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Biomedical subjects

T Christensen

Publications and source records attributed to T Christensen.

At least 127 records · Page 7Linked to original sources
PubMed1992

Natural radiation--a perspective to radiological risk factors of nuclear energy production.

Radiation doses from natural radiation and from man-made modifications on natural radiation, and different natural radiological environments in the Nodic countries are summarized and used as a perspective for the radiological consequences of nuclear energy production. The significance of different radiation sources can be judged against the total collective effective dose equivalent from natural radiation in the Nordic countries, 92,000 manSv per year. The collective dose from nuclear energy production during normal operation is estimated to 20 manSv per year and from non-nuclear energy production to 80 manSv per year. The increase in collective dose due to the conservation of heating energy in Nordic dwellings is estimated to 23,000 manSv per year, from 1973 to 1984. An indirect radiological danger index is defined in order to be able to compare the significance of estimated future releases of radionuclides from a final repository of spent nuclear fuel to the consequences of natural radionuclides in different environments. The danger index of natural radiological environments will not be significantly increased by future releases of nuclear fuel radionuclides.

Hot Temperature↗
PubMed1992

Decrease of extracellular taurine in the rat dorsal hippocampus after central nervous administration of vasopressin.

The extracellular amino acid concentrations in the left and right dorsal hippocampus of male rats were studied before and during application of vasopressin into the right hippocampus. The method of intracerebral microdialysis was used for both arginine vasopressin administration and monitoring of the composition of the extracellular fluid. The concentrations of 16 amino acids were measured by HPLC in the perfusate samples. The level of taurine declined 20% in the right hippocampus during perfusion with vasopressin, whereas o-phosphoethanolamine decreased in both sides, the left 20% and the right 24%. These alterations may be related to cerebral osmoregulation. Also, the levels of tyrosine and phenylalanine increased 15% and 35%, respectively, during administration of vasopressin. No changes of other amino acids were observed.

Amino Acids↗
PubMed1992

Neurocysticercosis: a short review and presentation of a Scandinavian case.

Cysticercosis is a disease entity caused by the larval form (Cysticercus cellulosae) of the pork tapeworm (Taenia solium). When man becomes the intermediate host, cysticercal cysts can develop in various organs. Neurocysticercosis, i.e. cysticercosis of the central nervous system, can lead to a broad range of neurological disturbances. The disease is usually confined to geographical regions where sanitation is poor but can occur among immigrants or travellers from such regions. Due to increased travel and immigration the disease may appear in non-endemic areas. We describe a recent case of neurocysticercosis in a 28-year-old Danish woman, who had been travelling in the Far East. She was successfully treated with praziquantel. A short review of the literature is given as the knowledge of the diagnosis and treatment of the disease has increased greatly in the last decade.

Adult↗
PubMed1992

Specific carbon-13 labelling of leucine residues in human growth hormone.

Biosynthetic human growth hormone specifically 13C-labelled in the carbonyl positions of all 26 leucine residues has been obtained by recombinant DNA techniques using 13C-labelled leucine and an E. coli strain that requires leucine. It is shown that, on the whole, the labelling is specific with no significant mislabelling as would have been the case had the 13C-labelled leucine been metabolized.

Carbon Isotopes↗
PubMed1991

Effect of phenylsuccinate on potassium- and ischemia-induced release of glutamate in rat hippocampus monitored by microdialysis.

The extracellular concentration of glutamate in rat hippocampus during physiological conditions, elevated extracellular K+ and global ischemia was followed by microdialysis and subsequent determination of glutamate by HPLC. The effect of phenylsuccinate, an inhibitor of the mitochondrial dicarboxylate carrier, was studied. It was found that while phenylsuccinate had no effect on the extracellular glutamate concentration during perfusion under physiological and ischemic conditions, the potassium-induced increase in the extracellular glutamate concentration was totally blocked by phenylsuccinate. Ischemia led to a pronounced glutamate overflow. The finding that phenylsuccinate could inhibit potassium-induced glutamate release into the extracellular space but not that induced by ischemia suggests that glutamate released under these conditions originates from different pools. Since glutamate released by a depolarizing concentration of potassium is likely to originate primarily from the transmitter pool, the ischemia-induced glutamate overflow may primarily be released from both the transmitter and the metabolic pool. This is compatible with the previous finding that phenylsuccinate specifically prevents biosynthesis of transmitter glutamate leaving the metabolic glutamate pool unaffected.

Animals↗
PubMed1991

[Cerebral cysticercosis].

A Danish woman aged 28 years who had travelled in the Far East developed cerebral symptoms with headache and visual disturbances. Migraine was suspected. Subsequent CT scanning revealed multiple processes and metastases were suspected. As the patient had travelled in the Far East 1 1/2 years previously, she was examined for neurocysticercosis. This diagnosis was established and the patient was successfully treated with praziquantel. On account of increased travelling activity, the possibility of neurocysticercosis should be borne in mind when dealing with patients with cerebral symptoms and relevant travelling histories.

