Direct observation of atomic scale surface relaxation in ortho twin structures in GaAs by XSTM

We have studied the (110) GaAs surface of a structure containing ortho twins by cross-sectional scanning tunnelling microscopy and we have compared the experimental results with ab initio density functional theory calculations and STM simulations. Both experimentally and theoretically we find that the surface of different twin crystallites are significantly displaced with respect to each other, parallel to the twin boundary. This result is explained by a surface relaxation of the atoms in the (110) GaAs surface and the difference between the atomic configuration of the ortho twins.

Review of the first 1502 cases of ECG-ST waveform analysis during labour in a teaching hospital

OBJECTIVE

To assess the impact of introduction of the STAN monitoring system.

STUDY DESIGN

Prospective observational study.

SETTING

Tertiary referral labour ward, St George's Hospital, London.

POPULATION

High-risk term pregnancies.

METHODS

We report all consecutive cases of intrapartum monitoring using the STAN S 21 fetal heart monitor. Cases with adverse neonatal outcome were evaluated in relation to the ST waveform analysis and cardiotocography (CTG).

MAIN OUTCOME MEASURES

Cord artery metabolic acidosis, neonatal encephalopathy (NNE) and reasons behind cases with poor outcome.

RESULTS

Between 2002 and 2005, there were 1502 women monitored by STAN. Based on combined STAN analysis in the 1502 women, action was indicated in 358 women (23.8%), while in 1108 women (73.8%) no action was indicated. Traces were not interpretable in 36 women (2.4%). Of the 836 cases (55.7%) where cord blood gases were available, there were 23 cases (2.8%) of metabolic acidosis and 16 of these (70%) were identified by STAN. Overall, there were 14 cases of NNE monitored by STAN. Retrospective analysis of these highlights human errors, such as poor CTG interpretation, delay in taking appropriate action and not following the guidelines.

CONCLUSIONS

Our experience suggests the need for more intense training on interpretation of CTG and strict adherence to guidelines.

The Effect of Miswak Extract on Plaque pH

The aim of this study was to document changes in plaque pH when an acidic challenge was followed by rinsing with miswak extract (Salvadora persica), and to evaluate the effect of miswak rinse on parotid gland secretion rate. Plaque pH was measured in 3-day-old plaque using the microtouch electrode. Rinsing with miswak extract, compared with water rinsing, resulted in protracted elevation of plaque pH (>6.0). The difference in plaque pH between miswak extract and water rinse was statistically significant at 30 min (p < 0.001). Rinsing with miswak extract stimulated parotid gland secretion (p < 0.01). In conclusion, miswak extract raised the plaque pH, suggesting a potential role in caries prevention.

The importance of coherence length in laser phototherapy of gingival inflammation—a pilot study

The aim of this study was to investigate if coherence length is of importance in laser phototherapy. Twenty patients with moderate periodontitis were selected. After oral hygiene instructions, scaling and root planing (SRP), one side of the upper jaw was randomly selected for HeNe (632.8 nm, 3 mW) or InGaAlP (650 nm, 3 mW) laser irradiation. One week after SRP, the following parameters were measured: pocket depth, gingival index, plaque index, gingival crevicular fluid volume, matrix metalloproteinase (MMP-8), interleukin (IL-8) and subgingival microflora. The irradiation (180 s per point, energy 0.54 J) was then performed once a week for 6 weeks. At the follow up examination, all clinical parameters had improved significantly in both groups. A more pronounced decrease of clinical inflammation was observed after HeNe treatment. MMP-8 levels were considerably reduced on the HeNe side, while there was no difference for IL-8 or microflora. Coherence length appears to be an important factor in laser phototherapy.

Cathodoluminescence studies of nanostructured semiconductors

Spatially and spectrally resolved cathodoluminescence in the scanning electron microscope is a very powerful technique for studying the optical properties of semiconductor structures, especially low-dimensional structures (structures with nanometre-sized features). The technique is generally nondestructive and can be combined with the normal imaging capabilities and analysis possibilities of the scanning electron microscope. This article gives an introduction to the technique and a number of examples of the possibilities of the technique.

