bluuebunny/crossref_metadata_2025 huggingface dataset:
Ninety percent success in palatal implants loaded 1 week after placement: a clinical evaluation by resonance frequency analysis
Authors: Crismani Adriano Giacomo , Bernhart Thomas , Schwarz Kerstin , Čelar Aleš Gaetano , Bantleon Hans‐Peter , Watzek Georg
Published: June 2006

Purpose: To investigate the behaviour of early loaded palatal implants when observed with resonance frequency analysis (RFA).

Subject, material and methods: Twenty patients (seven males and 13 females, mean age 26.4 years) received one palatal implant each (length: 4 mm, diameter: 3.3 mm; Orthosystem®) for maximum orthodontic anchorage. The implants' stability was observed by RFA. Measurements were carried out at the time of surgery, after first orthodontic loading and subsequently once a week over a period of 12 weeks.

Results: Two palatal implants were lost. The other 18 remained stable. The average period from insertion to first loading was 6.7±0.8 days. The mean orthodontic force applied was 272.2±73.2 cN. The implant stability quotient (ISQ) value at the time of surgery averaged 69.4±3.9. The mean ISQ value 6.7 days after insertion was 69.8±3.6. Twelve weeks post‐surgery the mean ISQ value was 69.8±3.5. A statistically significant decrease in stability was observed after 2 and 3 weeks post‐surgery (P=0.005 and 0.04).

Conclusion: The behaviour of early loaded palatal implants showed an initial decrease of the ISQ values. From 6 weeks post‐surgery onward the ISQ values increased. Within the limitations of this study, the results suggest that the healing time of palatal implants reported in the literature (12 weeks) should be discussed. An orthodontic loading of palatal implants 6 weeks post‐surgery with a force up to 400 cN seems to be justified. Yet further investigations are necessary to evaluate the behaviour of early loaded palatal implants considering observation periods of over 12 weeks.
Vertical distraction osteogenesis in the human mandible: a prospective morphometric study
Authors: Amir Lisa R. , Becking Alfred G. , Jovanovic Andreas , Perdijk Frits B. T. , Everts Vincent , Bronckers Antonius L. J. J.
Published: June 2006

Abstract: Vertical distraction osteogenesis has received considerable interest as a way to augment bone prior to implant placement. However, very little is known regarding the appropriate distraction protocols in the human mandible. In this study, we evaluate the effect of the distraction rate and the duration of neutrofixation on bone formation and closure of the gap in the human mandible. Vertical distraction was performed in the atrophic mandible of 16 edentulous patients, aged 62 ± 6 years. The bone was distracted for approximately 10 mm at a rate of either 0.5 or 1 mm/day. Bone biopsies were taken after 7–20 weeks of neutrofixation. Histological analysis demonstrated newly formed bone in the distraction gap in all biopsies. The bone was predominantly of the woven type. After 10 weeks of neutrofixation, the gap was bridged by new bone in two out of three intact samples in the 0.5 mm/day group, but not in two intact samples of the 1 mm/day group. Histomorphometry revealed longer bone trabeculae (P=0.02) and a somewhat increased bone volume in the area where new bone formation started (P=0.07) in the group of patients having the 0.5 mm/day of distraction rate than in the 1 mm/day group. We conclude that in elderly patients, a distraction rate of 0.5 mm/day results in faster osteogenesis in the distraction gap than a rate of 1 mm/day. A minimum of 10 weeks of neutrofixation seems to be needed to close a 10 mm gap after cessation of distraction.
Peri‐implant soft‐tissue health surrounding cement‐ and screw‐retained implant restorations: a multi‐center, 3‐year prospective study
Authors: Weber Hans P. , Kim David M. , Ng Mavis W. , Hwang Jae W. , Fiorellini Joseph P.
Published: June 2006

Objective: The purpose of this prospective clinical study was to evaluate peri‐implant soft‐tissue conditions and esthetic fulfillment during a 3‐year follow‐up period following prosthetic rehabilitation.

Material and methods: As part of a prospective multi‐center study, 152 ITI dental implants were placed in 80 patients in the maxillary anterior region. Fifty‐nine crowns (38.82%) were cement retained, while 93 (61.18%) crowns were screw retained. At loading and 3, 6, 12 and 36 months post‐loading, modified plaque index (MPI), sulcus bleeding index (SBI), keratinized mucosa (KM), gingival level (GL), and esthetic fulfillment were recorded.

Results: All patients completed the study and no complications were reported. While statistically not significant at all time points, cement‐retained crowns seemed to present a worsening trend in MPI and SBI scores. Interestingly, screw‐retained crowns seemed to present an opposite picture, their MPI and SBI scores improved over time. While plaque accumulation, prophylaxis and depth of crown margin significantly affected levels of sulcus bleeding, prophylaxis alone played a key role in reducing plaque accumulation. No soft tissue recession was observed in either cement‐ or screw‐retained crowns up to 3 years post‐loading. Esthetic fulfillment survey revealed that patients did not have a preference for crown types; however, dentists favored cement‐retained over screw‐retained crowns.

