Risk factors predicting disease severity and mortality in coronavirus disease 2019 Saudi Arabian patients.

CONTEXT: Coronavirus disease 2019 (COVID-19) became a global pandemic that may be associated with significant associated risk factors. AIMS: The aim of this study was to evaluate the factors predisposing risk to death in COVID-19 patients. SETTINGS AND DESIGN: This is a retrospective study that presents the demographic, clinical presentation, and laboratory findings on our patients to determine risk factors contributing to their COVID-19 outcome. METHODS: We used logistic regression (odds ratios) to examine associations between clinical findings and risk of death in COVID-19 patients. All analyses were done using STATA 15. RESULTS: A total of 206 COVID-19 patients were investigated, 28 of them died, and 178 survived. Expired patients were older (74.04 ± 14.45 vs. 55.56 ± 18.41 in those who survived) and mainly of male gender (75% vs. 42% in those who survived). The following factors were strong predictors of death: hypertension (OR: 5.48, 95% CI: 2.10-13.59, P < 0.001), cardiac disease (OR: 5.08, 95% CI: 1.88-13.74, P = 0.001), and hospital admission (OR: 39.75, 95% CI: 5.28-299.12, P < 0.001). In addition, blood group B was more frequent in expired patients (OR: 2.27, 95% CI: 0.78-5.95, P = 0.065). CONCLUSIONS: Our work adds to the current knowledge about the factors predisposing to death in COVID-19 patient. In our cohort, expired patients were of older age and male gender plus they were more likely to have hypertension, cardiac disease, and hospital severe disease. These factors might be used to evaluate risk of death in patients recently diagnosed of COVID-19.

Osteometric assessment of various mandibular morphological traits for sexual dimorphism in Jordanians by discriminant function analysis / Evaluación osteométrica de diversos rasgos morfológicos mandibulares para el dimorfismo sexual en jordanos mediante el análisis de funciones discriminantes

The aim of this study was to analyze the sexual dimorphism in the mandibles of Jordanians and derive a population specific equation for sex prediction. The employed sample comprised 270 cone beam computed tomography (CBCT) images of Jordanians (147 males and 123 females) aged 27-55 years. The images were rendered to 3D surface models, using customized software that provided various views for each mandible, on which measurements made of nine parameters (ramus height, right and left coronoids height, mandibular length, gonial angle, Intergonial breadth, Intercondylar breadth, mental and mandibular foramena) for the analysis of sex identification. The collected data sets were treated statistically using the Statistical Package SPSS version-21. Canonical discriminant function analysis was used to specify a parameter or combination of parameters that best separate the two sexes. Stepwise analysis together with leave-one-out classification procedure was applied (utilizing the Wilks lambda method), which identified six parameters that formed the best combination most precisely predicting sex. It also identified the predictors' coefficients from which a predictive equation for the Jordanian population was derived. The discriminant function group centroid discriminant scores for males and females and the sectioning cut-score were also defined. According to the equation, the function score for any set of measurements that is above the cut score is probably for a male individual whereas a score that was below the cut score is probably for a female subject.

El objetivo de este estudio fue analizar el dimorfismo sexual en las mandíbulas de los jordanos y derivar una ecuación específica de la población para la predicción del sexo. La muestra consistió en 270 imágenes de tomografía computarizada de haz cónico (CBCT) de jordanos (147 hombres y 123 mujeres) con edades entre los 27 y 55 años. Las imágenes se representaron en modelos de superficie 3D, utilizando software personalizado que proporcionó varias imágenes para cada mandíbula, en las que se midieron nueve parámetros (altura de la rama, altura de los procesos coronoides derecho e izquierdo, longitud mandibular, ángulo gonial, amplitud intergonial, amplitud intercondilar y foramen mandibular) para el análisis de la identificación de sexo. Los conjuntos de datos recopilados se trataron estadísticamente utilizando el programa estadístico SPSS versión-21. El análisis de función discriminante canónica se utilizó para especificar un parámetro, o una combinación de parámetros que separaran mejor los dos sexos. Se aplicó el análisis por pasos junto con el procedimiento de clasificación de dejar salir uno (utilizando el método de Wilks lambda), que identificó seis parámetros que formaban la mejor combinación que predecía con mayor precisión el sexo. También se identificó los coeficientes de los predictores a partir de los cuales se obtuvo una ecuación predictiva para la población jordana. Se definieron además, los puntajes discriminantes centroide del grupo para hombres y mujeres, además del puntaje de corte seccional. De acuerdo con la ecuación, el puntaje de la función para cualquier conjunto de medidas que está por encima del puntaje de corte es probablemente para un individuo masculino, mientras que un puntaje que estaba por debajo del puntaje de corte, probablemente era femenino.

