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Biomedical subjects

N Steiner

Publications and source records attributed to N Steiner.

At least 19 recordsLinked to original sources
PubMed2004

Morphohistological analysis and histochemistry of Feijoa sellowiana somatic embryogenesis.

Morphohistological analysis and histochemical studies were carried out during the induction and development of Feijoa sellowiana somatic embryos. Zygotic embryos were cultured on LPm medium containing 2,4-dichlorophenoxyacetic acid (20 microM) and glutamine (8 mM). Somatic embryogenesis could be induced from embryogenic cells that originated in meristematic centers or from clusters of cells. The presence of few starch grains and abundant protein bodies was observed in the globular and early torpedo stages, while in torpedo and cotyledonary-stage somatic embryos an enhanced synthesis of starch grains was associated with the accumulation of reserves to be used in the conversion of the embryos to plantlets. Proteins were predominantly observed in protoderm cells, as well as in the meristematic apical region of torpedo and cotyledonary-stage somatic embryos.

Feijoa↗
PubMed2002

Novel HLA-A locus alleles including A*01012, A*0306, A*0308, A*2616, A*2617, A*3009, A*3206, A*3403, A*3602 and A*6604.

This paper describes 10 novel HLA-A alleles that have been characterized by DNA sequencing. Seven alleles, A*0308, A*2616, A*3009, A*3206, A*3403, A*3602 and A*6604 carry motifs observed in other HLA-A alleles, suggesting that gene conversion has created this diversity. The remaining three alleles, A*01012, A*0306 and A*2617, contain polymorphisms not previously found in any "classical" class I allele. All alleles were identified due to unexpected probe hybridization patterns during routine SSOP typing. Exons 2 and 3 of each allele were subsequently characterized by DNA sequencing.

Alleles↗
PubMed2000

Seventeen more novel HLA-A locus alleles.

This paper describes seventeen novel HLA-A locus alleles: A*0106, *0235, *0236, *0237, *1105, *2302, *2303, *24032, *2422, *2424, *2503, *2613, *3007, *3203, *3204, *6809 and *6810. All alleles were identified due to unexpected probe reaction patterns during routine SSOP typing. Exons 2 and 3 of these alleles were subsequently characterized by DNA sequencing. The alleles represent a shuffling of sequence motifs, likely by interallelic conversion, expanding the diversity of the HLA system.

Alleles↗
PubMed2000

The relationship between HLA-B45 and B* 5002 in the five major U.S. population groups.

The antigen encoded by B*5002 differs in sequence from that encoded by B*5001 only at amino acid residue 167 (consensus tryptophan vs. serine) which results in B45 serologic reactivity. To search for B*5002, the frequencies of alleles encoding the serologically defined B45 antigen were determined by sequence-based typing in 5 major U.S. populations: Caucasians, African Americans, Asians/Pacific Islanders, Hispanics, and Native Americans. The percent of serologically defined B45-positive individuals in the 5 populations ranged from 0.7-9.0%. Thirty-two B45-positive individuals were randomly chosen, when available, for sequence-based typing from each ethnic group from a database of 82,979 consecutively typed unrelated individuals. The B*5002 allele was most prevalent in Hispanic (22%) and Caucasian (9%) individuals, while conspicuously absent in African Americans. In addition, a new allele associated with the B45 antigenic specificity, B*4502, has been identified from an African American individual of Middle Eastern descent. In light of the continuing need to reconcile differences between relationships determined by the sequence homologies among alleles and relationships based on the serologic determinants carried by allelic products when determining the level of HLA match for hematopoietic stem cell transplantation, it is suggested that B*5002 be recognized individually from other B*50 alleles when reporting HLA-B typings for clinical purposes.

Alleles↗
PubMed2000

DRB3 alleles with variations in the annealing sites of commonly used amplification primers.

New HLA alleles are often identified initially from observing uncommon patterns found in low-resolution typing performed via polymerase chain reaction using sequence-specific oligonucleotide probes (PCR-SSOP). Recently, the HLA-DR oligotyping analysis of two Caucasian, one Caucasian/American Indian and two African American individuals resulted in the identification of three novel DRB3 alleles. Using DRB-specific primer sets commonly employed in amplification-based typing, all four individuals were originally characterized as DRB3 negative. Direct sequencing identified DRB3*0104 (variation at codon 8, TCG instead of TTG), and DRB3*0101202 (variation at intron (-13), G instead of C). One individual appeared to carry a DR52-associated DRB1 allele without an associated DRB3 allele. Lack of conservation at the junction of intron 1 and exon 2 of the DRB3 gene suggests that commonly used DRB-specific primer sets may need to be modified.

Alleles↗
PubMed1998

Sequence of an HLA-B56 variant (B*5604) identified in the Korean population.

Three alleles encoding molecules with the B56 serologic specificity have been reported thus far. This study characterized an additional allele encoding a B56 molecule from two unrelated Korean individuals. The novel allele, B*5604, differs from B*5602 by a single nucleotide substitution at codon 103 (CTG-->GTG) resulting in an amino acid change from leucine to valine. The putative haplotype associated with the novel allele was A2-B*5604-Bw6-Cw7-DRB1*15-DRB5*02-DQA1*01-DQB 1*05.

