[Show abstract][Hide abstract] ABSTRACT: A hypofunction of the glutamatergic system and NMDA receptors in schizophrenia has been hypothesized. Therefore, stimulation of these receptors could be of benefit to patients with schizophrenia. D-cycloserine has been used for this purpose. This study reports the effects of 100 mg D-cycloserine, when added to typical antipsychotics in chronic schizophrenic patients exhibiting prominent negative symptoms, using a placebo-controlled, double-blind, parallel, design. D-cycloserine slightly worsened psychotic symptoms and general psychopathology as compared to placebo. D-cycloserine failed to change negative symptoms and had no effect on extrapyramidal symptoms. The exacerbation of schizophrenic symptoms may be explained by the antagonistic effects of this dose of D-cycloserine at the glycine recognition site of the NMDA receptor due to competition with the endogenous agonist glycine. Another explanation for the increase in psychopathology may be an interaction with the effects of antipsychotics on NMDA mediated neurotransmission. Thus, D-cycloserine in this study did not ameliorate schizophrenic symptoms. However, the fact that they actually worsened suggests that NMDA systems may be involved in the pathogenesis of schizophrenia. Further placebo-controlled studies with lower dosages of D-cycloserine, preferably in drug-free patients, are necessary to evaluate if D-cycloserine is of use for the treatment of patients with schizophrenia.
[Show abstract][Hide abstract] ABSTRACT: Long-term oxygen therapy (LTOT) has been shown to improve survival in hypoxaemic patients with chronic obstructive pulmonary disease (COPD). This has resulted in recommending the prescription of oxygen for at least 15 h day-1 in most European countries. In order to examine the prescription and usage of LTOT and to assess the adherence to international recommendations for its prescription, a survey was set up in a random sample of clients of the largest oxygen company in the Netherlands. After patients had been visited for an interview, additional postal surveys were sent to the physician who had prescribed LTOT and to the oxygen company. For 175 COPD patients the mean oxygen prescription and mean oxygen usage were 15.6 +/- 5.8 and 14.1 +/- 6.8 h day-1, respectively. In 62 patients (35%) oxygen was prescribed < 15 h day-1, more often by non-chest physicians than by chest physicians (P < 0.0001), and 91 patients (52%) used oxygen < 15 h day-1. Of 113 patients with a prescription > or = 15 h day-1, 39 (35%) used oxygen < 15 h day-1 and 74 for > or = 15 h day-1. The latter were prescribed oxygen for more h day-1, had been longer on LTOT, had a higher resting flow rate, were prescribed a concentrator, employed portable cylinders and used oxygen in public significantly more often than the former. We conclude that in a selected group of LTOT patients with COPD both oxygen prescription and usage were often inadequate, particularly if LTOT was prescribed by non-chest physicians.
Full-text · Article · Jan 1999 · Respiratory Medicine
[Show abstract][Hide abstract] ABSTRACT: D-Cycloserine, a partial agonist of the glycine recognition site of the N-methyl-D-aspartate (NMDA) receptor, may serve as a probe for human cerebral NMDA receptor function. Since NMDA receptors are involved in neuroendocrine secretion, changes in pituitary secretion in response to D-cycloserine administration could serve as a model for NMDA receptor activity. The effects of an oral dose of 500 mg D-cycloserine were assessed in a neuroendocrine challenge paradigm in 20 healthy male volunteers, using a double-blind, randomized placebo-controlled crossover design. Luteinizing hormone (LH) and cortisol secretion was studied, since preclinical studies indicate that these hormones increase in response to NMDA receptor stimulation. Furthermore, plasma homovanillic acid (HVA) secretion was studied, as NMDA receptors are suggested to be involved in the regulation of dopaminergic neurotransmission. D-cycloserine was readily absorbed and did not induce side-effects or changes in vital signs and mood scores. D-Cycloserine stimulated LH secretion and induced a significant rise of the area under the plasma concentration time curve of LH. D-Cycloserine did not stimulate cortisol or plasma HVA secretion. These neuroendocrine effects suggest that D-cycloserine may be used to assess human NMDA receptor function in cerebral disorders, such as schizophrenia.
