pH stability of individual folates during critical sample preparation steps in prevision of the analysis of plant folates

The stability and eventual interconversion of nine mono-glutamate folates (5-methyl-tetrahydrofolate, tetrahydrofolate, 5-formyltetrahydrofolate, 5,10-methenyltetrahydrofolate, 5,10-methylenetetrahydrofolate, dihydrofolate, 10-formylfolic acid, 10-formyltetrahydrofolate and folic acid) during the typical sample preparation steps (heat treatment for 10 min at 100 degrees C and incubation for 2 h at 37 degrees C) at different pH values have been investigated by LC-MS/MS. An LC-MS/MS method with isotopically labelled [(13)C(5)]5-methyltetrahydrofolate and [(13)C(5)] folic acid as internal standards has been developed with enhanced sensitivity using a Chromolith RP-18 column. 5-Methyltetrahydrofolate, folic acid and 10-formylfolic acid are relatively stable at different pHs (from 2 to 10) with and without heat treatment. Tetrahydrofolate shows instability at low pH. 5-Formyltetrahydrofolate and 5,10-methenyltetrahydrofolate can interconvert by changes in pH. Tetrahydrofolate and 5,10-methylenetetrahydrofolate can interconvert with formaldehyde or by changes in pH. Incubation at 37 degrees C for 2 h is much less aggressive for most folates as compared with heat treatment at 100 degrees C. At 37 degrees C most folates are stable at pH values between 4 and 8 except tetrahydrofolate and dihydrofolate, which are degraded at low pH. 10-Formyltetrahydrofolate and 5,10-methylenetetrahydrofolate cannot be quantified in the present method because these compounds are converted to 5,10-methenyltetrahydrofolate and tetrahydrofolate, respectively, in the acidic mobile phase. This study provides useful information for the analysis of folates in the future as well as for the interpretation of quantitative results from earlier work.

Folate fortification of rice by metabolic engineering

Rice, the world's major staple crop, is a poor source of essential micronutrients, including folates (vitamin B9). We report folate biofortification of rice seeds achieved by overexpressing two Arabidopsis thaliana genes of the pterin and para-aminobenzoate branches of the folate biosynthetic pathway from a single locus. We obtained a maximal enhancement as high as 100 times above wild type, with 100 g of polished raw grains containing up to four times the adult daily folate requirement.

Regulation of one-carbon metabolism in Arabidopsis: the N-terminal regulatory domain of cystathionine gamma-synthase is cleaved in response to folate starvation

In all organisms, control of folate homeostasis is of vital importance to sustain the demand for one-carbon (C1) units that are essential in major metabolic pathways. In this study we induced folate deficiency in Arabidopsis (Arabidopsis thaliana) cells by using two antifolate inhibitors. This treatment triggered a rapid and important decrease in the pool of folates with significant modification in the distribution of C1-substituted folate coenzymes, suggesting an adaptive response to favor a preferential shuttling of the flux of C1 units to the synthesis of nucleotides over the synthesis of methionine (Met). Metabolic profiling of folate-deficient cells indicated important perturbation of the activated methyl cycle because of the impairment of Met synthases that are deprived of their substrate 5-methyl-tetrahydrofolate. Intriguingly, S-adenosyl-Met and Met pools declined during the initial period of folate starvation but were further restored to typical levels. Reestablishment of Met and S-adenosyl-Met homeostasis was concomitant with a previously unknown posttranslational modification that consists in the removal of 92 amino acids at the N terminus of cystathionine gamma-synthase (CGS), the first specific enzyme for Met synthesis. Rescue experiments and analysis of different stresses indicated that CGS processing is specifically associated with perturbation of the folates pool. Also, CGS processing involves chloroplastic serine-type proteases that are expressed in various plant species subjected to folate starvation. We suggest that a metabolic effector, to date unidentified, can modulate CGS activity in vivo through an interaction with the N-terminal domain of the enzyme and that removal of this domain can suppress this regulation.

Cytosolic Hydroxymethyldihydropterin Pyrophosphokinase/Dihydropteroate Synthase from Arabidopsis thaliana

In plants, 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase/7,8-dihydropteroate synthase (mitHPPK/DHPS) is a bifunctional mitochondrial enzyme, which catalyzes the first two consecutive steps of tetrahydrofolate biosynthesis. Mining the Arabidopsis genome data base has revealed a second gene encoding a protein that lacks a potential transit peptide, suggesting a cytosolic localization of the isoenzyme (cytHPPK/DHPS). When the N-terminal part of the cytHPPK/DHPS was fused to green fluorescent protein, the fusion protein appeared only in the cytosol, confirming the above prediction. Functionality of cytHPPK/DHPS was addressed by two parallel approaches: first, the cytHPPK/DHPS was able to rescue yeast mutants lacking corresponding activities; second, recombinant cytHPPK/DHPS expressed and purified from Escherichia coli displayed both HPPK and DHPS activities in vitro. In contrast to mitHPPK/DHPS, which was ubiquitously expressed, the cytHPPK/DHPS gene was exclusively expressed in reproductive tissue, more precisely in developing seeds as revealed by histochemical analysis of a transgenic cytHPPK/DHPS promoter-GUS line. In addition, it was observed that expression of cytHPPK/DHPS mRNA was induced by salt stress, suggesting a potential role of the enzyme in stress response. This was supported by the phenotype of a T-DNA insertion mutant in the cytHPPK/DHPS gene, resulting in lower germination rates as compared with the wild-type upon application of oxidative and osmotic stress.