Alleles↗
PubMed1998

Clarification of HLA-B serologically ambiguous types by automated DNA sequencing.

Assignment of HLA-B types can be hampered by ambiguous reactivity of the typing sera resulting in inaccurate HLA-B assignments. In this study, 19 Korean samples exhibiting ambiguous serologic reactivities were characterized by DNA sequencing. Alleles identified from 7 samples were previously undetected in this population (B*1517, B*4101, B*4701, B*5001, and B*5106) and from 9 samples were common alleles in this population (B*4002, B*4003, B*4006, B*1501, B*1401, B*67012, and B*5401). Three samples were putative HLA-B homozygotes. Three major factors causing serologic ambiguity were identified: weak or false negative reactivity of typing sera (52.4%); cross or false positive reactivity of the sera (38.1%); and absence of information on the reaction patterns due to the lack of appropriate sera in the typing kit (e.g. B*4101 encoded molecule) or to the presence of recently characterized molecules (e.g. B*5106 encoded molecule) (9.5%). Overall, sequencing was helpful in clarifying ambiguous serologic reaction patterns improving the HLA typing for the Korean population.

Alleles↗
PubMed1998

Novel HLA-A and HLA-B alleles.

Nine novel HLA-A and HLA-B alleles are described: A*2609, A*6803, A*6806, B*1539, B*1540, B*2712, B*4103, B*5109, and B*5603. Most appear to have arisen by gene conversion events. B*5603 appears to have arisen by a reciprocal recombination event joining exon 2 of a B*55/ *56 allele with exon 3 of a B*15 allele. Serologically, the antigen encoded by this allele types with broad B22- and Bw6-specific alloantisera. Also unique, the antigen encoded by B*2712 does not react with B27-specific alloantisera but does react with Bw6-specific alloantisera.

Alleles↗
PubMed1998

Methods of hydration in palliative care patients.

A strong and often polarized debate has taken place during recent years concerning the consequences of dehydration in the terminally ill patient. When a patient has a severely restricted oral intake or is found to be dehydrated, the decision to administer fluids should be individualized and made on the basis of a careful assessment that considers problems related to dehydration, potential risks and benefits of fluid replacement, and patients' and families' wishes. This review discusses the assessment of hydration status in the terminal cancer patient and the options for fluid administration in the cases where evaluation of the patients' condition has led to this indication. These include different modes of hypodermoclysis, intravenous hydration, use of the nasogastric route, and proctoclysis. Arguments for and against rehydration have been previously addressed by other authors and fall outside the scope of this review.

Dehydration↗
PubMed1997

Diversity and evolution of the DRB1*03 family: description of DRB1*03022,*0307,*0308.

Three previously unreported DRB1*03 alleles are described, adding to the diversity of the DRB1 family of alleles. DRB1*03022 contains a silent substitution at codon 77. DRB1*0307 differs from DRB1*03011 by a substitution at codon 26 resulting in a predicted change from tyrosine to phenylalanine. DRB1*0308 is almost identical to DRB1*03011 differing at codon 58 which specifies the glutamic acid residue commonly found in DRB1*11 alleles. The new alleles (DRB1*03022,*0307,*0308) may have arisen by gene conversion-like events and add to the increasing complexity of the HLA system.

Alleles↗
PubMed1997

Analysis of HLA-A and -B serologic typing of bone marrow registry donors using polymerase chain reaction with sequence-specific oligonucleotide probes and DNA sequencing.

Unrelated volunteer donors (69) recruited by the National Marrow Donor Program were HLA typed by DNA-based methods for both the HLA-A and -B loci. Each donor had been previously typed by serology by at least two independent laboratories. Of the 69 samples, all serologic laboratories were in concordance for HLA-A in 62 typed samples and for HLA-B in 48 typed samples. Of the serologically concordant samples, 5 samples typed for HLA-A and 7 samples typed for HLA-B received DNA and serology types differing in their level of resolution. One sample typed for HLA-A and 3 samples typed for HLA-B by DNA methods gave different results from their serologic assignments. Of the samples exhibiting disparities among the different serologic typing laboratories, the DNA-defined types of 7 samples typed for HLA-A and 18 samples typed for HLA-B were consistent with at least one of the serologic assignments. The DNA types for the remaining 3 HLA-B typed samples did not agree with the serologic assignments and their alleles were subsequently sequenced. One of these sequences was a previously undefined allele, B*1537. Sharing of polymorphic sequences among HLA allelic products creates difficulties for consistent serologic assignments of some types complicating the process of identifying potential donors from bone marrow registries. Thus, the use of DNA-based typing techniques for characterization of donor class I types should allow a more consistent definition of types and should speed the donor selection process.

Bone Marrow Transplantation↗
PubMed1997

Characterization of an HLA-B62 variant (B*1538) exhibiting an additional B52 serologic reactivity.

