Thiyl Radical Trapped by Cobalt Catalysis: An Approach to Markovnikov Thiol-Ene Reaction

In the presence of a thiyl radical species, the catalytic Markovnikov thiol-ene reaction is challenging because it prefers to proceed via a radical pathway, thereby leading to anti-Markovnikov selectivity. In this work, a rare example of thiyl radical engaged in Markovnikov thiol-ene reaction enabled by cobalt catalysis is reported. This protocol features the avoidance of unique oxidants, exclusive regioselectivity, and broad substrate scope. Scalable synthesis and late-stage modification of complex molecules demonstrate the practicability of the protocol.

[The research of liver failure in Banna miniature pigs caused by amanita exitialis]

Objective: To explore the characteristics of Banna miniature pig liver failure induced by amanita exitialis. Methods: From September to October 2020, a reverse high performance liquid chromatography (RP-HPLC) method was used to determine the toxin content of amanita exitialis solution, and 2.0 mg/kg amanita exitialis solution (α-amanitins+β-amanitins) was administered orally to Banna miniature pigs. Toxic symptoms, blood biochemical indexes and histopathological changes of liver, heart and kidney were observed at each time point. Results: All Banna miniature pigs died within 76 h of exposure, and different degrees of digestive tract symptoms such as nausea, vomiting and diarrhea appeared between 6 and 36 h. The biochemical indexes of alanine aminotransferase, aspartate aminotransferase, total bilirubin, lactate dehydrogenase, myoglobin, creatine kinase isoenzyme, blood urea nitrogen and creatinine increased significantly at 52 h after exposure, and the differences were statistically significant compared with 0 h (P<0.05). The bleeding of liver and heart was obvious under macroscopic and microscopic observation, hepatocyte necrosis, renal tubule epithelial cell swelling. Conclusion: Large dose of amanita exitialis can cause acute liver failure of Banna miniature pigs, which is in line with the pathophysiological characteristics of acute liver failure, and lays a foundation for further research on the toxic mechanism and detoxification drugs of amanita exitialis induced liver failure.

[Molecular epidemiology and clinical characteristics of six cases of CA-MRSA pneumonia after influenza]

Objective: To summarize and analyze the strains' molecular epidemiology and clinical characteristics of 6 strains of post-influenza community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) pneumonia. Methods: Six cases of CA-MRSA pneumonia after influenza from 2014 to 2022 were retrospectively collected and CA-MRSA strains from each patient were cultured. Then, SCCmec typing, MLST typing, and spa typing were performed on the samples, which also included the procedures for the detection of virulence factors. Antibiotic susceptibility test was then performed on all 6 strains. Results: ST59-t437-Ⅳ was the predominant type in all the strains of CA-MRSA(2/6). Leukocidin (PVL) was detected in 5 cases, and hemolysin α (HLAα) and phenol soluble regulatory protein α (PSMα) were detected in 6 cases. Five of the cases included in this study were diagnosed with severe pneumonia. In terms of treatment, 4 cases received antiviral therapy, and 5 patients with severe pneumonia received anti-infection treatment with vancomycin as the first choice and were discharged after improvement of their condition. Conclusions: The molecular types and virulence factors of CA-MRSA after influenza infection could vary considerably. Our experiments also showed that secondary CA-MRSA infection after influenza was more common in young people with no underlying diseases and could cause severe pneumonia. Vancomycin and linezolid were the first-line drugs for treating CA-MRSA infection and were highly effective in improving the condition of diagnosed patients. We highlighted the importance of referring patients with severe pneumonia after influenza for etiological tests to determine whether they had CA-MRSA infection, so that they could be properly treated with anti-influenza agents and receive appropriate anti-CA-MRSA infection treatment.

Building a cobaloxime-based metal-organic framework for photocatalytic aerobic oxidation of arylboronic acids to phenols

Herein, the design and synthesis of an unprecedented cobaloxime-based zirconium metal-organic framework (Zr-TCPCo) with an she net is reported. This heterogeneous material as a photocatalyst exhibits excellent catalytic activity for aerobic oxidation of arylboronic acids to phenols. Recycling experiments demonstrate the stability and reusability of Zr-TCPCo as a robust catalyst.

