Selection on innate immunity and body condition in Florida scrub-jays throughout an epidemic

Opportunities to investigate selection in free-living species during a naturally occurring epidemic are rare; however, we assessed innate immunocompetence in Florida scrub-jays before the population suffered the greatest over-winter mortality in 20 years of study. Propitiously, three months prior to the epidemic, we had sampled a number of male breeders to evaluate a suite of physiological measures that are commonly used to estimate the overall health-state of an individual. There was a significant, positive selection gradient for both Escherichia coli bacterial killing capability and body condition, suggesting that directional selection had occurred upon each of these traits during the disease epidemic.     

Singular Value Decomposition of the Radial Distribution Function for Hard Sphere and Square Well Potentials

We compute the singular value decomposition of the radial distribution function for hard sphere, and square well solutions. We find that decomposes into a small set of basis vectors allowing for an extremely accurate representation at all interpolated densities and potential strengths. In addition, we find that the coefficient vectors describing the magnitude of each basis vector are well described by a low-order polynomial. We provide a program to calculate in this compact representation for the investigated parameter range.     

How can the functional reponse best be determined?

Summary We evaluated three methods for the analysis of functional response data by asking whether a given method could discriminate among functional responses and whether it could accurately identify regions of positive density-dependent predation. We evaluated comparative curve fitting with foraging models, linear least-squares analysis using the angular transformation, and logit analysis. Using data from nature and simulations, we found that the analyses of predation rates with the angular transformation and logit analysis were best at consistently determining the true functional response, i.e. the model used to generate simulated data. These methods also produced the most accurate estimates of the true regions of density dependence. Of these two methods, functional response data best fulfill the assumptions of logit analysis. Angularly transformed predation rates only approximate the assumptions of linear leastsquares analysis for predation rates between 0.1 and 0.9. Lack-of-fit statistics can reveal inadequate fit of a model to a data set where simple regression statistics might erroneously suggest a good match.     

Effects of selective cholecystokinin antagonists L364,718 and L365,260 on food intake in rats

The selective type A and B cholecystokinin (CCK) receptor antagonists L364,718 and L365,260 were used to identify the receptor subtype that mediates the satiety effect of endogenous CCK. Male rats (n = 12–13/group), fed ground rat chow ad lib, received L364,718 (0, 1, 10, 100, or 1000 μg/kg IP) or L365,260 (0, 0.1, 1, 10, 100, 1000, or 10,000 μg/kg IP) 2 h after lights off, and food intake was measured 1.5, 3.5, and 5.5 h later. L364,718 significantly stimulated 1.5-h food intake by more than 40% at 10 μg/kg and higher doses; cumulative intake at 3.5 and 5.5 h remained elevated by about 20% at 1000 and 100 μg/kg of L364,718, respectively. In contrast, L365,260 had no significant stimulatory effect on feeding at any dose. The potency of L365,260 for antagonizing gastrin-stimulated gastric acid secretion was examined in unanesthetized rats. Male rats (n = 14), prepared with gastric and jugular vein cannulas, received doubling doses of gastrin (G-17I) (0.16–5 nmol/kg/h IV), each dose for 30 min, and gastric juice was collected for each 30-min period. G-17I stimulated gastric acid output dose dependently; the minimal effective dose was 0.16 nmol/kg/h, while maximal output (5-fold above basal) occurred at 5 nmol/kg/h. L365,260 (0, 1, 10, 100, 1000, or 10,000 μg/kg IV), administered 30 min before continuous infusion of G-17I (1.25 or 5 nmol/kg/h), significantly inhibited acid output only at 10,000 μg/kg; cumulative 60-min output was decreased by 60%. These results suggest that CCK acts at CCK-A receptors to produce satiety during the dark period in ad lib-feeding rats.     

Inactivation of bradykinin and kallidin by cathepsin G and mast cell chymase

Human neutrophil cathepsin G and human skin chymase can inactivate bradykinin by cleavage at the carboxy terminal phenylalanyl-arginyl peptide bond of this polypeptide. The mast cell enzyme is far more effective than cathepsin G, the rates of hydrolysis being comparable to that found for angiotensin I to angiotensin II conversion (C.F. Reilly, D. Tewksbury, N. Schechter, and J. Travis, J. Biological Chemistry 257:8619-8622). This ability to both inactivate bradykinin and accelerate the production of angiotensin II may be of significance in the development of biochemical events associated with inflammation.     

Transfer of plasmid RP1 into chemolithotrophic Thiobacillus neapolitanus.

RP1, a broad-host-range incompatibility group P1 plasmid specifying multiple drug resistances, has been transferred into the chemolithotrophic bacterium Thiobacillus neapolitanus. The ability of T. neapolitanus to receive, express, and transmit RP1-encoded antibiotic resistances was examined. The data show that this obligate chemolithotroph can accept, replicate, and express heterologous plasmid DNA from a heterotrophic bacterium.     

Inter-alpha-trypsin inhibitor. Inhibition spectrum of native and derived forms

The conversion of inter-alpha-trypsin inhibitor (I alpha I) into active, acid-stable derivatives by proteolytic degradation has been tested with 10 different proteinases. Of these, only plasma kallikrein, cathepsin G, neutrophil elastase, and the Staphylococcus aureus V-8 proteinase were found to be effective, each releasing more than 50% of this activity. However, a strong correlation between inhibitor degradation and significant release of acid-stable activity could only be found with the V-8 enzyme. Inhibition kinetics for the interaction of native I alpha I, the inhibitory fragment released by digestion with S. aureus V-8 proteinase, or the related urinary trypsin inhibitor, with seven different proteinases indicated that all had essentially identical Ki values with an individual enzyme and, where measurements were possible, nearly identical second order association rate constants. Significantly, none of the five human proteinases tested, including trypsin, chymotrypsin, plasmin, neutrophil elastase, and cathepsin G, would appear to have low enough Ki values to be physiologically relevant. Thus, the role of native I alpha I or its degradation products in controlling a specific proteolytic activity is still unknown.     

Characterization of the binding activities of proteinase-adhesin complexes from Porphyromonas gingivalis.

Adhesins from oral bacteria perform an important function in colonizing target tissues within the dentogingival cavity. In Porphyromonas gingivalis certain of these adhesion proteins exist as a complex with either of two major proteinases referred to as gingipain R (arginine-specific gingipain) and gingipain K (lysine-specific gingipain) (R. N. Pike, W. T. McGraw, J. Potempa, and J. Travis, J. Biol. Chem. 269:406-411, 1994). With specific proteinase inhibitors, it was shown that hemagglutination by either proteinase-adhesin complex could occur independently of proteinase activity. Significantly, low concentrations of fibrinogen, fibronectin, and laminin inhibited hemagglutination, indicating that adherence to these proteins and not the hemagglutination activity was a primary property of the adhesin activity component of complexes. Binding studies with gingipain K and gingipain R suggest that interaction with fibrinogen is a major function of the adhesin domain, with dissociation constants for binding to fibrinogen being 4 and 8.5 nM, respectively. Specific association with fibronectin and laminin was also found. All bound proteins were degraded by the functional proteinase domain, with gingipain R being more active on laminin and fibronectin and gingipain K being more effective in the digestion of fibrinogen. Cumulatively, these data suggest that gingipain R and gingipain K, acting as proteinase-adhesin complexes, progressively attach to, degrade, and detach from target proteins. Since such complexes appear to be present on the surfaces of both vesicles and membranes of P. gingivalis, they may play an important role in the attachment of this bacterium to host cell surfaces.