Combined effects of increased water temperature and cyanobacterial compounds exert heterogeneous effects on survival and ecological processes in key freshwater species.

Climate change is increasing water temperature and intensifying the incidence of cyanobacterial blooms worldwide. However, the combined effects of increased temperature and microcystin concentrations as co-stressors on survival and ecological processes in freshwater species are unclear. Here, using purified MC-LR and crude extract of toxigenic Microcystis aeruginosa, we tested the individual and combined effects of three water temperatures (15, 20, 25 °C) and a range of environmentally relevant concentrations of dissolved microcystin and crude extract (0.01-10 µg·L-1) on survival, growth inhibition, grazing and predation rates in three freshwater species: phytoplankton (Scenedesmus quadricauda), zooplankton (Daphnia pulex), and an invertebrate predator (Ischnura elegans). Purified MC-LR exerted a higher growth inhibitory effect on S. quadricauda compared to crude extract with the same concentration of MC-LR, while neither treatment affected its chlorophyll-a content or survival of D. pulex. Crude extract reduced grazing and survival of D. pulex and I. elegans, respectively. The combined effect of higher temperature and crude extract reduced I. elegans survival by 50%. Increased temperature reduced prey handing time in I. elegans by 49%, suggesting a higher predation rate. However, warming together with higher concentrations of crude extract jointly increased zooplankton grazing and reduced damselfly predation. Taken together, these results suggest crude extract, and not necessarily microcystin, can affect survival and productivity in freshwater species, although these effects may vary unevenly across trophic levels. Our findings highlight the importance of complex ecological mechanisms by which warming can exacerbate toxic effects of cyanobacterial bloom extracts on survival and functions among species in eutrophic freshwaters.

Large-scale radio propagation path loss measurements and predictions in the VHF and UHF bands.

For decades now, a lot of radio wave path loss propagation models have been developed for predictions across different environmental terrains. Amongst these models, empirical models are practically the most popular due to their ease of application. However, their prediction accuracies are not as high as required. Therefore, extensive path loss measurement data are needed to develop novel measurement-oriented path loss models with suitable correction factors for varied frequency, capturing both local terrain and clutter information, this have been found to be relatively expensive. In this paper, a large-scale radio propagation path loss measurement campaign was conducted across the VHF and UHF frequencies. A multi-transmitter propagation set-up was employed to measure the strengths of radio signals from seven broadcasting transmitters (operating at 89.30, 103.5, 203.25, 479.25, 615.25, 559.25 and 695.25 MHz respectively) at various locations covering a distance of 145.5 km within Nigerian urban environments. The measurement procedure deployed ensured that the data obtained strictly reflect the shadowing effects on radio signal propagation by filtering out the small-scale fading components. The paper also, examines the feasibilities of applying Kriging method to predict distanced-based path losses in the VHF and UHF bands. This method was introduced to minimize the cost of measurements, analysis and predictions of path losses in built-up propagation environments.

Multimedia tools in the teaching and learning processes: A systematic review.

Access to quality education is still a major bottleneck in developing countries. Efforts at opening the access to a large majority of citizens in developing nations have explored different strategies including the use of multimedia technology. This paper provides a systematic review of different multimedia tools in the teaching and learning processes with a view to examining how multimedia technologies have proven to be a veritable strategy for bridging the gap in the provision of unrestricted access to quality education and improved learners' performance. The review process includes conducting an extensive search of relevant scientific literature, selection of relevant studies using a pre-determined inclusion criteria, literature analysis, and synthesis of the findings of the various studies that have investigated how multimedia have been used for learning and teaching processes. The review examines various case study reports of multimedia tools, their success and limiting factors, application areas, evaluation methodologies, technology components, and age groups targeted by the tools. Future research directions are also provided. Apart from text and images, existing tools were found to have multimedia components such as audio, video, animation and 3-D. The study concluded that the majority of the multimedia solutions deployed for teaching and learning target the solution to the pedagogical content of the subject of interest and the user audience of the solution while the success of the different multimedia tools that have been used on the various target groups and subjects can be attributed to the technologies and components embedded in their development.

A study of the diffusion characteristics of normal, delipidized and relipidized articular cartilage using magnetic resonance imaging.

