PubMed Health⌕ Search

Biomedical subjects

G Selke

Publications and source records attributed to G Selke.

7 recordsLinked to original sources
PubMed1999

Decreased memory performance in healthy humans induced by stress-level cortisol treatment.

BACKGROUND: Glucocorticoids (GCs) can regulate hippocampal metabolism, physiologic functions, and memory. Despite evidence of memory decreases during pharmacological GC treatment, and correlations between memory and cortisol levels in certain disease conditions, it remains unclear whether exposure to the endogenous GC cortisol at levels seen during physical and psychological stress in humans can inhibit memory performance in otherwise healthy individuals. METHODS: Randomized, double-blind, placebo-controlled comparison of 2 fixed oral doses of cortisol (40 mg/d and 160 mg/d using split doses to approximate circadian rhythm) given for 4 days to matched groups of healthy subjects (n = 51). Lower-dose treatment approximated cortisol exposure during mild stress, whereas the higher dose approximated cortisol exposure during major stress. Cognitive testing and plasma sampling were done at baseline, after 1 and 4 days of treatment, and after a 6-day washout period, hypothesizing dose-dependent decreases in verbal declarative memory. RESULTS: Cortisol treatment at the higher dose produced reversible decreases in verbal declarative memory without effects on nonverbal memory, sustained or selective attention, or executive function. A significant interaction between time and treatment condition for paragraph recall was explained by treatment-induced differences in performance after 4 treatment days, with lower immediate and delayed recall performance during higher-dose cortisol treatment compared with lower-dose treatment and placebo. CONCLUSIONS: Several days of exposure to cortisol at doses and plasma concentrations associated with physical and psychological stress in humans can-similar to pharmacological GC treatment-reversibly decrease specific elements of memory performance in otherwise healthy individuals.

Adult↗
PubMed1999

Ketamine-induced NMDA receptor hypofunction as a model of memory impairment and psychosis.

N-methyl-D-aspartate (NMDA) glutamate receptor antagonists are reported to induce schizophrenia-like symptoms in humans, including cognitive impairments. Shortcomings of most previous investigations include failure to maintain steady-state infusion conditions, test multiple doses and/or measure antagonist plasma concentrations. This double-blind, placebo-controlled, randomized, within-subjects comparison of three fixed subanesthetic, steady-state doses of intravenous ketamine in healthy males (n = 15) demonstrated dose-dependent increases in Brief Psychiatric Rating Scale positive (F[3,42] = 21.84; p < 0.0001) and negative symptoms (F[3,42] = 2.89; p = 0.047), and Scale for the Assessment of Negative Symptoms (SANS) total scores (F[3,42] = 10.55; p < 0.0001). Ketamine also produced a robust dose-dependent decrease in verbal declarative memory performance (F[3,41] = 5.11; p = 0.004), and preliminary evidence for a similar dose-dependent decrease in nonverbal declarative memory, occurring at or below plasma concentrations producing other symptoms. Increasing NMDA receptor hypofunction is associated with early occurring memory impairments followed by other schizophrenia-like symptoms.

Adult↗
PubMed1999

Glucose-induced increase in memory performance in patients with schizophrenia.

Previous investigations have found that increasing circulating glucose availability can increase memory performance in rodents, healthy humans, and individuals with dementia of the Alzheimer's type. In this study, patients with schizophrenia, healthy control subjects, and controls with bipolar affective disorder were tested using double-blind treatment with either 50 g anhydrous dextrose plus 4 mg sodium saccharin (for "taste") or 23.7 mg saccharin alone, followed by cognitive testing on a complex battery. At this glucose dose, verbal memory performance on a paragraph recall task was increased during the glucose condition relative to the saccharin condition in the patients with schizophrenia; this effect was not detected in either the psychiatric or normal controls. The results provide preliminary support for the hypothesis that memory performance can be improved in patients with schizophrenia by increasing circulating glucose availability and suggest the importance of further evaluation of therapeutic manipulations of glucose availability.

Adult↗
PubMed1998

Dose-dependent cortisol-induced increases in plasma leptin concentration in healthy humans.

BACKGROUND: Leptin is a hormone that regulates fat metabolism and appetite. The secretion of leptin is regulated by adiposity and, in the rodent, by factors such as insulin, beta-adrenergic agonists, and glucocorticoids (GCs). Increased secretion of the endogenous human GC, cortisol, occurs during stress and in disorders such as major depression. Pharmacological GCs can robustly increase plasma leptin concentrations in humans, leading us to hypothesize that cortisol may serve as a physiological regulator of human leptin secretion. METHODS: A randomized double-blind placebo-controlled comparison of 2 fixed oral dosages of cortisol (40 mg/d and 160 mg/d), given for 4 days to matched groups of healthy subjects (n=47). Low-dose treatment approximated GC output during mild stress, while high-dose treatment approximated GC output during maximal stress, spanning a range of GC secretion relevant to physiological stress. RESULTS: Cortisol produced dose-dependent and time-dependent increases in plasma leptin concentrations (time x treatment condition x body mass index; F6,123=10.73; P<.001). Initial treatment-induced increases in plasma leptin concentration returned toward baseline values during 4 treatment days, suggesting tolerance to this GC effect in these healthy subjects. CONCLUSIONS: The results indicate an important role for GCs in the short-term regulation of human leptin secretion. Glucocorticoid-induced increases in leptin secretion suggest a mechanism that may contribute to anorexia and weight loss during stress and disease states such as major depression, if these conditions are associated with sustained increases in plasma leptin concentrations.

Adipose Tissue↗
PubMed1998

The German experience in reference pricing.

Price regulation schemes function both as a means for public authorities to contain costs, and as an economic tool to support the national pharmaceutical industry. This twofold contradictory aim of public intervention in pharmaceutical demand and supply makes such pricing schemes difficult to apply. This article concerns the reference price scheme which concerns setting a price cap for each active ingredient, or group of active ingredients considered equivalent according to some feature (e.g. therapeutic effects and chemical structure). In 1989, the reference price scheme for reimbursable drugs was introduced in Germany to reduce pharmaceutical expenditure, which had been steadily increasing in the past. The study investigates the economic effects of introducing reference prices in Germany in order to assess whether this system has been effective in containing public pharmaceutical expenditure. We conclude that the reference price scheme is an effective tool for price control, but cost containment requires further measures.

Analgesics, Non-Narcotic↗
PubMed1997

Robust leptin secretory responses to dexamethasone in obese subjects.

Although leptin reverses obesity in rodents, its function and regulation in humans are unknown. Glucocorticoids have been reported to stimulate leptin production in both rodents and humans, but data assessing the effect of obesity on dynamic leptin secretory responses are unavailable. We, therefore, studied 52 lean and obese subjects [20 men and 32 women; aged 19-84 yr; body mass index (BMI) range, 16-47 kg/m2] randomized to treatment with dexamethasone (total dose, 10 mg/4 days) or placebo. Compared with placebo, dexamethasone increased (P = 0.0001) plasma leptin levels by 64-111% above baseline values within 2-4 days. The increases occurred in all ages, showed no sexual dimorphism, and were particularly robust in obese subjects. After dexamethasone treatment, significant interactions were observed between the change in plasma leptin and BMI (P = 0.0001), baseline plasma leptin (P = 0.0006) and plasma dexamethasone levels (P = 0.04), but not age (P = 0.28); an apparent interaction with plasma insulin no longer was significant after controlling for BMI. These results confirm dexamethasone-induced hyperleptinemia in humans and further demonstrate that the response is not defective in obesity.

Adult↗