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Effects of GradedHypophysectomy on theGonads of the Male CrestedNewt (Triturus CristatusCarnifex Laur.)Maria Sacerdote a & Valdo Mazzi aa Istituto di Anatomia comparata dell'Università diTorinoPublished online: 14 Sep 2009.

To cite this article: Maria Sacerdote & Valdo Mazzi (1973) Effects of GradedHypophysectomy on the Gonads of the Male Crested Newt (Triturus Cristatus CarnifexLaur.), Bolletino di zoologia, 40:3-4, 337-346, DOI: 10.1080/11250007309429247

To link to this article: http://dx.doi.org/10.1080/11250007309429247

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Boll. ZOO^., 40 : 337-346, 1973

EFFECTS O F GRADED HYPOPHYSECTOMY ON THE GONADS O F THE MALE CRESTED NEWT (TRITURUS CRISTATUS CARNIFEX TAUR.)

MARIA SACERDOTE and VALDO MA221 Istituto di Anatomia comparata dell’Universiti di Torino

(receiced July 16. 1973)

In the adenohypophysis of t!ie crested newt, the localization of various eel1 types as delineated by Mazzr in 1949 and further assessed by histophysiological studies (BCAZZI et al., 19GG), bioassay (~IAZZI et al., 1973) and immunological tests (VELLANO et al., 1!373), has enabled division of this gland into three main zones. They consist of a proximal, narrow region (Zone I), roughly parallel to the infundibular ventro-posterior wall, in contact, dorsally, with the lower margin of the intermediate lobe (Text fig. 1, I) ; a mid-dorsal (Zone 11) and a mid-ventral portion (Zone 111) extending from Zone I in a caudal direction (Text fig. 1, 11, 111).

Recently, the functional significance of pituitary zonation has been analyzed by checking the response given by some endocrine glands t o graded hypophyscctomy (A~AZZI, 1971). Zone I done (Text fig. 1, resection plane a-a), or supplemented with fragments of Zones I1 and I11 (Text fig. 1, resection plane b-b) were left in situ. The pars nervosa, pars inter- media and the hypothalamo-liypophyseal connections were consistently preserved. Evidence of the preferential concentration of ACTH-producing cells (type I11 bnsophils) within Zonc I (MAZZI, 1971) was provided by the fact that its presence mas sufficient to sustain practically normal cytological and histochemical patterns of interrenal activity (MAZZI et al., 1973), irrespective of the addition, if any, of portions of Zones I1 and 111, as confirmed by the administration of extracts from either Zone I or Zonc I1 plus Zone I11 to totally hypophysectomized animals. By contrast, when Zone I alone is preserved, thyroidal metabolism (PONS et nl., 1971) un- dergoes a striking depression comparable to that following total hypo- physectomy, whereas the rate of radioiodine uptake by the thyroid, the

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388

thyroxin blood level and thyroxin-tyrosine ratio are almost normal when portions of Zone I1 and 111 are also left in situ. In ' these pituitary re- gions in fact, thyreotropic cells (type I basophils) are profusely distri- buted.

The present note is concerned with the changes in spermatogenetic activity brought about by graded hypophysectomy in the same operated groups analyzed for thyreotropic and corticotropic activity by MAZZI (1971), PONS et al., (1072) and Jlazzr et al., (1973). Here, an attempt is made at correlating the observed changes with the frequency and activity of gona- dotropic cells (type I1 basophils) in thc pituitary residual node. It must be pointed out that in Nay, in the crested newt (GALGANO, 1944) primary spermatocytes have entered meiotic prophase, and the rate of spermato-

Pig. 1 - Diagram of a sagittal section of the pituitary in Trilurus crisfafus carnijez Laur. Line a-a indicates the plane of the surgical incision performed in the first experiment ; line b-b refers to the second. I, 11, I11 : regions into which the adenohypopliysis is subdivided. IL = intermediate lobe ; inf. = infundibulurn ; ME = median eminence ; NL = neural lobe ; P.S.C. = portal system capillaries.

type I aeidophils type I1 neidophils 0 type I basophils 0 type I1 basophils + type I11 basophils (from POSS ef al., 1073).

