ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

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Inhibition of cyclic 3′5′ monophosphate synthesis in rat testis by L-triiodothyronine (1981)

Flawia, M. M. ; Kornblihtt, A. R. ; Mendoza, D. ; [et al.]

Springer

Molecular and cellular biochemistry 34 (1981), S. 185-190

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ISSN: 1573-4919

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Summary Cytosolic adenylate cyclase activity from rat seminiferous tubules is inhibited by L-triiodothyronine (L-T3). In a typical dose-response curve, using Mn-ATP as substrate, no effect is observed at 10−10 M L-T3; about 15 to 25% inhibition is found in the range between 10−9 and 10−6 M L-T3 and finally a sharp enzyme inhibition is evident at increasing hormone concentrations from 10−6 to 10−4 M. Incubation of decapsulated testes with L-T3 leads to a decrease of intracellular cyclic AMP levels. Dose-response relationships for such effect are similar to those found for adenylate cyclase activity. In this case a clear response is observed at 10−8 M L-T3.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02359623

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2

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Protein kinase activities in Neurospora crassa (1982)

Glikin, G. C. ; Judewicz, N. D. ; Torres, H. N.

Springer

Molecular and cellular biochemistry 46 (1982), S. 121-126

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ISSN: 1573-4919

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Summary Molecular properties of Neurospora soluble protein kinase and cyclic AMP binding activities have been determined. Cyclic AMP-dependent Peak I kinase activity with a molecular weight of 118 000 is composed of two subunits, catalytic and regulatory, having molecular weights of 55 000 and 57 000, respectively. Cyclic AMP-independent Peak II kinase activity has a molecular weight of 56 000. Cyclic AMP-independent Peak III kinase has a molecular weight of 209 000.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00236778

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3

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Association of triiodothyronine binding activity to soluble adenylate cyclase in testicular preparations (1981)

Kornblihtt, A. R. ; Flawiá, M. M. ; Mendoza, D. ; [et al.]

Springer

Molecular and cellular biochemistry 36 (1981), S. 23-27

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ISSN: 1573-4919

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Summary Cytosolic adenylate cyclase activity from rat seminiferous tubules was purified by chromatography in DEAE-cellulose, hydroxylapatite and Bio-Gel A-0.5 m as well as by centrifugation in sucrose gradients. In all these purification steps, fractions with adenylate cyclase activity also contained binding activity for L-T3. Binding studies indicate the existence of two L-T3 receptor components associated to adenylate cyclase activity. The component exhibiting the highest hormone affinity has the lowest binding capacity.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02354828

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4

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Cyclic nucleotide phosphodiesterase activities in rat erythrocytes (1982)

Téllez-Iñón, M. T. ; Torres, H. N.

Springer

Molecular and cellular biochemistry 43 (1982), S. 161-166

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ISSN: 1573-4919

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology , Medicine

Notes: Summary Erythrocyte soluble phosphodiesterase activities show at least two interconvertible states: ‘aggregated’ and ‘non-aggregated’. In the former state the existence of a high affinity component for cyclic AMP is favoured and the system is more active with cyclic AMP than with cyclic GMP as substrate. When the system is in the ‘non-aggregated state’, no activity with cyclic GMP is detected. Conversion to the ‘non-aggregated state’ is enhanced by dilution or by addition of magnesium ions. Upon isoelectric focusing of erythrocyte soluble extracts, phosphodiesterase activities can be resolved in two peaks: one specific for cyclic AMP located at pH 4.66 and the other specific for cyclic GMP focused at pH 4.95. Evidence would indicate that aggregation affects the enzyme specific for cyclic AMP.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00223007

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5

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Effects of insulin on the adenylyl cyclase activity of isolated fat cell membranes (1978)

Torres, H. N. ; Flawià, M. M. ; Hernaez, L. ; [et al.]

