Updated core competencies in pharmacoepidemiology to inform contemporary curricula and training for academia, government, and industry

PURPOSE

The first paper to specify the core content of pharmacoepidemiology as a profession was published by an ISPE (International Society for Pharmacoepidemiology) workgroup in 2012 (Jones JK et al. PDS 2012; 21[7]:677-689). Due to the broader and evolving scope of pharmacoepidemiology, ISPE considers it important to proactively identify, update and expand the list of core competencies to inform curricula of education programs; thus, better positioning pharmacoepidemiologists across academic, government (including regulatory), and industry positions. The aim of this project was to update the list of core competencies in pharmacoepidemiology.

METHODS

To ensure applicability of findings to multiple areas, a working group was established consisting of ISPE members with positions in academia, industry, government, and other settings. All competencies outlined by Jones et al. were extracted from the initial manuscript and presented to the working group for review. Expert-based judgments were collated and used to identify consensus. It was noted that some competencies could contribute to multiple groups and could be directly or indirectly related to a group.

RESULTS

Five core domains were proposed: (1) Epidemiology, (2) Clinical Pharmacology, (3) Regulatory Science, (4) Statistics and data science, and (5) Communication and other professional skills. In total, 55 individual competencies were proposed, of which 25 were new competencies. No competencies from the original work were dropped but aggregation or amendments were made where considered necessary.

CONCLUSIONS

While many core competencies in pharmacoepidemiology have remained the same over the past 10 years, there have also been several updates to reflect new and emerging concepts in the field.

Trends in COVID-19 patient characteristics in a large electronic health record database in the United States: A cohort study

Background

Electronic health record (EHR) databases provide an opportunity to facilitate characterization and trends in patients with COVID-19.

Methods

Patients with COVID-19 were identified based on an ICD-10 diagnosis code for COVID-19 (U07.1) and/or a positive SARS-CoV-2 viral lab result from January 2020 to November 2020. Patients were characterized in terms of demographics, healthcare utilization, clinical comorbidities, therapies, laboratory results, and procedures/care received, including critical care, intubation/ventilation, and occurrence of death were described, overall and by month.

Results

There were 393,773 patients with COVID-19 and 56,996 with a COVID-19 associated hospitalization. A greater percentage of patients hospitalized with COVID-19 relative to all COVID-19 cases were older, male, African American, and lived in the Northeast and South. The most common comorbidities before admission/infection date were hypertension (40.8%), diabetes (29.5%), and obesity (23.8%), and the most common diagnoses during hospitalization were pneumonia (59.6%), acute respiratory failure (44.8%), and dyspnea (28.0%). A total of 85.7% of patients hospitalized with COVID-19 had CRP values > 10 mg/L, 75.5% had fibrinogen values > 400 mg/dL, and 76.8% had D-dimer values > 250 ng/mL. Median values for platelets, CRP, lactate dehydrogenase, D-dimer, and fibrinogen tended to decrease from January-March to November. The use of chloroquine/hydroxychloroquine during hospitalization peaked by March (71.2%) and was used rarely by May (5.1%) and less than 1% afterwards, while the use of remdesivir had increased by May (10.0%) followed by dexamethasone by June (27.7%). All-cause mortality was 3.2% overall and 15.0% among those hospitalized; 21.0% received critical care and 16.0% received intubation/ventilation/ECMO.

Conclusions

This study characterizes US patients with COVID-19 and their management during hospitalization over the first eleven months of this disease pandemic.

Ticagrelor or prasugrel in patients with acute coronary syndrome in relation to glomerular filtration rate

Objectives

The aim of this study was to assess the safety and efficacy of ticagrelor versus prasugrel for patients with acute coronary syndrome (ACS) according to their glomerular filtration rate (GFR).

Background

The outcomes of ticagrelor versus prasugrel in patients with ACS according to GFR have not been defined.

Methods

Patients (n=3985) with GFR available were categorized in three groups according to the tertiles of GFR. The primary endpoint was a composite of all-cause death, myocardial infarction and stroke at 1 year.

