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Biomedical subjects

G L Larsen

Publications and source records attributed to G L Larsen.

At least 19 recordsLinked to original sources
PubMed1996

Requirement for CD8+ T cells in the development of airway hyperresponsiveness in a marine model of airway sensitization.

To study the role of CD8+ T cells in allergic sensitization, we examined the effects of in vivo depletion of CD8+ T cells prior to sensitization on IgE production, immediate type cutaneous hypersensitivity and development of altered airway responsiveness. BALB/c mice were thymectomized and treated with anti-CD8 antibody resulting in depletion of CD8+ T cells (<1%) in spleen and lymphoid tissues. In these mice, sensitization to ovalbumin (OVA) via the airways still resulted in IgE anti-OVA responses and immediate cutaneous reactions to OVA, but the animals were unable to develop airway hyperresponsiveness, eosinophil infiltration of the lung parenchyma, or IL-5 production in the local lymph nodes of the airway. Transfer of CD8+ T cells from naive animals during sensitization (on day 8 of the 10-d protocol) fully restored the ability to develop airway hyperresponsiveness and this was accompanied by IL-5 production and eosinophil accumulation in the lung. These data indicate a critical role for CD8+ T cells in the production of IL-5 and the development of altered airway responsiveness after antigen sensitization through the airways.

Allergens↗
PubMed1996

Passive transfer of immediate hypersensitivity and airway hyperresponsiveness by allergen-specific immunoglobulin (Ig) E and IgG1 in mice.

In a proportion of atopic asthmatics, exposure to a relevant antigen is followed by chronic inflammation in the airways leading to altered airway responsiveness (AR). However, the mechanisms underlying the development of airway hyperresponsiveness still remain unclear. To elucidate the relationship between IgE-mediated reactions and airway hyperresponsiveness, a murine model of passive sensitization and airway challenge with ovalbumin (OVA) was developed using anti-OVA IgE and IgG antibodies from murine B cell hybridomas. Passive sensitization by intravenous injection of anti-OVA IgE resulted in immediate cutaneous hypersensitivity and, after airway challenge with OVA on two consecutive days, increased AR in BALB/c and SJL mice. Increased numbers of eosinophils were observed in bronchoalveolar lavage fluid, in cells extracted from the lungs, and in the peribronchial areas of BALB/c mice passively sensitized with IgE and challenged through the airways compared with nonsensitized mice. Eosinophil peroxidase activity was also elevated in lung tissue from these mice. Passive sensitization with anti-OVA IgG1 but not IgG2a or IgG3 was similarly associated with development of skin test reactivity and increased AR after airway challenge, accompanied by an increase in eosinophils in bronchoalveolar lavage fluid. These data suggest that IgE/IgG1-mediated reactions together with local challenge with antigen can result in allergic inflammation resulting in altered airway function.

Allergens↗
PubMed1996

Prevention of the development of immediate hypersensitivity and airway hyperresponsiveness following in vivo treatment with soluble IL-4 receptor.

The effects of local versus systemic treatment with soluble IL-4 receptors (sIL-4R) were tested in a model of allergen-induced immediate hypersensitivity responses in BALB/c mice. Mice sensitized through the airways to ovalbumin (OVA) by ultrasonic nebulization once a week for 4 weeks developed increased serum anti-OVA IgE and IgG1 antibody titers and these were accompanied by immediate-type skin test responses to the allergen. These responses were also associated with the development of increased airway responsiveness (AR) as monitored by electrical field stimulation of tracheal smooth muscle preparations in vitro. Sensitized mice, treated by intraperitoneal injections of sIL-4R (150 micrograms/injection) administered in parallel to the sensitization protocol, developed significant suppression of anti-OVA IgE, anti-OVA IgG1 antibody production and of immediate cutaneous hypersensitivity responses. Airway responsiveness was normalized to some extent. Total IgE production was only slightly reduced. These effects were comparable to the findings following intraperitoneal injection of monoclonal anti-IL-4 antibody. Administration of sIL-4R via the airways was also effective in inhibiting the development of immediate hypersensitivity responses, including IgE production, and was more potent in normalizing airway responsiveness. These effects were achieved at lower concentrations than needed for systemic treatment. These data suggest that delivery of sIL-4R via the airways can effectively modulate the development of immediate hypersensitivity and airway hyperresponsiveness in response to aerosolized allergen.

Aerosols↗
PubMed1996

Pretreatment with allergen prevents immediate hypersensitivity and airway hyperresponsiveness.

