PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Essential elements”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMed1995

An RNA pseudoknot is an essential structural element of the internal ribosome entry site located within the hepatitis C virus 5' noncoding region.

Translation of the human hepatitis C virus (HCV) RNA genome occurs by a mechanism known as "internal ribosome entry." This unusual strategy of translation is employed by naturally uncapped picornaviral genomic RNAs and several cellular mRNAs. A common feature of these RNAs is a relatively long 5' noncoding region (NCR) that folds into a complex secondary structure harboring an internal ribosome entry site (IRES). Evidence derived from the use of dicistronic expression systems, combined with an extensive mutational analysis, demonstrated the presence of an IRES within the HCV 5'NCR. The results of our continued mutational analysis to map the critical structural elements of the HCV IRES has led to the identification of a pseudoknot structure upstream of the initiator AUG. The evidence presented in this study is based upon the mutational analysis of the putative pseudoknot structure. This is further substantiated by biochemical and enzymatic probing of the wild-type and mutant 5'NCR. Further, the thermodynamic calculations, based upon a modified RNAKNOT program, are consistent with the presence of a pseudoknot structure located upstream of the initiator AUG. Maintenance of this structural element is critical for internal initiation of translation. The pseudoknot structure in the 5'NCR represents a highly conserved feature of all HCV subtypes and members of the pestivirus family, including hog cholera virus and bovine viral diarrhea virus.

Base Sequence↗
PubMed1996

[Methods and clinical significance of an oral tolerance test of essential trace element, especially an oral zinc tolerance test].

Oral administration of zinc (zinc tolerance test) was performed in 6 healthy adults, 11 patients with chronic hepatitis and 17 patients with liver cirrhosis to evaluate the ability of the digestive organs in patients with chronic hepatic diseases to absorb zinc. That is 300 mg of zinc sulfate powder (ZnSO4 7H2O)--equivalent to 68 mg of zinc--was dissolved in 200 ml of physiological saline solution, and the subjects received oral administration of the solution in a fasting condition during the early morning. The mean levels of serum Zn (ppm) at 0, 1, 2, and 3 hours after the test dose of ZnSO4 were 0.8 +/- 0.06, 1.66 +/- 0.21, 2.73 +/- 0.22 and 2.53 +/- 0.33 in cirrhotic patients, respectively. In most subjects, serum Zn levels peaked at 2 or 3 ours. The increase in serum Zn at 60 minutes during the base line Zn tolerance test was similar in patients and controls. The area under the curve was also significantly decreased in cirrhotic patients. These results will confirm the presence of diminished absorption by the intestinal tract in patients with liver cirrhosis.

Administration, Oral↗
PubMed1996

[Concentrations of essential trace elements in blood and introduction of analytical techniques].

Research on trace elements has been paid attention recently. In order to determine concentrations of various kinds of trace elements in biological materials, atomic absorption spectrophotometer is widely used. This instrument allows single element analysis at ppb levels. Microwave induced plasma-mass spectrophotometer (MIP-MS) or inductively coupled plasma-mass spectrophotometer (ICP-MS) permits multielement analysis at sub-ppb or ppt levels. These analytical instruments accept liquid samples only. Biological materials such as organs, tissue and blood must be digested in prior to apply into the instrument. Digesting methods, simplified wet ashing and microwave ashing are introduced.

Humans↗
PubMed1996

[Liver diseases and essential trace elements].

The significance of the biochemical and nutritional roles of trace elements is widely recognized, since metals are found as constituent components of many metalloproteins and metalloenzymes. Some trace elements such as copper act as cofactors against hepatic fibrosis in chronic liver diseases, particularly in the biosynthesis of collagen. As the disease progress from chronic hepatitis to liver cirrhosis, serum calcium, magnesium, phosphorus and zinc concentrations decrease, while the copper concentration increases. In the patients with hepatocellular carcinoma, serum concentrations of trace elements are similar to those of liver cirrhosis. In the patients with acute hepatitis, serum calcium, magnesium and zinc concentrations decrease, while phosphorus, iron and copper concentrations decrease. These trace element abnormalities may reflect such pathological conditions as liver dysfunction, cholestasis, hepatic fibrosis or liver regeneration.

Humans↗
PubMed2004

Requirement of a relatively high threshold level of Mg(2+) for cell growth of a rhizoplane bacterium, Sphingomonas yanoikuyae EC-S001.

Mg(2+) is one of the essential elements for bacterial cell growth. The presence of the magnesium cation (Mg(2+)) in various concentrations often affects cell growth restoration in plant-associating bacteria. This study attempted to determine whether Mg(2+) levels in Sphingomonas yanoikuyae EC-S001 affected cell growth restoration in the host plant and what the threshold level is. S. yanoikuyae EC-S001, isolated from the rhizoplane of spinach seedlings grown from surface-sterilized seeds under aseptic conditions, displayed uniform dispersion and attachment throughout the rhizoplane and phylloplane of the host seedlings. S. yanoikuyae EC-S001 did not grow in potato-dextrose broth medium but grew well in an aqueous extract of spinach leaves. Chemical investigation of the growth factor in the spinach leaf extract led to identification of the active principle as the magnesium cation. A concentration of ca. 0.10 mM Mg(2+) or more allowed S. yanoikuyae EC-S001 to grow in potato-dextrose broth medium. Some saprophytic and/or diazotrophic bacteria used in our experiment were found to have diverse threshold levels for their Mg(2+) requirements. For example, Burkholderia cepacia EC-K014, originally isolated from the rhizoplane of a Melastoma sp., could grow even in Mg(2+)-free Hoagland's no. 2 medium with saccharose and glutamine (HSG medium) and requires a trace level of Mg(2+) for its growth. In contrast, S. yanoikuyae EC-S001, together with Bacillus subtilis IFO12113, showed the most drastic restoring responses to subsequent addition of 0.98 mM Mg(2+) to Mg(2+)-free HSG medium. Our studies concluded that Mg(2+) is more than just the essential trace element needed for cell growth restoration in S. yanoikuyae EC-S001 and that certain nonculturable bacteria may require a higher concentration of Mg(2+) or another specific essential element for their growth.

Bacteriological Techniques↗