Data Science-Driven Analysis of Substrate-Permissive Diketopiperazine Reverse Prenyltransferase NotF: Applications in Protein Engineering and Cascade Biocatalytic Synthesis of (-)-Eurotiumin A

Prenyltransfer is an early-stage carbon-hydrogen bond (C-H) functionalization prevalent in the biosynthesis of a diverse array of biologically active bacterial, fungal, plant, and metazoan diketopiperazine (DKP) alkaloids. Toward the development of a unified strategy for biocatalytic construction of prenylated DKP indole alkaloids, we sought to identify and characterize a substrate-permissive C2 reverse prenyltransferase (PT). As the first tailoring event within the biosynthesis of cytotoxic notoamide metabolites, PT NotF catalyzes C2 reverse prenyltransfer of brevianamide F. Solving a crystal structure of NotF (in complex with native substrate and prenyl donor mimic dimethylallyl S-thiolodiphosphate (DMSPP)) revealed a large, solvent-exposed active site, intimating NotF may possess a significantly broad substrate scope. To assess the substrate selectivity of NotF, we synthesized a panel of 30 sterically and electronically differentiated tryptophanyl DKPs, the majority of which were selectively prenylated by NotF in synthetically useful conversions (2 to >99%). Quantitative representation of this substrate library and development of a descriptive statistical model provided insight into the molecular origins of NotF's substrate promiscuity. This approach enabled the identification of key substrate descriptors (electrophilicity, size, and flexibility) that govern the rate of NotF-catalyzed prenyltransfer, and the development of an "induced fit docking (IFD)-guided" engineering strategy for improved turnover of our largest substrates. We further demonstrated the utility of NotF in tandem with oxidative cyclization using flavin monooxygenase, BvnB. This one-pot, in vitro biocatalytic cascade enabled the first chemoenzymatic synthesis of the marine fungal natural product, (-)-eurotiumin A, in three steps and 60% overall yield.

Flavin-Dependent Monooxygenases NotI and NotI' Mediate Spiro-Oxindole Formation in Biosynthesis of the Notoamides

The fungal indole alkaloids are a unique class of complex molecules that have a characteristic bicyclo[2.2.2]diazaoctane ring and frequently contain a spiro-oxindole moiety. While various strains produce these compounds, an intriguing case involves the formation of individual antipodes by two unique species of fungi in the generation of the potent anticancer agents (+)- and (-)-notoamide A. NotI and NotI' have been characterized as flavin-dependent monooxygenases that catalyze epoxidation and semi-pinacol rearrangement to form the spiro-oxindole center within these molecules. This work elucidates a key step in the biosynthesis of the notoamides and provides an evolutionary hypothesis regarding a common ancestor for production of enantiopure notoamides.

Bile acid metabolites control Th17 and Treg cell differentiation

Bile acids are abundantly present in the mammalian gut, where they undergo bacteria-mediated transformation, generating a large pool of bioactive molecules. While they have been shown to affect host metabolism, cancer progression and innate immunity, it is unknown whether bile acids affect the function of adaptive immune cells such as T cells expressing IL-17a (Th17 cells) and regulatory T cells (Tregs) that mediate inflammatory and anti-inflammatory responses, respectively. By screening a small-molecule library primarily composed of bile acid metabolites, we identified two distinct derivatives of lithocholic acid (LCA), 3-oxoLCA and isoalloLCA, as specific regulators of Th17 and Treg cells. While 3-oxoLCA inhibited Th17 cell differentiation by directly binding to its key transcription factor RORγt (retinoid-related orphan receptor γt), isoalloLCA enhanced Treg differentiation through the production of mitochondrial reactive oxygen species (mitoROS), leading to increased FoxP3 expression. IsoalloLCA-mediated Treg enhancement required an intronic FoxP3 enhancer the conserved noncoding sequence 3 (CNS3), suggesting a distinct mode of action from other previously identified Treg enhancing metabolites that require CNS1. Lastly, oral administration of 3-oxoLCA and isoalloLCA to mice led to reduced Th17 and increased Treg cell differentiation in the intestinal lamina propria. Altogether, our data suggest novel mechanisms by which bile acid metabolites control host immune responses by directly modulating the Th17 and Treg balance.

Molecular Basis for Spirocycle Formation in the Paraherquamide Biosynthetic Pathway

The paraherquamides are potent anthelmintic natural products with complex heptacyclic scaffolds. One key feature of these molecules is the spiro-oxindole moiety that lends a strained three-dimensional architecture to these structures. The flavin monooxygenase PhqK was found to catalyze spirocycle formation through two parallel pathways in the biosynthesis of paraherquamides A and G. Two new paraherquamides (K and L) were isolated from a ΔphqK strain of Penicillium simplicissimum, and subsequent enzymatic reactions with these compounds generated two additional metabolites, paraherquamides M and N. Crystal structures of PhqK in complex with various substrates provided a foundation for mechanistic analyses and computational studies. While it is evident that PhqK can react with various substrates, reaction kinetics and molecular dynamics simulations indicated that the dioxepin-containing paraherquamide L is the favored substrate. Through this effort, we have elucidated a key step in the biosynthesis of the paraherquamides and provided a rationale for the selective spirocyclization of these powerful anthelmintic agents.

Retinal burns from laser pointers: a risk in children with behavioural problems

OBJECTIVE

To explore self-inflicted retinal burns from laser pointers in children.

METHODS

Literature review of laser pointer retinal injuries in childhood and online survey of UK Consultant Ophthalmologists. A cohort of local children with self-inflicted injury is described. The matter is topical. We review progress in recent legislation and policy change in the UK.

RESULTS

Four of 77 case reports of laser burns in childhood analysed reported psychological or behavioural issues. Three of four children in our cohort had such issues. Delay in diagnosis occurred in two of our patients. Structural retinal damage persisted for over 12 months in all four children (seven eyes). Our survey of UK ophthalmologists found 159 cases of injury (85% male), 80% under 20 years of age. The majority of the laser pointers were purchased online. Many patients (36%) suffered moderate vision loss (6/18 to 6/60 Snellen), while 17% (at least 11 patients) suffered severe vision loss (<6/60 Snellen).

CONCLUSION

We highlight the risk of macular damage and vision loss from handheld lasers specifically in children with behavioural, learning or mental health issues. The diagnosis may be difficult or delayed in such children. In children with uncertain macular changes, ophthalmologists should explore the history for possible instances of exposure to handheld lasers pointers. Regulatory authorities and manufacturers of handheld lasers need to be aware of the risk to children. Furthermore, there is a need to better inform parents, carers and teachers of the risk of ocular self-injury from such lasers pointers.

Wrong intraocular lens events-what lessons have we learned? A review of incidents reported to the National Reporting and Learning System: 2010-2014 versus 2003-2010

PurposeTo identify the causal factors in wrong intraocular lens (IOL) events from a national data set and to compare with similar historical data (2003-2010) prior to mandatory checklist use, for the purpose of developing strategies to prevent never events.MethodsData from wrong IOL patient safety incidents (PSIs) submitted to the National Reporting and Learning System (2010-2014) were reviewed by thematic analysis and compared with the data previously collected by the group using the same methodology.ResultsOne hundred and seventy eight wrong IOL PSIs were identified. The contributory factors included: transcription errors (n=26); wrong patient biometry (n=21); wrong IOL selection (n=16); changes in planned procedure (n=16); incorrect IOL brought into theatre (n=11); left/right eye selection errors (n=9); communication errors (n=9); and positive/negative IOL power errors (n=9). In 44 PSIs, no causal factor was reported, limiting the learning value of such reports. Compared with the data from previous years, biometry errors were much reduced but IOL transcription and documentation errors were greater, particularly if further checks did not refer to the original source documentation. IOL exchange surgery was reported in 45 cases.ConclusionsThe selection and implantation of the correct IOL is a complex process which is not adequately addressed by existing checking procedures. Despite the introduction of surgical checklists, wrong IOL incidents continue to occur and are probably under-reported. Human or behavioural factors are heavily implicated in these errors and need to be addressed by novel approaches, including simulation training. There is also scope to further improve the quality and detail of incident reporting and analysis to enhance patient safety.