The ability of subcutaneous pretreatment with an immunogenic peptide derived from Fel d I, the major cat protein, to suppress the development of allergic responses was examined in a mouse model of antigen-induced sensitization. BALB/c mice exposed to aerosolized Fel d I chain 1 peptide developed antigen-specific IgE responses, immediate cutaneous reactivity to the peptide, and increased airway responsiveness (AR). Both subcutaneous and intraperitoneal administration of the peptide prior to sensitization caused a 50% reduction in cutaneous reactivity which was associated with a decrease in serum anti-Fel d I chain 1 IgE and IgG1 antibody responses and an increase in specific IgG. Pretreatment with the peptide also suppressed spleen and lymph node proliferative responses to the peptide. However, only subcutaneous peptide injections could prevent the development of increased AR. Transfer of spleen cells from subcutaneously peptide-treated mice to sensitized recipients reduced serum antigen-specific IgE and IgG1 antibody responses and skin test reactivity, and prevented alterations in AR. These data suggest that IgE (and IgG1) responses and airway hyperresponsiveness induced by allergen sensitization via the airways can be modulated by subcutaneous administration of peptide. Further, the results define a model for investigating the modulatory effects of subcutaneous administration of immunogenic peptides or protein on an ongoing allergic response.

Aerosols↗
PubMed1995

Modulation of acetylcholine release in rabbit airways in vitro.

We investigated the effects of substance P (SP) and vasoactive intestinal peptide (VIP) on acetylcholine (ACh) released from nerve endings by electrical field stimulation (EFS) in rabbit airways in vitro. ACh release was directly measured using high-performance liquid chromatography with electrochemical detection. Airway smooth muscle (ASM) segments, dissected from the midtrachea down to the left mainstem bronchus, were obtained from New Zealand White rabbits and mounted in organ baths containing modified Krebs-Henseleit solution, physostigmine, and choline. EFS at 20 Hz was delivered for 15 min to define baseline ACh release (pmol per gram of tissue per minute). There were no significant regional differences in ACh release during these baseline studies. A second stimulation was then performed in the absence (control) and presence of one or more of the following substances: SP (10(-7) M), a nonpeptide antagonist of the NK1 receptor (10(-7) M CP-96,345; Pfizer), and VIP (10(-7) M). Results for ACh release are expressed as a percentage of the first stimulation (means +/- SE). SP significantly increased ACh release in all ASM segments. This effect was abolished by CP-96,345. VIP alone did not affect ACh release. However, it significantly decreased SP-induced ACh release in all ASM segments. We conclude that SP significantly increases ACh release, thus facilitating cholinergic neurotransmission; its effect is abolished by CP-96,345. VIP decreases SP-induced ACh release, indicating a modulatory effect on cholinergic neurotransmission.

Acetylcholine↗
PubMed1995

Human respiratory syncytial virus affects nonadrenergic noncholinergic inhibition in cotton rat airways.

A dysfunction of the nonadrenergic noncholinergic inhibitory (NANCi) system has been invoked as a possible mechanism underlying or contributing to altered airway function. In the present study we assessed whether human respiratory syncytial virus (HRSV) infection affects the airways' neurally mediated contractile and relaxant (NANCi) responses in vitro. NANCi responses were studied on tracheal smooth muscle (TSM) segments obtained from young adult cotton rats, a well-established model for HRSV infection. To assess NANCi responses, TSM segments were removed and placed in tissue baths containing modified Krebs-Henseleit, atropine (1 x 10(-6) M) and propranolol (5 x 10(-6) M). After contraction with neurokinin A (1 x 10(-5) M), electrical field stimulation (EFS) was applied at stimulation frequencies ranging from 5 to 30 Hz. The NANCi responses were measured and expressed as the mean (+/- SE) percent relaxation. To evaluate neurally mediated contractile responses, full frequency response curves (0.5-30 Hz) to EFS were also performed. We found significantly decreased NANCi responses in TSM segments obtained from infected cotton rats (n = 12) compared with control animals (n = 9) (P < 0.002). Furthermore, the contractile responses to EFS were increased in infected animals compared with the control group (P = 0.0001). These findings demonstrate that HRSV infection leads to an enhanced contractile response to EFS and a significant decrease in NANCi response in cotton rat airways in vitro. This disruption of the neural control of airways may lead to the development of altered airway function.

