Ultrastructural ontogeny of the labial gland apparatus in termite Prorhinotermes simplex (Isoptera, Rhinotermitidae).

The labial glands in Prorhinotermes simplex consist of secretory cells organized into acini, water sacs and the ducts connecting the gland parts to the basis of the labium. Acini are composed of central and parietal cells. Central cells type I contain predominantly lucent vacuoles and are involved probably in hydroquinone production. They are lacking in soldiers. Type II central cells produce vacuoles of proteinaceous content which are of the same electron density (type IIa) or present in more shades (type IIb). Type IIa cells are present in all older individuals, whereas type IIb are lacking in soldiers and neotenics. Type III cells represent a specific stage of type I cells development, but they are definite functional secretory cells in soldiers. Acini of first instar larvae contain undifferentiated cells which differentiate into type I cells during the second instar. Specific larval central cells start to change into type II cells during first instar. The central cells of presoldiers show a transition from the pseudergate into the soldier situation. The parietal cells keep a uniform structure throughout the whole ontogeny. Only one type of cells form the water sacs in all castes. The cells are very flat with scarce organelles. The water sac cells produce lipid-like secretion, small lucent vacuoles and bunches of angulated vacuoles. The water sac probably functions as water storage organ only. Ontogenetical changes in water sac development are small. The acinar ducts originate inside the acinus where they are formed by flat cells with rare organelles. At the acinus border, cells equipped with mitochondria, microvilli and basal invaginations appear. The water sac ducts are formed by flat cells with rare organelles. Acinar ducts outside the acinus and water sac ducts are equipped with taenidiuam.

Ultrastructure of epidermal glands in neotenic reproductives of the termite Prorhinotermes simplex (Isoptera: Rhinotermitidae).

The ultrastructure of epidermal glands in neotenic reproductives of Prorhinotermes simplex is described and their development is compared among young and old neotenics of both sexes. Secretory cells forming the epidermal gland are attached to the cuticle all over the body. The glands are formed by class 1 and class 3 secretory cells and corresponding canal cells with secretory function. Class 1 cells are sandglass-like and class 3 secretory units are located among them. Class 1 cells contain predominantly tubular endoplasmic reticulum, the major part represents the smooth and the minor the rough form. Numerous electron dense granules occur in the cytoplasm, they are always disintegrated prior to be released. Class 3 secretory cells contain a large amount of vacuoles, which are always lucent in males while newly produced vacuoles are dense in females. Dense vacuoles are frequently transformed into lucent ones before being released. Canal cells are locally equipped with microvilli. The conducting canal is surrounded by an electron dense secretion of regular inner structure. The cytoplasm of the canal cell contains numerous mitochondria, rough endoplasmic reticulum and a large proportion of microtubules. The young neotenic reproductives differ from the old ones by a lower amount of secretory products. Epidermal glands probably produce substances inhibiting the occurrence of superfluous reproductives.

Dinocampus (=Perilitus) coccinellae teratocyte-specific polypeptide: its accumulative property, localization and characterization.

Dinocampus (=Perilitus) coccinellae (Braconidae: Hymenoptera) teratocytes synthesize a teratocyte-specific polypeptide (TSP) with a high molecular weight of 540kDa. The TSP has a tendency to accumulate in the teratocyte cells without release after synthesis ([Okuda and Kadono-Okuda, 1995]), which was confirmed in this study. Pulse-chase fluorography indicated that teratocytes at a younger stage (6 days after parasitization)secreted negligible TSP into the medium after synthesis, while teratocytes at an older stage (11 days after parasitization)secreted the synthesized products into the medium, although the amount released was still low. Western blot with anti-TSP serum showed that only a small amount of TSP appeared in the parasitized host hemolymph, even when TSP synthesis by teratocytes was actively taking place, which also supported the accumulative nature of TSP. The immunoelectronmicroscopic studies revealed that the TSP was localized specifically in high electron-dense vacuoles. Lectin blot analysis identified TSP as a high mannose glycoprotein. The amino acid composition of the major subunit of the TSP was quite similar to that of nutritive proteins such as vitellogenin and storage proteins of some insects. These characterization data, together with the accumulation property of the TSP indicates that Dinocampus teratocyte primarily plays a nutritive role for the developing parasitoid larvae. TSP exhibited esterase activity, which indicates that TSP may have an additional function in the host-parasitoid reaction.