Defining response to anti-VEGF therapies in neovascular AMD

The introduction of anti-vascular endothelial growth factor (anti-VEGF) has made significant impact on the reduction of the visual loss due to neovascular age-related macular degeneration (n-AMD). There are significant inter-individual differences in response to an anti-VEGF agent, made more complex by the availability of multiple anti-VEGF agents with different molecular configurations. The response to anti-VEGF therapy have been found to be dependent on a variety of factors including patient's age, lesion characteristics, lesion duration, baseline visual acuity (VA) and the presence of particular genotype risk alleles. Furthermore, a proportion of eyes with n-AMD show a decline in acuity or morphology, despite therapy or require very frequent re-treatment. There is currently no consensus as to how to classify optimal response, or lack of it, with these therapies. There is, in particular, confusion over terms such as 'responder status' after treatment for n-AMD, 'tachyphylaxis' and 'recalcitrant' n-AMD. This document aims to provide a consensus on definition/categorisation of the response of n-AMD to anti-VEGF therapies and on the time points at which response to treatment should be determined. Primary response is best determined at 1 month following the last initiation dose, while maintained treatment (secondary) response is determined any time after the 4th visit. In a particular eye, secondary responses do not mirror and cannot be predicted from that in the primary phase. Morphological and functional responses to anti-VEGF treatments, do not necessarily correlate, and may be dissociated in an individual eye. Furthermore, there is a ceiling effect that can negate the currently used functional metrics such as >5 letters improvement when the baseline VA is good (ETDRS>70 letters). It is therefore important to use a combination of both the parameters in determining the response.The following are proposed definitions: optimal (good) response is defined as when there is resolution of fluid (intraretinal fluid; IRF, subretinal fluid; SRF and retinal thickening), and/or improvement of >5 letters, subject to the ceiling effect of good starting VA. Poor response is defined as <25% reduction from the baseline in the central retinal thickness (CRT), with persistent or new IRF, SRF or minimal or change in VA (that is, change in VA of 0+4 letters). Non-response is defined as an increase in fluid (IRF, SRF and CRT), or increasing haemorrhage compared with the baseline and/or loss of >5 letters compared with the baseline or best corrected vision subsequently. Poor or non-response to anti-VEGF may be due to clinical factors including suboptimal dosing than that required by a particular patient, increased dosing intervals, treatment initiation when disease is already at an advanced or chronic stage), cellular mechanisms, lesion type, genetic variation and potential tachyphylaxis); non-clinical factors including poor access to clinics or delayed appointments may also result in poor treatment outcomes. In eyes classified as good responders, treatment should be continued with the same agent when disease activity is present or reactivation occurs following temporary dose holding. In eyes that show partial response, treatment may be continued, although re-evaluation with further imaging may be required to exclude confounding factors. Where there is persistent, unchanging accumulated fluid following three consecutive injections at monthly intervals, treatment may be withheld temporarily, but recommenced with the same or alternative anti-VEGF if the fluid subsequently increases (lesion considered active). Poor or non-response to anti-VEGF treatments requires re-evaluation of diagnosis and if necessary switch to alternative therapies including other anti-VEGF agents and/or with photodynamic therapy (PDT). Idiopathic polypoidal choroidopathy may require treatment with PDT monotherapy or combination with anti-VEGF. A committee comprised of retinal specialists with experience of managing patients with n-AMD similar to that which developed the Royal College of Ophthalmologists Guidelines to Ranibizumab was assembled. Individual aspects of the guidelines were proposed by the committee lead (WMA) based on relevant reference to published evidence base following a search of Medline and circulated to all committee members for discussion before approval or modification. Each draft was modified according to feedback from committee members until unanimous approval was obtained in the final draft. A system for categorising the range of responsiveness of n-AMD lesions to anti-VEGF therapy is proposed. The proposal is based primarily on morphological criteria but functional criteria have been included. Recommendations have been made on when to consider discontinuation of therapy either because of success or futility. These guidelines should help clinical decision-making and may prevent over and/or undertreatment with anti-VEGF therapy.

Intravitreal bevacizumab injection in unrecognised early pregnancy

PURPOSE

The use of intravitreal vascular endothelial growth factor (VEGF) inhibitor medications has widened considerably to include indications affecting females of reproductive age.

PATIENTS AND METHODS

We present our experiences following intravitreal injection of bevacizumab during the first trimester of unrecognised pregnancies in four women.

RESULTS

All our patients were inadvertently exposed to bevacizumab within the first trimester when placental growth and fetal organogenesis take place. There were three cases of pregnancy without complication and one case of complicated pregnancy in which there was a significant past obstetric history.

CONCLUSION

This case series provides further insights into intravitreal injection of bevacizumab in early pregnancy. There is insufficient information to suggest that such use is safe, nor is there definitive evidence to suggest that it causes harm. We advise that ophthalmologists discuss pregnancy with women of childbearing age undergoing intraocular anti-VEGF injections. Should a woman become pregnant, counselling is needed to explain the potential risks and benefits, and the limited available data relating to the use of these agents in early pregnancy.

'Toy' laser macular burns in children

PURPOSE

Laser 'toys' can be purchased online and imported with relative ease; the variety of such devices is a potential public safety concern. We describe five children with maculopathy following exposure to laser 'toys'.

METHODS

Case series of maculopathy following exposure to laser 'toys'.

RESULTS

Five children were seen in our Ophthalmic Unit with macular injuries following exposure to laser 'toys'. Clinically, three children had an acute vitelliform-like maculopathy which resolved to leave sub-foveal retinal pigment epithelium changes with reduced vision. One case was complicated by a choroidal neovascular membrane.

CONCLUSION

Laser 'toys', which resemble laser pointers, are increasingly available over the internet. Such 'toys' may not meet safety standards. Retinal injury in childhood following exposure to laser 'toys' is a public safety concern.

Adverse ophthalmic reaction in poppers users: case series of 'poppers maculopathy'

BACKGROUND

Poppers are a recreational substance of abuse belonging to the alkyl nitrite family of compounds. In the United Kingdom, where they are legal to purchase but illegal to sell for human consumption, 10% of the general population have tried them. They are considered low risk to physical and mental health. Two recent case series from France demonstrated foveal pathology in individuals associated with poppers use.

METHOD

A case series of seven patients presenting to four hospitals in the United Kingdom with visual impairment and maculopathy associated with inhalation of poppers.

RESULTS

All patients experienced visual symptoms associated with poppers use. The majority had impaired visual acuity, central scotomata, distortion, or phosphenes. Clinical signs on fundoscopy ranged from normal foveal appearance to yellow, dome-shaped lesions at the foveola. Spectral domain optical coherence tomography (SD-OCT) showed varying degrees of disruption of the presumed inner segment/outer segment (IS/OS) junction.

DISCUSSION

Although poppers have been in use for several decades, in 2007, following legislative changes, there was a change in the most commonly used compound from isobutyl nitrite to isopropyl nitrite. There were no reports of 'poppers maculopathy' before this. Poppers maculopathy may be missed if patients are not directly questioned about their use. The disruption or loss of the presumed IS/OS junction on SD-OCT are a characteristic feature. Further study of maculopathy in poppers users is now needed. Raising public awareness of the ocular risks associated with their use may be necessary.