[Investigation on a case of Amanita neoovoidea poisoning]

This paper reported a case of poisoning caused by ingestion of Amanita neoovoidea. The patient experienced nausea, vomiting, oliguria, acute renal function injury, and was discharged after symptomatic support treatment and blood purification treatment. Given the different toxicity of different mushrooms, species identification of poisonous mushrooms can help clinicians in diagnosis and treatment.

Minisci reaction of heteroarenes and unactivated C(sp3)-H alkanes via a photogenerated chlorine radical

Here, an efficient Minisci reaction of heteroarenes and unactivated C(sp³)-H alkanes was achieved using an inexpensive FeCl₃ as a photocatalyst. The photogenerated chlorine radical contributed to the HAT of C-H and subsequently initiated this reaction. Surprisingly, salt water and even seawater can act as a chlorine radical source, which provided an enlightening idea for future organic synthesis methods.

Regulable cross-coupling of alcohols and benzothiazoles via a noble-metal-free photocatalyst under visible light

Here, we realize a regulable cross-coupling reaction using alcohols as alkylating reagents to functionalize benzothiazoles. Two types of cross-coupling products are obtained with the highest isolated yields of up to 99% and 90% for alkyl- and acetyl-derived benzothiazoles, respectively, which opens up a broad research prospect for expanding alcohols as alkylating reagents.

Direct visible-light-induced synthesis of P-stereogenic phosphine oxides under air conditions

Over the past two decades, visible-light-induced transformations have been regarded as being among the most environmentally benign and powerful strategies for constructing complex molecules and diverse synthetic building blocks in organic synthesis. However, the development of efficient photochemical processes for assembling enantiomerically pure molecules remains a significant challenge. Herein, we describe a simple and efficient visible-light-induced C–P bond forming reaction for the synthesis of P-chiral heteroaryl phosphine oxides in moderate to high yields with excellent ee values (97–99% ee). Even in the absence of transition metal or photoredox catalysts, a variety of P-chiral heteroaryl phosphine oxides, including chiral diphosphine oxide 41, have been directly obtained under air conditions. Density functional theory (DFT) calculations have shown that the reaction involves intersystem crossing and single electron transfer to give a diradical intermediate under visible light irradiation.

We describe a simple and efficient visible-light-induced C–P bond forming reaction for the synthesis of P-chiral heteroaryl phosphine oxides in moderate to high yields with excellent ee values (97–99% ee).

Recent Advances in Visible-Light Photoredox Catalysis for the Thiol-Ene/Yne Reactions

Visible-light photoredox catalysis has been established as a popular and powerful tool for organic transformations owing to its inherent characterization of environmental friendliness and sustainability in the past decades. The thiol-ene/yne reactions, the direct hydrothiolation of alkenes/alkynes with thiols, represents one of the most efficient and atom-economic approaches for the carbon-sulfur bonds construction. In traditional methodologies, harsh conditions such as stoichiometric reagents or a specialized UV photo-apparatus were necessary suffering from various disadvantages. In particular, visible-light photoredox catalysis has also been demonstrated to be a greener and milder protocol for the thiol-ene/yne reactions in recent years. Additionally, unprecedented advancements have been achieved in this area during the past decade. In this review, we will summarize the recent advances in visible-light photoredox catalyzed thiol-ene/yne reactions from 2015 to 2021. Synthetic strategies, substrate scope, and proposed reaction pathways are mainly discussed.

External oxidant-free and selective thiofunctionalization of alkenes enabled by photoredox-neutral catalysis

A photoredox approach was reported to realize a highly selective three-component thiohydroxylation, thioalkoxylation and thioamination of vinylarenes towards valuable vicinal S,O- and S,N-disubstituted molecules under mild conditions.

