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Biomedical subjects

M Da Prada

Publications and source records attributed to M Da Prada.

At least 127 records · Page 7Linked to original sources
PubMed1979

Plasma catecholamine and parathyroid hormone responses in cattle during treadmill exercise at simulated high altitude.

When steers were exposed to treadmill exercise at a simulated altitude of 3500 m, plasma concentrations of epinephrine and norepinephrine as well as of parathyroid hormone increased within minutes. Heart rate, erythrocyte number and plasma lactic acid level rose at the same time, whereas plasma free fatty acids showed a later increase. It is concluded, that the elevated parathyroid hormone levels were probably caused by sympathetic stimulation.

Altitude↗
PubMed1979

Storage pool disease: comparative fluorescence microscopical, cytochemical and biochemical studies on amine-storing organelles of human blood platelets.

The platelet content of ATP, ADP, serotonin (5-HT), dopamine, noradrenaline and adrenaline as well as the net uptake of radiolabelled 5-HT and mepacrine were subnormal in six patients with Storage Pool Disease (SPD). Fewer amine-storing organelles were found by fluorescence microscopy with the fluorescent probe mepacrine and by electron microscopy with a cytochemical (uranaffin) reaction specific for 5'-phosphonucleotides. Both methods showed that SPD platelets have atypical organelles with a reduced capacity to store amines, 5'-phosphonucleotides and mepacrine. The changes were most marked in platelets of the two patients who also had oculocutaneous albinism.

Adenosine Diphosphate↗
PubMed1979

Content and subcellular localization of catecholamines and 5-hydroxytryptamine in human and animal blood platelets: monoamine distribution between platelets and plasma.

1 The content of adrenaline (Ad), noradrenaline (NA) and dopamine was measured in human, guinea-pig, cat, rabbit and rat blood platelets by a highly sensitive and specific radioenzymatic method.2 In all platelet specimens analyzed, the content of the three catecholamines (CA) was several thousand times lower than that of 5-hydroxytryptamine (5-HT).3 In basal conditions, the NA concentration in platelets and plasma always exceeded that of Ad and dopamine.4 In rat and rabbit platelets, Ad, NA and dopamine were present only in the free (unconjugated) form.5 Platelets of rats with storage pool deficiency (Fawn-hooded) contained much less 5-HT and CA than normal rat platelets.6 Following restraint stress, platelets of Fawn-hooded rats, in contrast to normal rat platelets, did not accumulate CA in spite of a dramatic rise in plasma CA.7 Reserpine, a monoamine depletor, released CA as well as 5-HT from rabbit platelets in vivo.8 Subcellular fractionation experiments with rabbit platelets indicate that both CA and 5-HT are most concentrated in the fraction consisting of pure 5-HT organelles.9 Both in humans and rabbits the concentration gradient between platelets and plasma was much lower for CA than for 5-HT, indicating that a high affinity transport mechanism operates in vivo for 5-HT but not for CA.10 In conclusion, the present data show that both human and animal platelets contain Ad, NA and dopamine. The bulk of the CA seems to be stored as unconjugated amines together with 5-HT, histamine and p-octopamine in a multitransmitter storage site, namely the 5-HT organelle.

Adult↗
PubMed1978

Fluorescence microscopical study of 5-hydroxytryptamine storage organelles in mepacrine-incubated blood platelets of beige mice (Chediak-Higashi syndrome).

The number and fluorescence intensity of fluorescent granules (5-HT storage organelles) of mepacrine-incubated blood platelets of beige mice (Chediak-Higashi syndrome) are decreased compared to those of control mice platelets. This indicates both quantitative and qualitative changes of the 5-HT organelles, namely a reduced number and a reduced storage capacity, respectively.

Animals↗
PubMed1978

Parathyroid hormone responses to catecholamines and to changes of extracellular calcium in cows.

Modifications of the plasma level of immunoreactive parathyroid hormone (PTH) in cattle were induced by changes of the plasma concentrations of epinephrine, isoproterenol, or calcium. During abrupt hypocalcemia, PTH, obtained by infusions with ethylene glycol-bis (beta-aminoethylether) N, N'-tetraacetate (EGTA), increased during the first 4-8 min. After a transient decline, the hormone levels rose again and remained elevated. Infusions of calcium suppressed the hypocalcemia-induced augmentation of PTH levels within a few minutes. Prolonged epinephrine (and isoproterenol) infusions also rapidly increased PTH levels, however, in this case, they returned to basal concentrations after 50-60 min. Additional epinephrine infusions could not further raise PTH values. Moreover, three short-lasting infusions of epinephrine (7 min each), given at 30-min intervals, increased PTH levels to the same extent, whereas additional infusions were much less effective. The PTH response to epinephrine was completely restored, when the interval after a prolonged epinephrine infusion had been prolonged to > 100 min. During moderate hypocalcemia, occurring at the end of EGTA infusions and lasting for 90 min, the PTH response to a short-lasting epinephrine infusion (7 min) was more pronounced than in normocalcemic animals. During severe hypocalcemia, in which superimposed short-lasting infusions of EGTA (7 min) led to an additional abrupt fall of plasma calcium concentrations but not to a corresponding additional rise of the PTH levels, epinephrine rapidly and further increased PTH concentrations. On the other hand, at the end of prolonged infusions of epinephrine, when additional infusions of epinephrine were ineffective in raising PTH levels, EGTA-induced hypocalcemia consistently increased PTH concentrations. The EGTA-induced augmentation of PTH levels was enhanced by epinephrine and isoproterenol but not by propranolol. The present findings indicate, that variations of the extracellular calcium concentrations and beta-adrenergic agonists modify PTH levels by two different and independent mechanisms. On the other hand, it appears that the magnitude of change of the PTH levels to either stimulus is partially modulated by exposure to the other.

