Manipulating PEPC levels in plants

This review examines the current understanding of the structural, functional and regulatory properties of C4 and C3 forms of higher plant phosphoenolpyruvate carboxylase. The emphasis is on the interactive metabolic and post-translational controls acting on the enzyme in the physiological context of C4 photosynthesis and the anaplerotic pathway. A brief overview is given concerning the recent developments of PEPC-based genetic engineering of C3 plants with the aim of improving photosynthetic performance in normal and limiting environmental conditions. So far, in spite of achieving a considerable increase in PEPC levels, more work needs to be done with respect to the correct dosage and location before that goal is reached. Some unpublished results on the transformation of maize with a sorghum C4 PEPC cDNA are also presented. They show that it is possible to increase photosynthetic PEPC levels in this C4 plant and that the modification in enzyme content has a pleiotropic physiological impact and, notably, an improved water use efficiency when water is limited.     

How should xanthine oxidase-generated superoxide yields be measured?

The rate of formation of superoxide measured by its reduction of tetranitromethane (TNM) and by its reduction of ferric cytochrome c (Fe(III) cc) are in excellent agreement when the superoxide is generated from a simple chemical precursor. In contrast, the rate of formation of superoxide generated in the reaction of xanthine oxidase with acetaldehyde is much higher (up to a factor of 6) when measured with TNM and compared with Fe(III) cc. It is shown that Fe(III) cc measures superoxide that has diffused from the enzyme, and that TNM probably scavenges all the dioxygen that is reduced by one electron by the enzyme. The TNM traps enzyme-bound superoxide in competition with the second-electron transfer and proton transfer, which normally yield hydrogen peroxide. The proton transfer is probably rate determining, k(p) 相似文献   

Characterization of an echinocandin B-producing strain blocked for sterigmatocystin biosynthesis reveals a translocation in the stcW gene of the aflatoxin biosynthetic pathway

Echinocandin B (ECB), a lipopolypeptide used as a starting material for chemical manufacture of the anti-Candida agent LY303366, is produced by fermentation using a strain of Aspergillus nidulans. In addition to ECB, the wild-type strain also produces a significant level of sterigmatocystin (ST), a potent carcinogen structurally related to the aflatoxins. Characterization of a mutant designated A42355-OC-1 (OC-1), which is blocked in ST biosynthesis, was the result of a chromosomal translocation. The chromosomal regions containing the breakpoints of the translocation were isolated and DNA sequencing and PCR analysis of the chromosomal breakpoints demonstrated the translocation occurred within the stcW gene of the ST biosynthetic pathway, resulting in disruption of the open reading frame for this gene. Biochemical feeding studies indicate the involvement of this gene product in the conversion of averufin to 1-hydroxy versicolorone. This work demonstrates an effective synergy between classical strain improvement methods and molecular genetics. Journal of Industrial Microbiology & Biotechnology (2000) 25, 333–341. Received 27 April 2000/ Accepted in revised form 25 November 2000     

Hormonal correlates of reproductive seasonality in wild female hanuman langurs (Presbytis entellus)

To date, it is not known whether the seasonal occurrence of sexual behavior and mating in free-ranging Hanuman langurs at Ramnagar, Nepal, is correlated with seasonal changes in female ovarian function, and, if so, which factor(s) triggers the onset of the reproductive period. Using noninvasive fecal hormone analysis in combination with behavioral observations, this study was carried out to: 1) investigate and characterize seasonal patterns of ovarian cyclicity and timing of conception in wild langur females living in a highly seasonal habitat; and 2) examine the relationship between seasonal patterns of ovarian cyclicity, behavioral estrus, and female physical condition. Behavioral data and fecal samples were collected during a total period of 14 months from nine females living in a multi-male group. Physical condition of the females was assessed monthly by visual inspection, using a seven-fold scale. Ovulatory cycles and timing of conceptions were identified by the measurement of immunoreactive pregnanediol glucuronide (iPdG) in extracted feces. Hormone profiles in individual females revealed a clearly seasonal distribution in the occurrence of ovulatory cycles, which were restricted to the period from July to October. The distribution of female estrus behavior showed a similar seasonal pattern, and in total 88.2% of all estrus periods observed in the focal females were accompanied by ovulation. Onset of ovarian cycles as well as mating activities were strongly correlated with the onset of the rainy season. Females conceived, on average, in their second ovulatory cycle (pregnancy length: 211.6 +/- 3.4 days), with timing of conception being confined to the months when animals showed an improved physical condition. Collectively the present data clearly suggest that in seasonally-breeding langurs at Ramnagar, ecological conditions (rainfall, food availability, and quality) influence the onset of ovulations and timing of conceptions.     