Photoinduced Radical Cascade Cyclization: A Metal-Free Approach to Access Difluoroalkylated Dioxodibenzothiazepines

A simple and mild photoredox catalytic approach to access difluoroalkylated dioxodibenzothiazepines in high regioselectivity via radical cascade cyclization has been described herein. In contrast to previous methods, this strategy does not involve the use of transition-metal catalysts and avoids the potential disadvantages of inevitable toxicity and the tedious removal process of metal catalysts. The commercially available and inexpensive CF₂ precursors, wide substrate scope, and mild reaction conditions demonstrate the practicability of this approach.

[Three cases of mushroom poisoning caused by lethal Amanita species]

Mushroom poisoning with amatoxins can cause liver dysfunction in patients, and death in severe cases. The amatoxins detection by enzyme-linked immunosorbent assay (ELISA) can help early clinical diagnosis. Three patients were identified as α-amatoxin containing mushroom poisoning by ELISA. The first symptoms of patients was gastrointestinal symptoms, and liver function damage occured later. One patient gave up treatment and died. After received supportive treatments such as adsorption of toxins, catharsis, fluid supplementation to promote toxin metabolism and liver protection, 2 patients were recovered and discharged.

Photoredox/cobaloxime co-catalyzed allylation of amines and sulfonyl hydrazines with olefins to access α-allylic amines and allylic sulfones

Herein, we reported a dual-catalytic platform for the allylation of amines and sulfonyl hydrazines with olefins to selectively access α-allylic amines and allylic sulfones in good yields by combining photoredox catalysis and cobaloxime catalysis. This strategy avoided the use of a stoichiometric amount of terminal oxidant and the use of pre-functionalized allylic precursors, representing a green and ideal atom- & step-economical process. Good substrate scope and gram-scale synthesis demonstrated the utility of this protocol. Mechanistic studies revealed that a radical process is probably involved in this reaction.

Light-Promoted and Tertiary-Amine-Assisted Hydroxysulfenylation of Alkenes: Selective and Direct One-Pot Synthesis of β-Hydroxysulfides

A light-promoted and tertiary-amine-assisted strategy for efficient hydroxysulfenylation of both electron-rich and electron-deficient alkenes with thiophenols to selectively and directly access β-hydroxysulfides in one pot is described herein. In contrast to the previously reported thiol-oxygen co-oxidation reactions, this simple and sustainable approach features mild reaction conditions, high efficiency, and excellent functional group tolerance.

Directing-Group-Assisted Markovnikov-Selective Hydrothiolation of Styrenes with Thiols by Photoredox/Cobalt Catalysis

In contrast with the well-developed radical thiol-ene reaction to access anti-Markovnikov-type products, the research on the catalytic Markovnikov-selective hydrothiolation of alkenes is very restricted. Because of the catalyst poisoning of metal catalysts by organosulfur compounds, limited examples of transition-metal-catalyzed thiol-ene reactions have been reported. However, in this work, a directing-group-assisted hydrothiolation of styrenes with thiols by photoredox/cobalt catalysis is found to proceed smoothly to afford Markovnikov-type sulfides with excellent regioselectivity.

Selective photoredox decarboxylation of α-ketoacids to allylic ketones and 1,4-dicarbonyl compounds dependent on cobaloxime catalysis

The selective synthesis of allylic ketones and 1,4-dicarbonyl compounds by photoredox/cobaloxime co-catalysis and photoredox catalysis, respectively, is described herein.

Efficient acceptorless photo-dehydrogenation of alcohols and N-heterocycles with binuclear platinum(ii) diphosphite complexes

Binuclear platinum(ii) diphosphite complexes efficiently catalyzed the photo-dehydrogenation of alcohols and N-heterocycles (75 examples in total) under oxygen-free and acceptorless conditions at room temperature.

