Effect of Chlorine Substitution on the Biodegradability of Polychlorinated Biphenyls

Thirty-one isomers of polychlorinated biphenyl (PCB) were examined for biodegradability by two species of Alcaligenes and Acinetobacter. The following relationships between chlorine substitution and biodegradability of PCBs were observed. (i) Degradation decreased as chlorine substitution increased. PCB isomers containing more than four chlorines were less susceptible to degradation. (ii) PCBs containing two chlorines on either the ortho position of a single ring (i.e., 2,6-) or on both rings (i.e., 2,2′-) showed very poor degradability. (iii) PCBs containing all chlorine atoms on only a single ring were generally degraded faster than when the same number of chlorines were substituted on both rings. (iv) Preferential ring fission of the molecules occurred with nonchlorinated or lesser chlorinated rings. (v) The formation and accumulation of a yellow intermediate was always observed in 4′-chloro-substituted PCBs. (vi) Significant differences between the two organisms with respect to degradability were not observed except for 2,4,6-trichlorobiphenyl.     

Electron transport chain from glycerol 3-phosphate to nitrate in Escherichia coli.

It is known that in Escherichia coli two dehydrogenases of the flavoprotein kind can participate in the transfer of hydrogens from sn-glycerol 3-phosphate (G3P) to nitrate and that possession of either enzyme is sufficient to permit anaerobic growth on glycerol as carbon source and nitrate as hydrogen acceptor. Results from this study show that under such a growth condition a protein with light-absorption characteristics of cytochrome b1 is induced. If G3P, nitrate, and adenosine diphosphate are added anaerobically to a particulate fraction prepared from these cells, four reactions can be detected: (i) the reduction of the cytochrome b1-like protein, (ii) the formation of dihydroxyacetone phosphate (DHAP), (iii) the formation of nitrite, and (iv) the generation of adenosine 5'-triphosphate (ATP). The anaerobic G3P dehydrogenase system can yield an ATP-DHAP (or ATP-nitrite) molar ratio of about 0.2, whereas the aerobic G3P dehydrogenase system can yield a corresponding ratio of about 0.3. The hydrogen transfer activity is sensitive to respiratory inhibitors such as cyanide, Rotenone, and 2-heptyl-4-hydroxyquinoline-N-oxide.     

Electron-microscopic studies on developing intramural ganglia of the small intestine in human and rabbit fetuses.

Electron-microscopic studies were made on the appearance of synapses in the intramural ganglion (Auerbach) and findings were correlated with the onset and development of intestinal peristalsis in 6- to 30-week-old human and rabbit fetuses from the 12th day after conception until birth. At stage I, in which the small intestine shows no indication of a muscle layer or spontaneous peristalsis, primitive synapses containing several clear vesicles and a few cored vesicles are seen on neuroblasts and their processes (dendrites). At stage II, in which the circular muscle is developed and bidirectional peristalsis occurs, synaptic profiles can be classified into 3 types. Type 1 is the most numerous but seldom shows membrane specificity on the synaptic portion. Types 2 and 3 have small flattened vesicles and small round vesicles, respectively. They are further characterized by thickening of snyaptic membranes and aggregation of small clear vesicles associated with the presynaptic membrane. At stage III, the longitudinal muscle layer develops in the small intestine. At this stage, nerve terminals containing mainly cored vesicles have been observed and classified into types 4 and 5, according to their morphology. At stage IV, antiperistalsis no longer occurs and type 6 nerve terminals in the intramural ganglia can be recognized by their densely packed, large-cored vesicles. The possible physiological significance of the nerve terminals has been discussed.     

Site-directed mutagenesis by biolistic transformation efficiently generates inheritable mutations in a targeted locus in soybean somatic embryos and transgene-free descendants in the T1 generation