Conclusions: Peri‐implant soft tissues responded more favorably to screw‐retained crowns when compared with cement‐retained crowns. However, no soft‐tissue recession was observed in either type of crowns. Cement‐retained crowns were preferred by dentists, while patients were equally satisfied with either type of crowns they received.
Biodegradable polylactide membranes for bone defect coverage: biocompatibility testing, radiological and histological evaluation in a sheep model
Authors: Schmidmaier Gerhard , Baehr Karen , Mohr Svenja , Kretschmar Martin , Beck Stefan , Wildemann Britt
Published: June 2006

Abstract: Large bony defects often show a delayed healing and have an increasing risk of infection. Several materials are used for the coverage of large defects. These materials must be biocompatible, easy to use, and must have an appropriate stability to present a mechanical hindrance. Aim of this study was to investigate two different biodegradable membranes for defect coverage in a sheep model. Round cranial defects (1.5 cm diameter) were created in sheep. Six different treatments were investigated: defects without membrane, defects covered with a poly(d,l‐lactide) or with a 70/30 poly(l/d,l‐lactide) membrane and all defects with or without spongiosa filling. The sheep were sacrificed 12 or 24 weeks postoperatively. Bone formation in the defects was quantified by computer‐assisted measurements of the area of the residual defect on CT radiographs. Histomorphometry and host‐tissue response were evaluated by light microscopy. The biocompatibility was investigated by analyzing the amount of osteoclasts and foreign body cells. Both membranes served as a mechanical hindrance to prevent the prolapse of soft tissue into the defect. The biocompatibility test revealed no differences in the amount and distribution of osteoclasts at the two investigated time points and between the investigated groups. No negative effect on the tissue regeneration was detectable between the investigated groups related to the type of membrane, but a foreign body reaction around the two membrane types was observed. In the membrane‐covered defects, the spongiosa showed a progressing remodeling to the native bony structure of the cranium. The groups without spongiosa partly revealed new bone formation, without complete bridging in any group or at any time point. Comparing the 12 and 24 weeks groups, an increased bone formation was detectable at the later time point. In conclusion, the results of the present in vivo study reveal a good biocompatibility and prevention of soft tissue prolapse of the two used membranes without differences between the membranes. An enhanced remodeling of the spongiosa into native bony structures under the membranes was detectable, but no osteopromoting effect was observed due to the membranes.
Does rotational strain at screw tightening affect the attainment or maintenance of osseointegration?
Authors: Moriya Katsunori , Maruo Yukinori , Minagi Shogo
Published: June 2006

Objectives: This study investigated whether rotational strain affects osseointegration.

Material and Methods: A total of 135 male rats were divided into five groups: 2‐w rotation, 4‐w rotation, 8‐w rotation, 12‐w rotation and control. Two hundred and seventy implants were inserted in rat tibia. The control group received no strain, while the 2‐w, 4‐w, 8‐w and 12‐w rotation groups received rotational strain at 2, 4, 8 and 12 weeks after implant placement, respectively. Removal torque (N cm) was measured in vivo. Bone contact rate (%) was calculated histomorphologically. Immunostaining for osteonectin (ON), osteopontin (OPN) and osteocalcin (OCN) was performed. The removal torque and bone contact rate were analyzed using one‐way analyses of variance and the Scheffé method.

Results: At 4 weeks, the torque was significantly higher in the 2‐w rotation group (1.30±0.44 N cm) than in the control group (0.79±0.67 N cm). From 8 to 16 weeks, the strained groups showed no significant differences from the control group. From the bone contact rates, bone formation was larger in the 4‐week rotation group (62.9±10.7%) than in the control group (42.1±17.9%) at 8 weeks. The 4‐week rotation group showed higher bone contact rate (61.1±11.3%) compared with the other strained groups and maintained this higher value until 16 weeks, showing no significant difference from the control group (72±5.2%). At the implant–bone interface, OPN was widely distributed and OCN was detected at a low level; however, ON could not be observed in any group.

Conclusions: The bone contact rate changed when rotational strain was exerted at different periods after implant placement. However, the removal torque and distribution of extracellular matrix proteins were not adversely affected by the rotational strain.
IL‐1RN gene polymorphism is associated with peri‐implantitis
Authors: Laine Marja L. , Leonhardt Åsa , Roos‐Jansåker Ann‐Marie , Peña A. Salvador , Van Winkelhoff Arie Jan , Winkel Edwin G. , Renvert Stefan
Published: June 2006

Objectives: Interleukin (IL)‐1α, IL‐1β and their natural specific inhibitor IL‐1 receptor antagonist (IL‐1ra) play a key role in the regulation of the inflammatory response in periodontal tissues. Polymorphisms in the IL‐1 gene cluster have been associated with severe adult periodontitis. We aimed to investigate the IL‐1 gene cluster polymorphisms in patients with peri‐implantitis.

Material and methods: The study included 120 North Caucasian individuals. A total of 71 patients (mean age 68 years, 76% smokers) demonstrating peri‐implantitis at one or more implants as evidenced by bleeding and/or pus on probing and bone loss amounting to >3 threads on Brånemark implants and 49 controls (mean age 66 years, 45% smokers) with clinical healthy mucosa and no bone loss around the implants were recruited for the study. The titanium implants, ad modum Brånemark, had been in function for at least 2 years. Mouthwash samples were collected and used for genotyping of the bi‐allelic polymorphisms IL‐1A−889, IL‐1B+3953, IL‐1B−511 and a variable number of tandem repeat IL‐1RN gene polymorphisms using PCR technique.

Results: Significant differences were found in the carriage rate of allele 2 in the IL‐1RN gene between peri‐implantitis patients and controls (56.5% vs. 33.3%, respectively; odds ratios (OR) 2.6; 95% confidence interval (CI) 1.2–5.6; P=0.015). Logistic regression analysis taking smoking, gender and age into account confirmed the association between the IL‐1RN allele 2 carriers and peri‐implantitis (OR 3; 95% CI 1.2–7.6; P=0.02).

