Activity of Potassium Channels in CD8+ T Lymphocytes: Diagnostic and Prognostic Biomarker in Ovarian Cancer?

CD8+ T cells play a role in the suppression of tumor growth and immunotherapy. Ion channels control the Ca2+-dependent function of CD8+ lymphocytes such as cytokine/granzyme production and tumor killing. Kv1.3 and KCa3.1 K+ channels stabilize the negative membrane potential of T cells to maintain Ca2+ influx through CRAC channels. We assessed the expression of Kv1.3, KCa3.1 and CRAC in CD8+ cells from ovarian cancer (OC) patients (n = 7). We found that the expression level of Kv1.3 was higher in patients with malignant tumors than in control or benign tumor groups while the KCa3.1 activity was lower in the malignant tumor group as compared to the others. We demonstrated that the Ca2+ response in malignant tumor patients is higher compared to control groups. We propose that altered Kv1.3 and KCa3.1 expression in CD8+ cells in OC could be a reporter and may serve as a biomarker in diagnostics and that increased Ca2+ response through CRAC may contribute to the impaired CD8+ function.

Role of C-Terminal Domain and Membrane Potential in the Mobility of Kv1.3 Channels in Immune Synapse Forming T Cells

Voltage-gated Kv1.3 potassium channels are essential for maintaining negative membrane potential during T-cell activation. They interact with membrane-associated guanylate kinases (MAGUK-s) via their C-terminus and with TCR/CD3, leading to enrichment at the immunological synapse (IS). Molecular interactions and mobility may impact each other and the function of these proteins. We aimed to identify molecular determinants of Kv1.3 mobility, applying fluorescence correlation spectroscopy on human Jurkat T-cells expressing WT, C-terminally truncated (ΔC), and non-conducting mutants of mGFP-Kv1.3. ΔC cannot interact with MAGUK-s and is not enriched at the IS, whereas cells expressing the non-conducting mutant are depolarized. Here, we found that in standalone cells, mobility of ΔC increased relative to the WT, likely due to abrogation of interactions, whereas mobility of the non-conducting mutant decreased, similar to our previous observations on other membrane proteins in depolarized cells. At the IS formed with Raji B-cells, mobility of WT and non-conducting channels, unlike ΔC, was lower than outside the IS. The Kv1.3 variants possessing an intact C-terminus had lower mobility in standalone cells than in IS-engaged cells. This may be related to the observed segregation of F-actin into a ring-like structure at the periphery of the IS, leaving much of the cell almost void of F-actin. Upon depolarizing treatment, mobility of WT and ΔC channels decreased both in standalone and IS-engaged cells, contrary to non-conducting channels, which themselves caused depolarization. Our results support that Kv1.3 is enriched at the IS via its C-terminal region regardless of conductivity, and that depolarization decreases channel mobility.

Immune Synapse Residency of Orai1 Alters Ca2+ Response of T Cells

CRAC, which plays important role in Ca²⁺-dependent T-lymphocyte activation, is composed of the ER-resident STIM1 and the plasma membrane Orai1 pore-forming subunit. Both accumulate at the immunological synapse (IS) between a T cell and an antigen-presenting cell (APC). We hypothesized that adapter/interacting proteins regulate Orai1 residence in the IS. We could show that mGFP-tagged Orai1-Full channels expressed in Jurkat cells had a biphasic IS-accumulation kinetics peaked at 15 min. To understand the background of Orai1 IS-redistribution we knocked down STIM1 and SAP97 (adaptor protein with a short IS-residency (15 min) and ability to bind Orai1 N-terminus): the mGFP-Orai1-Full channels kept on accumulating in the IS up to the 60th minute in the STIM1- and SAP97-lacking Jurkat cells. Deletion of Orai1 N terminus (mGFP-Orai1-Δ72) resulted in the same time course as described for STIM1/SAP97 knock-down cells. Ca²⁺-imaging of IS-engaged T-cells revealed that of Orai1 residency modifies the Ca²⁺-response: cells expressing mGFP-Orai1-Δ72 construct or mGFP-Orai1-Full in SAP-97 knock-down cells showed higher number of Ca²⁺-oscillation up to the 90th minute after IS formation. Overall, these data suggest that SAP97 may contribute to the short-lived IS-residency of Orai1 and binding of STIM1 to Orai1 N-terminus is necessary for SAP97-Orai1 interaction.