Investigation of the extraction behavior of the main monoglutamate folates from spinach by liquid chromatography-electrospray ionization tandem mass spectrometry

An LC-MS/MS method has been developed for the determination of main monoglutamate folates in spinach with folic acid as an internal standard. A sample preparation with ultrafiltration (molecular weight cut-off membrane, 5 kDa) was followed by a chromatographic run of 14.2 min, rendering the method very simple and fast. The LODs in diluted spinach matrix were 0.02, 0.09, 0.05 and 0.03 ng/mL (0.037, 0.17, 0.092 and 0.055 microg/100 g calculated according to the fresh weight of spinach) for 5-methyltetrahydrofolate, tetrahydrofolate, 5-formyltetrahydrofolate, and 10-formylfolic acid, respectively. Using this method, the extraction behaviour of the main naturally occurring monoglutamate folates has been investigated in detail. It is found that 10 min of heating at 100 degrees C, incubation with rat serum at 37 degrees C (0.05 M phosphate buffer, pH = 6.5) for 4 h and the ratio of 10 (volume of extraction buffer versus the weight of sample, mL/g) are the optimal parameters for folate extraction from spinach. The final quantitative result of the individual folates in spinach is highly influenced by the pH (from 2.9 to 8.6) of the extraction buffer.

Free and total para-aminobenzoic acid analysis in plants with high-performance liquid chromatography/tandem mass spectrometry

para-Aminobenzoic acid (PABA), a precursor in the synthesis of folates in plants, is determined by liquid chromatography/tandem mass spectrometry (LC/MS/MS). In plants PABA can be converted into its beta-D-glucopyranosyl ester (PABA-Glc) and can also exist in its free form. In this work, we developed and validated a quantitative method to study free and total PABA in plants. The total PABA (free PABA plus PABA-Glc) can be evaluated after acid hydrolysis at 80 degrees C for 2 hours. The plant material is homogenized and the PABA content is quantified using the standard addition procedure. The validated method is selective, sensitive, simple, accurate, has a recovery between 99.6 to 102.5%, is reproducible (RSD between 1.4 and 4.4%), and is linear between 2.5 and 1538 ng/mL. Free and total PABA determinations in five vegetables showed that different plant species had different amounts of free and total PABA, and that the ratios of total versus free PABA were also variable. This new method could be valuable for studies of folate synthesis in plants.

Quantitative analysis of twelve sulfonamides in honey after acidic hydrolysis by high-performance liquid chromatography with post-column derivatization and fluorescence detection

A quantitative HPLC-fluorescence method for the simultaneous determination of 12 sulfonamides (sulfaguanidine, sulfanilamide, sulfacetamide, sulfadiazine, sulfathiazole, sulfapyridine, sulfamerazine, sulfamether, sulfamethazine, sulfamethoxypyridazine, sulfachloropyridazine and sulfadoxine) in honey was developed and validated. Sample pretreatment included acidic hydrolysis, followed by liquid-liquid extraction and solid-phase extraction on a strong cation exchanger. LC separation was performed in 45 min, with a total analysis time of 60 min. Identification and quantitation were based on retention time and fluorescence intensity, respectively. Peak area ratios of the target analytes and the internal standard were fit to a linear least-squares regression curve with a weighting factor of 1/x. Limits of detection and quantitation (LOQ) had values of 1 or 2 and 2 or 5 ng/g, respectively. Linearity was obtained with an average coefficient of determination (R2) higher than 0.997, over a dynamic range from the LOQ value up to 100ng/g. The method demonstrated good intra- and interbatch precision and accuracy. No interferences with the peaks of interest were observed throughout the chromatographic run. Sample pretreatment provided efficient cleanup, while post-column derivatization with fluorescamine proved to be a reproducible derivatization technique enabling a sensitive and rugged quantitative determination of sulfonamides.

Enhanced method performance due to a shorter chromatographic run-time in a liquid chromatography–tandem mass spectrometry assay for paclitaxel

Liquid chromatography-tandem mass spectrometry (LC-MS-MS) is often performed in a high-throughput environment. Unfortunately, with atmospheric pressure ionization (API) techniques, shorter run-times or reduced sample clean-up often result in ion or matrix suppression, which can lead to erroneous results. The present work on the analysis of paclitaxel compares ion suppression, sensitivity and linearity of a high-throughput LC-MS-MS method (0.8 min run-time, method B) to a method with increased separation (2.0 min run-time, method A). An atmospheric pressure chemical ionization (APCI) interface was used for both methods. The high-sample-throughput method uses an increased amount of organic solvent in the mobile phase (isocratic, 85% versus 70% of methanol) and a higher flow-rate (600 microl/min versus 400 micro/min). As a result, internal standard (docetaxel) and target analyte (paclitaxel) co-elute, close to, although separated from the solvent front. Ion suppression of both methods was evaluated by comparing pure standard to plasma and plasma containing a vehicle. Sensitivity and linearity were compared by injecting matrix matched calibration samples with both methods. Ion suppression by the vehicle Cremophor EL led to poor data quality for the standard method (A), while for the short method (B), ion suppression was compensated for by the co-eluting internal standard. The short method showed similar linearity but increased sensitivity by at least a factor five. This work provides a strategy to compensate for ion suppression without the use of labeled internal standards. In addition, a better sensitivity and a shorter run-time are noted.

