Estimating the latitudinal origins of migratory birds using hydrogen and sulfur stable isotopes in feathers: influence of marine prey base

Hydrogen stable isotope analysis of feathers is an important tool for estimating the natal or breeding latitudes of nearctic-neotropical migratory birds. This method is based on the latitudinal variation of hydrogen stable isotope ratios in precipitation in North America (deltaD(p)) and the inheritance of this variation in newly formed feathers (deltaD(f)). We hypothesized that the typically strong relationship between deltaD(p) and deltaD(f) would be decoupled in birds that forage in marine food webs because marine waters have relatively high deltaD values compared to deltaD values for local precipitation. Birds that forage on marine prey bases should also have feathers with high delta(34)S values, since delta(34)S values for marine sulfate are generally higher than delta(34)S values in terrestrial systems. To examine this potential marine effect on feather stable isotope ratios, we measured deltaD and delta(34)S in the feathers of nine different species of raptors from both inland and coastal locations across North America. Feathers from coastal bird-eating raptors had consistently higher deltaD and delta(34)S values than feathers from inland birds. Birds that had high delta(34)S values also deviated strongly from the typical relationship between deltaD(p) and deltaD(f). We recommend measuring both sulfur and hydrogen stable isotope ratios in feathers when some members of a migrant population could potentially forage in marine habitats. We suggest using a practical cutoff of delta(34)S >10 per thousand to remove marine-foraging birds from a migrant sample when using stable isotopes of hydrogen to estimate the latitudinal origins of migrants because high deltaD(f) values for marine-foraging birds could potentially distort estimates of origins.     

Lipid biosynthesis as a target for antibacterial agents

Fatty acid biosynthesis, the first stage in membrane lipid biogenesis, is catalyzed in most bacteria by a series of small, soluble proteins that are each encoded by a discrete gene (Fig. 1; Table 1). This arrangement is termed the type II fatty acid synthase (FAS) system and contrasts sharply with the type I FAS of eukaryotes which is a dimer of a single large, multifunctional polypeptide. Thus, the bacterial pathway offers several unique sites for selective inhibition by chemotherapeutic agents. The site of action of isoniazid, used in the treatment of tuberculosis for 50 years, and the consumer antimicrobial agent triclosan were revealed recently to be the enoyl-ACP reductase of the type II FAS. The fungal metabolites, cerulenin and thiolactomycin, target the condensing enzymes of the bacterial pathway while the dehydratase/isomerase is inhibited by a synthetic acetylenic substrate analogue. Transfer of fatty acids to the membrane has also been inhibited via interference with the first acyltransferase step, while a new class of drugs targets lipid A synthesis. This review will summarize the data generated on these inhibitors to date, and examine where additional efforts will be required to develop new chemotherapeutics to help combat microbial infections.     

Food choices and eating difficulty among elderly edentate patients in Greece

Aims: To evaluate food choice and eating difficulty experienced by older Greek edentate patients. Subjects: Three samples of patients seeking provision of replacement dentures were studied. A primary study of urban mainland U1 (n=54) and island rural R1 samples (n=84) was followed by a mainland urban U2 sample (n=119) in the Secondary study. Setting: Greek dental clinics. Intervention: Semi‐structured interviews (SSI) were employed, using both open and closed questions. Design: The primary study used SSI to identify eating difficulty experienced by two culturally different Greek groups. The secondary study established patterns of difficulty for comparisons between an urban Greek population and northern European urban studies. Main Outcome Measures: The prevalence of eating difficulty, the degree of difficulty eating specified foods and the exclusion of foods because difficult. Results: Most patients expressed difficulty eating at least one type of food, a high percentage of these patients were willing to eat foods found difficult, while others use particular methods of food preparation that make food easier to eat. Chicken illustrated the importance of specifying the method of cooking when questioning eating difficulties. Roast meats provided insight into the more difficult end of the food range. Raw vegetables were rated difficult. Apples and oranges were also food of particular interest. Conclusions: The semi‐structured interview method provides a succesful method to identify eating difficulty and food choices by older Greek complete denture wearers. Differences, probably largely cultural, were identified between Greek island rural and mainland urban communities. Greek food choices differed favourably from an English sample, strikingly in that Greek patients report continuing to eat difficult foods despite difficulty eating them. This may be relevant to health data on Greek populations that show better mortality statistics despite adverse factors such as high prevalence of smoking.     

Validation of indices for functional assessment of dentures

Aims: To validate an assessment of qualities of complete dentures that may relate to functional success. Subjects: A consecutive sample of 131 complete denture wearers took part in the study. Setting: a Greek department of prosthetic dentistry. Intervention : All participants and their dentures underwent clinical examination. Design: The Functional Assessment of Dentures (FAD) 10‐item criteria¹ describing clinical factors of denture quality was used. The rationale for selecting these particular criteria was to include a range of clinical factors to produce an overall assessment of complete dentures. The 10‐item scale was examined for Internal Consistency and Construct Validity providing a summated rating scale whose total score could be used as an index for the quality of dentures. Results: Both intra‐ and inter‐examiner agreement for all 10 dichotomous scale criteria were all good or very good; the intra‐examiner Kappa values were 0.72 to 0.91 and the inter‐ examiner values were 0.72 to 0.99. Statistical analysis revealed that a 7‐item summated rating scale could be constructed which has marginally better internal consistency (reliability) and Construct Validity with fewer questions. Conclusions: The FAD criteria¹ can be used to give good repeatability. The adjustments made to the original summation scale, if confirmed by new studies, would further increase the practical utility of a FAD index for general dentists. In due course with data from future studies, discrimination on weighting of items will be appropriate to relate the impact of denture quality on quality of life.     

