Pathological gamma oscillations, impaired dopamine release, synapse loss and reduced dynamic range of unitary glutamatergic synaptic transmission in the striatum of hypokinetic Q175 Huntington mice.

Huntington's disease (HD) is a severe genetically inherited neurodegenerative disorder. Patients present with three principal phenotypes of motor symptoms: choreatic, hypokinetic-rigid and mixed. The Q175 mouse model of disease offers an opportunity to investigate the cellular basis of the hypokinetic-rigid form of HD. At the age of 1 year homozygote Q175 mice exhibited the following signs of hypokinesia: Reduced frequency of spontaneous movements on a precision balance at daytime (-55%), increased total time spent without movement in an open field (+42%), failures in the execution of unconditioned avoidance reactions (+32%), reduced ability for conditioned avoidance (-96%) and increased reaction times (+65%) in a shuttle box. Local field potential recordings revealed low-frequency gamma oscillations in the striatum as a characteristic feature of HD mice at rest. There was no significant loss of DARPP-32 immunolabeled striatal projection neurons (SPNs) although the level of DARPP-32 immunoreactivity was lower in HD. As a potential cause of hypokinesia, HD mice revealed a strong reduction in striatal KCl-induced dopamine release, accompanied by a decrease in the number of tyrosine hydroxylase-(TH)- and VMAT2-positive synaptic varicosities. The presynaptic TH fluorescence level was also reduced. Patch-clamp experiments were performed in slices from 1-year-old mice to record unitary EPSCs (uEPSCs) of presumed cortical origin in the absence of G-protein-mediated modulation. In HD mice, the maximal amplitudes of uEPSCs amounted to 69% of the WT level which matches the loss of VGluT1+/SYP+ synaptic terminals in immunostained sections. These results identify impairment of cortico-striatal synaptic transmission and dopamine release as a potential basis of hypokinesia in HD.

Electrically silent neurons in the substantia gelatinosa of the rat spinal cord.

Substantia gelatinosa (SG) neurons are usually categorized on three main types: tonic, adapting and delayed firing (DFNs), based on characteristic firing response evoked by sustained stimulation. Here, the existence of electrically silent neurons (ESNs, 9.3%) is reported by using patch-clamp recording and confocal microscopy in spinal cord slices from 3-5 weeks-old rats. Those neurons does not generate spikes at their resting membrane potential (approximately -69 mV) but only at preliminary depolarization to > -60 mV In the latter case, spikes appeared starting from the end of stimulation, which is characteristic feature of DFNs. With the exception of APs block, all other passive and active electrophysiological properties of ESNs and DFNs were similar. Their main morphological properties (vertical orientation of dendritic tree and axonal trajectory) were close too. A distinctive feature of ESNs was larger amplitude of outward A-type K+ current (K(A)). The results suggest that the latter might cause a block of APs in ESNs, while these cells likely are a functional (i.e., non-firing) subtype of DFNs. The role of DFNs in descending control of pain transmission via modulation of its K(A) is hypothesized.

[Morphophysiologic properties of delayed firing neurons in substantia gelatinosa of the rat spinal cord.

Substantia gelatinosa (SG) neurons of the spinal cord are highly heterogeneous in their morphologic and physiologic properties. Based on characteristic firing response evoked by sustained depolarization, neurons can be categorized on three main types: tonic, adapting and delayed firing (DFNs). Here, properties of DFNs in spinal cord slices from 3-5 weeks-old rats were studied with the use of patch-clamp recording and confocal microscopy. Distinctive features of DFNs were increased rheobase (95.7 +/- 11.2 pA) and depolarized threshold to evoke action potential (-37.8 +/- 0.7 mV) than in neurons of other types. In voltage-clamp mode all DFNs expressed high amplitude outward A-type potassium current (K(A)), which started activation at approximately -70 mV, before Na+ current. Structurally, the majority of DFNs had vertically oriented dendritic tree, while their axons were not restricted to SG and projected predominantly to lamina I. Possible physiological functions of DFNs are discussed.

Time evolution of Lyman-alpha fine-structure components for Al XIII.

