Intranasal immunization with recombinant Ascaris suum 14-kilodalton antigen coupled with cholera toxin B subunit induces protective immunity to A. suum infection in mice

Animals can be rendered immune to Ascaris parasites by immunization with infectious-stage larvae. The specific parasite gene products that mediate protective responses in ascariasis are unknown. We have identified a cDNA encoding Ascaris suum 14-kDa antigen (As14) and evaluated the vaccinal effect of the Escherichia coli-expressed recombinant protein (rAs14). GenBank analysis showed that As14 has low similarity at the amino acid level to a Caenorhabditis elegans gene product and to antigens of the filarial nematodes but not to other known proteins. In addition, As14 homologues were found to be expressed in human and dog roundworms. In mice that received intranasal administration of rAs14 coupled with cholera toxin B subunit (rAs14-CTB), there was a 64% reduction of recovery of larvae compared with that in the nontreated group. The vaccinated mice showed a significant increase in the total serum immunoglobulin G (IgG) levels and the mucosal IgA responses. Elevation of the rAs14-specific IgE response was also seen. Measurement of the IgG subclasses showed a higher level of IgG1 and a lower level of IgG2a antibody response in the sera of the immunized mice, suggesting that protection was associated with a type II immune response. As14 is the first protective antigen against A. suum infection to be identified. Our immunization trial results in laboratory animals suggest the possibility of developing a mucosal vaccine for parasitic diseases caused by ascarid nematodes.

Molecular characterization of a troponin I-like protein from the hard tick Haemaphysalis longicornis

A cDNA expression library prepared from mRNA of Haemaphysalis longicornis (H. longicornis) was screened with a H. longicornis-infested rabbit serum. A cDNA encoding 27/30kDa proteins was cloned and designated P27/30 gene. The predicted amino acid sequence of the P27/30 gene shows a rather high homology (58% amino acid identities and 11% amino acid similarity) with Drosophila melanogaster troponin I clone E2. H. longicornis P27/30 possesses amino acid sequence of actin-binding domains of troponin I at the amino acid residues 128-148, suggesting that H. longicornis P27/30 is a troponin I-like protein. By immunoblot analysis, mouse anti-recombinant P27/30 serum reacted with major constituent protein bands in extracts of adult ticks, and also immunoreacted with muscle, cuticle, gut, and salivary gland in H. longicornis ticks. Moreover, immunohistochemistry using the anti-P27/30 serum showed a strong reactivity in muscle, suggesting that native P27/30 is expressed abundantly in that tissue.

Selective inhibition of skin fibroblast elastase elicits a concentration-dependent prevention of ultraviolet B-induced wrinkle formation

We previously reported that wrinkle formation in the skin following long-term ultraviolet B irradiation is accompanied by decreases in skin elasticity and the curling of elastic fibers in the dermis. We further showed that wrinkles could be repaired by treatment with retinoic acid and that this was concomitant with the recovery of skin elasticity ascribed to the repair of damaged elastic fibers. Those studies suggested that decreasing the tortuosity of dermal elastic fibers is an important factor involved in inhibiting or repairing wrinkle formation. Therefore, it is of particular interest to determine whether the inhibition of elastase activity in vivo would prevent the damage of dermal elastic fibers and might abolish wrinkle formation associated with the loss of skin elasticity. Because the major elastase in the skin under noninflammatory conditions is skin fibroblast elastase, we used a specific inhibitor of that enzyme to assess its biologic role in wrinkle formation. The hind limb skins of Sprague-Dawley rats were irradiated with ultraviolet B at a suberythemal dose three times a week for 6 wk. During that period, 0.1-10.0 mM N-phenetylphosphonyl-leucyl-tryptophane, an inhibitor of skin fibroblast elastase, was applied topically five times a week. N-phenetylphosphonyl-leucyl-tryptophane application at concentrations of 0.1-1.0 mM abolished wrinkle formation in a concentration-dependent manner, with a peak for inhibition at 1.0 mM. This inhibition was accompanied by a continued low tortuosity of dermal elastic fibers and a maintenance of skin elasticity. Measurement of elastase activity after 6 wk of ultraviolet B irradiation demonstrated that whereas phosphoramidon-sensitive elastase activity was significantly enhanced in the ultraviolet B-exposed skin, there was no significant increase in that activity in the ultraviolet B-exposed, N-phenetylphosphonyl-leucyl-tryptophane-treated skin. These findings suggest that skin fibroblast elastase plays an essential part in the degeneration and/or tortuosity of elastic fibers induced by cumulative ultraviolet B irradiation.

