Search PubMed⌕ Search

Biomedical subjects

J Born

Publications and source records attributed to J Born.

At least 55 records · Page 3Linked to original sources
PubMed2000

Dimensional complexity and power spectral measures of the EEG during functional versus predicative problem solving.

Electroencephalograms were recorded in 22 men while solving tasks of visual-pattern completion and during mental relaxation. They were primed (by foregoing trials) to solve these tasks either in a predicative or functional mode of thinking. Predicative thinking required that in order to complete the pattern the subject had to get involved with the logic of the static structure of the pattern and therefore had to recognize the recurrence of certain features of the elements (e.g., shape, color, and size). Functional thinking required involvement in a dynamic reading of the logic of the pattern and therefore to search for operations and actions to be performed on the pattern elements (e.g., pushing, mirroring, and rotating). The EEG complexity during predicative thinking decreased in comparison to functional thinking and mental relaxation, with this reduction being most pronounced over the right parietal cortex. A reduction in dimensional complexity during functional thinking as compared to mental relaxation, which was concentrated over the left central cortex, although significant, was less clear. The reduced EEG complexity during predicative thought, dominant over the right hemisphere, could reflect increased competitive inhibition among respective cortical neuron assemblies in association with the visual analysis of static element features, converging upon those predicates relevant for the solution.

Adult↗
PubMed2000

Interferon-alpha acutely impairs sleep in healthy humans.

We investigated the effects of two low doses of interferon-alpha (IFN-alpha) on nocturnal sleep in 18 healthy men by means of polysomnographic sleep recordings. At 1900h, human recombinant IFN-alpha (1000 or 10000 U/kg body weight) or placebo was administered subcutaneously. Between 2300h and 0700h subjects were allowed to sleep. In general effects were stronger at the dose of 10000 than 1000 U/kg body weight of IFN-alpha. Although, after IFN-alpha subjects experienced increased fatigue, the cytokine impaired the quality of nocturnal sleep. The higher dose of IFN-alpha suppressed slow wave sleep (17.8 +/- 2.0% vs 25.2 +/- 2.6% following placebo, P<0.003) but increased time spent in shallow sleep (P<0.05) during the first half of sleep time. Rapid eye movement (REM) sleep latency was postponed (P<0.02) and time spent in REM sleep was significantly decreased after IFN-alpha (P<0.04). The impairing influence of IFN-alpha on sleep in humans is in contrast with findings of sleep promoting effects of this cytokine in animals. Our data suggest that endogenous IFN-alpha may be a factor responsible for alterations of sleep, e.g. in the course of viral infections.

Adrenocorticotropic Hormone↗
PubMed2000

Eating habits, health status, and concern about health: a study among 1641 employees in the German metal industry.

BACKGROUND: Nutrition has been found to be associated with sociodemographic characteristics and concern about health. There is limited knowledge, however, of associations between blue-collar worker's diet, morbidity, and health care utilization. METHODS: We conducted a survey on eating habits, physical symptoms, health care utilization, health status, and concern about health in two German metal companies. A self-administered questionnaire was mailed to employees of whom 1641 participated in the study (response rate 54. 7%). RESULTS: Most employees were characterized by a combination of healthy and unhealthy eating elements. Using linear regression analyses adjusted for age, gender, and occupational status, healthy eating was negatively associated with stomach aches and headaches, but not with cardiovascular disease. Restricted activity days and days in hospital were associated with healthy eating, but self-assessed health status and physician consultations were not. Using stepwise multiple regression analysis, age, gender, and concern about health were strongly and morbidity was weakly related to diet. Occupational status, marital status, and number of children were not associated with nutrition. CONCLUSIONS: Health promotion programs should motivate younger and male employees to participate in and aim toward increasing concern about health.

Adult↗
PubMed2000

Slow cortical DC-potential responses to sweet and bitter tastes in humans.