Results

The primary endpoint occurred significantly more often in patients with low GFR compared to high GFR as well as in patients with low GFR compared to intermediate GFR (picture 1). Patients in the lowest GFR group had significantly higher ischemic and bleeding risks than patients in the intermediate (hazard ratio [HR] 1.93 and 1.68) or high GFR groups (HR 3.52 and 2.96). In the group with low GFR, the primary endpoint occurred in 103 of 677 ticagrelor patients (15.4%) and in 72 of 652 prasugrel patients (11.2%; (HR=1.45, [1.07–1.96], p=.016, picture 2). In addition, each single component of the primary endpoint and stent thrombosis were numerically lower with prasugrel compared with ticagrelor. Occurrence of myocardial infarction was 3.7% with prasugrel compared to 6.6% with ticagrelor (p=0.019). BARC 3–5 bleeding events were similar with ticagrelor and prasugrel (8.8% versus 7.1%, p=0.278). In the intermediate and high GFR group the primary endpoint and bleeding events were similar between prasugrel and ticagrelor.

Conclusions

The incidence of a composite endpoint (all-cause death, myocardial infarction or stroke) occurred less frequently in patients who received prasugrel compared to patients who received ticagrelor in the low GFR population, whereas rate of bleeding events was similar.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Supported by a grant (FKZ 81X1600501) from the German Center for Cardiovascular Research and the Deutsches Herzzentrum München, Germany. Primary endpoint according to GFRLow GFR: Prasugrel versus Ticagrelor

Impact of diabetes on outcome with drug-coated balloons versus drug-eluting stents: the BASKET-SMALL 2 trial

Objectives

To evaluate the impact of diabetes mellitus on 3 year clinical outcome in patients undergoing drug-coated balloon (DCB) or drug-eluting stent (DES) treatment for de-novo lesions.

Background

For the treatment of de-novo coronary small vessel disease DCB are non-inferior to DES regarding clinical outcome up to 3 years.

Methods

In this prespecified analysis of a multicenter, randomized, non-inferiority trial, including 758 patients with de-novo lesions in coronary vessels <3mm who were randomized 1:1 to DCB (n=382) or DES (n=376) and followed over 3 years for major adverse cardiac events (MACE: cardiac death, non-fatal myocardial infarction [MI], and target-vessel revascularization [TVR]), outcome was analyzed regarding the presence or absence of diabetes mellitus.

Results

In non-diabetic patients (n=506) rates of MACE (13.0% vs. 11.5%, hazard ratio [HR] 1.24, 95% confidence interval [CI] 0.73–2.09, p=0.43), cardiac death (2.8% vs. 2.9%, HR 0.97, 95% CI 0.32–2.92, p=0.96), non-fatal MI (5.1% vs. 4.8%, HR 1.00, 95% CI 0.44–2.28, p=0.99), and TVR (8.8% vs. 6.1%, HR 1.64, 95% CI 0.83–3.25, p=0.16) were similar in DCB and DES. In diabetic patients (n=252) rates of MACE (19.3% vs. 22.2%, HR 0.82, 95% CI 0.45–1.48, p=0.51), cardiac death (8.8% vs. 5.9%, HR 2.01, 95% CI 0.76–5.31, p=0.16), non-fatal MI (7.1% vs. 9.8%, HR 0.55, 95% CI 0.21–1.49, p=0.24) were similar in DCB and DES, whereas TVR was significantly lower with DCB compared to DES (9.1% vs. 15.0%, HR 0.40, 95% CI 0.17–0.94, p=0.036). In addition, need for TVR was highest in diabetic patients treated with DES (Picture 1).

Conclusions

The rates of MACE are similar in DCB and DES in de-novo coronary lesions of diabetic and non-diabetic patients. In diabetic patients the need for TVR was significantly lower with DCB compared to DES.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Basel Cardiovascular Research Foundation, and B Braun Medical AG. Picture 1

A study of cancer occurrence in users of mirabegron and antimuscarinic treatments for overactive bladder

OBJECTIVE

This post-authorization safety study (EU PAS Register Number: EUPAS16088) was designed to compare the incidence of cancer outcomes in patients treated with mirabegron versus antimuscarinic medications.

