The optic tectum of the sparrow—A COX-GOLGI study
1
$142 VOLTAGE-CLAMP STUDYOF HORIZONTAL CELLS IN CARP RETINA. J.C. ~ #YAMADA t M. t LOW t AND DJAMGOZ r M.B.A. Neurobioloqy Groupr Imperial Colleqe t London SW7 2BB t U.K. & #Electrotechnical Lab. t Tsukuba t Ibaraki 305 t Japan. The electromotive force (emf) of light-evoked synaptic currents and passive membrane proper- ties of horizontal cells (HCs) were studied by a voltage-clamp method. By using double-barrelled micro-electrodes cone- and rod-driven HCs in dark-adapted carp retina were voltage-clamped whilst perfusing 5 ~M dopamine which uncoupled the gap junctions. Current-voltage (I-V) relationships were measured using both rectangular and ramp functions of command voltage. Input impedances of HCs in darkness were 28 ~ 12 M~ (mean ~ s.d., n=72); the resting potentials were -37 ~ Ii mV (n=72). The I-V curve for some cells of all types showed a region of negative resistance consis- tent with the involvement of a Ca 2+ current. The I-V curves did not seem to correlate with par- ticular cell types. Synaptic currents (I s) evoked by monochromatic stimuli (460, 533, 688 nm) were measured at various clamped voltages. A reversal potential of I s to bright red background light was 9 mV more positive than the resting potential. In every type of HC the reversal potentials to brief light flashes of every colour were estimated by extrapolation of the Is-V curves and were consistently 9 mV more positive than resting potentials. Thus, the emfs of light-evoked synaptic currents of HCs are probably derived from K + and Na + and/or Ca 2+ gradients. MACROMOLECULAR ORGANIZATION OF DISK AND PLASMA MEMBRANES OF ROD OUTER SEGMENT IN THE RAT RETINA .KATSUYUKI MIYAGUCHI*, TAKAHIRO GOTOW* AND PAULO HITONARI HASHIMOTO, Department of Anatomy, Osaka University Medical School, 3-57 Nakanoshima 4, Kitaku, Osaka 530, Japan. Disk and plasma membranes of rod outer segment were examined with a rapid-freeze and deep-etch technique using fresh rat retina to know how membrane proteins, rhodopsin and other components, are macromolecularly organized. Paired disk membranes in the same disk were almost always attached to each other except at marginal areas where the intradiscal space appeared. Owing to such membrane attachment, particles within opposite membranes appeared to be fused with each other. On cytoplasmic surfaces (CS) of the disk and plasma membranes, two types of particle were observed: one is smaller (7-12 nm in diameter) and lower, the other is larger (11-15 nm in diameter) and taller. There were no detectable particle profiles, however, on the intradiscal surface of the disk membranes as well as on the extracellular surfaces of the plasma membranes. Some of the intramembrane particles (IMPs) on the P face of the disk membrane form strand-like profiles and corresponding grooves were detectable on the E face. Small particles on the CS were similar in distribution density to the IMPs on the P face, and they appeared to be continuous in structure, while CS large particles seemed to be attached to the disk membrane. These observations suggest strongly that CS small particles represent the cytoplasmic portion of the membrane protein, rhodopsin, and the large particles are extrinsic membrane components. Thus, small paticles might be the COOH terminal domain of rhodopsin, and large ones could be GTP-binding proteins and phosphodiesterase. 45. Visual system II. Anatomy and physiology THE OPTIC TECTUM OF THE SPARROW--A COX-GOLGI STUDY. TAKAORYU, Department of Anatomy, dichi Medical School, Minamikawachi, Tochigi 329-04, Japan. To achieve an understanding of the cytoarchitecture of the sparrow optic tectum, this experi- ment was conducted using a series of IO brains from young house sparrows. Each sparrow brain was surgically removed, and then fixed in 10% neutral formalin (PBS) for at least 2 weeks. Following the COX-GOLGI method (Van der Lees, ]956), serial coronal 6O~mcelloidin sections were carefully examined. Findings obtained concerning the neurons and fiber structures in the sparrow optic tectum were clearly confined in the following particular tectal laminae: l) Stratum opticum, 2) Stratum griesum et fibrosum superficiale, 3) Stratum griesum centrale, 4) Stratum album centrale, 5) Stra- tum griesum periventriculare, and 6) Stratum fibrosum periventriculare. Apart from the synaptic organization in the tectum, the present study of the morphology of the sparrow optic tectum is in general accord with some reports such as Jungherr (]945), Karten and Hodos (1967), LaVail and Cowan (Ig7]), and Stokes et al. (1974).
Transcript of The optic tectum of the sparrow—A COX-GOLGI study
$142
VOLTAGE-CLAMP STUDY OF HORIZONTAL CELLS IN CARP RETINA. J.C. ~ #YAMADA t M. t LOW t AND DJAMGOZ r M.B.A. Neurobioloqy Groupr Imperial Colleqe t London SW7
2BB t U.K. & #Electrotechnical Lab. t Tsukuba t Ibaraki 305 t Japan.
