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PURPOSE: Accurate surgical reconstruction of arterial vascular supply is a crucial part of living kidney transplantation (LDKT). The presence of multiple renal arteries (MRA) in grafts can be challenging. In the present study, we investigated the impact of ligation versus anastomosis of small accessory graft arteries on the perioperative outcome. METHODS: Clinical and radiological outcomes of 51 patients with MRA out of a total of 308 patients who underwent LDKT with MRA between 2011 and 2020 were stratified in two groups and analyzed. In group 1 (20 patients), ligation of accessory arteries (ARAs) and group 2 (31 patients) anastomosis of ARAs was performed. RESULTS: Significant differences were observed in the anastomosis-, surgery-, and warm ischemia time (WIT) in favor of group 1. Students t-test showed comparable serum creatinine levels of 2.33 (± 1.75) to 1.68 (± 0.83) mg/dL in group 1 and 2.63 (± 2.47) to 1.50 (± 0.41) mg/dL in group 2, were seen from 1 week to 1 year after transplant. No increased rates of Delayed graft function (DGF), primary transplant dysfunction and transplant rejection were seen, but graft loss and revision rates were slightly higher when the ARAs were ligated. Analysis of Doppler sonography revealed that segmental perfusion deficits tend to regenerate during the clinical course. CONCLUSION: Ligation of smaller accessory renal arteries may not affect the outcome of living kidney transplantation, except for a minor increase in the reoperation rate. Segmental perfusion deficits of the graft seem to regenerate in most cases as seen in Doppler sonography.
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Transplante de Rim , Humanos , Transplante de Rim/efeitos adversos , Artéria Renal/cirurgia , Doadores Vivos , Estudos Retrospectivos , Sobrevivência de Enxerto , Rim/diagnóstico por imagem , Rim/cirurgia , Rim/irrigação sanguínea , Resultado do TratamentoRESUMO
Ocean disposal of industrial waste from technical DDT [mainly 1,1'-(2,2,2-trichloroethane-1,1-diyl)bis(4-chlorobenzene), or 4,4'-DDT] manufacture occurred historically in the Southern California Bight. However, the paucity of historical records highlights uncertainties as to the mode, location, and timing of disposal or ongoing ecological effects of these wastes. This study combines sampling, chemical analysis, and numerical modeling of deep San Pedro Basin sediments revealing substantial DDT contamination that extends at least 25 km from the mainland. These findings narrate bulk DDT waste disposal to the offshore that peaked in the 1950s, prior to the onset of formal regulations; was agnostic to later-designated disposal sites; and has experienced sluggish transformation. Our findings further indicate an attenuating secondary source for the DDT daughter product, 1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethenyl]benzene (4,4'-DDE), which still deposits into deep San Pedro Basin sediments. While demonstrating the severity of DDT contamination to the region, these findings further define the burial potential of DDT wastes and inform the past, present, and future contamination potential that is needed to understand and predict ecological consequences. This work also points firmly to bulk, not containerized, disposal of DDT waste and to potential alternative contents of collocated waste.
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DDT , Resíduos Industriais , DDT/análise , Resíduos Industriais/análise , Monitoramento Ambiental , Oceanos e Mares , CaliforniaRESUMO
AbstractDeveloping organisms often plastically modify growth in response to environmental circumstances, which may be adaptive but is expected to entail long-term costs. However, the mechanisms that mediate these growth adjustments and any associated costs are less well understood. In vertebrates, one mechanism that may be important in this context is the highly conserved signaling factor insulin-like growth factor 1 (IGF-1), which is frequently positively related to postnatal growth and negatively related to longevity. To test this idea, we exposed captive Franklin's gulls (Leucophaeus pipixcan) to a physiologically relevant nutritional stressor by restricting food availability during postnatal development and examined the effects on growth, IGF-1, and two potential biomarkers of cellular and organismal aging (oxidative stress and telomeres). During food restriction, experimental chicks gained body mass more slowly and had lower IGF-1 levels than controls. Following food restriction, experimental chicks underwent compensatory growth, which was accompanied by an increase in IGF-1 levels. Interestingly, however, there were no significant effects of the experimental treatment or of variation in IGF-1 levels on oxidative stress or telomeres. These findings suggest that IGF-1 is responsive to changes in resource availability but is not associated with increased markers of cellular aging during development in this relatively long-lived species.
