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Morphological and histochemical observations on follicular atresia and interstitial gland tissue in the columbid ovary
GENERAL
AND
COMPARATIVE
Morphological
ENDOCRINOLOGY
(1976)
M,534-538
and Histochemical Observations on Follicular and Interstitial Gland Tissue in the Columbid Ovary
Atresia
A morphological and histochemical study has been made of follicular atresia and interstitial gland tissue in the ovary of the pigeon (Columba livia) and ring dove (Streptopelia decaocto). The building up of interstitial gland tissue of thecal origin is related to the atresia of previtellogenic and very early vitellogenic follicles. Their granulosa cells, after removing the ooplasmic contents, degenerate and disappear. The thecal-type interstitial gland cells distributed either in groups or singly in the ovarian stroma accumulate lipid droplets consisting of cholesterol, and/or its esters, triglycerides, and some phospholipids.
Primordial or “Balbiani Stage” Follicles in Atresia Atresia of the primordial follicles are best studied in frozen sections stained with Sudan black B. The first sign of their atresia is shrinkage; meanwhile the lipid bodies described in normal oocytes (Guraya, 1957, 1959) coalesce to form deeply sudanophilic masses consisting of cholesterol and/or its esters, triglycerides, and a trace of phospholipids. Atretic primordial follicles and their lipids are gradually resorbed without making any contribution to the interstitial cells. The number of atretic primordial oocytes was apparently greater in the winter ovaries.
As in other vertebrates (Guraya, 1973), folhcular atresia also occurs in the avian ovary. It has been classified into different types depending upon the size at which the follicles become atretic (Kern, 1972; Erpino, 1973), but the physiological significance of atretic follicles is still poorly understood. Using histological and histochemical techniques, the present study on pigeon and ring dove ovaries was undertaken to determine the nature of the relationships between the type of follicular atresia and the genesis of interstitial gland tissue. MATERIALS
AND METHODS
The ovaries of the pigeon (Columba livia) and ring dove (Streptopelia decaocro) were used for the present study. Specimens were collected at regular intervals throughout the year, ovarian material being fixed in Bouin’s fluid and processed for routine histological study. Fixing fluids and histochemical techniques used are summarized in Table 1, along with the results obtained.
OBSERVATIONS
Follicular atresia in pigeon and dove ovaries was seen throughout the year, but atresia of large follicles was seen only in those ovaries which showed extensive follicular growth. Atresia affects the primordial, or “Balbiani stage” previtellogenic and vitellogenic follicles; the latter develop during the breeding season.
Previtellogenic
@ 1976 by Academic Press, Inc. of reproduction in any form reserved.
in Atresia
During the atresia of previtellogenic and very early vitellogenic follicles, conspicuous morphological and histochemical changes occur in their components. The first signs of their atresia are erosion of the zona pellucida and distortion in the shape of the follicle (Fig. 1). Some atretic follicles appear more collapsed and rugose. The granulosa cells are separated from each other, indicating the dissolution of intercellular cohesion between them. Some granulosa cell nuclei immediately become pycnotic. The zona pellucida is broken at some places allowing the granulosa cells to
534 Copyright All rights
Follicles
535
NOTES
TABLE 1 HISTOCHEMICAL REACTIONS OF LIPIDS IN THE INTER~IITIAL GLAND CELLS’ Technique Sudan black B (SBB), 70% ethanol SBB*PE Acid haematein Nile blue Schultz reaction
Fixation
Reference
Lipids of interstitial gland cells
FCA + PC
Baker ( 1956)
+++
WB FCA FCA FCA
Baker (1946) Baker (1946) Pearse (1968) Gomori (1952)
+ to ++ p+++ ++ to +-I-+
+ PE + PC + PC + PC
a Key to abbreviations: *, after treatment with; FCA + PC, formaldehyde-calcium and postchromed in dichromate-calcium; P, pink; WB + PE, weak Bouin’s fluid followed by pyridine extraction; +, weak; ++, moderate; + ++, strong reaction; -, negative reaction.