Investigation of silver nanoparticles on titanium surface created by ion implantation technology

Objectives: Using dental Ti implants has become a well-accepted and used method for replacing missing dentition. It has become evident that in many cases peri-implant inflammation develops. The objective was to create and evaluate the antibacterial effect of silver nanoparticle (Ag-NP) coated Ti surfaces that can help to prevent such processes if applied on the surface of dental implants.

Methods: Annealing I, Ag ion implantation by the beam of an Electron Cyclotron Resonance Ion Source (ECRIS), Ag Physical Vapor Deposition (PVD), Annealing II procedures were used, respectively, to create a safely anchored Ag-NP layer on 1x1 cm² Grade 2 titanium samples. The antibacterial effect was evaluated by culturing Staphylococcus aureus (ATCC 29213) on the surfaces of the samples for 8 hours, and comparing the results to that of glass as control and of pure titanium samples. Alamar Blue assay was carried out to check cytotoxicity.

Results: It was proved that silver nanoparticles were present on the treated surfaces. The average diameter of the particles was 58 nm, with a 25 nm deviation and Gaussian distribution, the the filling factor was 25%. Antibacterial evaluation revealed that the nanoparticle covered samples had an antibacterial effect of 64.6% that was statistically significant. Tests also proved that the nanoparticles are safely anchored to the titanium surface and are not cytotoxic.

Conclusion: Creating a silver nanoparticle layer can be an option to add antibacterial features to the implant surface and to help in the prevention of peri-implant inflammatory processes. Recent studies demonstrated that silver nanoparticles can induce pathology in mammal cells, thus safe fixation of the particles is essential to prevent them from getting into the circulation.

Molecular background of Orai1 accumulation in the immunological synapse

CRAC channels have a vital role in the activation of T lymphocytes, through their calcium influx. CRAC is composed of the ER-membrane resident STIM1 (stromal interaction molecule 1) and the plasma membrane Orai1 pore-forming subunit. Both are accumulated at the interface of the immunological synapse (IS) between a T cell and an antigen-presenting cell (APC). CRAC channelopathies due to mutations in either Orai1 or STIM1 are characterized by severe combined immunodeficiency (SCID)-like disease, autoimmunity, muscular hypotonia, and ectodermal dysplasia. The down-regulation of actin-binding protein expression (e.g. HS1), which may be responsible for the immobilization of ion channels, hampers Ca2+-signaling and IS formation of T lymphocytes. We hypothesized that actin-binding proteins modulate the trafficking of the CRAC channels to the IS, which is crucial for the Ca2+-signaling. By means of GST-affinity assay we could show that HS1, which is an actin-regulatory adaptor protein, binds to the N-terminus of the Orai1. N-terminal truncated Orai1 channels (ΔN1: 1–74, ΔN2: 1–88) were created and expressed in Jurkat cells. Then Orai1 channel expressing Jurkat cells were conjugated to CD3/CD28 beads as an APC and Orai1 polarization was determined: the Orai1-ΔN1 mutant similar to the wild-type Orai1 redistributed to the IS but the Orai1-ΔN2 did not. Furthermore, the HS1 protein did not show IS-accumulation in cells expressing the Orai1-ΔN2 subunits unlike for those transfected with the Orai1-ΔN1 or the wild-type constructs. Overall, these data indicate that Orai1-HS1 interaction could contribute to the anchoring of the Orai1 in the IS and can affect the Ca2+-signaling upon T cell activation.

