Sulfation and sulfotransferases 6: Biochemistry and molecular biology of plant sulfotransferases

It is now well established that, in mammals, sulfate conjugation constitutes an important reaction in the transformation of xenobiotics and in the modulation of the biological activity of steroid hormones and neurotransmitter. The presence of a sulfate group on some molecules can also be a prerequisite for their biological function. For example, it is well known that the sulfate groups are directly involved in the molecular interaction between heparin and antithrombin III. In plants, sulfation also seems to play an important role in the intermolecular recognition and signaling processes, as indicated by the requirement of a sulfate moiety for the biological activity of gallic acid glucoside sulfate in the seismonastic and gravitropic movements of plants, and of Nod RM1 in the cortical cell division during early nodule initiation in Rhizobium meliloti-alfalfa interaction. In addition, recent studies indicate that flavonoid conjugates, including the sulfate esters, may play a role in the regulation of plant growth by strongly binding the naphthylphthalamic acid receptor, thus blocking the quercetin-stimulated accumulation of the auxin phytohormone. Although several sulfated metabolites are known to accumulate in a variety of plant species, the study of enzymes that catalyze the sulfation reaction in plants lagged considerably compared to those conducted with their mammalian homologs. This apparent lack of interest may have been because the function of plant-sulfated metabolites is difficult to predict, since their accumulation is often restricted to a limited number of species. Despite this limitation, several plant sulfotransferases (STs) have been characterized at the biochemical level, and the cDNA clones encoding six plant STs have been isolated. Based on sequence homology, the plant ST coding sequences are grouped under the SULT3 family, also known as the flavonol ST family. This review summarizes our current knowledge of the plant STs and focuses on the functional significance of the sulfate conjugation in plant growth, development, and adaptation to stress.

Calcitonin inhibits phospholipase A2 and collagenase activity of human osteoarthritic chondrocytes

Calcitonin (CT) is a known potent inhibitor of bone resorption but its effect on cartilage enzymatic degradation has been incompletely studied. Salmon CT, at a concentration of 0, 0.1, 0.25, 0.5, 2.5 and 50 ng/ml, was added at 24 or 72 h to the culture medium of chondrocytes from human osteoarthritic hips and knees. The spontaneous collagenolytic activity, measured using a radiolabeled type II collagen, was inhibited by CT in a dose-dependent manner. However, CT had no effect on the total collagenolytic activity assayed after APMA activation. Stromelysin and plasmin activity, measured by degradation of casein and a synthetic substrate, were also unaffected by CT. Chondrocyte phospholipase A2 activity, assayed using a labeled specific substrate, was decreased by CT. Chondrocyte pre-incubation with CT significantly decreased the cell binding of labeled TNF alpha, but did not affect IL-1 beta cell binding. Attachment of chondrocytes on fibronectin was markedly stimulated by CT, while attachment to type II collagen was not. Significant effects were obtained using at least 2 or 5 ng/ml of CT. CT appears to decrease collagenolytic activity by decreasing its activation and/or increasing its inhibition by tissue inhibitors of metalloproteinases (TIMP). CT might act on osteoarthritic chondrocyte activation via mechanisms such as phospholipase A2 activity, human necrosis factor-alpha or fibronectin receptor expression.

Homologous junctions formed between a vector and human genomic repetitive LINE-1 elements as a result of one-sided invasion

Studies on homologous recombination in mammalian cells between an exogenous DNA molecule containing a double-strand break and a homologous genomic sequence have indicated that there were at least two distinct types of homologous recombination processes, one that involved the formation of two homologous junctions and another that involved the formation of one homologous junction and one illegitimate junction. Both types of events are produced in gene targeting experiments. We have proposed a model to account for the later process called one-sided invasion. One-sided invasion has now been reported in numerous species belonging to different phyla and appears to be a universal mechanism. It has also been observed in normal human germ cells. The role of one-sided invasion is still unknown. Using a recombination assay between LINE-1 elements from the human genome and exogenous LINE-1 sequences, we have characterized the process of homologous junction formation in one-sided invasion. We found that at each of the homologous junctions, variable lengths of the vector L1 sequences had been replaced by genomic L1 sequences. We also found a homologous junction that involved three partners, suggesting that the homologous end could be released and become available for a second round of interaction.

