Mammalian Defensins: Structures and Mechanism of Antibiotic Activity

Antibiotic peptides are important effector molecules in host-parasite interactions throughout the living world. In vertebrates, they function in first-line host defense by antagonizing a wide range of microbes including bacteria, fungi, and enveloped viruses. The antibiotic activity is thought to be based on their cationic, amphipathic nature, which enables the peptides to impair vital membrane functions. Molecular details for such activities have been elaborated with model membranes; however, there is increasing evidence that these models may not reflect the complex processes involved in the killing of microbes. For example, the overall killing activity of the bacterial peptide antibiotic nisin is composed of independent activities such as the formation of target-mediated pores, inhibition of cell-wall biosynthesis, formation of nontargeted pores, and induction of autolysis. We studied the molecular modes of action of human defense peptides and tried to determine whether they impair membrane functions primarily and whether additional antibiotic activities may be found. We compared killing kinetics, solute efflux kinetics, membrane-depolarization assays, and macromolecular biosynthesis assays and used several strains of Gram-positive cocci as test strains. We found that membrane depolarization contributes to rapid killing of a significant fraction of target cells within a bacterial culture. However, substantial subpopulations appear to survive the primary effects on the membrane. Depending on individual strains and species and peptide concentrations, such subpopulations may resume growth or be killed through additional activities of the peptides. Such activities can include the activation of cell-wall lytic enzymes, which appears of particular importance for killing of staphylococcal strains

Enzymes of B-Ring-Deoxy Flavonoid Biosynthesis in Elicited Cell Cultures of "Old Man" Cactus (Cephalocereus senilis)

Article on enzymes of b-ring-deoxy flavonoid biosynthesis in elicited cell cultures of "Old Man" cactus (Cephalocereus senilis)

Evaluation of the Thrombelastograph Targeted Coagulation Assessment

Extracorporeal circulation predisposes patients to hemorrhagic risk which may increase both homologous transfusion requirements and the need for pharmacological intervention. The aim of this study was to evaluate the efficacy of a new diagnostic coagulation assay utilizing the thrombelastograph (TEG). Following Institutional Review Board approval, blood was drawn from healthy, non-medicated volunteers and four in vitro coagulopathic conditions were created, which included: hyperfibrinolysis (100% lysis), hypofibrinogenemia (<50 mg/dl), and both qualitative (1000 ug/ml nitroglycerin) and quantitative (<50 K/mm3) platelet abnormalities. Each of these four blood samples was then divided among four vials that contained known quantities of either: aminocaproic acid, fresh frozen plasma (FFP), platelet concentrate, or heparinase, and TEG profiles were completed. Twenty-one samples were evaluated and the following results were obtained. Hyperfibrinolysis- 100% correction of fibrinolytic potential in the aminocaproic acid vial, but none in the other vials. Qualitative platelet dysfunction- significantly improved time to coagulation in the platelet vial but not in the FFP, heparinase or aminocaproic acid vials. Quantitative platelet dysfunction- no significant difference observed between any vials. Hypofibrinogenemia- significant improvement in the TEG index in the FFP vial (-2.7 ± 0.5) when compared to the aminocaproic acid ( -8.6 ± 2.5, p<.001), platelet (-6.5 ± 0.5, p<.01) and heparinase (-8.8 ± 2.5, p<.001) vials. We conclude that this coagulation assessment assay may help in identifying the specific source of bleeding during surgeries where hyperfibrinolysis, hypofibrinogenemia, or qualitative platelet dysfunctions are present

Ultrafiltration of the Waste Plasma Effluent from Cardiopulmonary Bypass Circuit Contents Processed with a Cell-Washing Device

Blood conservation methods are commonly practiced throughout most hospitals that conduct cardiothoracic surgery. In an effort to reduce patients' exposure to homologous blood products and due to cost effectiveness of blood conservation techniques, this present study combines autotransfusion of the remaining blood in the extracorporeal circuit and ultrafiltration of the plasma effluent, and describes the resulting product. Seven patients, greater than 19 years of age, requiring cardiopulmonary bypass (CPB) were incorporated into this study. Exclusion criteria included age limitation. At termination of CPB, the remaining blood in the circuit was transferred to an autotransfusion machine and processed. Plasma (1054 ± 206 ml) effluent was collected directly from the centrifugal bowl and processed through a ultrafiltrator, with a constant flow rate and negative pressure, until the plasma effluent concentrated down to an end processed volume of approximately 150 ml. The following variables were either measured or calculated: plasma-concentrate volumes per three minute interval, inlet/outlet pressures of an ultrafiltrator, transmembrane pressure (TMP), plasma free hemoglobin, fibrinogen, total protein, and colloid osmotic pressure. The average ultrafiltrate volume taken off from the plasma effluent was 828 ± 237 ml, with an average ultrafiltrate volume of 115 ml in every three minute interval. The TMP did not change over the first 15 minutes of processing but became significantly elevated at the 18th minute interval and continued to increase and reach a maximum TMP of 286.5 ± 2.1 mmHg at the end of concentration. Fibrinogen levels increased from pre-concentration values of 118.2 ± 64 to 317 ± 177 mg/dl (p=.03) along with increases in plasma free hemoglobin from 97.7 ± 46 to 402.1 ± 180 mg/dl (p=.0002). The total protein concentration increased by over 330% from baseline values. Ultrafiltrating plasma effluent from autotransfused cell salvaged CPB circuit contents could prove beneficial, but further study is required to discover ways to separate unfavorable products, such as activated platelet-leukocyte products and reduced plasma free hemoglobin, and to lower heparin concentrations of the plasma-concentrate

Basal cell carcinoma risk and solar UV exposure in occupationally relevant anatomic sites: do histological subtype, tumor localization and Fitzpatrick phototype play a role? A population-based case-control study

Background!#!A two-fold risk increase to develop basal cell carcinoma was seen in outdoor workers exposed to high solar UV radiation compared to controls. However, there is an ongoing discussion whether histopathological subtype, tumor localization and Fitzpatrick phototype may influence the risk estimates.!##!Objectives!#!To evaluate the influence of histological subtype, tumor localization and Fitzpatrick phototype on the risk to develop basal cell carcinoma in highly UV-exposed cases and controls compared to those with moderate or low solar UV exposure.!##!Methods!#!Six hundred forty-three participants suffering from incident basal cell carcinoma in commonly sun-exposed anatomic sites (capillitium, face, lip, neck, dorsum of the hands, forearms outside, décolleté) of a population-based, case-control, multicenter study performed from 2013 to 2015 in Germany were matched to controls without skin cancer. Multivariate logistic regression analysis was conducted stratified for histological subtype, phototype 1/2 and 3/4. Dose-response curves adjusted for age, age!##!Results!#!Participants with high versus no (OR 2.08; 95% CI 1.24-3.50; !##!Conclusion!#!The risk to develop basal cell carcinoma in highly occupationally UV-exposed skin was doubled consistently, independent of histological subtype, tumor localization and Fitzpatrick phototype

Sampling strategies to capture single-cell heterogeneity.

Advances in single-cell technologies have highlighted the prevalence and biological significance of cellular heterogeneity. A critical question researchers face is how to design experiments that faithfully capture the true range of heterogeneity from samples of cellular populations. Here we develop a data-driven approach, illustrated in the context of image data, that estimates the sampling depth required for prospective investigations of single-cell heterogeneity from an existing collection of samples