Comparison of anodal and cathodal lesions and metal deposition in eliciting postoperative locomotion in the rat

Anodal lesions made with stainless steel electrodes elicited more vigorous running in the first 8 postoperative hr than cathodal lesions. Vigorous dose dependent running also followed 1 or 5 μg injections of FeCl₃ and CuCl₂ but was less vigorous following H₂O or HCl injections. Injections of other transition metals and AlCl₃ were ineffective. Particularly active sites for both lesions and injections were the dorsomedial n and the posterior hypothalamic n, but running also followed anterior hypothalamic-preoptic and anterior lateral hypothalamic lesions. Midbrain lesions did not elicit running. Behavioral tests administered at 24 hr failed to reveal persistent deficits correlated with effective lesion placements for running, but increasing the lesion size in the caudal hypothalamus decreased postlesion running and increased the occurrence and severity of postlesion akinesia and somnolence. A zone of tissue inflammation surrounded sites of anodal cavitation and sites of FeCl₃ and CuCl₂ injections. The results suggest that the irritative action of metals deposited by injection or lesion produce postoperative running and tissue inflammation, possibly concurrently.     

Neuroanatomic localization and memory processing in mice: the role of the dentate gyrus of the hippocampus

Both long-term memory (LTM) and short-term memory (STM) deficits in a 1-trial inhibitory avoidance task were produced in mice by the disruption of various hippocampal subfields. Disruption of neural tissue was accomplished by the mere presence of stainless steel electrodes and in addition, in most cases, by the spontaneous deposition of Fe⁺³ ions. LTM was impaired only in animals with bilateral Fe⁺³ ion deposition in the dentate gyrus. STM was impaired by tissue damage to various other regions of hippocampus. Bilateral deposition of Fe⁺³ ions in the dentate gyrus did not increase the severity of the STM deficit resulting from the concomitant damage to other hippocampal subfields. These data are interpreted to indicate that a high degree of neuroanatomical localization of function regarding memory processing occurs. Possible mechanisms by which Fe⁺³ ion deposition can interfere with the role of the dentate gyrus in information processing are discussed.     

Macroion-pairs and macroions in the kinetics of polymerization of hexamethylene oxide (oxepane)

Cationic polymerization of oxepane (hexamethylene oxide) ( 1 ) in CH₂Cl₂ and C₆H₅NO₂ as solvents was initiated with 1,3-dioxolan-2-ylium hexafluoroantimonate ( 2 ). Dissociation constants (K_D) of the ion-pairs of polyoxepane into ions were measured: K_D (in CH₂Cl₂, T = 25°C) = 2,8·10^?5 mol·l^?1 [ΔH_D = ?3,8 kJ·mol^?1 (?0,9 kcal·mol^?1), ΔS_D = ?98 J·mol^?1·K^?1 (?23,4 cal·mol^?1·K^?1)]; K_D (in C₆H₅NO₂, T = 25°C) = 1,6·10^?3 mol·l^?1 [ΔH_D = ?7,1 kJ·mol^?1 (?1,7 kcal·mol^?1), ΔS_D = ?78 J·mol^?1·K^?1 (?18,7 cal·mol^?1·K^?1)]; these values are close to those of the ion-pairs of polytetrahydrofuran. Rate constants k_p⁺ and k_p^±, determined from the kinetic measurements for degrees of dissociation of macroion-paris ranging from 0,02 to 0,21 (in CH₂Cl₂) and from 0,09 to 0,7 (in C₆H₅NO₂), were found to be identical within an experimental error of kinetic measurements. The activation parameters of propagation were measured and their dependences on the polarity of the polymerization mixtures are discussed.     

The anodic polymerization of 1,3,5-trioxane with tetraethylammonium hexachloroantimonate

The rate of anodic polymerization of 1,3,5-trioxane in the ethylene dichloride solution of tetraethylammonium hexachloroantimonate increases with an increase of current density and of initial monomer concentration. The species responsible for initiating the polymerization has been found spectrophotometrically to be H⁺SbCl₆^? which is generated “in situ” during electrolysis. The anodic oxidation of SbCl₆^? ions produces SbCl₆^· radicals which abstract hydrogen atoms from components of the reaction mixture to yield H⁺SbCl₆^?. Also FeCl₃, deposited at the anode during the electrolysis of tetraethylammonium chloride at an iron anode, initiates the polymerization of 1,3,5-trioxane. The electrochemical polymerization of 1,3,5-trioxane occurs also at other reactive metal electrodes with the hexachloroantimonate salt.     

