PubMed Health⌕ Search

Biomedical subjects

L Mortensen

Publications and source records attributed to L Mortensen.

30 records · Page 2Linked to original sources
PubMed1990

Persistent effects of ozone on needle water loss and wettability in Norway spruce.

Four-year-old, seed-grown trees of Norway spruce (Picea abies (L.) Karst.) were exposed in open-top chambers to charcoal-filtered air (8 h daily mean 54 microg O(3) m(-3)) over three consecutive summers (1986-1988). In mid-May 1988, before the third season of fumigation and more than 7 months after exposure to ozone the previous summer had terminated, daily rates of transpiration from intact shoots and water loss from excised needles were measured together with the amount of wax on the needle surface. In mid-July, 92 days after the beginning of the third year of exposure, the wettability of needles was assessed by measuring the contact angle of water droplets on the surface of needles. Exposure to 156 microg O(3) m(-3) resulted in a 16% increase in daily transpiration in current year's needles and a 28% increase in 1-year old needles. These effects were associated with slower stomatal closure in response to increasing water deficit in the needles previously exposed to 156 microg m(-3) ozone. The long-lasting nature of such ozone-induced effects could predispose trees to drought and winter desiccation. No significant effects of ozone were found on the amount of wax covering the needle surface, but a marked increase in the wettability of needles exposed to ozone was observed. The far reaching physiological consequences of these effects in the field and the possibility that similar disturbances may contribute to the decline of high-altitude forests of Norway spruce in Europe are discussed.

Journal Article↗
PubMed1990

Persistent stimulation of CO2 assimilation and stomatal conductance by summer ozone fumigation in Norway spruce.

CO(2) assimilation rate, stomatal conductance and chlorophyll content of current and previous years' needles of Norway spruce were measured in May 1988, 205 days after the cessation of ozone fumigation during the summer of 1987. Rates of assimilation were consistently higher for both needle year age classes for ozone fumigated trees in comparison to control trees, although only statistically significant for part of the day for current year's needles. A 26% and 48% stimulation, overall, in mean daily rates of assimilation for current and previous years' needles of ozone fumigated trees was observed. This was due to an enhanced apparent quantum yield and light saturated rate of assimilation of ozone fumigated trees. The temperature response regression of assimilation versus temperature was also greater, such that at any given temperature, assimilation was higher for ozone treated trees than control trees. Stomatal conductance was greater for ozone fumigated trees than the controls, but this was only marginally statistically significant. Moreover, there was a consistent increase in chlorophyll content in both year classes in ozone-treated trees. These results are discussed in relation to a possible long term effect of ozone fumigation upon the processes of conifer winter hardening and spring de-hardening.

Journal Article↗
PubMed1989

Single and double loop formation when deoR repressor binds to its natural operator sites.

Distal effects on the in vivo repression of the deo operon are thought to be mediated by the deoR repressor with DNA loop formation. Such loops are easily observed by electron microscopy when the oligomeric deoR repressor is added to a DNA fragment carrying the three genetically defined operators at their chromosomal distances. Upon binding of deoR to any two operators, single loops are formed, 280, 600, and 880 bp in size. With the deo operon, double loops are also formed, which are the combination of the 280 bp and 600 bp loops and the result of simultaneous binding of the protein to its three sites. The formation of both single and double loops is consistent with the long-range effects observed in vivo and with the cooperative involvement of all three operator sites in the repression.

Binding Sites↗
PubMed1989

Purification and characterization of the deoR repressor of Escherichia coli.

The deoR gene, which encodes the deor repressor protein in Escherichia coli, was fused to the strong Ptrc promoter in plasmid pKK233-2. The Ptrc promoter is kept repressed by lacI repressor to prevent cell killing. Induction of the Ptrc--deoR fusion plasmid resulted in the accumulation of 4% of the soluble protein as deoR protein. The deoR repressor protein was purified to 80% purity using conventional techniques; it has a mass of 28.5 kd and appears to exist as an octamer in solution. The deoR repressor is shown by DNase I footprinting to bind to the 16 bp palindromic sequence in the Pribnow box region of the deoP1 promoter. Also, the deoR repressor binds cooperatively in vitro to a DNA template with two deoR binding sites separated by 224 bp in keeping with the conclusion from genetic experiments that more than one operator is required for efficient repression of the deo operon.

