Antioxidant effect of omega-3 fatty acids on exercise-induced oxidative stress in rats

OBJECTIVE

The aim of this study is to examine the effects of omega-3 supplementation on Catalase (CAT) activity, Malondialdehyde (MDA), advanced oxidation protein products (AOPP) and reduced glutathione (GSH) levels in long-term aerobic exercises in rats.

MATERIALS AND METHODS

28 male Wistar albino rats (8 weeks old, 220-350 g body weight) were included in the study. The rats were given treadmill exercise for 20 minutes at an average speed of 15 cm/s, 5 days a week, for 8 weeks. The experiment was terminated at the end of the eighth week. Blood samples were taken. CAT, MDA, AOPP and GSH analyses were performed. SPSS v. 21 package program was used in the analysis of the data. The distribution of the data was examined with the normality homogeneity test, and it was determined that it was a normal distribution. As a result, the One-Way ANOVA test, one of the parametric tests, was used. Tukey test was used to determine the difference between groups. Significance levels were evaluated as (p < 0.05).

RESULTS

Statistical analysis showed a statistically significant difference between groups in CAT, MDA and GSH levels (p < 0.05), while there were no differences between the groups in AOPP levels (p > 0.05).

CONCLUSIONS

In the conclusion of the study, it was determined that omega-3 supplementation caused a decrease in MDA level, an increase in CAT activity and GSH level in rats exposed to chronic long-term exercise. Thus, it can be said that omega-3 supplementation in chronic long-term exercise will provide antioxidant protection against potential oxidative damage.

Efficiency and clinical results of bleomycin injection in the treatment of lymphatic malformations

Background

Lymphatic malformations (LMs) are rare congenital anomalies. The traditional treatment is surgical excision, but intralesional sclerosing agent injection is also preferred as the first-choice treatment because of postoperative frequent recurrences, poor cosmetic results, and high complication rate. We aimed to evaluate the efficacy of sclerosing agent injection used in the treatment of LMs in children.

Materials and Methods

We retrospectively analyzed the children who were treated for LM between January 2011 and January 2022. The lesion sizes of the patients who were injected with sclerosant (Bleomycin) under sedation anesthesia, measured by ultrasound before and after the treatment, were recorded, and the difference between them was statistically evaluated.

Results

Fifteen patients were retrospectively analyzed. The mean age was 45.2 ± 14.1 months. Of these, ten (66.6%) were male and five (33.3%) were female (F/M = 1/2). The mean age of male patients was 55 ± 20.1 months; the mean age of female patients was 25.8 ± 11. Seven patients had a single dose, two had twice, and six had three and more. The mean measurable size of macrocystic lesions before treatment was 55.2 ± 28.4 mm; after treatment, it was 23.8 ± 18.2 mm. Although no measurable shrinkage was detected in microcystic lesions, it was observed that the lesion shrank to allow surgical resection. With the statistical analysis, it was seen that there was a statistically significant difference between the dimensions before and after the treatment (P < 0.05) and the sclerosant injection had a great effect on the treatment (R: 0.89).

Conclusion

Intralesional injection of bleomycin is less effective for microcystic or mixed-type LMs, but provides an effective reduction for a safe surgical procedure. It is an effective treatment for macrocystic lesions.

Effects of curcumin administration on Nesfatin-1 levels in blood, brain and fat tissues of diabetic rats

OBJECTIVE

We evaluated the efficacy of curcumin administration on blood glucose levels and its relationship with nesfatin-1 levels in blood brain and adipose tissue of streptozotocin-induced diabetic rats.

MATERIALS AND METHODS

A total of 28 male rats were divided into four groups: control group, type 2 diabetes mellitus (DM) group, control plus curcumin group and type 2DM plus curcumin group. After fifteen days, blood samples were collected from sacrificed rats. Nesftain-1 levels were analysed from blood, brain, and fat tissues of rats in all groups.

RESULTS

Nesfatin-1 level was found to be significantly lower in blood, brain and fat tissues of type 2 DM rats compared to the control group. A significant decrease in fasting blood glucose levels was observed in the curcumin administration group compared to type 2 DM group. Improvement of fasting blood glucose level was accompanied by improvement of nesfatin-1 levels in blood, brain, and fat tissues.

CONCLUSIONS

As expected, curcumin administration caused significant improvement in fasting blood glucose levels. However, for the first time, we found marked improvements in nesfatin-1 levels in blood, brain, and fat tissues of type 2 DM rats. Thus, considering the crucial role of nesfatin-1 in regulation of glucose metabolism, it is logical to expect an interactive relationship between curcumin and nesfatin-1.