Conclusions: Our results provide evidence that IL‐1RN gene polymorphism is associated with peri‐implantitis and may represent a risk factor for this disease.
Formation of new bone during vertical distraction osteogenesis of the human mandible is related to the presence of blood vessels
Authors: Amir Lisa R. , Becking Alfred G. , Jovanovic Andreas , Perdijk Frits B. T. , Everts Vincent , Bronckers Antonius L. J. J.
Published: June 2006

Abstract: We examined the effect of distraction rate on blood vessel growth in intramembraneous ossification after vertical distraction osteogenesis in the human mandible. Six edentulous patients (aged 60±9 years) with a severely atrophic mandible underwent bone augmentation with distraction osteogenesis. Two distraction rates (0.5 and 1 mm/day) were compared and for each group three patients were analyzed. Vascular histomorphometry was carried out in two different areas in the distraction gap: (1) in the first and (2) in the second 1 mm area from the osteotomy line, representing the oldest and younger new‐bone area, respectively. Correlation analysis was performed between blood vessel parameters and the amount of new bone formed during distraction. Histological analysis demonstrated the presence of blood vessels throughout the soft connective tissue in the distraction gap. The volume density of blood vessels between the two investigated areas was significantly lower in the 1 mm/day groups, suggesting a delay in angiogenesis in this group of patients. A positive correlation between blood vessel volume and bone volume density was found in the younger new‐bone area but not in the oldest new‐bone area. This correlation was due to a higher number of blood vessels rather than to a larger size of the blood vessels. Our data suggest that the lower blood vessel density found in the patients with 1 mm/day distraction rate may be related to disruption of angiogenesis in the soft connective tissue of the gap or to a less optimal mechanical stimulation of cells involved in angiogenesis. This probably results in the slower rate of osteogenesis seen at the 1 mm/day distraction rate compared with the 0.5 mm/day distraction rate. The data support the concept that a positive relationship exists between the density of blood vessels and the formation of bone. For distraction of the human mandible in elderly patients, a distraction rate of 0.5 mm/day seems beneficial.
The effect of enamel matrix proteins and deproteinized bovine bone mineral on heterotopic bone formation
Authors: Donos Nikolaos , Kostopoulos Lambros , Tonetti Maurizio , Karring Thorkild , Lang Niklaus P.
Published: June 2006

Aim: To evaluate the osteoinductive potential of deproteinized bovine bone mineral (DBBM) and an enamel matrix derivative (EMD) in the muscle of rats.

Material and methods: Sixteen rats were used in this study. The animals were divided in three groups. Group A: a pouch was created in one of the pectoralis profundis muscles of the thorax of the rats and DBBM particles (Bio‐Oss®) were placed into the pouch. Healing: 60 days. Group B: a small pouch was created on both pectoralis profundis muscles at each side of the thorax midline. In one side, a mixture of EMD (Emdogain®) mixed with DBBM was placed into one of the pouches, whereas in the contralateral side of the thorax the pouch was implanted with DBBM mixed with the propylene glycol alginate (PGA – carrier for enamel matrix proteins of EMD). Healing: 60 days. Group C: the same procedure as group B, but with a healing period of 120 days. Qualitative histological analysis of the results was performed.

Results: At 60 days, the histological appearance of the DBBM particles implanted alone was similar to that of the particles implanted together with EMD or PGA at both 60 and 120 days. The DBBM particles were encapsulated into a connective tissue stroma and an inflammatory infiltrate. At 120 days, the DBBM particles implanted together with EMD or PGA exhibited the presence of resorption lacunae in some cases. Intramuscular bone formation was not encountered in any group.

Conclusion: The implantation of DBBM particles alone, combined with EMD or its carrier (PGA) failed to exhibit extraskeletal, bone‐inductive properties.
Transepidermal water loss reflects permeability barrier status: validation in human and rodentin vivoandex vivomodels
Authors: Fluhr Joachim W. , Feingold Kenneth R. , Elias Peter M.
Published: June 2006

Abstract: Permeability barrier function is measured with instruments that assess transepidermal water loss (TEWL), either with closed‐ or open‐loop systems. Yet, the validity of TEWL as a measure of barrier status has been questioned recently. Hence, we tested the validity of this measure by comparing TEWL across a wide range of perturbations, with a variety of methods, and in a variety of models. TEWL rates with two closed‐chamber systems (VapoMeter and H4300) and one closed‐loop system (MEECO) under different experimentalin vivoconditions were compared with data from four open‐loop instruments, i.e. TM 210, TM 300, DermaLab and EP 1. The instruments were comparedin vivoboth in humans and hairless mice skin subjected to different degrees of acute barrier disruption. The values obtained with bioengineering systems were correlated with absolute water loss rates, determined gravimetrically. Measurements with both closed and open systems correlated not only with each other, but each method detected different degrees of barrier dysfunction. Although all instruments differentiated among gradations in TEWL in the mid‐range of barrier disruptionin vivo, differences in very low and very high levels of disruption were less accurately measured with the H4300 and DermaLab systems. Nevertheless, a high Pearson correlation coefficient (r) was calculated for data from all instruments vs. gravimetrically assessed TEWL. Together, these results verify the utility of TEWL as a measure of permeability barrier status. Moreover, all tested instruments are reliable tools for the assessment of variations in permeability barrier function.
Expression of prothrombin, thrombin and its receptors in human scars
Authors: Artuc Metin , Hermes Barbara , Algermissen Bernd , Henz Beate M.
Published: June 2006