Hyper-reactive mononuclear cells and neutrophils in chronic periodontitis

OBJECTIVES

Stimulated mono- and polymorphonuclear cells from patients with periodontitis have shown increased release of interleukin-1beta (IL-1beta) and oxygen radicals, respectively. The aim was to study whether this hyper-reactivity could be found both in mono- and polymorphonuclear cells from the same patient, and whether there was a relation to the gene coding for IL-1beta (IL-1beta(+3953)).

MATERIAL AND METHODS

Peripheral mononuclear cells from 14 non-smoking and well-treated patients and pair-matched controls were incubated with opsonized Staphylococcus aureus and lipopolysaccharide (LPS). Released IL-1beta and tumour necrosis factor (TNF)-alpha were determined with ELISA. Generation of oxygen radicals from the Fcgamma-receptor-stimulated neutrophils was measured with chemiluminescence and the polymorphism at IL-1beta(+3953) was measured with polymerase chainreaction.

RESULTS

The mononuclear cells from the patients released more IL-1beta after incubation with LPS (p<0.001) and with bacteria (p<0.05). The release of TNF-alpha tended to be higher in the patient group. The peripheral neutrophils from the patients generated more oxygen radicals (p<0.06). We found no differences between the study groups regarding the IL-1beta(+3953) polymorphism.

CONCLUSION

The similarity in systemic inflammation between patients and controls suggests that the increased release/generation of IL-1beta and oxygen radicals from peripheral leukocytes in periodontitis patients is of a constitutional nature and of pathogenic relevance.

Characteristics of protein-carbohydrate interactions as a basis for developing novel carbohydrate-based antirejection therapies

The relative shortage of human organs for transplantation is today the major barrier to a broader use of transplantation as a means of treating patients with end-stage organ failure. This barrier could be partly overcome by an increased use of blood group ABO-incompatible live donors, and such trials are currently underway at several transplant centres. If xenotransplantation can be used clinically in the future, the human organ shortage will, in principle, be eradicated. In both these cases, carbohydrate antigens and the corresponding anti-carbohydrate antibodies are the major primary immunological barriers to overcome. Refined carbohydrate-based therapeutics may permit an increased number of ABO-incompatible transplantations to be carried out, and may remove the initial barriers to clinical xenotransplantation. Here, we will discuss the chemical characteristics of protein-carbohydrate interactions and outline carbohydrate-based antirejection therapies as used today in experimental as well as in clinical settings. Novel mucin-based adsorbers of natural anti-carbohydrate antibodies will also be described.

Carbohydrate-dependent inhibition of Helicobacter pylori colonization using porcine milk

Breast milk has a well-known anti-microbial effect, which is in part due to the many different carbohydrate structures expressed. This renders it a position as a potential therapeutic for treatment of infection by different pathogens, thus avoiding the drawbacks of many antibiotics. In a previous study, we showed that pigs express the Helicobacter pylori receptors, sialyl Lewis x (Le x) and Le b, on various milk proteins. Here, we investigate the pig breed- and individual-specific expression of these epitopes, as well as the inhibitory capacity of porcine milk on H. pylori binding and colonization. Milk proteins from three different pig breeds were analysed by western blotting using antibodies with known carbohydrate specificity. An adhesion assay was used to investigate the capacity of pig milk to inhibit H. pylori binding to neoglycoproteins carrying Le b and sialyl-di-Le x. alpha1,3/4-fucosyltransferase transgenic FVB/N mice, known to express Le b and sialyl Le x in their gastric epithelium, were colonized by H. pylori and were subsequently treated with Le b- and sialyl Le x-expressing or nonexpressing porcine milk, or water (control) only. The degree of H. pylori colonization in the different treatment groups was quantified. The expression of the Le b and sialyl Le x carbohydrate epitopes on pig milk proteins was breed- and individual specific and correlated to the ability of porcine milk to inhibit H. pylori adhesion in vitro and H. pylori colonization in vivo. Milk from certain pig breeds may have a therapeutic and/or prophylactic effect on H. pylori infection.

The short-term effects of low-level lasers as adjunct therapy in the treatment of periodontal inflammation

OBJECTIVES

The aim of this split-mouth, double-blind controlled clinical trial was to study the effects of irradiation with low-level lasers as an adjunctive treatment of inflamed gingival tissue.