Severe aortic regurgitation complicating Takayasu's arteritis.

We present an uncommon case of a 48-year-old female patient with symptomatic presentation of a severe aortic regurgitation with aneurysm of the ascending aorta and progressive dyspnea. Detailed investigation of laboratory tests and imaging identified Takayasu's arteritis (TA) as the underlying etiology. Computed tomography scan revealed complete occlusion of the right carotid artery as well as stenosis at the origins of left subclavian and vertebral arteries. In addition, cardiac magnetic resonance angiogram showed aneurysm at the proximal segment of right subclavian artery. Intervention with corticosteroids effectively diminished the need for immediate surgical intervention. Treating physicians should always consider differential diagnosis of TA in the presence of atypical clinical findings in all patients with cardiac problems especially when there is valve involvement.

Development of a composite resin disclosing agent based on the understanding of tooth staining mechanisms.

OBJECTIVES: To characterize the surface composition of dental enamel and composite resin, assess the ability of dyes with different affinities to stain these surfaces, and use this information to develop a disclosing agent that stains composite resin more than dental enamel. METHODS: One hundred and ten sound extracted teeth were collected and 60 discs of composite resin, 9 mm diameter and 3 mm thick, were prepared. X-ray photoelectron spectroscopy (XPS) was employed to determine the elemental composition on the different surfaces. A tooth shade spectrophotometer was used to assess the change in shade after staining the surfaces with different dyes. RESULTS: XPS analysis revealed that surfaces of both outer dental enamel and composite resin contained relatively high amounts of carbon, specifically hydrocarbons. Both dental enamel and composite surfaces were stainable with the hydrophobic dye (p<0.05); however, the composite resin was stained more than the dental enamel (p<0.05). CONCLUSIONS: The hydrophobic surface of dental enamel and composite resin might explain their high affinity to be stained by food and beverages containing hydrophobic molecules. The composite resin is more stainable by hydrophobic dyes than dental enamel. We used this information to develop an agent for disclosing composite resins that could be used to visualize composite resins that need to be removed. CLINICAL SIGNIFICANCE: Removal of composite resin can be problematic, time consuming and stressful to the dental practitioner. A composite disclosing agent would help the dental practitioner identify the composite resin and facilitate its removal without damaging the adjacent healthy tooth tissues.

Apert Syndrome: Late presentation and treatment challenges.

Apert syndrome is a rare autosomal dominant disorder characterized by craniosynostosis, craniofacial anomalies, and severe symmetrical syndactyly of the hands and feet. Anomalies of the viscera, skeleton and cardiovascular system have also been reported… Untreated craniosynostosis leads to inhibition of brain growth and an increase in intracranial and intraorbital pressure. Most cases are sporadic, resulting from new mutations with a paternal age effect. The prognosis of Apert Syndrome depends on the severity of brain malformation and early surgical interventions. We describe a Sudanese infant with Apert syndrome who presented for the first time at the age of three months and had limited options for intervention.

Hydrogen peroxide whitens teeth by oxidizing the organic structure.

