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Scanning Transmission X-ray microscopy (STXM) is a sensitive and selective probe for the penetration of rapamycin which is topically applied to human skin ex vivo and is facilitated by skin treatment with microneedles puncturing the skin. Inner-shell excitation serves as a selective probe for detecting rapamycin by changes in optical density as well as linear combination modeling using reference spectra of the most abundant species. The results indicate that mechanical damage induced by microneedles allows this drug to accumulate in the stratum corneum without reaching the viable skin layers. This is unlike intact skin which shows no drug penetration at all and underscores the mechanical impact of microneedle skin treatment. These results are compared to drug penetration profiles of other drugs highlighting the importance of skin barriers. High spatial resolution studies also indicate that the lipophilic drug rapamycin is observed in corneocytes. Attempts in data evaluation are reported to probe rapamycin also in the lipid layers between the corneocytes, which was not accomplished before. These results are compared to recent results on rapamycin uptake in skin where barrier impairment was induced by pre-treatment with the enzyme trypsin and drug formulations leading to occlusion.
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Known hereditary human diseases featuring impaired copper trafficking across cellular membranes involve ATP7A (Menkes disease, occipital horn disease, X-linked spinal muscular atrophy type 3) and ATP7B (Wilson disease). Herein, we report a newborn infant of consanguineous parents with a homozygous pathogenic variant in a highly conserved sequence of SLC31A1, coding for the copper influx transporter 1, CTR1. This missense variant, c.236T > C, was detected by whole exome sequencing. The infant was born with pulmonary hypoplasia and suffered from severe respiratory distress immediately after birth, necessitating aggressive mechanical ventilation. At 2 weeks of age, multifocal brain hemorrhages were diagnosed by cerebral ultrasound and magnetic resonance imaging, together with increased tortuosity of cerebral arteries. Ensuing seizures were only partly controlled by antiepileptic drugs, and the infant became progressively comatose. Laboratory investigations revealed very low serum concentrations of copper and ceruloplasmin. No hair shaft abnormalities were detected by dermatoscopy or light microscopic analyses of embedded hair shafts obtained at 4 weeks of life. The infant died after redirection of care and elective cessation of invasive mechanical ventilation at 1 month of age. This case adds SLC31A1 to the genes implicated in severe hereditary disorders of copper transport in humans.
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Transportador de Cobre 1 , Degeneração Hepatolenticular , Síndrome dos Cabelos Torcidos , Humanos , Lactente , Recém-Nascido , Ceruloplasmina/genética , Cobre , Transportador de Cobre 1/genética , ATPases Transportadoras de Cobre/genética , Degeneração Hepatolenticular/genética , Síndrome dos Cabelos Torcidos/genética , Mutação de Sentido IncorretoRESUMO
Alopecia areata (AA) is an autoimmune-mediated non-scarring hair loss whose stigmatizing effect may have a severe psychosocial impact. AA has been reported to be correlated with bullying, reduced quality of life (QoL) and psychiatric comorbidities. The effect of AA on QoL in adult patients has been systematically reviewed and found to be detrimental. No systematic evaluation of QoL in children with AA has been performed. The aim of this review is to systematically describe QoL in the child and adolescent population affected by AA. A systematic review of multiple databases and grey literature sources was conducted. Search terms included, but were not limited to, alopecia areata and quality of life. Only studies reporting results on health-related QoL in children and adolescents were included. We evaluated the studies regarding the risk of bias, and conceptual rigour concerning the quality of life and performed a descriptive synthesis of findings. Eight studies met the inclusion criteria, encompassing 358 participants with AA and 64 healthy peers. Seven studies were quantitative using four different standardized questionnaires and scores to measure QoL. One study used a qualitative design. All studies described impairment of children and adolescents' QoL by AA. The most consistently affected QoL domain was embarrassment and self-consciousness. Further psychosocial implications of AA included bullying and limiting participation in school or spare time activities. Existing evidence indicates a substantial impact of AA on QoL in children. In daily clinical practice as well as for developing new treatments QoL in paediatric AA plays a critical role. It should be considered a key outcome in clinical research and decision-making.
