Histological type of oncogenity and expression of cell cycle genes in tumor cells from human mesenchymal stem cells

In previous experiments, a novel tumor cell line, which was characterized by dominated F6 mutated from human mesenchymal stem cells (hMSCs), was developed. The mechanism and biological characteristics of this mutation are still unclear. In this study, the histological type of F6 cells was investigated by immunohistochemistry with specific markers: vimentin, CD117, desmin, NSE and vWF. The characteristics of proliferation and metastasis were shown by PCNA (proliferating cell nuclear antigen), and nm23 and cell cycle-related genes, such as p16, p21, p53 and pRb, were analyzed by RT-PCR and immunohistochemistry. The expression of hTRAP and BMI-1 were detected by real-time PCR and Western blotting. The activity of telomerase was analyzed by TRAP (telomerase repeat amplification protocol) assay. The results showed that multi-directional differentiation occurred in F6 cells, i.e., special markers of muscle, endothelial cell and nerve system were co-expressed in F6 cells, while hardly expressed in hMSCs. F6 cells maintained the same properties as of MSCs, such as negativity for both CD117 and vimentin. F6 cells exhibited strong positivity for PCNA and negativity for nm23. The cell cycle-related genes, such as p16, p21, p53 and pRb, were not detected in F6 cells, while the expression of hTRAP and BMI-1 was significantly higher. The activity of telomerase was also significantly higher in F6 cells than that in hMSCs. These findings indicated that multi-directional differentiation occurred during the transformation of hMSCs into F6 cells, and that the genes of cell cycle and cell senescence may also be associated with the neoplasia of adult stem cells.

Calvarial osteoclasts express a higher level of tartrate-resistant acid phosphatase than long bone osteoclasts and activation does not depend on cathepsin K or L activity

Bone resorption by osteoclasts depends on the activity of various proteolytic enzymes, in particular those belonging to the group of cysteine proteinases. Next to these enzymes, tartrate-resistant acid phosphatase (TRAP) is considered to participate in this process. TRAP is synthesized as an inactive proenzyme, and in vitro studies have shown its activation by cysteine proteinases. In the present study, the possible involvement of the latter enzyme class in the in vivo modulation of TRAP was investigated using mice deficient for cathepsin K and/or L and in bones that express a high (long bone) or low (calvaria) level of cysteine proteinase activity. The results demonstrated, in mice lacking cathepsin K but not in those deficient for cathepsin L, significantly higher levels of TRAP activity in long bone. This higher activity was due to a higher number of osteoclasts. Next, we found considerable differences in TRAP activity between calvarial and long bones. Calvarial bones contained a 25-fold higher level of activity than long bones. This difference was seen in all mice, irrespective of genotype. Osteoclasts isolated from the two types of bone revealed that calvarial osteoclasts expressed higher enzyme activity as well as a higher level of mRNA for the enzyme. Analysis of TRAP-deficient mice revealed higher levels of nondigested bone matrix components in and around calvarial osteoclasts than in long bone osteoclasts. Finally, inhibition of cysteine proteinase activity by specific inhibitors resulted in increased TRAP activity. Our data suggest that neither cathepsin K nor L is essential in activating TRAP. The findings also point to functional differences between osteoclasts from different bone sites in terms of participation of TRAP in degradation of bone matrix. We propose that the higher level of TRAP activity in calvarial osteoclasts compared to that in long bone cells may partially compensate for the lower cysteine proteinase activity found in calvarial osteoclasts and TRAP may contribute to the degradation of noncollagenous proteins during the digestion of this type of bone.

Comparison of different signal peptides for protein secretion in nonlytic insect cell system

Protein expression and secretion in insect cells have been widely studied in the baculovirus-infected insect cell system. In directly transfected insect cells only intracellular expression and purification of recombinant proteins have been studied in detail. To examine multiple recombinant protein variants, easy and fast expression and a purification screening system are required. The aim of this study was to establish an effective and rapid secretion system for human azurocidin using directly transfected insect cells. We also constructed and tested expression vectors possessing heterologous signal peptides derived from human azurocidin, yellow lupin diphosphonucleotide phosphatase/phosphodiesterase (PPD1), and papaya papain IV to secrete yellow lupin and red kidney bean purple acid phosphatases, PPD1, and papain IV. Our results demonstrate that the secretion vectors used here can direct recombinant proteins to the culture medium very effectively, allowing their simple purification on a small/medium scale. Based on secretion and activity analyses it seems that the azurocidin signal peptide is one of the most potent secretion signals.