Action on AMD. Optimising patient management: act now to ensure current and continual delivery of best possible patient care

In recent years, there have been significant advances in the clinical management of patients with wet age-related macular degeneration (wet AMD)—a rapidly progressing and potentially blinding degenerative eye disease. Wet AMD is responsible for more than half of registered severe sight impairment (blindness) in the United Kingdom, and patients who are being treated for wet AMD require frequent and long-term follow-up for treatment to be most effective. The clinical workload associated with the frequent follow-up required is substantial. Furthermore, as more new patients are diagnosed and the population continues to age, the patient population will continue to increase. It is thus vital that clinical services continue to adapt so that they can provide a fast and efficient service for patients with wet AMD. This Action on AMDdocument has been developed by eye health-care professionals and patient representatives, the Action on AMDgroup. It is intended to highlight the urgent and continuing need for change within wet AMD services. This document also serves as a guide for eye health-care professionals, NHS commissioners, and providers to present possible solutions for improving NHS retinal and macular services. Examples of good practice and service development are considered and can be drawn upon to help services meet the recommended quality of care and achieve best possible outcomes.

A review of safety incidents in England and Wales for vascular endothelial growth factor inhibitor medications

PURPOSE

To learn from patient safety incidents (PSIs) following recent introduction of vascular endothelial growth factor inhibitor medications (anti-VEGF) in ophthalmic care, as reported via a national incident reporting database.

METHODS

Thematic retrospective review of anti-VEGF medications PSIs as reported via clinical incident reporting methods in NHS care in England and Wales from 2003 to 2010, ascertained from database mining at the National Patient Safety Agency (NPSA).

RESULTS

In all, 166 relevant anti-VEGF incidents were reported. Reports have increased year on year from 2006. Incident severity as reported: 10 were reported as 'severe harm' and 23 as 'moderate harm'. The remainder were 'low' or 'no harm' events. The incident themes and/or causes found and by order of severity included: intra-ocular inflammation/endophthalmitis (n=16); treatment or follow-up delays (n=45); wrong medication (n=26); wrong eye/patient injection (n=17); missing records (n=12). Other problems included medication availability and refrigeration failures. We reflect on potential solutions for addressing the matters found. Systemic safety matters, stroke, subdural hemorrhage, and myocardial infarction (total n=3) followed anti-VEGF treatments.

CONCLUSION

Although infrequent, anti-VEGF medication PSIs or errors do occur and are thus a threat to quality. This review also provides supporting evidence to existing concerns and challenges surrounding age-related macular degeneration service pressures and provision. Lessons for improvement of care from a national incident reporting database for a frequently undertaken and recently introduced ophthalmic procedure were found. Suggestions are proposed for improving quality by reducing such problems based on analysis of such reports. Endophthalmitis reports following intra-vitreal injections suggest rigorous infection control measures are required.

MRSA and cataract surgery - reflections for practice

INTRODUCTION

Postoperative bacterial endophthalmitis is a devastating complication of cataract surgery. Methicillin-resistant Staphylococcus aureus (MRSA) endophthalmitis is rare. Recent debate over MRSA screening in United Kingdom (UK) National Health Service (NHS) hospital services has implications for cataract patients and ophthalmology services.

AIMS

To discuss issues for clinical practice as based on reflective experience at a UK district general NHS hospital in relation to care of MRSA-positive cataract patients.

METHODS

Retrospective case series and reflective practice.

RESULTS

Three cases presented highlight practice points around cataract patients colonized with MRSA. Known or determined MRSA-colonized patients should be treated with anti-microbial agents at time of cataract surgery known to be active against MRSA. Preventative treatment with intracameral vancomycin or intravenous teicoplanin alongside appropriate topical treatments may be of merit. Importantly fluoroquinolones, often prescribed by cataract surgeons, may have a selective effect favoring the proliferation of MRSA.

CONCLUSION

MRSA screening may cause unnecessary delays in cataract care and may represent a patient safety concern in its own right. Patients colonized with MRSA may safely undergo cataract surgery provided there is no evidence of periorbital infection and provided appropriate infection control and antibiotic prophylaxis measures are used. The well-prepared cataract surgeon needs to be aware of developments in infection control and should liaise with local clinical microbiology colleagues in relation to bacterial resistance to antibiotics.

Distraction index as a risk factor for osteoarthritis associated with hip dysplasia in four large dog breeds

OBJECTIVE

To determine if age, breed, gender, weight or distraction index (DI) influenced the risk of radiographic osteoarthritis (OA) of canine hip dysplasia (CHD) in four common dog breeds; the American bulldog, Bernese mountain dog, Newfoundland and standard poodle.

MATERIALS AND METHODS

This was a cross sectional prevalence study with 4349 dogs. Canine hips were evaluated using 3 radiographic projections: the hip-extended view, the compression view and the distraction view. The hip-extended view was examined for the presence of OA. The PennHIP distraction view was utilized to calculate the DI. For all breeds, a multiple logistic regression model incorporating age, weight, gender, and DI was created. For each breed, disease-susceptibility curves grouping dogs on the basis of age were constructed. Receiver-operating characteristic (ROC) curves were developed for each breed regardless of age.

RESULTS

For all breeds, DI was the most significant risk factor for the development of OA associated with CHD. Weight and age were also significant risk factors in all four breeds, but gender was not.

CLINICAL SIGNIFICANCE

Results from this study support previous findings, that irrespective of breed, the probability of radiographic OA increases with hip joint laxity as measured by the DI. Breed-specific differences in this relationship, however, warrant investigation of all breeds affected by CHD to determine inherent dependency of hip OA on joint laxity. Such findings guide veterinarians in helping dog breeders to make evidence-based breeding decisions and in informing dog owners to implement preventative treatments for CHD for dogs found to be at risk.

Candida endophthalmitis: A critical diagnosis in the critically ill

Three cases of candida endophthalmitis complicating critical illness in young adult surgical patients with implications for safer practice are presented. We highlight how early ophthalmological examination can aid in the management of such critically ill patients. Clinicians need to be vigilant for the early diagnosis and aggressive treatment of hospital acquired opportunistic candida infection in at risk patients. Time may be of the essence as sight and life are at risk.

Attitudes of community optometrists to smoking cessation: an untapped opportunity overlooked?

AIM

To assess community optometrists' attitudes and current behaviour regarding provision of smoking cessation advice in their practice.

METHODS

A self-completion postal questionnaire was sent to community optometrists in north-west England identified from the General Optical Council's practice lists.

RESULTS

Of 709 optometrists identified, 71.8% (509/709) returned the completed questionnaire. Few community optometrists routinely asked about smoking habits: only 6.2% (95% CI: 4.1-8.3) (n = 31) at new patient consultations, and 2.2% (95% CI: 0.9-3.5) (n=11) at follow-up visits. Reasons for optometrists not routinely providing smoking cessation advice included: not their role (35.4%, n=180), lack of time (22.0%, n=112) and forgetting to ask (21.4%, n=109). Overall 67.6% (95% CI: 63.5-71.7) (n=344) of community optometrists wanted to improve their knowledge of smoking and visual impairment with 56.2% (95% CI: 51.9-60.5) (n=286) requesting further training.

CONCLUSION

Despite low levels of current involvement, many optometrists were keen to receive training on smoking cessation topics. We suggest that there are untapped opportunities to develop brief interventions to promote smoking cessation services in community optometry settings.

