Spermatogenesis in Man

Transcription

1 Spermatogenesis in Man I. Nuclear Morphology During Spermatogenesis in Man BRUNETTO CHIARELLI, PH.D., ARTHUR FALEK, PH.D., KAREN J. BACK, B.S., and C. THOMAS COWART, M.D. THE SEQUENCE of transformations which the germinal cells undergo during spermatogenesis in man is well described at the histologic level.! Although histologic analysis is useful in the study of distribution of various kinds of cells in the tubule, sectioning and cytoplasmic material may complicate to some extent investigation of the nuclear morphology at the various stages of spermatogenesis. Dissection of a testicular biopsy specimen has permitted a study of the morphology of the nuclei existing in the seminiferous tissue. This report will describe the different kinds of nuclei observed. Our procedure, at present, does not permit us to follow the various stages of spermatogenesis in the maturation sequence. MATERIAL AND METHODS The testicular biopsy specimen was obtained from an 18-year-old male operated for a hydrocele. The size of the specimen was about 2 cu. mm. Immediately after biopsy the material was placed in a 0.7% sodium citrate solution and the tubules were carefully dissected. The dissected material was then fixed and stained in a 2% solution of aceto-orcein. After a period of more than 3 hr. a small segment of a single tubule was placed on a slide, a coverslip placed on it, and squashed in a firm but gentle manner so that the material inside the tubule was forced out. The temporary preparation can be made semipermanent by sealing the coverslip to the slide with clear lacquer. When not in use, the slides are kept in the refrigerator and thus far have been maintained without any alteration for a period of more than 5 weeks. From the Institute of Anthropology, University of Turin, Italy; and the Division of Human Genetics, Georgia Mental Health Institute, and the Department of Surgery, Division of Urology, Emory University, Atlanta, Ga. 758

2 VOL. 19,. No.5, 1968 SPERMATOGENESIS 759 RESULTS Figure 1 displays the nuclei of the various cells in the seminiferous tubule. Among the visible material are Sertoli cells, spermatogonia, spermatocytes, and spermatids. The nuclei of the tubular epithelium are easily distinguished from the others because of their elongated shapes (Fig. 2). The chromatin in the nucleus appears fibrous. The nuclei of the Sertoli cells (Fig. 3 rare generally' circular or slightly ovoid in shape. They are turgid in appearance, with a fine diffuse chromatin structure. A large hyperchromatic nucleolus at the center of the nucleus is a characteristic feature. In some of the Sertoli cells' nuclei it is possible to detect some structure, but the shape and size are 'variable..'... Our observations were similar to those of Clermont.! Like him, we were able to distinguish spermatogonia with different characteristics. We noted 3 types: (1) the dark Type A spermatogonia (Fig. 4, left), with the spherical or ovoid nucleus; (2) the pale Type A, with finely granulated chromatin; and (3) Type B (Fig. 4, center), with both. the lightly stained and coarsely granulated chromatin. It is possible, of course, that these 3 types represent different stages in the maturation of the spermatogonia. Our findings suggest a bridge between spermatogonia arid primary spermatocytes. The typical primary spermatocyte has a spherical latticelike nucleus containing granular chromatin (Fig. 5A). In some of these nuclei a condensation of the chromatin can be noted (Fig. 5B'). It is an'interesting suggestion that this condensation is a nucleolus. What is evident is that this condensation can be recognized at im early stage of the first meiotic division. Just prior to the leptotene stage of the first meiotic division is the classic "bouquet stage," in which the chromosomes seem to organize and pair. The leptotene stage shown in Fig. 6 clearly reveals the 2 chromatids of the bivalent and the chromomeric organization. I Diakinesis was the next clearly recognizable stage in our study of spermatogenesis. In Fig. 7 the 22 bivalents and the linearly organized X and Y chromosomes are presented. The structure of the bivalents is related to the number and location of the chiasma along the chromosome filament. After diakinesis the remaining stages of the reduction division are completed and the secondary spermatocytes are formed (Fig. 8). The nuclei of these spermatocytes are spherical, finely granulated, and contain some small globular masses. The size of the secondary spermatocyte is approximately half that of the primary ones. The second spermatocyte goes through a second maturation division (Fig. 9) to form the spermatid. The spermatid (Fig. 9a) appears struc-

3 760 CHIARELLI- ET AL. FERTILITY & STERILITY turally similar to the secondary spermatocyte, but somewhat smaller in size. There appear to be many stages in the development of the functional sperm, and the sequence seems to be a condensation of nuclear size with the shape progressing from round to dartoic or ovoid in appearance (Fig. 9 b, c, d). From studies on primates 2 other than man and from the material observed in this study, it appears that at an intermediate stage the maturing sperm is shaped like an acorn (Fig. 9 c). Except for Fig. 1, photographs were taken with a Zeiss photomicroscope. X Fig. 1 (top). Nuclei of cells in squash preparation of seminiferous tubule: from spelmatogonia to mature sperm. (X 512) Fig. 2 (bottom). Nuclei of tubular epithelium.

4 VOL. 19,. No.5, 1968 SPERMATOGENESIS Fig. 3. Nucleus of Sertoli cell: faintly stained nuclear material (a), central hyperchromatic nucleolus of variable outline (b). Fig. 4. Various types of primary spermatogonia exhibiting different histologic features in nucleolus. At left, dark Type A; center, pale Type A; at right, Type B with chromatin condensation at periphery. Fig. 5. Primary spermatocytes: (a) spherical nuclei with evenly dispersed, darkly stained chromatin; (b) nucleus with chromatin mass.

5 762 FERTILITY & STERILITY Fig. 6. Proleptotene (top) and leptotene (bottom) stages of first meiotic prophase.

6 VOL. 19,. No.5, 1968 SPERMATOGENESIS 763 Fig. 7. Meiotic chromosomes of man at diakinesis, with peculiar XY attachment.

7 -l o... =: >!:II t>1 t"' t"'... t>1 "I > t"' Fig. 8. Secondary spermatocytes (Inset b) and second meiotic division. Arrow points to chromosome which is probably X. At this stage it behaves differently from other chromosomes; arms appear straighter. R" Vl El C "I

8 VOL. 19,. No.5, 1968 SPERMATOGENESIS 765 Fig. 9. Chromatin maturation: (a) spermatid granular chromatin; (b) densely stained spermatids with indentations; (c) mushroom-shaped spermatid; (d) mature spermatozoa. SUMMARY A qualitative study of the morphologic changes which occur in the nuclei of the germinal tissue of the human male during the maturation stages is presented. A quantitative study of the frequency of different cells as well as the types of cells along the tubules in normal males is now in progress. Institute of Anthropology University of Turin Via Accademia Albertina 17, Turin, Italy REFERENCES 1. CLERMONT, Y Spermatogenesis in Man! A study of the spermatogonial population. Fertil Steril17:705, CIllARELLI, B., and EGOZCUE, J. Observations on the nuclear morphology of the spermatogenic cells of Macaca. Fertil Steril18:812; 1967.