Influence of a cellulosic ether carrier on the structure of biphasic calcium phosphate ceramic particles in an injectable composite material

An injectable composite material based on biphasic calcium phosphate (BCP) and a nonionic cellulose ether has been elaborated for use in percutaneous surgery for spine fusion. This paper reports the characterization results of this material by spectroscopic techniques including X-ray diffraction (XRD), infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) fitted with an energy dispersive X-Ray analysis system and high-resolution transmission electron microscopy (HR-TEM). From FTIR and XPS results, it was observed that the adhesion between the polymer and the ceramic might be insured by oxygen bridging developed through an ionic bonding between calcium ions and (C-O) groups of the polymer. Moreover, XPS showed attraction of Ca2+ ions in the polymer matrix, while the ceramic surface was modified in a HPO4(2-) -rich layer. These results suggest a possible dissolution/precipitation process at the interface ceramic/polymer. HR-TEM observations supported this hypothesis, showing a light contrasted fringe at the surface of the ceramic grains in the composite paste. As well, changes in the XRD spectra could indicate a small decrease in the crystal size of the BCP powder through the contact to polymer solution. In addition, SEM observation showed a decrease of the initial BCP granulometry. Aggregates of 80-200 microm seemed to be mostly dissociated in micrograins. The ceramic grains were coated with and bonded between each other by the polymer matrix, which acted as spacer in between the ceramic grains, creating a macroporous-like material structure.

Occurrence of monosialosyl pentahexaosylceramide GalNAc-GM1 as specific tumor-associated ganglioside of human head and neck squamous cell carcinomas

In a recent study of the ganglioside profiles of human head and neck squamous cell carcinomas versus normal tissue, one unidentified GX ganglioside was found exclusively in tumor extracts, migrating between GM1 and GD3 by thin-layer chromatography. To determine the chemical structure of this ganglioside which accounted for 3-8% of the total gangliosides, the lipid samples were pooled and separated by high-pressure liquid chromatography to obtain individual ganglioside species purified to homogeneity. The tumor-associated GX ganglioside was analyzed by gas-liquid chromatography, mass spectrometry and immunostaining on thin-layer plates with mouse monoclonal antibodies after enzymatic cleavage. The data allowed the identification of GX ganglioside as GalNAc-GM1 that has been reported as a very minor brain ganglioside in humans. Thus, GalNAc-GM1 is a specific tumor-associated ganglioside in human head and neck squamous cell carcinomas that could be potentially valuable for clinicians.

Increased serum C-reactive protein levels by immunonephelometry in patients with rapidly destructive hip osteoarthritis

OBJECTIVE

To compare serum C-reactive protein levels measured using a highly sensitive immunonephelometry method in patients with rapidly destructive versus slowly progressive hip osteoarthritis.

METHODS

Ten patients meeting criteria for rapidly destructive hip osteoarthritis were compared to 25 patients with slowly progressive hip osteoarthritis defined as less than 0.20 mm joint space loss over the last year. Serum C-reactive protein was assayed using an immunonephelometry method with a detection threshold of 0.17 mg/L and a coefficient of variation of less than 5%.

RESULTS

One patient in each group was excluded because of a C-reactive protein level greater than 15 mg/L. The mean C-reactive protein level in the remaining 33 patients was 3.05 +/- 3.46 mg/L (range, 0.10-14.9 mg/L). Mean C-reactive protein was significantly higher in the rapidly destructive group than in the slowly progressive group (5.61 +/- 4.75 versus 1.94 +/- 1.98 mg/L, P = 0.01), even after adjustment for potential confounding factors.

CONCLUSION

Our data suggest that rapidly destructive hip osteoarthritis may be associated with some degree of inflammation reflected by a small but significant increase in serum C-reactive protein levels.

