Caring for patients with pain during the COVID-19 pandemic: consensus recommendations from an international expert panel.

Chronic pain causes significant suffering, limitation of daily activities and reduced quality of life. Infection from COVID-19 is responsible for an ongoing pandemic that causes severe acute respiratory syndrome, leading to systemic complications and death. Led by the World Health Organization, healthcare systems across the world are engaged in limiting the spread of infection. As a result, all elective surgical procedures, outpatient procedures and patient visits, including pain management services, have been postponed or cancelled. This has affected the care of chronic pain patients. Most are elderly with multiple comorbidities, which puts them at risk of COVID-19 infection. Important considerations that need to be recognised during this pandemic for chronic pain patients include: ensuring continuity of care and pain medications, especially opioids; use of telemedicine; maintaining biopsychosocial management; use of anti-inflammatory drugs; use of steroids; and prioritising necessary procedural visits. There are no guidelines to inform physicians and healthcare providers engaged in caring for patients with pain during this period of crisis. We assembled an expert panel of pain physicians, psychologists and researchers from North America and Europe to formulate recommendations to guide practice. As the COVID-19 situation continues to evolve rapidly, these recommendations are based on the best available evidence and expert opinion at this present time and may need adapting to local workplace policies.

Cryotherapy after Total Knee Arthroplasty provides faster recovery and better ranges of motion in short term follow up. Results of a prospective comparative study.

Cryotherapy is applied in Total Knee Arthroplasty (TKA) to improve functional outcome. The aim of this study is to investigate whether an advanced cryotherapy device does not increase the risk of complications and improves knee function or decreases swelling. A prospective cohort of TKA patients was formed by a cryotherapy group and a control group. The primary outcome was complication ratio. Our secondary outcomes were functional results and swelling. No significant differences were found in complication ratio between 31 patients in the cryotherapy group and 31 patients in the control group. The cryotherapy group showed a significant better knee flexion and less swelling in the early rehabilitation phase. No differences were found at the other follow-up moments or in the other outcomes. This advanced cryotherapy device is safe in respect of postoperative complications, improves knee function and decreases swelling in the early rehabilitation phase. However, it is questionable if an advanced cryotherapy device with its additional costs is necessary to provide the desired effects of cryotherapy.

Label-free analysis of GPCR-stimulation: The critical impact of cell adhesion.

Label-free cell-based assays have been attracting growing attention in drug research. Optical approaches based on evanescent electric fields (e.g. EPIC, RWG/DMR, SPR) and electrochemical impedance analysis (ECIS, xCELLigence) are by far the most widespread techniques for such purposes. We compared three label-free approaches (ECIS, RWG/DMR and SPR) with respect to the activation of the human histamine H1 receptor (H1R) expressed by U-373 MG glioblastoma and genetically engineered HEK 293T cells. HEK 293T cells were either expressing the hH1R alone or in combination with the adhesion protein hMSR1. The ß2-adrenergic receptor (ß2-AR) expressed by bovine aortic endothelial cells (BAEC) served as a second cell model. Reduced cell adhesion to the surface of the sensing devices affected both, the optical and the impedance-based readout, but became much more obvious in case of RWG- or SPR-based assays. By contrast, the co-expression of hH1R and hMSR1 in HEK 293T cells strongly enhanced the signal compared to hH1R expression alone. As the sensitivity of the optical readouts is confined to a distance of 100-200nm from the surface, depending on the wavelength of the incident light, this observation is in accordance with tighter adhesion of the co-transfectants, inducing a shorter distance between the cell membrane and the substrate. Combining ECIS and SPR, allowing for simultaneous registration of both signals for a single cell population, provided a direct correlation of both readouts, when H1R or ß2-AR stimulation was investigated for the same cell populations. Cell adhesion was found to have a critical impact on the results of label-free cell monitoring, in particular when techniques based on evanescent electric fields are applied.

Label-free versus conventional cellular assays: Functional investigations on the human histamine H1 receptor.

