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Biomedical subjects

R F Lee

Publications and source records attributed to R F Lee.

At least 55 records · Page 3Linked to original sources
PubMed1985

Photochemical and microbial degradation of 2,4,5-trichloroaniline in a freshwater lake.

Surface waters from a eutrophic lake in northern Georgia were incubated with C-labeled 2,4,5-trichloroaniline to study the disappearance of the parent compound and production of CO(2). There was no degradation of the compound in the dark. Under 12 h of sunlight and 12 h of darkness, 28% of the trichloroaniline was degraded in both poisoned and untreated samples. Mineralization after 24 h in poisoned and untreated lake water was 5.5 and 6.8%, respectively. Thus, 81% of the mineralization was attributable to photochemical processes, and 19% was attributable to microbial processes. Most biological mineralization was due to microbes of bacterial size (<1.0 mum). Approximately 90% of the trichloroaniline bioaccumulated was associated with organisms larger than 1.0 mum, e.g., algae. When algae were removed by filtration, the amount of trichloroaniline mineralized increased to 9.4%, compared with 6.8% in the presence of algae. The excretion of organic compounds by algae may have inhibited bacterial mineralization of photoproducts.

Journal Article↗
PubMed1984

The adenovirus major late promoter TATA box and initiation site are both necessary for transcription in vitro.

Mutagenized DNA templates and HeLa whole cell extracts were used to study the effects of promoter-specific base changes on in vitro transcription. DNA templates where the initiating adenine (+1) was changed to thymidine (AT+1) in the adenovirus 2 major late transcription unit were transcribed with 50% efficiency of the unaltered template. We have described a mutant at the TATA box, where the A at position -28 was changed to a C (AC-28). Transcription efficiency was reduced to less than 20% of control in the AC-28 mutant (Concino et al., 1983, J. Biol. Chem. 258: 8493-8496). Primer extension analysis revealed increased 5' end heterogeneity for in vitro transcripts derived from AC-28 and AT+1 DNA templates. Specific transcription was completely abolished from AT+1 DNA templates when a second change was introduced within the TATA sequence, creating a double mutant (AC-28 . AT+1). Neither the AC-28 nor the AT+1 change alone had such an effect, suggesting a coordinated interaction in transcription initiation involving both the TATA box and the initiation site.

Adenoviruses, Human↗
PubMed1984

Microsomal cytochromes P-450 from marine crabs.

Cytochromes P-450 were isolated from the hepatopancreas of several species of crabs (Libinia emarginata, Callinectes sapidus, Menippe mercenaria and Uca minax). Elution profiles from an ion exchange column showed similar profiles for all species, indicating one broad cytochrome P-450 peak eluting at 0.2 M K Cl. Hydroxyapatite chromatography resolved the P-450 into three forms (cytochromes P-450I, P-450II and P-450III). The forms of cytochrome P-450 in the different crabs were compared with respect to their spectra and molecular weights. Cytochromes P-450I and P-450III from Callinectes, Menippe and Uca had slightly different spectral properties. The Soret peaks of the oxidized spectra had wavelength maxima of 414-416 nm, while the reduced spectra was 417-424 nm. The Soret peak of Libinia P-450II was 417 nm and 415 nm, for the oxidized and reduced forms, respectively. Molecular weights for cytochromes P-450I and P-450III ranged from 51,000 to 53,000. Libinia P-450II had a molecular weight of 49,000.

Animals↗
PubMed1983

Receptive and expressive wh-question performance by language-delayed children.

The receptive and expressive wh interrogative performance of language-delayed children was investigated. Results indicated a series of response strategies and expressive performance strikingly similar to normal children in the early stages of language acquisition. These results suggest that the delayed children develop the same order of acquisition and rules for questioning as normal children, but at a slower rate. Therapeutic activities should therefore follow the order of interrogative development presented in the normative research.

Child↗
PubMed1979

Lipids from nerve tissues of the horseshoe crab, Limulus polyphemus.

1. The predominant lipids of nerve cords, ganglion and brain from horseshoe crabs were cholesterol (11% of lipid) and phospholipid (81% of lipid). 2. Major phospholipids were phosphatidyl ethanolamine and phosphatidyl choline with lesser amounts of phosphatidyl serine and phosphatidyl inositol and sphingomyelin. 3. The phospholipid fraction was characterized by a high content of plasmalogen, i.e. alk-1-enyl acyl phosphatides, so that 42% of the ethanolamine phosphatides were the plasmalogen, phosphatidal ethanolamine. 4. Phosphatidyl choline and phosphatidyl ethanolamine were high in polyunsaturation with 20:4 and 20:5 major fatty acids. Sphingomyelin had predominantly long chain saturated fatty acids. 5. Cerebrosides and gangliosides, which are associated with vertebrate nerve tissues, were absent from nerves of horseshoe crabs.

Animals↗
PubMed1978

Serum lipoproteins in the spiny lobster, Panulirus interruptus.

1. Most of the lipids in the hemolymph of the spiny lobster, Panulirus interruptus, were associated with a high density lipoprotein (HDL3). The lipid of this lipoprotein was composed of phospholipid (88%), sterol (4%) and triglyceride (3%). 2. In animals fed 14C-labeled triglyceride radioactivity was not seen in the serum until 12 hr after feeding. Most of this serum radioactivity was associated with phosphatidyl choline. 3. Electron micrographs showed that negatively stained high density lipoproteins of the lobster had a polymorphic appearance.

Animals↗
PubMed1976

Effects of inhibitors of RNA and protein synthesis on aspartate transcarbamylase activity in etiolated plant tissue.

Aspartate transcarbamylase (ATCase) activity declines in etiolated cowpea (Vigna unguiculata L. Walp.) and soybean (Glycine max L. Merr.) hypocotyls between 3 and 11 days after planting. Treating cow-pea hypocotyls with cycloheximide (CH), actinomycin D (AMD), 6-methyl purine (6-MP), or cordycepin increases ATCase activity up to 740, 350, 465, and 305%, respectively, over water-treated controls 48 to 72 hours after treatment. In contrast erythromycin had no effect, and d-threo-chloramphenicol (CHL) reduced ATCase activity nearly 40%. CH, AMD, and CHL, whose effects were further characterized, each markedly reduced total RNA synthesis and protein synthesis. Respiration was stimulated by CH and AMD and reduced by CHL. In soybean, CHL-treated tissues and water-treated controls had comparable ATCase activities 48 hours after treatment, while AMD, 6-MP, and CH treatments reduced activities 29, 37, and 78%, respectively. The results suggest that the level of ATCase activity in etiolated cowpea hypocotyls is regulated by a mechanism or mechanisms that are interfered with by inhibition of RNA and protein synthesis. Possibly the mechanism is absent from etiolated soybean hypocotyls.

Journal Article↗
PubMed1972

Petroleum hydrocarbons: uptake and discharge by the marine mussel Mytilus edulis.

The common marine mussel Mytilus edulis has been observed to rapidly take up mineral oil, [(14)C]heptadecane, 1,2,3,4-tetrahydronaphthalene, [(14)C]toluene, [(14)C]naphthalene, and [(3)C]3,4-benzopyrene from seawater solution. This species of mussel did not metabolize any of these compounds, and transfer of the mussel to fresh seawater, after exposure to the hydrocarbon in solution, resulted in the discharge of most of the hydrocarbon, although significant amounts remained (between 1 and 400 micrograms per mussel). The nontoxic paraffinic hydrocarbons mineral oil and heptadecane were taken up (10 milligrams per mussel) to a much greater extent than the aromatic hydrocarbons (2 to 20 micro-grams per mussel).

Alkanes↗