Rescue of atretic follicles in vitro and in vivo

The purpose of this work was to determine if atretic follicles could be rescued and could return to the ovulatory pathway of development. Rats were given continuous infusions of 3H-thymidine (3H-thymidine (3H-TdR) resulting in uniform labeling of healthy antral follicles versus patchy labeling of atretic antral follicles. The infusion was then stopped and rats were subjected to experimental treatments known to stimulate follicular recruitment. Immature rats were given injections of pregnant mare's serum gonadotropin (PMSG) to provoke super-ovulation. Adult rats were hemicastrated to provoke compensatory follicular development in the remaining ovary. In addition, granulosa cells from individual follicles of adult rats were cultured in vitro. The differential labeling patterns, observed at the end of the treatment period, were used to determine, a posteriori, the condition of follicles as they had been at the start of the treatment period. Sparsely labeled cell cultures were found, indicating that some cells from atretic follicles were able to become established in tissue culture. However, there was no evidence that atretic follicles had revived in vivo. All follicles recruited for ovulation by PMSG or hemicastration were heavily and uniformly labeled. All poorly labeled follicles were clearly continuing their process of degeneration. These observations suggest that, despite continued viability of some granulosa cells in atretic follicles, once a follicle begins to degenerate in vivo, it will probably not return to the ovulatory pathway.     

The post-ovulatory follicles of blackbirds (Agelaius)

Post-ovulatory follicles of tricolored blackbirds (Agelaius tricolor) and redwinged blackbirds (A. phoeniceus) regress from 6.0 to 3.0 mm in length by two days after ovulation and remain less than 3.0 mm during incubation. The follicles of females feeding young average less than 1.0 mm. Serial sections of ovaries of birds in all stages of the nesting cycle show distinct post-ovulatory follicles up to 25 days after ovulation. Lymphocytes, granular polymorphonuclear leucocytes, macrophages, and fibroblasts invade the sloughed granulosa and the hemorrhaged theca interna after ovulation. Granulosa cells, epithelioid cells in the theca interna, and connective tissue cells in the theca externa are lipoidal and cholesterol-positive for at least ten days after ovulation. The rapid regression and histological evidence of degenerating tissue and the invasion of cell types characteristic of the inflammatory response suggest that the ovulated follicles are degenerating rather than secretory organs.     

Regeneration of atretic sheep ovarian follicles in vitro.

Large (4--6 mm diam.) and small (2--3 mm) atretic follicles were removed from sheep ovaries during the luteal phase of the cycle and maintained in organ culture without hormonal supplementation for up to 5 days. The structure, cell dynamics and steroid-producing capacity of the follicles were compared with those of non-atretic follicles of similar size. The granulosa layer of the atretic follicles invariably regenerated in culture, increasing in thickness more than 2- and 4-fold in large and small follicles respectively. This could not be accounted for by cell division which remained low throughout the culture period. In contrast, non-atretic follicles showed high mitotic activity during the first 24 h in culture: this was not associated with an increase in granulosa thickness in large follicles although there was a 4-fold increase in small ones. An increase in internuclear spacing, a measure of cell size plus intercellular space, partly accounted for the increase in granulosa thickness in atretic follicles. Even when granulosa cells remained in close apposition there was an almost total absence of gap junctions, a prominent feature in the granulosa of non-atretic follicles both in vivo and in vitro. Pyknotic nuclei and atretic bodies rapidly disappeared from the regenerating granulosa layer. The theca interna was restored in culture to a state ultrastructurally closely resembling that of non-atretic follicles in vivo. Total steroid secretion (oestradiol-17beta, testosterone plus progesterone) into the culture medium (pmol.mg tissue-1.24 h-1) was the same for atretic and non-atretic follicles of comparable size. There was, however, a marked difference in the type of steroid produced, largely related to a loss of aromatizing capacity in atretic follicles. The predominant steroid secreted by large non-atretic follicles was oestrogen, with slightly smaller amounts of testosterone, whereas the principal steroid secreted by large atretic follicles was progesterone. In small non-atretic and atretic follicles, the predominant steroid was testosterone, but the non-atretic follicles also secreted appreciable amounts of oestrogen. Addition of FSH to the culture medium did not restore aromatizing capacity to the atretic follicles.     

