The phylogenetic position of the musky rat-kangaroo and the evolution of bipedal hopping in kangaroos (Macropodidae: Diprotodontia)

Kangaroos and their relatives (family Macropodidae) are divided into the subfamilies Macropodinae (kangaroos, wallabies, pademelons) and Potoroinae (rat-kangaroos, potoroos, bettongs). The musky rat-kangaroo, Hypsiprymnodon moschatus, is traditionally allied with other potoroines, based primarily on the basis of osteological characters and aspects of the female reproductive system. Unlike other macropodids, however, which are capable of bipedal hopping, Hypsiprymnodon is a quadrupedal bounder and lacks several derived features of the pes and tarsus that are presumably adaptations for bipedal hopping. Other derived features, such as a complex stomach, loss of P2 with the eruption of P3, and reduction of litter size to one, are also lacking in Hypsiprymnodon but occur in all other macropodids. Thus, available evidence suggests that Hypsiprymnodon either is part of a monophyletic Potoroinae or is a sister taxon to other living macropodids. To test these hypotheses, we sequenced 1,170 bp base pairs of the mitochondrial genome for 16 macropodids. Maximum parsimony, minimum evolution, maximum likelihood, and quartet puzzling all support the hypothesis that macropodines and potoroines are united to the exclusion of Hypsiprymnodon. This hypothesis implies that characters such as bipedal hopping evolved only once in macropodid evolution. Aside from Hypsiprymnodon, the remaining macropodids separate into the traditional Macropodinae and Potoroinae. Macropodines further separate into two clades: one containing the New Guinean forest wallabies Dorcopsis and Dorcopsulus, and one consisting of the genera Macropus, Setonix, Thylogale, Onychogalea, Wallabia, Dendrolagus, Peradorcas, and Lagorchestes. Among potoroines, there is moderate support for the association of Bettongia and Aepyprymnus to the exclusion of Potorous. Divergence times were estimated by using 12S ribosomal RNA transversions. At the base of the macropodid radiation, Hypsiprymnodon diverged from other macropodids approximately 45 million years ago. This estimate is comparable to divergence estimates among families of Australasian possums based on single-copy DNA hybridization and 12S rRNA transversions. Macropodines and potoroines, in turn, diverged approximately 30 million years ago. Among macropodines, Dorcopsis and Dorcopsulus separated from other taxa approximately 10 million years ago.     

The origin of the Australasian marsupial fauna and the phylogenetic affinities of the enigmatic monito del monte and marsupial mole.

Alternative hypotheses in higher-level marsupial systematics have different implications for marsupial origins, character evolution, and biogeography. Resolving the position of the South American monito del monte (Order Microbiotheria) is of particular importance in that alternate hypotheses posit sister-group relationships between microbiotheres and taxa with disparate temporal and geographic distributions: pediomyids; didelphids; dasyuromorphians; diprotodontians; all other australidelphians; and all other marsupials. Among Australasian marsupials, the placement of bandicoots is critical; competing views associate bandicoots with particular Australasian taxa (diprotodontians, dasyuromorphians) or outside of a clade that includes all other Australasian forms and microbiotheres. Affinities of the marsupial mole are also unclear. The mole is placed in its own order (Notoryctemorphia) and sister-group relationships have been postulated between it and each of the other Australasian orders. We investigated relationships among marsupial orders by using a data set that included mitochondrial and nuclear genes. Phylogenetic analyses provide support for the association of microbiotheres with Australasian marsupials and an association of the marsupial mole with dasyuromorphs. Statistical tests reject the association of diprotodontians and bandicoots together as well as the monophyly of Australasian marsupials. The origin of the paraphyletic Australasian marsupial fauna may be accounted for by (i) multiple entries of australidelphians into Australia or (ii) bidirectional dispersal of australidelphians between Antarctica and Australia.     

Ribosomal RNA sequence phylogeny is not congruent with ascospore morphology among species in Ceratocystis sensu stricto

The genus Ceratocystis sensu stricto includes important fungal pathogens of woody and herbaceous plants. This genus is distinguished from species in Ceratocystis sensu lato by the presence of Chalara anamorphs. Ascospore shape has been used extensively in delineating Ceratocystis taxa, which show a large variety of ascospore shapes. Sequence analysis of one region of he 18S ribosomal RNA subunit and two regions of the 28S ribosomal RNA subunit showed that there was a majority of multiple substitutions at nucleotide sites and that there was a low transition/transversion ratio, T = 0.72. Both of these results suggest that these are well established, old species. Ascospore morphology, for the most part, was not congruent with the molecular phylogeny, and the use of morphological characters may be misleading in the taxonomy of these species.      