Osteoarthritic cartilage fibrillation is associated with a decrease in chondrocyte adhesion to fibronectin

OBJECTIVE

Cartilage destruction in osteoarthritis (OA) is generally accepted as a failed repair process. Cell adhesion is implicated in tissue repair. Therefore, adhesion of OA chondrocytes to extracellular matrix proteins was investigated.

DESIGN

Using chondrocytes from human OA femoral head cartilage, adhesion to fibronectin and type II collagen of cells from distinct areas showing an intact cartilage surface or a fibrillated cartilage surface was studied. Modulation of chondrocyte adhesion by both protein kinase C (PKC) inhibitors and glucosamine sulfate (GS) was also investigated.

RESULTS

A significant (P < 0.05) decrease in adhesion to fibronectin of chondrocytes from fibrillated cartilage, relative to those from grossly normal OA cartilage, was demonstrated. Adhesion to type II collagen was not modified by the chondrocyte origins (either from normal or fibrillated OA cartilage). Adhesion to fibronectin of cells from grossly intact cartilage was decreased by the addition of PKC and calmodulin-dependent kinase inhibitors, W7 and sphingosine, to the cell culture. Adhesion to fibronectin of chondrocytes from fibrillated cartilage was significantly (P < 0.05) increased after glucosamine sulfate treatment.

CONCLUSION

Fibrillation of cartilage from OA femoral head is associated with a defective adhesion of chondrocytes to fibronectin. The process is suggested to be dependent of PKC and/or calmodulin-dependent kinases and potentially reversible. Conceivably, it could play a role in OA cartilage destruction.

ABC50, a novel human ATP-binding cassette protein found in tumor necrosis factor-alpha-stimulated synoviocytes

We have used the recently developed technique of differential display polymerase chain reaction to seek for new genes modulated by tumor necrosis factor-alpha (TNF-alpha) in cultured synoviocytes. One PCR fragment was shown to correspond to a new gene that was mapped by high-resolution fluorescence in situ hybridization to band 6p21.33. The cDNA of this gene was cloned, and the deduced amino acid sequence revealed consensus motifs for the nucleotide binding folds of the ATP-binding cassette (ABC) family of proteins. However, a hydropathy curve showed that the polypeptide does not contain the transmembrane domains that are typical of the subfamily of ABC transporters and are associated with transporter/channel functions. The new gene, called ABC50, is the first human and mammalian ABC protein found to lack transmembrane domains. Homology with some yeast ABC proteins suggests that ABC50 codes for a new human ribosomal protein involved in translation of mRNA. It could therefore play a role in the enhancement of protein synthesis that follows TNF-alpha treatment of synoviocytes and thus participate in the inflammatory processes mediated by this cytokine. Furthermore, since TNF-alpha also modulates the expression of MHC class I genes, and these genes are known to map to 6p21.33, it is hypothesized that ABC50 and MHC class I are part of the same chromatin expression domain.

Analysis of glycosphingolipids of human head and neck carcinomas with comparison to normal tissue

Glycosphingolipids of head and neck carcinomas from six tumor-bearing patients were analyzed and compared to those of normal tissue from similar areas. The total glycosphingolipid content and the lipid-bound sialic acid were much higher in carcinomas than in normal tissue. Major neutral glycolipids were glucosylceramide, lactosylceramide, trihexosylceramide and paragloboside. Sulfatides were seen only in extracts from normal tissue which also showed a rather simple ganglioside pattern with #GM3 and GD3 as major species, whereas tumors showed additional species such as GM2 and GD2, along with a strong increase in LM1, GM1, GD1a and GT1b.