enter the ooplasm where they form conspicuous aggregations (Fig. l), though some granulosa cells still remain at the periphery of the follicle (Fig. 1). With the advancement of atresia, the ooplasm is gradually resorbed owing to its phagocytosis by the granulosa cells which are evenly distributed in the follicle cavity (Fig. 2). The zona pellucida has completely disappeared at this stage. The theta interna cells simultaneously hypertrophy to form large cells in the wall of the degenerated follicles (Fig. 2). They constitute the thecal-type interstitial gland cells which can
be easily distinguished from the surrounding undifferentiated stromal cells due to their increased size. The thecal-type interstitial gland cells are distributed in groups or cords in the wall of late degenerated follicles (Fig. 2). After removing the ooplasmic contents, the granulosa cells degenerate leaving behind the thecal-type interstitial gland cells surrounded by undifferentiated stromal cells (Figs. 3 and 4). Corresponding to various morphological changes in the atretic previteIIogenic and early vitellogenic follicles, there also occur conspicuous histochemical changes. The
FIG. 1. Portion of large previtellogenic follicle in early atresia from the pigeon ovary, showing the broken zona pellucida (ZP) and masses of granulosa cells (GC) in the ooplasm. The thecal layer (TL) consists of undifferentiated stromal cells. x 50. Photomicrographs 1 and 2 are prepared from paraffin wax embedded material fixed in Bouin’s solution and stained with iron haematoxylin.
536
NOTES
FIG. 2. Portion of large previtellogenic follicle in late atresia from the pigeon ovary, showing the complete removal of ooplasmic contents by the granulosa cells (GC) which fill the follicle cavity and are seen to be degenerating. The thecal cells have hypertrophied to form interstitial gland cells (IGC). x 100.
ooplasmic lipid bodies consisting of cholesterol and/or its esters, triglycerides, and some phospholipids in the normal oocyte (Guraya, 1957, 1959) finally form deeply sudanophilic lipoidal masses in the central ooplasm of atretic previtellogenic and very
FIG. 3. Follicle in a late stage of atresia from the pigeon ovary, showing interstitial gland cells (IGC) loaded with sudanophilic lipids. Deeply sudanophilic ooplasmic components are being resorbed by the granulosa cells. Note the remnants of ooplasm (RO) in the centre. x 100. Photomicrographs 3 and 4 are prepared from frozen sections of ovarian material fixed in formaldehyde-calcium, postchromed in dichromate-calcium, and coloured with Sudan black B.
early vitellogenic follicles (Figs. 3 and 4). The degenerating granulosa cells also accumulate lipid droplets of a similar histochemical nature. The hypertrophied thecal-type interstitial gland cells develop more lipids and form large sudanophilic patches in the wall of degenerated follicles (Figs. 3 and 4). The histochemical reactions of their lipid droplets show that they consist mainly of cholesterol and/or its esters, triglycerides, and some phospholipids (Table 1). The degenerated granulosa cells and their lipid accumulations gradually disappear, leaving behind the thecal-type interstitial gland cells distributed either in groups or singly in the ovarian stroma (Figs. 3 and 4). The amount of thecal-type interstitial gland tissue seen in the ovary is apparently related to the number of atretic previtellogenic and early vitellogenic follicles. Large Vitellogenic Follicles in Atresia Large atretic vitellogenic follicles appear during the breeding season though they are variable in number. The yolk bodies of atretic vitellogenic follicles form irregular masses which are gradually digested and
NOTES
537
FIG. 4. Final stage of atresia in the follicle of ring dove ovary, showing the sudanophilic masses of interstitial gland tissue (KC) lying in the surrounding stroma which is sudanophobic. Note the remnants of ooplasm and granulosa cells in the centre, which are deeply sudanophilic due to their degenerative changes. x 100.
