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G Daniels

Publications and source records attributed to G Daniels.

At least 37 records · Page 2Linked to original sources
PubMed2000

Expression of red cell surface antigens during erythropoiesis.

BACKGROUND AND OBJECTIVES: We have analysed the appearance and disappearance of cell surface markers during erythropoiesis, in vitro. MATERIALS AND METHODS: CD34+ haemopoietic progenitor cells were isolated from umbilical cord blood and cultured by three different methods, all in the presence of erythropoietin. The methods included two one-stage techniques, one serum-free, the other with serum present, and one serum-present two-stage method. RESULTS: The appearance of cell surface markers on the differentiating erythroid cells varied slightly from sample to sample, but differed more substantially between techniques, with the cells differentiating more rapidly in the culture media containing serum. The order of appearance of the markers, which was constant in the three methods, was as follows: glycophorin C, Kell, Rh-associated glycoprotein, glycophorin A, band 3, Rh proteins, and glycophorin B. CONCLUSION: Cell surface antigens can be used as markers for mapping the progress of erythroid differentiation during erythropoiesis.

Antigens, CD34↗
PubMed1999

Functional aspects of red cell antigens.

Over 250 blood group determinants are known and most of these are located on integral red cell proteins and glycoproteins. The functions of some of these structures are known: Diego (band 3) is the red cell anion exchanger; Kidd, a urea transporter; Colton (aquaporin 1), a water channel; Cromer (DAF) and Knops (CRI), complement regulators; Diego (band 3) and Gerbich (glycophorin C/D) link the red cell membrane and the membrane skeleton. The Duffy glycoprotein is a chemokine receptor that may act as a scavenger for inflammatory mediators in the peripheral blood, but is also exploited as a receptor by Plasmodium vivax merozoites. The functions of some blood group antigens can be speculated upon because of structural similarity to proteins and glycoproteins of known function. For example, the Lutheran, LW, and Ok glycoproteins are members of the immunoglobulin superfamily of receptors and signal transducers, the Rh proteins and related glycoproteins show homology to ammonium transporters, and the Kell glycoprotein resembles a family of endopeptidases. Yet most blood groups systems contain null phenotypes associated with no apparent pathology. If these blood group antigens have important functions, other structures must be able to carry out those functions in their absence. Almost nothing is known of the biological significance of blood group polymorphism.

Animals↗
PubMed1998

The Fy(x) phenotype is associated with a missense mutation in the Fy(b) allele predicting Arg89Cys in the Duffy glycoprotein.

The molecular basis of the three major alleles (Fy(a)/Fy(b)/Fy) of the Duffy (FY) blood group system has recently been established but the Fy(x) phenotype associated with weak expression of the Fy(b) and other FY antigens is poorly understood. In the Fy(x) genes of five unrelated British and Swedish donors with the Fy(a+b+weak) phenotype we found two missense mutations predicting amino acid changes Arg89Cys and Ala100Thr in the FY glycoprotein. The same mutations were found in two Fy(a-b+weak) samples from individuals of Swedish and Algerian origin. Their red blood cells showed a marked decrease in Fy(b), Fy3 and Fy6 expression measured by routine serology and flow cytometry. The rare FY genotypes Fy(x)Fy(x) and Fy(x)Fy were confirmed by family studies and DNA sequencing. Screening by allele-specific primer PCR (ASP-PCR) for these mutations among 100 Caucasian and 100 Black random blood donors indicated allele frequencies of 2.5% and 0% respectively. Ala100Thr alone was present in 33% of the Caucasians (but none of the Blacks) with no weakening of FY expression. A novel allele at the FY locus associated with the Fy(x) phenotype was studied. Mistyping of this weak Fy(b) antigen in clinical transfusion medicine may lead to delayed haemolytic transfusion reactions in immunized patients. A potential role for genomic typing is proposed.

Alleles↗
PubMed1998

Rainbow trout cytokine and cytokine receptor genes.