METHODS

Cohorts of mirabegron initiators during 2012-2018 were propensity-score matched to antimuscarinic medication initiators within real-world data sources (Danish National Registers, Swedish National Registers, Clinical Practice Research Datalink [UK], Optum [US], and Humana [US]). Incident cancer cases were identified during follow-up from direct linkage to cancer registers or validated through medical record review or through physician questionnaires. Comparisons of sex-specific composite cancer outcomes (cancer of the lung/bronchus, colon/rectum, melanoma of skin, urinary bladder, non-Hodgkin lymphoma, kidney/renal pelvis, pancreas, prostate in men and breast and uterus in women) were made overall and for person-time in the first year and after the first year following start of treatment, for all ages and for the subgroup ≥65 years.

RESULTS

Among the 80,637 mirabegron initiators matched to 169,885 antimuscarinic medication initiators, 68% were at least 65 years of age and 66% were women. Over 5000 incident cancer cases were observed overall. Incidence rates were higher for men than women for composite and individual cancer outcomes. The pooled fixed effects hazard ratios for composite cancer outcomes (all ages) were 1.05 (95% confidence interval [CI]: 0.98-1.14) for women and 1.06 (95% CI: 0.98-1.14) for men. Results were similar in persons ≥65 years.

CONCLUSIONS

The results suggest no association between mirabegron use and risk of cancer, compared with antimuscarinic medications, in either men or women. Registration: EU PAS Register Number: EUPAS16088.

Use of Bypassing Agents and Risk of Thromboembolic Events in Patients with Haemophilia and Inhibitors

Patients with haemophilia and inhibitors to factors VIII or IX require bypassing therapy. The primary safety concern of bypassing agents is thromboembolism; however, the incidence of thromboembolic adverse events (TAEs) in haemophilia patients with inhibitors remains poorly characterized. The aim of this study was to assess the incidence of TAEs following exposure to bypassing agents in patients with haemophilia. Using U.S. Medicaid database (2000–2010), we identified a cohort of 719 males (mean age: 10 years at cohort entry) with haemophilia A or B and use of either recombinant factor VIIa (rFVIIa) or activated prothrombin complex concentrate (aPCC). Patients were followed up until loss of insurance eligibility, end of study period, or the first occurrence of TAE. Exposure was assessed on as-treated basis, and outcomes were adjudicated through review of healthcare claims. During the observation of a total of 2,823 person-years (py; mean follow-up: 3.9 years), 22 TAEs were identified, leading to incidence rates of 4.2 events (95% confidence interval [CI]: 1.8–8.3) per 1,000 unexposed py; 15.4 events (95% CI: 6.7–30.3) per 1,000 aPCC-exposed py; 18.2 events (95% CI: 8.3–34.6) per 1,000 rFVIIa-exposed py; and 29.7 events (95% CI: 6.1–86.7) per 1,000 py of concomitant exposure to both agents. The results were consistent across sensitivity analyses. In conclusion, we found no difference in the rate of TAEs across agents, but the data are compatible with a possibly increased rate associated with a combination therapy, highlighting the need for continuing safety monitoring through prospective registries or observational data.

Development of Deep and Upper Neuronal Layers in the Domestic Cat, Sheep and Pig Neocortex

The neocortex plays a key role in cognition, volitional motor control and sensory perception and has undergone tremendous expansion during evolution. The mature neocortex consists of radially aligned neurons that are arranged in six layers. Layers II-VI are often split into two groups: deep and upper layers, both building up the so-called cortical plate during embryonic and foetal development. So far cortical neurogenesis, including the generation of deep and upper layers, has mostly been studied in laboratory rodents and primates. However, precise data for most companion animals are lacking. This study determined the main period of neurogenesis, specifically the timing of deep and upper layer generation, in the developing domestic cat, pig and sheep neocortex using immunohistochemistry for specific neuronal markers, that is Tbr1 and Brn2. We found that the general sequence of neural events is preserved among cat, pig, sheep and other mammalian species. However, we observed differences in the timing of the overall cortical neurogenic period and occurrence of distinct neural events when these three species were compared. Moreover, our data provide further evidence that the cortical neurogenic period and gestation length might be tightly related. Together, these data expand our current understanding of neocortex development and are important for future studies investigating neocortex development and expansion especially in companion animals.

