ABSTRACT
Incubation of the insect gland with [3H]inositol results in the incorporation of label into both phosphatidylinositol (PI) and the two polyphosphoinositides (PIP and PIP2). Upon stimulation with 5-HT the initial water-soluble metabolites released are inositol trisphosphate and inositol bisphosphate with no change in the level of inositol monophosphate, suggesting that the primary lipid substrate used by the receptor is one of the polyphosphoinositides (most likely PIP2) rather than PI. This conclusion was substantiated by showing that 5-HT was not able to release inositol or inositol monophosphate when the levels of the two polyphosphoinositides were reduced by lowering the level of ATP. The rate of breakdown of the polyphosphoinositides, as measured by the appearance of inositol phosphates, occurred with no apparent lag whereas the onset of the calcium-dependent change in transepithelial potential had a latency of approximately 1 sec. It is concluded that the primary action of 5-HT is to stimulate the hydrolysis of PIP2 into diacylglycerol and inositol trisphosphate. The latter may function as a second messenger to mobilize the calcium responsible for initiating some of the ionic events responsible for fluid secretion.
Subject(s)
Diptera/drug effects , Phosphatidylinositols/metabolism , Serotonin/pharmacology , Adenosine Triphosphate/metabolism , Animals , Diptera/metabolism , Female , Membrane Potentials/drug effects , Phosphatidylinositol Phosphates , Receptors, Serotonin/metabolism , Salivary Glands/drug effects , Salivary Glands/metabolismABSTRACT
The objective of this investigation was to examine whether fluorescent age pigment (FAP) was associated with the physiological rather than the chronological age of houseflies (Musca domestica) and to determine if the level of physical activity of individual flies was related to their FAP content. Distinction between the physiological age and the chronological age of the flies was made on the basis of flightlessness which occurs prior to death in all houseflies. Flies with shorter life expectancy become flightless earlier. Walking and flying activity of individual flies was measured by radar-Doppler instrumentation developed in this laboratory. The concentration of FAP, determined by fluorimetry, increased with age but the rate of increase was greater in flightless flies than in their flying cohorts of the same age. FAP content of individual flies tended to be greater in flies exhibiting relatively high levels of physical activity. The results of this study suggest that FAP concentration is associated with life expectancy and physical activity of houseflies.
Subject(s)
Aging , Houseflies/physiology , Melanins , Pigments, Biological/physiology , Animals , Fluorescence , Male , MovementSubject(s)
Houseflies/physiology , Motor Activity , Animals , Crowding , Energy Metabolism , Flight, Animal , Locomotion , Longevity , MaleSubject(s)
Life Expectancy , Motor Activity , Social Environment , Temperature , Animals , Female , Houseflies , MaleABSTRACT
An apparatus is described by means of which the power versus frequency spectrum of the photomultiplier current can be obtained for laser light scattered by streaming cytoplasm in the algal cell Chara corallina. A Doppler peak is noted in the spectrum which is abolished when cytoplasmic streaming is arrested by electrical stimulation. For 5 cells of Chara, this simple laser-Doppler velocimeter gave streaming velocities (46-7 mum s-1, S.D. +/- 4-8 at 20 degrees C) similar to those obtained for the same cells using the light microscope (44-3 mum s-1, S.D. +/- 5-3 at 20 degrees C). A narrow distribution of streaming velocities is indicated. The technique described provides a rapid, quantitative assay of the in vivo rheological properties of cytoplasm.
Subject(s)
Chlorophyta/physiology , Cytoplasmic Streaming , Lasers , MethodsABSTRACT
The apparent activity coefficients for sodium (gamma'Na) in the blood of six insect species have been calculated from measurements made with sodium-selective electrodes and a flame photometer. In every case gamma Na was significantly lower than that for this cation in free solution (gammaNa). In Periplaneta americana gammaNa varied considerably, during a period of 90 days, so that a relatively constant sodium activity (aNa) was maintained in the blood in the face of large variations in the total sodium content measured by flame photometry. Despite the relative constancy of aNa (of around 0.088M) appreciable fluctuations were observed in the sodium and potassium content of nervous connective over a period of 140 days. The values of aNa and aK were used to devise a satisfactory cockroach saline for use in experiments with isolated nerve cords.
Subject(s)
Cockroaches/physiology , Insecta/physiology , Periplaneta/physiology , Sodium/blood , Animals , Electrophysiology , Grasshoppers/physiology , Nerve Tissue/physiology , Potassium/blood , Rhodnius/physiology , Sodium Chloride/pharmacology , Species Specificity , Tenebrio/physiologyABSTRACT
Exposure to sodium-deficient (tris) saline caused an appreciable decline in the sodium content of intact connectives in the absence of equivalent reduction in the amplitude of the recorded action potentials. Return of sodium-depleted connectives to normal saline resulted in a rapid recovery of axonal function despite only a partial (less than 70%) recovery in sodium content. Replacement of sodium ions by those of lithium in the bathing medium resulted in a substantial accumulation of this cation. Lithium movements exhibited a marked asymetry, no significant decline in concentration being observed upon return to normal saline. These results are tentatively interpreted in terms of an exchangeable glial sodium fraction and are discussed in relation to extra-axonal sodium regulation.