Eye lens ageing in the dogfish (Mustelus canis).

1. Age-related alterations in the distribution of water-soluble, high molecular weight (colloidal), and water-insoluble proteins of the lens of smooth dogfish (Mustelus canis) were measured. 2. The ages of these animals ranged approx from 2 to 50 yr, during which time the lenses grew from 100 to 1500 mg (wet wt). The lenses contained approx 50% water. 3. Water-insoluble protein accumulated to a level greater than 50% of the total proteins by the time the animals reached maturity. The lenses of other animals, such as mammals and humans, would be opaque if they had a similar insoluble protein content. 4. Each protein fraction contained the same protein chains (mol. et 1900-25,000 daltons), as observed by SDS polyacrylamide gel electrophoresis, except the water-insoluble fraction, which seemed to contain several extra protein chains with higher molecular weights, which represent fiber cell membrane components. 5. Further purification of these fiber cell membranes indicated that their protein chain makeup was mainly from the same low molecular weight chains present in the soluble and high molecular weight colloidal proteins.     

Histogenesis of atretic ovarian follicles in a seasonally breeding bird

Histologic examination of ovaries from a non-migratory population of scrub jays (Aphelocoma coerulescens) disclosed a marked annual cycle in the incidence of atresia. Atretic follicles became more common as the nesting season progressed and were most abundant immediately after the cessation of breeding. Atresia involved a dissociation of granulosa cells and movement of these cells into the follicle. Subsequently, granulosa cells showed steatogenesis and ultimately disappeared simultaneously with the invasion of the follicle by ex-thecal gland cells. The data suggest that the diverse histology of avian atretic follicles reflects different stages in the process of atresia rather than multiple origins. Ovarian stromal glands apparently arise both from ex-thecal gland cells of atretic follicles and stromal connective tissue. A possible secretory role of atretic follicles is considered.     

In-vivo and in-vitro steroidogenic activity of post-ovulatory ovarian follicles of the rabbit

Pseudopregnancy was induced in rabbits by injection of 50 i.u. hCG into the lateral ear vein. Blood was collected on Days 0, 1, 2 and 6 after hCG from the lateral ear vein and, in some studies, from the ovarian vein as well. Ovaries were collected on Days 0, 1, 2 or 6 after hCG injection, and follicles (greater than 0.8 mm diam.) were obtained by microdissection. Concentrations of oestradiol-17 beta, testosterone and progesterone in blood and follicular homogenates were measured by RIA. Follicular steroidogenesis was increased significantly on Day 6 after ovulation, at the time when the corpus luteum transforms into an oestrogen-dependent tissue. The ability of developing post-ovulatory follicles to secrete steroids in vitro in response to a gonadotrophic stimulus also increased over this same time interval. Follicular oestradiol production on Days 1 and 2 of pseudopregnancy may synergize with the post-ovulatory secretion of FSH to promote further follicular growth in the pseudopregnant rabbit.     

Histological and histochemical studies on the subfornical organ of the squirrel monkey

