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Biomedical subjects

P John

Publications and source records attributed to P John.

At least 55 records · Page 3Linked to original sources
PubMed1995

Reversal of immunosuppression of lymphocyte proliferation caused by sera from persons with AIDS.

Sera from persons with AIDS contain inhibitors of lymphocyte proliferation. Inhibitory activity can be detected before the development of AIDS in humans. There appear to be at least three distinct suppressive moieties, one of which is prostaglandin E2. We and others had previously shown that serum samples from subjects with AIDS contained antibody to the cell line HUT 102B2. We attempted to remove this antibody and to determine if that action would also remove the inhibitory activity present in human immunodeficiency virus-positive sera. We incubated sera from subjects with AIDS with HUT 102B2 cells and tested the resultant supernatants for inhibition of cell proliferation. We found that this procedure significantly reversed inhibition by serum. Other cells and cell lines were similarly tested, but only HUT 102B2 cells absorbed the inhibitory product(s). However, we determined that secretory material from another cell line, MLA 144, also reversed inhibition. The physical characteristics of the supernatant were investigated. Thus, two procedures and likely separate products, possibly cytokines, reverse immunosuppression by sera from persons with AIDS.

Absorption↗
PubMed1994

Analysis of nickel refinery dusts.

After characterization of bulk samples by inductively coupled plasma emission spectroscopic (ICP-ES) quantitative analysis and X-ray powder diffraction studies, single particle techniques using quantitative image analysis, scanning electron microscopy--energy dispersive analysis by X-ray, and finally laser beam ionization mass spectrometry analysis (LIMA) for surface analysis have been applied to historical nickel refinery dust samples from the nickel refining plant at Clydach in Wales. There were two historical samples of processed material from 1920 and 1929. These samples had a remarkably small particle size range, mean 3 microns and range, 0.75-24 microns. The most significant difference in elemental composition was the presence of 10% arsenic in the 1920 sample compared with 1% in the 1929 sample. The X-ray spectra revealed the presence of NiO in both. However, surprisingly, CuO was identified only in the 1929 sample. Of particular interest was the presence of a component, in the 1920 sample only, identified as the mineral orcelite, a copper-iron-nickel-arsenide-sulphide mineral, predominantly, Ni5-XAs2. Using the LIMA technique, it was found that in both samples, arsenic and arsenic derivative peaks are prominent, indicating the surface availability of arsenic compounds.

Arsenic↗
PubMed1994

Successful treatment of invasive pulmonary aspergillosis in chronic granulomatous disease with orally administered itraconazole suspension.

A 3-yr-old boy with known chronic granulomatous disease presented with a left-sided chest wall mass. Extensive intrathoracic and extrathoracic aspergillosis was confirmed by CT scan-guided percutaneous biopsy. Initially, he was treated intravenously with liposomal amphotericin and subcutaneous gamma-interferon, but his clinical condition deteriorated over 7 wk of treatment. The amphotericin was therefore discontinued, and itraconazole in an oral suspension was begun. There was progressive clinical improvement after 3 months of this regime, and marked radiologic clearing was apparent after 8 months of treatment. A multicenter trial of this mode of therapy in patients with invasive aspergillosis is indicated.

Administration, Oral↗
PubMed1989

Cytochrome P-450-dependent metabolism of xenobiotics. A comparative study of rat hepatic and plant microsomal metabolism.

1. A comparison was made between rat hepatic and plant microsomal cytochrome P-450 and cytochrome P-450 linked enzymic activities. 2. The results show that, compared with plant microsomes, rat hepatic microsomal protein concentrations were 165-fold higher, and rat hepatic cytochrome P-450 concentration were 32-fold higher. 3. Rat hepatic Cytochrome P-450 linked enzyme activities were 1765-fold and 25-fold greater when compared with plant microsomes using aldrin and biphenyl as substrates, respectively. 4. Rats metabolised biphenyl to 2- and 4-hydroxybiphenyl, whereas plants produced only the latter metabolite. 5. Pretreatment of rats and plant tissues with biphenyl, Aroclor 1248 and the sodium salt of phenobarbital increased significantly the microsomal protein concentrations, and enzyme activities linked to cytochrome P-450. 6. Unlike rat microsomes, those of plants were unable to metabolise halosubstituted biphenyls at measurable rates.

