Divergent abiotic spectral pathways unravel pathogen stress signals across species.

Plant pathogens pose increasing threats to global food security, causing yield losses that exceed 30% in food-deficit regions. Xylella fastidiosa (Xf) represents the major transboundary plant pest and one of the world's most damaging pathogens in terms of socioeconomic impact. Spectral screening methods are critical to detect non-visual symptoms of early infection and prevent spread. However, the subtle pathogen-induced physiological alterations that are spectrally detectable are entangled with the dynamics of abiotic stresses. Here, using airborne spectroscopy and thermal scanning of areas covering more than one million trees of different species, infections and water stress levels, we reveal the existence of divergent pathogen- and host-specific spectral pathways that can disentangle biotic-induced symptoms. We demonstrate that uncoupling this biotic-abiotic spectral dynamics diminishes the uncertainty in the Xf detection to below 6% across different hosts. Assessing these deviating pathways against another harmful vascular pathogen that produces analogous symptoms, Verticillium dahliae, the divergent routes remained pathogen- and host-specific, revealing detection accuracies exceeding 92% across pathosystems. These urgently needed hyperspectral methods advance early detection of devastating pathogens to reduce the billions in crop losses worldwide.

Detection of Xylella fastidiosa in almond orchards by synergic use of an epidemic spread model and remotely sensed plant traits.

The early detection of Xylella fastidiosa (Xf) infections is critical to the management of this dangerous plan pathogen across the world. Recent studies with remote sensing (RS) sensors at different scales have shown that Xf-infected olive trees have distinct spectral features in the visible and infrared regions (VNIR). However, further work is needed to integrate remote sensing in the management of plant disease epidemics. Here, we research how the spectral changes picked up by different sets of RS plant traits (i.e., pigments, structural or leaf protein content), can help capture the spatial dynamics of Xf spread. We coupled a spatial spread model with the probability of Xf-infection predicted by a RS-driven support vector machine (RS-SVM) model. Furthermore, we analyzed which RS plant traits contribute most to the output of the prediction models. For that, in almond orchards affected by Xf (n = 1426 trees), we conducted a field campaign simultaneously with an airborne campaign to collect high-resolution thermal images and hyperspectral images in the visible-near-infrared (VNIR, 400-850 nm) and short-wave infrared regions (SWIR, 950-1700 nm). The best performing RS-SVM model (OA = 75%; kappa = 0.50) included as predictors leaf protein content, nitrogen indices (NIs), fluorescence and a thermal indicator (Tc), alongside pigments and structural parameters. Leaf protein content together with NIs contributed 28% to the explanatory power of the model, followed by chlorophyll (22%), structural parameters (LAI and LIDFa), and chlorophyll indicators of photosynthetic efficiency. Coupling the RS model with an epidemic spread model increased the accuracy (OA = 80%; kappa = 0.48). In the almond trees where the presence of Xf was assayed by qPCR (n = 318 trees), the combined RS-spread model yielded an OA of 71% and kappa = 0.33, which is higher than the RS-only model and visual inspections (both OA = 64-65% and kappa = 0.26-31). Our work demonstrates how combining spatial epidemiological models and remote sensing can lead to highly accurate predictions of plant disease spatial distribution.

Chlorophyll content estimation in an open-canopy conifer forest with Sentinel-2A and hyperspectral imagery in the context of forest decline.

