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Biomedical subjects

N P Verhoeff

Publications and source records attributed to N P Verhoeff.

45 records · Page 3Linked to original sources
PubMed1992

Focus localization in patients with partial epilepsy with 99Tcm-HMPAO SPECT under continuous surface EEG monitoring.

Our study was aimed at determining the validity of 99Tcm-HMPAO single photon emission computed tomography (SPECT) in the localization of the epileptogenic focus by correlating this diagnostic method with other auxiliary investigations such as surface EEG and X-ray transmission computed tomography (CT). Twenty-eight patients with partial epilepsy and spontaneous memory complaints were assessed with a 21-channel EEG recorded during psychometric evaluation of the memory complaints and with a 12-channel EEG during 99Tcm-HMPAO SPECT. No significant agreement was observed for total focus localization by the two EEGs, CT or SPECT. The EEGs were highly reproducible. Frontal and temporal pathology on CT resulted in frontal and temporal cold spots on SPECT on the same side in six patients. In addition, SPECT demonstrated frontal, temporal or posterior temporal-inferior parietal cold spots in nine patients without accompanying pathology on CT. It is concluded that CT and SPECT may provide complementary anatomical and functional information, respectively, to the EEG. Furthermore, SPECT may be complementary to CT in visualizing functional deficits without an anatomical correlate. The value of SPECT studies in partial epilepsy may be improved by increasing the resolution of the SPECT system and by simultaneous EEG monitoring.

Adult↗
PubMed1992

Nedocromil sodium inhibits the early and late asthmatic response to exercise.

A double-blind, crossover study was carried out to investigate the effect of nedocromil sodium on the dual asthmatic response to exercise challenge. Nineteen patients with a late response to bicycle exercise were randomly treated on two study days with 4 mg nedocromil sodium or a matched placebo aerosol, 30 min before commencing exercise. Peak flow was measured before exercise, at intervals up to 60 min after exercise, then hourly for up to 13 h. In 12 of the 19 patients an early reaction to exercise occurred. In 8 of these 12 patients the early reaction could be inhibited by nedocromil sodium (p less than 0.01) although in half of these patients placebo was also shown to be protective. In the case of the late reaction after exercise challenge, 4-13 h after exercise challenge, nine patients were clearly protected by pretreatment with nedocromil sodium (p less than 0.01) when the fall in peak expiratory flow rate was related to the pre-exercise baseline, four patients showed an equal protective effect of placebo and nedocromil sodium, whilst the others were not protected. When the late asthmatic response (fall in peak expiratory flow rate) after exercise challenge was related to control diurnal peak flow values, the number of responses was reduced; the protective effect of nedocromil sodium remained.

Adult↗
PubMed1991

Pharmacological implications for neuroreceptor imaging.

Neuroreceptor imaging is increasing in nuclear medicine. New generations of radioligands will be developed that will allow us to study neurotransmitter systems not studied before. In data interpretation, however, links will have to be made with the number of counts acquired in the image and the real radioactivity in the brain and then, via the specific activity (and known metabolic characteristics), with the concentration of the ligand. From this point, links will have to be made, via kinetic modelling, with receptor density and, if possible, with receptor affinity, with the final link with brain function at a neurophysiological level. In this article several properties of receptor pharmacology and function are discussed that might help with the interpretation. It is argued that there is a complex relationship between the data, as is apparent in the images recorded and the underlying pharmacology of the receptor. Caution should be exercised, however, when in drawing conclusions about the receptor status and the possible implications on pathophysiology.

Aging↗
PubMed1991

In vitro and in vivo D2-dopamine receptor binding with [123I]S(-) iodobenzamide ([123I]IBZM) in rat and human brain.

As a promising dopamine D2-receptor imaging agent for single photon emission computerized tomography (SPECT), [123I](S)-(-)-2-hydroxy-3-iodo-6-methoxy-N [(1-ethyl-2-pyrrolidinyl)methyl]benzamide ([123I]IBZM) has recently been synthesized in a modified way along with its precursor, S(-)BZM, and the stereoisomer R(+)BZM. The present study applied this new product to investigate in vitro and in vivo D2-receptor binding in rat brain and in postmortem human brain. In vitro saturation binding curves with [123I]IBZM for rat crude striatal membrane preparations yielded an affinity constant (Kd) of 0.28 nM confirming data in the literature. Displacement curves revealed an order of increasing potency as follows: R(+)BZM less than S(-)sulpiride = less than S(-)BZM less than S(-)IBZM. A similar order was obtained when [3H]spiperone was used as ligand. For human putamen and caudate nucleus membranes slightly higher Kd values (0.49 nM) were obtained. Rank order of displacing potency for the various drugs was similar to that found in the rat preparations. In vivo uptake of [123I]IBZM in rat brain following injection of 50 microCi (12-16 pmol) in the tail vein revealed an increase in the striatum-to-cerebellum ratio from 1.5 at 5 min to 6.9 at 2 h. The olfactory tubercle-to-cerebellum ratio was also raised from 1.6 to 3.3. Other brain regions tested failed to show statistically significant enhancements. Coinjection of 40 nmol S(-)IBZM, 4 mumol S(-)BZM or 200 nmol haloperidol displaced [123I]IBMZ when tested at 90 min. The use of 4 mumol R(+)BZM resulted in minor displacement only, demonstrating that stereospecificity of the displacement was present in vivo and in vitro. Displacements were also observed in substantia nigra and pons-medulla oblongata, but not in hippocampus or frontal and occipital cortex. The data provide the required background needed in order to initiate in vivo binding studies for D2-receptors in basal ganglia of human patients using [123I]IBZM in SPECT analyses.

