Evaluation of In Vitro and In Vivo Antiviral Activities of Vitamin D for SARS-CoV-2 and Variants

The COVID-19 pandemic has brought about unprecedented medical and healthcare challenges worldwide. With the continual emergence and spread of new COVID-19 variants, four drug compound libraries were interrogated for their antiviral activities against SARS-CoV-2. Here, we show that the drug screen has resulted in 121 promising anti-SARS-CoV-2 compounds, of which seven were further shortlisted for hit validation: citicoline, pravastatin sodium, tenofovir alafenamide, imatinib mesylate, calcitriol, dexlansoprazole, and prochlorperazine dimaleate. In particular, the active form of vitamin D, calcitriol, exhibits strong potency against SARS-CoV-2 on cell-based assays and is shown to work by modulating the vitamin D receptor pathway to increase antimicrobial peptide cathelicidin expression. However, the weight, survival rate, physiological conditions, histological scoring, and virus titre between SARS-CoV-2 infected K18-hACE2 mice pre-treated or post-treated with calcitriol were negligible, indicating that the differential effects of calcitriol may be due to differences in vitamin D metabolism in mice and warrants future investigation using other animal models.

Cytopathic Effect (CPE )-Based Drug Screening Assay for SARS-CoV-2

Identification of an effective antiviral for the treatment of COVID-19 is considered one of the holy grails in the bid to end the pandemic. However, the novelty of SARS-CoV-2, along with the little knowledge available about its infection characteristics at the beginning of this pandemic, challenges the scientific world on how one may be able to promptly identify promising drug candidates from a myriad of compound libraries. Here, we describe a cytopathic effect (CPE)-based drug screening assay for SARS-CoV-2 which allows for rapid assessment of drug compound libraries through pre- or posttreatment drug screening procedures and evaluation using a light microscope. By comparing the virus-induced CPE of the drug-treated cells against the vehicle and drug controls, potent drug candidates can be quickly identified for further downstream studies.

Drug repurposing for COVID-19: Approaches, challenges and promising candidates

Traditional drug development and discovery has not kept pace with threats from emerging and re-emerging diseases such as Ebola virus, MERS-CoV and more recently, SARS-CoV-2. Among other reasons, the exorbitant costs, high attrition rate and extensive periods of time from research to market approval are the primary contributing factors to the lag in recent traditional drug developmental activities. Due to these reasons, drug developers are starting to consider drug repurposing (or repositioning) as a viable alternative to the more traditional drug development process. Drug repurposing aims to find alternative uses of an approved or investigational drug outside of its original indication. The key advantages of this approach are that there is less developmental risk, and it is less time-consuming since the safety and pharmacological profile of the repurposed drug is already established. To that end, various approaches to drug repurposing are employed. Computational approaches make use of machine learning and algorithms to model disease and drug interaction, while experimental approaches involve a more traditional wet-lab experiments. This review would discuss in detail various ongoing drug repurposing strategies and approaches to combat the current COVID-19 pandemic, along with the advantages and the potential challenges.

Genetic diversity of the full length apical membrane antigen-1 of Plasmodium knowlesi clinical isolates from Peninsular Malaysia

The Plasmodium knowlesi apical membrane antigen-1 (PkAMA-1) plays an important role in the invasion of the parasite into its host erythrocyte, and it has been regarded as a potential vaccine candidate against human knowlesi malaria. This study investigates genetic diversity and natural selection of the full length PkAMA-1 of P. knowlesi clinical isolates from Peninsular Malaysia. Blood samples were collected from P. knowlesi malaria patients from Peninsular Malaysia. The PkAMA-1 gene was amplified from DNA samples using PCR, cloned into a plasmid vector and sequenced. Results showed that nucleotide diversity of the full length PkAMA-1 from Peninsular Malaysia isolates (π: 0.006) was almost similar to that of Sarawak (π: 0.005) and Sabah (π: 0.004) isolates reported in other studies. Deeper analysis revealed Domain I (π: 0.007) in the PkAMA-1 had the highest diversity as compared to Domain II (π: 0.004) and Domain III (π: 0.003). Z-test indicated negative (purifying) selection of the gene. Combined alignment analysis at the amino acid level for the Peninsular Malaysia and Sarawak PkAMA-1 sequences revealed 34 polymorphic sites. Thirty-one of these sites were dimorphic, and 3 were trimorphic. The amino acid sequences could be categorised into 31 haplotypes. In the haplotype network, PkAMA-1 from Peninsular Malaysia and Sarawak were separated into two groups.

Current Perspective of Antiviral Strategies against COVID-19

COVID-19 was declared a pandemic by the World Health Organization on March 11, 2020. This novel coronavirus disease, caused by the SARS-CoV-2 virus, has resulted in severe and unprecedented social and economic disruptions globally. Since the discovery of COVID-19 in December 2019, numerous antivirals have been tested for efficacy against SARS-CoV-2 in vitro and also clinically to treat this disease. This review article discusses the main antiviral strategies currently employed and summarizes reported in vitro and in vivo efficacies of key antiviral compounds in use.

