Utilisation of specialist epilepsy services and antiseizure medication adherence rates in a cohort of people with epilepsy (PWE) accessing emergency care

BACKGROUND

An epilepsy-related attendance at A&E is associated an increased risk of subsequent death within 6 months. Although further work is required to provide a definitive explanation to account for these findings, in the interim it would seem reasonable that services are designed to ensure timely access and provide support at a time of greatest risk. We aim to determine the frequency of patients accessing specialist neurology services following an epilepsy-related admission/unscheduled care episode and consider ASM adherence at the point of attendance.

METHODS

Patients were identified retrospectively via the NHS Greater Glasgow and Clyde live integrated epilepsy Dashboard following an unscheduled epilepsy-related admission or A&E attendance between 1st January 2022 and 30th June 2022. We calculated adherence to anti-seizure medication for a period of 6 months prior to admission and defined poor medication adherence as a medication possession ratio of less than 80 %. We evaluated the rate of any outpatient neurology clinic attendance in the subsequent 3, 6 and 12 months following an epilepsy-related unscheduled care episode. Additional clinical information was identified via the electronic patient records.

RESULTS

Between 1st Jan 2022 and 30th June 2022, there were 266 emergency care seizure-related attendances. The mean age at attendance was 46 years (range: 16-91). Most of PWE were males (63 %) and 37 % were females. Epilepsy classification-29.3 % had GGE, 41.7% had focal epilepsy, and in 29 % of cases the epilepsy was unclassified. Of the admissions, 107/ 266 (40.2 %) generated follow-up within 6 months of attendance. Poor medication adherence was noted in 54/266 (20.3 %). 28.2 % of cases had input from on-call neurology service during admission/ED attendance, and of those 60 % had ASM adjusted. 18 % of attendances had a background diagnosis of learning disability. One-third of attendances of PWE had a history of mental health disorder 35 % (93/266). 25 % of ED attendances noted an active history of alcohol consumption misuse or/and recreational drug use. 14 (5.5 %) of PWE died during the period of interest (12 months following the last ED visit). In 6/14 (42.3 %) death was associated with poor medication adherence.

CONCLUSION

This study demonstrates that a significant proportion of patients who experienced seizure-related admissions/ attendance did not access specialist neurology services in a timely manner. In addition, poor medication adherence remains a problem for a substantial number of people living with epilepsy. Early access to specialist services may go some way to improving care and reducing excessive mortality in PWE by allowing anti-seizure medication to be titrated and poor medication adherence to be addressed in those at greatest risk.

Measurement Models of Child Maltreatment and Associations With Suicidal Ideation Endorsement by Youth in Foster Care: A Multiverse Analytic Approach

Youth suicidal ideation is a prevalent experience, particularly among youth exposed to maltreatment, with a variety of indicators such as youth statements of ideation. To better understand suicidal ideation, and the associations with youth mental health outcomes, a fruitful path may be through the study of the dimensions (e.g., severity, frequency) of maltreatment exposure. While there exists extensive work on methods to best operationalize casefile records of maltreatment, such work has not been undertaken for youth self-reports, which are an important indicator of youth functioning following exposure. To address the lack of clarity of how to best operationalize youth self-reports of maltreatment, a multiverse analytic approach was taken to operationalize severity and frequency in a sample of 471 8- to 17-year-old children in foster care. We examined differences across measurement models and the models' associations with caregiver reports of youth suicidal ideation statements. Results indicate that the operationalizations used to define maltreatment resulted in differing measurement models that further differed in their associations with reports of youth suicidal ideation. This study highlights the importance of how researchers operationalize their data and the role dimensions of maltreatment have in further elucidating differential outcomes for youth exposed to maltreatment.

Specialist epilepsy service input following an epilepsy related unscheduled care episode

BACKGROUND

Emergency and unplanned epilepsy-related attendances are associated with an increased risk of subsequent death within 6 months. Although further work is required to provide a definitive explanation to account for these findings, in the interim it would seem reasonable that services are designed to ensure timely access and provide support at a time of greatest risk. We aim to determine the frequency of patients with epilepsy (PWE) accessing specialist neurology services following an epilepsy-related admission/unscheduled care episode.

METHODS

Patients were included in the cohort if they had at least 1 prescription for an anti-seizure medication and at least one epilepsy-related admission, emergency department attendance, or outpatient neurology clinic attendance between January 2011 and November 2021. We evaluated the rate of any outpatient neurology clinic attendance in the subsequent 6 months following an epilepsy related unscheduled care episode.

