Effects of Pymetrozine on biochemical parameters and the midgut ultrastructure of Anthonomus grandis Boheman (Coleoptera: Curculionidae)

Pymetrozine represents a class of compounds for the control of sucking insects. However, chewing insects have also shown sensitivity to this compound. Therefore, although pymetrozine has been demonstrated to have a direct action on sucking insects, it could also affect species like the boll worm Anthonomus grandis by promoting histological changes in the intestine and alterations in biochemical parameters such as glycogen, lipids, and glucose. The pymetrozine promoted histological changes are characterized by protrusions and detachments of columnar cells toward the intestinal lumen, presence of vacuolated regenerative cells, and removal of the epithelial lamina in some areas of the muscle layer. The ultrastructure of the midgut in the control group exhibited the basal labyrinth near the mid region of the cell, rough endoplasmic reticulum, Golgi complex, glycogen granules, mitochondria, electron-lucent vesicles, nucleus with well-defined nucleoli, and elongated microvillus. Pymetrozine promoted disarrangement in the basal labyrinth and generated numerous vacuoles and large protrusions between the epithelial lamina and muscular layer. No significant difference was observed in glucose content at 48 h after treatment; however, a significant increase was observed at 144 h after treatment. The glycogen content was reduced in the first 48 h of exposure to pmetrozine and reached the average content of the control insects at 144 h. Significant effects were observed in lipid contents, both in the first 48 h and at 144 h after treatment. Thus, we conclude that pymetrozine compromises the digestive physiology in these insects, affects reproduction, and consequently, it can be a potential alternative to reduce this pest species.

The Effect of Prolactin on the Number of Membrane-Associated Particles in Kidney Cells of the Euryhaline Teleost Gasterosteus Aculeatus during Transfer from Seawater to Freshwater: A Freeze-Etch Study

The membranes of kidney cells of 3-spined sticklebacks were examined in freeze-etch replicas. The numbers of particles adhering to surfaces and fracture faces of the outer cell membranes and the membranes of the basal labyrinth were determined. The latter membranes probably are the main location of ion-transporting enzyme complexes. The total number of particles per cell in freshwater fish exceeds that of seawater fish by about 50 % for the outer cell membrane, and by almost 200 % for the membranes of the basal labyrinth. After transfer of seawater fish to freshwater, particle numbers increase and their densities approximate freshwater values after 20 h. This rise in particle numbers coincides with the increase of ion-transporting activity of the cells known to take place after transfer to freshwater. The rate of increase of particle densities is enhanced after injection of ovine prolactin. This hormone is known to stimulate Na+/K+-ATPase activity of the basal labyrinth of teleost kidney cells. The results indicate that the particles represent enzyme complexes. The number of particles is probably under hormonal control. The increase in particle densities after transfer to freshwater is accompanied by a rise in the number of nuclear pores, which is noticeable by 10 h. No changes were observed in the density of the particles adhering to the fracture faces of gap junctions.

The Membranes of the Basal Labyrinth in Kidney Cells of the Stickleback, Gasterosteus Aculeatus, Studied in Ultrathin Sections and Freeze-Etch Replicas

The structure of the basal labyrinth in kidney cells of freshwater sticklebacks was studied in ultrathin sections (after fixation with permanganate, osmium tetroxide, and combinations of glutaraldehyde with osmium tetroxide) and in freeze-etch replicas (after pretreatment with glutaraldehyde and/or glycerol, or without pretreatment). The structure of the basal labyrinth in sticklebacks, and probably in other teleost species, differs essentially from the type of labyrinth found in kidney cells of mammals like the rat. In the latter animals, the space enclosed by the membranes of the labyrinth is intercellular. In the stickleback the labyrinth consists of an intracellular system of branched membranes lining narrow saccular spaces. These spaces communicate with the exterior of the cells by means of small pores, located in the lateral and basal parts of the outer cell membranes. All chemical fixation procedures used introduced specific structural artifacts. It is concluded that the structure of the basal labyrinth is relatively well preserved after fixation with potassium permanganate, with a mixture of glutaraldehyde and osmium tetroxide, or with osmium tetroxide when applied for 10 min only. The unit-membrane structure was, however, absent after all procedures involving osmium tetroxide. In freeze-etch replicas determinations were made of the numbers of small particles covering the surfaces and fracture faces of the membranes of the basal labyrinth and of the outer cell membranes. The numbers per unit area of surface proved to be markedly constant and specific for each of the four faces of both types of membranes. Specific differences were found between the particle densities of the outer cell membranes and the membranes of the basal labyrinth. This finding points to functional differences between these types of membranes. Particle densities were not influenced by pre-incubation with glycerol. After fixation with glutaraldehyde, the particles adhering to the outer and inner surfaces had decreased in number. It is concluded from this study that membrane structure, as revealed in thin sections as well as in freeze-etch replicas, is consistent with Singer's ‘fluid lipid-crystal protein’ model.

THE BASE OF THE PROXIMAL CONVOLUTED TUBULE CELLS OF RAT KIDNEY

The three dimensional arrangement of the compartments on the base of proximal convoluted tubule cells of rat kidney is described. An extracellular basal labyrinth is found to be enclosed by these compartments. The compartments with their mitochondria and the basal labyrinth are regarded as forming a functional unit. It is supposed that this basal unit serves for excretion of reabsorbed fluid from the cell into the labyrinth and for the development of hydrostatic pressure in the labyrinth to overcome the capillary pressure and to pass the reabsorbed fluid into the blood stream.