We present a comparison of measured and theoretically modeled Lyman-alpha intensity ratios of hydrogenlike Al XIII impurity ions in a deuterium base plasma in the COMPASS-D tokamak. The time evolution of the intensity ratios is computed from a collisional-radiative model using measured plasma parameters and compared with line-of-sight integral values measured using a high-resolution crystal spectrometer. The variations in the modeled values follow the experimental data in the case of the L-mode plasma, taking into account variations in the electron parameters during the discharges. Apparent discrepancies between the observed and calculated ratios in the case of the H-mode plasma are attributed to line blending due to satellites of nearby Fe emission.

Postsynaptic mechanism may contribute to inhibitory acetylcholine effect on GABAergic synaptic transmission in hippocampal cell cultures.

The effect of acetylcholine (ACh) on evoked GABAergic inhibitory postsynaptic currents (IPSCs) was studied in cell cultures of dissociated hippocampal neurons with established synaptic connections. Spontaneous IPSCs and IPSCs evoked by extracellular stimulation of a single presynaptic neuron were recorded. ACh inhibited the evoked IPSCs in most of the connections, although facilitation was also observed. Regardless of inhibitory or facilitatory effects on the evoked IPSCs, an enhanced spontaneous synaptic input to the postsynaptic neurons was usually observed. ACh-induced changes in the evoked IPSCs were usually accompanied by changes in paired pulse depression (PPD), which are thought to reflect presynaptic mechanisms of modulation. However, the time course of PPD changes did not always match that of the IPSC changes, suggesting a contribution of other, possibly postsynaptic, mechanism(s). To analyze this possibility, effects of ACh on responses to direct application of exogenous GABA were studied. In a proportion of the neurons (40%) ACh reversibly decreased GABA responses, indicating that postsynaptic mechanisms may also contribute to the inhibitory ACh effect on GABAergic transmission. We conclude that several different modulatory mechanisms of ACh action participate in the regulation of GABAergic transmission at the level of synaptic connection of a single GABAergic neuron.

Rat hippocampal neurons maintain their own GABAergic synaptic transmission in culture.

The whole-cell patch-clamp technique was used to record monosynaptic inhibitory postsynaptic currents (IPSCs) from pairs of hippocampal neurons cultured for 2-3 weeks. The application of fresh physiological solution for 2-3 min reversibly reduced the amplitude of evoked GABAergic IPSCs to 72.5% of control value. The amplitude and frequency of spontaneous IPSCs decreased too. The depression of evoked IPSCs was significantly smaller or absent if conditioned solution was applied (physiological solution which had been previously in contact with neurons for 30 min). Currents evoked by exogenously applied GABA were unaffected by fresh solution. These results suggest that hippocampal neurons release some endogenous substance(s), by which they up regulate presynaptically their own inhibitory synaptic transmission.

In vitro development of vertebrate central synapses.

This article deals with basic determinants of synaptic efficacy during development of glutamatergic and GABAergic synaptic transmission: location and number of release sites, release probability and single cell-activated (unitary) conductances. We hypothesize that both types of neuronal connections differ in major aspects of synaptogenesis. Disregarding the fact that various test models and cell types could render diverging results, it can be observed that glutamatergic terminals display a preference for dendrites, whereas GABAergic terminals select soma locations at initial stages of development. Glutamatergic synapses are characterised by receptor accumulation in the region of terminal apposition, whereas in GABAergic synapses receptor concentration is weak, if present at all. The expression of glutamate receptors (GluRs), but not GABAA receptors is under control of interneurons. Developmental changes in glutamatergic synaptic transmission have not yet been assessed by quantal analysis. For GABAergic synapses, first results are now available from a culture preparation of the rat superior colliculus. In general terms, functional maturation seemed to lag behind the formation of structurally differentiated release sites. Compound binomial analysis revealed that during in vitro development a considerable fraction of GABAergic terminals remained in a low efficacy release state (p < 0.2). A developmental increase in synaptic strength was reached by the appearance of singular highly effective release sites. Presynaptic maturation could be manipulated by long-term drug treatment. Addition of GluR antagonists significantly increased amplitudes and decreased the coefficients of variations of evoked inhibitory postsynaptic currents. Thus, the strength of inhibitory synaptic transmission could be influenced by the status of heteronymous synaptic input.

