Cholesterol and its anionic derivatives inhibit 5-lipoxygenase activation in polymorphonuclear leukocytes and MonoMac6 cells

5-Lipoxygenase (5-LO) is the key enzyme in the biosynthesis of leukotrienes (LTs), biological mediators of host defense reactions and of inflammatory diseases. While the role of membrane binding in the regulation of 5-LO activity is well established, the effects of lipids on cellular activity when added to the medium has not been characterized. Here, we show such a novel function of the most abundant sulfated sterol in human blood, cholesterol sulfate (CS), to suppress LT production in human polymorphonuclear leukocytes (PMNL) and Mono Mac6 cells. We synthesized another anionic lipid, cholesterol phosphate, which demonstrated a similar capacity in suppression of LT synthesis in PMNL. Cholesteryl acetate was without effect. Cholesterol increased the effect of CS on 5-LO product synthesis. CS and cholesterol also inhibited arachidonic acid (AA) release from PMNL. Addition of exogenous AA increased the threshold concentration of CS required to inhibit LT synthesis. The effect of cholesterol and its anionic derivatives can arise from remodeling of the cell membrane, which interferes with 5-LO activation. The fact that cellular LT production is regulated by sulfated cholesterol highlights a possible regulatory role of sulfotransferases/sulfatases in 5-LO product synthesis.     

Afferent inhibition and functional properties of neurons in the vibrissae projection area of the cat somatosensory cortex]

The aim of this study was to investigate the role of inhibitory processes in S-1 cortex of cats. The inhibition was evoked by "natural" afferent stimulation of the fascial vibrissae. For this purpose, two neighboring vibrissae were sequentially stimulated by mechanical deflection; single unit activity was recorded simultaneously from the cortex. Results showed that conditioning by afferent stimulation significantly influenced the directional sensitivity of cortical neurons. These data and analysis of spatial pattern of stimulated vibrissa indicate that detector neurons could be quickly modified during sensory processing.     

Effect of prenatal stress on learning of rats in the Morris test

Prenatal stress was found not to affect learning capability in Morris Water Maze in rats, although some difference was revealed in the rats behaviour. 2-month old rats who had been subjected to a prenatal stress, revealed an obvious trend towards less flexible strategy of behaviour and perseveration. At the age of 4 months, the difference between the control and experimental groups becomes negligible.     

Yeast as a model for studying the prion and amyloid occurrence

Recent data on the use of yeast as a model for studying the molecular basis of prion infection are summarized. In contrast to mammalian prions, which are related to incurable neurodegenerative diseases, yeast prions determine the appearance of non-chromosomally inherited phenotypic traits. Prions of yeast are structurally similar to amyloids of mammals and their replication involves not only growth, but also fragmentation of prion amyloid-like fibrils. In mammals the fragmentation should lead to an increase in infectious titer. The use of yeast for study of the mechanisms of human amyloidoses, development of new anti-prion drugs and search for new proteins with prion properties is described.     

Corona discharge at the tip of a tall object in the electric field of a thundercloud

Characteristics of a positive transient corona discharge near the tip of a tall solitary grounded object in the electric field of a thundercloud are studied analytically and numerically. The time evolution of the discharge current and the space distribution of the total electric field are simulated for different growth rates of the external field and the dimensions and geometry of the stressed electrode. The effect of aerosol ions is shown to be negligible at a short duration of the corona. The developed simplified analytical approach agrees with numerical simulations.     

CFTR is a monomer: biochemical and functional evidence

Although the CFTR protein alone is sufficient to generate a regulated chloride channel, it is unknown how many of the polypeptides form the channel. Using biochemical and functional assays, we demonstrate that the CFTR polypeptide is a monomer. CFTR sediments as a monomer in a linear, continuous sucrose gradient. Cells co-expressing different epitope-tagged CFTR provide no evidence of co-assembly in immunoprecipitation and nickel affinity binding experiments. Co-expressed wild-type and DF508 CFTR are without influence on each other in their ability to progress through the secretory pathway, suggesting they do not associate in the endoplasmic reticulum. No hybrid conducting single channels are seen in planar lipid bilayers with which membrane vesicles from cells co-expressing similar amounts of two different CFTR conduction species have been fused.     

Bovine mammary gland UDP-GalNAc:GlcNAcbeta-R beta1-->4-N- acetylgalactosaminyltransferase is glycoprotein hormone nonspecific and shows interaction with alpha-lactalbumin

We have identified a novel N -acetylgalactosaminyltransferase activity in lactating bovine mammary gland membranes. Acceptor specificity studies and analysis of products obtained in vitro by 400 MHz1H-NMR spectroscopy revealed that the enzyme catalyses the transfer of N - acetylgalactosamine (GalNAc) from UDP-GalNAc to acceptor substrates carrying a terminal, beta-linked N -acetylglucosamine (GlcNAc) residue and establishes a beta1-->4-linkage forming a GalNAcbeta1-->4GlcNAc ( N, N '-diacetyllactosediamine, lacdiNAc) unit. Therefore, the enzyme can be identified as a UDP-GalNAc:GlcNAcbeta-R beta1-->4-N- acetylgalactosaminyltransferase (beta4-GalNAcT). This enzyme resembles invertebrate beta4-GalNAcT as well as mammalian beta4- galactosyltransferase (beta4-GalT) in acceptor specificity. It can, however, be clearly distinguished from the pituitary hormone-specific beta4-GalNAcT by its incapability of acting with an elevated activity on a glycoprotein substrate carrying a hormone-specific peptide motif. Furthermore, the GalNAcT activity appeared not to be due to a promiscuous action of a beta4-GalT as could be demonstrated by comparing the beta4-GalNAcT and beta4-GalT activities of the mammary gland, bovine colostrum, and purified beta4-GalT, by competition studies with UDP-GalNAc and UDP-Gal, and by use of an anti-beta4-GalT polyclonal inhibiting antibody. Interestingly, under conditions where mammalian beta4-GalT forms with alpha-lactalbumin (alpha-LA) the lactose synthase complex, the mammary gland beta4-GalNAcT was similarly induced by alpha-LA to act on Glc with an increased efficiency yielding the lactose analog GalNAcbeta1-->4Glc. This enzyme thus forms the second example of a mammalian glycosyltransferase the specificity of which can be modified by this milk protein. It is proposed that the mammary gland beta4-GalNAcT functions in the synthesis of lacdiNAc- based, complex-type glycans frequently occurring on bovine milk glycoproteins. The action of this enzyme is to be considered when aiming at the production of properly glycosylated protein biopharmaceuticals in the milk of transgenic dairy animals.      

Quaternary structure of alpha-crystallin is necessary for the binding of unfolded proteins: a surface plasmon resonance study

The interactions between an oligomeric heat-shock protein, alpha-crystallin, and its individual subunits with unfolded proteins were monitored by surface plasmon resonance. Immobilization at the sensor chip allowed us for the first time to study isolated alpha-crystallin subunits under physiological conditions. We observe that these subunits, in contrast to alpha-crystallin oligomers, do not bind unfolded protein. Our data indicate that quaternary structure of alpha-crystallin is necessary for its chaperone-like activity.     

A technique for the operant conditioning to differentiate signals during reinforcement delay in primates

A new technique of training the primates to differentiate signals immediately during execution of the instrumental act (pushing the lever) was proposed. The technique makes it possible to study the processes of decision making during activation of the executive (motor) brain systems.