ICD-11 and DSM-5-TR prolonged grief symptoms and quality of life: A criterion validity test.

OBJECTIVE: Two similar but distinct versions of prolonged grief disorder (PGD) have recently been included in the International Classification of Diseases eleventh edition (ICD-11) and the Diagnostic and Statistical Manual of Mental Disorders - fifth edition, Text-Revision (DSM-5-TR). This study provides a criterion validity test of both new criteria sets of PGD, by examining concurrent and longitudinal associations of ICD-11 and DSM-5-TR prolonged grief symptoms with quality of life (QOL). METHODS: Bereaved adults completed a survey assessing ICD-11 and DSM-5-TR prolonged grief symptoms, depressive symptoms, insomnia symptoms and QOL at baseline and 6-month follow-up. RESULTS: Both ICD-11 and DSM-5-TR prolonged grief symptoms related negatively to QOL concurrently, while controlling for insomnia and depressive symptoms. ICD-11 prolonged grief symptoms, but not DSM-5-TR prolonged grief symptoms, predicted QOL at 6-month follow-up, while controlling for baseline QOL and insomnia and depression symptoms. CONCLUSIONS: Results provide consistent evidence for the criterion validity of ICD-11 PGD, but mixed evidence for the criterion validity of DSM-5-TR PGD. Study results can help guide attempts to optimize and harmonize future PGD criteria.

Characterization of the long-term effects of lethal total body irradiation followed by bone marrow transplantation on the brain of C57BL/6 mice.

PURPOSE: Total body irradiation (TBI) followed by bone marrow transplantation (BMT) is used in pre-clinical research to generate mouse chimeras that allow to study the function of a protein specifically on immune cells. Adverse consequences of irradiation on the juvenile body and brain are well described and include general fatigue, neuroinflammation, neurodegeneration and cognitive impairment. Yet, the long-term consequences of TBI/BMT performed on healthy adult mice have been poorly investigated. MATERIAL AND METHODS: We developed a robust protocol to achieve near complete bone marrow replacement in mice using 2x550cGy TBI and evaluated the impact of the procedure on their general health, mood disturbances, memory, brain atrophy, neurogenesis, neuroinflammation and blood-brain barrier (BBB) permeability 2 and/or 16 months post-BMT. RESULTS: We found a persistent decrease in weight along with long-term impact on locomotion after TBI and BMT. Although the TBI/BMT procedure did not lead to anxiety- or depressive-like behavior 2- or 16-months post-BMT, long-term spatial memory of the irradiated mice was impaired. We also observed radiation-induced impaired neurogenesis and cortical microglia activation 2 months post-BMT. Moreover, higher levels of hippocampal IgG in aged BMT mice suggest an enhanced age-related increase in BBB permeability that could potentially contribute to the observed memory deficit. CONCLUSIONS: Overall health of the mice did not seem to be majorly impacted by TBI followed by BMT during adulthood. Yet, TBI-induced alterations in the brain and behavior could lead to erroneous conclusions on the function of a protein on immune cells when comparing mouse chimeras with different genetic backgrounds that might display altered susceptibility to radiation-induced damage. Ultimately, the BMT model we here present could also be used to study the related long-term consequences of TBI and BMT seen in patients.

Deep learning image segmentation reveals patterns of UV reflectance evolution in passerine birds.

Ultraviolet colouration is thought to be an important form of signalling in many bird species, yet broad insights regarding the prevalence of ultraviolet plumage colouration and the factors promoting its evolution are currently lacking. In this paper, we develop a image segmentation pipeline based on deep learning that considerably outperforms classical (i.e. non deep learning) segmentation methods, and use this to extract accurate information on whole-body plumage colouration from photographs of >24,000 museum specimens covering >4500 species of passerine birds. Our results demonstrate that ultraviolet reflectance, particularly as a component of other colours, is widespread across the passerine radiation but is strongly phylogenetically conserved. We also find clear evidence in support of the role of light environment in promoting the evolution of ultraviolet plumage colouration, and a weak trend towards higher ultraviolet plumage reflectance among bird species with ultraviolet rather than violet-sensitive visual systems. Overall, our study provides important broad-scale insight into an enigmatic component of avian colouration, as well as demonstrating that deep learning has considerable promise for allowing new data to be brought to bear on long-standing questions in ecology and evolution.

Latitudinal gradients in avian colourfulness.

