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Biomedical subjects

D E Graves

Publications and source records attributed to D E Graves.

42 records · Page 3Linked to original sources
PubMed1980

Comparative studies of the binding of ethidium bromide and its photoreactive analogues to nucleic acids by fluorescence and rapid kinetics.

The binding studies of the interaction of ethidium bromide with DNA have been hampered by its reversibility, which prevents direct isolation and thus characterization of the complex. The recent development of photoaffinity labeling has provided a means to circumvent this problem. However, to be useful as a probe for the parent compound, a photosensitive analogue must be shown to interact in vivo and in vitro just as the parent analogue. These studies demonstrate by steady-state and nonosecond fluorescence and stopped-flow kinetics that one of the azido analogues of ethidium, 8-azido-3-amino-5-ethyl-6-phenylphenanthridinium chloride, binds nucleic acids quite similarly to ethidium bromide. The interaction of the other azide, 3,8-diazido-5-ethyl-6-phenyl-phenanthridinium chloride, with DNA is qualitatively different from that of the monoazide and ethidium bromide. These results suggest that the monoazide would serve as an ideal probe for determining the actual target sites of ethidium bromide in vivo and in vitro.

Animals↗
PubMed1979

Ethidium bromide enhancement of frameshift mutagenesis caused by photoactivatable ethidium analogs.

Ethidium azide analogs (3-amino-8-azido-ethidium monoazide and ethidium diazide) have been developed as photosensitive probes in order to analyze directly the reversible in vivo interactions of ethidium bromide. Our preliminary observations [11], relating the mutagenic potential of the monoazide analog of ethidium, have been extended and refined, using the highly purified ethidium azide analogs [5]. A number of physical-chemical studies indicate that the monoazide analog interaction with nucleic acids, prior to photolysis, resembles remarkably the interaction of the parent ethidium (unpublished). It was anticipated, therefore, that competition by ethidium for the ethidium monoazide mutagenic sites in Salmonella TA1538 would be observed when these drugs were used in combination. Previous results in fact showed a decreased production of frameshift mutants when ethidium bromide was added to the ethidium monoazide in the Ames assay [1]. However, more extensive investigations, reported here, have shown that this apparent competition was the result of neglecting the toxic effects of ethidium monoazide and its enhanced toxocity in the presence of ethidium bromide. Conversely, an enhancement of the azide mutagenesis and toxicity for both the mono- and diazide analogs was seen when ethidium bromide was used in combination with these analogs.

Azides↗
PubMed1977

Synthesis, separation and characterization of the mono- and diazide analogs of ethidium bromide.

Ethidium bromide is used to characterize nucleic acid secondary and tertiary structural properties and the biological consequences of drug interactions. The mono- and diazido analogs of ethidium have proven valuable as photoaffinity probes in chemical and biological studies on nucleic acids, since they render the ethidium-nucleic acid interaction covalent. Although both of these compounds have been synthesized previously, the published synthesis procedure for the monoazide is inadeqlate since a major portion of the product has been identified as the diazide analog. This lack of purity severely limits the usefulness for nucleic acid research. The procedure presented here for the synthesis, separation, purification and crystallization of these analogs should provide the quantities and quality of these important reagents needed to perform a variety of chemical and biological experiments.

Azides↗
PubMedDate not supplied

Postoperative transcutaneous oxygen measurement in the prediction of delayed wound healing and prosthetic fitting among amputees during rehabilitation. A pilot study.

Postoperative assessment of amputation wound healing remains largely subjective in nature, being based on the physician's clinical judgement. These considerations significantly impact on the rehabilitation course, as premature prosthetic fitting may result in wound breakdown. Alternatively, delayed healing may result in prolonged hospital length of stay. Few attempts have been made to correlate objective parameters of limb perfusion with amputation wound healing or prosthetic fitting outcome during the rehabilitation phase of treatment. A pilot study was conducted, in which the transcutaneous oxygen monitor, a noninvasive device measuring transcutaneous partial pressure of oxygen (tcpO2), was applied to the stumps of 11 consecutive above-or below-knee amputees admitted for rehabilitation after amputation. All patients were tested within 1 wk of admission and 45 days of amputation. The treatment team was blinded as to the test results. A direct correlation was observed between wound healing outcome and tcpO2 results (Fisher's exact test [FET], P = 0.03), and no patient with a tcpO2 of < or 15 mm Hg healed during their rehabilitation stay (FET, P = 0.006). TcpO2 of < or = 15 mm Hg was significantly correlated with prolonged length of stay (Point Biserial Correlation Coefficient [rpbi], = -0.835; P = 0.01), delayed prosthetic fitting (rpbi = 0.742; p = 0.01), and poorer wound healing at admission (rpbi = 0.932; P = 0.001). Postoperative tcpO2 measurement may have use in objectively identifying patients at greater risk of delayed wound healing and prosthetic fitting, although further study is warranted.

Aged↗
PubMedDate not supplied

Altered motor control and spasticity after spinal cord injury: subjective and objective assessment.

This study of measures of spasticity, or altered motor control, compares the clinically used Ashworth scale with a method based on surface electromyographic (sEMG) recordings called brain motor control assessment (BMCA) in a group of 97 subjects with spinal cord injury (SCI) and varying levels of motor dysfunction. In this paper, we describe how sEMG-derived scores relate to the severity of spasticity as judged clinically. When sEMG data from passive movements from the BMCA were analyzed by Ashworth category, we found that when the sEMG data were averaged for a limb, there was a significant difference between scores for those with Ashworth 0 vs. 2 and 3, and 1 vs. 2 and 3 (p<0.001), but not between 0 and 1. Analysis of the individual muscle scores improved the discrimination between Ashworth categories. Superiority of sEMG data over Ashworth category as an objective quantification of altered motor control ("spasticity") is argued.

Adult↗