Biomedical subjects

J W Pickering

Publications and source records attributed to J W Pickering.

At least 37 records · Page 2Linked to original sources

PubMed1989

Computed temperature distributions around ectatic capillaries exposed to yellow (578 nm) laser light.

We have numerically modelled the thermal effects of yellow (577 or 578 nm) light illumination on the ectatic blood vessels of port wine stains. We investigated the effect of the laser treatment parameters of light irradiance and illumination time on the extent of coagulation (coagulation thickness) of the endothelial cells of the ectatic vessels. We assumed that this coagulation is dependent on heating the cells to a critical temperature (coagulation temperature). We iteratively adjusted the treatment parameters so that the model vessels had a maximum temperature that did not exceed the boiling point of blood. Given the likely range of variation of coagulation temperature, coagulation thickness and vessel size, coagulation temperature was found to have the greatest effect on the treatment parameters. Variations in coagulation thickness had less influence, and the diameter of the ectatic vessel (typically in the 30-80 microns diameter range) had the least effect. The treatment parameters that have been shown clinically to cause purpura (e.g. 6-7 cm-2 in 360 microseconds) were also studied. The purpura seen by some workers using pulsed dye lasers is most likely to be the result of vaporisation of blood leading to the rupture of the vessel. We conclude that, in order to achieve coagulation with these short laser pulses, the choice of irradiance is critical.

Capillaries↗

PubMed1989

Histology of port wine stains after copper vapour laser treatment.

We report histological changes in four patients with port wine stains treated with 578 nm yellow light from a high power copper vapour laser. Histology showed that selective damage occurred to the ectatic blood-vessels in the dermis, without haemorrhage and damage to non-vascular structures, and without scarring. The initial damage to the overlying epidermis was not permanent, and the damaged ectatic vessels returned to normal size or were completely necrosed and replaced by collagen.

Adolescent↗

PubMed1989

Thermal profiles of blood vessels heated by a laser.

Thermal profiles of ectatic capillaries, modelled on those found in port wine stain birthmarks, are calculated by a method of finite differences. Yellow 578nm light is assumed to illuminate these vessels. The coagulation of endothelial cells is assumed to occur when the cells are heated to at least 70 degrees C. We model this by asking that a point 6 microns above the top of the vessel lumen attains a temperature of 70 degrees C. We constrain the parameters to prevent heating of blood above 100 degrees C, so as to avoid vapourisation. The treatment parameters of dose and illumination time are varied until they produce thermal profiles that show the model's coagulation conditions. being treated and are rather longer than the thermal relaxation time of the vessel and also much longer than the pulses of pulsed dye lasers.

Body Temperature↗

PubMed1984

Human monoclonal antibodies to cytokeratins associated with squamous cell carcinoma.

Human lymphocytes from a lymph node draining the tumor-bearing area of a patient with a large primary squamous cell carcinoma of the oral mucosa were fused with the nonproducer mouse myeloma, NS-1, to produce interspecies hybridomas. Of 95 hybridoma culture supernatants tested, 23 contained from 0.5 to 50 micrograms/ml of human IgM or IgG. Six supernatant fluids containing greater than 15 micrograms/ml of Ig were tested by indirect immunoperoxidase and immunofluorescence against sections of the autologous carcinoma. Five IgM (lambda) monoclonal antibodies stained the cytoplasm of autologous and allogeneic squamous carcinoma cells. All five monoclonal antibodies stained all layers of normal epidermis but each antibody stained the superficial keratin layer most intensely. Two of the five hybridoma antibodies were further tested. Both antibodies stained all types of normal epithelium; a network of fibers characteristic of intermediate filaments in cultured squamous carcinoma cells and cultured fibroblasts; Z lines in skeletal muscle; and axons in peripheral nerve fibers. We conclude that all five IgM monoclonal antibodies recognize cytokeratins associated with the autologous squamous cell carcinoma. Two of the five hybridoma antibodies recognize an antigenic determinant common to all types of intermediate filament proteins. These data indicate that cytokeratins released by squamous carcinoma cells induced an antibody response in this patient.

Animals↗

PubMed1983

Simulation of psychosis on a multiple-choice projective test.

The ability of a new multiple-choice group Rorschach instrument to differentiate 62 undergraduate students asked to simulate psychosis from 75 students and 55 schizophrenics given standard instructions was investigated. For each of 50 responses to miniature inkblots, normals and psychotics chose one of four alternative answers as most descriptive of what the stimulus looked like. Simulators responded as they thought a psychotic or insane person would. As hypothesized, simulators chose significantly more "good form but bizarre wording" responses than normals or psychotics, suggesting that the test is promising as a practical clinical indicator of attempts to simulate psychosis.

Adult↗

PubMed1982

A human myeloma cell line that does not express immunoglobulin but yields a high frequency of antibody-secreting hybridomas.

