The fine structure of the lutein cells in the mink (Mustela vison) with special reference to the secretory activity during pregnancy

Summary The ultrastructure of the lutein cells in the mink throughout pregnancy and the regression periodpost partum is described. To correlate the fine structure with the changes in the peripheral plasma progesterone levels, the concentrations of progesterone were measured by a rapid competitive protein-binding assay.Even during the delay period (e.g. as long the plasma progesterone levels remain at the basal level, <8ng/ml), the lutein cells in the mink exhibit structural criteria of functional activity. However, the increase in progesterone secretion is accompanied by some morphological transformations, characterized by the presence of more and more small dense homogenous bodies in the cytoplasm, which become irregular and scalloped during the stage with maximum release of progesterone. At this stage the agranular endoplasmic reticulum is often cisternal or vesicular.During the decline of the progesterone levels, typical and moderate electron-dense lipid droplets are found increasingly more within the lutein cells. The expanded agranular ER is now more sparse, while the granular ER becomes more pronounced, often forming parallel arrays. During this phase the mitochondria become elongated, dumb-bell, or cup shaped. After parturition the corpora lutea consist of cells in various stages of degeneration. At day 14post partum only a few lutein cells are still identifiable.Evidently the observed morphological changes take place in the lutein cells during the life span of corpora lutea. This feature lends further support to the concept that the mink lutein cells are steroid-producing cells and furthermore, that the corpora lutea may be the main sites of gestagen production during pregnancy.     

The ultrastructure of the corpus luteum of the guinea-pig

Summary An electron-microscopic investigation, based on the suggestion that differences seen in progesterone levels under differing hormonal conditions might be reflected in the ultrastructural organisation of the lutein cells of the guinea-pig was undertaken. Comparisons were made between corpora lutea taken from animals during the normal oestrous cycle, pregnancy and lactation, and after hysterectomy or hypophysectomy.The lutein cells from the oestrous cycle corpus luteum appeared to be of two types, light and dark. The former were more numerous. The main difference between them lay in the arrangement of the endoplasmic reticulum. Lutein cells from corpora lutea (with the exception of the old degenerating corpora lutea) all contained well-developed agranular endoplasmic reticulum, little granular endoplasmic reticulum, several electron-dense lipid granules, lysosomal bodies which ranged from small spherical bodies to large autophagic vesicles and mitochondria. The mitochondria were numerous, and in the corpus luteum of pregnancy, they were closely associated with the parallel arrays of granular endoplasmic reticulum.With minor exceptions, the lutein cells of the guinea-pig present a strikingly uniform picture despite their hormonal condition.The manner in which this uniformity of ultrastructure may be related to observed differences in progesterone levels in the corpus luteum of the guinea-pig is discussed.Meat and Livestock Commission (MLC) Scholar.The authors wish to thank Dr. J. S. Perry for doing the surgery involved in this work and for the specimens of corpora lutea of hysterectomy. They are also grateful to him for his helpful discussions and interest throughout.     

Structural characteristics of the corpus luteum during implantation in the rhesus monkey (Macaca mulatta)

Corpora lutea were obtained from ten pregnant rhesus monkeys during implantation, and the ultrastructure of granulosa and theca lutein cells was characterized. Specimens were individually staged with regard to the extent of implantation and the relationship to the rise in circulating progesterone and estrogen which is characteristic of early pregnancy. Structural changes characteristic of granulosa lutein cells occurring during implantation included: change in form of endoplasmic reticulum from predominantly agranular tubules to predominantly granular cisternae; reduction in size and number of lipid droplets; increase in area occupied by the Golgi and increase in length of the cisternae of the Golgi complex; development of numerous microvillus-lined intracellular spaces; increase in numbers of membrane-bound dense bodies including peroxisomelike bodies, multivesicular bodies within lobopodia, and other lysosomelike bodies; and alterations of mitochondrial cristae. These changes were suggestive of the production of a secretory protein, rapid utilization of existing steroid precursor reserves for the production of progesterone, and a reduction in capability for steroid precursor accumulation and processing by granulosa lutein cells. Structural changes characteristic of theca lutein cells occurring during implantation included an increase in size and number of lipid droplets, an increase in agranular endoplasmic reticulum, and an increase in area occupied by the Golgi complex. These changes were suggestive of an increased capability for steroid precursor accumulation and processing, perhaps for estrogen production, by the theca lutein cells.     

