Hormonal activation of ornithine decarboxylase in embryonic chick pelvic cartilage

1981 ◽  
Vol 241 (6) ◽  
pp. E454-E459
Author(s):  
W. M. Burch ◽  
H. E. Lebovitz
Keyword(s):  
Cyclic Amp ◽  
Ornithine Decarboxylase ◽  
Time Course ◽  
Embryonic Chick ◽  
Metabolic Factors ◽  
Rat Serum ◽  
In Vitro Organ Culture ◽  
Hormonal Activation ◽  
Stimulation Of

We assessed whether hormones and metabolic factors known to stimulate anabolic processes in the embryonic chick pelvic cartilage would stimulate ornithine decarboxylase (ODC) activity. In vitro organ culture of these pelvic cartilages in time-course experiments with N(6)-monobutyryl cyclic AMP (BtcAMP), insulin, and 5% rat serum demonstrated maximal stimulation of ODC activity between 4 and 6 h with each factor. However, at 2 h insulin and serum significantly stimulated ODC activity (P less than 0.05) and BtcAMP did not. ODC was stimulated above control (100%) with the following factors: parathyroid hormone (PTH) (555 +/- 15%), BtcAMP (324 +/- 34%), 1-methyl-3-isobutylxanthine (MIX) (223 +/- 6%), prostaglandin E1 (PGE1) (227 +/- 15%), 3,3',5-triiodothyronine (T3) (184 +/- 22%), insulin (182 +/- 14%), multiplication-stimulating activity (MSA) (178 +/- 6%), 5% rat serum (253 +/- 57%). THe increase in ODC activity seen with BtcAMP and insulin was not due to a change in Km or a decreased rate of degradation of the enzyme. Actinomycin D (1 microgram/ml) inhibited stimulation of ODC activity by T3 and the cyclic AMP-mediated factors (PTH, BtcAMP, MIX, PGE1), but had only minimal effects on ODC stimulation by insulin, MSA, or serum. Amanitin inhibited both BtcAMP and T3 stimulation of ODC, but had no effect on insulin stimulation of ODC. Thus, hormones and metabolic factors known to stimulate anabolic processes in chick embryonic pelvic cartilage also increase ODC activity through at least two mechanisms: transcriptional (cyclic AMP-mediated and T3) and posttranscriptional (insulin, serum, MSA).

scholarly journals In vitro stimulation of alkaline phosphatase activity in immature embryonic chick pelvic cartilage by adenosine

1982 ◽  
Vol 93 (2) ◽  
pp. 338-342 ◽  
Author(s):  
WM Burch ◽  
HE Lebovitz
Keyword(s):  
Alkaline Phosphatase ◽  
Cyclic Amp ◽  
Phosphatase Activity ◽  
Alkaline Phosphatase Activity ◽  
Maximal Response ◽  
Embryonic Chick ◽  
In Ovo ◽  
Developmental Age ◽  
Stimulation Of

Cyclic AMP content in embryonic chick pelvic cartilage increases significantly as the embryo ages from 8 to 10 d. This in ovo elevation in cyclic AMP content precedes maximal cartilage alkaline phosphatase activity by some 24 h. We studied whether this temporal relationship may be causally related, using an in vitro organ culture. Incubation of pelvic cartilage from 9- and 10-d embryos in medium containing monobutyryl cyclic AMP (BtcAMP) resulted in significant increases in alkaline phosphatase activity (220 and 66 percent, respectively) as compared to that of cartilages incubated in medium alone. This stimulation was both concentration- and time-dependent with maximal response at 0.5 mM BtcAMP and 4-h incubation, respectively. Similar incubations of cartilage in medium containing 1-methyl-3-isobutyl xanthine (MIX), 0.25 mM, also resulted in increased alkaline phosphatase activity (114 percent). However, pelvic cartilage from 11-d embryos incubated in medium containing BtcAMP or MIX showed no increase in alkaline phosphatase activity. We postulated that developmental age was the factor responsible for this difference in response and that immature cartilage (that with little or no alkaline phosphatase activity) would respond to BtcAMP whereas mature cartilage (that with significant alkaline phosphatase activity) would not. This was tested by incubating end sections of 11-d cartilage, which have little alkaline phosphatase activity, and center sections, which have significantly alkaline phosphatase activity, with both BtcAMP and MIX. Alkaline phosphatase activity in end sections (immature cartilage) was stimulated by BtcAMP and MIX, whereas it was not stimulated in the center sections. Actinomycin D and cycloheximide inhibited BtcAMP and MIX stimulation of alkaline phosphatase activity. Thus, the in vitro data suggest that cyclic AMP is a mediator for the stimulation of alkaline phosphatase activity in embryonic cartilage.

scholarly journals Interactions between adenylate cyclase and the yeast GTPase-activating protein IRA1.

