Nisin stimulates oxygen consumption by Staphylococcus aureus and Escherichia coli.

Nisin stimulated oxygen consumption by nongrowing, glucose-metabolizing Staphylococcus aureus and Escherichia coli cells, indicating a protonophore mode of action. A similar stimulation in E. coli cells osmotically stressed to disrupt the outer cell membrane confirmed the cytoplasmic membrane as the site of nisin action and showed that nisin uptake was not prevented by the outer membrane.     

Characterization of cross-bridge elasticity and kinetics of cross-bridge cycling during force development in single smooth muscle cells

Force development in smooth muscle, as in skeletal muscle, is believed to reflect recruitment of force-generating myosin cross-bridges. However, little is known about the events underlying cross-bridge recruitment as the muscle cell approaches peak isometric force and then enters a period of tension maintenance. In the present studies on single smooth muscle cells isolated from the toad (Bufo marinus) stomach muscularis, active muscle stiffness, calculated from the force response to small sinusoidal length changes (0.5% cell length, 250 Hz), was utilized to estimate the relative number of attached cross-bridges. By comparing stiffness during initial force development to stiffness during force redevelopment immediately after a quick release imposed at peak force, we propose that the instantaneous active stiffness of the cell reflects both a linearly elastic cross-bridge element having 1.5 times the compliance of the cross-bridge in frog skeletal muscle and a series elastic component having an exponential length-force relationship. At the onset of force development, the ratio of stiffness to force was 2.5 times greater than at peak isometric force. These data suggest that, upon activation, cross-bridges attach in at least two states (i.e., low-force-producing and high-force-producing) and redistribute to a steady state distribution at peak isometric force. The possibility that the cross-bridge cycling rate was modulated with time was also investigated by analyzing the time course of tension recovery to small, rapid step length changes (0.5% cell length in 2.5 ms) imposed during initial force development, at peak force, and after 15 s of tension maintenance. The rate of tension recovery slowed continuously throughout force development following activation and slowed further as force was maintained. Our results suggest that the kinetics of force production in smooth muscle may involve a redistribution of cross-bridge populations between two attached states and that the average cycling rate of these cross-bridges becomes slower with time during contraction.     

Induction of an immune response through the idiotypic network with monoclonal anti-idiotype antibodies in the carcinoembryonic antigen system.

Anti-idiotype antibodies can mimic the conformational epitopes of the original antigen and act as antigen substitutes for vaccination and/or serological purposes. To investigate this possibility concerning the tumor marker carcinoembryonic antigen (CEA), BALB/c mice were immunized with the previously described anti-CEA monoclonal antibody (MAb) 5.D11 (AB1). After cell fusion, 15 stable cloned cell lines secreting anti-Ids (AB2) were obtained. Selected MAbs gave various degrees of inhibition (up to 100%) of the binding of 125I-labeled CEA to MAb 5.D11. Absence of reactivity of anti-Id MAbs with normal mouse IgG was first demonstrated by the fact that anti-Id MAbs were not absorbed by passage through a mouse IgG column, and second because they bound specifically to non-reduced MAb 5.D11 on Western blots. Anti-5.D11 MAbs did not inhibit binding to CEA of MAb 10.B9, another anti-CEA antibody obtained in the same fusion as 5.D11, or that of several anti-CEA MAbs reported in an international workshop, with the exception of two other anti-CEA MAbs, both directed against the GOLD IV epitope. When applied to an Id-anti-Id competitive radioimmunoassay, a sensitivity of 2 ng/ml of CEA was obtained, which is sufficient for monitoring circulating CEA in carcinoma patients. To verify that the anti-Id MAbs have the potential to be used as CEA vaccines, syngeneic BALB/c mice were immunized with these MAbs (AB2). Sera from immunized mice were demonstrated to contain AB3 antibodies recognizing the original antigen, CEA, both in enzyme immunoassay and by immunoperoxidase staining of human colon carcinoma. These results open the perspective of vaccination against colorectal carcinoma through the use of anti-idiotype antibodies as antigen substitutes.     

