Fine structure of mycota

Fine structure of mycota

R. T. Moore 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. and J. H. McAlear -Ann. N.Y. Acad. Sci. 63, 793 (1956). -Cancer, vol. 1, p. 335. (Ed. Raven) Butt...

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R. T. Moore 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

and J. H. McAlear

-Ann. N.Y. Acad. Sci. 63, 793 (1956). -Cancer, vol. 1, p. 335. (Ed. Raven) Butterworth, London, 1957. LEVAN, A., Ann. N.Y. Acad. Sci. 63, 774 (1956). LEVAN, A. and HAUSCHKA, T. S., Hereditas, 39, 137 (1953). LUDFORD, R. J., J. Roy microscop. Sac. 73, 1 (1953). OSTERGREN, G., MOL&BAJER, J. and BAJER, A., Ann. N. Y. Acad. Sci. 90, 381 (1960). PARMENTIER, R. A. and DUSTIN, JR., P., Caryologia 4, 98 (1951). SCHRADER, F., Mitosis. Columbia University Press, 1953. TIXONEX, S. and THERMAN, E., Cancer Research 10, 431 (1950). TJIO, J. H. and LEVAN, A., Lunds Uniu. Arsskr. S.F. Avd. 2, Bd. 50, (1954).

FINE RECONSTRUCTION

FRO1\f

ENVELOPE

AND

ITS

R.T. Department

STRUCTURE

of Plant

Pathology, New York

SKIPPED

OF MYCOTA SERIAL

CONTINUITY

MOORE

WITH

and

Cornell University, State Department Received

J.H.

SECTIONS THE

PLASMA

THE

NUCI,EAF:

MEMBRANE

I”

McALEAR3

and the Division of Health, Albany,

January

OF

of Laboratories U.S.A.

and Research,

31, 1961

The continuity and/or close approach of the nuclear membrane with elements of the plasma membrane has been reported previously in several species of fungi [l, 3, 5, 71. In Stilbum zacalloxanthum [I], a Deuteromycete, these continuities were visualized as centripetal invaginations circling the cells because of the frequency of their appearance in longitudinal sections of the conidiophores. It is not improbable that comparable continuities also appear in some higher cell types of both plants and animals, although, at least in the latter group, they are facultative and generally rather transient. This is in contrast to some fungi in which such continuities tend to be more permanent. The phylogenetic significance of such membrane continuities is that they may provide evidence for the means of the formation of the cytomembrane systems of higher cell types. In the study presented here apothecia of the Ascomycete Mollisia sp. were collected from the field and fixed by a KMnO,-OsO, technique, described elsewhere [5], and embedded in methacrylate. The sections were examined in a Siemens Elmiskop I at a magnification of approximately 28,000 diameters. In Fig. 1 a reconstruction of the nuclear envelope and its plasma membrane association has been prepared from the skipped serial sections illustrated in Figs. 2, 1 This work was supported in part by Grant No. H-3493 from the National Heart Institute, Public Health Service. 2 This work was also supported in part by a research fellowship 9197-Cl to the senior author from the National Institute of Allergy and Infectious Diseases (Prof. R. P. Korf sponsor). 3 Present address: Electronmicroscope Laboratory, University of California, Berkeley. Experimental

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Fine structure of mycota

589

and 3. The reconstruction was prepared by tracing the membrane relationships in the two sections on celluloid sheets and superimposing them. The total thickness included in the reconstruction is in the order of 1000 to 1500 a units. This reconstruction suggests that the pores in the nuclear envelope are often non-circular or perhaps slit-like, as are the profiles of the continuities of the plasma and nuclear membranes.

Fig. I.-Reconstruction of a nuclear thick section from electron micrographs of skipped wrial sections shown in l:igs. 2 and 3. The upper, double line, section is reproduced from I:ig. 2: the lower, single line, section is reproduced from Fig. 3 (lettered points along this section are given primes). Letters n-j are pores; k is a point on the diverticulum; I the point of joining between the continuity and the plasma membrane. Pore a’ is delimited by wedges (b); pore f’ is indicated by a star (w). Thirkness of section 1000-1500 A.

