Biomedical subjects

M V Dahl

Publications and source records attributed to M V Dahl.

At least 37 records · Page 2Linked to original sources

PubMed1994

Effects of detergents on proliferation and metabolism of human keratinocytes.

Effects of low concentrations of detergents on cultured human foreskin keratinocytes were assessed in vitro. The viability and activity of keratinocytes were assessed by measuring reduction of a tetrazolium dye as an indicator of mitochondrial metabolism. The keratinocyte proliferative responses after incubation with detergents were assessed by a spectrophotometric assay employing crystal violet dye and a fluorometric assay determining total DNA content. Both the cationic detergent cetyltrimethylammonium bromide [CTAB] and the anionic detergent sodium lauryl sulfate [SLS] showed toxic effects on keratinocytes at concentrations as low as 3 micrograms/mg, but SLS was less toxic. However, both SLS and CTAB activated keratinocytes at very low concentrations. Proliferative activity and mitochondrial metabolism increased. Serum partially protected keratinocytes against toxic and stimulatory activities of both detergents. We suggest that detergents may directly damage keratinocytes and thereby produce irritant contact dermatitis, but activation of keratinocytes by low concentrations may also produce dermatitis, perhaps by causing keratinocytes to release cytokines.

Cell Division↗

PubMed1994

Chronic dermatophytosis: what is special about Trichophyton rubrum?

T. rubrum is especially suited to survive on the skin surface. We have presented data to show how it accomplishes this. We will now combine these data with our own thoughts to speculate about how T. rubrum has adapted to the skin of human beings. We believe the organism uses several different strategies. First, many infected patients cannot elicit a cell-mediated immune response to eliminate the fungus. The reasons for this are not completely clear, but trichophytin skin tests are negative at 48 hours despite persistent, chronic, and even widespread infections. Antigens are present on T. rubrum, just as they are on other dermatophytes, but differences in antigen penetration through the skin may prevent induction of immunity. Perhaps, neonatal exposure to the fungus or to cross-reacting antigens of molds may induce tolerance by confusing antigen recognition of self vs. nonself. More likely, persistent infection induces immunologic unresponsiveness by activating specific suppressor T cells. In fact, our attempts to clone T. rubrum-specific T cells from peripherals blood have always yielded suppressor cells, and these cells even suppress proliferation of the clone itself. Second, mannans from T. rubrum probably are better able to suppress cell-mediated immune reactions than are mannans from other fungi. T. rubrum may make more mannan than do other dermatophytes, and the mannan may be a more potent immunosuppressor than are mannans from other dermatophytes. Mannan apparently works by inhibiting critical steps in antigen processing or presentation. This inhibits the immune reaction. Perhaps, mannan even can prevent induction under certain circumstances. Third, T. rubrum is not especially aggressive compared with other dermatophytes. By remaining in the stratum corneum, it may evade immune surveillance, and may evade complement and polymorphonuclear leukocytes that would attach the organism if it tried to invade into viable epidermis. Finally, T. rubrum can survive off the human body as a spore. Its life cycle apparently lets spores desquamate and, thereby, remain plentiful in many human habitats. If a spore finds a warm, moist area of skin, it can crowd out normal flora and grow within the stratum corneum. T. rubrum's ability to infect and its ubiquitous presence account for the high incidence of infections. This, plus the ability of T. rubrum to evade host defenses, accounts for the high prevalence of infections with this fungus.

Animals↗

PubMed1993

Unilateral linear lichenoid eruption after bone marrow transplantation: an unmasking of tolerance to an abnormal keratinocyte clone?

Chronic cutaneous graft-versus-host disease may appear clinically as a lichenoid eruption. We describe a 26-year-old man who developed a unilateral linear lichenoid eruption 7 months after allogeneic bone marrow transplantation. We believe this represents an unusual form of localized, chronic graft-versus-host disease. The possible relationship to viral infection or cellular mosaicism and the clinical, histologic, and immunologic similarities to idiopathic lichen planus are discussed.

