In vivo mapping of drug-induced seizures with voltage-sensitive dye.

The voltage-sensitive dye diO-C2-5 was used to produce an in vivo map of the membrane potential in two types of seizures. Mild limbic seizures were induced in rats with kainic acid; clonic convulsive seizures were induced with bicuculline. Kainic acid animals showed various levels of neural depolarization during their seizures in limbic, thalamic, cortical, and brainstem sites. The bicuculline animals showed uniformly greater levels of neural depolarization during their seizures. The magnitude of these changes relative to controls varied across seizure models and reflected the different underlying neural mechanisms for each model. The ability of the technique to capture local electrical events provides a new tool in which to explore brain activity.

Seizure circuit analysis with voltage sensitive dye.

Voltage sensitive dye was used to produce a map of average membrane polarization for the purpose of analysing the circuitry involved in seizures. Dorsal hippocampus, ventral hippocampus, entorhinal cortex, substantia nigra and occipital cortex were selected to calculate the relative changes in polarization. Rats were induced with bicuculline to have convulsive seizures and mild limbic seizures with kainic acid. A 20 second sample of these seizures were recorded using the voltage sensitive dye. Control animals showed a relatively uniform polarization state in the five brain areas. The bicuculline seizure produced hyperpolarization in all five areas. The magnitude of the hyperpolarization varied among the regions to produce a distinctive pattern. The kainic acid seizure produced depolarization in the four limbic areas. The magnitude of the depolarization also varied, producing a different pattern compared with bicuculline or control. Future applications of this technique in animal models could help identify those areas in the brain which regulate seizure propagation, and the anatomical loci in which antiepileptic drugs interfere with this propagation. Ultimately, human applications would include linking voltage sensitive dyes with paramagnetic or positron emitting traces so that epileptic processes could be visualized using magnetic resonance imaging or positron emission computed tomography.

B cell dependent T lymphocyte responses in leishmaniasis.

The activation of B cell dependent T cells during Leishmania infection cannot be considered a trivial event, because their removal profoundly alters the course and outcome of infection within genetically susceptible and resistant mouse strains. The demonstration that idiotype recognizing T cells also appear within human populations sensitized to leishmanial antigens as a result of asymptomatic or subclinical infections supports a role for these cells in immunity. These cells are not demonstrable in patients with active visceral disease, so that their role in promoting specific unresponsiveness has not been extended to humans. Whether B cell dependent, idiotype specific T cells represent a functionally distinct T lymphocyte subset with unique regulatory activities remains to be determined.

Renal and related retroperitoneal abscesses: percutaneous drainage.

Renal and related retroperitoneal abscesses cause significant morbidity and mortality and almost always require drainage. The authors report 18 cases of percutaneous drainage of renal and related retroperitoneal abscesses, all of which were successfully managed. In 11 of these cases (61%), percutaneous drainage constituted the only treatment required. In the remaining seven (39%), the patients' clinical status improved after percutaneous drainage, and they were able to undergo subsequent elective nephrectomy with fewer complications. These results are comparable to those achieved with percutaneous abdominal abscess drainage and justify the use of percutaneous drainage for renal and related retroperitoneal abscesses as the therapeutic procedure of choice.