Graphene-based dental adhesive with anti-biofilm activity

Background

Secondary caries are considered the main cause of dental restoration failure. In this context, anti-biofilm and bactericidal properties are desired in dental materials against pathogens such as Streptococcus mutans. To this purpose, graphene based materials can be used as fillers of polymer dental adhesives. In this work, we investigated the possibility to use as filler of dental adhesives, graphene nanoplatelets (GNP), a non toxic hydrophobic nanomaterial with antimicrobial and anti-biofilm properties.

Results

Graphene nanoplatelets have been produced starting from graphite intercalated compounds through a process consisting of thermal expansion and liquid exfoliation. Then, a dental adhesive filled with GNPs at different volume fractions has been produced through a solvent evaporation method. The rheological properties of the new experimental adhesives have been assessed experimentally. The adhesive properties have been tested using microtensile bond strength measurements (µ-TBS). Biocidal activity has been studied using the colony forming units count (CFU) method. The anti-biofilm properties have been demonstrated through FE-SEM imaging of the biofilm development after 3 and 24 h of growth.

Conclusions

A significantly lower vitality of S. mutans cells has been demonstrated when in contact with the GNP filled dental adhesives. Biofilm growth on adhesive-covered dentine tissues demonstrated anti-adhesion properties of the produced materials. µ-TBS results demonstrated no significant difference in µ-TBS between the experimental and the control adhesive. The rheology tests highlighted the necessity to avoid low shear rate regimes during adhesive processing and application in clinical protocol, and confirmed that the adhesive containing the 0.2%wt of GNPs possess mechanical properties comparable with the ones of the control adhesive.

     

Clays in prebiological chemistry

Summary In this review an attempt is made to highlight the structures and properties of clay that may contribute to a better understanding of the role of clays in chemical evolution. The adsorption of organic molecules on clays has been demonstrated, as has the synthesis of bioorganic monomers in the presence of clays. For instance, amino acids (glycine, aspartic acid, threonine, alanine and others) as well as purines and pyrimidines, have been obtained from CO and NH₃ in the presence of clays at relatively high temperatures (250-325°C). Carbohydrates are also easily derived from formaldehyde at relatively low temperatures (80°C). The oligomerization of biochemical monomers, mediated by clays has also been shown to result in the formation of polymer molecules basic to life. For instance the condensation of amino acyl adenylates at room temperature in the presence of montmorillonite is known to yield polypeptides in discrete ranges of molecular weights with degrees of polymerization up to 56. Clays have also been found to affect the condensation of mononucleotides to oligonucleotides. Although the role of clays in the origin of metabolic pathways has not been demonstrated, it is possible that clays may have played a cooperative role with catalytic peptides in an intermediate stage of prebiological chemistry preceding the emergence of life on this planet.     

The purification of kallikrein from human whole saliva

• 1.1. A quick and simple procedure is described for purifying kallikrein from human whole saliva. The enzyme has been purified about 2700-fold with a yield of approx. 30%.
• 2.2. The procedure is based on the immediate fractionation of saliva by ion exchange chromatography. This is followed by a combination of affinity and high performance liquid chromatography.
• 3.3. The results indicate that another protein component binds to the enzyme at pH 8.0.
• 4.4. The homogeneity of the enzyme has been demonstrated by gel electrophoresis in the absence as well as in the presence of sodium dodecylsulfate.
• 5.5. A mol. wt of 40,100±1800 has been calculated from gel electrophores is experiments.
• 6.6. Sedimentation equilibrium in an analytical ultracentrifuge gave a mol. wt of 39,700.
• 7.7. The amino acid composition has been determined and it confirms that the enzyme has a low isoelectric point.
• 8.8. The presence of tryptophan has been demonstrated by absorption and fluorescence spectroscopy.

