Monocortical fixation for locking plate distal screws does not impair mechanical properties in open-wedge high tibial osteotomy.

BACKGROUND: The neurovascular bundle containing the deep peroneal nerve has a potential risk of injury during open-wedge high tibial osteotomy (OWHTO), particularly due to drilling for bicortical fixation at distal screw holes. Therefore, monocortical fixation is recommended for distal fixation of a long locking plate as long as good stability is ensured. The purpose of this study was to analyse the biomechanical properties of monocortical fixation of distal locking screws for OWHTO. METHODS: Three-dimensional models of bone and fixation materials simulating OWHTO were created using computed tomographic data of patients and material data of a T-shaped long locking plate and screws. Three of the four distal screws of the locking plate were chosen for a bicortical fixation or monocortical fixation procedure. In addition, loss of correction was assessed by measuring the medial proximal tibial angle (MPTA) in patients who underwent OWHTO with two bicortical and two monocortical distal fixation screws at 1 month and 1 year after surgery. RESULTS: No significant differences in stress were observed in either the normal or osteoporotic bone model between the monocortical and bicortical fixation models, including in the area of the lateral hinge at the osteotomy site. Furthermore, there were no significant differences in MPTA between the early post-operative period and 1-year follow-up. CONCLUSIONS: The monocortical fixation method for three distal screws of the locking plate did not worsen the mechanical properties of fixation for OWHTO using a long locking plate with four proximal and four distal screws. In actual surgery, the number of distal bicortical screws should be reduced based on the patient's condition, taking into account the risk of lateral hinge fracture and unexpected surgical complications. Using at least two bicortical screws would be practical considering the various factors related to reduced fixing ability.

Primary stability of different plate positions and the role of bone substitute in open wedge high tibial osteotomy.

BACKGROUND: The purpose of this study was to compare the mechanical fixation strengths of anteromedial and medial plate positions in osteotomy, and clarify the effects of bone substitute placement into the osteotomy site. METHODS: Twenty-eight sawbone tibia models were used. Four different models were prepared: Group A, the osteotomy site was open and the plate position was anteromedial; Group B, bone substitutes were inserted into the osteotomy site and the plate position was anteromedial; Group C, the osteotomy site was open and the plate position was medial; and Group D, bone substitutes were inserted into the osteotomy site and the plate position was medial. The loading condition ranged from 0 to 800N and one hertz cycles were applied. Changes of the tibial posterior slope angle (TPS), stress on the plate and lateral hinge were measured. RESULTS: The changes in the TPS and the stress on the plate were significantly larger in Group A than in Group C. These were significantly larger in Group A than in Group B, and in Group C than in Group D. There was no significant difference between Group B and Group D, and no significant difference between knee flexion angles of 0° and 10°. Stress on the lateral hinge was significantly smaller when bone substitute was used. CONCLUSIONS: A medial plate position was biomechanically superior to an anteromedial position if bone substitute was not used. Bone substitute distributed the stress concentration around the osteotomy gap and prevented an increase in TPS angle regardless of the plate position.

Biomechanical evaluation of the suture anchors used in open-door laminoplasty: a cadaveric study.