OBSERVATIONS ON THE FINE STRUCTURE OF LUTEIN CELLS

Corpora lutea from the period of delayed implantation and from early postimplantation stages of the armadillo, mink, and rat were fixed in buffered osmium tetroxide-sucrose or potassium permanganate. After rapid dehydration, the portions of the corpora lutea were embedded in either methacrylate or epoxy resin. Examination of the lutein cells by electron microscopy revealed the presence, in the better preserved material, of an extensive development of tubular agranular endoplasmic reticulum. Although the membranes of the endoplasmic reticulum are the most striking feature of the lutein cells of both stages of the three animals examined, very numerous large mitochondria with cristae that exhibit a variety of forms tending toward villiform, and protrusions and foldings of the lutein cell margins on the pericapillary space are also characteristic of these cells. Certain minor differences in the lutein cells of the species examined are also noted. No indications of conversion of mitochondria into lipid, of accumulation of lipid in the Golgi area, or of the protrusion of lutein cells into spaces between the endothelial cells, as suggested by other authors, were noted in these preparations. Some of the difficulties inherent in the visualization of the secretory activity of cells producing steroid hormones are briefly discussed.     

Fine structure of the corpus Luteum of the raccoon during pregnancy

Summary Ultrastructure of the granulosa lutein cells of the raccoon from throughout pregnancy has been described. The lutein cells often from epithelial cords which are separated by the connective tissues, capillaries and lymphatics. Based on the arrangements and modifications of the cytoplasmic organelles and inclusions, three types of lutein cells have been recognized. The type I lutein cells predominantly contain tubular, agranular endoplasmic reticulum, juxtanuclear Golgi complexes, a few round to rod-shaped mitochondria, some free ribosomes, and occasional lipid droplets. Occasionally the tubular cristae of mitochondria and tubular smooth endoplasmic reticulum appear contiguous. The type II cells contain abundant lace-like and/or stacked fenestrated endoplasmic reticulum cisternae that frequently form membranous whorls, some tubular, agranular endoplasmic reticulum, mitochondria, and lipid droplets. Mitochondria are usually small, but unusual large ones also occur. The small, rod-to round-shaped mitochondria usually have tubular cristae; but the large, oval, elongate, and cup shaped mitochondria possess tubular, lamellar, plate like, and whorl-like cristae. The plasma membranes of the cells are complexly elaborated and folded, especially when apposing each other. In favorable sections, strands of fenestrated cisternae appose the folds of the plasma membranes. In general, the amount of cytoplasmic organelles and inclusions vary greatly in the cells. The type III cells predominantly contain lipid droplets and sparse cytoplasmic organelles. The type I and II cells are found throughout pregnancy, but the type III cells are observed from mid gestation to term. The cytological features of type I and II cells suggest that they probably secrete most of the steroids, whereas the type III cells primarily store lipids.This research was supported by UPSHS grant AM-11376 and NIH contract 69-2136.     

Partial development of the steroidogenic ultrastructural features in degenerative corpora lutea after a single injection of pituitary extract in the Western painted turtle (Chrysemys picta)

Pituitary glands were removed from sexually mature female turtles (Chrysemys picta) and they were injected intraperitoneally (i.p.) into other mature females of the same species (experimental). In addition mature females of the same species received saline injection only (controls). Initially all the turtles used in this study were steroidogenically inactive with corpora lutea already undergoing luteolysis (degeneration) as these turtles had ovioposited their eggs approximately 2 weeks earlier. Forty-eight hour post injection the corpora lutea were removed from the control and experimental turtles. In the experimental turtles, the lutein granulosa cells developed ultrastructural features such as tubular and cisternal smooth endoplasmic reticulum (SER) and mitochondria with tubular cristae associated with lipid droplets. However, the controls maintained degenerative corpora lutea without steroidogenic ultrastructural features. The circulating progesterone (Pro) levels in the experimental turtles were significantly higher than the controls (P<0.049). Although the 48h development of steroidogenic ultrastructural features in the lutein granulosa cells was only partial in development, the effect of the pituitary taken from the inactive donor triggered an activating process within a short period, clear evidence of gonadotropic effect on the inactive corpora lutea. The present data offer interesting information on the short-term effect of gonadotropins during the non-reproductive period. This information may have useful implication under natural conditions particularly during the onset of a new reproductive cycle where the ovary is still inactive.     