RESULTS

Of the 6,449 PWE included in the cohort, 4,465 were included for analysis. At the end of the follow up period less than 40% were accessing specialist services within 6 months of an episode of admission/ unscheduled care episode. Around a third (31.1%) of deaths occurred within 6 months of an epilepsy-related admission, and in the majority of cases patients were not seen by an epilepsy specialist in the period between discharge and death. The frequency of mental health comorbidity in PWE accessing unscheduled care remains very high with almost 80% having a diagnosis of either depression or anxiety.

CONCLUSION

A significant proportion of PWE are not accessing specialist services in a timely manner following an episode of unscheduled care. Such provision may potentially provide an opportunity to reduce epilepsy related mortality by altering antiseizure medication doses and considering reversible factors associated with poor outcomes in PWE, such as poor medication adherence.

The impact of the COVID-19 pandemic on a cohort of adults with epilepsy

OBJECTIVES

The aim of this study was to assess the direct and indirect impacts of the COVID-19 pandemic on adults with epilepsy in Glasgow.

METHODS

We used routinely collected data for a previously identified cohort of patients with epilepsy to evaluate access to scheduled and unscheduled care with quarterly rates of inpatient admissions, outpatient attendance and accident & emergency attendance calculated. Anti-seizure medication prescribing and persistence, incidence of anxiety and depression and deaths for a cohort of patients with epilepsy was evaluated prior to the pandemic in comparison to during the pandemic, from 2015 to 2021.

RESULTS

All-cause mortality and epilepsy related mortality showed a statistically significant reduction during the pandemic. Although overall rates of out-patient hospital attendance dropped during the early stages of the pandemic (and had not returned to pre-pandemic levels by the end of 2021) epilepsy-related services saw maintenance of patient contact as a result of a rapid adoption of telephone clinics. A significant decrease in overall mortality was observed in PWE during the pandemic compared to the pre-pandemic period. COVID-19 was the single commonest cause of death in PWE during the pandemic (61/453) and 160 patients (3.7%) had at least 1 admission to hospital for COVID-19. Anti-seizure medication (ASM) prescribing remained rates remained stable during the pandemic. During the pandemic an average of 38.8% of cohort patients were treated for depression and 16.3% for anxiety per quarter, 8.2% and 12.4% of whom had not been previously treated for these conditions respectively.

CONCLUSION

We have shown that during a national lockdown, in the context of a pandemic, mortality in patients with epilepsy has reduced, while out-patient services were delivered remotely, primarily via the telephone. The reasons for this remain unclear but suggest that some of the excess mortality in people with epilepsy may be potentially avoidable by changes in lifestyle.

Trust and service engagement among people who inject drugs after release from prison

BACKGROUND

Compounding histories of injecting drug use and incarceration can marginalise people engaging with services, making it difficult for them to address their health and social welfare needs, particularly when they navigate community re-entry service supports. Drawing on Hall and colleagues' five components of trust, this paper seeks to understand how trust in service providers fosters (or inhibits) effective service engagement from the perspective of people who inject drugs during the prison post-release period.

METHODS

Between September 2018 and May 2020, qualitative in-depth interviews were completed with 48 adults (33 men, 15 women) recruited from SuperMIX (a longitudinal cohort study of people with a history of injection drug use in Victoria, Australia). Data relating to service engagement were coded against the five components of trust: competence, fidelity, honesty, global trust, and confidence.

RESULTS

Reflections of post-release service engagement frequently focused on interactions with community corrections (parole) officers. Depictions of trust were consistently portrayed within the context of negative experiences and deficits, whereby trusting provider relationships and interactions were rarely described. Most participants recounted a stark absence of fidelity (that is, "pursuing a [client's] best interests"), with some participants detailing circumstances in which their vulnerability was purposefully, almost strategically, exploited. These encounters nearly always had the consequence of impeding the participant's positive progression in the post-release integration period.

CONCLUSION

There is an urgent need to prioritise the client in health and social service delivery in the post-release transition-to-community period and recognise the importance of trust in delivering effective services to people whose life histories make them highly vulnerable to marginalisation.

'Not just one box that you tick off' - Deconstructing the hepatitis C care cascade in the interferon-free direct acting antiviral era from the client perspective

BACKGROUND

To achieve hepatitis C viral (HCV) elimination targets set by the World Health Organisation, pillars of the HCV care cascade are often referenced to track progress. The aim of this qualitative study was to explore the limitations of the care cascade framework through the real-world accounts of 'HCV journeys' among people who inject drugs (PWID), with particular attention to the intersection of PWID agency and structural determinants in the healthcare system.

