml (range 26-2292 pg/ml). Angiopoietin 2 concentrations in NPDR with CSMO were a median of 4000 pg/ml (range 1341-14 329 pg/ml). For both macular hole and PDR patients angiopoietin 2 was below the limit of detection.

CONCLUSIONS

Angiopoietin 2 concentration was twice that of angiopoietin 1 in NPDR with CSMO. Angiopoietin 2 is the natural antagonist of angiopoietin 1 which is thought to act as an anti-permeability agent. The predominance of angiopoietin 2 may allow VEGF induced retinal vascular permeability in patients with CSMO. The relatively low concentration of both angiopoietin 1 and 2 in patients with proliferative diabetic retinopathy may reflect the established nature of the neovascularisation in cases proceeding to vitrectomy.

Do blue light filters confer protection against age-related macular degeneration?

Age-related macular degeneration (AMD) is a major health problem in the developed world accounting for approximately half of all blind registrations. Current treatment options are unsuitable for the majority of patients and therefore the identification of modifiable risk factors that may inform disease prevention programmes is a priority. This review evaluates the long-held belief that blue light exposure has a role in the pathogenesis of AMD. Laboratory evidence has demonstrated that photochemical reactions in the oxygen-rich environment of the outer retina lead to the liberation of cytotoxic reactive oxygen species (ROS). These ROS cause oxidative stress which is known to contribute to the development of AMD. The precise chromopore that may be involved in the pathogenesis of AMD is unclear but the age pigment lipofuscin is a likely candidate. Its aerobic photoreactivity and adverse effects on antioxidant activity combined with its gradual accumulation over time suggests that its in vivo phototoxicity increases with age despite changes in the absorption characteristics of the crystalline lens. Evidence from animal studies confirms blue light's damaging potential but the results are not directly applicable to macular degeneration in humans. Studies of human macular pigment density and the risk of AMD progression following cataract surgery lend further weight to the hypothesis that blue light exposure has a role in the pathogenesis of AMD but the epidemiological evidence is equivocal. On balance the evidences suggests but does not yet confirm that blue light is a risk factor for AMD. Given the socio-economic impact of this disease and urgent need to identify modifiable risk factors, future work should include a large-scale clinical trial to evaluate the effect of blue blocking filters on AMD progression rates.

Differences in enquiries to CancerBACUP information service by living arrangements

The study's aim was to ascertain whether living alone is associated with the use of an independent cancer information service. An Enquirer Record Form is completed for every fifth enquirer to the service; two questions asking whether enquirers, patients, relatives/friends were living alone or with others where asked in association with the routine questions. A total of 552 callers were asked in a 5-week period, 77% of all callers in these categories. The main findings were: (1) the proportion of enquirers living alone was similar to the general population; (2) among enquirers, patients were more likely to live alone than relatives/friends; (3) requests differed by whether living alone and by type of enquirer, for example, significantly more people living with others requested emotional support than those living alone, and this contrast was most marked for patients than relatives/friends. This study, notwithstanding its limitations, highlights some of the differences in the use of a service and demonstrates the complexity of information and support seeking.

The pathogenesis of diabetic retinopathy: old concepts and new questions

Hyperglycaemia appears to be a critical factor in the aetiology of diabetic retinopathy and initiates downstream events including: basement membrane thickening, pericyte drop out and retinal capillary non-perfusion. More recently, focus has been directed to the molecular basis of the disease process in diabetic retinopathy. Of particular importance in the development and progression of diabetic retinopathy is the role of growth factors (eg vascular endothelial growth factor, placenta growth factor and pigment epithelium-derived factor) together with specific receptors and obligate components of the signal transduction pathway needed to support them. Despite these advances there are still a number of important questions that remain to be answered before we can confidently target pathological signals. How does hyperglycaemia regulate retinal vessels? Which growth factors are most important and at what stage of retinopathy do they operate? What is the preferred point in the growth factor signalling cascade for therapeutic intervention? Answers to these questions will provide the basis for new therapeutic interventions in a debilitating ocular condition.