Early Caries in an In Vivo Model: Structural and Nanomechanical Characterization

The utilization of rat models in cariology research has made substantial contributions to decipher mechanisms of caries formation and to develop preventive treatments. The existing rat models still have potential for improvement toward establishing a more accurate standard caries protocol to utilize in testing and/or developing new dental technologies. The current caries-scoring methods rely on optical microscopy-based techniques, which necessitates formation of highly advanced lesions. Moreover, models that facilitate the implementation of cariogenic bacteria by shifting the balance of oral flora through desalivation and/or antibiotic treatment create a nonnatural environment. Furthermore, there is a paucity of detailed structural and mechanical characterization on the resulting carious lesions. The purpose of this study was to develop a rat model that induces formation of mild carious lesions and to provide comprehensive structural and mechanical characterization. With this aim in mind, an in vivo model promoting progression of mild lesions was established with specific pathogen-free Sprague-Dawley rats. Cariogenic bacteria, Streptococcus mutans, was implemented into the oral flora without the use of antibiotics or desalivation surgery. During caries formation, progression of the infection was monitored by quantifying the relative abundance of S. mutans in oral flora with quantitative real-time polymerase chain reaction. A significant increase in colonization efficacy of S. mutans was detected during cariogenic challenge ( P < 0.01). The resulting carious lesions were analyzed by conventional light optical and scanning electron microscopy. A detailed structural and morphological characterization on fissure caries with different degrees of severity was provided. The changes in the morphology and demineralization state of the sound and carious tissues were quantified by energy-dispersive X-ray spectroscopy, and local mechanical properties were acquired with nanoindentation. The principles laid out in this work can be utilized in cariology research and developed into a standard protocol for future studies.

Soluble Klotho levels in diabetic nephropathy: relationship with arterial stiffness

OBJECTIVE

In this cross-sectional study, we investigate the relationship between soluble Klotho (s-Klotho) levels, markers of bone mineral metabolism and arterial stiffness in 109 diabetic nephropathy patients (median age 61.00± 9.77 years) and 32 healthy controls (median age 49.23 ± 7.32 years).

PATIENTS AND METHODS

Blood samples were collected to measure the levels of s-Klotho, and FGF23, serum creatinine, Calcium (Ca), Phosphorus (P), 25-hydroxyvitamin D3 (25hD) and parathyroid hormone (PTH). Pulse wave velocity (PWV) and blood pressure were also measured using a combined monitor.

RESULTS

s-Klotho, FGF23 and PTH levels were significantly higher and 25hD was significantly lower in the patients than in controls (p < 0.001). Systolic blood pressure, pulse pressure and PWV were also significantly higher in the patients (p < 0.001). s-Klotho, FGF23 and 25hD levels significantly varied between sub-groups according to CKD stages, defined according to the CKD epidemiology collaboration equation. A strong positive correlation was found between s-Klotho and FGF23 (r = 0.768, p = 0.001) levels, but not with other bone mineral metabolism, blood pressure or arterial stiffness parameters. Creatinine levels significantly differed (p = 0.009) between three s-Klotho-level sub-groups, with the high creatinine levels in the sub-group with the lowest s-Klotho levels and estimated glomerular filtration rate (eGFR).

CONCLUSIONS

There was no correlation between eGFR and s-Klotho levels. Arterial stiffness increased in CKD but was not related to s-Klotho or FGF23 levels. Among all parameters, FGF23 levels had the greatest effect on s-Klotho levels.

The antioxidant effect of Echinacea angustifolia and Echinacea purpurea in rat colitis model induced by acetic acid

BACKGROUND

Ulcerative colitis is a chronic inflammatory condition of the colon, and reactive oxidative metabolites (ROMs) play an important role in its pathogenesis. Alternative therapies such as herbal remedies are increasingly being used in the treatment of ulcerative colitis for better clinical outcome of ulcerative colitis and less adverse effects. Echinacea has many features including antioxidant and wound-healing properties. Hence, the present study was undertaken to evaluate the protective effect of Echinacea spp. on experimental colitis model induced by acetic acid in Wistar albino rats.

METHODS

Acute colitis was induced by intrarectal administration of acetic acid. Rats were divided into four groups, namely control, Echinacea-administered, Echinacea-administered-colitis and colitis. Malondialdehyde and total antioxidant status were assayed in tissue samples. Histopathological evaluation was also performed.