Adult↗

PubMed1993

Suppression of immunity and inflammation by products produced by dermatophytes.

When normal, previously uninfected hosts are exposed to dermatophytes under experimental occlusive conditions, infections develop and cell-mediated immunity is induced. Subsequent exposure to dermatophytes under the same conditions elicits an immune response that is capable of curing the infection, once occlusion is removed. Lymphocytes or monocytes involved in the immune response may produce cytokine growth factors that foster stratum corneum turnover and shedding of the fungus from the skin surface. Chronic dermatophyte infections develop when conditions of the local environment or virulence factors of the fungus outweigh the capabilities of cell-mediated immunity, or when a person does not develop cell-mediated immunity to fungal antigens. Even if immunity does develop, certain dermatophytes such as Trichophyton rubrum produce substances that diminish the immune response. One class of these substances, the mannans, can indirectly inhibit stratum corneum turnover. A nonresponsive host immune system or the suppression of the immune response by products produced by dermatophytes can prevent complete eradication of the fungus or predispose to reinfection.

Antifungal Agents↗

PubMed1993

Human keratinocytes synthesize, secrete, and degrade acetylcholine.

We previously reported that normal human keratinocytes express muscarinic receptors, and that acetylcholine induces attachment of these cells to each other. We have now studied the ability of human keratinocytes to synthesize, secrete, and degrade acetylcholine. To detect and localize the synthesizing enzyme choline acetyltransferase and degrading enzyme acetylcholinesterase, cultured cells and cryostat sections of normal human skin were pre-incubated with specific monoclonal antibodies and stained with an avidin-biotin complex/alkaline phosphatase. The choline acetyltransferase activity was assessed by the conversion of [3H]acetyl CoA to [3H]acetylcholine, and newly synthesized [3H]acetylcholine was detected using thin-layer chromatography. The acetylcholinesterase activity was measured spectrophotometrically. Both cholinergic enzymes were present in cultured keratinocytes, and in basal, spinous and granular epidermal cell layers. Choline acetyltransferase was visualized in the vicinity of cell nuclei, and acetylcholinesterase was observed in or near cell membranes. Newly synthesized acetylcholine was detected in both cell homogenates and culture supernatants. The estimated Vmax of the synthesis of labeled acetylcholine by homogenized keratinocytes was about 20 pmoles acetylcholine produced/mg protein/min at 37 degrees C. A single keratinocyte synthesized a mean of 2 x 10(-17) moles, and released 7 x 10(-19) moles acetylcholine per minute. Both cell homogenates and culture supernatants exhibited similar acetylcholinesterase activities indicating that human keratinocytes secrete acetylcholinesterase, too. Thus, we have demonstrated that normal human keratinocytes possess choline acetyltransferase and acetylcholinesterase, and synthesize, store, release, and degrade acetylcholine. Because human keratinocytes can also respond to acetylcholine, we believe that keratinocyte acetylcholine works in the epidermis as a local hormone.

Acetylcholine↗

PubMed1993

Agarose gel keratinocyte outgrowth system as a model of skin re-epithelization: requirement of endogenous acetylcholine for outgrowth initiation.

