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Biomedical subjects

E A Christensen

Publications and source records attributed to E A Christensen.

At least 19 recordsLinked to original sources
PubMed2001

A longitudinal study of health related quality of life and utility measures in patients with advanced breast cancer.

Health related quality of life (HRQOL) measures are now accepted as indicators of efficacy in the palliative treatment of cancer. Utility measures may also provide valuable information yet they have been applied less frequently. To assess the application of a time trade-off (TTO) utility measure and its concordance with the Spitzer uniscale and quality of life index (QLI) 38 women with advanced, symptomatic breast cancer were studied over a 12 month period. The correlation coefficient for QLI and TTO values was 0.54 and for uniscale and TTO 0.62. Using generalized estimating equations the regression of TTO scores on QLI and uniscale scores was significant at baseline. In longitudinal analyses results were significant only for QLI. Although all participants completed the HRQOL measures only 24 (63%) were prepared to trade time. The remaining 14 (32%) stated they felt too well to trade. Those prepared to trade time recorded significantly worse mean HRQOL scores throughout the study compared to those who felt too well to trade and had tumors which showed a poorer response to therapy. In this preliminary study utility and HRQOL scores were generally favorable throughout the 12 month study period and showed fair to moderate concordance. Further research in larger patient groups is required to better define the relationships between utility and HRQOL measures.

Adult↗
PubMed2000

Functional expression and biophysical properties of polymorphic variants of the human gap junction protein connexin37.

Connexin37 (Cx37) forms gap junction channels between endothelial cells, and two polymorphic Cx37 variants (Cx37-S319 and Cx37-P319) have been identified with a possible link to atherosclerosis. We studied the gap junction channel properties of these hCx37 polymorphs by expression in stably transfected communication-deficient cells (N2A and RIN). We also expressed a third, truncated variant (Cx37-fs254Delta293) and Cx37 constructs containing epitope tags added to their amino or carboxyl termini. All Cx37 constructs were produced by the transfected cells as demonstrated by RT-PCR and immunoblotting and trafficked to appositional surfaces between cells as demonstrated by immunofluorescence microscopy. Dual whole cell patch-clamping studies demonstrated that Cx37-P319, Cx37-S319, and Cx37-fs254Delta293 had large unitary conductances ( approximately 300 pS). However, addition of an amino terminal T7 tag (T7-Cx37-fs254Delta293) produced a single channel conductance of 120-145 pS with a 24-30 pS residual state. Moreover, the kinetics of the voltage-dependent decline in junctional current for T7-Cx37-fs254Delta293 were significantly slower than for the wild type, implying a destabilization of the transition state. These data suggest that the amino terminus of Cx37 plays a significant role in gating as well as conductance. The carboxyl terminal tail has lesser influence on unitary conductance and inactivation kinetics.

Amino Acid Sequence↗
PubMed1997

A comparison of time trade-off and quality of life measures in patients with advanced cancer.

Quality of life (QOL) measures are now accepted as indicators of efficacy in the palliative treatment of cancer. Utility measures may also provide valuable information in this area yet they have rarely been applied. To assess the concordance of QOL and utility scales, 93 patients with advanced, symptomatic cancer completed two QOL instruments, the Spitzer Quality of Life Index (QLI) and Spitzer Uniscale, and a time-trade off (TTO) question reflecting the utility of their health states. The scales were self-administered. All patients completed the QLI and Uniscale but only 37% of participants were prepared to trade time. The remainder comprised 39% who felt too well to trade time and 24% who did not wish to consider trading time at all. Those prepared to trade time had significantly worse scores on both QLI and Uniscale instruments than those who felt too well to trade. However the correlation between time traded and QLI and Uniscale scores was poor. We conclude that the TTO question used in this study, while not strongly related to QOL, provides a measure of the patient's attitude to their health state. This may explain why patients differ in their attitude to quantity vs. quality of life.

