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Biomedical subjects

C J Brooks

Publications and source records attributed to C J Brooks.

At least 19 recordsLinked to original sources
PubMed1995

Human vascular endothelial cells do not induce anergy in allogeneic CD4+ T cells unless costimulation is prevented.

Human vascular endothelial cells expressing MHC class II molecules have previously been shown to stimulate the proliferation of allogeneic CD4+ human T lymphocytes. Here we show that allogeneic CD4+ T cells from individual A (TA) respond to class II+ endothelial cells from individual B (EB) by inducing interleukin (IL)-2 mRNA, detectable by semiquantitative polymerase chain reaction, within 12 hr. Responding T cells (TA) that are harvested after 12 hr, rested for 3 days, and then re-exposed to the same class II+ EB stimulators can again respond by proliferation that is equivalent in degree to that observed with third-party class II+ endothelial cells (EC) as stimulators and a little greater than that observed in the primary responses. Incorporation of antibodies to LFA-3, an endothelial costimulatory molecule for T cells, or to both IL-2 and IL-2 receptor (R) during the first-round stimulation prevented the subsequent second-round proliferation of TA to class II+ EB but not to class II+ EC. This nonresponsiveness induced by anti-LFA-3 or anti-IL-2/IL-2R could be overcome by the incorporation of cyclosporine during the first-round stimulation or by incorporation of IL-2 during the second-round stimulation. These observations suggest that class II+ endothelial cells within allografts will not induce anergy in host CD4+ T cells unless costimulation is blocked or the ability of CD4+ T cells to respond by proliferation is prevented; even then the response may be modified by prevailing cyclosporine or IL-2 levels.

Antibodies↗
PubMed1995

Human vascular endothelial cells process and present autoantigen to human T cell lines.

The effectiveness of cultured human umbilical vein endothelial cells as accessory cells for T cell activation has been investigated using T cell clones and lines derived from patients with myasthenia gravis which were specific for different epitopes on the alpha subunit of the human acetylcholine receptor. The endothelial cells were induced with IFN-gamma to express HLA-DR and -DQ at high and low levels respectively. They could then efficiently present specific peptides of the alpha subunit to an HLA-DR- and an HLA-DQw5-restricted T cell line. They could also process epitopes for both T cell lines from the full-length recombinant alpha subunit (r1-437) of the human acetylcholine receptor, where the known epitopes are 80 amino acid residues apart. The endothelial presentation of r1-437, but not of the peptides, was sensitive to chloroquine inhibition. Presentation appeared slightly less efficient (by 1.5- to 3.0-fold) with endothelial cells than with presenting cells from peripheral blood. This may reflect differences in accessory signalling since mAb blocking studies suggested that ligands for CD28 provided important accessory signalling by peripheral blood presenting cells while LFA-3 was used by endothelial cells.

Antigen Presentation↗
PubMed1995

Endothelial cells and renal epithelial cells do not express the Wegener's autoantigen, proteinase 3.

Proteinase 3 (PR3) is the major antigen for autoantibodies (C-ANCA) against cytoplasmic components of neutrophils which are strongly associated with Wegener's granulomatosis (WG). Recent data that PR3 may be expressed by renal tubular epithelial cells and endothelial cells suggest potential for a direct pathogenic effect against these cells by C-ANCA or cytoxic T lymphocytes. Using a semi-quantitative polymerase chain reaction (PCR), ELISA and indirect immunofluorescence staining we studied endothelial and epithelial cell PR3 expression. By PCR, no PR3 expression was found in human umbilical vein endothelial cells (HUVEC) either untreated, or when treated with interferon-gamma (IFN-gamma) (200 U/ml, 6 h, 24 h), IL-1 (20 U/ml, 6 h), tumour necrosis factor-alpha, (TNF-alpha) (200 U/ml, 0, 1, 2, 4, 6 h) or IFN-gamma + TNF-alpha (6 h); iliac vein and artery endothelial cells did not express PR3 either. In contrast, PR3 was detected in HL60 cells and neutrophils by PCR, expression being confirmed by sequence analysis. Three PR3 MoAbs showed no binding to unstimulated or TNF-alpha-stimulated HUVEC either by ELISA or by indirect immunofluorescence staining. The epithelial cell line A549 expressed PR3 when assayed by PCR. However, three renal epithelial cell lines (two tubular and one glomerular) showed little or no PR3 expression by PCR or ELISA. These studies fail to demonstrate evidence for PR3 expression by endothelial cells, even when using the highly sensitive PCR assay. Whilst PR3 expression by A549 cells is intriguing, the relevance of this in the pathology of WG is doubtful considering the negligible expression by renal epithelial cell lines.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed1994

