Electronic light microscopy combined with spectrophotometry allows real-time analysis of structures at the subcellular level

Ultrasensitive label-free photothermal imaging, spectral identification, and quantification of cytochrome c in mitochondria, live cells, and solutions

Light-absorbing endogenous cellular proteins, in particular cytochrome c, are used as intrinsic biomarkers for studies of cell biology and environment impacts. To sense cytochrome c against real biological backgrounds, we combined photothermal (PT) thermal-lens single-channel schematic in a back-synchronized measurement mode and a multiplex thermal-lens schematic in a transient high resolution (ca. 350 nm) imaging mode. These multifunctional PT techniques using continuous-wave (cw) Ar+ laser and a nanosecond pulsed optical parametric oscillator in the visible range demonstrated the capability for label-free spectral identification and quantification of trace amounts of cytochrome c in a single mitochondrion alone or within a single live cell. PT imaging data were verified in parallel by molecular targeting and fluorescent imaging of cellular cytochrome c. The detection limit of cytochrome c in a cw mode was 5 x 10(-9) mol/L (80 attomols in the signal-generation zone); that is ca. 10³ lower than conventional absorption spectroscopy. Pulsed fast PT microscopy provided the detection limit for cytochrome c at the level of 13 zmol (13 x 10(-21) mol) in the ultrasmall irradiated volumes limited by optical diffraction effects. For the first time, we demonstrate a combination of high resolution PT imaging with PT spectral identification and ultrasensitive quantitative PT characterization of cytochrome c within individual mitochondria in single live cells. A potential of far-field PT microscopy to sub-zeptomol detection thresholds, resolution beyond diffraction limit, PT Raman spectroscopy, and 3D imaging are further highlighted.

Coenzyme Q10 reduces the toxicity of rotenone in neuronal cultures by preserving the mitochondrial membrane potential

Defects in mitochondrial energy metabolism due to respiratory chain disorders lead to a decrease in mitochondrial membrane potential (DeltaPsim) and induce apoptosis. Since coenzyme Q10 (CoQ10) plays a dual role as an antioxidant and bioenergetic agent in the respiratory chain, it has attracted increasing attention concerning the prevention of apoptosis in mitochondrial diseases. In this study the potential of CoQ10 to antagonize the apoptosis-inducing effects of the respiratory chain inhibitor rotenone was explored by video-enhanced microscopy in SH-SY5Y neuroblastoma cells. The cationic fluorescent dye JC-1 which exhibits potential-dependent accumulation in mitochondria was used as an indicator to monitor changes in DeltaPsim. The relative changes in fluorescence intensity after incubation with rotenone for 15 minutes were calculated. Pre-treatment with CoQ10 (10 or 100 microM) for 48 h led to a significant reduction of rotenone-induced loss of DeltaPsim. These results suggest, that cytoprotection by CoQ10 may be mediated by raising cellular resistance against the initiating steps of apoptosis, namely the decrease of DeltaPsim. Whether these data may provide new directions for the development of neuroprotective strategies has to be investigated in future studies.

Experimental hypoxia of STZ-diabetic rat myocardium and protective effects of Ginkgo biloba extract. II. Ultrastructural investigation of microvascular endothelium

Four months after induction of diabetes by intraperitonal injection of 60 mg streptozotocin/kg body weight wistar rats were exposed to an acute respiratoric hypoxia of 20 min duration. One group of the rats received daily Ginkgo biloba extract EGb 761 (100 mg/kg body weight). By means of qualitative and quantitative electron microscopic analysis we compared the hypoxia-induced ultrastructural alterations of the myocardial microvascular endothelium in normal, diabetic, and EGb-protected rats. Aim of the study was to compare the hypoxia tolerance of myocardial microvessels of normal and diabetic rats and to test the possibility of antioxidative protection. The results revealed that only some ultrastructural microvascular parameters of diabetic rats were stronger altered after acute hypoxia than normal ones, e.g. capillary dilatation, number of lysosomes, frequency of vesicles and fused vesicles, endothelial swelling, and structural state of mitochondria. Other parameters exhibited less severe alterations than in healthy rats, as luminal blebbing and protrusions, endothelial vacuoles, mitochondrial swelling, and pericapillary debris. Protective effects of EGb could be demonstrated on endothelial swelling, blebbing, vesiculation and vesicular fusioning, partly on vacuolization, but not on mitochondrial parameters. The results were discussed on pathobiochemical background. EGb 761 was estimated to be protective against hypoxic damage on myocardial microvessels also in diabetic condition, but the study should be completed by inclusion of a reoxygenation interval.

Effects of elevated intraocular pressure on haemoglobin oxygenation in the rabbit optic nerve head: a microendoscopical study

Intraocular pressure dependent reactions of optic nerve head vasculature and intracapillary haemoglobin oxygenation (HbO(2); oxygen saturation) were studied in the center and at the rim of the rabbit optic nerve head (ONH) as well as in the choroid, by a new combination of microendoscopy and simultaneous haemoglobin spectrophotometry. In 13 anesthetized albino rabbits the vasculature and the intracapillary Hb-oxygenation were studied by a microendoscope which was introduced into the eye bulb. Photometric measurements were performed via a beam splitter with the Erlangen micro-lightguide spectrophotometer (EMPHO) from the center of the endoscopic picture. The haemoglobin oxygenation was calculated by real time analysis of the spectral curves. Intraocular pressure was elevated stepwise from 20-80 mmHg. At the rim of the optic nerve head the vascular diameters as well as the intracapillary HbO(2)-values were stable till an intraocular pressure of 60 mmHg and decrease after IOP elevation to 70 and 80 mmHg. In contrast, in the center of the optic nerve head and in the choroid these parameters decline already from 40-50 mmHg on. At an IOP of 60 mmHg (P<0.01) and 70 mmHg (P<0.05) HbO(2)is significantly lower in the ONH center than at the rim. In the center and the choroid HbO(2)is well maintained between 20 and 40 mmHg. After pressure release at the end of the experiment HbO(2)increased to 94.3+/-4.6% (rim) and 98.8+/-1.5% (center) of the initial value at 20 mmHg (difference not significant).By the high spatial resolution of this new optical method we were able to demonstrate that the center of the optic nerve head is more sensitive to changes in intraocular pressure than the optic nerve head rim. Thus, tissue damage after critical haemodynamic and oxygenation parameters seems more probable in the relatively poor perfused center of the ONH than in the overperfused rim.