Ultrastructural changes in granulosa lutein cells and progesterone levels during preimplantation,implantation, and early placentation in the western spotted skunk

Summary The ultrastructure of corpora lutea obtained during the preimplantation, implantation and early postimplantation periods has been studied in 20 western spotted skunks. Fine structure of granulosa lutein cells was correlated with progesterone levels. The corpus luteum of the prolonged (7 month) preimplantation period contained undifferentiated small granulosa cells and differentiated large granulosa lutein cells. The former ranged in size between 12 and 20 and the latter between 20 and 45 . The ratio of small and large cells was about equal in an animal 2 days prior to nidation whereas only few small cells and numerous large cells were observed in an animal estimated to be 8 to 12 hours from nidation. Occasionally small cells were observed amidst large ones during the 24 hour nidation period, i.e. adhesion of trophoblast with the luminal uterine epithelium, but small cells were absent in animals after this period. Small cells had some smooth and rough endoplasmic reticulum, rod-shaped mitochondria with platelike cristae, small Golgi complex, and relatively smooth plasma membranes. Large lutein cells had abundant smooth endoplasmic reticulum, membranous whorls of smooth endoplasmic reticulum, usually round mitochondria with tubular and lamellar cristae, a well developed Golgi complex, variable amounts of lipid droplets, and highly plicated and ruffled plasma membranes. Peripheral plasma progesterone levels during the prolonged preimplantation period ranged between 1.1 and 7.9 ng/ml, but during implantation it was between 8 and 16.6 ng/ml. It is suggested that plasma progesterone levels fluctuate during the time of implantation and should not be regarded as a basis to predict actual nidation in the western spotted skunk.This research was supported in part by Grant Number HD06556 from the National Institute of Child Health and Human Development.     

OVARIAN STEROID CELLS : II. The Lutein Cell

The lutein cells of the rabbit exhibit fine structural variations during their life-span of 28 to 30 days. A systematic examination of the corpus luteum reveals that cellular distinctions may be recognized during the first, second, and third stages of pregnancy. The agranular endoplasmic reticulum reveals vesicular, tubular, and cisternal profiles after fixation with each of the following fixatives: glutaraldehyde, osmium tetroxide, and permanganate. The osmolality of the fixing solutions was varied with sucrose and recorded with an osmometer in order to determine the effect of osmotic concentration on the intracellular membranous profiles. It was determined that vesicles and short, branched tubules of similar structure are present in the agranular reticulum when the osmolalities are 300 to 800 milliosmols (iso-osmotic considered 300 milliosmols). At 900 milliosmols, the vesicular or tubular lumen is obliterated. Intracellular membrane profiles do not exhibit interconversions due to hyperosmotic fixative solutions. The agranular endoplasmic reticulum is randomly distributed as short tubular profiles during the first third of pregnancy. A continuity between these membranes and irregular, electron-opaque lipid masses is evident. When physiological and histochemical data indicate that the lutein cell may be storing sterol precursors, cytological observations show that the agranular endoplasmic reticulum exists in a more organized pattern within the cytoplasmic matrix. Vesicular and short tubular, circular aggregations as well as whorled cisternal patterns surround the larger, less electron-opaque lipid droplets. Surface views of cisternal agranular endoplasmic reticulum exhibit tubular extensions, accentuating the continuity between these two profiles. During the progress of pregnancy, the lutein cell increases in diameter, and accumulates both lipid inclusions and aggregations of intracellular membranes. The agranular endoplasmic reticulum may be peripherally packed and arranged parallel to the cell surface during later stages. In the postpartum, degenerating lutein cell, large myelin figures are present which form from the agranular endoplasmic reticulum. These cellular events are discussed in relation to lutein cell activity, including both secretion of product and storage of precursors.     