Adduct formation in quantitative bioanalysis: effect of ionization conditions on paclitaxel

Quantitative analysis of target compounds with liquid chromatography atmospheric pressure ionization mass spectrometry is sometimes hampered by adduct formation. In these situations, cationization with alkali metal ions instead of proton addition is often observed in the positive ion mode. This work studies the process of adduct formation and investigates potential strategies to control this phenomenon. Paclitaxel, a pharmaceutical chemotherapeutic agent, was used as a model compound. Electrospray (ESI), atmospheric pressure chemical ionization (APCI) and sonic spray ionization (SSI) are evaluated and compared. The work was performed on two different instruments, allowing the evaluation of different ionization behavior for different source design for electrospray, if any. Different mobile phase additives were compared, including acetic acid, formic acid, ammonium formate, and a range of primary amines. Continuous infusion was used for a fast screening, to detect optimal conditions. These were then further investigated in detail by LC-MS. The results indicate that electrospray is the more sensitive interface for this compound on the investigated apparatus. Unacceptable quantitative data were acquired without additives in the mobile phase. Generally, additives increased the reproducibility significantly. A response of mainly one ion was achieved with dodecylamine/acetic acid and acetic acid/sodium acetate. The data also point out the importance of evaluating adduct formation for compounds prone to this phenomenon during method development, especially in view of accurate quantitation.

Determination of total folate in plant material by chemical conversion into para-aminobenzoic acid followed by high performance liquid chromatography combined with on-line postcolumn derivatization and fluorescence detection

A procedure involving chemical conversion of all forms of folate present in plant material into para-aminobenzoic acid (PABA) and a liquid chromatographic-fluorimetric determination with on-line postcolumn derivatization is reported. All folates are cleaved with liberation of PABA by hydrogen peroxide followed by acid hydrolysis using concentrated hydrochloric acid (37%) at 110 degrees C for 6 h. The reaction yield for individual folates conversion to PABA ranged from 44.4 to 97.3%. PABA could be determined sensitively by on-line postcolumn derivatization with fluorescamine, the detection limit for PABA being 3.02 nM. On the basis of this principle, a method for the determination of total folate in plant material, including a purification step on an affinity column, is presented, which offers a sufficient sensitivity and selectivity for routine analysis of total folate in natural samples. The total folate contents of tomatoes, carrots, white cabbage, and spinach were determined, and the results were quite comparable to the data reported. The recovery of PABA and the comparison of total folate analysis in spinach on different occasions (over 6 months) are also reported. The method is reliable, universal for all folates, including polyglutamate and monoglutamate forms, and eliminates the need for a deconjugation step and multiple conversion reactions.

Colonic motility diagnosis based on colonic pressure

Manometry of the alimentary tract is a valuable and widely used means to evaluate and diagnose the function of the alimentary tract. However, the measurement can be inconvenient due to the invasive method used, and the many factors affecting results. Research on colonic pressure data is even more insufficient. This paper deals with colonic pressure data via an improved method ensuring that pressure data of the whole colon is available. The data is analysed based on the learning vector quantization (LVQ) method. Testing results show that this method distinguishes the normal data and the abnormal data, consistently with the original diagnoses. This method can serve as an assistant diagnosis of colonic motility and contributes to further research on colonic motility based on pressure data.

Steady-state kinetic characterization of substrates and metal-ion specificities of the full-length and N-terminally truncated recombinant human methionine aminopeptidases (type 2)

The steady-state kinetics of a full-length and truncated form of the type 2 human methionine aminopeptidase (hMetAP2) were analyzed by continuous monitoring of the amide bond cleavage of various peptide substrates and methionyl analogues of 7-amido-4-methylcoumarin (AMC) and p-nitroaniline (pNA), utilizing new fluorescence-based and absorbance-based assay substrates and a novel coupled-enzyme assay method. The most efficient substrates for hMetAP2 appeared to be peptides of three or more amino acids for which the values of k(cat)/K(m) were approximately 5 x 10(5) M(-1) min(-1). It was found that while the nature of the P1' residue of peptide substrates dictates the substrate specificity in the active site of hMetAP2, the P2' residue appears to play a key role in the kinetics of peptidolysis. The catalytic efficiency of dipeptide substrates was found to be at least 250-fold lower than those of the tripeptides. This substantially diminished catalytic efficiency of hMetAP2 observed with the alternative substrates MetAMC and MetpNA is almost entirely due to the reduction in the turnover rate (k(cat)), suggesting that cleavage of the amide bond is at least partially rate-limiting. The 107 N-terminal residues of hMetAP2 were not required for either the peptidolytic activity of the enzyme or its stability. Steady-state kinetic comparison and thermodynamic analyses of an N-terminally truncated form and full-length enzyme yielded essentially identical kinetic behavior and physical properties. Addition of exogenous Co(II) cation was found to significantly activate the full-length hMetAP2, while Zn(II) cation, on the other hand, was unable to activate hMetAP2 under any concentration that was tested.