The C-terminal HRET sequence of Kv1.3 regulates gating rather than targeting of Kv1.3 to the plasma membrane

Kv1.3 channels are expressed in several cell types including immune cells, such as T lymphocytes. The targeting of Kv1.3 to the plasma membrane is essential for T cell clonal expansion and assumed to be guided by the C-terminus of the channel. Using two point mutants of Kv1.3 with remarkably different features compared to the wild-type Kv1.3 (A413V and H399K having fast inactivation kinetics and tetraethylammonium-insensitivity, respectively) we showed that both Kv1.3 channel variants target to the membrane when the C-terminus was truncated right after the conserved HRET sequence and produce currents identical to those with a full-length C-terminus. The truncation before the HRET sequence (NOHRET channels) resulted in reduced membrane-targeting but non-functional phenotypes. NOHRET channels did not display gating currents, and coexpression with wild-type Kv1.3 did not rescue the NOHRET-A413V phenotype, no heteromeric current was observed. Interestingly, mutants of wild-type Kv1.3 lacking HRET(E) (deletion) or substituted with five alanines for the HRET(E) motif expressed current indistinguishable from the wild-type. These results demonstrate that the C-terminal region of Kv1.3 immediately proximal to the S6 helix is required for the activation gating and conduction, whereas the presence of the distal region of the C-terminus is not exclusively required for trafficking of Kv1.3 to the plasma membrane.

Fast camera studies at an electron cyclotron resonance table plasma generator

A simple table-size ECR plasma generator operates in the ATOMKI without axial magnetic trap and without any particle extraction tool. Radial plasma confinement is ensured by a NdFeB hexapole. The table-top ECR is a simplified version of the 14 GHz ATOMKI-ECRIS. Plasma diagnostics experiments are planned to be performed at this device before installing the measurement setting at the "big" ECRIS. Recently, the plasma generator has been operated in pulsed RF mode in order to investigate the time evolution of the ECR plasma in two different ways. (1) The visible light radiation emitted by the plasma was investigated by the frames of a fast camera images with 1 ms temporal resolution. Since the visible light photographs are in strong correlation with the two-dimensional spatial distribution of the cold electron components of the plasma it can be important to understand better the transient processes just after the breakdown and just after the glow. (2) The time-resolved ion current on a specially shaped electrode was measured simultaneously in order to compare it with the visible light photographs. The response of the plasma was detected by changing some external setting parameters (gas pressure and microwave power) and was described in this paper.

Functionalized liposomes loaded with siRNAs targeting ion channels in effector memory T cells as a potential therapy for autoimmunity

Effector memory T cells (TM) play a key role in the pathology of certain autoimmune disorders. The activity of effector TM cells is under the control of Kv1.3 ion channels, which facilitate the Ca(2+) influx necessary for T cell activation and function, i.e. cytokine release and proliferation. Consequently, the knock-down of Kv1.3 expression in effector TM's may be utilized as a therapy for the treatment of autoimmune diseases. In this study we synthesized lipid unilamellar nanoparticles (NPs) that can selectively deliver Kv1.3 siRNAs into TM cells in vitro. NPs made from a mixture of phosphatidylcholine, pegylated/biotinylated phosphoethanolamine and cholesterol were functionalized with biotinylated-CD45RO (cell surface marker of TM's) antibodies via fluorophore-conjugated streptavidin (CD45RO-NPs). Incubation of T cells with CD45RO-NPs resulted into the selective attachment and endocytosis of the NPs into TM's. Furthermore, the siRNA against Kv1.3, encapsulated into the CD45RO-NPs, was released into the cytosol. Consequently, the expression of Kv1.3 channels decreased significantly in TM's, which led to a remarkable decrease in Ca(2+) influx. Our results can form the basis of an innovative therapeutic approach in autoimmunity.

Analysis of the K+ current in human CD4+ T lymphocytes in hypercholesterolemic state

Atherosclerosis involves immune mechanisms: T lymphocytes are found in atherosclerotic plaques, suggesting their activation during atherogenesis. The predominant voltage-gated potassium channel of T cells, Kv1.3 is a key regulator of the Ca(2+)-dependent activation pathway. In the present experiments we studied the proliferation capacity and functional changes of Kv1.3 channels in T cells from healthy and hypercholestaeremic patients. By means of CFSE-assay (carboxyfluorescein succinimidyl ester) we showed that spontaneous activation rate of lymphocytes in hypercholesterolemia was elevated and the antiCD3/antiCD28 co-stimulation was less effective as compared to the healthy group. Using whole-cell patch-clamping we obtained that the activation and deactivation kinetics of Kv1.3 channels were faster in hypercholesterolemic state but no change in other parameters of Kv1.3 were found (inactivation kinetics, steady-state activation, expression level). We suppose that incorporation of oxLDL species via its raft-rupturing effect can modify proliferative rate of T cells as well as the gating of Kv1.3 channels.

