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T Nickelsen

Publications and source records attributed to T Nickelsen.

28 records · Page 2Linked to original sources
PubMed1988

Influence of dexamethasone on nocturnal melatonin production in healthy adult subjects.

There is no conclusive evidence supporting an interaction between the pineal gland and the hypothalamic-pituitary-adrenal axis. In this study, 11 healthy adults (six women, five men; aged 18-47 years) received a placebo the first night and 1 mg dexamethasone the next night at either 1800 or 2300 h. Administration of 1 mg of dexamethasone was followed by an attenuation of the nocturnal production of melatonin in 9 of 11 subjects. A significant reduction was found between melatonin plasma levels before and after dexamethasone at 0400 h (P less than 0.01, t test for dependent groups). It is suggested that dexamethasone affects nocturnal production of melatonin by means of mechanisms within the pineal gland.

Adolescent↗
PubMed1987

The influence of acute and subchronic administration of various antidepressants on early morning melatonin plasma levels in healthy subjects: increases following fluvoxamine.

The influence of various antidepressants on the morning levels of plasma melatonin was studied in human volunteers after acute and subchronic administration in weekly increasing doses over a period of three weeks. Two monoamine oxidase (MAO) inhibitors (tranylcypromine: irreversible type A and B; pirlindole: reversible type A), two reuptake inhibitors (maprotiline: selective for noradrenaline; fluvoxamine: selective for serotonin) and an alpha 1/alpha 2-adrenergic and serotonin S2-receptor antagonist (mianserin) were administered to groups of 4 to 7 healthy volunteers each. Two hours after a single oral dose at 9 a.m., at the end of each week and one week after the last dose, morning levels of melatonin were measured using a radioimmunological method. In addition, platelet MAO activity and the uptake of 14C-5-HT into platelets were determined. Plasma melatonin concentrations at 9 a.m. were significantly increased after the intake of 150 mg fluvoxamine the night before; whereas, administration of the same dose in the morning did not lead to increases in melatonin during the day. Following subchronic administration, plasma melatonin levels were significantly increased after the 1st (50 mg/day), 2nd (100 mg/day) and 3rd (150 mg/day) week of fluvoxamine intake in comparison to pre-drug levels. No changes in early morning levels of plasma melatonin were measured in the subjects receiving the other antidepressants, after acute as well as after subchronic administration. The results seem to indicate that following fluvoxamine intake at night, the early morning decline of melatonin is delayed. It is suggested that the underlying mechanism leading to a rise in morning melatonin levels cannot be explained solely on the basis of an inhibition of 5-HT reuptake and that other pharmacological properties of fluvoxamine may be involved.

Adult↗
PubMed1985

Combined first-pass and equilibrium radionuclide ventriculography and comparison with left ventricular/right ventricular stroke count ratio in mitral and aortic regurgitation.

Effective and total left ventricular (LV) stroke volume were assessed in 31 patients with verified aortic or mitral regurgitation, or both, and in 22 patients with normal valvular function using combined first-pass and equilibrium radionuclide ventriculography. The difference between these 2 volumes as a fraction of LV stroke volume was taken as the radionuclide regurgitant fraction. The results were compared with the LV/right ventricular (RV) stroke count ratio and with the angiographic regurgitant fraction according to the method of Sandler and Dodge. Radionuclide regurgitant fraction derived from 2 determinations with a time interval of 1 week showed good reproducibility (n = 15, r = 0.96, SEE = 9.1). Sensitivity was 100% for radionuclide regurgitant fraction and 87% for LV/RV stroke count ratio at equal specificity (100%). Radionuclide regurgitant fraction was more sensitive, especially in severely ill patients, in whom additional RV volume overload led to false-low or false-negative ratios. Angiographic and radionuclide regurgitant fraction showed linear correlation (r = 0.79, p less than 0.001). In contrast, because 5 patients had RV volume overload, only a weak correlation could be noticed between angiography and LV/RV stroke count ratio (r = 0.47, p less than 0.05). Excluding these patients, correlation substantially improved (r = 0.74, p less than 0.001). The combination of first-pass and equilibrium radionuclide ventriculography is a sensitive, specific and well reproducible method for the evaluation of mitral and aortic regurgitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Volumetric evaluation of aortic regurgitation by combined first-pass/equilibrium radionuclide ventriculography.