We selected an 8-azaguanine-resistant variant of a human myeloma cell line (RPMI 8226) by cloning the parental cells on a feeder layer of mouse spleen cells in the presence of increasing concentrations of 8-azaguanine. Culture media and cellfree extracts of both the parental and variant (8226 AR/NIP4-1) cell lines were assayed for production of immunoglobulin heavy and light chains by double immunodiffusion and for lambda-chain by radioimmunoassay. Secretion of free lambda-chain by the parental cell line was confirmed. In contrast, no immunoglobulin heavy or light chains were detected in culture medium of the variant cell line by either immunodiffusion or radioimmunoassay. No intracellular lambda-chain could be detected in the variant cells by radioimmunoassay of cellfree extracts or by immunofluorescence of fixed cells. Hybridomas were produced by fusion of 8226AR/NIP4-1 cells with lymphocytes from a mesenteric lymph node recovered at surgery from a hypertransfused renal transplant recipient. Twenty hybrid culture supernatants were assayed for immunoglobulin by double immunodiffusion, and 15 contained either IgG (lambda) or IgG (kappa). None produced IgM or IgA. An IgG (kappa)-producing hybridoma was shown by immunofluorescence not to express lambda-chain. A second fusion between the variant cell line and spleen cells from a renal transplant patient produced a stable hybridoma secreting IgM (lambda) antibody specific for the I antigen.

Animals↗

PubMed1981

Radioimmunoassay: a sensitive screening test for histoplasmosis and blastomycosis.

Currently available serologic tests for histoplasmosis and blastomycosis have limited sensitivity. In order to develop a more sensitive screening test, the radioimmunoassay (RIA) technique was adapted to detect circulating antibodies to Histoplasma mycelial, Histoplasma yeast, and Blastomyces yeast antigens. Results were compared with those of complement fixation (CF) using serums from 4 groups of subjects. Group 1 (n = 104) consisted of consecutive healthy blood donors from an endemic area. Group 2 (n = 8) had active histoplasmosis and Group 3 (n = 12) had active blastomycosis. Group 4 (n = 30) had other chronic lung diseases. Among Group 1 subjects, elevated titers to at least 1 antigen were found in 13% using RIA and 21% using CF. Only 50% of patients with active mycoses (Groups 2 and 3) had elevated CF titers to a homologous antigen, whereas the RIA test was positive in 19 of 20 patients (95%). Elevated titers to 1 or more antigens was found in Groups 1 and 4, and frequent cross-reactions among the antigens occurred with both tests, indicating low specificities for both RIA and CF. The RIA is a sensitive and rapid screening test for histoplasmosis and blastomycosis, and a negative RIA using the 3 antigens tested makes the diagnosis of active infection very unlikely in immunologically competent patients.

Adolescent↗

PubMed1979

Some structural properties of thymus leukemia antigen (TL) solubilized with detergent.

Plasma membranes were isolated from the leukemia cell line ASL1w and extracted with detergent (DOC). DOC solubilized more TL activity than could be detected on isolated membranes. However, extraction of membranes with LDS or EDTA solubilized only 17% and 4%, respectively, of the activity. This indicated that TL was not loosely associated with the membrane but rather was integrated into the lipid bilayer. At low concentrations of DOC (0.05%), TL was found to be largely aggregated and was also prone to autolysis. Neither aggregation nor autolysis was observed at a higher DOC concentration (0.5%). The apparent molecular weight of TL in 0.5% DOC was determined by Sephadex G-200 chromatography to be about 65,000-70,000. Digestion of a 0.5% DOC extract of TL with either papain or trypsin produced a fragment of TL of about 35,000 molecular weight. These fragments were similar in size to a fragment produced by autolysis. These data suggested that a region of the TL molecule was very prone to proteolytic attack. The 35,000 molecular weight proteolytic fragments bound specifically to lentil lectin affinity columns, which indicated that they retained at least part of the carbohydrate present on the native molecule.

Animals↗

PubMed1979

Selective cell surface expression of thymus leukemia antigen during S phase of the cell cycle.

The expression of the thymus leukemia antigen (TL) was studied on a murine leukemia cell line (ASL-1W) grown in vitro and separated into cell cycle phases by velocity sedimentation or growing synchronously in culture. The expression of TL was determined qualitatively by direct cytotoxicity and quantitatively by a modified inhibition of cytotoxicity assay. TL expression was found to vary with DNA synthesis. The hypothesis that expression is coordinately regulated with DNA synthesis, and the relationship of this to the restricted expression of TL on rapidly dividing cells is disucssed.

Animals↗

PubMed1979

Inhibition of growth of ASL-1w murine leukemia cells by anti-thymus leukemia antigen (TL) serum in the absence of complement.

Previous studies have shown that the cell surface expression of thymus leukemia antigen (TL) on ASL-1w leukemia cells varies with the progression of the cells through the growth cycle. Expression of TL is maximal in S phase, and its quantitative expression varies directly with DNA synthesis. In the present study, the effect of anti-TL serum on the growth of ASL-1w cells was examined. The antiserum, tested in the absence of complement, affected the growth of these cells in biphasic manner. When the antiserum concentration was 0.1% or greater, there was a rapid decline in the rate of DNA synthesis, and after 5 to 7 hr, cell death. When the antiserum concentration was 0.067% or less, the decline in the rate of synthesis of DNA did not become apparent until 5 to 6 hr after treatment. Under these conditions, there was approximately a 20% increase in cell number after 24 hr of culture. The hypothesis that treatment of ASL-1w cells with the lesser concentration of anti-TL serum blocks the cells in G2 phase of the cell cycle is discussed.

Animals↗

PubMed1976