Does knee replacement surgery for osteoarthritis improve survival? The jury is still out

BACKGROUND

The relation of knee replacement (KR) surgery to all-cause mortality has not been well established owing to potential biases in previous studies. Thus, we aimed to examine the relation of KR to mortality risk among patients with knee osteoarthritis (OA) focusing on identifying biases that may threaten the validity of prior studies.

METHODS

We included knee OA subjects (ages 50-89 years) from The Health Improvement Network, an electronic medical records database in the UK. Risk of mortality among KR subjects was compared with propensity score-matched non-KR subjects. To explore residual confounding bias, subgroup analyses stratified by age and propensity scores were performed.

RESULTS

Subjects with KR had 28% lower risk of mortality than non-KR subjects (HR 0.72, 95% CI 0.66 to 0.78). However, when stratified by age, protective effect was noted only in older age groups (>63 years) but not in younger subjects (≤63 years). Further, the mortality rate among KR subjects decreased as candidacy (propensity score) for KR increased among subjects with KR, but no such consistent trend was noted among non-KR subjects.

CONCLUSIONS

While a protective effect of KR on mortality cannot be ruled out, findings of lower mortality among older KR subjects and those with higher propensity scores suggest that prognosis-based selection for KR may lead to intractable confounding by indication; hence, the protective effect of KR on all-cause mortality may be overestimated.

Blood pressure and neuropsychological test performance in healthy postmenopausal women

PURPOSE

To study the association between blood pressure and neuropsychological test performance in healthy postmenopausal women.

METHODS

Data from 88 healthy postmenopausal women aged 46-73 years, who were not experiencing hot flashes, and who had participated in a prior drug trial, were analyzed to find whether baseline blood pressure was associated with impaired performance on neuropsychological testing done at 3 follow-up visits separated by 4 weeks. Factor analysis was used to reduce the dimensions of neuropsychological test performance. Mixed linear modeling was used to evaluate the association between baseline blood pressure and repeatedly measured neuropsychological test performance at follow-up in a complete case analysis (n=53). In a sensitivity analysis (n=88), multiple-imputation using the Markov Chain Monte Carlo method was used to account for missing data (blood pressure results) for some visits.

RESULTS

The variables recording neuropsychological test performance were reduced to two main factors (Factor 1=selective attention; Factor 2=complex processing). In the complete case analysis, the association between a 20-mmHg increase in diastolic blood pressure and Factor 1 remained statistically significant after adjusting for potential confounders, before adjusting for systolic blood pressure (slope=0.60; 95%CI=0.04,1.16), and after adjusting for systolic blood pressure (slope=0.76; 95%CI=0.06, 1.47). The positive slopes indicated an increase in the time spent performing a given task (i.e., a decrease in neuropsychological test performance). No other significant associations were found between systolic blood pressure and either factor. The results did not materially change after applying the multiple-imputation method.

CONCLUSIONS

An increase in diastolic blood pressure was associated with a decrease in neuropsychological test performance among older healthy postmenopausal women experiencing hot flashes.

Incidence of progressive multifocal leukoencephalopathy in patients without HIV

OBJECTIVE

To estimate the incidence rate (IR) of progressive multifocal leukoencephalopathy (PML) in patients without HIV.

METHODS

Within a large US health insurer database between January 2000 and June 2008, we conducted a retrospective observational study. We identified people with autoimmune diseases, chronic lymphocytic leukemia (CLL), non-Hodgkin lymphoma (NHL), or history of bone marrow or solid organ transplantation, and a general population cohort. We developed a PML case-finding algorithm and validated PML diagnoses in medical charts.

RESULTS

There were 138,469 patients with autoimmune diseases, 25,706 with NHL or CLL, and 8,778 with transplants. Among 699 people who met screening criteria for potential PML, 89 had a claim diagnosis of PML (International Classification of Diseases-9 046.3). Medical records were sought for 24 patients without HIV, and 6 had confirmed PML upon review of medical records. The PML IR was 2.4 (95% confidence interval [CI] 0.06-13.18) in the systemic lupus erythematosus cohort and 10.8 (95% CI 0.27-60.39) in the autoimmune vasculitis cohort per 100,000 person-years. In the NHL and CLL cohorts, the IR was 8.3 (95% CI 1.71-24.24) and 11.1 (0.28-61.74) per 100,000 person-years. The IR among patients with bone marrow transplantation was 35.4 per 100,000 person-years (95% CI 0.90-197.29). There were no cases of PML among patients with rheumatoid arthritis (95% CI 0.0-2.24), multiple sclerosis (95% CI 0.0-5.24), Sjögren disease (95% CI 0.0-21.84), or solid organ transplantation (95% CI 0.0-26.81).