The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated endonuclease 9 (Cas9) system is being rapidly developed for mutagenesis in higher plants. Ideally, foreign DNA introduced by this system is removed in the breeding of edible crops and vegetables. Here, we report an efficient generation of Cas9-free mutants lacking an allergenic gene, Gly m Bd 30K, using biolistic transformation and the CRISPR/Cas9 system. Five transgenic embryo lines were selected on the basis of hygromycin resistance. Cleaved amplified polymorphic sequence analysis detected only two different mutations in e all of the lines. These results indicate that mutations were induced in the target gene immediately after the delivery of the exogenous gene into the embryo cells. Soybean plantlets (T₀ plants) were regenerated from two of the transgenic embryo lines. The segregation pattern of the Cas9 gene in the T₁ generation, which included Cas9-free plants, revealed that a single copy number of transgene was integrated in both lines. Immunoblot analysis demonstrated that no Gly m Bd 30K protein accumulated in the Cas9-free plants. Gene expression analysis indicated that nonsense mRNA decay might have occurred in mature mutant seeds. Due to the efficient induction of inheritable mutations and the low integrated transgene copy number in the T₀ plants, we could remove foreign DNA easily by genetic segregation in the T₁ generation. Our results demonstrate that biolistic transformation of soybean embryos is useful for CRISPR/Cas9-mediated site-directed mutagenesis of soybean for human consumption.

     

Allelopathic effects of the revegetation species Juniperus sabina L. in semiarid areas of China

Landscape and Ecological Engineering - Juniperus sabina L. is a native evergreen conifer of the Mu Us Sandy Land. It has prostrating stems that can prevent sand shifting and is an important...     

Cortisol promotes stress tolerance via DAF-16 in Caenorhabditis elegans

In this study, we studied the effects of cortisol and cortisone on the age-related decrease in locomotion in the nematode Caenorhabditis elegans and on the tolerance to heat stress at 35 °C and to oxidative stress induced by the exposure to 0.1% H₂O₂. Changes in mRNA expression levels of C. elegans genes related to stress tolerance were also analyzed. Cortisol treatment restored nematode movement following heat stress and increased viability under oxidative stress, but also shortened worm lifespan. Cortisone, a cortisol precursor, also restored movement after heat stress. Additionally, cortisol treatment increased mRNA expression of the hsp-12.6 and sod-3 genes. Furthermore, cortisol treatment failed to restore movement of daf-16-deficient mutants after heat stress, whereas cortisone failed to restore the movement of dhs-30-deficient mutants after heat stress. In conclusion, the results suggested that cortisol promoted stress tolerance via DAF-16 but shortened the lifespan, whereas cortisone promoted stress tolerance via DHS-30.     

srGAP1 regulates lamellipodial dynamics and cell migratory behavior by modulating Rac1 activity

The distinct levels of Rac activity differentially regulate the pattern of intrinsic cell migration. However, it remains unknown how Rac activity is modulated and how the level of Rac activity controls cell migratory behavior. Here we show that Slit-Robo GAP 1 (srGAP1) is a modulator of Rac activity in locomotive cells. srGAP1 possesses a GAP activity specific to Rac1 and is recruited to lamellipodia in a Rac1-dependent manner. srGAP1 limits Rac1 activity and allows concomitant activation of Rac1 and RhoA, which are mutually inhibitory. When both GTPases are activated, the protrusive structures caused by Rac1-dependent actin reorganization are spatially restricted and periodically destabilized, causing ruffling by RhoA-induced actomyosin contractility. Depletion of srGAP1 overactivates Rac1 and inactivates RhoA, resulting in continuous spatiotemporal spreading of lamellipodia and a modal shift of intrinsic cell motility from random to directionally persistent. Thus srGAP1 is a key determinant of lamellipodial dynamics and cell migratory behavior.     

Farsenyl pyrophosphate synthase is a potential molecular drug target of risedronate in Babesia bovis

A cDNA encoding farnesyl pyrophosphate synthase of Babesia bovis (BbFPPS) has been isolated, cloned and characterized as molecular drug target. Sequence analysis revealed that BbFPPS contains an open reading frame of 1011 bp with predicted 336 amino acids and molecular mass of 38 kDa. Antiserum raised in mice against recombinant BbFPPS expressed in Escherichia coli specifically reacted with native protein of B. bovis parasites by Western blot analysis and indirect immunofluorescent test. Enzymatic assay using recombinant BbFPPS revealed that the K_m value of the enzyme for isopentenyl pyrophosphate and dimethylallyl pyrophosphate was 2.494 ± 1.536 μM. Risedronate inhibited the activity of BbFPPS yielding IC₅₀ value of 8.4 ± 1.2 nM. Furthermore, the in vitro growth of B. bovis was significantly inhibited in the presence of a micromolar concentration of risedronate (IC₅₀ = 4.02 ± 0.91 μM). No regrowth of B. bovis was observed at 10 μM of risedronate in the subsequent viability test. These results demonstrate that BbFPPS is the molecular target of risedronate, which could inhibit the in vitro growth of B. bovis.