Assessment of urinary hydroxypyridinium cross-links measurement in osteoarthritis

The aim of this study is to re-evaluate urinary collagen cross-links, previously proposed as markers of osteoarthritis (OA). The urinary excretion of collagen cross-links, pyridinoline (PYD) and deoxypyridinoline (DPD), was measured using high-performance liquid chromatography (HPLC) in 114 patients with OA, 19 patients with rheumatoid arthritis (RA) and 40 healthy subjects. An increase in PYD and DPD, expressed per millimole of creatinine, was confirmed in RA. However, PYD and DPD in patients with hip OA, knee OA and polyOA were similar, and did not differ from controls. In patients with radiographic end-stage OA, PYD and DPD were significantly higher than in patients with an early OA, but not significantly higher than in controls. The PYD/DPD ratio did not vary with the OA stage. Thus, urinary collagen cross-links are not elevated in OA, but could reflect bone sclerosis and/or erosion in late OA.

Phylogenetic inferences from chloroplast chlB gene sequences of Nephrolepis exaltata (Filicopsida), Ephedra altissima (Gnetopsida), and diverse land plants

The chloroplast chlB gene, involved in light-independent protochlorophyllide reduction, has been reported present in algae, in one bryophyte and some gymnosperms, but absent from various angiosperms. In this study, the complete or nearly complete chlB gene sequences from the fern Nephrolepis exaltata and the seed plant Ephedra altissima were determined. Comparison of five available land plant chlB sequences with a similar set of rbcL sequences, encoding the large subunit of ribulose 1,5-bisphosphate carboxylase, showed that the chlB rate of nonsynonymous substitution was about fourfold higher than for rbcL, while the chlB phylogeny resulted in a better resolution of the clades surveyed. The presence of chlB in other lineages of land plants was determined by amplification and sequencing of a chlB internal fragment, which was recovered from all the nonangiosperm taxa surveyed except Psilotum and Gnetum. The phylogenies derived from 23 land plant chlB sequences were largely congruent with the relationships inferred from other analyses. Neighbor-joining analysis supported the view that bryophytes are paraphyletic, with mosses as sister group to vascular plants. Within lycopodiophytes, Selaginella clustered with Lycopodium, but Isoetes was located basally to the other land plants. The various ferns surveyed were found to form a coherent group which derived after horsetails and which was sister group to seed plants. Our results strongly supported monophyly of the conifers-Ginkgo-cycads clade, where conifers were sister group to Ginkgo and cycads. The various phylogenies suggested an early divergence of the seed plant lineage leading to Ephedra.

Tc-99m MIBI brain SPECT of cerebellopontine angle tumors

To prospectively evaluate the imaging feasibility of Tc-99m sestamibi brain SPECT of cerebellopontine angle (CPA) tumors, seven patients with CPA lesions seen on CT or MRI and five normal control subjects underwent brain SPECT using a triple-headed camera. Five of these patients had acoustic neuromas, one had a meningloma, and the other had a vascular loop. Subsequently, four patients underwent surgery. In normal control subjects and patients with CPA lesions, there was Tc-99m sestamibi activity in the pituitary gland, choroid plexi, and extraocular muscles. The uptake in these structures, especially the choroid plexi could not be blocked by the oral administration of potassium perchlorate in two normal subjects. Four of seven patients with CPA lesions larger than 1.0 cm in diameter showed tumor uptake (3 acoustic schwannomas, 1 meningloma). Two small ( > 1.0 cm in diameter) intracanalicular type acoustic neuromas failed to show uptake, despite additional attenuation correction for the petrous bone. There was no abnormal uptake in the patient with a vascular loop in the CPA. Preliminary data suggest that, with the exception of small intracanalicular neuromas, CPA tumors can be imaged using Tc-99m sestamibi brain SPECT.

