[Fully-automatic microscopic image analysis and measuring of single fiber conduction velocity in the sural nerve of short-term diabetic rats].

Contrasting to the usual measurement of nerve conduction velocity, which only determines the conduction of the fastest fibers, single fiber measurement allows the registration of the conduction velocity of different fiber classes. The present experiment was performed to study whether electroneurophysiological and/or morphometrical parameters of group II fibers have changed after shortterm diabetes mellitus. Diabetes was induced in 28-d-old Lewis 1A-rats by administration of 60 mg/KG b.w. Streptozotocin. 60 d later, with the aid of an oscilloscope VKS 22-16 (VUKO Elektronische Geräte GmbH, Mühlheim) single fiber measurements were performed. Morphometry was carried out on semithin transverse sections of sural nerve with an automatic image analysis system A6471-AMBA/R (Robotron, Dresden). The mean plasma glucose level of diabetic animals was 27.1 +/- 2.7 mmol/l. The mean afferent conduction velocity was significantly reduced in diabetic animals. Furthermore, efferent fibers could be verified in sural nerve which showed also reduced conduction velocity in diabetic rats. Morphometry revealed significant reduction of thickness and area of myelin sheaths, whereas area of axons remained unchanged. Electroneurophysiological and morphometrical changes will be discussed with special emphasis to different fiber groups. It is suggested, that primary Schwann cell lesion is responsible for the observed findings.