A set of histamine H1 receptor (H1R) agonists and antagonists was characterized in functional assays, using dynamic mass redistribution (DMR), electric cell-substrate impedance sensing (ECIS) and various signaling pathway specific readouts (Fura-2 and aequorin calcium assays, arrestin recruitment (luciferase fragment complementation) assay, luciferase gene reporter assay). Data were gained from genetically engineered HEK293T cells and compared with reference data from GTPase assays and radioligand binding. Histamine and the other H1R agonists gave different assay-related pEC50 values, however, the order of potency was maintained. In the luciferase fragment complementation assay, the H1R preferred ß-arrestin2 over ß-arrestin1. The calcium and the impedimetric assay depended on Gq coupling of the H1R, as demonstrated by complete inhibition of the histamine-induced signals in the presence of the Gq inhibitor FR900359 (UBO-QIC). Whereas partial inhibition by FR900359 was observed in DMR and the gene reporter assay, pertussis toxin substantially decreased the response in DMR, but increased the luciferase signal, reflecting the contribution of both, Gq and Gi, to signaling in these assays. For antagonists, the results from DMR were essentially compatible with those from conventional readouts, whereas the impedance-based data revealed a trend towards higher pKb values. ECIS and calcium assays apparently only reflect Gq signaling, whereas DMR and gene reporter assays appear to integrate both, Gq and Gi mediated signaling. The results confirm the value of the label-free methods, DMR and ECIS, for the characterization of H1R ligands. Both noninvasive techniques are complementary to each other, but cannot fully replace reductionist signaling pathway focused assays.

Comparison of percutaneous electrical nerve stimulation and ultrasound imaging for nerve localization.

BACKGROUND: Percutaneous nerve stimulation (PNS) is a non-invasive technique to localize superficial nerves before performing peripheral nerve blocks, but its precision has never been evaluated by high-resolution ultrasound. This study compared stimulating points at the skin with the position of nerve structures determined by ultrasound. Correlations between distances and percutaneous stimulation thresholds were determined. METHODS: PNS was performed in 20 healthy volunteers systematically with a stimulating pen at the neck after attaching a transparent film with 49 (7×7) perforations. Stimulation thresholds were measured and impedance was controlled. Thereafter, an independent observer measured the depth (D) of the most superficial nerve structure with ultrasound. Distances between stimulating points and the most superficial nerve structure (S) were measured. Correlations between associated stimulating thresholds and distances D and S were calculated. RESULTS: The stimulating point with the lowest current was identical to the point closest to the nerve in only 10% of measurements. Median S was 12.6 (3.4-32.0) mm and D 7.6 (0.3-28.6) mm. Distances did not correlate with percutaneous stimulation thresholds. CONCLUSION: PNS with a stimulating pen is not a reliable technique for nerve localization in the brachial plexus as verified by high-resolution ultrasound.

Functional rehabilitation of mandibular continuity defects using autologous bone and dental implants - prognostic value of bone origin, radiation therapy and implant dimensions.

AIM: The aim of this retrospective study was to investigate prognostic parameters for the rehabilitation of mandibular continuity defects with free autologous bone and dental implants for patients after intraoral squamous cell carcinoma. METHODS: Following potential prognostic factors for implant survival were analyzed: bony bed (local bone versus augmented iliac crest bone), radiation dose (no radiation, <50 Gy, >or=50 Gy) and implant dimensions. Kaplan-Meier survival estimates of the inserted implants were performed. RESULTS: After 5 years, the cumulative survival rate of all investigated implants was 82.6%. Dental implantation into augmented bone resulted in a significantly lower survival rate (78.4%), compared to original local bone (92.8%). Modifications of implant dimensions as well as radiation therapy showed no significant impact on implant survival. CONCLUSION: For the investigated compromised collective, our results reveal a satisfactory long-term survival rate of dental implants even in augmented bone and underline the value of dental implantation for the functional rehabilitation of cancer patients.

Increasing the throughput of label-free cell assays to study the activation of G-protein-coupled receptors by using a serial agonist exposure protocol.