A Functional Role for Specific Spliced Variants of the α7β1 Integrin in Acetylcholine Receptor Clustering

The clustering of acetylcholine receptors (AChR) on skeletal muscle fibers is an early event in the formation of neuromuscular junctions. Recent studies show that laminin as well as agrin can induce AChR clustering. Since the α7β1 integrin is a major laminin receptor in skeletal muscle, we determined if this integrin participates in laminin and/or agrin-induced AChR clustering. The alternative cytoplasmic domain variants, α7A and α7B, and the extracellular spliced forms, α7X1 and α7X2, were studied for their ability to engage in AChR clustering. Immunofluorescence microscopy of C2C12 myofibers shows that the α7β1 integrin colocalizes with laminin-induced AChR clusters and to a much lesser extent with agrin-induced AChR clusters. However, together laminin and agrin promote a synergistic response and all AChR colocalize with the integrin. Laminin also induces the physical association of the integrin and AChR. High concentrations of anti-α7 antibodies inhibit colocalization of the integrin with AChR clusters as well as the enhanced response promoted by both laminin and agrin. Engaging the integrin with low concentrations of anti-α7 antibody initiates cluster formation in the absence of agrin or laminin. Whereas both the α7A and α7B cytoplasmic domain variants cluster with AChR, only those isoforms containing the α7X2 extracellular domain were active. These results demonstrate that the α7β1 integrin has a physiologic role in laminin-induced AChR clustering, that alternative splicing is integral to this function of the α7 chain, and that laminin, agrin, and the α7β1 integrin interact in a common or convergent pathway in the formation of neuromuscular junctions.     

Prophylactic and therapeutic effects of Mytilus edulis fatty acids on adjuvant-induced arthritis in male Wistar rats

Lipid-rich fractions from the flesh tissue of Mytilus edulis were obtained by solvent extraction and chromatographic separation, and tested for anti-inflammatory (AI) activity in vitro and in vivo. Inhibition of leukotriene production by isolated human neutrophils in response to calcium ionophore stimulation in the presence of exogenous arachidonic acid substrate was demonstrated for the hydrolysed triglyceride fraction of the crude lipid extract. This fraction was subsequently tested for in vivo AI activity using the mycobacterial adjuvant-induced polyarthritis rat model. The hydrolysed triglyceride fraction showed significant AI activity when dosed therapeutically (10 mg/kg BW/day, p.o., for 6 days from the onset of arthritis), decreasing body weight loss by 55% and hind paw swelling by 65% compared to the arthritic control. The (non-hydrolysed) crude lipid extract was effective when dosed prophylactically (30 mg/kg BW/day, p.o., for 16 days starting on day ?2 of arthritigen inoculation). Structural analysis by GC and GC–MS revealed in the extracts an abundance of EPA (20:5n-3) and DHA (22:6n-3) (37% of total fatty acids), along with a small quantity of a rare anti-inflammatory n-3 analogue of arachidonic acid, namely 7, 11, 14, 17-eicosatetraenoic acid (20:4n-3).     