Interaction of polystyryl radical with copper(II) complexes

The polymerization of styrene initiated by 2,2′-azoisobutyronitrile (AIBN) was studied in N,N-dimethylformamide (DMF) solution at 60°C in the presence of tetrakis(N,N-dimethylformamide)copper(II) perchlorate, and also in the presence of its monoazido copper(II) complex [Cu(DMF)₃N₃]⁺. The monoazido complex in DMF was prepared in situ by mixing solid sodium azide with tetrakis(N,N-dimethylformamide)copper(II) perchlorate in a mole ratio of 1:1. The nature of the complex was established by Job's method. The equilibrium constant K for the reaction [Cu(DMF)₄]²⁺ + N ? [Cu(DMF)₃N₃]⁺ + DMF determined by the limiting logarithmic method was found to be 1,25 · 10⁴l · mol^?1. The presence of [Cu(DMF)₄]²⁺ ions in the polymerization systems caused retardation, but [Cu(DMF)₃N₃]⁺ ions produced well defined induction periods. The rate constants at 60°C for the interaction of polystyryl radical towards [Cu(DMF)₄]²⁺ and [Cu(DMF)₃N₃]⁺ ions were calculated to be 6,6 · 10² and 5,74 · 10⁴ l · mol^?1 · s^?1, respectively.     

Anodal electrolytic brain lesions: How current and electrode metal influence lesion size and hyperphagiosity

Anodal electrolytic (DC) lesion were placed in the medial hypothalami of rats. With equal current parameters iron electrodes deposited more iron which produced larger lesions which produced greater weight gains than did stainless steel electrodes. Stainless steel electrode lesions were in turn larger and therefore more effective than equicoulombic lesions via platinum-iridium electrodes. Current delivered slowly via iron or steel electrodes produced larger lesions and as a result greater weight gains than did more rapid delivery of the same number of coulombs. Iron deposition appears to mediate iron and steel electrode lesions. Platinum electrode lesions seem to be mediated by oxygen bubbles and acidosis.     

On the 1,4‐cis‐Polymerization of Butadiene with the Highly Active Catalyst Systems Nd(C3H5)2Cl·1.5 THF/Hexaisobutylaluminoxane (HIBAO), Nd(C3H5)Cl2· 2 THF/HIBAO and Nd(C3H5)Cl2·2 THF/Methyl‐aluminoxane (MAO) – Degree of Polymerization,Polydispersity, Kinetics and Catalyst Formation

The allylneodymium chloride complexes Nd(C₃H₅)₂Cl·1.5 THF and Nd(C₃H₅)Cl₂·2 THF can be activated by adding hexaisobutylaluminoxane (HIBAO) or methylaluminoxane (MAO) in a ratio of Al/Nd = 30 for the catalysis of butadiene 1,4‐cis‐polymerization. A turnover frequency (TOF) of about 20 000 mol butadiene/(mol Nd·h) and cis‐selectivity of 95–97% are achieved under standard conditions ([BD]₀ = 2 m, 35°C, toluene). Molecular weight determinations indicate a low polydispersity (M̄_w (LS)/M̄_n (LS) = 1–1.5), the formation of only one polymer chain per neodymium and the linear increase of the degree of polymerization (DP) with the butadiene conversion, as observed for living polymerizations. First indications of chain‐transfer reaction occur only at the highest conversion or degree of polymerization. The rate law r_P = k_P[Nd][C₄H₆]^1.8 is derived for the catalyst system Nd(C₃H₅)₂Cl·1.5 THF/HIBAO and for the system Nd(C₃H₅)Cl₂·2 THF/MAO the rate law r_P = k_P[Nd] [C₄H₆]² with k_P = 3.24 L²/(mol²·s) (at 35°C). Taking into account the Lewis acidity of the alkylaluminoxanes and the characteristic coordination number of 8 for Nd(III) in allyl complexes the formation of an η³‐butenyl‐bis(η⁴‐butadiene)neodymium(III) complex of the composition [Nd(η³‐RC₃H₄)(η⁴‐C₄H₆)₂(X‐{AlOR}_n)₂] is assumed to be a single‐site catalyst for the chain propagation by reaction of the coordinated butadiene via the π‐allyl insertion mechanism and the anti‐cis and syn‐trans correlation to explain the experimental results.     