STUDY DESIGN: A cadaveric study. OBJECTIVE: To determine whether the use of suture anchors is warranted in cervical laminoplasty. SUMMARY OF BACKGROUND DATA: The use of suture anchors to stabilize elevated laminae has been popularized in laminoplasty. However, the validity of using suture anchors in laminoplasty has not been determined. METHODS: Six intact fresh frozen cadavers were used. Open-door laminoplasty with a hinge on the cadaver's left side was performed on levels C3-C7. Elevated laminae were stabilized by suture anchors equipped with strain gauges, which were placed on C3, C5, and C7 left lateral masses. After surgery, the cervical spine was manually loaded passively, and the mechanical loads on each suture anchor during each motion were measured. Finally, the incision was opened again, and the failure loads of the suture anchors were also measured. RESULTS: After cervical loading, all elevated laminae were confirmed to be intact without dislodgement or failure of the suture anchors. The loads during left rotation and left bending were significantly higher than those during the respective motion to the right at all levels, except in rotation at C3. The loads on the C5 anchors in flexion and left rotation and on the C7 anchors in extension were relatively high. The maximum load obtained in the present study was 14.9 N, which was one order of magnitude lower than the mean failure load of the suture anchors (131.7 N). CONCLUSION: Biomechanical laterality was demonstrated, reflecting the asymmetrical nature of open-door laminoplasty. The maximum load on the suture anchors was much lower than the failure load and was consistent with the stability of the suture anchors encountered in clinical cases. This may support the validity of using suture anchors in laminoplasty, although the loads during active motion may be higher than our results. LEVEL OF EVIDENCE: N/A.

Dimethylarsinous acid disturbs cytokinesis.

Dimethylarsinous acid (DMAIII) induced tetraploidy and multinucleation in V79 cells. While the highest yield of tetraploids and multinucleated cells was at 1.25 microM of DMAIII, the mitotic index was highest at DMAIII 2.5 microM due to mitotic arrest. Mitosis was not observed at 5 microM. We observed V79 cells treated with DMAIII and visualized with rhodamine-phalloidin. Abnormal actin location was observed in the dividing cells which were treated with DMAIII and visualized with rhodamine-phalloidin. These findings suggested strongly that DMAIII inhibits not only formation of the normal mitotic spindle but cytokinesis and induces the formation of multinuclear cells.

Toxicity of agricultural chemicals in Daphnia magna.

BACKGROUND: Daphnia magna is a useful aquatic organism for testing ecological toxicities of environmental pollutants. However, there were only a few studies on agricultural chemicals using these organisms. METHODS: We investigated acute and subchronic toxicities of 30 agricultural chemicals commonly used in Japan in D. magna. Acute toxicity of the agricultural chemicals was determined using the concentrations yielding 50% immobility of D. magna after 24 hr and 48 hr exposure as end points. D. magna was cultivated with the chemical and algae until the first brood production. Lethal toxicity and the number of survival broods were determined within 13 days. RESULTS: All insecticides among the agricultural chemicals exhibited the strongest acute toxicity (LC50 from 0.00053 to 0.037 mg/L). More than 50% of the herbicides and fungicides did not exhibit acute toxicity at 10 mg/L. Chlornitrofen, pencycuron, and fenitrothion showed significantly lower LC50 values at 8 days than at 24 hr and 48 hr. Isoprothiolane, flutolanil, and thiophanatemethyl significantly delayed the first brood at concentrations less than half of those for LC50 (8 days). Thiobencarb, iprodione, flutolanil, mepronil, and thiophanatemethyl significantly reduced the size of the first brood at concentrations less than half of those for LC50 (8 days). CONCLUSIONS: In this study, chlornitrofen, pencycuron, and fenitrothion were suggested to have slow-acting toxicity. Also, thiobencarb, iprodione, flutolanil, mepronil, and thiophanatemethyl were suggested to have parthenogenetic toxicity.

Osteoinduction with highly purified beta-tricalcium phosphate in dog dorsal muscles and the proliferation of osteoclasts before heterotopic bone formation.

The aim of the study was to examine the chronological histology of osteoinduction of highly purified beta-tricalcium phosphate (beta-TCP) implanted in dog dorsal muscles. Specimens were harvested on days 14, 28, 42, 56, 112 and 168 after implantation, and were analyzed by hematoxylin and eosin (HE) staining, tartrate-resistant acid phosphatase (TRAP) staining, immunohistochemistry, in situ hybridization, and silver impregnation. After day 28, abundant TRAP- and cathepsin K-positive multinucleated cells adhered to beta-TCP, suggesting that these cells are osteoclasts that can resorb beta-TCP. On day 56, new bone was formed and alpha1 chain of type I procollagen mRNA-positive osteoblasts lined the newly formed bone. Silver impregnation showed abundant collagen fibrils within the beta-TCP micropores. These results suggest that micropores function as a storage space for extracellular matrix components, including collagen. Newly formed bone never degenerated in the late stage, suggesting that beta-TCP has good biocompatibility and this material retains the conditions appropriate for osteointegration and bioresorption. In conclusion, beta-TCP has osteoinductivity after implantation in dog dorsal muscles without use of bone marrow cells or osteoinductive cytokines. The appearance of a large number of active osteoclasts precedes new bone formation.

