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Biomedical subjects

G van Dijk

Publications and source records attributed to G van Dijk.

At least 37 records · Page 2Linked to original sources
PubMed1998

Central infusion of glucagon-like peptide-1-(7-36) amide (GLP-1) receptor antagonist attenuates lithium chloride-induced c-Fos induction in rat brainstem.

Central infusion of glucagon-like peptide-1-(7-36) amide (GLP-1) and intraperitoneal (i.p.) injection of lithium chloride (LiCl) produce similar patterns of c-Fos induction in the rat brain. These similarities led us to assess the hypothesis that neuronal activity caused by i.p. injection of LiCl involves activation of central GLP-1 pathways. We therefore determined if third-ventricular (i3vt) infusion of a GLP-1 receptor antagonist would block LiCl-induced c-Fos expression in the brainstem. Relative to rats pretreated with i3vt infusion of vehicle, pretreatment with the potent GLP-1 receptor antagonist, des His1 Glu9 exendin-4 (10.0 microgram), significantly attenuated LiCl-induced (76 mg/kg; i.p.) c-Fos expression in several brainstem regions, including the area postrema, the nucleus of the solitary tract, and the lateral parabrachial nucleus. While central infusion of des His1 Glu9 exendin-4 also blocked GLP-1-induced (10.0 microgram) anorexia and c-Fos expression, the antagonist produced no independent effects on food intake or c-Fos expression. These results suggest that LiCl-induced c-Fos expression in the rat brainstem is mediated, at least in part, by GLP-1 receptor signaling.

Animals↗
PubMed1998

[Efficiency of mixed RASTs in serological screening of possibly allergic patients].

OBJECTIVE: To determine the age distribution of results of serological allergy screening using mixed-allergen radioallergoabsorbent tests (RASTs), and to determine the cost-effectiveness of mix RASTs. DESIGN: Retrospective. SETTING: University Hospital of Rotterdam; Dijkzigt Hospital and Sophia Children's Hospital, the Netherlands. METHODS: An analysis was made of the results of all determinations requested in a period of 3 years with use of the CAP Phadiatop test (aimed at IgE against a mixture of inhalant allergens) and the CAP f x 5 food mix test (aimed at IgE against a mixture of food allergens). RESULTS: The CAP Phadiatop test was positive most strongly and most frequently in patients aged 7 to 30 years. From the age of 2 years, there was a sharp rise of the number of positive CAP Phadiatop tests, but IgE against inhalant allergens was also found in over 10% of the children aged 0 and 1 year. Up to and including the age category of 6 years, over one-third of the sera submitted had a positive CAP f x 5 food mix test. From a budget point of view, preliminary screening with a mix RAST is the more advantageous the lower the allergy prevalence and the higher the mean number of CAP-RASTs to be requested per serum. CONCLUSION: A substantial saving of laboratory costs can be achieved by having mix RASTs such as CAP Phadiatop and CAP f x 5 food mix tests precede determinations of specific IgE against separate allergens; these savings will be the higher the smaller the proportion of positive results and the higher the mean number of separate RASTs to be requested per serum.

Adolescent↗
PubMed1998

Intraventricular GLP-1 reduces short- but not long-term food intake or body weight in lean and obese rats.

Glucagon-like-peptide-1 (7-36) amide (GLP-1), when infused into the third ventricle (I.V.T.), reduces short-term food intake. In the present experiments, we assessed whether I.V.T. administration of GLP-1 could influence long-term food intake and body weight of lean Long Evans rats and of fatty Zucker (fa/fa) rats. In Experiment 1, we replicated the observation that 10 microg GLP-1, given I.V.T., reduces one and 2 h food intake, and extended the observation to fatty Zucker rats. However, in both rat strains, 24 h food intake and body weight were unchanged by this acute treatment. In Experiment 2, GLP-1 (30 microg/day) was infused I.V.T. continuously for 4 days via an osmotic mini-pump. This treatment also had no effect on food intake or body weight in either Long-Evans or fatty Zucker rats. A control experiment verified that the GLP-1 remained biologically active over the duration of the infusion period. In a final experiment, Long-Evans rats were restricted to two 2 h periods of access to food each day for 6 days. Prior to each of these access periods, rats received either 15 microg of GLP-1 I.V.T. or a vehicle control injection. While GLP-1 significantly reduced food intake on the first day of treatment, this effect of GLP-1 rapidly disappeared such that it was reduced on the second day and absent on the third day; and there was no effect on body weight at any time. Collectively, the present experiments do not support the hypothesis that GLP-1, acting in the CNS, is an important regulator of long-term food intake and body weight.

