Infantile type of Niemann-Pick disease with developmental defects of the central nervous system

Clinical and morphologic manifestations of a rare disease developing, as a rule, in early life--an infantile variant of Niemann-Pick disease--are illustrated with a fatal case of a 6.5-month-old child. The diagnosis was established histochemically using, in particular, Smith-Dietrich method which provided differential diagnosis with cerebroside lipidosis (Gaucher's disease). In addition to typical enlargement of the liver, spleen and lymph nodes, cerebral and adrenal affection there appeared true porencephalia.     

Behavioral effects of stimulating positive reward sites in the central tegmentum of rhesus monkeys.

Rhesus monkeys with electrodes chronically implanted in reward sites in central tegmentum were given telemetered brain stimulation while they were free ranging alone or with cagemates. Stimulation seemed to induce a relaxed positive affect as measured by increased huddling, increased lipsmacking, reduced muscle tone, increased solicitation of grooming and increased grooming of other monkeys. Stimulation did not increase dominant/submissive interactions and seemed to have no effect on aggression or fear. These results are very different from those obtained from an anterolateral hypothalamic self-stimulation site and indicate that fibers which provide input from this area to anterolateral hypothalamus are not solely responsible for effects obtained in the anterolateral hypothalamic area.     

Single-tube mixed agglutination test for the detection of staphylococcal protein A.

A simple, rapid mixed agglutination test using sheep erythrocytes (SRBC) sensitized with rabbit hemolysin and intact viable staphylococci is described for the detection of bound staphylococcal protein A. Soluble protein A was heat extracted from 50 clinical isolates as well as the Cowan I and Wood 46 strains of Staphylococcus aureus and titered by a hemagglutination test using sensitized SRBC and dilutions of soluble protein A. Protein A could be detected in all of these supernatants including that of S. aureus Wood 46, a strain generally considered to be protein A negative. These organisms were later retested by the mixed agglutination test and even those staphylococcal isolates expressing very low heat-extractable soluble protein A concentrations (1:2 titers) were positive, confirming the sensitivity of the test. In a screen of clinical isolates, only 4 of 235 (1.8%) coagulase-positive isolates were negative in the mixed agglutination test. Of 25 coagulase-negative isolates, none yielded a positive reaction.     

Self-sustained rhythmic activity in the thalamic reticular nucleus mediated by depolarizing GABAA receptor potentials

Intracellular recordings from reticular thalamic (RE) neurons in vivo revealed inhibitory postsynaptic potentials (IPSPs) between RE cells that reversed and became depolarizing at the hyperpolarized membrane potentials that occur during sleep. These excitatory IPSPs can directly trigger low-threshold spikes (LTSs). The oscillatory mechanisms underlying IPSP-triggered LTSs crowned by spike bursts were investigated in models of isolated RE networks. In a one-dimensional network model, external stimulation evoked waves of excitation propagating at a constant velocity of 25-150 cells per second. In a large-scale, two-dimensional model of the reticular nucleus, the network showed transient or self-sustained oscillations controlled by the maximum conductance of the low-threshold calcium current and the membrane potential. This model predicts that the isolated reticular nucleus could initiate sequences of spindle oscillations in thalamocortical networks in vivo.     

Magnetic Collapse in Fe3Se4 under High Pressure

Electronic structure and magnetic properties of Fe3Se4 are calculated using the density functional approach. Due to the metallic properties, magnetic moments of the iron atoms in two nonequivalent positions in the unit cell are different from ionic values for Fe3+ and Fe2+ and are equal to M1=2.071μB and M2=−2.042μB, making the system ferrimagnetic. The total magnetic moment for the unit cell is 2.135μB. Under isotropic compression, the total magnetic moment decreases non-monotonically and correlates with the non-monotonic dependence of the density of states at the Fermi level N(EF). For 7% compression, the magnetic order changes from the ferrimagnetic to the ferromagnetic. At 14% compression, the magnetic order disappears and the total magnetic moment becomes zero, leaving the system in a paramagnetic state. This compression corresponds to the pressure of 114 GPa. The magnetic ordering changes faster upon application of an isotropic external pressure due to the sizeable anisotropy of the chemical bondings in Fe3Se4. The ferrimagnetic and paramagnetic states occur under pressures of 5.0 and 8.0 GPa, respectively. The system remains in the metallic state for all values of compression.     

Influence of Imaging on the Negative Appendectomy Rate in Pregnancy

Appendectomy is the most common non-gynecologic surgery performed during pregnancy. Little data exist on the accuracy of imaging studies in the diagnosis of appendicitis in pregnancy. The objective of this study was to evaluate the probability of ultrasound and computed tomography (CT) scan in diagnosing appendicitis in pregnancy, as reflected in the negative appendectomy rate. We retrospectively reviewed the charts of 86 pregnant women who underwent an appendectomy between January 1, 1997 and January 1, 2006. Patients were divided into three groups: clinical evaluation, ultrasound, and ultrasound followed by a CT scan. The clinical evaluation group had 13 patients, with a negative appendectomy rate of 54% (7/13). Fifty-five patients underwent an ultrasound alone, with a negative appendectomy rate 36% (20/55). In the ultrasound/CT group (n = 13), the negative appendectomy rate was 8% (1/13). There was a significant reduction in the negative appendectomy rate in the ultrasound/CT scan group compared to clinical evaluation group (54 vs 8%, p < 0.05). This reduction was not achieved in the ultrasound group when compared to the clinical evaluation group or the ultrasound/CT group (p = 0.05). A significant reduction was achieved when the ultrasound/CT group was compared to the patients in the ultrasound only group who had a normal or inconclusive ultrasound (p < 0.05). Our data documents a very high negative appendectomy rate in the pregnant patient. We recommend an ultrasound followed by a CT scan in patients with a normal or inconclusive ultrasound.     

Homeostatic synaptic plasticity can explain post-traumatic epileptogenesis in chronically isolated neocortex

Chronically isolated neocortex develops chronic hyperexcitability and focal epileptogenesis in a period of days to weeks. The mechanisms operating in this model of post-traumatic epileptogenesis are not well understood. We hypothesized that the spontaneous burst discharges recorded in chronically isolated neocortex result from homeostatic plasticity (a mechanism generally assumed to stabilize neuronal activity) induced by low neuronal activity after deafferentation. To test this hypothesis we constructed computer models of neocortex incorporating a biologically based homeostatic plasticity rule that operates to maintain firing rates. After deafferentation, homeostatic upregulation of excitatory synapses on pyramidal cells, either with or without concurrent downregulation of inhibitory synapses or upregulation of intrinsic excitability, initiated slowly repeating burst discharges that closely resembled the epileptiform burst discharges recorded in chronically isolated neocortex. These burst discharges lasted a few hundred ms, propagated at 1-3 cm/s and consisted of large (10-15 mV) intracellular depolarizations topped by a small number of action potentials. Our results support a role for homeostatic synaptic plasticity as a novel mechanism of post-traumatic epileptogenesis.