Biomedical subjects

Boris Gurevich

Publications and source records attributed to Boris Gurevich.

6 recordsLinked to original sources

PubMed2006

Brain neuroprotection by scavenging blood glutamate.

Excess glutamate in brain fluids characterizes acute brain insults such as traumatic brain injury and stroke. Its removal could prevent the glutamate excitotoxicity that causes long-lasting neurological deficits. As blood glutamate scavenging has been demonstrated to increase the efflux of excess glutamate from brain into blood, we tested the prediction that oxaloacetate-mediated blood glutamate scavenging causes neuroprotection in a pathological situation such as closed head injury (CHI), in which there is a well established deleterious increase of glutamate in brain fluids. We observed highly significant improvements of the neurological status of rats submitted to CHI following an intravenous treatment with 1 mmol oxaloacetate/100 g rat weight which decreases blood glutamate levels by 40%. No detectable therapeutic effect was obtained when rats were treated IV with 1 mmol oxaloacetate together with 1 mmol glutamate/100 g rat. The treatment with 0.005 mmol/100 g rat oxaloacetate was no more effective than saline but when it was combined with the intravenous administration of 0.14 nmol/100 g of recombinant glutamate-oxaloacetate transaminase, recovery was almost complete. Oxaloacetate provided neuroprotection when administered before CHI or at 60 min post CHI but not at 120 min post CHI. Since neurological recovery from CHI was highly correlated with the decrease of blood glutamate levels (r=0.89, P=0.001), we conclude that blood glutamate scavenging affords brain neuroprotection Blood glutamate scavenging may open now new therapeutic options.

Animals↗

PubMed2006

The effect of hypertonic (3%) saline with and without furosemide on plasma osmolality, sodium concentration, and brain water content after closed head trauma in rats.

Adding furosemide (F) to mannitol causes a greater decrease of brain volume, intracranial pressure, and brain water content (BW) as compared with mannitol alone. We examined whether adding F to hypertonic saline (HS) causes less increase of BW early after closed head trauma (CHT) as compared with HS alone. With institutional approval, 125 rats underwent sham surgery or CHT and then immediately received no treatment, HS (1.2 g/kg, 3% solution), or HS + F (2 mg/kg). In groups 1-10 (n = 8/group), the percent BW content was determined at 30, 60, or 120 minutes. In groups 11-14 (n = 8/group), physiologic values were determined at 0, 30, 60, and 120 minutes. At 120 minutes, the increase of BW caused by CHT (sham = 78.9 +/- 0.6% and CHT = 81.5 +/- 2.2%, mean +/- SD) was prevented by HS + F (78.0 +/- 0.8%) but not by HS (80.7 +/- 2.2%). Both HS and HS + F similarly increased plasma osmolality and sodium concentration. Post-CHT hypotension and acidosis (30 and 60 minutes) and decrease of hemoglobin concentration (120 minutes) were less with HS + F than with HS. We conclude that adding F to HS decreases BW without causing more increase of osmolality and Na than that caused by HS alone.

Animals↗

PubMed2005

Controlled-release oxycodone-induced seizures.

BACKGROUND: The use of the opioid oxycodone hydrochloride in the management of chronic pain is gaining popularity principally because of its tolerability. However, opioid-related seizure in patients with epilepsy or other conditions that may decrease seizure threshold has been described in the literature; in particular, oxycodone has been associated with seizure in a patient with acute renal failure. OBJECTIVE: The aim of this article was to report a patient with a history of seizures but normal renal and hepatic function who developed seizure on 2 occasions after oxycodone ingestion. METHODS: A 54-year-old male patient presented with a history of tonic-clonic seizures that developed immediately after intracranial surgery. Long-term treatment with carbamazepine 400 mg QD was started, and the patient was free of convulsions for approximately 7 years. The patient presented to us with severe headache that was nonresponsive to an NSAID and the opiate agonist tramadol. Treatment with controlled-release (CR) oxycodone and tramadol drops (50 mg QID if necessary) was started, and tonic-clonic seizures developed 3 days later. RESULTS: Based on laboratory analysis, the patient had normal renal and hepatic function. On discontinuation of oxycodone treatment, the seizures resolved. However, due to effective pain relief with oxycodone, the patient decided to continue treatment, and seizures recurred. Carbamazepine was then administered 4 hours before oxycodone dosing, which allowed continuation of treatment without seizure. CONCLUSIONS: A patient with a history of seizures controlled with long-term carbamazepine therapy developed seizures when he started treatment with oxycodone CR at recommended doses. Oxycodone CR should be used with extreme caution in patients with epilepsy or other conditions that may decrease seizure threshold.