To better understand the mechanisms of skin re-epithelization, we developed a simple technique that assays the outgrowth of human keratinocytes. Second-passage foreskin keratinocytes were inoculated at high cell density into 3-mm wells cut from agarose gels in standard 6-well tissue culture dishes. The cells settled on the dish bottom and formed a confluent colony. The cells at the periphery of the colony flattened, spread their cytoplasm, and moved away over the dish surface under the agarose gel. The morphology of migrating keratinocytes was observed microscopically through the transparent agarose, and the migration distance was measured after the gels were removed and after cells were fixed and stained. To determine which cell activities were involved in the outgrowth, the effects of cholinergic compounds on keratinocyte outgrowth were compared with their effects on keratinocyte proliferation, cell-plastic attachment, and spreading measured in separate sets of experiments. Outgrowth was inhibited by the specific inhibitor of acetylcholine synthesis bromoacetylcholine (0.05 mM) and restored by 5 mM exogenous acetylcholine. The irreversible muscarinic antagonist propylbenzilylcholine mustard (0.05 mM) abolished the restorative effects of exogenous acetylcholine, and also inhibited outgrowth of intact keratinocytes. In keratinocyte cell cultures, bromoacetylcholine stopped cell division. Propylbenzilylcholine mustard increased cell number, but interfered with cell-plastic attachment and spreading. This suggests that cell-matrix attachment, spreading, and locomotion of human keratinocytes, but not mitosis, mediate the earliest stages of skin re-epithelization, and that endogenous acetylcholine regulates these keratinocyte functions. Specifically, keratinocyte acetylcholine is required to initiate outgrowth.

Acetylcholine↗

PubMed1993

Computerized microassay of keratinocyte cell-plastic attachment and proliferation for assessing net stimulatory, inhibitory and toxic effects of compounds on nonimmortalized cell lines.

Testing of pharmacological agents that affect growth of epidermal keratinocytes (EK) requires a standardized assay. We have developed an assay measuring net effects of stimulatory (e.g. growth factors), inhibitory (e.g. methotrexate) or toxic (e.g. Triton X-100) compounds. The amount of crystal violet staining viable EK attached to the wells of standard 96-well microplates is measured in situ using an ELISA plate reader. Optical density readings are directly converted into cell counts by computer software. Counts obtained by this method strongly correlate with the results obtained using the [3H]thymidine uptake assay and direct cell counts. The assay standardizes measurements of nonimmortalized EK lines with different innate proliferative properties and allows accurate quantitation of EK numbers in the range of 2,500-500,000 EK/well.

Cell Adhesion↗

PubMed1993

The immunology of scabies.

Individuals with scabies react to bites by generating a cell-mediated immune response at the bite site. This elicits a very itchy papule that is often excoriated. Sometimes ulcerated papules, vasculitis, and nodules develop as a result of other immunologic reactions in skin. Immunologic reactions mediated by antibodies of the immunoglobulin G (IgG), IgM, and especially, IgE classes may also be involved. None of these reactions have been shown to eliminate all mites from the skin surface, but locally these reactions may prevent the epidemic multiplication of scabies' organisms on the skin surface, as observed in some patients with crusted scabies.

Acquired Immunodeficiency Syndrome↗

PubMed1992

Binding of Trichophyton rubrum mannan to human monocytes in vitro.

We recently reported that the mannan component of Trichophyton rubrum cell wall (TRM) has an inhibitory influence on cell-mediated immune function in vitro. We now describe experiments designed to identify the target cell for this effect of TRM. T. rubrum mannan labeled with fluorescein (FITC-TRM) was incubated with peripheral blood mononuclear leukocytes, monocytes, or lymphocytes. Binding and uptake of the FITC-TRM were monitored by fluorescence microscopy and flow cytometry. Approximately 10% of mononuclear leukocytes were stained with this reagent and the fluorescent cells appeared to be monocytes by morphology. Virtually all purified monocytes and no purified lymphocytes stained with FITC-TRM. Flow cytometry to analyze FITC-TRM monocyte-specific binding of FITC-TRM involved the use of a phycoerythrin-labeled anti-CD14 antibody to identify monocytes. The only cells stained with FITC-TRM were those stained with the monocyte-specific antibody. The ability of monocytes to endocytose mannan was assessed by fluorescence microscopy. Cells were exposed to FITC-TRM and washed, and the staining pattern recorded periodically over a 48-h incubation period. After 15 min, staining was homogeneous and involved the entire cell surface; by 30 min, "patching" was observed; by 90 min, bright granules had formed along the cell border and a large number of small granules were present in the cytoplasm; by 8-12 h, the fluorescent granules were enlarged in size and reduced in number; by 24-36 h, the intensity of cytoplasmic fluorescence began to diminish; and, after 48 h, all fluorescent staining had disappeared. An additional feature of staining during the 8-12-h period was the appearance of a large round bright spot in the nuclear region of each cell, which may represent nucleolar staining. A role for "mannan receptors" is suggested by observations that FITC-TRM binding was prevented by unlabeled TRM or pretreatment of the monocytes with trypsin. Our finding that monocytes selectively and specifically bind TRM appears to identify the monocyte rather than the lymphocyte as the target cell for the inhibitory effect of mannan on cell-mediated immune function.