Label-free, holistic assays, monitoring, for example, the impedance of cells on electrodes, are gaining increasing popularity in the evaluation of G-protein-coupled receptor (GPCR) ligands. It is the strength of these approaches to provide the integrated cellular response non-invasively, highly automated and with a device-dependent time resolution down to several milliseconds. With an increasing number of samples to be studied in parallel, the available time resolution is, however, reduced and the cost for the disposable sensor arrays may become limiting. Inspired by protocols from organ pharmacology, we investigated a simple serial agonist addition assay that circumvents these limitations in impedance-based cellular assays. Using a serial addition of increasing concentrations of a GPCR agonist while continuously monitoring the sample's impedance, we were able to establish a full concentration-response curve for the endogenous agonist histamine on a single layer of U-373 MG cells endogenously expressing the histamine 1 receptor (H1R). This approach is validated with respect to conventional, parallel agonist addition protocols and studies using H1R antagonists such as mepyramine. Applicability of the serial agonist addition assay was shown for other GPCRs known for their signaling via one of the canonical G-protein pathways, Gq, Gi/0 or Gs as well. The serial agonist addition protocol has the potential to further strengthen the output of label-free analysis of GPCR activation.

Distribution of organotin compounds in the bivalves of the Aegean Sea, Greece.

Five bivalve species--Mytilus galloprovinciallis (Mediterranean mussels), Venus gallina (stripped venus), Modiola barbatus L. (bearded horse mussels), Pecten jacobeus (scallops) and Callista chione (hard clams)--were collected from seven areas in Aegean Sea, Greece, between August 2001 and January 2003 and analyzed for organotins (OTs). The concentrations (as geometric means) found were 17.1 ng g-1 for tributyltin (TBT), 18.8 ng g-1 for dibutytltin (DBT), 7.8 ng g-1 for monobutyltin (MBT) and 13.0 ng g-1 for triphenyltin (TPhT) (wet weight), which are at similar or lower levels than those reported worldwide. Studying OTs distribution between different bivalve species, lower concentrations were observed in mediterranean mussels, possibly due to their growth in water column (grown on sea net pens in mussel farms), in contrast to the free-ranging species, collected from fishing grounds. Concentrations of the OTs in the examined bivalves varied seasonally.

Analysis of calcium channels by conditional mutagenesis.

Ca2+ influx through various ion channels is an important determinant of the cytosolic Ca2+ concentration, which plays a pivotal role in countless cellular processes. The cardiac L-type Ca2+ channel, Ca(v)1.2, represents a major pathway for Ca2+ entry and is in many cells expressed together with other high- and low-voltage-activated Ca2+ channels. This article will focus on the use of conditional transgenic mouse models to clarify the roles of Ca2+ channels in several biological systems. The phenotypes of conditional Ca2+ channel transgenic mice have provided novel, and often unexpected, insights into the in vivo function of L-type and T-type Ca2+ channels as mediators of signaling between cell membrane and intracellular processes in blood pressure regulation, smooth muscle contractility, insulin secretion, cardiac function, sleep, learning, and memory.

Improved glucuronide hydrolysis in the determination of urinary 1-hydroxypyrene.

The efficiency of the glucuronide hydrolysis in the determination of urinary 1-hydroxypyrene was investigated as a function of the reaction conditions. A significant improvement could be obtained by increasing the enzyme concentration described in the literature.

Pathogenesis of varroosis at the level of the honey bee (Apis mellifera) colony.

The parasitic mite Varroa destructor, in interaction with different viruses, is the main cause of honey bee colony mortality in most parts of the world. Here we studied how effects of individual-level parasitization are reflected by the bee colony as a whole. We measured disease progression in an apiary of 24 hives with differing degree of mite infestation, and investigated its relationship to 28 biometrical, physiological and biochemical indicators. In early summer, when the most heavily infested colonies already showed reduced growth, an elevated ratio of brood to bees, as well as a strong presence of phenoloxidase/prophenoloxidase in hive bees were found to be predictors of the time of colony collapse. One month later, the learning performance of worker bees as well as the activity of glucose oxidase measured from head extracts were significantly linked to the timing of colony collapse. Colonies at the brink of collapse were characterized by reduced weight of winter bees and a strong increase in their relative body water content. Our data confirm the importance of the immune system, known from studies of individually-infested bees, for the pathogenesis of varroosis at colony level. However, they also show that single-bee effects cannot always be extrapolated to the colony as a whole. This fact, together with the prominent role of colony-level factors like the ratio between brood and bees for disease progression, stress the importance of the superorganismal dimension of Varroa research.

Economic evaluation of allogeneic bone marrow transplantation: a rudimentary model to generate estimates for the timely formulation of clinical policy.

