Spectroscopic Measurements of Physiological Elements in Microdialysis Samples from Rat Brain,Flowering Plum Fruit and Pea

The basal levels of magnesium and copper in rat brain and flowering plum fruit dialysates, and the background concentration of calcium in pea dialysates have been determined with sensitive spectroscopic techniques including atomic absorption spectrometry and spectrophotometry based on amino G acid chlorophosphonazo. It is found that the magnesium level in flowering plum fruit dialysates is much lower than that in rat brain dialysates, indicating a considerable composition difference present between a plant dialysate and an animal one.

Prediction of rat liver transplantation outcomes using energy metabolites measured by microdialysis

Background: Warm ischemia jeopardizes graft quality and recipient survival in donation after cardiac death(DCD) transplantation. Currently, there is no system to objectively evaluate the liver quality from DCD. The present study tried to use energy metabolites to evaluate the donor liver quality. Methods: We divided 195 Sprague-Dawley rats into five groups: the control( n = 39), warm ischemic time(WIT) 15 min( n = 39), WIT 30 min( n = 39), WIT 45 min( n = 39), and WIT 60 min( n = 39) groups. Three rats from each group were randomly selected for pretransplant histologic evaluation of warm ischemiarelated damage. The remaining 36 rats were randomly divided into donors and recipients of 18 liver transplantations, and were subjected to postoperative liver function and survival analyses. Between cardiac arrest and cold storage, liver energy metabolites including glucose, lactate, pyruvate, and glycerol were measured by microdialysis. The lactate to pyruvate ratio(LPR) was calculated. Results: The changes in preoperative pathology with warm ischemia were inconspicuous, but the trends in postoperative pathology and aminotransferase levels were consistent with preoperative energy metabolite measurements. The 30-day survival rates of the control and WIT 15, 30, 45, and 60 min groups were 100%, 81.82%, 76.92%, 58.33%, and 25.00%, respectively. The areas under the receiver operating characteristic curves of glucose, lactate, glycerol, and LPR were 0.87, 0.88, 0.88, and 0.92, respectively. Conclusion: Glucose, lactate, glycerol, and LPR are predictors of graft quality and survival outcomes in DCD transplantation.

Recovery rates of combination antibiotic therapy using in vitro microdialysis simulating in vivo conditions

Microdialysis is a technique used to measure the unbound antibiotic concentration in the interstitial spaces, the target site of action. In vitro recovery studies are essential to calibrating the microdialysis system for in vivo studies. The effect of a combination of antibiotics on recovery into microdialysate requires investigation. In vitro microdialysis recovery studies were conducted on a combination of vancomycin and tobramycin, in a simulated in vivo model. Comparison was made between recoveries for three different concentrations and three different perfusate flow rates. The overall relative recovery for vancomycin was lower than that of tobramycin. For tobramycin, a concentration of 20μg/mL and flow rate of 1.0μL/min had the best recovery. A concentration of 5.0μg/mL and flow rate of 1.0μL/min yielded maximal recovery for vancomycin. Large molecular size and higher protein binding resulted in lower relative recoveries for vancomycin. Perfusate flow rates and drug concentrations affected the relative recovery when a combination of vancomycin and tobramycin was tested. Low perfusate flow rates were associated with higher recovery rates. For combination antibiotic measurement which includes agents that are highly protein bound, in vitro studies performed prior to in vivo studies may ensure the reliable measurement of unbound concentrations.

Determination of 6-Mercaptopurine in Rat Blood by Microdialysis Coupled with High Performance Liquid Chromatography on a Functionalized Multi-wall Carbon Nanotubes Modified Electrode

A new chemically modified electrode(CME) immobilized on the surface of multi-wall carbon nanotubes functionalized with carboxylic groups was fabricated. The results indicate that the CME exhibits efficiently electrocatalytic oxidation of 6-mercaptopurine(6-MP). The CME can be used as the working electrode in the liquid chromatography for the determination of 6-MP. The peak current of 6-MP is linearly changed with its concentration ranging from 4.0×10 -7 to 1.0×10 -4 mol/L with the calculated detection limit (S/N=3) of 2.0×10 -7 mol/L. Coupled with microdialysis sampling, the method has been successfully applied to assessing the content of 6-MP in rat blood.

