Sardul S. Guraya

Recent advances in the morphology, cytochemistry, and function of Balbiani's vitelline body in animal oocytes.

Publisher Summary This chapter discusses the recent advances in the morphology, cytochemistry, and function of Balbianis vitelline body in animal oocytes. The correlation of recent cytological, histochemical, and electron-microscope data has revealed that the Balbianis vitelline body in oocytes of different animal species represents the aggregation of different organelles and inclusions of diverse morphology and nature. Therefore, it shows extreme variability in development, organization, and composition among different animal species. The nature of the factors causing these variations has not been determined, but genetic, physiological, and environmental factors perhaps influence its formation and differentiation. Depending upon the animal species or group, the Balbianis vitelline body shows many combinations of various organelles and inclusions such as a yolk nucleus, mitochondria, Golgi bodies, annulate lamellae, multivesicular bodies, and lipid inclusions, which aggregate to a variable degree in the juxtanuclear cytoplasm.

Recent Progress in the Structure, Origin, Composition, and Function of Cortical Granules in Animal Egg

Publisher Summary This chapter discusses the recent progress in the structure, origin, composition, and function of cortical granules in animal egg. Cytochemical and morphological studies have shown the presence of cortical granules or alveoli in the oocytes of many animals but not in all. Where the cortical granules are present, they show a great diversity in their size, number, and ultrastructure. They may even vary in size and structure in different regions of the egg in the same species. The cortical granules are the secretory organelles that contain electron-dense material surrounded by a membrane. Their contents show either a homogeneous or a heterogeneous appearance because of the presence of different components. The results of various cytochemical and autoradiographic studies have revealed that the material of cortical granules consists of carbohydrates and proteins; some enzymes have also been reported in the cortical granules. The presence of granules or alveoli near the egg surface, which as a result of fertilization either are expelled to participate in the formation of a membranous structure or simply explode and release some substance constituting a gelatinous coat around the egg, is a widespread occurrence.

Recent Advances in the Morphology, Histochemistry, and Biochemistry of Steroid-Synthesizing Cellular Sites in the Nonmammalian Vertebrate Ovary

Publisher Summary This chapter discusses the recent advances in the morphology, histochemistry, and biochemistry of steroid-synthesizing cellular sites in the nonmammalian vertebrate ovary. In recent years, the steroidal secretions of the nonmammalian vertebrate ovary have also been identified by the use of modern steroid methodology. But correlations of steroidogenic activity with individual cell types or with cellular morphology have been little studied in the ovaries of different classes of vertebrates. However, correlation of histochemical, biochemical, and electron microscope studies on the mammalian ovary has revealed that the sites of steroidogenesis are the theca interna cells of the Graafian follicles, the luteal cells of the corpus luteum, and ovarian interstitial gland cells of thecal origin, which have been shown to possess similar cytological, histochemical, and biochemical features. Their most striking common features are (1) abundant diffuse lipids (lipoproteins) in the cytoplasm, which apparently derive from the abundant ultrastructural agranular endoplasmic reticulum, (2) well-developed cell organelles, especially the pleomorphic mitochondria, which have a complex system of internal cristae that are predominantly tubular, (3) the development of diffuse lipoproteins (or agranular endoplasmic reticulum), closely accompanied by the appearance of enzyme activities indicative of the biosynthesis of steroid hormones, (4) under certain physiological situations, stored lipid droplets in the cytoplasm, which consist of either phospholipids or phospholipids, triglycerides, and cholesterol and/or its esters, and (5) the capacity to form a variety of steroids in biochemical experiments in vitro . In this chapter, the morphological (including ultrastructural) and histochemical features of steroid-secreting gland cells in the ovary of the nonmammalian vertebrate are also compared and contrasted with those of various steroid-gland-cell species of the mammalian ovary.

Cellular and molecular biology of capacitation and acrosome reaction in spermatozoa.

A comparative account is given of advances in cellular and molecular biology of capacitation and acrosome reaction in spermatozoa by comparing and contrasting their biochemical and physiological changes in response to various factors in vivo and in vitro. It can now be stated that phenomena of sperm capacitation and acrosome reaction are endogenous molecular events occurring at the membrane level which can be modulated by external environmental factors. The molecular mechanisms and the signal transduction pathways mediating the process of capacitation and acrosome reaction are only partially defined and appear to involve modification of intracellular Ca2+ and other ions, lipid transfer, and phospholipid remodeling in the sperm plasma membrane as well as changes in protein phosphorylation. Evidences for the involvement of cAMP-dependent kinase pathway in the acrosome reaction are discussed. The mediation of one or more external signals by the sperm plasma membrane appears to activate this pathway after or simultaneously with the influx of Ca2+. Concurrent with or following entry of Ca2+, adenylate cyclase is activated, leading to increased concentrations of cAMP-activation of cAMP-dependent kinase and protein phosphorylation; the identity of such proteins and their role in the acrosome reaction must be determined. The roles of biological effectors of the acrosome reaction, such as ZP3 and follicular fluid are still to be defined at the molecular level. The gaps in our knowledge about the cellular and molecular aspects of capacitation and acrosome reaction are emphasized.

Cellular and Molecular Biology of Capacitation and Acrosome Reaction in Mammalian Spermatozoa

Publisher Summary This chapter reviews the information available on different aspects of capacitation and acrosome reaction (AR) and proposes a tentative but unified view of the mechanisms involved in these phenomena. The capacitation is achieved in the female reproductive tract; it is also accomplished outside the female reproductive tract in numerous in vitro studies using well-defined media in several mammalian species. There is reasonable consensus that capacitation involves no morphological change in spermatozoa that can be discerned, even under the electron microscope; it does facilitate the occurrence of a distant morphological event in spermatozoa known as AR. AR involves point fusions between the outer acrosomal membrane and overlying plasmalemma leading to the release of acrosomal contents or enzymes required at the site of fertilization. The capacitation involves two important changes at the molecular level in spermatozoa: (1) sperm surface alteration and/or intramembranal molecular mobility to facilitate Ca 2+ influx and (2) changes in sperm energetics through alterations in oxygen uptake and glucose utilization manifested in the form of changes in pattern of flagellar beat.

