M. Borgers

Photochemical stroke model: flunarizine prevents sensorimotor deficits after neocortical infarcts in rats.

We produced unilateral photochemical infarcts in the hindlimb sensorimotor neocortex of 186 rats by intravenous injection of the fluorescein derivative rose bengal and focal illumination of the intact skull surface. Infarcted rats showed specific, long-lasting deficits in tactile and proprioceptive placing reactions of the contralateral limbs, mostly the hindlimb. Placing deficits were most prominent during transition to immobility and/or when independent limb movements were required. Administration of flunarizine, a Class IV calcium antagonist, 30 minutes after infarction resulted in marked sparing of sensorimotor function in 30 rats. In contrast to 20 vehicle-treated rats, which remained deficient for at least 21 days, 15 (75%) of the rats treated with 1.25 mg/kg i.v. flunarizine showed normal placing on Day 1 after infarction, whereas the remaining five (25%) recovered within 5 days. Oral treatment of 10 rats with 40 mg/kg flunarizine was also effective. Neocortical infarct volume and thalamic gliosis, assessed 21 days after infarction, did not differ between 30 flunarizine- and 30 vehicle-treated rats. However, when 4-hour-old infarcts were measured in 16 rats, posttreatment with intravenous flunarizine reduced infarct size by 31%. In combination with appropriate behavioral analyses, photochemical thrombosis may constitute a relevant stroke model, in which flunarizine preserved behavioral function during a critical period, corresponding to the spread of ischemic damage.

Itraconazole, a new triazole that is orally active in aspergillosis.

Itraconazole is a new orally active triazole derivative with broad-spectrum antifungal activity. This drug is effective in experimental aspergillosis and possesses in vitro activity against various species and strains of Aspergillus. Morphological destruction of inoculated hyphae and complete inhibition of hyphal outgrowth in culture is obtained from 0.07 micrograms ml-1 (10(-7)M) onward. These properties make itraconazole a likely candidate for clinical evaluation in disseminated aspergillosis. Images

The neural cell adhesion molecules L1 and CHL1 are cleaved by BACE1 protease in vivo.

Background: The function and physiological substrates of BACE1 remain largely unknown. Results: Novel substrates for BACE1 were identified using large scale proteome analysis; L1 and CHL1 were validated in vivo. Conclusion: L1 and CHL1 are physiological substrates for BACE1. Significance: Identification of physiological substrates of BACE1 is important to understand its function and helps to predict potential side effects of BACE1 inhibitor drugs for Alzheimer disease. The β-site amyloid precursor protein-cleaving enzyme BACE1 is a prime drug target for Alzheimer disease. However, the function and the physiological substrates of BACE1 remain largely unknown. In this work, we took a quantitative proteomic approach to analyze the secretome of primary neurons after acute BACE1 inhibition, and we identified several novel substrate candidates for BACE1. Many of these molecules are involved in neuronal network formation in the developing nervous system. We selected the adhesion molecules L1 and CHL1, which are crucial for axonal guidance and maintenance of neural circuits, for further validation as BACE1 substrates. Using both genetic BACE1 knock-out and acute pharmacological BACE1 inhibition in mice and cell cultures, we show that L1 and CHL1 are cleaved by BACE1 under physiological conditions. The BACE1 cleavage sites at the membrane-proximal regions of L1 (between Tyr1086 and Glu1087) and CHL1 (between Gln1061 and Asp1062) were determined by mass spectrometry. This work provides molecular insights into the function and the pathways in which BACE1 is involved, and it will help to predict or interpret possible side effects of BACE1 inhibitor drugs in current clinical trials.

Cytochemical and Biochemical Studies of Yeasts After In Vitro Exposure to Miconazole

Yeast cells exposed to different doses of the antimycotic agent miconazole revealed important cytochemical changes in the topographic distribution of the phosphatases. A strong effect was observed on the behavior of oxidative and peroxidative enzymes. Decreased cytochrome c oxidase and peroxidase activity and increased catalase activity were seen after treatment with a fungistatic dose of miconazole, whereas a complete disappearance of these enzymes was observed after treatment with a minimal fungicidal dose of miconazole. This was in complete agreement with the quantitative biochemical data. A hypothesis is advanced concerning the possible involvement of peroxidase and catalase in the mechanism of action of this drug. Images