OBJECTIVES: The mechanism of tooth bleaching using peroxide oxidizers is not fully understood. It is unknown whether peroxide radicals make teeth whiter by deproteinizing, demineralizing, or oxidizing tooth tissues. This study was designed to define the mechanism of tooth bleaching and determine which of tooth enamel chemical components is/are affected by bleaching. METHODS: Sixty sound teeth were collected from adult patients. The teeth were divided into 6 equal groups (n=10). Groups 1, 2, 3 and 4 were treated for 4 days with one of the following solutions: deproteinizing (NaOH) that removes organic content, demineralizing (EDTA) that decalcifies the mineral content, oxidizing (H(2)O(2)) and distilled water (control). Group 5 and 6 were pre-treated with either deproteinizing or demineralizing solutions before treating them with oxidizing solutions for 4 days. Changes in enamel elemental ratios, crystallinity index and tooth shade parameters of the treated teeth were examined by means of EDS, Raman spectroscopy and shade-spectrophotometry. The data obtained was analysed with Wilcoxon Signed-Ranks Test, and the statistical significance was set at p<0.05. RESULTS: Tooth deproteinization increased the lightness by 4.8 ± 2.7°, tooth demineralization resulted in 8.5 ± 5.6° decrease in the lightness and tooth oxidization induced 19.9 ± 6.5° increase in the lightness. Oxidization of the deproteinized teeth did not influence shade parameters, but oxidation of the demineralized teeth resulted in 10.7 ± 5.8° increase in the lightness. CONCLUSION: Hydrogen peroxide does not induce significant changes in tooth enamel organic and inorganic relative contents, and it whitens teeth just by oxidizing their organic matrix. These findings are of great clinical significance since they explain the mechanism of tooth bleaching, and help understanding its limitations and disadvantages.

Regulation of enamel hardness by its crystallographic dimensions.

Enamel is a composite biomaterial comprising a minor organic matrix (~2%) and a hierarchically organized inorganic ultrastructure (~96-98%). Surprisingly, to date there is no available information in the literature regarding the possible role of the enamel ultrastructure on the nanoscale level in tooth macroscopic properties. Understanding this relationship is of special interest for restorative purposes in dentistry. Accordingly, this study was designed to investigate how enamel nanocrystals regulate its hardness. We performed microindentation analysis on 100 extracted human teeth. The tooth enamel hardness was quantified and correlated with changes in enamel chemical composition and crystallographic dimensions obtained from Fourier transform infrared spectroscopy and X-ray diffraction, respectively. Enamel hardness was not related to the variability in organic content, but was associated with the size of apatite crystals along the c-axis. This association followed the Hall-Petch model for polycrystalline materials, indicating that the optimal size of apatite nanocrystals (larger than the critical size) provides enamel with the greatest hardness, which enables teeth to survive the heavy wear over a human lifetime.

The role of enamel crystallography on tooth shade.

OBJECTIVES: Tooth shade is influenced by a combination of extrinsic-stains that are adsorbed to the enamel surface and by its intrinsic-shade resulting from the interaction of light with tooth structures. This study was designed to investigate how the variations in enamel ultrastructure may affect tooth optical properties. METHODS: One-hundred extracted teeth were collected from adult patients attending McGill-Undergraduate Dental Clinics. Shade-spectrophotometry, FTIR and XRD were used to assess tooth shade, enamel chemical composition and crystallography. The data obtained was analysed for Pearson correlation analysis and multiple linear regression analysis. The statistical significance was set at P < 0.05. RESULTS: Tooth shade parameters varied dramatically within the studied population. Pearson correlation analysis demonstrated that tooth hue was associated with enamel hydroxyapatite (HA) crystal size (R = -0.358; B = -0.866; P = 0.007), tooth chroma was associated with enamel HA carbonization (R = -0.419; B = -99.06; P = 0.005), and tooth lightness was associated with both enamel HA crystal size (R = -0.313; B = -1.052; P = 0.019) and the degree of HA carbonization (R = -0.265; B=-57.95; P = 0.033). Multiple linear regression analysis demonstrated that the size of enamel HA crystals and the relative content of mineral carbonate were the most important predictors for tooth shade lightness (P = 0.018) and chroma (P=0.008), respectively. In contrast, enamel organic content had no correlation with tooth shade. CONCLUSIONS: In the present study we have revealed that the tooth shade is regulated by the size of their HA enamel crystals. On the other hand, variation in the degree of enamel HA carbonization can also affect the tooth shade. These findings are of great relevance in dentistry since it provides better understanding of tooth aesthetics.

The knowledge and attitude about HIV/AIDS among Jordanian dental students: (Clinical versus pre clinical students) at the University of Jordan.