CONCLUSIONS

In this large population-based investigation of PML with thorough case finding and a known source population, the IR of medical record-confirmed PML was rare in non-HIV patient cohorts.

Strategies to mitigate diffuse phosphorus pollution during rewetting of fen peat soils

The cultivation of fen peat soils (Eutric Histosols) for agricultural purposes, started in Europe about 250 years ago, resulting in decreased soil fertility, increased oxidation of peat and corresponding greenhouse gas fluxes to the atmosphere, nutrient transfer to aquatic ecosystems and losses in total area of the former native wetlands. To prevent these negative environmental effects set-aside programs and rewetting measures were promoted in recent years. Literature results and practical experiences showed that large scale rewetting of intensively used agricultural Histosols may result in mobilisation of phosphorus (P), its transport to adjacent surface waters and an accelerated eutrophication. The paper summarises results from an international European Community sponsored research project and demonstrates how results obtained at different scales and from different scientific disciplines were compiled to derive a strategy to carry out rewetting measures. Based on this findings a simple decision support system (DSS) for a hydrologically sensitive area in the Droemling catchment in north-eastern Germany was developed and since 2005 practically used to prevent freshwater resources from non point P pollution.

A phase II clinical trial of ZD1839 (gefitinib) in combination with docetaxel as first-line treatment in patients with advanced breast cancer

1059

Background: We conducted a phase II multi-institutional trial of gefitinib and docetaxel as first-line treatment in patients with metastatic breast cancer. The primary objectives were to determine the clinical benefit rate (defined as the proportion of patients who experienced confirmed complete response or partial response or who had stable disease for at least 24 weeks) and the toxicity profile of the combination treatment. Methods: All patients had histologically confirmed breast cancer with metastatic disease. They may have received adjuvant chemotherapy, but no prior docetaxel or prior chemotherapy for metastatic disease. Patients received gefitinib 250 mg once daily and docetaxel 75 mg/m2 every 3 weeks, until tumor progression, toxicity or other reasons for discontinuation. Results: Between April 2003 and September 2004, 33 patients were enrolled at 11 participating institutions. Patients received a median of 5 cycles of treatment. The clinical benefit rate was 51.5% (95% CI: 33.5% - 69.2%). There was 1 confirmed complete response and 12 confirmed partial responses, and the overall objective response rate was 39.4% (95% CI: 22.9% - 57.9%). Four patients had stable disease for = 24 weeks. The median duration of clinical benefit was 10.9 months (95% CI: 6.0 - 17.6 months). The most common reason for study discontinuation was disease progression (16 patients), followed by toxicity (10 patients). Toxicities were mainly attributable to docetaxel, including = grade 3 neutropenia in 43% of patients. Conclusion: The combination of gefitinib and docetaxel is an active regimen in patients with previously untreated metastatic breast cancer. Further work is needed to determine which subset of patients with breast cancer will benefit from gefitinib.

No significant financial relationships to disclose.

Morphometric analysis of the retina from horses infected with the Borna disease virus

Borna disease (BD) is a fatal disorder of horses, often characterized by blindness. Although degeneration of retinal neurons has been demonstrated in a rat model, there are controversial data concerning whether a similar degeneration occurs in the retina of infected horses. To investigate whether BD may cause degeneration of photoreceptors and possibly of other neuronal cells at least at later stages of the disease, we performed a detailed quantitative morphologic study of retinal tissue from Borna-diseased horses. BD was diagnosed by detection of pathognomonic Joest-Degen inclusion bodies in the postmortem brains. Paraffin sections of paraformaldehyde-fixed retinae were used for histologic and immunohistochemical stainings. Numbers of neurons and Müller glial cells were counted, and neuron-to-Müller cell ratios were calculated. Among tissues from 9 horses with BD, we found retinae with strongly altered histologic appearance as well as retinae with only minor changes. The neuron-to-Müller cell ratio for the whole retina was significantly smaller in diseased animals (8.5 +/- 0.4; P < .01) as compared with controls (17.6 +/- 0.8). It can be concluded that BD in horses causes alterations of the retinal histology of a variable degree. The study provides new data about the pathogenesis of BD concerning the retina and demonstrates that a loss of photoreceptors may explain the observed blindness in infected horses.

