Vestibular function after spinal cord injury: preliminary results.

STUDY DESIGN: The excitability of the vestibular apparatus and pathways was studied in 10 patients with acute spinal cord injury (ASCI) and in 7 patients with chronic spinal cord injury (CHSCI). OBJECTIVES: Proprioceptive input that may be lost after spinal cord injury (SCI) is needed for integration with vestibular signals to produce proper postural control and perception of movement. This study examined whether there is a change in vestibular excitability after the disruption of the afferent proprioceptive input due to the spinal cord lesion. This study was carried out at Spine Injury Centre and Institute of Rehabilitation, Belgrade, Serbia. METHODS: A total of 10 patients with ASCI and 7 with CHSCI were compared to a group of 50 age-matched healthy subjects. The excitability of the vestibular pathways was studied by means of a modified caloric test in which the duration of postcaloric nystagmus was measured. RESULTS: ASCI patients with cervical lesions showed significantly reduced response durations (P<0.05). There was no difference in control values for ASCI and for CHSCI patients with thoracic or lumbal lesions. There was no difference in control values for cervical CHSCI patients. CONCLUSIONS: These results suggest that the vestibular response to caloric stimulation is supported by spinally mediated sensory input and that the loss of such input is compensated for over time. Further, these results show that the caloric test may be a useful tool for assessing the degree to which SCI disrupts multisensory integration in the vestibular system and tracking the process of reintegration.

An electrochemical method of measuring the oxidation rate of ferrous to ferric iron with oxygen in the presence of Thiobacillus ferrooxidans.

The oxidation of Fe(2+) with oxygen in sulfate solutions was studied in the presence of T. ferrooxidans. To measure the chemical activity of bacteria, and the oxidation rate of iron, the redox potentials of solutions were continuously monitored during the experiments. The redox potentials were simultaneously monitored on the platinum and pyrite indicator electrodes. The redox potential versus time curves were further used to calculate the basic kinetic parameters, such as the reaction orders, the activation energy, and the frequency factor. It was found that under atmospheric conditions, and at Fe(2+) < 0.001M, T < 25 degrees C, and at pH above 2.2, the oxidation of iron is governed by the following rate expression: -(d[Fe(2+)]) / dt = 1.62 x 10(11)C(bact) [H(+)] [Fe(2+)] p O(2)e(-(58.77/RT)). Below pH = 2.2, the oxidation rate is independent of H(+) Concentration.