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Biomedical subjects

A E Stuart

Publications and source records attributed to A E Stuart.

At least 19 recordsLinked to original sources
PubMed1979

Properties of anti-hairy cell serum.

An antiserum was prepared in rabbits against hairy leukaemic cells. After absorption with human erythrocytes, thymus and liver powder, the serum was passed through immunoabsorbent columns to remove extensive anti-plasma protein activity. Following these procedures, sensitive techniques failed to reveal residual activity against alpha-macroglobulins, beta2-microglobulin and other human plasma proteins. The antiserum reacted with normal B lymphocytes but not with T lymphocytes or monocytes. Positive reactions were seen in B cell lymphomas, chronic lymphocytic leukaemia, hairy-cell leukaemia and uninucleated Reed-Sternberg cells.

B-Lymphocytes↗
PubMed1979

Calcium channels in the high resistivity axonal membrane of photoreceptors of the giant barnacle.

1. The distribution of calcium channels in the cell membrane of the photoreceptor neurone of the giant barnacle, Balanus nubilus, was studied by recording intracellularly in or near the soma, in the axon, and near the presynaptic terminals. The membrane properties of these different regions of the cell could be studied by separately superfusing each region with test salines or by cutting the axon between two regions. 2. In the presence of tetraethylammonium (TEA) or 3-aminopyridine (3-AP), but not in their absence, Ca dependent action potentials could be evoked with depolarizing current pulses in the somatic, axonal, and terminal regions. Consequently, voltage-sensitive Ca channels and TEA-sensitive channels are present in all three regions of the cell. 3. The action potentials recorded from the three regions were similar in their slow times-to-peak (30-300 msec), long durations (0.2-2 sec in 100 mM-TEA), and long-lasting (0.2-10 sec) undershoots. The action potentials were inhibited by extracellular Co. 4. Clear differences were consistently observed between terminal action potentials and axonal or somatic action potentials in TEA. Terminal action potentials displayed a lower voltage threshold, faster rate of rise, and were less sensitive to inhibition by extracellular cobalt, suggesting that the Ca current is greater in the terminal region. 5. Bathing the receptor axon in low Ca or Co solutions led to a greater attenuation of large depolarizing components of the visual signal as they spread to the presynaptic terminals.

Action Potentials↗
PubMed1978

Ultrastructural studies of leucocytes which form rosettes with homologous erythrocytes in human auto immune haemolytic anaemia.

Leucocytes which form rosettes with himologous erythrocytes in auto-immune haemolytic anaemia, infectious mononucleosis and following the stimulation of lymphocyte cultures with PHA have been studied by electron microscopy. The studies showed that the predominant homologous rosette forming cell was lymphocytic and the evidence favoured the conclusion that they were non-immune in nature. This identification does not classify the lymphocyte as thymus or bone marrow derived. Just under half (44%) of the total lymphocytic RFC had perinuclear microfilaments and limited clearing of the plasma of ribosomes close to the cell membrane. These features are consistent with activated T lymphocytes. The remainder of the lymphocytic RFC had no features which allowed their identification as T or B cells. The form of contact between lymphocytic RFC and erythrocyte was mainly of a pointlike nature, with little deformation or invasion of the attached erythrocytes. Monocytes were the only other type of cell encountered with any frequency. Their prime distinguishing feature was the deformation of attached red cells which they caused.

Anemia, Hemolytic, Autoimmune↗
PubMed1978

Surface membrane characteristics of cells from human acute monocytic leukaemia.

The clinical and laboratory features of 4 patients with acute monocytic leukaemia are described. Surface membrane receptor studies of these patients have shown increasing strength of receptor expression occurs with increasing morphological maturity of the monocyte. In addition, the study shows that expression of membrane receptors can vary from patient to patient and also with time and treatment in an individual patient. A further finding has been the loss of positivity with specific anti-monocyte serum when the disease becomes refractory to therapy.

Adult↗
PubMed1978

Voltage sensitive calcium channels in the presynaptic terminals of a decrementally conducting photoreceptor.