BACKGROUND: The present study aimed to address the suspected deficiency in the level of understanding of HIV/AIDS among clinical and pre clinical dental students at the University of Jordan. In this cross-sectional study, structured questionnaires were distributed to fifth year dental students (n = 121) and to third year dental students (n = 144) in the academic year 2008/2009. FINDINGS: Significantly higher percentage of fifth-year students compared to third-year students felt that the teaching they received on cross-infection precautions and barrier dentistry was adequate (P < 0.001). Majority (84.2%) of fifth-year students were aware that individual carrying anti-HIV antibodies to be an HIV carrier, only 57.7% of third-year students were aware of this fact (P < 0.001). Majority recognized the association between Kaposi sarcoma, oral candidiasis and hairy leukoplakia with HIV/AIDS but knowledge of the association between HIV/AIDS with less frequent lesions was inadequate.Significantly higher proportion of third-year students compared to fifth-year (39.2% vs. 26.3%) thought that HIV patients should be referred to other centers or support groups for treatment (P = 0.04). CONCLUSIONS: The level of knowledge of Jordanian dental students about HIV and AIDS was generally acceptable; there were inadequacies, however, in their understanding regarding some aspects of AIDS epidemic which demands that dental school curriculum needs some improvement.

Study of the elution of fluconazole from a self-polymerizing acrylic resin and its activity against resistant Candida albicans.

The study aimed, firstly, to monitor the release of an antifungal drug, fluconazole, from a self-polymerizing poly(methyl methacrylate) (PMMA) denture base resin in artificial saliva and comparing it with the release in water; and secondly, to investigate the effect of the released drug on the growth of resistant and standard strains of Candida albicans. A high-performance liquid chromatography-ultra-violet (HPLC-UV) method was used in the analysis of the released eluates into distilled water from self-polymerized PMMA discs doped with the 10% fluconazole antifungal drug. The efficacy of the released drug against resistant and standard strains of C. albicans was monitored, using agar diffusion method. The results showed that fluconazole, can be successfully incorporated with the self-polymerized PMMA. The findings suggest that the drug leaches steadily out of the PMMA resin into artificial saliva and distilled water at mouth temperature and that sustained drug release continued throughout the 28 days test period. It was shown that the released drug demonstrated antifungal activity against both standard and resistant C. albicans. The findings of this investigation have a clinical value in terms of their significant contribution to the treatment of fungal infections of the oral cavity. The sustained release of antifungal drug from the PMMA resin clearly constitutes a new dosage form of the drug via the poly(methyl methacrylate) delivery system.

A new form of intraoral delivery of antifungal drugs for the treatment of denture-induced oral candidosis.

OBJECTIVES: To monitor the release of the antifungal drugs Fluconazole, Chlorhexidine and a combination of the two from an auto-polymerized poly (methyl methacrylate) (PMMA) denture base resin; and to investigate the effect of the released drugs upon the growth of Candida albicans. METHODS: A high performance liquid chromatography-Ultra violet (HPLC-UV) method was used in the analysis of the released drugs into distilled water from PMMA discs doped with the antifungal drugs Fluconazole (10%), Chlorhexidine (10%) and a combination of the two drugs (5% each). The antifungal efficacy of the released drugs was monitored, microbiologically, employing "well" technique on a Saborauds culture medium inoculated with a resistant strain of Candida albicans. RESULTS: It was shown that Fluconazole, Chlorhexidine and the combination of the two drugs can be successfully incorporated with PMMA. It was found that the drugs leach steadily out of the PMMA resin into distilled water at mouth temperature and that sustained drug release continued throughout the 28 days test period. It was also shown that the released drugs demonstrated an antifungal activity against the resistant Candida albicans and this was most remarkable in the combined drugs samples. CONCLUSIONS: The findings of this investigation have a clinical value in terms of their significant contribution to the treatment of fungal infections of the oral cavity. The sustained release of anti-fungal drugs from the PMMA resin clearly constitutes a new dosage form of these drugs via the poly (methyl methacrylate) delivery system.

Prevalence of temporomandibular joint disorders among students of the university of jordan.

