Biomedical subjects

E Perkins

Publications and source records attributed to E Perkins.

At least 37 records · Page 2Linked to original sources

PubMed1992

Use of allopurinol and deferoxamine in cellular protection during ischemia.

During cellular ischemia and death, many changes occur in the cell. These include the build-up of purines and lipid peroxidation. In this study, we evaluated the effectiveness of allopurinol, which blocks purine breakdown, and deferoxamine, which inhibits lipid peroxidation, as cytoprotective agents. Rats were subjected to middle cerebral artery occlusion and were treated with high or low doses of allopurinol or high or low doses of deferoxamine, with normal saline used as a control. Treatments were given 1 hour before, 1 hour after, or 5 hours after occlusion. The outcome was based on neurological status and infarct size. Both infarct size and neurological status were found to be improved in all treatment groups when compared to controls. This study suggests that the use of these agents prevents cellular damage during ischemia.

Allopurinol↗

PubMed1992

Differential inhibition of proliferation of human squamous cell carcinoma, gliosarcoma and embryonic fibroblast-like lung cells in culture by plant flavonoids.

We investigated the antiproliferative effect of two polyhydroxylated (quercetin and taxifolin) and two polymethoxylated (nobiletin and tangeretin) flavonoids against three cell lines in tissue culture. Tangeretin and nobiletin markedly inhibited the proliferation of a squamous cell carcinoma (HTB 43) and a gliosarcoma (9L) cell line at 2-8 micrograms/ml concentrations. Quercetin displayed no effect on 9L cell growth at these concentrations, while at 8 micrograms/ml it inhibited HTB 43 cell growth. Taxifolin slightly inhibited HTB 43 cell growth at 8 micrograms/ml, while moderately inhibiting HTB 43 cell growth at 2-8 micrograms/ml. The proliferation of a human lung fibroblast-like cell line (CCL 135) was relatively insensitive to low concentrations of the above flavonoids.

Carcinoma, Squamous Cell↗

PubMed1991

Antiproliferative effects of citrus flavonoids on a human squamous cell carcinoma in vitro.

We examined the effects of four plant flavonoids (quercetin, taxifolin, nobiletin and tangeretin) on the in vitro growth of a human squamous cell carcinoma cell line (HTB43). Cell cultures were treated with each flavonoid (2-8 micrograms/ml) for 3-7 days. Cell viability, as determined by counting cells, correlated well with that obtained from a colorimetric assay for cellular growth utilizing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. The polymethoxylated flavonoids, nobiletin and tangeretin, markedly inhibited cell growth at all concentrations tested on days 5 and 7. On day 3, the inhibition observed was 70-72% at 8 micrograms/ml, while on day 5, it ranged from 61-88% at 2-4 micrograms/ml. Quercetin and taxifolin exhibited no significant inhibition at any of the concentrations tested. This difference in activity may be due to the relatively greater membrane uptake of the polymethoxylated flavonoids since methoxylation of the phenolic groups decreases hydrophilicity of the flavonoid.

Antineoplastic Agents↗

PubMed1990

Microleakage of glass ionomer/composite laminate Class V restorations.

The aim of this investigation was to evaluate the effects on microleakage of pretreating dentin with polyacrylic acid (PAA), prior to placing a glass ionomer base/composite laminate restoration. Class V erosion-type lesions with the incisal margin on enamel and the cervical margin below the cemento-enamel junction (CEJ), were prepared in 50 sound extracted teeth. These teeth were divided into five dentin treatment groups: A) 10% PAA; B) 20% PAA; C) and D) 40% PAA; E) no dentin preconditioning. In groups A, B, C and E, a glass ionomer base was placed within 1 mm of the margins. In group D the glass ionomer base extended to the cervical margin. The glass ionomer base and the incisal enamel were etched with 37% phosphoric acid prior to placing a bonding agent and restoring with a composite. The restorations were finished and polished and the teeth were stored in distilled water at 37 degrees C for 7 days. They were thermocycled in 0.5% fuchsin dye for 500 cycles (5 degrees C to 60 degrees C), embedded in epoxy resin, and sectioned at 250 mu intervals through the restorations. The section of each tooth exhibiting the most severe dye penetration along the tooth/restoration interface was evaluated and scored both incisally and cervically: 0 = no leakage; 1 = leakage up to the glass ionomer base; 2 = leakage up to 1/2 the wall length; 3 = leakage exceeding 1/2 the wall length. Cervically, the median leakage for all groups was 3.0. Incisally, the median leakage for all the groups was 0.0.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrylic Resins↗

PubMed1989

The effects of the bioflavonoid quercetin on squamous cell carcinoma of head and neck origin.

