Anatomic considerations for immediate implant placement in the mandibular molar region: a cross-sectional study using cone-beam computed tomography.

BACKGROUND: There is concern regarding immediate implantation in the molar region because of discrepancy between socket size and inserted implant diameter. The purpose of this study was to assess the local anatomy of the posterior mandibular region in relation to immediate implant placement using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Using CBCT imaging data, 204 mandibular first molars and 201 mandibular second molars were assessed for the interradicular and alveolar bone dimensions, tooth sizes and proximity to vital structures. The cross-sectional mandibular shape and root configuration of these molars were determined. RESULTS: Distances to the inferior alveolar canal (IAC) from the root apices of the first molar were significantly greater than the second molar. Up to 14.5% of second molars had less than 10 mm of vertical bone height between the IAC and furcation bone crest. Interradicular bone width of < 3 mm was found in 57% of second molars. All first molars in this study had two to three roots while 16% of second molars presented with a single root. The prevalent mandible shape at the first and second molars was the parallel and undercut ridges, respectively. CONCLUSIONS: The mandibular second molars from samples of a Southeast Asian population presented with greater anatomical difficulties for immediate implant placement which include absent or inadequate interradicular bone thickness, higher incidence of unfavourable mandible shape and increased proximity to vital structures.

The presence of Merkel cells and CD10- and CD34-positive stromal cells compared in benign and malignant oral tumors.

BACKGROUND: To describe sequential changes in Merkel cells (MC), and CD10(+) and CD34(+) stromal cells (SC) during the transition from benign to malignant oral lesions and correlate with clinicopathologic parameters. MATERIALS AND METHODS: Changes in cytokeratin 20-positive (CK20(+)) Merkel cells, CD10(+) and CD34(+) SC were immunohistochemically examined in specimens of 28 oral verrucous carcinomas (VC), 32 squamous cell carcinomas (SCC) and 36 benign squamous lesions (BSL). Immunoreactivity and localized inflammation were measured quantitatively and/or semiquantitatively, and between-group results were statistically compared. RESULTS: The mean number of CD34(+) SC was significantly lower in VC (57.36) and SCC (33.81) than BSL (351.56, P < 0.001). However, the three tumor types had similar staining level and number of CD10(+) SC. We found a significant difference in the density of MC between BSL and VC (P < 0.001) or SCC (P < 0.001). The number of CK20(+) MC was significantly lower in highly inflamed specimens than mildly inflamed specimens (P = 0.001). CONCLUSION: CD34(+) SC and to a lesser extent MC, but not CD10(+) SC, reveal statistically different density during the transition from benign to malignant oral lesions. The correlations between the CD34(+) SC expression and squamous lesions may be associated with epithelial dysplasia and/or tumor invasion.

Fibrinogen adsorption and platelet lysis characterization of fluorinated surface-modified polyetherurethanes.

A polyetherurethane (PU) was modified using fluorinated surface-modifying macromolecules (SMMs). A double radiolabel method was used simultaneously to measure the number of adhered platelets ((51)Cr) and the quantity of adsorbed Fg ((125)I), in a cone-and-plate instrument. The objectives were to determine if adsorbed Fg levels correlated to platelet adhesion on the surfaces, and to assess if any reductions in platelet adhesion for the SMM-treated surfaces resulted from surface-induced platelet lysis, rather than changes directly related to lower platelet activation and attachment on the novel surfaces. Platelet lysis was determined from lactate dehydrogenase (LDH) and unbound (51)Cr released into plasma isolated from whole blood exposed to test materials. The corresponding Fg adsorption, evaluated under the same platelet adhesion conditions, did not account for the reduced platelet adhesion on the treated surfaces. LDH and (51)Cr platelet release were very low and indicated no statistically significant differences between the materials. It was therefore concluded that platelet lysis did not contribute to the reduction in platelet adhesion characteristic observed on the SMM-treated surfaces. More importantly, the work emphasizes that the platelet activation cannot be inferred to by assessing the quantity of fibrinogen as is commonly done in the literature. The finding suggests a much more complex mechanism of action for the SMM surface modifiers. On-going work is investigating other Fg parameters such as protein binding affinity and protein conformational state in order to establish the mechanism by which the fluorinated surface modifiers may be reducing platelet adhesion via intermediary changes in initial protein adsorption.