Molecular characterization of a 2-Cys peroxiredoxin from the human malaria parasite Plasmodium falciparum

We have identified the 2-Cys peroxiredoxin (PfPrx-1) from the human malaria parasite Plasmodium falciparum. The PfPrx-1 showed the highest identity at amino acid level to the type II Prx among the currently known six subfamilies of mammalian Prx. The sequence identity between the PfPrx-1 and the previously reported 1-Cys Prx of P. falciparum (PfPrx-2), which corresponded to mammalian type VI Prx, was 25%. This suggests that the parasite possesses two Prx subfamilies. The PfPrx-1 showed significant sequence similarities with those of 2-Cys peroxiredoxins of plants in the BLASTX search. This may reflect the consequences of a genetic transfer from an algal endosymbiont to the parasite nucleus during evolution. The recombinant PfPrx-1 protein (rPfPrx-1) was expressed as a histidine fusion protein in Escherichia coli and purified with Ni chromatography. The rPfPrx-1 existed as dimers under non-reducing conditions and dissociated into monomers in the presence of dithiothreitol. The PfPrx-1 protein also exists as a dimer in the parasites themselves. The reduction of the oxidized enzyme by the donation of electrons from E. coli thioredoxin (Trx)/Trx reductase system was demonstrated in its reaction with H(2)O(2), using the rPfPrx-1 protein. These results suggested that the PfPrx-1 can act as a terminal peroxidase of the parasite Trx system. An elevated expression of the PfPrx-1 protein seen in the trophozoite, the stage with active metabolism, suggests an association of the parasite Trx system with its intracellular redox control.

The role of elastases secreted by fibroblasts in wrinkle formation: implication through selective inhibition of elastase activity

We have previously demonstrated that decreases in skin elasticity, accompanied by increases in the tortuosity of elastic fibers, are important early events in wrinkle formation. In order to study the role of elastases in the degeneration of elastic fibers during wrinkle formation we examined the effects of an inhibitor of skin fibroblast elastase, N-phenethylphosphonyl-L-leucyl-L-tryptophane (NPLT), on wrinkle formation in hairless mice skin following UV irradiation. Dorsal skins of hairless mice were exposed daily to UV light for 18 weeks at doses of 65-95 mJ/cm2 and treated topically with 100 microL of 1 mM NPLT immediately after each UV irradiation. Wrinkles on dorsal skins were evaluated from week 6 through week 18. The daily exposure of mouse skin to UV light with less than 1 minimal erythemal dose significantly enhanced the activity of elastase in the exposed skin by week 4, and the elevated levels of elastase activity were significantly reduced by the in vitro incubation with NPLT in a dose-dependent manner to a level similar to that in unexposed mice skin, indicating that NPLT can efficiently inhibit the UV-inducible elastase activity. Topical application of NPLT significantly suppressed wrinkle formation when compared with vehicle controls by week 15 of treatment (P < 0.05). Histochemistry of elastic fibers with Orcein staining demonstrated that there were no obvious decreases of the fine elastic fibers in UV-exposed NPLT-treated skin in contrast to their marked decreases in the UV-exposed vehicle-treated skin. These findings suggest that skin fibroblast elastase plays a decisive role in wrinkle formation through the degeneration of elastic fiber.

