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Biomedical subjects

C Sachs

Publications and source records attributed to C Sachs.

At least 73 records · Page 4Linked to original sources
PubMed1989

Inadequate algorithm: a cause for 'incorrect pH 7.40 correction' in ionized calcium analysers.

As a preliminary step in a study of the effects of calcium ligands on the pH standardization of ionized calcium (Ca2+) measurements in blood, the slope of logCa2+ = f(pH) linear relationship characterizing the pH-sensitive calcium buffer capacity of the specimen was investigated in 12 serum pools on three different instruments. The pH 7.40 correction line should be horizontal. This was the case for the ICA-2 but not for the ICA-1 and the NOVA-8. The discrepancy was caused by an incorrect setting of the built-in slope correction factor in the ICA-2; coincidentally, its value was close to the effective slopes of the serum pools used in the study. Thus, the 'abnormal' behaviour of the ICA-1 and the NOVA-8 was caused by an inadequacy of the built-in algorithm to the characteristics of our serum pools. These findings lead us to reconsider the use of a fixed and constant correction factor to normalize actual ionized calcium values.

Algorithms↗
PubMed1989

Anticoagulant-induced preanalytical errors in ionized calcium determination on blood.

When anticoagulated blood is necessary for ionized calcium (Ca2+) measurements especially in urgent circumstances, the type (sodium or 'calcium-titrated' heparinate) as well as the form (aqueous or dry) of anticoagulant induce preanalytical errors. To quantify these modifications Ca2+ was measured in three aqueous solutions and in three serum pools in different 'sampling' conditions. Incomplete syringe filling and specimen volume/syringe nominal volume ratio effects were tested. Syringes were rinsed (i) with saline to yield 'pure' dilution effect ('solution-dilution'); (ii) with sodium heparinate to study binding; (iii) with calcium-titrated heparinate to evaluate 'calcium-distortion'. All types of errors increased when syringes were not filled to their nominal volume, especially on small-sized specimens. Detailed tables provide percentage error values for all sampling conditions. Thus, 'solution-dilution' can reach -5%; binding is always important (-15 to -50%). 'Calcium-distortion' is minimal, around 1.25 mmol/l Ca2+, but can reach -7% for high Ca2+ and +10% for low Ca2+.

Anticoagulants↗
PubMed1988

Autonomic cardiovascular responses in antecedent poliomyelitis.

Autonomically mediated cardiovascular responses were evaluated in 20 subjects with antecedent poliomyelitis and compared to data from an age- and sex-matched control group. The polio subjects had a lower heart rate response to the Valsalva manoeuvre but the same respiratory sinus arrhythmia as the controls. From this it is concluded that the polio subjects had a normal vagal function. The polio subjects had a greater initial heart rate increase but the same blood pressure response to the orthostatic position as the controls. This indicates a normal function of the sympathetic nerves. The greater heart rate increase is most likely caused by a displacement of blood to the legs because of muscle atrophy. The polio subjects had a smaller blood flow increase as an initial response to an isometric handgrip than the controls. This might be attributed to a reduced beta-adrenergic vasodilation, possibly due to a reduced central vasomotor drive. It is concluded that subjects with antecedent poliomyelitis have no significant dysfunction of the peripheral autonomic nerves. Thus, there is no deterioration of the peripheral autonomic nerve function in parallel with the progressive muscle atrophy and paralysis earlier described in post-polio subjects.

Adult↗
PubMed1987

Effects of prolactin on Na-K-ATPase activity along the rat nephron.

To test prolactin (PRL) action on osmoregulation in mammals, we evaluated in the rat the effect of this hormone on a major enzyme in renal regulation of water and electrolyte: renal Na-K-ATPase. Enzyme activity was determined by cytochemistry in medullary ascending limb (MAL) and distal convoluted tubule (DCT) from rats treated either by bromocriptine, or by PRL. Three hours after a bromocriptine injection (0.1 mg/100 g IP) a significant decrease of Na-K-ATPase activity is observed in both MAL (80% of control values, p less than 0.001) and DCT (78% p less than 0.01). Reciprocally, a significant (p less than 0.001) increase in enzyme activity is induced 3 h after a single PRL injection (140 micrograms/100 g IM), in both segments (MAL: 165%, DCT: 172% of control activities) and persists 6 h after the injection (MAL: 130%, DCT: 118%). Na-K-ATPase activity was correlated to plasma PRL levels (r = 0.78 in DCT, r = 0.89 in MAL). A direct effect of PRL on the tubule is suggested by results from experiments in which PRL, at various concentrations, is added in vitro on renal slices before Na-K-ATPase activity measurements. The increase in Na-K-ATPase activity exhibits a log-dose dependency with PRL concentration (p less than 0.01) and is still observed when AVP antagonist is added before PRL incubation, ruling out the possible role of AVP contamination of PRL. These results suggest a direct effect of PRL on renal Na-K-ATPase in MAL and DCT.

