Search PubMed⌕ Search

Biomedical subjects

B S Polla

Publications and source records attributed to B S Polla.

At least 127 records · Page 7Linked to original sources
PubMed1990

Calcium and the heat-shock response in the human monocytic line U-937.

In the human monocytic line U-937, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] increases cytosolic free calcium concentration ([Ca2+]i). 1,25-(OH)2D3 also enhances the synthesis of heat-shock proteins (HSPs) when U-937 cells are exposed to elevated temperatures. To establish whether these two effects of 1,25-(OH)2D3 are related, we examined the effects of calcium on the heat-shock (HS) response, as well as the influence of 1,25-(OH)2D3 on this system. The equilibrium dissociation constant (Kd) of the fluorescent probe used to measure [Ca2+]i, fura-2, at 37 and 45 degrees C was found to be 191 and 234 nM, respectively. Exposure of U-937 cells to 45 degrees C did not increase [Ca2+]i under conditions in which active efflux of the dye was prevented by the organic anion transport inhibitor probenecid (1 mM). In cells preincubated in calcium-free medium, with subsequent addition of 4 mM EGTA before HS, or exposed to the calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide (W-7), the increase in HSPs synthesis was not affected. Cell viability, assessed by [3H]thymidine uptake, was not different between cells exposed to HS in calcium-containing or calcium-free media. Moreover, the effects of 1,25-(OH)2D3 on the HS response were also observed in a calcium-depleted medium, indicating that the effects of 1,25-(OH)2D3 on HSP synthesis were not mediated by [Ca2+]i.

Benzofurans↗
PubMed1990

Heat (shock) and the skin.

Whereas hyperthermia has long been used in dermatology for the therapy of diseases as diverse as syphilis, gonorrhea, psoriasis or melanoma, the understanding of the biological effects of heat shock on the skin attracts new interests to an old field. The proteins induced by heat (stress, or heat shock proteins) appear to play a general role in protection from cellular injury and eventually in the natural defences from solar radiation. On the other hand, these ubiquitous proteins may also be involved in the immunopathology of diseases such as systemic lupus erythematosus or leprosy.

Heat-Shock Proteins↗
PubMed1990

Bleomycin primes monocytes-macrophages for superoxide production.

Bleomycin (BLM) induces lung inflammation and subsequent fibrosis in humans and animal models. We hypothesized that monocytes-macrophages represent target cells for BLM toxicity and participate in the initial stages of pulmonary inflammation. We developed an animal model of early lung lesions using systemic administration of BLM (2 U.100 g-1 body weight over 5 days) (BLM-rats). We observed a significant decrease in body weight and in serum angiotensin converting enzyme activity in BLM-rats as compared to matched controls rats, but no evidence of fibrosis was seen in optic microscopy of the lungs from BLM-rats. In contrast, electron microscopy revealed accumulation of intracapillary polymorphonuclear leucocytes and unusual presence of eosinophils. We then investigated the in vivo effects of BLM on the respiratory burst of monocytes-macrophages. As compared to control rats, production of superoxide (O2-) by alveolar macrophages from BLM-rats was increased upon stimulation with either phorbol myristate acetate (21.04 +/- 2.78 versus 11.45 +/- 2.26 nmol.10(6) cells.20 min-1, p less than 0.05) or opsonized zymosan (9.35 +/- 0.87 versus 7.03 +/- 0.66 nmol.10(6) cells.20 min-1, p less than 0.05). We also found in BLM-rats an increased number of circulating monocytes and an increased production of O2- by these cells. Monocytes-macrophages may represent a target cell in the early events of BLM toxicity in vivo and the increased production of O2- by these cells participates in tissue injury in pulmonary fibrosis.

Animals↗
PubMed1990

Precipitins in bird breeder's disease: how useful are they?