Although photoredox catalysis employing Ru(ii) and Ir(iii) complexes as photocatalysts has emerged as a versatile tool for oxidative C–H functionalization under mild conditions, the need for additional reagents acting as electron donor/scavenger for completing the catalytic cycle undermines the practicability of this approach. Herein we demonstrate that photo-induced oxidative C–H functionalization can be catalysed with high product yields under oxygen-free and acceptorless conditions via inner-sphere atom abstraction by binuclear platinum(ii) diphosphite complexes. Both alcohols (51 examples), particularly the aliphatic ones, and saturated N-heterocycles (24 examples) can be efficiently dehydrogenated under light irradiation at room temperature. Regeneration of the photocatalyst by means of reductive elimination of dihydrogen from the in situ formed platinum(iii)-hydride species represents an alternative paradigm to the current approach in photoredox catalysis.

Methylation-Based Age Estimation Model Construction and Its Effectiveness Evaluation

OBJECTIVES

To screen the DNA methylation loci associated with the age of Han males in northern China and to construct an age estimation model.

METHODS

Twenty-one candidate methylation loci were screened. The DNA methylation levels of 476 blood samples from Chinese Han males were detected for 21 amplicons using EpiTYPER technology platform, and data on 153 DNA methylation loci were obtained.

RESULTS

After correlation analysis, 8 age-related DNA methylation loci were finally screened. CpG1, CpG2, CpG4, CpG7, CpG8 were located on TRIM59, RASSF5, Clorf132, CSNK1D, ELOVL2,CpG5, CpG6 on PDE4C, and CpG3 on chr17:21452808. Based on the 8 loci, 352 samples were used for model construction. A multivariate linear regression age estimation model was constructed （R²=0.93）, with mean absolute deviation （MAD） of 2.69 years old. When 109 samples were used for model validation, the MAD was 3.80 years old. The test was repeated 3 times in 15 new samples, with MADs of 4.08, 4.68 and 3.93 years old, respectively.

CONCLUSIONS

The age estimation model on Han males in northern China constructed in this study can be used to estimate the age of victims and suspects and to narrow the scope of investigation, and therefore has practical application value.

Photoinduced synthesis of fluorinated dibenz[b,e]azepines via radical triggered cyclization

A simple, mild and efficient approach to access fluorinated dibenz[b,e]azepines via visible-light photoredox catalysis is presented.

Identifying key intermediates generated in situ from Cu(II) salt-catalyzed C-H functionalization of aromatic amines under illumination

Copper compounds involved in photocatalysis have recently spurred considerable interest for their novel transformations. However, mechanistic investigations are still in infancy. We find a new type of reaction, that is, Cu(II) salt-catalyzed C-H functionalization of aromatic amines triggered by visible light irradiation. An array of mechanistic observations, including high-resolution mass spectrometry, ultraviolet-visible absorption spectrum, electron spin resonance, x-ray absorption near-edge structure, and density functional theory calculation, have identified the key intermediates generated in situ in the transformation. Integration of single-electron transfer, singlet oxygen (¹O₂), and new absorption species, intermediate I and intermediate II formed in situ from Cu(II) salts and substrate amines or imines, respectively, is responsible for the N-H and C-H bond activation of secondary amines to couple with nucleophiles in air, thereby leading to the formation of quinoline, indolo[3,2-c]quinoline, β-amino acid, and 1,4-dihydropyridine derivatives in moderate to good yields under visible light irradiation at room temperature.

Platinum(ii) photo-catalysis for highly selective difluoroalkylation reactions

A platinum(ii) photo-catalysis for highly selective difluoroalkylation reactions with high efficiency, good substrate scope and high selectivity was developed.

Response to transarterial chemoembolization as a selection criterion for resection of hepatocellular carcinomas

BACKGROUND

Liver resection for intermediate (Barcelona Clinic Liver Cancer (BCLC) stage B) hepatocellular carcinoma (HCC) remains controversial. This study attempted to demonstrate the effectiveness of preresection transarterial chemoembolization (TACE) as a selection criterion for BCLC-B HCC.