It has long been suggested that tropical species are generally more colourful than temperate species, but whether latitudinal gradients in organismal colourfulness exist remains controversial. Here we quantify global latitudinal trends in colourfulness (within-individual colour diversity) by collating and analysing a photographic dataset of whole-body plumage reflectance information for >4,500 species of passerine birds. We show that male and female birds of tropical passerine species are generally more colourful than their temperate counterparts, both on average and in the extreme. We also show that these geographic gradients can be explained in part by the effects of several latitude-related factors related to classic hypotheses for climatic and ecological determinants of organismal colourfulness. Taken together, our results reveal that species' colourfulness peaks in the tropics for passerine birds, confirming the existence of a long-suspected yet hitherto elusive trend in the distribution of global biodiversity.

Foot Typology, Dynamic and Static Weight Distribution, and Radiographic Changes After Subtalar Arthroereisis in Juvenile Symptomatic Flexible Flat Feet.

Flexible flatfoot is among the most common skeletal disorders in childhood. This study describes the dynamic and static correction effects of subtalar arthroereisis in adolescents with flexible symptomatic flatfeet in comparison to normal subjects as well as to results before and after removal of metal. Eighteen adolescents with 25 symptomatic flexible flatfeet were treated surgically with a subtalar arthroereisis at a mean of 12.5 (10-16) years. At follow-up (mean 3.9 years, range 0.4-8), patients filled out the American Orthopaedic Foot and Ankle Society questionnaire, received radiographs and were examined using dynamic and static pedobarography as well as static hindfoot axis examination. Results were compared to healthy controls (n = 13; 26 feet). Surgically treated feet (n = 25) had better questionnaire results after surgery than before, but lower scores than healthy feet. Radiological parameters improved significantly after surgery. Removal of metal did not influence post-surgical results (follow-up 2.8 years). Surgically treated feet had larger contact areas than normal feet with predominance to the midfoot region. The relative maximum force, relative peak pressure and contact time were higher in the midfoot of treated feet compared to controls. When comparing pedobarography data of treated versus untreated feet of the same patients (subgroup n = 11 feet), there were no differences. Subtalar arthroereisis was able to effectively treat symptomatic flexible flatfeet in this population. Results improved significantly evaluating a questionnaire, radiographs, dynamic and static weight distribution, but were still worse than results of healthy feet. There was no relapse after removal of metal.

Prevalence of food addiction determined by the Yale Food Addiction Scale and associated factors: A systematic review with meta-analysis.

OBJECTIVE: To determine, through a systematic review with meta-analysis, the prevalence of food addiction (FA) using the Yale Food Addiction Scale (YFAS) and its derivatives exploring possible factors associated with the prevalence of FA in several contexts. METHODS: The following databases were searched: MEDLINE, ScienceDirect, LILACS, PsycArticles, CENTRAL, Greylit.org, and OpenGrey.eu. Studies that assessed FA using YFAS were included. Two independent reviewers assessed the eligibility of each report. Random-effects meta-analysis was performed to calculate the weighted prevalence of FA. Subgroup analyses and meta-regression were conducted to explore sources of heterogeneity. RESULTS: Of the 6425 abstracts reviewed, 272 studies were included. The weighted mean prevalence of FA diagnosis was 20% (95% CI: 18%; 21%). The prevalence of FA was higher in individuals with clinical diagnosis of binge eating (55%; 95% CI 34%; 75%). The prevalence in clinical samples was higher compared to non-clinical samples. Two studies included children only and no studies included only elderly people. CONCLUSIONS: Food addiction is a topic in which there has been a significant growth in studies. The highest prevalence was found in the group of participants with eating disorders and weight disorders. More studies with children and the elderly are needed.

Fractura de cadera en el adulto mayor: epidemiología y costos de la atención / Hip fracture in the elderly: epidemiology and costs of care

Resumen: Introducción: El objetivo general de la investigación fue describir la epidemiología y estimar los costos médicos directos de la fractura de cadera en el adulto mayor en México. Material y métodos: Se realizó un estudio observacional y transversal retrospectivo. Se utilizaron dos bases de datos obtenidas de la Dirección General de Información en Salud del período 2013-2018: egresos hospitalarios y procedimientos quirúrgicos. Las variables incluidas fueron: sexo, entidad federativa, edad, año de registro y tipo de fractura de acorde a la CIE-10; de igual forma, todos los insumos necesarios para la realización del procedimiento quirúrgico. Resultados: Se registraron 16,829 ingresos de pacientes con fractura de cadera. Las mujeres representaron 69% del total de pacientes, la edad en promedio fue de 79 años y la estancia hospitalaria fue de nueve días, 77% de las fracturas fueron de cuello de fémur y el promedio de los costos médicos directos de los procedimientos ascendieron a USD $45,122,228.00 para el período estudiado. Conclusión: El riesgo de caídas aumenta con la edad, especialmente en el grupo etario de 80-89 años, por lo que se espera que este tipo de patologías se incremente en los próximos años. De igual forma, los costos para la atención de estas fracturas representan un impacto económico para los sistemas de salud. De manera que la implementación de estrategias de prevención, por ejemplo, en caídas es el método más eficiente para contribuir al envejecimiento saludable.

