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PubMed2001

Regulation of virulence in Vibrio cholerae.

Vibrio cholerae causes the diarrheal disease cholera primarily because it expresses a colonization factor (toxin-coregulated pilus; TCP) and a potent toxin (cholera toxin; CT) within the human intestine. While the true environmental signals that induce CT and TCP expression within the intestine remain unknown, much progress has been made identifying the regulatory factors that modulate their expression. Transcriptional regulation of the genes encoding TCP and CT involves a cascade consisting of a number of regulatory factors located on recently acquired mobile genetic elements as well as others residing within the ancestral Vibrio genome. In vivo studies have revealed interesting differences between the regulation of TCP and CT expression in the laboratory and within the intestine.

Bacterial Outer Membrane Proteins↗

PubMed2004

Effects of autogenous bone graft impaction and tricalcium phosphate on anterior interbody fusion in the porcine lumbar spine.

Background Impaction grafting can be achieved inside the spinal fusion cages, but its effect on bone graft incorporation and spinal fusion has not been studied. Animals and methods We investigated the effect of impaction grafting on the bone graft healing and fusion potential of beta-tricalcium phosphate (beta-TCP) inside the carbon fiber reinforced spinal fusion device (Brantigan cage) in 10 Danish landrace pigs. Lumbar spine interbody fusion of L2/3, L4/5 and L6/7 using carbon fiber cages was performed on each pig. Cages filled with either loosely-packed autologous iliac bone graft, rod-impacted autologous bone graft or beta-TCP were randomly distributed to the three fusion levels. Half of the animals were followed for 8 weeks, and the other half for 16 weeks. Results Radiographs and CT evaluations showed that autograft levels had significantly better results than beta-TCP levels (p<0.001 Fisher's Exact Test). However, the difference between impacted and loosely-packed levels was not significant. Histomorphometric analysis showed no difference between the loosely-packed and impacted cages with regard to bone volume, bone marrow volume, cartilage and fibrous tissue volume, while both of the autograft levels differed from the beta-TCP levels in all of the aforementioned parameters. Fluorochrome studies demonstrated that bone mineral apposition rate was significantly higher in the impacted cages than in the loosely-packed cages at 16 weeks. Interpretation Manual impaction of autologous bone graft into the carbon fiber cages resulted in a faster mineral apposition rate by 16 weeks. Bone ingrowth and spinal fusion were not influenced by impaction grafting.

Animals↗

PubMed2004

Comparison of the effects of two different types of calcium supplementation on markers of bone metabolism in a postmenopausal osteopenic population with low calcium intake: a double-blind placebo-controlled trial.

OBJECTIVE: To investigate calcium supplements in postmenopausal women. Calcium supplements in postmenopausal women with a low calcium intake have been shown to prevent osteoporotic vertebral fracture, but calcium is variably absorbed and often poorly tolerated, which may limit effectiveness. METHODS: The study compared the efficacy and tolerability of 500 mg/day of calcium in the form of ossein-hydroxyapatite (OHC) versus 500 mg/day of tricalcium phosphate (TCP) and placebo in the prevention of postmenopausal bone loss. This was a prospective randomized study enrolling 153 postmenopausal osteopenic women. Serum and urine markers of bone turnover were collected at 3 and 6 months. Bone density measurement was performed at baseline and 6 months in all participants, and at 12 months in women taking OHC. RESULTS: At 3 and 6 months, both TCP and OHC decreased serum markers of bone formation significantly, compared with placebo. At 6 months, TCP and OHC decreased osteocalcin by 9.9% and 12.3%, respectively; the aminoterminal propeptide of type I procollagen (PINP) was decreased by 5.3% and 6.3%, respectively; bone-specific alkaline phosphatase was decreased by 4.3% and 6.7%, respectively, compared with baseline. The effects on bone resorption markers or on bone mineral density did not reach statistical significance, although OHC increased bone density by 0.8% at the spine at 12 months. Both forms of calcium were well tolerated and did not differ from placebo in terms of side-effects. CONCLUSIONS: While both OHC and TCP were well tolerated and significantly reduced bone turnover markers, the effect of ossein-hydroxyapatite seems slightly superior to that of tricalcium phosphate.

