Seasonal changes in populations of Caulerpa taxifolia var. distichophylla in the Maltese Islands

Caulerpa taxifolia var. distichophylla, an alien alga in the Mediterranean Sea, was first recorded from the Maltese Islands in 2013. Initial observations suggested that it underwent complete frond regression in winter, possibly due to the colder temperatures. Since then it has spread rapidly and has become abundant in the infralittoral in some localities. The present two-year study on the Maltese populations indicates that the alga is able to resist low seawater temperatures during the winter and is not regressing completely, potentially increasing its ecological impact.peer-reviewe

Placement of trans-sternal wires according to an ellipsoid pressure vessel model of sternal forces

Funding from the University of Malta Medical School (Grant IMF/014/11) and University of Malta Research Fund (Grant 31/389/10) is gratefully acknowledged.Dehiscence of median sternotomy wounds remains a clinical problem. Wall forces in thin-walled pressure vessels can be calculated by membrane stress theory. An ellipsoid pressure vessel model of sternal forces is presented together with its application for optimal wire placement in the sternum. Sternal forces were calculated by computational simulation using an ellipsoid chest wall model. Sternal forces were correlated with different sternal thicknesses and radio-density as measured by computerized tomography (CT) scans of the sternum. A comparison of alternative placement of trans-sternal wires located either at the levels of the costal cartilages or the intercostal spaces was made. The ellipsoid pressure vessel model shows that higher levels of stress are operative at increasing chest diameter (P < 0.001). CT scans show that the thickness of the sternal body is on average 3 mm and 30% thicker (P < 0.001) and 53% more radio-dense (P < 0.001) at the costal cartilage levels when compared with adjacent intercostal spaces. This results in a decrease of average sternal stress from 438 kPa at the intercostal space level to 338 kPa at the costal cartilage level (P = 0.003). Biomechanical modelling suggests that placement of trans-sternal wires at the thicker bone and more radio-dense level of the costal cartilages will result in reduced stress.peer-reviewe

Mechanism of sternotomy dehiscence

Research funded by the University of Malta.OBJECTIVES Biomechanical modelling of the forces acting on a median sternotomy can explain the mechanism of sternotomy dehiscence, leading to improved closure techniques. METHODS Chest wall forces on 40 kPa coughing were measured using a novel finite element analysis (FEA) ellipsoid chest model, based on average measurements of eight adult male thoracic computerized tomography (CT) scans, with Pearson's correlation coefficient used to assess the anatomical accuracy. Another FEA model was constructed representing the barrel chest of chronic obstructive pulmonary disease (COPD) patients. Six, seven and eight trans-sternal and figure-of-eight closures were tested against both FEA models. RESULTS Comparison between chest wall measurements from CT data and the normal ellipsoid FEA model showed an accurate fit (P < 0.001, correlation coefficients: coronal r = 0.998, sagittal r = 0.991). Coughing caused rotational moments of 92 Nm, pivoting at the suprasternal notch for the normal FEA model, rising to 118 Nm in the COPD model (t-test, P < 0.001). The threshold for dehiscence was 84 Nm with a six-sternal-wire closure, 107 Nm with seven wires, 127 Nm with eight wires and 71 Nm for three figure-of-eights. CONCLUSIONS The normal rib cage closely fits the ellipsoid FEA model. Lateral chest wall forces were significantly higher in the barrel-shaped chest. Rotational moments generated by forces acting on a six-sternal-wire closure at the suprasternal notch were sufficient to cause lateral distraction pivoting at the top of the manubrium. The six-sternal-wire closure may be successfully enhanced by the addition of one or two extra wires at the lower end of the sternotomy, depending on chest wall shape.peer-reviewe

Is there a biomechanical cause for spontaneous pneumothorax?

OBJECTIVES: Primary spontaneous pneumothorax has long been explained as being without apparent cause. This paper deals with the effect of chest wall shape and explains how this may lead to the pathogenesis of primary spontaneous pneumothorax. METHODS: Rib cage measurements were taken from chest radiographs in 12 male pneumothorax patients and 12 age-matched controls. Another group of 15 consecutive male thoracic computerised tomography (CT) were investigated using paramedian coronal and sagittal CT reconstructions to assess apical lung shape. A finite element analysis (FEA) model of a lung apex was constructed, including indentations for the first rib guided by CT scan data, to assess pleural stress. This model was tested using different anteroposterior diameter ratios, producing a range of thoracic indexes. RESULTS: The pneumothorax patients had a taller chest (P = 0.03), wider transversely (P = 0.009) and flatter (P = 0.03) when compared with controls, resulting in a low thoracic index. Prominent rib indentations were found anteriorly and posteriorly on the lung surface, especially on the first rib on CT. FEA of the lung revealed significantly higher stress (×5-×10) in the apex than in the rest of the lung. This was accentuated (×4) in low thoracic index chests, resulting in 20-fold higher stress levels in their apex. CONCLUSIONS: The FEA model demonstrates a 20-fold increase in pleural stress in the apex of chests with low thoracic index typical of spontaneous pneumothorax patients. Mild changes in thoracic index, as occurring in females or with aging, reduce pleural stress. Spontaneous pneumothorax occurring in young male adults may have a biomechanical cause.peer-reviewe