1991 ◽  
Vol 11 (9) ◽  
pp. 4591-4598 ◽  
Author(s):  
M R Mitts ◽  
J Bradshaw-Rouse ◽  
W Heideman
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Adenylate Cyclase System ◽  
Gtpase Activating Protein ◽  
Yeast Saccharomyces Cerevisiae ◽  
Strong Candidate ◽  
Sepharose 4B ◽  
Stimulation Of ◽  
Cyclic Amp Synthesis

The adenylate cyclase system of the yeast Saccharomyces cerevisiae contains many proteins, including the CYR1 polypeptide, which is responsible for catalyzing the formation of cyclic AMP from ATP, RAS1 and RAS2 polypeptides, which mediate stimulation of cyclic AMP synthesis by guanine nucleotides, and the yeast GTPase-activating protein analog IRA1. We have previously reported that adenylate cyclase is only peripherally bound to the yeast membrane. We have concluded that IRA1 is a strong candidate for a protein involved in anchoring adenylate cyclase to the membrane. We base this conclusion on the following criteria: (i) a disruption of the IRA1 gene produced a mutant with very low membrane-associated levels of adenylate cyclase activity, (ii) membranes made from these mutants were incapable of binding adenylate cyclase in vitro, (iii) IRA1 antibodies inhibit binding of adenylate cyclase to the membrane, and (iv) IRA1 and adenylate cyclase comigrate on Sepharose 4B.

scholarly journals Stimulus-secretion coupling in the neurohypophysis of the jerboa Jaculus orientalis.

1994 ◽  
Vol 195 (1) ◽  
pp. 19-34
Author(s):  
A Raji ◽  
J J Nordmann
Keyword(s):  
Time Course ◽  
Physiological State ◽  
Nerve Endings ◽  
Neurosecretory System ◽  
Channel Blockers ◽  
Vasopressin Release ◽  
Oxytocin Release ◽  
Stimulus Secretion Coupling ◽  
Stimulation Of

1. In many mammals, severe dehydration is known to cause exhaustion of the vasopressin content of the neural lobe. Here, we have examined the physiological state of the neurohypophysis of the jerboa Jaculus orientalis, a rodent inhabitant of a semi-desert climate. 2. Isolated neurohypophyses and neurosecretory nerve endings were perfused in vitro and vasopressin and oxytocin release were determined by radioimmunoassay. 3. Electrical stimulation of the neurohypophysis with bursts of pulses mimicking the activity of hypersecreting neuroendocrine neurones induced similar increases of secretion in both control animals and animals dehydrated for up to 2 months. Neurohormone release was greatly potentiated when the bursts of pulses were separated by silent intervals. 4. Prolonged stimulation of neurohypophyses from both control and dehydrated animals induced a sustained increase of vasopressin release; in contrast, oxytocin release under similar conditions showed a biphasic secretory pattern consisting of a transient increase that subsequently decreased to a steady level whose amplitude was similar to that for vasopressin. 5. K(+)-induced secretion was largely inhibited by the Ca2+ channel blockers nicardipine and omega-conotoxin, suggesting that in this neurosecretory system both L- and N-type calcium channels play a major role in stimulus-secretion coupling. Depolarization of isolated nerve endings using a fast-flow perifusion system showed that there was no difference in the amplitude and the time course of the secretory response in dehydrated and hydrated animals. 6. The results demonstrate that, despite the climatic conditions in which the jerboas live, their neural lobes retain the capacity to release, upon depolarization of the plasma membrane of the nerve endings, large amounts of neurohormone. It is concluded that the neurohypophyseal peptidergic release system in the dehydrated jerboa functions adequately even under extreme environmental stress.

Excretion in the house cricket: stimulation of rectal reabsorption by homogenates of the corpus cardiacum

1993 ◽  
Vol 185 (1) ◽  
pp. 305-323 ◽  
Author(s):  
J. H. Spring ◽  
S. A. Albarwani
Keyword(s):  
Time Course ◽  
Chloride Transport ◽  
Malpighian Tubule ◽  
Acheta Domesticus ◽  
Rectal Absorption ◽  
K Uptake ◽  
House Cricket ◽  
Tubule Fluid ◽  
Stimulation Of

1. We describe an in vitro perfused preparation of Acheta domesticus rectum which allows direct comparison of Malpighian tubule secretion and rectal absorption under identical conditions. Rectal absorption is stimulated four- to sixfold by corpora cardiaca (CC) homogenates and the stimulated rate is sufficiently rapid to account for all the fluid secreted by the tubules. 2. The time course for increased fluid absorption is similar to that required to stimulate electrogenic chloride transport in locusts and grasshoppers. Chloride is rapidly absorbed by the rectum under all conditions, along with lesser amounts of Na+ and K+. Unlike the situation in locusts, K+ uptake is unaffected by CC homogenates and the stimulated absorbate is NaCl-rich, similar in composition to the NaCl-rich tubule fluid produced under stimulated conditions. The absorbate is always slightly hypo-osmotic to the perfusate, reaching a maximum differential of approximately 15 mosmol l-1 following CC stimulation. 3. The antidiuretic factor that reduces tubule secretion does not promote fluid reabsorption by the rectum.