Involvement of Membrane Channels in Autoimmune Disorders

Ion channels are ubiquitous transmembrane proteins that are involved in a wide variety of cellular functions by selectively controlling the passage of ions across the plasma membrane. Among these functions many immune processes, including those in autoimmune reactions, also rely on the operation of ion channels, but the roles of ion channels can be very diverse. Here the participation of ion channels in three different roles in autoimmune processes is discussed: 1. ion channels in effector immune cells attacking other tissues causing autoimmune diseases, such as multiple sclerosis; 2. ion channels as direct targets of the immune system whereby loss of channel function leads to disease, as in myasthenia gravis; 3. ion channels whose function is modulated in the target cells by an apoptotic signal transduction cascade, such as the Fas/Fas ligand pathway. The numerous tasks that ion channels perform in autoimmune disorders and the wealth of information that has been gathered about them in recent years together provide a good basis for the design and production of drugs that may be effectively used in the therapy of these diseases.

pH-dependent modulation of Kv1.3 inactivation: role of His399

The Kv1.3 K(+) channel lacks N-type inactivation, but during prolonged depolarized periods it inactivates via the slow (P/C type) mechanism. It bears a titratable histidine residue in position 399 (equivalent of Shaker 449), a site known to influence the rate of slow inactivation. As opposed to several other voltage-gated K(+) channels, slow inactivation of Kv1.3 is slowed when extracellular pH (pH(o)) is lowered under physiological conditions. Our findings are as follows. First, when His399 was mutated to a lysine, arginine, leucine, valine or tyrosine, extracellular acidification (pH 5.5) accelerated inactivation reminiscent of other Kv channels. Second, inactivation of the wild-type channel was accelerated by low pH(o) when the ionic strength of the external solution was raised. Inactivation of the H399K mutant was also accelerated by high ionic strength at pH 7.35 but not the inactivation of H399L. Third, after the external application of blocking barium ions, recovery of the wild-type current during washout was slower in low pH(o). Fourth, the dissociation rate of Ba(2+) was pH insensitive for both H399K and H399L. Furthermore, Ba(2+) dissociation rates were equal for H399K and the wild type at pH 5.5 and were equal for H399L and the wild type at pH 7.35. These observations support a model in which the electric field of the protonated histidines creates a potential barrier for potassium ions just outside the external mouth of the pore that hinders their exit from the binding site controlling inactivation. In Kv1.3, this effect overrides the generally observed speeding of slow inactivation when pH(o) is reduced.

Two novel toxins from the Amazonian scorpion Tityus cambridgei that block Kv1.3 and Shaker B K(+)-channels with distinctly different affinities

Two novel toxic peptides (Tc30 and Tc32) were isolated and characterized from the venom of the Brazilian scorpion Tityus cambridgei. The first have 37 and the second 35 amino acid residues, with molecular masses of 3,871.8 and 3,521.5, respectively. Both contain three disulfide bridges but share only 27% identity. They are relatively potent inhibitors of K(+)-currents in human T lymphocytes with K(d) values of 10 nM for Tc32 and 16 nM for Tc30, but they are less potent or quite poor blockers of Shaker B K(+)-channels, with respective K(d) values of 74 nM and 4.7 microM. Tc30 has a lysine in position 27 and a tyrosine at position 36 identical to those of charybdotoxin. These two positions conform the dyad considered essential for activity. On the contrary, Tc32 has a serine in the position equivalent to lysine 27 of charybdotoxin and does not contain any aromatic amino acid. Due to its unique primary sequence and to its distinctive preference for K(+)-channels of T lymphocytes, it was classified as the first example of a new subfamily of K(+)-channel-specific peptides (alpha-KT x 18.1). Tc30 is a member of the Tityus toxin II-9 subfamily and was given the number alpha-KT x 4.4.