A comparison of covert and overt attention as a control option in a steady-state visual evoked potential-based brain computer interface

EEG data were recorded from occipital scalp regions of subjects who attended to an alternating checkerboard stimulus in one visual field while ignoring a similar stimulus of a different frequency in the opposite visual field. Classification of left/right spatial attention is attempted by extracting steady-state visual evoked potentials (SSVEPs) elicited by the stimuli to assess the potential use of such a spatial selective attention paradigm in a brain computer interface (BCI). Experimental setup and analysis procedure in a previous study in which eye movement is permitted are replicated in order to quantify differences in classification performance using overt and covert attention. Four variations of the basic paradigm, involving both feedback and addition of extra mental load, are studied for comparison. The average accuracy is found to be reduced by approximately 20% in the switch from overt to covert attention when no other specifications of the task are changed.

Attitudes and behaviour of ophthalmologists to smoking cessation

AIMS

Growing evidence suggests a causal association between smoking and eye disease. This study explores the current beliefs and practice among UK consultant ophthalmologists towards delivering smoking cessation advice to eye clinic attenders.

METHODS

A cross-sectional survey using a postal questionnaire of all UK NHS hospital based consultant ophthalmologists was conducted. The questionnaire explored whether: ophthalmologists identify the smoking status of their patients, advise about the increased risk of eye diseases among smokers, and deliver smoking cessation advice. The availability of departmental smoking cessation resources was also ascertained.

RESULTS

The response rate was 55% (485/886). Of the responders 79% were males. Only 35% of responders asked about smoking status every time or most times for new patients and 5% for follow-up patients. In all, 40% claimed to always or usually advise patients to quit smoking and 61% claimed to always or usually mention eye disease as a reason to quit. Only 14% assessed motivation to quit and 22% provided advice and assistance about how to stop smoking to smokers who wished to quit. Female ophthalmologists were more likely to undertake most aspects of smoking assessment and intervention. Only 18% of responders stated that their departments provide information about smoking for patients and 6% stated that support is available for patients wanting to quit smoking.

CONCLUSION

The assessment of smoking status and provision of targeted support for smokers to quit could be substantially improved in UK ophthalmology departments. There is a need to introduce smoking cessation support into routine ophthalmic practice and provide the resources to support this.

Cigarette smoking and thyroid eye disease: a systematic review

PURPOSE

To evaluate the epidemiological evidence for a causal association between tobacco smoking and thyroid eye disease (TED).

METHODS

Systematic review, including quality assessment, of published epidemiological studies and evaluation of the evidence using established causality criteria.

RESULTS

Fourteen papers describing 15 studies were included. There was a positive association between smoking and TED in four case-control studies when compared with control patients with Graves' disease but no ophthalmopathy (odds ratio (OR) 1.94-10.1) and in seven case-control studies in which control subjects did not have thyroid disease (OR 1.22-20.2). Two cohort studies examined the occurrence of new cases of TED; one study found an increased incidence of TED with smoking. Four cohort studies investigated progression or outcome of treatment in patients with established TED, three finding an association between smoking and poorer outcome. The quality of the studies was variable, but the association with smoking was strong in the most methodologically rigorous studies. Other evidence supporting a causal link was a consistent association across studies, a dose-response effect, a reduced risk of TED in ex-smokers, and a temporal relationship.

CONCLUSION

This systematic review provided strong evidence for a causal association between smoking and development of TED. Current-smokers were also more likely to experience disease progression or poorer outcome of treatment. Patients with Graves' disease and the general public should be educated about the risk of smoking and TED. These findings suggest that patients with Graves' disease or TED who are smokers should be given effective support to stop smoking.

Patient safety in cataract surgery

PURPOSE

The recent focus on healthcare errors and safety suggest that practitioners and policy makers might appraise their cataract surgical care from a patient safety perspective. This paper reviews patient safety issues relevant to cataract care. Causation and consequences of incidents in cataract surgery, with implications for policy, are discussed.

METHODS

Models of accident causation from other domains were drawn on and empirically applied to cataract care. Consultation was undertaken with experts in cataract surgery, patient safety, and in risk management. Feedback on patient safety was included from presentations made to staff and patients and from personal insights.

RESULTS

Ophthalmology teams should embrace steps to improve patient safety. The role of incident reporting is advanced, including the provision of a prompt menu of cataract patient safety incidents as suggested by the Royal College of Ophthalmologists.

CONCLUSIONS

Strict attention to detail, risk assessment, and careful consideration of the patient pathway is needed to enhance cataract care. Clinical errors, near misses and complications happen, and may provide an opportunity for learning to reduce the risk of similar events in the future. Investment in staffing and training, appropriate equipment, and development of a safety culture with patient involvement are key elements of safe cataract surgical care. Patients and the public expect that safe cataract care should be commissioned for them. Critical patient safety incidents, including incidents that have led to permanent harm, require careful analysis of underlying systems and/or root causes.

Smoking and age-related macular degeneration: a review of association

PURPOSE

Age-related macular degeneration (AMD) is the leading cause of severe and irreversible vision loss in the Western world. As there is no effective treatment for all types of AMD, identifying modifiable risk factors is of great importance. This review evaluates the epidemiological evidence associating smoking with AMD.

METHODS

Systematic review of published epidemiological studies evaluated against established criteria for evidence of a causal relationship.

RESULTS

In total, 17 studies (cross-sectional studies, prospective cohort studies, and case-control studies) were included in the review. A total of 13 studies found a statistically significant association between smoking and AMD with increased risk of AMD of two- to three-fold in current-smokers compared with never-smokers. Five studies found no association between smoking and AMD. There was also evidence of dose-response, a temporal relationship and reversibility of effect.

CONCLUSION

The literature review confirmed a strong association between current smoking and AMD, which fulfilled established causality criteria. Cigarette smoking is likely to have toxic effects on the retina. In spite of the strength of this evidence, there appears to be a lack of awareness about the risks of developing eye disease from smoking among both healthcare professionals and the general public.

Cataract care is mobile

Is the direction correct?

Direct costs of glaucoma and severity of the disease: a multinational long term study of resource utilisation in Europe

BACKGROUND

Resource utilisation and direct costs associated with glaucoma progression in Europe are unknown. As population progressively ages, the economic impact of the disease will increase.

METHODS

From a total of 1655 consecutive cases, the records of 194 patients were selected and stratified by disease severity. Record selection was based on diagnoses of primary open angle glaucoma, glaucoma suspect, ocular hypertension, or normal tension glaucoma; 5 years minimum follow up were required. Glaucoma severity was assessed using a six stage glaucoma staging system based on static threshold visual field parameters. Resource utilisation data were abstracted from the charts and unit costs were applied to estimate direct costs to the payer. Resource utilisation and estimated direct cost of treatment, per person year, were calculated.

RESULTS

A statistically significant increasing linear trend (p = 0.018) in direct cost as disease severity worsened was demonstrated. The direct cost of treatment increased by an estimated 86 for each incremental step ranging from 455 euro per person year for stage 0 to 969 euro per person year for stage 4 disease. Medication costs ranged from 42% to 56% of total direct cost for all stages of disease.

CONCLUSIONS

These results demonstrate for the first time in Europe that resource utilisation and direct medical costs of glaucoma management increase with worsening disease severity. Based on these findings, managing glaucoma and effectively delaying disease progression would be expected to significantly reduce the economic burden of this disease. These data are relevant to general practitioners and healthcare administrators who have a direct influence on the distribution of resources.

Perceptions of blindness related to smoking: a hospital-based cross-sectional study

AIMS

Smoking is associated with several serious eye diseases. Awareness of smoking and blindness, and its potential to act, as a stimulus to assist stopping smoking has not been investigated.

