Systematic evaluation of FRAP experiments performed in a confocal laser scanning microscope--part II: Multiple diffusion processes.

A procedure for a systematic evaluation of fluorescence recovery after photo-bleaching (FRAP) data is presented that allows one to determine distributions of diffusion coefficients. The method provides a straightforward and calibration-free way to quantify multiple diffusion processes when FRAP is measured as a function of time and space by means of confocal laser scanning microscopy. It is verified utilizing FRAP experiments on mixtures of differently sized fluorescent micro-spheres as realizations of discrete D distributions.

Systematic evaluation of FRAP experiments performed in a confocal laser scanning microscope.

The diffusion coefficient as well as the dimensionality of the diffusion process can be determined by straightforward and facile data analysis, when fluorescence recovery after photobleaching (FRAP) is measured as a function of time and space by means of confocal laser scanning microscopy. Experiments representing one-dimensional diffusion from a plane source or two-dimensional diffusion from a line source are readily realized. In the data analysis, the deviations of the actual initial conditions from ideal models are consistently taken into account, so that no calibration measurements are needed. The method is applied to FRAP experiments on solutions of Rhodamine B in glycerol and aqueous suspensions of polymethyl methacrylate microspheres.

Identification and imaging of OH (nu'' = O) and O(2) (nu'' = 6 or 7) in an automobile spark-ignition engine using a tunable KrF excimer laser.

Planar laser-induced predissociative fluorescence is applied to image state-specific densities of OH and hot O(2) inside an internal-combustion car engine. Improved instrumentation is described. It includes better imaging optics and a spectrometer that permits desired molecular quantum states to be selected and identified in real time. The OH (nu'' = 0) images are cleanly separated from the isooctane fuel and they display a thin superequilibrium region at the flame front. In contrast, vibrationally excited O(2) (nu'' = 6 or nu'' = 7) is uniformly distributed behind the front. Uneven and broken flame fronts are commonly observed.

Fluorescence imaging inside an internal combustion engine using tunable excimer lasers.

Tunable excimer lasers are used to obtain 2-D images of molecular (and some state-specific) density distributions inside a cylinder of a modified four-cylinder in-line engine that has optical access. Natural fluorescence (i.e., without a laser) is used for some OH pictures, normal laser-induced fluorescence (LIF) for those of NO and of the isooctane fuel, and laser-induced predissociative fluorescence (LIPF) for other OH pictures and for those of O(2). Relevant spectroscopy is done to find the laser and fluorescence frequencies needed to measure isolated species. LIPF works well at high pressures, is state specific, and is ideally suited to follow turbulent processes. No similar measurements in engines have been previously reported. Pictures are taken in succeeding engine cycles. Their sequence is either at a particular point of the engine's cycle to show cyclic fluctuations, or at succeeding portions of the cycle to illustrate the progress of the gasdynamics or of the combustion.

Effect of pregnancy on serum alanine concentration in normal and genetically diabetic mice.

Serum alanine concentration was determined in nonpregnant and pregnant normal control Swiss albino (SA) and genetically diabetic KK mice. The serum alanine levels were significantly lower in nonpregnant KK than in nonpregnant SA mice. Fasting elicited hypoglycemia, hypoinsulinemia and hypoalaninemia in both groups of pregnant mice. Oral administration of alanine in nonpregnant and pregnant mice resulted in a significant rise in blood sugar levels within 15 min in both groups. However, the initial blood sugar response to oral alanine was greater in pregnant than in nonpregnant mice. This increase in blood sugar response to exogenous alanine appears to be mediated by glucagon. The data suggest that pregnancy elicits hypoglycemia, hypoinsulinemia and hypoalaninemia in both nondiabetic and diabetic mice.

Elevated kidney glucosyltransferase activity in genetic prediabetic mice.

Glucosyltransferase activity in the renal cortex of genetic diabetic KK mice was significantly increased at 40 days of age when compared to that of Swiss albino and F1 hybrid mice. This increase in enzyme activity in the absence of glucose intolerance can be regarded as an earlier genetic marker for the diagnosis of diabetic microangiopathy.

Pre- and postnatal distribution of lipids in the liver of genetic diabetic mice.

Triglycerides, phospholipids, cholesterol and cholesterol esters were determined by thin layer chromatography in the fetal and neonate livers of normal (Swiss albino) and genetic diabetic (KK) mice. In general, the lipids were elevated in the fetal liver of the KK mice. Despite this elevation in liver lipids, no increase in the weight of the newborn was observed.

Prolonged fasting in mice: a more sensitive approach to genetic diabetes.

Effects of two different periods of fasting were studied on glucose tolerance and insulin response to glucose in genetically diabetic KK and nondiabetic C57BL/6J mice. Blood sugar levels of the KK mice did not differ markedly from those of the C57BL/6J mice at the fed state or after 8 h fasting. They were, however, significantly higher in the KK mice when fasted for 18 h. The serum IRI levels, which were at least twice as high in the KK mice, decreased more markedly after 18 h fasting. The KK mice showed impaired glucose tolerance after 8 h fasting, which became more pronounced after 18 h fasting. The insulin response to glucose in the KK mice was not altered after an 8-hour fast; it was, however, diminished greatly after an 18-hour fast. These data suggest that prolonged fasting is necessary to detect the diabetic traits in the KK mice. The C57BL/6J mice showed neither impaired glucose tolerance nor diminished insulin response to glucose at both periods of fasting. Studies with the F1 hybrids (KK male X C57BL/6J female), which carry half of the diabetic genes, suggest that the mode of inheritance of diabetes in the KK mice might be polygenic.