Conditional Expression of Smad7 in Pancreatic β Cells Disrupts TGF-β Signaling and Induces Reversible Diabetes Mellitus

Identification of signaling pathways that maintain and promote adult pancreatic islet functions will accelerate our understanding of organogenesis and improve strategies for treating diseases like diabetes mellitus. Previous work has implicated transforming growth factor-β (TGF-β) signaling as an important regulator of pancreatic islet development, but has not established whether this signaling pathway is required for essential islet functions in the adult pancreas. Here we describe a conditional system for expressing Smad7, a potent inhibitor of TGF-β signaling, to identify distinct roles for this pathway in adult and embryonic β cells. Smad7 expression in Pdx1 ⁺ embryonic pancreas cells resulted in striking embryonic β cell hypoplasia and neonatal lethality. Conditional expression of Smad7 in adult Pdx1 ⁺ cells reduced detectable β cell expression of MafA, menin, and other factors that regulate β cell function. Reduced pancreatic insulin content and hypoinsulinemia produced overt diabetes that was fully reversed upon resumption of islet TGF-β signaling. Thus, our studies reveal that TGF-β signaling is crucial for establishing and maintaining defining features of mature pancreatic β cells.     

Common Human 5′ Dopamine Transporter (SLC6A3) Haplotypes Yield Varying Expression Levels In Vivo

1. Individuals display significant differences in their levels of expression of the dopamine transporter (DAT; SLC6A3). These differences in DAT are strong candidates to contribute to individual differences in motor, mnemonic and reward functions. To identify “cis”-acting genetic mechanisms for these individual differences, we have sought variants in 5′ aspects of the human DAT gene and identified the haplotypes that these variants define.2. We report (i) significant relationships between 5′ DAT haplotypes and human individual differences in ventral striatal DAT expression assessed in vivo using [¹¹C] cocaine PET and (ii) apparent confirmation of these results in studies of DAT expression in postmortem striatum using [³H] carboxyflurotropane binding.3. These observations support the idea that cis-acting variation in 5′ aspects of the human DAT/SLC6A3 locus contributes to individual differences in levels of DAT expression in vivo. 5′ DAT variation is thus a good candidate to contribute to individual differences in a number of human phenotypes.These authors contributed equally to this article     

Functional characterization of the competence protein DprA/Smf in Escherichia coli

In several bacterial species that show natural transformation, dprA has been described as a competence gene. The DprA protein has been suggested to be involved in the protection of incoming DNA. However, members of the dprA gene family (also called smf) can be detected in virtually all bacterial species, which suggests that their gene products have a more general function. We examined the function of the DprA/Smf homologue of Escherichia coli. Escherichia coli dprA/smf is able to partially restore transformation in a Haemophilus influenzae dprA mutant, which shows that dprA/smf genes from competent and noncompetent species are interchangeable with respect to their involvement in natural transformation. From this, we conclude that natural transformation is probably an additional function of these genes. Subsequently, the dprA/smf gene was deleted in various recombination mutants of E. coli, and the resultant phenotype was tested. All the resultant E. coli dprA/smf mutants did not differ from their parent strains with respect to transformation, Hfr-conjugation, recombination and DNA repair. Therefore, a role of DprA/Smf in DNA recombination could not be established and the basic function of dprA/smf remains unclear.     

Simian immunodeficiency virus SIVagm.sab infection of Caribbean African green monkeys: a new model for the study of SIV pathogenesis in natural hosts

Caribbean-born African green monkeys (AGMs) were classified as Chlorocebus sabaeus by cytochrome b sequencing. Guided by these phylogenetic analyses, we developed a new model for the study of simian immunodeficiency virus (SIV) infection in natural hosts by inoculating Caribbean AGMs with their species-specific SIVagm.sab. SIVagm.sab replicated efficiently in Caribbean AGM peripheral blood mononuclear cells in vitro. During SIVagm.sab primary infection of six Caribbean AGMs, the virus replicated at high levels, with peak viral loads (VLs) of 10(7) to 10(8) copies/ml occurring by day 8 to 10 postinfection (p.i.). Set-point values of up to 2 x 10(5) copies/ml were reached by day 42 p.i. and maintained throughout follow-up (through day 450 p.i.). CD4(+) T-cell counts in the blood showed a transient depletion at the peak of VL, and then returned to near preinfection values by day 28 p.i. and remained relatively stable during the chronic infection. Preservation of CD4 T cells was also found in lymph nodes (LNs) of chronic SIVagm.sab-infected Caribbean AGMs. No activation of CD4(+) T cells was detected in the periphery in SIV-infected Caribbean AGMs. These virological and immunological profiles from peripheral blood and LNs were identical to those previously reported in African-born AGMs infected with the same viral strain (SIVagm.sab92018). Due to these similarities, we conclude that Caribbean AGMs are a useful alternative to AGMs of African origin as a model for the study of SIV infection in natural African hosts.     

