Asymptotic fractals in the context of grey-scale images.

The estimation of the fractal dimension in the case of concave log-log Richardson-Mandelbrot plots can be obtained by using asymptotic fractal equations. We demonstrate here, under asymptotic fractal conditions, that additional derivations making use of the Minkowski dilation in grey-scales lead to two asymptotes, one having a slope of 1 and the other a slope of DT-D + 1 (where DT is the topological dimension and D the fractal dimension). The resulting equation offers important advantages. It allows: (i) evaluation of scaling properties of a grey-scale image; (ii) estimation of D without any iteration and (iii) generation of texture and heterogeneity models. We concentrate here on the first two possibilities. Images from cultured cells in studies of cytoskeleton intermediate filaments and kinetic deformability of endothelial cells were used as examples.

Changes in flagellar movement of rat spermatozoa along the length of the epididymis: manual and computer-aided image analysis.

The different patterns of motility of rat spermatozoa during epididymal transit were studied in vitro using high-speed videomicroscopy. The sperm images were analysed after manual tracing as well as with a computer imaging system. The present work is the first which reports both the swimming path of the sperm head and the characteristics of flagellation in this species. The hook-shaped head of the rat spermatozoa allowed us to demonstrate the two-dimensional (2D) swimming movement compared to the three-dimensional (3D) sperm motion which was mainly related to rotation of the head. Immotile spermatozoa entered the initial segment of the testis and showed rigid flagella. The potential for sperm motility occurred abruptly in the proximal caput region, and different patterns of flagellation were observed: vibrating, motile in place, motile with a static curvature of the midpiece resulting in a spinning motion or a circular path, and forward progressive movement with regular rotation of the head. The pattern of sperm movement became homogeneous in the distal cauda where the whole sperm population swam in a straight line. A static curvature appeared in the midpiece portion when the spermatozoa reached the proximal caput region. The formation of the static curvature was observed on both sides of the rat flagellum which were easily indicated by the head-shaped projection of the head and the axonemal side of the principal wave. As soon as they moved, the spermatozoa successively initiated principal (P) and reverse (R) waves, but the waves were visible only distal to the static curvature. The midpiece stiffness progressively decreased during the epididymal maturation; simultaneously the static curvature showed a larger radius and then disappeared. Consequently, the initiation of waves which was first seen in the distal part of the flagellum of immature cells occurred progressively near the junction with the head of maturing spermatozoa. These changes in sperm motion previously shown in rams and now in rats might be a general phenomenon in mammals. The high resolution of this computer imaging system applied tosperm motion showing a well-characterized "side of the flagellum" should allow sensitive detection of biochemical effects on flagellar beating.

Effects of transient cerebral ischemia on the hippocampal dentate theta (theta) profile in the acute rat: a study 4-5 months following recirculation.

This study mainly describes the long-term effects of 20 min of cerebral ischemia on the profile of the presumed cholinergic theta rhythm in the rat dorsal hippocampal formation during ether anesthesia and injection of the muscarinic agonist agent arecoline. The experimental data were collected 4-5 months after ischemia. They show that ischemia results in a statistically significant reduction in both superficial and deep theta recorded from the CA1 area of the hippocampus and the dentate gyrus, respectively. Amplitude reduction is similar for both rhythms and co-varies positively with the extent of CA1 stratum pyramidale damage which, from light microscope observation, appeared to be the major neuroanatomical consequence of ischemic insult in the dorsal hippocampal formation. The medial septal nucleus-diagonal band of Broca complex involved in theta generation did not suffer visible anatomical damage. Moreover, no significant alteration in the spatial distribution and the density of hippocampal dentate acetylcholinesterase reaction product was seen in ischemic animals. These histological data were statistically confirmed by computerized image analysis. Finally, this is the first investigation to show that transient interruption of cerebral blood flow results in a long-lasting alteration of theta rhythm which is probably the major aspect of the basic activity of the hippocampal formation. Thus, the present findings obtained in the acute rat at 4-5 months postischemia confirm and extend, in most respects, our previous results collected in the chronic animal 2-29 days following 4-vessel occlusion. Possible significance of these findings for the hypothesis of the dependent generation sites of superficial and deep thetas in the hippocampus assumed to be crucial in learning and memory, is discussed.

Automated analysis of human sperm motility.

Sperm motility is a determinant parameter characterizing the fertilizing ability of a semen sample. An objective method for measuring this parameter based upon an automated analysis of microcinematographic recordings is presented. The system, which consists of a Cinescan H16, a Quantimet 720 image analyzer, and a PDP 11/34 minicomputer, allows a motility analysis to be performed in about 5 min.

A new method for automatic metaphase finding adaptable to different chromosome preparations.

A FORTRAN computer program, running on a Digital PDP 11-34 minicomputer, has been developed for use in conjunction with a Cambridge Quantimet 720 image analyzer for the investigation of metaphase preparations in routine cytogenetics. During a short initiation phase the program is adapted to the type of metaphase being analyzed. The program is fast and its performance is good, even at low microscopic magnifications. It has other uses in biology for all investigations and characterizations of small distinct elements widely spread within a preparation (e.g., autoradiography, bacteriology).