Biological Fingerprinting Analysis of Interaction Between Taxoids in Taxus and Microtubule Protein by Microdialysis Coupled with High-performance Liquid Chromatography/Mass Spectrometry for Screening Antimicrotubule Agents

Some natural products, such as traditional Chinese medicines（TCMs）, contain compounds with anticancer activity and have attracted a great interest in recent years as alternative anticancer therapies. A quick and convenient assay for screening antimicrotubule compounds in which in vitro microdialysis/high-performance liquid chromatography （HPLC） is used to monitor the binding of the compounds extracted from TCM Taxus cuspidata Siebold ＆ Zucc（Taxus） to microtubules is reported. It was observed that the extract of Taxus contains at least five compounds which have affinity interaction with microtubules by biological fingerprinting analysis, and they were identified as the taxoids of taxol, baccatin III, 10-deacetylbaccatin Ⅲ（10-DAB）, cephalomannine and 7-epi-10-deacetyltaxol （7-epi-10-DAT） based on the comparison of their high-performance liquid chromatographic/mass spectrometric and UV spectra with those of the standard samples, both assembly-promoting and disassembly-inhibiting characteristics of those compounds were evaluated. It was observed that baccatin Ⅲ and 10-DAB bound to microtubules and the binding degrees were influenced by GTP. Competitive binding behavior of taxol with other four taxoids to microtubules was also investigated.

Rapid Determination of Dopamine and Its Metabolites During in vivo Cerebral Microdialysis by Routine High Performance Liquid Chromatography With Electrochemical Detection

To determine dopamine and its metabolites during in vivo cerebral microdialysis by routine high performance liquid chromatography with electrochemical detection. Methods Microdialysis probes were placed into the right striatum of Wistar rat brains and perfused with Ringer＇s solution at a rate of 1.5 pL/min. A reverse phase HPLC with electrochemistry was used to assay DA, DOPAC, and HVA after cerebral microdialysates were collected every 20 minutes from awake and freely moving rats. In order to identify the reliability of this method, its selectivity, linear range, precision and accuracy were tested and the contents of DA, DOPAC, and HVA in rat microdialysates were determined. Results The standard curve was in good linear at the concentration ranging from 74 nmol/L to 1.5 pmol/L for DOPAC （r^2= 0.9996）, from 66 nmol/L to 1.3 gmol/L for DA （r^2=l.0000） and from 69 nmol/L to 1.4 pmol/L for HVA （r^2=0.9992）. The recovery of DOPAC （0.30, 0.77, 1.49 gmol/L）, DA （0,26, 0.69, 1.32 gmol/L）, and HVA （0.27, 0.71, 1.37 gmol/L） was 82.00±1.70%, 104.00±4.00%, 98.70±3.10%; 92.30± 1.50%, 105.30±2.30%, 108.00±2.00%; 80.00±7.80%, 107.69±8.00%, and 108.66±3.10%, respectively at each concentration. Their intra-day RSD was 3.3%, 3.4%, and 2.5%, and inter-day RSD was 4.2%, 2.3%, and 5.6%, respectively. The mean extracellular concentrations of DOPAC, DA, and HVA in rat brain microdialysates were 10.7, 2.4, and 9.2 gmol/L （n=6）, respectively. Conclusion The findings of our study suggested that the simple, accurate and stable method can be applied to basic researches of diseases related to monoamines neurotransmitters by cerebral microdialysis in rats.

Clinical microdialysis in neuro-oncology: principles and applications

Clinical microdialysis allows a discrete volume of the brain to be sampled for neurochemical analysis of neurotransmitters, metabolites, biomarkers, and drugs. The technique can be safely used in humans intraoperatively, in the intensive care unit, and in ambulatory settings. Microdialysis probes, micropumps, and analytical equipment are commercially available and have been used extensively for neurochemical monitoring in traumatic brain injury, stroke, and subarachnoid hemorrhage. There has been very limited use of microdialysis in neuro-oncology, but this technique has great promise in the study of the basic neurochemistry of brain tumors, alterations in neurochemistry in response to therapy, and the pharmacokinetics of chemotherapeutic agents. Microdialysis probes may also be used to deliver drugs while simultaneously permitting monitoring of neurochemical changes induced by this therapy.

