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Biomedical subjects

B Dixon

Publications and source records attributed to B Dixon.

At least 109 records · Page 6Linked to original sources
PubMed1993

Postimmunization (vaccination) injection-site reactions. A report of four cases and review of the literature.

Four patients each had a single subcutaneous nodule at the site of a previous vaccine injection; three after injection of diphtheria, tetanus, and pertussis vaccination and one after tetanus toxoid vaccination. Presentation was with a mass 4-22 months after vaccination at the site of injection. Histologically, three patients had a necrotizing granulomatous reaction with a surrounding infiltrate of lymphocytes, plasma cells, histiocytes, and associated fibrosis. The fourth patient demonstrated a lymphohistiocytic reaction with a predominance of histiocytic cells as well as associated plasma cells, fibroblasts, and fibrosis. The lymphoid infiltration in these reactions showed a predominance of T-lymphocytes over B-lymphocytes. Aluminum was demonstrated in necrotic foci, inflammatory stroma, and the granular cytoplasm of histiocytes with the aid of solochrome azurine and solochrome cyanine stains as well as by energy-dispersive x-ray microanalysis. The reactions are thought to be immunologic (hypersensitivity) reactions associated with the aluminum contents of the preparation.

Adolescent↗
PubMed1992

A nematode hemoglobin gene contains an intron previously thought to be unique to plants.

Hemoglobin genes from plants and animals both have a characteristic chromosomal organization. Plant hemoglobin genes contains a unique intron inserted into the heme-binding domain of exon 2. This intron has not been previously reported in animal globin genes, and its loss was hypothesized to have occurred early in the evolution of hemoglobins. We report here a unique six-intron, seven-exon internally duplicated nematode hemoglobin gene that contains an intron equivalent to the plant central intron in its first repeat. This nematode hemoglobin gene has lost both the central and the normal third intron in its second repeat. The nematode globin also contains a unique intron between its secretory peptide leader sequence and its coding sequence, which is absent in other extracellular invertebrate globin genes. Possible models to explain the head-to-tail duplication of this gene are discussed.

Amino Acid Sequence↗
PubMed1992

Isolation of a putative retrovirus pol gene fragment from trout.

1. A 220 bp DNA fragment was obtained from three different species of salmonids during PCR analysis using a primer sequence based on human beta-2 microglobulin. All of the 220 bp fragments showed strong homology to each other. 2. Several of the DNA sequences also contained protein reading frames. Searching DNA and protein databases revealed significant homology to a segment of the pol gene (reverse transcriptase) from various retroviruses. Phylogenetic analysis at both the DNA and the protein levels showed clustering of the fish sequences and the closest viral sequence was the Moloney murine leukaemia virus (MoMuLV). Southern analysis indicated that there are several copies of the gene dispersed throughout the salmonid genome. 3. Preliminary results suggest that these sequences may be unique to the family Salmonidae. This would suggest that this retrovirus was incorporated in the DNA of an ancestral salmonid prior to the evolution and divergence of this family of fish.

Amino Acid Sequence↗
PubMed1992

Did the ancestral globin gene of plants and animals contain only two introns?

All vertebrate globin genes contain two introns, while plant globin genes contain three. It is widely thought that the plant gene structure reflects the structure of the primordial globin gene and that a common ancestor of all animals lost the central intron shortly after the divergence of plants and animals more than one billion years ago. The recent discovery of a discordant central intron in some animal globin genes suggests that this model is incorrect. We propose that the typical vertebrate two-intron gene structure is the primordial eukaryotic form, and that following the divergence of plants and animals, a common ancestor of plants gained a central intron in the globin gene.

Amino Acid Sequence↗
PubMed1991

Isolation and sequencing of a cDNA for an unusual hemoglobin from the parasitic nematode Pseudoterranova decipiens.

A cDNA clone encoding a 333-amino acid hemoglobin was isolated from the nematode Pseudoterranova decipiens. The protein contains an 18-amino acid hydrophobic signal sequence and has a calculated mass of 37.6 kDa in the mature form. The predicted protein reveals an internal duplication of a 154-amino acid domain (51% identity). Both domains have significant sequence homology to other primitive hemoglobins, in agreement with a duplication event. Hydrophobicity plots reveal identical strongly hydrophobic regions in each domain, which are potential heme binding sites. This confirms previous suggestions that nematode hemoglobins can have two heme groups per molecule. In addition, each domain contains several conserved histidine motifs that may serve as potential copper binding sites. This result provides further evidence that hemoglobins may have evolved from a primitive cytochrome-like molecule.

Amino Acid Sequence↗
PubMed1990

The response of a rodent fibrosarcoma to superficial/interstitial photochemotherapy, chemotherapy or radiotherapy.

Growth and dose-response curves were established for a subcutaneously implanted isogenic fibrosarcoma in BD9 rats after treatment with photochemotherapy (PCT), using Photofrin II or polyhaematoporphyrin with superficial or interstitial 630 nm light, cyclophosphamide or gamma-irradiation. Tumour response to PCT increased with dose up to 200 J.cm-2 for superficial light or 200 J for interstitial light but no further response occurred after higher light doses. The maximum response after interstitial treatment was significantly greater than after superficial treatment where only a small margin of normal tissue was treated. The incidence of necrosis in the overlying skin was significantly less after interstitial than superficial light suggesting a better therapeutic ratio after interstitial than superficial PCT. Tumour response increased with the diameter of the treatment field after superficial light supporting the possibility of a tumour bed effect associated with PCT. The largest tumour that could be effectively treated with a single optical fibre was 12 mm. The dose-response curves for interstitial PCT and cyclophosphamide were similar but ionizing irradiation produced increasing tumour response throughout the range of doses used (5 to 30 Gy) and the maximum response was greater after radiotherapy than after PCT or chemotherapy suggesting that in this tumour model interstitial PCT is as effective as cyclophosphamide but less effective than radiotherapy.

Animals↗
PubMed1990

Anaerobes at work.

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Biotechnology↗
PubMed1990

Nursing education application of a computerized nursing expert system.

Nurse educators are required to be knowledgeable about a wide variety of complex health care problems in order to provide quality education. At the same time, they are given a multitude of other responsibilities such as participating in scholarly activity, advising students, maintaining an active role in nursing practice, and performing community service. These educators must find innovative ways to present current lectures while at the same time meeting their other obligations. The use of Creighton Online Multiple Modular Expert System (COMMES), a computerized decision support consultant, was evaluated as a technique for faculty use in developing and organizing new lecture content. The study found that COMMES was beneficial as a systematic prompt for lecture content, as a tool for organizing content, and as a means to verify completeness of lecture material.

Curriculum↗