Transforming growth factor-beta (TGF-beta) and interleukin-1 beta (IL-1 beta) have been cloned from rainbow trout (Oncorhynchus mykiss) in our laboratory. The trout TGF-beta is typical of members of the cysteine knot cytokine family, and has highest homology to TGF-beta 1, TGF-beta 4 and TGF-beta 5. The gene organisation is different to other TGF-beta genes despite the presence of seven exons. Trout IL-1 beta has less homology to known IL-1 beta s (49-56% amino acid similarity) but shows clear conservation of the secondary structure of the "mature peptide". An interleukin-converting enzyme cut site is not apparent however, and it remains to be determined whether fish IL-1 beta must be cleaved for biological activity. The trout IL-1 beta gene consists of six exons, one less than in mammals, with the missing exon at the 5' end of the gene. Two trout chemokine receptors have also been isolated in our laboratory, having high homology to CXC-R4 and CC-R7 (67% and 56% nucleotide identity respectively). With a view to studying the biological effects of fish cytokines we have also cloned the inducible nitric oxide (iNOS) and cyclooxygenase (COX-2) genes in trout. Both have high homology to known mammalian and chicken genes, and have been shown to be inducible in trout.

Amino Acid Sequence↗
PubMed1997

Blood group polymorphisms: molecular approach and biological significance.

Genes for 20 of the 23 human blood group systems have now been cloned and the molecular bases of the important polymorphisms within most of these systems are known. Most blood group polymorphisms are due to missense mutations resulting in amino acid substitutions, but other types of mutation are involved in blood group polymorphism including gene deletion, single base deletion, and exchange of genetic material between homologous genes. All the polymorphisms of the Kell system, for example, result from missense mutations. Comparison of the position of these mutations within the KEL gene with clusters of antigens determined by an immunochemical technique, suggests that the Kell-system antigens are not linear and are probably discontinuous. The biological significance of the proteins and glycoproteins carrying many of the blood group antigens is known, or at least can be speculated upon. Identification of the nonsense mutations responsible for some null-phenotypes has shown that these macromolecules are not usually essential for a healthy life. Little is known, however, about the biological significance of the blood group polymorphisms. Many macromolecules carrying blood group activity are receptors for pathogenic micro-organisms and these pathogens may well have played an important part in the evolution of blood group polymorphism. The Duffy-glycoprotein is a chemokine receptor, but also a receptor for the malarial parasite Plasmodium vivax A mutation within an erythroid-specific transcription factor binding site within the FY gene, common in people of African origin but rare in other ethnic groups, results in the absence of the glycoprotein from red cells and, therefore, resistance to P. vivax infection, but presence of the glycoprotein in other tissues, reducing any potential selective disadvantage.

Animals↗
PubMed1997

A mutation analysis on GYPC, the gene encoding the Gerbich blood group antigens.

The four exons of GYPC genomic DNA were amplified together with their flanking sequences and analysed by denaturing gradient gel electrophoresis (DGGE) or single-strand conformational analysis (SSCA). Exons 2 and 3 were amplified by a common set of primers so as to provide an internal control for exon deletion mutants. Ge:-2,-3,4(Ge) and Ge:-2,3,4(Yus) phenotypes were always associated with exon 3 and exon 2 deletions, respectively, as determined by DGGE. Ge:-2,-3,-4(Leach) was associated with a deletion of exons 3 and 4. Two single base mutations within exon 2 were detected, one of which represented the Ana allele and encoded an amino acid substitution. A previously undetected single base mutation in exon 3 encoded a Val61Ile substitution within the membrane spanning domain. DGGE analysis of exon 4 product revealed two distinct haplotypes of frequencies 41% and 59%. DGGE was not found suitable for analysis of exon 1, so SSCA was utilized. This method distinguished the single base mutation responsible for Wb antigen, but not that responsible for Dha.

Blood Group Antigens↗
PubMed1996

Denaturing gradient gel electrophoresis: a novel method for determining Rh phenotype from genomic DNA.

Denaturing gradient gel electrophoresis (DGGE) was carried out on PCR products amplified from exons 2 and 5 of RHD and RHCE. Exon 2 of RHD and exon 2 of the C allele of RHCE have an identical sequence, which differs from that of the c allele of RHCE. One band representing D and/or C, and another representing c, could be distinguished by DGGE of exon 2 amplifications of genomic DNA from individuals with the appropriate Rh phenotype. C and c could only be distinguished in D-negative samples. Exon 5 of RHD and exon 5 of the E and e alleles of RHCE all have different nucleotide sequences. Bands representing D, E and e could be distinguished following DGGE of the products of exon 5 amplification of genomic DNA from individuals with red cells of the appropriate Rh phenotype. In samples from individuals with VS+ red cells (V+ or V-) there was a shift of the band representing e. Sequencing demonstrated that VS is associated with a RHCE e sequence with a single base change predicting a Leu245 --> Val substitution in the Rh polypeptide. This substitution may be responsible for the VS and e5 antigens.