Animals↗
PubMed1991

Dynamic SPECT in two healthy volunteers to determine the optimal time for in vivo D2 dopamine receptor imaging with 123I-IBZM using the rotating gamma camera.

Dynamic SPECT was performed in two healthy male volunteers with a single slice brain dedicated camera (Strichman Medical Equipment 810, first study) and a rotating gamma camera (Siemens Dual Rota ZLC37, second study) to obtain information about the optimal imaging time for the dopamine D2 receptor specific ligand 123I-(S)-(-)-2-hydroxy-3-iodo-6-methoxy-N[(1-ethyl-2-pyrrolidinyl) methyl]-benzamide (123I-IBZM). Count rates in the basal ganglia and in several cerebral cortical regions were used to define specific and aspecific binding, respectively. On the basis of the first study, 90-150 min seemed the optimal time for rotating gamma camera 123I-IBZM-SPECT. On the basis of the second study the optimal period was considered to be 60-120 min. It is recommended to apply the same imaging time after injection in a protocol to all patients and volunteers as otherwise a comparison may not be reliable.

Adult↗
PubMed1990

In vivo characterisation of 3-iodo-6-methoxybenzamide 123I in humans.

3-Iodo-6-methoxybenzamide (123I-IBZM), a new Dopamine D2 receptor ligand, was used in conjunction with SME 810 brain tomography to study six subjects (one normal volunteer, four schizophrenics and one DAT patient). Initial Dynamic SPET was followed by multislice SPET. High-resolution images of the D2 receptor distribution in the basal ganglia were obtained. The specific binding in D2 receptors of the basal ganglia is highest from 2-4 h p.i. Patients on anti-psychotic drugs showed significantly lower specific binding. Dopamine D2 brain receptor availability in man may now be studied with SPET. Continuous data acquisition with single slice tomography is particularly important in the study of this type of radiotracers.

Adult↗
PubMed1990

Real and pseudo late asthmatic reactions after submaximal exercise challenge in patients with bronchial asthma. A new definition for late asthmatic responses after exercise challenge.

The late asthmatic reaction after exercise challenge remains a controversial issue. In this study, 21 patients recorded peak expiratory flow rate (PEFR) on two control days without performing exercise. There was no difference between both control days when PEFR at 1 h was compared with baseline PEFR and when PEFR at 4 to 13 hours was compared with baseline PEFR. After analyzing variation coefficients of baseline PEFR on a control day and exercise day, PEFR was not allowed to differ more than 15.3 percent in the same patient when comparing exercise day and control day for the late fall in PEFR in the study. In 17 of 81 patients, a late asthmatic reaction after exercise challenge was present when PEFR fall was greater than or equal to 20 percent compared with baseline PEFR value. In eight of the 17 patients, a real late asthmatic reaction to exercise challenge was present with a PEFR fall greater than or equal to 20 percent on at least three successive time points and who had a PEFR fall greater than or equal to 20 percent compared with corresponding clocktime on a control day. The late asthmatic reaction to exercise challenge is characterized not as a nonspecific epiphenomenon, but as a fall in PEFR of greater than or equal to 20 percent compared with baseline PEFR value and with corresponding clocktime on a control day on at least three successive time points. Graphic illustration of airway responses following exercises may facilitate the detection of a late asthmatic response.

Adult↗
PubMed1989

Immediate and late asthmatic responses induced by exercise in patients with reversible airflow limitation.

The existence and prevalence of late asthmatic responses to exercise in patients is uncertain. We investigated whether the late falls of peak expiratory flow rate (PEFR) after exercise challenge were still significant after comparison with the corresponding clocktime PEFR on a control day. We examined 86 patients with reversible airflow limitation, 79 with asthma and 7 with chronic obstructive pulmonary disease (COPD), all under regular treatment with bronchodilators and/or anti-inflammatory agents. Patients were randomized for a control day and an exercise day and PEFR was recorded hourly. On the exercise day, each patient underwent an 8 minute bicycle ride at 90% of predicted heart-rate. An early and a late asthmatic response to exercise were considered to occur when PEFR decreased by 10% or more on the exercise day compared to the corresponding clocktime PEFR on the control day. Thirty-three patients (38%) had a 10% or greater fall of PEFR at 4 to 13 hours after exercise when PEFR was compared with the corresponding clocktime on a control day. Seven (8%) had an isolated late asthmatic response, and 26 (30%) had a dual asthmatic response. We conclude that true late asthmatic responses develop after exercise in a significant number of patients with well controlled reversible airflow limitation.

Adolescent↗