101. Anatomical, Histological and Karyological Observations ... - J-Stage

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Proc. Japan

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60, Ser. B (1984)

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Anatomical, Histological and Karyological Observations of an XXY Male Black Rat born after r•Irradiation By Masayasu Y. WADA,*> Katsushi SUZUKI,* *> and Tosihide H. YOSIDA*** (Communicated by Sajiro MAKINO, M.J. A., Dec. 12, 1984)

In the mammalian species the XX or XY sex determining mechanism is commonly observed, but those with the XXY are rather sporadic and abnormal. In man, the XXY condition has been known as the Klinef elter's syndrome involving some of the gonadal dysgenesis (Klinefelter et al. 1942 ; Makino 1975 and some others). This syndrome occurs at a relatively high frequency in the human population (German 1971), but rare in the other mammals. Sporadic XXY males have been found in some domestic animals, including the bull, the pig and the horse (Hamori 1983). In the black rats, the XXY sex chromosomes were described in the F .~hybrids between the Ceylonese (Rattus rattus kandianus) and the Oceanian type black rats (R. rattus rattus) and also between the Japanese (Rattus rattus tanezumi) and the Thai black rats (R. rattus Thai) (Yosida 1979). According to him, these XXY black rats were always sterile. Russell and Chu (1961) and Cattanach (1961) have also reported the sterile XXY mice. Recently, an XXY male Ceylonese type black rat was obtained in the offspring born after r-irradiation. The present paper deals with the anatomical, histological and karyological observations of the XXY black rat. Material and method. The Ceylonese type black rats, (Rattus rattus kandianus) used in the present study, were obtained from a breeding colony of the National Institute of Genetics, where they were established by sister-brother matings for several generations from the specimens captured in Sri Lanka in 1978. The acute irradiation of 700R of r-ray (Cs13i) was applied to the hindquarter of 8 adult male black rats, and they were paired to non-irradiated females. One among 7 offspring thus obtained showed the XXY male. The chromosomes of the black rats were observed in the cultured cells of the tail tissue by our routine procedure (Yosida 1980). Serial conventional Giemsa, G- and C-band staining method (Wada and *' Odakyu Manazuru Botanical and Zoological Garden , Manazuru, Ashigarashimo-gun, Kanagawa-ken, Japan. **' Nippon Veterinary and Zootechnical College , Musashisakai, Tokyo, Japan. ***' National Institute of Genetics , Mishima, Japan (contribution no. 1586).

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Yosida 1983) was also applied. After the chromosome analysis, the rat was sacrificed for the further examinations with chloroform anaesthesia, and then fixed with 10% formalin solution for the anatomical observations. The testis and the accessory organs such as the epididymis, ductus def erens, seminal vesicles, coagulating glands, dorsal and ventral prostate, penis and preputial glands were removed and weighed. The testis fixed with the formalin was embedded in paraffin, sectioned and then stained with hematoxylin and eosin solutions. Results and discussion. 1) Karyological analysis : The normal karyotype of the Ceylonese type black rat (R. rattus kandianus) was characterized by having 40 chromosomes (20 pairs) as already described by Yosida et al. (1974). Among them 11 autosome pairs (nos. 1 to 10 and no. 13) were acro- or subtelocentrics, one autosome pair was a large metacentric (M2) which was resulted from the Robertsonian fusion between acrocentric pair nos. 11 and 12, and the remaining 7 autosome pairs were small metacentrics (nos. 14 to 20). The X element was a long acrocentric, similar to pair nos. 4 or 5, and the Y was a short acrocentric. The male had the X and Y, and the female had two X's. Among 7 offspring born after mating between y-irradiated males and non-irradiated females, one male had 41 chromosomes invariably in all 20 cells analyzed. In G-banding pattern analysis the X was clearly identified by two dark bands in the middle region of the long arm as described by Yosida (1980). On the basis of these characteristics this male rat was confirmed to have two X's and one Y (Fig. 1). As a cause of development of the

Fig. a

1. male

G-banding Ceylonese

karyotype type

of black

rat with XXY sex chromosomes born after r-irradiation.

