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81.
Morphological variation of layer III pyramidal neurones in the occipitotemporal pathway of the macaque monkey visual cortex 总被引:5,自引:5,他引:0
We compared the morphological characteristics of layer III pyramidal
neurones in different visual areas of the occipitotemporal cortical
'stream', which processes information related to object recognition in the
visual field (including shape, colour and texture). Pyramidal cells were
intracellularly injected with Lucifer Yellow in cortical slices cut
tangential to the cortical layers, allowing quantitative comparisons of
dendritic field morphology, spine density and cell body size between the
blobs and interblobs of the primary visual area (V1), the interstripe
compartments of the second visual area (V2), the fourth visual area (V4)
and cytoarchitectonic area TEO. We found that the tangential dimension of
basal dendritic fields of layer III pyramidal neurones increases from
caudal to rostral visual areas in the occipitotemporal pathway, such that
TEO cells have, on average, dendritic fields spanning an area 5-6 times
larger than V1 cells. In addition, the data indicate that V1 cells located
within blobs have significantly larger dendritic fields than those of
interblob cells. Sholl analysis of dendritic fields demonstrated that
pyramidal cells in V4 and TEO are more complex (i.e. exhibit a larger
number of branches at comparable distances from the cell body) than cells
in V1 or V2. Moreover, this analysis demonstrated that the dendrites of
many cells in V1 cluster along specific axes, while this tendency is less
marked in extrastriate areas. Most notably, there is a relatively large
proportion of neurones with 'morphologically orientation-biased' dendritic
fields (i.e. branches tend to cluster along two diametrically opposed
directions from the cell body) in the interblobs in V1, as compared with
the blobs in V1 and extrastriate areas. Finally, counts of dendritic spines
along the length of basal dendrites revealed similar peak spine densities
in the blobs and the interblobs of V1 and in the V2 interstripes, but
markedly higher spine densities in V4 and TEO. Estimates of the number of
dendritic spines on the basal dendritic fields of layer III pyramidal cells
indicate that cells in V2 have on average twice as many spines as V1 cells,
that V4 cells have 3.8 times as many spines as V1 cells, and that TEO cells
have 7.5 times as many spines as V1 cells. These findings suggest the
possibility that the complex response properties of neurones in rostral
stations in the occipitotemporal pathway may, in part, be attributed to
their larger and more complex basal dendritic fields, and to the increase
in both number and density of spines on their basal dendrites.
相似文献
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OBJECTIVE The impact of the menopause on androgen production is poorly understood. We have investigated the impact of the menopause, as well as other factors such as age, body mass index (BMI) and cigarette smoking, on ovarian and adrenal androgen levels in women aged 40–60 years. DESIGN Cross-sectional study of blood hormones sampled weekly over one month in volunteer 40–60-year-old women. SUBJECTS One hundred and forty-one women, aged between 40 and 60, recruited from community sources (non-clinical), not using hormone replacement or steroidal contraceptives, and with a current sexual partner. Fifty were categorized as premenopausal (ovulating), 37 as perimenopausal and 54 as post-menopausal. MEASUREMENTS The following variables were assessed; menopausal status (based on menstrual history and pattern and plasma progesterone), age, BMI, smoking, oestradiol (E2), oestrone (E1), LH, FSH, total testosterone (TT), androstenedione (A), SHBG, free androgen index (FAI), dihydroepiandrosterone (DHEA), dihydroepiandrosterone sulphate (DHEAS) and cortisol. RESULTS are based on multiple regression analysis. TT was positively related to A, BMI and LH. A was negatively related to age and FSH, and positively to DHEA, DHEAS and premenopausal status. SHBG was negatively related to BMI and positively to E1 and non-smoking. DHEA and DHEAS were negatively related to age and were higher in smokers. Both E1 and E2 were related to menopausal status and to FSH. Surprisingly, E2 was negatively related to BMI. CONCLUSIONS A variety of factors influence androgen production in this age group. Whereas it is difficult to predict the effect of menopause on androgen levels, LH stimulation of post-menopausal interstitial cells, modulated by a variety of factors including nutrition, and smoking, are likely to be relevant. 相似文献
85.
During 1939 and 1940, clinical examinations, including blood pressure observations, of a large proportion of the population of the Virgin Islands were made. It is the purpose of this article to analyze the blood pressure observations and to compare them with studies made in the United States and elsewhere. 相似文献
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