Tumor necrosis factor-alpha in serum of patients with inflammatory bowel disease as measured by a highly sensitive immuno-PCR

BACKGROUND

The significance of serum concentrations of tumor necrosis factor-alpha (TNF-alpha) in the pathogenesis of inflammatory bowel disease (IBD) is uncertain. We measured TNF-alpha in serum from IBD patients by immuno-PCR to analyze the relationship between TNF-alpha and pathophysiologic state in IBD.

METHODS

Serum samples were collected from 54 healthy blood donors, 29 patients with ulcerative colitis (UC; 46 samples), and 7 patients with Crohn disease (CD; 8 samples). DNA label was generated by PCR amplification using biotinylated primer and was bound with streptavidin to biotinylated third antibody. TNF-alpha sandwiched by antibodies was detected by PCR amplification of the DNA label.

RESULTS

TNF-alpha could be measured in all samples. The median serum concentration in IBD patients overall was approximately 390-fold higher than in healthy donors (median increase, 380-fold for UC, 640-fold for CD). The median serum TNF-alpha concentration was 1.7-fold higher in the active stage of UC than in the inactive stage (P <0.05), and this difference could be detected in individual patients.

CONCLUSIONS

Sensitive measurement of serum TNF-alpha could provide an important pathophysiologic marker for the presence and activity of IBD.

Characterization of phagocytic hemocytes in Ornithodoros moubata (Acari: Ixodidae)

Effects of fetal bovine serum (FBS) and complement on phagocytic activity in Ornithodaros moubata (Murray 1877) hemocytes and protease activity in the hemocytes were examined. At least three morphologically different cell types, granulocytes, plasmatocytes, and prohemocytes, were detected in hemolymph of O. moubata, and granulocytes and plasmatocytes showed phagocytic activity. FBS altered phagocytic activity of granulocytes, and complement affected phagocytic activity of plasmatocytes. Ticks were inoculated with fluorescent polystyrene beads in combination with FBS or complement. The average number of beads in granulocytes was significantly higher in the FBS injected group than the control (P < 0.01). The percentage of bead-ingesting plasmatocytes in complement inoculated ticks was significantly lower than that in heat-inactivated complement inoculated and control ticks (P < 0.05). Proteases of tick hemocytes localized in small granules in the cytoplasm not only in phagocytic hemocytes but also in prohemocytes. Results suggested modulation of tick hemocyte function through serum components, and digestion of phagocytosed foreign bodies in the hemocytes.

Visualization of nitric oxide production in the earthworm ventral nerve cord

Distribution of nitric oxide (NO)-producible neurons in the ventral nerve cord (VNC) of the earthworm was investigated by nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry. Some neurons (20-30 microm in diameter) were intensely stained and were localized in areas between the 1st and 2nd lateral nerves in the ventral side of VNC. In contrast, no neurons including giant fibers were stained in the dorsal side. Endogenous NO production from VNC was visualized using a fluorescent dye, diaminofluorescein-2 diacethyl (DAF-2 DA). When VNC was incubated in a saline, a relative high level of NO was produced from the ventral side, especially from NADPH-d-positive neurons. Under high-K+ stimulation, NO was also detected in the giant fibers in the dorsal side of VNC. Our results suggest that the earthworm VNC constantly and relative highly produces NO as a neuromodulator, and that NO produced from the ventral side sometimes reaches and affects the giant fibers. In conclusion, we successfully visualized NO in the earthworm VNC by clarifying both the distribution of NO-producible neurons and the endogenous NO production.

Identification of larval-stage antigens of ascaris suum recognized with immune sera from pigs

Antigens were identified from the third-stage larvae (L3) and lung-stage larvae of Ascaris suum by two-dimensional immunoblot method with antisera obtained from pigs that received chemically abbreviated Ascaris suum larval infections. Forty-seven and 13 spots were recognized as antigens from the L3 and lung-stage larvae, respectively. Their apparent molecular weight ranged from 20 to 101 kDa and their isoelectric point from 3.6 to 8.0. The present study provides a framework for further molecular cloning of those antigens and consequently leads to the development of recombinant peptide vaccines against A. suum.