Floristic relationships among vegetation types of new zealand and the southern andes: similarities and biogeographic implications

Background and Aims

Similarities between the floras of geographically comparable regions of New Zealand (NZ) and the southern Andes (SA) have interested biologists for over 150 years. The present work selects vegetation types that are physiognomically similar between the two regions, compares their floristic composition, assesses the environmental factors that characterize these matching vegetation types, and determines whether phylogenetic groups of ancestral versus modern origin are represented in different proportions in their floras, in the context of their biogeographic history.

Methods

Floristic relationships based on 369 genera of ten vegetation types present in both regions were investigated with correspondence analysis (CA) and ascending hierarchical clustering (AHC). The resulting ordination and classification were related to the environmental characteristics of the different vegetation types. The proportions of different phylogenetic groups between the regions (NZ, SA) were also compared, and between forest and non-forest communities.

Key Results

Floristic similarities between NZ and SA tend to increase from forest to non-forest vegetation, and are highest in coastal vegetation and bog. The floras of NZ and SA also differ in their phylogenetic origin, NZ being characterized by an ‘excess’ of genera of basal origin, especially in forests.

Conclusions

The relatively low similarities between forests of SA and NZ are related to the former being largely of in situ South American and Gondwanan origin, whereas the latter have been mostly reconstituted though transoceanic dispersal of propagules since the Oligocene. The greater similarities among non-forest plant communities of the two regions result from varied dispersal routes, including relatively recent transoceanic dispersal for coastal vegetation, possible dispersal via a still-vegetated Antarctica especially for bog plants, and independent immigration from Northern Hemisphere sources for many genera of alpine vegetation and grassland.Key words: Biogeographic history, floristic similarities, generic composition, local floras, New Zealand, phylogenetic origin, southern Andes, vegetation types     

Human prostate stromal cells stimulate increased PSA production in DHEA-treated prostate cancer epithelial cells

Dehydroepiandrosterone (DHEA) is commonly used as a dietary supplement and may affect prostate pathophysiology when metabolized to androgens and/or estrogens. Human prostate LAPC-4 cancer cells with a wild type androgen receptor (AR) were treated with DHEA, androgens dihydrotestosterone (DHT), T, or R1881), and E(2) and assayed for prostate specific antigen (PSA) protein and gene expression. In LAPC-4 monocultures, DHEA and E(2) induced little or no increase in PSA protein or mRNA expression compared to androgen-treated cells. When prostate cancer-associated (6S) stromal cells were added in coculture, DHEA stimulated LAPC-4 cell PSA protein secretion to levels approaching induction by DHT. Also, DHEA induced 15-fold more PSA mRNA in LAPC-4 cocultures than in monocultures. LAPC-4 proliferation was increased 2-3-fold when cocultured with 6S stromal cells regardless of hormone treatment. DHEA-treated 6S stromal cells exhibited a dose- and time-dependent increase in T secretion, demonstrating stromal cell metabolism of DHEA to T. Coculture with non-cancerous stroma did not induce LAPC-4 PSA production, suggesting a differential modulation of DHEA effect in a cancer-associated prostate stromal environment. This coculture model provides a research approach to reveal detailed endocrine, intracrine, and paracrine signaling between stromal and epithelial cells that regulate tissue homeostasis within the prostate, and the role of the tumor microenvironment in cancer progression.     

The rhizobial adhesion protein RapA1 is involved in adsorption of rhizobia to plant roots but not in nodulation

The effect of the rhizobium adhesion protein RapA1 on Rhizobium leguminosarum bv. trifolii adsorption to Trifolium pratense (red clover) roots was investigated. We altered RapA1 production by cloning its encoding gene under the plac promoter into the stable vector pHC60. After introducing this plasmid in R. leguminosarum bv. trifolii, three to four times more RapA1 was produced, and two to five times higher adsorption to red clover roots was obtained, as compared with results for the empty vector. Enhanced adsorption was also observed on soybean and alfalfa roots, not related to R. leguminosarum cross inoculation groups. Although the presence of 1 mM Ca2+ during rhizobial growth enhanced adsorption, it was unrelated to RapA1 level. Similar effects were obtained when the same plasmid was introduced in Rhizobium etli for its adsorption to bean roots. Although root colonization by the RapA1-overproducing strain was also higher, nodulation was not enhanced. In addition, in vitro biofilm formation was similar to the wild-type both on polar and on hydrophobic surfaces. These results suggest that RapA1 receptors are present in root but not on inert surfaces, and that the function of this protein is related to rhizosphere colonization.     

