Genetic affinities of inbred mouse strains of uncertain origin

Phylogenetic analyses of genetic data arising from 144 gene loci are used to describe the interrelationships among 24 widely used inbred strains of mice. An unordered-parsimony analysis gives a cladogram that is virtually identical to the known genealogy of the mouse strains. A loss-parsimony analysis is used to evaluate the hypothesis that the observed patterns of genetic divergence among these 24 strains can be explained by the segregation of residual heterozygosity arising from a small population of highly heterozygous mice. The loss-parsimony cladogram is very similar to both the unordered-parsimony cladogram and the known genealogy of the mice. The phylogenetic analyses of these 144 loci are integrated with data on the type and origin of the Y chromosome. Inclusion of the Y-chromosome data provides additional insights into the genetic composition of several of the original stocks used to produce the current inbred strains of mice. Ten strains of uncertain origin are contained in these analyses, including AKR, BUB, CE, I, NZB, P, RF, SJL, ST, and SWR. SJL is hypothesized to have been derived from the same Swiss albino stock previously used to produce SWR. The BUB strain appears to have had a complex origin and shows closest genetic similarity to SWR and ST. AKR and RF are shown to be closely related, while the I strain shows greatest genetic similarity to DBA/2 for the 144 loci. However, I and DBA possess different types of Y chromosome. The NZB strain shows genetic similarity to several stocks of both U.S. and European origins. The power of the genetic data used in these analyses reiterates that inbred strains of mice can be a valuable paradigm for studies in evolutionary biology.      

Protein kinase C mediates erythrocyte "programmed cell death" following glucose depletion

Glucose depletion of erythrocytes leads to activation of Ca²⁺-permeable cation channels, Ca²⁺ entry, activation of a Ca²⁺-sensitive erythrocyte scramblase, and subsequent exposure of phosphatidylserine at the erythrocyte surface. Ca²⁺ entry into erythrocytes was previously shown to be stimulated by phorbol esters and to be inhibited by staurosporine and chelerythrine and is thus thought to be regulated by protein phosphorylation/dephosphorylation, presumably via protein kinase C (PKC) and the corresponding phosphoserine/threonine phosphatases. The present experiments explored whether PKC could contribute to effects of energy depletion on erythrocyte phosphatidylserine exposure and cell volume. Phosphatidylserine exposure was estimated from annexin binding and cell volume from forward scatter in fluorescence-activated cell sorter analysis. Removal of extracellular glucose led to depletion of cellular ATP, stimulated PKC activity, led to translocation of PKC, enhanced serine phosphorylation of membrane proteins, decreased cell volume, and increased annexin binding, the latter effect being blunted but not abolished in the presence of 1 µM staurosporine or 50 nM calphostin C. The PKC stimulator phorbol-12-myristate-13-acetate (3 µM) and the phosphatase inhibitor okadaic acid (1–10 µM) mimicked the effect of glucose depletion and similarly led to translocation of PKC and enhanced serine phosphorylation, increased annexin binding, and decreased forward scatter, the latter effects being abrogated by PKC inhibitor staurosporine (1 µM). Fluo-3 fluorescence measurements revealed that okadaic acid also enhanced erythrocyte Ca²⁺ activity. The present observations suggest that protein phosphorylation and dephosphorylation via PKC and the corresponding protein phosphatases contribute to phosphatidylserine exposure and cell shrinkage after energy depletion. cell volume; eryptosis; calcium; okadaic acid; staurosporine     

CCR5- and CXCR4-Utilizing Strains of Human Immunodeficiency Virus Type 1 Exhibit Differential Tropism and Pathogenesis In Vivo

CCR5-utilizing (R5) and CXCR4-utilizing (X4) strains of human immunodeficiency virus type 1 (HIV-1) have been studied intensively in vitro, but the pathologic correlates of such differential tropism in vivo remain incompletely defined. In this study, X4 and R5 strains of HIV-1 were compared for tropism and pathogenesis in SCID-hu Thy/Liv mice, an in vivo model of human thymopoiesis. The X4 strain NL4-3 replicates quickly and extensively in thymocytes in the cortex and medulla, causing significant depletion. In contrast, the R5 strain Ba-L initially infects stromal cells including macrophages in the thymic medulla, without any obvious pathologic consequence. After a period of 3 to 4 weeks, Ba-L infection slowly spreads through the thymocyte populations, occasionally culminating in thymocyte depletion after week 6 of infection. During the entire time of infection, Ba-L did not mutate into variants capable of utilizing CXCR4. Therefore, X4 strains are highly cytopathic after infection of the human thymus. In contrast, infection with R5 strains of HIV-1 can result in a two-phase process in vivo, involving apparently nonpathogenic replication in medullary stromal cells followed by cytopathic replication in thymocytes.     