No preview · Article · Aug 1998 · Psychopharmacology
[Show abstract][Hide abstract] ABSTRACT: In patients prescribed long-term oxygen therapy (LTOT), compliance is often poor. Both patient- and treatment-related factors seem to be involved. As a base for improvements in LTOT, the characteristics and complaints of LTOT patients were investigated. A survey was set up in a random sample of clients of the largest oxygen company in the Netherlands. Patients were selected if they were > or = 18 years old, had a phone and if they had had oxygen equipment for > or = 6 months. All patients were visited at home by a medical student. Data are presented for a total of 528 patients (response rate 62%). The typical LTOT patient was a 70-year-old male with chronic obstructive pulmonary disease (COPD), who had had oxygen equipment for 3.5 years and who used oxygen cylinders and nasal cannulae for 13 h day-1. Twenty percent of the patients still smoked. Although LTOT was prescribed in 80% of the patients by a chest physician, prescription was often inadequate. Only 33% of the patients were informed adequately about the therapy. Twenty percent of the patients used oxygen for fewer hours per day than prescribed. Non-compliant patients were mainly men (P = 0.006) and more often ashamed of their therapy (P = 0.023) than compliant patients. The blood oxygen level was monitored regularly in 73% of the patients. Most complaints concerned the oxygen equipment, especially the concentrator. The single most important complaint had to do with restricted autonomy. Only 19% of the patients had no complaints at all. It is concluded that LTOT should be improved with regard to the education, motivation and monitoring of patients. The prescribing physician needs to be included in an education programme. Given the numerous problems these patients experience, LTOT should be improved in particular with regard to equipment convenience.
Full-text · Article · Feb 1998 · Respiratory Medicine
[Show abstract][Hide abstract] ABSTRACT: Definition of optimal magnetic resonance (MR) scanning plane and conventional MR sequence for the detection of mesial temporal sclerosis (MTS).
Coronal and axial T2-weighted images and axial T2-weighted images parallel to the long axis of the hippocampus (APLAH) and coronal inversion recovery (IR) images were obtained in patients with medically intractable temporal lobe epilepsy in their phase 1 preoperative evaluation. Thirty-three consecutive MR scans were reviewed by a panel of three radiologists. Twenty-three patients had MR abnormalities consistent with MTS, and ten scans were normal. To assess the best single scanning technique, another group of three radiologists, who were masked to all patient data, individually assessed the different planes and sequences of the 33 studies presented separately in a random fashion. For each plane and sequence, the likelihood (L) ratio for the correct diagnosis was determined separately.
For all planes considered separately, a likelihood ratio of 4.4 was optimal for the coronal T2-weighted images. The likelihood ratio of APLAH T2 was 2.2; of axial T2, 3.9; of coronal IR, indefinite because of 100% specificity.
For the assessment of MTS, coronal T2-weighted images were considered the best single scanning technique.
No preview · Article · Jun 1997 · Investigative Radiology
[Show abstract][Hide abstract] ABSTRACT: The effect of D-cycloserine, a partial agonist of the N-Methyl-D-Aspartate (NMDA) receptor, were assessed in a (neuroendocrine) challenge paradigm to to examine NMDA systems in male healthy volunteers, using a double-blind, placebo-controlled crossover design. Oral D-cycloserine (15, 50, and 150 mg) was readily absorbed and its plasma concentration increased dose-dependently. Behavioral and hormonal responses were measured for 240 minutes after administration of the drug. D-cycloserine was well tolerated and did not induce side-effects according to the Visual Analog Scales (VAS), the Brief Psychiatric Rating Scale (BPRS) and the Adverse Events Checklist (AEC) & codes. D-cycloserine failed to elicit a neuroendocrine response as evaluated by cortisol, prolactin, and luteinizing hormone (LH) plasma levels. The present result suggests that D-cycloserine can readily be administered to healthy volunteers but that, in the dosages used, neuroendocrine secretion fails to serve as a model for testing NMDA receptor function in humans.