RESULTS

Macroscopic and microscopic scores were significantly higher in colitis group compared to control, Echinacea and Echinacea-colitis groups (p < 0.001). There was no significant differences in respect of macroscopic and microscopic scores between control, Echinacea and Echinacea-colitis groups (p > 0.3, p > 0.22). Malondialdehyde levels were elevated in colitis group compared to other groups (p < 0.001). Total antioxidant status was significantly higher in Echinacea group compared with other groups and also significantly higher in Echinacea-colitis group compared with colitis group (p < 0.001, p < 0.001, respectively).

CONCLUSION

Echinacea may possibly have some therapeutic usefulness in the management of ulcerative colitis (Tab. 2, Fig. 4, Ref. 35).

Ghrelin prevents the development of dermal fibrosis in bleomycin-induced scleroderma

BACKGROUND

Scleroderma is a chronic inflammatory disease characterized by widespread fibrosis of the skin and the internal organs. Ghrelin is a polypeptide hormone produced by various tissues and inflammatory cells. In experimental studies, ghrelin has been shown to have anti-inflammatory and antioxidant effects, in addition to its metabolic actions.

AIM

To evaluate the potential preventive effects of ghrelin on a mouse model of bleomycin (BLM)-induced scleroderma.

METHODS

This study involved five groups of BALB/c mice (n = 7 in each group). Mice in the control group received 100 μL/day of phosphate-buffered saline (PBS) subcutaneously, while the other four groups were given 100 μg/day of BLM (dissolved in 100 μL PBS) subcutaneously. Three of the BLM-treated groups received intraperitoneal doses (10 ng/kg/day) of acylated, nonacylated or total ghrelin. Animals were killed at the end of the fourth week, and blood and tissue samples were collected for further analysis. Dermal thickness, serum levels of transforming growth factor-β1, numbers of inflammatory cells on the dermal layer and numbers of α-smooth muscle actin-positive cells were determined.

RESULTS

BLM increased dermal thickness, numbers of inflammatory cells on the dermal layer and activity of the myofibroblastic cells. Application of acylated, nonacylated and total ghrelin decreased the infiltration of inflammatory cells and the activity of the myofibroblastic cells, and reduced dermal fibrosis.

CONCLUSIONS

Based on these results, it appears that ghrelin has an antifibrotic action, in addition to the anti-inflammatory and antioxidant effects that have been documented previously. The pathogenic and therapeutic roles of ghrelin in scleroderma should be evaluated by further studies.

Biological response on a titanium implant-grade surface functionalized with modular peptides

Titanium (Ti) and its alloys are among the most successful implantable materials for dental and orthopedic applications. The combination of excellent mechanical and corrosion resistance properties makes them highly desirable as endosseous implants that can withstand a demanding biomechanical environment. Yet, the success of the implant depends on its osteointegration, which is modulated by the biological reactions occurring at the interface of the implant. A recent development for improving biological responses on the Ti-implant surface has been the realization that bifunctional peptides can impart material binding specificity not only because of their molecular recognition of the inorganic material surface, but also through their self-assembly and ease of biological conjugation properties. To assess peptide-based functionalization on bioactivity, the present authors generated a set of peptides for implant-grade Ti, using cell surface display methods. Out of 60 unique peptides selected by this method, two of the strongest titanium binding peptides, TiBP1 and TiBP2, were further characterized for molecular structure and adsorption properties. These two peptides demonstrated unique, but similar molecular conformations different from that of a weak binder peptide, TiBP60. Adsorption measurements on a Ti surface revealed that their disassociation constants were 15-fold less than TiBP60. Their flexible and modular use in biological surface functionalization were demonstrated by conjugating them with an integrin recognizing peptide motif, RGDS. The functionalization of the Ti surface by the selected peptides significantly enhanced the bioactivity of osteoblast and fibroblast cells on implant-grade materials.

Biomimetic Processing of Ceramics and Ceramic-Metal Composites

Biomimetic design and processing of laminated B4C-Al cermets, based on knowledge gained from the microstructure-property characterization of abalone shells, is described. In the nacre section of the shell, the microstructure is highly organized as CaCO3(aragonite) crystals, with a thickness of 0.25 μm, separated by a layer of organic matter 300–500 Å thick. This organization forms a miniature “brick and mortar” microstructure. The resultant strength and fracture toughness of the nacre, i.e., 180 MPa and 7 MPa-m1/2, are many orders of magnitude higher than those of monolithic CaCO3. The processing of laminated B4C-Al cermets, based on the microstructure of the nacre, was performed by a combination of tape casting of the ceramic and infiltration of the metal. The resultant cermets displayed a 40% increase in both fracture toughness and strength over monolithic B4C-Al cermets.

