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Biomedical subjects

A M van den Brink

Publications and source records attributed to A M van den Brink.

5 recordsLinked to original sources
PubMed2006

Intravital microscopy on a closed cranial window in mice: a model to study trigeminovascular mechanisms involved in migraine.

The purpose of the study was to develop a mouse model to study trigeminovascular mechanisms using intravital microscopy on a closed cranial window. In addition, we studied exogenous and endogenous calcitonin gene-related peptide (CGRP)-mediated vasodilation in dural arteries. Arteries in C57BL/6Jico mice were constricted with endothelin-1, which reduced the baseline diameter by 65-75%. Subsequently, vasodilation was induced by alpha-CGRP, capsaicin or transcranial electrical stimulation of perivascular trigeminal nerves in the absence or presence of different concentrations of BIBN4096BS or sumatriptan. Both alpha-CGRP and capsaicin induced vasodilation in preconstricted arteries. Transcranial electrical stimulation also induced current-dependent relaxation of dural arteries with 100 microA producing maximal dilation in the control group. BIBN4096BS blocked the responses evoked by alpha-CGRP and capsaicin, as well as electrical stimulation, whereas sumatriptan attenuated only vasodilation induced by electrical stimulation. This model is likely to prove useful in dissecting elements of the trigeminovascular system and for exploring pathophysiological aspects of migraine, especially in future studies using transgenic mice with mutations relevant to those observed in patients with migraine.

Animals↗
PubMed1998

Influence of electrode site and size on variability of magnetic evoked potentials.

Successive magnetic evoked potentials (MEPs) concern varying motor neurons. We investigated whether this MEP-specific source of variability depends on electrode site and size. Amplitude variability (standard deviation) was largest over the center of the hypothenar muscles. Latencies were longer at distal and proximal sites than at the center site. Large electrodes (10 cm2) did not decrease this source of amplitude variability compared with EEG electrodes, in contrast to other sources of variability.

Adult↗
PubMed1995

Angiotensin-converting enzyme in the human heart. Effect of the deletion/insertion polymorphism.

BACKGROUND: An insertion (I)/deletion (D) polymorphism of the angiotensin-converting enzyme (ACE) gene has been associated with differences in the plasma levels of ACE as well as with myocardial infarction, cardiomyopathy, left ventricular hypertrophy, and coronary artery disease. METHODS AND RESULTS: We determined the cardiac ACE activity and the ACE genotype in 71 subjects who died of noncardiac disorders. Cardiac ACE activity was significantly higher (P < .01) in subjects with the ACE DD genotype (12.7 +/- 1.9 mU/g wet wt) compared with subjects with the ID (8.7 +/- 0.8 mU/g) and the II (9.1 +/- 1.0 mU/g) genotypes. This difference was independent of sex, age, and the time required for tissue collection. CONCLUSIONS: Cardiac ACE activity is highest in subjects with the DD genotype. Elevated cardiac ACE activity in these subjects may result in increased cardiac angiotensin II levels, and this may be a mechanism underlying the reported association between the ACE deletion polymorphism and the increased risk for several cardiovascular disorders.

Adolescent↗
PubMed1993

Heterogeneity of intracellular calcium responses to parathyroid hormone and thrombin in primary osteoblast-like cells and UMR106-01 cells: correlations with culture conditions, intracellular calcium concentration and differentiation state.

The present study evaluates the effect of parathyroid hormone (PTH) on intracellular calcium. Intracellular calcium ion concentrations ([Ca2+]i) in fetal rat osteoblasts in primary culture (ROB) and in UMR106-01 osteogenic sarcoma cells were monitored as changes in the ratio (R) of Fura-2 fluorescence intensities in single cells as well as populations of cells. In both single ROB and UMR106-01 cells, addition of 10(-7) M rat PTH1-34 and 3 NIH units/ml human thrombin resulted in heterogeneous responses in R values and therefore [Ca2+]i. PTH-induced calcium responsiveness of ROB was dependent on culture conditions, such that response frequencies were positively correlated with the percentage of fetal calf serum in the culture medium. PTH responsive ROB and UMR106-01 cells had significantly higher resting [Ca2+]i than unresponsive cells. PTH- or thrombin-mediated calcium signalling appeared not to be correlated to alkaline phosphatase activity in single ROB. Low percentages of cells responded to PTH in comparison to thrombin suggesting that an increase in [Ca2+]i is not a common PTH signalling pathway in osteoblasts in primary culture. Our data suggest that activation of this signalling pathway by PTH is culture condition dependent, possibly via a cell-cycle related increase in sensitivity of the pathway.

Animals↗