Feinstruktur der Luteinzellen des Meerschweincheneierstocks während der Schwangerschaft und des Zyklus

Zusammenfassung Die Feinstructur der Luteinzellen des Meerschweinchens während Schwangerschaft (15., 35., 45., 50., 55., 63. und 2 Tage nach der Geburt) und Zyklus (9, 14, 16, 20 Tage nach der Ovulation) wurden elektronenmikroskopisch untersucht. In den aktiven Luteinzellen kann man konzentrisch um die Lipoidtropfen angeordnete Strukturen des agranulären endoplasmatischen Retikulum beobachten, die später durch Membranstrukturen des granulären endoplasmatischen Retikulum ersetzt werden. Die Mitochondrien sind rund und enthalten tubuläre Innenstrukturen, die Lipoidtropfen sind elektronenoptisch dicht. Während der Rückbildung des Corpus luteum setzt sich das endoplasmatische Retikulum aus ungeordneten Vesikeln und Tubuli zusammen, die Mitochondrien sind länglich oder verzweigt, die Lipoidtropfen elektronenoptisch hell. Die Bedeutung dieser feinstrukturellen Veränderungen in der Luteinzelle wird diskutiert.

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The ultrastructure of lutein cells in the guinea pig corpus luteum during pregnancy and oestrous cycle

Summary The fine structure of the lutein cells in guinea pigs corpora lutea of pregnancy (15th, 35th, 45th, 50th, 55th, 63th day and 2 days after birth) and during oestrous cycle (9, 14, 16, 20 days after ovulation) is described. During the active phase of the corpus luteum the formation of concentric whorls of agranular endoplasmic reticulum around lipid droplets is observed, but later the granular endoplasmic reticulum increases. In this stadium the mitochondria are round with tubulous cristae and the lipid droplets are increased in density. During the involution of the corpus luteum the endoplasmic reticulum does not form concentric whorls, the mitochondria are elongated, polymorphic, the lipid droplets have lower electron density. These ultrastructural changes in the lutein cells are discussed concerning the role of the cell organelles in the steroid synthesis.

Diese Arbeit wurde mit Unterstützung durch die Alexander von Humboldt Stiftung durchgeführt.     

Fate of the granulosa cells in the hen's follicle

Summary In an early growing follicle the single row of granulosa cells are in apposition — they have abundant Golgi substance and granular endoplasmic reticulum. During growth the granulosa cells become separated by wide intercellular spaces filled with perivitelline substance. The granulosa cells of the mature follicle immediately preceding ovulation have an agranular reticulum and numerous lipid droplets. Granulosa cells can be identified up to 72 h after ovulation. During the 72 h the cytoplasm becomes progressively replaced by lipid. The initial change in intracellular structure may indicate a shift in function towards production of progesterone followed by fatty degeneration preceding their final disintegration.     

Hormone-induced differentiation of agranular endoplasmic reticulum in the interstitial cells of the mouse testis

Summary The administration of chorionic gonadotrophin to prepuberal mice results in precocious maturation of the testicular interstitial cells. The cytoplasm of the nine-day-old cells is characterized by abundant lipid droplets, large numbers of glycogen particles and mitochondria. By contrast, the membranous organelles are poorly developed.Human chorionic gonadotrophin brings about mobilization of lipid droplets and glycogen particles, and differentiation of large areas of agranular endoplasmic reticulum.The present observations are in agreement with the reports that human chorionic gonadotrophin increases the secretion of testosterone and that the agranular endoplasmic reticulum is the site of storage of steroid and of the enzymes involved in the biosynthesis of androgens.     

