Synthesis and Secretion of Growth Hormone in the Rat Anterior Pituitary

1973 ◽  
Vol 12 (1) ◽  
pp. 23-35
Author(s):  
S. L. HOWELL ◽  
R.B. L. EWART
Keyword(s):  
Growth Hormone ◽  
Adenine Nucleotides ◽  
High Potassium ◽  
Granule Formation ◽  
Intact Cells ◽  
Storage Granule ◽  
Storage Granules ◽  
Ph Range

Partially purified storage granule fractions obtained from rat anterior pituitaries have been utilized to study some properties of the isolated growth hormone granules during incubation in vitro. The isolated granules showed optimal stability at room temperature in the pH range 5.5-6.5 and dissolved progressively with time at a rate which was unaffected by the presence of EDTA, EGTA, ouabain, magnesium ions, or by resuspension in hypotonic media. However, the granules were partially stabilized by the presence of calcium, tyramine or adenosine phosphates; ATP was most effective of the agents tested and induced almost complete stability. Agents known to stimulate the secretion of growth hormone from the intact cells, cyclic 3',5'-AMP, dibutyryl cyclic 3',5'-AMP, theophylline or high potassium concentrations, were each without significant effect on the isolated granules. The granule fraction was ineffective indegrading added 125I-growth hormone over a pH range of 4.5-8.5 and was unable specifically to bind exogenous 125I-growth hormone. Further experiments to elucidate a possible cytological role of nucleotides in stabilization of growth hormone during storage granule formation demonstrated that adenine nucleotides were not constituents of the isolated granules, nor were they secreted into the incubation medium concomitantly with growth hormone. Depletion of intracellular ATP levels has previously been shown to prevent the formation of growth-hormone storage granules, and it is suggested that one role of the nucleotide may be to facilitate the formation and stabilization of storage granules in the Golgi complex by interacting with the growth hormone to induce its precipitation.

Protein, not adenosine or adenine nucleotides, mediates platelet decrease in endothelial permeability

1997 ◽  
Vol 273 (5) ◽  
pp. H2304-H2311 ◽  
Author(s):  
Sandeep Patil ◽  
John E. Kaplan ◽  
Fred L. Minnear
Keyword(s):  
High Performance ◽  
Adenine Nucleotides ◽  
Endothelial Permeability ◽  
Platelet Response ◽  
Cell Monolayers ◽  
Adenosine Receptor Antagonist ◽  
Albumin Clearance ◽  
Protein Permeability

Platelets and platelet-conditioned medium (PCM) decrease endothelial protein permeability in vitro. Adenosine and a >100-kDa protein have previously been implicated as the soluble factors released from platelets that decrease endothelial permeability. The objective of this study was to further investigate the role of adenosine in this platelet response. Measurements of adenosine and its precursor adenine nucleotides by high-performance liquid chromatography were correlated with the assessment of permeability by125I-labeled albumin clearance and electrical resistance across endothelial cell monolayers derived from the bovine pulmonary artery. PCM contained micromolar concentrations of AMP, ADP, and ATP, but adenosine was below detectable levels (≤0.1 μM). Adenosine deaminase, an enzyme that converts adenosine to inactive inosine, or an adenosine-receptor antagonist did not block the platelet- or PCM-mediated decrease in endothelial permeability. A <3-kDa fraction of PCM that contained micromolar concentrations of AMP and ADP did not affect endothelial permeability, whereas a >3-kDa fraction that contained much reduced levels of AMP and ADP significantly decreased permeability. This activity of PCM was sensitive to insoluble trypsin. This study rules out adenosine and adenine nucleotides as primary factors in the platelet-induced decrease in endothelial permeability and suggests that the active factor is a protein.

Role of obestatin on growth hormone secretion: An in vitro approach

2009 ◽  
Vol 390 (4) ◽  
pp. 1377-1381 ◽  
Author(s):  
Yolanda Pazos ◽  
Carlos J.P. Álvarez ◽  
Jesús P. Camiña ◽  
Omar Al-Massadi ◽  
Luísa M. Seoane ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Hormone Secretion ◽  
Growth Hormone Secretion

scholarly journals Role of adenosine deaminase, ecto-(5'-nucleotidase) and ecto-(non-specific phosphatase) in cyanide-induced adenosine monophosphate catabolism in rat polymorphonuclear leucocytes

