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981.
Recruitment and growth of the sardineSardinops melanostictus fluctuated markedly in the Sea of Japan and adjacent waters between 1978 and 1993. Stock size was calculated using Virtual Population Analysis and average body length in each age class was determined by the number of annual rings on the scales. There is an inverse correlation between average water temperature at a depth of 50 m in the coastal area of the mainland of Japan in winter (January to March) and recruitmentR defined as the number of individuals at 1 year old. There is also an inverse correlation between spawning stock sizeE and reproductive success in (R/E). A multiple regression model using spawning stock size and water temperature in winter as independent variables can explain 73% of variance in reproductive success. It suggests that both density-dependent and density-independent factors perform important roles determining reproductive success. There is an inverse correlation between body length and stock size and this suggests that there is a density-dependent effect on the growth of the sardine. 相似文献
982.
To assess which hormones are capable of masculinizing the neural song system of zebra finch hatchlings, we implanted female hatchlings with estrogen (estradiol [E2], 75 μg, n = 9), testosterone (T, 75–88 μg, n = 13), androstenedione (AE, 75 μg, n = 7), progesterone (P, 117 μg, n = 10), or nothing (Blanks, n = 10) and compared these to unimplanted males (n = 7). Implants, consisting of a hormone and Silastic mixture encased in polyethylene tubing, were placed under the skin of the breast on the day of hatching. Birds were killed when they were subadult (58 to 68 days old). We measured volumes of area X, the higher vocal center (HVC), and the robust nucleus of the archistriatum (RA); measured soma sizes in the lateral magnocellular nucleus of the neostriatum (IMAN), HVC, and RA: and counted RA neurons. E2 masculinized all measures in the song system and nearly sex-reversed the size of RA neurons. T masculinized volumes of nuclei and soma sizes but not the number or spacing of RA neurons. E2 was always at least as effective as T in masculinizing measures of the song system and was usually more effective. AE and P did not significantly masculinize any measure. These data suggest that E2 is more potent than aromatizable androgens or P in masculinizing the female song system in development and that the action of E2 alone may be sufficient to masculinize the volume of song control nuclei and the size and number of neurons. © 1995 John Wiley & Sons, Inc. 相似文献
983.
拉萨郊区藏族跖纹主线走向分析 总被引:4,自引:1,他引:3
本文用茚三酮-味精法采集跖纹,体视显微镜下追踪跖纹主线走向,分析了250(男女各125人)拉萨效区藏族健康人的跖纹样本。结果显示:A线主要走向1区,其次是7区;B线亦多止于1区和7区;C线主要止于和9区;D线止于1区 频率最高;E线主要走向13区;P三叉缺失较多。Pz^d线止共位置较高(13区和11区),而P^f线止区较低(7区)。在民族和人种间进行了比较,提示藏族践纹主线走向有自己的特点,又呈现 相似文献
984.
控制大豆白花亲本籽粒脐色的基因有带R与r之分,带R基因的白花产本与紫花亲本杂交,F1代籽料出现蓝脐性状,其基因型为I-R-W1-tt。当控制脐色的基因有两对相差时(R、r;W1、w1)F2代籽粒脐色分离蓝脐与无色脐之比为9∶7。 相似文献
985.
一个恢复力受单基因控制的水稻CMS育性回复突变体 总被引:3,自引:0,他引:3
利用 ̄(60)Co-γ射线对具有印尼水田谷细胞质的籼稻细胞质雄性不育系Ⅱ-32A干种子进行诱变处理,获得了一育性回复突变体T24。育性基因未纯合的突变体分离出可育株和完全不育株,比例为3∶1;其与Ⅱ-32A和珍汕97A测交,F1代分离出1∶1的可育株和不育株。育性稳定株系与Ⅱ-32A和珍汕97A杂交,F2分离成3∶1的可育株和不育株。表明其育性回复是由一对基因显性突变所致。这一突变体对不育系的育性恢复机制不同于明恢63、20964等恢复系,后者表现为两对显性恢复基因作用。未观察到T24与亲本Ⅱ-32A除育性以外的其他性状的差异,因而两者构成育性恢复基因的近等基因系。本文还对不育系育性回复类型和T24的理论意义与育种价值进行了讨论。 相似文献
986.
