35-GHz transferred electron amplifiers

Goldwasser, R. E.; Rosztoczy, F.E.

doi:10.1109/proc.1973.9305

Cited by 10 publications

(3 citation statements)

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“…The reduced ability of the hormone to activate the adenylate cyclase of the middle cells (Table 1) reflects the decrease in the number of erythropoietin-responsive cells present in this fraction. Although not instant, the observed quick but transient stimulation of adenylate cyclase activity by erythropoietin is in agreement with the rapid activation of this enzyme by various agonists in other cell systems [33] and with the reported erythropoietin-induced biphasic increase in cAMP levels in rabbit bone marrow cells [9]. Our results show that maximal stimulation is achieved in less than 30 min, i.e.…”

Section: Discussionsupporting

confidence: 92%

“…There is no general agreement in the literature, however, concerning the involvement of cyclic nucleotides in the response elicited by erythropoietin or in erythropoiesis in general. Addition of erythropoietin was reported to cause a biphasic increase in cAMP levels in rabbit bone marrow cells [9], but to have no Correspondence to S. A. Bonanou-Tzedaki, Department of Biochemistry, King's College, Strand, London WCZR 2LS, England Abbreviations. GuoPP[NH]P, guanosine 5'-[B,y-imido]triphosphate; GDP[PS], guanosine 5'-0-(2-thiodiphosphate); ECS0, effective concentration for half-maximum activity.…”

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confidence: 99%

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Stimulation of the adenylate cyclase activity of rabbit bone marrow immature erythroblasts by erythropoietin and haemin

Bonanou‐Tzedaki

Setchenska

Arnstein

1986

European Journal of Biochemistry

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The effect of two agents of erythroid cell differentiation on the adenylate cyclase activity of fractionated rabbit bone marrow erythroblasts has been investigated.1. Addition of 0.2 U/ml erythropoietin to cell cultures causes a transient increase in the activity of plasma membrane adenylate cyclase, which is maximal by 20 min and disappears within 4 h. The magnitude of the response to hormonal stimulation depends on the stage of erythroid cell development and is greater in the more immature cells.2. Addition of 50 pM haemin to cultures of erythroblasts also causes an increase in the activity of adenylate cyclase, which differs from the effect of erythropoietin in kinetics and specificity of target cells. With immature cells the haemin-induced stimulation starts after the first hour and continues to increase up to 20 h of culture.3. Erythropoietin but not haemin can stimulate the basal activity of adenylate cyclase in an in vitro assay containing plasma membranes of immature erythroid cells. The degree of activation depends on the concentration of erythropoietin and is maximal with 0.2 -0.5 U/ml hormone (5 -12 nM). In the presence of guanine nucleotides the activation of adenylate cyclase by erythropoietin is increased further but the effect is not additive. With respect to the basal and the guanine-nucleotide-stimulated activities of adenylate cyclase erythropoietin acts differently from the B-agonist I-isoprenaline. The in vitro effect of erythropoietin is abolished by the B-thio analogue of GDP, GDP [PS], and extensive washing of membranes makes hormone action GTP-dependent.4. The stimulation of adenylate cyclase by the addition of erythropoietin to the reaction mixture is inversely related to the extent of previous hormonal stimulation of the cells from which the membranes were prepared. This loss of hormonal responsiveness is due to desensitization or receptor down-regulation and persists for up to 20 h.5. We conclude that in immature erythroblasts erythropoietin acts via a receptor and a guanine nucleotidebinding protein with high affinity for GTP (EC5,, < 10 nM), whereas haemin appears to activate adenylate cyclase indirectly, as a consequence of progressive perturbations of the plasma membrane.The glycoprotein hormone erythropoietin regulates the proliferation and differentiation of erythroid cells [l, 21.Haemin is one of a number of other compounds which also have a regulatory effect on the maturation of erythroleukaemic [3] or normal [4-61 erythroblasts. The mode of action of either erythropoietin or haemin is not clear. Many glycoprotein hormones elicit a biological response by activation of the adenylate cyclase system [7] and in eukaryotes cAMP can act as a mitogenic signal and can induce the transcription of specific genes [8]. There is no general agreement in the literature, however, concerning the involvement of cyclic nucleotides in the response elicited by erythropoietin or in erythropoiesis in general. Addition of erythropoietin was reported to cause a biphasic increase in cAMP levels in rab...

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Section: Discussionsupporting

confidence: 92%

mentioning

confidence: 99%

Stimulation of the adenylate cyclase activity of rabbit bone marrow immature erythroblasts by erythropoietin and haemin

Bonanou‐Tzedaki

Setchenska

Arnstein

1986

European Journal of Biochemistry

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“…Using some of the above described Gunn diodes, transferred electron amplifiers are built with 110 mW saturated power output and 3 GHz bandwidth at 35 GHz; 13 db small-signal gain and 16.2 db noise figure are observed (33). ABSTRACT PhosphosSlicate glass gettering of silicon wafers in which diodes had been formed has been studied.…”

Section: Device Performancementioning

confidence: 99%