Developmental changes of FABP concentration,expression, and intracellular distribution in locust flight muscle

M-FABP from flight muscle of the locust,Schistocerca gregaria, is similar to mammalian H-FABP in its physical characteristics and amino acid sequence. We have studied developmental changes using ELISA, Northern Blotting, and EM/immuno-gold techniques. M-FABP is found in cytoplasm and nuclei, but not in mitochondria. It is the most abundant soluble muscle protein in fully developed adult locusts, comprising 18% of the total cytosolic protein. However, no FABP is detectable at the beginning of the adult stage. Its concentration rises dramatically during the next 10 days, after which it reaches its maximal value. Expression apparently is turned on after adult ecdysis and continues for 10 days; thereafter, FABP mRNA diminishes and reaches a constant, but low level, probably needed to maintain the current FABP level. From a series of experiments employing metamorphosis-controlling hormones and antihormones it is evident that the induction of FABP expression is directly linked to metamorphosis.Abbreviations ELISA Enzyme Linked Immuno Sorbent Assay - FABP Fatty Acid-Binding Protein - H-FABP mammalian Heart Fatty Acid-Binding Protein - M-FABP locust flight Muscle Fatty Acid-Binding Protein     

Model simulations of continuous rotifer cultures

Derived from the Monod-model and regulating principles a regulation model of the rotifer development in chemostats was developed. The model was validated in continuous cultures of Brachionus angularis both in steady-states, when undisturbed, and in transient-states after perturbations by step changes of dilution rate or input substrate concentration. Simulations of the simple model monotonically approached steady-states, but cultures show overshoots and damped oscillations before reaching this state. After introducing time-lags into the model it depends on the size of the time lag if model rotifer densities reach stable steady-state values (at low time lags) or stable limit cycles with periodic oscillations (at high time lags). At even higher time lags chaotic conditions occur in the model with final extinction of the rotifers.     

Elemane-Type Sesquiterpene,Acetonide Derived Polyacetylene and Other Constituents from the Whole Plant of Gymnanthemum theophrastifolium (Schweinf. ex Oliv. & Hiern) H.Rob. and Their Chemophenetic Significance

The chemical investigation of the methanol extract of the whole plant of Gymnanthemum theophrastifolium (Schweinf. ex Oliv. & Hiern) H.Rob. (Asteraceae) led to the isolation of a new elemane-type sesquiterpene ( 1 ), a new acetonide derived polyacetylene ( 2 ) and a naturally occurring compound ( 3 ) from the plant kingdom along with sixteen known compounds ( 4 – 19 ). Their structures were elucidated by extensive NMR and MS analysis. This is the first report on the chemical constituents of G. theophrastifolium. Furthermore, compounds 12 , 13 , and 14 are reported for the first time from the family Asteraceae, while compound 9 is reported for the first time from the genus Gymnanthemum. Thus, the present results provide valuable insights to the chemophenetic knowledge of G. theophrastifolium, which is also discussed in this work.     

Sugar transport across the plasma membranes of higher plants

The fluxes of carbohydrates across the plasma membranes of higher-plant cells are catalysed mainly by monosaccharide and disaccharide-H⁺ symporters. cDNAs encoding these different transporters have been cloned recently and the functions and properties of the encoded proteins have been studied extensively in heterologous expression systems. Several of the proteins have been identified biochemically in these expression systems and their location in plants has been shown immunohistochemically or with transgenic plants which were transformed with reporter genes, expressed under the control of the promoters of individual transporter genes. In this paper we summarize the current knowledge on the molecular biology and biochemistry of higher-plant sugar transport proteins.     

Receptor-mediated endocytosis of storage proteins by the fat body of Helicoverpa zea

The selective uptake of storage proteins by the fat body of the corn earworm Helicoverpa zea is mediated by a membrane-bound receptor protein. In this study, the major storage proteins of this insect species, arylphorin and very high density lipoprotein, were directly labeled with colloidal gold-particles of different size. After the fat body had been incubated with the labeled storage proteins, the distribution of these proteins was examined by electron microscopy. Both storage proteins were found at the extracellular side of coated pits and within coated vesicles. Moreover, fusion products of several coated vesicles such as endosomes and multivesicular bodies contained both proteins in their lumen. Ultimately, the proteins accumulated in electron-dense storage granules. Equal numbers of either storage protein were present in each organelle, supporting the notion that a single receptor mediates the uptake of both proteins. In contrast, only small numbers of gold-labeled immunoglobulin G molecules were found in the organelles, indicating that the protein uptake is specific for storage proteins. The results show that storage protein uptake in this lepidoteran species occurs in a process of receptor-mediated endocytosis that is similar to the well-established uptake of specific proteins into mammalian tissues.     

Storage protein uptake in helicoverpa zea: Arylphorin and VHDL share a single receptor

The major lepidopteran storage protein arylphorin is selectively taken up into perivisceral fat body of prepupae by receptor mediated endocytosis. The arylphorin receptor was identified by ligand blotting and in vitro binding studies. Fat body membranes contain a glycosylated receptor protein with an apparent molecular weight of 80,000 that binds arylphorin with a K_D of 9.02 × 10^?8 M. Competitive binding experiments revealed that the arylphorin receptor is identical with the previously identified VHDL receptor. Apparently a single receptor mediates the uptake of structurally distinct storage proteins. This storage protein receptor is present only in perivisceral fat body and only during the period around pupation when both storage proteins are sequestered. © 1994 Wiley-Liss, Inc.     

