De Kock, Leon L.

English

De Kock Leon L.

University of Szeged

U N S O L V E D P R O B L E M S O F C A R O T I D B O D Y T I S S U E S b y L . L . DE К О Е К P r o f e s s o r o f N a t u r a l H i s t o r y D e p a r t m e n t , U n i v e r s i t y o f A b e r d e e n It g i v e s m e g r e a t p l easure t o a c c e p t a n i n v i t a t i o n t o c o n t r i b u t e a n ar t i c l e t o t h e s p e c i a l issue o f Acta Biologia Szcgediensis, t o c e l e b r a t e P r o f e s s o r A M B R U S A B R A H A M ' S 7 0 th b i r t h d a y . A l t h o u g h w e l l a c q u a i n t e d w i t h P r o f . ABRAHAM'S w o r k , it w a s n o t unt i l his r e c e n t v i s i t t o this c o u n t r y t h a t I b e c a m e t h o r o u g h l y f a m i l i a r w i t h t h e o u t s t a n d i n g q u a l i t y — a n d q u a n -t i t y — o f h i s w o r k . _ . . . -In a n e x c e l l e n t a n d c o m p r e h e n s i v e Iccture, g i v e n at this U n i v e r s i t y , P r o f . ABRAHAM w a s ab le t o g u i d e t h e a u d i e n c e , o f w h i c h m a n y w e r e b y n o m e a n s s p e c i a l i s t s in P r o f . A B R A H A M ' S f i -e ld o f t h e f i n e i n n e r v a t i o n , e s p e c i a l l y o f t h e c a r d i o - v a s c u l a r s y s t e m , t o a f u l l e r a p p r e c i a t i o n o f th i s i m p o r t a n t f i e l d . H i s Iccture g a v e m a n y t h e rare a n d v a l u a b l e p l easure o f h e a r i n g a m a s t e r in h i s subjec t s u m m a r i s i n g h i s l i f e ' s w o r k . H e d e m o n s t r a t e d in an e n d l e s s n u m b e r o f e x c e l l e n t p h o t o g r a p h s t h a t t h e f i ne s t n e r v e s u p p l y t o t h e c a r d i o v a s c u l a r s y s t e m is o f a s t o n i s -h ing c o m p l e x i t y a n d i n t e n s i t y a n d it g a v e t h o s e w o r k i n g in t h e f i e l d o f n e r v e s t a i n i n g a n e w s t i m u l u s o f w h a t c a n b e a c h i e v e d . P r o f . A B R A H A M h a d a l s o b r o u g h t w i t h h im h i s o w n h i s t o l o g i c a l p r e p a r a t i o n s o f c a r o t i d b o d y t i ssue a n d t h e s e I h a d t h e p l e a s u r e t o s t u d y in great d e t a i l a t m y o w n le i sure . T h e y w e r e b y f a r t h e m o s t b e a u t i f u l p r e p a r a t i o n s I h a d e v e r seen, w i t h e v e n t h e f in e s t f ibres s tan -d i n g o u t w i t h unsurpassed cr i spness a n d c l a r i t y . A n d , as it so o f t e n h a p p e n s , w h e n s t i m u l a t e d b y a p e r f e c t p r e p a r a t i o n f r c c h t h o u g h t s o n t h e subjec t c o m e t o m i n d , a n d w i t h it a n e w zes t f o r f u r t h e r research. T h e caro t id body is usually s i tua ted as a minu te swelling at the b i fu rca t ion of the c o m m o n caro t id a r t e ry . This tissue has so f a r been f o u n d in all invest i-gated m a m m a l s and bi rds ( D E K O C K , 1 9 5 9 ) . In all cases, it is character ised by the presence of a sinusoidal vascular bed wi th an intensive nerve supp ly and the presence of typical cells ( D E K O C K , 1 9 5 4 ) . I ts func t ion is general ly believed to be chemosensory, testing, as it were, the qual i ty of the c i rculat ing blood, es-pecially regards its oxygen con ten t , and sending i n f o r m a t i v e impulses to the resp i ra tory and vasoregula tory centres of the brain ( H E Y M A N S & N E I L , 1 9 5 8 ) . The t rue na tu re of the typ ica l cells is still unde r discussion, so a re the detai ls of innerva t ion . Us ing the l ightmicroscope it became a p p a r e n t tha t the typica l cells fell into t w o