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91.
Transforming growth factor beta regulates the inhibitory actions of epidermal growth factor during granulosa cell differentiation 总被引:1,自引:0,他引:1
The effects of transforming growth factor beta (TGF-beta) on epidermal growth factor (EGF) receptor content and EGF action were studied in cultured granulosa cells from immature diethylstilbestrol-implanted rats. During follicle-stimulating hormone (FSH)-induced differentiation in vitro, EGF receptors increased by 20-fold as measured by the binding of 125I-EGF to the intact cells. Addition of TGF-beta during the 48-h culture period amplified the stimulatory effects of FSH on EGF receptors up to 2-fold, with ED50 and maximal concentrations of 2.5 and 8 pM, respectively. Also TGF-beta alone in amounts from 1.6 to 16 pM increased EGF receptor content 4-fold. The stimulatory effects of TGF-beta were due to increased numbers of EGF receptors/cell, since the growth factor had no effect on the Kd (3-5 X 10(-11) M) of the high-affinity EGF binding site. TGF-beta action was observed within 20 h of granulosa cell culture and was maximal by 48 h of a 96-h culture. The stimulatory actions of TGF-beta in gonadotropin-induced cells were exerted through the cAMP effector system of the granulosa cell, since the growth factor also amplified the induction of EGF receptors by cholera toxin, forskolin, and 8-bromo-cAMP. The augmentation of EGF receptors by TGF-beta resulted in a parallel 2-fold increase in the inhibitory effects of EGF on FSH-induced cAMP production and luteinizing hormone receptor expression during granulosa cell development. TGF-beta did not increase granulosa cell numbers during culture although it elevated [3H]thymidine incorporation into DNA by 2-fold over that of FSH-treated cells. These results indicate that TGF-beta regulates the effects of both FSH and EGF during granulosa cell differentiation and provides evidence that ovarian function may be controlled by the combined actions of gonadotropins and multiple growth factors. 相似文献
92.
Increased 5-Hydroxytryptamine and Norepinephrine Release from Rat Brain Slices by the Red Sea Flatfish 总被引:1,自引:1,他引:0
The effect of the Red Sea flatfish toxin pardaxin was examined on K+-evoked and on basal release of either [3H]norepinephrine or [3H]5-hydroxytryptamine from preloaded rat cortical slices. The K+-induced release of the neurotransmitters was stimulated in a dose-related manner at concentrations ranging from 0.5 to 4 micrograms/ml. Basal release of the two transmitters was elevated to a lesser extent. Although the stimulation of evoked release was approximately equivalent for the two neurotransmitters, the response to 5-hydroxytryptamine was reversible whereas that of norepinephrine was not washed by 20 min of superfusion. The mechanisms involved in producing these actions of pardaxin are not known; however, they may be mediated by changes in electrolyte fluxes across the neuronal membranes. 相似文献
93.
用~(14)C-Pro和~3H_2-Tyr离体暗培养黄瓜子叶,发现细胞质、SECW和RCW中的Hyp/Pro和Idt/Tyr都随时间呈线性增加。这两种比值后两者高于前者,而两种比值增加速度之比在胞质部分最大、RCW中最小。表明在胞质和胞壁中都有Pro羟化和Tyr异联化过程,但羟化作用主要发生在胞质中,异联化主要在RCW中。 理化处理(高渗溶液和CHM)和放射性示踪证明胞质中存在HRGP库;它被分泌到胞壁后,先以离子键与壁结合,后转变为共价键与壁结合的伸展素。 相似文献
94.
95.
M. Vater A. S. Feng M. Betz 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1985,157(5):671-686
Summary The frequency-place map of the horseshoe bat cochlea was studied with the horseradish peroxidase (HRP) technique involving focal injections into various, physiologically defined regions of cochlear nucleus (CN). The locations of labeled spiral ganglion cells and their termination sites on inner hair cells of the organ of Corti from injections into CN-regions responsive to different frequencies were analyzed in three dimensional reconstructions of the cochlea. Horseshoe bats from different geographical populations were investigated. They emit orientation calls with constant frequency (CF) components around 77 kHz (Rhinolophus rouxi from Ceylon) and 84 kHz (Rhinolophus rouxi from India) and their auditory systems are sharply tuned to the respective CF-components.The HRP-map shows that in both populations: (i) the frequency range around the CF-component of the echolocation signal is processed in the second half-turn of the cochlea, where basilar membrane (BM) is not thickened, secondary spiral lamina (LSS) is still present and innervation density is maximal; (ii) frequencies more than 5 kHz above the CF-component are processed in the first halfturn, where the thickened BM is accompanied by LSS and innervation density is low; (iii) frequencies below the spectral content of the orientation call are represented in apical turns showing no morphological specializations. The data demonstrate that the cochlea of horseshoe bats is normalized to the frequency of the individual specific CF-component of the echolocation call.The HRP-map can account for the overrepresentation of neurons sharply tuned to the CF-signal found in the central auditory system. A comparison of the HRP-map with a map derived with the swollen nuclei technique following loud sound exposure (Bruns 1976b) reveals that the latter is shifted towards cochlear base by about 4 mm. This discrepancy warrants a new interpretation of the functional role of specialized morphological structures of the cochlea within the mechanisms giving rise to the exceptionally high frequency selectivity of the auditory system.Abbreviations
AVCN
anteroventral CN
-
BF
best frequency
-
BM
basilar membrane
-
CF
constant frequency
-
CN
cochlear nucleus
-
DCN
dorsal CN
-
FM
frequency modulated
-
HRP
horseradish peroxidase
-
IHC
inner hair cell
-
LSS
secondary spiral lamina
-
OHC
outer hair cell
-
PVCN
posteroventral CN
-
RF
resting frequency
-
RRc
Rhinolophus rouxi from Ceylon
-
RRi
Rhinolophus rouxi from India 相似文献
96.
Are Chaoborus larvae more abundant in acidified than in non-acidified lakes in Central Canada? 总被引:2,自引:0,他引:2
Eriksson et al (1980) hypothesized that the abundance of certain macroinvertebrate predators, such as larvae of the phantom midge Chaoborus , should increase in acidified lakes because of the elimination of fish. To examine the influence of pH and presence of fish on Chaoborus abundance, we surveyed Chaoborus populations in 33 lakes in Ontario, Canada which ranged in pH from 4.5 to 7.4. Chaoborus larvae were not more abundant in the acidified lakes that were devoid of fish than in the remaining lakes. Therefore, we concluded that pH and presence of fish are not prime determinants of total Chaoborus abundance in Canadian Shield lakes. We hypothesized that significant increases in Chaoborus abundance should only be anticipated when fish populations are eliminated by acidification of relatively nutrient rich lakes. 相似文献
97.
98.
曾子申;胡峻;利容千 《武汉植物学研究》1985,3(4):439-442
本文对我国栽培辣椒Capsicum annuum L.的四个品种即汉川椒、华椒一号、牛角椒和二金条进行了核型分析,其染色体数目均为2n=2x=24,核型公式均为2n=24=20m+2sm+2st,但汉川椒和华椒一号具一对随体,牛角椒和二金条具两对随体。本文还对它们的进化关系进行了讨论。 相似文献
99.
100.
Biotin has been converted to 2-(biotinylamido)ethanol and condensed to phosphorylated oligonucleotides in a solid phase synthesis. The 5'-biotinylated oligonucleotides were enzymatically coupled to other DNA fragments by T4 DNA ligase or T4 RNA ligase. The hybridization properties of such biotin-labeled oligonucleotide probes were studied. 相似文献