Use of physical restraints in rehabilitation settings: staff knowledge, attitudes and predictors.

AIM: This paper reports a study examining the knowledge, attitudes and practices of staff with regard to the use of restraints in rehabilitative settings, and quantifying the direct and indirect effects of the factors that influenced these practices. BACKGROUND: Nursing staff hold many misconceptions that support the continued use of physical restraints as a desirable technique in clinical settings to control clients. A number of previous studies measuring the knowledge, attitudes and/or practices of nursing staff towards the use of restraints have been conducted in acute, elder care, or psychiatric settings. However, not many have examined the predictors of staff practices when restraints are applied. In the study reported here, physical restraint was defined as any manual method or physical/mechanical device, material or equipment attached to a client's body so that their free movement was restricted. METHODS: A questionnaire was administered to 168 nursing staff in two rehabilitation centres in Hong Kong. The data were collected in 2002-2003 and the response rate was 80%. FINDINGS: Inadequate knowledge and negative attitudes on the use of restraints were found among staff. Most believed that good alternatives to restraints are not available, or they underestimated the physical and psychological impact of restraints on clients. Path analysis indicated that staff attitudes and their clinical experiences had positive direct effects on restraint use. In addition, level of knowledge and clinical experience had a positive indirect effect on practice by influencing attitudes. CONCLUSION: These data could serve as a basis for re-educating nursing staff on the subject. Staff with more clinical experience could give appropriate guidance to other members of staff on decisions to apply restraints. More effective alternative interventions to restraining clients should be explored. Once the gaps in knowledge are closed, more positive attitudes among staff towards the use of restraints can be cultivated, thus leading to a higher standard of nursing practice.

Fibrinogen surface distribution correlates to platelet adhesion pattern on fluorinated surface-modified polyetherurethane.

In previous work, it had been shown that platelet adhesion could be reduced by fluorinating surfaces with oligomeric fluoropolymers, referred to as surface-modifying macromolecules (SMMs). In the current study, two in vitro blood-contacting experiments were carried out on a polyetherurethane modified with three different SMMs in order to determine if altered platelet adhesion levels could be related to the pattern of adsorbed protein and more specifically to the manner in which fibrinogen (Fg) distribution occurs at the surface. In the first experiment, the materials were placed in whole human blood and the adherent platelets were viewed with high-resolution scanning electron microscopy (SEM). In a second experiment, the materials were incubated with human plasma with the absence of platelets. The plasma contained 5% fluorescent-Fg. The materials were then viewed with a fluorescence microscope and images were collected to define the distribution of high-density fluorescent-Fg areas. The SEM and fluorescent-Fg images were imported to Image Pro Plus imaging software to measure the area, length and circularity and a bivariate correlation test was conducted between the two sets of data. For area and length morphology parameters, there were high and significant correlations (r > 0.9, p < 0.05) between the platelets and Fg aggregates. The data suggest that the Fg distribution may serve as a predictor of platelet morphology/activation and provides insight into the non-thrombogenic character of biomaterials containing the fluorinated SMMs.

Kinetic characteristics of bacterial azo-dye decolorization by Pseudomonas luteola.

A Pseudomonas luteola strain expressing azoreductase activity was utilized to remove the color of an azo dye (reactive red 22) from contaminated solutions. The effects of substrate concentrations, medium compositions, and operation parameters (e.g., pH, temperature, dissolved oxygen, etc.) on decolorization of the azo dye by a P. luteola strain were systematically investigated to reveal the key factors that dominate the performance of azo-dye decolorization. The metabolites resulting from bacterial decolorization were analyzed by high-performance liquid chromatography (HPLC) and mass spectrometery (MS). The results show that the dissolved oxygen and glucose concentration retarded decolorization of reactive red 22 by P. luteola. The optimal azo-dye decolorization occurred at 37 degrees C, while more rapid decolorization took place over pH 7-9. Yeast extract and tryptone strongly enhanced the decolorization. The Michaelis-Menten model can satisfactorily describe the dependence of specific decolorization rate on the concentration of substrate (reactive red 22 or yeast extract). Decolorization of the azo dye by intact cells of P. luteola was essentially independent of the growth phase, whereas the azoreductase activity of the cell-free extract decreased in the order of late-stationary phase > early-stationary phase > mid-log phase. This suggests that mass transfer of the azo dye across the cell membrane may be the rate-limiting step. The HPLC and MS analyses suggest that both partial reduction and complete cleavage of the azo bond could contribute to decolorization of reactive red 22 by P. luteola.