Adult↗
PubMed1991

Radiation resistance of clinical Acinetobacter spp.: a need for concern?

As part of an epidemiological investigation of hospital infections caused by Acinetobacter spp. the radiation resistance of 15 clinical isolates and four reference strains was assessed. The radiation resistance (in D-6 values, viz. the dose necessary for reducing the initial number of colony forming units by a factor of 10(6)) was, in general, higher in the isolates of A. radioresistens than in the isolates of the A. calcoaceticus-A. baumannii complex and of A. lwoffi. However, the least resistant isolates of A. radioresistens had a D-6 value equal to or lower than the most resistant isolates of the other groups. The lowest D-6 values found were for two of the reference strains. The highest D-6 value was 35 kGy. Three isolates of A. johnsonii could not survive long enough in a dried preparation to make an assessment of the D-6 values possible. The radiation resistance of the 15 clinical isolates in the present study was higher than the resistance found in a study of similar isolates in 1970.

Acinetobacter↗
PubMed1991

Radiation resistance of microorganisms on unsterilized infusion sets.

Three different methods were used for detecting and isolating microorganisms with high radiation resistance from the microbial contamination on infusion sets prior to sterilization. By all three methods, microorganisms with a radiation resistance high enough to be a critical factor in a sterilization process (D-6 value greater than or equal to 30 kGy) were found with a frequency of approximately two colony forming units (cfu) per 100 product items, even though the product items in two of the series of analyses were irradiated with doses of 3-6 kGy. The frequency of occurrence of isolates with D-6 values greater than or equal to 30 kGy was 0.45 per 1000 cfu of the total aerobic count. Eight different isolates of microorganisms had D-6 values greater than or equal to 40 kGy when irradiated in dried laboratory preparation. All but one of these were classified according to morphologic criteria as Deinococcus, and all but one had nonlinear dose-response relationships in semilogarithmic presentation.

Bacteria↗
PubMed1986

In vitro induction of sister chromatid exchanges and chromosomal aberrations in peripheral lymphocytes of the oyster toadfish and American eel.

A series of experiments was conducted to characterize the proliferation of oyster toadfish lymphocytes in medium containing 5-bromodeoxyuridine (BrdUrd) and to determine the effectiveness of cytogenetic endpoints for assessing the genotoxic effects of in vitro exposure of toadfish and eel lymphocytes to known mammalian clastogens. Although the rate of proliferation of toadfish lymphocytes was low compared to that of mammalian lymphocytes, the effects of increasing BrdUrd concentrations were similar, in that proliferation exhibited a concentration-dependent inhibition for concentrations above 10 microM BrdUrd, and sister chromatid exchange (SCE) frequencies exhibited a concentration-dependent increase for concentrations above 100 microM BrdUrd. Mitomycin C (MMC) and ethylene dibromide (EDB) induced concentration-dependent increases in chromatid-type exchange and SCE frequencies with least effective concentrations (control SCE frequency divided by the slope of the least-squares line) for SCE induction by MMC (6.8 X 10(-9) M) and EDB (2.6 X 10(-4) M) that were comparable to or slightly lower than those that have been obtained with mammalian in vitro systems. In vitro exposure of toadfish lymphocytes to dimethoate (DIM) induced a concentration-dependent increase in SCE frequency with a least effective concentration of 2.8 X 10(-3) M that was much higher than that observed with mammalian in vitro systems. In vitro exposure of American eel lymphocytes to MMC also induced a concentration-dependent increase in the frequency of chromosomal aberrations and SCEs with a least effective concentration for SCE induction of 2.0 X 10(-9) M. These results indicate that cytogenetic endpoints can be effectively scored with cultured lymphocytes from these and perhaps other fish species with comparable karyotypes that contain an average of at least 0.07 pg DNA/chromosome.

Animals↗
PubMed1985

An investigation in use of videocassette techniques for enhancement of saccadic eye movements.