[Isolation and verification of Triticum aestivum-Eremopyrum orientale addition lines and substitution lines by GISH]

Eremopyrum is a potential genus in wheat improvement. To breed T. aestivum-Er. orientale additional and substitutional lines, chromosome number of 96 BC2F3 individuals were accounted. Fifteen plants with 2n = 43 and eight plants with 2n = 44 were checked out. GISH results of the individuals with 43 chromosomes showed that they blonged to three different monosomic additions. Two disomic additions, one double-monosomic addition, one trible-monosomic addition and one monosomic addition were found in the 2n = 44 individuals. One double-monosomic substitution and one monosomic substitution were obtained. We also proved that it is relatively easier to obtain addition lines in the selfing population than to obtain double-monosomic additions.

Cloning and characterization of a novel human class I histone deacetylase that functions as a transcription repressor

Histone acetylation alters chromatin state by modifying lysines on histone and plays an important role in modulating gene transcription. A dynamic balance of histone acetylation/deacetylation is maintained by histone acetyltransferases and histone deacetylases. Emerging evidence suggests that a family of histone deacetylases may exist to regulate diverse cellular functions, including chromatin structure, gene expression, cell cycle progression, and oncogenesis. We describe here a novel human histone deacetylase, named HDAC8, cloned from human kidney. HDAC8 encodes 377 amino acid residues and shares extensive homology to several known HDACs, in particular a histone deacetylase from Arabidopsis thaliana. Northern blot analyses revealed that HDAC8 expression pattern for HDAC8 is distinct from that for HDAC1 and HDAC3, and expression of HDAC8 mRNA occurs in multiple organs including heart, lung, kidney, and pancreas. HDAC8 mRNA was also observed in several cell lines derived from cancerous tissues. When expressed in HEK293 cells, HDAC8 exhibited deacetylase activity toward acetylated histone, indicating that this protein is a bona fide histone deacetylase. Its histone deacetylase activity was inhibited by trichostatin and other known histone deacetylase inhibitors. Furthermore, active recombinant HDAC8 was expressed and purified from Escherichia coli. When ectopically expressed in cells, HDAC8 was found to be localized to the nucleus. Co-transfection experiments demonstrated that expression of HDAC8 repressed a viral SV40 early promoter activity. These results indicate that HDAC8 is a novel member of the histone deacetylase family, which may play a role in the development of a broad range of tissues and potentially in the etiology of cancer.

Structural elements of ADP-ribosylation factor 1 required for functional interaction with cytohesin-1

ADP-ribosylation factor 1 (ARF1) is a 20-kDa guanine nucleotide-binding protein involved in vesicular trafficking. Conversion of inactive ARF-GDP to active ARF-GTP is catalyzed by guanine nucleotide exchange proteins such as cytohesin-1. Cytohesin-1 and its Sec7 domain (C-1Sec7) exhibit guanine nucleotide exchange protein activity with ARF1 but not ARF-like protein 1 (ARL1), which is 57% identical in amino acid sequence. With chimeric proteins composed of ARF1 (F) and ARL1 (L) sequences we identified three structural elements responsible for this specificity. Cytohesin-1 increased [35S]guanosine 5'-(gamma-thio)triphosphate binding to L28/F (first 28 residues of L, remainder F) and to a much lesser extent F139/L, and mut13F139/L (F139/L with random sequence in the first 13 positions) but not Delta13ARF1 that lacks the first 13 amino acids; therefore, a nonspecific ARF N terminus was required for cytohesin-1 action. The N terminus was not, however, required for that of C-1Sec7. Both C-1Sec7 and cytohesin-1 effectively released guanosine 5'-(gamma-thio)triphosphate from ARF1, but only C-1Sec7 displaced the nonhydrolyzable GTP analog bound to mut13F139/L, again indicating that structure in addition to the Sec7 domain is involved in cytohesin-1 interaction. Some element(s) of the C-terminal region is also involved, because replacement of the last 42 amino acids with ARL sequence in F139L decreased markedly the interaction with cytohesin-1. Participation of both termini is consistent with the crystallographic structure of ARF in which the two terminal alpha-helices are in close proximity. ARF1 residues 28-50 are also important in the interaction with cytohesin-1; replacement of Lys-38 with Gln, the corresponding residue in ARL1, abolished the ability to serve as substrate for cytohesin-1 or C-1Sec7. These studies have defined multiple structural elements in ARF1, including switch 1 and the N and C termini, that participate in functional interactions with cytohesin-1 (or its catalytic domain C-1Sec7), which were not apparent from crystallographic analysis.

Auxin deprivation induces synchronous Golgi differentiation in suspension-cultured tobacco BY-2 cells

To date, the lack of a method for inducing plant cells and their Golgi stacks to differentiate in a synchronous manner has made it difficult to characterize the nature and extent of Golgi retailoring in biochemical terms. Here we report that auxin deprivation can be used to induce a uniform population of suspension-cultured tobacco (Nicotiana tabacum cv BY-2) cells to differentiate synchronously during a 4-d period. Upon removal of auxin, the cells stop dividing, undergo elongation, and differentiate in a manner that mimics the formation of slime-secreting epidermal and peripheral root-cap cells. The morphological changes to the Golgi apparatus include a proportional increase in the number of trans-Golgi cisternae, a switch to larger-sized secretory vesicles that bud from the trans-Golgi cisternae, and an increase in osmium staining of the secretory products. Biochemical alterations include an increase in large, fucosylated, mucin-type glycoproteins, changes in the types of secreted arabinogalactan proteins, and an increase in the amounts and types of molecules containing the peripheral root-cap-cell-specific epitope JIM 13. Taken together, these findings support the hypothesis that auxin deprivation can be used to induce tobacco BY-2 cells to differentiate synchronously into mucilage-secreting cells.

