High prevalence of vertebral fractures in seizure patients with normal bone density receiving chronic anti-epileptic drugs.

People with epilepsy who take certain medications are at risk for developing osteoporosis and fractures of the vertebrae that commonly go undiagnosed. By using technology available in a bone density scan, we observed at least one fracture in many subjects with bone density in the normal and osteopenic range. PURPOSE/INTRODUCTION: Chronic use of antiepileptic drugs (AEDs), both enzyme-inducing (phenytoin, phenobarbital, carbamazepine, and primidone) and non-enzyme-inducing (i.e., valproate), is recognized as a cause of secondary osteoporosis. Vertebral compression fractures (VF) are the most common type of osteoporotic fractures and may confer an increased risk of future hip, wrist, and vertebral fractures. Vertebral compression fractures in the general population are frequently asymptomatic, and under-diagnosed. The purpose of this study is to describe the prevalence of VF in a cohort of male veterans with epilepsy on chronic AEDs. METHODS: The cohort for this study consisted of 146 male veterans who carried a diagnosis of epilepsy and were chronic users of AEDs known to cause osteoporosis (phenobarbital, phenytoin, carbamazepine, primidone, and valproate). Chronic AED use was defined as receiving an AED for at least 2 years. Subjects were previously seen in the osteoporosis clinic and had been evaluated by a dual-energy X-Ray absormetry (DXA) instrument including morphometric studies following a standard vertebral fracture assessment (VFA) protocol during the same DXA imaging acquisition session. RESULTS: The mean age was 63 years. Low bone mineral density defined as osteoporosis or osteopenia was observed in 29% and 43% respectively. We observed at least one VF in 41 % of the subjects who had normal BMD, 54% in the osteopenic range, and 75% in the osteoporotic range. CONCLUSIONS: By performing a VFA in addition to standard bone densitometric studies, we disclosed a large prevalence of compression fractures in individuals with epilepsy chronically treated with AEDs who had BMDs in the normal and osteopenic ranges. The addition of VFA or other imaging methods to evaluate VF should be included in the evaluation of bone health in individuals with epilepsy receiving AEDs since it may modify treatment recommendations to prevent future osteoporotic fractures.

A genetically encoded cyclobutene probe for labelling of live cells.

We have identified an aminoacyl-tRNA synthetase/tRNA pair for the efficient and site-specific incorporation of a cyclobutene-containing amino acid into proteins in response to an amber nonsense codon. Fast and fluorescent labeling of purified proteins and intact proteins in live cells was demonstrated using the inverse electron demand Diels-Alder reaction with a tetrazine.

Quorum sensing in the dimorphic fungus Candida albicans is mediated by farnesol.

The inoculum size effect in the dimorphic fungus Candida albicans results from production of an extracellular quorum-sensing molecule (QSM). This molecule prevents mycelial development in both a growth morphology assay and a differentiation assay using three chemically distinct triggers for germ tube formation (GTF): L-proline, N-acetylglucosamine, and serum (either pig or fetal bovine). In all cases, the presence of QSM prevents the yeast-to-mycelium conversion, resulting in actively budding yeasts without influencing cellular growth rates. QSM exhibits general cross-reactivity within C. albicans in that supernatants from strain A72 are active on five other strains of C. albicans and vice versa. The QSM excreted by C. albicans is farnesol (C(15)H(26)O; molecular weight, 222.37). QSM is extracellular, and is produced continuously during growth and over a temperature range from 23 to 43 degrees C, in amounts roughly proportional to the CFU/milliliter. Production is not dependent on the type of carbon source nor nitrogen source or on the chemical nature of the growth medium. Both commercial mixed isomer and (E,E)-farnesol exhibited QSM activity (the ability to prevent GTF) at a level sufficient to account for all the QSM activity present in C. albicans supernatants, i.e., 50% GTF at ca. 30 to 35 microM. Nerolidol was ca. two times less active than farnesol. Neither geraniol (C(10)), geranylgeraniol (C(20)), nor farnesyl pyrophosphate had any QSM activity.