Animals↗
PubMed1995

SP-induced contraction of airway smooth muscle in normal and allergen-sensitized rabbits: mechanism of action.

We studied the mechanisms involved in the airway smooth muscle (ASM) contraction to substance P (SP) in normal (control) and allergen-sensitized (immune) rabbits as well as immune rabbits exposed to allergen via the airways (immune challenged). Cumulative concentration-response curves to SP (1 x 10(-9) to 1 x 10(-4) M) were performed in ASM segments in the absence and presence of atropine (10(-5) M) in vitro. The maximal contractile response (g tension/g tissue) at 10(-4) M SP and ASM contractions at various concentrations of SP were expressed as means +/- SE. We found no difference in the contractile response to SP between control and immune animals. ASM segments obtained from immune-challenged rabbits were more responsive to SP. Atropine shifted to the right the concentration-response curves and decreased the maximal ASM contraction at 10(-4) M SP in all three groups; this effect, however, was greater in immune-challenged tissues. These findings demonstrate an increased contractile response to SP in immune-challenged animals mediated by a more pronounced facilitation of cholinergic neurotransmission. We conclude that the final ASM response to SP is the result of a complex interaction between direct effects on ASM and indirect effects through modulation of cholinergic neurotransmission.

Allergens↗
PubMed1995

Transfer of immediate hypersensitivity and airway hyperresponsiveness by IgE-positive B cells.

The role of allergen-specific sIgE+ B cells in the development of airway hyperresponsiveness to electrical field stimulation was examined in a murine model of allergic sensitization. Ovalbumin (OVA)-specific B cells (OVA+) were isolated from mice that were sensitized to aerosolized OVA. The OVA+ B cell population was shown to be distinct from the remaining, non-OVA-responsive B cells (OVA-). There was a high frequency of sIgE+ B cells and a low frequency of sIgG+ B cells in the OVA+ population compared with the OVA- population, where the ratio was reversed. Although both populations produced immunoglobulin in vitro, only the OVA+ cells secreted anti-OVA antibodies. Transfer of 10(6) OVA+ B cells or as few as 5 x 10(4) OVA+/sIgE+ B cells was able to transfer the capability for anti-OVA IgE synthesis and cutaneous reactivity to OVA in naive recipients. Exposure to OVA via the airways in addition to transfer of OVA+ B cells was necessary for development of airway hyperresponsiveness, whereas recipients challenged with an irrelevant allergen, ragweed, had normal airway function. Transfer of up to 10(7) OVA- B cells failed to induce production of anti-OVA IgE. Despite production of polyclonal IgE, recipients of OVA- B cells did not develop airway hyperresponsiveness after OVA challenge. We conclude that both allergen-specific IgE production and local challenge via the airways with specific allergen are necessary to change airway function in this model.

Animals↗
PubMed1995

Asthma in infants and small children.

The wheezy young child is a particularly challenging patient to treat. This article focuses on a diagnostic approach and some of the treatment issues peculiar to this age group. Specifically addressed are (1) the problem of differentiating asthma from wheezy bronchitis in babies and the clinical implications of this; (2) general concepts of treating babies in whom many commonly used drugs are not FDA approved; (3) inhalation therapy, especially the use of metered-dose inhalers with spacers; (4) the standard asthma drugs and their beneficial and adverse effects, with particular reference to inhaled steroids; and (5) the nonpharmacologic management of asthma. A brief discussion of long-term outcome is also included.

Asthma↗
PubMed1994

Inhibition of IgE production and normalization of airways responsiveness by sensitized CD8 T cells in a mouse model of allergen-induced sensitization.