Adult↗

PubMed1992

Dapsone suppresses integrin-mediated neutrophil adherence function.

The anti-inflammatory influence of dapsone may involve suppression of neutrophil chemotaxis to selected attractants, but other actions of the drug are likely also involved. We have discovered that dapsone may suppress migration of neutrophils to extravascular sites through inhibition of adherence functions required for neutrophil recruitment. Neutrophil adherence mediated by integrins (CD11/CD18 or Mac-1 family receptors) was measured in vitro in terms of binding of stimulated cells to albumin-coated wells of microtiter plates, using phorbol myristate acetate (PMA) and N-formylmethionyl-leucyl-phenylalanine (FMLP) as stimuli. Adherence was assessed by staining attached cells with crystal violet dye and measuring the dye concentration at OD590 using an automated plate reader. The role of integrins in this assay was confirmed by the ability of anti-integrin antibody to suppress stimulated neutrophil adherence. The OD590 value for cells adhering to albumin in the absence of stimulus and dapsone averaged 0.2 +/- 0.04 (SEM) over five experiments. In the presence of 0.1 microM PMA or 10(-6) M FMLP, the OD590 values averaged 0.88 +/- 0.1 and 0.75 +/- 0.12, respectively. Dapsone did not affect unstimulated neutrophil adherence but, when present with stimulus, produced a dose-related inhibitory effect on adherence. Fifty percent inhibitory doses were approximately 150 micrograms/ml dapsone for both stimuli. Sulfapyridine reproduced the inhibitory effect of dapsone, but two structurally related compounds, hydrochlorothiazide and furosamide, did not. The observed ability of dapsone to inhibit neutrophil chemotaxis under agarose to FMLP and interleukin-8 may also be explained by interference with integrin-mediated adherence required for motility in this assay system. To consider if dapsone might have a similar inhibitory influence on neutrophil adherence in vivo, we tested the stimulated adherence function of neutrophils isolated from three individuals on dapsone therapy for dermatitis herpetiformis. Stimulated adherence of patients' cells averaged less than 40 percent of the control value. Suppression of leukocyte integrin function may therefore also contribute to the ability of dapsone to inhibit neutrophil infiltration in neutrophilic dermatoses.

Cell Adhesion↗

PubMed1992

Epidermolysis bullosa acquisita induced by GM-CSF: a role for eosinophils in treatment-related toxicity.

A patient treated with granulocyte-macrophage colony-stimulating factor (GM-CSF) developed eosinophilia and epidermolysis bullosa acquisita. The bullae were subepidermal, and filled with an inflammatory infiltrate composed predominantly of eosinophils. Immunofluorescence studies disclosed linear deposition of IgG, IgA and C3 at the basement membrane zone and immunoelectron microscopy demonstrated antibody deposition in the lamina densa and sublamina densa region; however, the patient's serum did not contain circulating antibody to basement membrane zone antigens. Staining with monoclonal antibodies revealed dense deposits of both eosinophil peroxidase and eosinophil major basic protein at the dermal-epidermal junction. The eosinophilia and skin lesions resolved upon discontinuation of GM-CSF. This case provides evidence for two hypotheses: (1) GM-CSF induced proliferation and activation of eosinophils may contribute to some of the toxicities of GM-CSF treatment, and (2) activated granulocytes, including eosinophils, may mediate blister formation in epidermolysis bullosa acquisita.

