24 results on '"Kamber D"'
Search Results
2. How Does Management Voluntary Disclosure Behavior Influence Auditors’ Judgments?
- Author
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HILLISON, SEAN M., primary and VITTORI, KAMBER D., additional
- Published
- 2024
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3. Effects of Resveratrol-Loaded Cyclodextrin on the Quality Characteristics of Ram Spermatozoa Following Cryopreservation
- Author
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Ahmet Eser, Selin Yağcıoğlu, Ramazan Arıcı, Kamber Demir, and Kemal Ak
- Subjects
semen freezing ,resveratrol ,sperm quality assessments ,antioxidant ,Veterinary medicine ,SF600-1100 ,Zoology ,QL1-991 - Abstract
This study investigated the effects of pure and methyl-β-cyclodextrin loaded forms of resveratrol (10 µg/mL, 20 µg/mL, and 40 µg/mL) on ram sperm functions post-thawing. Semen samples were pooled and divided into ten groups: Control, RES10, RES20, RES40, CD10, CD20, CD40, RLC10, RLC20, and RLC40. The groups were pre-diluted with media containing the group-specific chemicals, followed by 15 min of incubation, dilution, and freezing. To assess the effects of the chemicals, a post-thaw sperm quality assessment was conducted. Motility and other velocity parameters were evaluated using computer-assisted semen analysis. The functional integrity of spermatozoa membranes was assessed with the hypo-osmotic swelling test, and the capacitation status of spermatozoa was determined through fluorescent microscopic evaluation. Additionally, flow cytometry was used to evaluate mitochondrial activity, oxidative stress, and the integrity of the sperm membrane and acrosome. The results indicated that cyclodextrin adversely affected sperm functions following freezing–thawing, notably increasing the rate of spermatozoa exhibiting pre-capacitation and mitochondrial activity by approximately 34% and 16%, respectively (p < 0.05). It was found that 20 µg/mL resveratrol prevented pre-capacitation (p < 0.05). Both resveratrol and resveratrol-loaded cyclodextrin groups improved post-thaw sperm qualities overall, demonstrating their utility for freezing ram semen. However, higher concentrations of resveratrol were found to negatively impact sperm functions.
- Published
- 2024
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4. Vacancy-oxygen complexes and their optical properties in AlN epitaxial films studied by positron annihilation.
- Author
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Uedono, A., Ishibashi, S., Keller, S., Moe, C., Cantu, P., Katona, T. M., Kamber, D. S., Wu, Y., Letts, E., Newman, S. A., Nakamura, S., Speck, J. S., Mishra, U. K., DenBaars, S. P., Onuma, T., and Chichibu, S. F.
- Subjects
OPTICAL properties ,EPITAXY ,POSITRON annihilation ,METAL organic chemical vapor deposition ,ALUMINUM nitride ,GALLIUM nitride ,CATHODOLUMINESCENCE ,COMPUTER simulation - Abstract
Vacancy-type defects in AlN grown by metal-organic vapor phase epitaxy (MOVPE) and lateral epitaxial overgrowth (LEO) using halide vapor phase epitaxy were probed by a monoenergetic positron beam. Doppler broadening spectra of the annihilation radiation were measured and compared to the spectra calculated using the projector augmented-wave method. For MOVPE-AlN, the concentration of vacancy-type defects was high near the interface between AlN and the GaN buffer layer, and the defect-rich region expanded from the interface toward the surface when the NH
3 flow rate increased. For the sample grown on the AlN buffer layer, however, the introduction of such defects was suppressed. For LEO-AlN, distinct deep emission peaks at 3–6 eV were observed in cathodoluminescence spectra. From a comparison between Doppler broadening spectra measured for LEO-AlN and computer simulated ones, an origin of the peaks was identified as complexes of Al vacancy (VAl ) and oxygen atoms substituting nitrogen sites such as VAl (ON )n (n=3 and 4). [ABSTRACT FROM AUTHOR]- Published
- 2009
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5. Determination of seminal characteristics in turkish aseel roosters
- Author
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Ebuderda GÜNAY, Ramazan ARICI, Hatice ŞENLİKÇİ, Selin YAĞCIOĞLU, Ahmet ESER, Kamber DEMİR, Serhat ALKAN, and Mamet ÇEŞMECİ
