Medullospinal vasomotor neurones mediate hypotension from stimulation of prefrontal cortex.

Electrical stimulation of the prefrontal cortex in anaesthetised, paralysed rats evokes transient hypotension. In this study we have endeavoured to determine whether this evoked response is mediated by the spinal cord-projecting vasomotor neurones of the rostroventrolateral medulla (RVL). The responses of RVL-spinal vasomotor neurones to electrical stimulation of the prefrontal cortex caused a period of inhibition of the neuronal activity in the majority of cases (11 out of 13 neurones tested, 85%) and a short period of excitation in the remaining 2 neurones (15%). The prefrontal cortex-evoked inhibition of RVL-spinal vasomotor neurones was eliminated by iontophoretic application of bicuculline, a GABAa receptor antagonist, to the RVL-spinal vasomotor neurones. Microinjection of 50 nl of bicuculline methiodide into the same area of the RVL where the neurones have been identified converted the prefrontal-evoked hypotension into a vasopressor response. These findings indicate that the hypotension evoked by stimulating the prefrontal cortex is mediated by GABAergic inhibition of the RVL-spinal vasomotor neurones.     

An electrophysiological correlate of protein kinase C isozyme distribution in cultured cerebellar neurons.

Protein kinase C (PKC) is a family of at least seven closely related molecules (isozymes) that vary in terms of their requirements for activation and their distribution among cells of the brain. A striking example of this differential distribution is seen in the cerebellum, where Purkinje cells express PKC-I, an isozyme that is strongly activated by both phorbol ester (PE), and low doses of cis-unsaturated fatty acid (c-UFA), while granule cells predominantly express PKC-II, an isozyme that is strongly activated by PE but not c-UFA. Both Purkinje and granule cells have large, easily recorded voltage-gated K currents. These currents are attenuated by PKC activators in several other varieties of neuron. We hypothesized that the effects of these two PKC activators would be predicted by the distribution of the relevant PKC isozyme, and that the delayed outward rectifier current, IK, would be attenuated by both PE and c-UFA in Purkinje cells, but only by PE in granule cells. This hypothesis was confirmed in perforated-patch recordings. The attenuation produced by both activators could be blocked by application of a specific PKC inhibitor, RO-31-8220, and could not be mimicked by inert forms of PE or c-UFA. To our knowledge, this study represents the first report of an electrophysiological correlate of PKC isozyme distribution.     

Overgrowth of a costochondral graft in reconstruction of the temporomandibular joint.

We report the case of a 3-year-old girl with temporomandibular ankylosis, which was treated with a costochondral graft and required two further resections because the grafted tissue had overgrown.     

Innervation of the trapezius muscle: is cervical contribution important to its function?

OBJECTIVE: To study the effect of the cervical plexus and the accessory nerve to the function of the trapezius muscle. STUDY DESIGN AND SETTING: Eighteen adult male Sprague-Dawley rats were randomly divided into three groups. The neurotomies were performed in the left sides and the right sides served as within-subject controls. In group A, the accessory nerve was transected. The C2-5 were transected in group B, and both of the accessory nerve and C2-5 were cut in group C. The electrophysiologic, myophysiologic, and histologic changes of the muscles were measured. RESULTS: There were significant differences (P < 0.05) between the three groups in the recovery rates of the transverse area of the muscles. The CMAP recorded from the experimental sides in group B were similar to the control sides. The values of the maximum tension of the tetanus contraction between the two sides showed no differences either (P > 0.05). CONCLUSION: The accessory nerve supplies the most important motor input to the trapezius. Motor innervations of the cervical plexus are not very significant.     

Computerized tomography based on DEI refraction information.

Conventional computerized tomography (CT) technique is based on the absorption contrast. In recent years, X-ray phase-contrast CT (PCCT) has been developing rapidly. It uses the phase information to reconstruct the object and provide high contrast and spatial resolution. Diffraction enhanced imaging (DEI) method is one of the three phase-sensitive X-ray imaging techniques. DEI method employs an analyzer crystal to extract the object's refraction information which can be used for CT. However, when DEI refraction CT is combined with the conventional CT algorithm, it should be satisfied that the refraction information of an arbitrary point in the object is invariable at every projection view. In this paper, the invariance condition of refraction information is analyzed and two feasible methods are provided for reconstruction. Using these two methods, two samples of weak absorption are reconstructed with the experimental data obtained at Beijing Synchrotron Radiation Facility (BSRF).     

Odontoma: a clinicopathologic study of 81 cases.

BACKGROUND AND PURPOSE: Odontoma is the most common odontogenic tumor. It includes 2 types, the compound and complex odontomas. There has not been a series study of the clinical and histologic features of odontomas from Taiwan. This study evaluated the clinicopathologic features of odontoma in Taiwanese. METHODS: Cases of odontoma treated from 1998 to 2002 identified from medical records were included. The microscopic features, radiographic features, and clinical history of the patients were reviewed and analyzed. RESULTS: A total of 81 odontomas in 81 patients (36 males and 45 females) were included. There were 62 compound and 19 complex odontomas. The mean age of the patients was 18 years with the majority of odontomas occurring in the first (32%) and second decade (38%) of life. Odontomas had a marked predilection for the maxilla (70%) and for the anterior region of the jaw (83%), particularly for the anterior maxilla (62%). Sixty four (79%) of the 81 odontomas were associated with 80 impacted teeth, including 71 permanent teeth, 2 deciduous teeth, and 7 supernumerary teeth. Of the 71 impacted permanent teeth, the maxillary central incisor (27%) was most commonly affected, followed by the maxillary canine (26%) and mandibular canine (24%). Histologic examination revealed enamel matrix in 90%, dentin in 100%, cementum in 88%, pulp tissue in 96%, fibrous capsule in 93%, ghost cells in 83%, reduced enamel epithelium in 86%, and nests of odontogenic epithelium in 58% of odontomas. Dentigerous cyst was associated with 9% of odontomas. CONCLUSIONS: In this series, odontomas occurred most often in the first and second decade of life. Although complex odontomas are usually found in the posterior jaw, in this Taiwanese series they were most commonly found in the anterior maxilla. Odontoma is frequently associated with an impacted tooth and occasionally with a dentigerous cyst. No recurrence of odontomas was found after surgical excision with follow-up of 1 to 15 years.     

1.5T超导磁共振制冷系统的工作原理及日常维护

介绍GE 1.5T超导磁共振制冷系统的组成和工作原理,讨论日常维护的要点及其必要性。