Diuresis in the cabbage white butterfly, Pieris brassicae: Water and ion regulation and the rôle of the hindgut

The significance of diuresis in the water and ion balance of newly emerged Pieris was examined by comparing the composition of haemolymph and urine during diuresis. The high potassium content of the urine results in a marked increase in the Na/K ratio of the haemolymph. The haemolymph osmolarity is well regulated, in spite of the very hypo-osmotic urine. By means of an isolated preparation of the ileum, it was shown that rapid resorption of potassium ions by this part of the hindgut is responsible for the low osmolarity of the urine.     

Beetle diuretic peptides: the response of mealworm (Tenebrio molitor) Malpighian tubules to synthetic peptides, and cross-reactivity studies with a dung beetle (Onthophagus gazella)

This paper reports the effects of different diuretic factors on the Malpighian tubules of beetles. Calcitonin (CT)-like peptides from silkmoth and mosquito increase fluid secretion in a dose-dependent manner in the tubules of Tenebrio molitor, but the cockroach CT-like peptide, Dippu-DH(31), has no effect. Thapsigargin induces a small but significant increase in tubule secretion rates. The interactions between different factors in mealworm tubules were explored by testing CT-like peptides, thapsigargin and the mealworm CRF-related diuretic factor Tenmo-DH(37) in various combinations, but no synergistic effects were observed. C-terminal fragments of the CRF-related diuretic peptides Locmi-DH(46) and Dippu-DH(46) fail to increase fluid secretion in mealworm tubules, unlike their corresponding whole peptides. Cross-reactivity of factors between beetle species was investigated using the scarabaeid Onthophagus gazella. Tenmo-DH(37) increases fluid secretion in isolated tubules of O. gazella in a dose-dependent manner, revealing a high degree of cross-reactivity in this distantly related beetle species. However, homogenates of O. gazella brains inhibited fluid secretion in mealworm tubules.     

Immunocytochemical localization of a diuretic hormone of the beetle Tenebrio molitor,Tenmo-DH(37), in nervous system and midgut

Although the mealworm Tenebrio molitor inhabits very dry environments, it has at least two diuretic peptides, which increase fluid secretion by the free portions of the Malpighian tubules. Unlike other insect corticotropin-releasing factor (CRF)-related peptides isolated to date, these are non-amidated peptides. The immunocytochemical localization of Tenmo-DH(37) was investigated using antisera raised against this hormone. Immunoreactive neurosecretory cells were found in the brain and abdominal ganglia with immunoreactive processes projecting to the peripheral nervous system. Intense staining of the neurohaemal release site, the corpora cardiaca, was observed. In addition, neurosecretory cells immunoreactive to Tenmo-DH(37) were found in the posterior midgut and a network of immunoreactive nerve processes extended over the surface of the midgut. Tenmo-DH(37) is widely distributed and its staining pattern resembles that found for other, amidated CRF-related diuretic peptides.     

Estimating glycoprotein carbohydrate chain structures by lectin reactivities in polyacrylamide gels

Complex mixtures of cellular glycoproteins contain a myriad of different carbohydrate chains that cannot be easily analyzed without rigorous purification of each individual glycoprotein. We have analyzed the carbohydrate chains in complex mixtures of cellular glycoproteins by separation using sodium dodecyl-sulfate polyacrylamide gel electrophoresis and interacting the gels with several 125I-labeled lectins. By use of in situ chemical modifications of the glycoproteins after their electrophoretic separation together with the known carbohydrate-binding specifities of several lectins, it has been possible to estimate glycoprotein carbohydrate chain structures. As an example we have examined the cellular glycoproteins of a ovary-colonizing metastatic variant of B16 melanoma and report the types of carbohydrate chains that are found on various melanoma glycoproteins.