Beta-2-glycoprotein I and urinary trypsin inhibitor levels in the plasma of pregnant and postpartum women.

Annexins (Anx) are a family of structurally related proteins that all bind to anionic phospholipids in a Ca(2+)-dependent manner. Some biological properties of beta-2-glycoprotein I (beta(2)-GPI) are similar to those of Anx IV and Anx V. Urinary trypsin inhibitor (UTI) helps to maintain normal pregnancy and prevent preterm delivery by inhibiting uterine contraction. However, plasma beta(2)-GPI and UTI levels have not been measured in normal pregnancy. The aim of this study is to clarify the levels of these parameters. Subjects were nonpregnant women (n=50), 120 pregnant women, and maternal subjects just after delivery (n=53) or postpartum (n=67). All of the subjects were healthy. Plasma levels of beta(2)-GPI, UTI, Anx IV, Anx V and other coagulation and fibrinolysis markers were measured by ELISA. The mean plasma level of beta(2)-GPI was significantly increased during the third trimester of pregnancy and 3 to 5 days after delivery. The mean plasma level of UTI was unchanged from the first trimester of pregnancy to the postpartum period. The mean plasma UTI level in vaginal delivery group was significantly higher than that in cesarean section group. beta(2)-GPI protein was expressed in some of the syncytiotrophoblasts. These data suggest that beta(2)-GPI might act to prevent blood clotting on the placental surfaces and also prevents disseminated intravascular coagulation in the microcirculation and maternal plasma. UTI levels might be kept constant by increased urinary excretion despite overproduction during pregnancy.

Safety assessment of paper and board food packaging: chemical analysis and genotoxicity of possible contaminants in packaging.

In order to identify potential genotoxicant(s) in recycled paperboard, samples were fractionated using multiple liquid/liquid extraction, and gel permeation chromatography, and analysed by gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry. The rec-assay was used as an indicator of genotoxicity. Genotoxicants in the recycled paperboard were identified as dehydroabietic acid (DHA) and abietic acid (AA). DHA and AA were detected in two out of five virgin products, and in all seven recycled products for food-contact use. Total amounts of DHA and AA were 240 and 990 microg/g in the virgin products and 200-990 microg/g in the recycled products. A good correlation was observed in the total amount of DHA and AA content determined in paper products and DNA-damaging activity. Moreover, genotoxic effects in paper products showed a good match with standard compounds, indicating that the genotoxic effects of these paper products was mostly attributable to DHA and AA.

Characterization of multidrug-resistance phenotypes and genotypes of Escherichia coli strains isolated from swine from an abattoir in Osaka, Japan.

A total of 455 highly tetracycline-resistant Escherichia coli strains were isolated from 84 healthy swine from abattoirs and it was found that 56.9, 43.1, 22.2, 15.4, 2.6 and 1.5% of strains were resistant to chloramphenicol, ampicillin, kanamycin, trimethoprim-sulphamethoxazole, ofloxacin and gentamicin respectively. Interestingly, E. coli strains isolated from certain finisher hog groups exhibited resistance against 2-7 antimicrobials, but strains isolated from multiparous sow groups in each herd were resistant to only 2-4 antimicrobial agents. When randomly selected 108 tetracycline-resistant isolates were tested for the presence of resistance genes, the following genes tet(A) (n = 6), tet(B) (n = 95), tet(D) (n = 1) or both tet(A) and tet(B) (n = 6) were found to be distributed among them. Furthermore, 52 isolates carried the integrase 1 gene and 24 strains gave five different PCR amplicon profiles using primers from the variable region of integron. Extensive nucleotide sequence analyses of these amplicons revealed the presence of dhfrI, dhfrXII, dfr17, aadA, aadA2, aadA5, aadA21, aacA4 and catB3 genes which code for different antibacterial resistance proteins.