Adult↗
PubMed1991

Functional cloning of BUD5, a CDC25-related gene from S. cerevisiae that can suppress a dominant-negative RAS2 mutant.

By searching for genes that behave like CDC25 of S. cerevisiae in their ability to counteract a dominant-negative RAS2 mutant in a wild-type RAS-dependent manner, we have isolated a CDC25-like homolog, BUD5. BUD5 is tightly linked to the MAT locus. Although overexpressed BUD5 cannot substitute for CDC25 function, we present evidence that its gene product can bind to the guanine nucleotide binding-deficient RAS2val19ala22 gene product and thereby counteract its dominant-negative effect. We propose that BUD5 is a member of a family of CDC25-related genes that encode activators of RAS and RAS-like proteins.

Amino Acid Sequence↗
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

Reversible pancreatic elastase-induced bronchial secretory cell metaplasia in the rat.

Porcine pancreatic elastase (PPE) causes irreversible secretory cell metaplasia (SCM) in the intrapulmonary bronchi of hamsters. To determine whether this lesion can be induced in another rodent species, PPE was transorally instilled into the lungs of anesthetized rats. Saline-treated rats served as controls. Animals were killed 1 week, 3 weeks and 3 months after enzyme treatment and the lungs were inflation-fixed with 4% formalin/1% glutaraldehyde in 0.1 M Na cacodylate buffer at pH 7.4. Transverse sections from 3 intrapulmonary airway levels were embedded in paraffin and in glycol methacrylate. The secretory cell index (SCI) was determined from PAS-stained paraffin sections using a standardized scale of 0 to 4. There were no significant differences between SCI values of PPE-treated rats and saline-treated controls at any time point. Secretory cells in methacrylate sections were subclassified into S1, S2 and S3 cells on the basis of increasing amounts of PAS-positive intracellular granules. At one week, there was no effect of PPE on airway level I secretory cells, but significant increases in numbers of S2 and S3 cells were seen in level II and in S3 cells in level III. At 3 weeks, the number of S1 cells were increased in level I and S2 and S3 cells were increased in level III; level II secretory cells were unaffected. Level III secretory cells had returned to normal by 3 months. There were no significant differences between treatment groups in the total number of secretory cells (S1 + S2 + S3) at any airway level or time point examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1991

Immunoglobulin and complement studies in children with Schönlein-Henoch Syndrome and other vasculitic diseases.

In 35 children with Schönlein-Henoch Syndrome (SHS) serum IgG, IgM, and IgA concentrations were increased in 15%, 21%, and 44% of cases, respectively. Seven children with other vasculitic syndromes (VS) had normal serum Ig concentrations. Serum concentration of IgG subclass IgG1 was increased in 72% of children with SHS and 57% with VS. In SHS this was related to the presence of arthritis, but inversely related to nephritic symptoms. Only a few children had IgG subclasses IgG2, IgG3, or IgG4 concentrations outside the normal ranges. Platelet associated Ig (PAIg) was found in 75% of children with SHS or VS. In SHS the identification of increased amounts of PAIgG was related to the presence of nephritis. The serum concentration of properdin, a component of the alternative complement system, was reduced in 21% of children with SHS. This was related to the presence of abdominal symptoms or nephritis. No cases of retinal vasculitis was observed, but 4 of 22 children with SHS had punctuate retinal haemorrhages. SHS and VS may be clinical variations of the same syndrome. The immunological aspects indicate a close relationship with autoimmune diseases.

Adolescent↗
PubMed1991

Effect of different phototherapy lights on retinal and choroidal blood flow.

The response of retinal (RBF) and choroidal (ChBF) blood flow to illumination with light with different spectra was investigated in spontaneously breathing newborn piglets. After 1 h in complete darkness, the animals were exposed to blue, white or green light in such a manner that equal energy was delivered to the eye. RBF and ChBF showed different flow responses. After 60 min exposure to blue light, RBF increased from 0.22 +/- 0.01 ml/min/g at baseline to 0.32 +/- 0.03 ml/min/g (+/- SEM) (p less than 0.03). Apart from this increase, RBF did not change significantly during any of the experimental settings. ChBF, on the other hand, was significantly affected by illumination. Thus, at 120 min of light exposure all three types of light decreased ChBF significantly from baseline (darkness) levels. Blue light decreased ChBF (mean +/- SEM) from 13.78 +/- 0.84 to 7.61 +/- 0.67 ml/min/g (p less than 0.01), white light from 17.43 +/- 1.86 to 9.86 +/- 1.07 ml/min/g (p less than 0.01), and green light from 14.13 +/- 1.64 to 8.31 +/- 1.30 ml/min/g (p less than 0.02). The results indicate that light is an important modulator of ChBF and to a certain extent also RBF. Further, the results suggest that ChBF and RBF are regulated differently.