Aged↗

PubMed2004

Effectiveness of personal protective equipment: relevance of dermal and inhalation exposure to chlorpyrifos among pest control operators.

This study assessed the effectiveness of a custom fit personal protective equipment (PPE) program aimed at reducing occupational exposure to pesticides. The intervention study was carried out on 15 pest control operators (PCOs) during mixing/loading and application of chlorpyrifos. Each worker was measured twice; first while the worker used PPE as normal (baseline measurement), and second after making some adjustments to the PPE (postintervention measurement). The applied intervention consisted of a tight-fitting, full-face respirator, fit-testing, long gloves, chemical-proof boots, a Tyvek hood, and an instruction video that was shown prior to putting on the PPE. A comprehensive evaluation program was used for the within-subject comparisons, including assessment of potential dermal exposure, actual dermal exposure, inhalation exposure, and internal dose as measured by the urinary metabolite 3,5,6-trichloro-2-pyridinol (TCP). The PPE program resulted in a significant increase in fit factors from a mean of 670 to 132,000. Actual dermal exposure levels decreased on average by fourfold after implementation of the PPE program (baseline AM = 132.1 microg; postintervention AM = 32.6 microg). The TCP levels in urine collected 24-32 hours after spray activities were lower in the postintervention data set (AM = 21.2 microg TCP/g creatinine vs. AM = 13.9 microg TCP/g creatinine). However, it is impossible to attribute these differences totally to the PPE program since workers had significant and varying urinary TCP levels before onset of spraying activities. Linear regression models showed that dermal exposure was only a predictive parameter for TCP levels in urine in the baseline data set. Although the results should be interpreted cautiously this study suggests a protective effect of the evaluated PPE program.

Administration, Cutaneous↗

PubMed1996

Microdosimetry and radiocurability: modelling targeted therapy with beta-emitters.

Tumour control probability (TCP) is a more relevant quantity than the dose distribution in the target volume for estimating the likely efficacy of any type of radiation therapy, be it external beam or targeted using radionuclides. This paper concentrates on a TCP modelling study, for tumour spheres of different radii assuming a uniform uptake of six different beta emitters (ranging from 67Cu to 90Y or 0.58 to 2.3 MeV in endpoint energy). The dose at varying radii, expressed as a fraction of the equilibrium dose, D beta (R)/Deq, was computed by numerical integration of the point-dose kernel over the sphere volume, and shows clearly the effect of electron disequilibrium for small radii and also at the edges of the spheres. These D beta(R)/Deq were converted into volume-dose distribution V(D) and thence into clonogenic cell numbers, n(D), from which the TCPs for spheres of different radii were computed, for different cumulated activities per unit mass, in megabecquerel hours per gram assuming a clonogenic cell density of 10(8) cm-3 and a tumour-cell radiosensitivity alpha of 1.0 Gy-1. Using V(D) rather than simply the mean dose decreases the TCP at both large and small tumour radii for a given number of megabecquerel hour per gram. Curves of iso-TCP go through a shallow minimum in megabecquerel hour per gram at a tumour radius approximately equal to the maximum beta-particle range. The fall in dose at small radii outweighs the reduction in cell number, making it improbable that micrometastases can be eliminated solely by beta-emitters targeted to the tumour cells. An explicit comparison with external-beam therapy for a fixed number of tumour cells divided into different numbers of spheres further emphasizes the difficulties caused by small tumours in beta-particle targeted therapy. Alternative strategies to overcome these limitations are briefly discussed.

Beta Particles↗

PubMed2004

Prostate implant evaluation using tumour control probability--the effect of input parameters.

In this paper, we examine the effect of treatment parameters in a model used to evaluate permanent prostate implants. The model considers the prostate to be composed of 12 sub-sections, each sub-section is assigned a cell density based on the probability of finding cancer foci in that sub-section. Wasted dose as a result of the dose rate from the implant falling below a level adequate to counteract repopulation was found to vary by 2-16% over the range of radiosensitivity and repopulation rates considered. Within the model, applied to five dose distributions, the uncertainty in the tumour control probability (TCP) values calculated for each sub-section as a result of differences in the model parameters, was found to be less than 12% in most cases for the good quality implants. The difference in TCP values was much larger for the poor quality implant. Substituting a heterogeneous distribution of alpha for a single mean value resulted in generally lower TCP values though introducing a cutoff value with a Gaussian distribution had a profound effect on the calculated values. Despite uncertainties in the parameters, the model was able to identify sub-sections at risk of local recurrence but as a result of these uncertainties, the TCP values can only be considered in the relative rather than absolute sense.

