Membrane composition modulates thiopental partitioning in bilayers and biomembranes.

The nonspecific interaction of thiopental with erythrocyte ghosts, synaptic membranes, microsomes and mitochondria has been measured at 25 degrees C and pH 6.6. In cholesterol-depleted erythrocyte ghosts the partition coefficient decreases with increasing cholesterol content. In sonicated liposomes made from egg lecithin and cholesterol the partition coefficient also decreases with increasing cholesterol content. The dependence of the partition coefficient on cholesterol content in the biological membranes, on average, parallels that in the lipid bilayers. The partition coefficient in lipid bilayers made from lipids extracted from erythrocyte ghosts was comparable to that in the corresponding egg lecithin/cholesterol bilayer. The partition coefficients of all the biomembranes are consistently lower than those in the corresponding egg lecithin/cholesterol bilayer, the free energy of transfer between biomembrane and corresponding bilayer being -1 kcal/mol.

Age-related synaptic changes in the central nucleus of the inferior colliculus of Fischer-344 rats.

The central nucleus of the inferior colliculus (ICc) is a major processing center for the ascending auditory pathways. Gamma-aminobutyric acid (GABA) and excitant amino acids (EAAs) are essential for coding many auditory tasks in the IC. Recently, a number of neurochemical and immunocytochemical studies have suggested an age-related decline in GABAergic inhibition in the ICc, and possibly excitant-amino-acid-mediated excitation as well. The objective of this study was to compare quantitatively changes in the synaptic organization of the ICc among three age groups (3, 19, and 28 months) of Fischer-344 rats. Immunogold electron microscopic methods were used to determine if there were age-related changes in the density, distribution, or morphology of GABA-immunoreactive (+) and GABA-immunonegative (-) synapses in the ICc. The data suggest similar losses of excitatory and inhibitory synapses in the ICc. There were significant reductions in the densities of GABA+ and GABA- synaptic terminals (approximately 30% and approximately 24%, respectively) and synapses (approximately 33% and approximately 26%, respectively) in the ICc of 28-month-old rats relative to 3-month-olds. The numeric values, which were adjusted to consider changes in volume of the IC with age, depict similar effects, although the effect magnitude for the adjusted values was reduced by approximately 9%. For both types of synapses, the decreases did not differ significantly from each other. The reductions in synaptic numbers appeared, to be related to a similar numeric decline in dendrites, in particular those with calibers of between 0.5 and 1.5 microm. The number and distribution of synaptic terminals on the remaining dendrites of GABA- neurons appeared not to undergo major age-related changes. GABA+ neurons, on the other hand, may have evolved patterns of synaptic and dendritic change during aging in which the distribution of synaptic terminals shifts to dendrites of larger caliber. In the 19-month group, the synaptic areas were elevated in terminals apposed to dendrites with calibers of 1.5 microm or less. However, this increase in synaptic size did not persist in the aged animals. No neuronal losses were detectable among the three age groups. Thus, the decrease in GABA and EAAs identified in the IC by previous studies may be attributable to synaptic and dendritic declines, rather than cell loss.

Telemedicine: a useful and necessary tool to improving quality of healthcare in the European Union.

Telemedicine is seen as a useful and potentially powerful tool: its use can improve the quality of healthcare while facing the challenge of reducing the costs. Telemedicine might evolve as a cost-effective alternative to the current forms of healthcare delivery. It can offer not only better access to--but also improved quality of--healthcare. Telemedicine can add considerable value for both, the healthcare professional and the patient. The paper sheds light on the infrastructural and financial aspects until the year 2000. The need for a strategy on European level is highlighted in order to facilitate the introduction of telemedicine on a European wide scale.

Microelectrophoretic application of antagonists of putative neurotransmitters onto various types of bulbar respiratory neurons.

