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B Akerman

Publications and source records attributed to B Akerman.

11 recordsLinked to original sources
PubMed1989

Orientational dynamics of T2 DNA during agarose gel electrophoresis: influence of gel concentration and electric field strength.

The understanding, on a molecular level, of the mechanisms responsible for the improved separation in DNA gel electrophoresis when using modulated electric fields requires detailed information about conformational distribution and dynamics in the DNA/gel system. The orientational order due to electrophoretic migration ("electrophoretic orientation") is an interesting piece of information in this context that can be obtained through linear dichroism spectroscopy [M. Jonsson, B. Akerman, and B. Nordén, (1988) Biopolymers 27, 381-414]. The technique permits measurement of the orientation factor S of DNA (S = 1 corresponds to perfect orientation) within an electrophoretic zone in the gel during the electrophoresis. It is reported that the degree of orientation of T2 DNA [170 kilo base pairs (kpb)] is considerable (S = 0.17 in 1% agarose at 10 V/cm) compared to relatively modest orientations of short fragments found earlier (for 23-kbp DNA, S = 0.03 in 1% agarose at 10 V/cm), showing that large DNA coils are substantially deformed during the migration. Growth and relaxation dynamics of the orientational order of the T2 DNA are also reported, as functions of gel concentration (0.3-2%), electric field strength (0-40 V/cm), and pulse characteristics. The rise profile of the DNA orientation, when applying a constant field, is a nonmonotonic function that displays a pronounced overshoot, followed by a minor undershoot, before it reaches steady-state orientation (after 12 s in 1% agarose, 9 V/cm). The orientational relaxation in absence of field shows a multiexponential decay in a time region of some 10 s, when most of the DNA anisotropy has disappeared. A surprising phenomenon is a memory over minutes of the DNA/gel system to previous pulses: with two consecutive rectangular pulses (of the same polarity), the orientational overshoot and undershoot as a response to the second pulse are significantly reduced compared to the first pulse. The time required to recover 90% of their amplitudes is typically 1200 s (1% agarose, 9 V/cm), which may be compared to the time required to relax 90% of the DNA orientation, which is only 6 s. The major part of the over- and undershoot recovery is thus a reorganization of a system in which DNA is already randomly oriented. The different response amplitudes and relaxation times, including the amplitude and recovery time of the overshoot, of the orientational order of DNA in the electrophoretic gel have been studied as functions of gel concentration and field strength. The results are discussed against relevant theories of polymer dynamics.

Chemical Phenomena↗
PubMed1988

Effects of macromolecular adjuvants on the duration of prilocaine. Experimental studies on the effect of variations of viscosity and sodium content and of inclusion of adrenaline.

Sodium hyaluronate (HA) and dextran (Dx) of different molecular weights and concentrations were used as adjuvants to prilocaine for studies of the duration of infraorbital nerve block in the rat (IONB) and spinal anaesthesia in the mouse (SA). A positive relation was found between duration of block on the one hand and the concentration as well as the molecular weight of the adjuvant on the other. A direct relation was found between the duration of block and the viscosity of the anaesthetic solution. Low-sodium-content solutions of plain prilocaine caused a markedly prolonged duration of the most profound degrees of IONB as compared to medium- or high-sodium-content solutions, while no differences between the solutions were found for the weakest intensity of IONB studied or for SA. Solutions of low-sodium-content containing prilocaine and HA were associated with significant prolongations of IONB and SA as compared to corresponding solutions of medium- or high-sodium content. Inclusion of adrenaline, 5 micrograms/ml, in solutions containing prilocaine and Dx significantly prolonged the duration of the most profound degrees of IONB and of SA. By contrast, the inclusion of adrenaline in solutions containing prilocaine and HA did not prolong the duration of IONB or SA. It is concluded that modulations of the viscosity of local anaesthetic solutions by the addition of macromolecular compounds strongly affect the duration of peripheral and central nerve blocks in experimental animals. A further prolongation is accomplished by reducing the sodium content of the solutions and, in the case of Dx-containing solutions, by inclusion of adrenaline in the anaesthetic solution. The possible mechanisms of these actions are discussed.

Adjuvants, Anesthesia↗
PubMed1985

Effects of adjuvants to local anaesthetics on their duration. I. Studies of dextrans of widely varying molecular weight and adrenaline in rat infraorbital nerve block.

Local anaesthetics of the amide type were studied in a modified rat infraorbital nerve block model, with which it was possible to determine varying degrees of sensory block. Of the agents investigated, 0.5% bupivacaine tended to give a longer duration of block than 2% prilocaine or 2% lidocaine, while 0.5% etidocaine had the shortest duration. The duration of prilocaine was prolonged by addition of adrenaline, 5 micrograms/ml, more than that of the other agents. Addition of dextrans of Mw 40-110 X 10(3) did not cause any prolongation of block induced by bupivacaine. When mixed with dextrans over a wide range of Mw (40-4900 X 10(3), prilocaine exhibited significant prolongations of its action by up to 200%. The extent of prolongation was dependent on the degree of block, the concentration of dextrans in the local anaesthetic solution, and the Mw of the dextran although in a less uniform way. An increase in the relative viscosity of the solutions might be a factor of importance for the prolonging effect of addition of dextran to local anaesthetics. Since a formulation providing analgesia of a long duration would be of clinical value, further studies on combinations of the comparatively low-toxicity agent prilocaine and macromolecular substances are of interest.

