Search PubMed⌕ Search

Biomedical subjects

W M Howell

Publications and source records attributed to W M Howell.

At least 91 records · Page 5Linked to original sources
PubMed1989

HLA class II DR, DQ, and DP restriction fragment length polymorphisms in rheumatoid arthritis.

HLA class II restriction fragment length polymorphisms (RFLPs) were studied in 43 individuals with established seropositive rheumatoid arthritis (RA) and in a group of healthy controls. All patients and controls were tissue typed for HLA-A, B, and DR antigens. Rapid, initial screening for RA associated RFLPs was conducted by pooling DNA samples from 11 HLA-DR4 positive patients with RA and comparing the RFLP patterns with those seen in a pool of DNA samples drawn from 11 HLA-DR4 positive healthy controls. Candidate RA associated RFLPs were examined in our full panel of patients with RA and controls. In most cases the RFLPs detected showed no significant association with RA. An exception was a 13.0 kb DraI DQ beta associated RFLP, which, when HLA-DR4 positive patients with RA and controls were considered alone, showed a weak positive association with susceptibility to RA. This RFLP was not associated with known DR, DQ, or Dw specificities. These results show a distinct paucity of class II RA associated RFLPs but may indicate a role for DQ beta genetic variation in the aetiology of RA.

Arthritis, Rheumatoid↗
PubMed1989

A comparison of serological, cellular and DNA-RFLP methods for HLA matching in the selection of related bone marrow donors.

Serological, cellular and DNA-RFLP (restriction fragment length polymorphism) methods of determining HLA compatibility between 10 leukaemic patients and potential related bone marrow donors were systematically compared. DR beta/DQ alpha/DQ beta/DNA-RFLP typing of these families gave results in agreement with those obtained by serological methods (matching for HLA-A, -B and -DR), supported by mixed lymphocyte culture (MLC) data, indicating the validity and accuracy of DNA-RFLP matching in transplantation. However, a significant minority of four leukaemic patients plus two healthy individuals were not clearly HLA-DR typable by serology, but all such individuals were easily typable by DNA-RFLP. These results were supported by MLC data, where available. In addition, all data were in agreement with previously reported correlations between DNA-RFLPs and HLA-DR serology, allowing unambiguous assignment of HLA-DR types where these were previously in doubt. These results demonstrate the value of DNA-RFLP HLA class II DR and DQ typing in leukaemic patients requiring marrow transplantation who are not clearly typable by traditional methods and suggest that this approach should constitute an important element of future HLA matching programmes for bone marrow transplantation.

Bone Marrow Transplantation↗
PubMed1988

Phenotypic and genotypic heterogeneity of peripheral T-cell lymphoma.

A series of 21 phenotypically characterised T-cell lymphomas histologically defined as lymphocytic, lymphoblastic, immunoblastic, AILD type, pleomorphic, T-zone and Lennert's T-cell lymphoma, were investigated for T-cell receptor (TcR) and immunoglobulin (Ig) gene rearrangements. Phenotypic analyses of frozen sections and cell suspensions were heterogeneous and in many cases no single T-cell marker recognised all of the malignant cells. Data derived by staining with antibodies reactive with antigens in paraffin embedded tissue were consistent with T NHL in all cases except lymphoblastic lymphoma. TcR gene rearrangements were observed in lymphocytic, lymphoblastic and immunoblastic lymphoma, however, in the remaining 14 phenotypically and histologically defined peripheral T-cell lymphomas, 2 showed rearrangement of TcR gamma and beta genes consistent with T NHL and 2 showed Ig JH rearrangements only, suggestive of either reactive T-cell populations masking cryptic disease or presence of tumour populations with aberrant gene rearrangement and expression of T lineage antigens. No Ig or TcR gene rearrangements were found in the remaining 10 cases, in which morphologically identifiable tumour cells comprised 10-90% of the cell population. In 3/6 cases tested some CD3 positive cells failed to stain with WT31 or beta F1, monoclonal antibodies that recognise determinants on combined TcR gamma beta or TcR beta chains respectively. Whether these cases represent tumours arising from an undetermined cell of origin or polyclonal expansions of T-cells remains to be determined. Our results confirm the phenotypic heterogeneity of histologically defined peripheral T-cell lymphoma and indicate that in these particular histological subtypes gene rearrangement analysis can also yield heterogeneous results which may be unhelpful in determining cell lineage and clonality.

DNA Probes↗
PubMed1983

Nucleolus organizer regions of the canine karyotype.

Silver-stained preparations of cultured lymphocytes obtained from 12 pure-bred dogs revealed the presence of nucleolus organizer regions (NORs) on four to seven chromosomes in females and five to eight chromosomes in males. All seven males had a NOR on the Y chromosome. The telomeric location of the NORs on the autosomes suggested by an earlier study was confirmed.