Monensin-induced redistribution of enzymes and products from Golgi stacks to swollen vesicles in plant cells

We have tested the hypothesis that monensin treatment of plant cells leads to the transfer of Golgi enzymes to the monensin-induced swollen vesicles using sycamore maple suspension-cultured cells and immunolabeling techniques. Cells treated for 20 and 60 min with 10 microM monensin were labeled with anti-V-H(+)-ATPase, anti-xyloglucan (XG) sidechain (CCRC-M1), anti-pectic polysaccharide (JIM7 and CCRC-M2), and anti-N-glycan (anti-beta Xyl, and anti-alpha Fuc) antibodies. Our results demonstrate that monensin causes most H(+)-ATPase to be displaced from the Golgi cisternae (label distribution in control cells: 11% cis, 32% medial, 57% trans cisternae) to the swollen vesicles, which explains why these vesicles remain swollen after detachment from the Golgi/trans Golgi network cisternae. We also show that the content of complete XG molecules (defined by completed trisaccharide sidechains) in the swollen vesicles increases 1.5-fold between the 20 and 60 min samples, suggestive of the transfer of functional XG backbone and sidechain synthesizing enzymes from the trans Golgi compartment to the swollen vesicles. In contrast, no increase in either anti-pectin antibody or N-glycan antibody labeling of the swollen vesicles was observed between the 20 min and 60 min monensin samples. Both of these latter types of molecules depend for their synthesis on enzymes located in multiple membrane compartments upstream from the trans Golgi cisternae, which greatly decreases the probability of transfer of complete enzyme systems to the swollen vesicles. Thus these latter findings do not contradict the anti-H(+)-ATPase and the anti-XG labeling data, which strongly support the Golgi enzyme displacement theory.

Separation of scrapie prion infectivity from PrP amyloid polymers

The prion protein (PrP) undergoes a profound conformational change when the cellular isoform (PrPC) is converted into the scrapie form (PrPSc). Limited proteolysis of PrPsc produces PrP 27-30 which readily polymerizes into amyloid. To study the structure of PrP amyloid, we employed organic solvents that perturb protein conformation. Hexafluoro-2-propanol (HFIP), which promotes alpha-helix formation, modified the ultrastructure of rod-shaped PrP amyloids; flattened ribbons with a more regular substructure were found. As the concentration of HFIP was increased, the beta-sheet content and proteinase K resistance of PrP 27-30 as well as prion infectivity diminished. HFIP reversibly decreased the binding of Congo red dye to the rods while inactivation of prion infectivity was irreversible. In contrast to 10% HFIP, 1,1,1-trifluoro-2-propanol (TFIP) did not inactivate prion infectivity but like HFIP, TFIP did alter the morphology of the rods and abolish Congo red binding. This study separates prion infectivity from the amyloid properties of PrP 27-30 and underscores the dependence of prion infectivity on PrPSc conformation. The results also demonstrate that the specific beta-sheet-rich structures required for prion infectivity can be differentiated from those needed for amyloid formation as determined by Congo red binding.

[Effects of recurrent laryngeal nerve on thyroid hormone secretion in rats]

The effects of recurrent laryngeal never (RLN) on serum thyroid hormones and thyroidal radioiodide uptake were examined in rats. The results are (1) Serum thyroxine (T4) level increased significantly after section of unilateral RLN. When the sectioned peripheral end was stimulated immediately after section, the serum T4 level went even significantly lower than the control within 30 minutes. (2) Radioiodide uptake by homolateral thyroid increased significantly after section of unilateral RLN. These results indicate that RLN normally exerts an inhibitory effect on thyroxine secretion possibly mediated by muscarinic receptors.

Different ARF domains are required for the activation of cholera toxin and phospholipase D

ADP-ribosylation factors (ARFs), initially described as activators of cholera toxin ADP-ribosyltransferase activity, regulate intracellular vesicular membrane trafficking and stimulate a phospholipase D (PLD) isoform. ARF-like (ARL) proteins are structurally related to ARFs but do not activate cholera toxin and have relatively little effect on PLD. A new human ARL gene termed hARL1, which shares 57% amino acid identity with hARF1, was identified using a polymerase chain reaction-based cloning method. To determine whether different structural elements are responsible for the activation structural elements are responsible for the activation of the A subunit of cholera toxin and PLD, chimeric proteins were constructed by switching the amino-terminal 73 amino acids of ARF1 and ARL1. The recombinant rL73/F protein, in which the amino-terminal 73 amino acids of ARL1 replaced those of ARF1, activated the A subunit of cholera toxin, whereas the rF73/L protein, in which the NH2-terminal 73 amino acids of ARF1 replaced those of ARL1, was inactive. The two chimeric proteins had quite opposite effects on PLD activity. rF73/L activated PLD as effectively as rARF1, whereas rL73/F protein activated PLD only slightly. It appears that the amino-terminal region of ARF1 is not critical for its action as a GTP-dependent activator of cholera toxin, whereas it is necessary for activation of the putative effector enzyme, PLD.