An investigation exploring the potential for the therapeutic application of videocassette techniques in vision therapy was undertaken. It was shown that a saccadic therapy program could be designed and produced with reasonable ease and simplicity. Clinical trials revealed the video method of saccadic therapy to be as effective as a standard method of therapy as to a significant change in saccadic ability. For validation of the research method, a control group was given pre- and post-testing; no significant change was found.

Child↗
PubMed1982

In-use tests of disinfectants.

In two different laboratories three methods were applied for in-use testing of 400 samples of disinfectants, primarily aldehyde and phenolic solutions, collected in 30 wards at 11 Danish hospitals. The results obtained with the Kelsey-Maurer test, the membrane filtration technique, and a standardized challenge test were in complete accordance, however, the challenge test revealed a few more inefficient samples, than the two other methods. For routine use at hospital laboratories the choice between the Kelsey-Maurer test or the modified Kelsey-Maurer technique using membrane filtration may be guided by the available equipment. The design and the application of a challenge test and pertinent criteria for test strains are discussed. Only about 3% of the samples failed to pass the tests, but a predominance (10%) of failures among the samples, received as number one in a series, underlines the didactic aspects of in-use testing. The study demonstrates that suitable methods exist and may be of value when introduced in the local policy of controlling disinfectants.

Bacillus↗
PubMed1981

Radiation-resistant micro-organisms isolated from textiles.

Towels from private homes and public offices and underwear contaminated by being used by employees at a public health laboratory were examined for occurrence of radiation-resistant bacteria and fungi. Three different methods were used for isolation of the most resistant organisms, one with multiplication of the microbial population prior to an irradiation used for selection, and two without this multiplication and with the organisms placed on membrane filters or in situ on the textiles, respectively. A total of 44 different strains were isolated. Differences in the three methods used for selection of the most radiation-resistant microorganisms were not reflected in the results. 16 pigment-producing Gram-positive cocci, tentatively classified as Micrococcus radiodurans, were the most radiation-resistant and were isolated in about half of the examinations. Other Gram-positive cocci, non-spore forming rods, some Nocardia and Candida parapsilosis strains and two Bacillus strains constituted the rest of the collection. Wtih few exceptions dose-response curves for the strains were upward convex. D-6 values were determined to be between 1.5 megarad for the most radiation sensitive, a Candida, and 5.7 megarad for the most resistant,, tentatively classified as M. radiodurans. The D-6 values for the Bacillus strains were in both cases 1.8 megarad, consistent with a D-value of 0.3 megarad. The same resistance is reported to be the maximum resistance for B pumilus, strain E601, commonly used as reference strain in the literature on radiation sterilization of medical devices and supplies.

Bacteria↗
PubMed1979

Biological indicators for the control of ethylene oxide sterilization.

A new biological indicator has been developed for the control of ethylene oxide sterilization, particularly for large scale sterilization of disposable medical equipment. The aim has been to provide the new indicator with the same resistance to the combined effect of ethylene oxide and water vapour as the biological indicator referred to by the health authorities in Scandinavia. The reference indicator contains spores of a Danish test strain, Bacillus subtilis, in sand. The new one contains spores of a test strain used extensively for biological indicators, viz. B. subtilis var. niger (B. globigii). The spores in the new preparation are dried in pieces of cotton yarn. The two indicators were exposed to ethylene oxide and water vapour in five different series of experiments and almost the same resistance was found. In simulated routine sterilization procedures, the new indicator was placed at locations not easily accessible for the gas and water vapour, and the results reflected the blockage of diffusion. The experiments included samples of household dust. The resistance of the microorganisms in the dust was compared with that of the biological indicators. Based on these comparisons, it is concluded that the resistance of the two biological indicators to ethylene oxide is in accordance with the official Scandinavian standard for sterilized medical equipment when used in the control of sterilization of products with low microbial contamination.

Bacillus subtilis↗