No preview · Article · Jun 1997 · Neuropsychopharmacology
[Show abstract][Hide abstract] ABSTRACT: A single type of high density lipoprotein (HDLp) binding sites is present at intact fat body tissue and in fat body membranes of larval and adult locusts. HDLp is bound with high affinity (Kd approximately 10(-7) M). This interaction does not require divalent cations and is heat-labile because heat-treatment of fat body membranes results in a substantial reduction of the maximal binding capacity. In addition to unlabeled HDLp and low density lipophorin (LDLp), human low density lipoprotein also seems to compete with radiolabeled HDLp for this binding site, suggesting a relaxed specificity. Induction of lipid mobilization with adipokinetic hormone did not change the binding characteristics of the fat body. An increase in the binding capacity of intact fat body tissue in the adult stage suggests that the number of cell surface binding sites is upregulated during development. However, the total number of HDLp binding sites appears to be constant, because larval and adult fat body membranes have similar binding capacities.
Full-text · Article · Jul 1996 · The Journal of Lipid Research
[Show abstract][Hide abstract] ABSTRACT: A corticotropin-releasing hormone (CRH) stimulation test with four cumulative doses of human CRH (0.01, 0.06, 0.2 and 1 microgram/kg body weight) and infusion of a low dose of [Arg8]-vasopressin (0.004 U/kg body weight/30 min) was performed in five depressed patients and six healthy subjects. Plasma samples for the measurement of cortisol, ACTH and beta-endorphin were taken at regular intervals and considered as measures of pituitary-adrenal function. A dose-response relationship between CRH and the hormones measured was found in patients and controls. Depressed patients already responded to the lowest dose of CRH with respect to cortisol release, whereas ACTH and beta-endorphin responded to the second and third doses, respectively. In control subjects the cortisol and ACTH response started after the third dose of CRH, whereas beta-endorphin responded significantly to the highest dose only. When both groups were compared, differences in response were found to the higher doses of CRH with respect to cortisol, ACTH and, less markedly, beta-endorphin and to the lowest dose of CRH with respect to cortisol. Although numbers are small, the data show 'blunting' of the ACTH response to the higher doses of CRH in patients with an enhanced cortisol response of the adrenals to lower and higher doses of CRH. There was no significant difference in response when CRH was used with vasopressin as compared to treatment with CRH alone. Thus, in this design vasopressin did not contribute significantly to CRH activity. The data suggest that pituitary cell sensitivity might be changed in depression as part of HPA dysfunction.
No preview · Article · Jan 1994 · European Neuropsychopharmacology
[Show abstract][Hide abstract] ABSTRACT: Spontaneous growth and growth responses to GH therapy vary considerably among girls with Turner's syndrome. In an attempt to clarify this variability, we assessed growth parameters, 24-h GH profiles, arginine-stimulated serum GH levels, and plasma insulin-like growth factor-I (IGF-I) concentrations in a group of 41 girls with Turner's syndrome with a mean (+/- SD) age of 13 +/- 3 yr (range, 6.7-18.9). We subsequently treated all girls with biosynthetic GH (24 IU/m2 x week) and documented the growth response after 1 yr of therapy. GH profiles were analyzed according to Pulsar and Cluster, and GH secretion rates were calculated by waveform-independent deconvolution (Pulse). Factor analysis selected the mean 24-h GH secretion rate and number of GH peaks according to Cluster and Pulse as the principal GH profile variables to be used for further analysis. The mean (+/- SD) daily pituitary GH secretion rate was 127 +/- 47 micrograms/L.24 h (range, 37-232). The GH secretion rate correlated inversely with body mass index (r = -0.45; P < 0.01; n = 41). There was no relationship between the GH secretion rate and the growth parameters before or after GH therapy. However, the number of GH peaks (Pulse) correlated negatively with baseline height velocity (r = -0.53; P = 0.03) and was a positive predictor for height velocity increment during the first year of GH therapy (r = 0.71, P = 0.001). The mean (+/- SD) IGF-I level was 217 +/- 91 ng/mL (range, 87-413). There was no relationship between GH secretion rate or growth parameters and IGF-I. However, the number of GH peaks correlated negatively with IGF-I (r = -0.49; P = 0.04; n = 17). We conclude that an elevated spontaneous GH pulse frequency pattern is associated with relatively low IGF-I levels and slow baseline growth in girls with Turner's syndrome and that girls with such a pulse pattern may benefit most from exogenous GH therapy.
