Neuroendocrine control of vitellogenesis in the dragonfly, Orthetrum chrysis (Selys) (Odonata: Libellulidae).

1. Histological correlative studies on the cerebral neurosecretory cells, the corpora allata and the oocyte development strongly suggest the involvement of cerebral NSM mostly produced by the A cells of pars intercerebralis and the CA hormone in the vitellogenesis. 2. Biochemical studies reveal the incorporation of haemolymph proteins and lipids in the yolk during vitellogenesis. 3. Exogenous administration of the extract of the brain-CC and FME demonstrates, to some extent, the stimulation of protein synthesis during vitellogenesis in the haemolymph by the cerebral NSM and the CA hormone, while the lipid metabolism lies, mostly, under the control of juvenile hormone.

Neurosecretory system of the ventral ganglia in the dragonfly, Orthetrum chrysis (Selys) (Odonata: Libellulidae).

The neurosecretory cells of the ventral ganglia in the adult dragonfly, Orthetrum chrysis, are classified into A, B, C1 and C2 cells. The neurosecretory material in the ventral ganglia is composed of PAS-positive material with 1-, 2-glycol groups and some proteins. The proteins rich in cystine or cysteine occur predominantly in the A cells, moderately in C cells and negligibly in B cells. Proteins containing arginine occur in A and B cells only, and those containing basic amino acids occur in C2 cells. The neurosecretory pathways and the neurohemal organs are also described.

The histological and histochemical studies on the ovary in relation to vitellogenesis in the dragonfly, Orthetrum chrysis Selys (Libellulidae: Odonata).

The ovaries consist of large number of panoistic ovarioles in the last instar nymph and the adult dragonfly Orthetrum chrysis (Selys). In the nymph the vitellaria are compactly filled with the primary oocytes and the vitellogenesis takes place only in the adult stage. During vitellogenesis oocytes change widely in their shape, size and cytological organisation and their developmental stages can be divided into pre-vitellogenic, early-vitellogenic, vitellogenic, late-vitellogenic and maturation age. PAS-positive material appears first around the germinal vesicle in the early-vitellogenic stage and lateron it migrates towards the periphery. Glycogen appears in the late-vitellogenic stage. DNA is abundantly present in the nuclei of the oocytes during the pre-vitellogenic and completely absent in early-vitellogenic, vitellogenic, late-vitellogenic and maturation stages. It is observed in the nuclei of follicular epithelial cells of all the stages. RNA is abundantly present in cytoplasm of the pre-vitellogenic oocytes but lateron is gradually decreases. During the early-vitellogenic and vitellogenic stages high concentration of RNA in the follicular epithelial cells has been observed. The protein bodies appear first in the interfollicular spaces and towards the periphery of the oocytes just near the enveloping follicular epithelial cells, during the early-vitellogenic stage suggesting the formation of yolk proteins from the haemolymph. In Orthetrum chrysis the sudanophilic bodies appear first in the follicular cells and then lie in the peripheral region of the oocytes suggesting the incorporation of yolk lipid either from the follicular epithelium or from the haemolymph through the follicular epithelium. The phospholipids are synthesised in pre-vitellogenic to the late-vitellogenic stages. In the late-vitellogenic stages the phospholipid granules are present abundantly in the follicular epithelium while in the maturation stage they disappear suggesting their utilisation in the formation of membranes like vitelline and chorion. The neutral fats are present in the form of large number of droplets in the oocytes during the maturation stage.

Correlative changes in the neurosecretory cells, corpus cardiacum and corpus allatum during egg maturation in the buffalo-fly, Lyperosia exigua (De Meijere) (Diptera: Muscidae).

The neurosecretory cells of pars intercerebralis, the corpus cardiacum and the corpus allatum are examined in histological sections of Lyperosia exigua females, fixed at daily interval during first cycle of egg maturation. The median neurosecretory A cells exhibit secretory activity by undergoing cyclical changes of synthesis and release with the advancing age and egg maturation. Similarly, a single corpus allatum also undergoes cyclical changes in volume and histological appearance in accordance with the yolk deposition in the developing oocyte.

Cephalic neuroendocrine system of the buffalo-fly, Lyperosia exigua (De Meijere) (Diptera: Muscidae).

In the adult buffalo-fly, L. exigua three groups of neurosecretory cells are present in each half of the brain; medial and lateral groups in the protocerebrum and ventral group in the tritocerebral region. The cerebral neurosecretory cells are classified as A and B cells. Both the cells are present in the medial, lateral and ventral groups. Histochemically, the neurosecretory material of these cells is composed of neutral mucopolysaccharides and proteins. The A cells are rich in cystine or cysteine amino acids, whereas B cells either lack them or may contain in negligible quantity but are rich in basic amino acids. A single pair or nerves, nervi corporis cardiaci, emerges out of the brain and merges with the recurrent nerve which later on enters the corpus cardiacum and terminates into the hypocerebral ganglion. The corpus cardiacum primarily functions as storage organ for cerebral neurosecretory material and secondarily may also produce its own hormone. The corpus allatum is composed of a single type of cells and some times it appears as syncytial structure. Cerebral neurosecretory material is never found in the corpus allatum.

Changes in the neuroendocrine system during post-embryonic development in the buffalo-fly, Lyperosia exigua (De Meijere) (Diptera: Muscidae).

The neurosecretory cells of the pars intercerebralis and ring gland are examined in histological sections of larva, pupa and adult of buffalo-fly, Lyperosia exigua fixed at various intervals during the rpost-embryonic development. Three paired medial groups of the neurosecretory cells are observed in the larval brain. These groups show their displacement during the larval-pupal-adult moult. The medial neurosecretory A cells exhibit secretory activity by undergoing cyclic changes of synthesis and release during post-embryonic development. The ecdysial glands and a single corpus allatum also undergo cyclical changes in volume and histological appearance in accordance with the larval-pupal-adult moult.

The cephalic neuroendocrine system in the beetle, Mylabris pustulata (thunb) (Meloidae: Coleoptera).

The cephalic neuroendocrine system in Mylabris pustulata includes neurosecretory cells in the brain, a pair of corpora cardiaca and corpora allata. There are three groups of the neurosecretory cells in each hemisphere of the brain-medial and lateral in the protocerebrum and central in tritocerebrum. They are classified into three types viz., A, B and C on the basis of staining affinities they exhibit. The axons of the medial, lateral and ventral neurosecretory cells constitute independently the medial, lateral and ventral neurosecretory pathways respectively inside the brain. The medial neurosecretory pathways emerge out of the brain as nervi corporis cardiaci I while the lateral and ventral neurosecretory pathways form collectively the other nerve, nervi corporis cardiaci II and innervate the CC. The CC contain two types of cells viz., the chromophilic, which are AF-positive and the chromophobic cells, which take the counterstain. The corpora allata are compact bodies and contain cells of one type but fluctuations in the nuclear size and the gland are occur frequently.