Phytase production by thermophilic mold Sporotrichum thermophile in solid-state fermentation and its application in dephytinization of sesame oil cake

The phytase production by Sporotrichum thermophile TLR50 was recorded on all the commonly used animal feed ingredients tested to varying degrees in solid-state fermentation. Enzyme production increased to 180 U/g of dry moldy residue (DMR) in sesame oil cake at 120 h and 45 degrees C at the initial substrate-to-moisture ratio of 1:2.5 and aw of 0.95. Supplementation of sesame oil cake with glucose and ammonium sulfate further enhanced phytase titer (282 U/g of DMR). An overall 76% enhancement in phytase production was achieved owing to optimization. The mold secreted acid phosphatase, amylase, xylanase, and lipase along with phytase. By the action of phytase, inorganic phosphate was liberated efficiently, leading to dephytinization of sesame oil cake.

Influence of pesticides and herbicides presence on phosphatase activity and selected bacterial microbiota of a natural lake system

Phosphatase activities (cell-bounded phosphatases "BP" and freely dissolved phosphatases "D P") in water samples from a natural lake "Laguna Grande" (Antequera, Málaga, Spain) amended with 50 microg/ml of selected insecticides, herbicides and fungicide captan were studied under laboratory controlled conditions (temperature and agitation). Our data show that dissolved alkaline phosphatase was the enzymatic activity that contributed in higher proportion to total lake water samples phosphatase status. The presence of organochlorinated insecticides (aldrin and lindane), organophosphorous insecticides (dimetoate, methidation and methyl-parathion), herbicide atrazine and fungicide captan significantly increased phosphatase activities after 28 days of incubation. However, these activities were not affected as a consequence of the addition of the herbicide simazine to the water samples. Heterotrophic mesophilic and psychrophilic aquatic bacteria counts as well as culturable phosphate solubilizing microorganisms, increased when the pesticides were added to lake water samples with herbicide simazine exception.

Evaluation of acid phosphatase as a confirmation test for Clostridium perfringens isolated from water

AIMS

To evaluate testing for acid phosphatase as an alternative method for the confirmation of Clostridium perfringens isolated from water.

METHODS AND RESULTS

Sixty-two reference strains of Clostridium were tested for their ability to produce acid phosphatase, as well as reduction of sulfite on tryptose sulfite cycloserine agar (TSC) and production of fluorescence in TSC supplemented with 4-methylumbelliferylphosphate (MUP). Additionally 155 environmental presumptive C. perfringens isolates from TSC incubated at 44 degrees C were identified and tested for acid phosphatase production and by the conventional MNLG (testing for motility, nitrate reduction, lactose fermentation and gelatin liquefaction) confirmation procedure. Twenty-seven strains from 15 species of Clostridium-reduced sulfite to some extent on TSC incubated at 44 degrees C, with a significant number of species being able to grow well at this temperature, indicating that a confirmation step is needed for the enumeration of C. perfringens on this medium. All 10 strains of C. perfringens tested, together with one strain each of Clostridium baratii and Clostridium rectum produced acid phosphatase. These also produced fluorescence on MUP supplemented TSC, as did 13 strains of acid phosphatase negative, sulfite-reducing clostridia, representing nine species. Of the environmental isolates, 114 were identified as C. perfringens of which 108 (94.7%) were confirmed by the acid phosphatase test compared with 104 (91.2%) by the MNLG tests.

CONCLUSIONS

Testing for acid phosphatase production is at least as reliable, and much simpler to perform, than the current standard confirmation MNLG procedure. Incorporation of MUP into TSC does not reliably improve the identification of presumptive C. perfringens.

SIGNIFICANCE AND IMPACT OF THE STUDY

Application of testing for acid phosphatase as a confirmation test for C. perfringens would substantially simplify the analysis for this bacterium from water samples, and reduce the analysis time to confirmed counts.