On the ultrastructure of granulosa lutein cells in porcine corpus luteum

Summary In young corpora lutea the endoplasmic reticulum membranes are sparse. A marked increase of smooth membranes then follows up to the peak of dioestrus. Continuities between smooth and rough endoplasmic reticulum are obvious during the same period. These observations suggest that the agranular membranes develop from the granular ones.During the most intense development of the endoplasmic reticulum the membranes show a tendency to be arranged in whorls. Since these are numerous only during the period of high progesterone secretion, a multitude of whorls constitutes a useful morphologic sign of high functional activity in the porcine granulosa lutein cells.During the first half of the oestrous cycle the increase in endoplasmic reticulum in general also parallels the increase in progesterone secretion. However, this secretion as well as ⁵-3-hydroxysteroid dehydrogenase activity declines earlier and more rapidly than the endoplasmic reticulum regresses. Steroid hormone synthesis may therefore be lacking although the agranular membranes appear morphologically normal.The mechanisms of induction of the endoplasmic reticulum membranes and enzymes active in steroid synthesis are discussed and it is suggested that luteinizing hormone (LH) may act as a trigger by increasing transport across membranes.Read at the Meeting of the Swedish Society for Pathology in Umeå, September 25, 1965 (Bjersing, 1966).This investigation was supported by grants from the Swedish Medical Research Council (Projects No. 13 X-78-01, 12 X-78-02, and 12 X-78-03).     

Effects of luteinizing hormone on luteal cell populations in hypophysectomized ewes

To examine the effect of purified LH on development and function of luteal cells, 27 ewes were assigned to: (1) hypophysectomy plus 2 micrograms ovine LH given i.v. at 4-h intervals from Days 5 to 12 of the oestrous cycle (oestrus = Day 0; Group H + LH; N = 7); (2) hypophysectomy with no LH replacement (Group N-LH; N = 6); (3) control (no hypophysectomy) plus LH replacement as in Group H + LH (Group S + LH; N = 7); (4) control with no LH treatment (Group S-LH; N = 7). Blood samples were collected at 4-h intervals throughout the experiment to monitor circulating concentrations of LH, cortisol and progesterone. On Day 12 of the oestrous cycle corpora lutea were collected and luteal progesterone concentrations, unoccupied receptors for LH and number and sizes of steroidogenic and non-steroidogenic luteal cell types were determined. Corpora lutea from ewes in Group H-LH were significantly smaller (P less than 0.05), had lower concentrations of progesterone, fewer LH receptors, fewer small luteal cells and fewer non-steroidogenic cells than did corpora lutea from ewes in Group S-LH. The number of large luteal cells was unaffected by hypophysectomy, but the sizes of large luteal cells, small luteal cells and fibroblasts were reduced. LH replacement in hypophysectomized ewes maintained luteal weight and the numbers of small steroidogenic and non-steroidogenic luteal cells at levels intermediate between those observed in ewes in Groups L-LH and S-LH. In Group H + LH ewes, luteal and serum concentrations of progesterone, numbers of luteal receptors for LH, and the sizes of all types of luteal cells were maintained. Numbers of small steroidogenic and non-steroidogenic cells were also increased by LH in hypophysectomized ewes. In Exp. II, 14 ewes were assigned to: (1) sham hypophysectomy with no LH replacement therapy (Group S-LH; N = 5); (2) sham hypophysectomy with 40 micrograms ovine LH given i.v. at 4-h intervals from Day 5 to Day 12 of the oestrous cycle (Group S + LH; N = 5); and (3) hypophysectomy plus LH replacement therapy (Group H + LH; N = 4). Experimental procedures were similar to those described for Exp. I. Treatment of hypophysectomized ewes with a larger dose of LH maintained luteal weight, serum and luteal progesterone concentrations and the numbers of steroidogenic and non-steroidogenic luteal cells at control levels.(ABSTRACT TRUNCATED AT 400 WORDS)     

SOME OBSERVATIONS ON THE FINE STRUCTURE OF THE LUTEIN CELLS OF X-IRRADIATED RAT OVARY

The ovaries of 10- to 13-week-old rats were exteriorized and irradiated with sterilizing doses of X-rays. Following treatment, the animals entered a phase of constant vaginal cornification. Animals were killed 8 to 12 wk after the onset of this phase, and their ovaries were prepared for electron microscopy. Tissue was fixed in glutaraldehyde, postfixed in osmium tetroxide (Millonig's, phosphate-buffered), and embedded in Epon. Lutein cells from these ovaries were compared with those from sham-irradiated controls. The cytoplasm of lutein cells from experimental animals was characterized by an increase in the amount of agranular endoplasmic reticulum and by an increase in the number of mitochondria. These mitochondria are more variable in external form and often possess increased numbers of villiform cristae. Other features noted were a decrease in the amount of cytoplasmic lipid granules and an increase in cell size and surface irregularity. The significance of the morphological findings is discussed in relation to ovarian hormone production in animals sterilized by X-irradiation.     