Aged↗

PubMed1992

Binding and uptake of Trichophyton rubrum mannan by human epidermal keratinocytes: a time-course study.

Trichophyton rubrum infects skin. This fungus or its products might affect the function of epidermal cells. We previously reported that T. rubrum mannan (TRM) exhibits a suppressive effect on proliferation of human lymphocytes. The goal of the present study was to investigate the possibility of direct interaction of TRM with cultured normal human epidermal keratinocytes (EK). Mannan, a cell wall glycoprotein, was extracted from T. rubrum by precipitation with cetyltrimethylammonium bromide and conjugated with fluorescein isothiocyanate (FITC-TRM). After incubation of EK with 50 micrograms/ml FITC-TRM for 30 min, the surface of EK showed bright fluorescent staining. EK cultures pretreated with non-labelled TRM remained unstained. The fate of TRM bound to EK surface was determined in a time-course study. After pulse exposure to FITC-TRM, EK cultures were washed and incubated for various time periods. The EK moved surface mannan to the one area of cell membrane, so that at 4-6 h, the homogeneous staining of the entire cell surface was replaced by staining in a "cap" pattern. By 12 h, FITC-TRM was taken up into the cell, brought to the nuclear area and concentrated in the EK nucleoli. During the next 3 days nucleolar and cytoplasmic staining of the cells was observed. The intensity of fluorescence gradually diminished. On the 4th day, the sharp staining of organelles disappeared; instead, a large number of small fluorescent granules were seen intra- and extracellularly. By the 6th day after exposure, no EK staining remained. Thus, EK specifically bound, internalized and apparently catabolized TRM.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Division↗

PubMed1991

Embolic abscesses in hereditary hemorrhagic telangiectasia.

Hereditary hemorrhagic telangiectasia is an inherited disorder in which patients may have multiple telangiectases and arteriovenous fistulas in the skin and internal organs. Patients can suffer from a variety of serious clinical complications, including abscess formation. We report two patients in whom neurologic symptoms developed from embolic abscesses, one for whom this complication was fatal. The reported incidence and microbiologic features of this complication are similar to that of endocarditis in patients with valvular heart disease. We believe that patients with hereditary hemorrhagic telangiectasia should receive similar antibacterial prophylaxis for procedures placing them at risk for bacteremia.

Abscess↗

PubMed1991

An immunoinhibitory cell wall glycoprotein (mannan) from Trichophyton rubrum.

Trichophyton rubrum causes 90% of chronic dermatophyte infections. Most patients with widespread chronic T. rubrum infection fail to express a delayed hypersensitivity reaction to intradermally injected trichophytin. We propose that cell-mediated immunity to T. rubrum may be suppressed in chronic infections by the mannan cell wall component of the fungus. The proposed suppressive effect of T. rubrum mannan on cell-mediated immunity was tested by measuring the ability of extracted mannan to inhibit lymphoproliferative responses of human mononuclear leukocytes to antigens, mitogens, and an anti-T-cell receptor antibody (anti-CD3) in vitro. Mannan was found to be highly antigenic in two of five donors and weakly antigenic in the other three. Despite its antigenic property, mannan exhibited a dose-related ability to inhibit lymphoproliferation stimulated by other agents including 1) antigens from Candida albicans, T. rubrum, and tetanus toxoid (ID50 = 250 micrograms/ml); 2) anti-CD3 antibody (ID50 = 250 micrograms/ml); and 3) Phaseolus limensis mitogenic lectin (ID50 = 64 micrograms/ml). Mannan added to cultures later than 24 h after initiation had no inhibitory influence, but culture of cells with mannan for a period of 24 h prior to the addition of stimulus enhanced the inhibitory effect of the glycoprotein. Lymphoproliferation in response to recombinant interleukin-2 (IL-2) was not inhibited. The influence of time of addition of mannan and the failure of mannan to inhibit IL-2-stimulated lymphoproliferation demonstrate that the suppressive effect of mannan must be pharmacologic rather than cytotoxic. The observed ability of T. rubrum cell wall mannan to suppress cell-mediated immune function in vitro may provide an important clue to a mechanism enabling the fungus to avoid elimination in chronically infected patients.

