to the peripheral vestibular organ, and
that there appear to be two groups with
different conduction velocities. Moreover, a parallel light- and electronmicroscopic study has confirmed the
existence of the direct cerebello-vestibular pathwayin the bullfrog by showing that section of the eighth nerve
extracranially produces degeneration of
both climbing and mossy fibers, as weil
as characteristic retrograde changes in
pathway in the frog implies that, at
least in this form, the cerebellum is
not involved in motor control exclusive-
ly, but has a sensory regulatory role
as well,
Ropo_ro Linas
WOLFGANG PRECHT
STEPHEN T. KITAI
American Medical Association,
Institute for Biomedical Research,
Chicago, Illinois 60610
the somas of Purkinje cells (15). The
latter finding (Fig. 2, top) directly confirms the thesis that Purkinje cells send
axons or axon collaterals to the vestibular organ. In addition, if the cerebellar cortex is removed, care being
taken not to injure the cerebellar nuclei, one can demonstrate degenerating synaptic boutons in contact with
the peripheral vestibular receptor cells
(Fig. 2, bottom)
(J75).
The aforementioned results demonStrate the existence of a cerebellovestibular efferent system in the frog.
Previous anatomical and physiological
Studies have indicated the presence of
an efferent system to the peripheral
vestibular organ. In the case of the cat,
light- (16) and electron-microscopical
studies (27) have revealed efferent terminals on the vestibular receptor cells.
Furthermore, direct-current potential
changes have been recorded from the
surface of the semicircular canals following stimulation of the central ner-
vous system (/8). In the frog, recent
electron-microscopical
studies
have
verified the existence of this efferent
system (79), which had been suspected
on the basis of earlier physiological
findings (20). The origin of the efferent
. system was, however, unknown,
Since the cerebellum develops in very
close relation with the stato-acoustic
system and since a certain component
of the vestibular projection to this center is direct in both lower (27) and
higher vertebrates (2), it seems possible that the cerebellum has some direct action upon the peripheral organ. Occasionally we observed directcurrent potential changes at the frog
vestibular organ following the stimulation of the auricular lobe; however, no
clear physiological meaning has so far
been attached to this finding.
Although the functional significance
of the cerebello-vestibular system has
not been ascertained, this system may
be inhibitory in nature, as is the olivocochlear
bundle
(22),
particularly
since Purkinje cells inhibit all target
cells so far studied (4). The demon-
stration of a direct cerebello-vestibular
1330
References and Notes
1.S. Ramon y Cajal, Histologie dui Systéme
Nervoux de ’Homme et des Wértebrés (Maloine, Paris, 1911).
2. J. Jansen and A. Brodal, Cerebellar Anatemy (Johan Grundt Tanum, Oslo, 1954).
3. F. Walberg and J. Jansen, Exp. Neurol. 3,
32 (1961); R. P. Eager, J. Comp. Neurol, 120,
81 (1963).
4. M. Ito and M, Yoshida, Experientia 20, 515
(1964); Exp. Brain Res. 2, 330 (1966); M. Ito,
M. Yoshida, K. Obata, Experientia 20, 575
(1964),
5. R. Llinds and J. F, Ayala, NeuropfAysiological Basis of Normal and Abnormal Motor
Activities, M, D. Yahr and D. P. Purpura,
Eds. (Raven Press, Hewiett, N.Y., 1967).
6. J. C. Eccles, R, Llinds, K. Sasaki, J. PAysiol.
182, 316 (1966).
7. R. Liinds and J. Bloedel, Science 155, 601 (1967).
8. R. Llinds, W. Precht, §S. Kitai, Brain Res.,
6, 371 (1967).
9. J, C. Eccles, R. Llinas, K. Sasaki, J. Physiol.
182, 268 (1966).
10. R. Linds and J, Bloedel, Brain Res. 3, 299
(1966-1967).
11. J. C. Eccles, R. Llinads, K, Sasaki, Exp.
Brain Res, 1, 82 (1966).
12. P. B. C. Matthews, C. G. Phillips, G.
Rushworth, /. Exp. Physiol. 43, 39 (1958).
13. R. Granit and C. G. Phillips, J. Physiol.
133, 520 (1956).
