Changes in the surface of Dipetalonema viteae (Filarioidea) during its development as shown by comparative peptide mapping

The cuticle of parasitic nematodes, the main contact site with the host, plays an important role in host-parasite interaction and thus also in immunological control. We compared different surface-iodinated life-stages of the filarial worm Dipetalonema viteae (microfilariae, infective 3rd-stage larvae (L3), adult males and females) with respect to changes in their surface composition. Autoradiographs of peptide maps show that all stages present an identical set of peptide spots reflecting common surface protein(s). Spots specific for larvae L3 show that the composition of the iodinated surface differs in microfilariae and adults i.e. it changes during development. Adults show a spot typical for males or females. Identical spots are found in L3. This suggests that a surface component is also sex specifi

Molecular weight determination of membrane proteins by sedimentation equilibrium at the sucrose or Nycodenz-adjusted density of the hydrated detergent micelle11Dedication: In memory of our late friend Martin Zulauf, who crashed with his ‘Ultralight’ on June 17, 1995 in France. He published more than 50 papers on detergents and their interactions with proteins. It was always a pleasure to work with him and we hope that this modest contribution will be in his sense.

AbstractThe determination of the molecular weight of a membrane protein by sedimentation equilibrium is complicated by the fact that these proteins interact with detergents and form complexes of unknown density. These effects become marginal when running sedimentation equilibrium at gravitational transparency, i.e., at the density corresponding to that of the hydrated detergent micelles. Dodecyl-maltoside and octyl-glucoside are commonly used for dissolving membrane proteins. The density of micelles thereof was measured in sucrose or Nycodenz. Both proved to be about 50% lower than those of the corresponding non-hydrated micelles. Several membrane proteins were centrifuged at sedimentation equilibrium in sucrose- and in Nycodenz-enriched solutions of various densities. Their molecular weights were then calculated by using the resulting slope value at the density of the hydrated detergent micelles, i.e. at gravitational transparency, and the partial specific volume corrected for a 50% hydration of the membrane protein. The molecular weights of all measured membrane proteins, i.e. of photosystem II complex, reaction center of Rhodobacter sphaeroides R26, spinach photosystem II reaction center (core complex), bacteriorhodopsin, OmpF-porin and rhodopsin from Bovine retina corresponded within ±15% to those reported previously, indicating a general applicability of this approach

A Sunscreen's Labeled Sun Protection Factor May Overestimate Protection at Temperate Latitudes: A Human In Vivo Study

We lack comparative data on sunscreens with comparable sun protection factors (SPFs), but with different levels of UVA protection, especially against cumulative erythema from repeated suberythemal exposure. Thus, we compared the protection from cumulative sunburn with two sunscreens labeled SPF 6, but with different UVR-absorbing properties, one that absorbs the UVB waveband and the other that absorbs UVB+UVA wavebands. We simulated sunlight typical of temperate latitudes to expose skin daily to suberythemal doses for 13 consecutive days. The study population consisted of eight fair-skinned sun-sensitive healthy young adults. Erythema was assessed by eye and objectively, and the SPF of each sunscreen was modeled with changes in solar UVR with time of day and latitude. The broad-spectrum sunscreen gave much better protection against cumulative erythema than the UVB sunscreen. The explanation for this is that UVA makes a greater contribution toward sunburn at temperate latitudes than under the laboratory conditions in which SPF is tested and assigned. The data support the current trend toward broad-spectrum sunscreen protection. They also show that labeled SPF is much more reliable with broad-spectrum sunscreens because SPF with primarily UVB sunscreens is dependent on time of day and latitude.JID JOURNAL CLUB ARTICLE: For questions, answers, and open discussion about this article, please go to http://www.nature.com/jid/journalclu

Dynamic Elastic Modulus of Porcine Articular Cartilage Determined at Two Different Levels of Tissue Organization by Indentation-Type Atomic Force Microscopy

Cartilage stiffness was measured ex vivo at the micrometer and nanometer scales to explore structure-mechanical property relationships at smaller scales than has been done previously. A method was developed to measure the dynamic elastic modulus, |E(*)|, in compression by indentation-type atomic force microscopy (IT AFM). Spherical indenter tips (radius = ∼2.5 μm) and sharp pyramidal tips (radius = ∼20 nm) were employed to probe micrometer-scale and nanometer-scale response, respectively. |E(*)| values were obtained at 3 Hz from 1024 unloading response curves recorded at a given location on subsurface cartilage from porcine femoral condyles. With the microsphere tips, the average modulus was ∼2.6 MPa, in agreement with available millimeter-scale data, whereas with the sharp pyramidal tips, it was typically 100-fold lower. In contrast to cartilage, measurements made on agarose gels, a much more molecularly amorphous biomaterial, resulted in the same average modulus for both indentation tips. From results of AFM imaging of cartilage, the micrometer-scale spherical tips resolved no fine structure except some chondrocytes, whereas the nanometer-scale pyramidal tips resolved individual collagen fibers and their 67-nm axial repeat distance. These results suggest that the spherical AFM tip is large enough to measure the aggregate dynamic elastic modulus of cartilage, whereas the sharp AFM tip depicts the elastic properties of its fine structure. Additional measurements of cartilage stiffness following enzyme action revealed that elastase digestion of the collagen moiety lowered the modulus at the micrometer scale. In contrast, digestion of the proteoglycans moiety by cathepsin D had little effect on |E(*)| at the micrometer scale, but yielded a clear stiffening at the nanometer scale. Thus, cartilage compressive stiffness is different at the nanometer scale compared to the overall structural stiffness measured at the micrometer and larger scales because of the fine nanometer-scale structure, and enzyme-induced structural changes can affect this scale-dependent stiffness differently

Assessment of the photo-degradation of UV-filters and radical-induced peroxidation in cosmetic sunscreen formulations

Photo-instability of common UV-filters is a well documented phenomenon. This study develops a method for concomitant measurement of photostability and photo-induced ROS generation in cosmetic formulations. Oil-in-water formulations containing three common UV filters (OMC, BMDBM, EHT), individually or combined, were further supplemented with phosphatidylcholine and exposed to UVA. All filters show spectral decrease after UVA exposure. OMC and EHT do not induce significant lipid-peroxidation (as measured by TBARS production) while BMDBM does. In the latter case, this is reduced when BMDBM is combined with OMC but not with EHT. Neither OMC nor EHT stabilize BMDBM with respect to loss of absorbance. ROS-generation assessed via TBARS formation was supported by EPR experiments. The UV-induced changes in UV-filter performance, as monitored in the model formulations and in commercial sunscreens, demonstrate that this is a simple and effective method for stability assessment of sunscreen filters under conditions of use

Early detection of aging cartilage and osteoarthritis in mice and patient samples using atomic force microscopy

The pathological changes in osteoarthritis-a degenerative joint disease prevalent among older people-start at the molecular scale and spread to the higher levels of the architecture of articular cartilage to cause progressive and irreversible structural and functional damage. At present, there are no treatments to cure or attenuate the degradation of cartilage. Early detection and the ability to monitor the progression of osteoarthritis are therefore important for developing effective therapies. Here, we show that indentation-type atomic force microscopy can monitor age-related morphological and biomechanical changes In the hips of normal and osteoarthritic mice. Early damage in the cartilage of osteoarthritic patients undergoing hip or knee replacements could similarly be detected using this method. Changes due to aging and osteoarthritis are clearly depicted at the nanometre scale well before morphological changes can be observed using current diagnostic methods. Indentation-type atomic force microscopy may potentially be developed into a minimally invasive arthroscopic tool to diagnose the early onset of osteoarthritis In situ