Bacterial morphotypes and early cellular responses in clinically infected and non-infected sites after combination therapy of guided tissue regeneration and allograft.

OBJECTIVES: To compare the bacterial morphotypes and early cellular responses in periodontally treated sites with and without pus formation after a combination of guided tissue regeneration (GTR) and allograft therapy. METHODS: 45 subjects with 80 sites having periodontal lesions with moderate to deep pockets and angular bone defects participated. 28 treated sites in 25 patients were included in the studies. 14 sites suffered from symptoms and signs of infection with pus formation during the healing period were assigned to the pus (P) group. Another 14 sites had asymptomatic healing and were assigned to the non-pus (NP) group. The GTR membranes were retrieved 4-6 weeks after surgery and processed for SEM examination. The bacterial morphotypes on the membranes were observed and photographed. Bacterial adhesion score (BAS, 0-5) and the presence of leukocytes and fibroblasts were estimated from photographs. RESULTS: The results showed that large numbers of bacteria (high BAS) were present on both sides of the coronal 2/3 of the membrane in both groups, irrespective of clinical conditions. At the apical 1/3 of the membrane, moderate numbers of bacteria were still found on the outer side in the P group. The BAS of rod-shaped bacteria were significantly higher in the P group than that of the NP group on the outer coronal 2/3 of the membrane. The frequency of the presence of fibroblasts (18.5%) at the apical 1/3 of the inner (tooth facing) side of the P group was much lower than that of the same location (28.6-29.6%) in the NP group. The presence of leukocytes and fewer numbers of fibroblasts on the GTR membrane were associated with greater BAS for rod- and filament-shaped bacteria. CONCLUSIONS: GTR membranes are commonly colonized by oral bacteria during retention, even on uncomplicated and tissue covered portions. The overt infection clinically (pus group) of the membrane-allograft treated sites is associated with a significantly elevated BAS of rod-shaped bacteria, and may be closely related to the occurrence of its adverse early healing responses (inflammation, pus formation, fewer fibroblasts and greater accumulation of leukocytes).

The effect of fluorinated surface modifying macromolecules on the surface morphology of polyethersulfone membranes.

Polyethersulfone (PES) has been recently adopted for membrane materials in applications such as ultrafiltration and haemodialysis. As a biomaterial, the factors which affect the blood compatibility of PES membranes include surface energetics, hydrophobicity, and surface morphology. Surface fluorination of materials has been found to create surfaces with improved blood compatibility and chemical stability. One novel approach to generating fluorinated polymer surfaces has included the use of fluorinated surface modifying macromolecules (SMMs). These macromolecules have been reported to establish fluorinated functional groups at surfaces of polymeric materials without significantly affecting the physical properties of the base polymer. However, to date there has been relatively little information published on the nature of the surface structure for PES materials containing these SMMs. In this study, synthesized SMMs with varying chemical compositions were characterized and blended with PES, and fabricated into flat sheet membranes. The bulk thermal transitions of PES materials were not significantly altered by the addition of 4 wt% SMMs. Contact angle data showed that the addition of SMMs in PES created more hydrophobic surfaces, accompanied by an increase in surface heterogeneity. X-ray photoelectron spectroscopy studies confirmed the presence of elemental fluorine at the surface. Through microscopy studies, it was shown that surface modification was achieved by the migration of SMM concentrated microdomains to the air-membrane interface. The generated microdomains (approximately 1-2 microm in diameter) are dispersed within the top 8 microm of the surface. The concentration of microdomains was gradually depleted from the surface to the bulk of the membrane. A schematic of the morphology for SMMs within the PES membrane surface was proposed.