TTV infection in children born to mothers infected with TTV but not with HBV, HCV, or HIV.

The TT virus (TTV) was isolated recently from the serum of a patient with post-transfusion hepatitis. TTV infection is widespread in the general population, and its prevalence increases continuously with age. The pathogenic role of TTV in liver disease remains controversial, and the source of transmission is still unclear. We investigated the pathogenicity and epidemiology of TTV infection in infants born to TTV DNA-positive mothers. Enrolled in this study were 22 mother-child pairs testing negative for antibodies to hepatitis B, hepatitis C, and the human immunodeficiency viruses (HIVs). The children were followed for 30 months after birth. Serum TTV DNA was detected by N22-PCR, and the PCR products were cloned and sequenced. The prevalence of TTV infection in children increased with age. Of the 22 children, 13 (59%) became positive for TTV DNA during the follow-up period. Of these 13 children, 6 (46%) had elevated levels of serum alanine aminotransferase (ALT), although the elevations were transient and mild. TTV viremia was not associated significantly with the abnormal ALT levels. Children with TTV viremia developed neither severe liver disease nor fulminant hepatitis. Phylogenetic analysis showed that, in 11 (85%) of the 13 pairs, the mother and child had the same genotype at the first PCR-positive time point. Among those 11 mother-child pairs, 6 (55%) had identical TTV nucleotide sequences. However, the genotype of predominant clones changed in 5 (50%) of 10 children who were positive for TTV DNA at two or more time points during the follow-up period. In conclusion, this study did not provide evidence that TTV infection is related to liver disease in children. Although the main source of TTV infection in children is presumed to be their mothers, transmitted via non-parenteral routes in the course of daily contact, intrafamilial carriers may also be sources of TTV infection.

Microbial metabolite of dimethylarsinic acid is highly toxic and genotoxic.

Dimethylarsinic acid [DMA, (CH(3))(2)AsO(OH)] causes cancer in the urinary bladder of rats. However, its mechanism of cancer or the ultimate carcinogenic form is not yet known. Rats administered dimethylarsinic acid excrete three unknown arsenic compounds (termed M-1, M-2, and M-3) in urine or feces, and these compounds are presumed to be produced by intestinal bacteria. Escherichia coli A3-6 isolated from a rat yielded two unknown arsenic compounds (M-2 and M-3) from dimethylarsinic acid and M-1 from trimethylarsine oxide (TMAO) in the presence of cysteine (Cys). Contents of M-2 and M-3 varied with cysteine concentration. The cytotoxicity and genotoxicity of the bacteria-free solution of dimethylarsinic acid or trimethylarsine oxide metabolized by E. coli A3-6 were studied using V79 cells. Dimethylarsinic acid (1 mM) metabolized by E. coli A3-6 in the presence of cysteine (1 mM) was highly cytotoxic (50% survival reduction concentration; 2.1 microM As) in V79 cells, and the toxic substance appeared to be M-2. The metabolite solution (at 2.5-10 microM total As) induced c-mitosis and tetraploids, and caused mitotic arrest, since it increased mitotic cells at the cytotoxic dose. The metabolite solution also significantly increased sister chromatid exchange (SCE) and chromosomal aberrations, most of which were chromatid gaps and chromatid breaks. A3-6 converted 96.1% of trimethylarsine oxide to M-1 in the presence of cysteine. This metabolite solution did not exhibit cytotoxicity or genotoxicity. The reported M-2 concentration in urine of rats administered levels of DMA via drinking water known to cause bladder tumors was sufficient to exhibit cytotoxic and genotoxic effects in urinary bladder. Thus, we hypothesize that intestinal bacteria play an important role in carcinogenicity of dimethylarsinic acid.