Animals↗
PubMed1978

Effects of alpha-adrenergic stimulation and blockade of plasma parathyroid hormone concentrations in cows.

Experiments were designed to investigate responses of immunoreactive parathyroid hormone (PTH) during alpha-adrenergic stimulation and blockade in cows. Alpha-adrenergic agonists (methoxamine, phenylephrine and noradrenaline, the beta-adrenergic action of which was blocked by propranolol) did not change PTH and free fatty acid levels, whereas they characteristically increased the blood pressure and decreased the heart rate. In contrast, alpha-adrenergic blockade by phentolamine progressively increased PTH levels. The elevated PTH concentrations, associated with increased plasma noradrenaline and free fatty acid levels, rising heart rate and decreasing blood pressure, indicated that all these changes can be related to a beta-adrenergic stimulatory mechanism. Beta-adrenergic stimulation was presumably responsible for the initial elevation of PTH concentrations, whereas, during the later phase of the phentolamine infusions, a concomitant hypocalcaemia probably also produced a stimulatory effect.

Adrenergic alpha-Agonists↗
PubMed1977

Uranaffin reaction: a new cytochemical technique for the localization of adenine nucleotides in organelles storing biogenic amines.

Amine storage organelles of aldehyde-fixed rabbit platelets have a strong affinity for uranyl ions before their dehydration and appear highly electron-dense when examined by electron microscopy; both the matrix and membrane of these organelles are intensely stained. This affinity, which is also shown by platelets of other species, including healthy reserpinized platelets, which contain no cytochemically demonstrable amine, show a positive uranaffin reaction. However, platelets and megakaryocytes of strains with storage pool deficiency (low adenosine-5'-triphosphate), including patients with Hermansky-Pudlak syndrome, are uranaffin negative. The cytochemical reaction, probably the result of an interaction between UO2++ ions and phosphate groups of 5'-phosphonucleotides, is also observed in adrenal medulla, sympathetic nerve terminals and ganglion cells, suggesting that the technique will be of considerable value in identification of aminergic neurons and in further elucidation of amine storage mechanisms.

Adenosine Triphosphate↗
PubMed1977

Mepacrine, a tool for investigating the 5-hydroxytryptamine organelles of blood platelets by fluorescence microscopy.

In the blood platelets of various species exposed to mepacrine, the average number of green-yellow fluorescent granules (probably identical with the 5-hydroxytryptamine [5-HT] storage organelles) corresponded to that of flashes emitted by the platelets on prolonged irradiation with violet-blue light. In platelets of fawn-hooded rats the number of granules did not markedly differ from that of normal rat platelets, but the fluorescence intensity and the uptake of mepacrine in vitro showed a marked decrease and the flashes were less numerous. The heavy population of human platelets exhibited considerably more granular structures than the light population. The data suggest that (1) in normal, mepacrine-loaded platelets one flash corresponds to one 5-HT organelle and (2) mepacrine is a useful tool for investigating the number and function of the 5-HT organelles in live platelets and possibly for studying platelet age.

Animals↗
PubMed1976

[Dynamics of plasma catecholamines and beta-adrenoreceptor functions. Use of a new radio-enzymatic micro-method].

The new method for simultaneous determination of noradrenaline (NA), adrenaline (A) and dopamine in 50 mul plasma has proved specific, sensitive and readily reproducible. In 6 healthy volunteers NA was 190 pg/ml and A 63 pg/ml in the supine position and rose during graded upright exercise to NA 819 pg/ml and A 161 pg/ml (150 watts; p less than 0.001 and less than 0.05 respectively). NA and A paralleled exercise tachycardia (r = 0.894; p less than 0.001) and renin stimulation (r = 0.620; p less than 0.001). 21 patients with essential hypertension exhibited relatively higher NA concentrations both at rest and during graded exercise (p less than 0.05 for both). Exercise-stimulated NA and A further rose following 0.15 mg/kg propranolol i.v. (p less than 0.01 and p less than 0.05 respectively). With increasing age and blood pressure, plasma catecholamine concentrations rise while the reactivity of heart rate and renin secretion decreases. Acute pharmacological blockade of beta-adrenoreceptors increases catecholamine overflow in similar fashion to the physiological dissociation of plasma catecholamines and adrenoceptor responsiveness.

Adult↗