With the advent of Sentinel-2, it is now possible to generate large-scale chlorophyll content maps with unprecedented spatial and temporal resolution, suitable for monitoring ecological processes such as vegetative stress and/or decline. However methodological gaps exist for adapting this technology to heterogeneous natural vegetation and for transferring it among vegetation species or plan functional types. In this study, we investigated the use of Sentinel-2A imagery for estimating needle chlorophyll (Ca+b) in a sparse pine forest undergoing significant needle loss and tree mortality. Sentinel-2A scenes were acquired under two extreme viewing geometries (June vs. December 2016) coincident with the acquisition of high-spatial resolution hyperspectral imagery, and field measurements of needle chlorophyll content and crown leaf area index. Using the high-resolution hyperspectral scenes acquired over 61 validation sites we found the CI chlorophyll index R750/R710 and Macc index (which uses spectral bands centered at 680 nm, 710 nm and 780 nm) had the strongest relationship with needle chlorophyll content from individual tree crowns (r2 = 0.61 and r2 = 0.59, respectively; p < 0.001), while TCARI and TCARI/OSAVI, originally designed for uniform agricultural canopies, did not perform as well (r2 = 0.21 and r2 = 0.01, respectively). Using lower-resolution Sentinel-2A data validated against hyperspectral estimates and ground truth needle chlorophyll content, the red-edge index CI and the Sentinel-specific chlorophyll indices CI-Gitelson, NDRE1 and NDRE2 had the highest accuracy (with r2 values >0.7 for June and >0.4 for December; p < 0.001). The retrieval of needle chlorophyll content from the entire Sentinel-2A bandset using the radiative transfer model INFORM yielded r2 = 0.71 (RMSE = 8.1 µg/cm2) for June, r2 = 0.42 (RMSE = 12.2 µg/cm2) for December, and r2 = 0.6 (RMSE = 10.5 µg/cm2) as overall performance using the June and December datasets together. This study demonstrates the retrieval of leaf Ca+b with Sentinel-2A imagery by red-edge indices and by an inversion method based on a hybrid canopy reflectance model that accounts for tree density, background and shadow components common in sparse forest canopies.

Previsual symptoms of Xylella fastidiosa infection revealed in spectral plant-trait alterations.

Plant pathogens cause significant losses to agricultural yields and increasingly threaten food security1, ecosystem integrity and societies in general2-5. Xylella fastidiosa is one of the most dangerous plant bacteria worldwide, causing several diseases with profound impacts on agriculture and the environment6. Primarily occurring in the Americas, its recent discovery in Asia and Europe demonstrates that X. fastidiosa's geographic range has broadened considerably, positioning it as a reemerging global threat that has caused socioeconomic and cultural damage7,8. X. fastidiosa can infect more than 350 plant species worldwide9, and early detection is critical for its eradication8. In this article, we show that changes in plant functional traits retrieved from airborne imaging spectroscopy and thermography can reveal X. fastidiosa infection in olive trees before symptoms are visible. We obtained accuracies of disease detection, confirmed by quantitative polymerase chain reaction, exceeding 80% when high-resolution fluorescence quantified by three-dimensional simulations and thermal stress indicators were coupled with photosynthetic traits sensitive to rapid pigment dynamics and degradation. Moreover, we found that the visually asymptomatic trees originally scored as affected by spectral plant-trait alterations, developed X. fastidiosa symptoms at almost double the rate of the asymptomatic trees classified as not affected by remote sensing. We demonstrate that spectral plant-trait alterations caused by X. fastidiosa infection are detectable previsually at the landscape scale, a critical requirement to help eradicate some of the most devastating plant diseases worldwide.

Understanding the temporal dimension of the red-edge spectral region for forest decline detection using high-resolution hyperspectral and Sentinel-2a imagery.

