Voluntary versus reflex regulation of maximal exercise flow: volume loops

We determined the efficiency with which maximal exercise ventilatory output could be mimicked voluntarily. Five normal subjects exercised to maximal volitional effort and flow:volume and pressure:volume loops, and end-expiratory lung volume (EELV) and breathing pattern were measured. All subjects increased expiratory flow rate and reduced EELV sufficiently so that the forced vital capacity loop was approximated during at least some portion of expiration, but the generation of pleural pressure remained effective, i.e., equal to or only slightly in excess of that required to produce maximal expiratory flow (Pmax). Subsequently, while at rest, subjects used visual feedback and were able to closely mimic the flow:volume, EELV, and breath-timing achieved in maximal exercise; however: (1) expiratory pressures were excessive and usually exceeded average Pmax; (2) abdominal expiratory muscle activity was increased, as indicated by positive shifts in expiratory gastric pressure; and (3) total ventilatory work was increased 15 to 40% greater than that achieved in maximal exercise. Maximal voluntary efforts (MVV) caused EELV to increase and ventilatory work was increased 20 to 300% greater than during maximal exercise. We conclude that accurate determination of maximal effective ventilatory output available for maximal exercise or precise quantitation of the metabolic cost of producing maximal exercise ventilation requires replication of the pressure:volume, breath-timing, and EELV characteristics achieved in maximal exercise.     

Natural Killer Cell Tolerance in Mice with Mosaic Expression of Major Histocompatibility Complex Class I Transgene

We have studied natural killer (NK) cell tolerance in a major histocompatibility complex (MHC) class I transgenic line, DL6, in which the transgene product was expressed on only a fraction of blood cells. In contrast with transgenic mice expressing the same transgene in all cells, NK cells from mosaic mice failed to reject transgene-negative bone marrow or lymphoma grafts. However, they retained the capability to reject cells with a total missing-self phenotype, i.e., cells lacking also wild-type MHC class I molecules. Tolerance against transgene-negative cells was demonstrated also in vitro, and could be broken if transgene-positive spleen cells of mosaic mice were separated from negative cells before, or after 4 d of culture in interleukin-2. The results provide support for selective NK cell tolerance to one particular missing-self phenotype but not to another. We suggest that this tolerance is determined by NK cell interactions with multiple cells in the environment, and that it is dominantly controlled by the presence of cells lacking a specific MHC class I ligand. Furthermore, the tolerant NK cells could be reactivated in vitro, which suggests that the tolerance occurs without deletion of the potentially autoreactive NK cell subset(s), and that it may be dependent upon the continuous presence of tolerizing cells.NK cells kill tumor cells and virus-infected cells (1–3), regulate hematopoiesis (4), and mediate rejection of MHC mismatched hematopoietic grafts (5, 6). The molecular interactions that take place during NK cell recognition are incompletely understood, but one important factor for NK cell sensitivity is the MHC class I expression of the target. In contrast with T cells, which require MHC class I expression by target cells to initiate lysis, NK cells preferentially kill cells lacking MHC class I expression (7–13). However, NK cell recognition does not depend on complete MHC class I deficiency on the graft. Failure of a target cell to express one specific MHC class I allele may be sufficient to trigger NK cells. This mechanism was suggested as one explanation of hybrid resistance, a phenomenon in which NK cells of F₁ hybrid mice reject parental hematopoietic grafts (reviewed in reference 6). According to the missing-self hypothesis, parental cells would be rejected by F₁ hybrid mice because they fail to express a complete set of host MHC class I alleles (7, 9). Evidence for this hypothesis has been obtained in experiments with MHC class I transgenic mice. Introduction of a D^d transgene in C57BL/6 (B6) mice conveyed NK cell–mediated rejection of nontransgenic, but otherwise syngeneic, grafts (14, 15). Transfection of the D^d gene to the sensitive target led to escape from rejection, suggesting that killing was triggered by missing self (16–18).The results described above suggest that the ability to recognize cells lacking one or several specific MHC class I alleles may represent a general strategy in NK cell function. The identification of MHC class I–specific inhibitory receptors on NK cells, such as the members of the Ly-49 family in the mouse (19–21) and the p58/p70 molecules in human (22–24) have recently given molecular support for this concept. When NK cells carrying these receptors meet target cells expressing the correct MHC class I ligands, lysis is inhibited (19, 21, 25, 26). Furthermore, host MHC class I alleles also influence the expression and function of the inhibitory receptors (27–30). These results emphasize the pivotal role of host MHC class I molecules in the development of NK cell specificity, and raise questions as to how MHC class I molecules educate NK cells and how self-tolerance is secured.In contrast with T and B cells, little is known regarding the mechanisms that induce NK cell tolerance and about the properties of the tolerant NK cells. Attempts to induce tolerance in F₁ mice by inoculating parental cells have been made (31–36), but the interpretations of such experiments have been difficult. First, the recipients were mostly adult mice containing mature NK cells, which may not be ideal for the study of how tolerance would develop normally. Second, the inoculated parental cells were in many cases mature immunocompetent cells, which makes it difficult to distinguish between specific tolerizing effects on NK cells and nonspecific effects of graft versus host disease. Third, there have been no studies of NK cell tolerance to cells lacking specific self-MHC class I alleles.In the present report, we have studied the development of the NK cell repertoire and NK cell tolerance to self in an MHC class I transgenic mouse (DL6) in which the transgene D^d/L^d (α1/α2 domains of D^d coupled to the α3 domain, transmembrane and intracellular domains of L^d) is spontaneously expressed in only a fraction (10–80%) of the hematopoietic cells. This model has allowed us to ask a number of questions about the role of host MHC class I molecules in NK cell development. (a) Are the MHC class I molecules expressed by the NK cells themselves sufficient to determine their specificity, or are interactions with other cells necessary? (b) If interactions with other cells are important, would the presence of cells selectively deficient in a particular MHC class I ligand dominantly control tolerance to these cells? Alternatively, would the interaction with cells expressing a particular ligand be sufficient to instruct NK cells to kill cells lacking this ligand? (c) Is tolerance to different missing-self phenotypes controlled selectively and independently? (d) Are potentially autoreactive NK cells deleted in a selection process or can they persist as anergized or specifically tolerized cells? (e) In the latter case, is the specificity of an NK cell a permanent property or can it be altered?     