MATERIALS AND METHODS

Seventeen patients with moderate periodontitis were included. After clinical examination, all teeth were scaled and root planed (SRP). One week after SRP, we took samples of gingival crevicular fluid (GCF) and subgingival plaque. The laser therapy was started 1 week later and continued once a week for 6 weeks. One side of the upper jaw was treated with active laser and the other with a placebo. The test side was treated with two low-level lasers having wavelengths of 635 and 830 nm. The patients then underwent another clinical examination with sampling of GCF and plaque. The GCF samples were analysed for elastase activity, interleukin-1beta (IL-1beta) and metalloproteinase-8 (MMP-8). We examined the subgingival plaque for 12 bacteria using DNA probes.

RESULTS

The clinical variables i.e. probing pocket depth, plaque and gingival indices were reduced more on the laser side than on the placebo one (p<0.01). The decrease in GCF volume was also greater on the laser side, 0, 12 microl, than on the placebo side, 0.05 microl (p=0.01). The total amount of MMP-8 increased on the placebo side but was slightly lower on the laser side (p=0.052). Elastase activity, IL-1beta concentration and the microbiological analyses showed no significant differences between the laser and placebo sides.

CONCLUSION

Additional treatment with low-level lasers reduced periodontal gingival inflammation.

Aberrant Neutrophil Reactions in Periodontitis

BACKGROUND

The aim of this study was to compare the activity of neutrophilic granulocytes in patients with severe periodontitis and patients with gingivitis alone.

METHODS

The study population comprised 22 patients with gingivitis and 44 with periodontitis. Samples of gingival crevicular fluid (GCF) were collected from untreated patients with gingivitis and from shallow and deep pockets in untreated patients with periodontitis. GCF samples were analyzed for lactoferrin, elastase, matrix metalloproteinase-8 and -9, and collagenolytic activity.

RESULTS

The free elastase activity and the neutrophil activity, estimated as the ratio between elastase and lactoferrin, were significantly higher in the samples from the periodontitis patients. These differences were also observed in shallow pockets in periodontitis patients compared to similar pockets in patients with gingivitis.

CONCLUSION

This study shows higher levels of free elastase in untreated patients with periodontitis, relative to inflammation-matched controls, which may explain the tissue destruction seen in periodontitis.

Carbohydrate phenotyping of human and animal milk glycoproteins

Breast-milk has a well-known anti-microbial effect, which is in part due to the many different carbohydrate structures expressed. This renders it a position as a potential therapeutic for treatment of infection by different pathogens, thus avoiding the drawbacks of many antibiotics. The plethora of carbohydrate epitopes in breast-milk is known to differ between species, with human milk expressing the most complex one. We have investigated the expression of protein-bound carbohydrate epitopes in milk from man, cow, goat, sheep, pig, horse, dromedary and rabbit. Proteins were separated by SDS-PAGE and the presence of carbohydrate epitopes on milk proteins were analysed by Western blotting using different lectins and carbohydrate-specific antibodies. We show that ABH, Lewis (Le)x, sialyl-Lex, Lea, sialyl-Lea and Leb carbohydrate epitopes are expressed mainly on man, pig and horse milk proteins. The blood group precursor structure H type 1 is expressed in all species investigated, while only pig, dromedary and rabbit milk proteins carry H type 2 epitopes. These epitopes are receptors for Helicobacter pylori (Leb and sialyl-Lex), enteropathogenic (H type 1, Lea and Lex) and enterotoxic Escherichia coli (heat-stable toxin; H type 1 and 2), and Campylobacter jejuni (H type 2). Thus, milk from these animals or their genetically modified descendants could have a therapeutic effect by inhibiting pathogen colonization and infection.

