Aqueous humour flow in the posterior chamber of the eye and its modifications due to pupillary block and iridotomy.

The anterior chamber (AC) and posterior chamber (PC) of the eye are connected through the pupil and are filled with aqueous humour. The aqueous flows from the posterior to the AC at an approximately constant rate, and the intraocular pressure is governed by this rate and the resistance to aqueous outflow. In some patients the iris and lens come into contact, leading to pressure build-up in the PC, peripheral axial shallowing of the AC and, possibly, to angle-closure glaucoma. This can lead to blindness, which may be prevented by surgically creating an iridotomy, that is a hole through the iris to facilitate the flow from the posterior to the AC. The problem of optimal size and location of an iridotomy is still poorly understood. In this article, we study aqueous flow in the PC and investigate how it is modified in the presence of an iridotomy. Our approach is based on the lubrication theory, which allows us to solve the problem semi-analytically. We treat the iridotomy as a point sink and assume that the flux through it is proportional to the pressure. We find that the ideal size and location of an iridotomy are influenced by various geometrical and fluid mechanical factors, the most relevant of which are the size of the hole and the length and height of the iris-lens channel. For certain iridotomy diameters, we find that the jet velocity through the iridotomy might be large enough to cause possible corneal damage.

Estrategias para la disminución y gestión del error humano en Toxicología Forense / Strategies for reduction and management of human error in forensic toxicology

La práctica de la toxicología forense, como cualquier otra actividad humana nunca está libre de errores. Se define al error humano en toxicología forense como cualquier acción o falta de la misma que condujera a un incumplimiento de unas tolerancias previamente definidas para un sistema analítico de medida. En ese sentido, los errores humanos son los responsables de la mayoría de los incidentes y accidentes que ocurren en un laboratorio. Los tipos de errores que se producen en un laboratorio son los relacionados con el operador, los relacionados con la tecnología e instrumentación y los errores relacionados con el método analítico. Los sistemas de calidad están diseñados para lograr una reducción de los eventuales errores que se puedan cometer en un laboratorio. La principal norma de aplicación a los laboratorios forenses es la UNE-EN ISO/IEC 17025:2005. Además, se dispone de las recomendaciones de la ILAC y de distintas organizaciones profesionales. Se discute en el presente trabajo como la implantación de un sistema de calidad y un modelo sistemático de gestión de errores en los laboratorios de toxicología forense puede conducir a una mayor fiabilidad de los resultados y un mejor servicio a la Administración de Justicia. Se propone la implantación en los laboratorios de una cultura de calidad que promueva la aceptación del error humano como algo inherente a nuestra condición sin que por ello desarrolle una indiferencia ante la aparición de los mismos (AU)

As any other human activity, forensic toxicology is never free of errors. A human error in forensic toxicology would be any action or lack of it leading to a breach of predefined tolerances for an analytic measurement system. Moreover, human errors are responsible for the majority of incidents and accidents that occur in a laboratory. The types of errors that occur in a laboratory are operator-related, technology-related and errors associated with the analytical method. Quality systems are designed to achieve a reduction of potential errors that may be committed in a laboratory. The standard applied to forensic laboratories is the UNEEN ISO/IEC 17025:2005. Forensic laboratories have also available ILAC and professional organizations guidelines. This paper presents the implementation of a quality system and model systematic of error management in forensic toxicology laboratories as the best way to obtain reliable results and achieve a better service to Justice Administration. The implementation of a culture of quality in the laboratories is proposed. Such culture must promote the acceptance of human error as inherent to our condition without developing an indifference to them (AU)

Traction on the retina induced by saccadic eye movements in the presence of posterior vitreous detachment.

Posterior vitreous detachment is a fairly common condition in elderly people. Tractions exerted by the detached vitreous on the retina may result in retinal tears and detachments. We studied how these tractions can arise from saccadic eye movements. Numerical simulations have been performed on a two-dimensional model of the vitreous chamber within a rigid spherical sclera, subjected to prescribed finite-amplitude rotations about a vertical axis. The vitreous chamber was assumed to be split into two regions: one occupied by the detached vitreous, modeled as an elastic viscous solid, and the other occupied by the separated liquefied vitreous, modeled as a Newtonian fluid. At the interface between the two phases, we also considered the presence of the vitreous cortex, modeled as an elastic membrane. We tested several different configurations of the interface. In all cases, we found that eye rotations generate large tractions on the retina close to the attachment points of the membrane. Comparing them, we identified configurations of the vitreous detachment that exhibit higher tractions. We also investigated how the response to saccadic movements depends on some physical parameters, in particular on the rheological properties of the solid phase and the membrane. The numerical simulations show that the generated tractions may be of the same order of magnitude as the adhesive force between the retina and the pigment epithelium. Therefore, the model provides a sound physical justification for the hypothesis that saccadic movements, in the presence of posterior vitreous detachment, could be responsible for high tractions on the retina, which may trigger retinal tear formation.