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genesis increases steadily up to a peak in the warmer months, t o dccline gradually until winter comes. Hence, during the period of time elapsed between operation (May or June) and gonad removal (October or No- vember), allowance being made for individuai differences and captivity conditions, the spermatogenctic cycle is completed.

MATERIAL AND JIETIIODS

Technical details about thc acliievcment of graded hypophysectomy to which the newts under study were subjected, have already been reported (NAZZI, 1971; POWS ef. al, 1972).

Fifty-six adult Trifurus crislatcts carnijex Laur. male spccimens were used. These animals were divided as follows.

Erperimenl I (May 18 - h’ovember 23, 1070)

Group I - 8 intact control individuals. Group I1 - 8 surgical animals. The pituitary remnant consisted of Zonc I alone,

additioned in tn-o cases by n small portion of Zonc 111. Both groups were reared in aqua- ria nt room temperature.

Group I11 - 8 intact control individuals. Group IV - 8 surgical animals. Zone I and n fragment of Zone 111 were prcscrwd.

Groups III and IV it-ere reared in n tliermostatic cupboard nt IOOC.

Ezperiment I1 (June 14 - October 4, 1071)

Group V - 8 intact control individuaIs. Group VI - 8 surgical animals, in which the pituitary Zone I along with por-

Group VII - 8 totally liypopliysectomized animals. These three groups were

The gonads of all the animals were fixed in Sanfelice fluid and embedded in pa- thick were stained with hemalum-

tions of Zones I1 and I11 had remained (Text fig. 1, resection plane b-b).

reared at room temperature.

ramn and celloidin according to Petcrfi. Sections 0 safranin-orange.

RESULTS

A brief survey of some seasonal secondary sex characters exhibited by each group is given in Table I, together with indications of the relative extent of the pituitary lobe and the activity of typc I1 basophils.

SPERBIATOGENESIS

Experiment I Group I (control animals reared nt room temperature). In all the

individuals spermatogenesis is active (Plate I, figs 6, 7) with regular meiotic

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process, while degeneration affecting late spermatogonia and spermatoeytes has already set in. Jlature sperms arc very abundant.

Group I1 [surgical animals reared a t room temperature. Zone I (subgroup a) and in some cases Zone I supplcmented with a fragment of Zone I11 (subgroup b) have remained].

I n two individuals (subgroup a) extensive degenerations resulted in a pronounced reduction of tlic gonad size. Just a few germ cells succeeded in evolving into spermatids (Plate 11, fig. 8 ) and mature sperms. In the other specimens (subgroup 6 ) a moderately-sized testis is found, in which full gametogenesis is achieved by a considerable number of cysts (Plate 11, fig. 9). I n the testis from an individual of this group a number of ooeytes in the zygotene stage (Plate 11, fig. 11 ; Plate 111, fig. 12) and primary oocytes in tlie 1st and 2nd growth phases were found within cysts in which also spermatogenesis (Plate 111, fig. 12) and spermiogenesis (Plate 11, fig. 11) mere under may, or which contained mature sperms (Plate 11, fig. 10). A number of protogonia, some of which display a particularly swollen nucleus with evident .chromatin strands (Plate 111, fig. 12), are also found within these cysts.

Group I11 (control animals moved to the thermostatic cupboard at 10oC on May 18). The testis, of normal size, consists of a region typically containing protogonia and spermetogoiiia in which a variable frequency of mitoses and degenerations are present, and a region made up of primary spermatocytes at the leptotene stage. Pachitcne and diplotene sperma- tocytes are either lacking or displaying badly clumped chromosomes. Chiasmata are lacking. An enormous number of anomalous metaphase- anaphases in which the chromosomes are stretched between tlie spindle poles (to about 25 p) are found to replace true metaphases (Plate 111, figs 13, 15). Some rarc cysts contain a few secondary spermatocytes or spermatids undergoing degeneration. No sperms are formed.