Aldrin↗
PubMed1989

Localization of the Enzymes of Fructan Metabolism in Vacuoles Isolated by a Mechanical Method from Tubers of Jerusalem Artichoke (Helianthus tuberosus L.).

Vacuoles isolated by a mechanical slicing method from developing tubers of Jerusalem artichoke (Helianthus tuberosus L.) contain activities of the two principal enzymes responsible for fructan synthesis: sucrose-sucrose fructosyl transferase and fructan-fructan fructosyl transferase. Both enzymes are associated with the vacuolar sap and not with the tonoplast. In vacuoles isolated from dormant tubers, the fructan-fructan fructosyl transferase activity remains in the vacuolar sap but the fructan exohydrolase activity is associated with the tonoplast. Fructan is hydrolysed by these vacuoles to fructose, which can be exported to the suspending medium. The localization of the enzymes of fructan metabolism in the vacuole has implications for the maintenance of fructan polymerisation.

Journal Article↗
PubMed1988

Effect of temperature on starch synthesis in potato tuber tissue and in amyloplasts.

A sharp temperature optimum is observed at 21.5 degrees C when the incorporation of [(14)C]sucrose into starch is measured with discs cut from developing tubers of potato (Solanum tuberosum L. cv Desirée). By contrast, increasing temperatures over the range 9 to 31 degrees C only enhance release of (14)C to respiratory CO(2) and incorporation of (14)C into the ethanolsoluble fraction. By comparison, starch synthesis in discs from developing corms of cocoyam (Colocasia esculenta L. Schott) is increased by raising the temperature from 15 to 35 degrees C. The significance of a relatively low temperature optimum for starch synthesis in potato is discussed in relation to the yield limitations imposed by continuously high soil temperatures. Amyloplasts isolated from protoplasts prepared from developing potato tubers contain activities of alkaline pyrophosphatase, NAD-dependent glyceraldehyde-3-phosphate dehydrogenase, fructose-1,6-bisphosphatase, and phosphoglucomutase in addition to ADP-glucose-pyrophosphorylase, starch phosphorylase and starch synthase. Cell-free amyloplasts released by thinly slicing developing potato tubers synthesize starch from [(14)C]triose-phosphate generated from [(14)C]fructose-1,6-bisphosphate in the reaction medium. This starch synthesis is inhibited by addition of 10 millimolar inorganic phosphate and requires amyloplast integrity, suggesting the operation of a triose-phosphate/inorganic phosphate exchange carrier at the amyloplast membrane. The temperature optimum at 21.5 degrees C observed with tissue discs is not observed with amyloplasts.

Journal Article↗
PubMed1988

HIV-1 infection abolishes CD4 biosynthesis but not CD4 mRNA.

In order to improve understanding of how HIV-1 infection down-modulates cell surface membrane expression of CD4, we have measured several parameters of CD4 expression in the human tumor T-cell lines CEM and MOLT-4 at different times after infection. Three independent HIV-1 isolates were used including one that encodes a truncated nef protein and another that appeared to be noncytolytic against CEM. The level of CD4 mRNA, the rate of biosynthesis of CD4 protein, and the percentage of CD4-positive cells were measured. With each viral isolate it was found that infection led to a specific and almost complete inhibition of CD4 protein biosynthesis. This substantially exceeded, at every time point after infection, a concomitant reduction in CD4 mRNA. Hence an inhibition of translation probably accounts for much of the decline in the rate of CD4 biosynthesis. This implicates a novel selective translational inhibition of host gene expression by HIV-1 as a factor in the disappearance of surface membrane CD4 from infected cultures.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Prenatal diagnosis of beta thalassaemia by reverse phase HPLC.

Reverse phase HPLC of radioactive globin chains has been compared to classical carboxy methyl cellulose chromatography for the prenatal diagnosis of beta thalassaemia. The two methods correlated highly (r = 0.97 p less than 0.0005) and provided an identical diagnosis for 40 fetal blood samples of fetuses homozygous or heterozygous for beta thalassaemia. The HPLC procedure was much faster and required fewer biochemical steps (no globin preparation). It was at least as accurate and more sensitive than the classical chromatography. A single column can be used for 150 analyses and is always ready to be used. Last but not least it is much less expensive than CMC chromatography.

Carboxymethylcellulose Sodium↗