Multimodal optical characterisation of collagen photodegradation by femtosecond infrared laser ablation.

Collagen is a structural component of the human body, as a connective tissue it can become altered as a result of pathophysiological conditions. Although the collagen degradation mechanism is not fully understood, it plays an important role in ageing, disease progression and applications in therapeutic laser treatments. To fully understand the mechanism of collagen alteration, in our study photo-disruptive effects were induced in collagen I matrix by point-irradiation with a femtosecond Ti-sapphire laser under controlled laser ablation settings. This was followed by multi-modal imaging of the irradiated and surrounding areas to analyse the degradation mechanism. Our multi-modal methodology was based on second harmonic generation (SHG), scanning electron microscope (SEM), autofluorescence (AF) average intensities and the average fluorescence lifetime. This allowed us to quantitatively characterise the degraded area into four distinct zones: (1) depolymerised zone in the laser focal spot as indicated by the loss of SHG signal, (2) enhanced crosslinking zone in the inner boundary of the laser induced cavity as represented by the high fluorescence ring, (3) reduced crosslinking zone formed the outer boundary of the cavity as marked by the increased SHG signal and (4) native collagen. These identified distinct zones were in good agreement with the expected photochemical changes shown using Raman spectroscopy. In addition, imaging using polarisation-resolved SHG (p-SHG) revealed both a high degree of fibre re-orientation and a SHG change in tensor ratios around the irradiation spot. Our multi-modal optical imaging approach can provide a new methodology for defining distinct zones that can be used in a clinical setting to determine suitable thresholds for applying safe laser treatments without affecting the surrounding tissues. Furthermore this technique can be extended to address challenges observed in collagen based tissue engineering and used as a minimally invasive diagnostic tool to characterise diseased and non-diseased collagen rich tissues.

Development and validation of a psychometric scale for assessing healthcare professionals' knowledge in radiation protection.

INTRODUCTION: Healthcare professionals must sufficiently understand ionising radiation and the associated protection measures to avoid unnecessarily exposing patients and staff to ionising radiation. Hence, a proper safety culture is important to lowering health risks. The development and establishment of an instrument that can indicate healthcare professionals' understanding/knowledge of radiation protection concepts can greatly contribute to a good safety culture. The purpose of the present study was to develop and psychometrically test the Healthcare Professional Knowledge of Radiation Protection (HPKRP) self-evaluation scale, which was designed to measure the knowledge level of radiation protection by healthcare professionals working with ionising radiation in a clinical environment. METHODS: The presented research employed a cross-sectional study design. Data were collected from eight Finnish hospitals in 2017. A total of 252 eligible nurses responded to the newly developed HPKRP scale. The face and content validity were tested with the Content Validity Index (CVI). Explorative factor analysis was used to test construct validity, whereas reliability was tested with Cronbach's alpha. RESULTS: Overall S-CVI for the HPKRP scale was 0.83. Exploratory factor analysis revealed a three-factor model for the HcPCRP scale containing 33 items. The first factor was defined by Radiation physics and principles of radiation usage, the second factor by Radiation protection, and the third factor by Guidelines of safe ionising radiation usage. These three factors explained 72% of the total variance. Cronbach's alpha coefficient for the scale ranged from 0.93 to 0.96. CONCLUSION: The results provide strong evidence for the validity and reliability of the HPKRP scale. Additionally, educators can use the scale to evaluate healthcare students' understanding in radiation safety before and after education.

Nurses' knowledge of radiation protection: A cross-sectional study.

