Intraspecific variation influences performance of moss transplants along microclimate gradients.

Identifying the environmental drivers of population dynamics is crucial to predict changes in species abundances and distributions under climate change. Populations of the same species might differ in their responses as a result of intraspecific variation. Yet the importance of such differences remains largely unexplored. We examined the responses of latitudinally distant populations of the forest moss Hylocomiastrum umbratum along microclimate gradients in Sweden. We transplanted moss mats from southern and northern populations to 30 sites with contrasting microclimates (i.e., replicated field common gardens) within a forest landscape, and recorded growth and survival of individual shoots over 3 yr. To evaluate the importance of intraspecific variation in responses to environmental factors, we assessed effects of the interactions between population origin and microclimate drivers on growth and survival. Effects on overall performance of transplanted populations were estimated using the product of survival and growth. We found differences between southern and northern populations in the response to summer temperature and snowmelt date in one of three yearly transitions. In this year, southern populations performed better in warm, southern-like conditions than in cold, northern-like conditions; and the reverse pattern was true for northern populations. Survival of all populations decreased with evaporation, consistent with the high hydric demands and poikilohydric nature of mosses. Our results are consistent with population adaptation to local climate, and suggest that intraspecific variation among populations can have important effects on the response of species to microclimate drivers. These findings highlight the need to account for differential responses in predictions of species abundance and distribution under climate change.

Progranulin mutations and amyotrophic lateral sclerosis or amyotrophic lateral sclerosis-frontotemporal dementia phenotypes.

OBJECTIVE: Mutations in the progranulin (PGRN) gene were recently described as the cause of ubiquitin positive frontotemporal dementia (FTD). Clinical and pathological overlap between amyotrophic lateral sclerosis (ALS) and FTD prompted us to screen PGRN in patients with ALS and ALS-FTD. METHODS: The PGRN gene was sequenced in 272 cases of sporadic ALS, 40 cases of familial ALS and in 49 patients with ALS-FTD. RESULTS: Missense changes were identified in an ALS-FTD patient (p.S120Y) and in a single case of limb onset sporadic ALS (p.T182M), although the pathogenicity of these variants remains unclear. CONCLUSION: PGRN mutations are not a common cause of ALS phenotypes.

Peptide binding to the most frequent HLA-A class I alleles measured by quantitative molecular binding assays.

Quantitative assays to measure the binding of defined synthetic antigenic peptides and purified MHC class I molecules are described for several common human HLA-A alleles (A1, A2.1, A3, A11 and A24). Under appropriate conditions, the binding of radiolabeled peptides to purified MHC class I molecules is very effective, highly specific, and appears to be dependent on the specific sequence motif of the peptide as defined by critical anchor residue positions. Establishment and optimization of the assay reveals that a relatively high fraction of the MHC class I molecules isolated from EBV transformed B cell line sources is capable of binding exogenously added peptide. Scatchard analysis for all alleles yields 5-10% occupancy values. There is a stringent peptide size requirement that is reflected by the direct influence of peptide length on the binding affinity. The peptide-MHC class I interactions demonstrate remarkable similarity to peptide-MHC class II interactions, both in overall affinity and kinetic behavior. The immunological relevance of the peptide-MHC class I binding assay is also demonstrated by measuring the affinity of a panel of previously described HLA restricted peptides for their HLA restriction element. In 91% (10/11) of the cases, the peptides bound with affinities of 50 nM or less, and in the remaining 9% (1/11) of the cases, in the 50 to 500 nM range. Thus, these data provide the first quantitative estimate of what level of HLA-A binding affinity is associated with a diverse panel of immunodominant CTL epitopes in man.

In Situ Detection of High Levels of Horizontal Plasmid Transfer in Marine Bacterial Communities.

Gene transfer of the conjugative plasmid pBF1 from Pseudomonas putida to indigenous bacteria in seawater was investigated with a detection system for gene transfer based on the green fluorescent protein (GFP) (C. Dahlberg et al., Mol. Biol. Evol. 15:385-390, 1998). pBF1 was tagged with the gfp gene controlled by a lac promoter which is down regulated in the donor cell by a chromosomal repressor (lacIq). The plasmid donor cells (Pseudomonas putida KT2442) subsequently do not express gfp. Transfer to recipient strains lacking the repressor results in expression of gfp. The transconjugant can subsequently be detected by epifluorescence microscopy on a single-cell level. By using this method, transfer of pBF1::gfp and expression of the gfp gene were first shown to occur during nutrient-limiting conditions to several defined recipient bacteria in artificial seawater. Second, we measured transfer of pBF1 from P. putida to the marine bacterial community directly in seawater samples, on a single-cell level, without limiting the detection of gene transfer to the culturable fraction of bacteria. Plasmid transfer was detected on surfaces and in bulk seawater. Seawater bacteria with different morphologies were shown to receive the plasmid. Gene transfer frequencies of 2.3 x 10(-6) to 2.2 x 10(-4) transconjugants per recipient were recorded after 3 days of incubation.

The effect of psychotomimetics on therapist--patient matching of speech "rhythms".

