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Intracytoplasmic Sperm Injection
Published in Botros Rizk, Ashok Agarwal, Edmund S. Sabanegh, Male Infertility in Reproductive Medicine, 2019
Emad Fakhry, Medhat Amer, Botros Rizk
Using an intrauterine microdialysis system to introduce low concentrations of hCG to the endometrium in the luteal phase (some proposed immediately after oocyte retrieval), showed better implantation rates. It acts in an autocrine-juxtracrine manner. Vascular endothelial growth factors were increased by hCG, confirming its role in angiogenesis, vascularization, and placentation of the endometrium. The benefit of the microdialysis system was debated by other investigators [59].
Microdialysis Techniques for Epilepsy Research
Published in Steven L. Peterson, Timothy E. Albertson, Neuropharmacology Methods in Epilepsy Research, 2019
John W. Dailey, Pravin K. Mishra
Dialysis is a process of passive diffusion of solute across a semipermeable membrane. In vivo microdialysis is essentially a dialysis procedure, but miniaturized to allow continuous sampling of molecules from extracellular fluid of animals and man. The principle of microdialysis is illustrated in Figure 11.1. A microdialysis probe is composed of a tube-like dialysis membrane or fiber attached to two rigid or semirigid transport tubes. Both the inlet and outlet transport tubes, as well as the dialysis fiber, are hollow. Although dialysis probes are quite small (200 to 600 μm in diameter), they can accommodate passage of several microliters of liquids through their lumen each minute. When used in experiments, the membrane portion of the probe is placed in the extracellular space of a tissue or tissue matrix and a liquid perfusion medium is pumped continuously through the dialysis fiber lumen. This perfusion medium usually has an ionic and osmotic composition similar to the extracellular fluid, but lacks the chemicals that are intended to be sampled. This way, molecules that can travel across the membrane diffuse into the medium from the extracellular space when the perfusion medium passes through the fiber. The perfusion medium at this point is termed dialysate as it contains the molecules from the extracellular space by virtue of dialysis. In some situations, the perfusion medium may contain an excess of certain chemicals such as a drug which can diffuse out into the extracellular space.
Pharmacokinetics and Pharmacodynamics of Drugs Delivered to the Lung
Published in Anthony J. Hickey, Sandro R.P. da Rocha, Pharmaceutical Inhalation Aerosol Technology, 2019
Stefanie K. Drescher, Mong-Jen Chen, Jürgen B. Bulitta, Günther Hochhaus
As driving forces for dissolution and diffusion are based on the free drug concentration gradient (Figure 6.4), it is recommended to take pulmonary tissue binding into consideration during the development of PBPK model. The binding of drug in lung has been determined through dialysis experiments with lung homogenate or in isolated perfused lung systems (Tronde et al. 2003). Microdialysis (Feurstein and Zeitlinger 2011) has also been evaluated, but is currently hampered by the fact that it is a highly invasive technique. Improvement of related techniques (e.g. determination of lung binding without destruction of the lung structures by homogenization), identification of lysosome trapping, specific interaction with lung components is incumbent.
High-grade glioma therapy: adding flexibility in trial design to improve patient outcomes
Published in Expert Review of Anticancer Therapy, 2022
Xiaobu Ye, Karisa C. Schreck, Byram H. Ozer, Stuart A. Grossman
A second invasive approach to determine intracerebral drug concentrations is through the use of microdialysis catheters [35,54–57]. These can be placed at the time of clinically indicated debulking surgery in residual contrast enhancing and non-enhancing tumor in patients with recurrent HGG. The agent of interest can be administered the day after surgery. As the microdialysis catheters recover unbound drug in the extracellular fluid of the brain tumor continuously for days, one can follow the arrival and departure of the drug, the time above the therapeutic concentration, and the area under the concentration-time curve in both enhancing and non-enhancing tumor. The catheters are pulled at the bedside at the end of the observation period. Unfortunately, there are many technical limitations to microdialysis as not all drugs are able to pass through the semipermeable membrane of the catheters, these catheters frequently malfunction (which is why several are placed at a time), and measurements come from a very small regions adjacent to the catheter.
Effects of tourniquet inflation on peri- and postoperative cefuroxime concentrations in bone and tissue
Published in Acta Orthopaedica, 2021
Pelle Hanberg, Mats Bue, Jesper Kabel, Andrea René Jørgensen, Christian Jessen, Kjeld Søballe, Maiken Stilling
The few clinical studies that have investigated antimicrobial concentrations during TQ application have been based on tissue specimens (Johnson 1987, Deacon et al. 1996). However, this approach suffers from important methodological limitations because sampling in clinical studies is limited to the time of surgery, free extracellular concentrations cannot be measured selectively, and drug concentrations are given by mass rather than volume (Landersdorfer et al. 2009). Microdialysis, on the other hand, allows for simultaneous and serial sampling of the free and active fraction of drugs in the interstitial space from multiple compartments, both peri- and postoperatively (Tottrup et al. 2016, Hanberg et al. 2020a). These features are desirable, as the majority of infections occur in the interstitial space. However, microdialysis remains a sampling technique that has limitations associated with calibration procedures and chemical assays (Landersdorfer et al. 2009, Kho et al. 2017). The major limitation of our study is the small sample size. Although a paired design and no statistically significant differences for the T > MIC (4 µg/mL) between TQ and non-TQ exposed tissues were demonstrated for this specific patient population, a larger study population may alter these findings. However, as all mean tissue cefuroxime concentrations were above 4 µg/mL approximately 4–5 times longer than the presented surgery time, any potential difference between the TQ and non-TQ exposed tissue may be without clinical relevance.
Antibiotic exposure at the site of infection: principles and assessment of tissue penetration
Published in Expert Review of Clinical Pharmacology, 2019
Nynke G. L. Jager, Reinier M. van Hest, Jeffrey Lipman, Jason A. Roberts, Menino O. Cotta
Microdialysis is, at this time, the preferred method for the determination of antibiotic concentrations in interstitial fluid, considering most infections are located extracellularly, and this method allows for multiple samples to be obtained per patient. The major drawback of this method is that the probes need to be surgically implanted in tissues other than skin, adipose tissue and muscle. Also, the recovery of samples needs to be calculated, which is time-consuming and prone to error. Another method to obtain interstitial fluid for analyte determination is by in vivo ultrafiltration, which has been described mainly in the veterinary literature. It has several characteristics in common with microdialysis: both methods measure free analyte concentrations in interstitial fluid. With ultrafiltration, however, the analyte concentration in the sample directly reflects the tissue concentration, so there is no conversion needed [68].