Cervical afferent pathway to inferior oblique motoneuron in the cat

The neuronal pathway implicated in the vertical cervico-ocular reflex (COR) was investigated electrophysiologically in chloralose anesthetized cats. The effect of bilateral C2 dorsal root afferent stimulation on inferior oblique motoneurons (IO-MN) was investigated by intracellular recording. Control disynaptic excitatory postsynaptic potentials elicited in IO-MNs following stimulation of the contralateral anterior semicircular canal nerve (ACN) were invariably facilitated by conditioning stimulation to both ipsilateral and contralateral C2 dorsal roots (DR) in all motoneurons tested. This result indicates that inputs from the C2 DR of both sides and the contralateral ACN converge onto secondary vestibular neurons ('common interneurons') which project directly to the IO-MN. Common interneurons mediating vestibular and cervical excitation to the IO-MNs were studied in the vestibular nuclei on the side opposite to the motoneurons by extracellular recording. Nineteen vestibular neurons were identified as common interneurons; they were distributed in the caudal half of the lateral nucleus and the rostral half of the descending nucleus. The present experiment provides electrophysiological evidence of the projection of upper cervical afferents to the ipsilateral vestibular nuclei. The difference in neuronal organization between the horizontal and vertical COR is also briefly discussed.

Common interneurones mediating cortical and tectal excitation of abducens motoneurones in the cat

Tectal and cortical effects on abducens motoneurones were examined with intracellular recording techniques in cats under chloralose anaesthesia. Abducens motoneurones exhibited disynaptic EPSPs after stimulation of the contralateral superior colliculus and cerebral peduncle. The tectal disynaptic EPSPs were observed invariably in all motoneurones tested, while the peduncular EPSPs were observed only in 40% of motoneurones after stimulation of the contralateral cerebral peduncle. However, the tectal disynaptic EPSPs were consistently facilitated by conditioning peduncular stimulation in all motoneurones tested. These results indicated that the disynaptic excitatory tecto-abducens and cortico-abducens pathways shared common premotor interneurones. The common interneurones which mediated the tectal and cortical disynaptic excitation of abducens motoneurones were explored in the pons. These interneurones were identified by the criteria that they were fired monosynaptically from both the tectum and the cerebral peduncle and were activated antidromically from the abducens nucleus. Systematic threshold mapping for the antidromic activation in and around the abducens nucleus indicated that they gave off many collateral branches in the nucleus. Such neurones were found in the nucleus reticularis pontis caudalis, being distributed in the area extending 0.8-3 mm rostral to the rostral pole of the abducens nucleus, 1.3-2.7 mm deep from the dorsal surface of the brain stem, and 0.8-1.8 mm lateral from the midline. The present experiments strongly suggest that a group of neurones in the paramedian pontine reticular formation make direct excitatory connexions with abducens motoneurones and play a role of common interneurones that transmit both tectal and cortical commands.

Weakly acidic pH-responsive liposomal content release induced by histidine-modified agents

Internal stimuli-responsive controlled release from liposomal vesicles is an innovative approach for site-specific delivery of therapeutic drugs. In this study, to enhance the endosomal pH control of drug release from liposomes, a series of histidine-modified pH-sensitive Cn-His (n = 8, 12, 18) agents were designed and utilized as triggers for liposomal content release. The pH-dependent properties of Cn-His-incorporated liposomes were characterized using dynamic light scattering, ζ-potential, and fluorescence spectroscopy. The liposomes maintained a relatively uniform size across all pH conditions. However, the ζ-potential exhibited positive values at endosomal acidic pH levels and neutral or negative values at physiological pH levels. Furthermore, acidic pH-dependent release of both polar content (carboxyfluorescein) and nonpolar content (Nile red) was observed from the Cn-His-incorporated liposomes. Notably, with C12-His as the pH sensitizer, the pH dependence of liposomal content release was significantly evident. This work establishes endosomal pH-controllable liposome platforms, laying the groundwork for developing clinically applicable triggered release formulations.

[Recurrence of febrile convulsions after the first diphtheria-pertussis-tetanus vaccination and measles vaccination in children with febrile convulsions: a questionnaire survey in Takamatsu City]

A questionnaire about convulsions and other adverse events after vaccination was sent to doctors who administered a diphtheria-pertussis-tetanus (DPT) vaccine (the first dose) or a measles vaccine between April 1, 1995 and December 31, 1997 in Takamatsu City to children with convulsions. DPT and measles vaccines were administered to 300 and 339 such children, respectively. Many of them had febrile seizures, the last of which had occurred before more than 1 year. Among them, 175 cases were administered with DPT and 180 with measles vaccine. There were recurrences of febrile convulsions after immunization in 2 (1.1%) of the cases given DPT and 3 (1.7%) of those given measles vaccination. According to the data of the Monitoring System for Adverse Events Following Immunization (the Ministry of Health and Welfare of Japan), the incidence of convulsion after immunization in healthy children between April 1, 1996 and September 30, 1997 was 0.4% after the first dose of DPT vaccination and 0.3% after measles vaccination. In comparison, the incidence was higher in children who had had febrile convulsions before more than one year. Especially, the rate of convulsions after measles vaccinations was significantly higher (p < 0.05) in children with febrile convulsions. These results suggest that the measles vaccination should be administered with caution to the children with previous febrile convulsions.