METHODS

An in-depth analysis was conducted on five case studies to better understand participant experiences 'behind the cascade pillars'. The five case studies were drawn from the ETHOS Engage cohort as exemplars of the real-world complexities of people's HCV cascade journeys. Inclusion criteria for the qualitative study were participant has voluntarily signed the informed consent form, aged ≥18 years, HCV antibody positive by self-report, clients of selected sites participating in the ETHOS Engage cohort, and sufficiently proficient in English to participate in an interview. Thirty-four semi-structured interviews were conducted with participants who had received or had not received HCV treatment to identify barriers and facilitators to HCV care.

RESULTS

Participants 'housed' at the 'HCV RNA diagnosed pillar' (n = 2; Will; Julie) reported withholding their HCV serostatus in certain healthcare settings for fear that disclosure would lead to discriminatory decision-making from their treating physician. among participants who had completed treatment (n = 3; Corey; John; Nora) two reported still being unsure of their HCV status >6 months post-treatment. Ongoing feelings of frustration and shame were expressed in this 'post-cure care pillar' due to a perceived lack of quality care from clinic services and continued uneasiness when discussing drug use and reinfection while receiving opioid agonist treatment (OAT). Both case 'categories' described often tenuous therapeutic relationships with their physicians and recommended task-shifting to nurses and trusted case workers for ongoing care.

CONCLUSION

The care cascade provides a linear, two dimensional snapshot of clinical targets. Our findings illuminate structural barriers not visible behind its 'static' pillars, presenting insights into experiences among PWID otherwise dismissed as 'disengaged' or 'lost to follow-up'.

Non-fatal opioid overdose, naloxone access, and naloxone training among people who recently used opioids or received opioid agonist treatment in Australia: The ETHOS Engage study

BACKGROUND

Overdose is a major cause of morbidity and mortality among people who use opioids. Naloxone can reverse opioid overdoses and can be distributed and administered with minimal training. People with experience of overdose are a key population to target for overdose prevention strategies. This study aims to understand if factors associated with recent non-fatal opioid overdose are the same as factors associated with naloxone access and naloxone training in people who recently used opioids or received opioid agonist treatment (OAT).

METHODS

ETHOS Engage is an observational study of people who inject drugs in Australia. Logistic regression models were used to estimate odds ratios for non-fatal opioid overdose, naloxone access and naloxone training.

RESULTS

Between May 2018-September 2019, 1280 participants who recently used opioids or received OAT were enrolled (62% aged >40 years; 35% female, 80% receiving OAT, 62% injected drugs in the preceding month). Recent opioid overdose (preceding 12 months) was reported by 7% of participants, lifetime naloxone access by 17%, and lifetime naloxone training by 14%. Compared to people receiving OAT with no additional opioid use, recent opioid, benzodiazepine (preceding six months), and hazardous alcohol use was associated with recent opioid overdose (aOR 3.91; 95%CI: 1.68-9.10) and lifetime naloxone access (aOR 2.12; 95%CI 1.29-3.48). Among 91 people who reported recent overdose, 65% had never received take-home naloxone or naloxone training.

CONCLUSIONS

Among people recently using opioids or receiving OAT, benzodiazepine and hazardous alcohol use is associated with non-fatal opioid overdose. Not all factors associated with non-fatal overdose correspond to factors associated with naloxone access. Naloxone access and training is low across all groups. Additional interventions are needed to scale up naloxone provision.

Urban manta rays: potential manta ray nursery habitat along a highly developed Florida coastline

The giant oceanic manta ray Mobula birostris was listed in the US Endangered Species Act as a threatened species in 2018, yet insufficient data exist on manta populations throughout US waters to designate critical habitat. Taxonomic and genetic evidence suggests that manta rays in the Western Atlantic are a separate species (M. cf. birostris) and little is understood about the ecology and life history of this putative species. The juvenile life stage of both M. birostris and M. cf. birostris is particularly understudied. Here, we are the first to describe the characteristics of a manta ray population along a highly developed coastline in southeastern Florida using boat-based surveys and photo identification of individuals. Fifty-nine manta individuals were identified between 2016 and 2019. All males were sexually immature based on clasper development, and 96% of females were classified as immature based on size and absence of mating scars or visible pregnancies. Twenty-five (42%) individuals were observed more than once during the study period and 8 individuals were sighted over multiple years. The occurrence of juveniles, high site fidelity and extended use of the study area by juvenile manta rays suggest that southeastern Florida may serve as a nursery habitat. High occurrence of fishing line entanglement (27% of individuals) and vessel strike injury were documented, and rapid wound healing was observed. Future research and conservation efforts will focus on identifying the physical and biological features of the potential nursery habitat and on mitigation of anthropogenic impacts.