Acid phosphatase production by Aspergillus niger N402A in continuous flow culture

The production of acid phosphatases (E.C.3.1.3.2, ACPs) by Aspergillus niger N402A is regulated by specific growth rate, as well as phosphate availability and pH, as demonstrated by studies in continuous flow culture. Specific ACP activity was highest when A. niger was grown at pH 6.3 (64+/-8 U g(-1)) or pH 2.8 (99+/-11 U g(-1)), at a dilution rate of 0.07 h(-1) and phosphate concentrations below 0.46 mM. ACP production was growth correlated for specific growth rates between 0.07 and 0.13 h(-1). Four different ACPs, including two phytases, were produced by A. niger N402A. The ACP and the phytase with maximal activities at pH 5.5 were differentially expressed at different culture pH values, with greater production at low pH.

Differential synthesis of phosphate-starvation inducible purple acid phosphatase isozymes in tomato (Lycopersicon esculentum) suspension cells and seedlings

This study compares the influence of phosphate (Pi) deprivation on the coordinate synthesis of the principle Pi-starvation inducible (PSI) acid phosphatase (AP) isozymes in a suspension cell culture with the homologous in planta system. Tomato suspension cells express three PSI purple AP isozymes: a heterodimeric intracellular AP (IAP) composed of 63 and 57 kDa subunits, and two monomeric secreted APs (SAPs) (84 kDa SAP1 and 57 kDa SAP2) localized in the culture media. Immunoblots probed with rabbit antibodies raised against purified SAP1 or IAP indicated the immunological distinctiveness of SAP1 relative to IAP and SAP2. Time-course studies of cells and seedlings undergoing a transition from Pi sufficiency to Pi deficiency revealed a close relationship between total IAP or SAP activity and relative amounts of antigenic IAP or SAP polypeptides. Upregulation of the pre-existing IAP in 6-day-old Pi-deficient (-Pi) suspension cells coincided with a 20-fold reduction in intracellular free Pi levels, which occurred 2 d prior to initial accumulation of SAP1 and SAP2 in the culture media. Similarly, root-specific SAP synthesis in -Pi seedlings occurred at least 7 d following IAP induction in roots or shoots. Preferential sequestration of limiting Pi to the leaves of the -Pi seedlings was suggested by the delayed induction of leaf versus root IAP. Our results confirm recent transcript profiling studies suggesting that PSI proteins are subject to both temporal and tissue-specific syntheses in- Pi plants.

Osteoclastogenesis in the nonadherent cell population of human bone marrow is inhibited by rhBMP-2 alone or together with rhVEGF

During bone development and repair, angiogenesis, osteogenesis, and bone remodeling are closely associated processes that share some common mediators. In the present study nonadherent human bone marrow mononuclear cells under the induction of sRANKL and M-CSF, differentiated into osteoclasts with TRAP-positive staining, VNR expression, and Ca-P resorptive activity. The effects of various combinations of rhBMP-2 (0, 3, 30, and 300 ng/mL) and rhVEGF (0 and 25 ng/mL) on osteoclastogenesis potentials were examined in this experimental system. The percentages of TRAP-positive multiple nucleated cells represent osteoclast differentiation potential, and the percentages of resorptive areas in the Ca-P coated plates resemble osteoclast resorption capability. The presence of rhBMP-2 at 30 and 300 ng/mL showed inhibitory effects on osteoclast differentiation and their resorptive capability in the human osteoclast culture system. rhVEGF (25 ng/mL) enhanced the resorptive function of osteoclast whenever it was used alone or combined with 3 ng/mL rhBMP-2. However, rhVEGF-induced resorptive function was inhibited by 30 ng/mL and 300 ng/mL rhBMP-2 in a dose-dependent manner. Statistical analysis demonstrated that an interactive effect exists between rhBMP-2 and rhVEGF on human osteoclastogenesis. These findings suggested that an interactive regulation may exist between BMPs and VEGF signaling pathways during osteoclastogenesis; exact mechanisms are yet to be elucidated.