dist inct types , t h e one a large, rounded cell, w i th in ter locking cytoplasmic extensions t o w a r d s o the r cells of its own t y p e ( type I cell, DE K O C K , 1 9 5 4 ) . T h e c o m p a r a t i v e l y clear cy toplasm, of this cell carries a r ound , vesicular nucleus wi th one to t w o nucleoli, and marked cy top lasmic inclusions, such as conspicuous mitochondria, endoplasmic reticuli, excre tory vesicles and osmiophil ic granules. T h e o the r cell ( t y p e I I cell) has i r regular cy top lasmic outlines, whe reby most of the cy top lasm sprawls between t y p e I cells. T h e cell J I Лсгя Biologica 1 6 2 L. L. L>F KOCK is densely g r a n u l a r and carr ies on oblong nucleola ted nucleus and mitochondria. Its cy top lasm ensheathes f i n e n e r v e fibres. Wi th the in t roduct ion of the electron microscope (E. M.) it was hoped to solve f inal questions of i nne rva t ion , and especially the place of synap t i c t r ans -mission between ei ther t y p e of cell and the ne rve supp ly ; a p rob lem which has a l r eady been solved f o r the o ther known chemorecep tors of the tongue a n d nose, as well as fo r a number of inver tebra te chemoreceptors ( D E L O R E N Z O , 1 9 5 8 ; T R U J I L L O - C E N O Z , 1 9 5 7 ; F . N G S T O M , 1 9 5 3 ; S C H A N Z , 1 9 5 3 ; B L O O M , 1 9 5 4 , a n d D E T H I E R , 1 9 5 5 ) . H o w e v e r , it appea r s t h a t the caro t id body tissue represents an especially complex problem aggrava ted by the fac t t h a t it is not like o the r chemorecep to r s or ienta ted t o w a r d s one surface, but lies enmeshed in a twisted sinusoidal system. So f a r , previous worker s h a v e been able to conf i rm the presence of t w o cell types, using the E. M . and the view was deve loped tha t t y p e I cell repre-sents the t rue receptor cell, a l though direct evidence of synapses were r a the r scanty. T y p e I I cell, consequent ly was considered a sustent icular o r s u p p o r t i n g cell ( T A N G E , 1 9 5 9 ; G A R N E R et al . 1 9 5 8 ; Ross , 1 9 5 9 ) . These f ind ings a re a t present unde r review by the au tho r , using the l igh t -and electron-microscopes. T w o approaches are o p e n : (i) T h a t the s t ructure a n d stimulus t ransmission of caro t id body tissue fa l l s in line with the basic s t ruc tures and stimulus t ransmission of the o the r k n o w n chemorecept ive o rgans — which as will be shown below — are indeed all fo l lo -wing the common pr inciple of a receptor cell accompanied by a second t y p e of cell. (ii) T h a t the chemorecep t ive p a t h w a y in the caro t id body may be based on ent i rely d i f f e r en t pr inc ip les and that its basic s t ruc ture is not c o m p a r a b l e to o the r chemoreceptors . (i) In discussing the f i r s t a rgument the w o r k of DE L O R E N Z O comes t o mind in which he describes the E .M. p ic ture of the rabbi t ' s tongue papillae foliate: „ t w o cytological d i f f e r e n t cells, the gus ta to ry receptor cell a n d the sustent icular cell, can be c lear ly d i s t inguished" ( D E L O R E N Z O , 1958) . In the same pape r he gives a descr ip t ion of these t w o cells. I t is interest ing to no te tha t his descr ipt ion of the receptor cell does in no w a y agree with the descr ip-t ion of the caro t id body ' s al leged receptor cell ( t y p e I), bu t would r a t h e r r e fe r to t y p e I I cells, the alleged suppor t ing o r sustent icular cell. D E L O R E N Z O con-tinues: „ T h e y " ( the receptor cells) „a re charac ter ised by a basal ly loca ted , elon-gated nuscleus in which a