INTRODUCTION: Nursing roles are changing, as several countries have amended legislation so that nurses can make referrals for medical imaging examination that utilize ionising radiation. Nevertheless, nurses' radiation knowledge remains a poorly studied concept. The aim of the study was to characterize Finnish nurses' knowledge of radiation use and radiation safety. In this study, nurses were working in operating theaters, first aid clinics and cardiology laboratories. METHODS: A cross-sectional design was applied in which data were simultaneously collected from nurses working in eight hospitals. All nurses working in operating theaters, first aid clinics and cardiology laboratories (N = 1500) at the hospitals in Finland were invited to participate in the study. The response rate was 17% (n = 252). The employed Healthcare Professional Knowledge of Radiation Protection (HPKRP) scale included three areas of knowledge: radiation physics, biology and principles of radiation use; radiation protection; and guidelines of safe ionizing radiation use. Descriptive statistics and logistic regression analyses were used to identify factors that influence these three areas. RESULTS: Nurses reported high knowledge levels in radiation protection but low knowledge levels in radiation physics, biology and principles of radiation use. Moreover, nurses who had not received radiation education reported lower knowledges across all three areas than the nurses who had completed education. CONCLUSION: This study identified one major factor that significantly affects nurses' radiation knowledge, namely, having completed medical radiation education, as this factor positively influenced all three of the included areas of radiation knowledge factors. Therefore, healthcare organizations should concentrate on providing education to all nurses working with, or exposed to, radiation.

Time constant of isovolumic pressure fall in the intact canine left ventricle.

The two standard methods of computation of the time constant of the isovolumic single exponential decay of the left ventricular pressure were compared in anaesthetised, artificially ventilated, closed chest dogs in 87 experiments. In 23 additional experiments, carried out under basal steady state conditions, the time constant attained a mean (SD) value of 32(5) ms when computed according to the method with zero pressure asymptote assumption (Tz) and 39(7) ms when estimated according to a fit with variable pressure asymptote (Tv). Phenylephrine infusion significantly prolonged Tz from 31(6) to 46(12) and Tv from 39(7) to 92(52) ms. The increase in Tv was significantly greater than that in Tz. Propranolol increased Tv by 50% but Tz remained unaltered. Isoproterenol significantly decreased Tz from 33(2) to 18(3) and Tv from 38(3) to 29(3) ms. The decrease in Tz was significantly greater than that in Tv. Calcium chloride and atrial pacing decreased time constants, but volume loading by dextran infusion did not affect them. With regard to the whole material, the linear regression analysis yielded 0.776 as the coefficient of correlation between Tz and Tv. The two methods of time constant calculation appeared to diverge significantly always when changes in afterload or sympathetic activity were involved. These results indicate the dependence of relaxation on afterload but the independence on preload or ejection timing. In the light of these results the zero pressure asymptote method is recommended for the time constant computation as the practical choice when relaxation of the intact left ventricle is assessed.

Multiphoton luminescence imaging of chemically functionalized multi-walled carbon nanotubes in cells and solid tumors.

The intrinsic nonlinear photoluminescence (PL) property of chemically functionalized multi-walled nanotubes MWNTs (f-MWNTs) is reported in this study. f-MWNTs are imaged in fixed lung epithelial cancer cells (A549) and Kupffer cells in vitro, and in subcutaneously implanted solid tumors in vivo, for the first time, using multiphoton PL and fluorescence lifetime imaging (FLIM). Multiphoton imaging in the near-infrared excitation region (∼750-950 nm), employed in this study in a label-free manner, provides sensitivity and resolution optimal to track f-MWNTs within intra-cellular compartments and facilitates tumour imaging and sentinel lymph node tracking in vivo. Wider applications include employing this technique in live imaging of f-MWNTs in biological milieu to facilitate image-guided drug delivery.

Electromechanical delay in the intact dog heart.

A computer method was developed for the determination of electromechanical delay defined as the time between the onset of Q-wave and the onset of the left ventricular systolic pressure rise. It was validated for heart catheterization studies on 56 intact anaesthetized beagle dogs in 86 sessions. The mean basal value of the electromechanical delay was 22 +/- 4 msec. Heart rate, contractility, preload and afterload were changed by atrial pacing and by infusions of calcium chloride, isoproterenol, propranolol, dextran and phenylephrine. Increase of heart rate by pacing from the spontaneous rate of 90 per min to 240 per min prolonged the electromechanical delay from 21 +/- 5 to 33 +/- 14 msec (P less than 0.001). Otherwise the duration of electromechanical delay changed independently of the heart rate. If it changed, the direction of the change followed that of the pre-ejection period. Its proportion of the pre-ejection period varied from 26 to 52%. The electromechanical delay shortened when a positive inotropic effect was noticed or the presystolic fibre length increased.