Brachytherapy↗

PubMedDate not supplied

Human adipose-derived adult stem cells produce osteoid in vivo.

Adult subcutaneous fat tissue is an abundant source of multipotent cells. Previous studies from our laboratory have shown that, in vitro, adipose-derived adult stem (ADAS) cells express bone marker proteins including alkaline phosphatase, type I collagen, osteopontin, and osteocalcin and produce a mineralized matrix as shown by alizarin red staining. In the current study, the ADAS cell ability to form osteoid in vivo was determined. ADAS cells were isolated from liposuction waste of three individual donors and expanded in vitro before implantation. Equal numbers of cells (3 x 10(6)) were loaded onto either hydroxyapatite/tricalcium phosphate (HA-TCP) cubes or the collagen/HA-TCP composite matrix, Collagraft, and then implanted subcutaneously into SCID mice. After 6 weeks, implants were removed, fixed, and demineralized and sectioned for hematoxylin and eosin staining. Osteoid formation was observed in 80% of HA-TCP implants loaded with ADAS cells. Only 20% of Collagraft implants were positive for the presence of osteoid matrix. Whereas 100% of HA-TCP implants loaded with hFOB 1.19 cells formed osteoid, Collagraft loaded with hFOB 1.19 cells displayed a high degree of adipose tissue within the matrix. Immunostaining of serial sections for human nuclear antigen demonstrated that the osteoid contained human cells. Osteoid formation was not observed in control HA-TCP or Collagraft matrices implanted without cells. In summary, the data demonstrate the ability of ADAS cells to form osteoid matrix in vivo. Because of their abundance and accessibility, ADAS cells may prove to be a novel cell therapeutic for bone repair and regeneration.

Adipose Tissue↗

PubMed2003

Radioprotective and antitumor activity evaluation of newly synthesized adamantyl tenocyclidines.

Several adamantyl derivatives of thienyl phencyclidine (tenocyclidine; TCP) were newly sythesized and characterized: adamantyl derivatives containing piperidine (TAPIP), pyrrolidine (TAPYR), and morpholine (TAMORPH) groups. Their biological activity was evaluated by in vitro testing of their effect on the proliferative and reproductive ability (cytotoxicity) of a human tumor cell strain and nonmalignant mouse fibroblasts in culture. We also tested them for their radioprotective effect after ionizing irradiation, and as anticancer agents on the same human tumor cell strain. Compared with TCP, adamantyl derivatives are less toxic and have outstanding radioprotective properties. These derivatives (especially TAMORPH) increase apoptotic death of human malignant cells. The radiation-modifying effect studied on C3Hf mice in vivo showed that the adamantyl derivatives of TCP have a more enhanced radioprotective effect and that they are less toxic than TCP itself. The present data are discussed and compared with those previously reported for structurally related phencyclidine derivatives.

Animals↗

PubMedDate not supplied

Intramuscular bone induction by the simultaneous administration of recombinant human bone morphogenetic protein 2 and bisphosphonate for autobone graft.