The operational monitoring of forest decline requires the development of remote sensing methods that are sensitive to the spatiotemporal variations of pigment degradation and canopy defoliation. In this context, the red-edge spectral region (RESR) was proposed in the past due to its combined sensitivity to chlorophyll content and leaf area variation. In this study, the temporal dimension of the RESR was evaluated as a function of forest decline using a radiative transfer method with the PROSPECT and 3D FLIGHT models. These models were used to generate synthetic pine stands simulating decline and recovery processes over time and explore the temporal rate of change of the red-edge chlorophyll index (CI) as compared to the trajectories obtained for the structure-related Normalized Difference Vegetation Index (NDVI). The temporal trend method proposed here consisted of using synthetic spectra to calculate the theoretical boundaries of the subspace for healthy and declining pine trees in the temporal domain, defined by CItime=n/CItime=n+1 vs. NDVItime=n/NDVItime=n+1. Within these boundaries, trees undergoing decline and recovery processes showed different trajectories through this subspace. The method was then validated using three high-resolution airborne hyperspectral images acquired at 40 cm resolution and 260 spectral bands of 6.5 nm full-width half-maximum (FWHM) over a forest with widespread tree decline, along with field-based monitoring of chlorosis and defoliation (i.e., 'decline' status) in 663 trees between the years 2015 and 2016. The temporal rate of change of chlorophyll vs. structural indices, based on reflectance spectra extracted from the hyperspectral images, was different for trees undergoing decline, and aligned towards the decline baseline established using the radiative transfer models. By contrast, healthy trees over time aligned towards the theoretically obtained healthy baseline. The applicability of this temporal trend method to the red-edge bands of the MultiSpectral Imager (MSI) instrument on board Sentinel-2a for operational forest status monitoring was also explored by comparing the temporal rate of change of the Sentinel-2-derived CI over areas with declining and healthy trees. Results demonstrated that the Sentinel-2a red-edge region was sensitive to the temporal dimension of forest condition, as the relationships obtained for pixels in healthy condition deviated from those of pixels undergoing decline.

Unmanned aerial platform-based multi-spectral imaging for field phenotyping of maize.

BACKGROUND: Recent developments in unmanned aerial platforms (UAP) have provided research opportunities in assessing land allocation and crop physiological traits, including response to abiotic and biotic stresses. UAP-based remote sensing can be used to rapidly and cost-effectively phenotype large numbers of plots and field trials in a dynamic way using time series. This is anticipated to have tremendous implications for progress in crop genetic improvement. RESULTS: We present the use of a UAP equipped with sensors for multispectral imaging in spatial field variability assessment and phenotyping for low-nitrogen (low-N) stress tolerance in maize. Multispectral aerial images were used to (1) characterize experimental fields for spatial soil-nitrogen variability and (2) derive indices for crop performance under low-N stress. Overall, results showed that the aerial platform enables to effectively characterize spatial field variation and assess crop performance under low-N stress. The Normalized Difference Vegetation Index (NDVI) data derived from spectral imaging presented a strong correlation with ground-measured NDVI, crop senescence index and grain yield. CONCLUSION: This work suggests that the aerial sensing platform designed for phenotyping studies has the potential to effectively assist in crop genetic improvement against abiotic stresses like low-N provided that sensors have enough resolution for plot level data collection. Limitations and future potential uses are also discussed.

[Best practices for the safe use of parenteral nutrition multi-chamber bags. Spanish Society of Hospital Pharmacist's Clinical Nutrition Group]. / Buenas prácticas para el uso seguro de las bolsas tricamerales de nutrición parenteral.

Patient security is one of the key aspects of the Health-System. Parenteral Nutrition is included in the ISMP's list of high-alert medication, being its appropiate use an essential element in maximizing effectiviness while minimizing the potential risk of errors associated with its use. Multi-chamber bags offer several advantages versus pharmacy bespoke bags. However, their apparent simplicity may induce to misuse, asuming their use requires limited consideration, thus increasing the risk of potential errors. For this reason, the Spanish Society of Hospital Pharmacist's Clinical Nutrition Group considered it essential to develop a list of safety practices regarding the use of parenteral nutrition multi-chamber bags. These recommendations are based on practices globally accepted to diminish errors in PN therapy.

