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Biomedical subjects

H L Friedman

Publications and source records attributed to H L Friedman.

At least 37 records · Page 2Linked to original sources
PubMed1986

Chronic treatment with Ro 15-1788 distinguishes between its benzodiazepine antagonist, agonist and inverse agonist properties.

Ro 15-1788 (flumazepil) is an imidazodiazepine that is able to antagonise most of the behavioural actions of the benzodiazepines, as well as having some intrinsic effects. Acute administration of Ro 15-1788 (10 mg/kg) decreases social interaction between male rats and elevates exploratory head-dipping. After 5 days of pretreatment there was tolerance to the former effect, although Ro 15-1788 retained its ability to antagonise the effects on social interaction of the beta-carboline, FG 7142. Ro 15-1788 also retained its ability to elevate head-dipping: additionally, the chronically-treated rats had elevated motor activity and rearing scores. The acute effects of lorazepam in the holeboard were unchanged by chronic pretreatment with Ro-15-1788. The plasma and brain concentrations after acute administration of lorazepam were unchanged following chronic administration of Ro 15-1788. After chronic treatment the brain concentrations of Ro 15-1788 were unchanged. It is unlikely that pharmacokinetic factors could underlie the different behavioural changes following chronic treatment.

Animals↗
PubMed1978

Lifetimes of complexes of the antibiotic X-537A (lasalocid A) with physiological cations in methanol. Determination by NMR using a dissociative shift reagent.

Using a magnetic resonance method we have determined the lifetimes of the following complexes of X-537A (HX) in methanol solution at 25 degrees C, BaX+, 132 microseconds; SrX+, 34 microseconds; CaX+, 24 microseconds, and KX, 15 microseconds, each with an estimated uncertainty of 30%. For NaX and LiX the lifetimes are too short to measure by the present method. The lifetime found for BaX+ is considerably shorter than the result obtained by Patel and Shen using a different method. The present method depends upon the broadening of the resonance lines of certain protons in X- due to reactions such as X- + Ba2+ = BaX+, when the resonance of the proton in the "free" X- has been shifted from its normal frequency by Pr(III) which acts via the exchange PrX3 in equilibrium PrX2+ + X-. To determine the lifetimes of interest the equations for a three-state spin system were derived; under the relevant conditions the final equations take the form of the Swift-Connick equations for a two-state system, with the characteristics of one of the states dependent upon the PrX3 concentration. This dependence is used to extract the life-times from the data in a novel and simple way.

Anti-Bacterial Agents↗
PubMed1976

Ion binding by X-537A. Equilibrium and rate of complexation of Co(2+) in methanol.

The reaction of X-537A (XH) with Co(2+) in methanol to form the complex CoX(+) has been studied fluorometrically to determine the equilibrium constant as a function of temperature. The effect of complexation on the proton NMR spectrum of the X-537A was studied to determine the kinetics of complex formation. Comparing the data for the reaction XM(+) leads to X(-) + M(2+) in methanol at 25 degrees for several M(2+) we find that the equilibrium constants increase in the order CoX(+) less than MnX(+) and span only a factor of 5 while the rate constants increase in the order NiX(+) less than CoX(+) less than MnX(+) and span a factor of more than 100.

Anti-Bacterial Agents↗
PubMed1975

Ion binding by X-537A. Rates of complexation of Ni2+ and Mn2+ in methanol.

The rates of complexation are studied through the effects of the paramagnetic ions upon the magnetic resonances of three of the proton species in X-537A = XH. For the dissociation of the complex MX+ leads to M2+ + X- at 25 degrees the rate is (2.4 plus or minus 0.4) x 10(2) sec-1 for Ni2+ and in the range from 2 x 10(4) to 1 x 10(6) sec-1 for Mn2+. For the Ni2+ complex the activation parameters are also determined and discussed in terms of the details of the process. The difference in rate constants found here is much greater than the difference in the dissociation constants.

Anti-Bacterial Agents↗