Ami Oren

Relation of oxygen uptake to work rate in normal men and men with circulatory disorders

The relation between the increase in oxygen uptake (VO2) and increase in work rate (WR) between unloaded pedaling and maximal work during incremental cycle ergometer exercise was studied in normal men, men with uncomplicated systemic hypertension and ambulatory men with various cardiovascular diseases. The postulation was that impaired peripheral oxygen delivery would reduce the ratio of the oxygen utilized relative to work performed. The ratio of increase in VO2 to increase in WR (delta VO2/delta WR) was relatively constant: 10.29 +/- 1.01 ml/min/W in normal men (n = 54) for exercise 6 to 14 minutes in duration with uniform work increments of 15, 20, 25 or 30 W/min, regardless of age. The value in men with uncomplicated systemic hypertension (n = 24) was not significantly different from that of normal men. However, more than half of the men with peripheral vascular disease (n = 7) or pulmonary vascular disease (n = 5) or men who had electrocardiographic abnormalities during exercise (n = 39) had a significantly lower delta VO2/delta WR, 8.29 +/- 1.17 ml/min/W (p less than 0.05) especially evident as maximal work rates were approached. Thus, delta VO2/delta WR during incremental exercise testing is predictable for normal men and a reduction in this ratio indicates cardiovascular dysfunction.

Determinants of Staphylococcus aureus nasal carriage.

ABSTRACT Nasal carriage of Staphylococcusaureus has been identified as a risk factor for community-acquired and nosocomial infections. We screened 230 donors of diverse ethnic and socioeconomic backgrounds and identified 62 (27%) whose nasal secretions were colonized by S.aureus. In 18 donors in whom the various regions of the nasal luminal surface were separately sampled, the predominant region of S. aureus colonization was the moist squamous epithelium on the septum adjacent to the nasal ostium. Nasal fluid from carriers was defective in killing endogenousS. aureus and nasal carrier isolates ofS. aureus but not a laboratoryS. aureus strain. Transmission electron microscopy revealed that S.aureus isolates incubated in nasal fluid from carriers for 2 h at 37°C were less damaged than those incubated in noncarrier fluid and were coated with an electron-dense layer. Compared with that from healthy donors and patients with acute rhinitis, nasal fluid from carriers contained elevated concentrations of the neutrophil-derived defensins human neutrophil peptides 1 to 3 (47- and 4-fold increases, respectively), indicative of a neutrophil-mediated inflammatory host response to S.aureus colonization. The concentration of the inducible epithelial antimicrobial peptide human β-defensin 2 was also highly elevated compared to that in healthy donors, in whom the level was below the detection limit, or patients with acute rhinitis (sixfold increase). Thus, nasal carriage of S.aureus takes hold in nasal fluid that is permissive for colonization and induces a local inflammatory response that fails to clear the colonizing bacteria.

In human epidermis, β-defensin 2 is packaged in lamellar bodies

Abstract The skin presents a mechanical, as well as an immunological barrier to infection, and displays considerable innate immune capacity. Recently, cultured human keratinocytes were described to produce and export a microbicidal peptide human β-defensin 2 (HBD-2). Immunogold was used to label ultrathin cryosections of stimulated, cultured human epidermis. HBD-2 was found to be stored in the lamellar bodies (LBs) of the stimulated keratinocytes of the spinous layer of the epidermis. HBD-2 was also found in the intercellular space. These findings suggest that HBD-2 is released with the contents of the LBs. Along with other investigations, our findings indicate that the lipid “permeability” barrier of the skin contains antimicrobial substances.

Antimicrobial and anti-inflammatory activity of chitosan-alginate nanoparticles: a targeted therapy for cutaneous pathogens

Advances in nanotechnology have demonstrated potential application of nanoparticles for effective and targeted drug delivery. Here, we investigated the antimicrobial and immunological properties and the feasibility of using nanoparticles to deliver antimicrobial agents to treat a cutaneous pathogen. Nanoparticles synthesized with chitosan and alginate demonstrated a direct antimicrobial activity in vitro against Propionibacterium acnes, the bacterium linked to the pathogenesis of acne. By electron microscopy imaging, chitosan-alginate nanoparticles were found to induce disruption of the P. acnes cell membrane, providing a mechanism for the bactericidal effect. The chitosan-alginate nanoparticles also exhibited anti-inflammatory properties as they inhibited P. acnes induced inflammatory cytokine production in human monocytes and keratinocytes. Furthermore, benzoyl peroxide, a commonly used anti-acne drug, was effectively encapsulated in the chitosan-alginate nanoparticles and demonstrated superior antimicrobial activity against P. acnes compared to benzoyl peroxide alone while demonstrating less toxicity to eukaryotic cells. Together, these data suggest the potential utility of topical delivery of chitosan-alginate nanoparticle encapsulated drug therapy for the treatment of dermatologic conditions with infectious and inflammatory components.