BACKGROUND: This study aimed to investigate the prevalence of temporomandibular disorder (TMD) among students of the University of Jordan. METHODS: Information about the symptoms of TMD and the possible risk factors were collected using specifically designed questionnaires. The collected data sets were treated statistically using the SPSS release 14 package. RESULTS: The results of the present investigation showed that pain in or about the ears or cheeks was the most prevalent symptom whereas locking of the temporomandibular joint (TMJ) was the least prevalent. Nearly one-third of the investigated sample (31.4%, 346/1103) had no symptoms of TMD whereas 68.6% (757/1103) had at least one symptom. Students of health science studies had significantly the highest risk in developing TMJ clicking compared to students studying pure science or humanitarian studies. CONCLUSIONS: TMD is of a high prevalence among students of the University of Jordan, particularly among students of health and science studies, which signify the role of stress in the development and/or progression of TMD. The findings of this study are alarming and entailing further investigations to identify risk factors associated with TMD in order to establish measures for prevention and treatment. KEYWORDS: TMD; Clicking; Health sciences; Humanitarian studies.

The effects of disinfectants on dimensional accuracy and surface quality of impression materials and gypsum casts.

BACKGROUND: The study aimed to evaluating the effect of disinfecting impression materials on the dimensional accuracy and surface quality of the resulting casts. METHODS: Impressions of a steel die constructed according to ANSI/ADA specification No.18 were made with each of alginate, addition cured silicone, condensation cured silicone and zinc oxide eugenol paste, and disinfected consequently by each of 0.2% chlorhexidine gluconate, 1% sodium hypochlorite, 2% gluteraldehyde for 5 minutes, and 0.5% sodium hypochlorite for 10 minutes. Dimensions of the disinfected impressions and their resultant casts were measured using a computerized digital caliper, and the dimensional changes were calculated. Reproduction of detail and surface quality of the resultant casts were assessed by grading casts surfaces according to a specific scoring system. RESULTS: The 0.5% sodium hypochlorite was found to produce the least dimensional changes in all the impression materials. Corsodyl produced the maximum changes in both alginate and zinc-oxide eugenol while addition-cured silicon was most affected by Gluteraldehyde and condensation-cured silicon was most affected by Hexana. The dimensional changes, however, were minimal and clinically insignificant. Addition-cured silicon showed the best surface quality and dimensional stability followed by condensation-cured silicon. Alginate and zinc-oxide eugenol had poorer surface quality and were affected to a higher extent by the disinfection procedures. CONCLUSIONS: The results were comparable with the standard specifications for dimensional stability. Recommendations were made for the use of 10 minutes immersion in 0.5% sodium hypochlorite as the most appropriate disinfection protocol to the investigated impression materials. KEYWORDS: Disinfectants; Gypsum casts; Impressions; Alginate; Addition-cured silicone; Sodium hypochlorite.

The relationships of the maxillary central incisors and canines to the incisive papilla in Jordanians.

AIM: The validity of the relationship between the maxillary anterior teeth and the incisive papilla and the pertinence of this relationship to Jordanians was examined. METHODS AND MATERIALS: A computerized digital caliper (CDC) tool was developed and used in the measurements which were made on scanned images of dental casts of 298 Jordanians. The distances from a tangent to the labial surface of the central incisors to the midpoint and the posterior border of the incisive papilla were measured. The tool was also used in marking the exact point on the incisive papilla of the intersection with the line that connected the tips of the maxillary canines. The data sets were analyzed statistically and comparisons among various sets were drawn at a 95% confidence level. RESULTS: Gender had no significant effect on the relationship of the incisive papilla to the maxillary anterior teeth, whereas this relationship was significantly influenced by the incisal classifications of the examined subjects. CONCLUSION: Differences between the Jordanian scores and the Caucasian norms were insignificant. CLINICAL SIGNIFICANCE: Therefore, the guidelines recommended for Caucasians could be used as starting points in the preliminary location of maxillary incisors and canine teeth during construction of dentures for Jordanians.

Comparative electrochemical investigation of the effect of aging on corrosion of dental amalgam.

