ObjectiveTo explore the projections of the long descending propriospinal tracts to lumbar enlargement. Method　Anterograde tracing with cupric-silver staining. 10 animals were injected b biotinylated dextran in the upper cervical cord. Following survival times of 14 days, projections of the long descending propriospinal tracts were immunohistochemically demonstrated in the lumbar enlargement.Results　The degenerated terminals and labeled terminals were found in the bilateral gray matter of the lumbar enlargement, but predominantly ipsilaterally. The terminals were widely distributed in laminal Ⅴ-Ⅸ, heavily Ⅶ and Ⅷ. Conclusion　The long descending propriospinal tract from the upper cervical cord projects to the lumbar enlargement.

The direct spinal projections from the cerebellar nuclei in the rabbit were retro gradely traced by unilateral injection of WGA-HRP into different levels of the spinal cord, including the cervical, thoracic and lumbar segments. The labeled neurons in the cerebellar nuclei were constantly seen in those animals, in which the upper cervical segments (C_(2-4)) were injected. No labeled neurons could be found in the cerebellar nuclei following injection into the lower cervical cord (C_(6-8)) or more caudal segments. All labeled neurons were located in the caudal parts of the fastigial and the interposed nuclei on the side contralateral to the injection. The results show that there are crossed projections from the cerebellar nuclei directly to the upper cervical cord. This study provide certain morphological evidences for further investigation of some aspects of cerebellar functions on motor coordination.

Objective: To compare the histopathological changes after neo-adjuvant radiotherapy and to elucidate the mechanism of radiotherapy in rectal cancer. Methods: 80 patients with rectal cancer in pTNM stage Ⅱ or Ⅲ were enrolled between April 2000 and December 2002.They were randomly assigned to surgery alone or preoperative neo-adjuvant radiotherapy.The conventional radiotherapy scheme was followed: 40 Gy in 2.0 Gy fractions.The treatment last 4 weeks and it is usually followed by an interval of 1-2 weeks before the operation.Pathological changes including necrosis of tumor and changes of matrix and vessels were graded. Results: Significant tumor regression(RCRG 1) was seen in 14 cases(35 percent) after radiotherapy,while partially tumor regression(RCRG 2) was seen in 18 cases(45 percent).Significant necrosis was observed in 72.5 percent of cases after preoperative radiotherapy,most foci of adenocarcinoma were replaced by fibrosis in 80 percent of cases,and intimal thickening in most of the vessels were seen in 77.5 percent of cases.The frequency of these pathological changes after radiotherapy was significantly more than control group. Conclusion: Necrosis,fibrosis and thickening of vascular intima in the rectal cancer tissue after radiotherapy is more frequent than those without radiotherapy.It may be the potential reason for increased resection rate and sphincter-saving after radiotherapy.

Cofactor balance plays an important role in producing enzymes, pharmaceuticals and chemicals. To meet the demand of industrial production, microbes should maintain a maximal carbon flux towards target metabolites without fluctuations in cofactor. We reviewed the physiological function of cofactor and discussed detailed strategies to manipulate cofactor balance through biochemical engineering and metabolic engineering. Furthermore, we indicated future research needs to further regulate cofactor balance.

To quickly and efficiently understand the intracellular metabolic characteristics of industrial microorganisms, and to find potential metabolic engineering targets, genome-scale metabolic network models (GSMMs) as a systems biology tool, are attracting more and more attention. We review here the 20-year history of metabolic network model, analyze the research status and development of GSMMs, summarize the methods for model construction and analysis, and emphasize the applications of metabolic network model for analyzing intracellular metabolic activity of microorganisms from cellular phenotypes, and metabolic engineering. Furthermore, we indicate future development trend of metabolic network model.
Industrial Microbiology ; Metabolic Engineering ; Metabolic Networks and Pathways ; genetics ; Models, Biological ; Systems Biology