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The number of patients presenting with frontal fibrosing alopecia (FAA) is increasing not only in hair clinics. The recognition of the peculiar clinical pattern and associated symptoms is an important prerequisite to ensure adequate counseling and therapeutic management of the patients. Experimental studies and a range of case series give first insights into the pathogenesis, possible trigger factors, clinical course of disease and treatment options. The clinical spectrum of FFA extends beyond the typical recession of the frontal hair line initially observed in postmenopausal women. Younger women, men and rarely adolescents may also be affected. Band-like extension to the occiput, diffuse bitemporal hair thinning, eyebrow and body hair involvement as well as facial papules are part of the clinical spectrum. Similar to lichen planopilaris, inflammation and fibrosis with involvement of the stem cell region result in permanent loss of hair follicles. Which additional factors contribute to the characteristic pattern remains to be elucidated. Currently, therapeutic management largely relies on anti-inflammatory treatment with combined topical, intralesional and systemic administration depending on disease activity. The chronic progressive course, sometimes even in the absence of pronounced inflammation remains a challenge for both the affected individuals and the treating physicians. Controlled studies are required to develop evidence-based recommendations and to explore novel treatment strategies.
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Líquen Plano , Couro Cabeludo , Adolescente , Alopecia/diagnóstico , Alopecia/tratamento farmacológico , Sobrancelhas/patologia , Feminino , Fibrose , Humanos , Inflamação/patologia , Líquen Plano/diagnóstico , Líquen Plano/tratamento farmacológico , Masculino , Couro Cabeludo/patologiaRESUMO
Alopecia areata (AA) is a chronic, immune-mediated disease characterized by acute or chronic non-scarring hair loss, with a heterogeneity in clinical manifestations ranging from patchy hair loss to complete scalp and body hair loss. An overview of the up-to-date pathophysiology and the underlying signaling pathways involved in AA together with diagnostic and therapeutic recommendations will be provided. Current treatments, including topical, systemic and injectable interventions show varying response and frequent relapses reflecting the unmet clinical need. Thus, the new emerging concepts and therapeutic approaches, including Janus kinase inhibitors are eagerly awaited. Traditional and emerging therapies of AA will be discussed, in order to provide physicians with guidance for AA management. Since the latter is so challenging and often tends to take a chronic course, it can have an enormous psychosocial burden on patients, compromising their quality of life and often causing depression and anxiety. Therefore, the psychosocial aspects of the disease need to be evaluated and addressed, in order to implement appropriate psychological support when needed.
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Alopecia em Áreas , Alopecia , Alopecia em Áreas/diagnóstico , Alopecia em Áreas/tratamento farmacológico , Humanos , Imunoterapia , Qualidade de Vida , Recidiva , Couro CabeludoRESUMO
Evidence suggests that preventive dressings applied on sacral skin help to prevent pressure ulcers. However, possible performance differences of different dressing types are unclear. An exploratory randomized crossover trial with intra-individual comparisons was conducted to compare the effects of three different multi-layer foam dressings (Mepilex Border Sacrum, ALLEVYN Life Sacrum and Optifoam Gentle Sacrum) compared to no dressing on the sacral skin. Healthy female volunteers (n = 12, mean age 72 years) wore three different dressings on their sacral skin for 3.5 hours while lying supine on a standard hospital mattress. At regular intervals, subjects performed standardized movements to enhance shear loads. Skin surface temperature, stratum corneum hydration, erythema, skin roughness and the interleukin 1 alpha (IL-1α) concentration per total protein were measured at baseline and after the lying periods. After 3.5 hours, the median skin temperature increased in all four groups between 3.0°C and 3.8°C with only minor differences between the no dressing and the dressing groups. Median stratum corneum hydration increased during the lying period in all groups with highest increases in the Optifoam Gentle Sacrum (7.3 arbitrary units) and no dressing group (7.0 arbitrary units). There was a median decrease of the mean roughness (Rz) in the Optifoam Gentle Sacrum group of -6.3 µm but no relevant changes in the other groups. After loading, the erythema index was highest in the ALLEVYN Life Sacrum and no dressing groups. Highest releases of IL-1α were observed in the ALLEVYN Life Sacrum and Optifoam Gentle Sacrum groups, in the Mepilex Border Sacrum group changes were minor. Study results indicate, that the application of preventive dressings on sacral skin during loading do not cause additional occlusion compared to loading without dressings when lying supine. Different dressings cause different cutaneous responses during loading.