Inorganic Gels with Nanometer-Sized Particles

Fundamental issues involving interactions and packing of nanometer-sized particles are being investigated as an extension of previous experimental studies on larger submicron particles and in relationship to general theoretical work on colloidal systems. Relationships between particle interaction energies and packing indicate (1) dense gels can be formed in stable systems by minimization of the hydrodynamic radius and (2) dense clusters can be formed in flocculated systems by the use of weakly attractive particles where particle restructuring occurs. Novel techniques for the formation of nanostructures within polymeric matrices are also introduced to address gel cracking problems.

Mechanical Properties of Colloidal Gels

A colloidal suspension can be either dispersed or flocculated depending on the interaction between the colloidal particles. If the interaction is repulsive, particles can relax to the minimum of the potential due to their neighboring particles, and the system can reach an equilibrium dispersed state. In the case of attractive interaction, particles form aggregates that settle to the bottom of the container. As the concentration of particles is increased, the overcrowding of the aggregates produces a continuous network throughout the suspension before they settle and a colloidal gel is formed. A major difference between a colloidal gel and a colloidal suspension is that the gel can sustain finite stress and is therefore viscoelastic. Previously we studied the storage modulus and the yield strain of boehmite gels and found that they are related to the particle concentration in a power-law fashion [1]. Similar scaling behavior of the shear modulus was found for other colloidal particulate networks by Buscall et al. [2]. We developed a scaling theory [1] which successfully explains the experimental results on boehmite gels. The theory further predicts that there can be two types of power-law behavior depending on the relative elastic strength of the clusters to that of the links between clusters within the gel network. Furthermore, there can be a crossover from one type of behavior to the other as the particle concentration is varied.

Mechanical Property-Microstructural Relationships in Abalone Shell

The microstructure and mechanical properties of abalone shell were studied. It was found that fracture strength, αf, is 180 MPa, and fracture toughness, KIC, is 7 ± 3 MPa-m1/2; these values are comparable with or better than most “high technology” ceramic materials. The microarchitecture of the nacre section of the red abalone shell is similar to a “brick and mortar” structure, where CaCO3is the brick and organic matter is the mortar, constituting 95% and 5% of the microstructure by volume, respectively. This impressive combination of af and KIcvalues is attributed to the laminated structure of the shell with hard and thick (0.25±0.5 μm) CaCO3and superplastic and thin (20–30 nm) organic components. Although there are several toughening mechanisms operating in the shell, fractographic studies identified sliding of CaCO3layers and bridging by the organic layers to be the most effective ones. These phases also have a strong interface. The results of our experiments are discussed in the context of using abalone shell as a model for the design of synthetic laminates such as cermet (ceramic-metal) and cerpoly (ceramic-polymer) composites.

Synthesis of Ultrafine, Multicomponent Particles Using Phospholipid Vesicles

Because of their unique properties of self-assembly and selective ion permeability across the lipid bilayers, phospholipid vesicles were used as reaction vessels for the synthesis of ultrafine, multicomponent ceramic particles containing Y, Ba, Cu, and Ag. Chemical inhomogeneities in the system were limited to the individual particle size (< 50 nun), which was a considerable improvement over particles prepared using bulk precipitation routes. The consistent barium deficiency was a serious problem that arose when attempting to control the stoichiometry of the multicomponent system. Our experimental evidence suggests that chemical interactions between the barium cations and the vesicleforming phospholipid may inhibit the precipitation of barium salts. In a parallel study, we performed consolidation studies on vesicle-precipitated Ag2O particles before and after the removal of the phospholipid molecules. Particle packing was greatly improved in the surfactant coated particles. This demonstrates the multifunctionality of this biomimetic system in which the vesicle membrane simultaneously acts as: (i) a reaction cell for particle precipitation, (ii) an ion selective membrane that affects precipitation kinetics, (iii) a barrier to prevent spontaneous agglomeration of the ultrafine particles, and (iv) a lubricant/dispersantth atfacilitatesp article rearrangementd uring consolidation.

