Myocardial 11C-diacylglycerol accumulation and left ventricular remodeling in patients after myocardial infarction.

Left ventricular (LV) remodeling after myocardial infarction (MI) is a maladaptive process that increases the risk of heart failure and death. The myocardial phosphoinositide cycle, which is located downstream from several neurohumoral factors, plays a crucial role in LV remodeling. Our animal studies demonstrated that 1-[1-11C]butyryl-2-palmitoyl-rac-glycerol (11C-DAG) can be used to visualize regions with an activated phosphoinositide cycle. Therefore, we examined whether myocardial 11C-DAG accumulation assessed by PET is relevant to LV enlargement and systolic dysfunction in post-MI patients. METHODS: We performed PET with 11C-DAG in 13 post-anteroseptal MI patients and 4 healthy volunteers. We placed regions of interest on the noninfarcted myocardium and calculated the myocardium-to-left atrial (LA) chamber ratio of 11C-DAG accumulation. RESULTS: The myocardium-to-LA chamber ratio of 11C-DAG was significantly higher in the post-MI patients (mean +/- SD, 1.73 +/- 0.35) compared with that of the healthy volunteers (mean +/- SD, 1.25 +/- 0.13; P < 0.05). In the post-MI patients, the myocardium-to-LA chamber ratio of (11)C-DAG was significantly correlated with the LV end-diastolic volume index (r = 0.79, P < 0.01) and the plasma concentration of brain natriuretic peptide (r = 0.85, P < 0.001) and negatively correlated with the LV ejection fraction (r = -0.69, P < 0.01). CONCLUSION: These findings suggest that the myocardial 11C-DAG accumulation assessed by PET is relevant to LV enlargement, LV systolic dysfunction, and humoral activation in post-MI patients. This new imaging strategy based on intracellular signaling may contribute to the assessment and treatment of post-MI patients.     

Epinephrine is an enhancer of rat intestinal absorption.

Some physiological substances, including acetylcholine and nitric oxide, are useful candidates for stimulation of intestinal absorption of drugs. In the present study, we elucidated the ability of epinephrine (Epi) to stimulate the intestinal absorption of drugs. We evaluated the ability of Epi to enhance absorption of macromolecules using dextran (Mw 4000 Da), which is poorly absorbed from the intestine, as a model compound in situ in a closed loop of the rat jejunum. Treatment of the jejunum with Epi resulted in significant increase in absorption of dextran in a dose-dependent fashion. The area under the curve (AUC) from 0 to 4 h in the Epi-treated jejunum was 13-fold higher than that in the vehicle-treated jejunum. The absorption-enhancing activity of Epi was 40-fold higher than that of caprate, a clinically used absorption-enhancer of drugs. In the experimental conditions used in this study, histological injury of the mucosa and perturbation of the mucosal membrane were not observed in the Epi-treated jejunum. Treatment with an antagonist of alpha-adrenergic receptors attenuated the stimulation of intestinal absorption by Epi, and treatment with an agonist of alpha-adrenergic receptors resulted in enhancement of intestinal absorption. While an antagonist of beta-adrenergic receptors enhanced the absorption-enhancing effect of Epi, an agonist of beta-adrenergic receptors stimulated intestinal absorption. These results indicate that stimulation of adrenergic receptors may be a novel strategy for intestinal absorption of drugs.     

Clinical evaluation of cefixime in children

A new beta-lactamase-stable oral cephem antibiotic, cefixime (CFIX), was evaluated for safety, efficacy and pharmacokinetics in children. CFIX was effective in 19 of 20 cases (95%) with bacterial infections. The drug was especially effective against the cases of pneumonia due to beta-lactamase-producing H. influenzae or B. catarrhalis. Pharmacokinetic parameters of CFIX (3 mg/kg) with premeal administration were as follows: Kel 0.328 +/- 0.066 hr-1, T 1/2 2.14 +/- 0.36 hrs, AUC 10.9 +/- 8.7 micrograms X hr/ml, and Vd/F 1.64 +/- 1.42 L/kg. In most of the cases tested, the urinary excretion rate in 12 hours was 5 to 17%. A dose of 3 mg/kg twice daily seems to be adequate for a regular treatment.     