Abstract:  The coagulation system is thought to play a pivotal role during the initial phase of wound healing, but mechanisms and cells involved are only partly understood. We have therefore examined human scars for the expression of thrombin, its precursor prothrombin and the thrombin receptors, thrombomodulin (TM) and protease‐activated receptor‐1 (PAR‐1), compared with normal skin. Biopsies of scars were obtained from primary excision sites of melanoma patients (n = 20) and were compared with normal skin distant from the scar (n = 10), using immunohistochemistry. In addition, polymerase chain reaction analyses were performed on scar versus normal tissue and on cultured keratinocytes, fibroblasts and endothelial cells before and after stimulation with selected cytokines known to be active in wound healing. Normal epidermis was stained for prothrombin, thrombin, TM and PAR‐1, and dermal tissue was stained only for TM and PAR‐1. In scar tissue, thrombin and TM were upregulated in the epidermis and all four molecules in the dermis, independent of the age of the scars. In tissue extracts, mRNA expression of PAR‐1 and prothrombin expression were, however, unchanged and TM even slightly decreased in scars, compared with normal skin. On analysis of cultured cells, keratinocytes expressed mRNA for PAR‐1, TM and prothrombin, endothelial cells for PAR‐1 and TM, and fibroblasts for PAR‐1. An upregulation of PAR‐1 mRNA was induced in fibroblasts on exposure to tumor necrosis factor‐α (TNF‐α), while it remained unchanged in endothelial cells in response to TNF‐α. A downregulation of TM was induced in endothelial cells on exposure to TNF‐α. These findings, showing a marked modulation of thrombin, PAR‐1 and TM even in older human scar tissue, suggest that the coagulation system is not only involved during clotting, but also during the inflammatory and tissue remodelling phases of wound healing.
Resveratrol inhibits proliferation of human epidermoid carcinoma A431 cells by modulating MEK1 and AP‐1 signalling pathways
Authors: Kim Arianna L. , Zhu Yucui , Zhu Huijie , Han Lydia , Kopelovich Levy , Bickers David R. , Athar Mohammad
Published: June 2006

Abstract:  Resveratrol (trans‐3,4′,5‐trihydroxystilbene) is a naturally occurring polyphenolic phytoalexin found in grapes, and has been shown to inhibit the growth of various types of cancer cells. We investigated the mechanism of the antiproliferative effect of resveratrol in A431‐transformed keratinocytes harbouring mutant p53, and show that it is accompanied by G1 cell cycle arrest, which coincides with a marked inhibition of G1 cell cycle regulatory proteins, including cyclins A and D1 and cyclin‐dependent kinase (CDK)6 and p53‐independent induction of p21WAF1. Cell cycle arrest was also associated with the accumulation of hypophosphorylated Rb and p27KIP1. Resveratrol inhibited mitogen‐activated protein kinase/extracellular signal‐regulated kinase kinase (MEK)1 > extracellular signal‐regulated protein kinase (ERK)1/2 signalling, downregulated c‐Jun, and suppressed activating protein (AP)‐1 DNA‐binding and promoter activity. In addition, the inhibition of MEK1 > ERK1/2 signalling appears to be independent of retinoblastoma protein (pRb) hypophosphorylation in A431 cells, as PD098059 did not suppress pRb phosphorylation. Our results demonstrate that resveratrol affects multiple cellular targets in A431 cells, and that the downregulation of both AP‐1 and pRb contributes to its antiproliferative activity in these cells.
Adsorption and interactions of dentine phosphoprotein with hydroxyapatite and collagen
Authors: Milan Anna M. , Sugars Rachael V. , Embery Graham , Waddington Rachel J.
Published: June 2006

Dentine phosphoprotein (DPP) has been proposed to both promote and inhibit mineral deposition during dentinogenesis. The present study aimed to investigate the molecular interactions of DPP and dephosphorylated DPP (DPP‐p) with hydroxyapatite (HAP). Bovine DPP was purified and dephosphorylated by alkaline phosphatase to obtain DPP‐p. DPP and DPP‐p adsorption to HAP was determined along with their ability, when free in solution or bound to collagen, to influence HAP‐induced crystal growth. Absorption isotherms suggested that lower DPP concentrations (1.5–6.25 µg ml−1) demonstrated a reduced affinity for HAP compared with higher protein concentrations (12.5–50.0 µg ml−1). Dephosphorylated DPP had a much reduced affinity for HAP compared with DPP. Dentine phosphoprotein inhibited seeded HAP crystal growth, in a dose‐dependent manner, whilst removal of the phosphate groups reduced this inhibition. When bound to collagen fibrils, DPP significantly promoted the rate of HAP crystal growth over 0–8 min. Conversely, DPP‐p and collagen significantly decreased the rate of crystal growth over 0–18 min. These results indicate a major role for the phosphate groups present on DPP in HAP crystal growth. In addition, concentration‐dependent conformational changes to DPP, and the interaction with other matrix components, such as collagen, are important in predicting its dual role in the mineralization of dentine.
Impaired mastication modifies the dynamics of bolus formation
Authors: Yven Claude , Bonnet Laurent , Cormier David , Monier Sandra , Mioche Laurence
Published: June 2006