Analysis of Variance↗
PubMed1998

Central infusion of melanocortin agonist MTII in rats: assessment of c-Fos expression and taste aversion.

Like leptin (OB protein), central infusion of the nonspecific melanocortin agonist MTII reduces food intake for relatively long periods of time (i.e., 12 h; W. Fan, B. A. Boston, R. A. Kesterson, V. J. Hruby, and R. D. Cone, Nature; 385: 165-168, 1997). To test the hypothesis that MTII may influence ingestive behavior via mechanisms similar to those that mediate the effects of leptin, we infused a single dose of MTII into the third ventricle (i3vt) of Long-Evans rats and examined three dependent measures that have been studied following i3vt infusion of leptin: 1) effects on long-term food intake and body weight (48 h), 2) patterns of c-Fos expression in the brain, and 3) conditioned taste aversion learning. Similar to leptin, MTII reduced 48-h food intake (1.0 nmol dose), reduced body weight at 24 and 48 h (0.1 and 1.0 nmol doses, respectively), and induced c-Fos expression in the paraventricular nucleus of the hypothalamus and the central nucleus of the amygdala. In contrast to leptin, MTII was found to produce conditioned taste aversions. These results are consistent with the hypothesis that MTII may influence regulatory behavior via mechanisms similar to those that mediate the effects of leptin.

Administration, Oral↗
PubMed1997

Insulin in the arcuate nucleus of the hypothalamus reduces fat consumption in rats.

Data are accumulating that insulin acting in the central nervous system is a physiological regulator of food intake and body weight, presumably via its effect in the hypothalamus. The present study investigated whether infusion of a small dose of insulin into two major hypothalamic insulin-binding areas also has an effect on diet selection and behavior. At the beginning of the dark period, rats received local bilateral infusions of 4 microU of insulin or vehicle during 34 min into the arcuate (ARC) or paraventricular (PVN) nucleus of the hypothalamus. Consumption of carbohydrate (C)-, protein (P)-, and fat (F)-enriched food and time spent on certain behaviors (drinking, resting, grooming, rearing, exploring/sniffing) were assessed during the first nocturnal hour. In addition, 21-h diet selection was assessed. The percentage contribution of macronutrients (C/P/F) to total energy content of the C-, P-, and F-enriched diets was 71.9/17.2/10.9, 45.8/43.4/10.8, and 47.1/17.5/35.4, respectively. During the first hour, infusion of insulin into the PVN increased grooming behavior compared to infusion of the vehicle. Although infusion of insulin had no effect on diet selection during the first hour, insulin infused in the ARC caused a reduction in F-enriched food consumption and total intake of F (as a macronutrient) over the 21-h period without altering total food intake. Infusion of a higher dose of insulin (10 microU) into the third ventricle had no effect on any of the assessed parameters. The data are explained to indicate that insulin (being an indicator of a positive energy balance) adjusts body weight homeostasis by modulating the preference for fat, at least at the level of the ARC, but not at the PVN.

Animals↗
PubMed1997

Ethanol-induced c-Fos expression in rat lines selected for low and high alcohol consumption.

Selectively bred rat lines, developed to model genetic contributions to alcohol abuse, include the Indiana alcohol-preferring (P) and alcohol-nonpreferring (NP) lines, and the Alko-Alcohol (AA) and Alko-Nonalcohol (ANA) lines. Preferring and nonpreferring lines were compared in their response to intraperitoneal injection of either ethanol or isotonic saline using c-Fos expression as a marker of neuronal activity. Although line differences were noted in several brain regions, the principal finding was that alcohol-nonpreferring lines (NP and ANA) displayed greater c-Fos expression in the locus coeruleus (LC) relative to the alcohol-preferring lines (P and AA) following injection of 3.0 g ethanol/kg. These data point to the LC as an area which may play a role in the differences in voluntary ethanol consumption between rat lines genetically bred for low and high ethanol preference.