OBJECTIVE: To investigate corrosion in dental amalgam and evaluate the effects of composition and long-term aging on the alloy's corrosion behavior. METHOD AND MATERIALS: A sample of high-copper and low-copper formulations was employed. Corrosion tests were performed using a 3-electrode polarization cell. Anodic polarization curves were drawn, and the potential and the current density corresponding to the first anodic peak were registered. Scanning electron microscopy was performed, and the different metallurgical phases of the alloy's microstructure were examined and analyzed chemically using an energy-dispersive x-ray technique. The amalgams' corrosion behavior was evaluated at 1 week and after aging in a simulated oral environment for 6 months, 1 year, and 2 years. Data were analyzed using analysis of variance (ANOVA)Scheffe post hoc test at a .05 significance level. RESULTS: The potential values recorded by the high-copper amalgam were higher (P <.05) than those scored by the low-copper alloy. This was attributed to the presence of a tin-mercury, g2, phase in larger quantities in the low-copper amalgam than in the high-copper alloy. For both formulations the potentials increased significantly (P <.05) by about 70 mV after 2 years. This was ascribed to the gradual elimination of the corrosion-susceptible g2 phase and formation of a tin-copper, h, phase, particularly in the high-copper amalgam. CONCLUSION: High-copper amalgam exhibited better resistance to corrosion than the low-copper alloy. Aging in a simulated oral environment improved corrosion behavior for both high- and low-copper amalgams.

Papillon-Lefèvre syndrome with albinism: a review of the literature and report of 2 brothers.

BACKGROUND: Papillon-Lefèvre syndrome (PLS) is a very rare autosomal recessive disorder characterized by palmoplantar hyperkeratosis and severe early onset of destructive periodontitis leading to premature loss of both primary and permanent dentitions. The etiopathogenesis of the condition suggests that there is a genetic basis for susceptibility to specific virulent pathogens. Variation in the clinical presentation of PLS has recently been observed. OBJECTIVE: The objective was to present the first report, which describes the concurrence of PLS and albinism. The etiology, pathology, and management of the condition were reviewed and genetic analysis was performed. SUBJECTS AND CLINICAL PRESENTATION: The probands are Jordanian brothers aged 13 and 20 years on their initial presentation. The parents were second cousins and not affected. The patients exhibited the typical clinical features of PLS with type 1 oculocutaneous albinism (OCA1). They also had increased susceptibility to infection manifested in recurrent tonsillitis, respiratory tract infection, pyoderma, onychogryphosis, and other pathosis. Skin biopsy demonstrated hyperkeratosis, focal parakeratosis, hypergranulosis, and acanthosis. Ectopic calcification of the dura was noticed in one of the probands. Hematological parameters tested were within the normal limits. The probands were tested for mutations in the causative genes of PLS and OCA1, cathepsin C (CTSC), and tyrosinase, respectively. Independent mutations (c.318-1G>A and c.817G>C/p.W272C) were identified in CTSC and tyrosinase, respectively. The probands were homozygous and their sister who had only PLS was homozygous for the same (CTSC) mutation but heterozygous for tyrosinase gene. CONCLUSION: We hope that this report of coinheritance PLS and albinism will initiate further investigations to disclose other possible variations that may enhance our knowledge on gene mutations of this intriguing syndrome.

Durability of acrylic tooth bond to polymeric denture base resins.

The effect of ageing in simulated mouth conditions on bond strength between acrylic teeth and denture base resins was evaluated. Bonding was tested in tension according to ADA specification No. 15. The data was analysed using two-way analysis of variance and Tukey test at P < 0.05. The ageing effect on bond strength became significant after six months of exposure when bonding of acrylic teeth to heat-cured and autopolymerised resins was significantly reduced, P = 0.001 and P = 0.03 respectively. The bond strength value of the autopolymerised resin to acrylic tooth after one year in test environment was half the acceptable value of 31.0 MPa suggested by the ADA specification No. 15, whereas tooth bond strength to heat-cured resin was acceptable even after one year of exposure.

Immunogenicity and safety of a hexavalent meningococcal outer-membrane-vesicle vaccine in children of 2-3 and 7-8 years of age.