Mastication is a complex sensory‐motor activity whereby a food product is transformed into a bolus. Consumers mainly perceive the sensory properties of the food during the intra‐oral manipulation of the product. Consequently, the quality of the chewing process could have consequences on the perception of sensory properties and food choice. By focusing on meat products, this study aimed to analyze the influence of dental status on (i) dynamic adaptation of the chewing behavior (evaluated by electromyography) to the changes in texture during bolus formation and (ii) bolus properties (mechanical resistance and saliva incorporation) obtained from meat of different initial textures. Two groups of subjects (dentate subjects and denture wearers), known to present highly different chewing efficiency, were compared. For both groups, salivary flow rates were evaluated at rest and after stimulation by chewing (paraffin and meat). The salivary flow rates, assessed during chewing of a nonedible matrix (paraffin), were a good predictor of salivary flow rates induced by meat chewing for both groups of subjects. Salivary flow rates were not affected by the dental status. In contrast, the chewing behavior varied between groups. For denture wearers, the chewing pattern was strongly impaired and not adapted to the changes in meat structure during bolus formation. Denture wearers swallowed less fragmented boli than dentate subjects, but boli had a similar level of moisture for both groups of subjects.
The Hungarian version of the Oral Health Impact Profile
Authors: Szentpétery András , Szabó Gyula , Marada Gyula , Szántó Ildikó , John Mike T.
Published: June 2006

Oral health‐related quality of life (OHRQoL) is increasingly of interest in dentistry. The current internationally accepted instruments used to measure OHRQoL need to be cross‐culturally adapted for use in other cultural environments. It was the aim of the present study to develop a Hungarian version of the Oral Health Impact Profile (OHIP‐H) following accepted guidelines. The original English‐language version was translated into Hungarian, back‐translated into English, and tested for its psychometric properties. Construct validity was tested on 144 prosthodontic patients and 200 randomly selected subjects. A priori hypothesized associations between OHIP summary scores and self‐reported oral health and six self‐reported oral conditions were investigated. The pattern of the observed associations supported the new instrument's construct validity. Responsiveness tested in 28 oral surgery patients was indicated by a statistically significant mean OHIP score change from 39.2 to 23.0. Test–retest reliability was demonstrated by intraclass correlation coefficients of 0.81–0.90 for OHIP summary scores and subscales in 31 prosthodontic patients. Cronbach's alpha values between 0.71 and 0.96 proved to have high internal consistency. Adequate psychometric properties in typical patient populations make the new instrument suitable for assessment of OHRQoL in Hungary.
Immunological and molecular detection of human immunodeficiency virus in saliva, and comparison with blood testing
Authors: Yapijakis Christos , Panis Vassilis , Koufaliotis Nikos , Yfanti Georgia , Karachalios Stefanos , Roumeliotou Anastasia , Mantzavinos Zacharias
Published: June 2006

In order to test the detection feasibility of human immunodeficiency virus (HIV) in saliva, a three‐method blind screening analysis was conducted. Sixty‐eight individuals were studied, comprising 34 HIV carriers and 34 noncarriers (controls) of matched gender and age. An oral examination preceded saliva and blood sampling of studied individuals. All samples were tested blind for HIV by using two immunological methods [Oraquick‐compatible enzyme‐linked immunosorbent assay (ELISA) and a fluorescent immunoenzymatic method (ELFA)], confirmed by western blotting, and a simple molecular method (polymerase chain reaction amplification of a relatively constant viral DNA region), confirmed by DNA hydridization. Compared with the controls, about twice as many HIV carriers had oral health problems, including periodontal disease. ELFA resulted in 33/34 positives and 34/34 negatives in saliva, while it detected 34/34 positives and 34/34 negatives in blood. ELISA performed even better, with correct assignment of all positives and negatives in both saliva and blood. The PCR method, at three annealing temperatures, surprisingly detected all positive samples, while it gave no false‐positive result. In conclusion, the detection of anti‐HIV in saliva may achieve accuracy of 97.1–100%, comparable with that in blood. Furthermore, this study suggests that a highly accurate molecular method of HIV detection may be feasible, although the studied carriers had rather homogeneous characteristics.
In vitro fracture behavior of maxillary premolars with metal crowns and several post‐and‐core systems
Authors: Fokkinga Wietske A. , Kreulen Cees M. , Le Bell‐Rönnlöf Anna‐Maria , Lassila Lippo V. J. , Vallittu Pekka K. , Creugers Nico H. J.
Published: June 2006

The in vitro fracture behavior of severely damaged premolars, restored with metal crowns with limited ferrule and several post‐and‐core systems, was investigated. Crowns of maxillary premolars were removed and canals were prepared with Gates Glidden drills and with Parapost drills. Groups of 11 samples were each treated with cast post‐and‐cores (Parapost XP, Wironium Plus) (group 1), prefabricated metal posts (Parapost XH) (group 2), prefabricated glass fiber posts (Parapost FiberWhite) (group 3), and custom‐made glass fiber posts (EverStick Post) (group 4). Posts and composite cores and metal crowns in groups 2, 3, and 4 were adhesively cemented. Post‐and‐cores and crowns in group 1 were cemented with phosphate cement. Thermocycling was performed (6,000×, 5–55 °C). Two static load tests (30°) were applied. During the first load test (preloading) no failures occurred. Failure modes from the second load test were categorized into favorable and unfavorable failures. Mean failure loads among the four groups (group 1, 1845 N; group 2, 1718 N; group 3, 1812 N; and group 4, 1514 N) were not significantly different. Unfavorable failures were root fractures and favorable failures were postcrown displacements. No differences in frequencies of unfavorable/favorable failures were seen among the groups. The results suggest that different post‐and‐core systems have no influence on the fracture behavior of severely damaged premolars restored with metal crowns with limited ferrule.
Foamy Virus Capsid Assembly Occurs at a Pericentriolar Region Through a Cytoplasmic Targeting/Retention Signal in Gag
Authors: Yu Shuyuarn F. , Eastman Scott W. , Linial Maxine L.
Published: June 2006

