Over-estimation of curve length using a semi-automatic digitizer

A high cell recovery (92%) was found for centrifugation (10 min, 70 g) of fixed cells, compared to a 37% cell recovery for unit gravity sedimentation (60 min, room temperature) of fixed cells. The lymphocyte-monocyte ratio in centrifugation preparations was found identical to the ratio in control smears, as determined by using non-specific esterase activity. Unit gravity sedimentation preparations showed a specific loss of lymphocytes when compared to control smears.

MORPHOMETRY

OVER-ESTIMATION A SEMI-AUTOMATIC J. Cornelisse, G. Vrensen

OF CURVE LENGTH DIGITIZER T. Van den Berg

USING

and

Department of Morphology and Department of Visual System Analysis, The Netherlands Ophthalmic Research Institute, Post Office Box 12141, 1100 AC Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands

The use of computers in morphometrics is extending rapidly. However, the application of computers requires also knowledge of the special qualities and pitfalls of these modern tools. A computer connected with a digitizer tablet does not see our continuous reality, but an array with discrete points. From the position of the cursor on the tablet the nearest point of the array is After moving the cursor along a read. curve a series of coordinate pairs will represent this curve. The actual selection of coordinates depends on cursor speed and on the characteristics of the instrument. The task of a measuring program is to reconstruct the real properties of the curve within the desired accuracy. Improper algorithms can cause serious over-estimation up to a maximum of 41%.

Syrian hamsters (strain 910 8262) suffer from a genetically determined involving heart and skele. polymyopathy, tal musculature. In heart muscle the course of the disease shows a phasic pattern: (I) O-6 weeks--no necrosis, (II) 6-12 weeks--multifocal necrosis followed by infiltration of mononuclear round cells and calcification, (III) be. yond 12 weeks--no new necrotic foci, scar formation and calcification. The aim of the study was to investigate the effect of a low calcium diet on the mitochondrial compartment of the heart muscle cells. The left ventricular wall of 2, 4, 8, 12, 24 and 36 weeks old BIO 8262 (normal diet), BIO 8262 (Low Ca diet) and healthy control hamsters was used for perfusion fixation and processed for electron microscopy. The stereological measurements were performed by point counting. A low calcium diet prevented calcification completely and delayed the onset of necrosis in BIO hamsters. The volume densities of mitochondria and myofibrils (per volume of muscle fibres) were decreased after a low calcium intake with respect to the BIO hamsters (normal diet). With respect to healthy control animals the volume density of the mitochondria increased but the volume density of the myofibril decreased in both groups of BIO hamster When the volume of the mitochondria was related to the volume of the myofibrils no difference between normal diet ~10 hamsters and low Cd diet hamsters was found, but a more striking increase was found with respect to the healthy control animals. Surface-tovolume ratio studies showed that the mitochondria are distinctly swollen in both groups of BIO hamsters. These findings are taken to support the view that in BIO 8262 hamsters the cardiocyte mitochondria accumulate calcium as a consequence of an increased intracellular calcium content caused by an underlving defect in the sarcolemma.

PROBLEMS IN THE QUANTITATIVE OF COMPLEX-SHAPED SYNAPSES EFFECT MUSCLE SYRIAN

OF A LOW CALCIUM DIET ON HEART MITOCHONDRIA IN CARDIOMYOPATHIC HAMSTERS. A STEREOLOGICAL STUDY

G. Egberink Department phology, Nijmegen,

and A. Stadhouders of Submicroscopic MorUniversity of Nijmegen, The Netherlands

STEREOLOGY

D. M. G. De Groot Medical Biological P. 0. BOX 45, 2280 Netherlands

Laboratory TNO, AA Rijswijk, The

In the hipocampus of ageing rats both "classical" disc-like as well as