Barriers and facilitators to engaging in hepatitis C management and DAA therapy among general practitioners and drug and alcohol specialists-The practitioner experience

BACKGROUND

Since the advent of interferon-free, direct-acting antiviral (DAA) therapies for hepatitis C virus (HCV) infection, prescriber restrictions have been removed worldwide, permitting HCV management outside of hospital-based clinics. To date, there is limited knowledge of the practitioner experience with DAA treatments, particularly among those new to HCV care. The aim of this qualitative study was to investigate barriers and facilitators for HCV management among general practitioners (GPs) who prescribe opioid agonist therapy (OAT) and drug and alcohol specialists.

METHODS

In-depth, semi-structured telephone interviews were conducted between September 2018 and April 2019. Practitioners from across Australia were purposively sampled and questioned on barriers and facilitators to HCV management in their clinic(s). Data were coded and analysed with iterative categorisation and thematical analysis.

RESULTS

Thirty practitioners were interviewed. Participants expressed professional fulfillment in managing HCV care and many benefited from specialist mentorship. Most participants expressed frustration with ongoing implementation barriers, notably, a lack of onsite phlebotomy services and liver disease staging equipment. Poor venous access among persons who inject drugs was elucidated as a major barrier to treatment initiation. Some participants did not receive clinic manager support to engage in HCV care.

CONCLUSION

To achieve HCV targets set by WHO by 2030, practitioners require additional implementation support. As HCV testing remains a barrier to linkage to care, practitioners should be kept well-informed of diagnostic developments. Findings also underscore the importance of initial specialist mentorship with further evidence needed for practitioners based in rural regions.

CTCF genetic alterations in endometrial carcinoma are pro-tumorigenic

CTCF is a haploinsufficient tumour suppressor gene with diverse normal functions in genome structure and gene regulation. However the mechanism by which CTCF haploinsufficiency contributes to cancer development is not well understood. CTCF is frequently mutated in endometrial cancer. Here we show that most CTCF mutations effectively result in CTCF haploinsufficiency through nonsense-mediated decay of mutant transcripts, or loss-of-function missense mutation. Conversely, we identified a recurrent CTCF mutation K365T, which alters a DNA binding residue, and acts as a gain-of-function mutation enhancing cell survival. CTCF genetic deletion occurs predominantly in poor prognosis serous subtype tumours, and this genetic deletion is associated with poor overall survival. In addition, we have shown that CTCF haploinsufficiency also occurs in poor prognosis endometrial clear cell carcinomas and has some association with endometrial cancer relapse and metastasis. Using shRNA targeting CTCF to recapitulate CTCF haploinsufficiency, we have identified a novel role for CTCF in the regulation of cellular polarity of endometrial glandular epithelium. Overall, we have identified two novel pro-tumorigenic roles (promoting cell survival and altering cell polarity) for genetic alterations of CTCF in endometrial cancer.

ASCT2/SLC1A5 controls glutamine uptake and tumour growth in triple-negative basal-like breast cancer

Alanine, serine, cysteine-preferring transporter 2 (ASCT2; SLC1A5) mediates uptake of glutamine, a conditionally essential amino acid in rapidly proliferating tumour cells. Uptake of glutamine and subsequent glutaminolysis is critical for activation of the mTORC1 nutrient-sensing pathway, which regulates cell growth and protein translation in cancer cells. This is of particular interest in breast cancer, as glutamine dependence is increased in high-risk breast cancer subtypes. Pharmacological inhibitors of ASCT2-mediated transport significantly reduced glutamine uptake in human breast cancer cell lines, leading to the suppression of mTORC1 signalling, cell growth and cell cycle progression. Notably, these effects were subtype-dependent, with ASCT2 transport critical only for triple-negative (TN) basal-like breast cancer cell growth compared with minimal effects in luminal breast cancer cells. Both stable and inducible shRNA-mediated ASCT2 knockdown confirmed that inhibiting ASCT2 function was sufficient to prevent cellular proliferation and induce rapid cell death in TN basal-like breast cancer cells, but not in luminal cells. Using a bioluminescent orthotopic xenograft mouse model, ASCT2 expression was then shown to be necessary for both successful engraftment and growth of HCC1806 TN breast cancer cells in vivo. Lower tumoral expression of ASCT2 conferred a significant survival advantage in xenografted mice. These responses remained intact in primary breast cancers, where gene expression analysis showed high expression of ASCT2 and glutamine metabolism-related genes, including GLUL and GLS, in a cohort of 90 TN breast cancer patients, as well as correlations with the transcriptional regulators, MYC and ATF4. This study provides preclinical evidence for the feasibility of novel therapies exploiting ASCT2 transporter activity in breast cancer, particularly in the high-risk basal-like subgroup of TN breast cancer where there is not only high expression of ASCT2, but also a marked reliance on its activity for sustained cellular proliferation.