Foamy viruses (FV) are unusual retroviruses that differ in many aspects of their life cycle from the orthoretroviruses such as human immunodeficiency virus. Similar to Mason–Pfizer monkey virus (MPMV), FV assemble into capsids intracellularly. The capsids are then transported to a cellular membrane for acquisition of envelope (Env) glycoproteins and budding. However, unlike MPMV, budding of FV is dependent upon the presence of Env. Previous work suggested that FV Env proteins are localized to the endoplasmic reticulum (ER) where budding takes place. However, very little was known about the details of FV assembly. We have used immunofluorescence and electron microscopy to visualize the intracellular location of FV assembly and budding. We have found that, as in the case of MPMV, FV capsids assemble at a pericentriolar site in the cytoplasm. Surprisingly, FV Env is mostly absent from this site and, contrary to expectations, FV capsid structural protein (Gag) is absent from the ER. Gag and Env only co‐localize at the trans‐Golgi network, suggesting that Env–Gag interactions that are required for viral egress from the cell, occurs at this site. Finally, inhibitor studies suggest an important role of microtubule networks for foamy viral assembly and budding.
The crystal structure of a hyperthermostable subfamily II isocitrate dehydrogenase from Thermotoga maritima
Authors: Karlström Mikael , Steen Ida H. , Madern Dominique , Fedöy Anita‐Elin , Birkeland Nils‐Kåre , Ladenstein Rudolf
Published: June 2006

Isocitrate dehydrogenase (IDH) from the hyperthermophile Thermotoga maritima (TmIDH) catalyses NADP+‐ and metal‐dependent oxidative decarboxylation of isocitrate to α‐ketoglutarate. It belongs to the β‐decarboxylating dehydrogenase family and is the only hyperthermostable IDH identified within subfamily II. Furthermore, it is the only IDH that has been characterized as both dimeric and tetrameric in solution. We solved the crystal structure of the dimeric apo form of TmIDH at 2.2 Å. The R‐factor of the refined model was 18.5% (Rfree 22.4%). The conformation of the TmIDH structure was open and showed a domain rotation of 25–30° compared with closed IDHs. The separate domains were found to be homologous to those of the mesophilic mammalian IDHs of subfamily II and were subjected to a comparative analysis in order to find differences that could explain the large difference in thermostability. Mutational studies revealed that stabilization of the N‐ and C‐termini via long‐range electrostatic interactions were important for the higher thermostability of TmIDH. Moreover, the number of intra‐ and intersubunit ion pairs was higher and the ionic networks were larger compared with the mesophilic IDHs. Other factors likely to confer higher stability in TmIDH were a less hydrophobic and more charged accessible surface, a more hydrophobic subunit interface, more hydrogen bonds per residue and a few loop deletions. The residues responsible for the binding of isocitrate and NADP+ were found to be highly conserved between TmIDH and the mammalian IDHs and it is likely that the reaction mechanism is the same.
Identification and characterization of a collagen‐induced platelet aggregation inhibitor, triplatin, from salivary glands of the assassin bug, Triatoma infestans
Authors: Morita Akihiro , Isawa Haruhiko , Orito Yuki , Iwanaga Shiroh , Chinzei Yasuo , Yuda Masao
Published: June 2006

To facilitate feeding, certain hematophagous invertebrates possess inhibitors of collagen‐induced platelet aggregation in their saliva. However, their mechanisms of action have not been fully elucidated. Here, we describe two major salivary proteins, triplatin‐1 and ‐2, from the assassin bug, Triatoma infestans, which inhibited platelet aggregation induced by collagen but not by other agents including ADP, arachidonic acid, U46619 and thrombin. Furthermore, these triplatins also inhibited platelet aggregation induced by collagen‐related peptide, a specific agonist of the major collagen‐signaling receptor glycoprotein (GP)VI. Moreover, triplatin‐1 inhibited Fc receptor γ‐chain phosphorylation induced by collagen, which is the first step of GPVI‐mediated signaling. These results strongly suggest that triplatins target GPVI and inhibit signal transduction necessary for platelet activation by collagen. This is the first report on the mechanism of action of collagen‐induced platelet aggregation inhibitors from hematophagus invertebrates.
Charging of tRNA with non‐natural amino acids at high pressure
Authors: Giel‐Pietraszuk Malgorzata , Barciszewski Jan
Published: June 2006

We show a simple and reliable method of tRNA aminoacylation with natural, as well as non‐natural, amino acids at high pressure. Such specific and noncognate tRNAs can be used as valuable substrates for protein engineering. Aminoacylation yield at high pressure depends on the chemical nature of the amino acid used and it is up to 10%. Using CoA, which carries two potentially reactive groups ‐SH and ‐OH, as a model compound we showed that at high pressure amino acid is bound preferentially to the hydroxyl group of the terminal ribose ring.
Evaluation of low flow estimation techniques for ungauged catchments
Authors: Patel Junaid A.
Published: June 2006