This study examined the effects of lysergic acid (LSD) and dextroamphetamine (DA) on therapist--patient matching of speech rhythms (mean phrase period) in psychotherapy. LSD, DA, and placebo (PL) were administered repeatedly over a 1 1/2-year period to seven patients in a randomized double-blind design. The second, fourth, and sixth encounters with LSD, DA, and PL were analyzed. These therapy dialogues were processed by an on--off detector of speech which computed probabilities of vocalizing when already talking (T), when listening (L), and when pausing (P) for therapist and patient, respectively. The mean phrase period for the therapist and the patient was calculated from the vocalization probabilities (T, P). The results show that both LSD and DA significantly enhance therapist-patient matching of mean phrase period in the earliest (second) session, an effect that disappears for both drugs, but later for DA (sixth session) than for LSD (fourth session). At no time was this effect observed in PL sessions, nor was the matching a simple function of a therapist--patient convergence of the components (T, P) of the mean phrase period.

Performance of forest bryophytes with different geographical distributions transplanted across a topographically heterogeneous landscape.

Most species distribution models assume a close link between climatic conditions and species distributions. Yet, we know little about the link between species' geographical distributions and the sensitivity of performance to local environmental factors. We studied the performance of three bryophyte species transplanted at south- and north-facing slopes in a boreal forest landscape in Sweden. At the same sites, we measured both air and ground temperature. We hypothesized that the two southerly distributed species Eurhynchium angustirete and Herzogiella seligeri perform better on south-facing slopes and in warm conditions, and that the northerly distributed species Barbilophozia lycopodioides perform better on north-facing slopes and in relatively cool conditions. The northern, but not the two southern species, showed the predicted relationship with slope aspect. However, the performance of one of the two southern species was still enhanced by warm temperatures. An important reason for the inconsistent results can be that microclimatic gradients across landscapes are complex and influenced by many climate-forcing factors. Therefore, comparing only north- and south-facing slopes might not capture the complexity of microclimatic gradients. Population growth rates and potential distributions are the integrated results of all vital rates. Still, the study of selected vital rates constitutes an important first step to understand the relationship between population growth rates and geographical distributions and is essential to better predict how climate change influences species distributions.

Abundance of Tn3, Tn21, and Tn501 transposase (tnpA) sequences in bacterial community DNA from marine environments.

The occurrence of the tnpA genes of the transposons Tn3, Tn21, and Tn501 was assessed in total bacterial community DNA isolated from different marine environments. The PCR technique was employed, together with most probable number statistics, to determine the abundance of the target tnpA genes. All three genes could be detected, and the Tn21 tnpA sequences predominated in all samples. The smallest amount of total community DNA in which the Tn21 tnpA sequence could be detected was 0.037 ng, and on the basis of our results, we estimated that this sequence was present in 1 of 1,000 to 10,000 bacteria. Hybridization of the PCR products with the respective tnpA probes verified the Tn21 and Tn501 tnpA sequences but only some of the Tn3 tnpA amplification products. The distribution and dissemination of transposons in natural bacterial communities are discussed.

The effects of LSD-25 and dextroamphetamine on the use of defensive language.

Verified that psychotomimetics attenuate verbal defense mechanisms. This was accomplished by reanalyzing the 5-minute monologues of 7 neurotic depressives who participated in a project (Mechaneck, Feldstein, Dahlberg, & Jaffe, 1968) that examined the effects of LSD and dextroamphetamine on timing aspects of speech. Dosages were subhallucinatory: 15-25 mg dextroamphetamine, 50-100 mg LSD, and a matching placebo. Volunteers received each drug (double-blind) seven or eight times on a random schedule over a 1 1/2-year period; there was a 3-week intertrial interval. The patient provided 5-minute monologues both before and after drug effects. The monologues were transcribed and scored for formal measures of defensive language. Results indicated that LSD caused individuals to make more personal statements and to use explanation and evaluations less often. Dextroamphetamine was found to decrease the use of nonpersonal references.

The cell-binding domains of plasminogen and their function in plasma.

Plasminogen binding sites are expressed by a wide variety of cell types and serve to promote fibrinolysis and local proteolysis. In this study, the recognition specificity of cells for plasminogen has been examined, primarily using platelets as models. Analyses with plasminogen fragments implicated residues 79-337 (or 353), comprising the first three kringles of plasminogen, as a primary recognition site for plasminogen binding to both thrombin-stimulated and nonstimulated platelets. Other regions of plasminogen, namely residues 354-439 and 442-790, can also participate in the interaction, and these other regions contribute differentially to the binding of the ligand to stimulated and nonstimulated platelets. Binding to nucleated cells, with U937 cells serving as the prototype, is dependent upon a recognition specificity similar to that of unstimulated platelets. Binding of Glu-plasminogen, the native form of the molecule, to thrombin-stimulated platelets has been shown previously to require platelet fibrin. By comparing the interaction of Glu-plasminogen and its degradation product, Lys-plasminogen, with thrombin-stimulated platelets, it is concluded that the cell surface uniquely enhances the affinity of Glu-, but not Lys-plasminogen, for fibrin. Finally, we have demonstrated that cellular receptors and interactive sites within plasminogen are available in the plasma environment. Thus, the functions ascribed to cellular plasminogen receptors can occur within a physiologic setting.