The ergonomics of jettisoning escape hatches in a ditched helicopter.

The first formal investigation of the problem of location, operation and jettison of escape windows and hatches of helicopters following ditching has been conducted in a new simulator. There were 48 aircrew who attempted 298 escapes using a variety of 24 escape routes and 9 different types of escape hatches. Overall results, while superficially indicating that the task was easy, in fact revealed many unforeseen problems. Specifically, there was no standardization of hatches and levers, there were problems with location and operation of levers principally due to poor design, and an ergonomics study has not been conducted to investigate the problem. Underwater escape training with hatches in position must be mandatory for all who fly off-shore or over water for a living, and further research should be conducted to design a better standard hatch and jettison system.

Accidents, Aviation↗
PubMed1993

Synergistic interactions of CD4+ and CD8+ T cell subsets with human vascular endothelial cells in primary proliferative allogeneic responses.

The ability of subcultured human vascular endothelial cells (EC) to provide immune accessory functions for proliferative responses of highly purified allogeneic CD4+ and CD8+ T cells has been examined. CD4+ T cells proliferated in response to IFN-gamma-pretreated EC which expressed class II molecules, but not to untreated EC. CD8+ T cells proliferated to MHC class I molecules expressed on both untreated and IFN-gamma-treated EC. Combined populations of CD4+ and CD8+ T cells showed synergistic, rather than additive, responses to both untreated and IFN-gamma-treated EC. Furthermore, CD8+ T cells were able to induce MHC class II expression on endothelial cells and this induction could be inhibited by an anti-IFN-gamma mAb. The synergistic response obtained by co-culturing CD4+ and CD8+ T cells with vascular EC was completely inhibited by the same anti-IFN-gamma mAb. These studies suggest that CD4+ and CD8+ T cells recognise and proliferate to allogeneic MHC molecules expressed by EC. CD4+ and CD8+ responses are synergistic under the conditions tested and this synergism appears to be due to induction of MHC class II antigens on EC by IFN-gamma secreted from CD8+ T cells.

Antigen-Presenting Cells↗
PubMed1991

Gas chromatographic assay of methyltestosterone in tablets.

A simple gas chromatographic procedure has been developed for the determination of methyltestosterone in bulk powders and in tablets. Two new silyl ether derivatives of methyltestosterone have been prepared using dimethylethylsilylimidazole (DMESI) and dimethylisopropylsilylimidazole (DMiPSI). The method is accurate and selective for methyltestosterone within the concentration range 0.1-1.5 micrograms microliters-1.

Chromatography, Gas↗
PubMed1991

Gas chromatography and mass spectrometry of dimethylethylsilyl ether derivatives of norethisterone metabolites in plasma.

Metabolites isolated from human plasma after oral administration of norethisterone were assayed as their novel dimethylethylsilyl ether derivatives by gas chromatography--mass spectrometry--ion selective monitoring. The major metabolite is 3 alpha, 5 alpha-tetrahydronorethisterone. The unchanged drug is present in a measurable amount even after 8 h of drug administration. The method is accurate, precise and highly sensitive.