Nano-Mechanical Properties Across Dentin-Enamel Junction of Adult Human Incisors

The structure and mechanical properties of the dentin-enamel junction (DEJ) in human teeth play a critical role in transferring stress from hard enamel to soft dentin efficiently in order to preserve the longevity of this functionally gradient biocomposite. In this investigation, nano-hardness and elastic modulus of incisor teeth were studied across the dentin-enamel junction. It was found that, over a length scale of between 15 to 25 μm, there were decreasing trends in the values of both hardness and elastic modulus across the DEJ zone profiling from enamel to dentin. Images obtained, using atomic force and scanning electron microscopy techniques, from polished surfaces of cross-sectioned teeth samples showed an interpenetrating microstructure of enamel and dentin at the DEJ zone. These results suggest that the nano-mechanical property profiles across the DEJ were due to a continuous variation in the relative amount of enamel and dentin. These characteristics of the DEJ zone could be significant for describing the structural and mechanical coupling of the two structures. By increasing the interfacial contact area across the two mineralized tissues, stresses are dissipated into the softer dentin, thus reducing interfacial stress concentrations at the DEJ. This promotes effective load transfer from the hard enamel to soft dentin.

Structure and mechanical properties of Ank/Ank mutant mouse dental tissues--an animal model for studying periodontal regeneration

Enamel, dentine and cementum are dental tissues with distinct functional properties associated with their unique hierarchical structures. Some potential ways to repair or regenerate lost tooth structures have been revealed in our studies focused on examining teeth obtained from mice with mutations at the mouse progressive ankylosis (ank) locus. Previous studies have shown that mice with such mutations have decreased levels of extracellular inorganic pyrophosphate (PP(i)) at local sites resulting in ectopic calcification in joint areas and in formation of a significantly thicker cementum layer when compared with age-matched wild-type (WT) tissue [Ho AM, Johnson MD, Kingsley DM. Role of the mouse ank gene in control of tissue calcification and arthritis. Science 2000;289:265-70; Nociti Jr FH, Berry JE, Foster BL, Gurley KA, Kingsley DM, Takata T, et al. Cementum: a phosphate-sensitive tissue. J Dent Res 2002;81:817-21]. As a next step, to determine the quality of the cementum tissue formed in mice with a mutation in the ank gene (ank/ank), we compared the microstructure and mechanical properties of cementum and other dental tissues in mature ank/ank vs. age-matched WT mice. Backscattered scanning electron microscopy (SEM) imaging and transmission electron microscopy (TEM) analyses on mineralized tissues revealed no decrease in the extent of mineralization between ank/ank cementum vs. WT controls. Atomic-force-microscopy-based nanoindentation performed on enamel, dentine or cementum of ank/ank vs. age-matched WT molars revealed no significant difference in any of the tested tissues in terms of hardness and elastic modulus. These results indicate that the tissue quality was not compromised in ank/ank mice despite faster rate of formation and more abundant cementum when compared with age-matched WT mice. In conclusion, these data suggest that this animal model can be utilized for studies focused on defining mechanisms to promote cementum formation without loss of mechanical integrity.

Controlled failure mechanisms toughen the dentino-enamel junction zone

STATEMENT OF PROBLEM

The dentino-enamel junction (DEJ) durably unites dissimilar hard brittle enamel and tough flexible dentin. In contrast to artificial bonds between restorations and dentin, the DEJ rarely fails except when it is affected by inherited disorders. Knowledge of DEJ toughening mechanisms is important in understanding inherited disorders, in biomimetic engineering of junctions between artificial restorations and teeth, and in tissue-engineering a DEJ.

PURPOSE

The purpose of this study was to identify specific DEJ-zone failure mechanisms and to survey the fracture toughness of the human DEJ zone.

MATERIAL AND METHODS

Fracture toughness indentations were made at 3 sites across the DEJ zone of 10 human incisor teeth. Failure modes identified using optical microscopy and fracture toughness (MPa.m(1/2)) were calculated following Vickers microindentation. Site mean values were then calculated and compared using 1-way analysis of variance (alpha=.05).

RESULTS

The DEJ did not undergo catastrophic interfacial delamination; instead, damage was distributed over a broad zone. The primary damage mode involved cracking and damage dispersion in the specialized first-formed enamel close to the DEJ. Multiple, somewhat convoluted and sometimes branching, cracks spread and diffused damage over a wide area of adjacent enamel rather than producing catastrophic interfacial failure. Other secondary mechanisms included short microcracks in the DEJ adjacent dentin with possible cracked bridging, as well as plastic deformation of the DEJ without delamination. A DEJ-zone fracture toughness of approximately 0.8 to 0.9 MPa.m(1/2) was calculated.

CONCLUSION

DEJ-zone damage occurred primarily within the adjacent layer of specialized first-formed enamel, and the optical DEJ interface resisted delamination.