Arsenate-induced renal agenesis in rats

The developmental origin of arsenate-induced renal agenesis was investigated. Pregnant Wistar rats were each injected once ip with 45 mg/kg sodium arsenate at day 10 (sperm day = day 0). Pregnancy was terminated at various times following injection and the embryos recovered and serially sectioned. Renal agenesis resulted when the mesonephric duct failded to give rise to a ureteric bud with subsequent failure of induction of the metanephric blastema. The underlying defect was retardation in growth of the mesonephric duct, first observed 48 hours after arsenate injection. A shortened mesonephric duct also resulted in a failure of the mesonephros to attain normal size and in the male resulted in absence of the ductus deferens, seminal vesicle a variable portion of the epididymis. Due to the intimate association of the mesonephric and growing paramesonephric ducts, a shortened mesonephric duct resulted in a shortened paramesonephric duct with resultant lack of a uterine horn.     

Giemsa-based cytological assessment of area,shape and nucleus:cytoplasm ratio of goblet cells of rabbit bulbar conjunctiva

Goblet cells were visualized in impression cytology specimens from bulbar conjunctiva of the rabbit eye using Giemsa staining. Highly magnified images were used to generate outlines of the goblet cells and their characteristic eccentric nuclei. Using sets of 10 cells from 15 cytology specimens, I found that the longest dimension of the goblet cells averaged 16.7 ± 2.3 μm, the shortest dimension averaged 14.4 ± 1.8 μm and the nucleus averaged 6.3 ± 0.8 μm. The goblet cells were ellipsoid in shape and the longest:shortest cell dimension ratio averaged 1.169 ± 0.091. The goblet cell areas ranged from 108 to 338 μm² (average 193 ± 50 μm²). The area could be predicted reliably from the longest and shortest dimensions (r² = 0.903). The areas of goblet cell nuclei were 15–58 μm² (average 33 ± μm²) and the nucleus:cytoplasm area fraction was predictably greater in smaller goblet cells and less in the larger goblet cells (Spearman correlation = 0.817). The nuclei were estimated to occupy an average of 9.5% of the cell volume. The differences in size, shape and nucleus:cytoplasm ratio may reflect differences in goblet cell maturation.     

Synthesis and secretion of selenoprotein P by cultured rat astrocytes

Selenoprotein P is an extracellular protein that has been postulated to have an oxidant defense function. It has survival-promoting properties for cultured neurons and its mRNA is present in the brain. This study sought to determine the primary structure of rat brain selenoprotein P and to assess its production by cultured brain cells. The cDNA of selenoprotein P was isolated from a rat brain cDNA library and was found to encode the same peptide sequence as rat liver cDNA. Thus the primary structure of brain selenoprotein P is the same as selenoprotein P from liver. Astrocytes and a cerebellar granule cell preparation (CGC) were obtained from rat brains and established in culture. The CGC was estimated to contain up to 5% glial cells. Both preparations were shown to contain selenoprotein P mRNA. During incubation with (75)Se-labeled selenite, both cell preparations secreted a (75)Se-labeled protein into the medium that corresponded in size to selenoprotein P. Also, the (75)Se-labeled protein could be precipitated from both media with an antiserum to selenoprotein P. This shows that astrocytes and the CGC secrete selenoprotein P. Selenoprotein P is made in the brain and may have an oxidant defense function there.     

EGF-stimulation activates the nuclear localization signal of SHP-1

Protein tyrosine phosphatase SHP-1 plays a critical role in the regulation of a variety of intracellular signaling pathways. SHP-1 is predominantly expressed in the cells of hematopoietic origin, and is recognized as a negative regulator of lymphocyte development and activation. SHP-1 consists of two Src homology 2 (SH2) domains and one protein tyrosine phosphatase (PTP) domain followed by a highly basic C-terminal tail containing tyrosyl phosphorylation sites. It is unclear how the C-terminal tail regulates SHP-1 function. We report the examination of the subcellular localization of a variety of truncated or mutated SHP-1 proteins fused with enhanced green fluorescent protein (EGFP) protein at either the N-terminal or the C-terminal end in different cell lines. Our data demonstrate that a nuclear localization signal (NLS) is located in the C-terminal tail of SHP-1 and the signal is primarily defined by three amino-acid residues (KRK) at the C-terminus. This signal is generally blocked in the native protein and can be exposed by fusing EGFP at the appropriate position or by domain truncation. We have also revealed that this NLS of SHP-1 is triggered by epidermal growth factor (EGF) stimulation and mediates translocation of SHP-1 from the cytosol to the nucleus in COS7 cell lines. These results not only demonstrate the importance of the C-terminal tail of SHP-1 in the regulation of nuclear localization, but also provide insights into its role in SHP-1-involved signal transduction pathways.