Localization of calcium in skeletal and cardiac muscle

SummaryThe requirement of calcium (Ca2+) in the excitation-contraction coupling of both skeletal and cardiac muscle is well established. However, the exact location of the intracellular storage sites of Ca2+ is not firmly established. We report here on the ultrastructural distribution of Ca2+ in white and red skeletal muscle and in cardiac muscle of the rat using combined phosphate-pyroantimonate (PPA) and oxalate-pyroantimonate (OPA) procedures. The methods are based on (a) stabilization and/or trapping of Ca2+ during the primary fixation step in glutaraldehyde by potassium phosphate or oxalate; (b) subsequent wash-out of all non-trapped cations such as Na+ and Mg2+ in potassium phosphate or oxalate; (c) conversion of the complexed or trapped Ca2+ into an electron-dense calcium pyroantimonate salt in 100 μm-thick tissue sections; and (d) wash-out of the excess potassium pyroantimonate at alkaline pH.With the OPA procedure, mitochondria of all muscle types showed little precipitate. The junctional sarcoplasmic reticulum was stongly reactive in relaxed white skeletal muscle, negative in contracted white fibres and negative in red skeletal and cardiac muscle, independent of the state of relaxation-contraction. Other organelles were essentially free of deposits.With the PPA method, the precipitate was almost exclusively confined to the sarcolemma and its T-tubular invaginations in cardiac and slow skeletal muscle, and was absent in fast skeletal muscle. Apart from occasional deposits in mitochondria, all other organelles were free of precipitate. The sarcolemma-associated deposits were clearly confined to the inner leaflet of the lipid bilayer. The amount of precipitate varied within the contraction cycle, relaxed cells possessing the highest density.Exposure of the tissue to La3+ resulted in the complete absence of sarcolemma-bound precipitate suggesting that the Ca2+ is exchangeable. Furthermore, these cytological data suggest a basic difference in Ca2+ storage between white skeletal muscle on the one hand, and red skeletal and cardiac muscle on the other.

Cardioprotective effects of lidoflazine during 1-hour normothermic global ischemia.

The cardioprotective effects of lidofiazine, a drug with calcium homeostatic properties, were investigated in dogs subjected to 1 hour of normothermic global ischemia, followed by reperfusion. None of the eight control dogs could be weaned from the extracorporeal bypass, confirming the severity of the ischemic model. All eight acutely pretreated dogs showed rapid recovery from the prolonged ischemic arrest and could support their own circulation. Recovery of preischemic values was 95% for systolic aortic pressure, 71% for diastolic aortic pressure, 99% for left ventricular dP/dt max and 80% for cardiac output. Light and electron microscopy and calcium cytochemistry were performed on left ventricular biopsies taken before, during and after ischemic arrest. In the control dogs, loss of structural integrity of the sarcolemma and mitochondria was prominent at the end of the ischemic period. Intracellular edema, hypercontraction of sarcomeres and great accumulation of calcium in severely damaged mitochondria occurred after 5 and 30 minutes of reperfusion. In the lidofiazine‐treated dogs, such lesions were largely prevented during the ischemic period and completely reversed after reperfusion. These observations suggest that the tolerance to ischemia is markedly augmented by lidoflazine.

Flunarizine reduces cerebral infarct size after photochemically induced thrombosis in spontaneously hypertensive rats.

The cerebroprotective effect of flunarizine was studied in a minimally invasive model of photochemically induced cerebral infarction in spontaneously hypertensive rats. Intravenous administration of the photosensitizing dye rose bengal and intense focal illumination of the brain produced a deep cortical infarction that resulted from singlet oxygen-induced peroxidative injury to the endothelial membrane, subsequent platelet adhesion, and eventual thrombus formation. The infarct size was calculated from area measurements on consecutive histologic sections prepared from the brain cortex 4 hours after the onset of the insult. Oral treatment with 40 mg/kg flunarizine 3 hours before photoexcitation resulted in a significant reduction of the median infarct size from 11.75 mm3 in the untreated group to 6.40 mm3 in the treated group (n = 13, p less than 0.001). At this dose, flunarizine had no effect on systemic blood pressure. In a separate experiment the area of thrombotic obstruction was quantified 30 minutes after the onset of light exposure. Flunarizine did not significantly reduce early thrombus formation (2.28 mm3 in the untreated and 1.78 mm3 in the treated group) (n = 12, p = 0.2). The infarcted area at 4 hours was considerably larger than the initial thrombotic area. Protection with flunarizine against development of cortical infarction has been unequivocally shown. Although some effect may already be present at the early stage of lesion formation, the major protective action admittedly occurred in the later postinsult period when the lesion was expanding.(ABSTRACT TRUNCATED AT 250 WORDS)

