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Biomedical subjects

A R Putnam

Publications and source records attributed to A R Putnam.

7 recordsLinked to original sources
PubMed2003

Modeling a submicrometer electrostatic motor.

Numerical models are developed for a recently proposed submicrometer device that uses the electric field energy of a biased parallel-plate semiconducting capacitor to propel a piston through the open capacitor gap. Through variation of design parameters or applied external bias, actuator forces on the order of hundreds of piconewtons are developed for device size scales ranging from 10(-7) m to 10(-4) m per side. A rotary configuration of the device is also presented.

Computer Simulation↗
PubMed1992

Antifungal anthracycline antibiotics, spartanamicins A and B from Micromonospora spp.

Spartanamicins A and B, two antifungal antibiotics, were produced by a culture of Micromonospora spp. strain No. MSU-43097 (ATCC 53803), isolated from a potted soil containing asparagus (Asparagus officinalis L.) plants. The antibiotics were isolated from the mycelial cake using organic solvents. The structures of spartanamicins A and B were determined by spectral and chemical means. Spartanamicin B is more active as an antifungal compound than it's analogue, A. The minimum inhibitory concentration for spartanamicin B on Candida albicans and Aspergillus, Cladosporium, Cryptococcus, Rhodotorula and Staphylococcus spp. ranged from 0.2 to 1 microgram/ml. It was not active against Staphylococcus aureus, Escherichia coli and Citrobacter spp. but some strains of S. aureus were sensitive.

Anthracyclines↗
PubMed1990

In vitro antibacterial activity of faeriefungin, a new broad-spectrum polyene macrolide antibiotic.

The in vitro activity of faeriefungin, a new pentaene macrolide lactone antibiotic produced by Streptomyces griseus var. autotrophicus, against 263 clinical bacterial isolates was examined. In contrast to the related fungicidal antibiotics nystatin and amphotericin B, which show no activity against bacteria, faeriefungin showed bactericidal activity against all species of gram-positive bacteria examined. MICs for these species ranged from 8 to 64 micrograms/ml, and the MIC for 90% of the isolates tested was 32 micrograms/ml. Isolates of some fastidious gram-negative species, including Neisseria gonorrhoeae, N. meningitidis, and Haemophilus influenzae, were slightly susceptible to faeriefungin, with MICs ranging from 16 to 128 micrograms/ml, but all members of the families Enterobacteriaceae and Pseudomonadaceae, with the exception of Pseudomonas cepacia, were completely resistant to faeriefungin at the concentrations tested. Faeriefungin is also active against fungi, nematodes, and mosquito larvae. The mode of action of faeriefungin against both bacteria and fungi is under investigation.

Anti-Bacterial Agents↗
PubMed1982

Quantification of allelopathic potential of sorghum residues by novel indexing of richards' function fitted to cumulative cress seed germination curves.

The inhibitory activity of aqueous extracts of field-grown sorghum (Sorghum bicolor cv. Bird-a-boo) herbage and roots was quantitatively indexed by three aspects of cumulative cress (Lepidium sativum cv. Curlycress) seed germination: the germination onset; weighted mean rate; and final germination percentage. Extract potency was greatest for herbage collected four weeks after planting but declined sharply thereafter as the plants matured. About 91% of the inhibitory activity obtained from four-week-old herbage was in a low molecular weight fraction. Differential effects of herbage and root extracts on cress seed germination suggest that the nature and/or proportion of biologically active substances extractable from these plant parts is dissimilar.

Journal Article↗
PubMedDate not supplied

Herbicidal effects of geldanamycin and nigericin, antibiotics from Streptomyces hygroscopicus.

Geldanamycin (2) and nigericin (1) (primarily the Na+ salt) are responsible for the phytotoxicity of a Streptomyces hygroscopicus strain found to be highly active in our screens for producers of herbicidal antibiotics. After extraction from the cells, the compounds were purified with column and thin layer layer chromatography on silica gel, bioassayed for inhibition of garden cress (Lepidium sativum L.) radicle elongation, and identified with ms, ir, nmr, and co-chromatography with authentic standards. Both caused 50% reduction in garden cress radicle growth at concentrations of 1-2 ppm and nearly complete inhibitions at 3-4 ppm. Symptoms of toxicity differed markedly for the two compounds. Geldanamycin at high concentrations caused radicles to turn brown and disintegrate, whereas, nigericin did not cause visible necrosis. Geldanamycin is structurally similar to the herbimycins, which are also produced by S. hygroscopicus and have been reported to have herbicidal activity. The phytotoxicity of geldanamycin and nigericin has stimulated investigation of their potential for use as natural product herbicides.

Anti-Bacterial Agents↗
PubMedDate not supplied

Faeriefungin: a new broad-spectrum antibiotic from Streptomyces griseus var. autotrophicus.

Faeriefungin, a polyol polyene macrolide lactone antibiotic, was isolated from the mycelium of Streptomyces griseus var. autotrophicus, MSU-32058/ATCC 53668, collected from the soil sample of a fairy ring in an old lawn in Lansing, Michigan. Faeriefungin has some properties similar to the previously reported polyene macrolides, mycoticin and flavofungin, but possesses different physiochemical and biological properties. Aspergillus, Fusarium, Microsporum, Trichophyton, and Alternaria spp. were completely inhibited by faeriefungin at 3.2 micrograms/ml, Candida spp. at 5.5 micrograms/ml, and Pythium, Phialophora, Leptosphaeria spp., and some selected Gram-negative penicillin-resistant strains of Neisseria gonorrhoeae at 16.0 micrograms/ml. At a concentration of 100 ppm, it caused 100% mortality of mosquito larvae (Aedes aegypti, Rockefeller strain) and free-living nematodes (Panagrellus redivivus). Unlike the related polyene macrolides, faeriefungin is crystalline and stable with broad-spectrum antimicrobial and insecticidal activity. Preliminary cytotoxicity studies with human erythrocytes and rat liver epithelial cells indicated that faeriefungin and amphotericin B have comparable toxicity. Solution nmr study has indicated that faeriefungin is a mixture of two compounds, faerifungins A [1] and B [2], and that they differ in the attachment of a H or an Me at C-33.

Acetylation↗