Precipitating antibodies to avian antigens play a controversial role in the diagnosis of bird breeder's disease (BBD). In order to establish the sensitivity, specificity and accuracy of precipitins in our laboratory, we conducted a prospective study including 128 sera received in 1988 for determination, by immunoelectrophoresis, of avian precipitins. Accurate information was obtained for 90 patients; definitive clinical diagnosis was given by the patient's own physician. We found a high sensitivity (86%), specificity (93%) and accuracy (92%) of avian precipitins in the diagnosis of BBD. Bayes' theorem was applied to determine the predictive value of the test with varying disease prevalence, and established that precipitins were particularly valuable for low or medium a priori probability. Using the receiver operating characteristic (ROC) curve we evaluated the effects of varying the positivity threshold of precipitins. The threshold used in this study appeared to offer the best compromise between sensitivity and specificity. These results suggest that the diagnostic value of avian precipitins in the work-up of BBD should be reconsidered, also because they represent a simple, cheap and non-invasive diagnostic test.

Adolescent↗
PubMed1989

[Use of precipitins in the diagnosis of bird fancier's lung: apropos of 2 cases].

Bird breeder's disease is a frequent diagnosis among the forms of extrinsic allergic alveolitis seen in the urban environment. We report two illustrative cases and discuss the respective roles of broncho-alveolar lavage cells and precipitating antibodies against avian antigens in the diagnostic work-up and the pathogenesis of the disease. In 1988 we evaluated over 100 sera from all over Switzerland with clinical suspicion of bird breeder's disease. In this cohort preliminary results show sensitivity of 85% and specificity of 92% for the presence of precipitins against avian antigens in the diagnosis of bird breeder's disease. The results suggest that this non-invasive test deserves revaluation as a diagnostic tool in bird breeder's disease.

Alveolitis, Extrinsic Allergic↗
PubMed1989

1,25-dihydroxyvitamin D3 induces responsiveness to the chemotactic peptide f-Met-Leu-Phe in the human monocytic line U937: dissociation between calcium and oxidative metabolic responses.

In the human premonocytic line U937, 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) induces a functional NADPH oxidase, that is responsive to both phorbol esters and opsonized zymosan. The chemotactic peptide f-Met-Leu-Phe (fMLP) did not, however, induce superoxide generation by these cells. This was not due to the absence of receptors for fMLP. Although there was no significant binding of [3H]-fMLP to undifferentiated U937 cells, preincubation with 1,25-(OH)2D3 induced expression of specific and saturable binding sites. Moreover, fMLP induced a rapid and reversible rise in cytosolic free Ca2+ concentration ([Ca2+]i) in 1,25-(OH)2D3-treated U937 cells, but not in control or 24,25-dihydroxyvitamin D3 (24,25-(OH)2D3)-treated cells. This [Ca2+]i response was dependent on concentrations of both fMLP and 1,25-(OH)2D3 and was observed at physiologic concentrations of the hormone (approximately 25 pM). The rise in [Ca2+]i induced by fMLP in 1,25-(OH)2D3-treated U937 cells was blocked by pertussis toxin and presumably mediated by inositol (1,4,5)-trisphosphate generation. These results indicate that in U937 cells differentiated with 1,25-(OH)2D3, inositol phosphate-mediated [Ca2+]i responses to fMLP are uncoupled from NADPH oxidase activation.

Calcitriol↗
PubMed1988

[Humidifier disease. Role of endotoxins and precipitating antibodies].

A case of an acute form of humidifier disease secondary to the inhalation of endotoxins (humidifier fever) is reported. The respective roles of endotoxins and precipitating antibodies in the diagnosis of the two forms of humidifier disease are discussed. This appears to be an important epidemiological problem in Switzerland, since the authors see approximately one case a month. With respect to treatment, preventive measures are necessary and usually sufficient.

Adult↗
PubMed1988

Heat shock inhibits NADPH oxidase in human neutrophils.

The heat shock response is a conserved, physiological, transient cellular response to injury. Several studies have suggested a link between the heat shock response and oxidative injury. We have investigated the effects of heat shock on superoxide anion generation by human neutrophils stimulated with opsonized zymosan or phorbol myristate acetate. Human neutrophils exposed to elevated temperatures or to the heavy metal cadmium synthetized a variety of heat shock proteins. In parallel to this protein synthesis, we observed a selective, reversible and temperature-dependent inhibition of NADPH oxidase activation, which was independent from variations of cytosolic pH or thiol group oxidation. Inhibition of NADPH oxidase by heat shock appeared related to the synthesis of heat shock proteins and may represent an intrinsic cellular mechanism to down regulate superoxide production.

Cadmium↗
PubMed1988

A tissue-specific DNase I-hypersensitive site in a class II A alpha gene is under trans-regulatory control.

