184

.$BSTRACTS

Insulin-Binding P. KERN,

Impairment

J. PICARD

of Plasma Membrane

AND I?. REONAVLT,

Receptors in Heriditary

Diabetic

Mice

f’ur1’s

The interaction between insulin and its receptors was st)udied with liver plasma membranes of hereditary diabetic mice (KK strain) as compared to normal mice (Swiss strain). Using an identical procedure for preparation and incubation, results indicate that KK mice plasma membranes bind 50-600/6 as much insulin per mg of protein as those of the control mice. Scatchard analysis suggests that this decrease in binding is due to a decrease in the number of receptor sites in the membrane of the diabetic mice, the variations being statistically significant. In contrast to the decrease of insulin recept,ors, the plasma membranes of the diabetic mice were similar to those of the control animals, no difference was found in membrane markrr enzymes activity, hexosamines and sialic acid content,s or protein subunit structure. The relation between this decrease in insulin receptors and other pathological alterations occurring in the diabetic mice will be discussed.

Glycosyltransferase E. Roux

of Platelet

AND F. REGNAULT,

Plasma Membrane

in Diabetes

Paris

Among the different haemo-rheological factors which could be involved in the pathogenesis of diabetic retinopathy, platelet modifications may play an important role. ADP and collagen aggregation disorders in diabetes cannot be related to the surface charge alterations of platelets because no variation of N-acetyl neuraminic acid concentration was found in diabetic platelets. To investigate the possible origin of these aggregation disorders in diabetic patients we studied the enzymatic activity of platelet membrane. Galactosyl and glucosyl transferase which could be part of the aggregation process have been studied using a modified collagen acceptor and [W]UDP glucose and galactose. The glycosyl transferase modification observed in diabetic patients are a first step in the cornprehension of aggregation disorders.

Enzymes in Lacrimal

Secretion

N. J. VAN HAERINGEN

AND E. GLASIIX,

Amsterckzm

In human tear fluid the activity of 12 enzymes of energy-producing metabolism can be detected. Rather high values are found for lactate dehydrogenase, pyruvate kinase, malate dehydrogenase and amylase, with fluctuating activities during lacrimal secretion. The similarity in enzyme pattern of the lacrimal gland and tear fluid and the discordance of enzyme activities of serum and tear fluid suggest a lacrimal source for these enzymes.

A New System for Studying Retinal Metabolism JI. TSACOPOCLOS,

R. BAKER

AND S. LEVY.

in situ

Genecn

A new small, lightweight and highly versatile micromanipulator-fibre optic illumination system has been developed in our laboratory for the introduction and precise positioning of microelectrodes in preretinal vitreous and retina. The moving portion of the system co-axially surrounds the total length of the microelectrode in a telescope fashion (electrode into fibre optic illumination system and the latter into micromanipulator) so that the whole axis moves in unison. The micromanipulator is attached to the sclera by means of a ring adapted to the form of the eye. It allows for slow, smooth reproducible movements (to as small as 2 pm). It can move an electrode in any direction without changing the eye’s orientation. Platinum tissue-PO, electrodes (3-5pm diameter sensing tip) and glass pH sensitive tissue electrodes (l-10pm in diameter) are introduced into the system for retinal measurements. The tips of these electrodes as well as the fundus are illuminated for microscopy by the fibre optic system. This system provides new experimental possibilities for studying ret,inal tissue metabolism in sit’u.