     

Acatalasemia in the mouse and other species

Genetic control of the level of blood catalase activity was first demonstrated in 1927. At present, such control has been demonstrated or suggested for nine different species, including man, the most studied. The development of an acatalasemic strain of mice has permitted a wide variety of experimental approaches, including most of those used in humans. Among those approaches which cannot readily be applied to man but have been used in acatalasemic mice are investigations of sensitivity to radiation lethality, mechanism of awareness to radiation, possible use as a model for replacement therapy for inborn errors of metabolism, and catalase in tissues other than erythrocytes. These are described, together with genetic, immunological, and other studies comparable to similar work on acatalasemic humans.This paper was presented at a symposium entitled Genetic Control of Mammalian Metabolism held at The Jackson Laboratory, Bar Harbor, Maine, June 30–July 2, 1969. The symposium was supported in part by an allocation from NIH General Research Support Grant FR 05545 from the Division of Research Resources to The Jackson Laboratory.Work supported by the United States Atomic Energy Commission.     

Genetics and physiology of the rel system of Bacillus subtilis

Summary Stringent factor (ATP:GTP-3 pyrophosphotransferase) has been purified from wild type Bacillus subtilis and it has been shown that guanosine tetra- and pentaphosphate (ppGpp and pppGpp) are synthesized in vitro in the presence of ribosomes, unacylated tRNA and its specific codon, as has been demonstrated in Escherichia coli. relA, the genetic determinant for the stringent factor, has been mapped on the B. subtilis chromosome by transduction and is found between aroD and leu.The relC locus, defined by mutations which were originally selected by resistance to thiostrepton, has been mapped adjacent to spoOH in the order cysA, spoOH, relC, rif.Stringent factor and ribosomes are functional for the in vitro synthesis of (p)ppGpp in early stages of sporulation (up to at least 4 h). This contradicts the findings of other laboratories.     

Heterogeneity of haplotypes among patients with severe Cooley disease in Eastern Sicily

Summary There is a large variation of clinical severity among thalassemic patients in Sicily. A heterogeneous molecular basis has already been demonstrated among the patients presenting with thalassemia intermedia. The same approach, based mostly on linked haplotypes of the gene cluster polymorphisms and in some cases on the demonstration of the molecular defect itself, was used to investigate 55 patients presenting with severe Cooley anemia, all maintained under permanent transfusion regimen. A large heterogeneity was demonstrated in the observed haplotypes, and only a limited overlap with those already found in thalassemia intermedia. It has been noted that many of the patients are compound heterozygotes, the various observed associations making the antenatal diagnosis at the DNA level difficult in the near future.     

Isolation and polyphasic characterization of a novel hyper catalase producing thermophilic bacterium for the degradation of hydrogen peroxide

A newly isolated microbial strain of thermophilic genus Geobacillus has been described with emphasis on polyphasic characterization and its application for degradation of hydrogen peroxide. The validation of this thermophilic strain of genus Geobacillus designated as BSS-7 has been demonstrated by polyphasic taxonomy approaches through its morphological, biochemical, fatty acid methyl ester profile and 16S rDNA sequencing. This thermophilic species of Geobacillus exhibited growth at broad pH and temperature ranges coupled with production of extraordinarily high quantities of intracellular catalase, the latter of which as yet not been reported in any member of this genus. The isolated thermophilic bacterial culture BSS-7 exhibited resistance against a variety of organic solvents. The immobilized whole cells of the bacterium successfully demonstrated the degradation of hydrogen peroxide (H₂O₂) in a packed bed reactor. This strain has potential application in various analytical and diagnostic methods in the form of biosensors and biomarkers in addition to applications in the textile, paper, food and pharmaceutical industries.     

Metabolism of alkylbenzenes, alkanes, and other hydrocarbons in anaerobic bacteria