This paper assesses the capacity to provide semipermeability of the synthetic layer of surface-active phospholipids created to replace the depleted surface amorphous layer of articular cartilage. The surfaces of articular cartilage specimens in normal, delipidized, and relipidized conditions following incubation in dipalmitoyl-phosphatidylcholine and palmitoyl-oleoyl-phosphatidylcholine components of the joint lipid mixture were characterized nanoscopically with the atomic force microscope and also imaged as deuterium oxide (D2O) diffused transiently through these surfaces in a magnetic resonance imaging enclosure. The MR images were then used to determine the apparent diffusion coefficients in a purpose-built MATLAB(®)-based algorithm. Our results revealed that all surfaces were permeable to D2O, but that there was a significant difference in the semipermeability of the surfaces under the different conditions, relative to the apparent diffusion coefficients. Based on the results and observations, it can be concluded that the synthetic lipid that is deposited to replace the depleted SAL of articular cartilage is capable of inducing some level of semipermeability.

Load-unloading response of intact and artificially degraded articular cartilage correlated with near infrared (NIR) absorption spectra.

The conventional mechanical properties of articular cartilage, such as compressive stiffness, have been demonstrated to be limited in their capacity to distinguish intact (visually normal) from degraded cartilage samples. In this paper, we explore the correlation between a new mechanical parameter, namely the reswelling of articular cartilage following unloading from a given compressive load, and the near infrared (NIR) spectrum. The capacity to distinguish mechanically intact from proteoglycan-depleted tissue relative to the "reswelling" characteristic was first established, and the result was subsequently correlated with the NIR spectral data of the respective tissue samples. To achieve this, normal intact and enzymatically degraded samples were subjected to both NIR probing and mechanical compression based on a load-unload-reswelling protocol. The parameter δr, characteristic of the osmotic "reswelling" of the matrix after unloading to a constant small load in the order of the osmotic pressure of cartilage, was obtained for the different sample types. Multivariate statistics was employed to determine the degree of correlation between δr and the NIR absorption spectrum of relevant specimens using Partial Least Squared (PLS) regression. The results show a strong relationship (R(2)=95.89%, p<0.0001) between the spectral data and δr. This correlation of δr with NIR spectral data suggests the potential for determining the reswelling characteristics non-destructively. It was also observed that δr values bear a significant relationship with the cartilage matrix integrity, indicated by its proteoglycan content, and can therefore differentiate between normal and artificially degraded proteoglycan-depleted cartilage samples. It is therefore argued that the reswelling of cartilage, which is both biochemical (osmotic) and mechanical (hydrostatic pressure) in origin, could be a strong candidate for characterizing the tissue, especially in regions surrounding focal cartilage defects in joints.

Application of near infrared (NIR) spectroscopy for determining the thickness of articular cartilage.

The determination of the characteristics of articular cartilage such as thickness, stiffness and swelling, especially in the form that can facilitate real-time decisions and diagnostics is still a matter for research and development. This paper correlates near infrared spectroscopy with mechanically measured cartilage thickness to establish a fast, non-destructive, repeatable and precise protocol for determining this tissue property. Statistical correlation was conducted between the thickness of bovine cartilage specimens (n=97) and regions of their near infrared spectra. Nine regions were established along the full absorption spectrum of each sample and were correlated with the thickness using partial least squares (PLS) regression multivariate analysis. The coefficient of determination (R²) varied between 53 and 93%, with the most predictive region (R²=93.1%, p<0.0001) for cartilage thickness lying in the region (wavenumber) 5350-8850 cm⁻¹. Our results demonstrate that the thickness of articular cartilage can be measured spectroscopically using NIR light. This protocol is potentially beneficial to clinical practice and surgical procedures in the treatment of joint disease such as osteoarthritis.

Non-destructive evaluation of articular cartilage defects using near-infrared (NIR) spectroscopy in osteoarthritic rat models and its direct relation to Mankin score.