The proteolysis of immunoglobulin G with long-acting thyroid-stimulating activity

1. Proteolysis of immunoglobulin G with long-acting thyroid-stimulating activity with papain and pepsin shortened the duration of thyroid stimulation in mice prepared for the McKenzie (1958) bioassay. The time-course appeared to be related to molecular size. 2. The activity after proteolysis was recovered solely in the electrophoretically slow F(ab)-fragment. 3. There was no immunological cross-reaction between pituitary thyroid-stimulating hormone and the active fragments of the long-acting thyroid stimulator despite their similar behaviour in the bioassay. 4. The implications of these findings are discussed.     

Spatial and temporal gene expression patterns occur during corm development.

We investigated gene expression patterns that occur during taro corm development. Two-dimensional gel electrophoresis identified several different prevalent proteins that accumulate during corm development. Microsequencing studies indicated that some of these proteins are related to taste-modifying proteins, such as curculin and miraculin, and proteins found in other storage organs, such as sporamin and the Kunitz trypsin inhibitor. A curculin-encoding cDNA clone, designated as TC1, was identified that corresponds to a highly prevalent 1-kb corm mRNA. The TC1 mRNA accumulates during corm development, is more prevalent in corm apical than basal regions, and is either absent, or present at low concentrations, in other vegetative organs such as the leaf and root. In situ hybridization experiments showed that the TC1 mRNA is highly concentrated in corm storage parenchyma cells and is absent, or present in reduced concentrations, in other corm cells and tissues. Our results show that corm development is associated with the differentiation of specialized cells and tissues, and that these differentiation events are coupled with the temporal and spatial expression of corm-specific genes.     

Effects of pair migratory behavior on breeding phenology and success in a partially migratory shorebird population

In migratory systems, variation in individual phenology can arise through differences in individual migratory behaviors, and this may be particularly apparent in partial migrant systems, where migrant and resident individuals are present within the same population. Links between breeding phenology and migratory behavior or success are generally investigated at the individual level. However, for breeding phenology in particular, the migratory behaviors of each member of the pair may need to be considered simultaneously, as breeding phenology will likely be constrained by timing of the pair member that arrives last, and carryover effects on breeding success may vary depending on whether pair members share the same migratory behavior or not. We used tracking of marked individuals and monitoring of breeding success from a partially migrant population of Eurasian oystercatchers (Haematopus ostralegus) breeding in Iceland to test whether (a) breeding phenology varied with pair migratory behavior; (b) within‐pair consistency in timing of laying differed among pair migratory behaviors; and (c) reproductive performance varied with pair migratory behavior, timing of laying, and year. We found that annual variation in timing of laying differed among pair migratory behaviors, with resident pairs being more consistent than migrant and mixed pairs, and migrant/mixed pairs breeding earlier than residents in most years but later in one (unusually cold) year. Pairs that laid early were more likely to replace their clutch after nest loss, had higher productivity and higher fledging success, independent of pair migratory behavior. Our study suggests that the links between individual migratory behavior and reproductive success can vary over time and, to a much lesser extent, with mate migratory behavior and can be mediated by differences in laying dates. Understanding these cascading effects of pair phenology on breeding success is likely to be key to predicting the impact of changing environmental conditions on migratory species.     

Bulk hydrogen stable isotope composition of seaweeds: Clear separation between Ulvophyceae and other classes

Little is known about the bulk hydrogen stable isotope composition (δ²H) of seaweeds. This study investigated the bulk δ²H in several different seaweed species collected from three different beaches in Brazil, Australia, and Argentina. Here, we show that Ulvophyceae (a group of green algae) had lower δ²H values (between ?94‰ and ?130‰) than red algae (Florideophyceae), brown algae (Phaeophyceae), and species from the class Bryopsidophyceae (another group of green algae). Overall the latter three groups of seaweeds had δ²H values between ?50‰ and ?90‰. These findings were similar at the three different geographic locations. Observed differences in δ²H values were probably related to differences in hydrogen (H) metabolism among algal groups, also observed in the δ²H values of their lipids. The marked difference between the δ²H values of Ulvophyecae and those of the other groups could be useful to trace the food source of food webs in coastal rocky shores, to assess the impacts of green tides on coastal ecosystems, and to help clarify aspects of their phylogeny. However, reference materials for seaweed δ²H are required before the full potential of using the δ²H of seaweeds for ecological studies can be exploited.