Possible role of cyclic GMP in stimulus-secretion coupling by salt gland of the duck

1979 ◽  
Vol 237 (5) ◽  
pp. C200-C204 ◽  
Author(s):  
D. J. Stewart ◽  
J. Sax ◽  
R. Funk ◽  
A. K. Sen
Keyword(s):  
Cyclic Amp ◽  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
Salt Gland ◽  
Domestic Ducks ◽  
Stimulus Secretion Coupling ◽  
Stimulation Of

Stimulation of salt galnd secretion in domestic ducks in vivo increased the cyclic GMP concentration of the tissue, but had no effect on cyclic AMP levels. Methacholine, which is known to stimulate sodium transport by the glands both in vivo and in vitro, stimulated ouabain-sensitive respiration in salt gland slices. Cyclic GMP stimulated ouabain-sensitive respiration to the same extent as methacholine. Guanylate cyclase stimulators, hydroxylamine and sodium azide, also stimulated ouabain-sensitive respiration. The stimulation of ouabain-sensitive respiration by methacholine was blocked either by atropine or by removal of calcium from the incubation medium. The stimulation of ouabain-sensitive respiration by cyclic GMP still occurred in the absence of calcium. The above observations seem to indicate that cyclic GMP acts as a tertiary link in the process of stimulus-secretion coupling in the tissue.

scholarly journals Alteration of Platelet Cyclic AMP (cAMP) by Ethanol

1977 ◽  
Author(s):  
D.H. Cowan ◽  
M. Kikta ◽  
D. Baunach
Keyword(s):  
Cyclic Amp ◽  
Platelet Function ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Platelet Dysfunction ◽  
Camp Metabolism ◽  
Subnormal Level ◽  
Camp Levels ◽  
Stimulation Of

Studies of cAMP in human platelets exposed to ethanol were done to assess one possible mechanism for ethanol-related platelet dysfunction. Ingestion of ethanol by 3 subjects produced blood ethanol levels from 65-76 mM. Thrombocytopenia occurred in 1 subject and impaired platelet function occurred in all. Platelet cAMP decreased 36,51, and 59% below control levels. Infusion of ethanol to 2 normals produced blood ethanol levels of 43 mM and decreased platelet cAMP by 15% and 22%. Incubation of normal platelets with 86 mM ethanol in vitro decreased cAMP from 13.8 ± 2.9 (1 SD) to 9.4 ± 3.5 (p<0.02). By contrast, ethanol did not impair the increase in cAMP that occurred with 1.3 μM PGE1. Further, ethanol enhanced the increase in cAMP produced by 2.0 mM papaverine (Pap) by 160-220% and that produced by Pap + PGE1 by 58%. Dopamine, 0.1 mM, caused a 23% decrease in the basal level of cAMP, a 31% decrease below the subnormal level of cAMP seen with ethanol alone, and a 41% reduction in the increased level of cAMP produced by Pap + ethanol. The effect of ethanol on platelet cAMP metabolism is complex. Ethanol reduces basal levels of cAMP, does not decrease elevated levels that result from PGE1 stimulation of adenylate cyclase, and augments the inhibitory effect of Pap on platelet phosphodiesterase (PDE). Despite causing a decrease in basal cAMP levels, ethanol may impair platelet function by potentiating the effect of agents or other conditions which increase cAMP. The effect of ethanol on Pap-stimulated PDE activity may be blocked by dopamine, a neuropharmacologic agent that is actively accumulated by platelets.

Stimulation of aromatase activity in the fetal rat testis by cyclic AMP and FSH

1988 ◽  
Vol 118 (3) ◽  
pp. 485-489 ◽  
Author(s):  
J.-P. Weniger ◽  
A. Zeis
Keyword(s):  
Cyclic Amp ◽  
Specific Activity ◽  
Isotopic Dilution ◽  
Aromatase Activity ◽  
Dibutyryl Cyclic Amp ◽  
Rat Testis ◽  
Fetal Rat ◽  
Fetal Rats ◽  
Stimulation Of

ABSTRACT The effect of dibutyryl cyclic AMP and FSH on oestrogen biosynthesis was investigated in testes from 18- to 21-day-old fetal rats cultured in vitro in the presence of tritiated testosterone. Oestrone and oestradiol concentrations were measured by determination of constant specific activity after isotopic dilution. Dibutyryl cyclic AMP and FSH markedly stimulated the conversion of testosterone into both oestrone and oestradiol at all stages studied. Oestradiol synthesis was stimulated by two- to sevenfold, while stimulation of oestrone synthesis was even greater. The results demonstrate that the aromatase enzyme system of the fetal rat testis responds to cyclic AMP and FSH. J. Endocr. (1988) 118, 485–489

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