Understanding arsenic carcinogenicity by the use of animal models.

Although numerous epidemiological studies have indicated that human arsenic exposure is associated with increased incidences of bladder, liver, skin, and lung cancers, limited attempts have been made to understand mechanisms of carcinogenicity using animal models. Dimethylarsinic acid (DMA), an organic arsenic compound, is a major metabolite of ingested inorganic arsenics in mammals. Recent in vitro studies have proven DMA to be a potent clastogenic agent, capable of inducing DNA damage including double strand breaks and cross-link formation. In our attempts to clarify DMA carcinogenicity, we have recently shown carcinogenic effects of DMA and its related metabolites using various experimental protocols in rats and mice: (1) a multi-organ promotion bioassay in rats; (2) a two-stage promotion bioassay by DMA of rat urinary bladder and liver carcinogenesis; (3) a 2-year carcinogenicity test of DMA in rats; (4) studies on the effects of DMA on lung carcinogenesis in rats; (5) promotion of skin carcinogenesis by DMA in keratin (K6)/ornithine decarboxylase (ODC) transgenic mice; (6) carcinogenicity of DMA in p53(+/-) knockout and Mmh/8-OXOG-DNA glycolase (OGG1) mutant mice; (7) promoting effects of DMA and related organic arsenicals in rat liver; (8) promoting effects of DMA and related organic arsenicals in a rat multi-organ carcinogenesis test; and (9) 2-year carcinogenicity tests of monomethylarsonic acid (MMA) and trimethylarsine oxide (TMAO) in rats. The results revealed that the adverse effects of arsenic occurred either by promoting and initiating carcinogenesis. These data, as covered in the present review, suggest that several mechanisms may be involved in arsenic carcinogenesis.

Levels of annexin IV and V in the plasma of pregnant and postpartum women.

Annexin (Anx) V is pivotal in the maintenance of pregnancy by preventing the activation of blood coagulation. The homology of the amino acid sequence between Anx IV and Anx V is highest in Anx family proteins. However, little is known about the roles of Anx IV in pregnancy. The aim of this study is to clarify the roles of circulating Anx IV and Anx V in normal pregnancy. Subjects were non-pregnant women (n = 50), 120 pregnant women, and maternal subjects just after delivery (n = 53) or postpartum (n = 67). Anx IV in the plasma of non-pregnant women was at a concentration 20 times that of Anx V. The plasma levels of Anx IV suddenly increase after delivery, but Anx V levels remain low during this period. Anx IV and Anx V exert similar levels of anticoagulant activity. Anx IV protein was expressed on the basal surface of syncytiotrophoblasts; Anx V protein, on the apical surface of syncytiotrophoblasts. These results suggest that Anx IV enters the maternal bloodstream just after delivery and might play a role in preventing disseminated intravascular coagulopathy, and that Anx V helps to prevent clotting in the placenta during pregnancy.

Chemical analysis and genotoxicological safety assessment of paper and paperboard used for food packaging.