Protein, leucine aminopeptidase, esterase, acid phosphatase and photosynthetic responses of oleander (Nerium oleander L.) during cold acclimation and freezing treatments

Six-month-old oleander (Nerium oleander L.) pot plants, derived from vegetative propagation by cuttings, were tested for their ability to cold hardening. Damage of the non-acclimated (NA) plants was visible when treated by low freezing temperatures (below -2 degrees C). The responses of total proteins, leucine aminopeptidase (LAP), esterase (EST) and acid phosphatase (ACP) isoforms of NA and cold-acclimated (CA; 4 degrees C for 14 days) plants were compared using polyacrylamide gel electrophoresis. These molecular markers were also compared in NA and CA plants which received for 2h temperatures of 0, -2, -4, -6 and -8 degrees C. A new 38-kDa polypeptide appeared from day 7 to 14 during the acclimation treatment in the bark extracts and on day 14 in the leaf extracts. The above-mentioned polypeptide band (38 kDa) strongly appeared in all freezing treatments (0, -2, -4, -6 and -8 degrees C) in both bark and leaf extracts of the CA plants. Alterations in the number and the intensity of LAP and EST isoforms as well as in the intensity of ACP isoforms were observed in both bark and leaf of the CA oleander plants. A newly expressed EST isoform is proposed as biochemical marker for the cold acclimation treatment. CO2 assimilation rates (A) as well as transpiration rates (E) in NA plants were positive in 0 degrees C and negative in all temperatures below zero in the freezing treatments. In contrast, CO2 assimilation rates (A) and transpiration rates (E) were positive in CA plants in all temperatures of freezing treatment. A significant decrease (P<0.05) in chlorophyll (Chl) a, Chl a+b concentration and Chl a/b ratio were noticed in oleander plants during the acclimation treatment (from day 0 to 14), while Chl b concentration was unchanged at the respective time. On the other hand, no significant (P<0.05) differences were observed in the freezing treatments.

Effect of dermal exposure to paraphenylenediamine and linear alkylbenzene sulphonate in guinea pigs

OBJECTIVE

To study the effects of paraphenylenediamine (PPD) and linear alkylbenzene sulphonate (LAS) alone and in combination on the skin.

METHODS

Forty-eight guinea pigs were divided equally into 4 groups and exposed to PPD (4 mg/kg), LAS (12 mg/kg) and PPD (4 mg/kg) plus LAS (12 mg/kg) for 30 days. The biochemical parameters such as acid phosphatase, gtutathione-s-transferase, glutathione peroxidase, glutathione, lipid peroxidation and histamine contents in exposed skin were estimated. The histopathological examination of the exposed skin was also carried out.

RESULTS

The skin enzymes, lipid peroxidation, and histamine increased while glutathione decreased in skin. The simultaneously exposed group showed additive toxic effects. The histopathological examination showed severe hyperkeratosis, thickening of collagen fibres and vacuolisation of epidermal cells in PPD plus LAS exposed skin.

CONCLUSION

The findings of the present study suggest that simultaneous exposure to PPD and LAS has additive toxic effects.

IL-4 Inhibits Bone-Resorbing Activity of Mature Osteoclasts by Affecting NF-κB and Ca2+ Signaling

IL-4 is an important immune cytokine that regulates bone homeostasis. We investigated the molecular mechanism of IL-4 action on bone-resorbing mature osteoclasts. Using a highly purified population of mature osteoclasts, we show that IL-4 dose-dependently inhibits receptor activator of NF-kappaB ligand (RANKL)-induced bone resorption by mature osteoclasts. We detected the existence of IL-4R mRNA in mature osteoclasts. IL-4 decreases TRAP expression without affecting multinuclearity of osteoclasts, and inhibits actin ring formation and migration of osteoclasts. Interestingly, IL-4 inhibition of bone resorption occurs through prevention of RANKL-induced nuclear translocation of p65 NF-kappaB subunit, and intracellular Ca(2+) changes. Moreover, IL-4 rapidly decreases RANKL-stimulated ionized Ca(2+) levels in the blood, and mature osteoclasts in IL-4 knockout mice are sensitive to RANKL action to induce bone resorption and hypercalcemia. Furthermore, IL-4 inhibits bone resorption and actin ring formation by human mature osteoclasts. Thus, we reveal that IL-4 acts directly on mature osteoclasts and inhibits bone resorption by inhibiting NF-kappaB and Ca(2+) signaling.

