The prevalence of emotional abuse in children living in Sub-Saharan Africa - A systematic review

OBJECTIVES

This study is meant to put a focus on the prevalence of emotional abuse in low-income states like the Sub-Saharan region.

METHODOLOGY

Searching PubMed, Google scholar, and web of science during February and April 2021 a total of 2264 articles were identified, 27 met the inclusion criteria. We added the results of 13 VAC (Violence Against Children and Youth) studies, conducted by UNICEF capturing information about experienced sexual, physical, or emotional violence in 13-24-year-olds, as well as 56 MIC (Multiple Indicator Cluster) studies, conducted by the CDC to research the disciplinary methods used with children aged 1-14 years in the past month by older household members. Finally, in a meta-analytic approach, we aimed to calculate a pooled estimate of the prevalence.

RESULTS

The included studies depicted a wide range in prevalence rates across countries. For example, while the VAC study in Lesotho in 2018 showed low incidence rates of emotional violence (6.9 % Females, 3.8 % Males), the average prevalence recorded by the MIC study was as high as 57.8 % for females and 59.2 % for males. On average, the MIC studies displayed a higher incidence and the discrepancy of prevalence of emotional abuse between females and males was small. Calculating a pooled estimate of the prevalence was not possible, due to the heterogeneity of the data.

CONCLUSIONS

In general countries displayed a high prevalence. A standardized use of a uniform definition of emotional abuse might help to display a more homogenous data set in the future, giving the opportunity for pooled estimates of prevalence.

Prevalence of unnecessary antibiotic use in European hospitals – a systematic review

Background

Antibiotics (AB) are essential to modern day medicine as prophylaxis and therapy. Yet, unnecessary use has various negative effects on individual and global health, such as antimicrobial resistance (AMR) and contribution to high greenhouse gas (GHG) emissions of the healthcare sector. This systematic review provides an overview of unnecessary AB use in European hospitals in order to present possible ways forward.

Methods

The systematic review followed PRISMA guidelines, included as databases were: Embase, ProQuest Environmental Science Collection, PubMed, ScienceDirect, Scopus and Web of Science. Studies conducted among adult in-patients in EU/EEA countries were included if they provided assessment methodology, included a clear standard of measurement and chart reviews were used as evaluation basis.

Results

Fifty-six included studies were categorised into the following three groups: (1) Studies using an established evaluation method; 20 studies belong to this group, 18 used the same, established approach. Eleven of these studies performed an observational audit, while the interventions in the remaining studies were of educational or advisory nature. Unnecessary AB use ranged from 1.5% to 51% of all observed prescriptions. Outcomes of interventions showed great variation of effects on unnecessary use (-34.7% - +11.6). (2) Studies using a newly developed, clearly stated evaluation method (4 studies); (3) Studies which conform with established evaluation methods but the processes were not specified (32 studies). Results are subject to further analysis.

Conclusions

The studies included reported a great range of unnecessary AB use in adult in-patients, for both prophylactic and therapeutic indications. Evaluation methods of unnecessary AB use vary greatly between studies. In future research, comprehensive application of established approaches is essential for better overview and identification of key areas for AMR and GHG emission reduction activities.

Key messages

• Unnecessary antibiotic use varies greatly among studies conducted in European adult in-patients.

• In future research, wider application of established evaluation methods will improve comparability and targeting of interventions.

The economic burden of treating uncomplicated hypertension in Sub-Saharan Africa: a systematic literature review

Background and Objectives

Hypertension is one of the leading cardiovascular risk factors with high numbers of undiagnosed and untreated patients in Sub Saharan Africa (SSA). The health systems and affected people are often overwhelmed by the social and economic burden that comes with the disease. However, the research on the economic burden and consequences of hypertension treatment remains scare in SSA. The objective of our review was to compare different hypertension treatment costs across the continent and identify major cost drivers.

Material and Methods

Systematic literature searches were conducted in multiple databases (e.g., PubMed, Web of Science, Google Scholar) for peer reviewed articles written in English language with a publication date from inception to Jan. 2022. We included studies assessing direct and indirect costs of hypertension therapy in SSA from a provider or user perspective. The search and a quality assessment were independently executed by two researchers. All results were converted to 2021 US Dollar.