Aldosterone↗
PubMed1987

Parathyroid response to aluminum in vitro: ultrastructural changes and PTH release.

The endocrine response of porcine parathyroid gland tissue slices in vitro to aluminum was studied by electron microscopy and radioimmunoassay of PTH. Medium aluminum concentrations were 20 to 500 ng/ml covering the range corresponding to concentrations reported in the plasma of aluminum-intoxicated hemodialyzed patients. Aluminum inhibited iPTH-release and caused severe cell alterations. This inhibition was incomplete and there was an aluminum-insensitive iPTH-release capacity. This phenomenon seemed to be due to heterogeneous parathyroid cell population as regards aluminum sensitivity, perhaps linked to the spontaneous asynchronous cyclic parathyroid cell changes. Sensitivity to aluminum was modulated by the extra-cellular calcium concentration. Sensitivity to extra-cellular calcium concentration variations persisted in aluminum intoxicated tissues. The severity of the observed cell lesions induced by high concentrations of aluminum suggested that the recovery of an iPTH-release capacity when parathyroid tissue was withdrawn from a toxic environment and switched to aluminum-free media is more likely to be due to activation of a "less-sensitive to aluminum" cell pool than to a true reversibility of the toxic effect.

Alum Compounds↗
PubMed1987

Autonomic cardiovascular responses in distal myopathy (Welander).

Autonomically mediated cardiovascular responses were evaluated in 9 patients with Welander distal myopathy and compared to data from an age- and sex-matched control group. The myopathy patients had a normal respiratory sinus arrhythmia and a normal heart rate response to the Valsalva menoeuvre, indicating a normal vagal function. They had a normal initial heart rate response to the orthostatic position, indicating a normal function of the sympathetic nerves. The main difference between the groups was found in the orthostatic position. The myopathy patients reacted with a greater increase in systolic blood pressure and a smaller heart rate increase than the controls. This suggests an altered peripheral vasomotor function, possibly with a more predominant activation of alfa than beta adrenergic receptors leading to vasoconstriction. In addition, a low forearm blood flow at rest and a les pronounced blood flow increase during the isometric handgrip were found in the myopathy patients. This finding could also be explained by proneness to vasoconstriction. It is concluded that patients with Welander distal myopathy have no signs of dysfunction of the peripheral autonomic nerves.

Adult↗
PubMed1987

The occurrence of HLA-DR2 in clinically established narcolepsy.

Of 25 patients with a longstanding diagnosis of narcolepsy 23 were HLA-DR2 positive. The 2 DR2 negative patients were misdiagnosed when retrospectively interviewed. HLA-DR2 determination is a valuable tool for ascertaining the narcolepsy diagnosis in uncertain cases.

Adult↗
PubMed1987

Hypocalcaemic effect of WR-2721, S-2 (3-aminopropylamino) ethyl-phosphorothioic acid in an anuric haemodialysis patient.

The radio- and chemoprotective agent, S-2 (3-aminopropylamino) ethyl-phosphorothioic acid (WR-2721) has been reported to lower hypercalcaemia in patients with cancer, probably by increased renal calcium excretion and decreased parathyroid hormone (PTH) secretion and bone calcium resorption. The present study reports the first clinical use of WR-2721 in an anuric haemodialysis patient with severe secondary hyperparathyroidism. The drug was administered intravenously at different doses, i.e. 150, 300, and 500 mg/m2. The infusion was followed by a striking decrease of plasma immunoreactive (i) PTH within 30 min. The nadir of the iPTH decrease was reached at 60 min and was followed by a steady return to previous values. Serum ionised calcium decreased more progressively from 1.55 mmol/l initially to 1.30 mmol/l at 4 h after the 300-mg dose, remained at that level at 24 h, but rose again to pre-infusion values after 48 h. The extent and duration of the decrease in plasma iPTH and ionised calcium were dose-dependent. The circulating iPTH at 24 h was inversely related to the corresponding plasma ionised calcium concentration and had risen above preinfusion values at that time. Plasma concentrations of three other hormones, i.e. renin, insulin, and prolactin, were not affected by the administration of WR-2721. In conclusion, WR-2721 can induce a decrease in serum ionised calcium in the absence of any excretory kidney function. The rapid effect of the drug on circulating iPTH supports the notion of an interference with PTH secretion or catabolism.

Amifostine↗
PubMed1985

Autonomic cardiovascular responses in old age.

