Biomedical subjects

C V Jensen

Publications and source records attributed to C V Jensen.

22 records · Page 2Linked to original sources

PubMed1991

Inhibition in postischemic rat hippocampus: GABA receptors, GABA release, and inhibitory postsynaptic potentials.

We have investigated the GABAergic system in rat hippocampus at 1 hour and up to 21 days following 20 min of global cerebral ischemia. Distribution of 3H-GABA (in excess of unlabeled baclofen) and 3H-Ro-15-1788 (benzodiazepine antagonist) binding sites in hippocampus was studied utilizing quantitative autoradiography. The 3H-GABA binding was unchanged (p greater than 0.01) after ischemia, whereas the 3H-Ro-15-1788 binding decreased significantly (p less than 0.01) in all hippocampal subfields 1-21 days after ischemia. Using microdialysis in CA1, we found that K(+)-stimulated GABA release at 1 hour and 1 day after ischemia was unchanged (p greater than 0.01) in comparison to preischemic controls. Electrophysiological recordings were made from CA1 of hippocampal slices prepared from rats sacrificed 1 hour, 1 day and 2 days after ischemia. Field potentials evoked by stimulation of the Schaffer collaterals showed no differences (p greater than 0.01) from those taken from controls. Postischemic intracellular recordings from the CA1 pyramidal cells showed that fast and slow inhibitory postsynaptic potentials were readily evoked on orthodromic stimulation. Together with our previous morphological results, demonstrating survival of hippocampal interneurons following ischemia, we conclude that hippocampal GABAergic interneurons preserve their inhibitory potential in the period preceding delayed CA1 pyramidal cell death. This conclusion taken together with the observation that postischemic 3H-Ro-15-1788 binding in hippocampus declined, suggest that benzodiazepines (by increasing the receptor affinity), GABA analogs, and GABA uptake inhibitors may be useful in the treatment of ischemic CA1 pyramidal cell death in the rat.

Animals↗

PubMed1991

A computer program for randomizing patients with near-even distribution of important parameters.

In clinical trials, the methods for achieving an event or near-even distribution of important patient parameters have been tedious and often disappointing. In this paper, a computer program for minimizing differences between experimental groups with respect to such important parameters, based on a method described by Traves (Clin. Pharmacol. Ther. London 15, 443, 1974) is presented. The program is available from the author.

Clinical Trials as Topic↗

PubMed1989

Calcium-imaging with Fura-2 in isolated cerebral microvessels.

Cerebral microvessels were isolated from rat hippocampus with a modified, mild collagenase digestion and loaded with the calcium fluoroprobe, Fura-2. Using a fluorescence microscope with quartz optics and an image analyser, it was possible to measure the intracellular concentration of free calcium ions [Ca2+]i in single microvessels for the first time. A resting level of (90 +/- 28) nmol/l (+/- SD, n = 24) was calculated which immediately rose after ionomycin application. The temporal resolution for [Ca2+]i of our set-up was 0.7 s. By image processing, sequences of digitized fluorescence images of single microvessels were colour-coded in terms of [Ca2+]i with a spatial resolution up to 1.5 microns (pixel size). Both the temporal and spatial resolution make our system suitable for investigation of calcium-mobilizing receptors of the blood-brain barrier.

Animals↗

PubMedDate not supplied

Effect on the content of n-acetylaspartate, total creatine, choline containing compounds, and lactate in the hippocampus of rats exposed to aromatic white spirit for three weeks measured by NMR spectroscopy.

Several epidemiological studies of workers occupationally exposed to white spirit show that neuropsychiatric disorders are a frequent cause of early disability pension in this population compared with non-exposed controls. In the rat, we have demonstrated that exposure to different kinds of white spirit induces changes in neurotransmitter concentrations, indices of oxidative stress, and electrophysiological parameters. Others have confirmed that acute behavioural effects can be induced by short-term high-level exposure. With NMR spectroscopy technique it is possible to study neurochemical parameters in vivo, and to examine the same subjects repeatedly over time. NMR spectroscopy was used to study the effects of organic solvents in rats. Rats were exposed to 0, 400 ppm, or 800 ppm of aromatic white spirit 6 hr/day, 7 days/week for 3 weeks. During the first week, the rats showed signs of irritation of mucous membranes, and appeared to be sedated. Both types of effect gradually diminished during the second week. The rats were examined by single volume of interest (VOI) NMR spectroscopy. N-acetylaspartate, creatinine and phosphocreatinine, and choline containing compounds were measured in the hippocampus and surrounding regions. The concentration of N-acetylaspartate for the three groups was found to be in the range of 8.2-8.5 mM with a standard deviation of 0.6-0.9. There was no difference between the three groups. In a previous study no change in the number of astrocytes in hippocampus was found following exposure to white spirit for six months. Since N-acetylaspartate is thought to be a marker for neurons, the results of these two studies indicate that white spirit does not produce a marked neuronal loss. However, it was not possible to show effect of trimethyltin. In this study trimethyltin was used as a "positive control'. The NMR technique can be applied to the rat, and it is possible to obtain reasonable signal-to-noise ratios.

Animals↗