Two-dimensional hard x-ray beam compression by combined focusing and waveguide optics

A two-dimensionally confining x-ray channel waveguide structure is combined with a high gain Kirkpatrick-Baez prefocusing mirror system yielding a hard x-ray beam with a cross section of 25 x 47 nm(2) (FWHM). Unlike the previously employed resonant beam coupling scheme, the incoming beam is coupled in from the front side of the waveguide and the waveguided beam is no longer accompanied by spurious reflected or transmitted beams. The field distribution in the waveguide channel has been calculated numerically. The calculated transmission and far-field intensity pattern are in good agreement with the experimental results.

Electrophysiological alterations and upregulation of ATP receptors in retinal glial Müller cells from rats infected with the Borna disease virus

Infection with the neurotropic Borna disease virus (BDV) causes an immune-mediated neurological disease in a broad range of species. In addition to encephalitis, BDV-infected Lewis rats develop a retinitis histologically characterized by the loss of most retinal neurons. By contrast, the dominating retinal macroglia, the Müller cells, do not degenerate. It is known from several models of neurodegeneration that glial cells may survive but undergo significant alterations of their physiological parameters. This prompted us to study the electrophysiology and ATP-induced changes of intracellular Ca(2+)-concentration ([Ca(2+)](i)) in Müller cells from BDV-infected rat retinae. Freshly isolated cells were used for whole-cell patch-clamp recordings. Whereas neither zero current potentials nor membrane resistances showed significant alterations, the membrane capacitance increased in cells from BDV-infected rats during survival times of up to 8 months. This process was accompanied by a decrease in K(+) current densities. Müller cells from BDV-infected rats were characterized by expression of a prominent fast-inactivating A-type K(+) current which was rarely found in control cells. Moreover, the number of cells displaying Na(+) currents was slightly increased after BDV-infection. ATP evoked increases in [Ca(2+)](i) in Müller cells within retinal wholemounts of both control and BDV-infected animals. However, the number of ATP-responding isolated cells increased from 24% (age-matched controls) to 78% (cells from animals > or =18 weeks after infection). We conclude that in BDV-induced retinopathy, reactive rat Müller cells change their physiological parameters but these changes are different from those in Müller cells during proliferative vitreoretinopathy in man and rabbit.

Changes of the organotypic retinal organization in Borna virus-infected Lewis rats

Retinae of Borna disease virus (BDV)-infected Lewis rats were investigated with emphasis on long-term changes in organotypic tissue organization and glia-neuron relationship. Virus inoculation was attained via intracerebral BDV injection. Following survival times ranging between two and eight months, the retinal thickness was reduced up to one third of that of controls. Photoreceptor segments were completely extinguished and the number of neurons was dramatically reduced. The typical laminar organization of the retina was largely dissolved. Electron microscopy revealed severe spongy degeneration. Large numbers of activated microglia and macrophages were found, both cell types performing very active phagocytosis. The microglial cells expressed an extraordinary phenotype as characterized by large numbers of processes, with some of them penetrating the endfeet of Müller cells and others establishing highly complex interdigitations with vacuolized swellings and endings of neuronal processes. Müller cells were not reduced in number but displayed clear indications of gliosis such as alterations in the immunoreactivity for filament proteins and glutamine synthetase, significantly thickened stem processes, and an altered pattern of K(+) currents in patch-clamp recordings. These findings demonstrate for the first time long-term neuron-glia interactions in the retina of BDV-infected rats. Moreover, the data contribute to our knowledge on structural and functional alterations accompanying persisting virus infection in the central nervous system.

Facilitation of artificial retinal detachment for macular translocation surgery tested in rabbit

PURPOSE

For macular translocation surgery, the native attached retina has to be detached either locally or completely. Although different surgical techniques are used, there is a general search for supporting procedures that facilitate and accelerate the retinal detachment.