Intracerebral co-grafting of Schwann's cells and fetal adrenal medulla in the treatment of Parkinson's disease

Intracerebral co-grafting of Schwann's cells and human fetal adrenal medullary tissue was performed in 10 patients with Parkinson's disease. One to six months after grafting, symptoms were improved significantly for 1 to 3 grade. Among them, 2 patients resumed nearly normal daily activities. Long-term follow-up showed that the symptoms were not improved satisfactorily in some patients. It is considered that careful selection of patients, administration of amantadine, and co-grafting of Schwann's cells which prompts the survival of chromaffin cells are essential to better results.

[Protective effect of tetrandrine on pancreatic islet cells damaged by alloxan in rats]

Tetrandrine (TET, 100 mg/kg) injected intraperitoneally could prevent rats from diabetes induced by alloxan. After 48 h of injection of alloxan, the blood sugar of the preventive group decreased from the control value of 25.46 +/- 1.21 mmol/L to 7.63 +/- 0.44 mmol/L (P < 0.001) while the serum insulin level increased to 11.33 +/- 1.97 microU/ml and the plasma glucagon concentration to 66.85 +/- 5.07 pg/ml respectively from the control group's value of 7.13 +/- 0.45 microU/ml and 90.35 +/- 8.33 pg/ml. In glucose tolerance test, TET 100 mg/kg showed that the abnormal glucose tolerance induced by alloxan could be improved. The blood sugar area under the glucose tolerance curve of the preventive group decreased from the control groups level of 113.28 +/- 5.02 mmol.h/L to 29.45 +/- 1.63 mmol.h/L (P < 0.001). Immunohistochemical observation of islet beta cells confirmed that TET could markedly prevent beta cells from injuries induced by alloxan and there was no obvious change in the appearance of islet beta cells in the preventive group. The above results suggested that TET could protect pancreatic islet beta cells from injuries caused by Alloxan.

[Bone metabolism in pregnant women]

Serum ionized calcium, tartrate-resistant acid phosphatase (TR-ACP) and alkaline phosphatase (ALP) were measured in 80 pregnant women in different gestational weeks. The results showed that calcium level decreased significantly as the gestation week increased. Calcium level of umbilical cord was higher than that of third trimester of pregnancy. It indicated that calcium could be transported to fetus across the placenta against the concentration gradient. Both TR-ACP and ALP activity elevated as gestation week increased. This may suggest that the bone metabolism is very active in pregnant women.

Alpha-tocopherol content of breast milk in China

The alpha-tocopherol content of breast milk was measured in 71 mothers of preterm and term infants in China. The mean alpha-tocopherol content of breast milk was much lower than that reported in developed countries. alpha-Tocopherol levels were higher in colostrum and then decreased in the transition milk. Mothers of preterm infants produced colostrum with a slightly higher alpha-tocopherol content than that of the mothers of term infants. However, alpha-tocopherol levels in transition milk were similar in both groups.

Alpha-tocopherol concentrations in human milk from mothers of preterm and full-term infants in China

alpha-Tocopherol content in breast milk of 28 mothers who delivered preterm infants (preterm milk) and 43 mothers who delivered full-term infants (term milk) were measured. alpha-Tocopherol concentration in preterm milk did not differ significantly from that of term milk in the first 12 days of lactation (P > 0.05). There is a higher alpha-tocopherol concentration in the early colostrum, however, it decreases with the lactational days significantly. The investigation suggests that early breast-feeding would be beneficial to the improvement of vitamin E intake in neonates during the early life.

Effects of seasonality on blood ionized calcium in early neonatal periods

The levels of whole blood ionized calcium were observed in 200 healthy neonates in the first week of life in spring and in summer. Levels of blood ionized calcium were lower in neonates born in spring compared to those of neonates born in summer. The levels of blood ionized calcium in adults did not change in different seasons. This study suggested that seasonality had a significant effect on blood ionized calcium in early neonatal life.

Effect of brefeldin A on the structure of the Golgi apparatus and on the synthesis and secretion of proteins and polysaccharides in sycamore maple (Acer pseudoplatanus) suspension-cultured cells

Brefeldin A (BFA), a specific inhibitor of Golgi-mediated secretion in animal cells, has been used to study the organization of the secretory pathway and the function of the Golgi apparatus in plant cells. To this end, we have employed a combination of electron microscopical, immunocytochemical, and biochemical techniques to investigate the effects of this drug on the architecture of the Golgi apparatus as well as on the secretion of proteins and complex cell wall polysaccharides in sycamore maple (Acer pseudoplatanus) suspension-cultured cells. We have used 2.5 and 7.5 micrograms/mL of BFA, which is comparable to the 1 to 10 micrograms/mL used in experiments with animal cells. Electron micrographs of high-pressure frozen and freeze-substituted cells show that although BFA causes swelling of the endoplasmic reticulum cisternae, unlike in animal cells, it does not induce the disassembly of sycamore maple Golgi stacks. Instead, BFA induces the formation of large clusters of Golgi stacks, an increase in the number of trans-like Golgi cisternae, and the accumulation in the cytoplasm of very dense vesicles that appear to be derived from trans Golgi cisternae. These vesicles contain large amounts of xyloglucan (XG), the major hemicellulosic cell wall polysaccharide, as shown by immunocytochemical labeling with anti-XG antibodies. All of these structural changes disappear within 120 min after removal of the drug. In vivo labeling experiments using [3H]leucine demonstrate that protein secretion into the culture medium, but not protein synthesis, is inhibited by approximately 80% in the presence of BFA. In contrast, the incorporation of [3H]fucose into N-linked glycoproteins, which occurs in trans-Golgi cisternae, appears to be affected to a greater extent than the incorporation of [3H]xylose, which has been localized to medial Golgi cisternae. BFA also affects secretion of complex polysaccharides as evidenced by the approximate 50% drop in incorporation of [3H]xylose and [3H]fucose into cell wall hemicelluloses. Taken together, these findings suggest that at concentrations of 2.5 to 7.5 mu g/mL BFA causes the following major changes in the secretory pathway of sycamore maple cells: (a) it inhibits the transport of secretory proteins to the cell surface by about 80% and of hemicelluloses by about 50%; (b) it changes the patterns of glycosylation of N-linked glycoproteins and hemicelluloses; (c) it reduces traffic between trans Golgi cisternae and secretory vesicles; (d) it produces a major block in the transport of XG-containing, dense secretory vesicles to the cell surface; and (e) it induces the formation of large aggregates of Golgi apparatus of plant and animal cels share many functional and structural characteristics, the plant Golgi apparatus possesses properties that make its response to BFA unique.