Class II major histocompatibility complex molecules are integral membrane glycoproteins whose distribution is limited to certain tissues. To identify the molecular basis for such specificity, the chromatin configuration of the class II A alpha gene was examined in intact nuclei from various cell types. We show that there are three DNase I-hypersensitive sites in the A alpha gene. One of these sites, located near the promoter region, is specific to cells that normally express class II molecules at some stage of differentiation. Furthermore, this tissue-specific site appears to be under trans-regulatory control.

Animals↗
PubMed1988

1,25-Dihydroxyvitamin D3 increases the toxicity of hydrogen peroxide in the human monocytic line U937: the role of calcium and heat shock.

1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) increases synthesis of heat shock proteins in monocytes and U937 cells and protects these cells from thermal injury. We examined whether 1,25-(OH)2D3 would also modulate the susceptibility of U937 cells to H2O2-induced oxidative stress. Cell viability was assessed by trypan blue exclusion and [3H]thymidine incorporation into DNA. Prior incubation for 24 h with 1,25-(OH)2D3 (25 pM or higher) unexpectedly increased H2O2 toxicity. Since cellular Ca2+ may be a mediator of cell injury we investigated effects of altering extracellular Ca2+ ([Ca2+]e) on 1,25-(OH)2D3-enhanced H2O2 toxicity as well as effects of 1,25-(OH)2D3 and H2O2 on cytosolic free Ca2+ concentration ([Ca2+]f). Basal [Ca2+]f in medium containing 1.5 mM Ca as determined by fura-2 fluorescence was higher in 1,25-(OH)2D3-pretreated cells than control cells (137 versus 112 nM, P less than 0.005). H2O2 induced a rapid increase in [Ca2+]f (to greater than 300 nM) in both 1,25-(OH)2D3-treated and control cells, which was prevented by a reduction in [Ca2+]e to less than basal [Ca2+]f. The 1,25(OH)2D3-induced increase in H2O2 toxicity was also prevented by preincubation with 1,25-(OH)2D3 in Ca2+-free medium or by exposing the cells to H2O2 in the presence of EGTA. Preexposure of cells to 45 degrees C for 20 min, 4 h earlier, partially prevented the toxic effects of H2O2 particularly in 1,25-(OH)2D3-treated cells, even in the presence of physiological levels of [Ca2+]e. Thus 1,25-(OH)2D3 potentiates H2O2-induced injury probably by increasing cellular Ca2+ stores. The 1,25-(OH)2D3-induced amplification of the heat shock response likely represents a mechanism for counteracting the Ca2+-associated enhanced susceptibility to oxidative injury due to 1,25-(OH)2D3.

Calcitriol↗
PubMed1988

Differential induction of class II gene expression in murine pre-B-cell lines by B-cell stimulatory factor-1 and by antibodies to B-cell surface antigens.

We have previously reported that BSF-1 and an alloantibody to the B-cell differentiation antigen Lyb2 induce class II gene expression in two Ia negative pre-B-cell lines. Two questions were asked in these studies. The first question is whether the different stimuli which we and others have shown to induce class II expression in B-cells act via the same signal transduction mechanisms. The second question is whether the traditionally accepted pathway of B-cell differentiation, as defined by immunoglobulin (Ig) gene rearrangement, is applicable to other events that occur during B-cell differentiation. In this report, we have therefore examined a large panel of pre-B-cell lines at different stages of Ig gene rearrangement in an attempt to 1) identify the stage in B-cell development where class II gene expression occurs and where it becomes inducible by BSF-1 or anti-Lyb2, and 2) compare the signal transduction mechanisms used by these ligands. The majority of pre-B-cell lines tested did not express BSF-1 receptors and were consequently noninducible for class II by BSF-1; such cell lines were, however, inducible for class II expression by anti-Lyb2 and, in addition, by antibodies to the B220 membrane glycoprotein. The induction of class II molecules by BSF-1 and by anti-Lyb2 and anti-B220 differed in several respects: 1) Induction by anti-Lyb2 and anti-B220 did not require the presence of BSF-1 receptors; 2) BSF-1 selectively induced class II antigen expression while anti-Lyb2 and anti-B220 induced the expression of other surface markers as well; and 3) PGE2 inhibited BSF-1 but not antibody-mediated class II induction. Finally, the presence of receptors for BSF-1 and the baseline expression of cell surface Ia was shown to be unlinked to Ig gene rearrangement and expression in this series of pre-B-cell lines. The independent regulation of Ia and Ig genes observed here may reflect a branching rather than a linear pathway for B-cell differentiation. The differentiation of pre-B-cells to mature Ig-secreting cells should probably not be defined solely by rearrangement of Ig genes, since this is likely to represent an oversimplified view of B-cell differentiation.