Routine determination of flumequine in kidney tissue of pig using automated liquid chromatography

A high-performance liquid chromatographic assay is described as a routine analytical method for the determination of flumequine (FLU) and its hydroxylated metabolite (OH-FLU) in pig kidney tissue. Kidney samples (2 g) containing FLU and OH-FLU were extracted by liquid-liquid extraction with ethyl acetate (10 ml). Analytical separations were performed by reversed-phase HPLC with fluorometric detection at 252 nm excitation and 356 nm emission under gradient conditions. The mobile phase was acetonitrile-2.7.10(-3) M oxalic acid in water (pH 2.5). The assay is specific and reproducible within the flumequine range of 0.050-2.5 micrograms/g and recovery at 0.050 microgram/g was 94.8%.

[Torsades de pointes in a patient under long-term maprotiline therapy. Apropos of a case]

The authors report the case of a patient who presented with wave burst arrhythmia related to long-term treatment with maprotiline. This case is interesting, as few cases of this type of complication have been reported in patients receiving long-term tetracyclic antidepressants, and the development of such a complication indicates the need for regular electrocardiographie surveillance of patients treated with heterocyclic antidepressants. Lastly, prolonged intensive care monitoring is required in the case of maprotiline-induced wave burst arrhythmia.

Determination of fumagillin in muscle tissue of rainbow trout using automated ion-pairing liquid chromatography

A high-performance liquid chromatographic assay is described as a routine analytical method for the determination of fumagillin in rainbow trout muscle tissue. Muscle tissue samples (1 g) containing fumagillin were deproteinized with 8 ml of an acetonitrile-water mixture (2:6, v/v). The extracts were purified with a Bond Elut Octyl C8 cartridge column, washed with a water-methanol mixture (95:5, v/v; 4 ml) and fumagillin was eluted with acetonitrile (1 ml). Analytical separations were performed by reversed-phase HPLC with UV detection at 351 nm under gradient conditions. The mobile phase was acetonitrile-0.005 M tetrabutyl ammonium phosphate in water (pH 7.8). The assay is specific and reproducible within the fumagillin range of 20-1000 ng/g and recovery at 20 ng/g was 69.2%. Sample preparation involves the use of a robotic sample preparation system. Gravimetric validation of all operations enabled Good Laboratory Practices to be observed.

Mutational analyses of Tay-Sachs disease: studies on Tay-Sachs carriers of French Canadian background living in New England

Tay-Sachs disease (TSD) results from mutations in HEXA that cause Hex A deficiency. Heterozygote-screening programs have been applied in groups with an increased TSD incidence, such as Ashkenazi Jews and French Canadians in Quebec. These programs are complicated by benign mutations that cause apparent Hex A deficiency but not TSD. Benign mutations account for only approximately 2% of Jewish and approximately 36% of non-Jewish enzyme-defined carriers. A carrier frequency of 1/53 (n = 1,434) was found in an ongoing prospective analysis of persons of French Canadian background living in New England by using an enzyme-based assay. DNA from enzyme-defined carriers from this population was analyzed to determine the molecular basis of Hex A deficiency. Samples (36) were tested for common mutations, and samples that were negative for these were screened for uncommon or novel mutations by using SSCP analysis. Exons showing mobility shifts were sequenced, and most mutations were confirmed by restriction enzyme digestion. Known disease-causing mutations were found in nine samples (four had a 7.6-kb deletion found in 80% of French Canadian TSD alleles), and known benign mutations were found in four samples. Seven novel changes were identified, including G748A in four samples. The molecular basis of Hex A deficiency in this carrier population differs from that of French Canadian TSD patients. Screening centers should be aware of the presence of benign mutations among U.S. French Canadians or Franco-Americans.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pulmonary embolism associated with right auricular thrombus. Apropos of 2 cases]