The electromotive force (emf) of light-evoked synaptic currents and passive membrane proper-
ties of horizontal cells (HCs) were studied by a voltage-clamp method. By using double-barrelled
micro-electrodes cone- and rod-driven HCs in dark-adapted carp retina were voltage-clamped whilst
perfusing 5 ~M dopamine which uncoupled the gap junctions. Current-voltage (I-V) relationships
were measured using both rectangular and ramp functions of command voltage. Input impedances of
HCs in darkness were 28 ~ 12 M~ (mean ~ s.d., n=72); the resting potentials were -37 ~ Ii mV
(n=72). The I-V curve for some cells of all types showed a region of negative resistance consis-
tent with the involvement of a Ca 2+ current. The I-V curves did not seem to correlate with par-
ticular cell types. Synaptic currents (I s) evoked by monochromatic stimuli (460, 533, 688 nm)
were measured at various clamped voltages. A reversal potential of I s to bright red background
light was 9 mV more positive than the resting potential. In every type of HC the reversal
potentials to brief light flashes of every colour were estimated by extrapolation of the Is-V
curves and were consistently 9 mV more positive than resting potentials. Thus, the emfs of
light-evoked synaptic currents of HCs are probably derived from K + and Na + and/or Ca 2+ gradients.
MACROMOLECULAR O R G A N I Z A T I O N OF DISK AND PLASMA MEMBRANES OF ROD O U T E R SEGMENT IN THE R A T R E T I N A .KATSUYUKI MIYAGUCHI* , T A K A H I R O GOTOW* AND P A U L O H I T O N A R I H A S H I M O T O , D e p a r t m e n t of A n a t o m y , O s a k a U n i v e r s i t y Medica l S c h o o l , 3 -57 N a k a n o s h i m a 4, K i t a k u , O s a k a 530, J a p a n .
D i s k a n d p l a s m a m e m b r a n e s o f r o d o u t e r s e g m e n t w e r e e x a m i n e d w i t h a r a p i d - f r e e z e a n d d e e p - e t c h t e c h n i q u e u s i n g f r e s h r a t r e t i n a to k n o w h o w m e m b r a n e p r o t e i n s , r h o d o p s i n a n d o t h e r c o m p o n e n t s , a r e m a c r o m o l e c u l a r l y o r g a n i z e d . P a i r e d d i s k m e m b r a n e s in t h e s ame d i s k w e r e a lmos t a l w a y s a t t a c h e d to e a c h o t h e r e x c e p t a t m a r g i n a l a r e a s w h e r e t h e i n t r a d i s c a l s p a c e a p p e a r e d . O w i n g to s u c h m e m b r a n e a t t a c h m e n t , p a r t i c l e s w i t h i n o p p o s i t e m e m b r a n e s a p p e a r e d to b e f u s e d w i t h e a c h o t h e r . On c y t o p l a s m i c s u r f a c e s (CS) o f t h e d i s k a n d p l a s m a m e m b r a n e s , two t y p e s of p a r t i c l e w e r e o b s e r v e d : o n e is s m a l l e r (7 -12 nm in d i a m e t e r ) a n d l o w e r , t h e o t h e r i s l a r g e r (11-15 nm in d i a m e t e r ) a n d t a l l e r . T h e r e w e r e n o d e t e c t a b l e p a r t i c l e p r o f i l e s , h o w e v e r , o n t h e i n t r a d i s c a l s u r f a c e of t h e d i s k m e m b r a n e s as well a s o n t h e e x t r a c e l l u l a r s u r f a c e s o f t h e p l a s m a m e m b r a n e s . Some o f t h e i n t r a m e m b r a n e p a r t i c l e s ( IMPs) on t h e P f a c e o f t h e d i s k m e m b r a n e f o r m s t r a n d - l i k e p r o f i l e s a n d c o r r e s p o n d i n g g r o o v e s w e r e d e t e c t a b l e on t h e E f a c e . Small p a r t i c l e s on t h e CS w e r e s i m i l a r in d i s t r i b u t i o n d e n s i t y to t h e IMPs o n t h e P f a c e , a n d t h e y a p p e a r e d to b e c o n t i n u o u s in s t r u c t u r e , wh i l e CS l a r g e p a r t i c l e s s e e m e d to b e a t t a c h e d to t h e d i s k m e m b r a n e . T h e s e o b s e r v a t i o n s s u g g e s t s t r o n g l y t h a t CS smal l p a r t i c l e s r e p r e s e n t t h e c y t o p l a s m i c p o r t i o n o f t h e m e m b r a n e p r o t e i n , r h o d o p s i n , a n d t h e l a r g e p a r t i c l e s a r e e x t r i n s i c m e m b r a n e c o m p o n e n t s . T h u s , smal l p a t i c l e s m i g h t b e t h e COOH t e r m i n a l d o m a i n o f r h o d o p s i n , a n d l a r g e o n e s c o u l d b e G T P - b i n d i n g p r o t e i n s a n d p h o s p h o d i e s t e r a s e .
45. Visual system II. Anatomy and physiology THE OPTIC TECTUM OF THE SPARROW--A COX-GOLGI STUDY. TAKAO RYU, Department of Anatomy, dichi
Medical School, Minamikawachi, Tochigi 329-04, Japan.
To achieve an understanding of the cytoarchitecture of the sparrow optic tectum, this experi-
ment was conducted using a series of IO brains from young house sparrows. Each sparrow brain was
surgically removed, and then fixed in 10% neutral formalin (PBS) for at least 2 weeks. Following
the COX-GOLGI method (Van der Lees, ]956), serial coronal 6O~m celloidin sections were carefully
examined.
Findings obtained concerning the neurons and fiber structures in the sparrow optic tectum were
clearly confined in the following particular tectal laminae: l) Stratum opticum, 2) Stratum
griesum et fibrosum superficiale, 3) Stratum griesum centrale, 4) Stratum album centrale, 5) Stra-
tum griesum periventriculare, and 6) Stratum fibrosum periventriculare.
Apart from the synaptic organization in the tectum, the present study of the morphology of the
sparrow optic tectum is in general accord with some reports such as Jungherr (]945), Karten and
Hodos (1967), LaVail and Cowan (Ig7]), and Stokes et al. (1974).
