UCLA forum in medical sciences最新文献

{"title":"Timing of major ontogenetic events in the visual cortex of the rhesus monkey.","authors":"P Rakic","doi":"10.1016/b978-0-12-139050-1.50008-2","DOIUrl":"https://doi.org/10.1016/b978-0-12-139050-1.50008-2","url":null,"abstract":"<p><p>The place and time of origin, the migration and eventual disposition of neurons of the monkey visual cortex were studied by autoradiography in animals killed at various intervals after 3H-thymidine pulse labeling at embryonic (E) and early postnatal (P) stages. All neurons destined for the visual cortex are generated during about a 2-month period between E45 and E102. Neuron position in the cortical laminae correlates systematically with time of cell origin; neurons destined for deeper cortical positions are generated earlier, and more superficial ones progressively later. Thus, most neurons in layer VI are born between E45 and E60, in layer V between E60 and E70, in layer IV between E70 and E80, and in layers III and II between E80 and E102. No neurons, but numerous glia, are generated within the cortical plate itself. Initially young neurons are produced almost exclusively in the ventricular zone. Later they are probably generated in both ventricular and subventricular zones, and by the end of the proliferative period the subventricular zone becomes the predominant source of new cells. At the time when all neurons destined for the monkey visual cortex have already been produced, primary fissures are barely indicated on the cerebral surface and no secondary fissure appears as yet. Autoradiographic analyses indicate that at early stages young neurons move to the cortical plate relatively synchronously and at a fast rate, whereas at later stages there are considerable differences in the rates of cell migration. At early stages when the migration pathway is relatively short, the external process of the ventricular cell may stretch across almost the entire migratory distance. It is possible that nuclei move without interruption within their own cylinders of cytoplasm, a mechanism which might account for the rapid, synchronous movement of cell bodies as seen in the autoradiographic material. During later stages when young neurons, mostly of subventricular origin, move across a distance which is more than 10 times the length of their leading process, migrating cells follow radial glial guides across the widened intermediate zone and through densely packed cortical plate. This type of cell displacement seems to proceed less synchronously and require more time. It is proposed that two different mechanisms of cell displacement might exist: one in operation at early stages of cortical formation when mostly ventricular cells migrate, and another utilized by subventricular cells at later stages.</p>","PeriodicalId":76774,"journal":{"name":"UCLA forum in medical sciences","volume":" 18","pages":"3-40"},"PeriodicalIF":0.0,"publicationDate":"1975-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"11999514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Discussion: effects of caudate nuclei removal versus frontal cortex lesions in kittens.","authors":"J R Villablance","doi":"","DOIUrl":"","url":null,"abstract":"","PeriodicalId":76774,"journal":{"name":"UCLA forum in medical sciences","volume":" 18","pages":"395-9"},"PeriodicalIF":0.0,"publicationDate":"1975-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12376017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hepatic phenylalanine hydroxylase and PKU.","authors":"S Kaufman","doi":"10.1016/b978-0-12-139050-1.50032-x","DOIUrl":"10.1016/b978-0-12-139050-1.50032-x","url":null,"abstract":"<p><p>The conversion of phenylalanine to tyrosine in mammalian tissues is catalyzed by a complex enzyme system composed of several essential enzymes and cofactors. All of these components have been assayed in liver biopsy samples from patients with the classic form of PKU. They are all present except for phenylalanine hydroxylase, thus establishing this enzyme as the missing component. This conclusion has been confirmed in immunotitration experiments with a specific antiserum to phenylalanine hydroxylase. With the use of a highly sensitive assay for the hydroxylase, 0.27% of the normal activity of phenylalanine hydroxylase has been detected in a liver sample from a patient with classic PKU. There is some evidence that this low level of catalytic activity is due to the presence of a nutant form of the enzyme rather than to very low levels of the normal enzyme. These results rule out the possibility that clasic PKU is caused by a deletion mutation. The finding that the properties of the enzyme are different from the normal enzyme also suggests that the low hydroxylase activity in PKU is not caused by a regulatory hene mutation, but rather by a mutation in the gene that codes for the structure of the hydroxylase.</p>","PeriodicalId":76774,"journal":{"name":"UCLA forum in medical sciences","volume":" 18","pages":"445-58"},"PeriodicalIF":0.0,"publicationDate":"1975-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12376019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Normal and aberrant neuronal development in the cerebral cortex of human fetus and young infant.","authors":"D P Purpura","doi":"10.1016/b978-0-12-139050-1.50014-8","DOIUrl":"https://doi.org/10.1016/b978-0-12-139050-1.50014-8","url":null,"abstract":"<p><p>Several approaches utilized in ontogenetic investigations in laboratory animals have been explored in preliminary studies of morphogenetic events in the human cerebral cortex. 1. Golgi studies of dendritic growth cones, filopodia, and other developmental processes have permitted specification of the maximal phase of dendritic growth and differentiation of pyramidal neurons in the hippocampus. This period spans the twentieth to twenty-eighth week of fetal development. 2. Studies of the temporal pattern of appearance of the axonal plexus of the stratum pyramidale suggest that axosomatic synaptic pathways in the hippocampus develop relatively late in respect to the appearance of axospinodendritic inputs. 3. Dendritic spine development is evident at 26 weeks g.a. in the hippocampus but not in the visual cortex. Most hippocampal pyramidal neurons have acquired a full complement of spines by 6 months postnatally. The presence of severe metabolic and cardiorespiratory disturbances and/or chromosomal abnormalities significantly influences dendritic spine morphology and development. 4. The general morphological features of several varieties of neurons in the cisual cortes of a 32-week-old preterm infant are considered in respect to the electrographic characteristics of this infant's visual evoked responses. The observations in this and other cases illustrate the manner in which ontogenetic problems susceptible to inquiry in laboratory animals can serve to guide similar morphophysiological studies of normal and aberrant developmental events in human brain.