METHODS

The study included patients with BCLC-B HCC who underwent liver resection after TACE. The tumour response to TACE was evaluated according to the modified Response Evaluation Criteria in Solid Tumours (mRECIST). Patients with a complete or partial response comprised the responder group, whereas those with stable or progressive disease were classified as non-responders.

RESULTS

A total of 242 patients were included. After between one and eight sessions of TACE, 141 patients were included in the responder group: 37 patients (15·3 per cent) who achieved a complete response and 104 who had a partial response. The cumulative 1-, 3- and 5-year overall survival rates were 97·2, 88·7 and 75·2 per cent respectively in the responder group, compared with 90·1, 67·3 and 53·5 per cent among 101 non-responders (P < 0·001). Tumour-free survival rates were also better among responders than non-responders (P < 0·001). In multivariable analysis, independent predictors of overall and tumour-free survival were response to TACE and microvascular invasion (all P < 0·001).

CONCLUSION

mRECIST may represent selection criterion for intermediate HCC for surgical treatment.

Combining visible light catalysis and transfer hydrogenation for in situ efficient and selective semihydrogenation of alkynes under ambient conditions

By combining visible light catalysis and transfer hydrogenation, we are able to convert a series of alkynes to their corresponding alkenes in high chemical yields.

The singlet excited state of BODIPY promoted aerobic cross-dehydrogenative-coupling reactions under visible light

We disclose for the first time that the singlet excited state (¹PS*) of BODIPY rather than triplet excited state (³PS*) can drive C–H bond activation to form C–C and C–P bonds smoothly upon irradiation by visible light.

A highly efficient and selective aerobic cross-dehydrogenative-coupling reaction photocatalyzed by a platinum(II) terpyridyl complex

Thanks to the superior redox potential of platinum(II) complex compared with that of Ru(bpy)3(2+) in the excited state, an efficient and selective visible-light-induced CDC reaction has been developed by using a catalytic amount (0.25 %) of 1. With the aid of FeSO4 (2 equiv), the corresponding amide could not be detected under visible-light irradiation (λ=450 nm), but the desired cross-coupling product was exclusively obtained under ambient air conditions. A spectroscopic study and product analysis revealed that the CDC reaction is initiated by photoinduced electron-transfer from N-phenyltetrahydroisoquinoline to the complex. An EPR (electron paramagnetic resonance) experiment provides direct evidence on the generation of superoxide radical anion (O2(-·)) rather than singlet oxygen ((1)O2) under irradiation of the reaction system, in contrast to that reported in the literature. Combined, the photoinduced electron-transfer and subsequent formation of superoxide radical anion (O2(-·)) results in a clean and facile transformation.

Tauroursodeoxycholate, a chemical chaperone, prevents palmitate-induced apoptosis in pancreatic β-cells by reducing ER stress

BACKGROUND

Free fatty acids (FFA) can have deleterious effects on β-cells and promote type 2 diabetes, a process known as lipotoxicity. Recently, the induction of endoplasmic reticulum (ER) stress is one mechanism proposed to contribute to the detrimental effects of FFA on β-cells. Tauroursodeoxycholic acid (TUDCA) has been reported to show cytoprotective effects by alleviating ER stress induced by some cytotoxic stimuli. The aim of this study was to investigate the effects of TUDCA on FFA (palmitate)-induced apoptosis and ER stress in rat islet β-cells.

METHODS

The rat pancreatic β-cell line INS-1 was cultured with palmitate (0.5 mM), or cultured togther with TUDCA (100 μM), Annexin V-fluorescein-isothiocyanate/propidium iodide flow cytometry was used to assess apoptosis in INS-1 cells. Cell viability was evaluated with MTT reduction conversion assay. The expressions of ER stress marker GRP78, ER stress-associated pro-apoptotic effectors CHOP and ATF4 were detected by Western blotting.

RESULTS

TUDCA significantly reduced palmitate-induced cell apoptosis and growth inhibition in INS-1 cells. TUDCA also attenuated palmitate-induced expressions of GRP78, CHOP and ATF4 in INS-1 cells.