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Úlcera por Pressão , Idoso , Bandagens , Estudos Cross-Over , Feminino , Humanos , Úlcera por Pressão/prevenção & controle , Sacro , CicatrizaçãoRESUMO
BACKGROUND: We previously reported the Alopecia Areata Consensus of Experts study, which presented results of an international expert opinion on treatments for alopecia areata. OBJECTIVE: To report the results of the Alopecia Areata Consensus of Experts international expert opinion on diagnosis and laboratory evaluation for alopecia areata. METHODS: Fifty hair experts from 5 continents were invited to participate in a 3-round Delphi process. Consensus threshold was set at greater than or equal to 66%. RESULTS: Of 148 questions, expert consensus was achieved in 82 (55%). Round 1 consensus was achieved in 10 of 148 questions (7%). Round 2 achieved consensus in 47 of 77 questions (61%). The final face-to-face achieved consensus in 25 of 32 questions (78%). Consensus was greatest for laboratory evaluation (12 of 14 questions [86%]), followed by diagnosis (11 of 14 questions [79%]) of alopecia areata. Overall, etiopathogenesis achieved the least category consensus (31 of 68 questions [46%]). LIMITATIONS: The study had low representation from Africa, South America, and Asia. CONCLUSION: There is expert consensus on aspects of epidemiology, etiopathogenesis, clinical features, diagnosis, laboratory evaluation, and prognostic indicators of alopecia areata. The study also highlights areas where future clinical research could be directed to address unresolved hypotheses in alopecia areata patient care.
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Alopecia em Áreas/diagnóstico , Consenso , Dermatologia/normas , Carga Global da Doença , Alopecia em Áreas/epidemiologia , Alopecia em Áreas/etiologia , Alopecia em Áreas/terapia , Comorbidade , Técnica Delphi , Dermatologia/métodos , Dermoscopia , Folículo Piloso/diagnóstico por imagem , Folículo Piloso/crescimento & desenvolvimento , Folículo Piloso/patologia , Humanos , Cooperação Internacional , Guias de Prática Clínica como Assunto , Prognóstico , Fatores de Risco , Índice de Gravidade de DoençaRESUMO
PURPOSE: To determine the efficacy of specifically targeted interventions in palliative care, sequential use of the Demoralization Scale (DS) could be a useful approach. This study's main objective was to evaluate the weekly use of the DS for palliative care inpatients. Secondary objectives were the analysis of the DS, self-perceived strain, and personal benefits of the assessment. METHODS: Patients admitted to 3 palliative care units (PCUs) were tested for eligibility and asked to complete the DS weekly. Self-perceived strain was rated on a numeric scale (0-10). Open questions about strain and helpfulness of the survey were asked. RESULTS: Over 10 months, 568 patients were admitted to the PCUs; 193 patients were eligible. A total of 120 patients participated once, of whom only 41 (34.1%) participated at least twice. The mean self-perceived strain caused by the assessment was 1.53 at T1 (N = 117, SD = 2.27, max = 8). CONCLUSIONS: While the single use of the DS in PCUs seems justified in view of the possibility to detect severe demoralization with overall low to moderate strain and self-perceived helpfulness for patients, the feasibility of the sequential use of the DS has to be regarded critically. Our study undermines the complexity of assessing changes in self-reported psychological phenomena with end-of-life patients at a PCU. The most limiting factors for participating twice were that patients were either discharged from hospital or declined further participation.