Group IV (surgical animals reared at IOOC. Presence of Zone I and a portion of Zone 111 of tlie adenohypopliysis). I n all the animals tlie testis is much reduced in size. Sperrnatogcnesis is stationary at the lepto- tene stage of meiotic prophase. Massive degeneration of spermntogonia and primary sperniatocytes has occurred, although spermatogonial divi- sions are still found.

Bxperimen II

early October. All the groups mere reared a t room temperature from mid-June to

Group V (control animals). At autopsy, the testes, normal in size,

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consist of protogonia, spermatogonia and plentiful cysts with mature sperms, meiosis and spermiogenesis having already been fully achieved.

Group T71 (surgical animals. The adenohypophyseal Zone I along with portions of Zones I1 and I11 remained: Text fig. 1, line b-b). The testis volume is moderately reduced. As compared with controls, a consid- erable delay in spermatogenesis is evident, since besides mature spernis, the various stages of meiosis are still in progress, secondary spernintocytes and spermatids being also plentiful. Spermiogcncsis is under way.

Group VII (totally hypophysectoniized individnnls). The extrcnicly reduced, thread-like gonads arc largely made up of traces of cysts and Connective tissue in which protogonin arc spa~scly scnttcrcd.

DISCUSSION

Intact crested newts reared in aquaria at room tcmperature from the middle of Xay to November or from early Junc to October, show a fairly normal stimulation of gonadal activity. Differences may exist in the rate of development of the seasonal secondary sex characters, which in turn are less conspicuous than those exhibited by newts living under natural conditions.

Diirercnces in the gonadal response to graded hypophysectomy ap- pear t o be closely correlated with the amount of the residual pituitary tissue. When less than 10% of it is left over, a sharp decrcasc in tlic testis volume is seen to occur, although gamctogcnetic activity is still present in a few cysts (Plate 11, fig. S), in contrast to totally hypophysectomized animals in which the gonad is largely made up of traces of cysts, connective tissue and sparse protogonia. Both the testis volume and rate of spermato- genesis rise with the increase in the pituitary remnant (Plate 11, fig. 9). Some delay was observed in thc unfolding of the complete gamctoge- nctic cycle.

In higher vertebrates, for instance in the dog (GAXOXG and HUBIE, 1056), ablation of 2/3 of the pituitary results in the inhibition of the acti- vity of the male gonad. According to LICIIT and PEARSON (1968) the rate of gonad regression in the reptile Anolis carolirzerzsis is at its highest when less than 10% of the pituitary gland is maintained. In the crested newt, as reported above, the presence of evcn less than 10% of the adenohy- pophysis appears to succeed in activating meiosis and ipermiogcnesis.

At autopsy, either in October or late November, the pituitary of both control and surgical newts reared at room temperature exhibits

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P L A T E 1

Xanra SacEnDom and VALDO MAZZI - E,ec t of graded hgpopligsectoiiq, ete.

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1' 1. A T rS I1

Fig. S - Surgical animal reared tinder tlic same conditions as bcforc (Icss than 10% of tlic adcnolrypoplrysis liacl rcsidnated). Spermatogenesis, tliongli confined to a fccw cysts, lias takcn placc and progressed tip to spcrmatids. 140 x .

9 - Surgical animal (about layb of tlic adcnoliypopliysis liad rcsiduated). \'a- rious pliascs of spermatogenesis and many cysts containing spcrni bundles can bc sccn. 70 X .

Fig. 10 - Oogcncsis in tlic testis of a surgical animal. Xotc sercrnl oocytcs and a cyst in wliicli a large oocytc in the carly 2nd growth pcriod together wit11 two sperm bundles are contained. 140 X .