Non-surgical treatment of knee osteoarthritis

Knee osteoarthritis is one of the most common degenerative diseases causing disability in elderly patients. Osteoarthritis is an increasing problem for ageing populations, such as that in Hong Kong. It is important for guidelines to be kept up to date with the best evidence-based osteoarthritis management practices available. The aim of this study was to review the current literature and international guidelines on non-surgical treatments for knee osteoarthritis and compared these with the current guidelines in Hong Kong, which were proposed in 2005. Internationally, exercise programmes for non-surgical management of osteoarthritis have been proven effective, and a pilot programme in Hong Kong for comprehensive non-surgical knee osteoarthritis management has been successful. Long-term studies on the effectiveness of such exercise programmes are required, to inform future changes to guidelines on osteoarthritis management.

Co-infections of ectoparasite species in synanthropic rodents of western Sarawak, Malaysian Borneo

Little is known regarding infestation of ectoparasites in synanthropic rodents in Sarawak, Malaysia. A total of 44 rodents from three species (Rattus rattus, Rattus tiomanicus and Sundamys muelleri) were trapped from four residential areas in western Sarawak, Malaysia, for ectoparasites screening. A total of 117 ectoparasites from three hard tick species (Ixodes granulatus, Haemaphysalis sp. 1, Haemaphysalis sp. 2), three mesostigmatid mite species (Laelaps echidninus, Laelaps sedlaceki, and Laelaps nuttalli), one trombiculid mite (chigger species), and one louse species (Hoplopleura sp.), were recovered from 32 infected rodents (72.73% infestation). Infestations by multiple ectoparasite species on the same rodent individuals were recorded in R. rattus and R. tiomanicus (28.1%, n=9) in this study, while Sundamys muelleri was only infested with L. echidninus. One R. rattus individual was co-infected with ticks, louse, and mesostigmatid mite. L. echidninus was the generalist ectoparasite species that infected all three rodent species in three of the residential areas studied. Ectoparasite species diversity was significantly different among four residential areas based on Shannon index and diversity t-test (p-value <0.05). This study provides the first record of the association of synanthropic rodents with multiple ectoparasite infections in residential areas of western Sarawak, Malaysia.

Human Coronaviruses: A Review of Virus-Host Interactions

Human coronaviruses (HCoVs) are known respiratory pathogens associated with a range of respiratory outcomes. In the past 14 years, the onset of severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) have thrust HCoVs into spotlight of the research community due to their high pathogenicity in humans. The study of HCoV-host interactions has contributed extensively to our understanding of HCoV pathogenesis. In this review, we discuss some of the recent findings of host cell factors that might be exploited by HCoVs to facilitate their own replication cycle. We also discuss various cellular processes, such as apoptosis, innate immunity, ER stress response, mitogen-activated protein kinase (MAPK) pathway and nuclear factor kappa B (NF-κB) pathway that may be modulated by HCoVs.

Use of activated carbon as a support medium for H2S biofiltration and effect of bacterial immobilization on available pore surface

The use of support media for the immobilization of microorganisms is widely known to provide a surface for microbial growth and a shelter that protects the microorganisms from inhibitory compounds. In this study, activated carbon is used as a support medium for the immobilization of microorganisms enriched from municipal sewage activated sludge to remove gas-phase hydrogen sulfide (H2S), a major odorous component of waste gas from sewage treatment plants. A series of designed experiments is used to examine the effect on bacteria-immobilized activated carbon (termed "biocarbon") due to physical adsorption, chemical reaction, and microbial degradation in the overall removal of H2S. H2S breakthrough tests are conducted with various samples, including microbe-immobilized carbon and Teflon discs, salts-medium-washed carbon, and ultra-pure water-washed carbon. The results show a higher removal capacity for the microbe-immobilized activated carbon compared with the activated carbon control in a batch biofilter column. The increase in removal capacity is attributed to the role played by the immobilized microorganisms in metabolizing adsorbed sulfur and sulfur compounds on the biocarbon, hence releasing the adsorption sites for further H2S uptake. The advantage for activated carbon serving as the support medium is to adsorb a high initial concentration of substrate and progressively release this for microbial degradation, hence acting as a buffer for the microorganisms. Results obtained from surface area and pore size distribution analyses of the biocarbon show a correlation between the available surface area and pore volume with the extent of microbial immobilization and H2S uptake. The depletion of surface area and pore volume is seen as one of the factors which cause the onset of column breakthrough. Microbial growth retardation is due to the accumulation of metabolic products (i.e., sulfuric acid); and a lack of water and nutrient salts in the batch biofilter are other possible causes of column breakthrough.