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Charadriiformes , Fator de Crescimento Insulin-Like I , Animais , Senescência Celular , Envelhecimento , AlimentosRESUMO
Viral haemorrhagic septicaemia virus (VHSV) is a negative-sense single-stranded RNA virus that infects more than 140 different fish species. In this study, zebrafish larvae were employed as in vivo model organisms to investigate progression of disease, the correlation between propagation of the infection and irreversibility of disease, cell tropism and in situ neutrophil activity towards the VHSV-infected cells. A recombinant VHSV strain, encoding "tomato" fluorescence (rVHSV-Tomato), was used in zebrafish to be able to follow the progress of the infection in the live host in real-time. Two-day-old zebrafish larvae were injected into the yolk sac with the recombinant virus. The virus titre peaked 96 hr post-infection in zebrafish larvae kept at 18°C, and correlated with 33% mortality and high morbidity among the larvae. By utilizing the transgenic zebrafish line Tg(fli1:GFP)y1 with fluorescently tagged endothelial cells, we were able to demonstrate that the virus initially infected endothelial cells lining the blood vessels. By observing the rVHSV-Tomato infection in the neutrophil reporter zebrafish line Tg(MPX:eGFP)i114 , we inferred that only a subpopulation of the neutrophils responded to the virus infection. We conclude that the zebrafish larvae are suitable for real-time studies of VHS virus infections, allowing in vivo dissection of host-virus interactions at the whole organism level.
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Septicemia Hemorrágica Viral/virologia , Neutrófilos/metabolismo , Novirhabdovirus/fisiologia , Tropismo/fisiologia , Peixe-Zebra , Animais , Modelos Animais de DoençasRESUMO
Vaccine development is important for sustainable fish farming and novel vaccines need to be efficacy tested before release to the market. Challenge of fish with the pathogen towards which the vaccine has been produced can be conducted either by external exposure though bathing or cohabitation, or by bypassing the mucosa through injection. The latter approach is often preferred since it is easier to control than the former. However, injection is not a very natural route of infection, and the bypass of the mucosa may result in a different efficacy profile of experimental fish compared to farmed fish, for which the vaccines are targeted. The zebrafish is by now a well established practical vertebrate model species due in part to its size and ease of maintenance and genetic manipulation. Here we use zebrafish as a model to visualize and compare the development of infection of Vibrio anguillarum on and in the fish following injection or bathing. Injection of 103 bacteria per fish resulted in approximately 50% mortality by day 4 post-injection. Similar mortality levels were reached in the other group by bathing in 1.25 × 109 bacteria for 1 min. The spreading of bacteria was followed for the first 24 h after injection/bathing by immunohistochemistry and optical projection tomography. The tissues and organs where bacteria were detected differed significantly as a result of time as well as treatment. In the bath group, bacteria were initially found on external surfaces including gut. After 24 h V. anguillarum still persisted in gut but had now also spread to the blood. In the injection group bacteria were found in the blood throughout all sampling times, as well as in the hypodermis and body cavity at most sampling times.
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Progressão da Doença , Doenças dos Peixes/microbiologia , Vibrioses/veterinária , Vibrio/fisiologia , Peixe-Zebra , Animais , Modelos Animais de Doenças , Doenças dos Peixes/imunologia , Tomografia Óptica/veterinária , Vibrioses/imunologia , Vibrioses/microbiologiaRESUMO
Femtosecond time-resolved, fully resonant electronically enhanced coherent anti-Stokes Raman scattering (FREE-CARS) spectroscopy, incorporating a two-color excitation scheme, is used to demonstrate selective and sensitive gas-phase detection of the hydroxyl (OH) radical in a reacting flow. Spectral resolution of the emitted FREE-CARS signal allows simultaneous detection of temperature and relative OH mole fraction under single-laser-shot conditions in a laminar ethylene-air flame. By comparison to previously reported OH concentration and temperature measurements, we demonstrate excellent single-shot temperature accuracies (â¼2% deviation from adiabatic flame temperature) and precisions (â¼2% standard deviation), with simultaneous relative OH concentration measurements that demonstrate high detection sensitivity (100-300 ppm).