High-sensitivity analysis of cyanide by capillary electrophoresis with fluorescence detection

A capillary electrophoretic method for a high-sensitivity analysis of cyanide has been developed. Cyanide was derivatized with 2,3-naphthalenedialdehyde and taurine to give a fluorescent product of 1-cyanobenz[f]isoindole. This compound was detected with high sensitivity by fluorescence detection. The detection limit was 0.1 ng/mL, and the calibration curve was linear over the range 0.1-200 ng/mL. The precision of the migration time of within-run assays (n = 6) of 1 ng/mL cyanide standard solution was 0.14%. The precision of the peak area for the same runs was 1.0%. This method was applicable to blood analysis. Detection of the cyanide derivative by UV was also examined.

Molecular characterization of a peroxiredoxin from the hard tick Haemaphysalis longicornis

Antioxidant enzymes in eukaryotes play an important role in protection against the oxygen radicals generated during aerobic metabolism. Here we report the cloning and characterization of a cDNA encoding the antioxidant enzyme peroxiredoxin from the hard tick Haemaphysalis longicornis (HlPrx). HlPrx is 939 bp long and contains a 101 bp non-translated sequence at the 5' end and a polyadenylation singnal followed by a poly(A) tail at the 3' end. HlPrx encodes a full-length protein with a predicted molecular mass of 26 kDa that possesses one cysteine residue at amino acid 49 that is conserved among Prx proteins of various species. GenBanktrade mark analysis showed that the deduced amino acid sequence had significant similarity to mammalian and plant Prxs at the amino acid level. A DNA-nicking assay revealed that Escherichia coli-expressed recombinant HlPrx (rHlPrx) inhibited oxidative-nicking of supercoiled plasmid DNA. Two-dimensional immunoblot analysis with mouse antirHlPrx serum showed reaction with a major constituent protein spot in extracts of adult ticks. In addition, immunoblot analysis showed that rHlPrx was immunoreacted with serum from rabbits repeatedly infested with H. longicornis. Localization analysis using mouse antirHlPrx serum revealed that native HlPrx was highly expressed in the salivary gland of the tick. Moreover, Northern blot analysis showed that the level of HlPrx transcripts was increased during blood sucking. The present results indicate that HlPrx may be an important detoxifying enzyme during the normal life span as well as during blood sucking in ticks.

Lipopolysaccharide-induced IL-18 secretion from murine Kupffer cells independently of myeloid differentiation factor 88 that is critically involved in induction of production of IL-12 and IL-1beta

IL-18, produced as biologically inactive precursor, is secreted from LPS-stimulated macrophages after cleavage by caspase-1. In this study, we investigated the mechanism underlying caspase-1-mediated IL-18 secretion. Kupffer cells constantly stored IL-18 and constitutively expressed caspase-1. Inhibition of new protein synthesis only slightly reduced IL-18 secretion, while it decreased and abrogated their IL-1beta and IL-12 secretion, respectively. Kupffer cells deficient in Toll-like receptor (TLR) 4, an LPS-signaling receptor, did not secrete IL-18, IL-1beta, and IL-12 upon LPS stimulation. In contrast, Kupffer cells lacking myeloid differentiation factor 88 (MyD88), an adaptor molecule for TLR-mediated-signaling, secreted IL-18 without IL-1beta and IL-12 production in a caspase-1-dependent and de novo synthesis-independent manner. These results indicate that MyD88 is essential for IL-12 and IL-1beta production from Kupffer cells while their IL-18 secretion is mediated via activation of endogenous caspase-1 without de novo protein synthesis in a MyD88-independent fashion after stimulation with LPS. In addition, infection with Listeria monocytogenes, products of which have the capacity to activate TLR, increased serum levels of IL-18 in wild-type and MyD88-deficient mice but not in caspase-1-deficient mice, whereas it induced elevation of serum levels of IL-12 in both wild-type and caspase-1-deficient mice but not in MyD88-deficient mice. Taken together, these results suggested caspase-1-dependent, MyD88-independent IL-18 release in bacterial infection.

