Comparative Study of Alkaline, Saline, and Mixed Saline–Alkaline Stresses with Regard to Their Effects on Growth, Nutrient Accumulation, and Root Morphology of Lotus tenuis

Both saline and alkaline conditions frequently coexist in nature; however, little is known about the effects of alkaline and salt?Calkaline stresses on plants. We performed pot experiments with four treatments, control without salt addition and three stress conditions??neutral, alkaline, and mixed salt?Calkaline??to determine their effects on growth, nutrient accumulation and root architecture in the glycophytic species Lotus tenuis. Neutral and alkaline salts produced a similar detrimental effect on L. tenuis growth, whereas the effect of their combination was synergistic. Neutral salt addition, alone or mixed with NaHCO₃, led to significant leaf Na⁺ build up and reduced K⁺ concentration. In contrast, in plants treated with NaHCO₃ only, Na⁺ levels and the Na⁺/K⁺ ratio remained relatively unchanged. Proline accumulation was not affected by the high pH in the absence of NaCl, but it was raised by the neutral salt and mixed treatments. The total root length was reduced by the addition of NaCl alone, whereas it was not affected by alkalinity, regardless of the presence of NaCl. The topological trend showed that alkalinity alone or mixed with NaCl turned the root more herringbone compared with control roots, whereas no significant change in this index was observed in the treatment with the neutral salt only. The pattern of morphological changes in L. tenuis root architecture after the alkaline treatment (in the absence of NaCl) was similar to that found in the mixed salt?Calkaline treatment and different from that observed in neutral salt. A unique root morphological response to the mixed salt?Calkaline stress was the reduction in the ratio between xylem vessels and root cross-sectional areas.     

Secondary alcohol dehydrogenase catalyzes the reduction of exogenous acetone to 2-propanol in Trichomonas vaginalis

Secondary alcohols such as 2-propanol are readily produced by various anaerobic bacteria that possess secondary alcohol dehydrogenase (S-ADH), although production of 2-propanol is rare in eukaryotes. Specific bacterial-type S-ADH has been identified in a few unicellular eukaryotes, but its function is not known and the production of secondary alcohols has not been studied. We purified and characterized S-ADH from the human pathogen Trichomonas?vaginalis. The kinetic properties and thermostability of T.?vaginalis S-ADH were comparable with bacterial orthologues. The substantial activity of S-ADH in the parasite's cytosol was surprising, because only low amounts of ethanol and trace amounts of secondary alcohols were detected as metabolic end products. However, S-ADH provided the parasite with a high capacity to scavenge and reduce external acetone to 2-propanol. To maintain redox balance, the demand for reducing power to metabolize external acetone was compensated for by decreased cytosolic reduction of pyruvate to lactate and by hydrogenosomal metabolism of pyruvate. We speculate that hydrogen might be utilized to maintain cytosolic reducing power. The high activity of Tv-S-ADH together with the ability of T.?vaginalis to modulate the metabolic fluxes indicate efficacious metabolic responsiveness that could be advantageous for rapid adaptation of the parasite to changes in the host environment.     

Structure-Guided Expansion of the Substrate Range of Methylmalonyl Coenzyme A Synthetase (MatB) of Rhodopseudomonas palustris

Malonyl coenzyme A (malonyl-CoA) and methylmalonyl-CoA are two of the most commonly used extender units for polyketide biosynthesis and are utilized to synthesize a vast array of pharmaceutically relevant products with antibacterial, antiparasitic, anticholesterol, anticancer, antifungal, and immunosuppressive properties. Heterologous hosts used for polyketide production such as Escherichia coli often do not produce significant amounts of methylmalonyl-CoA, however, requiring the introduction of other pathways for the generation of this important building block. Recently, the bacterial malonyl-CoA synthetase class of enzymes has been utilized to generate malonyl-CoA and methylmalonyl-CoA directly from malonate and methylmalonate. We demonstrate that in the purple photosynthetic bacterium Rhodopseudomonas palustris, MatB (RpMatB) acts as a methylmalonyl-CoA synthetase and is required for growth on methylmalonate. We report the apo (1.7-Å resolution) and ATP-bound (2.0-Å resolution) structure and kinetic analysis of RpMatB, which shows similar activities for both malonate and methylmalonate, making it an ideal enzyme for heterologous polyketide biosynthesis. Additionally, rational, structure-based mutagenesis of the active site of RpMatB led to substantially higher activity with ethylmalonate and butylmalonate, demonstrating that this enzyme is a prime target for expanded substrate specificity.     