1. Intracellular recordings were made from the presynaptic regions of the photoreceptors of the median ocellus of the giant barnacle, Balanus nubilus.2. Millivolt changes in membrane potential near the dark resting level in the terminals elicit post-synaptic activity and consequently must be sufficient to modulate transmitter release from these endings.3. In normal saline the terminal voltage usually changes in a graded manner to increasing intensities of illumination of the cell. When the terminal region is superfused with saline containing TEA, 3-AP or high concentrations of K, an all-or-none action potential can be elicited consistently by light or injected current.4. The peak value of this action potential depends on the Ca concentration in the saline. The action potential can be generated if Sr or Ba ions replace Ca, but is reduced or blocked if Mg, Co, or Mn ions are added to the saline. It is virtually unaffected by TTX or replacement of Na with TMA ions in the saline. These results suggest that Ca carries most or all of the inward current during the action potential.5. The action potential is followed by a large undershoot which can last several seconds. The amplitude and duration of the action potential and the duration of the undershoot all grow in increasing concentrations of TEA up to 400 mM, the highest concentration tested. The threshold for the action potential decreases as the concentration of TEA is increased to 10 mM; increasing the concentration further has no effect on the threshold. These observations suggest that TEA blocks a voltage-sensitive potassium conductance at low concentrations but has less effect on the current responsible for the undershoot.6. Electrophysiological and pharmacological evidence suggests that the Ca channels are concentrated in the presynaptic terminals of this photoreceptor.

Action Potentials↗
PubMed1978

Cell receptor studies on six anaplastic tumours of the thyroid.

Cell suspensions from six anaplastic thyroid tumours were studied for expression of lymphocyte and macrophage surface markers, and results were correlated with electron microscopy, clinical extent of disease, and response to radiotherapy. The clinical presentation of the disease was similar in all six patients. In five cases, many of the cells showed surface immunoglobulin. Electron microscopy was available on three of these and showed appearances in keeping with malignant lymphoma. The single case whose cells did not show surface immunoglobulin had an entirely different ultrastructure and was probably a carcinoma. This case was the only one that did not achieve complete remission with radiotherapy and the patient died from extensive local recurrence. It is concluded that receptor techniques are of value in distinguishing between malignant lymphoma and other anaplastic tumours of the thyroid, particularly when the results are correlated with histology.

Aged↗
PubMed1977

Rosetting and other reactions of the Reed-Sternberg cell.

Clustering of lymphocytes around Reed-Sternberg cells was noticed in single cell suspensions made from viable Hodgkin's lymphoid tissue. Cytocentrifugation of the suspension showed that clustering also occurred around a smaller cell type, thought to be the precursor of the classical Reed-Sternberg cell. Time-lapse cine films taken of the clustering showed unceasing activity on the part of the lymphocytes migrating over the surface of the central cell. Reed-Sternberg cells were reacted with anti-monocyte serum using indirect fluorescence techniques. In its mature form at least, the Reed-Sternberg cell showed no activity with the antiserum. No immunoglobulin was detected in the Reed-Sternberg cell using fluorescence techniques, but a few Reed-Sternberg cells showed diffuse cytoplasmic staining using the peroxidase-labelled antibody technique. Membrane receptor tests showed the lymphocytes surrounding the Reed-Sternberg cell to be T-cells. After proteolytic enzyme treatment to free lymphocytes from the surface, the Reed-Sternberg cell bound IgG-coated red blood cells indicating a probable Fc receptor. Cytochemistry demonstrated weak non-specific esterase activity in a small minority of Reed-Sternberg cells, and absence of acid phosphatase, alkaline phosphatase and peroxidase. A subpopulation of lymphocytes with distinctive segmentation of the nucleus was noted. These were often to be seen participating in lymphocyte rosettes around the Reed-Sternberg cell.

Cells, Cultured↗
PubMed1977

Correlation of surface receptors with histological appearance in 29 cases of non-Hodgkin lymphoma.

The receptor patterns of cell suspensions from 29 cases of non-Hodgkin lymphoma were correlated with the histology of the nodes from which the cells were taken. Twenty-two were judged to be predominantly or largely B-cell, and because of this preponderance these were divided by a method based on the distribution of surface immunoglobulin and the expression of Fc and C3 receptors. "Mature" B-cell and B-mixed tumours showing capping surface Ig with Fc and/or C2 receptors correlated well with a nodular growth pattern, and consisted of what Rappaport (1966) calls "poorly differentiated" lymphocytes equivalent to the "small cleaved" cells as defined by Lukes and Collins (1975). Ten of the 14 patients in this receptor category are alive between 12 and 30 months after diagnosis. Receptor-silent and "immature" B-cell tumours with non-capping surface Ig correlated predominantly with the Rappaport histiocytic lymphoma and Lukes and Collins' large cleaved and large non-cleaved lymphomas, though these histological categories also included a wide variety of other receptor types such as T-cell, Receptor-overlap and the single true Macrophage tumour. Five of the 11 patients with receptor-silent or immature B-cell tumours are alive between 7 and 15 months after the diagnosis. Diffuse mixed and diffuse poorly differentiated lymphocytic lymphomas in Rappaport's classification correlated poorly with receptors, mature and immature B-cell tumours being equally represented.