Alcohol Drinking↗
PubMed1997

Central leptin stimulates corticosterone secretion at the onset of the dark phase.

Leptin, a hormone secreted by adipose tissue in proportion to body adiposity, is proposed to be involved in the central nervous regulation of food intake and body weight. In addition, evidence is emerging that leptin regulates neuroendocrine and metabolic functions as well, presumably via its action in the central nervous system (CNS). To investigate this regulatory effect of leptin, we infused 3.5 microg of human leptin directly into the third cerebral ventricle (i3vt) of lean male Long-Evans rats, 90 min before the onset of their dark phase. Before and after infusion, blood samples were withdrawn through indwelling catheters for assessment of hormonal (plasma corticosterone, insulin, leptin), autonomic (plasma norepinephrine, epinephrine), and metabolic (plasma glucose) parameters. I3vt leptin caused an increase in plasma corticosterone and plasma leptin levels relative to the control condition. The effects of i3vt leptin on corticosterone secretion became particularly apparent after the onset of the dark phase. The results of the present study indicate that i3vt leptin stimulates the hypothalamo-pituitary-adrenal (HPA) axis, particularly when rats normally encounter their largest meals. These results are consistent with the possibility that high circulating leptin levels may underlie the increased activity of the HPA axis that is generally characteristic of human obesity and most animal models of obesity.

Analysis of Variance↗
PubMed1997

[Technical problems with superstructures for the maxilla].

The dental lab is an important factor in treating patients with severely resorbed maxillae with implants, but it still occurs that the dental technician is not or not enough involved in the treatment planning of these patients. In this article a number of frequently occurring problems is discussed, especially the number and the location of implants, the space for the superstructure and the planning of the costs. Some suggestions for improvements are proposed.

Bone Resorption↗
PubMed1996

Overfeeding, autonomic regulation and metabolic consequences.

The autonomic nervous system plays an important role in the regulation of body processes in health and disease. Overfeeding and obesity (a disproportional increase of the fat mass of the body) are often accompanied by alterations in both sympathetic and parasympathetic autonomic functions. The overfeeding-induced changes in autonomic outflow occur with typical symptoms such as adiposity and hyperinsulinemia. There might be a causal relationship between autonomic disturbances and the consequences of overfeeding and obesity. Therefore studies were designed to investigate autonomic functioning in experimentally and genetically hyperphagic rats. Special emphasis was given to the processes that are involved in the regulation of peripheral energy substrate homeostasis. The data revealed that overfeeding is accompanied by increased parasympathetic outflow. Typical indices of vagal activity (such as the cephalic insulin release during food ingestion) were increased in all our rat models for hyperphagia. Overfeeding was also accompanied by increased sympathetic tone, reflected by enhanced baseline plasma norepinephrine (NE) levels in both VMH-lesioned animals and rats rendered obese by hyperalimentation. Plasma levels of NE during exercise were, however, reduced in these two groups of animals. This diminished increase in the exercise-induced NE outflow could be normalized by prior food deprivation. It was concluded from these experiments that overfeeding is associated with increased parasympathetic and sympathetic tone. In models for hyperphagia that display a continuously elevated nutrient intake such as the VMH-lesioned and the overfed rat, this increased sympathetic tone was accompanied by a diminished NE response to exercise. This attenuated outflow of NE was directly related to the size of the fat reserves, indicating that the feedback mechanism from the periphery to the central nervous system is altered in the overfed state.

Animals↗
PubMed1996

Intraventricular leptin reduces food intake and body weight of lean rats but not obese Zucker rats.