Quercetin exhibits antitumor activity. We investigated the effect of quercetin on the in vitro and in vivo growth of two squamous cell carcinoma cell lines and a normal human lung fibroblast-like cell line. The in vivo effect was evaluated using implantable cell growth chambers implanted subcutaneously in immunocompetent rats. Quercetin was injected intraperitoneally, and multiple dosages were tested. Cells were counted on days 1, 3, 5, and 7, and growth curves were constructed. Quercetin caused inhibition of growth in both squamous cell carcinoma lines. Effect on the fibroblast-like human lung cells was noted only at the maximum concentration. Significant growth inhibition of squamous cell carcinoma was observed in implantable cell growth chambers retrieved 3 days after quercetin treatment. Quercetin appears to possess a cytotoxic effect on squamous cell carcinoma of head and neck origin both in vivo and in vitro. The inhibitory effect on malignant cells appears to be selective and dose-dependent.

Animals↗

PubMed1989

Identification and characterization of the maltose permease in genetically defined Saccharomyces strain.

Saccharomyces yeasts ferment several alpha-glucosides including maltose, maltotriose, turanose, alpha-methylglucoside, and melezitose. In the utilization of these sugars transport is the rate-limiting step. Several groups of investigators have described the characteristics of the maltose permease (D. E. Kroon and V. V. Koningsberger, Biochim. Biophys. Acta 204:590-609, 1970; R. Serrano, Eur. J. Biochem. 80:97-102, 1977). However, Saccharomyces contains multiple alpha-glucoside transport systems, and these studies have never been performed on a genetically defined strain shown to have only a single permease gene. In this study we isolated maltose-negative mutants in a MAL6 strain and, using a high-resolution mapping technique, we showed that one class of these mutants, the group A mutants, mapped to the MAL61 gene (a member of the MAL6 gene complex). An insertion into the N-terminal-coding region of MAL61 resulted in the constitutive production of MAL61 mRNA and rendered the maltose permease similarly constitutive. Transformation by high-copy-number plasmids containing the MAL61 gene also led to an increase in the maltose permease. A deletion-disruption of MAL61 completely abolished maltose transport activity. Taken together, these results prove that this strain has only a single maltose permease and that this permease is the product of the MAL61 gene. This permease is able to transport maltose and turanose but cannot transport maltotriose, alpha-methylglucoside, or melezitose. The construction of strains with only a single permease will allow us to identify other maltose-inducible transport systems by simple genetic tests and should lead to the identification and characterization of the multiple genes and gene products involved in alpha-glucoside transport in Saccharomyces yeasts.

Cloning, Molecular↗

PubMed1989

Preservation of brain tumor specimens for drug sensitivity testing.

To examine the feasibility of shipment of brain tumor specimens to a central laboratory for drug sensitivity testing, an experimental gliosarcoma (9L) was grown subcutaneously in rats, harvested, stored, and disaggregated. Growth of the disaggregated tumor cells in monolayer culture was evaluated after storage for various times at 2 to 6 degrees C and 37 degrees C in saline and minimum essential medium. Growth potential was maintained for 24 hours when tumor specimens were stored under refrigerated conditions and was best maintained when specimens were stored in saline. Specimens stored at 37 degrees C grew best when stored in minimum essential medium, but growth potential was lost after 12 hours unless the specimens were refrigerated. Shipment of tumor specimens to a central laboratory for drug sensitivity testing appears to be feasible, since under most circumstances, specimens should reach the laboratory for processing within 24 hours of their removal. Storage and transport of specimens in saline on wet ice appears to be optimal.

Antineoplastic Agents↗

PubMed1988

MAL63 codes for a positive regulator of maltose fermentation in Saccharomyces cerevisiae.

Genetic analysis of the MAL6 locus has previously yielded mal6 mutants which fall into a single complementation group and which are noninducible for maltase and maltose permease. However, the strains used in these studies contained additional partially functional copies of MAL1 (referred to as MAL1g) and MAL3 (referred to as MAL3g). Using a strain lacking MALg genes, we have isolated two classes of mutants and these classes correspond to mutations in MAL63 and MAL61, two genes of the MAL6 complex. Disruptions of MAL63 are noninducible for maltase and maltose permease and for their corresponding mRNAs. The mal6 mutants are shown to map to MAL63. Inducer exclusion as a cause of the noninducible phenotype of the mal63 mutations has been eliminated by constructing a mal63 mutant in a strain constitutive for maltose permease; the strain remains noninducible. These results rigorously demonstrate that MAL63 is a regulatory gene which plays a positive role in the regulation of maltose fermentation.

Chromosome Mapping↗

PubMed1981

Improving maternity services: useful research--and the other kind.

'There is no room in the health service for impractical research,' says Elizabeth Perkins, research and development officer, Nottinghamshire Area Health Education Unit, and honorary research fellow, Department of Adult Education, Nottingham University. Her book 'Education for childbirth and parenthood' was reviewed in last week's 'Journal'.

Female↗

PubMed1978