Effects of hypophysectomy on plastocyst survival, progesterone secretion and nidation in the spotted skunk.

12 female skunks were hypophysectomized during the 7-month preimplantation period. Sham operations were performed on 7 skunks by drilling through the basisphenoid but without exposing the pituitary. 22 skunks remained as controls. Complete hypophysectomy significantly reduced peripheral plasma progesterone levels within 40 days while there was a tendency for values to increase in sham hypophysectomized skunks. The only obvious effect hypophysectomy had on ovarian histology during the preimplantation period was the abolition of all antral follicles; corpora lutea remained unchanged for up to 90 days. Blastocysts from hypophysectomized skunks were undergoing a slow attrition of cells after Day 34, and there was some indication that hypophysectomy may have a deleterious effect as early as Day 22. Hypophysectomy significantly prolonged the preimplantation period in 6 out of 7 skunks. It was concluded that the pituitary is essential for initiation of nidation.     

Ultrastructural analysis of the granulosa — Luteal cell transition in the ovary of the dog

The transition from ovarian granulosa to lutein cell during the estrus cycle of 60 pregnant and non-pregnant beagle bitches was analyzed by light and electron microscopy (both 100 and 1000 KV). Early proestrus was characterized by a gradual rise in serum estrogen levels, hyperplasia of the granulosa cells, the accumulation of follicular fluid, and the development of tortuous intercellular channels. During the second half of proestrus, serum estrogen levels continued to rise, but growth, division, and differentiation of the granulosa cells was minimal. Estrus was marked by the first acceptance of the male and a well-defined LH peak In the subsequent 24 hour period, the granulosa-lutein cells hypertrophy rapidly and develop a large Golgi apparatus, small profiles of granular endoplasmic reticulum, numerous microfilaments, and large gap junctions between the cells. Mitochondria also proliferate, enlarge, and elongate, but retain lamelliform cristae. Luteinization of the cells and progesterone secretion begin just after ovulation which in turn occurs about 24 hours after the LH peak. On the third and fourth day of estrus, numerous small vesicles of agranular endoplasmic reticulum fill the extoplasm and the mitochondria swell up and round off. The vesicles rapidly fuse into whorled and flattened cisternae or anastomosing tubules of agranular endoplasmic reticulum, while the mitochondria develop tubulovesicular cristae. These structures gradually become organized with respect to the basal lamina. The Golgi apparatus is centered over the pole of the nucleus that faces the pericapillary space. Stacked and whorled cisternae of agranular ER develop in the lateral margins and avascular end of the cell while mitochondria and tubular elements of agranular ER predominate in the central medial and most basal portions of the cytoplasm. Microfilaments are ubiquitous and appear to be instrumental in this orientation process. The cell surface develops three distinct regional specializations that coincide with the underlying cellular compartments: interconnecting pleomorphic folds fill the pericapillary space; long tenous microvilli project from the lateral cell surface and form tortuous intercellular channels and canaliculi; and large gap junctions form along the margins of the cell furthest removed from the basal lamina. By the sixth day of estrus, the granulosa-luteal cell transition is nearly complete and serum progesterone levels are on the rise.     