- Subjects
aseel rooster ,ornamental poultry ,seminal characteristic ,Veterinary medicine ,SF600-1100 - Abstract
Ornamental poultry is a hobby that has been of interest for centuries. The history of ornamental poultry associations in Europe dates back to the 19th century and to the Ottoman period in Turkiye. One of the most popular ornamental poultry species is Aseel roosters. Aseel roosters are indigenous of Pakistan and India, and they have been bred for competition during the Ottoman period. This study aims to determine the spermatological characteristics of Turkish Aseel roosters. In the study, 10 Aseel roosters were used, and semen was collected by the abdominal massage method twice a week. The sperm motility was estimated by a hot plate phase-contrast microscope under 400´ magnification. The sperm concentration of each ejaculate was determined by hemocytometer and percentages of viable, dead, and abnormal spermatozoa was calculated using eosin-nigrosine staining. Acrosome membrane integrity of rooster spermatozoa were assessed using fluorescein isothiocyanate-conjugated peanut agglutin (FITC-PNA). Spermatozoa membrane functionality was assessed with the hypoosmotic (HOS) test. The spermatological data obtained as a result of the experiment are as follows; ejaculate volume average 308.49±12.14 μL, spermatozoa motility 89.66±0.47%, spermatozoa concentration 2.39±0.10x109/mL, The general total morphological defect rate 17.19±0.75%, viability 85.45±0.88%, acrosome integrity rates 98.26±0.09%, and pH 7.81±0.02.
- Published
- 2023
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6. Effects of melatonin addition to the cold storage medium on cumulus oocyte complex apoptosis, viability and in vitro maturation rates of cat oocytes
- Author
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Ramazan ARICI, Kemal AK, Serhat PABUCCUOĞLU, Sema BİRLER, Kamber DEMİR, Selin YAĞCIOĞLU, Ahmet ESER, Nur ERSOY, İdil ORUÇ, Gül BAKIRER ÖZTÜRK, Evrim KÖMÜRCÜ BAYRAK, Bilge ÖZSAİT SELÇUK, Andaç KILIÇKAP, and Mithat EVECEN
- Subjects
soğukta saklama ,melatonin ,kedi ovaryumları ,i̇n vitro maturasyon ,apoptozis ,bax ,bcl-2 ,Veterinary medicine ,SF600-1100 - Abstract
Usage of oocytes obtained from ovaries aft er long-term cold storage for in vitro embryo production is a promising tool for the protection of wildlife and endangered animal species. Mammalian oocytes are susceptible to oxidative stress with regard to the high lipid content of plasma membranes. Melatonin is known as a powerful antioxidant and anti-apoptotic agent due to its ability to eliminate toxic oxygen derivatives and reduce the formation of reactive species. Th is study was performed to verify the optimal environmental conditions for long-term preservation of cat ovaries (Felis domesticus) by adding diff erent concentrations of melatonin (500, 750 and 1000 μM) to the storage medium (0.9% NaCl) as an antioxidant to be preserved at 4°C for 24 h. To determine the eff ect of melatonin on cat oocytes collected from stored ovaries, the anti and proapoptotic gene levels in cumulus oophorus, the in vitro maturation rates, the cell membrane and oocytes viability were evaluated. In all melatonin added groups regardless of whether they are stored in the cold; Pro-apoptotic gene levels (BAX) were determined to be upregulated however, antiapoptotic gene levels (BCL-2) were downregulated in cumulus cells (P
- Published
- 2022
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7. Ammonothermal bulk GaN substrates for LEDs
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Jiang, W., additional, Ehrentraut, D., additional, Kamber, D. S., additional, Downey, B. C., additional, Cook, J., additional, Grundmann, M., additional, Pakalapati, R. T., additional, Yoo, H., additional, and D'Evelyn, M. P., additional
- Published
- 2014
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8. Improved Neuronal Adhesion to the Surface of Electronic Device by Engulfment of Protruding Micro-Nails Fabricated on the Chip Surface.
- Author
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Spira, M.E., Kamber, D., Dormann, A., Cohen, A., Bartic, C., Borghs, G., Langedijk, J.P.M., Yitzchaik, S., Shabthai, K., and Shappir, J.