nucleolus is usual ly present . The ka ryop la sm is un i -fo rmly dense, fo l lowing OsO* and K M N O i f ixa t ion . Th is is to be con t ra s t ed with the large, round and less dense nucleus of the suppor t i ng ce l l" ( D E L O R E N -ZO, 1958). E N G S T R O M , in a descr ip t ion of the o l f a c t o r y cells also men t ions t w o dis-t inct cell types, whereby t h e o l f ac to ry cell is again , as in the tongue, the cell wi th the dense nucleus, su r rounded by scanty cy top la sm which is d iv ided i n t o m a n y distal processes (dendri tes) , whi le the suppor t i ng cell is bu lky , w i th a large, vesiculated nucleus and a cy top lasm rich in in t race l lu la r inclusions ( E N G S T R O M , 1953). Even insect chemosensory units a p p e a r to adhere to the t w o cell t y p e a r rangement , wi th the suppor t ing cell represented by the bu lky , h igh ly a c t i v e P R O B L E M S O F C A R O T I D B O D Y T I S S U E S 1 6 3 cell. In the b l o w f l y labclla the chemorecept ive uni t consists of a receptor o r nerve cell wi th dense cy top lasm, small nucles and a c c o m p a n y i n g bulky t ro-chogen and to rmogen cells wi th large, vesicular nuclei a n d re la t ively clear cy-toplasm ( H O G S O N , 1 9 5 6 ) . I f , thus these general rules of s t ruc ture in o the r chemoreceptors are appl ied to those suggested fo r caro t id b o d y tissues, it becomes ev ident t h a t the agreement is no t ve ry sa t i s fac to ry . Th is is f u r t h e r aggrava ted by the fac t t ha t in all o the r chemoreceptors a cu t t ing of the i r ne rve supply causes a degenera t ion of the receptor cells. Th i s is no t the case in the carot id body , where the alleged recep-tor cells ( t y p e I ) d o not degenera te unde r these c i rcumstances ( M E I J L I N G , 1 9 3 8 ) . T h e r e is thus a possibil i ty tha t in the carotid body the t y p e I cell, gene-rally considered to be the receptor cell, is ei ther ent i rely d i f f e r e n t in s t ruc ture to o the r chemorecep tors and t ha t , in this case a b iochemical ly d i f f e r e n t mecha-nism m a y be at w o r k , c o m p a r e d wi th the one of o ther cbemoreceptor units , or tha t it is no t the receptor cell or at least not a cbemoreceptor cell in the usual sense. T h e same wou ld a p p l y to t y p e II cell, the alleged suppor t i ng cell, which in the caro t id body wou ld lack all the ea rmarks of the o the r suppor t ing cells, which are all h ighly active, obviously biochemical ly c o m p l e m e n t a r y cells to their receptor cells. (ii) T h e second line of app roach to t h e histology and cy to logy of the ca-rotid body is t o detect in its s t ruc ture any evidence which m a y t h r o w light on the existence of a non- typ ica l m o d e of reception, when c o m p a r e d wi th the chemosensory uni ts of tas te and smell. Such an a p p r o a c h may be necessary when the discrepancies, out l ined abo-ve, a re considered. In search of any obvious d i f fe rences between caro t id body tissue and o the r chemoreceptors the m o d e of the ne rve supply comes to mind . Whi le the ne rve f ibres supp ly ing the tas te buds and the o l fac to ry epithelium f o l l ow a more or less s t ra ight course, this is not so in the carot id b o d y . As was so well demons -trated in the excellent p r e p a r a t i o n s of human caro t id b o d y tissue by P r o f . A B R A H A M , the f ibres, on en te r ing the sinusoidal region, begin to spiral in eve r -increasing coils, encircl ing groups of t y p e I and t y p e II cells. T h e E. M. p ic tu-res, t aken so f a r by the au