Liver disease knowledge and acceptability of non-invasive liver fibrosis assessment among people who inject drugs in the drug and alcohol setting: The LiveRLife Study

BACKGROUND

The aim of this study was to assess factors associated with baseline knowledge of HCV and liver disease, acceptability of transient elastography (TE) assessment (FibroScan(®)), and willingness and intent to receive HCV treatment among persons with a history of injection drug use participating in a liver health promotion campaign.

METHODS

The LiveRLife campaign involved three phases: (1) campaign resource development; (2) campaign resource testing; and (3) campaign implementation. Participants were enrolled in an observational cohort study with recruitment at four clinics - one primary health care facility, two OST clinics, and one medically supervised injecting centre - in Australia between May and October 2014. Participants received educational material, nurse clinical assessment, TE assessment, dried blood spot testing, and completed a knowledge survey.

RESULTS

Of 253 participants (mean age 43 years), 68% were male, 71% had injected in the past month, and 75% self-reported as HCV positive. Median knowledge score was 16/23. In adjusted analysis, less than daily injection (AOR 5.01; 95% CI, 2.64-9.51) and no daily injection in the past month (AOR 3.54; 95% CI, 1.80-6.94) were associated with high knowledge (≥16). TE was the most preferred method both pre- (66%) and post-TE (89%) compared to liver biopsy and blood sample. Eighty-eight percent were 'definitely willing' or 'somewhat willing' to receive HCV treatment, and 56% intended to start treatment in the next 12 months. Approximately 68% had no/mild fibrosis (F0/F1, ≥2.5 to ≤7.4kPa), 13% moderate fibrosis (F2, ≥7.5 to ≤9.4kPa), 10% severe fibrosis (F3, ≥9.5 to ≤12.4kPa), and 9% had cirrhosis (F4, ≥12.5kPa).

CONCLUSION

Liver disease and HCV knowledge was moderate. High acceptability of TE by PWID provides strong evidence for the inclusion of TE in HCV-related care, and could help to prioritise HCV treatment for those at greatest risk of liver disease progression.

Slowing down of adult body mass index trend increases in England: a latent class analysis of cross-sectional surveys (1992-2010)

BACKGROUND

The prevalence of excess body weight, commonly measured as body mass index (BMI)≥25 kg m(-2), has increased substantially in many populations worldwide over the past three decades, but the rate of increase has slowed down in some western populations.

OBJECTIVE

We address the hypothesis that the slowing down of BMI trend increases in England reflects a majority sub-population resistant to further BMI elevation.

DESIGN

Pseudo-panel data derived from annual cross-sectional surveys, the Health Surveys for England (1992-2010). Trends in median BMI values were explored using regression models with splines, and gender-specific mixture model (latent class analysis) were fit to take an account of increasing BMI distribution variance with time and identify hidden subgroups within the population.

SUBJECTS

BMI was available for 164 155 adults (men: 76 382; women: 87 773).

RESULTS

Until 2001, the age-adjusted yearly increases in median BMI were 0.140 and 0.139 kg m(-2) for men and women, respectively, decreasing thereafter to 0.073 and 0.055 kg m(-2) (differences between time periods, both P-values<0.0001). The mixture model identified two components--a normal BMI and a high BMI sub-population--the proportions for the latter were 23.5% in men and 33.7% in women. The remaining normal BMI populations were 'resistant' with minimal increases in mean BMI values over time. By age, mean BMI values in the normal BMI sub-population increased greatest between 20 and 34 years for men; for women, the increases were similar throughout age groups (slope differences, P<0.0001).

CONCLUSION

In England, recent slowing down of adult BMI trend increases can be explained by two sub-populations--a high BMI sub-population getting 'fatter' and a majority 'resistant' normal BMI sub-population. These findings support a targeted, rather than a population-wide, policy to tackle the determinants of obesity.