Peroxycarbenium-mediated C-C bond formation: applications to the synthesis of hydroperoxides and peroxides.

The Lewis acid-mediated reaction of alkene nucleophiles with peroxyacetals provides an effective route for the synthesis of homologated peroxides and hydroperoxides. In the presence of Lewis acids such as TiCl(4), SnCl(4), and trimethylsilyl triflate, peroxyacetals and peroxyketals undergo reaction with allyltrimethylsilane, silyl enol ethers, and silyl ketene acetals to afford homoallyl peroxides, 3-peroxyketones, and 3-peroxyalkanoates, respectively. Reactions of peroxyacetals are Lewis acid dependent; TiCl(4) promotes formation of ethers while SnCl(4) and trimethylsilyl triflate promote formation of peroxides. Lewis acid-promoted reactions of silylated hydroperoxyacetals furnish silylated hydroperoxides, which can be deprotected to homologated hydroperoxides. Hydroperoxyketals undergo Lewis acid-mediated allylation to furnish 1,2-dioxolanes via attack of hydroperoxide on the intermediate carbocation. Lewis acid-mediated cyclization of unsaturated peroxyacetals furnishes 1,2-dioxanes, 1,2-dioxepanes, and 1,2-dioxacanes through 6-endo/exo, 7-endo/endo, and 8-endo/endo pathways. The corresponding reactions involving 6-endo/endo and 5-endo/exo pathways were unsuccessful.

Biphasic release of immunoreactive endothelins following acute pulmonary thromboembolism in pigs.

The purpose of this investigation was to study the role of endothelins (ETs) in the pathogenesis of acute pulmonary thromboembolism (PTE). Eighteen piglets (20 +/- 3 kg) were anesthetized and ventilated with 100% oxygen, five of them then served as controls. Acute thromboembolic injury in the lung was induced by injecting 15-25 ml of preformed clots into the left lower lobar pulmonary artery during thoracotomy. Pulmonary arterial pressure (Ppa) increased by at least 2.5-fold from baseline. During the subsequent 8 h, seven blood samples were collected from the left atrium and assayed for immunoreactive ETs. The results showed that following PTE: (1) Ppa remained elevated but cardiac output remained constant throughout the experiments; (2) plasma level of immunoreactive ETs increased in the embolized group compared to controls and the profile of immunoreactive ET release suggested a biphasic response. We conclude that the release of these vasocontractile and bronchoconstrictive mediators after PTE may contribute to ventilation perfusion mismatching and account for the pulmonary hypertension and deterioration of gas exchange that are often seen clinically.

Ozonolysis in the presence of Lewis acids: directed addition to carbonyl oxides.

The presence of Lewis acids strongly influences the distribution of products from alkene ozonolysis. Delivery of alkoxide and phenoxide ligands to a coordinated carbonyl oxide affords hydroperoxyacetals under aprotic conditions.

A novel procedure for daily measurements of hemodynamical, hematological, and biochemical parameters in conscious unrestrained rats.

Accurate and chronic measurements of various parameters in conscious animals are fundamental for depicting pathological chronic conditions and their etiology in many experimental models, but they are often difficult to achieve. The aim of the present work was to develop and describe step-by-step a reproducible surgical procedure and daily manipulations for continuous, chronic use of conscious rats as models towards a better understanding of various cardiovascular and renal diseases and the testing of novel pharmacological drugs. The complete apparatus involved the use of a series of specialized devices (harness, rotating swivel, revolving arm) supporting a flexible, permanently implanted vascular catheter into the left femoral artery up to the abdominal aorta connected to a miniaturized individual peristaltic pump for delivering fluid at a constant rate. Such a set-up also enabled easy, quick, and reproducible daily blood sampling for the evaluation of more than 20 parameters, including the monitoring of heart rate (HR) and blood pressure in freely moving conscious rats. The overall success and survival rate reached 98% over 14 days and could be extended further. This model represents a much needed and valuable advance in surgical research techniques to evaluate the hemodynamic, hematological, biochemical, pharmacokinetic, and toxicological profile of any new drugs over time in conscious animal models such as rats. What makes this procedure satisfactory is the long-term reliable arterial access and reproducibility of the methodological approach for accurate and continuous measurements, minimizing the stress or invasiveness associated with the use of currently employed systems.