PURPOSE: To provide an evidence-based approach to the formulation of clinical policy with respect to allogeneic bone marrow transplantation (BMT) that involves perceived trade offs between two major factors: costs and consequences. The report also highlights key informational deficiencies. PATIENTS AND METHODS: Adults with acute myeloid leukemia (AML) in second complete remission (2CR) and those with acute lymphoblastic leukemia (ALL) in first complete remission (1CR) were assigned to BMT or control groups solely on the availability of a suitable donor. All hospital-borne costs were estimated, based on services used according to manual chart review, in four categories: diagnostic and therapeutic costs, professional fees, drug costs, and ward costs. Incremental costs and incremental life-years were calculated, and the quotient determined a cost per life-year gained by BMT for AML (2CR) and ALL (1CR). RESULTS: The incremental cost (in 1992 Canadian dollars) per life-year gained by BMT (cost-effectiveness) for AML (2CR) was $29,200; and for ALL (1CR) it was minus $29,200. CONCLUSION: For AML (2CR), allogeneic BMT creates better outcomes than standard treatment, but is more costly. For ALL (1CR), both the costs and outcomes are similar for BMT and standard therapy. Quality adjustments made to life-years gained did not change these conclusions.

Neuropathological findings after continuous intrathecal administration of S(+)-ketamine for the management of neuropathic cancer pain.

Questions have been raised about the potential neurotoxicity of the neuraxial use of ketamine although ketamine and its active enantiomer S(+)-ketamine have been used intrathecally and epidurally (caudally) for the management of perioperative pain and in a variety of chronic pain syndromes. Clinical experience following neuraxial administration of S(+)-ketamine has been documented without reference to local central nervous system toxicity following this approach. In addition, there are no preclinical safety data regarding stability, compatibility, and neurotoxicity on intrathecal use of single S(+)-ketamine or combinations of S(+)-ketamine, morphine, bupivacaine, and clonidine. In the present case, the continuous intrathecal administration of S(+)-ketamine, in combination with morphine, bupivacaine, and clonidine resulted in adequate pain relief in a patient suffering from intractable neuropathic cancer pain. However, postmortem observation of the spinal cord and nerve roots revealed severe histological abnormalities including central chromatolysis, nerve cell shrinkage, neuronophagia, microglial upregulation, and gliosis. Based on our results, neuraxial administration of S (+)-ketamine cannot be recommended for clinical practise before a systematic study of toxicology of neuraxial S(+)-ketamine in animals or humans has been performed.

Porcine choroid plexus cells in culture: expression of polarized phenotype, maintenance of barrier properties and apical secretion of CSF-components.

We have successfully cultured choroid plexus epithelial cells from porcine brain in pure form by the addition of cytosine arabinoside to the culture medium which prevented growth of other contaminating cells. We characterized the cells in culture by the presence of desmoplakin, fibronectin, thrombospondin, and the zonula occludens protein ZO-1 in comparison to frozen fractions of the isolated choroid plexus tissue. The cells in culture express those marker proteins and moreover exhibit a polarized phenotype which was expected from the presence of tight junction strands that correlate to an electrical resistance of 120 Ohm.cm2 measured across the cell monolayer on a permeable support. Permeability studies with fluorescein-labeled dextrans also indicate a biochemical tightness. The polarity of the cells is demonstrated by the presence of microvilli and cilia on the surface of the cultured cells as well as by the laser scanning microscopic determination of the apical localization of the ZO-1-protein and the Na+K(+)-ATPase. Thrombospondin and fibronectin were found to be localized at the basolateral membrane side. The cells in culture secrete medium containing prealbumin predominantly into the apical compartment which demonstrates that they are able to release medium containing CSF-proteins and therefore verifies the usefulness of this in vitro model.

Effects of nitric oxide donors on cardiac contractility in wild-type and myoglobin-deficient mice.