1980 ◽  
Vol 186 (3) ◽  
pp. 907-918 ◽  
Author(s):  
A C Newby
Keyword(s):  
Adenosine Deaminase ◽  
Adenine Nucleotides ◽  
Specific Inhibitor ◽  
Adenosine Monophosphate ◽  
Polymorphonuclear Leucocytes ◽  
Intact Cells ◽  
Endogenous Substrates ◽  
A Minor

1. The role of adenosine deaminase (EC 3.5.4.4), ecto-(5'-nucleotidase) (EC 3.1.3.5) and ecto-(non-specific phosphatase) in the CN-induced catabolism of adenine nucleotides in intact rat polymorphonuclear leucocytes was investigated by inhibiting the enzymes in situ. 2. KCN (10mM for 90 min) induced a 20-30% fall in ATP concentration accompanied by an approximately equimolar increase in hypoxanthine, ADP, AMP and adenosine concentrations were unchanged, and IMP and inosine remained undetectable (less than 0.05 nmol/10(7) cells). 3. Cells remained 98% intact, as judged by loss of the cytoplasmic enzyme lactate dehydrogenase (EC 1.1.1.27). 4. Pentostatin (30 microM), a specific inhibitor of adenosine deaminase, completely inhibited hypoxanthine production from exogenous adenosine (55 microM), but did not black CN-induced hypoxanthine production or cause adenosine accumulation in intact cells. This implied that IMP rather than adenosine was an intermediate in AMP breakdown in response to cyanide. 5. Antibodies raised against purified plasma-membrane 5'-nucleotidase inhibited the ecto-(5'-nucleotidase) by 95-98%. Non-specific phosphatases were blocked by 10 mM-sodium beta-glycerophosphate. 6. These two agents together blocked hypoxanthine production from exogenous AMP and IMP (200 microM) by more than 90%, but had no effect on production from endogenous substrates. 7. These data suggest that ectophosphatases do not participate in CN-induced catabolism of intracellular AMP in rat polymorphonuclear leucocytes. 8. A minor IMPase, not inhibited by antiserum, was detected in the soluble fraction of disrupted cells.

scholarly journals The C2 domain of the Rsp5 ubiquitin ligase binds membrane phosphoinositides and directs ubiquitination of endosomal cargo

2004 ◽  
Vol 165 (1) ◽  
pp. 135-144 ◽  
Author(s):  
Rebecca Dunn ◽  
Deborah A. Klos ◽  
Adam S. Adler ◽  
Linda Hicke
Keyword(s):  
Ubiquitin Ligase ◽  
Protein Trafficking ◽  
C2 Domain ◽  
Intact Cells ◽  
Membrane Interaction ◽  
Cargo Protein ◽  
Membrane Protein Trafficking ◽  
Cargo Proteins

Ubiquitin ligases of the Nedd4 family regulate membrane protein trafficking by modifying both cargo proteins and the transport machinery with ubiquitin. Here, we investigate the role of the yeast Nedd4 homologue, Rsp5, in protein sorting into vesicles that bud into the multivesicular endosome (MVE) en route to the vacuole. A mutant lacking the Rsp5 C2 domain is unable to ubiquitinate or sort biosynthetic cargo into MVE vesicles, whereas endocytic cargo is ubiquitinated and sorted efficiently. The C2 domain binds specifically to phosphoinositides in vitro and is sufficient for localization to membranes in intact cells. Mutation of a lysine-rich patch on the surface of the C2 domain abolishes membrane interaction and disrupts sorting of biosynthetic cargo. Translational fusion of ubiquitin to a biosynthetic cargo protein alleviates the requirement for the C2 domain in its MVE sorting. These results demonstrate that the C2 domain specifies Rsp5-dependent ubiquitination of endosomal cargo and suggest that Rsp5 function is regulated by membrane phosphoinositides.

scholarly journals Fluorescence analysis of the interaction of isometamidium with Trypanosoma congolense

1993 ◽  
Vol 292 (1) ◽  
pp. 31-35 ◽  
Author(s):  
D Zilberstein ◽  
J Wilkes ◽  
H Hirumi ◽  
A S Peregrine
Keyword(s):  
Time Course ◽  
Fluorescence Analysis ◽  
Trypanosoma Congolense ◽  
Sub Saharan Africa ◽  
Temperature Dependent ◽  
Intact Cells ◽  
Uptake Process ◽  
Sub Saharan