La seguridad del paciente es un aspecto clave de la asistencia sanitaria. La Nutrición Parenteral está incluida en la lista de medicamentos de alto riesgo del ISMP, siendo su uso apropiado un elemento esencial para maximizar su efectividad y minimizar el riesgo potencial de errores asociados con su empleo. Las bolsas tricamerales presentan numerosas ventajas frente a las elaboradas en los Servicios de Farmacia. Sin embargo, su aparente simplicidad puede inducir a un uso inadecuado de las mismas, al asumir que su utilización requiere considerar menos aspectos, incrementando con ello el riesgo potencial de errores. Por este motivo, el Grupo de Nutrición Clínica de la SEFH consideró necesario elaborar una relación de buenas prácticas para el uso seguro de las bolsas tricamerales de NP. Estas recomendaciones están basadas en prácticas globalmente aceptadas para disminuir los errores con el empleo de NP.

[Subacute care of stroke-affected patients. Satisfaction and results]. / Atención subaguda al paciente con ictus. Satisfacción y resultados.

OBJECTIVE: To determine the satisfaction of the stroke inpatients and their caregivers in Rehabilitation Service and to analyze the effectiveness, social risk, and discharge destination. MATERIAL AND METHOD: Prospective longitudinal cohort multicenter study. An analysis was made of the social risk (Gijón Scale), co-morbidity (Charlson Index), disability (Barthel Index), effectiveness of the rehabilitation treatment, satisfaction (Pound Questionnaire) and discharge destination of 241 patients. An evaluation was also made on 119 caregivers 6 months post-stroke, recording age, family relationship, time care-giving, satisfaction with the information/training, and accessibility to the rehabilitation team. RESULTS: The patient profile is a 71 year-old male, with low/intermediate social risk, high co-morbidity and total/severe dependence, with 27.1% living alone. Almost all (96.6%) of the patients claimed to be satisfied/very satisfied with the treatment, with satisfaction with the recovery being lower (80.3%). The effectiveness was 32.5 ± 20.4. Home was the discharge destination of 81.7% of the patients.The average age of the caregivers was 58.8 ± 12.3 years, and 73.9% were women. The time dedicated to care-giving was over 6 hours per day in the 62% of the cases. Being satisfied/very satisfied with the received information was recorded by 89.9% of the caregivers. CONCLUSIONS: Patients admitted for stroke rehabilitation achieve significant functional gain during hospitalization and return to their homes in most cases. The satisfaction with the rehabilitation treatment and received information is high. The training of the caregiver is an aspect that needs improving.

Automatic identification of agricultural terraces through object-oriented analysis of very high resolution DSMs and multispectral imagery obtained from an unmanned aerial vehicle.

Agricultural terraces are features that provide a number of ecosystem services. As a result, their maintenance is supported by measures established by the European Common Agricultural Policy (CAP). In the framework of CAP implementation and monitoring, there is a current and future need for the development of robust, repeatable and cost-effective methodologies for the automatic identification and monitoring of these features at farm scale. This is a complex task, particularly when terraces are associated to complex vegetation cover patterns, as happens with permanent crops (e.g. olive trees). In this study we present a novel methodology for automatic and cost-efficient identification of terraces using only imagery from commercial off-the-shelf (COTS) cameras on board unmanned aerial vehicles (UAVs). Using state-of-the-art computer vision techniques, we generated orthoimagery and digital surface models (DSMs) at 11 cm spatial resolution with low user intervention. In a second stage, these data were used to identify terraces using a multi-scale object-oriented classification method. Results show the potential of this method even in highly complex agricultural areas, both regarding DSM reconstruction and image classification. The UAV-derived DSM had a root mean square error (RMSE) lower than 0.5 m when the height of the terraces was assessed against field GPS data. The subsequent automated terrace classification yielded an overall accuracy of 90% based exclusively on spectral and elevation data derived from the UAV imagery.

Rehabilitation efficiency and destination on discharge after stroke.