An ideal substitute for bone graft is autobone tissue, of which there is an ample supply of the required form and with vascularity. Our strategy is to generate intramuscular autogenous bone by administering recombinant human bone morphogenetic protein 2 (rhBMP-2) with beta-tricalcium phosphate (beta-TCP) as a carrier, and to transplant this bone as a muscle-pedicled autograft. However, in a previous study (Jingushi et al., J. Orthop. Sci. 7, 490, 2002), bone resorption occurred early after bone induction. This study was conducted to determine whether rhBMP-2-induced bone tissue could be maintained by simultaneous administration of bisphosphonate, and to investigate whether the induced bone could be used for bone grafting. In this study, we first applied rhBMP-2 alone to a beta-TCP disk and inoculated it into rat quadriceps muscle. Bone area and the number of tartrate-resistant acid phosphatase (TRAP)-positive cells in the induced bone disk peaked at 2 weeks, and induced bone resorption occurred later. Bisphosphonate and rhBMP-2 were then simultaneously applied to a beta-TCP disk and inoculated as in the first experiment. The addition of bisphosphonate decreased the number of TRAP-positive cells and increased the bone area and compression strength at 4 weeks. In the last experiment, a rhBMP-2 applied beta-TCP disk treated with or without bisphosphonate was free-grafted to parietal bone 4 weeks after inoculation. Both bone disks united similarly. We concluded that the concurrent use of bisphosphonate prevented bone absorption attributed to osteoclast activity after bone induction by rhBMP-2. The bisphosphonate application did not disturb the union of induced bone to host bone.

Animals↗

PubMed2006

Absorption of calcium from milks enriched with fructo-oligosaccharides, caseinophosphopeptides, tricalcium phosphate, and milk solids.

BACKGROUND: Adequate intakes of calcium are required for optimal bone health and protection against chronic disease. Dairy products are an excellent source of calcium. OBJECTIVE: The absorption of calcium from a range of fortified milks was measured in humans with the use of stable isotopes. DESIGN: Fifteen volunteers participated in a randomized, controlled, double-blind crossover study. Five types of semi-skimmed (1.9% fat) milk drinks were administered with a light breakfast: standard milk (control milk); milk enriched with calcium from milk solids and tricalcium phosphate [(TCP) MSS milk]; milk enriched with calcium from concentrated milk (CON milk); milk with added fructo-oligosaccharides [(FOSs) FOS milk]; and milk with added caseinophosphopeptides [(CPPs) CPP milk]. All the milks were labeled with 42Ca as CaCl2. The MSS milk was also labeled with 44Ca as TCP. The quantity of calcium in each drink was kept the same by varying the volume given. RESULTS: Calcium absorption did not differ significantly between the control milk and the calcium-fortified milks (MSS and CON milk) or the FOS and CPP milks. However, calcium absorption from the TCP added to the MSS milk was significantly higher than that from the control milk (27.5 +/- 7.6% and 24.5 +/- 7.3%, respectively; P = 0.003). CONCLUSIONS: Calcium-enriched milks are a valuable source of well-absorbed calcium. Absorption of added calcium as TCP was higher than that of calcium from the control milk, but the addition of FOSs or CPPs did not significantly increase calcium absorption. Further research is needed to ascertain the cost-effectiveness and public health benefits of consuming fortified milks.

Adult↗

PubMed1999

Effects of microbial phytase supplementation on egg production, eggshell quality, and mineral retention of laying hens fed different levels of phosphorus.

A 20-wk feeding trial (21 to 40 wk of age) was conducted to evaluate the effects of phytase supplementation on egg production, egg quality, nutrient retention, and P excretion of laying hens fed diets containing different levels of P. Nine hundred and sixty ISA Brown hens were randomly allocated to completely randomized block arrangement of four diets: corn-soybean diet (1.4% tricalcium phosphate, TCP) without (T1, control) and with phytase (T2); 0.7% TCP (T3) or 0% TCP (T4) diet with phytase. Dietary microbial phytase was added at a level of 500 U/kg. Both hen-day and hen-housed egg production of T2 were significantly (P < 0.05) higher than other treatments, which were not different among themselves. Egg weights were also significantly (P < 0.05) different among treatments ,with T2 being the highest. Feed consumption of T2 was significantly (P < 0.05) higher than other treatments but feed conversion ratio was not significantly different from others. Specific gravity and shell thickness of the eggs were highest in the control (T1) but eggshell strength and broken egg to total egg ratio were not different among treatments. Haugh units were not different among treatments. Retention of Ca, P, Mg, Fe, and Zn were greater (P < 0.05) in phytase-supplemented groups. There were significant (P < 0.05) differences in excretion of ash, P, and Zn. The excretion of these components were highest in the control, whereas P excretion was significantly lower in the T3 and T4 groups. In conclusion, supplementation of the microbial phytase to normal corn-soybean diet improved egg production and can reduce TCP level in the diet without affecting egg production and egg quality. Significant reduction of P excretion can be also achieved.