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Morte , Desmoralização , Cuidados Paliativos/psicologia , Psicometria/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Viabilidade , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Inquéritos e Questionários , Adulto JovemRESUMO
ABSTRACT: We report on a congenital tumor of the face and scalp in a male newborn, histologically proven to contain melanocytes, cartilage, and bone, vascular, and neural tissue as part of a pigmented congenital tumor. Thus, this tumor was classified as a cutaneous cephalic neurocristic hamartoma.
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Neoplasias Faciais/patologia , Hamartoma/patologia , Neoplasias de Cabeça e Pescoço/patologia , Crista Neural/patologia , Couro Cabeludo/patologia , Neoplasias Cutâneas/patologia , Vasos Sanguíneos/patologia , Osso e Ossos/patologia , Cartilagem/patologia , Neoplasias Faciais/congênito , Hamartoma/congênito , Neoplasias de Cabeça e Pescoço/congênito , Humanos , Recém-Nascido , Masculino , Melanócitos/patologia , Tecido Nervoso/patologia , Neoplasias Cutâneas/congênito , Carga TumoralRESUMO
BACKGROUND AND OBJECTIVES: Gene mutations within the leptin-melanocortin signaling pathway lead to severe early-onset obesity. Recently, a phase 2 trial evaluated new pharmacological treatment options with the MC4R agonist setmelanotide in patients with mutations in the genes encoding proopiomelanocortin (POMC) and leptin receptor (LEPR). During treatment with setmelanotide, changes in skin pigmentation were observed, probably due to off-target effects on the closely related melanocortin 1 receptor (MC1R). Here, we describe in detail the findings of dermatological examinations and measurements of skin pigmentation during this treatment over time and discuss the impact of these changes on patient safety. METHODS: In an investigator-initiated, phase 2, open-label pilot study, 2 patients with loss-of-function POMC gene mutations and 3 patients with loss-of-function variants in LEPR were treated with the MC4R agonist setmelanotide. Dermatological examination, dermoscopy, whole body photographic documentation, and spectrophotometric measurements were performed at screening visit and approximately every 3 months during the course of the study. RESULTS: We report the results of a maximum treatment duration of 46 months. Skin pigmentation increased in all treated patients, as confirmed by spectrophotometry. During continuous treatment, the current results indicate that elevated tanning intensity levels may stabilize over time. Lips and nevi also darkened. In red-haired study participants, hair color changed to brown after initiation of setmelanotide treatment. DISCUSSION: Setmelanotide treatment leads to skin tanning and occasionally hair color darkening in both POMC- and LEPR-deficient patients. No malignant skin changes were observed in the patients of this study. However, the results highlight the importance of regular skin examinations before and during MC4R agonist treatment.
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Melanocortinas , Receptor Tipo 4 de Melanocortina , Humanos , Leptina/genética , Mutação , Obesidade , Projetos Piloto , Receptor Tipo 4 de Melanocortina/genética , Pigmentação da Pele/genéticaRESUMO
Pressure ulcers/injuries are caused by sustained loading and deformation of skin and underlying soft tissues. Prophylactic dressings are recommended as an adjunct to other preventive measures such as repositioning and offloading. The aim of this study was to investigate the effects of prophylactic soft silicone multi-layered foam dressings on the skin structure and function of the two most common pressure areas, sacrum and heel, with and without loading. An exploratory randomised cross-over trial using intra-individual comparisons was conducted. Eight healthy volunteers (mean age 27.5 years) were assigned to three groups and either spent 2.5 hours on a standard hospital mattress lying in supine position with and without dressings or spent 2.5 hours with dressings applied but without loading. Skin temperature, stratum corneum, and epidermal hydration increased in all groups irrespective of wearing a dressing and/or loading. Mean roughness decreased at the heels. Reactive hyperaemia and the release of interleukin 1 alpha were associated with loading only. Results suggest that the occlusive effects of dressings are similar or only slightly greater than those observed with non-loading or loading without dressings. Thus, a dressing does not cause additional irritation or skin changes during loading but it may reduce the inflammatory response.