Fig. 11 - (Sanic prcparation as bcforc). Oocytc in tlic carly sccond growth pcriod and R fcw elongating spermatids within tlrc sanic cyst (ccntrc) ; zygotcnc oocytes (right ccntrc) ; oocytcs in tlic first growth period (left ccntrc) ; spermatids and a protogoniuni with two follicular cells can bc sccn in the

Fig,

cyst on tlic lower left. 4-5 30 x.

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1' I. A T E 111

Fig. 12 - (Sniiic ~ircpnrntion). Cyst containing soiiic protogonin (lower right) in which slciidcr cliroinntin tlircntls arc visiblc. 1,argc cyst (ccntrc) with iiiciotic spcr- niatocytcs and tlircc xygotcnc oocytcs. Top riplit, portion of cyst containing pacliitcnc spcrmntocytcs. 8% x .

Ipig. 13 - Xorninl nniiiinl phccd at l O O c in iiiid-Jhy. iholiinlous i i i C t ~ ~ ) ~ i n ~ C - ~ n ~ i ~ ) ~ l n -

ses arc plentiful. 315 x. Figs. 13, 16 - Comparison bctwccn nornial iiictap~iasc 1 froin a normal control ani-

mal (14) nnd anonlalous mctnpliasc-nnnplinscs froiii a control animnl plnccd n t 10oC in niid-JIny (15). 050 X .

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moderatcly active Typc I1 basopliils (Plate I, figs 1, 4, 5), whilc a definite rcgrcssion of thc gonad in tlic hibernating surgical animals is associated with tIic definite atrophy of these cells in the pituitary remnant (Plate I, fig. 3). I3y contrast, in the control hibernating animals displaying highly developed sccondary sex characters (see Table I), the activity of Type I1 bnsophils is enhanccd (Plate I, fig. 3). These results lend strong support to thc assumption that in the crested newt, as in other amphibian species (VAN OORDT, 1968), Type I1 basophils arc gonadotropin-producing cells. In the amphibians, thc problem of the existencc either of a single cell type endowed with the dual ability of producing FSH and LH or two types of gonadotropic cells producing PSH and LI€ respectively, is still open (DOERR-SCIKOTT and Dunors, 1073). Circumstantial evidence in favour of the first altcrnative in the crested newt appears to bc provided by the findings reported here. In the case of subtotal adenoliypophysectomy, in fact, when the residual nodule consists almost entirely of corticotropic cells (Typc I11 basophils : sce ~ I A Z Z I , 1071 ; ~ I A Z Z I et nl., 1073) and few Typc I1 basophils, spcrrnatogenesis was seen to progress, even though to a limited extent. As is known, in the crested newt (VELLANO, 1068) as in mammals (LOSTROII, 10GO), FSH and L H are needed for spermatogenesis to set in and unfold regularly.

As concerns gonadotropic cell distribution in the crested ncwt, the direct ratio of gonadal activity to the amount of residual adcnohypophyseal tissuc reveals the absence of a preferential concentration of gonadotropic cells, ns already suggested by cytological analysis (1\IAZZI et nl., 106G, 1073).

We should like to deal now with the peculiar gonadal changes which occurred in two cases, although an attempt a t correlating them with the activity of gonadotropic cells will not be made.

I n a surgical animal from Group 11, reared at room temperature, plentiful oocytes mere found. As is known, the occurrence of oocytcs in the testis of the crested newt is not uncommon. In the present case, in a number of cysts containing both oocytes in the 2nd growth period and male cells a t advanced stages of spcrmatogencsis (Plate 111, fig. 12) or spermiogenesis (Plate 11, fig. 11) protogonia were also found, which cxhi- bited a swollen nucleus with evident slender cliromatin threads (Plate 111, fig. 12). Somc recollection was tlicreby suggested of the concept of cab- breviatcd oogenesis )) advanced by BECCARI (1025) for the Bidder's organ in Bufo viridis and later (1933) for oocytcs arising in the testis of Triturus- cristattts cariziJex after homotransplantation of fragments of male gonad.