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Lipid oxidation has been linked to plasma membrane damage leading to cell death. In previous work, we examined the effect of oxidation on bilayer permeability by replacing defined amounts of an unsaturated lipid species with the corresponding phospholipid product that would result from oxidative tail scission of that species. This study adds the cleaved tail fragment, better mimicking the chemical results of oxidation. Permeability of PEG12-NBD, a small, uncharged molecule, was measured for vesicles with oxidation concentration corresponding to between 0 and 18 mol % of total lipid content. Permeability was measured using a microfluidic trap to capture the vesicles and spinning disk confocal microscopy (SDCM) to measure the transport of fluorescent PEG12-NBD at the equatorial plane. The thicknesses of lipid bilayers containing oxidized species were estimated by measuring capacitance of a black lipid membrane while simultaneously measuring bilayer area. We found that relative to chemically modeled oxidized bilayers without tail fragments, bilayers containing cleaved tail groups were less permeable for the same degree of oxidation. Curiously, membrane capacitance measurements indicated that the addition of tail fragments to chemically modeled oxidized bilayers also thinned these bilayers relative to samples with no tail fragments; in other words, the more permeable membranes were thicker. Above 12.5% chemically modeled oxidation, compositions both with and without the cleaved tail groups showed pore formation. This work highlights the complexity of the relationship between chemically modeled lipid bilayer oxidation and cell membrane properties.
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Colesterol/química , Dimiristoilfosfatidilcolina/química , Bicamadas Lipídicas/química , Fosfatidilcolinas/química , Fosfatidiletanolaminas/química , Avidina/química , Azóis/química , Biotina/química , Permeabilidade da Membrana Celular , Capacitância Elétrica , Corantes Fluorescentes/química , Dispositivos Lab-On-A-Chip , Nitrobenzenos/química , Oxirredução , Polietilenoglicóis/química , Rodaminas/química , Eletricidade EstáticaRESUMO
A resonantly enhanced, two-color, femtosecond time-resolved coherent anti-Stokes Raman scattering (CARS) approach is demonstrated and used to explore the nature of the frequency- and time-dependent signals produced by gas-phase nitric oxide (NO). Through careful selection of the input pulse wavelengths, this fully resonant electronically enhanced CARS (FREE-CARS) scheme allows rovibronic-state-resolved observation of time-dependent rovibrational wavepackets propagating on the vibrationally excited ground-state potential energy surface of this diatomic species. Despite the use of broadband, ultrafast time-resolved input pulses, high spectral resolution of gas-phase rovibronic transitions is observed in the FREE-CARS signal, dictated by the electronic dephasing timescales of these states. Analysis and computational simulation of the time-dependent spectra observed as a function of pump-Stokes and Stokes-probe delays provide insight into the rotationally resolved wavepacket motion observed on the excited-state and vibrationally excited ground-state potential energy surfaces of NO, respectively.
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The human ether-a-go-go related gene (hERG) encodes the potassium channel Kv11.1, which plays a key role in the cardiac action potential and has been implicated in cardiac disorders as well as a number of off-target pharmaceutical interactions. The electrophysiology of this channel has been predominantly studied using patch clamp, but lipid bilayers have the potential to offer some advantages, including apparatus simplicity, ease of use, and the ability to control the membrane and solution compositions. We made membrane preparations from hERG-expressing cells and measured them using droplet bilayers, allowing measurement of channel ensemble currents and 13.5 pS single channel currents. These currents were ion selective and were blockable by E-4031 and dofetilide in a dose-dependent manner, allowing determination of IC50 values of 17 nM and 9.65 µM for E-4031 and dofetilide, respectively. We also observed time- and voltage- dependent currents following step changes in applied potential that were similar to previously reported patch clamp measurements.