Microdialysis in awake macaque monkeys for central nervous system pharmacokinetics

Background: The brain bioavailability of novel small molecules developed to address central nervous system disease is classically documented through ex vivo or in vivo analyses conducted in rodent models. Data acquired in rodent models are, however,not easily transferrable to human as the pharmacokinetic and pharmacodynamics profiles of the species are quite different.Methods: Using drugs selected for their differential transport across the blood-brain barrier, we here demonstrate the feasibility of brain microdialysis in normal vigil macaque monkey by measuring brain extracellular fluid bioavailability of carbamazepine, digoxin, oxycodone, and quinidine.Results: All drugs, but digoxin, were found in dialysate samples. Drugs that are substrate of P-glycoprotein show a difference of bioavailability or brain pharmacokinetic parameters between rodents and primates.Conclusion: Data suggest that brain microdialysis in vigil macaque monkey, the species of choice for classic pharmacokinetic/pharmacodynamics studies could help predicting human brain bioavailability of a small molecule depending on the protein involved in the efflux transport from the brain.

EFFECTS OF TRANSIENT FOREBRAIN ISCHEMIA AND RADIX SALVIAE MILTIORRHIZAE (RSM) ON EXTRACELLULAR LEVELS OF MONOAMINE NEUROTRANSMITTERS AND METABOLITES IN THE GERBIL STRIATUM-An in vivo Microdialysis Study

The aim of this study was to investigate the effect of 30 min forebrain ischemia, followed by 120 min reperfusion on extracellular fluid (ECF) levels of dopamine (DA), norepinephrine (NE), serotonin (5-HT) and their metabolites, homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the striatum of gerbils, so as to obtain further information on the mechanism of Radix Salviae Miltiorrhizae (RSM)-induced neuroprotection. Microdialysis was used to sample the extracellular space. Dialysate was measured by high performance liquid chromatography with electrochemical detector (HPLC-ED). ECF DA, NE levels increased from basal levels by 282, 227 and 221 folds, by 9.14, 8.51 and 8.25 folds, respectively for the three ischemic duration (0-10; 11-20; 21-30 min). ECF DA, NE, 5-HT levels in the RSM-treated group were significantly decreased as compared with those in the control group during ischemia (P

Characteristics and pharmacokinetics of tripterygium glycosides nano-carries transdermal delivery systems:skin-blood synchronous microdialysis and numerical simulation

The traditional Chinese medicine tripterygium glycosides(TPG)is used clinically to treat some Rheumatism,Eczema,immunosuppression and tumor,with the activities of hypnosis,antipyretic,analgesic,antiinflammatory,allergy and antitumor.However TPG has low water solubility and low skin permeability,so its clinical use is limited.Transdermal delivery systems can provide a controlled drug release rate that can keep constant concentrations of drug in the plasma for up to multiple days,improved patient compliance,and the possibility ofreducing the rate and severity of side effects.In this study,a fast and sensitive technique skin-blood two sites synchronous microdialysis coupled with LC-MS was used to study the pharmacokinetic parameter of three different formulations(TPG nanoemulsion,TPG nanoemulsion based gels and TPG gel).Creating a multilayer model,use the model to simulate the three formulations dynamics in transdermal-drug delivery system.The experiment results showed that the TPG nanoemulsion,TPG nanoemulsion based gels can significantly raise the drug concentrations in skin more than that of TPG gels.The numerical simulation results indicating that TPG gel and TPG nanoemulsion are close to practical measurements,only in the concentration increase phase the numerical simulation result has some difference with the experimental results.TPG nanoemulsion based gels have significant difference with the experimental results,both in concentration increase stage and concentration decreasing stage,but its trend was same.The study shows that the skin-blood synchronous microdialysis technique provided a new method for the pharmacokinetics study of nanocarriers transdermal delivery systems.In addition,the microdialysis technique combined with mathematical modeling provides a very good platform for the further study of transdermal delivery system.