BACKGROUND: Predicting functional recovery of patients is key for setting the objectives of the rehabilitation programme and making decisions on their destination on discharge. Many variables have an impact on disability and quality of life after stroke, including patient age, comorbidity, severity of neurological deficit, state of mind and social risk. Accordingly, it is also essential from a care perspective to optimise the functional recovery and efficiency of rehabilitation programmes, exploring their relationship with these variables. AIM: To analyze the efficiency of post-stroke rehabilitation, identifying factors that most strongly influence functional recovery and destination on discharge. DESIGN: Multicentre prospective cohort study SETTING/POPULATION: All patients admitted to the Rehabilitation Units of the two hospitals after stroke over eight months METHODS: Collected data on sociodemographic characteristics, social risk (Gijón Scale), comorbidity (Charlson Index), neurological severity (National Institute of Health Stroke Scale), daily living functioning scale (Barthel Index), length of hospital stay and destination on discharge. RESULTS: We included 241 patients, with a mean stay of 35±22 days, 81.5% returning home on discharge. On admission 45.2% were totally dependent, and this figure fell to 12.8% on discharge, the mean Barthel Index score increasing by 32.5 points. Neurological severity, hemiparetic severity, impairment of deep sensation and trunk control on admission were the mayor variables influence on rehabilitation efficiency (P<0.001). Destination on discharge was most closely associated with civil status, social risk and Barthel Index score (P<0.001). The likelihood of transferring to residential care is 3- and 2.71-fold higher among patients with total dependence and high comorbidity scores, respectively. CONCLUSION: Many variables influence on outcomes of stroke inpatient rehabilitation. CLINICAL REHABILITATION IMPACT: Comprehensive assessments are required to predict patient recovery, efficiency and plan for discharge.

[Hereditary glaucoma associated with oculodentodigital dysplasia]. / Glaucoma hereditario asociado a displasia oculodentodigital.

CASE REPORT: A newborn evaluated at 20 days old due to occasional nystagmus. Her mother had presented with oculodentodigital dysplasia (ODDD) and glaucoma. The physical examination revealed opaque micro-corneas, and horizontal nystagmus. The tonometry showed 35 mm Hg in OD and 40 mm Hg in OS and the fundus examination was normal. She had a narrow nasal bridge with narrow nostrils, and fourth and fifth finger syndactylyl in both hands. A bilateral trabeculectomy was performed with a good response. DISCUSSION: ODDD is a rare autosomal dominant disease with heterogeneous phenotype manifestations. The most frequent cause of loss of visual acuity is the glaucoma, requiring long-term follow up with periodical control of the intraocular pressure (IOP).

[Body weight profile in acute mesenteric ischemia. Experimental study in New-Zealand rabbits]. / Perfil del peso corporal en la isquemia mesenterica aguda. Estudio experimental en conejos Nueva Zelanda.

INTRODUCTION AND OBJECTIVES: There are few investigation studies that relate acute mesenteric ischemia and body weight in animal experimentation. The aim is to studying whether initial weight loss is related to the magnitude of the aggression induced by clamps of the superior mesenteric artery for 30 and 60 minutes, and whether reperfusion ischemia may hinder weight recovery in surviving animals at the end of 11 weeks of experimental work with New Zealand rabbits through a valid experimental model. MATERIALS AND METHOD: 80 animals (rabbits) were distributed in four series of 20 each one: series I (control), animals were weighed for 11 weeks; series II (simulated surgery); series III (mesenteric ischemia for 30 minutes); series IV (mesenteric ischemia for 60 minutes). We induced ischemia by clamping the superior mesenteric artery. Animals from series II, III, and IV were weighed 24 hours before the surgical procedure and weekly after surgery along their survival, until completing 11 weeks. For weight analysis, an ANOVA test was used by confronting the percentage weight variation according to the series. All animals were necropsied to know the cause of death and histological lesions of the intestinal mucosa. RESULTS: Series I had a linear weight increase until the end of the observation period. Series II, III and IV had a significant initial decrease of the percentage weight during the first post-surgical week, with a recovery towards the end of the study, but significantly lower as compared to the control series. Significant differences have also been found in weight recovery at 11 weeks between series II and series III and IV, and between ischemic series. CONCLUSIONS: Animals in series II, III, and IV reached at the end of the study a percentage weight significantly lower to that obtained by series I. In the experimental animal mesenteric ischemia-reperfusion processes, the initial percentage weight loss in the postsurgical period is influenced not only by ischemia time but also by pre-and postsurgical manipulations; by contrast, the longer ischemia time is, the greater weight loss at the end of the study will be.