Summary Detailed studies have been made on the distribution of several enzymes in the subfornical organ (SFO) of the squirrel monkey. In this species, the nerve cells of the SFO show reactions of varying intensity for enzymes of the glycolytic and aerobic pathways. The nerve cells, glial cells and ependymal cells of the SFO and the choroid plexus are equipped with enzymes of the Embden-Meyerhof (EM) pathway, pentose cycle and tricarboxylic acid (TCA) cycle. Many nerve cells and oligodendroglia in the body of this organ are rich in enzymes of the TCA cycle and the pentose cycle and thus presumably have the capacity of producing adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide phosphate (NADPH₂) [reduced triphosphopyridine nucleotide (TPNH)]. In the neurons, ATP is probably used as energy for synaptic transmission, active transport, secretion and various other metabolic processes, whereas NADPH₂ is used for synthetic processes such as the production of fatty acids and some amino acid conversion (e.g., conversion of phenylalanine into tyrosine). The SFO and its stalks contain both cholinergic and adrenergic neurons and fibers. The outermost layer of the perivascular sheath gives a positive reaction for enzymes of the gylcolytic pathways (EM pathway, pentose cycle and TCA cycle), whereas the inner layer of this sheath shows negligible activity for these enzymes. On the other hand, the whole sheath (inner and outer layers) exhibits strong staining for Mg⁺⁺-activated adenosine triphosphatase (ATPase), and moderate staining for Ca⁺⁺-activated ATPase. This sheath, rich in ATPase, may carry on active transport and such related functions. Since the outermost layer contains various enzymes of the glycolytic pathways, it is possible that the ATP required for these functions is produced in this layer.Visiting scientist from the Department of Anatomy, Tokyo Medical and Dental University, Tokyo, JapanT. R. Shanthaveerappa in previous publications.     

中国大鲵闭锁卵泡的显微和超微结构观察

用光镜和电镜观察了中国大鲵卵泡闭锁过程和闭锁小体的显微和超微结构。结果显示 ,大鲵闭锁小体是卵泡细胞侵噬卵母细胞并增殖形成细胞团 ,膜细胞未参与。在大部分卵泡处于缓慢生长期时 ,未发现卵泡闭锁现象 ;在 5、 6月份 ,卵巢内大部分卵母细胞进入卵黄形成前期 ,部分卵泡闭锁 ,但闭锁小体细胞的类固醇激素分泌结构特征不明显 ;在 7、 8月份 ,大多数卵母细胞处于卵黄形成期 ,闭锁小体细胞具有管泡状嵴线粒体、丰富的滑面内质网和脂滴、发达的高尔基体等。这些细胞学特征表明闭锁小体可分泌类固醇激素 ,以调节正常卵子的成熟。在大鲵中观察到的闭锁小体属于排卵前黄体     

Morphologic analysis of atretic follicles in the Chinese soft-shelled turtle,Pelodiscus sinensis

The Chinese soft-shelled turtle (Pelodiscus sinensis) and its eggs have been utilized as both a source of nutrition and medicine for thousands of years. In the present study, follicular atresia was investigated by morphological analysis as an important factor affecting clutch size. Results showed that follicular atresia can be divided into four stages: (1) development of follicular cell disorder; (2) massive cellular proliferation in the ooplasm with elimination of yolk granules; (3) large amounts of erythrocytes appearing in the ooplasm; (4) gradual degeneration of atretic follicles. For the first time, we have shown follicular atresia to be a dynamic process in P. sinensis and found that yolk granules are eliminated by both liquefaction as well as non-liquefaction processes. The present study may provide detailed morphologic analysis for further research into egg quality and clutch size in P. sinensis.     

Regression in the ovary of Myxine glutinosa L. (Cyclostomata) II. Electron microscope studies of atretic follicles

In the atretic follicle of the open involutionary type an opening in the wall of the follicle is formed through which granulosa cells and yolk platelets are emitted. Migrating cells of the theca layer invade the follicular lumen and absorb phagocytotically residues of granulosa cells. On the other hand, atretic follicles of the closed involutionary type show yolk platelets which remain in the follicular lumen and are dissolved there. The granulated residue of the yolk platelets and the residue of the granulosa cells are absorbed phagocytotically by migrating cells. The follicular atresia of both degenerating types can be regarded as a process exclusively devoted to the purpose of resorbing atretic oocytes. No indications for the production of steroid hormones were found.