Volatile organic compound adsorption in a gas-solid fluidized bed

Fluidization finds many process applications in the areas of catalytic reactions, drying, coating, combustion, gasification and microbial culturing. This work aims to compare the dynamic adsorption characteristics and adsorption rates in a bubbling fluidized bed and a fixed bed at the same gas flow-rate, gas residence time and bed height. Adsorption with 520 ppm methanol and 489 ppm isobutane by the ZSM-5 zeolite of different particle size in the two beds enabled the differentiation of the adsorption characteristics and rates due to bed type, intraparticle mass transfer and adsorbate-adsorbent interaction. Adsorption of isobutane by the more commonly used activated carbon provided the comparison of adsorption between the two adsorbent types. With the same gas residence time of 0.79 seconds in both the bubbling bed and fixed bed of the same bed size of 40 mm diameter and 48 mm height, the experimental results showed a higher rate of adsorption in the bubbling bed as compared to the fixed bed. Intraparticle mass transfer and adsorbent-adsorbate interaction played significant roles in affecting the rate of adsorption, with intraparticle mass transfer being more dominant. The bubbling bed was observed to have a steeper decline in adsorption rate with respect to increasing outlet concentration compared to the fixed bed. The adsorption capacities of zeolite for the adsorbates studied were comparatively similar in both beds; fluidizing, and using smaller particles in the bubbling bed did not increase the adsorption capacity of the ZSM-5 zeolite. The adsorption capacity of activated carbon for isobutane was much higher than the ZSM-5 zeolite for isobutane, although at a lower adsorption rate. Fourier transform infra-red (FTIR) spectroscopy was used as an analytical tool for the quantification of gas concentration. Calibration was done using a series of standards prepared by in situ dilution with nitrogen gas, based on the ideal gas law and relating partial pressure to gas concentration. Concentrations up to 220 ppm for methanol and 75 ppm for isobutane were prepared using this method.

Removal of odorous sulphur-containing gases by a new isolate from activated sludge

Biological treatment of odorous sulphur-containing compounds is attracting attention due to its benign eco-friendliness, energy-savings and low operating costs. As the biological treatment efficiency of dimethylsulphide (DMS) reported was often low and variable, selection of useful DMS-degrading microorganisms is of importance for the enhancement of the biological deodorizing process. This paper reports the successful isolation of a DMS-degrading bacterium from activated sludge, using the enrichment isolation technique. The isolate was identified by 16S rRNA gene sequencing, and found to belong to the alpha group of Proteobacteria, with an identity of 99.4% and 99.1% to the 16S rRNA gene sequences of Afipia felis and Pseudomonas carboxydohydrogena, respectively. The isolate was able to metabolize DMS as well as hydrogen sulphide (H2S). A batch experiment was performed to assess the removal characteristics of DMS by the isolate. The results showed that over half of DMS could be removed by the isolate in 3 hours when the initial DMS amount was approximately 10 micromol and 25 micromol. Removal of H2S by the isolate was evaluated by a continuous test in a 2-L gas-bubbling bottle. Although part of the H2S removal by the mineral medium itself was observed in the control test, the majority of H2S removal was believed to be attributed to the metabolic activity of the isolate. In conclusion, the isolate might be potentially useful for the enhancement of the biological deodorizing processes.

Batch experiment on H2S degradation by bacteria immobilised on activated carbons

Biological treatments of odorous compounds, as compared to chemical or physical technologies, are in general ecologically and environmentally favourable. However, there are some inefficiencies relative to the media used in biofiltration processes, such as the need for an adequate residence time; the limited lifetime, and pore blockage of media, which at present render the technology economically non-viable. The aim of the study is to develop novel active media to be used in performance-enhanced biofiltration processes, by achieving an optimum balance and combination of the media adsorption capacity with the biodegradation of H2S through the bacteria immobilised on the media. An enrichment culture was obtained from activated sludges in order to metabolise thiosulphate. Batch-wise experiments were conducted to optimise the bacteria immobilisation on activated carbon, so as to develop a novel "biocarbon". Biofilm was mostly developed through culturing the bacteria with the presence of carbons in mineral media. SEM and BET tests of the carbon along with the culturing process were used to identify, respectively, the biofilm development and biocarbon porosity. Breakthrough tests evaluated the biocarbon performance with varying gas resistance time, inlet H2S concentration, and type of support materials. Fundamental issues were discussed, including type of support material, mode of bacteria immobilisation, pore blockages, and biodegradation kinetics, etc. This batch-wise study provides a basis for our future research on optimisation of the biofiltration process using a bio-trickling reactor.

Root and canal morphology of Thai mandibular molars

AIM

To investigate the root and canal morphology of 351 mandibular permanent molars collected from an indigenous Thai population.

METHODOLOGY

The cleaned teeth were accessed, the pulp dissolved by sodium hypochlorite under ultrasonication and the pulp system injected with Indian ink. The teeth were rendered clear by demineralization and immersion in methyl salicylate. The following observations were made: (i) number of roots and their morphology; (ii) number of root canals per tooth; (iii) number of root canals per root; (iv) root canal configuration in each root using Vertucci's classification, with additional modifications; and (v) presence and location of lateral canals and intercanal communications.

RESULTS

Of 118 mandibular first molars, 13% had a third disto-lingual root. In three-rooted teeth, 80% of the main distal roots and 100% of the disto-lingual roots had type 1 canal systems. Of 60 mandibular second molars, 10% had C-shaped roots, the majority of which had type 1 (33%) or type IV (33%) canal systems. Of 173 third molars, 68% had two separate roots, 20% had fused roots and 11% had a single C-shaped root; the majority had two canals (61%).

CONCLUSIONS

This study suggests that Thai molars exhibit features of both Caucasian and Chinese teeth.

Root and canal morphology of Burmese maxillary molars

AIM

To investigate the root and canal morphology of Burmese maxillary molars using a canal staining and tooth clearing technique.

