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Speeialia

v e r y d e n s e f r a m e w o r k t h r o u g h w h i c h t h e canaliculi anastomose. I n t h e p i n e a l p a r e n c h y m e , one c a n also o b s e r v e a c o n s i d e r a b l e n u m b e r of fine canaliculi m e a s u r i n g 1-3 a m i n d i a m e t e r (Figure 2, arrows). T h e n e r v e e n d i n g s a n d collagenous fibre b u n d l e s are n o t e a s y t o d i s t i n g u i s h f r o m p i n e a l a n d i n t e r s t i t i a l cell processes. Discussion. T h e s c a n n i n g e l e c t r o n m i c r o s c o p e shows a s u r p r i z i n g s t r u c t u r e of t h e p a r e n c h y m a l p i n e a l canaliculi. I t n o t o n l y c o n f i r m s t h e e x i s t e n c e of ' i n t e r f a c i a l lakes' a n d ' c a v i t i e s of c i r c u m l u m i n a l a r r a y s '1, 3, b u t also clearly demonstrates their numerous ramifications. The abundance of fine canaliculi of 1-3 a m f o r m s a n e t w o r k of l a b y r i n t h a l i n t e r c e l l u l a r spaces which, v e r y p r o b a b l y , come i n t o c o n t a c t w i t h e v e r y p i n e a l cell. T h e a n a l y s i s of t h e p i n e a l g l a n d ' s p a r e n c h y m a t o u s c h a n n e l s w i t h t h e s c a n n i n g e l e c t r o n microscope suggests a c o n t i n u i t y of all canaliculi a n d casts a n e w l i g h t o n t h e i r significance. QuAY'S e x p e r i m e n t s , s h o w i n g t h e existence of a d a i l y r h y t h m of p i n e a l canaliculi, suggest t h e i r f u n c t i o n a l d y n a m i s m . A c c o r d i n g to QIJAY'S o b s e r v a t i o n s 9 a n d o u r

EXPERIENTIA 31/9

results, i t is e v i d e n t t h a t t h e p i n e M g l a n d p a r e n c h y m a tous channels have a much more important histophysiological role t h a n was a s s u m e d u p to now.

Summary. T h e s c a n n i n g e l e c t r o n m i c r o s c o p e h a s s h o w n rich r a m i f i c a t i o n s of t h e p a r e n c h y m a l canaliculi f o r m i n g a t h r e e - d i m e n s i o n a l n e t w o r k of a n a s t o m o s i n g i n t e r c e l l u l a r spaces in t h e r a t p i n e a l gland. E v e r y p i n e a l cell seems t o b e i n c o n t a c t w i t h t h i s c h a n n e l s y s t e m . A n a b u n d a n c e of cellular processes c a n be f o u n d w i t h i n t h e canaliculi w h i c h m a y p l a y a n i m p o r t a n t role in t h e h i s t o p h y s i o l o g y of t h e p i n e a l b o d y . R. KRSTId 11

Institut d'Histologie et d'Embryologie, Universitd de Lausanne, Rue du Bugnon 9, CH-IOI7 Lausanne (Switzerland), 27 April 7975.

u Dedicated to Prof. Dr. rned. W. BARGMANN on the occasion of his 70th birthday.