Antigens bearing the B62 serologic specificity are a heterogeneous group being encoded by at least 10 alleles and are widespread in most populations including the Korean population (10.5%). This study characterized a new allele encoding a B62 molecule with extra B52 serologic reactivity from a Korean family and unrelated individuals. Based on the DNA sequence, it appears that the single nucleotide substitution at codon 171 (TAC-->CAC), resulting in an amino acid change from tyrosine to histidine, is responsible for creating the extra reactivity. B*1538 was confirmed by PCR-SSP using a primer annealing to codon 171 in two additional unrelated individuals also exhibiting the same serologic reaction pattern. The haplotype associated with the novel allele, A31-B*1538-Bw6-Cw3-DRB1*1101-DRB3*02-DQB1*0301, was identified in the family members and two unrelated individuals. The novel B*1538 allele and its associated haplotype adds to the HLA diversity in this population.

Genetic Variation↗
PubMed1997

Visual-field measurements and driving eligibility.

BACKGROUND: A 50-year-old black man with an ocular history of open-angle glaucoma was seen for a vision rehabilitation examination, with goals of improving his vision for work and determining his eligibility for driving. He was referred to the clinic through state services for the visually impaired. METHODS: A low-vision evaluation was performed and baseline information was obtained, including distance- and near-visual acuities, visual fields, and subjective refraction. This information was used to determine if he was eligible for services and if any low-vision devices would benefit him. RESULTS: The patient demonstrated moderately decreased visual acuity in the right eye (6/15) and very reduced visual acuity in the left eye (6/120). His visual fields varied depending on the test performed, ranging from 85 degrees to 140 degrees horizontal diameter. He was able to remove his spectacles and perform near tasks quite well. CONCLUSIONS: The patient was counseled that if he used one of the field tests he could qualify for services, but if he chose the other test he would qualify for driving and not qualify for services. The ramifications of using different field tests and understanding their parameters when assessing eligibility for services and benefits can be significant.

Automobile Driving↗
PubMed1996

Cellular crossreactivity. Implications for solid organ transplantation matching.

This study evaluates the cellular crossreactivity among DR11, DR13, and DR8 molecules using TLC reagents generated in reciprocal priming combinations where the responder and stimulator cells express different microvariants of DR11. The large majority of T lymphocyte clones (TLC) derived from such stimulation detect not only the product of the specific DR11 allele expressed by the stimulator but also detect subsets of DR molecules that span serologic specificities. Thus, TLC generated in response to DR(alpha,beta1*1102) detect DR(alpha,beta1*1103) and products of specific DR13, DR8, DR2 and DR4 alleles. Whereas, TLC generated in response to DR(alpha,beta1*1104) detect DR(alpha,beta1*1101), DR(alpha,beta1*1103), and products encoded by specific DR8 and DR2 but not DR13 or DR4 alleles. Since DR11 microvariants cannot be identified serologically, this type of mismatch certainly occurs frequently between DR11 serologically matched donors and recipients. Particularly affected are populations, such as the African American population, that exhibit extensive HLA diversity and exhibit different frequencies of HLA alleles compared with those of the majority of serologically matched cadaveric donors. Rapid methods of DNA-based HLA typing now makes it feasible to utilize this methodology for allele level identificaiton of recipient and donor alleles. Based on the strength of the alloproliferative responses and on the recognition patterns of the TLC reported here, we suggest that retransplant patients might benefit by excluding subsequent donors expressing DR molecules that in vitro demonstrate strong cellular crossreactivity with DR molecules expressed by the previous donor(s) as well as those DR molecules shared with the previous donor(s). Since such a matching schema has the potential to improve retransplant allograft survival, particularly in patients from minority population groups, it should be evaluated clinically.

Alleles↗
PubMed1996

Novel alleles HLA-B*7802 and B*51022: evidence for convergency in the HLA-B5 family.

We have characterized two novel HLA-B alleles, B*7802 and B*51022. The Caucasian-derived variant B*7802 most resembles the African-derived variant B*7801, from which B*7802 differs by two nucleotides. Only one of these modifications, however, is translated: a tyrosine for aspartate substitution occurs at residue 74 in B*7802, while the second nucleotide difference reflects a proximal synonymous substitution in codon 23. A second variant, B*51022, differs synonymously only at codon 23 from B*51021. Comparative analysis of the B5 CREG demonstrates that other pairs of B5 alleles differ synonymously only at codon 23 or synonymously at codon 23 and non-synonymously at a second more distal location. Contrary to the genesis of like pairs of B5 alleles via introduction of coordinate yet distant mutagenic events onto a single B5 progenitor, we postulate that synonymously different B5 progenitor molecules, B5ATT and B5ATC, are evolving in convergence to generate homologous B5 allele pairs differing silently at codon 23. Our finding that B*7802 is a single amino acid away from complete convergence with B*7801 and that B*51022 and B*51021 are in complete convergence is exemplary of such evolution.

Alleles↗