Effects of toxins Pi2 and Pi3 on human T lymphocyte Kv1.3 channels: the role of Glu7 and Lys24

Pandinus imperator scorpion toxins Pi2 and Pi3 differ only by a single amino acid residue (neutral Pro7 in Pi2 vs. acidic Glu7 in Pi3). The binding kinetics of these toxins to human Kv1.3 showed that the decreased ON rate (k(ON) = 2.18 x 10(8) m(-1)sec(-1) for Pi2 and 1.28 x 10(7) m(-1)sec(-1) for Pi3) was almost entirely responsible for the increased dissociation constant (K(d)) of Pi3 (K(d) = 795 pm) as compared to Pi2 (K(d) = 44 pm). The ionic strength dependence of the association rates was exactly the same for the two toxins indicating that through-space electrostatic interactions can not account for the different ON rates. Results were further analyzed on the basis of the three-dimensional structural models of the toxins. A 3D structure of Pi3 was generated from the NMR spectroscopy coordinates of Pi2 by computer modeling. The Pi3 model resulted in a salt bridge between Glu7 and Lys24 in Pi3. Based on this finding our interpretation of the reduced ON rate of Pi3 is that the intramolecular salt bridge reduces the local positive electrostatic potential around Lys24 resulting in decreased short-range electrostatic interactions during the binding step. To support our finding, we constructed a 3D model of the Ser-10-Asp Charybdotoxin mutant displaying distinctly reduced affinity for Shaker channels. The mutant Charybdotoxin structure also displayed a salt bridge between residues Asp10 and Lys27 equivalent to the one between Glu7 and Lys24 in Pi3.

Blockage of human T lymphocyte Kv1.3 channels by Pi1, a novel class of scorpion toxin

Using the patch-clamp technique we determined that Pandinus imperator toxin Pi1, a recently described peptide toxin having four disulfide bridges instead of the usual three in scorpion toxins, blocked Kv1.3 channels of human T lymphocytes from the extracellular side with a 1:1 stoichiometry. Kv1.3 block was instantaneous and removable with toxin-free extracellular solution. The toxin did not influence activation or inactivation of the channels. We found that Pi1 blocked Kv1.3 with less affinity (K(d) = 11.4 nM) than the structurally related three disulfide bridge containing toxins Pi2 (50 pM) and Pi3 (0.5 nM). The fourth disulfide bridge in Pi1 had no influence on the channel binding ability of the toxin; the less effective block was due to differences in amino acid side chain properties at positions 11 and 35.

Avoidable mortality. Is it an indicator of quality of medical care in eastern European countries?

Age-standardized time trends (1979-1988) for avoidable mortality in two Eastern European countries (Hungary and Czechoslovakia) and selected developed countries (England and Wales, France, Italy, Japan, Portugal and USA) have been analysed. Mortality from both all avoidable causes and all other causes declined in the selected developed countries during the period of observation, the decline in rates for avoidable causes was faster than that for all other causes. In Hungary and Czechoslovakia the death rates from both groups of causes increased in the first part of the period studied and a decline in mortality from both types of causes could be observed from 1985. As a consequence, the difference in avoidable mortality between the Eastern European countries and the developed countries increased by the end of the observation. Studies on mortality from individual amenable causes showed that the death rates are usually much higher in Hungary and Czechoslovakia than in the developed countries and the differences did not diminish during the period of study. In Hungary and Czechoslovakia the bad pattern of mortality from conditions amenable to medical interventions is believed to reflect, at least in part, the crisis in the health services which these countries have experienced for the past decades.

Interference by the new antibiotic cefpirome and other cephalosporins in clinical laboratory tests, with special regard to the "Jaffé" reaction

The new cephalosporin, cefpirome, was investigated for its possible interference in clinical laboratory tests, especially the determination of creatinine. Tests for bilirubin, cholesterol, protein, urea, and uric acid were also studied. A selection of commercially available compounds such as cefoperazone, cefazolin, cefamandole, cefoxitin, latamoxef, ceftriaxon, cefotiam, cephaloridine, cephalotin, cefotaxime, cefazedone and cefuroxime, and cefodizime (a compound under development) were also included in these investigations. Interference was found only with the "Jaffé method" for the determination of creatinine. Pronounced interactions with alkaline picrate were observed with cefpirome, cefoxitin, cephalotin and cephaloridine, whereas the other compounds showed only weak reaction or no reaction at all. The cephalosporins did not interfere in any of the other tests mentioned above. Care must therefore be taken in the determination of creatinine in samples from patients under treatment with these drugs. The assay methods of choice at present are enzymatic or specific HPLC assays.