Cloning and preliminary characterization of a novel cuticular antigen from the filarial parasite Dirofilaria immitis

We have described here the cloning and partial characterization of a cDNA encoding a cuticular antigen of Dirofilaria immitis. A 48-h third-stage larval D. immitis cDNA library was immunoscreened with sera raised in mice against third-stage larval cuticles (mouse anti-L3 cuticle antisera). A strongly immunoreactive clone (L3MC4) was isolated. Sequence analysis of L3MC4 showed that it was a partial length cDNA. The missing 5' end of the clone was amplified by PCR from D. immitis adult female first-strand cDNA using the nematode 22-base splice leader sequence and a L3MC4-specific antisense primer. The composite cDNA sequence comprised 616 bases (nDiL3MC4) encoding a full-length protein of 146 amino acids (DiL3MC4). GenBank analysis showed that DiL3MC4 shared some homology to an unknown C. elegans gene product (31%) at the amino acid level. However, there were no related filarial expressed sequence tags in the current GenBank database. Antibodies to recombinant DiL3MC4 (rDiL3MC4) identified a 19-kDa native antigen in the adults and in the L3 and L4 larval stages of D. immitis. In addition, the antibodies bound to the cortical layers of the L3 cuticle, as revealed by immuno-gold electron microscopy. The native protein was not detected in larval and adult excretory-secretory products. Immunoblot analysis showed that serum from a rabbit that was repeatedly injected with a small number of D. immitis third stage larvae reacted with rDiL3MC4. Thus, DiL3MC4 is a novel cuticular antigen of a filarial parasite.

Identification of surface proteins and antigens from larval stages of Ascaris suum by two-dimensional electrophoresis

An understanding of the biology of the cuticle in the larval stages of Ascariodea is of importance since the cuticle molecules not only possess a variety of functions related to survival but also have a potential role as a target for immunoprophylaxis. Thus, we made a preliminary characterization of surface proteins and antigens from 3rd-stage larvae (L3) and lung-stage larvae of Ascaris suum using two biotin-derivatives and two-dimen sional polyacrylamide gel electrophoresis (2D-PAGE). The proteins labelled with biotin comprised a total of 37 and 32 spots, with molecular weights (Air) ranging from 15 to 101 kDa and isoelectric points (pI) from 3.8 to 7.6, in L3 and lung-stage larvae, respectively. The profiles revealed that the individual spots bound to one or both biotin derivatives. In addition, stage-common and stage-specific spots were found in L3 and lung-stage larvae. 2D-PAGE/immunoblotting analysis was performed with antisera from rabbits repeatedly inoculated with A. suum L3. Nineteen spots were recognized as surface antigens, with Mr ranging from 32 to 66 kDa and pI from 4.9 to 7.6, from L3 and lung-stage larvae after alignment of the immunoblots with the profile of the surface proteins. These spots were found to include stage-common and stage-specific antigens. Identification of surface proteins by biotin labelling combined with 2D-PAGE allows a substantial shortening of sample preparation time for the target proteins, and will be a viable method for protein analysis of surface proteins and antigens of A. suum L3 and lung-stage larvae.

Heat-induced apoptosis via caspase-3 activation in tumour cells carrying mutant p53