A fatally mistaken fruit juice drink: an unordinary way of cocaine intoxication.

Cocaine is one of the drugs of abuse more frequently consumed in Spain. Furthermore, Spain due to its geographical position is used by trafficker's organizations as the port of entrance of cocaine in the European Union. We present here a case of a fatal intoxication caused by a mistake in the cocaine distribution net in our country. Cocaine was concealed in a tropical juice only sold by the Internet.

Mathematical model of flow in the vitreous humor induced by saccadic eye rotations: effect of geometry.

Saccadic eye rotations induce a flow in the vitreous humor of the eye. Any such flow is likely to have a significant influence on the dispersion of drugs injected into the vitreous chamber. The shape of this chamber deviates from a perfect sphere by up to 10-20% of the radius, which is predominantly due to an indentation caused by the lens. In this paper we investigate theoretically the effect of the domain shape upon the flow field generated by saccades by considering an idealized model. The posterior chamber geometry is assumed to be a sphere with a small indentation, undergoing prescribed small-amplitude sinusoidal torsional oscillations, and, as an initial step towards understanding the problem, we treat the vitreous humor as a Newtonian fluid filling the chamber. The latter assumption applies best in the case of a liquefied vitreous or a tamponade fluid introduced in the vitreous chamber after vitrectomy. We find the flow field in terms of vector spherical harmonics, focusing on the deviation from the flow that would be obtained in a perfect sphere. The flow induced by the departure of the domain geometry from the spherical shape has an oscillating component at leading order and a smaller-amplitude steady streaming flow. The oscillating component includes a circulation cell formed every half-period, which migrates from the indentation towards the center of the domain where it disappears. The steady component has two counter-rotating circulations in the anterior part of the domain. These findings are in good qualitative agreement with the experimental results of Stocchino et al. (Phys Med Biol 52:2021-2034, 2007). Our results predict a significant reduction in the expected time for drug dispersal across the eye compared with the situation in which there is no fluid flow present.

Patología cerebro-vascular hemorrágica en adultos asociada al consumo de cocaína / Cerebral haemorrhage in adults associated with the use of cocaine

La cocaína es la segunda droga de comercio ilegal más consumida en España después del cannabis. El número de pacientes atendidos en los servicios de urgencias tras consumir cocaína y los casos de muerte secundarios al consumo de la misma han ido aumentando hasta multiplicarse por seis en los últimos años. El consumo de este alcaloide ocasiona efectos nocivos, constatados sobre diferentes órganos y sistemas corporales, e incluso la muerte. A nivel del SNC destaca, por su gravedad e incidencia, la patología cerebro-vascular hemorrágica (PCVH). Este tipo de cuadro se halla asociado al consumo de drogas ilícitas entre el 9,5% y el 34% de los accidentes vasculares en menores de 45 años, siendo la cocaína la más frecuentemente implicada en su presentación. Por otro lado, la rotura de un aneurisma o malformación arteriovenosa se ha detectado hasta en el 50% de los pacientes con PCVH secundarios al consumo de cocaína. Presentamos tres casos de muerte súbita en adultos por patología cerebro-vascular hemorrágica asociada al consumo de cocaína

Cocaine is the second most frequent illegal drug consumed in Spain after cannabis. A significant increase has occurred in the number of individuals treated in emergency departments after cocaine use just as in the number of cocaine-related deaths. These rates have been actually multiplied by six in the latest years. Cocaine causes injury in different organ systems, even death. In the CNS the use of cocaine is frequently associated with cerebral haemorrhage. Stroke in young adults below 45 years is usually related to drug use between 9,5% and 34% of cases, and cocaine is the most frequently mentioned drug. Otherwise, even 50% of cocainerelated stroke is the result of rupture of saccular aneurysms involving the arteries at the base of the brain and vascular malformation. In this paper, we present three cases of sudden death in adults due to cerebral haemorrhage associated with cocaine use

Tissue concentrations of MDMA and its metabolite MDA in three fatal cases of overdose.

The recreational use of amphetamine derivatives has become increasingly popular in our country in past recent years. Their use is especially common among young people participating in dance parties known as "raves." As a direct consequence of their increased use, the number of fatal cases in which these compounds have been involved have increased dramatically since the second half of the last decade. In our laboratory, we have registered 25 cases related to amphetamine derivatives use since 1996. Three of them were deeply studied and the results obtained are presented in this paper. This information may be useful for the interpretation of the results obtained in toxicological analysis in the cases in which death may be attributed to MDMA use.

New method for determination of ten pesticides in human blood.