METHODS

Pars plana vitrectomies were performed in pigmented rabbits. In all experimental groups, a local retinal detachment was created by infusing the test solution with a thin glass micropipette attached to a glass syringe. In control animals a standard balanced salt solution was used at room temperature, in combination with a standard vitrectomy light source. In two test groups, a calcium- and magnesium-free solution was used for the vitrectomy, under illumination by a standard light source in group I (solution at room temperature) and group II (solution heated up to body temperature). In group III the rabbits were dark-adapted for half an hour, and then, during surgery, a red filter was used in front of the light source (standard balanced salt solution at room temperature). After the rabbits were killed at the end of surgery, the adherence of the retinal pigment epithelium (RPE) to the neural retina in the detachment area was quantified microscopically, and the morphologic integrity of the detached retinal tissue was examined by light and electron microscopy. No electrophysiology was performed.

RESULTS

In all four groups, it was possible to detach the retina. The maximum adherence of the RPE cells to the neural retina was observed in the control group. Virtually no decrease in adherence was found in test group II (36 degrees C solution without calcium and magnesium), whereas a significant decrease was seen in both group I (calcium- and magnesium-free solution at room temperature) and group III (dark adaptation-red light technique; standard balanced salt solution at room temperature). In none of the experimental groups was any obvious damage of the retinal structure observed, even after exposure to the test solutions for 60 minutes.

CONCLUSIONS

Both dark adaptation (red illumination) and the use of a calcium chloride- and magnesium chloride-free solution (at room temperature) can facilitate retinal detachment in macular translocation surgery. Both techniques are proposed as a gentle support for the operation, because they protect an intact RPE cell layer and do not cause retinal damage at the ultrastructural level.

Retinal pigment epithelium melanin granules are phagocytozed by Müller glial cells in experimental retinal detachment

The ability of retinal Müller glial cells to perform phagocytosis in vivo is studied in a rabbit model of experimental retinal detachment where pigment epithelial cells are occasionally detached together with the neural retina. While macrophages and/or microglial cells phagocytoze most of the cellular debris at the sclerad surface of the detached retinae, some Müller cells accumulate melanin granules. The granules are virtually intact at the ultrastructural level, and are surrounded by a membrane. They are often located close to the sclerad end of the cells, but some are distributed throughout the outer stem process up to the soma. It is concluded that rabbit Müller cells in vivo are capable of phagocytosis and of transporting the phagocytozed material within their cytoplasm.

Laser scanning and electron microscopic evidence for rapid and specific in vivo labelling of cholinergic neurons in the rat basal forebrain with fluorochromated antibodies

Recently developed methods for the selective labelling of cholinergic basal forebrain neurons containing the low-affinity neurotrophin receptor p75 (p75(NTR)) in vivo and in vitro are based on carbocyanine 3 (Cy3)-tagged antibodies directed against p75(NTR). The present study focuses on the maintenance of this neuronal label after injection of such fluorescent antibodies into the cerebral ventricle. One, 3, and 10 days after injection this marker exclusively stains neurons immunoreactive for the cholinergic markers choline acetyltransferase and vesicular acetylcholine transporter in the rat medial septum, diagonal band and nucleus basalis. Thirty days after injection the in vivo labelling was nearly abolished. Predominant labelling of lysosomes was shown by electron microscopic analysis following photoconversion of the Cy3-label to an electron-dense reaction product. The pre-labelling of cholinergic neurons might facilitate pharmacological and electrophysiological approaches in living slices and cell culture systems as well as detailed investigations focused on the transport of neurotrophins in vivo and in animals with experimentally altered p75(NTR) expression.

Gadopentetate dimeglumine as a contrast agent in common carotid arteriography

BACKGROUND AND PURPOSE

Despite improvements in noninvasive imaging, some patients with contraindications to iodine-based contrast material still require angiography for the evaluation of carotid stenosis. Our aim was to assess the utility of gadopentetate dimeglumine as an intraarterial contrast agent in common carotid angiography.