Processing of hedonic stimulus quality is assumed to be accompanied by a tuning of cortical arousal and excitability. In this pilot study in 11 healthy humans scalp-recorded DC potentials were assessed during application of a sweet (sucrose) and bitter (quinine hydrochloride) taste, i.e., primary reinforcers of positive and negative quality. Muscular, ocular, and skin potential activity were controlled. Application of sucrose induced a widespread positive DC-potential shift with an amplitude of 40-50 microV and persisting for more than 120-s post-stimulus onset. Following administration of quinine hydrochloride, this positive shift was reduced, most distinctly between 48- and 88-s post-stimulus onset. The reduction appeared to be most consistent at anterior midline recording sites (Fz, Cz). It is assumed that the higher DC-potential positivity during sweetness than during bitterness points to a differential tuning of cortical excitability by a widespread decrease in depolarization of apical dendrites.

Adult↗
PubMed2000

Early sleep triggers memory for early visual discrimination skills.

Improvement after practicing visual texture discrimination does not occur until several hours after practice has ended. We show that this improvement strongly depends on sleep. To specify the process responsible for sleep-related improvement, we compared the effects of 'early' and 'late' sleep, dominated respectively by slow-wave and rapid eye movement (REM) sleep. Discrimination skills significantly improved over early sleep, improved even more over a whole night's sleep, but did not improve after late sleep alone. These findings suggest that procedural memory formation is prompted by slow-wave sleep-related processes. Late REM sleep may promote memory formation at a second stage, only after periods of early sleep have occurred.

Adult↗
PubMed2000

Changes in direct current (DC) potentials and infra-slow EEG oscillations at the onset of the luteinizing hormone (LH) pulse.

An essential function of the neuroendocrine system lies in the coordination of hypothalamo-pituitary secretory activity with neocortical neuronal activity. Cortical direct current (DC) potential shifts and EEG were monitored in conjunction with the circulating concentration of luteinizing hormone (LH) in humans while asleep to assess a hypothalamic-neocortical interaction. The onset of an LH pulse was accompanied (i) at frontocortical locations by a transient positive DC potential shift of approximately 3 min duration and peak amplitude 50 microV; (ii) at frontal and central locations by an increase in power of infra-slow EEG oscillations for periodicities between 64 and 320 s. Results uniquely demonstrate a coupling of hypothalamo-pituitary activity with regulation of neocortical excitability.

Activity Cycles↗
PubMed2000

Preserved hypothermic response to hypoglycemia after antecedent hypoglycemia.

Hypoglycemia is known to decrease the body temperature and to stimulate counterregulatory hormone secretion. Although it is well established that antecedent hypoglycemia reduces the hormonal response to subsequent hypoglycemia, the effects of antecedent hypoglycemia on the subsequent hypothermic response are obscure. In the present study, body temperature was measured orally during a total of 90 glucose clamp experiments in 45 healthy men. The clamps lasted 6 hours and were performed under 6 different experimental conditions: a euglycemic clamp with a low rate of insulin infusion, 1.5 mU/kg x min (low insulin-eu), a euglycemic clamp with a high rate of insulin infusion, 15.0 mU/kg x min (high insulin-eu), a hypoglycemic clamp with a low rate of insulin infusion, 1.5 mU/kg x min (low insulin-hypo), a hypoglycemic clamp with a high rate of insulin infusion, 15.0 mU/kg x min (high insulin-hypo), and 2 hypoglycemic clamps following an antecedent 2.5-hour hypoglycemia (56 mg/dL) induced by either a low (1.5 mU/kg x min, low insulin-ante-hypo) or a high (15.0 mU/kg x min, high insulin-ante-hypo) rate of insulin infusion. Plasma glucose was maintained normal during the euglycemic clamps and was decreased stepwise during the hypoglycemic clamps (76 --> 66 --> 56 --> 46 mg/dL). During the hypoglycemic clamps, body temperature decreased by 0.26 degrees +/- 0.09 degrees C in low insulin-hypo, 0.28 degrees +/- 0.09 degrees C in high insulin-hypo, 0.29 degrees +/- 0.09 degrees C in low insulin-ante-hypo, and 0.41 + 0.11 degrees C in high insulin-ante-hypo (all P < .01). There were no differences in the hypothermic response to hypoglycemia among the different hypoglycemic conditions (P > .1 for all comparisons). In contrast, body temperature remained unchanged during the euglycemic clamps, so the changes in body temperature differed significantly during the euglycemic clamps versus the hypoglycemic clamps (P < .05 for all comparisons). The data show that the body temperature decreases during hypoglycemia and this decrease is influenced neither by antecedent hypoglycemia nor by circulating insulin levels.