The protein encoded by the obese (ob) gene, leptin, is secreted from adipose tissue and is proposed to act in the brain as an important regulator of food intake and body weight. To investigate the direct effects of leptin within the CNS, we injected 3.5 microg of either mouse or human leptin into the third ventricle (ICV) of lean Long-Evans rats or obese (fa/fa) Zucker rats, in which obesity results from a mutation in the leptin receptor gene. ICV administration of leptin reduced 4-h food intake in both deprived and non-deprived lean rats. In addition, repeated ICV administration produced a long-lasting reduction in body weight while peripheral administration of the same dose had no effect. ICV administration of the same dose of leptin into the third ventricle of obese Zucker rats did not reduce food intake. These results are consistent with the hypothesis that leptin has direct actions in the CNS as an afferent signal related to the state of energy stores in adipose tissue. Furthermore, insensitivity to these central effects of leptin may be an important determinant of obesity.

Animals↗
PubMed1996

[Prosthetic reconstruction after oncological surgery in the head and neck region].

The aim of maxillofacial prosthetics is the treatment of patients with head and neck disease in a multidisciplinary way. Intraoral and facial defects are preferably reconstructed by surgical transplantation methods. Patient factors and oncologic factors determine the indication of prosthetic reconstructions. The treatment of patients with an intraoral or facial defect should be based on a close cooperation between maxillofacial prosthetist and MFP technician. The rehabilitation process and the specific role of each are described.

Dental Technicians↗
PubMed1995

Energy homeostasis, autonomic activity and obesity.

Obesity is often accompanied by alterations in both sympathetic and parasympathetic autonomic functions. The present paper summarizes the results of a number of studies designed to investigate autonomic functioning in normal, genetically, and experimentally obese rats. Particular emphasis is given to autonomic functioning and dysfunctioning in relation to the processes that are involved in the regulation of peripheral energy substrate homeostasis. It is concluded that alterations in autonomic regulation in obesity are determined by causal factors such as overeating, genetic make-up, age and/or the duration of obesity.

Animals↗
PubMed1995

Glucose homeostasis and sympathoadrenal activity in mercaptoacetate-treated rats.

The effect of the fatty acid oxidation inhibitor, sodium mercaptoacetate (MA, 600 mumol/kg) on peripheral energy substrate metabolism was investigated in rats with permanent heart catheters. Rats were either fed, 48-h food deprived, or exercising for 30 min. Before and after intravenous MA injection, stress-free blood samples were taken for measurement of blood glucose, plasma free fatty acids (FFA), insulin, epinephrine (E), and norepinephrine (NE) concentrations. In fed animals, MA increased blood glucose, plasma FFA, and NE and decreased insulin concentrations. Plasma E levels did not change. In 48-h-deprived animals, MA elevated low baseline glucose concentrations to levels observed in MA-treated fed animals. Plasma insulin concentrations decreased to almost undetectable levels. Plasma catecholamines and FFA were increased compared to fed rats. In exercising rats, MA caused an exaggerated increase of blood glucose and a pronounced reduction of plasma insulin without affecting exercise-induced FFA and catecholamine responses. The data revealed that the mechanisms that regulate blood glucose concentrations during MA treatment are dependent on the nutritional state and ambient energy expenditure.

Adrenal Glands↗
PubMed1995

Effects of GLP-1 and 2,5-anhydro-D-mannitol on insulin secretion and plasma glucose in mice.