Criteria for Patient Selection and Multidisciplinary Evaluation and Treatment of the Weight Loss Surgery Patient

Objective: To provide evidence‐based guidelines for patient selection and to recommend the medical and nutritional aspects of multidisciplinary care required to minimize perioperative and postoperative risks in patients with severe obesity who undergo weight loss surgery (WLS). Research Methods and Procedures: Members of the Multidisciplinary Care Task Group conducted searches of MEDLINE and PubMed for articles related to WLS in general and medical and nutritional care in particular. Pertinent abstracts and literature were reviewed for references. Multiple searches were carried out for various aspects of multidisciplinary care published between 1980 and 2004. A total of 3000 abstracts were identified; 242 were reviewed in detail. Results: We recommended multidisciplinary screening of WLS patients to ensure appropriate selection; preoperative assessment for cardiovascular, pulmonary, gastrointestinal, endocrine, and other obesity‐related diseases associated with increased risk for complications or mortality; preoperative weight loss and cessation of smoking; perioperative prophylaxis for deep vein thrombosis and pulmonary embolism (PE); preoperative and postoperative education and counseling by a registered dietitian; and a well‐defined postsurgical diet progression. Discussion: Obesity‐related diseases are often undiagnosed before WLS, putting patients at increased risk for complications and/or early mortality. Multidisciplinary assessment and care to minimize short‐ and long‐term risks include: comprehensive medical screening; appropriate pre‐, peri‐, and postoperative preparation; collaboration with multiple patient care disciplines (e.g., anesthesiology, pulmonary medicine, cardiology, and psychology); and long‐term nutrition education/counseling.     

Engineering the processive run length of Myosin V

The processive motor myosin V has a high affinity for actin in the weak binding states when compared with non-processive myosins. Here we test whether this feature is essential for myosin V to walk processively along an actin filament. The net charge of loop 2, a surface loop implicated in the initial weak binding between myosin and actin, was increased or decreased to correspondingly change the affinity of myosin V for actin in the weak binding state, without changing the velocity of movement. Processive run lengths of single molecules were determined by total internal reflection fluorescence microscopy. Reducing the net positive charge of loop 2 significantly decreased both the affinity of myosin V for actin and the processive run length. Conversely, the addition of positive charge to loop 2 increased actin affinity and processive run length. We hypothesize that a high affinity for actin allows the detached head of a stepping myosin V to find its next actin binding site more quickly, thus decreasing the probability of run termination.     

The impact of ecological variability on the reproductive endocrinology of wild female African elephants

Non-invasive endocrine methods enable investigation of the relationship between ecological variation and ovarian activity and how this impacts on demographic processes. The underlying physiological factors driving high variation in inter-calving intervals among multi-parous African elephants offer an interesting system for such an investigation. This study investigates the relationship between Normalized Differential Vegetation Index (NDVI), an ecosystem surrogate measure of primary productivity, and fecal progestin concentrations among wild female elephants. Matched fecal samples and behavioral data on reproductive activity were collected from 37 focal individuals during the two-year study. Linear mixed models were used to explore the relationship between fecal 5alpha-pregnane-3-ol-20-one concentrations and the independent variables of NDVI, calf sex, female age, gestation day, and time since last parturition. Among both non-pregnant and pregnant females, fecal 5alpha-pregnane-3-ol-20-one concentrations were significantly correlated with time-specific NDVI indicating a strong relationship between ecological conditions and endocrine activity regulating reproduction. In addition, the age of a female and time since her last parturition impacted hormone concentrations. These results indicate that the identification of an individual's reproductive status from a single hormone sample is possible, but difficult to achieve in practice since numerous independent factors, particularly season, impact fecal hormone concentrations. Regardless of season, however, fecal 5alpha-pregnane-3-ol-20-one concentrations below 1 microg/g were exclusively collected from non-pregnant females, which could be used as a threshold value to identify non-pregnant individuals. Collectively the information generated contributes to a better understanding of environmental regulation of reproductive endocrinology in wild elephant populations, information salient to the management and manipulation of population dynamics in this species.