Mast cells and angiogenesis

Angiogenesis is tightly regulated by pro- and anti-angiogenic factors. Secreting mast cells are able to induce and enhance angiogenesis via multiple in part interacting pathways. They include mast cell-derived (i) potent pro-angiogenic factors such as VEGF, bFGF, TGF-beta, TNF-alpha and IL-8, (ii) proteinases and heparin, that release heparin-binding pro-angiogenic factors lodged on cell surfaces and in the extracellular matrix (ECM), (iii) histamine, VEGF, and certain lipid-derived mediators that induce microvascular hyperpermeability having pro-angiogenic effects, (iv) chemotactic recruitment of monocytes/macrophages and lymphocytes that are able to contribute with angiogenesis-modulating molecules, (v) activation of platelets that release pro-angiogenic factors, (vi) activation of neighboring stationary non-mast cells, which secrete pro-angiogenic factors, ECM-degrading proteinases and stem cell factor which attracts, mitogenically stimulates and activates mast cells, (vii) auto- and paracrine stimulation of mast cells by stem cell factor, (viii) recruitment of mast cells by pro-angiogenic factors such as VEGF, bFGF and TGF-beta. As a result of ECM-degradation and changes in the microenvironment following initial mast cell secretion, the mast cell populations may change significantly in number, phenotype and function. In tumor models, mast cells have been shown to play a decisive role in inducing the angiogenic switch which precedes malignant transformation. There is, moreover, strong evidence that mast cells significantly influence angiogenesis and thus growth and progression in human cancers.     

Experimental kerma coefficients for carbon deduced from microscopic cross sections at 96 MeV incident neutron energy

The double-differential cross sections for (n, px), (n, dx), (n, tx), (n, 3Hex) and (n, alphax) reactions in carbon have been measured at 96 MeV incident neutron energy. The various charged particles (inclusive spectra) were identified using deltaE-E techniques. From the experimental data, energy- and angle-differential as well as production cross sections were determined, and subsequently the partial and total kerma coefficients. The deduced partial and total kerma coefficients were compared to previous experimental results and theoretical calculations. The findings indicate that the deduced kerma coefficients for the hydrogen isotopes are in good agreement with those deduced from a previous measurement, and that the kerma coefficient values, in particular of the hydrogen isotopes, are systematically higher than values obtained from recent model calculations, which consequently resulted in a total kerma coefficient which is up to 30% higher than predicted by the calculations.     

Dermatophytosis: fluorostaining enhances speed and sensitivity in direct microscopy of skin,nail and hair specimens from dermatology outpatients

Direct microscopy of keratinised specimens is a standard screening procedure that assists clinicians to differentiate true superficial mycoses from non‐fungal disorders of the skin, nail and hair. Most clinical dermatologists use bright‐field microscopy when searching for dermatophyte fungi in clinical samples while laboratory‐based mycologists increasingly favour fluorescence microscopy in order to optimise visualisation of fungal elements. This study compared the validity and speediness of fluorescence microscopy vs. conventional light microscopy when screening for fungi in 206 dermatological samples from dermatology outpatients. Both senior dermatologist and a less experienced investigator (medical student) attained high and comparable levels of specificity (91.7–93.8%), positive predictive value (77.1–81.4%) and negative predictive value (83.7–89.9%) using either method. Fluorostaining with Blankophor prior to fluorescence microscopy increased the sensitivity by 22 ± 1% as compared to light microscopy of unstained samples. For both investigators, the time required to identify fungal elements by the fluorescence‐based technique was reduced by at least 50%, thus improving the performance of direct microscopy in the clinical setting.     