Isometamidium chloride (Samorin) is the only compound recommended for prophylaxis against bovine trypanosomiasis in sub-Saharan Africa. The fluorescence property of this compound was used to investigate the interaction of the molecule with in vitro-derived bloodstream forms of Trypanosoma congolense IL 1180. Incubation of isometamidium with trypanosomes at 37 degrees C for 180 min resulted in a gradual alteration of the lambda max. with time (from 600 to 584 nm) and an increase in the intensity of trypanosome-associated fluorescence of approx. 2-fold. The alteration in fluorescence was temperature-dependent and inhibited by the addition of N-ethylmaleimide. In contrast, with intact cells addition of digitonin caused a rapid increase in fluorescence intensity to approximately four times that observed with intact cells. Uptake of isometamidium was also determined using radiolabelled drug; the results indicated that the time course of the uptake process resembled the fluorescence profile and was temperature-dependent. The results therefore indicate that the alteration of fluorescence is due to interaction of isometamidium with an intracellular component(s) and that isometamidium is transported across the plasma membrane via a protein carrier. The data also indicate that the described fluorescence technique can be used to investigate the role of membrane transport in resistance to isometamidium.

scholarly journals Serotonin and the Control of Salivation in the Blowfly Calliphora

1985 ◽  
Vol 114 (1) ◽  
pp. 307-328
Author(s):  
Barry Andrew Trimmer
Keyword(s):  
Serotonin Receptor ◽  
Channel Blocker ◽  
Cerebral Ganglion ◽  
Thoracic Ganglion ◽  
Calliphora Vicina ◽  
Main Body ◽  
High Potassium ◽  
Heat Stable

The possibility that serotonin acts as a neurohormone stimulating salivation in the blowfly Calliphora vicina was studied by investigation of salivation induced by injections of high-potassium saline. Induced salivation is rapid and appears to be mediated by an active factor released into the haemolymph (High Potassium Salivary Gland Factor: HKSGF) since it is antagonized by cadmium (a calcium channel blocker) and by gramine (a serotonin-receptor blocker). The action of HKSGF on salivary glands in vitro is indistinguishable from that of serotonin: (a) it generates serotoninlike transepithelial potential changes, (b) its effect on salivation is antagonized by gramine, (c) it is as heat stable as serotonin, (d) it has the same solubility in a variety of organic solvents, (e) it is unaffected by incubation with leucine aminopeptidase or trypsin and (d) it is inactivated by rat liver monoamine oxidase type A (a serotonin deaminating enzyme). Radioenzyme assay of haemolymph from high-potassium injected flies shows that the amount of serotonin present could account for all of the retrievable bioactivity. Significant amounts of serotonin were found in the cerebral ganglion, the thoracic ganglion and nerves attached to the thoracic ganglion. Nerve sectioning experiments demonstrated that the abdominal nerves and the anterior nerves supplying the neck muscles are not involved in the normal salivatory response. However the cerebral-thoracic connective must be intact and it is suggested that release of serotonin is effected close to the main body of the thoracic ganglion. Some of the implications of the neurohormonal role of serotonin are discussed.

scholarly journals Tyrosine phosphorylation of lamin A by Src promotes disassembly of nuclear lamina in interphase

2021 ◽  
Vol 4 (10) ◽  
pp. e202101120
Author(s):  
Ching-Tung Chu ◽  
Yi-Hsuan Chen ◽  
Wen-Tai Chiu ◽  
Hong-Chen Chen
Keyword(s):  
Tyrosine Phosphorylation ◽  
Genomic Instability ◽  
Posttranslational Modifications ◽  
Nuclear Lamina ◽  
Serine Phosphorylation ◽  
Lamin A ◽  
Intact Cells ◽  
Structure And Activity

Lamins form the nuclear lamina, which is important for nuclear structure and activity. Although posttranslational modifications, in particular serine phosphorylation, have been shown to be important for structural properties and functions of lamins, little is known about the role of tyrosine phosphorylation in this regard. In this study, we found that the constitutively active Src Y527F mutant caused the disassembly of lamin A/C. We demonstrate that Src directly phosphorylates lamin A mainly at Tyr45 both in vitro and in intact cells. The phosphomimetic Y45D mutant was diffusively distributed in the nucleoplasm and failed to assemble into the nuclear lamina. Depletion of lamin A/C in HeLa cells induced nuclear dysmorphia and genomic instability as well as increased nuclear plasticity for cell migration, all of which were partially restored by re-expression of lamin A, but further promoted by the Y45D mutant. Together, our results reveal a novel mechanism for regulating the assembly of nuclear lamina through Src and suggest that aberrant phosphorylation of lamin A by Src may contribute to nuclear dysmorphia, genomic instability, and nuclear plasticity.

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