Penbutolol Pharmacokinetics: the influence of concomitant administration of cimetidine

A possible interaction of penbutolol and cimetidine was investigated in healthy volunteers treated orally for 7 days. The plasma levels of unmetabolized penbutolol showed a slight but non-significant increase. The biphasic elimination kinetics of penbutolol (half-lives 0.8 and 17 h) was not affected by coadministration of cimetidine. Plasma levels of penbutolol were not significantly altered by chronic treatment with cimetidine, whereas the levels of 4-hydroxypenbutolol and 4-hydroxypenbutolol glucuronide were significantly reduced.

Penbutolol and furosemide in a fixed-dose combination-bio-equivalence of two formulations

Twelve healthy male volunteers participated in an open cross-over study designed to test whether two fixed-dose combination formulations of penbutolol (40 mg) and furosemide (20 mg), an ordinary and a film-coated tablet, are bio-equivalent. Penbutolol capsules (40 mg) and 20 mg furosemide tablets (Lasix; Hoechst) served as reference formulations. The maximum concentration of furosemide was significantly depressed in the case of fixed-dose combinations, reflecting a possible pharmacokinetic interaction between penbutolol and furosemide. However, the area under the concentration versus time curve for furosemide and its cumulative urinary excretion and diuretic effect were not influenced by penbutolol. On the basis of plasma concentration versus time data and urinary parameters, the two fixed-dose formulations are bio-equivalent.

Rapid fluorimetric procedure for the analysis of fendosal in plasma and data following oral dosing

A simple, rapid, and sensitive procedure is described for the determination of Fendosal in plasma. After extraction of Fendosal from buffered plasma, the drug is determined by measurement of the fluorescence induced by irradiation with short-wave ultra-violet (UV) light. The complete procedure can be completed in less than 2 h; one technician can perform up to 50 assays in one working day. The limit of detection corresponds to 0.1 microgram ml-1 plasma. Drug concentration and induced fluorescence were linearly related over the concentration range 0--8 micrograms ml-1.

Fluorometric determination of clobazam, a 1,5-benzodiazepine, in human plasma

A fluorometric procedure for clobazam, a 1,5-benzodiazepine, based on a fluorophore formed upon irradiation of the drug using short wavelength UV light (254 nm) for 35 min is presented. Fluorescence is linear over a 100-6400-ng/ml range using excitation and emission wavelengths of 350 and 400 nm, respectively. Application of the method to the determination of clobazam in spiked human plasma samples revealed that the drug can be determined at nanogram per milliliter levels with an accuracy of 1-5%. The procedure is specific for clobazam in samples containing its major plasma metabolite, N-desmethylclobazam, and also in samples containing 1,4-benzodiazepines and other selected drugs. A plasma level-time profile after oral administration of a single 40-mg dose of clobazam to a healthy adult male is also illustrated.

Kinetics and metabolism of clobazam in animals and man

1 The pharmacokinetic behaviour of the psychotropic drug clobazam, a 1,5 benzodiazepine, and its metabolism were studied with the ¹⁴C-labelled compound in rats, dogs, monkeys and man. The absorption was practically complete in all three animal species. Clobazam was not excreted in the unchanged form by all species. The main metabolite in plasma of monkeys, dogs and man was N-demethylclobazam. The metabolites were partially in the conjugated form.

2 The binding to serum proteins (concentration range 0.05-10 μg/ml serum) amounted to between 66% (in rats) and 85% (in man). The maximal levels of total radioactivity (original compound and metabolites) in blood were 0.24 ± 0.043 μg Equ/ml (2-4 h) in doses and 0.67-0.82 μg Equ/ml (0.5-1 h) in rhesus monkeys. These levels were markedly higher than those in rats with values of 0.064 ± 0.012 μg Equ/ml (∼0.5 h). The elimination of radioactivity from blood occurred in two phases.

