Evidence for multiple open and inactivated states of the hKv1.5 delayed rectifier

We previously found in human blood a fraction of low-density lipoprotein (LDL) that is characterized by a reduced content of sialic acid. Desialylated LDL also has a low neutral carbohydrate level, decreased content of major lipids, small size, high density, increased electronegative charge and altered tertiary apolipoprotein B structure. Unlike native LDL, this fraction of desialylated (multiple-modified) LDL induces the accumulation of lipids in smooth muscle cells cultured from unaffected human aortic intima, i.e. it exhibits atherogenic properties. In this study, we attempted to elucidate the mechanism of desialylation and other changes in the multiple-modified LDL by investigating the possibility of LDL modification by different cells and the blood plasma. A 24-h incubation at 37 degrees C of lipoprotein with intact endotheliocytes, hepatocytes, macrophages and smooth muscle cells or cell homogenates did not cause alterations either in the physical properties or in the chemical composition of native LDL. On the other hand, a significant fall in the lipoprotein sialic acid level was observed already after a 1-h incubation of native LDL with an autologous plasma-derived serum. While LDL sialic acid level continuously decreased, LDL became capable of inducing the accumulation of total cholesterol in the smooth muscle cells cultured from unaffected human aortic intima after 3 h of incubation. Starting from the sixth hour of LDL incubation with serum, a steady decrease in the lipoprotein lipid content was observed as well as the related reduction of LDL size. Following 36 h of incubation, an increase in the negative charge of lipoprotein particles was also seen. Prolonged incubation of LDL with plasma-derived serum (48 and 72 h) leads to the loss of alpha-tocopherol by the LDL as well as to an increase in LDL susceptibility to copper oxidation and to accumulation of cholesterol covalently bound to apolipoprotein B, a marker of lipoperoxidation. Degradation of apolipoprotein B starts within the same period of time. Hence, desialylation of LDL particles represents one of the first or the primary act of modification which is, apparently, a sufficient prerequisite for the development of atherogenic properties. Subsequent modifications just enhance the atherogenic potential of LDL. The loss of sialic acid by LDL occurred at neutral pH and was not inhibited by the sialidase inhibitor 2,3-dehydro-2-deoxy-N-acetylneuraminic acid. The [3H]sialic acid removed from LDL was not found in free form, but in the plasma fraction precipitated by trichloroacetic acid. These data along with the fact that cytidine-5'-triphosphate inhibited LDL desialylation suggest that enzymes close to sialyltransferases play a role in this process. Thus, this study demonstrated that the LDL modification processes imparting atherogenic properties to this lipoprotein can take place in human blood plasma. Multiple modification of LDL is a cascade of successive changes in the lipoprotein particle: desialylation, loss of lipids, reduction in particle size, increase of its electronegative charge and peroxidation of lipids.     

Evidence that the behaviors in the Mouse Defense Test Battery relate to different emotional states: a factor analytic study

The Mouse Defense Test Battery (MDTB) has been designed to investigate defensive responses of Swiss-Webster mice confronted with a natural threat, a rat. These behaviors include flight, avoidance, defensive threat/attack reactions, and risk assessment activities. In the present study, a factor analysis was used to examine potential relationships between these behavioral responses. Five independent Factors were extracted from the 17 parameters obtained in the MDTB. Both Factor 1 and Factor 2 include cognitive aspects of defensive behaviors that appear to be related to the process of acquiring and analyzing information in the presence of threatful stimuli (i.e., risk assessment). Flight/avoidance responses heavily loaded on Factor 3 and to a lesser extent on Factor 4. Several defensive threat/attack reactions (i.e., upright postures and biting) highly loaded on Factor 4 and biting also loaded on Factor 3. Finally, the variables that loaded highly on Factor 5 were the number of wall rearings and climbings following the removal of the rat and the immobility time when the subject was trapped in a straight alley. Although the meaning of this latter Factor is not clear at present. Factors 1 to 4 seemingly relate to anxiety. Taken together with recent drug findings from the MDTB, the present analysis further supports the idea that this model provides measures that reflect different aspects of anxiety.