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Biomedical subjects

L Simpson

Publications and source records attributed to L Simpson.

At least 217 records · Page 12Linked to original sources
PubMed1968

Effect of acriflavin on the kinetoplast of Leishmania tarentolae. Mode of action and physiological correlates of the loss of kinetoplast DNA.

The loss of kinetoplast DNA in Leishmania tarentolae, which occurs in the presence of low concentrations of acriflavin, was found to be a result of selective inhibition of replication of this DNA. Nuclear DNA synthesis was relatively unaffected and cell and kinetoplast division proceeded normally for several generations. An approximately equal distribution of parental kinetoplast DNA between daughter kinetoplasts resulted in a decrease in the average amount of DNA per kinetoplast. The final disappearance of the stainable kinetoplast DNA occurred at a cell division in which all the remaining visible kinetoplast DNA was retained by one of the daughter cells. The selective inhibition of kinetoplast DNA synthesis was caused by a selective localization of acriflavin in the kinetoplast. The apparent intracellular localization of dye and the extent of uptake at a low dye concentration could be manipulated, respectively, by varying the hemin (or protoporphyrin IX) concentration in the medium and by adding red blood cell extract (or hemoglobin). Hemin and protoporphyrin IX were found to form a complex with acriflavin. During growth in acriflavin, cells exhibited an increasing impairment of colony-forming ability and rate of respiration. No change in the electrophoretic pattern of total cell soluble proteins was apparent. The data fit the working hypothesis that the loss of kinetoplast DNA leads to a respiratory defect which then leads to a decrease in biosynthetic reactions and eventual cell death. A possible use of the selective localization of acriflavin in the kinetoplast to photooxidize selectively the kinetoplast DNA is suggested.

Acriflavine↗
PubMedDate not supplied

Schizodeme analysis of Trypanosoma cruzi stocks from South and Central America by analysis of PCR-amplified minicircle variable region sequences.

Kinetoplast DNA (kDNA) was isolated from 56 stocks of Trypanosoma cruzi isolated from human patients, animals and insects from Brazil, Venezuela, Colombia and Costa Rica. Comparison of the patterns of digested kDNA on acrylamide gels led to the grouping of several stocks into two schizodemes. Schizodeme analysis was also performed using a set of 330-bp fragments representing all the variable regions of the minicircle DNA molecules, which were obtained by PCR amplification of the kDNA using conserved region primers. The results of this analysis were consistent with the analysis using total kDNA, but the more informative restriction profiles allowed the construction of additional schizodemes. In addition, two oligomers were generated from variable region sequences of cloned minicircles from a Y and a Cl strain, and these were used as schizodeme-specific probes to detect homologous sequences in the amplified minicircle DNAs. The results indicate that a combination of restriction enzyme fingerprinting and hybridization of amplified variable region minicircle DNA with schizodeme-specific probes can be used for both sensitive detection and classification of T. cruzi.

Animals↗
PubMedDate not supplied

A central role for adenosine in the hypotension elicited by hypoxia in anesthetized rats.

Brief inhalation of an oxygen-deficient (5%) gas mixture evoked a rapidly developing, profound hypotension in anesthetized rats. Recovery upon reoxygenation was also rapid. A potential involvement of adenosine in the genesis of this hypotension was evaluated with various peripherally administered adenosine antagonists. Caffeine (10 mg/kg), which readily crosses the blood-brain barrier, significantly attenuated the hypoxia-evoked hypotension. 8-p-Sulphophenyltheophylline and xanthine amine congener, which do not readily penetrate the blood-brain barrier, had little effect on the magnitude of the hypotension. The data suggests that hypoxia-elicited hypotension in anesthetized rats results from the activation of central adenosine receptors.

Adenosine↗