Low flow indices are of interest for a number of water‐related applications. Conventionally, low flow indices are derived from continuous streamflow data; however, these data may not always be available for analysis. A number of techniques have therefore been developed for low flow estimation in ungauged catchments. These approaches vary in complexity and in the amount of initial data required to generate the low flow model. In the UK, software is available which assists in low flow estimation for ungauged catchments. However, certain desktop studies only require a simple evaluation of low flows, with specific low flow indices, such as the Q95 index, being of interest. In this case, the use of such software may not be justified or required in the first instance. This paper demonstrates that a simple regression model is adequate for low flow estimation for multisite analysis where the order magnitude of the low flow index is of importance.
Habitat, environment and niche: what are we modelling?
Authors: Kearney M.
Published: June 2006

The terms ‘habitat’, ‘environment’ and ‘niche’ are used inconsistently, and with some confusion, within the ecological literature on species distribution and abundance modelling. Here I suggest interrelated working definitions of these terms whereby the concept of habitat remains associated with descriptive/correlative analyses of the environments of organisms, while the niche concept is reserved for mechanistic analyses. To model the niche mechanistically, it is necessary to understand the way an organism's morphology, physiology, and especially behaviour, determine the kinds of environment it experiences when living in a particular habitat, and it is also necessary to understand how those environmental conditions affect fitness (growth, survival and reproduction). While distributions can potentially be predicted by modelling descriptions or correlations between organisms and habitat components, we must model an organism's niche mechanistically if we are to fully explain distribution limits. A mechanistic understanding of the niche is also critical when we want to predict an organism's distribution under novel circumstances such as a species introduction or climate change.
Extrapair paternities in black‐browed Thalassarche melanophris, grey‐headed T. chrysostoma and wandering albatrosses Diomedea exulans at South Georgia
Authors: M. Burg Theresa , P. Croxall John
Published: June 2006

Extrapair paternities (EPP) are relatively common in passerines, but rare in seabirds. Like most seabirds, albatrosses are long lived, form long‐term pair bonds and require biparental care for chick‐rearing. Microsatellite analyses of 327 chicks from black‐browed Thalassarche melanophris, grey‐headed T. chrysostoma and wandering albatrosses Diomedea exulans over two breeding seasons revealed the presence of EPP in all three species. Though EPP rates varied between species and years, up to 21% of offspring were the result of extrapair matings. Rates were highest in wandering albatrosses (6–21%) followed by grey‐headed (3–10%) and black‐browed (0–9%) albatrosses. EPP rates were lower in 1998 compared to 1999 in both black‐browed and grey‐headed albatrosses, whereas the reverse was true for wandering albatrosses. Interspecific differences in EPP rates may reflect differences in breeding phenology and sexual size dimorphism. Differences in timing and frequency of breeding may promote different opportunities for interactions with birds other than their normal partner. The different breeding habitat, dispersion and mate‐attraction rituals in wandering albatross, together with the disparity in size between the sexes may also offer more scope for higher rates of EPP. Despite extensive sampling within each colony, we were unable to identify sires for many of the extrapair young; however males from other colonies were involved, raising interesting questions regarding the timing and nature of such events.
Assessment of Sorbent Reactivation by Water Hydration for Fluidized Bed Combustion Application
Authors: Montagnaro Fabio , Salatino Piero , Scala Fabrizio , Wu Yinghai , Anthony Edward J. , Jia Lufei
Published: June 2006

Disposal of fluidized bed combustion (FBC) solid residues currently represents one of the major issues in FBC design and operation, and contributes significantly to its operating cost. This issue has triggered research activities on the enhancement of sorbent utilization for in situ sulfur removal. The present study addresses the effectiveness of the reactivation by liquid water hydration of FB spent sorbents. Two materials are considered in the study, namely the bottom ash from the operation of a full-scale utility FB boiler and the raw commercial limestone used in the same boiler. Hydration-reactivation tests were carried out at temperatures of 40°C and 80°C and for curing times ranging from 15minutes to 2d, depending on the sample. The influence of hydration conditions on the enhancement of sulfur utilization has been assessed. A combination of methods has been used to characterize the properties of liquid water-hydrated materials.
Complete Cap 4 Formation Is Not Required for Viability inTrypanosoma brucei
Authors: Zamudio Jesse R. , Mittra Bidyottam , Zeiner Gusti M. , Feder Marcin , Bujnicki Janusz M. , Sturm Nancy R. , Campbell David A.
Published: June 2006

In kinetoplastids spliced leader (SL) RNA istrans-spliced onto the 5′ ends of all nuclear mRNAs, providing a universal exon with a unique cap. Mature SL contains an m7G cap, ribose 2′-O methylations on the first four nucleotides, and base methylations on nucleotides 1 and 4 (AACU). This structure is referred to as cap 4. Mutagenized SL RNAs that exhibit reduced cap 4 aretrans-spliced, but these mRNAs do not associate with polysomes, suggesting a direct role in translation for cap 4, the primary SL sequence, or both. To separate SL RNA sequence alterations from cap 4 maturation, we have examined two ribose 2′-O-methyltransferases inTrypanosoma brucei. Both enzymes fall into the Rossmann fold class of methyltransferases and model into a conserved structure based on vaccinia virus homolog VP39. Knockdown of the methyltransferases individually or in combination did not affect growth rates and suggests a temporal placement in the cap 4 formation cascade: TbMT417 modifies A2and is not required for subsequent steps; TbMT511 methylates C3, without which U4methylations are reduced. Incomplete cap 4 maturation was reflected in substrate SL and mRNA populations. Recombinant methyltransferases bind to a methyl donor and show preference for m7G-capped RNAs in vitro. Both enzymes reside in the nucleoplasm. Based on the cap phenotype of substrate SL stranded in the cytosol, A2, C3, and U4methylations are added after nuclear reimport of Sm protein-complexed substrate SL RNA. As mature cap 4 is dispensable for translation, cap 1 modifications and/or SL sequences are implicated in ribosomal interaction.
Hypovirus Papain-Like Protease p29 Suppresses RNA Silencing in the Natural Fungal Host and in a Heterologous Plant System
Authors: Segers Gerrit C. , van Wezel Rene , Zhang Xuemei , Hong Yiguo , Nuss Donald L.
Published: June 2006