Shikimic acid is an intermediate metabolite in the synthesis of aromatic amino acids in Escherichia coli and a synthetic precursor of Tamiflu. The biosynthesis of shikimic acid requires blocking the downstream shikimic acid consuming pathway that leads to inefficient production and cell growth inhibition. In this study, a dynamic molecular switch was constructed by using growth phase-dependent promoters and degrons. This dynamic molecular switch was used to uncouple cell growth from shikimic acid synthesis, resulting in the production of 14.33 g/L shikimic acid after 72 h fermentation. These results show that the dynamic molecular switch could redirect the carbon flux by regulating the abundance of target enzymes, for better production.
Escherichia coli/genetics* ; Escherichia coli Proteins/genetics* ; Industrial Microbiology/methods* ; Metabolic Engineering ; Shikimic Acid/metabolism*

As a platform chemical, acetoin has a great potential of application in medicine and food industries. In order to improve the efficiency of acetoin production, Bacillus amyloliquefaciens was treated by atmospheric and room temperature plasma and gamma rays. Two-round screening was adopted for obtaining positive mutants, and the best mutant B. amyloliquefaciens H-5 produced acetoin up to 68.2 g/L in shake flask. Then, culture conditions were optimized in 5-L fermentor to enhance acetoin production. Finally, 85.2 g/L acetoin was produced by B. amyloliquefaciens H-5, which was increased by 26.8% compared with that of the original strain B. amyloliquefaciens FMME088. These results indicated that the high-producing strain can be obtained efficiently by compound mutagenesis, which has a promising prospect for commercial scale process.

Human activities increase the concentration of atmospheric carbon dioxide (CO₂), which leads to global climate warming. Microbial CO₂ fixation is a promising green approach for carbon neutral. In contrast to autotrophic microorganisms, heterotrophic microorganisms are characterized by fast growth and ease of genetic modification, but the efficiency of CO₂ fixation is still limited. In the past decade, synthetic biology-based enhancement of heterotrophic CO₂ fixation has drawn wide attention, including the optimization of energy supply, modification of carboxylation pathway, and heterotrophic microorganisms-based indirect CO₂ fixation. This review focuses on the research progress in CO₂ fixation by heterotrophic microorganisms, which is expected to serve as a reference for peaking CO₂ emission and achieving carbon neutral by microbial CO₂ fixation.
Carbon Cycle ; Carbon Dioxide/metabolism* ; Heterotrophic Processes ; Humans ; Synthetic Biology

L-arginine (L-Arg) is an alkaline amino acid that possesses various function groups and acts as an important precursor for useful chemical synthesis. L-Arg derivatives are widely applied in pharmaceutical, food and cosmetic industries. Environment friendly and cost-effective production of L-Arg derivatives by enzymatic catalysis provides significant advantages over chemical synthesis and microbial fermentation. In this article, several typical L-Arg derivatives and their enzymatic production processes are highlighted. Furthermore, prospect is also addressed about enzymatic production of L-Arg derivatives.

L-2-aminobutyric acid (L-ABA) is an important chemical raw material and chiral pharmaceutical intermediate. The aim of this study was to develop an efficient method for L-ABA production from L-threonine using a trienzyme cascade route with Threonine deaminase (TD) from Escherichia. coli, Leucine dehydrogenase (LDH) from Bacillus thuringiensis and Formate dehydrogenase (FDH) from Candida boidinii. In order to simplify the production process, the activity ratio of TD, LDH and FDH was 1:1:0.2 after combining different activity ratios in the system in vitro. The above ratio was achieved in the recombinant strain E. coli 3FT+L. Moreover, the transformation conditions were optimized. Finally, we achieved L-ABA production of 68.5 g/L with a conversion rate of 99.0% for 12 h in a 30-L bioreactor by whole-cell catalyst. The environmentally safe and efficient process route represents a promising strategy for large-scale L-ABA production in the future.
Aminobutyrates ; chemical synthesis ; Bacillus thuringiensis ; enzymology ; Candida ; enzymology ; Escherichia coli ; enzymology ; Formate Dehydrogenases ; metabolism ; Leucine Dehydrogenase ; metabolism ; Threonine ; metabolism ; Threonine Dehydratase ; metabolism