Effects of G l u c a g o n and I n s u l i n on t h e P a n e t h Cells of the M o u s e D u o d e n u m T h e coarse c y t o p l a s m i c s e c r e t o r y g r a n u l e s are c h a r a c t e r i s t i c of P a n e t h cells (PC). T h e f u n c t i o n of t h e s e cells h a s r e m a i n e d largely u n k n o w n . H o w e v e r , i t h a s b e e n s h o w n t h a t PC secrete digestive e n z y m e s , especially p e p t i d a s e s , i n t o t h e i n t e s t i n a l l u m e n 1, a n d t h e s e c r e t i o n m e c h a n i s m seems to be r e g u l a t e d b y t h e s y m p a t h e t i c a n d p a r a s y m p a t h e t i c n e r v o u s s y s t e m s 2. I t was s h o w n earlier t h a t o r d i n a r y food does n o t h a v e a n y a p p a r e n t effect o n t h e s e cells 3. H o w e v e r , t h e r e c e n t o b s e r v a t i o n s b y t h e p r e s e n t a u t h o r s i n d i c a t e d t h a t , following fasting, t h e secretion m e c h a n i s m is s t i m u l a t e d b y food a n d f a s t i n g itself r e t a r d s t h e s e c r e t o r y a c t i v i t y of PC 4. Trasylol| a n i n h i b i t o r of t r y p s i n a n d p r o t e i n a s e a c t i v i t y , also seems to i n h i b i t t h e s e c r e t i o n m e c h a n i s m of PC 5. Therefore, t h e p r e s e n t p r e l i m i n a r y i n v e s t i g a t i o n was d e s i g n e d t o see w h e t h e r g l u c a g o n a n d i n s u l i n do h a v e a n y effect o n PC. Material and methods. 18 m a l e a n d f e m a l e a d u l t a l b i n o mice, d e s c e n d a n t s of a s t r a i n used in t h e D e p a r t m e n t of A n a t o m y , were used. T h e mice were f a s t e d for 1 d a y before t h e e x p e r i m e n t s b u t were allowed t o d r i n k t a p water ad libitum. T h e m a t e r i a l c o n s i s t e d of 3 g r o u p s of mice. T h e mice of t h e g l u c a g o n g r o u p received a n i.p. dose of 100 a g of g l u c a g o n (Novo). T h e s e mice were killed 1 h l a t e r a n d i n t e s t i n a l s a m p l e s were t a k e n i m m e d i a t e l y f r o m t h e m i d d u o d e n u m ; fixed in a b u f f e r e d a q u e o u s 4 % f o r m a l d e h y d e s o l u t i o n a t p H 7.2; e m b e d d e d in p a r a f f i n w a x ; s e c t i o n e d a t 7 a m a n d s t a i n e d w i t h B e s t ' s c a r m i n e m e t h o d 6. T h e mice of t h e i n s u l i n g r o u p received a n i.p. dose of 4 I U i n s u l i n (Novo). T h e s a m p l e s were t a k e n i h l a t e r a n d t r e a t e d as a b o v e . T h e c o n t r o l mice were o n l y f a s t e d for 1 d a y a n d t h e s a m p l e s were t a k e n as above. E a c h g r o u p c o n s i s t e d of 6 mice. T h e n u m b e r of secret o r y g r a n u l e s of 100 P C d e r i v e d f r o m e a c h m o u s e was c o u n t e d . O n l y t h e r e l a t i v e n u m b e r of s e c r e t o r y g r a n u l e s was d e t e r m i n e d a n d t h e significance of t h e differences b e t w e e n t h e e x p e r i m e n t a l a n d c o n t r o l g r o u p s was estim a t e d , u s i n g t h e S t u d e n t ' s t-test. T h e l i g h t m i c r o s c o p i c a l m o r p h o m e t r i c m e t h o d , t o g e t h e r w i t h its r e p r o d u c t i b i l i t y , h a v e b e e n discussed in d e t a i l p r e v i o u s l y 2. Results. A f t e r g l u c a g o n t r e a t m e n t t h e n u m b e r of s e c r e t o r y g r a n u l e s of P C i n c r e a s e d h i g h l y s i g n i f i c a n t l y

(p < 0.001), i.e. f r o m 12.1 ~: 0.1 (SEM) to 15.5 :t: 0.2 (Figures 1 a n d 2), in t h e d u o d e n u m . T h e size of s e c r e t o r y g r a n u l e s of PC, as e s t i m a t e d visually, r e m a i n e d q u i t e u n c h a n g e d following g l u c a g o n t r e a t m e n t . One dose of i n s u l i n also i n c r e a s e d s i g n i f i c a n t l y (p < 0.01) t h e c o u n t of PC g r a n u l e s ; i.e. f r o m 12.1 ~: 0.2 to 13.0 • 0.1 (Figures 1 a n d 2) 1 h a f t e r a d m i n i s t r a t i o n , w h e r e a s t h e size of t h e g r a n u l e s r e m a i n e d u n c h a n g e d . Discussion. T h e p r e s e n t r e s u l t s s h o w e d t h a t g l u c a g o n a n d insulin were able to increase t h e n u m b e r of s e c r e t o r y g r a n u l e s of PC, w h i c h o b v i o u s l y i n d i c a t e s t h a t t h e secret i o n of c y t o p l a s m i c g r a n u l e s f r o m PC is i n h i b i t e d . G l u c a gon p l a y s a n i m p o r t a n t role as a stress h o r m o n e a n d r e g u l a t e s e.g. t h e c o n c e n t r a t i o n of glucose of t h e s e r u m v, s G l u c a g o n is also able to i n h i b i t t h e secretion of g a s t r i n o, h y d r o c h l o r i c acid 10,n, t h e e x o c r i n e s e c r e t i o n of t h e p a n c r e a s 12, a n d t h a t of v a r i o u s p r o t e i n s f r o m t h e s a l i v a r y g l a n d s 13. T h e a b o v e a n d t h e p r e s e n t o b s e r v a t i o n s s u g g e s t t h e a c t i v e role of g l u c a g o n in t h e r e g u l a t i o n of digestion.