Aromatic and aliphatic hydrocarbons are the main constituents of petroleum and its refined products. Whereas degradation of hydrocarbons by oxygen-respiring microorganisms has been known for about a century, utilization of hydrocarbons under anoxic conditions has been investigated only during the past decade. Diverse strains of anaerobic bacteria have been isolated that degrade toluene anaerobically, using nitrate, iron(III), or sulfate as electron acceptors. Also, other alkylbenzenes such as m-xylene or ethylbenzene are utilized by a number of strains. The capacity for anaerobic utilization of alkylbenzenes has been observed in members of the -, -, - and -subclasses of the Proteobacteria. Furthermore, denitrifying bacteria and sulfate-reducing bacteria with the capacity for anaerobic alkane degradation have been isolated, which are members of the - and -subclass, respectively. The mechanism of the activation of hydrocarbons as apolar molecules in the absence of oxygen is of particular interest.The biochemistry of anaerobic toluene degradation has been studied in detail. Toluene is activated by addition to fumarate to yield benzylsuccinate, which is then further metabolized via benzoyl-CoA. The toluene-activating enzyme presents a novel type of glycine radical protein. Another principle of anaerobic alkylbenzene activation has been observed in the anaerobic degradation of ethylbenzene. Ethylbenzene in denitrifying bacteria is dehydrogenated to 1-phenylethanol and further to acetophenone; the latter is also metabolized to benzoyl-CoA. Naphthalene is presumably activated under anoxic conditions by a carboxylation reaction. Investigations into the pathway of anaerobic alkane degradation are only at the beginning. The saturated hydrocarbons are mostlikely activated by addition of a carbon compound rather than by desaturation and hydration, as speculated about in some early studies. An anaerobic oxidation of methane with sulfate as electron acceptor has been documented in aquatic sediments. The process is assumed to involve a reversal of methanogenesis catalyzed by Archaea, and scavenge of an electron-carrying metabolite by sulfate-reducing bacteria. Among unsaturated non-aromatic hydrocarbons, anaerobic bacterial degradation has been demonstrated and investigated with n-alkenes, alkenoic terpenes and the alkyne, acetylene.     

Estrogen as a Multi-Active Neuroprotective Agent in Traumatic Injuries

In the past decade, research has demonstrated that estrogens role in physiology and development is far more complicated than previously assumed. Among these discoveries, there has been an increased recognition of the impact estrogen has in neurodevelopment, central nervous system physiology, and neuropathophysiology. These observations have led many researchers to consider using estrogen pharmacotherapeutically, at physiologic or supraphysiologic doses, for a variety of injury and toxicity models. In this short review, the effects of estrogen as an anti-apoptotic agent, as an anti-oxidant, and as an anti-inflammatory agent are discussed. Finally, the possibility of using estrogen as a neuroprotectant in neurotrauma is addressed.Special issue dedicated to Dr. Lawrence F. Eng.     

A new highly polymorphic marker in the 5' untranslated region of HLA-F shows strong allelic association with haemochromatosis

The 5 untranslated region of HLA-F contains a polypurine tract comprising repeats of tri- and hexa-nucleotide motifs. We have recently demonstrated that this polypurine tract is highly polymorphic by using the polymerase chain reaction. Here, we demonstrate that some of the alleles can be explained by a deletion of approximately 100 by DNA and show that alleles of this novel, highly polymorphic locus are as strongly associated with haemochromatosis as HLA-A3 or D6S105-8. The observed frequency of heterozygosity at HLA-RF is extremely high (95%) and this locus has been found to be informative in pedigrees that are non-informative at HLA-A and D6S105. We also show an example of replication slippage at HL,A-F in one pedigree.     

Sex-linked erythrocyte antigens of the domestic pig

It has been demonstrated that the domestic pig has a blood group systems whose haplotypes (complex alleles) are formed by at least three closely linked loci that are located, like the MIC2 locus of human blood group systems, in the homologous region of sex chromosomes.     

Immunohistochemistry in the analysis of mouse aggregation chimaeras

Summary We have used cellular mosaicism in chimaeric mice to study the clonal organization of normal tissues. The mosaicism has been demonstrated in sections and in whole mounts of intestinal epithelium, aortic endothelium and retinal pigment epithelium using H2 antigens and a carbohydrate polymorphism recognized byDolichos biflorus lectin as strain-specific markers.The results show that the epithelium of each adult intestinal crypt is derived from a single progenitor cell. Because crypts of differing genotype may contribute cells to the same villus, the pathways of cell migration up the villi can be demonstrated. The ability to stain mosaic patches in two dimensions in large intact sheets of epithelium has permitted a more satisfactory analysis in terms of clonal development than was previously possible with data from tissue sections. We have adapted statistical procedures from plant ecology to examine the scale of clustering of patches of like genotype, and thence to recognize descendent clones, i.e. groups of cells which are not contiguous, but are related by descent from a common ancestor in embryogenesis.The 1985Histochemical Journal Lecture given by Dr Ponder at York on 10 July, 1985 at the invitation of the Royal Microscopical Society.     