Full-text · Article · Jun 1993 · Journal of Clinical Endocrinology & Metabolism
[Show abstract][Hide abstract] ABSTRACT: 1. Sterol composition of the aboral body-wall of male specimens of Asterias rubens starved for three weeks, was compared with that of male sea stars which during the starvation period had been exposed to cadmium (100).2. Sterol composition of non-exposed animals appeared to be constant as assessed over a period of four years.3. Cadmium-exposure strongly influenced sterol composition. The effect was related to the reproductive cycle, effects being different in the spermatogenic and the aspennatogenic phase.4. Effects on total C27-, C28-,Δ7.22-, and some individual sterols showed abrupt changes in November and March, coinciding with the start and the end of the reproductive cycle.5. In one experiment additional parameters were determined. Cadmium-exposure resulted in a significant increase of polar lipids in the body-wall and a decrease of the sterol/phospholipid ratio. The increase of polar lipids was accompanied by a decrease of C28-sterols. Consequences for viscosity are discussed.6. Cadmium-exposure also resulted in a decrease of phosphatidylserine and an increase of phosphatidylethanolamine.
No preview · Article · Mar 1993 · Comparative Biochemistry and Physiology Part C Comparative Pharmacology
[Show abstract][Hide abstract] ABSTRACT: Different doses dexamethasone (0.25, 0.5, and 1 mg) or cortisol (30, 60, and 120 mg) were administered PO at 2230h to 39 depressed patients and 20 healthy subjects on nonsuccessive days. The inhibiting capacity of the two steroids on hypothalamo-pituitary axis (HPA) function was evaluated by measuring the plasma levels of cortisol, ACTH, and β-endorphin at 0900h and 1530h each day following treatment. Baseline levels of the hormones were measured before starting treatment. A dose-dependent suppressive effect of both steroids on the plasma levels of cortisol, ACTH, and β-endorphin was found both in patients and controls, except for the 0900h levels of cortisol after cortisol treatment. The effects were most profound in the morning. Differences between patients and controls were observed after cortisol treatment, but not dexamethasone, with respect to cortisol, ACTH, and β-endorphin plasma levels in the morning. Cortisol treatment discriminated dexamethasone nonsuppressors from suppressors (patients and controls) and patients categorized as dexamethasone suppressors from controls in a way that dexamethasone treatment could not. The data favour the idea of impaired corticosteroid feedback beyond the pituitary level as part of HPA dysfunction.
No preview · Article · Feb 1993 · Psychoneuroendocrinology
[Show abstract][Hide abstract] ABSTRACT: A multicenter dose-response study evaluated the effect of two different doses of biosynthetic GH on auxological and biochemical parameters in 38 prepubertal children with GH deficiency (GHD). Twenty-one were newly diagnosed, while 17 transfer patients had been on GH treatment for at least 1 yr before the study. New and transfer patients alike were treated with either 2 or 4 IU GH/m2.day sc. At evaluation all new patients had completed 1 yr of treatment, while transfers had completed 2 yr of treatment under study. In the new patients both doses resulted in a significant increase in height velocity (HV) and height SD score (SDS), with comparable bone maturation. After correction for the severity of GHD, the increase in HV SDS was significantly greater with 4 IU than with 2 IU (P less than 0.01). In the transfer patients HV, height SDS, and predicted adult height only increased significantly with 4 IU (P less than 0.05). Bone maturation was comparable for the two doses. There was a significant correlation between first year growth response and GH dose. In the new patients, the plasma insulin-like growth factor-I (IGF-I) concentration increased significantly without a significant difference between dosage groups. There was a positive correlation between growth response and increment of plasma IGF-I SDS. In new and transfer patients alike, above normal plasma IGF-I levels were observed, particularly with 4 IU. Hemoglobin-A1 remained constant with both GH doses in both groups, while cholesterol and LDL levels tended to decrease. In the new patients, the mean apolipoprotein-A1 level was lower than the control value after 1 yr on 4 IU GH. Treatment with 4 IU GH/m2.day led to a greater growth response than a dose of 2 IU in newly diagnosed as well as previously treated GHD patients. Bone maturation was comparable for both doses. No adverse effects were observed with the higher GH dose, but the long term effects on IGF-I and lipid metabolism need further attention.