VHDJH TO JH JOINING IS NOT BLOCKED IN μ-CHAIN-PRODUCING PRE-B CELLS,IMPLYING THE BREAKDOWN OF ALLELIC EXCLUSION

Intracytoplasmic μ-positive pre-B cells (μ⁺V_H315^? cells) transformed with Abelson virus continuously produced cells (μ⁺V_H315⁺ cells) that were double-stained by anti-μ and anti-V_H315 antibodies which specifically recognized the immunoglobulin heavy chain variable region identical or closely related to that of MOPC315 myeloma protein. Southern blot analysis indicated that the μ⁺V_H315⁺ cells were generated from the μ⁺V_H315- cells by the V_H315·D·J_H2 to a germline J_H3 joining on the non-productive V_H315·D·J_H2 allele, which resulted in the production of μ-chains with variable region detectable by anti-V_H315 antibodies. Therefore, it is strongly indicated that V_HDJ_H to J_H joining is not blocked in μ-chain-producing pre-B cells, and thus is free from allelic exclusion machinery.     

Action of manganese ions on automatic activity of myocardial fibers induced by nickel ions

Automatic electrical activity of the myocardial fibers was evoked by keeping a strip of myocardium from the frog ventricle for 5–8 h in Ringer's solution containing NiCl₂·6H₂O in a concentration of 4–5 mM. Next, MnCl₂·4H₂O was added to this solution in a concentration of 1–10 mM. Under the influence of Mn⁺⁺ ions in concentrations of 1–5 mM in 70% of experiments the automatic activity was abolished in the course of 1–2 min. In the remaining experiments the automatic activity lasted 3–30 min, but in the course of time it became irregular and then disappeared altogether. With concentrations of Mn⁺⁺ ions of 6–10 mM automatic activity disappeared in 83% of experiments in the first 1–2 min, and in the rest it lasted 3–25 min. After the disappearance of the automatic activity in all cases in response to a single electric pulse secondary discharges appeared; their number varied from one to several dozens; i.e., the effect of the Ni⁺⁺ ions still continued to some extent. It is postulated that the reason for this partial preservation of the effect of Ni⁺⁺ ions after the action of Mn⁺⁺ ions is that these ions are antagonistists with respect to their action on the slow sodium-calcium current.     

Effects of hydroxyl radicals on KATP channels in guinea-pig ventricular myocytes

 We studied the effects of oxygen free radicals on the ATP-sensitive potassium channel (K_ATP channel) of guinea-pig ventricular myocytes. Single K_ATP channel currents were recorded from inside-out patches in the presence of symmetrical K⁺ concentrations (140 mM in both bath and pipette solutions). Reaction of xanthine oxidase (0.1 U/ml) on hypoxanthine (0.5 mM) produced superoxide anions (·O₂ ^-) and hydrogen peroxide (H₂O₂). Exposure of the patch membrane to ·O₂ ^- and H₂O₂ increased the opening of K_ATP channels, but this activation was prevented by adding 1 μM glibenclamide to the bath solution. In the presence of ferric iron (Fe³⁺: 0.1 mM), the same procedure produced hydroxyl radicals (·OH) via the iron-catalysed Haber-Weiss reaction. ·OH also activated K_ATP channels; however, this activation could not be prevented by, even very high concentrations of glibenclamide (10 μM). These different effects of glibenclamide suggest that the mode of action of these oxygen free radicals on K_ATP channels is different and that ·OH is more potent than ·O₂ ^-/H₂O₂ in activating K_ATP channels in the heart. Received: 14 July 1998 / Received after revision: 5 September 1998 / Accepted: 14 September 1998     

Degradation of articular cartilage by copper and hydrogen peroxide

When porcine articular cartilage particles were incubated in the presence of Cu²⁺ and H₂O₂ at pH 7.4, solubilization of collagen and proteoglycan was observed. Both agents were necessary and the rate of solubilization was concentration dependent. Other transition metal ions showed much lower catalytic activity. The solubilized polypeptides were polydispersed in size and the hydroxyproline content of the larger fragments was 13% by weight. Further incubation of the released material with Cu²⁺ and H₂O₂ resulted in further degradation and partial destruction of hydroxyproline residues. Competitive studies with scavengers of OH· and¹O₂ as well as the effect of D₂O excluded these two species as major mediators in this system.     

