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Biomedical subjects

G Drivas

Publications and source records attributed to G Drivas.

At least 19 recordsLinked to original sources
PubMed2002

Erythrocyte ferritin in patients with chronic renal failure and heterozygous beta-thalassemia.

AIM: The aim of this research is to study the variance of erythrocyte ferritin (EF) in patients with chronic renal failure (CRF) and heterozygous beta-thalassemia (beta-TA), as well as the use of EF as a more reliable index for assessing the body iron status. METHODS: We studied 63 subjects with CRF, 40 subjects with heterozygous beta-TA, 53 subjects with CRF and heterozygous beta-TA and 24 normal subjects. In 11 patients with CRF and heterozygous beta-TA, sternal bone marrow aspiration was performed to evaluate iron stores in the bone marrow. EF was determined in the hemolysate of washed erythrocytes by a radioimmunoassay. RESULTS: EF showed the strongest correlation with bone marrow iron (p < 0.001) in comparison with the remaining hematological parameters that were examined. Patients with CRF without heterozygous beta-TA showed an increase in serum ferritin (SF), even in cases of iron deficiency. In the group of heterozygous beta-TA without renal failure, 22.5% of patients showed an increased EF content up to 150 ag/cell and a tendency for iron overload. Patients with CRF and heterozygous beta-TA showed a high value of EF, up to 200 ag/cell, and iron overload in 22.6%, almost the same proportion as in the previous group. It was also observed that a high value of SF does not indicate iron overload for these patients. In the group of hemodialysis, patients without heterozygous beta-TA who were under erythropoietin (EPO) treatment presented iron deficiency. Many patients with CRF and heterozygous beta-TA who were taking EPO presented iron overload, while very few of them presented iron deficiency. CONCLUSION: These findings suggest that EF is a reliable index for assessing the iron status in patients with CRF and heterozygous beta-TA.

Bone Marrow↗
PubMed1997

A T42A Ran mutation: differential interactions with effectors and regulators, and defect in nuclear protein import.

Ran, the small, predominantly nuclear GTPase, has been implicated in the regulation of a variety of cellular processes including cell cycle progression, nuclear-cytoplasmic trafficking of RNA and protein, nuclear structure, and DNA synthesis. It is not known whether Ran functions directly in each process or whether many of its roles may be secondary to a direct role in only one, for example, nuclear protein import. To identify biochemical links between Ran and its functional target(s), we have generated and examined the properties of a putative Ran effector mutation, T42A-Ran. T42A-Ran binds guanine nucleotides as well as wild-type Ran and responds as well as wild-type Ran to GTP or GDP exchange stimulated by the Ran-specific guanine nucleotide exchange factor, RCC1. T42A-Ran.GDP also retains the ability to bind p10/NTF2, a component of the nuclear import pathway. In contrast to wild-type Ran, T42A-Ran.GTP binds very weakly or not detectably to three proposed Ran effectors, Ran-binding protein 1 (RanBP1), Ran-binding protein 2 (RanBP2, a nucleoporin), and karyopherin beta (a component of the nuclear protein import pathway), and is not stimulated to hydrolyze bound GTP by Ran GTPase-activating protein, RanGAP1. Also in contrast to wild-type Ran, T42A-Ran does not stimulate nuclear protein import in a digitonin permeabilized cell assay and also inhibits wild-type Ran function in this system. However, the T42A mutation does not block the docking of karyophilic substrates at the nuclear pore. These properties of T42A-Ran are consistent with its classification as an effector mutant and define the exposed region of Ran containing the mutation as a probable effector loop.

Amino Acid Substitution↗
PubMed1996

The small nuclear GTPase Ran: how much does it run?

Ran is one of the most abundant and best conserved of the small GTP binding and hydrolyzing proteins of eukaryotes. It is located predominantly in cell nuclei. Ran is a member of the Ras family of GTPases, which includes the Ras and Ras-like proteins that regulate cell growth and division, the Rho and Rac proteins that regulate cytoskeletal organization and the Rab proteins that regulate vesicular sorting. Ran differs most obviously from other members of the Ras family in both its nuclear localization, and its lack of sites required for post-translational lipid modification. Ran is, however, similar to other Ras family members in requiring a specific guanine nucleotide exchange factor (GEF) and a specific GTPase activating protein (GAP) as stimulators of overall GTPase activity. In this review, the multiple cellular functions of Ran are evaluated with respect to its known biochemistry and molecular interactions.

Animals↗
PubMed1994

Aberrant function of the Ras-related protein TC21/R-Ras2 triggers malignant transformation.