The truncated glucagon-like peptide-1 (GLP-1(7-36)amide or GLP-1) stimulates insulin secretion, enhances glucose elimination and is of potential interest in diabetes treatment. We studied the hypoglycemic action of GLP-1 in normal mice when given alone or together with the fructose analogue, 2,5-anhydro-D-mannitol (2,5-AM), which inhibits glycogenolysis and gluconeogenesis. GLP-1 (32 nmol/kg iv) lowered plasma glucose levels after 25 min to 4.6 +/- 0.2 mmol/l compared with 7.3 +/- 0.4 mmol/l in controls (P < 0.001). Also 2,5-AM (0.5 mumol/kg iv) reduced plasma glucose levels, to 5.6 +/- 0.3 mmol/l (P < 0.01). When given together, the glucose lowering action of GLP-1 and 2,5-AM was additive, since the 25 min glucose level was 2.8 +/- 0.2 mmol/l. At 5 min after injection, GLP-1 had increased plasma insulin levels to 693 +/- 68 pmol/l compared with 342 +/- 42 pmol/l in controls (P < 0.01). 2,5-AM abolished this increase. Furthermore, GLP-1 (32 nmol/kg) did not affect the glycogen content, neither in the liver nor in the gastrocnemic muscle in samples taken at 30 min after injection. Moreover, in isolated islets incubated at 3.3 and 8.3 mmol/l glucose, 2,5-AM at 75 mmol/l inhibited glucose-stimulated insulin secretion (P < 0.05) showing that 2,5-AM inhibits insulin secretion both in vivo and in vitro. We conclude that GLP-1 may reduce plasma glucose levels also to levels below the basal levels under normal conditions, and that an insulin- and liver-independent action of the peptide contributes to its hypoglycemic action in normal animals.

Animals↗
PubMed1994

Hormonal and metabolic effects of paraventricular hypothalamic administration of neuropeptide Y during rest and feeding.

To investigate the role of neuropeptide Y (NPY) in the paraventricular nucleus of the hypothalamus (PVN) in the regulation of autonomic outflow, hormonal (plasma insulin and catecholamines), metabolic (blood glucose and plasma free fatty acids) and cardiovascular (heart rate and main arterial pressure) indices were measured before, during, and after bilateral infusion of NPY (1.0, 0.2, 0.04 micrograms in 1 microliter synthetic CSF) into the PVN of conscious resting rats. Administration of the highest dose (1.0 microgram/microliter) caused bradycardia and reduced circulating norepinephrine levels without effecting circulating fuels, insulin or epinephrine. In a second experiment, feeding-induced changes in hormonal and metabolic indices were assessed after NPY administration (1.0 microgram/microliter) into the PVN. During and after feeding, NPY enhanced the feeding-induced insulin response (P < 0.01) and attenuated the feeding-induced norepinephrine response (P < 0.05). The results of the present study suggest that stimulation of NPY receptors in the PVN decreases sympathetic activity and increases parasympathetic activity in resting conditions, and that these effects are potentiated during feeding.

Animals↗
PubMed1994

Effect of anaesthetizing the region of the paraventricular hypothalamic nuclei on energy metabolism during exercise in the rat.

The ventromedial and posterior hypothalamic nuclei are known to influence glucoregulation during exercise. The extensive projections of the paraventricular hypothalamic nucleus (PVN) to the sympathetic nervous system suggest that the PVN also may be involved in glucoregulation during exercise. The region of the PVN was anaesthetized with bupivacaine before running (26 m min-1) or continued rest, via previously implanted bilateral brain cannulas aimed at the dorsal aspect of the PVN. Control rats were treated identically to PVN-anaesthetized rats, but were not infused. Blood, for determination of plasma concentrations of metabolites and hormones, was drawn from a tail artery, and 3H-glucose was infused in a tail vein for glucose turnover determinations. At rest, no significant changes in plasma concentrations of metabolites or hormones were induced by anaesthesia of the region of the PVN. During exercise, glucose production and utilization and plasma concentrations of glucose, lactate, glycerol, noradrenaline, adrenaline, corticosterone, and glucagon increased (P < 0.02) and plasma insulin decreased (P < 0.02) in all rats. However, initially in exercise, adrenaline (4.3 +/- 0.8 vs. 7.9 +/- 1.0 nmol l-1 in controls, P < 0.05, t = 6 min) and later corticosterone levels (1.37 +/- 0.06 vs. 1.69 +/- 0.10 nmol l-1 in controls, P < 0.05, t = 20 min) were attenuated by PVN anaesthesia. Initially during exercise, glucose utilization was higher and plasma glucose lower in PVN-anaesthetized rats compared to controls (16.6 +/- 0.8 vs. 12.7 +/- 0.6 mumol min-1 100 g-1 and 7.1 +/- 0.2 vs. 8.1 +/- 0.2 mmol l-1, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