1 A. D. HALLY, J. Anat. 92, 268 (1958). A. AHONEN, Acta physiol, seand. Suppl. 398, 1 (1973). 3 j . S. TRIER, V. LORENZON and K. GROEHLER, Gastroenterology

53, 240 (1967). 4 A. AHONEN and A. PENTTILA, Seand. J. Gastroenterol., 10, 347 (1975). A. ARON~N and A. PEN~TIL/~, Experientia, 31, 577 (1975). P. LAUREN and T. E. SORVARI, Stair Teehnol. 42, 311 (1967). 7 S. R. BLOOM, Postgrad. med. J. 49, 607 (1973). s A. LINDSEY, F. SANTEUSANI0, J. BRAATEN, G. R. FALOONA and

R. H. UNGER, J. Am. med. Ass. 227, 757 (1974). 9 H. D. BEGKER, D. D. REEDER and J. C. THOMPSON, Gastroenterology 65, 28 (1973).

is T. M. LIN, D. C. EVANS and G. F. SPRAY, Archs. int. Pharmaeodyn. Th6r. 202, 304 (1973). ix T. M. LIN, D. C. EVANS and G. F. SPRAY,Arehs. int. Pharmaeodyn. Th6r. 202, 314 (1973). 19 M. MERCADIER, J. P. CHIGOT and J. P. CLOT, M6d. Chir. Dig. ~, 101 (1974). is S. KOJIMA, M. IKEDA and A. TSUJIMOTO, Jap. J. Pharmae. 23, 588 (1973).

15.9. 1975

Speeialia

gran/pc 20 18 16

12 10 8 6

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Fig. 1. The effect of glucagon and insulin on the number of secretory granules of PC of the mouse duodenmn (means and SEM). The counting was made from 600 paneth cells derived equally from 6 different animals in each group. 100 ~zg of glueagon or 4 IU of insulin per mouse was administrated I b before the samples were taken.

insulin

PC 1..5o lOO 5o

0

glu~agon LI

PC 150 100

0

.o

o,I

22 7s 2"6 "28"

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~2' '/," '6'

8

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12 1/, 16 18 20 22 con~roJ

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24 26

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1075

T h e p r e s e n t r e s u l t s s h o w e d t h a t t h e e f f e c t of g l u c a g o n o n P C of t h e m o u s e w a s q u i t e s i m i l a r t o t h a t of f a s t i n g *. Prolonged fasting induces hypoglycaemia, w h i c h is f o l l o w e d b y a n i n c r e a s e of s e r u m glucagon14,15. T h e i n h i b i t o r y e f f e c t of f a s t i n g o n t h e s e c r e t i o n of t h e P C granules may therefore be mediated through the action of g l u c a g o n . T h e s a m e w o u l d a l s o b e v a l i d f o r t h e m e c h a n i s m o f t h e e f f e c t o f i n s u l i n o n PC. I n s u l i n i n c r e a s e s s e r u m g l u c a g o n ~6 a n d t h e p r e s e n t o b s e r v a t i o n s s h o w e d t h a t i n s u l i n s l i g h t l y i n h i b i t e d t h e s e c r e t i o n of P C ; h o w e v e r , t h i s e f f e c t w a s n o t so s t r o n g as t h e e f f e c t o f glucagon. P r e v i o u s s t u d i e s h a v e s h o w n t h a t t h e size o f P C granules has increased following vagotomy, sympathectom y , o r t h e t r e a t m e n t of t h e m i c e w i t h T r a s y l o l | 2, 5. T h e size of P C g r a n u l e s w a s also s h o w n t o i n c r e a s e w i t h t h e a g e of m i c e ~7, is. T h e p r e s e n t o b s e r v a t i o n s s u g g e s t e d t h a t glucagon or insuling did not have any apparent effect on t h e size of P C g r a n u l e s . G l u c a g o n is a n i m p o r t a n t c a t a b o l i c hormone and markedly inhibits the protein synthesis of h e p a t o c y t e s ~9. I t a l s o e x e r t s a m a r k e d e f f e c t o n t h e c a r b o h y d r a t e , l i p i d a n d p r o t e i n m e t a b o l i s m of l i v e r cells ~9, and may therefore exert its action on PC through metabolic effects.