Loss of the antiangiogenic pigment epithelium-derived factor in patients with angiogenic eye disease

Retinal neovascularization characterizes proliferative diabetic retinopathy (PDR). Pigment epithelium-derived factor (PEDF) has been shown to be a major antiangiogenic growth factor in the mammalian eye. PEDF expression is suppressed by hypoxia, and changes in PEDF have been correlated to the development of retinal neovascularization in animal models of hypoxic eye disease. However, whether this concept of a reduced angiogenesis inhibitor holds true in humans is as yet unclear. In this study, we analyzed the in vivo regulation of PEDF in patients with and without hypoxic eye disease. We used immunoblots to measure PEDF in ocular fluids obtained from 64 nondiabetic and diabetic patients. In addition, immunohistochemistry of PEDF was carried out in specimens of normal human retinas and retinas with various degrees of diabetic retinopathy. The PEDF concentrations in patients with PDR (P < 0.001) or extensive nondiabetic retinal neovascularization caused by retinal-vein occlusion (P < 0.001) were lower than in control patients. Levels of PEDF were replenished in PDR patients with previous retinal scatter photocoagulation compared with PDR patients without previous photocoagulation (P = 0.01). Immunohistochemistry revealed an interstitial staining pattern as expected for a secreted protein, with an intense staining in retinas of patients without proliferative eye disease. However, in patients with PDR, little or no staining was detectable. Our data strongly support the concept that retinal angiogenesis is induced by loss of the major angiogenesis inhibitor in the eye, PEDF, in combination with an increased expression of angiogenic growth factors such as vascular endothelial growth factor. Our findings suggest that substitution of angiogenesis inhibitors may be an effective approach in the treatment of PDR.

Retinal photodamage

The retina represents a paradox, in that, while light and oxygen are essential for vision, these conditions also favour the formation of reactive oxygen species leading to photochemical damage to the retina. Such light damage seems to be multi-factorial and is dependent on the photoreactivity of a variety of chromophores (e.g., vitamin A metabolites, lipofuscin, melanin, flavins, porphyrins, carotenoids) endogenous to the retina. The aim of this article is to provide a detailed review of our current understanding of the photochemistry and photobiology of these chromophores and to consider how they may contribute to retinal ageing and pathology.

Investigating women's preferences for intrapartum care: home versus hospital births

There is an increasing amount of evidence to suggest that the clinical outcomes associated with a home birth for low risk women are at least as good, if not better than, the clinical outcomes associated with giving birth in hospital. If it is the case that there is little or no difference in clinical outcomes between the two modes of delivery, then traditional measures of benefit used in health economics, e.g. quality adjusted life years (QALYs), would detect little or no difference between the alternative modes of delivery. From this, the conclusion would be that the utility values associated with each mode of delivery are similar. However, women may still have clearly defined preferences relating to the way in which maternity care is provided. This paper uses the economic technique of conjoint analysis to assess the relative value attached to several main characteristics associated with the process of maternity care during the intrapartum stage for women who have actively chosen to give birth at home relative to women who have given birth in hospital. It was found that respondents who had chosen a home birth valued continuity of carer, a homely environment and the ability to make their own decisions about what happens during labour and delivery. In contrast, hospital birth respondents placed a relatively high value on access to an epidural for pain relief and not needing to be transferred to another location during labour if a problem arose. The results of the study suggest that women have clearly defined preferences for characteristics associated with the process of intrapartum care that would be unlikely to be detected by traditional benefit measures used in health economics. This finding is important where policy issues relating to aspects of maternity care service delivery are being considered.

Inhibition of RPE lysosomal and antioxidant activity by the age pigment lipofuscin

PURPOSE

To determine whether lipofuscin is detrimental to lysosomal and antioxidant function in cultured human retinal pigment epithelial (RPE) cells.

METHODS

Isolated lipofuscin granules were fed to confluent RPE cultures and the cells maintained in basal medium for 7 days. Parallel cultures were established that did not receive lipofuscin. Cultures were either exposed to visible light (390-550 nm) at an irradiance of 2.8 mW/cm(2) or maintained in the dark at 37 degrees C for up to 24 hours. Cells were subsequently assessed for cell viability, lysosomal enzyme activity, and antioxidant capacity.

RESULTS

There was no loss of cell viability during the first 3 hours of light exposure, whereas a 10% loss of viability was observed in lipofuscin-fed cultures after 6 hours' exposure to light. Activities of acid phosphatase, N-acetyl-beta-glucuronidase, and cathepsin D were decreased by up to 50% in lipofuscin-fed cells exposed to light compared with either unfed cells or cells maintained in the dark. There was also a decrease in the antioxidant potential of RPE cells. Catalase and superoxide dismutase activities decreased by up to 60% and glutathione levels by 28% in light-exposed lipofuscin-fed cells compared with unfed cells or cells maintained in the dark.