An approach to corrosion control during electrical stimulation

A form of cathodic protection has been developed for controlling the corrosion of stainless steel electrodes during electrical stimulation. The protection is achieved by using biphasic stimulation pulses with a slight (<-1%) charge imbalance in favor of the cathodic phase. Testsin vitro indicate that the “safe” charge limit (the charge density per phase at which corrosion first becomes serious) can be at least tripled by the use of imbalanced pulses. If confirmed by testsin vivo, this result may find application in the field of intramuscular stimulation where the present “safe” charge limit for stainless steel electrodes (#40 μC cm^?2) does not permit an adequate range of stimulation intensities.     

Improved Ag/AgCl pressure electrodes

When electrodes are used to measure slowly varying signals such as the slow wave in the gastrointestinal tract (0·01 to 10 Hz) it is necessary that the impedances of the electrodes are low at these frequencies, and the drift must also be low. We have carried out a programme of (a) electrode surface pretreatment, (b) electrolytic AgCl deposition, (c) impedance measurements, (d) electrode storage methods and (e) noise and drift measurements. Optimal preplating treatment was found to be roughening of the cleaned Ag surface. The electrode impedance could be lowered by about an order of magnitude using 50 μm Al₂O₃ abrasive powder. The impedance measured at fixed frequencies (0·01 to 0·05 Hz etc) plotted against the plating product (mAs cm⁻²) showed a sharp minimum at 3 mAs cm⁻². This mimimum was very sharp at the very low frequencies. This indicates a critical dependence of impedance on the plating product. Storage of the electrodes in saturated AgCl solution was found to be better than any other method tried. Electrodes pretreated as above and optimally plated showed drift voltages of less than 1 μV min⁻¹ and noise voltages of less than 1 μV. The low drift allowed the use of d.c. coupling during slow wave measurement on intestinal smooth muscle. The waveform in this case approximated the intracellular one closely. The electrode impedance could be described accurately in the frequency range from 0·01 Hz to 1 kHz by the relationships R=1851×f^−0·347Ω and |X|=1190×f^−0·356Ω where f=frequency in Hertz.     

Aqueous polymerization of methacrylamide initiated by KMnO4/H2C2O4 redox system

The polymerization of methacrylamide initiated by potassium permanganate/oxalic acid redox system has been studied at 35 ± 0.2°C in a nitrogen atmosphere. The rate of polymerization is independent of the activator (oxalic acid) concentration within the range 5·10^?3 to 10·10^?3 mole·1^?1, except at very high (above 10·10^?3 mole·1^?1) or at very low (below 5·10^?3 mole·1^?1) concentrations of the activator. The rate varies linearly at low monomer concentration (up to 5.87·10^?2 mole·1^?1). The catalyst exponent decreases from nearly unity (0.91) to 0.66 with increase in concentration of the catalyst (KMnO₄) probably due to participation of primary radicals in the termination of the growing chain. The addition of strong acid (H₂SO₄) within the range 5 · 10^?4–15 · 10^?4 mole · l^?1, shows a constant pH of 2.7 resulting in no change in initial rate. With activator alone (H₂C₂O₄ · 2H₂O), within the pH range 2.7 to 2.9 an optimum is observed. The initial rate increases with increase in polymerization temperature. The overall energy of activation as calculated from the ARRHENIUS plot has been found to be 15.1 kcal · mole^?1 within the temperature range 30–50°C. Organic solvents (water miscible only) depress the initial rate and the maximum conversion. Small amounts of neutral salts (KCl and Na₂SO₄), however, show no appreciable effect on the polymerization rate, but small amounts of manganous salts (MnSO₄) can increase the initial rate to a considerable extent. High concentrations of MnSO₄ result in termination of the growing chain. A complexing agent, Na₂F₂, decreases the initial rate but increases the maximum conversion. Introduction of fresh catalyst at intermediate stages of polymerization increases both the rate of the reaction and the conversion.     