The demonstration of acid phosphatase in cultured 3T3 mouse cells

Summary Acid phosphatase has been demonstrated ultrastructurally in 3T3 and SV40-3T3 mouse cells using sodium -glycerophosphate and p-nitrophenyl phosphate as substrate. The former substrate only demonstrates the enzyme in lysosomes and elements of the Golgi apparatus while the latter demonstrates it in the cisternae of the endoplasmic reticulum and in the cell surface as well as at lysosomal sites. The significance of surface acid phosphatase activity is discussed in terms of sublethal autolysis.     

Phenotypic effects of genetic variability in human clock genes on circadian and sleep parameters

Circadian rhythms and sleep are two separate but intimately related processes. Circadian rhythms are generated through the precisely controlled, cyclic expression of a number of genes designated clock genes. Genetic variability in these genes has been associated with a number of phenotypic differences in circadian as well as sleep parameters, both in mouse models and in humans. Diurnal preferences as determined by the selfreported Horne-Östberg (HÖ) questionnaire, has been associated with polymorphisms in the human genes CLOCK, PER1, PER2 and PER3. Circadian rhythm-related sleep disorders have also been associated with mutations and polymorphisms in clock genes, with the advanced type cosegrating in an autosomal dominant inheritance pattern with mutations in the genes PER2 and CSNK1D, and the delayed type associating without discernible Mendelian inheritance with polymorphisms in CLOCK and PER3. Several mouse models of clock gene null alleles have been demonstrated to have affected sleep homeostasis. Recent findings have shown that the variable number tandem polymorphism in PER3, previously linked to diurnal preference, has profound effects on sleep homeostasis and cognitive performance following sleep loss, confirming the close association between the processes of circadian rhythms and sleep at the genetic level.     

Body rate decoupling using haltere mid-stroke measurements for inertial flight stabilization in Diptera

Halteres, the modified rear wings of Diptera, have long been recognized as sensory organs necessary for basic flight stability. These organs, which act as vibrating structure gyroscopes, are known to sense strains proportional to Coriolis accelerations. While compensatory responses have been demonstrated that indicate the ability of insects to distinguish all components of the body rate vector, the specific mechanism by which the halteres are able to decouple the body rates has not been clearly understood. The research documented in this report describes a potential mechanism, using averaged strain and strain rate at the center of the haltere stroke, to decouple the inertial rate components. Through dynamic simulation of a nonlinear model of the haltere 3-dimensional trajectory, this straightforward method was demonstrated to provide an accurate means of generating signals that are proportional to three orthogonal body rate components. Errors associated with residual nonlinearity and rate-coupling were quantified for a bilaterally reconstructed body rate vector over a full range of pitch and yaw rates and two roll rate conditions. Models that are compatible with insect physiology are proposed for performing necessary signal averaging and bilateral processing.

Conservation of the COP9/signalosome in budding yeast

Background

Variation at the PPARG locus may influence susceptibility to type 2 diabetes and related traits. The Pro12Ala polymorphism may modulate receptor activity and is associated with protection from type 2 diabetes. However, there have been inconsistent reports of its association with obesity. The silent C1431T polymorphism has not been as extensively studied, but the rare T allele has also been inconsistently linked to increases in weight. Both rare alleles are in linkage disequilibrium and the independent associations of these two polymorphisms have not been addressed.

