Dissection of DNA damage and repair pathways in live cells by femtosecond laser microirradiation and free-electron modeling

Understanding and predicting the outcome of the interaction of light with DNA has a significant impact on the study of DNA repair and radiotherapy. We report on a combination of femtosecond pulsed laser microirradiation at different wavelengths, quantitative imaging, and numerical modeling that yields a comprehensive picture of photon-mediated and free-electron-mediated DNA damage pathways in live cells. Laser irradiation was performed under highly standardized conditions at four wavelengths between 515 nm and 1,030 nm, enabling to study two-photon photochemical and free-electron-mediated DNA damage in situ. We quantitatively assessed cyclobutane pyrimidine dimer (CPD) and γH2AX-specific immunofluorescence signals to calibrate the damage threshold dose at these wavelengths and performed a comparative analysis of the recruitment of DNA repair factors xeroderma pigmentosum complementation group C (XPC) and Nijmegen breakage syndrome 1 (Nbs1). Our results show that two-photon-induced photochemical CPD generation dominates at 515 nm, while electron-mediated damage dominates at wavelengths ≥620 nm. The recruitment analysis revealed a cross talk between nucleotide excision and homologous recombination DNA repair pathways at 515 nm. Numerical simulations predicted electron densities and electron energy spectra, which govern the yield functions of a variety of direct electron-mediated DNA damage pathways and of indirect damage by ^•OH radicals resulting from laser and electron interactions with water. Combining these data with information on free electron-DNA interactions gained in artificial systems, we provide a conceptual framework for the interpretation of the wavelength dependence of laser-induced DNA damage that may guide the selection of irradiation parameters in studies and applications that require the selective induction of DNA lesions.

Highly standardized multicolor femtosecond fiber system for selective microphotomanipulation of deoxyribonucleic acid and chromatin

We present a three-color femtosecond Er/Yb:fiber laser enabling highly specific and standardized nonlinear optical manipulation of live cells. The system simultaneously provides bandwidth-limited 80-fs pulses with identical intensity envelope centered at wavelengths of 515, 775, and 1035 nm in the focus of a confocal microscope. We achieve this goal by combining high-order dispersion control via, for example, chirped fiber Bragg gratings with proper bandwidth management in each nonlinear conversion step. Wavelength-selective and noninterfering induction of deoxyribonucleic acid (DNA) photoproducts and DNA strand breaks, as well as fluorescence photoactivation of a photoactivatable green fluorescent protein (PA-GFP)-histone fusion protein, are demonstrated. The capability to introduce different types of DNA lesions and perform photoswitching experiments in a selective manner is essential for quantitative studies on DNA repair and chromatin dynamics.

Changes in ductus venosus flow profile in twin-twin transfusion syndrome: role in risk stratification

OBJECTIVES

To evaluate changes in ductus venosus (DV) waveforms and the timing of these changes in twin-twin transfusion syndrome (TTTS), to relate these to disease severity and to assess the clinical applicability of the suggested measurements in the prediction of TTTS.

METHODS

DV time intervals and velocity-time integrals (VTI) normalized to cardiac cycle and total VTI, respectively, as well as velocity ratios were analyzed in 149 monochorionic diamniotic (MCDA) twin pairs. Pregnancies were assigned to the following groups: uncomplicated MCDA (n = 29); TTTS Stages I+II (n = 50); TTTS Stages III+IV (n = 49); and pre-TTTS (n = 21), of which 14 remained stable and seven progressed to TTTS. Intertwin differences were calculated as larger/recipient minus smaller/donor and related to disease severity. Receiver-operating characteristics curve analysis was used to distinguish TTTS vs uncomplicated MCDA and pre-TTTS progressing to TTTS vs non-progressing pre-TTTS. Intra- and interobserver reliability of measurement of DV parameters were evaluated using intraclass correlation coefficients (ICCs).

RESULTS

No intertwin differences in DV parameters were found in uncomplicated MCDA pregnancies. Diastolic VTIs and filling times were significantly shorter in recipient twins in TTTS cases and in larger pre-TTTS twins in comparison with their cotwins. Time intervals, VTIs and velocity ratios correlated significantly with Quintero stages. An intertwin difference in early filling time (eT) normalized to cardiac cycle, eT (%) ≤ -3.6%, could differentiate TTTS from uncomplicated MCDA pregnancies (82.8% sensitivity; 79.8% specificity) and eT (%) ≤ -2.8% predicted progression to TTTS (73.1% sensitivity; 67.4% specificity).

CONCLUSIONS

DV flow profiles and timing of waveform events are already altered in pre-TTTS and early-stage disease, reflecting abnormal ventricular filling and circulatory imbalance. Intertwin comparison of filling times and VTI may allow prediction of evolving TTTS in MCDA pregnancies. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Tissue Doppler imaging in fetuses with aortic stenosis and evolving hypoplastic left heart syndrome before and after fetal aortic valvuloplasty

OBJECTIVES

Fetal aortic valvuloplasty can improve filling and reduce afterload of the left ventricle in critical aortic stenosis. Success of an intrauterine intervention is currently measured by technical success, clinical survival and eventual postnatal biventricular physiology. In the present study we investigated the use of tissue Doppler imaging (TDI) to evaluate changes in ventricular function assessed before and after prenatal aortic valvuloplasty.

METHODS

Between October 2008 and December 2012, cardiac function was assessed by TDI before and after intervention in 23 fetuses that underwent technically successful valvuloplasty for critical aortic stenosis and in which postnatal outcome was known. The measurements were transformed into gestational age-independent Z-scores where appropriate.