Abstract: Introduction: The aim of this study was to describe the epidemiology and to estimate the direct medical costs of hip fracture among elderly patients in Mexico. Material and methods: An observational, cross sectional and retrospective study was undertaken. Hospital discharge and surgical procedures for the period 2013-2018 were the databases used for the analysis, and obtained from General Directorate of Health Information. Variables included were sex, federal entity, age, year of discharge, and fracture type according to the CIE-10; and also, the supplies needed for the surgical procedures. Results: A total of 16,829 patients with hip fracture were discharge, 69% were women, and the mean for age was 79 years old and for the hospital stay length was nine days. The most frequent fracture type was the femur neck with 77% and the average medical costs was USD$45,122,228.00. Conclusion: Falling risks increase with age, especially in patients among 80-89 years of age, hence, is expected that this type of pathology increases in the following years. The medical costs for treatment of hip fracture represents an economic impact on health services. For that reason, the implementation of prevention strategies, risk of falling for example, is the one of most efficient approach.

[Hip fracture in the elderly: epidemiology and costs of care]. / Fractura de cadera en el adulto mayor: epidemiología y costos de la atención.

INTRODUCTION: The aim of this study was to describe the epidemiology and to estimate the direct medical costs of hip fracture among elderly patients in Mexico. MATERIAL AND METHODS: An observational, cross sectional and retrospective study was undertaken. Hospital discharge and surgical procedures for the period 2013-2018 were the databases used for the analysis, and obtained from General Directorate of Health Information. Variables included were sex, federal entity, age, year of discharge, and fracture type according to the CIE-10; and also, the supplies needed for the surgical procedures. RESULTS: A total of 16,829 patients with hip fracture were discharge, 69% were women, and the mean for age was 79 years old and for the hospital stay length was nine days. The most frequent fracture type was the femur neck with 77% and the average medical costs was USD$45,122,228.00. CONCLUSION: Falling risks increase with age, especially in patients among 80-89 years of age, hence, is expected that this type of pathology increases in the following years. The medical costs for treatment of hip fracture represents an economic impact on health services. For that reason, the implementation of prevention strategies, risk of falling for example, is the one of most efficient approach.

INTRODUCCIÓN: El objetivo general de la investigación fue describir la epidemiología y estimar los costos médicos directos de la fractura de cadera en el adulto mayor en México. MATERIAL Y MÉTODOS: Se realizó un estudio observacional y transversal retrospectivo. Se utilizaron dos bases de datos obtenidas de la Dirección General de Información en Salud del período 2013-2018: egresos hospitalarios y procedimientos quirúrgicos. Las variables incluidas fueron: sexo, entidad federativa, edad, año de registro y tipo de fractura de acorde a la CIE-10; de igual forma, todos los insumos necesarios para la realización del procedimiento quirúrgico. RESULTADOS: Se registraron 16,829 ingresos de pacientes con fractura de cadera. Las mujeres representaron 69% del total de pacientes, la edad en promedio fue de 79 años y la estancia hospitalaria fue de nueve días, 77% de las fracturas fueron de cuello de fémur y el promedio de los costos médicos directos de los procedimientos ascendieron a USD $45,122,228.00 para el período estudiado. CONCLUSIÓN: El riesgo de caídas aumenta con la edad, especialmente en el grupo etario de 80-89 años, por lo que se espera que este tipo de patologías se incremente en los próximos años. De igual forma, los costos para la atención de estas fracturas representan un impacto económico para los sistemas de salud. De manera que la implementación de estrategias de prevención, por ejemplo, en caídas es el método más eficiente para contribuir al envejecimiento saludable.

Role of Tryptophan Residues in the Toxicity and Photosensitized Inactivation of Escherichia coli α-Hemolysin.