Anti-pig antibody adsorption efficacy of {alpha}-Gal carrying recombinant P-selectin glycoprotein ligand-1/immunoglobulin chimeras increases with core 2 {beta}1, 6-N-acetylglucosaminyltransferase expression

We have previously described the construction of a P-selectin glycoprotein ligand-1-mouse immunoglobulin Fc fusion protein, which when transiently coexpressed with the porcine alpha1,3 galactosyltransferase in COS cells becomes a very efficient adsorber of xenoreactive, anti-pig antibodies. To relate the adsorption capacity with the glycan expression of individual fusion proteins produced in different cell lines, stable CHO-K1, COS, and 293T cells producing this fusion protein have been engineered. On alpha1,3 galactosyltransferase coexpression, high-affinity adsorbers were produced by both COS and 293T cells, whereas an adsorber of lower affinity was derived from CHO-K1 cells. Stable coexpression of a core 2 beta1,6 N-acetylglucosaminyltransferase in CHO-K1 cells led to increased alpha-Gal epitope density and improved anti-pig antibody adsorption efficacy. ESI-MS/MS of O-glycans released from PSGL-1/mIgG(2b) produced in an alpha1,3 galactosyl- and core 2 beta1,6 N-acetylglucosaminyltransferase expressing CHO-K1 cell clone revealed a number of structures with carbohydrate sequences consistent with terminal Gal-Gal. In contrast, no O-glycan structures with terminal Gal-Gal were identified on the fusion protein when expressed alone or in combination with the alpha1,3 galactosyltransferase in CHO-K1 cells. In conclusion, the density of alpha-Gal epitopes on PSGL-1/mIgG(2b) was dependent on the expression of O-linked glycans with core 2 structures and lactosamine extensions. The structural complexity of the terminal Gal-Gal expressing O-glycans with both neutral as well as sialic acid-containing structures is likely to contribute to the high adsorption efficacy.

Subgingival plaque microbiota in Saudi Arabians after use of miswak chewing stick and toothbrush

BACKGROUND

The chewing stick, the miswak, is used in many developing countries as the traditional means for oral hygiene. It is prepared from the roots, twigs and stem of Salvadora persica or other alternative local plants.

OBJECTIVES

To compare the effects of the chewing stick miswak (from S. persica) and toothbrush on subgingival plaque microflora among Saudi Arabian individuals. Further, to investigate whether components extracted from S. persica may interfere with the subgingival plaque micro-organisms.

MATERIAL AND METHODS

Fifteen healthy Saudi Arabian male volunteers aged 21-36 years were included in a single-blind, randomized cross-over study. The participants were taught how to use each device properly. Plaque sampling for DNA test was performed at the baseline, 1 week after professional tooth cleaning, and after 3 weeks of either miswak or toothbrush use. Identification and quantification of microbial species were performed by the checkerboard method, using whole genomic, digoxigenin-labelled DNA probes. Inhibition zones around miswak were examined on agar plates with Actinobacillus actinomycetemcomitans and the leukotoxicity of this bacterium was analyzed in a bioassay with macrophages+/-extracts of miswak.

RESULTS

Miswak and toothbrushing had a similar influence on the levels of the subgingival microbiota. However, A. actinomycetemcomitans was significantly more reduced by miswak (p<0.05) than by toothbrushing. These results were supported by our in vitro results which, indicated that extracts from S. persica might interfere with the growth and leukotoxicity of A. actinomycetemcomitans.

CONCLUSIONS

In contrast to toothbrush use, miswak use significantly reduced the amount of A. actinomycetemcomitans in the subgingival plaque.

The short-term effectiveness of non-surgical treatment in reducing protease activity in gingival crevicular fluid from chronic periodontitis patients

OBJECTIVES

The aim of this study was to evaluate the short-term effect of non-surgical periodontal treatment on protease activity in gingival crevicular fluid (GCF) of patients with chronic periodontitis.

MATERIAL AND METHODS

After clinical examination, in which pocket probing depth, probing attachment level, plaque and bleeding indices were recorded, gingival fluid samples from 21 chronic periodontitis patients were collected from gingivitis (GP) and periodontitis (PP) sites with an intracrevicular washing method. Samples were taken in the same way from a group of patients with gingivitis alone (GG). The periodontitis patients received non-surgical periodontal treatment and were re-evaluated 30 days later. We compared elastase and collagenase activities before and after treatment. The former activity was measured with a low-weight substrate (S-2484) and inhibited by alpha-1-antitrypsin. Matrix-metalloproteinase-8 (MMP-8) was measured with an ELISA and collagenolytic activity with fluorescein-conjugated collagen type I as substrate.