Apoptosis plays an important role in heat-induced cell death. However, the mechanism of heat-induced apoptosis has not yet been elucidated. In the present study, the signal transduction pathway underlying heat-induced apoptosis was investigated in heat-resistant HeLa cells carrying mutant p53 gene and heat sensitive HeLa cells that had been transduced with an antisense TNF gene. Induction of mutant p53, but not p21/WAF-1, was observed after heat treatment of both the resistant and sensitive cells. Heat-induced cytotoxicity was not inhibited in either cells with interleukin-1beta-converting enzyme (ICE: caspase-1) like protease inhibitor Ac-YVAD-CHO. In contrast, there was 48% and 63% inhibition of cytotoxicity in HeLa and transfectants, respectively, with a caspase-3 inhibitor (Ac-DEVD-CHO). Heat-induced apoptosis was also prevented by administration of Ac-DEVD-CHO in both cells. In addition, an augmentation of heat-induced cytotoxicity in transfectants was almost completely inhibited by Ac-DEVD-CHO. Further, caspase-3 mRNA expression was increased remarkably in heat-treated HeLa cells and transfectants. Taken together, these results suggest that activation of caspase-3 is involved in the signal transduction pathway of heat-induced apoptosis of the tumour cells carrying mutant p53.

Removal of hydrogen peroxide by a 1-cysteine peroxiredoxin enzyme of the filarial parasite Dirofilaria immitis

Prior studies have shown that filarial nematodes can effectively metabolize hydrogen peroxide in excess of that generated by activated host cells. However, the mechanisms of H2O2 removal by the filarial parasites are unclear. Herein we report the results of studies carried out on the biochemical activity and on immunolocalization of a recombinant peroxiredoxin (Prx) enzyme from the dog filarial parasite Dirofilaria immitis. A full-length cDNA encoding a 1-Cys Prx enzyme from the dog heartworm D. immitis was expressed in Escherichia coli as a recombinant polyhistidine fusion protein (rDiPrx-1). rDiPrx-1 was capable of reducing H2O2 in the presence of dithiothreitol. The apparent kinetic constants determined for DiPrx-1 using H2O2 as a substrate were a Michaelis constant (Km) of 16.28 mM and a maximal velocity (Vmax) of 16 micromol/min(-1). Consistent with the enzyme activity, D. immitis adult worms could detoxify exogenously added H2O2 in vitro. Antibodies to rDiPrx-1 identified a 27-kDa native antigen in parasite extracts and larval and adult excretory-secretory products. The antibodies were used to localize the native antigen to the lateral hypodermal chords of both male and female worms by immunohistochemistry. In addition, labeling was seen in the afibrillar muscle cells in male worms and in some areas of the uterine wall in female worms. Thus, DiPrx-1 is the first parasite Prx to be shown to detoxify exogenously added H2O2 in an in vitro system.

Biotin-labeled proteins of Eimeria tenella sporozoite

To identify surface proteins of eimerian sporozoite, Eimeria tenella sporozoites were labeled with biotin-LC-hydrazide, and analyzed by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and Western blotting. More than 200 sporozoite proteins were recognized with silver staining after 2D-PAGE. Among them, 7 biotin-labeled proteins were detected as surface molecules after Western blotting and reaction with horseradish peroxidase conjugated streptavidin. Their molecular masses ranged from 23 to 117 kilo daltons and their isoelectric points from 4.3 to 6.3. It appears that the biotin-labeling technique can be used to analyze of surface proteins of eimerian parasites.

Cloning and characterisation of a peroxiredoxin from the swine roundworm Ascaris suum

Antioxidant enzymes in parasites play an important role in protection against the oxygen radicals by generating during aerobic metabolism, as well as in defence against host immune cell assault. Here we report the cloning and characterisation of a cDNA encoding peroxiredoxin from Ascaris suum (AsPrx). AsPrx is 776bp long and contains the nematode 22bp splice leader sequence at the 5' end and polyadenylation signal followed by poly(A) tail at the 3' end. AsPrx codes a full-length protein with a predicted molecular mass of 22. 6kDa, and possesses two cysteine residues at amino acid 49 and 168 that are conserved among Prx proteins. GenBank() analysis showed that the deduced amino acid sequence had significant similarity to parasite and mammalian Prx at the amino acid level. DNA nicking revealed that Escherichia coli-expressed recombinant AsPrx (rAsPrx) is enzymatically inhibited to form oxidative-nicking of supercoiled plasmid DNA. Two-dimensional immunoblot analysis with mouse anti-rAsPrx serum reacted two major constituent protein spots in extracts of adult female worms, suggesting that the native AsPrx might be function as a major antioxidant enzyme in Ascaris suum.