The authors report two cases of serious pulmonary embolism, derived from venous thrombus (inferior vena cava in one case, superficial femoral vein in the other), associated with mobile thrombus of the right auricle, with a very rapidly favourable course after intravenous fibrinolysis. This treatment was extremely effective, allowing rapid haemodynamic improvement and resolution of the thrombus in less than 24 hours. No major haemorrhagic complications or recurrent emboli were observed. Fibrinolysis, in serious pulmonary embolism associated with thrombus of the right auricle, therefore appears to be a useful treatment, particularly in patients admitted to centres in which emergency embolectomy cannot be performed.

Gangliosides from normal and osteoarthritic joints

A decrease in all major gangliosides, contrasting with a marked increase in the GM3 third band (3B-GM3), has been demonstrated in osteoarthritic fibrillated cartilage. We found the 3B-GM3 in osteoarthritic fibrillated, grossly intact and osteophytic human cartilage, but it was undetectable in pig and bovine cartilage, bone, synovium, synovial fluid white cells, erythrocytes, and various extracellular tissues. We made a similar finding with lactosyl ceramide, the GM3 neutral glycolipid precursor. The search for an antibody against the 3B-GM3, as a possible specific antigenic marker of osteoarthritis (OA), was unsuccessful. However, an antibody against a molecule very close to 3B-GM3 on high performance thin layer chromatography, which will probably be identified as a glycosylphosphatidylinositol, was found in the serum of some patients with OA.

Integration of a vector containing a repetitive LINE-1 element in the human genome

Mammalian cells contain numerous nonallelic repeated sequences, such as multicopy genes, gene families, and repeated elements. One common feature of nonallelic repeated sequences is that they are homeologous (not perfectly identical). Our laboratory has been studying recombination between homeologous sequences by using LINE-1 (L1) elements as substrates. We showed previously that an exogenous L1 element could readily acquire endogenous L1 sequences by nonreciprocal homologous recombination. In the study presented here, we have investigated the propensity of exogenous L1 elements to be involved in a reciprocal process, namely, crossing-overs. This would result in the integration of the exogenous L1 element into an endogenous L1 element. Of over 400 distinct integration events analyzed, only 2% involved homologous recombination between exogenous and endogenous L1 elements. These homologous recombination events were imprecise, with the integrated vector being flanked by one homologous and one illegitimate junction. This type of structure is not consistent with classical crossing-overs that would result in two homologous junctions but rather is consistent with one-sided homologous recombination followed by illegitimate integration. Contrary to what has been found for reciprocal homologous integration, the degree of homology between the exogenous and endogenous L1 elements did not seem to play an important role in the choice of recombination partners. These results suggest that although exogenous and endogenous L1 elements are capable of homologous recombination, this seldom leads to crossing-overs. This observation could have implications for the stability of mammalian genomes.

Chloroplastic genomes of Ginkgo biloba and Chlamydomonas moewusii contain a chlB gene encoding one subunit of a light-independent protochlorophyllide reductase

We have cloned and sequenced a Chlamydomonas moewusii chloroplastic DNA fragment that includes a 563 amino-acid open reading frame (ORF563, chlB) presenting 89% amino-acid homology with ORF513 from Marchantia polymorpha. It is also homologous to ORF510 from Pinus thunbergii but includes two insertions absent in both M. polymorphia and P. thunbergii. The derived polypeptide is 54% similar to the product of bchB from Rhodobacter capsulatus, identified as one subunit of a light-independent NADH-protochlorophyllide reductase. We also isolated and sequenced an homologous chloroplastic gene from the gymnosperm Ginkgo biloba. Northern hybridizations performed on RNA isolated from synchronized Chlamydomonas eugametos cells showed higher expression between the tenth hour of light and the eighth hour of darkness, peaking during the first 2 h of darkness.