Evaluation of the Effects of Corticosteroids on Histamine Release by ex Vivo Cutaneous Microdialysis

The purpose of the study was to evaluate the effects of corticosteroids on histamine release and to compare their potency with the MacKenzie classification based on their vasoconstrictor effects. Thanks to ex Vivo cutaneous microdialysis, we studied histamine-induced release over a period of time on excised abdominal skin from women. Eight corticosteroids were topically applied with occlusive dressing onto the skin, above probes, before anti-IgE injection. Histamine levels were assessed by an EIA method. In order to compare the different corticosteroids, AUC was calculated allowing an estimation of the amount of released histamine for 60 min of ex vivo cutaneous microdialysis. Diflucortolone 0.1% and micronized betamethasone dipropionate 0.05% are considered as corticosteroids with high potency in MacKenzie classification. Betamethasone dipropionate associated with propylene glycol 0.05%, belongs to a stronger class in Mackenzie classification. Our results showed that the decrease in histamine release was more important with difluocortolone than with both of these corticosteroids. Therefore there was no correlation between the vasoconstrictor potency of topical corticosteroids and their ability to inhibit histamine release.

Outcome following severe traumatic brain injury TBI correlates with serum S100B but not brain extracellular fluid S100B:An intracerebral microdialysis study

S100B protein is released by astrocytes into the brain extracellular fluid following acute brain injury and elevated levels in CSF and serum have been shown to correlate with patient outcome following traumatic brain injury. A prospective study of brain extracellular fluid (ECF) and serum S100B levels in 12 patients with severe head injury (GCS ≤ 8) was undertaken using intracerebral microdialysis to investigate whether a correlation with ECF S100B and outcome could be confirmed. Patient outcomes were assessed at 6 months using the Glasgow Outcome Scale (GOS) and divided into two outcome groups: group A, 8 survivors with either a good recovery or moderate disability (GOS scores of 4 or 5);and group B, 4 patients who died (GOS 1). Peak serum levels of S100B were significantly greater in group B (mean 6.03 ng/ml) compared with group A (mean 0.73 ng/ml) (P = 0.009). Group A had a mean peak S100B in the extracellular compartment of 186 ng/ml compared to 150 ng/ml in group B. There was no significant difference between the mean peak brain ECF S100B concentrations for the 2 outcome groups (P = 0.932). We confirm that intracerebral microdialysis can be used to sample S100B concentrations from brain extracellular fluid and our results suggest that the ECF S100B levels were variable and that there was no significant difference between the good outcome and poor outcome groups. In contrast, the serum levels of S100B of patients with a poor outcome were significantly higher than those with a good outcome.

Intracerebral Microdialysis in Neurosurgery for Obsessive-Compulsive Disorder: Report of 2 Preliminary Cases

Neurosurgery for psychiatric disorders, notably for obsessive-compulsive disorder (OCD), was initiated in Venezuela in the decade of 1970, and consisted since that time in the classic stereotactic anterior cingulotomy. In order to know further about the physiopathology of this disorder, we performed intracerebral microdialysis in 2 patients who were operated on. The aim was to measure changes in extracellular neurotransmitters within the basal ganglia. The microdialysis probes were stereotactically placed in the right caudate nucleus and in the dorsomedial nucleus of the right thalamus. The microdialysis was done before the left cingulotomy, during the pause and after the right cingulotomy. Glutamate and gamma-aminobutyric acid (GABA) changes were similar in the caudate nucleus of both patients, whereas in the dorsomedial nucleus the changes were opposite among the 2 patients. Although this study does not bring enough data to explain such differences yet, the existence of dynamic changes in the neurochemistry of the basal ganglia during cingulotomy shows that intracerebral microdialysis can help in the understanding of the pathophysiology of OCD and eventually in the design of new surgeries with better results.

