Daily Variations in the Responses to Papaverine but not Theophylline in Rat Aorta

The presence of temporal patterns in the responses of vascular smooth muscle to relaxing agents have been known. The aim of this study was to examine the variations in the in vitro sensitivity of rat aorta to papaverine and theophylline in both endothelium-intact and -denuded rings. The animals were synchronized with a 12-h light: 12-h dark schedule. Rat thoracic aorta rings were obtained from animals sacrificed at six different times (09:00, 13:00, 17:00, 21:00, 01:00 and 05:00) of the day. Tissues were precontracted submaximally with phenylephrine and then were relaxed by papaverine (10^?8 ? 10^?4 M) and theophylline (10^?7 ? 10^?3 M) applied cumulatively. The responses to most of the concentrations and EC₅₀ values for papaverine demonstrated an ultradian rhythm with an 8 h periodicity. Time-dependent variations were not found in the responses to theophylline. The results are discussed in relation with the time-dependent differences in signal transducing mechanisms.     

Structure and function relationship of phosphatidylglycerol in the stabilization of the phosphatidylethanolamine bilayer

Differential scanning calorimetry was used to examine the structure-function relationship of the phospholipids on the L alpha-phase stabilization of phosphatidylethanolamine (PE). Phosphatidylglycerol (PG) was chosen as a model stabilizer. Dielaidoylphosphatidylethanolamine (DEPE) was mixed with various PGs to study the effects of (i) chain length, (ii) chain unsaturation, and (iii) chain number of the stabilizer on the L alpha-phase stabilization. At low concentrations of stabilizer, both bilayer stabilization and destabilization were observed. Phase separations also were seen, as revealed by split peaks of the L beta----L alpha transition; these were particularly prone to occur in the destabilization cases. When saturated PGs were compared, shorter chains (C12:0 and C14:0) promoted bilayer stabilization whereas longer chains (C16:0 and C18:0) promoted bilayer destabilization. Unsaturated PG with larger hydrophobic volumes (C18:2) favored bilayer destabilization, relative to unsaturated PG with smaller hydrophobic volumes (C18:1). Lyso-PG (C14:0) showed higher bilayer stabilization activity than their double-chain counterparts. Thus, at low concentrations of stabilizer, the acyl chain composition plays a vital role in bilayer-phase stabilization. However, at higher concentrations (greater than or equal to 8 mol %), all PGs become active bilayer stabilizers. This is probably because the increased head-group hydration becomes the dominant factor in the stabilization. The effect of acyl chain composition of the stabilizer was also studied by using small unilamellar vesicles composed of dioleoylphosphatidylethanolamine (DOPE). Fluorescence quenching of calcein entrapped in liposomes was used to monitor the stability of the liposomes. Similar acyl chain effects on liposomal stabilization were obtained.(ABSTRACT TRUNCATED AT 250 WORDS)     

Is the alpha rhythm a control parameter for brain responses?

 The main goal of the present study is to develop a conceptual analysis of alpha response in the brain based on single sweep evaluation. A new method was employed to estimate a set of single-sweep parameters and quantify the oscillatory behaviour of single, electroencephalograph (EEG) sweeps. It was aimed to demonstrate that brain alpha responses are governed by spontaneous alpha activity and to validate the principle of brain response excitability. Because the spontaneous alpha activity depends on both the topology of recording and the subject’s age, topology and age models were used. Spontaneous and evoked alpha activity were recorded at frontal and occipital sites in three groups of subjects: 3-year-old children, young adults and middle-aged subjects. Amplitude, enhancement and phase-locking of single alpha responses to visual stimuli were analysed. Major results showed that: (1) visual alpha responses could be recorded only if the alpha rhythm was developed in the spontaneous EEG independent of electrode location; (2) middle-aged adults showed more expressed frontal spontaneous alpha activity in comparison with young adults; (3) accordingly, alpha responses with higher amplitude and stronger phase-locking were produced over the frontal brain area in middleaged than young adults. These results validate the principle of brain response excitability and demonstrate that a shift towards frontal brain areas for both the spontaneous and evoked alpha activity occurs with increasing age in adults. The results are discussed in the context of the diffuse and distributed alpha system of the brain. Age-dependent changes in frontal alpha activity are suggested to be related to frontal brain functioning during aging. Received: 6 November 1995 / Accepted in revised form: 13 March 1997     

The relationship between the growth retardative effect of CCC and ethylene production

The ethylene production of the hypocotyls of CCC-treated bean plants was studied, and it was concluded that the treatment induced changes in the quantity of ethylene produced by the apical and basal hypocotyl parts. The ethylene production of the basal hypocotyl parts showed considerable increase on the effect of the treatment, in comparison with the control. The obtained results suggest a possible relationship between the longitudinal-growth inhibiting, stem-thickness inducing, root-formation stimulating effects of CCC and the effect exerted on ethylene production.     

The morphological and anatomical properties of Lamium lycium (Lamiaceae), endemic to Turkey

In this study, the morphological and anatomical features of Lamium lycium Boiss. (Lamiaceae) are described in detail. L. lycium has a perennial tap-root, and the stem is ascending and clearly quadrangular. The leaves are simple and broadly ovate to narrowly ovate in shape. The inflorescense is a verticillate cyme. The corolla is purple and the upper lip is hooded. For anatomy, the cross-sections of root, stem, leaf, petiole, calyx, corolla and generative organs were examined and the anatomical features of the taxon are discussed. The morphological features were in most respects congruent with previous reports. However, the anatomy of L. lycium has not been studied before and the results are here compared with trose of previous studies on other members of Lamiaceae. Furthermore, glandular trichomes are illustrated. The results are presented with photographs and tables.     

DEVELOPMENT OF GENETICALLY ENCODED FLUORESCENT PROTEIN CONSTRUCTS OF HYPERTHERMOPHILIC MALTOSE-BINDING PROTEIN

Circularly permuted green fluorescent protein (cGFP) was inserted into the hyperthermophilic maltose binding protein at two different locations. cGFP was inserted between amino acid residues 206 and 207, or fused to the N-terminal of maltose binding protein from Thermotoga maritima. The cloned DNA constructs were expressed in Escherichia coli cells, and purified by metal chelate affinity chromatography. Conformational change upon ligand binding was monitored by the increase in fluorescence intensity. Both of the fusion proteins developed significant fluorescence change at 0.5 mM maltose concentration, whereas their maltose binding affinities and optimum incubation times were different. Fluorescent biosensors based on mesophilic maltose binding proteins have been described in the literature, but there is a growing interest in biosensors based on thermostable proteins. Therefore, the developed protein constructs could be models for thermophilic protein-based fluorescent biosensors.     

Effect of Time on Endothelium-Dependent Relaxations in Mice and Rat Thoracic Aortas

Temporal variations in the endothelium-dependent relaxant effects of acetylcholine (ACh) in mice and histamine (HA) in rat thoracic aorta have been studied. The relaxations induced by higher concentrations of ACh and HA were significantly dependent on the time the tissues were obtained. However, neither EC 50 (the concentration inducing half of the maximum response) values for ACh and HA, nor K B (antagonist dissociation constant) values for atropine and diphenhydramine were found to be statistically significant depending upon the time of obtaining aorta preparations. These results show that the in vitro responsiveness of mice and rat thoracic aortas to endothelium-dependent relaxant effects of ACh and HA, respectively, changes over a 24-h period. These variations might be dependent on a temporal rhythm in post-receptor events, i.e., guanylate cyclase-cGMP-phosphodiesterase system which mediates responses to endothelium-derived relaxing factor(s).