6-Phytase↗

PubMed1998

Effects of nitric oxide modulation on tumour blood flow and microvascular permeability in C6 glioma.

C6 glioma strongly express nitric oxide synthase. Rats bearing C6 tumours were pre-treated with i.v. Ng-nitro-L-arginine methyl ester (L-NAME), 3-morpholinosydnonimine (SIN-1) or saline before local cerebral blood flow (LCBF) or tumour capillary permeability (TCP) was measured by the [14C]iodoantipyrine autoradiographic or [14C]alpha-amino-isobutyric acid techniques. L-NAME and SIN-1 caused significant TBF alterations (-44% and +136%, respectively) with less marked (-15% and +33%) alterations in normal brain. Calculated cerebrovascular resistance changes within tumour were indeed selective. Baseline TCP was increased compared with normal brain (20-fold). L-NAME and SIN-1 administration did not alter TCP. These effects have significant implications for human malignant glioma management. Selective i.v. manipulation of LCBF, without significant changes in TCP, could increase the efficacy of chemotherapy, radiotherapy or provide better peritumoural oedema control.

Animals↗

PubMed1993

Solubility of calcium salts and carrageenan used in infant formulas did not influence calcium absorption in rats.

Calcium absorption from tricalcium phosphate (TCP) was compared to that from calcium chloride, CaCl2, in the presence and absence of carrageenan in the rat model. There was no difference in percent calcium absorption as indicated by femur uptake of TCP or CaCl2 intrinsically labeled with 45Ca given by gavage (78.4 +/- 9.6 vs. 80.0 +/- 5.9, respectively). Thus, the difference in solubility of the two salts did not influence calcium absorption. When TCP was delivered by gavage in a solution containing 1% carrageenan, calcium absorption was not decreased compared to that of a control without carrageenan. In this model, calcium from TCP in the presence of up to 1% carrageenan is well absorbed.

Animals↗

PubMed1999

Case-matching methodology as an adjunct to trauma performance improvement for evaluating lengths of stay and complications.

OBJECTIVE: To apply case-matching methodology to a statewide trauma registry to identify for peer review one trauma center's patients with "unexpected" survival deaths, complications or prolonged length of stay in hospital (H-LOS) or in Intensive Care Unit (ICU-LOS). METHODS: Matching patients were defined by mechanism of injury, age, physiology and intubation status on emergency department admission, preexisting conditions, and the pattern and severity of anatomic injury. Matches for one trauma center's 1997 patients (TCP) were sought from other centers' patients (SWP) submitted to the statewide registry from October 1, 1993, though December 31, 1997. A minimum of 20 SWP matches was required for creating a matching group. TCP were compared with matching SWP for survival, H-LOS, and ICU-LOS and the occurrence of complications. Unexpected survivors and deaths identified by matching (by using the standard 50% cutpoint) were also evaluated by TRISS and the American College of Surgeon's Committee on Trauma. A patient whose complications occurred in less than 10% of matching patients or whose H-LOS or ICU-LOS exceeded the 90th percentile of its matching SWP were also designated for peer review. RESULTS: The potential matching pool included 69,660 SWP. At least one SWP match was found for 565 (92.9%) of the 608 TCPs. The average, median, and maximum number of matches were 917.6, 235, and 6,504 patients, respectively. The 451 patients with 20 or more SWP matches were further studied. Case matching and TRISS agreed on the identification of five unexpected deaths; the American College of Surgeon's Committee on Trauma agreed on four of five. Peer review included, however, that none of the deaths were clinically unexpected. Case matching identified 14 TCP with 29 complications; only 4 of those patients had undergone concurrent peer review. Retrospective review revealed two preventable and potentially seven preventable complications. There were 35 TCP patients with prolonged H-LOS and 24 with prolonged ICU-LOS. Peer review of those cases identified that complications and problems related to discharge planning contributed to the prolonged ICU-LOS (20.8% and 25.0%) and the H-LOS (20.% and 48.6%), respectively. CONCLUSION: Peer review of patients identified by case-matching methodology uncovered opportunities for system improvement that were missed by the concurrent performance improvement process. This method may also allow identification of anticipated H-LOS and ICU-LOS to promote earlier discharge.