Recent advances in the morphology, histochemistry, and biochemistry of steroid-synthesizing cellular sites in the testes of nonmammalian vertebrates.

Publisher Summary This chapter discusses the recent advances in the morphology, histochemistry, and biochemistry of steroid-synthesizing cellular sites in the testes of nonmammalian vertebrates. The general basic functions of the vertebrate testis are twofold: the production of spermatozoa and the secretion and release of hormones. The most striking common features of steroid producing cells of mammalian gonads are: (1) abundant diffusely distributed lipoproteins in the cytoplasm; (2) abundant membranes of smooth reticulum; (3) mitochondria with predominantly tubular cristae; (4) development of diffuse lipoprotein, accompanied by enzyme activity indicative of the biosynthesis of steroid hormones; (5)under certain physiological conditions, stored cholesterol-positive lipid droplets; and (6) capacity to form a variety of steroids in biochemical experiments in vitro. The correlation of recent electron microscope and histochemical studies on the steroid-synthesizing cellular sites in the ovaries of different groups of nonmammalian vertebrates revealed that they also possess the cytological, histochemical, and biochemical features specific to steroid gland cells of mammalian gonads.

Recent advances in the morphology, histochemistry, biochemistry, and physiology of interstitial gland cells of mammalian ovary.

Publisher Summary This chapter discusses the recent advances in the morphology, histochemistry, biochemistry, and physiology of interstitial-gland cells of mammalian ovary. Although the comparable interstitial-gland cells of the mammalian ovary has been the subject of many investigations during the last several years, they are least understood in terms of steroidogenesis. Divergent opinions about their identity, origin, and function continue to be expressed by anatomists, reproductive physiologists, and pathologists. The correlation of recent electron microscope, and histochemical and biochemical data has revealed the presence of interstitial-gland cells in developing, maturing, and adult ovaries of mammals. Their presence has also been shown in the postmenopausal ovaries of women. However, the amount and distribution of interstitial cells vary greatly from species to species, as well as with the ovarian cycle. These variations may be due to endocrine, nervous, or genetic factors. The ovarian interstitial-gland cells commonly occurring in the mammalian ovary have been placed in two broad categories, namely, primary and secondary interstitial gland cells, depending upon their origin and the sequence of their development.

Morphology of ovarian changes during the reproductive cycle of the fish, Mystus tengara (Ham.)

A study has been made of the morphological and histological changes of the cat fish (Mystus tengara) ovary during its reproductive cycle in natural and confined waters. This fish is oviparous and breeds once a year during the rainy season (July throught September). Factors responsible for bringing about spawning in fishes are discussed and the onset of spawning in Mystus is attributed to monsoon rains. In the ovarian cycle 7 phases have been recognised, whic are based on the gross morphological changes in the ovary, the percentage and duration of different developmental stages of oocytes, the average diameter and the gonosmatic index. They are: 1) immature virgin (November-February); 2) preparatory virgin (March-April); 3) maturing virgin (April-May); 4) pre-spawning virgin (June); 5) spawning (July-August); 6) depletion (September), and 7) recoupment (October-November). Oocyte growth has been divided into 9 stages. The ova diameter and gonosomatic index are maximum in July and minimum in November and December.

Morphology, Histochemistry, and Biochemistry of Human Oogenesis and Ovulation

Publisher Summary This chapter discusses the development, structure, chemistry, and physiology of ovarian oocytes in human and subhuman primates. The results of ultrastructural, histochemical, and biochemical investigations are summarized in the chapter. Based on these results, it can be stated that primordial oocytes undergo the process of differentiation during the prenatal and postnatal periods, when ooplasmic organelles of diverse nature gradually accumulate in the cytoplasm. The results also suggest that the ribonucleoproteins demonstrated histochemically in the ooplasm and its organelles are derived from lampbrush chromosomes, as the differentiation and development of these organelles closely corresponds to the appearance of lampbrush chromosomes. The integrated results of various techniques as discussed in the chapter show that the primordial oocytes of human and subhuman primates are metabolically active. From the correlation of available ultrastructural, histochemical, and biochemical data on the process of ovulation, it has become increasingly clear that the rupture of a follicle is the end result of a series of definitive changes, which are brought about by lysosomal hydrolases within the follicular wall, in response to the action of the luteinizing hormone. Further studies are needed to work out the details of origin and the nature of these enzymes, and the control mechanisms in relation to their activity in bringing about the disintegration of stromal tissue.

Recent advances in the morphology, histochemistry, and biochemistry of the developing mammalian ovary.

Publisher Summary This chapter discusses the recent advances in the morphology, histochemistry, and biochemistry of the developing mammalian ovary. The developing mammalian ovary undergoes complex developmental changes during the prenatal and postnatal periods before it becomes structurally and functionally mature. The nature of these changes could not be determined more precisely in earlier studies because of the limitations of the techniques used. The chapter describes the summary and integration the results obtained with diverse techniques to obtain deeper insights into the normal development, differentiation, structure, interrelationships, chemistry, and physiology of various components of the developing mammalian ovary during the prenatal and postnatal periods. In this chapter the morphological (including ultra structural), histochemical, and biochemical features of steroid-secreting gland cells in the developing ovary of mammals are also compared and contrasted with those of various steroid gland cells in the mature gonads of mammals and non-mammalian vertebrates.