Ethers↗
PubMed1991

Immersed clo insulation in marine work suits using human and thermal manikin data.

The immersed clo value of a series of 11 marine work suits has been measured using both humans and a thermal manikin. In still water, there is no significant difference in the measurements. Turbulent water significantly reduces the immersed clo value. The manikin errs on the safe side and consistently overestimates this decrement in insulation, and the reasons for this are discussed. Not intended to replace human physiological testing, the manikin is an excellent apparatus for the examination of conditions not easily or ethically possible to represent using humans. A good fitting suit with efficient neck, wrist and ankle closures which reduce flushing of water is essential to make an effective marine work suit.

Adult↗
PubMed1987

Loss of cabin pressure in Canadian Forces transport aircraft, 1963-1984.

A review of all transport aircraft accidents and incidents in the Canadian Forces over the last 22 years (1963-1984) has been carried out. There have been 47 cases of serious loss of cabin pressurization. Altitudes varied from 2133 to 11277 m (7000 to 37,000 ft). The CC 130 Hercules appears to be the most vulnerable (62%). The most common cause was mechanical in origin (70%). There were two definite cases of hypoxia, and oxygen masks were deliberately deployed in nine cases. No deaths or permanent injuries occurred. Loss of pressurization is an extremely low, but definite risk to the pilot and passengers, thus aeromedical training with practical demonstrations in the hypobaric chamber for aircrew and flight attendants should continue.

Accidents, Aviation↗
PubMed1986

Ship/rig personnel abandonment and helicopter crew/passenger immersion suits: the requirements in the North Atlantic.

Protection from hypothermia and drowning are the primary requirements for an immersion suit system during ship, rig, or helicopter abandonment in the North Atlantic. In order to achieve this, the suit must be dry and comfortable. The problems involved in manufacturing such a suit are discussed and the fact is that there is still not a suit in existence that fulfills all the criteria.

Aerospace Medicine↗
PubMed1984

Loss of cabin pressure in Canadian Forces ejection seat aircraft, 1962-1982.

A review of all aircraft accidents and incidents in the Canadian Forces over the last 20 years (1962-1982) has been carried out. There have been 47 cases of serious loss of cabin pressurization in ejection seat equipped aircraft. Altitudes varied from 15,000 to 54,000 ft (4,572-16,459 m). No one aircraft appears to be more vulnerable. The most common cause was problems with the canopy seal (25%). There were three cases of hypoxia and two cases of decompression sickness. No deaths or permanent injuries occurred. Loss of pressurization is an extremely low, but definite risk to the pilot and aeromedical training with practical demonstration in the hypobaric chamber should continue.

Accidents, Aviation↗
PubMed1984

Water survival: 20 years Canadian Forces aircrew experience.

A 20 year review of Canadian Forces (CF) aircrew ejection/ditching, survival/rescue times and injury patterns in salt and fresh water is presented. Of the 595 A, B, and C category accidents which have been reviewed (1962-1982), 37 were water-entry. Of the 116 crew which were involved, 38 died (4 in fresh water). The Sea King helicopter is most at risk from sea water immersion, and the single-engine Otter has been the most vulnerable to fresh water immersion. A water immersion can be expected approximately once every 170,000 h of total flying time. In 92% of cases, the crew had less than 1 min warning that immersion was imminent and in 78% had less than 15 s to make a practical response. There were two clinical cases of hypothermia. In the absence of injuries, aircrew trained in water survival, qualified on the Dilbert Dunker, and who are strong swimmers or sports divers, have a better chance to survival. Time to rescue in all cases was under 3 h, and in 16 out of 24 cases crew members were rescued in under 15 min.

Accidents, Aviation↗
PubMed1984

Head and neck injuries in Canadian Forces ejections.

This paper reviews the head and neck injuries experienced by Canadian Forces Aircrew who ejected while wearing the DH 41-2 helmet during the period from 1 Jan. 1972 through 31 July 1982. Pre and post-ejection factors, including a review of helmet performance, are presented.