Adolescent↗

PubMed1994

Risk of pancreatic carcinoma in tropical calcifying pancreatitis: an epidemiologic study.

To assess the risk of pancreatic cancer in subjects with tropical calcifying pancreatitis (TCP), we have followed 185 patients with TCP from the Diabetes Research Center in Madras, India for an average of 4.5 years. The diagnosis of TCP was based upon long-standing epigastric pain, laboratory tests, presence of pancreatic calculi, endoscopic retrograde cholangiopancreatography (ERCP) findings, and ultrasonography. During the follow-up period, 24 patients died from all causes, with 6 deaths (25%) from cancer of the pancreas. Three pancreatic cancers were biopsy positive. Average age at onset of pancreatic cancer was 45.6 +/- 7.3 years--considerably younger than for Western populations. When compared with the background pancreatic cancer rate, subjects with TCP appear to have a significantly increased risk of pancreatic cancer: relative risk = 100, 95% CI = 37-218. Even under the most stringent assumptions (restricting the analysis to biopsy-proven cases, assuming that the true background rate of pancreatic cancer in Madras resembles high-risk Western populations, assuming that tropical pancreatitis begins at birth) the risk is still elevated: relative risk = 5, 95% CI = 1.03-3-14.6. The exact mechanism linking various forms of pancreatitis to pancreatic cancer remains to be elucidated.

Adult↗

PubMed1999

Posterolateral lumbar intertransverse process spine arthrodesis with recombinant human bone morphogenetic protein 2/hydroxyapatite-tricalcium phosphate after laminectomy in the nonhuman primate.

STUDY DESIGN: A nonhuman primate lumbar intertransverse process arthrodesis model was used to evaluate recombinant human bone morphogenetic protein 2 (rhBMP-2) in a hydroxyapatite-tricalcium phosphate (HA-TCP) carrier as a complete bone graft substitute. OBJECTIVES: To assess the ability of a ceramic material to serve as a carrier for various doses of rhBMP-2 as a bone graft substitute in a primate model of posterolateral intertransverse process spinal fusion after laminectomy. SUMMARY OF BACKGROUND DATA: The reported non-union rates for posterolateral lumbar spine fusion with autogenous iliac crest bone range from 5-35%. Recombinant human bone morphogenetic protein 2 has shown potential to serve as a bone graft substitute for posterolateral intertransverse process spine fusion. Although a resorbable collagen sponge was a suitable carrier in rabbits and dogs, it was too compressible for the paraspinal muscles in rhesus monkeys. This failure of the collagen carrier has prompted evaluation of the feasibility of an alternative carrier material and the required dose of rhBMP-2. METHODS: Twenty-one adult rhesus monkeys underwent a laminectomy at L4-L5 followed by bilateral intertransverse process arthrodesis via the same midline incision (n = 16) or a minimally invasive video-assisted posterolateral approach (n = 5). Bone graft implants on each side consisted of either 5 cm3 of autogenous iliac crest bone or 60:40 HA-TCP blocks (1.2 x 0.5 x 3.7 cm) loaded with a solution containing 0, 6, 9, or 12 mg of rhBMP-2 per side. The monkeys were killed 24 weeks after surgery. Inspection, manual palpation, radiography, and histology were used to assess fusion and to detect any bony growth into the laminectomy defect. RESULTS: Fusion was not achieved in any of the monkeys treated with autogenous iliac crest bone graft. Both of the monkeys treated with the HA-TCP blocks with 0 mg rhBMP-2 achieved fusion. All 15 monkeys treated with the HA-TCP blocks and either of the three doses of rhBMP-2 achieved solid fusion. Two animals had extension of the fusion on one side because of malpositioned ceramic block. The results in animals fused via the minimally invasive video-assisted technique were the same as inthose fused with the open technique. Histologic analysis showed some ingrowth of bone into the ends but not-through the ceramic block in the absence of rhBMP-2. When the ceramic blocks were loaded with rhBMP-2 there was a dose-dependent increase in the amount and quality of bone throughout the ceramic carrier based on qualitative assessment. No significant bone encroachment on the exposed thecal sac through the laminectomy defect was observed in any of the monkeys. CONCLUSION: Hydroxyapatite-tricalcium phosphate proved to be a suitable carrier for rhBMP-2 in the posterolateral spine fusion model in rhesus monkeys. Even in the presence of a laminectomy defect, there was no evidence of bone induction outside the confines of the ceramic carrier.