CONCLUSIONS

Lipofuscin has the capacity to reduce the efficacy of the lysosomal and antioxidant systems in RPE cells that may play an important role in retinal ageing and the development of age-related macular degeneration.

Comparison of cerebrospinal fluid transport in fetal and adult sheep

We quantified cerebrospinal fluid (CSF) transport (conductance) and CSF outflow resistance in late-gestation fetal and adult sheep using two methods, a constant pressure infusion method and a bolus injection technique into the lateral ventricles. No significant differences in CSF conductance (fetus 0.013 +/- 0.002, adult 0.014 +/- 0.003 ml x min(-1) x cm H(2)O(-1)) or CSF outflow resistance (fetus 83.7 +/- 9.8, adult 84.7 +/- 19.7 cm H(2)O x ml(-1) x min) were observed. To confirm CSF transport to plasma in fetal animals, (125)I- or (131)I-labeled human serum albumin (HSA) was injected into the lateral ventricles. The tracer entered fetal plasma with an average mass transport rate of 1.91 +/- 0.47% injected/h (n = 9). In two fetuses, we monitored the tracer appearance in plasma and cervical and thoracic duct lymph after injection of radioactive HSA into the ventricular CSF. As was the case in adult animals, fetal tracer concentrations increased in all three compartments over time, with the highest concentrations measured in lymph collected from the cervical lymphatics. These results 1) indicate that global CSF transport parameters in the late-gestation fetus and adult sheep are similar and 2) suggest an important role for extracranial lymphatic vessels in CSF transport before birth.

Do men with prostate or colorectal cancer seek different information and support from women with cancer?

Male cancer patients' use of a national cancer information service, their requests and key predictors of these over the period April 1996 to March 1998 are presented, in comparison with women. The most frequent requests of 411 prostate, 162 male and 217 female colorectal cancer patients were similar: site-specific information, emotional support, publications, specific therapies. Research or clinical trials (P < 0.05), diet and nutrition (P < 0.001) requests differed between men with prostate and colorectal cancers; complementary therapies (P < 0.05), prognosis (P < 0.05) requests differed between male and female colorectal cancer patients. Among prostate cancer patients, employed men aged 60+ were more likely to need emotional support than retired men aged 70 +; men < 59 years old were more likely to request publications, but less likely to enquire about specific therapies than others. Among male colorectal cancer patients, employed men were less likely to request site-specific information, but more likely to need emotional support than retired men; patients from geographical areas other than Thames were more likely to request publications; patients from manual classes were less likely to enquire about specific therapies than those from non-manual classes. The complexity of information and support seeking behaviour is demonstrated; no pattern was found among men or in comparison with women. Further research is needed to enable development of services that are appropriate to individual needs and concerns.

The role of the retinal pigment epithelium: topographical variation and ageing changes

The retinal pigment epithelium (RPE) is a single layer of post-mitotic cells, which functions both as a selective barrier to and a vegetative regulator of the overlying photoreceptor layer, thereby playing a key role in its maintenance. Through the expression and activity of specific proteins, it regulates the transport of nutrients and waste products to and from the retina, it contributes to outer segment renewal by ingesting and degrading the spent tips of photoreceptor outer segments, it protects the outer retina from excessive high-energy light and light-generated oxygen reactive species and maintains retinal homeostasis through the release of diffusible factors. The ageing characteristics of the RPE suggest that in addition to cell loss, pleomorphic changes and loss of intact melanin granules, significant metabolic changes occur resulting, at least in part, from the intracellular accumulation of lipofuscin. This pigment has been shown to be highly phototoxic and has been linked to several oxidative changes, some leading to cell death. While the aetiology of age-related macular degeneration is complex and is as yet unresolved, it is likely that accelerated ageing-like changes in the RPE play a fundamental role in the development of this condition.