Results

Of 3999 results identified in the initial search, 33 were selected for data extraction. Costs differed between countries, costing perspectives and cost categories. Only 25% of the SSA countries were mentioned in the studies, with Nigeria dominating the research with a share of 27% of the studies. We identified 15 results each from a user or provider perspective. Medication costs were accountable for the most part of the expenditures with a range from 1.70$ to 97.06$ from a patient perspective and 0.09$ to 193.55$ from a provider perspective per patient per month. Major cost drivers were multidrug treatment, inpatient or hospital care and having a comorbidity like diabetes.

Conclusion

Hypertension poses a significant economic burden for patients and governments in SSA. Interpreting and comparing the results from different countries and studies is difficult as there are different financing methods and cost items are defined in different ways. However, our results identify medication costs as one of the biggest cost contributors. When fighting the economic burden in SSA, reducing medication costs in form of subsidies or special interventions needs to be considered.

Trial registration

Registration: PROSPERO, ID CRD42020220957.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-13877-4.

Long-term outcomes of in utero Ramadan exposure: a systematic review

Background

Previous systematic reviews have documented perinatal health effects of in utero Ramadan exposure on children. Our study aims to review possible long-term consequences.

Methods

Following PRISMA guideline, we searched PubMed, PsycINFO, EconLit, Index Islamicus, Web of Science, Cochrane Library, WHO Global Index Medicus, WHO Virtual Health Library and Google Scholar for original research articles analysing any long-term outcome of in utero Ramadan exposure, excluding maternal and perinatal outcomes.

Results

Fourteen studies from 4874 non-duplicate search results were included. Most studies suggest negative consequences from in utero Ramadan exposure on health as well as on economic outcomes later in adulthood. Higher under-five mortality rate, higher mortality under three months and under one year, shorter stature, lower body mass index, increased incidence of vision, hearing and learning disabilities, lower math, writing and reading scores, as well as lower probability to own a home were associated with Ramadan exposure during conception or first trimester of pregnancy. Further, age and sex of the child seem to play a pivotal role on the association.

Conclusions

Existing studies suggest that in utero Ramadan exposure may adversely impact long-term health and economic well-being. However, evidence is limited. Meanwhile, increasing awareness of the potential risks of Ramadan fasting during pregnancy should be raised among pregnant women and clinicians and other antenatal care workers should promote better maternal healthcare.

Key messages

In utero Ramadan exposure may adversely impact long-term health and economic well-being. Some negative effects are observed particularly when Ramadan occurred during the first trimester of pregnancy.

We still dońt know who bleeds in Dengue. A systematic review of the literature

Background

Already, Dengue affects 400 million individuals every year. Its main drivers, urbanization, globalization, and climate change, however, will spread the disease even further and potentially threaten billions. In Dengue, bleeding occurs frequently. Severe bleeding strongly increases mortality and immediate medical response is crucial for survival. Predicting the occurrence and course of bleeding in advance would improve clinical outcome, reduce unnecessary hospitalization, and improve economic efficiency.

Methods

Following the PRISMA-guidelines, we conducted a systematic review of the literature to identify predictors of bleeding in acute confirmed Dengue. We searched Pubmed, Web of Science, IRIS, LILACS, and the Cochrane Archives and included all prospective longitudinal studies restricting neither language nor study sample characteristics.

Results

We included 19 studies but found that most data suffered from high risk of bias because of poor reporting and not accounting for confounding. Only five studies were more reliable, and they unanimously reported that age-, and platelet count predicted bleeding severity. The body of evidence was too weak to draw conclusions for the other 23 markers investigated. Crucially, the researchers had defined central concepts in fundamentally different ways and thus prevented the comparison of their findings.

Conclusions

Our systematic review of the literature showed that more research is needed to create a reliable prediction model for bleeding in Dengue. We have moderate certainty that platelet count- and age predict bleeding severity. Our study exposed the urgent need to improve the quality of research in Dengue epidemiology. Most importantly, our findings illustrate the necessity to harmonize central concepts within the Dengue research community. To tackle the challenge that Dengue is bound to become, we need dialogue across research groups and collaboration that overcomes the limited impact of individual studies.