Self-assembly of the infectious bursal disease virus capsid protein, rVP2, expressed in insect cells and purification of immunogenic chimeric rVP2H particles by immobilized metal-ion affinity chromatography.

A gene encoding a structural protein (VP2) of a local strain (P3009) of infectious bursal disease virus (IBDV) was cloned and expressed using the baculovirus expression system to develop a subunit vaccine against IBDV infection in Taiwan. The expressed rVP2 proteins formed particles of approximately 20-30 nm in diameter. Those particles were partially purified employing sucrose density gradient ultracentrifugation, and the purified particles were recognized by a monoclonal antibody against the VP2 protein of IBDV P3009. To facilitate the purification of the particles, the VP2 protein was engineered to incorporate a metal ion binding site (His)(6 )at its C-terminus. The chimeric rVP2H proteins also formed particles, which could be affinity-purified in one step with immobilized metal ions (Ni(2+)). Particle formation was confirmed by direct observation under the electron microscope. The production level of rVP2H protein was determined to be 20 mg/L in a batch culture of Hi-5 cells by quantifying the concentration of the purified proteins. The chicken protection assay was performed to evaluate the immunogenicity of the rVP2H protein. When susceptible chickens were inoculated with the recombinant rVP2H proteins (40 microg/bird), virus-neutralizing antibodies were induced, thereby conferring a high level of protection against the challenge of a very virulent strain of IBDV. In conclusion, the most significant finding in this work is that both of the expressed rVP2 and rVP2H proteins can form a particulate structure capable of inducing a strong immunological response in a vaccinated chicken.

Correlation of chi orientation with transcription indicates a fundamental relationship between recombination and transcription.

Cross-over hot-spot instigator (Chi) sequences (5'-GCTGGTGG-3') are abundant, strand-specific, sequences, which locally increase recombination in Escherichia coli. Located within G-rich 'recombination islands', Chi orientations correlate with the orientations both of DNA replication and of transcription. Consistent with evidence from eukaryotic systems for a fundamental relationship between recombination and transcription, we find for E. coli Chi sequences, and for Haemophilus influenzae Chi-like sequences, that orientations correlate better with transcription than with replication. Complying with Szybalski's transcription direction rule, open reading frames in these prokaryotes have purine-rich mRNA-synonymous DNA strands. Hence, the G-richness of 'recombination islands' may reflect their correspondence with 'transcriptional islands' (genes). Comparison of a natural with the corresponding shuffled sequence, indicates a base order-dependent island unit of approx. 1kb. 1998 Elsevier Science B.V.

Motor power pharmacodynamics of subarachnoid hyperbaric 5% lidocaine in the sitting position.

BACKGROUND: Repetitive dynamometric measurement using a plantar flexion power device (PFPD) provides detailed data describing the onset and offset of motor block following spinal administration of lidocaine. The aim of this study was to evaluate administration of two doses of spinal lidocaine in the sitting position to determine whether our dynamometric model produces data consistent with our current understanding of the pharmacokinetics of subarachnoid, hyperbaric, 5% lidocaine. METHODS: Twenty male patients (54 to 80 yr) undergoing cystoscopy received spinal anaesthesia with either 75 mg (n = 10) or 100 mg of hyperbaric lidocaine 5%, in the sitting position, under standardised conditions. Plantar flexion muscle power was recorded during onset and offset of anaesthesia using a load cell interfaced with a computer (PFPD). RESULTS: Onset of paralysis following spinal block in the sitting position was rapid and complete with motor power declining exponentially to 5% of preoperative values by 8.5 min in all patients. There was no difference in decay or recovery of plantar flexion motor power data between dosage groups in the sitting position. Measurement using the PFPD shows that onset of motor paralysis is described by an exponential decay and that motor recovery occurs at a fixed rate. Extent of block to cold and pinprick was similar in both dosage groups in the sitting position (median T4). CONCLUSION: This study shows that in the sitting position, doses less than 75 mg of 5% hyperbaric lidocaine are required to significantly improve ambulatory times.