removed by granulosa cells or phagocytes. There is little or no transformation of their thecal cells into interstitial gland cells. DISCUSSION The morphological changes occurring in different components of atretic follicles in pigeon and ring dove ovaries are basically the same as those described for other bird species (Marshall and Coombs, 1957; Erpino, 1973). The degenerative changes in the ooplasm and follicular epithelium in previtellogenic and early vitellogenic follicles appear to provide some kind of stimulus to the thecal cells which simultaneously hypertrophy to form interstitial gland cells as also described for other nonmammalian vertebrates and mammals (Guraya, 1973, 1976). The formation of interstitial gland tissue from the thecal cells of atretic follicles has also been reported in rook and scrub jays (Marshall and Coombs, 1957; Erpino, 1973) but not in white-crowned sparrows (Kern, 1972). It is suggested that the ovary of the latter should be investiwith histochemical techniques gated applied to frozen sections. Interstitial gland cells are quite distinct from the thecal gland cells of Dahl (1972), which originate from
the surface epithelium of the postnatal ovary in the fowl. Thus, the avian ovary contains interstitial cells of both epithelial and stromal origin. The interstitial gland cells of stromal origin differentiate in close association with the atretic previtellogenic and early vitellogenic follicles as already stated. The most important physiological significance of follicular atresia in the ovaries of vertebrates appears to be the building up of the thecal-type interstitial gland cells which are now known to possess the ultrastructural and histochemical features of well-established steroid gland cells (Lofts and Bern, 1972; Guraya, 1973, 1976). These features indicative of steroidogenesis consist of the presence of abundant agranular endoplasmic reticulum, mitochondria with complex internal structure, steroidogenic enzymes, and cholesterol-positive lipid droplets. Thus, it can be stated that the thecal-type interstitial gland cells of pigeon and dove ovaries, which also show cholesterol-positive lipid droplets, are probably the steroid secretors. Divergent opinions have been expressed about the nature of steroid hormones formed by the ovarian interstitial gland cells in different
groups of vertebrates (Guraya, 1973, 1976). Baker, J. R. (1956). Improvements in the Sudan black technique. Quarr. J. Microsc. Sci. 97, 621-623. They may be progestins, oestrogens, and Crews, D.. and Licht, P. (1974). Inhibition of corpora androgens. Similar hormones may also be atretica of ovarian sensitivity to environmental produced by the thecal-type interstitial and hormonal stimulation in the lizard, Anolis gland tissue of the columbid ovary, which carolinensis. Endocrinology 95, 102-106. constitutes the steroidogenic tissue. The Dahl, E. (1972). Studies of the fine structure of ovarian interstitial tissue. VII. The postnatal evoluthecal gland cells originating from the surtion of the thecal gland in the domestic fowl. Z. face epithelium in the fowl ovary have also Zetlforsch. 135, 553-561. been shown to possess the ultrastructural Erpino, M. J. (1973). Histogenesis of atretic ovarian features of steroid-secreting cells (Dahl, follicles in a seasonally breeding bird. J. Morphol. 139, 239-250. 1972). This indicates that the avian ovary contains different types of interstitial cells Gomori, C. (1952). “Microscopic Histochemistry.” University of Chicago Press, Chicago. which possess the ultrastructural and his- Guraya, S. S. (1957). Histochemical studies of lipids tochemical features of steroid-secreting in oocytes. I. Lipids in the oogenesis of Columba cells (see review by Guraya, 1976). Correlalivia. Quart. J. Microsc. Sci. 98, 407-423. tive ultrastructural, biochemical, and Guraya, S. S. (1959). Histochemical studies of lipids in oocytes. IV. Lipids in the oogenesis of Callus physiological studies should be carried out domesticus. Streptopelia senegalensis and Strepto determine precisely the nature of steroid topelia decaocto. Res. Bull. Panjab Univ. 10, hormones formed by different types of 119-130. interstitial cells, and their roles in the repro- Guraya, S. S. (1973). Follicular atresia. Proc. Indian Nat. Sci. Acad. 39B, 311-332. ductive processes of female birds. The conS. S. (1976). Recent advances in the sensus of some recent biochemical and his- Guraya, morphology, histochemistry and biochemistry of tochemical findings is that androgens are steroid-synthesizing cellular sites in the nonproduced in the interstitial cells that arise mammalian vertebrate ovary. Znr. Rev. Cytol. 