Circadian rhythm of sperm release in the gypsy moth, Lymantria dispar: ultrastructural study of transepithelial penetration of sperm bundles.

Release of mature bundles of spermatozoa from the testis into the vas deferens is a critical but poorly understood step in male insect reproduction. In moths, the release of sperm bundles is controlled by a circadian clock which imposes a temporal gate on the daily exit of bundles through the terminal epithelium-a layer of specialized epithelial cells separating testis follicles from the vas deferens. The sequence of cellular events associated with the daily cycle of sperm release was investigated by scanning and transmission electron microscopy. In the hours preceding sperm release, there is a solid barrier between the testis and the vas deferens formed by the interdigitation of cytoplasmic processes of adjacent terminal epithelial cells. At the beginning of the sperm release cycle, sperm bundles protrude through this barrier while the terminal epithelial cells change their shape and position relative to the bundles. Subsequently, the cyst cells enveloping the sperm bundles break down and spermatozoa move out of the testis through the exit channels formed between the epithelial cells. Afterwards, cyst cell remnants and other cellular debris are released into the vas deferens lumen, and the epithelial barrier is reconstructed due to phagocytic activity of its cells. These data provide a foundation on which to build an understanding of the cellular mechanisms of clock-controlled sperm release in insects.

Iron-ascorbate cleavable malic enzyme from hydrogenosomes of Trichomonas vaginalis: purification and characterization.

Two isoforms of NAD(P)(+)-dependent malic enzyme (EC 1.1.1.39) were isolated from hydrogenosomes of Trichomonas vaginalis. A positively charged isoform at pH 7 was obtained in a single purification step using cation-exchange chromatography. The second isoform, negatively charged at pH 7.5, was partially purified using a combination of anion-exchange and affinity chromatography. Both isoforms displayed similar physical and kinetic properties. Molecular weight determination of the native enzyme suggested a homotetrameric arrangement of the 60 kDa subunits. The enzyme utilized NAD+ (Km, 6-6.3 microM) preferentially to NADP+ (Km, 125-145 microM). The NAD(+)-dependent activity showed a broad pH optimum with maximum under alkaline conditions (pH 9) likely to be present inside hydrogenosomes. Immunocytochemical studies using a polyclonal rabbit antibody raised against purified T. vaginalis malic enzyme proved hydrogenosomal localization of the enzyme. Subfractionation of hydrogenosomes suggested an association of the malic enzyme with the hydrogenosomal membranes. The 60 kDa malic enzyme subunit was highly sensitive to non-enzymatic cleavage by an iron-ascorbate system resulting in two enzymatically inactive fragments of about 31 kDa. Microsequencing of the fragments revealed that the 60 kDa subunit was cleaved at the metal-binding site between Asp279-Ile280. The enzyme inactivation was inhibited by an excess of manganese. Iron-dependent posttranslational modification might contribute to the regulation of malic enzyme activity in vivo.

Amino acid sequence of Sp23, a structural protein of the spermatophore of the mealworm beetle, Tenebrio molitor.

In this paper we present the amino acid sequence of Sp23, a structural protein of the spermatophore of the mealworm beetle (Tenebrio molitor). This is the first report of the primary structure of a spermatophorin. The protein is rich in proline (24%), relatively rich in tyrosine (9%) and glutamine (10%), and does not contain sulfur-containing amino acids. In the carboxyl-terminal half of the protein a peptide motif is repeated which is similar to a repetitive motif in a group of dipteran chorion proteins.