In 16 men with normal valvular function (group 1) and 23 men and one woman with isolated aortic regurgitation (group 2) effective stroke was determined by first-pass radionuclide ventriculography. Total left ventricular stroke volume was derived from equilibrium radionuclide ventriculography using a geometric approach for the end-diastolic volume multiplied by the ejection fraction. The difference between the two stroke volumes as a fraction of total left ventricular stroke volume was taken as radionuclide regurgitant fraction. Radionuclide lv/rv stroke count ratio was calculated as the ratio of end-diastolic-end-systolic count-rate differences from the left and right ventricles. All patients underwent left heart catheterization. Angiographic regurgitant fraction was evaluated by the method of Sandler and Dodge in 16 patients of group 2. In the others, aortic regurgitation was quantified in 5 grades of severity. Group l was classified correctly by both radionuclide regurgitant fraction and lv/rv stroke count ratio (specificity 100%). In group 2 the radionuclide regurgitant fraction was elevated in all (from + 20% to +88%, sensitivity 100%), radionuclide lv/rv stroke count ratio in 19 of 24 cases (from 0.6 to 5.6, sensitivity 79%). The angiographic regurgitant fraction correlated well with the radionuclide regurgitant fraction (r = 0.78), whereas no significant correlation was found between the angiographic stroke volume ratio (i.e. left ventricular stroke volume/cardiac output per beat) and radionuclide stroke count ratio (r = 0.10) due to the high rate of false-negative results of the latter method.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

[Limitations of scintigraphically determined left-ventricular/right-ventricular stroke volume in the evaluation of the severity of aortic valve insufficiency].

Noninvasive evaluation of aortic regurgitation can be performed by the radionuclide determination of the left/right ventricular stroke volume ratio. This ratio proved to have a relatively low sensitivity. Therefore, we conducted a study comprising 25 patients with angiographically verified aortic regurgitation in order to look for characteristics of patients with false-negative results. In 5 patients with aortic regurgitation the scintigraphically determined left/right ventricular stroke volume ratio was within normal range. In 3 other patients with severe regurgitation the radionuclide ratio was distinctly lower when compared with the angiographic stroke volume ratio (calculated from the left ventricular stroke volume and effective stroke volume). Left heart failure was observed in all these 8 patients, 7 of 8 patients showed additional right heart failure. Only 2 of the other 17 patients had signs of left heart failure. In the 8 patients with discrepant results, the roentgenographically determined heart volume was increased (1617 vs 1057 ml; 2p less than 0.001), left ventricular ejection fraction decreased (31 vs 60%; 2p less than 0.001), and mean pulmonary artery and right atrial pressure were elevated (38 vs 18 mm Hg; 2p less than 0.001; 11 vs 6 mm Hg; 2p less than 0.001). We conclude that in patients with aortic regurgitation, congestive heart failure associated with functional pulmonic and tricuspid regurgitation and geometric reasons can lead to a reduced sensitivity of the radionuclide left/right ventricular stroke volume ratio.

Aortic Valve Insufficiency↗
PubMed1983

Studies on cortisol substitution therapy in patients with adrenal insufficiency.

To eight patients with Addison's disease 25 mg of cortisone acetate or cortisol, respectively, was given orally. Thereafter blood samples were taken and analysed for total cortisol, "free" (not protein bound) cortisol and ACTH. Furthermore, urine cortisol excretion and the cortisol binding capacity of the plasma were determined. We found that after the substitution therapy the increase of the plasma cortisol was variable and reached its maximum after 45 to 240 minutes. However, if the resorption time was subtracted the individual differences were less pronounced and plasma cortisol levels above 8 micrograms/dl could be maintained for about six hours. When cortisol was taken instead of cortisone acetate the increase of the plasma cortisol was steeper, decreasing then more rapidly. Plasma "free" cortisol ranged from 2.75 to 6.19% in relation to total cortisol and closely paralleled the level of total cortisol in each patient during the course of the experiment. The excretion of unconjugated cortisol in urine amounted to 56.5 +/- 26 micrograms (SE) and was better correlated to the concentration of "free" cortisol than to total plasma cortisol. The behaviour of plasma ACTH levels was variable. Great fluctuations with high morning levels and good suppression was observed in patients having their substitution tablet only in one single morning dose. From these biochemical data recommendations for the substitution therapy in patients with adrenal insufficiency were given.

Addison Disease↗
PubMed1983

Distribution of testosterone in plasma proteins during replacement therapy with testosterone enanthate in patients suffering from hypogonadism.

In five hypogonadal men treated with 250 mg of testosterone enanthate once every three weeks, total testosterone, "free" testosterone and the percent of testosterone bound to the sex hormone-binding globulin (SHBG) and albumin were determined during three weeks. Immediately after the injection total plasma testosterone rapidly increased about four times the starting level closely paralleled by the concentration of "free" testosterone. We found that if the concentration of SHBG had been reached albumin took over the surplus of the testosterone. Whereas in the first and second week after the injection, high and sufficient levels of testosterone were determined, both total and "free" testosterone approached the lower limit of the normal male range in the third week, i.d. 300 ng/dl, or 5 ng/dl, respectively. In one patient with hypalbuminemia, "free" testosterone decreased during the third week below 3 ng/dl though his total testosterone remained sufficient high. This patient complained about symptoms of androgen deficiency. We explained this with his impaired capacity to bind the excess of testosterone by albumin. We concluded that though the concentration of total testosterone may be sufficient high, "free" testosterone can decrease to very low levels due to disturbance in the distribution of the androgen between the plasma proteins.

Adolescent↗