44, from the ovarian stroma (see Guraya, 365-409. 1976); they actually seem to correspond to Kern, M. D. (1972). Seasonal changes in the reproductive system of female white-crowned the thecal gland cells of Dahl (1972), which sparrow, Zonotrichia leucophrys gambelli. in have an epithelial origin rather than a captivity and in the field: I. The ovary. Z. stromal origin. Oestrogens are produced in Zellforsch. 126, 297-319. the interstitial gland cells derived from the Lofts, B., and Bern, H. A. (1972). The functional morphology of steroidogenic tissue. In “Steroids theta interna of atretic follicles. The variin Nonmammalian Vertebrates” (D. R. Idler, able nature and amount of steroid hored.), pp. 37-117. Academic Press, London/New mones may be related to fluctuations in difYork. ferent steroid gland cell types. Marshall. A. J.. and Coombs, J. A. (1957). The inThe atretic vitellogenic follicles finally teraction of environmental, internal and behavioural factors in the rook, Corvus frugileugs. disappear from the ovary without making a Proc.Zool.Soc.London 128, 545-589. visible contribution to the interstitial gland Pearse, A. G. (1%8). “Histochemistry. Theoretical tissue; they correspond to the corpora atand Applied,” 2nd ed. J. & A. Churchill, London. retica of Crews and Licht (1974) in the reptilian ovary. SARDUL S. GURAYA REFERENCES Baker, J. R. (1946). The histochemical recognition of lipine. Quart. 3. Microsc. Sci. 87, 441-470.
Department of Zoology College of Basic Sciences and Humanities Punjab Agricultural University, Ludhiana Punjab, India Accepted July 29, 1976
AND
COMPARATIVE
Morphological
ENDOCRINOLOGY
(1976)
M,534-538
and Histochemical Observations on Follicular and Interstitial Gland Tissue in the Columbid Ovary
Atresia
A morphological and histochemical study has been made of follicular atresia and interstitial gland tissue in the ovary of the pigeon (Columba livia) and ring dove (Streptopelia decaocto). The building up of interstitial gland tissue of thecal origin is related to the atresia of previtellogenic and very early vitellogenic follicles. Their granulosa cells, after removing the ooplasmic contents, degenerate and disappear. The thecal-type interstitial gland cells distributed either in groups or singly in the ovarian stroma accumulate lipid droplets consisting of cholesterol, and/or its esters, triglycerides, and some phospholipids.
Primordial or “Balbiani Stage” Follicles in Atresia Atresia of the primordial follicles are best studied in frozen sections stained with Sudan black B. The first sign of their atresia is shrinkage; meanwhile the lipid bodies described in normal oocytes (Guraya, 1957, 1959) coalesce to form deeply sudanophilic masses consisting of cholesterol and/or its esters, triglycerides, and a trace of phospholipids. Atretic primordial follicles and their lipids are gradually resorbed without making any contribution to the interstitial cells. The number of atretic primordial oocytes was apparently greater in the winter ovaries.
As in other vertebrates (Guraya, 1973), folhcular atresia also occurs in the avian ovary. It has been classified into different types depending upon the size at which the follicles become atretic (Kern, 1972; Erpino, 1973), but the physiological significance of atretic follicles is still poorly understood. Using histological and histochemical techniques, the present study on pigeon and ring dove ovaries was undertaken to determine the nature of the relationships between the type of follicular atresia and the genesis of interstitial gland tissue. MATERIALS
AND METHODS
The ovaries of the pigeon (Columba livia) and ring dove (Streptopelia decaocro) were used for the present study. Specimens were collected at regular intervals throughout the year, ovarian material being fixed in Bouin’s fluid and processed for routine histological study. Fixing fluids and histochemical techniques used are summarized in Table 1, along with the results obtained.