CONCLUSIONS

Our results thus suggested that TUDCA could protect INS-1 cells from palmitate-induced injury, which might be due to the amelioration of ER stress and blocking the ATF4/CHOP signaling pathway.

Effect of light irradiation on anthocyanin production by suspended culture of Perilla frutescens

After a series of experiments on photoperiodicity and light intensity under daylight supplied by an ordinary fluorescent lamp in cultivations using a flask and a roux bottle, it was found that irradiation at 27.2 W/m(2) for the whole period was effective for anthocyanin production by a suspended culture of Perilla frutescens (shiso). A high amount of anthocyanin pigments, 3.0 g/L, was obtained in a bubble column bioreactor after 10 days of cultivation at an aeration rate of 0.1 vvm with light irradiation at 27.2 W/m(2), while 2 g/L was obtained at 13.6 W/m(2) and very little at 54.4 W/m(2). A high amount of anthocyanin pigments, 2.9 g/L, was also produced using an aerated and agitated bioreactor at an agitation speed of 130 rpm, an aeration rate of 0.1 vvm and light irradiation intensity of 27.2 W/m(2). The amount of anthocyanin produced was more than twice that without light irradiation, Keeping the other cultivation conditions the same. The results obtained also showed that the amount of anthocyanin pigment accumulated in a shake flask could be rather well reproduced in bioreactors for both aerated culture, and aerated and agitated culture, by improving the conditions of light irradiation, which conspicuously affects metabolite formation.

Damage of Escherichia coli membrane by bactericidal agent polyhexamethylene guanidine hydrochloride: micrographic evidences

AIMS

The purpose of this study was to provide micrographic evidences for the damaged membrane structure and intracellular structure change of Escherichia coli strain 8099, induced by polyhexamethylene guanidine hydrochloride (PHMG).

METHODS AND RESULTS

The bactericidal effect of PHMG on E. coli was investigated based on beta-galactosidase activity assay, fluorescein-5-isothiocyanate confocal laser scanning microscopy, field emission scanning electron microscopy and transmission electron microscopy. The results revealed that a low dose (13 microg ml(-1)) of PHMG slightly damaged the outer membrane structure of the treated bacteria and increased the permeability of the cytoplasmic membrane, while no significant damage was observed to the morphological structure of the cells. A high dose (23 microg ml(-1)) of PHMG collapsed the outer membrane structure, led to the formation of a local membrane pore across the membrane and badly damaged the internal structure of the cells. Subsequently, intracellular components were leaked followed by cell inactivation.

CONCLUSIONS

Dose-dependent membrane disruption was the main bactericidal mechanism of PHMG. The formation of the local membrane pores was probable after exposure to a high dose (23 microg ml(-1)) of PHMG. Micrographic evidences were provided about the damaged membrane structure and intracellular structure change of E. coli.

SIGNIFICANCE AND IMPACT OF THE STUDY

The presented information helps understand the bactericidal mechanism of PHMG by membrane damage.

Every-other-day interferon beta-1b versus once-weekly interferon beta-1a for multiple sclerosis (INCOMIN Trial) II: analysis of MRI responses to treatment and correlation with Nab

BACKGROUND

In RRMS, clinical exacerbations are usually associated with different types of active lesions at MRI, including: hyperintense lesions on T1-weighted post-gadolinium sequences; new hyperintense lesions or enlarging old lesions on PD/T2-weighted scans; or new hypointense lesions on T1-weighted pre-Gd sequences.

OBJECTIVE/METHODS

Primary outcome was the occurrence of patients with at least one active MRI lesion of the different types indicated above during treatment with 250 microg every other day (EOD) interferon beta (IFNbeta)-1b or 30 microg once weekly (OW) IFNbeta-1a in outpatients with RRMS (INCOMIN Trial).