Transcriptional profiling on chromosome 19p indicated frequent downregulation of ACP5 expression in hepatocellular carcinoma

Chromosomal rearrangements unraveled by spectral karyotyping (SKY) indicated frequent chromosome 19 translocations in hepatocellular carcinoma (HCC). In an effort to characterize the aberrant 19 rearrangements in HCC, we performed positional mapping by fluorescence in-situ hybridization (FISH) in 10 HCC cell lines. SKY analysis indicated structural rearrangements of chromosome 19 in 6 cell lines, 4 of which demonstrated recurring 19p translocations with different partner chromosomes. Using fluorescence-labeled BAC probes, physical mapping indicated a breakpoint cluster between 19p13.12 and 19p12. A corresponding transcriptional mapping by cDNA array on 19p suggested the differential expression of a single downregulated gene ACP5 (tartrate-resistant acid phosphatase type 5). Quantitative RT-PCR confirmed the reduced expression of ACP5 and indicated a strong correlation of its repressed expression only in cell lines that contain a 19p rearrangement (p = 0.004). We further examined the expression of ACP5 in a cohort of 82 primary tumors and 74 matching nonmalignant liver tissues. In the primary HCC examined, a reduction of ACP5 transcripts by 2 to as much as 1,000-fold was suggested in 67% of tumors (55/82 cases). When compared to adjacent nonmalignant tissues, 46% of tumors (34/74 cases) demonstrated a lower expression level (p = 0.015). On closer examination, a high significance of ACP5 repression was suggested in the cirrhotic HCC subgroup that was derived from chronic hepatitis B infected patients (55%; 30/54 cases; p = 0.001). Functional examination of ACP5 ectopic expression in HCC cells further demonstrated a significant growth inhibitory effect of ACP5 on tumor cell survival (p < 0.001). In our study, the novel finding of common ACP5 downregulation in HCC may provide basis for further investigations on the role of acid phosphatase in hepatocarcinogenesis.

Expression of Escherichia coli AppA2 phytase in four yeast systems

To develop an effective fermentation system for producing Escherichia coliphytase AppA2, we expressed the enzyme in three inducible yeast systems: Saccharomyces cerevisiae (pYES2), Schizosaccharomyces pombe (pDS472a), and Pichia pastoris (pPICZ alphaA), and one constitutive system: P. pastoris (pGAPZalphaA). All four systems produced an extracellular functional AppA2 phytase with apparent molecular masses ranging from 51.5 to 56 kDa. During 8-day batch fermentation in shaking flasks, the inducible Pichia system produced the highest activity (272 units ml(-1) medium), whereas the Schizo. pombe system produced the lowest activity (2.8 units ml(-1)). The AppA2 phytase expressed in Schizo. pombe had 60-75% lower K(m)for sodium phytate and 28% higher heat-stability at 65 degrees C than that expressed in other three systems. However, all four recombinant AppA2 phytases had pH optimum at 3.5 and temperature optimum at 55 degrees C and similar efficacy in hydrolyzing phytate-phosphate from soybean meal.

The effect of hindlimb immobilization on acid phosphatase, metalloproteinases and nuclear factor-κB in muscles of young and old rats

Age-associated muscle wasting (sarcopenia of old age) is a major problem in elderly people, however, the mechanisms of muscle proteolysis in aging remain obscure and enigmatic. Possible reasons for loss of skeletal muscle mass with aging may be attributed to multiple and complex proteolytic systems. The purpose of the present study was to explore the kinetics of activation of extracellular hydrolytic and proteolytic systems in muscles of hindlimbs immobilized by external fixation of 24-month-old female Wistar rats, in comparison with those of 6-month-old rats. Results show that elevated acid phosphatase activities (lysosomal hydrolytic enzyme activated mainly in macrophages) in immobilized limb muscles of young animals, differ from old animals. In young rats external fixation resulted in significantly elevated acid phosphatase activities (50-55%; p<0.05) after 4 weeks of immobilization, whereas in old animals similar increases were observed already during the first and second weeks of immobilization. The extracellular proteolytic enzymes, matrix metalloproteinases (MMP-2 and -9), were also differentially activated in old animals compared to young animals. In young animals, as shown in previous studies, both MMP-2 and -9 activities were elevated significantly in immobilized muscles. In this study of old animals, only MMP-2 activity was detected, with no significant elevation in the immobilized muscles of old animals. In addition, the levels of the transcription factor Nuclear Factor-kappaB (NF-kappaB) in nuclear extracts of old rat muscles, as detected by ELISA, showed a biphasic pattern after immobilization, suggesting that NF-kappaB could be activated by different processes in the atrophy process, at least in the old age. In conclusion, it seems that the kinetics of activation of extracellular hydrolytic and proteolytic systems differ in muscles of old animals compared to young animals.