α-Hemolysin (HlyA) is an extracellular protein toxin secreted by uropathogenic strains of Escherichia coli that inserts into membranes of eukaryotic cells. The main goal of this work was to investigate the involvement of tryptophan (W) residues in the hemolytic activity of HlyA. We investigated the hemolytic activity of six single-point mutant proteins, in which one of the four Ws was replaced by cysteine (C) or leucine (L). We also analyzed the photoinactivation of HlyA with pterin (Ptr), an endogenous photosensitizer, as a method of unspecific oxidation of W and tyrosine (Y) residues. HlyA photoinactivation was analyzed by ultraviolet-visible spectrophotometry, hemolytic activity measurement, fluorescence spectroscopy, and electrophoretic analysis. The results indicate that Ws are important in the hemolytic process. Specifically, the chemical structure of the amino acid at position 578 is important for the acylation of HlyA at residue K563. Furthermore, the exposure of HlyA to ultraviolet radiation, with energy similar to that experienced under sun exposure, in the presence of Ptr induces the inactivation of the toxin, causing chemical changes in, at least, W and Y, the rate of damage to W residues being faster than that observed for Y residues. This work not only deepens our understanding of the structure-function relationship of the toxin but also introduces the possibility of using photoinactivation of HlyA for potential applications such as obtaining innocuous molecules for vaccine production and the elimination of the toxin from contaminated surfaces and drinking water.

Social subordination induced by early life adversity rewires inhibitory control of the prefrontal cortex via enhanced Npy1r signaling.

Social hierarchies are present in most mammalian species. In nature, hierarchies offer a tradeoff between reduction of in-group fighting between males, at the expense of an asymmetric sharing of resources. Early life experiences and stress are known to influence the rank an individual attains in adulthood, but the associated cellular and synaptic alterations are poorly understood. Using a maternal separation protocol, we show that care-deprived mice display a long-lasting submissive phenotype, increased social recognition, and enhanced explorative behavior. These alterations are consistent with an adaptation that favors exploration rather than confrontation within a group setting. At the neuronal level, these animals display dendritic atrophy and enhanced inhibitory synaptic inputs in medial prefrontal cortex (mPFC) neurons. To determine what could underlie this synaptic modification, we first assessed global gene expression changes via RNAseq, and next focused on a smaller subset of putatively altered synaptic receptors that could explain the changes in synaptic inhibition. Using different cohorts of maternally deprived mice, we validated a significant increase in the expression of Npy1r, a receptor known to play a role in maternal care, anxiety, foraging, and regulation of group behavior. Using electrophysiological recordings in adult mice while blocking NPY1R signaling, we determined that this receptor plays a key role in enhancing GABAergic currents in mice that experience maternal deprivation. Taken together, our work highlights the potential of regulating NPY1R in social anxiety disorders and the alterations induced in brain circuitry as a consequence of early life stress and adversity.

Chemical Modifications of Globular Proteins Phototriggered by an Endogenous Photosensitizer.

The main goal of the present work was to investigate the damages photoinduced by pterin (Ptr), an endogenous photosensitizer present in human skin under pathological conditions, on a globular protein such as ubiquitin (Ub). Particular attention has been paid on the formation of covalent adducts between Ptr and the protein that can behave as photoantigen and provoke an immune system response. Here, a multifaceted approach including UV-visible spectrophotometry, fluorescence spectroscopy, electrophoresis, size exclusion chromatography, and mass spectrometry is used to establish the Ub changes triggered by UV-A irradiation in the presence of Ptr. Under anaerobic conditions, the only reaction corresponds to the formation of a covalently bound Ptr-Ub adduct that retains the spectroscopic properties of the free photosensitizer. A more complex scheme is observed in air-equilibrated solutions with the occurrence of three different processes, that is, formation of a Ptr-Ub adduct, dimerization, and fragmentation of the protein.

Photochemistry of tyrosine dimer: when an oxidative lesion of proteins is able to photoinduce further damage.