METHODOLOGY

Maxillary molars (239) were collected from indigenous Burmese patients and designated; first (90), second (77), third (72) molars. Following pulp tissue removal and canal system staining with Indian ink, the teeth were decalcified with 10% nitric acid, dehydrated and cleared with methyl salicylate. The following features were evaluated: (i) number of roots and morphology; (ii) number of canals per root: (iii) root canal configuration (Vertucci's classification); (iv) number of apical foramina per root; (v) number and location of lateral canals; and (vi) the presence of intercanal communications.

RESULTS

All first and second molars had three separate roots, whilst third molars had one of five different root forms, of which three separate (25%) or fused (31%) roots were most prevalent. The majority of palatal (100%) and disto-buccal (96%) roots possessed one canal (type I). The prevalence of mesio-buccal roots with two canals decreased from first to third molars (68%, 49%, 39%, respectively); type II (two orifices, one apical foramen) and IV (two orifices, two apical foramina) configurations were the most common. Single/fused rooted third molars had a range of number and type of canals. Most roots in all molars had one apical foramen, those with four apical foramina were confined to third molars. Intercanal communications were most prevalent in mesio-buccal roots and two/three fused rooted third molars. Lateral canals were most prevalent in the apical third of the roots of all molars.

CONCLUSIONS

The mesio-buccal roots of Burmese maxillary molars possessed a variety of canal system types. Over 50% of the first and second molars had a second mesio-buccal canal, of which over 20% had intercanal communications. The palatal and disto-buccal canals mainly had type I canals. Lateral canals were equally prevalent in all tooth types but were most common in the apical third.

A new in vitro model for the study of microbial microleakage around dental restorations: a preliminary qualitative evaluation

AIM

The aim of this study was to develop an in vitro model to replicate microbial microleakage at a tooth/ restoration interface using a constant depth film fermentor (CDFF).

METHODOLOGY

Amalgam restorations were placed in machined bovine dentine cylinders and sealed externally with varnish, leaving a 1-mm perimeter exposed around the tooth/restoration interface. The dentine cylinders were housed in a CDFF and 300-microm thick microcosm dental plaques were grown over their exposed surfaces. The biofilms were maintained with a mucin-containing artificial saliva for up to 8 weeks. Cylinders were aseptically removed from the CDFF (at 1, 2, 4, & 8 weeks) and surface-decontaminated with validated protocols prior to splitting and sampling of apposing amalgam and dentine surfaces. Scanning electron microscopy (SEM) was used to ascertain the position and structure of the bacterial aggregates. Bacterial viability was determined by vital staining of the bacteria in situ.

RESULTS

At all sampling times, SEM showed cocci, rods and filaments on both amalgam and dentine surfaces; some originated as cascades from the surface biofilm and extended into the tooth/restoration microspace. Vital staining showed the majority of bacteria from both dentine and amalgam surfaces to be viable.

CONCLUSION

This preliminary investigation showed that the CDFF may be a valuable tool for the in vitro study of the dynamics of microbial microleakage around dental restorations.

Root and canal morphology of Burmese mandibular molars

AIM

To study the root canal morphology of Burmese mandibular molars using a canal staining and tooth clearing technique.

METHODOLOGY

Mandibular molars (331) were collected from indigenous Burmese patients and designated; first (139), second (134), third (58) molars. Following pulp tissue removal and staining of the canal systems with Indian ink, the teeth were decalcified and rendered clear with methyl salicylate. Under magnification (x3), the following features were evaluated: (i) root number and morphology, (ii) number of canals per root, (iii) root canal configuration (Vertucci's classification), (iv) number of apical foramina per root, (v) number and location of lateral canals and (vi) the presence of intercanal communications.

RESULTS

Most of the mandibular molars had two separate roots (90% in first molars, 58% in second molars, 53% in third molars) and three-rooted teeth were (10%) confined to first molars. C-shaped roots occurred in 22.4% of mandibular second molars and a further 14.9% had two fused roots. The majority (81-100%) of conical distal roots possessed a simple type I (single canal) configuration. Whilst the canal system of mesial roots was more complex: 52-85% contained two canals, of which type II (two orifices, one foramen) and type IV (two separate canals) were the most prevalent. A broad range of 6.5-70% had intercanal communications. Fused/single-rooted molars had a wide variety of canal system types but intercanal communications were rare except in C-shaped roots (33%) of second molars. The majority of roots of all molars contained one or two apical foramina (91-96%) and the apical third had the highest prevalence of lateral canals.

CONCLUSIONS

There was a high prevalence of three-rooted mandibular first molars and C-shaped roots/canals in mandibular second molars from a Burmese population. Conical roots tend to have simple canal systems, whilst flatter/broader roots have more complex canal systems.

A novel application of NMR microscopy: measurement of water diffusion inside bioadhesive bonds

The self-diffusion coefficient of water (D) inside bioadhesive bonds formed by dry and prehydrated hydrophilic matrices has been spatially resolved using nuclear magnetic resonance (NMR) microscopy. One-dimensional profiles showing the variation of D inside bioadhesive bonds were calculated from nine diffusion-weighted profiles obtained immediately after bond formation and every 5 min for 30 min. The resulting data indicated that the hydration state of a hydrophilic matrix can significantly and dramatically influence the dynamics of water movement inside a bioadhesive bond.