The development of a method for functional assessment of dentures

Aims: To design and validate a method of assessing complete dentures from a functional standpoint. Subjects: A random sample of 40 complete denture wearers took part in the study. Setting: A university clinical department of prosthetic dentistry. Intervention: We undertook a pilot study to refine the protocol and criteria. All participants and their dentures were examined by two authors independently, with no prior knowledge of the patients'complaints. Design: We defined nine clinical factors of functional quality and applied criteria with binary scoring. We analysed the scores for these factors for inter‐rater reliability. Results: The method proved simple to apply and took less than 5 minutes to complete. The inter‐examiner agreement for all factors was 86% to 100% giving Kappa scores of 0.64 to 1.00 (all Good or Very Good). Conclusions: This study successfully demonstrates that the technique, which we call the Functional Assessment of Dentures (FAD), can give good inter‐examiner reliability. It can therefore be used separately as a routine diagnostic tool and to investigate the relationship between denture qualities and functional ‘outcome’ such as difficulty eating or dietary selection.     

Development of a bioartificial nerve graft. II. Nerve regeneration in vitro

A promising alternative for the repair of peripheral nerve injuries is the bioartificial nerve graft, or BNG, comprised of a tubular conduit preseeded with Schwann cells, which are an effective substrate for enhancing nerve regeneration. The physical properties of the conduit, porosity and wall thickness, as well as the Schwann cell seeding density, were tested for their effect on axon growth using rat dorsal root ganglia. These parameters can influence the amount of nutrients and growth factors made available to the neural tissue. Results show that a greater wall thickness and lower porosities have a detrimental effect on the growth of the axons. Over a four week period, axons extended 3.2 mm for the optimum case (DeltaR = 0.82 mm, epsilon = 0.75) compared to 1.8 and 1.6 mm for a lower porosity (0.55) and a greater wall thickness (1.4 mm), respectively. A maximum in the growth rate occurs at a porosity of 75% for Schwann cell seeded conduits but not for unseeded ones. When compared to mass transfer predictions, the results suggest that, at higher porosities, more growth factors diffuse out of the conduit, while at low porosities there is competition for nutrients. Increasing the Schwann cell seeding density enhances growth but also leads to an increase in the number of axons along the length of the conduit. This is indicative of branching of the axons, which requires additional resources to maintain and can lead to painful neuroma formation. Wall thickness and porosity were found not to have any significant effect on the axon number sprouting from the dorsal root ganglia and the mean diameter (p > 0.05). Considerations need to be made, not just on the polymer used, but also on its porosity, wall thickness, and Schwann cell seeding density. These parameters can be adjusted to create a bioartificial nerve graft that provides the optimal environment for nerve growth.     

Sensing performance of protein C immuno-biosensor for biological samples and sensor minimization

Protein C (PC) is an important anticoagulant and antithrombotic agent in human blood plasma. PC deficiency can result in clotting complications that interfere with oxygen and nutrient transport. A fiber-optic biosensor is being developed to provide real time diagnosis of PC deficiency. The PC sensor was tested to quantify PC level in human plasma. The signal intensity obtained from the plasma sample was 30% of the buffered sample, possibly due to the increased viscosity. The feasibility of monitoring PC level in animal cell culture broth and animal milk was tested. For the cell culture broth, 80% of signal was observed. However, the decrease was consistent over the sensing range. For whole and 1:100 diluted bovine milk, the signals were 60 and 78% of buffered sample, respectively. The biosensor length was reduced from 12.5 to 6 cm with sufficient sensitivity. To increase the sensor reusability, various elution buffers were applied after each sensing. Triethylamine elution buffer provided the best sensor regeneration capability and increased the number of assays from 2.5 to 7 times for 6 cm fibers.     

Gene expression response to misfolded protein as a screen for soluble recombinant protein

Proper protein folding is key to producing recombinant proteins for structure determination. We have examined the effect of misfolded recombinant protein on gene expression in Escherichia coli. Comparison of expression patterns indicates a unique set of genes responding to translational misfolding. The response is in part analogous to heat shock and suggests a translational component to the regulation. We have further utilized the expression information to generate reporters responsive to protein misfolding. These reporters were used to identify properly folded recombinant proteins and to create soluble domains of insoluble proteins for structural studies.     

Characterization of two TCR transgenic mouse lines specific for herpes simplex virus

To better understand the T cell-mediated processes involved in the immune response to herpes simplex virus type 1 (HSV-1)infection, two HSV-specific T cell receptor (TCR) transgenic mouse lines were produced. These mice (gBT-I.1 and gBT-I.3) are MHC class I-restricted and specific for the immunodominant peptide from HSV glycoprotein B (gB), gB498-505. Although derived from the same clone, the mice differ in the chromosomal location of the TCR transgenes and show marked differences in TCR alpha/beta expression on both CD4+ and CD8+ cells in the thymus. Despite this, peripheral CD8+ Tcells from both mice express equally high levels of the transgenic TCR and bind the KbgB498-505 tetramer to the same degree. In concordance with this, both were shown to respond equally well in vitro upon stimulation with the gB498-505 peptide or HSV-infected cells. These data show that selection of broadly equivalent peripheral T-cell subsets can occur in the presence of distinctly different thymic T-cell subsets.