Motor and non-motor sequence learning in children and adolescents with cerebellar damage.

Cerebellar involvement in motor and non-motor sequence learning was examined with serial reaction time tasks (SRT). Our sample consisted of 8 children and adolescents who had undergone surgical removal of a benign posterior fossa tumor (PFT) during childhood. None of them had undergone chemotherapy or cranial radiation therapy (CRT). Ages ranged from 1-11 years at surgery and 9-17 years at testing. The children were tested not earlier than 2.5 years after surgery (M = 5.9 years), enabling brain plasticity and recovery of functions. Their performance was compared with a matched control sample. The PFT group was not impaired in the implicit learning of sequences, as reflected in their performance in blocks with a repeated sequence, both before and after a random block. However, in the perceptual task, their performance deteriorated more than that of the control group when a random block was introduced, suggesting that it was more difficult for the patients to respond flexibly or change their response set when encountering changing task demands. These results are in line with another study by our group on task switching with the same patients.     

Detection of proteinous toxins using the Bio-Threat Alert system, part 3: effects of heat pretreatment and interfering substances

We previously reported that the Guardian Bio-Threat Alert (BTA) system could detect (detection limit: about 0.1 μg/ml) staphylococcal enterotoxin B (SEB), botulinum toxins (BTX) A and B, and ricin, with no interference by white-powdered materials or colored matrices. In this study, the capability of the BTA system was further assessed. With 10 min of preheating at 60°C, all toxins could be detected, but with preheating at 80°C, BTX A and B and ricin became undetectable. About 20% SEB could be detected after heating at 80°C, but this detection ability was completely removed after heating at 100°C. The effects of chemicals usually used for decontamination, such as sodium hypochlorite, hydrogen peroxide, formaldehyde, and sodium nitrite, on the detectability of SEB, BTX A, or ricin in the BTA system were also tested. The concentrations giving 50% line intensity for SEB, BTX A, and ricin were 3.1, 11, and 15 μM for sodium hypochlorite and 88, 210, and 60 mM for formaldehyde, respectively. The addition of hydrogen peroxide or sodium nitrite did not decrease the detectability even when used at high concentrations.     

Long-term potentiation at single fiber inputs to hippocampal CA1 pyramidal cells.

Despite extensive investigation, it remains unclear whether presynaptic and/or postsynaptic modifications are primarily responsible for the expression of long-term potentiation (LTP) in the CA1 region of the hippocampus. Here we address this issue by using techniques that maximize the likelihood of stimulating a single axon and thereby presumably a single synapse before and after the induction of LTP. Several basic properties of synaptic transmission were examined including the probability of neurotransmitter release (Pr), the quantal size (q), and the so-called potency, which is defined as the average size of the synaptic response when release of transmitter does occur. LTP was routinely associated with an increase in potency, whereas increases in Pr alone were not observed. LTP was also reliably induced when baseline Pr was high, indicating that synapses with high Pr can express LTP. These results suggest that the mechanism for the expression of LTP involves an increase in q and is difficult to explain by an increase in Pr alone.     

Eight Days of Cyclosporine Overdose: A Case Report

A 25–year-old woman was admitted to the hospital because of rising trough cyclosporine concentrations thought to be due to self-administration of 4 times the normal dosage of the drug for 8 days. Her symptoms included colicky central abdominal pains and urinary retention; her serum creatinine concentrations were elevated. Whole blood cyclosporine and metabolite concentrations were measured by high-performance liquid chromatography and monoclonal radioimmunoassays. The highest reported trough cyclosporine concentration was 5877 ng/ml, and AM1 (M17) concentration was 3425 ng/ml. A cyclosporine half-life of 91 hours was calculated. Nine days after the agent was discontinued the patient's serum creatinine concentration had returned to normal and her symptoms resolved. Due to the availability of three sizes of cyclosporine capsules, and the need for frequent dosage changes, continued vigilance is necessary to ensure that patients understand their drug regimen.     

Histiocytic necrotizing lymphadenitis (Kikuchi's disease)

Histiocytic necrotizing lymphadenitis (Kikuchi's disease) is a benign disorder predominantly of young women who present with cervical adenopathy. It has, on occasion, been misdiagnosed as a malignant neoplasm. Little mention of this condition has appeared in the otolaryngologic literature. A patient with Kikuchi's disease is reported and the pertinent literature is reviewed. Because both the clinical and pathological aspects of Kikuchi's disease are important in establishing the diagnosis, effective consultation between the head and neck surgeon and the pathologist is crucial.     

Thermal analysis of the bone surface induced by laser radiation

High energy laser has emerged to be an important surgical tool in medical technology. However, the application of laser energy to drill or cut a bone is still in an experimental state. In order to estimate the adequacy of laser heating of bone surface and at the same time minimize the damage to the bone tissue, we developed a mathematical model of the temperature distribution in bone due to laser irradiation. The thermal analysis shows that the temperature distribution depends on several parameters, including the density, the specific heat, and the thermal conductivity of the osseous tissue.     

Childhood Malignant Thymoma: Clinical, Therapeutic, and Immunohistochemical Considerations

Malignant thymomas are among the least common mediastinal tumors in the pediatric age group. Thymomas are considered malignant on the basis of macroscopic and microscopic invasiveness. As only 20 well-documented cases involving children have been reported in the literature, the pattern of responsiveness to therapy and the value of prognostic signs is obscure. Two cases of malignant pediatric thymomas are reported with pathognomonic histoimmunological features of aggressive thymoma. One was cured, with a follow-up of 70 months, and one died while on therapy. Analysis of the histological features and the immunoperoxidase staining displays the complexity of pediatric thymomas and the inability to prognosticate the outcome, respectively.