Effect of monensin on plant Golgi: re-examination of the monensin-induced changes in cisternal architecture and functional activities of the Golgi apparatus of sycamore suspension-cultured cells

We have re-examined the effects of the ionophore monensin on the Golgi apparatus of sycamore maple suspension-cultured cells using a combination of high pressure freezing, immunocytochemical and biochemical techniques. Exposure of the cells to 10 microM monensin, which reduces protein secretion by approximately 90%, resulted first in the swelling of the trans-Golgi network, then of the trans-most trans-cisterna, the remaining trans-cisternae, and finally of the cis and medial cisternae. We postulate that these different rates of swelling reflect an underlying hierarchy of compartmental acidification with the trans-Golgi network being the most acidic compartment. Recovery occurred in the reverse sequence. Previous studies have suggested that the large swollen vesicles that accumulate in the cytoplasm of monensin-treated cells arise from the swelling and detachment of entire trans-cisternae. However, based on the many membrane blebbing configurations seen in association with the trans-Golgi network and the trans-Golgi cisternae of monensin-treated cells, and the fact that the surface area of the trans-Golgi cisternae is about five times greater than the surface area of the swollen vesicles, it appears that the swollen vesicles are produced by a budding mechanism. After 35–40 min of monensin treatment, cells with smaller, non-swollen, compact Golgi stacks began to appear and rapidly increased in number, contributing &gt; 60% of the cell population after 60 min and &gt; 80% after 100 min. In contrast, large numbers of swollen vesicles persisted in the cytoplasm of all cells for over 100 min. Since azide treatment of monensin-treated cells can prematurely induce the unswelling response and cellular ATP levels drop substantially after 45 min of monensin treatment, we propose that un-swelling of the Golgi stacks is due to a monensin-induced decline in ATP levels in the cells. Immunocytochemical labeling of the high pressure frozen cells with anti-xyloglucan antibodies demonstrated that the concentration of xyloglucan, a hemicellulose, in the swollen vesicles increased with time. This increase in vesicle contents may explain why these swollen vesicles do not contract in parallel with the Golgi stacks. In vivo labeling experiments with [3H]fucose, [3H]UDP-glucose and [3H]leucine demonstrated that monensin-treatment not only inhibited protein secretion, but also cellulose synthesis. Protein synthesis, on the other hand, was reduced only slightly during the first 30 min of treatment, but quite strongly between 30 and 60 min, consistent with the observed drop in ATP levels after &gt; 40 min of exposure to monensin.(ABSTRACT TRUNCATED AT 400 WORDS)

Functional compartmentation of the Golgi apparatus of plant cells : immunocytochemical analysis of high-pressure frozen- and freeze-substituted sycamore maple suspension culture cells

The Golgi apparatus of plant cells is engaged in both the processing of glycoproteins and the synthesis of complex polysaccharides. To investigate the compartmentalization of these functions within individual Golgi stacks, we have analyzed the ultrastructure and the immunolabeling patterns of high-pressure frozen and freeze-substituted suspension-cultured sycamore maple (Acer pseudoplatanus L.) cells. As a result of the improved structural preservation, three morphological types of Golgi cisternae, designated cis, medial, and trans, as well as the trans Golgi network, could be identified. The number of cis cisternae per Golgi stack was found to be fairly constant at approximately 1, whereas the number of medial and trans cisternae per stack was variable and accounted for the varying number of cisternae (3-10) among the many Golgi stacks examined. By using a battery of seven antibodies whose specific sugar epitopes on secreted polysaccharides and glycoproteins are known, we have been able to determine in which types of cisternae specific sugars are added to N-linked glycans, and to xyloglucan and polygalacturonic acid/rhamnogalacturonan-I, two complex polysaccharides. The findings are as follows. The beta-1,4-linked d-glucosyl backbone of xyloglucan is synthesized in trans cisternae, and the terminal fucosyl residues on the trisaccharide side chains of xyloglucan are partly added in the trans cisternae, and partly in the trans Golgi network. In contrast, the polygalacturonic/rhamnogalacturonan-I backbone is assembled in cis and medial cisternae, methylesterification of the carboxyl groups of the galacturonic acid residues in the polygalacturonic acid domains occurs mostly in medial cisternae, and arabinose-containing side chains of the polygalacturonic acid domains are added to the nascent polygalacturonic acid/rhamnogalacturonan-I molecules in the trans cisternae. Double labeling experiments demonstrate that xyloglucan and polygalacturonic acid/rhamnogalacturonan-I can be synthesized concomitantly within the same Golgi stack. Finally, we show that the xylosyl residue-linked beta-1,2 to the beta-linked mannose of the core of N-linked glycans is added in medial cisternae. Taken together, our results indicate that in sycamore maple suspension-cultured cells, different types of Golgi cisternae contain different sets of glycosyl transferases, that the functional organization of the biosynthetic pathways of complex polysaccharides is consistent with these molecules being processed in a cis to trans direction like the N-linked glycans, and that the complex polysaccharide xyloglucan is assembled exclusively in trans Golgi cisternae and the trans Golgi network.