Fine structure of the gular gland of the free-tailed bat Tadarida brasiliensis

The gular gland of the bat Tadarida brasiliensis is a specialized sebaceous gland located in the skin of the suprasternal region of adult males. It consists of an aggregation of simple branched tubulo-acinar gland units, the number of which varies seasonally. Each acinus is composed of densely packed sebaceous cells at various stages of differentiation. Acinar basal cells and cells of the epithelium of the ducts can differentiate into sebaceous cells. Two main changes appear in the cytoplasm concurrent with the sebaceous transformation: the differentiation of cytoplasmic organelles and the deposition of lipid material. The appearance of a different type of mitochondrion and the development of large numbers of ribosomes and polyribosomes can be recognized in the cytoplasm at an early stage of differentiation. Concomitant with the deposition of significant numbers of lipid droplets, the cells develop abundant agranular endoplasmic reticulum occurring mainly as scattered tubular cisternae. These at times form whorls surrounding lipid droplets. At later stages, the cisternae of the agranular endoplasmic reticulum often occur in crystalline arrays between secretory oil droplets. The roles of the different cytoplasmic organelles, especially in relation to the production of sebum, are discussed.     

Pituitary control of ovarian activity in the lizard, Agama agama

The principal ovarian structures in Agama agama are non-yolky and yolky follicles, corpora lutea and atretic follicles. Hypophysectomy affects all stages of vitellogenesis and follicular atresia results. Atresia involves resorption and digestion of yolk by the granulosa cells, which eventually undergo a fatty degeneration. Immature follicles and corpora lutea are not affected by hypophysectomy.
Injections of 0.2 mg FSH (NIH-FSH-S3 ovine) on alternate days for 14 days not only maintain vitellogenesis in hypophysectomized animals, but also tend to overstimulate the small follicles to synthesize yolk. A similar dose of LH(NIH-LH-SII ovine) fails to maintain vitellogenesis in hypophysectomized animals, while a higher dose of 0.4 mg LH tends to overstimulate the small follicles. An unusual rupture of yolky follicles in FSH injected lizards is reported and a possible development of such follicles into corpora lutea is discussed.     

THE FINE STRUCTURE OF TESTICULAR INTERSTITIAL CELLS IN GUINEA PIGS

In guinea pig testes perfused with either glutaraldehyde or osmium tetroxide fixative, the cytoplasm of the interstitial cells contains an exceptionally abundant agranular endoplasmic reticulum. The reticulum in central regions of the cell is a network of interconnected tubules, but in extensive peripheral areas the reticulum is commonly organized into closely packed, flattened cisternae which are fenestrated. Occasional small patches of the granular reticulum occur in the cytoplasm and connect freely with the agranular reticulum. The mitochondria have a dense matrix and contain cristae and some tubules. The Golgi complex is disperse and shows no evidence of secretory material. The cytoplasm also contains lipid droplets. Lipofuscin pigment granules are probably polymorphic residual bodies and contain three components: (1) a dense material which at high magnification shows a 75-A periodicity; (2) a medium-sized lipid droplet; and (3) a cap-like structure. In glutaraldehyde-perfused testis the interstitial cell cytoplasm appears to have the same density from cell to cell, and the agranular reticulum is tubular or cisternal but not in the form of empty vesicles. Thus the "dark" and "light" cells and the vesicular agranular reticulum sometimes encountered in other fixations may be artifacts. Biochemical results from other laboratories, correlated with the present findings, indicate that the membranes of the agranular endoplasmic reticulum in guinea pig interstitial cells are the site of at least two enzymes of androgen biosynthesis, the 17-hydroxylase and the 17-desmolase.     

Structural changes in the granulosa lutein cells of pregnant cows between 60 and 245 days.

The structural changes in the granulosa lutein cells in the pregnant cows between 60 and 245 days, were observed. The polyhedral or pump cells has an acidophilic cytoplasm around the spherical nucleus. The glycogen granules increased in number up to 230 days of pregnancy. The lipid globules increased in size and amount during advanced pregnancy. The mitochondria showed a wide range of variations in shape and size. The matrix of many mitochondria contained dense inclusions which replaced the entire matrix in late pregnancy. The endoplasmic reticulum was chiefly of smooth type but a few stacks of the rough variety could be seen in the early days of pregnancy. Sometimes, whorls of smooth-surfaced endoplasmic reticulum enclosing mitochondria were seen. The Golgi complex was fully developed in the granulosa cells of all cases studied. The dense granules and lipid globules increased in size and number in the older corpora lutea. The cell surface showed numerous infolding of the plasma membrane.