thor , con f i rm tha t even the f inest f ibres cont inue to spiral round single t y p e I and II cells wi thout obvious synap t i c t e rmina t ions . I t could also be observed tha t the t y p e I cell is no t only ensheathed by tvpe II cells (Ross, 1959) (hence the presumpt ion tha t it is the suppor t i ng cell), but tha t t y p e I cell, in tu rn , sends pseudopodia- l ike extensions of its cy top lasm into the cell body of t y p e I I cell. Fu r the r , in all cases so f a r seen, t y p e I cell is separa ted f r o m the nearest blood vessel by a th in cy top lasmic layer of t y p e I I cell, which would thus be is closer con tac t w i th the b lood supply than type I cell. T h e s ignif icance of these s t ruc tura l specialisations — n o n e of which h a v e so f a r been t aken in to considerat ion — are at present unde r de ta i led invest i-gation. It is hoped t h a t their results t h r o w new light on the p rob lems of chemo-reception in t h e caro t id b o d y . M a y I conc lude this ar t ic le wi th m y sincerest t h a n k s to P ro f . A B R A H A M f o r the s t imulat ion I received f r o m his work , and wish f o r m a n y f r u i t f u l years to come. I I 5 1 6 4 L . L. D E K O C K References B L O O M , G . : S tud ies o n the o l f a c t o r y epi thel ium o f the f rog and the toad w i t h t h e a i d o f light and e lec tron m i c r o s c o p y . Zisch. Zellforsch. 41, 8 9 — 1 0 0 (1954) , DETHIER, V. G . : T h e p h y s i o l o g y and his to logy of the c o n t a c t c h e m o r e c e p t o r s o f t h e b l o w f l y . Quart. Rev. Biol. 30, 3 4 8 — 3 7 1 (1955) . ENGSTRÖM, H . & BLOOM, G . : T h e structure o f the o l f a c t o r \ region in man . Acta Oto-Laryngol. 43, 1 1 — 2 1 (1953) . G A R N E R , С . M . & D U N C A N , D . : O b s e r v a t i o n s on the f ine structure of the carot id b o d \ . Anat. Ree., 130, 691—710 (1958). H E Y M A N S , C . & N E I L , E . : R e f l e x o g c n i c areas of the c a r d i o v a s c u l a r system. ( C h u r c h i l l , L o n d o n , 1958) . H O G S O N , E . S. & R O E D E R , K . D . : E lec tro -phys io log ica l s tudies o f ar thropod chemorecept ion' . . ] . Cell. & Сотр. Physiol., 48, 51—76 (1956) . D E K O C K , L . L . : T h e i n t r a - g l o m e r u l a r tissues of the c a r o t i d b o d y . Acta Anal. 21, 101 — 116 ( 1 9 5 4 ) . D E K O C K , L . L . : T h e carot id b o d y system of the h igher vertebrates . Acta Anat., 37, 2 6 5 — 2 7 9 ( 1 9 5 9 ) . D E L O R E N Z O , A . J . : Electron m i c r o s c o p i c observat ions on the taste buds of the rabbit . ]. Biopb. & Biochem. Cytol., 4, 1 4 3 — 1 5 0 ( 1 9 5 8 ) . M E I J L I N G , H . A . : Bau und I n n e r v a t i o n v o n g lomus carot i cum und Sinus earot ieus . Acta Neerl. Morph., 1, 1 9 3 — 2 8 8 (1938) . R o s s , L. L.: Electron microscop ic o b s e r v a t i o n s of the carot id body o f the cat. ]. Biopb. & Biochcm. Cytol., 6, 2 5 3 — 2 6 2 (1959) . SCHANZ, M . : D e r Gcruchs inn des K a r t o f f e l k ä f e r s . 7.tsch. vergl. Physiol., 35, 3 5 3 — 3 7 9 (1953) . I R U J I L L O - C L N O Z , O . : Electron m i c r o s c o p i c s t u d y o f the rabbit gus ta tory bud. Ztscb. Zell forsch., 46, 2 7 2 — 2 8 0 ( 1 9 5 7 ) . WILLIS, A . G . & TANGE, J. D . : T h e argentophi l cel ls o f the h u m a n c a r o t i d b o d y . Am. ]. Anat.. 105, 141 — 1 6 4 ( 1 9 5 9 ) . 

Unsolved problems of carotid body tissues

http://acta.bibl.u-szeged.hu/21575/1/biologica_009_161-164.pdf

Unsolved problems of carotid body tissues

Abstract

Similar works

Full text

Available Versions

University of Szeged