Pseudopod and foodcup formation in Amoeba proteus

the presence of ;1-fluorouracil arc unable (0 synthesize DS.4 and consrcptct~ll~ fLtil to undergo any further divisions. This is apparently a permanent block since even after prolonged rccowry il G-4 hr) follo\ving treatment the cells failed to etitcbr diyisiott. X similar immediate blockage of 1)NX synthesis was noted by I)uncan atttl \Voods [2] and Martinez-Pica and Duncan [C;] following treatment with 5antitioitracil. The! found that 5aminouracil inhibited synthesis of L)X;=\ without immediatel>halting mitotic activity. The divisions in progress at the time of treatment continue, f)ut there is no duplication of DN;\ in the resting stage following a division occurring in the presence of 5atninouracil. Eroded regions of the chromosomes (regions deficient in DNA) are conspicuous at anaphase where the\- are frequently visible at corresponding locations and clelimit similar lengths of sister chrotnosomes. From the above results it appears that .<-fluorouracil blocks the synthesis of D?j,\ almost itnmediately. thus producing the eroded regions of the chromosomes evident at anaphase and preventing duplication of DNA in the resting stage following a normal mitotic division. The spindle effect and the effect on chromosomal elimination might possibly be due to the fact that %fluorouracil also interferes with the synthesis of RNX. REFERENCES BOSCH, I-., HARBEHS, E. and HEIDELBERGER, DU~~CAN. R. and LVOODS, P., Chromosomn 3. GORDON, hI. P. and ST.~EHLIS, hr., J. dm. 1. 2.

1. 5. 6. 7. 8.

C., C~mcu Research 18, 335 (1958). 6, 15 (1953). Chem. Sot. 80, 2310 (1958). H.4NDsctlUnlAct~ER, R. E., b’edercction Proc. 16, 191 (1957). nI?\HONEY, iv. (;., BERGER, C. A. and \VITZ(US, R. R., Snture 191, 627 (19til). iu4RTINEZ-PICO, L. and DUNCAN, R., Cyfoloyitc 20, 378 (1955). TAYLOR, J. H., HALIT, \V’. F. and TUNG, J., Proc. Sdl. Amd. Sri. 48, 190 (19(i2,. \VITKUS, E. R. and BERGER, (:. &\., J. Heredity 35. 131 (1914).

PSEUDOPOD

AND FOODCUP FORMATION K. W. JEON’ Zoology

Department,

and King’s

Received

March

IN

L. G. E. College.

AMOEBA PROTEUS

BELL

London,

England

30, 1962

IT has been found that mater, in which Hydra viridis or Tetrahymenu pyriformis have been cultured, will activate nucleate and enucleate Amoeba proteus to form pseudopods and food cups. Amoebae migrate towards pieces of living or heat-killed Hydra and try to engulf them; this they succeed in doing if the pieces are small enough (Fig. 1 a-c). The mechanism appears to depend on the stimulation of local pseudopod formation. This can be shown by placing a fine pipette containing either Hydra or Tetrahymena 1 British Council Scholar. Experimental

Cell

Reseurch

27

Pseudopod

Fig.

1 u-C.-Amoeba

Fig. The

2n-c.-Pseudopod pipette has been

proteus

and foodcup formation

migrating

towards

formation stimulated moved a short distance

a piece by proximity in 2~.

351

in Amoeba proteus

of living

Hydra

of a pipette

tentacle. containing

Experimental

Hydra

Ceil

tissue.

Research

27

352 material near to an amoeba. A pse~~dqwd I’orms wherever the pipette is plxctl (Fig. ZWC), even from the rear end of a locomoting animal. E’ipettes filled with Chalkle>-‘s niediiun do not have this action. Pieces of the sea anemone, .Artf~rnor~itc sulocctcc, and tissues from tadpoles of ,‘icnop~ts IWU~.S do not elicit pseudopods. Time lapse cinemaphotograph~ has been used to analysr these phenomena. Pseudopods can be made to form from a retreating pseudopod, without at first halting or reversing the direction of cytoplasmic flow in the old pseudopod. This suggests that neither cytoplasmic flow as in the fountain zone theory 111 nor as resulting from contraction at the rear of the cell [3] is of primary itnportance in pseudopod formation. The facts reported here are compatible with the view that locomotion is cow trolled by local surface extension [ 21. Investigations are proceeding on the identification of the substauces involved: their mode of action; and the relationship of this phenomenon to the general phenomena of cell migration and adhesion. \Ve are grateful to Dr. S. Hawkins

to Dr. L. \Volpert for his interest and for supplying for giving us some enucleate Amoebae.

Amoebae

and

REFERENCES 1. 2. 3.

R., in The Cell. Vol. II, Brachet ant1 Rlirsky, 1961. IjELL, L. G. E., .I. 7‘/wrmficol Hiol. 1. 104 il9Gl). GOLDACRE. R., Inkrn. Rw. Cyto/. 1. 135 (1952).

.\LLEN,

SEPARrlTION

OF PLANT

AND THE

NATURE

eels., p. 135. .\cademic

CELLS WITH

Press,

New

York,

HEXAMETAPHOSPHATE

OF INTERCELLULAR

BONDING

D. S. LETHAM Fruit

Research

Division,

Department -Auckland.

of Scientijic New Zealand

Received

tZpri1 11, 1962

and Industrial

Research,

ETK~~.LENEDI.~~~INETETRA~cETATE (EDTA) has been found useful for separating plant cells prior to determining cell number and size in tissues [4, 6, 71. Studies based on the separation of cells with EDT‘4 have also provided information about the nature of intercellular bonding [3]. It appears likely that this separation of cells is largely dependent on the chelation of calcium and possibly magnesium ions of the middle lamella [l, 61. EDTA is an effective macerating agent at pH 10 and moderately elevated temperatures [6]. At pH values below 8 at normal temperature, however, EDT-4 is only weakly active with many plant tissues. A search was therefore made for a chelating agent which would show better macerating activity under these Experimenfal

Cell

Research

27