Bacterial Proteins↗
PubMed1987

Nonspecific psychological distress, psychosocial stressors and delusional psychosis. A comparison with psychiatrically symptom free surgical controls.

The purpose of the study was to examine patients with delusional psychosis regarding characteristic personality traits as illustrated by nonspecific psychological distress, and psychosocial stress prior to onset of the psychosis. The design of the study was a comparison of first-admitted psychiatric patients with delusional psychosis and psychiatrically symptom free surgical controls. Patients with delusional psychosis reported significantly more psychosocial stress than controls during the 3 months prior to admission. They also reported significantly higher mean values than controls on the subscales named poor self-esteem, helplessness-hopelessness, dread, sadness, anxiety and approval of rule breaking on the schedule of nonspecific psychological distress. In discriminating patients with delusional psychosis and surgical controls, approval of rule breaking, helplessness-hopelessness, and severity of psychosocial stressors were the most informative variables. Patients with delusional psychosis will be followed up in order to analyze if nonspecific psychological distress and psychosocial stressors are of importance for the prediction of the course and the outcome.

Adaptation, Psychological↗
PubMed1984

Prediction of survival in adults with acquired Bi- or pancytopenia.

In a retrospective study of 44 adults with acquired bi- or pancytopenia without evidence of any causal disorder, the survival curve suggested the existence of a subgroup of short survivors, mainly with aplastic anaemia, with death within 4 months. The initial values of 14 single clinical, blood and bone marrow variables were significantly associated with survival less than 4 months. Stepwise multiple logistic regression analyses identified 2 combinations of variables displaying significant simultaneous associations with short survival: (i) increased % of non-myeloid bone marrow cells and haemorrhagic manifestations initially; (ii) increased % of non-myeloid marrow cells, circulating erythroblasts and no history of any drug exposure. The predictive capacities of a resulting estimate of the probability of short survival and of previously introduced prognostic indices were approximately equal. The frequency of a correct prediction of a survival shorter than 4 months was in the range of 0.71-0.78 and that of longer survival in the range of 0.74-0.94.

Adolescent↗
PubMed1981

The applicability of simple blood and bone marrow variables in prediction of acute leukaemia in patients with acquired bi- or pancytopenia.

A retrospective study of 44 patients presenting with acquired bi- or pancytopenia (B/PC) and no evidence of any causal disorder was carried out. 12 patients developed acute non-lymphoblastic leukaemia after 2-51 months. Compared to the nonleukaemic subjects the preleukaemic patients at the onset of B/PC had significantly higher counts of myeloblasts and other myelopoietic cells in the bone marrow, more cellular marrows due to more dense cellularities of all compartments, higher blood granulocyte and monocyte counts, more pronounced anisocytosis, and in some cases a small number of circulating myeloblasts. A stepwise multiple logistic regression analysis identified 3 combinations of variables displaying significant simultaneous association with subsequent leukaemic transformation. Among these the combination of marrow myeloblast percentage and blood granulocyte count might be applicable to early prospective identification of patients with preleukaemic B/PC.

Acute Disease↗
PubMedDate not supplied

Sorbent removal of adriamycin in vitro and in vivo.

Adriamycin adsorption to four sorbents, uncoated activated charcoal, acrylic hydrogel-coated activated charcoal, a polystyrene non-ionic resin, and a pyrolized resin, was determined in vitro in aqueous and plasma solutions. Uncoated charcoal and pyrolized resin were most efficient in removing Adriamycin from these solutions. Four hours after an iv bolus of Adriamycin (2.5 mg/kg) to beagle dogs, acrylic hydrogel-coated activated charcoal hemoperfusion was performed. Extraction of Adriamycin averaged 43% throughout the 3-hour hemoperfusion period and resulted in a 20-fold increase in total body elimination of Adriamycin but plasma drug concentrations returned towards control values following hemoperfusion. Pharmacokinetic analysis of plasma Adriamycin profiles suggested that reduction of tissue concentrations of Adriamycin could be attained if hemoperfusion periods were extended. It is suggested that hemoperfusion may be useful in reducing blood levels of Adriamycin in patients with hepatic disease or accidental overdosage, but that reduction of tissue levels of Adriamycin would require extended or repeated hemoperfusion treatments.

Adsorption↗