Deposit free electrolytic brain lesions: Methodologic and histologic observations

The morphologic features of deposit free electrolytic brain lesions made by passing cathodal current through stainless steel electrodes or anodal current through platinum-iridium electrodes were studied. Both procedures produced lesions which resemble those made with radio frequency current in that they are composed of a central cavity surrounded by a narrow annulus of pathologic tissue and are equally effective in grey and white matter. It was found that problems of current blockage due to gas formation and of irregular lesion configuration can be minimized by increasing the electrode tip exposure and decreasing the intensity of the current. Lesions made with a platinum anode were more uniformly of smooth, spherical shape than were cathodal lesions. Reliable relationships between coulombs of current and lesion volumes were demonstrated for both cathodal and anodal deposit-free procedures.     

Free radicals in colloidal systems: Formation and decay of radicals in the tensides α-hexadecyl-ω-hydroxypoly(oxyethylene) and α-tetradecyl-ω-(sodium sulfonato)tri(oxyethylene)

Organic radicals were produced in the tensides C₁₆H₃₃(OCH₂CH₂)₂₁OH and C₁₄H₂₉(OCH₂CH₂)₃-SO₃Na in aqueous solutions using a short pulse of high energy electrons. The radicals were formed by OH attack on the (OCH₂CH₂)_x-parts of the tensides. The decay of the 250nm absorption of the radicals was recorded at different initial radical concentrations and tenside concentrations. Several radicals could be produced in one micelle. Radicals formed in the same micelle decay within microseconds or faster. The half life time τ₁ in a micelle carrying two radicals is 2,0·10^?6 s for C₁₆H₃₃(OCH₂CH₂)₂₁ OH and less than 6·10^?7 s for C₁₄H₂₉(OCH₂CH₂)₃SO₃Na. A model for intramicellar radical-radical reactions is proposed according to which the rate is faster in tensides of high critical micelle concentration. Single radicals in micelles of C₁₆H₃₃(OCH₂CH₂)₂₁OH can deactivate each other without leaving the micelles. This intermicellar reaction is discussed in terms of the rate of diffusion-controlled micelle-micelle encounters, an encounter time of 7·10^?8s, and the above time τ₁ for intramicellar reaction. The observed rate constant 2k of intermicellar reaction is 3,5·10⁶ mol^?1·l·s^?1. At low tenside concentrations, the bimolecular rate constant increases since more single tenside radicals are present in solution. They react rapidly (ca. 10⁸ mol^?1·l·s^?1) with radicals in micelles. Single radicals in C₁₄H₃₃(OCH₂CH₂)₃-SO₃Na micelles cannot directly react with each other because of the Coulombic repulsion between two anionic micelles. Reaction occurs after the exit of a tenside radical from its micelle, the rate of which depends on the micellar equilibrium M_n?M_n?1+M (M: tenside molecule; n: agglomeration number of micelle). A single radical in solution reacts with a single radical in a micelle with 2k = 1,0·10⁸ mol^?1·l·s^?1 and with another single radical in solution with 4,0·10⁷ mol^?1·l·s^?1.γ-Irradiation of both tensides in aqueous solution leads to slight increases in viscosity, followed by turbidity beyond the “gel dose” and phase separation. These effects are explained in terms of crosslinking of tenside molecules. Formation of a large network requires bridges between all participating tenside molecules (not only bridges between micelles).     

Function of implanted cathodes in electrode-induced bone growth

The application of microampere direct current (d.c.) to electrodes implanted in bone results in a proliferative response that has been found useful in the treatment of certain types of fracture. The mechanism of this response is unknown. In this investigation, the d.c. polarisation properties of 11 implantable cathode materials were measured,in vitro andin vivo, and then related to the conditions known to produce the osteogenic response. From these data, limiting parameters for clinical use of the various electrodes can be determined. Nitrogen purge experiments showed the dependence of the current on molecular oxygen and suggested that the products of oxygen reduction (H₂O₂, O₂ ⁻, OH·, OH⁻ etc.) may mediate the proliferation of bone by appropriate cells in the region of the electrode. The presence of these intermediates, some of which are free radicals, and their possible side effects needs further study.     