Summary. T h e e f f e c t of g l u c a g o n a n d i n s u l i n o n t h e p a n e t h ceils (PC) o f t h e d u o d e n u m of t h e m o u s e w a s investigated using light microscopy. Both glucagon and i n s u l i n w e r e a b l e to i n c r e a s e s i g n i f i c a n t l y t h e n u m b e r o f t h e s e c r e t o r y g r a n u l e s of P C . T h i s p o s s i b l y m e a n s t h a t t h e s e h o r m o n e s a r e c a p a b l e of i n h i b i t i n g t h e s e c r e t i o n of PC. A . A H O N E N 2~ a n d A. P E N T T I L A 21 Department o/ Anatomy and Department o/Forensic Medicine, University o[ Helsinki, Siltavuorenpenger 20b, S F - 0 0 1 7 0 Helsinki (Finland), 21 A p r i l 1975. 14 J. M. BASSET, Aust. J. biol. Sci. 25, 1277 (1972). 15 A. CHERRINGTON, M. VRANIC, P. FONO a n d N, KOVACEVIC, Can.

J. Physiol. Pharmac. 50, 946 (1972). a6 j. E. GERICH, J. H. KARAMAand P. H. FORSHttM, J. din. Endocr. Metab..37, 479 {1973). 17 K. KUROS~JMI, Int. Rev. Cytol. 11, 1 (1961). la H. M. SELZMAN and R. A. LIEBELT, J. cell Biol. 15, 136 (1962). 19 I. WEINSTEIN, H . A. I~LAUSNER a n d M, HEIMBERG, B i o c h i m .

2

4

6

8

10

12 14

16 18

biopbys. Acta 296, 300 (1973). 2o This work was supported by grants from the Emil Aaltonen Foun-

Fig. 2. Distribution of PC as a function of the nmnber of granules. The mean values of the granule counts are nlarked with dotted lines.

R o l e of S i a l i c A c i d i n t h e M a i n t e n a n c e

dation, Tampere, and

2t the Sigrid Jus~lius Foundation, Helsinki, Finland.

of C e l l S u r f a c e R i g i d i t y

Recently, abundant information has been accumulated w i t h r e s p e c t t o t h e f u n c t i o n of t h e sialic a c i d s a t cell s u r f a c e 1. I t is n o w w e l l k n o w n t h a t sialic a c i d s f o r m a n integral component of t h e c a r b o h y d r a t e prosthetic g r o u p s of g l y c o p r o t e i n s 2 4 a n d of a c i d m u c i n s 2 of t h e cell surface. It has been postulated that the primary function of t h e sialic a c i d m o l e c u l e is t o c o n f e r s t r u c t u r a l r i g i d i t y o n g l y c o p r o t e i n s 5 of cell m e m b r a n e s . WEISS ~ h a s s h o w n r e m o v a l of sialic a c i d r e s i d u e s f r o m t h e s u r f a c e s of s a r c o m a 37 cells i n c r e a s e s t h e o v e r a l l c e l l u l a r d e f o r m a b i l i t y . The increase in the deformability may very well be e x p l a i n e d as t h e loss of r i g i d i t y of t h e cell m e m b r a n e in a b s e n c e of sialic acid. H o w e v e r , n o a t t e m p t h a s b e e n

m a d e s o f a r t o d e m o n s t r a t e t h e loss of t h e r i g i d i t y of t h e cell m e m b r a n e in a b s e n c e of sialic a c i d a n d t h e s u b s e q u e n t f a t e of t h e s e cells. T h e p r e s e n c e of sialic a c i d in t h e cell m e m b r a n e o f a l a r g e free l i v i n g p r o t o z o a , Amoeba, h a s r e c e n t l y b e e n 9 L. WEISS, J. natn. Cancer Inst. 50, 3 (1973). 2 A. GOTTSCHALK, The Chemistry and Biology o/ Sialic Acids and Related Substances (Cambridge University Press, Cambridge 1960). 3 A. GOTTSCHALK, Perspect. Biol. Med. 5, 327 (1962). 4 A. GOTTSCHALK,Rev. pure appl. Cbem. 72, 46 (1962). 5 A. GOTTSCHALK, Nature 786, 949 (1960). 6 L. WE'tSS, J. Cell Biol. 26, 735 (1965).

Effects of glucagon and insulin on the Paneth cells of the mouse duodenum.

The effect of glucagon and insulin on the paneth cells (PC) of the duodenum of the mouse was investigated using light microscopy. Both glucagon and in...
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