On metronomic chemotherapy: modulation of angiogenesis mediated by VEGE-A

Tumors are angiogenesis dependent. Preclinical studies have shown that well-tolerated continuous low dose, i.e. metronomic, chemotherapy can exert significant antiangiogenic effects pe rse and thereby a greater antitumor influence than conventional chemotherapy with high, spaced-out bolus doses. There are however, no means of quantitatively assessing the antiangiogenic effect of chemotherapy in tumors. We therefore used a surrogate tumor-free, non-surgical rat mesentery model and quantitatively studied the dose effect of metronomic treatment with cisplatin, cyclophosphamide, doxorubicin, fluorouracil and paclitaxel on VEGF-A-mediated angiogenesis, a characteristic of tumors. Cyclophosphamide and paclitaxel treatment exerted significant dose-dependent antiangiogenic effects, whereas doxorubicin treatment produced insignificant effects. By contrast, metronomic cisplatin and fluorouracil treatment occasionally significantly stimulated angiogenesis in a dose-dependent, non-linear manner. To our knowledge, this is the first report of metronomic chemotherapy stimulating angiogenesis in vivo. The data suggest that the angiogenic response to cisplatin, cyclophosphamide, fluorouracil and paclitaxel was significantly influenced by the presence of antioxidants in the vehicles or when co-treated with N-acetylcystein, a widely used free-radical scavenger. The data relating to the metronomic scheduling were compared with bolus treatment data for the identical agent formulations in the same experimental model. Cisplatin, cyclophosphamide and paclitaxel caused approximately the same overall, agent-specific angiogenesis-modulating effects following metronomic and bolus treatments. Moreover, apparently secondary delayed effects of chemotherapy affected capillary sprouting.     

New p53-based anti-cancer therapeutic strategies

Thep53 gene is frequently mutated in human tumours and therefore an important target for therapeutic intervention. Several p53-based strategies for treatment of cancer are currently under development.p53 gene therapy has resulted in tumour regression in patients with lung cancer. A mutant adenovirus can obliterate tumour cells carrying mutant p53 or lacking p53, but is unable to replicate in normal cells. Furthermore, current studies suggest that reactivation of mutant p53 proteins in tumours using small p53-activating molecules may initiate p53-dependent apoptosis and thus eliminate the tumour.     

Expression of serotonergic receptors in psoriatic skin

Psoriasis appears to be influenced by stress, which causes release of adrenal hormones. Serotonin, or hormonal actions on serotonin and serotonin receptors, may have a role in psoriasis. Distribution of serotonin receptors was studied in involved and noninvolved skin in patients with psoriasis and compared to normal skin, by using immunohistochemistry and antibodies to 5-HT1A, 5-HT2A and 5-HT3 receptors (R). There was a decreased (P<0.001) number of 5-HT1AR positive cells, the majority being tryptase positive, in involved and noninvolved psoriatic papillary dermis, compared to normal skin. 5-HTlAR expression was also found in the upper part of the epidermis, on vessel walls and on melanocytes. 5-HT2AR expressing papillary mononuclear cells, CD3 positive, were increased (P<0.001 and P<0.01, respectively) in involved and noninvolved psoriatic skin, compared to normal skin, an increase (P<0.01) also being found in the involved compared to noninvolved skin. Expression of 5-HT3R could be found in the basal epidermal layer of noninvolved but not in the involved skin of psoriasis, where it was only found in the acrosyringium. The present findings are compatible with the 5-HT1A and 5-HT2A receptors having antagonistic functions, and raise the possibility of using receptor specific drugs in the treatment of psoriasis.     

The expression of serotonin transporter protein correlates with the severity of psoriasis and chronic stress

Psoriasis may be worsened by stress and mood disorders. There is an increased expression of the serotonin transporter protein (SERT) in involved psoriatic skin as compared to non-involved psoriatic skin and normal skin. The aim of this study was to investigate if the increased expression of SERT in psoriasis correlates with the severity of disease, chronic stress, and depression. Biopsies from involved and non-involved skin from the back of 20 patients with chronic plaque psoriasis were immunohistochemically analysed, using a monoclonal antibody to SERT. The severity of psoriasis was assessed for each patient using the Psoriasis area and severity index (PASI). Levels of depression and chronic stress were measured using Beck’s Depression Inventory (BDI) and the salivary cortisol test, respectively. A positive correlation (r = 0.53; p < 0.05) between PASI and the numbers of SERT-positive dendritic cells in the epidermis of involved psoriatic skin was determined. We also observed a negative correlation (r = ?0.46; p < 0.05) between salivary cortisol ratio levels and the numbers of SERT-positive cells in the epidermis of involved psoriatic skin, indicating a correlation between SERT expression and chronic stress. The serotonergic system may be involved in the chronic inflammation evident in psoriatic skin. Through modulating the levels of SERT, there might be a therapeutic possibility for reducing chronic inflammation in psoriasis.