Surface pretreatment for prolonged survival of cemented tibial prosthesis components: full- vs. surface-cementation technique]

Aseptic loosening of tibial components due to degradation of the interface between bone cement and metallic tibial shaft component is still a persistent problem, particularly for surface-cemented tibial components. The surface cementation technique has important clinical meaning in case of revision and for avoidance of stress shielding. This study was done to prove crack formation in the bone cement near the metallic surface when this is not coated. We propose a newly developed coating process by SiOx-PVD layering to avoid crack formation. A biomechanical model for a vibration fatigue test was done to prove that crack formation can be significantly reduced in the case of coated surfaces. It was found that coated tibial components showed a highly significant reduction of cement cracking near the metal/bone cement interface (p < 0.01) and a significant reduction of gap formation in the metal-to-bone cement interface (p < 0.05). Coating dramatically reduces hydrolytic- and stress-related crack formation at the prosthesis metal/bone cement interface. This leads to a more homogenous load transfer into the cement mantle which should reduce the frequency of loosening in the metal/bone cement/bone interfaces. With surface coating of the tibial component it should become possible that surface-cemented TKAs reveal similar loosening rates as TKAs both surface- and stem-cemented. This would be an important clinical advantage since it is believed that surface cementing reduces metaphyseal bone loss in the case of revision and stress shielding for a better bone health.     

Surface pretreatment for prolonged survival of cemented tibial prosthesis components: full- vs. surface-cementation technique

Background  

One of few persisting problems of cemented total knee arthroplasty (TKA) is aseptic loosening of tibial component due to degradation of the interface between bone cement and metallic tibial shaft component, particularly for surface cemented tibial components. Surface cementation technique has important clinical meaning in case of revision and for avoidance of stress shielding. Degradation of the interface between bone cement and bone may be a secondary effect due to excessive crack formation in bone cement starting at the opposite metallic surface.     

Resorbable PLLA-PGA plate and screw fixation in pediatric craniofacial surgery: clinical experience in 1883 patients

The need to provide rigid bony fixation in the surgical treatment of craniofacial deformities has inspired an on-going evolution of surgical innovations and implants. Because of the young age of many treated craniosynostosis patients and the unique pattern of cranial vault growth, the extensive implantation of metal devices is potentially problematic. The use of resorbable plate and screw devices offers all of the benefits of rigid fixation without many of their potential risks. Since the introduction of resorbable plate and screw devices in 1996, tens of thousands of craniofacial patients have received implants, but long-term results from a large series have yet to be reported. A combined prospective and retrospective analysis was done on 1883 craniosynostosis patients under 2 years of age treated by 12 surgeons from seven different geographic locations over a 5-year period who used the same type of resorbable bone fixation devices (poly-L-lacticpolyglycolic copolymer). Specifically, the incidence of postoperative infection, fixation device failure, occurrence of delayed foreign-body reactions, and the need for reoperation resulting from device-related problems were determined. Technical difficulties and trends in device use were also noted. From this series, significant infectious complications occurred in 0.2 percent, device instability primarily resulting from postoperative trauma occurred in 0.3 percent, and self-limiting local foreign-body reactions occurred in 0.7 percent of the treated patients. The overall reoperation rate attributable to identifiable device-related problems was 0.3 percent. Improved bony stability was gained by using the longest plate geometries/configurations possible and bone grafting any significant gaps across plated areas that were structurally important. The specific types of plates and screws used evolved over the study period from simple plates, meshes, and threaded screws to application-specific plates and threadless push screws whose use varied among the involved surgeons. This report documents the safety and long-term value of the use of resorbable (LactoSorb) plate and screw fixation in pediatric craniofacial surgery in the infant and young child. Device-related complications requiring reoperation occurred in less than 0.5 percent of the implanted patients, which is less frequent than is reported for metallic bone fixation. Resorbable bone fixation for the rapidly growing cranial vault has fewer potential complications than the traditional use of metal plates, screws, and wires.     

Impact of novel coronavirus disease (COVID-19) lockdown on ambient air quality of Saudi Arabia

The outbreak of COVID-19 has spread globally affecting human activities but with improvement in ambient air quality. The first case of the virus in the Kingdom of Saudi Arabia was on the 2nd of March 2020. The impact of COVID-19 lockdown on the ambient air quality of the Kingdom of Saudi Arabia for the first time using data from nine cities was determined in this study. Hourly air quality data, based on concentrations of carbon monoxide (CO), particulate matter (PM₁₀), sulfur dioxide (SO₂), nitrogen dioxide (NO₂) and ozone (O₃), and meteorological conditions (atmospheric temperature, relative humidity, and wind speed) of the nine cities studied were obtained from Saudi Arabian General Authority of Meteorology and Environmental Protection (GAMEP), for the period between January 2019 to May 2020. Significant variation (p < 0.05) was recorded for the five atmospheric pollutants across the cities before and during the lockdown, with lower concentrations during the lockdown except for the concentration of O₃ in Tabuk, Al Qasim, and Haql. This can be a result of NO and O₃ reaction, causing the inability of effective O₃ depletion. The percentage changes in concentrations of CO (33.60%) and SO₂ (44.16%) were higher in Jeddah; PM₁₀ (91.12%) in Riyadh, while NO₂ (44.35%) and O₃ (18.98%) were highest in Makkah. However, even though there was a decrease in pollutants concentrations during the lockdown, the concentrations for CO, PM₁₀, SO₂, NO_2, and O₃ were still above WHO 24 h and annual mean limit levels. The COVID-19 lockdown in the Kingdom of Saudi Arabia revealed the possibility of significant atmospheric pollutant reduction by controlling traffic, activities by industries, and environmentally friendly transportation programs such as green commuting programs.     