3 After repeated daily administration of oral doses, the 24-h blood levels accumulated in rats to about three times the initial value. In dogs the 24-h serum concentrations remained practically unchanged. Long-term treatment with clobazam in monkeys neither caused enzyme induction nor other processes retarding metabolism and elimination.

4 Both after a single oral and intravenous dose, more than two-thirds of the radioactivity administered to rats was excreted with the faeces. Dogs, however, excreted about three-quarters of the radioactivity with the urine, irrespective of the route of administration. In monkeys, the excretion also occurred mainly in the urine. In all three species, renal excretion was similarly rapid to that from blood or plasma.

5 Apart from gastro-intestinal tract, liver and kidneys, the distribution in rats and dogs was remarkably even within the range of maximal blood levels. In the rat brain, the concentration amounted to only one-third of that in the blood. Special accumulations were not found. In dogs, the concentration in the brain was as high as that in the blood.

6 In rats, kinetics and metabolism were not significantly changed by pregnancy.

7 For metabolism studies in the four species (man, monkey, dog and rat) urine and faeces (and in some cases also serum) were examined after a single dose or repeated administration. The number and kind of metabolites detected in the individual species were partially different. In autoradiographic studies, exceptionally up to 14 radioactive spots were found for clobazam.

8 The structures of the metabolites were elucidated by independent methods, mainly mass spectrometry. In addition to the original substance, eight metabolites were identified for clobazam amounting to 70-90% of the total number of metabolites, depending on the species.

The two most important chemical changes of clobazam during metabolism are dealkylation and hydroxylation. Dealkylation at nitrogen-(1), particularly pronounced in the species dog, does not differ between the 1,4- and 1,5-benzodiazepines. The difference in metabolism is only pronounced in oxidative decomposition.

9 In contrast to diazepam, the 4′ position of the phenyl ring of clobazam seems to be particularly favourable for introduction of a hydroxyl function. In dogs, hydroxylation at the 9 position plays an additional important role. It results in the formation of the metabolite 9-hydroxy-N-demethylclobazam by which this species is markedly distinguished from the other three species.

It is remarkable that clobazam is not hydroxylated at the 3-position. This is obviously a characteristic of the 1,5-benzodiazepines and helps to distinguish them from the 1,4-benzodiazepines such as diazepam.

Pharmacokinetic investigations on diminazene and rolitetracycline in comparison to a combination of both

Serum level tests were carried out on healthy cows with a combination drug of one part Berenil and two parts Reverin. When compared with the commercial preparations Berenil (Diminazene) and Reverin (Rolitetracycline), the kinetic behaviour of Reverin in the combination preparation was identical. In the case of Berenil, administered in the form of the combination drug, the second slow elimination phase with a 63 hour half-life, as found after the administration of Berenil only, could not be observed. Eight hours after administration of the combination only minimal Berenil serum levels were detectable, after 24 hours the levels were lower than the limit of detection. This has a practical bearing on the question of residues.

[Studies on the bio-availability of tolbutamide (author's transl)]

Two different batches of Rastinon 1,0 Hoechst were administered, a year apart, to two groups of healthy subjects (ten and six men, respectively) without any difference in effect on blood sugar being found. The blood sugar concentration was measured in six healthy men before and after oral administration of 1,000 mg tolbutamide (as Rastinon 1,0 Hoechst or tolbutamid tablets Ratiopharm), in a blind test. After tolbutamide Ratiopharm, the area under the blood sugar concentration-time curves was only 29 percent (0-4 hafter medication) and 32 percent (4-8 h after medication) of that after Rastinon 1,0 (P 2alpha less than 0.01), with marked scatter between individuals. Maximal serum concentration was 80 percent below that after Rastinon. The first measurable value was reached 0.8 plus or minus 0.2 h after medication of Rastinon and 3.6 plus or minus 0.8 h after tolbutamide Ratiopharm. The areas under the serum concentration under the curves after tolbutamide Ratiopharm were only 16 percent (0-4 h after medication) and 19 percent (0-8 h after medication) of those after Rastinon (P 2alpha less than 0.05 and 0.01, respectively). The differences demonstrate that tolbutamide Ratiopharm tablets and Rastinon 1,0 Hoechst are not equivalent biologically and therapeutically.