Oxygen modulates the release of urokinase and plasminogen activator inhibitor-1 by retinal pigment epithelial cells

The aims of this study were to examine the effect of oxygen, in the presence or absence of exogenous growth factors, on the release of plasminogen activators and plasminogen activator inhibitor-1 by cultured human retinal pigment epithelial cells. Antigen and activity levels of urokinase, tissue plasminogen activator and plasminogen activator inhibitor were measured in conditioned media after cells were exposed to three different oxygen environments: hypoxia, normoxia and hyperoxia. Overall proteolytic balance was determined by zymography. The effects of exogenous basic fibroblast growth factor and transforming growth factor-beta were also examined. it was found that retinal pigment epithelial cells released urokinase, tissue plasminogen activator and plasminogen activator inhibitor in measurable quantities. After 48 h, urokinase levels were highest at normoxia, reaching 7.2ng/10(6) cells (+/-2.0 SEM), whereas plasminogen activator inhibitor 1 levels were highest at hyperoxia, reaching 67.5ng/10(6) cells (+/-3.7 SEM). Tissue plasminogen activator levels were minimal (<0.5ng/10(6) cells) and unaffected by both oxygen and growth factors. Overall proteolytic activity was also greatest at normoxia. Fibroblast growth factor stimulated urokinase production dose-dependently, but plasminogen activator inhibitor only minimally. Transforming growth factor-beta stimulated plasminogen activator inhibitor production dose-dependently but urokinase only at higher concentrations. These results suggest that both oxygen tension and growth factors may interact to modulate the proteolytic properties of the human retinal pigment epithelium.

'Dividing the desolation': clients views on the benefits of a cancer counselling service

This paper describes clients' accounts of the benefits they derived from a short course of cancer counselling provided within a humanist framework. Three hundred and two clients who had attended at least one session of a short course of cancer counselling received an evaluation form, which incorporated both fixed-choice and open-ended questions. One hundred and forty two (47%) clients returned evaluation forms; those who had attended more sessions were significantly more likely to do so. Quantitative data were analysed using SPSS (Statistical Package for the Social Sciences) for Windows and qualitative data using a thematic approach. Almost all clients indicated that they felt they had benefited from counselling. Analysis of the open-ended questions identified nine main benefits of counselling and four key avenues or processes through which clients derived these benefits. Overall, counselling was seen as helping them to work through powerful thoughts and feelings and so to come to terms with cancer and to regain a sense of control in their lives. The benefits of a short course of counselling which clients identified reflect the aims of humanistic counselling which are not well captured by psychiatric assessments or most standard research instruments. In evaluating cancer counselling services, assessments which include these client-defined outcomes may provide a more sensitive way of gauging the value of counselling to a non-clinic population.

An evaluation of a cancer counselling service

The CancerBACUP London Counselling Service offered short-term face-to-face counselling to self-referred cancer patients and their relatives and friends, provided by experienced supervised counsellors working within a humanistic theoretical framework. This study aimed to identify its clients' characteristics, use of the service, extent of perceived benefits and satisfaction with the service. Sociodemographic data were collected in Data Sheets from all 384 clients who booked an appointment over 18 months; they were predominantly female, < 50 years old and from non-manual social classes. Significantly more people in those classes and in the 30-59 age group attended three or more sessions. Three hundred and nine clients who attended at least once were sent an Evaluation Form; 142 responded. The probability of the Evaluation Forms' return was greater for those who had completed more sessions; the great majority of respondents felt that they had benefited, and were satisfied with the service. This study, notwithstanding its limitations, shows that a short course of counselling may be perceived by clients to be helpful; it also raises other issues of value to those involved in cancer services and/or counselling provision.

Regulation of tyrosinase expression and activity in cultured human retinal pigment epithelial cells