No preview · Article · May 1992 · Journal of Clinical Endocrinology & Metabolism
[Show abstract][Hide abstract] ABSTRACT: 1.1. The effect of photoperiod on steroid metabolism in Asterias rubens was studied.2.2. Daylength was artificially shortened in 3 weeks from long-day (LD 18/6) to short-day (LD 6/18) conditions and its effect on the metabolism of pregnenolone and dehydroepiandrosterone was studied in homogenates of gonad and pyloric caeca tissue from male and female seastar.3.3. Pregnenolone metabolism did not change during the experiment when the animals were kept continuously under the same (long-day) conditions. Pregnenolone metabolism was intensified by decreasing daylength. The production of progesterone reached its maximum at a daylength comparable to that in autumn (LD 12/12), and that of an unidentified steroid at an even shorter daylength.4.4. Metabolism of dehydroepiandrosterone was influenced by photoperiod. There were indications that androstenedione production is maximal at fall conditions. This was evident for an as yet unidentified steroid.5.5. Metabolism of DHEA strongly increased during the experiment in animals which were kept continuously under long-day conditions. It is discussed that this may be a reaction to crowding.
No preview · Article · Dec 1991 · Comparative biochemistry and physiology. B, Comparative biochemistry
[Show abstract][Hide abstract] ABSTRACT: To study platelet activation as a phenomenon that may precede development of angiopathy in diabetes mellitus, we compared platelet adhesion and thrombus formation in a flow system with blood from insulin-dependent (type I) diabetic subjects with and without macroangiopathy and age- and sex-matched control subjects. Adhesion and thrombus formation on matrix of cultured human endothelial cells (ECM) and adhesion on matrix of human fibroblasts (FBM) were studied after exposure to flowing blood at shear rates of 300 and 1300 s-1 and exposure times of 1, 3, 5, and 10 min (and 20 min in adhesion experiments). Blood was anticoagulated with trisodium citrate (1:10 vol/vol, 110 mM) or low-molecular-weight heparin ([LMWH] 20 U/ml). Endothelial cell cultures were either unstimulated or stimulated with 4 beta-phorbol 12-myristate 13-acetate (PMA) 16 h before isolating their matrix. Platelet adhesion on ECM and FBM in citrated and LMWH-anticoagulated blood was identical in diabetic patients and control subjects, with comparable increases of adhesion with increasing perfusion times. Platelet aggregate formation on ECM of PMA-stimulated cells with LMWH-anticoagulated blood was similar in diabetic patients, whether macroangiopathy was present, compared with control subjects. Fibrin deposition and fibrinopeptide A generation during perfusion were comparable in diabetic and control subjects. Platelet thromboxane B2 formation after stimulation with arachidonic acid was increased in diabetic patients without macroangiopathy compared with age- and sex-matched control subjects. In the perfusion system, the patterns of platelet adhesion and aggregate formation on extracellular matrix in flowing blood of diabetic patients (with or without macroangiopathy), and healthy age- and sex-matched control subjects followed a similar pattern.(ABSTRACT TRUNCATED AT 250 WORDS)
[Show abstract][Hide abstract] ABSTRACT: This study was designed to investigate the susceptibility of the parthenogenetic eggs of Daphnia magna to cadmium, zinc, copper, and lead. Early life stages of D. magna proved to be highly tolerant to heavy metal toxicity in comparison with later stages. This relatively high tolerance might be explained by the structural constitution of the eggs.
No preview · Article · Jul 1989 · Ecotoxicology and Environmental Safety