OBJECTIVE: The aim of this study was to demonstrate the potential of near-infrared (NIR) spectroscopy for categorizing cartilage degeneration induced in animal models. METHOD: Three models of osteoarthritic degeneration were induced in laboratory rats via one of the following methods: (1) menisectomy (MSX); (2) anterior cruciate ligament transection (ACLT); and (3) intra-articular injection of mono-ido-acetate (1 mg) (MIA), in the right knee joint, with 12 rats per model group. After 8 weeks, the animals were sacrificed and tibial knee joints were collected. A custom-made near-infrared (NIR) probe of diameter 5 mm was placed on the cartilage surface and spectral data were acquired from each specimen in the wave number range 4,000-12,500 cm(-1). Following spectral data acquisition, the specimens were fixed and Safranin-O staining was performed to assess disease severity based on the Mankin scoring system. Using multivariate statistical analysis based on principal component analysis and partial least squares regression, the spectral data were then related to the Mankin scores of the samples tested. RESULTS: Mild to severe degenerative cartilage changes were observed in the subject animals. The ACLT models showed mild cartilage degeneration, MSX models moderate, and MIA severe cartilage degenerative changes both morphologically and histologically. Our result demonstrates that NIR spectroscopic information is capable of separating the cartilage samples into different groups relative to the severity of degeneration, with NIR correlating significantly with their Mankin score (R(2) = 88.85%). CONCLUSION: We conclude that NIR is a viable tool for evaluating articular cartilage health and physical properties such as change in thickness with degeneration.

Acoustic, mechanical and near-infrared profiling of osteoarthritic progression in bovine joints.

Early-stage treatments for osteoarthritis are attracting considerable interest as a means to delay, or avoid altogether, the pain and lack of mobility associated with late-stage disease, and the considerable burden that it places on the community. With the development of these treatments comes a need to assess the tissue to which they are applied, both in trialling of new treatments and as an aid to clinical decision making. Here, we measure a range of mechanical indentation, ultrasound and near-infrared spectroscopy parameters in normal and osteoarthritic bovine joints in vitro to describe the role of different physical phenomena in disease progression, using this as a basis to investigate the potential value of the techniques as clinical tools. Based on 72 samples we found that mechanical and ultrasound parameters showed differences between fibrillated tissue, macroscopically normal tissue in osteoarthritic joints, and normal tissue, yet did were unable to differentiate degradation beyond that which was visible to the naked eye. Near-infrared spectroscopy showed a clear progression of degradation across the visibly normal osteoarthritic joint surface and as such, was the only technique considered useful for clinical application.

Assessment of common hyperelastic constitutive equations for describing normal and osteoarthritic articular cartilage.

With the aim of providing information for modelling joint and limb systems, widely available constitutive hyperelastic laws are evaluated in this paper for their ability to predict the mechanical responses of normal and osteoarthritic articular cartilage. Load-displacement data from mechanical indentation were obtained for normal and osteoarthritic cartilage at 0.1 s(-1) and 0.025 s(-1) and converted to the stress-stretch ratio. The data were then fitted to the Arruda-Boyce, Mooney-Rivlin, neo-Hookean, Ogden, polynomial, and Yeoh hyperelastic laws in the MATLAB environment. Although each of the hyperelastic laws performed satisfactorily at the higher rate of loading, their ability to fit experimental data at the lower loading rate varied considerably. For the preferred models, coefficients were provided for stiff, soft, and average tissues to represent normal and degraded tissue at high and low loading rates. The present authors recommend the use of the Mooney-Rivlin or the Yeoh models for describing both normal and degraded articular cartilage, with the Mooney-Rivlin model providing the best compromise between accuracy and required computational power.

Diffuse reflectance near infrared spectroscopy can distinguish normal from enzymatically digested cartilage.

A non-destructive, diffuse reflectance near infrared spectroscopy (DR-NIRS) approach is considered as a potential tool for determining the component-level structural properties of articular cartilage. To this end, DR-NIRS was applied in vitro to detect structural changes, using principal component analysis as the statistical basis for characterization. The results show that this technique, particularly with first-derivative pretreatment, can distinguish normal, intact cartilage from enzymatically digested cartilage. Further, this paper establishes that the use of DR-NIRS enables the probing of the full depth of the uncalcified cartilage matrix, potentially allowing the assessment of degenerative changes in joint tissue, independent of the site of initiation of the osteoarthritic process.