- Published
- 2007
- Full Text
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9. Effects of ovary transport and storage temperature on in vitro maturation and cumulus cell apoptosis rates in cat oocytes
- Author
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Mithat EVECEN, Kamber DEMİR, Ramazan ARICI, Selin YAĞCIOĞLU, Nur ERSOY, Nilhan COŞKUN, Elif ARMUTAK, Ayça ÜVEZ, Ebru GÜREL GÜREVİN, Ahmet ESER, Hatem ATALLA, Kemal AK, Serhat PABUCCUOĞLU, and Sema BİRLER
- Subjects
cat ,ovary ,transport temperature ,oocyte ,cumulus ,apoptosis ,Veterinary medicine ,SF600-1100 - Abstract
The objective of the present study was to examine the effects of two different transport temperature (37°C vs 4°C) and cold storage of ovaries for 24 h on cumulus cell apoptosis and maturation rates of cat oocytes in vitro. Ovaries were collected from 15 ovariohysterectomized domestic cats and maintained and transported to the laboratory in phosphate buffer saline at 37°C and 4°C. In order to determine the effects of storing time, some ovaries transported at 4°C were stored at the same temperature for 24 h. Selected cumulus oocyte complexes (COCs) were matured for 48 h at 38°C in four-well petri dishes containing 500 μL of modified oviduct medium (mSOF) under mineral oil in a 5% CO2 incubator with nearly 100% humidified. The morphological features of apoptosis were analysed in the cumulus cells at the beginning of in vitro maturation in both transporting temperature groups and after 24 h of cold stored group. The degree of apoptosis in cumulus cells were measured by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL). The IVM rates of oocytes were determined using Hoechst (33342) staining. Although the apoptotic morphological features were seen rarely and in similar rates in 37 and 4°C transporting groups (19.40 and 21.55%, P>0.001), it was seen more intensely in the 24 h cold stored group (34.80%, P0.05), and importantly lower at 4°C transporting and 24 h cold stored groups (18.90%, P
- Published
- 2018
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10. Effect of Different Cooling Rates on Embryo Survivability and Pregnancy Rates in Freezing Sheep Embryos
- Author
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Elif KARAMAN ÖZTÜRK, Kamber DEMİR, Ramazan ARICI, Sema BİRLER, Serhat PABUCCUOĞLU, and Mithat EVECEN
- Subjects
Koyun ,embriyo transferi ,soğutma hızı ,embriyo dondurma ,Veterinary medicine ,SF600-1100 - Abstract
Çalışmanın ilk bölümünde, mezbahadan sağlanan ovaryumlardan kazanılan oositler (n=2990) olgunlaştırma medyumu içerisinde 24 saat süreyle olgunlaştırıldı. Ardından, 20 saat süreyle İn Vitro Fertilizasyona (İVF) bırakıldılar. Yarıklanma gösteren embriyolar (n=1305), Sentetik Ovidukt Fluid (SOF) medyumu içerisine alınarak altı gün süresince İn Vitro Kültüre (İVK) bırakıldılar. İVK sonrası elde edilen morula-blastosist aşamasındaki embriyolar rastlantısal şekilde üç farklı dondurma hızı grubuna eşit olarak ayrıldılar (Grup I: 0,5 °C /dk, Grup II: 0,8 °C /dk, Grup III: 1 °C /dk). Her bir gruptaki embriyolar (n=50), 1,5 M etilen glikol bulunan dondurma medyumu içerisinde farklı soğutma hızlarında donduruldu. Sonuçta 0,5 °C/dk soğutma hızının en başarılı grup olduğu belirlendi (P
- Published
- 2016
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11. Effect of different transport temperatures of cattle and sheep ovaries on in vitro maturation of oocytes
- Author
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Özdaş, O. B., Taş, M., Umut, C., Mithat, E., Bacinoǧlu, S., Kamber, D., Kemal AK, and Ileri, K. I.
12. Distribution and role of proteasome in the transformation of an axon into a growth cone after axotomy.
- Author
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Kamber, D. and Spira, M. E.