Ultrastructural and electron diffraction of the bone-ceramic interfacial zone in coral and biphasic CaP implants

We investigated the influence of natural coral implants used as a bone substitute on the quality of bone ingrowth in rabbits 2, 3, and 6 weeks after implantation. Explants were characterized by transmission electron microscopy and electron diffraction. Bone ingrowth has been previously demonstrated by light microscopy, however, few have been performed in electron microscopy to compare mineralized tissue ingrowth in coral implants which occurs at the expense of calcium carbonate to that of calcium phosphate (CaP) implants. The interface between coral aragonite and mineralized tissue or bone was abrupt, with no invasion of the aragonite structure by newly formed crystals, as occurs in micropores when biphasic CaP (BCP) ceramics were used. The restoring process appears to be different from that induced by BCP implants. Precipitation of needle-like apatite crystals on the CaCO3 implant surface was not observed. Instead, apatitic smooth-shaped crystals formed in aggregates. The coral dissolution process does not release phosphate and so precipitation of apatite does not occur in the micropores of the coral implant, thereby limiting the formation of an apatite layer and hence bone bonding to the outer surface of the implant. In addition, on the outer surface of the implant, close to bone and a phosphorus source, the CaP crystals that do form are in aggregates presumably due to the carbonate and mismatch between the aragonite and the apatite. This seems to result in a delayed bone attachment or weaker bone bonding than CaP implants which encourage an epitaxial biological crystal deposition.

Interaction of per 3,6-anhydro-alpha cyclodextrins (alpha 36CD) and lead-alpha 36CD complex with biological systems

The interactions of per (3,6 anhydro) alpha cyclodextrin (alpha 36CD) and of lead-alpha 36CD complex with biological systems were tested by NMR, ESR and electronic microscopy using erythrocytes and model membranes. It was found that the haemolytic activity of alpha 36CD alone was seven fold lower than that of natural alpha cyclodextrin (evaluated by the concentration inducing 50% haemolysis, DH50 = 35 mM). Conversely, the formation of the complex resulted in an increase of haemolytic properties, with DH50 of 1 mM. The mechanism proposed was an increased membrane diffusion by endocytosis of the complex, leading to higher amounts of intracellular lead.

Inhibition of anti-CD3 antibody-induced mouse T cell activation by pentoxifylline in combination with rapamycin or A77 1726 (leflunomide)

Pentoxifylline (PTX), rapamycin (RAP), and leflunomide are potent immunomodulatory drugs with differing modes of action. In order to develop new drug combinations for immunotherapy, we tested the effects of PTX in combination with RAP or A77 1726 (the active metabolite of leflunomide) on in vitro T cell activation in a mouse model system. T lymphocytes in spleen cell preparations were stimulated with anti-CD3 monoclonal antibody alone, or in the presence of PTX (25-200 microg/ml), RAP (0.5-5.0 ng/ml), A77 1726 (2.5-10.0 microM), PTX/RAP (25-200 microg/ml and 0.5-5.0 ng/ml, respectively), or PTX/A77 1726 (25-200 microg/ml and 2.5-10.0 microM, respectively). Anti-CD3-induced T cell proliferation was inhibited in a dose-dependent fashion by the individual drugs. An additive inhibitory effect was observed in cultures treated with PTX/RAP or PTX/A77 1726. The effects of PTX, RAP, A77 1726, PTX/RAP, or PTX/A77 1726 (at concentrations approximating the IC50 of individual drugs for inhibition of lymphoproliferation) on anti-CD3-activated killer (AK) cell induction, CD25 expression, and interleukin (IL)-2 synthesis in anti-CD3-activated spleen cell cultures were also determined. Alone, each drug was able to suppress AK cell induction to varying degrees. PTX plus RAP exhibited strong synergism, while the combination of PTX and A77 1726 had an additive inhibitory effect on AK cell induction. CD25 expression was only weakly inhibited by A77 1726, but the percentage of CD25-expressing cells was greatly reduced in cultures treated with PTX or RAP. The combination of PTX and RAP had an additive inhibitory effect on CD25 expression while PTX and A77 1726 together had an effect equivalent to PTX alone. IL-2 synthesis was inhibited by PTX but was unaffected by RAP or A77 1726. Treatment with PTX plus RAP led to a further reduction in IL-2 production but co-treatment with PTX and A77 1726 approximated the inhibitory effect of PTX alone. We conclude that the combination of PTX and RAP is noteworthy for its potent immunomodulatory activity and may be of use in clinical situations where it is desirable to prevent T cell activation.