Although the human Ras proteins are members of a large superfamily of Ras-related proteins, to date, only the proteins encoded by the three mammalian ras genes have been found to possess oncogenic potential. Among the known Ras-related proteins, TC21/R-Ras2 exhibits the most significant amino acid identity (55%) to Ras proteins. We have generated mutant forms of TC21 that possess amino acid substitutions analogous to those that activate Ras oncogenic potential [designated TC21(22V) and TC21(71L)] and compared the biological properties of TC21 with those of Ras proteins in NIH 3T3 and Rat-1 transformation assays. Whereas wild-type TC21 did not show any transforming potential in vitro, both TC21(22V) and TC21(71L) displayed surprisingly potent transforming activities that were comparable to the strong transforming activity of oncogenic Ras proteins. Like Ras-transformed cells, NIH 3T3 cells expressing mutant TC21 proteins formed foci of morphologically transformed cells in monolayer cultures, proliferated in low serum, formed colonies in soft agar, and developed progressive tumors in nude mice. Thus, TC21 is the first Ras-related protein to exhibit potent transforming activity equivalent to that of Ras. Furthermore, mutant TC21 proteins also stimulated constitutive activation of mitogen-activated protein kinases as well as transcriptional activation from Ras-responsive promoter elements (Ets/AP-1 and NF-kappa B). We conclude that aberrant TC21 function may trigger cellular transformation via a signal transduction pathway similar to that of oncogenic Ras and suggest that deregulated TC21 activity may contribute significantly to human oncogenesis.

3T3 Cells↗
PubMed1993

Ran/TC4: a small nuclear GTP-binding protein that regulates DNA synthesis.

Ran/TC4, first identified as a well-conserved gene distantly related to H-RAS, encodes a protein which has recently been shown in yeast and mammalian systems to interact with RCC1, a protein whose function is required for the normal coupling of the completion of DNA synthesis and the initiation of mitosis. Here, we present data indicating that the nuclear localization of Ran/TC4 requires the presence of RCC1. Transient expression of a Ran/TC4 protein with mutations expected to perturb GTP hydrolysis disrupts host cell DNA synthesis. These results suggest that Ran/TC4 and RCC1 are components of a GTPase switch that monitors the progress of DNA synthesis and couples the completion of DNA synthesis to the onset of mitosis.

Amino Acid Sequence↗
PubMed1991

Ras-like genes and gene families in the mouse.

Four human RAS-like cDNAs and a mouse genomic DNA fragment were used to define novel mouse Ras-like genes and gene families. Inheritance of DNA restriction fragment length variants associated with these genes in recombinant inbred and backcross mice allowed definition of 12 genetic loci, nine of which were mapped, to chromosomes (Chr) 2, 4, 7, 8, 9, and 17. Two possible clusters of Ras-like and/or G protein genes were identified, on Chrs 9 and 17.

Animals↗
PubMed1987

Comparative study between iohexol and iopromide for aortofemoral arteriography.

A double-blind clinical trial was performed on 50 patients in order to compare omnipague (iohexol) and Ultravist-300 (iopromide) for peripheral arteriography. Both contrast media were well tolerated, but there was less body heat and pain in the Ultravist group. There were no idiosyncratic reactions or significant changes in blood pressure before and after the injection.

Adolescent↗
PubMed1984

Is there a "gold standard" for human serum vitamin B12 assay?

In a study from four laboratories using two commercial vitamin B12 radioassays (impure hog intrinsic factor concentrate containing both intrinsic factor and R binders (IF + R) to measure total corrinoids and the same concentrate presaturated with cobinamide (Cbi) to block B12 binding sites on R binder (IF + R + Cbi) to measure only cobalamins), the rank order of results was generally the same. The concordance between the two tests for classifying sera as normal or deficient was 91% in 311 serum samples. Three percent of sera below the "true B12" (B12 binding to IF + R + Cbi) normal cut-off point were not below the cut-off point for normal "total B12" (B12 binding to IF + R); 6% of sera below the total B12 normal cut-off point were not below true B12 cut-off point. The correlations between Euglena gracilis and the radioassays were 0.80 and 0.83 in the 50 serum samples that also had E. gracilis serum vitamin B12 levels. Lactobacillus leichmannii serum vitamin B12 levels were determined in 49 of the 311 serum samples and results were comparable with results obtained by four radioassay binder systems: IF + R, IF + R + Cbi, highly purified hog IF, and saliva R binder. The closest correlate with L. leichmannii was radioassay using IF + R as binder (r = 0.93), then IF + R + Cbi (r = 0.92), pure IF (r = 0.80), and pure R (r = 0.73). The key to reliable results appears not to reside in a particular assay but rather in determining for each assay its own range of results in participants determined clinically and morphologically normal vs. participants with deficient vitamin B12 (with B12 deficiency defined independently of a serum B12 assay). When laboratory assay results differ from clinical judgment, further evaluation is the appropriate course. There is no "gold standard" for human serum vitamin B12 assay.

Biological Assay↗
PubMed1983

A simultaneous study of the polymorphism of five proteins in the serum and the urine of nephrotic patients.

The phenotypes of the haptoglobin (Hp), ceruloplasmin (Cp), group-specific component (Gc), transferrin (Tf), and third component of complement (C3) were determined simultaneously in the serum and urine of patients with proteinuria secondary to nephrotic syndrome of various types. In a large number of cases the patterns of Hp, Cp, and C3 phenotypes in the urine showed marked deviations from those in the corresponding serum either in the mobility or the number of their electrophoretic bands. The monomeric Hp and the Cp were found to have a very augmented urine/serum ration in some cases. Such differences were not detected in the electrophoretic appearance of the Gc and Tf phenotypes. Our results imply that in the proteinuria of the nephrotic syndrome, factors other than molecular weight interfere in the passage of proteins through the glomerular wall.

Adolescent↗