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Bandagens , Calcanhar , Úlcera por Pressão , Sacro , Adulto , Estudos Cross-Over , Humanos , Úlcera por Pressão/prevenção & controle , Região SacrococcígeaRESUMO
The skin surface microbiome and its role in skin diseases have received increasing attention over the past years. Beyond, there is evidence for a continuous exchange with the cutaneous immune system in healthy skin, where hair follicles (HFs) provide unique anatomical niches. Especially, scalp HFs form large tubular invaginations, which extend deeply into the skin and harbour a variety of microorganisms. The distinct immunology of HFs with enhanced immune cell trafficking in superficial compartments in juxtaposition to immune-privileged sites crucial for hair follicle cycling and regeneration makes this organ a highly susceptible structure. Depending on composition and penetration depth, microbiota may cause typical infections, but may also contribute to pro-inflammatory environment in chronic inflammatory scalp diseases. Involvement in hair cycle regulation and immune cell maturation has been postulated. Herein, we review recent insights in hair follicle microbiome, immunology and penetration research and discuss clinical implications for scalp health and disease.
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Alopecia em Áreas/metabolismo , Folículo Piloso/metabolismo , Microbiota , Couro Cabeludo/imunologia , Couro Cabeludo/metabolismo , Couro Cabeludo/fisiologia , Alopecia , Animais , Dermatite Seborreica/metabolismo , Cabelo , Folículo Piloso/imunologia , Folículo Piloso/fisiologia , Humanos , Sistema Imunitário , Inflamação , Queratinócitos/citologia , Camundongos , Psoríase , Couro Cabeludo/patologia , Pele/imunologia , Pele/metabolismo , Dermatopatias/metabolismoRESUMO
The anatomy of the hair follicle and the dynamics of its barrier provide a special space for interactions between macromolecules and the underlying tissue. Translocation across the hair follicle epithelium and immune recognition have been confirmed for proteins, nucleic acids, engineered particles, virus particles and others. Tissue responses can be modulated by pro-inflammatory stimuli as demonstrated in penetration and transcutaneous immunization studies. Even under physiological conditions, hair follicle openings are filled with exogenous material ranging from macromolecules, engineered particles to natural particles including diverse communities of microbes. The exposed position of the infundibulum suggests that local inflammatory insults could disturb the finely tuned balance and may trigger downstream responses that initiate or facilitate local outbreaks of inflammatory hair diseases typically occurring in close spatial association with the infundibulum as observed in cicatricial alopecia. The question as to how microbial colonization or deposition of contaminants on the surface of the hair follicle epithelium interact with the barrier status under the influence of individual predisposition, may help us understand local flare-ups of inflammatory hair diseases. Specifically, learning more about skin barrier alterations in the different types of inflammatory hair diseases and cross-talk with exogenous compounds could give new insights in this less explored aspect of hair follicle homeostasis. Such knowledge may not only be used to develop supportive measures to maintain a healthy scalp. It may have wider implications for our understanding on how external factors influence inflammation and immunological responses in the skin.
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BACKGROUND: A systematic review failed to identify any systemic therapy used in alopecia areata (AA) where use is supported by robust evidence from high-quality randomized controlled trials. OBJECTIVE: To produce an international consensus statement on the use and utility of various treatments for AA. METHODS: Fifty hair experts from 5 continents were invited to participate in a 3-round Delphi process. Agreement of 66% or greater was considered consensus. RESULTS: In the first round, consensus was achieved in 22 of 423 (5%) questions. After a face-to-face meeting in round 3, overall, consensus was achieved for only 130 (33%) treatment-specific questions. There was greater consensus for intralesional treatment of AA (19 [68%]) followed by topical treatment (25 [43%]). Consensus was achieved in 45 (36%) questions pertaining to systemic therapies in AA. The categories with the least consensus were phototherapy and nonprescription therapies. LIMITATIONS: The study included a comprehensive list of systemic treatments for AA but not all treatments used. CONCLUSION: Despite divergent opinions among experts, consensus was achieved on a number of pertinent questions. The concluding statement also highlights areas where expert consensus is lacking and where an international patient registry could enable further research.