METHODS

A cross-sectional survey using a structured interview of adult patients attending district general hospital ophthalmology, general surgery, and orthopaedic clinics. The interview investigated the awareness and fear of blindness for three established smoking-related diseases, and a distractor condition (deafness), and the likelihood that smokers would quit on developing early signs of each condition.

RESULTS

Response was 89.1% (358/402). In all, 183 (51.1%) of responders were male and 175 (48.9%) female. Only 9.5% of patients believed that smoking was definitely or probably a cause of blindness, compared with 92.2% for lung cancer, 87.6% for heart disease, and 70.6% for stroke. Patients ranked their fear of each of the five conditions, scoring five for the most feared and one for the least feared. Patients were significantly (P<0.01) less fearful of blindness (mean score 2.80) than lung cancer (3.89), heart disease (3.58), and stroke (3.35). About one-half of smokers stated that they would definitely or probably quit smoking if they developed early signs of blindness or the three established smoking-related conditions, with no significant differences in proportions for these four conditions.

CONCLUSION

The findings suggest that awareness of the risk of blindness from smoking is low, but that the fear of blindness is as compelling a motivation to quit as fear of lung cancer, heart disease, and stroke. The link between smoking and eye disease should be publicised to help reduce smoking prevalence.

Reflective consideration of postoperative endophthalmitis as a quality marker

PURPOSE

To study the incidence of acute postoperative presumed infectious endophthalmitis (PIE) in a UK district general hospital over a 10-year period. Consideration of such departmental healthcare-associated infection frequency rates as part of reflective and comparative quality practice in the light of local concerns.

METHODS

Hospital-based retrospective case series: 12 831 cataract extraction operations from 01/01/1995 to 31/12/2004 were studied. All cases of PIE within 6 weeks of cataract surgery were ascertained and investigated in a standardised format. PIE incidence rate per 1000 cataract surgical procedures was contrasted with the existing literature.

RESULTS

Seven isolated PIE cases occurred following phacoemulsification. None followed extra-capsular extractions. The PIE rate was 0.55 [95% CI; 0.22 to 1.12] cases per 1000 cataract extractions, or one PIE case within 6 weeks of surgery in every 1833 [95% CI; 893 to 4545] cataract operations undertaken. Five cases were culture positive. Details of PIE cases are presented.

CONCLUSION

PIE incidence rates in our department are slightly lower than reported case series in similar settings. Whether this is due to a variety of preventive measures deployed locally and/or methods of case ascertainment in published studies is problematic and is discussed. Departmental benchmarking data is important in relation to rare, but critical, patient safety incidents. Collection and monitoring of endophthalmitis outcomes is of merit and may inform patient choice. Surgical site infection surveillance systems of relevance are discussed. Implications for making healthcare safer, including reflective practice are, discussed in relation to cataract care.

Neuropeptides and the control of food intake in fish

The brain, particularly the hypothalamus, integrates input from factors that stimulate (orexigenic) and inhibit (anorexigenic) food intake. In fish, the identification of appetite regulators has been achieved by the use of both peptide injections followed by measurements of food intake, and by molecular cloning combined with gene expression studies. Neuropeptide Y (NPY) is the most potent orexigenic factor in fish. Other orexigenic peptides, orexin A and B and galanin, have been found to interact with NPY in the control of food intake in an interdependent and coordinated manner. On the other hand cholecystokinin (CCK), cocaine and amphetamine-regulated transcript (CART), and corticotropin-releasing factor (CRF) are potent anorexigenic factors in fish, the latter being involved in stress-related anorexia. CCK and CART have synergistic effects on food intake and modulate the actions of NPY and orexins. Although leptin has not yet been identified in fish, administration of mammalian leptin inhibits food intake in goldfish. Moreover, leptin induces CCK gene expression in the hypothalamus and its actions are mediated at least in part by CCK. Other orexigenic factors have been identified in teleost fish, including the agouti-related protein (AgRP) and ghrelin. Additional anorexigenic factors include bombesin (or gastrin-releasing peptide), alpha-melanocyte-stimulating hormone (alpha-MSH), tachykinins, and urotensin I. In goldfish, nutritional status can modify the expression of mRNAs encoding a number of these peptides, which provides further evidence for their roles as appetite regulators: (1) brain mRNA expression of CCK, CART, tachykinins, galanin, ghrelin, and NPY undergo peri-prandial variations; and (2) fasting increases the brain mRNA expression of NPY, AgRP, and ghrelin as well as serum ghrelin levels, and decreases the brain mRNA expression of tachykinins, CART, and CCK. This review will provide an overview of recent findings in this field.

Ethnic aspects of acute primary angle closure in a UK mulicultural conurbation

AIM

To investigate the incidence and ethnic distribution of patients with symptomatic acute primary angle closure (APAC) who presented to a UK hospital serving a multicultural conurbation by a population-wide case series investigation.

METHODS

Case series chart review of patients aged 30 years and above, who required laser peripheral iridotomy (LPI) for a primary acute angle closure event over a 7-year period. Demographic data for cases were compared to the local resident census data.

RESULTS

A total of 46 local residents aged > or =30 years required LPI for APAC. In all, 96% of patients were Caucasian compared to the local resident population of 89% Caucasian. The overall annual APAC rate for Bolton was 4.14 cases per 100 000 population (95% CI 3.03-5.52). The standardised incidence ratio for the South Asian population was 0.78 (95% CI 0.02-4.34) and 26.6 (95% CI 0.67-148.40) for the Chinese population.

CONCLUSIONS

APAC incidence in South Asians was similar to that among Caucasians. The incidence of APAC patients treated in this UK department is consistent with international experience. Individuals of Chinese ethnicity were at an enhanced risk of APAC. However, these results should be interpreted with caution, as patient numbers are small.

Can ophthalmic requests for neuroimaging be improved?

AIM

To review and set guidelines for all neuroradiological referrals from the ophthalmic service in a typical UK district general hospital.

METHOD

Patients referred for diagnostic neuroimaging were identified from the radiology database over a 1-year period. A case note review was undertaken. The clinical indication for and results of neuroimaging performed were ascertained. The justification for neuroimaging was determined.

RESULTS

Of the total 31,411 patients that were seen in the eye department, 103 (0.32%) had diagnostic neuroradiological imaging performed. The indications for imaging were: suspected compressive lesion of the anterior visual pathway in 57 patients (55.3%), acquired ocular motility disturbance in 20 patients (19.4%), suspected orbital pathology in 11 patients (10.6%), cerebrovascular accident in nine patients (8.7%), and six patients (5.8%) were imaged for either headache or sinusitis. Radiological lesion detection rate was highest for cerebrovascular accident (88.8%) and lowest acquired for ocular motility disturbance (4.9%).

CONCLUSION

Ophthalmic requests for diagnostic neuroimaging were found to be unnecessary in only 9% of patients. Guidelines for the referral of ophthalmic patients for neuroimaging are discussed.