Impact of Chronic Periodontitis on Levels of Glucoregulatory Biomarkers in Gingival Crevicular Fluid of Adults with and without Type 2 Diabetes

The relationship between diabetes and periodontal disease is bidirectional, but information about the effect of chronic periodontitis on the levels of the glucoregulatory biomarkers locally in gingival crevicular fluid (GCF) is limited. The aim of this study was to compare the levels of 10 glucoregulatory biomarkers in GCF, firstly in subjects with type 2 diabetes (T2DM) presenting with and without chronic periodontitis and secondly, in subjects without diabetes, with and without chronic periodontitis. The material comprised a total of 152 subjects, stratified as: 54 with T2DM and chronic periodontitis (G1), 24 with T2DM (G2), 30 with chronic periodontitis (G3) and 44 without T2DM or periodontitis (G4). The levels of the biomarkers were measured using multiplex biometric immunoassays. Periodontal pocket depths were recorded in mm. Subsets G1 and G2 and subsets G3 and G4 were compared independently. Among T2DM subjects, GIP, GLP-1 and glucagon were significantly up-regulated in G1 compared to G2. Moreover, there were no statistical differences between the two groups regarding C-peptide, insulin, ghrelin, leptin and PAI-1. Comparisons among individuals without T2DM revealed significantly lower amounts of C-peptide and ghrelin in G3 than in G4. The number of sites with pocket depth ≥ 4mm correlated negatively with C-peptide (Spearman’s correlation co-efficient: -0.240, P < 0.01) and positively with GIP and visfatin (Spearman’s correlation co-efficient: 0.255 and 0.241, respectively, P < 0.01). The results demonstrate that chronic periodontitis adversely influences the GCF levels of glucoregulatory biomarkers, as it is associated with disturbed levels of biomarkers related to the onset of T2DM and its medical complications.     

Production of surfactin from <Emphasis Type="Italic">Bacillus subtilis</Emphasis> MZ-7 grown on pharmamedia commercial medium

Background  

Commercial medium (Pharmamedia) was investigated for the production of surfactin by Bacillus subtilis MZ-7. Different media (defined, semi-defined, and complex media) were compared for the production of surfactin after fixing the least influential variables in standardized fermentation conditions. Carbohydrate and nitrogen supplements were also tried to improve production in Pharmamedia.     

Antagonistic activity against nosocomial clinical isolates withBacillus subtilis MZ-7

Antibacterial activities were detected in thirty-six bacteria from six soil samples. One strain designated as Mz-7 produced an inhibitory substance which was active against number of Gram-positive bacteria as well as clinical isolates obtained from a local hospital. Strain Mz-7 was identified asBacillus subtilis by 16S rRNA sequence analysis and standard biochemical tests. Maximum production was observed at mid of stationary phase slightly before sporulation took place. Optimum conditions for growth were standardised. The antibiotic product was purified by chloroform precipitation and detected by polyacrylamide gel electrophoresis and mass spectrometry. It has lipopeptide nature and did not lose its activity on treatment at different pH values, temperatures and enzymes. The pronounce activity against multidrug resistant clinical isolates and the favourable biochemical properties of this antibiotic from the newly isolate strain suggest a new and effective agent against resistance in pathogenic microbes.     

The Sorption of Ketotifen Fumarate by Chitosan

The purpose of this investigation was to determine the mechanism of interaction between ketotifen fumarate and chitosan at different pH values. The specific surface area of chitosan was determined using gas sorption analyzer. The sorption experiments were conducted at pH 7 and 10 using two different particle size ranges of chitosan. The solutions were prepared at constant ionic strength and buffer concentration, with only varying the pH. The rotating bottle method was used for measuring the sorption. The average specific surface areas for the two different particle size ranges of chitosan were found to be 4.56 and 0.74 m²/g. The Langmuir-like equation and a model independent equation were both applied to the sorption experimental data. The extent of ketotifen uptake at pH 7 for small and large particles of chitosan was found to be 1,073 and 2,204 mg/g respectively. While the extent of ketotifen uptake at pH 10 for small and large particles of chitosan was found to be 4 and 11 mg/g respectively. The aforementioned results indicated that sorption of ketotifen fumarate at pH 7 is extremely high compared to pH 10 and that the sorption increases by decreasing the specific surface area of chitosan. Based on the results obtained, the following conclusions were reached. Ketotifen might be absorbed into the bulk structure of chitosan in addition to being adsorbed on the surface and the ability of chitosan to swell at pH 7 has a significant role in increasing its uptake.     

A highly unusual palindromic transmembrane helical hairpin formed by SARS coronavirus E protein

The agent responsible for the recent severe acute respiratory syndrome (SARS) outbreak is a previously unidentified coronavirus. While there is a wealth of epidemiological studies, little if any molecular characterization of SARS coronavirus (SCoV) proteins has been carried out. Here we describe the molecular characterization of SCoV E protein, a critical component of the virus responsible for virion envelope morphogenesis. We conclusively show that SCoV E protein contains an unusually short, palindromic transmembrane helical hairpin around a previously unidentified pseudo-center of symmetry, a structural feature which seems to be unique to SCoV. The hairpin deforms lipid bilayers by way of increasing their curvature, providing for the first time a molecular explanation of E protein's pivotal role in viral budding. The molecular understanding of this critical component of SCoV may represent the beginning of a concerted effort aimed at inhibiting its function, and consequently, viral infectivity.