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891.
Sixteen male swamp sparrows, Melospiza georgiana, were reared by hand in the laboratory and exposed in infancy to tape-recorded songs. Training ended around 2 months of age. Samples of singing were tape recorded sporadically from the age of 50 to 90 days and on a weekly basis from about 95 to 400 days. Analysis revealed that explicit rehearsal of learned songs did not begin, on the average, until 240 days after the last exposure to training songs. Swamp sparrows can commit song syllables to memory and produce imitations of them 8 months later with no rehearsal in the interim. 相似文献
892.
Gary A. Borkan David E. Hults Peter J. Mayer 《American journal of physical anthropology》1982,25(Z3):181-202
The field of gerontology is remarkably diverse; yet there has been relatively little investigation of physical anthropological issues in aging research. This review explores gerontologic topics of actual and/or potential interest to physical anthropologists. The evolution of aging presents a theoretical dilemma in that postreproductively expressed traits may be outside the influence of natural selection. The physiological changes of aging comprise a diversified mosaic of physical deterioration as would be expected from an evolutionary model. Studies of prehistoric aging are limited to estimating lifespan, which may not be indicative of rate of aging. Considerable attention has been devoted to body composition and aging, and notable findings include a loss of lean tissue with age and relatively constant (though redistributing) fat mass. Osteoporosis is a major problem of aging in females, as is tooth loss in both sexes. The study of variation in rates of aging is only beginning, and a number of approaches to measuring biological age in adulthood are presented. Determining the associations of lifestyle, economic, and nutritional status with biological age may reveal sources of variation in rates of aging and may be of practical importance. 相似文献
893.
Peter Järver 《生物化学与生物物理学报:生物膜》2006,1758(3):260-263
894.
Kenneth Pomerantz Yvonne Maddox Franco Maggi Estelle Ramey Peter Ramwell 《Life sciences》1980,27(13):1233-1236
The stable breakdown product of prostacyclin, 6-keto-PGF1α, was estimated in plasma samples after incubation with rat aortic rings. The 6-keto-PGF1α concentration obtained with the male aortae was two-fold higher than that of the female. Ovariectomy markedly increased 6-keto-PGF1α six-fold, but castration had no effect. Estradiol and progesterone treatment of the ovariectomized female suppressed (by 50%) and enhanced (two-fold) 6-keto-PGF1α. Testosterone was without effect in gonadectomized males and females. Castrate males did not respond to gonadal steroid treatment. 相似文献
895.
Blood prostaglandin A levels were measured in ten healthy subjects under different conditions of collection and storage.Plasma levels ranged from 1.20 to 1.81 ng/ml (M ± SE = 1.50 ± 0.10) in 5 females to 1.23 to 1.68 ng/ml (1.45 ± 0.09) in 5 males, when centrifuged and frozen immediately after collection. Storate at 4°C for varying times up to 24 hours and at 22°C (room temperature) up to 4 hours did not affect mean plasma concentrations significantly, but increased the range obtained to 1.00 to 2.47 ng/ml for both male and female groups.Serum concentrations differed in males and females and were lower than corresponding mean plasma values for males and higher for females. Mean serum concentrations were 1.77 ± 0.08 ng/ml in females and 1.18 ± 0.05 ng/ml in males and did not change significantly up to 24 hours of storage at 4°C.These results suggest that prostaglandin A assayed in both plasma and serum under the conditions described is stable and should allow for greater flexibility in sampling under different experimental conditions. 相似文献
896.
897.
Burkhard Scherer Wolfgang Siess Peter C. Weber 《Prostaglandins & other lipid mediators》1977,13(6):1127-1139
The estimation of prostaglandin (PG) E2 and of PGF2α by radioimmunoassay is described in detail. PGE2 was measured after conversion to either PGB2 or PGF2α and the results compared to bioassay. The methods were used to follow the excretion of PGE2 and PGF2α after salt loading in rabbits. A marked reduction of PGE2 levels was observed at high NaCl intake, while PGF2α excretion remained unchanged. 相似文献
898.
899.
900.