</p>","PeriodicalId":76774,"journal":{"name":"UCLA forum in medical sciences","volume":" 18","pages":"141-69"},"PeriodicalIF":0.0,"publicationDate":"1975-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/b978-0-12-139050-1.50014-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"11348068","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unit recordings during Pavlovian conditioning.","authors":"J Olds","doi":"10.1016/b978-0-12-139050-1.50026-4","DOIUrl":"https://doi.org/10.1016/b978-0-12-139050-1.50026-4","url":null,"abstract":"<p><p>The aim is to find some switches in the brain and to characterize them if possible as either temporary and requiring some reverberatory process or as more stable and structural. There were five assumptions involved; (a) that the very large population of neurons in the brain could be effectively sampled in a limited set of experiments; (b) that a middle kind of electrodes could direct themselves to a sufficiently stable single unit population to permit extended conditioning experiments: (c) that averaging could be used to eliminate the effects of all unwanted variables that were not correlated with the main auditory signals: (d) that latency mapping would permit the tracing of a signal even through the multiple-channeled pathways of the brain (and would help us to identify switching points; (e) that a middle kind of conditioning (not Pavlovian entirely nor Slinner experiment with the clear CS of a Pavlovian one...</p>","PeriodicalId":76774,"journal":{"name":"UCLA forum in medical sciences","volume":" 18","pages":"343-71"},"PeriodicalIF":0.0,"publicationDate":"1975-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12376016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Prenatal nutrition and neurological development.","authors":"J Dobbing","doi":"10.1016/b978-0-12-139050-1.50030-6","DOIUrl":"https://doi.org/10.1016/b978-0-12-139050-1.50030-6","url":null,"abstract":"","PeriodicalId":76774,"journal":{"name":"UCLA forum in medical sciences","volume":" 18","pages":"401-20"},"PeriodicalIF":0.0,"publicationDate":"1975-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12376018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neuronal sprouting after hippocampal lesions.","authors":"G Lynch","doi":"10.1016/b978-0-12-139050-1.50010-0","DOIUrl":"https://doi.org/10.1016/b978-0-12-139050-1.50010-0","url":null,"abstract":"<p><p>It appears that aberrant but functional circuitry can rapidly develop after removal of particular afferent projections. The parameters describing this process appear to vary according to (1) the age at which the experimental manipulation was performed, (2) the specific afferent being studied, and (3) the particular input which is eliminated or possibly the brain region which is deafferented. It must also be emphasized that abnormal growth is not always found after lesions even in situations which a priori appear appropriate. Hopefully, these anatomical and physiological results obtained in a relatively \"simple\" brain system will be of help in evaluating the role played by abnormal wiring in the development of behavioral deficits.</p>","PeriodicalId":76774,"journal":{"name":"UCLA forum in medical sciences","volume":" 18","pages":"93-9"},"PeriodicalIF":0.0,"publicationDate":"1975-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12376021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Discussion: Phenylalanine hydroxylase in human kidney; relevance to Phenylketonuria.","authors":"J E Ayling","doi":"10.1016/b978-0-12-139050-1.50033-1","DOIUrl":"10.1016/b978-0-12-139050-1.50033-1","url":null,"abstract":"","PeriodicalId":76774,"journal":{"name":"UCLA forum in medical sciences","volume":" 18","pages":"459-65"},"PeriodicalIF":0.0,"publicationDate":"1975-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12415314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Brainstem substrates of sensory information processing and adaptive behavior.","authors":"J S Bucheald","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Emerging clinical and experimental data suggest that the brainstem may be an important part of the functional matrix from which normal mental development and behavior evolve. Although the brainstem has not been a focal point in considering etiologies of mental retardation nor even in analyses of adaptive behavior, information processing within both the brainstem sensory nuclei and adjacent reticular formation may indeed be one of the most critical and relevant areas for such investigations. Data are summarized from several ongoing experiments which are designed to explore the capacity of the brainstem to encode sensory, especially acoustic, stimuli and to modulate the resultant sensory information so as to produce a \"learned\" response. Such data indicate that in the absence of forebrain or even midbrain structures, a simple conditioned response can be supported by the brainstem. The reticular neuropil is considered particularly important to this response acquisition and is conceptualized as a structure which can receive and transmit acoustic information with retention of specific stimulus coding. It is further suggested that independent associative and reflex functions of the reticular formation may be highly significant in neonatal behavior but, with the development of descending influences from higher centers during maturation, these functions may become largely masked. In order to develop a temporal frame of reference for brainstem structures potentially involved in sensory information processing and learning phenomena \"time constants of response plasticity\" are being established for different levels of the brainstem system.</p>","PeriodicalId":76774,"journal":{"name":"UCLA forum in medical sciences","volume":" 18","pages":"315-33"},"PeriodicalIF":0.0,"publicationDate":"1975-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"11999515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of interference with cerebellar maturation on the development of locomotion. An experimental model of neurobehavioral retardation.","authors":"J Altman","doi":"10.1016/b978-0-12-139050-1.50009-4","DOIUrl":"https://doi.org/10.1016/b978-0-12-139050-1.50009-4","url":null,"abstract":"","PeriodicalId":76774,"journal":{"name":"UCLA forum in medical sciences","volume":" 18","pages":"41-91"},"PeriodicalIF":0.0,"publicationDate":"1975-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12415313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}