The functional role of CD8 T cells in in vivo IgE production, immediate cutaneous reactivity, and altered airways responsiveness (AR) was examined in a murine model of allergen-induced sensitization. Exposure of BALB/c mice to nebulized OVA triggered an IgE anti-OVA response in the serum, immediate-type skin test responses to OVA, and the development of increased AR (as measured by nonspecific reactivity to electrical field stimulation). In spleens of sensitized mice, analysis of the distribution of CD4/CD8 T cell subpopulations revealed an increase in total numbers of CD8 T cells. Transfer of purified spleen CD8 T cells from OVA-sensitized mice (CD8OVA) to sensitized recipients reduced serum IgE anti-OVA production by roughly 50%. Furthermore, studies of in vitro Ig production indicated that mononuclear cells from recipients of CD8 cells (CD8OVA > CD8PBS) produced less IgE and IgG1 antibodies, whereas in vitro IgG2a production was enhanced. The suppression of IgE production in recipients of CD8OVA T cells was associated with the failure to respond to intradermal challenge with OVA. The increase in AR found in sensitized mice was prevented after transfer of CD8OVA cells. When CD8 T cells from nonimmunized animals (CD8PBS) were used for the transfer into sensitized recipients, serum anti-OVA IgE was decreased by only 20%, whereas skin test reactivity and AR were not significantly affected. The ex vivo analysis of the pattern of cytokine-producing lymphocytes by immunofluorescence microscopy indicated that the sensitization procedure increased the fraction of IFN-gamma- and IL-4-positive cells in the spleen. Further in vitro analysis demonstrated that a high percentage of CD8 T cells were positive for IFN-gamma, whereas IL-4 was produced mainly by CD4 T cells. These data suggest that CD8 T cells may play an important role in the negative regulation of IgE production and AR and that IFN-gamma may be a relevant mediator of the functions of CD8 T cells in this model.

Animals↗
PubMed1994

Decrease in the airways' nonadrenergic noncholinergic inhibitory system in allergen sensitized rabbits.

A decrease in the airways' nonadrenergic noncholinergic inhibitory (NANC-i) system is one of the mechanisms that may contribute to allergen-induced changes in neural control within airways. We measured the airways' neurally mediated contractile and relaxant (NANC-i) responses in tracheal segments and left mainstem bronchus (LMB) from normal (control), immune (ragweed sensitized), and immune challenged rabbits. Immune rabbits were sensitized to mixed ragweed extract through parenteral injections from birth, while the immune challenged group had an additional airway exposure to aerosolized ragweed 48 hours prior to the in vitro studies. Neurally mediated contractile responses to electrical field stimulation (EFS) were increased in the immune challenged group, with the increase most significant in tracheal smooth muscle at a stimulation frequency of 20 Hz. To assess NANC-i responses, airway smooth muscle (ASM) segments from these groups were placed in tissue baths containing atropine (10(-6) M) and propranolol (5 x 10(-6) M). After contraction of the tissue with neurokinin A (NKA, 10(-5) M), the NANC-i response to EFS at 20 Hz was measured and reported as the mean (+/- SEM) percent relaxation. No significant differences were seen in the contractile responses of ASM segments to NKA among the three groups. The tracheal segments showed a significantly different NANC-i relaxation response among all groups: in the control group, 29.1 +/- 3.7; in the immune group 15.8 +/- 2.3%; and in the immune challenged group, 2.1 +/- 4.2%.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergens↗
PubMed1994

Legionella and Pneumocystis pneumonias in asthmatic children on high doses of systemic steroids.

Asthma is increasingly treated as an inflammatory disease with inhaled and/or systemic corticosteroids. We report 3 cases of unusual pneumonias associated with high doses of oral steroids. Two patients contracted Legionella pneumonia and one patient contracted Pneumocystis carinii pneumonia. With increasing usage, it is important for physicians to be aware of the possible infectious complications of high dose steroids. This report highlights the risk of corticosteroid treatment in asthma in predisposing to opportunistic infections that have not heretofore been readily associated with asthma.

Asthma↗
PubMed1994

Increased acetylcholine release in tracheas from allergen-exposed IgE-immune mice.

Increased release of acetylcholine (ACh) from airway parasympathetic nerve endings is one mechanism that may contribute to increases in airway responsiveness in immunoglobulin E (IgE)-immune allergen-exposed animals. We measured ACh released from murine tracheas following electrical field stimulation in vitro. BALB/c mice were immunized by exposure to an aerosol of 1% ovalbumin in sterile phosphate-buffered saline for 20 min/day for 10 days. At this time, levels of ovalbumin-specific IgE were proportionately higher than ovalbumin-specific IgG. As a control, nonimmune mice were similarly exposed to phosphate-buffered saline alone. Forty-eight hours after the last aerosol, tracheas were removed for assessment of either the contractile responses to electrical field stimulation and a cholinergic agonist (methacholine or ACh) or release of ACh produced by electrical field stimulation. ACh in the bath was measured using high-performance liquid chromatography with electrochemical detection. The stimulation frequencies causing one-half the maximal contractile response to electrical field stimulation were 4.1 +/- 0.2 and 2.8 +/- 0.2 Hz (P = 0.0001) for nonimmune and immune mice, respectively, whereas the molar concentrations of methacholine causing one-half of the maximal contractile response did not significantly differ. In addition, the dose-response curves of immune and nonimmune tracheas to ACh were superimposable. A significant increase in ACh release was demonstrated at both 10 and 20 Hz in tracheas from immune mice. ACh release (pmol.g tissue-1.min-1) from nonimmune and immune murine tracheas, respectively, were 140 +/- 8 and 205 +/- 22 (P = 0.013) at 10 Hz and 147 +/- 13 and 227 +/- 14 (P = 0.008) at 20 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1994

Maturation of nonadrenergic noncholinergic inhibitory system in normal and allergen-sensitized rabbits.