Changes in specific markers of haemostasis during reduction mammoplasty

We have investigated the time course of the coagulation and fibrinolytic changes during moderate surgical trauma (elective reduction mammoplasty) in the absence of other confounding factors that could affect haemostasis. Specific markers for coagulation (prothrombin fragment 1.2 (F1.2), thrombin-antithrombin III complex (TAT)) and fibrinolysis (plasmin-antiplasmin complex (PAP) and D-dimer) were examined. Blood samples were obtained in 20 ASA I anaesthetized female patients at T0 (before operation), T75 (during operation) and T150 (before the end of operation). There was a progressive increase in blood loss during operation:mean 110 (SD 80) ml at T75 and 470 (180) ml at T150. This was associated with a significant increase in plasma concentrations of F1.2, PAP and D-dimer at T150 only (P < 0.05 vs T0). We conclude that moderate surgical trauma with blood losses greater than 300 ml can activate thrombin generation and fibrinolysis during operation.

Abnormal uptake of Tc-99m MIBI, a novel myocardial imaging agent, in the lungs of patients with systemic sclerosis

OBJECTIVE

Fibrosing alveolitis is a prominent feature of systemic sclerosis (SSc), and accounts for much of the morbidity and mortality of this disease. Sensitive techniques for the detection and monitoring of fibrosing alveolitis could target patients for early therapeutic intervention. The objective of this small pilot study was to assess the frequency and clinical significance of abnormal lung uptake of Tc-99m MIBI, a novel radionuclide imaging agent that selectively accumulates in cells rich in mitochondria.

METHODS

Sixteen patients with SSc and evidence of pulmonary involvement were studied. The uptake of radionuclide in the lungs, and the ratio of pulmonary to cardiac uptake were evaluated after intravenous injection of Tc-99m MIBI. Results were correlated with clinical and laboratory parameters.

RESULTS

Lung uptake of Tc-99m MIBI was increased in all 16 SSc patients compared to control patients with coronary heart disease but no evidence of pulmonary abnormality. The degree of isotope uptake in the lungs was correlated with the extent of maximal skin induration and with radiologic evidence of interstitial lung disease, but not with other clinical or laboratory parameters of disease activity or extent of pulmonary involvement. The ratio of pulmonary to cardiac uptake of isotope was also increased in patients with SSc compared to controls.

CONCLUSION

Accumulation of Tc-99m MIBI is abnormally elevated in the lungs of SSc patients with pulmonary involvement. Isotope accumulation in the lungs may be related to activation of fibroblasts or endothelial cells. The specificity and sensitivity of Tc-99m MIBI scanning in the detection and monitoring of pulmonary involvement, and its potential role in the management of SSc, deserve further investigation.

The enzyme involved in sulfation of the turgorin, gallic acid 4-O-(beta-D-glucopyranosyl-6'-sulfate) is pulvini-localized in Mimosa pudica

A sulfotransferase (ST) which catalyzes the transfer of sulfate from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to gallic acid glucoside was characterized from microsomal preparations of Mimosa pudica. The product of the reaction was found to co-elute on HPLC with the periodic leaf movement factor 1 (PLMF-1)(gallic acid beta-D-gluco-pyranosyl-6'-sulfate). The distribution of the enzyme activity was restricted to plasma membrane preparations from primary, secondary and tertiary pulvini. The M. pudica ST activity was inhibited in a dose-dependent manner in the presence of an antibody raised against the flavonol 3-sulfotransferase of Flaveria chloraefolia, suggesting structural similarities between the two proteins. Western blot analysis of M. pudica protein extracts using these antibodies indicated the presence of a cross-reactive polypeptide with an apparent molecular mass of 42,000 Da whose distribution correlates with the presence of the gallic acid glucoside ST activity. Indirect immunogold labeling of resin-embedded sections from tertiary pulvini showed a specific localization of gold particles on the sieve-tube plasma membranes. The label distribution was uniform and other cellular organelles and membrane systems displayed little or no labeling. The results of the Western blot and immunocytochemical studies are consistent with the detection of the gallic acid glucoside ST activity in plasma membrane preparations of M. pudica pulvini cells. The specific tissue distribution of the ST in motor organ phloem cells suggests that this is the site of synthesis and/or accumulation of PLMF-1 and supports the proposed hypothesis that PLMF-1 may be acting as a chemical signal during the seismonastic response of M. pudica.