Anesthetics, Local↗
PubMed1985

Effects of adjuvants to local anaesthetics on their duration. II. Studies of some substituted dextrans and other macromolecules in rat infraorbital nerve block.

The effects of adding various macromolecular substances to 2% prilocaine on duration of rat infraorbital nerve block were investigated. The tested substances consisted of dextrans with lipophilic or charged substituents as well as other neutral or highly charged macromolecules. Most of the adjuvants caused significant prolongations of sensory block. For substituted dextrans the duration of sensory block degree 3 amounted to between 120% (3% capryldextran II) and 350% (3% carboxymethyldextran) in comparison to prilocaine plain. The corresponding values for hydroxypropylstarch (3%) alginic acid (0.5%), beta-cyclodextrin (1.5%) and hyaluronic acid (0.25%) were about 170%, 285% and 380%, respectively. The results suggest that the increased duration of local analgesia by prilocaine is related to increased viscosity of the solution produced by the macromolecular compounds. The mechanism seems to be of a physical character, and hyaluronic acid seems to be worthy of further studies.

Alginates↗
PubMed1979

Penetration enhancers and other factors governing percutaneous local anaesthesia with lidocaine.

The percutaneous penetration of the local anaestetic lidocaine was investigated in the guinea-pig. Three different types of composition were employed: lidocaine hydrochloride in aqueous solution, lidocaine base in an aqueous alcoholic solvent mixture and lidocaine base in aqueous solutions of dipolar aprotic solvents. The latter solvents included simple tertiary aliphatic amides, amides related to dimethylacetamide, some cyclic amides as well as a number of miscellaneous compounds. The degree of dermal anaesthesia was noted in each case. In addition, the uptake and distribution of lidocaine in the skin and its absorption into the blood were studied using tritium-labelled drug. The results show that the percutaneous penetration of lidocaine is dependent on the concentration of the agent, the time of epicutaneous application of the composition, whether the agent was used as salt or free base, and the nature of the solvent medium. Lidocaine base in aqueous dimethylacetamide was most effective in producing percutaneous local anaesthesia.

Amides↗
PubMed1979

Effect of different types of anaesthesia including percutaneous local anaesthesia on survival of experimental skin flaps.

Local anaesthesia by epicutaneous application of the ketocaine solution A2358 gave survival of experimental skin flaps in the guinea pig which corresponded on average to 71% of the total flap. The survival after pentobarbitone anaesthesia, general anaesthesia with ether, and infiltration of prilocaine without and with adrenalin varied between 41 and 53%. The difference in effect between percutaneous anaesthesia with A2358 and the other procedures was statistically significant (p less than 0.001). Epicutaneous application of A2358 followed by one of the other forms of anaesthesia gave a flap survival that did not differ from that following local anaesthesia with A2358 alone, except when followed by injection of prilocaine with adrenalin. The improved survival after epicutaneously applied A2358 is probably attributable to an effect on the peripheral vascular bed resulting in increasing blood supply and nutrition. It may be possible that A2358, for example, could be used in man as a complement to other forms of anaesthesia to provide enhanced tissue survival in skin flaps.

Anesthesia, General↗
PubMedDate not supplied

Antinociceptive effects of localized administration of opioids compared with lidocaine.

To study possible antinociceptive effects of perineurally administered opioids, the rat infraorbital nerve block (IONB) model was employed for investigations of opioids (morphine, meperidine, buprenorphine, ethylketocyclazocine, and fentanyl) of differing receptor selectivity and physicochemical properties such as lipid solubility. Only meperidine in doses greater than 1 mg/kg produced localized analgesia, the duration of which increased dose-dependently. Naloxone failed to counteract the analgesic effects of meperidine. It is concluded that meperidine exerted its effect by a local anesthetic action and not by the activation of opioid receptors in the peripheral nerve. The local anesthetic potency of meperidine was compared with that of lidocaine in peripheral nerve blocks (IONB in rats and sciatic nerve block in guinea pigs), in central nerve blocks (epidural anesthesia in guinea pigs and spinal anesthesia in mice), and in infiltration anesthesia in guinea pigs. Time to onset of block was generally longer for meperidine. Equal amounts of the drugs produced motor blocks of similar durations except in epidural anesthesia where meperidine was clearly shorter. Sensory blocks were longer with meperidine than with lidocaine when applied in equal amounts to the infraorbital nerve and subarachnoidally. The two agents caused a similar duration of sensory block in infiltration anesthesia. Meperidine was shorter than lidocaine in epidural anesthesia. The characteristics of blocks induced by the two agents may be explained by structural differences and associated differences in physicochemical properties such as lipid solubility and pKa.

Analgesia, Epidural↗