- Published
- 2003
13. Ammonothermal bulk GaN substrates for LEDs
- Author
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Streubel, Klaus P., Jeon, Heonsu, Tu, Li-Wei, Strassburg, Martin, Jiang, W., Ehrentraut, D., Kamber, D. S., Downey, B. C., Cook, J., Grundmann, M., Pakalapati, R. T., Yoo, H., and D'Evelyn, M. P.
- Published
- 2014
- Full Text
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14. Automation of batch wastewater treatment systems using programmable logic controllers
- Author
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Alleman, J. E., Sweeney, M. W., and Kamber, D. M.
- Subjects
AUTOMATION ,SEWAGE - Published
- 1989
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15. The Effect of Cholesterol-Loaded Cyclodextrin and Resveratrol Compounds on Post-Thawing Quality of Ram Semen.
- Author
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Ahmet E, Ramazan A, Selin Y, İzem SA, Nur E, Kamber D, Mithat E, and Kemal A
- Subjects
- Male, Animals, Sheep physiology, Semen Analysis veterinary, Stilbenes pharmacology, Stilbenes chemistry, Semen drug effects, Semen physiology, Resveratrol pharmacology, Resveratrol chemistry, Resveratrol administration & dosage, Cyclodextrins chemistry, Cyclodextrins pharmacology, Semen Preservation veterinary, Semen Preservation methods, Cholesterol, Cryopreservation veterinary
- Abstract
Ram sperm are more vulnerable to freezing than those of most other farm animals. During sperm freezing, the cell membrane loses some of its cholesterol, which regulates signalling mechanisms and prevents premature capacitation. Resveratrol (RES) increases the fluidity of the cell membrane, which becomes peroxidized during freezing and reduces free radicals. In this study, the effectiveness of RES, cholesterol-loaded cyclodextrin (CLC) and their combinations in ram sperm cryopreservation were investigated. The collected semen was divided into two equal volumes: One was diluted with tris-citric acid-glucose medium (TCG) containing CLC, whereas the other was diluted with a CLC-free TCG solution. After examining motility, both groups were further divided into two equal volumes, forming the following working groups: control (no RES, no CLC); RES (20 µg/mL); CLC (2 mg CLC/120 × 10
6 sperm); and RES + CLC (RES 20 µg/mL + 2 mg CLC/120 × 106 sperm). These groups were diluted with media containing their respective additives. Post-thawing, the samples were analysed for motility, acrosome and membrane integrity, membrane functionality, mitochondrial activity, capacitation status, oxidative stress and DNA integrity. CLC preserved sperm total motility, acrosome and plasma membrane integrity and decreased the rate of early capacitation (p < 0.05). RES had no significant effect on sperm quality before freezing and post-thawing (p > 0.05). However, RES + CLC increased mitochondrial activity post-thawing (p < 0.05). In conclusion, CLC minimized sperm membrane damage caused by cryopreservation in ram sperm. RES alone was ineffective, and the combination of RES and CLC did not yield a positive synergistic effect on ram spermatological parameters., (© 2025 The Author(s). Veterinary Medicine and Science published by John Wiley & Sons Ltd.)- Published
- 2025
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16. Enhanced cellular internalization of near-infrared fluorescent single-walled carbon nanotubes facilitated by a transfection reagent.
- Author
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Levin N, Hendler-Neumark A, Kamber D, and Bisker G
- Subjects
- Humans, Indicators and Reagents, Microscopy, Fluorescence, Polyethylene Glycols, Nanotubes, Carbon, Adenocarcinoma
- Abstract
Functionalized single-walled carbon nanotubes (SWCNTs) hold immense potential for diverse biomedical applications due to their biocompatibility and optical properties, including near-infrared fluorescence. Specifically, SWCNTs have been utilized to target cells as a vehicle for drug delivery and gene therapy, and as sensors for various intracellular biomarkers. While the main internalization route of SWCNTs into cells is endocytosis, methods for enhancing the cellular uptake of SWCNTs are of great importance. In this research, we demonstrate the use of a transfecting reagent for promoting cell internalization of functionalized SWCNTs. We explore different types of SWCNT functionalization, namely single-stranded DNA (ssDNA) or polyethylene glycol (PEG)-lipids, and two different cell types, embryonic kidney cells and adenocarcinoma cells. We show that internalizing PEGylated functionalized SWCNTs is enhanced in the presence of the transfecting reagent, where the effect is more pronounced for negatively charged PEG-lipid. However, ssDNA-SWCNTs tend to form aggregates in the presence of the transfecting reagent, rendering it unsuitable for promoting internalization. For all cases, cellular uptake is visualized by near-infrared fluorescence microscopy, showing that the SWCNTs are typically localized within the lysosome. Generally, cellular internalization was higher in the adenocarcinoma cells, thereby paving new avenues for drug delivery and sensing in malignant cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)
- Published
- 2024
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17. Sperm-cell DNA fragmentation prediction using label-free quantitative phase imaging and deep learning.