Peroxides as oxidative enzyme inhibitors: mechanism-based inhibition of a cysteine protease by an amino acid ozonide.

A stable ozonide derived from Cbz-L-Phe accomplishes rapid and stoichiometric inhibition of papain at less than 100 microM concentration under conditions where formation of the corresponding aldehyde is negligible. Oxidation of the active site thiolate by the bound peroxide is believed to lead to formation of an inactive sulfenate or sulfenic acid. Reduction of the ozonide in excess DMSO provides a convenient method for in situ generation of a peptide aldehyde.

Lewis acid-mediated displacements of alkoxydioxolanes: synthesis of a 1,2-dioxolane natural product.

[formula: see text] Addition of electron-rich alkenes to the peroxycarbenium ions derived from Lewis acid-mediated ionization of 3-alkoxy-1,2-dioxolanes provides an efficient route for the synthesis of substituted 1,2-dioxolanes. The methodology is illustrated with a rapid synthesis of a 1,2-dioxolane natural product related to the plakinic acids.

The many aspects of endothelins in ischemia-reperfusion injury: emergence of a key mediator.

The endothelins (ETs) are regulatory peptides, distributed in many organ systems and producing potent physiological effects. They are the most powerful vasoconstrictive substances known today. They also act as promitogens. Many data supporting pathophysiological roles for ETs are reported, especially regarding diseases related to the vascular system, such as hypertension, pulmonary hypertension, preeclampsia, ischemic heart diseases, renal failure, subarachnoidal hemorrhage, and cerebral ischemia. The development of drugs blocking ET binding to its receptors (antagonists) and the biosynthesis of ETs (ECE inhibitors) presently attracts great interest in terms of establishing new treatments for diseases in which ETs are believed to be involved. Here we review the evidence supporting a role for ETs in the various etiologies related to ischemia-reperfusion injury, such as is found in heart disease, cerebral ischemia, and organ transplantation.

Synthesis of E,E-diene hydroperoxides via photoisomerization of protected hydroperoxides.

A general approach to E,E-diene hydroperoxides is described based upon photoisomerization of readily available Z,E-diene monoperoxyketals. Protection of a Z,E-diene hydroperoxide as the 2-methoxypropyl peroxyketal is followed by iodine-mediated photoisomerization to produce a mixture enriched in the E,E isomer. After chromatographic purification, deprotection of the peroxyketal with mild acid furnishes the E,E-diene hydroperoxide.

The resolution of racemic hydroperoxides: a chromatography-based separation of perketals derived from arachidonic, linoleic, and oleic acid hydroperoxides.

In spite of the importance of optically pure unsaturated hydroperoxides in biology, chemistry, and medicine, no general method for synthesizing these labile compounds has been reported. We have developed a chiral vinyl ether that reacts with racemic hydroperoxides to give diastereomeric perketals in high yield. These perketals can be separated by liquid chromatography and the chiral group removed to provide highly enriched hydroperoxide enantiomers (greater than 99% enantiomeric excess). The chiral reagent that has been most successful in our hands is the 2-propenyl ether derived from trans-2-phenylcyclohexanol. By use of this vinyl ether, perketals are readily formed from hydroperoxides, they are stable to normal- and reverse-phase chromatography, and the hydroperoxide is regenerated from the perketal without racemization in high yield with mild acid. Several chiral hydroperoxides have been resolved by this procedure: alpha-phenethyl hydroperoxide, 2-octyl hydroperoxide, and a number of hydroperoxides derived from oleic, linoleic, and arachidonic acids.