Some factors affecting the concentration of available chlorine in commercial sources of sodium hypochlorite

AIMS

To evaluate the availability, effect of storage, dilution and heating on some commercial sources of sodium hypochlorite (NaOCl).

METHODOLOGY

All pharmacies in a Regional Health Authority were telephone surveyed to establish the proprietary and nonproprietary NaOCl products available, their cost and concentration. Ninety-six freshly produced bottles of a commercially available thin household bleach (J. Sainsbury's) were randomly stored in four different modes (full 1 L bottles in dark at room temperature, half-empty 1 L bottles under the same conditions, full 200 mL bottles under the same conditions, full 200 mL bottles stored at 37 degrees C) up to 6 months. The available chlorine in the bleach solutions was evaluated at specific time intervals (0, 1, 2 weeks, 1, 2, 3, 4, 6 months) using iodometric titration. Four brands of commercially available bleaches (J. Sainsbury's Thin Household Bleach, Tesco's Value Bleach, Tesco's Red Label Bleach, Safeway's Savers Bleach) were diluted (by 1 : 1, 1 : 2 or 1 : 3 dilution factors) and samples taken from each dilution for titration to test predictability. NaOCl solutions (5% w/w) were heated in covered or uncovered beakers up to 60-85 degrees C. Samples were taken from each beaker at time 0 and each h up to 4 h, for titration.

RESULTS

Of the 116 pharmacies, 33% could supply a proprietary product and 53% a nonproprietary product. In all, 78% were able to supply a NaOCl product. There was no significant difference (P < 0.05) in available chlorine at baseline between the different modes of storage. After storage at room temperature for 6 months, there were no significant differences (3% of original; P > 0.05) between the different modes of storage. When the storage temperature was 37 degrees C, however, there was a significant difference (38% of original; P < 0.01) at 6 months. Comparison of baseline with the concentrations of available chlorine at 6 months showed significant differences (P < 0.01) for all conditions. The available chlorine concentration in four brands of 'thin' supermarket bleaches could be predictably reduced according to the dilution factor. When 5% NaOCl was heated to 60-85 degrees C for up to 4 h, the available chlorine was increased to 6% in covered solutions and 9% in uncovered solutions.

CONCLUSIONS

Both proprietary and nonproprietary solutions of NaOCl should be relatively easily obtainable in the UK. Stored under appropriate conditions, commercially available thin bleaches and nonproprietary solutions of NaOCl may be diluted to obtain predictable concentrations. Heating solutions of NaOCl may cause unpredictable changes to the concentration, depending upon conditions.

Effect of exposing dentine to sodium hypochlorite and calcium hydroxide on its flexural strength and elastic modulus

AIM

The aim of this study was to evaluate the effect of sodium hypochlorite (NaOCl) solutions (3%, 5%) and saturated calcium hydroxide (Ca(OH)2) solution, individually and consecutively, on the flexural strength and modulus of elasticity of standardized dentine bars.

METHODOLOGY

Standardized plano-parallel dentine bars (n = 121) were divided into five test groups and one control group. The control group 1 consisted of dentine bars, stored in normal saline until testing. The dentine bars in the five test groups were treated by exposure to the following solutions; group 2--3% NaOCl, 2 h; group 3--5% NaOCl, 2 h; group 4--saturated Ca(OH)2 solution, 1 week; group 5--3% NaOCl, 2 h and then saturated Ca(OH)2 solution 1 week; group 6--5% NaOCl, 2 h and then saturated Ca(OH)2 solution 1 week. The dentine bars were then loaded to failure in a three-point bend test.

RESULTS

The data revealed a significant (P < 0.001) decrease in the modulus of elasticity and flexural strength of the dentine bars treated with 3% and 5% NaOCl. There was no significant difference in the flexural strength and the modulus of elasticity between the 3% and 5% NaOCl groups. Exposure to Ca(OH)2 significantly (P < 0.001) reduced the flexural strength but had no significant effect on the modulus of elasticity. The groups treated with sodium hypochlorite followed by calcium hydroxide did not have moduli of elasticity and flexural strengths that were significantly different from those treated only with sodium hypochlorite.

CONCLUSIONS

NaOCl (3 & 5%) reduced the modulus of elasticity and flexural strength of dentine. Saturated Ca(OH)2 reduced the flexural strength of dentine but not the modulus of elasticity. Sequential use of NaOCl and Ca(OH)2 has no additional weakening effect.

Effect of sodium hypochlorite on mechanical properties of dentine and tooth surface strain

AIM

The aim of this study was to test the null hypothesis that sodium hypochlorite irrigation of root canals does not alter the properties of dentine and contribute to the weakening of root-treated teeth.

METHODOLOGY

The effect of two concentrations (0.5%, 5.25%) of sodium hypochlorite (NaOCl) and saline on (i) the elastic modulus and flexural strength of machined dentine bars, and (ii) changes in strain of 'whole' extracted human teeth were evaluated. One hundred standardized plano-parallel dentine bars (> 11.7 x 0.8 x 0.8 mm) were randomly divided into the three groups, immersed for 2 h in the respective solutions and then subjected to a three-point bend test. Changes in strain of each of 10 teeth on cyclical nondestructive occlusal loading were measured using electrical resistance strain gauges bonded to the cervical aspects. Each tooth had its crown and enamel reduced and root canal prepared. These were irrigated sequentially in a series of four separate, 30-minute regimes; initial-saline, 0.5% NaOCl, 5.25% NaOCl and final-saline. The changes in strains after each irrigation regime were compared.

