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Biomedical subjects

D H Lynch

Publications and source records attributed to D H Lynch.

97 records · Page 6Linked to original sources
PubMed1981

Relationship between epidermal Langerhans cell density ATPase activity and the induction of contact hypersensitivity.

Langerhans cells have been implicated as playing a crucial role as antigen-processing cells in the induction of positive immune responses to antigens presented through the skin. We have investigated the effects of carcinogenic doses of UVB-irradiation, psoralen plus UVA light (PUVA), PABA containing sunscreen preparations, and topically applied corticosteroids on both Langerhans cell densities and immunologic responsiveness to contact sensitizers applied to the treated site. The data presented demonstrate that UV-irradiation of skin or topical application of corticosteroids can create a local milieu in which DNFB cannot function as an effective stimulator of contact hypersensitivity. Further, we have shown that the effect induced by UV light is reversible, does not appear to be related to the numerous tissue destructive effects of UVB-irradiation, and that the correlation with the density of ATPase-positive cells is not absolute.

4-Aminobenzoic Acid↗
PubMed1981

The effects of ultraviolet irradiation on the generation of anti-tumor cytotoxic effector cell responses in vitro.

The effects of irradiation of lymphoid cells in vitro with ultraviolet (UV) light were studied using radiation sources that are widely used both in the study of photocarcinogeneic mechanisms and by commercial tanning parlors (FS40 sunlamps). Low doses of direct exposure of cells was found to abrogate the differentiation events that lead to the generation of functional cytotoxic T lymphocytes (CTL). UV irradiation of cells in vitro induces alterations that, although not immediately obvious, lead to cell death during the next several days in tissue culture. Energy titration experiments demonstrated that both primed T cells and accessory cells were sensitive to the effects of direct UV-exposure; T cells were found to be much more sensitive than accessory cells. A 90% decrease in CTL generation could be affected with as little as 10 sec of UV exposure. These effects appear to be caused by wavelengths in the UVB range (280 to 320 nm), since exposure of cells to much higher doses of energy in the UVA range (320 to 400 nm) were not inhibitory. The spectrum of wavelengths in the UV region is large (200 to 400 nm). The data presented here demonstrate that it is overly simplistic to assume that all wavelengths in the UV spectrum mediate their effects via identical mechanisms. Furthermore, the wavelengths at which a given amount of energy is emitted appears to be much more important than the absolute amount of energy (in joules) which biologic systems are subjected.

Animals↗
PubMed1980

The LEW.BN(2R) strain: a recombinant in the rat MHC.

Cell-mediated cytolytic (CMC) responses resulting from immunizations between rat strains considered to be RT1 (Ag-B) identical (LEW.B3:BN) are capable of detecting a membrane determinant(s) controlled by a locus linked to RT1, which has been designated Ag-L. The Ag-L gene region has been isolated in a recombinant line, tentatively designated as LEW.BN(2R), and has been assigned the RT1r5 haplotype. The data presented demonstrate that the genes responsible for MLR stimulation in the 2R strain are of LEW origin. In addition, LEW.B3 anti-BN CTL appear to recognize multiple specificities, only one of which is in the 2R strain. Some of the remaining specificities in BN may be the result of interactions between undetected genes that have been separated in the LEW.B3 and 2R strains.

Alleles↗
PubMed1980

Analysis of cytotoxic effector cell populations by kinetic and monolayer adsorption techniques.

Cytolytically active lymphocytes were generated by immunizations between rat strains and evaluated by both kinetic and monolayer adsorption techniques. Kinetic analysis yields two values (Ka and Vmax), which are characteristic of interactions between individual effector and target cell populations. The Ka values this obtained correlate with the quantitative level of adsorption of CTL onto cellular monolayers, and we conclude that Ka is a measure of the binding avidity of effector and target cells.

Animals↗
PubMed1978

Genetic identification of a locus linked to the rat MHC that codes for a membrane antigen detectable with cytotoxic lymphocytes.

Cell-mediated cytolytic (CMC) responses resulted from immunizations between rat strains purported to be identical at Ag-B, the major histocompatibility complex (MHC), but differing at other loci not linked to Ag-B. In vivo-priming followed by secondary in vitro stimulation was required to generate a measurable CMC response as determined by a 51Cr-release assay. Neither in vivo nor in vitro stimulation alone was adequate. The CMC responses generated in a strain combination considered Ag-B identical (LEW . B3:BN) were specific for a determinant controlled by a gene linked to Ag-B, which has been designated Ag-L. The CMC response appears not to be restricted to sygeneity at Ag-B. In addition, the data presented demonstrate a recombinant between Ag-B and Ag-L, and suggest that the gene has failed to transfer with the MHC during the isolation of the LEW . B3 and F-344 . B3 congenic strains.

Animals↗
PubMedDate not supplied

Nitrogen availability from composts for humid region perennial grass and legume-grass forage production.

Perennial forages may be ideally suited for fertilization with slow N release amendments such as composts, but difficulties in predicting N supply from composts have limited their routine use in forage production. A field study was conducted to compare the yield and protein content of a binary legume-grass forage mixture and a grass monocrop cut twice annually, when fertilized with diverse composts. In all three years from 1998-2000, timothy (Phleum pratense L.)-red clover (Trifolium pratense L.) and timothy swards were fertilized with ammonium nitrate (AN) at up to 150 and 300 kg N ha(-1) yr(-1), respectively. Organic amendments, applied at up to 600 kg N ha(-1) yr(-1) in the first two years only, included composts derived from crop residue (CSC), dairy manure (DMC), or sewage sludge (SSLC), plus liquid dairy manure (DM). Treatments DM at 150 kg N ha(-1) yr(-1) and CSC at 600 kg N ha(-1) yr(-1) produced cumulative timothy yields matching those obtained for inorganic fertilizer. Apparent nitrogen recovery (ANR) ranged from 0.65% (SSLC) to 15.1% (DMC) for composts, compared with 29.4% (DM) and 36.5% (AN). The legume component (approximately 30%) of the binary mixture acted as an effective "N buffer" maintaining forage yield and protein content consistently higher, and within a narrower range, across all treatments. Integrating compost utilization into livestock systems that use legume-grass mixtures may reduce the risk of large excesses or deficits of N, moderate against potential losses in crop yield and quality, and by accommodating lower application rates of composts, reduce soil P and K accumulation.

Animal Feed↗