Totarol content and cytotoxicity varies significantly in different types of propolis

Propolis is a complex honeybee product deposited in the beehives, where it protects the hive and its occupants from microbial infection. Propolis has several reported medical applications in view of its numerous bioactive properties. The water insoluble fraction of crude Maltese honeybee propolis was extracted in methanol. Analysis by gas chromatography – mass spectrometry (GC-MS) showed the diterpenoid totarol to be the predominant constituent in all samples. The evaporated methanol residue was dissolved in dimethyl sulphoxide (DMSO) and used for cytotoxicity testing on human cancer cell lines using standard 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assays. Results obtained show that the propolis collected from Malta has cytotoxic activity in cancer cells in vitro. However, propolis collected from different sites, only a few miles apart and at different times of the year, showed marked variations in the cytotoxicity, which correlated clearly with totarol content. This reflects the differences in the species of plants, on which the bees had foraged and indicates the importance of collection site and season of collection on the bioactivity of propolis products.peer-reviewe

Placement of sternal wires in median sternotomy closure

Dehiscene of median sternotomy wounds remains a clinical problem. Sternal forces can be calculated by thin shell theory and this data may be used to guide optimal wire placement in the sternum during median sternotomy wiring.peer-reviewe

Number of wires required for median sternotomy closure

The use of biomechanical techniques can help model the forces that act on median sternotomy closures and determine the mechanisms of median sternotomy dehiscene. This can guide changes in sternal wiring techniques in order to reduce the appreciable morbidity and morality of median sternotomy dehiscene.peer-reviewe

Rib morphology

Human ribs are angulated. There are changes in rib angulation that occur with body growth. Rib angulation was correlated with the vectors of chest wall forces estimated by an ellipsoid biomechanical model using finite element analysis.peer-reviewe

Horse owners’ behaviour: suspecting and reporting of Hendra virus cases

Hendra virus infection is a zoonotic disease which spreads from bats to horses and from horses to people. Transmission spillovers are rare events, but can be fatal to horses and people when they do occur. To date, HeV cases have only occurred in Queensland and northern New South Wales with a total of 83 confirmed cases in horses up to September 2018. The National Hendra Virus Research Program (NHeVRP) was funded by Commonwealth, NSW and Qld governments after a spike in Hendra virus infections in 2011. The “Horse owners and Hendra virus: a longitudinal cohort study to evaluate risk” (HHALTER) project was a component of the NHeVRP and involved collection of survey information from horse owners from 2012 to 2014. The fourth survey in a series of five included questions about owners’ attitudes to reporting a suspected Hendra case. The data are presented here using categorical analysis techniques to explore the relationships between attitudes towards reporting of a case and risk perception and demographic information. Of a total cohort of 1,449 responders, there were 613 (42%) participants responding to some or all of survey four. There were 592 responses to the question “If you saw unusual signs of disease (muscle twitching, nasal discharge etc) in one of your horses, how likely do you think you would be to... consider Hendra virus as a possibility”. Of these 81 said they would not think of Hendra as a possibility at all and 191 thought that Hendra was very or extremely likely. The findings of this study reinforce the importance of an existing/good relationships between horse owners and veterinarians and also identify that the presence of severe or unusual signs of disease would be 'drivers' for reporting a suspect HeV case. Data presented here are likely to represent a ‘best case’

Longitudinal cohort study of horse owners : HHALTER : horse owners and Hendra virus : a longitudinal study to evaluate risk

This report was prepared for the Rural Industries Research and Development Corporation in relation to the National Hendra Virus Research Program. It summarises the findings of a three-year mixed methods research study designed to capture factors that influence horse owner Hendra virus (HeV) risk mitigation practices. This research supports the Rural Industries Research and Development Corporation (RIRDC) Hendra Virus Research Priority 2: Improved strategies to prevent transmission of HeV. However, it may also contribute to Research Priority 3: Capacity to detect and respond effectively to HeV incidents