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Alopecia em Áreas/terapia , Administração Oral , Administração Tópica , Corticosteroides/uso terapêutico , Fatores Etários , Alopecia em Áreas/tratamento farmacológico , Terapia Combinada , Terapias Complementares , Técnica Delphi , Fármacos Dermatológicos/uso terapêutico , Prova Pericial , Humanos , Injeções Intralesionais , Fototerapia , Índice de Gravidade de Doença , Resultado do TratamentoRESUMO
BACKGROUND: International studies indicate deficits in end-of-life care that can lead to distress for patients and their next-of-kin. The aim of the study was to translate and validate the "Care of the Dying Evaluation" (CODE) into German (CODE-GER). METHODS: Translation according to EORTC (European Organisation for Research and Treatment of Cancer) guidelines was followed by data collection to evaluate psychometric properties of CODE-GER. Participants were next-of-kin of patients who had died an expected death in two hospitals. They were invited to participate at least eight, but not later than 16 weeks after the patient's death. To calculate construct validity, the Palliative care Outcome Scale (POS) was assessed. Difficulty and perceived strain of answering the questionnaire were assessed by a numeric scale (0-10). RESULTS: Out of 1137 next-of-kin eligible, 317 completed the questionnaire (response rate: 27.9%). Data from 237 main sample participants, 38 interraters and 55 next-of-kin who participated for repeated measurement were analysed. Overall internal consistency, α = 0.86, interrater reliability, ICC (1) = 0.79, and retest-reliability, ICC (1, 2) = 0.85, were good. Convergent validity between POS and CODE-GER, r = -.46, was satisfactory. A principal component analysis with varimax rotation showed a 7-factor solution. Difficulty, M = 2.2; SD ± 2.4, and perceived strain, M = 4.1; SD ± 3.0, of completing the questionnaire were rather low. CONCLUSION: The results from the present study confirm CODE-GER as a reliable and valid instrument to assess the quality of care of the dying person. More over our study adds value to the original questionnaire by proposing a deepened analysis of obtained data. The development of seven subscales increases its potential for further surveys and research. TRIAL REGISTRATION: This study was registered retrospectively on the 25th of January 2018 at the German Clinical Trials Register ( DRKS00013916 ).
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Família/psicologia , Inquéritos e Questionários/normas , Assistência Terminal/normas , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Cuidados Paliativos/normas , Psicometria/instrumentação , Qualidade de Vida , Reprodutibilidade dos Testes , Estudos Retrospectivos , TraduçõesRESUMO
PURPOSE: Providing high-quality care for the dying is essential in palliative care. Quality of care can be checked, compared, and improved by assessing responses from bereaved next-of-kin. The objectives of this study are to examine quality of care in the last 2 days of life of hospitalized patients considering specific aspects of their place of care. METHODS: The "Care of the Dying Evaluation" (CODE™) questionnaire, validated in German in 2018 (CODE-GER), examines quality of care for the patient and support of next-of-kin, allocating values between 0 (low quality) and 4 (high quality). The total score (0-104) is divided into subscales which indicate support/time given by doctors/nurses, spiritual/emotional support, information/decision-making, environment, information about the dying process, symptoms, and support at the actual time of death/afterwards. Next-of-kin of patients with an expected death in specialized palliative care units and other wards in two university hospitals between April 2016 and March 2017 were included. RESULTS: Most of the 237 analyzed CODE-GER questionnaires were completed by the patient's spouse (42.6%) or children (40.5%) and 64.1% were female. Patients stayed in hospital for an average of 13.7 days (3-276; SD 21.1). Half of the patients died in a specialized palliative care unit (50.6%). The CODE-GER total score was 85.7 (SD 14.17; 25-104). Subscales were rated significantly better for palliative care units than for other wards. Unsatisfying outcomes were reported in both groups in the subscales for information/decision-making and information about the dying process. CONCLUSION: The overall quality of care for the dying was rated to be good. Improvements of information about the dying process and decision-making are needed. TRIAL REGISTRATION: DRKS00013916.