Key messages

We know too little about predictors of bleeding in Dengue. Reliable data is needed to identify new markers and to confirm existing markers that are carried by a weak body of evidence. We urge investigators to collaborate. To overcome the limitations of individual studies, we need better comparability and a scientific dialogue based on common definitions of core concepts in Dengue.

Impacts of international labor migration on the mental health and well-being of left-behind children

Background

Labor migration is a challenge for the globalised world due to its long-term effects such as the formation of transnational families with the particularly vulnerable groups of left-behind children (LBC). These families, where family members of migrant workers are 'left-behind' are becoming common practice in many developing countries. In this systematic literature review, we aimed to investigate the impacts of parental labor migration on the mental health and well-being of their LBC.

Methods

Following the PRISMA guidelines, we performed a systematic literature search in English using PubMed, PsychINFO, Web of Science, Cochrane Library and Google Scholar for studies, investigating mental health and well-being among LBC who live in transnational families. Case-reports, qualitative studies as well as opinion papers were excluded. We summarized the evidence and additionally compared quantitative results.

Results

25 studies were selected for the final analysis. We found that mental health and well-being outcomes of LBC differ across regions and sometimes even within regions. Only studies conducted in South America and South Asia observed purely negative effects. Overall, LBC show abnormal SDQ (Strengths and Difficulties Questionnaire) scores and report higher levels of depression and loneliness, than children who do not live in transnational families. Evidence suggests that gender of migrant parent, culture and other transnational family characteristics such as family arrangement, the role of the mother and the role of the father contribute to the well-being and psychological health of LBC.

Conclusions

International migration of parents has more negative than positive effects (e.g. through remittances) on the mental health and well-being of LBC. However, the effects strongly depend on family arrangements and care giving practices in migrants' sending countries.

Key messages

Further research utilizing longitudinal data is needed to better explore the complex and long-term effects of parental migration on LBC. Multidimensional family characteristics are crucial and should be better explored when examining the impacts of migratory separation on left-behind children.

Toronto aortic stenosis quality of life questionnaire (TASQ): validation in TAVI patients

BACKGROUND

Aortic stenosis (AS) is a common cardiac condition whose prevalence increases with age. The symptom burden associated with severe aortic stenosis (AS) can introduce significant lifestyle disruptions and if left untreated can lead to a poor prognosis. Quality of life (QoL) is an important consideration in these patients. The TASQ is a QoL tool that was developed for aortic stenosis patients. We evaluated the psychometric properties of this specific questionnaire in patients who underwent transcatheter aortic valve implantation (TAVI), which is a therapeutic option for patients with severe aortic stenosis (AS).

METHODS

The properties of the TASQ in measuring QoL were evaluated in AS patients undergoing TAVI. Patients presenting for the TAVI procedure (N = 62) were evaluated pre-TAVI, at discharge, 1-month, and 3-month follow-ups. Demographic information as well as caregiver status, and daily activities were recorded. In addition to the TASQ, they completed the KCCQ (Kansas City Cardiomyopathy Questionnaire) and the IIRS (Illness Intrusiveness Rating Scale).

RESULTS

The TASQ is a 16-item self-administered questionnaire that assesses AS-specific QoL across five domains: physical symptoms; physical limitations; emotional impact; social limitations, and health expectations. TASQ subscales are internally consistent (α = 0.74-0.96) and showed significant improvements from baseline across assessments (p < 0.001). Construct validity evidence was demonstrated by correlations consistent with theoretically derived hypotheses across time points.

CONCLUSIONS

The TASQ is a brief measure of AS-specific QoL that is sensitive to change in patients undergoing TAVI. Items on the TASQ capture important QoL concerns reported by AS patients, suggesting this is a measure of relevant and meaningful outcomes for this patient population. Detection of early improvements in QoL by the TASQ is promising, with important implications for the evaluation of procedural outcomes in this population.

