Pruritus of poison oak dermatitis-other views

The use of the do-not-resuscitate order has become accepted medical practice. To date, however, no study has been done of how often it is used or factors associated with its use. Reports of all deaths of inpatients occurring during calendar year 1981 at San Bernardino County Medical Center were eligible for study. Retrospective review of the 237 cases indicated that a do-not-resuscitate order had been written for 165 (69.6%) of the patients. Comparison of reports of those for whom such an order had been written with those for whom no order had been written indicated that a do-not-resuscitate order was not associated with age, sex, ethnicity or pay status. Indices of mental clarity, however, were associated with orders not to resuscitate; those patients residing in nursing homes, and not alert and oriented on admission were overrepresented in the group given this order. Primary discharge diagnosis was also associated with such an order, as was an increased duration of hospital stay.     

Component analysis of the urushiol content of poison ivy and poison oak

The partial separation and quantitation of the components of the urushiol fraction of poison ivy and poison oak are discussed. The urushiol fraction of poison ivy is primarily composed of C₁₅ side-chain catechol, while the urushiol extract of poison oak is principally the C₁₇ homolog. The presence of a C₁₇ homolog in ivy and a C₁₅ homolog in poison oak urushiol is also detected. Each of these catechol derivatives contain a mixture of congeners which are partially separated by the GLC system used. In each case the tri-olefinic component occurs in greatest abundance and the mono-olefinic congener is least abundant; no saturated material was detected. The compounds were analyzed as trimethylsilyl derivatives and a qualitative analysis was accomplished by GC-MS.     

A murine model system for contact sensitization to poison oak or ivy urushiol components

A murine model of contact sensitization to components of poison oak or ivy urushiol oils was developed. Sensitization was effected by painting such compounds on abdominal skin, and was routinely assessed by challenging on the ears and monitoring increases in ear thickness. Sensitization to 3-heptadecylcatechol (HDC, a component of poison oak urushiol) was studied in detail. Contact sensitivity as indicated by ear swelling reactions was observed from 2 until around 25 days after primary abdominal painting with HDC. In all cases maximal ear swelling occurred 3–4 days after HDC challenge. Sensitivity could also be assessed by monitoring the uptake of radioiodinated deoxyuridine at the ear challenge site, and this correlated with the ear swelling assay in terms of kinetics. The sensitization effect induced by HDC had properties of delayed-type hypersensitivity, being antigen specific, and transferable with sensitized lymph node and spleen cells but not by serum. Also, T cells were required for activity as transfer with spleen cells was abrogated by treatment with anti-Thy-1.2 antibody and complement. In this system HDC and 3-pentadecylcatechol (PDC, a component of poison ivy urushiol oil) were completely cross-reactive both in sensitization and challenge, and both compounds also cross-reacted with native urushiol oil itself. Thus murine sensitization to HDC can be used as a model system for investigating mechanisms for the immunogenicity of such catechols.     

Stem hydraulic properties of vines vs. shrubs of western poison oak,Toxicodendron diversilobum

Summary This study investigated the effect of mechanical support on water transport properties and wood anatomy of stems of western poison oak, Toxicodendron diversilobum (T. & G.) Greene. This plant grows as a vine when support is present but as a shrub when support is absent. I compared vines and shrubs growing naturally in the field and those produced from cuttings of 11 source plants in a common garden. Huber value (xylem transverse area/distal leaf area) was lower but specific conductivity (water volume · time^-1 · xylem transverse area^-1 · pressure gradient^-1) was higher in supported than unsupported plants both in the field and the common garden. The opposing effects of Huber value and mon garden. The opposing effects of Huber value and specific conductivity resulted in the same values of leafspecific conductivity (LSC, water volume · time^-1 · distal leaf area^-1 · pressure gradient^-1) for supported and unsupported shoots at a given site. Therefore, for the same rates of evapotranspiration, supported and unsupported shoots will have the same pressure gradients in their stems. Vessel lumen composed a higher proportion of stem cross-section in supported than unsupported plants (due to slightly wider vessels and not to greater vessel density). These results suggest that the narrow stems of supported plants are compensated hydraulically by the production of wider vessels: at a given site, poison oak plants co-ordinate their leaf and xylem development such that their stems achieve the same overall conductive efficiencies (LSCs), regardless of support conditions.     

Strong poison revisited

Selenium in the form of selenocysteine plays an essential role in a number of proteins, but its role in non-enzymatic biochemistry is also important. In this short review we discuss the interactions between inorganic selenium, arsenic and mercury under physiological conditions, especially in the presence of glutathione. This chemistry is obviously important in making the arsenic and mercury unavailable for more toxic interactions, but in the process it suggests that a side-effect of chronic arsenic and/or mercury exposure is likely to be functional selenium deficiency.     

Enrichment and function of urushiol (poison ivy)-specific T lymphocytes in lesions of allergic contact dermatitis to urushiol

The frequencies of urushiol (poison ivy)-specific T cells were determined in the lesional skin and peripheral blood of patients with allergic contact dermatitis to urushiol. Lesions of urushiol dermatitis were biopsied and the T cells retrieved. Frequencies of Ag-specific cells were determined by limiting dilution assay. Enrichment of urushiol specific T cells was detected in lesional skin or blister fluid of five of five of these donors as well as seven of seven donors with urushiol patch tests. There was also enrichment relative to tetanus toxoid specific T cells in blood and skin of six of seven donors. The frequency of lesional T cells specific for urushiol was less than 1/100 and generally less than 1/1000. Furthermore, the frequency of urushiol specific T cells was often less than 1/10,000 in the peripheral blood during an acute eruption. Autoreactive T cells that proliferated to autologous irradiated PBMC were also enriched in skin lesions relative to blood in 5/5 urushiol patch tests. These autoreactive T cells were expanded and found to be CD4+. It has been proposed that such autoreactive T cells recognize autologous DR and may have a role in immunoregulation. Urushiol-specific T cells were expanded from limiting dilution wells of two donors and characterized. The majority of the urushiol-specific cells were CD8+, and 13/43 lines were suppressive for PWM-induced IgG synthesis.