Umbilical cord transection in twin-reverse arterial perfusion syndrome with the use of a coaxial bipolar electrode (Versapoint).

Umbilical-cord occlusion has been proposed for the treatment of twin-reverse arterial perfusion syndrome (TRAP). Transection of the umbilical cord is necessary in patients with monoamniotic or 'pseudomonoamniotic' TRAP to avoid subsequent cord entanglement and demise of the pump twin. We present a case of TRAP in which the umbilical cord was successfully ligated with suture and transected with the Versapoint electrode.

Vegetation stress detection through chlorophyll a + b estimation and fluorescence effects on hyperspectral imagery.

Physical principles applied to remote sensing data are key to successfully quantifying vegetation physiological condition from the study of the light interaction with the canopy under observation. We used the fluorescence-reflectance-transmittance (FRT) and PROSPECT leaf models to simulate reflectance as a function of leaf biochemical and fluorescence variables. A series of laboratory measurements of spectral reflectance at leaf and canopy levels and a modeling study were conducted, demonstrating that effects of chlorophyll fluorescence (CF) can be detected by remote sensing. The coupled FRT and PROSPECT model enabled CF and chlorophyll a + b (Ca + b) content to be estimated by inversion. Laboratory measurements of leaf reflectance (r) and transmittance (t) from leaves with constant Ca + b allowed the study of CF effects on specific fluorescence-sensitive indices calculated in the Photosystem I (PS-I) and Photosystem II (PS-II) optical region, such as the curvature index [CUR; (R675.R690)/R2(683)]. Dark-adapted and steady-state fluorescence measurements, such as the ratio of variable to maximal fluorescence (Fv/Fm), steady state maximal fluorescence (F'm), steady state fluorescence (Ft), and the effective quantum yield (delta F/F'm) are accurately estimated by inverting the FRT-PROSPECT model. A double peak in the derivative reflectance (DR) was related to increased CF and Ca + b concentration. These results were consistent with imagery collected with a compact airborne spectrographic imager (CASI) sensor from sites of sugar maple (Acer saccharum Marshall) of high and low stress conditions, showing a double peak on canopy derivative reflectance in the red-edge spectral region. We developed a derivative chlorophyll index (DCI; calculated as D705/D722), a function of the combined effects of CF and Ca + b content, and used it to detect vegetation stress.

[Serotonin syndrome: report of a fatal case and review of the literature]. / Síndrome serotoninérgico: presentación de un caso de evolución letal y revisión de la literatura.

We report here the case of a patient with fluoxetine and selegiline induced serotonin syndrome, which presented as encephalopathy, generalized myoclonias, fever, stiffness and sweating, complicated with acute renal failure, rhabdomyolysis and disseminated intravascular coagulation findings. The patient died 6 days after admission. This syndrome is discussed, with an analysis of its causes, pathophysiology and therapy. A special emphasis is placed on the clinical issues and differential diagnosis with the malignant neuroleptic syndrome and other clinical entities with which it could be mistaken. General recommendations are provided to avoid this poorly characterized syndrome that, as in our patient, may have a fatal outcome.

The decade 1989-1998 in Spanish psychology: an analysis of research in psychobiology.

In this paper, we present an analysis of the research published during the 1989-1998 decade by tenured Spanish faculty members from the area of psychobiology. Database search and direct correspondence with the 110 faculty members rendered a list of 904 psychobiological papers. Classification and analysis of these papers led to the definition of at least 70 different research trends. Topics are grouped into several specific research areas: Learning and Memory; Development and Neural Plasticity; Emotion and Stress; Ethology; Neuropsychology; Sensory Processing; and Psychopharmacology. The international dissemination of this research, published in journals of high impact index, and the increasing number of papers are two noteworthy features.