The chemical and thermal stability of the acetamido group of (R)- and (S)-atenolol: Synthetic and chromatographic studies

The chemical stability of the acetamido moiety of the β-blocker atenolol toward possible dehydration causing a nitrile formation during an acid-catalyzed chiral derivatization procedure with O,O′-(R,R)-diacylated tartaric acid anhydrides was elucidated. All the necessary reference compounds including the oxazolidine-2-one derivatives of the respective aminopropanols were synthesized, their structures confirmed by various spectroscopic methods, and chromatographically compared using HPLC and GC-MS. In the course of this work it was shown that the acetamido moiety of atenolol is quite stable toward dehydrating agents but shows a significant thermolability, e.g., in the injection system of a GC, which leads to the dehydrated form of atenolol namely, “nitriloatenolol.” © 1994 Wiley-Liss, Inc.     

Seston dynamics and bivalve feeding in the Bay of Marennes-Oléron (France)

Within the framework of an investigation into the carrying capacity of the Bay of Marennes-Oléron (France) for bivalve culture, thein situ uptake of suspended particulate material by oysters (Crassostrea gigas) and mussels (Mytilus edulis) was determined in experiments with benthic ecosystem tunnels. Very high fluctuations in seston quantity and quality were observed within and between tidal cycles. The percentage of organic carbon was inversely related to seston quantity at low concentrations. Organic carbon was diluted by resuspension of material rich in inorganic matter. At high seston concentrations a constant level of about 2% organic carbon was found. The C/N ratio was relatively constant throughout the seasons and fairly low (6.5 to 8.4). Owing to the presence of bivalves large fluxes of suspended particulate material were observed in thein situ measurements. Selective retention of organic carbon or nitrogen could not be demonstrated. Clearance rates based on chlorophyll uptake were within a normal range compared to other studies. A large contribution to the food of the bivalves seemed to be formed by resuspended microphytobenthos. Judged by the low C/N ratio, the food was of good quality. Although its quantity was variable by dilution, it may support largely the carrying capacity of the Bay of Marennes-Oléron for the cultivation of bivalves. Communication no. 687 of the Netherlands Institute of Ecology, Centre for Estuarine and Coastal Ecology, Yerseke, the Netherlands.     

Control of mitochondrial respiration. The contribution of the adenine nucleotide translocator depends on the ATP- and ADP-consuming enzymes

The consequence of the complexity of the metabolic network on the amount of control strength of adenine nucleotide translocator was investigated with isolated rat liver mitochondria. Two experimental systems were compared: (i) mitochondria in the presence of yeast hexokinase (hexokinase system) and (ii) the same system plus additional pyruvate kinase (pyruvate kinase system). In both systems the control strength was analysed for the adenine nucleotide translocator by inhibitor titration studies with carboxyatractyloside and for the hexokinase or pyruvate kinase by changing their relative activities. Experimental results were compared with computer simulation of these systems and that of a third one, where the extramitochondrial ATP / ADP ratio was held constant by perifusion (perifusion system). The results demonstrate quite different flux-dependent control strength of the translocator in the three systems. In the hexokinase system the control strength of the translocator on mitochondrial respiration was zero up to respiration rates of about 60 nmol O₂/mg protein per min. For higher rates, the control strength increased until the maximum value (0.45) was reached in the fully active state. Here, the same value was also found in the pyruvate kinase system. In all other states of respiration the translocator exerts a higher control strength in the pyruvate kinase system than in the hexokinase system. This different behaviour was attributed to the various changes in the adenine nucleotide pattern caused by partial inhibition of the translocator in the hexokinase and pyruvate kinase system. The data clearly show that the sharing of control strength depends not only on the respiration rate but also on the complexity of the metabolic system.     

Growth yields of green sulfur bacteria in mixed cultures with sulfur and sulfate reducing bacteria

1. Dry weight yields from mixed cultures ofProsthecochloris aestuarii orChlorobium limicola with the sulfur reducingDesulfuromonas acetoxidans were determined on different growth limiting amounts of acetate, ethanol or propanol. The obtained yields agreed well with values predicted from stoichiometric calculations. 2. From mixed cultures of twoChlorobium limicola strains withDesulfovibrio desulfuricans orD. gigas on ethanol as the growth limiting substrate, dry weight yields were obtained as calculated for the complete utilization of the ethanol by the mixed cultures. 3. Dry weight yield determinations for two pure cultures ofChlorobium limicola with different growth limiting amounts of sulfide in the absence and presence of excess acetate confirmed that acetate is incorporated byChlorobium in a fixed proportion to sulfide; compared to the yield in the absence of acetate the yield is increased two to threefold in the presence of acetate. 4. The lowest possible sulfide concentrations necessary for optimal growth of mixed cultures of eitherProsthecochloris orChlorobium withDesulfuromonas on acetate were 7–8 mg H₂S per liter of medium. 5. Doubling times at the growth rate limiting light intensities of 5, 10, 20, 50, 100 and 200 lux were determined under optimal growth conditions for the following phototrophic bacteria:Prosthecochloris aestuarii, Chlorobium phaeovibriodes, Chromatium vinosum andRhodopseudomonas capsulata. Reasonably good growth was still obtained withProsthecochloris at 10 and 5 lux light intensity at which no growth of the purple bacteria could be observed.