Analgesics, Opioid↗

PubMed2005

A first-order statistical smoothing approximation for the coherent wave field in random porous random media.

An important dissipation mechanism for waves in randomly inhomogeneous poroelastic media is the effect of wave-induced fluid flow. In the framework of Biot's theory of poroelasticity, this mechanism can be understood as scattering from fast into slow compressional waves. To describe this conversion scattering effect in poroelastic random media, the dynamic characteristics of the coherent wavefield using the theory of statistical wave propagation are analyzed. In particular, the method of statistical smoothing is applied to Biot's equations of poroelasticity. Within the accuracy of the first-order statistical smoothing an effective wave number of the coherent field, which accounts for the effect of wave-induced flow, is derived. This wave number is complex and involves an integral over the correlation function of the medium's fluctuations. It is shown that the known one-dimensional (1-D) result can be obtained as a special case of the present 3-D theory. The expression for the effective wave number allows to derive a model for elastic attenuation and dispersion due to wave-induced fluid flow. These wavefield attributes are analyzed in a companion paper.

Journal Article↗

PubMed2005

Wave-induced fluid flow in random porous media: attenuation and dispersion of elastic waves.

A detailed analysis of the relationship between elastic waves in inhomogeneous, porous media and the effect of wave-induced fluid flow is presented. Based on the results of the poroelastic first-order statistical smoothing approximation applied to Biot's equations of poroelasticity, a model for elastic wave attenuation and dispersion due to wave-induced fluid flow in 3-D randomly inhomogeneous poroelastic media is developed. Attenuation and dispersion depend on linear combinations of the spatial correlations of the fluctuating poroelastic parameters. The observed frequency dependence is typical for a relaxation phenomenon. Further, the analytic properties of attenuation and dispersion are analyzed. It is shown that the low-frequency asymptote of the attenuation coefficient of a plane compressional wave is proportional to the square of frequency. At high frequencies the attenuation coefficient becomes proportional to the square root of frequency. A comparison with the 1-D theory shows that attenuation is of the same order but slightly larger in 3-D random media. Several modeling choices of the approach including the effect of cross correlations between fluid and solid phase properties are demonstrated. The potential application of the results to real porous materials is discussed.

Elasticity↗

PubMed2004

Determining minimum alveolar anesthetic concentration of halothane in rats: the effect of incremental change in halothane concentration and number of crossovers.

Computer simulations for the technique of estimating minimum alveolar anesthetic concentration (MAC) in patients (quantal design) suggest that incremental concentration changes and the number of crossovers affect MAC. We hypothesized that these variables may also apply to estimating MAC in rats (bracketing design). This study tested that hypothesis and also examined whether these variables might mask differences in MAC between groups in which MAC might be expected to differ (pregnant [P] versus nonpregnant [NP]). There were 2 cohorts (n = 27 and n = 30 rats). Each cohort included NP females, females in early P, and females in late P. MAC was tested by using an incremental concentration change of 0.20% and one within-subject crossover in the first cohort and by using an increment size of 0.10% and four crossovers in the second cohort. MAC was statistically significantly increased in the three groups in the second cohort (NP, 1.16 +/- 0.12; early P, 1.14 +/- 0.10; late P, 1.07 +/- 0.10; mean +/- sd) compared with values in the three comparable groups in the first cohort (NP, 0.95 +/- 0.06; early P, 1.01 +/- 0.09; late P, 0.93 +/- 0.13). Values did not differ among groups within each cohort. Post hoc simulations indicated that up to 36% of the difference between cohorts was due to increment size, with the balance due to experimental factors. Our findings confirmed the hypothesis that increment size affects estimates of MAC when a bracketing design is used.

Anesthetics, Inhalation↗