1. The effects of the nitric oxide (NO) donors S-nitroso-N-acetylpenicillamine (SNAP), sodium(Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (DEA-NONOate), and (Z)-1-[N-(2-Aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA-NONOate) on force of contraction (F(c)) were studied in atrial and ventricular muscle strips obtained from wild-type (WT) and myoglobin-deficient (myo(-/-)) mice. 2. SNAP slightly reduced F(c) in preparations from WT mice at concentrations above 100 microM; this effect was more pronounced in myo(-/-) mice. 3. DEA-NONOate reduced F(c) in preparations from myo(-/-) mice to a larger extent than those from WT mice. 4. DETA-NONOate reduced F(c) in preparations from myo(-/-) but not from WT mice. 5. Pre-incubation with an inhibitor of the soluble guanylyl cyclase (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one; 100 microM) prevented the effects of SNAP, DEA-NONOate and DETA-NONOate on F(c) in myo(-/-) mice. 6. It is suggested that, in physiological conditions, myoglobin acts as intracellular scavenger preventing NO from reaching its intracellular receptors in cardiomyocytes, whereas, in myoglobin-deficient conditions, NO is able to reduce contractility via activation of the soluble guanylyl cyclase/cyclic GMP pathway.

Activation of soluble guanylyl cyclase by YC-1 in aortic smooth muscle but not in ventricular myocardium from rat.

1. The effects of YC-1 (3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole), an activator of soluble guanylyl cyclase, on tension, levels of cyclic GMP and cyclic AMP, and cardiac L-type Ca2+-current (I[Ca(L)]) were investigated in aortic smooth muscle and ventricular heart muscle from rat. 2. YC-1 (0.1-30 microM) induced a concentration-dependent relaxation in aortic rings precontracted with phenylephrine (3 microM). The relaxant effects of YC-1 were reversed by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (30 microM; ODQ), potentiated by zaprinast (10 microM) and antagonized by Rp-8-Br-cGMPS (100 microM). 3. In ventricular heart muscle strips, YC-1 (30 microM) exhibited no effects on force of contraction (Fc) in the absence or presence of either zaprinast (10 microM) or 3-isobutyl-1-methylxanthine (30 microM). Fc was slightly increased by YC-1 (30 microM) in the presence of isoprenaline (100 nM), but this effect was not influenced by ODQ (30 microM). 4. Cardiac I[Ca(L)] was not significantly affected by YC-1 (30 microM), either in the absence or presence of isoprenaline (30 nM). 5. In aortic rings, cyclic GMP levels were increased almost 3 fold by YC-1 (30 microM); this effect was abolished by ODQ (30 microM). In isolated ventricular cardiomyocytes, cyclic GMP levels were not affected by YC-1 (30 microM) but almost doubled by activation of particular guanylyl cyclase with atriopeptin II (100 nM). 6. YC-1 (30 microM) did not increase cyclic AMP levels either in aortic rings or in ventricular cardiomyocytes. In contrast, isoprenaline (3 microM) increased cyclic AMP levels about two fold in both tissues. In cardiomyocytes, the effect of isoprenaline (3 microM) was slightly enhanced by YC-1 (30 microM). 7. It is concluded that relaxation of smooth muscle preparations by YC-1 is mediated mainly by activation of soluble guanylyl cyclase and subsequent increase in cyclic GMP levels. The failure of YC-1 to affect cardiac Fc, levels of cyclic GMP, and I[Ca(L)] suggests that soluble guanylyl cyclase is not influenced by YC-1 in rat heart muscle or only barely present in this tissue.

Failure of 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) to inhibit soluble guanylyl cyclase in rat ventricular cardiomyocytes.

1. The effects of 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), an inhibitor of soluble guanylyl cyclase (sGC), were investigated in aortic rings and ventricular cardiomyocytes from rats. The production of cyclic GMP was stimulated by NO.-donors or carbachol. Additionally, the effects of ODQ were studied in cytosolic extracts from both tissues in which the cyclic GMP production was stimulated by S-nitroso-N-acetylpenicillamine (SNAP). 2. In endothelium-intact aortic rings, SNAP (100 microM), 2,2'-(hydroxynitrosohydrazino)bis-ethana-mine (DETA NONOate; 100 microM), or carbachol (10 microM) increased cyclic GMP levels about 4 fold. These effects were abolished by ODQ (50 microM). 3. In cardiomyocytes, SNAP (100 microM), DETA NONOate (100 microM), or carbachol (10 microM) increased cyclic GMP levels about 2 fold. These effects were not affected by ODQ (50 microM). 4. In cytosolic extracts from aortic rings and cardiomyocytes, SNAP (100 microM) induced about 50 fold increases in cyclic GMP levels. ODQ (50 microM) reduced these effects by about 50%. 5. In extracts from cardiomyocytes, increases by SNAP (100 microM) of cyclic GMP levels were attenuated by myoglobin dependent on concentration: at 300 microM myoglobin, SNAP (100 microM) increased cyclic GMP levels only 3 fold. Inhibitory effects of ODQ (50 microM) were abolished by 300 microM myoglobin. 6. It is suggested that both NO. and ODQ can bind to myoglobin which, at high concentrations. can diminish their effects on sGC. Such a scavenger function of myoglobin could explain why NO. and ODQ exert only minor effects in cardiomyocytes (with high myoglobin content) but strong effects in aortic tissue (virtually devoid of myoglobin).