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Condutividade Elétrica , Canais de Potássio Éter-A-Go-Go/química , Animais , Antiarrítmicos/química , Canal de Potássio ERG1 , Células HEK293 , Humanos , Bicamadas Lipídicas , Camundongos , Piperidinas/química , Piridinas/químicaRESUMO
Target DNA fragments at 10 fM concentration (approximately 6 × 10(5) molecules) were detected against a DNA background simulating the noncomplementary genomic DNA present in real samples using a simple, PCR-free, optics-free approach based on electromechanical signal transduction. The development of a rapid, sensitive, and cost-effective nucleic acid detection platform is highly desired for a range of diverse applications. We previously described a potentially low-cost device for sequence-specific nucleic acid detection based on conductance change measurement of a pore blocked by electrophoretically mobilized bead-(peptide nucleic acid probe) conjugates upon hybridization with target nucleic acid. Here, we demonstrate the operation of our device with longer DNA targets, and we describe the resulting improvement in the limit of detection (LOD). We investigated the detection of DNA oligomers of 110, 235, 419, and 1613 nucleotides at 1 pM to 1 fM and found that the LOD decreased as DNA length increased, with 419 and 1613 nucleotide oligomers detectable down to 10 fM. In addition, no false positive responses were obtained with noncomplementary, control DNA fragments of similar length. The 1613-base DNA oligomer is similar in size to 16S rRNA, which suggests that our device may be useful for detection of pathogenic bacteria at clinically relevant concentrations based on recognition of species-specific 16S rRNA sequences.
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DNA/química , Transdução de Sinais , Limite de DetecçãoRESUMO
Recirculating aquaculture systems (RAS) have become more attractive due to reduced water consumption and effluent discharge. However, intensification of production increases the risk of introducing pathogens at farming sites. The emergence of uncultivable pathogens and RAS pathobiome diversity shifts the traditional disease paradigm from "one pathogen, one disease" to complex multiple-pathogen disease cases. Piscine orthoreovirus genotype 3 (PRV-3) is an excellent example, as it is capable of inducing anemia and heart pathology resembling heart and skeletal muscle inflammation under experimental conditions, and is associated with increased mortality in association with other pathogens in the field. The aim of this study was to develop a method for detection of multiple pathogens and putative pathogens, as co-infections are common in aquaculture. To do this, in the pilot study, we mapped the pathobiome of RAS-farmed rainbow trout (Oncorhynchus mykiss) (commercial RAS, farm A) using both standard diagnostic methods and metabarcording (16S rRNA) to investigate the gill microbiome. During this study, we observed infections with multiple pathogens, and detected two putative gill pathogens Candidatus Branchiomonas cysticola and Candidatus Piscichlamydia salmonis, both of which have been linked with complex gill disease in Atlantic salmon (Salmo salar). Based on the pilot study, we developed and tested a high throughput qPCR (HT-qPCR) chip targeting 22 viral and bacterial pathogens and putative pathogens, followed by a surveillance of a fish cohort in a commercial RAS farm during production (farm B). Co-infection with PRV-3 and Ca. B. cysticola combined with stress inducing management practices may explain the severe disease outbreak observed (37% mortality). The time course study sets the base for a future screening scheme for disease prediction and addresses limitations of the method when testing environmental DNA/RNA.