Larval development of silver sea bream (Sparus sarba): ontogeny of RNA-DNA ratio, GH, IGF-I, and Na(+)-K(+)-ATPase

To ascertain some of the important biochemical and molecular events that take place during early larval development of silver sea bream (Sparus sarba), we undertook a study of changes in the morphology as well as the ontogeny of the RNA-DNA ratio, growth hormone (GH), insulin-like growth factor I (IGF-I) messenger RNA abundance, Na(+)-K(+)-ATPase subunit mRNA abundance, and Na(+)-K(+)-ATPase enzyme activity. Larvae samples were collected at 1 to 46 days posthatch (dph). At 7 dph the yolk sac was fully absorbed, and from 28 dph onward larvae underwent rapid developmental changes to the juvenile stage. The RNA-DNA ratio was highest at 1 dph, decreased to low levels between 7 and 21 dph, then increased by 28 dph, and then again by 46 dph. The ontogenetic profiles of GH, IGF-I, and Na(+)-K(+)-ATPase alpha1 and beta1 subunits were studied using reverse transcriptase polymerase chain reaction, coupled with radioisotope hybridization of immobilized DNA. Growth hormone abundance reached a constant and high level from 35 dph onward, whereas the IGF-I level reached a peak at 35 dph and then significantly decreased. Both Na(+)-K(+)-ATPase alpha1 and beta1 subunit mRNAs increased up to 35 dph, however, at 46 dph the alpha1 subunit remained high whereas the beta1 subunit decreased. Na(+)-K(+)-ATPase activity was low in 1-dph larvae but increased rapidly as development progressed. The importance of these findings is discussed within the context of larval development.

Cultured gill epithelia from freshwater tilapia (Oreochromis niloticus): effect of cortisol and homologous serum supplements from stressed and unstressed fish

Procedures for the preparation and culture of branchial epithelia from dispersed gill cells of freshwater tilapia (Oreochromis niloticus) are described. Epithelia were cultured on permeable supports (terephthalate membranes, "filters") and bathed on both the apical and basolateral side with isotonic media containing 6% fetal bovine serum (FBS). When the apical medium was replaced with freshwater (pseudo in vivo asymmetrical culture conditions), transepithelial resistance (TER) increased markedly, transepithelial potential became negative, and paracellular permeability decreased. The physiological effects of cortisol and 10% homologous (tilapia) serum were investigated. Tilapia serum (TS) was prepared from unstressed and stressed fish and therefore allowed comparison between the effects of homologous serum derived from fish in differing physiological states. Under both symmetrical and asymmetrical culture conditions, cortisol significantly elevated TER across cultured tilapia gill epithelia, indicative of a significant increase in epithelial "tightness." Cortisol reduced transepithelial Na + and Cl? movement and paracellular permeability. The glucocorticoid agonist dexamethasone elicited a similar response, which was inhibited by the glucocorticoid antagonist (receptor blocker) RU486. Cortisol did not stimulate active ion transport across epithelia under either symmetrical or asymmetrical culture conditions. In epithelia supplemented with TS from stressed fish, physiological changes in cultured preparations were consistent with those observed in FBS + cortisol-supplemented epithelia. Differences between the physiological status of epithelia supplemented with TS from unstressed and stressed fish could be abolished with RU486. Using TS as a medium supplement did not stimulate active ion transport under asymmetrical culture conditions, although Na +-K +-ATPase activity increased in TS-supplemented epithelia relative to FBS-supplemented preparations.

Evaluation of the management of optic neuritis: audit on the neurological and ophthalmological practice in the north west of England

The management of acute optic neuritis by neurologists and ophthalmologists in the north west of England was assessed in the light of the Optic Neuritis Treatment Trial (ONTT) recommendations. A questionnaire on a fictitious case of typical unilateral optic neuritis was mailed to all consultant ophthalmologists and neurologists working in the North West and Merseyside Health Authorities. They were then asked to comment on management of the case. Fifty two out of 86 ophthalmologists and 20 out of 28 neurologists replied. The overall response rate was 63%. Sixty five per cent of neurologists and 46% of ophthalmologists would investigate a typical case of acute optic neuritis further. Forty six per cent of neurologists and 36% of ophthalmologists were likely to arrange MRI of the brain or orbit. Significantly more neurologists (55%) than ophthalmologists (9%) chose to treat with intravenous methylprednisolone (p<0.005). Significantly more ophthalmologists (64%) than neurologists (32%) chose not to give steroids (p<0.025). Oral prednisolone alone was rarely selected for treatment. Respondents were more likely to discuss multiple sclerosis with the referring doctor than with the patient. Only 32% of ophthalmologists and 20% of neurologists would clearly mention the possibility of improvement to the patient. Clear differences in practice between ophthalmologists and neurologists remain. A consensus on practice guidelines on the issues raised might be useful.

The cultured branchial epithelium of the rainbow trout as a model for diffusive fluxes of ammonia across the fish gill

A novel branchial epithelial preparation grown in L-15 medium in culture was used as a model system for understanding the diffusion of ammonia across the gills of the rainbow trout Oncorhynchus mykiss. The epithelium is known to contain both respiratory and mitochondria-rich cells in the approximate proportion in which they occur in vivo and to exhibit diffusive fluxes of Na+ and Cl– similar to in vivo values, but does not exhibit active apical-to-basolateral transport of Na+. Transepithelial resistance and paracellular permeability are also known to increase when the apical medium is changed from L-15 medium (symmetrical conditions) to fresh water (asymmetrical conditions). In the present study, net basolateral-to-apical ammonia fluxes increased as basolateral total ammonia concentration, basolateral-to-apical pH gradients and basolateral-to-apical PNH3 gradients were experimentally increased and were greater under asymmetrical than under symmetrical conditions. The slope of the relationship between ammonia flux and PNH3 gradient (i.e. NH3 permeability) was the same under both conditions and similar to values for other epithelia. The higher fluxes under asymmetrical conditions were explained by an apparent diffusive flux of NH4+ that was linearly correlated with transepithelial conductance and was probably explained by the higher electrochemical gradient and higher paracellular permeability when fresh water was present on the apical surface. In this situation, NH4+ diffusion was greater than NH3 diffusion under conditions representative of in vivo values, but overall fluxes amounted to only approximately 20 % of those in vivo. These results suggest that branchial ammonia excretion in the intact animal is unlikely to be explained by diffusion alone and, therefore, that carrier-mediated transport may play an important role.

Effect of cortisol on the physiology of cultured pavement cell epithelia from freshwater trout gills

Cortisol had dose-dependent effects on the electrophysiological, permeability, and ion-transporting properties of cultured pavement cell epithelia derived from freshwater rainbow trout gills and grown on cell culture filter supports. Under both symmetrical (L15 media apical/L15 media basolateral) and asymmetrical (freshwater apical/L15 media basolateral) culture conditions, cortisol treatment elevated transepithelial resistance, whereas permeability of epithelia to a paracellular permeability marker (polyethylene glycol-4000) decreased. Cortisol did not alter the Na(+)-K(+)-ATPase activity or the total protein content of the cultured preparations. During 24-h exposure to asymmetrical conditions, the net loss rates of both Na(+) and Cl(-) to the water decreased with increasing cortisol dose, an important adaptation to dilute media. Unidirectional Na(+) and Cl(-) flux measurements and the application of the Ussing flux-ratio criterion revealed cortisol-induced active uptake of both Na(+) and Cl(-) under symmetrical culture conditions together with an increase in transepithelial potential (positive on the basolateral side). Under asymmetrical conditions, cortisol did not promote active ion transport across the epithelium. These experiments provide evidence for the direct action of cortisol on cultured pavement cell epithelia and, in particular, emphasize the importance of cortisol for limiting epithelial permeability.