- Author
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Noy L, Barnea I, Mirsky SK, Kamber D, Levi M, and Shaked NT
- Subjects
- Male, Humans, DNA Fragmentation, Semen, Spermatozoa, Sperm Injections, Intracytoplasmic methods, Fertilization in Vitro methods, Deep Learning
- Abstract
In intracytoplasmic sperm injection (ICSI), a single sperm cell is selected and injected into an egg. The quality of the chosen sperm and specifically its DNA fragmentation have a significant effect on the fertilization success rate. However, there is no method today to measure the DNA fragmentation of live and unstained cells during ICSI. We present a new method to predict the DNA fragmentation of sperm cells using multi-layer stain-free imaging data, including quantitative phase imaging, and lightweight deep learning architectures. The DNA fragmentation ground truth is achieved by staining the cells with acridine orange and imaging them via fluorescence microscopy. Our prediction model is based on the MobileNet convolutional neural network architecture combined with confidence measurement determined by distances between vectors in the latent space. Our results show that the mean absolute error for cells with high prediction confidence is 0.05 and the 90th percentile mean absolute error is 0.1, where the range of DNA fragmentation score is [0,1]. In the future, this model may be applied to improve cell selection by embryologists during ICSI., (© 2022 International Society for Advancement of Cytometry.)
- Published
- 2023
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18. Monitoring the Activity and Inhibition of Cholinesterase Enzymes using Single-Walled Carbon Nanotube Fluorescent Sensors.
- Author
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Loewenthal D, Kamber D, and Bisker G
- Subjects
- Acetylcholinesterase, Biomarkers, Butyrylcholinesterase, Cholinesterase Inhibitors pharmacology, Nanotubes, Carbon, Nerve Agents, Pesticides
- Abstract
Cholinesterase enzymes are involved in a wide range of bodily functions, and their disruption is linked to pathologies such as neurodegenerative diseases and cancer. While cholinesterase inhibitors are used as drug treatments for diseases such as Alzheimer and dementia at therapeutic doses, acute exposure to high doses, found in pesticides and nerve agents, can be lethal. Therefore, measuring cholinesterase activity is important for numerous applications ranging from the search for novel treatments for neurodegenerative disorders to the on-site detection of potential health hazards. Here, we present the development of a near-infrared (near-IR) fluorescent single-walled carbon nanotube (SWCNT) optical sensor for cholinesterase activity and demonstrate the detection of both acetylcholinesterase and butyrylcholinesterase, as well as their inhibition. We show sub U L
-1 sensitivity, demonstrate the optical response at the level of individual nanosensors, and showcase an optical signal output in the 900-1400 nm range, which overlaps with the biological transparency window. To the best of our knowledge, this is the longest wavelength cholinesterase activity sensor reported to date. Our near-IR fluorescence-based approach opens new avenues for spatiotemporal-resolved detection of cholinesterase activity, with numerous applications such as advancing the research of the cholinergic system, detecting on-site potential health hazards, and measuring biomarkers in real-time.- Published
- 2022
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19. Biomarker Candidates for Tumors Identified from Deep-Profiled Plasma Stem Predominantly from the Low Abundant Area.