Development of spontaneous synaptic activity in culture of the chick spinal cord neurons.

Spontaneous postsynaptic currents in chick spinal cord neurons cultured for up to three weeks were recorded by using standard whole-cell patch-clamp techniques. Beginning with approximately the 7th to 14th day in vitro, giant postsynaptic currents, mediated presumably by glycine, were single synaptic events (inhibitory postsynaptic currents). After the 14th day in vitro excitatory postsynaptic currents appeared. Both types of currents were predominantly arranged in bursts. This pattern of synaptic activity did not change appreciably during further cultivation. Characteristics of inhibitory postsynaptic currents were studied. Decay of the majority of giant inhibitory postsynaptic currents was two-exponential. Time-constants of the decay (fast and slow) increased with depolarization and decreased with increasing temperature. Decay of miniature inhibitory postsynaptic currents was single exponential and did not depend on the membrane potential. Strychnine at concentrations of 1-2 microM was found not only to reduce the amplitude of giant inhibitory postsynaptic currents but also to prolong their decay. The time-constant of the slow component of the decay was mostly affected during the inhibitor action. Repeated binding of glycine to postsynaptic receptors due to a large presynaptic release is proposed as an explanation for the properties of giant inhibitory postsynaptic currents decay. Correlations between the development of synaptic networks under in vivo and in vitro conditions are discussed.

Glycine conductance changes in chick spinal cord neurons developing in culture.

Whole-cell glycine-activated currents were investigated in chick spinal cord neurons cultivated for up to three weeks. Based on the morphological and electrophysiological characteristics of neurons, two different types of nerve cells were distinguished during the first few days in culture. The first type consisted of "mature" nerve cells which appear to be motoneurons. They died by five to seven days in vitro. Immature neurons or neuroblasts constituted another type of nerve cell. They developed in culture and became differentiated neurons. Glycine-activated currents were elicited in both types of neurons during different periods in vitro. Sensitivity to glycine of "mature" neurons decreased from two to five days in vitro: ED50 for agonist action increased from 0.4 to 1.3 mM. The sensitivity of neuroblasts to this transmitter increased during differentiation: ED50 decreased from 1.4 to 0.12 mM on three to 14 days in vitro, respectively. Changes in glycine-activated conductance of these developing neurons were investigated later on. The conductance in differentiated neurons was markedly sensitive to membrane potential, while neuroblasts did not show such dependence. Voltage sensitivity was due to voltage-dependent kinetics of the ion channel. Desensitization kinetics of the glycine-activated currents were double-exponential. The time constant for the slow desensitizing component was dependent on glycine concentration, which was not the case for the fast component. The increase in glycine sensitivity of the neuroblasts was accompanied by deceleration of desensitization kinetics of the agonist-activated currents. A remarkable feature of the currents elicited in neuroblasts was their extremely long time course after rapid agonist removal from the cells. The properties of these long-term currents suggest that a large fraction of the receptors are desensitized, even during quite short applications of the transmitter. The presence of glycine in the culture medium did not affect the increase of neuronal sensitivity to the agonist. The block of spontaneous bioelectric activity by adding tetrodotoxin to the culture medium abolished developmental changes in glycine-activated conductance. Possible mechanisms for the changes in transmitter sensitivity of the neurons are considered.

The computer and your practice.

A sophisticated computer system allows a urology practice to run more efficiently and provides better control. All problems were not solved with the installation of such a system, and we developed a few problems that did not exist before computerization. However, this system has allowed our practice to grow with fewer additions to the office staff than would have been possible previously, and it has been our experience that the benefits far outweigh the problems.

Vesical exstrophy with epispadias. Twenty-year follow-up.

A case we believe to be the longest with successful anatomic closure of exstrophy and epispadias witholt reflux or incontinence is reported. The persistence of the squamous metaplasia in the bladder despite twenty years of "turn-in" is noteworthy. The original method of closure reveals no "secret" to account for the success. The method of repair of traumatic rupture is presented.

Delayed transection of urethra by mersilene tape.

This report is of a patient with complete urethral transection after undergoing a mersilene sling urethral suspension. This unusual complication eventually presented as anterior urethral pseudodiverticulum containing the mersilene tape with a secondary calculus.