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At least 55 records · Page 3Linked to original sources
PubMed1973

Zinc: a trace element essential in vitamin A metabolism.

Zinc is necessary to maintain normal concentrations of vitamin A in plasma. By using animals deficient in both zinc and vitamin A, it was demonstrated that zinc is necessary for normal mobilization of vitamin A from the liver. These results suggest that cases of depressed vitamin A in plasma, unresponsive to vitamin A therapy, may respond to zinc supplementation.

Animals↗
PubMed1985

Point mutations implicate repeated sequences as essential elements of the CYC7 negative upstream site in Saccharomyces cerevisiae.

The transcription of the CYC7 gene of Saccharomyces cerevisiae, encoding the iso-2-cytochrome c protein, is controlled by two upstream regulatory elements, a positive element and a negative element. The nature of the DNA sequences in the negative element were investigated in a two-part approach. The first involved the construction of a CYC7-galK fusion gene which placed the coding sequence of the Escherichia coli galactokinase gene under the regulation of the CYC7 upstream sequences. This fusion allowed the quantitation by galactokinase enzyme assays of the effects on gene expression of a variety of previously isolated deletion mutations within the negative site. The results suggested that the negative site contained three related sequences. This hypothesis was tested in the second part of these studies, the selection of point mutations within the region of the negative site which led to increased CYC7 expression. Point mutations were introduced by a technique which induced mutations within a localized region at high efficiency. All but one of the mutations involved more than a single base-pair change. The mutations followed the pattern that multiple base-pair changes occurred in one repeat or single base-pair changes occurred in two repeats, with the exception of one mutant, which had a single base-pair change in one repeat. This pattern of mutations and the base pairs that were altered strongly supported the hypothesis that the repeats are integral elements of the negative site.

Base Sequence↗
PubMed1988

Three sequence-specific DNA-protein complexes are formed with the same promoter element essential for expression of the rat somatostatin gene.

We identified three sequence-specific DNA-protein complexes which are formed after in vitro binding of nuclear extracts, derived from neuronal (CA-77, rat brain) or non-neuronal (HeLa) cells, to positions -70 to -29 of the rat somatostatin promoter. The protein(s) responsible for the formation of the three sequence-specific complexes was fractionated from rat brain whole cell extracts by DEAE-Sepharose chromatography. The critical contact residues of the factor(s) in each complex, as determined by methylation interference analyses, are located within positions -59 to -35, which is protected from DNase I digestion; these include the G residues of a TGACGTCA consensus also found in the cAMP-responsive human enkephalin (positions -105 to -76) and E1A-inducible adenovirus type 5 E3 (positions -72 to -42) promoters. Competition assays with these heterologous promoters reveal that the factor(s) of each complex displays approximately 50-fold greater affinity for the somatostatin promoter-binding site. Synthetic oligonucleotides spanning positions -70 to -29 of the somatostatin promoter and containing single-base substitutions of the G residues in the TGACGTCA consensus were utilized in competition assays. The G residues located in the center of the module are the most critical determinants in the formation of the three sequence-specific complexes. Deletions disrupting the TGACGTCA consensus abolish not only formation of the three complexes in vitro but also expression of the somatostatin promoter in vivo, suggesting that formation of one or more of these complexes is essential for transcription of the rat somatostatin gene.

Adenoviridae↗
PubMed1991

[Silicon, a trace element essential for living organisms. Recent knowledge on its preventive role in atherosclerotic process, aging and neoplasms].

Having briefly analyzed the role of silicon specially in the metabolism of connective and bone tissue, the author describes conditions induced by silicon deficit and poisoning due to this metal. The most recent findings concerning the role of silicon in delaying the onset and reducing the extension of atherosclerotic processes are also illustrated.

Aging↗
PubMed1990

Environmental safety: an essential element of quality care.

Quality care results when nurses conform to standards of practice. Health care providers are accountable for compliance with laws that set standards for environmental safety, standards set by accrediting bodies, state practice acts, and community and institutional standards. Conformance with standards requires continuous monitoring, updating of information, and staff education. The PACU is a busy place with rapid changes in patient census, patient status, and staffing needs. It may seem difficult to allot time for safety education and practice sessions. The authors offer suggestions, using fire safety as an example, for providing a safe environment for patients and personnel in the PACU.

Accident Prevention↗