Cytological and toxicological properties of a decoction used for managing tumors in Southwestern Nigeria.

The cytological and toxicological potentials of an ethanol extract of a decoction used in South Western Nigeria for the management of breast tumors were evaluated using mice and Allium cepa models. The oral administration of the extract to the mice within the range of 400-1600 mg kg(-1) b. wt., dosage did not result in any mortality until 2000 mg kg(-1) body weight (b. wt.), when 60% mortality occurred. The LD50 of the extract administered intraperitoneally, was 400 mg kg(-1) b. wt. Furthermore, the extract induced macroscopic and microscopic changes causing a dose-related root growth inhibition and chromosomal aberrations in Allium cepa. The effect of the extract was more pronounced at 1600 mg kg((-1), dose while the EC50 was at 380 mg after 72 h. This decoction may present cytological and toxicological potential for managing breast tumors and corroborates its use in ethno medicine.

An alternative mechanical parameter for assessing the viability of articular cartilage.

This paper is a sequel to previously published findings showing that mechanical indentation alone cannot clearly discriminate between normal and degraded articular cartilage. Consequently, the structural elasticity potential Rc = epsilon r/sigma i, which combines indentation stress sigma i with near-instantaneous rebound epsilon r following unloading, is hypothesized as a potential cartilage assessment parameter, which arguably measures the integrity of the collagen fibre-proteoglycan entrapment system. To establish the validity of our hypothesis, samples of normal intact, artificially degraded, and osteoarthritic bovine cartilage were subjected to quasi-static compression at 0.1 s(-1) and 0.025 s(-1) to 30 per cent strain and then unloaded. A significant reduction in recovery was observed for artificially and naturally degraded samples in the first 5s following unloading (p < 0.01). The structural elasticity potential provided a considerable improvement over the results obtained using the individual indentation and rebound parameters to distinguish between paired normal and artificially degraded samples and indicated a high statistical significance of p < 0.005 when applied to the differentiation of normal and osteoarthritic samples.

Prevalence and Awareness about Chlamydial Infection in Women Undergoing Infertility Evaluation in Lagos; Nigeria

Purpose: To determine the prevalence and level of awareness of genital Chlamydia trachomatis infection and possible correlative factors among women undergoing infertility evaluation. Methods: The study involved analysis of demographics and results of chlamydia screening in 77 infertile women undergoing evaluation over a six month period in Lagos; Nigeria. Results: The mean age was 32 + 6.4 yr (range 20-39 yr). Chlamydia screening was positive in 14 (18.2). Awareness about the existence; symptomatology; mode of infection and complications was poor. Statistically significant correlation existed between prevalence of chlamydia infection and age; previous history of sexual infection and minimum of one sexual partner in the last one year (p 0.05). The prevalence also increased in secondarily infertile and married women. Conclusion: Chlamydia prevalence was relatively high in women undergoing infertility evaluation in Lagos; with positive correlative factors being increasing age of women; previous sexual infection and one or more sexual partners

Lamellar lubrication in vivo and vitro: friction testing of hexagonal boron nitride.

Phospholipid molecules (PLs) in vivo and graphite, molybdenum disulfide, tungsten disulfide and hexagonal boron nitride (h-BN) in vitro are good examples of frictionless lubricants. PLs and solid materials have the ability to form multi-bilayer or layered structures similar to lamellate solid. It has been confirmed experimentally that PLs as lamellar lubricants protect the surface of joints against wear while acting as frictionless lubricant. An experimental study has been conducted on the friction properties of h-boron nitride on porous non-full journal bearings. The porous non-full journal bearings were a mixture of 97.5 wt.% Fe and 2.5 wt.% Cu powder, and compressed to a density of 5.9 g/cm(3). The porosity of non-full journal bearings were 15.5 and 27.8 wt.% and were impregnated with vaseline and vaseline+5 wt.% h-BN. Additionally, the two additives SFR NLGI #2 (or SFR 2522) grease and graphite grease were used for comparison to h-BN. The tribological tests were performed on a four-ball machine under load of 49 daN, and a friction tribotester. The above experiment strongly suggested that h-BN has the ability to lubricate under load with very low friction coefficient comparable to phospholipids. Relatively low surface energy and low adhesion between the crystallites are giving the additives low friction coefficient. The results of the experimental studies showed that h-BN as an additive in vaseline possesses friction reducing properties, and excellent anti-wear properties.

