Functional and structural insight into properdin control of complement alternative pathway amplification

Properdin (FP) is an essential positive regulator of the complement alternative pathway (AP) providing stabilization of the C3 and C5 convertases, but its oligomeric nature challenges structural analysis. We describe here a novel FP deficiency (E244K) caused by a single point mutation which results in a very low level of AP activity. Recombinant FP E244K is monomeric, fails to support bacteriolysis, and binds weakly to C3 products. We compare this to a monomeric unit excised from oligomeric FP, which is also dysfunctional in bacteriolysis but binds the AP proconvertase, C3 convertase, C3 products and partially stabilizes the convertase. The crystal structure of such a FP-convertase complex suggests that the major contact between FP and the AP convertase is mediated by a single FP thrombospondin repeat and a small region in C3b. Small angle X-ray scattering indicates that FP E244K is trapped in a compact conformation preventing its oligomerization. Our studies demonstrate an essential role of FP oligomerization in vivo while our monomers enable detailed structural insight paving the way for novel modulators of complement.     

Variance in female responses to the fine structure of male song in the field cricket, Gryllus integer

Although female mating preferences are a focus of current controversy,little detailed information exists on female preferences withinnatural populations. In the field cricket Gryllus integer, malecalls attract sexually receptive females, and females preferentiallymove toward male calls with longer calling bouts (periods ofcalling containing no pause greater than 0.10 s in real time).This study investigated female preferences for other variablesof the male song, including syllable period, chirp pause, andnumber of syllables per chirp. Male song was measured in thefield to determine mean values for each variable in nature.Female preferences were determined using a locomotor-compensatordevice, on which females ran in response to sequential playbacksof synthesized male song. Mean female preferences correspondedroughly to mean male song variables. Nonetheless, females variedgreatly in their responses to synthesized calls differing insyllable period, syllable number, and chirp pause. Moreover,individual females who were more selective for any one variablealso tended to be more selective for others. These results showthat females may differ from one another in their mating preferencesand degrees of selectivity, even within a single population.     

Evidence for Balancing Selection at Hla

HLA data from the A and B loci for 22 populations were compared with the neutrality expectations from Ewens' sampling theory. In 25 of 44 cases, there was significantly less homozygosity than expected. Although a number of factors can affect homozygosity in this manner, upon close examination only symmetrical balancing selection appears to be consistent with these data.     

Effects of cortisol implants on the PKX myxosporean causing proliferative kidney disease in rainbow trout, Salmo gairdneri

The myxosporean (PKX) that causes proliferative kidney disease in salmonid fishes is found primarily in the kidney interstitium of clinically affected fish, where it invokes a severe inflammatory response. Incomplete spores are observed in the lumen of kidney tubules in recovering fish. PKX-infected rainbow trout, Salmo gairdneri, were immunosuppressed with cortisol implants to determine if a reduction in renal interstitial inflammation would enhance the development of the parasite. Immunosuppression of these fish was indicated by high plasma cortisol levels, chronic mortality due to opportunistic pathogens, and depressed leucocrits when compared to infected fish not receiving cortisol implants. Cortisol-treated PKX-infected fish had 20 times the density of interstitial PKX compared with nontreated fish, but showed less interstitial inflammation. All of the former group examined at 4 wk postimplantation exhibited intraluminal sporogonic forms of PKX, whereas no sporogonic forms were detected in the nontreated fish. Suppression of the inflammatory response clearly enhanced the parasite's ability to reach the sporogonic stage, but did not induce complete development of the spore. Possibly the kidney tubules of rainbow trout do not provide the proper physiological environment for complete sporulation of PKX and a nonsalmonid fish may be the primary host.     

The coelomic envelope to vitelline envelope conversion in eggs of Xenopus laevis

An amphibian egg recovered from the body cavity is enclosed by a coelomic egg envelope. Upon transport down the oviduct, the envelope is converted to the vitelline envelope. The coelomic and vitelline envelopes are distinct in terms of sperm penetrability, ultrastructural morphology, and radioiodination profiles. In this study, the macromolecular compositions of these two envelopes were determined. Isolated envelopes were compared by one- and two-dimensional gel electrophoresis, peptide mapping, and radiolabeling. A protein with a molecular weight of 57,000 (57K) was present in the vitelline envelope but was absent in the coelomic envelope. A glycoprotein with a molecular weight of 43K in the coelomic envelope was converted to a component with a molecular weight of 41K in the vitelline envelope. The 43K-molecular weight component of the coelomic envelopes could be radioiodinated by lactoperoxidase but no labeling of the 41K-molecular weight component occurred in the vitelline envelope. Peptide mapping using limited proteolysis established that the 43K-molecular weight component of the coelomic envelope was a precursor to the 41K-molecular weight component of the vitelline envelope. These molecular alterations may underlie the ultrastructural and physiological changes occurring in these envelopes.     

A dye-binding induced conformational transition of poly-(methacrylic acid) by Auramine O in aqueous solutions. I. Experimental results

Binding of auramine O to poly-(methacrylic acid) (PMA) has been established over a large range of C⁰_p/C⁰_d values using spectroscopic methods (UV absorption and visible fluorescence emission spectra), equilibrium and sedimentation dialysis, potentiometric and viscosimetric titrations. All the results show qualitative agreement with those obtained previously with the system crystal violet-PMA although the binding seems to be less strong for auramine O than for crystal violet. From dialysis experiments binding isotherms were obtained at three different degrees of neutralization α'; at α' = 0.10 the results could be fitted to a Langmuir isotherm but at α' equal to 0.40 and 0.65 deviations with respect to such an isotherm occur. The results of potentiometric and viscosimetric titrations confirm that the conformational transition which the dye-free PMA exhibits upon ionization is affected by the dye binding. The region in which the conformational transion occurs is broadened and is less sharply defined in the presence of auramine O.