- Author
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Tognetti M, Sklodowski K, Müller S, Kamber D, Muntel J, Bruderer R, and Reiter L
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- Biomarkers, Blood Proteins analysis, Humans, Male, Proteome metabolism, Pancreatic Neoplasms, Proteomics
- Abstract
The plasma proteome has the potential to enable a holistic analysis of the health state of an individual. However, plasma biomarker discovery is difficult due to its high dynamic range and variability. Here, we present a novel automated analytical approach for deep plasma profiling and applied it to a 180-sample cohort of human plasma from lung, breast, colorectal, pancreatic, and prostate cancers. Using a controlled quantitative experiment, we demonstrate a 257% increase in protein identification and a 263% increase in significantly differentially abundant proteins over neat plasma. In the cohort, we identified 2732 proteins. Using machine learning, we discovered biomarker candidates such as STAT3 in colorectal cancer and developed models that classify the diseased state. For pancreatic cancer, a separation by stage was achieved. Importantly, biomarker candidates came predominantly from the low abundance region, demonstrating the necessity to deeply profile because they would have been missed by shallow profiling.
- Published
- 2022
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20. Evaluation of endogenous urinary biomarkers for indirect detection of urine adulteration attempts by five different chemical adulterants in mass spectrometry methods.
- Author
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Steuer AE, Kamber D, and Kraemer T
- Subjects
- Chromatography, High Pressure Liquid methods, Glycine analogs & derivatives, Glycine urine, Humans, Hydrogen-Ion Concentration, N-Acetylneuraminic Acid urine, Uric Acid analogs & derivatives, Uric Acid urine, Urine Specimen Collection methods, Biomarkers urine, Mass Spectrometry methods, Nitrites chemistry, Substance Abuse Detection methods, Urinalysis methods
- Abstract
Reliable detection of urine adulteration attempts to circumvent positive drug testing represents a critical step for laboratories in abstinence control settings. An ideal workflow for high-throughput testing would involve simultaneous detection of adulteration attempts in the same run with drug detection. Monitoring of degraded or oxidized endogenous urinary compounds as indirect markers has been previously evaluated for that purpose exemplified for the adulterant potassium nitrite (KNO
2 ). Fifteen, previously identified endogenous markers should now be evaluated for their general applicability to detect adulteration attempts for the adulterants hypochlorite-based bleach (NaOCl), peroxidase and peroxide (H2 O2 ), pyridinium chlorochromate (PCC), and iodine (I2 ). Initial experiments revealed similar results for the tested adulterants regarding degradation of indolylacryloylglycine (IAG), uric acid (UA), or UA derivatives. 5-Hydroxyisourate (HIU), the oxidation product of UA, was however only formed by KNO2 , PCC, and H2 O2 . Amino acids showed larger adulterant-dependent differences. All reactions were shown to be influenced by the adulterant concentration and the urinary pH with large variances depending on compound and adulterant. Except for HIU/PCC, all markers were stable within +/- 30% variation for all adulterants at -20°C. Receiver operating characteristics indicated best sensitivity and specificity over all adulterants for IAG (specificity 0.9, sensitivity 1.0) and UA (specificity 1.0, sensitivity 0.9). HIU gave best results for KNO2 , PCC, and H2 O2 and N-acetylneuraminic acid for PCC and H2 O2 , respectively. When integrating a limited number of targets into existing screening methods, monitoring of UA, IAG, N-acetylneuraminic acid, and HIU is recommended., (© 2018 John Wiley & Sons, Ltd.)- Published
- 2019
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21. Suitability evaluation of new endogenous biomarkers for the identification of nitrite-based urine adulteration in mass spectrometry methods.