The effect of age on autonomically mediated cardiovascular responses to certain manoeuvres was studied in 15, healthy, old men and women (60-80 years). The results were compared with groups of healthy young (about 25 years) and middle-aged (about 45 years) subjects. There was no significant reduction in cardiovascular responses between the young and middle-aged groups. Respiratory sinus arrhythmia, and heart rate, blood-pressure and contralateral forearm blood flow increases to isometric hand grip, as well as the heart rate decrease during a dive reflex test, were significantly attenuated in the old age group. The Valsalva ratio, and the heart rate and blood-pressure changes during an 8 min orthostatic test did not differ between the old and the two younger age groups. There seems to be only a moderate attenuation of autonomic cardiovascular responses to about 60 years, after which there is a more rapid decline. The difference in reduction between different responses, even those mediated by the same type of autonomic nerve, suggests that the decreased responses are not due to an isolated impaired function of the peripheral autonomic nerve. The impairment may be due to the receptor organ or a combination of defects in function of several parts of the autonomic nervous system in old age.

Adult↗
PubMed1985

Cardiovascular responses and plasma catecholamines in old age.

Plasma catecholamines and haemodynamic responses to isometric handgrip, orthostatic body position and dynamic cycle exercise were studied in 10 healthy old men (mean age 71 years) and 10 healthy young men (mean age 26 years). At rest, plasma noradrenaline (NA) was significantly higher in the old age group. During handgrip there were greater increases in heart rate and blood-pressure in the young rather than in the old men, while forearm blood-flow increase was similar in the two age groups, and there was no increase in NA in either groups. In the orthostatic position heart rate increased in the young men only, and forearm blood-flow decreased more in the young than in the old men. NA concentration increased similarly in both age groups. During dynamic exercise the increases in both the heart rate and the blood-pressure, at similar relative submaximal as well as maximal loads, were smaller in the old men. At maximal work NA and adrenaline (A) concentrations were higher in the young men, while at the lowest load, NA concentration was higher in the old men. Similar increases in exercise heart rate, blood-pressure or rate of perceived exertion corresponded to lower increases in NA in the old men. It can be concluded that old men, compared with young men, have a reduced maximal capacity to release NA and A upon provocation. In addition, the sensitivity for catecholamines in the target organ is reduced with age, as suggested by the smaller increases in heart rate and blood-pressure for a given increase in NA during exercise. The higher basal NA level and the higher NA level, during moderate provocation, may suggest a compensatory increase in activity.

Adult↗
PubMed1985

Autonomic cardiovascular responses in parkinsonism: effect of levodopa with dopa-decarboxylase inhibition.

Autonomically mediated cardiovascular responses to certain manoeuvres were studied in 20 parkinson patients, 24 h off levodopa-decarboxylase inhibitor medication and again one h after medication. Results were compared with 15 healthy control subjects. The heart rate at rest was higher in parkinson, the respiratory sinus arrhythmia was lower, while the Valsalva ratio, the heart rate and blood pressure responses during an orthostatic test and the heart rate response to a dive reflex test were normal. These findings indicate a normal function of peripheral autonomic nerves and a possible central parasympathetic dysfunction. There were significantly attenuated responses of heart rate, blood pressure and contralateral forearm blood flow to an isometric handgrip. Since the peripheral autonomic nerves seemed to be normal, these results could be related to a reduced central command and/or diminished stimulation of postulated peripheral ergoreceptors in parkinsonism. There was no major effect on the cardiovascular responses by the acutely administered medication.

Aged↗
PubMed1985

Autonomic function in amyotrophic lateral sclerosis: a study of cardiovascular responses.

Autonomically mediated cardiovascular responses were evaluated in 15 ALS patients and compared with 15 healthy subjects. The respiratory sinus arrhythmia, the heart rate response to a Valsalva manoeuvre, to isometric handgrip and to a dive reflex test was normal, indicating a normal function of vagal nerves. The heart rate and blood pressure responses during an orthostatic test were normal, indicating a normal function of sympathetic nerves. The increase in blood pressure and blood flow in the contralateral forearm which occurs on handgrip in healthy subjects was reduced in the ALS patients. The cause of this is unclear, but could be related to decreased function of "ergoreceptors" or altered vascular reactivity in atrophic muscle.

Aged↗
PubMed1985

[Introduction to the use of selective electrodes in clinical biology].

The relatively recent distribution of apparati which allow cation measurement by electrometry presents the biologist with a certain number of difficulties inherent to this methodology. A review of the principles of electrochemistry, limited to the facts necessary to master use of these apparati and avoiding the dissipated effort inevitably incurred by consulting treatises, is of an evident practicality. The points concerning, in particular, application in clinical biology have been treated in detail, whether they involved the definition of direct and indirect potentiometries, or the concepts of activity and of concentration, or the explanation of the actual problems posed by the plasma/plasmatic water difference and by electrometry/flame photometry comparison measurement. A survey of the different types of standard electrodes in biology completes this works.

Blood Chemical Analysis↗