Phospholipase A2 activity in herniated lumbar discs. Clinical correlations and inhibition by piroxicam

STUDY DESIGN

Prospective study of phospholipase A2 activity in the serum and intervertebral discs of patients undergoing surgery for sciatica due to disc herniation.

OBJECTIVES

To determine correlations between herniated disc phospholipase A2 and clinical, radiographic, and anatomic signs of common sciatica; to evaluate serum phospholipase A2 activity as a marker of disc phospholipase A2; and to investigate the in vivo effect of piroxicam on disc phospholipase A2.

SUMMARY OF BACKGROUND DATA

Several studies suggest disc inflammation as a mechanism of sciatica due to disc herniation, and phospholipase A2 emerges as a key enzyme of cartilage and disc tissues.

METHODS

Phospholipase A2 activity was determined, using the degradation of a specific substrate, in the serum and discs of 31 patients (14 treated with acetaminophen and 17 treated with piroxicam) undergoing surgery for sciatica due to lumbar disc herniation. Visual analog scale for pain, Dallas Pain Questionnaire, Lasègue's sign, radiographic stage of degeneration of the herniated disc, volume of disc herniation shown by computed tomography, and surgical findings were recorded.

RESULTS

Disc phospholipase A2 activity was independent of the patient's age or sex, the radiologic stage of disc degeneration, and the volume of the herniation, and showed no significant correlation with Lasègue's sign or pain measured on a visual analog scale. The correlation between disc phospholipase A2 and the Dallas category of items measuring the impact of pain on daily activities approached the level of significance (P = 0.07). Disc phospholipase A2 activity was significantly higher in cases of sequestrated discs than in other herniations. Disc phospholipase A2 was significantly correlated with serum phospholipase A2, and was significantly lower in patients treated with piroxicam than in those treated with acetaminophen.

CONCLUSIONS

Disc phospholipase A2 is thought to participate in the physiopathology of sciatica and to bemodulated by nonsteroidal anti-inflammatory drug therapy. Serum phospholipase A2 is suggested as a biologic marker of disc inflammation in patients with sciatica.

Interlaboratory evaluation of short tandem repeat triplex CTT

An interlaboratory comparison of typing results for Short Tandem Repeats (STRs) at the GenBank loci HUMCSF1PO, HUMTPOX, HUMTH01, and HUMVWFA31 using the "CTT triplex" and "CTTv quadruplex" has been evaluated. These STRs all have a nominal four basepair (bp) repeat. Seven different samples were distributed to 41 laboratories. The 34 laboratories that returned results used a wide variety of analytical systems. Comparable results were obtained for all samples at all loci when results were reported as an allelic name. Raw sizing results obtained from internal-lane sizing standards differed by nearly five bp at some loci. Many different factors contribute to this observed sizing variability, including choice of sizing standards and matrix composition. Although sizing results can be made more comparable by locus-specific offsets or calibration to a comprehensive set of alleles at each locus, samples typed to the allelic name can now be validly compared regardless of analytical method. Interlaboratory comparison of raw allelic size remains problematic.

Moving health care education into the community

The A+ Asthma Club, an educational program developed for elementary school children in inner-city schools, is offered through a series of six sessions during school hours with an additional three booster sessions. This article describes how the program was designed, its theoretical basis, the curriculum and its staffing.

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.