Seven antagonists of putative neurotransmitters were applied to bulbar respiratory neurons and, for comparison, also to unspecific cells. The antagonists exerted distinct effects when released alone, permitting to draw conclusions about receptor properties of the various cell types. With strychnine, specific antagonist of glycine, excitation prevailed in EI, I and E neurons. With bicuculline, specific antagonist of GABA, excitation preponderated in EI and E cells. About half of the unspecific neurons were activated and the remainder were unresponsive. GDEE (glutamatediethylester), antagonist of glutamate, excited part of the IE neurons and inhibited part of the E units, while the remainder of both types as well as 2 EI cells tested were not affected. With flupentixol, antagonist of dopamine, excitation prevailed in I neurons. About half of the IE and E units remained unaffected, while in the remainder E cells inhibition preponderated over excitation. With yohimbine, an alpha-adrenoceptor blocker, inhibition prevailed in E units. The two EI as well as the majority of the I neurons remained unaffected, with two cells of the latter type being activated. Propranolol, a beta-adrenoceptor blocker, inhibited about half of the E neurons, while the remainder as well as most IE and the 2 EI cells tested were not affected. Cyproheptadine, an antagonist of 5-HT, excited most E neurons. As concerns NE-receptors, those of the alpha-type might be involved in activation of part of the E cells only, whereas all other NE effects (inhibition or activation) are mediated by CNS-specific receptors different from the alpha- and beta-type. 5-HT effects apparently are mediated by two different receptor types.

Microelectrophoretic application of putative neurotransmitters onto various types of bulbar respiratory neurons.

Six putative neurotransmitters and the beta-receptor excitant isoproterenol were applied to bulbar respiratory neurons classified according to their burst discharge in the respiratory cycle and, for comparison, also to "unspecific" cells. With glycine inhibition occurred in I and prevailed in unspecific neurons. With GABA inhibition preponderated in I and E neurons. Glutamate excited E neurons. With dopamine inhibition prevailed in I and unspecific neurons. The majority of E neurons remained unaffected. With NE excitation occurred in EI and preponderated in I, IE, E and unspecific neurons, while some IE and E neurons were inhibited. The effects of isoproterenol did not allow any clear statement about receptor properties. In I units, however, activation was more frequent than inhibition. With 5-HT excitation prevailed in IE neurons. About half of the I cells remained unaffected and in the remainder inhibition preponderated over activation. This suggests the existence of two 5-HT-specific receptors in I and IE neurons. Comparison of the single effects revealed differences in the receptor properties of the various cell types. Results suggest that some cell types possess dopaminergic receptors and that these differ from NE-receptors, which have been found in all cell types. NE-receptor stimulation apparently can result in neuronal activation or inhibition.

Suppression of scientific research: bahramdipity and nulltiple scientific discoveries.

The fairy tale The Three Princes of Serendip can be taken to be allegorical of not only chance discovery (serendipity) but of other aspects of scientific discovery as well. Just as Horace Walpole coined serendipity, so can the term bahramdipity be derived from the tale and defined as the cruel suppression of a serendipitous discovery. Suppressed, unpublished discoveries are designated nulltiples. Several examples are presented to make the case that bahramdipity is an existent aspect of scientific discovery. Other examples of non-ideal scientific research and discovery are provided in order to contrast and clarify the meaning and use of bahramdipity. Additional allegories of scientific discovery are taken from the tale and a hope for the strengthening of scientific integrity is expressed.

Projections of color coding retinal neurons in urodele amphibians.

Optic fiber projection in the brain of Salamandra salamandra was investigated by degeneration techniques. Terminal fields are described in the thalamus and in the optic tectum. Microelectrode recordings were performed from ganglion cells in the retina and from their terminals in the thalamus and tectum in Salamandra and Triturus alpestris. 'On' cells showed maximal sensitivity either in the blue or in the yellow spectral region; they project to the thalamus. Color coding 'on-off' cells project to the tectum opticum. In Triturus a seasonal change in these neurons occurs. Probably due to transition of vitamin A2 into vitamin A1 the spectral sensitivity is different. In springtime blue-red opponent-color neurons were recorded, in fall however, blue-yellow neurons were found.