Animals↗
PubMed1987

Murine class II (Ia) molecules associate with human invariant chain.

Polymorphic class II (Ia) major histocompatibility complex (MHC) gene products associate intracytoplasmically with a third nonpolymorphic class II molecule, the invariant chain (Ii), which is encoded by gene(s) unlinked to the MHC. Although the role of the Ii chain in the expression of cell surface Ia molecules is unclear, it has been suggested that the Ii chain helps in the assembly and intracellular transport of class II antigens. In this study, we demonstrate that the murine polymorphic class II antigens of an interspecies mouse-human hybrid, which has segregated the murine invariant chain gene, associates with the human invariant chain gene intracytoplasmically. The murine Ia antigens are expressed on the cell surface and can function as restriction elements in antigen presentation to T cells. The biochemical analysis demonstrates that the regions of the Ii gene that are critical to its interaction with Ia molecules are conserved between species.

Animals↗
PubMed1987

Thermal injury by laser pulses: protection by heat shock despite failure to induce heat-shock response.

Pulsed lasers produce a variety of therapeutically useful effects in tissues by thermal mechanisms. In contrast with conventional hyperthermia, pulsed lasers rapidly induce extremely high temperatures confined to small areas within the tissues. It is not established, however, how cellular damage and repair responses differ between conventional and pulsed laser-induced hyperthermia. We have addressed this question by examining the induction of cellular heat-shock proteins (HSPs) and protection by heat-shock response against pulsed laser vs conventional hyperthermia. Cultured human dermal fibroblasts at confluency were exposed to single microsecond, 10.6-microns-wavelength pulses from a pulsed CO2 laser at radiant exposures between 0 and 1.3 J/cm2. Cell monolayers were directly exposed after removal of overlying medium. Positive control for the ability of the cells to synthesize of HSPs was obtained by heating the cells for 20 min in a water bath at 45 degrees C or 47 degrees C. The cultures were then labeled with L-[35S] methionine (Met), and proteins analyzed by sodium dodecyl sulfate polyacrylamide and two-dimensional gel electrophoresis 2 hr after exposure. The morphological alterations induced by laser or heat were similar under phase contrast microscopy. Conventional heating induced a heat-shock response, with the appearance of HSPs 2 hours after heating. In contrast, synthesis of HSPs could not be detected following laser irradiation, even at exposures decreasing both cell viability and incorporation of [35S] Met into cellular protein. Pre-exposure of cells to temperatures which induced synthesis of HSPs, however, significantly decreased cell death induced by subsequent laser irradiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Line↗
PubMed1987

Hormone 1 alpha,25-dihydroxyvitamin D3 modulates heat shock response in monocytes.

Monocytes, which play a central role in inflammatory reactions, are exposed to elevated temperatures in febrile states or to potential cellular toxins (e.g., reactive oxygen species, immune mediators). We analyzed the heat shock (HS) response in human peripheral blood monocytes and the monocytic line U937 compared with that in dermal fibroblasts. After HS, U937 cells and fibroblasts synthesized mainly the 70- and 83-kDa HS proteins (HSPs), whereas the spectrum of HSPs synthesized by monocytes varied over the range 41-45 degrees C. Incubation with hydrogen peroxide induced synthesis of the 70-kDa HSP in monocytes only. The hormone 1 alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3] that protects monocytes from thermal injury had similar effects on the HS response in U937 cells, increasing synthesis of HSPs and levels of HSP 70 mRNA and partially preventing the decrease in normal protein synthesis, whereas interferon-gamma had no effect. 1,25-(OH)2D3 did not modify the HS response in fibroblasts, although these cells contained cellular receptors for 1,25-(OH)2D3. 1,25-(OH)2D3 could play a specific role in modulating the HS response in monocytes and related cells.

Calcitriol↗