OBSERVATIONS
Follicular atresia in pigeon and dove ovaries was seen throughout the year, but atresia of large follicles was seen only in those ovaries which showed extensive follicular growth. Atresia affects the primordial, or “Balbiani stage” previtellogenic and vitellogenic follicles; the latter develop during the breeding season.
Previtellogenic
@ 1976 by Academic Press, Inc. of reproduction in any form reserved.
in Atresia
During the atresia of previtellogenic and very early vitellogenic follicles, conspicuous morphological and histochemical changes occur in their components. The first signs of their atresia are erosion of the zona pellucida and distortion in the shape of the follicle (Fig. 1). Some atretic follicles appear more collapsed and rugose. The granulosa cells are separated from each other, indicating the dissolution of intercellular cohesion between them. Some granulosa cell nuclei immediately become pycnotic. The zona pellucida is broken at some places allowing the granulosa cells to
534 Copyright All rights
Follicles
535
NOTES
TABLE 1 HISTOCHEMICAL REACTIONS OF LIPIDS IN THE INTER~IITIAL GLAND CELLS’ Technique Sudan black B (SBB), 70% ethanol SBB*PE Acid haematein Nile blue Schultz reaction
Fixation
Reference
Lipids of interstitial gland cells
FCA + PC
Baker ( 1956)
+++
WB FCA FCA FCA
Baker (1946) Baker (1946) Pearse (1968) Gomori (1952)
+ to ++ p+++ ++ to +-I-+
+ PE + PC + PC + PC
a Key to abbreviations: *, after treatment with; FCA + PC, formaldehyde-calcium and postchromed in dichromate-calcium; P, pink; WB + PE, weak Bouin’s fluid followed by pyridine extraction; +, weak; ++, moderate; + ++, strong reaction; -, negative reaction.
enter the ooplasm where they form conspicuous aggregations (Fig. l), though some granulosa cells still remain at the periphery of the follicle (Fig. 1). With the advancement of atresia, the ooplasm is gradually resorbed owing to its phagocytosis by the granulosa cells which are evenly distributed in the follicle cavity (Fig. 2). The zona pellucida has completely disappeared at this stage. The theta interna cells simultaneously hypertrophy to form large cells in the wall of the degenerated follicles (Fig. 2). They constitute the thecal-type interstitial gland cells which can
be easily distinguished from the surrounding undifferentiated stromal cells due to their increased size. The thecal-type interstitial gland cells are distributed in groups or cords in the wall of late degenerated follicles (Fig. 2). After removing the ooplasmic contents, the granulosa cells degenerate leaving behind the thecal-type interstitial gland cells surrounded by undifferentiated stromal cells (Figs. 3 and 4). Corresponding to various morphological changes in the atretic previteIIogenic and early vitellogenic follicles, there also occur conspicuous histochemical changes. The
FIG. 1. Portion of large previtellogenic follicle in early atresia from the pigeon ovary, showing the broken zona pellucida (ZP) and masses of granulosa cells (GC) in the ooplasm. The thecal layer (TL) consists of undifferentiated stromal cells. x 50. Photomicrographs 1 and 2 are prepared from paraffin wax embedded material fixed in Bouin’s solution and stained with iron haematoxylin.