Unusually high levels of n-6 polyunsaturated fatty acids in whale sharks and reef manta rays

Fatty acid (FA) signature analysis has been increasingly used to assess dietary preferences and trophodynamics in marine animals. We investigated FA signatures of connective tissue of the whale shark Rhincodon typus and muscle tissue of the reef manta ray Manta alfredi. We found high levels of n-6 polyunsaturated fatty acids (PUFA), dominated by arachidonic acid (20:4n-6; 12–17 % of total FA), and comparatively lower levels of the essential n-3 PUFA—eicosapentaenoic acid (20:5n-3; ~1 %) and docosahexaenoic acid (22:6n-3; 3–10 %). Whale sharks and reef manta rays are regularly observed feeding on surface aggregations of coastal crustacean zooplankton during the day, which generally have FA profiles dominated by n-3 PUFA. The high levels of n-6 PUFA in both giant elasmobranchs raise new questions about the origin of their main food source.

Biology, ecology and conservation of the Mobulidae

The Mobulidae are zooplanktivorous elasmobranchs comprising two recognized species of manta rays (Manta spp.) and nine recognized species of devil rays (Mobula spp.). They are found circumglobally in tropical, subtropical and temperate coastal waters. Although mobulids have been recorded for over 400 years, critical knowledge gaps still compromise the ability to assess the status of these species. On the basis of a review of 263 publications, a comparative synthesis of the biology and ecology of mobulids was conducted to examine their evolution, taxonomy, distribution, population trends, movements and aggregation, reproduction, growth and longevity, feeding, natural mortality and direct and indirect anthropogenic threats. There has been a marked increase in the number of published studies on mobulids since c. 1990, particularly for the genus Manta, although the genus Mobula remains poorly understood. Mobulid species have many common biological characteristics although their ecologies appear to be species-specific, and sometimes region-specific. Movement studies suggest that mobulids are highly mobile and have the potential to rapidly travel large distances. Fishing pressure is the major threat to many mobulid populations, with current levels of exploitation in target fisheries unlikely to be sustainable. Advances in the fields of population genetics, acoustic and satellite tracking, and stable-isotope and fatty-acid analyses will provide new insights into the biology and ecology of these species. Future research should focus on the uncertain taxonomy of mobulid species, the degree of overlap between their large-scale movement and human activities such as fisheries and pollution, and the need for management of inter-jurisdictional fisheries in developing nations to ensure their long-term sustainability. Closer collaboration among researchers worldwide is necessary to ensure standardized sampling and modelling methodologies to underpin global population estimates and status.

The use and abuse of photographic identification in sharks and rays

The use of photography to discriminate between individuals in a population using natural markings or aberrations is increasingly being utilized to support field research on elasmobranchs. This non-intrusive method has facilitated investigation of a wide variety of subjects including population composition, abundance estimates, residency and movement, demography and social behaviours. Here the first detailed review of photo-identification as a research technique for sharks and rays is provided, and its assumptions, current applications and potential highlighted. The limitations and practical considerations of photographic studies are also investigated with recommendations on initial survey design and ongoing data collection using current technology. Future directions are also explored with an emphasis on a move towards standardized approaches and automated recognition programmes to facilitate global collaborative work.

How large is the world's largest fish? Measuring whale sharks Rhincodon typus with laser photogrammetry

Laser photogrammetry was found to be a promising new cost-effective technique for measuring free-swimming whale sharks Rhincodon typus. Photogrammetric measurements were more precise than visual size estimates by experienced researchers, with results from the two methods differing by 9· 8 ± 1· 1% (mean ±s.e.). A new metric of total length and the length between the fifth gill and first dorsal fin (r² = 0· 93) is proposed to facilitate easy, accurate length measurements of whale sharks in the field.

Reproductive ecology of the reef manta ray Manta alfredi in southern Mozambique

The application of a photographic identification methodology using the unique ventral surface markings (natural spot patterns) of an observed population in southern Mozambique enabled many aspects of the reproductive ecology of reef manta rays Manta alfredi to be examined. The region encompassing the study site was identified as a mating ground for M. alfredi based on observations of mating events and fresh mating scars on females. The distribution of these pectoral fin scars was highly biased and indicated a strong lateralized behavioural trait, with 99% of these scars occurring only on the left pectoral fin. No other elasmobranch has been reported to display behavioural lateralization. The study region also acts as a birthing ground, with individuals typically giving birth in the austral summer period after a gestation of c. 1 year. Reproductive periodicity in M. alfredi was most commonly biennial, but a few individuals were pregnant in consecutive years, confirming an annual ovulatory cycle. The production of a single pup appears to be the normal situation, although observations in the wild as well as during opportunistic dissections of individuals killed by fisheries revealed that two pups are conceived on occasion. Many aspects of the study have contributed to the limited baseline data currently available for this species and have highlighted the potential need for more conservative conservation strategies.