- Author
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Steuer AE, Arnold K, Kamber D, and Kraemer T
- Subjects
- Biomarkers urine, Chromatography, Liquid, Cold Temperature, Healthy Volunteers, Humans, Hydrogen-Ion Concentration, Nitrites pharmacokinetics, Oxidation-Reduction, Single-Blind Method, Histidine urine, Methylhistidines urine, Nitrites urine, Substance Abuse Detection methods, Tandem Mass Spectrometry methods, Uric Acid urine
- Abstract
Urine adulteration to circumvent positive drug testing is a fundamental challenge for toxicological laboratories all over the world. Untargeted mass spectrometry (MS) methods used in metabolomics had previously revealed uric acid (UA), histidine, methylhistidine, and their oxidation products, for example 5-hydroxyisourate (HIU) as potential biomarkers for urine adulteration using potassium nitrite (KNO
2 ). These markers should be further evaluated for their reliability, stability, and routine applicability. Influence of KNO2 concentration, urinary pH, reaction time, and stability at room temperature, 4°C, and - 20°C was determined in urine under varying conditions. Analysis was performed after protein precipitation with acetonitrile by liquid chromatography-high resolution mass spectrometry (LC-HRMS). Receiver operating characteristics (ROC) analysis was applied for cut-off evaluation after biomarker quantification (n = 100 per group). Blinded measurements (n = 50) were performed to check the general applicability to identify adulterated samples under routine conditions. The higher the adulterant concentration, the lower the concentrations of histidine, methylhistidine, and UA. In return, amounts of their oxidation products increased. Highest changes were observed under weak acid conditions (pH 4-5). Storage at -20°C ensured sufficient stability for all oxidative markers over one month. ROC evaluated biomarker performance and application to unknown samples revealed satisfying results, with HIU as the most suitable biomarker (positive predictive value (PPV) 100%), followed by UA (PPV 93%). HIU and UA proved suitable markers to identify urine adulteration using KNO2 and are ready for implementation into routine MS procedures., (© 2018 John Wiley & Sons, Ltd.)- Published
- 2019
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22. Changing gears from chemical adhesion of cells to flat substrata toward engulfment of micro-protrusions by active mechanisms.
- Author
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Hai A, Kamber D, Malkinson G, Erez H, Mazurski N, Shappir J, and Spira ME
- Subjects
- Actins metabolism, Action Potentials, Animals, Aplysia, Biocompatible Materials, Cells, Cultured, Cortactin metabolism, Cytoskeleton physiology, Cytoskeleton ultrastructure, Excitatory Postsynaptic Potentials, Gene Transfer Techniques, Gold Compounds, Green Fluorescent Proteins genetics, Green Fluorescent Proteins metabolism, Microscopy, Confocal, Microscopy, Electron, Scanning, Neurites physiology, Neurites ultrastructure, Neurons ultrastructure, Synapses physiology, Synapses ultrastructure, Cell Culture Techniques instrumentation, Cell Culture Techniques methods, Neurons physiology
- Abstract
Microelectrode arrays increasingly serve to extracellularly record in parallel electrical activity from many excitable cells without inflicting damage to the cells by insertion of microelectrodes. Nevertheless, apart from rare cases they suffer from a low signal to noise ratio. The limiting factor for effective electrical coupling is the low seal resistance formed between the plasma membrane and the electronic device. Using transmission electron microscope analysis we recently reported that cultured Aplysia neurons engulf protruding micron size gold spines forming tight apposition which significantly improves the electrical coupling in comparison with flat electrodes (Hai et al 2009 Spine-shaped gold protrusions improve the adherence and electrical coupling of neurons with the surface of micro-electronic devices J. R. Soc. Interface 6 1153-65). However, the use of a transmission electron microscope to measure the extracellular cleft formed between the plasma membrane and the gold-spine surface may be inaccurate as chemical fixation may generate structural artifacts. Using live confocal microscope imaging we report here that cultured Aplysia neurons engulf protruding spine-shaped gold structures functionalized by an RGD-based peptide and to a significantly lesser extent by poly-l-lysine. The cytoskeletal elements actin and associated protein cortactin are shown to organize around the stalks of the engulfed gold spines in the form of rings. Neurons grown on the gold-spine matrix display varying growth patterns but maintain normal electrophysiological properties and form functioning synapses. It is concluded that the matrices of functionalized gold spines provide an improved substrate for the assembly of neuro-electronic hybrids.
- Published
- 2009
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23. Local calcium-dependent mechanisms determine whether a cut axonal end assembles a retarded endbulb or competent growth cone.