[Serum phospholipase A2 activity in osteoarthritis]

Serum phospholipase A2 activity in 67 osteoarthritis patients and 17 controls was determined using a radiolabeled specific substrate. Serum phospholipase A2 activity was significantly higher in osteoarthritis patients (115 +/- 73.6 dpm/h/ml) than in controls (45 +/- 25 dpm/h/ml) (p = 0.002). In 41 osteoarthritis patients, serum phospholipase A2 activity was unrelated to age, time since onset of osteoarthritis symptoms, duration of morning stiffness, Lequesne's index, roentgenographic stage of osteoarthritis, number of joints with osteoarthritis, erythrocyte sedimentation rate, or serum C-reactive protein levels. In 12 osteoarthritis patients who were evaluated twice at a mean interval of 46 days, changes in serum phospholipase A2 activity were unrelated to changes in Lequesne's index. Blind evaluation of long-term joint space loss was performed in 14 patients; serum phospholipase A2 activity increased only in those patients with progressive joint space loss, but the difference was not statistically significant as compared with the controls. These data suggest that serum phospholipase A2 activity is not useful in practice as a marker for osteoarthritis.

Allele frequency data for VNTR locus D17S79: identification of an internal HaeIII polymorphism in the black population

D17S79 is one of several highly polymorphic VNTR loci commonly used to generate DNA profiles for forensic identity testing and parentage determination. In this study, we used Southern hybridization analysis of HaeIII-digested genomic DNA to compile D17S79 allele frequency databases for the Caucasian, Southeast Asian, East Indian, and Black populations of Southern Ontario. In our Black population sample, low-molecular-weight D17S79 alleles are relatively common and approximately 7% of the individuals have three-band hybridization patterns due to a HaeIII restriction site polymorphism within a common D17S79 allele. The internal HaeIII site generates an allele consisting of two HaeIII fragments of approximately 980 and 420 bp. The estimated frequency of this "split-allele" in our Black population is 0.035. Since this allele was not observed in the other population groups, the internal HaeIII polymorphism probably originated within the Black population. Although the existence of low-molecular-weight alleles and the internal HaeIII polymorphism could affect the interpretation of some VNTR patterns, they are of little or no forensic consequence to the frequencies assigned to VNTR profiles.

Targeting of histone tails by poly(ADP-ribose)

After Zn2+ finger-mediated binding to a DNA break, poly(ADP-ribose) polymerase becomes automodified with long polymers of ADP-ribose. These nucleic acid-like polymers may facilitate DNA repair by noncovalently interacting with neighboring proteins. Using a novel screening technique, we have identified histones as the predominant poly(ADP-ribose)-binding species in human keratinocytes, rat hepatocytes, frog eggs, and yeast. Polymer binding is confined specifically to the histone domains responsible for DNA condensation, i.e. histone tails. Our results indicate that polymers of ADP-ribose are targeted to sites of DNA strand breaks by poly(ADP-ribose) polymerase and subsequently function to alter chromatin conformation through noncovalent interactions with histone tails.

Characterization of gangliosides from normal and osteoarthritic human articular cartilage

OBJECTIVE

Glycosphingolipids (GSLs) are biologically active molecules in the physiology and pathology of cells. Since changes in GSLs might be associated with the impaired metabolism of articular cartilage in osteoarthritis (OA), we investigated gangliosides from normal and OA human cartilage.

METHODS

OA and control cartilage was obtained from patients with hip OA and femoral neck fracture, respectively. Gangliosides were extracted and quantified by determining their lipid-bound sialic acid concentration. Major gangliosides were identified by immuno-detection on thin-layer plates, purified by high performance liquid chromatography, and analyzed for their carbohydrate, fatty acid, and long-chain base composition.