The purpose of this study was to investigate the regulation of tyrosinase gene expression and activity in cultured human retinal pigment epithelial (RPE) cells. The tyrosinase promoter (Ty.prom) region (400 bp) was PCR amplified and cloned into a modified mammalian expression vector (pcDNA3.1) upstream of a firefly luciferase (Luc) cDNA and was designated 'pcDNA3.1-Ty.prom.Luc'. The plasmid was co-transfected into RPE cells with a second mammalian expression plasmid (pRL-TK) containing a herpes simplex virus thymidine kinase promoter region upstream of Renilla Luc in a protocol designated the 'dual luciferase assay' (DLA). After co-transfection, cells were treated with a range of potential melanogenic agents; basic fibroblast growth factor (bFGF), methyl methane sulphonate, alpha-melanocyte stimulating hormone, verapamil, phorbol myristate acetate, cholera toxin (CT), pigment epithelium derived factor (PEDF), and L-tyrosine. The expression of tyrosinase promoter and enzymatic activities were determined 48 hr post-transfection using the DLA and DOPA oxidase assays, respectively. Tyrosinase activity could not be detected in RPE cells with any of the treatments. Tyrosinase promoter activity was significantly up-regulated in RPE cells treated with bFGF, PEDF, verapamil, CT and tyrosine compared with control cells. In conclusion, the tyrosinase gene is not only expressed but can be regulated in response to different chemicals in cultured human RPE cells. However, it appears that RPE cells in culture lack a post-transcriptional and/or translational modification point(s), which are necessary for tyrosinase enzymic activity.

[A retinoid constituent of lipofuscin, A2-E, is a photosensitizer in human retinal pigment epithelial cells]

BACKGROUND

A fluorescent compound of lipofuscin, A2-E, has been shown to impair lysosomal function and to increase the intralysosomal pH of human retinal pigment epithelial (RPE) cells. This study addressed the phototoxic potential of A2-E on RPE cells.

METHODS

A2-E accumulation was confirmed by fluorescence microscopy and fluorescence-activated cell sorter analysis. Acridine orange staining allowed assessment of lysosomal integrity and intralysosomal pH. Phototoxic properties of A2-E were determined by exposing A2-E-free and A2-E-fed RPE cell cultures to short-wavelength visible light and assessing cell viability and lysosomal integrity.

RESULTS

Intralysosomal accumulation of A2-E was confirmed. Acridine orange staining showed that the A2-E was located in the lysosomal compartment and induced an elevation of intralysosomal pH. Exposure of A2-E fed cells to light resulted in a significant loss of cell viability by 72 h which was not observed in either RPE cells maintained in the dark or A2-E-free cultures exposed to light. Toxicity was associated with a loss of lysosomal integrity.

CONCLUSION

A2-E is detrimental to RPE cell function by a variety of mechanisms including inhibition of lysosomal degrading capacity, loss of membrane integrity, and phototoxicity. Such mechanisms could contribute to retinal aging and to retinal diseases associated with excessive lipofuscin accumulation.

The role of oxidative stress in the pathogenesis of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blind registration in the developed world, and yet its pathogenesis remains poorly understood. Oxidative stress, which refers to cellular damage caused by reactive oxygen intermediates (ROI), has been implicated in many disease processes, especially age-related disorders. ROIs include free radicals, hydrogen peroxide, and singlet oxygen, and they are often the byproducts of oxygen metabolism. The retina is particularly susceptible to oxidative stress because of its high consumption of oxygen, its high proportion of polyunsaturated fatty acids, and its exposure to visible light. In vitro studies have consistently shown that photochemical retinal injury is attributable to oxidative stress and that the antioxidant vitamins A, C, and E protect against this type of injury. Furthermore, there is strong evidence suggesting that lipofuscin is derived, at least in part, from oxidatively damaged photoreceptor outer segments and that it is itself a photoreactive substance. However, the relationships between dietary and serum levels of the antioxidant vitamins and age-related macular disease are less clear, although a protective effect of high plasma concentrations of alpha-tocopherol has been convincingly demonstrated. Macular pigment is also believed to limit retinal oxidative damage by absorbing incoming blue light and/or quenching ROIs. Many putative risk-factors for AMD have been linked to a lack of macular pigment, including female gender, lens density, tobacco use, light iris color, and reduced visual sensitivity. Moreover, the Eye Disease Case-Control Study found that high plasma levels of lutein and zeaxanthin were associated with reduced risk of neovascular AMD. The concept that AMD can be attributed to cumulative oxidative stress is enticing, but remains unproven. With a view to reducing oxidative damage, the effect of nutritional antioxidant supplements on the onset and natural course of age-related macular disease is currently being evaluated.