The meaning of self-reported death anxiety in advanced cancer

BACKGROUND

Death anxiety is important but understudied in palliative care. New self-report measurements have been developed, but their interpretation and clinical utility may not be evident.

AIM

To inform our understanding of death anxiety in patients with advanced cancer by exploring the relationship between this self-reported symptom and its clinical presentation.

DESIGN

Participants were part of a psychotherapy trial in advanced cancer. First therapy session transcripts were analyzed using interpretive description in patients reporting low, moderate, and high death anxiety on the Death and Dying Distress Scale (DADDS).

SETTING/PARTICIPANTS

A total of 16 participants (10 women and 6 men) with advanced or metastatic cancer were sampled from the Princess Margaret Cancer Centre, Toronto, Canada. Six participants reported low death anxiety scores (Death and Dying Distress Scale: 0-19), five moderate (Death and Dying Distress Scale: 20-50), and five high (Death and Dying Distress Scale: 51-75).

RESULTS

The low death anxiety group exhibited psychological readiness for death, or contrastingly, non-reflectiveness about death. The moderate group recognized the imminence of mortality, which impacted treatment decisions and future plans. Prior experience with death was discussed as raising the salience of mortality. The high group felt dominated by powerful emotions and could not make sense of their situation. Their distress was exacerbated by substantial relational concerns.

CONCLUSION

Self-reported death anxiety is affected by the awareness and ability to reflect on mortality. Death and Dying Distress Scale scores may facilitate exploration of this symptom as part of a clinical assessment and may serve to guide treatment approaches. Greater attention to death anxiety is consistent with and recommended by contemporary approaches to palliative care.

Prevalence of work-related rhino-conjunctivitis and respiratory symptoms among domestic waste collectors

Waste collectors may suffer from acute and chronic health effects caused by organic dust (bioaerosols). Pathophysiological symptoms may originate either from allergic or irritative pathomechanisms, but an explicit distinction of the etiology is often complicated although crucial for proper risk assessment and workplace prevention. In this cross-sectional study, a total of 69 male waste collectors from the Ruhr area in Germany underwent a customized testing protocol including a modified questionnaire, basic clinical examination, spirometry, and immunologic parameters. Subjects were classified according to their work tasks into loaders (n=27), floaters (n=29), and drivers (n=13). We found that a high percentage of the workers had complaints (eyes 29.0%, nose 39.1%, and cough 34.8%) which were strongly work-related. Multiple logistic regression analyses indicated that duration of employment in waste collection (per 10 years) was associated with an increased prevalence of cough (OR=1.64, 95% CI 0.81; 3.35) and chronic bronchitis (OR=2.18, 95% CI 0.80; 5.92). An association between rhinitis and cough (OR=2.62, 95% CI 0.94; 7.27) was found, which supports the association between the prevalence of upper and lower airway disease. Furthermore, when adjusting for smoking status, atopic subjects suffered more frequently from irritation of the lower airways as indicated by cough (OR=2.71, 95% CI 0.91; 8.08). In conclusion, the study demonstrates associations between the prevalence of upper and lower airway disease in waste collectors. Notably, an underlying allergic disease in waste collectors could be suspected more commonly than previously reported.

Depression and hopelessness in patients with acute leukemia: the psychological impact of an acute and life-threatening disorder

OBJECTIVE

Acute leukemia (AL) is a life-threatening cancer associated with substantial morbidity and mortality, particularly in older adults. Given that there has been little research on the psychological impact of such malignancies with acute onset, we assessed the prevalence and correlates of depression and hopelessness in patients with AL.

METHODS

Three hundred forty-one participants were recruited within 1 month of diagnosis or relapse and completed the Beck Depression Inventory-II (BDI-II), Beck Hopelessness Scale (BHS), Memorial Symptom Assessment Scale, and other psychosocial measures. Multivariate regression analyses identified correlates of depression and hopelessness.