Background subtraction for low-loss transmission electron energy-loss spectroscopy

We present a technique for removing the zero-loss background from electron energy-loss spectra at very low energies (down to approximately 2eV), generating results that are superior in a number of ways to the results of standard Fourier deconvolution techniques. Our technique is based on a separately measured background spectrum which is spline-interpolated and matched to the zero-loss peak in the low-loss spectrum using curve-fit techniques. The data points are weighted with the use of a semi-empirical model of the random error in the data produced by a spectrometer. We demonstrate in tests on real-world data that this model accounts for the random error within the energy range of interest. We discuss practical details of implementation and present detailed comparisons of the results of various algorithms on a piece of test data obtained from a carbon nanotube sample. Compared to the standard techniques, our algorithm tends to be more consistent, less dependent on arbitrary parameters, and better able to quantify spectral features with small signal-to-noise ratios, particularly those at very low energies.

Regulated gene expression dictates enamel structure and tooth function

Enamel is a complex bioceramic tissue. In its final form, enamel is a reflection of the unique molecular and cellular activities occurring during organogenesis. From the ectodermal origins of ameloblasts, their gene activity and protein expression profiles exist for the sole purpose of producing a mineralized shell, almost entirely devoid of protein, deposited over the 'bone-like' dentine. The interface between enamel and dentine is referred to as the dentine enamel junction and it is also unique in its biology. This review article is narrow in its scope. We restrict our review to selected advances in our understanding of the genetic, molecular and structural aspects of enamel biology. We present a model of enamel formation that relates gene expression to the assembly of an extracellular protein matrix that in turn controls the structural hierarchy and mechanical aspects of enamel and the tooth organ.

Biological organization of hydroxyapatite crystallites into a fibrous continuum toughens and controls anisotropy in human enamel

Enamel forms the outer surface of teeth, which are of complex shape and are loaded in a multitude of ways during function. Enamel has previously been assumed to be formed from discrete rods and to be markedly aniostropic, but marked anisotropy might be expected to lead to frequent fracture. Since frequent fracture is not observed, we measured enamel organization using histology, imaging, and fracture mechanics modalities, and compared enamel with crystalline hydroxyapatite (Hap), its major component. Enamel was approximately three times tougher than geologic Hap, demonstrating the critical importance of biological manufacturing. Only modest levels of enamel anisotropy were discerned; rather, our measurements suggest that enamel is a composite ceramic with the crystallites oriented in a complex three-dimensional continuum. Geologic apatite crystals are much harder than enamel, suggesting that inclusion of biological contaminants, such as protein, influences the properties of enamel. Based on our findings, we propose a new structural model.

Enamel biomineralization defects result from alterations to amelogenin self-assembly

Enamel formation is a powerful model for the study of biomineralization. A key feature common to all biomineralizing systems is their dependency upon the biosynthesis of an extracellular organic matrix that is competent to direct the formation of the subsequent mineral phase. The major organic component of forming mouse enamel is the 180-amino-acid amelogenin protein (M180), whose ability to undergo self-assembly is believed to contribute to biomineralization of vertebrate enamel. Two recently defined domains (A and B) within amelogenin appear essential for this self-assembly. The significance of these two domains has been demonstrated previously by the yeast two-hybrid system, atomic force microscopy, and dynamic light scattering. Transgenic animals were used to test the hypothesis that the self-assembly domains identified with in vitro model systems also operate in vivo. Transgenic animals bearing either a domain-A-deleted or domain-B-deleted amelogenin transgene expressed the altered amelogenin exclusively in ameloblasts. This altered amelogenin participates in the formation an organic enamel extracellular matrix and, in turn, this matrix is defective in its ability to direct enamel mineralization. At the nanoscale level, the forming matrix adjacent to the secretory face of the ameloblast shows alteration in the size of the amelogenin nanospheres for either transgenic animal line. At the mesoscale level of enamel structural hierarchy, 6-week-old enamel exhibits defects in enamel rod organization due to perturbed organization of the precursor organic matrix. These studies reflect the critical dependency of amelogenin self-assembly in forming a competent enamel organic matrix and that alterations to the matrix are reflected as defects in the structural organization of enamel.

Chemical peritonitis associated with high dialysate acetaldehyde concentrations

BACKGROUND

During the standard heat sterilization process of lactate-buffered peritoneal dialysis (PD) solutions, glucose degrades to form compounds called glucose degradation products such as acetaldehyde, formaldehyde, or glyoxal. Despite evidence that these products may be responsible for some in vitro cytotoxic effects induced by commercially available PD fluids, data on their acute or chronic effects on the human peritoneum is scarce.