Judith D. DePue Matthew M. Clark Laurie Ruggiero Meredith L Medeiros Vincent Pera 《Obesity (Silver Spring, Md.)》1995,3(3):241-248
This study identified facilitators and obstacles to maintenance of weight loss following a very-low-calorie-diet and behavior modification program. A survey was mailed to a random sample of 178 program completers and received a 61% response rate; the most frequent follow-up period was more than 2 years. Twenty-nine percent reported weighing the same (within 10 lbs) or less than the end of their participation in the treatment program (maintainers), while 71% reported their present weight was a mean of 65% higher than their initial weight loss (regainers). Maintainers were significantly more likely to report engaging in regular aerobic exercise, attending a maintenance support group, and confidence in their ability to manage their weight in the future, while regainers were more likely to report stress and motivation as frequent weight management obstacles. Respondents consistently identified the need for low/no cost ongoing support. Maintainers and relapsers reported similar challenges in managing their weight, yet with different results, suggesting the need to identify subgroups for which different post-treatment support options could be applied. 相似文献
987.
Ansgar Büschges 《Developmental neurobiology》1995,27(4):488-512
Local nonspiking interneurons in the thoracic ganglia of insects are important premotor elements in posture control and locomotion. It was investigated whether these interneurons are involved in the central neuronal circuits generating the oscillatory motor output of the leg muscle system during rhythmic motor activity. Intracellular recordings from premotor nonspiking interneurons were made in the isolated and completely deafferented mesothoracic ganglion of the stick insect in preparations exhibiting rhythmic motor activity induced by the muscarinic agonist pilocarpine. All interneurons investigated provided synaptic drive to one or more motoneuron pools supplying the three proximal leg joints, that is, the thoraco-coxal joint, the coxa-trochanteral joint and the femur-tibia joint. During rhythmicity in 83% (n=67) of the recorded interneurons, three different kinds of synaptic oscillations in membrane potential were observed: (1) Oscillations were closely correlated with the activity of motoneuron pools affected; (2) membrane potential oscillations reflected only certain aspects of motoneuronal rhythmicity; and (3) membrane potential oscillations were correlated mainly with the occurrence of spontaneous recurrent patterns (SRP) of activity in the motoneuron pools. In individual interneurons membrane potential oscillations were associated with phase-dependent changes in the neuron's membrane conductance. Artificial changes in the interneurons' membrane potential strongly influenced motor activity. Injecting current pulses into individual interneurons caused a reset of rhythmicity in motoneurons. Furthermore, current injection into interneurons influenced shape and probability of occurrence for SRPs. Among others, identified nonspiking interneurons that are involved in posture control of leg joints were found to exhibit the above properties. From these results, the following conclusions on the role of nonspiking interneurons in the generation of rhythmic motor activity, and thus potentially also during locomotion, emerge: (1) During rhythmic motor activity most nonspiking interneurons receive strong synaptic drive from central rhythm-generating networks; and (2) individual nonspiking interneurons some of which underlie sensory-motor pathways in posture control, are elements of central neuronal networks that generate alternating activity in antagonistic leg motoneuron pools. © 1995 John Wiley & Sons, Inc. 相似文献
988.
989.
杉木,火力楠纯林及混交林细根周转的研究 总被引:87,自引:13,他引:74
系统研究了杉木、火力楠纯林及混交林细根生物量、生产力及年周转率。结果表明,杉木、火力楠纯林及混交林活细根生物量分别为880、3035和1560kg.ha^-1;死细根生物量为235、398和565kg.ha^-1;细根年周转率为1.29、1.42和1.40;年生产量为1137、4318和2179kg.ha^-1;年死亡量为497.595和1149kg.ha^-1,分别相当于林分枯枝落叶年凋落量为3 相似文献
990.