Control of protein synthesis by extracellular Na+ in cultured fibroblasts.

In chick embryo fibroblasts (CEFs), a partial substitution of extracellular Na+ with other cations or carbohydrates decreased the intracellular Na+ content without altering the K+ level. Concomitantly, a significant decrease in the serum-dependent rate of protein synthesis occurred. This phenomenon appeared to be quickly reversible upon reconstitution of the correct extracellular Na+ concentration in the culture medium.

[The physiopathologic bases of the neurotoxicity of phosphorus chelating agents containing soluble aluminum salts in patients with renal insufficiency].

To what extent can damage to the central and peripheral nervous systems be ascribed to chronic aluminum (Al) intoxication taken as a chelating agent for phosphorus, to limit hyperphosphatemia in uremic patients? Since Al is normally eliminated by the renal route, its accumulation in uremia has to be ascribed to a reduced or abolished renal clearance of the metal, which results in preferential toxicity for certain tissues, especially nervous tissue, which shows difficulty in eliminating Al, even after intake has been stopped. This review discusses, on the basis of toxicologic, experimental and clinical data, the possible pathogenic steps of Al neurotoxicity in uremia, considering: the damage to axonal transport in which Al intoxication tends to affect the components of the cytoskeleton, the polymerization phase of the alpha and beta tubulin constituents of neurotubules, and the normal translocation of neurofilaments from the perikaryon to more distal positions of the axon; the abnormalities in the brain pool of adrenergic, cholinergic and GABA neurotransmitters; the increase in permeability and changes in perm-selectivity of the blood-brain-barrier, with further loss of neurotransmitters and with acquisition, from the systemic circulation, of neurotransmitter-like substances such as hormones, monoamines and peptides, which may adversely modulate synaptic and membrane functions; the cerebral energy metabolism and particularly the hexokinase reaction, by Al replacement of the Mg-ion in the Mg-ATP complex, so that phosphorylation of glucose to G6P is blocked; the interaction of Al with calmodulin by displacement of the Ca-ion and subsequent formation of a stable Al-calmodulin complex with a cytotoxic effect due to the increase in the intracellular calcium concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased sensitivity to protein kinase C activation in aortas of spontaneously hypertensive rats.

The aortic muscle of spontaneously hypertensive (SHR) and normotensive control (WKY) rats was stimulated with phorbol esters and the contractile response was measured as isometric tension. Phorbol esters are known activators of protein kinase C. The aortas of SHR were characterized by the following distinct alterations in the response to phorbol myristate acetate: (1) increased sensitivity: half-maximal force was achieved at 62 +/- 6 nmol/l phorbol myristate acetate in SHR and 105 +/- 8 nmol/l in WKY; (2) increased contractility: the maximal force developed by phorbol myristate acetate was greater in SHR aortas (1.

The vasodilator effect of human atrial natriuretic factor (99-126) on human omental arteries.

The effect of synthetic human atrial natriuretic factor [ANF-(99-126)] on human omental arteries was investigated. The compound produced concentration-dependent relaxation, 10, 50 and 90% of maximum effect being observed at about 1, 10 and 100 nmol/l, respectively. These concentrations are considerably higher than those measured by radio-immunoassay in human plasma, even under extreme conditions (0.

Muscle and serum magnesium in pulmonary intensive care unit patients.

Muscle specimens by means of quadriceps femoris needle biopsy and blood samples were obtained in 32 patients consecutively admitted to a pulmonary ICU for chronic obstructive pulmonary disease and acute respiratory failure, and in 30 age and sex-matched healthy control subjects. Muscle magnesium (Mg) and potassium (K) content was assessed by atomic absorption spectrophotometry; serum electrolytes were also measured. The presence of clinical and biochemical correlates of low serum and muscle Mg was investigated.

Dietary sodium change in primary aldosteronism. Atrial natriuretic factor, hormonal, and vascular responses.