RESULTS

Mean ± SD gestational age at intervention was 27.5 ± 3.1 weeks. Of the 23 fetuses, 14 had biventricular outcome. Before intervention all left ventricular (LV) TDI-derived parameters and mitral annular plane systolic excursion (MAPSE) were severely abnormal. It was possible to demonstrate considerably improved cardiac function after technically successful valvuloplasty. Among fetuses with postnatal biventricular outcome, TDI-derived LV myocardial peak velocity during early diastole (E') and myocardial peak velocity during systole in the ejection phase (S') significantly increased, E'/myocardial peak velocity during late diastole with atrial contraction (A') increased towards normal values, and LV transmitral-to-mitral-annular diastolic velocity ratio (E/E') and myocardial performance index (MPI') decreased but remained abnormally elevated. In addition, right ventricular A', S' and MPI' significantly improved after intervention.

CONCLUSION

Technically successful fetal aortic valvuloplasty led to significantly improved myocardial performance. It was possible to use TDI to detect distinct changes in ventricular function and TDI-derived parameters correlated with a biventricular outcome after birth. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Urinary tract infection prophylaxis using Escherichia coli 83972 in spinal cord injured patients

PURPOSE

Escherichia coli 83972 was previously shown to establish bladder colonization in select patient groups. We evaluate the safety and feasibility of using bacterial interference with E. coli 83972 to prevent urinary tract infection in spinal cord injured patients.

MATERIALS AND METHODS

A total of 21 men and women with neurogenic bladder secondary to spinal cord injury underwent intravesical inoculation with E. coli 83972. Frequency of symptomatic urinary tract infection before and after colonization was compared.

RESULTS

Successful long-term bladder colonization was achieved in 13 study participants. Mean duration of colonization was 12.3 months (range 2 to 40). Subjects had no symptoms of urinary tract infection while colonized with E. coli 83972 (0 infection per 18.4 patient-years). Successfully colonized subjects had experienced a mean of 3.1 symptomatic urinary tract infections per year (range 2 to 7) before colonization. Symptomatic infection also occurred in 4 subjects who were not successfully colonized with E. coli 83972 and in 7 others after spontaneous loss of colonization. Colonized subjects reported subjective improvement in quality of life with respect to urinary tract infection while colonized.

CONCLUSIONS

E. coli 83972 may be safely used to establish long-term asymptomatic bladder colonization in spinal cord injured subjects. Preliminary findings suggest that colonization with E. coli 83972 may reduce the frequency of urinary tract infection in patients with neurogenic bladder secondary to spinal cord injury.

Injuries due to letter bombs

In Austria in late 1993 ten letter bombs were sent to outstanding persons who have been engaged in the care of foreigners. Four of these bombs detonated, when they were opened by the addressee. The remaining six bombs were discovered in time and could be deactivated by specialists. The construction of these bombs and the lesions sustained by the four victims will be discussed. The injuries mainly concerned the left hand, i.e., the hand used by right-handed persons to hold a letter when opening it. The way holding the letter was of crucial influence on the degree of injury, as with the same explosive charge (which can be assumed deducing from the investigation of the deactivated bombs) injuries varied considerably. They ranged from minor tissue-lesions to mutilated fingers and the risk of exsanguination.

[Electroshock devices as weapon]

13 electric shock weapons were investigated. The authors measured the electrical output and observed the effects on corpses and test persons. The electric shock weapons produced only moderate pain and did not stop the disposing capacity. The electrocardiogram and the circulation parameters were not influenced. The electric shock weapons tested might have only a limited deterrent effect and might be able to cause fatal complications under circumstances. Drug use and heart disease might enhance the risk.

Shots fired with silencers--a report on four cases and experimental testing

Four cases of homicide, in which silenced firearms were used, are reported and supplemented by data from experimental investigations regarding wound features, marks, traces, and ballistic behavior. Wound features are largely determined by the construction of the silencer. In one case, even a muzzle imprint was produced by a silenced weapon fired at contact range. In general, silencers are likely to result in a decrease in bullet energy and accelerated energy release in the target (tissue). In terms of wound morphology, silencers produced a reduction in or even a lack of the contact ring (ring of dirt). In close-range and contact wounds, any features indicative of shots fired at close range were missing (such as soot deposit and powder tattooing). It is also worth mentioning that biological matter may get into the silencer in shots fired at contact range.

[Gunshot wounds of the head in soldiers wearing military helmets-- general aspects and experiments and observations on the biomechanics and wound morphology]

With respect to wound ballistics, the situation is different if the person wearing a military helmet suffers head injuries from a bullet. The mechanisms of injury were investigated in four experimental series and supplemented by a case history. The study showed surprising results: in the majority of cases, the helmet does not protect the wearer, but instead intensifies the damage caused by the bullet. The reasons for this phenomena are changes in the stability of the projectile and deformation of or damage to the bullet. All of these mechanisms result in the bullet striking the tissue with higher energy. In this investigation, Kevlar helmets were also tested, which are not penetrated by 9 X 19 mm parabellum bullets. Even so, however, severe injuries of the skull and brain can occur because the projectile causes intensified impressions on the skull under the helmet and, in addition, an acceleration of the head.

[Teeth as an intermediate target--a cause for rapid disintegration of the full metal-jacketed bullets used by the military]

Sharp-pointed full metal-jacketed bullets fired from assault rifles are expected to have a low tendency of deformation or destruction within biological tissues. In principle this also should apply to small calibre projectiles .223. If a bullet penetrates the oral region, contact with teeth can cause early break up and even total disintegration of the projectile. Under such circumstances the fragments are possibly retained within the body. A case of accidental gunshot injury to the head inflicted with an assault rifle AUG Steyr. 223 of the Austrian army serves to demonstrate and discuss the wound ballistic effects in relation to the altered behaviour of the projectile. Analogous findings were reproduced in experimental models.