Diffusing Capacity for Carbon Monoxide as a Predictor of Gas Exchange during Exercise

In patients with pulmonary disease, the diffusing capacity for carbon monoxide has been used to predict abnormal gas exchange in the lung. However, abnormal values for arterial blood gases during exercise are likely to be the most sensitive manifestations of lung disease. We compared the single-breath diffusing capacity for carbon monoxide at rest with measurements of gas exchange during exercise, including arterial oxygen tension, the alveolar-arterial difference in oxygen tension, the arterial-end-tidal difference in carbon dioxide tension, and the dead-space/tidal-volume ratio in 276 current and former shipyard workers. Sixteen workers had a diffusing capacity for carbon monoxide below 70 percent of predicted; one or more measurements of gas exchange during exercise were abnormal in 14. In contrast, of 96 men who had abnormal gas exchange during exercise, only 14 had a diffusing capacity for carbon monoxide below 70 percent of predicted. Neither the type nor the degree of abnormality in gas exchange could be predicted from the diffusing capacity. We conclude that diffusing capacity for carbon monoxide at rest is a specific but insensitive predictor of abnormal gas exchange during exercise and that, if indicated, measurements of arterial blood gases should be obtained during exercise.

Defensins: microbicidal and cytotoxic peptides of mammalian host defense cells.

Multicellular organisms contain specialized cells (granulocytes, macrophages, cytotoxic lymphocytes, natural killer cells, etc.) that can selectively destroy invading microbes, larger parasites, and abnormal or senescent host cells. All cells that manifest microbicidal/cytotoxic activity contain cytoplasmic granules that are released on contact onto the appropriate target. Analysis of these granules has shown that they contain a variety of lyric enzymes and microbicidal or cytotoxic proteins. Although it is by no means certain how individual microbicidal and cytotoxic proteins contribute to the destruction of their targets, the ability of these proteins to permeabilize biological membranes appears to be a common theme. The granules of neutrophils, eosinophils, and killer lymphocytes have been particularly rich sources of such proteins. This review is focussed on defensins, small and highly abundant microbicial and cytotoxic peptides of mammalian phagocytes.

Membrane-targeted synergistic activity of docosahexaenoic acid and lysozyme against Pseudomonas aeruginosa.

Antimicrobial polypeptides, including lysozymes, have membrane perturbing activity and are well-documented effector molecules of innate immunity. In cystic fibrosis, a hereditary disease with frequent lung infection with Pseudomonas aeruginosa, the non-esterified fatty acid DA (docosahexaenoic acid), but not OA (oleic acid), is decreased, and DA supplementation has been shown to improve the clinical condition in these patients. We hypothesized that DA may, either alone or in conjunction with lysozyme, exert antibacterial action against Ps. aeruginosa. We found that DA and lysozyme synergistically inhibit the metabolic activity of Ps. aeruginosa, in contrast with OA. Electron microscopy and equilibrium dialysis suggest that DA accumulates in the bacterial membrane in the presence of lysozyme. Surface plasmon resonance with live bacteria and differential scanning calorimetry studies with bacterial model membranes reveal that, initially, DA facilitates lysozyme incorporation into the membrane, which in turn allows influx of more DA, leading to bacterial cell death. The present study elucidates a molecular basis for the synergistic action of non-esterified fatty acids and antimicrobial polypeptides, which may be dysfunctional in cystic fibrosis.

Effects of Chronic Acid-Base Changes on the Rebreathing Hypercapnic Ventilatory Response in Man

The CO2 rebreathing method can be very useful to test the hypercapnic ventilatory response in patients, including those with chronic acid-base changes (e.g. chronic metabolic acidosis due to renal failure). The ventilatory response to hypercapnia (CO2-R) was measured in 4 normal men by the rebreathing method under control conditions (CaCO3: 0.1 g.kg-1.day-1) and with induced metabolic acidosis (NH4Cl: 0.3 g.kg-1.day-1) and alkalosis (NaHCO3: 0.7 g.kg-1.day-1). The slope of the CO2-R did not change as a result of the acid-base alterations, but was shifted to the left of normal by metabolic acidosis, and to the right by metabolic alkalosis. These results compare favorably with previous reports on the CO2-R as measured by the steady-state technique, and validate the rebreathing method as a reliable and useful technique for evaluating CO2-R in man with altered acid-base states.

Murine 32D cl3 cells — A transfectable model of phagocyte granule formation

Granulocytes expose phagocytized microbes to microbicidal substances that are stored in cytoplasmic granules and delivered by fusion to the phagocytic vacuoles (phagosomes). To determine if the murine myeloid cell line 32D c13 is suitable as a genetic model of protein translocation to granules and phagosomes, we permanently transduced 32D c13 cells with human HNP-1 defensin cDNA, incubated them with opsonized zymosan, and immunostained them for human defensin HNP-1. Although their phagocytic rate was much slower than that of neutrophil granulocytes, 32D c13 cells ingested zymosan into vacuoles that accumulated most of the transgenic defensin. The 32D c13 cell line should be useful for studies of the targeting of proteins to granules and phagosomes.