Functional compartmentation of the Golgi apparatus of plant cells : immunocytochemical analysis of high-pressure frozen- and freeze-substituted sycamore maple suspension culture cells

The Golgi apparatus of plant cells is engaged in both the processing of glycoproteins and the synthesis of complex polysaccharides. To investigate the compartmentalization of these functions within individual Golgi stacks, we have analyzed the ultrastructure and the immunolabeling patterns of high-pressure frozen and freeze-substituted suspension-cultured sycamore maple (Acer pseudoplatanus L.) cells. As a result of the improved structural preservation, three morphological types of Golgi cisternae, designated cis, medial, and trans, as well as the trans Golgi network, could be identified. The number of cis cisternae per Golgi stack was found to be fairly constant at approximately 1, whereas the number of medial and trans cisternae per stack was variable and accounted for the varying number of cisternae (3-10) among the many Golgi stacks examined. By using a battery of seven antibodies whose specific sugar epitopes on secreted polysaccharides and glycoproteins are known, we have been able to determine in which types of cisternae specific sugars are added to N-linked glycans, and to xyloglucan and polygalacturonic acid/rhamnogalacturonan-I, two complex polysaccharides. The findings are as follows. The beta-1,4-linked d-glucosyl backbone of xyloglucan is synthesized in trans cisternae, and the terminal fucosyl residues on the trisaccharide side chains of xyloglucan are partly added in the trans cisternae, and partly in the trans Golgi network. In contrast, the polygalacturonic/rhamnogalacturonan-I backbone is assembled in cis and medial cisternae, methylesterification of the carboxyl groups of the galacturonic acid residues in the polygalacturonic acid domains occurs mostly in medial cisternae, and arabinose-containing side chains of the polygalacturonic acid domains are added to the nascent polygalacturonic acid/rhamnogalacturonan-I molecules in the trans cisternae. Double labeling experiments demonstrate that xyloglucan and polygalacturonic acid/rhamnogalacturonan-I can be synthesized concomitantly within the same Golgi stack. Finally, we show that the xylosyl residue-linked beta-1,2 to the beta-linked mannose of the core of N-linked glycans is added in medial cisternae. Taken together, our results indicate that in sycamore maple suspension-cultured cells, different types of Golgi cisternae contain different sets of glycosyl transferases, that the functional organization of the biosynthetic pathways of complex polysaccharides is consistent with these molecules being processed in a cis to trans direction like the N-linked glycans, and that the complex polysaccharide xyloglucan is assembled exclusively in trans Golgi cisternae and the trans Golgi network.

[Protective effect of verapamil against alloxan-induced damage on pancreatic islet beta-cells in rats]

An experimental diabetes model was produced by intravenous injection of alloxan. Verapamil (40 mg/kg) administered intraperitoneally 30 minutes prior to alloxan was able to decrease serum glucose from 22.93 +/- 1.37 mmol/L to 8.79 +/- 0.83 mmol/L after 48 hours of injection of alloxan. Histological findings showed that the number of secretory granules in beta cells of the pancreatic islet of rats pretreated with verapamil was markedly increased as compared to rats treated with alloxan alone.

Morphological evidence for newly discovered double projection spinal neurons

A novel population of spinal neurons is shown to terminate in two nuclei: the lateral cervical nucleus and the dorsal column nuclei. Nuclear yellow and Fast blue injected respectively into these nuclei are retrogradely transported to common neurons in the lumbosacral dorsal horn. The bifurcation of these neurons' axons appears to occur at the cervico-thoracic junction. These results indicate that some dorsal horn neurons transmit sensory information to two distinct nuclei. The two projections and their branching points may play a special role in neuronal communication.

[Peripheral nerve tumor with rhabdomyosarcomatous differentiation (malignant "triton" tumor)--report of 3 cases]

In this paper, 3 cases of malignant "triton" tumor are reported. By special stain, immunohistochemistry and electron microscopy, coexistence of rhabdomyoblasts and Schwann's cell elements was demonstrated. Case 1 was associated with von Recklinghausen disease; in case 3, the tumor developed within a nerve; both had background of malignant schwannoma. Case 2 was a girl with congenital giant pigmented nevus. Her tumor was composed predominantly of rhabdomyoblasts element but by immunohistochemistry, it was confirmed that her tumor also occurred within a nerve. The criteria of diagnosis, differential diagnosis and histogenesis are discussed.