Cell response in mixtures of surfactant-culture medium--towards a systemic approach to cell-based treatments for focal osteoarthritis.

Osteoarthritis (OA), the most common form of arthritis is a degenerative joint disease, which causes severe long-term pain and physical disability. It is becoming more important to improve diagnosis and understanding of the disease process and subsequently develop new intervention to delay or even reverse the disease progress. Our study was designed to combine two relatively novel treatment techniques, autologous chondrocyte transplantation (ACT) and proposed application of medical remedies based on surface-active phospholipids. To this end we exposed chondrocyte to culture environments with mixtures of culture medium and phospholipid solutions. Following various culture periods, cell survival and well-being were determined by measuring proliferation and assessing morphological features, and comparing these with the behaviour of cells grown in classical which were not mixed with surfactant, i.e., control culture medium. Scanning electron microscopy and light microscopy demonstrate that the cells exposed to mixtures with surfactant were as healthy as those in the control environment with polygonal morphology, while proliferation assay indicated a noticeably higher level of proliferation over similar periods, for cells cultured in media that was mixed with surfactants. Also, the cells in media with unsaturated surfactants responded better than those cultured in mixtures containing saturated surfactant.

Joint laminate degradation assessed by reflected ultrasound from the cartilage surface and osteochondral junction.

The ability to quantify and qualify the progression of joint degeneration is becoming increasingly important in surgery. This paper examines the patterns of relative ultrasound reflection from normal, artificially and naturally degraded cartilage-on-bone, particularly investigating the potential of the ratio of reflection coefficients from the surface and osteochondral junction in distinguishing normal from osteoarthritic tissue. To this end, the reflection coefficients from the articular surface and osteochondral junction of normal cartilage-on-bone samples were calculated and compared to samples after the removal of proteoglycans, disruption of the collagen meshwork, delipidization of the articular surface and mechanical abrasion. Our results show that the large variation across normal and degraded joint samples negates the use of an isolated bone reflection measurement and to a lesser extent, an isolated surface reflection. The relative surface to bone reflections, calculated as a ratio of reflection coefficients, provided a more consistent and statistically significant (p < 0.001) method for distinguishing each type of degradation, especially osteoarthritic degradation, and due to the complementary relationship between surface and bone reflections was found to be an effective method for distinguishing degraded from normal tissue in the osteoarthritic joint, independent of the site of initiation of the osteoarthritic process.

In vitro reversal of the load-bearing properties of lipid-depleted articular cartilage following exposure to phospholipid surfactant solutions.

BACKGROUND: A microscopic layer of surface active phospholipids overlays the articular cartilage of the knee. Its depletion in osteoarthritic joints results in loss of lubrication and load-bearing efficiency. We hypothesize that exposure of articular cartilage to the dominant unsaturated phospholipid component of knee surfactant can regenerate the load-bearing properties of the tissue. This was evaluated by studying the stress-strain and stiffness characteristics of normal intact and lipid-depleted cartilage exposed to lipid-based surfactants for known durations. METHODS: Normal intact, lipid-depleted and surfactant-treated bovine articular cartilage specimens were compressed at 0.5mm/min to a maximum strain of 40% and their stress-strain and stiffness data were compared. FINDINGS: The stiffness of lipid-depleted samples increased by 40% on average relative to the normal; after exposure of the same samples to saturated surfactant for one and 24h, the average stiffness decreased by 25% and 62%, respectively from this high value. On the other hand, exposure of delipidized specimens to a mixture of selected unsaturated surfactant species for one and 24h resulted in a reduction of 85% and 90% in the stiffness of the depilidized samples respectively, largely reversing the effect of lipid removal to a level much closer to that of the normal intact cartilage and therefore better than that obtained with incubation in the saturated surfactant. INTERPRETATION: Lipid loss in articular cartilage results in a consistent increase in stiffness relative to normal tissue stiffness. This consequence of lipid loss can be partially reversed by the reintroduction of surface active phospholipids. The results of this study show that the lipid components of cartilage play an important role in determining the compliance of the loaded tissue.

