scholarly journals REVERSIBLE CHANGES OF PROTEIN CONFIGURATION IN STIMULATED NERVE STRUCTURES

1957 ◽  
Vol 40 (4) ◽  
pp. 635-652 ◽  
Author(s):  
Georges Ungar ◽  
Emil Aschheim ◽  
Stacy Psychoyos ◽  
Dominick V. Romano
Keyword(s):  
Structural Changes ◽  
Sulfhydryl Group ◽  
Protein Molecule ◽  
Alkaline Solutions ◽  
Side Group ◽  
Two Peaks ◽  
Protein Configuration ◽  
Ionization Ratio ◽  
Stimulation Of

Changes in the configuration of proteins were studied by the modifications of the ultraviolet absorption of their alkaline solutions. These were expressed in terms of the ratio O.D.pH12/O.D.pH7, termed side-group ionization ratio (SGIR). This ratio showed two peaks; one at 300 to 305 mµ is known to correspond to the phenolic hydroxyl of tyrosine and another at 245 mµ seems to be caused by the ionization of the sulfhydryl group of cysteine. The SGIR of extracts from electrically stimulated nerve structures was found to be consistently and significantly higher than that of similar extracts from resting tissues. The phenomenon was observed in isolated nerves (frog and rat sciatic) stimulated in vitro and in the cerebral cortex of cats, dogs, and rats after stimulation of their afferents. The increase in SGIR was reversible if the stimulated structures were allowed to rest. Prolonged stimulation, in addition to causing structural changes, also caused breakdown of proteins and the appearance of proteolytic activity. The latter, studied on a synthetic substrate, could be detected even after shorter stimuli, together with configurational changes but without proteolysis. The structural changes detected with the spectrophotometric method are closely related to reversible denaturation as produced by urea. The changes probably involve rupture of hydrogen bonds which loosens the protein molecule and perhaps changes its affinity for different ions. It is possible that such a process may play a role in the mechanism of excitation.

FATE OF NEUROHYPOPHYSIAL GRANULE MEMBRANES AFTER SECRETION IN THE RAT: GENERATION OF A NEW APPARENT ORGANELLE BY FREEZING AND THAWING SECRETORY GRANULES

1981 ◽  
Vol 88 (1) ◽  
pp. 115-123
Author(s):  
JEAN H. LACEY ◽  
B. T. PICKERING
Keyword(s):  
Density Gradient Centrifugation ◽  
Secretory Granules ◽  
Gradient Centrifugation ◽  
Hormone Release ◽  
Freezing And Thawing ◽  
Granule Fraction ◽  
Two Peaks ◽  
Stimulation Of

The contents and membranes of the secretory granules in the rat neurohypophysis were labelled in vivo with [35S]cysteine and [3H]choline respectively. Density-gradient centrifugation of the labelled granules showed the membrane label to be distributed largely between two peaks: one associated with intact granules and one with the characteristics of empty granule envelopes. Stimulation of hormone release in vitro led to the movement of membrane label from the intact granule fraction to the other one, consistent with the recapture of membrane as large vesicles. Freezing and thawing the crude granule fraction, ostensibly to aid osmotic fracture, produced a single membrane component with a density intermediate between the two original fractions.

Early Platelet-Collagen Interactions in Whole Blood and Their Modifications by Aspirin and Dipyridamole Evaluated by a New Method (Basic Wave)

1985 ◽  
Vol 54 (04) ◽  
pp. 799-803 ◽  
Author(s):  
José Luís Pérez-Requejo ◽  
Justo Aznar ◽  
M Teresa Santos ◽  
Juana Vallés
Keyword(s):  
Whole Blood ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
White Blood Cells ◽  
Reversible Aggregation ◽  
Inhibitory Compounds ◽  
Rapid Generation ◽  
Stimulation Of ◽  
Collagen Stimulation

SummaryIt is shown that the supernatant of unstirred whole blood at 37° C, stimulated by 1 μg/ml of collagen for 10 sec, produces a rapid generation of pro and antiaggregatory compounds with a final proaggregatory activity which can be detected for more than 60 min on a platelet rich plasma (PRP) by turbidometric aggregometry. A reversible aggregation wave that we have called BASIC wave (for Blood Aggregation Stimulatory and Inhibitory Compounds) is recorded. The collagen stimulation of unstirred PRP produces a similar but smaller BASIC wave. BASIC’s intensity increases if erythrocytes are added to PRP but decreases if white blood cells are added instead. Aspirin abolishes “ex vivo” the ability of whole blood and PRP to generate BASIC waves and dipyridamole “in vitro” significantly reduces BASIC’s intensity in whole blood in every tested sample, but shows little effect in PRP.

DER EINFLUSS VON RESERPIN AUF DIE ANTITHYREOIDALE WIRKUNG VON KALIUMPERCHLORAT

1962 ◽  
Vol 39 (3) ◽  
pp. 423-430
Author(s):  
H. L. Krüskemper ◽  
F. J. Kessler ◽  
E. Steinkrüger
Keyword(s):  
Thyroid Gland ◽  
Male Rats ◽  
Normal Male ◽  
Tissue Respiration ◽  
List Type ◽  
Morphological Alterations ◽  
Hormone Synthesis ◽  
Stimulation Of

ABSTRACT 1. Reserpine does not inhibit the tissue respiration of liver in normal male rats (in vitro). 2. The decrease of tissue respiration of the liver with simultaneous morphological stimulation of the thyroid gland after long administration of reserpine is due to a minute inhibition of the hormone synthesis in the thyroid gland. 3. The morphological alterations of the thyroid in experimental hypothyroidism due to perchlorate can not be prevented with reserpine.

EFFECT OF ACTINOMYCIN D ON TSH-INDUCED STIMULATION OF THYROIDAL PROTEIN SYNTHESIS IN THE RAT

1974 ◽  
Vol 77 (1) ◽  
pp. 64-70 ◽  
Author(s):  
Gustav Wägar
Keyword(s):  
Protein Synthesis ◽  
Actinomycin D ◽  
The Other ◽  
Leucine Incorporation ◽  
Short Term ◽  
Other Hand ◽  
Thyroid Glands ◽  
Translational Level ◽  
Stimulation Of

ABSTRACT Whether the short-term regulation of thyroidal protein synthesis by TSH occurs at the transcriptional or the translational level was tested by measuring the effect of actinomycin D (act D) on the TSH-induced stimulation of L-14C-leucine incorporation into the thyroidal proteins of rats. TSH was injected 6 h before the rats were killed. The thyroid glands were then removed and incubated in vitro in the presence of L-14C-leucine for 2 h. The pronounced stimulation of leucine incorporation in the TSH-treated animals was depressed as compared with controls but still significant even when the animals had been pre-treated with 100 μg act D 24 and 7 h before sacrifice. On the other hand, act D strongly decreased incorporation of 3H-uridine into RNA. Short-term regulation of thyroidal protein synthesis by TSH appears to be partly but not wholly dependent on neosynthesis of RNA. Hence regulation may partly occur at the translation level of protein synthesis.

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