Accidents, Aviation↗
PubMed1983

Selective reactions in the analytical characterisation of steroids by gas chromatography-mass spectrometry.

The analytical characterization, by GC-MS, of individual compounds in mixtures of steroids, such as occur frequently in biological extracts, is difficult because of the close similarities in structure and properties of many components. The improved separating power of capillary (open-tubular) columns alleviates the problem, but does not solve it fully: for example, the coincidence of retention times of two different compounds may still be virtually complete. Comparative analyses on two distinctively different phases afford one valuable application of selectivity, but may not always be feasible when costly columns are required. Comparative analyses of the sample, before and after effecting its modification by well-defined reactions, are inexpensive and are particularly when selective transformations are used. The use of the microbial enzyme cholesterol oxidase as a selective oxidant for 3 beta-hydroxysteroids (chiefly limited to 4-ene, 5-ene and 5 alpha-types) is illustrated for a model mixture of androstanols related to the boar pheromone (5 alpha, 16-androsten-3 alpha-ol). Retention regularities and changes in mass spectra enhance the reliability of identifications. An exploratory application of cholesterol oxidase in the analysis of minor "polar" sterols in human serum is reported. Most of the known minor sterols are good substrates for the enzyme, and their transformation products yield distinctive GC-MS data, as exemplified for the 7 alpha- and 7 beta-hydroxycholesterols. Another convenient and versatile selective reagent is methaneboronic acid, which yields cyclic esters of suitably constituted diols. These derivatives have shorter retention times (on "non-polar" phases) than the di-TMS ethers, chiefly by virtue of their much lower molecular weights. The mass spectra of cyclic boronates generally show clear molecular ions, also fragmentations that complement the information obtainable from the di-TMS ethers. These features are illustrated for a group of diols and triols of the 5 alpha-pregnane series.

Androstanes↗
PubMed1980

Selective reactions in the analysis and characterization of steroids by gas chromatography-mass spectrometry.

Gas chromatography-mass spectrometry (GC-MS) is a technique especially suitable for the analysis and characterization of steroids, and its power has been extensively demonstrated. The efficacy of GC-MS is limited, nevertheless, by the fact that steroid mixtures - whether of natural origin only, or augmented by synthetic analogs - often contain similar components that are poorly distinquished. The fortuitous overlap of gas chromatographic peaks from disparate compounds also impairs the definition of retention data. Controlled modification of the sample by means of selective reactions is therefore a valuable adjunct to the application of GC-MS. Two examples are discussed: (a) the enzyme cholesterol oxidase, isolated from various microorganisms, catalyzes the oxidation of many 3 beta-hydroxy-5-enes (with concomitant isomerization) to 4-en-3-ones; 3 beta-hydroxy-5 alpha-steroids are also oxidized to the corresponding 3-ones, but other steroids (3 alpha-hydroxy- or 5 beta-isomers, etc.) are unaffected. The mild conditions required (pH 7, 30 C) are advantageous for the analysis of sensitive steroids, and the retention index increments, as well as the mass spectra of the ketones, are characteristic. The enzyme accepts as substrates a wide range of 3 beta-hydroxysteroids, tolerating oxygenation in ring B and even catalyzing the oxidation of 2-oxacholesterol to the expected lactone; and (b) Steroids possessing 1,2-diol or 1,3-diol groupings include estriols, 2-hydroxyestrone, 20,22-dihydroxycholesterols, ecdysones, brassinolide and many corticosteroids. The selective formation of cyclic derivatives can provide several analytically useful features, such as convenient retention times, moderate mass increments (24 amu for a methaneboronate), distinctive mass spectra and usually abundant molecular ions. These are exemplified for 5-pregnene-3 beta, 20,21-triols and for 20,22-dihydroxycholesterol as well as its enzymic oxidation product.

Boronic Acids↗