Springer

The journal of membrane biology 43 (1978), S. 1-18

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ISSN: 1432-1424

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Summary Insulin decreased markedly the adenylyl cyclase activity associated with fat cell membranes purified by centrifugation in sucrose gradients. The hormone effect was not readily evident in crude membrane preparations. The kinetics of this effect indicate that some time was required for the onset of the insulin-induced inactivation. This lag period decreased when the insulin concentration was increased. The hormone dose dependence for adenylyl cyclase inactivation measured at a fixed time (3 min) showed a 10 to 15% decrease in activity at 1 to 30 μU per ml insulin; 30 to 40% at 100 to 1000 μU per ml; and 75% at 0.1 U per ml. The insulin effect was completely abolished by 0.1mm GMP-P(NH)P, 10mm fluoride, or 50 ng per ml glucagon, or by increasing the Mn++ concentration to 4mm. In addition, it was partially reversed by the addition of a fraction from the sucrose gradient, which contained soluble factors. The kinetics of the adenylyl cyclase-catalyzed reaction were studied using ATP or AMP-P(NH)P as adenylyl donor, and Mn++ or Mg++ as divalent cation, in the absence or presence of insulin. With ATP and Mg++ there was a striking reduction of the transient reaction rates after 1.5 min of incubation. Under these conditions the insulin effect was not evident. On the contrary, with ATP and Mn++ this spontaneous reduction of activity was less evident; however, in the presence of insulin there was a clear and marked reduction of the transient reaction rate measured after 1.5 min of incubation. With AMP-P(NH)P the kinetic data were qualitatively similar to those observed with ATP. It is concluded that under certain assay conditions adenylyl cyclase may be converted to an inactive enzyme form, and that such a conversion is more evident in the presence of Mg++ than with Mn++. In the latter case, insulin appears to enhance the rate of this conversion.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01869039

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6

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Kinetic studies of adenylyl cyclase of fat cell membranes (1978)

Torres, H. N. ; Flawiá, M. M. ; Medrano, J. A. ; [et al.]

Springer

The journal of membrane biology 43 (1978), S. 19-44

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ISSN: 1432-1424

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Summary The kinetic behavior of the adenylyl cyclase activity associated with fat cell membranes purified by centrifugation on sucrose gradients was studied. Under most of the conditions explored, with either Mn++ or Mg++ as the divalent cation in the assay mixtures, the time courses of the reaction were not linear. In the absence of modifiers (i.e., basal activity) or in the presence of insulin, the rate tended to decrease with time; on the other hand, with fluoride or GMP-P(NH)P the curves were concave upwards. To simplify analysis of the results, two kinetic components were defined: an “initial component” corresponding to the transient rate measured between zero time and 1.5 min of assay and a “final component” corresponding to the transient rate determined between 3 and 5 min. Over the entire range of Mn++ concentration explored (0.5 to 6.0mm), the basal initial rates were slightly higher than the final ones. With Mg++ in the range between 1.5 and 2.5mm, the final rates were fourfold lower than the initial ones. Higher or lower Mg++ concentrations gave velocity ratios equivalent to those observed with Mn++. Insulin clearly decreased the final rates at Mn++ concentrations up to 2.5mm. With higher concentrations the effects were completely reversed. The effects of insulin on initial rates measured with Mn++, or the initial or final rates measured with Mg++, were less evident. Stimulation of adenylyl cyclase activity by fluoride was most pronounced on the final rates. In addition, this stimulation was higher with Mg++ than with Mn++. Isoproterenol stimulation of adenylyl cyclase was negligible in the presence of Mn++ (0.5 to 6.0mm). With Mg++ (0.5 to 6.0mm), stimulation was more evident on the final rates. *** DIRECT SUPPORT *** A0130063 00002

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01869040

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7

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Kinetic studies of adenylyl cyclase of fat cell membranes (1978)

Torres, H. N. ; Flawiá, M. M. ; Medrano, J. A. ; [et al.]

Springer

The journal of membrane biology 43 (1978), S. 45-69

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ISSN: 1432-1424

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Summary The kinetics of fat cell adenylyl cyclase were studied, with AMP-P(NH)P and Mn++ or Mg++ as the divalent cation. In general, the reaction times were not linear. In the presence of fluoride or GMP-P(NH)P, the time curves were concave upwards; in other cases (i.e., basal activity, insulin, or isoproterenol), transient rates tended to decrease with time during the assay. Kinetic data were analyzed according to a previously described procedure (Torreset al., 1978b) which isolates two kinetic components: initial and final. With AMP-P(NH)P, kinetic activities were about ten times lower than those for ATP. With Mn++, activities were at least two-times higher than for Mg++. Spontaneous inactivation of adenylyl cyclase was higher in assays containing Mg++ than in those supplemented with Mn++. In the latter case, insulin was able to increase the inactivation rate. Fluoride and isoproterenol both activated adenylyl cyclase in both the initial and final kinetic components; under most of the conditions explored, their effects on the final component appeared to be more dramatic. Assays with GMP-P(NH)P showed inhibited activity in the initial component and increased activity in the final one. When the results obtained with AMP-P(NH)P are compared with those of ATP (Torreset al., 1978b. J. Membrane Biol. 43:000), the following differences were found: (i) in the presence of insulin and Mn++, cyclase inactivation was higher with AMP-P(NH)P than with ATP; (ii) fluoride stimulation of the final component was more marked with ATP than with AMP-P(NH)P; (iii) cyclase stimulation by isoproterenol was slightly higher with the nucleotide analog; and (iv) GMP-P(NH)P stimulation of the final component resulted in higher activity with ATP than with AMP-P(NH)P.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01869041

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