Barnidipine block of L-type Ca(2+) channel currents in rat ventricular cardiomyocytes.

The effects of barnidipine and nifedipine on L-type Ca(2+) current (I(Ca(L))) were investigated in ventricular cardiomyocytes from rats. Both barnidipine and nifedipine reduced I(Ca(L)) in a concentration and voltage dependent manner; the EC(50) were 80 and 130 nM at a holding potential of -80 mV, respectively, and 18 and 6 nM at -40 mV, respectively. Both drugs induced a leftward shift of the steady-state inactivation curve of I(Ca(L)). Using a twin pulse protocol, the relationships between the amount of block of I(Ca(L)) by either drug, seen during the second pulse, and the length of the first pulse were described by monoexponential functions reflecting onset of block, dependent on drug concentration. The onset of block by barnidipine was three times faster than that by nifedipine. With both drugs, recovery of I(Ca(L)) was 50 times slower than under control conditions and described by monoexponential functions reflecting offset of block (independent of drug concentration). The offset of block with barnidipine was three times slower than that with nifedipine. The time constants of block and unblock of I(Ca(L)) by both drugs were used to calculate binding and unbinding and to predict their effects at two frequencies. It is suggested that barnidipine exhibits a higher affinity to the inactivated Ca(2+) channel state as compared to nifedipine.

The quartz crystal microbalance as a novel means to study cell-substrate interactions in situ.

The quartz crystal microbalance (QCM) was first introduced as a mass sensor in gas phase and in vacuum. Since oscillator circuits capable of exciting shear vibrations of quartz resonators under liquid loading have been developed, the QCM became accepted as a new, powerful technique to follow adsorption processes at solid-liquid interfaces in chemical and biological research. Lately, the QCM technique has attracted considerable interest as a novel means to monitor cell-substrate interactions of mammalian cells in vitro. Because the establishment and modulation of cell-substrate contacts is important for many physiological processes, and potent techniques to measure these interactions noninvasively are rare, the present review highlights applications of the QCM technique in this field. The suitability of the QCM device to monitor attachment and spreading of mammalian cells in real time has been well established. The QCM response is dependent on the individual cell type that is examined. In order to identify the sources for these cell-type-specific results of QCM readings, and to understand the information content of the signal, attempts have been made to decompose the overall QCM response into subcellular contributions. The aforementioned subjects, together with a condensed introduction into the QCM technology, are included in this article.

Porcine Choroid plexus epithelial cells in culture: regulation of barrier properties and transport processes.

The epithelial cells of the choroid plexus are the structural basis of the blood-cerebrospinal fluid (CSF)-barrier. Here we summarise our recent efforts to culture those cells mainly on permeable supports in vitro. Isolated from porcine brains, we report a simple protocol for the primary culture using cytosine arabinoside as an additive that is cytotoxic for other cells except the plexus epithelial cells. Enhanced barrier properties are obtained by withdrawal of serum from the culture medium after confluency is reached. Cells improve their polarity, permeability for hydrophilic substrates is lowered, electrical resistance is increased tenfold, and a pH-gradient is built up across the cell monolayer. Polarised secretion of proteins and most importantly fluid secretion into the apical filter compartment was attained and proven to be dependent on the Na(+),K(+)-ATPase activity. Active transport processes (penicillin G, riboflavin, myo-inositol, ascorbic acid) were studied and clearly showed the involvement of the organic anion transporter. The permeability of the barrier was found to be regulated by cyclic adenosine monophosphate (cAMP). Moreover, we report that cell proliferation and differentiation is controlled by components of the extracellular matrix. The present culture model could now be used as an in vitro system to quantify drug transport across the blood-CSF-barrier.