The effects of nerve growth factor and ganglioside GM1 on the anti-proliferative activity of cocaine in PC12 cells.

The anti-proliferative activity of cocaine was determined in PC12 phenochromocytoma cells. The effects of nerve growth factor (NGF) and ganglioside GM1 (GM1) on the toxicity of this stimulant of abuse was examined over a period of 72 h. Cocaine (40 microM-320 microM) exhibited a dose-dependent inhibition of cellular proliferation as determined by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) reduction. While NGF (100 ng/ml) and GM1 (100 microM) alone partially reversed the cocaine-induced inhibition of proliferation, the combination of NGF and GM1 afforded additional protection that was greater than that of either agent individually.

A PCR-based marker tightly linked to the nematode resistance gene, Mi, in tomato.

A PCR-based codominant marker has been developed which is tightly linked to Mi, a dominant genetic locus in tomato that confers resistance to several species of root-knot nematode. DNA from tomato lines differing in nematode resistance was screened for random amplified polymorphic DNA markers linked to Mi using decamer primers. Several markers were identified. One amplified product, REX-1, obtained using a pair of decamer primers, was present as a dominant marker in all nematode-resistant tomato lines tested. REX-1 was cloned and the DNA sequences of its ends were determined and used to develop 20-mer primers. PCR amplification with the 20-mer primers produced a single amplified band in both susceptible and resistant tomato lines. The amplified bands from susceptible and resistant lines were distinguishable after cleavage with the restriction enzyme Taq I. The linkage of REX-1 to Mi was verified in an F2 population. This marker is more tightly linked to Mi than is Aps-1, the currently-used isozyme marker, and allows screening of germplasm where the linkage between Mi and Aps-1 has been lost. Homozygous and heterozygous individuals can be distinguished and the procedure can be used for rapid, routine screening. The strategy used to obtain REX-1 is applicable to obtaining tightly-linked markers to other genetic loci. Such markers would allow rapid, concurrent screening for the segregation of several loci of interest.

The root-knot nematode resistance gene (Mi) in tomato: construction of a molecular linkage map and identification of dominant cDNA markers in resistant genotypes.

A dominant allele at the Mi locus on chromosome 6 of tomato (Lycopersicon esculentum Mill) confers resistance to three species of root-knot nematodes (Meloidogyne). The resistance, which is associated with a localized necrotic response, was originally introduced into tomato from the wild species Lycopersicon peruvianum. As a step towards the molecular cloning of Mi, we have identified closely linked DNA markers from both cDNA and genomic DNA libraries as restriction fragment length polymorphisms (RFLPs). DNA from tomato populations segregating for nematode resistance was analyzed to generate a high-resolution genetic map of this region. Additional information on gene order was obtained by comparing the size of the introgressed L. peruvianum chromosomal segment within a collection of nematode-resistant tomato lines. Among the four cDNA markers that are tightly linked to Mi, three are dominant, i.e. L. peruvianum-specific. One cDNA marker corresponds to a gene family comprising 20-30 members, one of which is diagnostic for all nematode-resistant genotypes tested. The presence of non-homologous sequences around the Mi gene may contribute to the suppression of recombination in this region of the genome in crosses heterozygous for Mi. The potential of 'walking' from closely linked markers to Mi is discussed.

Molecular transfer of nematode resistance genes.

Recombinant DNA techniques have been used to introduce agronomically valuable traits, including resistance to viruses, herbicides, and insects, into crop plants. Introduction of these genes into plants frequently involves Agrobacterium-mediated gene transfer. The potential exists for applying this technology to nematode control by introducing genes conferring resistance to nematodes. Transferred genes could include those encoding products detrimental to nematode development or reproduction as well as cloned host resistance genes. Host genes that confer resistance to cyst or root-knot nematode species have been identified in many plants. The best characterized is Mi, a gene that confers resistance to root-knot nematodes in tomato. A map-based cloning approach is being used to isolate the gene. For development of a detailed map of the region of the genome surrounding Mi, DNA markers genetically linked to Mi have been identified and analyzed in tomato lines that have undergone a recombination event near Mi. The molecular map will be used to identify DNA corresponding to Mi. We estimate that a clone of Mi will be obtained in 2-5 years. An exciting prospect is that introduction of this gene will confer resistance in plant species without currently available sources of resistance.