The physiological effects of 3,5',3'-triiodo-L-thyronine alone or combined with cortisol on cultured pavement cell epithelia from freshwater rainbow trout gills

The effects of 3,5',3'-triiodo-L-thyronine (T3; 10 or 100 ng ml(-1)), alone or combined with cortisol (500 ng ml(-1)), on the physiological properties of cultured pavement cell epithelia from freshwater rainbow trout gills were assessed. T3 had dose-dependent effects on electrophysiological, biochemical, and ion transporting properties of cultured epithelia in both the absence and the presence of cortisol. These included reduced transepithelial resistance (TER), increased net Na(+) and Cl(-) movement (basolateral to apical) under asymmetrical culture conditions (freshwater apical/L15 media basolateral), and elevated Na(+)-K(+)-ATPase activity. However, paracellular permeability was elevated only in high-dose T3-treated preparations. In T3 + cortisol-treated epithelia, similar T3-induced alterations in TER, net Na(+) and Cl(-) movement, and paracellular permeability were observed, whereas the activity of Na(+)-K(+)-ATPase was further elevated. Under symmetrical culture conditions (L15 medium apical/L15 medium basolateral), T3 had no effect on transepithelial Na(+) and Cl(-) transport, which was passive. However, T3 + cortisol treatment resulted in active Na(+) extrusion (basolateral to apical). Under asymmetrical conditions, hormone treatment did not change the pattern of ion movement (active Na(+) extrusion, active Cl(-) uptake). These experiments demonstrate that cultured pavement cell epithelia from freshwater rainbow trout are T3-responsive and provide evidence for the direct action of T3 and the interaction of T3 and cortisol on the physiology of this preparation.

Procedures for the preparation and culture of 'reconstructed' rainbow trout branchial epithelia

Techniques for the in vitro 'reconstruction' of freshwater rainbow trout branchial epithelia using the primary culture of gill cells on permeable polyethylene terephthalate cell culture filter supports are described. Representing models of the freshwater fish gill, epithelia grown by two separate techniques are composed of branchial pavement cells with or without the inclusion of mitochondria-rich (MR) cells. The generation of epithelia consisting of pavement cells only (via a method called single seeded inserts = SSI) involves an initial period of flask culture during which time MR cells, that appear unable to attach to the culture flask base, are excluded from the general cell populace. Alternately, the generation of a heterogeneous epithelia consisting of both pavement cells and MR cells (via a method called double seeded inserts = DSI) is facilitated by the direct seeding of cells into cell culture filter inserts. Critical to this second procedure is the repeat seeding of filter inserts over a two day period. Repeat seeding appears to allow MR cells to nest amongst the attached cell layer generated by the first day's seeding. The use of cell culture filter supports allows free access to both the apical and basolateral compartment of the epithelium and is ideal for experimental manipulation. Cells are grown under symmetrical conditions (apical media/basolateral media) and epithelium growth is measured as a function of transepithelial resistance (TER). When the epithelia exhibit a plateau in growth they can be subjected to asymmetrical conditions (freshwater apical/media basolateral) in order to assess gill cell function as in vivo.

A maxi Cl(−) channel in cultured pavement cells from the gills of the freshwater rainbow trout Oncorhynchus mykiss

Primary cultures of pavement cells from the gills of a freshwater fish, the rainbow trout Oncorhynchus mykiss, have been studied for the first time using the patch-clamp technique. Gigaohm seals were obtained in approximately 95 % of cells studied, and channel activity was evident in a high proportion (&gt;90 %). A large-conductance Cl(−) channel was evident in 6 % of cell-attached and in 31 % of inside-out patches. Single-channel conductance in inside-out patches was 372 pS, and current/voltage relationships were linear over the range −60 to +60 mV. The channel was activated by patch excision, and activation was often associated with polarization of the patch. The mean number of channels per patch was 1.9, and there were several subconductance states. The relationship between channel activity (NP(o)) and voltage was in the form of an inverted U, and channel activity was highest between 0 and +20 mV. Large-conductance Cl(−) channels showed a progressive time-dependent reduction in current in response to sustained polarization to voltages outside the range −20 mV to +20 mV. Permeability ratios (P) of Cl(−) to other anions were P(HCO3)/P(Cl)=0.81, P(SO4)/P(Cl)=0.31 and P(isethionate)/P(Cl)=0.53. The channel was blocked by Zn(2+), SITS, DIDS and diphenylamine carboxylate. This is the first description of a large-conductance Cl(−) channel in gill cells from freshwater or marine species. Possible functions of the channel are discussed.

Age differences in dynamic measures of EEG

Eighteen older adults and 18 younger adults were compared on two quantitative measures describing changes over time in the spatial distribution of running EEG. EEG was collected from 128 electrodes under resting eyes-open and eyes-closed conditions and during performance of a 13 minute sustained attention task. One EEG measure, the recrudescence rate, represented the number of changes in the location of the highest squared voltage per second. A second EEG measure consisted of the algorithmic complexity of changes in the location of the highest squared voltage over time. Regardless of the task condition, older adults had significantly higher scores than younger adults on both the recrudescence rate and the measure of algorithmic complexity. The implications of the results for neurologically-based theories of performance declines in older adults are discussed.

Transport properties of cultured branchial epithelia from freshwater rainbow trout: a novel preparation with mitochondria-rich cells

A new double-seeded insert (DSI) technique is described for culture of branchial epithelial preparations from freshwater rainbow trout on filter supports. DSI epithelia contain both pavement cells and mitochondria-rich (MR) cells (15.7+/−2.5 % of total cell numbers). MR cells occur singly or in clusters, are voluminous, open apically to the ‘external environment’ and exhibit ultrastructural characteristics similar to those found in the ‘chloride cells’ of freshwater fish gills. After 6–9 days in culture with Leibovitz's L-15 medium on both surfaces (symmetrical conditions), transepithelial resistance (TER) stabilized at values as high as 34 k capomega cm(2), indicative of electrically ‘tight’ epithelia. The density of MR cells, the surface area of their clusters and transepithelial potential (TEP; up to +8 mV basolateral positive, mean +1.9+/−0.2 mV) were all positively correlated with TER. In contrast, preparations cultured using an earlier single-seeded insert (SSI) technique contained only pavement cells and exhibited a negligible TEP under symmetrical conditions. Na(+)/K(+)-ATPase activities of DSI preparations were comparable with those in gill filaments, but did not differ from those of SSI epithelia. Replacement of the apical medium with fresh water to mimic the in vivo situation (asymmetrical conditions) induced a negative TEP (−6 to −15 mV) and increased permeability to the paracellular marker PEG-4000. Under symmetrical conditions, unidirectional Na(+) and Cl(−) fluxes were in balance, and there was no active transport by the Ussing flux ratio criterion. Under asymmetrical conditions, there were large effluxes, small influxes and evidence for active Cl(−) uptake and Na(+) extrusion. Unidirectional Ca(2+) fluxes were only 0.5-1.0 % of Na(+) and Cl(−) fluxes; active net Ca(2+) uptake occurred under symmetrical conditions and active net extrusion under asymmetrical conditions. Thus, DSI epithelia exhibit some of the features of the intact gill, but improvements in culture conditions are needed before the MR cells will function as true freshwater ‘chloride cells’.

Hypercortisolemia does not affect the branchial osmoregulatory responses of the marine teleost Sparus sarba

The effect of cortisol treatment on branchial Na(+)-K(+)-ATPase subunit mRNA abundance, enzyme activity, chloride cell number/morphometrics and serum electrolyte levels were investigated for the marine teleost Sparus sarba. Groups of fish received intraperitoneal injections of cortisol at a concentration of 4 micrograms/g body weight, daily, over a seven-day period. This dose of cortisol was sufficiently high enough to maintain a condition of hypercortisolemia as serum cortisol levels in treated fish were eleven fold higher than controls at time of sacrifice. By using branchial Na(+)-K(+)-ATPase alpha- and beta-subunit cDNA clones we were able to demonstrate that cortisol administration to S. sarba caused a significant elevation in the abundance of alpha-mRNA whereas the levels of beta-mRNA were unchanged. In addition Na(+)-K(+)-ATPase activity remained unaltered by cortisol administration. Branchial chloride cell number, exposure, apical area as well as serum Na+ and Cl- levels remained unchanged after cortisol administration. The results of this study suggest that elevated cortisol level may not necessarily translate into modulated branchial Na(+)-K(+)-ATPase activity and chloride cell function in hypo-osmoregulating marine fish.