RESULTS

17.8% reported clinically significant depressive symptoms (BDI-II ≥ 15), 40.4% of which were in the moderate-severe range (BDI-II ≥ 20). 8.5% reported significant symptoms of hopelessness (BHS ≥ 8). Depression was associated with greater physical symptom burden (adjusted R(2)  = 48.4%), while hopelessness was associated with older age and lower self-esteem (adjusted R(2)  = 45.4%). Both were associated with poorer spiritual well-being.

CONCLUSIONS

Clinically significant depressive symptoms were common early in the course of AL and related to physical symptom burden. Hopelessness was less common and associated with older age and lower self-esteem. The results suggest that whereas depression in AL may be related to disease burden, the preservation of hope may be linked to individual resilience, life stage, and realistic prognosis.Copyright © 2015 John Wiley & Sons, Ltd.

Cellular and Soluble Inflammatory Markers in Induced Sputum of Composting Plant Workers

Inflammatory processes, including respiratory symptoms, can be induced among workers in composting plants exposed to bioaerosols containing microorganisms and their compounds. We evaluated inflammatory processes in the lower respiratory tract via cellular and soluble mediator profiles in induced sputum (IS). IS samples of 140 current (35% smokers) and 49 former compost workers (29% smokers) as well as 29 white-collar workers (17% smokers) were collected and analyzed for the cell count and composition, and for soluble biomarkers. Significant differences between current and former compost workers and white-collar workers were detected for total cell count (p=0.0004), neutrophils (p=0.0045), sCD14 (p=0.008), and 8-isoprostane (p<0.0001). IS of non-smoking former compost workers showed lower concentrations of IL-8, total protein, immunoreactive MMP-9 and sCD14, compared with non-smoking current compost workers. 10.1% of the study population was suffering from chronic bronchitis with significant differences (p=0.018) between former compost workers (24.5%), current workers (5%), and white-collar workers (10.3%). Significantly lower IL-8 (p=0.0002), neutrophils (p=0.001), and MMP-9 (p=0.0023) values were measured in healthy subjects compared with subjects with chronic bronchitis. In conclusion, changes in lower airways were detected by analysis of biomarkers in IS of current exposed and, to a lesser extent, in IS of former compost workers. These effects are especially pronounced in subjects with chronic bronchitis.

The methodological soundness of literature reviews addressing three potential zoonotic public health issues

Literature reviews are important information sources for multiple stakeholders in zoonotic public health with limited time to keep up with the rapid increase in primary research in this field. However, their validity depends on their methodological soundness. The study purpose was to evaluate the methodological soundness of literature reviews in zoonotic public health. Relevant reviews (n = 132) published between January 2000 and August 2006 were identified on three issues: Mycobacterium avium ssp paratuberculosis as a potential cause of Crohn's disease in humans (30 reviews); antimicrobial use in animals as a risk factor for antimicrobial resistance in human pathogens (36); and the zoonotic potential of transmissible spongiform encephalopathies (66). The zoonotic aspect of the issue was the focus of 59 reviews and a subsection of 73 reviews. Two independent reviewers evaluated reviews using 13 criteria: 10 previously validated in the medical field, and three applicable to aetiology research. No review met more than eight of 13 criteria for methodological soundness; two articles met only one criterion. Two reviews described methods for identifying relevant primary research. In only two and four reviews respectively, authors conducted quantitative syntheses of research evidence or reported summarized measures of effect for the zoonotic risk to humans. Recommendations for future research and economic impact were provided in 64 and 10 reviews respectively. In 14 reviews, conclusions exceeded evidence presented. The various review authors' position on the evidence for the zoonotic association and the zoonotic risk to public health were inconsistent for all three issues. Reviews addressing potential zoonotic public health issues lack structured and transparent methodology preventing the end user from assessing the review's validity. These reviews should adhere to structured scientific principles similar to what is used for primary research articles.

Protocol design and current status of CLIVIT: a randomized controlled multicenter relevance trial comparing clips versus ligatures in thyroid surgery

BACKGROUND

Annually, more than 90000 surgical procedures of the thyroid gland are performed in Germany. Strategies aimed at reducing the duration of the surgical procedure are relevant to patients and the health care system especially in the context of reducing costs. However, new techniques for quick and safe hemostasis have to be tested in clinically relevance randomized controlled trials before a general recommendation can be given. The current standard for occlusion of blood vessels in thyroid surgery is ligatures. Vascular clips may be a safe alternative but have not been investigated in a large RCT.