SUBJECTS AND METHODS

This case presentation is based on an observation of 21 aseptic peritonitis cases of unknown aetiology. All cases appeared within one month in a university hospital PD unit that had a peritonitis rate of 1 episode/26 patient months and 55 active patients on CAPD. Acetaldehyde level in the bags was assayed by gas chromatography.

RESULTS

Twenty-one patients presented with signs of peritonitis including cloudy dialysate and abdominal tenderness with additional abdominal pain in 11 patients and vomiting in one. In all cases, cultures and Gram stains were negative for micro-organisms. Fever was not observed in any patient. Average dialysate white blood cell count was 1795/mm(3). All patients were free of intraperitoneal medication when symptoms appeared. Patients were using PD solutions from a newly established domestic production plant. Apparently all patients with symptoms of peritonitis used bags with the same lot number and the solution in the bags appeared to be darker in colour than that in bags with other lot numbers. Chemical analysis of the unused PD solution samples revealed acetaldehyde levels of 17-20 p.p. m. in bags containing darker solution, which is very high compared with the usual acetaldehyde level of 6 p.p.m. in heat-sterilized PD solutions.

CONCLUSIONS

Based on the above findings, we hypothesize that higher levels of acetaldehyde and possibly other glucose degradation products may have been an aetiological factor in these 21 cases of chemical peritonitis. Our observation suggests that acetaldehyde, in concentrations 3-4 times higher than the usual level in commercially available PD solutions, may induce acute sterile peritonitis in CAPD patients.

A genetic analysis of crystal growth

The regulation of crystal morphology by proteins is often observed in biology. It is a central feature in the formation of hard tissues such as bones, teeth and mollusc shells. We have developed a genetic system in the bacterium Escherichia coli to study the protein-mediated control of crystal growth. We have used the crystallization of gold as a model system and found polypeptides that control the morphology of the resulting gold crystals. Analysis of the crystallization process influenced by these polypeptides indicates they act catalytically by an acid mechanism. Our results suggest that the concepts and methods of microbial genetics are general and can be applied to substances not commonly found in biological systems.

Response to triple treatment with omeprazole, amoxicillin, and clarithromycin for Helicobacter pylori infections in continuous ambulatory peritoneal dialysis patients

In this study, the response to triple treatment with omeprazole, amoxicillin, and clarithromycin was investigated in continuous ambulatory peritoneal dialysis (CAPD) patients with Helicobacter pylori (Hp) infections. The study enrolled 20 CAPD patients (11 male, 9 female) who had dyspeptic complaints. The mean age of the patients was 46 (range: 21-65). The study also enrolled, as a control group, 124 patients (66 male, 58 female) who had no systemic disease, but who had upper gastrointestinal endoscopy for dyspeptic complaints. The mean age of the patients in the control group was 47 years (range: 20-74 years). Upper gastrointestinal endoscopy, rapid urease test (CLO test), and direct histologic examination were carried out to detect Hp infection. Hp infection was detected in 10 cases (50%) in the CAPD group and in 53 cases (43%) in the control group. In both groups, patients with Hp infection received the triple treatment of omeprazole 20 mg twice daily for 30 days, amoxicillin 500 mg thrice daily for 15 days, and clarithromycin 500 mg thrice daily for 15 days. To assess response to treatment, upper gastrointestinal endoscopy, CLO test, and direct histologic examination were repeated 3 months after initiation of the treatment. Hp was eradicated in all of the 11 CAPD patients (100%), and in 42 of the control patients (92%). Our results suggest that the triple treatment with omeprazole, amoxicillin, and clarithromycin for Hp infection is as effective in CAPD patients as in the normal population.

Spin-stretching of DNA and protein molecules for detection by fluorescence and atomic force microscopy

We have developed a rapid and efficient way of stretching DNA and denatured protein molecules for detection by fluorescence microscopy and atomic force microscopy (AFM). In the described method, a viscous drag created by transient rotational flow stretches randomly coiled DNA molecules or denatured proteins. Stretching is achieved by dispensing a droplet of sample solution containing DNA or denatured protein on a MgCl2-soaked mica surface. We present fluorescent images of straightened lambdaDNA molecules and AFM images of stress-shared, reduced von Willebrand factor as well as straightened lambdaDNA. The described quick and reliable spin-stretching technique will find wide applications in the analysis of single biopolymer molecules.