536
NOTES
FIG. 2. Portion of large previtellogenic follicle in late atresia from the pigeon ovary, showing the complete removal of ooplasmic contents by the granulosa cells (GC) which fill the follicle cavity and are seen to be degenerating. The thecal cells have hypertrophied to form interstitial gland cells (IGC). x 100.
ooplasmic lipid bodies consisting of cholesterol and/or its esters, triglycerides, and some phospholipids in the normal oocyte (Guraya, 1957, 1959) finally form deeply sudanophilic lipoidal masses in the central ooplasm of atretic previtellogenic and very
FIG. 3. Follicle in a late stage of atresia from the pigeon ovary, showing interstitial gland cells (IGC) loaded with sudanophilic lipids. Deeply sudanophilic ooplasmic components are being resorbed by the granulosa cells. Note the remnants of ooplasm (RO) in the centre. x 100. Photomicrographs 3 and 4 are prepared from frozen sections of ovarian material fixed in formaldehyde-calcium, postchromed in dichromate-calcium, and coloured with Sudan black B.
early vitellogenic follicles (Figs. 3 and 4). The degenerating granulosa cells also accumulate lipid droplets of a similar histochemical nature. The hypertrophied thecal-type interstitial gland cells develop more lipids and form large sudanophilic patches in the wall of degenerated follicles (Figs. 3 and 4). The histochemical reactions of their lipid droplets show that they consist mainly of cholesterol and/or its esters, triglycerides, and some phospholipids (Table 1). The degenerated granulosa cells and their lipid accumulations gradually disappear, leaving behind the thecal-type interstitial gland cells distributed either in groups or singly in the ovarian stroma (Figs. 3 and 4). The amount of thecal-type interstitial gland tissue seen in the ovary is apparently related to the number of atretic previtellogenic and early vitellogenic follicles. Large Vitellogenic Follicles in Atresia Large atretic vitellogenic follicles appear during the breeding season though they are variable in number. The yolk bodies of atretic vitellogenic follicles form irregular masses which are gradually digested and
NOTES
537
FIG. 4. Final stage of atresia in the follicle of ring dove ovary, showing the sudanophilic masses of interstitial gland tissue (KC) lying in the surrounding stroma which is sudanophobic. Note the remnants of ooplasm and granulosa cells in the centre, which are deeply sudanophilic due to their degenerative changes. x 100.
removed by granulosa cells or phagocytes. There is little or no transformation of their thecal cells into interstitial gland cells. DISCUSSION The morphological changes occurring in different components of atretic follicles in pigeon and ring dove ovaries are basically the same as those described for other bird species (Marshall and Coombs, 1957; Erpino, 1973). The degenerative changes in the ooplasm and follicular epithelium in previtellogenic and early vitellogenic follicles appear to provide some kind of stimulus to the thecal cells which simultaneously hypertrophy to form interstitial gland cells as also described for other nonmammalian vertebrates and mammals (Guraya, 1973, 1976). The formation of interstitial gland tissue from the thecal cells of atretic follicles has also been reported in rook and scrub jays (Marshall and Coombs, 1957; Erpino, 1973) but not in white-crowned sparrows (Kern, 1972). It is suggested that the ovary of the latter should be investiwith histochemical techniques gated applied to frozen sections. Interstitial gland cells are quite distinct from the thecal gland cells of Dahl (1972), which originate from
the surface epithelium of the postnatal ovary in the fowl. Thus, the avian ovary contains interstitial cells of both epithelial and stromal origin. The interstitial gland cells of stromal origin differentiate in close association with the atretic previtellogenic and early vitellogenic follicles as already stated. The most important physiological significance of follicular atresia in the ovaries of vertebrates appears to be the building up of the thecal-type interstitial gland cells which are now known to possess the ultrastructural and histochemical features of well-established steroid gland cells (Lofts and Bern, 1972; Guraya, 1973, 1976). These features indicative of steroidogenesis consist of the presence of abundant agranular endoplasmic reticulum, mitochondria with complex internal structure, steroidogenic enzymes, and cholesterol-positive lipid droplets. Thus, it can be stated that the thecal-type interstitial gland cells of pigeon and dove ovaries, which also show cholesterol-positive lipid droplets, are probably the steroid secretors. Divergent opinions have been expressed about the nature of steroid hormones formed by the ovarian interstitial gland cells in different