In vitro studies of fatty acid metabolism in vitamin B6 deficient rats.

The oxidation of [1-14C]palmitate, [1-14C]linoleate, and [1-14C]arachidonate as well as their incorporation into lipids was investigated in vitamin B6 deficient rats using liver slices and isolated mitochondria. In experiments on fatty acid oxidation in liver slices, we observed a decrease in the production of 14CO2 from radioactive palmitate and linoleate, but not from arachidonate. In the case of mitochondria, we detected no difference between the deficient rats and the controls with linoleats; however, there was an increase in the oxidation of palmitate in the deficient rats as compared to the controls. Experiments on the incorporation of radioactivity into lipids showed an increase in radioactivity from [1-14C]palmitate and [1-14C]linoleate in the triglyceride, phospholipid and cholesterol fractions of deficient rats. In the case of [1-14C]arachidonate, no difference was observed between the two groups of rats. These experiments showed that major changes occurred in metabolism of palmitate and linoleate and strongly suggested that the decrease in the arachidonate content previously observed in rat tissues could not be explained by alteration in the metabolism of this fatty acid.

[Effect of pyridoxine deficiency on fatty acid metabolism in the rat]. / Influence d'une carence de pyridoxine sur le métabolisme des acides gras chez le rat.

We have studied the effect of pyridoxine deficiency on rat liver fatty acid synthetase using acetyl-1-14C-CoA. We have observed no significant difference in the synthetase activity between the deficient and ad libitum control rats. From in vivo experiments with palmitate-1-14C, linoleate-1-14C or arachidonate-1-14C, we noted an increase in the oxidation of all fatty acids in the deficient animals. Studies with the same tracers on their incorporation rate into liver triglycerides and phospholipids showed an increase in the rate of incorporation of palmitate and linoleate within lipids of deficient rats, but no significant difference was seen with arachidonate.

Relation between drug-induced central nervous system effects and plasma levels of diazepam in man.

Pharmacodynamic effects and plasma levels of diazepam were studied in healthy male volunteers at different dose levels. Responses to diazepam were quantified, using instruments which measured body sway (statometry) and psychomotor performance (stressalyser tests). High dose-related correlations were obtained between drug-induced changes in test parameters and drug plasma levels, both with regard to stimulant and depressive effects. Techniques were devised for evaluating and comparing the efficacy and usefulness of different types of tests, taking into account critical thresholds, slopes and error estimates, correcting for changes in predrug levels and control (nondrug) trials.

Effects of pyridoxine deficiency on the composition of plasma and liver fatty acids in rats fed low and high fat diets.

A study was made of the effect of pyridoxine deficiency on the fatty acids of liver and plasma in rats fed diets containing 1, 10, or 20% fat. Both ad libitum-fed and pair-fed control rats were used. In pyridoxine deficiency, arachidonic acid decreased with a concomitant increase in linoleic acid. Incubation of liver slices with [1-14C]acetate showed no significant alteration of fatty acid synthesis in pyridoxine-deficient rats fed 1 or 10% fat when compared with the ad libitum-fed control rats, but revealed a marked increase in cholesterogenesis compared with either control group. Incubations with [1-14C]linoleate resulted in no differences in the synthesis of arachidonate between the experimental and the ad libitum-fed control rats. Incubations with [5,6,8,9,11,12,14,15-3H]arachidonate showed decreased incorporation of this fatty acid in total liver lipids in pyridoxine-deficient rats compared with ad libitum fed control rats. We concluded that the diminution in arachidonate observed in liver lipids of pyridoxine-deficient rats does not result from a lower conversion of linoleate into arachidonate, but possibly from an increased degradation of this fatty acid.