We investigated the functional existence of the nonadrenergic noncholinergic inhibitory (NANCi) system in developing rabbit airways in vitro. Furthermore, we evaluated the effect of parenteral exposure to a specific allergen (ragweed) on the maturation of this neural pathway. NANCi responses were studied on tracheal smooth muscle (TSM) segments obtained from normal and ragweed-sensitized New Zealand White rabbits at 1, 2, 4, and 12 wk of age. The TSM segments were removed and placed in tissue baths containing modified Krebs-Henseleit solution, atropine (1 x 10(-5) M), and propranolol (5 x 10(-6) M). After contraction with neurokinin A (1 x 10(-5) M), electrical field stimulation was applied at stimulation frequencies ranging from 5 to 30 Hz to determine the frequency that produced maximal relaxation. The NANCi response to EFS was measured and expressed as the mean (+/- SE) percent relaxation at 20 Hz, because this stimulation frequency gave the maximal NANCi response at each age studied. TSM segments obtained from control rabbits at 1 wk of age did not demonstrate a NANCi response at the frequencies of stimulation used. By contrast, a reproducible NANC relaxation was demonstrated in TSM from 2-, 4-, and 12-wk-old rabbits. The magnitude of this response was 27 +/- 4.7 (n = 10), 29 +/- 4.8 (n = 9), and 37 +/- 4% (n = 18), respectively. The same experiments performed on TSM segments obtained from ragweed-sensitized animals gave significantly decreased values of NANCi response. In 2-, 4-, and 12-wk-old rabbits, the NANCi responses were 11.5 +/- 3.4 (n = 9), 11 +/- 2 (n = 13), and 16 +/- 4.2% (n = 14).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1994

Increased airways responsiveness in mice depends on local challenge with antigen.

In Balb/C mice, painting the skin with ovalbumin (OVA) over a period of 14 days resulted in sensitization of the animals. This was documented by the appearance of OVA-specific IgE and IgG1 antibodies and increased total serum IgE levels. In addition, in regional (inguinal) lymph nodes of sensitized animals, OVA-specific T cell proliferative responses and increased IgE and IgG production could be detected in vitro. Sensitized animals also developed immediate cutaneous responses to intradermal injection of OVA. In contrast to previous results following OVA sensitization via the airways, increased airways responsiveness to electrical field stimulation (AREFS) of tracheal smooth muscle preparations was not observed in skin-sensitized mice. Only 24 h after a single local challenge of the airways with aerosolized OVA on Day 14 could a significant increase in AREFS be observed in skin-sensitized but not nonsensitized control mice. These data indicate that sensitization of Balb/C mice to OVA via the skin provides an effective means for inducing a systemic IgE and IgG1 antibody response and immediate cutaneous hypersensitivity. Despite these IgE and IgG1-mediated responses, however, the development of altered function as reflected in an increase in AREFS was dependent on challenge with the allergen via the airways.

Administration, Cutaneous↗
PubMed1994

Effect of AT-125 on the metabolism of propachlor and the glutathione conjugates of propachlor and bromobenzene in rat.

1. Dosing rats with the gamma-glutamyl-transpeptidase inhibitor AT-125 results in the excretion of free glutathione in the urine of rat: this treatment did not lead to the excretion of glutathione conjugates of orally dosed xenobiotics, neither did AT-125 increase the biliary excretion of glutathione conjugates. 2. Dosing rat with AT-125 prior to dosing with 2-chloro-N-isopropylacetanilide decreased the excretion of 2-methylsulphonylacetanilide metabolites from 23% of the dose to < 0.5%. 3. We conclude that glutathione and glutathione-xenobiotic conjugates are probably not processed in vivo by the same pathway, and that AT-125 can alter the in vivo transport of mercapturic acid pathway metabolites.

Acetanilides↗