The influence of lipid-extraction method on the stiffness of articular cartilage.

BACKGROUND: One of the known characteristics of osteoarthritis is the loss of articular cartilage lipids. Therefore, it is important to study how lipids influence the functions of the tissue. This can only be done successfully by indirect analysis involving the extraction of lipids and subsequent assessment of the delipidized matrix. Therefore, for accuracy, the procedure for lipid extraction must not induce any other modification in the samples to be assessed. Hence, we compare three rinsing agents and methods in this study. METHODS: Normal and delipidized articular cartilage samples were tested under compressive loading at 4 loading velocities to obtain and compare their stiffness values. FINDINGS: Chloroform rinsing resulted in a 45% decrease in the stiffness of cartilage at low strain-rates (10(-2)/s and 10(-1)/s) on average with a corresponding increase of 55% at higher strain-rate of 10/s relative to the normal. Ethanol rinsed cartilage exhibited a corresponding decrease of 40% at the low strain-rates while exhibiting an increase of about 20% at the highest loading rates. Propylene glycol rinsing resulted in a decrease of approximately 20% in stiffness, while an increase of up to 5% at high rates of loading. INTERPRETATION: The loss of lipids modifies the stiffness of articular cartilage at all loading rates. The relatively larger deviation of the stiffness of chloroform-rinsed samples relative to the normal is probably a consequence of the drying process involved in rinsing protocol. It is probable that the results of milder rinsing agents, used without vacuum drying, are more reflective of physiological delipidization effects on the tissue. Consequently, we recommend propylene glycol and its associated protocol for extracting lipids from articular cartilage.

Conceptual fracture parameters for articular cartilage.

BACKGROUND: Superficial cracks can occur in articular cartilage due to trauma or wear and tear. Our understanding of the behaviour of such cracks in a loaded matrix is limited. A notable study investigated the growth of cracks induced in the bottom layer of the matrix. This paper extends existing studies, characterizing the propagation of superficial cracks and matrix resistance under tension at varying rates of loading. METHODS: Cartilage strips with artificially induced superficial cracks were subjected to tensile loading at different loading velocities using a miniature tensile testing device. Load-displacement data, video and still images were recorded for analysis. FINDINGS: The propagation of superficial cracks in articular cartilage does not follow the classical crack tip advance that is characteristic of most engineering materials. Instead, the crack tip exhibited a negligible movement while the side edges of the crack rotated about it, accompanied by matrix stretching and an upward pull (necking) of the bottom layer of the sample. As loading progresses, the crack edges stretch and rotate to assume a position parallel to the articular surface, followed by the final fracture of the matrix at a point just below the crack tip. Using the recorded mechanical data and images, an analogous poroelastic fracture toughness, Kp(Ic)=1.83 MPa.square root mm (SD 0.8) is introduced. INTERPRETATION: It is extremely difficult for a superficial crack to propagate through articular cartilage. This may be because of the energy dissipation from the crack due to the movement and exudation of water, and large stretching of the matrix.

In vitro degradation of articular cartilage: does trypsin treatment produce consistent results?

It is common practice in laboratories to create models of degraded articular cartilage in vitro and use these to study the effects of degeneration on cartilage responses to external stimuli such as mechanical loading. However, there are inconsistencies in the reported action of trypsin, and there is no guide on the concentration of trypsin or the time to which a given sample can be treated so that a specific level of proteoglycan depletion is achieved. This paper argues that before any level of confidence can be established in comparative analysis it is necessary to first obtain samples with similar properties. Consequently, we examine the consistency of the outcome of the artificial modification of cartilage relative to the effects of the common enzyme, trypsin, used in the process of in vitro proteoglycan depletion. The results demonstrate that for a given time and enzyme concentration, the action of trypsin on proteoglycans is highly variable and is dependent on the initial distribution and concentration of proteoglycans at different depths, the intrinsic sample depth, the location in the joint space and the medium type, thereby sounding a note of caution to researchers attempting to model a proteoglycan-based degeneration of articular cartilage in their experimental studies.