Animals↗

PubMed2006

Osteopromotion by a beta-tricalcium phosphate/bone marrow hybrid implant for use in spine surgery.

STUDY DESIGN: Experimental animal study. OBJECTIVE.: Evaluate osteopromotive properties of a beta-tricalcium phosphate (TCP) implant with different osteogenic substances in an animal study. SUMMARY OF BACKGROUND DATA: Current research in spine surgery is focusing on resorbable bone implants because of the high morbidity after iliac crest graft harvesting. Therefore, several osteoconductive scaffolds are combined with osteoinductive substances. METHODS: In 14 sheep, a critical size defect was performed on both tibiae. The sheep were randomized into 3 groups (4 sheep each) and a control group (2 sheep). In the treatment groups, the defects were filled with the beta-TCP scaffold impregnated with either venous blood, bone marrow from sternal aspiration, or a concentrated mononuclear cell suspension derived from sternal bone marrow aspiration. The sheep in each group were euthanized 6 and 12 weeks after the operation; the investigation included quantitative computerized tomography and histology. RESULTS: The best bone formation occurred in the bone marrow group after 6 and 12 weeks, whereas no difference was found between the cell and venous blood groups. Only the bone marrow group showed bone formation inside the scaffold after 6 weeks. We conclude that a beta-TCP scaffold filled with bone marrow aspiration creates a biologic resorbable bone substitute with high osteopromoting capacity. Surprisingly, no better bone formation occurred in the concentrated cells group, which may be a result of technical reasons and needs to be further evaluated. CONCLUSIONS: The combination of beta-TCP and bone marrow has superior osteopromotive properties to venous blood or concentrated mononuclear cells and can be used effectively as a substitute to iliac crest graft.

Animals↗

PubMed2002

Evolutionary and functional analyses of variants of the toxin-coregulated pilus protein TcpA from toxigenic Vibrio cholerae non-O1/non-O139 serogroup isolates.

The toxin-coregulated pilus (TCP) is a critical determinant of the pathogenicity of Vibrio cholerae. This bundle-forming pilus is an essential intestinal colonization factor and also serves as a receptor for CTXphi, the filamentous phage that encodes cholera toxin (CT). TCP is a polymer of repeating subunits of the major pilin protein TcpA and tcpA is found within the Vibrio pathogenicity island (VPI). In this study genetic variation at the tcpA locus in toxigenic isolates of V. cholerae was investigated and three novel TcpA sequences from V. cholerae strains V46, V52 and V54, belonging to serogroups O141, O37 and O8, respectively, were identified. These novel tcpA alleles grouped into three distinct clonal lineages. The polymorphisms in TcpA were predominantly located in the carboxyl region of TcpA in surface-exposed regions of TCP fibres. Comparison of the genetic diversity among V. cholerae isolates at the tcpA locus with that of aldA, another locus within the VPI, and mdh, a chromosomal locus, revealed that tcpA sequences are far more diverse than these other loci. Most likely, this diversity is a reflection of diversifying selection in adaptation to the host immune response or to CTXphi susceptibility. An assessment of the functional properties of the variant tcpA sequences in the non-O1 V. cholerae strains was carried out by analysing whether these strains could be infected by CTXphi and colonize the suckling mouse. Similar to El Tor strains of V. cholerae O1, in vitro CTXphi infection of these strains required the exogenous expression of toxT, suggesting that in these strains ToxT regulates TCP expression and that these TcpA variants can serve as CTXphi receptors. All the V. cholerae non-O1 serogroup isolates tested were capable of colonizing the suckling mouse small intestine, suggesting that the different TcpA variants could function as colonization factors.

Alleles↗