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According to this concept, protogonia would directly turn into primary oocytes in tlie growth period without undergoing tlie caryological stages typical of meiotic propliase. This possibility was further discussed by IZADI (1943), VAKNINI and BUSETTO (1946) and PADOA and PICCHI (1017) in the Bidder’s organ of the common toad. I n tlie present case, however, con- spicuous zygotcne oocytes were observed (Plate 11, fig. 11 ; Plate 111, fig. 12) ; hence regular oogcnesis may be assumed to take place.

Peculiar changes in spermatogenesis mere noticed a t autopsy in all of the intact animals placed at lOoC in mid-May, mlien meiotic prophase ~(GALGANO, 1944) had already set in. In late November, in the vast majority of cysts leptotene spematocytes have not progresscd further, since normal zygotcne or pachitene stages have not differentiated. Chiasmata are lacking. lIetaphase I is replaced by an anomalous metapliase-anaphase in which chromosomes are stretched betmeen the spindle poles to a striking extent (about 25 p) apparently sticking together by their ends at the level of the equatorial plane (Plate 111, figs. 13, 15).

According to WIIITE (lDiG), BENAZZI and LEPORI (1948), MANCISO (195I)), in various hybrids espcrimentally obtained in the genus Trilurus (for further details on some of these hybrids, see NANcINo and SCALI, 1964; SCALT and BfANcmo, 1968) instead of a true metaphase I, a very largc number of cells undergo an anomalous metaphase-anaphase comparable to that just described liere in the pure crested newt.

u Localized stickiness 8 of chromosomcs at the spindle equatorial plane, induced experimentally by ionizing radiations, was extensively discussed by EVANS (10G2). It is believed to depend upon interchromosome exchanges between sub-chromatid units. AIoreover, on the basis of original and other workers’s investigations, Evaxs (loc. cit.) states that u these half-chromatid exchankes are known to occur naturally in both plants and animals, especially following genetic imbalance due to hybridiz- ation D.

Lastly, as regards tlic failure of chromosome pairing and chiasmn formation elicited by the sudden drop in environmental temperature - as it mould appear to be tlie case in the ncwts placed a t l O O C when sperma- tocytes are in tlie leptotene stage - an attractive explanation would be thc rcpressioii of both DNA and protein syntheses during early meiotic prophase, which are essential for the construction of thc u synaptoncmal

.complex )) (for details on this process see SOTELO, lOG9 ; DE ROBERTIS,

.NO~ISSKI and SAEZ, 1070).

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In the crested newt, partial ablation of the adenohypophysis elicits changes in- both the testis volume and spermatogenetic activity in close correlation with the amount of residual pituitary tissue. The presence of less than 10% of the adenohypophysis is. enough for meiosis and spermiogenesis to be activated in a small number of cysts. These results suggest the absence of a preferential concentration of gonadotropic cells, iden- tifiable with type I1 basophils, according to MAZZI et at. (19GG). In addition, oogenesis. up to the formation of oocytcs in the early second growth phase is described in the testis of a partially ndenohypophyysectomized specimen. Peculiar anomalies coneerning- meiotic meta-anaphase in the testis of all the normal animals placed a t IOOC from mid- May to late hTovember are also reported.

RIASSUNTO

Net tritonc crestato l’asportazione parziale dell’adenoipofisi provoea variazioni del volume del testicolo e dell’attivitk spermatogenetica strettamentc correlabili nlla quantith del tessuto ipofisario residuato. La prcsenza di meno del 10% dell’adenoipofisi E suffciente ad nttivare la meiosi c la spermatogenesi in un piccolo numero di cisti. Que- sti risultati indicano chc non esiste una concentrazione preferenziale delle ccllule gona- dotrope, identificabili eon le ccllule basofile del I1 tipo secondo BLzzr el at. (1OGG).

Vcngono inoltrc deseritte, nel testicolo di nnimali parzialmente ipofisectomizzati, ovociti in maturazione e, in quello di animali normal; posti in vasehe a 100C n met& Maggio e ivi mantcnuti fino a Novembre, peeuliari anomalie della meta-anafase meiotiea,

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