METHODS/DESIGN

CLIVIT (Clips versus Ligatures in Thyroid Surgery) is an investigator initiated, multicenter, patient-blinded, two-group parallel relevance randomized controlled trial designed by the Study Center of the German Surgical Society. Patients scheduled for elective resection of at least two third of the gland for benign thyroid disease are eligible for participation. After surgical exploration patients are randomized intraoperatively into either the conventional ligature group, or into the clip group. The primary objective is to test for a relevant reduction in operating time (at least 15 min) when using the clip technique. Since April 2004, 121 of the totally required 420 patients were randomized in five centers.

DISCUSSION

As in all trials the different forms of bias have to be considered, and as in this case, a surgical trial, the role of surgical expertise plays a key role, and will be documented and analyzed separately. This is the first randomized controlled multicenter relevance trial to compare different vessel occlusion techniques in thyroid surgery with adequate power and other detailed information about the design as well as framework. If significant, the results might be generalized and may change the current surgical practice.

Automated analysis of digital fundus autofluorescence images of geographic atrophy in advanced age-related macular degeneration using confocal scanning laser ophthalmoscopy (cSLO)

Background

Fundus autofluorescence (AF) imaging using confocal scanning laser ophthalmoscopy (cSLO) provides an accurate delineation of areas of geographic atrophy (GA).

Automated computer-assisted methods for detecting and removing interfering vessels are needed to support the GA quantification process in longitudinal studies and in reading centres.

Methods

A test tool was implemented that uses region-growing techniques to segment GA areas. An algorithm for illuminating shadows can be used to process low-quality images. Agreement between observers and between three different methods was evaluated by two independent readers in a pilot study. Agreement and objectivity were assessed using the Bland-Altman approach.

Results

The new method (C) identifies vascular structures that interfere with the delineation of GA. Results are comparable to those of two commonly used procedures (A, B), with a mean difference between C and A of -0.67 mm² (95% CI [-0.99, -0.36]), between B and A of -0.81 mm², (95% CI [-1.08, -0.53]), and between C and B of 0.15 mm² (95% CI [-0.12, 0.41]). Objectivity of a method is quantified by the mean difference between observers: A 0.30 mm² (95% CI [0.02, 0.57]), B -0.11 mm² (95% CI [-0.28, 0.10]), and C 0.12 mm² (95% CI [0.02, 0.22]).

Conclusion

The novel procedure is comparable with regard to objectivity and inter-reader agreement to established methods of quantifying GA. It considerably speeds up the lengthy measurement process in AF with well defined GA zones.

Prevalence of hepatitis E virus antibodies in Canadian swine herds and identification of a novel variant of swine hepatitis E virus

Swine hepatitis E virus is a newly identified potentially zoonotic virus from pigs of particular concern for possible direct transmission to a human xenotransplant recipient by organ transplantation. In the present study, prevalence of serum antibodies to hepatitis E virus was examined in Canadian swine herds. A total of 998 serum samples collected from 6-month-old healthy slaughter hogs were examined by enzyme immunoassay and Western blot analysis for antibodies to the recombinant open reading frame 3 (ORF3) protein of hepatitis E virus expressed in Escherichia coli. These samples represented more than 80 different swine production units from five major swine-producing provinces across Canada. From this study, 594 samples (59.4%) were found to be positive for hepatitis E virus antibody. The seroprevalence was higher in Quebec (88.8%) and Ontario (80.1%) than in Alberta and Saskatchewan (38.3%). By PCR using a pair of oligonucleotide primers deduced from the ORF2 sequence of human hepatitis E virus, a specific hepatitis E virus sequence was recovered from feces of pigs. The nucleotide sequence identity between the U.S. swine hepatitis E virus and the Canadian isolate (SK3) was only 85.8%, suggesting that genotypic variations may exist in swine hepatitis E virus in North America. Among 165 serum samples collected from humans in Saskatchewan, 2.4% were found to be positive for antibodies to the hepatitis E virus ORF3 protein. Our data indicate that hepatitis E virus is highly prevalent in commercial swine populations in Canada and support the suggestion that the swine hepatitis E virus may be an important zoonotic agent for humans.