The occurrence of slit-like pores in the nuclear membrane of somatic fungal nuclei could explain some of the rather large gaps frequently found in such nuclear membranes in thin sections. In that portion of the membrane system connecting the plasma and nuclear membranes a diverticulum (D) similar to that which was tentativcl! interpreted as a developing mitochondrion in Slilbum 131 is seen. In the higher plants the nuclear membrane is formed by the aggregation of entioplasmic reticulum about the chromosomes [4, 61. These membranes then migrate peripherally and fuse to form the nuclear envelope. As continuities of the plasma membrane and the endoplasmic reticulum are well established in a variety of higher cell types, it would seem likely that in some fungi a similar phenomenon occurs, which perhaps reflects a more primitive 1eveI of evolution, one in which the endoplasmic reticulum remains continuous with the nuclear membrane during its forma-

R. T. Moore and J. E-I. McAIear

590

Figs. 2 and S.-Skipped MoZlisia sp., x 84,000. Experimental

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serial

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24

sections

through

a dikaryotic

cell of the discomycetous

Ascomycete,

Fine structure

.?!I 1

of mycotcl

Iiry: (f-j, nuclear pores; k, a point on the divcrticulum conlinuity (C) with the plasma membrane (I’). Sections t~uclcus (S) arc also present.

(11); I, the point of a mitochondrion

of juncture (.7/) and

of tht anothrr

C. H. O’Neill

and L. Wolpert

tion. The forming of the nuclear membrane in fungi showing direct continuities of this structure with the plasma membrane is envisaged as involving the association of internalized plasma membrane, which may first associate around the nuclear region with other invaginations to produce slit-like pores, and then later, perhaps, anastamose in a manner similar to the vesicles of higher cell types to form a more continuous limiting enclosure of the nucleus. This offers further phylogenetic evidence in support of the hypothesis previously stated [2,3] that the discontinuous membranes of higher cell types may have evolved from the plasma membrane of primitive bacteria-like organisms through a cell type similar to that seen in the fungus Mollisia described above, in which the internal membranes are for some time, at least, generally part of an invagination of the plasma membrane. REFERENCES 1. 2. 3. 4. 5.

EDWARDS, G. A. and EDWARDS, M. R., Am. .I. Botany 47, 622 (1960). MCALF.AR, J. H., Ph.D. Thesis, Harvard, 1958. MCALEAR, J. H. and EDWARDS, G. A., Ezptl. Cell Research 16, 689 (1959). MOLLENHAUER, H. H., Am. J. Botany 47, 401 (1960). MOORE, R. T., Fine Structure of Mycota. 1. Electron microscopy of the discomycete Nova Hedwigia. (In press.) 6. PORTER, K. R. and MACHADO, R. D., J. Uiophys. Biochem. Cytol. 7, 167 (1960). 7. SHATKIN, A. J. and TATUM, E. I>., J. Biophys. Biochem. Cytol. 6, 423 (1959).

ISOLATION

OF THE C. H. Zoology

OF AMOEBA

CELL MEMBRANE O’NEILL

Department,

and King’s

Received

March

Ascodesmis.

PROTEUS

L. WOLPERT

College,

London,

England

27, 1961

T HE cell surface membrane of the amoeba is of considerable importance both in cell movement and in pinocytosis, though its precise role is not clear. It is capable of large changes in form while acting as a relatively tough mechanical barrier, and in pinocytosis at least it appears that new membrane must be formed at the surface. In order to gain some understanding of such processes in molecular terms we have attempted to obtain isolated membranes. Until Neville’s recent report on the isolation of liver cell membranes, there have been almost no reports on techniques for obtaining relatively pure preparations of membranes in quantity from cells other than the red blood cell [5]. The technique we report here is different from that used by Neville. Extraction of Amoeba proteus cells in 45 per cent buffered glycerol or 2.4 M (saturated) sucrose causes the membrane to lift away from a contracted internal Experimental

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