Differences in the fusion and resorption activity of human osteoclasts after stimulation with different growth factors released from a polylactide carrier

Previous in vivo studies were able to demonstrate the efficacy of locally released growth factors IGF-I, TGF-beta1, and BMP-2 from a poly(D,L-lactide) (PDLLA) implant coating on fracture healing. In vitro studies using human osteoblast-like cells showed an enhanced collagen-1 production due to growth factor application without an effect of the PDLLA on the investigated parameter. Both bone-forming osteoblasts and bone-resorbing osteoclasts are important during bone formation and fracture healing. The aim of this study was to investigate the influence of different growth factors and the polylactide coating into which they were incorporated on isolated osteoclasts. In vitro studies using human osteoclast-like cells derived from peripheral blood mononuclear cells (PBMNCs) were performed. Titanium K-wires coated with the lactide loaded with IGF-I and TGF-beta1 (alone and in combination) or BMP-2 were added to the culture in a non-contact manner and the fusion, resorption activity (pit formation assay), and TRAP 5b synthesis of the cells were analyzed. Differences in the effect of the growth factors were seen depending on the differentiation state of the cells. The fusion of the monocytes to multinuclear osteoclasts was significantly enhanced by the application of TGF-beta1 both alone and in combination with IGF-I. No effect was seen after application of IGF-I alone or BMP-2. The resorption activity of the osteoclasts analyzed on dentine chips was significantly enhanced after application of TGF-beta1 or BMP-2. These results indicate a differentiation-dependent effect of growth factors on osteoclasts. TGF-beta1 affects both the osteoclastogenesis and the activity of osteoclasts, whereas BMP-2 had an effect only on the activity of mature osteoclasts but not on the fusion of the PBMNCs.

Eccentric localization of osteocytes expressing enzymatic activities, protein, and mRNA signals for type 5 tartrate-resistant acid phosphatase (TRAP)

Enzymatic activity of type 5 tartrate-resistant acid phosphatase (TRAP) has been regarded as one of the reliable markers for osteoclasts and their precursors. The presence of TRAP activity in osteocytes near the bone resorbing surface has also been pointed out in some reports. However, the significance of TRAP reactions in osteocytes remains controversial and, in fact, there is no agreement as to whether the histochemical enzyme reactions in osteocytes represent the TRAP enzyme generated by the respective osteocytes or is a mere diffusion artifact of the reaction products derived from the nearby osteoclasts. Current histochemical, immunohistochemical, and in situ hybridization studies of rat and canine bones confirmed TRAP enzyme activity, TRAP immunoreactivity, and the expression of Trap mRNA signals in osteocytes located close to the bone-resorbing surface. TRAP/Trap- positive osteocytes thus identified were confined to the areas no further than 200 microm from the bone-resorbing surface and showed apparent upregulation of TRAP/Trap expression toward the active osteoclasts. Spatial and temporal patterns of TRAP/Trap expression in the osteocytes should serve as a valuable parameter for further analyses of biological interactions between the osteocytes and the osteoclasts associated with bone remodeling.

Characterization and properties of acid phosphatases with phytase activity produced by Aspergillus caespitosus

High levels of thermostable acid phosphatases were produced by Aspergillus caespitosus in culture media supplemented with xylan birchwood or agricultural residues, as carbon sources. The optimal culture conditions for production of phosphatases were 40 degrees C and pH 6.0. Extra- and intra-cellular acid phosphatases were purified by chromatography on DEAE-cellulose, followed by concanavalin A-Sepharose affinity separation. Both extra- and intra-cellular enzymes were glycoproteins showing 63.0 and 58.3% of carbohydrate content respectively. Molecular masses estimated on Sepharose CL-6B column were 186 and 190+/-15 kDa, and 84 and 74+/-5 kDa according to SDS/PAGE, for extra- and intra-cellular acid phosphatases respectively. Taken together, these results suggest that both native enzymes were homodimers. Optimum temperature and pH for both phosphatase activities were 80 degrees C and 5.5 respectively. The extra- and intra-cellular acid phosphatases were stable for more than 60 min at 60 degrees C. The extracellular acid phosphatase was slightly inhibited by NaF, in contrast with the significant inhibition of the intracellular form. KH(2)PO(4) inhibited both activities equally. Both extra- and intracellular acid phosphatases were tartarate-resistant. Among several phosphorylated substrates used, the extracellular enzyme preferentially hydrolysed p-nitrophenyl phosphate. Kinetic parameters calculated for the hydrolysis of p-nitrophenyl phosphate by extracellular acid phosphatase were h (Hill coefficient)=1.2, K(0.5)=0.082 mM and V(max)=4.43 units/mg, whereas the intracellular enzyme exhibited Michaelian kinetics with K(m)=0.029 mM and V(max)=0.082 unit/mg. Phytase activity was also observed for both the enzymes, suggesting that they could be useful for biotechnological applications.