The tyrosine dimer (Tyr2), a covalent bond between two tyrosines (Tyr), is one of the most important modifications of the oxidative damage of proteins. This compound is increasingly used as a marker of aging, stress and pathogenesis. At physiological pH, Tyr2 is able to absorb radiation at wavelengths significantly present in the solar radiation and artificial sources of light. As a result, when Tyr2 is formed in vivo, a new chromophore appears in the proteins. Despite the biomedical importance of Tyr2, the information of its photochemical properties is limited due to the drawbacks of its synthesis. Therefore, in this work we demonstrate that at physiological pH, Tyr2 undergoes oxidation upon UV excitation yielding different products which conserve the dimeric structure. During its photodegradation different reactive oxygen species, like hydrogen peroxide, superoxide anion and singlet oxygen, are produced. Otherwise, we demonstrated that Tyr2 is able to sensitize the photodegradation of tyrosine. The results presented in this work confirm that Tyr2 can act as a potential photosensitizer, contributing to the harmful effects of UV-A radiation on biological systems.

Sexual selection predicts the rate and direction of colour divergence in a large avian radiation.

Sexual selection is proposed to be a powerful driver of phenotypic evolution in animal systems. At macroevolutionary scales, sexual selection can theoretically drive both the rate and direction of phenotypic evolution, but this hypothesis remains contentious. Here, we find that differences in the rate and direction of plumage colour evolution are predicted by a proxy for sexual selection intensity (plumage dichromatism) in a large radiation of suboscine passerine birds (Tyrannida). We show that rates of plumage evolution are correlated between the sexes, but that sexual selection has a strong positive effect on male, but not female, interspecific divergence rates. Furthermore, we demonstrate that rapid male plumage divergence is biased towards carotenoid-based (red/yellow) colours widely assumed to represent honest sexual signals. Our results highlight the central role of sexual selection in driving avian colour divergence, and reveal the existence of convergent evolutionary responses of animal signalling traits under sexual selection.

Abnormal mGluR-mediated synaptic plasticity and autism-like behaviours in Gprasp2 mutant mice.

Autism spectrum disorder (ASD) is characterized by dysfunction in social interactions, stereotypical behaviours and high co-morbidity with intellectual disability. A variety of syndromic and non-syndromic neurodevelopmental disorders have been connected to alterations in metabotropic glutamate receptor (mGluR) signalling. These receptors contribute to synaptic plasticity, spine maturation and circuit development. Here, we investigate the physiological role of Gprasp2, a gene linked to neurodevelopmental disabilities and involved in the postendocytic sorting of G-protein-coupled receptors. We show that Gprasp2 deletion leads to ASD-like behaviour in mice and alterations in synaptic communication. Manipulating the levels of Gprasp2 bidirectionally modulates the surface availability of mGluR5 and produces alterations in dendritic complexity, spine density and synaptic maturation. Loss of Gprasp2 leads to enhanced hippocampal long-term depression, consistent with facilitated mGluR-dependent activation. These findings demonstrate a role for Gprasp2 in glutamatergic synapses and suggest a possible mechanism by which this gene is linked to neurodevelopmental diseases.

The genome structure of Arachis hypogaea (Linnaeus, 1753) and an induced Arachis allotetraploid revealed by molecular cytogenetics.

Peanut, Arachis hypogaea (Linnaeus, 1753) is an allotetraploid cultivated plant with two subgenomes derived from the hybridization between two diploid wild species, A. duranensis (Krapovickas & W. C. Gregory, 1994) and A. ipaensis (Krapovickas & W. C. Gregory, 1994), followed by spontaneous chromosomal duplication. To understand genome changes following polyploidy, the chromosomes of A. hypogaea, IpaDur1, an induced allotetraploid (A. ipaensis × A. duranensis)4x and the diploid progenitor species were cytogenetically compared. The karyotypes of the allotetraploids share the number and general morphology of chromosomes; DAPI+ bands pattern and number of 5S rDNA loci. However, one 5S rDNA locus presents a heteromorphic FISH signal in both allotetraploids, relative to corresponding progenitor. Whilst for A. hypogaea the number of 45S rDNA loci was equivalent to the sum of those present in the diploid species, in IpaDur1, two loci have not been detected. Overall distribution of repetitive DNA sequences was similar in both allotetraploids, although A. hypogaea had additional CMA3+ bands and few slight differences in the LTR-retrotransposons distribution compared to IpaDur1. GISH showed that the chromosomes of both allotetraploids had preferential hybridization to their corresponding diploid genomes. Nevertheless, at least one pair of IpaDur1 chromosomes had a clear mosaic hybridization pattern indicating recombination between the subgenomes, clear evidence that the genome of IpaDur1 shows some instability comparing to the genome of A. hypogaea that shows no mosaic of subgenomes, although both allotetraploids derive from the same progenitor species. For some reasons, the chromosome structure of A. hypogaea is inherently more stable, or, it has been at least, partially stabilized through genetic changes and selection.