Base Sequence↗
PubMed1995

Treatment guidelines for patients with hyperthyroidism and hypothyroidism. Standards of Care Committee, American Thyroid Association.

OBJECTIVE: To develop a set of minimum clinical guidelines for use by primary care physicians in the evaluation and management of patients with hyperthyroidism and hypothyroidism. PARTICIPANTS: Guidelines were developed by a nine-member ad hoc Standards of Care Committee of the American Thyroid Association (the authors of this article). The participants were selected by the committee chair and the president of the American Thyroid Association on the basis of their clinical experience. The committee members represented different geographic areas within the United States, in order to take into account different practice styles. EVIDENCE: Guidelines were developed on the basis of expert opinion of the participants, as well as on available published information. CONSENSUS PROCESS: Input was obtained from all of the participants, each of whom wrote an initial section of the document. A complete draft document was then written by three participants (P.A.S., D.S.C., and E.G.L.) and resubmitted to the entire committee for revision. The revised document was then submitted to the entire membership of the American Thyroid Association for written comments, which were then reviewed (mainly by P.A.S., D.S.C., and E.G.L.). Many of the suggestions of the American Thyroid Association members were incorporated into the final draft, which was then approved by the Executive Council of the American Thyroid Association. The entire process, from initial drafts to final approval, took approximately 18 months. CONCLUSIONS: A set of minimum clinical guidelines for the diagnosis and treatment of hyperthyroidism and hypothyroidism were developed by consensus of a group of experienced thyroidologists. The guidelines are intended to be used by physicians in their care of patients with thyroid disorders, with the expectation that more effective care can be provided, and at a cost savings.

Antithyroid Agents↗
PubMed1995

Blood letting for BSL: the effects of timing and sites on blood volume.

The purpose of this study was to establish the most appropriate timing and site for obtaining an adequate volume of blood for accurate measurement of blood sugar levels by blood glucose monitors. The 248 samples of blood used in the study were collected from 18 men and 16 women recruited from a group of people with type II diabetes mellitus who were attending an outpatient Diabetes Centre. Neither the timing between lancing and collecting the blood nor the sites from which blood was obtained significantly affected the volume of blood samples. Sufficient blood to give an accurate measure of blood sugar levels from monitors requiring 30, 15-18 and five microlitres of blood was obtained from 37%, 65% and 98% of the procedures respectively.

Adult↗
PubMed1994

Glycophorin He(Sta) of the human red blood cell membrane is encoded by a complex hybrid gene resulting from two recombinational events.

A complex glycophorin (GP) variant of the human red blood cell membrane exhibiting both He and Sta antigens was characterized at the molecular level. Restriction mapping identified two novel Msp I fragments derived from the 5' and 3' portions of the GPHe(Sta) gene, respectively. Genomic DNA, including exons II-V and their splice junctions, was amplified by polymerase chain reaction, and the nucleotide sequences were determined. Comparison with the GPA and GPB sequences showed the presence in GPHe(Sta) of multiple recombinational breakpoints. In the 5' region of the variant gene, a sequence covering a portion of exon II to intron 2 had been transferred from GPA to GPB, resulting in a B-A-B hybrid structure. Such a gene conversion-like event introduced a number of templated and untemplated nucleotide replacements and was the direct cause for the expression of the He antigen. In the 3' region of the variant gene, an unequal crossover from GPB to GPA took place in the third intron at a recombination site apparently identical to that observed in the B-A hybrid GPSta type A gene. These results indicated that GPHe(Sta) occurs as a B-A-B-A hybrid gene, most likely originating from a two-step mechanism of homologous recombination. Transcript analysis showed the maturation from the GPHe(Sta) pre-mRNA of two shortened mRNAs of which the exon III-deleted species encodes both the He and Sta antigens.

Amino Acid Sequence↗
PubMed1994

Lymphedema: the seemingly forgotten complication.

Lymphedema, a frequent and debilitating symptom in patients who undergo treatment for breast cancer, is often neglected. This article outlines a therapeutic strategy and provides a case study that illustrates that effective in-home treatment of this complication is possible. Effective treatment can dramatically improve the quality of life of this patient population.

Aged↗