MELANIN PIGMENT I N THE BRAIN O F THE GORILLA

ALEXANDRA ADLER Neurologacal Unit, Boston Czty Hospatal and Departnaent of Neurology,

Hurz;ard Medical School, Boston, Massachusdts

ONE TEXT FIGURE AND ONE PLAT~E (FOUR FIGURES)

I t has been the general opinion (Bauer, '09 ; Obersteiner, '12; Spatz, '27) that melanin pigmentation of the substaritia nigra and locus coeruleus is peculiar to the human brain. HOTV- ever, Scherer ( '39) published observations 011 the brains of soiiie higlicr and lower primates, which showed that melanin was present in the substantia nigra of all the primates which lie had examined. In all instances the size of the melanin gran- ules was smaller, their number less and their coloration lighter than in adult human brains. The pigmentation was more pro- nounced in anthropoids than in the lower apes. Chimpanzees and orangutans were the only antliropoids in his series. Ap- parently because of the extreme difficulty in obtaining such material, his series did not include the brain of the highest anthropoid, the gorilla.

MATERIAL

Tlic material fo r this study consists of the brain of an adult Gorilla hcringei, which was collected by the McGill University C'ongo Expedition in 1938, under the direction of RIr. Duncan RI. Hodgson. The material was presented to the Department of Anatomy of the Harvard Medical School through the cwurtesy and interest of Mr. Hodgson and Mr. Harold ?J. Coolidge, J r . I wish to express riiy gratitude to Prof . George B. Wislocki, mlio put the gorilla's brain at my disposal for

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this special study. Ih. 11. J . Sclierei. kindly sent for com- parison a few sectioiis of the substantia nigra of a chinipanzee, which lie had used in liis publication ( ’39).

METHODS

After fixation in formalin, the blain aiid the brain ,stem of the gorilla wc’i*e cut in seven frontal slabs aiid embedded in celloidin. The whole inaterial then as cut witli tlie Godt1ar.d- Nico brain niicrotome a t 30 p. Several sections containing the substaiitia nigrit n w e cut a t 15 p. Three sets werc riiadc; one set was mounted without staining, one stained with light toluicliri blue a id the third stained by Lovez’ method for myelin sheaths.

RESULTS

Macroscopic drscripfiow

In cross sections tlie substantia iiigra presented a dark gray coloratioii (fig. 1). It was riot so black as in adult man.

Microscopic drsc,ripfion

Substaizfia nigra. The pigment is dark brov711 and varies in amount in the different ganglion cells. All of tliese cells have ~iielaiiiii pigmclnt (fig. 2 ) . The intlividual granules can be clis- tinguished without any evidence of corigloiiieratioii (fig. 3). The pigiiieiit extcuds into the dendrites, bu t not into the axon. It is iiot found within the nuclcus of the cell. This is true of melanin pigmentatioii in the ganglion cells of all species.

Lorus cocrulezis. In contrast to tlic dark hrowri color of tlie pig’rrieiit in the substantia riigra that of the locus coeruleus of this aiiiiiial is light brom7n. Here ilie syanules are dustlike a i d much fiiicr tlian in the substantia riigra (fig. 4). All of tlie cells of the locus coeruleus contain melanin pignient, as they do in tlie siibstantia nigra, but the granules are more widely dispersed and sparser. The granules are clearly visilnlc in the unstained sectioris as well as in those stained with toluidirl hlue.

MELANIN I N T H E BRAIN O F THE GOI;ILIA 503

Conaparisosz with the braiiz of chirvLpniazee. Tlic melanin granules in the substantia nigra of the chimpanzee are finer and less dense than in that of the gorilla (fig. 5). Their color is not dark brown but is yellowish. Some of the ganglioii cells of tlie substantia nigra of the chimpanzee are not pigmeiited whereas there are no unpigmented cells in the gorilla. The pigment in the chinipanzee is easily masked by all stains whereas it is clearly visible under the toluiclin blue stain in tlie gorilla. This is particularly true of the locus coeruleus.

Fig. 1 Substantin nigra in adult gorilla. X 12.