To study the reactogenicity and immunogenicity of a hexavalent meningococcal outer-membrane-vesicle vaccine (OMV), two different dosages of this vaccine (7.5 and 15 microg of individual PorA proteins) consisting of vesicles expressing class 1 outer-membrane proteins (OMPs) of subtypes P1.7,16; P1.5,2; P1.19,15 and P1.5(c), 10; P1.12,13; P1.7(h),4 were administered to a group of 7-8 year (n=165) and a group of 2-3 year old children (n=172). Control groups of children with similar ages were vaccinated against hepatitis B. All participants received three injections. Pre- and postimmunisation sera were tested for bactericidal antibodies against six isogenic meningococcal vaccine strains expressing different PorA proteins. Antibody titres against OMP of the two different vesicles (PL16215 and PL10124) were measured by ELISA. The meningococcal hexavalent OMV vaccine was well tolerated. No statistically significant differences were seen between the high and low dose of hexavalent meningococcal OMV vaccine. The percentage of children showing a fourfold increase of bactericidal antibody titres against the specific serosubtype varied in toddlers from 28 to 98% and in older children from 16 to 100%. Both ELISA antibody titres and bactericidal activity showed the highest level in the youngest age-group.

Strand breakage in poly(C), poly(A), single- and double-stranded DNA induced by nanosecond laser excitation at 193 nm.

Single- and double-stranded calf thymus DNA and two polynucleotides (0.4 mM) were studied in aqueous solution at pH approximately 7 using pulsed, 20 ns laser excitation at 193 nm. Monophotonic ionization of the nucleic acids is suggested from the linear dependences of the concentration of ejected electrons and the number of single- and double-strand breaks (ssb, dsb, respectively) on laser intensity (IL) in the range (0.2-3) x 10(6) W cm-2. The quantum yields of formation of hydrated electrons (phi e-) and ssb and dsb (phi ssb and phi dsb) are therefore independent of IL. In contrast, under 248 nm excitation these quantum yields increase linearly with IL under otherwise comparable conditions. Nevertheless, several effects and mechanistic implications are analogous using lambda exc = 193 and 248 nm. For polycytidylic acid, poly(C), in Ar-saturated solution for example, the efficiency of ssb per radical cation (eta RC = phi ssb/phi e-) is similar to the efficiency of ssb per OH radical (eta OH). For polyadenylic acid, poly(A), and single- and double-stranded DNA eta RC (lambda exc = 193 nm) is significantly smaller than eta OH. The ratio phi ssb (N2O)/phi ssb (Ar) is approximately 2 for poly(C), approximately 4 for poly(A) approximately 10 for DNA; the conversion of hydrated electrons into OH radicals in N2O-saturated solution and smaller eta RC than eta OH values in the case of DNA account for these results. For double-stranded DNA phi dsb does not depend on IL but increases linearly with the dose, indicating an accumulative effect of two ssb to generate one dsb. The critical distance for this event is 60-85 phosphoric acid diester bonds.

Single- and double-strand break formation in double-stranded DNA upon nanosecond laser-induced photoionization.

Double-stranded (ds) calf thymus DNA (0.4 mM), excited by 20 ns laser pulses at 248 nm, was studied in deoxygenated aqueous solution at room temperature and pH 6.7 in the presence of a sodium salt (10 mM). The quantum yields for the formation of hydrated electrons (phi c-), single-strand breaks (phi ssb) and double-strand breaks (phi dsb) were determined for various laser pulse intensities (IL). phi c- and phi ssb increase linearly with increasing IL; however, phi ssb has a tendency to reach saturation at high IL (greater than 5 X 10(6) Wcm-2). The ratio phi ssb/phi c-, representing the number of ssb per radical cation, is about 0.08 at IL less than or equal to 5 X 10(6) Wcm-2. For comparison, the number of ssb per OH radical reacting with dsDNA is 0.22. On going from argon to N2O saturation, phi ssb and phi dsb become larger by factors of approximately 5 and 10-15, respectively. This enhancement is produced by attack on DNA bases by OH radicals generated by N2O-scavenging of the photoelectrons. While phi ssb is essentially independent of the dose (Etot), phi dsb depends linearly on Etot in both argon- and N2O-saturated solutions. The linear dependence of phi dsb implies a square dependence of the number of dsb on Etot. This portion of dsb formation is explained by the occurrence of two random ssb, generated within a critical distance (h) in opposite strands. For both argon- and N2O-saturated solutions h was found to be of the order of 40-70 phosphoric acid diester bonds. On addition of electron scavengers such as 2-chloroethanol (or N2O plus t-butanol), phi dsb is similar to that in neat, argon-saturated solutions. Thus, hydrated electrons are not involved in the chemical pathway leading to laser-pulse-induced dsb of DNA.