Atrial natriuretic factor (ANF) may be physiopathologically involved in several clinical conditions including human hypertension. However, few data are available regarding this putative hormone and its relationship to aldosterone, blood pressure, and vascular responsiveness to alpha-adrenergic receptor stimulation in primary aldosteronism, a volume-expanded, low-renin model of human hypertension. For this reason, the behavior of supine and upright plasma ANF as related to aldosterone, blood pressure, and forearm alpha-adrenergic sensitivity (plethysmographic technique) to intra-arterial norepinephrine infusion was studied in eight patients with primary aldosteronism (five with adenomas, three with hyperplasia) before and at the end of two sequential 1-week low (20 mmol/day) and high sodium (200 mmol/day) diet periods.

Myoplasmic Ca2+-force relationship studied with fura-2 during stimulation of rat aortic smooth muscle.

The intracellular Ca indicator fura-2 was used for simultaneous measurements of intracellular free Ca (Ca2+i) and force in arterial smooth muscle. Rat aortic medial rings were submitted to fluorometry in a geometrical arrangement resembling that of adherent cell layers. A rigid force-transducing system served to immobilize the tissue and record the developed force quasi-isometrically.

Enhancement of mitochondrial tyrosine kinase activity following viral transformation.

A tyrosine protein kinase activity has been detected in the mitochondrial fraction purified from normal and virus-transformed cultured cells. The addition of serum to cells whose growth was restricted by serum limitation induced a marked decrease of tyrosine kinase activity associated with the mitochondrial fraction. At all the culture conditions tested this enzyme activity always resulted several fold higher in the virus-transformed cells than in the normal parental cells.

Identification and characterization of tyrosine kinase activity associated with mitochondrial outer membrane in sarcoma 180 cells.

Tyrosine protein kinase activity has been detected in the mitochondrial fraction purified from sarcoma 180 tumor cells. Following hypotonic disruption of mitochondria, tyrosine kinase activity appeared to cosediment with monamine oxidase, marker enzyme of mitochondrial outer membrane; meanwhile, serine and threonine kinases were found to be associated with the inner membrane and matrix of mitochondria. Mitochondrial tyrosine kinase(s) showed thermosensitivity and Mn2+ dependence, useful properties for its characterization and separation from tyrosine kinases associated with other particulate fraction and from serine and threonine kinases associated with mitochondria.

Adrenal response in the pathogenesis of arterial hypertension in workers exposed to high noise levels.

Some neuroendocrine parameters known as stress indices were examined in two groups of healthy male workers in a glass factory: the first group (60 subjects) was exposed to high environmental noise levels [greater than 90 dB(A)]; the second group (52 subjects) was exposed to low noise levels [less than 78 dB(A)]. Subjects with histories of cardiovascular diseases or high arterial pressure were excluded from the study. In both groups serum catecholamines and cortisol, and urinary vanilmandelic and homovanillic acids were evaluated at the beginning and middle of morning and afternoon work-shifts, by high performance liquid chromatography with electrochemical detection.

Physiological stimuli to atrial natriuretic peptide secretion in normal humans.

We tested the response of plasma atrial natriuretic peptide (ANP) levels to the following physiological stimuli: postural changes; head-out water immersion; and physical exercise. Plasma ANP (p-ANP) levels were assessed by a specific, sensitive radio-immunoassay. Plasma ANP rose significantly when posture shifted from upright to recumbent for 1 h, but fell again to basal values after 10 min standing.

Multicomponent analysis of amino acid transport System L in normal and virus-transformed fibroblasts.

Amino acid transport System L in both normal Balb/c 3T3 cells and in those transformed with simian virus 40 (SV 3T3) was analysed kinetically under two different experimental conditions. Under 'zero-trans' conditions the results for both types of cell could be interpreted satisfactorily in terms of System L consisting of two components (L1 and L2) characterized by different Km values. This conclusion is in agreement with previous reports.

Hyperosmolarity-induced stress proteins in chick embryo fibroblasts.

The effects of a short exposure of chick embryo fibroblasts to a hyperosmolar medium on monovalent cation content, rate of protein synthesis, and polypeptide pattern expression were studied. The hyperosmolar shock gave an immediate and pronounced inhibition of the protein-synthesis rate temporally related to a marked alteration of the intracellular Na+ content. Following the return of the cells to an osmolar environment, the internal Na+ content quickly resumed its previous level, while the recovery of the protein-synthesis rate was more gradual.