Prader--Willi syndrome: 16-year experience in Hong Kong

Prader-Willi syndrome(PWS) is an important,wellrecognized syndromic form of neurodevelopmental disorder. The incidence is about 1 in 15,000-25,000 live births,and it affects both males and females(Vogels et al.,2004).The underlying genetic defects occur at an imprinted region on chromosome 15q11-13.Within this region,some genes only express on the maternally inherited chromosome 15,like UBE3A and ATP10C;while other genes only express on the paternally inherited chromosome 15,like MKRN3,MAGEL2, NDN,C15orf2,SNURF-SNRPN,and a number of small     

Hybridization of somatic cells derived from mouse and Syrian hamster: Evolution of karyotype and enzyme studies

Somatic hybrids of drug-resistant mutant hamster and mouse cell lines have been isolated and propagated in long-term culture and have been studied in respect to karyotype and three enzymes. During the course of propagation the long-surviving hybrid clones show progressive loss of telocentric chromosomes associated in at least one case with loss of mouse enzyme. Hybrid clones showed hybrid molecules for malate dehydrogenase (MDH), lactate dehydrogenase (LDH), and 6-phosphogluconate dehydrogenase (6PGD) made up by recombination of parental subunits.This work was supported by National Institutes of Health Grant HD 00486.     

A suspected parasite spill-back of two novel Myxidium spp. (Myxosporea) causing disease in Australian endemic frogs found in the invasive Cane toad

Infectious diseases are contributing to the decline of endangered amphibians. We identified myxosporean parasites, Myxidium spp. (Myxosporea: Myxozoa), in the brain and liver of declining native frogs, the Green and Golden Bell frog (Litoria aurea) and the Southern Bell frog (Litoria raniformis). We unequivocally identified two Myxidium spp. (both generalist) affecting Australian native frogs and the invasive Cane toad (Bufo marinus, syn. Rhinella marina) and demonstrated their association with disease. Our study tested the identity of Myxidium spp. within native frogs and the invasive Cane toad (brought to Australia in 1935, via Hawaii) to resolve the question whether the Cane toad introduced them to Australia. We showed that the Australian brain and liver Myxidium spp. differed 9%, 7%, 34% and 37% at the small subunit rDNA, large subunit rDNA, internal transcribed spacers 1 and 2, but were distinct from Myxidium cf. immersum from Cane toads in Brazil. Plotting minimum within-group distance against maximum intra-group distance confirmed their independent evolutionary trajectory. Transmission electron microscopy revealed that the brain stages localize inside axons. Myxospores were morphologically indistinguishable, therefore genetic characterisation was necessary to recognise these cryptic species. It is unlikely that the Cane toad brought the myxosporean parasites to Australia, because the parasites were not found in 261 Hawaiian Cane toads. Instead, these data support the enemy-release hypothesis predicting that not all parasites are translocated with their hosts and suggest that the Cane toad may have played an important spill-back role in their emergence and facilitated their dissemination. This work emphasizes the importance of accurate species identification of pathogens relevant to wildlife management and disease control. In our case it is paving the road for the spill-back role of the Cane toad and the parasite emergence.     