Chronic Disease↗

PubMed1990

Flare factors and atopic dermatitis: the role of allergy.

Atopic dermatitis is a genetically determined eczematous skin disease strongly influenced by environmental conditions called flare factors. Allergic reactions are one such flare factor. These reactions include contact urticaria, allergic contact dermatitis, and late phase reactions. Contact urticaria could induce eczema by eliciting scratching. A late phase reaction may be involved in eczema produced by prolonged epicutaneous applications of antigens in individuals with immediate sensitivity to these antigens. Mechanisms of allergic contact dermatitis might also elicit dermatitis. Environmental allergens may include mold, dust, mite, pollens, foods, danders and bacteria.

Allergens↗

PubMed1989

Topical capsaicin treatment of chronic postherpetic neuralgia.

Uncontrolled studies have indicated that topically applied capsaicin may be a safe and effective treatment for postherpetic neuralgia. In a double-blind study 32 elderly patients with chronic postherpetic neuralgia were treated with either capsaicin cream or its vehicle for a 6-week period. Response to treatment was evaluated by visual analogue scales of pain and of pain relief, together with changes in a categoric pain scale and in a physician's global evaluation. Significantly greater relief in the capsaicin-treated group compared with vehicle was observed for all efficacy variables. After 6 weeks almost 80% of capsaicin-treated patients experienced some relief from their pain. Because capsaicin avoids problems with drug interactions and systemic toxicity, we suggest that topical capsaicin be considered for initial management of postherpetic neuralgia.

Administration, Topical↗

PubMed1989

Inhibition of growth of Trichophyton rubrum by the myeloperoxidase-hydrogen peroxide-chloride system.

The myeloperoxidase-hydrogen peroxide-chloride (MPO-H2O2-Cl) system is an antimicrobial system of polymorphonuclear leukocytes. We demonstrated that the MPO-H2O2-Cl system is fungicidal for Trichophyton rubrum. Fungal growth of a synchronous cell culture of T. rubrum germlings was assayed by measuring the uptake of tritiated N-acetyl-D-glucosamine, and the viability of the fungi was assayed by counting colony-forming units. Cytotoxins produced by the interaction of myeloperoxidase with hydrogen peroxide and chloride ion were fungicidal for T. rubrum. Growth inhibition was abolished in the presence of catalase or L-methionine. Polymorphonuclear leukocytes through the MPO-H2O2-Cl system may prevent invasion and sepsis by dermatophytes even in the absence of specific immunity.

Acetylglucosamine↗

PubMed1989

Hereditary mucoepithelial dysplasia. Case report and review of the literature.

Hereditary mucoepithelial dysplasia, a dyshesive, dyskeratotic epithelial syndrome caused by an abnormality in desmosomes and gap junctions, involves the mucosae, skin, hair, eyes, and lungs. A 16-year-old patient had nontender, fire-red mucosae; keratosis pilaris; diffuse, nonscarring alopecia; cataracts; photophobia; corneal vascularization; and decreased visual acuity. Histologic examination of gingival sections showed a dyshesive epithelium with atrophy, dyskeratosis, lack of keratinization, and unusual cytoplasmic inclusions. Results of electron microscopic studies showed a reduced number of desmosomes, amorphous intercellular material, and cytoplasmic inclusions resembling tonofilaments and gap junction material. The patient described in this report represents an apparently sporadic case of hereditary mucoepithelial dysplasia. Other cases described previously in the literature are reviewed. We believe this disorder should be brought to the attention of dermatologists because patients with hereditary mucoepithelial dysplasia have numerous skin problems and are susceptible to recurrent infection and potentially fatal bullous lung disease. Also, misinterpreted abnormal results from cervical Pap smears could lead to hysterectomy being performed unnecessarily on these patients.

Adolescent↗