Influence of diagnostic and treatment factors in the population pharmacokinetics of gentamicin.

Using the NONMEM program, the population kinetics of gentamicin were retrospectively studied in a series of 51 patients with different pathologies undergoing treatment (single or three daily doses) with gentamicin whose serum gentamicin levels were being monitored. Renal function, the type of treatment and cancer proved to be the covariates which affected drug clearance, while patient weight was found to govern the distribution volume. The distribution coefficient of gentamicin in the patients was 0.37 litres/kg, justifying gentamicin doses higher than those used conventionally. The optimized population model allowed us to simulate drug serum levels at 8 and 12h, as well as the area under the curve of gentamicin and its variability in patients with high distribution volumes when dosage regimens based on a single daily dose administration are implemented.

Retinal image quality in the rodent eye.

Many rodents do not see well. For a target to be resolved by a rat or a mouse, it must subtend a visual angle of a degree or more. It is commonly assumed that this poor spatial resolving capacity is due to neural rather than optical limitations, but the quality of the retinal image has not been well characterized in these animals. We have modified a double-pass apparatus, initially designed for the human eye, so it could be used with rodents to measure the modulation transfer function (MTF) of the eye's optics. That is, the double-pass retinal image of a monochromatic (lambda = 632.8 nm) point source was digitized with a CCD camera. From these double-pass measurements, the single-pass MTF was computed under a variety of conditions of focus and with different pupil sizes. Even with the eye in best focus, the image quality in both rats and mice is exceedingly poor. With a 1-mm pupil, for example, the MTF in the rat had an upper limit of about 2.5 cycles/deg, rather than the 28 cycles/deg one would obtain if the eye were a diffraction-limited system. These images are about 10 times worse than the comparable retinal images in the human eye. Using our measurements of the optics and the published behavioral and electrophysiological contrast sensitivity functions (CSFs) of rats, we have calculated the CSF that the rat would have if it had perfect rather than poor optics. We find, interestingly, that diffraction-limited optics would produce only slight improvement overall. That is, in spite of retinal images which are of very low quality, the upper limit of visual resolution in rodents is neurally determined. Rats and mice seem to have eyes in which the optics and retina/brain are well matched.

Behavioral estimates of absolute visual threshold in mice.

Behavioral measurements on the water maze show night blindness in albino mice but cortical recordings show no difference between pigmented and congenic albino mice. Consequently we have measured the absolute threshold in albino and pigmented mice using an operant method. The estimated threshold value is -5.3 log cd/m2 for albino mice and -5.5 log cd/m2 for the pigmented mice. We conclude that threshold values depend on the behavioral paradigm used. Operant behavioral thresholds show that albino and pigmented mice detect levels of light similar to their VEP thresholds. Cognitive differences might influence the estimation of absolute behavioral threshold in albino animals.

1-Octadecene as a solvent for ferrofluids for intraocular use.

PURPOSE: 1-Octadecene is a hydrocarbon with one double bond in its structure that could serve as a solvent for ferrofluids. The aim of this pilot study was to obtain preliminary information on intraocular tolerance to 1-octadecene. METHODS: Vitreous compression with perfluoropropane gas was achieved in 20 eyes of albino rabbits. Four days after gas injection a fluid-gas exchange was undertaken. Sixteen eyes received 1-octadecene. Four eyes received balanced salt solution. Eyes were obtained at 3, 7, 14 and 30 days. The samples were fixed in 10% buffered formalin, processed in paraffin and sections were stained with hematoxylin and eosin. RESULTS: Emulsification of the oil bubble was observed in 31.25% of the cases by the fifth day; light microscopy showed normal retinal architecture in all the eyes and epiretinal and vitreous macrophages in 50% of the eyes. CONCLUSIONS: 1-Octadecene does not appear to have any retinal cytotoxic effect but elicits an inflammatory response in the vitreous activity.