RESULTS

The total ganglioside content of OA cartilage was decreased by 40% (per mg of DNA). Major gangliosides, GM3 and GD3, separated into 3 on thin-layer chromatography bands. All were decreased except for the lowest migrating band of GM3, which was increased 5-fold. This ganglioside had the same carbohydrate moiety and fatty acids as the other two, but differed by a long-chain base composed mainly of C20-sphingosine.

CONCLUSION

OA cartilage is characterized by a decrease in all gangliosides except GM3, which demonstrates a large increase in the lowest band. These results indicate that there are changes in the biochemical composition of chondrocyte membranes in OA. The causes and roles of these changes remain to be determined.

Shedding of GD2 ganglioside in patients with retinoblastoma

Retinoblastoma is a rare tumor of the young child with an intraocular localization that leads to certain problems of diagnosis. With the aim of defining a biochemical marker--which is still lacking for this disease--the gangliosides of a pool of fresh retinoblastoma tumors were analyzed. The ganglioside pattern was shown to have GM3, GM2, GM1, GD3, GD2, GD1b and GT1b as the major components. The occurrence of a high concentration of GD2 in the tumors led us to investigate the possibility of changes in the level of GD2 in the sera of retinoblastoma patients, using quantitative immunostaining with GD2-specific mouse monoclonal antibodies (MAbs). In 9 out of 10 tumor-bearing patients, the serum level of GD2 ganglioside was significantly higher than the average value found in normal individuals. A 2-year follow-up of patients showed that successful treatment resulted in a rapid decrease in the serum level of GD2 down to the normal range, from which a subsequent elevation was seen only in relapsing patients. Although the clinical study needs further development, the results obtained to date suggest that GD2 is shed in the serum of tumor-bearing patients and that the level of GD2 could be a potential serum marker of human retinoblastoma.

Metalloprotease activity, phospholipase A2 activity and cytokine concentration in osteoarthritis synovial fluids

Collagenase, stromelysin and phospholipase A2 (PLA2) activity as well as interleukin-1 beta (IL-1 beta), tumor necrosis factor alpha (TNF alpha) and interleukin 6 (IL-6) concentration were determined in the knee joint synovial fluid (SF) of 26 patients with osteoarthritis (OA) and with rheumatoid arthritis (RA). Collagenase and stromelysin were detected in 80.7 and 69.2% of OA SF, respectively. When present, the mean activity of both enzymes was approximately two times lower in OA than in RA SF. PLA2 activity was present in all SF with no significant difference between OA and RA SF. IL-1 beta, TNF alpha and IL-6 were found in 0, 96.1 and 84.6% of OA SF, respectively. Mean TNF alpha and IL-6 concentration was also lower in OA than in RA SF. Metalloprotease activity correlated weakly with IL-6 level and enzymatic activities were unrelated with TNF alpha in OA SF.

The effects of high molecular weight- and low molecular weight-heparins on superoxide ion production and degranulation by human polymorphonuclear leukocytes

High molecular weight (HMW) and low molecular weight (LMW) heparins affected superoxide ion production and degranulation by polymorphonuclear leukocytes (PMNL) isolated from either chronic hemodialyzed patients or healthy controls. Low concentrations in HMW-heparin, below 1.76 aXa IU/ml for patients and 1.34 aXa IU/ml for controls, increased O2- production started by phorbol myristate acetate. High concentrations above these values decreased it. Increasing LMW-heparin concentrations constantly decreased O2- production using the same stimulus. Myeloperoxidase (MPO) released by PMNL was found to be significantly HMW- and LMW-heparins dose-dependent. The addition of calcium chloride significantly increased MPO release. Lactoferrin release was not dose-dependent of HMW- or LMW-heparins. However, an increase of the percentage of positive responses for lactoferrin release was observed in the simultaneous presence of HMW-heparin and CaCl2 compared to HMW-heparin alone. Lysozyme release was also not dose-dependent of HMW- or LMW-heparins. An increase of the percentage of positive responses for lysozyme release was observed in the presence of CaCl2 alone compared to HMW-heparin.