This study presents the research on the chemical analysis and genotoxicity of 28 virgin/recycled paper products in food-contact use. In the chemical analysis, paper products were extracted by reflux with ethanol, and analyzed by gas chromatography/mass spectrometry. 4,4'-bis(dimethylamino)benzophenone (Michler's ketone: MK), 4,4'-bis(diethylamino)benzophenone (DEAB), 4-(dimethylamino)benzophenone (DMAB) and bisphenol A (BPA) were found characteristically in recycled products. Seventy-five percent of the recycled paper products contained MK (1.7-12 microg/g), 67% contained DEAB (0.64-10 micro g/g), 33% contained DMAB (0.68-0.9 microg/g) and 67% contained BPA (0.19-26 microg/g). Although, BPA was also detected in virgin paper products, the detection levels in the recycled products were ten or more times higher than those in the virgin products. The genotoxicity of paper and paperboard extracts and compounds found in them were investigated by Rec-assay and comet assay. Of the 28 products tested by Rec-assay using Bacillus subtilis, 13 possessed DNA-damaging activity. More recycled than virgin products (75% against 25%) exhibited such activity, which, of the compounds, was observed in BPA, 1,2-benzisothiazoline-3-one (BIT), 2-(thiocyanomethylthio)benzothiazole, 2,4,5,6-tetrachloro-isophthalonitrile, 2,4,6-trichlorophenol (TCP), and pentachlorophenol. The critical toxicant in one virgin paper product was concluded to be BIT. Eight samples with DNA-damaging activity were also tested by comet assay using HL-60 cells; six induced comet cells significantly (five times or higher than the control) without a decrease of viable cells. TCP, BZ, DEAB, and BIT also caused a slight increase in comet cells. In conclusion, we showed that most recycled paper products contain chemicals such as MK, DEAB, DMAB, and BPA, and possess genotoxicity. However, the levels of the chemicals in the recycled products could not explain their genotoxic effects.

Determination of trivalent methylated arsenicals in rat urine by liquid chromatography-inductively coupled plasma mass spectrometry after solvent extraction.

A method for the determination of trivalent arsenicals in urine was examined. Trivalent arsenicals, extracted as complexes with diethylammonium diethyldithiocarbamate (DDDC) into carbon tetrachloride, were determined by liquid chromatography-inductively coupled plasma mass spectrometry (LC-ICP-MS). The trivalent methylated arsenicals monomethylarsonous acid (MMA(III)), dimethylarsinous acid (DMA(III)), and trimethylarsine (TMA) were detected in urine of rats that had received dimethylarsinic acid (DMA(V)) or monomethylarsonic acid (MMA(V)) at concentration of 200 microg ml(-1) in drinking water for 24 weeks. This method is the first to permit quantification of trivalent methylated arsenicals in urine without significant changes in concentration during storage or pretreatment.

Urinary sulfur-containing metabolite produced by intestinal bacteria following oral administration of dimethylarsinic acid to rats.

Our long-term oral administration of dimethylarsinic acid (DMAV) in rats revealed that three unidentified metabolites, M-1, M-2, and M-3, were detected in urine and feces. DMAV and trimethylarsine oxide (TMAO) were converted to M-2 and M-3 and M-1 by Escherichia coli strain A3-6 isolated from the ceca of DMAV-administered rats, respectively. In this study, we report on the mechanism of production and the chemical properties of these unknown metabolites. To investigate the pattern of conversion of DMAV or TMAO by A3-6 in the presence of cysteine (Cys), arsenic metabolites of DMAV or TMAO in medium after incubation with A3-6 and Cys were analyzed by liquid chromatography with inductively coupled plasma mass spectrometry (LC-ICP-MS). DMAV was reduced to dimethylarsinous acid (DMAIII) to form M-2 in the presence of Cys and A3-6, and M-2 was further converted to M-3. TMAO was rapidly converted to M-1 by A3-6. The cytotoxicity of the unidentified metabolites was investigated. M-2 was more cytotoxic than DMAV, M-1, and M-3 in V79 cells. The cytotoxicity of M-2 in HL-60 cells was decreased by the addition of superoxide dismutase, suggesting that the cytotoxicity of M-2 might be due to the production of reactive oxygen species. In addition, we examined the chemical properties of M-2 by LC-ICP-MS and LC-MS. M-2 was oxidized to DMAV by hydrogen peroxide, suggesting that M-2 may be a reduced form of DMAV. M-2 was consistent with the reactant of DMAV with metabisulfite-thiosulfate reagent but not DMAIII by analyses of LC-ICP-MS and LC-MS. The molecular weight of M-2 was 154, and M-2 was a sulfur-containing metabolite.