Redox control of aryl sulfotransferase specificity

Aryl sulfotransferase IV from rat liver has the very broad substrate range that is characteristic of the enzymes of detoxication. With the conventional assay substrates, 4-nitrophenol and PAPS, sulfation was considered optimal at pH 5.5 whereas the enzyme in the physiological pH range was curiously ineffective. These properties would seem to preclude a physiological function for this cytosolic enzyme. Partial oxidation of the enzyme, however, results not only in a substantial increase in the rate of sulfation of 4-nitrophenol at physiological pH but also in a shift of the pH optimum to this range and radically altered overall substrate specificity. The mechanism for this dependence on redox environment involves oxidation at Cys66, a process previously shown to occur by formation of a mixed disulfide with glutathione or by the formation of an internal disulfide with Cys232. Oxidation at Cys66 acts only as a molecular redox switch and is not directly part of the catalytic mechanism. Underlying the activation process is a change in the nature of the ternary complex formed between enzyme, phenol, and the reaction product, adenosine 3',5'-bisphosphate. The reduced enzyme gives rise to an inhibitory, dead-end ternary complex, the stability of which is dictated by the ionization of the specific phenol substrate. Ternary complex formation impedes the binding of PAPS that is necessary to initiate a further round of the reaction and is manifest as profound, substrate-dependent inhibition. In contrast, the ternary complex formed when the enzyme is in the partially oxidized state allows binding of PAPS and the unhindered completion of the reaction cycle.

A review of the effects of manipulation of the cysteine residues of rat aryl sulfotransferase IV

Aryl sulfotransferase IV from rat liver has the broad substrate range that is characteristic of the enzymes of detoxication. With the standard assay substrates, 4-nitrophenol and 3'-phosphoadenosine 5'-phosphosulfate (PAPS), sulfation is optimum at pH 5.4 whereas the reaction is minimal in the physiological pH range. These properties preclude a physiological function for this cytosolic enzyme. Partial oxidation of the enzyme, however, results not only in an increase in the rate of sulfation but also in a shift of the pH optimum to the physiological pH range. The mechanism for this dependence on the redox environment involves oxidation at Cys66, the cysteine residue that is conserved throughout the phenol sulfotransferase family. As documented by mass spectroscopic methods, oxidation by GSSG leads to the formation of an internal disulfide between Cys66 and Cys232; for mutants at Cys232, the oxidation product is a mixed disulfide of Cys66 and glutathione. Both of these disulfide species activate the enzyme and allow it to function at a pH optimum in the physiological range. The activated enzyme differs from the reduced form by a more circumscribed substrate spectrum. All five mutants, in which each of the cysteines of the sulfotransferase subunit have been changed to serine, are catalytically active. Only Cys66 is required for the redox response.

Control of activity through oxidative modification at the conserved residue Cys66 of aryl sulfotransferase IV

Oxidation at Cys66 of rat liver aryl suflotransferase IV alters the enzyme's catalytic activity, pH optima and substrate specificity. Although this is a cytosolic detoxification enzyme, the pH optimum for the standard assay substrate 4-nitrophenol is at pH 5.5; upon oxidation, the optimum changes to the physiological pH range. The principal effect of the change in pH optimum is activation, which is manifest by an increase in K'cat without any major influence on substrate binding. In contrast, with tyrosine methyl ester as a substrate, the enzyme's optimum activity occurs at pH 8.0; upon oxidation, it ceases to be a substrate at any pH. The presence of Cys66 was essential for activation to occur, thereby providing a putative reason underlying the conserved nature of this cysteine throughout the phenol sulfotransferase family. Mapping of disulfides by mass spectrometry showed the critical event to be the oxidation of Cys66 to form a disulfide with either Cys232 or glutathione, either one is effective. These results point to a mechanism for regulating the activity of a key enzyme in xenobiotic detoxication during cellular oxidative stress.

