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Biomedical subjects

M Lederman

Publications and source records attributed to M Lederman.

At least 55 records · Page 3Linked to original sources
PubMed1982

Cancer of the oropharynx: classification and natural history.

The development, comparative anatomy, and function of the oropharynx are briefly described. The text book descriptions of the anatomical boundaries of the oropharynx are commented on and an attempt is made to define these boundaries more rigidly and accurately. Although the advantages and limitations of the UICC classification of oropharyngeal cancer is accepted, an alternative classification is suggested based on the function of the site involved rather than its descriptive anatomy. This has resulted in a necessary rearrangement of the tumor sites and subsites. Subdivision into three sites is suggested: 1. An anterior or glosso-epiglottic; 2. Lateral or tonsillar; 3. Postero-superior or pharyngoepiglotti. The main change has been in the lateral group, the faucial pillars being separated from the tonsil and reallocated. Three different forms of tonsillar cancer are described in some detail; the linguo (glosso) tonsillar sulcus receives mention. A general account is given of the remaining anterior and posterior sites.

Epiglottis↗
PubMed1980

In vitro production of human fecal mutagen.

The feces of some normal humans were previously shown to be mutagenic by the Salmonella mutagenicity assay with strain TA100. In the present study, the mutagenicity of feces of certain donors can be increased by anaerobic incubation for 96 h. The increase in mutagenicity did not occur upon incubation in the cold or in air, in the presence of antimicrobial agents or if the feces were sterilized by heat. On thin-layer chromatographs, the relative mobility of fecal mutagen for all donors after incubation was the same in any one of 4 different solvent systems. The major mutagenicity appears to be due to a single type of compound which may be produced by anaerobic bacteria.

Adult↗
PubMed1980

Characterization of a mutagenic bacterial product in human feces.

Mutagens detectable with the Ames assay have been found in the feces of apparently healthy individuals and the incidence of this mutagenic activity was found to be greater in a population at high risk for colon cancer than in a population at low risk. A compound accounting for the mutagenic activity has been isolated by high performance liquid chromatography. Two closely related forms which behave identically chemically could be resolved. The compound was active on Salmonella typhimurium TA98 and TA100, had a characteristic ultraviolet absorption spectrum with maxima at about 320, 340, and 365 nm, fluoresced green in long wavelength ultraviolet light, and had the same mobility on the thin-layer chromatography as the mutagenic activity in a direct ether extract of feces. The compound was unstable in air but could be stabilized in the presence of butylated hydroxytoluene. Upon oxidation the compound lost its mutagenicity and its ultraviolet absorption spectrum underwent a blue shift so that the absorption maxima were at 295, 310, and 325 nm. Determination of the structure of the mutagen has been difficult since the compound was not volatile and production of a volatile derivative has not been successful. On thin-layer chromatography plates the compound reacted with reagents that detect chlorinated compounds. By thermal energy analysis it did not appear to contain a nitroso group. The compound increased in concentration upon anaerobic incubation of feces at 37 C and this increase was prevented by cold, air, and antimicrobial agents. This suggests to us that the fecal flora produces the compound.

Bacteria↗
PubMed1974

Multiple transport components for putrescine in Escherichia coli.

Putrescine uptake was studied in cultures of Escherichia coli K-12 grown in media of high or low osmolarity. When grown in high osmolarity medium, a transport system of low K(m) and low V(max) was found. For cultures grown in a medium of low osmolarity, the kinetics of putrescine uptake was more complex and consistent with the existence of an additional transport system of higher K(m) and V(max). This conclusion is supported by the isolation of mutants in which one or the other system appears to be defective and by the ability of chloramphenicol to block the expression of the second transport system. Both systems appear to prefer putrescine over other compounds, since several basic amino acids and other polyamines competed only weakly for transport. The action of both uptake systems was shown to cause significant displacement of intracellular putrescine. Both systems also are at least partially energy dependent.

Amino Acids↗
PubMed1973

Medulloblastoma--treatment and prognosis. A study of seventeen cases in ten years.

In a series of 17 biopsy-proved cases of medulloblastoma all patients were treated by megavoltage irradiation in the Stanford University Division of Radiation Therapy. The entire craniospinal axis was treated in each case. The five-year survival in the series was 27 percent. Two ten-year survivors were studied in detail. The major longterm disability was inhibition of growth of the vertebral column. In this series, a normal tissue nominal standard dose of at least 1275 rets was necessary for tumor control.

Adolescent↗