Coinparisom toitla the braiiz of inam. The melanin pigment in the substantia iiigra and locus coeruleus of man is dark gray-black in color in contrast to the brown color in tlie gorilla. In adult man no individual granules can be distinguished in tlie majority of ganglion cells, because the pigment has con- glomerated. The size of the granules is larger in adult niaii than in the gorilla. It is known that ill man pigmentation be- gins at about the age of 4 years, aftcr mliich there is an

504 ALEXANDRA ADLER

increase in the amount of pigment and in the size of the gra11- ules. The ganglion cell of the 4-year-old child is about identical

and in the size of the granules. The color, however, in tlw young child and in adult man is black, wlicreas in the gorilla it is brown.

One pathologic condition in man, postencephalitic Parkin - sonisiii, is lmown to be associated with a decrease of m(~1aniii pigmentation in the ganglion cells of the substantia nigra. The distribution of the remaining pigment in such cases, however, is quite different from that in ganglion cells of aiiimals with only a slight amount of pigment. I n postencephalitic Parkin- sonisin, the residual pigment is comriionly located in one corner of the nerve cell (fig. G ) , whereas in animals with slight amount of pigment it is evenly distributed throughout the cell. I n addition, the color of the melanin does not change in post- encephalitic Pai*kinsonism, but always remains gray to black as compared with the brown to yellow shade in apes.

Mcla.niw, in pia l melanopltores. There were only a few scattered melanin granules in the melanophores of the pia of the gorilla. There is, however, 110 parallelism between the presence of melanin in ganglion cells and that in melanophores. The same holds true for conditions found in the Amphibia ( Adler, '39).

with that of the adult gorilla in the amount of pigment a t ' 1011

SUMMARY

1. Large amounts of inelanin are present in the substantia nigra and locus coeruleus of the adult gorilla.

2. In the gorilla the pigment is darker and more intense and is collected in granules which are larger in size than in thcl chimpanzee and in lower primates.

3. As compared with adult man, the melanin pigment in the gorilla is lighter and less intense arid the granules are finer. I n size of granules and amount of pigment the ganglion cells of the substantia nigra arid locus coeruleus a re about identical with those of the corresponding regions in the 4-year-old child. The pigment, however, is dark grayblack in the child, as it is in adult man, whereas in the gorilla it is brown.

MELAXIN IN THE BRAIN OF THE G0IXLT.A 505

4. In color and distribution, the iiielaniii of the substaiitia nigra of man iii posteiicephalitic Parkinsonism, a disease as- sociated with a loss of pigmentation of the substantia nigra, is different from that found normally in this region in aninials.

LITERATURE CITED

ADLEK, A. Melanin pigiiiciit in the central nerTous system of vrrtebrates.

BAVER, J. 1909 Die Substantia nigra Soemmeringii. Arb. a. d. Keurol. Inst.

OEERSTEIINER, H. Anleituug beini Studium des Baues der ncrvosen Centrxl-

SCTIERER, 11. J. Melanin pigmentation of the substantia iiigra in primates.

SPATZ, H. 1927 Physiologie uud Pathologie der Stammganglien. Haildburh d.

1939 J. Comp. Neur., vol. 7 0 , pp. 315-325.

Wien, Bd. 17, S. 435-512.

organe. Leipzig und Wien.

J. Comp. Neur., vol. 71, pp. 91-95.

norm. 11. pathol. Physiol., Bd. 10, S. 318.

1912

1939

PLATE 1

EXPLANATIOU O F FIGIJRES

Pliotoni icrograpi:s

2 Substanin nigia, adult gorilla, toliiidiii blue stain. X 48. 3 4 5 X 1000. 6 Ganglion cell i11 substantia nigra of postenccplr:ilitic Parkinsonism, adult

Ganglion ccll i n substaiitia n i g w of gorilla, toliiidin blue stain. Ganglion cell iii locus cocruleus of gorilla, toluidin blue stain. Ganglion cell in euhstantia n igra of ehimpa~izee, unstained section.

patient, toluidin hluc stain. x 1000.

X 1000. X 1000.

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XELANLN I N THE BRAIN OF THE GORILLA ALEXANDRA AD1.ER

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