Lesion was made individually to the various cortical areas in 14 rats.The cortico- fugal fibers terminating into cochlear nuclei were traced in sections by means of the modified Nauta and Fink-Heimer silver staining method.The results were as follows: 1.After damaging the auditory area or somato-sensory area 1(SI)of the cerebral cortex unilaterally,degenerating fibers were found bilaterally in the ventral and dorsal cochlear nuclei.This result showed that the above cortical areas have direct descending connection with the cochlear nuclei. 2.No degenerating fibers were found in the cochlear nuclei after the ablation of the motor or visual area of the cerebral cortex,which demonstrated that the cochlear nuclei do not receive descending fibers from the above cortical areas. 3.The pathway from the cerebral cortex to the cochlear nuclei was:The descending fibers which originated from the auditory area or SI area ipsilaterally passed through the capsula interna and basis pedunculi,and part of these fibers passed dorsally and downward to the lateral portion of the reticular formation of the midbrain;and from there the fibers passed through the lemniscus lateralis and dorsal acustic stria to the cochlear nuclei of the ipsilateral side.The cochlear nuclei in contralateral side also received the corticofugal fibers by way of the dorsal acustic stria.These fibers might cross to the contralateral side at the region in the posterior commissure,superior colliculus commissure and inferior colliculus commissure.

Objective:To investigate the present situation, methods, advantages and problems of bilingual teaching in medical cytobiology for medical undergraduates. Methods: The bilingual teaching project of medical cytobiology was considered comprehensively from various angles, such as the teaching aim, methodology, teacher training, teaching material selection and examination in specialized course. Conclusion: It is a very important strategic project to develop bilingual education in China. The course of bilingual teaching for medical undergraduates should be student-oriented and carried out step by step.

OBJECTIVETo study the relationship between targeting vector structure and homologous recombination rate and investigate whether the mouse p16(INK4a) plays a role in tumor suppression.

METHODSA conditional targeting vector with 2.0 kb EcoR I/Xba I fragment as short arm and 5.9 kb SpeI/NotI fragment as long arm was built. Of the 2 direct locus crossing- over(loxPs) in the vector, one was inserted at 240 bp upstream of the initiate code of p16(INK4a) exon 1a and the other at 1633 bp downstream of the initiate code. Both exon 1a and the selection marker Neo will be deleted in targeted cells when mediated by Cre. After linearlization and purification, t he targeting vector was introduced into ES cells through electroporation.

RESULTSTwenty-four G418- and gancyclovir-resistant ES cell colonies were picked out and one of them was confirmed as positive by Southern hybridization.

CONCLUSIONTargeting vectors with 2 TK genes flanking the homologous arms are likely to produce good result of homologous recombination.

Animals ; Anti-Bacterial Agents ; pharmacology ; Antiviral Agents ; pharmacology ; Base Sequence ; Cell Division ; drug effects ; genetics ; Cell Line ; Cyclin-Dependent Kinase Inhibitor p16 ; genetics ; Drug Resistance ; genetics ; Embryo, Mammalian ; cytology ; drug effects ; metabolism ; Exons ; genetics ; Ganciclovir ; pharmacology ; Genetic Vectors ; genetics ; Gentamicins ; pharmacology ; Mice ; Molecular Sequence Data ; Recombination, Genetic ; Stem Cells ; cytology ; drug effects ; metabolism ; Thymidine Kinase ; genetics ; metabolism ; Transfection