RESULTS

All clinical parameters showed a significant improvement after treatment (p<0.05) which was accompanied by a significant reduction in the values of total elastase activity, free elastase, MPP-8 and collagenolytic activity in both GP and PP sites (p<0.05). However, the latter sites continued to have higher levels of MMP-8 and collagenolytic activity than the former ones after treatment. The free elastase activity and the proportion of free elastase in GP and PP samples after treatment remained higher than in untreated GG samples.

CONCLUSION

This study shows that the clinical improvements after non-surgical treatment are accompanied by reductions in protease and neutrophil activities.

Evaluation of various attenuation corrections in lung SPECT in healthy subjects

The effect of increasingly more sophisticated attenuation correction methods on image homogeneity has been studied in seven healthy subjects. The subjects underwent computed tomography (CT), single photon emission computed tomography (SPECT) and transmission computed tomography (TCT) of the thorax region in the supine position. Density maps were obtained from the CT and TCT studies. Attenuation corrections were performed using five different methods: (1) uniform correction using only the body contour; (2) TCT based corrections using the average lung density; (3) TCT based corrections using the pixel density; (4) CT based corrections using average lung density; and (5) CT based corrections using the pixel density. The isolated attenuation effects were assessed on quotient images generated by the division of images obtained using various attenuation correction methods divided by the non-uniform attenuation correction based on CT pixel density (reference method). The homogeneity was calculated as the coefficient of variation of the quotient images (CV(att)), showing the isolated attenuation effects. Values of CV(att) were on average 12.8% without attenuation correction, 10.7% with the uniform correction, 8.1% using TCT map using the average lung density value and 4.8% using CT and average lung density corrections. There are considerable inhomogeneities in lung SPECT slices due to the attenuation effect. After attenuation correction the remaining inhomogeneity is considerable and cannot be explained by statistical noise and camera non-uniformity alone.

Clostridium difficile: prevalence in horses and environment, and antimicrobial susceptibility

REASONS FOR PERFORMING STUDY

Clostridium difficile has been associated with acute colitis in mature horses.

OBJECTIVES

To survey C. difficile colonisation of the alimentary tract with age, occurrence of diarrhoea and history of antibiotic therapy; and to study the occurrence and survival of C. difficile in the environment and antimicrobial susceptibility of isolated strains.

METHODS

A total of 777 horses of different breeds, age and sex were studied. Further, 598 soil samples and 434 indoor surface samples were examined. Antimicrobial susceptibility of 52 strains was investigated by Etest for 10 antibiotics.

RESULTS

In horses that developed acute colitis during antibiotic treatment, 18 of 43 (42%) were positive to C. difficile culture and 12 of these (28%) were positive in the cytotoxin B test. Furthermore, C. difficile was isolated from a small number of diarrhoeic mature horses (4 of 72 [6%]) with no history of antibiotic treatment, but not from 273 healthy mature horses examined or 65 horses with colic. An interesting new finding was that, in normal healthy foals age < 14 days, C. difficile was isolated from 1/3 of foals (16 of 56 [29%]). All older foals (170) except one were negative. Seven of 16 (44%) nondiarrhoeic foals treated with erythromycin or gentamicin in combination with rifampicin were also excretors of C. difficile. On studfarms, 14 of 132 (11%) outdoor soil samples were positive for C. difficile in culture, whereas only 2 of 220 (1%) soil samples from farms with mature horses were positive for C. difficile (P = < 0.001). By PCR, it was demonstrated that strains from the environment and healthy foals can serve as a potential reservoir of toxigenic C. difficile. The experimental study conducted here found that C. difficile survived in nature and indoors for at least 4 years in inoculated equine faeces. The susceptibility of 52 strains was investigated for 10 antibiotics and all were susceptible to metronidazole (MIC < or = 4 mg/l) and vancomycin (MIC < or = 2 mg/l).

CONCLUSIONS

C. difficile is associated with acute colitis in mature horses, following antibiotic treatment. Furthermore, C. difficile was isolated from 1 in 3 normal healthy foals age < 14 days.

POTENTIAL RELEVANCE

Strains from healthy foals and the environment can serve as a potential reservoir of toxigenic C. difficile.