Results

We have genotyped a large population with type 2 diabetes (n = 1107), two populations of non-diabetics from Glasgow (n = 186) and Dundee (n = 254) and also a healthy group undergoing physical training (n = 148) and investigated the association of genotype with body mass index. This analysis has demonstrated that the Ala12 and T1431 alleles are present together in approximately 70% of the carriers. By considering the other 30% of individuals with haplotypes that only carry one of these polymorphisms, we have demonstrated that the Ala12 allele is consistently associated with a lower BMI, whilst the T1431 allele is consistently associated with higher BMI.

Conclusion

This study has therefore revealed an opposing interaction of these polymorphisms, which may help to explain previous inconsistencies in the association of PPARG polymorphisms and body weight.     

Adaptation of <Emphasis Type="Italic">Lactobacillus acidophilus</Emphasis> to Thermal Stress Yields a Thermotolerant Variant Which Also Exhibits Improved Survival at pH 2

Loss in probiotic viability upon exposure to stressful storage and transport conditions has plagued the probiotic market worldwide. Lactobacillus acidophilus is an important probiotic that is added to various functional foods. It is known to be fairly labile and susceptible to temperature variations that it encounters during processing and storage which increases production cost. It has been repeatedly demonstrated that pre-exposure to sub-lethal doses of stress, particularly, temperature and pH, leads to improved survival of various probiotics when they subsequently encounter the same stress of a much greater magnitude. Attempts to adapt L. acidophilus to temperatures as high as 65 °C to arrive at a thermotolerant variant have not been reported previously. To improve viability at elevated temperatures, we gradually adapted the L. acidophilus NCFM strain to survival at 65 °C for 40 min. Following adaptation, the variant showed a 2-log greater survival compared to wild-type at 65 °C. Interestingly, this thermotolerant variant also demonstrated a 2-log greater stability compared to wild-type at pH 2.0. The improved pH and temperature stress tolerance exhibited by this variant remained unaltered even when the strain was lyophilized. Moreover, the thermotolerant variant demonstrated improved stability compared to wild-type when stored for up to a week at 37 and 42 °C. Probiotic properties of the variant such as adherence to epithelial cells and antibacterial activity remained unaltered. This strain can potentially help address the issue of significant loss in viable cell counts of L. acidophilus which is typically encountered during probiotic manufacture and storage.     

Improving the efficiency of evolutionary de novo peptide design: strategies for probing configuration and parameter settings

Evolutionary molecular design based on genetic algorithms (GAs) has been demonstrated to be a flexible and efficient optimization approach with potential for locating global optima. Its efficacy and efficiency are largely dependent on the operations and control parameters of the GAs. Accordingly, we have explored new operations and probed good parameter setting through simulations. The findings have been evaluated in a helical peptide design according to "Parameter setting by analogy" strategy; highly helical peptides have been successfully obtained with a population of only 16 peptides and 5 iterative cycles. The results indicate that new operations such as multi-step crossover-mutation are able to improve the explorative efficiency and to reduce the sensitivity to crossover and mutation rates (CR-MR). The efficiency of the peptide design has been furthermore improved by setting the GAs at the good CR-MR setting determined through simulation. These results suggest that probing the operations and parameter settings through simulation in combination with "Parameter setting by analogy" strategy provides an effective framework for improving the efficiency of the approach. Consequently, we conclude that this framework will be useful for contributing to practical peptide design, and gaining a better understanding of evolutionary molecular design.     

Control and manipulation of gene expression during tomato fruit ripening

Ripening is a complex developmental process involving changes in the biochemistry, physiology and gene expression of the fruit. It is an active process characterised by changes in all cellular compartments. cDNA cloning has been used as an approach to analyse changes in gene expression during fruit ripening. This has revealed that several genes are switched on specifically during fruit ripening, including one encoding polygalacturonase (PG), a major cell wall protein. These cDNA clones have been used to study the expression of the genes in normal and ripening mutant fruits, and under environmental stress conditions.The PG gene has been isolated and it has been demonstrated that 1450 bases 5 of the coding region are sufficient for the tissue- and development-specific expression of a bacterial marker gene in transgenic tomatoes. Antisense RNA techniques have been developed to generate novel mutant tomatoes in which the biochemical function of this enzyme and its involvement in fruit softening has been tested.