Low-loss Electron Energy-loss Spectroscopy and Dielectric Function of Biological and Geological Polymorphs of CaCO(3)

: Previous work on microstructural characterization has shown variations in terms of defects and organization of nanostructures in the two polymorphs of calcium carbonate, calcite, and aragonite in mollusc shells. Large variations in mechanical properties are observed between these sections which have been attributed to variations in composite microstructure as well as intrinsic properties of the inorganic phases. Here we present local low-loss electron energy-loss spectroscopic (EELS) study of calcitic and aragonitic regions of abalone shell that were compared to geological (single-crystal) counterpart polymorphs to reveal intrinsic differences that could be related to organismal effects in biomineralization. In both sets of samples, local dielectric function is computed using Kramer-Kronig analysis. The electronic structures of biogenic and geological calcitic materials are not significantly different. On the other hand, electronic structure of biogenic aragonite is remarkably different from that of geological aragonite. This difference is attributed to the increased contribution from single electron excitations in biogenic aragonite as compared to that of geological aragonite. Furthermore, an apparent bound characteristic of the Re(1/epsilon) is observed for biological samples which suggests a "quasi-plasmon"-like nature of the collective excitations. Implications of these changes are discussed in the context of macromolecular involvement in the making of the microstructures and properties in biogenic phases.

Sharp DNA bends as landmarks of protein-binding sites on straightened DNA

We have developed a fluorescence-based method for mapping single or multiple protein-binding sites on straightened, large-size DNA molecules (> 5 kbp). In the described method, protein-DNA complexes were straightened and immobilized on a flat surface using surface tension. A fraction of the immobilized complexes displayed a sharp DNA bend with two DNA segments extending from the apex. The presence of DNA-binding proteins at the apex was verified by atomic force microscopy. The position of protein binding relative to the ends of the DNA molecule was determined by measuring the length of two DNA segments using fluorescence microscopy. We demonstrate the potential of the fluorescence-based method to localize protein-binding sites on the DNA template and to evaluate relative binding affinity. The proposed protein-binding-site mapping technique is simple and easy to perform. Practical applications include screening for DNA-binding proteins and the localization of protein-binding sites on large segments of DNA.

Neural network model of on-off units in the fly visual system: simulations of dynamic behavior

We analyze the dynamic properties of a neural network model for on-off spiking neurons recorded in the first optic chiasm of the fly visual system. The model consists of two parallel pathways and three sequential processing stages. The first stage models photoreceptors. At the second stage, the signal is segregated into on- and off-pathways. These pathways are proposed to correspond to two populations of amacrine cells. At the third stage, the on- and off-pathways converge to on-off neurons. Furthermore, according to the model, on-off neurons interact via recurrent connections. This stage is proposed to correspond to lamina L4 neurons. In response to luminance increments and decrements, the model exhibits a three-component response and suggests pathways for each of the components. When stimulated by a train of pulses, the model exhibits fast adaptation for frequencies higher than about 5 Hz. Furthermore, adaptation to on- and off-pulses occurs independently. When the frequency of stimulation is reduced, the unit recovers rapidly from its adapted state. The temporal modulation transfer function has its peak around 7 Hz. The phase characteristics show a phase lead for low temporal frequencies changing to a phase lag for high frequencies. These model predictions are compared with data from Jansonius and van Hateren (1991).

An introduction to biomimetics: a structural viewpoint

Biomimetics is a newly emerging interdisciplinary field in materials science and engineering and biology in which lessons learned from biology form the basis for novel technological materials. It involves investigation of both structures and physical functions of biological composites of engineering interest with the goal of designing and synthesizing new and improved materials. This paper discusses microarchitectural aspects of some structural biocomposites, presents microstructural criteria for future materials design and processing, and identifies areas of future research.

Inclined-Field Structure, Morphology, and Pinning of the Vortex Lattice in Microtwinned YBa 2 Cu 3 O 7

A detailed small-angle neutron scattering study of the vortex lattice in a single crystal of YBa(2)Cu(3)O(7) was made for a field of 0.5 tesla inclined at angles between 0 and 80 degrees to the crystalline c axis. The vortex lattice is triangular for all angles, and for angles less than or equal to 70 degrees its orientation adjusts itself to maximize the pinning energy to densely and highly regularly spaced twin planes. These observations have important implications for the microscopic flux-pinning mechanism, and hence for the critical current achievable in YBa(2)Cu(3)O(7). For large angles (about 80 degrees) the vortex lattice consists of independent chains in the orientation predicted by anisotropic London theory.