Corrigendum: Mega-evolutionary dynamics of the adaptive radiation of birds.

This corrects the article DOI: 10.1038/nature21074.

Mega-evolutionary dynamics of the adaptive radiation of birds.

The origin and expansion of biological diversity is regulated by both developmental trajectories and limits on available ecological niches. As lineages diversify, an early and often rapid phase of species and trait proliferation gives way to evolutionary slow-downs as new species pack into ever more densely occupied regions of ecological niche space. Small clades such as Darwin's finches demonstrate that natural selection is the driving force of adaptive radiations, but how microevolutionary processes scale up to shape the expansion of phenotypic diversity over much longer evolutionary timescales is unclear. Here we address this problem on a global scale by analysing a crowdsourced dataset of three-dimensional scanned bill morphology from more than 2,000 species. We find that bill diversity expanded early in extant avian evolutionary history, before transitioning to a phase dominated by packing of morphological space. However, this early phenotypic diversification is decoupled from temporal variation in evolutionary rate: rates of bill evolution vary among lineages but are comparatively stable through time. We find that rare, but major, discontinuities in phenotype emerge from rapid increases in rate along single branches, sometimes leading to depauperate clades with unusual bill morphologies. Despite these jumps between groups, the major axes of within-group bill-shape evolution are remarkably consistent across birds. We reveal that macroevolutionary processes underlying global-scale adaptive radiations support Darwinian and Simpsonian ideas of microevolution within adaptive zones and accelerated evolution between distinct adaptive peaks.

Photooxidation of Tryptophan and Tyrosine Residues in Human Serum Albumin Sensitized by Pterin: A Model for Globular Protein Photodamage in Skin.

Human serum albumin (HSA) is the most abundant protein in the circulatory system. Oxidized albumin was identified in the skin of patients suffering from vitiligo, a depigmentation disorder in which the protection against ultraviolet (UV) radiation fails because of the lack of melanin. Oxidized pterins, efficient photosensitizers under UV-A irradiation, accumulate in the skin affected by vitiligo. In this work, we have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to induce structural and chemical changes in HSA under UV-A irradiation. Our results showed that Ptr is able to photoinduce oxidation of the protein in at least two amino acid residues: tryptophan (Trp) and tyrosine (Tyr). HSA undergoes oligomerization, yielding protein structures whose molecular weight increases with irradiation time. The protein cross-linking, due to the formation of dimers of Tyr, does not significantly affect the secondary and tertiary structures of HSA. Trp is consumed in the photosensitized process, and N-formylkynurenine was identified as one of its oxidation products. The photosensitization of HSA takes place via a purely dynamic process, which involves the triplet excited state of Ptr. The results presented in this work suggest that protein photodamage mediated by endogenous photosensitizers can significantly contribute to the harmful effects of UV-A radiation on the human skin.

Salud y caridad en una villa de Chile Central: génesis del Hospital San José de Parral: 1875-1885 / Health and charity in a village of Central Chile: genesis of San José Hospital in Parral: 1875-1885

Esta investigación tiene como propósito estudiar las dinámicas que permitieron la creación del hospital de Parral en el último cuarto del siglo XIX. En base a fuentes primarias inéditas, se estudian las demandas sociales que se generaron para la construcción y funcionamiento de dicho centro médico, como asimismo la llegada y establecimiento de algunos de los primeros hombres de salud en la ciudad. Finalmente, se concluye que la creación del hospital fue el resultado de la tensión entre prácticas y discursos de una conjugación de factores locales y externos. (AU)

Determination of the required HLB values of some essential oils.

The required HLB values of eucalyptus, lippia and peppermint essential oils were determined using droplet size analysis and turbidimetric method on emulsions prepared with emulsifier blends of varying HLB values. The percentage increase in mean droplet diameter and the degree of dispersion of droplet sizes were determined before and after centrifugation of the emulsions. The HLB value of the emulsion with the least dispersion ratio or the least percentage increase in mean droplet diameter was taken as the required HLB of the respective essential oil. The turbidimetric method was validated by the existence of correlation (r=-0.958) between the mean droplet diameter and the turbidity of the emulsions. The turbidity curve went through a maximum at the HLB value where the mean droplet diameter was least. Based on these methods, the required HLB values of eucalyptus, lippia and peppermint oils were determined as 9.8, 12.1 and 12.3, respectively (P<0.05). Liquid paraffin was used as a reference standard and its required HLB fell within literature value.