B-Lymphocytes↗
PubMed1977

Activated T-cell in autoimmune haemolytic anaemia.

In 12 of 14 patients with clinically active autoimmune haemolytic anaemia high levels (9-78%) of homologous and autologous rosetting cells were found in the peripheral blood. In 10 of these patients, who were observed over a period of 2 years, the levels bore a direct relationship to the activity of the disease. The cells so identified were T-lymphocytes. The role of cells, identified by this method in AIHA, is discussed.

Adolescent↗
PubMed1977

Morphology and responses to light of the somata, axons, and terminal regions of individual photoreceptors of the giant barnacle.

1. The median eye of the giant barnacle, B. nubilus, comprises four large photoreceptor neurones which are visible under the dissecting microscope for almost their entire length. We have studied the structure of, and the responses to light recorded in, the somata, axons, and terminal regions of these neurones.2. The photoreceptor somata, each 40-70 mum in diameter, extend numerous light-sensitive dendritic processes whose membranes form rhabdomeric microvilli. Recordings from the soma show that dim light evokes a steady, noisy depolarization; brighter light elicits a transient depolarization which decays to a maintained plateau, followed by a hyperpolarization when the light is turned off.3. Light-induced voltage changes spread decrementally along the photoreceptor axons, which average 10 mm in length and 25 mum in diameter. In distal parts of the axon, near the presynaptic terminals, depolarizations and hyperpolarizations can be as large as 50% or more of their values in the soma.4. There is no demonstrable electrical coupling between photoreceptor neurones as shown by simultaneous recordings from two receptor somata or axons.5. Each photoreceptor axon enters the mid line commissure of the supraoesophageal ganglion, bifurcates, and arborizes in a restricted zone of neuropil in each hemiganglion. The large size of the terminal processes of these neurones and their characteristic cytoplasmic inclusions enable one to trace them with the electron microscope as they branch in the neuropil.6. The terminal processes subdivide and end in 1-3 mum diameter branches which are the sites of apparently chemical synapses. Vesicle-containing, presynaptic loci on these processes of the receptor cell are invariably apposed to two post-synaptic processes from cells as yet unidentified.

Animals↗
PubMed1977

Passive signal propagation and membrane properties in median photoreceptors of the giant barnacle.

1. The light-induced electrical responses of barnacle photoreceptors spread decrementally along the cells' axons. The decay of the depolarizing and hyperpolarizing components of the visual signal was studied by recording intracellularly from single receptor axons of the median ocellus of the giant barnacle.2. The resistance of the photoreceptor neurone decreases markedly when the cell is depolarized with respect to its dark resting potential of -60 mV. This rectification results in differential attenuation of the depolarizing and hyperpolarizing components of the visual signal as they spread down the axon. Consequently, the visual signal entering the synaptic region is conspicuously distorted.3. Bathing the photoreceptor axons in sodium-free or calcium-free saline or in isotonic sucrose does not significantly affect the spread of the visual signal to the terminals. Thus the signal is not amplified by an ionic mechanism along the axon.4. Membrane characteristics of the photoreceptor for hyperpolarizing voltage changes were estimated from (a) the ratio of the amplitudes of the visual signals recorded simultaneously in the axon and in the soma, (b) the time constant, and (c) the input resistance of the cell. All three independent measurements are consistent with a length constant 1 to 2 times the total length of the cell (lambda = 10-18 mm) and an unusually high membrane resistivity of about 300 kOmega cm(2). This resistivity enables the receptor potential to spread passively to the terminal region.5. Electron microscopic examination of receptor axons reveals an investment of glial lamellae, but demonstrates neither unusual structures which would lead to a high apparent membrane resistivity, nor junctions between cells which would seal off the extracellular space. Thus the observed high resistivity appears to be an intrinsic property of the receptor membrane.

Animals↗
PubMed1976

Identification of human mononuclear cells by anti-monocyte serum.

An antiserum to human leukaemic monocytes was raised in rabbits. Adsorption with human thymocytes and chronic lymphatic leukaemia cells rendered the antiserum specific for cells of the human myeloid and monocytic cell series. Additional adsorption with granulocytes left a weak, but specific, activity for monocytes. The cells in normal peripheral blood with which the antiserum reacts by an immunoperoxidase technique have typical monocyte morphology. Cells with typical lymphocyte morphology do not react with the antiserum, but a few cells with intermediate morphology were also stained by the antiserum. Using the antiserum as a marker, the precursor cells of the monocytic and myeloid cell series were traced in the bone marrow.

Animals↗