Animals↗
PubMed1979

Chromosome core structure revealed by silver staining.

Chromosomes were subjected to either prolonged hypotonic solution pretreatment or aging. Both conditions greatly loosened and dispersed the overlying epichromatin from the central chromosome core structure. This was followed by silver staining and examination with bright-field microscopy. The chromosome core selectively reduced the silver and stained black while the surrounding epichromatin stained yellow. A single core was seen extending the length of each chromatid. Nucleolus organizer regions appeared to be attached to the core, while kinetochores seemed to be specialized regions of the core itself. Cytochemical tests indicated that the core component(s) responsible for silver staining was non-histone protein(s).

Adenocarcinoma↗
PubMed1978

A rapid technique for producing silver-stained nucleolus organizer regions and trypsin-giemsa bands on human chromosomes.

A simple and rapid technique is described whereby the nucleolus organizer regions (NORs) of human chromosomes can be differentially stained with silver. This staining is followed by trypsin-Giemsa banding on the same metaphase chromosomes. The metaphases simultaneously exhibit silver-stained NORs and G bands, allowing for the unequivocal identification of all chromosomes and greatly facilitating studies involving the NOR-bearing acrocentrics.

Azure Stains↗
PubMed1978

Silver stain reveals nucleolus organizer regions on a satellited Yq chromosome.

Chromosomes from a patient with a satellited Yq were stained with a silver procedure that differentially stains nucleolus organizer regions. The Yqs stained heavily in all cells examined, indicating the presence of ribosomal cistrons at this region. The Yqs also entered into satellite associations with the D and G group chromosomes at a frequency greater than would be expected through chance.

Azure Stains↗
PubMed1977

Visualization of centriole-bodies using silver stain.

Duplicate staining of human metaphase chromosomes, first with Giemsa followed by silver, revealed the presence of two small silver-stained bodies not seen in the Giemsa stained metaphases. Similar bodies were subsequently found in the metaphases of several animal groups. The size, structure, spatial relationships to the nucleus, behavior throughout the cell cycle, and apparent universal presence of these bodies suggest that they are either centrioles or associated centriolar structures. These centriole-bodies can be seen throughout the cell cycle, even in hypotonically spread C-metaphase chromosome plates. The silver stain procedure allows enough resolution to distinguish parent and daughter centriole-bodies at interphase, thus permitting visualization of the replication, maturation and separation stages of these bodies with the light microscope.

Animals↗
PubMed1977

Visualization of ribosomal gene activity: silver stains proteins associated with rRNA transcribed from oocyte chromosomes.

Cricket oocyte chromosomes were stained with silver at pachytene when certain chromosome regions are active in rDNA amplification and rRNA transcription. The silver preferentially stained the known locations of 18S + 28S ribosomal cistrons. Cytochemical tests revealed that the silver binds neither to the rDNA nor transcribed rRNA, but rather to proteins which rapidly associate with the freshly-transcribed rRNA. As rRNA transcription proceeds, the quantity of silver stainable proteins progressively increases. The silver procedure can be used to visualize gene activity at the rDNA sites with conventional light microscopy.

Animals↗
PubMed1976

Karyotypic analysis and evidence of tetraploidy in the North American paddlefish, Polyodon spathula.

A model chromosome number of 120 was obtained for the ancient fish. Polyodon spathula (Pisces: Chondrostei). The karyotype consists of 48 macrochromosomes and 72 microchromosomes. The microchromosomes are like those found in certain other primitive fishes as well as in reptiles and birds. The possiblity that Polyodon is a species of tetraploid origin is strongly suggested by the fact that the 120 chromosomes are easily arranged into 30 groups of four homologs each. Evolutionary comparisons are made with other primitive fish groups.

Animals↗
PubMed1976

Negative silver staining in A-T and satellite DNA-rich regions of human chromosomes.

Human metaphase chromosomes were stained with silver following a pretreatment with a heated alkaline solution. The most conspicuous feature of the stained metaphases was the omission of silver staining in the secondary constrictions of chromosomes 1,9 and 16, and on the distal Yq. Our evidence indicates that the negative silver binding is due to the preferential removal or alteration of non-histone proteins associated with these regions. The cytochemical significance of these findings is discussed.

Adenine Nucleotides↗
PubMed1976

Human nucleolar organizer chromosomes: satellite associations.

The D and G group chromosomes from cultured human lymphocytes exhibit single and multiple satellite associations when stained with silver. Unlike earlier methods this simple and highly repeatable procedure shows physical attachments between satellited regions of various acrocentric autosomes. After studying 1,000 satellite associations from 118 normal individuals, it was found that both single and multiple associations occur with frequencies that correlate with random expectancies.

Cell Nucleolus↗