Transcripts of MYB-like genes respond to phosphorous and nitrogen deprivation in Arabidopsis

In Arabidopsis thaliana (L.) Heynh., AtPhr2 and AtNsr1 encode proteins with MYB-like and alpha-helical domains. They resemble CrPsr1, a nuclear-localized MYB protein that is critical for acclimation to phosphorous (P) starvation in the alga Chlamydomonas reinhardtii. Reverse transcription-polymerase chain reaction analysis of the first unique exons indicated that AtPhr2 mRNA increased as early as 6 h after P deprivation (-P), whereas nitrogen deprivation (-N) had no effect. The AtNsr1 mRNA level increased exclusively under -N, an increase first noted by 2 days in -N. In spite of P- and N-specific effects on expression of AtPhr2 and AtNsr1 there appeared to be P-N cross-talk at the whole-plant level. Total non-secreted acid phosphatase activity increased under both -P and -N within 2 days of deprivation. Further, the pho2-1/pho2-1 mutant, reported to be a phosphate accumulator, showed no increase in AtPhr2 mRNA in response to -P and a 70% reduction in the response of AtNsr1 mRNA to -N. Consistent with this pattern, there was no increase in acid phosphatase activity in pho2-1/pho2-1 plants deprived of P or N. However, when deprived of P, pho2-1/pho2-1 plants accumulated much higher levels of nitrate. T-DNA disruption of AtNsr1 resulted in altered expression of at least one nitrate transporter (AtNRT2.5). Further evidence of cross-talk between N and P responses was altered expression of N-responsive genes in pho2-1/pho2-1.

Glow discharge plasma pretreatment enhances osteoclast differentiation and survival on titanium plates

Despite the fact that several reports have demonstrated osteoclast activity on various bioactive ceramics, osteoclast functions on surface-modified titanium have not come under focus. This study aimed to examine whether the increasing surface energy of glow discharge plasma (GDP) involved in protein adhesion containing the RGD (Arg-Gly-Asp) sequence affects osteoclast responses on titanium plates. We examined osteoclast differentiation and survival rates on titanium plates with and without GDP. The amounts of osteoclasts on titanium plates were not increased by GDP after 1 week. However, osteoclast differentiation was greatly activated by GDP pretreatment, as tartrate-resistant acid phosphatase synthesis significantly increased on the titanium plates with GDP. Additionally, since the presence of osteoclasts was detected only on the titanium plates with GDP, even after 4h cultivation in a coculture test, the osteoclasts survival rate was increased by GDP pretreatment. As osteoclast responses were affected even on surface modified metallic materials, we concluded that novel approaches are needed not only for osteoclastic resorption on ceramic materials but also for osteoclast responses on surface-modified metallic materials.

Phosphate or phosphite addition promotes the proteolytic turnover of phosphate-starvation inducible tomato purple acid phosphatase isozymes

Within 48 h of the addition of 2.5 mM phosphate (HPO42-, Pi) or phosphite (H2PO3-, Phi) to 8-day-old Pi-starved (-Pi) tomato suspension cells: (i) secreted and intracellular purple acid phosphatase (PAP) activities decreased by about 12- and 6-fold, respectively and (ii) immunoreactive PAP polypeptides either disappeared (secreted PAPs) or were substantially reduced (intracellular PAP). The degradation of both secreted PAP isozymes was correlated with the de novo synthesis of two extracellular serine proteases having M(r)s of 137 and 121 kDa. In vitro proteolysis of purified secreted tomato PAP isozymes occurred following their 24 h incubation with culture filtrate from Pi-resupplied cells. The results indicate that Pi or Phi addition to -Pi tomato cells induces serine proteases that degrade Pi-starvation inducible extracellular proteins.