Adult↗
PubMed2000

Comparison of the inhibitory effect of insulin and hypoglycemia on insulin secretion in humans.

Although both insulin and hypoglycemia are known to inhibit endogenous insulin secretion, their potency to suppress insulin secretion has not been directly compared thus far. The serum C-peptide concentration was measured during 28 euglycemic and 28 stepwise hypoglycemic (4.1,3.6, 3.1, and 2.6 mmol/L) clamp experiments using either a low-rate (1.5 mU x min(-1) x kg(-1)) or high-rate (15.0 mU x mU(-1) x kg(-1)) insulin infusion. The experiments lasted 6 hours and were performed in 28 lean healthy men. During both the euglycemic and hypoglycemic clamps, serum insulin was approximately 40-fold higher during the high-rates versus low-rate insulin infusion (euglycemia, 24,029 +/- 1,595 v 543 +/- 34 pmol/L; hypoglycemia, 23,624 +/- 1,587 v 622 +/- 32 pmol/L). Under euglycemic conditions, serum C-peptide decreased from 0.54 +/- 0.04 to 0.41 +/- 0.05 nmol/L during the low-rate insulin infusion (P < .05) and from 0.55 +/- 0.07 to 0.27 +/- 0.09 nmol/L during the high-rate insulin infusion (P < .001). Under hypoglycemic conditions, serum C-peptide decreased from 0.50 +/- 0.03 to 0.02 +/- 0.01 nmol/L during the low-rate insulin infusion (P< .001) and from 0.46 +/- 0.07 to 0.02 +/- 0.01 nmol/L during the high-rate insulin infusion (P< .001). In the euglycemic clamp condition, the high-rate insulin infusion reduced the C-peptide concentration more than the low-rate insulin infusion (P < .05). Independent of the rate of insulin infusion, the decrease in C-peptide was distinctly more pronounced during hypoglycemia versus euglycemia (P < .001). These data indicate that insulin inhibits insulin/C-peptide secretion in a dose-dependent manner. Hypoglycemia is a much stronger inhibitor of insulin secretion than insulin itself.

Adult↗
PubMed2000

Increase in systolic blood pressure and catecholamine level during hyperinsulinemia in a placebo-controlled euglycemic clamp in healthy subjects.

Hyperinsulinemia has been shown to induce vasodilation and activation of the sympathetic nervous system. Whether these effects result in changes in blood pressure (BP) is discussed controversially. We measured BP and catecholamine levels in 50 healthy subjects during a 40-min baseline phase and during a 100-min euglycemic clamp phase. In a double-blind, between-subject comparison, 30 subjects were infused with 1.5mU insulin/kg x min, 20subjects were infused with saline solution. Insulin levels increased during insulin infusion from (mean+/-SE) 23.7 0.6 pmol/l to 406.2+/-3.0 pmol/l, but remained unchanged during placebo infusion. Blood glucose levels were identical during both conditions. Systolic BP increased from 116.6+/-1.5 mmHg to 119.8+/-1.8 mmHg during insulin infusion and decreased from 116.6+/-2.3 mmHg to 114.0+/-2.4 mmHg during placebo infusion (p<0.001, for the difference between the effects of insulin vs. placebo). Heart rate was higher during insulin infusion as compared to placebo infusion (63.8+/-1.9 vs. 60.9+/-2.4 beats/min, p<0.05). Norepinephrine levels increased from 1.25+/-0.09 to 1.58+/-0.12 nmol/l during insulin infusion and remained unchanged during placebo infusion (1.24+/-0.09 vs. 1.29+/-0.11 pmol/l; p<0.001). Epinephrine levels were also higher during insulin as compared to placebo infusion (249.8+/-17.4 vs. 212.8+/-21.1 pmol/l, p<0.001). The changes did not depend on whether the subject experienced his first or second clamp. Data demonstrate reproducable increasing effects of hyperinsulinemia within the normal physiological range on catecholamine release and systolic BP in healthy humans.