Facilitation of Serotonergic Activity and Amnesia in Rats Caused by Intravenous Anesthetics

Background: Midazolam and propofol often provoke retrograde amnesia after recovery from anesthesia in humans. Because an increase in central serotonergic activity impairs learning and memory, the authors examined the relation between changes in the serotonergic activity caused by intravenous anesthetics and memory.

Methods: Changes in extracellular concentrations of monoamines and their metabolites were investigated in rat striatum by a microdialysis procedure, and the effects of intraperitoneal injections of midazolam (5 mg/kg), propofol (60 mg/kg), and pentobarbital (15 mg/kg) were then examined. To evaluate the behavioral alteration with these agents, the authors used a step-through passive avoidance test.

Results: Midazolam and propofol slightly increased the extracellular concentration of 5-hydroxytryptamine in the striatum, although pentobarbital did not produce any changes. Midazolam and propofol increased the extracellular concentration of 5-hydroxyindoleacetic acid, a metabolite of 5-hydroxytryptamine, with the peak values each 138% and 138% of that in saline-injected animals, respectively. However, pentobarbital decreased the 5-hydroxyindoleacetic acid concentration to 61% of that in the saline group. Administration of midazolam or propofol immediately after the completing the passive avoidance learning reduced step-through latencies after 24 h, although pentobarbital-injected animals maintained a consistent performance. The effects of midazolam and propofol on step-through latencies were completely antagonized by intracerebroventricular administration of spiroxatrine (5 [mu]g), a 5-hydroxytryptamine 1A antagonist, 30 min before training.     

Repetitive firing properties in subpopulations of the chick Edinger Westphal nucleus.

The avian Edinger Westphal nucleus, through the ciliary ganglion, controls accommodation, iris constriction, and blood flow through the choroid. In live brainstem slices, the nucleus is easily identifiable as an olive-shaped cluster of neurons dorsal to the oculomotor nerve and nucleus. Intracellular recordings from neurons in the nucleus identified two classes of responses to sustained (300 to 500 ms) injections of depolarizing current. One set of cells fired action potentials for the duration of the pulse while a second set of cells fired action potentials only transiently, during the first 50 to 100 ms, after which they remained silent regardless of the size of the depolarization. Intracellular recordings followed by injections of the fluorescent dye lucifer yellow revealed that repetitively firing cells were located in the lateral half of the nucleus while non-repetitively or transiently firing cells were located in the medial half. These locations correspond to different Edinger Westphal subdivisions which have distinct inputs and target populations. The varying firing patterns are discussed with reference to the known functions of the subdivisions in which they occur. Replacement of calcium by magnesium in the extracellular medium had no effect on the number of action potentials fired by non-repetitively firing cells, suggesting that a calcium-activated potassium current is not responsible for suppressing repetitive firing in these cells. In contrast, in repetitively firing cells removal of extracellular calcium increased the frequency of action potential discharge and decreased the amplitude of afterhyperpolarizations following single action potentials. Addition of cadmium to the bath medium had similar effects.(ABSTRACT TRUNCATED AT 250 WORDS)     

-Hydroperoxy diethyl peroxide, an unusual natural compound isolated from an ascidian (Phallusia mammillata): acute toxicity in DDY mice

-Hydroperoxy diethyl peroxide, a novel compound found in the tunic of ascidians, has two peroxide moieties per molecule. Since ascidians are a widely served food item in Japan, human exposure to this compound potentially exists in the seafood preparation industries. No toxicological data have so far been published on this compound, and so we determined the intraperitoneal 6-day LD₅₀ in mice and conducted histopathological examinations. The 6-day LD₅₀, was found to be 199 mg/kg with 95% confidence limits of 126–314 mg/kg. Histopathological examination revealed necrosis induced in a variety of cells that had been directly exposed to the compound. These cells included hepatocytes, parenchymal pancreatic cells and fat cells. It is concluded that direct contact with this compound is likely to elicit cellular necrosis of various organs. The specific toxicological effects are probably dependent on the route of exposure.