RESULTS

There was a significant decrease in elastic modulus of the dentine bars immersed in 5.25% NaOCl compared with the saline group (P < 0.01). There was also a significant decrease in flexural strength of the dentine bars in the 5.25% NaOCl group compared to both the saline and 0.5% NaOCl groups (P < 0.01). The strain data from the nondestructive tooth loading tests revealed significant increases in tensile strain between the initial-saline and the final-saline stages (P < 0.01). Significant increases in compressive strains were also found between initial-saline and 5.25% NaOCl; and between 0.5% NaOCl and 5.25% NaOCl stages (P < 0.01).

CONCLUSIONS

The null hypothesis was rejected, 5.25% NaOCl reduced the elastic modulus and flexural strength of dentine. Irrigation of root canals of single, mature rooted premolars with 5.25% NaOCl affected their properties sufficiently to alter their strain characteristics when no enamel was present.

Circulating immune complexes of xanthine oxidase in normal subjects

An antigen-specific enzyme-linked immunosorbent assay (ELISA) was developed to detect immune complexes of xanthine oxidase (XODIC), and applied to assay serum XODIC in normal subjects. It was found that XODIC of both IgM and IgG isotypes could be detected in all the 85 sera tested. XODIC levels as a percentage of total xanthine oxidase antibody (XODAb) in the free and bound forms were mostly less than 20%, and there was also significant correlation in XODIC and XODAb levels for both IgM and IgG isotypes. The implications of these findings are discussed.

Characterization of a trifluoroethanol-induced partially folded state of alpha-lactalbumin

The protein alpha-lactalbumin exists in a partially folded molten globule state at pH 2.0, the A state. This state is believed to be compact, possessing a similar amount of secondary structure to the native state but having a flexible tertiary structure comprised mainly of non-specific hydrophobic clustering of residues. Addition of trifluoroethanol (TFE) to bovine, human and guinea pig alpha-lactalbumin at pH 2.0 has been found in each case to induce a conformational transition in the A state as monitored by circular dichroism, nuclear magnetic resonance chemical shifts, and 1-anilinonaphthalene-8-sulphonate binding. The mid-point of this transition is near 15% (v/v) TFE and is effectively complete by 50% (v/v) TFE at 315 K. Far ultraviolet circular dichroism ellipticities at 208 nm and 220 nm, usually taken as a measure of the degree of helical character, are substantially more negative in the TFE state than in the A state. Furthermore, backbone amide protons protected from solvent exchange in the A state are generally at least as strongly protected in the TFE state; patterns of protection appear similar in the two states and include at least part of both the B and C alpha-helices. One major difference from the A state is nevertheless evident: the ability to bind the fluorescent probe 1-anilinonaphthalene-8-sulphonate, characteristic of molten globule states, is lost in the TFE state. Like the A state, the TFE state of alpha-lactalbumin shows little chemical shift dispersion of side-chain resonances. Extensive line broadening in the nuclear magnetic resonance spectra, characteristic of slow conformational averaging in the A state, is, however, much reduced in the TFE state. The line narrowing observed in the TFE state has made it possible to obtain directly sequence-specific assignments for about 25% of the 123 residues of bovine alpha-lactalbumin in 50% (v/v) TFE. Two helices are amongst regions of structure so far identified from short-range backbone nuclear Overhauser enhancement (NOE) connectivities in two-dimensional spectra of the TFE state. One of the helices (residues 86 to 96) corresponds to the C-helix in the native structure. The other (residues 35 to 41) corresponds, however, to a region of the sequence that is not helical in the native state. The partially folded state of alpha-lactalbumin formed in TFE, therefore, supports both native and non-native secondary structure in the absence of persistent long-range tertiary structure.

HTLV-1-associated cutaneous disease: a clinicopathological and molecular study of patients from the U.K

The clinicopathological features of eight patients with cutaneous disease associated with HTLV-1 infection are reviewed. All were U.K. residents of West Indian extraction, and two are currently alive. Disease remained confined to the skin in two patients. Five patients with a cutaneous prodromal phase developed leukaemia after a median duration of 124 months (3 months-21 years), and in one of these combination chemotherapy produced a sustained clinical remission for 20 months. Two patients developed cutaneous disease after remission of their leukaemia. Cutaneous lesions were heterogeneous and included localized papules, a generalized papulonodular eruption, diffuse and localized erythematous plaques, pompholyx-like lesions on the palms and soles, and tumours. The histology of the skin lesions was also variable, and consisted of a heavy dermal infiltrate with lymphocytes, histiocytes, plasma cells, eosinophils and cytologically atypical mononuclear cells. Epidermotropism was present in biopsies from five patients. Tumour cells with large, densely staining, pleomorphic nuclei, arranged in rows between collagen bundles, were present in the majority of cases. In one patient the infiltrate also consisted of epithelioid cells and multinucleated giant cells. Six cases were classified histologically as pleomorphic T-cell lymphoma, and two as cerebriform or mycosis fungoides type. Molecular studies revealed a clonal T-cell population associated with monoclonal integration of HTLV-1 provirus in tissue DNA from six patients. In two patients HTLV-1 integration was established retrospectively using enzymatic in vitro amplification of a specific HTLV-1 po1 gene sequence in DNA extracted from paraffin-embedded sections. This study indicates that the clinical and pathological features of HTLV-1-associated cutaneous disease are diverse. Patients may have disease confined to the skin for prolonged periods, either at presentation or following clinical relapse--cutaneous adult T-cell lymphoma. Molecular techniques allow distinction from other types of cutaneous T-cell lymphoma, and provide an opportunity for retrospective studies of archival material.