Adolescent↗
PubMed2000

Rhythms of pituitary-adrenal activity during sleep in patients with Cushing's disease.

Previous studies have indicated a dependence of nocturnal pituitary-adrenal secretory activity on central nervous sleep processes in healthy humans: Under normal physiological conditions the release of ACTH/cortisol is inhibited during early sleep and becomes entrained to periods of NonREM sleep during late sleep. Here, we compared nocturnal dynamics in plasma concentrations of ACTH/cortisol in 7 patients with Cushing's disease with those of 7 healthy controls matched in age and sex with the patients. The patients in part were repeatedly tested. The total of 13 nights is composed of 7 nights of hyperpulsatile secretion pattern (5 patients) and 6 nights from hypopulsatile secretion pattern (4 patients). After an adaptation night polysomnographic sleep recordings were obtained and blood was sampled every 15 min between 23.00 and 7.00 h. Controls displayed the typical minimum in ACTH/cortisol concentrations during the early part of the night and maximum concentrations during the late part of the night, whereas ACTH/cortisol levels of Cushing patients indicated a relatively constant elevated pituitary-adrenal activity throughout the night, lacking any circadian variation. Autocorrelation functions revealed the presence of cortisol secretory rhythms with a similar period length in healthy controls (155.6+/-17.4 min) and patients with a hyperpulsatile pattern (142.4+/-6.6 min). In patients displaying hypopulsatility, no significant rhythmicity was observed. However, regardless of the type of secretory pulsatility, adrenal secretory activity started predominantly during periods of NonREM sleep (p<0.01) in healthy controls as well as in patients with Cushing's disease. This data indicates that the normal nocturnal circadian oscillation of pituitary-adrenal activity is absent in Cushing patients, whereas a link between pituitary-adrenal activity and ultradian rhythms of sleep appears to be preserved.

Activity Cycles↗
PubMed2000

Event-related brain potentials and working memory function in healthy humans after single-dose and prolonged intranasal administration of adrenocorticotropin 4-10 and desacetyl-alpha-melanocyte stimulating hormone.

Neuropeptides of the adrenocorticotropin/melanocorticotropin (ACTH/MSH) family are most potent modulators of cognitive function. Their neurobehavioral activity is principally encoded in the 4-10 fragment of the ACTH/MSH molecule; in humans, it has been shown to pertain primarily to functions of attentive stimulus/response processing. The aims of this study were (1) to examine the effects of ACTH 4-10 on event-related brain potentials (ERPs) and behavioral indicators of stimulus encoding within the working memory; (2) to compare the effects after a single dose and after prolonged treatment with ACTH 4-10; and (3) to compare the effects of ACTH 4-10 with those of desacetyl-alpha-MSH (i.e., ACTH 1-13 amide), which, like ACTH 4-10, binds to the known brain melanocortin receptors (MC-Rs) but with distinctly higher affinity. Double-blind, placebo-controlled experiments were performed in 60 healthy control subjects. The authors monitored ERPs and reaction times while these subjects performed an auditory vigilance task ("oddball"). Recall was tested on a verbal short-term memory task including different word categories (neutral, rare, food, sex). After a single (1 mg) as well as prolonged intranasal administration (1 mg/day over a period of 6 weeks), ACTH 4-10 enhanced the positive slow wave in ERPs to target stimuli of the vigilance task (p < 0.05), but left classic P3 unaffected. Moreover, single-dose and prolonged administration of ACTH 4-10 increased the rate of false responses during vigilance (p < 0.01). In the short term, ACTH 4-10 also impaired recall of neutral words (p < 0.05). Equimolar doses of desacetyl-alpha-MSH did not influence ERPs, neither after a single dose nor after prolonged treatment. Similar to ACTH 4-10, desacetyl-alpha-MSH increased the error rate during vigilance and acutely impaired the recall of neutral words. The increase in ERP slow-wave positivity, in conjunction with behavioral impairments after treatment with ACTH 4-10, complemented previous results of inferior focusing of attention and a less concise structure of thought after administration of ACTH 4-10. The changes indicated an impairment in differential processing of relevant versus irrelevant contents within the working memory, and, in this regard, might mimic aspects of psychopathologic disturbances of attention and thought processes. Their persistence after prolonged treatment with ACTH 4-10 suggests an activation of mechanisms subserving the consolidation of the peptide's effects. The poor efficacy of desacetyl-alpha-MSH suggests that the known MC-Rs may be irrelevant for mediating cognitive effects of this neuropeptide family.