Cloning and characterization of the gene encoding O-acetylserine lyase from Streptococcus suis

We have cloned and sequenced a gene encoding O-acetylserine lyase from Streptococcus suis. The gene encodes a protein of 309 amino acids with a calculated molecular mass of 32,038 Da. The deduced amino acid sequence showed more extensive similarities to the CysK proteins than to the CysM proteins of other bacteria. The cloned gene was inserted into a pTrcHisB histidine hexamer expression vector. A 38-kDa fusion protein was expressed in a cysMK auxotrophic mutant of Salmonella typhimurium and complemented the auxotrophic properties of the mutant. Furthermore, the transformants could grow in minimal defined media supplemented with not only sulfide but also thiosulfate as a sole sulfur source. These data indicated that the cloned gene encodes a protein that was a functional homolog of the CysM in S. typhimurium.

DNA polymorphism of srRNA gene among Eimeria tenella strains isolated in Japan

DNA polymorphism in twelve starains of Eimeria tenella isolated from various places in Japan was examined using 1.l kb small subunits ribosomal RNA amplified by PCR. Genetic variation was evaluated by random amplification of polymorphic DNA (RAPD) analysis. DNA fingerprint patterns were grouped into two, indicating that at least two DNA polymorphisms exist in Japanese E. tenella strains.

Transforming growth factor-beta1 (TGF-beta1) induces thrombopoietin from bone marrow stromal cells, which stimulates the expression of TGF-beta receptor on megakaryocytes and, in turn, renders them susceptible to suppression by TGF-beta itself with high specificity

The present study was designed to test the concept that platelets release a humoral factor that plays a regulatory role in megakaryopoiesis. The results showed that, among various hematoregulatory cytokines examined, transforming growth factor-beta1 (TGF-beta1) was by far the most potent enhancer of mRNA expression of bone marrow stromal thrombopoietin (TPO), a commitment of lineage specificity. The TPO, in turn, induced TGF-beta receptors I and II on megakaryoblasts at the midmegakaryopoietic stage; at this stage, TGF-beta1 was able to arrest the maturation of megakaryocyte colony-forming units (CFU-Meg). This effect was relatively specific when compared with its effect on burst-forming unit-erythroid (BFU-E) or colony-forming unit-granulocyte-macrophage (CFU-GM). In patients with idiopathic thrombocytopenic purpura (ITP), the levels of both TGF-beta1 and stromal TPO mRNA were correlatively increased and an arrest of megakaryocyte maturation was observed. These in vivo findings are in accord with the aforementioned in vitro results. Thus, the results of the present investigation suggest that TGF-beta1 is one of the pathophysiological feedback regulators of megakaryopoiesis.

Identification of an asparagine amidohydrolase from the filarial parasite Dirofilaria immitis

The nematode cuticle is a complex extracellular structure which is secreted by an underlying syncytium of hypodermal cells. Recent studies have demonstrated that the cuticle of parasitic nematodes is a dynamic structure with important absorptive, secretory, and enzymatic activities. In addition, the cuticle serves as a protective barrier against the host. A 48-h third stage larval Dirofilaria immitis cDNA library was immunoscreened with sera raised against larval cuticles. One clone, L3MC4 that reacted strongly with the anti-cuticle antisera was sequenced. The composite cDNA sequence comprises 2073 bp coding for a full-length protein of 590 amino acids. GenBank analysis showed that DiAsp had significant similarity to a Caenorhabditis elegans gene-product (54% identity) and to other asparaginases at the amino acid level. Escherichia coli-expressed recombinant DiAsp (rDiAsp) catalysed the hydrolysis of asparagine to aspartate and ammonia. Antibodies raised against D. immitis larval cuticles reacted with rDiAsp in immunoblots. This is the first report of identification of a cDNA clone encoding an asparaginase enzyme from a parasitic nematode.