Conjugative plasmids isolated from bacteria in marine environments show various degrees of homology to each other and are not closely related to well-characterized plasmids.

Mercury resistance plasmids were exogenously isolated, i.e., recovered after transfer to a model recipient bacterium, from marine air-water interface, bulk water, and biofilm communities during incubation in artificial seawater without added nutrients. Ninety-five plasmids from different environments were classified by restriction endonuclease digestion, and 12 different structural plasmid groups were revealed. The plasmid types isolated from different habitats and from different sampling occasions showed little similarity to each other based on their restriction endonuclease patterns, indicating high variation and possibly a low transfer between microhabitats and/or a different composition of the microbial communities at different sites and times. With another approach in which probes derived from one of the isolated plasmids and a mercury resistance (mer) probe from Tn501 were used, similarities between plasmids from several different groups were found. The plasmids were further tested for their incompatibility by use of the collection of inc/rep probes (B/O, com9, FI, FII, HI1, HI2, I1, L/M, N, P, Q, U, W, Y) described by Couturier et al. (M. F. Couturier, P. Bex, L. Bergquist, and W. K. Maas, Microbiol. Rev. 52:375-395, 1988). Hybridizations did not reveal any identity between the 12 plasmid groups and any of the inc/rep probes tested. The results indicate that plasmids isolated from different marine habitats have replication and/or incompatibility systems that are different from the well-characterized plasmids that are commonly used in plasmid biology. This shows the need for the use of more relevant plasmids in studies of plasmid activity in the environment and development of new inc/rep probes for their characterization.

The relationship of defensive language behavior in patient monologues to the course of psychoanalysis.

Examined the relationship of the time-course of psychoanalysis to progressive alteration of defensive language behavior in 7 patients. Spontaneous 5-minute monologues were recorded over 1 1/2 years of three-times-a-week individual psychotherapy. Weintraub and Aronson's (1962) formal measures of defensive language were used: nonpersonal references, negators, qualifiers, retractors, explaining expressions of feeling, and evaluators. The magnitude of defensive speech displayed by a patient was able to predict significantly the duration of psychoanalysis undergone by that patient in 4 of 7 cases.

Gangliosides interact directly with plasminogen and urokinase and may mediate binding of these fibrinolytic components to cells.

Receptors for the fibrinolytic molecules plasminogen and urokinase are expressed at high capacity on a wide variety of peripheral blood cells and transformed cell lines. We have considered whether gangliosides, components of the outer leaflets of cell membranes, may modulate the interactions of these fibrinolytic ligands with cells. Radiolabeled plasminogen and urokinase bound directly to insolubilized gangliosides. The interactions were saturable and were 50% inhibited by 2.2 microM unlabeled plasminogen or 12 nM unlabeled urokinase, respectively. A panel of gangliosides inhibited binding of both ligands to U937 monocytoid cells, and the order of decreasing inhibitory effectiveness was GD1a greater than GM1 greater than GT1b greater than GM2, while GM3 was minimally effective. The individual components of gangliosides, hexoses, hexosamines, sialic acid, GM1 pentasaccharide, ceramides, and glucocerebrosides were ineffective in in inhibiting the binding of plasminogen and urokinase either to cells or to insolubilized gangliosides. Binding of both ligands to endothelial cells and granulocytes and binding of plasminogen to platelets were also inhibited by gangliosides. U937 cells were cultured with gangliosides to allow incorporation of these glycolipids into the cell membranes. After 3 days of culture, both urokinase binding and plasminogen binding to the cells became enhanced. These results suggest that gangliosides can directly bind to these fibrinolytic components and may mediate or modulate the interactions of plasminogen and urokinase with a variety of cell types.

Kin selection and parasite evolution: higher and lower virulence with hard and soft selection.

Conventional models predict that low genetic relatedness among parasites that coinfect the same host leads to the evolution of high parasite virulence. Such models assume adaptive responses to hard selection only. We show that if soft selection is allowed to operate, low relatedness leads instead to the evolution of low virulence. With both hard and soft selection, low relatedness increases the conflict among coinfecting parasites. Although parasites can only respond to hard selection by evolving higher virulence and overexploiting their host, they can respond to soft selection by evolving other adaptations, such as interference, that prevent overexploitation. Because interference can entail a cost, the host may actually be underexploited, and virulence will decrease as a result of soft selection. Our analysis also shows that responses to soft selection can have a much stronger effect than responses to hard selection. After hard selection has raised virulence to a level that is an evolutionarily stable strategy, the population, as expected, cannot be invaded by more virulent phenotypes that respond only to hard selection. The population remains susceptible to invasion by a less virulent phenotype that responds to soft selection, however. Thus, hard and soft selection are not just alternatives. Rather, soft selection is expected to prevail and often thwart the evolution of virulence in parasites. We review evidence from several parasite systems and find support for soft selection. Most of the examples involve interference mechanisms that indirectly prevent the evolution of higher virulence. We recognize that hard selection for virulence is more difficult to document, but we take our results to suggest that a kin selection model with soft selection may have general applicability.