Multivariate analysis of angiographic, histologic, and electrocardiographic data in patients with coronary heart disease

In 61 consecutive patients undergoing aortocoronary bypass grafting, angiographic and electrocardiographic (ECG) changes were studied. Histologic delineation of myocardium was obtained by analysis of transmural biopsy specimens acquired at the time of surgery. The use of principal-component analysis revealed three definite groups of patients. Group I comprised patients with histologic findings associated with severe left anterior descending coronary artery (LAD) stenosis, without abnormal wall motion or ejection fraction. ECG abnormalities were limited to ST changes. Group II comprised patients with severe myocardial cell degeneration with only modest fibrosis associated with severe LAD stenosis and severely impaired wall motion. The incidence of infarction on the ECG was low. Group III patients had important myocardial cell degeneration with severe fibrosis associated with severe LAD stenosis, severely depressed wall motion, and significantly impaired ejection fraction. In this group there was a high incidence of infarction apparent on the ECG. Postoperative follow-up (24 months) showed a total survival of 94.4% in group I, 92.8% in group II, and only 72.7% in group III. This identification of subtypes of coronary artery disease seems to be helpful in estimating patient prognosis after coronary surgery.

Promotion of pseudomycelium formation of Candida albicans in culture: a morphological study of the effects of miconazole and ketoconazole.

The effects of miconazole and its new derivative ketoconazole on Candida albicans have been evaluated by light and electron microscopy. The growth characteristics and morphology of C. albicans in culture for various periods of time in a solution consisting of Eagles minimum essential medium supplemented with amino acids and fetal calf serum are emphasized. This medium, normally used for culturing mammalian cells, promotes a rather fast growth of C. albicans and favours the development of pseudomycelium. The obvious interest in using such culture conditions for drug evaluation is the prevalence of pseudomycelium, which in vivo is the predominant pathological form of C. albicans. Suppression of pseudomycelium formation is found in the 10-9 to 10-7 M concentration range of the imidazoles. Growth retardation and the destruction of both yeast and pseudomycelial forms brought about by incubating the cells with 10-9 to 10-4 M of the drugs are reported. At low doses these changes include the alteration of cell division, an increase in cell volume and a progressive deterioration of subcellular organelles at the cell periphery. At higher doses the involvement of all other organelles is observed finally leading to complete cell necrosis.

Acute function of secreted amyloid precursor protein fragment APPsα in synaptic plasticity

The key role of APP in the pathogenesis of Alzheimer disease is well established. However, postnatal lethality of double knockout mice has so far precluded the analysis of the physiological functions of APP and the APLPs in the brain. Previously, APP family proteins have been implicated in synaptic adhesion, and analysis of the neuromuscular junction of constitutive APP/APLP2 mutant mice showed deficits in synaptic morphology and neuromuscular transmission. Here, we generated animals with a conditional APP/APLP2 double knockout (cDKO) in excitatory forebrain neurons using NexCre mice. Electrophysiological recordings of adult NexCre cDKOs indicated a strong synaptic phenotype with pronounced deficits in the induction and maintenance of hippocampal LTP and impairments in paired pulse facilitation, indicating a possible presynaptic deficit. These deficits were also reflected in impairments in nesting behavior and hippocampus-dependent learning and memory tasks, including deficits in Morris water maze and radial maze performance. Moreover, while no gross alterations of brain morphology were detectable in NexCre cDKO mice, quantitative analysis of adult hippocampal CA1 neurons revealed prominent reductions in total neurite length, dendritic branching, reduced spine density and reduced spine head volume. Strikingly, the impairment of LTP could be selectively rescued by acute application of exogenous recombinant APPsα, but not APPsβ, indicating a crucial role for APPsα to support synaptic plasticity of mature hippocampal synapses on a rapid time scale. Collectively, our analysis reveals an essential role of APP family proteins in excitatory principal neurons for mediating normal dendritic architecture, spine density and morphology, synaptic plasticity and cognition.