- Author
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Kamber D, Erez H, and Spira ME
- Subjects
- Actin Cytoskeleton metabolism, Actin Cytoskeleton ultrastructure, Animals, Aplysia cytology, Axonal Transport physiology, Axotomy, Calpain metabolism, Cell Membrane metabolism, Cell Membrane ultrastructure, Cells, Cultured, Central Nervous System cytology, Cytoplasm metabolism, Cytoplasm ultrastructure, Ganglia, Invertebrate cytology, Ganglia, Invertebrate metabolism, Growth Cones ultrastructure, Membrane Fusion physiology, Microtubules metabolism, Microtubules ultrastructure, Models, Animal, Spectrin metabolism, Transport Vesicles metabolism, Transport Vesicles ultrastructure, Aplysia metabolism, Calcium metabolism, Calcium Signaling physiology, Central Nervous System metabolism, Growth Cones metabolism, Nerve Regeneration physiology
- Abstract
The transformation of a cut axonal end into a growth cone (GC), after axotomy, is a critical event in the cascade leading to regeneration. In an earlier series of studies we analyzed the cellular cascades that transform a cut axonal end into a competent GC. We found that axotomy of cultured Aplysia neurons leads to a transient elevation of the free intracellular Ca2+ concentration ([Ca2+]i), calpain activation and localized proteolysis of submembranal spectrin. These events are associated with the formation of distinct microtubule (MT) based vesicle traps that accumulate anterogradely transported vesicles that fuse with the spectrin free plasma membrane in support of the growth process (Erez, H., Malkinson, G., Prager-Khoutorsky, M., De Zeeuw, C.I., Hoogenraad, C.C., and Spira, M.E. 2007. Formation of microtubule-based traps controls the sorting and concentration of vesicles to restricted sites of regenerating neurons after axotomy. J. Cell Biol. 176: 497-507.; Erez, H., and Spira, M.E. 2008. Local self-assembly mechanisms underlie the differential transformation of the proximal and distal cut axonal ends into functional and aberrant growth cones. J. Comp. Neurol. 507: spc1.). Here we report that under conditions that limit calcium influx into the cut axonal end, axotomy leads to the formation of endbulbs (EBs) rather than to competent GCs. Under these conditions typical MT based vesicle traps are not formed, and Golgi derived vesicles concentrate at the very tip of the cut axon. Since under these conditions the spectrin barrier is not cleaved, vesicle fusion with the plasma membrane and actin polymerization are retarded and growth processes are impaired. We conclude that the immediate assembly of competent GC or an EB after axotomy is the outcome of autonomous local events that are shaped by the magnitudes of the [Ca2+]i gradients at the site of injury.
- Published
- 2009
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24. Calcium-induced exocytosis from actomyosin-driven, motile varicosities formed by dynamic clusters of organelles.
- Author
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Malkinson G, Fridman ZM, Kamber D, Dormann A, Shapira E, and Spira ME
- Subjects
- Actins drug effects, Actins metabolism, Action Potentials, Animals, Aplysia, Cells, Cultured, Cytochalasin D pharmacology, Ganglia, Invertebrate cytology, Membrane Fusion physiology, Microscopy, Confocal, Microscopy, Electron, Transmission, Myosin Type II metabolism, Neurites physiology, Neurites ultrastructure, Nucleic Acid Synthesis Inhibitors pharmacology, Presynaptic Terminals physiology, Actomyosin metabolism, Calcium metabolism, Exocytosis physiology, Neurons physiology, Neurons ultrastructure, Organelles physiology
- Abstract
Varicosities are ubiquitous neuronal structures that appear as local swellings along neurites of invertebrate and vertebrate neurons. Surprisingly little is known about their cell biology. We use here cultured Aplysia neurons and demonstrate that varicosities are motile compartments that contain large clusters of organelles. The content of varicosities propagate along neurites within the plasma membrane "sleeve", split and merge, or wobble in place. Confocal imaging, retrospective immunolabeling, electron microscopy and pharmacological perturbations reveal that the motility of the varicosities' organelle content occurs in concert with an actin scaffold and is generated by actomyosin motors. Despite the motility of these organelle clusters within the cytoplasm along the neurites, elevation of the free intracellular calcium concentration within varicosities by trains of action potentials induces exocytosis followed by membrane retrieval. Our observations demonstrate that varicosities formed in the absence of postsynaptic cells behave as "ready to go" prefabricated presynaptic terminals. We suggest that the varicosities' motility serves to increase the probability of encountering a postsynaptic cell and to rapidly form a functional synapse.
- Published
- 2006
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