Characterization of osteoclasts from patients harboring a G215R mutation in ClC-7 causing autosomal dominant osteopetrosis type II

Autosomal dominant osteopetrosis II (ADOII) is a relatively benign disorder caused by a missense mutation in the ClCN7 gene. In this study, we characterize the osteoclasts from patients with ADOII, caused by a G215R mutation, and investigate the effect on osteoclast function in vitro. Osteoclasts from ADOII patients and healthy age- and sex-matched controls, were used to evaluate osteoclastogenesis, cell fusion, acidification, and resorptive activity. ADOII osteoclasts in vivo have increased number and size. However, in vitro we observed no significant changes in the osteoclast formation rate, the morphology, and the expression of markers, such as cathepsin K and tartrate-resistant acid phosphatase. When mature ADOII osteoclasts were investigated on mineralized bone, they degraded the bone material, however only to 10 to 20% of the level in controls. We show by acridine orange, that the reduced chloride transport leads to reduced acidification. We show that the residual activity is sensitive to inhibitors of cathepsins and chloride channels, confirming that resorption is reduced but present. In conclusion, this is the first functional in vitro study of human ADOII osteoclasts. We show normal osteoclastogenesis in ADOII osteoclasts. However, the residual activity of the ClC-7 channel in ADOII osteoclasts does not allow sufficient acidification and thereby resorption.

Histopathological and Cell Enzyme Studies of Calcium Phosphate Cements

New types of self-setting calcium phosphate cement (N-CPC), which do not contain tetracalcium phosphate, were recently developed. N-CPCs harden in 10 minutes with phosphate solution as the cement liquid, and form hydroxyapatite as the set product. The objectives of the present study were to evaluate the biocompatibility (Study I) and cell enzyme activity of N-CPCs and a conventional CPC (Study II). Four experimental cements were tested: (1) dicalcium phosphate anhydrous (DCPA) and calcium oxide; (2) DCPA and calcium hydroxide; (3) tricalcium phosphate and calcium carbonate; and (4) DCPA and tetracalcium phosphate. Phosphate solution was used as the cement liquid for cements (1)-(3), and water for cement (4). Sintered hydroxyapatite particles (5) were used as a control. The test materials were implanted subcutaneously in rats. Four weeks after operation, the animals were sacrificed and histopathological observations were performed. Cements (2) and (3) showed no inflammatory reaction, and were surrounded only by very thin fibrous connective tissues. The histopathological reactions of N-CPCs were nearly identical and were similar to (4) and (5). In addition, effects of alkaline phosphatase (ALP-ase) activity--invoked by the presence of cements (3) and (4)--on osteoblast-like cells derived from dog alveolar bone were also examined because ALP-ase activity is closely related to new bone formation. These results indicated that (3) and (4) were highly compatible with subcutaneous tissues and suggested that these cements may enhance new bone formation.

Regulation of osteoclast protease expression by RANKL

Receptor activator of NF-kappaB ligand (RANKL) is essential for osteoclast (OC) differentiation/activation and functions through its receptor RANK at the surface of the osteoclastic cells. This study investigated for the first time the direct effects of hRANKL on protease/protease inhibitor expressions and protease activities in purified rabbit osteoclast cultures, using semi-quantitative RT-PCR, gelatin zymography, and enzymatic assays. RANKL was shown to exert in vitro pro-resorptive effects by increasing osteoclast marker expressions (Tartrate resistant acid phosphatase (TRAP) and cathepsin K), MMP-9 expression, and pro-MMP-9 activity and by diminishing TIMP-1 expression, leading to an up-regulation of the MMP-9/TIMP-1 ratio.

Expression, purification, crystallization and preliminary X-ray diffraction studies of recombinant class B non-specific acid phosphatase of Salmonella typhimurium

The aphA gene of Salmonella enterica sv. Typhimurium strain MD6001 was cloned in the multicopy plasmid pBluescript SK(-). The recombinant AphA protein was purified to homogeneity. The protein crystallized in the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 112.4, b = 130.2, c = 139.6 A. Consistent with the self-rotation function, there are two tetramers in the asymmetric unit, indicating a solvent content of approximately 54%. The crystals are composed of biologically active AphA molecules.