Coexistent cutaneous T-cell lymphoma and B-cell chronic lymphocytic leukaemia

Three patients with cutaneous T-cell lymphoma (CTCL) are reported who had concurrent B-cell chronic lymphocytic leukaemia (B-CLL). The separate lineage and clonal nature of the individual lymphoid malignancies were confirmed by gene-rearrangement analysis. The chronology of the illnesses did not support the hypothesis that CTCL predisposes to the development of B-cell proliferative disorders. There was no clear association with immunosuppressive therapy, and HTLV-1 studies were negative in all patients. Consequently, we speculate that a lymphoid stem cell defect, which may lead to the development of either aberrant B- or T-cell clones, may be responsible for such cases of dual lymphoid neoplasia.

An epidemiological survey of respiratory morbidity among granite quarry workers in Singapore: radiological abnormalities

This report presents baseline findings from the first of a series of epidemiological studies to evaluate inter alia the effects of control measures introduced in 1972-79 to reduce dust exposure in all quarries in Singapore. The prevalence of radiological abnormalities among 219 currently employed quarry workers were estimated according to a number of parameters of dust exposure. Large-sized chest x-ray films were read, independently and in random order, by a panel of three experienced readers, who were "blinded" to the personal particulars and exposure of the subjects, using standard chest x-ray films to record opacities according to the International Standard Classification of Radiographs of Pneumoconioses. Silicosis as defined by radiological small opacities (both rounded and irregular) of profusion 1/1 or greater as read by at least two readers were noted in 11 subjects. The prevalence of silicosis was 12.5% in highly exposed drilling and crushing workers, and 0.8% in maintenance and transportation workers with low level exposure to granite dust. Among those who were first exposed to granite dust after 1979, no cases of silicosis were noted in any quarry worker. It is concluded that reduction in dust exposure since 1979 has so far been successful in producing nil or negligible risks of silicosis among active quarry workers over ten years, but further follow-up studies are needed.

An epidemiological survey of respiratory morbidity among granite quarry workers in Singapore: chronic bronchitis and lung function impairment

Respiratory symptoms of chronic bronchitis and measurements of lung function were studied in an epidemiological survey of the total population of workers currently employed in granite quarries in Singapore. There were 85 rock drilling and crushing workers with current exposure in high levels of silica dust. Their respiratory parameters were studied with reference to an internal comparison group of 154 quarry maintenance and transport workers with low dust exposure, and an external comparison group of 148 Telecoms postal delivery workers with no granite dust exposure. The highly exposed workers showed greater prevalences of chronic cough and phlegm, a mean reduction of 5% in forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). The increased respiratory morbidity were independent of other factors such as age and smoking. Similar results were also noted after excluding those with silicosis (defined radiologically as profusion greater than 1/1 as read by at least two of three readers). This study strongly indicates a demonstrable risk of "occupational" bronchitis (mucus hypersecretion) and obstructive and restrictive lung function impairment, apart from the "classical" risk of silicosis. Measures taken to protect the health of workers exposed to silica dust should also be based on considerations taken to protect against the risk of these respiratory disorders as well.

A study of silica nephrotoxicity in exposed silicotic and non-silicotic workers

The possible human nephrotoxicity of silica has often been suggested by previous anecdotal reports and uncontrolled clinical studies of silicotic patients. Urinary excretions of albumin, alpha-1-microglobulin (AMG), and beta-N-acetyl-glucosaminidase (NAG) were measured in 33 male workers exposed to silica (mean duration of employment 16 years) and 19 male age matched non-exposed subjects with no history of primary or secondary renal diseases. Significantly higher urinary excretions of albumin and AMG were found in the workers exposed to silica. Silicotic subjects (n = 7) also had significantly high excretions of albumin, AMG, and NAG. All but one of the silicotic patients had ceased exposure from three to 17 years before the study. Our findings suggest that prolonged exposure to silica is associated with chronic irreversible nephrotoxicity in exposed workers.