Mutations in cell division cycle genes CDC36 and CDC39 activate the Saccharomyces cerevisiae mating pheromone response pathway.

Conditional mutations in the genes CDC36 and CDC39 cause arrest in the G1 phase of the Saccharomyces cerevisiae cell cycle at the restrictive temperature. We present evidence that this arrest is a consequence of a mutational activation of the mating pheromone response. cdc36 and cdc39 mutants expressed pheromone-inducible genes in the absence of pheromone and conjugated in the absence of a mating pheromone receptor. On the other hand, cells lacking the G beta subunit or overproducing the G alpha subunit of the transducing G protein that couples the receptor to the pheromone response pathway prevented constitutive activation of the pathway in cdc36 and cdc39 mutants. These epistasis relationships imply that the CDC36 and CDC39 gene products act at the level of the transducing G protein. The CDC36 and CDC39 gene products have a role in cellular processes other than the mating pheromone response. A mating-type heterozygous diploid cell, homozygous for either the cdc36 or cdc39 mutation, does not exhibit the G1 arrest phenotype but arrests asynchronously with respect to the cell cycle. A similar asynchronous arrest was observed in cdc36 and cdc39 cells where the pheromone response pathway had been inactivated by mutations in the transducing G protein. Furthermore, cdc36 and cdc39 mutants, when grown on carbon catabolite-derepressing medium, did not arrest in G1 and did not induce pheromone-specific genes at the restrictive temperature.

Nucleotide sequence of the yeast cell division cycle start genes CDC28, CDC36, CDC37, and CDC39, and a structural analysis of the predicted products.

The nucleotide sequences of the yeast cell division cycle start genes CDC36, CDC37, and CDC39 are presented. An open reading frame corresponding in size and mapped position to the mRNA for each gene was revealed. These sequences, as well as that of the CDC28 gene, were analyzed for the presence of consensus sequences postulated to be transcriptional or translational signals, or to be involved in mRNA processing. In addition, the predicted protein products of the four genes were subjected to a number of structural and statistical analyses including codon usage bias analysis, secondary structure analysis and hydropathicity analysis.

Four- and five-coordinate species in nickel-reconstituted hemoglobin and myoglobin: Raman identification of the nickel-histidine stretching mode.

Nickel(II)-reconstituted hemoglobin (NiHb) and myoglobin (NiMb) and model Ni porphyrins have been investigated by Soret-resonance Raman difference spectroscopy. Two sets of frequencies for the oxidation-state and core-size marker lines in the region from 1300 to 1700 cm-1 indicate two distinct sites in NiHb. Only one of these sites is evident in the Raman spectra of NiMb. This result is consistent with the UV-visible absorption spectrum of NiHb, which shows two Soret bands at 397 and 420 nm and one Soret at 424 nm for NiMb. Excitation at the blue Soret component of NiHb with 406.7-nm laser radiation preferentially enhances the set of Raman marker lines typical of Ni-protoporphyrin IX [Ni(ProtoP )] in noncoordinating solvents. The wavelength of the blue Soret component and the Raman spectrum indicate four-coordination for this site in NiHb. Laser excitation in the red Soret band enhances a set of lines whose frequencies are compatible with neither four- nor six-coordinate frequencies but are intermediate between the two. The red Soret band of the proteins is also considerably less red shifted than six-coordinate Ni-porphyrin models. These results suggest that Ni in the second site possesses a single axial ligand. Raman spectra of 64Ni-reconstituted and natural abundance Ni-reconstituted hemoglobins, obtained simultaneously in a Raman difference spectrometer, have identified the Ni-ligand stretch at 236 cm-1. The line shifts to 229 cm-1 for the 64Ni-reconstituted Hb. For a pure Ni-ligand stretch a 10-cm-1 shift would be predicted.(ABSTRACT TRUNCATED AT 250 WORDS)