Four-way ligation for construction of a mammalian cell-based full-length antibody display library

A unique four-way ligation strategy was developed for rapid construction of a full-length antibody library. A mammalian expression vector was constructed that contained dual mammalian expression cassettes and sequences recognized by the unique restriction enzymes BsmBI, BstXI, and SfiI. Both full-length light-chain and variable domain of heavy-chain genes were inserted into the vector in one step by four-way ligation, and full-length bivalent antibodies were displayed on mammalian cell surfaces. Using this strategy, only 2 weeks were required to successfully construct high-quality, full-length human antibody libraries.     

Matrilin-4 is processed by ADAMTS-5 in late Golgi vesicles present in growth plate chondrocytes of defined differentiation state

The two aggrecanases ADAMTS-4 and ADAMTS-5 have been shown to not only play roles in the breakdown of cartilage extracellular matrix in osteoarthritis, but also mediate processing of matrilins in the secretory pathway. The matrilins are adaptor proteins with a function in connecting fibrillar and network-like components in the cartilage extracellular matrix. Cleavage resulting in processed matrilins with fewer ligand-binding subunits could make these less efficient in providing matrix cohesion. In this study, the processing and degradation of matrilin-4 during cartilage remodeling in the growth plate of the developing mouse long bones were studied in greater detail. We show that ADAMTS-5 and a matrilin-4 neoepitope, revealed upon ADAMTS cleavage, colocalize in prehypertrophic/hypertrophic chondrocytes while they are not detected in proliferating chondrocytes of the growth plate. ADAMTS-5 and the cleaved matrilin-4 are preferentially detected in vesicles derived from the Golgi apparatus. The matrilin-4 neoepitope was not observed in the growth plate of ADAMTS-5 deficient mice. We propose that in the growth plate ADAMTS-5, and not ADAMTS-4, has a physiological function in the intracellular processing of matrilins and potentially of other extracellular matrix proteins.     

Relations Between River Plant Richness in the Portuguese Floodplains and the Widespread Water Knotgrass <Emphasis Type="Italic">(Paspalum Paspalodes</Emphasis>)

We examined the variability of macroinvertebrate assemblage structure, species identities, and functional feeding group composition in relation to stream size, tributary position, and in-stream factors in a boreal watershed in Finland. Our study included three riffle sites in each of three stream sections in each of three stream size classes. Multi-response permutation procedure, indicator value method, and canonical correspondence analysis revealed clear differences in assemblage structure among the stream size classes, with a gradual increase of species richness as the stream size increased. Significant differences in assemblage structure were also found among the tributary river systems. The functional feeding group composition broadly followed the river continuum concept, i.e., headwaters were dominated by shredders, gatherers, or filterers, whereas scrapers increased in relative abundance with stream size. There was, however, considerable variation in the functional feeding group composition both among and within the headwater stream sections. Our findings refer to a strong influence of stream size on macroinvertebrate assemblages, but also factors prevailing at the scale of individual riffles should be considered in biodiversity conservation of lotic ecosystems.     

Addiction: Decreased reward sensitivity and increased expectation sensitivity conspire to overwhelm the brain's control circuit

Based on brain imaging findings, we present a model according to which addiction emerges as an imbalance in the information processing and integration among various brain circuits and functions. The dysfunctions reflect (a) decreased sensitivity of reward circuits, (b) enhanced sensitivity of memory circuits to conditioned expectations to drugs and drug cues, stress reactivity, and (c) negative mood, and a weakened control circuit. Although initial experimentation with a drug of abuse is largely a voluntary behavior, continued drug use can eventually impair neuronal circuits in the brain that are involved in free will, turning drug use into an automatic compulsive behavior. The ability of addictive drugs to co‐opt neurotransmitter signals between neurons (including dopamine, glutamate, and GABA) modifies the function of different neuronal circuits, which begin to falter at different stages of an addiction trajectory. Upon exposure to the drug, drug cues or stress this results in unrestrained hyperactivation of the motivation/drive circuit that results in the compulsive drug intake that characterizes addiction.