Gradient Structural Bone-Like Apatite Induced by Chitosan Hydrogel via Ion Assembly

Polymers with negatively charged groups (?COOH, ?OH or ?PO₄H₂) were frequently adopted to induce or promote apatite deposition through electrostatic interaction. However, chitosan with positively charged groups (?NH₂) was ignored, although it could bind most of metal ions through chelation. Based on the chelation properties of the amino group, a chitosan hydrogel obtained via physical cross-linking was used as template for ion assembly. Gradient structural bone-like apatite induced by chitosan hydrogel was achieved via ion assembly within a few hours under ambient conditions, in which amino groups of chitosan acted as anchors between chitosan and apatite nucleation. The phase and component of bone-like apatite were similar to apatite in rabbit ribs according to XRD patterns and FT-IR spectra. XRD results revealed that bone-like apatite was carbonated apatite and preferred growth orientation in the direction of c-axis. The profile of elements distribution in chitosan suggested that the content of calcium and phosphorous elements decreased with the increase of depth along the radius direction, which was accompanied by the formation of apatite-rich regions near the outer layer. When chitosan was dipped in calcium ions solution, Ca²⁺ ions bound amino groups of chitosan and formed chitosan/calcium ions complexes (CS–NH₂…Ca²⁺). CS–NH₂…Ca²⁺ subsequently attracted negatively-charged phosphate ions through electrostatic interaction. When ion assembly finished, Ca and P ions in the chitosan hydrogel converted into ACP with Ca/P ratio of 1.19. ACP converted into bone-like apatite with Ca/P ratio of 2.01 after alkali treatment.     

Internally charged palladium hydride reference electrode — Part 1: The effect of charging current density on long-term stability

The diffusion of H₂ in the α-and β-phase of palladium hydride was measured electrochemically and found to agree very well with results reported in the literature. The α-β phase transition on continuous electrolysis of Pd wire and Pd foil electrodes was found to be strongly dependent on both charging current and charging time. An internally-charged Pd wire electrode on continuous charging gave a stable open circuit voltage of+53·5±4 mV against r.h.e. over a test period of 330 h in N₂ saturated 0·5M H₂SO₄ solution. The pH response and reproducibility of such an electrode was superior to conventional palladium hydride electrodes. The potential of this electrode can still be maintained in air saturated solutions, provided higher charging currents are used. It was also shown that β-phase palladium hybride gave an irreproducible pH response.     

Functional polymers, 32. 5-Methoxy- and 5-hydroxy-2H-benzotriazol-2-yl mono- or disubstituted resorcinols or phloroglucinols

Four new 5-methoxy-2H-benzotriazol-2-yl mono- or di-substituted resorcinols and phloroglucinols 5a, b and 6a, b were synthesized by reaction of resorcinol or phloroglucinol with 4-methoxy-2-nitrobenzenediazonium chloride in a 1:1 or 1:2 mole ratio and subsequent reductive cyclization with zinc and sodium hydroxide. The methoxy groups of all four compounds were cleaved with dry hydrogen bromide gas in dimethylformamide leading to the corresponding hydroxyl derivatives 7a, b and 8a, b in nearly quantitative yields. Unlike the reaction of phloroglucinol with a large excess of 2-nitrobenzenediazonium chloride, which gave the trisubstituted product, with 4-methoxy-2-nitrobenzenediazonium chloride no phloroglucinol derivative with three 5-methoxy-2H-benzotriazol-2-yl groups could be obtained. All the resulting products were characterized by their IR, ¹H, and ¹³C NMR, and UV spectra. The resorcinol derivatives (both methoxy- and hydroxy-) Showed λ_max of 345 nm and an absorption coefficients as high as 4 · 10⁴ l · mol^–1 · cm^?1, and the phloroglucinol derivatives a λ_max of 350 nm and an absorption coefficient as high as 4,5 · 10⁴ l · mol^?1 · cm^?1.