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Aquicultura , Coinfecção , Doenças dos Peixes , Oncorhynchus mykiss , Animais , Oncorhynchus mykiss/virologia , Oncorhynchus mykiss/microbiologia , Aquicultura/métodos , Coinfecção/microbiologia , Coinfecção/veterinária , Coinfecção/virologia , Doenças dos Peixes/virologia , Doenças dos Peixes/microbiologia , Reação em Cadeia da Polimerase em Tempo Real/métodos , RNA Ribossômico 16S/genética , Brânquias/virologia , Brânquias/microbiologia , Microbiota/genéticaRESUMO
PURPOSE: Ultrasound (US) is the primary imaging modality when a testicular tumor is suspected. Superb microvascular imaging (SMI) is a novel, highly sensitive Doppler technique that allows quantification of flow signals by determination of the Vascular Index (VI). The aim of the present study is to investigate the diagnostic significance of the SMI-derived VI in normal testicular tissue and testicular cancer. METHODS: This retrospective analysis included patients who underwent testicular US in our department from 2018 to 2022. Inclusion criteria were: i) sufficient image quality of the stored images, ii) US with standardized SMI-default setting (colour gain of 44 ± 5), iii) patient age ≥ 18 years, and iv) normal testicular findings or testicular tumor with histopathological workup. US examinations were performed as part of clinical routine using a high-end ultrasound system (Aplio i800/i900, Canon Medical Systems Corporation, Tochigi, Japan). Statistical analysis included Chi-square test and Mann-Whitney U tests and receiver operating characteristic (ROC) curve analysis. RESULTS: A total of 62 patients (31 each with normal findings and testicular tumors) were included. The VI differed statistically significantly (p < 0.001) between normal testis (median 2.5 %) and testicular tumors (median 17.4 %). Like vascular patterns (p < 0.001), the VI (p = 0.030) was shown to distinguish seminomas (median 14.8 %), non-seminomas (median 17.6 %) and lymphomas (median 34.5 %). CONCLUSIONS: In conclusion, our study has shown the VI to be a quantitative tool that can add information for differentiating testicular tumor entities. While further confirmation in larger study populations is desirable, our results suggest that the VI may be a useful quantitative parameter.
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Neoplasias Testiculares , Humanos , Masculino , Neoplasias Testiculares/diagnóstico por imagem , Estudos Retrospectivos , Adulto , Pessoa de Meia-Idade , Testículo/diagnóstico por imagem , Testículo/irrigação sanguínea , Idoso , Adulto Jovem , Ultrassonografia Doppler/métodosRESUMO
Background and objective: Kidney transplant recipients (KTRs) have an increased risk of developing genitourinary cancers, including prostate cancer (PCa), which is expected to become more prevalent due to an aging KTR population. Thus, knowledge of surgical outcomes, including treatment of PCa, within this unique cohort is required. Methods: Data of 62 KTRs undergoing radical prostatectomy (RP) between 2006 and 2023 at nine urologic transplant centers were analyzed. Complications were assessed using the Clavien-Dindo classification. Perioperative outcomes were evaluated, and a follow-up was conducted. Overall survival (OS), biochemical recurrence-free survival (BRFS), and death-censored graft survival were determined via the Kaplan-Meier method and log-rank testing. Key findings and limitations: Overall, 50 open radical retropubic RPs and 12 robot-assisted RPs (RARPs) were included. The intraoperative blood loss was lower after RARP, but operative time was longer. Of the patients, 50% experienced no postoperative complication, and grade ≥3 complications were observed in 14.5%. There was no graft loss related to RP. A histopathologic analysis revealed pN1 in 8.1% and positive surgical margins in 25.8% of the cases. At a median follow-up of 48.5 mo, the median OS was 128 (95% confidence interval [CI] 71.2-184.8) mo, BRFS was 106 (95% CI 55.8; 156.2) mo, and graft survival was 127 (95% CI 66.7-187.3) mo. Limitations include the retrospective design, and variations between groups and centers. Conclusions and clinical implications: Our findings support RP as a feasible and safe treatment option for localized PCa in KTRs with acceptable oncologic outcome. Special care is required in screening and awareness for the risk of understaging. Patient summary: This study analyzed the safety and effectiveness of two prostate cancer surgery methods-open and robot-assisted surgery-in the special group of kidney transplant recipients. Both surgical methods were performed safely with acceptable oncologic outcomes; however, sample size was too small to draw definite conclusions between the two operative methods.