Relationship between corneal thickness and measured intraocular pressure in a general ophthalmology clinic

OBJECTIVE

To assess whether central corneal thickness (CCT) is a confounding factor in the classification of patients attending for glaucoma assessment in a district general hospital.

DESIGN

Cross-sectional study by a single observer.

PARTICIPANTS

Patients attending a general ophthalmic clinic: 235 clinically normal eyes, 52 eyes with normal-tension glaucoma (NTG), 335 eyes with primary open-angle glaucoma (POAG), 12 eyes with pseudoexfoliative glaucoma (PXE), 42 eyes with chronic angle closure glaucoma (CACG), and 232 glaucoma suspect (GS) eyes.

INTERVENTION

Central corneal thickness was measured using ultrasonic pachymetry.

MAIN OUTCOME MEASURE

Correlation of CCT and diagnosis.

RESULTS

Mean CCT was 553.9 microm (95% confidence intervals [CI] for the mean, 549.0-558.8 microm) in the clinically normal eyes, 550.1 microm (95% CI, 546.6-553.7 microm) in the POAG eyes, 514.0 microm (95% CI, 504.8-523.3 microm) in the NTG eyes, 530.7 microm (95% CI, 511.2-550.1 microm) in the PXE eyes, 559.9 microm (95% CI, 546.8-573.0 microm) in the CACG eyes, and 579.5 microm (95% CI, 574.8-584.1 microm) in the GS eyes. The differences of mean CCT between the groups were highly significant (P< 0.001 analysis of variance). Eighty-five percent of eyes with NTG and only 36% of eyes with POAG had a mean CCT of 540 microm or less. Thirteen percent of eyes with POAG and 42% of GS eyes had a mean CCT greater than 585 microm.

CONCLUSIONS

The CCT measurement is desirable in patients attending for glaucoma assessment in a district general hospital to avoid misclassification resulting from the relationship between CCT and tonometric pressure. Central corneal thickness alone is not an accurate predictor for the clinical diagnosis in this group of eyes. However, many eyes diagnosed as having NTG have thin corneas, which would tend to lower the tonometrically recorded intraocular pressure (IOP), so the finding of a less-than-normal thickness cornea introduces some doubt as to the diagnosis of NTG. For the GS eyes, most eyes had thick corneas, which would tend to increase the tonometrically recorded IOP. Thus, GS eyes with modest elevation of IOP and a thick cornea may be at low risk of progressing to POAG. Thus, many patients with "high IOPs" and a thick CCT do not necessarily have high IOPs and may not need to be followed as GS eyes.

Hormonal modulation of branchial Na+-K+-ATPase subunit mRNA in a marine teleost Sparus sarba

The effect of hormone treatment on the abundance of Na+-K+-ATPase alpha- and beta-subunit mRNA in Sparus sarba branchial tissue was investigated. Groups of seawater (33/1000) and hypo-osmotic (6/1000) acclimated fish were injected daily, with either saline, cortisol, recombinant bream growth hormone (rbGH) or ovine prolactin (oPRL). Total RNA from branchial tissue was analyzed by Northern blotting using PCR amplified Na+-K+-ATPase alpha- and beta-subunit cDNA clones. Na+-K+-ATPase alpha- and beta- subunit transcripts of 3.3kb and 2.4kb respectively, were detected and their abundance, after hormone treatment was assessed using RNA dot blots. The abundance of subunit mRNAs increased 1.4-1.9 fold, relative to controls, after cortisol treatment. The alpha:beta mRNA ratio also increased in cortisol treated seawater acclimated fish. Growth hormone treatment did not cause any significant changes in Na+-K+-ATPase subunit mRNA, whereas prolactin significantly reduced alpha-subunit mRNA levels by approximately 0.5 fold in both seawater and hypo-osmotic conditions. The data from this study add further support to the generally accepted roles that cortisol and prolactin have in the modulation of Na+-K+-ATPase activity. It can be concluded from this study that S. sarba branchial Na+-K+-ATPase subunit expression is multihormonally regulated.

Effects of GH, prolactin and cortisol on hepatic heat shock protein 70 expression in a marine teleost Sparus sarba

Heat shock protein 70 (HSP70) expression was assessed in hepatic tissue of a marine teleost Sparus sarba after exogenous hormone administration. Using a PCR-amplified, homologous HSP70 cDNA clone, as a probe in Northern analysis, we detected a 2.3 kb transcript which was elevated after exposure to a temperature 7 degrees C above the ambient. For our studies on hormonal effects on HSP70 expression, groups of fish were administered recombinant bream GH (rbGH), ovine prolactin (oPRL) or cortisol daily over a 7-day period. Quantification of hepatic HSP70 transcript revealed that the administration of GH and PRL significantly reduced HSP70 mRNA abundance by 42% and 54% from saline-injected fish respectively. Also hepatic HSP70 levels were reduced by 76% and 64% as determined by immunoblotting after rbGH and oPRL treatment respectively. The administration of exogenous cortisol did not alter hepatic HSP70 mRNA or protein levels in S. sarba. The results obtained in this study are the first evidence for hormonal modulation of heat shock protein expression in fish. The significance of these results is discussed within the context of current knowledge on the roles of these hormones in teleostean stress response.

Effects of prolactin and growth hormone on strategies of hypoosmotic adaptation in a marine teleost, Sparus sarba

Silver seabream (Sparus sarba) held in seawater (33 per thousand) or acclimated to a hypoosmotic environment of 6 per thousand were given intraperitoneal injections of saline (0.8% NaCl), recombinant bream growth hormone (rbGH, 1 microg/g), or ovine prolactin (oPRL, 6microg/g) for 7 consecutive days. Serum Na+ levels were unaffected by hypoosmotic acclimation and rbGH and oPRL treatment. Treatment of seawater fish with oPRL resulted in hyperchloremia. In 6 per thousand, saline-treated fish exhibited elevated branchial chloride cell (CC) numbers and exposure indices, all of which were markedly reduced by oPRL. CC numbers and morphometrics were unaffected by oPRL in seawater fish. In contrast, rbGH treatment of seawater fish resulted in elevated CC numbers, apical area, and fractional area and, in 6 per thousand fish, elevated CC fractional area and exposure numbers. Branchial Na+-K+-ATPase activity reduced in saline-treated fish adapted to 6% but was unaffected by rbGH regardless of salinity. oPRL reduced activity in both seawater and 6 per thousand-adapted fish. Neither hypoosmotic adaptation nor oPRL had any effect on renal Na+-K+-ATPase activity whereas rbGH reduced activity in both 33 and 6 per thousand. Saline-treated fish adapted to 6 per thousand exhibited reduced Na+-K+-ATPase activity in most regions of the intestine. Treatment with rbGH did not change intestinal Na+-K+-ATPase activity of seawater fish but elevated activity in the anterior regions (esophagus and stomach) of 6 per thousand-adapted fish. Treatment with oPRL elevated Na+-K+-ATPase activity throughout the gastrointestinal tract of seawater fish and in the anterior reaches of 6 per thousand-adapted fish. The data indicated that the as yet uncharacterized osmoregulatory roles of PRL and GH in seabream may warrant further attention as the present study connoted differing responses to that of other teleosts studied.