Cell adhesion molecules in stromal corneal dystrophies

The aim of the present study was to investigate the expression pattern of different cell adhesion molecules in corneal stromal dystrophies. Fifteen corneal buttons from patients diagnosed with three different types of stromal corneal dystrophies and healthy corneas were investigated. Paraffin embedded sections were stained immunohistochemically with monoclonal antibodies against human intercellular adhesion molecule-1 (ICAM-1), endothelial selectin (E-selectin) and endothelial cadherin (E-cadherin) using the avidin-biotin-peroxidase-complex technique. The sections were compared to normal eye bank controls. In corneas from granular dystrophy patients ICAM-1 was expressed focally in epithelial cells and in keratocytes, and expressed diffusely in endothelial cells. In corneas from macular dystrophy patients diffuse epithelial staining was observed and the stromal and endothelial expression was found to be similar to that of granular dystrophy. In lattice dystrophy, only the epithelial cells and endothelium were intensively positive for ICAM-1. E-selectin was not present on any layer of the corneal specimens. E-cadherin was observed only in the epithelium of all three types of corneal dystrophies. Normal corneas did not express any of the investigated adhesion molecules. We found different expression patterns of adhesion molecules in corneas from stromal dystrophies. Our results suggest that adhesion molecules may be involved in the pathogenesis of corneal stromal dystrophies.     

Erythroid expansion and survival in response to acute anemia stress: the role of EPO receptor, GATA-1, Bcl-xL and caspase-3

Erythropoietic stress occurs under conditions of tissular hypoxia, such as anemia. Functional relationships between erythroid bone marrow (BM) proliferation, differentiation, the expression of survival and apoptotic related proteins, as well as the features of the BM microenvironment upon acute anemic stress, are not fully elucidated. To achieve this aim, CF-1 Swiss mice were injected with a single dose of 5-fluorouracil (5-FU, 150 mg/kg ip) and a multiparametric analysis was conducted for 20 days. Apoptosis (TUNEL assay), BM architecture organization (scanning electronic microscopy), proliferation (DNA assay), differentiation (clonogenic cultures), expression of survival erythroid related proteins (EPO-R, GATA-1, Bcl-xL) as well as the expression of apoptotic- related proteins (Bax, activated Caspase-3) by Western blotting, were evaluated. Experimental data showed that apoptosis, arrest of cell proliferation and disruptions of BM architecture were maximal within the first period of acute stress (1-3 days). Bax and caspase-3 overexpressions were also coincident during this acute period. Moreover, from day 5 upon drug challenge BM responds to acute stress through the EPO-EPO-R system, prompting expressions of GATA-1 and Bcl-xL. Erythroid proliferation rates and red-cell-committed progenitors enhanced in a coordinated way to restore the size and function of the red cell compartment. A second overexpression wave of active caspase-3 was noticed during stress recovery. Together, these results indicate that in response to acute stress a dramatic increase in CFU-E (erythroid colony forming units) population is concomitant with upregulation of EPO-R, GATA-1 and Bcl-xL in the BM erythroid compartment, and that these concurrent processes are crucial for acquiring proper erythroid cell functionality without delayed response to tissular hypoxia.     

Evolution of mate-choice imprinting: competing strategies

Mate‐choice imprinting, the determination of mating preferences at an early age based on an individual's observation of adults, plays a role in mate choice in a wide variety of animals. Theoretical work has thus far been focused either on the effects of mate‐choice imprinting on the evolution of the male trait used as a mating cue, or on the evolution of imprinting against a nonimprinting background. We ask the question: if multiple types of imprinting are possible in a species, which is likely to evolve? We develop a haploid population genetic model to compare the evolution of three forms of imprinting: paternal, maternal, and oblique (nonparental adult) imprinting. We find that paternal imprinting is the most likely to evolve, whereas maternal and oblique are nearly equivalent. We identify two factors that determine a strategy's success: its “imprinting set,” the set of individuals imprinted upon, and phenogenotypic disequilibrium, the association between imprinted preferences and mating cues. We assess the predictive power of these factors, and find that the imprinting set is the primary determinant of a strategy's success. We suggest that the imprinting set concept may be generalized to predict the success of additional imprinting strategies, such as mate‐choice copying.