Male endocrine functions in workers with moderate exposure to lead

Evidence for the effect of occupational exposure to lead on the male endocrine system is conflicting. This study evaluated the primary (testicular) and secondary (hypothalamo pituitary testicular) effects of exposure to lead in 122 current lead workers and 49 non-exposed workers. The mean current blood lead concentration was 35.2 (range 9.6-77.4) micrograms/dl in the exposed workers, and 8.3 (range 2.6-14.8) micrograms/dl in the non-exposed workers. Concentrations of plasma luteinising hormone (LH) and follicle stimulating hormone (FSH) were both significantly higher in the exposed workers, but testosterone (T) was not significantly different between the two groups. In older exposed workers, however (greater than or equal to 40 years), plasma T concentrations were significantly lower, but LH and FSH concentrations were not significantly different. Compared with non-exposed workers, those exposed for less than 10 years had significantly raised LH and FSH and normal T concentrations whereas those exposed for 10 or more years had significantly lower T, and normal LH and FSH concentrations. The concentrations of LH and FSH showed a moderate increase in relation to blood lead concentrations in the range of 10 micrograms/dl to 40 micrograms/dl and thereafter reached a plateau or declined. No apparent trend for plasma T concentrations occurred. No significant difference in prolactin (PRL) concentration was noted. It is concluded that moderate exposure to lead was associated in dose related fashion with small but measurable changes in male endocrine functions that reflected both primary and secondary effects of lead on the testes and the hypothalamo pituitary testicular axis.

Pulmonary effects of polyvinyl chloride dust exposure on compounding workers

Spirometry, chest radiography, environmental measurements, and a questionnaire on respiratory symptoms were used to evaluate the effects of exposure to polyvinyl chloride (PVC) dust on 171 Chinese and Malay PVC compounding workers in comparison with an unexposed reference group. Workers with high cumulative PVC dust exposure had a lower forced expiratory volume in 1 s and forced vital capacity, and a higher prevalence of radiological profusion of small opacities. Wheezing or chest tightness was also significantly more frequent in this group. Unlike previous studies, the PVC compounding workers in this study were exposed to only negligible amounts, if any, of vinyl chloride monomer or thermal degradation products of PVC such as hydrogen chloride, phosgene, or chlorine. The conclusion was drawn that a low grade of pneumoconiosis and a small degree of lung function impairment is associated with PVC dust exposure. Reversible airways obstruction is also likely and warrants further investigation.

Human xanthine oxidase antibody levels: variation between males and females in Chinese and Europeans

Levels of antibody specific for Xanthine oxidase (XODAb) of the immunoglobulin classes IgG, IgM and IgA have been determined in the sera of blood donors of Chinese and European ethnic origin by immunoassay. No significant differences were found between the two ethnic groups. Significant differences were found in the distribution, of XODAb IgM levels between Chinese males and females and European males and females (chi 2 = 8.262, P = 0.025; chi 2 = 9.423, P = less than 0.001). Since the age range of the female blood donors is 16-49 years, it was postulated that the higher IgM XODAb levels in the females was the result of autoimmunisation by endothelial Xanthine oxidase during menstruation. A group of post-menopausal women showed significantly lower IgM XODAb levels compared to the blood donors (chi 2 = 31.748, P = less than 0.0005). IgM levels in a group of older men were also significantly lower (chi 2 = 3.895, P = less than 0.05) but the difference was much less marked. Unlike the younger males and females there was no significant difference in the distribution of XODAb IgM levels between older males and females. The results seem to support the hypothesis of menstrual auto-immunisation.

Enzyme-linked immunosorbent assay for determination of antibodies to xanthine oxidase

An enzyme-linked immunosorbent assay (ELISA) was developed to detect IgG, IgA and IgM antibodies to xanthine oxidase. The method used xanthine oxidase to coat sample wells on microtitre plates. The anti-xanthine oxidase concentrations were determined by reference to standard curves constructed by coating plates with anti-IgG, anti-IgA and anti-IgM to capture antibodies of different classes in standard human serum. The standard curves for IgG, IgA and IgM had a working range of 0 to about 60 ng/ml, and all results with commercial quality control serum fell within expected ranges. The coefficients of variation (CV) for within-batch precision (n = 30) and between-batch precision (n = 20) for IgG and IgM were about 9% and 12% respectively. The detection limit was 2 ng/ml. The ELISA was applied to assay serum samples of 110 Chinese and 110 European healthy subjects. A positively-skewed distribution in their anti-xanthine oxidase IgG and IgM levels was observed.

The other side of the corneal endothelium

New high-magnification biomicroscopes, the specular microscope and now the in-tandem confocal microscope, provide new images of the corneal endothelium in vivo. These are not always easy to interpret, and correlation with the morphology of the endothelium as seen in dead, fixed specimens is necessary. One such image is of the anterior surface with the confocal microscope. It exhibits a mosaic of hexagonal cells. This surface has not been specifically investigated previously in fixed preparations and the in vivo appearance does not correlate with the structure deduced from transmission electron micrographs. These indicate that the bases of endothelial cells are in the form of thin processes that would not present an image of clearly defined cell outlines. Therefore, the anterior surface of corneal endothelium stripped from ox and human corneas has been examined with the scanning electron microscope. It was found that the basal cell membranes extend processes to neighbouring cells and that some of these seem to unite. The possibility that these findings are artefactual has been examined by comparing them with published transmission and scanning electron micrographs, and it has been concluded that the processes of the basal cell membranes are real.

Effect of preservation on the elasticity of human aortic valve homografts

The elastic properties of preserved human aortic homografts after different storage times in antibiotic-nutrient medium solution have been measured. There was a definite loss of elasticity within nine months leading to a rapid decrease after a year of preservation. It is likely that satisfactory valve function depends on its elasticity, and these studies indicate that aortic valves which have been exposed to antibiotic media for more than nine months should not be used in valve replacement surgery.