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Biomedical subjects

J Adamson

Publications and source records attributed to J Adamson.

At least 55 records · Page 3Linked to original sources
PubMed1988

Evidence for clonal development and stem cell origin of M7 megakaryocytic leukemia.

Previous studies have shown that acute nonlymphocytic leukemias are clonal diseases in which there is heterogeneity in the pattern of stem cell differentiative expression. To determine whether M7 megakaryocytic leukemia is a clonal disease and to evaluate the differentiative expression of the cells involved by the leukemia we studied a patient with megakaryocytic leukemia who was heterozygous for the X-chromosome-linked glucose-6-phosphate dehydrogenase (G6PD). The diagnosis of megakaryocytic leukemia was based on results obtained with the immunogold method and ultrastructural studies with the monoclonal anti-Gplla/IIIb antibody, 10E5. Direct testing of blood and marrow mononuclear cells and blood platelets demonstrated only A-type G6PD, whereas skin exhibited both B and A enzymes. The results indicate that the megakaryocytic leukemia in this patient was clonal at the time of study. To determine the differentiative expression of the stem cells, granulocyte/macrophage colony forming units and erythroid burst forming units were cultured and the resultant colonies were tested for G6PD. The results indicate that the stem cells involved by the leukemia exhibited differentiative expression multipotent for the megakaryocytic and granulocytic pathways, but no definitive conclusion could be made regarding the erythroid lineage.

Clone Cells↗
PubMed1988

Noncortical origins of the spinal motor evoked potential in rats.

Motor evoked potentials (MEPs) were recorded from the spinal cord, sciatic nerve, or both during transcortical electrical stimulation in the rat. Four peaks could be consistently identified in the spinal MEP. The latency and amplitude of the peaks varied differentially with intensity and polarity of stimulation. Conduction velocity for Peak 1 of the MEP was 43 m/sec. Bilateral sciatic nerve MEPs were present after unilateral cortical stimulation. The spinal MEP was elicited by stimulation of areas outside the motor cortex, and the response persisted during subcortical stimulation and after motor cortex ablation. We present evidence suggesting that components of the spinal MEP in rats arise from pathways outside the motor cortex.

Action Potentials↗
PubMed1987

An investigation of possible age-related changes in the inferior alveolar artery in man.

An histological examination of inferior alveolar arteries removed at post-mortem, from 16 human subjects failed to show significant age-related changes in luminal patency which would lead to narrowing and eventual obliteration of this structure. It is suggested that the artery continues, throughout life, to provide the major internal blood supply to the mandible.

Adolescent↗
PubMed1985

Platelet-derived growth factor enhances in vitro erythropoiesis via stimulation of mesenchymal cells.

The growth of erythroid colonies (from erythroid colony-forming cells) and erythroid bursts (from burst-forming cells [BFU-E]) is enhanced in the presence of serum as compared with plasma. A significant proportion of the enhanced growth is due to the platelet release product, platelet-derived growth factor (PDGF). Colony growth in cultures of whole marrow cells in platelet-poor plasma-derived serum (PDS) and erythropoietin was enhanced in a dose-dependent fashion by increasing concentrations of purified human PDGF with optimal enhancement at 12.5 ng/ml. However, no effect of platelet-release products or PDGF was observed on nonadherent human marrow cells or peripheral blood BFU-E, suggesting that an accessory cell population was required for the effect of PDGF on hematopoietic progenitors. In a two-layer culture system, pure populations of fibroblasts or smooth muscle cells, known to be present in the marrow microenvironment, restored the response of nonadherent marrow cells in the overlayer to PDGF and also conferred responsiveness to peripheral blood BFU-E. Endothelial cells in the two-layer culture system and macrophages, in contrast, lacked the ability to restore the enhancing effect of PDGF. Because other platelet-release mitogenic products are also found in serum, a monospecific anti-PDGF IgG preparation was added to cultures grown in platelet rich plasma-derived serum. Only partial reduction in colony and burst growth was seen, suggesting that other platelet-release products were acting in this system. These results demonstrate that PDGF enhancement of human hematopoietic progenitor cell growth requires mesenchymal cells, and provide an example and mechanism by which growth factors may influence hematopoietic progenitors via cells of the marrow microenvironment.

Bone Marrow↗
PubMed1984

Recovery of the ipsilateral oculotectal projection following nerve crush in the frog: evidence that retinal afferents make synapses at abnormal tectal locations.

The ipsilateral oculotectal projection in the frog is a topographic mapping of the binocular part of the visual field of one eye on the ipsilateral tectal lobe. The underlying neuronal circuitry consists of the topographic, crossed retinotectal projection and an intertectal pathway which relays information from a given point in one tectal lobe to the visually corresponding point in the other. During optic nerve regeneration, there is a period when the terminals of retinotectal afferents are found at abnormal locations in the opposite tectal lobe. Whether they form functional synapses at this time is not known. If so, one would expect to observe correlated abnormalities in the ipsilateral oculotectal projection. To determine whether such abnormalities exist, we have made parallel electrophysiological studies of the recovery of the retinotectal and ipsilateral oculotectal projections following crush of one optic nerve. The earliest stage of recovery was characterized by a lack of significant topographic order in the retinotectal projection and by the absence of a physiologically observable ipsilateral projection. Within a short time, the retinotectal projection became topographically organized and a similarly organized ipsilateral projection appeared. While topographic, the retinotectal projection at intermediate times was abnormal in that the multiunit receptive fields recorded at individual tectal loci were greatly enlarged. Multiunit receptive fields were similarly enlarged in the ipsilateral projection. In addition, some ipsilateral fields included areas of visual space not normally represented in the projection. The abnormalities in both projections subsequently disappeared over the same time course. Throughout recovery there was a high correlation between multiunit receptive field sizes in the contralateral tectal lobe and those at visually corresponding points in the ipsilateral tectal lobe. Enlarged multiunit receptive fields in the contralateral tectal lobe could not be accounted for in terms of optical or retinal abnormalities since single unit receptive field sizes were normal. Nor could they be accounted for in terms of changes in recording characteristics since simultaneously recorded fields activated by the undisturbed eye were normally sized. We conclude that the enlarged fields in the contralateral tectal lobe indicate the presence at individual tectal loci of afferents from wider than normal retinal regions. Similar considerations ruled out optical, retinal, and recording abnormalities as the explanation for the enlarged multiunit receptive fields in the ipsilateral tectal lobe.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1981

Loss and grief.

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Attitude to Death↗
PubMed1981

"The weakest link".

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Patient Care Team↗
PubMed1980

In vitro tests for distinguishing possible immune-mediated aplastic anemia from transfusion-induced sensitization.

Forty-two patients with aplastic anemia (AA) were studied to determine whether or not transfusion-induced sensitization is responsible for the in vitro inhibition by patient lymphocytes of HLA-identical erythroid burst-forming units (BFU-E). The results indicate that lymphocytes from 12 of 34 transfused patients inhibited normal colony growth. In contrast, lymphocytes from none of the 8 untransfused patients demonstrated inhibition. These data were interpreted to mean that coculture studies would not be useful for identifying immune-mediated AA in transfused patients. Therefore, in order to identify possible immune-related AA, we assayed BFU-E from patient blood before and after T-cell depletion. In all 32 patients studied, BFU-E failed to grow from peripheral blood cells before T-cell depletion, but in 8 cases, normal-appearing BFU-E grew after T cells had been removed. Growth of patient BFU-E colonies was inhibited in 6 cases when patient T cells were added back to the culture, indicating that in these 6 patients, an "autoimmune" mechanism may have been present.

Anemia, Aplastic↗