Animals↗
PubMed1991

Acupuncture in the treatment of Graves' ophthalmopathy. A blinded randomized study.

Seventeen patients with Graves' ophthalmopathy, all euthyroid for at least one year, were included in a blinded trial to test the effect of acupuncture twice a week during two months on the eye disease, assessed by an ophthalmologist and computed tomography of the eye muscle volume. No significant change was found in eye muscle volume, Hertel measure, palpebral aperture, intraocular pressure, Hess chart, nor was there any statistically significant improvement of the irritative conjunctival symptoms.

Acupuncture Therapy↗
PubMed1990

Skeletal muscle enzyme activities and metabolic substrates during exercise in patients with postoperative fatigue.

Subjective fatigue was quantified before and 20 days after uncomplicated elective abdominal surgery in 12 patients and compared with changes in heart rate, enzyme activities and skeletal muscle substrates before and after bicycle exercise for 10 min at 65 per cent of patients' preoperative maximum work capacity. Fatigue increased from a mean(s.e.m.) preoperative level of 2.5(0.5) arbitrary units to 4.6(0.5) on postoperative day 20 (P less than 0.01). Body-weight, triceps skinfold thickness and arm circumference decreased postoperatively (P less than 0.02). Postoperative values of muscle enzyme activities indicative of oxidative phosphorylation capacity (citrate synthase and 3-OH-acyl coenzyme A dehydrogenase) were lower than preoperative values (P less than 0.05). Lactate dehydrogenase was unaltered and resting values of muscle glycogen and adenosine triphosphate were higher after operation (P less than 0.05). In response to exercise, heart rate, muscle glucose, glucose-6-phosphate and lactate increased (P less than 0.05), while muscle glycogen and creatine phosphate decreased (P less than 0.05). Increase in postoperative fatigue correlated with the increase in heart rate (P less than 0.05), while no significant correlations were found between fatigue and muscle parameters. Our results suggest that lack of exercise and malnutrition may be of importance in the decrease in work capacity and in fatigue after operation.

Abdomen↗
PubMed1990

Interdependence and nodule specificity of cis-acting regulatory elements in the soybean leghemoglobin lbc3 and N23 gene promoters.

The qualitative and quantitative contributions of four separate cis-acting DNA elements controlling the root nodule-specific soybean leghemoglobin lbc3 gene were analyzed in transgenic Lotus corniculatus plants. Expression from internal deletions in the 5' region between positions -49 and -1956 was monitored from a CAT reporter gene. The strong positive element (SPE; -1090, -947) responsible for high-level expression was demonstrated to be an organ-specific element by deleting proximal nodule-specific control elements. Deletion of the downstream qualitative organ-specific element (OSE; -139, -102) containing the putative nodulin consensus sequences 5'AAAGAT and 5'CTCTT resulted in a low expression level. Efficient SPE enhancement is therefore dependent on the organ-specific element, which by itself does not enhance expression. This quantitative effect of the immediate upstream region carrying the consensus sequences was also found in hybrid promoter studies using the soybean nodulin N23 gene promoter, suggesting the involvement of these motifs in a regulatory mechanism for nodulin genes. Deletion of the lbc3 negative element (NE, -102, -49) linking the SPE and OSE onto the TATA box did not lead to unregulated expression. These results indicate that interaction between positive, negative and neutral qualitative elements controls lbc3 expression. Binding of the nuclear protein NAT2 at the lbc3 weak positive element (WPE; -230, -170) is probably not directly required for this mechanism.

Base Sequence↗
PubMed1990

Single-strand breaks in the DNA of human cells exposed to visible light from phototherapy lamps in the presence and absence of bilirubin.

Clinical evidence indicates that phototherapy of hyperbilirubinaemia in newborn infants is a safe and efficient form of therapy. The short-term side effects are not serious and seem to be well controlled. There are few long-term follow-up studies of phototherapy-treated infants. Therefore one cannot completely exclude the possibility that side effects can be found in future studies. With this background we undertook the present study of possible genotoxic effects of phototherapy. Human cells of the established glioblastoma cell line TMG-1 were used. The cells were exposed to visible light in the presence of different concentrations of bilirubin or in the absence of bilirubin. DNA was unwound in alkaline solution and the induction of strand breaks was assayed by a method taking advantage of the fluorescence from the dye Hoechst 33258. Blue light induced single-strand breaks in the DNA of cells in culture in the absence of bilirubin. During irradiation of bilirubin solutions with blue and green phototherapy light, long-lived toxic photoproducts were formed under in vitro conditions. At high and clinically relevant bilirubin concentrations, the effects of blue and green light were relatively similar. At low concentrations, there was a smaller effect of green light as expected from the absorption spectrum of bilirubin. It remains to be seen whether the genotoxic effect observed in the present studies can occur in vivo.

Bilirubin↗