Three components in the light-induced current of the Limulus ventral photoreceptor

1. Light-induced currents were measured in Limulus ventral nerve photoreceptors using a two-electrode voltage clamp. Three kinetically distinct components in the light-induced current could be distinguished by varying the light adaptation state of the photoreceptor and the intensity of the stimulus light. 2. The components could be partly separated by choosing appropriate stimulus intensities and dark adaptation time. Thus the properties of the components could be separately studied. The first component is the first to recover after a light adaptation, appears temporally first in the light-induced response, has the lowest activation threshold and is the smallest. The second component needs a longer time to recover after an adapting illumination and its kinetics differ from that of the other components. Applying a bright stimulus to a dark-adapted cell a third component can be observed late in the response. 3. The time to peak of the first and the third components depended on the stimulus intensity, but not on the dark adaptation time. The time to peak of the second component became shorter the longer the dark adaptation time. For a constant adaptation state the time to the maximum of component 2 was independent, but those of components 1 and 3 were dependent on the membrane voltage. 4. To exclude the possibility of the contribution of voltage-gated currents, light-activated currents were measured at clamp potentials more negative than -50 mV after adding 4-aminopyridine into the bath solution or injecting tetraethyl-ammonium chloride into the cell. The properties of the three components remained unchanged under these conditions. 5. The I-V curve of the first component was flat at negative membrane potentials and had a strong outward rectification at positive membrane potentials. The I-V curve of component 3 showed a negative resistance at potentials more negative than about -30 mV. In contrast, the I-V curve for the second component was always nearly linear. 6. No membrane potential was found where the light-induced current was zero. Instead, current traces close to the reversal potential showed a complex waveform indicating different reversal potentials for the three components. 7. The results indicate that the current components are caused by three different populations of light-sensitive channels. The different activations, deactivations and recovery kinetics of the components suggest that the three types of channels are activated by distinct intracellular transmitters.

Electrogenic Na(+)-Ca2+ exchanger, the link between intra- and extracellular calcium in the Limulus ventral photoreceptor

1. Limulus ventral photoreceptors were injected with Arsenazo III and the internal change in the calcium concentration, [Ca2+]i, was measured under voltage clamp conditions. It is shown that in response to a light flash the rising phase of the [Ca2+]i is independent of the clamp voltage, Vm. This observation is contrary to other results reported in the literature. Experiments are reported that resolve this contradiction (see paragraph 4). 2. The relaxation of the [Ca2+]i after a bright light flash was observed to have a fast and slow phase. A function consisting of the sum of an exponential and a ramp was fitted to the relaxation. The fast phase, characterized by the time constant of the exponential, was observed not to depend on Vm, while the slow phase, characterized by the slope of the ramp, was strongly dependent on Vm. Furthermore the slope of the slow phase is shown to depend on the external Na+ concentration, but not the time constant of the fast phase. 3. In the dark the [Ca2+]i was observed to increase when the cell was depolarized and to decrease when the cell was hyperpolarized. This observation was more pronounced when the cell was continuously illuminated. 4. When the cell was clamped to a depolarizing voltage before illumination of the cell, the maximum of the calcium indicator signal was observed to depend on how long the cell had been clamped before applying the light stimulus. This experiment resolves the contradiction mentioned in paragraph 1. 5. The results presented here are consistent with the interpretation that a Na(+)-Ca2+ exchanger with a stoichiometry greater than 2:1 is the predominant link between intra- and extracellular calcium. Secondly that the light-induced intracellular calcium increase comes from a release by intracellular stores. Finally a measurable uptake of calcium occurs after a light-induced release, possibly by the internal calcium stores. The two-phase recovery of [Ca2+]i after a light flash is interpreted as being a calcium uptake by the internal stores, the fast phase, and removal by the electrogenic Na(+)-Ca2+ exchanger, the slow phase.