Administration, Intranasal↗
PubMed2000

Glucose metabolism rather than insulin is a main determinant of leptin secretion in humans.

Circulating plasma insulin and glucose levels are thought to be major regulators of leptin secretion. There is evidence from in vitro and animal experiments that glucose metabolism rather than insulin alone is a main determinant of leptin expression. Here, we tested the hypothesis that in humans also leptin secretion is primarily regulated by glucose uptake and only secondarily by plasma insulin and glucose. In 30 lean and healthy men we induced 4 experimental conditions by using the blood glucose clamp technique. A total of 60 hypoglycemic and euglycemic clamps, lasting 6 h each, were performed. During these clamps insulin was infused at either high (15.0 mU/min x kg) or low (1.5 mU/min x kg) rates, resulting in low-insulin-hypo, high-insulin-hypo, low-insulin-eu, and high-insulin-eu conditions. Serum leptin increased from 0-360 min by 20.5 +/- 4.1% in the low-insulin-hypo, 33.6 +/- 7.6% in the high-insulin-hypo, 39.6 +/- 6.0% in the low-insulin-eu, and 60.4 +/- 7.6% in the high-insulin-eu condition. Multiple regression analysis revealed a significant effect of circulating insulin (low vs. high insulin; P = 0.001) and blood glucose (hypoglycemia vs. euglycemia; P = 0.001) on the rise of serum leptin. However, when the total amount of dextrose infused during the clamp (grams of dextrose per kg BW) was included into the regression model, this variable was significantly related to the changes in serum leptin (P = 0.001), whereas circulating insulin and glucose had no additional effect. These findings in humans support previous in vitro data that leptin secretion is mainly related to glucose metabolism.

Adult↗
PubMed2000

Adaptation of cognitive function to hypoglycemia in healthy men.

OBJECTIVE: Antecedent hypoglycemia reduces hypoglycemic counterregulation and symptoms, thereby provoking the hypoglycemia unawareness syndrome. The effects of antecedent hypoglycemia on hypoglycemia-induced cognitive dysfunction are less well established. RESEARCH DESIGN AND METHODS: To determine whether antecedent hypoglycemia also reduces hypoglycemic cognitive dysfunction, we performed stepwise hypoglycemic clamp experiments (4.1, 3.6, 3.1, and 2.6 mmol/l) during a 6-h period in 30 young healthy men. A total of 15 subjects additionally received a 2.5-h antecedent hypoglycemic clamp (3.1 mmol/l) on the preceding day (prior-hypo group), whereas the other 15 subjects did not (control group). Cognitive function was assessed by auditory-evoked brain potentials (AEBPs) and reaction time during a vigilance task and short-term memory recall. Tests were performed during the stepwise hypoglycemic clamp at baseline and at each hypoglycemic plateau. RESULTS: In both groups, performance on all measures of cognitive function deteriorated during stepwise hypoglycemia (all P < 0.01). However, after antecedent hypoglycemia, the hypoglycemia-induced decrease in the amplitude of the P3 of the AEBP was distinctly reduced compared with the control condition (P < 0.05). Also, short-term memory performance was less impaired in the prior-hypo group than in the control group (P < 0.005), and a minor hypoglycemic impairment of reaction time (P < 0.05) was evident in the prior-hypo group. CONCLUSIONS: Data provide evidence that a single episode of mild antecedent hypoglycemia (3.1 mmol/l) attenuates several aspects of cognitive dysfunction during subsequent hypoglycemia 18-24 h later.

Adaptation, Physiological↗
PubMed2000

Selective influence of the menstrual cycle on perception of stimuli with reproductive significance: an event-related potential study.