XXY male, it is considered either one of the non-disjunction of the X chromosome in the course of oogenesis or spermatogenesis. In the mouse the non-disjunction is considered to occur in spermatogenesis (Russell and Chu 1961), but in man more frequently in the oogenesis

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XXY Male Black Rat born after r-Irradiation

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(Ferguson-Smith et al. 1964; German 1971 and others). It has been already described that several chromosomal alterations such as breakages and translocations were induced by the r-irradiation in the black and Norway rats (Yosida 1983). The present XXY male should be due to a descendant from the male parent irradiated with 1-rays. 2) Anatomical examinations : The XXY rat seemed to be a normal male from the external characteristics by having the usual scrotum and penis, although a testicular hypoplasia was detected and the testis was smaller and softer than the normal one. The weight of a testicle in the XXY male was 378 mg which was approximately one-fourth of the normal specimen (ca. 1600 mg). The accessory organs were all formed but reduced in their size and weight (Figs. 2 and 3). The most severely affected organ was of the preputial gland,

Figs. 2 and 3. Genital organs of the normal and XXY black rats. 2: Normal specimen. 3: XXY specimen. (A) testis, (B) epididymis, (C) ductus deferens, (D) seminal vesicle, (E) coagulating gland, (F) bladder, (G) ventral prostate, (H) preputial gland and (I) penis. In the XXY specimen, the right testis used for the chromosome analysis is not appeared. These two figures are taken by the same magnification.

which was only 30 mg in the XXY specimen, but 206 mg in the normal male. The weight of the other accessory organs was all about 1/22/3 to those of the normal male. The adrenal weight was comparable to the normal, but the kidney weight was about 3/4 to that of the normal specimen, representing the feminine characteristics. Although well developed mammary gland was sometimes observed in the adult Klinef elter patients (Makino 1975), it was not observed in the present case. 3) Histological observations : The results of histological examination of the testis in the XXY male were summarized as follows. All of the seminif erous tubules were reduced in their diameter and the germ cell layers were markedly degenerated. The hyaline deposits in some lumen of the tubules were observed. The lumen was occupied predominantly by the Sertoli cells. No spermatogenesis was observed in the entire tubules, suggesting that the XXY rat was sterile. Relatively numerous numbers of the Leydig cells were observed in

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Fig. 4. Histological observations on the testis of the normal and XXY black rats. A : Section of the normal rat testis, stained with hematoxylin and eosin (X175). B : High magnification of A (X350). C: Testis of the XXY black rat. Degenerated seminiferous tubules, in which the normal spermatocytes are not included, are observed. (X175). D : High magnification of C (X350).

the interstitium (Fig. 4). These findings were well agreement with that of the seminiferous tubule dysgenesis or the Klinefelter's syndrome in man (Makino 1975). Acknowledgment. The present authors are grateful to Emeritus Professor Saj iro Makino, M. J. A., for his critical reading of this manuscript. References Cattanach, B. M.: Genet. Res. Camb., 2, 156-160 (1961). Ferguson-Smith, M. A. et atl.: Lancet, i, 46 (1964). German, J.: Southern, Med. J., 64, 73-80 (1971). H,amori, D.: Constitutional Disorders and Hereditary Diseases in Domestic Animals. Elsevier Scientific Publishing Co., Amsterdam-Oxford-New York (1983). Klinefelter, H. F., Reifenstein, E. C., and Allbright, F.: J. Clin. Endocr., 2, 615627 (1942). Makino, S.: Human Chromosomes. Igaku Shoin Ltd., Tokyo (1975). Russell, L. B., and Chu, E. H. Y.: Pron. Nat. Acad. Sci. Wash., 47, 571-575 (1961). Wada, M. Y., and Yosida, T. H.: La Kromosomo (in press). Yosida, T. H.: Jap. Jour. Genet., 54, 27-34 (1979). Cytogenetics of the Black Rat. Univ. Tokyo Press, Tokyo (1980). Proc. Japan Acad., 59B, 263-266 (1983). Yosida, T. H. et al.: Cytologia, 39, 753-758 (1974).