Quantitative assessment of apoptotic and proliferative gingival keratinocytes in oral and sulcular epithelium in patients with gingivitis and periodontitis

BACKGROUND

Periodontal disease is caused by a chronic infection inducing an inflammatory reaction that leads to a breakdown of tooth-supporting tissue. The maintenance of an equilibrium between the host defence and microorganisms in the sulcus is essential to preserve health. All multicellular organisms have mechanisms for killing their own cells, and use physiological cell death for defence, development, homeostasis and ageing. Apoptosis and proliferation are very important phenomena in regulating this and a disturbance is often associated with disease e.g. cancer, AIDS, Alzheimer's disease, rheumatoid arthritis.

OBJECTIVE

The aim of this study was to determine whether the number of apoptotic and proliferative gingival keratinocytes differed between patients with gingivitis and those with periodontitis.

MATERIAL AND METHODS

The distribution of neutrophil elastase, PCNA/cyclin, DNA fragmentation (apoptosis) and p53 was determined with immunocytochemical techniques. We used paraffin-embedded sections from gingival biopsies and did quantitative analyses.

RESULTS AND CONCLUSION

These showed that 5-12% of the keratinocytes in the basal layers of the epithelium proliferated in the two groups. Fewer apoptotic cells were seen in the oral epithelium than in the sulcus in all subjects in both groups. Only in the most apical part of the sulcus, close to the junctional epithelium, did the number of apoptotic keratinocytes exceed the proliferative ones in patients with periodontitis.

Oral health and cardiovascular disease in Sweden

OBJECTIVE

The purpose of the present study was to assess the relation between dental health and cardiovascular disease in an adult Swedish population.

MATERIAL AND METHOD

A questionnaire was sent to 4811 randomly selected Swedes. It contained 52 questions about dental care habits, oral health, cardiovascular disease and their socio-economic situation. Odd ratios for all cardiovascular diseases (CVD) and the subgroup myocardial infarction, stroke and high blood pressure were calculated with a logistic regression model adjusted for age, gender, smoking, income, civil status and education. These ratios were calculated for subjects > or =41 years since few people suffer from CVD before this.

RESULTS

The national questionnaire was answered by 2839 (59%) people between 20-84 years of age and, of them, 1577 were 41 years of age or more. We found a significant association between self-reported bleeding gums (odds ratio 1.60, p=0.0017), presence of dentures (odds ratio 1.57, p=0.0076) and known CVD, which has also been reported in international studies. However, no association between loose teeth, deep pockets and known CVD was detected.

CONCLUSION

The results indicate that oral health and, especially gingival inflammation is associated with CVD.

Role of the glutamyl alpha-carboxylate of the substrate glutathione in the catalytic mechanism of human glutathione transferase A1-1

The Glu alpha-carboxylate of glutathione contributes to the catalytic function of the glutathione transferases. The catalytic efficiency of human glutathione transferase A1-1 (GST A1-1) in the conjugation reaction with 1-chloro-2,4-dinitrobenzene is reduced 15 000-fold if the decarboxylated analogue of glutathione, dGSH (GABA-Cys-Gly), is used as an alternative thiol substrate. The decrease is partially due to an inability of the enzyme to promote ionization of dGSH. The pK(a) value of the thiol group of the natural substrate glutathione decreases from 9.2 to 6.7 upon binding to GST A1-1. However, the lack of the Glu alpha-carboxylate in dGSH raised the pK(a) value of the thiol in the enzymatic reaction to that of the nonenzymatic reaction. Furthermore, K(M)(dGSH) was 100-fold higher than K(M)(GSH). The active-site residue Thr68 forms a hydrogen bond to the Glu alpha-carboxylate of glutathione. Introduction of a carboxylate into GST A1-1 by a T68E mutation increased the catalytic efficiency with dGSH 10-fold and reduced the pK(a) value of the active site bound dGSH by approximately 1 pH unit. The altered pK(a) value is consistent with a catalytic mechanism where the carboxylate contributes to ionization of the glutathione thiol group. With Delta(5)-androstene-3,17-dione as substrate the efficiency of the enzyme is decreased 24 000-fold while with 4-nitrocinnamaldehyde (NCA) the decrease is less than 150-fold. In the latter reaction NCA accepts a proton and, unlike the other reactions studied, may not be dependent on the Glu alpha-carboxylate for deprotonation of the thiol group. An additional function of the Glu alpha-carboxylate may be productive orientation of glutathione within the active site.