Oxidative stress promotes ligand-independent and enhanced ligand-dependent tumor necrosis factor receptor signaling

Tumor necrosis factor (TNF) receptor 1 (TNFR1, p55) and 2 (TNFR2, p75) are characterized by several cysteine-rich modules in the extracellular domain, raising the possibility that redox-induced modifications of these cysteine residues might alter TNFR function. To test this possibility, we examined fluorescence resonance energy transfer (FRET) in 293T cells transfected with CFP- and YFP-tagged TNFRs exposed to the thiol oxidant diamide. Treatment with high concentrations of diamide (1 mm) resulted in an increase in the FRET signal that was sensitive to inhibition with the reducing agent dithiothreitol, suggesting that oxidative stress resulted in TNFR self-association. Treatment of cells with low concentrations of diamide (1 mum) that was not sufficient to provoke TNFR self-association resulted in increased TNF-induced FRET signals relative to the untreated cells, suggesting that oxidative stress enhanced ligand-dependent TNFR signaling. Similar findings were obtained when the TNFR1- and TNFR2-transfected cells were pretreated with a cell-impermeable oxidase, DsbA, that catalyzes disulfide bond formation between thiol groups on cysteine residues. The changes in TNFR self-association were functionally significant, because pretreating the HeLa cells and 293T cells resulted in increased TNF-induced NF-kappaB activation and TNF-induced expression of IkappaB and syndecan-4 mRNA levels. Although pretreatment with DsbA did not result in an increase in TNF binding to TNFRs, it resulted in increased TNF-induced activation of NF-kappaB, consistent with an allosteric modification of the TNFRs. Taken together, these results suggest that oxidative stress promotes TNFR receptor self-interaction and ligand-independent and enhanced ligand-dependent TNF signaling.     

Linkage of cystic fibrosis locus and polymorphic DNA markers in 14 families

Linkage relationships between the cystic fibrosis (CF) locus and three polymorphic DNA markers were examined in 14 families, five of which were of Hispanic origin. Tight linkage was found between the CF locus and MET (maximum lod score = 7.16 at theta = .001), and between CF and pJ3.11 (maximum lod score = 3.87 at theta = .001). We observed two recombinations between CF and collagen, yielding a maximum lod score of 0.359 at theta = .125, and one recombination in the cluster CF-MET-pJ3.11. Analysis by the seriation method indicates the order COL-pJ3.11-CF-MET.     

Giardia lamblia: detection and characterization of calmodulin

Calmodulin was detected in Giardia lamblia by radioimmunoassay and cyclic AMP phosphodiesterase activation. This protein was purified to apparent homogeneity by fast protein liquid chromatography with a yield of 260 ng of calmodulin/mg of protozoan protein. Purity was established by gel electrophoresis, gel filtration, and ion exchange chromatography. The parasite calmodulin has properties characteristic of calmodulin isolated from other eukaryotes, e.g., an apparent molecular weight of 16.7 kD; activation in calcium dependent manner of bovine heart cyclic nucleotide phosphodiesterase; and sensitivity to known calmodulin antagonists.     

Relationships among net primary productivity, nutrients and climate in tropical rain forest: a pan-tropical analysis

Tropical rain forests play a dominant role in global biosphere-atmosphere CO(2) exchange. Although climate and nutrient availability regulate net primary production (NPP) and decomposition in all terrestrial ecosystems, the nature and extent of such controls in tropical forests remain poorly resolved. We conducted a meta-analysis of carbon-nutrient-climate relationships in 113 sites across the tropical forest biome. Our analyses showed that mean annual temperature was the strongest predictor of aboveground NPP (ANPP) across all tropical forests, but this relationship was driven by distinct temperature differences between upland and lowland forests. Within lowland forests (相似文献