M.D. Fernández

Effect of Desmethyl Tirilazad, Dizocilpine Maleate and Nimodipine on Brain Nitric Oxide Synthase Activity and Cyclic Guanosine Monophosphate during Cerebral Ischemia in Rats

The present study was designed to evaluate the effects of pretreatment with a combination of desmethyl tirilazad (21-aminosteroid) plus dizocilpine maleate (N-methyl-D-aspartate receptor antagonist) and nimodipine (calcium channel antagonist) on constitutive nitric oxide synthase (cNOS) activity and cyclic guanosine monophosphate (cGMP) levels in brain homogenates of rats subjected to global cerebral transient ischemia induced by bilateral clamping of the carotids for 30 min and reduction of arterial pressure (to 50–60 mm Hg) by intravenous infusion of trimethaphan (30 mg/kg). Our results show that cerebral ischemia produced an increase in cNOS activity and cGMP levels in brain homogenates. Pretreatment with desmethyl tirilazad or dizocilpine maleate or nimodipine individually significantly suppressed (p < 0.01) the increase in cNOS activity and cGMP levels induced by cerebral ischemia, which may be related to their neuroprotective effect. Similar results were obtained with pretreatment by a combination of desmethyl tirilazad plus dizocilpine maleate plus nimodipine.

VALIDATION OF TEMPERATURE SIMULATION BASED ON FINITE ELEMENT ANALYSIS IN SUBSTRATES HEATED BY ELECTRIC CABLE

This study presents a two-dimensional model of the thermal behavior of electric cable heating systems for substrates in greenhouses, developed in a transient state by using a general-purpose finite element code. In this model, the thermal properties of substrate can be introduced directly by layers or estimated by methods that allow the determination of the apparent thermal conductivity and the heat capacity per volume depending on other physical properties of the substrate, so that variations can be introduced at different depths. The authors performed a more detailed analysis of the surface layer and assigned a lower value to the moisture content in the top 10 mm. To facilitate the simulation of the different geometries of the heating system and of the boundary conditions, the boundary conditions were parameterized. The model was validated by using an experimental test consisting of nine geometric configurations for substrate electric cable heating using a sand substrate. Temperature was measured at nine locations and moisture content was measured at three locations inside the substrate. The experimental validation was conducted after simulating each geometric configuration of heating during three days, under various environmental and operational conditions. The comparison of the simulated results with experimental data from seven temperature probes at different positions revealed an RMSE of 0.80°C. The RMSE was 0.57°C for the substrate layer between the surface and a depth of 150 mm, which was the zone of greater interest in this study. Because the errors are acceptable, and maximum values occur in zones different from the root development zone, the authors claim that the model can describe the thermal state of heated substrates accurately and can be used as a tool to design and monitor this type of installations.

In memoriam R.J. Domenjoz

On March 7 this year, Prof. Robert J. Domenjoz died at the age of 89 years. Pharmacology is extremely indebted to him. He founded the journal in 1959, which was named Medicina Experimentalis and some years later renamed Medicina et Pharmacologia Experimentalis still in the tradition that Latin was the medical language.