Dynamic Cerebral Microdialysis during Pallidotomy and Thalamotomy in Parkinson’s Disease: A Preliminary Neurochemical Study

In Parkinson’s disease (PD), dopaminergic neurons reduce the regulation of glutamatergic (glutamate-Glu) input from the cortex to neostriatum (caudate and putamen nuclei) consequently leading to a hyperactivity of globus pallidus internae (GPi) neurons that release gamma-amino-butyric acid (GABA) into the thalamic ventrolateral (VL) nucleus. The objective of the present experiment was to measure changes in GABA and Glu in the caudate and the thalamus of 2 patients during the application of electrical stimuli following either a pallidotomy or a thalamotomy. Proper insertion of the electrode was tested by applying high frequency electrical pulses (HFEP). During these procedures, we obtained neurochemical information placing cerebral (CMD) microdialysis probes in caudate nucleus and VL nucleus of ipsi- and contra-lateral thalamus. In VL thalamus, extracellular GABA decreased during HFEP, tending to reach previous levels once HFEP was finalized. Following the pallido- or thalamotomy GABA decreased again. Similarly, in the contralateral VL thalamus, extracellular GABA levels showed a similar but less pronounced profile but did not show any decrement after the lesion. Caudate Glu decreases when HFEP is applied to the GPi and recovers to previous levels after HFEP, but did not decrease again after lesion (GPi-tomy), instead it continued to rise. These results suggest that HFEP exerts a similar but reversible biochemical effect as thermopallido- or thermothalamotomy on GABA extracellular concentration in the ipsilateral VL thalamus. We also observe a distant effect of HFEP, but not of thermolesion, on contralateral thalamic GABA and ipsilateral caudate Glu.

微透析(微灌注)技术在经皮给药制剂中的研究进展

通过梳理微透析(微灌注)技术的原理及特性,总结其在经皮给药制剂研究中的应用现状,分析了存在的问题和挑战,对未来发展方向进行展望,并提出相关建议,为该领域的进一步研究提供参考。

基于微透析结合UPLC的弩药微乳经皮给药后多成分皮肤药动学研究

目的考察弩药微乳多成分在自制探针上的回收率与温度、灌流速度、浓度的关系,研究弩药微乳多成分在家兔皮肤组织中的药动学特征。方法采用UPLC测定绿原酸、苯甲酰新乌头原碱、杠柳毒苷、新乌头碱质量浓度;采用增量法与减量法探究温度、灌流速度、质量浓度对探针回收率的影响,UPLC测定弩药微乳经皮给药后不同时间点透析液中多成分含量变化,并用DAS2.0软件处理数据。结果升高温度,各成分探针回收率逐渐提高;流速越大,药物回收率越低,且回收率与探针周围药物质量浓度关系不大。弩药微乳中绿原酸、苯甲酰新乌头原碱、杠柳毒苷、新乌头碱在皮下组织中的药动学参数C max分别为(3.24±0.36)(1.04±0.29)(4.78±2.15)(2.86±0.55)μg·mL^(-1);AUC 0-∞分别为(52.42±30.84)(7.70±3.73)(42.23±13.93)(22.68±12.51)h·μg·mL^(-1)。结论首次采用微透析在体实时取样技术,建立UPLC检测方法,对弩药微乳经皮给药后多成分皮肤药动学进行研究,为弩药微乳后续的考察及应用提供参考。

Future of neurocritical care:Integrating neurophysics,multimodal monitoring,and machine learning