Effect of smoking on the central circulation at rest and during exercise as studied by radiocardiography.

The pulmonary vessels are the first target of tobacco smoke in the circulatory system, but the functional changes occurring in the pulmonary circulation are poorly understood. Hence 46 volunteers were studied by radiocardiography under the following conditions: 1. At rest before and after smoking 2 cigarettes (15 men); 2. After repeated ergometer exercise (5 min, 100 W) with and without smoking (13 men); and 3. Control experiments under the corresponding conditions without smoking (18 subjects). A significant increase occurred in heart rate, cardiac output and systolic arterial blood pressure after smoking when at rest, but an almost significant decrease in pulmonary dispersion volume , whereas the heart rate and pulmonary capillary pressure attained significantly higher values after than before smoking in the exercise tests, with a significant decrease observed in stroke volume, pulmonary blood volume and pulmonary dispersion volume. It is concluded that smoking impairs physical performance, increases pulmonary capillary pressure and reduces pulmonary blood volume and probably the number of open capillaries.

Electrocardiogram of the reindeer, Rangifer tarandus tarandus.

Electrocardiograms were recorded for 50 Finnish reindeer of age 1 day to 9 years, using standard and unipolar extremity leads in the frontal plane. The range of heart rate was 40-250 beats per minute. Atrial and ventricular depolarization times were 5-10 ms shorter in newborn calves than in other reindeer, and showed only minor variance with respect to heart rate. The duration of depolarization was dependant on heart rate, and was more rapid in young calves. A-V conduction time decreased with increasing heart rate. The mode of the QRS vector was 280-290 degrees, and the mode of the T vector 200-230 degrees in the older animals, but 100-120 degrees in young calves. The main deflection in the QRS complex was S in the leads II, III and aVF.R was dominant in aVL and I.

Nanomorphology of polythiophene-fullerene bulk-heterojunction films investigated by structured illumination optical imaging and time-resolved confocal microscopy.

Structured illumination microscopy (SIM) and time-resolved confocal fluorescence microscopy are applied to investigate the nanomorphology of thin films comprising typical blends of the conjugated polymer, poly (3-hexylthiophene) (P3HT), and [6, 6]-phenyl C61-butyric acid methyl ester (PCBM), used for organic photovoltaic applications. SIM provides evidence for the presence of a thin emissive region around the crystalline regions of PCBM and at the tips of rod-like domains. The time-resolved measurements show that the emission surrounding the PCBM rods is longer lived than the bulk of the film. The two modes of microscopy provide complementary evidence indicating that electron-hole separation is inhibited between the polymer and the large PCBM-rich domains in these regions. We show here that structured illumination microscopy is a viable method of gaining additional information from these photovoltaic materials, despite their weak emission.

Pulmonary circulation in the reindeer.

Right heart catheterizations were performed in 56 sessions on 25 reindeer with determinations of blood pressure and oxygen saturation. Cardiac output was calculated from cineangiocardiograms. When the animals were placed in prone position, heart rate was about 50/min, mixed venous blood oxygen saturation 68 to 72%, right ventricular systolic pressure 27 mmHg, pulmonary arterial pressure 25/16/11 mmHg, pulmonary arterial wedge pressure 6--8 mmHg and pulmonary transfer time 4 to 5 cardiac cycles. When the animals were placed on their side, the heart rate rose to 90 b/min, mixed venous blood oxygen saturation decreased by about 4% and the right ventricular and pulmonary arterial pressures increased by about 10 mmHg; pulmonary arterial wedge pressure did not change. Hypoxemia led to an increase in heart rate, cardiac output and pulmonary arterial pressure; the latter two measures tended to increase whenever the heart rate increased. Under the conditions stated here, an increased pulmonary vascular resistance was calculated when pulmonary arterial pressure was increased.