METHODS

Twelve patients with suspected carotid artery stenosis were enrolled in the study. In addition to the standard injection sequences with iohexol, common carotid arteriograms were obtained after administration of gadopentetate dimeglumine. Neurologic status and vital signs were monitored during and for 6 hours after the examination. For each injection, five independent observers, blinded to the contrast agent used, measured the percentage of carotid stenosis and assessed their confidence in grading the stenosis, the overall quality of the examination, and, in cases of decreased quality, the reason(s) for it. Statistical analysis was done with paired and unpaired t-tests with equal variances.

RESULTS

No patient had an adverse clinical outcome, and measurements of carotid artery stenosis showed no statistically significant differences between the gadopentetate dimeglumine and iohexol examinations. Overall image quality and observer confidence in measurements of stenosis on the gadolinium-based studies were slightly but significantly lower than those of identical iodine-based studies.

CONCLUSION

Gadopentetate dimeglumine may be an alternative to iodine in selected patients undergoing carotid angiography. Although overall image quality of the gadolinium studies is slightly inferior to that of the iohexol studies, measurements of carotid artery stenosis are similar for the two examinations.

Neuron-glia interactions in the rat retina infected by Borna disease virus

Neuron-glia interactions in the Borna disease virus (BDV)-infected rat retina were investigated with emphasis on the ultrastructural characterization of degenerative alterations in the ganglion cell and photoreceptor layer. Immuno- and cytochemical techniques were applied to label microglia, macrophages and Müller (macroglial) cells. Four weeks after intracerebral infection of adult rats, the total thickness of the retina was considerably diminished, primarily due to the loss of photoreceptor segments and ganglion cells. A gradual reduction of both plexiform layers was also observed. There was a remarkable increase in the number of microglial cells, predominantly in the ganglion cell and the inner plexiform layers. Ultrastructural analysis confirmed that microglia, but also macrophages, were involved in phagocytosis accompanying severe neuronal degeneration in the ganglion cell and the photoreceptor layer. In contrast, Müller cells showed moderate morphological and cytochemical alterations, indicating that Müller cells play only a minor role in early stages of BDV-induced retinitis. Monitoring neuron-glia interactions in BDV-induced retinopathy, combined with the application of different protocols of immunosuppression effecting the BDV virus and/or the microglia, might help to establish specific strategies to suppress BDV-induced neuronal degeneration.

Selective in vivo fluorescence labelling of cholinergic neurons containing p75(NTR) in the rat basal forebrain

The cholinergic system of the rat basal forebrain is used as a model for the homologous region in humans which is highly susceptible to neuropathological alterations as in Alzheimer's disease. Cholinergic cells in the basal forebrain express the low-affinity neurotrophin receptor p75NTR. This has been utilized for selective immunolesioning of cholinergic neurons after internalization of an immunotoxin composed of anti-p75NTR and the ribosome-inactivating toxin saporin. However, the goal of many studies may be not the lesion, but the identification of cholinergic cells after other experimentally induced alterations in the basal forebrain. Therefore, a novel cholinergic marker was prepared by conjugating the monoclonal antibody 192IgG directed against p75NTR with the bright red fluorochrome carbocyanine 3 (Cy3). Three days after intraventricular injection of Cy3-192IgG the fluorescence microscopic analysis revealed a pattern of Cy3-labelled cells matching the distribution of cholinergic neurons. Apparently the marker was internalized within complexes of p75NTR and Cy3-192IgG which were then retrogradely transported to the cholinergic perikarya of the basal forebrain. In addition to the even labelling of somata, a strong punctate-like Cy3-immunofluorescence was seen in structures resembling lysosomes. The specificity of the in vivo staining was proven by subsequent immunolabelling of choline acetyltransferase (ChAT) with green fluorescent Cy2-tagged secondary antibodies. In the medial septum, the diagonal band and the nucleus basalis only cholinergic neurons were marked by Cy3-192IgG. In parallel experiments, digoxigenylated 192IgG was not detectable within cholinergic basal forebrain neurons after intraventricular injection. Presumably, this modified antibody could not be internalized. On the other hand, digoxigenylated 192IgG was found to be an excellent immunocytochemical marker for p75NTR as shown by double labelling including highly sensitive mouse antibodies directed against ChAT. Based on the present findings, future applications of the apparently non-toxic Cy3-192IgG and other antibodies for fluorescent in vivo and in vitro labelling are discussed.