Myelin figures occurring in the peripheral nerve bundle of human skin

440 MYELIN

FIGURES OCCURRING IN THE PERIPHERAL BUNDLE OF HUMAN SKIN

NERVE

A. CHARLES Departments

of Dermatology

and Biomolecular

Structure,

The University,

Leeds, England

Received February 2, 1958

s

TOECKENIUS [4] first reported the laminated structure of tissue mast cell granules, which had also been observed in these laboratories. Subsequently Policard et al. [2] and Stoeckenius [5] reported the laminated construction of myelinated figures arising from red blood corpuscles after their ingestion by phagocytizing macrophages. The present communication shows that a similar structure occurs, or can arise, in the endoneurium of the peripheral nerve bundle of human skin. Material was obtained from the scalp of a male aged 57 years under general anaesthesia for craniotomy and removal of tumour. After cutting into suitably sized cubes the material was fixed in 1 per cent osmium tetroxide in Verona1 buffer pH 7.4 [l]. Fixation commenced about ten minutes after excision. Subsequent treatment followed the usual routine methods, and terminated in the embedding of the material by polymerization in methacrylate monomer at 45°C. In Fig. 1 the relationship of the myelin figures (boxed) to one of the nerve myelin sheaths (m) is shown, while the inset Fig. 2 is an enlargement of the boxed region. We see here the same multi-centric laminated whorls as were described by Stoeckenius [5]. In some cases, indicated by (s) in Fig. 2, the laminations are replaced by a homogenous material of the same density, due presumably to the laminations being seen in surface section. The dimensions of the laminations in the endoneurium agree approximately with those given by Stoeckenius for the mast cell granules, which my own observations confirm, the laminae being about 100 A part and about 50 A thick, with a clearer region of about 50 A between. These dimensions differ somewhat from those found for the myelin figures of the phagocytized red blood cell which themselves show appreciable variation, so that it may be difficult to gain an idea of the nature of the lipid from such measurements. A 100 A period seems true also for the myelin sheath of the medullated nerve, but the denser lamellae in this case are much more sharply defined than in the endoneurial structures, and the latter do not show the 50 A period [3] faintly observable in the myelin sheath when Fig. 1 is further enlarged.

Fig. I.--Section of a peripheral nerve bundle showing the relationship between one of the myelinated nerve sheaths (m) and the myelin figures (boxed) found in the endoneurium. x 60,000. Fig. 2.-Enlargement of the myelin figures in the boxed area of Fig. 1, showing the multi-centric laminated structure. In some cases (s) the granules have a homogenous structure which may partly be due to the laminations being seen in surface section and possibly also to the presence of non-laminated material. x 110,000. Experimental

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Myelin figures in peripheral nerve

E.rperimental

441

Cell Research 14

H. F. Sfich and J. M. Naylor

442

Originally I was inclined to draw comparison between the laminated structures in the endoneurium and the laminations of the mast cell granule. Such a well-organized structure, I thought, associated as it was in the mast cell with secretory products, must surely have a function. But the publications [2,5] mentioned above make it fairly clear that this assumption was not justified; the laminations are a result of the physico-chemical behaviour of various lipids, the molecular mechanism of which is a point of interest [2, 51. I am pleased to be able to express my great indebtedness to Mr. A. E. Wall, Neurosurgeon at the Leeds General Infirmary, for his greatly valued co-operation in providing material. REFERENCES 1. PALADE, G. E., J. Expptl. Med. 95, 285 (1952). 2. POLXARD, A., BESSIS, M. and BRETON-GORIUS, J., Exptl. 3. SJBSTRAND, F. S., Experientia 9, 68 (1953). 4. STOECKENIUS, W., Exptl. Cell Research 11, 656 (1956). 5. -

Cell Research 13, 184 (1957).

ibid. 13, 410 (1957).

VARIATION

OF DESOXYRIBONUCLEIC

OF SPECIFIC

CHROMOSOME

H. F. STICH

ACID

CONTENT

REGIONS1

and J. M. NAYLOR

Saskatchewan Research Unit of the National Cancer Institute of Canada, Saskutoon, Canada, and Field Husbandry Department, University of Saskatchewan, Saskutoon, Canada Received February 20, 1958

AN exact correlation between the DNA content and the chromosome set was originally postulated by Boivin et al. [4], Mirsky and Ris [9], and has been confirmed by numerous microphotometric measurements on various tissues of animals and plants [ 15,171. The few published contradictory results that indicated variation in the amount of DNA in diploid nuclei were based on the one wave-length method; these have been questioned, and attributed to technical errors [15]. However, there are cases described where DNA containing corpuscles are extruded from the chromosomes or nuclei [2, 141 and these do not agree with the established view. Similarly, certain factors such as temperature apparently induce departures from DNA constancy in some plant nuclei [8]. The present study has been undertaken to investigate this problem of constancy or inconstancy of the DNA-content per chromosome set. r Acknowledgements are given to Dr. H. Bauer for suggestion of the material used in this study and to Dr. J. Rempel for assistance in obtaining the larvae. Following the completion of this work, sim.ilar experimental results and conclusions, based on U.V. absorption measurements with salivary chromosomes of Rhynchosciara have been reported by Rudkin and Corlette (Proc. Nat. Acad. Sci. 43, 964 (1957). We are grateful to Drs. J. Schultz and G. T. Rudkin for calling our attention to this report. Experimental

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