Multimodal monitoring(MMM)in the intensive care unit(ICU)has become increasingly sophisticated with the integration of neurophysical principles.However,the challenge remains to select and interpret the most appropriate combination of neuromonitoring modalities to optimize patient outcomes.This manuscript reviewed current neuromonitoring tools,focusing on intracranial pressure,cerebral electrical activity,metabolism,and invasive and noninvasive autoregulation moni-toring.In addition,the integration of advanced machine learning and data science tools within the ICU were discussed.Invasive monitoring includes analysis of intracranial pressure waveforms,jugular venous oximetry,monitoring of brain tissue oxygenation,thermal diffusion flowmetry,electrocorticography,depth electroencephalography,and cerebral microdialysis.Noninvasive measures include transcranial Doppler,tympanic membrane displacement,near-infrared spectroscopy,optic nerve sheath diameter,positron emission tomography,and systemic hemodynamic monitoring including heart rate variability analysis.The neurophysical basis and clinical relevance of each method within the ICU setting were examined.Machine learning algorithms have shown promise by helping to analyze and interpret data in real time from continuous MMM tools,helping clinicians make more accurate and timely decisions.These algorithms can integrate diverse data streams to generate predictive models for patient outcomes and optimize treatment strategies.MMM,grounded in neurophysics,offers a more nuanced understanding of cerebral physiology and disease in the ICU.Although each modality has its strengths and limitations,its integrated use,especially in combination with machine learning algorithms,can offer invaluable information for individualized patient care.

药物经皮渗透性研究方法进展

经皮给药系统中药物的经皮渗透特性直接关系到药物临床应用的安全性和有效性。在经皮给药制剂的开发过程中,药物渗透性评估可以预测药物的皮肤渗透特性,有助于理解产品的质量和性能,为药品研发提供重要考察指标。目前,研究者们开发了多种药物皮肤渗透性研究方法,其中体外透皮试验最为常用,主流测定方法是Franz扩散池法;数学模型渗透性预测、动物实验等研究方法也可被用来研究药物渗透性,此外还有平行人工膜渗透模型研究、光谱技术及微透析技术等新的研究方法。本文对这些研究方法进行展开介绍,期望对研究者提供一定的参考作用。

基于微透析技术的付罐疗法在体经皮促渗作用评价

目的:建立芍药苷的经皮微透析方法,探究付罐疗法(FCT)在体经皮促渗效果。方法:通过增量法和减量法对微透析探针的体外回收率和传递率进行测定,并利用反向渗析法校正探针对芍药苷的在体回收率;以SD大鼠为动物模型,含5%氮酮处理的芍药苷溶液作为阳性对照组,3号罐留罐法产生负压为-0.30 MPa处理10 min作为FCT促渗处理组,采用皮下微透析取样技术结合HPLC法测定付罐疗法对芍药苷的经皮药动学的影响。结果:增量法和减量法所测得的芍药苷的探针体外回收率与传递率基本一致,药物与渗析膜间无相互作用;芍药苷的在体回收率为(51.71±0.75)%。FCT促渗处理组能显著提高芍药苷的透皮速率0.0767μg/min(空白组0.0042μg/min),降低时滞,对芍药苷的促渗倍数(ER)为18.26;5%氮酮组促渗倍数(17.69)比FCT组低。结论:付罐对芍药苷具有明显的在体经皮促渗作用,提示付罐疗法可作为一种新型的经皮给药物理促渗技术进行应用。

参芩凝胶中小檗碱、黄芩苷经皮微量渗析取样方法的建立及促渗工艺评价

目的 建立参芩凝胶中小檗碱、黄芩苷的经皮微量渗析取样方法,并对参芩凝胶的促渗工艺进行评价。方法以小檗碱、黄芩苷回收率、损失率为指标,采用增量法、减量法对灌注速度、取样间隔、灌注液浓度进行考察,研究反渗析法是否可应用于探针体内回收率的计算;将探针植入大鼠皮下,考察探针在12 h内的体内回收率稳定性;并通过透皮实验考察冰片对参芩凝胶透皮性能的影响。结果 灌注速度确定为1μL/min,取样间隔确定为30 min;灌注液浓度考察结果表明药物浓度对探针体外回收率无明显影响,同一浓度平行条件下,探针体外回收率与空白耗损率大致相等,说明反渗析法适用于计算探针体内回收率;探针植入皮下在12 h内回收率保持相对稳定。3%冰片能显著提升参芩凝胶中黄芩苷的透过量,对小檗碱的透过量也有一定的提升作用。结论 优选的微量渗析取样法可用于黄芩苷、小檗碱的经皮微量渗析取样的研究;冰片对参芩凝胶具有一定促渗作用。