Two phenol sulfotransferase species from one cDNA: nature of the differences

A phenol sulfotransferase from rat liver (EC 2.8.2.9), expressed in Escherichia coli from a single cDNA, was purified as two separable but catalytically active proteins. The proteins appeared to be identical to each other and to the natural liver sulfotransferase by comparison of their amino acid constitution, amino-terminal end group, and interaction with a polyclonal antibody raised against the liver enzyme. Each of the recombinant forms, alpha and beta, catalyzed the sulfuryl group transfer from 4-nitrophenylsulfate to an acceptor phenol, a reaction in which 3'-phospho-adenosine 5'-phosphate (PAP) is a necessary intermediate. Only form beta, however, catalyzes the physiological transfer of a sulfuryl group from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to the free phenol. Evidence is presented that sulfotransferase alpha, but not beta, has 1 mol of PAP tightly bound per enzyme dimer. The ability to utilize PAPS as a sulfate donor could be altered: form alpha could be treated and purified as form beta to acquire the ability to use PAPS, whereas form beta was treated by extended incubation with PAP, lost its ability to use PAPS, and was purified as form alpha.

Lack of influence of modulators of epoxide metabolism on the genotoxicity of trans-anethole in freshly isolated rat hepatocytes assessed with the unscheduled DNA synthesis assay

The aniseed food flavour trans-anethole was implicated as a weak hepatocarcinogen only in female Sprague Dawley-CD rats administered high doses (1% in the diet for 121 wk). However, this substance is apparently non-genotoxic in a range of test systems. Anethole is metabolized in the rat along three primary pathways, one of which is epoxidation across the double bond of the side-chain. The epoxides of a number of the alkenylbenzene family of food flavours, of which anethole is a member, are putative genotoxins, being bacterial mutagens but not mammalian carcinogens. The authors have previously shown that the cytotoxicity of anethole is enhanced when the cellular epoxide defence mechanisms of conjugation with reduced glutathione and hydration by cytosolic epoxide hydrolase are severely compromised. They now report, however, that modulation of epoxide metabolism in cultured cells by the same mechanisms fails to induce unscheduled DNA synthesis (UDS) by anethole nor was there a UDS response in hepatocytes of female rats dosed with anethole in vivo. The epoxide of anethole was synthesized for the first time in this investigation and tested directly. As expected, it was markedly cytotoxic but not genotoxic. Anethole epoxide has chemical characteristics that differ from those of other structurally similar epoxides being labile to hydrolysis in aqueous media at physiological pH and temperature. This gives greater relevance to tests of its genotoxicity after formation within the hepatocyte rather than by adding the epoxide extracellularly to the culture medium. The direct and indirect demonstration of the lack of induction of UDS by anethole epoxide provides further support for the hypothesis that marginal hepatocarcinogenicity observed in female rats given 1% anethole in the diet for 121 wk was not initiated by a genotoxic event.

Influence of modulators of epoxide metabolism on the cytotoxicity of trans-anethole in freshly isolated rat hepatocytes

The effect of modulating epoxide metabolism by inhibiting microsomal and cytosolic epoxide hydrolases and depleting glutathione, on the cytotoxicity of trans-anethole has been examined in freshly isolated rat hepatocytes in suspension. Hepatocytes derived from female Sprague-Dawley CD rats by collagenase perfusion were incubated in suspension and sampled at intervals over a 6-hr period. Cytotoxicity was assessed by the leakage of lactate dehydrogenase into the culture medium and in the cells after lysis. Glutathione was determined by fluorimetry. Anethole showed a dose-dependent cytotoxicity at concentrations ranging from 5 x 10(-4) to 5 x 10(-3) M, with concentrations of 10(-3) M and above causing greater than 63% leakage of lactate dehydrogenase in 6 hr. Microsomal epoxide hydrolase was inhibited by trichloropropene oxide (10(-4) M) and cyclohexene oxide (10(-3) M), and cytosolic epoxide hydrolase by 4-fluorochalcone oxide (5 x 10(-4) M). Cellular glutathione was depleted by diethyl maleate (5 x 10(-4) M), and its synthesis inhibited by 2.5 x 10(-3) M-L-buthionine (S,R)-sulphoximine. Suspensions treated with a sub-cytotoxic concentration of anethole (5 x 10(-4) M) showed a rapid increase in cytotoxicity when 4-fluorochalcone oxide was present (complete loss of viability within 2 hr), while pretreatment of hepatocytes with diethyl maleate in combination with buthionine sulphoximine, to deplete glutathione, slowly increased the cytotoxic response at later times (after 4 hr of incubation). The association of the effects of 4-fluorochalcone oxide with the inhibition of cytosolic epoxide hydrolase is strengthened by the inability of chalcone oxide, a close structural analogue of 4-fluorochalcone oxide, which has no effect on epoxide hydrolase or glutathione conjugation, to influence the effects of anethole on hepatocytes. These data are discussed in terms of the role of anethole epoxide in the cytotoxicity of trans-anethole.