groups of vertebrates (Guraya, 1973, 1976). Baker, J. R. (1956). Improvements in the Sudan black technique. Quarr. J. Microsc. Sci. 97, 621-623. They may be progestins, oestrogens, and Crews, D.. and Licht, P. (1974). Inhibition of corpora androgens. Similar hormones may also be atretica of ovarian sensitivity to environmental produced by the thecal-type interstitial and hormonal stimulation in the lizard, Anolis gland tissue of the columbid ovary, which carolinensis. Endocrinology 95, 102-106. constitutes the steroidogenic tissue. The Dahl, E. (1972). Studies of the fine structure of ovarian interstitial tissue. VII. The postnatal evoluthecal gland cells originating from the surtion of the thecal gland in the domestic fowl. Z. face epithelium in the fowl ovary have also Zetlforsch. 135, 553-561. been shown to possess the ultrastructural Erpino, M. J. (1973). Histogenesis of atretic ovarian features of steroid-secreting cells (Dahl, follicles in a seasonally breeding bird. J. Morphol. 139, 239-250. 1972). This indicates that the avian ovary contains different types of interstitial cells Gomori, C. (1952). “Microscopic Histochemistry.” University of Chicago Press, Chicago. which possess the ultrastructural and his- Guraya, S. S. (1957). Histochemical studies of lipids tochemical features of steroid-secreting in oocytes. I. Lipids in the oogenesis of Columba cells (see review by Guraya, 1976). Correlalivia. Quart. J. Microsc. Sci. 98, 407-423. tive ultrastructural, biochemical, and Guraya, S. S. (1959). Histochemical studies of lipids in oocytes. IV. Lipids in the oogenesis of Callus physiological studies should be carried out domesticus. Streptopelia senegalensis and Strepto determine precisely the nature of steroid topelia decaocto. Res. Bull. Panjab Univ. 10, hormones formed by different types of 119-130. interstitial cells, and their roles in the repro- Guraya, S. S. (1973). Follicular atresia. Proc. Indian Nat. Sci. Acad. 39B, 311-332. ductive processes of female birds. The conS. S. (1976). Recent advances in the sensus of some recent biochemical and his- Guraya, morphology, histochemistry and biochemistry of tochemical findings is that androgens are steroid-synthesizing cellular sites in the nonproduced in the interstitial cells that arise mammalian vertebrate ovary. Znr. Rev. Cytol. 44, from the ovarian stroma (see Guraya, 365-409. 1976); they actually seem to correspond to Kern, M. D. (1972). Seasonal changes in the reproductive system of female white-crowned the thecal gland cells of Dahl (1972), which sparrow, Zonotrichia leucophrys gambelli. in have an epithelial origin rather than a captivity and in the field: I. The ovary. Z. stromal origin. Oestrogens are produced in Zellforsch. 126, 297-319. the interstitial gland cells derived from the Lofts, B., and Bern, H. A. (1972). The functional morphology of steroidogenic tissue. In “Steroids theta interna of atretic follicles. The variin Nonmammalian Vertebrates” (D. R. Idler, able nature and amount of steroid hored.), pp. 37-117. Academic Press, London/New mones may be related to fluctuations in difYork. ferent steroid gland cell types. Marshall. A. J.. and Coombs, J. A. (1957). The inThe atretic vitellogenic follicles finally teraction of environmental, internal and behavioural factors in the rook, Corvus frugileugs. disappear from the ovary without making a Proc.Zool.Soc.London 128, 545-589. visible contribution to the interstitial gland Pearse, A. G. (1%8). “Histochemistry. Theoretical tissue; they correspond to the corpora atand Applied,” 2nd ed. J. & A. Churchill, London. retica of Crews and Licht (1974) in the reptilian ovary. SARDUL S. GURAYA REFERENCES Baker, J. R. (1946). The histochemical recognition of lipine. Quart. 3. Microsc. Sci. 87, 441-470.
Department of Zoology College of Basic Sciences and Humanities Punjab Agricultural University, Ludhiana Punjab, India Accepted July 29, 1976