Faith, hope, and charity: an in-depth interview study of cancer patients' information needs and information-seeking behavior

OBJECTIVE: To explore why cancer patients do not want or seek information about their condition beyond that volunteered by their physicians at times during their illness. DESIGN: Qualitative study based on in-depth interviews. SETTING: Outpatient oncology clinics at a London cancer center. PARTICIPANTS: 17 patients with cancer diagnosed in previous 6 months. Main outcome measures Analysis of patients' narratives to identify key themes and categories. RESULTS: While all patients wanted basic information on diagnosis and treatment, not all wanted further information at all stages of their illness. Three overarching attitudes to their management of cancer limited patients' desire for and subsequent efforts to obtain further information : faith, hope, and charity. Faith in their doctor's medical expertise precluded the need for patients to seek further information themselves. Hope was essential for patients to carry on with life as normal and could be maintained through silence and avoiding information, especially too detailed or "unsafe" information. Charity to fellow patients, especially those seen as more needy than themselves, was expressed in the recognition that scarce resources-including information and explanations-had to be shared and meant that limited information was accepted as inevitable. CONCLUSIONS: Cancer patients' attitudes to cancer and their strategies for coping with their illness can constrain their wish for information and their efforts to obtain it. In developing recommendations, the government's cancer information strategy should attend to variations in patients' desires for information and the reasons for them.

Influence of pigment content, intracellular calcium and cyclic AMP on the ability of human retinal pigment epithelial cells to contract collagen gels

PURPOSE

The aim of the study was to determine to what extent collagen gel contraction could be reduced by calcium and calmodulin antagonists and agents that elevate cyclic AMP in order to develop a pharmacological approach to prevent/arrest RPE contraction of epiretinal membranes in proliferative vitreoretinopathy. We also explored a possible role of pigment in collagen gel contraction.

METHOD

We measured RPE mediated contraction of 3D collagen gels in the presence and absence of the calcium and calmodulin antagonists TMB8, Verapamil and Tamoxifen and the cAMP elevating agents IBMX and Forskolin. The effect of pigment on collagen gel contraction was assessed by comparing gel contraction mediated by RPE cells re-pigmented with melanin with that mediated by unpigmented RPE. The effect of IBMX on RPE proliferation was assessed using a BrdU ELISA and the effects of IBMX on RPE cytoskeleton and cell shape were assessed using Actin and Cytokeratin immunocytochemistry.

RESULTS

We report that both cAMP elevating agents and calcium and calmodulin antagonists reduce RPE mediated collagen gel contraction. Cyclic AMP elevation was more effective than a reduction in calcium in reducing contraction. There were no significant advantages in combining both approaches. The presence of melanin had no effect on gel contraction. Calcium antagonists and particularly agents which elevate cAMP caused RPE cells in collagen gels to extend fewer and shorter processes. cAMP elevation in particular caused RPE cells to become more rounded and develop arborized cell processes. Immunostaining for actin and cytokeratin revealed changes in cytoskeletal organisation in response to IBMX in that cells contained less actin than untreated cells and concentrated cytokeratins more centrally.

CONCLUSION

We have identified two possible pharmacological approaches which may provide a new direction for preventing or slowing down the development of PVR.

Optimization of non-viral gene transfer to human primary retinal pigment epithelial cells

PURPOSE

To optimise the high efficiency, non-viral transfer of DNA to retinal pigment epithelial (RPE) cells in vitro.

METHODS

A mammalian expression vector (pcDNA3.1) containing a firefly luciferase (luc) cDNA was used to transfect RPE cells using different chemical methods; calcium phosphate, DEAE-dextran and, liposomes-based transfection techniques. Transfection was optimised for both dose and time of exposure. The efficiency of gene transfer and cytotoxicity was measured 48 hours post-transfection using luciferase and MTT assays, respectively. The percentage of transfected cells (using optimal conditions) was determined with a construct expressing a jellyfish green fluorescent protein (GFP) using flow cytometery.

RESULTS

Calcium phosphate and DEAE-dextran techniques failed to transfect the vector and led to high cytotoxicity. Liposomes-based methods successfully transferred the vector to RPE cells, but the efficiency varied for different liposomes; Tfx-50 > Lipofectin > Lipofectamine > Cellfectin > DMRIE-C. No significant cytotoxicity was observed with any of the liposome treatments. Optimal transfection was achieved with Tfx-50 at a 3:1 ratio of DNA:liposome; between 12-15% of cells being transfected.

CONCLUSIONS

Efficient and non-toxic transfer of functional genes into primary RPE cells in vitro can be successfuly achieved by liposomes-based techniques. Tfx-50 appears to be a promising non-viral vector for RPE gene transfer.