RESULTS

The number of patients with at least one 'active' lesion, evaluated over the two-year follow-up, was significantly (P = 0.014) lower in the EOD IFNbeta-1 b arm (1 3/76, 17%) then in the OW IFNbeta-1a arm (25/73, 34%). NAb frequency over two-year follow-up was 22/65 (33.8%) in the EOD IFNbeta-1b arm and 4/62 (6.5%) in the OW IFNbeta-1a arm, significantly greater in the EOD IFNbeta-1b arm.

CONCLUSIONS

The development of MRI active lesions is strongly reduced by EOD-IFNbeta-1b compared with OW-IFNbeta-1a, indicating that EOD-IFNbeta-1b is more effective than OW-IFNbeta-1a in reducing ongoing inflammation and demyelination in MS. Logistic regression showed that NAb status did not affect the risk of MRI activity.

Hyperproduction of L-glutamate oxidase in submerged fermentation of Streptomyces sp. N1 with culture pH control and calcium addition

Production of L-glutamate oxidase (GluOx) by Streptomyces sp. N1 was investigated by controlling culture pH at 6.2, 6.7, 7.0, and 7.3 in a 5-L stirred fermentor. The corresponding GluOx activities obtained were 2.8, 4.2, 6.0, and 5.3 U/mL, respectively. Microbial growth was inhibited by increasing the medium pH from 6.2 to 7.0. The inhibitory effect was also observed in plate colony growth under incubation with a different initial pH value. The effect of calcium on GluOx production was also studied in the pH-controlled bioreactor. When the culture pH was controlled at 6.2 or 7.0, GluOx production could not be improved or was only improved slightly by initial addition of calcium to the medium. However, when the culture pH was kept at 6.7, initial Ca2+ addition (60 mM) conspicuously enhanced GluOx production up to 9.3 U/mL, which was about twofold of that without Ca2+ addition. The enzyme production level was the highest ever reported in the literature. During fermentation the inhibition of cell growth by Ca2+ addition was observed. For the morphological changes, the cells mostly existed as pellets in the medium without Ca2+ addition, whereas few pellets were found and almost all the cells were dispersed mycelia in the broth with Ca2+ addition.

Biochemical engineering of the production of plant-specific secondary metabolites by cell suspension cultures

Plant cell culture has recently received much attention as a useful technology for the production of valuable plant-derived secondary metabolites such as paclitaxel and ginseng saponin. The numerous problems that yet bewilder the optimization and scale-up of this process have not been over emphasized. In spite of the great progress recorded in recent years towards the selection, design and optimization of bioreactor hardware, manipulation of environmental factors such as medium components, light irradiation, shear stress and O2 supply needs detailed investigations for each case. Recent advances in plant cell processes, including high-density suspension cultivation, continuous culture, process monitoring, modeling and control and scale-up, are also reviewed in this chapter. Further developments in bioreactor cultivation processes and in metabolic engineering of plant cells for metabolite production are expected in the near future.

Diffusion-weighted MR in reversible wernicke encephalopathy

Diffusion-weighted images (DWI) of a patient with Wernicke encephalopathy were obtained during routine MR examination. Mammillary bodies were hyperintense on T2-weighted and enhanced on T1-weighted images; on DWI, a mild hyperintensity was noticed. Calculation of the apparent diffusion coefficient (ADC) demonstrated an increased diffusion on the affected regions; the hyperintensity on DWI was probably due to a "T2-shine-through" effect. These findings are consistent with the presence of extracellular oedema, without significant neuronal damage. The patient recovered promptly after thiamine administration, and MR alterations disappeared. The favourable evolution indicates that no relevant neuronal death occurred. This is consistent with DWI findings. DWI are more sensitive than ordinary T1- and T2-weighted images to neuronal irreversible damage, and may differentiate between neuronal necrosis and extracellular oedema in various brain pathologies. The demonstration of a limited neuronal damage may represent a favourable prognostic factor in patients with WE.