Virulence-attenuating hypoviruses of the speciesCryphonectriahypovirus 1 (CHV1) encode a papain-like protease, p29, that shares similarities with the potyvirus-encoded suppressor of RNA silencing HC-Pro. We now report that hypovirus CHV1-EP713-encoded p29 can suppress RNA silencing in the natural host, the chestnut blight fungusCryphonectria parasitica. Hairpin RNA-triggered silencing was suppressed inC. parasiticastrains expressing p29, and transformation of a transgenic green fluorescent protein (GFP)-silenced strain with p29 resulted in an increased number of transformants with elevated GFP expression levels. The CHV1-EP713 p29 protein was also shown to suppress both virus-induced and agroinfiltration-induced RNA silencing and systemic spread of silencing in GFP-expressing transgenicNicotiana benthamianaline 16c plants. The demonstration that a mycovirus encodes a suppressor of RNA silencing provides circumstantial evidence that RNA silencing in fungi may serve as an antiviral defense mechanism. The observation that a phylogenetically conserved protein of related plant and fungal viruses functions as a suppressor of RNA silencing in both fungi and plants indicates a level of conservation of the mechanisms underlying RNA silencing in these two groups of organisms.
Nature of the Periplastidial Pathway of Starch Synthesis in the CryptophyteGuillardia theta
Authors: Deschamps Philippe , Haferkamp Ilka , Dauvillée David , Haebel Sophie , Steup Martin , Buléon Alain , Putaux Jean-Luc , Colleoni Christophe , d'Hulst Christophe , Plancke Charlotte , Gould Sven , Maier Uwe , Neuhaus H. Ekkehard , Ball Steven
Published: June 2006

The nature of the periplastidial pathway of starch biosynthesis was investigated with the model cryptophyteGuillardia theta. The storage polysaccharide granules were shown to be composed of both amylose and amylopectin fractions with a chain length distribution and crystalline organization very similar to those of starch from green algae and land plants. Most starch granules displayed a shape consistent with biosynthesis occurring around the pyrenoid through the rhodoplast membranes. A protein with significant similarity to the amylose-synthesizing granule-bound starch synthase 1 from green plants was found as the major polypeptide bound to the polysaccharide matrix. N-terminal sequencing of the mature protein proved that the precursor protein carries a nonfunctional transit peptide in its bipartite topogenic signal sequence which is cleaved without yielding transport of the enzyme across the two inner plastid membranes. The enzyme was shown to display similar affinities for ADP and UDP-glucose, while theVmaxmeasured with UDP-glucose was twofold higher. The granule-bound starch synthase fromGuillardia thetawas demonstrated to be responsible for the synthesis of long glucan chains and therefore to be the functional equivalent of the amylose-synthesizing enzyme of green plants. Preliminary characterization of the starch pathway suggests thatGuillardia thetautilizes a UDP-glucose-based pathway to synthesize starch.
On the power of plotless density estimators for statistical comparisons of plant populations
Authors: Steinke I. , Hennenberg K.J.
Published: June 2006

Reliable density estimations of plant populations and their statistical comparison are fundamental in many ecological studies. Typical sampling methods are plotless density estimators (PDE) and plot counts. A simulation study was performed to examine the power of these sampling methods for the statistical comparison of the densitiesof two plant populations. The variable area transect estimator, the ordered distance estimator, and Byth’s T-square estimator were considered and compared with the quadrat count estimator. The relative root-mean-squared error and the relative bias were used to explore the quality of the estimators, and robust confidence intervals and standard deviation estimators were given. Tests were developed to compare the population densities of two independent populations, and the performance of the tests was examined. All simulations were run for spatially random and aggregate data patterns. For completely random data, all estimators and all tests behaved well if they were based on the same sampling intensity. For the aggregate pattern, all PDE’s were negatively biased, but the quadrat count estimator was unbiased. Nonparametric confidence intervals had the most robust performance for aggregate data. The results of the presented simulation study demonstrate that plant ecologists should avoid PDE for both density estimation and statistical testing except when the pattern of a population is known to follow a completely random spatial pattern. Instead, the use of the plot count estimator is recommended.
microRNAs in seeds: modified detection techniques and potential applications
Authors: Martin Ruth C. , Liu Po-Pu , Nonogaki Hiroyuki
Published: June 2006

microRNAs (miRNAs) are small (21–24 nucleotides), single-stranded RNAs that regulate target gene expression at transcriptional and posttranscriptional levels. miRNAs play crucial roles in plant development, maintenance of homeostasis, and responses to environmental signals. miRNAs and their target genes, which can be computationally predicted in plants, are expressed in developing and germinating seeds as in other plant tissues, suggesting that miRNAs may be involved in the regulation of gene expression in seeds. Profiling multiple miRNAs expressed in developing and germinating seeds, characterizing their expression patterns in a spatio-temporal manner, and elucidating their biological functions will provide information essential for understanding the mechanisms of seed development and germination. In this review, an overview of the recent technical advances in seed miRNA research and their potential applications for plant, specifically seed, research are presented.