An analytical method was developed for precise identification and quantitation of 10 pesticides in human blood. The pesticides studied, which have appeared frequently in actual cases, were endosulfan, lindane, parathion, ethyl-azinphos, diazinon, malathion, alachlor, tetradifon, fenthion and dicofol (o-p' and p-p' isomers). The current method replaces an earlier method which involved liquid-liquid extraction with a mixture of n-hexane-benzene (1 + 1). The extraction is performed by solid-phase extraction, with C18 cartridges and 2 internal standards, perthane and triphenylphosphate. Eluates were analyzed by gas chromatography (GC) with nitrogen-phosphorus and electrochemical detectors. Results were confirmed by GC-mass spectrometry in the electron impact mode. Blood blank samples spiked with 2 standard mixtures and an internal standard were used for quantitation. Mean recoveries ranged from 71.83 to 97.10%. Detection and quantitation limits are reported for each pesticide. Examples are provided to show the application of the present method to actual samples.

Deaths from pesticide poisoning in Spain from 1991 to 1996.

Data on 184 deaths from pesticide poisonings that occurred in Spain from 1991 to 1996 have been collated via a survey from the National Institute of Toxicology, Sevilla. Organophosphates and carbamates accounted for the majority of the cases. Other substances involved were organochlorines such as endosulfan and the herbicide paraquat.

Tricompartmental kinetics of the organophosphorous pesticide dimethoate.

We present a study on the distribution and persistence of the organophosphorous pesticide, dimethoate, in the Wistar rat. Dimethoate's levels in blood and tissues were determined using gas chromatography with a NPD detector. The toxicokinetic profile was estimated by non-linear regression using the software program PCNONLIN, which concluded that a tricompartmental model best described dimethoate's behavior in the rat body.

Pesticides and immunosuppression: the risks to public health.

There is substantial experimental, epidemiological and other evidence that many pesticides in widespread use around the world are immunosuppressive. This poses a potentially serious health risk in populations highly exposed to infectious and parasitic diseases, subject to malnutrition, and inadequately serve by curative health programmes. An expanded programme of research is needed to investigate this potential risk and to design precautionary measures.

Malathion and dichlorvos toxicokinetics after the oral administration of malathion and trichlorfon.

We studied the distribution and persistence of malathion and dichlorvos in the Wistar rat and established their toxicokinetics with the help of the PCNONLIN software program.

Coefficient of distribution of some organophosphorous pesticides in rat tissue.

Coefficient of distribution in tissue is proposed as an indicator of the affinity of xenobiotics for different tissues and their tendency to accumulate. The present study shows the distribution of some organophosphorous pesticides in rat tissues. Using the coefficient of distribution we established the preference of these insecticides for the various tissues. Each pesticide had a specific pattern of affinity for different tissues.

The influence of pH on the degradation kinetics of some organophosphorous pesticides in aqueous solutions.

This paper reports on the stability of 6 organophosphorous insecticides in ethanol-water at pH 2.0, 7.5 and 8.5. The kinetics of insecticide degradation and the corresponding parameters were calculated from the data obtained by analyses of the residual parental compounds. Pesticide degradation was found to proceed by 2 distinct mechanisms.

Accounting for environmental assets.

A country can cut down its forests, erode its soils, pollute its aquifers and hunt its wildlife and fisheries to extinction, but its measured income is not affected as these assets disappear. Impoverishment is taken for progress.

Economic aid and the environment.

PIP: Approximately 1/3 of the signatories of the Montreal Protocol on ozone depletion were developing countries lacking the resources to pay for its implementation. Germany announced at 25% reduction of carbon dioxide emissions by 2005, the Netherlands, the UK, and Japan promised similar steps. The southern hemisphere has to reduce emissions with improved technology from the northern hemisphere, as 45% of greenhouse gases are generated there. There is need to finance such initiatives: $20-50 billion a year is required by 2000 to help these countries. The world Resources Institute proposed a green investment fund for the environment or Ecovest. It was first proposed in eastern Europe by the Nordic Environmental Finance Corporation (NEFCO) in 1990 with an initial capital of $47 million. The US Overseas Private Investment Corporation set up a $100 million for-profit Environmental Investment Fund for eastern Europe and the developing world for sustainable agriculture, forest management, eco-tourism, renewable energy, and pollution prevention. Debt-for-nature swaps between nongovernmental agencies and governments to purchase debt at discount have been paid in bonds for nature conservation in Bolivia, Ecuador, Costa Rica, the Philippines, Zambia, and Madagascar. $69 million of Costa Rica's debt was converted in 2 years to save parks, protected areas, and finance reforestation. The debts of some African countries have been written off by donor countries. The Bush Administration proposed to write off parts of Latin America's $7 billion debt. The Global Environment Fund of the World Bank proposed to lend $300-400 million a year for environmental projects in developing countries and in eastern Europe. The main goals are to protect the ozone layer, prevent deforestation and desertification, and clean up pollution. Some companies finance reforestation in Guatemala to offset their own emissions.^ieng