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Direct measurements of arterial blood pressure most commonly use bulky external instrumentation containing a pressure transducer connected to an ex vivo fluid-filled arterial line, which is subject to several sensing artifacts. In situ blood pressure sensors, typically solid state piezoresistive, capacitive, and interferometric sensors, are unaffected by these artifacts, but can be expensive to produce and miniaturize. We have developed an alternative approach to blood pressure measurement based on deformation of an elastic tube filled with electrolyte solution. We have constructed an analytical model describing the deformation of a fluid-filled tube part of which is exposed to external pressure, with the remaining part unexposed. The model predicts pressure-induced change in dimension of the internal electrolyte-filled volume and a resultant change in its electrical resistance, which can be measured to determine the pressure and is the basis for the sensor operation. We have applied the model to find the pressure sensitivity of fractional change in resistance as a function of device material and dimensional parameters. Construction and testing of a device is described in the following paper.
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Monitores de Pressão Arterial , Catéteres , Condutividade Elétrica , Eletrodos Implantados , Eletrólitos/química , Modelos Teóricos , Pressão , ElasticidadeRESUMO
Direct measurements of arterial blood pressure most commonly use bulky external instrumentation containing a pressure transducer connected to an ex vivo fluid-filled arterial line, which is subject to several sensing artifacts. In situ blood pressure sensors, typically solid state piezoresistive, capacitive, and interferometric sensors, are unaffected by these artifacts, but can be expensive to produce and miniaturize. We have developed an alternative approach to blood pressure measurement based on deformation of an elastic tube filled with electrolyte solution. Simple measurement of the electrical conductance of this solution as the tube dimensions change allows determination of the external pressure. The sensor is made from inexpensive materials and its miniaturization is straightforward. In vitro static testing of initial sensor prototypes mounted on a catheter tip showed a linear response with applied pressure and a resolution of 1 mmHg. In vivo sensing followed catheterization of the sensor into the femoral artery of a porcine model through a 7F catheter port. The sensor performed comparably to a commercial pressure transducer also connected to the catheter port. Due to its scalability and cost, this sensor has the potential for use in a range of pressure sensing applications, such as measurement of intracranial, spinal, or interstitial pressures.
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Monitores de Pressão Arterial , Catéteres , Eletrodos Implantados , Eletrólitos/química , Pressão , Animais , Calibragem , Elasticidade , Desenho de Equipamento , Feminino , SuínosRESUMO
We show measurements of the human cardiac potassium ion channel Kv11.1 (hERG) in droplet bilayers incorporated directly from commercial membrane preparations of HEK293 cells. Although we do not obtain ensemble conductance kinetics and rectification observed in patch clamp measurements of hERG, ensemble currents measured in our system showed inhibition dependent on astemizole and E-4031 concentration, with IC50 values similar to those found with patch clamp. The availability of engineered HEK cells expressing a variety of ion channels, combined with the simplicity of the inhibition measurement, suggest that droplet bilayers may have considerable technological potential for determination of ion channel drug potency.