In this study, we examined changes in the event-related potential (ERP) to stimuli with and without reproductive significance occurring during the menstrual cycle. Eleven spontaneously cycling women were tested during three menstrual phases (menses, ovulatory phase, luteal phase) differing in plasma concentrations of gonadal hormones. ERPs were recorded while subjects were presented with slides showing pictures from four different stimulus categories (sexual stimuli, babies, people occupied with body care, ordinary people). Slides were presented randomly in the context of two tasks, requiring either affective processing (i.e., to judge the emotional content of a slide as positive, neutral, or negative) or structural processing (i.e., to estimate the number of parallel thin lines inserted in each picture). Menstrual phase primarily affected a late positive component (LPC) peaking 550-600 ms poststimulus. The effects were as follows: (i) During the ovulatory phase, amplitude of the LPC to sexual stimuli was larger than that evoked by the other stimulus categories. (ii) This relationship was not apparent during the other menstrual phases or (iii) during the ovulatory phase when the task required structural processing. The ovulatory increase in LPC positivity to sexual stimuli suggests a greater valence of these stimuli during a phase of increased sexual desire. The data indicate a specific effect of the menstrual cycle on the processing of sexual stimuli that increases with deeper emotional processing.

Adult↗
PubMed2000

EES in rare benign tumors.

Endoscopic Endonasal Surgery (EES) can successfully be carried out for benign tumors such as osteomas, benign vascular tumors, pituitary adenomas, pneumoceles and benign fibrous tumors. This report concerns a Belgian perspective documenting our experience in 49 such cases. Among them are 33 cases of pituitary adenoma. Thanks to the experience accumulated in the surgical management of inflammatory sinusal disease, these tumors were able to be removed, totally or partially, under endoscopic guidance with the aid of powered endoscopic instrumentation, and in some cases, CO2 laser fiber. Advantages are well-known; lower cost, shorter stay in hospital, lower morbidity, lower cosmetic or functional disabilities. We emphasize the need for the surgeon to be able to switch the endoscopic procedure to an external one if difficulties occur or the tumor is more extensive than expected.

Adolescent↗
PubMed2000

Minimally invasive endoscopic management of malignant sinonasal tumours.

A large retrospective study from two belgian institutions of 78 patients who underwent minimally invasive endoscopic management for malignant sinonasal tumors from, 1992-1999 is presented. We attempt to assess the results of this less invasive approach. The spectrum of disease included adenocarcinoma, squamous cell carcinoma, olfactory neuroblastoma and other malignant tumors. All patients were treated primarily for cure. 66 patients were operated on by a purely endoscopic technique, while 9 patients had a simultaneous neurosurgical and endoscopic approach, and 3 a limited orbital approach. 16 patients (20.5%) presented with local recurrence, 6 patients (7.7%) sustained distant metastases and 7 patients (9%) presented simultaneous local recurrence and distant metastases. The 2-years and 5-years survival rates of the whole group were respectively 73.1% and 52.3%, while the adenocarcinoma group exhibits a significantly better prognosis than other histological types with 2-years and 5-years survival rates of 89.8% and 63.8%. Patients who could be treated purely endoscopically had a significantly better survival in comparison to patients treated by an external and endoscopic approach. Morbidity was minimal and the local control rate as well as survival rates were comparable to literature data. Endoscopic resection was adequate, providing clear margins and en bloc removal in most cases. Our results encourage us to use this minimally invasive approach in selected cases as a reliable alternative to the systematic use of an exclusively external approach.

Adolescent↗
PubMed2000

Scalp recorded direct current potential shifts associated with quenching thirst in humans.

As an indicator of cortical excitability, direct current (DC) potentials were recorded from thirsted subjects before, during and after drinking 400 ml of water. Self-rated thirst was distinctly reduced after drinking. Compared with control conditions in which the subjects remained thirsty, during drinking a widespread negative potential shift occurred averaging over -70 microV at Cz. At the transition from the consumatory phase to the postconsumption phase, a slow positive potential shift commenced that was most pronounced over the anterior cortex (averaging over +40 microV at Fz) and persisted for more than 3 min after drinking. Control conditions excluded muscle activity, ocular movements, and changes in body fluid and serum osmolality as possible non-neuronal sources of the DC-potential changes. The sequence of negative and positive potential shifts associated with drinking indicates a coordinate regulation of cortical excitability that may facilitate consumatory behavior and its context-dependent encoding into memory.

Adult↗