14. P. Andersen, J. C, Eccles, P. E. Voorhoeve,
J. Neurophysiol. 27, 1138 (1964).
15. D. Hillman, unpublished results.
16. G. L. Rasmussen and R. R. Gazek, Anat.
Rec. 130, 361 (1958); A. E. Petroff, ibid, 121,
352 (1955),
17. J. Wersall, Acta Oto-Laryngol. Suppl. 126,
1 (1956); H. Engstrém, Acta Oto-Larynegoi.
49, 109 (1958).
18. O. Sala, Oto-Laryngol. Suppl. 197, 1 (1965).
19, L. Gleisner, P. G. Lundquist, J. Wersall,
J, Ultrastruc. Res. 18, 234 (1967).
20. R. S. Schmidt, Acta Oto-Laryngol. 56, St
(1963); L. Gleisner and N. G. Henriksson,
Acta Oto-Laryngoi. Suppl. 192, 90 (1963).
a1. O. Larsell, J. Comp. Neurol. 36, 89 (1923).
22. R. Galambos, J. Neurophysiol. 19, 424 (1956);
J. Fex, Acta Physiol, Scand. Suppl. 189, 1
(1962); J. E. Desmedt and P, Monaco,
Nature 192, 1263 (1961).
11 September 1967
n
Erythrocyte Transfer RNA: Change during Chick Development
Abstract, Radioactive aminoacyl transfer RNA’s isolated from erythrocytes
in the blood of 4-day-old chick embryos and from reticulocytes of adult chickens
were analyzed by chromatography on methylated albumin kieselguhr and freon
columns, Embryonic and adult methiony] transfer RNA’s showed qualitative and
quantitative differences in both chromatographic systems. The patterns for arginyl,
seryl, and tyrosyl transfer RNA’s in the two cell types were similar, while the
leucyl transfer RNA patterns suggested a difference.
Structural modification of transfer
RNA (tRNA) may play a regulatory
function in cell differentiation and me-
tabolism (7). With methylated albumin
kieselguhr (MAK) chromatography,
Kano-Sueoka and Suecka (2) demon-
strated an alteration in leucyl-tRNA
after bacteriophage T2 infection of
Escherichia coli; this finding was confirmed by Waters and Novelli (3), using the reversed-phase chromatography
developed by Kelmers et al. (4). Kaneko and Doi (5) found a change during sporulation of Bacillus subtilis in
the elution pattern of valyl-tRNA from
MAK columns.
To look for changes in specific
tRNA’s during development, we used
avian immature red cells as a test system and compared the chromatographic
profiles of aminoacyl-tRNA’s from red
cells present in the blood of 4-day-old
chick embryos and of reticulocytes of
adult chickens. The techniques in this
study were MAK (2) and freon columns (6). Of the five aminoacyl-
tRNA’s examined, only the methionyltRNA gave a strikingly different elution pattern.
Aduit chickens (White Leghorn) were
made anemic by daily injection (for
3 days) of 15 mg of phenylhydrazine
fin 0.14 tris( hydroxymethyl) aminomethane
(tris)
buffer, pH 7.2] and
were bled on the 6th day. Eggs from
the same strain were incubated at 37°C
for 4 days, and blood cells were collected by bleeding the embryos. Blood
cells from either source were washed
twice with 0.145M NaCl, 5 x 10°*M
KCl, and 0.0015M Megtl., and once
with 0.14544 NaCl, 5 x 10°4*M FeCl,
and 0.01M phosphate buffer (pH
7.4); 0.12 ml of packed embryonic cells
was suspended in the latter medium
supplemented with glucose (200 mg/
ml) with a total volume of 0.5 ml.
For adult cells, 0.5 ml of packed cells
was similarly incubated in a total volume of 2.0 ml. To cells previously
incubated at 38°C for 10 minutes,
MC. or 3H-labeled amino acid (5 to
10 wc) and the 19 remaining nonradio-
active amino acids (1 ,»mole of each)
were added. After incubation for an
additional
12 minutes,
cycloheximide
(10°4M4) was added to inhibit protein
synthesis (7) and thus prevent the transSCIENCE, VOL. 158