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The surname and name of Christoph (name) Ostgathe (surname) are reversed.
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Based on experimental concentration depth profiles of the antiinflammatory drug dexamethasone in human skin, we model the time-dependent drug penetration by the 1D general diffusion equation that accounts for spatial variations in the diffusivity and free energy. For this, we numerically invert the diffusion equation and thereby obtain the diffusivity and the free-energy profiles of the drug as a function of skin depth without further model assumptions. As the only input, drug concentration profiles derived from X-ray microscopy at three consecutive times are used. For dexamethasone, skin barrier function is shown to rely on the combination of a substantially reduced drug diffusivity in the stratum corneum (the outermost epidermal layer), dominant at short times, and a pronounced free-energy barrier at the transition from the epidermis to the dermis underneath, which determines the drug distribution in the long-time limit. Our modeling approach, which is generally applicable to all kinds of barriers and diffusors, allows us to disentangle diffusivity from free-energetic effects. Thereby we can predict short-time drug penetration, where experimental measurements are not feasible, as well as long-time permeation, where ex vivo samples deteriorate, and thus span the entire timescales of biological barrier functioning.
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Dexametasona/administração & dosagem , Epiderme/metabolismo , Administração Cutânea , Dexametasona/farmacocinética , Difusão , Humanos , Microscopia , Modelos Químicos , Absorção Cutânea , Raios XRESUMO
Based on experimental drug concentration profiles in healthy as well as tape-stripped ex vivo human skin, we model the penetration of the antiinflammatory drug dexamethasone into the skin layers by the one-dimensional generalized diffusion equation. We estimate the position-dependent free-energy and diffusivity profiles by solving the conjugated minimization problem, in which the only inputs are concentration profiles of dexamethasone in skin at three consecutive penetration times. The resulting free-energy profiles for damaged and healthy skin show only minor differences. In contrast, the drug diffusivity in the first 10 µm of the upper skin layer of damaged skin is 200-fold increased compared to healthy skin, which reflects the corrupted barrier function of tape-stripped skin. For the case of healthy skin, we examine the robustness of our method by analyzing the behavior of the extracted skin parameters when the number of input and output parameters are reduced. We also discuss techniques for the regularization of our parameter extraction method.
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Anti-Inflamatórios/farmacocinética , Dermatite/metabolismo , Dexametasona/farmacocinética , Modelos Teóricos , Pele/metabolismo , Difusão , Humanos , Fenômenos Fisiológicos da PeleRESUMO
Most antimicrobial peptides (AMPs) and their synthetic mimics (SMAMPs) are thought to act by permeabilizing cell membranes. For antimicrobial therapy, selectivity for pathogens over mammalian cells is a key requirement. Understanding membrane selectivity is thus essential for designing AMPs and SMAMPs to complement classical antibiotics in the future. This study focuses on membrane permeabilization induced by SMAMPs and their selectivity for membranes with different lipid compositions. We measure release and fluorescence lifetime of a self-quenching dye in lipid vesicles. Apart from the dose-response, we quantify the strength of individual leakage events, and, employing cumulative kinetics, categorize permeabilization behavior. We propose that differing selectivities in a series of SMAMPs arise from a combination of the effect of the antimicrobial agent and the susceptibility of the membrane (with a given lipid composition) for certain types of leakage behavior. The unselective and hemolytic SMAMP is found to act mainly by the asymmetry stress mechanism, mediated by hydrophobic insertion of SMAMPs into lipid layers. The more selective SMAMPs induced leakage events occurring stochastically over several hours. Lipid intrinsic properties might additionally amplify the efficiency of leakage events. Leakage behavior changes with both the design of the SMAMP and the lipid composition of the membrane. Understanding how leakage behavior contributes to the selectivity and activity of antimicrobial agents will aid the design and screening of antimicrobials. An understanding of the underlying processes facilitates the comparison of membrane permeabilization across in vitro and in vivo assays.