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Avaliação Pré-Clínica de Medicamentos/instrumentação , Canais de Potássio Éter-A-Go-Go/química , Bicamadas Lipídicas/química , Potenciais da Membrana/efeitos dos fármacos , Técnicas Analíticas Microfluídicas/instrumentação , Bloqueadores dos Canais de Potássio/química , Bloqueadores dos Canais de Potássio/farmacologia , Canal de Potássio ERG1 , Desenho de Equipamento , Análise de Falha de Equipamento , Canais de Potássio Éter-A-Go-Go/efeitos dos fármacos , Ativação do Canal Iônico/efeitos dos fármacosRESUMO
Membrane permeability assays play an important role in assessing drug transport activities across biological membranes. However, in conventional parallel artificial membrane permeability assays (PAMPA), the membrane model used is dissimilar to biological membranes physically and chemically. Here, we describe a microfluidic passive permeability assay using droplet interface bilayers (DIBs). In a microfluidic network, nanoliter-sized donor and acceptor aqueous droplets are alternately formed in cross-flowing oil containing phospholipids. Subsequently, selective removal of oil through hydrophobic pseudo-porous sidewalls induces the contact of the lipid monolayers, creating arrayed planar DIBs between the donor and acceptor droplets. Permeation of fluorescein from the donor to the acceptor droplets was fluorometrically measured. From the measured data and a simple diffusion model we calculated the effective permeabilities of 5.1 × 10(-6) cm s(-1), 60.0 × 10(-6) cm s(-1), and 87.6 × 10(-6) cm s(-1) with donor droplets at pH values of 7.5, 6.4 and 5.4, respectively. The intrinsic permeabilities of specific monoanionic and neutral fluorescein species were obtained similarly. We also measured the permeation of caffeine in 10 min using UV microspectroscopy, obtaining a permeability of 20.8 × 10(-6) cm s(-1). With the small solution volumes, short measurement time, and ability to measure a wide range of compounds, this device has considerable potential as a platform for high-throughput drug permeability assays.
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Bioensaio/instrumentação , Bicamadas Lipídicas/química , Microfluídica , Bioensaio/métodos , Cafeína/química , Concentração de Íons de Hidrogênio , Permeabilidade , Água/químicaRESUMO
Infrared photodissociation (IRPD) spectra are reported for a proline-chloride anion cluster along with its d2- and d7-isotopomers. The spectral data indicate that proline is in its neutral form as opposed to a zwitterion, and computations are in agreement in that some neutral conformers are energetically low-lying and reproduce the observed spectra. Zwitterionic conformers are predicted to be essentially as stable as the neutral ones and should be significantly populated; however, there is no evidence for these structures in the IRPD spectra. An exploration of the potential energy surface for the loss of chloride anion, the observed fragmentation channel, reveals that it is 8.4 kcal mol(-1) more difficult to break apart the zwitterionic cluster ion. This is a reflection of the 15.8 kcal mol(-1) estimate for the gaseous proline zwitterion-neutral energy difference. Kinetic results suggest the presence of two photolabile populations in similar amounts (i.e., 56 vs 44%). The more abundant structure is also the more labile species, and the neutral form of proline is assigned to this cluster ion. The less abundant and slower fragmenting structure consequently is zwitterionic. As originally suggested by Evans et al. in general, it appears that in this instance both spectral and kinetic data are needed to determine the structure of the proline-chloride anion cluster.
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Aminoácidos/química , Cloretos/química , Prolina/química , Teoria Quântica , Ânions/química , Estrutura Molecular , Método de Monte Carlo , Processos Fotoquímicos , Espectrofotometria InfravermelhoRESUMO
Carbon dioxide laser cutters are used to cut and engrave on various types of materials, including metals, wood, and plastics. Although many are equipped with fume extractors for removing airborne substances generated during laser cutting, gases and particulate matter can be released upon opening the lid after completion. This study focused on investigating laser cutting acrylic sheets and associated emissions. Real-time instruments were utilized to monitor both particulate concentrations and size distributions, while the patented Tsai diffusion sampler was used to collect particulate samples on a polycarbonate membrane and transmission electron microscopy (TEM) grid. Identification of released gases consisted of the use of gas sampling with Teflon gas bags followed by analysis using gas chromatography-mass spectrometry (GC-MS). A portable ambient infrared air analyzer was used to quantify the concentrations of the chemicals released by laser cutting activities. The results of the study found that a significant concentration of particulate matter, including nanoplastic particles ranging 15.4-86 nm in particle sizes, and microplastics with agglomerates were released each time the laser cutter lid was opened and were observed to gradually increase in concentration for a period of at least 20 min after the completion of a cut. The GC-MS gaseous samples primarily contained methyl methacrylate at a low level close to the detection limit of the infrared air analyzer.