Improvement of Panax notoginseng cell culture for production of ginseng saponin and polysaccharide by high density cultivation in pneumatically agitated bioreactors

A Panax notoginseng cell culture was successfully scaled up from shake flask to 1.0-L bubble column reactor and concentric-tube airlift reactor. High-density bioreactor batch cultivation was carried out using a modified MS medium. The maximum cell density in batch cultures reached 20.1, 21.0 and 24.1 g/L in the shake flask, bubble column and airlift reactors, respectively, and their corresponding biomass productivity was 950, 1140 and 1350 mg/(L x d) for each. The productivity of ginseng saponin was 70, 96 and 99 mg/(L x d) in the flask, bubble column and airlift reactors, respectively; and the polysaccharide productivity reached 104, 119 and 151 mg/(L x d) for each. Furthermore, a fed-batch cultivation strategy was developed on the basis of specific oxygen uptake rate (SOUR), i.e., sucrose feeding before a sharp decrease of SOUR, and the highest cell density of 29.7 g/L was successfully achieved in the airlift bioreactor on day 17 with a very high biomass productivity of 1520 mg/(L x d). The concentrations of ginseng saponin and polysaccharide reached about 2.1 and 3.0 g/L, respectively, and their productivity was 106 (saponin) and 158 mg/(L x d) (polysaccharide). This work successfully demonstrated the high-density bioreactor cultivation of P. notoginseng cells in pneumatically agitated bioreactors and the reproduction of the shake flask culture results in bioreactors. The cell density, biomass productivity, production titer and productivity of both ginseng saponin and polysaccharide obtained here were the highest that have been reported on a reactor scale for all the ginseng species.

Improvement of the performance of H2O2 oxidation at low working potential by incorporating TTF-TCNQ into a platinum wire electrode for glucose determination

A micro-biosensor was constructed by incorporating the organic conducting salt tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) into a platinized platinum (Pt) wire and further covering with the electrochemical polymerical heteropolypyrrole film, in which glucose oxidase (GOx) was entrapped. The enzyme electrode can sensitively determine glucose at a low working potential, mainly based on the oxidation of H2O2. The incorporated TTF-TCNQ can significantly improve the oxidation of H2O2 on the electrode, although a part of the TTF-TCNQ functions as a mediator. Compared with the same electrode prepared without TTF-TCNQ incorporated, the TTF-TCNQ modified electrode had better performance characteristics at a working potential of 200 mV (versus SCE). The response time to 90% of the steady value was shortened from about 40 s to less than 10 s, the lower limit of the linear response was greatly extended from about 1.6 mM to 10 microM, the linear range was shifted from 1.6-10.0 to 0.01-5 mM and the sensitivity was increased from about 1 to 1.5 microA/mM. The electrode was quite stable. For continuous operation, the electrode could work for about 5 weeks and only lost 60% of its original sensitivity. Stored at 4 degrees C for intermittent determinations, the electrode kept 80% sensitivity for over 6 months. Due to covering the electrode with a non-conductive heteropolypyrrole film, ascorbate, urate and 4-acetamidophenol caused only negligible current response at an applied potential of 200 mV.

Production of ginseng and its bioactive components in plant cell culture: current technological and applied aspects

Ginseng (the root of Panax ginseng CA Mayer) is a valuable oriental herb, which has been used in traditional Chinese medicine for thousands of years, both as a disease-healing drug and a general tonic. The medicinal value of ginseng is now also widely recognized in the west and the world ginseng market is expanding. The current supply of ginseng depends mainly on field cultivation, which is a slow and laborious process. Plant cell and tissue culture methods have been explored as potentially more efficient alternatives for the mass production of ginseng and its bioactive components. Research into ginseng cell and tissue cultures started in the early 1960s and commercial applications have been underway since the late 1980s. The ginseng cell culture has continued to attract considerable research and development effort in recent years as scientists seek to understand and optimize the culture conditions. In this paper, we review recent studies on ginseng cell culture processes, focusing on the physiological and bioengineering factors affecting the productivity of ginseng biomass and useful metabolites (e.g. ginseng saponin and polysaccharide) and the progress and concerns in large-scale applications.